Ternary material, preparation method thereof and battery slurry, positive electrode and lithium battery

Abstract

The invention discloses a ternary material and a preparation method thereof and a battery slurry, a positive electrode and a lithium battery. The ternary material is represented by a general formula of LiNi<1-x-y>Co<x> M<y>O<2>, wherein M is Mn or Al, and 0<x<1, 0<y<1, x+y<1. The particulate matter of the ternary material comprises three layers of particles which include primary particles having acrystal structure, middle particles formed by partially fusing multiple primary particles and secondary balls formed by aggregating the intermediate particles. The particulate matter of the ternary material includes the three layers of particles at the same time, so that the material simultaneously has excellent low-temperature performance and rate performance of the small particles and excellenthigh-temperature storage and high-temperature cycling performance of big particles.

Description

technical field [0001] The invention relates to the field of lithium battery production, in particular to a ternary material, a preparation method thereof, battery slurry, a positive electrode and a lithium battery. Background technique [0002] Lithium-ion batteries have attracted widespread attention due to a series of remarkable advantages such as high working voltage, high specific energy, light weight, small size, long cycle life, no memory effect, fast charging and discharging, and no environmental pollution. The two major tasks of lithium-ion battery research are to improve performance (mainly high energy density and power density, long life, safety) and reduce cost. The cathode material is the key to improving the performance of lithium-ion batteries, which determines the main performance indicators of lithium-ion batteries. [0003] In recent years, the new layered lithium intercalation ternary material Li-Ni-Co-Mn-O composite oxide has developed rapidly, and its r...

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Problems solved by technology

This method has the following problems: ①After the material has been sintered at high temperature for a long time, the primary particles are large, generally exceeding 500nm, or even reaching the micron level. The specific surface of this large particle material is small, so high temperature storage and high temperature cycle performance It is not bad, and the compaction density is also high, but the low-temperature performance and high-current rate performance are poor, which cannot meet the requirements of power batteries for high-rate performance; Elemental materials, lithium elements need to diffuse into the secondary ball of the precursor at high temperature, which requires long-term high-temperature sintering, and the addition of lithium salts that exceed the theoretical measurement value by nearly 10% can ensure the full distribution of lithium, which will increase the cost of materials ; In addition, the excess lithium salt that has not fully diffused into the interior of the secondary ball will be distributed on the surface of the secondary ball in the form of free lithium, which will cause the pH of the material to be high, and the powder impedance of the material is also large, which will eventually During the high-temperature storage and cycle process, the thickness of the battery changes greatly and the internal resistance increases greatly, which greatly reduces the safety performance of the battery.

This method has the following problems: ① The ternary material is prepared by the traditional hydrothermal method, the primary particles are small (generally within 300nm), and loosely dispersed, it is difficult to agglomerate into secondary balls, and the specific surface area of ​​the material is large. The contact area is large, the capacity, low temperature and magnification of the material are good, but the compacted density of the material is low, generally only 2.9g / cm 3 , far lower than the ternary materials prepared by the solid-state method, and the energy density is about 20% lower than that of the solid-state method; this makes the high-temperature storage, high-temperature cycle and room temperature cycle performance of the material poor, and cannot reach the power battery ② The ternary materials prepared by the traditional hydrothermal method, due to the low lithium content, are generally lower than the theoretical stoichiometric ratio. In the later high-temperature sintering process, lithium will be further lost. After the material is deficient in lithium, it will cause the final The cycle performance of the battery is poor and the battery life is short

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