Battery Gas Analysis
Lithium-ion Battery Gas Analysis is the study of gases generated inside or released from lithium-ion batteries during normal operation, abuse (thermal, electrical, or mechanical), or failure events (such as thermal runaway). Gas generation in lithium-ion batteries can indicate: Electrolyte decomposition, Overcharging / over-discharging, thermal runaway, internal short circuits, aging and degradation. These gases can be toxic, flammable, or corrosive, posing significant risks.
This analysis is critical to understand the degradation mechanism and improving battery design. Common gas release and cause and resulting hazards are summarized in Table 1.
Table 1: Common gas release, source and hazards summary
| Gas | Source | Properties / Hazards |
|---|---|---|
| CO₂ (Carbon dioxide) | Electrolyte decomposition, SEI breakdown | Inert, increases internal pressure |
| CO (Carbon monoxide) | Decomposition of carbonate solvents | Toxic, flammable |
| H₂ (Hydrogen) | Reaction of lithium with electrolyte or moisture | Highly flammable |
| CH₄ (Methane) | Electrolyte decomposition | Flammable |
| C₂H₄ (Ethylene) | SEI formation and decomposition | Flammable, commonly used as SEI marker |
| C₂H₆ (Ethane) | Electrolyte decomposition | Flammable |
| HF (Hydrogen fluoride) | LiPF₆ decomposition, reaction with moisture | Corrosive, highly toxic |
| POF₃ (Phosphoryl fluoride) | LiPF₆ salt decomposition | Toxic, corrosive |
Equipment used:
- Inhouse BSI’s gas sampling setup to gas from a swollen pouch cell or from cylindrical and prismatic cell
- Gas analysis done by most common technique called GC-MS according to ASTM D1945 “Standard Test Method for Analysis of Natural Gas by Gas Chromatography”.
- In addition, Fourier Transform Infrared Spectroscopy (FTIR) for specific bonds in molecule and Gas Chromatography–Thermal Conductivity Detector (GC-TCD) for gases like H2, CO2.
Application of gas analysis:
- Thermal runaway testing
- Understanding propagation and hazards
- Aging Studies
- Detecting gas evolution during long-term cycling
- Abuse Testing
- Overcharging, crushing, penetration, or heating
- Failure Analysis
- After an incident or battery fire
- Electrolyte Optimization
- Testing new formulations for stability
FAQ:
1. What is the purpose of gas analysis?
Characterize Hazards
- Identify flammability of vent gas mixture (H₂, CH₄, CO, hydrocarbons).
- Detect toxic gases (HF, HCl, CO, NOₓ).
- Quantify gas release (self-sustaining combustion risk).
Safety Design Inputs
- Explosion risk (Lower/Upper Flammability Limits, detonation potential).
- Sizing of venting systems (pressure relief design).
- Fire suppression strategies (e.g., water vs. inert gas effectiveness).
Root Cause Analysis
- Trace decomposition pathways of electrolytes, solvents, polymers, or active materials.
- Assess severity at different states of charge or temperatures.
2. Can gas analysis help prevent thermal runaway?
Indirectly—by understanding decomposition pathways and identifying high-risk chemistries, engineers can design safer cells, better cooling, and stronger enclosures.
3. What techniques are used for gas analysis?
Typical methods include Gas Chromatography (GC), Mass Spectrometry (MS), Infrared Spectroscopy (FTIR), and Electrochemical Gas Sensors.
4. How is gas data applied in engineering practice?
- Designing flame arrestors and vent geometries
- CFD modeling of gas dispersion in enclosures
- Benchmarking battery components for safety