Rechargeable batteries are used in mobile phones, cameras, laptops, and cars, leading to a gradual increase in demand for these batteries. These batteries generally consist of two electrodes, separated by an electrolyte that facilitates the charge transfer between them. These electrodes are composite devices consisting of at least four different materials: an active material, a conductive additive, a polymer binder, and a current collector. These materials determine the performance of the batteries in terms of cycling performance, energy density, mechanical integrity, and ionic and electronic mobility. ¹

Due to the casting procedure, the accumulation of the conductive additive, and the failure of the adhesive during the cycling process, the electrode materials distribute non-uniformly. This leads to a non-uniform distribution of its microstructural properties, producing heterogeneous electrodes with increased resistance and local current density variation. It also affects the charge movement and the cycle life of the battery. ^3,4

The ambiguous effect of the electrode microstructure on the battery performance has lead to the development of different analytical techniques that provide specific information on these structures. Herein, we use scanning electron microscopy (SEM), scanning electrochemical microscopy (SECM), and battery cycling to study the micro and macrostructure effects on battery performance.

SECM is a probing technique that scans the electrode surface laterally, to obtain a measure of the electrode’s local conductivity. ^5,6 This will help us find disconnected areas and quantify inhomogeneous microstructure distribution. From this, we can correlate microstructural inhomogeneity and battery performance by combining the SEM and SECM data with the data from cycling testing. This presentation will show the primary correlation between electrode microstructure materials and battery performance.

References:

1. Stein M, Chen CF, Robles DJ, Rhodes C, Mukherjee PP. Non-aqueous electrode processing and construction of lithium-ion coin cells. J Vis Exp. 2016;2016(108):1-10. doi:10.3791/53490
2. Marks T, Trussler S, Smith AJ, Xiong D, Dahn JR. A Guide to Li-Ion Coin-Cell Electrode Making for Academic Researchers. J Electrochem Soc. 2011;158(1):A51. doi:10.1149/1.3515072
3. Müller S, Eller J, Ebner M, Burns C, Dahn J, Wood V. Quantifying inhomogeneity of lithium ion battery electrodes and its influence on electrochemical performance. J Electrochem Soc. 2018;165(2):A339-A344. doi:10.1149/2.0311802jes
4. Xu R, Yang Y, Yin F, et al. Heterogeneous damage in Li-ion batteries: Experimental analysis and theoretical modeling. J Mech Phys Solids. 2019;129(2019):160-183. doi:10.1016/j.jmps.2019.05.003
5. Ventosa E, Schuhmann W. Scanning electrochemical microscopy of Li-ion batteries. Phys Chem Chem Phys. 2015;17(43):28441-28450. doi:10.1039/c5cp02268a
6. Polcari D, Dauphin-Ducharme P, Mauzeroll J. Scanning Electrochemical Microscopy: A Comprehensive Review of Experimental Parameters from 1989 to 2015. Chem Rev. 2016;116(22):13234-13278. doi:10.1021/acs.chemrev.6b00067