Periodic Reporting for period 1 - OptiCarb (Optimising hard carbon anodes for efficient energy storage in sodium-ion batteries)
Reporting period: 2021-11-01 to 2023-10-31
The OptiCarb project addresses a central challenge in the development of sodium-ion batteries (SIBs): the poor performance of conventional carbon anodes. While hard carbons have emerged as the most promising alternative due to their high capacity and cost-effectiveness, their complex atomic structure has limited a clear understanding of sodium storage mechanisms. This knowledge gap has hindered the design of high-performing electrodes. OptiCarb was launched to overcome this bottleneck by developing realistic atomistic models of hard carbons and using them to uncover the fundamental mechanisms governing sodium intercalation and adsorption. The ultimate goal was to guide the rational design and synthesis of optimized carbon electrodes, thereby accelerating the commercial viability of SIBs as a sustainable alternative to lithium-ion batteries.
Over the course of the project, OptiCarb successfully achieved all its scientific and training objectives. Using a novel molecular dynamics protocol, a database of over 75 atomistic carbon models was generated, covering a range of porosities and graphitisation degrees. These models were validated through simulated TEM/XRD patterns and mechanical tests, and are now openly available in a dedicated GitHub repository. A key outcome was the first realistic simulation of sodium storage under applied potential, revealing the interplay between structure and electrochemical performance. Notably, the project pivoted from studying hydrogen-functionalised carbons to sulfur-doped variants, which showed enhanced reversibility and performance. These findings were published in open-access journals, presented at major international conferences (including five invited talks), and integrated into a public web-based tool (3D-VIS) to assist in pore structure analysis. A model-guided synthesis of hard carbon anodes was also experimentally validated, demonstrating improved battery performance and confirming the feasibility of the modelling approach.
OptiCarb has gone well beyond the current state of the art by establishing the first end-to-end framework linking atomistic carbon modelling to real-world battery optimisation. Previous models relied on idealised slit-pore structures that failed to capture the complexity of hard carbons; OptiCarb’s simulations introduced structural realism at scale, integrating graphitic domains, curvature, and defects. The project also pioneered the use of ReaxFFNa-C simulations under applied potential, offering unprecedented insight into sodium storage mechanisms. These innovations have direct industrial relevance, reducing trial-and-error in electrode development and offering a scalable pathway for the rational design of advanced battery materials. Societally, the project contributes to the EU’s Green Deal and Net Zero ambitions by enabling sustainable, lithium-free energy storage solutions. Its open-access tools and data infrastructure promote transparency, reproducibility, and wide adoption, while the training and career development aspects have led to the creation of a new research group at King's College London, ensuring long-term scientific and socio-economic impact.