It is possible to increase the energy storage of automobile power battery to 400 WHr/kg.
In order to turn the battery into a "muscle man", it is necessary to design a feasible processing technology in addition to obtaining reasonable anode and cathode materials.
Focus on new lithium-sulfur batteries and lithium-air batteries, and their energy density is expected to reach 500 WHr/kg.
This well-known scientific research project in Ou Yangming is supported by the National Key R&D Program, and its full name is "Research on Key Technologies of High Specific Energy Power Battery and Related Basic Scientific Issues". Based on the high-capacity lithium-rich manganese-based cathode material developed by the research team, the energy storage capacity of automotive power batteries may be increased to 400 WHr/kg.
In recent years, with the strong support of national policies, China's new energy vehicles have been rapidly popularized, but it is still difficult to straighten out the "stem" of "not daring to go to the outer suburbs and counties". Breaking the limit of 500 kilometers for a single trip will greatly promote the promotion of electric vehicles. However, the carrying capacity of vehicles is limited, and how to store as much electric energy as possible in a limited volume has become the key goal of scientific research.
Xia Dingguo, the project leader and professor of Peking University, said: "To further improve the energy density of lithium-ion batteries, the specific capacity of cathode materials is the key." According to Xia Dingguo, on the basis of previous work, the research team deeply understood the stability mechanism of lithium-rich materials and the generation mechanism of anion redox, and optimized the performance of lithium-rich materials by regulating the anion redox mechanism.
In other words, the first question the team encountered was: What is the "impact" on the redox ability of anions? Revealing this rule will guide the team to approach and find electrodes with excellent performance. The research team also found that the geometric structure between atoms in a substance will affect the structure of electrons, thus affecting the redox ability of anions. This study clarifies the relationship between structure and efficiency, and hopes to improve the electrochemical performance of electrode materials through structural design.
"It is an important way to increase the lithium content in cathode materials and let more anions participate in redox reaction stably." Xia Dingguo said that the development of high-capacity lithium-rich cathode materials makes it possible to further improve the energy density of power batteries. The project team not only prepared a high-capacity lithium-rich cathode material and two high-capacity and high-stability lithium-rich materials-carbon composite materials, but also prepared a high-capacity lithium battery cathode material.
In order to turn the battery into a "muscle man", it is necessary to design a feasible processing technology in addition to obtaining reasonable anode and cathode materials. For example, lithium-rich compounds need to be well dispersed in the electrode, which should not only maintain the content of more than 60% in the system, but also not condense into blocks. The more uniform the dispersion, the better the reversibility and the better the charging and discharging efficiency.
At present, the battery needs to be further improved. Xia Dingguo introduced that there are two key problems that "dendritic lithium" restricts the battery progress and battery safety of the new system. Relevant experiments show that after 10-50 cycles, the voltage attenuation is obvious and the electrode does not work.
Dendritic lithium is unique to lithium ion batteries using liquid electrolyte. Lithium ions are reduced and crystallized into dendrites and grow continuously, which may puncture the diaphragm to some extent. Scientists are currently seeking a breakthrough from two angles. One is coating, and the other is studying solid electrolyte.
Xia Dingguo emphasized that "the development of high energy density lithium-ion power battery needs the development of electrode materials, electrolyte and high safety approaches, and it also needs the progress of new analysis methods and battery preparation technology".
In addition to increasing the energy density of lithium-ion batteries to 400 WHr/kg, the project team will also focus on new lithium-sulfur batteries and lithium-air batteries, and their energy density is expected to reach 500 WHr/kg. Chen Liquan, an academician of China Academy of Engineering, said that lithium-air batteries are one of the development directions of power batteries. "The hydrogen-oxygen fuel cell that is developing vigorously now must use metal cans to ensure the safety of hydrogen, while the lithium-air battery (the negative electrode is oxygen in the air) only needs a mustard bag. In terms of practicality and cost, lithium-air batteries should also be developed. "