Lithium Battery Electrolyte Additive for Cycle Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving long-life performance due to the high interfacial reactivity and unstable crystal structure of Ni-enriched Ni-Co-Mn-based oxides, which accelerate deterioration during cycles, limiting their energy density and lifespan.
Innovation Solution
An electrolyte solution for lithium secondary batteries is developed, comprising a lithium salt, solvent, and bis(4-(trifluoromethoxy)phenyl) oxalate as a negative-electrode additive, which forms a solid electrolyte interphase (SEI) on the negative electrode, improving low-resistance characteristics and increasing lifespan, with optimal addition amounts between 0.2% to 2.0% by weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ni-enriched Ni-Co-Mn-based oxides are used to increase positive electrode capacity, then energy density is improved, but interfacial reactivity increases and crystal structure stability decreases, accelerating deterioration during cycles
Solution Approach 1:
The patent introduces an electrolyte composition as an intermediary medium between the Ni-enriched positive electrode and the negative electrode. This electrolyte contains specific additives (cyclic carbonate 10-30 vol%, chain carbonate 70-90 vol%, and fluoroethylene carbonate 5-20 vol%) that form protective interfacial films on the positive electrode surface. These films act as mediators that reduce direct contact between the high-reactivity Ni-enriched oxide and the electrolyte, thereby suppressing interfacial reactivity and stabilizing the crystal structure during cycling while maintaining high capacity.
Solution Approach 2:
The patent modifies the chemical composition parameters of the electrolyte by incorporating specific ratios of cyclic carbonate, chain carbonate, and fluoroethylene carbonate. This parameter change in the electrolyte composition leads to the formation of a stable solid electrolyte interphase (SEI) on the positive electrode, which protects the Ni-enriched oxide from degradation. The optimized electrolyte parameters enable the battery to achieve both high energy density and long cycle life by controlling the interfacial chemistry.
2Quantity of substance
If the positive electrode charging voltage is increased to achieve higher capacity, then energy density is improved, but electrode material stability decreases, making it difficult to secure long-life performance
Solution Approach 1:
The electrolyte composition serves as a protective intermediary layer between the high-voltage positive electrode and the bulk electrolyte. The specific additive combination (cyclic carbonate, chain carbonate, and fluoroethylene carbonate) forms a stable interfacial film that mediates the interaction at high charging voltages. This intermediary film prevents direct exposure of the electrode material to harsh electrolyte conditions, thereby maintaining material stability even at elevated charging voltages that enable higher capacity.
Solution Approach 2:
The patent changes the electrolyte composition parameters by incorporating fluoroethylene carbonate at 5-20 vol%, which has unique properties for forming stable films at high voltages. This parameter modification in the electrolyte enables the system to withstand higher charging voltages without compromising electrode material stability, thus achieving both high energy density and long-term performance.
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 solution enhances ion conductivity, high-temperature durability, and high-rate characteristics, maintaining discharge retention of 94% or greater after 200 cycles, suitable for vehicle batteries, by forming an effective SEI and reducing cell resistance.
Implementation Method 1
bis(4-(trifluoromethoxy)phenyl) oxalate as a negative-electrode additive, which forms a solid electrolyte interphase (SEI) on the negative electrode
Implementation Method 2
an electrolyte serving as a medium for transferring a lithium ion
Data Source
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AI summary
Disclosed are an electrolyte solution for lithium secondary batteries capable of increasing the lifetime of the lithium secondary batteries and a lithium secondary battery including the same. Provided also is an electrolyte solution for lithium secondary batteries including a lithium salt, a solvent and a negative-electrode additive. The negative-electrode additive preferably includes bis(4-(trifluoromethoxy)phenyl) oxalate represented by the following Formula 1.