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IEST In-Situ Gas Evolution Solutions Power Major ACS Nano Breakthrough: Quantitatively Reveals Initial Gas Evolution Behavior in Li-Rich Cathodes
Updated on 2026/07/10
Table of Contents
Abstract
In 2025, Prof. Dongliang Peng and Prof. Qingshui Xie’s team at Xiamen University, in collaboration with Prof. Jun Lu’s team at Zhejiang University and Argonne National Laboratory, published a study in ACS Nano titled “Modulating Surface Anionic Redox Chemistry toward Highly Stable Li-Rich Cathodes with Negligible Oxygen Loss.” The work addresses the central failure modes of lithium-rich layered oxide (LLO) cathodes — irreversible oxygen release, low first-cycle Coulombic efficiency, severe interfacial side reactions, and long-term capacity/voltage decay — through a dual-reductive-gas interfacial co-treatment strategy that builds an amorphous transition-metal sulfate/sulfite protective layer, an in-situ spinel transition layer, and engineered defect structures on both the secondary particle surface and internal primary particle surfaces of the Li-Rich Cathodes. The IEST GVM2200 in-situ gas evolution monitoring instrument was used to track pouch cell volume change during initial cycling — providing the key in-situ, quantitative evidence linking the engineered surface chemistry to suppressed gas evolution in batteries and improved Li-rich cathode interfacial stability.
📄 Source Paper
Research Teams: Prof. Dongliang Peng & Prof. Qingshui Xie (Xiamen University); Prof. Jun Lu (Zhejiang University); Argonne National Laboratory, USA
DOI: 10.1021/acsnano.5c00630
| Journal: ACS Nano, 2025, 19, 15886–15895
| Institutions: Xiamen University; Zhejiang University; Argonne National Laboratory
✓ IEST Instrument acknowledged — IEST In-Situ Battery Gassing Volume Analyzer (GVM2200) used in this research
Figure 1. Surface anionic redox modulation enabling highly stable, low-oxygen-release Li-rich cathodes.
1. Research Background: Why Do Li-Rich Cathodes Need In-Situ Gas Evolution Monitoring?
Lithium-rich layered oxide cathode materials offer capacity advantages that exceed conventional commercial cathodes, making them an important candidate for next-generation high-energy-density lithium-ion batteries. However, their high capacity derives primarily from anionic (oxygen) redox reactions — a process that is frequently accompanied by irreversible lattice oxygen release.
Particularly during the initial charge-discharge process, over-oxidation can trigger O₂ release, electrolyte oxidative decomposition, non-uniform CEI film growth, and structural collapse — ultimately causing reduced first-cycle Coulombic efficiency, capacity fade, and voltage decay. Beyond conventional electrochemical testing and structural characterization, directly, in-situ, and quantitatively capturing the volume change caused by cell gassing is therefore an important method for evaluating the oxygen stability and interfacial stability of Li-rich cathode materials.
2. The Key Role of GVM2200: Moving Gas Evolution Behavior from “Outcome Observation” to “Process Quantification”
This study employed a dual-reductive-gas interfacial co-treatment to construct a composite surface structure on Li-Rich Cathode particles that combines protective and regulatory functions. On one hand, this structure reduces direct electrode/electrolyte contact, suppressing side reactions; on the other hand, a reversible SO₃²⁻/SO₄²⁻ redox couple participates in the electrochemical reaction, mitigating the oxygen-centered octahedral distortion and structural collapse caused by over-oxidation.
DEMS (differential electrochemical mass spectrometry) results (Figure 2a) show that the surface-modified AS-LLO cathode exhibits significantly reduced O₂ release during initial cycling, demonstrating higher oxygen redox reversibility and interfacial stability. Further, the IEST GVM2200 was used to record real-time volume-change curves for LLO and AS-LLO pouch cells during initial cycling (Figure 2b): the mass-normalized volume change of the AS-LLO pouch cell during initial cycling was significantly smaller than that of the unmodified LLO cell — demonstrating that the initial gas evolution in batteries behavior was effectively suppressed.
Compared to observing gas release or cycling performance alone, GVM2200 more directly and intuitively reflects the impact of Li-rich cathode oxygen release and interfacial side reactions on cell-level volume evolution. This result translates material-level “improved lattice oxygen stability” into cell-level “reduced volume change” — providing more direct evidence for evaluating the safety and practical viability of Li-Rich Cathodes.
Figure 2. Surface modulation suppresses oxygen release and cell volume change in Li-rich cathodes.
3. IEST GVM2200: Application Value for Li-Rich Cathode Research
The GVM2200 in-situ battery gassing volume analyzer (Figure 3) is based on the Archimedes buoyancy principle, using high-precision sensors to monitor cell volume change in real time during testing — revealing gas evolution behavior at the material, electrolyte, electrode-interface, and full-cell levels under various operating conditions.
Figure 3. The IEST GVM2200 in-situ gas evolution volume monitoring instrument.
The GVM2200 is broadly applicable to gas evolution in batteries research across lithium-ion and emerging battery chemistries, including:
- Oxygen release and volume change analysis during initial activation of cathode materials.
- Interfacial side-reaction and gassing evaluation for high-voltage cathode materials generally.
- Comparative gassing-suppression evaluation of different surface coating, doping, or structural modification strategies.
- Analysis of how electrolyte formulations, additives, and film-forming systems affect cell gassing behavior.
- In-situ volume-change monitoring under high-temperature storage, overcharge, cycling aging, and other stress conditions.
- Safety evaluation at the material level, pouch-cell level, and engineering-validation stage.
AS-LLO vs Pristine LLO: Key Results Summary
| Parameter | Pristine LLO | AS-LLO (Surface-Modified) |
|---|---|---|
| First-cycle O2 release (DEMS) | Higher | Significantly reduced |
| Oxygen redox reversibility | Lower | Higher |
| Interfacial side reactions | More pronounced | Suppressed |
| Mass-normalized pouch cell volume change (GVM2200) | Larger | Significantly smaller |
| First-cycle Coulombic efficiency | Lower | Improved |
| Structural stability (oxygen-centered octahedra) | More distortion/collapse risk | Mitigated via SO32-/SO42- redox buffering |
4. Summary
This study, through a dual-reductive-gas interfacial co-treatment strategy, achieved effective modulation of surface anionic redox chemistry in Li-Rich Cathodes, substantially reducing irreversible oxygen release during initial cycling and significantly improving material cycling stability. The IEST GVM2200 in-situ gas evolution volume monitoring instrument played an important role in this work: by continuously and quantitatively monitoring pouch cell volume change in real time during initial cycling, GVM2200 provided key evidence validating the low-gassing characteristics and interfacial stability improvement of the AS-LLO cathode material.
From “oxygen release mechanism analysis” to “cell-level volume change validation,” GVM2200 provides a powerful in-situ characterization tool for gas evolution research, safety evaluation, and engineering development of high-energy-density cathode materials.
5. Original Article
Hualong Wu, Jiahao Dong, Jiantao Li, Guiyang Gao, Liang Lin, Ailin Liu, Hongfei Zheng, Guanyi Wang, Junxiang Liu, Laisen Wang, Jie Lin, Khalil Amine, Dong-Liang Peng, Qingshui Xie, and Jun Lu. Modulating Surface Anionic Redox Chemistry toward Highly Stable Li-Rich Cathodes with Negligible Oxygen Loss. ACS Nano, 2025, 19, 15886–15895.
6. FAQs
6.1 What causes initial oxygen release during the first cycle of a Li-rich cathode?
Initial oxygen release during the first cycle of Li-rich cathodes occurs because the high capacity of lithium-rich layered oxide materials derives largely from anionic (lattice oxygen) redox reactions rather than transition-metal redox alone. During initial charging, over-oxidation of the lattice oxygen can trigger irreversible O₂ release, which in turn drives electrolyte oxidative decomposition, non-uniform CEI film growth, and structural collapse near the particle surface. This cascade of effects is the primary reason Li-rich cathodes typically show lower first-cycle Coulombic efficiency than conventional transition-metal-redox cathodes, and why controlling this initial gassing event is critical for practical cell safety and performance.
6.2 How does in-situ gas evolution monitoring for Li-rich cathodes work?
In-situ gas evolution monitoring for Li-rich cathodes, as performed with the IEST GVM2200, uses the Archimedes buoyancy principle combined with high-precision sensors to continuously track the volume of a pouch cell in real time as it cycles. As internal gas is generated from oxygen release and electrolyte side reactions, the cell’s measured volume increases proportionally, providing a direct, quantitative, mass-normalized readout of gassing severity without requiring cell disassembly. This complements gas-composition techniques such as DEMS (differential electrochemical mass spectrometry), which identifies which gases are produced, by directly quantifying the net physical consequence — cell swelling — that determines practical safety and pack-level design margins.
6.3 How does surface modification achieve oxygen release suppression in Li-rich layered oxides?
Oxygen release suppression in Li-rich layered oxides was achieved in this study through a dual-reductive-gas interfacial co-treatment that builds a composite surface structure on both the secondary particle exterior and internal primary particle surfaces. This structure combines an amorphous transition-metal sulfate/sulfite protective layer, an in-situ spinel transition layer, and engineered defect structures. The protective layer physically reduces direct electrode/electrolyte contact to suppress side reactions, while a reversible SO₃²⁻/SO₄²⁻ redox couple participates in the electrochemical reaction, buffering the oxygen-centered octahedral distortion that would otherwise drive lattice collapse under over-oxidation. Together, these mechanisms modulate the surface anionic redox chemistry to make oxygen redox substantially more reversible.
6.4 Why is pouch cell volume change a better safety indicator than DEMS gas composition data alone?
DEMS (differential electrochemical mass spectrometry) identifies which specific gas species — such as O₂ — are released and in what relative quantity, providing crucial mechanistic insight into the chemistry. However, DEMS alone does not directly quantify the physical consequence that matters most for practical cell safety and pack design: how much the cell swells. In-situ pouch cell volume change monitoring, such as with the IEST GVM2200, translates material-level chemistry improvements directly into a cell-level physical metric that engineers can use for safety margins, pack clamping design, and swelling-related failure prediction. In this study, combining DEMS (showing reduced O₂ release) with GVM2200 (showing reduced mass-normalized volume change) provided complementary mechanistic and practical evidence for the AS-LLO cathode’s improved interfacial stability.
6.5 What other applications does the GVM2200 support beyond Li-rich cathode research?
Beyond Li-rich cathode initial oxygen release studies, the GVM2200 in-situ gas evolution monitoring instrument supports a broad range of battery gassing research, including interfacial side-reaction and gassing evaluation for high-voltage cathode materials generally; comparative assessment of different surface coating, doping, or structural modification strategies for gassing suppression; analysis of how electrolyte formulations, additives, and SEI/CEI film-forming systems affect cell gassing behavior; in-situ volume-change monitoring under high-temperature storage, overcharge, and cycling aging conditions; and safety evaluation spanning material-level screening through pouch-cell-level and engineering-validation-stage testing.
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