Evolution of safety risks during battery degradation: mechanisms and implications

TY - JOUR

T1 - Evolution of safety risks during battery degradation

T2 - mechanisms and implications

AU - Zhao, Yiwen

AU - Deng, Junjun

AU - Sun, Zhenyu

AU - Lin, Ni

AU - Li, Weihan

N1 - Publisher Copyright: © 2026 The Authors. Published by Published by Elsevier B.V. and Science Press on behalf of Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. This is an open access article under the CC BY license. http://creativecommons.org/licenses/by/4.0/

PY - 2026/6

Y1 - 2026/6

N2 - Degradation and safety are the fundamental imperatives of batteries, tightly intertwined and inseparable. Only by understanding the coupled mechanisms of degradation and thermal runaway (TR) can we gain control over battery safety across the entire lifecycle. In this work, we investigate commercial 20 Ah NCM/graphite pouch cells subjected to low-temperature and fast-charging coupled protocols, and track how their degradation from the beginning of life (BOL) to the end of life (EOL) reshapes TR behavior. By combining electrochemical diagnostics with multi-scale post-mortem characterization, adiabatic TR tests on full cells, electrode-level differential scanning calorimetry and post-TR gas chromatography, we build a stage-resolved framework that links interfacial composition, lithium plating and structural damage to changes in TR onset, heat release and gas composition. The results reveal a clear degradation critical point at around 90% remaining capacity, at which the dominant degradation mode shifts from mild loss of lithium inventory to lithium-plating-driven accelerated aging with pronounced interface reconstruction, leading to reduced T1/T2, stronger low-temperature anode exotherms and a transition from CO2-dominated to H2– and hydrocarbon-rich vented gases. Notably, loss of active material already initiates in the BOL → CP stage, although capacity fade remains predominantly governed by loss of lithium inventory. With further degradation towards EOL, superposed interfacial thickening, cathode cracking and loss of active material further narrow the safety margin and increase TR severity relative to the remaining energy. This work provides a concise mechanistic link between specific degradation signatures and TR metrics, offering practical guidance for defining aging-aware safety envelopes and designing low-temperature fast-charging/discharging strategies for energy storage systems.

AB - Degradation and safety are the fundamental imperatives of batteries, tightly intertwined and inseparable. Only by understanding the coupled mechanisms of degradation and thermal runaway (TR) can we gain control over battery safety across the entire lifecycle. In this work, we investigate commercial 20 Ah NCM/graphite pouch cells subjected to low-temperature and fast-charging coupled protocols, and track how their degradation from the beginning of life (BOL) to the end of life (EOL) reshapes TR behavior. By combining electrochemical diagnostics with multi-scale post-mortem characterization, adiabatic TR tests on full cells, electrode-level differential scanning calorimetry and post-TR gas chromatography, we build a stage-resolved framework that links interfacial composition, lithium plating and structural damage to changes in TR onset, heat release and gas composition. The results reveal a clear degradation critical point at around 90% remaining capacity, at which the dominant degradation mode shifts from mild loss of lithium inventory to lithium-plating-driven accelerated aging with pronounced interface reconstruction, leading to reduced T1/T2, stronger low-temperature anode exotherms and a transition from CO2-dominated to H2– and hydrocarbon-rich vented gases. Notably, loss of active material already initiates in the BOL → CP stage, although capacity fade remains predominantly governed by loss of lithium inventory. With further degradation towards EOL, superposed interfacial thickening, cathode cracking and loss of active material further narrow the safety margin and increase TR severity relative to the remaining energy. This work provides a concise mechanistic link between specific degradation signatures and TR metrics, offering practical guidance for defining aging-aware safety envelopes and designing low-temperature fast-charging/discharging strategies for energy storage systems.

KW - Degradation

KW - Lithium-ion batteries

KW - Mechanisms

KW - Safety

UR - https://www.scopus.com/pages/publications/105034613255

U2 - 10.1016/j.jechem.2026.02.040

DO - 10.1016/j.jechem.2026.02.040

M3 - Article

AN - SCOPUS:105034613255

SN - 2095-4956

VL - 117

SP - 782

EP - 799

JO - Journal of Energy Chemistry

JF - Journal of Energy Chemistry

ER -