18650 lithium rechargeable battery

South Korea develops 18650 lithium rechargeable battery cellulose separator

To prevent battery leakage and short circuit, a porous film is usually applied between the two electrodes of the battery for isolation. Recently, researchers at the Ulsan National Institute of Science and Technology in South Korea designed a cellulose nanomat (c-mat) separator, adding a thin layer of porous cellulose on a thicker layer of macroporous polymer, effectively solving the contradiction that traditional electrode separators are difficult to balance between leakage prevention and efficient ion transmission.

The researchers recently published a paper in Nano Express, saying that the new c-mat separator they developed has a thinner functionalized nanofiber on the upper layer and a thicker polymer on the lower layer. By fine-tuning the thickness of the two layers, a delicate balance is achieved between leakage prevention and supporting rapid ion transmission: the tiny nanopores of the cellulose layer can prevent current leakage between the electrodes; the larger pores of the polymer layer serve as ion "highways" to support rapid charge transmission. It also has an important advantage. At a high temperature of 60°C, the battery using the c-mat membrane still retains 80% of its power after 100 cycles, while the battery with a traditional polymer separator at the same temperature only retains 5% of its power.

The researchers explained that lithium salts and water in commercial batteries react with each other to produce harmful byproducts such as manganese ions, which leads to a significant loss of power at high temperatures. The nanoporous cellulose on the c-mat membrane can chelate with manganese ions to prevent them from participating in the reaction, and the macroporous polymer layer can also capture the acidic reactants that produce manganese ions, so there are fewer manganese ions at the beginning.

Li Shanyang, a co-author of the paper and a professor at the School of Energy and Chemistry of the university, said that their research proved that the active cellulose c-mat isolation layer can reduce the side effects of manganese ions and improve the cycle performance of batteries at high temperatures, which is better than the most advanced traditional isolation membrane technology.

Next, they plan to modify the isolation layer so that it can be used in the next generation of rechargeable batteries such as sodium ion batteries, lithium-sulfur batteries and metal ion batteries. Li Shanyang predicts that the next generation of high-performance batteries using c-mat as isolation membranes have good high-temperature stability and can be used not only in electric vehicle batteries and grid storage systems, but also in seawater desalination and heavy metal ion monitoring.

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