Negative Electrode Undercoating for Stronger Battery Layer Bonding
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Solution Overview
Problem
Existing lithium-ion batteries face issues with the detachment of negative active material layers from the current collector due to volume expansion, leading to film exfoliation, increased internal resistance, and deteriorated cycle performance.
Innovation Solution
A negative electrode plate design featuring an undercoating layer with single-walled carbon nanotubes and a G/D ratio of 15 to 120, which enhances the bonding force between the active material and the current collector while maintaining low internal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional negative active material layer is directly applied to the current collector, then the manufacturing process is simple, but the bonding force is low and film exfoliation occurs during volume expansion
Solution Approach 1:
An undercoating layer is introduced as an intermediary between the current collector and the negative active material layer. This undercoating layer comprises carbon nanotubes, conductive polymer, and binder, serving as a buffer that accommodates volume expansion while maintaining strong bonding to both the current collector and the active material layer, thereby preventing film exfoliation.
Solution Approach 2:
The undercoating layer is composed of a composite material system including carbon nanotubes for structural support and conductivity, conductive polymer for flexibility and bonding, and binder for adhesion. This composite structure provides both mechanical strength to prevent exfoliation and electrical conductivity to maintain performance.
2Reliability
If the negative active material layer is directly applied to the current collector, then the internal resistance may be low initially, but the cycle performance deteriorates due to film exfoliation
Solution Approach 1:
The undercoating layer is applied in advance to the current collector before the negative active material layer. This preliminary action creates a protective interface that anticipates and prevents the volume expansion-induced detachment that would otherwise occur during cycling, thereby ensuring long-term reliability.
Solution Approach 2:
The undercoating layer acts as a mediator that absorbs mechanical stress from volume expansion, preventing the transmission of damaging forces to the interface between the active material layer and current collector, thus maintaining cycle performance.
3Reliability
If carbon nanotubes with low G/D ratio are used in the undercoating layer, then the bonding force is high, but the internal resistance increases
Solution Approach 1:
The G/D ratio of carbon nanotubes in the undercoating layer is specifically controlled within the range of 1 to 6. This parameter optimization balances the structural integrity and conductivity of the nanotubes, ensuring both adequate bonding force and low internal resistance for optimal battery performance.
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 proposed design achieves a high bonding force and low internal resistance, improving the cycle performance and first-cycle Coulombic efficiency of lithium-ion batteries.
Implementation Method 1
The inorganic conductive agent includes single-walled carbon nanotubes. A G/D ratio of a Raman spectrum of the single-walled carbon nanotubes is 15 to 120
Data Source
AI summary
A negative electrode plate includes a negative current collector, an undercoating layer disposed on a surface of the negative current collector, and a negative active material layer disposed on a surface of the undercoating layer. The undercoating layer includes an inorganic conductive agent, a conductive polymer, and a binder. The inorganic conductive agent includes single-walled carbon nanotubes. A G/D ratio of a Raman spectrum of the single-walled carbon nanotubes is 15 to 120.