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Tris(trimethylsilyl) Phosphite as an Efficient Electrolyte Additive for a High-Voltage Li-Rich Disordered Rocksalt
Mathieu Cogniard1, Irina Profatilova1, Mélanie Pichardo1
1Université Grenoble Alpes, CEA, Liten, DEHT, Grenoble 38000, France.
ACS Applied Materials & Interfaces
|May 6, 2026
Summary
Tris(trimethylsilyl) phosphite (TMSPI) significantly enhances the performance of manganese-based disordered rocksalt (DRX) cathodes by improving capacity retention and rate capability. This electrolyte additive mitigates degradation, enabling stable high-voltage operation for advanced lithium-ion batteries.
Area of Science:
- Materials Science
- Electrochemistry
- Energy Storage
Background:
- Manganese-based Li-rich cation-disordered rocksalt (DRX) materials offer high energy density as alternatives to Ni-rich layered oxides.
- High-voltage operation (up to 4.8 V vs Li/Li+) is necessary for DRX materials to activate oxygen redox and achieve high capacities.
- This high-voltage operation accelerates electrolyte and full system degradation, posing a significant challenge for practical applications.
Purpose of the Study:
- To address the voltage-driven instability of Mn-based DRX materials by screening electrolyte additives.
- To identify an effective additive that improves the electrochemical performance and cycling stability of Li2MnO2F (LMOF).
- To elucidate the mechanism by which the additive enhances performance and mitigates degradation.
Main Methods:
- Screening of electrolyte additives in conventional carbonate-based electrolytes using the model DRX compound Li2MnO2F (LMOF).
- Electrochemical characterization, including capacity retention and rate capability tests (up to 5C).
- Multitechnique investigation combining operando online electrochemical mass spectrometry (OEMS), electrochemical characterization, and post-mortem analyses.
Main Results:
- Tris(trimethylsilyl) phosphite (TMSPI) demonstrated significant improvements, increasing capacity retention by 60% over 80 cycles and nearly doubling discharge rate capability at 5C.
- TMSPI validated in LMOF//graphite full cells, achieving 220 mAh·g-1 capacity and satisfactory cycling stability.
- TMSPI mitigates manganese cation dissolution, suppresses aluminum current collector corrosion, and limits impedance growth at the positive electrode interface.
Conclusions:
- TMSPI effectively enhances the electrochemical performance of high-voltage DRX positive electrodes.
- The additive scavenges acidic species, protons, water, and fluoride ions, forming silane derivatives and mitigating degradation pathways.
- Electrolyte engineering via rational additive design is a scalable strategy to improve the stability and performance of DRX materials for next-generation batteries.
