Understanding the Stability of NMC811 in Lithium-Ion Batteries with Water-in-Salt Electrolytes,ACS Applied Energy Materials

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Understanding the Stability of NMC811 in Lithium-Ion Batteries with Water-in-Salt Electrolytes
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2022-08-16 , DOI: 10.1021/acsaem.2c01722
Maximilian Becker _{1,

2} , Wengao Zhao ₁ , Francesco Pagani ₁ , Claudia Schreiner ₁ , Renato Figi ₁ , Walid Dachraoui ₁ , Rabeb Grissa ₁ , Ruben-Simon Kühnel ₁ , Corsin Battaglia ₁

Affiliation

The high practical capacity and high average de-/lithation potential of LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) renders it one of the most prominent cathode materials for lithium-ion batteries. Here, we investigate the compatibility of NMC811 with non-flammable water-in-salt electrolytes. These highly concentrated aqueous solutions possess a much extended electrochemical stability window compared to common dilute aqueous electrolytes and can comfortably accommodate 4 V-class cathodes. We find that common degradation phenomena observed when cycling NMC811 in organic electrolytes such as surface phase transformation, transition metal dissolution, and particle cracking, also occur in water-in-salt electrolytes, but the enhanced salt concentration of a water-in-salt/ionic-liquid hybrid electrolyte effectively diminishes these effects. Furthermore, we find that self-discharge reactions of NMC811 at a high state of charge with aqueous electrolytes lead to NMC811 protonation and irreversible capacity losses. Protonation represents an additional challenge that needs to be overcome when combining NMC811 with non-flammable aqueous electrolytes.

中文翻译：

使用盐包水电解质了解 NMC811 在锂离子电池中的稳定性

_{LiNi 0.8} Mn _0.1 Co _0.1 O ₂的高实用容量和高平均脱锂/锂化潜力(NMC811) 使其成为最突出的锂离子电池正极材料之一。在这里，我们研究了 NMC811 与不易燃的盐包水电解质的相容性。与普通的稀水性电解质相比，这些高浓度水溶液具有大大扩展的电化学稳定性窗口，并且可以舒适地容纳 4 V 级阴极。我们发现在有机电解质中循环 NMC811 时观察到的常见降解现象，如表面相变、过渡金属溶解和颗粒破裂，也发生在盐包水电解质中，但盐包水的盐浓度增加/离子液体混合电解质有效地减少了这些影响。此外，我们发现 NMC811 在高充电状态下与水性电解质的自放电反应导致 NMC811 质子化和不可逆的容量损失。将 NMC811 与不易燃的水性电解质结合使用时，质子化是一个需要克服的额外挑战。

更新日期：2022-08-16

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