How do solid state batteries work

2025-06-14

Solid-state batteries refer to lithium batteries that use solid electrolytes instead of traditional electrolytes. They can be divided into semi-solid batteries and all-solid-state batteries according to the amount of solid electrolytes used. Usually, we use 10% of the liquid content in the battery as the dividing line between semi-solid batteries and liquid batteries, while all-solid-state batteries will use solid electrolytes completely, and the liquid content will drop to 0%.

Solid-state lithium batteries are mainly composed of positive electrodes, negative electrodes and solid electrolytes. The most essential difference is that the electrolyte and diaphragm of liquid batteries are replaced with solid electrolytes, so that no or less diaphragms and electrolytes are used.

Working principle of solid-state batteries

1. The positive electrode usually uses lithium metal or similar materials. When lithium ions move from the solid electrolyte to the positive electrode, the positive electrode material undergoes an oxidation reaction and releases electrons.

2. The negative electrode generally uses lithium alloys or similar materials. When lithium ions move from the solid electrolyte to the negative electrode, the negative electrode material undergoes a reduction reaction and receives electrons.

3. The solid electrolyte is composed of conductive solid materials, such as lithium-containing inorganic salts, polymers or ceramic materials. This electrolyte has high ion mobility and low resistance, and has high chemical stability.

Advantages of solid-state batteries

Solid electrolytes are not fluid compared to electrolytes, so the direct contact between solids and solid particles is poor, and electrochemical instability leads to many interface problems. However, compared with liquid batteries, the potential advantages of solid-state batteries are:

High safety: non-volatile and non-flammable solid electrolytes are safer than organic electrolytes.

Good temperature adaptability: All-solid-state batteries can operate in a wider temperature range, especially at higher temperatures.

High energy density: All-solid-state batteries are expected to solve the safety problem of metal lithium negative electrodes (lithium dendrites). And then improve the energy density of lithium-ion batteries based on the current commercial lithium-ion graphite and silicon-carbon negative electrodes.

Simplify the design of cells, modules, and systems: Since solid electrolytes are not fluid, internal series can be used.

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