New solid-state battery material is sourced from trees

One of the most abundant renewable resources we have on the planet is trees. Tree farms worldwide grow all types of trees for use in making construction materials, paper, and a litany of other items. Researchers from Brown University are working to create batteries that could be used for electric vehicles and other more efficient and safer products than today's lithium-ion batteries. The problem with lithium-ion batteries today is that they can overheat and catch fire when damaged.

The research team published a paper demonstrating a solid ion conductor made from a combination of copper and cellulose nanofibrils. The latter component is polymer tubes that are derived from wood. Researchers say the material they create is paper-thin and offers ion conductivity between 10 and 100 times better than other polymer ion conductors discovered previously.

The breakthrough could be used to create a solid battery electrolyte or as an ion-conducting binder for use in the cathode of future all-solid-state batteries. When the team combined copper with cellulose nanofibrils, they discovered that cellulose nanofibrils that are typically non-insulating provided faster lithium-ion transport inside the polymer chains. The material represents a record high ionic connectivity among all electrodes conducted of a solid polymer.

Modern lithium-ion batteries rely on liquid electrolytes and form small lithium metal filaments known as dendrites. The problem with dendrites is that they can lead to short-circuits and fires due to the flammable chemicals used in liquid electrolytes. There is no issue with dendrite penetration by switching to solid electrolytes, and batteries can be constructed using non-flammable materials.

Typically, solid electrolytes are forms of ceramic materials prone to cracking and breaking due to stresses in manufacturing and use. However, the new material revealed in the study is thin and flexible, similar to a sheet of paper, despite having conductivity similar to various ceramics.