Stabilizing high-voltage LiCoO2 cathodes with dielectric coating: Insights into polarization-driven Li+ transport

• Dielectric coating enhances the stability of LiCoO₂ cathodes at 4.5 V operation. • BaTiO₃ and Ba(Zr,Ti)O₃ coatings reduce interfacial resistance and improve Li-ion diffusion coefficient. • BZT-coated cathodes cut charge-transfer resistance by 60% and boost Li⁺ diffusion fivefold. • Dielectric coating suppresses cracks and retains high capacity during 300-cycle high-rate cycling. • A new surface modification strategy enables high-energy and long-life Li-ion batteries. The electrochemical capacity of lithium cobalt oxide (LiCoO₂, LCO)-based secondary batteries can be enhanced by increasing the cutoff voltage, thereby improving energy density. However, increasing the cutoff voltage accelerates interfacial side reactions and structural instabilities, leading to a more complex and unstable electrode–electrolyte interface. These problems can be overcome using various techniques such as surface coating, doping, and use of electrolyte additives In this study, we enhanced the cycling stability of LCO under high-voltage conditions through surface modification with BaTiO₃ and Ba(ZrₓTi₁₋ₓ)O₃ dielectrics, which exhibit distinct polarization characteristics. This stabilized the electrode/liquid electrolyte interface, thereby reducing crack formation during Li-ion insertion and extraction. Analysis of the Li-ion diffusion rates in the different dielectric/LCO composites clarified the relationship between the polarization characteristics in the dielectric region and Li-ion transport behavior and explained the mechanism by which the composites facilitate high-power lithium-ion battery operation.