New Electrolyte Design Strategy for High-Performance Thick Electrode-based Lithium Ion Batteries

Highly loaded electrodes are considered a promising approach for increasing the energy density of lithium ion batteries while reducing non-active material costs. Until now, however, this advantage has come at the cost of reduced performance: Because lithium ions must travel longer distances, cells with thick electrodes lose a significant amount of capacity, particularly at higher charge and discharge rates. A research team from the MEET Battery Research Center at the University of Münster and the Helmholtz Institute Münster of Forschungszentrum Jülich has now demonstrated that this challenge can be overcome using ester-based electrolytes.

Improved Ion Transport Increases Cycle Stability and High-rate Performance

To improve the performance of lithium-ion batteries with thick electrodes, the research team investigated electrolytes based on an ester (methyl acetate (MA)) as solvent. Compared to conventional carbonate-based electrolytes, these exhibit significantly better mass transport properties. This allows lithium ions to be transported more quickly through the internal pore networks of the electrodes- a crucial advantage for thick electrodes. In LiFePO4 || graphite cells with an areal capacity of 5.4 mAh/cm², the ester-based electrolytes enabled stable charge and discharge cycles at a C-rate of 1C/1C. After 1,000 cycles, the cells still retained 87 percent of their original capacity. By comparison, cells with conventional carbonate-based electrolytes had already dropped to only about 20 percent of their initial capacity after just 50 cycles.

Until now, ester-based electrolytes have primarily been studied for lithium ion batteries with thin electrodes to improve their fast-charging and/or sub-zero temperature performance. “Our study shows that the superior ion transport of ester-based electrolytes also enables stable high C-rate performance in cells with thick electrodes", explains MEET researcher Chirag Vankani. This performance boost is due to reduced polarization caused by mass transport, which suppresses lithium metal plating. This effect highlights the critical role that electrolyte design plays in the power density of high-energy-density cells. “The study opens up a new path to combining high energy density with a long lifetime,” summarizes Dr Markus Börner, Head of the MEET Research Division “Cell System”.

Detailed Results Online Available

The entire study has been published by the authors Chirag Vankani, Anindityo Arifiadi, Dr Johannes Kasnatscheew, Dr Markus Börner, MEET Battery Research Center, as well as Peng Yan, Helmholtz Institute Münster of Forschungszentrum Jülich and Prof. Dr Martin Winter, MEET Battery Research Center and Helmholtz Institute Münster of Forschungszentrum Jülich in the journal “Advanced Energy & Sustainability Research“.