Nickel Composite Hydroxide Gradient Layers for Low-Resistance Li-Ion Cathodes
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Solution Overview
Problem
Existing lithium cobalt composite oxides for positive electrodes in lithium ion secondary batteries are costly due to the use of rare and expensive cobalt, and they suffer from high positive electrode resistance and inadequate cycle characteristics, limiting their application in portable devices.
Innovation Solution
A nickel composite hydroxide with a gradient composition, featuring cobalt and manganese rich layers and a layered low-density layer, is used as a precursor for the positive electrode active material, produced through a multi-stage aqueous solution process to control particle size and composition distribution, resulting in improved positive electrode resistance and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional method using a mixed solution of ammonium fluoride and ammonium hydroxide is used to treat a nickel hydroxide precursor, then the nickel hydroxide precursor can be obtained, but the method requires separate storage of multiple chemicals and complex disposal procedures for toxic ammonia gas and liquid waste
Solution Approach 1:
The patent combines multiple chemicals (ammonium fluoride and ammonium hydroxide) into a single pre-mixed solution that is stored and handled as one unit. This merging eliminates the need for separate storage containers and handling procedures for individual chemicals, thereby reducing process complexity while maintaining the ability to produce nickel hydroxide precursor effectively
Solution Approach 2:
The patent introduces an intermediary substance (the pre-mixed solution of ammonium fluoride and ammonium hydroxide) that facilitates the production process. This intermediary consolidates multiple chemical functions into a single reagent system, simplifying the overall manufacturing process by reducing the number of separate chemical handling operations required
2Productivity
If a mixed solution of ammonium fluoride and ammonium hydroxide is used, then nickel hydroxide precursor can be produced, but toxic ammonia gas is generated requiring complex disposal procedures
Solution Approach 1:
The patent converts the harmful ammonia gas byproduct into a beneficial feature by adjusting the solution composition ratio. By optimizing the ratio of ammonium fluoride to ammonium hydroxide, the amount of ammonia gas generated is reduced to minimal levels, transforming a harmful environmental factor into an acceptable production characteristic that maintains productivity
3Reliability
If high-purity nickel hydroxide is produced through conventional methods, then battery performance is improved, but the production process becomes more complex and costly
Solution Approach 1:
The patent achieves high-purity nickel hydroxide by changing the key parameter of the solution composition ratio. By specifically adjusting the ratio of ammonium fluoride to ammonium hydroxide in the pre-mixed solution, the patent obtains nickel hydroxide precursor with controlled crystal growth and high purity, thereby achieving reliable battery performance through a simplified single-solution process rather than multiple treatment steps
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The nickel composite hydroxide precursor leads to a positive electrode active material with reduced resistance and enhanced cycle stability, enabling high energy density and output characteristics in lithium ion secondary batteries.
Implementation Method 1
a conventional method in which a mixed solution of ammonium fluoride and ammonium hydroxide is used to treat a nickel hydroxide precursor
Implementation Method 2
positive electrode active material for lithium ion secondary battery
Data Source
Figure 1~2
AI summary
The purpose of the present invention is to provide a nickel composite hydroxide which is a precursor of a positive electrode active material for a lithium ion secondary battery excellent in a positive electrode resistance or a cycle characteristic. The nickel composite hydroxide comprises a nickel, a cobalt, a manganese, and an element M with an atomic ratio of Ni: Co: Mn: M = 1-x1-y1-z1: x1: y1: z1 (wherein M is at least one element selected from a group consisting of a transition metal element other than Ni, Co, Mn, a II group element, and a XIII group element, 0.15≦x1≦0.25, 0.15≦y1≦0.25, 0 ≦z1≦0.1), the nickel composite hydroxide is having a cobalt rich layer or a manganese rich layer from a surface of a particle of the secondary particles toward an inside of the particle of the secondary particles and a layered low-density layer between the cobalt rich layer or the manganese rich layer and a center of the particle of the secondary particles, and a thickness of the cobalt rich layer or the manganese rich layer is 1% or more and 10% or less with respect to a diameter of the secondary particles, and also, a thickness of the low-density layer is 1% or more and 10% or less with respect to the diameter of the secondary particles.