High-Nickel Positive Active Material Blend for Crack-Resistant Cycling
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Solution Overview
Problem
High nickel-based positive active materials in lithium batteries suffer from internal cracks during long-term charge and discharge cycles, leading to safety issues and reduced battery performance due to side reactions with the electrolyte, which compromises cycle-life and energy density.
Innovation Solution
A combination of secondary particles and single particles made from lithium nickel-based composite oxides with high nickel content, including Ni, Co, Mn, Al, Zr, and Mg, is used to enhance particle strength and prevent cracking, thereby improving cycle-life and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high nickel-based positive active materials are used to secure high capacity, then energy density is improved, but internal cracks occur during long-term charge and discharge cycles
Solution Approach 1:
The positive active material is divided into two particle types: single particles with high strength and secondary particles with aggregated structure. This segmentation allows each particle type to fulfill different functions - single particles provide crack resistance while secondary particles contribute to capacity, resolving the contradiction between energy density and cycle-life
Solution Approach 2:
The invention creates a composite particle system combining single particles and secondary particles in specific ratios. This composite structure leverages the strengths of both particle types - the structural integrity of single particles and the high capacity characteristics of secondary particles - to simultaneously achieve high energy density and long cycle-life
2Object-affected harmful factors
If single particles are used to reduce side reaction with electrolyte, then specific surface area is reduced, but internal cracks still occur when increasing electrode density
Solution Approach 1:
The particle system is segmented into single particles optimized for reducing side reactions and secondary particles optimized for maintaining structural integrity during cycling. This segmentation allows each particle type to address specific problems without compromising overall performance
Solution Approach 2:
The invention optimizes the ratio of single particles to secondary particles, as well as the size distribution and composition of each particle type. By adjusting these parameters, the system achieves both low side reaction rates and high resistance to internal cracking during long-term cycling
3Use of energy by moving object
If mixed particles with different sizes are used to increase energy density, then capacity is improved, but cracks inside particles occur during long-term cycles
Solution Approach 1:
The invention creates a composite particle system where single particles (with high strength) and secondary particles (with high capacity) are combined in optimized ratios. This composite approach maintains particle strength while achieving high energy density, preventing the crack formation that occurs in conventional mixed-particle systems
Data Source
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AI summary
Provided are a positive active material for a rechargeable lithium battery, and rechargeable lithium battery including the same, the positive active material including a first positive active material in a form of secondary particles in which a plurality of primary particles are aggregated, including a lithium nickel-based composite oxide having a nickel content of greater than or equal to about 80 mol% based on the total amount of elements excluding lithium and oxygen, and a second positive active material in a form of single particles, including a lithium nickel-based composite oxide having a nickel content of greater than or equal to about 80 mol% based on the total amount of elements excluding lithium and oxygen wherein the lithium nickel-based composite oxide of the second positive active material includes Ni, Co, Mn, Al, Zr, and Mg.