Role of Na+ in the Cation Disorder of [Li1-xNax]NiO2 as a Cathode for Lithium-Ion Batteries

초록

LiNiO2 is a promising cathode material for lithium ion batteries because of its high specific capacity (approximately 220 mA h g(-1)). However, there are several challenging issues in the development of LiNiO2, including its poor cycle and rate performance because of its structural deterioration due to thermodynamically unstable Ni3+. This paper demonstrates the role of Na+ in the electrochemical performance and structural stability of [Li1-xNax]NiO2 (x = 0, 0.005, 0.01, 0.025, and 0.05). Charge disproportionation Ni3+. Ni2+ and Ni4+ in LiNiO2 increases the cation mixing of Li+ and Ni2+ during cycling, resulting in the poor cycle performance of LiNiO2. However, Na+ in [Li1-xNax]NiO2 mitigates the charge disproportionation because of the larger size of Na+ than Li+, leading to the improved structural stability of [Li1-xNax]NiO2. Consequently, Na+-doped LiNiO2 alleviates the increase in the cation mixing of Li+ and Ni2+ during cycling compared to bare LiNiO2. This results in the improved cycle performance of [Li1-xNax]NiO2 (x = 0.05), such as approximately 76% of capacity retention after 100 cycles. Moreover, the substitution of Li+ with Na+ in LiNiO2 improves the storage characteristics of [Li1-xNax]NiO2, leading to a negligible capacity loss even after long-term storage. (c) 2018 The Electrochemical Society.

키워드