Entropy-assisted doping strategy enabling chemo-mechanically reliable ultrahigh-Ni Co-free polycrystalline cathode for commercializable lithium-ion batteries.

Recently, Co-free Ni-rich cathodes have received extensive concerns as a competitive candidate for next-generation sustainable lithium-ion batteries (LIBs) due to their high-capacity/operation voltage merits and elimination of expensive Co component. However, it is extremely challenging to solve the issues involving their intrinsic chemo-mechanical instabilities triggered by anisotropic lattice stress and short cycle life. Herein, we rationally incorporate tiny quintuple high-valence cations to engineer an entropy-assisted LiNi0.9Mn0.085Nb0.003W0.003Sb0.003Ta0.003Mo0.003O2 (denoted as EL-N9-3) as a competitive cathode for LIBs. Thanks to such multi-component synergistic superiorities, the five-cations modulated EL-N9-3 is endowed with a robust lattice structure and optimized crystallographic texture, thereby significantly strengthening lattice oxygen framework, mitigating surface side-reactions and irreversible phase transitions, and further prohibiting the microcracks formation and reproduction. The well-designed EL-N9-3 cathode demonstrates exceptional long-cycle duration, showing a competitive capacity retention of 86.7% after 200 cycles at an elevated cut-off potential of 4.5 V. Besides, the EL-N9-3-based pouch-type full cell can steadily sustain 500 cycles within a wide voltage window of 2.8 - 4.4 V at 1 C rate, with 70.8% capacity retention. This work proves that the entropy-assisted complex doping strategy is an effective avenue to achieve advanced Co-free ultrahigh-Ni layered cathodes, definitely expediting their extensive utilization in next-generation LIBs.