Tracking the active lithium (Li) inventory in an electrode shows the true state of a Li battery, akin to a fuel gauge for an engine. However, non-destructive Li inventory tracking is currently unavailable. Here we used the theoretical capacity of a transition metal oxide to convert capacity into a Li inventory analysis. The Li inventory in electrodes was tracked reliably to show how battery formulations and test methods affect performance. Contrary to capacity, Li inventory tracking reveals stoichiometric variations near the electrode–electrolyte interface. Verifiable results rationalized differences in measurements, clarifying and reducing interferences from cell formulations and experimental manipulations. By tracing four variables from formation to end-of-life, we characterize electrode and cell performance with a thermodynamic framework. Accurate rationalization of subtle differences in Li inventory utilization promises precise battery engineering, evaluation, failure analysis and risk mitigation. The method could be applicable from cell design optimization and fabrication to battery management, improving battery performance and reliability.

跟踪电极中的活性锂 (Li) 库存可显示锂电池的真实状态，类似于发动机的燃油表。然而，非破坏性锂库存跟踪目前不可用。在这里，我们使用过渡金属氧化物的理论容量将容量转换为锂库存分析。可靠地跟踪电极中的锂库存，以显示电池配方和测试方法如何影响性能。与容量相反，锂库存跟踪揭示了电极-电解质界面附近的化学计量变化。可验证的结果合理化了测量差异，澄清并减少了细胞配方和实验操作的干扰。通过追踪从形成到寿命结束的四个变量，我们利用热力学框架来表征电极和电池的性能。锂库存利用率细微差异的准确合理化可实现精确的电池工程、评估、故障分析和风险缓解。该方法可适用于从电池设计优化和制造到电池管理，提高电池性能和可靠性。