The invention relates to chemical protection of a metal surface.
Electrochemical cells containing a metallic anode, a cathode and a solid or solvent-containing electrolyte are known in the art. Such batteries have limitations over repeated charge/discharge cycles and may have drops in their charge and discharge capacity over repeated cycles as compared to their initial charge and discharge capacity. Additionally, an initial capacity of solid batteries is often less than desirable. There is therefore a need in the art for an improved battery having a high initial capacity and maintains such a capacity on repeated charge and discharge cycles.
Another problem associated with electrochemical cells is the generation of dendrites over repeat charge and discharge cycles. Dendrites may be formed on the anode when the electrochemical cell is charged. The dendrite may grow over repeated cycles and lead to a reduced performance of the battery or a short circuit not allowing the charge and discharge of the battery. There is therefore a need in the art for a battery and electrode with an improved cycle life and limits the formation of a dendrite.
An electrochemical cell includes an anode having a metal material having an oxygen containing layer. The electrochemical cell also includes a cathode and an electrolyte. The anode includes a protective layer formed on the metal material by reacting a D or P block precursor with the oxygen containing layer.
The term electrochemical cell as used herein refers to a device having an anode, cathode and an ion-conducting electrolyte interposed between the two. The electrochemical cell may be a battery, capacitor or other such device. The battery may be of a primary or secondary chemistry. The battery may have a solid electrolyte or a liquid electrolyte. The term anode as used herein refers to an electrode, which oxidizes during a discharge cycle.
There is disclosed an electrochemical cell having an anode including a metal material having an oxygen containing layer. The anode metal material may be alkaline metals or alkaline earth metals as indicated in the periodic table. Non-limiting examples of metal materials include: lithium, aluminum, sodium, and magnesium. In a preferred aspect of the invention the metal material is lithium.
The oxygen containing layer may be formed by exposing the metal material to the atmosphere or may otherwise be formed on the metal material. The electrochemical cell also includes a cathode, which may be formed of any suitable material. An electrolyte is interposed between the anode and cathode and may be of any suitable form including solid electrolytes liquid electrolytes and gel polymer electrolytes, which are a polymer matrix swollen with solvent and salt. Solid electrolytes could be polymer-type, inorganic layer or mixtures of these two. Examples of polymer electrolytes include, PEO-based, and PEG based polymers. Inorganic electrolytes could be composed of sulfide glasses, phosphide glasses, oxide glasses and mixtures thereof. An example of a liquid electrolyte includes carbonate solvent with dissolved metal-ion salt, for example 1M LiPF6 in ethylene carbon/diethyl carbonate (EC/DEC).
The anode of the electrochemical cell includes a chemically bonded protective layer formed thereon by reacting a D or P block precursor with the oxygen containing layer. The term D or P block precursor includes compounds that have elements in the D or P block of the periodic table. Examples of D or P block elements include phosphorus, boron, silicon, titanium, molybdenum, tantalum, vanadium to name a few. The D or P block precursor may be an organo-metallic compound. Examples of organo-metallic compounds include: inter-metallic compounds, alloys and metals having organic substituents bonded thereon. In a preferred aspect of the invention D or P block precursors may include silicon, boron or phosphorous. The D or P block precursors react with the oxygen containing layer of the metal material to form the protective layer.
In one embodiment, the D or P block precursor may be a chemical compound of the formula: AR1R2X wherein A is selected from phosphorous or boron, X is a halogen or halogen containing compound and R1 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons, R2 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons.
The halogen may be chlorine, bromine, fluorine, and iodine. The alkyl, alkoxy, and aromatic groups may be fluorinated or partially fluorinated.
The alkyl group may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, tert-pentyl, iso-octyl, tert-octyl, 2-ethyhexyl, nonyl, decyl, undecyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, 1-methylcyclopentyl, 1-methylcyclohexyl, 1-methylcyclohexyl, and 1-methyl-4-isopropylcyclohexyl, although other alkyl groups not listed may be used by the invention. The alkyl group may also be functionalized. Suitable functional groups include: ether, sulfide, sulfoxide to name a few.
The aromatic group may be phenyl groups, phenyl groups having alkyl substituents in the para, meta or ortho position, and polyaromatic compounds. Examples of suitable polyaromatic compounds include naphthalene derivatives.
In another embodiment of the invention, the D or P block precursor may be a chemical compound of the formula: AR1R2R3R4X wherein A is phosphorous, X is a halogen or halogen containing compound and R1 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen R2 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen, R3 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen, R4 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen.
In the case where the compound includes double bonded oxygen or other double bonded substituent, the number of R groups may be less than four total.
As with the previously described embodiment, the description of the halogens, alkyl, alkoxy and aromatic groups are the same and are not repeated.
In another embodiment of the invention, the D or P block precursor may be a chemical compound of the formula: SiR1R2R3X wherein, X is a halogen or halogen containing compound and R1 is selected from hydrogen, halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons, R2 is selected from hydrogen, halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons R3 is selected from hydrogen, halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons.
As with the previously described embodiments, the description of the halogens, alkyl, alkoxy and aromatic groups are the same and are not repeated.
In another aspect, the chemical protection layer may not be bonded to the metal material as described above. In this application, the anode of the electrochemical cell also covered by a protective layer formed thereon by reacting a D or P block precursor with the oxygen containing layer. The D or P block precursor may include the same types of materials as described above including: a compound of the formula: AR1R2X wherein A is selected from phosphorous or boron, X is a halogen or halogen containing compound and R1 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons, R2 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons; a compound of the of the formula: AR1R2R3R4X wherein A is phosphorous, X is a halogen or halogen containing compound and R1 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen R2 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen, R3 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen, R4 is selected from halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, aromatic groups having from 1 to 20 carbons, or oxygen; and a chemical compound of the formula: SiR1R2R3X wherein, X is a halogen or halogen containing compound and R1 is selected from hydrogen, halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons, R2 is selected from hydrogen, halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons R3 is selected from hydrogen, halogens, alkyl groups having from 1 to 20 carbons, alkoxy groups containing 1 to 20 carbons, or aromatic groups having from 1 to 20 carbons.
In addition to the compounds identified above, an additional oxygen containing species may be included with the D or P block precursor and react to form the chemical protection layer. Suitable oxygen containing species may include: oxygen, water vapor, and other oxygen containing compounds.
In the embodiment in which the chemical protection layer is not bonded to the surface of the metal material, the D or P block precursor reacts with the oxygen containing layer of the metal material and/or with any additional oxygen containing species to initiate the decomposition, hydrolysis, polymerization or other reaction of the D or P block precursor to form a layer that is not bonded to the surface of the metal material.
In the experiments detailed in the examples section, lithium metal strips were exposed to various precursor compounds. The lithium strips were placed in a sealed flask at room temperature in an inert atmosphere containing the precursor compound. The strips were exposed to the precursor a suitable period of time for the precursor to react with the metal oxygen containing layer on the lithium to form the protective layer. Various analysis procedures were performed including: impedance tests, IR spectroscopy tests, and differential scanning calorimetry tests on the various samples.
An untreated sample of the lithium metal and a sample treated with chlorotrimethyl silane for 240 seconds according to the above procedure were analyzed using IR spectroscopy, as shown in
An untreated sample of the lithium metal and a sample treated with chlorotrimethyl silane according to the above procedure were analyzed using differential scanning calorimetry, as shown in
Impedance tests were performed on various treated samples of lithium and untreated lithium as a reference. The experimental setup used is shown in
An untreated sample of the lithium metal and a sample treated with Tetra Ethyl orthosilicate according to the above procedure were analyzed. Impedance tests were performed on the treated sample of lithium and untreated lithium as a reference. The experimental setup used is shown in
Referring to
The invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.
This application is a continuation of U.S. patent application Ser. No. 12/396,223 filed Mar. 2, 2009, which is a continuation-in-part of U.S. patent application Ser. No. 11/457,525 filed Jul. 14, 2006, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | 12396223 | Mar 2009 | US |
Child | 14513507 | US |
Number | Date | Country | |
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Parent | 11457525 | Jul 2006 | US |
Child | 12396223 | US |