NaSICON Solid-State Cell Surface Layer Against Sodium Dendrites

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Solution Overview

Problem

Solid-state sodium batteries face dendrite formation issues at high current densities, leading to short circuits and rendering the batteries unusable, limiting their operational efficiency and commercial viability.

Innovation Solution

A solid-state cell with a NaSICON electrolyte and a continuous material layer or modified chemical composition on its outer surface is used to prevent dendrite formation, allowing for higher current densities without expensive chemicals or complex technology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high current densities are used in solid-state sodium batteries, then operational efficiency and power output are improved, but dendrite formation occurs leading to short circuits and battery failure

Engineering Contradiction:

Improvecurrent densityVSAvoiddendrite formation resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies local quality by creating a surface-modified region on the electrolyte with different properties from the bulk. The outer surface is chemically modified to have enhanced dendrite resistance, while the interior maintains its original high ionic conductivity. This allows the battery to operate at high current densities without dendrite formation at the critical electrode-electrolyte interface.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the chemical composition parameter of the electrolyte surface by introducing a different stoichiometry or phase at the outer surface compared to the bulk NaSICON material. This parameter change creates a surface layer with enhanced stability against sodium dendrite penetration, enabling safe operation at current densities above 1 mA cm⁻² where conventional electrolytes would fail.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If conventional electrolyte materials are used, then manufacturing simplicity is maintained, but dendrite formation limits current density to below 1 mA cm⁻²

Engineering Contradiction:

Improveelectrolyte fabricationVSAvoidcurrent density

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent applies preliminary action by pre-modifying the electrolyte surface during the manufacturing process before battery assembly and operation. The surface modification is performed in advance to create dendrite-resistant properties, eliminating the need for complex operational controls or additional components during battery operation. This approach maintains manufacturing simplicity while enabling higher current densities.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the electrolyte surface is modified to prevent dendrites, then dendrite tolerance is improved, but manufacturing complexity may increase

Engineering Contradiction:

Improvedendrite toleranceVSAvoidmanufacturing process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies self-service by designing a manufacturing process where the electrolyte material itself provides the surface modification function. The electrolyte composition or processing conditions are adjusted so that the material self-organizes or self-modifies during standard fabrication to create the protective surface layer, eliminating the need for separate coating steps or complex additional processing equipment.

Inventive Principle:

Principle #25Self-service

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 solution enables stable operation at current densities up to 2-3 mA/cm², significantly improving the tolerance to dendrite formation and enhancing the battery's efficiency and usability.

Implementation Method 1

A well-known sodium ion conductor is Na1+xZr2(SiO4)x(PO4)3−x, (0≤x≤3). This compound is also known as NZSP and crystallizes in rhombohedral or monoclinic structures. Such compounds are also called NaSICON after the acronym of 'Na Super Ionic Conductor'.

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

In the third region of the electrolyte a continuous material layer may be arranged. Alternatively, a chemical composition of the outer surface is changed in the third region of the electrolyte. It has shown that during operation of solid-state cells with an electrolyte containing NaSICON at high current densities, metallic sodium filaments are formed on the outer surface of the electrolyte. Like classical dendrite formation inside the electrolyte, these can lead to a short circuit and thus to the destruction of the cell.

Methodology Applied

Scientific EffectDendrite formation prevention through surface modification:

Data Source

PatentUS20230387455A1Solid state cell and associated manufacturing method

Publication Date: 2023.11.30 FORSCHUNGSZENTRUM JULICH GMBH

AI summary

A solid-state cell, a solid-state battery, and an associated method for producing a solid-state cell is disclosed. A solid-state cell has an electrolyte comprising NaSICON. The solid-state cell comprises a first electrode arranged at a first region of the electrolyte and a second electrode arranged at a second region of the electrolyte. A continuous material layer is arranged at least a third region of the electrolyte on an outer surface of the electrolyte. Alternatively, a chemical composition of the outer surface in the third region of the electrolyte is changed. In this way, the formation of filaments and/or dendrites can be effectively prevented and operation at significantly increased current densities is possible.