Irreversible Anion Oxidation Leads to Dynamic Charge Compensation in the Ru-Poor, Li-Rich Cathode Li₂Ru_(0.3)Mn_(0.7)O₃
Abstract
Conventional cathodes for Li-ion batteries are layered transition-metal oxides that support Li⁺ intercalation charge-balanced by redox on the transition metals. Oxidation beyond one electron per transition metal can be achieved in Li-rich layered oxides by involving structural anions, which necessitates high voltages and complex charge compensation mechanisms convoluted by degradation reactions. We report a detailed structural and spectroscopic analysis of the multielectron material Li₂Ru_(0.3)Mn_(0.7)O₃, chosen due to its low Ru content. Ex situ and operando spectroscopic data over multiple cycles highlight the changing charge compensation mechanism. Notably, over half of the first-cycle capacity is attributed to O₂ gas evolution and reversible O redox is minimal. Instead, reduced Ru and Mn species are detected in the bulk and on the surface, which then increasingly contribute to charge compensation as more metal reduction occurs with cycling. Permanent structural changes linked to metal migration are observed with EXAFS and Raman analysis.
Additional Information
This work was supported as part of the Center for Synthetic Control Across Length-scales for Advancing Rechargeables (SCALAR), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0019381. J.J.Z. acknowledges support from the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1745301. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We thank Wanli Yang and Tien-Lin Lee for assistance with the RIXS and HAXPES experiments, respectively. The ALS was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Contract No. DE-AC02-05CH11231. The authors acknowledge Diamond Light Source for time on Beamline I09 under Proposal SI127494. Inductively-coupled plasma mass spectrometry was performed in the Resnick Sustainability Institute's Water and Environment Lab at the California Institute of Technology.Additional details
- Eprint ID
- 119068
- Resolver ID
- CaltechAUTHORS:20230206-9587900.28
- DE-SC0019381
- Department of Energy (DOE)
- DGE-1745301
- NSF Graduate Research Fellowship
- DE-AC02-06CH11357
- Department of Energy (DOE)
- DE-AC02-05CH11231
- Department of Energy (DOE)
- David and Lucile Packard Foundation
- Created
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2023-03-09Created from EPrint's datestamp field
- Updated
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2023-03-09Created from EPrint's last_modified field
- Caltech groups
- Resnick Sustainability Institute