Secondary battery, preparation method thereof, copolymer and device

The invention discloses a secondary battery, a preparation method thereof, a copolymer and a device. The secondary battery includes a binder for binding a first substance and a second substance, the binder including a copolymer including at least a first monomer unit represented by formula (I), a second monomer unit represented by formula (II), and a third monomer unit represented by formula (III). According to the secondary battery provided by the invention, the binding power between the first substance and the second substance can be effectively increased by containing the specific binder, so that the electrochemical performance of the secondary battery is improved;