A new lithium-rich layer-structured cathode material with improved electrochemical performance and voltage maintenance

Lithium-rich layered oxides (LRLOs) are highly attractive cathode materials for next-generation lithium-ion batteries because of their high reversible capacity, but poor cycle performance and voltage decay are two main problems that strongly limit their practical applications. These challenges also apply to the Ru-based LRLOs of Li₂RuO₃. The Li₂RuO₃ cathode material is highly attractive because of their high conductivity and favourable electrochemical reaction kinetics. To overcome the problems associated with Li₂RuO₃, in contrast to normal single atom doping, here, we propose a Na, Cr co-doping strategy with the design of Li_2−xNa_xRu_0.95Cr_0.05O₃ (x = 0, 0.02, 0.06, and 0.1) series materials. Cr doping increases capacity, and Na doping suppresses voltage decay. As a result, the discharge capacity of the optimal Li_1.98Na_0.02Ru_0.95Cr_0.05O₃ sample over 240 mAh/g after 50 charge-discharge cycles at 0.2 C is maintained, and the capacity retention reaches a value of 80.5% compared with 69.1% for the undoped Li₂RuO₃. The value of the voltage decay in the Li_1.98Na_0.02Ru_0.95Cr_0.05O₃ sample is 125 mV after 100 cycles at a rate of 1 C, and the voltage decay is 188.4 mV for the undoped Li₂RuO₃. This finding will expand the scope for designing novel layered electrodes with excellent performance.