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Novel Membrane Technology Enables Long-Term Gas Analysis of Batteries, Revealing Failure Mechanisms
Release time:
2026-04-08
Novel Membrane Technology Enables Long-Term Gas Analysis of Batteries, Revealing Failure Mechanisms
Graphene oxide-based separation membrane prevents solvent interference, enabling realistic study of battery degradation over hundreds of hours.
Technical Background
The MDEMS (Membrane Separation Differential Electrochemical Mass Spectrometry) system schematic (left image) shows a graphene oxide-based gas separation membrane. This membrane selectively blocks volatile organic solvent molecules (such as DEC, EMC) from entering the mass spectrometer (MS), while allowing dissolved gases (such as H₂, O₂, CO, CO₂, C₂H₄) generated in NCM811-graphite full cells to be carried by argon flow to the mass analyzer for detection. The corresponding gas evolution data (H₂ and CO₂) during cycling at 45°C (right image) shows that the combination of carbon-coated NCM811 cathode with LiDFOB additive significantly suppresses gas emissions compared to unmodified cells, validating the effectiveness of this strategy in enhancing battery stability.
The Challenge
Differential Electrochemical Mass Spectrometry (DEMS) is a powerful tool for tracking gaseous products during battery operation, providing critical insights into reaction mechanisms and safety. However, when applied to lithium-ion batteries containing organic electrolytes, conventional DEMS faces a major challenge: standard hydrophobic PTFE membranes cannot block volatile solvent molecules such as dimethyl carbonate (DMC) and diethyl carbonate (DEC). These solvents enter the mass spectrometer, causing signal interference, contaminating the ion source, and accelerating electrolyte dry-out, leading to premature cell failure within one to two days. This short testing window and unrealistic electrolyte conditions make it difficult to study long-term degradation mechanisms.
The Breakthrough
To address this, a team led by Professor Chen Yuhui at Nanjing Tech University developed the Membrane Separation DEMS (MDEMS) system. The core of this innovation is a graphene oxide-based membrane that selectively allows small gas molecules (e.g., H₂, CO₂, C₂H₄) to pass through while effectively blocking larger organic solvent molecules.
This membrane design solves two problems simultaneously: preventing solvent interference in detection and maintaining electrolyte composition by preserving solvent vapor pressure within the cell. As a result, the MDEMS system supports stable operation for hundreds of hours, closely simulating real battery conditions.
Research Findings
Using MDEMS, the team investigated how lithium difluoro(oxalato)borate (LiDFOB) additives and carbon coatings on cathode materials affect gas generation in NCM811-graphite full cells.
They discovered that while LiDFOB initially suppresses gas generation effectively, it is gradually consumed by transition metal ions dissolved from the NCM811 cathode as they migrate to the graphite anode, thereby damaging the solid-electrolyte interphase (SEI).
Applying a carbon coating on the cathode significantly suppresses metal ion dissolution, thereby protecting the SEI and reducing gas generation. The combination of LiDFOB with carbon coating synergistically delays battery failure, particularly at 45°C.
Outlook
This study demonstrates that MDEMS is a robust platform for investigating gas evolution mechanisms in batteries with volatile electrolytes. The technology is also applicable to other battery systems beyond lithium-ion. Future work will integrate MDEMS with other in-situ characterization methods to build a more comprehensive understanding of battery failure.
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