Quantitative Decoupling of Oxygen‐Redox and Manganese‐Redox Voltage Hysteresis in a Cation‐Disordered Rock Salt Cathode
Date Published |
06/2023
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Publication Type | Journal Article
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Authors | |
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DOI |
10.1002/aenm.202300241
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Abstract |
Pronounced voltage hysteresis in Li-excess cathode materials is commonly thought to be associated with oxygen redox. However, these materials often possess overlapping oxygen and transition-metal redox, whose contributions to hysteresis between charge and discharge are challenging to distinguish. In this work, a two-step aqueous redox titration is developed with the aid of mass spectrometry (MS) to quantify oxidized lattice oxygen and Mn3+ /4+ redox in a representative Li-excess cation-disordered rock salt—Li1.2Mn0.4Ti0.4O2 (LMTO). Two MS-countable gas molecules evolve from two separate titrant-analyte reactions, thereby allowing Mn and O redox capacities to be decoupled. The decoupled O and Mn redox coulombic efficiencies are close to 100% for the LMTO cathode, indicating high charge-compensation reversibility. As incremental Mn and O redox capacities are quantitatively decoupled, each redox voltage hysteresis is further evaluated. Overall, LMTO voltage hysteresis arises not only from an intrinsic charge-discharge voltage mismatch related to O redox, but also from asymmetric Mn-redox overvoltages. The results reveal that O and Mn redox both contribute substantially to voltage hysteresis. This work further shows the potential of designing new analytical workflows to experimentally quantify key properties, even in a disordered material having complex local coordination environments. |
Journal |
Advanced Energy Materials
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Volume |
13
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Year of Publication |
2023
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Issue |
21
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ISSN Number |
1614-6832
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URL | |
Short Title |
Advanced Energy Materials
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Refereed Designation |
Refereed
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Organizations | |
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