Conductive Electrode Plate Composition for Thin-Sheet Extrusion
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Solution Overview
Problem
Existing carbon-plastic electrode compositions for zinc-bromine batteries face challenges in achieving a balance of electrical conductivity, chemical resistance, and processability, particularly when manufacturing thin sheets using conventional extrusion processes.
Innovation Solution
A thermoplastic composition comprising 35 wt% to 70 wt% high density polyethylene, 25 wt% to 55 wt% graphite filler, and 2 wt% to 15 wt% carbon powder with a BET surface area of at least 50 m2/g, which is processed to achieve a volume electrical resistivity of less than 5 ohm·cm and a melt flow rate suitable for forming thin sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high carbon content is used to improve electrical conductivity, then volume resistivity improves, but the composition becomes too brittle and less easily extrudable
Solution Approach 1:
The patent changes the particle size parameter of the carbon black filler, using ultrafine carbon black with specific surface area of 100-200 m²/g instead of conventional carbon black. This parameter change allows achieving high electrical conductivity at lower carbon content levels, thereby maintaining extrudability while improving conductivity.
Solution Approach 2:
The patent creates a composite material system combining polypropylene-ethylene copolymer with ultrafine carbon black and silica. This composite approach allows the carbon black to provide conductivity while the polymer matrix and silica filler maintain structural integrity and processability, resolving the brittleness issue associated with high carbon content.
2Reliability
If high carbon content is used to improve electrical conductivity, then volume resistivity improves, but permeability to liquids increases
Solution Approach 1:
The patent changes the carbon black particle size parameter to ultrafine dimensions with high specific surface area, which provides efficient conductivity pathways at lower loadings. This reduces the total carbon content needed, thereby maintaining lower permeability to liquids while achieving the required electrical conductivity.
Solution Approach 2:
The patent uses silica as a filler that copies or replaces part of the volume traditionally occupied by carbon black. This allows achieving structural integrity and controlling permeability while using optimized carbon black loading for conductivity, preventing the permeability increase that would result from high carbon content.
3Ease of manufacture
If polypropylene-ethylene copolymer is used as base polymer, then processability is good, but the material is susceptible to oxidative attack and swelling
Solution Approach 1:
The patent introduces silica as an intermediary filler that forms a barrier network within the polymer matrix. This silica structure acts as a mediator that prevents direct contact between bromine and the polymer chains, protecting against oxidative attack while maintaining the processability benefits of the polypropylene-ethylene copolymer.
Solution Approach 2:
The patent creates a composite material system where polypropylene-ethylene copolymer provides processability, silica provides chemical resistance through barrier formation, and ultrafine carbon black provides conductivity. This multi-component composite resolves the contradiction between processability and chemical resistance.
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 composition exhibits excellent electrical conductivity, chemical resistance, and processability, enabling the successful manufacture of thin sheets for zinc-bromine battery electrodes with improved durability and performance.
Implementation Method 1
a conductive carbon black powder... The composition has a volume electrical resistivity of less than 5 ohm·centimeter
Implementation Method 2
from about 25 wt % to about 55 wt % of at least one graphite filler; and from about 2 wt % to about 15 wt % of a carbon powder filler... The composition has a volume electrical resistivity of less than 5 ohm·centimeter
Data Source
AI summary
Aspects of the disclosure relate to a composition including: from about 35 wt % to about 70 wt % of at least one polyethylene polymer; from about 25 wt % to about 55 wt % of at least one graphite filler; and from about 2 wt % to about 15 wt % of a carbon powder filler having a BET surface area of at least 50 square meters per gram (m2/g). The polyethylene polymer has a density of at least 0.94 gram per cubic centimeter (g/cm3), a melt flow rate (MFR) of at least 10 g per 10 minutes (g/10 min) measured at 190° C. and 21.6 kilogram (kg), and an Environmental Stress-Cracking Resistance (ESCR) of at least 500 hours. The composition has a volume electrical resistivity of less than 5 ohm·centimeter (ohm·cm) and a MFR of at least 4 g/10 min measured at 280° C. and 21.6 kg.