The key to breakthrough in battery technology bottleneck of new type of energy storage equipment

As we all know, electric vehicles are regarded as the future development direction of automobiles because of their clean and energy-saving features, but the main technical bottleneck faced by the development of electric vehicles is battery technology. This is mainly manifested in the following aspects: First, the battery's energy storage density refers to the amount of energy stored in a certain space or mass of matter, and it is necessary to solve the problem of how far an electric vehicle can run on a single battery. The second is the battery's charging performance. People want electric vehicles to be refueled like oil and can be completed in minutes, but the time-consuming problem is always an insurmountable obstacle to battery technology. With hours of recharging time, many people interested in electric cars are discouraged. Therefore, some people call the charging performance of an electric vehicle battery as a real bottleneck in the development of an electric vehicle.

At present, lithium batteries and super capacitor technology are mainly used in battery technology, and lithium batteries and super capacitors have their own lengths. Lithium-ion batteries have a high energy storage density of 120 watts/kilogram to 150 watts/kilogram, and supercapacitors have a low energy storage density of 5 watts/kilogram. However, lithium batteries have a low power density of 1 kW/kg, and supercapacitors have a power density of 10 kW/kg. At present, a large number of research efforts are focused on increasing the power density of lithium-ion batteries or increasing the energy storage density of supercapacitors, but the challenges are enormous.

The new study bypassed the challenge by using graphene as a magical material. Graphene has become the first choice for new energy storage equipment due to its following characteristics: It is the most known material with the highest conductivity, five times higher than copper; it has strong heat dissipation capacity; its low density is four times lower than copper and its weight is lighter When the surface area is twice that of carbon nanotubes, the strength exceeds that of steel; the high Young's modulus and the highest intrinsic strength; the specific surface area (that is, the total area per unit mass of material) is high; displacement reactions are not likely to occur.

The new device allows electric vehicles to be fully charged in less than 1 minute. The new energy storage device is also called a graphene surface lithium-ion exchange battery, or simply referred to as a surface-mediated battery (SMCS), which concentrates the advantages of a lithium battery and a super capacitor. With high power density and high energy storage density characteristics. Although current energy storage devices have not adopted optimized materials and structures, their performance has surpassed that of lithium-ion batteries and supercapacitors. The new device's power density (ie, the maximum output power of a battery divided by the weight or volume of the entire fuel cell system) is 100 kW/kg, which is 100 times higher than a commercial lithium-ion battery and 10 times higher than a super capacitor. High power density, high energy transfer rate, and reduced charging time. In addition, the new battery has an energy storage density of 160 W/kg, which is comparable to a commercial lithium-ion battery and is 30 times higher than a conventional super capacitor. The greater the energy storage density, the more energy is stored.

The key to SMC is its very large graphene surface at the cathode and anode. When making batteries, researchers placed lithium metal on the anode. At the first discharge, lithium metal ionizes and migrates to the cathode through the electrolyte. The ions pass through the pores on the surface of the graphene and reach the cathode. During the charging process, due to the large surface area of ​​the graphene electrode, a large amount of lithium ions can rapidly migrate from the cathode to the anode, forming high power density and high energy density. The researchers explained that the exchange of lithium ions on the porous electrode surface can eliminate the time required for the insertion process. In the study, the researchers prepared various graphene materials such as graphene oxide, monolayer graphene, and multilayer graphene to optimize the material configuration of the device. The next step will focus on the cycle life of the battery. Current research shows that after 1000 times of charging, 95% capacity can be retained; after 2000 times of charging, no crystal structure has been found. Researchers also plan to explore the impact of different lithium storage mechanisms on device performance.

Studies have shown that when the weight is the same, only the SMC that has not been optimized replaces the lithium-ion battery. The driving distance of the SMC or lithium-ion battery electric vehicle is the same, but the charging time of the SMC is less than one minute, while the lithium-ion battery requires several hour. The researchers believe that the SMC will perform better after optimization.

If electric vehicles are widely popular in the future and the charging station is set at a gas station, the result will be a very interesting scenario, that is, the charging time of electric vehicles will be faster than refueling, and it is also cheaper than refueling. The researchers said that in addition to electric vehicles, the device can also be used for renewable energy storage (such as stored solar and wind energy) and smart grid.