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Identifying Structure-Performance Relations for Fast-Charge Battery Anodes
Case Study
Royce’s Industrial Collaboration Project (ICP) awarded £123K towards this project, which focused on developing a new understanding of fast-charging mechanisms in graphite and disordered carbon anodes for next generation Li-ion batteries to develop batteries capable of charging safely in minutes for EV applications and beyond.
Fast-charging of lithium-ion cells often causes capacity loss and limited cycle life, hindering their use in high-power applications. Graphite, which is widely used in commercial Li-ion cells, is particularly poor at fast-charge in terms of capacity retained and cell degradation. In contrast, disordered carbon anodes are very well suited for fast-charge as they retain high capacity at high charging rates as well as resisting lithium plating. However, the physical processes that explain the differences in performance are not fully understood.
HE Carbon Supercap Ltd (HE) has produced a new form of disordered carbon anode (dC) using a patented methodology which exhibits significant advantages in fast-charge performance compared to the current state-of-the-art graphite anode, without the prohibitively high irreversible capacity losses typically observed for other disordered carbons or Silicon. This Royce ICP project sought to establish a greater depth of understanding of the origin of the improved performance, in order to facilitate the translation of this technology from proof-of-concept to pilot scale production.
The project employed advanced operando characterisation, electrochemical analysis and a multi-physics model to identify and quantify chemical and physical constraints during fast-charging, comparing state-of-the-art graphite and nanocluster carbon (a disordered carbon) anodes. The combination of modelling material phase separation phenomena together with coupled ion-electron transfer theory reveal significant insight. The active material strongly influences charge transfer kinetics and solid-state lithium diffusion. Unlike graphite, nanocluster carbon supports lithium insertion without phase separation, enabling faster lithium diffusion, better volume utilization and lower charge transfer resistance. Furthermore, through this Royce ICP project, we were able to demonstrate the practical implications of these material phenomena through multi-layer pouch cells made with nanocluster carbon anodes, which withstand over 5,000 fast-charge cycles at 2C without significant degradation (< 10% at reference 0.2C).
“The mass adoption of electric vehicles (EVs) is critical to achieving Net Zero. However, the slow charging times for EVs is widely seen as a barrier to consumer adoption. Replacing the graphite anode with disordered carbon could offer a way to achieve high energy Li-ion batteries capable of charging safely in less than 15 minutes. However, the origin of the improved lithiation dynamics in these disordered carbons remains poorly understood. Here, an interdisciplinary team from the Universities of Oxford, Warwick, Nottingham and Pisa uncover the dynamic processes occurring in a high-performance disordered carbon anode materials produced by HE Carbon Supercap.”
Dr Robert House
Senior Research Fellow, Department of Material, University of Oxford
Collaborators
This project brought together academic groups at Oxford, Nottingham, Pisa and Warwick with a breadth of expertise spanning advanced energy materials characterisation, electrochemistry and modelling. Tackling the challenge of understanding the mechanisms of fast-charge performance of HE Carbon Supercap’s disordered carbon anode material required a multimodal approach involving operando techniques to capture the dynamic processes occurring during battery operation.
The Royce capabilities for operando X-ray diffraction at the Centre of Energy Materials Research (CEMR), Oxford University, as well as for inert atmosphere preparation and transfer to the DCCEM electron microscope suite, was essential to fulfil the project requirements.
Funding
Funding amount (whole grant and amount to Royce Partner)– £123k (£77k to Oxford)