How Does An All Solid State Battery Work?

At the University of Texas at Austin, a 94-year old professor of engineering and his team continues to work on their invention—batteries. John Goodenough, one of the inventors of the most commonly used batteries — the lithium-ion battery. At present, Goodenough is working on an all solid state battery, a low-cost cell that offers a long life cycle, fast discharging and charging rates, and high energy density.

According to Professor Goodenough, one of the reasons for battery-driven cars not being widely adopted is the drawbacks associated with the commercially available lithium-ion batteries. Among the factors he includes are safety, cost, energy density, life cycle, and the rates of charging and discharging of the battery. Goodenough is of the view the all solid state battery will address all these problems.

As the journal, Energy & Environmental Science describes it, the non-combustible battery has an energy density of nearly three times that of lithium-ion batteries currently in use. As an electric vehicle derives its driving range from the energy density of the battery cell, a higher energy density helps to propel the vehicle more kilometers between charges. The number of discharging and charging cycles that the UT Austin battery allows is also greater, and that equates to batteries that are longer lasting. Where the typical charging time for batteries in use today is in hours, the researchers claim their battery attains full charge within minutes.

The difference between the two types of batteries lies in their electrolyte. At present, batteries we commonly use contain a liquid electrolyte for transporting ions between their anode and cathode. When charged very quickly, metal whiskers or dendrites form on the electrodes, and these can traverse through the liquid electrolyte to form a short circuit. The result can result in explosions and fires.

The new battery replaces the liquid electrolyte with a glass-based one, and normal electrodes with alkali-metal anodes. According to Goodenough and his senior research fellow, Maria Helena Braga, this prevents the creation of dendrites, mitigating the hazard of short circuits.

Additionally, in the glass electrolyte, there is no lithium. Rather, the researchers have used low-cost sodium instead. Sodium is cheaper, as it can be easily extracted from widely available seawater. According to Braga, that makes the new batteries much more environment friendly compared to those containing lithium-ions.

Conventional batteries cannot use alkali-metal anodes with lithium, sodium, or potassium. However, this technology allows the new batteries to attain their high energy densities and longer life cycles.

Plummeting temperatures freeze up the liquid electrolyte, preventing normal batteries from operating in low temperatures. This has been a major obstacle in practical use of batteries. However, the all-soli-state glass electrolyte has no such drawbacks, and can easily operate down to extremely cold temperatures of -20°C.

Braga began working on solid-state electrolytes while still in the University of Porto in Portugal. She has been collaborating with Professor Goodenough and Andrew J Murchinson, another researcher at UT Austin, since two years ago.
The glass electrolyte simplifies fabrication of the battery cell, as it allows them to plate the alkali metals and strip them on both the anode and the cathode sides, without creating dendrites.