Wooden separator?

Source: Next-gen battery electrolyte made from wood offers record conductivity

. . . cellulose nanofibrils found in wood as their starting point.

These wood-derived polymer tubes were combined with copper to form a solid ion conductor boasting a conductivity similar to ceramics and between 10 and 100 times better than other polymer ion conductors. According to the team, this is because the addition of copper creates space in between the cellulose polymer chains for "ion superhighways" to form, enabling the lithium ions to travel with record efficiency.

“By incorporating copper with one-dimensional cellulose nanofibrils, we demonstrated that the normally ion-insulating cellulose offers a speedier lithium-ion transport within the polymer chains,” said study author Liangbing Hu. “In fact, we found this ion conductor achieved a record high ionic conductivity among all solid polymer electrolytes.”​

Curious lab result. Still a long way to go before production batteries. I'd like to see in cell phones first.

Bob Wilson