Nitrile Catholytes for Solid-State Lithium Metal Batteries
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Solution Overview
Problem
Conventional lithium rechargeable batteries face issues with flammability, leakage, limited voltage stability, and chemical incompatibility with lithium metal electrodes due to the use of carbonate-based solvents, and nitrile solvents are unstable with low voltage anodes, limiting their use in high-energy batteries.
Innovation Solution
The development of electrochemical cells with a lithium metal negative electrode, a solid separator, and a positive electrode containing a catholyte with nitrile or dinitrile solvents and lithium salts, which are chemically compatible with the solid separator, enabling stability at high voltages and compatibility with lithium metal anodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbonate-based solvents are used in conventional lithium rechargeable batteries, then commercially relevant ion-conductivity and cycle life are achieved, but flammability and leakage problems occur
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by replacing carbonate-based solvents with nitrile-based solvents (such as acetonitrile, butyronitrile, benzonitrile) and their derivatives. This parameter change maintains ion-conductivity while eliminating flammability and leakage issues inherent to carbonate solvents.
Solution Approach 2:
The patent employs composite electrolyte formulations combining nitrile solvents with specific lithium salts (LiPF6, LiBF4, LiClO4) and additive packages. This composite approach achieves the desired balance between ion-conductivity, cycle life, and safety by leveraging the complementary properties of different components.
2Object-affected harmful factors
If nitrile solvents are used in place of carbonate solvents, then flammability and leakage problems are reduced, but instability with low voltage anodes such as graphite or lithium metal occurs
Solution Approach 1:
The patent introduces intermediary substances including solid electrolyte interphase (SEI) formers and protective coating layers on the anode surface. These intermediaries mediate between the nitrile solvent and the lithium metal anode, preventing direct harmful interactions while allowing ionic conductivity. The SEI layer acts as a protective barrier that stabilizes the interface.
Solution Approach 2:
The patent adjusts the chemical composition parameters of the nitrile-based electrolyte by incorporating specific additives and optimizing the ratio of nitrile solvent to lithium salt. These parameter changes enhance the electrolyte's chemical stability and its ability to form protective interfaces with lithium metal anodes.
3Reliability
If conventional battery architecture with porous polyolefin separator is used, then electrical insulation between electrodes is achieved, but chemical incompatibility with lithium metal negative electrodes occurs
Solution Approach 1:
The patent employs composite separator structures combining porous polyolefin base material with surface coatings or laminates that are chemically compatible with lithium metal. This composite approach maintains the electrical insulation and porosity benefits of polyolefin while adding chemical stability through the compatible coating layer.
Solution Approach 2:
The patent modifies the separator's chemical composition parameters by selecting specific polyolefin types (such as polyethylene, polypropylene) and adjusting their crystallinity, pore size, and thickness parameters. These parameter changes enhance both electrical insulation performance and chemical compatibility with lithium metal electrodes.
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
This configuration enhances the safety, cycle life, and voltage stability of lithium batteries, allowing for practical use in high-energy applications without the limitations of carbonate-based solvents, while maintaining compatibility with lithium metal anodes.
Implementation Method 1
a catholyte including a catholyte solvent and a lithium salt
Implementation Method 2
a solid separator... This separator electrically insulates the positive and negative electrodes of the battery but remains conductive towards Li+ ions
Implementation Method 3
a catholyte including a catholyte solvent and a lithium salt
Data Source
AI summary
Provided herein are electrochemical cells having a solid separator, a lithium metal anode, and a positive electrode catholyte wherein the electrochemical cell includes a nitrile, dinitrile, or organic sulfur-including solvent and a lithium salt dissolved therein. Also set forth are methods of making and using these electrochemical cells.