With the development of electric vehicles, the demand for long-life power lithium batteries is increasing. Lithium-rich manganese-based lithium battery cathode materials have attracted much attention due to their high specific capacity, high working voltage, good thermal stability, and low cost. They are potential power cathode materials. However, they themselves have low efficiency in the cycle. , Poor cycle performance and rate performance, serious voltage drop, and no matching high-voltage electrolyte, hindering its further commercialization and industrialization development. The advanced energy storage materials and technology research group led by Wu Jianfei, a researcher at the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences, has developed a number of modification strategies and key technologies for the development bottleneck of lithium-rich manganese-based cathode materials, and obtained relevant research results (Journal of Alloys and Compounds, 744 (2018): 41-50, ACS Applied Materials & Interfaces 2020, online; patent CN201911201192.1, CN201811106607.2, CN202010098277.8), in order to solve the development problems of the industrialization of lithium-rich manganese-based cathode materials Lay the research foundation.
As one of the important elements in power battery cathode materials, cobalt plays an important role in stabilizing the material structure and improving cycle and rate performance. However, as a non-renewable metal, cobalt is scarce, and limited cobalt resources cannot support the unlimited development space of new energy vehicles. In addition, cobalt has a great impact on the cost of the cathode material itself. Due to the increasing demand for cobalt, the price of cobalt continues to increase, posing a challenge to the low cost of the battery industry. The scarcity and high price of cobalt will gradually limit the future of the electric vehicle market. If the cobalt content in batteries is reduced or even eliminated, electric vehicles will be more cost-effective. Therefore, it is very important to develop cathode materials with low cobalt content. Low-cobalt or even cobalt-free has gradually become the trend of battery development. Cobalt-free batteries were born based on this reality. Therefore, the industry has made a lot of efforts in cobalt-free batteries. Work hard. One of the technical challenges facing the removal of cobalt or less cobalt in the cathode material is how to solve the problems of lithium-nickel mixing and metal elution, otherwise the stability, cycle performance, and rate of the cathode material are poor. The universal "cobalt-free" concept is to reduce the cobalt content in the positive electrode material and "compensate" by doping and coating other elements to ensure the structural stability of the positive electrode material.
Recently, Wu Jianfei's research group has achieved cobalt-free based on lithium-rich cathode materials and developed a high-performance cobalt-free lithium-rich manganese-based cathode battery system, which reduces the cost of cathode materials and further improves the electrochemical performance of lithium-rich cathode materials. While the first discharge specific capacity of the cobalt-free lithium-rich manganese-based cathode material reaches 250 mAh·g-1 (Figure A), the lithium-rich cathode material after cobalt removal has improved its cycle life. It has passed 300 mAh·g-1 at a rate of 0.5C. After a charge and discharge cycle, there is still a high capacity retention rate of 96% (the ordinary lithium-rich cathode material is only 50%, Figure B). In addition, the rate performance has also been improved and the recovery rate is high (Figure C). The cobalt-free lithium-rich manganese-based system has excellent performance in suppressing the voltage drop during the cycle, and there is almost no obvious voltage drop after 100 cycles (Figure F); even after a long cycle of high current, the structure of the cathode material is Can maintain good stability (Figure L). At the same time, the system uses a lower concentration of lithium salt electrolyte (<1M-LiPF6) than the ordinary system, which improves the electrochemical performance of cobalt-free lithium-rich materials and further reduces the cost of the battery system.
The development of the cobalt-free lithium-rich manganese-based cathode material system realizes the real cobalt-free cathode material, reduces the cost of the cathode material, improves the cycle stability of the lithium-rich manganese-based cathode material, and inhibits the voltage plateau during the cycle. This will further highlight the competitive advantage of lithium-rich cathode materials with other cathode materials. For the battery industry, this can reduce the cost of lithium batteries, increase their lifespan, increase the range of electric vehicles, and provide key material solutions for long-range power lithium batteries. The development of this system will enrich the cobalt-free battery market, further promote the development of cobalt-free batteries, and is expected to realize the industrial application of cobalt-free lithium-rich manganese-based lithium-ion batteries, which has important commercialization prospects and application value (patent CN202011120181.3) .
Electrochemical performance (AF) and related structural characterization (GL) of cobalt-free lithium-rich manganese-based cathode material system
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