Non-Aqueous Electrolyte Composition for Soluble NaBF4 Sodium-Ion Cells
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Solution Overview
Problem
Sodium-ion batteries face challenges with electrolyte compositions, particularly with sodium tetrafluoroborate (NaBF4) having low solubility in organic carbonate-based solvents, leading to inadequate ionic conductivity and inferior electrochemical performance compared to lithium-ion batteries, and existing alternatives like ionic liquids are costly and inefficient.
Innovation Solution
A novel non-aqueous electrolyte composition using a solvent system comprising propylene carbonate combined with one or more further organo carbonate-based solvents and glycol diethers or glycol ether acetates, along with optional sulfone group-containing solvents, to enhance solubility and electrochemical performance of sodium-containing salts like NaBF4 and NaPF6.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If NaBF4 is used as the electrolyte salt in organic carbonate-based solvents, then cost effectiveness is improved, but solubility decreases leading to low ionic conductivity
Solution Approach 1:
The patent uses a composite solvent system combining multiple organic carbonate-based solvents (EC, PC, DEC, DMF) in specific ratios to achieve both high NaBF4 solubility and high ionic conductivity. This composite approach allows the electrolyte to simultaneously satisfy cost requirements and performance requirements that cannot be met by single solvents alone.
Solution Approach 2:
The patent optimizes the concentration of NaBF4 salt in the electrolyte solution (ranging from 0.5M to 2M) and adjusts the ratio of different solvent components to maximize solubility and ionic conductivity. By changing these parameters, the system achieves high performance with the cost-effective NaBF4 salt rather than expensive alternatives.
2Reliability
If ionic liquids are used to improve solubility of NaBF4, then ionic conductivity increases, but cost increases significantly
Solution Approach 1:
The patent replaces expensive ionic liquids with cheaper organic carbonate-based solvents that can achieve comparable or superior ionic conductivity when used in optimized composite formulations. This substitution dramatically reduces cost while maintaining the high ionic conductivity required for practical sodium-ion battery operation.
Solution Approach 2:
The patent achieves high ionic conductivity through optimized salt concentration and solvent ratio parameters in the organic carbonate system, eliminating the need for expensive ionic liquids. The specific parameter ranges identified (0.5-2M NaBF4, specific solvent ratios) provide a cost-effective pathway to high performance.
3Ease of manufacture
If traditional organic carbonate-based electrolytes are used, then cost is reduced, but electrochemical performance deteriorates due to low solubility
Solution Approach 1:
The patent creates a composite electrolyte system using multiple organic carbonate-based solvents (EC, PC, DEC, DMF) in optimized ratios to simultaneously achieve high solubility of NaBF4 and high electrochemical performance. This composite approach maintains cost effectiveness while overcoming the limitations of individual solvents.
Solution Approach 2:
The patent optimizes key parameters including NaBF4 concentration (0.5-2M) and solvent component ratios to maximize electrochemical performance. These parameter optimizations enable traditional organic carbonate-based electrolytes to achieve performance levels previously only attainable with expensive alternatives.
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 proposed electrolyte composition significantly improves ionic conductivity and electrochemical performance, reducing first cycle loss and maintaining high specific capacity in sodium-ion cells, especially when used with hard carbon anodes, while being cost-effective and sustainable.
Implementation Method 1
NaBF4 has very low solubility in organic carbonate-based electrolyte solvents... a novel non-aqueous electrolyte composition using a solvent system comprising propylene carbonate combined with one or more further organo carbonate-based solvents and glycol diethers or glycol ether acetates, to enhance solubility and electrochemical performance
Implementation Method 2
Ionic conductivity and electronic insulation, these are necessary to maintain cell operation by Na+ transport... significantly improves ionic conductivity and electrochemical performance
Implementation Method 3
Electrochemical stability—there must be a large separation of high and low onset potentials for decomposition by oxidation or reduction, respectively... maintaining high specific capacity in sodium-ion cells
Data Source
AI summary
The invention relates to novel non-aqueous electrolyte compositions comprising: a) a sodium-containing compounds of the general formula NaMFX and b) a solvent system comprising a first solvent component i) which comprises propylene carbonate and one or more further organo carbonate-containing solvents, and a second solvent component ii) which comprises one or more glycol diethers and/or one or more glycol ether acetates; wherein the molar ratio of propylene carbonate:one or more glycol diethers and/or one or more glycol ether acetates is in the range 1:0.1 to 1:3.