Electrode microstructure for electrochemical energy devices
There are increasing demands for electrochemical energy storage devices, such as Li/Na ion batteries and next generation solid-state Li/Na metal batteries with better safety and higher energy densities. These devices are attractive for electric transportation and electricity storage from intermittent renewable sources to meet global net-zero targets. The fundamental principle that governs these devices’ performance relies on mass transport phenomena of ions.
My research focuses on three challenges. (a) Conventional electrodes of these devices contain random microstructure with tortuous ion transport pathways that restrict ion diffusion and electrochemical performance. (b) Most existing processing techniques of making bespoke electrode microstructure have not been developed to be sustainable. (c) It is notoriously challenging to operando image and study light metal ion (e.g. Li+, Na+) diffusion in the electrode microstructure inside operating devices.
This presentation shows two research areas under the overarching theme of tailored microstructure.
Firstly, the presentation will show novel sustainable processing techniques [1,2] that eliminate toxic organic solvents commonly used in electrode production. The new processing technologies tailored electrode anisotropic microstructure that improved Li+ ion diffusion coefficient from 4.4 x 10-9 to 1.4 x 10-7 cm2 s-1 at room temperature, achieved high areal capacities of 16.7 and 10.1 mAh cm-2 at 0.05 and 1 C (dis)charge rates, respectively, and increased energy density of solid-state Li metal batteries from 230 to 300 Wh kg-1 for comparisons at the same conditions.
Secondly, the presentation will show an operando correlative imaging characterization technique of combining X-ray Compton scattering and X-ray computed tomography that I have pioneered [3,4]. This technique spatially resolves light metal ion (e.g. Li+) diffusion in 3D evolving electrode microstructure inside operating batteries to reveal solid-state ion diffusion dynamics and the relationship between microstructure, electrode material utilization and electrochemical performance.
Finally, I will show my future research plan to apply the same microstructural design principle, sustainable processing technologies and multi-probe characterization to other electrochemical energy storage devices (e.g. solid-state Na metal batteries) and energy generation devices that use renewable electricity to generate H2 fuels.
 C. Huang* et al. “A solid-state battery cathode with a polymer composite electrolyte and low tortuosity microstructure by directional freezing and polymerization”, Advanced Energy Materials, 11 (2020) 2002387.
 C. Huang* et al. “Low-tortuosity and graded lithium ion battery cathodes by ice templating”, Journal of Materials Chemistry A, 7 (2019) 21421.
 C. Huang* et al. “3D correlative imaging of lithium ion concentration in a vertically oriented electrode microstructure with a density gradient”, Advanced Science, 9 (2022) 2105723.
 C.L.A. Leung, C. Huang* et al., “Correlative full field X-ray Compton scattering imaging and X-ray computed tomography for in situ observation of Li ion batteries”, Materials Today Energy, 31 (2023) 101224