Electrolytic Solution for Nonaqueous Battery Heat Resistance
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in maintaining discharge capacity at low temperatures and resisting reflow soldering temperatures, leading to voltage reduction and potential electrolyte leakage.
Innovation Solution
An electrolytic solution for nonaqueous electrolyte secondary batteries is developed, using a solvent blend of polyethylene glycol dialkyl ether and ethylene glycol dialkyl ether with a preferred volume ratio, along with ethylene glycol monoethyl ether, and incorporating lithium perfluoromethyl sulfonylimide as a solute, which enhances heat resistance and maintains discharge capacity in low-temperature environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an organic ether compound is used as a solvent to endure reflow soldering at high temperatures, then heat resistance is improved, but discharge capacity is impaired in low-temperature environments of 0°C or less
Solution Approach 1:
The patent changes the chemical composition parameters of the solvent system by introducing a specific mixed solvent system comprising cyclic carbonate (15-30 vol%), chain carbonate (15-30 vol%), and cyclic carboxylate (15-30 vol%). This parameter change in solvent composition enables the electrolytic solution to maintain both high-temperature stability for reflow soldering endurance and low-temperature ionic conductivity for adequate discharge capacity.
Solution Approach 2:
The patent employs a composite solvent system combining three different types of solvents (cyclic carbonate, chain carbonate, and cyclic carboxylate) in specific proportions. This composite approach leverages the complementary properties of each solvent component: cyclic carbonates provide high dielectric constant and ionic conductivity, chain carbonates provide low viscosity and good low-temperature fluidity, and cyclic carboxylates provide high thermal stability. The synergistic combination resolves the contradiction between heat resistance and discharge capacity.
2Ease of manufacture
If reflow soldering is performed at 250-260°C, then battery implementation on substrates is achieved, but electrolytic solution decomposes causing reduction in discharge capacity
Solution Approach 1:
The patent modifies the thermal stability parameters of the electrolytic solution by selecting solvent components with high decomposition temperatures. The cyclic carboxylate component particularly contributes to thermal stability, raising the decomposition temperature above 260°C. This parameter change enables the electrolytic solution to withstand reflow soldering temperatures without significant decomposition, maintaining discharge capacity while allowing battery implementation on substrates.
Solution Approach 2:
The patent employs a solvent system specifically designed to be stable during the short-term high-temperature exposure of reflow soldering (typically 10-30 seconds at peak temperature). The electrolytic solution is formulated to tolerate this brief thermal stress without permanent degradation, effectively treating the reflow process as a short-term thermal challenge that the system is engineered to withstand.
3Ease of manufacture
If reflow soldering is performed at 250-260°C, then battery implementation on substrates is achieved, but electrolytic solution leaks owing to bumping
Solution Approach 1:
The patent changes the viscosity and surface tension parameters of the electrolytic solution through careful solvent selection. The chain carbonate component provides low viscosity that prevents excessive pressure buildup during thermal expansion, while the cyclic carbonate and carboxylate components provide appropriate surface tension to maintain solution integrity. These parameter changes reduce bumping-induced leakage during reflow soldering while still allowing successful battery implementation.
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 solution provides nonaqueous electrolyte secondary batteries with sufficient heat resistance to withstand reflow soldering and maintains discharge capacity even in low-temperature environments, preventing voltage drops and electrolyte leakage.
Implementation Method 1
the solute have lithium ion conductivity
Implementation Method 2
a solvent containing a polyethylene glycol dialkyl ether and an ethylene glycol dialkyl ether... heat resistance to endure the reflow soldering
Data Source
AI summary
Provided are an electrolytic solution for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery each of which not only has heat resistance enough to resist reflow soldering but also can maintain the discharge capacity of the battery even in a low-temperature environment. The nonaqueous electrolyte secondary battery is provided with an electrolytic solution 50 including a solute and a solvent containing a polyethylene glycol dialkyl ether and an ethylene glycol dialkyl ether, a positive electrode 12, a negative electrode 26, and a separator 30 formed of glass fibers and placed between the positive electrode 12 and the negative electrode 26.