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 LiNi_0.9Mn_0.05Ti_0.025Al_0.025O₂ to engineer rock-salt Li_4+xNi_1-xWO₆ stabilized LiNi_0.9Mn_0.035Ti_0.025Al_0.025W_0.015O₂ (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 Li_4+xNi_1-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·g⁻¹ at 0.2C and 5C, respectively, and contributes a high reversible capacity of 171.4 mAh·g⁻¹ at 0.5C after 200 cycles (voltage delay: 5 mV) and 88.4 mAh·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.

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