*2.1.2 Al-selenium batteries*

Selenium composite prepared with carbon meso-porous material (2 nm < pore size <50 nm) can enhance the encapsulation of Se in the Al-Se batteries as shown in **Figure 2C** [32]. The CMK-3 carbon demonstrated that it exhibited a hexagonal meso-porous structure favorable for being host material in Al-Se batteries as shown in **Figure 2c**. The CMK-3 carbon nanorods showed a large pore volume of 1.78 cm3 g−1, a high surface area about 1632 m2 g−1, and a uniform pore size of 3.4 nm. The Al-Se battery based on Se@CMK-3 cathode delivers an initial discharge capacity of 218 mA h g−1 at 100 mA g−1 and a relatively high discharged potential above 1.5 V as shown in **Figure 2d**. Hollow selenium carbon nanotube (Se@CT) with a specific surface area of 61.49 m2 g−1 and pore diameter of 3.36 nm was also demonstrated as cathode material in Al-Se batteries [6]. The Se@CT cathode exhibited an initial discharge capacity of 447.2 mA h g−1 at 200 mA g−1 with a voltage of about 1.6 V. The capacity retains 83.5% even after the 200 cycles at 500 mA g−1. The carbon materials in Se@ CT cathode reside their structural stability of Se, reduce the dissolution of selenide products, and also avoid the volume change of Se during the electrochemical process. Therefore, mesoporous structure and pore size are important to stabilize the Se cathode as well as enhance the electrochemical performance. Mesoporous carbon fibers (MCFs) size from 2.7 to 8.9 nm prepared and demonstrated the effect of pore size on the electrochemical performance of Al-Se batteries [32]. The Al-Se battery based on MCFs material with pore size of 7.1 nm exhibited a good capacity of 366 mA h g−1. The chloroaluminate ion diffusivity greatly affects in the mesopore size of MCFs composite Se cathode. The carbon well-designed structures may provide the chloroaluminate ion transportation as well as charge transportation during charge/ discharge processes, which enhances the electrochemical behavior of Al-Se batteries.

### *2.1.3 Al-Te cathode batteries*

The electrical conductivity of Te cathode is very high [12]. Hence, utilization ratio of active material is large and also exhibited good rate performance in Al ion batteries. *Advanced Chalcogen Cathode Materials for Lithium-Ion Batteries DOI: http://dx.doi.org/10.5772/intechopen.103042*

Te cathode is easily prepared by coating the slurry of Te powder, acetylene black, and binder on current collector, without any host materials as shown in **Figure 2e** [20]. The Al-Te battery exhibited with raw material an initial capacity of 913 mA h g−1 at 20 mA g−1 with a potential of 1.4 V as shown in **Figure 2f**. The Al-Te battery delivers a good rate performance at different current densities due to the high electrical conductivity of Te. However, Te batteries exhibited capacity fading due to its leaching of soluble telluride from the cathode. Further, the rGO materials were introduced to encapsulate Te nanowires in Al-Te battery [6]. This Te/rGO cathode battery exhibited a capacity of 1026 mA h g−1 at 500 mA g−1 and also delivers a considerable capacity beyond 100 cycles at 1.0 and 2.0 A g−1. The rGO materials suppress the dissolution of telluride into electrolyte indicating better utilization of Te. Further, N-doped porous carbon materials coupled with rGO also introduced as a host materials for the improvement of the stability of Al-Te batteries [33]. The rGO materials are easily encapsulated soluble tellurium species under physical and chemical confinements. Therefore, the Al-Te batteries exhibited excellent cyclic ability. It exhibited initial specific capacity of 935.5 mA h g−1 and 467.5 mA h g−1 after 150 cycles with the Te loading of 70 wt%. Thus, a host material with well-designed structure, such as porous conductive matrix with specific components is necessary for cathode materials in Al-SSTs batteries.

#### **2.2 Interfacial problems in sulfur batteries**

In the case of sulfur lithium-ion batteries, during the discharge/charge reaction, the sulfur required to be tightly attached to a host with sustainable conduction of Li<sup>+</sup> and e<sup>−</sup> . Generally, the cathodic reaction occurs at the host/elemental sulfur/liquid electrolyte interface. The carbon nano materials such as graphene, carbon nanotube (CNT), or carbon nanofiber and metal sulfide are the indispensable 2D materials to sulfur host. The modified host materials with only nano-sized pores alone cannot accommodate the sulfur and completely reduce suppression of the shuttle effect in the LiPS [34]. Therefore, in recent years the development of interface components for Li-S batteries is most impartment [28, 35]. One of the main strategies is that the coating of materials exhibited several merits such as fast electrical and ionic transmission capability, uniform thickness, and stable distribution of composition on the surface of cathode materials without effect of volume.

The another most prominent strategy is that in situ growth of nano transition metal oxides (sulfide) [36] or the loading of nano transition metals [37, 38] on the carbon surface leads to overcome the poor contact between sulfur and carbon materials. In this process, (sulfides, oxides, nitrides, etc.) compounds are added or doped some of the elements (N, S and co-NS) and their derivatives. Therefore, polar bonds are generated between host and sulfur; those provided fast transmission of electrons as well as increase the ions redox reactions at the interface.

#### *2.2.1 Inter facial problems in nano metal sulfides (oxide)*

Various nano metal oxides have interacted with LiPS through strong chemical bonds, which are reducing the shuttle effect. In particular, oxygen-rich compounds such as V2O3 [39], TiO2 [40, 41], SnO2 [42], Co3O4 [43], MnO2 [44, 45]) successfully prepared as LiPS traps to enhance the cyclic stability. The high conductive Ni foam/ graphene/carbon nanotubes/MnO2 nanoflakes (NGCM) were proposed in which interconnected Ni foam, graphene, and carbon nanotubes of the NGCM sponge facilitated

efficient electron transfer. The NGCM sponge showed good wettability and interfacial contact with the Li-S electrolyte, and the MnO2 nano flakes exhibited electro-catalytic effects as well as strong chemisorption on LiPS [46]. The porous and double-shelled architecture decreases the ion transfer distance, Uniform sulfur distribution offers active interfaces as well as decreases volume changes. Luo et al. developed spinel Ni-Co oxide double-shelled microspheres (NCO-HS), which consisted of defective spinel NiCo2O4–x, as the multifunctional sulfur host material. The S@NCO-HS prepared under high sulfur loading exhibited minimum capacity fading rate of 0.045% per cycle over 800 cycles with high areal specific capacity of 6.3 mAh cm−2 at 5 C.
