The successful operation of lithium batteries at low temperatures promotes the further development of battery technology

by:CTECHi     2021-07-13

At this stage, lithium-ion batteries have become the most important power source for electric vehicles. Its development has undergone three generations of technology development. Among them, lithium cobalt oxide cathode is the first generation, and lithium manganese oxide and lithium iron phosphate are the second generation. , The ternary technology is the third generation.

With the development of positive and negative electrode materials in the direction of higher gram capacity and the gradual maturity and improvement of safety technology, higher energy density cell technology is moving from the laboratory Move towards industrialization and apply it to more scenarios.

In fact, the reason why lithium metal batteries are expected to be high is that pure lithium metal anodes have excellent energy density compared with the current common graphite/copper hybrid materials. Relying on the advantages of high energy density and high safety, lithium-ion batteries have completely occupied the consumer electronics market in just over ten years and have made remarkable achievements.

As a solution that carries lithium ions back and forth between the two poles of the battery during the cycle, the importance of the electrolyte in a battery is self-evident. Normally, low-temperature batteries require an additional heating system.

But now, the lithium metal battery being developed by the University of California San Diego (UCSD) research team is expected to charge and discharge efficiently at extremely low temperatures. The purpose of the researchers is to develop an electrolyte that does not freeze and can maintain the mobility of lithium ions between the electrodes at low temperatures.

In fact, so far, many studies have focused on choosing electrolytes that are not easy to freeze and can keep lithium ions moving quickly between the electrodes. In this study, the researchers found that it is not necessarily how fast the electrolyte moves ions, but how easily the electrolyte releases ions and deposits them on the anode.

Researchers made these findings by comparing the battery performance of two electrolytes: one binds weakly to lithium ions, and the other strongly binds to lithium ions. Lithium metal batteries with weakly bound electrolytes perform better at -60 degrees Celsius, and can maintain strong operation after 50 cycles. In contrast, batteries with strongly bound electrolytes stop working after only two cycles.

After cycling the batteries, the researchers separated them and compared the lithium metal deposits on the anode. The difference between the two is also obvious. In cells that are weakly bound to electrolytes, the deposits are smooth and uniform, while in cells that are strongly bound to electrolytes, the deposits are lumpy and needle-like.

In the test, the experimental results show that the battery maintains 84% u200bu200band 76% of the capacity in 50 cycles at -40 degrees Celsius and -60 degrees Celsius, respectively . The researchers said that such performance is unprecedented.

Further research on such proof-of-concept batteries has shown that weakly bound electrolytes can allow ions to be deposited more uniformly on the battery anode, while strong bound electrolytes can cause lumps and Needle-like deposits (dendrites). Dendrite is another important public relations direction to improve the performance of lithium batteries, because it may cause serious failures such as short-circuit failure of the battery.

Currently, society has entered the era of new energy. In the era of new energy, electrification is an inevitable trend. The world dominated by lithium-ion batteries is also being commercialized by others. Of emerging battery technologies open up important new market opportunities. The breakthrough battery technology will also play a central role in the future energy system, pushing mankind far away.

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