A universal multifunctional dual cation doping strategy towards stabilized ultra-high nickel cobalt-free lithium layered oxide cathode

Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries (LIBs) because of their relatively high capacity and low cost. Nevertheless, the high nickel content would induce bulk structure degradation and interfacial environment deterioration, and the absence of Co element reduces the lithium diffusion kinetics, severely limiting the performance liberation of this kind of cathodes. Herein, a multifunctional Ti/Zr dual cation co-doping strategy has been employed to improve the lithium storage performance of LiNi0.9Mn0.1O2 (NM91) cathode. On the one hand, the Ti/Zr co-doping weakens the Li+/Ni2+ mixing through magnetic interactions due to the inexistence of unpaired electrons for Ti4+ and Zr4+, increasing the lithium diffusion rate and suppressing the harmful coexistence of H1 and H2 phases. On the other hand, they enhance the lattice oxygen stability because of the strong Ti–O and Zr–O bonds, inhibiting the undesired H3 phase transition and lattice oxygen loss, improving the bulk structure and cathode-electrolyte interface stability. As a result, the Ti/Zr co-doped NM91 (NMTZ) exhibits a 91.2% capacity retention rate after 100 cycles, while that of NM91 is only 82.9%. Also, the NMTZ displays better rate performance than NM91 with output capacities of 115 and 93 mA h g−1 at a high current density of 5 C, respectively. Moreover, the designed NMTZ could enable the full battery to deliver an energy density up to 263 W h kg−1, making the ultra-high nickel cobalt-free lithium layered oxide cathode closer to practical applications.