Toward efficient Si-based anodes for Li-ion batteries for EV application

Abstract

Abstract Li-ion batteries technology dominates the market today because it exhibits both high gravimetric and volumetric energy density as well as a long lifespan. However, to satisfy current demands, especially for electrical vehicle application, many improvements on Li-ion batteries are necessary. Increasing the energy density of Li-ion batteries requires the development of new electrode materials with higher charge capacities. On the anode side, silicon (Si) has attracted interest due to its high theoretical capacity of 3579 mAh g-1, which is ten times higher than the conventional graphite used in commercial Li-ion batteries. However, practical application is limited because of poor cycling stability. In this dissertation, the development of a Si-based anode which meets a rational design for a full cell configuration has been studied. The first approach has been the development of Si/mesoporous carbon (Si/MC) composites as an active material. Si/MC composites were synthesized by dispersing Si nanoparticles in a 3D Resorcinol-Formaldehyde (RF) polymer, followed by carbonization and HF etching. The second approach has been the selection of the proper commercial conductive additives to improve the electrical conductivity of Si/MC anodes. Graphite, Super C65, Super C45, and a combination of graphite and Super C65 were compared. The third approach for dealing with the initial capacity loss has been the use of electrolyte additives. The effect of three different electrolyte additives : vinyl carbonate (VC), succinic anhydride (SA), and lithium bis(oxalato)borate (LiBOB) on the electrochemical performance of Si/MC anodes were investigated. The as-prepared Si-based anode by using a facile synthesis exhibited a discharge capacity of > 800 mAhg-1 with average columbic efficiency of 99% over 400 cycles. Additionally, the as-prepared Si/MC anode was coupled with a commercial Li[Ni1/3Mn1/3Co1/3]O2 (NMC) cathode to see the limiting working potential in a full cell configuration.