Electrochemical Degradation Mechanisms in Lithium-Ion Battery Electrolytes

Electrochemical degradation in lithium-ion battery electrolytes stems from both oxidative and reductive processes that break down solvent molecules and conducting salts. At high potentials, carbonate-based solvents undergo anodic oxidation, producing reactive intermediates that initiate autocatalytic decomposition cycles and generate gases such as CO₂ and POF₃. Conversely, at the anode, reductive decomposition forms a complex solid–electrolyte interphase (SEI) that passivates the electrode but can evolve unfavourably under thermal or mechanical stress. Transition metal dissolution from high-voltage cathodes further catalyses electrolyte breakdown, leading to capacity fade and safety risks. Advances in in situ spectroscopy, mass spectrometry and computational modelling have revealed pathways including solvent transesterification, salt hydrolysis and inorganic carbonate reactions. Insights into these mechanisms are crucial for the rational design of electrolyte formulations, additive schemes and electrode architectures that enhance cycle life and reliability in applications ranging from electric vehicles to grid storage.

Research from Nature Portfolio

Recent studies have directly visualised gas evolution in operating cells using neutron imaging, revealing how O₂, CO₂ and other gaseous species form at distinct electrode interfaces during cycling. This work has quantified gassing rates, separated anode and cathode contributions and highlighted the role of transition metal dissolution in exacerbating electrolyte breakdown under high-voltage conditions. Complementary investigations using radiolysis have provided an accelerated ageing platform for carbonate solvents, identifying major degradation products (H₂, CH₄, C₂H₆, CO, CO₂) and elucidating redox-driven reaction networks. By replicating electrochemical ageing without applied bias, this approach has confirmed key pathways of solvent and salt decomposition and offered a versatile tool to probe non-electrochemical degradation phenomena.

Electrochemical Degradation Mechanisms in Lithium-Ion Battery Electrolytes publication trend

The graph below shows the total number of articles in electrochemical degradation mechanisms in lithium-ion battery electrolytes across all publications each year (not limited to Nature Index journals).

Technical terms

Solid–Electrolyte Interphase (SEI): Thin passivation layer on the anode formed by reductive decomposition of electrolyte components, essential for stabilising lithium-ion transport.

LiPF₆: Lithium hexafluorophosphate, a widely used conducting salt in carbonate electrolytes prone to hydrolysis and thermal decomposition, yielding reactive fluorophosphate species.

Online Electrochemical Mass Spectrometry (OEMS): In situ analytical technique that detects and quantifies gaseous products during battery cycling, providing real-time insight into degradation pathways.

Radiolysis: Generation of reactive radicals and ions in electrolyte solvents by ionising radiation, used to simulate accelerated ageing and study non-electrochemical decomposition.

Transesterification: Chemical exchange of alkyl groups between carbonate solvents, catalysed by reactive intermediates, which alters solvent composition and influences degradation behaviour.

References

1. Decomposition of LiPF6 in High Energy Lithium-Ion Batteries Studied with Online Electrochemical Mass Spectrometry. Journal of The Electrochemical Society (2016).
2. Gas Evolution in Operating Lithium-Ion Batteries Studied In Situ by Neutron Imaging. Scientific Reports (2015).
3. Understanding Electrolyte Decomposition of Graphite/NCM811 Cells at Elevated Operating Voltage. Journal of The Electrochemical Society (2019).
4. Elementary Decomposition Mechanisms of Lithium Hexafluorophosphate in Battery Electrolytes and Interphases. ACS Energy Letters (2022).
5. Radiolysis as a solution for accelerated ageing studies of electrolytes in Lithium-ion batteries. Nature Communications (2015).