Nickel Composite Hydroxide Layering for Low-Cost Li-Ion Cathodes
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Solution Overview
Problem
Existing lithium cobalt composite oxide-based lithium ion secondary batteries are costly due to the use of rare and expensive cobalt compounds, limiting their applicability and necessitating the development of more affordable alternatives with improved positive electrode resistance and cycle characteristics.
Innovation Solution
A nickel composite hydroxide with a specific atomic ratio of Ni:Co:Mn:M, comprising secondary particles with primary particles aggregated, and featuring a cobalt or manganese rich layer and a layered low-density layer, is used as a precursor to a positive electrode active material. This material is produced through a method involving nucleation and particle growth processes in controlled pH and atmospheric conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium cobalt composite oxide is used as positive electrode active material, then high voltage (4 V-class) and ease of synthesis are achieved, but cost increases significantly due to expensive cobalt compounds
Solution Approach 1:
The patent applies local quality by creating a core-shell structure where the center layer contains high cobalt content (x2≥0.5) to maintain high voltage performance, while the outer layer has reduced cobalt content (x1<x2) to lower cost. This spatial variation in composition allows different regions to serve different functions: the core provides voltage stability while the outer layer reduces expensive material usage.
Solution Approach 2:
The patent uses composite materials by combining nickel, cobalt, and manganese in a gradient composition within a single particle structure. The composite hydroxide precursor (Ni1-x1-y1-z1Cox1MnymMz1(OH)2+α1) transforms into a composite oxide (Li1+uNi1-x1-y1-z1Cox1MnymMz1O2+β1) that integrates multiple elements to achieve both high voltage characteristics and cost reduction by replacing some cobalt with cheaper nickel and manganese.
2Ease of manufacture
If lithium nickel composite oxide is used to reduce cost, then lower material cost is achieved, but positive electrode resistance and cycle characteristics deteriorate
Solution Approach 1:
The patent addresses positive electrode resistance by concentrating cobalt in the center layer (x2≥0.5) where it provides excellent electrical conductivity and voltage stability. The outer layer uses reduced cobalt content but maintains nickel and manganese for structural stability, creating a gradient that optimizes both conductivity and cost.
Solution Approach 2:
The patent introduces a layered low-density layer between the outer layer and center layer that acts as a buffer zone. This low-density layer (with lower metal content than surrounding layers) prevents excessive diffusion of elements during firing while maintaining the gradient composition, thereby cushioning against potential degradation and preserving cycle characteristics.
3Ease of manufacture
If lithium nickel composite oxide is used to reduce cost, then lower material cost is achieved, but cycle characteristics worsen
Solution Approach 1:
The gradient composition with cobalt concentrated in the center layer provides structural stability and resistance to degradation during cycling. The outer layer with nickel and manganese offers cost reduction while the gradual transition in composition prevents abrupt changes that could cause particle cracking or structural collapse over repeated charge-discharge cycles.
Solution Approach 2:
The layered low-density layer serves as a protective buffer that prevents excessive element diffusion during the firing process and subsequent cycling. This cushioning layer maintains the integrity of the gradient composition structure, thereby preserving cycle characteristics by preventing structural degradation over time.
4Reliability
If cobalt rich layer is formed to improve positive electrode resistance, then resistance is reduced, but cost increases due to higher cobalt content
Solution Approach 1:
The patent resolves this contradiction by creating a center layer with high cobalt content (x2≥0.5) that provides excellent electrical conductivity and low positive electrode resistance. However, this cobalt-rich core is surrounded by an outer layer with reduced cobalt content (x1<x2), which lowers the overall cobalt usage and cost while maintaining the beneficial electrical properties in the conductive pathways.
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 results in a positive electrode active material with enhanced resistance and cycle characteristics, achieving high output and capacity with reduced variation, thereby addressing the cost and performance limitations of existing lithium cobalt composite oxide batteries.
Implementation Method 1
A nickel composite hydroxide with a specific atomic ratio of Ni:Co:Mn:M, comprising secondary particles with primary particles aggregated, is used as a precursor to a positive electrode active material. This material is produced through a method involving nucleation and particle growth processes in controlled pH and atmospheric conditions.
Implementation Method 2
A nickel composite hydroxide with a specific atomic ratio of Ni:Co:Mn:M, comprising secondary particles with primary particles aggregated, and featuring a cobalt or manganese rich layer and a layered low-density layer, is used as a precursor to a positive electrode active material.
Data Source
AI summary
A nickel composite hydroxide includes nickel, cobalt, 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≤0.25, 0.15≤y1≤0.25, 0≤z1≤0.1), the nickel composite hydroxide having a cobalt or manganese rich layer from a surface of a particle of the secondary particles toward an inside of the secondary particles and a layered low-density layer between the cobalt or manganese rich layer and a center of the particle of the secondary particles, and a thickness of the cobalt or manganese rich layer and low-density layer is 1% or more and 10% or less to a diameter of the secondary particles.