Nickel-Based Positive Electrode with Radial Primary Particles
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Solution Overview
Problem
Rechargeable lithium batteries using lithium nickel manganese cobalt composite oxide or lithium cobalt oxide as positive active materials face issues with cycle-life, increased resistance, and insufficient capacity due to cracking during charging and discharging.
Innovation Solution
A positive electrode with a nickel-based active material comprising a first secondary particle with radially arranged primary particles and a second monolith structure, achieving an X-ray diffraction peak intensity ratio of I(003)/I(104) greater than or equal to 3, is developed, along with a method involving heat-treatment in oxidizing gas atmospheres to enhance the electrode's structure and properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium nickel manganese cobalt composite oxide or lithium cobalt oxide is used as positive active material, then capacity is improved, but cycle-life decreases and resistance increases due to cracking during charging and discharging
Solution Approach 1:
The positive active material is divided into primary particles and secondary particles (agglomerates of primary particles). This segmentation allows the material to maintain high capacity while reducing internal stress and cracking during charging-discharging cycles, thereby improving cycle-life
Solution Approach 2:
The patent applies different structural characteristics to different parts of the positive active material: primary particles provide high capacity, while secondary particles provide structural stability. This local differentiation resolves the contradiction between capacity and cycle-life
2Quantity of substance
If lithium nickel manganese cobalt composite oxide or lithium cobalt oxide is used as positive active material, then capacity is improved, but resistance increases due to cracking during charging and discharging
Solution Approach 1:
Dividing the material into primary and secondary particles reduces cracking, which in turn reduces resistance increase during cycling while maintaining high capacity
Solution Approach 2:
The positive active material is pre-formed with a specific particle structure (primary particles agglomerated into secondary particles) before battery assembly. This preliminary structural preparation prevents cracking and resistance increase during subsequent charging-discharging cycles
3Ease of manufacture
If conventional positive active material structure is used, then manufacturing is simpler, but high temperature stability is insufficient
Solution Approach 1:
The patent changes the structural parameters of the positive active material (primary particle size, secondary particle composition, radial arrangement ratio) to achieve high temperature stability. These parameter adjustments are made during the heat treatment process, maintaining ease of manufacture while improving thermal stability
4Reliability
If radial arrangement structure is implemented in primary particles, then lithium diffusion is enhanced and cycle-life is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the radial arrangement ratio (ratio of radially arranged primary particles to total primary particles) within a specific range (5-50%). This parameter optimization achieves improved cycle-life and lithium diffusion while avoiding excessive manufacturing precision requirements
Solution Approach 2:
The positive active material is designed as a composite structure with both radially arranged primary particles and non-radially arranged primary particles. This composite approach balances performance improvement with manufacturing feasibility
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 improves cycle-life, efficiency, and high-temperature stability while maintaining high capacity, reducing the likelihood of cracking and enhancing lithium diffusion, thereby improving the overall performance of the rechargeable lithium battery.
Implementation Method 1
subjecting a first precursor to a first heat-treatment in a first oxidizing gas atmosphere to obtain a first nickel-based oxide
Implementation Method 2
subjecting a first precursor to a first heat-treatment in a first oxidizing gas atmosphere to obtain a first nickel-based oxide
Implementation Method 3
subjecting a second precursor to a second heat-treatment in a second oxidizing gas atmosphere to obtain a second nickel-based oxide having a monolith structure
Implementation Method 4
subjecting a second precursor to a second heat-treatment in a second oxidizing gas atmosphere to obtain a second nickel-based oxide having a monolith structure
Implementation Method 5
subjecting the mixture to third heat-treatment in a third oxidizing gas atmosphere to obtain a positive active material including a first positive active material and a second positive active material having a monolith structure
Implementation Method 6
subjecting the mixture to third heat-treatment in a third oxidizing gas atmosphere to obtain a positive active material including a first positive active material and a second positive active material having a monolith structure
Implementation Method 7
coating the positive active material slurry on a current collector, and then drying it to prepare a positive electrode
Data Source
AI summary
A positive electrode for a rechargeable lithium battery includes a positive active material for a rechargeable lithium battery that includes a first positive active material including a secondary particle including at least two agglomerated primary particles, where at least a portion of the primary particles has a radial arrangement structure, and a second positive active material having a monolith structure, wherein the first and second positive active materials each include a nickel-based positive active material, and an X-ray diffraction (XRD) peak intensity ratio (I(003)/I(104)) of the positive electrode is greater than or equal to about 3. Further embodiments provide a method of manufacturing the positive electrode for rechargeable lithium battery, and a rechargeable lithium battery including the same.