Nano-single-crystal co-free li-rich Mn-based layered cathode for long-cycling high-energy lithium-ion batteries

Although high energy density Li-rich layered oxide is a promising cathode due to its extremely high energy density (≥ 1000 Wh kg^-1), the commercialization is largely hindered by lattice oxygen escape, voltage fading, and short lifetime during cycling. Single-crystalline engineering is believed to be an effective strategy to solve these problems. However, low-cost Li-rich Co-free layered cathode is mainly synthesized by molten salt-assisted method followed by additional washing and recalcination, which is not only a multi-step method but also lack economy and universality. Herein, we introduce nano-single-crystalline engineering into the synthesis of low-cost Li-rich Co-free layered cathode materials by a simple solid-state reaction using mixed lithium salt. In contrast to polycrystal cathode, monodisperse nano-single-crystal facilitates Li⁺ diffusion between electrolyte and cathode. Benefiting from this feature, monodisperse single-crystalline morphology can suppress oxygen escape, limit phase transition and the resulting microcracks, and reduce electrolyte erosion side reaction (transition metals ion dissolution/surface structure degeneration). The single-crystal Li-rich cathode materials have the high first Coulombic efficiency (77.97 %), remarkable rate performance and excellent cycling stability of 92.7 % after 200 cycles at 1C rate. Hence, this new single-crystalline engineering technology demonstrates potential for general application to synthesize Li-rich cathode for long-life high-energy-density lithium-ion batteries.