Abstract
The industrial lignin used here is a byproduct from Kraft pulp mills, extracted from black liquor. Since lignin is inexpensive, abundant and renewable, its utilization has attracted more and more attention. In this work, lignin was used for the first time as binder material for LiFePO4 positive and graphite negative electrodes in Li-ion batteries. A procedure for pretreatment of lignin, where low-molecular fractions were removed by leaching, was necessary to obtain good battery performance. The lignin was analyzed for molecular mass distribution and thermal behavior prior to and after the pretreatment. Electrodes containing active material, conductive particles and lignin were cast on metal foils, acting as current collectors and characterized using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge cycles. Good reversible capacities were obtained, 148 mAh·g−1 for the positive electrode and 305 mAh·g−1 for the negative electrode. Fairly good rate capabilities were found for both the positive electrode with 117 mAh·g−1 and the negative electrode with 160 mAh·g−1 at 1C. Low ohmic resistance also indicated good binder functionality. The results show that lignin is a promising candidate as binder material for electrodes in eco-friendly Li-ion batteries.
Highlights
Li-ion batteries have attracted considerable attention due to their high energy density, high efficiency, long life and environmentally friendly operation
Polyethylene glycol (PEG) 400, dried acetone >99.9% purity and the electrolyte consisting of 1 M LiPF6 salt in ethylene carbonate (EC): Diethyl carbonate (DEC) 1:1 by weight were obtained from Merck
This study is the first attempt to use lignin as binder material for Li-ion battery electrodes, and it shows that lignin is a promising binder material for both LiFeO4 positive and graphite negative electrodes
Summary
Li-ion batteries have attracted considerable attention due to their high energy density, high efficiency, long life and environmentally friendly operation. Magasinski et al explored a novel binder consisting of poly (acrylic acid) (PAA) for Si-based anodes, which can be dissolved in water and in an environmentally friendly organic solvent, ethanol [13]. Conductive materials, such as polyaniline (PANI), polypyrrole (PPy), and conducting polymer hydrogels (CPHs), have been demonstrated as binder materials for electrodes in Li-ion batteries, in particular where the active material undergoes volume changes during cycling [14,15,16]. The rate capabilities of both the positive and the negative electrodes are presented
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