All-Inorganic Battery Electrolytes for Low-Flammability SEI Stability
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Solution Overview
Problem
Existing lithium-ion batteries face safety concerns due to the flammability and instability of organic electrolyte solutions, particularly at high temperatures and voltages, leading to issues such as dendrite formation and cell rupture, which limit their application in high-energy storage systems.
Innovation Solution
A solvent system comprising a mixture of primary solvent phosphoranimine (PA) derivatives and co-solvents like cyclotriphosphazene (Pz) derivatives, with optional monomeric phosphorus (MP) compound additives, is used to replace organic solvents, forming a stable solid electrolyte interphase (SEI) and enhancing safety and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic electrolyte solutions are used in lithium-ion batteries, then good ion conductivity and electrochemical performance are achieved, but flammability and thermal stability deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing organic carbonates with inorganic phosphoranimine and cyclotriphosphazene compounds. This fundamental parameter change transforms the electrolyte from flammable organic-based to non-flammable inorganic-based, while maintaining necessary ionic conductivity through molecular structure design of the phosphorus-containing compounds.
Solution Approach 2:
The patent creates a composite electrolyte system combining phosphoranimine (PA) derivatives as primary solvents with cyclotriphosphazene (Pz) derivatives as co-solvents. This composite approach integrates the advantages of both compound classes: PA provides low viscosity and good ion transport, while Pz contributes to SEI stability and electrochemical performance, achieving both safety and functionality.
2Reliability
If organic solvents are used to achieve low viscosity and high ion transport, then electrochemical performance is improved, but thermal stability and decomposition resistance worsen
Solution Approach 1:
The patent modifies the physical and chemical parameters of the electrolyte by using inorganic phosphorus-based compounds with specific molecular structures. The phosphoranimine compounds provide low viscosity for efficient ion transport, while the cyclotriphosphazene components contribute to high thermal stability and decomposition resistance, achieving both productivity and reliability.
Solution Approach 2:
The composite electrolyte system combines phosphoranimine and cyclotriphosphazene derivatives to achieve complementary properties. The PA component ensures low viscosity and high ion mobility, while the Pz component provides thermal stability and resistance to decomposition, together resolving the contradiction between ion transport efficiency and thermal stability.
3Power
If high current density is achieved through high charge carrier concentration, then power output is improved, but dendrite formation and cell rupture increase
Solution Approach 1:
The patent introduces cyclotriphosphazene derivatives as intermediary substances that mediate between the electrode and the phosphoranimine-based electrolyte. These Pz compounds facilitate the formation of a stable solid electrolyte interphase (SEI) layer that acts as a protective intermediary, preventing direct contact between high-concentration charge carriers and the electrode surface, thereby suppressing dendrite formation while maintaining high power output.
Solution Approach 2:
The electrolyte composition is designed to preliminarily form a stable SEI layer before high current density operation begins. The cyclotriphosphazene components preferentially react with electrode surfaces to create a protective interface layer in advance, which then prevents dendrite formation during subsequent high-power operation, allowing safe achievement of high power output.
4Adaptability or versatility
If operating temperature range is expanded to include low temperatures, then versatility is improved, but electrolyte stability and liquid state maintenance worsen
Solution Approach 1:
The patent adjusts the molecular structure parameters of the phosphoranimine and cyclotriphosphazene compounds to achieve appropriate melting points and viscosity characteristics. By carefully selecting substituent groups and molecular weights, the electrolyte maintains liquid state across a wide temperature range while preserving compositional stability and preventing crystallization or solidification at low temperatures.
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 all-inorganic electrolyte system significantly reduces flammability and enhances the stability of lithium-ion batteries, preventing dendrite formation and improving safety, making them suitable for high-energy storage applications.
Implementation Method 1
forming a stable solid electrolyte interphase (SEI) and enhancing safety and stability
Implementation Method 2
The all-inorganic electrolyte system significantly reduces flammability and enhances the stability of lithium-ion batteries
Data Source
AI summary
An all-inorganic electrolyte formulation for use in a lithium-ion battery system comprising at least one of each a phosphoranimine, a phosphazene, a monomeric organophosphate and a supporting lithium salt. The electrolyte preferably has a melting point below 0° C., and a vapor pressure of combustible components at 60.6° C. sufficiently low to not produce a combustible mixture in air, e.g., less than 40 mmHg at 30° C. The phosphoranimine, phosphazene, and monomeric phosphorus compound preferably do not have any direct halogen-phosphorus bonds. A solid electrolyte interface layer formed by the electrolyte with an electrode is preferably thermally stable ≥80° C.