High-Voltage Electrolyte Composition for Stable Cathode Protective Films
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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, creating a synergistic effect that resolves the contradiction between film formation and long-term stability.
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 protective film formation and long-term stability at high potentials, using parameter adjustment to resolve the contradiction.
2Use of energy by moving object
If the working voltage is increased above 4.4V to increase capacity density, then the energy storage capacity is improved, but the oxidation activity of the positive electrode material increases and stability decreases, causing electrolyte decomposition
Solution Approach 1:
The electrolyte composition acts as an intermediary between the high-voltage cathode material and the solvent, with the dinitrile, trinitrile, and propyl propionate components forming a protective interface that enables high voltage operation while preventing direct harmful interactions between the electrode and solvent.
Solution Approach 2:
The patent uses a composite electrolyte system combining dinitrile compound, trinitrile compound, and propyl propionate that works synergistically to enable stable operation at voltages above 4.4V, resolving the contradiction between high energy density and electrolyte stability.
3Use of energy by moving object
If conventional electrolyte formulations are used to achieve high voltage operation, then the energy density is improved, but the DC internal resistance increases due to electrolyte decomposition
Solution Approach 1:
The patent converts the potentially harmful decomposition reactions into beneficial protective film formation. The dinitrile, trinitrile, and propyl propionate components undergo controlled decomposition to form a stable protective film that prevents further harmful decomposition, thus converting the initial harmful effect into a beneficial protective mechanism that reduces DC internal resistance.
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 can form a protective film on the cathode of the electrochemical device
Implementation Method 2
the electrolyte comprises a compound comprising two cyano groups (herein also referred to as 'a dinitrile compound'), a compound comprising three cyano groups (herein also referred to as 'a trinitrile compound'), and propyl propionate
Implementation Method 3
at high voltages, 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
Implementation Method 4
which makes the electrolyte decompose on the surface of the positive electrode easily or cause deterioration of the battery material
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, wherein, about 2.2 wt %≤(X+Y)≤about 8 wt %, about 0.1≤(X/Y)≤about 2.3, about 5 wt %≤Z≤about 50 wt %, 1 wt %<Y<5 wt %, and about 0.02≤(Y/Z)≤about 0.3; wherein wherein the dinitrile compound is one or more compounds selected from the group consisting of butanedinitrile, adiponitrile, and 1,4-dicyano-2-butene; and the trinitrile compound is one or more compounds selected from the group consisting of 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile and 1,2,3-tris(2-cyanoethoxy)propane.