Electrolyte Composition for Stable Electrode Passivation Layers
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Solution Overview
Problem
Existing electrochemical apparatuses face challenges in achieving optimal stability of protective films at positive and negative electrode interfaces, which affects high- and low-temperature performance.
Innovation Solution
Incorporating lithium tetrafluoroborate and a compound of Formula I into the electrolyte, with specific mass percentages, forms a thin and robust passivation layer at the electrode interfaces, enhancing stability and impedance, and improving ionic conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electrolyte components are used, then the electrolyte can maintain basic ionic conductivity, but the stability of protective films at positive and negative electrode interfaces is insufficient
Solution Approach 1:
The patent employs a composite electrolyte system combining lithium tetrafluoroborate (LiBF4) with fluorinated cyclic carbonate compounds (FEC, DFEC, TFP). This composite approach creates synergistic effects where LiBF4 provides lithium ions and the fluorinated cyclic carbonates form stable protective films rich in F and S elements at electrode interfaces, simultaneously improving film stability and ionic conductivity without excessive complexity
Solution Approach 2:
The patent optimizes specific parameter ranges: LiBF4 mass percentage (0.1-2%), fluorinated cyclic carbonate mass percentage (0.01-5%), and their ratio (0.005≤F/(A+B)≤0.5). These parameter adjustments enable the formation of thin, robust passivation layers that enhance interface stability while maintaining acceptable electrolyte complexity
2Reliability
If the passivation layer is made thicker to improve stability, then interface stability improves, but ionic conductivity decreases
Solution Approach 1:
The patent controls the mass percentages of LiBF4 (0.1-2%) and fluorinated cyclic carbonates (0.01-5%) with a specific ratio (0.005≤F/(A+B)≤0.5) to form passivation layers of optimal thickness. This parameter optimization ensures the protective films are thin enough to maintain high ionic conductivity while being sufficiently stable to provide reliable interface protection
Solution Approach 2:
The fluorinated cyclic carbonate compounds concentrate fluorine and sulfur elements specifically at the electrode interface regions, creating locally enhanced protective films. This localized enrichment provides high interface stability without requiring thick uniform layers throughout the electrolyte, thereby maintaining good ionic conductivity in the bulk electrolyte
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 electrolyte composition improves the stability and low-temperature discharge performance of electrochemical apparatuses by forming a thin passivation layer rich in S and F elements, reducing impedance and increasing ionic conductivity.
Implementation Method 1
forming a thin passivation layer rich in S and F elements at the electrode interface
Implementation Method 2
the compound of Formula I can form a positive electrode interface passivation layer and/or a negative electrode interface passivation layer of lithium-containing inorganic compounds rich in S and F elements at the electrode interface
Implementation Method 3
effectively improving the ionic conductivity at the electrode plate interface
Data Source
AI summary
An electrolyte includes lithium tetrafluoroborate and a compound of Formula Iwhere a mass percentage A of the lithium tetrafluoroborate satisfies 0.1%≤A≤2%, and a mass percentage B of the compound of Formula I satisfies 0.010%≤B≤20%.