High performance (1 − x)LiMnPO4·xLi3V2(PO4)3/C composite cathode materials prepared by a sol–gel method

Abstract

A series of (1 − x)LiMnPO₄·xLi₃V₂(PO₄)₃/C (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) composite nanoparticles are synthesized as cathode materials for lithium-ion batteries by the sol–gel method, using N,N-dimethyl formamide as a dispersing agent. The structure and morphology of the as-prepared materials are analyzed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The materials exhibit good crystallinity and a grain size of about 20–100 nm. The 0.5LiMnPO₄·0.5Li₃V₂(PO₄)₃/C composite delivers the best initial specific discharge capacity of 150.5 mA h g⁻¹ at 0.05C in the voltage range of 2.5–4.4 V, and it exhibits excellent reversible capacities of 150.5, 135.1, 127.0, 122.5 and 115.7 mA h g⁻¹ at charge–discharge rates of 0.05, 0.1, 0.2, 0.5, and 1C, respectively. Finally, 0.5LiMnPO₄·0.5Li₃V₂(PO₄)₃/C retained 142.9 mA h g⁻¹ (95%) of the initial specific discharge capacity after 50 cycles, demonstrating excellent cyclability. Compared with the LiMnPO₄/C, its rate capability and cycle performance are both remarkably improved.