As an indispensable part of the lithium-ion battery (LIB), a binder takes a small share of less than 3% (by weight) in the cell; however, it plays multiple roles. The binder is decisive in the slurry rheology, thus influencing the coating process and the resultant porous structures of electrodes. Usually, binders are considered to be inert in conventional LIBs. In the pursuit of higher energy density, many new binders are being developed for specific targets, such as the high-voltage (typically, ? 4.5 V) cathodes, conversion/alloy-type cathodes/anodes with large volume effect, and solid-state batteries (SSBs), in which these binders demonstrate their various functions. They may influence the solid electrolyte interface component, ensure the electrode/electrolyte interfacial stability, transport ions/electrons in the electrodes, provide adhesion and flexibility to solid-state electrolyte (SSE) films, etc. Here in this review, we try to summarize the advances on binders, among which the ones for high-voltage cathode materials, thick electrodes, micro-sized silicon particles, SSEs and SSBs are highlighted. We believe that the advanced functional binders would play decisive roles in the future development of high-energy–density LIBs and SSBs.