Double-Layer Positive Electrode Plate for Lower Charging Polarization
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Solution Overview
Problem
Battery polarization, particularly electrochemical and concentration polarization, adversely affects the capacity and cycling performance of lithium-ion batteries, limiting their development and application in energy storage and electric vehicles.
Innovation Solution
A positive electrode plate with a double-layer structure, comprising a lithium-containing phosphate of olivine structure as the lower layer and a cobalt-containing lithium metal oxide as the upper layer, to match lithium-ion kinetics with current density distribution, reducing charging polarization and improving battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer positive electrode structure is used, then the device complexity is low, but the charging polarization is high and capacity performance is limited
Solution Approach 1:
The positive electrode is divided into two distinct layers: a first positive electrode layer containing lithium-containing phosphate of olivine structure, and a second positive electrode layer containing cobalt-containing lithium metal oxide. This segmentation allows each layer to perform specialized functions, with the first layer providing stable structure and the second layer providing high lithium-ion kinetics, thereby reducing charging polarization without excessive complexity increase.
Solution Approach 2:
Different regions of the positive electrode are assigned different material compositions and properties. The first layer uses lithium-containing phosphate for structural stability, while the second layer uses cobalt-containing lithium metal oxide for superior lithium-ion conductivity. This local differentiation optimizes performance at each interface, particularly at the electrolyte-contacting upper layer, reducing polarization effects.
2Ease of manufacture
If lithium-ion kinetics are not optimized in the positive electrode, then the manufacturing process is simple, but the capacity performance and cycling performance are poor
Solution Approach 1:
The patent optimizes the lithium-ion kinetics by changing the material composition parameter of the second positive electrode layer to cobalt-containing lithium metal oxide, which has superior lithium-ion conductivity compared to traditional materials. This parameter change in material composition directly improves capacity performance and cycling performance while maintaining a manufacturable double-layer structure.
3Ease of manufacture
If the positive electrode material distribution is uniform, then the manufacturing process is simple, but the current density distribution does not match lithium-ion kinetics, leading to high polarization
Solution Approach 1:
The patent implements non-uniform material distribution by placing cobalt-containing lithium metal oxide in the second layer that contacts the electrolyte, where high lithium-ion kinetics are most needed. The lithium-containing phosphate is placed in the first layer closer to the current collector. This spatial differentiation of material properties matches current density distribution and reduces polarization voltage.
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
The double-layer structure effectively reduces charging polarization, enhances capacity maintenance, and improves cycling performance by optimizing lithium-ion conductivity and electrolyte infiltration, thus enhancing battery efficiency.
Implementation Method 1
the second positive electrode active material with better lithium-ion kinetics is arranged on the upper layer of the positive electrode film layer with a better electrolyte infiltration degree
Implementation Method 2
concentration polarization of an electrolyte solution on the battery performance
Data Source
AI summary
The positive electrode plate comprises a current collector, a first positive electrode active material layer, and a second positive electrode active material layer; the first positive electrode active material layer is arranged on at least one side of the current collector, and the second positive electrode active material layer is arranged on the first positive electrode active material layer; the first positive electrode active material layer comprises a first positive electrode active material, the second positive electrode active material layer comprises a second positive electrode active material, the first positive electrode active material comprises a lithium-containing phosphate of olivine structure, and the second positive electrode active material comprises a cobalt-containing lithium metal oxide. The positive electrode plate can effectively improve the influence of the concentration polarization of a battery on the performance of the battery, thereby helping to improve the capacity and cycle performance of the battery.