Positive electrode active material, positive electrode plate, and non-aqueous electrolyte secondary battery
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Solution Overview
Problem
Existing positive electrode materials in non-aqueous electrolyte secondary batteries face challenges in achieving good cycling performance and input-output properties due to oxidative degradation and structural changes caused by lithium-rich composite oxides, as well as expansion and shrinkage of nickel-rich composite oxides, leading to capacity degradation.
Innovation Solution
A positive electrode active material comprising a first lithium-rich composite oxide with larger secondary particles and a second nickel-rich composite oxide with smaller secondary particles, balanced by a specific particle size ratio and content, along with the inclusion of carbon nanotubes and carbon black to enhance electronic conductivity and reduce structural stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium-rich composite oxide is used as positive electrode active material, then volumetric energy density is improved, but oxidative degradation occurs leading to capacity degradation
Solution Approach 1:
The patent uses a composite material system consisting of lithium-rich composite oxide particles combined with nickel-rich composite oxide particles. This composite structure allows the lithium-rich material to provide high volumetric energy density while the nickel-rich material counteracts oxidative degradation, thus resolving the contradiction between energy density and cycling performance.
Solution Approach 2:
The patent applies local quality by creating particles with non-uniform composition distribution. Specifically, the lithium-rich composite oxide particles have a core-shell structure where the composition varies from core to surface, allowing different regions to perform different functions: the core provides high capacity while the surface layer reduces oxidative degradation.
2Power
If nickel-rich composite oxide is used as positive electrode active material, then input-output properties are improved, but expansion and shrinkage occurs leading to capacity degradation
Solution Approach 1:
The patent combines nickel-rich composite oxide with lithium-rich composite oxide in a composite particle structure. The nickel-rich component provides excellent input-output properties while the lithium-rich component buffers the expansion and shrinkage stresses, maintaining structural integrity over cycling and preventing capacity degradation.
3Use of energy by moving object
If secondary particles with large aggregation number are used, then volumetric energy density is improved, but particle size increases affecting performance
Solution Approach 1:
The patent optimizes the aggregation number parameter of secondary particles to fall within the range of 10 to 100. This parameter control allows the particles to achieve sufficient packing density for high volumetric energy density while maintaining a particle size that does not adversely affect electrochemical performance, thus resolving the contradiction between energy density and particle size.
Data Source
AI summary
A positive electrode active material comprises a first active material represented by a formula (I) that is secondary particles each consisting of 50 or more primary particles aggregated together, as well as a second active material represented by a formula (II) that is at least one of single particles and secondary particles each consisting of 2 to 10 primary particles aggregated together. The formula (I) and the formula (II) are as specified in the claims. A content of the first active material in the positive electrode active material is from 20 to 70 mass %. A ratio (D150/D250) of an average particle size (D150) of the first active material to an average particle size (D250) of the second active material is from 2.45 to 5.95.