The development of high-energy low-cost lithium-ion batteries has sparked interest in ultrahigh-Ni Co-free layered cathodes that offer high capacity, low cost, and environmental friendliness. Yet, their widespread deployment is impeded by the challenges posed by the large magnetic moments of Ni and Mn, as well as the aggregation of the highly spin-unstable high-spin state of Ni3+ at the interface. Herein, an efficient three-in-one strategy of internal Al and external Zr is proposed to achieve an ultrastable single-crystal ultrahigh-Ni Co-free cathode, Li(Ni0.90Mn0.08Al0.02)0.98Zr0.02O2 (NMAZ). The strong AlO6 ligands prevent the formation of high-spin Ni3+. Surface-enriched Zr restricts the diffusion of Ni within the NiO6 octahedron. The single-crystal structure reduces unwanted reactions with the electrolyte. Consequently, NMAZ achieves a favorable unity of material cost and electrochemical performance by reducing the resource expense by >7.5% than conventional Co-containing single-crystal LiNi0.88Mn0.08Co0.04O2 (NMC) and demonstrating excellent calendar lifespan performance. Moreover, it shows better phase stability under high dissociation conditions, alleviates the harmful H2-H3 phase transformation, and avoids the release of lattice oxygen due to the overlap of Co3+/4+ 3d and O2- 2p orbitals upon deep delithiation.
Shen et al. (Fri,) studied this question.