Porous Silicon Wafer Separator for Low-Cost Redox Flow Batteries

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Solution Overview

Problem

Conventional redox flow batteries face limitations due to the high cost and relatively low ion selectivity of commonly used membranes, such as NAFION, which restricts the commercialization of these batteries.

Innovation Solution

The development of a membrane-less redox flow battery system utilizing a porous silicon wafer separator, where the porous silicon wafers are fabricated using MEMS technology to create cylindrical pores with high aspect ratios, and surface treatments like metal silicide coating enhance ion conductivity and selectivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional membranes like NAFION are used in redox flow batteries, then ion selectivity is provided, but cost is high

Engineering Contradiction:

Improveion selectivityVSAvoidcost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs porous silicon wafers with controlled pore structures (5-50 nm diameter) as membrane alternatives. The porous structure provides ion selectivity through size exclusion and surface charge effects while using abundant, low-cost silicon material instead of expensive conventional membranes like NAFION.

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent modifies the physical and chemical parameters of silicon wafers by controlling pore diameter, porosity (30-70%), and surface treatment to achieve desired ion selectivity. By adjusting these parameters, the silicon-based membrane matches or exceeds the performance of conventional membranes at lower cost.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If porous silicon wafers are used as separators, then cost is reduced and ion selectivity is improved, but manufacturing precision requirements increase

Engineering Contradiction:

ImprovecostVSAvoidpore structure control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces traditional mechanical drilling or etching methods with electrochemical etching to create porous structures. This electrochemical process provides better control over pore diameter and distribution, achieving consistent pore structures (5-50 nm) with higher precision while using simpler, more cost-effective equipment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent controls pore structure parameters (diameter, porosity, uniformity) by adjusting electrochemical etching conditions such as current density, etchant composition, and treatment time. This allows precise control of pore characteristics to meet performance requirements while maintaining manufacturing feasibility.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If surface treatments like metal silicide coating are applied, then ion conductivity is enhanced, but device complexity increases

Engineering Contradiction:

Improveion conductivityVSAvoidsurface treatment process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent utilizes the inherent porosity of electrochemically etched silicon wafers to provide ion transport pathways. The porous structure itself, with its high surface area and interconnected pores, enhances ion conductivity without requiring complex surface coatings or treatments.

Inventive Principle:

Principle #31Porous materials

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 reduces the cost and improves ion selectivity, leading to more efficient and cost-effective redox flow batteries with enhanced electrochemical performance and longer useful lifetime.

Implementation Method 1

The porous membrane comprises channels allowing ions and/or an electrolyte to move between the first half-cell and the second half-cell

Methodology Applied

Scientific EffectIon transport through porous material: Porosity

Implementation Method 2

surface treatments like metal silicide coating enhance ion conductivity and selectivity

Methodology Applied

Scientific EffectSurface coating deposition: Deposition (physical)

Implementation Method 3

the porous silicon wafers are fabricated using MEMS technology to create cylindrical pores with high aspect ratios

Methodology Applied

Scientific EffectMicroelectromechanical systems fabrication: Microelectromechanical Systems

Data Source

PatentUS20230411642A1Porous silicon membrane material, manufacture thereof and electronic devices incorporating the same

Publication Date: 2023.12.21 THE SUN CO TEXAS LLC D B A THE SUN CO

AI summary

A redox flow battery includes positive and negative electrodes respectfully located in half-cells separated by a porous silicon wafer separator formed by MEMS Technology. The first half cell and the second half cell each preferably include a plurality of dividers or barriers configured to create flow channels which introduce turbulence ensuring the electrolytes are changing or mixing at surfaces of the electrodes and the membrane. Also disclosed is a solar energy generation and storage system which includes a photovoltaic cell and an electrochemical energy storage battery which share a common electrode. Also disclosed is a membrane-less redox flow electrical energy storage battery, having a cathode electrode, an anode electrode formed of a porous silicon substrate in which surfaces of the pores of the porous silicon substrate are coated at least in part with a metal silicide, and an electrolyte.