## 2 Electrodes and Electrolytes for Lithium-Based Batteries
### Electrodes
#### 2.1.1 Anodes  
Lithium is the most attractive anode material because of its high theoretical capacity (3860 mAh/g) and its lowest negative electrochemical potential (-3.040 V vs. SHE). Despite these advantageous intrinsic properties, there are massive challenges to the successful incorporation of lithium metal anodes into commercial lithium-based batteries. The foremost obstacle is the formation of lithium metal dendrites during cycling, which can cause thermal run-away [84]. Since the first patent for a dichalcogenide lithium metal battery was awarded to Moli Energy in 1980, numerous strategies have been developed to manage the formation of dendrites [85]. Approaches such as electrolyte additives [86], artificial solid electrolyte interface (SEI) layers [87] and engineering of the interfacial layers and lithium host [88; 89] have offered moderate successes. A very appealing solution is the use of a solid electrolyte mechanical barrier to inhibit dendrite growth, which will be discussed in detail later. With increasing interest in SSBs, recent investigations into lithium-metal anodes have focused on the nucleation kinetics, flow behavior and host-matrix type electrode supports in SSBs. For example, using conductive atomic force microscopy, Lushta et al. [90] described the characteristic temperature-independent energy barriers to lithium nucleation and growth on a Li\({}_{1+\times}\)Al\({}_{x}\)Ti\({}_{2-\times}\)(PO\({}_{4}\))\({}_{3}\) (LATP) type solid conductive glass substrate. Interestingly, the nucleation was shown only to occur on the LATP and not on the interspersed insulating AlPO\({}_{4}\). Silicon (Si) with a specific capacity (3580 mAh/g) similar to lithium metal anode is an attractive anode material for the next generation of batteries [91]. The primary challenge to further implementation of the Si anode is the volume expansion in excess of 300% when fully intercalated with lithium. The associated stresses induce structural failure causing pulverization of the particles, which results in poor capacity retention and inferior coulombic efficiency [92]. Strategies to improve this bottleneck such as surface engineering (pores) [93], size and shape control (nanowires/tubes) [94; 95; 96], surface modification [97], component modulation (M-Si alloying) and encapsulation in a carbon-rich matrix (graphene, graphdiyne) are widely studied. Throughout these strategies, maintenance of mechanical and conductive networks and interfacial contact are the thematic challenges. Here, we introduce recent works on Si engineering to improve the performance of LIBs. Shang et al. [98] recently synthesized 2D-graphdiyne-wrapped silicon nanoparticles (Si-NPs), which showed a capacity of 4122 mAh/g at 0.2 A/g and 1988 mAh/g at 10 A/g. Zhou et al. [99] used a different approach to ensure transport across the carbon support by using an N-doped graphite coating (8-12 nm) of Si-NPs to facilitate Li\({}^{+}\) mobility. Xu et al. [100] reported the encapsulation of Si-NPs in a spiderweb-like carbon structure by using graphene oxide anchors. Hwang et al. [101] synthesized porous silicon nanowires by metal-assisted chemical etching of boron-doped p-type Si(100) wafers with Ag nanoparticles. By controlling the doping concentration through an acid-mediated synthesis, the authors achieved high surface area silicon nanowires (up to 260 m\({}^{2}\)/g) with a low charge transfer resistance of 9 Ohms. Li et al. [102] demonstrated the creation of a Si-NP/C composite anode with high tap-density (-1.0 g/cm\({}^{3}\)) anchored onto flake graphite. Graphitic carbon is the most widely used anode material for commercial LIBs. Energy is stored via lithium intercalation between constituent graphene sheets with a fully lithiated formula of LiC\({}_{6}\). Studies on the insertion of Li in carbon are still active. The super-dense phase of lithium intercalated between a graphene bilayer was reported by Kuhne et al. [103].