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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

O3-type NaNi1/3Fe1/3Mn1/3O2 (NFM) is one of the most representative cathode materials with low cost and high capacity advantages. However, the sluggish diffusion kinetics and severe cathode–electrolyte interfacial reaction are serious roadblocks to commercialization. Hereby, a novel method of in situ V-modification is well-designed to play dual roles in reconstructing the crystal lattice and interface structure. Notably, the broadened layer spacing of O–Na–O and shortened TM–O bond are attributed to successful doping of V5+ into the bulk, accelerating the transmission of sodium ions and improving the structure stability. Concomitantly, the construction of a thin surface coating layer is beneficial for mitigating volume expansion and inhibiting structural degradation, which is validated by in situ X-ray diffraction coupled with the synchrotron X-ray absorption spectroscopy. Consequently, the rationally designed V-modified NFM cathode exhibits excellent cycling performances, exhibiting great capacity retention of 75.8% after 500 cycles at 2C in a half cell, and 85.6% capacity retention is observed after 150 cycles at 1C in the full cell. This work provides new insights into the development of O3-type layered oxide cathodes toward long-cycle life applications for large-scale energy storage systems. [ABSTRACT FROM AUTHOR]

The TiO2 anode for sodium-ion batteries (SIBs) is currently drawing increased attention owing to its stable cycling performance. However, the storage performance is still extremely inadequate, especially for its low initial coulombic efficiency (ICE). In order to further improve the ICE, a good match of the electrolyte and binder is crucial, due to the fact that a solid electrolyte interface (SEI) is irreversibly formed on the surface, which will be very important for its reversible capacity. As an attempt, TiO2 nanocrystallites are prepared by an electrochemical method. When applied as the anode for SIBs, the TiO2 electrode with the sodium carboxymethylcellulose binder and ether-based electrolyte presents an impressive capacity of 166.23 mA h g−1 at 2C after 4800 cycles, much higher than that with the polyvinylidene fluoride binder and carbonate-based electrolyte. A series of characterization studies reveal that the charge transfer at the interface between the electrolyte and electrode and the SEI film are the key factors determining the electrochemical properties. Importantly, the dual optimization of the binder and electrolyte is revealed to be an effective means to enhance the ICE of TiO2 up to 81.6%, thus greatly contributing to better guidance on the design of TiO2 anodes with ultra-high ICE for SIBs. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectric polymer P(VDF-TrFE-CTFE) is attracting increasing attention for electronic applications due to its high dielectric constant and relaxation characteristic. However, the low breakdown strength and premature saturation of polarization of this polymer have hampered its practical application severely. In this work, carbon quantum dots (CQDs) with functional groups and size of about 5 nm have been incorporated to overcome these issues. The nanocomposite with 0.1 wt% CQDs presents significantly improved breakdown strength and discharge energy density. Its breakdown strength (Eb) has been increased by 30.7% up to 340 kV mm−1. Due to the Coulomb blockade effect, the electrons can be restrained in the deep traps, which is favorable for the improvement of breakdown strength. Besides, the abundant functional groups around CQDs are beneficial to form adequate hydrogen bonds, resulting in increased crystallinity and breakdown strength as well. Additionally, the discharge energy density has been improved by 41.7% up to 6.8 J cm−3. The study demonstrates the effective enhancement of breakdown strength and energy density by ultralow loading of CQDs for P(VDF-TrFE-CTFE) polymer. [ABSTRACT FROM AUTHOR]

With the large-scale application of lithium-ion batteries, the recycling of retired LIBs has been a crucial problem to address. Among the spent LIBs, LiFePO4 (LFP) recycling is urgently needed as it is one of the most extensively utilized cathodes in the sustainable development of LIBs. However, traditional pyro-/hydro-metallurgical recycling methods are normally complicated and uneconomical. Here, we exhibit an efficient and green method with a simple route to regenerate a degraded LiFePO4 cathode, through which the cathode sheets are directly broken down into aluminum foil, high-purity FePO4 and lithium-containing solution by the introduction of hydrogen peroxide as a leaching reagent. The leaching efficiency of Li exceeds 96.3% with scarce Al and Fe, and the regenerated LiFePO4 from recovered FePO4 displays excellent rate capability and long-term cycling stability. This research greatly reduces the processing steps and chemical consumption, which is conducive to the sustainable industrial development of spent lithium-ion batteries. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The recycling of spent lithium-ion batteries (LIBs) is a crucial issue that has engaged extensive attention worldwide, along with the rapidly increasing usage of lithium-ion batteries. State-of-art recycling approaches, in terms of chemical leaching, have imperfections such as excessive chemical consumption, tedious recycling procedure and aggravated secondary pollution. In this research, a green and closed-loop route for the recycling of spent LiFePO4 involving oxidation leaching is demonstrated. By properly adjusting or controlling the leaching parameters, the leaching efficiency of lithium is up to 97.6% with the introduction of hydrogen peroxide, which is facilitated to achieve the transformed high-purity lithium carbonate and iron phosphate. The oxidation reaction mechanisms are clarified through thermodynamic and kinetic analyses, which identified that the oxidation leaching reaction is co-controlled by the internal diffusion and chemical reaction. Consequently, LiFePO4 cathode materials are regenerated by utilizing the obtained raw materials, as expected, which deliver superior cycling stability with less than 1% of capacity loss after 300 cycles and excellent rate performances. This research embodies the possibility of efficient recycling of LiFePO4 from spent lithium-ion batteries based on the principles of green chemistry that is possibly committed to the sustainability of the lithium-ion battery industry. [ABSTRACT FROM AUTHOR]

As a highly safe and low-cost cathode material for lithium-ion batteries, LiFePO4 predominately suffers from undesirable rate performance, arising from its inferior conductivity, during practical applications. Herein, LiFePO4 modified with a modulated band structure, as theoretically predicted, was successfully designed to overcome this deficiency. Notably, replacing the Li sites with Ti4+ led to tuned band structures, giving rise to an effective reduction of the forbidden bandwidth and the activated delocalization of the d-orbital electrons, as clearly observed using density functional theory calculations. Importantly, it also induces the shrinkage of the particle size, reducing the transport distance for Li+ inside the particles, as verified using Rietveld refinement of the X-ray diffraction spectra. As expected, electronic transfer and Li+ transport are synchronously accelerated thanks to the appropriate doping of Ti4+ in the olivine lattice, confirmed based on the measurement of the conductivity and calculations of the Li+ diffusion coefficient. Hence, the as-optimized cathode (0.5% Ti4+-LFP/C) exhibits an excellent rate capacity (135 mA h g−1 at 10C within 2.5–4.2 V) with superior long-term cycling stability (78% capacity retention after 3000 cycles). Based on these results, the dramatic improvement in the rate performance achieved via modulating the band structures and the ionic diffusion may provide novel opportunities for the development of olivine cathode materials. [ABSTRACT FROM AUTHOR]

Spinel LiMn2O4 is a promising cathode material for lithium-ion batteries ascribed to its steady bulk structure and abundant manganese sources. Nevertheless, severe capacity decay due to the Jahn–Teller effect and spontaneous disproportionation reaction seriously hampers its extensive application, especially at high-temperature or high-potential operation circumstances. Attributed to the strengthening of the crystallographic structure and the inhibition of Mn3+ side reactions, element substitution has become one of the most momentous tactics in the modification of LiMn2O4. Here, we comprehensively review the developments on restraining capacity fading and enhancing the performances of LiMn2O4 through element substitution. Primarily, the capacity fading mechanism of LiMn2O4 has been thoroughly recapitulated. Subsequently, our summary is proposed based on two categories, which are phase evolution and solid solution strengthening invoked by element substitution, and the latter can be subdivided into structure strengthening and Li+ diffusion kinetics boosting. More importantly, we put forward a methodological approach for future element substitution research studies. This report will shed light on the future direction of LiMn2O4 cathode material optimization. [ABSTRACT FROM AUTHOR]

A dynamic hydrophobic molecular membrane (DHM) of quaternary phosphonium salts has been in situ constructed on an electrified anode. The DHM can act as a resistor to regulate the distribution and reduction rates of zinc species, thus refining grains and facilitating the formation of dendrite-free zinc anodes to improve battery cycle stability. [ABSTRACT FROM AUTHOR]

As a promising cathode material for high performance lithium ion batteries, olivine LiMnxFe1−xPO4 (LMFP) combines the high safety of LiFePO4 and the high energy density of LiMnPO4. However, there are still obstacles to overcome for achieving higher rate performance, especially its inherent low electronic conductivity and Li+ diffusion coefficient. Here, the restricting factors for realizing high rate performance LMFP cathode materials are reviewed systematically. The bulk properties that affect the internal ion transport and electronic conduction are thoroughly expounded, particularly the phase transition mechanism, lattice distortion, point defects, element doping, Fe/Mn ratio and particle morphology. Moreover, the effect of utilizing a carbon-based/non-carbon material coating for improving the interface structure on rate performance is discussed comprehensively. A particular emphasis is placed on the design of LMFP-based batteries with high rate capability as well from the aspect of cell preparation technology, including the electrolyte selection and electrode design. Finally, on the basis of state-of-the-art understanding of bulk properties, the interface structure and cell preparation engineering, several technical challenges and research trends in improving the rate performance of LMFP cathode materials are proposed. [ABSTRACT FROM AUTHOR]

Bismuthene was prepared via the oxidation of Zintl clusters by electrochemical cathodic corrosion. It was found that the conversion of Zintl clusters from Bi22− to Bi2 occurred in the electrolyte having short alkyl chains due to the faster kinetics of highly reactive carbocation. Considering that c-Na3Bi exists in a wide voltage range, monitored by in situ XRD, a new wide peak for the as-obtained bismuthene in the CV curve was noticed, which benefits the improvement of electrochemical performances. [ABSTRACT FROM AUTHOR]

Konjac glucomannan (KGM) featuring abundant oxygen functional groups has been elaborately designed to enhance Zn reversibility. Importantly, –OH and C＝O groups as active sites could redistribute the Zn2+ concentration field and modulate the plating/stripping rate, further enabling uniform Zn deposition without dendrite growth. The Zn@KGM anode enables an advanced Zn-ion supercapacitor to deliver an impressive rate performance and cycling stability (up to 5000 cycles accompanied by a coulombic efficiency of 99.8%). [ABSTRACT FROM AUTHOR]

Sodium-ion capacitors (SICs), as new-generation electrochemical energy-storage systems, have combined the advantages of high energy and power densities, meeting the urgent demand for versatile electronic equipment and grid energy-storage stations. Nevertheless, the electrochemical performance of SICs is seriously restricted by the kinetic mismatch between the battery-type anode and capacitor-type cathode. In this work, N-doped 3D carbon (NHPC) delivered a high reversible specific capacity of 197 mA h g−1 at 2 A g−1, and the mechanism of its electrochemistry mainly involved strong pseudocapacitive storage that promoted quick physical adsorption/desorption. Moreover, further activation of NHPC yielded nitrogen-doped hierarchical porous activated carbon (NHPAC), which displayed a large specific surface area of 1478 m2 g−1 with abundant meso/macropores, and brought about fast adsorption/desorption of anions on its surface. The full-carbon SIC device benefitted from the similar material systems used for its anode and cathode, and hence achieved a high energy density of 115 W h kg−1 at 200 W kg−1 as well as long-term cyclability in the potential range of 0–4.0 V. This rational strategy of kinetic matching might open up a potential avenue for the development of additional advanced SICs. [ABSTRACT FROM AUTHOR]

As an efficient method to promote the electrochemical performances of carbon materials for sodium-ion batteries (SIBs), heteroatom (S, N, etc.) doping has attracted significant interest from researchers, and great efforts have been devoted to explore the functional mechanism of SIBs. Heteroatom doping enlarges the layer distance of carbon, provides more active sites, and enhances the conductivity for the promotion of sodium storage; however, the influences of heteroatom-containing precursors on the structures, morphologies and electrochemical sodium storage performances of carbon materials have rarely been explored. In this study, a series of S/N co-doped carbon materials (SNC) has been designed, and the influences of the S contents in precursors on the structures and morphologies of the carbon materials have been evaluated. Furthermore, the electrochemical sodium storage performances of the obtained materials have been investigated. With the introduction of S, the insertion/extraction behaviors of Na+ in the microcrystals of carbon materials were obviously enhanced. Meaningfully, the integrated influence of the precursor S content on the materials and sodium storage performances obtained in this study can contribute to the design and preparation of similar materials. [ABSTRACT FROM AUTHOR]

In this study, N-rich carbon coated interconnected CoSnO3 nanoboxes (CoSnO3–NCs) with controllable amounts of N-rich carbon ranging from 7.5% to 24.6% were firstly prepared by the carbonization of CoSnO3–MOFs. Impressively, the preparation of CoSnO3–MOFs has been realized for the first time by directly utilizing CoSnO3 as the precursor under solvent-free conditions, bridging between the cobalt(ii) ion in the skeleton of CoSnO3 and the 2-methylimidazole. Interestingly, the growth of these CoSnO3–MOFs can be manipulated by changing the amount of 2-methylimidazole used, resulting in a tunable N-rich carbon content. Furthermore, the electrochemical storage behavior of these materials for SIBs was initially explored. Compared with the pure CoSnO3, the as-resulted CoSnO3–NC materials showed largely enhanced sodium storage performance with a reversible capacity of 493.9 mA h g−1 at a current density of 0.1 A g−1 after 100 cycles. Moreover, the as-prepared materials showed an excellent high rate storage performance with a remarkable capacity of 273.8 mA h g−1 at 1 A g−1 after 1000 cycles. This work provides a new approach for constructing Co–MOFs as well as providing an efficient N-rich carbon-coating route, which may be expanded to other Co-based oxides and can greatly expand the development of new species of Co-based MOFs. [ABSTRACT FROM AUTHOR]

Restricted by their high specific surface area and porous structures, activated carbon (AC) materials display poor performances, such as a low initial coulombic efficiency in sodium-ion batteries (SIBs). Nevertheless, it is an ideal choice for carriers, where the high specific surface area is indispensable. Herein, a novel strategy to design S-doped carbon employing durian shell-based AC (DSAC) as the template is proposed and the effect of the amount of DSAC additive was investigated in detail. Impressively, an optimized amount of DSAC additive would contribute to the good dispersion of poly-2-thiophenemethanol (sulfur source) as well as an increased number of active sites for Na storage, thus resulting in excellent electrochemical performance. A high reversible specific capacity of 345 mA h g−1 was attained and the specific capacity of 264 mA h g−1 was retained after 200 cycles. In particular, a high initial coulombic efficiency of 56.02% and remarkable rate capability of 100.02 mA h g−1 were achieved at 5 A g−1 even after 4500 cycles. Meaningfully, the proposed route used to prepare carbon materials for SIBs can effectively facilitate the further application of AC and the construction of high-performance electrode materials for SIBs. [ABSTRACT FROM AUTHOR]

As an anode material for sodium-ion batteries (SIBs), antimony (Sb) has attracted significant interest due to its high theoretical specific capacity. However, it suffers from a huge volume change during the sodiation–desodiation process that leads to poor cyclability. Herein, cross-linked carbon nanosheet frameworks (CCNFs) and Sb nanoparticles (NPs) were combined to construct a high-performance anode material for SIBs. In this composite, Sb nanoparticles were tightly anchored on the carbon frameworks; this provided enhanced structural stability to Sb and prevented the agglomeration during the charge–discharge process. Sb provides a high specific capacity, and the carbon frameworks ensure structural integrity and conductive networks. Moreover, due to this synergistic effect, the as-prepared Sb/CCNFs composite exhibits an excellent cycle stability and rate performances. Considering both the capacity and rate property, the overall performances of the obtained Sb/CCNFs reach the highest level in comparison with those of the reported Sb/C composites. The reversible (charge) capacity can remain 549.3 mA h g−1 after 100 cycles at a current density of 100 mA g−1. Moreover, a superior rate performance is observed as the reversible capacity still reaches 318 mA h g−1 at a high current density of 3200 mA g−1. Therefore, this study proposes an effective methodology to improve the key performances of the SIB anode. [ABSTRACT FROM AUTHOR]

The conventional strategies for obtaining S/N-codoped carbon materials suffer from a series of problems caused by their complicated experimental procedures. Here, S,N-codoped carbon nanosheets were firstly prepared by a solvent-free one-pot method, displaying an ultra-thin sheet-like structure, a tunable interlayer distance ranging from 0.37 nm to 0.41 nm, and a large surface area up to 809 m2 g−1. When they were used as an anode for sodium-ion batteries (SIBs), an outstanding sodium-ion storage performance of 380 mA h g−1 was acquired at 100 mA g−1, which can be attributed to the expanded interlayer distance caused by the introduction of the large covalent radius-sulfur. The initial coulombic efficiency improved to 60.9%, which may benefit from N-doping. Most importantly, an excellent rate capability of ∼178 mA h g−1 was observed at a current density of 5 A g−1 after 5000 cycles, which is among best of the state-of-the-art carbon-based SIBs. Interestingly, the morphology of the obtained carbon materials can be tuned from bulk to flake by adjusting the sulfur content or temperature. Given this, this work provides a new method to construct co-doped carbon (especially tri-doped and multi-doped carbon) and shows that the strategy of co-doping of heteroatoms can effectively optimize the nano/microstructure and enhance the rate capability of the carbon materials. [ABSTRACT FROM AUTHOR]

Hollow-sphere ZnSe is successfully obtained through Ostwald ripening. Carbon nanoparticles are designed and utilized to form a wrapped carbon network as a conductive buffering matrix by subsequent annealing. The ZnSe/C composites, as anode materials for lithium-ion batteries (LIBs), exhibit excellent Li+ storage properties, delivering a high reversible capacity of 573.7 mA h g−1 at 1.0 A g−1 after 800 cycles. Even upon increasing the high current density to 20.0 A g−1, the reversible capacity can achieve 318.8 mA h g−1 after 5000 cycles. The superior rate capability is confirmed through the current density return from 20.0 to 1.0 A g−1, and ZnSe/C composites still recover up to 469 mA h g−1, with a retention of 92%. The enhanced electrochemical performances of ZnSe/C composites are attributed to the unique structure and the introduction of conductive carbon networks, which can improve the Li+ diffusion coefficient in the insertion and extraction process. Furthermore, the interconnected network also alleviates the volume variation during cycling and further enhances the structural stability. [ABSTRACT FROM AUTHOR]

Hierarchical anatase TiO2 homogeneously tuned by using carbon through Ti–C bonds has been designed, exploiting carbon quantum dots as uniform carbon additives and functionalization inducers for structure tailoring and surface modification. The fabricated pinecone-like structure constructed by ultrafine subunits presents a highly increased surface area (202.4 m2 g−1) and abundant mesopores. Surface bonded carbon significantly boosts its electronic conductivity derived from both the conductive carbon and accompanied oxygen vacancies. When utilized in sodium-ion batteries, it delivers a high reversible specific capacity of 264.1 mA h g−1 at a rate of 0.1C (33.6 mA g−1) and still maintains 108.2 mA h g−1 even after 2000 cycles at 10C with a retention of 94.7% outstandingly. Notably, its Na+ intercalation pseudocapacitive behavior is enhanced by the modulated TiO2/carbon interfaces, facilitating a fast (de-)sodiation process. Combining the elaborate hierarchical structure with the unique surface composition, synergetic merits are noticed when the promoted kinetics, improved electronic conductivity, increased electrolyte penetration areas and shortened Na+ diffusion length are achieved simultaneously, giving rise to remarkable high-rate capabilities and long-term cyclability. [ABSTRACT FROM AUTHOR]

Carbon coated anatase TiO2 hollow spheres (CCAnTHSs) are prepared through the carbon wrapping of etched amorphous TiO2 solid spheres (AmTSSs). The as-obtained CCAnTHS composite is applied as an anode material for sodium-ion batteries (SIBs) for the first time, delivering excellent cycle stability. At a high current density of 5C, a reversible capacity of 140.4 mA h g−1 remained after 500 cycles. Especially, at a 25C rate it could still reach 84.9 mA h g−1 after 80 cycles. Briefly, the sodium storage performance of CCAnTHSs are superior to these of the amorphous TiO2 solid spheres and bare anatase TiO2 hollow spheres, mainly benefitting from the advantages of a unique hollow structure with a large specific surface area and a carbon coating with high electronic conductivity. [ABSTRACT FROM AUTHOR]

Cypress leaf-like Sb was prepared by a facile chemical replacement reaction. The sodium storage behavior of the obtained product was firstly investigated, giving a superior electrochemical performance with a high reversible capacity of 629 mA h g−1 after 120 cycles, close to its theoretical capacity (660 mA h g−1). [ABSTRACT FROM AUTHOR]

A C quantum dot coated Mn3O4 composite (Mn3O4/Cdots) has been obtained for the first time by a green alternating voltage electrochemical approach. It is interesting to note that the morphology of Mn3O4 particles in the composite can be induced to form an octahedral structure through the introduction of C quantum dots. In particular, the as-produced Mn3O4/Cdots composite utilized as an anode material for lithium ion batteries demonstrates excellent electrochemical performances, showing an enhanced reversible discharge capacity of 934 mA h g−1 after 50 cycles at a current density of 100 mA g−1 which is almost five times as much as that of pure Mn3O4. [ABSTRACT FROM AUTHOR]

Rutile TiO2 microspheres anchored by nanoneedle clusters, as a new class of anode materials, are successfully employed for sodium-ion batteries and manifested good energy storage behavior. The initial discharge capacity of 308.8 mA h g−1 is obtained and a high reversible capacity of 121.8 mA h g−1 is maintained after 200 cycles at a current density of 0.1 C, exhibiting a high capacity retention of 83.1%. All these merits are not only ascribed to the rutile TiO2 crystal structure, but also thanks to the porous morphology of hundreds of nanoneedle clusters in favor of sodium diffusion and accommodating the strain during the sodiation and desodiation processes. Therefore, it is highly expected that rutile TiO2, as a feasible electrochemical sodium storage material, can be a new promising candidate as an anode for sodium-ion batteries. [ABSTRACT FROM AUTHOR]

N-doped TiO2 nanorods decorated with carbon dots with enhanced electrical-conductivity and faster charge-transfer have been fabricated utilizing a simple hydrothermal reaction process involving TiO2 powders (P25) and NaOH in the presence of carbon dots followed by ion exchange and calcination treatments. Due to the merits of the carbon dots, doping and nanostructures, the as-designed N–TiO2/C-dots composite utilized as anode materials for lithium-ion batteries can sustain a capacity of 185 mA h g−1 with 91.6% retention even at a high rate of 10 C over 1000 cycles. It is interesting to note that the ratios of capacitive charge capacity during such high rates for the N–TiO2/C-dots composite electrodes are higher than those at low rates, which likely explains the observed excellent rate capabilities. In contrast to lithium-ion batteries, sodium-ion batteries have gained more interest in energy storage grids because of the greater abundance and lower cost of sodium-containing precursors. The as-obtained N–TiO2/C-dots composites reported here and utilized as anode materials for sodium-ion batteries exhibit excellent electrochemical performances, including substantial cycling stabilities (the capacity retention ratios after 300 cycles at 5 C is 93.6%) and remarkable rate capabilities (176 mA h g−1 at 5 C, 131 mA h g−1 at 20 C); such performances are the greatest ever reported to date over other structured TiO2 or TiO2 composite materials. [ABSTRACT FROM AUTHOR]

Sb porous hollow microspheres (PHMSs) were prepared by a replacement reaction employing Zn microspheres (MSs) as templates. The obtained Sb PHMSs were first applied as anode materials for sodium-ion batteries (SIBs) and showed a high reversible capacity of 617 mA h g−1 at a current density of 100 mA g−1 after 100 cycles, exhibiting a high capacity retention of 97.2%. Even at a high current density of 3200 mA g−1, the reversible capacity can also reach 312.9 mA h g−1. The superior electrochemical performance of Sb PHMSs can be attributed to the unique structural characteristic of Sb with porous and hollow structure, which can accommodate the volume change and facilitate the Na+ diffusion during the sodiation and desodiation process. [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs) tuned porous NiCo2O4 sphere composites are prepared for the first time via a reflux synthesis route followed by a post annealing treatment. Benefiting from the advantages of the unique porous structure with a large specific surface area, high mesoporosity and superior electronic conductivity, the as-obtained CQDs/NiCo2O4 composite electrode exhibits high specific capacitance (856 F g-1 at 1 A g-1), excellent rate capability (83.9%, 72.5% and 60.8% capacity retention rate at 20, 50 and 100 A g-1, respectively) and exceptional cycling stability (98.75% of the initial capacity retention over 10 000 cycles at 5 A g-1). Furthermore, the assembled AC//CQDs/NiCo2O4 asymmetric supercapacitor manifests a high energy density (27.8 W h kg-1) at a power density of 128 W kg-1 or a high power density (10.24 kW kg-1) at the reasonable energy density of 13.1 W h kg-1 and remarkable cycling stability (101.9% of the initial capacity retention over 5000 cycles at 3 A g-1). The results above suggest a great potential of the porous CQDs/NiCo2O4 composites in the development of high-performance electrochemical energy storage devices for practical applications. [ABSTRACT FROM AUTHOR]

Correction for 'Highly stable zinc metal anode enabled by oxygen functional groups for advanced Zn-ion supercapacitors' by Kangyu Zou et al., Chem. Commun., 2021, 57, 528–531, DOI: 10.1039/D0CC07526D. [ABSTRACT FROM AUTHOR]

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.

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.)

Antimony sulfide (Sb 2 S 3 ) has drawn widespread attention as an ideal candidate anode material for sodium-ion batteries (SIBs) due to its high specific capacity of 946 mA h g -1 in conversion and alloy reactions. Nevertheless, volume expansion, a common flaw for conversion-alloy type materials during the sodiation and desodiation processes, is bad for the structure of materials and thus obstructs the application of antimony sulfide in energy storage. A common approach to solve this problem is by introducing carbon or other matrices as buffer material. However, the common preparation of Sb 2 S 3 could result in environmental pollution and excessive energy consumption in most cases. To incorporate green chemistry, natural stibnite ore (Sb 2 S 3 ) after modification via carbon sheets was applied as a first-hand material in SIBs through a facile and efficient strategy. The unique composites exhibited an outstanding electrochemical performance with a higher reversible capacity, a better rate capability, as well as an excellent cycling stability compared to that of the natural stibnite ore. In short, the study is expected to offer a new approach to improve Sb 2 S 3 composites as an anode in SIBs and a reference for the development of natural ore as a first-hand material in energy storage., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Rutile TiO2 microspheres anchored by nanoneedle clusters, as a new class of anode materials, are successfully employed for sodium-ion batteries and manifested good energy storage behavior. The initial discharge capacity of 308.8 mA h g(-1) is obtained and a high reversible capacity of 121.8 mA h g(-1) is maintained after 200 cycles at a current density of 0.1 C, exhibiting a high capacity retention of 83.1%. All these merits are not only ascribed to the rutile TiO2 crystal structure, but also thanks to the porous morphology of hundreds of nanoneedle clusters in favor of sodium diffusion and accommodating the strain during the sodiation and desodiation processes. Therefore, it is highly expected that rutile TiO2, as a feasible electrochemical sodium storage material, can be a new promising candidate as an anode for sodium-ion batteries.

The ion-migration mechanism of Na3V2(PO4)2F3 is investigated in Na3V2(PO4)2F3-Li hybrid-ion batteries for the first time through a combined computational and experimental study. There are two Na sites namely Na(1) and Na(2) in Na3V2(PO4)2F3, and the Na ions at Na(2) sites with 0.5 occupation likely extract earlier to form Na2V2(PO4)2F3. The structural reorganisation is suggested to make a stable configuration of the remaining ions at the centre of Na(1) sites. After the extraction of the second Na ion, the last ion prefers to change occupation from 1 to 0.5 to occupy two Na(2) sites. The insertion of predominant Li ions also should undergo structural reorganization when the first Li ion inserts into the centre of Na(1) site theoretically forming NaLiV2(PO4)2F3, and the second ion inserts into two Na(2) sites to form NaLi2V2(PO4)2F3. More than a 0.3 Li ion insertion would take place in the applied voltage range by increasing the number of sites occupied rather than occupy the vacancy in triangular prismatic sites. An improved solution-based carbothermal reduction methodology makes Na3V2(PO4)2F3 exhibit excellent C-rate and cycling performances, of which the Li-inserted voltage is evaluated by first principles calculations.

NiSb alloy hollow nanospheres (HNSs) obtained by galvanic replacement were firstly applied as anode materials for lithium ion batteries, giving the best electrochemical performances for NiSb alloy materials so far with a high reversible capacity of 420 mA h g(-1) after 50 cycles, close to its theoretical capacity (446 mA h g(-1)).