LNMO Electrolyte Additive Gassing — PatSnap Eureka
Electrolyte Additive Engineering for Gassing Suppression in LNMO Cathode Systems
High-voltage LiNi₀.₅Mn₁.₅O₄ cathodes operating at 4.7–4.98 V exceed the oxidative stability of conventional electrolytes, driving continuous CO₂ and CO evolution. Engineered additives that preferentially decompose to form passivating CEI films are the primary lever for suppressing this gassing cascade.
Gassing Mechanisms at the LNMO/Electrolyte Interface
Gassing in high-voltage lithium-ion systems arises from two coupled phenomena. The first is direct oxidative decomposition of carbonate solvents at the LNMO cathode surface — a process confirmed by neutron imaging at the Paul Scherrer Institute, which observed real-time gas evolution in operating LiNi₀.₅Mn₁.₅O₄/graphite pouch cells and demonstrated that LNMO/graphite cells gas more persistently than LiFePO₄/graphite counterparts. Primary gases generated are CO₂, CO, and trace hydrocarbons.
The second pathway is electrode crosstalk driven by transition-metal (TM) dissolution. Mn and Ni ions dissolving from the LNMO cathode deposit on the graphite anode, catalyzing further electrolyte decomposition and generating high-surface-area lithium metal deposits that ultimately lead to rollover failure — as established by the University of Münster's MEET Battery Research Center.
Dalhousie University quantified cathode-side dominance by showing that pouch bags containing only delithiated NMC442 electrodes and electrolyte — without a paired negative electrode — generated far greater quantities of CO₂ than full cells. This reveals that in full cells, CO₂ generated at the cathode is partially consumed by lithiated graphite at the anode, masking the true extent of cathode-side decomposition.
The patent landscape analysis available via PatSnap Eureka shows that oxidative decomposition of inactive electrode materials — binders, carbon black, and current collector interfaces — at potentials above 4.7 V vs. Li/Li⁺ further contributes cumulatively to total gas load, a subtlety systematically investigated by the MEET group.
Film-Forming Additive Strategies for CEI Construction
The primary engineering lever is deploying additives with oxidation potentials just below the LNMO plateau (~4.7 V), causing preferential decomposition and deposition of a passivating CEI that physically and chemically separates electrolyte from the active cathode surface.
PTSI — Barrier Against HF Attack at 4.98 V
p-Toluenesulfonyl isocyanate (PTSI), evaluated at Shenzhen University at only 0.5 wt% loading, generated a stable SEI/CEI film on LNMO surfaces that provided a barrier against HF attack produced from LiPF₆ hydrolysis. It improved first-cycle capacity by 36.0 mAh/g and enabled operation at 4.98 V with improved cycling retention compared to additive-free cells. The PTSI-derived film's sulfonyl and isocyanate functionalities bind to surface sites more robustly than carbonate-derived films.
+36.0 mAh/g first-cycle capacity · Shenzhen Univ. 20194TP — Cost-Efficient CEI for 4.9 V Operation
4-Trifluoromethylphenylboronic acid (4TP), introduced by South China Normal University at 2 wt% loading, achieved high capacity retention of LNMO/Li cells cycled to 4.9 V. Boronic acid derivatives can form CEI films at competitive cost compared to elaborate synthetic additives. The fluorinated aryl group was critical for oxidative stability at the LNMO voltage window.
2 wt% loading · South China Normal Univ. 2021TMSPi/LiDFOB — Dual-Site CEI and SEI Passivation
Uppsala University demonstrated that combining tris(trimethylsilyl) phosphite (TMSPi) with lithium difluoro(oxalato)borate (LiDFOB) in LiPF₆-based carbonate electrolytes yields a synergistic outcome in LNMO-graphite full cells. TMSPi oxidizes on the LNMO surface prior to electrolyte solvent decomposition to form a stable CEI, while LiDFOB preferentially forms a stable SEI on the graphite anode — simultaneously reducing cathode-side gassing and anode-side SEI thickening.
Dual-site passivation · Uppsala Univ. 2023CEMAImTFSI — HOMO-Guided Preferential Oxidation
The functionalized ionic liquid 1-cyanoethyl-2-methyl-3-allylimidazolium bis(trifluoromethanesulfonimide) (CEMAImTFSI), studied by Hebei University of Technology, has a higher HOMO energy than EC and DMC, enabling preferential oxidation and migration to the LiNi₀.₅Mn₁.₅O₄ cathode surface to participate in SEI formation, thereby protecting the electrode from further oxidative degradation.
HOMO-guided design · Hebei Univ. of Tech. 2020Additive Classes, Mechanisms, and Institutional Contributions
Mapping the additive chemistry landscape and key research contributors across more than 40 analyzed literature entries and patents in the LNMO gassing suppression field.
Additive Class vs. Primary Gassing Suppression Mechanism
Five major additive classes address LNMO gassing through distinct mechanistic pathways, from CEI passivation to TM scavenging.
Key Institutional Contributors to LNMO Additive Research
The University of Münster / MEET is the single most prolific contributor, followed by Dalhousie University with UHPC-based gas evolution studies.
Evolution of Additive Sophistication: From Single-Additive to Synergistic Multi-Component Systems
Clear progression from single-additive approaches (VC, FEC) to computationally guided multi-additive systems co-engineering CEI and SEI simultaneously.
Fluorophosphate and Multi-Additive Systems for Crosstalk and Gassing Control
Because gassing and electrode crosstalk are mechanistically coupled, the highest-tier engineering approach designs additive systems that simultaneously suppress both phenomena.
Fluorophosphates Scavenge Dissolved Transition Metals
Fluorophosphates — either added directly as LiDFP or generated in situ by ethylene carbonate elimination from fluorinated solvents — were identified by the MEET Battery Research Center as particularly effective for scavenging dissolved TMs and preventing their deposition on the graphite anode. Validated on NCM523 at high voltage, demonstrating suppression of the rollover failure cascade.
PES211 Ternary System: XPS-Confirmed Multi-Site Action
The ternary additive system "PES211" — 2% prop-1-ene-1,3-sultone (PES) + 1% methylene methane disulfonate (MMDS) + 1% TTSPi — significantly improved capacity retention, impedance, and gas evolution in NMC442/graphite pouch cells at 4.7 V. XPS confirmed PES and MMDS preferentially react to form stable SEI films at both electrodes, while TTSPi undergoes preferential chemical reaction at the graphite surface and modifies LiPF₆ reactivity.
UHPC Confirms Synergistic Multi-Additive Superiority
Dalhousie University established using ultra-high precision coulometry (UHPC) and gas evolution measurements that combinations of VC, ethylene sulfate (DTD), tris(trimethylsilyl) phosphate (TTSP), and TTSPi act synergistically — reducing parasitic reactions at the positive electrode above 4.1 V, improving coulombic efficiency, reducing charge-endpoint slippage, and decreasing cell impedance more effectively than 2% VC alone.
Nitrile Co-Additives Reduce Storage Gassing
Dalhousie University showed that 2 wt% succinonitrile (SN) combined with 2 wt% VC reduced reversible capacity loss and gas generation during storage at 4.5 V and 60 °C for NMC442/graphite cells, compared to VC alone. The associated impedance increase from SN required further mitigation by ethylene sulfite (ES) and TTSPi — illustrating that nitrile co-additives function best within a broader multi-component system.
Additive Performance Comparison for LNMO Gassing Suppression
Side-by-side comparison of validated additive systems across mechanism, loading, voltage window, and key institutional source.
| Additive / System | Loading | Voltage Window | Primary Mechanism | Key Outcome | Source |
|---|---|---|---|---|---|
| PTSI | 0.5 wt% | Up to 4.98 V | CEI film, HF barrier | +36.0 mAh/g first-cycle capacity | Shenzhen Univ. 2019 |
| 4TP (boronic acid) | 2 wt% | 4.9 V | Fluorinated aryl CEI film | High capacity retention, cost-efficient | S. China Normal 2021 |
| TMSPi + LiDFOB | Dual additive | LNMO/graphite full cell | Dual-site CEI + SEI | Simultaneous cathode + anode passivation | Uppsala Univ. 2023 |
| VC + DTD + TTSP + TTSPi | Multi-component blend | Above 4.1 V | Synergistic parasitic reaction reduction | Better CE, lower impedance vs. 2% VC alone | Dalhousie 2014 |
| PES211 (PES+MMDS+TTSPi) | 2%+1%+1% | 4.7 V NMC442 | Multi-site SEI/CEI, HF suppression | XPS-confirmed stable SEI at both electrodes | Dalhousie 2016 |
| SN + VC | 2 wt% + 2 wt% | 4.5 V / 60 °C storage | Nitrile co-additive gas reduction | Reduced storage gas vs. VC alone | Dalhousie 2015 |
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HOMO/LUMO-guided molecular design is enabling next-generation additive discovery for LNMO systems.
What the Research Tells Us About LNMO Gassing Suppression
Gassing in LNMO systems originates from both cathode-side oxidative solvent decomposition and anode-side TM-catalyzed electrolyte breakdown. Paul Scherrer Institute neutron imaging directly confirmed continuous gassing in LNMO/graphite cells during operation, while Dalhousie University demonstrated that cathode-side oxidation is the dominant source.
Common additives including VC and FEC are insufficient for LNMO systems because they cannot suppress TM dissolution and electrode crosstalk, allowing the gassing cascade to proceed via the anode surface — as concluded by the University of Münster's MEET Battery Research Center in 2021.
The field has evolved clearly from single-additive approaches to multi-additive synergistic systems, and from empirical screening to computationally guided molecular design using HOMO/LUMO-based additive selection. There is a growing recognition that CEI and SEI must be co-engineered simultaneously to address both gassing loci, as demonstrated by Uppsala University's 2023 TMSPi/LiDFOB dual-site passivation study.
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LNMO Electrolyte Additive Gassing — Key Questions Answered
LNMO cathodes operate at approximately 4.7–4.98 V vs. Li/Li⁺, a regime that far exceeds the oxidative stability of conventional carbonate-based electrolytes. The resulting electrolyte oxidation drives continuous gas evolution — primarily CO₂, CO, and trace hydrocarbons — which causes cell swelling, impedance rise, capacity fade, and safety hazards. Neutron imaging at the Paul Scherrer Institute confirmed that LNMO/graphite cells gas more persistently than LiFePO₄/graphite counterparts.
Gassing arises from two coupled phenomena: direct oxidative decomposition of carbonate solvents at the high-voltage cathode surface, and indirect gassing triggered by transition-metal (TM) dissolution and electrode crosstalk. Dalhousie University showed that pouch bags containing only delithiated NMC442 electrodes and electrolyte generated far greater quantities of CO₂ than full cells, highlighting that cathode-side oxidation reactions are a dominant gassing source.
The University of Münster's MEET Battery Research Center demonstrated that common additives such as vinylene carbonate (VC) and fluoroethylene carbonate (FEC) failed to suppress the TM dissolution/deposition cycle, even though FEC produced a more homogeneous distribution of deposited metals. Because VC and FEC cannot suppress transition-metal dissolution and electrode crosstalk, the gassing cascade proceeds via the anode surface.
Uppsala University demonstrated that combining TMSPi with lithium difluoro(oxalato)borate (LiDFOB) in LiPF₆-based carbonate electrolytes in LNMO-graphite full cells yields a synergistic outcome: TMSPi oxidizes on the LNMO surface prior to electrolyte solvent decomposition to form a stable CEI, while LiDFOB, with a lower reduction potential than ethylene carbonate (EC), preferentially forms a stable SEI on the graphite anode. This dual-site passivation strategy simultaneously reduces cathode-side gassing and anode-side SEI thickening.
Fluorophosphates — either added directly (e.g., LiDFP) or generated in situ by ethylene carbonate elimination from fluorinated solvents — were identified by the MEET Battery Research Center as particularly effective for scavenging dissolved TMs and preventing their deposition on the graphite anode. The fluorophosphate approach was validated on LiNi₀.₅Co₀.₂Mn₀.₃O₂ (NCM523) at high voltage and demonstrated to suppress the rollover failure cascade.
HOMO/LUMO-guided molecular design is enabling next-generation additive discovery, where molecules with higher HOMO energies than conventional solvents are computationally pre-screened to ensure preferential oxidation at the LNMO cathode. Hebei University of Technology illustrated this for ionic liquid additives: a functionalized ionic liquid with a higher HOMO energy than EC and DMC was shown to preferentially oxidize and migrate to the LiNi₀.₅Mn₁.₅O₄ cathode surface to participate in SEI formation, thereby protecting the electrode from further oxidative degradation.
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References
- An electrolyte additive for the improved high voltage performance of LiNi0.5Mn1.5O4 (LNMO) cathodes in Li-ion batteries
- Re-evaluating common electrolyte additives for high-voltage lithium ion batteries
- Electrochemical Analysis for Enhancing Interface Layer of Spinel LiNi0.5Mn1.5O4 Using p-Toluenesulfonyl Isocyanate as Electrolyte Additive
- Critical Review on cathode–electrolyte Interphase Toward High-Voltage Cathodes for Li-Ion Batteries
- A High Precision Study of Electrolyte Additive Combinations Containing Vinylene Carbonate, Ethylene Sulfate, Tris(trimethylsilyl) Phosphate and Tris(trimethylsilyl) Phosphite in Li[Ni1/3Mn1/3Co1/3]O2/Graphite Pouch Cells
- The Effect of Some Nitriles as Electrolyte Additives in Li-Ion Batteries
- Suppressing Electrode Crosstalk and Prolonging Cycle Life in High-Voltage Li Ion Batteries: Pivotal Role of Fluorophosphates in Electrolytes
- Additives for Cycle Life Improvement of High-Voltage LNMO-Based Li-Ion Cells
- The Effects of a Ternary Electrolyte Additive System on the Electrode/Electrolyte Interfaces in High Voltage Li-Ion Cells
- Cost-Efficient Film-Forming Additive for High-Voltage Lithium–Nickel–Manganese Oxide Cathodes
- Tris(trimethylsilyl) Phosphite and Lithium Difluoro(oxalato)borate as Electrolyte Additives for LiNi0.5Mn1.5O4-Graphite Lithium-Ion Batteries
- Effect of FSI Based Ionic Liquid on High Voltage Li-Ion Batteries
- Gas Evolution in Operating Lithium-Ion Batteries Studied In Situ by Neutron Imaging
- Rapid Impedance Growth and Gas Production at the Li-Ion Cell Positive Electrode in the Absence of a Negative Electrode
- Conventional Electrolyte and Inactive Electrode Materials in Lithium-Ion Batteries: Determining Cumulative Impact of Oxidative Decomposition at High Voltage
- Fluorinated Electrolytes for 5-V Li-Ion Chemistry: Probing Voltage Stability of Electrolytes with Electrochemical Floating Test
- Multifunctional electrolyte additive for improved interfacial stability in Ni-rich layered oxide full-cells
- Paul Scherrer Institute — Neutron Imaging Research
- U.S. Department of Energy — Battery Research Programs
- International Energy Agency — Battery Technology Outlook
All data and statistics on this page are sourced from the references above and from PatSnap's proprietary innovation intelligence platform, which aggregates over 2 billion data points from global patent databases and scientific literature.
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