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Say goodbye to inflammable and explosive hazards, scientists have developed new lithium batteries
2019-05-21
来源：转载自第三方
With the rapid development of digital products such as mobile computers, the use of batteries has become more frequent. But the safety of the battery has been plaguing people. Lithium-ion batteries are easily burned when damaged due to their dependence on flammable components. Now, researchers report that they have redesigned these batteries to make use of non-flammable materials. In addition, new batteries may even store more power than existing models.
Lithium-ion batteries contain three main components: two storage electrodes and a liquid organic electrolyte that separates them. During charging and discharging, the electrolyte transports lithium ions back and forth between the electrodes, but these electrolytes are flammable.
In recent years, researchers have attempted to replace these organic electrolytes with solid electrolytes or water-based electrolytes that do not ignite. However, if the operating voltage of these water-based batteries exceeds 1.23 volts (V), which is even lower than the operating voltage of a 1.5V AA battery, the electrode material reacts with water molecules to break them down into hydrogen and oxygen. It usually causes an explosion. However, when the researchers kept the operating voltage below the 1.23V threshold, the final battery stored energy was much lower than the traditional lithium-ion battery, which operated at about 4V.
In 2015, a research team led by Wang Chunsheng, a materials scientist at the University of Maryland, Parker, reported that they developed a new salt-rich water-based electrolyte. This salt-containing aqueous electrolyte (WiSE) promotes a protective solid barrier around the electrode, which prevents the electrode from tearing water molecules inside the electrolyte. However, the electrode material in these batteries can only reach an operating voltage of 3V.
In 2017, when Wang Chunsheng and his colleagues reported that they have developed a positive electrode material that is compatible with 4V voltage and can work with WiSE, the prospects are bright. Then there is only the negatively charged electrode left. Today, Wang Chunsheng and his colleagues have done this. They reported in Nature on May 8 that they have developed a graphite-based cathode that can work with WiSE at 4V or higher.
New electrode materials include bromine and chlorine, which are protected from water-based electrolytes by locking the reactive electrode material in solid salt particles around the electrodes. The lithium in the battery is surrounded by solid lithium-bromine and lithium-chloride salt particles around a graphite electrode composed of a carbon atom layer. When the battery is charged, the bromine and chlorine atoms discard the lithium atoms, electrons are passed to the cathode, and wedged between the layers of graphite carbon to form another compact solid. The voltage difference between the two electrodes then drives the positively charged lithium ions through the water-based electrolyte to the anode where they meet the electrons provided by the external circuitry.
When the battery is discharged during use, lithium ions will abandon these electrons and flow to the cathode. The electrons return to the cathode through an external circuit where the bromine and chlorine atoms catch them. These charges will diffuse out of the graphite. Lithium ions then grab them and reform the solid salt particles, which remain in place until the next charge.
Wang Chunsheng and his colleagues noted that their cathode materials have been able to store approximately 30% more charge than conventional cathode materials. But it remains to be seen whether a full battery, including a new electrolyte, will ultimately store more energy than a commercial battery.
The new WiSE battery will not require cobalt, a toxic metal in a traditional lithium-ion cathode. In the Democratic Republic of the Congo, cobalt mining is associated with widespread miners’ deaths, which are usually children. The cobalt mines in the Democratic Republic of the Congo are relatively abundant. The new battery is not only safer for consumers, but also safer for miners and the environment.
Edited by Suzhou Yacoo Science Co., Ltd.
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