High-voltage LiCoO2 is a promising cathode material for ultrahigh-energy lithium-ion batteries, particularly in the commercialization of 5G technology. However, achieving long-term operational stability remains a significant challenge. Herein, a quaterpolymer additive with multiple functional groups is introduced to enhance the electrochemical performance of LiCoO2 cathode at 4.5 V. The capacity remains 96% after 100 cycles at room temperature and 94.4% after 50 cycles even at 45 °C. The sulfonate and ester groups of the quaterpolymer additive serve as lithium carriers, providing high voltage resistance and fast ionic conductivity with increased lithium-ion diffusion coefficients during the charge/discharge processes. The incorporation of a quaterpolymer additive also improves the dispersion properties and peel strength of the LiCoO2 cathodes. The coordination between the sulfonate groups and Li+ as well as the amine-based derivatives and Lewis acid of PF5 is expected to disrupt the Li+ solvation shell and deactivate the PF5 reactivity, therefore suppressing electrolyte decompositions. Furthermore, the superior interactions between sulfate ester (O atoms)/amide (N atoms) groups of copolymer additive and superficial cobalt atoms of LiCoO2 provide a compensating charge to Co, inhibiting the surface cobalt dissolution, irreversible oxygen redox reaction, and the detrimental LiCoO2 phase transition from O3 to H1-3. The use of a tiny amount of polymer additive presents an effective approach to stabilizing high-voltage LiCoO2, offering valuable insights for the design of high-energy battery materials.
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