Investigation of the Battery Temperature Gradient and its Influence on Battery Aging from Different Thermal Management Methods Under the Application of Electric Tools

Due to its spatial efficiency, phase-change materials (PCMs) are particularly welcomed in the application of the electric tools where extremely high current at 10~15 C-rate is needed. With the Samsung 18650 20R Nickel-Cobalt-Manganese batteries, this study explores the temperature distribution from battery core to surface at extreme working current (15 C) with thermal conductive or storage wrapping materials including HDPE, thermal conductive sheet, thermal conductive adhesive, and PCMs. The proposed temperature distribution prediction model is validated with experimental data. The results indicate that the best battery surface temperature decrease is 18.60 ℃ when 2mm PCMs are applied. The discharge capacity of batteries is thus prolonged by 80-100 % compared to the naked battery cell. On the other hand, the battery core temperature reduction is much lower, only by 6.40 ℃ (from 139.70 ℃ to 133.29 ℃). Accordingly, the internal temperature gradient rises from 35.92 ℃ to 48.12 ℃. This is due to the heat generation exceeded the heat exported from the core to the outside under the 15C working condition of the electric tool. The study further evaluates the effects of high temperature gradient and finds that the capacity fade 90-250 % times faster with 2mm PCMs wrapping.