The promotion of phase transitions for Ni-based layered cathode towards enhanced high-voltage cycle stability

Ni-based layered oxide LiNi0.8Co0.1Mn0.1O2 shows great promise for high-energy lithium-ion batteries. But the realization of its high capacity is often at the expanse of chemical and structural stability because deeply delithiation upon charge can leave the structure more vulnerable. Herein, we demonstrate that this problem can be alleviated by concurrently introducing some of Na+ and Ti4+ to obtained Li0.98Na0.01Ni0.78Co0.1Mn0.1Ti0.02O2 (NT-NCM). The co-doping successfully accelerates the phase transition process (H1 to H2 and to H3), and the enhanced reversible capacity and capacity retention at a high cut-off voltage of 4.5 V are achieved with the NT-NCM electrode. This is possible due to the less lattice stress and mechanical degradation after co-doping during prolonged cycling; the enlarged c axis distance and reduced Li+/Ni2+ mixing for doped one assist in enhancing the Li-ion transportation.