Nanostructured Li 3 V 2 (PO 4 ) 3 /C composite as high-rate and long-life cathode material for lithium ion batteries

Effect of Reducing Agent on Solution Synthesis of Li3V2(PO4)3 Cathode Material for Lithium Ion Batteries

In this study, Li₃V₂(PO₄)₃ (LVP) powders are prepared by a solution synthesis method. The effects of two reducing agents on crystal structure and morphology and electrochemical properties are investigated. Preliminary studies on reducing agents such as oxalic acid and citric acid, are used to reduce the vanadium (V) precursor. The oxalic acid-assisted synthesis induces smaller particles (30 nm) compared with the citric acid-assisted synthesis (70 nm). The LVP powders obtained by the oxalic acid exhibit a higher specific capacity (124 mAh g⁻¹ at 1C) and better cycling performance (122 mAh g⁻¹ following 50 cycles at 1C rate) than those for the citric acid. This is due to their higher electronic conductivity caused by carbon coating and downsizing the particles. The charge-discharge plateaus obtained from cyclic voltammetry are in good agreement with galvanostatic cycling profiles.

Synergetic effect of Na-doping and carbon coating on the electrochemical performances of Li3-x Na x V2(PO4)3/C as cathode for lithium-ion batteries

Carbon coated Li3-x Na x V2(PO4)3/C (x = 0.04, 0.06, 0.10, 0.12, 0.18) cathode materials for lithium-ion batteries were synthesized via a simple carbothermal reduction reaction route using methyl orange as the reducing agent, which also acted as the Na and carbon sources. The influence of various Na-doping levels on the structure and electrochemical performance of the Li3-x Na x V2(PO4)3/C composites was investigated. The valence state of vanadium, the form of residual carbon and the overall morphology of the Li2.90Na0.10V2(PO4)3/C, which showed the highest initial specific discharge capacity of 128 mA h g-1 at the current density of 0.1C (1C = 132 mA g-1) among this series of composites, were further examined by X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy, respectively. The results indicated that a well crystallized structure of Na-doped Li2.90Na0.10V2(PO4)3 coated by a carbon matrix is obtained. In the further electrochemical measurements, the Li2.90Na0.10V2(PO4)3/C cathode material shows superior discharge capacities of 124, 118, 113, 106 and 98 mA h g-1 at 0.3, 0.5, 1, 2 and 5C, respectively. High capacity retention of 97% was obtained after 1100 cycles in long-term cyclic performance tests at 5C. The reason for such a promising electrochemical performance of the as-prepared Li2.90Na0.10V2(PO4)3/C has also been explored, which revealed that the synergetic effect of the Na-doping and carbon coating provide enlarged Li+ diffusion channels and the increased electronic conductivity.

Nanostructured Li3 V2 (PO4 )3 Cathodes

To further increase the energy and power densities of lithium-ion batteries (LIBs), monoclinic Li₃ V₂ (PO₄ )₃ attracts much attention. However, the intrinsic low electrical conductivity (2.4 × 10^-7 S cm^-1 ) and sluggish kinetics become major drawbacks that keep Li₃ V₂ (PO₄ )₃ away from meeting its full potential in high rate performance. Recently, significant breakthroughs in electrochemical performance (e.g., rate capability and cycling stability) have been achieved by utilizing advanced nanotechnologies. The nanostructured Li₃ V₂ (PO₄ )₃ hybrid cathodes not only improve the electrical conductivity, but also provide high electrode/electrolyte contact interfaces, favorable electron and Li⁺ transport properties, and good accommodation of strain upon Li⁺ insertion/extraction. In this Review, light is shed on recent developments in the application of 0D (nanoparticles), 1D (nanowires and nanobelts), 2D (nanoplates and nanosheets), and 3D (nanospheres) Li₃ V₂ (PO₄ )₃ for high-performance LIBs, especially highlighting their synthetic strategies and promising electrochemical properties. Finally, the future prospects of nanostructured Li₃ V₂ (PO₄ )₃ cathodes are discussed.

Three-dimensional Li3V2(PO4)3/C nanowire and nanofiber hybrid membrane as a self-standing, binder-free cathode for lithium ion batteries

A three-dimensional (3D) mace-like Li₃V₂(PO₄)₃/C nanowire and nanofiber hybrid membrane was prepared for self-standing, bind-free electrodes.

Rational Design and Facial Synthesis of Li3V2(PO4)3@C Nanocomposites Using Carbon with Different Dimensions for Ultrahigh-Rate Lithium-Ion Batteries

Li3V2(PO4)3 (LVP) particles dispersed in different inorganic carbons (LVP@C) have been successfully synthesized via an in situ synthesis method. The inorganic carbon materials with different dimensions including zero-dimensional Super P (SP) nanospheres, one-dimensional carbon nanotubes (CNTs), two-dimensional graphene nanosheets, and three-dimensional graphite particles. The effects of carbon dimensions on the structure, morphology, and electrochemical performance of LVP@C composites have been systematically investigated. The carbon materials can maintain their original morphology even after oxidation (by NH4VO3) and high-temperature sintering (850 °C). LVP@CNT exhibits the best electrochemical performances among all of the samples. At an ultrahigh discharge rate of 100C, it presents a discharge capacity of 91.94 mAh g(-1) (69.13% of its theoretical capacity) and maintains 79.82% of its original capacity even after 382 cycles. Its excellent electrochemical performance makes LVP@CNT a promising cathode candidate for lithium-ion batteries.

Effects of morphology on the electrochemical performances of Li3V2(PO4)3 cathode material for lithium ion batteries

The effects of various morphologies on the electrochemical performances of Li₃V₂(PO₄)₃ (LVP) were summarized and discussed.