The LiV3O8 Superlattice Cathode with Optimized Zinc Ion Insertion Chemistry for High Mass-Loading Aqueous Zinc-Ion Batteries.

Resolving the sluggish transport kinetics of divalent Zn2+ in the cathode lattice and improving mass-loading performance are crucial for advancing the zinc-ion batteries (AZIBs) application. Herein, PEO-LiV3O8 superlattice nanosheets (PEO-LVO) with expanded interlayer spacing (1.16 nm) are fabricated to provide a high-rate, stable lifetime, and large mass-loading cathode. The steady in-plane expansion without shrinkage after the first cycle, but reversible H+/Zn2+ co-insertion in PEO-LVO are demonstrated by operando synchrotron X-ray diffraction and ex situ characterizations. Moreover, the large capacity of PEO-LVO is traced back to the optimized Zn2+ insertion chemistry with increased Zn2+ storage ratio, which is facilitated by the interlayer PEO in lowering the Zn2+ diffusion barrier and increased number of active sites from additional interfaces, as anticipated by density functional theory. Due to the optimized ion insertion resulting in stalled interfacial byproducts and rapid kinetics, PEO-LVO achieves excellent high mass-loading performance (areal capacity up to 6.18 mAh cm-2 for freestanding electrode with 24 mg cm-2 mass-loading and 2.8 mAh cm-2 at 130 mA cm-2 for conventional electrode with 27 mg cm-2 mass-loading). As a proof-of-concept, the flexible all-solid-state fiber-shaped AZIBs with high mass-loading woven into a fabric can power an electronic watch, highlighting the application potential of PEO-LVO cathode.

High-Capacity and Long-Lifespan Aqueous LiV3O8/Zn Battery Using Zn/Li Hybrid Electrolyte.

Aqueous zinc-ion batteries (AZIBs) are promising candidates for large-scale energy storage because of their low cost and high safety. However, their practical applications are impeded by low energy density and short service life. Here, an aqueous Zn2+/Li+ hybrid-ion battery is fabricated using the LiV3O8 nanorods as the cathode, metallic Zn as the anode, and 3 M Zn(OTf)2 + 0.5 M LiOTf aqueous solution as the electrolyte. Compared with the batteries using pure 3 M Zn(OTf)2 electrolyte, the cycle performance of the hybrid-ion battery is significantly improved. After 4000 cycles at 5 A g1, the remaining capacity is 163.9 mA h g-1 with impressive capacity retention of 87.0%. Ex-situ XRD, ex-situ XPS, and SEM tests demonstrate that the hybrid electrolyte can inhibit the formation of the irreversible Zn3(OH)2V2O7·2H2O by-product and restrict Zn dendrite growth during cycling, thereby improving the cycle performance of the batteries.

CNTs/LiV3O8/Y2O3 Composites with Enhanced Electrochemical Performances as Cathode Materials for Rechargeable Solid-State Lithium Metal Batteries.

Solid-state lithium metal battery (SSLMB) is regarded as a safer energy storage system compared to the liquid one. The performance of the SSLMB depends on the cathode performance and the side reactions derived from the interface of the cathode and the electrolyte, which becomes much severe at high temperatures. Herein, we carried out a facile spray-drying route to prepare a CNTs/LiV3O8/Y2O3 (M-LVO-Y) composite. The synthesized cathode material exhibits an outstanding Li+ storage performance with a high reversible capacity of 279.9 mA h g-1 at 0.05 A g-1, excellent power capability (182.5 mA h g-1 at 2 A g-1), and a long cycle lifespan of 500 cycles with a capacity retention of 66.5% at a current density of 1 A g-1. The fabricated rechargeable solid-state Li/M-LVO-Y-2 lithium metal battery (LMB) with a poly(ethylene oxide) (PEO)-based solid polymer electrolyte (SPE) achieves a high discharge capacity of 302.1 mA h g-1 at 0.05 A g-1 and a stable cycling performance with the highest capacity of 72.1% after 100 cycles at 0.2 A g-1 and 80 °C. The above battery performance demonstrates that SSLMBs with the CNTs/LiV3O8/Y2O3 cathode and the PEO-based SPE film can provide high energy density and are suitable for applying in a high-temperature environment.

Electrochemical Behaviors of a Vapor-Phase Polymerized Conductive Polymer Coated on LiV3O8 in Li-Metal Rechargeable Batteries.

A new coating method called vapor-phase polymerization (VPP) is used to coat a conductive polymer on LiV3O8 (LVO) surfaces for the first time in lithium-metal secondary batteries to protect the interface layer and enhance the electrochemical properties of the cathode. The VPP method can be used to coat an appropriate amount of the polymer and homogeneously coat the LVO active material surfaces because of the use of vapor-phase monomers. The presence of the coating layer was confirmed by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Polymer coating of LVO by VPP results in enhanced cyclic stability and rate capability at various C-rates. At 0.2 C-rate, it has high specific capacities of 254.7 and 272.2 mA h g-1 in the first and second cycles, respectively. Further, the capacity retention is 94.6% from the 2nd cycle to the 100th cycle. The improved electrochemical performance is attributed to the homogeneously conductive polymer formed by VPP, which can improve the electrical conductivity of the active material and inhibit dissolution by preventing direct contact with the electrolyte.

LiV3O8/Polydiphenylamine Composites with Significantly Improved Electrochemical Behavior as Cathode Materials for Rechargeable Lithium Batteries.

Although LiV3O8 is regarded as a potential cathode candidate for rechargeable lithium batteries, it has been restricted by its weak dissolution and lattice structure change. Here, polydiphenylamine is successfully introduced to trigger the evolution of LiV3O8 material through an in situ oxidative polymerization method, significantly improving the electrochemical properties and inhibiting the adverse reaction. Expectedly, the 10 wt % LiV3O8/polydiphenylamine composite delivers a high initial specific discharge capacity of 311 mAh g-1, which decreases to 272 mAh g-1 after 50 cycles at the current density of 60 mA g-1. Even at a high current density of 2000 mA g-1, it still exhibited a reversible specific capacity of 125 mAh g-1 after 50 cycles. Quantitative kinetics analysis confirms the fundamental reasons for the enhanced rate capability. The ex situ X-ray diffraction and scanning electron microscopy results suggest that 10 wt % LiV3O8/polydiphenylamine composite possesses an ultrahigh structural stability during cycling.

LiV3O8/Polytriphenylamine Composites with Enhanced Electrochemical Performances as Cathode Materials for Rechargeable Lithium Batteries.

LiV3O8/polytriphenylamine composites are synthesized by a chemical oxidative polymerization process and applied as cathode materials for rechargeable lithium batteries (RLB). The structure, morphology, and electrochemical performances of the composites are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, galvanostatic discharge/charge tests, and electrochemical impedance spectroscopy. It was found that the polytriphenylamine particles were composited with LiV3O8 nanorods which acted as a protective barrier against the side reaction of LiV3O8, as well as a conductive network to reduce the reaction resistance among the LiV3O8 particles. Among the LiV3O8/polytriphenylamine composites, the 17 wt % LVO/PTPAn composite showed the largest d100 spacing. The electrochemical results showed that the 17 wt % LVO/PTPAn composite maintained a discharge capacity of 271 mAh·g-1 at a current density of 60 mA·g-1, as well as maintaining 236 mAh·g-1 at 240 mA·g-1 after 50 cycles, while the bare LiV3O8 sample retained only 169 and 148 mAh·g-1, respectively. Electrochemical impedance spectra (EIS) results implied that the 17 wt % LVO/PTPAn composite demonstrated a decreased charge transfer resistance and increased Li⁺ ion diffusion ability, therefore manifesting better rate capability and cycling performance compared to the bare LiV3O8 sample.

High Rate and Stable Li-Ion Insertion in Oxygen-Deficient LiV3O8 Nanosheets as a Cathode Material for Lithium-Ion Battery.

Low performance of cathode materials has become one of the major obstacles to the application of lithium-ion battery (LIB) in advanced portable electronic devices, hybrid electric vehicles, and electric vehicles. The present work reports a versatile oxygen-deficient LiV3O8 (D-LVO) nanosheet that was synthesized successfully via a facile oxygen-deficient hydrothermal reaction followed by thermal annealing in Ar. When used as a cathode material for LIB, the prepared D-LVO nanosheets display remarkable capacity properties at various current densities (a capacity of 335, 317, 278, 246, 209, 167, and 133 mA h g-1 at 50, 100, 200, 500, 1000, 2000, and 4000 mA g-1, respectively) and excellent lithium-ion storage stability, maintaining more than 88% of the initial reversible capacity after 200 cycles at 1000 mA g-1. The outstanding electrochemical properties are believed to arise largely from the introduction of tetravalent V (∼15% V4+) and the attendant oxygen vacancies into LiV3O8 nanosheets, leading to intrinsic electrical conductivity more than 1 order of magnitude higher and lithium-ion diffusion coefficient nearly 2 orders of magnitude higher than those of LiV3O8 without detectable V4+ (N-LVO) and thus contributing to the easy lithium-ion diffusion, rapid phase transition, and the excellent electrochemical reversibility. Furthermore, the more uniform nanostructure, as well as the larger specific surface area of D-LVO than N-LVO nanosheets may also improve the electrolyte penetration and provide more reaction sites for fast lithium-ion diffusion during the discharge/charge processes.