The invention relates to a waterborne binder and a lithium battery containing the same. The binder comprises a component A and a component B, wherein the component A comprises one or more selected from a group consisting of polyglutamic acid as shown in a formula I which is defined in the specification and derivatives thereof; the mass fraction of the component A is 0.01 to 100%; and mass fraction of the component B is 0 to 99.99%. The binder is water-soluble, green and environment-friendly and can improve the first-cycle efficiency and cycle performance of the lithium battery. The lithium battery containing the binder has higher first-cycle efficiency and longer cycle performance.