Electrolyte Composition for Stable Cathode Films at High Voltage
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Solution Overview
Problem
High-voltage electrochemical devices face issues with increased oxidation activity and stability of positive electrode materials, leading to electrolyte decomposition and decreased battery capacity, which existing solutions fail to adequately address without increasing DC internal resistance.
Innovation Solution
An electrolyte comprising a dinitrile compound, a trinitrile compound, and propyl propionate, within specific weight percentage ratios, forms a protective film that inhibits solvent decomposition and reduces DC internal resistance, while additional components like fluoroether and cyclic phosphonic anhydride enhance long-term storage performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dinitrile compound is used to form a protective film on the cathode, then the decomposition of the solvent is inhibited, but the protective film itself decomposes on the surface of the cathode at high potential, causing the inhibition effect to be unsustainable
Solution Approach 1:
The patent combines dinitrile compound, trinitrile compound, and propyl propionate to form a composite protective film. The dinitrile compound provides initial film formation, the trinitrile compound enhances film stability at high potentials, and propyl propionate contributes to overall film durability. This composite approach creates a protective film that maintains both stability and long-term inhibition effect at high voltages above 4.4V.
Solution Approach 2:
The patent optimizes the weight percentages of each component (dinitrile: 0.01-10%, trinitrile: 0.01-10%, propyl propionate: 5-50%) to achieve the desired balance between film stability and duration. By adjusting these compositional parameters, the protective film's decomposition resistance is enhanced while maintaining sustained inhibition capability throughout the battery's operational life.
2Quantity of substance
If high-voltage electrochemical devices are developed to increase capacity density, then the capacity density is improved, but the oxidation activity of the positive electrode material increases and stability decreases, causing electrolyte decomposition
Solution Approach 1:
The protective film formed by the dinitrile compound, trinitrile compound, and propyl propionate acts as an intermediary layer between the electrolyte and the cathode surface. This film mediates the interaction by providing a stable interface that prevents direct contact between the electrolyte and high-potential cathode material, thereby inhibiting electrolyte decomposition while allowing the high-voltage device to operate at increased capacity density.
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 effectively inhibits the increase in DC internal resistance, achieving high capacity density and excellent cycle and storage performances by forming a stable protective film that sustains at high potentials.
Implementation Method 1
the dinitrile compound, a trinitrile compound, and propyl propionate, a firm protective film which is not easily decomposed on the surface of the cathode at a high potential can be formed
Data Source
AI summary
An electrolyte including a dinitrile compound, a trinitrile compound, and propyl propionate. Based on the total weight of the electrolyte, the weight percentage of the dinitrile compound is X, the weight percentage of the trinitrile compound is Y, and the weight percentage of the propyl propionate is Z; where about 2 wt %≤(X+Y)≤about 11 wt %, about 0.1≤(X/Y)≤about 8, and about 0.01≤(Y/Z)≤about 0.3. The dinitrile compound comprises a compound of Formula (5): N—R2—(O—R3)n—O—R4—CN (5). The electrolyte is capable of effectively inhibiting the increase in DC internal resistance of an electrochemical device so that the electrochemical device has excellent cycle and storage performance.