Ion exchange-induced LixMgyBOz coating synergized with reinforced bulk doping enables fast-charging long-cycling high-voltage LiCoO2

Abstract

Under high-voltage conditions (>4.5 V vs. Li⁺/Li), the practical application of LiCoO₂ (LCO) is severely limited by irreversible structural degradation and interfacial instability. Herein, we propose a computationally guided “occupancy-exchange” strategy that enables the in situ self-assembly of a robust Li_xMg_yBO_z (LMBO) amorphous coating on LCO via Mg–Na ion exchange. Theoretical calculations reveal the thermodynamic feasibility and interfacial driving force of this exchange, offering fundamental insights into the spontaneous formation of a stable coating. In this architecture, Na doping into the LCO lattice enhances Li⁺ de-intercalation kinetics and bulk structural stability, while the LMBO surface layer effectively mitigates interfacial degradation by stabilizing lattice oxygen, reducing electrolyte corrosion, and preventing transition-metal dissolution. This synergistic bulk-surface stabilization strategy endows the modified LCO (N-LCO@LMBO) with exceptional cycling stability and fast-charging performance at 4.6 V, achieving a discharge capacity of 171.3 mA h g⁻¹ after 500 cycles at 1C and maintaining 163.7 mA h g⁻¹ after 1000 cycles at 3C. Remarkably, this work achieves the first demonstration of an LCO-based cathode capable of enduring 5C fast-charging at 4.7 V, maintaining 82.1% capacity after 500 cycles, setting a new benchmark for higher voltage, fast-charging lithium cobalt oxide systems. Furthermore, a pouch cell assembled with N-LCO@LMBO and graphite delivers an initial capacity exceeding 400 mA h and retains 92.8% of its capacity after 500 cycles under 3C fast-charging conditions, highlighting its potential for practical applications. Building on these results, this strategy is further extended to commercial LCO, demonstrating its universality and scalability. This work opens a new avenue for the rational design of stable layered cathode materials via targeted ion-exchange mechanisms.