SnO2-Embedded Nanoporous Carbon Electrode with a Reaction-Buffer Space for Stable All-Solid-State Li Ion Batteries

Implementation of Different Conversion/Alloy Active Materials as Anodes for Lithium-Based Solid-State Batteries

To complement or outperform lithium-ion batteries with liquid electrolyte as energy storage devices, a high-energy as well as high-power anode material must be used in solid-state batteries. An overlooked class of anode materials is the one of conversion/alloy active materials (e.g., SnO2, which is already extensively studied in liquid electrolyte-based batteries). Conversion/alloy active materials offer high specific capacities and often also fast lithium-ion diffusion and reaction kinetics, which are required for high C-rates and application in high-energy and high-power devices such as battery electric vehicles. To date, there are only very few reports on conversion/alloy active materials─namely, SnO2─as anode material in sulfide-based solid-state batteries, with a relatively complex electrode design. Otherwise, conversion-alloy active materials are used as a seed layer or interlayer for a homogeneous Li deposition or to mitigate the formation and growth of the SEI, respectively. Within this work, four different conversion/alloy active materials─SnO2, Sn0.9Fe0.1O2, ZnO, and Zn0.9Fe0.1O─are synthesized and incorporated as negative active materials ("anodes") in composite electrodes into SSBs with Li6PS5Cl as solid electrolyte. The structure and the microstructure of the as-synthesized active materials and composite electrodes are investigated by XRD, SEM, and FIB-SEM. All active materials are evaluated based on their C-rate performance and long-term cyclability by galvanostatic cycling under a constant pressure of 40 MPa. Furthermore, light is shed on the degradation processes that take place at the interface between the active material and solid electrolyte. It is evidenced that the decomposition of Li6PS5Cl to LiCl, Li2S, and Li3P at the anode is amplified by Fe substitution. Lastly, a 2D sheet electrode is designed and cycled to tackle the interfacial degradation processes. This approach leads to an improved C-rate performance (factor of 3) as well as long-term cyclability (factor of 2.3).

Patterning Design of Electrode to Improve the Interfacial Stability and Rate Capability for Fast Rechargeable Solid-State Lithium-Ion Batteries

Patterned electrodes were developed for use in solid-state lithium-ion batteries, with the ultimate goal to promote fast-charging attributes through improving electrochemically activated surfaces within electrodes. By a conventional photolithography, patterned arrays of SnO₂ nanowires were fabricated directly on the current collector, and empty channel structures formed between the resulting arrays were customized through modifying the size and interval of the SnO₂ patterns. The composite electrolyte comprising Li₇La₃Zr₂O₁₂ and poly(ethylene oxide) was exploited to secure intimate interfacial contact at the electrode/electrolyte junction while preserving ionic conductivity in the bulk electrolyte. The potential and limitation of the electrode patterning approach were then explored experimentally. For example, the electrochemical behaviors of patterned electrodes were investigated as a function of variations in microchannel structures, and compared with those of conventional film-type electrodes. The findings show promise to improve electrode dynamics when electrochemical reaction kinetics could be hindered by poor interfacial characteristics on electrodes.