Solid electrolyte separator bonding agent

Abstract

Set forth herein are electrochemical cells which include a negative electrode current collector, a lithium metal negative electrode, an oxide electrolyte membrane, a bonding agent layer, a positive electrode, and a positive electrode current collector. The bonding agent layer advantageously lowers the interfacial impedance of the oxide electrolyte at least at the positive electrode interface and also optionally acts as an adhesive between the solid electrolyte separator and the positive electrode interface. Also set forth herein are methods of making these bonding agent layers including, but not limited to, methods of preparing and depositing precursor solutions which form these bonding agent layers. Set forth herein, additionally, are methods of using these electrochemical cells.

Description

BACKGROUND[0001]This application claims priority to, and the benefit of, US Provisional Patent Application No. 62 / 336,474, filed, May 13, 2016, entitled SOLID ELECTROLYTE SEPARATOR BONDING AGENT, and US Provisional Patent Application No. 62 / 448,294, filed Jan. 19, 2017, entitled SOLID ELECTROLYTE SEPARATOR BONDING AGENT, the entire contents of each of which are herein incorporated by reference in their entirety for all purposes.[0002]In a rechargeable Li+ ion battery, Li+ ions move from a negative electrode to a positive electrode during discharge and in the opposite direction during charge. This process produces electrical energy (Energy=Voltage×Current) in a circuit connecting the electrodes, which is electrically insulated from, but parallel to, the Li+ ion conduction path. The battery's voltage (V versus Li) is a function of the chemical potential difference for Li situated in the positive electrode as compared to the negative electrode and is maximized when Li metal is used as ...

AI Technical Summary

Benefits of technology

The patent describes a new electrochemical stack design for a lithium battery that includes a lithium metal negative electrode, a positive electrode, and a gelforce bonding layer made of a lithium salt, a polymer, and a solvent. This layer is positioned between the electrolyte separator and the positive electrode to protect the lithium metal negative electrode from exposure to the polymer or solvent. The bonding layer reduces the interfacial impedance between the electrolyte separator and the positive electrode, leading to improved performance of the lithium battery.

Problems solved by technology

However, liquid electrolytes suffer from several problems including flammability during thermal runaway, outgassing at high voltages, and chemical incompatibility with lithium metal negative electrodes.

Despite these advantages, solid electrolytes are still insufficient in several regards for commercial applications.

Moreover, even in the absence of delamination, solid interfaces tend not to perfectly align with each other.

If a solid lithium metal negative electrode is laminated to a solid electrolyte, and the solid electrolyte (i.e., separator), on the opposing side, is laminated to a positive electrode, each solid interface (Li-separator & Separator-Cathode) may have insufficient electrical contact due to areas where one solid interface does not perfectly align and contact another solid interface.

Areas of non-contact between the solid electrolyte and the positive electrode result in impedance rises which reduce a battery's power and capacity.

To date and the best of Applicant's knowledge, there are no public disclosures of commercially viable solid electrolyte separators which interface with a solid positive electrode with a sufficiently low interfacial resistance suitable for a commercial application.

When, for example, a solid separator such as a lithium-stuffed garnet electrolyte monolith contacts a positive electrode, there may be interfacial impedance between the solid electrolyte and the positive electrode due to poor wetting of the positive electrode, or its catholyte, onto the solid electrolyte surface, low ion-conductivity in either the separator or the electrode, or chemical reactions between the positive electrode and the solid electrolyte which produce side products detrimental to electrochemical performance.

However, no reported methods to date address these challenges for a battery that uses a lithium metal negative electrode.

For example, while some researchers combined liquid electrolytes with lithium-stuffed garnets, the electrolytes used were insufficiently dense or of the incorrect form factor to protect a lithium metal negative electrode from exposure to the volatile components of the electrolyte.

Also, for example, these electrolytes were insufficiently dense or of the incorrect form factor to protect an electrochemical cell from lithium dendrite growth.

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