Morpholine-N-oxide electrolyte additive for lithium ion batteries
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Solution Overview
Problem
Lithium ion secondary batteries exhibit poor performance at high voltage and high temperature due to issues such as transition metal dissolution, reduced cyclic stability, and poor high-temperature storage performance, which existing electrolytes with alkylene oxide or aniline-based additives fail to adequately address.
Innovation Solution
An electrolyte additive with a morpholine structure, where a nitrogen atom is oxidized to form an inner salt, reducing the likelihood of oxidative decomposition and improving solubility, is used to enhance the formation of a stable solid electrolyte membrane on the negative electrode, thereby improving cyclic stability and high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electrolytes with alkylene oxide or aniline-based additives are used, then membrane formation on negative electrode is improved, but the additives are easily oxidized on positive electrode surfaces, reducing cyclic stability
Solution Approach 1:
The patent employs a composite electrolyte system combining fluorinated cyclic carbonate (FCC) as the primary solvent with morpholine-N-oxide as the additive. This composite approach leverages the high voltage stability of FCC and the membrane-forming capability of morpholine-N-oxide, creating a synergistic effect that resolves the contradiction between membrane quality and cyclic stability. The morpholine-N-oxide structure with its N→O coordinate bond provides both the desired membrane formation and resistance to oxidation.
Solution Approach 2:
The patent introduces fluorine substitution in the cyclic carbonate structure, changing the chemical parameters of the electrolyte solvent. The fluorinated cyclic carbonate (FCC) exhibits higher oxidation resistance and electrochemical stability compared to traditional carbonates, enabling the electrolyte to maintain performance at high voltages (up to 4.5V) and high temperatures while preserving cyclic stability.
2Power
If high voltage and high temperature conditions are applied, then battery power output is improved, but transition metal dissolves and migrates to negative electrode, causing gas production and structure deterioration
Solution Approach 1:
The morpholine-N-oxide additive acts as an intermediary protective layer on the negative electrode surface. This intermediary SEI membrane selectively blocks transition metal migration while maintaining lithium ion conductivity. The morpholine ring structure with N→O coordinate bond provides a stable interface that prevents direct contact between dissolved metals and the negative electrode, thereby suppressing gas production and structural degradation during high-power operation.
Solution Approach 2:
The patent utilizes fluorinated cyclic carbonate to modify the electrochemical window and stability parameters of the electrolyte. The fluorine substitution increases the oxidation potential and thermal stability of the solvent, enabling the battery to operate at higher voltages and temperatures without triggering transition metal dissolution and decomposition reactions that lead to gas production.
3Ease of manufacture
If conventional electrolyte composition is used, then manufacturing simplicity is maintained, but high-temperature storage performance and high-voltage performance are poor
Solution Approach 1:
The patent modifies the electrolyte composition parameters by introducing fluorinated cyclic carbonate and morpholine-N-oxide in specific ratios. The fluorinated solvent provides high-temperature stability and voltage resistance, while the morpholine-N-oxide additive enhances membrane formation. This parameter optimization allows the electrolyte to maintain excellent storage performance at high temperatures and deliver high-voltage performance without complicating the manufacturing process.
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 use of the electrolyte additive with the morpholine structure leads to improved stability and cyclic stability of the battery, allowing for effective Li+ ion conduction and preventing solvent insertion, thus enhancing the battery's performance at high temperatures and voltages.
Implementation Method 1
the dissolved-out transition metal may be migrated to a negative electrode so as to be reduced, and then deposited on the surfaces of the negative electrode
Implementation Method 2
improve the membrane formation of fluoroethylene carbonate on the surfaces of negative electrode
Implementation Method 3
effective Li+ ion conduction
Implementation Method 4
a nitrogen atom is oxidized to form an inner salt, reducing the likelihood of oxidative decomposition
Data Source
AI summary
The present disclosure provides an electrolyte additive, an electrolyte and a lithium ion secondary battery containing the same. The electrolyte additive has a structure of Formula (1), wherein R1 is hydrogen, a phenyl, a cyano group, an alkyl cyano group or a C1 to C6 alkyls, and each of R2 to R5 is independently selected from hydrogen or a C1 to C6 alkyl. By means of the electrolyte additive, the electrolyte and the lithium ion secondary battery containing the same of the present disclosure, a technical effect of improving electric performance of the lithium ion secondary battery at high voltage and high temperature is achieved.