## 4 Electrodes and Electrolytes for SSTFBs
### Thin-film Electrodes
#### 4.1.2 Cathodes
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Materials** & **Crystalline** & **Discharge** & **Current** & **Discharge** & & **Discharge** & \\
**Structure** & **Rate (C)** & **Density** & **Capacity** & **Density** & **(g/cm\({}^{3}\))** & **Capacity** & **(\(\upmu\)Ah/cm\({}^{2}\)** \\  & & & (\(\upmu\)A/cm\({}^{2}\))** & **(mAh/g)** & & **\(\upmu\)m** \\ \hline LTO \({}^{\text{a}}\) & (111)-Oriented & & 10 & 157 & 3.38 & 53 & [348] \\ LTO \({}^{\text{a}}\) & (111)-Oriented & & 60 & 146 & 3.38 & 49 & [348] \\ LTO \({}^{\text{a}}\) & (100) Epitaxial & 3 & & 313 & 3.38 & 106 & [349] \\ LTO \({}^{\text{a}}\) & (110) Epitaxial & 3 & & 277 & 3.38 & 94 & [349] \\ LTO \({}^{\text{a}}\) & (111) Epitaxial & 3 & & 283 & 3.38 & 96 & [349] \\ LTO \({}^{\text{b}}\) & (111)-Oriented & 0.5 & & **7** & 3.38 & 25 & [350] \\ LTO \({}^{\text{b}}\) & (111)-Oriented & 95 & & **62** & 3.38 & 21 & [350] \\ LTO \({}^{\text{c}}\) & (111)-Oriented & & 10 & 110 & 3.38 & 37 & [354] \\ LNVO \({}^{\text{a}}\) & Amorphous & & 100 & **979** & 4.19 & 410 & [365] \\ LNVO \({}^{\text{b}}\) & Amorphous & & 100 & **1878** & 4.19 & 787 & [359] \\ LNVO \({}^{\text{b}}\) & Amorphous & & 75 & 1100 & 4.19 & 461 & [358; 360] \\ LNVO \({}^{\text{b}}\) & Polycrystalline & & 75 & 850 & 4.19 & 356 & [358; 360] \\ TNO \({}^{\text{a}}\) & Polycrystalline & & 35 & **398** & 4.42 & 176 & [361] \\ TNO \({}^{\text{a}}\) & Polycrystalline & & 50 & **324** & 4.42 & 143 & [361] \\ \hline \hline \end{tabular} Bold discharge capacity values in (mAh/g) are back-calculated from the data in (\(\upmu\)Ah/cm\({}^{2}\)\(\upmu\)m). Materials with superscript a, b and c represent the corresponding thin films deposited by PLD, radio frequency (RF) sputtering and CVD, respectively.  
\end{table} 
Table 6: Comparison of the discharge capacity among different anode materials. life. Sonoyama et al. [383] grew (111)-oriented LMO thin films on both STO and alumina substrates showing that the discharge capacity of the LMO films on STO was smaller than that of the LMO films on Al\({}_{2}\)O\({}_{3}\). Most films grown by RF sputtering, sol-gel, and CVD showed polycrystalline structures [386; 387; 388; 389; 390; 391]. The discharge capacity ranged from 43 to 80 mAh/g, depending on the deposition method and the crystallinity of the films. NMC thin films were mainly deposited via PLD and RF sputtering [392; 393; 394; 395; 396]. Prathibha et al. [394] grew polycrystalline Li(Ni\({}_{0.5}\)Co\({}_{0.25}\)Mn\({}_{0.25}\))O\({}_{2}\) thin films with mainly (001) and (104) orientations on Au-coated Si substrates via RF sputtering, obtaining a good discharge capacity of 57.5 \(\mu\)Ah/cm\({}^{2}\)\(\upmu\)m. Tan et al. [392] reported the orientation control of NMC sputtered thin films with different post-annealing temperatures ranging from 400 \({}^{\circ}\)C to 700 \({}^{\circ}\)C. In this work, the dominant orientation of the films changed from (104) to a mixture of (110) and (104). The authors demonstrated that the thin film annealed at 700 \({}^{\circ}\)C showed the best performance with the highest percentage of (110) oriented grain. Highly (001)-oriented NMC thin films were also synthesized on Au-buffered stainless steel substrates at 750 \({}^{\circ}\)C by Jacob et al. [393] in which the films showed a discharge capacity of 187 mAh/g. Table 7 summarizes the discharge capacities of different thin-film cathodes. Among LCO, NMC and LMO, the NMC cathode showed the best performance (\(\sim\)120 mAh/g) at a discharge rate of 0.1 C. In terms of the crystalline structure effect, epitaxial thin films showed a superior performance relative to polycrystalline and amorphous thin films.