Lithium-Ion Battery Separator Ratios for Mechanical Abuse Safety
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium-ion batteries face safety concerns due to short circuits between positive and negative electrodes during mechanical abuse, leading to thermal runaway and exothermic reactions.
Innovation Solution
The lithium-ion battery design includes specific ratios for the puncture force and thickness of the separator, positive and negative electrode current collectors, and their respective active layers, reducing short-circuit points and thermal runaway through controlled contact during mechanical abuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the separator and current collectors are made thinner to increase energy density, then the volumetric specific energy improves, but the mechanical strength decreases leading to easier puncture and short circuits during mechanical abuse
Solution Approach 1:
The patent employs composite material structures for both the separator and current collectors. The separator uses a composite of polyolefin base film with ceramic coating layers, while current collectors use metal foils with surface coatings. These composite structures provide enhanced mechanical strength and puncture resistance compared to single-material structures, allowing thinner designs that maintain safety while improving energy density.
Solution Approach 2:
The patent specifies precise parameter ranges for thickness and puncture force: separator thickness 3-16 μm with puncture force 1-8 N, current collector thickness 3-20 μm with puncture force 1-10 N. By optimizing these parameters within defined ranges, the patent achieves the optimal balance between mechanical strength and energy density, preventing both excessive thickness (reducing energy density) and excessive thinness (reducing mechanical strength).
2Reliability
If the separator and current collectors are made stronger and thicker to prevent short circuits during mechanical abuse, then the safety improves, but the volumetric specific energy decreases
Solution Approach 1:
The patent uses composite material structures where the separator combines polyolefin base film with ceramic coating layers, and current collectors combine metal foils with surface coatings. These composites achieve high strength-to-thickness ratios, providing excellent puncture resistance without excessive thickness, thereby maintaining safety while preserving volumetric specific energy.
Solution Approach 2:
The patent defines specific parameter ranges: separator thickness 3-16 μm with puncture force 1-8 N, current collector thickness 3-20 μm with puncture force 1-10 N. These optimized parameters ensure sufficient mechanical strength for safety while minimizing thickness to maintain high energy density, resolving the contradiction between safety and energy efficiency.
3Reliability
If the separator thickness is increased to prevent thermal runaway, then the safety improves, but the ionic conductivity and low temperature performance deteriorate
Solution Approach 1:
The separator uses a composite structure with a polyolefin base film and ceramic coating layers. The ceramic coating provides thermal stability and puncture resistance for safety, while the porous structure and appropriate thickness (3-16 μm) maintain ion transport pathways, preserving ionic conductivity and low-temperature performance despite the enhanced safety features.
Solution Approach 2:
The patent specifies separator thickness of 3-16 μm, which is thin enough to maintain good ion conductivity and low-temperature performance, yet combined with ceramic coating to achieve sufficient puncture force (1-8 N) for safety. This parameter optimization resolves the contradiction between safety and ionic conductivity.
Data Source
AI summary
A lithium-ion battery includes a positive electrode plate, a negative electrode plate and a separator provided between the positive electrode plate and the negative electrode plate. The separator includes a base film; and the puncture force A of the separator, the thickness B of the base film, the puncture force C of the positive electrode current collector, the thickness D of the positive electrode current collector, the puncture force E of the negative electrode current collector and the thickness F of the negative electrode current collector satisfy a specific ratio, the contact between the positive electrode and the negative electrode under mechanical abuses can be reduced, thereby decreasing the formation of short circuit points, reducing heat generation, lowering the probability of thermal runaway, and improving the safety performance of the battery.