Lithium Battery Electrolyte Oxidation Stability
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Solution Overview
Problem
Lithium secondary batteries face safety issues due to electrolyte decomposition and oxidation at high potentials, leading to potential combustion and reduced lifespan, especially with the use of high-voltage cathode materials like spinel-structure lithium nickel-based metal oxides.
Innovation Solution
An electrolyte composition comprising 1 to 60 wt % cyclic carbonate and 40 to 99 wt % linear solvent, specifically using fluoroethylene carbonate (FEC) and dimethyl carbonate (DMC), enhances oxidation stability, improving the rate and lifespan characteristics of lithium secondary batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional electrolytes are used in lithium secondary batteries with high-voltage cathode materials (spinel-structure lithium nickel-based metal oxides), then high voltage and energy density can be achieved, but the electrolyte undergoes oxidation and decomposition at potentials above 4.2 V, leading to safety issues and reduced lifespan
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific cyclic carboxylate component and optimizing the ratio of cyclic carbonate to linear carbonate within 5:95 to 40:60 weight ratios. This parameter modification enables the electrolyte to maintain stability at high potentials above 4.2 V while preserving high energy density characteristics.
Solution Approach 2:
The patent creates a composite electrolyte system by combining multiple components: cyclic carboxylate (new component), cyclic carbonate (EC, PC), and linear carbonate (DMC, DEC, EMC). This composite approach synergistically improves oxidation resistance while maintaining ion conductivity and energy density required for high-voltage lithium secondary batteries.
2Power
If the operating voltage of lithium secondary batteries is increased to 4.2 V or higher to improve energy density, then higher energy output is achieved, but the electrolyte starts to decompose and may reach ignition point, resulting in combustion risk
Solution Approach 1:
The patent converts the harmful oxidation reaction that occurs at high voltage into a beneficial protective mechanism. The cyclic carboxylate component preferentially reacts with trace water and impurities at high potentials, forming a stable protective film on the cathode surface that prevents further electrolyte decomposition and eliminates combustion risk while enabling sustained high-voltage operation.
Solution Approach 2:
The cyclic carboxylate acts as an intermediary substance between the high-voltage cathode material and the carbonate electrolyte. It mediates the interface interactions by forming a stable solid electrolyte interface (SEI) layer that prevents direct contact and harmful reactions between the electrolyte and cathode, thereby eliminating combustion risk while maintaining high discharge voltage.
3Quantity of substance
If spinel-structure lithium nickel-based metal oxides are used as cathode active materials to achieve high voltage (4.7 V average), then energy density is improved, but the electrolyte is oxidized generating by-products such as gas, which deteriorates secondary battery safety
Solution Approach 1:
The cyclic carboxylate component performs preliminary protective action by reacting with trace water and impurities before they can cause harmful electrolyte oxidation. This preliminary reaction forms a stable protective interface on the cathode surface, preventing subsequent oxidation reactions that would generate gas by-products, thereby maintaining high capacity while eliminating safety deterioration.
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 optimized electrolyte composition significantly enhances the oxidation stability and overall performance of lithium secondary batteries, maintaining high voltage and capacity while ensuring safety and extended lifespan, even with high-voltage cathode materials.
Implementation Method 1
the non-aqueous electrolyte acts as a medium through which lithium ions migrate between the anode and the cathode
Implementation Method 2
when a lithium secondary battery is overcharged to 4.2 V or higher, the electrolyte starts to decompose
Data Source
AI summary
Disclosed are an electrolyte for a lithium secondary battery which includes a non-aqueous solvent and a lithium salt and a lithium secondary battery including the same. The electrolyte includes 1 to 60 wt % of a cyclic carbonate and 40 to 99 wt % of a linear solvent based on a total weight of the non-aqueous solvent.