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Wadsley–Roth phased niobates are promising anode materials for lithium‐ion batteries, while their inherently low electrical conductivity still limits their rate‐capability. Herein, a novel doped Mo1.5W1.5Nb14O44 (MWNO) material is facilely prepared via an ionothermal‐synthesis‐assisted doping strategy. The detailed crystal structure of MWNO is characterized by neutron powder diffraction and aberration corrected scanning transmission electron microscope, unveiling the full occupation of Mo6+‐dopant at the t1 tetrahedral site. In half‐cells, MWNO exhibits enhanced fast‐rechargeability. The origin of the improved performance is investigated by ultraviolet–visible diffuse reflectance spectroscopy, density functional theory (DFT) computation, and electrochemical impedance spectroscopy, revealing that bandgap narrowing improves the electrical conductivity of MWNO. Furthermore, operando X‐ray diffraction elucidates that MWNO exhibits a typical solid‐solution phase conversion‐based lithium‐ion insertion/extraction mechanism with reversible structural evolution during the electrochemical reaction. The boosted lithium‐ion diffusivity of MWNO, due to the Mo6+/W6+ doping effect, is confirmed by a galvanostatic intermittent titration technique and DFT. With the simultaneously enhanced electrical conductivity and lithium‐ion diffusivity, MWNO successfully demonstrates its fast‐rechargeability and practicality in the LiNi0.5Mn1.5O4‐coupled full‐cells. Therefore, this work illustrates the potential of ionothermal synthesis in energy storage materials and provides a mechanistic understanding of the doping effect on improving material's electrochemical performance. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs)‐based anode materials of high theoretical capacities have been intensively studied for lithium‐ion storage. However, their poor high‐rate capability and cycling stability remain to be effectively resolved. Herein, a novel ion exchange (IE)‐assisted indirect carbon coating strategy is proposed to realize high performance freestanding TMO‐based anodes for flexible lithium‐ion batteries (FLIBs). This approach effectively avoids the possible side reaction of oxide reduction, enhances degrees of graphitization of the carbon coating, and preserves advantageous nanostructure of the starting template, leading to enhanced electrical conductivities, alleviated volume variation induced structural instability, fast lithium‐ion diffusion pathways and enhanced electron transfer kinetics. As a proof of concept, IE‐prepared carbon coated NiO nanosheet arrays with excellent structural and electrochemical stability are developed as freestanding anodes for LIBs and FLIBs, which exhibit outstanding electrochemical performances superior to most state‐of‐the‐art NiO‐based anodes reported in recent years. The product anode delivers a high areal capacity (3.08 mAh cm−2 at 0.25 mA cm−2), outstanding high‐rate capability (1.78 mAh cm−2 at 8 mA cm−2) and excellent cycling stability (over 300 cycles). Further pouch cell tests confirm the excellent flexibility of the freestanding electrode against mechanical deformation with well‐maintained electrochemical performance under folding. [ABSTRACT FROM AUTHOR]

Transition metal fluorides as Li-free conversion-type cathode materials have high theoretical specific capacities, however, their preparation strategy, sluggish electrochemical kinetic and poor cyclability have impeded their wide adoption in lithium-ion batteries. Herein, a facile in-situ synthesis of porous metal-fluoride-carbon composites is accomplished via simultaneous polytetrafluorethylene-based hard template etching and metal fluorination. This not only facilitates fast electron transfer and lithium-ion diffusion kinetics, but also buffers severe volume fluctuation during lithiation/delithation and enables the formation of a uniform and thin Li 2 CO 3 /LiF-rich cathode-electrolyte interphase. As a proof of concept, the as-prepared porous FeF 3 @C (p-FeF 3 @C) indeed exhibits a high specific capacity of 230 mAh g−1 at 0.1 C together with an excellent capacity retention of 92.5% at 1 C for 200-cycles. Moreover, the practicality of the strategy is demonstrated by the superb electrochemical performance of the full-cells coupled with pre-lithiated graphite anodes. Therefore, the proposed novel synthetic strategy will enlighten the future design of high-performance metal-fluoride-carbon composites with porous structure for energy storage applications. [Display omitted] • Porous iron-fluoride-carbon composites (p-FeF 3 @C) is synthesized via simultaneous polytetrafluorethylene-based hard template etching and metal fluorination. • A uniform and thin Li 2 CO 3 /LiF-rich cathode-electrolyte interphase can be formed on the p-FeF 3 @C. • p-FeF 3 @C exhibits a high specific capacity of 230 mAh g−1 at 0.1 C and a high capacity retention of 92.5% at 1 C for 200-cycles. • Full-cell of p-FeF 3 @C with pre-lithiated graphite anodes exhibits superb electrochemical performance. [ABSTRACT FROM AUTHOR]

• A novel NaCl-based solvent-free method is developed to synthesis high entropy oxides. • NaCl is employed as a hard template with spatial confinement effect. • NPHEO delivers a high reversible specific capacity of 1143.6 mAh/g at 0.2 A/g. • NPHEO can stably cycle over 600 cycles at 1 A/g with a capacity retention of 71.8%. High-entropy oxide (HEO) is a promising anode material for lithium-ion battery (LIB) due to the synergistic effect of various metal species. Conventional HEO preparations typically involve a solid-state route or liquid-phase mixing followed by high-temperature calcination, leading to either a small surface area or environmental contamination. Herein, a novel, facile solvent-free preparation of HEOs is introduced, applying inert salt, NaCl, as an easily removable, eco-friendly and recyclable template. This approach realizes high-purity porous HEO (NPHEO) with specific surface area (28.1 m2 g−1) for high-performance lithium-ion batteries. With the enhanced electrochemical kinetics, the NPHEO anodes deliver a high reversible specific capacities of 1143.6 at 0.2 A/g. In addition, the NPHEO-based cells exhibit a desirable rate capability of 315.7 mAh/g at 5 A/g. At 1 A/g the cell delivers a good cyclability of 71.8 % capacity retention over 600 cycles, corresponding to an average coulombic efficiency of above 99.94 % per cycle. Ex-situ X-ray diffraction and in-situ electrochemical impedance spectroscopy experiments further probe the structural evolution and electrochemical behavior during lithiation/delithiation, confirming the structural stability and fast electrochemical kinetics of NPHEO. The proposed advanced synthesis approach offers a new platform for the preparation of HEOs with high quality. [ABSTRACT FROM AUTHOR]

Li 4-x Mg x Ti 5 O 12 (0 ≦ X ≦ 0.2) anode material was synthesized by a solid-state method using Li 2 CO 3 , MgO and anatase TiO 2 . The effects of Mg element doping on the crystal structure, phase composition, morphology and electrochemical properties of Li 4-x Mg x Ti 5 O 12 were investigated by XRD, SEM and EDX. The electrochemical properties of Li 4-x Mg x Ti 5 O 12 were characterized through Cyclic voltammetry and AC impedance experiments. The results indicated that when x = 0.10, the resultants show better electrochemical performance in higher rates cycle stability and the polarization degree. The initial discharge capacity reaches 122.5 mAh/g at 2 C, and the discharge capacity still remains 119.3 mAh/g after 100 cycles. [ABSTRACT FROM AUTHOR]

• The electrochemical property of Li 4 T 5 O 12 electrode can be improved by mixing liquid metal alloy. • The LM-LTO electrode exhibits superior rate and cycling performance. • LM is beneficial to the conductivity improvement of composite electrode. The spinel lithium titanate (Li 4 Ti 5 O 12 , LTO) has attracted special attention for its low cost, stable structure and little safety issue. However, LTO displays a low electronic conductivity, which seriously impedes its practical applications at remarkable rate capability. Herein, to improve the electrochemical properties of LTO, this research constructed a novel composite anode by mixing the GaSn liquid metal (LM) nanoparticles with LTO. The composite anode's phase structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical data indicate that LM-LTO electrode delivers a better rate capability (52% retention from 10 mA/g to 500 mA/g) as well as long cyclic stability (76% retention after 1000 cycles at 200 mA/g). Therefore, this work opens a new avenue for fabricating better rate performance and safer lithium ions battery. [ABSTRACT FROM AUTHOR]