*3.2. Problems Confronting the Solid-State Battery and Potential Solutions*

It is a fact that the cost per cell or cost per pack is very high for EV applications, and the same goes for the energy per cell and pack as well. This goal is quite sincere, even though the expected level of safety is compromised. Here is a list of some of the issues that scientists are now working to resolve:

• Due to the weak wetting between lithium and the solid electrolyte, an interfacial resistance forms. Solid electrolytes, especially those made of ceramic, exhibit very high interfacial resistance due to insufficient wetting of Li. Li is therefore ineligible for use in solid-state batteries. It was discovered that solid electrolytes made of polymers exhibit improved Li wetting while having less ionic conductivity than their ceramic counterparts. In light of this, polymer/ceramic composites can be used as electrolytes to address the Li wetting problem [86].


During the process of developing a cell based on ceramic material, there are a lot of heat pressing techniques being utilized, as illustrated in Figure 4. Moreover, this step is performed to ensure the proper but smooth relation or contact between the electrode and its electrolyte. Today, the design engineering may easily perform this process, whereas it is observed that the bulk type of solid-state batteries may produce enough retention capacity [93]. On the other hand, the scalability is also one of the main constraints of bulktype batteries. Thus, one may opt for polymer composites as a true solution during the massive production of these products. Furthermore, Li metal creeps while being operated on at high temperatures. Therefore, in modern methods it is suggested to engage Li metal in a process that actually reduces the creep tendency [94,95].

**Figure 4.** Battery production for process parameter optimization [94].
