Li3VO4 Research Articles

Fast kinetics for lithium storage rendered by Li3VO4 nanoparticles/porous N-doped carbon nanofibers

Li3VO4 (LVO) has been recognized as an alternative anode material for lithium-ion batteries (LIBs) because of its appropriate lithium storage potential and capacity merits. However, its practical application is seriously hindered by slow reaction kinetics stemming from poor electronic conductivity. Herein, Li3VO4/porous N-doped carbon nanofibers (LVO/PNC NFs) are firstly designed and fabricated via an electrospinning method, utilizing the thermal decomposition characteristics of polylactic acid (PLA). The porous N-doped carbon nanofibers provide efficient electrolyte diffusion paths and facilitate ion transport. In addition, LVO nanoparticles are uniformly dispersed along the nanofibers to effectively inhibit particle aggregation. The obtained LVO/PNC NFs are evaluated as anodes for LIBs and deliver high reversible capacity of 768 mAh g−1 after 300 cycles at 0.2 A g−1, along with excellent rate capability (average capacity of 355 mAh g−1 at 8 A g−1 after 6 periodic rate testing) and long cycling life (286 mAh g−1 after 2000 cycles at 4 A g−1). The special porous nanofiber represents an effective strategy for improving the electronic conductivity, inhibiting particle aggregation, and ensuring rapid ion/charge transport towards advanced energy storage technologies.

Comprehensive Investigation of the Crystal Structure of Cation-Disordered Li3VO4 as a High-Rate Anode Material: Unveiling the Dichotomy between Order and Disorder.

This study investigates mechanochemical synthesis and cation-disordering mechanism of wurtzite-type Li3VO4 (LVO), highlighting its promise as a high-performance anode material for lithium-ion batteries and hybrid supercapacitors. Mechanochemical treatment of pristine LVO using a high-energy ball mill results in a "pure cation-disordered" LVO phase, allowing for meticulous analysis of cation arrangement. The X-ray and neutron diffraction study demonstrates progressive loss of order in LVO crystal with increasing milling duration. High-resolution transmission electron microscopy reveals disrupted lattice fringes, indicating cationic misalignment. Pair-distribution function analysis confirms loss of cation arrangements and the presence of short-range order. Combination of these multiple analytical techniques achieves a comprehensive understanding of cation regularity and clearly demonstrates order/disorder dichotomy in cation-disordered materials, ranging from short (<8 Å) to middle-long range (8-30 Å), using an integrated superstructure model of the cation-disordered LVO crystals. Electrochemical testing reveals that mechanochemically treated LVO exhibits superior rate capability, with a 70% capacity retention at a high current density of 50C-rate. Lithium diffusion coefficient measurements demonstrate enhanced lithium-ion mobility in the mechanochemically treated LVO, attributed to cation-disordering effect. These findings provide valuable insights into mechanochemical cation-disordering in LVO, presenting its potential as an efficient anode material for lithium-ion-based electrochemical energy storage.

Integrated Li3VO4 and boron doped carbon microspheres with high tap density for high-rate and durable lithium storage

As an essential representative of novel anode materials with high capacity and safe voltage, Li3VO4 (LVO) still suffers from the challenges of low electronic conductivity and low tap density of nanostructures. Herein, a strategy of nanoization and recombination is proposed to synthesize the integrated LVO and boron doped carbon microspheres (LVO/BC-MS-550) with high tap density via a chemical crosslink method to improve the Li-ion storage performance. LVO/BC-MS-550 is consisted of the well-dispersed LVO nano-crystals in tightly stacked carbon spheres derived from the cross-linked network of boric acid (BA) and polyvinyl alcohol (PVA). By introducing conductive and continuous carbon framework, the LVO crystals are controlled to grow in the confined region with mitigated volume changes, as well as the enhanced electronic conductivity. Benefiting from the constructive advantages, LVO/BC-MS-550 anode delivers a specific capacity of 512.1 mAh g−1 at the current density of 0.2 A g−1 (0.34 C) after 300 cycles, and ultra-long cycling performance of 231.8 mAh g−1 over 5000 cycles at the charging/discharging current density of 4/2 A g−1, exhibiting rapid pseudo-capacitance reaction kinetics. This work provides valuable insights into the fabrication of in situ three-dimensional crosslinked carbon and LVO composites for alternative grid-scale electrochemical applications.

Enhanced all-solid-state battery performance through in-situ construction of interface modification layer

The development of high-performance all-solid-state lithium batteries (ASSLBs) relies on improving the interface stability between layered oxide cathodes and sulfide electrolytes, as well as the structural stability of cathode active materials. While coating technology is considered an effective solution, the fabrication of these coating materials using economically viable and scalable manufacturing processes remains a comprehensive and challenging task. In this study, a combination of first-principles calculations and experiments is employed to propose, for the first time, a simple and scalable aqueous process to in-situ construct an Li3VO4 (LVO) buffer coating on the surface of LiCoO2(LCO) cathode, which exhibits high ionic conductivity, relatively low electronic conductivity, and high oxidation limit. The LVO buffering coating not only facilitates the migration of lithium ions at the interface, effectively suppresses interface side reactions, and reduces interface impedance, but also enhances the mechanical and structural stability of the cathode material. As a result, the LCO/LPSC/Li-In ASSLBs with 2% LVO coating exhibit an initial discharge capacity of up to 145.6 mAh g−1 at room temperature (0.1C), with a capacity retention of 94.89% after 100 cycles. Furthermore, the ASSLBs demonstrate good capacity and cycle stability under extreme testing conditions, including high voltage, high temperature, and low temperature, especially exhibiting an initial discharge capacity of up to 114.9 mAh g−1 at −20 °C.

Insights into the multi-functional lithium difluoro(oxalate)borate additive in boosting the Li-ion reaction kinetics for Li3VO4 anodes.

The rational design of a solid electrolyte interphase (SEI) with high ionic conductivity and high electrochemical stability is significantly important in improving the electrochemical performance of anode materials. Herein, lithium difluoro(oxalate)borate (LiDFOB) is used as an electrolyte additive to generate protective SEI films on Li3VO4 (LVO) anodes. The addition of LiDFOB is beneficial to form a dense, uniform, stable and LiF-richer SEI, which is helpful to boost the Li-ion storage kinetics. In addition, the generated SEI can inhibit the further decomposition of electrolytes and maintain the morphology of LVO anodes during charge/discharge processes. As a result, LVO-based anodes exhibit a much higher capacity (769.5 mA h g-1 at 0.5 A g-1), enhanced rate performance (243.3 mA h g-1 at 5.0 A g-1) and excellent long-term cycling stability (209.9 mA h g-1 after 5000 cycles) when cycled in 1 wt% LiDFOB addition electrolyte. This work confirms that LiDFOB is a promising multi-functional additive for LiPF6 electrolytes and provides new insights into SEI construction towards high-performance LVO anodes.

Boosting Zinc Storage Performance of Li3 VO4 Cathode Material for Aqueous Zinc Ion Batteries via Carbon-Incorporation: A Study Combining Theory and Experiment.

In the search for sustainable cathode materials for aqueous zinc ion batteries (AZIBs), vanadium (V)-based materials have garnered interest, primarily due to their abundance and multiple oxidation states. Among the contenders, Li3 VO4 (LiVO) stands out for its affordability, high specific capacity, and elevated ionic conductivity. However, its limited electrical conductivity results in significant resistance polarization, limiting its rate capability, especially under high currents. Through density functional theory (DFT) calculations, this study evaluates the electrochemical implications of carbon (C) incorporation within the LiVO matrix. The findings indicate that C integration significantly ameliorates the conductivity of LiVO. Moreover, C serves as a barrier, mitigating direct interactions between Zn2+ and LiVO, which in turn expedites Zn2+ diffusion. When considering various C materials for this role, glucose is emerged as the optimal candidate. The LiVO/C-glucose composite (LiVO/C-G) is observed to undergo dual phase transitions during charge-discharge cycles, resulting in an amorphous vanadium-oxygen (VO) derivative, paving the way for subsequent electrochemical reactions. Collectively, the insights pave a promising avenue for refining AZIB cathode design and performance.

Lithium Polyacrylate as Lithium and Carbon Source in the Synthesis of Li3 VO4 for High-Rate and Long-Life Li-Ion Batteries.

Li3 VO4 is a promising anode material for use in lithium-ion batteries, however, the conventional synthesis methods for Li3 VO4 anodes involve the separate use of lithium and carbon sources, resulting in inefficient contact and low crystalline quality. Herein, lithium polyacrylate (LiPAA) was utilized as a dual-functional source and an in-situ polymerization followed by a spray-drying method was employed to synthesize Li3 VO4 . LiPAA serves a dual purpose, acting as both a lithium source to improve the crystal process and a carbon source to confine the particle size within a desired volume during high-temperature treatment. Additionally, the in-situ synthesis of a porous carbon decorating skeleton prevents the growth and agglomeration of Li3 VO4 particles and provides abundant ion/electron diffusion channels and contact areas. Based on the synthesis route and the constructed primary-secondary structure, the Li3 VO4 anodes obtained in this study exhibit an impressive capacity of 596.2 mAh g-1 . Moreover, they demonstrate enhanced rate performance over 600 cycles during 10 periods of rate testing, as well as a remarkably long lifespan of 5000 cycles at high currents. The utilization of LiPAA as a dual-functional source represents a broad approach that holds great potential for future research on high-performance electrodes requiring both lithium and carbon sources.

A green recyclable Li3VO4-pectin electrode exhibiting pseudocapacitive effect as an advanced anode for lithium-ion battery

Battery system design and development is prioritizing environmentally friendly recycling processes to ensure a sustainable future for our planet. The reuse of active materials in Li-ion batteries is critical for this goal. Herein, we investigated the electrochemical performance of Li3VO4 (LVO) anode with pectin as a binder. Our Li-ion half-cells showed stable capacity of 230 mAh g−1 at a current density of 0.02 A g−1 after 100 cycles. In addition, we observed a novel enhanced specific capacity of 400 mAh g−1 during delithiation at a high current density of 1 A g−1, which did not occur during lithiation. This higher capacity was can be attributed to the pseudocapacitive lithium storage behavior in the LVO-pectin electrode, as identified by CV and EIS analyses. The heterostructure of LVO-pectin resulted in an interfacial surface charge that contributed to the capacity, as demonstrated by impedance spectroscopy in conjunction with the distribution of relaxation times. The utilization of pectin as an eco-friendly binder demonstrated nearly 90 % material recovery and 100 % capability for subsequent re-lithiation, indicating recyclability. Furthermore, the pseudocapacitive effect becomes increasingly dominant in regenerated LVO-pectin cells. These results exemplify a promising approach towards the development of environmentally friendly Li-ion batteries with high energy and power density.

Surface Modification of Li3VO4 with PEDOT:PSS Conductive Polymer as an Anode Material for Li-Ion Capacitors.

Li3VO4 (LVO) is a highly promising anode material for lithium-ion batteries, owing to its high capacity and stable discharge plateau. However, LVO faces a significant challenge due to its poor rate capability, which is mainly attributed to its low electronic conductivity. To enhance the kinetics of lithium ion insertion and extraction in LVO anode materials, a conductive polymer called poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is applied to coat the surface of LVO. This uniform coating of PEDOT:PSS improves the electronic conductivity of LVO, thereby enhancing the corresponding electrochemical properties of the resulting PEDOT:PSS-decorated LVO (P-LVO) half-cell. The charge/discharge curves between 0.2 and 3.0 V (vs. Li+/Li) indicate that the P-LVO electrode displays a capacity of 191.9 mAh/g at 8 C, while the LVO only delivers a capacity of 111.3 mAh/g at the same current density. To evaluate the practical application of P-LVO, lithium-ion capacitors (LICs) are constructed with P-LVO composite as the negative electrode and active carbon (AC) as the positive electrode. The P-LVO//AC LIC demonstrates an energy density of 107.0 Wh/kg at a power density of 125 W/kg, along with superior cycling stability and 97.4% retention after 2000 cycles. These results highlight the great potential of P-LVO for energy storage applications.

In/Ce Co-doped Li3VO4 and Nitrogen-modified Carbon Nanofiber Composites as Advanced Anode Materials for Lithium-ion Batteries.

Li3VO4 (LVO) is considered as a novel alternative anode material for lithium-ion batteries (LIBs) due to its high capacity and good safety. However, the inferior electronic conductivity impedes its further application. Here, nanofibers (nLICVO/NC) with In/Ce co-doped Li3VO4 strengthened by nitrogen-modified carbon are prepared. Density functional theory calculations demonstrate that In/Ce co-doping can substantially reduce the LVO band gap and achieve orders of magnitude increase (from 2.79 × 10-4 to 1.38 × 10-2 S cm-1) in the electronic conductivity of LVO. Moreover, the carbon-based nanofibers incorporated with 5LICVO nanoparticles can not only buffer the structural strain but also form a good framework for electron transport. This 5LICVO/NC material delivers high reversible capacities of 386.3 and 277.9 mA h g-1 at 0.1 and 5 A g-1, respectively. Furthermore, high discharge capacities of 335 and 259.5 mA h g-1 can be retained after 1200 and 4000 cycles at 0.5 and 1.6 A g-1, respectively (with the corresponding capacity retention of 98.4 and 78.7%, respectively). When the 5LICVO/NC anode assembles with commercial LiNi1/3Co1/3Mn1/3O2 (NCM111) into a full cell, a high discharge capacity of 191.9 mA h g-1 can be retained after 600 cycles at 1 A g-1, implying an inspiring potential for practical application in high-efficiency LIBs.

Hierarchical Self-Assembly Strategy for Scalable Synthesis of Li3VO4/N Doped C Nanosheets for High-Rate Li-Ion Storage.

While the comprehensive merits of high safety and high capacity make Li3VO4 (LVO) a potential anode material for lithium-ion batteries, the practical application of LVO was severely impeded by the unfavorable high-rate capability and unscalable preparation. Here, LVO/N doped C nanosheets (LVO@NC NSs) assembled from primary LVO@NC nanoparticles are prepared via a scalable and concise spray drying approach. The 2D morphology and the interconnected LVO@NC constituents endow the LVO@NC NSs with continuously excellent reaction activity, leading to prominent rate performance. When cycling at 0.2 A g-1, the obtained LVO@NC NSs exhibit a high charge capacity of 628.4 mAh g-1 after 300 cycles, showing little improvement compared with the initial charge capacity. After 9 periods of rate testing ranging from 0.1 to 6.0 A g-1 for 460 cycles, a high charge capacity of 610.3 mAh g-1 remains. It also exhibits an outstanding long lifespan at the charge/discharge currents of 3.0/6.0 A g-1, delivering a high charge capacity of 277.0 mAh g-1 in the 5000th cycle. The scalable and concise preparation as well as the enhanced high-rate capability of the LVO@NC NSs make them hold great promise as an anode candidate for high-power lithium-ion storage devices.

Enhancing the Li+ Diffusion in Li3VO4 by Coupling with Reduced Graphene Oxide for Lithium-Ion Batteries

Background: Owing to the excellent theoretical specific capacity and safety intercalation potential, Li3VO4 (LVO) has been proposed as an advanced anode material for lithium ions batteries (LIBs). However, the LVO suffers from low electronic conductivity that limits its commercialization. Objective: The reduced graphene oxide (rGO) is recommended to couple with micro-LVO particles aiming to enhance the conductivity of composite electrodes. Method: The LVO@rGO composite is synthesized by a facile hydrothermal method. The morphology, crystallinity, valance state and electrochemical behavior of LVO@rGO are characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical workstation, respectively. Further, the LIBs’ performance is explored by making a coins-type half-cell LIBs battery via battery system. Results: The Li+ diffusion rate of the optimized LVO@rGO electrode is 7.67×10-23 cm2/s, which improves two orders of magnitudes of pure LVO electrode. As a result, the LVO@rGO anode delivers a reversible capacity of 190.1 mAh/g at 0.1 A/g after 100 cycles, which is even twice higher than that of pure LVO anode (90.6 mAh/g). Besides, it exhibits superior rate capability, i.e. a reversible capability of 285.0, 220.2, 158.7, 105.2 and 71.7 mAh/g at 0.05, 0.1, 0.2, 0.5 and 1.0 A/g, respectively. Conclusion: The high conductivity and flexible texture enable rGO an idea building block to enhance the Li ion diffusion of whole electrode. On the other hand, it is instrumental in alleviating the aggregation of host materials, leading to high specific surface and specific capacity.

Dual Active and Kinetically Inter-Promoting Li3VO4/Graphene Anode Enabling Printable High Energy Density Lithium Ion Micro Capacitors

Planar micro-supercapacitors (MSCs) with high energy/power densities and long cycle life are expected to expedite the development of the future wearable miniaturized electronics. However, its low energy density issue always falls short in ever-increasing demands of specific energy consumption. Herein, a dual active and kinetically inter-promoting Li3VO4 (LVO)/graphene composite is designed as the anode for high energy density lithium ion micro capacitors (LIMCs). The LVO nanoparticles are evenly confined on graphene nanosheets through an atomic layer pre-deposition (ALD) technique, which substantially disperses the nucleation site and impedes the coarse grain growth in the successive solid-state formation of LVO. The much-promoted reaction kinetics of LVO and graphene substrate with sufficient diffusion space in the interdigital electrodes of LIMCs synergistically boost the three-dimensional and efficiently lithium ion storage behavior. The LVO/graphene exhibits extraordinary rate capability (98.5 mAh g−1 at 40 A g−1 (100 C)) and long-term stability. All the current collectors and asymmetric interdigital electrodes are spray printed, opening a facile and delicate technique for a large-scale production of LIMCs. The LIMCs deliver a superior volumetric energy density of 51.4 mWh cm−3, excellent flexible and cyclic stability, demonstrating a great potential for the future miniaturized, flexible, and high-performance energy storage devices.

Controllable synthesis of Li3VO4/N doped C nanofibers toward high-capacity and high-rate Li-ion storage

Li3VO4 (LVO) is a promising anode material with comprehensive advantages of energy density and safety performance. However, it suffers from unsatisfactory performance correlating with intrinsic poor reaction kinetics. Herein, morphology-controlled synthesis of LVO/N doped C nanofibers (LVO/NC NFs) is successfully realized via a concise electrospinning approach using low-cost raw materials. The designed LVO/NC NFs show excellent reaction kinetics which result in high pseudocapacitive Li-ion storage throughout cycling, giving rise to ultra-high capacity and prominent rate performance. It delivers discharge capacity of 750 mAh g−1 after 400 cycles at 0.2 A g−1, and 545 mAh g−1 after 900 cycles at 2.0 A g−1. After 2 period rate performance testing from 0.2 to 4.0 A g−1 over 170 cycles, the discharge capacity still reverts to 717 mAh g−1 when the current decreases back to 0.2 A g−1. Tuning the reaction kinetics of LVO via facile electrospinning provides a feasible strategy for constructing high-performance LVO-based anode material.

Improving electrochemical performance of LiMn0.5Fe0.5PO4 cathode by hybrid coating of Li3VO4 and carbon

LiMnxFe1-xPO4(0.5≤x≤1) has been regarded as a promising cathode material for lithium-ion batteries due to its competitive energy density and excellent thermal stability, yet its rate capability and capacity retention during long cycles remain to be further improved. Herein, a hybrid layer composed of Li3VO4 (LVO) and carbon was designed and successfully coated on LiMn0.5Fe0.5PO4 (LMFP) nanorods via a wet ball-milling method combined with the heat treatment. This layer performs as not only a protector to maintain the structural integrity of LMFP but also a conductor to induce the fast transport of both Li-ions and electrons. LMFP modified with the hybrid layer of carbon and 3 wt% LVO (LMFP/C-3LVO) exhibits super long cycling stability over 1000 cycles at 5 C, with considerable capacity retention of 91.5%. Even at a high rate of 10 C, LMFP/C-3LVO can also deliver a substantial discharge capacity of 125 mAh•g−1. The favorable kinetics of the modified composite were confirmed in detail by EIS and GITT measurement. When paired with the modified Li4Ti5O12/C anode, LMFP/C-3LVO shows a stabilized discharge capacity of 107 mAh•g−1 over 120 cycles at 1 C. Our strategy on ionic/electronic dual-conductive hybrid layer provides a guideline on the synthesis and modification of high-performance cathode materials.

(Invited) Evolution of Supercapacitors Towards Climate Change–Promoting Effective Solar/Regenerative Energy Utilization

1. Microcurrents for Macroefficiency: Effective harvesting of solar energy under low-sunlight conditions Under low-sunlight conditions—dawn, dusk, and occlusion by clouds—the electric current produced by a photovoltaic cell (PVC) drops to a microscopic trickle, which conventional solar-power systems simply discard. Here we show that these tiny currents may in fact be effectively captured and used for substantial energy harvesting, significantly improving overall system efficiency. Our system involves an innovative mechanism, enabled by sensors and an AI-powered microcontroller, for automatically routing PVC currents through conventional (standard-current) or modified (microscopic-current) circuits. A decisive role in the design of our system is played by the rapid pace of global climate change; as we show, changes in the magnitude of sunlight-intensity variations over just the past ten years are an essential driver of the surprisingly large efficiency gains enabled by our innovation. In this talk we introduce the basic ideas of our technique, present results of a prototype study achieving 17% improvement in power-system efficiency, and discuss a variety of promising applications.2. Supercharging Solar Cells with The Next Generation Supercapacitors Li-ion based hybrid supercapacitors and their functional materials are being vigorously researched in hopes to improve their capacity/voltage and therefore their energy density(Figure 1). Transition metal oxides are among the most popular materials utilized in this purpose. Thanks to high voltage and associated high energy density, they are tuned as both high energy and high-power materials. We have developed “Nanohybrid” capacitor (NHC) based on the single-nanocrystalline Li4Ti5O12 (LTO, 5-20 nm) negative and active carbon positive electrodes, showing ultrafast charge-discharge capability up to 300C (=12 s) with a 3-hold energy density of EDLC.1) To further increase the energy density of NHC, currently we are expanding the search for alternative materials of LTO negative electrode, which possess i) higher capacity such as TiO2(B)2) with 2-hold theoretical capacity (= 335 mAh g-1) compared to LTO, and ii) lower reaction potential (higher cell voltage) such as Li3VO4 (LVO)3) and Y2Ti2O5S2 (YTOS). The present talk will mainly describe ultrafast/stable pseudocapacitive electrochemistry of LVO and YTOS as promising negative electrodes for replacing NHC, which can achieve higher cell voltage from 3.85 to 4.4 V. The volumetric energy density for the hybrid (YTOS//AC) will reach up to 4-fold of EDLC. The talk will also cover the 3rd generation “SuperRedox” capacitor which further replace the positive AC electrode by ultrafast nanocrystalline Li3V2(PO4)3, whereby the energy density will be 6-fold of EDLC. References 1) Naoi, et al., ACC. Chem. Research, 46(5), 1075 (2013).2) Naoi, E. Iwama, W. Naoi, P. Simon et al., Adv. Mater., 28, 6751 (2016).3) Iwama, K. Kisu, W. Naoi, P. Rozier, P. Simon, K. Naoi et al., ACS Nano, 10(5), 5398 (2016). Figure 1

Heterogeneous nucleation of Li3VO4 regulated in dense graphene aerogel for lithium ion capacitors

Achieving both high gravimetric and volumetric rate performances of the anode for lithium ion capacitors (LICs) is still a challenge. Herein, we propose a dense Li3VO4 (LVO)/graphene aerogel (GA) composite as the two active components anode, the crystalline and particle size of LVO can be regulated in the GA that provides abundant heterogeneous nucleation sites to prevent the agglomeration and preferred growth of LVO. The dense LVO/GA exhibits significantly improved electrochemical performances. The gravimetric/volumetric specific capacity can reach up to 84.4 mAh g−1 and 63.3 mAh cm−3 at the very high current density of 16 A g−1, as well as the 85% capacity retention after 5000 cycles at 8 A g−1. This superior performance is contributed from the facilitated diffusion rate of confined LVO clusters in GA, the accelerated electron transport offered by the three dimensional (3D) graphene skeleton that closely surrounds LVO, and the fast electrochemical kinetics boosted by the combined dense structure. The LICs exhibit excellent energy/power densities (maximum 122.2 W h kg−1, 8.8 kW kg−1). We believe that this two active components design demonstrates an unparalleled function that the single active material cannot realize, and provide a promising road propelling the development of high performance LICs.

Insights into the Charge Storage Mechanism of Li3VO4 Anode Materials for Li‐Ion Batteries

AbstractBall‐milled Li3VO4 (LVO) offers higher practical specific charge values and better cycle stability than the pristine, μm‐scale material due to improved electronic conductivity within the electrode. Although the theoretical specific charge of LVO is estimated to be 592 mAh g−1, its practical reversible specific charge retains 220 mAh g−1 (1.12 Li+) on long‐term cycling. At a very low rate of C/200 (=3 mA g−1), ball‐milled Li3VO4‐based anodes accomplish an almost full lithiation state of x=2.97 Li+ in Li3+xVO4. At the end of the first delithiation, the recovered LVO phase is able to only reversibly (de)lithiate about 1.8 Li+ in the following cycles. A careful investigation of the charge storage mechanism of LVO by operando X‐ray diffraction revealed that the irreversible specific charge “loss” in the first cycle is mainly associated with an irreversible structural transformation via an intermediate phase on the first lithiation of LVO that leads to clear mechanistic differences in the reaction pathways between the first lithiation and delithiation.

Ball milling-derived nanostructured Li3VO4 anode with enhanced surface-confined capacitive contribution for lithium ion capacitors

To balance the kinetics gap between anode/cathode of lithium ion capacitors (LICs), we developed a straightforward ball milling method to tune the electrochemical performance of Li3VO4 (LVO) particles. After the mechanical crushing, the particle size of the pristine LVO with a densely bulky structure is reduced significantly; furthermore, a partial transition from V5+ to V4+ may induce the oxygen vacancy, resulting into the shortened Li+ diffusion path and low diffusion barrier. More active sites are exposed, and the long-range ordering of the structure is disturbed, leading to a fast Li+ transport on the surface or subsurface. The calculated capacitive contribution ratio achieves 49.6% at the lowest scan rate. The LICs deliver high energy and power densities (max. 108.5 Wh kg−1 at 114.5 W kg−1, 1180 W kg−1 at 21 Wh kg−1), revealing the efficiency of ball milling to facilitate the surface-induced capacitive contribution toward high-performance LICs.

Carbon-coated Li3VO4 with optimized structure as high capacity anode material for lithium-ion capacitors

Due to the high capacity, moderate voltage platform, and stable structure, Li3VO4 (LVO) has attracted close attention as feasible anode material for lithium-ion capacitor. However, the intrinsic low electronic conductivity and sluggish kinetics of the Li+ insertion process severely impede its practical application in lithium-ion capacitors (LICs). Herein, a carbon-coated Li3VO4 (LVO/C) hierarchical structure was prepared by a facial one-step solid-state method. The synthesized LVO/C composite delivers an impressive capacity of 435mAh/g at 0.07A/g, remarkable rate capability, and nearly 100% capacity retention after 500 cycles at 0.5 A/g. The superior electrochemical properties of LVO/C composite materials are attributed to the improved conductivity of electron and stable carbon/LVO composite structures. Besides, the LIC device based on activated carbon (AC) cathode and optimal LVO/C as anode reveals a maximum energy density of 110Wh/kg and long-term cycle life. These results provide a potential way for assembling the advanced hybrid lithium-ion capacitors.