Polymer Electrolyte Lithium Cell for High-Nickel NMC Stability
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Solution Overview
Problem
There is a need for improved lithium metal cell assemblies that offer high specific discharge capacity, high capacity retention, and are flexible, safe, and robust, while also being compatible with lithium metal anodes.
Innovation Solution
An electrochemical cell comprising a polymer gel electrolyte with a combination of lithium salts, including LiDFTFSI, and a cross-linked polyacrylate polymer, paired with a lithium nickel manganese cobalt oxide material (NMC9xx) as the cathode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If NMC materials with high nickel content are used to increase energy density, then the specific discharge capacity is improved, but the structural stability and safety deteriorate
Solution Approach 1:
The patent modifies the chemical composition parameters of the electrolyte by incorporating LiDFTFSI salt and adjusting the carbonate solvent ratios (EC/EMC/DMC) to stabilize the interface with high-nickel NMC cathodes, enabling safe operation at 4.3V without structural degradation
Solution Approach 2:
The electrolyte is formulated as a composite system combining multiple lithium salts (LiDFTFSI and LiPF6) with a ternary carbonate solvent mixture, creating synergistic effects that simultaneously enhance capacity retention and structural stability of the NMC cathode
2Use of energy by moving object
If operating voltage is increased to improve energy density, then the energy output is improved, but the electrolyte decomposition and corrosion increase
Solution Approach 1:
The electrolyte composition is designed in advance to prevent decomposition at high voltages through the use of LiDFTFSI salt, which forms a protective interface layer on the NMC cathode before degradation can occur, enabling stable operation at 4.3V
3Quantity of substance
If lithium metal anode is used to increase capacity, then the energy density is improved, but the compatibility with conventional electrolytes deteriorates
Solution Approach 1:
The electrolyte composition parameters are optimized by adjusting the ratio of carbonate solvents and incorporating LiDFTFSI salt to create a stable solid electrolyte interface (SEI) on lithium metal anodes, preventing dendrite formation and enabling long-term cycling 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 combination of the cathode active material and the polymer electrolyte composition provides an electrochemical cell with enhanced specific discharge capacity, coulombic efficiency, and capacity retention, while also allowing for operation at high voltages and improved compatibility with lithium metal anodes.
Implementation Method 1
an electrolyte allowing for the exchange of lithium cations between the electrodes
Implementation Method 2
During the discharge of the battery, lithium cations flow from the cathode to the anode through the electrolyte. Conversely, during the charging of the battery, lithium cations flow from the anode to the cathode through the electrolyte
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to an electrochemical cell comprising lithium as anode material, a nickel-rich NMC material as cathode material and a polymer electrolyte comprising a cross-linked acrylate polymer and a combination of lithium salts comprising lithium ((difluoromethyl)sulfonyl)((trifluormethyl)sulfonyl imide. It also relates to a method for the preparation of such electrochemical cell and to its use as a battery.