With the great development of new energy vehicles and power batteries, lithium-ion batteries have become predominant due to their advantages. For the battery to run safely, stably, and with high efficiency, the precise and reliable prognosis and diagnosis of possible or already occurred faults is a key factor. Based on lithium-ion batteries’ aging mechanism and fault causes, this paper summarizes the general methods of fault diagnosis at a macro level. Moreover, lithium-ion battery fault diagnosis methods are classified according to the existing research. Therefore, various fault diagnosis methods based on statistical analysis, models, signal processing, knowledge and data-driven are discussed in depth. Finally, the main challenges faced by fault diagnosis technology and future directions for possible research and development are put forward.

The thermal management system of a power battery is crucial to the safety of battery operation; however, for the phase-change material (PCM) thermal management system of a battery, the thermal cycling of phase-change material under large discharge rate conditions will lead to thermal conductivity degradation and thermal stress problems. A method of manufacturing PCM containers with metal fins to package pure phase-change material is put forward to solve the problem. The system temperature under different conditions is studied using numerical and experimental methods. A thermal resistance model is built to analyze the thermal transfer performance of PCM containers with fins. The results show that the PCM container structure can effectively control the battery temperature within the suitable temperature range under the low discharge rate, but the maximum temperature of the battery pack at the high discharge rate of 3 C will exceed the optimum operating temperature range. Adding fins can reduce the maximum temperature and improve the system temperature uniformity. By combining fins with forced-air cooling, the maximum temperature and maximum temperature difference of the battery pack at a high discharge rate can be effectively reduced.