Alternative Binder for Silicon Based Anodes in Lithium-Ion Batteries Towards Elevated Temperatures

Li-ion batteries are one of the most promising systems for mobile energy storage. While carbon based anodes have been well explored and applied in most of commercially available Li-ion batteries, the investigation of silicon based anode materials is still in progress. Silicon as active material has the capability to exceed and replace all other anode materials in future lithium-ion batteries due to the highest specific capacity among all other anode materials. For ambient temperature lithiation of bulk silicon, the lithium richest phase Li₁₅Si₄ achieves a specific capacity of 3579 mAh g^-1.^[1]

One major drawback of silicon is its volume change (up to 300%) during the lithiation, which leads to mechanical stress of the anode and a poor cycling stability.

Although many efforts have been made in changing the binder, different active material combinations and adapting a composition of carbonate based electrolytes, these cell systems suffer from a breakdown in functionality at ambient as well as elevated temperatures up to 60°C.^[2,3]Besides the volume expansion, it is expected that the decomposition of the electrolyte is the main reason for the fast end of life at elevated temperatures.

With respect to the increasing demand of environmentally-friendly electrode manufacturing, we focused on water solvable binders and compared an alternative new binder to carboxy methyl cellulose (CMC), which is well known as a standard binder for silicon and silicon composite based electrodes.^[4,5]In this work we propose an alternative binder which shows a stable cycling at room temperature as well as at 60°C with the usage of organic carbonate based electrolytes.

Moreover, we present different spectroscopic analysis to understand the binding mechanisms of the different binder systems of silicon based and silicon / graphite composite electrodes accompanied by electrochemical measurements.

We kindly thank the Deutsche Forschungsgemeinschaft (DFG) for the funding of the project SPP 1473 - WeNDeLIB (WI 2727/4-1).

[1] M.N. Obrovac, L. Christensen, Electrochem. Solid-State Lett. 7 (2004), A93-A96.

[2] C.L. Campion et al., J.  Electrochem. Soc. 152 (2005), A2327-A2334.

[3] N.S. Hochgatterer et al., Electrochem. Solid-State Lett. 11 (5) (2008), A76-A80.                                        

[4] Li, Jing, R. B. Lewis, and J. R. Dahn. Electrochem. Solid-State Lett. 10.2 (2007), A17-A20.                   

[5] S. Lux et al., J.  Electrochem. Soc. 157(3) (2010), A320.