Polymer Electrolyte for NMC Cathodes With DES Encapsulation
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Solution Overview
Problem
Conventional lithium secondary batteries with liquid electrolytes pose safety risks due to flammability and leakage, while solid electrolytes face challenges in achieving high ionic conductivity, broad electrochemical window, and compatibility with high-potential cathode materials like NMC622 or NMC811.
Innovation Solution
A polymer electrolyte comprising a polymeric network based on specific (meth)acrylamide monomers effectively encapsulates deep eutectic solvents and is compatible with high-voltage cathode active materials, such as NMC622, offering high anodic stability and mechanical flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid electrolytes are used in lithium secondary batteries, then high ionic conductivity is achieved, but safety risks increase due to flammability and leakage
Solution Approach 1:
The patent employs a composite solid electrolyte consisting of a polymer matrix (polyacrylonitrile or polyacrylamide) combined with lithium salt (LiClO4, LiBF4, or LiPF6). This composite structure provides both the mechanical stability and safety of solid materials while maintaining ionic conductivity through the lithium salt, thereby resolving the contradiction between safety and ionic conductivity.
Solution Approach 2:
The patent changes the physical state of the electrolyte from liquid to solid by using polymer-based solid electrolytes. This parameter change eliminates flammability and leakage issues inherent in liquid electrolytes while maintaining the necessary ionic conductivity for battery operation through careful selection of polymer matrix and lithium salt components.
2Reliability
If solid electrolytes are used to improve safety, then flammability and leakage risks are reduced, but compatibility with high-potential cathode materials like NMC622 or NMC811 is limited
Solution Approach 1:
The patent modifies the chemical composition parameters of the solid electrolyte by selecting specific polymer matrices (polyacrylonitrile or polyacrylamide) and lithium salts that are chemically compatible with high-potential cathode materials like NMC622 and NMC811. This enables the solid electrolyte to withstand higher operating voltages while maintaining safety advantages.
Solution Approach 2:
The composite solid electrolyte structure allows optimization of both safety and compatibility by combining a polymer matrix that provides mechanical stability with a lithium salt that ensures chemical compatibility with high-potential cathode materials, thereby resolving the contradiction between safety and adaptability.
3Strength
If conventional solid polymer electrolytes like PEO are used, then mechanical flexibility is provided, but anodic stability is limited to potentials around 4.0 V vs. Li+/Li
Solution Approach 1:
The patent changes the chemical structure parameters by replacing PEO with polyacrylonitrile or polyacrylamide matrices, which have different chemical properties that enable higher anodic stability. These polymers can withstand potentials above 4.0 V vs. Li+/Li while maintaining mechanical flexibility, thus resolving the contradiction between mechanical properties and electrochemical stability.
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 electrolyte exhibits excellent cycling stability and compatibility with high-potential electrode materials, enhancing the safety and performance of electrochemical cells.
Implementation Method 1
a polymer electrolyte which comprises a polymeric network which is compatible with deep eutectic solvents
Implementation Method 2
which is compatible with high-voltage cathode active materials, in particular NMC622... which has high anodic stability
Implementation Method 3
an electrochemical cell... wherein the cathode comprises cathode active material comprising Li, M and O
Data Source
AI summary
The present invention relates to an electrochemical cell comprising an anode, a polymer electrolyte and an NMC type cathode active material. The polymer electrolyte comprises an electrolyte composition, preferably comprising a deep eutectic solvent (DES), and a polymer network having a polyacrylamide backbone.