Compared with the high-nickel ternary batteries and all-solid-state lithium batteries that are currently in the industry, the field of lithium-rich manganese-based batteries, which are highly anticipated, has always been tepid.
Promising lithium-rich manganese-based cathode material
Electric vehicles are new strategic products to solve energy and environmental problems. However, electric vehicles still face problems such as short cruising range, high cost and lack of safety, which seriously restricts the large-scale promotion and application of electric vehicles. Thus, the research and development of next-generation 300-400Wh / kg lithium battery power is an inevitable trend of the future development of materials and technology lithium.
At the same time, from the current technology point of view, by reducing the mass ratio of inactive materials in the cell to increase the energy density of the battery, almost reached the limit of technology, the use of positive and negative materials with higher energy density is to improve battery energy. A more efficient technical approach to density.
We know that the first criterion for designing a battery is capacity matching, that is, the capacity of the positive and negative electrodes should be matched. At present, the specific capacity of the positive electrode of the lithium ion battery is very low, and the quality in the battery is very large (1 g of the graphite negative electrode material should match more than 2 g of the positive electrode material); if the silicon carbon negative electrode is used, the matching amount of the positive electrode material is larger. Therefore, the industry's demand for a new generation of high-capacity cathode materials is particularly urgent.
Among the known positive electrode materials, the lithium-rich manganese-based positive electrode material has a specific discharge capacity of 250 mAh/g or more, which is almost twice the actual capacity of the currently commercialized positive electrode material; and the material is cheaper manganese. Mainly, the precious metal content is small, compared with the commonly used lithium cobalt oxide and nickel cobalt manganese ternary cathode materials, not only low cost, but also good safety. Therefore, lithium-rich manganese-based cathode materials are considered to be ideal for next-generation lithium-ion batteries, and are the key to lithium batteries exceeding 400 watt-hours/kg or even 500 watt-hours/kg.
Recently, Ouyang Minggao, an academician of the Chinese Academy of Sciences and executive vice president of the China Electric Vehicles 100, said at a "hot spot exchange meeting" that the main technical progress of domestic power batteries is that the power battery unit will be 300 watt-hour in 2020. The goal of /kg is achievable. "By 2025, we hope to hit the target of 400 watt-hours/kg. At this time, we need to change the positive electrode material. There are several kinds of optional positive electrode materials. At present, the breakthrough in the key projects of new energy vehicles is high-capacity rich. Lithium manganese based cathode material." Ouyang Minggao said.
Road-rich lithium-rich manganese-based power battery
Although lithium-rich manganese-based cathode materials have the absolute advantage of discharge specific capacity, to apply them to lithium-ion batteries, the following key technical problems must be solved: one is to reduce the first irreversible capacity loss; the other is to improve the rate performance and circulation. Lifetime; the third is to suppress the voltage decay of the cyclic process. At present, there are many ways to solve this material problem: coating, acid treatment, doping, pre-circulation, heat treatment, etc., but these methods can only improve the performance of materials in some aspects, and there is no comprehensive solution. Therefore, some insiders even predict that it is not realistic to realize the industrial application of lithium-rich manganese-based power batteries.
It can be seen that although the prospects are good, the lithium-rich manganese-based power battery still has a long way to go. However, Battery China Network has also learned that since the research on lithium-rich manganese-based materials in China has warmed up since 2010, the exploration of some research institutes and battery companies has never stopped.
At present, two research institutes have undertaken the frontier basic project. One is the physical institute. The surface voltage modification makes the voltage decay problem of the lithium-rich manganese-based positive electrode better solved. After 100 weeks of charging and discharging cycle, the attenuation is controlled within 2%. It should be said that this is a major progress. The other is Peking University's team, which first developed a lithium-rich manganese-based cathode material with a capacity of 400 mAh/g, which is beneficial for achieving a battery energy density target of 400 watt-hours/kg or higher. But the current cycle is not very good.
In terms of enterprises, from the survey of the China Battery and Power Supply Industry Association Power Battery Application Branch in 2017, many companies including Yanyou Power and AVIC Lithium have a planning layout in the field of lithium-rich manganese-based power batteries.
Dangsheng Technology's “Preparation Method for Lithium-Ion Battery Rich Lithium-Based Cathode Material Precursor†was awarded the national invention patent in September 2017. It is understood that the invention prepares a lithium-rich manganese-based positive electrode material precursor with high density and sphericity and good fluidity by co-precipitation method, and has high yield, simple process and environmental friendliness, and contributes to realization of lithium-rich manganese-based cathode material. Mass production. However, the invention patent has not yet been applied to the actual production of Dangsheng Technology.
In addition, Jiangte Electric has mass-produced lithium-rich manganese-based cathode materials, and its technical level has reached international advanced level. The manufacturing process has applied for patents; Guoxuan Hi-Tech also has a patent for the preparation of lithium-rich manganese-based cathode materials.
And Yuyou Power has already taken the lead in the industry. In December 2017, Yuyou Power announced that after eight years of research and development, the company's R&D team used a variety of composite conductive agents (such as graphene and carbon nanotubes) in the battery manufacturing process through material nano-materialization and carbon layer coating technology. The high-conductivity conductive material) improves the material rate performance, and successfully developed a lithium-rich manganese-based flexible packaging power battery. According to Dr. Chen Guangsen, General Manager of Yanyou Power, the energy density of lithium-rich manganese-based power batteries that can be mass-produced at present is 200-220Wh/kg, and is expected to reach 350Wh/kg in 2020.
The author believes that from the development direction of the cathode material, the lithium-rich manganese-based material has the advantages of high voltage and high capacity at the same time, and the cost is lower than that of the ternary material. With the maturity of the lithium-rich manganese-based cathode material in the future, and the high-voltage electrolyte With the breakthrough of supporting key materials technology, lithium-rich manganese-based power batteries have become the mainstream products of high-energy lithium-ion batteries in the future. It should be noted that the close cooperation of the entire industrial chain will enable the industrialization of lithium-rich manganese-based power cells to go faster and more stable.
Author: Caowu Jia
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