Lignin in storage and renewable energy applications: A review

Lignin is a cheap, abundant and non-toxic group of complex phenolic polymers obtained in large amounts from the papermaking and cellulosic biofuel industries. Although the application of lignin has been explored in these and several more industries, there are limited applications of lignin in the energy industry. However, numerous research revealed a great interest in the exploration of this renewable biopolymer in storage energy devices. Some of these applications include the use of lignin as an expander for lead–acid batteries, electrodes for primary and rechargeable batteries, electrodes for electronic double layer capacitors and electrochemical pseudocapacitors, and to feed different types of fuel cells. The use of lignin in energy storage devices improves not only the performance of these devices but also decreases the price and toxicity, contributing to obtaining greener energy devices. Based on the above, this review provides an overview of the main research work related to the use of lignin as a renewable component, suitable to replace some synthetic and toxic compounds used in the fabrication of energy storage devices with particular emphasis on batteries, advanced supercapacitors, and solar and fuel cells.