Battery Separator Pore Gradient for Fast Charging Without Lithium Plating
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Solution Overview
Problem
Lithium-ion batteries face challenges in fast charging performance due to differences in lithium ion intercalation and deintercalation capabilities between positive and negative electrode materials, leading to lithium precipitation on the negative electrode surface.
Innovation Solution
A secondary battery design featuring a separator with a bimodal pore size distribution, where the pore size on the side facing the negative electrode is larger than on the side facing the positive electrode, within specific ranges (60 nm to 500 nm and 5 nm to 55 nm respectively), to control lithium ion transmission velocity and prevent precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the charging rate is increased to improve fast charging performance, then the transmission speed of lithium ions between electrodes is improved, but lithium ions precipitate on the negative electrode surface due to mismatched intercalation/deintercalation capabilities
Solution Approach 1:
The separator is designed with asymmetric pore size distribution, where the pore size on the negative electrode side (60-500 nm) is larger than on the positive electrode side (5-55 nm). This local structural differentiation allows faster lithium ion transmission to the negative electrode, matching its lower intercalation capability during fast charging, while preventing lithium precipitation through controlled pore geometry.
2Productivity
If the pore size on the negative electrode side is increased to facilitate lithium ion transmission, then fast charging performance is improved, but the separator structure becomes more complex
Solution Approach 1:
The invention optimizes specific pore size parameters within defined ranges (60-500 nm on negative electrode side, 5-55 nm on positive electrode side) to achieve fast charging performance. By controlling pore size as a key parameter rather than changing overall separator complexity, the solution maintains structural simplicity while improving productivity.
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 controlled pore size distribution improves fast charging performance and reduces lithium precipitation, enhancing the overall cycling performance and safety of the secondary battery.
Implementation Method 1
lithium ions continuously intercalate and deintercalate between positive and negative electrode materials, and shuttle back and forth between positive and negative electrodes through an electrolyte
Implementation Method 2
the transmission speed of lithium ions in the separator is controlled, so that the number of lithium ions that can be transmitted to the negative electrode plate through the separator matches the number of lithium ions that can be intercalated into the negative electrode material
Data Source
Figure 1~2
AI summary
A secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. The separator includes a base film, where a pore size distribution of the base film is a bimodal distribution. A pore size on a side of the base film facing the negative electrode plate is larger than a pore size on a side of the base film facing the positive electrode plate. The pore size on the side of the base film facing the negative electrode plate is 60 nm to 500 nm, and the pore size on the side of the base film facing the positive electrode plate is 5 nm to 55 nm. This can improve the fast charging performance of the secondary battery and alleviate lithium precipitation.