Composite Cathode Solid Electrolyte Safety
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Solution Overview
Problem
Lithium-ion batteries face safety concerns due to the risk of explosion and health hazards from vaporized electrolyte and toxic hydrogen fluoride formation during mechanical damage, such as in vehicle accidents, primarily due to the flammability and reactivity of solvents and conducting salts like LiPF6.
Innovation Solution
A composite cathode is developed with a higher volume and weight fraction of solid inorganic lithium-ion conductors, reducing the amount of liquid electrolyte, including LiPF6, and incorporating interconnected pores to lower contact resistance and enhance safety by minimizing the risk of ignition and toxic gas formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid electrolyte with conducting salt LiPF6 is used in lithium-ion battery, then electrical conductivity and lithium ion transport are achieved, but safety hazards arise from flammability and toxic hydrogen fluoride formation
Solution Approach 1:
The patent changes the physical state parameter of the electrolyte from liquid to solid by using inorganic solid electrolytes (such as lithium phosphorus oxynitride, lithium aluminum phosphate, or lithium lanthanum zirconium oxide). This parameter change eliminates the flammability and toxic gas formation issues associated with liquid electrolytes while maintaining lithium ion conductivity.
Solution Approach 2:
The patent employs composite cathode structures combining active cathode material particles with inorganic solid electrolyte materials. This composite approach enables the system to achieve both the electrical conductivity and lithium ion transport functions of traditional liquid electrolytes while eliminating their safety hazards through the use of non-flammable solid inorganic materials.
2Reliability
If solid inorganic lithium-ion conductors are used in higher volume fraction, then safety is improved by reducing flammable solvents, but contact resistance may increase
Solution Approach 1:
The patent applies local quality by creating a coating on the surface of active cathode material particles that contains the inorganic solid electrolyte. This localized application ensures that the solid electrolyte is positioned where it is most needed - at the interface between particles - thereby maintaining good contact and low resistance while still achieving the safety benefits of reduced liquid electrolyte content.
Solution Approach 2:
The patent utilizes porous structures in the cathode coating that allow the solid inorganic electrolyte to form continuous conductive pathways between particles. The porous architecture maintains adequate contact between electrolyte regions, preventing excessive contact resistance even when liquid electrolyte is significantly reduced or eliminated.
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 design reduces the risk of ignition and health hazards by minimizing the amount of flammable solvents and toxic conducting salts, improving safety performance in lithium-ion batteries, especially in motor vehicle applications.
Implementation Method 1
a solid inorganic lithium-ion conductor, and a liquid electrolyte, the solid inorganic lithium ion conductor in the composite cathode being present in a higher volume fraction and weight fraction than the liquid electrolyte
Data Source
AI summary
A composite cathode is provided which includes a collector, an active cathode material, a binder, a solid inorganic lithium-ion conductor and a liquid electrolyte. The solid inorganic lithium ion conductor is present in the composite cathode in a higher volume and weight proportion than the liquid electrolyte. A method for forming the composite cathode is also provided, and a lithium ion battery is provided which includes a composite cathode having a collector, an active cathode material, a binder, a solid inorganic lithium ion conductor and a liquid electrolyte.