Kraft Lignin - an Alternative Sustainable Binder Material for Green Li-Ion Batteries

Abstract

The binder material plays an important role in the electrodes for Li-ion batteries, keeping good electrochemical stability and adhesion with the current collectors. The conventional binder for the commercial Li-ion batteries is poly vinylidene fluoride (PVDF). However, it requires dissolving in an organic solvent, typically N-methyl-2-pyrrolidione (NMP), which is toxic and expensive. Kraft lignin is a byproduct which is extracted from pulp and paper industries by the LignoBoost process [1]. Its utilization has gained considerable attention due to its reasonable cost, relatively high purity and being renewable. In this work, kraft lignin was used for the first time as a binder material in Li-ion batteries [2]. It is more environmental friendly and potentially less expensive compared to the PVDF binder. Electrodes, LiFePO4 positive and graphite negative electrodes bound by kraft lignin, were characterized using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge cycles. Results show that the electrodes have good reversible capacities about 150 mAh g-1 for positive electrode and 300 mAh g-1 for negative electrode cycled at C/10, and fairly good rate capabilities. The negatives have a very high cycling stability with about 98% retention after 50 cycles cycled at C/4. It illustrates that lignin is a promising alternative sustainable binder material for green Li-ion batteries. Reference 1. Tomani, P., The lignoboost process. Cellulose Chemistry & Technology, 2010. 44(1): p. 53. 2. Lu, H., et al., Lignin as a Binder Material for Eco-Friendly Li-Ion Batteries. Materials, 2016. 9(3): p. 127. Figure 1