Tannic Acid As a Binder in Silicon Anodes for Lithium-Ion Batteries

Increasing demand for portable electronic devices, electric vehicles, and grid scale energy storage has spurred interest in developing high capacity rechargeable lithium ion batteries (LIBs). Due to this interest, researchers have been extensively studying materials with high lithium ion storage capability, such as silicon, to replace the graphite anode in LIBs. Silicon is a non-toxic, abundantly available material and has a theoretical gravimetric capacity of 3500 mAh/g with a low operating potential of 0 to 1 V vs. Li/Li + . However, silicon has not yet been commercialized as an anode material due to large volume variation (>300 %) during lithiation and delithiation. This causes pulverization and loss of electrical contact between components, leading to capacity degradation and short battery cycle life. These problems can be overcome by using a binder that can hydrogen bond with the silicon particles. Here, we demonstrate utilization of tannic acid (TA), a natural polyphenol derived from wood, as a binder for silicon anode in lithium ion batteries. The resulting silicon electrodes demonstrate good cycling stability with a capacity of 1000 mAh/g for 200 cycles. This cycling stability can be attributed to the presence of the many hydroxyl (OH) groups (14.8 mM of -OH per g of TA) that hydrogen bond with the silicon particles’ OH groups. Additionally, water processability makes the electrode synthesis process environmentally friendly. This work demonstrates that a molecule with high hydrogen bonding capability can be used as a binder. Furthermore, future modifications of TA can further improve its performance as a binder for silicon anodes.