Low-Cost Al2O3 Coating Layer As a Preformed SEI on Natural Graphite Powder To Improve Coulombic Efficiency and High-Rate Cycling Stability of Lithium-Ion Batteries

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Abstract
Coulombic efficiency especially in the 1st cycle, cycling stability and high rate performance are crucial factors for commercial Li-ion batteries (LIBs). To improve them, in this work, Al2O3-coated natural graphite powder was obtained through a low-cost and facile sol-gel method. Based on a comparison of various coated amounts, 0.5mol% Al(NO3)3 (vs. mol of graphite) could bring about a smooth Al2O3 coating layer with proper thickness, which could act as a preformed solid electrolyte interface (SEI) to reduce the regeneration of SEI and lithium ions consumption during subsequent cycling. Furthermore, we examined the advantages of Al2O3 coating by relating energy levels in LIBs using density functional theory calculations. Owing to its proper bandgap and lithium ion conduction ability, the coating layer performs the same function as a SEI does, preventing electron from getting to the outer electrode surface and allowing lithium ion transport. Therefore, as a preformed SEI, the Al2O3 coating layer reduces extra cathode consumption observed in commercial LIBs.
Funding Information
  • State Administration of Foreign Experts Affairs (B14040)
  • Ministry of Education of the People's Republic of China (B14040, xjj2014044)
  • National Natural Science Foundation of China (21203145, 21343011, 21503158)
  • Natural Science Foundation of Shaanxi Province (2014JM6231, 2014JQ2-2007, 2014JQ2079)
  • Research Grants - Short-Term Grants, 2015 (57130097)

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