Researchers at Tohoku University in Japan have developed a polymer solid-state electrolyte for lithium-ion batteries that is safer than commonly used electrolytes while maintaining device conductivity.
In a paper published in the journal iScience, the scientists explained that liquid ethylene carbonate (EC, Ethylene Carbonate) and its gel were chosen as lithium-ion electrolytes due to their voltage resistance and ionic conductivity. However, these materials are very flammable.
And polymer solid electrolytes are considered to be safer than EC electrolytes. Substances such as polyethylene glycol (PEG, PolyEthylene Glycol) have been proposed as shock-resistant lithium-ion electrolytes. However, the PEG-based polymer electrolyte crystallizes at room temperature, resulting in a dramatic drop in Li-ion conductivity to 10-6 S/cm at room temperature.
To solve this problem, a research team from Northeastern University developed a new polymer solid-state electrolyte that combines a porous polymer membrane with several micrometer pores with a photocrosslinkable PEG-based polymer electrolyte.
This solid polymer electrolyte achieves a wide potential window (4.7V), and high lithium ion conductivity of 10-4S/cm, comparable to liquid electrolytes and can meet practical needs. The lithium-ion migration number is also high (0.39) .
Due to the principle of natural diffusion, the direction of lithium-ion transport in the electrolyte is not fixed. The distance of its movement is several μm to 10 μm, and it does not always move linearly between electrodes, which is also one of the reasons for the decay of ionic conductivity. But the new study shows that when photocrosslinkable PEG-based solid polymer electrolytes are combined with micron-scale porous membranes, performance can be significantly improved.
According to the researchers, the polymer solid-state electrolyte not only performs well but also effectively prevents the formation of lithium dendrites that cause short circuits.
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