Alkaline Battery Positive Electrode Pore Volume Optimization
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Solution Overview
Problem
Alkaline batteries face difficulties in enhancing discharge characteristics in the middle-rate current range, as increasing the loading weight of manganese dioxide leads to reduced diffusion rates due to expansion of manganese dioxide particles during discharge, limiting their capacity and duration in this current range.
Innovation Solution
The alkaline batteries incorporate a positive electrode with a higher loading weight of manganese dioxide and a specific range of cumulative pore volumes (0.0035 ml/g to 0.0070 ml/g) to maintain diffusion paths for the electrolyte, ensuring enhanced discharge characteristics in both low- and middle-rate current ranges by adjusting the pressure during the formation of the positive electrode material mixture pellet to form and maintain larger gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the loading weight of manganese dioxide is increased to enhance capacity, then the discharge capacity increases, but the diffusion rate of electrolyte decreases due to expansion of manganese dioxide particles during discharge
Solution Approach 1:
The patent applies porous materials by controlling the pore volume of the positive electrode material mixture to be 0.0035 ml/g to 0.0070 ml/g. This porous structure maintains diffusion paths for the electrolyte even when manganese dioxide particles expand during discharge, thereby preserving the diffusion rate while allowing increased loading weight of manganese dioxide for higher capacity.
Solution Approach 2:
The patent changes physical parameters by optimizing the pore volume within a specific range (0.0035 ml/g to 0.0070 ml/g) and controlling the loading weight of manganese dioxide to be 9.30 g or more. These parameter changes enable simultaneous achievement of high capacity and maintained diffusion rate by balancing the amount of active material with the available pore space for electrolyte transport.
2Quantity of substance
If the amount of positive electrode active material and electrolyte is increased to increase discharge capacity, then the discharge capacity increases, but it becomes difficult to enhance discharge characteristics in middle-rate current range
Solution Approach 1:
The patent uses porous materials with controlled pore volume (0.0035 ml/g to 0.0070 ml/g) in the positive electrode material mixture. This porous structure allows increased amount of manganese dioxide (9.30 g or more) while maintaining sufficient electrolyte access through the pore network, thereby achieving high discharge capacity with improved discharge characteristics in middle-rate current range.
Solution Approach 2:
The patent creates a composite material system by combining manganese dioxide particles with a controlled pore structure and electrolyte. This composite positive electrode material mixture allows the coexistence of high active material loading and adequate electrolyte distribution, enabling both high discharge capacity and good discharge characteristics in middle-rate current range.
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 approach results in improved discharge capacity and duration in both low- and middle-rate current ranges, with AA alkaline batteries achieving 230 mAh/g or more and AAA alkaline batteries achieving 260 mAh/g or more per unit weight of manganese dioxide, surpassing conventional battery performance.
Implementation Method 1
a technique of increasing the porosity in a positive electrode material mixture so as to store a larger amount of an electrolyte in a positive electrode
Implementation Method 2
expansion of manganese dioxide particles during discharge
Implementation Method 3
diffusion paths for an electrolyte during discharge can be assured
Data Source
AI summary
An AA alkaline battery includes a positive electrode containing larger than or equal to 9.30 g of manganese dioxide. An AAA alkaline battery includes a positive electrode containing larger than or equal to 4.09 g of manganese dioxide. The cumulative pore volume of pores having diameters from 0.97 μm to 10.2 μm, both inclusive, is in the range from 0.0035 ml/g to 0.0070 ml/g, both inclusive, in measurement of pore size distribution in the positive electrode performed by mercury intrusion porosimetry.