Simultaneous Bulk Doping and Surface reconstruction Engineering by SeS₂ Treatment Enable Stable High-Voltage...

Exposing LiCoO₂ (LCO) to voltages over 4.35 V induces both irreversible H1-3/O1 phase transformation and severe interfacial reactivity, whose synergistic effects cause substantial capacity loss. Herein, an ingenious surface reconstruction and bulk doping of LCO are proposed to overcome the above bottlenecks via selenium disulfide (SeS₂) treatment. In detail, the substitution of O-sites by Se stabilizes the lattice oxygen of LCO, alleviating harmful phase transitions. Furthermore, the formation of a stable heterojunction between the Li₂SO₃/Li₂SO₄/Li₂SeO₄ composite coating and LCO grains contributes to the suppression of interfacial side reactions and provides a mechanical cushioning effect that alleviates anisotropic lattice stress. Meanwhile, the mixed coating can also provide Li to ensure continuous Li⁺ supplement, facilitating Li⁺ diffusion. More importantly, an inorganic-rich cathode-electrolyte interphase (CEI) layer is generated, further improving the bulk structural robustness and interfacial charge transport. Ultimately, the SeS₂-LCO exhibits a superior cyclability under 4.6 V high-voltage conditions, achieving 80.6% capacity retention at 1 C for LCO/Li half cells after 400 cycles compared with P-LCO of 37.8%. Our work introduces a bulk-surface synergistic modification approach to stabilize the LCO crystal structure, which can be extended to more sophisticated coating and multiple elements doping for constructing better high-voltage LCO batteries.