CNT Negative Electrode Structure to Suppress Binder Migration
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Solution Overview
Problem
The adhesion between the negative electrode active material layer and the current collector in lithium secondary batteries is compromised due to binder migration during the electrode preparation process, leading to reduced productivity and performance.
Innovation Solution
A negative electrode design incorporating carbon nanotube structures with specific properties, including a network formed by bonded single-walled carbon nanotube units, is used to enhance adhesion by suppressing binder migration and maintaining conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional negative electrode without binder is used, then the electrode structure is simple and manufacturing is easier, but the electrode strength is insufficient and cycle stability deteriorates
Solution Approach 1:
The patent uses porous carbonized resin particles as the core component of the negative electrode. These particles provide both structural integrity and lithium ion insertion/extraction sites. The porous structure allows lithium ions to penetrate deeply into the particle interior, enhancing capacity while maintaining electrode strength without requiring additional binder materials.
Solution Approach 2:
The negative electrode is constructed as a composite structure consisting of carbonized resin particles combined with conductive carbon materials and lithium compound particles. This composite approach provides mechanical strength through the carbon matrix while the lithium compounds provide electrochemical activity, eliminating the need for separate binder components.
2Quantity of substance
If lithium powder or metal lithium is used as lithium source, then lithium ion supply is sufficient, but safety issues arise due to dendrite formation and internal stress
Solution Approach 1:
The patent changes the physical and chemical parameters of the lithium source by using lithium compounds (such as lithium carbonate, lithium hydroxide, or lithium oxide) instead of metallic lithium or lithium powder. These compounds have lower reactivity, preventing dendrite formation and internal stress while still providing sufficient lithium ions through electrochemical reactions during charging cycles.
Solution Approach 2:
The lithium compounds used in the electrode act as a sacrificial lithium source that gradually releases lithium ions during initial charging cycles. Once the lithium ions are extracted from these compounds, they are effectively consumed, providing a controlled and safe lithium supply mechanism that eliminates safety hazards associated with metallic lithium.
3Quantity of substance
If high-capacity lithium compounds are used in the negative electrode, then charge-discharge capacity is improved, but internal stress increases causing particle disintegration
Solution Approach 1:
The patent applies local quality by creating a multi-component structure where different materials serve different functions. The carbonized resin particles provide mechanical strength and structural stability, while the lithium compounds embedded within or on the surface of these particles provide high-capacity lithium ion storage. This spatial differentiation allows the electrode to achieve high capacity without compromising particle integrity.
Solution Approach 2:
The carbonized resin matrix acts as a cushioning structure that accommodates the volume changes and internal stresses generated by lithium compounds during charge-discharge cycles. This pre-existing structural framework prevents particle disintegration by distributing mechanical stresses throughout the electrode, allowing the use of high-capacity lithium compounds without sacrificing particle integrity.
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 carbon nanotube structures improve negative electrode adhesion, maintain conductivity, and enhance battery life performance while increasing productivity by preventing binder migration and reducing resistance.
Implementation Method 1
a negative electrode for a secondary battery, which comprises: porous carbonized resin particles; and lithium compound particles, wherein the lithium compound particles are present inside and/or on the surface of the porous carbonized resin particles
Data Source
Figure 1
AI summary
The present invention relates to a negative electrode including a negative electrode active material layer, wherein the negative electrode active material layer includes a negative electrode active material, a binder, a conductive agent, and a dispersant, wherein the conductive agent includes a carbon nanotube structure in which a plurality of single-walled carbon nanotube units are bonded side by side, the carbon nanotube structure has an average length of 1 um to 20 um, and QBR according to Equation 1 is in a range of 1 to 1.75. QBR=Bs/Bf wherein Bs is an average value of the number of binders which is measured in a range from an upper surface of the negative electrode active material layer to a distance corresponding to 15% of a total thickness of the negative electrode active material layer in a direction toward a lower surface of the negative electrode active material layer, and Bf is an average value of the number of binders which is measured in a range from the lower surface of the negative electrode active material layer to a distance corresponding to 15% of the total thickness of the negative electrode active material layer in a direction toward the upper surface of the negative electrode active material layer.