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Advantages and disadvantages of LiCoO2 cobalt cathode material and improvement methods

by:dcfpower     2021-03-29

The cobalt-based cathode material is mainly LiCoO2. In 1980, some scientists proposed to use LiCoO2 as the cathode material. It belongs to the α-NaFeO2 type layered structure, which is more suitable for the extraction and insertion of Li⁺, because of its relatively layered structure. It is stable and exhibits relatively good electrochemical performance. Due to its simple preparation process, it has been applied earlier. When LiCoO2 is used as the positive electrode of a lithium ion battery, the battery's operating voltage is generally above 3.6V. The theoretical capacity of LiCoO2 can reach 273mAh/g. Of course, LiCoO2 as a positive electrode also has some defects. For example, it is affected by its own structure, which does not guarantee that all Li⁺ can reversibly undergo de-intercalation reactions, especially after multiple charges and discharges, its crystal structure will undergo some changes. , Its capacity will be reduced, resulting in a decline in its cycle performance, and because of the relatively small reserves of cobalt on the earth, the thermal stability is not very good, and it is also unstable under overcharge and pollutes the environment. The production cost is high and the price is high. expensive. While people are constantly looking for alternatives, they are also constantly improving their performance.

Figure 1 shows a schematic diagram of lithium cobalt oxide:

Figure 1 Schematic diagram of layered LiCoO2

Currently, The main method to improve the performance of LiCoO2 is to dope it with some metal elements. For example, people will choose some transition metals, such as zinc, iron, chromium, nickel, manganese, titanium, etc., and some non-transition metals such as magnesium, aluminum, strontium, calcium, etc. The specific method is to adjust the ions of these metals in LiCoO2 appropriately Doping in the ratio of, occupying part of the cobalt ion position in the lattice, so that afterwards, certain metal ions can play the effect of making the original lithium cobalt oxide structure more stable, so that Li⁺ cannot be used during the battery reaction. The phenomenon of fully reversible deintercalation has been improved, and the cycle performance of lithium-ion batteries has been enhanced; in addition, there are some metal ions that can be more efficient and use the positive electrode activity of the battery as much as possible, so that the capacity of the battery can be increased to a certain extent. Improved; in addition, there are some metal ions that can increase the conductivity of the material. Of course, although the doping of these metal elements can improve the performance of certain aspects of the material, it may also reduce some of the properties of other aspects. Fish and bear's paws cannot be used at the same time. In addition, at present, the technical process for these doping is still There are some difficulties, so the main thing is to work harder on the performance and manufacturing process of the LiCoO2 material to make its functions better and to further reduce the production cost.

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