An industrial waste, a little plastic, plus a not-so-high temperature, may be the fuse that detonated the next battery revolution. Researchers from the National Institute of Standards and Technology (NIST), the University of Arizona, and the Seoul National University in South Korea have teamed up to create a cheap, high-power lithium-sulfur battery. Researchers said that the performance of the new battery can be compared with the current market mainstream battery, and after 500 charge and discharge cycles, the function is not damaged.
In the past decades, the energy density of lithium-ion batteries has been continuously increasing, and is widely used in smart phones and other fields. However, lithium-ion batteries require a bulky cathode (usually made of cobalt oxide and other materials) to “receive†lithium ions, limiting the further increase in battery energy density. This means that for applications such as long-distance electric vehicles that require more energy density, lithium-ion batteries are a bit out of place.
As a result, scientists turned their attention to lithium-sulfur batteries, the slimmer “little cousin†of lithium-ion batteries, whose cathodes are made primarily of sulfur, a cheap by-product of the oil industry. The "weight" of sulfur is only half that of cobalt. Therefore, the same volume of sulfur accommodates twice as many lithium ions as cobalt oxide, which makes the energy density of lithium-sulfur batteries several times that of lithium-ion batteries.
However, sulfur cathodes also have two major disadvantages. First, sulfur is easily combined with lithium, and the resulting compound crystallizes. Second, continuous charge-discharge cycles make the sulfur cathode easily broken. Therefore, a typical lithium-sulfur battery becomes a few cycles. Useless things.
According to a report from the Physicists Organization Network on June 4, in order to create a stable sulfur cathode in the latest research, the researchers heated sulfur to 185 degrees Celsius and melted a chain of sulfur with a chain of eight atoms to melt. They mixed sulfur chains with diisobutylene (DIB, a carbon-based plastic precursor), and diisobutylene linked the sulfur chains together, resulting in a mixed polymer. They refer to this process as "reverse vulcanization" because it is similar to the process used to make rubber tires. The key difference is that in the tires, the carbonaceous material collects into a large piece and the sulphur accumulates in it.
Scientists explained that the addition of diisobutylene made the sulfur cathode less likely to break and also prevented the crystallization of lithium sulfur compounds. Studies have shown that the optimal mixing of sulfur and diisobutylene is between 10% and 20% of the total mass of diisobutylene. If too little, the cathode cannot be protected; if too much, diisobutylene with inactive electrochemical properties will reduce the energy density of the cell.
Tests show that after 500 cycles, the battery's energy density is still more than half of the original. Jeffrey Penn, a chemist at the University of Arizona, said that other lithium-sulfur batteries still in the experimental stage have the same performance, but their manufacturing costs are high and they are difficult to industrialize.
NIST's materials scientist Christopher Sowers said that despite this, this lithium-sulfur battery will not be marketed in the short term, and sulfur is easily burned in the air, so any economically viable lithium-sulfur battery needs to be very harsh. Safety tests can be put on the market. (Liu Xia)
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