HK1171113B - Anode material having a uniform metal-semiconductor alloy layer - Google Patents

Description

Anode material with uniform metal-semiconductor alloy layer

The patent application of the invention is a divisional application of an invention patent application with an international application number of PCT/US2009/041012, an international application date of 2009, 4, 17, and an application number of 200980113838.9 entering the Chinese national stage, and an invention name of "anode material with uniform metal-semiconductor alloy layer".

Technical Field

The present invention relates to an anode material having a uniform metal-semiconductor alloy layer, and a method for preparing the anode material. The anode material may be used for a non-aqueous electrolyte secondary battery.

Background

A non-aqueous electrolyte secondary battery is a rechargeable battery in which ions move between an anode and a cathode through a non-aqueous electrolyte. The non-aqueous electrolyte secondary battery includes a lithium ion battery, a sodium ion battery, and a potassium ion battery, and other kinds of batteries.

A lithium ion battery is a common type of non-aqueous electrolyte secondary battery in which lithium ions move between an anode and a cathode through an electrolyte. The benefits and problems of lithium ion batteries are examples of the benefits and problems of other non-aqueous electrolyte secondary batteries; the following embodiments exemplarily relate to a lithium ion battery, but are not limited thereto. In a lithium ion battery, lithium ions move from an anode to a cathode during discharge, and from the cathode to the anode during charge. Lithium ion batteries are a very desirable energy source due to their high energy density, high power and long shelf life. Lithium ion batteries are commonly used in consumer electronic devices, and are currently one of the most popular types of batteries for portable electronic devices due to their high energy-to-weight ratio, lack of memory effect, and slow charge loss when not in use. Because of these advantages, lithium ion batteries are increasingly being used in a variety of applications, including automotive, military, and aerospace applications.

Fig. 1 is a cross-sectional view of a prior art lithium ion battery. The cell 15 has a cathode current collector 10 on which a cathode 11 is mounted. The cathode current collector 10 is covered with a separator 12 on which is disposed an assembly of an anode current collector 13 and an anode 14. The separator 12 is filled with an electrolyte capable of transporting ions between the anode and the cathode. The current collectors 10, 13 are used to collect the electrical energy generated by the battery 15 and connect it to an external device so that the external device can obtain the electrical energy and transfer it to the battery during recharging.

The anode of the non-aqueous electrolyte secondary battery may be made of a composite or monolithic type anode material. In a composite anode, particulate anode material is actually bound together with a binder to form a matrix of particles and binder. For example, the anode can be made by binding carbon particles together with a polymeric binder. Monolithic anodes are anodes that are not made by the addition of a physical binder material. For example, any method of manufacturing a silicon anode may be used in which silicon molecules are connected to each other without using an additional binder to form a bulk type film. Examples of bulk anode materials include single crystal silicon, polycrystalline silicon, and amorphous silicon. Monolithic anodes can also be formed by fusing or sintering particles of anode material, or by vacuum deposition and chemical deposition.

During charging of a lithium ion battery, lithium leaves the cathode, passes through the electrolyte in the separator in the form of lithium ions, and then enters the anode. During discharge, lithium ions leave the anode material, move through the electrolyte in the separator, and reach the cathode. Elements such as aluminum, silicon, germanium, and tin can react with lithium ions for use in high capacity anodes. An anode material capable of reacting with lithium has an active region where lithium can react and an inactive region where lithium does not react. The ratio of active to inactive area of the anode affects the efficiency of the cell.

For the reaction of lithium ions in the lithium active material, there is a significant volume difference between the reacted state and the extracted state; the lithium active anode material in the reacted state (activated state) occupies a volume significantly larger than in the extracted state (activated state). Thus, there is a large proportional change in anode volume during each charge-discharge cycle. In lithium active anodes, cracks often form in the anode material during cyclic volume changes. With repeated cycling, these cracks can propagate, causing portions of the anode material to separate from the anode. The separation of some of the anode portions due to cycling is called spalling. Exfoliation results in a reduction in the amount of active anode material electrically connected to the current collector of the battery, resulting in a loss of capacity.

Silicon anodes are an excellent candidate for lithium ion batteries because of its high capacity for lithium, but a significant reduction in capacity occurs due to cyclic exfoliation. By reducing the range of the charge-discharge voltage window applied across the silicon anode in a lithium ion battery, capacity loss due to cycling can be prevented because expansion and contraction can change with charge state. But the operational capacity of the battery is also reduced by reducing the range of the charge-discharge voltage window. Furthermore, silicon is a poor conductor and often must be formulated with conductive additives to be used as an anode material. These conductive additives reduce the active area-to-inactive area ratio, thereby reducing the energy density of the battery. The conductive additive is a conventional material, such as carbon black, which is added to the anode particles and mixed prior to bonding the anode particles.

Another method of increasing the conductivity of the anode material is to deposit a layer of conductive material on the anode material. Methods of depositing the conductive layer include vapor deposition, electrodeposition, and electroless deposition. When depositing material on a resistive substrate such as silicon using any of the methods described above, the deposition on the anode is generally non-uniform. For example, when electroless and electroplating metals such as nickel, the deposition rate on nickel surfaces is significantly higher than on non-similar surfaces such as silicon. Deposition of these significant kinetic changes on different materials can cause the deposition process to produce surface defects, pores, and undeposited areas. For a line-of-sight deposition process, such as vacuum deposition from a target, some areas of the non-planar surface that are not directly in-line of sight are deposited significantly less, or none, reducing thickness uniformity. In addition, these coatings do not adhere well because the adhesion strength of the deposited metal to the semiconductor material in these coating methods is poor. Poor adhesion strength, poor uniformity, and poor minimum thickness of these coatings can result in poor cycle life, power, energy, and reliability.

Disclosure of Invention

The present invention relates to a nonaqueous electrolyte secondary battery, and a durable anode material and an anode for the nonaqueous electrolyte secondary battery. The invention also relates to methods for producing these anode materials. In the present invention, a layer of a metal-semiconductor alloy is formed on an anode material by: a portion of the anode material is contacted with a solution comprising ions of the metal to be deposited and a dissolution component for dissolving a portion of the semiconductor in the anode material. When the anode material is contacted with the solution, the dissolution component dissolves a portion of the semiconductor in the anode material, thereby providing electrons for reducing metal ions and depositing metal on the anode material. After deposition, the anode material and metal are annealed to form a uniform metal-semiconductor alloy layer.

Drawings

FIG. 1 is a cross-sectional view of a prior art lithium ion battery;

fig. 2 shows a displacement process according to an exemplary embodiment of the present invention.

Fig. 3 shows a semiconductor particle coated with a metal-semiconductor alloy layer.

Fig. 4 shows semiconductor particles formed on a current collector and immersed in an electrolyte.

Fig. 5 shows an anode comprising a pillar of semiconductor particles having a metal-semiconductor alloy layer.

Fig. 6A-6D show a wide variety of anode configurations.

Detailed Description

The inventors of the present invention have discovered that by coating a metal on a semiconductor-containing anode material using a displacement plating process followed by annealing, a thin, uniform metal-semiconductor alloy coating can be formed to improve conductivity while the weight fraction of active anode material is increased to reduce anode swelling without a significant loss in efficiency.

The uniform metal-semiconductor alloy coating on the anode material provides a conductivity that is significantly better than the conductivity of the semiconductor structure of the anode itself. For example, conventional silicon powders have a resistivity of 1 to 100 Ω/cm; while the resistivity of the nickel silicide layer having a NiSi composition is 10 to 60 μ Ω/cm. This provides a great advantage for use in non-aqueous electrolyte secondary batteries, such as lithium ion batteries, because the coating also reduces the amount of conductive additive required to make a working anode. Because the nickel silicide itself can be lithiated reversibly, the combination of pure nickel silicide on silicon forms an anode material with both excellent conductivity and excellent lithium cycling capability. The specific energy density of the electrode can also be improved by adding less additives to the electrode because the content of inactive materials in the electrode is less.

The uniform metal-semiconductor alloy coating on the anode material also provides uniform high conductivity, thereby improving the ability to uniformly lithiate the surface of the anode material, which in turn allows uniform expansion of the anode material, thereby reducing capacity degradation due to spalling. The metal deposition and metal-semiconductor alloy formation performed according to embodiments of the present invention is not dependent on the crystal orientation of the anode material.

The method of the present invention is superior to other methods used to make metal-semiconductor alloy coatings for anodes in non-aqueous electrolyte secondary batteries due to selectivity, uniformity, and improved conductivity of the resulting material. These beneficial properties allow the resulting anode materials to provide improved first charge/discharge cycle efficiency, longer cycle life, more uniform charge/discharge, higher rate capability, and higher specific energy density when used in non-aqueous electrolyte batteries, as compared to currently used anode materials.

The present invention relates to a method for forming an anode material comprising a metal-semiconductor alloy layer. The method comprises the following steps: preparing an anode material comprising a semiconductor material; contacting a portion of the anode material with a metal ion solution comprising metal ions and a displacement solution comprising a dissolution component for dissolving a portion of a semiconductor in the anode material, the portion of the anode material comprising a semiconductor material; dissolving a portion of the semiconductor material from a portion of the anode material; reducing metal ions to metal by electrons generated by dissolution of the semiconductor material; depositing a metal on a portion of the anode material; annealing portions of the anode material and the deposited metal to form a metal-semiconductor alloy layer.

In the method of the present invention, an anode material comprising a uniform metal-semiconductor alloy layer is formed. A portion of an anode material comprising a semiconductor material is contacted with a metal ion solution comprising metal ions and a displacement solution comprising a dissolved component. The metal ion solution and displacement solution are optionally pre-mixed prior to contacting with the portion of the anode material. The term "dissolution component" means a component capable of promoting dissolution of the semiconductor material. The dissolved components include fluorides, chlorides, peroxides, hydroxides, permanganates, and the like. Preferred dissolution components are fluorides and hydroxides. The most preferred dissolved component is fluoride. Some of the semiconductor material in the portion of the anode material in contact with the dissolved component dissolves in the solution. The dissolution of the semiconductor reduces the metal ions in the displacement solution to metal. The metal is deposited from solution onto portions of the anode material. Portions of the anode material and the deposited metal are then annealed to convert the deposited metal to a metal-semiconductor alloy.

The anode material in the present invention may be fine particles in the form of powder having various shapes such as spheres, flakes, fibers, and the like. In the present invention, the anode material may be of a monolithic type. In the present invention, the anode material may also be in the form of a woven fabric (collection of fibers).

One specific example of nickel and silicon is shown in the following embodiment. However, the method of the present invention may be used to deposit many other metals, for example other base metals such as copper or cobalt, or noble metals such as silver, gold, platinum, palladium or rhodium. Preferably, the metal ion solution contains primarily ions of one metal, but may also contain ions of multiple metals. Semiconductor materials that may be used in the present invention include silicon, germanium, or alloys thereof, such as alloys of silicon or germanium with tin, zinc, and manganese. The semiconductor material may also be a compound, for example a group III-V compound, such as aluminum antimonide (AlSb), indium antimonide (InSb), gallium arsenide (GaAs) and indium phosphide (InP); or group II-VI compounds such as cadmium telluride (CdTe) and cadmium selenide (CdSe).

For embodiments in which nickel is deposited on a silicon-containing anode material, nickel ions may be provided to the metal ion solution by adding a nickel-containing salt (e.g., nickel sulfate or nickel chloride); the dissolved component may be hydrolyzed fluoride ions such as ammonium fluoride or hydrofluoric acid. In the case of silicon, the base material dissolves in the solution, providing the electrons used to deposit the nickel. The silicon on the surface of the anode material dissolves into the solution. On the surface of the silicon-containing anode material, nickel ions are reduced, a metallic nickel film is deposited and then converted into nickel silicide by annealing. Since the process requires dissolution of silicon for the deposition of nickel, deposition occurs only at locations where silicon can dissolve. Thus, the film deposited on the silicon surface is extremely uniform, unlike electroless or electrodeposition processes. Because the process also involves the replacement of silicon atoms to deposit nickel atoms, the adhesion of the metal coating on silicon is superior to that of electroless deposition processes by this process.

Contact between the metal ion solution, the displacement solution, and a portion of the anode material can be accomplished in a variety of ways, including partial immersion and complete immersion, coating, and spraying. Fig. 2 is a schematic diagram of a displacement process in which anode material 21 is immersed in a vessel 22 containing a solution 23 of a pre-mixed metal ion solution and a displacement solution. As shown, the anode material 21 in fig. 2 is in the form of particles. In fig. 2, the anode material is immersed in a solution 23. However, only a portion of the anode material 21 may be in contact with the solution 23. The solution 23 contains the required amount of the salt of the metal to be deposited, as well as the appropriate concentration of the dissolved component. Generally, the solution contacted with the anode material comprises about 0.01 to 1M, preferably 0.02 to 0.5M, of metal ions; the solution also contains 0.02-8M, preferably 0.5-5M, of a dissolution component. The pH value of the contact solution is 6-11, preferably 8-10; the temperature is 40-98 deg.C, preferably 50-98 deg.C. The solution 23 may be held in the container 22 for a specified length of time within a set temperature range for metal displacement. When the desired thickness of metal is achieved, the anode material is removed from the solution, rinsed, dried and annealed.

The average thickness of the metal deposited by this method on the anode material may be about 100 nanometers to 3 microns. Thinner coatings do not provide the advantages of the present invention. The thickness of the coating may be greater than 3 microns, but is not cost effective.

Annealing is optionally performed in an inert atmosphere to form a uniform metal-semiconductor alloy coating. For example, if in an embodiment where nickel is deposited on silicon, the annealing atmosphere contains too much oxygen, the deposited nickel may be converted to nickel oxide, rather than nickel silicide, during the annealing step. Waidmann et al in "Microelectronic Engineering"; some annealing conditions for obtaining nickel silicide layers with good conductivity and good alloy uniformity are disclosed in volume 83, stages 11-12, pages 2282-2286. In one embodiment, the annealing may be performed using a rapid thermal annealing process at a temperature of about 500 ℃. Different annealing conditions may provide silicides with different conductivities due to the formation of different alloy compositions. The annealing conditions can be adjusted by varying the temperature and time of annealing to achieve a particular conductivity.

In some cases, such as when a short anneal cycle is required due to process time limitations, the anneal conditions may be designed such that not all of the deposited metal is converted to a metal-semiconductor alloy. Excess metal can hinder lithiation of the metal-semiconductor alloy and the semiconductor material. In this case, excess metal not converted to the metal-semiconductor alloy may be etched away using a solution capable of selectively etching the metal without etching the metal-semiconductor alloy. For example, a sulfuric acid solution in hydrogen peroxide can selectively etch nickel without etching nickel silicide.

In one embodiment of the method of the present invention, the solution in contact with the anode material comprises about 0.02-0.5M Ni in the form of nickel sulfate²⁺About 0.5-5M NH₄Fluoride in the form F, at a pH of about 8 to 10; the temperature is about 50-98 deg.C.

In another embodiment of the method of the present invention, the solution in contact with the anode material comprises about 0.02-0.5M Ni in the form of nickel sulfate²⁺About 0.5-5M of H₂O₂Peroxide in the form of a pH of about 8 to 10; the temperature is about 50-98 deg.C.

The method of the present invention is used to prepare anode materials having a uniform metal-semiconductor alloy layer. The metal-semiconductor alloy layer on the anode prepared by the method of the present invention is preferably nickel silicide. Other metals which may also be used on the anode prepared by the method of the present invention include other base metals such as copper and cobalt, or noble metals such as silver, gold, platinum, palladium or rhodium. Preferably, the metal-semiconductor alloy on the anode prepared by the method of the present invention has a thickness of about 100 nm to 3 μm.

A non-aqueous electrolyte secondary battery may be manufactured using the anode material prepared by the method of the present invention. A battery is formed by combining the anode of the present invention with a cathode and an electrolyte in a planar or three-dimensional structure as is known in the art. See, for example, Long et al, "Three-Dimensional Battery architecture", Chemical Reviews, 2004, 104, 4463-. The non-aqueous electrolyte secondary battery of the present invention may be a lithium ion battery, a sodium ion battery, a potassium ion battery or other kinds of non-aqueous electrolyte secondary batteries. The non-aqueous electrolyte secondary battery includes an anode formed of an anode material having a metal-semiconductor alloy layer, a cathode, and a non-aqueous electrolyte.

In another embodiment, the invention is directed to a method for forming an anode comprising a metal-semiconductor alloy layer, the method comprising the steps of: preparing a particulate anode material comprising a semiconductor material; contacting the particulate anode material with a metal ion solution comprising metal ions and a displacement solution comprising a dissolution component for dissolving a portion of the semiconductor material in the particulate anode material; dissolving a portion of the semiconductor material from the particulate anode material; reducing the metal ions to metal by electrons generated by dissolution of the semiconductor; depositing the metal on the particulate anode material; shaping the particulate anode material; sintering the particulate anode material such that the particulate anode material coalesces. The semiconductor materials, metals, and dissolved components are the same as those described previously in this application. The method optionally comprises the steps of: annealing the particulate anode material and the deposited metal to form a metal-semiconductor alloy layer prior to shaping the particulate anode material.

In another embodiment, the invention is directed to a method for forming an anode comprising a metal-semiconductor alloy layer, the method comprising the steps of: preparing a particulate anode material comprising a semiconductor material; shaping the particulate anode material; contacting the particulate anode material with a metal ion solution comprising metal ions and a displacement solution comprising a dissolution component for dissolving a portion of the semiconductor material in the particulate anode material; dissolving a portion of the semiconductor material from the particulate anode material; reducing the metal ions to metal by electrons generated by dissolution of the semiconductor; depositing the metal on the particulate anode material; sintering the particulate anode material such that the particulate anode material coalesces. The semiconductor materials, metals, and dissolved components are the same as those described previously in this application.

In the present invention, the anode particles containing a semiconductor are coated with a metal or metal-semiconductor alloy, and then subjected to shaping and sintering to form an anode. The anode formed by this method has the advantages of the metal-semiconductor alloy layer described above, but also has sufficient porosity to form an increased surface area for ionic reaction with the electrolyte from the non-aqueous electrolyte secondary battery. The increased contact area with the electrolyte results in an extremely high weight fraction of active semiconductor anode material. The step of sintering the coated particles of semiconductor anode material comprises heating the coated material at a temperature well below the melting point of the semiconductor material until the particles adhere to each other. The operation of sintering the particles may be performed after the operation of annealing the coated particles to form the metal-semiconductor alloy, or the annealing and sintering steps may be performed simultaneously.

Fig. 3 shows semiconductor particles 30 within a coated metal-semiconductor alloy layer 31. Fig. 4 shows a layer 41 of sintered semiconductor particles formed on a current collector 40, immersed in an ion-containing electrolyte 43, as part of a battery. Since the metal-semiconductor alloy coating 44 on the semiconductor particles 45 is electrically conductive, the sintered particles are electrically connected to each other and to the current collector. This allows for a uniform charge distribution on the sintered semiconductor particle layer 41. Since the layer 41 of sintered semiconductor particles is porous, the layer 41 has an increased surface area for contact with the electrolyte 43.

Fig. 5 shows an anode using pillars 51 of sintered semiconductor particles with a metal-semiconductor layer. The pillars 51 are formed on the current collector 50. Fig. 6A through 6D show that a wide variety of other anode structures 60 can be formed from sintered semiconductor particles having a metal-semiconductor alloy layer. A cathode structure 61 that may be used with the anode structure 60 in a battery is shown in fig. 6A-6D.

The particulate anode material having the metal-semiconductor alloy layer can be shaped using a die or coated onto a structure. Coating can be accomplished using conventional methods, such as reverse roll, or using more advanced techniques, such as electrophoretic deposition.

Preferably, the metal-semiconductor layer on the semiconductor anode material is thick enough to provide adhesion and cohesion of the particles, but thin enough not to control the electrochemical performance of the electrode. In one embodiment, the metal-semiconductor alloy coating comprises from about 0.1 to about 5 percent by volume of the total particle volume, and the particle may have a diameter of from about 0.001 to about 100 microns. The particles can have a wide variety of shapes, including flakes and rods. Since the particle shape may be irregular, the diameter of a particle is defined as the longest distance from one point of the particle to another.

One embodiment of the invention includes a nickel foil or mesh coated with sintered silicon particles.

A non-aqueous electrolyte secondary battery may be manufactured using the anode material prepared by the method of the present invention. The non-aqueous electrolyte secondary battery of the present invention may be a lithium ion battery, a sodium ion battery, a potassium ion battery or other kinds of non-aqueous electrolyte secondary batteries. The non-aqueous electrolyte secondary battery includes an anode having a metal-semiconductor alloy layer, a cathode, and a non-aqueous electrolyte.

The following examples further illustrate the invention. These examples are intended to illustrate the invention only and are not to be construed as limiting.

Examples

Example 1: immersion nickel deposition on particulate anode materials

A sample of 2 grams of powdered silicon particles (-325 mesh) was prepared containing 0.1M NiSO₄.6H₂O and 5MNH₄F in 50 ml of solution for 30 seconds. The pH of the solution was maintained at 8.5 and the working temperature was 85 ℃. The deposition was performed with the powder on filter paper placed in a buchner funnel. Vigorous bubbling was observed during the deposition, indicating that nickel displacement reactions occurred. The solution was drained by applying a vacuum on a buchner funnel. The sample was rinsed with deionized water for 10 minutes to remove trace amounts of salt contaminants. The powder was collected and dried in air at 80 ℃ for 12 hours. Then, the powder is in H₂/N₂The silicide was formed by annealing at a maximum temperature of 550 c for 2 hours (including heating and cooling times) in an atmosphere.

The prepared anode material is subjected to 100 reversible cycles, the silicon equivalent value (silicon equivalent) exceeds 1200 mAh/g, and the average coulomb efficiency of 100 cycles is 99.8%. This is in contrast to the case where only silicon powder was used, where the silicon capacity had decreased to less than 330 mAh/g at the 10 th charge-discharge cycle.

Example 2: immersion nickel deposition on particulate anode materials

A sample of 2 grams of powdered silicon particles (-325 mesh) was prepared containing 0.1M NiSO₄.6H₂O and 5MNH₄F in 50 ml of solution for 30 seconds. The pH of the solution was maintained at 8.5 and the working temperature was 85 ℃. The deposition was performed with the powder on filter paper placed in a buchner funnel. Vigorous bubbling was observed during the deposition, indicating that nickel displacement reactions occurred. The solution was drained by applying a vacuum on a buchner funnel. The sample was rinsed with deionized water for 10 minutes to remove trace amounts of salt contaminants. The powder was collected and dried in air at 80 ℃ for 12 hours. Then, the powder is in H₂/N₂The silicide was formed by annealing at a maximum temperature of 550 c for 2 hours (including heating and cooling times) in an atmosphere.

The powder obtained was dried at 70 ℃ in 10ml of H₂SO₄+40 mL of 3% H₂O₂Is immersed for 3 minutes to remove any excess nickel, leaving behind the silicide.

Example 3: sintering of nickel silicide coated silicon particle networks

The powder consisting of nickel silicide-coated particles prepared according to example 2 was dispersed in an aqueous solution containing carboxymethyl cellulose and coated on a nickel screen. The coated mesh was dried to remove water and then heated to 1000 ℃ under an argon atmosphere so that the nickel silicide coated particles sintered to each other and to the nickel mesh. The sintered electrode produced is used as an anode in lithium ion batteries.

Example 4: sintering of nickel-coated silicon particle networks

A sample of 2 grams of powdered silicon particles (-325 mesh) was prepared containing 0.1M NiSO₄.6H₂O and 5MNH₄F in 50 ml of solution for 30 seconds. The pH of the solution was maintained at 8.5 and the working temperature was 85 ℃. The deposition was performed with the powder on filter paper placed in a buchner funnel. Vigorous bubbling was observed during the deposition, indicating that nickel displacement reactions occurred. The solution was drained by applying a vacuum on a buchner funnel. Sample leaching with deionized waterFor 10 minutes to remove trace amounts of salt contaminants. The powder was dispersed in an aqueous solution containing carboxymethyl cellulose and coated on a nickel mesh. The coated mesh was dried to remove water and then heated to 1000 ℃ under an argon atmosphere, thereby forming a nickel silicide coating on the silicon particles while sintering the nickel silicide coated particles to each other and to the nickel mesh. The sintered electrode produced is used as an anode in lithium ion batteries.

Example 5: sintering of a mesh coated with silicon particles and then coated with nickel

The first silicon particles were dispersed in an aqueous solution containing carboxymethyl cellulose and coated on a nickel mesh. The resulting web comprising silicon particles was coated with nickel using a dip-displacement coating process. The coated mesh was dried to remove water and then heated to 1000 ℃ under an argon atmosphere, thereby forming a nickel silicide coating on the silicon particles while sintering the nickel silicide coated particles to each other and to the nickel mesh. The sintered electrode obtained is used as an anode in a nonaqueous electrolyte battery.

While the invention has been described with respect to a particularly preferred embodiment, it will be understood that various modifications may be made without departing from the scope of the invention.

Claims (13)

1. A method for forming a particulate anode comprising a metal-semiconductor alloy layer, the method comprising:

preparing a particulate anode material comprising a semiconductor material, wherein the semiconductor material is silicon, or an alloy thereof;

contacting a portion of the anode material with a metal ion solution comprising metal ions and a displacement solution comprising a dissolved component, wherein the portion of the anode material comprises the semiconductor material; the dissolved component is a fluoride, chloride, peroxide, hydroxide or permanganate;

dissolving a portion of the semiconductor material from a portion of the anode material;

reducing the metal ions to metal by electrons generated by dissolution of the semiconductor material;

depositing the metal on the portion of the anode material, wherein the average thickness of the deposited metal is from 100 nanometers to 3 micrometers;

annealing portions of the anode material and deposited metal to form a metal-semiconductor alloy layer on the particulate anode material, the metal-semiconductor alloy being an alloy of the deposited metal and semiconductor material; and

shaping the particulate anode material, shaping the particulate anode material using a mold, or coating the particulate anode material on a structure.

2. A method for forming an anode comprising a metal-semiconductor alloy layer, the method comprising the steps of:

preparing a particulate anode material comprising a semiconductor material, wherein the semiconductor material is silicon, or an alloy thereof;

contacting the particulate anode material with a metal ion solution comprising metal ions and a displacement solution comprising a dissolved component; the dissolved component is a fluoride, chloride, peroxide, hydroxide or permanganate;

dissolving a portion of the semiconductor material from the particulate anode material;

reducing the metal ions to metal by electrons generated by dissolution of the semiconductor material;

depositing a metal on the particulate anode material, wherein the average thickness of the deposited metal is from 100 nanometers to 3 micrometers;

shaping the particulate anode material, shaping the particulate anode material using a mold, or coating the particulate anode material on a structure; and

sintering the shaped particulate anode material such that the particulate anode material coalesces to form an anode having a metal-semiconductor alloy layer on the sintered anode material, the metal-semiconductor alloy being an alloy of the deposited metal and semiconductor material.

3. The method of claim 2, further comprising the steps of: annealing the particulate anode material and the deposited metal to form a metal-semiconductor alloy layer prior to shaping the particulate anode material.

4. The method of claim 1 or 2, wherein the metal ion solution and displacement solution are pre-mixed prior to contacting with the anode material.

5. The method of claim 1 or 2, wherein the semiconductor is silicon.

6. The method of claim 1 or 2, wherein the metal is a precious metal or a base metal.

7. The method of claim 1 or 2, wherein the metal is nickel or copper and the semiconductor material is silicon.

8. The method of claim 4, wherein the pre-mixed solution comprises (a)0.02-0.5M Ni²⁺And (b)0.5 to 5M of a fluoride or 0.5 to 5M of a peroxide.

9. A method for forming an anode material comprising a metal-semiconductor alloy layer, the method comprising the steps of:

preparing an anode material comprising a semiconductor material, wherein the semiconductor material is silicon, or an alloy thereof;

contacting a portion of the anode material with a metal ion solution comprising metal ions and a displacement solution comprising a dissolved component, wherein the portion of the anode material comprises the semiconductor material; the dissolved component is a fluoride, chloride, peroxide, hydroxide or permanganate;

dissolving a portion of the semiconductor material from the portion of the anode material;

reducing the metal ions to metal by electrons generated by dissolution of the semiconductor material;

depositing a metal on the portion of the anode material, wherein the average thickness of the deposited metal is from 100 nanometers to 3 micrometers;

annealing portions of the anode material and the deposited metal to form a metal-semiconductor alloy layer on the anode material, the metal-semiconductor alloy being an alloy of the deposited metal and a semiconductor material; and

shaping the anode material, shaping the anode material using a mold, or coating the anode material on a structure.

10. The method of claim 9, wherein the anode material is monolithic.

11. A particulate anode made according to the method of claim 1.

12. A monolithic anode produced according to the method of claim 2 or 10.

13. A non-aqueous electrolyte secondary battery comprising the anode of claim 11 or 12, a cathode, and a non-aqueous electrolyte.