A new lithium-ion battery that can withstand extreme cold and heat has been successfully developed. Engineers at the University of California, San Diego have developed a lithium-ion battery, which performs well in both extreme cold and extreme heat, and a new lithium-ion battery that can withstand extreme cold and extreme heat has been successfully developed.

Recently, engineers at the University of California, San Diego (UCSD) have developed a new type of lithium-ion battery, which is said to perform well in extreme cold and high temperature, while still storing a lot of energy.

According to the researchers, this "feat" was achieved by developing a new electrolyte. This electrolyte is not only durable in a wide temperature range, but also compatible with high-energy anode and cathode. The above research results were recently published in the Proceedings of the National Academy of Sciences (PNAS).

Zheng Chen, a professor of nano-engineering at UCSD Jacob Institute of Engineering and a senior author of the study, said that the on-board battery developed based on this technology can enable electric vehicles to travel further even in cold climate. In addition, they can reduce the need for cooling system to prevent the battery pack of vehicles from overheating in hot weather.

Chen explained: "High temperature is a big challenge for automobile batteries. In electric vehicles, the battery pack is usually located in the chassis, closer to the hot road. In addition, the battery will generate heat due to the passage of current during operation. If the battery can't withstand this high temperature, the performance will drop rapidly. "

In the test, the energy capacity of the battery at -40℃ and 50℃ is 87.5% and 1 15.9% respectively. At these temperatures, they also have high Coulomb efficiencies of 98.2% and 98.7% respectively, which means that the battery can carry out more charge and discharge cycles before stopping working.

The above excellent performance is attributed to the unique electrolyte developed by Chen and his colleagues. It is made of liquid solution of dibutyl ether and lithium salt. One of the characteristics of dibutyl ether is its weak combination with lithium ions. In other words, when the battery is running, electrolyte molecules can easily release lithium ions.

In previous studies, researchers found that this weak molecular interaction can improve the performance of batteries at sub-zero temperatures. In addition, dibutyl ether is easy to absorb heat (boiling point is 14 1℃) because it remains liquid at high temperature.

Other advantages

In addition, another special feature of this electrolyte is that it is compatible with lithium-sulfur battery, which is a rechargeable battery. Its anode is made of lithium metal and its cathode is made of sulfur. Lithium-sulfur battery has higher energy density and lower cost, and is an important part of the next generation battery technology.

It is understood that lithium-sulfur batteries store twice as much energy per kilogram as today's lithium-ion batteries, which can double the cruising range of electric vehicles without increasing the weight of the battery pack. In addition, compared with the cobalt used as the cathode of traditional lithium ion batteries, the reserves of sulfur are more abundant.

However, lithium-sulfur batteries also have problems. Both cathode and anode are super-active. Sulfur cathode is very active and will dissolve during the operation of the battery; At high temperature, this problem will become more serious. Lithium metal anode is easy to grow dendrites, which will lead to short circuit and even fire. Therefore, lithium-sulfur batteries can only be recycled for dozens of times at most.

"If you want a battery with high energy density, you usually need to use very harsh and complicated chemicals," Chen said. "High energy means more reactions, which means less stability and more degradation. Making a stable high-energy battery is an arduous task in itself, and it is even more challenging to try to do this in a wider temperature range. "

The dibutyl ether electrolyte developed by UCSD research team can prevent these problems. Even at extreme temperatures, the battery they tested has a longer cycle life than a typical lithium-sulfur battery. Chen said, "Our electrolyte helps to improve the cathode side and anode side, while providing high conductivity and stability".

A new lithium-ion battery that can withstand extreme cold and heat has been successfully developed. Engineers at the University of California, San Diego have developed a lithium-ion battery, which performs well in extreme cold and hot conditions, and can also store a lot of electric energy. A paper published in the Proceedings of the National Academy of Sciences this week describes the high-temperature resistant battery.

Zheng Chen, a professor of nano-engineering at the Jacob School of Engineering at the University of California, San Diego, and a senior author of the study, said that this kind of battery can make electric vehicles travel further in cold climates with a single charge; It can also reduce the need for a cooling system to prevent the vehicle's battery pack from overheating in hot weather.

The researchers tested the battery at a temperature below freezing point. Image source: David Baillot/ University of California, San Diego

In the test, the proof-of-concept battery retains 87.5% and 1 15.9% electric energy capacity at -40℃ and 50℃, respectively. At these temperatures, they also have high Coulomb efficiencies of 98.2% and 98.7% respectively, which means that the battery can carry out more charge and discharge cycles before stopping working.

Researchers have developed a better electrolyte, which is cold-resistant and heat-resistant, and compatible with high-energy anode and cathode. The electrolyte is made of a solution of dibutyl ether and lithium salt. One of the characteristics of dibutyl ether is its weak combination with lithium ions. When the battery is running, electrolyte molecules can easily release lithium ions.

Another special feature of this electrolyte is that it is compatible with lithium-sulfur batteries. Lithium-sulfur batteries are an important part of the next generation battery technology, because they are expected to achieve higher energy density and lower cost. The cathode and anode of lithium-sulfur battery have super reactivity. At high temperature, lithium metal anode is easy to form a needle-like structure called dendrite, which can pierce some parts of the battery and cause short circuit of the battery. In this way, the lithium-sulfur battery can only last for dozens of cycles.

Dibutyl ether electrolyte can prevent these problems, even at high and low temperatures. The battery they tested has a longer cycle life than a typical lithium-sulfur battery. The research team also designed a more stable sulfur cathode by grafting sulfur cathode onto polymer. This can prevent more sulfur from dissolving into the electrolyte.

The team said that the next research work will include expanding the chemical composition of the battery, optimizing the battery to work at higher temperatures, and further extending the cycle life.

A new type of lithium-ion battery that can withstand extreme cold and heat has been successfully developed. A new type of lithium-ion battery can work at both the low temperature of minus 40℃ and the high temperature of 50℃. The cathode of this new type of battery is made of sulfur, and the battery can store more energy. This is a new study by the University of California, San Diego.

This kind of battery can increase the driving range of electric vehicles in cold temperatures. In addition, they can also be used in satellites, spacecraft, high-altitude drones and submarines. Zheng Chen, a professor of nanotechnology at the University of California, San Diego, said: By greatly expanding the operating window of lithium batteries, we can provide more powerful electrochemical substances for applications other than electric vehicles.

At present, the combination of graphite anode and lithium metal oxide cathode of battery can not handle extreme temperature well. High temperature will aggravate the already highly active chemical environment inside the battery, trigger the side reaction of decomposing electrolyte and other battery materials, and lead to irreversible damage. At the same time, low temperature will thicken the liquid electrolyte, so lithium ions move slowly in it, resulting in power loss and slow charging.

Keeping the battery warm or heating it from the inside is helpful to solve the low temperature problem. Researchers have previously designed electrolytes to expand the temperature range of batteries, but this can improve the performance at low temperature or high temperature, but not at the same time.

Professor Zheng Chen's team's research "Solvent Selection Criteria for Temperature-resistant Lithium-sulfur Batteries" was published in the Proceedings of the National Academy of Sciences (PNAS) on July 5th. They said that the core of the new extreme temperature-resistant battery is to find a new electrolyte.

They make electrolyte by dissolving lithium salt in dibutyl ether solvent. Different from the existing vinyl carbonate solvent for batteries, the new material will not freeze or evaporate easily at the temperature of-100℃. In addition, the binding force between solvent molecules and lithium ions is weak, so lithium ions move freely in it, even at the freezing temperature.

The UCSD team solved the problem of sulfur cathode degradation by attaching sulfur to plastic substrate. At the same time, the new electrolyte allows the uniform transport of lithium ions, so they have no chance to stick together and form dendrites.

In the team test, the prototype battery lasted for 200 cycles, and the original capacity still exceeded 87% at-40 C. At 50°C, the battery capacity increased by 65,438+05%. Professor Zheng Chen said that higher temperature will increase the charge transfer and the diffusion of lithium ions through the electrolyte to the electrode, thus pushing the capacity and energy limit of the battery.

Cai, the first author of this study and a postdoctoral researcher in nanotechnology at the University of California, San Diego, prepared a battery bag for testing at temperatures below freezing.

Another special feature of this electrolyte is that it is compatible with lithium-sulfur battery, which is a rechargeable battery. Its anode is made of lithium metal and its cathode is made of sulfur. Lithium-sulfur battery has higher energy density and lower cost, and is an important part of the next generation battery technology.

They store twice as much energy per kilogram as today's lithium-ion batteries-they can double the cruising range of electric vehicles without increasing the weight of the battery pack. In addition, compared with the cobalt used as the cathode of traditional lithium ion batteries, the source of sulfur is more abundant and there are fewer problems.

However, there are other problems in lithium-sulfur battery-its cathode and anode are too active. The sulfur anode is very active and will dissolve during the operation of the battery. This problem will become more serious at high temperature. Lithium metal anode is easy to form needle-like structure, called dendrite, which can pierce some parts of the battery and cause short circuit of the battery. Therefore, lithium-sulfur batteries can only last dozens of cycles.

"If you want a battery with high energy density, you usually need to use very precise and complex chemicals," Zheng Chen said. "High energy means more reactions, which means lower stability and more degradation. Making stable high-energy batteries is an arduous task in itself-it is even more challenging to try to do this in a wide temperature range. 」

The dibutyl ether electrolyte developed by UCSD research team can prevent these problems, even at high and low temperatures. The battery they tested has a longer cycle life than a typical lithium-sulfur battery. "Our electrolyte helps to improve the cathode and anode sides while providing high conductivity and interfacial stability," Zheng Chen said.

The team also designed a more stable sulfur cathode by grafting sulfur cathode onto polymer. This can prevent more sulfur from dissolving into the electrolyte.

The next steps include expanding the chemical composition of the battery, optimizing it to work at higher temperature, and further extending the cycle life.

Zheng Chen, a professor of nanoengineering at the University of California, San Diego, said.

The increase in capacity is not necessarily a good thing, because it will also overload the battery. In order to solve this problem, researchers must further improve the chemical composition of the battery so that it can maintain more charging cycles. They also plan to increase energy density through more cell engineering. At present, the density of the new battery is only slightly higher than that of today's lithium-ion battery, which is almost the same as the theoretical promise of lithium sulfur. "We can increase the energy density by at least 50%," Zheng Chen said. "This is hope, this is a promise. 」