Negative Electrode Roughness and Binder Layer for Fast Charging
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Solution Overview
Problem
Existing rechargeable lithium batteries face challenges in achieving high-energy density, high-capacity, and fast charge characteristics due to inadequate adhesion between the negative active material layer and the current collector, leading to capacity fading and reduced cycle-life.
Innovation Solution
A negative electrode design featuring a surface roughness of 2 µm to 8 µm for the negative active material layer, combined with a binder layer between the current collector and the negative active material layer, enhances adhesion and maintains stability during charging and discharging, thereby improving adhesion and fast charge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a smooth negative active material layer is used, then manufacturing is easier, but adhesion to current collector deteriorates and cycle-life reduces
Solution Approach 1:
The patent applies surface roughening to create a curved/uneven surface topology on the negative active material layer with controlled roughness (Ra 0.5-5 μm). This curvature increase enhances mechanical interlocking with the current collector, resolving the adhesion problem while maintaining manufacturing feasibility through controlled coating processes.
Solution Approach 2:
The patent introduces local quality variation by creating specific surface roughness characteristics in the negative active material layer. Different regions have optimized roughness properties to balance adhesion enhancement with manufacturing ease, allowing the surface to provide improved bonding without requiring complete restructuring of the coating process.
2Reliability
If surface roughness is increased to improve adhesion, then cycle-life improves, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent optimizes specific parameters including surface roughness (Ra 0.5-5 μm), binder content (5-20 wt%), and curing conditions to achieve the desired balance between adhesion and manufacturability. By controlling these parameters within specific ranges, the patent maintains manufacturing precision while achieving the roughness needed for improved cycle-life.
Solution Approach 2:
The patent applies partial roughening rather than complete surface restructuring, using moderate roughness levels (Ra 0.5-5 μm) that provide sufficient adhesion improvement without excessive manufacturing complexity. This partial action approach achieves the necessary performance enhancement while maintaining practical manufacturing control.
3Strength
If binder content is increased to improve adhesion, then adhesion strength improves, but energy density decreases
Solution Approach 1:
The patent optimizes binder content within a specific range (5-20 wt%) to achieve the minimum necessary adhesion strength without excessive binder addition. This parameter optimization ensures sufficient bonding while minimizing the volume occupied by non-active materials, thereby preserving energy density.
Solution Approach 2:
The patent uses partial action by applying just enough binder (5-20 wt%) to achieve adequate adhesion without over-binding. This controlled approach provides sufficient bonding strength while avoiding the energy density penalty that would result from excessive binder content.
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 design achieves improved adhesion, leading to enhanced cycle-life characteristics and high-rate charge and discharge performance, with the binder layer maintaining stability even during volume changes of the active material.
Implementation Method 1
a binder layer between the current collector and the negative active material layer, wherein the negative active material layer has a surface roughness of about 2 μm to about 8 μm
Implementation Method 2
a negative electrode including an active material capable of intercalating and deintercalating lithium ions
Implementation Method 3
Electrical energy is produced by oxidation and reduction reactions when lithium ions are intercalated/deintercalated at the positive and negative electrodes
Data Source
Figure 1
Figure 2(A)~2(D)
Figure 3
AI summary
Examples of this disclosure include a negative electrode for a rechargeable lithium battery, and a rechargeable lithium battery including the same. The negative electrode for the rechargeable lithium battery includes a current collector, a negative active material layer, and a binder layer between the current collector and the negative active material layer, wherein the negative active material layer has a surface roughness of about 2 µm to about 8 µm.