From slurry to system: Uncovering the evolving bottlenecks of micron-sized silicon anodes in half- and full-cells

Silicon is a promising replacement for graphite in next-generation lithium-ion battery (LIB) anodes due to its high specific capacity and low lithiation potential. However, its substantial volume change during (de-)lithiation severely compromises structural integrity and accelerates degradation, hindering practical implementation. In this work, we establish a direct link between aqueous slurry processing and electrode performance. By tuning the slurry solid content and coating thickness, we fabricate distinct micro-architectures to decouple the effects of areal loading and porosity. Comprehensive half-cell tests reveal a clear, stress-dependent evolution of the failure mechanism: from a balance between kinetics and stress-buffering at low depth-of-discharge (DoD), to a regime dominated by mechanical stress from areal loading at higher DoD, culminating in an operational limit where all architectures fail. Asymmetric rate tests further identify de-lithiation as the primary kinetic bottleneck, also governed by areal loading. Crucially, when integrated to practical Si||NMC811 full-cells with controlled N/P ratios, these distinct anode-level differences are masked. The long-term capacity fade becomes nearly identical for different anodes, suggesting that the performance bottleneck shifts to a shared system-level limitation. However, we identify that an increase in anode loading leads to more stable voltage profiles, a consequence of it operating at a shallower per-gram depth-of-discharge.