Among the award recipients is 97-year-old Mr. Goodenough, known as the father of lithium batteries. He continues to work on the front lines, contributing to the next generation of lithium battery technology, "solid-state batteries".
What is a solid-state battery?
Traditional lithium batteries consist of a positive electrode, a negative electrode, a liquid electrolyte, and a separator. During charging and discharging, lithium ions swing back and forth between the positive and negative electrodes, with the liquid electrolyte serving as the medium for this movement.
Solid-state batteries convert liquid electrolyte into solid electrolyte, meaning there is no liquid electrolyte between the positive and negative electrodes, while lithium ions can still travel back and forth between the positive and negative electrodes.
To give a vivid example, all-solid-state batteries are equivalent to changing the lithium-ion travel path from a "waterway" to a "landway".
Solid-state batteries are generally called all-solid-state batteries. Currently, there are claims on the market that solid-state batteries have been successfully developed or even mass-produced. In reality, this type of battery adds some solid electrolyte to the liquid electrolyte, or adds organic electrolyte to the solid electrolyte.
Strictly speaking, it cannot be called a solid-state battery, as the emphasis here is on the fact that the electrolyte is completely solid.
Advantages of solid-state batteries
Compared to liquid electrolyte batteries, all-solid-state batteries have seven inherent advantages:
Safety accidents such as battery fires caused by electrolyte leakage or evaporation will not occur. At the same time, the use of non-flammable solid electrolytes instead of flammable liquid electrolytes significantly improves battery safety.
It can achieve rapid discharge (whether it can achieve rapid charging is still questionable in the industry);
High-voltage positive and negative electrode materials that were previously unusable due to electrolyte dissolution can be used, thereby significantly improving the energy density of the battery;
Battery self-discharge is significantly reduced;
Increased freedom in battery design allows for lighter and more compact batteries with the same capacity.
Because solid-state batteries do not contain liquid, they allow for multi-layered designs within the cells, significantly reducing the amount of material used in battery assembly casings and further reducing the weight of the battery.
The bare battery cell does not smoke, catch fire, or explode after physical impact and destructive testing.
The challenges of solid-state batteries
Currently, there are two major technical challenges to be solved for all-solid-state batteries:
First, ionic conductivity:
Currently, solid electrolytes can be divided into three systems: solid polymers, oxides, and sulfides. However, regardless of the system, their ionic conductivity is still much lower than that of liquid electrolytes. Ionic conductivity, i.e., the lithium ion throughput, directly determines the smoothness of lithium ion transport between the positive and negative electrodes.
Second, interfacial impedance;
Solid electrolytes have high interfacial impedance. Traditional liquid electrolytes and positive and negative electrodes are in contact via liquid/solid contact, which provides good interfacial wettability and prevents large impedance between the interfaces.
Solid electrolytes and positive and negative electrodes are in contact via a solid/solid interface, which has a small contact area and poor compactness, resulting in higher interfacial impedance, which affects the transport of lithium ions between the interfaces.
When will solid-state batteries be mass-produced?
Solid-state batteries are the most promising next-generation battery technology for mass production, which has become a consensus in the industry and scientific community. It is undoubtedly a high ground that many research institutions, car companies, battery manufacturers and countries around the world are paying attention to and vying for.
Currently, there are approximately 50 companies, startups, and research institutions worldwide dedicated to solid-state battery technology research.
According to statistics, Chinese universities rank first in the world in the number of SCI articles published, while Japan accounts for more than half of the global patents. In Europe and the United States, the number of related startups is increasing year by year.
In terms of automakers, Toyota and Volkswagen are currently among the leading automakers in solid-state battery deployment. Toyota has stated that it will officially launch the battery before the 2020 Summer Olympics.
Volkswagen, on the other hand, is more conservative and expects solid-state battery products to be used in vehicles no earlier than 2025.
