Cellulose for optimized energy storage

This project will develop graphite and cellulose-based electrodes for energy storage with optimized capacity/cost ratio.

The world is moving towards using an increasing amount of renewable energy where the energy storage in the form of batteries and super capacitors (SC) will be important components. The applications for energy storage is growing exponentially in parallel to the industry's transformation towards using renewable energy.

At Mid Sweden University, we have several projects that focus on energy storage in SC, for example it is used in cars in order to take advantage of the braking energy or in off-grid street lights that becomes self-sufficient. Common to all these projects is that they are part of our strategic action KM2 (square kilometers) at Mid Sweden University, where we use knowledge and processes from the paper industry to produce large functional surfaces at low cost.

In our SC, a composite of cellulose and graphite is used as electrode material in which the graphite is the active material that can store energy. The graphite is exfoliated into graphene or nano-graphite to obtain as much internal surface area as possible because it is proportional to the capacitance (the energy storage capacity). The cellulose acts as a binder and dispersant in this system and it has been treated chemically and mechanically to obtain cellulose nanofibrils (CNF).

Both CNF and graphene can be manufactured from a variety of raw materials and the process can be treated in different ways. Today, the processes are often optimized to manufacture as fine and pure materials as possible. For the SC, this is not necessary, but simple materials work very well. Therefore, the electrodes can be made with a considerably better capacity/cost ratio. We have results from Mid Sweden University that shows this, where we even got improved energy storage with a somewhat simpler material.

In this project we will investigate the properties of different pulps and how much they need to be treated, both chemically and mechanically, to get super capacitors with as high capacitance as possible. We will use dissolving, CTMP and kraft pulp as the starting material and two different types of graphite to produce the best and most cost-effective electrode material for energy storage.