The invention discloses a preparation method of a high-performance lithium battery, which comprises the following steps of placing a thermal adhesive diaphragm between a positive plate and a negativeplate, and preparing a battery cell, the thermal adhesive diaphragm being a diaphragm having an adhesion effect on an electrode material at a preset temperature or pressure; carrying out preheating and/or flat pressing treatment on the battery cell, wherein the temperature of the preheating treatment is greater than or equal to the softening temperature of the thermal adhesive material and is lessthan the melting temperature of the thermal adhesive material, the pressure intensity of the flat pressing treatment is greater than or equal to the yield limit of the hot viscous material; carryingout shaping treatment on the preheated and/or flattened battery cell; and carrying out post-treatment on the shaped battery cell to obtain the lithium ion battery. Correspondingly, the invention alsoprovides the lithium battery prepared by the method. By adopting the method, the energy consumption reduction, process condition simplification, equipment simplification and raw material simplification can be realized at the same time, and the battery is high in appearance size consistency and stability and high in performance consistency and stability.