Toward Achieving High Areal Capacity in Silicon-Based Solid-State Battery Anodes: What Influences the Rate-Performance?

Achieving high areal capacity and rate performance insolid-statebattery electrodes is challenging due to sluggish charge carrier transportthrough thick all-solid composite electrodes, as the transport stronglyrelies on the microstructure and porosity of the compressed composite.Introducing a high-capacity material like silicon for such a purposewould require fast ionic and electronic transport throughout the electrode.In this work, by designing a composite electrode containing Si nanoparticles,a superionic solid electrolyte (SE), and a carbon additive, the possibilityof achieving areal capacities over 10 mAh & BULL;cm(-2) and 4 mAh & BULL;cm(-2) at current densities of 1.6mA & BULL;cm(-2) and 8 mA & BULL;cm(-2), respectively, at room temperature is demonstrated. Using DC polarizationmeasurements, impedance spectroscopy, microscopic analyses, and microstructuremodeling, we establish that the route to achieve high-performanceanode composites is microstructure modulation through attaining highsilicon/solid electrolyte interface contacts, particle size compatibilityof the composite components, and their well-distributed compact packingin the compressed electrode.