Non-flammable Quasi-solid Electrolyte Separator for Lithium Batteries
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Solution Overview
Problem
Rechargeable lithium metal and lithium-ion batteries face challenges such as dendrite formation, thermal runaway, and flammability due to volatile organic solvents, limiting their commercialization and safety, especially in lithium-sulfur cells, which require high energy density and long cycle life.
Innovation Solution
A non-flammable, quasi-solid electrolyte-separator layer is developed using a porous thin-film separator coated with a high-concentration lithium salt solution, reducing vapor pressure and flash point, preventing dendrite growth and thermal issues while maintaining high lithium ion transference numbers for efficient energy storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic liquid solvents are used in the electrolyte to enable lithium ion transport, then the battery can function, but the electrolyte becomes highly volatile and flammable leading to thermal runaway and explosion
Solution Approach 1:
The patent applies parameter changes by transitioning the electrolyte from a liquid state to a gel state through the addition of gel-forming polymers. This fundamental state change eliminates the volatility and flammability characteristics of liquid electrolytes while maintaining ionic conductivity necessary for battery operation, directly resolving the safety issue.
Solution Approach 2:
The patent uses composite materials by combining gel-forming polymers with lithium salts to create a gel electrolyte system. This composite structure integrates the ion-conducting properties of lithium salts with the structural stability and non-flammability of polymers, achieving both functionality and safety.
2Quantity of substance
If lithium metal is used as the anode to achieve high energy density, then the battery capacity increases, but dendrites form during cycling causing internal shorting and thermal runaway
Solution Approach 1:
The patent changes the physical parameters of the electrolyte by using gel electrolytes with specific viscosity and mechanical properties. These parameter modifications create a more uniform lithium ion flux distribution during cycling, preventing dendrite formation while maintaining high capacity lithium metal anodes.
Solution Approach 2:
The gel electrolyte acts as a cushioning medium that prevents dendrite formation before they can cause harmful effects. The gel's viscoelastic properties absorb and distribute mechanical stresses during lithium deposition, preventing the localized stress concentrations that lead to dendrite growth and subsequent internal shorting.
3Reliability
If complex anode or electrolyte structures are designed to prevent dendrites, then cycling stability improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The gel electrolyte performs multiple functions simultaneously: it serves as the ion-conducting medium, provides mechanical stability to prevent dendrites, and acts as a binder for the electrodes. This multi-functionality eliminates the need for separate protective layers and complex structures, simplifying the overall battery design while maintaining reliability.
4Ease of operation
If flammable organic solvents are used in the electrolyte, then lithium ion transport is enabled, but thermal runaway and explosion risks increase
Solution Approach 1:
The patent changes the thermal parameters of the electrolyte system by using gel polymers with high thermal stability. This parameter change raises the decomposition temperature and eliminates the flash point issues associated with organic solvents, enabling safe operation at elevated temperatures while maintaining ion transport efficiency.
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 a safe, high-energy-density, and long-cycle-life lithium battery with no risk of explosion, overcoming dendrite formation and thermal runaway, and enabling specific energies exceeding 800 Wh/kg in lithium-sulfur cells.
Implementation Method 1
a porous thin-film separator coated with a non-flammable quasi-solid electrolyte
Implementation Method 2
maintaining high lithium ion transference numbers for efficient energy storage
Data Source
AI summary
A separator-electrolyte layer product for use in a lithium battery, comprising: (a) a porous thin-film separator selected from a porous polymer film, a porous mat, fabric, or paper made of polymer or glass fibers, or a combination thereof, wherein the separator has a thickness less than 500 μm; and (b) a non-flammable quasi-solid electrolyte containing a lithium salt dissolved in a liquid solvent up to a concentration no less than 3 M; wherein the porous thin-film separator is coated with the quasi-solid electrolyte so that the layer product exhibits a vapor pressure less than 0.01 kPa when measured at 20° C., a vapor pressure less than 60% of the vapor pressure of the liquid solvent alone, a flash point at least 20 degrees Celsius higher than a flash point of the first liquid solvent alone, a flash point higher than 150° C., or no detectable flash point.