Nickel-Rich Cathode Particle Structure for High-Voltage Cycle Stability
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Solution Overview
Problem
Nickel-based lithium transition metal oxides in rechargeable lithium batteries face challenges with low packing density, lower capacity per unit volume, and reduced stability during high voltage driving, necessitating improvements in packing density, thermal stability, and cycle-life characteristics.
Innovation Solution
A positive active material is developed with nickel-based lithium transition metal oxide secondary particles composed of polycrystalline primary particles, each formed from 2 to 10 single crystals, and a specific composition (Li x Ni 1-a-b-c Co a Mn b M c O 2 ) with controlled particle sizes and crystal structure stability, prepared through a method involving co-precipitation and heat-treatment of transition metal precursors with a high Li/metal mole ratio and inert surfactant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If nickel-based lithium transition metal oxide is used to increase discharge capacity per unit weight, then battery capacity is improved, but packing density and capacity per unit volume decrease
Solution Approach 1:
The positive active material is divided into primary particles (0.5-5 μm) that aggregate to form secondary particles (10-40 μm). This segmentation allows optimization of both specific capacity and packing density by controlling the size and aggregation structure of particles at different hierarchical levels.
Solution Approach 2:
The invention changes physical parameters including particle size distribution (primary particles 0.5-5 μm, secondary particles 10-40 μm), crystal structure (layered structure with specific XRD peak intensity ratios I(003)/I(104) of 1.6-2.0), and chemical composition (Li x Ni 1-a-b-c Co a Mn b M c O 2 with specific ranges) to simultaneously achieve high specific capacity and high packing density.
2Quantity of substance
If nickel-based lithium transition metal oxide is used to achieve high capacity, then discharge capacity is improved, but thermal stability and high voltage stability are reduced
Solution Approach 1:
The invention uses composite nickel-based lithium transition metal oxide with multiple elements (Ni, Co, Mn, and additional element M) in a layered structure. This composite composition provides high capacity while the specific crystal structure and element distribution enhance thermal stability and high-voltage stability.
Solution Approach 2:
By adjusting chemical composition parameters (x, a, b, c in Li x Ni 1-a-b-c Co a Mn b M c O 2) and crystal structure parameters (layered structure with controlled peak intensity ratios), the invention achieves both high discharge capacity and improved thermal/high-voltage stability.
3Quantity of substance
If nickel-based lithium transition metal oxide is used to achieve high capacity, then discharge capacity is improved, but cycle-life characteristics at high voltage are reduced
Solution Approach 1:
The multi-element composite structure (Li, Ni, Co, Mn, M) with layered crystal structure provides high capacity while enhancing structural stability during cycling. The specific composition and structure reduce degradation mechanisms, improving cycle-life characteristics at high voltage.
Solution Approach 2:
The hierarchical particle structure with primary particles (0.5-5 μm) aggregating into secondary particles (10-40 μm) with controlled polycrystalline composition (2-10 single crystals per primary particle) enhances structural stability and ion transport, improving cycle-life characteristics while maintaining high capacity.
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 battery capacity and improves high-voltage cycle-life characteristics by increasing the density and structural stability of the positive active material, reducing gas generation and improving thermal stability.
Implementation Method 1
mixing an aqueous solution including a nickel compound and a cobalt compound with a basic solution, performing a co-precipitation reaction followed by drying the resultant to prepare a transition metal precursor
Implementation Method 2
mixing the transition metal precursor, a lithium compound, and an inert surfactant and performing heat-treatment to prepare a positive active material
Data Source
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AI summary
An embodiment provides a positive active material for a rechargeable lithium battery including nickel-based lithium transition metal oxide secondary particles in which a plurality of primary particles are aggregated, wherein the primary particles include polycrystalline primary particles composed of 2 to 10 single crystals and the single crystal has a particle diameter of about 0.5 µm to about 3 µm.