# A Review on Nanocomposite Materials for
## 5 Anode Materials  
### Carbon Based Anodes  
Carbon based anode materials are the industry standard in Li-ion batteries, and graphitic carbon is the dominant one due to its favorable electrochemical properties (i.e., low and near flat operating voltage of ~0.25 V vs. Li/Li\({}^{+}\)), low cost, and chemical and mechanical stability [125; 126]. Graphite has a theoretical capacity of 372 mAh/g with the stoichiometry of LiC\({}_{6}\). Non-graphitic carbons such as hard carbons have higher specific capacity and cycle life, good rate capabilities and lower cost of production; however, they suffer from low density and larger irreversible capacity and hysteresis in the voltage profile [127]. The metal-carbon composites have been extensively studied to improve the performance of carbon anode materials [128; 129; 130; 131; 132; 133; 134; 135]. The composite anodes, in general, showed improved performance than simple mechanical mixing of the metals with the anode materials [125]. The chemically deposited Ag on graphite improved the cycle life, which was attributed to the enhanced electron conduction between graphite particles due to low electrical resistance of Ag. Additionally, the capacity of the Ag-graphite composite cathode was superior to the graphite cathode alone since Ag can form LiAg alloy upon interaction with Li [128]. Moreover, Ag deposited graphite was shown to be more resistant to humidity (i.e., ~1000 ppm) which is beneficial for easy manufacturing of Li-ion batteries [129; 130]. The microencapsulation of graphite with nanosized Ni showed improvement in initial charge-discharge performance, Coulombic efficiency and cycle life. The proposed mechanism for the improvement in the initial charge-discharge behavior (i.e., decrease in irreversible capacity) was the passivation of the graphite edge surfaces by Ni deposition which in return reduces the highly active edge surface area that is exposed to the electrolyte, and makes the edge surfaces less permeable to the solvated Li ions [131; 132]. Similar effects were also observed for Cu deposited natural graphite, in addition to the suppression of electrolyte decomposition and solvated Li ion co-intercalation, improvement in high rate capability was reported due to enhanced charge-transfer properties [133]. The Al deposition of natural graphite improved the cycle life and rate capability remarkably due to decreased charge-transfer resistance during cycling [134]. The other metals studied for metal-graphite composites include Au, Bi, In, Pb, Pd, Sn and Zn, and all these metal coatings, which were prepared by vacuum evaporation technique, improved the rate capability [135]. The rate capability was found to be dependent on the film thickness, too thick coatings limit the Li mobility hence reduces the rate capability. Carbon coating is another strategy to improve the electrochemical performance of the graphite [136; 137; 138; 139]. One of the methods to enhance the low temperature performance of Li-ion batteries is to utilize propylene carbonate (i.e., PC, melting point = \(-\)49 \({}^{\circ}\)C) based solvents instead of ethylene carbonate (i.e., EC, melting point = 38 \({}^{\circ}\)C) based ones. However, it is well known that PC decomposes on the graphite surface; therefore, cannot form a stable solid electrolyte interphase (SEI) layer on the graphite surface which leads to diminished cycle life [140]. The studies conducted on carbon coated graphite prepared by thermal and chemical vapor decomposition techniques showed that Coulombic efficiency can be improved significantly since carbon coating acts as a buffer zone between graphite and the PC based electrolyte, and leads to compact and thinner SEI layer as shown in Figure 12[137; 138; 139]. If carbon coated graphite anode is utilized in Li-ion battery manufacturing, high rolling and calendaring pressures should be avoided since high pressures can destroy the carbon coating [137]. The carbon coating also stores Li hence does not adversely affect the specific capacity of the graphite [139].