Physical Chemistry, Short talk
PC-016

Quantifying interface diffusion in Li ion battery cathode materials

P. Benedek1, O. K. Forslund2, E. Nocerino2, N. Yazdani1, Y. Sassa2,4, M. Medarde3, M. Månsson2, V. Wood1*
1ETH Zürich, 2KTH Stockholm, 3Paul Scherrer Institut, 4Chalmers University

To be able to reduce internal cell resistances that limit charging rates in a lithium ion battery, a detailed understanding of the underlying charge diffusion processes is crucial. While there are numerous known techniques that can determine the diffusion coefficients in the bulk of a material, measuring diffusion through interfaces is challenging [1]. Nonetheless, as interfaces often are rate-limiting, methods to determine interface diffusion are sought after.

Here, we show an approach to study diffusion at interfaces using muon spin spectroscopy. By performing measurements on LiFePO4 platelets with different sizes, we determine how diffusion through the LiFePO4 (010) interface differs from that in the center of the particle (i.e., bulk diffusion). We perform ab initio calculations to aid the understanding of the results and show the relevance of our interfacial diffusion measurement to electrochemical performance through cyclic voltammetry measurements. These results indicate that surface engineering can be used to improve the performance of lithium-ion batteries [2].

Figure 1.  A muon pulse interacts with the LiFePO4 particles leading to a spin rotation of the muon. Inset: Depending on the ion dynamics, the muon spin rotation changes eventually leading to an effective probe of ion dynamics.

[1] Yiyang Li, Hungru Chen, et al., Nat. Mater., 2018, 17, 915-922.
[2] Peter Benedek, Ola K. Forslund, et al., ACS Appl. Mater. Interfaces, 2020, 12, 16243-16249.