Sodium Solid Electrolyte Doping for Higher Ionic Conductivity
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Solution Overview
Problem
Current solid electrolytes for all-solid-state sodium batteries, such as Na3SbS4, do not exhibit sufficient ionic conductivity, which limits the discharge capacity and cycle number of these batteries.
Innovation Solution
Partial substitution of Sb in Na3SbS4 with pentavalent elements like W or Mo introduces defects, enhancing ionic conductivity, and the resulting solid electrolyte is produced through mechanical milling and pressing, followed by heat treatment to form glass ceramics with a cubic crystal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Na3SbS4 is used as solid electrolyte, then atmospheric stability is improved, but ionic conductivity is insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of Na3SbS4 by substituting Sb with elements having different valence states (such as W6+ or Mo6+ replacing Sb5+). This parameter change introduces structural defects that enhance ionic conductivity while maintaining the atmospheric stability of the base material.
Solution Approach 2:
The patent creates composite solid electrolyte materials by combining Na3SbS4 with other elements (W, Mo, etc.) to form substituted compounds like Na3-xSb1-xWxS4. This composite approach leverages the atmospheric stability of Na3SbS4 while introducing the high ionic conductivity characteristics of the substituted elements.
2Power
If solid electrolyte with higher ionic conductivity is required, then charge/discharge capacity is improved, but material complexity increases
Solution Approach 1:
The patent optimizes the substitution ratio parameter (x in Na3-xSb1-xWxS4) to achieve the desired ionic conductivity and charge/discharge capacity. By carefully controlling this parameter, the patent balances performance improvement with material simplicity, avoiding excessive complexity while achieving the target power output.
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 modified solid electrolyte exhibits significantly higher ionic conductivity, improving the charge/discharge capacity and cycle life of all-solid-state sodium batteries, with optimal performance achieved when W is substituted for Sb up to 12% and the electrolyte is in the form of glass ceramics.
Implementation Method 1
mixing raw materials for production of the solid electrolyte with mechanical milling
Implementation Method 2
pressing the obtained mixture
Implementation Method 3
heated at a temperature of 250° C. to 300° C. for 0.1 hours or more
Implementation Method 4
form glass ceramics with a cubic crystal structure
Implementation Method 5
pentavalent Sb is partially substituted with an element that is not pentavalent to introduce defects in the Na3SbS4 structure, thereby arriving at the present invention
Data Source
AI summary
A solid electrolyte for an all-solid-state sodium battery, represented by formula: Na3−xSb1−xαxS4, wherein α is selected from elements that provide Na3−xSb1−xαxS4 exhibiting a higher ionic conductivity than Na3SbS4, and x is 0<x<1.