Multilayer Cathode Binder Structure for Overcharge Heat Suppression
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Solution Overview
Problem
Lithium secondary batteries face instability and risk of overheating during overcharging, leading to potential explosions due to the separation of electrode layers and inadequate flame retardation, which existing technologies fail to adequately address.
Innovation Solution
A positive electrode with a multilayer structure, comprising a first layer with a melamine-based binder and a second layer with a different binder, enhances adhesion and stability by controlling temperature and reducing gas generation during overcharging, utilizing a melamine-based compound to absorb heat and prevent internal short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a melamine-based flame retardant is added to prevent cell ignition during overcharge, then flame retardant properties are improved, but electrode adhesion deteriorates causing separation between electrode active material layer and current collector layer
Solution Approach 1:
The electrode structure is segmented into multiple layers with different binder compositions. The first layer (near current collector) uses melamine-based binder for flame retardation, while the second layer (outer layer) uses non-melamine binder for adhesion, dividing the electrode into functional zones that resolve the contradiction between flame retardancy and adhesion
Solution Approach 2:
Different regions of the electrode are assigned different binder qualities: the inner layer near the current collector has high melamine content for flame retardation, while the outer layer has low or no melamine content for optimal adhesion. This local differentiation allows each region to perform its specific function without compromising the other
2Quantity of substance
If overcharge protection is delayed, then charging capacity is improved, but cell temperature increases causing internal short circuit and potential explosion
Solution Approach 1:
The melamine-based binder acts in advance during normal charging to suppress exothermic reactions between the positive electrode active material and electrolyte. By preventing heat generation early in the charging process, the binder enables higher charging capacity without subsequent temperature rise that would lead to internal short circuit
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 multilayer structure effectively prevents overheating and adhesion issues, reducing the risk of ignition and improving the overall stability and safety of lithium secondary batteries during overcharging.
Implementation Method 1
the adhesion of an electrode is deteriorated, and thus an electrode active material layer and a current collector layer are separated when the electrode is prepared
Implementation Method 2
a first mixture layer of a positive electrode active material and a reaction inhibitor which inhibits a thermal reaction between the positive electrode active material and a nonaqueous electrolyte
Data Source
Figure 1
AI summary
The present invention provides a positive electrode for a secondary battery including a positive electrode active material layer formed on a surface of a positive electrode collector, wherein the positive electrode active material layer has a multilayer structure including a first positive electrode active material layer formed on the positive electrode collector and a second positive electrode active material layer formed on the first positive electrode active material layer, the first positive electrode active material layer includes a positive electrode active material, a first binder which is a melamine-based compound, and a second binder which is different from the melamine-based compound, and the second positive electrode active material layer includes a second positive electrode active material and the first binder which is a melamine-based compound, and provides a lithium secondary battery including the positive electrode for a secondary battery.