# A Review on the Thermal Hazards of the Lithium-Ion Battery and the Corresponding Countermeasures
## 6 Summary and Outlook  
With the global energy policy transitioning from fossil energy to renewable energy, LIBs, as a type of energy storage method, show great advantages over other kinds of batteries. Therefore, they have attracted considerable attention. However, the safety concerns regarding LIB are still a main obstacle that hinder large-scale applications of LIBs in many fields. Benefiting from the fast spread of information today, incidents of fire or explosions induced by LIBs are often reported ranging from \begin{table}
\begin{tabular}{c p{284.5 pt}} \hline \hline
**Class** & **Description** \\ \hline A & Fires in ordinary combustible materials such as wood, cloth, paper, rubber and many plastics. \\ \hline B & Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols and flammable gases. \\ \hline C & Fires that involve energized electrical equipment. \\ \hline D & Fires in combustible metals such as magnesium, titanium, zirconium, sodium, lithium and potassium. \\ \hline K & Fires in cooking appliances that involve combustible cooking media. \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Classification of fires. mobile telephones and EVs to airplanes. These incidents greatly threaten consumers' lives and property, while damage human's confidence on LIBs, thereby restricting the progression of their use. Therefore, paying more attention to the thermal hazards of LIBs and the corresponding countermeasures is of great importance. Generally, the thermal hazards of LIBs can be caused by several abusive factors, e.g., physical, electrical and thermal factors, manufacturing defect and battery aging. The physical factor can trigger electrical abuse, and the electrical abuse releases heat which will further induce thermal abuse; namely, thermal hazard and even thermal runaway. During the process of battery thermal hazard, a series of destructive reactions among battery components such as the decomposition of electrodes/electrolytes, the reaction between electrodes, the reaction between electrode and electrolyte, etc. are induced, substantial heat is released and quantities of combustible gases are generated. Besides battery components, the thermal hazards of a single battery and a battery pack are also reviewed. For the former, the thermal hazards that are generally exhibited are high-temperature, ejection, combustion, explosion and toxic gases during thermal runaway. While for a battery pack, thermal failure propagation provides a thermal hazard in addition to thermal runaway. Thermal failure propagation will aggravate the thermal hazard further, resulting in a serious incident. In addition, the influence of low-pressure environment and cathode chemistry on the thermal hazard of LIBs is discussed here. However, it still lacks sufficient examinations on the thermal behavior of LIBs under low pressure, the hazard difference between normal condition and low-pressure condition is worth noting in future research. In an aim to decrease the thermal hazards of LIBs as much as possible, certain management or countermeasures must be implemented. In current work, the measures discussed were (1) the usage of safety devices inside battery; (2) the application of FR additives; (3) the thermal management of battery; (4) the warning of thermal hazard and (5) firefighting upon the occurrence of a hazard. However, challenges still remain. Effective FR additives and thermal management systems still need to be developed to meet the requirement of practices including performance, cost and so on. The current warning method is not sufficiently sensitive to give the humans the time necessary to escape danger or take the appropriate measurements. Moreover, standard guidelines for the fighting of battery fire remain to be formulated and promulgated. In short, to decrease the challenges of battery thermal hazards and create LIBs that better benefit humankind, there is still a lot of work to do.