Apples to Apples: Shift from Mass Ratio to Additive Molecules per Electrode Area to Optimize Li-Ion Batteries

Electrolyte additives in liquid electrolyte batteries can trigger the formation of a protective interphase (SEI) atthe electrodes that aims to suppress side reactions at the electrodes. Studies of varying amounts of additives have been done over the last years, providing a comprehensive understanding of the impact of the electrolyte formulation on the lifetime of the cells. However, these studies mostly focus on the variation of the mass fraction of additive in the electrolyte while disregarding the ratio (radd) of the additive's amount of substance (nadd) to the electrode area (Aelectrode). Herein we utilize our extremely accurate automatic battery assembly system (AUTOBASS) to vary electrode area and amount of substance of the additive. The data provides strong evidence that reporting the mass ratios of electrolyte components is insufficient and the mol of additive relative to the electrodes' area should be reported. Herein, the two most utilized additives, namely fluoroethylene carbonate (FEC) and vinylene carbonate (VC) were studied. Each additive was varied from 0.1 wt.-% - 3.0 wt.-% for VC, and 5 wt.-% - 15 wt.-% for FEC for two mass loadings of 1 mAh/cm2 and 3 mAh/cm2. To engage the community to find better descriptors, such as the proposed radd, we publish the dataset alongside this manuscript.

Codes and mechanical parts of the project:

AutoBASS 2.0: GitHub - Helge-Stein-Group/AutoBASS at AutoBASS_2.0

液态电解质电池中的电解质添加剂可触发电极表面保护性界面（固体电解质界面，Solid Electrolyte Interphase, SEI）的形成，旨在抑制电极处的副反应。过去数年中，学界已针对不同添加剂用量开展了大量研究，全面阐明了电解质配方对电池循环寿命的影响。然而，此类研究大多聚焦于电解质中添加剂的质量分数变化，却忽略了添加剂的物质的量（$n_{ ext{add}}$）与电极面积（$A_{ ext{electrode}}$）的比值（$r_{ ext{add}}$）。

本文中，我们借助高精度全自动电池组装系统（AUTOBASS）实现了电极面积与添加剂物质的量的精准调控。本数据集有力证实，仅报告电解质组分的质量比值并不充分，还应同时报告相对于电极面积的添加剂物质的量。本研究选取了两种最常用的电解质添加剂：氟代碳酸乙烯酯（fluoroethylene carbonate, FEC）与碳酸亚乙烯酯（vinylene carbonate, VC）。针对1 mAh/cm²和3 mAh/cm²两种电极面容量设置，VC的添加量范围为0.1 wt.%~3.0 wt.%，FEC的添加量范围为5 wt.%~15 wt.%。为推动学界探索更优的性能描述参数（如本文提出的$r_{ ext{add}}$），我们随本学术论文公开了本数据集。

本项目的代码与机械部件：
AutoBASS 2.0：GitHub - Helge-Stein-Group/AutoBASS at AutoBASS_2.0