Electrode Oxide Layer Thickness Gradient for Lithium Ion Distribution
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in achieving high energy density and excellent capacity retention due to uneven lithium ion distribution and material deterioration within the electrode mixture layer, leading to decreased capacity and increased resistance during charge-and-discharge cycles.
Innovation Solution
The battery incorporates a positive electrode with a unique electrode mixture layer structure, featuring a first portion with a thicker oxide layer near the current collector to manage excess voltage and a second portion with a thinner oxide layer further away, optimizing lithium ion distribution and preventing material deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density of the positive electrode mixture is increased to achieve high energy density, then the energy density of the positive electrode is improved, but the uniformity of lithium ion distribution and material stability deteriorate
Solution Approach 1:
The patent applies local quality by creating two distinct regions within the electrode mixture layer: a first portion near the current collector with a thicker oxide layer (0.5-100 nm) and a second portion farther away with a thinner oxide layer (0.1-5 nm). This spatial variation in oxide layer thickness addresses the uniformity problem while maintaining high overall density, as each region is optimized for its specific location's lithium ion transport needs.
Solution Approach 2:
The electrode mixture layer is segmented into two distinct portions based on their distance from the current collector. The first portion (thicker oxide layer) handles the interface region where lithium ion insertion/extraction occurs, while the second portion (thinner oxide layer) maintains density and structural integrity. This segmentation allows each region to perform its function optimally without compromising the other.
2Quantity of substance
If the density of the positive electrode mixture is increased to achieve high energy density, then the energy density of the positive electrode is improved, but material deterioration accelerates
Solution Approach 1:
The oxide layer is formed preliminarily on the active material particle surfaces before electrode assembly. This pre-formed protective layer prevents material deterioration during subsequent charge-and-discharge cycles by stabilizing the particle surfaces and preventing unwanted reactions with the electrolyte, thus ensuring long-term capacity retention while maintaining high density.
Solution Approach 2:
The patent uses composite materials by combining active material particles with surface-formed oxide layers. The oxide layer acts as a protective composite structure that enhances the stability and reliability of the high-density electrode mixture, preventing material deterioration while maintaining the high energy density achieved through increased particle density.
3Reliability
If a uniform oxide layer is formed on all active material particles, then material protection is improved, but lithium ion distribution uniformity and capacity retention deteriorate
Solution Approach 1:
The patent implements local quality by forming oxide layers with different thicknesses in different regions: a thicker oxide layer (0.5-100 nm) in the first portion near the current collector for enhanced protection during lithium ion insertion/extraction, and a thinner oxide layer (0.1-5 nm) in the second portion to maintain lithium ion distribution uniformity and capacity retention.
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
This design effectively suppresses the deviation of material deterioration across the electrode mixture layer, maintaining high energy density and excellent capacity retention by ensuring uniform lithium ion distribution and reducing resistance.
Implementation Method 1
In the first portion of the electrode mixture layer, a first oxide layer is formed on surfaces of the active material particles... The first oxide layer has a thickness of more than 0.5 nm and 100 nm or less... In the second portion of the electrode mixture layer, a second oxide layer is formed on surfaces of the active material particles... The second oxide layer has a thickness of 0.5 nm or more and less than 100 nm
Implementation Method 2
The electrode mixture layer includes a first portion having the first surface and a second portion having a second surface... The first portion has a thickness of at least 20% of the thickness of the electrode mixture layer... The second portion has a thickness of at least 20% of the thickness of the electrode mixture layer
Data Source
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AI summary
According to one embodiment, an electrode is provided. The electrode includes an electrode mixture layer and a current collector having at least one surface on which the electrode mixture layer is supported. The electrode mixture layer contains active material particles containing Li and at least one transition metal. The electrode mixture layer includes a first surface being in contact with the current collector and a second surface separated by a thickness T of the electrode mixture layer from the first surface. The electrode mixture layer includes a first portion having the first surface and a second portion having the second surface. In each of the first portion and the second portion of the electrode mixture layer, each of a first oxide layer and a second oxide layer is formed on surfaces of the active material particles. The thickness of the first oxide layer is more than the thickness of the second oxide layer.