Nickel-containing composite hydroxide and production process therefor, positive-electrode active material for a nonaqueous-electrolyte secondary battery and production process therefor, and nonaqueous-electrolyte secondary battery
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Solution Overview
Problem
Lithium nickel-containing composite oxides for secondary batteries face challenges in achieving high energy density and low irreversible capacity due to limitations in particle size and reactivity, particularly when the average particle size exceeds 20 μm, leading to increased non-lithium occupancy and reduced battery performance.
Innovation Solution
A nickel-containing composite hydroxide with a controlled BET value and specific particle size range (20 μm to 50 μm) is synthesized, maintaining reactivity with lithium compounds, and used as a precursor to produce a lithium nickel-containing composite oxide with a layered hexagonal crystal structure, optimizing the battery's energy density and irreversible capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the average particle size of nickel-containing composite hydroxide is increased to 20 μm or more to improve filling ability and energy density, then the energy density increases, but the reactivity with lithium compound decreases and non-lithium occupancy increases
Solution Approach 1:
The nickel-containing composite hydroxide is divided into primary particles (0.01-0.4 μm) that aggregate to form secondary particles (20-50 μm). This segmentation allows the primary particles to maintain high reactivity with lithium compound while the secondary particles provide large size for improved filling ability and energy density.
Solution Approach 2:
The invention creates a hierarchical structure where different regions of the particle system have different properties: primary particles have high specific surface area and reactivity, while secondary particles have large size for filling. This local quality differentiation resolves the contradiction between reactivity and energy density.
2Volume of moving object
If the average particle size of nickel-containing composite hydroxide is increased to improve filling ability, then the filling ability improves, but the BET value decreases leading to reduced reactivity
Solution Approach 1:
The particle system is segmented into primary particles (0.01-0.4 μm) with high BET values (5-50 m²/g) that aggregate to form secondary particles (20-50 μm). This segmentation enables the secondary particles to have large volume for improved filling ability while the primary particles maintain high BET values for reactivity.
Solution Approach 2:
The invention transitions from considering only single particle size to a two-dimensional particle size distribution (primary and secondary particles). This dimensional change allows simultaneous optimization of filling ability (controlled by secondary particle size) and reactivity (controlled by primary particle BET value).
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 approach results in a nonaqueous-electrolyte secondary battery with enhanced energy density and reduced irreversible capacity, achieving high initial discharge capacity and Coulomb efficiency while maintaining safety and cost-effectiveness.
Implementation Method 1
JP 3,614,670 (B2) describes technology of obtaining a lithium nickel-containing composite oxide having a layered hexagonal crystal structure by first obtaining nickel-containing composite hydroxide by adding alkali to a mixed aqueous solution of metal salt as raw material and performing co-precipitation
Implementation Method 2
a firing process of performing firing of the lithium mixture that was formed in the mixing process in an oxygen atmosphere at a temperature of 650° C. to 850° C.
Implementation Method 3
a material from which lithium ions can be desorbed and to which lithium ions can be inserted is used as the active material for the negative electrode and positive electrode
Data Source
AI summary
Provided is a nickel-containing composite hydroxide that is a precursor of a positive-electrode active material with which a nonaqueous-electrolyte secondary battery having a low irreversible capacity and a high energy density can be configured. An aqueous alkaline aqueous solution and a complexing agent are added to an mixed aqueous solution including at least nickel and cobalt to regulate the pH (measured at a reference liquid temperature of 25° C.) of this mixed aqueous solution to 11.0 to 13.0, the ammonium concentration to 4 to 15 g/L, and the reaction temperature to 20° C. to 45° C. Using stirring blades having an inclination angle of 20° to 60° with respect to a horizontal plane, the mixture is stirred to conduct a crystallization reaction under such conditions that when the nickel-containing composite hydroxide to be obtained is roasted in air at 800° C. for 2 hours, the roasted composite hydroxide has a BET value of 12 to 50 m2/g. Thus a nickel-containing composite hydroxide expressed by Ni1−x−yCoxAlyMt(OH)2+α (where, 0<x≤0.20, 0<y≤0.15, 0≤t≤0.10, 0≤α0.50, and M is one or more kind of element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr and Y), or the general formula: Ni1−k−zCoxMnzMt(OH)2+α (where 0<x≤0.50, 0<z≤0.50, x+z≤0.70, 0≤t≤0.10, 0≤α≤0.50, and M is one or more kind of element selected from among Mg, Ca, Ba, Nb, Mo, V, Ti, Zr and Y) is obtained.