Tungsten-based Li-rich rock salt stabilized Co-free Ni-rich layered oxide cathodes

Dual-element-doped Co-free Ni-rich LiNiO2-based cathodes demonstrate great potential for high-energy lithium-ion batteries (LIBs). Nevertheless, they suffer from serious Li+/Ni2+ mixing, irreversible phase transitions, structural degradation and side reactions at the cathode/electrolyte interface. Herein, W is purposively introduced into LiNi0.9Mn0.05Ti0.025Al0.025O2 to engineer rock-salt Li4+xNi1-xWO6 stabilized LiNi0.9Mn0.035Ti0.025Al0.025W0.015O2 (LNMTAWO) cathode. In situ characterizations, together with electrochemical analysis, demonstrate that Mn, Ti and Al can effectively enhance the reversibility of phase transitions, stabilize the TM-O bonds under high voltage and relieve voltage decay. The rock-salt Li4+xNi1-xWO6 can prevent the overgrowth of grain size, avoid the exposure of active materials into electrolytes and decrease the side reaction. Benefitting from the dual-element synergistic effects, the LNMTAWO cathode offers high reversible capacities of 228.7 and 150.8 mAh center dot g(-1) at 0.2C and 5C, respectively, and contributes a high reversible capacity of 171.4 mAh center dot g(-1) at 0.5C after 200 cycles (voltage delay: 5 mV) and 88.4 mAh center dot g(-1) at 10C after 500 cycles. Such design of rock-salt structure symbiotically grown on Ni-rich cathodes by introducing high-valence elements would provide rational guidelines on engineering high-energy Co-free Ni-rich LIB cathodes.