PVDF-HFP Polymer Gel Electrolyte for Low-Resistance Lithium Cells
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Solution Overview
Problem
Solid-state batteries face challenges with low power capabilities due to interfacial resistance and void spaces, and all batteries suffer from diminished power generation at cold temperatures, necessitating the development of high-performance solid-state and semi-solid battery designs that improve contact and interaction between active particles and electrolytes, and enhance energy density, especially at cold start temperatures.
Innovation Solution
A polymer gel electrolyte composed of a polymeric blend of PVDF-HFP and PVDF, combined with plasticizers such as ethylene carbonate and gamma butyrolactone, and lithium salts like LiTFSI and LiBF4, is used to form a non-flowing gel electrolyte that enhances electrochemical performance by improving contact resistance and cold cranking amps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solid-state electrolyte particles are used, then thermal stability and shelf life are improved, but power capabilities deteriorate due to interfacial resistance and void spaces
Solution Approach 1:
The patent uses a composite electrolyte system combining solid-state electrolyte particles (providing thermal stability) with a polymer gel matrix containing plasticizers (improving ionic conductivity). This composite structure allows the solid particles to maintain thermal stability while the gel matrix fills void spaces and reduces interfacial resistance, thereby improving power capabilities.
Solution Approach 2:
The polymer gel electrolyte acts as an intermediary between the solid-state electrolyte particles and the electrodes. It improves contact and interaction at interfaces, reducing interfacial resistance while allowing the solid-state particles to maintain their thermal stability benefits.
2Power
If liquid electrolytes are used, then power capabilities are improved, but thermal stability and safety deteriorate due to flammability
Solution Approach 1:
The patent creates a composite gel electrolyte that combines the high ionic conductivity of liquid electrolytes with the thermal stability of solid polymers. The polymer matrix provides thermal stability and prevents flammability, while the liquid plasticizers within the gel maintain good power capabilities and ionic conductivity.
Solution Approach 2:
The patent changes the physical state of the electrolyte from purely liquid to a gel state, which modifies the parameters of both power capability and thermal stability. The gel structure maintains the beneficial properties of liquid electrolytes while adding the thermal stability characteristic of solid materials.
3Reliability
If solid-state electrolyte layer is used, then safety is improved, but contact and interaction between particles and electrodes deteriorate due to limited contact and void spaces
Solution Approach 1:
The patent employs a porous polymer gel matrix that can accommodate solid-state electrolyte particles while maintaining good contact. The porous structure allows the gel to penetrate and fill void spaces, improving contact between particles and electrodes while the solid-state nature maintains safety.
Solution Approach 2:
The polymer gel acts as an intermediary material that improves contact and interaction between solid-state particles and electrodes. It fills gaps and enhances interfacial contact while the solid-state electrolyte particles maintain the safety benefits.
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 polymer gel electrolyte reduces contact resistance and improves electrochemical performance, including cold cranking amps, while eliminating the need for liquid electrolytes, thereby enhancing thermal stability and energy density.
Implementation Method 1
The polymer gel electrolyte includes a polymeric blend including polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polyvinylidene fluoride (PVDF)... one or more lithium salts
Implementation Method 2
one or more plasticizers selected from the group consisting of: ethylene carbonate (EC), diethyl carbonate (DEC), vinyl ethylene carbonate (VEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), propylene carbonate (PC), gamma butyrolactone (GBL)...
Data Source
AI summary
A polymer gel electrolyte for an electrochemical cell that cycles lithium ions is provided. The polymer gel electrolyte includes a polymeric blend comprising polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and polyvinylidene fluoride (PVDF), wherein a mass ratio of PVDF-HFP to PVDF is greater than or equal to about 1.5:1 to less than or equal to about 19:1 in the polymeric blend. Further, one or more plasticizers are included selected from the group consisting of: ethylene carbonate (EC), diethylene carbonate (DEC), vinyl ethylene carbonate (VEC), dimethylene carbonate (DMC), ethylmethylene carbonate (EMC), propylene carbonate (PC), gamma butyrolactone (GBL), diethylene glycol dimethyl ether (Diglyme), triethylene glycol dimethyl ether (Triglyme), tetraethylene glycol dimethyl ether (Tetraglyme), Triethyl Phosphate (TEP), 1-butyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide (BMIM-TFSI), 1-Ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide (EMI-TFSI), alkyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (PY-TFSI), piperidinium bis(trifluoromethanesulfonyl)imide (PP-TFSI), N-alkyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYRA-TFSI), and combinations thereof. The polymer gel electrolyte also includes one or more lithium salts.