Abstract: Lithium secondary batteries has a wide application prospect in portable consumer electronic products, electric vehicles and energy storage etc. owing to its advantages of high energy density, long cycle life, no memory effect and environmentally friend. At present, the energy density and safety of lithium secondary batteries are the hot spot in the world. However, for conventional lithium-ion batteries with liquid electrolytes, although various improvement measures have been taken from the aspects of materials, modules, power management, thermal management and system design, the safety issues in high-energy density cells are still prominent, and it is difficult to avoid the problem of thermal runaway completely. Therefore, in order to improve the safety of lithium ion battery, the development of non-flammable solid-state lithium battery is a necessary way to solve the safety problem of conventional lithium ion battery. This paper compares cell structures between the traditional liquid lithium ion battery and solid-state lithium battery, and their respective advantages and disadvantages are summarized. The fundamental causes of safety problems in traditional liquid lithium ion batteries are analyzed, and the approach of replacing the liquid electrolyte with solid-electrolyte is put forward as the best solution to solve the problem of safety issues in lithium ion batteries. Finally, the high safety characteristics of solid-state lithium-ion batteries are confirmed depending on the safety test results of some kind of solid-state lithium batteries which are developed independently.

Key words: solid-state lithium battery, cell structure, high energy density, reason-analysis, safety