Electrolyte Composition for High-Voltage Cathode Film Stability
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Solution Overview
Problem
High-voltage electrochemical devices face challenges with increased oxidation activity and stability issues 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 composition comprising a dinitrile compound, a trinitrile compound, and propyl propionate, within specific weight percentage ranges, 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 solvent decomposition is inhibited, but the protective film decomposes at high potential and the inhibition effect cannot be sustained
Solution Approach 1:
The patent combines dinitrile compound, trinitrile compound, and propyl propionate to form a composite protective film. The trinitrile compound with three cyano groups provides enhanced stability at high potentials compared to dinitrile alone, while propyl propionate contributes to film formation and overall stability. This composite approach creates a protective film that maintains both protection capability and structural integrity at high voltages above 4.4V.
Solution Approach 2:
The patent modifies the chemical composition parameters of the protective film by introducing trinitrile compound with a higher cyano group count and propyl propionate. These parameter changes in molecular structure and composition enable the film to withstand high potential conditions that would decompose simpler protective films, thereby sustaining the inhibition effect long-term.
2Quantity of substance
If high-voltage electrochemical devices are developed to increase capacity density, then energy storage capacity increases, but oxidation activity of positive electrode material increases and stability decreases
Solution Approach 1:
The electrolyte composition acts as an intermediary between the high-voltage cathode material and the solvent. The dinitrile, trinitrile, and propyl propionate form a protective interface layer that mediates the interaction, preventing direct contact and harmful oxidation reactions between the high-potential cathode and the solvent, thereby enabling high capacity density operation with maintained stability.
Solution Approach 2:
The electrolyte additives perform preliminary protective action by forming a stable protective film on the cathode surface before harmful oxidation and solvent decomposition can occur. This pre-formed barrier prevents the adverse effects of high voltage oxidation activity, allowing the device to operate at high potentials without immediate degradation.
3Reliability
If existing solutions are used to address high-voltage stability issues, then some protection is provided, but DC internal resistance increases
Solution Approach 1:
The patent optimizes the concentration parameters and molecular structure of the protective film components. The specific combination of dinitrile, trinitrile, and propyl propionate at controlled ratios creates a film with appropriate thickness and conductivity characteristics, achieving high-voltage stability without excessive resistance that would hinder performance.
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 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 can form a protective film on the cathode of the electrochemical device, so as to inhibit the decomposition of the solvent
Implementation Method 2
the oxidation activity of the positive electrode material increases, and the stability decreases, which makes the electrolyte decompose on the surface of the positive electrode easily
Data Source
AI summary
An electrochemical device, including an electrode and an electrolyte. The 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. Wherein about 2 wt %≤(X+Y)≤ about 11 wt %, about 0.1≤(X/Y)≤ about 8. The electrode including a coating, which including a single-sided sub-coating and a double-sided coating, the electrode with the single-sided sub-coating has an electrode compaction density D1, and the electrode with the double-sided coating has an electrode compaction density D2, where about 0.8≤D1/D2≤ about 1.2. The electrolyte and D1/D2 of the electrodes has a significant effect on the cycle performance of the electrochemical device.