Positive Electrode Particle Grading for High-Energy Secondary Batteries
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Solution Overview
Problem
Conventional secondary batteries face limitations in energy density and cycle life due to issues with compaction density and side reactions, particularly when using high-nickel positive electrode materials.
Innovation Solution
A secondary battery design incorporating an agglomerated positive electrode material with a volume average particle size of 8 μm to 15 μm and a quasi-single crystalline positive electrode material with a volume average particle size of 2.5 μm to 4 μm, at a mass ratio greater than or equal to 1, to enhance compaction density and service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-nickel positive electrode materials are used to increase energy density, then the energy density is improved, but the compaction density decreases and service life shortens
Solution Approach 1:
The positive electrode material is segmented into two distinct particle size ranges: coarse particles (8-15 μm) and fine particles (2.5-4 μm). This segmentation allows each particle type to fulfill different functions - coarse particles provide structural stability and fine particles fill voids to improve compaction density, thereby resolving the contradiction between energy density and service life
Solution Approach 2:
Different regions of the electrode structure are assigned different particle sizes to optimize local properties. The coarse particles (0.1-0.6 μm primary particle size) provide mechanical strength and structural integrity in regions requiring stability, while fine particles (0.8-2 μm primary particle size) are placed in regions requiring high compaction density, achieving both high energy density and long service life through spatial differentiation
2Use of energy by moving object
If the positive electrode plate compaction density is increased to improve energy density, then the energy density is improved, but the service life decreases due to increased corrosion
Solution Approach 1:
The invention changes the particle size parameters of the positive electrode material, specifically using a dual-size distribution with Dv50 of 8-15 μm and 2.5-4 μm. This parameter change reduces the specific surface area compared to uniformly fine particles, thereby reducing the contact area with the electrolyte and minimizing corrosion while maintaining high compaction density and energy density
3Ease of manufacture
If uniformly sized particles are used to simplify manufacturing, then the manufacturing process is simplified, but the compaction density and space utilization decrease
Solution Approach 1:
Rather than using uniformly sized particles, the invention segments particles into two size categories that can be independently controlled during manufacturing. This segmentation enables better packing efficiency as the size-graded particles fill voids more effectively, achieving higher compaction density (3.6-3.8 g/cm³) while maintaining manufacturing feasibility through separate particle preparation and mixing steps
Data Source
AI summary
A secondary battery comprises a positive electrode plate. The positive electrode plate is provided with a positive electrode active material. The positive electrode active material comprises an agglomerated positive electrode material and a monocrystalline-like positive electrode material. The agglomerated positive electrode material has a volume average particle size Dv50 of 8 μm-15 μm. The agglomerated positive electrode material has a primary particle size of 0.1 μm-0.6 μm. The monocrystalline-like positive electrode material has a volume average particle size Dv50 of 2.5 μm-4 μm. The monocrystalline-like positive electrode material has a primary particle size of 0.8 μm-2 μm. The mass ratio of the agglomerated positive electrode material to the monocrystalline-like positive electrode material is greater than or equal to 1.