||Suppressing capacity fading and voltage decay of Li-rich layered cathode material by a surface nano-protective layer of CoF2 for lithium-ion batteries.
||Chong, S. K; Chen, Y. Z; Yan, W.W; Guo, S.W; Tan, Q; Wu, Y. F; Jiang, T; Liu, Y.
||Journal of Power Sources
||Li-rich layered oxides have been regarded as valuable cathode materials for high energy density lithium-ion
batteries. However, high initial irreversible capacity, bad rate capability, as well as serious capacity fading
and voltage decay hinder their commercial application. In this paper, a nano CoF2 protective layer is coated
on the surface of Li1.2Ni0.2Mn0.6O2 via a facial wet chemistry method. A high initial discharge capacity of
264.4 mAh g1 is obtained for 0.5% CoF2-coated sample and 259.1 mAh g1 for 1% CoF2-coated sample
owing to the suppression of irreversible release of O2 and the contribution of electrochemical conversion of
CoF2/LiF. Furthermore, 1% CoF2-coated sample exhibits the excellent rate capability of 167.5 mAh g1 at 5 C
rate, the superior cycling stability with the capacity retention of 241.0 mAh g1 and the ameliorative voltage
drop of 0.312 V at 0.1C after 100 cycles. The enhanced rate performance as well as stability of capacity and
voltage can be attributed to the nano coatings which inhibit the electrolyte-electrode side reaction,
enhance the electrochemical kinetics and mitigate structure transition from layered to spinel phase.