Lithium Battery Separator Wettability and Safety via Viscous Electrolyte
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Solution Overview
Problem
Lithium secondary batteries face issues with poor wettability of separators by non-aqueous electrolyte solutions, leading to deteriorated charging and discharging performance, safety concerns due to low-viscosity solvents, and increased risk of liquid leaks and flammability.
Innovation Solution
A lithium secondary battery design featuring a porous separator with a coating layer of inorganic particles and binder polymer, combined with a non-aqueous electrolyte solution of specific viscosity and lithium salt concentration, enhancing wettability and safety by using high-viscous solvents and appropriate lithium salts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low-viscous non-aqueous solvents are used to improve separator wettability, then charging/discharging performance is improved, but safety deteriorates due to increased flammability and liquid leak risk
Solution Approach 1:
The patent changes the viscosity parameter of the non-aqueous solvent from low-viscous (equal to or slightly more than 1.0 cP) to high-viscous (more than 1.0 cP and equal to or less than 5.0 cP). This parameter change simultaneously improves separator wettability while reducing flammability and liquid leak risk, thereby resolving the safety issue without sacrificing charging/discharging performance.
Solution Approach 2:
The patent uses composite non-aqueous electrolyte solutions containing multiple components including high-viscous non-aqueous solvents (viscosity >1.0 cP and ≤5.0 cP at 25°C), lithium salts, and additives. This composite approach allows the system to achieve both good separator wettability and improved safety by combining the benefits of different materials with complementary properties.
2Productivity
If low-viscous non-aqueous solvents are used to enhance wettability, then charging/discharging characteristics are improved, but flammability increases leading to safety issues
Solution Approach 1:
The patent changes the viscosity parameter of the non-aqueous solvent to a specific range (more than 1.0 cP and equal to or less than 5.0 cP at 25°C). This parameter optimization maintains good charging/discharging characteristics while significantly reducing flammability compared to low-viscous solvents, thereby resolving the harmful effect without sacrificing productivity.
Solution Approach 2:
The patent applies different viscosity characteristics to different functional requirements: the high-viscous non-aqueous solvent (viscosity >1.0 cP and ≤5.0 cP) provides both adequate wettability for good charging/discharging characteristics and inherent safety benefits through reduced volatility and flammability, creating a locally optimized solution that addresses both productivity and safety concerns.
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 improves the wettability of the separator, enhances charging and discharging performance, and increases safety by reducing the risk of leaks and flammability, while maintaining thermal stability.
Implementation Method 1
a porous coating layer coated on at least one surface of the porous substrate and having inorganic particles and a binder polymer, the inorganic particles being connected and fixed to each other by means of the binder polymer, the porous coating layer having pores therein formed by interstitial volumes among the inorganic particles
Data Source
AI summary
A lithium secondary battery includes a cathode, an anode, a separator interposed between the cathode and the anode, and a non-aqueous electrolyte solution obtained by dissolving lithium salt in a non-aqueous solvent. The separator includes a porous substrate having pores; and a porous coating layer located on at least one surface of the porous substrate and having inorganic particles and a binder polymer, the inorganic particles being connected and fixed to each other by means of the binder polymer, the porous coating layer having pores therein formed by interstitial volumes among the inorganic particles. The non-aqueous electrolyte solution has a viscosity of 1.4 cP or above at 25° C. This lithium secondary battery gives improved safety and excellent charging/discharging characteristics due to a low risk of leakage of a non-aqueous electrolyte solution and good wettability of separator with the solvent.