Multi-Layer Lithium Cathode Structure for Thick-Electrode Polarization
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Solution Overview
Problem
Lithium secondary batteries with thick-film electrode plates experience performance deterioration due to non-uniform charge/discharge characteristics and polarization, especially when using NCM-based cathode active materials, which are vulnerable to high-voltage instability and polarization-induced potential differences.
Innovation Solution
A cathode with a multi-layer structure comprising different cathode active materials, where a high Ni content layer is close to the current collector and a low Ni content layer is close to the separator, minimizing polarization and improving lifespan characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the film thickness of the electrode plate is increased to achieve high capacity, then the battery capacity is improved, but the polarization during charging and discharging increases due to longer movement distance of electrons and lithium ions
Solution Approach 1:
The electrode plate is divided into multiple regions with different thicknesses. Specifically, a first region with greater thickness is provided to increase overall capacity, while a second region with smaller thickness is provided to reduce polarization and improve charge/discharge uniformity. This segmentation allows different parts of the electrode to serve different functions.
Solution Approach 2:
Different regions of the electrode plate are given different local properties through varying thickness. The first region has larger thickness for high capacity, while the second region has smaller thickness for low polarization. This local quality variation optimizes both capacity and performance uniformity across the electrode.
2Quantity of substance
If NCM-based cathode active material is used to increase capacity and reduce cost, then the battery capacity is improved and cost is reduced, but high-voltage stability deteriorates and polarization increases
Solution Approach 1:
The cathode active material composition is varied locally across different regions. The first region uses NCM-based material with higher nickel content for high capacity, while the second region uses material with lower nickel content for improved high-voltage stability. This local composition variation allows both high capacity and voltage stability to be achieved simultaneously.
Solution Approach 2:
The cathode uses a composite structure combining different NCM-based materials with varying nickel contents in different regions. This composite approach allows the battery to benefit from both the high capacity of high-nickel material and the voltage stability of low-nickel material.
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 multi-layer cathode structure enhances battery capacity while suppressing deterioration and improving lifespan and high-temperature stability, making it suitable for high-capacity lithium secondary batteries.
Implementation Method 1
electrical energy is produced by an oxidation-reduction reaction occurring when lithium ions are absorbed/desorbed in/from a cathode and an anode
Implementation Method 2
the increase in film thickness of the electrode plate due to thickening causes an increase in a polarization during charging and discharging. This polarization is caused by a potential difference in the thickness direction of the electrode plate.
Data Source
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AI summary
Provided are a cathode for a secondary battery, a manufacturing method therefor, and a lithium secondary battery comprising same, the cathode comprising: a cathode current collector; a first layer which is arranged on at least one surface of the cathode current collector and which comprises a first cathode active material; and a second layer which is arranged on the first layer and which comprises a second cathode active material, wherein the first cathode active material is represented by the following chemical formula 1, the second cathode active material is represented by the following chemical formula 1 or 2, and the first cathode active material and the second cathode active material are different from each other. <Chemical formula 1> LixNiyM1-yO2 <Chemical formula 2> LiαCoβM'1-βO2 See the Detailed Description of the Invention for the definitions of x, y, a, p, M and M' in the formulas.