Quantification of lithium inventory loss in micro silicon anode via titration-gas chromatography

The commercialization of silicon as an anode material for lithium-ion batteries has been largely impeded by its severe volume changes during cell operation, causing continuous loss of Li inventory. As such, it is vital to understand and quantify the sources of capacity fade in order to design effective mitigation strategies. Herein, we design a method based on Titration Gas Chromatography (TGC) to reveal a non-linear volume expansion in μSi anode during the lithiation process. The severe volume expansion towards the end of lithiation leads to accelerated SEI formation and conductive pathway loss, resulting in a large amount of trapped Li–Si alloy accumulation. The TGC method is also applied to investigate μSi anodes with two different binders: Sodium Carboxymethyl Cellulose (CMC-Na) and Polyacrylic Acid (PAA). The primary reason for capacity loss for anode with CMC-Na binder is trapped Li–Si alloy, which can be mitigated by using more robust PAA binder. The Sate of Charge (SoC) control principle is also investigated in μSi-LFP full cells with both binders by tuning the N/P ratios (1.5–3). The results indicate binder robustness is crucial for mitigating the trapped Li–Si alloy accumulation in μSi anode.