Nonaqueous Electrolyte Composition for High-Output Lithium Secondary Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity, long life, and high output, especially when scaled up for larger applications like motor vehicles, as existing improvements have not adequately addressed the need for sufficient performance.
Innovation Solution
The use of a lithium secondary battery configuration that includes a positive electrode and a negative electrode with specific compositions and properties, along with a nonaqueous electrolyte containing specific compounds such as cyclic siloxane, fluorosilane, and acid salts, to enhance low-temperature discharge characteristics and maintain high output and capacity.
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 modifying the electrolyte composition parameters - specifically using a non-aqueous electrolyte containing cyclic carbonate (15-40 vol%), chain carbonate (30-60 vol%), and cyclic carboxylate (5-30 vol%). This optimized parameter combination 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 employs composite materials by creating a multi-component electrolyte system that combines different types of carbonates and carboxylates. This composite electrolyte formulation (mixing cyclic carbonate, chain carbonate, and cyclic carboxylate) provides synergistic effects that enable both large battery size and high output performance, overcoming the limitations of single-component electrolytes in scaled-up battery applications
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 uses parameter changes by adjusting the electrolyte composition to include cyclic carboxylate (5-30 vol%), particularly γ-butyrolactone, which has high dielectric constant and maintains good ionic conductivity at low temperatures. This parameter optimization enables the battery to maintain both high capacity (4.0 Ah or more) and acceptable low-temperature discharge characteristics, resolving the trade-off between capacity and temperature performance
3Duration of action of stationary object
If batteries are designed for long cycle life, then durability improves, but output performance may be compromised
Solution Approach 1:
The patent applies composite materials by formulating a multi-component electrolyte system where cyclic carbonate provides stable SEI formation for long cycle life, chain carbonate ensures high ionic conductivity for output performance, and cyclic carboxylate enhances overall stability. This composite approach achieves both durability (60% capacity retention after 500 cycles at 45°C) and high output performance (70% or more discharge capacity ratio at 10C/0.2C rate) simultaneously
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 improved low-temperature discharge characteristics, high output, and extended cycle life, making them suitable for large-scale applications like motor vehicles while using less expensive materials.
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.]