TWI642225B - Battery electrode structures for high mass loadings of high capacity active materials - Google Patents

Abstract

A battery electrode structure that maintains a high-quality load of a high-capacitance active material in an electrode (that is, a large amount per unit area) without deteriorating its cycle efficiency is provided. These mass loading levels correspond to capacitances per unit area per electrode suitable for commercial electrodes, even if the active materials are kept thin and generally below their cracking limit. A battery pack electrode structure can include a plurality of template layers. An initial template layer can include a nanostructure attached to a substrate and having a controlled density. This initial layer can be formed using a layer of controlled thickness source material disposed on, for example, a substantially inert substrate. An additional one or more template layers are then formed on the initial layer resulting in a multilayer template structure having specific characteristics such as surface area, thickness, and porosity. The multilayer template structure is then coated with a high capacitance active material.

Description

High-capacity battery pack electrode structure with high capacitance active material

Cross-reference to related applications

U.S. Provisional Patent Application Serial No. 61/406,047, entitled "BATTERY ELECTRODE STRUCTURES FOR HIGH MASS LOADINGS OF HIGH CAPACITY ACTIVE MATERIALS", filed on October 22, 2010, which is hereby incorporated by reference. The title of AMPRP 017 P) is hereby incorporated by reference in its entirety.

This application is also a part of the continuation application of U.S. Patent Application Serial No. 13/039,031 (Attorney Docket No. AMPRP012US), entitled "TEMPLATE ELECTRODE STRUCTURES FOR DEPOSITING ACTIVE MATERIALS", filed on March 2, 2011, which is hereby incorporated by reference. The non-provisional case of US Provisional Patent Application No. 61/310,183 (Attorney Docket No. AMPRP012PUS), entitled "ELECTROCHEMICALLY ACTIVE STRUCTURES CONTAINING SILICIDES", filed on March 3, 2010, for all purposes All of these are incorporated herein by reference.

This application is also a continuation-in-part application of U.S. Patent Application Serial No. 13/069,212 (Attorney Docket No. AMPRP011US), filed on March 22, 2011, entitled "INTERCONNECTING ELECTROCHEMICALLY ACTIVE MATERIAL NANOSTRUCTURES" The application dated March 22, 2010 is A non-provisional provision of U.S. Provisional Patent Application Serial No. 61/316,104 (Attorney Docket No. AMPRP011PUS), which is incorporated herein by reference in its entirety for all purposes.

This application is also a part of the continuation application of U.S. Patent Application Serial No. 13/114,413 (Attorney Docket No. AMPRP014US), entitled "MULTIDIMENSIONAL ELECTROCHEMICALLY ACTIVE STRUCTURES FOR BATTERY ELECTRODES", filed on May 24, 2011, which is hereby incorporated by reference. The non-provisional case of US Provisional Patent Application No. 61/347,614 (Attorney Docket No. AMPRP014P), entitled "MULTIDIMENSIONAL ELECTROCHEMICALLY ACTIVE STRUCTURES FOR BATTERY ELECTRODES", filed on May 24, 2010.

All of the patent applications listed above are hereby incorporated by reference in their entirety for all purposes.

High capacitance electrochemically active materials are highly desirable for battery pack applications. However, such materials exhibit substantial volume changes during battery cycle, such as expansion during lithiation and shrinkage during delithiation. For example, germanium expands by as much as 400% during the lithiation of its theoretical capacitance or Li _4.4 Si structure to about 4200 mAh/g. The volume change of this magnitude causes comminution of the active material structure, loss of electrical connection, and capacitance degradation.

Providing a high-capacitance material as a nanostructure can solve some of these problems. The nanostructure has a size of at least one nanometer, and the expansion-contraction along this dimension tends to be less destructive than the expansion-contraction along the larger side and size. Thus, the nanostructure can remain substantially intact during the battery cycle. However, it is difficult to integrate multiple nanostructures into a battery electrode layer with sufficient active material loading. This integration involves establishing and maintaining electrical interconnections between such nanostructures and current collectors, and in many cycles on current collectors or some of them Mechanical support for these nanostructures is provided on his substrate. In addition, smaller nanostructures often do not provide a sufficient amount of high capacitance active material in certain electrode designs. For example, if the nano film is kept thinner than the typical cracking limit of the high capacitance active material, depositing the nano film onto the conventional flat substrate does not provide sufficient active material loading. In addition, many of the processes proposed for making nanostructures are slow and often involve expensive materials. For example, silver catalysts and expensive etching solutions are used to etch nanowires from bulk particles. The growing long crystalline germanium structure can also be a relatively slow process and can involve expensive catalysts such as gold.

A battery electrode structure that maintains a high-quality load of a high-capacitance active material in an electrode (that is, a large amount per unit area) without deteriorating its cycle efficiency is provided. These mass loading levels correspond to the capacitance per unit area of the electrode suitable for commercial electrodes, even if the active material is kept thin and typically below its cracking limit. The battery electrode structure can include a plurality of template layers. The initial template layer can include a nanostructure attached to the substrate and having a controlled density. This initial layer can be formed using a layer of controlled thickness source material disposed on, for example, a substantially inert substrate. An additional one or more template layers are then formed on the initial layer resulting in a multilayer template structure having specific characteristics such as surface area, thickness, and porosity. The multilayer template structure is then coated with a high capacitance active material.

In some embodiments, an electrode material includes a conductive layer, a layer of a first nanostructure positioned on the conductive layer, and a second nanostructure positioned on the layer of the first nanostructure layer. The first nanostructures comprise one or more metal halides. The electrode material also includes a coating of one of the electrode active materials covering at least a portion of the first nanostructures and the second nanostructures. Examples of metal halides that may be included in the first nanostructures include nickel telluride, cobalt telluride, copper telluride, silver telluride, chromium telluride, titanium telluride, aluminum telluride, zinc telluride, and iron telluride. More specific examples of the metal telluride include Ni ₂ Si, NiSi, NiSi ₂ , and combinations thereof. The conductive layer can comprise stainless steel. Examples of the electrode active material include crystalline cerium, amorphous cerium, cerium oxide, cerium oxynitride, tin-containing material, cerium-containing material, and carbon-containing material.

In some embodiments, the layer of the first nanostructures comprises a plurality of nanowires rooted to the conductive layer. The electrode material can have a porosity of between about 30% and 50%. The coating of the electrode active material may comprise a plurality of layers. At least some of the plurality of layers may have different porosities. For example, the plurality of layers can include an inner layer and an outer layer. The inner layer can have a porosity that is lower than the outer layer. The plurality of layers can include at least some layers having different hydrogen concentrations or (more typically) different compositions. In some embodiments, at least some of the plurality of layers have different morphology. In some embodiments, the coating of the electrode active material is positioned between at least a portion of the layer of the first nanostructures and the layer of the second nanostructures. One of the layers of the second nanostructures may comprise carbon nanofibers and/or multi-dimensional metal telluride structures. The multi-dimensional metal telluride structure can include a support structure to which a plurality of metal halide nanowires are attached.

An electrode assembly is provided, the electrode assembly comprising: a conductive substrate for conducting current between an electrode active material and a battery terminal; and an electrode material. The electrode material in turn includes a layer of a first nanostructure attached to the conductive substrate. The first nanostructures comprise one or more metal halides. The electrode material also includes a layer of a second nanostructure positioned on the layer of the first nanostructures and covering at least a portion of the first nanostructures and the electrode activity of the second nanostructures One of the materials is coated. The first nanostructures and the second nanostructures provide electrical communication between the electrode active material and the conductive substrate.

There is also provided an electrochemical cell comprising a first electrode, a second electrode and an electrolyte, the electrolyte providing ionic communication between the first electrode and the second electrode. The first electrode may include a conductive layer, a layer of a first nanostructure positioned on the conductive layer, a layer of a second nanostructure positioned on the layer of the first nanostructure, and covering the layer Coating at least a portion of the first nanostructure and one of the electrode active materials of the second nanostructure. The first nanostructures can include one or more metal halides.

A method of making an electrode is also provided. The method can involve receiving a substrate having a substrate material and forming a source material layer having a controlled thickness. The source material layer can comprise a different metal than the substrate material. The method can continue to form a plurality of template nanostructures having metal halides attached to the substrate material by chemically reacting the metal with the hafnium-containing precursor. The method can then proceed to form a coating of one of the electrochemically active materials on the template nanostructures. The electrochemically active material is configured to acquire and release lithium ions during cycling. A plurality of template nanostructures promote conduction to and from the electrochemically active material. In certain embodiments, forming the coating of the electrochemically active material involves forming a first portion of the coating using thermal chemical vapor deposition and forming one of the coatings using plasma enhanced chemical vapor deposition. section. The method can also involve controlling the porosity of the coating of the electrochemically active material using one or more of the following techniques: doping, etching, ion implantation, and annealing. In certain embodiments, the coating forming the electrochemically active material involves multi-step thermal chemical vapor deposition.

These and other embodiments are further described below with reference to the drawings.

100‧‧‧Substrate

102‧‧‧ basal layer

104‧‧‧ source layer

106‧‧‧Residual source layer

108‧‧‧Intermediate template structure

110‧‧‧Template structure

112‧‧‧Template layer

315‧‧N. nanostructure

320‧‧‧Single layer template/initial template layer

340‧‧‧High capacitance active materials

360‧‧‧Second template layer

370‧‧‧Initial template layer

380‧‧‧Additional template layer

400‧‧‧Methods for making electrode layers

500‧‧‧Partially assembled electrochemical cells

502‧‧‧ positive electrode active layer

502a‧‧‧ positive electrode active layer

502b‧‧‧ positive electrode active layer

503‧‧‧ Positive Collector

504‧‧‧Negative electrode active layer

504a‧‧‧Negative electrode active layer

504b‧‧‧Negative electrode active layer

505‧‧‧negative collector

506‧‧‧Separator

506a‧‧‧Separator

506b‧‧‧Separator

600‧‧‧roll battery

602‧‧ hood

604‧‧‧negative electrode

606‧‧‧ positive electrode

608‧‧‧ mandrel

612‧‧‧ Short and small protrusions

614‧‧‧negative short projections

700‧‧‧roll battery

702‧‧‧Rectangular prismatic cover

704‧‧‧ positive electrode

706‧‧‧Negative electrode

801a‧‧‧Battery

801b‧‧‧Battery

801c‧‧‧Battery

801d‧‧‧Battery

801e‧‧‧Battery

802‧‧‧ Positive Collector

803a‧‧‧ positive electrode

803b‧‧‧ positive electrode

804‧‧‧negative collector

805a‧‧‧negative electrode

805b‧‧‧negative electrode

806a‧‧‧Separator

806b‧‧‧Separator

902‧‧‧Spiral wound positive electrode

904‧‧‧Negative electrode

906‧‧‧Separator

908‧‧‧Short protrusion

910‧‧‧ Short protrusions

912‧‧‧ Cover

914‧‧‧Insulated gasket

916‧‧‧ battery cover

918‧‧‧ Cover

920‧‧‧ Seal

1002‧‧‧ Coulomb efficiency

1004‧‧‧Delithization Capacitor

1A-1C are schematic representations of electrode substrates at different stages of template formation, in accordance with some embodiments.

Figure 1D is a scanning electron microscope image of a nanostructure template containing a nickel-doped nickel nanowire.

FIG. 1E is a scanning electron microscope image of a nanostructure template containing a nickel germanium halide wire, wherein carbon nanofibers (CNF) are deposited on a nickel neodymium nitride wire.

FIG. 1F is a scanning electron microscope image of a nanostructure template containing a nickel-deposited nickel nanowire, wherein a layer of a multi-dimensional nickel-deposited nickel structure is deposited on a nickel-nenetized nickel nanowire.

2A to 2C are scanning electron microscope images of three electrode layers having different porosities.

3A is a single layer mold containing a highly capacitive active material coated in accordance with some embodiments. A schematic representation of the electrode layers of the plates.

3B is a scanning electron microscope image of an electrode layer containing a single layer of a nickel telluride template coated with an amorphous germanium.

3C is a schematic representation of an electrode layer containing a multilayer template formed from a single layer template and carbon nanofibers (CNF), in accordance with certain embodiments.

3D is a scanning electron microscope image of an electrode layer containing a multilayer template formed of a nickel telluride template and carbon nanofibers (CNF) coated with amorphous germanium.

3E is a schematic representation of an electrode layer comprising a multilayer template formed from a single layer template and a multi-dimensional telluride structure ("hairball"), in accordance with some embodiments.

3F is a scanning electron microscope image of an electrode layer comprising a multilayer template formed of a nickel telluride template and a multi-dimensional nickel-deposited nickel structure coated with an amorphous germanium.

4A is a process flow diagram corresponding to a method of fabricating a battery electrode layer, in accordance with some embodiments.

4B to 4E illustrate short-range (SRO) ratios of Raman spectra of four amorphous germanium layers deposited using different process conditions.

4F is a schematic representation of a residual stress model for a multilayer electrode layer structure in accordance with some embodiments.

5A-5B are top and side schematic views of an illustrative electrode configuration, in accordance with some embodiments.

6A-6B are top and perspective schematic views of an illustrative circularly wound battery in accordance with some embodiments.

7 is a top plan view of an illustrative prismatic wound battery in accordance with some embodiments.

8A-8B are top and perspective schematic views of an illustrative stack of electrodes and separator sheets, in accordance with some embodiments.

9 is a schematic cross-sectional view of an example of a wound battery according to an embodiment.

Figure 10 is a circulation data corresponding to a battery fabricated using the electrode materials described herein.

In the following description, numerous specific details are set forth The invention may be practiced without some or all of the specific details. In other instances, well-known program operations have not been described in detail so as not to unnecessarily obscure the invention. While the invention will be described in conjunction with the specific embodiments, it is understood that the invention

The high capacitance electrochemically active material can be formed into a nanostructure for use in a rechargeable battery pack. Nanostructures are less likely to degrade during battery cycle than larger structures. In particular, it is less likely to smash and/or lose electrical contact with each other due to the lower mechanical stress accumulated in the nanostructure during lithiation. However, integrating the nanostructure into a battery electrode layer with sufficient active material loading can be challenging (due to its small size) and requires many electrical connections to be established and maintained within the electrode. For example, it is difficult to mechanically configure, support, and electrically interconnect many small nanostructures and it is difficult to maintain such configurations and interconnections over a large number of expansion-contraction cycles. In addition, nanoparticles having a diameter of only 50 to 100 nanometers will have to rely on hundreds and even thousands of particle-to-particle connections and possibly intermediate conductive structures to transfer current in a typical electrode design. As the nanoparticles expand and then shrink, the initial connections, for example, formed by direct contact of the nanoparticles and/or conductive additives are often lost. When expanded, the nanoparticles will push away from each other and with the other components. During delithiation, the same nanoparticle shrinks and due to electrode elastic constraints, the original contact may be lost. This can result in unattached active particles that become inactive in effect. Nanofilms have been proposed as an alternative to nanostructures. It is formed in a relatively small thickness (eg, less than 500 nanometers) to avoid cracking during cycling. Unfortunately, the nanofilm deposited on a flat substrate contains only a very small amount of active material on the surface area of the electrode and is therefore impractical for most battery pack applications.

High surface area substrates help to increase the loading of the active material while keeping the structure of the active material relatively small. Such substrates, when coated with an active material, can produce higher capacitance per unit area (based on the surface area of the flat electrode) than conventional flat substrates. The high surface area substrate can be formed by roughening the surface of the substrate or forming a template on the surface of the initial flat substrate. For example, a flat metal substrate can be processed to form a germanium nanostructure extending from the surface of the substrate. The addition of the nanostructure substantially increases the total surface area available for coating. These telluride nanostructures can serve as high surface area templates for coating active materials. In some embodiments, the telluride nanostructure can be formed into a nanowire having a rooted end or intermediate portion of the substrate. The rooted end can form an integral structure with the surface of the substrate. In some cases, at the interface with the substrate, the nanowires may not have clearly defined morphological boundaries. As a result, the nanowires can have excellent mechanical adhesion to the substrate and low electrical contact resistance.

Some template nanostructures may be difficult to grow beyond certain dimensions. For example, when a metal halide template is formed, the growth of the salt is limited by the diffusion rate of the germanium and the metal through the phase of the individual telluride. Only relatively short structures can be formed resulting in a thin template layer, for example, for a nickel-niobium nickel nanowire, having a thickness of less than 10 to 20 microns. These telluride structures do not provide sufficient surface area to support sufficient active material. If the active material is applied to the template such that the thickness of the coating does not exceed the breaking limit of the active material, then the total amount of active material per unit area may not be sufficient for commercially viable electrodes.

Furthermore, the formation of a telluride nanostructure on a metal surface having an excess of source metal (such as the formation of a nickel-deposited nickel nanowire on a thick nickel foil) may result in undesirable deposition near the substrate of the telluride nanostructure. Such undesirable deposition may result in an increase in the total electronic resistance of the electrodes and other undesirable effects. Ultimately, the deposition thickness of many active materials is limited to their cracking limit (eg, for amorphous germanium, hundreds of nanometers). These constraints limit electrode design options and the use of high capacitance active materials in commercial battery packs.

Novel template layer structures and fabrication techniques are provided and described herein. These structures allow for higher mass loading of high capacitance active material per unit area of the electrode without exceeding this The breaking limit of the active material. The higher mass load corresponds to a higher capacitance per unit area of the electrode and, in some embodiments, corresponds to a higher capacitance of the electrochemical cell. Controlling the thickness of the active material coating and maintaining it below the fracture limit results in more robust cycle performance characteristics.

An initial template layer can be formed on the relatively inert substrate during template formation. For example, the substrate used to form the template may include a base layer and a source layer. Only the source layer is consumed during stencil fabrication while the substrate layer remains substantially intact. The source layer can have a controlled thickness to control the density and length of the formed template structure. The source layer can be fully consumed during the formation of the nanostructure template layer. For example, a nickel metal layer having a controlled thickness can be used as the template source material. The layer is exposed to a ruthenium precursor (such as decane) until the layer is fully consumed. In the process of the process, a niobium nickel nanostructure is formed. These deuterated nickel nanostructures act as a template layer.

In some embodiments, the initial layer is enhanced by forming an additional one or more template layers on an initial template layer. The resulting structure is referred to herein as a multilayer template structure. Additional layers may be formed using prefabricated structures, such as carbon nanofibers (CNF) and/or multi-dimensional telluride structures, sometimes referred to as "hairball" or "urchin" structures. Each of these multi-dimensional telluride structures can generally have a central support structure and a plurality of metal halide nanowires attached to the support structure and extending in different directions away from the support structure. This configuration gives a "hairball" appearance to these structures. In some embodiments, the template structure of the additional template layer can be formed directly on the initial template layer, which is further described in US Patent Application entitled "TEMPLATE ELECTRODE STRUCTURES FOR DEPOSITING ACTIVE MATERIALS", filed March 2, 2011 In the context of the description of the stencil structure, the application is hereby incorporated by reference in its entirety in its entirety in its entirety in its entirety in its entirety in its entirety in U.S. Patent Application No. 5, filed on May 24, 2011, entitled "MULTIDIMENSIONAL ELECTROCHEMICALLY ACTIVE STRUCTURES FOR BATTERY ELECTRODES" In the context of the description of the multi-dimensional telluride structure, the application is hereby incorporated by reference in its entirety.

In certain embodiments, battery performance and active material loading can be substantially improved by using various novel active material coating structures. For example, a multilayer active material coating can be formed on the template structure. Various deposition and post-deposition treatment techniques are described below to achieve the desired composition and morphology and dimensional structure within such active material coatings.

Typical electrode materials or electrode structures may include different layers that should be distinguished from one another. In particular, the "active material layer" should be distinguished from the "template layer" and "electrode layer". A "template layer" is a layer formed from one or more template structures, such as a deuterated nickel nanowire. The initial template layer is formed on the surface of the substrate. In embodiments involving a germanide nanowire, the initial layer can be about 10 to 20 microns thick. Additional template layers can be formed on the initial template layer to form a multilayer template structure. The thickness of the multilayer template structure is equal to the sum of the thicknesses of the individual template layers.

The "active material layer" is a thin layer of an active electrode material (such as an amorphous germanium) formed on the template layer structure. The active material layer is often referred to as an active material coating because it is often formed from a coating template that is structured by the active material. The thickness of the active material layer/coating is typically selected to be less than the fracture limit for a given lithiated grade of material. The fracture limit can be further adjusted by varying the porosity of the active material coating and other parameters.

Multiple template layers can be stacked one on top of the other, and such layers are generally parallel to the substrate surface. On the other hand, the active material coating follows the contour of the stencil structure. In certain embodiments, the active material coating can be considered to surround the shell of the template nanostructure within the template layer. In certain embodiments, the active material coating can have multiple layers that form a multilayered active material coating or structure.

"Electrode layers" are commonly used in the art to describe collective structures formed on one or both sides of a conductive substrate. This structure includes the active material and various other components that can be added to provide mechanical support and electrical conductivity within the electrode layer. In some embodiments, the electrode layer comprises A combination of a template layer and an active material coating.

1A-1B are schematic representations of templates at different stages of their formation, in accordance with some embodiments. FIG. 1A illustrates an initial stage in which substrate 100 has a base layer 102 and a source layer 104. As described further below with respect to FIG. 4A, the template forming process can begin by depositing a source layer on the substrate layer. In some embodiments, the substrate layer 102 contains little or no source material that can be used to form the template structure. In fact, the substrate layer 102 can include an inert material at least on its top surface. In such embodiments, the base layer 102 needs to be inert only under the process conditions used during template formation. For example, the stainless steel foil may remain substantially inert during the formation of the nickel beneficiation nanowires from the nickel layer deposited on the stainless steel foil. However, further heating of this stainless steel foil can result in the formation of iron telluride and other by-products. Thus, process conditions can be specifically controlled to avoid undesirable reactions and interactions with the substrate layer 102, as further explained in the context of FIG. 4A. In other embodiments, the substrate does not have a distinctive base layer and source layer, and the same material is used as both, for example, a metal substrate and a source during the formation of the vapor.

The substrate layer 102 can be fabricated from a variety of conductive materials and acts as a current collector for the active material. Some examples of substrate materials include copper, copper coated with metal oxides, stainless steel, titanium, aluminum, nickel, chromium, tungsten, metal nitrides, metal carbides, carbon, carbon fibers, graphite, graphite films, carbon networks, Conductive polymers or combinations of the above (including multilayer structures). The base layer material can be formed as a foil, film, mesh, foam, laminate, wire, tube, particle, multilayer structure, or any other suitable configuration. In certain embodiments, the substrate material is a metal foil having a thickness between about 1 micrometer and 50 micrometers or, more specifically, between about 5 micrometers and 30 micrometers.

Examples of materials for the source layer 104 include any of a number of materials that form a telluride nanostructure. Such materials include nickel, cobalt, copper, silver, chromium, titanium, iron, zinc, aluminum, tin, and combinations thereof. Examples of some alloys include nickel/phosphorus, nickel/tungsten, nickel/chromium, nickel/cobalt, nickel/iron, and nickel/molybdenum. Source layer 104 can be at least about 10 nanometers thick, or more specifically, at least about 100 nanometers thick. In a more specific embodiment, the nickel source layer is between about 100 nanometers and 300 nanometers thick. In another particular embodiment, the nickel phosphate source layer is between 300 nanometers and 10 nanometers. In some exemplary embodiments, the nickel phosphate layer is about 500 nanometers thick, or about 1.5 microns thick, or about 8 microns thick. The source layer can also be fabricated from NiFe, NiW, and NiMo alloys having a thickness between about 0.5 microns and 10 microns.

The particular thickness of source layer 104 can result in specific characteristics of the resulting template layer. For example, it has been discovered that thicker source layers can result in the formation of denser and/or longer germanium structures. For example, two nickel layers having different thicknesses are exposed to decane under typical nickel telluride forming conditions, and then weight gain is tested. Samples with a 100 nm layer exhibited a gain of 0.04 mg per square centimeter, while samples with a 300 nm layer exhibited a gain of 0.1 mg per square centimeter. These experimental results demonstrate that some of the template properties can be controlled by forming a source layer having a particular thickness. Additionally, such characteristics can be controlled to affect the surface area available for the coating, and thus the resulting mass loading of the active material layer.

In some embodiments, the substrate can have an intermediate protective layer (not shown) formed between the base layer and the source layer. This protective layer can be made from an inert material and can protect the substrate layer from exposure to reactive species (eg, decane). When a protective layer is used, it is possible to use a material that reacts with decane (if it is in direct contact) with the substrate. The various examples of the intermediate layer are described in U.S. Patent Application Serial No. 12/944,576, filed on Nov. 11, 2010, entitled <RTIgt;"INTERMEDIATE LAYERS FOR ELECTRODE FABRICATION" Incorporated herein. In addition to or instead of providing protective properties, an intermediate layer can be used to enhance adhesion between the template structure and the substrate layer. Other intermediate layers that provide other desirable features can also be used.

In some embodiments, the source material is provided in the form of particles or other discrete structures. These structures are still described as the source layer 104 formed on the surface of the substrate layer. These discrete structures can be provided to have at least about 10 nanometers or, more specifically, about 10 nanometers and 500 nanometers. The layer of thickness between. In certain embodiments, the precursor particles are used to control the porosity of the resulting electrode layer and have a diameter between about 1 micrometer and 3 micrometers.

FIG. 1B illustrates an intermediate stage of template formation in which an intermediate template structure 108 is formed on residual source layer 106. Some of the original source materials have been consumed to form the intermediate template structure 108. Thus, the residual source layer 106 shown in FIG. 1B is typically thinner than the initial source layer 104 shown in FIG. 1A. At this stage, there may still be some remaining source material to support further growth of the intermediate template structure 108. In certain embodiments, the residual layer 106 can include a reaction product of a source material that forms an alloy that causes some expansion. Thus, in such embodiments, the residual layer 106 may sometimes be thicker than the original source layer 104. A particular example would be the formation of a very metal rich telluride phase, such as nickel telluride or copper telluride, where the residual layer can expand as it forms an alloy with the tantalum. Appropriate selection of the residual layer composition and processing conditions will positively affect the efficacy and volumetric energy density of the electrode.

FIG. 1C illustrates the final stage of the template forming operation that ultimately forms the template structure 110. In the depicted embodiment, the template structure 110 has its end that is rooted to the substrate layer 102. The stencil structure 110 can be between about 5 nanometers and 100 nanometers in diameter (i.e., before the active material is deposited) or, more specifically, between about 10 nanometers and 50 nanometers. Additionally, the template structure 110 can be between about 1 micrometer and 100 micrometers in length, or more specifically between about 2 micrometers and 25 micrometers. In the depicted embodiment in which the stencil structure 110 extends substantially perpendicular to the planar surface of the substrate layer, this length corresponds to the thickness of the stencil layer 112. The template layer 112 can have a porosity of at least about 50%, or more specifically at least about 75%, or even at least about 90%. The porosity of the template layer 112 excluding any active material should be distinguished from the porosity of the active layer (i.e., the thin layer of active material formed on the surface of the template structure 110) or the porosity of the electrode layer.

In the embodiment depicted in FIG. 1C, the residual source layer 106 has been substantially consumed. The thickness of the initial source layer 104 can be specifically selected such that most or all of the source material is ultimately consumed during template formation. This method eliminates undesirable materials (such as metal halides) Formation at the interface with the substrate layer. For example, if a fragile telluride phase is formed on a surface, various stresses generated before, during, or after deposition of the active material may cause cracking of the phase of the telluride. Some of the phases may also have poor adhesion to the underlying substrate or the active material above. Another example demonstrates some of the disadvantages of having a thick (e.g., at least about 500 nm) nickel film. Nickel is known to diffuse relatively quickly into the ruthenium structure. If some residual nickel remains at the interface, it can react with helium at high temperatures during the deposition of tantalum, and "consumption" is intended as part of the active material. This can in turn cause an unbalanced electrochemical cell (i.e., an insufficient amount of negative active material) and possibly overcharge. Additionally, this initial thickness can be selected to achieve a certain density and length of the template structure as described above.

Typically, the templating material is highly electrically conductive and mechanically stable under the stresses experienced by the expansion and contraction of the active material during cycling. Examples of suitable templating materials include metal tellurides (eg, copper telluride, nickel telluride, aluminum telluride), carbon, certain metals or semiconducting oxides (eg, zinc oxide, tin oxide, indium oxide, cadmium oxide, aluminum oxide, Titanium dioxide, cerium oxide) and certain metals (copper, nickel, aluminum). In a particular embodiment, the template structure is formed as a nanowire and includes a telluride. The telluride nanowire may have a material composition that varies along its length, that is, a source material that is higher at the root (near) end of the source material than near the free (far) end of the nanowire. concentration. Depending on the type of source material, this variability can be reflected in the different morphology and stoichiometric phase of the telluride. For example, the deuterated nickel nanowire may include one, two or all three phases of deuterated nickel, that is, Ni ₂ Si, NiSi, and NiSi ₂ . It is believed that the higher nickel content phase forms a strong bond with nickel metal. Therefore, this variability provides a relatively strong adhesion of the deuterated nickel nanowire to the substrate layer and reduces contact resistance. The conductivity and lithium irreversibility of these different niobium nickel phases also change.

Tapered nanowires can also result from greater availability of metal near the substrate/support rooting end of the nanowire. In certain embodiments, the average diameter near the substrate/support rooting end is at least about two times the average diameter near the free end. In other words, the substrate of the nanowire can be large enough to touch each other even at the proximal end on the surface of the substrate, but The diameter of the base to the tip is reduced, so the distal tip is free and unconnected. In a more specific embodiment, the ratio of the diameter between the near nanowire end and the far nanowire end is at least about 4, or, more specifically, at least about 10. A wider substrate can help maintain adhesion to the substrate.

Figure 1D is a scanning electron microscope image of a deuterated nickel nanowire containing a nanostructure template. These nanowires are deposited directly onto roll-hardened nickel foil available from Carl Schlenk AG of Roth, Germany. The foil was first oxidized at 300 ° C for one minute in an air containing processing chamber at a pressure of 50 Torr. The foil was then heated to 450 ° C and a process gas containing 1% decane by volume was introduced into the chamber for ten minutes. The resulting germanide nanowires have a diameter of from about 10 to 50 nanometers and a length of from about 1 to 30 microns. The density of the nanowires is between about 10% and 70%. As can be seen from the SEM image in Figure 1D, the nanowires form a template with a relatively large surface area. The substrate carrying the template was punched into a disk shape of about 15 mm in diameter to construct a coin type battery.

In certain embodiments, the initial nanostructure template layer formed on the substrate does not provide sufficient surface area and/or thickness for deposition of the desired active material. As explained above, each flat electrode surface area may require some minimum surface area of the template to achieve sufficient active material loading. To provide additional surface area, one or more additional template layers may be provided on the initial template layer to form a multilayer template structure. For example, the initial telluride template can be coated with a carbon nanofiber (CNF) layer. FIG. 1E is a scanning electron microscope image of a nanostructure template containing a nickel germanium halide wire, wherein carbon nanofibers (CNF) are deposited on a nickel neodymium nitride wire.

In some embodiments, the available surface area of the initial telluride template is increased by providing a second structural layer that forms the second template layer. Such structures of the second template layer can have properties similar to those of the initial layer, for example, both can be electrically conductive and form a porous template layer that can be used for coating the active material. In a particular embodiment, the second template layer comprises a fiber or linear nanostructure. Examples of such structures include carbon fibers, carbon nanotubes, and telluride nanowires. In other embodiments, the multi-dimensional nanostructure can be placed in one or more additional template layers. An example of such a structure has a central core to which a plurality of metal halide nanowires are attached to form a "hairball" or "snowball"-like structure. In this example, the metal halide nanowires extend in different directions away from the central core. Figure 1F is a scanning electron microscope image of a nanostructure template containing a layer of deuterated nickel nanowires and a layer of a niobium nickel hair ball structure on a nickel neodymium nanowire.

The structure of the additional template layer may be made of the same material as the initial layer (eg, a telluride), or may be made from a different material (eg, a carbonaceous material, a different telluride). The multilayer template structure can be at least about 10 nanometers thick, or more specifically, at least 50 nanometers thick or even at least 100 nanometers thick. An additional template layer can be deposited after the initial layer is coated with the active material. In another configuration, an additional template layer is deposited prior to coating the initial layer with the active material, and then, the two layers of the template are coated with the active material. Various sequences of operations are further described below with reference to FIG. 4A.

The stencil structure can provide mechanical support for the active material coating and/or electrical connection to the active material coating. The nanostructure template has a much higher surface area than a flat substrate, allowing the formation of a thin active material coating while still providing a sufficient amount of active material per unit area of the electrode (the flat surface of the electrode). The active material coating typically has a thickness below the breaking limit of the active material used and the morphological structure of the active material. For example, the amorphous germanium coating can have a thickness of less than about 300 nanometers, or, more specifically, less than about 100 nanometers. However, the various new structures and deposition and processing techniques described herein that alter the morphological properties of the active material coating allow for increased coating thicknesses beyond typical fracture limits. In one example, multiple layers of active material coating can be formed, in which case each layer has a different composition, entity, and/or morphological structure. In a particular embodiment, the multilayer active material coating comprises an inner and outer amorphous germanium layer. The inner layer has a lower porosity than the outer layer.

Examples of negative electrochemically active materials that can be deposited on the template include, but are not limited to, various cerium-containing materials (eg, crystalline germanium, amorphous germanium, other tellurides, cerium oxide, suboxides, and nitrogen oxides). Other examples of negative electrochemically active materials that may be used include tin-containing materials (eg, tin, tin oxide), antimony, carbonaceous materials, various metal hydrides (eg, MgH ₂ ), tellurides, phosphides, and nitrides. . Other examples include carbon-bismuth combinations (eg, carbon coated ruthenium, coated ruthenium carbon, ruthenium-doped carbon, carbon doped ruthenium and alloys including carbon and ruthenium), carbon-ruthenium combinations (eg, , carbon coated ruthenium, coated ruthenium carbon, ruthenium-doped carbon and carbon-doped ruthenium) and carbon-tin combination (for example, coated carbon tin, tin coated carbon, doped with Tin carbon and tin doped with carbon). A high capacitance active material is generally defined as an active material having a theoretical lithiation capacitance of at least about 700 mAh/g. Examples of the positive electrochemically active material that can serve as a coating include various lithium metal oxides (for example, LiCoO ₂ , LiFePO ₄ , LiMnO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _X Co _Y Al _Z O2, LiFe ₂ (SO 4 ) ₃ ), carbon fluoride, metal fluoride such as iron fluoride (FeF ₃ ), metal oxide, sulfur, and combinations thereof. Doped and non-stoichiometric changes in these positive and negative active materials can also be used. Examples of the dopant include elements from Groups III and V of the periodic table (for example, boron, aluminum, gallium, indium, antimony, phosphorus, arsenic, antimony, and antimony) and other suitable dopants (for example, Sulfur and selenium).

The active material is coated on the template structure to form an electrode or, more specifically, an electrode layer. As mentioned above, the electrode layer typically has a thickness comparable to the thickness of the upper template layer, which may itself comprise a plurality of template layers. The porosity of the electrode layer is generally lower than the porosity of the corresponding overall template layer because the active material occupies some void space between the template structures. The electrode layer porosity generally depends on the composition and thickness of the active material coating and the cycling characteristics of the battery (the depth of charge and discharge). It has been found that a suitable porosity of an electrode layer having an amorphous tantalum coating is between about 20% and 80%, or more specifically between about 30% and 60%. These ranges of porosity provide both sufficient active material loading and space for active material expansion and ion mobility. 2A-2C are scanning electron microscope (SEM) images of three different electrode layers having different porosities in the range of 30% and 50%.

The active material coating may itself be a porous structure, typically having internal voids of a size that is much smaller than the size of the voids associated with the porosity of the overall two-layer template nanostructure. the above The electrode layer porosity values listed do not take into account the porosity of the active material coating. Experimental data indicates that higher active material porosity (i.e., internal porosity of the active material coating) and other associated factors result in batteries with better cycle performance. In certain embodiments, the porosity within the active material coating is controlled to achieve the desired battery performance.

The active material can be deposited directly onto the initial single layer template. FIG. 3A is a schematic representation of an electrode layer containing a plurality of nanostructures 315 constituting a single layer template 320. The template 320 is coated with a high capacitance active material 340. Sometimes, the initial template layer 320 provides sufficient surface and/or thickness for deposition of the high capacitance active material 340. For example, high rate battery applications typically use thinner electrodes to achieve their high electron and ionic conductivity required to generate and attract high currents. In one configuration, the area density density of the high capacitance active material is between about 1.5 milligrams and 4.5 milligrams per square centimeter. These densities are converted to a total thickness of the active material coating template between about 10 microns and 40 microns. 3B is a scanning electron microscope image of an electrode layer containing a single layer of a nickel telluride template coated with an amorphous germanium.

In some embodiments, the initial template layer formed on the substrate does not provide sufficient surface area for deposition of the desired amount of active material, and an additional template layer is formed on the initial template layer. Examples of materials that can be used to create such additional layers include carbon nanofibers (CNF) and multi-dimensional telluride structures. 3C is a schematic representation of an electrode layer comprising a multilayer template formed from a first layer 340 of a nanostructured telluride template and a second template layer 360 of carbon nanofibers (CNF). Both template layers are coated with high capacitance active. For the sake of clarity, the active material coating is not shown in Figure 3C. The active material coating may be performed in one step after forming each template layer sequentially or after forming all of the template layers. 3D is a scanning electron microscope image of an electrode layer containing a multilayer template formed of a nickel telluride template and carbon nanofibers (CNF) coated with amorphous germanium.

Figure 3E is a schematic representation of an electrode layer comprising a multilayer template formed from an initial template layer 370 of a germanide nanowire and an additional template layer 380 of a multi-dimensional germanide structure. Both template layers are coated with a high capacitance active material. For clarity and simplicity, not shown in Figure 3E Active material coating. The multi-dimensional telluride structure can be used to form electrodes of any thickness, for example, deposited continuously on the initial template layer 370 until it does not meet desirable characteristics. The additional template layer 380 helps to thicken the overall template beyond the length of the original template structure. For electrode layers fabricated from multiple template layers, there is typically no upper thickness limit. This feature allows us to form a battery electrode layer with a large mass of active material per unit area (and therefore a very high capacitance per unit area). The multilayer template structure can be stacked up to any thickness required for capacitance and other battery performance parameters (eg, cycle rate). For example, it is useful to use a thicker electrode layer for high capacitance applications while using a thinner, more conductive battery electrode layer to achieve high cycle rates (high charge and/or discharge current). .

Various combinations of template layers can be used, in which case the individual layers are fabricated from a variety of different materials and/or nanostructured forms. Examples of suitable materials for the template include telluride, carbon (fu or other), nitrides, carbides, and the like. Almost any material that can be formed into a suitable nanostructure and that does not aggressively consume cerium (or other corresponding active material coating) at temperatures up to about 500 ° C or 600 ° C can be used as the template material. In some configurations, the templating material is electrically conductive. Examples of suitable template nanostructures include nanowires, hairballs, nanofibers, nanotubes, spheres, cones, rods, wires, arcs, saddles, flakes, ellipsoids, spikes, tracked Structure, etc.

The second layer of template structure can be bonded to the substrate or underlying template structure using a polymeric binder and/or active material coating. For example, if a coating of active material is deposited after the second layer of template has been added, the active material itself can join the template layers together. Such a combination method is further described in U.S. Patent Application Serial No. 13/039,031, filed on Mar. 2, 2011, entitled &lt;RTIgt; </RTI> </RTI> </RTI> </RTI> </ RTI> </ RTI> </ RTI> <RTIgt; The application is hereby incorporated by reference. 3F is a scanning electron microscope image of an electrode layer comprising a multilayer template formed of a nickel-plated nickel template and a nickel-doped nickel multi-layer structure coated with an amorphous germanium.

4A is a process flow diagram corresponding to method 400 for fabricating an electrode layer, in accordance with some embodiments. Method 400 can begin by receiving a substrate having a substrate layer during operation 402. Various substrate examples are described above. The method 400 can continue with operation 404 during which a source layer having a controlled thickness is formed on the substrate. Examples of techniques that may be used during operation include physical vapor deposition (PVD), chemical vapor deposition (CVD), or other techniques suitable for producing a uniform thickness of controlled thickness. Various source layer examples are described above. In a particular embodiment, a layer of nickel having a thickness between about 100 nanometers and 500 nanometers is deposited on one or both sides of the stainless steel or tungsten foil. The foil can be between about 5 microns and 50 microns thick. Other examples of techniques for depositing a source layer include spin coating a nickel-containing sol-gel solution layer having a thickness between about 100 nm and 10 microns onto a support foil or for self-combining nickel on a foil Langmuir-Blodgett method for nanoparticle and/or nanowires.

Operation 404 can also involve treating the surface of the source layer, for example, to increase its surface roughness and/or change its surface composition. Examples of processing techniques include introducing a telluride precursor (eg, a ruthenium, a metal, and/or a catalyst-containing material) into the surface to chemically modify the surface (eg, forming oxides, nitrides, carbides, initials) The telluride structure, and by treatment with various oxidizing agents and reducing agents) and physically modifying the surface (eg, by laser ablation and/or plasma treatment to increase surface roughness). Other examples include changing grain orientation, annealing, sonication, doping, and ion implantation. The modified surface of the source layer enhances the formation of the template structure during operation 406.

In certain embodiments, the source layer is oxidized at a temperature between about 150 ° C and 500 ° C (more specifically, about 250 ° C) in a gas stream containing oxygen and other suitable oxidizing agents for about 0.1 minutes. A time period between 10 minutes (or more specifically, about one minute). It has been found that some oxidation helps to roughen the surface and contributes to the initial formation of the nickel structure. Without being bound by any particular theory, the rough oxide edge can act as a long crystal site during the formation of the telluride. Additionally, the oxide can act as a mask to allow for crystal growth only at the small holes. Another function of the oxide can be to adjust the diffusion rate of the metal to the reaction site. rate. It has also been found that excessive oxidation can be detrimental to the formation of telluride. Thus, the oxidation conditions can be optimized for each metal-containing material and structure containing such materials.

The method 400 can continue with the formation of the template structure during operation 406, for example, using CVD. For example, a process gas comprising a ruthenium containing precursor (eg, decane) can flow into the CVD chamber. In certain embodiments, the volume concentration of decane in the process gas is less than about 10%, or more specifically less than about 5%, or even less than about 1%. In a particular embodiment, the concentration of decane is about 1%. The process gas may also include one or more carrier gases such as argon, nitrogen, helium, hydrogen, oxygen (but typically without decane), carbon dioxide, and methane. The gas and/or substrate can be maintained at a temperature between about 350 ° C and 500 ° C (or more specifically between about 425 ° C and 475 ° C). The duration of deposition can be between about 1 minute and 30 minutes, or more specifically between about 5 minutes and 15 minutes. In embodiments where a non-tellurized nanostructure is used, appropriate adjustments to the vapor phase precursor and other process conditions can be used.

In a particular embodiment, the process conditions are varied during operation 406. For example, during the formation of the telluride structure, decane can be introduced at a relatively high concentration to promote the growth of the crystal, and then, for example, further sulphide formation is directed from the rooted end of the structure toward the tip of the growth. When the source metal diffusion is limited, the concentration is reduced. Additionally, the process temperature can be kept low initially and then increased to promote diffusion of the metal. In general, process conditions can be varied to control the physical properties (eg, length, diameter, shape, orientation, area density) and morphological properties of the formed template structure (eg, a stoichiometric phase that ensures high conductivity of the telluride, For example, distribution along the length, crystallization/amorphous). Other process conditions that may vary during operation 406 include compositions of the gas mixture (in addition to the variable decane concentrations described above), various flow rates and patterns and/or chamber pressures. If PECVD (plasma enhanced chemical vapor deposition) technology is used, the power output and frequency of the plasma generator can also be changed. CVD can also be used.

Method 400 can continue with forming an additional template layer during operation 408. In this operation In the process, a single layer template is transformed into a multi-layer template structure. For example, as mentioned, the initial telluride template can be coated with a carbon nanofiber (CNF) layer. In another embodiment, the initial telluride template is coated with a layer of a multi-dimensional telluride structure, such as a hair bulb. The CNF or multi-dimensional telluride structure can be suspended in a liquid to form a slurry, and then applied to the initial layer using a "squeegee" technique or a spray technique (followed by drying). It should be noted that additional template layers may be formed before or after the initial template layer is coated with the active material, as further described in the context of decision block 414.

The method 400 then proceeds to form a coating of the active material on the single or multiple layer template structure during operation 410. Deposition of the active material coating can involve CVD, PVD, electroplating, electroless plating, or solution deposition. An example of PECVD technology will now be described in more detail. The template layer and/or process gas supplied to the chamber is heated to between about 200 ° C and 400 ° C, or more specifically between about 250 ° C and 350 ° C. The gas delivered to the chamber may include a ruthenium containing precursor (eg, decane) and one or more carrier gases (eg, argon, nitrogen, helium, hydrogen, carbon dioxide, and methane). In a particular example, the concentration of decane in the mash is between about 5% and 20%, or more specifically between about 8% and 15%. The gas may also include a dopant-containing material such as a phosphine. RF power can be delivered between about 10 W and 1000 W, which is typically dependent on the size of the chamber and other factors.

Method 400 can then proceed with optional post deposition processing during operation 412. Examples of post deposition processing techniques include chemical etching, annealing, and coating. In certain embodiments, a coating of a carbonaceous material is deposited on the high capacitance active material. In another embodiment, the amorphous germanium coating deposited in 410 is chemically etched to introduce apertures into the active material coating. In certain embodiments, a solid reaction phase technique or a liquid phase deposition technique is used. For example, a liquid containing an active material material can be deposited onto a template and then physically or chemically converted into a solid active material. In a particular embodiment, the orthosilicic acid containing tetraethylorthosilicate (TEOS) sol - gel of liquid (SiO ₂₎ is deposited onto the template, followed by chemical reduction of silicon.

Various process technologies and process conditions are described in more detail on May 24, 2011. U.S. Patent Application Serial No. 13/114,413 (Attorney Docket No. AMPRP014US) entitled "MULTIDIMENSIONAL ELECTROCHEMICALLY ACTIVE STRUCTURES FOR BATTERY ELECTRODES", for the purpose of describing such process technology and process conditions, the application is incorporated by reference. Incorporated herein.

Different deposition techniques, process conditions, and/or precursors can result in active material coatings having different characteristics. In certain embodiments, operations 408 through 412 (decision block 414) are repeated to form a multilayer active material coating that demonstrates superior battery performance characteristics compared to a single layer of active material coating. In one example, a first layer/coating of amorphous germanium is deposited using PECVD techniques followed by a second layer/coating of amorphous germanium deposited by thermal CVD techniques, or vice versa. Each of the two active material coatings has a different crystallinity, porosity, density, concentration of impurities (e.g., hydrogen), vacancies, and residual stress levels. A series of tests were performed to determine the effect of process conditions on the atomic density of germanium. In the first test, germanium was deposited using a thermal CVD technique at 520 ° C, resulting in a structure having 95% germanium and 5% hydrogen and having a density of 5.40 E22 atoms per cubic centimeter. In a second test, a thermal CVD technique was used but a germanium was deposited at a higher temperature of 550 ° C, which resulted in a structure having 98% germanium and 1% hydrogen and having a density of only 5.16 E22 atoms per cubic centimeter. Finally, in the third test, ruthenium was deposited at 520 ° C using PECVD techniques, resulting in a structure having 89% bismuth and 11% hydrogen and having a density of 5.88 E22 atoms per cubic centimeter.

In another example, a set of process conditions (eg, substrate temperature, chamber pressure, composition of precursors) is used, a first layer/coating of amorphous germanium is deposited using thermal CVD techniques, and another set of conditions is used. A second layer/coating is also deposited using thermal CVD techniques. In yet another embodiment, the first layer/coating of amorphous germanium is deposited and then etched to form a porous amorphous germanium layer. A second layer/coating of amorphous germanium is deposited on the porous layer. The second layer/coating may or may not undergo a similar etch. At least the higher porosity of the first inner layer helps to overcome large volume changes of the multilayer structure during the cycle.

It has been discovered that short-range disorder in the structure of the active material can greatly affect various battery performance characteristics. For example, different CVD techniques produce different short range order (SRO) ratios, which have affected cycle life. 4B through 4E illustrate the short-range ratios of four amorphous germanium coatings deposited using different process conditions. Figure 4B corresponds to an undoped amorphous germanium deposited using a PECVD process. Figure 4C corresponds to a layer of germanium deposited at 520 °C using thermal CVD techniques. The curve-fitting was used to determine that the ordered (crystalline) 矽 phase was mainly at the 520 cm ^-1 position. Another peak at about 480 cm ^-1 corresponds to amorphous germanium. Figure 4D corresponds to a doped germanium material deposited using PECVD techniques performed at about 550 °C. It can be observed from curve fitting that PECVD causes almost all germanium to deposit in an amorphous state. The SRO ratio of germanium deposited using thermal CVD at 520 ° C was 4%, while for germanium deposited at 550 ° C it was about 14%.

It has also been found that residual stress in the active material coating can have a significant effect on the stability of such structures during cycling (i.e., lithiation and delithiation). Various deposition and post-deposition treatment process parameters have been investigated to determine the effect of these parameters on residual stress levels. For example, it has been discovered that some forms of etching and rapid thermal annealing can help reduce residual stress in the amorphous germanium structure and greatly improve the cycle life of the resulting battery.

Furthermore, small initial defects formed in the active material coating can be further produced during subsequent processing (eg, post deposition processing and formation of additional coating layers). For example, even small cracks can cause most of the active material coating to wrinkle and loosen contact with the underlying stencil structure. 4F is a schematic representation of a residual stress model for a multilayer electrode structure in accordance with some embodiments. This model has been developed from the Linear Elastic Fracture Mechanics (LEFM) for multilayer coatings to estimate stress levels. According to this model, materials having different coefficients of thermal expansion (CTE) can be used to match the tension between the layers and reduce the initial stress to less than about 1 GPa. This, in turn, can help prevent cracking and separation of the coating at least during processing, in which case the materials are subject to severe thermal fluctuations. It has been found that the particular tailoring of such properties of the active material coating helps to overcome some of the stress-induced cracking described above. In other words, more active materials can be deposited on the same template structure without sacrificing battery tracking. Loop performance while improving its total capacitance.

5A is a plan view of a partially assembled electrochemical cell using the electrodes described herein, in accordance with an embodiment of the present invention. The battery has a positive electrode active layer 502, and the positive electrode active layer 502 exhibits a major portion covering the positive current collector 503. The battery also has a negative electrode active layer 504 that is shown to cover a major portion of the negative current collector 505. Between the positive electrode active layer 502 and the negative electrode active layer 504 is a separator 506.

In one embodiment, the negative electrode active layer 504 is slightly larger than the positive electrode active layer 502 to ensure that lithium ions released from the positive electrode active layer 502 are trapped by the active material of the negative active layer 504. In one embodiment, the negative active layer 504 extends beyond the positive active layer 502 by at least about 0.25 mm and 5 mm in one or more directions. In a more specific embodiment, the negative layer extends between about 1 mm and 2 mm beyond the positive layer in one or more directions. In some embodiments, the edge of separator 506 extends beyond at least the outer edge of negative active layer 504 to provide complete electronic insulation of the negative electrode from other battery components.

Figure 5B is a cross-sectional view of a partially assembled electrochemical cell 500 using the electrodes described herein, in accordance with an embodiment of the present invention. Battery 500 includes a positive current collector 503 having a positive electrode active layer 502a on one side and a positive electrode active layer 502b on the opposite side. Battery 500 also includes a negative current collector 505 having a negative electrode active layer 504a on one side and a negative electrode active layer 504b on the opposite side. A separator 506a is present between the positive electrode active layer 502a and the negative electrode active layer 504a. The separator 506 serves to maintain mechanical separation between the positive electrode active layer 502a and the negative electrode active layer 504a, and acts as a sponge to acquire an electrolyte (not shown) to be added later. The ends of the current collectors 503, 505 on which the active material is absent may be used to connect to appropriate terminals (not shown) of the battery.

Electrode layers 502a, 504a, current collectors 503, 505, together with separator 506a, can be considered to form an electrochemical cell. The full stack 500 shown in Figure 5B includes electrode layers 502b, 504b and an additional separator 506b. A current collector 503 can be shared between adjacent batteries, 505. When such stacking is repeated, the result is a battery or battery pack having a capacitance that is greater than the capacitance of a single battery cell.

Another way to make a battery pack or battery with a large capacitance is to make a very large battery cell and roll it onto itself to make multiple stacks. The cross-sectional schematic illustration in Figure 6A shows the length and narrowness of an electrode and two separator sheets that can be wound together to form a battery or battery (sometimes referred to as a jellyroll 600). The roll battery is shaped and sized to fit the inner dimensions of the curved (usually cylindrical) cover 602. The roll battery 600 has a positive electrode 606 and a negative electrode 604. The blank space between the electrodes is a separator piece. A roll battery can be inserted into the cover 602. In some embodiments, the roll battery 600 can have a mandrel 608 at the center that establishes an initial winding diameter and prevents the inner coil from occupying a central axial region. The mandrel 608 can be made of a conductive material, and in some embodiments it can be part of a battery terminal. 6B shows a perspective view of a roll-to-roll battery 600 having positive short projections 612 and negative short projections 614 extending from a positive current collector (not shown) and a negative current collector (not shown), respectively. The short projections can be welded to the current collector.

The length and width of the electrode depend on the total size of the battery and the thickness of the active layer and current collector. For example, a conventional 18650 battery having a diameter of 18 mm and a length of 65 mm can have electrodes between about 300 mm and 1000 mm long. The shorter electrodes corresponding to lower rate/higher capacitance applications are thicker and have fewer turns.

A cylindrical design may be desirable for some lithium ion batteries because the electrodes may expand during cycling and thus exert pressure on the outer casing. It is useful to use a cylindrical outer casing that is as thin as possible while still maintaining sufficient pressure on the battery (with good safety margin). The prismatic (flat) cell can be similarly wound, but its cover can be flexible such that it can be bent along the longer side to accommodate internal pressure. In addition, the pressure may be different in different portions of the battery and the corners of the prismatic battery may be empty. An empty pocket in a lithium ion battery is not desirable because the electrode tends to be unevenly pushed to this recess during expansion of the electrode. Inside the cave. In addition, the electrolyte can collect in the empty pockets and leave a dry zone between the electrodes, thereby negatively affecting lithium ion transport between the electrodes. However, for certain applications, such as those specified by rectangular appearance dimensions, prismatic batteries are suitable. In some embodiments, prismatic cells use stacked rectangular electrodes and separator sheets to avoid some of the difficulties encountered with wound prismatic cells.

FIG. 7 illustrates a plan view of a wound prismatic roll battery 700. The roll battery 700 includes a positive electrode 704 and a negative electrode 706. The blank space between the electrodes is a separator piece. The roll battery 700 is enclosed in a rectangular prismatic cover 702. Unlike the cylindrical roll battery shown in Figures 6A and 6B, the winding of the prismatic roll battery begins with a flat extension in the middle of the roll battery. In one embodiment, the roll battery can include a mandrel (not shown) in the middle of the roll battery with the electrode and separator wound on the mandrel.

Figure 8A illustrates a cross section of a stacked battery including a plurality of cells (801a, 801b, 801c, 801d, and 801e), each cell having a positive electrode (e.g., 803a, 803b), a positive current collector (e.g., 802). A negative electrode (eg, 805a, 805b), a negative current collector (eg, 804), and a separator (eg, 806a, 806b) between the electrodes. Each current collector is shared by adjacent batteries. One of the advantages of stacked batteries is that the stack can be fabricated in almost any shape, which is particularly suitable for prismatic batteries. The current collector tabs typically extend from the stack and are introduced to the battery pack terminals. Figure 8B shows a perspective view of a stacked battery including a plurality of batteries.

Once the electrodes are configured as described above, the battery pack is filled with an electrolyte. The electrolyte in a lithium ion battery can be a liquid, a solid or a gel. A lithium ion battery having a solid electrolyte is also referred to as a lithium polymer battery.

A typical liquid electrolyte includes one or more solvents and one or more salts, at least one of which includes lithium. During the first charge cycle (sometimes referred to as a formation cycle), the organic solvent in the electrolyte may partially decompose on the surface of the negative electrode to form a solid electrolyte phase boundary layer (SEI layer). The phase boundaries are typically electrically insulating but can conduct ions, allowing lithium ions to pass. Phase boundary The decomposition of the electrolyte in the charge sub-cycle is prevented later.

Some examples of non-aqueous solvents suitable for some lithium ion batteries include the following: cyclic carbonates (e.g., ethyl carbonate (EC), propyl carbonate (PC), butyl carbonate (BC), and carbonic acid. Vinyl Ethyl Ester (VEC), lactones (eg, γ-butyrolactone (GBL), γ-valerolactone (GVL), and α-angelica lactone (AGL)), linear carbonates (eg, carbonic acid) Dimethyl ester (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), methyl propyl carbonate (MPC), dipropyl carbonate (DPC), methyl butyl carbonate ( NBC) and dibutyl carbonate (DBC), ether (for example, tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane (DME), 1, 2-diethoxyethane and 1,2-dibutoxyethane), nitrites (for example, acetonitrile and adiponitrile), linear esters (for example, methyl propionate, methyl pivalate, special Butyl valerate and octyl pivalate), decylamine (for example, dimethylformamide), organic phosphates (for example, trimethyl phosphate and trioctyl phosphate) and organic compounds containing S=O groups (eg, dimethylhydrazine and divinyl fluorene), and combinations thereof.

A non-aqueous liquid solvent can be used in combination. Examples of combinations include the following combinations: cyclic carbonate-linear carbonate, cyclic carbonate-lactone, cyclic carbonate-lactone-linear carbonate, cyclic carbonate-linear carbonate-lactone , cyclic carbonate-linear carbonate-ether, and cyclic carbonate-linear carbonate-linear ester. In one embodiment, a cyclic carbonate can be combined with a linear ester. Further, a cyclic carbonate can be combined with a lactone and a linear ester. In a particular embodiment, the ratio of cyclic carbonate to linear ester is between about 1:9 to 10:0, preferably 2:8 to 7:3 by volume.

The salt for the liquid electrolyte may include one or more of the following: LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ LiCF ₃ SO ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso-C ₃ F ₇ ), a lithium salt having a cycloalkyl group (for example, (CF ₂ ) ₂ (SO ₂ ) _2x Li and (CF ₂ ) ₃ (SO ₂ ) _2x Li), and combination. Common combinations include LiPF ₆ and LiBF ₄ , LiPF ₆ and LiN(CF ₃ SO ₂ ) ₂ , LiBF ₄ and LiN(CF ₃ SO ₂ ) ₂ .

In one embodiment, the total concentration of salts in the liquid non-aqueous solvent (or combination of solvents) is at least about 0.3 M; in a more specific embodiment, the salt concentration is at least about 0.7 M. The upper concentration limit can be driven by the dissolution limit, or can be no greater than about 2.5 M; in a more specific embodiment, no greater than about 1.5 M.

A solid electrolyte is usually used without a separator because it acts as a separator itself. It is electrically insulated, conducts ions and is electrochemically stable. In the solid electrolyte configuration, a lithium-containing salt (which may be the same as the liquid electrolyte battery described above) is used, but unlike being dissolved in an organic solvent, it is held in a solid polymer composite. An example of a solid polymer electrolyte may be an ion-conducting polymer prepared from a monomer containing atoms having un-co-electron pairs attached to and moving between lithium ions available for the electrolyte salt during conduction, For example, a chloride or copolymer of polyvinylidene fluoride (PVDF) or a derivative thereof, poly(chlorotrifluoroethylene), poly(ethylene-chlorotrifluoro-ethylene) or poly(fluorinated ethylene-propylene), poly Ethylene oxide (PEO) and formaldehyde-bonded PEO, PEO-PPO-PEO crosslinked with trifunctional urethane, poly(bis(methoxy-ethoxy-ethoxy))-phosphazene (MEEP), triol type PEO crosslinked with a difunctional urethane, poly((oligo)ethylene oxide) methacrylate-co-alkali metal methacrylate, polyacrylonitrile (PAN), Polymethyl methacrylate (PNMA), polymethacrylonitrile (PMAN), polyoxyalkylene and copolymers and derivatives thereof, acrylate-based polymers, other similar solvent-free polymers, condensed or crosslinked To form a combination of the foregoing polymers of different polymers and a physical mixture of any of the foregoing polymers. Other less conductive polymers can be used in combination with the above polymers to improve the strength of thin laminates including: polyester (PET), polypropylene (PP), polyethylene naphthalate. Diester (PEN), polyvinylidene fluoride (PVDF), polycarbonate (PC), polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTFE).

Figure 9 illustrates a cross-sectional view of a wound cylindrical battery in accordance with an embodiment. The roll battery includes a spiral wound positive electrode 902, a negative electrode 904, and two sheets of separator 906. The roll battery is inserted into the battery cover 916, and the cover 918 and the gasket 920 are used to seal the battery. In some cases, cover 912 or cover 916 includes a security device. For example, a safety vent or a flush valve can be used to pop open when excessive pressure builds up in the battery pack. Again, a positive thermal coefficient (PTC) device can be incorporated into the conduction path of the cover 918 to reduce damage that can be caused when the battery is subjected to a short circuit. The outer surface of the cover 918 can serve as a positive terminal, while the outer surface of the battery cover 916 can serve as a negative terminal. In an alternate embodiment, the polarity of the battery pack is reversed and the outer surface of the cover 918 acts as a negative terminal and the outer surface of the battery cover 916 acts as a positive terminal. The tabs 908 and 910 can be used to establish a connection between the positive and negative electrodes and the corresponding terminals. A suitable insulating gasket 914 can be inserted to prevent the possibility of an internal short circuit. For example, Kapton ^TM film can be used for internal insulation. During manufacture, the lid 918 can be flattened to the cover 916 to seal the battery. However, prior to this operation, an electrolyte (not shown) is added to fill the porous space of the roll battery.

For lithium ion batteries, a hard cover is typically required, and a lithium polymer battery can be loaded into a flexible, foil (polymer laminate) cover. A variety of materials can be selected for the cover. For lithium-ion battery packs, Ti-6-4, other Ti alloys, Al, Al alloys and 300 series stainless steels are suitable for positive-conducting hood parts and end caps, and commercially pure Ti, Ti alloys, Cu, Al, Al alloys Ni, Pb and stainless steel may be suitable for the negative conductive cover portion and the end cover.

A lithium ion battery pack that can form a battery pack or a battery pack or is part of a battery pack includes one or more lithium ion electrochemical cells of the present invention, each battery containing an electrochemically active material. In addition to batteries, lithium-ion battery packs can also include a power management circuit to control power balance between multiple batteries, control charging and discharging parameters, ensure safety (thermal and electrical dissipation), and other purposes. Individual cells can be connected in series and/or in parallel to form a battery having suitable voltage, power, and other characteristics.

In addition to the battery pack applications described above, metal halides can be used in fuel cells (eg, for negative electrodes, positive electrodes, and electrolytes), heterojunction solar cell active materials, various types of current collectors, and/or absorbing coatings. in. Some of these applications offer high surface area from free metal telluride structures, high conductivity of germanide materials, and fast and inexpensive Deposition technology benefits.

A series of tests were performed on batteries fabricated using the various techniques described above. Figure 10 illustrates the cycle data corresponding to one of the batteries. In particular, Figure 10 illustrates coulombic efficiency 1002 and delithiation capacitor 1004 over 160 cycles. The cell maintains a stable capacitance of over 1000 mAh/g over many cycles. The coulombic efficiency is at least 99.1% in each cycle.

Although the foregoing invention has been described in detail, it is understood that It should be noted that there are many alternative ways of implementing the procedures, systems, and devices of the present invention. Therefore, the present embodiments are to be considered as illustrative and not restrictive.

Claims (16)

An electrode comprising: a substrate; a first layer of nanostructures rooted to the substrate; an electrochemically active inner layer coated with the first a layer, the electrochemically active inner layer has a first porosity; and an electrochemically active outer layer coated with the electrochemically active inner layer, the electrochemically active outer layer having a different One of the first porosity is the second porosity. The electrode of claim 1, wherein the first layer of the nanostructure comprises one or more metal silicides. The electrode of claim 2, wherein the one or more metal halides are selected from the group consisting of nickel silicides, cobalt silicides, copper silicides, silver telluride (silver silicides), silver silicides, titanium silicides, aluminum silicides, zinc silicides, and iron silicides. The electrode of claim 3, wherein the nickel halide is selected from the group consisting of Ni ₂ Si, NiSi, and NiSi ₂ and combinations thereof. The electrode of any one of claims 1 to 4, wherein the electrochemically active material comprises one or more materials selected from the group consisting of: cerium, silicon oxides, silicon oxynitride (silicon) Oxy-nitrides), tin-containing materials, niobium-containing materials, and carbonaceous materials. The electrode of any one of claims 1 to 4, wherein the electrochemically active inner layer comprises amorphous germanium, and the electrochemically active outer layer comprises amorphous germanium. The electrode of claim 6, wherein the electrochemically active inner layer and the electrochemically active outer layer have different hydrogen concentrations. The electrode of claim 1, wherein the electrochemically active inner layer has different compositions from the electrochemically active outer layer. The electrode of claim 1, wherein the electrochemically active inner layer has different morphologies from the electrochemically active outer layer. The electrode of claim 1, wherein the electrochemically active inner layer has a lower porosity than the electrochemically active outer layer. An electrode assembly comprising: a conductive substrate for conducting current between an electrode active material and a battery terminal; and an electrode material comprising: a layer of a first nanostructure attached to the conductive substrate, The first nanostructures comprise one or more metal halides; a coating of one of the electrode active materials covering at least a portion of the first nanostructures, the coating comprising an inner layer having a first porosity And an outer layer having a second porosity different from the first porosity, wherein the first nanostructures provide electronic communication between the electrode active material and the conductive substrate. An electrochemical cell comprising: a first electrode as claimed in claim 1; a second electrode; and an electrolyte providing an ion connection between the first electrode and the second electrode through. A method of fabricating an anode for a battery, the method comprising the steps of: providing a plurality of nanostructures; depositing over the nanostructures using a plasma enhanced chemical vapor deposition (PECVD) method a first layer of germanium; and a second layer of germanium deposited over the first layer of germanium using a thermal CVD method. The method of claim 13, wherein the first ruthenium layer has a first porosity and the second ruthenium layer has a second porosity that is different from the first porosity. The method of claim 13, wherein the nanostructures comprise one or more metal halides. The method of claim 15, wherein the one or more metal halides are selected from the group consisting of: nickel telluride, cobalt telluride, copper telluride, silver telluride, chromium telluride, titanium telluride, aluminum telluride, zinc telluride And bismuth iron.