Preparation method of composite cathode material for lithium ion battery

Abstract

The invention relates to a preparation method of a composite cathode material for a lithium ion battery. The preparation method is characterized by comprising two steps of: preparing a nickel cobalt manganese oxide precursor, and preparing monocrystal layered cobalt lithium oxide grains and polycrystal layered nickel cobalt manganese oxide grains by high-temperature sintering, so that a whole composite cathode material can be grown in a fusing way. Due to the high-temperature sintering, the monocrystal layered cobalt lithium oxide and the polycrystal layered nickel cobalt manganese oxide can be grown into the whole composite cathode material in the fusing way, and the monocrystal layered cobalt lithium oxide grains play a part in supporting, so that the breaking of the material due to rolling of the polycrystal layered nickel cobalt manganese oxide grains can be avoided, and the compacted density of the material can be improved; due to the polycrystal layered nickel cobalt manganese oxide grains, the material is guaranteed to be high in discharge specific capacity and discharge voltage, and the composite cathode material is guaranteed to have the characteristics of being high in energy density, high in discharge voltage and high in compacted density; and by adopting the preparation method, the content of the cobalt element in the cathode material can be reduced, the material cost can be reduced, the preparation method is simple in process, and the preparation method is suitable for large-scale production.

Description

technical field [0001] The invention belongs to the technical field of lithium ion battery materials, and in particular relates to a preparation method of a composite positive electrode material for lithium ion batteries. Background technique [0002] Layered lithium cobalt oxide cathode material, as the originator of lithium ion battery cathode materials, has never stopped exploring its performance since 1980. So far, layered lithium cobalt oxide still accounts for 85% of lithium ion batteries in electronic products. left and right markets, and after 30 years of development, its performance has reached its limit. [0003] Due to the unprecedented demand for energy density of 3C products, and the sudden emergence of new materials with high energy density, the defects of layered lithium cobalt oxide in terms of energy density are unprecedentedly exposed: in terms of gram capacity, due to the structural defects of layered lithium cobalt oxide, Although its theoretical capacit...

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Problems solved by technology

[0003] Due to the unprecedented demand for energy density of 3C products, and the sudden emergence of new materials with high energy density, the defects of layered lithium cobalt oxide in terms of energy density are unprecedentedly exposed: in terms of gram capacity, due to the structural defects of layered lithium cobalt oxide, Although its theoretical capacity is 275mAh / g, the actual reversible specific capacity is generally around 140mAh / g; in terms of high voltage, 4.3V is already the limit for ordinary layered lithium cobalt oxide and high-voltage electrolyte.

Although the layered nickel oxide cobalt manganese lithium cathode material reduces the use of scarce cobalt elements and reduces the cost, the reversible specific capacity is between 2.75-4.3V, the reversible specific capacity is above 160mAh / g, and it can withstand high voltage above 4.3V, but Due to the crystallinity of the material itself, the layered nickel-cobalt-manganese-lithium secondary particles are crushed during the electrode preparation process, and the compacted density is generally 3.7g / cm 3 Below, the volumetric energy density of the single layered nickel-cobalt-manganese-lithium oxide cathode material is still lower than that of the layered cobalt oxide lithium. The main reason for cobalt lithium

The current general process is to simply mix layered lithium cobalt oxide and layered nickel cobalt manganese lithium oxide, but this simple physical mixing method has the disadvantages of high cost, low discharge voltage and compaction density

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