(93b) A Novel Binder to Improve the Electrochemical Performance of Si/C Anode of Lithium Batteries

Recently, with the raising concern on energy and environmental issues caused by the usage of non-renewable fossil fuel, energy storage device such as lithium-ion batteries (LIBs), supercapacitors, are holding great promise for transportation purpose like electric vehicles. In order to achieve high-energy-density LIBs, Si has been extensively investigated due to its high theoretical specific capacity of 3580mAh g-1 for the complete transition to Li15Si7.[1] However, its practical applications are limited by the dramatic volume changes (400%) during lithium insertion and extraction, which lead to the pulverization and electrode peel off. There are several methods to buffer or constrain the volume changes of Si based electrodes, among which binders are very critical in maintaining the electrode integrity.[2]

In this short term, the novel binder (Alg-α- Li2C2O4) was prepared by mixing sodium alginate (Alg), α-cyclodextrin and Li2C2O4 with certain weight ratio. Thermal Gravimetric Analyzer (TGA) shows that α-cyclodextrin and Li2C2O4 have good thermal stability. Cycle performance tests show that cells with the composite binder has better performance than that of PVDF, or Alg. The composite binder can improve the discharge capacity of the Si/C half cells and improve the rate properties. Scanning electron microscope (SEM) is performed on the electrodes with different binders before and after cycling, indicates that the cycled Si/C electrode with Alg-α- Li2C2O4 binder is more stable than those formed when using PVDF and Alg binder. The Fourier transformation infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements reveal that the hydrogen bonding is formed between the Si surface and the polar groups (-OH, -COOH) of Alg-α- Li2C2O4, endow the novel binder some self-healing capability.

• Choi N S, Ha S Y, Lee Y, et al. J. Electrochem. Sci. 6(2), 35-49 (2015).
• Ryou M, Kim J, Lee I, et al. Advanced Materials, 2013, 25(11):1570-1570.