Improved Cycling Performance of Silicon/Carbon-Electrodes by Surface Modification of Active Materials and Neutralization of Poly(Acrylic Acid)-Binder

摘要

Silicon (Si) containing anodes for lithium ion batteries have recently attracted much attention due to the reversible electrochemical alloying of lithium and the high specific capacity of Si.[l] However, the significant volume changes of Si occurring during the alloying and de-alloying process lead to an unacceptable capacity fading of such electrodes.[2] The increase of the mechanical stability of Si-based electrodes requires the development of binders which interact with Si and can inhibit the loss of the electronic contact between the active material particles and the conductive carbon network.[3] In this contribution, we present new methods for the optimization of the cycling performance of Si containing electrodes which are prepared with poly(acrylic acid) (PAA) as binder. The influence of the neutralization of PAA with lithium hydroxide on the irreversible capacity during the formation cycles and the cycling stability of electrodes are investigated. Furthermore, the Si/binder-ratio has been varied for the optimization of the composition and the cycling performance of electrodes. A possible mechanism of the interaction between PAA and its neutralized derivatives is postulated, based on the chemical interactions between binder and surface groups of the active materials.