Graphite Negative Electrode Plate to Resist Manganese Deposition
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Solution Overview
Problem
Manganese dissolution from the positive electrode in lithium-ion secondary batteries leads to irreversible capacity loss and deteriorates cycle performance due to manganese ions depositing on the negative electrode, disrupting the electrochemical reaction.
Innovation Solution
The negative electrode plate is designed with specific parameters including the ratio of diffraction peak intensities, porosity, and resistivity that prevent manganese entry, maintaining the integrity of the negative active material layer and ensuring high kinetic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the negative electrode plate uses a graphite material with high porosity to improve lithium ion transport, then the rate performance is improved, but manganese ions from the positive electrode can more easily penetrate and deposit on the negative electrode, causing capacity loss
Solution Approach 1:
The patent applies local quality by creating a protective coating layer on the negative electrode surface that has different properties from the bulk graphite material. This coating layer specifically blocks manganese ions while allowing lithium ions to pass through, thereby locally modifying the electrode surface to prevent harmful deposition without affecting the overall high porosity and rate performance of the graphite structure
Solution Approach 2:
The protective coating layer acts as an intermediary between the positive and negative electrodes. It selectively interacts with different ion types: blocking manganese ions from penetrating into the graphite while permitting lithium ions to transport freely. This mediator resolves the contradiction by providing differential selectivity based on ion size and charge characteristics
2Stability of the object's composition
If the negative electrode plate density is increased to improve structural stability, then manganese ion penetration is reduced, but lithium ion transport kinetics are slowed down, reducing rate performance
Solution Approach 1:
The patent segments the negative electrode into two distinct functional zones: a dense protective coating layer at the surface that blocks manganese ions, and a high-porosity graphite bulk interior that facilitates rapid lithium ion transport. This segmentation allows each zone to optimize its local density for its specific function, resolving the contradiction between structural stability and transport kinetics
3Quantity of substance
If the negative electrode plate porosity is increased to improve lithium ion diffusion, then capacity is maintained, but manganese ion deposition is enhanced, leading to capacity loss
Solution Approach 1:
The patent changes the physical-chemical parameters of the negative electrode surface by applying a protective coating with different pore size, surface charge, and chemical composition compared to the bulk graphite. This parameter change creates selective permeability that maintains high lithium ion diffusion through the porous structure while blocking manganese ions based on their different ionic radii and electrochemical properties
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 the cycle performance and rate performance of the lithium-ion secondary battery by reducing manganese deposition and maintaining effective lithium ion channels, thereby improving capacity retention and overall battery stability.
Implementation Method 1
the negative electrode plate can block manganese in the electrolyte outside the negative active material layer, effectively preventing manganese from entering the inside of the negative active material layer
Implementation Method 2
the generated manganese ions are dissolved in the electrolyte, migrated and deposited on the negative electrode, and then the manganese ions are ion-exchanged with lithium in the negative electrode
Implementation Method 3
the negative active material comprises a graphite material... ensuring that the negative active material layer has high kinetic performance of delithiation and lithiation
Implementation Method 4
ensuring that the negative active material layer has high kinetic performance of delithiation and lithiation
Data Source
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AI summary
This application discloses a negative electrode plate and a lithium-ion secondary battery, wherein the negative electrode plate includes a negative electrode current collector and a negative active material layer disposed on at least one surface of the negative electrode current collector, and wherein the negative active material layer includes a graphite material; wherein a ratio r between diffraction peak intensity of (004) crystal surface and diffraction peak intensity of (110) crystal surface of the negative electrode plate, a porosity s of the negative electrode plate, and a resistivity t of the negative electrode plate satisfy: 0.05≤100×sr×t≤10. The negative electrode plate and the lithium-ion secondary battery provided by this application can simultaneously achieve high safety performance, cycle performance and rate performance.