Abstract: The present disclosure discloses a composite binder for a self-extinguishing lithium ion battery and a lithium ion battery. The composite binder is obtained by adding ammonium polyphosphate and polyacrylic acid into a solvent to prepare a mixed solution and then carrying out thermal treatment on the above mixed solution. The present disclosure combines the flame retardancy of ammonium polyphosphate with the feature of polyacrylic acid to inhibit volume expansion, so that a stable solid electrolyte interface (SEI) film is formed on the surface of the prepared lithium ion battery during the cycling, thereby significantly promoting the electrochemical performance of the lithium ion battery while improving the flame retardancy of the battery; besides, ammonium polyphosphate and polyacrylic acid can be crosslinked after being heated due to the interaction of hydrogen bonds to form a three-dimensional network structure, which significantly improves the structural stability of the battery.