Manganese-based composite positive electrode material and preparation method therefor

Abstract

The invention relates to the manufacturing technical field of a battery material, and particularly to a manganese-based composite positive electrode material and a preparation method therefor. Through the matching of a manganese source, a lithium source, a chromium source, a lanthanum source, a binder, a solvent and spinel lithium manganate particles, the spinel lithium manganate particles can be taken as the core; a high-valance lithium-rich phase can be formed in the middle layer and a low-valence Li<2>MnO<2> phase can be formed in the outer layer; consequently, the spinel lithium manganate energy storage part is formed in the interior; the high-valance lithium-rich phase energy storage part is formed in the middle; the Li<2>MnO<2> phase energy storage part is formed in the outer layer; the specific capacity of the positive electrode material is effectively improved; the outer layer of the spinel lithium manganate particles is coated with the low-valance-state material, so that the dissolution of the spinel lithium manganate and the attenuation of the high-valence lithium-rich phase in the middle layer are effectively restrained; and the outer layer is coated with the phase with much lithium, so that the rate of decay of the positive electrode is effectively lowered and the specific capacity of the positive electrode material is improved.

Description

technical field [0001] The invention relates to the technical field of battery material production, in particular to a manganese-based composite positive electrode material and a preparation method thereof. The invention belongs to the field of electrochemical engineering and industrial devices, and it can be used as an electrode active material in a lithium ion battery system of an aqueous solution and an organic electrolyte or a lithium battery system of an organic electrolyte. Background technique [0002] Since human society entered into industrialization, there has been a huge demand for coal and oil and other mineral energy. With the huge consumption of non-renewable energy such as coal and oil, resources are increasingly scarce. The greenhouse effect intensified by carbon dioxide emissions and the increasingly serious pollution of the air and ecological environment have posed a serious threat to the earth on which we live. Vigorously developing renewable energy such ...

AI Technical Summary

Problems solved by technology

[0005] In the early stage of research on cathode materials for lithium-ion batteries, there were mainly several systems such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide. It is the main positive electrode material used in today's commercial lithium-ion batteries, but cobalt is expensive and poor in safety, especially in large-scale and power-type batteries. It is mainly used in small electronic devices, and it is difficult to store energy in electric vehicles. Promotion of large application fields; lithium nickel oxide (LiNiO2) has a layered structure similar to lithium cobalt oxide, high specific energy, good cycle performance, and moderate price, but the conditions for preparing lithium nickel oxide are extremely harsh and are not widely used; lithium manganese Oxygen materials have the advantages of rich raw materials, low cost, and no environmental pollution, but their dissolution at higher temperatures causes capacity loss, low cycle life, and low specific capacity. Although in the prior art, some researchers have targeted this type of product Doping with Ni, Co, Cr and other elements to improve the Li / Mn ratio can achieve the purpose of improving the above defects, but the specific capacity of the prepared lithium manganese oxide material is still about 120-130mAh / g, making the lithium ion battery poor performance

Moreover, the cost of doping materials with elements such as Ni and Co increases more

[0006] For this reason, other technical means have appeared in the prior art, such as phosphate LiMPO 4 (M=Fe, Co, Ni, Mn, V, etc.), Li 3 V 2 (PO 4 ) 3 , Silicate Li 2 MSiO 4 (M=Fe, Mn) and titanate Li 2 MTiO 4 (M=Ni, Fe, Mn), but the specific capacity of the material in the above-mentioned prior art is still low, and then the specific energy of the battery that causes preparation is still low, even some materials also can cause electrolysis because of the high potential. The liquid decomposes, which shortens the service life of the battery

[0007] The reason for the above phenomenon is that whether it is layered LiMO 2 (including LiCoO 2 、LiNi 1 / 3 co 1 / 3 mn 1 / 3 o 2 and its congeners), or spinel-type LiMn 2 o 4 , or olivine-type LiMPO 4 etc., each molecule of which contains only one variable 1-valent transition element atom, so that the lithium ion that can be removed during charging is at most one, LiMO with the smallest molecular weight 2 , its theoretical specific capacity is about 274mAh / g, so that when it ensures the stability of the crystal structure, only 0.5-0.65 lithium ions can be removed, so that its actual specific capacity is about 140mAh / g, resulting in the following The specific energy of the battery prepared by it as the positive electrode material of the battery is low; and, the solid solution material of layered and spinel or the olivine type material, etc., when it has the trivalent, tetravalent and M valence of lithium-rich manganese, It can make its specific capacity higher, but after this kind of material is prepared into a battery, due to the high voltage of the lithium-rich manganese material, it is easy to cause the electrolyte to decompose, and the specific capacity decays quickly, making the service life of the prepared battery poor.