Sodium Ion Ceramic Coating for Low-Temperature Battery Interfaces

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Solution Overview

Problem

Molten sodium batteries face limitations due to high operating temperatures, which hinder widespread adoption, primarily because of poor wetting of molten sodium on sodium ion-conducting ceramics like β″-Al2O3 and NaSICON at temperatures below 200°C, leading to increased interfacial resistance and reduced battery performance.

Innovation Solution

Coating sodium ion-conducting ceramics with materials such as tin, bismuth, lead, antimony, germanium, silicon, or gold to form a sodium intermetallic phase, which enhances sodium ion conduction and reduces interfacial resistance, allowing for improved charge transfer and wetting at lower temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high operating temperatures (300-350°C) are used to achieve facile charge transfer between molten sodium and solid electrolyte, then charge transfer efficiency is improved, but battery longevity decreases, materials cost increases, and safety is compromised

Engineering Contradiction:

Improvecharge transfer efficiencyVSAvoidbattery safety and longevity

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent changes the operating temperature parameter from high (300-350°C) to low (below 200°C) by introducing a coating layer that modifies the interfacial properties between molten sodium and solid electrolyte, enabling efficient charge transfer at lower temperatures through altered wetting characteristics

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a coating layer as an intermediary substance between molten sodium and solid electrolyte that improves interfacial wetting and reduces contact angle, facilitating efficient charge transfer without requiring high operating temperatures

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If temperature is lowered below 200°C to improve battery safety and longevity, then safety and lifespan are improved, but wetting of molten sodium on solid electrolyte deteriorates, leading to increased interfacial resistance

Engineering Contradiction:

Improvebattery safety and lifespanVSAvoidcharge transfer efficiency

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The coating layer acts as an intermediary that mediates the interaction between molten sodium and solid electrolyte at low temperatures, improving wetting properties and reducing interfacial resistance without requiring high operating temperatures

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The coating layer changes the interfacial energy parameters between molten sodium and solid electrolyte, modifying contact angle and wetting characteristics to enable efficient charge transfer at low temperatures where these parameters would otherwise be unfavorable

Inventive Principle:

Principle #35Parameter changes

3Power

If coating materials are deposited on solid electrolyte to improve wetting at low temperatures, then interfacial resistance is reduced, but device complexity increases due to additional coating layers

Engineering Contradiction:

Improveinterfacial charge transfer efficiencyVSAvoidcoating layer structure

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent applies coating materials selectively to the surface of the solid electrolyte where they are most needed - at the interface with molten sodium - rather than modifying the entire device structure, thus improving interfacial properties with minimal added complexity

Inventive Principle:

Principle #3Local quality

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 formation of a sodium intermetallic phase on the ceramic surface significantly lowers interfacial resistance and improves battery performance, enabling efficient operation at temperatures below 200°C and extending the lifespan of molten sodium batteries.

Implementation Method 1

forming a sodium ion-conducting sodium-tin, sodium-bismuth, sodium-lead, sodium-antimony, sodium-germanium, sodium-silicon, or sodium-gold intermetallic phase on the surface of the sodium ion-conducting type ceramic by sodium electrochemical reaction

Methodology Applied

Scientific EffectElectrochemical reaction: Electrolysis

Implementation Method 2

depositing a coating comprising tin, bismuth, lead, antimony, germanium, silicon, or gold on a surface of the sodium ion-conducting ceramic

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS20230207787A1Method to Improve Sodium Electrochemical Interfaces of Sodium Ion-Conducting Ceramics

Publication Date: 2023.06.29 NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA LLC

AI summary

The present invention is directed to the modification of sodium electrochemical interfaces to improve performance of sodium ion-conducting ceramics in a variety of electrochemical applications. Enhanced mating of the separator-sodium interface by means of engineered coatings or other surface modifications results in lower interfacial resistance and higher performance at increased current densities, enabling the effective operation of molten sodium batteries and other electrochemical technologies at low and high temperatures.