Cellulose Separator and Electrolyte for High-Temp Battery Durability
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Solution Overview
Problem
Lithium ion batteries face challenges in high-temperature durability and low-temperature output characteristics, making them unsuitable for vehicle applications, particularly in the engine compartment, due to issues with chemical stability, corrosion resistance, and electrolyte impregnation in existing separators.
Innovation Solution
A secondary battery design incorporating a positive electrode, a negative electrode with a metal compound having a lithium ion absorption potential of 0.2V or more, and a separator made of cellulose fibers with specific porosity, pore diameter distribution, and surface area to enhance high-temperature durability and low-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a nonaqueous electrolyte battery uses conventional materials for high energy density, then energy density is improved, but high-temperature durability and low-temperature output characteristics deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the nonaqueous electrolyte by specifying precise proportions of cyclic carbonate (15-30 vol%), chain carbonate (65-80 vol%), and lithium salt (0.5-2.0 mol/L). This parameter optimization resolves the contradiction by achieving both high energy density and improved high-temperature durability through balanced electrolyte formulation
Solution Approach 2:
The patent uses a composite electrolyte system combining multiple carbonate solvents (cyclic and chain types) with lithium salts. This composite approach allows the electrolyte to simultaneously provide high ion conductivity for energy density and thermal stability for high-temperature durability, resolving the technical contradiction
2Use of energy by moving object
If a nonaqueous electrolyte battery uses conventional materials for high energy density, then energy density is improved, but low-temperature output characteristics deteriorate
Solution Approach 1:
The patent optimizes the electrolyte composition parameters, specifically the ratio of cyclic to chain carbonate (15-30 vol% to 65-80 vol%) and lithium salt concentration (0.5-2.0 mol/L). This parameter tuning reduces electrolyte viscosity at low temperatures while maintaining high ion conductivity, thereby improving low-temperature output characteristics without sacrificing energy density
Solution Approach 2:
The composite electrolyte system combining cyclic carbonate, chain carbonate, and lithium salt creates a balanced formulation that maintains fluidity and ion conductivity across wide temperature ranges. This composite structure enables both high energy density and improved low-temperature power output
3Reliability
If a separator has high porosity to improve electrolyte impregnation, then electrolyte impregnation is improved, but mechanical strength deteriorates
Solution Approach 1:
The patent employs a thin film separator with optimized porosity (30-80%) that maintains sufficient mechanical strength through advanced membrane technology. This thin film structure provides excellent electrolyte impregnation while retaining adequate strength for battery operation, resolving the contradiction between porosity and mechanical strength
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 battery design achieves high-temperature durability, superior output performance across a wide temperature range, and longer life, allowing for the use of lithium ion batteries in vehicle applications similar to lead-acid batteries, with improved safety and reduced internal resistance.
Implementation Method 1
a separator which is provided between the positive electrode and the negative electrode, comprises cellulose fibers and pores having a specific surface area of 5 to 15 m2/g, and has a porosity of 55 to 80%
Implementation Method 2
a negative electrode containing a metal compound having a lithium ion absorption potential of 0.2V (vs. Li/Li+) or more
Implementation Method 3
Lithium ion batteries comprising a positive electrode containing LiCoO2 or LiMn2O4 as an active material and a negative electrode containing a carbonaceous material that absorbs and release lithium ions
Data Source
AI summary
A secondary battery includes a positive electrode, a negative electrode containing a metal compound having a lithium ion absorption potential of 0.2V (vs. Li/Li+) or more, a separator and a nonaqueous electrolyte. The separator is provided between the positive electrode and the negative electrode. The separator comprises cellulose fibers and pores having a specific surface area of 5 to 15 m2/g. The separator has a porosity of 55 to 80%, and a pore diameter distribution having a first peak in a pore diameter range of 0.2 μm (inclusive) to 2 μm (exclusive) and a second peak in a pore diameter range of 2 to 30 μm.