What is the difference between solid-state batteries and lithium-ion batteries?

At present , most of the electric vehicles and energy storage systems use lithium-ion batteries . Although they have high energy density and fast charging speed, they have problems such as safety. Therefore, the industry is actively developing solid-state batteries , expecting it to replace traditional lithium-ion batteries.

What is a solid state battery?

Solid-state batteries are a type of battery technology. Unlike lithium-ion batteries and lithium-ion polymer batteries that are commonly used today, solid-state batteries are batteries that use solid electrodes and solid electrolytes.

In solid-state ionics, a solid-state battery is a battery that uses solid electrodes and a solid electrolyte. Solid-state batteries generally have lower power density and higher energy density. Due to the high power-to-weight ratio of solid-state batteries, they are ideal batteries for electric vehicles .

What is a lithium-ion battery?

A lithium-ion battery is a secondary battery (rechargeable battery) that mainly relies on the movement of lithium ions between the positive and negative electrodes to work. During the charging and discharging process, Li+ intercalates and deintercalates back and forth between the two electrodes: during charging, Li+ is deintercalated from the positive electrode, intercalated into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; during discharge, the opposite is true.

Lithium-ion batteries were first developed by Sony Corporation of Japan in 1990. It is to intercalate lithium ions into carbon (petroleum coke and graphite) to form a negative electrode (traditional lithium batteries use lithium or lithium alloys as the negative electrode). LixCoO2 is commonly used as cathode material , LixNiO2 and LixMnO4 are also used, and the electrolyte is LiPF6 + diethylene carbonate (EC) + dimethyl carbonate (DMC).

What is the difference between solid-state batteries and lithium-ion batteries?

The main difference between solid-state batteries and lithium-ion batteries is the electrolyte. The electrolyte of lithium ions is liquid and exists in the form of gel and polymer, making it difficult for the weight of the battery to drop. In addition, the energy of a single lithium battery pack is not high, so multiple battery packs must be connected in series, adding further weight. The cost of engineering, manufacturing and installing the battery pack accounts for a large proportion of the overall cost of an electric vehicle.

In addition to weight issues, electrolytes are also flammable, unstable at high temperatures, have thermal runaway issues, and could lead to serious fires in the event of a car accident. Electrolytes also tend to freeze at low temperatures, reducing battery life . In addition, the electrolyte will corrode the internal components of the battery, and the process of charging and discharging will also generate dendrites, reducing the capacity, performance and life of the battery.

There is no heavy liquid electrolyte inside a solid-state battery, but a solid electrolyte in the form of glass, ceramic, or other materials. The overall structure of solid-state batteries is similar to that of traditional lithium-ion batteries, and the charging and discharging methods are similar, but because there is no liquid, the interior of the battery is tighter, the volume is smaller, and the energy density is increased. If the lithium-ion battery in the electric vehicle is replaced by a solid-state battery of the same volume, the electric capacity can theoretically be increased by more than 2 times.

In addition, the solid-state lithium battery is lighter in weight, and does not require the monitoring, cooling and thermal insulation system of the lithium-ion battery. The chassis can free up more space for the battery, which greatly increases the battery life of the electric vehicle.

In addition, solid-state batteries can be charged faster than lithium-ion batteries, have no corrosion problems, and have a longer life. Regarding the working temperature, the solid-state battery is thermally stable and will not freeze at low temperatures, which can ensure the battery life of electric vehicles for users living in middle and high latitudes.