Initial formaldehyde generation as a predictive marker for long-term stability of Ni-rich Li-ion batteries under abusive conditions

Electrolyte decomposition significantly impacts the long-term stability of Li-ion batteries, generating liquid and gaseous byproducts. This study focuses on formaldehyde formation, a critical byproduct from CO2 reduction in Ni-rich Li-ion batteries. Through experimental and computational analyses, formaldehyde emerges from carbonate-based electrolyte decomposition. Examining overcharge, over-discharge, and fast charging conditions, formaldehyde concentration sharply increases under overcharge, indicating severe electrolyte breakdown, while over-discharge shows a gradual rise. Fast charging similarly elevates formaldehyde levels, underscoring the link between electrolyte decomposition and abusive conditions. Importantly, this research proposes utilizing formaldehyde concentration from the initial cycle as a predictive marker for assessing long-term Ni-rich Li-ion battery stability trends. Elevated initial formaldehyde indicates potential capacity fade and accelerated degradation, enabling proactive mitigation strategies. The study elucidates mechanisms governing formaldehyde formation, providing a foundation for developing electrolyte formulations and electrode materials with enhanced decomposition resistance and improved stability. This investigation contributes to the fundamental understanding of electrolyte decomposition in Ni-rich Li-ion batteries and presents a novel approach to predicting long-term performance based on initial formaldehyde measurements, advancing high-performance and reliable energy storage solutions. [Display omitted] •Formaldehyde predicts stability in Ni-rich Li-ion batteries under stress.•CO2 reduction to formaldehyde marks electrolyte decomposition's critical pathway.•Overcharge significantly accelerates formaldehyde production, hinting at rapid degradation.•Precise formaldehyde measurement via NMR improves battery health evaluation.•Research inspires advanced battery designs limiting formaldehyde generation.