MPN-Carbonate Electrolyte for Low-Temperature Metal Ion Cells
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Solution Overview
Problem
Commercially available lithium ion cells with organic carbonate-based electrolytes face challenges in low temperature performance due to the high melting temperature of linear carbonates, which affects the ionic conductivity and viscosity, necessitating an alternative electrolyte for enhanced low temperature performance.
Innovation Solution
A metal ion cell design incorporating a solvent mixture of 3-methoxypropionitrile (MPN) and at least one linear carbonate solvent, with a lithium salt like LiPF6, to create an electrolyte system that operates effectively at low temperatures, improving ionic conductivity and Coulombic Efficiency (CE) while maintaining energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear carbonate solvents are used in the electrolyte, then low viscosity and good ionic conductivity are achieved, but low temperature performance deteriorates due to high melting temperature
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing 3-methoxypropionitrile (MPN) with a specific mass ratio of ≥0.1 compared to linear carbonate solvents. This parameter change modifies the freezing point and viscosity characteristics of the electrolyte, enabling it to maintain liquid state and ionic conductivity at low temperatures where conventional linear carbonates would solidify.
Solution Approach 2:
The patent creates a composite electrolyte system by combining MPN with linear carbonate solvents (DMC, DEC, or EMC) in specific ratios. This composite approach leverages the low viscosity and good ionic conductivity of linear carbonates while MPN contributes low melting point characteristics, achieving synergistic effects that resolve the contradiction between viscosity/conductivity and low temperature performance.
2Quantity of substance
If cyclic carbonate solvents are used in the electrolyte, then high dipole moments are achieved, but viscosity increases
Solution Approach 1:
The patent modifies the electrolyte composition by using MPN which provides adequate dipole moment for ionic solvation while maintaining low viscosity. The specific mass ratio of MPN to linear carbonate (≥0.1) is optimized to achieve the right balance between dipole moment (affecting ionic interaction) and viscosity (affecting ion mobility).
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 MPN-based electrolyte system enhances low temperature performance and energy density by maintaining capacity retention and improving discharge rate capability, as demonstrated by increased Coulombic Efficiency and capacity retention in lithium titanium oxide/lithium manganese oxide (LTO/LMO) cells.
Implementation Method 1
The electrolyte provides the medium through which lithium ions are transported between the cathode and the anode
Implementation Method 2
carbonate-based electrolytes, particularly linear carbonates, lack low temperature performance because of their high melting temperature
Data Source
AI summary
A metal ion cell that includes a positive electrode with a cathode active material configured to store and release metal ions: a negative electrode with an anode active material that operates at a potential that is not less than 0.6 volts (V) versus Li/Lit; and an electrolyte that incorporates one or more (e.g., lithium) metal salts and a solvent mixture that includes 3-methoxypropionitrile (MPN) and at least one linear carbonate. The MPN in the electrolyte may have a mass ratio of ≥0.1 as compared to the at least one linear carbonate. The at least one linear carbonate includes one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), or ethyl methyl carbonate (EMC). The solvent mixture may also include a mixture of carbonates, such that the mass percentage of the linear carbonate ranges from 10% to 90% compared to the overall mass of the mixture of carbonates.