A battery is usually made up of a cathode, an anode and an electrolyte. If the cathode and anode are compared to two docks, then the electrolyte is the channel between them.
An all-solid-state battery replaces the electrolyte with a solid, which is like filling in that sea in the middle. It allows ions to pass through while naturally keeping the cathode and anode apart.
A battery pack built from cells like these could, under ideal conditions, deliver a range of 1,500 kilometers, enough to get you from Shanghai to Guangzhou on a single charge.