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Unstable Zn interface with serious detrimental parasitic side‐reactions and uncontrollable Zn dendrites severely plagues the practical application of aqueous zinc‐ion batteries. The interface stability was closely related to the electrolyte configuration and Zn2+ depositional behavior. In this work, a unique Zn‐ion anchoring strategy is originally proposed to manipulate the coordination structure of solvated Zn‐ions and guide the Zn‐ion depositional behavior. Specifically, the amphoteric charged ion additives (denoted as DM), which act as zinc‐ion anchors, can tightly absorb on the Zn surface to guide the uniform zinc‐ion distribution by using its positively charged −NR4+ groups. While the negatively charged −SO3− groups of DM on the other hand, reduces the active water molecules within solvation sheaths of Zn‐ions. Benefiting from the special synergistic effect, Zn metal exhibits highly ordered and compact (002) Zn deposition and negligible side‐reactions. As a result, the advanced Zn||Zn symmetric cell delivers extraordinarily 7000 hours long lifespan (0.25 mA cm−2, 0.25 mAh cm−2). Additionally, based on this strategy, the NH4V4O10||Zn pouch‐cell with low negative/positive capacity ratio (N/P ratio=2.98) maintains 80.4 % capacity retention for 180 cycles. A more practical 4 cm*4 cm sized pouch‐cell could be steadily cycled in a high output capacity of 37.0 mAh over 50 cycles. [ABSTRACT FROM AUTHOR]

Hybrid supercapacitors (HSCs) comprising a battery‐type cathode and capacitive anode have recently become a research hotspot. Nevertheless, the low capacity utilization, poor kinetic behavior, and unstable structure of a single battery‐type oxide cathode restrict the overall performance of the device. Herein, the carbon quantum dots (CQDs) modified NiO/Co3O4 heterostructured flower‐like microspheres are constructed, and enhanced specific capacity, rate capability, and cycling performance are achieved when used as the cathode for HSCs. This is attributed to the fact that the modification of bifunctional CQDs as size regulators and conductive agents and the construction of heterostructure can not only improve the specific surface area and provide more electroactive sites, thereby enhancing the charge storage performance but also regulate the electronic structure and boost the interface charge transfer capability and electronic conductivity, thereby boosting the reaction kinetics and cycle stability. The enhanced electrochemical kinetic behavior is revealed by electrochemical kinetic analyses based on cyclic voltammetry, electrochemical impedance spectroscopy tests and density functional theory calculations. Meanwhile, the electrochemical reaction process and energy storage mechanism are illustrated by ex‐situ X‐ray diffraction and X‐ray photoelectron spectroscopy characterizations. Furthermore, an HSC is further constructed using the CQDs/NiO/Co3O4 heterostructured flower‐like microspheres as the cathode, simultaneously achieving high energy density (40.9 Wh kg−1), high power density (24 kW kg−1), and splendid cyclic stability (94.2% capacity retention after 5000 cycles at 10 A g−1). These synergistic modification strategies of bifunctional CQDs modification and heterostructure design provide a valuable direction for the design and development of HSCs with both high energy density and high power density. [ABSTRACT FROM AUTHOR]

Prussian blue (PB) has emerged as a promising cathode material in aqueous batteries. It possesses two distinct redox centers, and the potassium ions (K+) are unevenly distributed throughout the compound, adding complexity to the interpretation of the K+ insertion/de‐insertion kinetic mechanism. Traditional ensemble‐averaged measurements are limited in uncovering the precise kinetic information of the PB particles, as the results are influenced by the construction of the porous composite electrode and the redox behavior from different particles. In this study, the electrochemical processes of individual PB particles were investigated using nano‐impact electrochemistry. By varying the potentials, different types of transient current signals were obtained that revealed the kinetic mechanism of each oxidation/reduction reaction in combination with theoretical simulation. Additionally, a partially contradictory conclusion between single‐particle analysis and the ensemble‐averaged measurement was discussed. These findings contribute to a better understanding of the electrochemical processes of cathode materials with multiple redox centers, which facilitates the development of effective strategies to optimize these materials. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries are inherently safe, but the severe dendrite growth and corrosion reaction on zinc anodes greatly hinder their practical applications. Most of the strategies for zinc anode modification refer to the research of lithium metal anodes on surface regulation without considering the intrinsic mechanisms of zinc anode. Herein, we first point out that surface modification cannot permanently protect zinc anodes due to the unavoidable surface damage during the stripping process by solid–liquid conversion. A bulk‐phase reconstruction strategy is proposed to introduce abundant zincophilic sites both on the surface and inside the commercial zinc foils. The bulk‐phase reconstructed zinc foil anodes exhibit uniform surfaces with high zincophilicity even after deep stripping, significantly improving the resistance to dendrite growth and side reactions. Our proposed strategy suggests a promising direction for the development of dendrite‐free metal anodes for practical rechargeable batteries with high sustainability. [ABSTRACT FROM AUTHOR]

The use of a sacrificial cathode additive as a pre‐metallation method could ensure adequate metal sources for advanced energy storage devices. However, this pre‐metallation technique suffers from the precise regulation of decomposition potential of additive. Herein, a molecularly compensated pre‐metallation (Li/Na/K) strategy has been achieved through Kolbe electrolysis, in which the electrochemical oxidation potential of a metal carboxylate is manipulated by the bonding energy of the oxygen–metal (O–M) moiety. The electron‐donating effect of the substituent and the low charge density of the cation can dramatically weaken the O–M bond strength, further bringing out the reduced potential. Thus, sodium acetate exhibits a superior pre‐sodiation feature for sodium‐ion battery accompanied with a large irreversible specific capacity of 301.8 mAh g−1, remarkably delivering 70.6 % enhanced capacity retention in comparison to the additive‐free system after 100 cycles. This methodology has been extended to construct a high‐performance lithium‐ion battery and a lithium/sodium/potassium‐ion capacitor. [ABSTRACT FROM AUTHOR]

High‐capacity cathodes and anodes in energy storage area are required for delivering high energy density due to the ever‐increasing demands in the applications of electric vehicles and power grids, which suffer from significant safety concerns and poor cycling stability at the current stage. All‐solid‐state lithium batteries (ASSLBs) have been considered to be particularly promising within the new generation of energy storage, owing to the superiority of safety, wide potential window, and long cycling life. As the key component in ASSLBs, individual solid electrolytes that can meet practical application standards are very rare due to poor performance. To the present day, numerous research efforts have been expended to find applicable solid‐state electrolytes and tremendous progress has been achieved, especially for garnet‐type solid electrolytes. Nevertheless, the garnet‐type solid electrolyte is still facing some crucial dilemmas. Hence, the issues of garnet electrolytes' ionic conductivity, the interfaces between electrodes and garnet solid electrolytes, and application of theoretical calculation on garnet electrolytes are focuses in this review. Furthermore, prospective developments and alternative approaches to the issues are presented, with an aim to improve understanding of garnet electrolytes and promote their practical applications in solid‐state batteries. [ABSTRACT FROM AUTHOR]

High‐working potential layered oxides as cathode materials have been considered as an effective way to improve the energy density of Na‐ion batteries (NIBs) to enhance their competitiveness as a promising alternative for lithium ion batteries in large‐scale energy storage applications. However, they generally suffer irreversible phase transition, large volume change and electrolyte corrosion when charged to high voltage (>4.2 V), resulting in poor cyclic stability. In this work, a P2@tunnel heterostructure cathode material is designed and obtained by wet chemistry combined with solid‐state reaction method. Moreover, partly of the Ti4+ ions which are designed for the tunnel structure is also doped into the P2 phase under high temperature annealing process, resulting in expanded crystal parameters and smooth charge‐discharge profiles. The stable tunnel structure layer can effectively protect the layered P2 type cathode material from corrosion by electrolyte upon high voltage and alleviate the crack propagated from the particle surface. Therefore, the P2@tunnel heterostructure cathode can still maintain a discharge capacity of 146.3 mAh g−1 while the discharge capacity of pristine P2 type cathode is only 114.4 mAh g−1 after 100 cycles at 0.25 C, it also reveals superior cyclic stability and rate performance compared to the pristine P2 type cathode. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries have rapidly developed recently as promising energy storage devices in large‐scale energy storage systems owing to their low cost and high safety. Research on suppressing zinc dendrite growth has meanwhile attracted widespread attention to improve the lifespan and reversibility of batteries. Herein, design methods for dendrite‐free zinc anodes and their internal mechanisms are reviewed from the perspective of optimizing the host–zinc interface and the zinc–electrolyte interface. Furthermore, a design strategy is proposed to homogenize zinc deposition by regulating the interfacial electric field and ion distribution during zinc nucleation and growth. This Minireview can offer potential directions for the rational design of dendrite‐free zinc anodes employed in aqueous zinc‐ion batteries. [ABSTRACT FROM AUTHOR]

Engineering interfacial properties of metal‐sulfides toward excellent electrochemical capability is imperative for advanced energy‐storage materials. However, they still suffer from an unclear mechanism of capacity fading, along with ineffective physical–chemical evolution. Herein, a highly‐effective Sb2S3 with double carbon is designed with interfacial SbC bonds and double carbon, which boosts promoting of ion transferring and alleviates the separation of both active phases (Sb, S). Through "voltage‐cutting" manners, the key elements of capacity improvement about phase transitions are further determined. As expected, even at 5.0 A g−1, the lithium‐storage capacity remains about 674 mAh g−1. Utilized as sodium ion battery (SIB) anode, the rate capacity still reaches up to 366 mAh g−1 at 3.0 A g−1, much larger than that of Sb2S3. Obtaining the full cell of Ni–Fe Prussian blue analog versus M‐Sb2S3@DC, the reversible capacity is 330 mAh g−1 at 0.5 A g−1. Supported by kinetic analysis, the excellent rate properties are determined by the surface‐controlling behaviors, mainly resulting from the decreased capacitive resistance and improved ion moving. Furthermore, the reassembling evolution of active phases is revealed in detail by ex situ techniques. This work is expected to offer significant insights into interfacial evolutions toward advanced energy‐storage systems. [ABSTRACT FROM AUTHOR]

Demand for energy in day to day life is increasing exponentially. However, existing energy storage technologies like lithium ion batteries cannot stand alone to fulfill future needs. In this regard, potassium ion batteries (KIBs) that utilize K ions in their charge storage mechanism have attracted considerable attention due to their unique properties and are therefore established as one of the future battery systems of interest among the scientific community. Nevertheless, the development and identification of appropriate electrode materials is very essential for practical applications. This review features the current development in KIBs electrode and electrolyte materials, the present challenges facing this technology (in the commercial aspect), and future aspects to develop fully functional KIBs. The potassium storage mechanisms, evolution of the KIBs, and the advantages and disadvantages of each category of materials are included. Additionally, various approaches to enhance the electrochemical performances of KIBs are also discussed. This review is not only an amalgamation of different viewpoints in literature, but also contains concise perspectives and strategies. Moreover, the potential emergence of a novel class of K‐based dual ion batteries is also analyzed for the first time. [ABSTRACT FROM AUTHOR]

Attracted by the high specific capacity and energy density, transition metal‐sulfides exhibit great application potential as sodium‐ion batteries anode, but still suffer from the uncontrolled separation of M/S phase and inferior conductivity. Herein, the flower‐like Fe1‐xS@Sb@C (FF) is rationally tailored, accompanied by double‐layer heterojunctions and C–S–Sb/Sb–S–Fe “bridge” bonds. Meanwhile, the bimetallic phases/boundary defects and built‐in electric fields are formed with a strong electronic coupling effect, effectively alleviating the separation of the M/S phase (Fe/Sb and S), and significantly enhancing ion/e− conductivity. As expected, FF delivers an ultra‐fast sodium‐ions storage rate capacity of 436.5/334.3 mAh g−1 even at 10.0/20.0 A g−1. When the operation temperature is lowered to ‐5 °C, the reversible capacity can still remain at ≈349.7 mAh g−1. Assisted by the detailed kinetic analysis and theoretical calculations, their great ion‐storage abilities mainly derive from improved interfacial Na+/e− transfer and surface/near‐surface redox behaviors. Moreover, the reassembling evolution of active phases is revealed by in/ex situ techniques, further demonstrating the stable adsorption/anchoring of intermediate reaction products Fe/Sb–S phases on the heterointerface, accompanying high reversible conversion‐alloying reaction. Given this, this interesting work is anticipated to offer an in‐depth insight into capacity fading mechanism, and effective strategy to design metal‐sulfur anodes for advanced sodium‐ion systems. [ABSTRACT FROM AUTHOR]

Secondary charge batteries have captured numerous attentions, owing to their abundant raw, portability, and high energy density. As the main ions‐storage carrier, the electrode materials serve vital roles on the properties of whole battery system. Currently, MoSe2 is regarded as rising star of transition metal dichalcogenides, displaying unique layered structure, high electronic conductivity, as well as narrow energy band. These advantages enable their widely application on hydrogen evolution reactions and solar cells. Recently, a plenty of researching activities on MoSe2/carbon are triggered due to large interplanar spacing and high ions/e− migration rate. In this review, the recent achievements of diverse MoSe2/carbon on great energy‐storage domains are solidly summarized from bonding types (surface‐loading, internal‐wrapped) and dimensional controlling (1D nanotubes/nanofibers, 2D graphene/nanosheets, 3D carbon framework/sphere). Meanwhile, the related Li/Na ions‐storage mechanisms are also concluded. Furthermore, for MoSe2/carbon with better electrochemical properties, the opportunities and perspectives in the future are also suggested. This review throws light on the systematic developments of advanced MoSe2/carbon, and confirms its exploring potential on lithium‐ion batteries/sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

The sodium storage performance of NiS2 suffer from low initial coulombic efficiency and poor cycling stability which are ascribed to the volume expansion and collapse of the structure during the charge/discharge transformation process. Compared with composites, encapsulating NiS2 in carbon framework is more effective in buffering for the volume expansion and enhancing the electronic conductivity of sodium‐ion batteries. In this work, NiS2 decorated with bifunctional carbon (NiS2@C@C), where nickel dimethylglyoxime and polyaniline are employed as the precursor and carbon source, respectively, are obtained. Since the introduced carbon layer suppresses the volume expansion and enhances both the electronic conductivity and charge transfer of Na+, the attained NiS2@C@C displays outstanding sodium storage performance. At a current density of 0.1 A g−1, a high reversible specific capacity of 580.8 mAh g−1 remains even after 100 cycles. The first coulombic efficiency (79.65%) and rate performance (448 mAh g−1 at 1.6 A g−1) of NiS2@C@C are also remarkable. Extraordinarily, the excogitation of NiS2 decorated with bifunctional carbon is also significant for the preparation of similar materials. Through the sulfuration of nickel dimethylglyoxime wrapped with polyaniline, bifunctional carbon decorated NiS2 (NiS2@C@C) is prepared. Benefitting from the ingenious design, the sodium storage performance of NiS2@C@C electrodes is greatly superior to undecorated NiS2 electrodes. This work might supply an effective excogitation for the practical application of transitional metal sulfides in sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-performance cathode materials for all-organic proton full-battery are synthesized. • Organic copolymers of tertiary amines exhibit nanorod-like morphology. • The device delivers energy densities of 33.9 & 9.6 Wh kg−1 at 423 & 1880 W kg−1. • The assembled proton battery can operate even at −25 °C with > 93% of capacity retention. High-performance aqueous all-organic rechargeable batteries are promising candidates for cost-effective, safe, and environment-friendly next-generation energy storage devices. Herein, two organic copolymers with nanorod-like morphology (AN-TA, and AN-PA), composed of different tertiary amines, are synthesized as the cathode material for an aqueous proton battery. The individual copolymer electrodes possess the dominated diffusion-controlled electrode kinetics resulting from the proton insertion/de-insertion along with the surface-controlled processes in 2 M HCl and 2 M H 2 SO 4. Among the two copolymers, AN-PA exhibits the maximum specific capacity of 145 mAh g−1 at 1 A g−1 and then, even at the higher current density of 10 A g−1, it possesses the capacity as 110 mAh g−1 in 2 M HCl. The assembled aqueous proton battery comprising of AN-PA as a cathode delivers the capacity of 80 mAh g−1 at 1 A g−1 in 2 M HCl. The maximum deliverable energy density of 33.9 Wh kg−1 is achieved at the power density of 423 W kg−1. Notably, our proton battery can well operate at the sub-zero temperature of −25 °C with a cell voltage of 1.1 V. More importantly, the device retains 84 % of the initial capacity after 1000 cycles at 2 A g−1 and exhibits the retention of specific capacity of about > 93% when compared to that of room temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Composite hydrogel of perylenetetracarboxylic diimide and reduced graphene oxide is prepared. • Electrolyte of ammonium acetate with a record concentration of 32 molality (m) is used. • Battery-supercapacitor hybrid device well operates at 1.9 V from –20 to 50 °C. • It delivers an energy density of 12.9 W h kg−1 at a power density of 827 W kg−1. • The device retains 74 % of the initial capacity after 3000 cycles at 1 A g−1. Developing battery-supercapacitor hybrid devices (BSHs) is viewed as an efficient route to shorten the gap between supercapacitors and batteries. In this study, a composite hydrogel consisting of perylene tetracarboxylic diimide (PTCDI) and reduced graphene oxide (rGO) is tested as the anode for BSHs in the electrolyte of ammonium acetate (NH 4 Ac) with a record concentration of 32 molality (m). This water-in-salt electrolyte exhibits a wide electrochemical stability window of 2.13 V and high conductivity of 23.3 mS cm−1 even at −12 °C. Molecular dynamics calculations and spectroscopic measurements reveal that a favorable water-acetate interaction occurs in a high concentration NH 4 Ac electrolyte. On the other hand, the study of electrode kinetics in 32 m NH 4 Ac demonstrates a high capacitive contribution to charge storage in PTCDI-rGO although an electrode redox reaction involves reversible enolization of carbonyl groups in PTCDI. This result suggests fast NH 4 +-ion intercalation kinetics in charge–discharge processes. Furthermore, the electrode performance is improved by optimizing the loading amount of rGO in composites. The best-performing composite electrode delivers the maximum capacity of 165 mAh g−1 at 0.5 A g−1 and sustains a great capacity retention of 66% at 8 A g−1. Finally, an all-organic BSH device is tested in a broad temperature window from −20 to 50 °C and is well operated at 1.9 V regardless of operating temperatures. Due to the synergetic effect of splendid electrolyte properties and high anode capacities, BSH devices possess the maximum energy density of 12.9 Wh kg−1 at the power density of 827 W kg−1 and retain 74 % of the initial capacity after 3000 cycles at 1 A g−1. Our study paves a novel route towards designing inexpensive and environmentally friendly BSH devices with high performances. [ABSTRACT FROM AUTHOR]

The Sb@CN nanofibers are efficiently fabricated and present excellent potassium storage performance, especially the long cycle stability with a reversible capacity of of 360.2 mAh g−1 at 50 mA g−1 after 200 cycles and 212.7 mAh g−1 after 1000 cycles even at 5000 mA g−1, which is one of the most outstanding potassium storage performances of Sb anode up to now. Antimony-based materials with high theoretical capacity are known as promising anodes for potassium-ion batteries (PIBs). However, they still face challenges from the large ionic radius of the K ion, which has sluggish kinetics. Much effort is needed to exploit high-performance electrode materials to satisfy the reversible capacity of PIBs. In this paper, nano Sb confined in N-doped carbon fibers (Sb@CN nanofibers) were successfully prepared through an electrospinning method, which was designed to improve potassium storage performances. Sb@CN nanofibers benefit from the fact that the synergy between the porous nanofiber frame structure and the uniformly distributed Sb nano-components in the carbon matrix can effectively accelerate the ion migration rate and reduce the mechanical stress caused by K+ insertion/extraction, Sb@CN nanofiber electrodes thus exhibited excellent potassium storage performance, especially long cycle stability, as expected. When utilized as a PIB anode, they delivered high reversible capacity of 360.2 mAh g−1 after 200 cycles at 50 mA g−1, and a particularly stable capacity of 212.7 mAh g−1 was also obtained after 1000 cycles even at 5000 mA g−1. Given such outstanding electrochemical performances, this work is expected to provide insight into the development and exploration of advanced alloy-type electrodes for PIBs. [ABSTRACT FROM AUTHOR]

Potassium-ion battery (PIB) is a promising candidate in grid energy storage field because of the abundant potassium resource and its low cost. More efforts should be made to research anode material with long cycling performance due to the fading potassium capacity of graphite. Honeycomb hard carbon (HHC) with uniform pore structure and weakly ordered turbostratic domains was successfully prepared from carbon quantum dots (CQDs) through the calcination with the assistance of SiO 2 nanospheres. As anode material for PIBs, HHC delivered a high specific capacity of 195.3 mA h g−1 and 67.43% capacity retention after 150 cycles at a current density of 0.1 A g−1. The electrochemical behaviors of HHC electrode were investigated in detail by electrochemical impedance spectroscopy (EIS) at various voltages and calculation of capacitive contribution, exhibiting favorable potassium storage property. Image 1 • Honeycomb hard carbon is prepared from carbon quantum dots. • Honeycomb hard carbon exhibits great potassium storage performances. • Honeycomb hard carbon/K electrode exhibits favorable kinetic behaviors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The DTBC-Zn anode was designed via an interfacial dissolution-coordination strategy. • The DTBC network improves the thermos-kinetics properties of Zn anode. • Zn2+ migrate along the coordination skeletons to achieve (0 0 2) plane deposition. • The DTBC-Zn anode enabled dendrite-free and by-product-free Zn deposition. Severe side reactions and dendrite growth are widespread in zinc anodes due to the aqueous electrolyte and the inhomogeneity of the Zn surface. Constructing an artificial interfacial layer on the zinc anode is a direct and effective strategy to solve these problems. Herein, a dithio-bridged chelate (DTBC) network consisting of zinc dimethyldithiocarbamate molecules was in situ constructed on the zinc surface via a facile interfacial dissolution-coordination strategy. The experiment and theoretical calculation revealed that the DTBC network simultaneously improves the thermos-kinetics properties of zinc anode. Moreover, the dithio groups in the DTBC network can induce the preferred plating of Zn along the (0 0 2) crystal plane and suppress dendrite growth. The DTBC-Zn electrode delivered an extended lifetime of over 1200 h with an ultralow polarization of ∼27.3 mV at 0.5 mA cm−2. The capacity retention rate of DTBC-Zn|MnO 2 full cell was as high as 97.98 % after 1600 cycles, further confirming the feasibility of the robust dithio-bridged chelate network for stabilizing thermo-kinetics of zinc anode. This work contributes a simple and effective way to construct high-performance zinc anodes for aqueous zinc ion batteries. [ABSTRACT FROM AUTHOR]

3D porous carbon encapsulated SnO 2 nanoparticles composite (SnO 2 -PC) prepared by an efficient in situ methodology was applied as anode for sodium ion batteries (SIBs). It delivered a high reversible specific capacity of 280.1 mAh g −1 after 250 cycles at a current density of 100 mA g −1 , with ultrahigh capacity retention of 91.63%. Notably, it can Exhibit 100 mAh g −1 after 1000 cycles even at a high current density of 1600 mA g −1 . These greatly enhanced electrochemical properties of SnO 2 -PC composite can be attributed to the superior structure that the electrical conductivity of the composite was improved by the porous carbon matrix, moreover, it can serve as a cushion during the process of Na ion insertion/extraction into the composite. Significantly, this kind of in situ synthesis method is portable for other similar composite. [ABSTRACT FROM AUTHOR]

The impacts of Cu substitution upon the cycling stability of Na x MO 2 (M = Fe, Mn) cathodes are systematically studied. Evidenced by CuO segregation and XPS analysis, the average valence of Mn can hardly reach +4, possibly owing to the production of Mn(II). It is proposed that, Cu substitution can efficiently enhance the cycling stability by reducing the content of Mn(III) and suppressing the electrochemical activities of Mn4+/3+ redox couple. • Cycling stability of Na x MO 2 (M = Cu, Fe, Mn) cathodes are systematically studied. • CuO segregation is evidenced to be associated with the limited valent state of Mn. • Adding Cu2+ actually lower Mn valence by decreasing Mn(III) and generating Mn(II). • Cu2+-substitution may enhance the cycling stability mainly by suppressing Mn(III). Adding Cu2+ has substantially boosted the practical potentiality of Fe/Mn-based layered cathodes for sodium ion batteries (SIBs) owing to the enhanced stabilities, which were previously ascribed to the raised valence of Mn. Herein, the roles of Cu2+ are verified by investigating Cu2+-substituted materials with the stoichiometry of Na 0.5+x Cu x Fe 0.5-x Mn(IV) 0.5 O 2. Surprisingly, it is found that Mn valence can hardly reach the expected value (IV) even by adjusting Cu2+ content. For the first time, the separation of CuO, which has been previously detected but rarely explained, is ascribed to the restrained chemical states of Mn. Detailed analyses show that, Mn(II) is generated while Mn(III) is decreased in pace of Cu2+ substitution, actually lowering down the oxidation states of Mn. Moreover, Mn4+/3+ redox can be efficiently restricted by importing Cu2+. Albeit the loss of capacity, the cycling stability is greatly enhanced, achieving a high capacity retention of 92.3% after 200 cycles within 4.2–2.5 V. Therefore, the suppression of Jahn-Teller Mn(III) should be intrinsically responsible for the superior cycling stability after Cu2+ substitution. These findings may present a new sight to probe the roles of Cu in layered Na x MO 2 system for the design of advanced cathodes for SIBs. [ABSTRACT FROM AUTHOR]

• Mn2+ dissolution enabled MnO to be an active cathode for aqueous Zn-ion battery. • A H+/Zn2+ co-insertion mechanism of the as-activated Mn 1-x O cathode was proposed. • A MnO nanochain@Graphene scroll configuration was obtained by hydrothermal method. • Cycling stability of MnO electrode was greatly enhanced by graphene wrapping. Aqueous Zn-ion batteries (ZIBs) attract ever-growing attention due to low cost, high safety, and environmental friendliness. Among the limited cathode candidates, manganese-based oxides stand out owing to large ion channels and multiple valence of Mn. Notably, MnO, thought to be inactive before, actually exhibits high energy densities in AZIBs, thus arousing wide interests. Herein, the electrochemical behavior of MnO electrode is extensively investigated in ZnSO 4 electrolytes with different concentration of MnSO 4. It is confirmed that the inactive MnO is electrochemically activated during the initial charge process. Greatly, the initial capacity and the following cycling stability of MnO electrode strongly depends on the concentration of MnSO 4 , indicating that the activation of MnO could be attributed to Mn dissolution, leading to the higher valence of Mn as evidenced by ex-situ XPS analysis. Greatly, a H+/Zn2+ co-insertion mechanism is suggested for the as-activated Mn 1-x O electrode according to the ex-situ XRD results. In addition, by constructing a core-sheath MnO@N-doped graphene scrolls (MnO@NGS) configuration through a modified hydrothermal process, the reversible capacity of MnO has been successfully improved to 288 mAh g−1 (0.1 A g−1), leading to high energy density of 367 mWh g−1. More importantly, benefiting from the graphene wrapping and sufficient internal voids, 98% of the initial capacity can be retained after 300 cycles (0.5 A g−1), much better than the unmodified MnO and MnO 2 electrodes. This work is expected to deepen the understanding of the charge-storage mechanism of MnO and help to design durable manganese-based cathodes for ZIBs. [ABSTRACT FROM AUTHOR]

Ion migration is the most fundamental process in the field of energy storage and conversion. During the charge-discharge cycle, the (de)intercalation of guest ions in solid host particles as electrode materials change the distribution of element, phase and stress in the particle and give rise to crushing and degradation, which will influence the electrochemical behavior of the particles. New methods are constantly being proposed to probe the electrochemical reactions on individual particle for understanding the mechanism of the process. In this short review, we highlight some pioneer works from two different perspectives, namely direct electrochemical detection methods, such as nano-impact method, nanoprobe detection and flowing particle analysis, and indirect optical analysis methods utilizing X-ray imaging, infrared near-field nanoscopy, Raman microscopy and surface plasmon resonance microscopy. [ABSTRACT FROM AUTHOR]

• Sb 2 S 3 (Sb 2 Se 3) nanodots/C composites have been successfully fabricated. • They all deliver the excellent K+ storage performances. • The volume changes have been calculated and analyzed for the first time. Antimony-based materials with high theoretical capacity have been considered as a promising anode materials for potassium-ion batteries (PIBs). Unfortunately, the large volume expansion leads to rapid capacity fading and poor rate capability. In this work, Sb 2 S 3 (Sb 2 Se 3) nanodots/carbon composites are constructed through pyrolysis and co-sulfurization (selenylation) process of sodium stibogluconate for the first time. In the composite, Sb 2 S 3 (Sb 2 Se 3) nanodots with diameters of 15–25 nm are uniformly inlaid into S(Se)-doped carbon skeleton. Notably the ultrafine nanodots can remarkedly shorten the ions diffusion distance with enhanced kinetic process. Also the S(Se)-doped carbon would provide the stable structure support and conductive path. When applied as the anode for PIBs, they all show satisfactory potassium-storage properties in terms of high reversible capacity and superior rate capability, especially the excellent electrochemical performances of Sb 2 Se 3 nanodots/carbon with a reversible capacity of 312.03 mAh g−1 at 1000 mA g−1 after 200 cycles, which can be attributed to the synergistic effect of nanodots and doped carbon, minimizing potassiation-induced deformations and facilitating the reversible adsorption of K ions. More importantly, the volume changes during the K+ intercalation/deintercalation process have been analyzed in details, which is well consistent with the result of electrochemical performance, as expected. [ABSTRACT FROM AUTHOR]

Nitrogen or phosphorus doping is a commonly used method to ameliorate the electrochemical properties of carbonaceous material. In this study, nitrogen-rich carbon nanosheets are first prepared and then annealed with NaH 2 PO 4 to synthesize phosphorus doping nitrogen-rich carbon nanosheets. Two obtained materials are utilized as anodes of sodium-ion batteries and potassium-ion batteries, revealing that phosphorus doping can improve sodiation capacity (247.9 vs. 175.1 mA h g−1) and lower potassiation capacity (207.2 vs. 242.6 mA h g−1). To explore the inner reason for this phenomenon, Na+ and K+ diffusion coefficients are surveyed through galvanostatic intermittent titration technique, showing that the electrode with large ion diffusion coefficient delivers a large capacity. This work provides some use for reference in introduction of heteroatoms to carbonaceous anode materials of sodium-ion batteries and potassium-ion batteries. Image 1 • Carbon nanosheets with high P and N contents were prepared. • P-doped N-rich carbon nanosheets exhibited higher sodiation capacity. • N-rich carbon nanosheets performed better in K-storage than Na-storage. • The electrode with large ion diffusion coefficient delivers a large capacity. [ABSTRACT FROM AUTHOR]