Amorphous ionically conductive metal oxides and sol gel method of preparation

Abstract

Amorphous lithium lanthanum zirconium oxide (LLZO) is formed as an ionically-conductive electrolyte medium. The LLZO comprises by percentage of total number of atoms from about 0.1% to about 50% lithium, from about 0.1% to about 25% lanthanum, from about 0.1% to about 25% zirconium, from about 30% to about 70% oxygen and from 0.0% to about 25% carbon. At least one layer of amorphous LLZO may be formed through a sol-gel process wherein quantities of lanthanum methoxyethoxide, lithium butoxide and zirconium butoxide are dissolved in an alcohol-based solvent to form a mixture which is dispensed into a substantially planar configuration, transitioned through a gel phase, dried and cured to a substantially dry phase.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 12 / 848,991, filed Aug. 2, 2010, which is a continuation-in-part of U.S. patent application Ser. No. 12 / 163,044 filed Jun. 27, 2008, which claims priority to U.S. Provisional Application No. 60 / 947,016, filed Jun. 29, 2007, the entirety of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]A battery cell is a useful article that provides stored electrical energy that can be used to energize a multitude of devices, particularly portable devices that require an electrical power source. The cell is an electrochemical apparatus typically formed of at least one ion-conductive electrolyte medium disposed between a pair of spaced-apart electrodes commonly known as an anode and a cathode. Electrons flow through an external circuit connected between the anode and cathode. The electron flow is caused by the chemical-reaction-based electric potenti...

AI Technical Summary

Benefits of technology

The present invention provides an amorphous oxide-based compound with a specific formula and a method for synthesizing it. The compound has a unique structure and properties that make it useful in various applications, such as electrochemical cells and sensors. The method involves dissolving alkali metal and metal oxide precursors in an alcohol-based solvent and dispensing it in a planar configuration, through a gel phase, and drying and curing it to a dry phase. The resulting compound has a high degree of purity and can be used in various applications without the need for additional purification steps.

Problems solved by technology

Despite the benefits provided by certain anode materials and electrolytes, the materials themselves and, often, the combination of a particular electrode material and a particular electrolyte can cause problems in cell performance and, in some instances, can create a hazardous condition.

As a further example of problems, certain liquids that are useful as effective electrolytes can create hazardous conditions when serving as components of a lithium-ion battery.

One reason is that liquid electrolytes often react detrimentally with desirable electrode substances such as lithium even though the liquid is non-aqueous.

Another reason that liquid electrolytes can be undesirable is the need to prevent electrolytic material from freely flowing beyond a predetermined geometric boundary configuration.

For example, leakage of electrolyte solution from the battery container is typically undesirable.

Another problem with liquid electrolytes is that some solvents that are used as effective non-aqueous, liquid electrolytes are flammable and have a relatively high vapor pressure.

The combination of flammability and high-vapor pressure creates a likelihood of combustion.

Further in this regard, batteries that use lithium-based anodes can pose severe safety issues due to the combination of a highly volatile, combustible electrolyte and the active nature of lithium metal.

Some of the problems associated with particular cell electrodes and electrolyte can result in internal failure of the cell.

One type of internal failure is the discharge of electric current internally, within the cell, rather than externally of the cell.

Internal discharge may also be referred to as “self-discharge.” Self-discharge can result in high current generation, overheating and ultimately, a fire.

A primary cause of self-discharge has been dendritic lithium growth during recharge of a rechargeable battery.

In turn, vaporization of the electrolyte can produce extreme pressure within the battery housing or casing which can ultimately lead to rupture of the housing or casing.

The temperatures that result from an electrical short circuit within a battery are sometimes high enough to ignite escaping electrolyte vapors thereby causing continuing degradation and the release of violent levels of energy.

Although these lithium-ion batteries are much safer than earlier designs, violent failures still occur.

However, these materials have limitations.

In addition, it has to be produced using a reactive sputtering process in a low vacuum environment which can be very expensive.

LiPON is also unstable in contact with water which eliminates its possible use as a protective electrolyte in battery systems where exposure to moisture or ambient air may occur.

On the other hand LiSICON and NaSICON structure-type materials are stable in contact with water but are unstable in contact with lithium.

When in contact with lithium this class of materials turns dark and can conduct electric current by electron flow thus minimizing usefulness as electrolyte separators.

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