Experimental and numerical analysis to identify the performance limiting mechanisms in solid-state lithium cells
Mei-Chin Pang1, Yucang Hao, Monica Marinescu
1Department of Mechanical Engineering, Imperial College London, Exhibition Road, South Kensington Campus, London, SW7 2AZ, UK. gregory.offer@imperial.ac.uk.
Physical Chemistry Chemical Physics : PCCP
|September 26, 2019
Summary
Solid-state lithium batteries show promise for improved safety and energy density. This study reveals solid diffusion in LiCoO2 limits performance under pulse conditions, suggesting a model-based design approach for optimization.
Area of Science:
- Materials Science
- Electrochemistry
- Battery Technology
Background:
- Solid-state lithium batteries offer enhanced safety and energy density compared to conventional lithium-ion batteries.
- Commercialization hinges on understanding performance limitations under dynamic operational conditions, such as pulsed currents.
- Identifying bottlenecks is crucial for optimizing solid-state battery design and real-world application.
Purpose of the Study:
- To experimentally analyze and computationally model solid-state battery behavior under dynamic pulse operating conditions.
- To identify the key performance-limiting mechanisms during pulsed charge and discharge cycles.
- To propose an optimized cell design strategy based on simulation insights.
Main Methods:
- Experimental analysis combined with electrochemical impedance spectroscopy and distribution of relaxation times.
- Continuum modeling using a simplified set of governing equations, validated against experimental data.
- Parameter estimation from experimental measurements for accurate model calibration.
Main Results:
- Charge transfer kinetics at interfaces occur on the microsecond to millisecond timescale.
- A simplified model effectively reproduces experimental observations during various pulse profiles.
- Solid-state diffusion within the bulk LiCoO2 electrode is identified as the primary performance limitation, especially at lower states of charge.
- Enhanced ionic conductivity of the solid electrolyte shows diminishing returns beyond 10⁻⁴ S cm⁻¹ due to the solid diffusion bottleneck.
Conclusions:
- Solid diffusion in the LiCoO2 electrode is a critical bottleneck for solid-state batteries under pulse conditions.
- Improving ionic conductivity alone has limited impact once solid diffusion is the limiting factor.
- A holistic, model-based approach to cell design is recommended for optimizing performance under specific operating conditions.
