Advantages of solid-state vs. liquid lithium batteries

The solid-state battery sector regained market interest in the first half of 2024 following new breakthroughs in the industry abroad. In January, Maxell, a leading Japanese battery company, developed a cylindrical all-solid-state battery that boasts 25 times the capacity of a conventional square battery. Additionally, Power Co, a subsidiary of Volkswagen Group, conducted endurance tests on Quantum Scape solid-state batteries, and the findings revealed that the batteries could achieve an ultra-long life of 500,000 kilometers, retaining 95% of their capacity despite being charged and discharged for 1,000 times. Such strong and virtually non-decaying endurance is a powerful validation of the potential of solid-state batteries, which has attracted significant attention.

What are solid-state batteries?

As the name implies, a solid-state battery is a battery in which all the components that make up the battery are solid. Conventional secondary batteries use a liquid as the electrolyte, but solid-state batteries use a solid as the electrolyte.

The core difference between solid-state batteries and liquid batteries lies in the electrolyte. Lithium-ion batteries are basically composed of two electrodes (a cathode and an anode) made of metal and an electrolyte that fills the space between them. Solid-state batteries use solid-state electrolyte to replace the liquid electrolyte and diaphragm in traditional liquid lithium batteries.

Liquid lithium-ion battery is a kind of secondary battery (rechargeable battery), the battery is usually carbon material as the negative electrode, lithium-containing compounds as the positive electrode, lithium-containing inorganic salts dissolved into the organic compounds as the electrolyte, through the lithium ions in the positive and negative electrodes of the oxidation of the redox for the release and storage of energy, electrolyte as a lithium-ion transfer medium.

Advantages of solid-state batteries

1. Good safety. Liquid electrolyte batteries are flammable and explosive, easily causing safety hazards. Solid electrolyte can inhibit lithium dendrite, not easy to burn, not easy to burst, no electrolyte leakage, will not occur at high temperatures, such as side reactions. No short circuit due to lithium dendrite piercing the diaphragm under high current, no side reaction at high temperature, no combustion due to gas generation.
2. High energy density. It is commonly believed that achieving an energy density of over 500Wh/kg in a liquid electrolyte battery is impossible. However, by implementing a full solid-state electrolyte, the battery can eliminate the need for an embedded lithium graphite anode and instead utilize lithium metal as the anode. This innovation significantly reduces the amount of anode materials required, resulting in a remarkable improvement of the entire battery's energy density. Research and development in solid-state batteries could potentially provide an energy density of up to 300-400Wh/kg.
3. Strong cycle life. Solid electrolyte solves the problem of solid electrolyte interfacial film formed by liquid electrolyte during charging and discharging and lithium dendritic phenomenon, which greatly improves the cycling and service life of lithium batteries, and ideally, it can reach about 45,000 times.

Solid-state batteries have their limitations and drawbacks. One such issue is the high interface impedance that occurs due to the solid-state connection between the electrolyte and electrode material. This leads to a weak effective contact between the two, resulting in low ion transport kinetics within the solid matter.

Currently, all-solid-state batteries are primarily in the phase of research, development, and experimental production around the globe. However, various factors are hindering the commercialization of such batteries, including immature material technology and preparation techniques, as well as exorbitant production costs. High-cost production processes have led many battery manufacturers to shift their focus towards developing semi-solid state batteries that are affordable and have decent energy density.

Sunpack is a leading lithium battery manufacturer, who stand alongside industry peers such as CATL and EVE, diligently following market trends. They are currently investing significant capital, resources, and expertise into researching and developing solid-state batteries, with the goal of quickly realizing technological innovation in the new energy market.