A solid electrolyte is like a sponge for lithium ions. In a regular lithium battery, ions float in a liquid, like fish in an aquarium. In a solid-state battery, they have to squeeze through the crystal lattice, like through narrow corridors. The more free spots in the lattice, the faster ions travel from one electrode to the other.
Neutrons create these free spots. A stream of neutrons from a reactor hits the material LiBO2. Neutrons are captured by boron-10 and lithium-6 nuclei, which then decay into other elements. In place of the former atoms, voids, vacancies, remain. Lithium ions can jump into these vacancies, and the whole flow of ions speeds up. Inside the crystal grains, conductivity increased by almost 20%, and at the grain boundaries — by more than 80%.
The irradiation did not destroy the crystal order. The material remained solid and kept its structure. The gamma radiation produced by the boron decay additionally helped relieve electrical stress at the grain boundaries. This stress had been hindering ion passage, and now the path is freer.
This method is like fine-tuning the material. You can irradiate only the needed areas, dosing the neutron flux. For future solid-state batteries, this is a step toward electrolytes that conduct ions almost as well as liquids, but without the risk of leakage or fire.
Boron-10 loves neutrons so much that it is used in control rods of nuclear reactors: it absorbs neutrons and slows down the chain reaction.
In Andy Weir's novel "The Martian," the protagonist uses a radioisotope thermoelectric generator for heating — here, neutrons don't heat but rearrange the crystal to make ions run faster.