Extended cycle life in lithium-ion batteries through lithium supplementation from Li$_2$C$_4$O$_4$@SiO$_2$ microcapsules

The formation of a solid electrolyte interphase (SEI) in lithium-ion batteries consumes active lithium ions, resulting in loss of capacity and decreased cycle life. Most prelithiation methods only address the initial lithium depletion by compensating with a source of lithium ions, overlooking the ongoing lithium consumption through continuous degradation processes. In this study, Li$_2$C$_4$O$_4$@SiO$_2$ microcapsules are presented, in which Li$_2$C$_4$O$_4$ serves as an additional source of lithium ions and the porous SiO$_2$ shell prevents unwanted catalytic reactions, ensuring sustained lithium availability throughout the cycling. The microcapsules are synthesized using a wet impregnation method and characterized using various techniques to confirm their structural, morphological, and compositional properties. Ex situ nuclear magnetic resonance (NMR) analysis demonstrated lithium-ion mobility, and electrochemical tests in full-cell configurations with graphite and graphite/silicon anodes confirmed improved capacity retention and cycle life. This work highlights the potential of microencapsulated lithium-ion sources to improve battery performance in various lithium-ion systems and opens a pathway for battery cells with self-healing functionality that can be triggered on demand.