Nonaqueous Electrolyte Composition for High-Output Lithium Secondary Batteries
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity, long life, and high output, especially when scaled up for larger applications such as motor vehicles, as existing improvements have not adequately addressed the need for sufficient performance and durability.
Innovation Solution
The use of specific compositions and properties for the positive and negative electrodes, combined with a nonaqueous electrolyte containing compounds like cyclic siloxane, fluorosilane, and acid salts, enhances the battery's performance by improving lithium ion occlusion and release capabilities, leading to improved low-temperature discharge characteristics and cycle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional small lithium secondary batteries are merely enlarged for large battery applications, then battery size increases, but output performance becomes insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the electrolyte composition with specific ratios of cyclic carbonate (15-30 vol%), chain carbonate (65-80 vol%), and cyclic carboxylate (0.5-5 vol%). This chemical parameter optimization enables large batteries to achieve sufficient output performance (discharge capacity ratio at 10C/0.2C rate of 70% or more) while maintaining high capacity, resolving the contradiction between battery size enlargement and output performance
Solution Approach 2:
The patent uses composite materials by combining multiple electrolyte components (cyclic carbonate, chain carbonate, and cyclic carboxylate) in specific proportions. This composite electrolyte system works synergistically to provide both the ionic conductivity needed for high output and the stability required for large battery applications, enabling large batteries to achieve 70% or more discharge capacity ratio without merely scaling up conventional designs
2Quantity of substance
If battery capacity is increased for high energy density applications, then energy storage improves, but low-temperature discharge characteristics deteriorate
Solution Approach 1:
The patent changes the electrolyte composition parameters by incorporating cyclic carboxylate (0.5-5 vol%) alongside optimized ratios of cyclic and chain carbonates. This parameter modification lowers the electrolyte's freezing point and maintains ionic conductivity at low temperatures, enabling batteries to deliver 70% or more of their capacity even in cold conditions while maintaining high overall capacity
Solution Approach 2:
The cyclic carboxylate component acts as an intermediary substance that mediates between the conflicting requirements of high capacity and low-temperature performance. It forms a stable solvation structure that facilitates lithium ion mobility at low temperatures without compromising the battery's overall capacity, thus resolving the contradiction between energy storage and cold-weather performance
3Quantity of substance
If battery size is enlarged for motor vehicle applications, then energy capacity increases, but cycle life becomes insufficient
Solution Approach 1:
The patent applies beforehand cushioning by adding cyclic carboxylate (0.5-5 vol%) to the electrolyte composition before battery operation begins. This component preemptively forms a stable protective film on the electrode surfaces during initial cycles, preventing electrolyte decomposition and electrode degradation. This prior protection enables large batteries to achieve 500 cycles or more with less than 20% capacity loss, sufficient for motor vehicle applications
Solution Approach 2:
The cyclic carboxylate serves as an intermediary that mediates between high energy capacity and long cycle life requirements. It forms a stable interface layer between the electrolyte and electrodes, preventing harmful reactions that would otherwise limit cycle life in large-capacity batteries. This intermediary protection enables the battery to maintain performance over 500 cycles while delivering high energy capacity for motor vehicle use
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
This configuration results in lithium secondary batteries with enhanced low-temperature discharge characteristics, high output, and extended cycle life, making them suitable for large-scale applications like motor vehicles while maintaining cost-effectiveness.
Implementation Method 1
a nonaqueous electrolyte which contains a cyclic siloxane compound of formula (1), a fluorosilane compound of formula (2), a compound of formula (3), compound having an S—F bond in the molecule, nitric acid salt, nitrous acid salt, monofluorophosphoric acid salt, difluorophosphoric acid salt, acetic acid salt, or propionic acid salt
Implementation Method 2
a positive electrode and a negative electrode each having a specific composition and specific properties and capable of occluding/releasing lithium
Data Source
AI summary
A lithium secondary battery comprising: a positive electrode and a negative electrode which each has a specific composition and specific properties; and a nonaqueous electrolyte which contains a cyclic siloxane compound represented by general formula (1), fluorosilane compound represented by general formula (2), compound represented by general formula (3), compound having an S—F bond in the molecule, nitric acid salt, nitrous acid salt, monofluorophosphoric acid salt, difluorophosphoric acid salt, acetic acid salt, or propionic acid salt in an amount of 10 ppm or more of the whole nonaqueous electrolyte. This lithium secondary battery has a high capacity, long life, and high output.[In general formula (1), R1 and R2 are an organic group having 1-12 carbon atoms and n is an integer of 3-10. In general formula (2), R3 to R5 are an organic group having 1-12 carbon atoms; x is an integer of 1-3; and p, q, and r each are an integer of 0-3, provided that 1≤p+q+r≤3. In general formula (3), R6 to R8 are an organic group having 1-12 carbon atoms and symbol A is a group constituted of H, C, N, O, F, S, Si, and/or P.]