Abstract: With the rapid development of battery electric vehicles, there has been a higher demand for increased energy density and safety in power batteries. The blade battery has significantly enhanced space utilization and addressed the issue of low energy density in conventional Lithium iron phosphate batteries(LFP). A model combining 1D electrochemical with a 3D thermal model is developed to investigate the following three aspects. Firstly, the effect of environmental temperature, charge rate, and heat transfer coefficient on the electrochemical properties of blade batteries with varying lengths is studied. Through the use of the DC impedance decomposition method(DCR), the primary physicochemical process that affects the electrochemical performance of the long/short blade battery is identified and traced. Secondly, the influence of the above three variables on temperature distribution and temperature rise process at the end of charging of the long/short blade batteries is investigated. Furthermore, a heat production decomposition (HPD) study is carried out to demonstrate the heat production of each component. Thirdly, the influence of battery size and heat transfer coefficient on battery temperature uniformity is explored, and several helpful proposals that benefit to temperature uniformity are suggested. The main results are as follows ① The effect of blade battery length on electrochemical performance is attributed to the different collector resistance, and the resistance increases as the length of the battery increases. Additionally, the thermal performance is affected by the length of the blade battery, which is dependent on internal heat production, conduction, and surface dissipation. According to the results, as the length increases, there will be a corresponding increase in heat production and temperature difference of the battery. ② The three factors mentioned above displayed varying effects on electrochemical and thermal properties. On the one hand, the environmental temperature and heat transfer coefficient have little influence on electrochemical properties and heat production constitution. On the other hand, as the charging rate increases, the capacity declines noticeably because of the rise in overpotential, and heat production increases considerably both reversible heat and irreversible heat. Additionally, the temperature uniformity improves in length direction with the increasing heat transfer coefficient. Moreover, improving thermal conductivity is proven another effective way to temperature uniformity. According to the simulations, the L400 shows the best temperature consistency among the three different battery sizes, containing the L400, L800, and L1200. In summary, decreasing the length of the battery and improving the thermal conductivity of the material are effective methods to enhance temperature uniformity in each direction of the batteries.

Key words: blade batteries, multiscale electrochemical-thermal coupling model, direct current impedance decomposition, heat production analysis, temperature field design