Electronic modification of NaCrO<sub>2</sub> <i>via</i> Ni<sup>2+</sup> substitution as efficient cathode for sodium-ion batteries
Jingyao Cai, Yanbing Zhu, Zhiguo Zhang, Jiandong Zhang, Liyuan Tian, Pengkun Gao, Yali Zhang, Mingkui Wang, Yan Shen
Abstract
The feature of high theoretical capacity, long thermal stability, and low-cost fabrication offers the layered transition metal oxide NaCrO2 as an excellent candidate for sodium-ion batteries. Here, we show an effective method for electronic modulation of NaCrO2 by partial substitution of Cr3+ with low-valent Ni2+ to produce NaCr0.95Ni0.05O2 as an efficient cathode for these batteries. We found that Ni2+ substitution plays a critical role in the ionic character of transition metal-oxygen bonds, which increases the interlayer separation and thus improves sodium-ion diffusion kinetics. Furthermore, Ni2+ substitution reduces the deterioration of NaCrO2 throughout charge-discharge processes and thus boosts the cycle performance of the materials. The resultant NaCr0.95Ni0.05O2 cathode displays a remarkable rate performance with specific capacities of 91.2 mAh g-1 at 50 C and a high retention (~80%) of the initial capacity after cycling for 1,000 cycles at 10 C.