The charge and discharge curves of both LiCoO 2/honeycomb LLT half-cells are shown in Figure 7. It is clearly observed that the internal resistance was reduced by increase of electrode–electrolyte contact area. The impedance spectra of both LiCoO 2/honeycomb LLT cells are shown in Figure 6. The contact between active material and electrolyte was much better. Figure 5(b) shows a cross-sectional SEM image of honeycomb electrolyte after impregnation of a mixture of LiCoO 2 with its precursor sol. The space can be reduced by application of the sol–gel method. This space decreases the electrode–electrolyte contact area and causes an increase of internal resistance of the cell. This normal impregnation technique produced a large space between electrode and honeycomb electrolyte by shrinkage of the LiCoO 2 particle during the calcination. Figure 5(a) displays a cross-sectional SEM image of honeycomb electrolyte after impregnation of ethanol suspension containing LiCoO 2 followed by calcination. However, the injection is not easy some specialized technique is required. Real space lattice vectors in this case are a 1 = a/2 (3, √3) and a 2 = a/2 (3, √3), where a ≈ 1.42 Å is C–C bond length, which is twice the radius of resonance band atomic radius (C res ≈ 0.71 Å) and occupies an area of 0.17 nm 2 (4.3 nm × 4 Å).īy injection of active material into the honeycomb holes, the all-solid-state battery can be fabricated. The basic unit cell identified in the rectangle as shown in the figure consists of two equivalent C atoms (1) and (2). For the band structure calculations of graphene honeycomb lattice, tight binding approximation is used as shown in Fig. 1.4.2B. The σ bonds in all carbon allotropes are responsible for the mechanical strength of that material. The electronic properties of graphene are attributed to these bands. These π bonds are generally half filled and hybridize together to form π and π∗ bands. In addition to three σ bonds, each carbon atom also forms a π bond oriented out of plane (z direction) as shown in Fig. 1.4.2C. In graphene, each carbon atom is part of a hexagonal structure in a two-dimensional plane and forms a σ bond with three neighboring carbon atoms, having an average interlayer distance of 1.42 Å. Graphene stability is due to its tightly packed carbon atoms and sp 2 orbital hybridization. Each C atom in graphene undergoes sp 2 hybridization between one 2s and two 2p orbitals resulting in sp 2 hybridized orbital. It can be regarded as two interleaving triangular lattices. The carbon atoms in graphene are situated in honeycomb lattice due to their sp 2 hybridization. The honeycomb structure is the basic building block of all carbon allotropes (shown in Fig. 1.4.2A) such as follows: (1) stacked honeycomb structure assembles into three-dimensional graphite, (2) two-dimensional structure constitutes graphene, (3) rolled honeycomb structure gives rise to one-dimensional carbon nanotubes (CNTs), and (4) wrapped honeycomb structure produces zero-dimensional fullerenes.
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