Layered Positive Electrode Structure for Penetration-Resistant Li-Ion Cells
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Solution Overview
Problem
Existing lithium secondary batteries face issues with low penetration resistance when pierced by external objects, leading to potential ignition or explosion, despite having high capacity and thermal stability requirements for applications like electric vehicles.
Innovation Solution
A positive electrode structure with two distinct layers, where the first layer contains smaller particles and a higher specific surface area, enhancing adhesive force with the current collector, and the second layer has larger particles, reducing elongation and increasing resistance to penetration, thereby improving safety and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional positive electrode is used, then the battery structure is simple, but the battery cannot be charged at high rates due to poor Li ion permeability
Solution Approach 1:
The positive electrode is segmented into multiple layers including a current collector, positive electrode active material layer, and buffer layer. This layered segmentation allows each layer to perform its specific function optimally, enabling high-rate charging while maintaining structural integrity
Solution Approach 2:
The invention introduces a buffer layer that is positioned between the current collector and the positive electrode active material layer, adding a new dimensional layer to the electrode structure. This additional layer provides a pathway for Li ion permeation that enhances charging rate without fundamentally complicating the overall electrode architecture
2Reliability
If the positive electrode is designed for high Li ion permeability, then charging rate improves, but the electrode structure becomes complex
Solution Approach 1:
A buffer layer acts as an intermediary between the current collector and the positive electrode active material layer. This intermediary layer facilitates Li ion transport and provides a stable interface, improving reliability without requiring complex structural modifications to the active material itself
Solution Approach 2:
The buffer layer is designed with porous characteristics that enhance Li ion permeability. The porous structure provides multiple pathways for ion transport, improving reliability while maintaining a relatively simple layered electrode configuration
3Speed
If a buffer layer is introduced to improve Li ion permeability, then charging rate increases, but the number of components increases
Solution Approach 1:
The buffer layer serves multiple functions simultaneously: it provides a pathway for Li ion permeation, maintains structural stability during charging/discharging cycles, and facilitates efficient electron transport. This multi-functionality allows the electrode to achieve high charging rates without requiring multiple separate components for each function
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 dual-layer structure enhances penetration resistance, reduces short circuit risk, and ensures safe operation by minimizing contact area and increasing resistance, thus preventing overcharge and improving overall battery safety.
Implementation Method 1
it has been difficult to charge at a high rate due to poor Li ion permeability, and it has also been difficult to obtain sufficient electron conduction
Implementation Method 2
10 to 40 wt % of a binder based on the total weight of the positive electrode active material
Data Source
Figure 1~2
AI summary
The present technology relates to a positive electrode for a lithium secondary battery, and the positive electrode includes: a first positive electrode mixture layer contacting a positive electrode current collector; and at least one second positive electrode mixture layer arranged on the first positive electrode mixture layer. Herein, the first positive electrode mixture layer includes a first positive electrode active material and a first binder, and the second positive electrode mixture layer includes a second positive electrode active material and a second binder. Further, an average particle diameter (D50) the first positive electrode active material is smaller than an average particle diameter (D50) of the second positive electrode active material and is equal to or less than 3µm, and a specific surface area(BET) of the first positive electrode active material is equal to or greater than 3 m2/g.