AUTONEWS

Double-layer electrode design powers next-gen silicon-based batteries for faster charging and longer range EVs

New research, led by Queen Mary University of London, demonstrates that a double-layer electrode design, guided by fundamental science through operando imaging, shows remarkable improvements in the cyclic stability and fast-charging performance of automotive batteries, with strong potential to reduce costs by 20–30%.

The research, published today in Nature Nanotechnology, was led by Dr. Xuekun Lu, Senior Lecturer in Green Energy at Queen Mary University of London.

In the study, the researchers introduce an evidence-guided double-layer design for silicon-based composite electrodes to tackle key challenges in the Si-based electrode— a breakthrough with strong potential for next-generation high-performance batteries.

The evolution of automotive batteries has been driven by ever-increasing demand for driving range and charging speed since EVs took off 15 years ago. Silicon electrodes can provide 10 times higher theoretical capacity and faster charging, but their large-scale deployment is held back by substantial volume changes of up to 300% during charge/discharge cycles. This means they degrade quickly and don't last long.

Silicon is a promising negative electrode material for high-energy batteries, but its volume changes during cell cycling cause rapid degradation, limiting its loading to about 10 wt.% in conventional graphite/Si composite electrodes. Overcoming this threshold requires evidence-based design for the formulation of advanced electrodes. Here we combine multimodal operando imaging techniques, assisted by structural and electrochemical characterizations, to elucidate the multiscale electro-chemo-mechanical processes in graphite/Si composite negative electrodes. 

We demonstrate that the electrochemical cycling stability of Si particles strongly depends on the design of intraparticle nanoscale porous structures, and the encapsulation and loss of active Si particles result in excessive charging current being directed to the graphite particles, increasing the risk of lithium plating. We also show that heterogeneous strains are present between graphite and Si particles, in the carbon-binder domain and the electrode’s porous structures. 

Focusing on the volume expansion of the electrode during electrochemical cycling, we prove that the rate performance and Si utilization are heavily influenced by the expansion of the carbon-binder domain and the decrease in porosity. Based on this acquired knowledge, we propose a tailored double-layer graphite/Si composite electrode design that exhibits lower polarization and capacity decay compared with conventional graphite/Si electrode formulations.

Multiscale multimodal operando imaging revealing the microstructural evolutions of graphite/micro-Si composite electrodes. Credit: Dr. Xuekun Lu

Assisted by multiscale multimodal operando imaging techniques, this research reveals unprecedented insights into the electro-chemo-mechanical processes of the graphite/silicon composite electrodes. Guided by these improved mechanistic understandings, a novel double-layer architecture is proposed, which addresses key challenges in material design, exhibiting significantly higher capacity and lower degradation compared to conventional formulations.

Dr. Xuekun Lu, who led the study, said, "In this study, for the first time, we visualize the interplay between microstructural design and electro-chemo-mechanical performance across length scales—from single particle to full electrode—by integrating multimodal operando imaging techniques.

"This study opens new avenues for innovating 3D composite electrode architectures, pushing the boundaries of energy density, cycle life, and charging speed in automotive batteries, and there by accelerating large-scale EV adoption."

Professor David Greenwood, CEO of the WMG High Value Manufacturing Catapult Center commented, "High silicon anodes are an important technology pathway for high energy density batteries in applications like automotive. This study offers a much deeper understanding of the way in which their microstructure affects their performance and degradation, and will provide a basis for better battery design in the future."

Provided by Queen Mary, University of London