Introduction to the differences between solid state batteries and lithium-ion batteries

Currently, electric vehicles and energy storage systems use mostly lithium-ion batteries, and while they have high energy density and fast charging speeds, they have safety and other issues. Therefore, the industry is actively developing solid-state batteries, expecting it to replace the 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, which 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. Since solid state batteries have a higher power to weight ratio, it is a very desirable battery for electric vehicles .

What is a lithium ion battery?

A lithium-ion battery is a secondary battery (rechargeable battery) that works by moving lithium ions between the positive and negative electrodes. In the process of charging and discharging, Li+ is embedded and de-embedded back and forth between the two electrodes: when charging, Li+ is de-embedded from the positive electrode and embedded in the negative electrode through the electrolyte, and the negative electrode is in the state of lithium enrichment; the opposite is true in the case of discharging.

Lithium-ion batteries were first developed by Sony in Japan in 1990. It is the lithium ion embedded in carbon (petroleum coke and graphite) to form the anode (traditional lithium battery with lithium or lithium alloy for the anode). The anode material is commonly used as LixCoO2, but also LixNiO2, and LixMnO4, and the electrolyte is LiPF6 + ethylene carbonate (EC) + dimethyl carbonate (DMC).

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

The main difference between solid-state batteries and lithium-ion batteries is in the electrolyte. The electrolyte for lithium-ion is liquid, in the form of gels and polymers, making it difficult to drop the weight of the battery. In addition, a single lithium-ion battery pack does not have much energy, so multiple packs must be connected in series, allowing the weight to increase even further. The cost of engineering, manufacturing and installing battery packs accounts for a large percentage of the overall cost of an EV.

In addition to the weight issue, the electrolyte is also flammable and unstable at high temperatures, with thermal runaway issues that could lead to serious fires in the event of a crash. Electrolytes are also prone to freezing at low temperatures, reducing the battery's range. In addition, the electrolyte will corrode the internal components of the battery, and the charging and discharging process will produce dendrites, reducing the capacity, performance and life of the battery.

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

And solid-state lithium batteries are lighter in weight, and do not require lithium-ion battery monitoring, cooling and insulation system, the chassis can empty more space to place the battery, so that the electric car range greatly increased.

In addition, solid-state batteries charge faster than lithium-ion batteries, and there are no corrosive issues, giving them a longer lifespan. Regarding operating temperatures, solid-state batteries are thermally stable and also don't freeze at low temperatures, which ensures EV range for users living in mid to high latitudes.