Investigation of expansion and potential of Si-dominant anodes with binder modification in full cells

Silicon as anode material in lithium-ion batteries shows immense volume change during (de-)lithiation. This swelling is an important factor to consider when developing Si anodes for practical applications, but also the utilization and behavior of both electrodes. Using Si capacity only partially results in less volume change, thus mitigating degradation. The impact of cell balancing and voltage window for limitation of capacity is investigated in full pouch cells via reference electrode and expansion measurement setup. Therefore, this work shows Si-dominant anodes with to different extends partially neutralized polyacrylic acid (PAA), cycled in normal and mild voltage ranges to reveal the impact on anode behavior and expansion. PAA binder is beneficial for silicon-containing anodes and neutralization of PAA improves the performance of this binder. In this work, it is shown that binder modification also has a large impact on anode coating expansion and silicon utilization in a voltage range of 3.0–4.2 V. Differences in performance between PAA neutralization degrees are not as prominent in case of 3.3–4.2 V voltage window. The reduced utilization of Si in this case leads to an over five times higher cycle life for all binder variations, at the same time sacrificing capacity. Limiting the capacity of a pure micro-Silicon anode helps to stabilize it during cycling. The limitation via voltage shows immensely increased cycle life. The electrochemical behavior of the anode is revealed by usage of a LFP reference electrode in full cells. Additionally, the influence of polyacrylic acid (PAA) neutralization degree on the swelling of micro-Silicon anodes is investigated. • Capacity-limited Si anodes show improved cycle life with 3.3–4.2 V in the full-cell. • Less swelling observed in 3.3–4.2 V than 3.0–4.2 V. • Swelling indifferent to binder modification in 3.3–4.2 V. • Stronger swelling observed for Si anodes with acidic PAA binder Li 0 PAA in 3.0–4.2 V. • Higher Si capacity usage with Li x PAA binder than acidic PAA in 3.0–4.2 V.