Electrolyte Regulating toward Stabilization of Cobalt-Free Ultrahigh-Nickel Layered Oxide Cathode in Lithium-Ion Batteries

Cobalt (Co)-free ultrahigh-nickel (Ni) layered oxides exhibit dual competitive advantages in reducing the cathode cost and boosting the energy density, promising the sustainable development of batteries for electric vehicles. However, the increased Ni content and the resulting more highly oxidative Ni4+ potentially induce severe capacity fading due to the aggravated side reactions at the cathode surface, limiting the practical applications. Here, we evaluate the compatibility of two localized high-concentration electrolytes (LHCEs) with LiNi0.96Mg0.02Ti0.02O2 (NMT) cathode under a high charging voltage of 4.4 V in lithium-ion batteries. The LHCE with ethylene carbonate as additive enables the formation of effective interfacial layers on both the NMT cathode and graphite anode, realizing a capacity retention of 97.2% after 200 cycles and high reversible capacities of ∼180.2 and ∼185.8 mAh g–1 at 5C charge rate and 5C discharge rate, respectively, at 25 °C. This work provides a promising approach to enable Co-free ultrahigh-Ni layered oxides for practical applications.