Multi-Layer Cathode Structure for Thick-Film Battery Polarization
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Solution Overview
Problem
Thick-film electrode plates in lithium secondary batteries suffer from non-uniform charge/discharge characteristics, leading to increased polarization and deterioration of overall battery performance.
Innovation Solution
A cathode with a novel multi-layer structure is proposed, comprising a cathode current collector, a first layer with a high Ni content lithium transition metal oxide, and a second layer with a low Ni content lithium transition metal oxide, to mitigate polarization and improve 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 increases and charge/discharge characteristics deteriorate
Solution Approach 1:
The cathode active material layer is divided into multiple sub-layers with different compositions and thicknesses. This segmentation allows each sub-layer to contribute differently to the overall performance, enabling high capacity while maintaining good charge/discharge characteristics by reducing polarization effects in any single thick layer.
Solution Approach 2:
Different regions of the cathode active material layer are assigned different compositions and thicknesses. The local quality varies across the layer, with specific areas optimized for capacity while other areas are optimized for electrochemical performance, thereby resolving the contradiction between high capacity and good charge/discharge characteristics.
2Ease of manufacture
If a thick-film electrode plate is used to reduce substrate thickness and lower unit cost, then manufacturing cost is reduced, but battery performance deteriorates due to increased electron and lithium ion movement distance
Solution Approach 1:
The thick cathode active material layer is segmented into multiple thinner sub-layers, which maintains the overall thickness for high capacity and cost-effectiveness while reducing the electron and lithium ion movement distance within each sub-layer, thereby preserving battery performance.
Solution Approach 2:
The problem of long movement distance in a thick layer is addressed by introducing a vertical dimension through multi-layer structure. Each sub-layer provides a shorter diffusion path, effectively reducing the movement distance in the thickness direction while maintaining the overall electrode thickness for high capacity.
3Quantity of substance
If NCM-based cathode active material is mixed with LCO to increase capacity and reduce cost, then battery capacity and cost are improved, but high-voltage stability decreases and potential increases due to polarization
Solution Approach 1:
The cathode is segmented into multiple sub-layers with different compositions (NCM and LCO in different ratios). This segmentation allows the high-capacity NCM material to be combined with the high-stability LCO material in a controlled manner, achieving high overall capacity while maintaining high-voltage stability through the stabilizing effect of LCO in specific sub-layers.
Solution Approach 2:
The cathode uses a composite structure of NCM-based and LCO-based active materials arranged in a multi-layer configuration. This composite material approach combines the high capacity of NCM with the high voltage stability of LCO, achieving both improved capacity and maintained stability that cannot be achieved with either material alone.
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 effectively suppresses deterioration due to polarization, enhancing the lifespan characteristics and high-temperature stability of lithium secondary batteries.
Implementation Method 1
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
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.LixNiyM1−yO2 <Chemical formula 1>LiαCoβM′1−βO2 <Chemical formula 2>See the Detailed Description of the Invention for the definitions of x, y, a, p, M and M′ in the formulas.