Profiting the Co-Modifications of Li2SnO3 Coating and Sn4+ Doping in Co-Free Ni-Rich Cathode Particles for Lithium-Ion Batteries

Abstract

Layered oxides with high nickel content are advanced cathode materials for high-energy-density lithium-ion batteries but still suffer from severe voltage decay and cycling instability. Herein, a nano-Li2SnO3 coating and Sn4+-doping co-stabilized Co-free LiNi0.8Mn0.2O2 (NM-82) cathodes were synthesized through the adsorption of tin dioxide sol, followed by high-temperature calcination. Profiting from co-benefits, the electrochemical reversibility and rate capability of the NM-82 electrode have been significantly improved. Herein, the NM-82 electrode modified with 2 wt % Li2SnO3 (NM@Sn-2) achieves the largest specific capacity with remarkable capacity retention. The enhanced cycle stability is also revealed in the graphite/NM@Sn-2 soft pack battery, which features a reversible capacity of 173.20 mA h g–1 and a high capacity retention of 90.54%, outperforming those of the NM-82 cathode (154.09 mA h g–1 and 81.23%) at 0.2 C after 300 cycles. The improved performance of the NM@Sn-2 cathode originates from its stronger structure, lower Li/Ni cation mixing degree, and faster Li+ kinetics, also verified by theoretical calculations. Therefore, the one-step construction of nano-Li2SnO3 coating coupling with Sn4+ doping strategy shows a promising strategy to mitigate the capacity deterioration of the Co-free Ni-rich layered oxides.