Low-EC Electrolyte Additive for High-Voltage Lithium Cathodes
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Solution Overview
Problem
Cobalt-free lithium nickel manganese-based oxide positive electrodes in rechargeable lithium batteries experience structural instability and transition metal elution under high voltage and high temperature conditions, leading to performance deterioration and reduced cycle-life characteristics.
Innovation Solution
A rechargeable lithium battery design incorporating a non-aqueous organic solvent with less than 5 wt% ethylene carbonate and an additive represented by Chemical Formula 1, which includes a substituted or unsubstituted C3 to C6 heteroaryl group, effectively reduces transition metal elution and stabilizes the positive electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cobalt-free lithium nickel manganese-based oxide is used as positive electrode active material to increase energy density, then energy density is improved, but transition metal elution occurs under high voltage conditions leading to performance deterioration
Solution Approach 1:
The patent introduces a specific electrolyte additive (compound of formula 1 with heteroaryl or heterocyclic group containing nitrogen) as an intermediary substance that mediates between the positive electrode and electrolyte. This additive forms a protective interface layer that prevents direct contact and harmful reactions between the lithium nickel manganese oxide and the electrolyte, thereby suppressing transition metal elution while maintaining high voltage operation capability
Solution Approach 2:
The patent modifies the electrolyte composition parameters by limiting ethylene carbonate to less than 5 wt% and incorporating specific additives (formula 1 compounds at 0.01-5 wt%). These parameter changes alter the electrochemical environment to reduce oxidation potential and prevent structural collapse of the positive electrode material under high voltage conditions
2Use of energy by moving object
If high voltage region is utilized to expand voltage region and increase energy density, then energy density is improved, but electrolyte solution oxidation occurs leading to positive electrode deterioration
Solution Approach 1:
The patent converts the potentially harmful high voltage condition into a beneficial operational range by introducing the electrolyte additive that raises the oxidation potential threshold. The additive transforms the high voltage environment from a harmful condition causing electrolyte decomposition into a beneficial operating range that enables higher energy density without electrolyte oxidation
Solution Approach 2:
The electrolyte additive acts as a mediator that prevents direct oxidation of the electrolyte solution by the high voltage potential. It forms a protective interface that blocks electron transfer and chemical reactions between the electrolyte and electrode, allowing high voltage operation without electrolyte decomposition
3Power
If high temperature environment is utilized to improve battery performance, then output characteristics are improved, but transition metal elution is aggravated leading to capacity reduction
Solution Approach 1:
The electrolyte additive (formula 1 compound) serves as a thermal stabilizer and protective intermediary that becomes particularly effective at high temperatures. It forms a thermally stable protective layer on the positive electrode surface that prevents transition metal dissolution even under elevated temperature conditions, allowing the battery to operate at high temperatures without aggravated metal elution
4Ease of manufacture
If conventional electrolyte composition is used to simplify manufacturing, then ease of manufacture is improved, but structural collapse of positive electrode occurs under high voltage leading to gas generation
Solution Approach 1:
The patent modifies electrolyte composition parameters in a controlled manner - limiting ethylene carbonate to less than 5 wt% and adding specific compounds of formula (1) at 0.01-5 wt%. These parameter changes are straightforward to implement in manufacturing while providing significant protection against positive electrode structural collapse and gas generation under high voltage conditions
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 solution enhances high-voltage and high-temperature characteristics, suppressing structural collapse and gas generation, thereby improving battery stability and cycle-life while reducing internal resistance.
Implementation Method 1
the additive includes a compound represented by Chemical Formula 1... effectively protecting the positive electrode... suppress or reduce structural collapse of the positive electrode
Implementation Method 2
an electrolyte solution including a non-aqueous organic solvent, a lithium salt, and an additive... a positive electrode including a positive electrode active material... reduces elution of transition metals
Data Source
Figure 1
AI summary
A rechargeable lithium battery is provided, the rechargeable lithium battery including an electrolyte solution including a non-aqueous organic solvent, a lithium salt, and an additive; positive electrode including a positive electrode active material; and a negative electrode including a negative electrode active material, wherein the non-aqueous organic solvent includes less than 5 wt% of ethylene carbonate based on a total weight of the non-aqueous organic solvent, the positive electrode active material includes lithium nickel manganese-based oxide, and the additive is represented by Chemical Formula 1. Chemical Formula 1 is as defined in the specification.