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The carbon coating strategy has emerged as an indispensable approach to improve the conductivity of polyanionic cathodes. However, owing to the complex reaction process between precursors of carbon and cathode, establishing a unified screening principle for carbonaceous precursors remains a technical challenge. Herein, we reveal that carbonaceous precursor pyrolysis chemistry undeniably influences the formation process and performance of Na 3 V 2 (PO 4 ) 3 (NVP) cathodes from in situ insights. By investigating three types of carbonaceous precursors, it is found that O/H-containing functional groups can provide more bonding sites for cathode precursors and generate a reducing atmosphere by pyrolysis, which is beneficial to the formation of polyanionic materials and a uniform carbon coating layer. Conversely, excessive pyrolysis of functional groups leads to a significant amount of gas, which is detrimental to the compactness of the carbon layer. Furthermore, the substantial presence of residual heteroatoms diminishes graphitization. In this case, it is demonstrated that carbon dots (CDs) precursors with suitable functional groups can comprehensively enhance the Na + migration rate, reversibility, and interface stability of the cathode material. As a result, the NVP/CDs cathode displays outstanding capacity retention, maintaining 92% after 10,000 cycles at a high rate of 50 C. Altogether, these findings provide a valuable benchmark for carbon source selection for polyanionic cathodes.

Metallic zinc has been regarded as an ideal anode material for aqueous batteries due to its high capacity, abundance, and low toxicity. Numerous strategies have been proposed for anode protection to address its intrinsic deficiencies. However, existing methods can only suppress dendrite growth at limited current densities, and achieving stable cycling at high rates remains a great challenge. Herein, density functional theory (DFT) reveals that Mn-MOF, with a distinctive π-π stacking structure (π-MOF), can induce accelerated ion transfer dynamics, providing high-speed pathways for Zn 2+ flux, which can enable stable deposition even at high rates. As anticipated, the π-MOF@Zn anode exhibits remarkable stability for over 1900 h with the lowest voltage hysteresis (71 mV) at a current density of 10 mA cm -2 . This study presents a viable approach to enhance the interface stability of high-rate metal anodes by modulating charge or ion behavior at the interface.

Polycrystalline lithium manganese oxide (LMO) is known to suffer from severe surface structure degradation and electrochemical polarization due to its mixed crystal plane orientations. A hexagonal prism single-crystal LMO (LMOS-HP), engineered through the SrO-induced preferential growth effect, features the most stable {111} top surfaces and the fastest Li + diffusion {110} side surfaces, effectively addressing these challenges. Consequently, LMOS-HP exhibits superior electrochemical capability, with only 0.021% capacity fading per cycle after 500 cycles and achieves a discharge capacity of 81.9 mAh g -1 at 20C. This innovative design offers a promising approach for tuning surface crystal orientation to improve performance.

Al impurity is among the most likely components to enter the spent lithium-ion battery (LIB) cathode powder due to the strong adhesion between the cathode material and the Al current collector. However, high-value metal elements tend to be lost during the deep removal of Al impurities to obtain high-purity metal salt products in the conventional hydrometallurgical process. In this work, the harmful Al impurity is designed as a beneficial ingredient to upcycle high-voltage LiCoO 2 by incorporating robust Al-O covalent bonds into the bulk of the cathode assisted with Ti modification. Benefiting from the strong Al-O and Ti-O bonds in the bulk, the irreversible phase transitions of the upcycled R-LCO-AT have been significantly suppressed at high voltages, as revealed by in situ XRD. Moreover, a Li + -conductive Li 2 TiO 3 protective layer is constructed on the surface of R-LCO-AT by pinning slow-diffusion Ti on the grain boundaries, resulting in improved Li + diffusion kinetics and restrained interface side reactions. Consequently, the cycle stability and rate performance of R-LCO-AT were significantly enhanced at a high cutoff voltage of 4.6 V, with a discharge capacity of 189.5 mAhg -1 at 1 C and capacity retention of 92.9% over 100 cycles at 4.6 V. This study utilizes the detrimental impurity element to upcycle high-voltage LCO cathodes through an elaborate bulk/surface structural design, offering a strategy for the high-value utilization of spent LIBs.

Direct regeneration is an effective strategy of spent lithium iron phosphate (S-LFP), with the principal aspect being the selection of the lithium source and reductant. Here, assisted with a thermodynamically favourable reaction involving a bifunctional organic lithium salt (lithium citrate), the single-step regeneration of S-LFP is successfully achieved. The structure and composition of the regenerated LFP are significantly restored, demonstrating excellent electrochemical performance (142.7 mA h g -1 ) with no degradation after 200 cycles.

Lithium carbon dioxide (Li-CO 2 ) batteries, noted for their high discharge voltage of approximately 2.8 V and substantial theoretical specific energy of 1876 Wh kg -1 , represent a promising avenue for new energy sources and CO 2 emission reduction. However, the practical application of these batteries faces significant hurdles, particularly at high current densities and over extended cycle lives, due to their complex reaction mechanisms and slow kinetics. This paper delves into the recent advancements in cathode catalysts for Li-CO 2 batteries, with a specific focus on the designing philosophy from composition, geometry, and homogeneity of the catalysts to the proper test conditions and real-world application. It surveys the possible catalytic mechanisms, giving readers a brief introduction of how the energy is stored and released as well as the critical exploration of the relationship between material properties and performances. Specifically, optimization and standardization of test conditions for Li-CO 2 battery research is highlighted to enhance data comparability, which is also critical to facilitate the practical application of Li-CO 2 batteries. This review aims to bring up inspiration from previous work to advance the design of more effective and sustainable cathode catalysts, tailored to meet the practical demands of Li-CO 2 batteries., (© 2024 Wiley‐VCH GmbH.)

On the basis of the sustainable concept, organic compounds and carbon materials both mainly composed of light C element have been regarded as powerful candidates for advanced electrochemical energy storage (EES) systems, due to theie merits of low cost, eco-friendliness, renewability, and structural versatility. It is investigated that the carbonyl functionality as the most common constituent part serves a crucial role, which manifests respective different mechanisms in the various aspects of EES systems. Notably, a systematical review about the concept and progress for carbonyl chemistry is beneficial for ensuring in-depth comprehending of carbonyl functionality. Hence, a comprehensive review about carbonyl chemistry has been summarized based on state-of-the-art developments. Moreover, the working principles and fundamental properties of the carbonyl unit have been discussed, which has been generalized in three aspects, including redox activity, the interaction effect, and compensation characteristic. Meanwhile, the pivotal characterization technologies have also been illustrated for purposefully studying the related structure, redox mechanism, and electrochemical performance to profitably understand the carbonyl chemistry. Finally, the current challenges and promising directions are concluded, aiming to afford significant guidance for the optimal utilization of carbonyl moiety and propel practicality in EES systems.

The practical application of solid polymer electrolyte is hindered by the small transference number of Li+, low ionic conductivity and poor interfacial stability, which are seriously determined by the microenvironment in polymer electrolyte. The introduction of functional fillers is an effective solution to these problems. In this work, based on density functional theory (DFT) calculations, it is demonstrated that the anion vacancy of filler can anchor anions of lithium salt, thereby significantly increasing the transference number of Li+ in the electrolyte. Therefore, flower-like SnS2-based filler with abundant sulfur vacancies is prepared under the regulation of functionalized carbon dots (CDs). It is worth mentioning that the CDs dotted on the surface of SnS2 have rich organic functional groups, which can serve as the bridging agent to enhance the compatibility of filler and polymer, leading to superior mechanical performance and fast ion transport pathway. Additionally, the in-situ formed Li2S/Li3N at the interface of Li metal and electrolyte facilitate the fast Li+ diffusion and uniform Li deposition, effectively mitigating the growth of lithium dendrites. As a result, the assembled lithium metal batteries exhibit excellent cycling stability, reflecting the superiority of the carbon dots derived vacancy-rich inorganic filler modification strategy., (© 2024 Wiley‐VCH GmbH.)

Transition metal selenides (TMSs) are receiving considerable interest as improved anode materials for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) due to their considerable theoretical capacity and excellent redox reversibility. Herein, ZIF-12 (zeolitic imidazolate framework) structure is used for the synthesis of Cu 2 Se/Co 3 Se 4 @NPC anode material by pyrolysis of ZIF-12/Se mixture. When Cu 2 Se/Co 3 Se 4 @NPC composite is utilized as an anode electrode material in LIB and SIB half cells, the material demonstrates excellent electrochemical performance and remarkable cycle stability with retaining high capacities. In LIB and SIB half cells, the Cu 2 Se/Co 3 Se 4 @NPC anode material shows the ultralong lifespan at 2000 mAg -1 , retaining a capacity of 543 mAhg -1 after 750 cycles, and retaining a capacity of 251 mAhg -1 after 200 cycles at 100 mAg -1 , respectively. The porous structure of the Cu 2 Se/Co 3 Se 4 @NPC anode material can not only effectively tolerate the volume expansion of the electrode during discharging and charging, but also facilitate the penetration of electrolyte and efficiently prevents the clustering of active particles. In situ X-ray difraction (XRD) analysis results reveal the high potential of Cu 2 Se/Co 3 Se 4 @NPC composite in building efficient LIBs and SIBs due to reversible conversion reactions of Cu 2 Se/Co 3 Se 4 @NPC for lithium-ion and sodium-ion storage., (© 2024 Wiley‐VCH GmbH.)

A separator modification strategy was proposed by placing nitrogen-doped carbon fibers (NCF700) in the middle of the separator to prevent direct contact between the coating and the rigid zinc metal anode, resulting in coating cracks. The NCF700 coating can homogenize the electric field distribution and increase the transference number of zinc ions. Therefore, the battery assembled with the NCF700 coated separator exhibits superior cycling stability compared to the bare separator.

Layered sodium transition-metal oxides generally encounter severe capacity decay and inferior rate performance during cycling, especially at a high state of charge. Herein, defect concentration is rationally modulated to explore the impact on electrochemical behavior in NaNi 1/3 Fe 1/3 Mn 1/3 O 2 layered oxides. Bulk vacancies are increased through annealing in an oxygen-rich atmosphere, demonstrated by electron paramagnetic resonance measurement. It is found that the cathode with enriched oxygen vacancies exhibits significantly enhanced reversibility of redox reactions with a higher initial Coulombic efficiency of 90.0%. Furthermore, the reduced volume variations during the initial charge/discharge process are also confirmed by in situ X-ray diffraction. As a result, the oxygen-vacancy-rich cathode shows great cycling stability and superior rate performances. Also, full cells deliver a specific capacity of approximately 145.2 mAh g -1 at 0.5 C, with a high capacity retention of 78.3% after 100 cycles. This work presents a viable strategy for designing Na + intercalated cathodes with a high-energy density.

The structural failure of Na2Mn[Fe(CN)6] could not be alleviated with traditional modification strategies through the adjustable composition property of Prussian blue analogues (PBAs), considering that the accumulation and release of stress derived from the MnN6 octahedrons are unilaterally restrained. Herein, a novel application of adjustable composition property, through constructing a coordination competition relationship between chelators and [Fe(CN)6]4- to directionally tune the enrichment of elements, is proposed to restrain structural degradation and induce unconventional energy coupling phenomenon. The non-uniform distribution of elements at the M1 site of PBAs (NFM-PB) is manipulated by the sequentially precipitated Ni, Fe, and Mn according to the Irving-William order. Electrochemically active Fe is operated to accompany Mn, and zero-strain Ni is modulated to enrich at the surface, synergistically mitigating with the enrichment and release of stress and then significantly improving the structural stability. Furthermore, unconventional energy coupling effect, a fusion of the electrochemical behavior between FeLS and MnHS, is triggered by the confined element distribution, leading to the enhanced electrochemical stability and anti-polarization ability. Consequently, the NFM-PB demonstrates superior rate performance and cycling stability. These findings further exploit potentialities of the adjustable composition property and provide new insights into the component design engineering for advanced PBAs., (© 2024 Wiley‐VCH GmbH.)

Sodium-ion batteries (SIBs) have significant potential for applications in portable electric vehicles and intermittent renewable energy storage due to their relatively low cost. Currently, hard carbon (HC) materials are considered commercially viable anode materials for SIBs due to their advantages, including larger capacity, low cost, low operating voltage, and inimitable microstructure. Among these materials, renewable biomass-derived hard carbon anodes are commonly used in SIBs. However, the reports about biomass hard carbon from basic research to industrial applications are very rare. In this paper, we focus on the research progress of biomass-derived hard carbon materials from the following perspectives: (1) sodium storage mechanisms in hard carbon; (2) optimization strategies for hard carbon materials encompassing design, synthesis, heteroatom doping, material compounding, electrolyte modulation, and presodiation; (3) classification of different biomass-derived hard carbon materials based on precursor source, a comparison of their properties, and a discussion on the effects of different biomass sources on hard carbon material properties; (4) challenges and strategies for practical of biomass-derived hard carbon anode in SIBs; and (5) an overview of the current industrialization of biomass-derived hard carbon anodes. Finally, we present the challenges, strategies, and prospects for the future development of biomass-derived hard carbon materials.

Garnet solid-state electrolyte Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZTO) holds significant promise. However, the practical utilization has been seriously impeded by the poor contact of Li|garnet and electron leakage. Herein, one new type of garnet-based solid-state battery is proposed with high performance through the disparity in interfacial energy, induced by the reaction between trace fluorinated carbon dots (FCDs) and Li. The work of adhesion of Li|garnet is increased by the acquired Li-FCD composite, which facilitates an intimate Li|garnet interface with the promoted uniform Li + deposition, revealed by density functional theory (DFT) calculations. It is further validated that a concentrated C-Li 2 O-LiF component at the Li|garnet interface is spontaneously constructed, due to the significant disparity in interfacial energy between C-Li 2 O-LiF|LLZTO and C-Li 2 O-LiF|Li. Furthermore, The electron transport and Li dendrites penetration are effectively hindered by the formed Li 2 O and LiF. The Li-FCD|LLZTO|Li-FCD symmetrical cells demonstrate stable cycling performance for over 3000 hours at 0.3 mA cm -2 and 800 hours at 0.5 mA cm -2 . Furthermore, the LFP|garnet|Li-FCD full cell exhibits remarkable cycling performance (91.6 % capacity retention after 500 cycles at 1 C). Our research has revealed a novel approach to establish a dendrite-free Li|garnet interface, laying the groundwork for future advancements in garnet-based solid-state batteries., (© 2024 Wiley-VCH GmbH.)

The electric eel is known as the most powerful creature to generate electricity with a discharge voltage up to 860 V and peak current up to 1 A. These surprising properties are the results of billions of years of evolution on the electrical biological structure and bulk, and now have triggered great research interest in electric eel biomimetics for designing innovated configurations and components of energy storage and conversion devices. In this review, first, the bioelectrical behavior of electric eels is surveyed, followed by the physiological structure to reveal the discharge characteristics and principles of electric organs and electrocytes. Additionally, underlying electrochemical mechanisms and models for calculating the potential and current of electrocytes are presented. Central to this review is the recent progress of electric-eel-inspired innovations and applications for energy storage and conversion, particularly including novel power sources, triboelectric nanogenerators, and nanochannel ion-selective membranes for salinity gradient energy harvesting. Finally, insights on the challenges at the moment and the perspectives on the future research prospects are critically compiled. It is suggested that energy-related electric eel biomimetics will greatly boost the development of next-generation high performance, green, and functional electronics., (© 2023 Wiley‐VCH GmbH.)

Layered sodium transition-metal (TM) oxides generally suffer from severe capacity decay and poor rate performance during cycling, especially at a high state of charge (SoC). Herein, an insight into failure mechanisms within high-voltage layered cathodes is unveiled, while a two-in-one tactic of charge localization and coherent structures is devised to improve structural integrity and Na + transport kinetics, elucidated by density functional theory calculations. Elevated Jahn-Teller [Mn 3+ O 6 ] concentration on the particle surface during sodiation, coupled with intense interlayer repulsion and adverse oxygen instability, leads to irreversible damage to the near-surface structure, as demonstrated by X-ray absorption spectroscopy and in situ characterization techniques. It is further validated that the structural skeleton is substantially strengthened through the electronic structure modulation surrounding oxygen. Furthermore, optimized Na + diffusion is effectively attainable via regulating intergrown structures, successfully achieved by the Zn 2+ inducer. Greatly, good redox reversibility with an initial Coulombic efficiency of 92.6%, impressive rate capability (86.5 mAh g -1 with 70.4% retention at 10C), and enhanced cycling stability (71.6% retention after 300 cycles at 5C) are exhibited in the P2/O3 biphasic cathode. It is believed that a profound comprehension of layered oxides will herald fresh perspectives to develop high-voltage cathode materials for sodium-ion batteries.

Ni/Mn-based oxide cathode materials have drawn great attention due to their high discharge voltage and large capacity, but structural instability at high potential causes rapid capacity decay. How to moderate the capacity loss while maintaining the advantages of high discharge voltage remains challenging. Herein, the replacement of Mn ions by Ga ions is proposed in the P2-Na 2/3 Ni 0.2 Mn 0.8 O 2 cathode for improving their cycling performances without sacrificing the high discharge voltage. With the introduction of Ga ions, the relative movement between the transition metal ions is restricted and more Na ions are retained in the lattice at high voltage, leading to an enhanced redox activity of Ni ions, validated by ex situ synchrotron X-ray absorption spectrum and X-ray photoelectron spectroscopy. Additionally, the P2-O2 phase transition is replaced by a P2-OP4 phase transition with a smaller volume change, reducing the lattice strain in the c-axis direction, as detected by operando/ex situ X-ray diffraction. Consequently, the Na 2/3 Ni 0.21 Mn 0.74 Ga 0.05 O 2 electrode exhibits a high discharge voltage close to that of the undoped materials, while increasing voltage retention from 79% to 93% after 50 cycles. This work offers a new avenue for designing high-energy density Ni/Mn-based oxide cathodes for sodium-ion batteries., (© 2023 Wiley‐VCH GmbH.)

Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) is currently drawing increased attention as a sodium-ion batteries (SIBs) cathode due to the cost-effective and NASICON-type structure features. Owing to the sluggish electron and Na + conductivities, however, its real implementation is impeded by the grievous capacity decay and inferior rate capability. Herein, multivalent cation substituted microporous Na 3.9 Fe 2.9 Al 0.1 (PO 4 ) 2 (P 2 O 7 ) (NFAPP) with wide operation-temperature is elaborately designed through regulating structure/interface coupled electron/ion transport. Greatly, the derived Na vacancy and charge rearrangement induced by trivalent Al 3+ substitution lower the ions diffusion barriers, thereby endowing faster electron transport and Na + mobility. More importantly, the existing Al-O-P bonds strengthen the local environment and alleviate the volume vibration during (de)sodiation, enabling highly reversible valence variation and structural evolution. As a result, remarkable cyclability (over 10,000 loops), ultrafast rate capability (200 C), and exceptional all-climate stability (-40-60 °C) in half/full cells are demonstrated. Given this, the rational work might provide an actionable strategy to promote the electrochemical property of NFPP, thus unveiling the great application prospect of sodium iron mixed phosphate materials., (Copyright © 2024. Published by Elsevier B.V.)

The utilization rate of active sites in cathode materials for Zn-based batteries is a key factor determining the reversible capacities. However, a long-neglected issue of the strong electrostatic repulsions among divalent Zn 2+ in hosts inevitably causes the squander of some active sites (i.e., gap sites). Herein, we address this conundrum by unraveling the "gap-filling" mechanism of multiple charge carriers in aqueous Zn-MoS 2 batteries. The tailored MoS 2 /(reduced graphene quantum dots) hybrid features an ultra-large interlayer spacing (2.34 nm), superior electrical conductivity/hydrophilicity, and robust layered structure, demonstrating highly reversible NH 4 + /Zn 2+ /H + co-insertion/extraction chemistry in the 1 M ZnSO 4 +0.5 M (NH 4 ) 2 SO 4 aqueous electrolyte. The NH 4 + and H + ions can act as gap fillers to fully utilize the active sites and screen electrostatic interactions to accelerate the Zn 2+ diffusion. Thus, unprecedentedly high rate capability (439.5 and 104.3 mAh g -1 at 0.1 and 30 A g -1 , respectively) and ultra-long cycling life (8000 cycles) are achieved., (© 2024 Wiley-VCH GmbH.)

Ultrafast-charging is the focus of next-generation rechargeable batteries for widespread economic success by reducing the time cost. However, the poor ion diffusion rate, intrinsic electronic conductivity and structural stability of cathode materials seriously hinder the development of ultrafast-charging technology. To overcome these challenges, an interfacial dynamics and thermodynamics synergistic strategy is proposed to synchronously enhance the fast-charging capability and structural stability of polyanion cathode materials. As a case study, a Na 3 V 2 (PO 4 ) 3 composite (NVP/NSC) is successfully obtained by introducing an interface layer derived from N/S co-doped carbon dots. Density functional theory calculations validate that the interfacial bonding effect of V-N/S-C significantly reduces the Na + transport energy barrier. D-band center theory analysis confirms the downward shift of the V d-band center enhances the strength of the V-O bond and considerably inhibits irreversible phase transformation. Benefitting from this interfacial synergistic strategy, NVP/NSC achieves a high capability and excellent cycling stability with a surprisingly low carbon content (2.23%) at an extremely high rate of 100C for 10 000 cycles (87.2 mA h g -1 , 0.0028% capacity decay per cycle). Furthermore, a superior performance at 5C (115.3 mA h g -1 , 92.1% capacity retention after 800 cycles) is exhibited by the NVP/NSC‖HC full cell. These findings provide timely new insights for the systematic design of ultrafast-charging cathode materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Difluoroethylene carbonate (DFEC) featuring abundant fluorine atoms has been proposed as a multifunctional electrolyte additive to boost the stability of the electrolyte-electrode interphase of lithium metal batteries. Thus, introducing the DFEC additive enables a high capacity retention rate of the Li||NCM811 full cell (up to 75% after 200 cycles) at 4.5 V high voltage.

Fluorinated carbon dots (FCDs) have garnered interest owing to their distinct physicochemical properties. Nevertheless, intricate synthesis procedures and quite low fluorine doping levels limit its development and application. Herein, we propose a facile approach based on the Claisen-Schmidt reaction to realize gram-scale synthesis of highly fluorinated carbon dots (up to 20.79 at. %) at room temperature and atmospheric pressure, and a comprehensive exploration of the specific reaction mechanism is conducted. Furthermore, in consideration of the high fluorine content, good dispersibility, and compatibility with polymer electrolyte, the synthesized FCDs are utilized as an additive for PEO-based solid electrolytes of a Li battery to improve its ionic conductivity, interface stability, and mechanical properties. The introduction of FCDs can not only reduce the crystallinity of PEO and enhance the interaction of polymer chains, but also facilitate the establishment of uninterrupted pathways and in situ fluorination at the interface, which is substantiated by both theoretical calculations and experimental findings. As a result, the lithium symmetrical battery can operate stably for 1000 h at a current density of 0.4 mA cm -2 . Simultaneously, the LiFePO 4 /Li battery utilizing the composite electrolyte exhibits a capacity of 130.3 mAh g -1 over 300 cycles while maintaining a capacity retention rate of 95.10%. This study develops a strategy for synthesizing highly fluorinated carbon dots, which demonstrate a useful influence on PEO electrolytes, thus boosting the advancement of FCDs and solid-state batteries.

Electric eels generate electricity with a discharge voltage of up to 860 V under ionic gradients, providing a fascinating example to inspire viable and flexible power sources. However, hitherto reported eel-related devices are strictly restricted by complicated fabrication and environmental energy input. Herein, an electric-eel-type bi-ionic gradient battery (BGB) is performed by cationic and anionic polyelectrolyte hydrogels featuring simplified units and self-energy supply. Benefiting from ionic bonds with opposite charges in the polymer chain, bianion gradients as well as ion selective migration pathways are synchronously constructed and integrated units are enabled. As a result, an open-circuit voltage of 0.54 V and a short-circuit current density of 13 μA cm -2 are generated by a BGB unit. Moreover, a voltage output up to 60 V is derived from integrated BGB devices, demonstrating the potential to drive wearable and implantable electronics. In this case, these artificial electric systems could overcome the great challenges of environmentally friendly, biocompatible, low-cost, and soft power sources, providing in-depth insights into the development of clean and sustainable power generation technologies.

Sodium layered oxides feature in high capacity and diverse composition, however, are plagued by various issues including limited kinetics and interfacial instability with residual alkali. Conventional substitution/doping and heterogeneous coating are promising to tackle the problems of bulk and surface, respectively, but normally insufficient to address both. Herein, a post-substitution strategy is proposed to modify primary sodium-layered-oxide particles that can simultaneously deal with bulk and surficial issues. As a typical example, post Ti-substitution for O3-NaNi 1/3 Fe 1/3 Mn 1/3 O 2 is successfully performed by adjusting thermodynamic driving force, resulting in depth-controllable Ti infusion from surface to bulk, as proved by energy dispersive spectroscopy maps collected at the cross-section. Residual alkali species are efficiently diminished and benefited from the surface-to-bulk osmotic reaction, significantly improving Coulombic efficiency. Moreover, remarkable enhancements in reversible capacity (135 mAh g -1 at C/10), rate capability (74% retention at 5 C), and long-term cycling stability (80% retention after 300 cycles at 2 C) are achieved by manipulating gradient-like Ti distribution in a primary particle that brings with increased kinetics and strengthened interfacial stability, surpassing those given by rough heterotic coating and homogeneous Ti-substitution. Such post-substitution is expected to provide a universal strategy to modify primary layered-oxide particles for developing advanced cathode materials of SIBs., (© 2023 Wiley-VCH GmbH.)

Carbon dots (CDs) have attracted significant attention in the energy, environment, and biology fields due to their exceptional physicochemical properties. However, owing to the multifarious precursors and complex reaction mechanisms, the production of carbon dots from organic molecules is still a mysterious process. Inspired by the color change of sodium hydroxide ethanol solution after standing for some time, in this work, we thoroughly investigated the reaction mechanism from alcohol molecules to carbon dots through a lot of experiments and theoretical calculations, and it was found that the rate-controlling reaction is the formation of aldehydes, and it is also confirmed that there is a self-catalysis reaction, which can accelerate the conversion from alcohol to aldehyde, further facilitating the final formation of CDs. After the rate-controlling reaction of alcohol to aldehyde, under strongly alkaline conditions, an aldol reaction occurs to form unsaturated aldehydes, followed by further condensation and polymerization reactions to form long carbon chains, which are cross-linked and dehydrated to form carbon dots with a carbon core and surface functional groups. Additionally, it is found that the reaction can be largely accelerated with the assistance of electricity, which indicates the great prospect of industrial production. Furthermore, the obtained CDs with rich functional groups can be utilized as electrolyte additives to optimize the deposition behavior of Na metal, manifesting great potential towards safe and stable Na metal batteries., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The high-throughput scalable production of low-cost and high-performance electrode materials that work well under high power densities required in industrial application is full of challenges for the large-scale implementation of electrochemical technologies. Here, motivated by theoretical calculation that Mo-S-C heterojunction and sulfur vacancies can reduce the energy band gap, decrease the migration energy barrier, and improve the mechanical stability of MoS 2 , the scalable preparation of inexpensive MoS 2-x @CN is contrived by employing natural molybdenite as precursor, which is characteristic of high efficiency in synthesis process and energy conservation and the calculated costs are four orders of magnitude lower than MoS 2 /C in previous work. More importantly, MoS 2- x @CN electrode is endowed with impressive rate capability even at 5 A g -1 , and ultrastable cycling stability during almost 5000 cycles, which far outperform chemosynthesis MoS 2 materials. Obtaining the full SIC cell assembled by MoS 2- x @CN anode and carbon cathode, the energy/power output is high up to 265.3 W h kg -1 at 250 W kg -1 . These advantages indicate the huge potentials of the designed MoS 2- x @CN and of mineral-based cost-effective and abundant resources as anode materials in high-performance AICs., (© 2023 Wiley-VCH GmbH.)

High-voltage aqueous rechargeable energy storage devices with safety and high specific energy are hopeful candidates for the future energy storage system. However, the electrochemical stability window of aqueous electrolytes is a great challenge. Herein, inspired by density functional theory (DFT), polyethylene glycol (PEG) can interact strongly with water molecules, effectively reconstructing the hydrogen bond network. In addition, N, N-dimethylformamide (DMF) can coordinate with Zn 2+ , assisting in the rapid desolvation of Zn 2+ and stable plating/stripping process. Remarkably, by introducing PEG400 and DMF as co-solvents into the electrolyte, a wide electrochemical window of 4.27 V can be achieved. The shift in spectra indicate the transformation in the number and strength of hydrogen bonds, verifying the reconstruction of hydrogen bond network, which can largely inhibit the activity of water molecule, according well with the molecular dynamics simulations (MD) and online electrochemical mass spectroscopy (OEMS). Based on this electrolyte, symmetric Zn cells survived up to 5000 h at 1 mA cm -2 , and high voltage aqueous zinc ion supercapacitors assembled with Zn anode and activated carbon cathode achieved 800 cycles at 0.1 A g -1 . This work provides a feasible approach for constructing high-voltage alkali metal ion supercapacitors through reconstruction strategy of hydrogen bond network., (© 2023 Wiley-VCH GmbH.)

Rechargeable aqueous zinc-ion batteries (AZIBs) are among the most promising candidates for next-generation energy-storage devices. However, the large voltage polarisation and infamous dendrite growth hinder the practical application of AZIBs owing to their complex interfacial electrochemical environment. In this study, a hydrophobic zinc chelate-capped nano-silver (HZC-Ag) dual interphase is fabricated on the zinc anode surface using an emulsion-replacement strategy. The multifunctional HZC-Ag layer remodels the local electrochemical environment by facilitating the pre-enrichment and de-solvation of zinc ions and inducing homogeneous zinc nucleation, thus resulting in reversible dendrite-free zinc anodes. The zinc deposition mechanism on the HZC-Ag interphase is elucidated by density functional theory (DFT) calculations, dual-field simulations, and in situ synchrotron X-ray radiation imaging. The HZC-Ag@Zn anode exhibited superior dendrite-free zinc stripping/plating performance and an excellent lifespan of >2000 h with ultra-low polarisation of ≈17 mV at 0.5 mA cm -2 . Full cells coupled with a MnO 2 cathode showed significant self-discharge inhibition, excellent rate performance, and improved cycling stability for >1000 cycles. Therefore, this multifunctional dual interphase may contribute to the design and development of dendrite-free anodes for high-performance aqueous metal-based batteries., (© 2023 Wiley-VCH GmbH.)

Solid-state batteries can ensure high energy density and safety in lithium metal batteries, while polymer electrolytes are plagued by slow ion kinetics and low selective transport of Li + . Metal-organic frameworks (MOFs) are proposed as emerging fillers for solid-state poly(ethylene oxide)(PEO) electrolytes, however, developing functionalized MOFs and understanding their roles on ion transfer has proven challenging. Herein, combining computational and experimental results, the functional group regulation in MOFs can effectively change surficial charge distribution and limit anion movement is revealed, providing a potential solution to these issues. Specifically, functionalized 2D MOF sheets are designed through molecular engineering to construct high-performance composite electrolytes, where the electron-donating effect of substituents in 2D-MOFs effectively limits the movement of ClO 4 - and promotes mechanical properties and ion migration numbers (0.36 up to 0.64) of PEO. As a result, Li/Li cells with composite electrolyte exhibit superior cyclability for 1000 h at a current density of 0.2 mA cm -2 . Meanwhile, the solid LiFePO 4 /Li battery delivers highly reversible capacities of 148.8 mAh g -1 after 200 cycles. These findings highlight a new approach for anion confinement through the use of functional group electronic effects, leading to enhanced ionic conductivity, and a feasible direction for high-performance solid-state batteries., (© 2023 Wiley-VCH GmbH.)

Improving the performance of quasi-solid-state gel polymer electrolytes is critical for addressing issues at the Zn anode-electrolyte interface of high-performance flexible Zn-air batteries (FZABs). In this study, a highly interconnected porous poly(vinyl alcohol)/poly(ethylene glycol) (PVA/PEG) hydrogel electrolyte was fabricated via an ice-crystal template for FZABs. The mechanical toughness and stability of the gel electrolytes can be reinforced by the formation of a PEG-PVA cross-linking network. The three-dimensional PVA/PEG porous skeleton greatly increased electrolyte uptake and accelerated ion transport, leading to high ionic conductivity (42.5 mS cm -1 ). In-situ synchrotron radiation X-ray imaging revealed that the PVA/PEG network can effectively inhibit dendrite growth and the hydrogen evolution reaction. The assembled FZABs exhibited superior cycle stability, high power density (109 mW cm -3 ), and excellent flexibility and structural stability under bending conditions, thus showing great potential for future applications in flexible and wearable electronic device technologies.

Although both electromagnetic and charge transfer (CT) mechanisms play a role in surface-enhanced Raman scattering (SERS), the contribution of the latter is limited by poor CT efficiency. Herein, we propose molecular-enhanced Raman spectroscopy (MERS) for the first time and develop a simple strategy to induce strong CT-enhanced Raman signals using a phosphoester (POE) electron-transfer bridge. Consequently, an excellent POE-enhanced Raman effect was found when various mono-, bis-, and trisaminobenzene compounds were used as probe analytes. Quantification analysis of this MERS effect revealed that the enhancement ratio and factor of the POE molecules can be up to 87% and ∼10 9 , respectively. Spectroscopic analysis and density functional theory calculation confirmed that this effect was because of the formation of intermolecular hydrogen bonds, which promotes CT via electronic reorganization and enhances the Raman signals of target analytes. These results demonstrate the feasibility of MERS for highly CT-enhanced Raman signals.

Solid-state polymer electrolytes are highly anticipated for next generation lithium ion batteries with enhanced safety and energy density. However, a major disadvantage of polymer electrolytes is their low ionic conductivity at room temperature. In order to enhance the ionic conductivity, here, graphene quantum dots (GQDs) are employed to improve the poly (ethylene oxide) (PEO) based electrolyte. Owing to the increased amorphous areas of PEO and mobility of Li + , GQDs modified composite polymer electrolytes achieved high ionic conductivity and favorable lithium ion transference numbers. Significantly, the abundant hydroxyl groups and amino groups originated from GQDs can serve as Lewis base sites and interact with lithium ions, thus promoting the dissociation of lithium salts and providing more ion pathways. Moreover, lithium dendrite is suppressed, associated with high transference number, enhanced mechanical properties and steady interface stability. It is further observed that all solid-state lithium batteries assembled with GQDs modified composite polymer electrolytes display excellent rate performance and cycling stability., (© 2023 Wiley-VCH GmbH.)

Sodium layered oxides always suffer from sluggish kinetics and deleterious phase transformations at deep-desodiation state ( i.e ., >4.0 V) in O3 structure, incurring inferior rate capability and grievous capacity degradation. To tackle these handicaps, here, a configurational entropy tuning protocol through manipulating the stoichiometric ratios of inactive cations is proposed to elaborately design Na-deficient, O3-type Na x TmO 2 cathodes. It is found that the electrons surrounding the oxygen of the TmO 6 octahedron are rearranged by the introduction of MnO 6 and TiO 6 octahedra in Na-deficient O3-type Na 0.83 Li 0.1 Ni 0.25 Co 0.2 Mn 0.15 Ti 0.15 Sn 0.15 O 2-δ (MTS15) with expanded O-Na-O slab spacing, giving enhanced Na + diffusion kinetics and structural stability, as disclosed by theoretical calculations and electrochemical measurements. Concomitantly, the entropy effect contributes to the improved reversibility of Co redox and phase-transition behaviors between O3 and P3, as clearly revealed by ex situ synchrotron X-ray absorption spectra and in situ X-ray diffraction. Notably, the prepared entropy-tuned MTS15 cathode exhibits impressive rate capability (76.7% capacity retention at 10 C), cycling stability (87.2% capacity retention after 200 cycles) with a reversible capacity of 109.4 mAh g -1 , good full-cell performance (84.3% capacity retention after 100 cycles), and exceptional air stability. This work provides an idea for how to design high-entropy sodium layered oxides for high-power density storage systems.

Further popularization of ultrahigh-Ni layered cathodes for high-energy lithium-ion batteries (LIBs) is hampered by their grievous structural and interfacial degeneration upon cycling. Herein, by leveraging the strong electronegativity and low solubility properties of Sb element, a multifunctional modification that couples atomic/microstructural reconstruction with interfacial shielding is well designed to improve the LiNi 0.94 Co 0.04 Al 0.02 O 2 (NCA) cathode by combining Sb 5+ doping and Li 7 SbO 6 coating. Notably, a robust O framework is established by regulating local O coordination owing to the incorporation of a strong Sb-O covalence bond, leading to the inhibited lattice O evolution at high voltage, as revealed by synchrotron X-ray absorption spectroscopy. Moreover, the radially aligned primary particles with (003) crystallographic texture and refined/elongated sizes are achieved by the pinning of Sb on grain boundaries and are confirmed by scanning transmission electron microscopy, resulting in the fast Li + diffusion and mitigated particle cracking. Additionally, in situ construction of the Li 7 SbO 6 ionic conductive layer on grain boundaries can effectively boost interfacial stability and Li + kinetics. As a result, the optimal Sb-modified NCA delivers a high capacity retention of 94.6% after 200 cycles at 1 C and a good rate capacity of 183.9 mAh g -1 at 10 C, which is expected to be applied to next-generation advanced LIBs.

Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) is an attractive candidate for Na + batteries (SIBs) and Li + batteries (LIBs). However, the real implementation of NFPP has been critically restrained by the inferior intrinsic electronic conductivity. Herein, in situ carbon-coated mesoporous NFPP, obtained via freeze drying and heat treatment, demonstrates highly reversible insertion/extraction of Na + /Li + . Mechanically, the electronic transmission and structural stabilities of NFPP are significantly enhanced by the graphitized carbon coating layer. Chemically, the porous nanosized structure shortens Na + /Li + diffusion paths and increases the contact area between the electrolyte and NFPP, ultimately rendering fast ion diffusion. Greatly, long-lasting cyclability (88.5% capacity retention for over 5000 cycles), decent thermal stability at 60 °C, and impressive electrochemical performances are demonstrated in LIBs. The insertion/extraction mechanisms of NFPP in both SIBs and LIBs are systematically investigated, confirming its small volume expansion and high reversibility. The superior electrochemical performances and the insertion/extraction mechanism investigation confirm the feasibility of utilizing NFPP as a cathode material for Na + /Li + batteries.

It is urgent to develop high-temperature dielectrics with high energy density and high energy efficiency for next-generation capacitor demands. Metal-organic frameworks (MOFs) have been widely used due to their structural diversity and functionally adaptable properties. Doping of metal nodes in MOFs is an effective strategy to change the band gap and band edge positions of the original MOFs, which helps to improve their ability to bind charges as traps. In this work, the incorporation of ultralow loading (<1.5 wt%) of novel bimetallic MOFs (ZIF 8-67) into the polyetherimide (PEI) polymer matrix is exhibited. With the addition of ZIF 8-67, the breakdown strength and energy storage capacity of ZIF 8-67/PEI nanocomposites are significantly improved, especially at high temperatures (200 °C). For example, the energy densitiy of the 0.5 wt% ZIF 8-67/PEI nanocomposite is up to 2.96 J cm -3 , with an efficiency (η) > 90% at 150 °C. At 200 °C, the discharge energy density of 0.25 wt% ZIF 8-67/PEI nanocomposites can still reach 1.84 J cm -3 with a η > 90%, which is nine times higher than that of pure PEI (0.21 J cm -3 ) under the same conditions, and it is the largest improvement compared with the previous reports., (© 2023 Wiley-VCH GmbH.)

Transition metal selenides anodes with fast reaction kinetics and high theoretical specific capacity are expected to solve mismatched kinetics between cathode and anode in Li-ion capacitors. However, transition metal selenides face great challenges in the dissolution and shuttle problem of lithium selenides, which is the same as Li-Se batteries. Herein, inspired by the density functional theory calculations, heterogeneous can enhance the adsorption of Li 2 Se relative to single component selenide electrodes, thus inhibiting the dissolution and shuttle effect of Li 2 Se. A heterostructure material (denoted as CoSe 2 /SnSe) with the ability to evolve continuously (CoSe 2 /SnSe→Co/Sn→Co/Li 13 Sn 5 ) is successfully designed by employing CoSnO 3 -MOF as a precursor. Impressively, CoSe 2 /SnSe heterostructure material delivers the ultrahigh reversible specific capacity of 510 mAh g -1 after 1000 cycles at the high current density of 4 A g -1 . In situ XRD reveals the continuous evolution of the interface based on the transformation and alloying reactions during the charging and discharging process. Visualizations of in situ disassembly experiments demonstrate that the continuously evolving interface inhibits the shuttle of Li 2 Se. This research proposes an innovative approach to inhibit the dissolution and shuttling of discharge intermediates (Li 2 Se) of metal selenides, which is expected to be applied to metal sulfides or Li-Se and Li-S energy storage systems., (© 2023 Wiley-VCH GmbH.)

Nickel-rich layered electrode material has been attracting significant attention owing to its high specific capacity as a cathode for lithium-ion batteries. Generally, the high-nickel ternary precursors obtained by traditional coprecipitation methods are micron-scale. In this work, the submicrometer single-crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM) cathode is efficiently prepared by electrochemically anodic oxidation followed by a molten-salt-assisted reaction without the need of extreme alkaline environments and complex processes. More importantly, when prepared under optimal voltage (10 V), single-crystal NCM exhibits a moderate particle size (∼250 nm) and strong metal-oxygen bonds due to reasonable and balanced crystal nucleation/growth rate, which are conducive to greatly enhancing the Li + diffusion kinetics and structure stability. Given that a good discharge capacity of 205.7 mAh g -1 at 0.1 C (1 C = 200 mAh g -1 ) and a superior capacity retention of 87.7% after 180 cycles at 1 C are obtained based on the NCM electrode, this strategy is effective and flexible for developing a submicrometer single-crystal nickel-rich layered cathode. Besides, it can be adopted to elevate the performance and utilization of nickel-rich cathode materials.

Given the inherent features of open tunnel-like structures, moderate lithiation potential (1.0-3.0 V vs Li/Li + ), and reversible redox couples (Nb 5+ /Nb 4+ and Nb 4+ /Nb 3+ redox couples), niobium-based oxides with Wadsley-Roth crystallographic shear structure are promising anode materials. However, their practical rate capability and cycling stability are still hindered by low intrinsic electronic conductivity and structural stability. Herein, ultrathin carbon-confined Nb 12 O 29 materials with rich oxygen vacancies (Nb 12 O 29- x @C) were designed and synthesized to address above-mentioned challenges. Computational simulations combined with experiments reveal that the oxygen vacancies can regulate the electronic structure to increase intrinsic electronic conductivity and reduce the Li + diffusion barrier. Meanwhile, the carbon coating can enhance structural stability and further improve the electronic conductivity of the Nb 12 O 29 material. As a result, the as-prepared Nb 12 O 29- x @C exhibits high reversible capacity (226 mAh g -1 at 0.1 A g -1 ), excellent high-rate performance (83 mAh g -1 at 5.0 A g -1 ), and durable cycling life (98.1% capacity retention at 1.0 A g -1 after 3000 cycles). The lithium storage mechanism and structural stability of Nb 12 O 29- x @C were also revealed by in situ X-ray diffraction (XRD), ex situ X-ray photoelectron spectroscopy (XPS), and ex situ Raman spectroscopy. When applied as the anode of lithium-ion capacitors (LICs), the as-built LIC achieves high energy density (72.4 Wh kg -1 ) within the voltage window of 0.01-3.5 V, demonstrating the practical application potential of the Nb 12 O 29- x @C materials.

Efficient bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital for rechargeable Zn-air batteries (ZABs). Herein, an oxygen-respirable sponge-like Co@C-O-Cs catalyst with oxygen-rich active sites was designed and constructed for both ORR and OER by a facile carbon dot-assisted strategy. The aerophilic triphase interface of Co@C-O-Cs cathode efficiently boosts oxygen diffusion and transfer. The theoretical calculations and experimental studies revealed that the Co-C-COC active sites can redistribute the local charge density and lower the reaction energy barrier. The Co@C-O-Cs catalyst displays superior bifunctional catalytic activities with a half-wave potential of 0.82 V for ORR and an ultralow overpotential of 294 mV at 10 mA cm -2 for OER. Moreover, it can drive the liquid ZABs with high peak power density (106.4 mW cm -2 ), specific capacity (720.7 mAh g -1 ), outstanding long-term cycle stability (over 750 cycles at 10 mA cm -2 ), and exhibits excellent feasibility in flexible all-solid-state ZABs. These findings provide new insights into the rational design of efficient bifunctional oxygen catalysts in rechargeable metal-air batteries., (© 2023. The Author(s).)

The aqueous zinc-ion battery is considered as one of the best alternatives to lithium-ion batteries due to its low cost and high safety. However, the inevitable dendrite growth, byproduct formation, and the side reactions have inhibited the application of aqueous zinc-ion batteries. In this work, the electronegative nitrogen and sulfur-codoped carbon dots (NSCDs) are proposed as an electrolyte additive to regulate the uniform distribution of zinc ions and inhibit the growth of dendrites. It was found that only a small amount of NSCD additive (0.2 mg mL -1 ) exerted a significant influence in electrochemical performance; the symmetrical cell can operate stably for 2000 h with a low voltage hysteresis of 33 mV at the current density of 1 mA cm -2 , and a high Coulombic efficiency (CE) of 99.5% can be obtained after 250 cycles.

Zinc ion batteries (ZIBs) suffer from severe corrosion effects and dendrite growth on the unstable anode/electrolyte interface (AEI) during the plating/stripping process. Therefore, it is of great significance to build a stable AEI enabling a long lifetime for ZIBs. Herein, trace tea polyphenols (TP) were introduced firstly as additive of zinc acetate electrolyte to protect zinc anode from corrosion invasion and boost uniform zinc deposition, thus achieving reversible dendrite-free zinc anode. In situ synchrotron radiation X-ray imaging was conducted to illustrate the positive role of TP molecules in the uniform plating process of zinc. The stable AEI induced by the specific adsorption of TP molecules reduced hydrogen and oxygen evolution side reactions and increased the coulombic efficiency. The TP additive with an ultralow dosage of 0.028 g L -1 delivered favorable cycling stability of 720 h at 0.5 mA cm -2 and 0.5 mAh cm -2 . The Zn-Na 3 V 2 (PO 4 ) 3 full cell assembled with the hybrid Zn(Ac) 2 -TP electrolyte contributed an energy density of 130 mAh g -1 at the current density of 0.2C and enhanced cycling stability of 78% retention after 300 cycles. These results will provide new insights into additive engineering for aqueous electrolytes and the fundamental understanding of AEI phenomena for high performance ZIBs., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

LiCoO 2 (LCO) is widely applied in today's rechargeable battery markets for consumer electronic devices. However, LCO operations at high voltage are hindered by accelerated structure degradation and electrode/electrolyte interface decomposition. To overcome these challenges, co-modified LCO (defined as CB-Mg-LCO) that couples pillar structures with interface shielding are successfully synthesized for achieving high-energy-density and structurally stable cathode material. Benefitting from the "Mg-pillar" effect, irreversible phase transitions are significantly suppressed and highly reversible Li + shuttling is enabled. Interestingly, bonding effects between the interfacial lattice oxygen of CB-Mg-LCO and amorphous Co x B y coating layer are found to elevate the formation energy of oxygen vacancies, thereby considerably mitigating lattice oxygen loss and inhibiting irreversible phase transformation. Meanwhile, interface shielding effects are also beneficial for mitigating parasitic electrode/electrolyte reactions, subsequent Co dissolution, and ultimately enable a robust electrode/electrolyte interface. As a result, the as-designed CB-Mg-LCO cathode achieves a high capacity and excellent cycle stability with 94.6% capacity retention at an extremely high cut-off voltage of 4.6 V. These findings provide new insights for cathode material modification methods, which serves to guide future cathode material design., (© 2022 Wiley-VCH GmbH.)

Exploring new materials with high stability and capacity is full of challenges in sustainable energy conversion and storage systems. Metal-organic frameworks (MOFs), as a new type of porous material, show the advantages of large specific surface area, high porosity, low density, and adjustable pore size, exhibiting a broad application prospect in the field of electrocatalytic reactions, batteries, particularly in the field of supercapacitors. This comprehensive review outlines the recent progress in synthetic methods and electrochemical performances of MOF materials, as well as their applications in supercapacitors. Additionally, the superiorities of MOFs-related materials are highlighted, while major challenges or opportunities for future research on them for electrochemical supercapacitors have been discussed and displayed, along with extensive experimental experiences., (© 2022. The Author(s).)

Sodium layered oxides generally suffer from deep-desodiation instability in P2 structure and sluggish kinetics in O3 structure. It will be great to design P2/O3 biphasic materials that bring the complementary merits of both structures. However, such exploration is hindered by the ambiguous mechanism of material formation. Herein, supported by theoretical simulations and various spectroscopies, we prove that P2/O3 biphasic structures essentially originate from the internal heterogeneity of cationic potential, which can be realized by constraining the temperature-driven ion diffusion during solid-state reactions. Consequently, P2/O3 biphasic Na 0.7 Ni 0.2 Cu 0.1 Fe 0.2 Mn 0.5 O 2- δ with well-designed quaternary composition is successfully obtained, exhibiting much-improved rate capabilities (62 mAh g -1 at 2.4 A g -1 ) and cycling stabilities (84% capacity retention after 500 cycles) than its single-phase analogues. Furthermore, synchrotron-based diffraction and X-ray absorption spectroscopy are employed to unravel the underlying sodium-storage mechanism of the P2/O3 biphasic structure. This work presents new insights toward the rational design of advanced layered cathodes for sodium-ion batteries., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2022. Published by Elsevier B.V.)

2D layered Sn-based materials have attracted enormous attention due to their remarkable performance in sodium-ion batteries. Nevertheless, this promising candidate involves a complex Na + -storage process with multistep conversion-alloying reactions, which induces the uneven dispersion of heterogeneous intermediate accompanied by severe agglomeration of metallic Sn 0 , inescapably resulting in poor reaction reversibility with sluggish rate capability and inferior cyclic lifespan. Herein, a delicately layered heterostructure SnSSe/C consisting of defect-rich SnSSe and graphene is designed and successfully achieved via a facile hydrothermal process. The equal anionic substitution of Se in SnSSe crystal can trigger numerous defects, which can not only facilitate Na + diffusion but also accelerate the nucleation process by inducing quantum-dot-level uniform distribution of heterogeneous intermediates, Na 2 Se/Na 2 S and Sn 0 . Concurrently, in situ formed uniform Na 2 Se/Na 2 S grain boundaries confined by this unique layered heterostructure may effectively suppress the agglomeration of metallic Sn 0 nanograins and boost the reversibility of conversion-alloying reaction. As a result, the SnSSe/C displays significant improvement in Na-storage performance, in terms of remarkable rate capability and ultralong cycling lifespan. This work, focusing on controlling intermediate distribution, provides an effective strategy to boost reaction reversibility, which can be wildly employed in conversion-based electrodes for energy storage regions., (© 2022 Wiley-VCH GmbH.)

Highlights: The chemical process of local oxidation-partial reduction-deep coupling for stibnite reduction of carbon dots (CDs) is revealed by in-situ high-temperature X-ray diffraction. Sb 2 S 3 @xCDs anode delivers high initial coulombic efficiency in lithium ion batteries (85.2%) and sodium ion batteries (82.9%), respectively. C-S bond influenced by oxygen-rich carbon matrix can restrain the conversion of sulfur to sulfite, well confirmed by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations. CDs-induced Sb-O-C bond is proved to effectively regulate the interfacial electronic structure. The application of Sb 2 S 3 with marvelous theoretical capacity for alkali metal-ion batteries is seriously limited by its poor electrical conductivity and low initial coulombic efficiency (ICE). In this work, natural stibnite modified by carbon dots (Sb 2 S 3 @xCDs) is elaborately designed with high ICE. Greatly, chemical processes of local oxidation-partial reduction-deep coupling for stibnite reduction of CDs are clearly demonstrated, confirmed with in situ high-temperature X-ray diffraction. More impressively, the ICE for lithium-ion batteries (LIBs) is enhanced to 85%, through the effect of oxygen-rich carbon matrix on C-S bonds which inhibit the conversion of sulfur to sulfite, well supported by X-ray photoelectron spectroscopy characterization of solid electrolyte interphase layers helped with density functional theory calculations. Not than less, it is found that Sb-O-C bonds existed in the interface effectively promote the electronic conductivity and expedite ion transmission by reducing the bandgap and restraining the slip of the dislocation. As a result, the optimal sample delivers a tremendous reversible capacity of 660 mAh g -1 in LIBs at a high current rate of 5 A g -1 . This work provides a new methodology for enhancing the electrochemical energy storage performance of metal sulfides, especially for improving the ICE., (© 2022. The Author(s).)

Carbon dots (CDs) are considered as excellent structural regulator for metal oxides (MOs) due to their abundant functional groups, superior dispersibility, and ultrasmall size (<10 nm). Herein, a new approach is proposed to construct porous pomegranate-like MOs/CDs composite based on the CDs-induced in situ growth mechanism of ion adsorption-multipoint surface nucleation-crosslinking agglomeration. The proposed methodology is successfully applied to prepare SnO 2 /CDs, Cu 2 O/CDs, and Fe 2 O 3 /CDs composites, respectively, demonstrating its universality to metal oxides. Taking SnO 2 /CDs composite as a case study for anode material in lithium-ion batteries, it exhibits high lithium storage capacity, excellent cycling stability, and a special feature of capacity increase upon cycling. This study provides a new idea for the design of metal oxides materials tuned by CDs and broadens the application of CDs in the field of material synthesis., (© 2022 Wiley-VCH GmbH.)

Bi-doped carbon dots (Bi-CDs) with rich polar groups and good compatibility were employed as co-deposition electrolyte additives to homogenize Li + flux for dendrite-free Li deposition. High coulombic efficiency (99.0%) and long-term stability (800 h) with reduced overpotential (∼15 mV) were achieved after introducing Bi-CDs in conventional electrolyte for high-performance Li-S batteries.

Highlights: Interfacial bonding strategy has been successfully applied to address the high overpotential issue of sacrificial additives, which reduced the decompositon potential of Na 2 C 2 O 4 from 4.50 to 3.95 V. Ultra-low-dose technique assisted commercial sodium ion capacitor (AC//HC) could deliver a remarkable energy density of 118.2 Wh kg -1 as well as excellent cycle stability. In-depth decomposition mechanism of sacrificial compound and the relative influence after pre-metallation were revealed by advanced in situ and ex situ characterization approaches. Sacrificial pre-metallation strategy could compensate for the irreversible consumption of metal ions and reduce the potential of anode, thereby elevating the cycle performance as well as open-circuit voltage for full metal ion capacitors (MICs). However, suffered from massive-dosage abuse, exorbitant decomposition potential, and side effects of decomposition residue, the wide application of sacrificial approach was restricted. Herein, assisted with density functional theory calculations, strongly coupled interface (M-O-C, M = Li/Na/K) and electron donating group have been put forward to regulate the band gap and highest occupied molecular orbital level of metal oxalate (M 2 C 2 O 4 ), reducing polarization phenomenon and Gibbs free energy required for decomposition, which eventually decrease the practical decomposition potential from 4.50 to 3.95 V. Remarkably, full sodium ion capacitors constituted of commercial materials (activated carbon//hard carbon) could deliver a prominent energy density of 118.2 Wh kg -1 as well as excellent cycle stability under an ultra-low dosage pre-sodiation reagent of 15-30 wt% (far less than currently 100 wt%). Noteworthily, decomposition mechanism of sacrificial compound and the relative influence on the system of MICs after pre-metallation were initially revealed by in situ differential electrochemical mass spectrometry, offering in-depth insights for comprehending the function of cathode additives. In addition, this breakthrough has been successfully utilized in high performance lithium/potassium ion capacitors with Li 2 C 2 O 4 /K 2 C 2 O 4 as pre-metallation reagent, which will convincingly promote the commercialization of MICs., (© 2022. The Author(s).)