Nickel Composite Oxide Cracks for Battery Cycle Life
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries using lithium nickel composite oxides face significant capacity degradation due to excessive nickel at the lithium occupying position, leading to reduced charge and discharge capacity over repeated charging and discharging cycles.
Innovation Solution
A nickel-alkali metal-containing composite oxide with cracks on the surface of primary particles is used, formed through an ion-exchange reaction between sodium and lithium in a molten salt, which relieves volume variation during charging and discharging, maintaining high capacity over increased cycle counts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel composite oxide with excessive nickel at lithium occupying position is used, then discharge capacity increases, but charge and discharge capacity decreases rapidly over repeated cycles
Solution Approach 1:
The positive electrode active material is segmented into primary particles (0.1-10 μm) that aggregate to form secondary particles (1-50 μm). This segmentation allows the material to accommodate volume expansion and contraction during charging and discharging cycles, reducing stress and preventing capacity degradation while maintaining high discharge capacity.
Solution Approach 2:
The primary particles are pre-formed through controlled synthesis before aggregation into secondary particles. This preliminary structuring ensures that the material has the appropriate morphology and surface characteristics to handle volumetric changes during operation, preventing excessive stress accumulation that would lead to capacity fade.
2Length of moving object
If primary particles aggregate to form secondary particles, then particle size increases, but electrical adhesion deteriorates
Solution Approach 1:
The particle structure is segmented into primary particles (0.1-10 μm) that maintain their individual identity while aggregating into secondary particles (1-50 μm). This segmentation ensures that the surface area for electrical contact is preserved, maintaining good electrical adhesion while achieving the desired particle size for electrode fabrication.
Solution Approach 2:
The primary particles on the surface of secondary particles have specific properties (small size, high surface area) that are optimized for electrical contact and adhesion, while the overall secondary particle structure provides the appropriate size for electrode processing. This local quality differentiation resolves the contradiction between particle size and electrical adhesion.
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 effectively suppresses capacity degradation by maintaining electrical adhesion and preventing swelling of the positive electrode mix, ensuring high capacity and extended cycle life for non-aqueous electrolyte secondary batteries.
Implementation Method 1
formed through an ion-exchange reaction between sodium and lithium in a molten salt
Implementation Method 2
cracks on the surface of primary particles is used, formed through an ion-exchange reaction between sodium and lithium in a molten salt, which relieves volume variation during charging and discharging
Data Source
AI summary
An object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery, which can solve the problem that the capacity remarkably decreases with an increase of the number of charging and discharging cycles in a high capacity non-aqueous electrolyte secondary battery using a positive electrode active material for a non-aqueous electrolyte secondary battery made of particles of an alkali metal composite oxide containing nickel.A positive electrode active material for a non-aqueous electrolyte secondary battery, comprising a nickel-alkali metal-containing composite oxide having cracks on the surface of primary particles is used.