Enhancing the stability of Li2NiO2 cathode additive with polyborosiloxane coating for high-energy lithium-ion batteries

Li2NiO2 has garnered considerable interest as a Li-excess cathode additive for high-energy lithium-ion batteries (LIBs), attributed to its high irreversible capacity during the initial cycle and an operating voltage comparable with that of commercial cathode materials. However, its integration into practical applications is limited by its suboptimal cycling performance owing to moisture instability and gas evolution. To surmount these obstacles, we developed a hybrid surface coating strategy employing polyborosiloxane (PBS)—a structural derivative of polydimethylsiloxane (PDMS) synthesized with boric acid (H3BO3)—applied to a Li2NiO2 cathode additive. The bi-functional of the PBS layer enhances moisture resistance and ionic conductivity on the Li2NiO2 surface. A hydrophobic, elastic PDMS matrix offers conformal coverage, forestalling adverse moisture-induced side reactions. The introduction of H3BO3 into the PDMS matrix on the Li2NiO2 surface fosters the formation of Li–B–O bonds, thus augmenting the ionic conductivity of the coating. This innovative approach with the PBS layer significantly diminishes the interfacial resistance and improves the cycling performance of Li2NiO2 while preventing substantial structural degradation. In a full-cell configuration incorporating a PBS-coated Li2NiO2 cathode additive with a LiNi0.8Co0.1Mn0.1O2 cathode and a SiOx/Graphite anode, the enhanced energy density and sustained stable cycling performance exceed 300 cycles. This hybrid layer can aid in producing longer-lasting, more efficient LIBs that can fulfill the requirements for use in high-energy storage solutions.