Design of Li2FeSiO4 cathode material for enhanced lithium-ion storage performance

The practical use of Li2FeSiO4 (LFS) is largely restricted by its inherent low electronic conductivity and slow lithium ions diffusion rate. Carbon (C) coating has been widely used to improve the electrochemical performance of LFS, but it can reduce the tap density and block lithium ion transmission. Herein, we design and synthesize the LFS/C/C/Li3PO4 composites with elaborate structure that the elemental Cu is encapsulated by LFS particles and Li3PO4 distributes both inside LFS particles and the surface carbon layer. The as-prepared samples with the unique structure depict enhanced electronic/ionic conductivities and kinetic properties due to the synergistic effect of Li3PO4 and Cu. LFS-4, which contains 2 wt% Cu and 2.42 wt% Li3PO4, exhibits the best rate performance with an average discharge specific capacity of 165.8, 142.9, 119.2, 102.1, 83.3 and 60.4 mAh g at(-1), 2, 5, 10, 20 and 40 C rate (1 C = 165.6 mA g(-1)) Over 800 cycles, a capacity of 116.2 mAh g(-1) is maintained under the high current density of 10 C with the capacity retention of 88.9%. The study indicates that the rational design of hybrid material with multi-functional engineering possesses important significance in cathode materials for lithium-ion batteries.