Polymer Composite Cathode for High-Voltage NMC Stability
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Solution Overview
Problem
Conventional lithium secondary batteries use liquid electrolytes that are inflammable and pose safety risks, while solid electrolytes face challenges in achieving high ionic conductivity, broad electrochemical window, and compatibility with high-potential cathode materials like NMC622 or NMC811, and require a stable polymer backbone for encapsulating liquid electrolytes.
Innovation Solution
A composite cathode comprising a polymer electrolyte with a polymeric network based on specific (meth)acrylamide monomers that encapsulates deep eutectic solvents and is compatible with high-potential cathode active materials, such as NMC622, achieved by polymerizing a precursor composition containing a first monomer and a crosslinker, forming a three-dimensional polymer network.
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 inflammability and leakage
Solution Approach 1:
The patent employs a composite solid electrolyte comprising a polymer matrix (polyacrylonitrile or polyacrylamide) combined with lithium salt (LiTFSI) and deep eutectic solvent. This composite structure integrates the safety benefits of solid polymers with the ionic conductivity of liquid electrolytes, eliminating inflammability and leakage risks while maintaining high ion transport capability.
2Reliability
If conventional solid polymer electrolytes like PEO are used, then mechanical stability is improved, but anodic stability is limited to potentials around 4.0 V vs. Li+/Li
Solution Approach 1:
The patent changes the chemical parameters of the polymer electrolyte by selecting polyacrylonitrile or polyacrylamide as the base polymer and combining it with deep eutectic solvent and LiTFSI. This parameter change raises the anodic stability limit from 4.0 V (PEO) to above 4.3 V, enabling compatibility with high-potential cathode materials like NMC622 and NMC811.
3Reliability
If solid composite electrolytes are developed to improve safety, then ionic conductivity and electrochemical stability must be balanced, but finding a polymer backbone stable to sol-gel synthesis and compatible with high-potential cathodes is difficult
Solution Approach 1:
The patent performs preliminary selection of polymer backbones (polyacrylonitrile or polyacrylamide) that are inherently stable to sol-gel synthesis conditions before proceeding with electrolyte formulation. This preliminary action ensures that the polymer structure remains intact during synthesis, avoiding degradation while maintaining electrochemical stability for high-voltage applications.
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 composite cathode exhibits excellent cycling stability and high anodic stability, making it suitable for high-voltage applications and providing mechanical flexibility.
Implementation Method 1
a polymer electrolyte which comprises a polymer network and an electrolyte composition, wherein the electrolyte composition comprises a deep eutectic solvent (DES)
Implementation Method 2
Solid-state batteries have significantly reduced EHS (environmental, health and safety) hazards
Data Source
AI summary
The present invention relates to a solid composite cathode comprising a polymer electrolyte and high-potential 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.