Wire-in-Wire TiO2/C Nanofibers Free-Standing Anodes for Li-Ion and K-Ion Batteries with Long Cycling Stability and High Capacity

Facile synthesis of in situ carbon-coated CoS2 micro/nano-spheres as high-performance anode materials for sodium-ion batteries

In situ carbon-coated CoS2 micro/nano-spheres were successfully prepared by sulfuric calcination using the solvothermal method with glycerol as the carbon source without introducing extraneous carbon. This method prevents carbon agglomeration and avoids the cumbersome steps of the current technology. The composite demonstrates excellent sodium storage capacity as an anode material for sodium-ion batteries. The initial charge and discharge capacities were 1027 and 1224 mA h g-1 at 50 mA g-1, respectively, with an initial coulombic efficiency of 83.9%. The capacity of CoS2@C at 350 °C was maintained at 937 mA h g-1 after 140 cycles at a current density of 2 A g-1. The outstanding electrochemical performance is mainly attributed to the nanostructure design and the presence of in situ carbon. As revealed by the kinetic analysis, the pseudo-capacitive behaviour also contributed to the excellent electrochemical performance.

ZnSe/SnSe Heterostructure Incorporated with Selenium/Nitrogen Co-Doped Carbon Nanofiber Skeleton for Sodium-Ion Batteries

Effective strategies toward building exquisite nanostructures with enhanced structural integrity and improved reaction kinetics will carry forward the practical application of alloy-based materials as anodes in batteries. Herein, a free-standing 3D carbon nanofiber (CNF) skeleton incorporated with heterostructured binary metal selenides (ZnSe/SnSe) nanoboxes is developed for Na-ion storage anodes, which can facilitate Na+ ion migration, improve structure integrity, and enhance the electrochemical reaction kinetics. During the carbonization and selenization process, selenium/nitrogen (Se/N) is co-doped into the 3D CNF skeleton, which can improve the conductivity and wettability of the CNF matrices. More importantly, the ZnSe/SnSe heterostructures and the Se/N co-doping CNFs can have a synergistic interfacial coupling effect and built-in electric field in the heterogeneous interfaces of ZnSe/SnSe hetero-boundaries as well as the interfaces between the CNF matrix and the selenide heterostructures, which can enable fast ion/electron transport and accelerate surface/internal reaction kinetics for Na-ion storage. The ZnSe/SnSe@Se,N-CNFs exhibit superior Na-ion storage performance than the comparative ZnSe/SnSe, ZnSe and SnSe powders, which deliver an excellent rate performance (882.0, 773.6, 695.7, 634.2, and 559.0 mAh g-1 at current rates of 0.1, 0.2, 0.5, 1, and 2 A g-1) and long-life cycling stability of 587.5 mAh g-1 for 3500 cycles at 2 A g-1.

Production of the C/TiO2 composite with a high-performance electrochemical property from titanium-rich sludge via in-situ C coating

Resource recycling from waste-water and sludge is an important part of the 14th Five-Year Plan in China. The emerging titanium-based coagulants have drawn growing attentions due to their strong coagulation capability in water purification and value-added Ti-loaded sludge production. Management and recovery of the high value-added sludge into functional nanomaterials is highly significant for both sludge reduction and environmental remediation. The present study was carried out to investigate the recycle of the coagulated Ti-loaded sludge to produce functional C/TiO2 composites as the anode materials for lithium-ion batteries (LIBs). It is the first time that the application of the Ti-loaded wastewater sludge derived C/TiO2 was evaluated for LIBs. The experimental results showed that the carbon coating through in-situ carbonization of the sludge produced the C/TiO2 composites with a high specific surface area, stable structural integrity, and excellent electrochemical properties that would facilitate Li+ diffusion in long-term LIBs usage. The C/TiO2 composites calcinated from the polytitanium sulfate-coagulated sludge at 800°C (N2) exhibited the best electrochemical performance during the cycling tests (601 mAh/g at 100 mA/g after 200 cycles). The research work demonstrates the promising prospect of the recycle and value-added utilization of the Ti-loaded sludge in the production of high-performance C/TiO2 composites for energy storage applications. This study provides a new way for the management and reuse of Ti-loaded waste-sludge.

Layered Potassium Titanium Niobate/Reduced Graphene Oxide Nanocomposite as a Potassium-Ion Battery Anode

With graphite currently leading as the most viable anode for potassium-ion batteries (KIBs), other materials have been left relatively under-examined. Transition metal oxides are among these, with many positive attributes such as synthetic maturity, long-term cycling stability and fast redox kinetics. Therefore, to address this research deficiency we report herein a layered potassium titanium niobate KTiNbO5 (KTNO) and its rGO nanocomposite (KTNO/rGO) synthesised via solvothermal methods as a high-performance anode for KIBs. Through effective distribution across the electrically conductive rGO, the electrochemical performance of the KTNO nanoparticles was enhanced. The potassium storage performance of the KTNO/rGO was demonstrated by its first charge capacity of 128.1 mAh g-1 and reversible capacity of 97.5 mAh g-1 after 500 cycles at 20 mA g-1, retaining 76.1% of the initial capacity, with an exceptional rate performance of 54.2 mAh g-1 at 1 A g-1. Furthermore, to investigate the attributes of KTNO in-situ XRD was performed, indicating a low-strain material. Ex-situ X-ray photoelectron spectra further investigated the mechanism of charge storage, with the titanium showing greater redox reversibility than the niobium. This work suggests this low-strain nature is a highly advantageous property and well worth regarding KTNO as a promising anode for future high-performance KIBs.

Fe2O3 for stable K-ion storage: mechanism insight into dimensional construction from stress distribution and micro-tomography

Fe2O3 is considered a potential electrode material owing to its high theoretical capacity, low cost, and non-toxic characteristics. However, the significant volume expansion and structural degradation during charging and discharging hinder its application in potassium ion batteries. The electrochemical properties of the electrode material are primarily influenced by the diffusion efficiency of ions and the mechanics of the object. From the construction of a one dimensional structure, a three-dimensional flower-like Fe2O3 with a high specific surface and low-dimensional spherical Fe2O3 were prepared. Considering the convenience and visualization of the research, micron-scale Fe2O3 was prepared, although the larger particle size will lose part of the capacity. Notably, compared with the spherical structure, the specific capacity of the flower structure was increased by about 100%. The von Mises stress distribution on the two structures was simulated by the finite element method, revealing the mechanism of electrode failure induced by volume expansion and confirming the vital role of the multidimensional system in relieving stress concentration and improving electrochemical performance. Furthermore, synchrotron radiation soft X-ray absorption spectrum and X-ray micro-tomography revealed the phase transformation process and reaction mechanism of Fe2O3 in potassium ion batteries. The dimensional structure construction strategy reported here can provide theoretical support for modifying transition metal oxides.

Built-In Electric Field-Driven Ultrahigh-Rate K-Ion Storage via Heterostructure Engineering of Dual Tellurides Integrated with Ti3C2Tx MXene

Exploiting high-rate anode materials with fast K+ diffusion is intriguing for the development of advanced potassium-ion batteries (KIBs) but remains unrealized. Here, heterostructure engineering is proposed to construct the dual transition metal tellurides (CoTe2/ZnTe), which are anchored onto two-dimensional (2D) Ti3C2Tx MXene nanosheets. Various theoretical modeling and experimental findings reveal that heterostructure engineering can regulate the electronic structures of CoTe2/ZnTe interfaces, improving K+ diffusion and adsorption. In addition, the different work functions between CoTe2/ZnTe induce a robust built-in electric field at the CoTe2/ZnTe interface, providing a strong driving force to facilitate charge transport. Moreover, the conductive and elastic Ti3C2Tx can effectively promote electrode conductivity and alleviate the volume change of CoTe2/ZnTe heterostructures upon cycling. Owing to these merits, the resulting CoTe2/ZnTe/Ti3C2Tx (CZT) exhibit excellent rate capability (137.0 mAh g-1 at 10 A g-1) and cycling stability (175.3 mAh g-1 after 4000 cycles at 3.0 A g-1, with a high capacity retention of 89.4%). More impressively, the CZT-based full cells demonstrate high energy density (220.2 Wh kg-1) and power density (837.2 W kg-1). This work provides a general and effective strategy by integrating heterostructure engineering and 2D material nanocompositing for designing advanced high-rate anode materials for next-generation KIBs.

Sand-Fixation Model for Interface Engineering of Layered Titania and N/O-Doped Carbon Composites to Enhance Potassium/Sodium Storage

Layered titania (L-TiO2 ) holds great potential for potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs) due to their high specific capacity. Synthesizing L-TiO2 functional materials for high-capacity and long cyclability battery remains challenging due to the unstable and poor conductivity of bare L-TiO2 . In nature, plant growth can stabilize land by preventing sands from dispersing following desertification. Inspired by nature's "sand-fixation model," Al3+ "seeds" are in situ grown on layered Ti3 C2 Tx "land." Subsequently, NH2 -MIL-101(Al) "plants" with Al as metal nodes are grown on the Ti3 C2 Tx "land" by self-assembly. After annealing and etching processes (similar to desertification), NH2 -MIL-101(Al) is transformed into interconnected N/O-doped carbon (MOF-NOC), which not only acts as a plant-like function to prevent the pulverization of L-TiO2 transformed from Ti3 C2 Tx but also improves the conductivity and stability of MOF-NOC@L-TiO2 . Al species are selected as seeds to improve interfacial compatibility and form intimate interface heterojunction. Systematic ex situ analysis discloses that the ions storage mechanism can be endowed by mixed contribution of non-Faradaic and Faradaic capacitance. Consequently, the MOF-NOC@L-TiO2 electrodes exhibit high interfacial capacitive charge storage and outstanding cycling performance. The interface engineering strategy inspired by "sand-fixation model" provides a reference for designing stable layered composites.

Design of Gradient Ti Reconstituted Fe2O3 Anodes with Enhanced Lithium Affinity Modulated Electronic Structures: First-Principles Calculations and Experiment Verification

High-performance conversion transition metal oxides are strong candidates for advanced anode materials for lithium-ion batteries. However, the poor intrinsic conductivity and the large volume changes during battery operation are important constraints to its practical application. The heterogeneous atom doping strategy is an important way to modulate the electronic structure and surface states of the host materials. Herein, theoretical calculations reveal that heteroatomic Ti doping and its ionic or electronic compensation mechanisms can well modulate the electronic structure of Fe₂O₃ and change the surface Li-ion affinity. A Ti concentration gradient modification strategy for Fe₂O₃ is proposed to construct high-performance electrode materials. As a Li-ion battery anode, Ti concentration gradient-doped Fe₂O₃ achieves excellent long-cycle stability, with a reversible capacity of 1001.9 mAh g^-1 at 1 A g^-1 for 1200 cycles, and even maintains a reversible specific capacity compared to the theoretical capacity of commercial graphite electrodes at 2 A g^-1 for 2000 cycles. This combination of theoretical calculations and experiments offers ways to intelligently design and develop alkali metal ion batteries.

Interface Engineering of Fe7S8/FeS2 Heterostructure in situ Encapsulated into Nitrogen-Doped Carbon Nanotubes for High Power Sodium-Ion Batteries

Heterostructure engineering combined with carbonaceous materials shows great promise toward promoting sluggish kinetics, improving electronic conductivity, and mitigating the huge expansion of transition metal sulfide electrodes for high-performance sodium storage. Herein, the iron sulfide-based heterostructures in situ hybridized with nitrogen-doped carbon nanotubes (Fe7S8/FeS2/NCNT) have been prepared through a successive pyrolysis and sulfidation approach. The Fe7S8/FeS2/NCNT heterostructure delivered a high reversible capacity of 403.2 mAh g-1 up to 100 cycles at 1.0 A g-1 and superior rate capability (273.4 mAh g-1 at 20.0 A g-1) in ester-based electrolyte. Meanwhile, the electrodes also demonstrated long-term cycling stability (466.7 mAh g-1 after 1,000 cycles at 5.0 A g-1) and outstanding rate capability (536.5 mAh g-1 at 20.0 A g-1) in ether-based electrolyte. This outstanding performance could be mainly attributed to the fast sodium-ion diffusion kinetics, high capacitive contribution, and convenient interfacial dynamics in ether-based electrolyte.

Single-Phase Ternary Compounds with a Disordered Lattice and Liquid Metal Phase for High-Performance Li-Ion Battery Anodes

Si is considered as the promising anode materials for lithium-ion batteries (LIBs) owing to their high capacities of 4200 mAh g-1 and natural abundancy. However, severe electrode pulverization and poor electronic and Li-ionic conductivities hinder their practical applications. To resolve the afore-mentioned problems, we first demonstrate a cation-mixed disordered lattice and unique Li storage mechanism of single-phase ternary GaSiP2 compound, where the liquid metallic Ga and highly reactive P are incorporated into Si through a ball milling method. As confirmed by experimental and theoretical analyses, the introduced Ga and P enables to achieve the stronger resistance against volume variation and metallic conductivity, respectively, while the cation-mixed lattice provides the faster Li-ionic diffusion capability than those of the parent GaP and Si phases. The resulting GaSiP2 electrodes delivered the high specific capacity of 1615 mAh g-1 and high initial Coulombic efficiency of 91%, while the graphite-modified GaSiP2 (GaSiP2@C) achieved 83% of capacity retention after 900 cycles and high-rate capacity of 800 at 10,000 mA g-1. Furthermore, the LiNi0.8Co0.1Mn0.1O2//GaSiP2@C full cells achieved the high specific capacity of 1049 mAh g-1 after 100 cycles, paving a way for the rational design of high-performance LIB anode materials.

Electrospun carbon-based nanomaterials for next-generation potassium batteries

Rechargeable potassium (K) batteries that are of low cost, with high energy densities and long cycle lives have attracted tremendous interest in affordable and large-scale energy storage. However, the large size of the K-ion leads to sluggish reaction kinetics and causes a large volume variation during the ion insertion/extraction processes, thus hindering the utilization of active electrode materials, triggering a serious structural collapse, and deteriorating the cycling performance. Therefore, the exploration of suitable materials/hosts that can reversibly and sustainably accommodate K-ions and host K metals are urgently needed. Electrospun carbon-based materials have been extensively studied as electrode/host materials for rechargeable K batteries owing to their designable structures, tunable composition, hierarchical pores, high conductivity, large surface areas, and good flexibility. Here, we present the recent developments in electrospun CNF-based nanomaterials for various K batteries (e.g., K-ion batteries, K metal batteries, K-chalcogen batteries), including their fabrication methods, structural modulation, and electrochemical performance. This Feature Article is expected to offer guidelines for the rational design of novel electrospun electrodes for the next-generation K batteries.

Lithium Vanadium Oxide/Graphene Composite as a Promising Anode for Lithium-Ion Batteries

Lithium vanadium oxide (Li₃VO₄, LVO) is a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (394 mAh g^-1) and safe working potential (0.5-1.0 V vs. Li⁺/Li). However, its electrical conductivity is low which leads to poor electrochemical performance. Graphene (GN) shows excellent electrical conductivity and high specific surface area, holding great promise in improving the electrochemical performance of electrode materials for LIBs. In this paper, LVO was prepared by different methods. SEM results showed the obtained LVO by sol-gel method possesses uniform nanoparticle morphology. Next, LVO/GN composite was synthesized by sol-gel method. The flexible GN could improve the distribution of LVO, forming a high conductive network. Thus, the LVO/GN composite showed outstanding cycling performance and rate performance. The LVO/GN composite can provide a high initial capacity of 350.2 mAh g^-1 at 0.5 C. After 200 cycles, the capacity of LVO/GN composite remains 86.8%. When the current density increased from 0.2 C to 2 C, the capacity of LVO/GN composite only reduced from 360.4 mAh g^-1 to 250.4 mAh g^-1, demonstrating an excellent performance rate.

Hollow CoS2 anchored on hierarchically porous carbon derived from Pien Tze Huang for high-performance supercapacitors

The development of electrode materials with a high specific capacitance, power density, and long-term stability is essential and remains a challenge for developing supercapacitors. Cobalt sulfides (CoS₂) are considered one of the most promising and widely studied electrode materials for supercapacitors. Herein, CoS₂ and hierarchical porous carbon derived from Pien Tze Huang waste are assembled into a cobalt sulfide/carbon (CoS₂/PZH) matrix composite using a one-step hydrothermal method to resolve the challenges of supercapacitors. The resulting CoS₂/PZH composite material exhibits a hierarchical porous structure with hollow CoS₂ embedded in a PZH framework. The uniform dispersion of the hierarchical porous structure CoS₂/PZH is achieved due to the PZH framework, while the uniform decoration of the porous PZH with the hollow CoS₂ prevents the PZH from stacking easily. Moreover, the excellent synergistic effect of the hierarchical porous and hollow structure of CoS₂/PZH can shorten the electron/ion diffusion channels, expose additional active sites, and provide stable structures for subsequent reactions. As a result, the CoS₂/PZH composite material displays a high initial specific capacity of 447.5 F g^-1 at 0.5 A g^-1, a high energy density of 22.38 W h kg^-1, and long-term cycling stability (a retention rate of 92.3% over 10 000 cycles at 5 A g^-1).

A Novel Hybrid Point Defect of Oxygen Vacancy and Phosphorus Doping in TiO2 Anode for High-Performance Sodium Ion Capacitor

Although sodium ion capacitors (SICs) are considered as one of the most promising electrochemical energy storage devices (organic electrolyte batteries, aqueous batteries and supercapacitor, etc.) due to the combined merits of battery and capacitor, the slow reaction kinetics and low specific capacity of anode materials are the main challenges. Point defects including vacancies and heteroatoms doping have been widely used to improve the kinetics behavior and capacity of anode materials. However, the interaction between vacancies and heteroatoms doping have been seldomly investigated. In this study, a hybrid point defects (HPD) engineering has been proposed to synthesize TiO₂ with both oxygen vacancies (OVs) and P-dopants (TiO₂/C-HPD). In comparison with sole OVs or P-doping treatments, the synergistic effects of HPD on its electrical conductivity and sodium storage performance have been clarified through the density functional theory calculation and sodium storage characterization. As expected, the kinetics and electronic conductivity of TiO₂/C-HPD3 are significantly improved, resulting in excellent rate performance and outstanding cycle stability. Moreover, the SICs assembled from TiO₂/C-HPD3 anode and nitrogen-doped porous carbon cathode show outstanding power/energy density, ultra-long life with good capacity retention. This work provides a novel point defect engineering perspective for the development of high-performance SICs electrode materials.

Multicomponent Composite Membrane with Three-Phase Interface Heterostructure as Photocatalyst for Organic Dye Removal

A multicomponent composite membrane (P-S-T/C) with three-phase interface heterostructure is ingeniously designed. A polydopamine (PDA)-modified conductive carbon fiber cloth (CFC) is used as the substrate. Activated poly(vinylidene fluoride) (PVDF) with titanium dioxide (TiO2) and a silicon dioxide (SiO2) aerogel are electrospun as the top layer. The three-phase interface heterostructure was formed by TiO2, conductive CFC, and the SiO2 aerogel. Its photocatalytic performance is validated by photodegradation of organic dyes in a low-oxygen (O2) water environment. On combining with the capillary condensation of a bilayer structure, P-S-T/C exhibits excellent removal capability for anionic and cationic dyes. Moreover, P-S-T/C exhibits excellent stability and recyclability under simulated sunlight. The mechanism study indicates that the separated photogenerated carriers diffuse to the composite membrane surface rapidly on the three-phase interface of P-S-T/C. The abundant O2 adsorbed on the porous SiO2 aerogel surface acts as an electron (e-)-trapping agent, which can also decrease the work function of the composite materials. Superoxide radicals (•O2 -) play a dominant role in the reaction of photodegradation supported by a free radical-trapping experiment. This work paves a way to design a membrane with photocatalytic performance by constructing the interface heterostructure.

Electrolyte formulation strategies for potassium-based batteries

Potassium (K)-based batteries are viewed as the most promising alternatives to lithium-based batteries, owing to their abundant potassium resource, lower redox potentials (-2.97 V vs. SHE), and low cost. Recently, significant achievements on electrode materials have boosted the development of potassium-based batteries. However, the poor interfacial compatibility between electrode and electrolyte hinders their practical. Hence, rational design of electrolyte/electrode interface by electrolytes is the key to develop K-based batteries. In this review, the principles for formulating organic electrolytes are comprehensively summarized. Then, recent progress of various liquid organic and solid-state K+ electrolytes for potassium-ion batteries and beyond are discussed. Finally, we offer the current challenges that need to be addressed for advanced K-based batteries.

Carbon-Encapsulated Ni3 Se4 /CoSe2 Heterostructured Nanospheres: Sodium/Potassium-Ion Storage Anode with Prominent Electrochemical Properties

Heterogeneous structures are used as energy storage devices because of their ability to accelerate charge transfer, which greatly contributes to the rate capability of devices. However, the construction of heterostructures with conspicuous electrochemical properties remains a huge challenge. In this study, a design of heterostructured Ni₃ Se₄ /CoSe₂ nanospheres encapsulated by a carbon shell (Ni₃ Se₄ /CoSe₂ @C) synthesized through facile hydrothermal and annealing methods is presented. The Ni₃ Se₄ /CoSe₂ @C exhibits excellent cyclic performance with a capacity of 420 mA h g^-1 at 0.5 A g^-1 after 100 cycles for Na-storage and 330.1 mA h g^-1 at 0.1 A g^-1 after 200 cycles for K-storage. The excellent cyclic performance can be attributed to the carbon coating that maintains the structural stability and enhances electrical conductivity, and significantly, the heterostructures that promote ion/electron transport. The sodium storage mechanism of the Ni₃ Se₄ /CoSe₂ @C is revealed by ex situ X-ray powder diffraction, ex situ high-resolution transmission electron microscopy, and in situ electrochemical impedance spectra analyses. The first principles density functional theory calculation is performed to prove that the heterostructure on the Ni₃ Se₄ /CoSe₂ interface can induce an electric field and thus improve the electrochemical reaction kinetics. This study provides an effective approach for constructing heterostructured composites for high-performance alkaline batteries.

Simple way of making free-standing cathode electrodes for flexible lithium-ion batteries

The flexible electrodes used in the lithium-ion battery (LIB) offer an excellent opportunity to be bent and folded without deforming their electrochemical characteristics. However, a flexible electrode does not include metal foil as a current collector, limiting the LIB's flexibility and weakening the mechanical strength. This study fabricates flexible LiFePO₄ (LFP) free-standing electrodes by a scalable and straightforward solution-based etching process. The obtained free-standing electrodes show capacities and bending performances that are similar to the conventional electrodes with aluminum current collectors. This study opens a new avenue for developing a free-standing electrode for low-cost and flexible lithium-ion batteries.

The flexible electrodes used in the lithium-ion battery (LIB) offer an excellent opportunity to be bent and folded without deforming their electrochemical characteristics.

Templated synthesis of 2D TiO2 nanoflakes for durable lithium ions battery

In this work, the 2D TiO2 nanoflakes were prepared by employing MXene as sacrificial template for durable lithium ions batteries (LIBs) anode. Essentially, the high crystalline anatase TiO2 nanoparticles compacted...

A flexible Mn0.5Ti2(PO4)3/C nanofiber film with superior cycling stability for potassium-ion batteries

First-principles calculations indicate that Mn_0.5Ti₂(PO₄)₃ is more suited to potassium-ion storage because of its lower energy gap than that of KTi₂(PO₄)₃. A flexible Mn_0.5Ti₂(PO₄)₃/C nanofiber film (F-MTP/C NFF) has been first synthesized via electrospinning and applied to potassium-ion batteries as a self-standing anode. An integral carbon conductive network, unique one-dimensional nanostructure, and exceptional mechanical flexibility give F-MTP/C NFF outstanding potassium-ion storage performance. Impressively, the self-standing F-MTP/C NFF electrode delivers a high specific capacity of 218 mA h g^-1 at 0.02 A g^-1 and shows ultra-long cycling stability of 2000 cycles at 1 A g^-1. This work may give a new insight into developing NASICON-type Ti-based materials as flexible electrodes for potassium-ion batteries.

Porous Co2VO4 Nanodisk as a High-Energy and Fast-Charging Anode for Lithium-Ion Batteries

The Li⁺ diffusion coefficient of Co₂VO₄ is evaluated by theoretical calculation to be as high as 3.15 × 10^–10 cm² s⁻¹, theoretically proving Co₂VO₄ a promising anode in fast-charging lithium-ion batteries.

A hexagonal porous Co₂VO₄ nanodisk (PCVO ND) structure is designed, featuring a high specific surface area of 74.57 m² g⁻¹ and numerous pores with a pore size of 14 nm.

The PCVO ND shows excellent fast-charging performance (a high average capacity of 344.3 mAh g⁻¹ at 10 C for 1000 cycles with only 0.024% capacity loss per cycle for 1000 cycles).

High-energy–density lithium-ion batteries (LIBs) that can be safely fast-charged are desirable for electric vehicles. However, sub-optimal lithiation potential and low capacity of commonly used LIBs anode cause safety issues and low energy density. Here we hypothesize that a cobalt vanadate oxide, Co₂VO₄, can be attractive anode material for fast-charging LIBs due to its high capacity (~ 1000 mAh g⁻¹) and safe lithiation potential (~ 0.65 V vs. Li⁺/Li). The Li⁺ diffusion coefficient of Co₂VO₄ is evaluated by theoretical calculation to be as high as 3.15 × 10^–10 cm² s⁻¹, proving Co₂VO₄ a promising anode in fast-charging LIBs. A hexagonal porous Co₂VO₄ nanodisk (PCVO ND) structure is designed accordingly, featuring a high specific surface area of 74.57 m² g⁻¹ and numerous pores with a pore size of 14 nm. This unique structure succeeds in enhancing Li⁺ and electron transfer, leading to superior fast-charging performance than current commercial anodes. As a result, the PCVO ND shows a high initial reversible capacity of 911.0 mAh g⁻¹ at 0.4 C, excellent fast-charging capacity (344.3 mAh g⁻¹ at 10 C for 1000 cycles), outstanding long-term cycling stability (only 0.024% capacity loss per cycle at 10 C for 1000 cycles), confirming the commercial feasibility of PCVO ND in fast-charging LIBs.

Flexible SnTe/carbon nanofiber membrane as a free-standing anode for high-performance lithium-ion and sodium-ion batteries

Flexible electrode plays a key role in flexible energy storage devices. The SnTe/C nanofibers membrane (SnTe/CNFM) with excellent mechanical flexibility has been successfully synthesized for the first time through electrospinning, and it demonstrates outstanding electrochemical performance as free-standing anode for lithium/sodium-ion batteries. The SnTe/CNFM electrode delivers a discharge capacity of 526.7 mAh g^-1 at 1000 mA g^-1 after 1000 cycles in lithium-ion half-cells and a discharge capacity of 236.5 mAh g^-1 at 500 mA g^-1 after 80 cycles in lithium-ion full-cells with a LiFePO₄ cathode. Not only that, it shows a discharge capacity of 182.7 mAh g^-1 at 200 mA g^-1 after 200 cycles in sodium-ion half-cells and a high discharge capacity of 207.0 mAh g^-1 at 500 mA g^-1 after 50 cycles in sodium-ion full-cells with a Na_0.44MnO₂ cathode. Moreover, the prepared SnTe/CNFM exhibits good mechanical flexibility. The SnTe/CNFM can still return to its original state without any breakage after bending, curling, folding and kneading. These results indicate that SnTe/CNFM is expected to become one of the promising free-standing anodes for lithium/sodium-ion batteries.

Robust hollow TiO2 spheres for lithium/sodium ion batteries with excellent cycling stability and rate capability

We report a facile solvothermal synthesis of hollow TiO2 nanospheres using phenolic resin nanospheres as templates under magnetic stirring condition, followed by annealing, which demonstrate excellent lithium/sodium storage performance.