Development status and research progress of power battery for pure electric vehicles

Compared to the traditional electrochemical power source, lithium ion batteries (LIBs) have the advantages of higher energy density, longer life, and absence of any memory effect, and thus have attracted widespread research interest around the world. After Sony Inc. invented and produced the first commercial 18650 cell, many domestic and international research centers and companies have promoted the industrialization of LIBs. With the development of LIB technology, its application scope has extended from traditional consumer electronics to the new energy vehicles (NEVs) and energy storage fields. NEVs include pure electric vehicles (PEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). LIBs have been the main driving force for PEVs to date, and their cathode technology development process has had three generations, i.e., the first using LiCoO₂, the second using LiMn₂O₄ and LiFePO₄, and the third generation using Li(Ni_xCo_yMn_1-x-y)O₂. With the development of cathode and anode materials with higher capacities and the increased reliability of LIB safety technology (including separators with higher temperature resistance, electrolytes with higher voltage resistance, and other protection methods), cells with higher energy densities and longer lives can be developed and applied in the future. These improvements will enable PEVs to travel longer distances, which is the most critical issue to customers. This paper provides a review of the development status of the power battery industry and an analysis of the direction of LIB technology with respect to the following: (1) the cathode/anode materials used, including the higher Ni content in Li(Ni_xCo_yMn_1-x-y)O₂, along with its structural modification, and the stability of silicon and improvements in its efficiency and cycle life; (2) the design technology, including the electrode and structure designs developed using simulation technology, theoretical modeling, and experimental methods based on Taguchi design; and (3) advances in process technology, including mixing and coating processes. Based on the above information, a clear picture of the technical direction was provided for LIBs in the PEV field.