Highly stable operation of LiCoO2 at cut-off ≥ 4.6 V enabled by synergistic structural and interfacial manipulation

Elevating the charge cut-off voltage is the most effective approach for boosting the energy density of LiCoO2 (LCO), which however is hindered by accelerated structural devastation and interfacial degradation at high voltages, e.g. >= 4.6 V vs. Li/Li+. In this work, we propose a synergistic strategy by designing a Mg doped and Se coated LCO (LCO-Mg@Se). The strong Mg-O bond greatly stabilizes the layered structure of LCO, to alleviate the lattice parameter variation during deep delithiation. Se surface treatment, acting as an artificial CEI layer, interacts with O2-: 2p during deep stage of charge, effectively weakening the Co: 3d-t(2g) - O2-: 2p hybridization. Moreover, the Se coating layer could inhibit the parasitic side reactions and refrains the electrolyte corrosion toward the electrolyte-cathode interface, further mitigating the phase transformation to disordered rock salt phase at LCO particle surface and reducing the generation of resistive byproducts. These cooperative efforts enable the substantially enhanced high-voltage electrochemical performance of LCO-Mg@Se, achieving 147 mAh g(-1) after 1000 cycles (72.9% retention) at charge cut-off 4.6 V and 148 mAh g(-1) after 400 cycles at charge cut-off 4.65 V. The high-temperature cycling performance and thermal stability are greatly enhanced as well. This bifunctional structure/interface engineering approach provides scalable design ideas for developing cathode materials for high energy density batteries.

Automated summary

In this work, a synergistic strategy of Mg doping and Se coating is proposed to enhance the high-voltage electrochemical performance and cycling life of LiCoO2 as a cathode material for high energy density batteries.