Lithium plating hurdle overcome for swift EV charging

The details regarding their research are published in the journal Nature Communications. 

Safe and durable

Fast charging of lithium-ion batteries can cause a phenomenon known as lithium plating. It happens when lithium ions accumulate on the negative electrode of the battery rather than intercalating into it, creating a coating of metallic lithium that keeps expanding. This might harm the battery, reduce its longevity, and result in short circuits that might start a fire or explode. 

According to Dr. Xuekun Lu, lithium plating may be significantly reduced by improving the graphite negative electrode's microstructure. Fine-tuning the particle and electrode morphology for a homogenous reaction activity and decreased local lithium saturation is the key to suppressing lithium plating and improving the battery's performance since the graphite negative electrode is made up of small, randomly dispersed particles.

"Our research has revealed that the lithiation mechanisms of graphite particles vary under distinct conditions, depending on their surface morphology, size, shape, and orientation. It largely affects the lithium distribution and the propensity of lithium plating. Assisted by a pioneering 3D battery model, we can capture when and where lithium plating initiates and how fast it grows. This is a significant breakthrough that could have a major impact on the future of electric vehicles," said Dr. Lu in a media statement.

Higher charging capacity

The work advances the knowledge of the physical mechanisms governing lithium redistribution inside graphite particles during fast charging and offers fresh perspectives for creating enhanced fast-charging methods. This understanding could enable an effective charging procedure while lowering the danger of lithium plating.  

The team says their work provides new "insights into developing advanced fast charging protocols by improving the understanding of the physical processes of lithium redistribution within graphite particles during fast charging." This suggests electric vehicles might cover a greater distance on a single charge. 

These findings are a breakthrough in the development of electric vehicle batteries. They could lead to faster charging, longer-lasting, and safer electric cars, making them a more attractive option for consumers. 

Abstract

The phase separation dynamics in graphitic anodes significantly affect lithium plating propensity, which is the major degradation mechanism that impairs the safety and fast charge capabilities of automotive lithium-ion batteries. In this study, we present a comprehensive investigation employing operando high-resolution optical microscopy combined with non-equilibrium thermodynamics implemented in a multi-dimensional (1D+1D to 3D) phase-field modeling framework to reveal the rate-dependent spatial dynamics of phase separation and plating in graphite electrodes. Here we visualize and provide a mechanistic understanding of the multistage phase separation, plating, inter/intra-particle lithium exchange and plated lithium back-intercalation phenomena. A strong dependence of intra-particle lithiation heterogeneity on the particle size, shape, orientation, surface condition and C-rate at the particle level is observed, which leads to the early onset of plating spatially resolved by a 3D image-based phase-field model. Moreover, we highlight the distinct relaxation processes at different state-of-charges (SOCs), wherein thermodynamically unstable graphite particles undergo a drastic intra-particle lithium redistribution and inter-particle lithium exchange at intermediate SOCs, whereas the electrode equilibrates much slower at low and high SOCs. These physics-based insights into the distinct SOC-dependent relaxation efficiency provide a new perspective toward developing advanced fast charge protocols to suppress plating and shorten the constant voltage regime.