# A Review on the Thermal Hazards of the Lithium-Ion Battery and the Corresponding Countermeasures
## 5 Management and Countermeasures
### Battery Management System  
In practical applications, LIBs are required to operate at different conditions where a complicated temperature environment such as high temperature, low temperature and a largely varying temperature etc. may be involved. As stated by many scholars, temperature greatly affects battery from both safety and performance points of view [230; 231; 232; 233; 234]. Hence, it is of great importance to configure an efficient battery management system (BMS) that allows for control of battery temperature and prevents the occurrence of thermal hazard. BMS applied in EV is usually comprised of sensors, actuators and controllers, and it is used to achieve three main aims: (1) to protect battery from being damaged; (2) to make battery operate within the proper voltage and temperature interval; (3) to maintain the performance of battery to meet the requirement of vehicles [235]. Traditionally, BMS can be briefly divided into two categories: internal thermal management (ITM) and external thermal management (ETM), which is further displayed in Figure 17.  
ITM, also known as intrinsic safety management, refers to those thermal management methods applied at the battery level in which the thermal management strategies exist in the core region of the battery monomer. One common approach is via optimizing battery components to be safer so that less heat is generated and better uniformly can be achieved. [PERSON] et al. [236] proposed a cooling method to remove the heat generated within the lead-acid battery by means of controlling electrolyte circulation rate. Their results showed that such an approach could provide a uniform temperature field and the temperature could be controlled to a desirable level. As shown in Figure 18a, [PERSON] et al. [237] introduced a particular type of internal cooling method, where liquid electrolyte served as a coolant and flowed through the micro-channels dispersed in electrodes. Besides, [PERSON] et al. [238] developed a novel system that utilized an internal evaporator with micro-channels incorporated in a thick current collector and then applied to side cooling, see Figure 18b. Figure 17: Summary of battery thermal management systems including the external management system (air cooling system, liquid cooling system, PCM cooling system) and the internal management system (alternating current, component optimization). Another way to achieve ITM is via the application of alternating current (AC) that can efficiently heat battery without a substantial change of SOC. [PERSON] et al. [239] first proposed using AC to warm battery up rather than using an external heater. For this method, the heating rate increased with the increasing signal amplitude, however the effect of signal frequency on the heating performance was not taken into account. To address this problem, [PERSON] et al. [240] proposed an effective strategy to analyze the optimal frequency. Their results demonstrated that constant frequency was more promising than variable one for engineering realization and the optimal frequency could be evaluated according to the intermediate temperature. Nevertheless, in practical applications, the ITM method is difficult to operate and some disadvantages such as low cooling efficiency and temperature gradient etc. also limit its usage [240]. Comparatively, another BMS, i.e., ETM has received a more universal application. Corresponding to the ITM, ETM refers to the thermal management methods that improve heat dissipation from external environment. In order to promote heat dissipation, it is important to choose  
Figure 18: Internal thermal management: (**a**) internal cooling by micro-channel in electrode, adopted from Ref. [237]; (**b**) internal cooling by micro-channel evaporator in current collector, adopted from Ref. [238]. a suitable medium. On the basis of the medium, ETM can be further divided into three kinds: air cooling system (ACS), liquid cooling system (LCS) and PCM cooling system (PCM-CS).