Alkaline Dry Battery Cathode Density Layout for Swelling Control
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Solution Overview
Problem
In alkaline dry batteries, increasing the density of manganese dioxide in the positive electrode to enhance capacity leads to significant expansion during discharge, particularly at the center of the battery, causing an increase in the outer diameter and potential jamming or failure in devices.
Innovation Solution
The alkaline dry battery design incorporates a positive electrode with manganese dioxide and a conductive agent, where the average density of manganese dioxide is maintained between 2.80 to 3.00 g/cm³, with a center density 98% or less of the average end densities, and surface hardness 48% or less of the average end surface hardness, to manage expansion and prevent outer diameter increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the density of manganese dioxide in the positive electrode is increased to enhance capacity, then the battery capacity is improved, but the outer diameter of the battery increases due to expansion during discharge
Solution Approach 1:
The patent applies local quality by creating a non-uniform density distribution of manganese dioxide within the positive electrode pellets. The center portion has a lower density (98% or less of the average end density) compared to the end portions, which allows the center to expand more during discharge without increasing the overall outer diameter. This localized density variation resolves the contradiction by enabling high capacity through overall high density while preventing outer diameter increase through strategic low-density zones.
Solution Approach 2:
The patent changes the density parameter of manganese dioxide from a uniform distribution to a controlled non-uniform distribution. Specifically, the density at the center portion is reduced to 98% or less of the average end density, creating a density gradient that accommodates expansion. This parameter change allows the battery to maintain high capacity while suppressing outer diameter increase during discharge.
2Quantity of substance
If the density of manganese dioxide is increased to secure high capacity, then the capacity is improved, but the surface hardness decreases leading to potential structural issues
Solution Approach 1:
The patent applies local quality by creating different density and hardness characteristics in different regions of the positive electrode. The end portions maintain higher density and consequently higher surface hardness, providing structural strength. The center portion has lower density and lower surface hardness (48% or less of average end surface hardness), allowing expansion without compromising overall structural integrity. This spatial differentiation resolves the contradiction between high capacity and adequate strength.
Solution Approach 2:
The patent changes the surface hardness parameter by controlling the density distribution of manganese dioxide. The surface hardness at the center portion is reduced to 48% or less of the average end surface hardness through controlled density reduction. This parameter change allows the center to be more compliant for expansion while the ends maintain sufficient hardness for structural support, resolving the capacity-strength contradiction.
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
This configuration secures high capacity while suppressing the increase in the battery's outer diameter, reducing the risk of jamming and maintaining structural integrity.
Implementation Method 1
manganese dioxide expands at the time of discharging, so that the entire positive electrode expands
Data Source
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AI summary
An alkaline dry battery includes a bottomed cylindrical battery case; a positive electrode packed in the battery case and including n hollow cylindrical pellets; a negative electrode disposed in a hollow portion of the pellets; a separator interposed between the positive electrode and the negative electrode; and an alkaline electrolytic solution. The positive electrode includes manganese dioxide and a conductive agent, n is an integer of 1 or more, and an average density of manganese dioxide of the positive electrode is 2.80 to 3.00 g/cm3. The density dc of manganese dioxide in the center portion in the height direction of the positive electrode is 98% or less of an average value de of density of manganese dioxide in each of both end portions.