Study of spherical Li_1.2-xNa_xMn_0.534Ni_0.133Co_0.133O₂ cathode based on dual Li⁺/Na⁺ transport system for Li-ion batteries

The Na-doped layered Li_1.2-xNa_xMn_0.534Ni_0.133Co_0.133O₂ (x = 0, 0.05, 0.1 and 0.15) cathode materials with porous spherical structure for lithium-ion batteries have been successfully prepared via a facile co-precipitation method. The dual Li⁺/Na⁺ transport system is Li_1.2-xNa_xMn_0.534Ni_0.133Co_0.133O₂ cathode materials companying with dual Li⁺/Na⁺ electrolyte, which exhibits an improved initial charge-discharge efficiency, cycling stability and rate capability, compared with pristine Li_1.2Mn_0.534Ni_0.133Co_0.133O₂. Electrochemical results verify that Li_1.1Na_0.1Mn_0.534Ni_0.133Co_0.133O₂ delivers the initial charge/discharge capacity of 329.68/277.86 mAh g⁻¹ with improved initial coulombic efficiency of 84.28% at 0.1C, and shows good cycling performance with a capacity retention of 76.5% after 100 cycles at 1C much higher than 37.9% of the pristine sample. Such outstanding performance of Li_1.2-xNa_xMn_0.534Ni_0.133Co_0.133O₂ is mainly attributed to: on the one hand, the small particle size and porous structure are helpful to increase the electrochemical active surface, shorten dual Li⁺/Na⁺ diffusion pathway, thus enhancing the energy storage properties. On the other hand, the design of dual Li⁺/Na⁺ transport system enables to enlarge interlayer, stabilize crystal structure and exert mutual diffusion or transportation of Li⁺ and Na⁺.