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<p>With the evolution toward longer-life lithium-ion batteries, accelerated aging tests are critically required for life assessment. However, there has been no accelerated ageing test for high-capacity prismatic cells, whose increased dimensions induce challenges, such as pronounced thermal gradients, uneven current distributions, and heterogeneous mechanical stresses. To bridge the gap, this work adopted a framework combining acceleration factor analysis, half-cell aging mode assessment, ultrasonic scanning, electrolyte composition analysis, and SEM characterization to evaluate the acceleration effects and elucidate the multiscale degradation mechanisms of 280 Ah large-format prismatic cells under coupled thermal-electrical stresses. It has been found that the ambient temperature for accelerated aging tests can be increased from 55°C to 85°C, which can increase the time-based average acceleration factor from 8.21 to 22.36, peaking at 27.06, and consequently reduce the testing duration to roughly 3.7% of the normal aging. In general, the accelerated-aging pathway preserves the same dominant degradation mechanism as normal long-term cycling. It is identified that ageing mechanisms are still very much dependent on temperatures, with sluggish kinetics promoting lithium plating at low temperatures, i.e., below 0°C, causing severe capacity fade; while at elevated temperatures, i.e., above 65°C, the influence of current diminishes, and thermally dominated ageing prevails. Cyclable lithium depletion was identified as the dominant cause of capacity loss. Negative-electrode material degradation contributed less than 3.2%, whereas active-material loss in the LFP cathode was negligible under high-temperature aging conditions. However, compared with previous studies on small-capacity cells, the degradation trajectories exhibit distinct features. For example, “knee points” disappear under high-temperature conditions. A temperature-dependent rate-effect reversal is also observed, and an extended temperature window is identified for mechanism-consistent accelerated aging of large-format LFP cells. Ultrasonic inspection, electrolyte analysis, and SEM observations revealed multiscale structural instabilities, including electrolyte depletion, separator melting, and graphite pulverization, confirming the coupled thermal-electrochemical degradation pathways.</p>

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Insights from accelerated aging of long-life, high-capacity LiFePO4 prismatic batteries under coupled thermal-electrical stresses

  • 期刊论文

  • 发表日期：

    2026年5月25日

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  • Peng Wang,
  • Dongbin Nan,
  • Xinyu Wang,
  • Zhiyuan Zhuang,
  • Hailong Li,
  • Rui Xiong

摘要

With the evolution toward longer-life lithium-ion batteries, accelerated aging tests are critically required for life assessment. However, there has been no accelerated ageing test for high-capacity prismatic cells, whose increased dimensions induce challenges, such as pronounced thermal gradients, uneven current distributions, and heterogeneous mechanical stresses. To bridge the gap, this work adopted a framework combining acceleration factor analysis, half-cell aging mode assessment, ultrasonic scanning, electrolyte composition analysis, and SEM characterization to evaluate the acceleration effects and elucidate the multiscale degradation mechanisms of 280 Ah large-format prismatic cells under coupled thermal-electrical stresses. It has been found that the ambient temperature for accelerated aging tests can be increased from 55°C to 85°C, which can increase the time-based average acceleration factor from 8.21 to 22.36, peaking at 27.06, and consequently reduce the testing duration to roughly 3.7% of the normal aging. In general, the accelerated-aging pathway preserves the same dominant degradation mechanism as normal long-term cycling. It is identified that ageing mechanisms are still very much dependent on temperatures, with sluggish kinetics promoting lithium plating at low temperatures, i.e., below 0°C, causing severe capacity fade; while at elevated temperatures, i.e., above 65°C, the influence of current diminishes, and thermally dominated ageing prevails. Cyclable lithium depletion was identified as the dominant cause of capacity loss. Negative-electrode material degradation contributed less than 3.2%, whereas active-material loss in the LFP cathode was negligible under high-temperature aging conditions. However, compared with previous studies on small-capacity cells, the degradation trajectories exhibit distinct features. For example, “knee points” disappear under high-temperature conditions. A temperature-dependent rate-effect reversal is also observed, and an extended temperature window is identified for mechanism-consistent accelerated aging of large-format LFP cells. Ultrasonic inspection, electrolyte analysis, and SEM observations revealed multiscale structural instabilities, including electrolyte depletion, separator melting, and graphite pulverization, confirming the coupled thermal-electrochemical degradation pathways.