High-Ni Positive Electrode Composition Against Layered Structure Collapse
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Solution Overview
Problem
Lithium-transition metal composite oxides with high Ni content in positive electrodes for non-aqueous electrolyte secondary batteries experience structural collapse during charge-discharge cycles, leading to decreased capacity and stability due to excessive Li abstraction and surface reactions with the electrolyte.
Innovation Solution
A positive electrode with a lithium-transition metal composite oxide having a layered structure containing Ni and Mn, where Ni constitutes 80-95 mol% and Mn 0-20 mol% of the metal elements, with specific X-ray diffraction peak ratios and porosity within the composite oxide particles to stabilize the structure and inhibit electrolyte reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high Ni content (≥80 mol%) is used in lithium-transition metal composite oxide to increase energy density, then battery capacity is improved, but layered crystal structure collapses during charge-discharge cycles due to excessive Li abstraction
Solution Approach 1:
The patent applies local quality by creating a dual-structure composite oxide where different regions have different compositions: a core region with high Ni content (0.80≤y≤0.95) for high capacity, and a surface region with lower Ni content (0.70≤y≤0.85) for structural stability. This spatial variation in composition allows the battery to achieve high energy density while preventing structure collapse during cycling.
Solution Approach 2:
The patent uses composite materials by combining two lithium-transition metal composite oxides with different Ni contents into a single active material system. The core-shell structure integrates a high-Ni core (LixNi0.80-0.95M1-a-bMn aObO2) with a low-Ni shell (LixNi0.70-0.85M1-a-bMn aObO2), creating a composite that exhibits both high capacity and excellent cycle stability.
2Quantity of substance
If high Ni content is used to increase capacity, then energy density is improved, but surface reactions with electrolyte increase causing deterioration
Solution Approach 1:
The patent applies local quality by creating a protective surface layer with modified composition (lower Ni, higher Mn and/or O) that reduces harmful surface reactions with the electrolyte, while maintaining the high-Ni core for capacity. The surface region's different chemical composition provides resistance to electrolyte decomposition.
Solution Approach 2:
The low-Ni surface layer acts as an intermediary between the high-Ni core and the electrolyte, reducing direct contact and harmful reactions between the reactive high-Ni material and the electrolyte. This intermediate layer serves as a protective barrier that allows ion transport while preventing detrimental surface reactions.
3Productivity
If repeated charge-discharge cycles are performed to utilize high capacity, then battery performance is improved, but structure collapse occurs resulting in decreased capacity
Solution Approach 1:
The patent uses composite materials by creating a core-shell structured composite oxide where the high-Ni core provides capacity and the low-Ni shell provides structural stability during cycling. This composite structure enables the battery to withstand repeated charge-discharge cycles without structure collapse.
Solution Approach 2:
The patent applies beforehand cushioning by pre-forming a stable low-Ni surface layer that cushions and protects the high-Ni core from structural degradation during charge-discharge cycles. This pre-existing protective layer prevents the onset of structure collapse before it can occur.
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 solution enhances the charge-discharge cycle characteristics and maintains high battery capacity by stabilizing the layered structure and reducing surface reactions, resulting in improved cycle performance and capacity retention.
Implementation Method 1
a lithium-transition metal composite oxide having a layered structure and containing at least Ni and Mn
Implementation Method 2
a half-value width of a diffraction peak of a (003) plane is less than or equal to 0.14°, and a diffraction peak ratio between a (104) plane and the (003) plane
Data Source
AI summary
A positive electrode active material included in this non-aqueous electrolyte secondary battery positive electrode includes a lithium-transition metal composite oxide. The lithium-transition metal composite oxide contains 80-95 mol % of Ni and 0-20 mol % of Mn, and 3-8 mol % of a metal element other than Li is present in a Li layer of the lithium-transition metal composite oxide. The ratio m/n of the half width m of the diffraction peak for the (003) plane to the half width n of the diffraction peak for the (110) plane in an x-ray diffraction pattern obtained by x-ray diffraction of the positive electrode active material satisfies 0.72≤m/n≤0.85. The lithium-transition metal composite oxide is formed from secondary particles that are aggregates of primary particles, the internal porosity of the secondary particles being 1%-5%.