Improved Performance of a Ni, Co-Doped LiMn<sub>2</sub>O<sub>4</sub> Electrode for Lithium Extraction from Brine
You Wu, Pitong Shi, Yijun Zhong, Rui Cai
Abstract
Electrochemical extraction of Li + from salt lakes has the characteristics of high efficiency and low energy consumption, now becoming a research hotspot. The asymmetric lithium capacitor composed of de-lithiated Li 1– x Ni 0.025 Co 0.025 Mn 1.95 O 4 (LNCMO) and activated carbon is used as a system for electrochemical recovery of Li + . The consequence of cyclic voltammetry shows that lithium-ion diffusion is a process control step and Ni, Co doping is beneficial to improving the diffusion of lithium ions in the low-potential oxidation process and high-potential reduction process. The discharge capacity of LNCMO during a 50-cycle process is 122 mAh g –1 with a retention rate of 97.93% at 1 C, which is higher than that of the LiMn 2 O 4 (LMO)/AC system (107 mAh g –1 with a retention rate of 83.92%), proving that Ni, Co doping restrains the disproportionation reaction of LMO and increases the Li + diffusion coefficient of LMO, leading to a higher capacity and better cycle performance in brine. In 30 mM LiCl solution, the Li + extraction capacity of 1.86 mmol g –1 is obtained with an energy of 3.97 Wh mol –1 Li + under the optimal extraction conditions ( i = 0.75 mA, T = 20 min). After 15 times of Li + insertion/extraction in simulated brine/recovery solution, the purity of the recovery solution reached 94.59%, indicating that the LNCMO/activated carbon system has good selectivity for Li ions and stability.