Polyphosphazene Solid-State Electrolytes for Flame-Resistant Li Batteries
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Solution Overview
Problem
Existing lithium-ion and lithium metal batteries face safety concerns due to the flammability of organic liquid electrolytes, which can lead to thermal runaway and explosions. Conventional ionic liquid compositions have drawbacks such as high viscosity, the shuttle effect, and reactivity with lithium metal, resulting in poor performance and high costs.
Innovation Solution
A quasi-solid or solid-state electrolyte system comprising a polyphosphazene polymer and a lithium salt, where the lithium salt occupies a weight fraction from 0.1% to 50% based on the total weight of the lithium salt and the polyphosphazene polymer combined. The polyphosphazene polymer permeates into the electrodes and is chemically bonded to the active materials and conductive additives, acting as a binder and enhancing electrolyte stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional ionic liquid compositions are used as electrolyte, then fire resistance is improved, but viscosity increases and lithium ion transport becomes difficult
Solution Approach 1:
The patent uses a composite electrolyte system combining ionic liquid with solid polymer matrix (such as PEO) and inorganic fillers (such as Li1.3Al0.3Ti0.3Nb0.3O2 or Li2SiO3). This composite structure allows the ionic liquid to provide fire resistance while the solid polymer and inorganic fillers create pathways for lithium ion transport, reducing the negative impact of high viscosity.
Solution Approach 2:
The patent modifies the physical and chemical parameters of the ionic liquid by selecting specific cations and anions (such as imidazolium, pyridinium, or ammonium cations with CF3SO3- or PF6- anions) and adjusting their molecular structure. This parameter optimization reduces viscosity while maintaining fire resistance, enabling better lithium ion conductivity.
2Object-affected harmful factors
If ionic liquids are used as electrolyte, then fire resistance is improved, but the shuttle effect remains severe allowing polysulfide migration
Solution Approach 1:
The patent introduces a solid polymer matrix and inorganic filler particles as intermediary phases between the ionic liquid and the electrode materials. These intermediaries physically block the migration of lithium polysulfides while allowing lithium ion transport, thereby suppressing the shuttle effect and improving cycle life while maintaining the fire resistance provided by the ionic liquid.
3Object-affected harmful factors
If ionic liquids are used as electrolyte, then fire resistance is improved, but reactivity with lithium metal increases consuming lithium and depleting electrolyte
Solution Approach 1:
The patent extracts or removes the highly reactive components from direct contact with lithium metal by introducing a solid polymer matrix and inorganic filler layers. These layers act as protective barriers that prevent direct reaction between the ionic liquid and lithium metal anode, reducing lithium consumption and electrolyte depletion while preserving the fire-resistant properties of the ionic liquid.
4Speed
If inorganic solid-state electrolyte is used, then conductivity is improved, but interfacial impedance with electrodes increases
Solution Approach 1:
The patent creates a composite electrolyte system where inorganic solid-state electrolyte particles are dispersed in an ionic liquid-polymer matrix. The inorganic particles provide high lithium ion conductivity pathways, while the ionic liquid-polymer continuous phase ensures good interfacial contact with electrodes and reduces interfacial impedance, combining the advantages of both materials.
5Speed
If inorganic ceramic electrolyte is used, then conductivity is improved, but mechanical properties and film-forming ability deteriorate due to brittleness
Solution Approach 1:
The patent combines brittle inorganic ceramic electrolyte particles with a flexible ionic liquid-polymer matrix to form a composite electrolyte. The inorganic ceramic particles provide high lithium ion conductivity, while the polymer matrix provides mechanical flexibility and ductility, compensating for the brittleness of the ceramic material and enabling better film-forming ability.
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 proposed electrolyte system is highly flame-resistant, with a significantly increased flash point, reducing the risk of fires and explosions. It maintains good lithium-ion conductivity and cycle life, while being compatible with existing battery production facilities.
Implementation Method 1
The polyphosphazene polymer permeates into the electrodes and is chemically bonded to the active materials and conductive additives, acting as a binder
Implementation Method 2
a quasi-solid or solid-state electrolyte in ionic communication with the anode and the cathode
Data Source
AI summary
A rechargeable lithium battery comprising an anode, a cathode, and a quasi-solid or solid-state electrolyte in ionic communication with the anode and the cathode, wherein the electrolyte comprises a polyphosphazene polymer and a lithium salt dissolved or dispersed in the polymer, wherein the lithium salt occupies a weight fraction from 0.1% to 50% based on the total weight of the lithium salt and the polyphosphazene polymer combined; wherein the polyphosphazene polymer permeates into the anode and/or the cathode and in physical contact with the anode active material inside the anode and/or in physical contact with or chemically bonded to the cathode active material inside the cathode; and wherein the electrolyte further comprises from 0% to 50% by weight of a non-aqueous liquid solvent dispersed in the polymer, based on the total weight of the lithium salt, the polymer, and the non-aqueous liquid solvent combined.