A battery component made of an ion-permeable material that prevents contact between electrode tabs of opposite polarity within the battery from causing a short circuit.
Note: Mixed solid-liquid electrolyte lithium-ion batteries, all-solid-state lithium-ion batteries, the material that isolates the positive and negative electrodes can also be considered to be a type of diaphragm, but will generally be referred to as a solid electrolyte membrane, solid electrolyte membrane in English.