No one wants to use a new battery on an old car, and it's best for an electric car to have as long a battery life as a car.
Ten years after the use of the car, the attenuation of lithium-ion batteries is best within 20%, and the battery power is still strong for batteries with increasing energy density.
So far, the attenuation mechanism of lithium-ion batteries has been more and more understood, the generation of lithium plating and lithium dendrites, the parasitic reaction of electrodes, especially cathodes and electrolytes, the mechanical strain of electrode materials caused by the embedding and de-embedding of lithium ions, the degradation of electrolytes, etc. are the root causes of lithium-ion battery attenuation.
Academic scientists are also "showing their own magic skills" to find solutions to the above reasons, but they are inseparable from one point, that is, the material, the degree of understanding of the material, especially the internal strength of the scientist.
A team of researchers at the University of Queensland in Australia, after a lot of painstaking screening and testing of numerous chemical materials, finally determined a metal rare earth element, lanthanum (La), which can significantly slow down the attenuation of lithium-ion batteries.
At present, the lithium-ion batteries used in electric vehicles, the electrolyte is liquid, and the reaction and interface characteristics that occur at the interface between the electrode and the electrolyte play a key role in the cycle life and safety of lithium-ion batteries.
Studies on the reaction of electrodes to electrolytes have been conducted for about 40 years, and the previous research progress has been relatively slow. However, the growth in demand for electric vehicles in recent years has led to the rapid development of this research.
The scientists of this study aimed to prevent the electrode from reacting with the electrolyte as much as possible, slowing down the degradation of the electrode material, while using materials that could not affect the ion conductivity.
They first mixed many metal elements from the material library into the main lattice of the cathode material of the lithium-ion battery, and tested them one by one to analyze the effect of the dopant on the electrode structure, solubility limit and battery performance.
Eventually they discovered the special effects of lanthanum (La) on the lattice. When observing the spinel structure using the synchrotron X-ray powder diffraction pattern, it was found that La was miscible with the cathode material, and in addition, La doping significantly reduced the crystal mass during the sintering process, indicating that the diffusion of large La ions in the lattice encountered important obstacles.
This suggests that la's miscible nature allows enough surface diffusion to better cover the electrode material at high temperatures without worrying about mutual diffusion.
Therefore, La's doping can be used as a perfect passivation layer to reduce the corrosion caused by the reaction of the electrode with the electrolyte during the charge and discharge cycle of the lithium-ion battery.
Since the lithium nickel manganese oxygen cathode material is relatively easy to degrade in lithium-ion batteries, which is also a challenge to limit its practical application, therefore, the battery prepared with this material to test the passivation layer can more clearly observe its protective effect on the cathode material.
Next, they prepared a new type of lithium-ion battery with a positive electrode material of lithium-nickel manganese oxygen and containing a passivation layer formed by La doping, and a negative electrode material of graphite, and tested its storage performance.
At a high voltage of 26°C and 4.8 V, the capacity retention rate of the whole battery after 1000 charge and discharge cycles is about 80%.
These 1,000 cycles are measured at a relatively high specific current, which is equivalent to doubling the life of a lithium-nickel-manganese oxygen battery with a relatively short life.
In addition, the analysis of the electrochemical impedance spectrum shows that the resistance of the battery with the passivation layer is about 2 times lower than that of the control battery! The increase in resistance after a long cycle of the battery will cause the battery to heat up, which is a manifestation of performance degradation.
It shows that the battery with the passivation layer is not so easy to heat up, and the performance is still good after 1000 charge and discharge cycles. This method stabilizes the cathode material of the battery and greatly slows down its degradation during charge and discharge.
Professor Zhoulian Wang, who led the study, said: "Our process will extend battery life for many things, from smartphones and laptops to power tools and electric vehicles. ”
"The protective coating added by this new approach paves the way for these abundant high-voltage materials to be used in the next generation of high-energy batteries."
Currently, their findings are published in the academic journal Nature Communications.
This article is the original of science and technology cool probe, plagiarism must be investigated!
The author is a doctor of the Chinese Academy of Sciences, a researcher of the American Fujian University, science and technology control, contact with front-line scientific and technological research and development, willing to share, welcome to pay attention to science and technology cool detective.