@article{chen_kim_huang_2022, title={Exploration of the dislocation-electrochemistry relation in LiFePO4 cathode materials}, volume={237}, ISSN={["1873-2453"]}, DOI={10.1016/j.actamat.2022.118158}, abstractNote={Defects, such as dislocations, in electrode materials play a significant role in the performance of lithium-ion batteries. The dislocation-electrochemistry relation has only been observed experimentally and not been fully clarified. Computational studies on this mechanism were also very limited, especially the altered cyclic voltammetry behaviors and associated effective diffusivity. This work focuses on the influences of few characteristics of dislocations on the electrochemical performance of an anisotropic cathode material, lithium iron phosphate (LiFePO 4 ). Utilizing linear elastic mechanics and the superposition principle, we study stress and displacement fields of a LiFePO 4 particle containing different densities and orientations of dislocations. With the mechanical-electrochemical coupling effects expressed by the modified Butler-Volmer equation and using the finite different method, the cyclic voltammetry curves for different dislocation configurations in the particle are investigated. Our results show that introducing dislocations can shift and distort the cyclic voltammetry curves, especially at one specific dislocation orientation. It is also found that the Li-ion molar fraction-dependent partial molar volume is an important prerequisite of the distortion in cyclic voltammetry curves. Moreover, the altered cyclic voltammetry curves at different scanning rates indicate the improvements of electrical power, stored electrical energy, and the effective diffusivity of lithium. Our discrete dislocation model indicates that the capacity loss of LiFePO 4 nanoparticles can be alleviated by introducing tailored dislocations. This study assists the understanding of electrode materials with pre-existing dislocations and provides strategies of using defect engineering to improve the kinetic performance in lithium-ion batteries.}, journal={ACTA MATERIALIA}, author={Chen, Hongjiang and Kim, Sangwook and Huang, Hsiao-Ying Shadow}, year={2022}, month={Sep} }
 @article{raj_dickerson_nagpure_kim_niu_xiao_liaw_dufek_2020, title={Communication-Pressure Evolution in Constrained Rechargeable Lithium-metal Pouch Cells}, volume={167}, ISSN={["1945-7111"]}, DOI={10.1149/1945-7111/ab6439}, abstractNote={Understanding the role of pressure on improving cycle life for high energy rechargeable lithium metal batteries (LMBs) is crucial for their adoption in practical applications. In this work, a fixed-gap test fixture is developed to monitor stack pressure of a multi-layer, 300 Wh kg−1 LMB over 245 cycles. During early cycling, a linear fade in discharge capacity is mirrored by a steady increase in baseline pressure. In later cycles, cell failure is linked to a large increase in baseline pressure due to irreversible side reactions such as continued SEI formation and gas evolution, as corroborated by incremental capacity analysis.}, number={2}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Raj, Abhi and Dickerson, Charles C. and Nagpure, Shrikant C. and Kim, Sangwook and Niu, Chaojiang and Xiao, Jie and Liaw, Boryann and Dufek, Eric J.}, year={2020}, month={Jan} }
 @article{kim_raj_li_dufek_dickerson_huang_liaw_pawar_2020, title={Correlation of electrochemical and mechanical responses: Differential analysis of rechargeable lithium metal cells}, volume={463}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2020.228180}, abstractNote={Recently, interest in high energy rechargeable lithium metal batteries has increased. Application of pressure has been identified as a distinct means to increase cycle life for these cells, but there is still a disconnect between the evolution of electrochemical and mechanical responses. For this study, lithium/NMC622 pouch cells are cycled under two different pressure conditions and pressure evolution is monitored. Applying pressure with an appropriate experimental setup not only improves performance, but also enables collection of additional information that compliments cell electrochemistry. By jointly comparing differential pressure (dP dV−1) and differential capacity (dQ dV−1) analysis, the combined electrochemical and mechanical cell responses are analyzed. It is found that while little change in cell capacity and dQ dV−1 are observed, changes in cell pressure can be used to provide in operando information on the lithium metal electrode for full pouch cells. The changes in pressure suggest it is possible to track the evolution of electrode structure from a flatter electrode early in life to a more porous negative electrode prior to the point where cell capacity begins to dramatically fade.}, journal={JOURNAL OF POWER SOURCES}, author={Kim, Sangwook and Raj, Abhi and Li, Bin and Dufek, Eric J. and Dickerson, Charles C. and Huang, Hsiao-Ying and Liaw, Boryann and Pawar, Gorakh M.}, year={2020}, month={Jul} }
 @article{kim_chen_shadow huang_2018, title={Coupled Mechanical and Electrochemical Analyses of Three-Dimensional Reconstructed LiFePO4 by Focused Ion Beam/Scanning Electron Microscopy in Lithium-Ion Batteries}, volume={16}, ISSN={2381-6872}, url={http://dx.doi.org/10.1115/1.4040760}, DOI={10.1115/1.4040760}, abstractNote={Limited lifetime and performance degradation in lithium ion batteries in electrical vehicles and power tools is still a challenging obstacle which results from various interrelated processes, especially under specific conditions such as higher discharging rates (C-rates) and longer cycles. To elucidate these problems, it is very important to analyze electrochemical degradation from a mechanical stress point of view. Specifically, the goal of this study is to investigate diffusion-induced stresses and electrochemical degradation in three-dimensional (3D) reconstructed LiFePO4. We generate a reconstructed microstructure by using a stack of focused ion beam-scanning electron microscopy (FIB/SEM) images combined with an electrolyte domain. Our previous two-dimensional (2D) finite element model is further improved to a 3D multiphysics one, which incorporates both electrochemical and mechanical analyses. From our electrochemistry model, we observe 95.6% and 88.3% capacity fade at 1.2 C and 2 C, respectively. To investigate this electrochemical degradation, we present concentration distributions and von Mises stress distributions across the cathode with respect to the depth of discharge (DoD). Moreover, electrochemical degradation factors such as total polarization and over-potential are also investigated under different C-rates. Further, higher total polarization is observed at the end of discharging, as well as at the early stage of discharging. It is also confirmed that lithium intercalation at the electrode-electrolyte interface causes higher over-potential at specific DoDs. At the region near the separator, a higher concentration gradient and over-potential are observed. We note that higher over-potential occurs on the surface of electrode, and the resulting concentration gradient and mechanical stresses are observed in the same regions. Furthermore, mechanical stress variations under different C-rates are quantified during the discharging process. With these coupled mechanical and electrochemical analyses, the results of this study may be helpful for detecting particle crack initiation.}, number={1}, journal={Journal of Electrochemical Energy Conversion and Storage}, publisher={ASME International}, author={Kim, Sangwook and Chen, Hongjiang and Shadow Huang, Hsiao-Ying}, year={2018}, month={Aug}, pages={011010} }
 @article{kim_huang_2016, title={Mechanical stresses at the cathode–electrolyte interface in lithium-ion batteries}, volume={31}, ISSN={0884-2914 2044-5326}, url={http://dx.doi.org/10.1557/jmr.2016.373}, DOI={10.1557/jmr.2016.373}, abstractNote={Abstract}, number={22}, journal={Journal of Materials Research}, publisher={Cambridge University Press (CUP)}, author={Kim, Sangwook and Huang, Hsiao-Ying Shadow}, year={2016}, month={Oct}, pages={3506–3512} }