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Polymer-based solid electrolytes have been extensively studied for solid-state lithium metal batteries to achieve high energy density and reliable security. But, its practical application is severely limited by low ionic conductivity and slow Li+ transference. Herein, based on the "binary electrolytes" of poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) and lithium salt (LiTFSI), a kind of eutectogel hybrid electrolytes (EHEs) with high Li+ transference number was developed via tuning the spontaneous coupling of charge and vacated space generated by Li-cation diffusion utilizing the Li6.4La3Zr1.4Ta0.6O12 (LLZTO) dopant. LLZTO doping promotes the dissociation of lithium salt, increases Li+ carrier density, and boosts ion jumping and the coordination/decoupling reactions of Li+. As a result, the optimized EHEs-10% possess a high Li-transference number of 0.86 and a high Li+ conductivity of 3.2×10−4 S·cm−1 at room temperature. Moreover, the prepared EHEs-10% composite solid electrolyte presents excellent lithiumphilic and compatibility, and can be tested stably for 1,200 h at 0.3 mA·cm−2 with assembled lithium symmetric batteries. Likewise, the EHEs-10% films match well with high-loading LiFePO4 and LiCoO2 cathodes (> 10 mg·cm−2) and exhibit remarkable interface stability. Particularly, the LiFePO4//EHEs-10%//Li and LiCoO2//EHEs-10%//Li cells deliver high rate performance of 118 mA·hg−1 at 1 C and 93.7 mAh·g−1 at 2 C with coulombic efficiency of 99.3% and 98.1%, respectively. This work provides an in-depth understanding and new insights into our design for polymer electrolytes with fast Li+ diffusion. [ABSTRACT FROM AUTHOR]

As recently explored lithium-ion battery (LIB) anode materials, transition metal vanadates have attracted much attention due to their excellent electrochemical performance. In this work, we successfully synthesized solid Co3V2O8 microspheres (sCVO MSs) via a facile and controllable hydrothermal reaction, and the magical formation mechanism was also revealed by the different morphologies of sCVO MSs at different reaction times. When tested as LIB anode materials, sCVO MSs showed superior reversible capacities (∼780 mA h g−1 after 250 cycles at 1000 mA g−1 and as high as 550 mA h g−1 even after 400 cycles at 5000 mA g−1) and excellent rate performance (a capacity of ∼500 mA h g−1 at a current density of 2000 mA g−1). It is accordingly demonstrated that uniform sCVO MSs have great potential to be used as high-performance LIB anodes. [ABSTRACT FROM AUTHOR]

Transition metal vanadates have attracted much attention for high capacity anodes of lithium ion batteries (LIBs). However, they have obvious drawbacks (short cycle-lives and low rate performance) because of the intrinsically low electronic conductivity and serious volume variation during Li-ion desorption and insertion. In particular, pure Co3V2O8 micro-pencils (pCVO MPs) have a stable and regular crystal structure, large tap density and uniform grain size, but, unfortunately, they have not exhibited expected electrochemical performance. Herein, we report the successful preparation of reduced graphene oxide coated Co3V2O8 micro-pencils (rGO@CVO MPs) through a facile approach combining hydrothermal synthesis with thermal reduction. When tested as anodes for LIBs, rGO@CVO MPs exhibit superior electrochemical performance compared to that of pure Co3V2O8 micro-pencils (pCVO MPs). The anodes of rGO@CVO MPs show a high reversible capacity of 760 mA h g−1 over 200 cycles at 200 mA g−1, and 500 mA h g−1 can remain after 500 cycles at 1000 mA g−1, with an increase in 200 mA h g−1 in contrast to the pCVO MPs. It is consequently demonstrated that the composite material (rGO@CVO MPs) is a promising anode material for LIBs. [ABSTRACT FROM AUTHOR]

Si nanoparticle (Si-NP) composite anode with high rate and long cycle life is an attractive anode material for lithium-ion battery (LIB) in hybrid electric vehicle (HEV)/pure electric vehicle (PEV). In this work, a carbon nanotube (CNT)/reduced graphene oxide (rGO)/Si nanoparticle composite with alternated structure as Li-ion battery anode is prepared. In this structure, rGO completely wraps the entire Si/CNT networks by different layers and CNT networks provide fast electron transport pathways with reduced solid-state diffusion, so that the stable solid-electrolyte interphase layer can form on the whole surface of the matrix instead of on single Si nanoparticle, which ensure the high cycle stability to achieve the excellent cycle performance. As a result, the CNT/rGO/Si-NP anode exhibits high performances with long cycle life (≈455 mAh g−1 at 15 A g−1 after 2000 cycles), high specific charge capacity (≈2250 mAh g−1 at 0.2 A g−1, ≈650 mAh g−1 at 15 A g−1), and fast charge/discharge rates (up to 16 A g−1). This nanostructure anode with facile and low-cost synthesis method, as well as excellent electrochemical performances, makes it attractive for the long life cycles at high rate of the next generation LIB applications in HEV/PEV. [ABSTRACT FROM AUTHOR]

Abstract In the past four years, transition metal vanadates have received booming attention as anode materials for lithium ion batteries (LIBs) due to their outstanding specific capacities, decent cycling performance and superior rate properties. Among them, Co 3 V 2 O 8 is the most reported species. However the cobalt is expensive, thus the replacement of cobalt would be a favorable route. So far, mixed vanadates have been rarely reported because of the remarkable difficulty in fabrication, among which cobalt/nickel mixed vanadates are the most attractive. In this work, a facile and green hydrothermal method with organic linker has been developed, to achieve modulated cobalt/nickel mixtures. It was corroborated by the X-ray diffraction (XRD) patterns and cyclic voltammetry (CV) profiles that single phase of cubic Co 3 V 2 O 8 crystal structures were formed. The mixed vanadates demonstrated ultrahigh reversible capacity of over ∼1800 mAh/g at the current density of 0.2 A/g after ∼200 cycles and superb rate capability of ∼600 mAh/g at 4 A/g. The enhanced electrochemical performances of the higher-nickel-ratio indicated their considerable potential as high-capacity anode materials in LIBs. Graphical abstract Image 1 Highlights • Cobalt/nickel mixed vanadates were obtained via one-step and green hydrothermal process. • The mixed vanadates maintain the cubic crystal of Co 3 V 2 O 8 with nickel doping. • Higher concentration of doped nickel induced uniform nanoparticles smaller than 100 nm. • CoNi 2 V 2 O 8 delivered reversible capacity of 1800 mAh/g at 0.2 A/g and 600 mAh/g at 4 A/g. [ABSTRACT FROM AUTHOR]

Cobalt vanadates have been demonstrated as superior anode candidates for lithium ion batteries (LIBs) owing to their unique advantages, such as superb specific capacity, low operating potential, and excellent cycling stability. Among the cobalt vanadates, Co 3 V 2 O 8 manifests tremendous potential of commercialization because of their controllable particle size and morphology. In this study, we readily synthesized both hollow and solid Co 3 V 2 O 8 micro-pencils and thoroughly compared their electrochemical properties. Employed as anode for LIBs, the hollow Co 3 V 2 O 8 exhibited much higher initial specific capacity than the solid ones (∼1200 mAhg −1 vs. ∼680 mAhg −1 ). When tested at 1000 mAg −1 , the hollow Co 3 V 2 O 8 displayed superior reversible capacity over the solid ones (∼650 mAhg −1 vs. ∼450 mAhg −1 after 300 cycles), benefiting from the hollow architecture. Moreover, the hollow micro-pencils showed better rate performance, with outstanding stability and capacity loss when higher current density was applied. The comparative study demonstrated the hollow Co 3 V 2 O 8 is more efficient than the solid ones for LIB anodes. Based on the comparison on pure micro-pencils, further approach (e.g. graphene coating) can be exploited for superior performance towards ultimate application in lithium-ion batteries. [ABSTRACT FROM AUTHOR]