Mesoporous Li3VO4/C Submicron-Ellipsoids Supported on Reduced Graphene Oxide as Practical Anode for High-Power Lithium-Ion Batteries

The Lithium Storage Mechanism of Zero-Strain Anode Materials with Ultralong Cycle Lives

At present, graphite is a widely used anode material in commercial lithium-ion batteries for its low cost, but the large volume expansion (about 10%) after fully lithiated makes the material prone to cracking and even surface stripping in the cycle. Therefore, the development of zero-strain anode materials (volume change <1%) is of great significance. LiAl5O8 is a zero-strain insertion anode material with a high theoretical specific capacity. However, the Li+ storage mechanism remains unclear, and the cycle life as well as fast-charging capability need to be greatly improved to meet the practical requirements. In this study, LiAl5O8 nanorods are prepared by utilizing aluminum ethoxide nanowires as a soft template and doped with the Zr element to further improve the Li+ diffusion coefficient and electronic conductivity, which in turn improves cycle and rate performances. The Zr-doped LiAl5O8 presents a high reversible capacity of 227.2 mAh g-1 after 20,000 cycles under 5 A g-1, which significantly outperforms the state-of-the-art anode materials. In addition, the Li+ storage mechanisms of LiAl5O8 and Zr-doped LiAl5O8 are clearly clarified with a variety of characterization techniques including nuclear magnetic resonance. This work greatly promotes the practical process of zero-strain insertion anode materials.

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.

"Fast-Charging" Anode Materials for Lithium-Ion Batteries from Perspective of Ion Diffusion in Crystal Structure

"Fast-charging" lithium-ion batteries have gained a multitude of attention in recent years since they could be applied to energy storage areas like electric vehicles, grids, and subsea operations. Unfortunately, the excellent energy density could fail to sustain optimally while lithium-ion batteries are exposed to fast-charging conditions. In actuality, the crystal structure of electrode materials represents the critical factor for influencing the electrode performance. Accordingly, employing anode materials with low diffusion barrier could improve the "fast-charging" performance of the lithium-ion battery. In this Review, first, the "fast-charging" principle of lithium-ion battery and ion diffusion path in the crystal are briefly outlined. Next, the application prospects of "fast-charging" anode materials with various crystal structures are evaluated to search "fast-charging" anode materials with stable, safe, and long lifespan, solving the remaining challenges associated with high power and high safety. Finally, summarizing recent research advances for typical "fast-charging" anode materials, including preparation methods for advanced morphologies and the latest techniques for ameliorating performance. Furthermore, an outlook is given on the ongoing breakthroughs for "fast-charging" anode materials of lithium-ion batteries. Intercalated materials (niobium-based, carbon-based, titanium-based, vanadium-based) with favorable cycling stability are predominantly limited by undesired electronic conductivity and theoretical specific capacity. Accordingly, addressing the electrical conductivity of these materials constitutes an effective trend for realizing fast-charging. The conversion-type transition metal oxide and phosphorus-based materials with high theoretical specific capacity typically undergoes significant volume variation during charging and discharging. Consequently, alleviating the volume expansion could significantly fulfill the application of these materials in fast-charging batteries.

Zero-Strain Insertion Anode Material of Lithium-Ion Batteries

The insertion type materials are the most important anode materials for lithium-ion batteries, but their insufficient capacity is the bottleneck of practical application. Here, LiAl₅ O₈ nanowires with high theoretical capacity and Li-ions diffusion coefficient are prepared and studied as an insertion anode material, which exhibits zero-strain properties upon electrochemical cycling. However, the poor electronic conductivity of LiAl₅ O₈ definitely sacrifices the capacity and limits the rate performance. Therefore, compact LiAl₅ O₈ and carbon composite are further synthesized, in which nanosized LiAl₅ O₈ particles are uniformly embedded in an amorphous carbon matrix. It displays a reversible capacity of 490.9 mAh g^-1 at 1 A g^-1 , and the capacity rises continuously to 996.8 mAh g^-1 after 1000 cycles due to the interfacial storage mechanism, that the excess Li⁺ ions can be accommodated in the grain boundaries and C/LiAl₅ O₈ interfaces.

Ga2O3–Li3VO4/NC nanofibers toward superb high-capacity and high-rate Li-ion storage

Porous Ga2O3–Li3VO4/N-doped C nanofibers consisting of ultrafine nanoparticles embedded in nanoflakes were designed and firstly prepared via electrospinning, showing superb high-rate Li-ion storage.

Novel Li3 VO4 Nanostructures Grown in Highly Efficient Microwave Irradiation Strategy and Their In-Situ Lithium Storage Mechanism

The investigation of novel growth mechanisms for electrodes and the understanding of their in situ energy storage mechanisms remains major challenges in rechargeable lithium-ion batteries. Herein, a novel mechanism for the growth of high-purity diversified Li3 VO4 nanostructures (including hollow nanospheres, uniform nanoflowers, dispersed hollow nanocubes, and ultrafine nanowires) has been developed via a microwave irradiation strategy. In situ synchrotron X-ray diffraction and in situ transmission electron microscope observations are applied to gain deep insight into the intermediate Li3+ x VO4 and Li3+ y VO4 phases during the lithiation/delithiation mechanism. The first-principle calculations show that lithium ions migrate into the nanosphere wall rapidly along the (100) plane. Furthermore, the Li3 VO4 hollow nanospheres deliver an outstanding reversible capacity (299.6 mAh g-1 after 100 cycles) and excellent cycling stability (a capacity retention of 99.0% after 500 cycles) at 200 mA g-1 . The unique nanostructure offers a high specific surface area and short diffusion path, leading to fast thermal/kinetic reaction behavior, and preventing undesirable volume expansion during long-term cycling.

In situ interfacial architecture of lithium vanadate-based cathode for printable lithium batteries

Most Li₃VO₄ anodes are obtained by pre-architecture methods in which Li₃VO₄ anode materials are prepared with more than six key processes including high-temperature annealing and long preparation time. Herein, we propose an in situ post-architecture strategy including Li₃VO₄-precursor solution (ink) preparation and then annealing at 250°C. The integrated Li₃VO₄ based electrode not only possesses good electrical conductivity and porous microstructure but also has superior stability because of Cu anchoring and inclusion by in situ catalysis. The integrated electrode demonstrates a high reversible capacity (865 mA h g^-1 at 0.2 A g^-1) and good cyclability (100% capacity retention after 200 cycles at 1 A g^-1). More importantly, the post-architecture electrode has a high energy density of 773.8 Wh kg^-1, much higher than reported Li₃VO₄-based materials, as well as most cathodes. Therefore, the electrode could be used to the printable cathode of low-voltage high-energy-density lithium batteries.

Vanadium-Based Materials: Next Generation Electrodes Powering the Battery Revolution?

ConspectusAs the world transitions away from fossil fuels, energy storage, especially rechargeable batteries, could have a big role to play. Though rechargeable batteries have dramatically changed the energy landscape, their performance metrics still need to be further enhanced to keep pace with the changing consumer preferences along with the increasing demands from the market. For the most part, advances in battery technology rely on the continuing development of materials science, where the development of high-performance electrode materials helps to expand the world of battery innovation by pushing the limits of performance of existing batteries. This is where vanadium-based compounds (V-compounds) with intriguing properties can fit in to fill the gap of the current battery technologies.The history of experimenting with V-compounds (i.e., vanadium oxides, vanadates, vanadium-based NASICON) in various battery systems, ranging from monovalent-ion to multivalent-ion batteries, stretches back decades. They are fascinating materials that display rich redox chemistry arising from multiple valency and coordination geometries. Over the years, researchers have made use of the inherent ability of vanadium that undergoes metamorphosis between different coordination polyhedra accompanied by transitions in the oxidation state for reversible intercalation/insertion of more than one guest ions without breaking the structure apart. Such infinitely variable properties endow them with a wide range of electronic and crystallographic structures. The former attribute varies from insulators to metallic conductors while the latter feature gives rise to layered structures or 3D open tunnel frameworks that allow facile movement of a wide range of metal cations and guest species along the gallery. Accompanied by a growing stringent requirements for energy storage applications, most V-compounds face difficulty in resolving the problems of their own lack competitiveness mostly due to their intrinsically low ionic/electronic conductivity. The key to producing vanadium-based electrodes with the desired performance characteristics is the ability to fabricate and optimize them consistently to realize certain specifications through effective engineering strategies for property modulation.In this Account, we aim to provide a comprehensive article that correlates the fundamental of charge storage mechanism to crystallographic forms and design principle for V-compounds. More importantly, the essential roles played by engineering strategies in the property modulation of V-compounds are pinpointed to further explain the rationale behind their anomalous behavior. Apart from that, we further summarize the key theoretical and experimental results of some representative examples for tuning of properties. On the other hand, advances in characterization techniques are now sufficiently mature that they can be relied upon to understand the reaction mechanism of V-compounds by tracing real-time transformation and structural changes at the atomic scale during their working state. The mechanistic insights covered in this Account could be used as a fundamental guidance for several key strategies in electrode materials design in terms of dimension, morphology, composition, and architecture that govern the rate and degree of chemical reaction.

Fiber-Shape Na3V2(PO4)2F3@N-Doped Carbon as a Cathode Material with Enhanced Cycling Stability for Na-Ion Batteries

To overcome intrinsic low electronic conductance, delicately designed fiber-shape Na₃V₂(PO₄)₂F₃@N-doped carbon composites (NVPF@C) have been prepared for boosting Na-storage performance. This distinctive interlinked three-dimensional network structure can effectively facilitate electron/Na-ion transportation by decreasing the NVPF particle size to shorten the ionic diffusion paths and introducing a conducting N-doping carbon scaffold to improve electronic conductivity. Benefiting from the favorable structural design and fascinating reaction kinetics, the modified NVPF@C material demonstrates superior sodium-storage performance with 109.5 mAh g^-1 high reversible capacity at a moderate current of 0.1 C, excellent rate tolerance of 78.9 mAh g^-1 at a high rate of 30 C, and gratifying long-term cyclability (87.8% capacity retention after 1000 cycles at 20 C; 83.4% capacity retention after 1500 round trips at a ultrahigh rate of 50 C). The fascinating electrochemical performance remains stable when NVPF@C was examined as the cathode material for a full cell, suggesting the fiber-shape NVPF@C as one of the most promising applicable materials for sodium-ion batteries. Moreover, the approach of the three-dimensional conductive network by electrospinning is proposed as a strategy of efficiency and promising prospect to enhance the electrochemical property of other materials for sodium-ion batteries.

Superior Li-ion storage of VS4 nanowires anchored on reduced graphene

Research on VS4 is lagging due to the difficulty in its tailored synthesis. Herein, unique architecture design of one-dimensional VS4 nanowires anchored on reduced graphene oxide is demonstrated via a facile solvothermal synthesis. Different amounts of reduced graphene oxide with VS4 are synthesized and compared regarding their rate capability and cycling stability. Among them, VS4 nanowires@15 wt% reduced graphene oxide present the best electrochemical performance. The superior performance is attributed to the optimal amount of reduced graphene oxide and one-dimensional VS4 nanowires based on (i) the large surface area that could accommodate volume changes, (ii) enhanced accessibility of the electrolyte, and (iii) improvement in electrical conductivity. In addition, kinetic parameters derived from electrochemical impedance spectroscopy spectra and sweep rate dependent cyclic voltammetry curves such as charge transfer resistances and Li+ ion apparent diffusion coefficients both support this claim. The diffusion coefficient is calculated to be 1.694 × 10-12 cm2 s-1 for VS4 nanowires/15 wt% reduced graphene oxide, highest among all samples.

Boosting the Deep Discharging/Charging Lithium Storage Performances of Li3VO4 through Double-Carbon Decoration

With high theoretical capacity, good ionic conductivity, and suitable working plateaus, Li₃VO₄ has emerged as an eye-catching intercalation anode material for lithium storage. However, Li₃VO₄ suffers from poor electrical conductivity and 20% volume variation under deep discharging/charging conditions. Herein, we present a "double-carbon decoration" strategy to tackle both issues. Deflated balloon-like Li₃VO₄/C/reduced graphene oxide (LVO/C/rGO) microspheres with continuous electron transport pathways and sufficient free space for volume change accommodation are fabricated through a facile spray-drying method. Under deep discharging/charging conditions (0.02-3.0 V), LVO/C/rGO achieves a high intercalation capacity of 591 mA h g^-1. With high capacity and outstanding stability, LVO/C/rGO outperforms other intercalation anode materials (such as graphite, Li₄Ti₅O₁₂, and TiO₂). In situ X-ray diffraction measurement reveals that the lithium storage is realized through both solid-solution reaction and two-phase reaction mechanisms. A LVO/C/rGO//LiNi_0.8Co_0.15Al_0.05O₂ lithium-ion full cell is also assembled. In such full cell, LVO/C/rGO also demonstrates high specific capacity and excellent cycling stability. The above results manifest that the LVO/C/rGO anode has the potential to be applied in the next-generation high-performance lithium-ion batteries.

High-Crystallinity Urchin-like VS4 Anode for High-Performance Lithium-Ion Storage

VS₄ anode materials with controllable morphologies from hierarchical microflower, octopus-like structure, seagrass-like structure to urchin-like structure have been successfully synthesized by a facile solvothermal synthesis approach using different alcohols as solvents. Their structures and electrochemical properties with various morphologies are systematically investigated, and the structure-property relationship is established. Experimental results reveal that Li⁺ ion storage behavior in VS₄ significantly depends on physical features such as the morphology, crystallite size, and specific surface area. According to this study, electrochemical performance degrades on the order of urchin-like VS₄ > octopus-like VS₄ > seagrass-like VS₄ > flower-like VS₄. Among them, urchin-like VS₄ demonstrates the best electrochemical performance benefiting from its peculiar structure which possesses large surface area that accommodates the volume change to a certain extent, and single-crystal thorns that provide fast electron transportation. Kinetic parameters derived from EIS spectra and sweep-rate-dependent CV curves, such as charge-transfer resistances, Li⁺ ion apparent diffusion coefficients and stored charge ratio of capacitive and intercalation contributions, both support this claim well. In addition, the EIS measurement was conducted during the first discharge/charge process to study the solid electrolyte interface (SEI) formation on urchin-like VS₄ and kinetics behavior of Li⁺ ion diffusion. A better fundamental understanding on Li⁺ storage behavior in VS₄ is promoted, which is applicable to other vanadium-based materials as well. This study also provides invaluable guidance for morphology-controlled synthesis tailored for optimal electrochemical performance.

Multidimensional Synergistic Nanoarchitecture Exhibiting Highly Stable and Ultrafast Sodium-Ion Storage

Conversion-type anodes with multielectron reactions are beneficial for achieving a high capacity in sodium-ion batteries. Enhancing the electron/ion conductivity and structural stability are two key challenges in the development of high-performance sodium storage. Herein, a novel multidimensionally assembled nanoarchitecture is presented, which consists of V₂ O₃ nanoparticles embedded in amorphous carbon nanotubes that are then coassembled within a reduced graphene oxide (rGO) network, this materials is denoted V₂ O₃ ⊂C-NTs⊂rGO. The selective insertion and multiphase conversion mechanism of V₂ O₃ in sodium-ion storage is systematically demonstrated for the first time. Importantly, the naturally integrated advantages of each subunit synergistically provide a robust structure and rapid electron/ion transport, as confirmed by in situ and ex situ transmission electron microscopy experiments and kinetic analysis. Benefiting from the synergistic effects, the V₂ O₃ ⊂C-NTs⊂rGO anode delivers an ultralong cycle life (72.3% at 5 A g^-1 after 15 000 cycles) and an ultrahigh rate capability (165 mAh g^-1 at 20 A g^-1 , ≈30 s per charge/discharge). The synergistic design of the multidimensionally assembled nanoarchitecture produces superior advantages in energy storage.

Smart Construction of Integrated CNTs/Li4Ti5O12 Core/Shell Arrays with Superior High-Rate Performance for Application in Lithium-Ion Batteries

Exploring advanced high-rate anodes is of great importance for the development of next-generation high-power lithium-ion batteries (LIBs). Here, novel carbon nanotubes (CNTs)/Li₄Ti₅O₁₂ (LTO) core/shell arrays on carbon cloth (CC) as integrated high-quality anode are constructed via a facile combined chemical vapor deposition-atomic layer deposition (ALD) method. ALD-synthesized LTO is strongly anchored on the CNTs' skeleton forming core/shell structures with diameters of 70-80 nm the combined advantages including highly conductive network, large surface area, and strong adhesion are obtained in the CC-LTO@CNTs core/shell arrays. The electrochemical performance of the CC-CNTs/LTO electrode is completely studied as the anode of LIBs and it shows noticeable high-rate capability (a capacity of 169 mA h g^-1 at 1 C and 112 mA h g^-1 at 20 C), as well as a stable cycle life with a capacity retention of 86% after 5000 cycles at 10 C, which is much better than the CC-LTO counterpart. Meanwhile, excellent cycling stability is also demonstrated for the full cell with LiFePO₄ cathode and CC-CNTs/LTO anode (87% capacity retention after 1500 cycles at 10 C). These positive features suggest their promising application in high-power energy storage areas.

A ZnS nanocrystal/reduced graphene oxide composite anode with enhanced electrochemical performances for lithium-ion batteries

A simple route for the preparation of ZnS nanocrystal/reduced graphene oxide (ZnS/RGO) by a hydrothermal synthesis process was achieved. The chemical composition, morphology, and structural characterization reveal that the ZnS/RGO composite is composed of sphalerite-phased ZnS nanocrystals uniformly dispersed on functional RGO sheets with a high specific surface area. The ZnS/RGO composite was utilized as an anode in the construction of a high-performance lithium-ion battery. The ZnS/RGO composite with appropriate RGO content exhibits a high reversible specific capacity (780 mA h g^-1), excellent cycle stability over 100 cycles (71.3% retention), and good rate performance at 2C (51.2% of its capacity when measured at a 0.1C rate). To further investigate this ZnS/RGO anode for practical use in full Li-ion cells, we tested the electrochemical performance of the ZnS/RGO anode at different cut-off voltages for the first time. The presence of RGO plays an important role in providing high conductivity as well as a substrate with a high surface area. This helps alleviate the typically problems associated with volume expansion and shrinkage during prolonged cycling. Additionally, the RGO provides multiple nucleation points that result in a uniformly dispersed film of nanosized ZnS that covers its surface. Thus, the high surface area RGO enables high electronic conductivity and fast charge transfer kinetics for ZnS lithiation/delithiation.

Constructing Li3VO4 nanoparticles anchored on crumpled reduced graphene oxide for high-power lithium-ion batteries

Li₃VO₄ is considered to be one of the most promising anode materials for lithium-ion batteries (LIBs) because of its outstanding safety performance and energy density.

Optimization of Rate Capability and Cyclability Performance in Li3 VO4 Anode Material through Ca Doping

A series of Ca-doped lithium vanadates Li_3-x Ca_x VO₄ (x=0, 0.01, 0.03, and 0.05) are synthesized successfully through a simple sol-gel method. XRD patterns and energy-dispersive X-ray spectroscopy (EDS) mappings reveal that the doped Ca²⁺ ions enter into the lattice successfully and are distributed uniformly throughout the Li₃ VO₄ (LVO) grains. XRD spectra and SEM images show that Ca doping can lead to an enlarged lattice and refined Li₃ VO₄ particles. A small quantity of V ions will transfer from V⁵⁺ to V⁴⁺ in the Ca-doped samples, as demonstrated by the X-ray photoelectron spectroscopy (XPS) analysis, which leads to an increase of an order of magnitude in the electronic conductivity. Improved rate capability and cycling stability are observed for the Ca-doped samples, and Li_2.97 Ca_0.03 VO₄ exhibits the best electrochemical performance among the studied materials. The initial charge/discharge capacities at 0.1 C increase from 480/645 to 527/702 mA h g^-1 as x varies from 0 to 0.03. The charge capacity of Li_2.97 Ca_0.03 VO₄ at 1 C retains 95.3 % of its initial value after 180 cycles, whereas the capacity retention is only 40 % for the pristine sample. Moreover, Li_2.97 Ca_0.03 VO₄ maintains a high discharge capacity of 301.7 mA h g^-1 at a high discharge rate (4 C), whereas the corresponding value is only 95.2 mA h g^-1 for the pristine LVO sample. The enhanced cycling and rate performances are ascribed to the increased lithium ion diffusivity and electrical conductivity induced by Ca doping.

Peapod-like Li3 VO4 /N-Doped Carbon Nanowires with Pseudocapacitive Properties as Advanced Materials for High-Energy Lithium-Ion Capacitors

Lithium ion capacitors are new energy storage devices combining the complementary features of both electric double-layer capacitors and lithium ion batteries. A key limitation to this technology is the kinetic imbalance between the Faradaic insertion electrode and capacitive electrode. Here, we demonstrate that the Li₃ VO₄ with low Li-ion insertion voltage and fast kinetics can be favorably used for lithium ion capacitors. N-doped carbon-encapsulated Li₃ VO₄ nanowires are synthesized through a morphology-inheritance route, displaying a low insertion voltage between 0.2 and 1.0 V, a high reversible capacity of ≈400 mAh g^-1 at 0.1 A g^-1 , excellent rate capability, and long-term cycling stability. Benefiting from the small nanoparticles, low energy diffusion barrier and highly localized charge-transfer, the Li₃ VO₄ /N-doped carbon nanowires exhibit a high-rate pseudocapacitive behavior. A lithium ion capacitor device based on these Li₃ VO₄ /N-doped carbon nanowires delivers a high energy density of 136.4 Wh kg^-1 at a power density of 532 W kg^-1 , revealing the potential for application in high-performance and long life energy storage devices.

Metal–organic framework derived carbon-confined Ni2P nanocrystals supported on graphene for an efficient oxygen evolution reaction

Metal–organic framework derived carbon-confined Ni₂P nanocrystals supported on graphene with high effective surface area, more exposed active sites, and enhanced charge transport were successfully designed.

Symmetric Electrodes for Electrochemical Energy-Storage Devices

Increasing environmental problems and energy challenges have so far attracted urgent demand for developing green and efficient energy-storage systems. Among various energy-storage technologies, sodium-ion batteries (SIBs), electrochemical capacitors (ECs) and especially the already commercialized lithium-ion batteries (LIBs) are playing very important roles in the portable electronic devices or the next-generation electric vehicles. Therefore, the research for finding new electrode materials with reduced cost, improved safety, and high-energy density in these energy storage systems has been an important way to satisfy the ever-growing demands. Symmetric electrodes have recently become a research focus because they employ the same active materials as both the cathode and anode in the same energy-storage system, leading to the reduced manufacturing cost and simplified fabrication process. Most importantly, this feature also endows the symmetric energy-storage system with improved safety, longer lifetime, and ability of charging in both directions. In this Progress Report, we provide the comprehensive summary and comment on different symmetric electrodes and focus on the research about the applications of symmetric electrodes in different energy-storage systems, such as the above mentioned SIBs, ECs and LIBs. Further considerations on the possibility of mass production have also been presented.

Enhanced Electrochemical Performance of Ultracentrifugation-Derived nc-Li3VO4/MWCNT Composites for Hybrid Supercapacitors

Nanocrystalline Li3VO4 dispersed within multiwalled carbon nanotubes (MWCNTs) was prepared using an ultracentrifugation (uc) process and electrochemically characterized in Li-containing electrolyte. When charged and discharged down to 0.1 V vs Li, the material reached 330 mAh g(-1) (per composite) at an average voltage of about 1.0 V vs Li, with more than 50% capacity retention at a high current density of 20 A g(-1). This current corresponds to a nearly 500C rate (7.2 s) for a porous carbon electrode normally used in electric double-layer capacitor devices (1C = 40 mA g(-1) per activated carbon). The irreversible structure transformation during the first lithiation, assimilated as an activation process, was elucidated by careful investigation of in operando X-ray diffraction and X-ray absorption fine structure measurements. The activation process switches the reaction mechanism from a slow "two-phase" to a fast "solid-solution" in a limited voltage range (2.5-0.76 V vs Li), still keeping the capacity as high as 115 mAh g(-1) (per composite). The uc-Li3VO4 composite operated in this potential range after the activation process allows fast Li(+) intercalation/deintercalation with a small voltage hysteresis, leading to higher energy efficiency. It offers a promising alternative to replace high-rate Li4Ti5O12 electrodes in hybrid supercapacitor applications.