Nanoparticle silicon−graphite composite electrodes are a viable way to advance the cycle life and energy density of lithium-ion batteries. However, characterization of composite electrode architectures is complicated by the heterogeneous mixture of electrode components and nanoscale diameter of particles, which falls beneath the lateral and depth resolution of most laboratory-based instruments. In this work, we report an original laboratory-based scanning probe microscopy approach to investigate composite electrode microstructures with nanometerscale resolution via contrast in the electronic properties of electrode components. Applying this technique to silicon-based composite anodes demonstrates that graphite, SiO x nanoparticles, carbon black, and LiPAA binder are all readily distinguished by their intrinsic electronic properties, with measured electronic resistivity closely matching their known material properties. Resolution is demonstrated by identification of individual nanoparticles as small as ∼20 nm. This technique presents future utility in multiscale characterization to better understand particle dispersion, localized lithiation, and degradation processes in composite electrodes for lithium-ion batteries.

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Nanocomposite Si-graphite electrodes are a viable option for increasing the energy density and life of lithium-ion battery anodes. In comparison to model systems (e.g., Si wafer and Si thin film), Si nanoparticles, ranging in diameter from tens to hundreds of nanometers, have higher rate capacity and improved fracture toughness.1, 2 However, characterization efforts to better understand localized degradation mechanisms and heterogeneous aging behaviors of distinct components—Si, graphite, binder, and conductive carbon—in Si-based nanocomposite anodes through cycling are hindered by the limited information that can be achieved at the nanoscale using traditional microscopy techniques. To date, high resolution, three-dimensional structural visualization of the Si-based composite electrode has relied upon techniques like X-ray nano-computed tomography3, 4, that provide morphological information but not electronic or chemical information. In this work, we report a novel lab-scale scanning probe microscopy-based approach to map the 3-D nanostructure of composite anodes via contrast in their components’ intrinsic electronic properties. By incorporating experimental nanoscale electronic resistivity data through interpolation, volumes can be extracted to represent distinct constituent phases of the composite electrode. This approach presents an opportunity for relatively high throughput, nanoscale characterization of composite anodes and cathodes to investigate phenomena such as particle dispersion in electrode preparation and electrode evolution through cycling. Ultimately, this technique shows future utility for the multiscale understanding of structural evolution and degradation processes within lithium-ion batteries. Figure 1: Interpolated resistivity layers captured within a Si-Carbon(C) composite electrode, processed to extract C-rich and Si-rich volumes. R. C. de Guzman, J. Yang, M. M.-C. Cheng, S. O. Salley, and K. Y. Simon Ng, Journal of Materials Science, 48 (14), 4823-4833 (2013). S.-L. Chou, J.-Z. Wang, M. Choucair, H.-K. Liu, J. A. Stride, and S.-X. Dou, Electrochemistry Communications, 12 (2), 303-306 (2010). O. O. Taiwo, M. Loveridge, S. D. Beattie, D. P. Finegan, R. Bhagat, D. J. L. Brett, and P. R. Shearing, Electrochimica Acta, 253 85-92 (2017). J. Wu, F. Ma, X. Liu, X. Fan, L. Shen, Z. Wu, X. Ding, X. Han, Y. Deng, W. Hu, and C. Zhong, Small Methods, 3 (10), (2019). Figure 1