How lasers can push silicon-graphite anodes towards next-generation battery

Invited: Graphite anode material is commonly used in lithium-ion batteries. Due to the demand for a significantly increased energy density for xEVs (electromotive vehicles), there is worldwide a strong effort to add nano-sized silicon particles to composite graphite electrodes. Silicon has the benefit to provide one order of magnitude higher gravimetrical energy density than graphite. However, a bottleneck of silicon is its huge volume expansion of about 300 % during electrochemical cycling which induces high compressive stress and subsequent film delamination, crack formation, and finally degradation of electrochemical cells. ... mehrIn this study, thick film graphite, silicon, and silicon–graphite composite electrodes were developed and subsequently ultrafast laser structured in order to reduce compressive stress during electrochemical cycling and diffusion overpotential. The latter one is a critical issue at elevated power densities and for high film thicknesses, i.e., mass loading. By laser ablation, grid structures were introduced into the electrodes and 3D elemental mapping could demonstrate that new lithium-ion diffusion pathways arise along the structure's sidewalls and are activated with increasing power densities. It was successfully shown that laser structured electrodes benefit from a homogenous lithiation, reduced compressive stress, and an overall improved electrochemical performance in comparison to unstructured electrodes. A reduced mechanical and chemical cell degradation was achieved with structured electrodes in comparison to unstructured ones and design rules for silicon–graphite electrode architectures were derived. Laser structuring of electrodes offers a new manufacturing tool for next-generation battery production to overcome current limitations in electrode design and cell performance.

Invited: Graphite anode material is commonly used in lithium-ion batteries. Due to the demand for a significantly increased energy density for xEVs (electromotive vehicles), there is worldwide a strong effort to add nano-sized silicon particles to composite graphite electrodes. Silicon has the benefit to provide one order of magnitude higher gravimetrical energy density than graphite. However, a bottleneck of silicon is its huge volume expansion of about 300 % during electrochemical cycling which induces high compressive stress and subsequent film delamination, crack formation, and finally degradation of electrochemical cells. ... mehrIn this study, thick film graphite, silicon, and silicon–graphite composite electrodes were developed and subsequently ultrafast laser structured in order to reduce compressive stress during electrochemical cycling and diffusion overpotential. The latter one is a critical issue at elevated power densities and for high film thicknesses, i.e., mass loading. By laser ablation, grid structures were introduced into the electrodes and 3D elemental mapping could demonstrate that new lithium-ion diffusion pathways arise along the structure's sidewalls and are activated with increasing power densities. It was successfully shown that laser structured electrodes benefit from a homogenous lithiation, reduced compressive stress, and an overall improved electrochemical performance in comparison to unstructured electrodes. A reduced mechanical and chemical cell degradation was achieved with structured electrodes in comparison to unstructured ones and design rules for silicon–graphite electrode architectures were derived. Laser structuring of electrodes offers a new manufacturing tool for next-generation battery production to overcome current limitations in electrode design and cell performance.