Porous-electrode Modeling of Li-ion Batteries
Zhiqiang Chen defended his PhD thesis at the department of Electrical Engineering on November 4th.
The investigated porous-electrode model can extract the aging mechanisms in various working conditions and provide optimal working conditions to extend the battery lifetime.
Li-ion batteries nowadays have become ubiquitous in our daily life, from mobile electronics to electric vehicles and the storage system for the power grid. As an energy storage device, the stored energy and power are expected to be as high as possible to meet the rapidly increasing demands for energy. At the same time, the safety and lifetime are rising as significant issues with the extensive applications of Li-ion batteries. Exploring new battery chemistries is always helpful for advanced Li-ion batteries, but the path to commercialization is always challenging. At present, traditional battery chemistries are still the best candidates for commercial Li-ion batteries. Optimal designs for manufacturing and optimal use for applications will take great advantage of these existing battery chemistries and enhance the battery performance at a minimum expense.
Porous structures are widely used for the main components of a commercial Li-ion battery, such as the negative electrode, the positive electrode and separator. The complexity of porous structures makes it difficult and laborious to experimentally study the structure-performance relations. Instead, the porous-electrode model has been proven to be a powerful and efficient tool to simulate Li-ion batteries by the parameterization of governing equations. In this thesis, a porous-electrode model has been adopted to investigate the relations between the design parameters and battery performance, and between operational conditions and battery lifetime. It is found that the parameters of a porous electrode have a great impact on shaping the internal reactions, further tuning the battery performance, such as the battery output voltage and overpotential. It turned out that a surface film grows on the battery electrodes and causes a considerable capacity loss during operation. The applied current has a significant influence on the battery capacity loss during cycling. State-of-charge below 20% and a low environmental temperature at a stand-by mode, i.e. storage, benefits the lifetime.
In the meantime, a quite interesting phenomenon related to reaction waves is found and experimentally verified. This finding provides an important viewpoint for understanding the nature of electrochemical reactions and explaining voltage artifacts in porous electrodes.
Title of PhD thesis: ‘Porous-electrode Modeling of Li-ion Batteries’
Supervisor: Peter Notten