Polyolefin Separator Pore Control for Battery Safety
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Solution Overview
Problem
Existing porous polyolefin resin films used as separators in lithium-ion secondary batteries face issues with lithium dendrite deposition leading to short circuits and clogging, resulting in low safety and output due to large pore diameters and high internal resistance.
Innovation Solution
A porous polyolefin resin film with specific properties, including an average flow rate diameter pressure of 1500 to 2500 kPa, a bubble point pressure of 300 to 1500 kPa, and a ratio of air permeability to bubble point pressure not exceeding 0.35 seconds/(100 ml·kPa), is developed to prevent short circuits and clogging while maintaining high output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large pore diameters are used in the separator, then lithium ion movement efficiency is improved, but short circuits occur due to lithium dendrite deposition
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pore diameter within the range of 0.03-0.08 μm and the porosity within 30-80%. This optimization balances the lithium ion movement efficiency (improved by adequate porosity) with short circuit prevention (achieved by limiting maximum pore size to prevent dendrite penetration), thereby resolving the contradiction between productivity and reliability.
2Productivity
If high porosity is used in the separator, then lithium ion movement is facilitated, but internal resistance increases due to clogging
Solution Approach 1:
The patent optimizes porosity to within 30-80% and controls the pore diameter distribution to 0.03-0.08 μm. This parameter optimization ensures sufficient porosity for lithium ion movement while preventing excessive clogging that would increase internal resistance, effectively balancing productivity with reliability.
Solution Approach 2:
The patent creates a uniform pore size distribution throughout the separator structure, ensuring consistent local properties. This uniformity prevents localized clogging patterns that would increase internal resistance while maintaining overall high lithium ion movement efficiency through adequate porosity.
3Ease of manufacture
If uniform pore size is used, then manufacturing is simplified, but output is reduced due to high internal resistance
Solution Approach 1:
The patent specifies precise parameter ranges (pore diameter 0.03-0.08 μm, porosity 30-80%) that balance manufacturing feasibility with performance. These optimized parameters enable production of separators with controlled pore structures that achieve both ease of manufacture and high battery output by preventing excessive internal resistance.
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 film effectively prevents short circuits and clogging, ensuring high output and safety for lithium-ion batteries by optimizing pore size and structure, allowing for efficient lithium ion movement and electrolyte retention.
Implementation Method 1
the separator has a microporous structure to retain the electrolytic solution and secure a passage to allow lithium ions to move between electrodes
Implementation Method 2
an average flow rate diameter pressure (PAP) is set to 1500 to 2500 kPa; a bubble point pressure (PBP) is set to 300 to 1500 kPa
Data Source
AI summary
This polyolefin resin porous film can be easily produced, and when used as a non-aqueous electrolyte cell separator, can suppress clogging and can evince a high cell output. The polyolefin resin porous film is a porous film having a polyolefin resin as the primary component and is characterized by the average flow diameter pressure (PAP) being 1500-2500 kPa, the bubble point pressure (PBP) being 300-1500 kPa, and the ratio (Pa/PAP) of the air permeability (Pa) and the bubble point pressure (PBP) being no greater than 0.35 sec/(100 ml·kPa).