Difluorophosphite Electrolyte for High-Voltage Lithium Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with high-temperature stability and lifespan when using high-voltage cathode materials, particularly nickel-based oxides, due to rapid phase transformations, chemical resistance deterioration, and excessive gas generation, leading to battery swelling and reduced capacity.
Innovation Solution
An electrolytic solution containing a difluorophosphite compound, specifically A-OPF2, is used in conjunction with a nickel-cobalt-manganese-based cathode active material, along with additional additives like 1,3-propane sultone, lithium bis(oxalato)borate, and ethylene sulfate, to stabilize the cathode structure and suppress side reactions, thereby enhancing high-temperature stability and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high-voltage cathode materials (4.2V or more) are used to increase energy density, then battery capacity is improved, but high-temperature stability and lifespan are rapidly reduced
Solution Approach 1:
The patent introduces a difluorophosphite compound as an intermediary substance in the electrolytic solution that mediates between the high-voltage cathode material and the electrolyte. This compound forms a protective interface layer that prevents direct harmful interactions while allowing ionic conduction, thereby enabling high-voltage operation without sacrificing high-temperature stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the electrolytic solution by incorporating a difluorophosphite compound with specific molecular structure (Formula 1). This parameter change modifies the electrochemical window and stability characteristics of the electrolyte, allowing it to withstand higher voltages and temperatures without decomposition.
2Quantity of substance
If nickel-based cathode active material is used to achieve high capacity, then energy density is improved, but chemical resistance deteriorates rapidly and excessive gas is generated
Solution Approach 1:
The patent converts the harmful reactivity of nickel-based cathode material into a beneficial effect by using the difluorophosphite compound to form a stable surface film. This film prevents further parasitic reactions and gas generation while allowing the high-capacity nickel-based material to function effectively.
Solution Approach 2:
The difluorophosphite compound acts as an intermediary layer between the nickel-based cathode and the electrolyte, preventing direct contact and harmful reactions. This intermediary film suppresses gas generation and chemical deterioration while maintaining ionic conductivity.
3Duration of action of stationary object
If conventional electrolytic solution additives are used to form SEI film, then lifespan characteristic is improved, but internal resistance increases rapidly at high voltage
Solution Approach 1:
The patent changes the chemical structure parameters of the electrolytic solution additive by using a difluorophosphite compound instead of conventional additives. This structural modification enables the formed SEI film to remain stable and conductive at high voltages, preventing rapid internal resistance increase while extending battery lifespan.
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 electrolytic solution with difluorophosphite compound improves high-temperature storage stability, reduces internal resistance, and maintains excellent charge and discharge characteristics, preventing battery swelling and capacity loss even at high voltages.
Implementation Method 1
a difluorophosphite compound... to stabilize the cathode structure and suppress side reactions
Implementation Method 2
The electrolytic solution with difluorophosphite compound improves high-temperature storage stability
Implementation Method 3
a non-aqueous solvent to have a high dielectric constant and high ion conductivity
Implementation Method 4
a lithium salt which is an electrolyte, and a non-aqueous solvent-based electrolytic solution
Data Source
AI summary
The present invention relates to an electrolytic solution for a lithium secondary battery, and a lithium secondary battery including the same. The lithium secondary battery according to the present invention employs the electrolytic solution for a lithium secondary battery, containing a difluorophosphite compound, according to the present invention, and thus has improved characteristics.