Johannes Wandt

• Zimmermann, Cara; Wandt, Johannes; Kayl, Jonas; Hueggenberg, Laurin; Goldbach, Daniel & Erhard, Simon [Show all 8 contributors for this article] (2026). Influence of the Electrolyte Amount on the Aging Behavior of 4695 Lithium-Ion Batteries. Journal of the Electrochemical Society. ISSN 0013-4651. 173(17). doi: 10.1149/1945-7111/aea055. Full text in Research Archive Show summary

  This study investigates the effect of varying electrolyte amounts on the aging behavior of lithium-ion batteries using 4695 cells containing a high-nickel NMC cathode and a graphite-silicon composite anode. Eight pore filling ratios (PFRs), ranging from approximately half-filled pores to fully saturated pores with additional free electrolyte, are examined. All cells undergo 720 cycles of accelerated aging between 0% and 80% state of charge at 50 °C with a C-rate of 0.5 C. Despite significant differences in electrolyte amount, all cells exhibit remarkably similar capacity fade and resistance increase during cyclic aging. However, subsequent fast charging tests reveal that cells with very low or high PFRs show rapid capacity loss and increased resistance due to lithium plating. For high PFRs, this is attributed to electrolyte motion induced salt inhomogeneity (EMSI), while for low PFRs, increased capacity loss results from higher initial and aging-induced resistance caused by incomplete electrode wetting. In contrast, cells with intermediate PFRs demonstrate stable fast charging performance. Furthermore, moment of inertia measurements were applied for the first time to monitor the evolution of electrolyte amount during cycle life. These findings emphasize the significant influence of aging conditions on the optimal electrolyte amount for ensuring long-term battery durability.

• Düsdieker, Marco; Wandt, Johannes; Li, Jiahao; Solchenbach, Sophie; Kopp, Linus & Kirst, Cedric [Show all 8 contributors for this article] (2026). Morphology-Driven Degradation in High-Nickel NMC Lithium-Ion Battery Cathodes: Role of Single- and Polycrystalline Particle Ratio. Journal of the Electrochemical Society. ISSN 0013-4651. 173(13). doi: 10.1149/1945-7111/ae7e5a. Full text in Research Archive Show summary

  This study investigates multilayer and single-layer pouch cells with varying single-crystalline to polycrystalline ratios under cyclic-aging with full and partial state-of-charge windows, as well as calendar-aging. Measurements at the full-cell level include capacity retention measurements, pseudo open-circuit voltage profiling, and electrochemical impedance spectroscopy to monitor performance evolution. Post-mortem analysis of harvested electrodes employs electrochemical impedance spectroscopy and the galvanostatic intermittent titration technique. Finally, single-layer pouch cells with systematically varied single-crystalline to polycrystalline ratios are analyzed to quantify morphology-dependent aging effects. The results show that cycling between 0 and 100% state of charge accelerates capacity fade. Cycling at both high and low states of charge induces detrimental synergistic aging effects, including impedance growth and a pronounced splitting of the H2–H3 transition plateau. Restricting the state of charge window significantly mitigates degradation. Calendar-aging at 100% state of charge shows no plateau-splitting. The single-crystalline to polycrystalline ratio strongly influences aging and plateau-splitting. Single-crystalline electrodes maintain stable voltage profiles and low impedance rise, whereas polycrystalline electrodes exhibit marked overpotential increase and plateau shifts. Blended electrodes reveal heterogeneous aging behavior, which is visible as plateau-splitting in pseudo open-circuit voltage curves.

• Kvalsund, Kris David; Chakram-Nybru, Cecilie; Landesfeind, Johannes & Wandt, Johannes (2026). Influence of the C-Rate on the Electrolyte Motion Induced Salt Inhomogeneity (EMSI) Effect in a Commercially Available 18650 Lithium-Ion Battery Cell. Journal of the Electrochemical Society. ISSN 0013-4651. 173(9). doi: 10.1149/1945-7111/ae63fe. Full text in Research Archive
• Hsiao, Hao Chen; Goldbach, Daniel; Li, Jiahao; Baghernejad, Masoud; Adam, Alexander & Waldmann, Thomas [Show all 8 contributors for this article] (2026). Electrolyte Motion-Induced Salt Inhomogeneity (EMSI) Can Occur Across Cell Formats: A Mechanistic Study in Single-layer Pouch Cells and Mitigation Strategies. Journal of the Electrochemical Society. ISSN 0013-4651. 173. doi: 10.1149/1945-7111/ae2f9f. Full text in Research Archive Show summary

  Electrolyte-motion–induced salt inhomogeneity (EMSI) is increasingly recognized as a failure mode in fast-charging. However, its generality beyond large jelly-roll cells has remained unclear. In this work, we present this effect for the first time in single-layer pouch cells. EMSI arises whenever two conditions coincide: charge-induced pore-volume reduction with pore filling ratio >1 and strong through-plane salt polarization. We reproduce the reported EMSI fingerprint, a reversible, week-scale rise in ohmic resistance accompanied by rate-dependent capacity loss and use it as a diagnostic marker. Direct mapping by ion chromatography and ATR-FTIR spectroscopy reveals centimeter-scale LiPF₆ gradients, with up to ∼3× center-to-edge differences across 2.5 cm after ∼20 equivalent fast-charge cycles. These gradients require nearly a week to dissipate and coincides with edge-localized Li deposition. Their homogenization is tracked by a reversible drop in high-frequency resistance during the cell rest period. A coupled pseudo-3D electrochemical-fluid model reproduces the experimental trends and illustrates how the resistance evolves. Parameter scans of electrolyte amount, charge/discharge rate, temperature, and silicon content chart the onset conditions and motivate actionable mitigation strategies. Together, these results establish EMSI as a general design and testing challenge across cell formats whenever electrode stacks are mechanically constrained.

• Wilhelm, Rebecca; Schuster, Robin; Kutsch, Tobias; Qian, Simon; Mahl, Johannes & Kratky, Tim [Show all 9 contributors for this article] (2025). Exploring the Electrochemical Stability Window of an All-Solid-State Composite Cathode via a Novel Operando Tender XPS Setup. ACS Applied Materials & Interfaces. ISSN 1944-8244. 17(26), p. 38571–38586. doi: 10.1021/acsami.5c01672. Full text in Research Archive Show summary

  All-solid-state batteries (ASSBs) have the potential to provide greater energy density than conventional batteries based on liquid electrolytes. Here, an operando ASSB cell setup for tender X-ray photoelectron spectroscopy (XPS) was developed, and the interface of a Ni-rich layered transition metal oxide cathode active material (CAM) and an Li6PS5Cl (LPSCl) solid electrolyte (SE) was evaluated during initial charge/discharge cycles. After validating the cell performance against a conventional pouch cell operated at high compression, intermittent galvanostatic cycling was performed, and XPS data were recorded as a function of state of charge (SOC). Upon the initial charge of the cell to ≈3.3 VLi, the LPSCl appears to decompose into LiCl, Li3PS4, and polysulfides, whose amount gradually increases with potential. Upon further charge, at a potential higher than ≈3.8 VLi, initially, present sulfate and sulfite impurities decompose, and at ≈74% SOC (corresponding to a cathode potential of ≈4.10 VLi), surface reconstruction of the CAM particles due to lattice oxygen release is detected. In addition, at potentials beyond ≈4.6 VLi, a decrease of the S 1s counts of the sum of the LPSCl, the thiophosphate, and polysulfide species suggests the formation of elemental sulfur that is lost via sublimation into the vacuum chamber.

• Zimmermann, Cara; Tacconis, Camilla; Solchenbach, Sophie; Goldbach, Daniel; Erhard, Simon & Wandt, Johannes [Show all 7 contributors for this article] (2025). Characterization of Cylindrical Lithium-Ion Batteries with Varying Electrolyte Amounts at Beginning of Life. Journal of the Electrochemical Society. ISSN 0013-4651. 172(5). doi: 10.1149/1945-7111/add438. Full text in Research Archive Show summary

  This study investigates the impact of the electrolyte amount on the electrical performance at beginning of life in high energy cylindrical lithium-ion batteries. We investigate cylindrical 4695 prototype cells with varying pore filling ratios (PFRs), defined as the ratio of electrolyte volume to pore volume within anode, cathode, and separator. The PFR ranges from roughly half-filled pore volume to completely filled pore volume with additional free electrolyte. It is found that the energy and resistance remain constant as long as the PFR100 (at 100% SoC) > 1.00. As soon as the PFR100 < 1.00, the cell energy decreases, and the resistance increases with decreasing PFR. We also demonstrate the application of moment of inertia (MoI) measurements as a complementary technique to validate PFR calculations. Additionally, an analytical equation is developed to describe the relation between the electrolyte mass expelled from the jelly roll vs measured MoI change, isolating the contribution of electrolyte motion. This work lays the foundation for a subsequent study on the influence of PFR on the aging of cylindrical cells.

• Scharf, Janik; Lüders, Christian von; Matysik, Frank-Michael; Misiewicz, Casimir; Wandt, Johannes & Berg, Erik J. (2024). Gas evolution in large-format automotive lithium-ion battery during formation: Effect of cell size and temperature. Journal of Power Sources. ISSN 0378-7753. 603, p. 1–11. doi: 10.1016/j.jpowsour.2024.234419. Full text in Research Archive
• Solchenbach, Sophie; Tacconis, Camilla; Martin, Aurora Gomez; Peters, Verena; Wallisch, Lea & Stanke, Anna [Show all 16 contributors for this article] (2024). Electrolyte motion induced salt inhomogeneity - a novel aging mechanism in large-format lithium-ion cells. Energy & Environmental Science. ISSN 1754-5692. doi: 10.1039/d4ee03211j. Full text in Research Archive

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