Bimodal Positive Electrode Powder for High-Density Li-Ion Cathodes
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Solution Overview
Problem
Current lithium-ion battery positive electrode materials, such as LiCoO2, face challenges in achieving high energy density and cycle stability due to brittleness and resource limitations, particularly for large batteries, where high nickel content increases brittleness and electrode biting issues during manufacturing, and particle breaking during cycling.
Innovation Solution
A bimodal lithium transition metal oxide powder mixture with a specific particle size distribution and composition, comprising large spherical polycrystalline and small monolithic particles, is used to enhance energy density and reduce brittleness, allowing for higher pressed densities without particle breaking and electrode biting, achieved through a combination of materials with controlled particle sizes and morphologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel content is used to increase capacity and gravimetric energy density, then the capacity increases, but the material becomes more brittle and causes particle breaking and electrode biting
Solution Approach 1:
The patent divides the positive electrode material into two distinct particle size segments: large particles (D50: 10-40 μm) providing structural integrity and high density, and small particles (D50: 2-4 μm) providing capacity. This segmentation allows each size fraction to fulfill different functional requirements, resolving the contradiction between capacity and brittleness.
Solution Approach 2:
The patent applies local quality by assigning different roles to different particle sizes within the same material system. Small particles are optimized for electrochemical capacity while large particles provide mechanical strength. This local differentiation allows the system to simultaneously achieve high capacity and low brittleness.
2Volume of stationary object
If high pressed density is achieved to increase volumetric energy density, then more powder can be packed into given volume, but particle breaking occurs during compression
Solution Approach 1:
The patent implements a nested structure where small particles fill the interstitial spaces between large particles during compression. This nesting arrangement maximizes powder packing density without requiring excessive compression force that would cause particle breaking, as the small particles naturally settle into the voids created by the larger particles.
Solution Approach 2:
The patent creates a composite particle size distribution system combining large and small particles in specific weight ratios (15-60 wt% small particles). This composite approach allows the system to achieve high pressed density through optimized packing while the presence of both size fractions reduces stress concentration that would otherwise cause particle breaking.
3Reliability
If cobalt content is increased to improve battery performance, then energy density and cycle life improve, but cost increases significantly for large batteries
Solution Approach 1:
The patent changes the compositional parameters by using lithium transition metal oxide with controlled nickel content (0.30≤x≤0.92) and adding dopants (0≤d≤0.10) to optimize performance while controlling cobalt content. This parameter optimization allows achieving acceptable cycle life without requiring high cobalt content, thereby reducing material cost.
Data Source
AI summary
A bimodal lithium transition metal oxide based powder mixture comprising a first and a second lithium transition metal oxide based powder. The first powder comprises a material A having a layered crystal structure comprising the elements Li, a transition metal based composition M and oxygen and has a particle size distribution with a span <1.0. The second powder has a monolithic morphology and a general formula Li1+bN′1-bO2, wherein −0.03≤b≤0.10, and N′=NixM″yCozEd, wherein 0.30≤x≤0.92, 0.05≤y≤0.40, 0.05≤z≤0.40 and 0≤d≤0.10, with M″ being one or both of Mn or Al, and E being a dopant different from M″. The first powder has an average particle size D50 between 10 and 40 μm. The second powder has an average particle size D50 between 2 and 4 μm. The weight ratio of the second powder in the bimodal mixture is between 20 and 60 wt %.