Segmented Positive Electrode for High-Output Lithium-Ion Batteries
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Solution Overview
Problem
Lithium iron phosphate-based non-aqueous electrolyte secondary batteries face challenges in achieving high energy and output densities due to its lower electron conductivity, requiring a large amount of electrically conductive material, which decreases the positive active material content and battery capacity.
Innovation Solution
A non-aqueous electrolyte secondary battery design with a positive electrode active material layer divided into two regions: one primarily composed of lithium iron phosphate and the other of a lithium-transition metal composite oxide, optimized to reduce the content of electrically conductive material while maintaining high energy and output densities, especially in low State of Charge (SOC) regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large quantity of electrically conductive material is used to reduce resistance in the positive electrode active material layer, then the electron conductivity is improved, but the content proportion of the positive active material decreases and the battery capacity reduces
Solution Approach 1:
The positive electrode active material layer is divided into two distinct regions: a first region containing mainly lithium iron phosphate and a second region containing mainly lithium-transition metal composite oxide. This segmentation allows each region to have optimized conductivity characteristics, with the lithium-transition metal composite oxide providing higher conductivity in the second region, thereby reducing the overall need for electrically conductive material while maintaining good electron conductivity across the electrode.
Solution Approach 2:
Different regions of the positive electrode active material layer are given different material compositions tailored to their specific functions. The first region uses lithium iron phosphate for its electrochemical properties, while the second region uses lithium-transition metal composite oxide for its superior electrical conductivity. This local differentiation optimizes the balance between conductivity and active material content without requiring uniform distribution of electrically conductive material throughout the entire layer.
2Use of energy by moving object
If the content proportion of positive active material is increased to achieve high energy density, then the energy density is improved, but the electron conductivity decreases and output density suffers
Solution Approach 1:
The positive electrode active material layer is segmented into two regions with different material compositions. The first region contains mainly lithium iron phosphate for energy storage, while the second region contains mainly lithium-transition metal composite oxide for enhanced conductivity. This segmentation enables the electrode to achieve both high energy density (through high active material content) and good electron conductivity (through the conductive second region) simultaneously.
Solution Approach 2:
The positive electrode active material layer is constructed as a composite structure combining lithium iron phosphate and lithium-transition metal composite oxide in distinct regions. This composite approach leverages the advantages of both materials: lithium iron phosphate provides stable electrochemical performance and high energy density, while lithium-transition metal composite oxide provides superior electrical conductivity, thereby achieving both high energy density and maintained conductivity.
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 enhances energy and output densities across a wide range of SOC regions, including low SOC conditions, by optimizing the proportions and distribution of lithium iron phosphate and lithium-transition metal composite oxide, thereby improving battery performance and capacity.
Implementation Method 1
non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector
Implementation Method 2
lithium iron phosphate has a lower driving potential than other positive active material materials and has an average charging and discharging potential of approximately 3.4 V (vs. Li/Li+)
Data Source
AI summary
Provided is a non-aqueous electrolyte secondary battery which exhibits excellent energy density and excellent input/output density (and especially output density in low SOC regions). This invention discloses a non-aqueous electrolyte secondary battery that includes a positive electrode, a negative electrode and a non-aqueous electrolyte. The positive electrode includes a positive electrode current collector and a positive electrode active material layers formed on the positive electrode current collector. The positive electrode active material layer has two regions that are demarcated in a surface direction of the positive electrode current collector, which are a first region 14a containing mainly a positive active material of lithium iron phosphate, and a second region 14b containing mainly a positive active material of a lithium-transition metal composite oxide.