Alkaline Battery Separator Pore Structure for Short-Circuit Shielding
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Solution Overview
Problem
Conventional alkaline battery separators face challenges in achieving a balance between sufficient shielding properties to prevent internal short-circuits and high liquid retention, particularly due to limitations in controlling pore diameter and fiber orientation during manufacturing.
Innovation Solution
A separator composed of a wet nonwoven fabric with alkali-resistant cellulose and synthetic fibers, bound by a binder component, with specific pore diameter and liquid retention characteristics, is developed to enhance shielding and liquid retention properties. The fabric has an average pore diameter of 1 to 10 µm, a maximum pore diameter of 20 to 60 µm, and a swelling ratio of 30 to 45% in a 40% KOH solution, achieved through precise control of fiber orientation and refining processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pore diameter of the separator is reduced to improve shielding property, then the shielding property improves, but the liquid retention property deteriorates
Solution Approach 1:
The patent applies local quality by creating a multi-layer structure where different layers have different pore diameter characteristics. The first layer has a smaller average pore diameter for shielding, while the second layer has a larger average pore diameter for liquid retention. Each layer performs its specific function locally, resolving the contradiction between shielding and liquid retention.
Solution Approach 2:
The separator is segmented into multiple layers with different pore diameter characteristics. Instead of using a single uniform layer, the patent divides the separator into a first layer and a second layer, each with optimized pore structures for different functions. This segmentation allows simultaneous achievement of shielding and liquid retention properties.
2Reliability
If the average pore diameter is controlled to improve shielding property, then the shielding property improves, but the ion conduction property deteriorates
Solution Approach 1:
The separator is divided into multiple layers where the first layer with smaller pore diameter provides shielding without significantly blocking ion conduction, while the second layer with larger pore diameter ensures sufficient ion conduction pathways. This segmentation resolves the contradiction between shielding and ion conduction.
Solution Approach 2:
Different layers are assigned different pore diameter characteristics tailored to their specific functions. The first layer locally provides shielding with smaller pores, while the second layer locally provides ion conduction with larger pores, allowing both functions to coexist without mutual interference.
3Duration of action of stationary object
If synthetic fibers and cellulose fibers are mixed to improve durability, then the durability improves, but the shielding property deteriorates
Solution Approach 1:
The patent segments the fiber composition by function, with the first layer primarily using cellulose fibers for shielding and the second layer using synthetic fibers for durability and liquid retention. This functional segmentation allows each fiber type to excel at its designated task without compromising overall performance.
Solution Approach 2:
The separator uses a composite structure combining cellulose fibers and synthetic fibers in different layers. The cellulose-based first layer provides shielding, while the synthetic fiber-containing second layer provides durability and liquid retention, creating a composite material system that achieves multiple properties simultaneously.
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 solution provides improved reliability against internal short-circuits and maintains excellent liquid retention, enhancing the discharging characteristics and shielding properties of alkaline batteries, while also optimizing the aspect ratio of tensile strength for better workability and ion permeability.
Implementation Method 1
a liquid retention rate of the wet nonwoven fabric during immersion in a 40% by mass KOH solution is 400 to 700%
Implementation Method 2
prevention of an internal short circuit due to contact between the positive electrode active material and the negative electrode active material or due to conductive metal oxide capillary crystals (dendrite)
Data Source
Figure 1
AI summary
The present invention provides a separator for alkaline batteries and an alkaline battery improving reliability of prevention in internal short-circuits, and having good liquid retention and shielding property. To achieve this, the separator for alkaline batteries is made from a wet nonwoven fabric which contains at least alkali-resistant cellulose fibers and alkali-resistant synthetic fibers bound using a binder component; wherein an average pore diameter of the wet nonwoven fabric is 1 to 10 µm. Moreover, the separator for alkaline batteries uses the wet nonwoven fabric having a maximum pore diameter of 20 to 60 µm, a liquid retention rate of 400 to 700% during immersion in a 40% by mass KOH solution, and a swelling ratio of 30 to 45% during immersion in a 40% by mass KOH solution.