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Lithium electrochemical cell containing diethylcarbonate as an electrolyte solvent additive

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Publication number
USH723H
USH723H US07215664 US21566488A USH723H US H723 H USH723 H US H723H US 07215664 US07215664 US 07215664 US 21566488 A US21566488 A US 21566488A US H723 H USH723 H US H723H
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US
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Prior art keywords
lithium
solvent
dec
li
electrolyte
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
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US07215664
Inventor
Edward J. Plichta
Steven M. Slane
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US Secretary of Army
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US Secretary of Army
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    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/056Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566Liquid materials
    • H01M10/0569Liquid materials characterised by the solvents
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of or comprising active material

Abstract

An electrochemical cell comprising lithium as the anode, the lithium intelating compound Lix CoO2 (O<X<1) as the cathode, and a solution of a lithium salt in a mixed organic solvent of methylformate and diethylcarbonate as the electrolyte.

Description

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates in general to a lithium electrochemical cell and in particular, to a lithium electrochemical cell including lithium as the anode, the lithium intercalating compound Lix CoO2 (0<x<1) as the cathode, and a solution of a lithium salt in a mixed organic solvent of methyl formate (MF) and diethylcarbonate (DEC) as the electrolyte.

BACKGROUND OF THE INVENTION

This application is copending with U.S. patent application Ser. No. 125,642, filed Nov. 1, 1987, now U.S. Pat. No. 4,786,499 for "Lithium Electrochemical Cell Including Aprotic Solvent-Dialkyl Carbonate Solvent Mixture" and assigned to a common assignee. In that application, there is described and claimed a lithium electrochemical cell including lithium as the anode, non-stoichiometric (NS)-V6 O13 as the cathode, and a solution of a lithium salt in a mixed organic solvent of methyl formate and diethylcarbonate as the electrolyte.

Another lithium intercalating compound, to wit, Lix CoO2 (0<x<1) is particularly attractive for battery applications because of its inherently high energy content. However, the known Lix CoO2 cathode material/solvent combinations are susceptible to oxidation during charge and reduction during discharge that results in losses in cell capacity and cycle-life. In addition to oxidation and reduction of the electrolyte, both the cathode and anode are subject to reaction with the solvent and electrolyte. This can result in poor lithium cyclability and structural rearrangement of the active material which may limit rechargeability.

SUMMARY OF THE INVENTION

The general object of this invention is to provide an improved lithium electrochemical cell including Lix CoO2 (0<x<1) as the cathode active material. A more particular object of the invention is to provide an intercalating solvent system for Lix CoO2 (0<x<1) that produces higher energy lithium cells also characterized by increased resistance to solvent oxidation and improved lithium cycling efficiencies.

It has now been found that the aforementioned objects can be attained by employing a system including lithium as the anode, Lix CoO2 (0<x<1) as the cathode, and a solution of a lithium salt in a mixed organic solvent of MF and DEC as the electrolyte.

The solution can be, for example, 1 to 2 mol dm-3 LiAsF6 in the mixed organic solvent. Though the use of LiAsF6 as the electrolyte salt is preferred, other electrolyte salts can be used such as the soluble salts of light metals, for example, tetrafluoroborates, tetrachloroaluminates, perchlorates, hexafluorophosphates, and halides of lithium.

The mass percent of the DEC in the mixed organic solvent can vary from 10 to 100 mass percent. The instant invention identifies and demonstrates that the addition of DEC to ester containing electrolytes, such as LiAsF6 in MF, results in significant improvements in the electrolytes resistance to electrochemical oxidation and improved lithium cycling efficiencies. In addition, when these electrolytes containing the DEC additives are used in Li/Lix CoO2 electrochemical cells, there is significant improvements in the cell cycling behavior over cells without the DEC additive.

DESCRIPTION OF THE DRAWING AND THE PREFERRED EMBODIMENT

The drawing compares cycling results obtained for additions of DEC and dimethylcarbonate (DMC) to LiAsF6 in MF electrolyte in a Li/Lix CoO2 electrochemical cell.

The drawing shows the dramatic improvement in cycling behavior for the electrolyte containing DEC as opposed to DMC. The Li/Lix CoO2 cells are cycled between either 4.3 V to 3.5 V or 4.3 V to 2.5 V where the charging rate is 0.5 mAcm2, the discharge rate is 2 0 mAcm2, and the temperature is 25° C. The Lix CoO2 cathodes include a mixture of 80 weight percent Lix CoO2, 10 weight percent carbon diluent, and 10 weight percent Teflon binder. The cathode mixture is roll pressed onto aluminum substrates and sintered in a vacuum oven at 280° C. for 1 hour. The cycling is performed on identically prepared cells consisting of flag electrodes sealed in a glass pressure vessel where Celgard 2400 is used as separators and a glass fiber wick for drawing electrolyte in between the electrode.

Interestingly, homologues of DEC such as DMC have been utilized in lithium cells and are known to be sufficiently stable towards lithium. However, although DMC and DEC show structural similarities, they behave very differently in the presence of lithium, both chemically and electrochemically. DMC produces a high cycling efficiency of 80 percent as compared to DEC which is 0 percent. This is due to the reactive nature of DEC with lithium as opposed to the more stable DMC solvent. However, even though DMC is more stable with lithium, its addition to the LiAsF6 -MF electrolyte does not result in the improved results observed with DEC. Therefore, where the successful use of DMC as a solvent in lithium cells may imply the possible use of a similar solvent such as DEC, this is not made obvious due to the lack of lithium stability of the neat DEC electrolyte, thus precluding such applications. Furthermore, one would not find obvious the discovery that a mixture of the unstable solvent DEC with another solvent would produce an improved mixture suitably stable for use in a lithium cell. It is only through its addition to other ester electrolytes that the use of DEC in lithium cells is possible.

The use of DEC as a solvent additive in electrolytes for use in either primary, rechargeable, or reserve electrochemical cells is not considered to be limited to the instance where lithium is the anode. That is, other light metals or composites may be applicable as the anode such as sodium, potassium and aluminum, or any conductively doped polymeric material or similar compound. Moreover, the positive electrode or cathode, may be any oxide, sulfide or combinations of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, niobium, molybdenum, hafnium, tantalum, or tungsten or any conductively doped polymeric material or similar compound.

We wish it to be understood that we do not desire to be limited to the exact details as described for obvious modifications will occur to a person skilled in the art.

Claims (5)

What is claimed is:
1. An electrochemical cell comprising lithium as the anode, the lithium intercalating compound Lix CoO2 (0<x<1) as the cathode, and a solution of a lithium salt in a mixed organic solvent of methylformate and diethylcarbonate as the electrolyte.
2. An electrochemical cell according to claim 1 wherein the mass percent of the diethylcarbonate in the mixed organic solvent of methylformate and diethylcarbonate can vary from about 10 to 100 mass percent in the electrolyte.
3. An electrochemical cell according to claim 2 wherein the solution of lithium salt is 1-2 mol dm-3 LiAsF6 in methylformate.
4. An electrochemical cell according to claim 1 wherein the Lix CoO2 cathode consists of a mixture of about 80 weight percent Lix CoO2, about 10 weight percent carbon diluent and about 10 weight percent Teflon binder roll pressed onto aluminum substrates and sintered in a vacuum oven at 280° C. for 1 hour.
5. An electrochemical cell according to claim 4 wherein the mass percent of the diethylcarbonate in the mixed organic solvent of methylformate and diethylcarbonate can vary from about 10 to 100 mass percent in the electrolyte and wherein the solution of lithium salt is 1-2 mol dm-3 LiAsF6 in methylformate.
US07215664 1988-07-06 1988-07-06 Lithium electrochemical cell containing diethylcarbonate as an electrolyte solvent additive Abandoned USH723H (en)

Priority Applications (1)

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US07215664 USH723H (en) 1988-07-06 1988-07-06 Lithium electrochemical cell containing diethylcarbonate as an electrolyte solvent additive

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07215664 USH723H (en) 1988-07-06 1988-07-06 Lithium electrochemical cell containing diethylcarbonate as an electrolyte solvent additive
CA 599186 CA1306001C (en) 1988-07-06 1989-04-19 Lithium electrochemical cell containing diethylcarbonate asan electrolyte solvent additive

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USH723H true USH723H (en) 1990-01-02

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CA (1) CA1306001C (en)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5147739A (en) * 1990-08-01 1992-09-15 Honeywell Inc. High energy electrochemical cell having composite solid-state anode
US5284721A (en) * 1990-08-01 1994-02-08 Alliant Techsystems Inc. High energy electrochemical cell employing solid-state anode
US20060093873A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093872A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Medical device having lithium-ion battery
US20060093918A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093916A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093921A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093871A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20080020279A1 (en) * 2004-10-29 2008-01-24 Medtronic, Inc. Lithium-ion battery
US20080020278A1 (en) * 2004-10-29 2008-01-24 Medtronic, Inc. Lithium-ion battery
US20090274849A1 (en) * 2008-04-30 2009-11-05 Medtronic, Inc. Formation process for lithium-ion batteries
US7635541B2 (en) 2004-10-29 2009-12-22 Medtronic, Inc. Method for charging lithium-ion battery
US7927742B2 (en) 2004-10-29 2011-04-19 Medtronic, Inc. Negative-limited lithium-ion battery
US9077022B2 (en) 2004-10-29 2015-07-07 Medtronic, Inc. Lithium-ion battery
US9287580B2 (en) 2011-07-27 2016-03-15 Medtronic, Inc. Battery with auxiliary electrode
US9587321B2 (en) 2011-12-09 2017-03-07 Medtronic Inc. Auxiliary electrode for lithium-ion battery

Cited By (45)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5147739A (en) * 1990-08-01 1992-09-15 Honeywell Inc. High energy electrochemical cell having composite solid-state anode
US5284721A (en) * 1990-08-01 1994-02-08 Alliant Techsystems Inc. High energy electrochemical cell employing solid-state anode
US20060093916A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093872A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Medical device having lithium-ion battery
US20060093918A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093873A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093923A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Medical device having lithium-ion battery
US20060093921A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093871A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Lithium-ion battery
US20060093917A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Medical device having lithium-ion battery
US20060093913A1 (en) * 2004-10-29 2006-05-04 Medtronic, Inc. Medical device having lithium-ion battery
US20080020279A1 (en) * 2004-10-29 2008-01-24 Medtronic, Inc. Lithium-ion battery
US20080020278A1 (en) * 2004-10-29 2008-01-24 Medtronic, Inc. Lithium-ion battery
US7337010B2 (en) 2004-10-29 2008-02-26 Medtronic, Inc. Medical device having lithium-ion battery
US7563541B2 (en) 2004-10-29 2009-07-21 Medtronic, Inc. Lithium-ion battery
US20090208845A1 (en) * 2004-10-29 2009-08-20 Medtronic, Inc. Lithium-ion battery
US7582387B2 (en) 2004-10-29 2009-09-01 Medtronic, Inc. Lithium-ion battery
US20100009245A1 (en) * 2004-10-29 2010-01-14 Medtronic,Inc. Lithium-ion battery
US20090286158A1 (en) * 2004-10-29 2009-11-19 Medtronic, Inc. Lithium-ion battery
US7635541B2 (en) 2004-10-29 2009-12-22 Medtronic, Inc. Method for charging lithium-ion battery
US7642013B2 (en) 2004-10-29 2010-01-05 Medtronic, Inc. Medical device having lithium-ion battery
US7641992B2 (en) 2004-10-29 2010-01-05 Medtronic, Inc. Medical device having lithium-ion battery
US7931987B2 (en) 2004-10-29 2011-04-26 Medtronic, Inc. Lithium-ion battery
US20100015528A1 (en) * 2004-10-29 2010-01-21 Medtronic, Inc. Lithium-ion battery
US7662509B2 (en) 2004-10-29 2010-02-16 Medtronic, Inc. Lithium-ion battery
US7682745B2 (en) 2004-10-29 2010-03-23 Medtronic, Inc. Medical device having lithium-ion battery
US20100076523A1 (en) * 2004-10-29 2010-03-25 Medtronic, Inc. Method of preventing over-discharge of battery
US9077022B2 (en) 2004-10-29 2015-07-07 Medtronic, Inc. Lithium-ion battery
US7794869B2 (en) 2004-10-29 2010-09-14 Medtronic, Inc. Lithium-ion battery
US20100239908A1 (en) * 2004-10-29 2010-09-23 Medtronic, Inc. Lithium-ion battery
US7803481B2 (en) 2004-10-29 2010-09-28 Medtronic, Inc, Lithium-ion battery
US7807299B2 (en) 2004-10-29 2010-10-05 Medtronic, Inc. Lithium-ion battery
US7811705B2 (en) 2004-10-29 2010-10-12 Medtronic, Inc. Lithium-ion battery
US7858236B2 (en) 2004-10-29 2010-12-28 Medtronic, Inc. Lithium-ion battery
US9065145B2 (en) 2004-10-29 2015-06-23 Medtronic, Inc. Lithium-ion battery
US7879495B2 (en) 2004-10-29 2011-02-01 Medtronic, Inc. Medical device having lithium-ion battery
US7883790B2 (en) 2004-10-29 2011-02-08 Medtronic, Inc. Method of preventing over-discharge of battery
US7927742B2 (en) 2004-10-29 2011-04-19 Medtronic, Inc. Negative-limited lithium-ion battery
US7740985B2 (en) 2004-10-29 2010-06-22 Medtronic, Inc. Lithium-ion battery
US8105714B2 (en) 2004-10-29 2012-01-31 Medtronic, Inc. Lithium-ion battery
US7875389B2 (en) 2004-10-29 2011-01-25 Medtronic, Inc. Lithium-ion battery
US20090274849A1 (en) * 2008-04-30 2009-11-05 Medtronic, Inc. Formation process for lithium-ion batteries
US8980453B2 (en) 2008-04-30 2015-03-17 Medtronic, Inc. Formation process for lithium-ion batteries
US9287580B2 (en) 2011-07-27 2016-03-15 Medtronic, Inc. Battery with auxiliary electrode
US9587321B2 (en) 2011-12-09 2017-03-07 Medtronic Inc. Auxiliary electrode for lithium-ion battery

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Publication number Publication date Type
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