The commercialization of high-energy batteries with lithium-rich cathode materials exhibiting combined cationic/anionic redox processes awaits the elimination of certain practical bottlenecks. Among these, large voltage hysteresis remains the most obscure from a fundamental thermochemical perspective. Here, we study this issue by directly measuring, via isothermal calorimetry, the heat generated by Li/Li₂Ru_0.75Sn_0.25O₃ (Li/LRSO) cells during various cycling conditions, with LRSO being a ‘model’ Li-rich layered cathode. We show how this heat thermodynamically relates to the lost electrical work that is crucial for practical applications. We further reveal that anionic redox on charging and discharging adopts different metastable paths having non-identical enthalpy potentials, such that the overall Li content no longer remains the unique reaction coordinate, unlike in fully path-reversible cationic redox. We elucidate how quasi-static voltage hysteresis is related to heat dissipated due to non-equilibrium entropy production. Overall, this study establishes the great benefits of isothermal calorimetry for enabling energy-efficient electrode materials in next-generation batteries.

具有展示出组合的阳离子/阴离子氧化还原工艺的富含锂的阴极材料的高能电池的商业化正在等待消除某些实际的瓶颈。其中，从基本热化学的角度来看，大电压迟滞仍然是最模糊的。在这里，我们通过等温量热法直接测量Li / Li ₂ Ru _0.75 Sn _0.25 O ₃产生的热量来研究这个问题。（Li / LRSO）电池在各种循环条件下的运作，其中LRSO是“模型”富含锂的分层阴极。我们展示了这种热量在热力学上如何与电力损耗有关，而电力损耗对于实际应用至关重要。我们进一步揭示，在充电和放电时，阴离子氧化还原采用具有不同焓焓的不同亚稳路径，因此，与完全路径可逆的阳离子氧化还原不同，总的Li含量不再保持唯一的反应坐标。我们阐明了准静态电压磁滞与非平衡熵产生所产生的热量之间的关系。总体而言，这项研究建立了等温量热法在下一代电池中使用节能电极材料的巨大优势。