MXPA99007475A - Polyimide battery - Google Patents

Abstract

A battery having at least one anode (14), at least one cathode (15), and at least one electrolyte (16) disposed between the anode and the cathode is presented. Each anode (14) comprises an anode current collector (11) and an anode composite material (21) which includes a first, soluble, amorphous thermoplastic polyimide, an electronic conductive filler, and an intercalation material. Each cathode (15) comprises a cathode current collector (12) and a cathode composite material (22) which includes a second soluble, amorphous, thermoplastic polyimide, an electronic conductive filler, and a metal oxide. Lastly, each electrolyte (16) comprises a third soluble amorphous, thermoplastic polyimide and a lithium salt. The process for preparing the battery comprises the steps of preparing an anode slurry,a cathode slurry, and an electrolyte solution;casting a film of the electrolyte solution to form an electrolyte layer;coating each of the anode slurry and the cathode slurry on respective current collectors to form an anode and a cathode;drying the electrolyte layer, the anode and the cathode;and assembling the electrolyte layer, anode, and cathode to form a battery.

Description

POLYIMIDE BATTERY CROSS REFERENCE WITH RELATED APPLICATIONS This application claims the benefit of the Provisional Application of the United States of America No. 60 / 086,237, filed on February 12, 1997, and fully incorporated herein as reference and the benefit of a United States Application. of America No. 09 / 021,027 which subsequently as the granted patent of United States of America No. 5,888,672.

TECHNICAL FIELD The present invention relates to lithium ion batteries. In particular, it is related to lithium ion batteries manufactured with amorphous soluble thermoplastic polyimides.

BACKGROUND OF THE INVENTION The technology of lithium batteries is a relatively new field and the subject of intense research. The main characteristics of the battery that are intended to improve through new research are size, weight, energy density, capacity, lower self-discharge speeds, cost and environmental safety. The goal is simplify manufacturing techniques and improve adhesion between layers to produce a dry cell battery that is small and light, has a long life, has a higher energy density and contains few or no toxic compounds that can enter the environment when discarding it. These batteries are useful for many applications, such as, for example, supply or power supply for cell phones, smart cards, calculators, laptops and electrical appliances. Schmutz et al. (U.S. 5,470,357) focus on the problem of adhesion between the electrode and the collector elements. Its solution is the pretreatment of the collector elements in which a solution of 0.25% to 3.0% of a polymeric material compatible with the matrix polymer is applied to the lamella or collector grid and dried to form a coating film. The resulting coated collector element is heated to make the polymer adherent. The coated and pretreated collector element is further processed by applying the appropriate electrode composition to form an anode or a cathode. These electrode and separator elements are formulated as layers of plasticized matrix compositions that are laminated with the electrically conductive collector elements to form a Unitary battery cell structure. Gozdz et al. (U.S. 5,587,253) discloses a lithium ion battery with an electrolyte / separator composition comprising a copolymer of polyvinylidene fluoride and a plasticizer. The crystalline structure of the polyvinylidene fluoride copolymer requires the introduction of plasticizers to interrupt or alter the crystalline regions of the copolymer matrix, simulating an amorphous region that leads to greater ionic conductivity. In addition, the introduction of plasticizers helps to reduce the vitreous transition temperature of the polymer, allowing it to undergo flow by melting or softening during the operation of the battery. This helps to facilitate the mobilization of the ions through the membrane. Optionally, the plasticizer should be replaced with an electrolyte saline solution containing another combined plasticizer of ethylene carbonate and dimethyl carbonate. The battery is formed by laminating separately each composite anode and cathode compositions in the mesh grid current collectors. Gozdz et al. Also focuses on the problem of adhesion by superficially cleaning the electrode elements in a common copper bright solution, rinsing in water, air drying. coating by immersion in an acetone solution of the copolymer solution and dry them to an adherent state. In particular, each electrode is prepared by cutting a film and placing it on or superimposing it on the coated grid by dipping to form an even element. The even element was placed between adherent polyethylene terephthalate regulator sheets and then passed through a rolling station. An electrode / collector pair was laminated with an interposed electrolyte separating membrane. In order to activate the battery, a significant amount of the plasticizer comprising the polymer matrices of the laminated layers, particularly the separator / electrolyte layer, was extracted from the laminated battery structure. The extracted battery structure is then activated during the preparation for the load / discharge cycle test by immersion, in an atmosphere essentially free of moisture. During the dive, the battery was impregnated in an amount of a 1M electrolyte solution of LiPF6 in 50:50 of ethylene carbonate (EC): dimethyl carbonate (DMC) for approximately 20 minutes, during which the battery was impregnated in an amount of solution that practically replaced the plasticizer extracted with the EC / DMC solution. Skotheim et al. (U.S. 5,601,947) rebels solid "gel-type" electrolytes consisting of a high molecular weight polymer matrix in which an electrolytic salt was dissolved, then subsequently swelled with a low molecular weight liquid (propylene carbonate, ethylene carbonate, glimes, low molecular weight polysiloxanes and mixtures thereof) which acts effectively as a plasticizer for the salt-polymer matrix. Useful gel-type electrolytes include sulfonated polyimides which have been swollen or swollen. The introduction of these plasticizers affect the dimensional stability of the material since they have the tendency to exude outside the material, causing it to return to an inflexible and brittle state. This affects the ionic mobility of the system and causes adhesion to fail. hang (U.S. 5,407,593) teaches that the main trajectory for ion transport in a polymeric electrolyte is through the amorphous region of a polymer matrix. In this way, the ionic conductivity of a polymeric electrolyte can be increased by decreasing the crystalline region and increasing the amorphous region of the polymer matrix. The methods frequently used to achieve this are: (1) preparing a new polymer such as for example a copolymer or a polymer with network structure; (2) add non-soluble additives to improve the electrolytic properties; and (3) add soluble additives to provide a new path to ionic conductivity. Polymers having high dielectric constants are good matrices for preparing polymer electrolytes. However, because they have high glass transition temperatures or high degrees of crystallinity, they do not result in desirable polymer electrolytes. To remedy this, Whang reveals a polymeric electrolyte that contains non-volatile components. This ensures that changes in conductivity and composition due to the volatilization of some of the compounds contained therein do not occur. In this way, the conductivity remains constant. The polymer electrolytes of their invention include a polar polymer matrix, a dissociable salt and a polyether or polyester oligomer plasticizer with halogenated end groups. Fujimoto et al. (U.S. 5,468,571) discloses a secondary battery with a negative electrode comprising carbon powder, the particles constituting the powder are consolidated with a polyimide binder. The polyimide can be either a thermoset polyimide or a thermoplastic polyimide, the former includes both types, condensation type and addition type. A representative example of polyimide resins of the condensation type is one that is obtained by curing thermally (condensation reaction by dehydration) a solution of a polyamide acid (an intermediate of the polyimide) in N-methyl-2-pyrrolidone. The polyamide acid is obtained in turn by reacting an aromatic diamine with an aromatic tetracarboxylic acid anhydride. The thermal curing is preferably conducted at a temperature of at least 350 degrees C for at least two hours to complete the condensation reaction by dehydration. They observed that if the polyimide intermediate with which the condensation reaction has not been completed by dehydration, remains at the negative electrode after thermal curing, it can, when the battery temperature becomes abnormally high, condense to release water , which will react vigorously with lithium. Addition-type polyimides also require thermal curing. An object of the present invention is to provide a polyimide battery that is based on a thermoplastic, amorphous and soluble polyimide. Another object is to provide a polyimide electrolyte that does not require swelling or the introduction of plasticizers. Another object is to provide a polyimide battery that exhibits excellent inter-layer adhesion.

Other object is to provide a polyimide battery that is capable of dissolving a large amount of lithium salt. Another object is to provide a polyimide battery that is environmentally safe. Another object is to provide a polyimide battery that exhibits a high ionic conductivity with an insubstantial change within a range of temperatures and pressures. Another object is to provide a process for preparing a polyimide battery. Another object is to provide a process for preparing a polyimide battery that does not require pretreatment of the current collectors. Another object is to provide a process for preparing a polyimide battery that does not require curing of the polyimide. Another object is to provide a process for preparing a polyimide battery that does not require heating the polyimide above its glass transition temperature. Another object is to provide a process for preparing a polyimide battery that does not require high temperature and high pressure to form the battery. Another object is to provide a battery of flexible polyimide.

SUMMARY OF THE INVENTION In the present invention, a polyimide battery having excellent inter-layer adhesion, flexibility and showing high ionic conductivity is presented. (lxl0 ~ 4 ohms "1 cm" 1) within a range of temperatures and pressures. The battery comprises at least one anode, at least one cathode and at least one electrolyte located between the anode and the cathode. Each anode comprises an anode current collector, a first amorphous and soluble thermoplastic polyimide, an electronic conductive charge and an intercalation material. Each cathode comprises a cathode current collector, a second amorphous and soluble thermoplastic polyimide, an electronic conductive charge and a metal oxide. Finally, each electrolyte comprises a thermoplastic, amorphous and soluble third polyimide and a lithium salt. The first, second and third thermoplastic, amorphous and soluble polyimides may or may not have the same chemical composition and may exist in various combinations thereof. The manufacture of the battery is simple and requires a minimum number of steps. Anodic paste was prepared from the first amorphous and soluble thermoplastic polyimide solution, a conductive charge electronics and an interleaving material. A cathodic paste comprising a second amorphous and soluble thermoplastic polyimide solution, an electronic conductive filler and a metal oxide was also prepared. Finally, an electrolyte solution comprising a third amorphous and soluble thermoplastic polyimide solution and a lithium salt was prepared. The electrolyte solution is cast or emptied like a film to form an electrolyte layer. The anodic paste covers a first current collector to form an anode and the cathode paste covers a second current collector to form a cathode. The electrolyte layer, the anode and the cathode are dried. The anode is charged with lithium ions by embedding the anode in a lithium salt solution. Finally, the anode, the electrolyte layer and the cathode are assembled to form a battery. This manufacturing technique provides several advantages over the previous techniques. One advantage is that the current collectors do not have to support any pre-treatment process before the anodic and cathodic pulps are applied. In addition, the anodic and cathodic pulps are applied by coating the opposing current collectors to laminate them over the current collectors. Because polyimide is a thermoplastic, amorphous and soluble polyimide, it already exists as a powder completely imidized before it is mixed in the system. In turn, there is no need to heat the anode, cathode and electrolyte layer to a high temperature to drive the polymerization reaction. Instead, heat is applied at a low temperature to remove the solvent and dry the polymer. In addition, because the imidization has already occurred before the polymer is placed in the system, there are no byproducts of the condensation reaction, such as water, to interact with the lithium salt. Finally, the amorphous property of the polyimide offers a natural path for ionic conductivity. In turn, there is no need to create a path through the addition of plasticizers or other low molecular weight additives. The resulting battery is flexible, exhibits excellent inter-layer adhesion and exhibits ionic conductivity within a range of temperatures. The additional objects and advantages of the invention will be partially explained in the following description and, in part, will be obvious from the description or may be learned by practicing the invention. The objects and advantages of the invention will be obtained by the instrumentation of combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate a complete embodiment of the invention, in accordance with the best forms developed so far for the practical application of the principles thereof, and in which: Figure 1 is a perspective view of the polyimide battery of the present invention. Figure 2 is a cross-sectional view taken along lines II-II of Figure 1. Figure 3 is a graph of conductivity at various temperatures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyimide battery of the present invention exhibits excellent intercoat adhesion, is flexible, environmentally safe and exhibits an ionic conductivity within a range of temperatures and pressures. The battery comprises at least one anode, at least one cathode and at least one electrolyte located between each anode and each cathode. The anode, cathode and electrolyte can be applied as very thin layers or layers less than a thousandth of an inch thick. Because of this capability, the anode, cathode and electrolyte can be stacked in multiple layers in a manner similar to a multilayer circuit board. In turn, the battery can include combinations such as: 1) an anode, an electrolyte and a cathode; 2) two anodes, two electrolytes and one cathode; 3) two cathodes, two electrolytes and one anode; 4) many anodes, many electrolytes and many cathodes; or 5) a dipolar configuration in such a way that a cathode is bent or folded around an anode, which has been surrounded by the electrolyte. This last configuration depends on the desired application for the battery. Figure 1 shows the simplest configuration of the battery 10, wherein there is an anode current collector 11 and a cathodic current collector 12 projecting from the main body portion of the battery for connection to the desired circuitry and for supplying the voltage and current or to recharge the battery. The main body portion is enclosed in a cover film 13, which is a single or multi-layer film not permeable to gases or liquids. Preferably, the cover film is a very thin and high barrier rolled foil or foil film of the type which is suitable for the application and which is easily processable with respect to the formation of the battery. Many of these cover films are well known in the industry, such as for example the KAPAK KSP-150 film or the tri-laminated film KSP-120 produced by Kapak, Inc. Alternatively, the 48-gauge multilayer film can also be used.

PET / LDPE / .000285, produced by Sealright Flexible Packaging Group. Referring now to Figure 2, a representative cross-section of the composition of the battery 10 is presented. Each anode 14 comprises an anode current collector 11, a first amorphous and soluble thermoplastic polyimide (not shown), an electronic conductive charge ( not shown) and an interleaving material (not shown). The anodic current collector 11 can be prepared from any material known to those skilled in the art. It is an electrical conductive member made of a metal, such as aluminum. Preferably, the anodic current collector 11 is a thin expanded foil (approximately 0.5-1.0 thousandths of an inch) which has regular openings therein, such as those found in a mesh or screen. A portion of the anodic current collector 11 extends from the main body of the battery 10 to provide an external connection means but, most of the anodic current collector 11 is located inside the cover 13 and enclosed in a composite material Anodic 21. The anodic composite material 21 is comprised of a first amorphous and soluble thermoplastic polyimide, an electronic conductive filler and an intercalation material. The first Thermoplastic, amorphous and soluble polyimide is any thermoplastic, amorphous and soluble polyimide known to those skilled in the art. The first amorphous and soluble thermoplastic polyimide may have the same chemical composition as the second and third thermoplastic, amorphous and soluble polyimides or may have a chemical composition different from these, which are used for the cathode and the electrolyte, respectively. In particular, these polyimides include, but are not limited to, MATRIMID XU5218, available commercially from Ciba-Geigy.; ULTEM 1000, available commercially from General Electric; and LaRC-CP1, LaRC-CP2 and LaRC-SI, all of which can be obtained from Imitec, Inc., Schenectady, New York. Any electronic conductive charge known to those skilled in the art can be mixed with the first amorphous and soluble thermoplastic polyimide and with a solvent to form a paste. Examples of the electronic conductive charge include, but are not limited to: conductive carbon, carbon black, graphite, graphite fiber and graphite paper. In addition to the electronic conductive charge, an intercalation material also forms part of the anode. Any intercalation material known to those skilled in the art can be used and, in particular, is selected from the group consisting of: coal, activated carbon, graphite, petroleum coke, a lithium alloy, nickel powder and a low-voltage lithium intercalation compound. As an alternative embodiment, the anode may additionally comprise a lithium salt. Any lithium salt known to those skilled in the art may be used but, in particular, those selected from the group consisting of: LiCl, LiBr, Lil, Li (C104), Li (BF4), Li (PF6), Li (AsFs) ), Li (CH3C02), L1 (CF3S03), Li (CF3S02) 2N, Li (CF3S02) 3, Li (CF3C02), Li (B (C6H5) 4), Li (SCN) and Li (N03). More preferably, the lithium salt is Li (PFs). The addition of the lithium salt to the anode results in an increase in ionic conductivity. The cathode 15 comprises a cathode current collector 12. As with the anode current collector, a portion of the cathode current collector 12 extends from the main body of the battery 10 to provide an external connection means. However, most of the cathode current collector 12 is located within the cover 13 and is enclosed within the cathodic composite material 22. The cathode current collector 12 is any cathode current collector known to those skilled in the art and , preferably, is a thin expanded metal foil (ranging from about 0.25 to 1.0 mils) which has apertures therein. From preference, ^ the metal is copper. The openings usually have a regular configuration, such as that found in a mesh or screen. The cathodic composite material 22 is comprised of a second amorphous and soluble thermoplastic polyimide, an electronic conductive filler and a metal oxide. The second thermoplastic, amorphous and soluble polyimide may or may not be of the same chemical composition as the first and third thermoplastic, amorphous and soluble polyimides, which are respectively used in the anode and in the electrolyte. The second amorphous and soluble thermoplastic polyimide can be any thermoplastic, amorphous and soluble polyimide known to those skilled in the art. Specific examples include, but are not limited to: MATRIMID XU5218, commercially available from Ciba-Geigy; ULTEM 1000P, commercially available from General Electric; LaRC-CPl, LaRC-CP2 and LaRC-Si obtainable all from Imitec, Inc., Schenectady, New York. Any electronic conductive charge known to those skilled in the art can be mixed with the second amorphous and soluble thermoplastic polyimide and with a solvent to form a paste. Examples of these electronic conductive charges include, but are not limited to: conductive carbon, carbon black, graphite, graphite fiber, and graphite paper. In addition, the cathode comprises a metal oxide. Any oxide Metal known to those skilled in the art can be used but, in particular, the metal oxide is selected from the group consisting of: LiCo02; LiMn02; LiNi02; V6013; V205; and LiMn204. As an alternative embodiment, the cathode may additionally comprise a lithium salt. Any lithium salt known to those skilled in the art can be used but, in particular, those selected from the group consisting of: LiCl, LiBr, Lil, Li (C!? 4), Li (BF4), Li (PF6) , Li (AsF6), Li (CH3C02), Li (CF3S03), Li (CF3S02) 2N, Li (CF3S02) 3, Li (CF3COz), Li (B (C6H5) 4), Li (SCN) and Li (N03) ). More preferably, the lithium salt is Li (PF6). As with the anode, the addition of a lithium salt to the cathode results in an increase in ionic conductivity. The electrolyte 16 is located between the anode 14 and the cathode 15. The electrolyte 16 comprises a thermoplastic, amorphous and soluble third polyimide and a lithium salt 23. The thermoplastic, amorphous and soluble third polyimide can be any thermoplastic, amorphous and soluble polyimide , known to those skilled in the art and may or may not be of the same chemical composition as the first and second thermoplastic, amorphous and soluble polyimides, which are respectively used for the anode and the cathode. Specific examples include, but are not limited to: MATRIMID XU5218 commercially available from Ciba-Geigy; ULTEM 1000P, available commercially from General Electric; LaRC-CPl, LaRC-CP2 and LaRC-Si, available from Imitec, Inc., Schenectady, New York. The lithium salt is any lithium salt known to those skilled in the art. In particular, the lithium salt is a member selected from the group consisting of: LiCl, LiBr, Lil, Li (C104), Li (BF4), Li (PFs), Li (AsF6), Li (CH3C02), Li ( CF3S03), Li (CF3S02) 2N, Li (CF3S02) 3, Li (CF3C02), Li (B (C6HS) 4), Li (SCN) and Li (N03). More preferably, the lithium salt is Li (PF6). In a preferred embodiment, the electrolyte comprises from about 2% by weight to about 10% by weight of the amorphous and soluble thermoplastic polyimide and from about 1% to about 12% by weight of the lithium salt. The key of the invention resides in thermoplastic, amorphous and soluble polyimides. The thermoplastic, amorphous and soluble polyimides used in the present invention are completely imidized and are usually in powder form. In order to produce the film, the coating or a paste of the polyimide, it must be dissolved in a solvent such as N, N-methylpyrrolidinone (NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF). Note that the polyimides dissolve in these solvents. The solvent is not used to swell or swell the polymer and the polymer does not it will swell or sponge since it is a thermoplastic. Also, because the polyimides are completely imidized, there is no need to further cure them at higher temperatures, which can cause damage to the battery. Instead, the polyimides are dried at the point of flammability of the solvent strictly for the purpose of eliminating it. No further polymerization will occur, so there are no byproducts of the condensation reaction (water) that interact with the lithium salts. The amorphous characteristic of the polyimide provides an unobstructed path for ionic mobility, unlike the previously used crystalline or semicrystalline polymers. In addition, it was discovered that large amounts of lithium salts could dissolve in these polyimide solutions without altering the polymer matrix. Finally, these polyimides exhibited excellent adhesion to current collectors, as well as excellent inter-layer adhesion. This adhesion between layers reduces the resistance and the effects of polarization in the battery. The chemical compositions of the first, second and third thermoplastic, amorphous and soluble polyimides can exist in various combinations. For example, the three polyimides can be the same, such as, for example, MATRIMID XU5218. Alternatively, they can there are other combinations, such as: 1) the first and second polyimides are the same and the third one is different; 2) the first and third polyimides are the same and the second one is different; 3) the second and third polyimides are the same and the first one is different; or 4) the three polyimides are different. The manufacturing process of the polyimide battery of the present invention is easier than previous processes. In particular, the process does not require the pretreatment of the current collectors. In addition, the polyimide polymer does not require additional curing nor does it need to be heated above its vitreous transition temperature to be processed. Finally, the polyimide battery does not require high temperature or pressure to form the laminate. The process comprises several steps. First, an anode paste comprising a first amorphous and soluble thermoplastic polyimide solution was prepared; an electronic conductive charge and an intercalation material. The first thermoplastic, amorphous and soluble polyimide solution is prepared by mixing from about 8% to about 20% by weight of a powder of the first amorphous and soluble thermoplastic polyimide with about 80% to about 92% by weight of a solvent. The powder of the first polyimide thermoplastic, amorphous and soluble may or may not have the same chemical composition as that found in the electrolyte or cathodic paste. As an alternative embodiment, lithium salt is added to the first amorphous and soluble thermoplastic polyimide solution. A cathodic paste comprising a second amorphous and soluble thermoplastic polyimide solution was prepared; an electronic conductive charge and a metal oxide. The second thermoplastic, amorphous and soluble polyimide solution was prepared by mixing from about 8% to about 20% by weight of a powder of the thermoplastic, amorphous and soluble second polyimide with from about 80% to about 92% by weight of a solvent. The powder of the second amorphous and soluble thermoplastic polyimide may or may not have the same chemical composition found in the electrolyte or in the anodic paste. As an alternative embodiment, lithium salt is added to the second amorphous and soluble thermoplastic polyimide solution. An electrolyte solution comprising a third amorphous and soluble thermoplastic polyimide solution and a lithium salt was prepared. The third amorphous and soluble thermoplastic polyimide solution was prepared by mixing from about 8% to about 20% by weight of the powder of the first amorphous, thermoplastic polyimide. soluble with about 80% to about 92% by weight of a solvent. To form a solution, about 20% to about 35% of a lithium salt was dissolved in about 65% to about 80% by weight of a solvent. The solution is then mixed with the first amorphous and soluble thermoplastic polyimide solution to form the electrolyte solution. The electrolyte comprises from about 2% by weight to about 10% by weight of the amorphous and soluble thermoplastic polyimide and from about 1% by weight to about 12% by weight of the lithium salt. An electrolyte layer is formed when casting or emptying a film of the electrolyte solution. The film is cast using the normal thin film methodology, such as spinning casting or using a scraper blade to stretch the solution to a film that varies from about 0.25 mils to about 20 mils in thickness. The electrolyte layer was dried using any method known to those skilled in the art and, in particular, in an oven at about 70 to about 150 degrees C for about 20 to about 60 minutes to expel the solvent. In particular, the electrolyte layer can be completely dried in an oven at approximately 150 degrees C for approximately 30 to 60 minutes to create a tough, smooth, flexible and opaque film. An anode is formed by coating the first anode collector with the anode paste. Any coating technique known to those skilled in the art can be used, as long as it is not lamination. These coating techniques include, but are not limited to: vapor deposition, dip coating, rotary coating, stencil coating and coating with a brush. The preparation of the current collector is not required. In addition, the anode paste is applied to the first current collector in a relatively thin layer. The anode is dried using any method known to those skilled in the art and, in particular, in a gravity flow oven for about 20 to about 60 minutes at about 70 to 150 degrees C to expel the solvent and leave an adherent film . Preferably, the anode can be dried completely in an oven at about 150 degrees C for 30 to 60 minutes. It was observed that the anodic paste had excellent adhesion to the first current collector. The anode was charged with lithium ions by immersing the anode in a 1 Molar lithium salt solution for about 20 to about 45 minutes.

The lithium salt solution comprises a lithium salt dissolved in a 50/50 mixture of ethylene carbonate.

(EC) / propylene carbonate (PC). After the anode has finished immersing, it is dried by wiping to remove the excess solution. A cathode is formed by coating a second current collector with the cathode paste. Any coating technique known to those skilled in the art can be used, provided it is not lamination. These coating techniques include, but are not limited to: vapor deposition, dip coating, rotary coating, stencil coating and coating with a brush. As with the anode, the preparation of the current collector is not required. The cathodic paste is applied to the second current collector in a relatively thin layer. The cathode is dried using any method known to those skilled in the art and, in particular, in an oven for about 20 to about 60 minutes at about 70 to 150 degrees C to expel the solvent and leave an adherent film. Alternatively, the cathode can be completely dried in an oven at approximately 150 degrees C for about 30 to 60 minutes. It was observed that the cathodic paste had an excellent adhesion to the second current collector. The anode, the electrolyte layer and the cathode are assembled to form the battery. The assembly process occurs using various methods. In one embodiment, the anode is provided. At least one drop of the electrolyte solution is applied to the anode. A drop is defined as the amount expressed from a standard pipette. The lower side of the electrolyte layer is placed on the anode, in such a way that the electrolyte solution is located between them. At the top side of the electrolyte layer at least one drop of the electrolyte solution is applied. Alternatively, one drop of the electrolyte solution could be applied to the cathode instead of the electrolyte layer. The cathode is placed on the upper side of the electrolyte layer, where the electrolyte solution is located between them to form a unit. The unit is heated to a temperature sufficient to allow the electrolyte solution to dry and, where each amorphous and soluble thermoplastic polyimide undergoes softening or melt flow. The softening of the polymer allows intimate lateral contact between the layers to occur, finally forming a uniform unit that is self-adhesive and exhibits excellent adhesion between the interleaved layers. After the unit is heated, it is allowed to cool to room temperature. As Additional step, the unit is placed in a protective box and charged to 0.5 milliamperes using a constant voltage or a constant current. As an alternative method for assembly, the electrolyte layer, the anode and the cathode are dried to an adherent state. The battery is assembled by providing the anode. The electrolyte layer is placed on the anode. The cathode is placed on the electrolyte layer to form the unit. Pressure is applied to the unit. The pressure may be minimal such as, for example, pressing only the layers by hand or applying pressure to a press. The amount of pressure required is sufficient to admit the intimate contact that will be made between the layers. In an additional step of the process, the unit is heated to a temperature where each amorphous and soluble thermoplastic polyimide suffers from melt flow. The unit is then allowed to cool to room temperature. Finally, the unit is enclosed in a protective box and charged to 0.5 milliamperes using a constant voltage or a constant current. The polyimide batteries that result from this process show excellent inter-layer adhesion, are flexible and show an ionic conductivity within a range of temperatures.

EXAMPLES Example 1 An electrolyte solution was prepared, in accordance with the following formulation: Raw material% by weight Li (PF6) 8.5 MATRIMID XU5218 6.4 NMP 85.1 8.0 grams of Li (PFs) were dissolved in 40 grams of NMP in a dry inert atmosphere and with constant stirring to form a solution. In a separate flask, 6.0 grams of MATRIMID XU5218, amorphous and soluble thermoplastic polyimide, available commercially from Ciba-Geigy, was dissolved in 40 grams of NMP. To the soluble polyimide solution was then added the lithium salt solution with constant stirring. A film was cast using a scraper blade set to a thickness of 6 to 8 mils. The film was dried in an oven at about 140 degrees C for about 30 to 45 minutes to provide a tough, soft, flexible and opaque film with a thickness of approximately 0.5 mil. The conductivity test was conducted in the electrolyte layer at various temperatures. The temperature cycle included an increase ramp and a retention at 80 degrees C followed by two ramps up and down from room temperature to 60 degrees C. The value of log (e "* 2pF) was approximately l.lxlO9 throughout this sequence of temperatures. = e0 e "* 2pF where e0 = 8.85 x lO" 14.! "" 1 cm "1, the value of s was lxlO" 4 ohms "1cm" 1 throughout this temperature range. are shown in Figure 3.

Example 2 An anode was prepared in accordance with the following formulation: Raw Material% by weight Graphite 46.0 Black smoke 2.4 Li (PF6) 2.3 MATRIMID XU5218 3.4 NMP 45.9 The amorphous and soluble thermoplastic polyimide, MATRIMID XU5218, commercially available from Ciba-Geigy, was dissolved in a portion of the NMP to form a polyimide solution. Graphite and carbon black were added to the polyimide solution. In a separate flask Li (PF6) was dissolved in a portion of the solvent to form the lithium salt solution. The lithium salt solution was added to the polyimide solution to form a paste. The pulp was milled in a ball mill for approximately 60 minutes. The paste was then left with the remaining solvent and ground in a ball mill for another 60 minutes. The resulting anodic slurry coated an aluminum strip and dried in an oven for about 20 to 60 minutes at about 70 to 150 degrees C. The anode was charged with lithium ions by immersing the anode in a 1 Molar lithium salt solution for about 20 to about 45 minutes. The lithium salt solution comprises Li (PFß) dissolved in a 50/50 mixture of ethylene carbonate (EC) / propylene carbonate (PC) to form a 1 Molar solution. After the anode immersion ended, it was dried by wiping to remove the excess solution. Example 3 A cathode was prepared in accordance with the following formulation: Raw Material% by weight Metal Oxide 42. 34 Black Smoke 4. 77 Li (PF6) 2. 24 MATRIMID XU5218 4. 84 NMP 45. 81 The amorphous and soluble thermoplastic polyimide, MATRIMID XU5218, commercially available from Ciba-Geigy, was dissolved in a portion of the NMP to form a polyimide solution. To the polyimide solution was added the oxide and the carbon black. In a separate flask Li (PF6) was dissolved in a portion of the solvent to form a lithium salt solution. The lithium salt solution was added to the polyimide solution to form a paste. The pulp was milled in a ball mill for approximately 60 minutes. The paste was then left with the remaining solvent and ground in a ball mill for another 60 minutes. The resulting cathode paste coated a copper strip and dried in an oven for about 20 to 60 minutes at about 70 to 150 degrees C.

Example 4 A battery was prepared using the electrolyte layer of Example 1, the anode of Example 2, and the cathode of Example 3. A drop of the electrolyte solution prepared in Example 1 was applied to the surface of the anode. Electrolyte layer was placed on the anode, in such a way that the electrolyte solution served as an adhesive. A second drop of the electrolyte solution was applied to the upper side of the electrolyte layer and to the cathode placed on top of it. The unit was then manually compressed and placed in an oven. The unit was heated to approximately 150 degrees C for approximately 30 to 60 minutes. The unit was then allowed to cool to room temperature and any sign of delamination was observed. There was no failure in adhesion between layers. The unit was then placed inside a protective box and charged to 0.5 milliamperes using constant voltage or constant current, forming a final battery product.

Example 5 Several batteries of example 4 were connected to energize a cell phone. A cell phone was used to make several local and long distance calls. Each call lasted approximately five minutes without interruption. The batteries were recharged after each call. The above description and drawings are only illustrative of the preferred embodiments achieved by the objects, features and advantages of the present invention and, it is not intended that the present invention be limited thereto. Any modification to the present invention that falls within the spirit and scope of the following claims is considered part of the present invention.

Claims (22)

1. CLAIMS: 1. A battery comprising: at least one anode, each anode comprising: an anode current collector; a first amorphous and soluble thermoplastic polyimide, wherein the polyimide is soluble in a solvent selected from the group consisting of: N, N-methylpyrolidinone (NMP); dimethylacetamide (DMAc) and dimethylformamide (DMF); an electronic conductive charge; and an intercalation material; at least one cathode, each cathode comprises: a cathode current collector; a second amorphous and soluble thermoplastic polyimide, wherein the polyimide is soluble in a solvent selected from the group consisting of: N, N-methylpyrolidinone (NMP); dimethylacetamide (DMAc) and dimethylformamide (DMF); an electronic conductive charge; and a metal oxide; and at least one electrolyte located between each anode and each cathode, wherein each electrolyte comprises: a thermoplastic, amorphous and soluble third polyimide, wherein the polyimide is soluble in a solvent selected from the group consisting of: N, N-methylpyrolidinone ( NMP); dimethylacetamide (DMAc) and dimethylformamide (DMF) and a lithium salt.
2. 2. A battery according to claim 1, wherein at least two of the thermoplastic polyimides, amorphous and soluble first, second and third, have the same chemical composition.
3. 3. A battery according to claim 1 or 2, wherein the cathode and / or the anode further comprises a lithium salt.
4. A battery according to any of the preceding claims, wherein the lithium salt is selected from the group consisting of: LiCl, LiBr, Lil, Li (C104), Li (BF4), Li (PFg), Li (AsF6) , Li (CH3C02), Li (CF3S03), Li (CF3S02) 2N, Li (C-F3S02) 3, Li (CF3C02), Li (B (C6HS) 4), Li (SCN), and Li (N03).
5. 5. A battery according to claim 4, wherein the lithium salt is Li (PF6).
6. A battery according to any one of the preceding claims, wherein the anode current collector and / or the cathode current collector comprise a foil or foil of expanded metal having openings.
7. A battery according to claim 6, wherein the anodic current collector comprises an expanded foil or foil having openings.
8. A battery according to claim 6 or 7, wherein the cathode current collector comprises a foil or expanded copper foil having openings.
9. 9. A battery according to any of the preceding claims, wherein the intercalating material is selected from the group consisting of: carbon, activated carbon, graphite, petroleum coke, a lithium alloy, nickel powder and a low-voltage lithium intercalation compound.
10. 10. A battery according to any of the preceding claims, wherein the metal oxide is selected from the group consisting of: LiCo02; LiMn02; LiNi02; V6013; V205; and LiMn204.
11. 11. An electrolyte comprising a thermoplastic, amorphous and soluble polyimide, wherein the polyimide is soluble in a solvent selected from the group consisting of: N, N-methylpyrolidinone (NMP); dimethylacetamide (DMAc) and dimethylformamide (DMF) and a lithium salt.
12. 12. An electrolyte according to claim 11, wherein the lithium salt is selected from the group consisting of: LiCl, LiBr, Lil, Li (C104), Li (BF4), Li (PF6), Li (AsFg), Li (CH3C02), Li (CF3S03), Li (CF3S02) 2N, Li (CF3S02) 3, Li (CF3C02), Li (B (C6H5) 4), Li (SCN), and Li (N03).
13. 13. An electrolyte according to claim 11 or 12 comprising from about 2% by weight to about 10% by weight of a thermoplastic, amorphous and soluble polyimide and from about 1% by weight to about 12% by weight of a lithium salt.
14. 14. A process to prepare a battery that it comprises the steps of: a) preparing an anddic paste comprising a first amorphous and soluble thermoplastic polyimide dissolved in a solvent selected from the group consisting of: N, N-methylpyrolidinone (NMP); dimethylacetamide (DMAc) and dimethylformamide (DMF); an electronic conductive load and an intercalation material; b) preparing a cathodic paste comprising a second amorphous and soluble thermoplastic polyimide dissolved in a solvent selected from the group consisting of: N, N-methylpyrolidinone (NMP); dimethylacetamide (DMAc) and dimethylformamide (DMF); an electronic conductive charge and a metal oxide; c) preparing an electrolyte solution comprising a thermoplastic, amorphous and soluble third polyimide dissolved in a solvent selected from the group consisting of: N, N-methylpyrolidinone (NMP); dimethylacetamide (DMAc) and dimethylformamide (DMF); and a lithium salt; d) casting a film of the electrolyte solution to form an electrolyte layer; e) coating the anode pulp with a first current collector to form an anode; f) coating the cathodic paste with a second current collector to form a cathode; g) Dry the electrolyte layer, the anode and the cathode; h) immersing the anode in a lithium salt solution; and i) assembling the anode, the electrolyte layer and the cathode to form a battery.
15. 15. A process according to claim 14, wherein one or more of the thermoplastic, amorphous and soluble polyimide solutions is prepared by mixing powder of the thermoplastic, amorphous and soluble polyimide with a solvent.
16. 16. A process according to claim 14 or 15, wherein a lithium salt is added to the first and / or second amorphous and soluble thermoplastic polyimide solution.
17. 17. A process according to any of claims 14-16, wherein the battery is assembled by: a) providing the anode; b) apply at least one drop of the electrolyte solution to the anode; c) place the electrolyte layer on the anode, where the electrolyte solution is located between them; d) apply to the electrolyte layer at least one drop of the electrolyte solution, - e) place the cathode on the layer of electrolyte, where between these is placed the electrolyte solution to form a unit or assembly; f) heating the unit to a temperature sufficient to allow the electrolyte solution to dry and, where each of the thermoplastic, amorphous and soluble polyimides suffers melt flow; and g) cool to unity at room temperature.
18. 18. A process according to any of claims 14-16, wherein the electrolyte layer, the anode and the cathode are dried to an adherent state.
19. 19. A process according to claim 18, wherein the battery is assembled by: a) providing the anode; b) place the electrolyte layer on the anode; c) placing the cathode on the electrolyte layer to form a unit; and d) apply presidn to the unit.
20. 20. A process according to claim 19, further comprising the step of heating the unit to a temperature where each of the thermoplastic, amorphous and soluble polyimides undergo melt flow and cool to unity at room temperature.
21. 21. A process according to claims 14-20 which further comprises the step of enclosing the unit in a protective box.
22. 22. A battery obtained by a process according to any of claims 14-21.