# Feasible Energy Density Pushes of Li-Metal vs. Li-Ion Cells
## 6 Liquid Electrolytes vs. Solid Electrolytes for LMBs  
The first LMB was already based on a \"Li-metal\" anode combined with organic liquid electrolyte (LiPF\({}_{6}\)- propylene carbonate) [41]. However, the use of metallic lithium form coupled with an organic liquid electrolyte caused the dendrite formations which eventually led to an internal short circuit and thus to a thermal runaway since porous polymer-based separators do not provide a sufficient physical barrier to stop the spread of dendrites. In addition, the existing liquid electrolytes are toxic and flammable due to the fluorinated salt LiPF\({}_{6}\) carbonate solvents respectively [19]. [PERSON] et al., studied various liquid electrolytes for Li-metal anodes, in order to give a comprehensive understanding of the liquid electrolyte/lithium-metal anode limitations. They have shown that the most common problems associated with low CE are issued by fragile solid electrolyte interphase (SEI) [32]. The typical inorganic components of SEI are \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Battery Capacity (kWh)** & **Usable Capacity (kWh)** & **Energy Capacity 90\%** & **1 Change Consumption (kWh/100 km)** & **EoL 1 (km)** & **EoL 2 (km)** & **Required Cycles 1** & **Required Cycles 2** \\ \hline
50 & 45 & & 300 & & & 500 & 1000 \\
95 & 86 & 15 & 570 & 150,000 & 300,000 & 263 & 526 \\
200 & 180 & & 1200 & & & 125 & 250 \\ \hline
50 & 45 & & 225 & & & 666 & 1332 \\
95 & 86 & 20 & 430 & 150,000 & 300,000 & 349 & 698 \\
200 & 180 & & 900 & & & 167 & 334 \\ \hline
50 & 45 & & 180 & & & 833 & 1666 \\
95 & 86 & 25 & 340 & 150,000 & 300,000 & 441 & 882 \\
200 & 180 & & 720 & & & 208 & 416 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Theoretical calculations of EoL cycles for different EV types. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Cycle** & **CE** & **Li Consumption** & **XLi** \\ \hline
500 & & & 122 \\
1000 & 0.99 & 0.8 & 18,530 \\
1500 & & & & \(2.8\times 10^{6}\) \\
3000 & & & & \(9.9\times 10^{12}\) \\ \hline
500 & & & & 10 \\
1000 & 0.995 & 0.8 & 120 \\
1500 & & & & 1474 \\
3000 & & & & \(2.7\times 10^{6}\) \\ \hline
500 & & & & 1 \\
1000 & 0.9995 & 0.8 & 1.3 \\
1500 & 0.8995 & 0.8 & 1.7 \\
3000 & & & & 3.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Need of CE and excess lithium for different cycle scenarios. Li\({}_{2}\)CO\({}_{3}\), LiF, Li\({}_{2}\)O, and LiOH [42] and it has been shown that increasing the amount of LiF in the SEI structure passivates the SEI layer and helps to increase CE [43]. In order to obtain higher LiF species, it is important to have a liquid electrolyte composition with high donatable fluorine concentration (DFC) [32]. As a result, among liquid electrolytes, fluorinated electrolytes such as lithium bis(fluorosulfonyl)imide (LiFSI) in fluoroethylene carbonate (FEC) provide longer cycle life. However, their cost is higher than that of conventional LiPF\({}_{6}\) in carbonate electrolytes. The replacement of a liquid electrolyte with a solid electrolyte, which is also acting as a separator, would create an inert solid system that could solve the problems mentioned above. In addition, solid-state batteries do not have a liquid junction, which facilitates the formation of series-connected cells in a pack, and the absence of this junction eliminates unnecessary volume, resulting in higher volumetric energy densities. Typically, organic liquid electrolytes for commercialized Li-ion batteries show conductivities of about 2 \(\times\) 10\({}^{-2}\) S/cm at room temperature and this value is slightly decreased to 5 \(\times\) 10\({}^{-3}\) S/cm with the integration of common porous polyolefin separators [44]. As a result, solid electrolytes have to compete with at least these high ionic conductivity values.