BYD said the company has developed a lithium battery production method to prevent the collapse of positive electrode material particles and the formation of lithium dendrites in the negative electrode, thus extending the battery's cycle life. The abstract shows that the disclosure relates to a lithium battery and its production method. The lithium battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The electrolyte contains a polymer and lithium salt, the polymer being poly carbonate and/or poly ether. After at least one charge-discharge cycle, the concentration spatial gradient of the polymer in the electrolyte decreases along the direction from the positive electrode to the negative electrode, and the concentration spatial gradient of the lithium salt increases along the direction from the positive electrode to the negative electrode. The disclosed electrolyte contains polycarbonate and/or polyether polymers and lithium salt, and as the battery cycle progresses, the concentration spatial gradient of the polymer decreases from the positive electrode to the negative electrode, and the concentration spatial gradient of the lithium salt increases from the positive electrode to the negative electrode, effectively avoiding the collapse of positive electrode material particles and the formation of negative electrode lithium dendrites, thus extending the battery's cycle life.