Continuum modelling and parameterisation of Li-ion batteries, focusing on LMFP.

Lithium-ion batteries are vital as the UK transitions to more sustainable power generation and transportation technologies, and the government has identified batteries and energy storage as crucial for the future economy. However, we still lack fundamental understanding of some of the underlying electrochemical behaviours of batteries, especially regarding their long-term degradation and performance over lifetime.

Modelling is vital to help us test out new ideas and develop diagnostic tools to assess battery performance, limitations, and lifetimes of Li-ion cells from data. Battery simulations typically employ coupled electrochemical/thermal models, derived from first principles.

This project focuses on creating and using device models for lithium-ion cells that have LiMnFePO4 (shortened to LMFP) positive electrode materials. LMFP is a variation on LiFePO4 (LFP), the latter being a popular, durable and thermally stable positive electrode material for Li-ion cells. LMFP cells are considered to correct many of the deficiencies associated with traditional LFP, such as lower energy density and a very flat open circuit voltage (OCV) curve. LMFP improves on this by blending LFP with manganese.

LMFP cells have interesting properties but also share some of the challenges of LFP, such as hysteresis in the open circuit voltage, and LMFP may also be less durable than LFP. Other challenges for LMFP include stability and safety issues, for example caused by manganese dissolution, where research on novel coatings or electrolyte modifications is of interest.

There is a need to improve the understanding of the performance and lifetime of LMFP cells, which exhibit similar phase-separating behaviours to LFP. Modelling of degradation mechanisms is unexplored, and a better theoretical understanding of issues such as structural reorganisation, phase transitions and side reactions is needed.

This project will explore LMFP modelling from bottom up, physics-based perspective, aiming to develop novel approaches for open circuit voltage, hysteresis, and degradation models, including adapting thermodynamics and hysteresis models over lifetime. The project will also include in-house testing of LMFP cells, to provide reliable and reproducible data for our models. This will enable improved performance, durability and safety of use of this technology in industrial applications.

This project is in collaboration with Fortescue Zero. This research aligns with the EPSRC Research Area of Energy Storage.