MXPA00008067A - Plating metal negative electrodes under protective coatings - Google Patents

Abstract

A method for forming lithium electrodes having protective layers involves plating lithium (16) between a lithium ion conductive protective layer (18) and a current collector (14) of an"electrode precursor". The electrode precursor is formed by depositing the protective layer on a very smooth surface of a current collector. The protective layer is a glass such as lithium phosphorus oxynitride and the current collector is a conductive sheet such as a copper sheet. During plating, lithium ions move through the protective layer and a lithium metal layer plates onto the surface of the current collector. The resulting structure is a protected lithium electrode. To facilitate uniform lithium plating, the electrode precursor may include a"wetting layer"which coats the current collector.

Description

ELECTRODEPOSITATION OF NEGATIVE METAL ELECTRODES UNDER PROTECTIVE COATINGS DESCRIPTION Antecedents and field of the invention This invention relates to negative electrodes for use in batteries (for example, lithium electrodes for use in lithium-sulfur batteries). More particularly, this invention relates to methods for forming alkali metal electrodes having a thin vitreous or amorphous protective layer. In theory, some alkaline metal electrodes could provide very high energy density batteries. The low lithium equivalent weight gives this one a particular attraction as a battery electrode component. Lithium provides more energy by volume than traditional battery, nickel and cadmium standards. Unfortunately, no rechargeable metal lithium battery has been successful on the market until now. The failure of metallic lithium rechargeable batteries is mainly due to cell cycling problems. During repeated charging and discharging cycles, lithium dendrites gradually grow out of the metallic lithium electrode, through the electrolyte, and finally make contact with the positive electrode. This causes an internal short circuit in the battery, causing the battery to become unusable after relatively few cycles. During cyclization, "mossy" deposits can also grow on the lithium electrodes which can be dislodged from the negative electrode and thereby reduce the capacity of the battery. To deal with the poor behavior of lithium in cyclization in liquid electrolyte systems, some researchers have proposed to coat the face facing the electrolyte of the negative lithium electrode with a "protective layer." Said protective layer should conduct lithium ions, but at the same time should avoid contact between the surface of the lithium electrode and the mass of the electrolyte. Many techniques to apply the protective layers have not been successful. Some thought that the protective layers of metallic lithium were formed in situ by reaction between metallic lithium and compounds in the electrolyte of the cells which comes into contact with lithium. Most of these films in situ are grown by a controlled chemical reaction after the battery is assembled. Generally, such films have a porous morphology that allows part of the electrolyte to penetrate the bare surface of the metallic lithium. In this way, they fail to adequately protect the lithium electrode. Several preformed protective layers of lithium have been contemplated. For example, U.S. Patent No. 5,314,765 (issued to Bates on May 24, 1994) describes an ex situ technique for manufacturing a lithium electrode containing a thin layer of lithium bombarded lithium oxynitride ( "LIPON") or a related material. The LIPON is a unique vitreous ion conductor (conducts lithium ion) which has been studied as a potential electrolyte for solid state lithium microbatteries that are manufactured in silicon and used to power integrated circuits (see United States patents of America Nos. 5,597,660, 5,567,210, 5,338,625, and 5,512,147, all issued to Bates et al.). In both in situ and ex situ techniques, to make a lithium protected electrode, one must start with a clean and smooth lithium source on which to deposit the protective layer. Unfortunately, the most commercially available lithium has a surface roughness that is in the same order as the thickness of the desired protective layer. In other words, the lithium surface has protuberances and grooves as large as or almost as large as the thickness of the protective layer. As a result, most of the deposition processes contemplated can not form a void-free protective layer on the lithium surface. In this way, lithium battery technology still lacks an efficient mechanism to protect negative lithium electrodes.

Summary of the invention The present invention provides an improved method for the formation of active metal electrodes having protective layers. Active metals include those metals that can benefit from a protective layer when used as electrodes. The method involves electrodepositing the active metal between a protective layer and a current collector on an "electrode precursor." The electrode precursor is formed by depositing the protective layer on a very smooth surface of a current collector. Because the surface on which the protective layer is deposited is very smooth, the protective layer has a higher quality than when deposited directly on the thick metallic lithium. During electrodeposition, the active metal ions move through the protective layer and a layer of active metal is electrodeposited on the surface of the current collector. The resulting structure is a protected active metal electrode. To facilitate uniform electrodeposition, the electrode precursor may include a "wetting layer" which covers the current collector. One aspect of the invention provides a method for manufacturing an alkali metal electrode, such method can be characterized by the following sequence: (a) providing an alkaline metal electrode precursor to an electrochemical cell, the electrode precursor includes a collector of current and a vitreous or amorphous protective layer that forms a substantially impenetrable layer that is a single, ionic conductive conductor for ions of an alkali metal; and (b) electrodepositing the alkali metal through the protective layer to form a layer of the alkali metal between the current collector and the protective layer to form the alkali metal electrode. Preferably, the alkali metal electrode precursor also includes a humectant layer located between and adhered to the current collector and the protective layer. The wetting layer facilitates uniform deposition of the alkali metal on the current collector. Note that the current collectors are typically inert to the alkali metal and therefore do not provide good electrodeposition surfaces. Often the alkali metal is electrodeposited irregularly on the surface. In a preferred embodiment, the wetting layer (i) is intercalated with alkali metal ions driven by the single ionic conductor or (ii) is alloyed with the alkali metal having ions driven by the ionic-single conductor. The alkali metal can be electrodeposited in situ or ex situ. In the case in situ, a battery of the electrode precursor and other battery elements are assembled including an electrolyte and a positive electrode. The electrode precursor is then converted to an alkali metal electrode by means of an initial charging operation in which the lithium is electrodeposited from the positive electrode. The battery can be either a primary battery or a secondary battery. Before the electrodepositing stage, the batteries do not contain free alkali metal. This allows a safe transport and a long storage life. Only when a battery cell is ready to use is it charged for the first time to form the alkaline metal electrode. Only then does it contain free alkali metal. In the case ex situ, the electrode is formed in an electrolytic cell that is separated from the battery in which it is finally assembled. After this the electrode is removed from the electrochemical cell and assembled in a battery. The present invention also relates to alkali metal electrode precursors which can be characterized by the following characteristics: (a) a current collector; (b) a vitreous or amorphous protective layer which forms a substantially impenetrable layer which is a single, ionic conductive conductor for alkali metal ions; and (c) a humectant layer located between and adhered to the current collector and the protective layer. As mentioned in the method of this invention, the wetting layer (i) is intercalated with alkali metal ions driven by the single ionic conductor or (ii) is alloyed with the alkali metal having ions driven by the single ionic conductor. The current collector is typically a layer of metal such as copper, nickel, stainless steel, or zinc. Alternatively, it can be a sheet of metallized plastic or other metallized insulating sheets. If the material of the wetting layer is alloyed with the alkali metal, it may be silicon, magnesium, aluminum, lead, silver, or tin, for example. If the wetting layer is intercalated with alkali metal ions, this may be carbon, titanium sulfide, or iron sulfide, for example.

If the alkali metal is lithium, the protective layer must be conductive for the lithium ions. Examples of suitable conductive lithium ion protective layer materials include lithium silicates, lithium borates, lithium aluminates, lithium phosphates, phosphorus oxynitrides "and lithium, lithium silicosulfides, lithium borosulfides, lithium aluminosulfides, and phosphosulphides Lithium-specific examples of protective layer materials include 6LiI-Li3P0-P2S5, B203-LiC03-Li3P04, Lil-Li = 0-SiO2, and LixPOyNz (LIPON) Preferably, the protective layer has a thickness of between about 50 angstroms and 5 micrometers (more preferably between about 500 angstroms and 2000 angstroms) Preferably, the protective layer has a conductivity (for an alkali metal ion) of between about 10 ~ 8 and about 10"2 (ohm-cm) -1. As mentioned, the electrodes and electrode precursors of this invention can be assembled in alkaline metal batteries. In a specific embodiment, the invention provides alkaline metal batteries that can be characterized by the following characteristics: (a) a positive electrode comprising a source of mobile alkali metal ions in charge; (b) a precursor for a negative alkali metal electrode as described above; and (c) an electrolyte.

Preferably, the alkali metal is at least one of lithium and sodium. The electrolyte can be liquid, polymer, or gel. In a particularly preferred embodiment, the positive electrode includes at least one of alkali metal sulfides, alkali metal polysulfides. Examples of convenient primary batteries include manganese dioxide batteries, batteries (CF) x-lithium, lithium-thionyl chloride batteries, lithium-sulfur dioxide batteries, lithium-iron sulfide batteries (Li / EeS2), lithium polyaniline batteries, and lithium-iodine batteries. Examples of suitable secondary batteries include lithium-sulfur batteries, cobalt-lithium oxide batteries, nickel-lithium oxide batteries, manganese-lithium oxide batteries, and vanadium-lithium oxide batteries. Other batteries that use active metals other than lithium can also be used. These include the other alkali metals and alkaline earth metals. These and other features of the invention will be described and will be exemplified in the following drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of the steps associated with a first preferred embodiment of the invention which includes forming an electrode precursor and converting it into an electrode electrodeposing lithium onto a current collector. Figure 2 is a schematic illustration of the steps associated with a second preferred embodiment of the invention which includes forming an electrode precursor and converting it into an electrode by electrodeposing lithium onto a wetting layer provided on a current collector. Figure 3 is a block diagram of a battery formed of an electrode of the present invention. Figure 4 is a schematic illustration of the oxidation states of a sulfur catholyte during the in situ formation of the lithium electrode and subsequent cyclization. Figure 5 is a graph of cell potential against charge state for a sulfur catholyte of a lithium-sulfur cell. Figure 6 is - a graph illustrating that after twenty charge / discharge cycles, almost all of the lithium in an electrode prepared according to this invention remained in the electrode.

Detailed description of the preferred modalities Use of an electrode precursor In the following description, the invention is presented in terms of certain specific compositions, configurations and processes to help explain how it can be put into practice. The invention is not limited to these specific modalities. For example, although much of the following discussion focuses on lithium systems, the invention pertains more broadly also to other active metal battery systems (eg, batteries having negative electrodes of alkali metals and alkaline earth metals). Figures 1 and 2 illustrate two preferred applications for the present invention. Consider first Figure 1, a current collector 14 is provided. This should be a conductive material with at least one upper surface that is very smooth. On this smooth surface, a protective layer 18 is formed by means of a convenient process such as sputtering or chemical vapor deposition. The protective layer 18 must be a single, ionic conductor, ionic conductor of the active metal used in the electrode (eg, lithium). Because the protective layer 18 is deposited on a very smooth surface, it will also be smooth and continuous. The resulting structure is referred to here as a "electrode precursor" 17. This can be transported, stored, and handled in some other way without the precautions normally required for a metallic lithium electrode. Finally, the metallic lithium is electrodeposited on the current collector 14 from a lithium ion source to produce a lithium electrode 10. The lithium ions move through the protective layer 18 and come into contact with the current collector. 14 where they are reduced to form metallic lithium. Thus, the electrode 10 includes a metallic lithium layer 16 sandwiched between the current collector 14 and the protective layer 18. Because the lithium layer is formed after the protective layer (instead of having the protective layer formed on the lithium as it happens in the conventional processes), the protective layer is of high quality. That is, the protective layer is generally free of voids and adheres when produced in accordance with this invention. Figure 2 illustrates another preferred embodiment of the present invention. This procedure may be appropriate when the current collector is made of a material that does not allow lithium electrodeposition uniformly. For example, copper current collectors - do not provide good surfaces to electrodeposite lithium. Lithium tends to be electrodeposited on copper in discontinuous areas. To overcome this problem, a "wetting layer" can be formed on the current collector to reduce the surface energy at the interface of the electrodeposited lithium and the current collector. As shown in Figure 2, an electrode precursor 17 'is created from the current collector 14, the protective layer 18 and a wetting layer 15. Note that the wetting layer 15 is sandwiched between the current collector 14 and the protective layer 18. Like the electrode precursor 17, the electrode precursor 17 'can be operated and stored without special precautions for alkaline metal electrodes. A 1-0 'electrode is formed by electroplating a lithium layer 16 on the wetting layer 15 and the current collector 14. Thus, the electrode 10' comprises a stack including a current collector as the bottom layer, a protective layer single ion conductor as the top layer, a wetting layer on the current collector, and a metallic lithium layer between the wetting layer and the protective layer. The wetting layer 15 may, but not necessarily, be integrated into the lithium layer 16 during electrodeposition. For example, if the wetting layer 15 is deposited as an aluminum layer, it can form a lithium / aluminum alloy when the lithium layer 16 is formed. Note that in both electrodes 10 and 10 ', the current collector 14 includes a first surface that is exposed to the environment and a second surface that makes intimate contact with the lithium layer 16 (or possibly the wetting layer 15). The lithium layer 16 includes a first surface which forms the interface with the current collector 14 (or possibly the wetting layer 15) and a second surface which makes intimate contact with the protective layer 18. In turn, the protective layer 18 includes a first surface which contacts the second surface of the lithium layer 16. Finally, the protective layer 18 includes a second surface that is exposed to the environment. Interfaces on the surfaces of the lithium layer 16 must be sufficiently continuous or intimate so as to prevent contact of moisture, air, electrolyte, and other environmental agents with metallic lithium. Further; the interface the lithium and the current collector must provide a low resistance electronic contact.

Preferably, the current collectors used with this invention form a physically rigid layer of material that is not alloyed with lithium. They must be electronically conductive and not reactive to moisture, gases in the atmosphere (for example, oxygen and carbon dioxide), electrolytes and other agents, are likely to be found before, during and after the manufacture of a battery. Examples of materials useful as current collectors for this invention include copper, nickel, many forms of stainless steel, zinc, chromium, and compatible alloys thereof. The current collector should not be alloyed with, easily migrate into, or otherwise detrimentally affect the electrochemical properties of the lithium layer 16. This also ensures that the material of the current collector is not redistributed during the charge and discharge cycles in which the lithium is alternately electrodeposited and consumed electrolytically. In a preferred embodiment, the current collector may have a thickness between about 1 and 25 microns (more preferably between about 6 and 12 microns). In an alternative embodiment, the current collector is provided as a layer of metallized plastic. In this case, the current collector can be much thinner than a freestanding current collector. For example, the metal-on-plastic layer may be in the range of 500 angstroms to 1 micron thick. Plastic support layers suitable for use with this type of current collector include polyethylene terephthalate (PET), polypropylene, polyethylene, polyvinyl chloride (PVC); polyolefins, polyimides, etc. The metallic layers placed on such plastic substrates are preferably inert to lithium (for example, they are not alloyed with lithium) and may include at least those materials listed above (for example, copper, nickel, stainless steel, and zinc). An advantage of this design is that it forms a relatively light current / support manifold for the electrode. In an alternative embodiment, the current collector 14 is coated with an electronically non-conductive outer layer such as a second protective layer. In this mode, a current collector or terminal must be attached to the lithium electrode. This can take the form of a metal tag or other electronically conducting member that extends beyond the protective layers. The current collector can be prepared by a conventional technique to produce current collectors. For example, current collectors may be provided as sheets of commercially available metals or metallized plastics. The surfaces of such current collectors can be prepared by means of standard techniques such as electrode polishing, sanding, grinding, and / or cleaning. At this point, the surface of the current collector must be smoother than the thickness of the protective vapor layer subsequently deposited on it. For example, a current collector with a surface roughness in the order of micrometers would not be suitable for the deposition of a 1000 angstrom glass layer. Alternatively, the metals in the current collector can be formed by a more exotic technique such as the evaporation of the metal on a substrate, the physical or chemical vapor deposition of the metal on a substrate, etc. Such processes can be performed as part of a continuous process to build the electrode. Other sub-processes used in the continuous process could include the subsequent deposition of an aluminum layer (an example of a wetting layer) and a lithium layer. Each stage in the continuous process could be carried out under vacuum. While the material comprising the current collector is preferably inert to lithium, this makes it somewhat difficult to deposit a smooth cohesive layer of lithium on the current collector. For this reason, the present invention can employ a layer of "wetting" material on the current collector to facilitate uniform deposition of lithium in a subsequent step. An object of this invention when using the wetting layer is to prevent lithium from being electrodeposited preferentially in one or some locations where it grows so thick that it fractures the protective glass layer. Thus, during the initial electrodeposition cycle, the lithium should be electrodeposited uniformly on the surface of the current collector to avoid fracture. The humectant material should be selected so as to decrease the electrodeposition energy. Several materials can be used for this function. Two general classes of suitable materials include (1) materials that are alloyed with lithium and (2) materials that are interspersed with lithium. Examples of materials that fall into the first class include silicon, magnesium, aluminum, lead, silver and tin. Materials that fall into the second class include carbon, titanium sulfide (TiS2), and iron sulfide (FeS2). Regardless of the selected wetting material, only a very small amount of it should be used. If much of this material is present, it can affect the electrochemical properties of the electrode. Each of these materials will affect the redox potential of the electrodes. In some embodiments, the wetting layer is between about 50 and 1000 angstroms thick. The wetting material should be formed with as smooth a surface as possible. The thickness r.-m.s. of the start layer should not be greater than the anticipated thickness of the glass layer to be subsequently deposited. Suitably smooth layers can be deposited by various processes. Examples of suitable processes include physical vapor deposition (e.g. evaporation or sputtering) of aluminum or magnesium wetting layers. Alternatively, chemical vapor deposition can be used to deposit carbon, silicon, titanium sulfide, and iron sulfide. As long as the thickness of the wetting layers remains relatively thin, (for example, within 50 to 1000 angstroms in thickness), these will generally not get too uneven. Preferably, the wetting layer remains in place during successive electrode cycles. In most cases, the wetting material will remain under the protective layer because the protective layer will not conduct the ions of the wetting layer. For example, if the protective layer is a single ion conductor for lithium and the wetting layer is aluminum, the aluminum ions will not pass through the protective layer. Thus, the proper choice of a protective layer and a wetting layer will ensure that the wetting layer does not migrate through the cell employing the electrode. In addition, the wetting layer can be "secured" in place within the matrix of the current collector. In other words, the current collector can be modified chemically with a wetting material. In a preferred embodiment, this is achieved by having a degraded composition near the surface of the current collector in which the concentration of the material of the wetting layer increases towards the surface. The protective layer 18 serves to protect the metallic lithium in the electrode during the cycling of the cell. This must protect metallic lithium from electrolyte attack and should reduce the formation of dendrites and mossy deposits. In addition, layer 18 must be substantially impenetrable to environmental agents. Thus, it must be substantially free of pores, defects and any path that allows air, moisture, electrolyte, and other external agents to penetrate it to the metallic layer 16. In this aspect, the composition, thickness, and method of manufacture can all be important in imparting to layer 18 the necessary protective properties. These characteristics of the protective layer will be described in detail below. Preferably, the protective layer 18 is so impenetrable to ambient humidity, carbon dioxide, oxygen, etc., that a lithium electrode can be operated under ambient conditions without the need for elaborate dry box conditions as typically used to process other lithium electrodes. Because the protective layer described here provides such good protection for lithium (or other reactive metal), it is contemplated that electrode 10 (or 10 ') may have a rather long storage life outside a battery. Thus, the invention not only contemplates batteries that contain the negative electrode 10, but the same negative electrodes that are not used. Such negative electrodes can be provided in the form of sheets, rolls, chains, etc. Finally, they are integrated with other battery components to make a battery. The reinforced stability of the batteries of this invention will greatly simplify this manufacturing process. The protective layer must be a glass or amorphous material that conducts the lithium ion but does not conduct other ions significantly. In other words, it must be a unique ionic conductor. This must also be stable for the voltage scale used in the cell under consideration. In addition, it must be chemically stable to the electrolyte, at least within the voltage range of the cell. Finally, it must have a high ionic conductivity for the lithium ion. The protective layer can be formed directly on the wetting layer by any convenient process. This can be deposited on the wetting layer by techniques such as physical vapor deposition and chemical vapor deposition. In a preferred embodiment, this is deposited by chemical vapor deposition reinforced by plasma (PECVD). Examples of convenient physical vapor deposition processes include ion bombardment and evaporation (e.g., evaporation by electronic beam). A PECVD technique is described in U.S. Patent Application No. 09 / 086,665, filed May 19, 1998, entitled "PROTECTIVE COATINGS FOR NEGATIVE ELECTRODES" which has been incorporated. here previously by way of reference. Lithium or other active material is provided to the electrode electrochemically by electrodeposing it on the current collector / wetting agent below the protective layer. This can be achieved either in situ or ex situ. In the ex situ case, electrodeposition occurs in a system that is separate from the final battery or cell in which the electrode is used. Thus, the lithium electrode is preformed before introduction into the battery. In the case in situ, the compound including the current collector, the wetting agent, and the protective layer is assembled in a battery containing a positive electrode fully discharged. The fully discharged positive electrode contains all the lithium or other metal necessary to cycle the cell. After the cell has been assembled, it undergoes a charge cycle in which the lithium (or other metal) is driven from the positive electrode and placed on the negative electrode under the protective layer. In the ex situ case, the current collector / wetting agent / protective layer is provided to an electrolytic solution containing an electrolyte and a lithium ion source (eg, a metallic lithium source). The lithium ion source and the electrode precursor serve as electrodes and are connected by means of a current source. If a metal current collector (i.e., one that does not have an insulating support such as PET) is used, the exposed face of the metal current collector must be masked to prevent the lithium or other metal from being electrodeposited therein. The object is to ensure that all lithium is electrodeposited through the protective layer and on the side of the current collector that has the wetting agent. The electrolyte is preferably an organic solvent of high conductivity. This should be made as conductive as possible to increase the efficiency of the electrodeposition operation. The more conductive the material, the less energy will be required for the electrodeposition of lithium or other metal onto the composite electrode. Examples of suitable electrolytes could include alkylene carbonates such as dimethyl carbonate, ethylene carbonate and propylene carbonate, ethers such as monoglyme CH3 (OCH2CH2) OCH3, diglyme CH3 (OCH2CH2) 2OCH3, triglyme CH3 (OCH2CH2) 3OCH3, tetraglime CH3 ( 0CH2CH2) OCH3, tetrahydrofuran, and polyethers such as polyethylene oxide, dimethyl sulfoxide, sulfolane, tetraethyl sulfonamide, dimethyl formamide, diethyl formamide, dimethyl acetamide, etc. Other suitable solvents are known in the art. Normally the solvent will include a conductivity enhancing agent, such as lithium trifluoromethylsulfonimide. During the electrodeposing operation, the composite electrode on which the lithium will be electrodeposited becomes negative and the lithium electrode source becomes positive. The current is controlled until a defined number of Coulombs has passed. This defined number is set to correspond to the amount of lithium that will be electrodeposited. The current determines how fast lithium is electrodeposited. Preferably, it is electrodeposited as quickly as possible without causing the protective layer to fracture, lose adhesion, or otherwise lose its protective function. When possible, it may be desirable to perform the electrodeposition operation at a relatively high temperature (eg, between about 50 and 100 degrees centigrade) in order to increase the conductivity of the electrolyte and thereby accelerate the electrodeposition process. In the case in if you, the lithium needed to form the negative electrode is obtained from the cathode or catholyte where it can be kept safely for long periods. In this procedure, the cell is constructed essentially the same as would be done with a normal lithium electrode. However, there is no free lithium, in the negative electrode before the first charge cycle. The finished cell is in the downloaded state. Because there is no free metallic lithium present in the fully assembled cell, (before the initial charge), such cells can be stored safely for long periods and transported equally without reduction in storage life.

Composition of the protective layer The protective layer 18 is preferably composed of a glassy or amorphous material which is conductive for alkali metal ions of the alkali metal comprising the layer 16. Preferably, the protective layer 18 does not conduct anions such as Ss ** generated during the discharge of a metal. sulfur electrode (or other anions produced with other positive electrodes), or anions present in the electrolyte such as perchlorate ions from the dissociation of lithium perchlorate. To provide the required ionic conductivity, the protective layer typically contains a mobile ion such as an alkali metal cation of the negative electrode metal. Many convenient unique ionic conductors are known. Among the suitable glasses are those that can be characterized as containing a "modifier" portion and a "network forming" portion. The modifier is often an alkali metal oxide in layer 16 (i.e., the metal ion for which the protective layer 18 is conductive). The network former is often an oxide or polymeric sulfide. One example is lithium silicate glass 2 Li20-1 Si02 and another example is sodium borosilicate glass 2 Na20 * l Si02-2B203.

The modifier / network former glasses employed in this invention may have the general formula (M20) X (AnDm), where M is an alkali metal, A is boron, aluminum, silicon, or phosphorous, D is oxygen or sulfur. The values of n and m are dependent on the valence of A. X is a coefficient that varies and depends on the desired properties of the glass. Generally, the conductivity of the glass increases as the value of X decreases. However, if the value of X becomes too small, separate phases of the modifier and the network former emerge. Generally, the glass must remain in a single phase, so that the value of X must be chosen carefully. The highest concentration of M20 should be that which provides the stoichiometry of the fully ionic salt of the network-former. For example Si02 is a polymeric covalent material; As the Li20 is added to the silica, the 0-0 bonds are broken producing Si-0 Li +. The limit of addition of Li20 is in the completely ionic stoichiometry, which for silica would be Li Si04, or 2Li20-Si02 (Li20 * 0.5Si02). Any addition of Li20 beyond this stoichiometry would necessarily lead to the separation of the Li20 and LiSi04 phase. Phase separation of a glass composition typically occurs well before the fully ionic composition, but this is dependent on the thermal history of the glass and can not be calculated from the stoichiometry. Therefore the ion limit can be seen as a higher maximum beyond which the phase separation will occur independently of the thermal history. The same limitation can be calculated for all trainers in the network, ie Li3B03 or 3 Li20-B203, Li3A103 or 3 Li20-Al203, etc. Obviously, the optimal values of X will vary and will depend on the modifier and network trainer employed. Examples of the modifier include lithium oxide Li20, lithium sulphide (Li2S), lithium selenide (Li2Se), sodium oxide (Na20), sodium sulfide (Na2S), sodium selenide (Na2Se), potassium oxide (K20), potassium sulfide (K2S) , potassium selenide (K2Se), etc. , and combinations of them. Examples of network former include silicon dioxide (Si02), silicon sulphide (SiS2), silicon selenide (SiSe2), boron oxide (B203), boron sulfide (B2S3), boron selenide (B2Se3), oxide aluminum (Al203), aluminum sulfide (A12S3), aluminum selenide (Al2Se3), phosphorous pentoxide (P205), phosphorous pentasulfide (P2S5), phosphorus pentaselenide (P2Se5), phosphorus tetroxide (P04), phosphorus tetrasulfide (PS), phosphorus tetraselenide (PSe), and related network formers. "Doped" versions of the protective glasses of two previous parts can also be used. Often the dopant is a simple halide of the ion for which the glass is conductive. Examples include lithium iodide (Lil), lithium chloride (LiCl), lithium bromide (LiBr), sodium iodide (Nal), sodium chloride (NaCl), sodium bromide (NaBr), etc. Such doped glasses can have the general formula (M20) X (AnDm) • Y (MH) where Y is a coefficient and MH is a metal halide. The addition of metal halides to the glasses is quite different than the addition of metal oxides or network modifiers to the glasses. In the case of the addition of network modifiers, the covalent nature of the glass is reduced with the increase in the addition of the modifier and the glass becomes more ionic in nature. The addition of metal halides is more understood in terms of the addition of a salt (MH) to a solvent (the glass modifier / former). The solubility of a metal halide (MH) in a glass will also depend on the thermal history of the glass. In general, it has been found that the ionic conductivity of a glass increases as the concentration of the dopant (MH) increases to the phase-separation point. However, very high concentrations of MH additive can cause hygroscopic glass and therefore susceptible to being attacked by residual water in the electrolytes of the battery, therefore it would be desirable to use a graduated interface where the concentration of the halide decreases as a function of the distance from the surface of the negative electrode. A convenient doped glass of halide is Li20 • YLiCl • XB203 • -ZSi02. Some other single ion conductive glasses can also be employed as a protective layer used with this invention. An example is lithium phosphorus oxynitride glass called LIPON which is described in "A Stable Thin-Film Lithium Electrolyte: Lithium Phosphorus Oxynitride" (Lithium Thin Film Stable Electrolyte: Lithium Phosphorus Oxinitrate) J. Electrochem. Soc., 144, 524 (1997) and which is incorporated herein by reference. An exemplary composition for the LIPON is Li2.gP? 3.3No.5- Examples of other glass films that can work include 6LiI-Li3P0-P2S5 and B203-LiC? 3-Li3P04. With respect to thickness, the protective layer 18 should be as thin as possible while effectively protecting the metal electrode. Thinner layers have several benefits. Among these are flexibility and low ionic strength. If a layer becomes too thick, the electrode can not bend easily without fracturing or otherwise damaging the protective layer. Also, the overall resistance of the protective layer is a function of the thickness. However, the protective layer must be thick enough to prevent the electrolyte or certain aggressive ions from touching the underlying alkaline metal. The proper thickness will depend on the deposition process. If the deposition process produces a high quality protective layer, then a fairly thin layer can be used. A high quality protective layer will be smooth and continuous and free of pores or defects that could provide a path for metallic lithium or harmful agents from the electrolyte. For many protective layers, the optimum thickness varies between approximately 50 angstroms and 5 microns. More preferably, the thickness will vary between about 100 angstroms and 3,000 angstroms. Even more desired, the thickness will vary between approximately 500 angstroms and 2,000 angstroms. For many high quality protective layers, an optimum thickness will be approximately 1000 angstroms. In addition, the composition of the protective layer must have an inherently high ionic conductivity (e.g., between about 10 ~ 8 and about 10 ~ 2). (cm-oh) "1) Obviously, if a thin layer of relatively good quality can be deposited, a material with a relatively low conductivity may be desirable, however, if relatively thicker layers are required to provide adequate protection, it will be It is essential that the composition of the protective layer has a relatively high conductivity.

Battery design The batteries of this invention can be constructed in accordance with different known processes for assembling components of cells and cells. Generally, the invention finds application in any cell configuration. The exact structure will depend mainly on the intended use of the battery unit. Examples include thin film with porous separator, thin film polymeric laminates, gelatinous (ie spirally wound) roll, prismatic, coin cell, etc. Generally, batteries employing the negative electrodes of this invention will be manufactured with an electrolyte. It is possible, however, that the protective layer could serve as a solid-state electrolyte in its own right. If a separate electrolyte is used, it can be in liquid, solid (for example, polymer), or gel state. This can be fabricated together with the negative electrode as a unitary structure (e.g., as a laminate). Such unitary structures will often employ a solid phase or gel electrolyte.

The negative electrode is separated from the positive electrode, and both electrodes can be in material contact with an electrolyte separator. The current collectors touch the positive and negative electrodes in a conventional manner and allow an electric current to be extracted by means of an external circuit. In a typical cell, all components will be enclosed in a suitable cover, plastic for example, with only the current collectors extending beyond the cover. With this, the reactive elements, such as sodium or lithium in the negative electrode, as well as other elements of the cell are protected. Referring now to Figure 3, a cell 310 is shown according to a preferred embodiment of the present invention. The cell 310 includes a negative current collector 312 that is formed of an electronically conductive material. The current collector serves to conduct electrons between a terminal of the cell (not shown) and a negative electrode 314 (such as lithium) to which the current collector 312 is fixed. The negative electrode 314 is made of lithium or other similarly similar material. reagent, and includes a protective layer 308 formed opposite the current collector 312. It makes contact with the current collector 312 by means of a wetting layer 313. The negative electrode 314 or the protective layer 308 contacts an electrolyte in a region of electrolyte 316. As mentioned, the electrolyte can be liquid, gel, or solid (e.g., polymer). To simplify the discussion of Figure 3, the electrolyte will be referred to as "liquid electrolyte" or simply "electrolyte." An optional separator in region 316 prevents electronic contact between the positive and negative electrodes. A positive electrode 318 touches the side of the separator layer 316 opposite the negative electrode 314. Because the electrolyte region 316 is an electronic insulator and an ion conductor, the positive electrode 318 is ionically coupled but is electronically isolated from the negative electrode. 314. Finally, the side of the positive electrode 318 opposite the electrolyte region 316 is fixed to a positive current collector 320. The current collector 320 provides an electronic connection between a positive terminal "of cell (not shown) and the electrode positive 318. The current collector 320, which provides the current connection to the positive electrode, must resist degradation in the electrochemical environment of the cell and must remain substantially unchanged during discharge and charging., the current collectors are sheets of conductive material such as aluminum or stainless steel. The positive electrode can be fixed to the current collector by forming it directly on the current collector or by pressing a preformed electrode onto the current collector. Mixtures of positive electrodes formed directly preferentially on the current collectors have good adhesion. Films of positive electrode can also be cast or pressed onto the expanded metal sheets. Alternatively, metal conductors can be fixed to the positive electrode by folding-sealing, spray metallization, sputtering, or other techniques known to those of ordinary skill in the art. Some positive electrode can be pressed together with the electrolyte separator sandwiched between the electrodes. To provide a good electrical conductivity between the positive electrode and a metal container, an electronically conductive matrix of, for example, carbon or aluminum powders or fibers or metallic mesh is used. A separator can occupy all or a portion of the electrolyte compartment 316. Preferably, this will be a highly porous / permeable material such as a felt, paper or microporous plastic film. It must also resist the attack of the electrolyte and other components of the cell under the potentials experienced within the cell. Examples of suitable separator include glass, plastic, ceramic and porous membranes thereof, among other separators known to those of ordinary skill in the art. In a specific embodiment, the separator is Celgard 2300 or Celgard 2400 available from Hoechst Celanese of Dallas, Texas. In an alternative mode, no separator is used. The protective layer on the negative electrode prevents the positive and negative electrodes from contacting each other and performs the function of a separator. In such cases, the protective layer must be tenacious. This can be relatively thick and can be made of a material that is resistant to cracking and abrasion. In some embodiments of the invention, the cell can be characterized as a "thin film" or "thin layer" cell. Such cells have relatively thin electrodes and electrolyte separators. Preferably, the positive electrode is no thicker than about 300μm, more desirably no thicker than about 150μm, and preferably no thicker than about 100μm. The negative electrode is preferably no thicker than about 100μm and more desirably no thicker than about 100μm. Finally, the electrolyte separator (when in a fully assembled cell) is no thicker than about 100μm and more preferably no thicker than about 40μm. The present invention can be used with any of a variety of battery systems employing a highly reactive negative electrode such as lithium or another alkali metal. For example, any positive electrode used with lithium metal or lithium ion batteries can be used. These include manganese and lithium oxide, cobalt and lithium oxide, nickel and lithium oxide, vanadium oxide and lithium, etc. Mixed oxides of these compounds such as nickel-cobalt-lithium oxide can also be used. As will be explained in more detail below, a preferred application of the electrodes of this invention is in the lithium-sulfur batteries. Even though the above examples are oriented to rechargeable batteries, the invention can also find application in primary batteries. Examples of such primary batteries include manganese-lithium oxide batteries, (CF) -lithium chloride batteries, lithium sulfur dioxide batteries and lithium-iodine batteries. These batteries would normally have lithium electrodeposited ex if you, and then have a long storage life due to the protective coating. The protective layer allows one to use a reactive metallic lithium electrode in a manner that resembles the use of lithium-ion batteries. Lithium-ion batteries were developed because they had a longer cycle life and better safety features than metallic lithium batteries. The relatively short cycle life - of metallic lithium batteries has been due, in part, to the formation of lithium dendrites which grow from the lithium electrode through the electrolyte and to the positive electrode where they short-circuit the cells. Not only do these shorts prematurely kill the cells, they impose a serious security risk. The protective layer of this invention avoids dendrite formations and thereby improves the cycle life and safety of metallic lithium batteries. In addition, the batteries of this invention will work better than lithium ion batteries because they do not require a carbon intercalation matrix to support lithium ions. Because the carbon matrix does not provide a source of electro-chemical energy, it simply represents deadweight that reduces the energy density of a battery. Because the present invention does not employ a carbon intercalation matrix, it has a higher energy density than a conventional lithium ion cell while at the same time providing a better cycle life and safety than the metallic lithium batteries studied up to now.

In addition, the metallic lithium batteries of this invention do not have a large irreversible loss of capacity associated with the "formation" of lithium ion batteries.

Lithium-sulfur batteries Positive sulfur electrodes and metal-sulfur batteries are described in U.S. Patent No. 5,686,201 issued to Chu on November 11, 1997 and U.S. Patent Application No. 08 / 948,969 naming Chu et al. as inventors and filed on October 10, 1997. Both documents are incorporated herein by reference. The positive sulfur electrodes preferably include in their theoretically fully charged state sulfur and an electronically conductive material. In some discharge state, the positive electrode will include one or more polysulfides and possibly sulphides, which are polysulfides and sulphides of the metal or metals found in the negative electrode. In some embodiments, the fully charged electrode may also include some amount of such sulfides and / or polysulfides. The positive electrode is manufactured in such a way that it allows the electrons to move easily between the sulfur and the electronically conductive material, and allows the ions to move between the electrolyte and the sulfur. Thus, a great use of sulfur is achieved, even after many cycles. If the lithium-sulfur battery employs a solid-state electrolyte or gel, the positive electrode must include an electronic conductor (eg, carbon) and an ion conductor (eg, polyethylene oxide) in addition to the electroactive sulfur material. If the battery uses a liquid electrolyte, the positive electrode may require only an electronic conductor in addition to the electroactive sulfur material.

The electrolyte itself penetrates the electrode and acts as the ion conductor. In the case of a liquid electrolyte cell, the design of the battery can assume two formats: (1) all the active sulfur (elemental sulfur, polysulfides and sulphides of the positive electrode) is dissolved in electrolyte solution (one-phase positive electrode) and (2) the active sulfur is distributed between a solid phase (sometimes precipitated) and a liquid phase. When the cells of the sulfur-metal battery of this invention include a liquid electrolyte, that electrolyte must maintain many or all of the sulfur discharge products in solution and therefore available for the electrochemical reaction. Thus, they preferably solubilize relatively low molecular weight lithium sulfide and polysulfides. In a particularly preferred embodiment, the electrolyte solvent has repeating ethoxy units (CH2CH20). This can be a glime or related compound. It is believed that such solvents coordinate strongly with lithium and therefore increase the solubility of the discharge products of lithium-sulfur batteries. Suitable liquid electrolyte solvents are described in more detail in U.S. Patent Application No. 08 / 948,969, previously incorporated by reference. It should be understood that the electrolyte solvents of this invention may also include cosolvents. Examples of such additional cosolvents include sulfolane, dimethyl sulfone, dialkyl carbonates, tetrahydrofuran (THF), dioxolane, propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), butyrolactone, N-methylpyrrolidinone. , dimethoxyethane (DME or glime), hexamethylphosphoramide, pyridine, N, N-diethylacetamide, N, N-diethylformamide, dimethylsulfoxide, tetramethylurea, N, N-dimethylacetamide, N, N-dimethylformamide, tributylphosphorate, trimethylphosphate, N, N, N ', N'-tetraethylsulfamide, tetraethylenediamine, tetramethylpropylene diamine, pentamethyldiethylenetriamine, methanol, ethylene glycol, polyethylene glycol, nitromethane, trifluoroacetic acid, trifluarmetanesulfonic acid, sulfur dioxide, boron trifluoride, and combinations of such liquids.

The protective layers used in this invention can allow the use of electrolyte solvents that work well with sulfides and polysulfides but can attack lithium. Examples of solvents in this category --- include amine solvents such as diethylamine, ethylenediamine, tributylamine, amides such as dimethylacetamide and hexamethylphosphoramide (HMPA), etc. Exemplary but optional electrolyte salts for the battery cells incorporating the electrolyte solvents of this invention include, for example, lithium trifluoromethanesulfonimide (LiN (CF3S02) 2), lithium triflate (LiCF3S03), lithium perchlorate (LiC10) , LiPF6, LiBF, and LiAsF6, as well as corresponding salts that depend on the choice of metal for the negative electrode, for example, the corresponding sodium salts. As indicated above, the electrolyte salt is optional for the cells of the battery of this invention, in those in which during the discharge of the battery, the metal sulphides or polysulfides formed can act as electrolyte salts, for example, MX / ZS where -x = 0 to 2 and z is the valence of the metal. As mentioned, the cells of the battery of this invention may include a solid state electrolyte. An exemplary solid state electrolyte separator is a ceramic or glass electrolyte separator that essentially does not contain liquid. Specific examples of ceramic solid state electrolyte separators include beta-alumina type materials such as sodium beta, glass or ceramic Nasicon ™ or LisiconM alumina. Polymeric electrolytes, porous membranes, or combinations thereof are exemplary of a type of electrolyte separator to which an aprotic organic plasticizer liquid may be added in accordance with this invention for the formation of a solid state electrolyte separator that generally contains less than 20% of liquid. Suitable polymeric electrolytes include polyethers, polyimines, polythioethers, polyphosphazenes, polymer blends, and the like, and mixtures and copolymers thereof in which a suitable electrolyte salt has optionally been added. Preferred polyethers are polyalkylene oxides, more preferably, polyethylene oxide. In the gel state, the electrolyte separator contains -generally at least 20% (weight percent) of an organic liquid (see the liquid electrolytes listed above for examples), with the liquid being immobilized by the inclusion of a gelling agent. . Many gelling agents can be used such as polyacrylonitrile, polyvinylidene difluoride (PVDF), or polyethylene oxide (PEO).

It should be understood that some systems employing liquid electrolytes are commonly referred to as having "polymer" separating membranes. Such systems are considered liquid electrolyte systems within the context of this invention. The membrane separators used in these systems actually serve to hold the liquid electrolyte in small pores by capillary action. Essentially, a porous or microporous network provides a region for the entrainment of the liquid electrolyte. Such separators are described in U.S. Patent No. 3,351,495 assigned to W. R. Grace & Co. and U.S. Patents Nos. 5,460,904, 5,540,741, and 5,607,485 all assigned to Bellcore, for example. Each of these patents is incorporated herein by reference. The fully charged state of some cells of this invention does not require that the positive electrode be completely converted to elemental sulfur. It may be possible in some cases to have the electrode, positive in a very oxidized form of lithium polysulfide, for example, as in Li2Sx where x is five or greater. The fully charged positive electrode may also include a mixture of such polysulfides together with elemental sulfur and possibly even some sulfide. It should be understood that during loading, the positive electrode may not be of generally uniform composition. That is, there will be some amount of sulfur, sulfur, and a variety of polysulfides with various values of x. Also, even though the electrochemically active material includes some substantial fraction of "sulfur," this does not mean that the positive electrode must rely exclusively on the sulfur for its electrochemical energy. The electronic conductor in the positive electrode preferably forms an interconnected matrix so that there always exists a clean current path of the positive current collector at any position in the electronic conductor. This provides a high availability of electroactive sites and sustained accessibility to load carriers during repeated cyclizations. Often such electronic conductors will be fibrous materials such as felt or paper. Examples of suitable materials include a carbon paper obtainable from Lydall Technical Papers Corporation of Rochester, NH and a graphite felt available from the Electrosynthesis Company of Lancaster, NY. The sulfur is preferably dispersed uniformly in a composite matrix containing an electronically conductive material. Preferred weight proportions of sulfur to electron conductor in the positive sulfur-based electrodes of this invention, in a fully charged state are at most about 50: 1, preferably at most about 10: 1, and more desirably at at most about 5: 1. The sulfur considered in these proportions includes sulfur in the precipitated phase or in the solid phase as well as the sulfur dissolved in the electrolyte. Preferably, the ratio by weight of electronic conductor to binder is at least about 1: 1 and more preferably at least about 2: 1. The positive sulfur-based compound electrode may further include and optionally performance enhancing additives such as binders, electrocatalysts (eg, phthalocyanines, metallocenes, curcurmin (Reg. No. 3051-11-4 from Aldrich Catalog Handbook of Fine Chemicals; Aldrich Chemical Company, Inc., 1001 West St. Paul Avenue, Milwaukee, WI) among other electrocatalysts), surfactants, dispersants (for example, to improve the homogeneity of the electrode ingredients), and protective layer forming additives to protect an electrode negative lithium (for example, organosulfur compounds, phosphates, iodides, iodine, metal sulfides, nitrides, and fluorides). The preferred binders (1) do not buff in the liquid electrolyte and (2) allow partial but not complete wetting of the sulfur by the liquid electrolyte.

Examples of suitable binders include Kynar available from Elf Atochem of Philadelphia, PA, polytetrafluoroethylene dispersions, and polyethylene oxide (approximately 900k molecular weight for example). Other additives include electroactive organodisulfide compounds that employ a disulfide bond in the main structure of the compound. The electrochemical energy is generated by reversibly breaking the disulfide bonds in the main structure of the compound. During loading, the disulfide bonds are reformed. Examples of suitable organodisulfide compounds for use with this invention are presented in U.S. Patent Nos. 4,833,048 and 4,917,974 issued to DeJonghe et al. and U.S. Patent No. 5,162,175 issued to Visco et al. The cells of the battery of this invention can be "secondary" rechargeable cells. Unlike primary cells that are only discharged once, the secondary cells of this invention cycle between discharge and charge at least twice. Typically, the secondary cells of this invention cycle at least 50 times, each having a sulfur utilization (measured as a fraction of 1675 mAh / g sulfur yield during the cycle discharge phase) of at least about 10% . More preferably, at least 50 cycles will have a minimum sulfur utilization of at least about 20% (preferably at least about 30%). Alternatively, the secondary cells of this invention will cycle at least twice, with each cycle achieving at least 50% utilization of sulfur at the positive electrode. The use of an in situ process to form a lithium electrode in a lithium-sulfur cell according to this invention provides a simple mechanism for controlling the oxidation state of the positive electrode during the cycling of the normal cell. For example, the designer can design the cell so that very few, if any, highly reduced species such as lithium sulfide are produced during cyclization. This can be achieved by using as the lithium source a relatively highly oxidized species (eg, Li2S2) (positive electrode) for the in formation of the negative lithium electrode. Since all lithium cells come originally from Li2S2, the positive electrode of a fully discharged cell will have species whose average oxidation state corresponds to Li2S2. This prevents the formation of Li2S in any important amount. Note that very small species such as Li2S are relatively insoluble compared to much more oxidized species and therefore may be undesirable with liquid electrolyte cells. That is, many cell designs require that most or all of the sulfur species remain in solution. If the sulfur is reduced in an insoluble form (eg, Li2S or a related species), it may lose electrical contact with the electrode / current collector and thus become unavailable for the electrochemical reaction. This reduces the capacity of the cell and the energy density. Figure 4 schematically illustrates the general concept of controlling the oxidation state of the positive electrode. Initially, a cell 401 is assembled. This includes a negative electrode precursor 402, a separator 409, and a cathode / catholyte 411. The catholyte 411 is a Li2S4 solution that penetrates through the separator 409 to come into contact with the layer 407. It also comes in contact with a positive electrode 415 which can be a carbon mesh or plush in contact with an aluminum current collector. The electrode precursor 402 includes a current collector 403 (e.g., a copper foil), a wetting layer 405 (e.g., aluminum), and a protective layer of lithium conductive glass 407. When cell 401 is ready for initial use, it is charged to form the lithium electrode. This results in the application of a negative potential to the current collector 403 and a positive potential to the current collector 415. Positively charged lithium ion leaves the Li2S4, traverses the ion conductor of glass 407, and is reduced to metallic lithium the current collector 4Q3 and are alloyed with aluminum from layer 405. As shown in Fig. 4, a lithium electrode 402 'is formed. This includes a lithium layer 413 located between the glass protective layer 407 and the current collector 403. It comes into contact with the current collector 403 through an Al / Li 405 'alloy. The charge produced by the lithium electrode 402 'also oxidizes the catholyte species to an average oxidation state higher than LiS. For example, it can produce a charged catholyte 411 'which contains highly oxidized polysulfide species such as Li2Ss as well as possibly elemental sulfur. Fully charged lithium-sulfur 401 can be discharged to produce useful electrochemical energy. During discharge, the negative electrode 4Q2 'is gradually oxidized and the metallic lithium in layer 413 is converted to lithium ions which move through the protective layer 407 and into the catholyte 411'. The highly oxidized polysulfides and the elemental sulfur are reduced by reaction with the lithium ions released by the negative electrode 402 '. As a result, catholyte species decrease the oxidation state on average. As shown in Figure 4, the normal discharge state of cell 401 includes the negative electrode discharged 402"and catholyte 411. Note that electrode 402" no longer includes lithium layer 413 because it has been consumed . As a result, electrode 402"includes current collector 403, Li / Al 405 wetting layer, and protective layer 407. Catholyte 411 includes reduced polysulfide species such as Li2S4. Note that in the original cell, the Li2S was chosen for the catholyte so that the sulfur compounds always had a relatively high oxidation state (greater than the Li2S) even during the total discharge. Thus, all sulfur species tend to remain in solution, because they never reach an oxidation state that approaches Li2S. Subsequent charge / discharge cycles convert the negative electrode between the charged state 402 'in which a lithium layer 413 is formed and the discharged state 402"in which part or all of the layer 413 is consumed. catholyte between the charged state 411 'in which oxidized species such as elemental sulfur and Li2Ss are formed and the discharged state 411 in which reduced species such as Li2S are formed, however, no strongly reduced species are formed (less soluble) such as Li2S Figure 5 is a cell potential graph 501 against the state of charge for a sulfur catholyte of a typical lithium-sulfur cell The cell voltage (abscissa) is a function of the state of charge (ordinate) of the cathode / sulfur catholyte The slope of the graph reflects the fact that different sulfur-containing species have different redox potentials against lithium species, a lithium-sulfur cell that It has 100 percent sulfur as the cathode / catholyte will have a cell voltage of approximately 2.5 volts. As that cell is discharged, the state of charge of the catholyte (and the composition) changes so that polysulphides are formed and the potential of the cell decreases. The potential curve has a highlight in an average cathode / catholyte composition of about Li2S8 as illustrated in the graph. The curve remains relatively flat during the further reduction in the charge state until the average composition is reduced below approximately Li2S2, at which point the potential drops rapidly until the fully reduced state (Li2S) is reached.

A lithium-sulfur cell design can limit the scale of the Li-S potential curve over which the cell operates between loading and unloading. The size of the scale-depends on the relative amounts of lithium and sulfur in the system. When the relative amount of lithium is low the potential scale of the cell is narrow. When the relative amount of lithium is high the potential scale of the cell is large. Bars 503 and 505 represent two different lithium-sulfur cells. Cell 503 has a relatively small scale that implies a relatively low ratio of Li: S, while cell 505 has a larger scale which implies a higher ratio of -Li: S. In situ cells in which the initial source of lithium are very small sulfur species rich in lithium (eg, Li2S), the potential scale is higher. In addition, the relative position of the potential scale in the global Li-S potential curve depends on the composition of the starting lithium source. Much more oxidized species (eg, a mixture that includes Li2S4 and LiSß) in the lithium source provide cells that also operate to the left in the potential curve of Figure 4.

Examples The following results have been observed: 1. In an aprotic solvent in the presence of lithium polysulfide, as in the described catholyte, bright lithium can be electrodeposited through the DE-LIPON layer on the copper surface (example 1). Under similar conditions, electrodeposition on the uncoated copper foil did not provide any lithium coating. 2. This LIPON / copper structure electrodeposited with lithium is a usable anode. Example 2 demonstrates its ability to cyclize in the presence of the catholyte. 3. This electrodeposited lithium is also essentially a fully active anode. Example 3 shows that the availability of lithium after twenty cycles is at least 98% of the active lithium of the original anode. An experimental system was prepared as follows. A LIPON / copper compound was made by sputtering LIPON onto a copper film, similar to a process described by Bates et. in Solid State Ionics, 53-56 (1992), 647 654 which is incorporated herein by reference. He became a LIPON witness by means of simple fusion. A LIPON control preform was made by heating 11.5 gm of lithium phosphate powder purchased from Alfa Aesar at 1250 ° C (heating rate of 80 ° C / min) in a 95/5 Pt / Au crucible (diameter 23-34) mm of base, of slightly tapered wall), staying at that temperature for 15 minutes, followed by cooling at 80 ° C / min until the temperature dropped below 300 ° C. This preform was sized according to a desirable shape with a "medium" 3M Drywall Screen. The weight of the finished control was approximately 9.5 gm. A 3.30 cm (1.3") Minimak ion bombardment head (manufactured by US Inc.) energized by an RF10 energy source (from RF Plasma Products) was used to ionically bomb the LIPON on the Cu sheet (0.01 mm thickness). , by Schlank). The particular conditions for this run were 20 millitor of nitrogen, with a nitrogen expenditure of 20 sccm, RIF energy of 75 direct watts, 0 reflected watts, objective distance to substrate of 8 cm, and duration of 58 Under such conditions of sputtering, LIPON apparently formed reactively on the surface of the substrate.Cons cells were constructed with the LIPON / Cu anode precursor, a polpylene separator (0.58 mm thick, by Hollensworth Vose) which also serves as a catholyte deposit, and a C / Al cathode current collector. The Cu piece was approximately 2 cm x 2 cm, while the other components were approximately 1 cm x 1 cm. Copper was placed on the anode lead plate, while a stainless steel plate (approx. 1 cm x 1 cm), under a light spring tension, served as the contact cathode. The cells, unless otherwise mentioned, were filled with a catholyte, a solution of lithium sulfide in tetraglime containing 3 moles of sulfur and 0.75 moles of lithium / liter, with 0.5 moles / liter of lithium trifluoromethanesulfonimide as the electrolyte of support for. The cells were designed to easily seal and disassemble easily. Electrical maneuvers and measurements were performed in a Maccor cell cycler.

Examples 1. Cell # D042 was constructed as described above. It was charged at 100 microa-mperes for one hour. It was disassembled then. An even and bright lithium film could be easily seen on the copper surface through the transparent LIPON glass layer. An experiment was carried out in parallel in which the only variation was that the copper sheet was not covered with LIPON. This did not provide any lithium coating nor for voltage indications during charging nor for physical observation during disassembly. 2. Cell # D049 was constructed as described above. It was charged at 100 microamps for 2 hours. This was then cycled to 100 microamps for 15 minutes of discharge followed by 15 minutes of charging, for 100 cycles. Except for a minimum rise and fall of apparent internal resistance of the cell, much of which is attributed to the change in ambient temperature, the cell behaved remarkably steadily throughout the cyclization. 3. Cell # D111 was built as described above, except that the sputtering process was carried out for 85 minutes at 78 watts direct power. It was initially determined electrically that there was no metallic lithium on the surface of the copper anode. The cell was then loaded at 10 microamps for 10 min, then at 100 microamps for 2 hours, then cyclization at 10-0 microamps, 15 min discharge / 15 min load, for 20 cycles. The cell was then put into a cleaning mode, when it was discharged at 100 microamps until the potential of the closed circuit reached 2.0 V, at that time the current was decreased to 20 microamps, at a closed circuit potential of 2.0 V. This stage cleaning was integrated to 188.2 microamps-hr, indicating a minimum of 188.2 microamps-hr of active lithium anode that remained at the end of the cyclization. In other words, after a total of 201.6 microamps-hr of initially electrodeposited lithium was cycled 20 times at 25 microamps-hr per cycle, a minimum of 188.2 microamps-hr remained available. In other words, a total of 701.6 (201.6 + 20 cycles x 25 / cycle) microamperes / hr of Li were electrodeposited on the copper anode, and at the end 688.2 (188.2 + 20 cycles x 25 / cycle) microamperes-hr of download, they were registered. See figure 6. The term "minimum" should be emphasized, since obviously, from the definition of the end point of the cleaning step used, there is still unused lithium available at the end of the cleaning step.

Other modalities The foregoing describes the present invention and its preferred embodiments. It is expected that numerous modifications and variations will be presented in the practice of this invention for those persons with average knowledge in the field. For example, the invention may provide overload protection as described in United States of America patent application No. 08 / 686,609, filed July 26, 1996, and entitled "RECHARGEABLE POSITIVE ELECTRODES" and "RECHARGEABLE POSITIVE ELECTRODES" and U.S. Patent Application No. 08 / 782,245, filed March 19, 1997, and entitled OVERCHARGE PROTECTION SYSTEMS FOR RECHARGEABLE BATTERIES (OVERLOAD PROTECTION SYSTEMS FOR RECHARGEABLE BATTERIES). Such modifications and variations are encompassed within the following claims.

All - the references cited here are incorporated as a reference for all purposes.

Claims (31)

1. A method for manufacturing an alkali metal electrode, the method comprises: (a) providing an alkaline metal electrode precursor in an electrochemical cell, the electrode precursor includes a current collector and a glassy or amorphous protective layer that forms a layer substantially impenetrable and which is a single ionic conductor, conductive for ions of an alkali metal; and (b) electrodepositing the alkali metal through the protective layer to form a layer of the alkali metal between the current collector and the protective layer to form the alkali metal electrode. The method according to claim 1, further characterized in that the alkali metal electrode precursor further comprises a wetting layer located between and adhered to the current collector and the protective layer, wherein the wetting layer (i) is interspersed with alkali metal ions driven by the single ionic conductor or (ii) is alloyed with the alkali metal having ions driven by the single ionic conductor. 3. The method according to claim 1, further characterized in that the electrochemical cell is a discharged battery and wherein electrodeposing the alkali metal to form the electrode is an initial charging operation. 4. The method according to claim 3, further characterized in that the battery is a primary battery. The method according to claim 3, further characterized in that it further comprises transporting the discharged battery before electrodepositing the alkali metal to form the alkali metal electrode. 6. The method according to claim 1, further characterized in that it further comprises (c) removing the alkali metal electrode from the electrochemical cell. 7. The method according to claim 6, further characterized in that it further comprises (d) assembling a battery that includes the alkaline metal electrode. The method according to claim 1, further characterized in that the alkaline metal electrode is provided in a primary battery selected from the group consisting of manganese dioxide and lithium batteries, (CF) X and lithium batteries, batteries of thionyl and lithium chloride, sulfur dioxide and lithium batteries, lithium iron sulphide batteries (Li / FeS2), polyaniline and lithium batteries, and lithium iodine batteries. The method according to claim 1, further characterized in that the alkaline metal electrode is provided in a secondary battery selected from the group consisting of lithium-sulfur batteries, cobalt oxide and lithium batteries, nickel oxide batteries and lithium, manganese oxide and lithium batteries, and batteries of vanadium oxide and lithium. 10. An alkaline metal electrode precursor characterized in that it comprises: a current collector; a vitreous or amorphous protective layer that forms a substantially impenetrable layer which is an ionic conductor, conductive for ions of an alkali metal; and a humectant layer located between and adhered to the current collector and the protective layer, wherein the wetting layer (i) is intercalated with alkali metal ions conducted by the ion conductor or (ii) is alloyed with the alkali metal having ions driven by the ion conductor. 11. The alkaline metal electrode precursor according to claim 10, further characterized in that the current collector is a metal layer. 1

2. The alkaline metal electrode precursor according to claim 11, further characterized in that the metal is selected from the group consisting of copper, nickel, stainless steel, and zinc. 1

3. The alkaline metal electrode precursor according to claim 10, further characterized in that the current collector is a metallized plastic sheet. 1

4. The alkaline metal electrode precursor according to claim 10, further characterized in that the wetting layer comprises a material that is alloyed with the alkali metal. 1

5. The alkaline metal electrode precursor according to claim 14, further characterized in that the material of the wetting layer is selected from the group consisting of silicon, magnesium, aluminum, lead, silver and tin. 1

6. The alkaline metal electrode precursor according to claim 10, further characterized in that the wetting layer comprises a material which is intercalated with ions of the alkali metal. 1

7. The alkaline metal electrode precursor according to claim 7, further characterized in that the material of the wetting layer is selected from the group consisting of carbon, titanium sulfide and iron sulfide. 1

8. The alkaline metal electrode precursor according to claim 10, further characterized in that the protective layer is conductive for lithium ions. 1

9. The alkaline metal electrode precursor according to claim 10, further characterized in that the protective layer includes at least one of a lithium silicate, a lithium borate, a lithium aluminate, a lithium phosphate, phosphorus oxynitride. and lithium, a lithium silicosulfide, a lithium borosulfide, a lithium aluminosulfide, and a lithium phosphosulphide. 20. The alkaline metal electrode precursor according to claim 10, further characterized in that the protective layer has a thickness of between about 50 angstroms and 5 microns. 21. The alkaline metal electrode precursor according to claim 20, further characterized in that the protective layer has a thickness of between about 500 angstroms and 2000 angstroms. 22. The alkaline metal electrode precursor according to claim 10, further characterized in that the protective layer has a conductivity of between about 10_8 and about 10_2 (ohm-cm) _ ?. 23. A battery comprising: a) a positive electrode comprising a source of mobile alkali metal ions in charge; b) a precursor for a negative alkali metal electrode including a current collector, a vitreous or amorphous protective layer that forms a substantially impenetrable layer which is an ionic conductor, conductive for ions of an alkali metal, and a wetting layer located between and adhered to the current collector and the protective layer, wherein the wetting layer (i) is intercalated with alkali metal ions driven by the ion conductor or (ii) is alloyed with the alkali metal having ions driven by the ion conductor; and c) an electrolyte. 24. The battery cell according to claim 23, further characterized in that the alkali metal comprises at least one of lithium and sodium. 25. The battery cell according to claim 23, further characterized in that the protective layer includes at least one of a lithium silicate, a lithium borate, a lithium aluminate, a lithium phosphate, a lithium phosphorus nitride. , a lithium silicosulfide, a lithium borosulfide, a lithium aluminosulfide, and a lithium phosphosulfide. 26. The battery cell according to claim 23, further characterized in that the protective layer has a thickness of between about 50 angstroms and 3000 angstroms. 27. The battery cell according to claim 23, further characterized in that the electrolyte is a liquid electrolyte. 28. The battery cell according to claim 23, further characterized in that the electrolyte is a polymer or gel electrolyte. 29. The battery according to claim 23, further characterized in that the positive electrode includes an electrochemically active material that is selected from the group consisting of alkali metal sulfides, alkali metal polysulfides, and combinations thereof. 30. The battery according to claim 23, further characterized in that the battery is a primary battery selected from the group consisting of batteries of manganese dioxide and lithium, batteries of (CF) X and lithium, thionyl chloride and lithium batteries, lithium sulfur dioxide batteries, lithium iron sulfide batteries (Li / FeS2), polyaniline and lithium batteries, and iodine and lithium batteries. The battery according to claim 23, further characterized in that the battery is a secondary battery selected from the group consisting of lithium-sulfur batteries, lithium cobalt oxide batteries, nickel-lithium oxide batteries, batteries of manganese oxide and lithium, and batteries of vanadium oxide and lithium.