Method for pre-lithifying electrodes using lithium silicon alloy

Abstract

This invention provides a method for pre-lithifying electrodes in a single step. [Solution] The method involves contacting an electrode with one or more particles of a LixSiy alloy by scattering a plurality of particles onto the surface of an electrode comprising a current collector and a layer of active material disposed thereon, wherein the plurality of particles are in a substantially solvent-free powder form and are applied in a single step, at least about 95 volume percent of the particles are in the size range of about 1 micrometer to about 70 micrometers, each of the LixSiy alloys contains lithium in a content range of about 15 wt% to about 60 wt%, the contact of the electrode is performed on the surface of the electrode, and the active material is selected from the group consisting of graphite, silicon, silicon oxide(s), and graphite combined with silicon and / or silicon oxide(s).

Description

Background Art

[0001] Lithium-ion batteries are used in various household appliances and are increasingly being adopted in electric vehicles. Researchers and developers are focusing on improving the performance of lithium-ion batteries for such applications. In this regard, anode materials such as graphite, silicon, silicon oxide(s), and graphite combined with silicon and / or silicon oxide(s) have been used / tested. One concern with such anode materials is the loss of lithium during cycling. Of particular concern is the lithium loss in the first cycle, as lithium loss is typically large in the first cycle.

[0002] Prelithiation of the anode material can help compensate for lithium loss in lithium-ion batteries. To the best knowledge of the present inventors, fine lithium metal powder is the most commonly used commercially available prelithiation additive. However, there are several issues with using lithium metal powder to prelithiate the anode, which hinder its application. For example, the inherent lightness of lithium metal powder and the electrostatic force between particles make it prone to floating and also prone to causing significant issues regarding safe handling and accurate application and dosing; also, the high reactivity of lithium metal makes it difficult to adapt to industrial battery production lines.

[0003] Attempts have been made to address these challenges. For example, in "Artificial Solid Electrolyte Interphase-Protected LixSiy Nanoparticles: An Efficient and Stable Prelithiation Reagent for Lithium-Ion Batteries," Zhao et al. state: "We recently demonstrated that LixSiy nanoparticles (NPs) synthesized by thermal alloying can function as high-capacity prelithiation reagents, but their chemical stability in battery processing environments continues to improve." Zhao et al. further state: "Currently, the only industrial prelithiation reagents in powder form are microscale stabilized lithium metal powders (SLMPs) (FMC Lithium Corp.), which effectively compensate for the irreversible capacity loss in the first cycle of various anode materials, such as SiO and Si-CNT composites. However, synthesizing SLMPs in the laboratory is difficult, and other practical challenges continue to be addressed." See J. Am.Chem.Soc., 2015, 137(26), pp 8372-8375. In this same publication, Zhao et al. propose a surface modification method to improve the stability of LixSiy nanoparticles by forming a continuous and dense coating by utilizing the reduction of 1-fluorodecane on the LixSiy surface. However, the application of such surface treatment techniques is costly and cumbersome to implement in an industrial production environment. Furthermore, dense coatings can degrade the performance of Li-containing particles.

[0004] Therefore, there is a need for novel and improved methods for pre-lithifying anodes, such as silicon-based anodes, in particular methods that effectively prevent irreversible lithium loss during the first charge-discharge cycle. [Overview of the project]

[0005] The invention described herein is a method for pre-lithitating an electrode, comprising contacting the electrode with a plurality of particles of one or more LixSiy alloys, wherein at least about 95 volume percent of the particles are in the size range of about 1 micrometer to about 200 micrometers, and each of the LixSiy alloys is about 10 Mass % ~about 90 Mass % The above requirements are met by providing the above method which includes lithium having a content in the range of . Furthermore, at least one of the LixSiy alloys is about 10 Mass % ~about 70 Mass % The range, or approximately 15 Mass % ~about 60 Mass % The range, or about 40 Mass % ~about 50 Mass % The present invention provides a method having a lithium content in the range of . Furthermore, the present invention provides a method in which two or more of the particles are in the size range of about 1 micrometer to about 150 micrometers, or about 1 micrometer to about 70 micrometers, or about 1 micrometer to about 50 micrometers. Furthermore, the present invention provides a method in which at least one of the LixSiy alloys is in contact with an organic material. Furthermore, the present invention provides a method in which at least one of the LixSiy alloys is in contact with an inorganic material. Furthermore, the present invention provides a method in which the electrode is a graphite-based electrode or a silicon-based electrode. Furthermore, the present invention provides a method in which the pre-lithification of the electrode is carried out substantially in the absence of a solvent. Furthermore, the present invention provides a method in which the pre-lithification of the electrode is carried out in the presence of a solvent. Furthermore, the present invention provides a method in which the pre-lithification of the electrode is carried out on the surface of the electrode. Furthermore, the present invention provides an electrode pre-lithified by the method of this invention, a battery comprising such an electrode, a battery in which the electrode is an anode, and a battery in which the anode is adapted to release a greater amount of lithium when the battery undergoes a first charge-discharge cycle than would be released if the anode had not been pre-lithified by the method of this invention.

[0006] In addition, the inventions described herein provide a pre-lithified electrode by the method described herein; and also provide a battery comprising such electrode, wherein such electrode may be either an anode or a cathode. In particular, a battery comprising an anode and a cathode is provided, wherein the anode is pre-lithified by the method of the present invention and is adapted to receive and store lithium released from the cathode, and to release more lithium during the first charge-discharge cycle than would be released if the anode had not been pre-lithified by the method of the present invention. Under certain conditions, as can be determined by a person skilled in the art assuming the teachings of this application, at least a portion to substantially all of the lithium may be released from the pre-lithified anode as the battery undergoes the first charge-discharge cycle. The amount of lithium released from the pre-lithified anode depends, as is well known to a person skilled in the art, on the operating and processing conditions, and on the state of the lithium in the LixSiy alloy(s) used during pre-lithification, for example, whether such lithium is active or inactive. Based on the teachings of this specification, a person skilled in the art can prepare a pre-lithified anode which is adapted to release more lithium during the first charge-discharge cycle than would be released if the anode had not been pre-lithified by the method of this invention.

[0007] Various LixSiy alloys are known to be used as anode materials in lithium batteries. However, as an active material, the capacity of LixSiy rapidly decreases during cycling. In "Li-Rich Li-Si Alloy As A Lithium-Containing Negative Electrode Material Towards High Energy Lithium-Ion Batteries" by Iwamura et al., the following is described: "Shigematsu's group found that the first delithiation and lithium-ion capacities of Li21Si5 were 650 and 300 mAhg."-1 -Li21Si5, which produced 37mAhg in the fourth cycle. -1 -It has been reported that the value decreases rapidly down to Li21Si5.

[0008] The inventors have found that micrometer-sized LixSiy molecules / particles are highly stable in a drying chamber and even in NMP (N-methyl-2-pyrrolidone), a solvent commonly used in the lithium-ion battery industry. Furthermore, they found that such molecules / particles are considerably more stable in humidified air than expected. In addition, these micrometer-sized LixSiy molecules / particles exhibited unexpectedly high pre-lithiation efficiency. All of this is demonstrated by the following considerations.

[0009] The above invention will be better understood by referring to the figures. [Brief explanation of the drawing]

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

[0011] In certain embodiments of the inventions described herein, at least one LixSiy alloy is about 10 Mass % ~about 90 Mass %It has a lithium content in the range of . In certain embodiments of the invention described herein, at least one of the LixSiy alloys is about 10 Mass % ~about 70 Mass % It has a lithium content in the range of . In certain embodiments of the invention described herein, at least one of the LixSiy alloys is about 15 Mass % ~about 60 Mass % It has a lithium content in the range of . In certain embodiments of the invention described herein, at least one of the LixSiy alloys is about 40 Mass % ~about 50 Mass % It has a lithium content within the range of 19.8. For illustrative purposes only, without limiting this invention, Mass % A known LixSiy alloy having a lithium content of 50.9 Mass % There are known LixSiy alloys having lithium content, and the lithium content of these alloys is suitable for use in the method of this invention.

[0012] In certain embodiments of the inventions described herein, at least about 95 volume percent of the plurality of particles are in the size range of about 1 micrometer to about 200 micrometers. In other embodiments, at least about 97 volume percent, or at least about 99 volume percent, or about 100 volume percent of the plurality of particles are in the size range of about 1 micrometer to about 200 micrometers. In certain embodiments of the inventions described herein, two or more of the particles are in the size range of about 1 micrometer to about 50 micrometers.

[0013] In certain embodiments of the inventions described herein, at least one LixSiy alloy is coated. In certain embodiments of the inventions described herein, at least one LixSiy alloy is coated with an organic substance. In certain embodiments of the inventions described herein, at least one LixSiy alloy is coated with an inorganic substance.

[0014] The terms “coated” and “surface-treated” have the same meaning as used herein, i.e., a LixSiy alloy being coated or surface-treated is in contact with or has been in contact with a substance that coats or surface-treated the alloy, and optionally subsequently subjected to or has been subjected to a treatment such as heat treatment. Referring to Example 11, the LixSiy alloy is coated (surface-treated) with an organic substance. Referring to Example 12, the LixSiy alloy is coated (surface-treated) with an organic substance.

[0015] In certain embodiments of the inventions described herein, the prelithiation of an electrode with the LixSiy alloy described herein is carried out in the presence of a solvent. Suitable solvents, including NMP, are known to those skilled in the art. In other embodiments of the inventions described herein, the prelithiation of an electrode is carried out substantially in the absence of a solvent. When used herein, “substantially in the absence of a solvent” is intended to indicate that a solvent is not intentionally introduced into the prelithiation process. In certain embodiments of the inventions described herein, the electrode is graphite-based or silicon-based. In certain embodiments of the inventions described herein, the prelithiation of an electrode is carried out on at least a portion of at least one surface of the electrode. In certain embodiments of the inventions described herein, the prelithiation of an electrode is carried out by combining one or more of the LixSiy alloys described herein with one or more conductive additives to form a combination, and by bringing at least a portion of the electrode into contact with the combination. Suitable conductive additives are known to those skilled in the art and include, but are not limited to, carbon black. In certain embodiments of the inventions described herein, prelithiation of an electrode is performed by combining one or more LixSiy alloys with a conductive additive, a binder, and optionally other suitable additives well known to those skilled in the art, and by bringing at least a portion of the electrode into contact with the combination. In certain embodiments of the inventions described herein, prelithiation of an anode is performed by blending one or more LixSiy alloys with various additives, an anode active material, and a solvent, and then coating the mixture onto a current collector to form an electrode. The solvent is coated or uncoated Li x Si y Any solvent compatible with the alloy may be used, and may contain NMP.

[0016] As is well known to those skilled in the art, typically, an electrode includes a portion or layer known as a "current collector", and a portion or layer including graphite, silicon, silicon oxide(s), or graphite combined with silicon and / or silicon oxide(s). In an anode, the current collector typically includes copper. In a cathode, the current collector typically includes aluminum. In certain aspects of the invention described herein, pre-lithiation of an electrode is performed by contacting one or more LixSiy alloys with one or more suitable substances including an additive, an active material, or a solvent, and then contacting the current collector with one or more LixSiy alloys. The current collector is then combined with a portion or layer including graphite, silicon, silicon oxide(s), or graphite combined with silicon and / or silicon oxide(s) to form an electrode. The solvent may be any solvent suitable for use with the LixSiy alloy, such as NMP.

[0017] Various LixSiy alloys suitable for use in the invention described herein can be produced thermochemically or electrochemically. Depending on the reaction parameters, Li21Si5, Li4.7Si2, Li12Si7, and other such LixSiy alloys with varying lithium contents can be formed. Also, these LixSiy alloys can be pulverized and sieved, such that the resulting LixSiy alloy powder has a certain desired particle size and can be collected. These types of LixSiy alloys are commercially available, for example, from Albemarle Corporation.

[0018] The electrodes can be lithiated / pre-lithiated with the LixSiy alloy particles according to the invention described herein by any suitable method, as is well known to those skilled in the art, including those carried out in the presence of a solvent and those carried out in the absence of a solvent. As used herein, the terms "being lithiated" and "being pre-lithiated" should also be used interchangeably. Some or substantially all of the lithium from such pre-lithiated electrodes will be released during the first charge-discharge cycle of a battery containing the anode. The amount of lithium released depends on the operating and processing conditions, as well as the state of lithium in the LixSiy alloy used for pre-lithiation, e.g., whether such lithium is active or inactive, all of which are well known to those skilled in the art. This release of lithium is an amount suitable to compensate for some or all of the inherent first-cycle loss of lithium, mainly into graphite or silicon anodes. For example, the release of lithium from such pre-lithiated anodes is greater than the release when the same anode was not pre-lithiated by the method of this invention. As shown by the examples and related figures, the first-cycle loss can be substantially completely compensated by the lithiation / pre-lithiation method of this invention.

[0019] The pre-lithiation methods described herein are suitable for any electrode well known to those skilled in the art, and are particularly well suited for graphite-based electrodes and silicon-based electrodes. Any such electrode may already contain some lithium. The pre-lithiation methods described herein are suitable for any anode and / or any cathode.

Examples

[0020] The following examples illustrate the principles of this invention. It is understood that this invention is not limited to any one specific embodiment illustrated herein in any example or the remainder of this patent application.

[0021] Example 1 44 Mass % A lithium silicon alloy having a Li content was pulverized using a rotary mill and sieved using US standard sieves; powders between 80 mesh and 200 mesh were collected. The nominal sieve openings of the 80 mesh and 200 mesh sieves are 177 microns and 74 microns, respectively. Approximately 1 gram of the obtained powder was transferred to a weighing bottle in a glove box filled with argon. The sealed weighing bottle was then transferred to a drying room with a dew point of -40°C. The sample was exposed to the air in the drying room and the change in weight of the sample was recorded. Any weight increase suggests a lithium reaction. After the first 6 hours, there was a negligible weight change (0.05%). The inventors further measured a negligible weight change (-0.1%) even after 1 day (24 hours).

[0022] Example 2 (Comparative Example) Approximately 1 gram of commercially available lithium powder, having a lithium content of >99% and a particle size of approximately 50 micrometers, was transferred to a weighing bottle in a glove box filled with argon. The sealed weighing bottle was then transferred to a drying room with a dew point of -40°C. The sample was exposed to the air in the drying room and the change in sample weight was recorded. The inventors measured a weight loss of 0.2% of the lithium powder, which was caused by the volume of the powder that buoyed.

[0023] Example 3 Approximately 0.6 grams of the same lithium-silicon powder used in Example 1 was transferred to a weighing bottle in a glove box filled with argon. The sealed weighing bottle was then placed in a laboratory fume hood with ambient air. The temperature was recorded as 25°C and the relative humidity as 55.6%. The sample was exposed to ambient air, and no combustion was observed.

[0024] Example 4 Some of the same lithium silicon alloy powder used in Example 1 was scattered onto a pre-fabricated graphite anode (graphite:conductive additive:binder = 88:5:7, 4.7 mg / cm2 added, porosity 40%), and then rolled with a rolling pin. The resulting anode was a graphite layer doped with LixSiy powder.

[0025] Example 5 A coin cell, identified as "Cell Number 1," was assembled from the anode obtained in Example 4, using lithium foil as the counter electrode and 1 M LiPF6 in 3 / 7EC / EMC (ethylene carbonate / ethyl methyl carbonate) as the electrolyte. The open-circuit voltage (OCV) of the cell was measured to be approximately 0.46 V. The cell was left standing at OCV for 12 hours, and then the lithiation process (Step 1) was started at C / 20 when the voltage reached 0.002 V. The subsequent delithiation (Step 2) was also started at C / 20 when the voltage reached 1.5 V. The specific capacities recorded are shown in Figure 1, along with the lithiation capacity of graphite (412 mAh / g) and the delithiation capacity of graphite (457 mAh / g).

[0026] As shown in this embodiment, the delithiation capacity in the first cycle was shown to be higher than the lithiation capacity, which suggests that this LixSiy powder from Example 1 can function as a pre-lithiation agent in lithium-ion batteries.

[0027] Example 6 The coin cell identified as "Cell No. 2" was also assembled and tested from the anode obtained from Example 4, using lithium foil as the counter electrode and 1M LiPF6 in 3 / 7EC / EMC as the electrolyte. The results are shown in Figure 2. The OCV of Cell No. 2 was recorded as 0.47V, the lithiation capacity (see Step 1) was recorded as 402mAh / g graphite, and the delithiation capacity (see Step 2) was recorded as 428mAh / g graphite.

[0028] As shown in this embodiment, the delithiation capacity in the first cycle was shown to be higher than the lithiation capacity, which suggests that this LixSiy powder from Example 1 can function as a pre-lithiation agent in lithium-ion batteries.

[0029] Example 7 A coin cell, identified as "cell number 3," was assembled from the anode obtained from Example 4, using lithium foil as the counter electrode and 1M LiPF6 in 3 / 7EC / EMC as the electrolyte. The cell's open-circuit voltage (OCV) was measured to approximately 0.47V. The cell was left standing at OCV for 12 hours, and then the delithiation process (step 1) was started at C / 20 when the voltage reached 1.5V. As shown in Figure 3, this initial delithiation capacity was recorded as 48.9mAh / g of graphite for cell number 3. (For comparison, a typical graphite anode without any prior lithiation would have a near-zero initial delithiation capacity when tested using the first delithiation step, as it would not contain lithium.) As shown in Figure 3, cell number 3 was then lithiated at C / 20 when the voltage reached 0.002V (step 2). The subsequent delithiation (step 3) was also performed at C / 20 when the voltage reached 1.5V. The specific capacities recorded are shown in Figure 3, along with the lithium-ionized capacity of graphite (450 mAh / g) and the delithiation-ionized capacity of graphite (406 mAh / g).

[0030] As shown in this embodiment, cells having a graphite layer doped with LixSiy powder from Example 1 demonstrated a delithiation capacity of 48.9 mAh / g regardless of the lithiumization cycle, suggesting that this LixSiy powder can function as a pre-lithiation agent in lithium-ion batteries.

[0031] Example 8 The coin cell identified as cell number 1 from Example 7 was cycled more than three times at C / 10 after the initial C / 20 cycle. The Coulomb efficiency (CE) was given by Equation 1 [CE = delithiation capacity / lithiation capacity]. * Calculated using [100%]. As shown in Figure 4, the first CE is higher than 100%, and the CE for the remaining cycles is 99%.

[0032] Example 9 44 Mass % A lithium silicon alloy with a Li content was pulverized by a centrifugal mill and sieved using a US standard sieve; powder with a mesh size of less than 325 was collected. The nominal mesh opening of a 325-mesh sieve is 44 microns. Approximately 1 gram of the obtained powder was transferred to a weighing bottle in a glove box filled with argon, and the weight increase in a drying chamber (dew point of -41.4°C) was recorded as 0.7% after the first 7 hours.

[0033] Example 10(a) In a glove box filled with argon, 14.015 grams of lithium rods and 11.022 grams of silicon chips were placed in a tantalum crucible, and 56.0 Mass % A target lithium silicon alloy with a lithium content of was used. The crucible was then placed in an oven inside a glove box and heated to 750°C, stirred, and heated for a further 1 hour. The resulting alloy was poured into a cooling tray. After cooling to room temperature, the alloy was crushed with a hammer and then transferred to a ball mill. The material was ground in the ball mill using 10 mm stainless steel balls at 100 rpm, 300 rpm, and 400 rpm for various periods. The alloy after grinding was not fractured, but consisted of large, damaged aggregates, suggesting that the material was too soft to be ground into a powder.

[0034] Example 10(b) In a glove box filled with argon, 5.718 grams of lithium rods and 19.245 grams of silicon chips were placed in a tantalum crucible, and 22.9 Mass %A target lithium silicon alloy with a lithium content of was used. The crucible was then placed in an oven inside a glove box and heated to 700°C, stirred, and heated for a further 1 hour. The resulting alloy was poured into a cooling tray. After cooling to room temperature, the alloy was crushed with a hammer and then transferred to a ball mill. The material was ground in the ball mill using 3 mm stainless steel balls at 100 rpm for 1 hour, and then at 300 rpm for 30 minutes. The resulting powder material was sieved using a US standard sieve; the powder that passed through the 325 mesh sieve was collected.

[0035] The actual lithium content of the obtained material was determined to be 22.3% by acid titration. Mass % The material obtained by XRD (X-ray diffraction) was Li 12 It was confirmed to contain Si7.

[0036] Approximately 1 gram of the obtained powder was transferred to a weighing bottle in a glove box filled with argon, and the weight increase in a drying room (dew point of -41.4°C) was recorded as 0.7% after the first 7 hours.

[0037] Some of the sieved lithium silicon alloy powder was scattered onto a pre-fabricated graphite anode (graphite:conductive additive:binder = 88:5:7, 7.1 mg / cm2 added, porosity 40%), and then rolled with a spatula. The amount of LixSiy powder added was measured to be approximately 1.05 mg / cm2.

[0038] Five coin cells were assembled from the obtained anodes using lithium foil as the counter electrode and 1M LiPF6 in 3 / 7EC / EMC as the electrolyte. The open-circuit voltage (OCV) of the cells was measured to be approximately 0.597V to 0.634V. The cells were left standing at OCV for 12 hours, and then delithiation was started at C / 20 when the voltage reached 1.5V. The average initial delithiation capacity was recorded as 37.8mAh / g of graphite.

[0039] Example 11 A portion (15 grams) of lithium silicon alloy powder from Example 9, containing 44% lithium and sieved through a 325-mesh screen, was mixed in a glass flask under an argon atmosphere with 33.2 mL of 2% LiBOB solution (LiBOB = lithium bis(oxalato)borate) in anhydrous PC / DMC (1:1 wt / wt; PC = propylene carbonate; DMC = dimethyl carbonate) and stirred at room temperature for 2 hours. The resulting suspension was filtered in the absence of air, dried under vacuum at room temperature, heated to 200°C, and then dried again under vacuum. After sieving through a 325-mesh screen, 12 grams of gray powder was collected. New exothermic reactions could be observed in the DSC of the treated lithium silicon alloy, which were not present in the untreated lithium silicon alloy.

[0040] Approximately 1 gram of the obtained LiBOB-treated powder was transferred to a weighing bottle in a glove box filled with argon, and the negligible weight increase in the drying chamber (dew point -42.6°C) was recorded after the first 7 hours (-0.06). Mass % ).

[0041] Some of the sieved LiBOB-treated lithium silicon alloy powder is mixed with a pre-fabricated graphite anode (graphite:conductive additive:binder = 88:5:7, 7.1 mg / cm³). 2 The mixture was added, scattered on a surface with a porosity of 40%, then rolled with a spatula, and the lithium silicon powder was added at a rate of approximately 1.05 mg / cm³. 2 It was measured as follows.

[0042] Five coin cells were assembled from the obtained anodes using lithium foil as the counter electrode and 1M LiPF6 in 3 / 7EC / EMC as the electrolyte. The open-circuit voltage (OCV) of the cells was measured to be approximately 0.460V to 0.467V. The cells were left standing at OCV for 12 hours, and then the delithiation process was started at C / 20 when the voltage reached 1.5V. The average initial delithiation capacity was recorded as 64.1 mAh / g of graphite.

[0043] Example 12 44 Mass % A lithium silicon alloy with a Li content was pulverized by a centrifugal mill and sieved using a US standard sieve; powder with a mesh size of less than 325 was collected. The nominal mesh opening of a 325-mesh sieve is 45 microns. Approximately 10 grams of the obtained powder was transferred to a stainless steel crucible. Polyisobutylene (PIB; average molecular weight approximately 1,000,000) in hexane. Mass % The solution was added until all the powders were wet. Approximately 6 grams of PIB were used in the hexane solution. The alloy and polymer solutions were stirred until homogeneous. The crucible was then placed in an oven inside an argon glove box and heated to 600°C. The oven was maintained at 600°C for 3 hours, then the crucible was removed and allowed to cool to room temperature.

[0044] Approximately 1 gram of the obtained powder was transferred to a weighing bottle in a glove box filled with argon, and the weight increase in a drying chamber (dew point of -42.6°C) was recorded as 0.5% after the first 8 hours. XRD (X-ray diffraction) confirmed that the obtained material contained Li12Si7, and the carbon content in the obtained material was approximately 0.14% when measured with a TOC (Total Organic Carbon) analyzer.

[0045] Example 13 A portion (5.0 grams) of the lithium silicon alloy powder from Example 9, containing 44% lithium and particles sieved through a 325-mesh screen, was prepared as a slurry in a drying chamber with the following formulation: -97% Lithium Silicon Alloy Powder -2% PIB binder -1% conductive additive - Hexane as a solvent - Approximately 37.5% solids A pre-fabricated graphite anode (graphite:conductive additive:binder = 88:5:7, 7.1 mg / cm2 added, porosity 40%) was brought into contact with the obtained slurry using a doctor blade on a slip table. After air drying, the obtained anode contained graphite with a surface layer containing 97% lithium silicon alloy.

[0046] Five coin cells were assembled from air-dried anodes using lithium foil as the counter electrode and 1M LiPF6 in 3 / 7EC / EMC as the electrolyte. The open-circuit voltage (OCV) of the cells was measured to be approximately 0.4V. The cells were left standing at OCV for 12 hours, and then the delithiation process was started at C / 20 when the voltage reached 1.5V. The average initial delithiation capacity was recorded as 90mAh / g of graphite.

[0047] Example 14 A portion (5.0 grams) of the lithium silicon alloy powder from Example 9, containing 44% lithium and particles sieved through a 325-mesh screen, was prepared as a slurry in a drying chamber with the following formulation: -97% Lithium Silicon Alloy Powder -2% PVDF (Polyvinylidene (di)fluoride) Binder -1% conductive additive - Hexane as a solvent - Approximately 43.4% solids A pre-fabricated graphite anode (graphite:conductive additive:binder = 88:5:7, 7.1 mg / cm2 added, porosity 40%) was brought into contact with the resulting slurry using a doctor blade on a slip table, and then dried in a vacuum oven at 50°C for 20 minutes. The resulting anode contained graphite with a surface layer containing 97% lithium silicon alloy.

[0048] Two coin cells were assembled from oven-dried anodes using lithium foil as the counter electrode and 1M LiPF6 in 3 / 7EC / EMC as the electrolyte. The open-circuit voltage (OCV) of the cells was measured to be approximately 0.470V.

[0049] advantage This invention is advantageous in that certain Li alloys are more stable than Li itself. For example, about 10-90 Mass %LixSiy alloy powder having a Li content is stable for more than 24 hours in a drying chamber and is quite stable in humidified air; it is considerably easier to handle compared to Li itself, thereby considerably facilitating the application and administration process when applied to electrodes.

[0050] Although the present invention has been described in terms of one or more preferred embodiments, it should be understood that other modifications may be made without departing from the scope of the invention as described in the following claims.

Claims

1. A method for pre-lithifying an electrode, comprising contacting the electrode with a plurality of particles of one or more LixSiy alloys, wherein at least about 95 volume percent of the particles are in the size range of about 1 micrometer to about 200 micrometers, and each of the LixSiy alloys contains lithium in the range of about 10% to about 90% by weight.

2. The method according to claim 1, wherein at least one of the LixSiy alloys has a lithium content in the range of about 10% by weight to about 70% by weight.

3. The method according to claim 1, wherein at least one of the LixSiy alloys has a lithium content in the range of about 15% by weight to about 60% by weight.

4. The method according to claim 1, wherein at least one of the LixSiy alloys has a lithium content in the range of about 40% by weight to about 50% by weight.

5. The method according to claim 1, wherein two or more of the particles are in the size range of about 1 micrometer to about 150 micrometers.

6. The method according to claim 1, wherein two or more of the particles are in the size range of about 1 micrometer to about 70 micrometers.

7. The method according to claim 1, wherein two or more of the particles are in the size range of about 1 micrometer to about 50 micrometers.

8. The method according to claim 1, wherein at least one of the LixSiy alloys is in contact with an organic substance.

9. The method according to claim 1, wherein at least one of the LixSiy alloys is in contact with an inorganic substance.

10. The method according to claim 1, wherein the electrode is a graphite-based electrode or a silicon-based electrode.

11. The method according to claim 1, wherein the pre-lithiation of the electrode is carried out substantially in the absence of a solvent.

12. The method according to claim 1, wherein the prelithiation of the electrode is carried out in the presence of a solvent.

13. The method according to claim 1, wherein the pre-lithiation of the electrode is performed on the surface of the electrode.

14. An electrode pre-lithified by the method described in claim 1.

15. A battery comprising the electrode described in claim 14.

16. The battery according to claim 15, wherein the electrode is an anode.

17. The anode, when the battery undergoes the first charge-discharge cycle, releases more than would be released if the anode had not been pre-lithified by the method described in claim 1. The battery according to claim 16, which is adapted to release an amount of lithium.

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