Alkaline Battery Separator with Layered Cellulose Structure
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Solution Overview
Problem
Alkaline battery separators face challenges in achieving both satisfactory electrolyte retention and anti-short circuit capability, with conventional separators either compromising on liquid impregnate property or increasing internal resistance due to dendrite formation and impact susceptibility.
Innovation Solution
A laminate structure comprising a coarse layer and a dense layer, where the coarse layer contains a specific ratio of alkaline-resistant cellulose fibers with varying Canadian Standard Freeness (CSF) values, reducing maximum pore size and enhancing electrolyte retention, while the dense layer provides improved impact resistance and anti-short circuit properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the separator uses a dense layer to prevent short-circuiting, then anti-short circuit capability is improved, but liquid impregnate property deteriorates
Solution Approach 1:
The separator is divided into two distinct layers: a dense layer (5-20 μm) for anti-short circuit capability and a coarse layer (20-50 μm) for liquid impregnation. This segmentation allows each layer to specialize in one function, resolving the contradiction between density and liquid absorption.
Solution Approach 2:
Different regions of the separator have different structures optimized for different functions. The dense layer adjacent to electrodes provides barrier function, while the coarse layer provides liquid reservoir and conduction function. This local differentiation resolves the contradiction by applying appropriate density only where needed for short-circuit prevention.
2Reliability
If the separator uses highly densified structure to prevent dendrite penetration, then anti-short circuit capability is improved, but internal resistance increases
Solution Approach 1:
The separator separates the barrier function (dense layer) from the conduction function (coarse layer). The dense layer prevents dendrite penetration with thickness 5-20 μm, while the coarse layer provides low-resistance ion conduction pathways, thus resolving the contradiction between density and internal resistance.
3Quantity of substance
If the separator uses unbeaten or unrefined fibers in the liquid impregnate layer, then liquid impregnate property is improved, but pore size increases leading to dendrite formation
Solution Approach 1:
The separator divides the liquid impregnation function (coarse layer with unbeaten fibers) from the barrier function (dense layer with small pores). The coarse layer uses unbeaten cellulose fibers to maximize liquid absorption without concern for pore size, while the dense layer provides the necessary barrier against dendrites.
4Volume of moving object
If the separator occupies small space to increase active material amount, then battery capacity is improved, but impact resistance deteriorates
Solution Approach 1:
The separator uses a thin dense layer (5-20 μm) adjacent to electrodes for space efficiency, combined with a thicker coarse layer (20-50 μm) for impact resistance. This local differentiation allows the separator to be thin overall while maintaining buckling resistance through the coarse layer's structural properties.
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 proposed separator achieves effective electrolyte retention, prevents short-circuiting due to dendrites, and offers enhanced impact resistance, ensuring better discharge performance and prolonged battery life.
Implementation Method 1
a coarse layer (A) and a dense layer (B) denser than the coarse layer, the coarse layer (A) including an alkaline-resistant synthetic fiber (A), an alkaline-resistant binder fiber (A) and an alkaline-resistant cellulose fiber (A)
Implementation Method 2
A separator is interposed between the cathode and the anode to separate these electrodes and prevent short-circuiting
Implementation Method 3
withstand, after incorporated into a battery, buckling caused by impacts due to vibrations or accidental drops during transport or handling
Data Source
AI summary
Provided are an alkaline battery separator and an alkaline battery including the separator. The separator includes at least a coarse layer and a dense layer denser than the coarse layer. The coarse layer contains an alkaline-resistant cellulose fiber having a freeness value of 350 to 650 ml as a whole in the proportion of 25 to 65% by weight. The alkaline-resistant cellulose fiber includes at least two kinds of alkaline-resistant cellulose fibers having different freeness with each other. The difference in freeness value between the alkaline-resistant cellulose fibers having the highest and lowest freeness values is 300 to 700 ml. The dense layer contains an alkaline-resistant cellulose fiber which as a whole has a freeness value of 0 to 400 ml. The separator has a maximum pore size of 65 µm or smaller, and a liquid absorption capacity of 5 g/g or higher.