Method for manufacturing negative electrode of battery pack

Abstract

The present invention discloses a method for manufacturing a negative electrode for manufacturing a battery pack. A method for manufacturing an electrode material for an electrode in an electrochemical cell for cycling lithium ions is provided, wherein a protective coating is applied to an electrode precursor material. The electrode precursor may be a composition containing silicon. The protective coating is selected from: an oxide-based coating, a fluoride-based coating, and a nitride-based coating. The method also includes lithiating the electrode precursor material in a continuous process. The continuous process is performed in a reactor having a first reaction chamber and a second reaction chamber to form a lithiated electrode material including the protective coating.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a negative electrode material for an electrochemical cell that cycles lithium ions, and a method for manufacturing an electrode material for an electrode in an electrochemical cell that cycles lithium ions. Background Art

[0002] This section provides background information related to the present disclosure which is not necessarily prior art.

[0003] The present disclosure relates to a continuous method of forming a pre-lithiated electroactive material with a protective coating for a negative electrode of a lithium-ion electrochemical cell.

[0004] Lithium-ion batteries can be used in a variety of consumer products and vehicles. Typical electrochemically active materials used to form the negative electrode or anode of such batteries include lithium-graphite intercalation compounds, lithium-silicon alloying compounds, lithium-tin alloying compounds, and lithium alloys. Although graphite compounds are the most common, there has been an increased interest in anode materials with high specific capacities (compared to conventional graphite) recently. For example, silicon has the highest known theoretical lithium loading capacity, making it one of the most promising materials for rechargeable lithium-ion batteries.

[0005] However, current silicon-containing negative electrode materials can potentially suffer from serious disadvantages. For example, during the initial lithiation and delithiation cycles, silicon-based electroactive materials can experience excessive volume expansion and contraction. In addition, the initial lithiation process of silicon-based electroactive materials can promote the improvement of surface roughness. In addition, additional volume changes can occur during the successive charge and discharge cycles of silicon electroactive materials. Such volume changes can lead to fatigue cracking and burning of electroactive materials. This can potentially lead to the loss of electrical contact between the silicon-containing electroactive material and the rest of the battery cell and the consumption of electrolyte to form a new solid electrolyte interface (SEI), resulting in a decrease in electrochemical cycling performance, reduced Coulomb charge capacity retention (capacity decay) and limited cycle life.

[0006] This is particularly true at the electrode loading levels required to use electrodes containing silicon in high energy lithium ion batteries such as those used in transportation applications. It would therefore be desirable to develop methods of making electroactive materials containing silicon, or other electroactive materials that undergo significant volume changes during lithium ion cycling, that can minimize capacity fade and maximize charge capacity in commercial lithium ion batteries with long life, particularly for transportation applications. Summary of the invention

[0007] This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[0008] The present disclosure relates to a method for manufacturing an electrode material for an electrochemical cell that cycles lithium ions. In certain aspects, the method includes applying a protective coating to a negative electrode precursor by atomic layer deposition (ALD) in a first reaction chamber of a reactor. The negative electrode precursor includes silicon. The protective coating is selected from: an oxide-based coating, a fluoride-based coating, and a nitride-based coating. The method also includes transferring the negative electrode precursor to a second reaction chamber of the reactor, and lithiating the negative electrode precursor to form a negative electrode material including the protective coating and a coating containing lithium.

[0009] In one aspect, the protective coating is selected from the group consisting of aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin oxide (SnO2), zinc oxide (ZnO), lithium fluoride (LiF), aluminum fluoride (AlF3), aluminum oxyfluoride (AlFO), aluminum nitride (AlN), silicon nitride (SiN), and combinations thereof.

[0010] In one aspect, the protective coating comprises aluminum oxide (Al2O3).

[0011] In one aspect, lithiation is performed by thermal evaporation.

[0012] In one aspect, the first reaction chamber defines a plurality of deposition zones.

[0013] In a further aspect, the plurality of deposition zones each include a first region for introducing an oxidant and a second region for introducing one or more ALD precursors.

[0014] In one aspect, the reactor is a vacuum chamber defining a first reaction chamber and a second reaction chamber.

[0015] In one aspect, the protective coating has a thickness of greater than or equal to about 1 nm to less than or equal to about 25 nm.

[0016] In one aspect, the lithium-containing coating has a thickness of greater than or equal to about 1 micron to less than or equal to about 50 microns.

[0017] In one aspect, the method is performed continuously in a roll-to-roll process.

[0018] The present disclosure also relates to a method of manufacturing an electrode material for an electrode in an electrochemical cell that circulates lithium ions. The method includes applying a protective coating selected from: an oxide-based coating, a fluoride-based coating, and a nitride-based coating to an electrode precursor material. The method further includes lithiation of the electrode precursor material, the lithiation occurring in a continuous process performed in a reactor having a first reaction chamber and a second reaction chamber. In this manner, the method forms a lithiated electrode material including a protective coating.

[0019] In one aspect, the method further comprises applying a protective coating on the electrode precursor material in the first reaction chamber, and lithiating the electrode precursor material in the second reaction chamber. Alternatively, the method comprises lithiating the electrode precursor material in the first reaction chamber; and applying a protective coating on the electrode precursor material in the second reaction chamber.

[0020] In one aspect, the protective coating is selected from the group consisting of aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin oxide (SnO2), zinc oxide (ZnO), lithium fluoride (LiF), aluminum fluoride (AlF3), aluminum oxyfluoride (AlFO), aluminum nitride (AlN), silicon nitride (SiN), and combinations thereof.

[0021] In one aspect, the protective coating comprises aluminum oxide (Al2O3).

[0022] In one aspect, the application of the protective coating is an atomic layer deposition (ALD) process.

[0023] In one aspect, the first reaction chamber defines a plurality of deposition zones, each of which includes a first region for introducing an oxidant and a second region for introducing one or more ALD precursors.

[0024] In one aspect, lithiation is performed by thermal evaporation.

[0025] In one aspect, the reactor is a vacuum chamber defining a first reaction chamber and a second reaction chamber.

[0026] In one aspect, the protective coating has a thickness of greater than or equal to about 1 nm to less than or equal to about 25 nm. The lithium-containing coating optionally has a thickness of greater than or equal to about 1 micron to less than or equal to about 50 microns.

[0027] In one aspect, the method is performed continuously in a roll-to-roll process.

[0028] The present invention discloses the following clauses:

[0029] 1. A method for manufacturing a negative electrode material for an electrochemical cell for circulating lithium ions, the method comprising:

[0030] applying a protective coating onto a negative electrode precursor by atomic layer deposition (ALD) in a first reaction chamber of a reactor, wherein the negative electrode precursor comprises silicon and the protective coating is selected from: an oxide-based coating, a fluoride-based coating; and

[0031] The negative electrode precursor is transferred to a second reaction chamber of the reactor, and the negative electrode precursor is lithiated to form a negative electrode material comprising a protective coating and a coating containing lithium.

[0032] 2. The method according to clause 1, wherein the protective coating is selected from the group consisting of aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin oxide (SnO2), zinc oxide (ZnO), lithium fluoride (LiF), aluminum fluoride (AlF3), aluminum oxyfluoride (AlFO), aluminum nitride (AlN), silicon nitride (SiN) and combinations thereof.

[0033] 3. The method of clause 1, wherein the protective coating comprises aluminum oxide (Al2O3).

[0034] 4. The method according to clause 1, wherein the lithiation is carried out by thermal evaporation.

[0035] 5. The method of clause 1, wherein the first reaction chamber defines a plurality of deposition zones.

[0036] 6. The method of clause 5, wherein the plurality of deposition zones each comprises a first region for introducing an oxidant and a second region for introducing one or more ALD precursors.

[0037] 7. The method of clause 1, wherein the reactor is a vacuum chamber defining a first reaction chamber and a second reaction chamber.

[0038] 8. The method of clause 1, wherein the protective coating has a thickness of greater than or equal to about 1 nm to less than or equal to about 25 nm.

[0039] 9. The method of clause 1, wherein the lithium-containing coating has a thickness of greater than or equal to about 1 micron to less than or equal to about 50 microns.

[0040] 10. The method of clause 1, wherein the method is performed continuously in a roll-to-roll process.

[0041] 11. A method for producing an electrode material for an electrode in an electrochemical cell for cycling lithium ions, the method comprising:

[0042] A protective coating selected from the group consisting of an oxide-based coating, a fluoride-based coating, and a nitride-based coating is applied to an electrode precursor material in a continuous process conducted in a reactor having a first reaction chamber and a second reaction chamber, and the electrode precursor material is lithiated to form a lithiated electrode material including the protective coating.

[0043] 12. The method of clause 11, further comprising applying a protective coating on the electrode precursor material in the first reaction chamber; and lithiating the electrode precursor material in the second reaction chamber; or

[0044] An electrode precursor material is lithiated in a first reaction chamber; and a protective coating is applied to the electrode precursor material in a second reaction chamber.

[0045] 13. The method according to clause 11, wherein the protective coating is selected from the group consisting of: aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin oxide (SnO2), zinc oxide (ZnO), lithium fluoride (LiF), aluminum fluoride (AlF3), aluminum oxyfluoride (AlFO), aluminum nitride (AlN), silicon nitride (SiN) and combinations thereof.

[0046] 14. The method of clause 11, wherein the protective coating comprises aluminum oxide (Al2O3).

[0047] 15. The method of clause 11, wherein the protective coating is applied by atomic layer deposition (ALD).

[0048] 16. The method of clause 11, wherein the first reaction chamber defines a plurality of deposition zones, each of which comprises a first region for introducing an oxidant and a second region for introducing one or more ALD precursors.

[0049] 17. The method according to clause 11, wherein the lithiation is carried out by thermal evaporation.

[0050] 18. The method of clause 11, wherein the reactor is a vacuum chamber defining a first reaction chamber and a second reaction chamber.

[0051] 19. The method of clause 11, wherein the protective coating has a thickness of greater than or equal to about 1 nm to less than or equal to about 25 nm.

[0052] 20. The method according to clause 11, wherein the method is performed continuously in a roll-to-roll process.

[0053] Further areas of applicability will become apparent from the description provided herein.The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The drawings described herein are for illustrative purposes only of selected embodiments and not all possible embodiments, and are not intended to limit the scope of the present disclosure.

[0055] Figure 1 is a schematic diagram of an exemplary electrochemical battery cell.

[0056] Figure 2 is an illustration of a cross-sectional view of a particle of a negative electroactive material having a multilayer coating including a lithium-containing coating and an atomic layer deposition (ALD) protective coating prepared according to certain aspects of the present disclosure.

[0057] Figure 3 is an illustration of a reactor for performing a continuous method for forming particles of negative electroactive material having a multi-layer coating according to certain aspects of the present disclosure, the reactor comprising a first reaction chamber for applying an ALD protective coating and a second connected reaction chamber for applying a coating containing lithium by thermal evaporation.

[0058] Figure 4 An illustration showing a cross-sectional view of a negative electrode incorporating a plurality of particles of a negative electroactive material having a multi-layer coating prepared according to certain aspects of the present disclosure, including a lithium-containing coating and an ALD protective coating.

[0059] Figure 5A Illustration showing a cross-sectional view of a negative electrode incorporating a plurality of negative electroactive material particles having a multi-layer coating, wherein an ALD protective coating is applied to a prefabricated electrode formed according to certain aspects of the present disclosure.

[0060] Figure 5B Illustration showing a cross-sectional view of a negative electrode incorporating a plurality of particles of negative electroactive material having multiple layers of coatings (including a lithium-containing coating and an ALD protective coating) applied to the electroactive particles, and which are subsequently formed into an electrode according to certain aspects of the present disclosure.

[0061] Figure 6 is an illustration of a reaction chamber for performing a continuous process for forming particles of negative electroactive material having a multi-layer coating according to certain aspects of the present disclosure, the reaction chamber comprising a first reaction chamber for applying a coating containing lithium by thermal evaporation and a connected second reaction chamber for applying an ALD protective coating.

[0062] Figure 7 An alternative variation of a reaction chamber for performing a continuous ALD process is shown.

[0063] Figure 8 An alternative variation of an illustration of a reactor for performing a continuous process for forming particles of negative electroactive material having a multi-layer coating according to certain aspects of the present disclosure is shown, the reactor comprising a first reaction chamber for applying an ALD protective coating and a second connected reaction chamber for applying a coating containing lithium by thermal evaporation.

[0064] Fig. 9 Comparative discharge capacity and capacity retention performance of an anode having uncoated silicon and an anode having silicon particles having a multilayer coating prepared according to certain aspects of the present disclosure, including a lithium-containing coating and an ALD protective coating, are shown.

[0065] Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0066] Exemplary embodiments are provided so that the present disclosure is complete and fully conveys the scope of the present disclosure to those skilled in the art. Many specific details, such as examples of specific compositions, components, devices and methods, are set forth to provide a full understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, and that the exemplary embodiments may be embodied in many different forms, and none of them should be considered to limit the scope of the present disclosure. In some exemplary embodiments, well-known methods, well-known device structures, and well-known technologies are not described in detail.

[0067] The terms used herein are only for describing specific exemplary embodiments, and are not intended to be limiting. Unless the context clearly indicates otherwise, as used herein, the singular forms "one", "an" and "the" may be intended to also include plural forms. The terms "comprise", "include", "cover" and "have" are compatible, and therefore specify the presence of the features, elements, compositions, steps, integers, operations and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. Although the open term "comprising" should be understood as a non-limiting term for describing and claiming the various embodiments described herein, in some aspects, the term may be understood as alternatively being a more restrictive and limited term, such as "consisting of..." or "consisting essentially of..." Thus, for any given embodiment of a narration composition, material, component, element, feature, integer, operation and / or method step, the present disclosure also specifically includes an embodiment consisting of or essentially consisting of such narrated compositions, materials, components, elements, features, integers, operations and / or method steps. In the case of “consisting of,” alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations, and / or method steps, while in the case of “consisting essentially of,” any additional compositions, materials, components, elements, features, integers, operations, and / or method steps that materially affect the basic and novel characteristics are excluded from such embodiments, but any compositions, materials, components, elements, features, integers, operations, and / or method steps that do not materially affect the basic and novel characteristics may be included in the embodiments.

[0068] Any method steps, processes, and operations described herein should not be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless expressly identified as being in an order of performance. It is also understood that additional or alternative steps may be employed unless otherwise stated.

[0069] When a component, element, or layer is referred to as being "on," "engaged," "connected," or "coupled" to another element or layer, it may be directly on, engaged, connected, or coupled to another component, element, or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being directly on, "directly engaged," "directly connected," or "directly coupled" to another element or layer, there may be no intervening elements or layers. Other words used to describe relationships between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated enumerated items.

[0070] Although the terms first, second, third, etc. can be used to describe various steps, elements, components, regions, layers and / or sections in this article, unless otherwise stated, these steps, elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish a step, element, component, region, layer or section from another step, element, component, region, layer or section. Unless the context clearly indicates, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in this article. Therefore, the first step, element, component, region, layer or section discussed below can be referred to as the second step, element, component, region, layer or section without departing from the teaching of exemplary embodiments.

[0071] For ease of description, spatially or temporally relative terms may be used herein, such as "before," "after," "inside," "outside," "below," "below," "lower," "upper," etc., to describe the relationship of one element or feature to other (one or more) elements or (one or more) features as shown in the drawings. The spatially or temporally relative terms may be intended to encompass different orientations of a device or system in use or operation other than the orientation shown in the drawings.

[0072] Throughout this disclosure, numerical values ​​represent approximate measurements or range limits to cover slight deviations from a given value and embodiments having approximately the values ​​mentioned and embodiments having exactly the values ​​mentioned. Except in the working examples provided at the end of the detailed description, all numerical values ​​of parameters (such as amounts or conditions) in this specification (including the appended claims) should be understood to be modified by the term "approximately" in all cases, regardless of whether "approximately" actually appears before the numerical value. "Approximately" means that the numerical value allows a certain slight imprecision (close to the exact value of the value to a certain extent; approximately or reasonably approximate the value; almost). If the imprecision provided by "approximately" is not understood in this art in this common sense, then "approximately" used herein refers to at least the deviation that can be caused by the common methods of measuring and using such parameters. For example, "approximately" may include less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and optionally less than or equal to 0.1% deviation in some aspects.

[0073] Additionally, disclosure of ranges includes disclosure of all values ​​within the entire range and further subdivided ranges, including endpoints and subranges given within those ranges.

[0074] As used herein, unless otherwise indicated, the terms "composition" and "material" are used interchangeably to refer broadly to a material containing at least a preferred chemical constituent, element or compound, but which may also contain additional elements, compounds or materials (including trace amounts of impurities).

[0075] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0076] The present disclosure provides methods for making improved electrodes (and electrochemical cells including improved electrodes) that enhance the robustness and integrity of active materials in the electrodes while reducing operational inefficiencies caused by, for example, loss of active lithium ions during the first battery cycle. In particular, the present disclosure provides methods for simultaneously lithiating an electroactive material (e.g., a silicon-based composition) of an electrode, such as pre-lithiating an electroactive material, and applying a mechanical protective coating to the electroactive material. The method can be performed in a reactor having separate reaction chambers. In this way, the processes of lithiation and applying a protective coating can be performed simultaneously without exposing the electrode / active material to the atmosphere, which saves time, eliminates the need to evacuate these chambers, and improves the quality of the formed electrode. Lithiation establishes a lithium reserve in the negative electrode of the battery. The reserved lithium compensates for lithium lost during the cycling of the electrochemical cell, including during the first cycle, thereby reducing capacity loss over time. The protective coating reduces mechanical degradation and minimizes any increase in surface roughness during initial and subsequent lithiation / delithiation cycles.

[0077] A typical lithium-ion battery includes a first electrode (such as a positive electrode or cathode) opposite a second electrode (such as a negative electrode or anode) and a separator and / or electrolyte disposed therebetween. Typically, in a lithium-ion battery pack, the battery packs or cells can be electrically connected in a stacked or wound configuration to increase the overall output. Lithium-ion batteries operate by reversibly transferring lithium ions between a first electrode and a second electrode. For example, during charging of the battery, lithium ions can move from the positive electrode to the negative electrode, and move in the opposite direction when the battery is discharged. The electrolyte is suitable for conducting lithium ions and can be in liquid, gel or solid form.

[0078] For example, an exemplary and schematic illustration of an electrochemical cell (also referred to as a battery) 20 is shown in Figure 1. Although the illustrated example includes a single cathode and a single anode, those skilled in the art will recognize that the present disclosure also contemplates various other configurations, including those having one or more cathodes and one or more anodes and various current collectors and electroactive layers disposed on or adjacent to one or more surfaces of the current collectors. The battery pack 20 includes a negative electrode 22 (e.g., an anode), a positive electrode 24 (e.g., a cathode), and a separator 26 (e.g., a microporous polymer separator) disposed between the two electrodes 22, 24. The separator 26 contains an electrolyte 30, which may also be present in the negative electrode 22 and the positive electrode 24. The negative electrode current collector 32 may be disposed at or near the negative electrode 22, and the positive electrode current collector 34 may be disposed at or near the positive electrode 24. An interruptible external circuit 40 and a load device 42 connect the negative electrode 22 (via its current collector 32) and the positive electrode 24 (via its current collector 34).

[0079] The battery 20 can generate current during discharge by a reversible electrochemical reaction that occurs when the external circuit 40 is closed (to connect the negative electrode 22 and the positive electrode 24) and the potential of the negative electrode 22 is lower than that of the positive electrode. The chemical potential difference between the positive electrode 24 and the negative electrode 22 drives the electrons generated by the reaction at the negative electrode 22 (e.g., oxidation of intercalated lithium) through the external circuit 40 toward the positive electrode 24. The lithium ions also generated at the negative electrode 22 are simultaneously transferred toward the positive electrode 24 via the electrolyte solution 30 contained in the separator 26. The electrons flow through the external circuit 40, and the lithium ions move through the separator 26 containing the electrolyte 30, thereby forming intercalated lithium at the positive electrode 24. As described above, the electrolyte 30 is also generally present in the negative electrode 22 and the positive electrode 24. The current passing through the external circuit 40 can be utilized and directed through the load device 42 until the lithium in the negative electrode 22 is exhausted and the capacity of the battery 20 is reduced.

[0080] The battery pack 20 can be charged or re-energized at any time by connecting an external power source to the lithium-ion battery pack 20 to reverse the electrochemical reactions that occur during the battery pack discharge process. Connecting the external power source to the battery pack 20 promotes the reaction at the positive electrode 24 (e.g., non-spontaneous oxidation of intercalated lithium) to produce electrons and lithium ions. The lithium ions flow back through the separator 26 through the electrolyte 30 toward the negative electrode 22, thereby replenishing the negative electrode 22 with lithium (e.g., intercalated lithium) for use in the next battery pack discharge event. Thus, a complete discharge event followed by a complete charging event is considered to be a cycle in which lithium ions circulate between the positive electrode 24 and the negative electrode 22. The external power source that can be used to charge the battery pack 20 may vary depending on the size, structure, and specific end use of the battery pack 20. Some notable and exemplary external power sources include, but are not limited to, AC-DC converters and motor vehicle alternators connected to the AC power grid through a wall outlet.

[0081] In many lithium-ion battery configurations, each of the negative electrode current collector 32, the negative electrode 22, the separator 26, the positive electrode 24, and the positive electrode current collector 34 is prepared as a relatively thin layer (e.g., a few microns to a fraction of a millimeter or less in thickness) and assembled in an electrically parallel arrangement to connect the layers to provide a suitable electrical energy and power group. The negative electrode current collector 32 and the positive electrode current collector 34 collect and move free electrons to and from the external circuit 40, respectively.

[0082] In addition, the separator 26 works as an electrical insulator by being sandwiched between the negative electrode 22 and the positive electrode 24 to prevent physical contact and thus prevent a short circuit from occurring. The separator 26 not only provides a physical barrier and an electrical barrier between the two electrodes 22, 24, but also contains the electrolyte solution in a network of open pores during the cycling of lithium ions to facilitate the operation of the battery pack 20.

[0083] The battery pack 20 may also include a variety of other components that, although not depicted herein, are known to those skilled in the art. For example, the battery pack 20 may include a housing, gaskets, terminal caps, tabs, battery terminals, and any other conventional components or materials that may be located within the battery pack 20 (including between or around the negative electrode 22, the positive electrode 24, and / or the separator 26). Figure 1 The battery 20 shown in FIG. 1 includes a liquid electrolyte 30 and shows a representative concept of the battery operation. However, as known to those skilled in the art, the battery 20 may also be a solid-state battery including a solid-state electrolyte that may have a different design.

[0084] As described above, the size and shape of the battery pack 20 can vary depending on the specific application for which it is designed. Battery-powered vehicles and handheld consumer electronic devices are two examples in which the battery pack 20 will most likely be designed to different sizes, capacities, and power output specifications. The battery pack 20 can also be connected in series or in parallel with other similar lithium-ion cells or batteries to produce greater voltage output, energy, and power when the load device 42 requires it. Therefore, the battery pack 20 can generate a current toward the load device 42, which is part of the external circuit 40. When the battery pack 20 is discharged, the load device 42 can be powered in whole or in part by the current through the external circuit 40. Although the electric load device 42 can be any number of known electric devices, some specific examples include electric motors for electrified vehicles, laptop computers, tablet computers, cellular phones, and cordless power tools or appliances. The load device 42 can also be a power generation device that charges the battery pack 20 for the purpose of storing electrical energy.

[0085] The present technology relates to improved electrochemical cells, particularly lithium ion batteries. In various cases, such batteries are used in vehicle or automotive transportation applications (e.g., motorcycles, boats, tractors, buses, motorbikes, trailers, campers, and tanks). However, the present technology may also be employed in a wide variety of other industries and applications, including, by way of non-limiting example, aerospace components, consumer products, devices, buildings (e.g., houses, offices, sheds, and warehouses), office equipment and furniture, and industrial equipment machinery, agricultural or farm equipment, or heavy machinery.

[0086] Re-reference Figure 1 , the positive electrode 24, the negative electrode 22, and the separator 26 can each contain an electrolyte solution or system 30 within its pores, the electrolyte solution or system 30 being capable of conducting lithium ions between the negative electrode 22 and the positive electrode 24. Any suitable electrolyte 30 capable of conducting lithium ions between the negative electrode 22 and the positive electrode 24, whether in solid, liquid, or gel form, can be used in the lithium ion battery 20. In certain aspects, the electrolyte 30 can be a non-aqueous liquid electrolyte solution comprising a lithium salt dissolved in an organic solvent or a mixture of organic solvents. Many conventional non-aqueous liquid electrolyte 30 solutions can be employed in the lithium ion battery 20.

[0087] In certain aspects, electrolyte 30 can be a non-aqueous liquid electrolyte solution comprising one or more lithium salts dissolved in an organic solvent or a mixture of organic solvents. For example, a non-limiting list of lithium salts that can be dissolved in an organic solvent to form a non-aqueous liquid electrolyte solution includes lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalate)borate (LiB(C2O4)2) (LiBOB), lithium difluorooxalatoborate (LiBF2(C2O4)), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethane)sulfonyl imide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2) (LiSFI), and combinations thereof.

[0088] These and other similar lithium salts can be dissolved in various non-aqueous aprotic organic solvents, including but not limited to various alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), aliphatic carboxylates (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain structure ethers (e.g., 1,2-dimethoxyethane, 1-2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane), sulfur compounds (e.g., sulfolane), and combinations thereof.

[0089] In some cases, the porous separator 26 may include a microporous polymer separator comprising a polyolefin. The polyolefin may be a homopolymer (derived from a single monomer component) or a heteropolymer (derived from more than one monomer component), which may be linear or branched. If the heteropolymer is derived from two monomer components, the polyolefin may present any copolymer chain arrangement, including those of block copolymers or random copolymers. Similarly, if the polyolefin is a heteropolymer derived from more than two monomer components, it may also be a block copolymer or a random copolymer. In some aspects, the polyolefin may be a blend of polyethylene (PE), polypropylene (PP), or PE and PP, or a multilayer structured porous film of PE and / or PP. Commercially available polyolefin porous separator films 26 include CELGARD® 2500 (single-layer polypropylene separator) and CELGARD® 2320 (three-layer polypropylene / polyethylene / polypropylene separator) available from Celgard LLC.

[0090] In some aspects, the spacer 26 may further include one or more of a ceramic coating and a heat-resistant material coating. The ceramic coating and / or the heat-resistant material coating may be disposed on one or more sides of the spacer 26. The material forming the ceramic layer may be selected from: aluminum oxide (Al2O3), silicon dioxide (SiO2), and combinations thereof. The heat-resistant material may be selected from: Nomex, aramid, and combinations thereof.

[0091] When the separator 26 is a microporous polymer separator, it can be a single layer or a multilayer laminate, which can be manufactured by a dry or wet process. For example, in some cases, a single polyolefin layer can form the entire separator 26. In other aspects, the separator 26 can be a fiber membrane having a large number of pores extending between the relative surfaces and having an average thickness of, for example, less than 1 mm. However, as another example, multiple discrete layers of similar or dissimilar polyolefins can be assembled to form a microporous polymer separator 26. In addition to polyolefins, the separator 26 may also include other polymers, such as but not limited to polyethylene terephthalate (PET), polyvinylidene fluoride (PVdF), polyamide, polyimide, poly (amide-imide) copolymer, polyetherimide and / or cellulose, or any other material suitable for generating a desired porous structure. The polyolefin layer and any other optional polymer layer can be further included in the separator 26 in the form of a fiber layer to help provide the separator 26 with appropriate structural and porosity properties. In certain aspects, the separator 26 may also be mixed with a ceramic material, or its surface may be coated with a ceramic material. For example, the ceramic coating may include aluminum oxide (Al2O3), silicon dioxide (SiO2), titanium dioxide (TiO2), or a combination thereof. A variety of conventionally available polymers and commercial products are contemplated for forming the separator 26, as well as many manufacturing methods that can be used to manufacture such microporous polymer separators 26.

[0092] In various aspects, the solid electrolyte (SSE) (not shown) may be substituted for Figure 1 The SSE may be disposed between the positive electrode 24 and the negative electrode 22. The SSE facilitates the transfer of lithium ions while mechanically isolating the negative electrode from the positive electrodes 22, 24 and providing electrical insulation between the negative electrode and the positive electrodes 22, 24. By way of non-limiting example, the SSE may include LiTi2(PO4)3, LiGe2(PO4)3, Li7La3Zr2O 12 、Li3xLa 2 / 3 -xTiO3, Li3PO4, Li3N, Li4GeS4, Li 10 GeP2S 12 , Li2S-P2S5, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li3OCl, Li 2.99 Ba 0.005 C10 or a combination thereof.

[0093] The positive electrode 24 can be formed of a lithium-based active material that can sufficiently undergo lithium intercalation and deintercalation, or alloying and dealloying, while serving as the positive terminal of the battery pack 20. An exemplary common type of known material that can be used to form the positive electrode 24 is a layered lithium transition metal oxide. For example, in some aspects, the positive electrode 24 can include one or more materials having a spinel structure, such as lithium manganese oxide (Li (1+x) Mn2O4, where 0.1 ≤ x ≤ 1), lithium manganese nickel oxide (LiMn (2-x) Ni x O4, where 0 ≤ x ≤ 0.5) (e.g., LiMn 1.5 Ni 0.5 O4); one or more materials having a layered structure, such as lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (Li(Ni x Mn y Co z )O2, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1 and x + y + z = 1) (e.g., LiMn 0.33 Ni 0.33 Co 0.33 O2) or lithium nickel cobalt metal oxide (LiNi (1-x-y) Co x M y O2, where 0 < x < 0.2, y < 0.2 and M can be Al, Mg, Ti, etc.); or a lithium iron polyanion oxide having an olivine structure, such as lithium iron phosphate (LiFePO4), lithium manganese iron phosphate (LiMn 2-x Fe x PO4, where 0 < x < 0.3), or lithium iron fluorophosphate (Li2FePO4F).

[0094] In certain variations, the electroactive material can be blended with an electronically conductive material that provides an electronic conduction path and / or at least one polymeric binder material that improves the structural integrity of the electrode. For example, the electroactive material and the electronically conductive or conductive material can be slurry cast with such binders as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM) rubber or carboxymethyl cellulose (CMC), nitrile rubber (NBR), styrene-butadiene rubber (SBR), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate or lithium alginate. The conductive material can include carbon-based materials, powdered nickel or other metal particles, or conductive polymers. The carbon-based materials can include, for example, graphite, acetylene black (such as KETCHEN TM black or DENKA TMThe conductive polymers include particles of carbon fiber, nanotubes, graphene, etc. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole, etc. In some aspects, a mixture of conductive materials can be used. The positive electrode current collector 34 can be formed of aluminum (Al) or any other suitable conductive material known to those skilled in the art.

[0095] Negative electrode 22 comprises an electroactive material in the form of a lithium host material that is capable of acting as a negative terminal of a lithium ion battery. Negative current collector 32 may comprise a metal containing copper, nickel, or alloys thereof, or other suitable conductive materials known to those skilled in the art. In certain aspects, positive current collector 34 and / or negative current collector 32 may be in the form of a foil, a slit mesh, and / or a woven mesh.

[0096] In certain aspects, the present disclosure provides methods for manufacturing a negative electrode 22 (e.g., an anode) incorporating an improved electrochemically active negative electrode material. As discussed above, certain negative electroactive materials undergo significant volume expansion during lithium cycling (e.g., are capable of accepting the insertion of lithium ions through lithiation or "intercalation" during the charging process of the electrochemical cell, and releasing lithium ions through delithiation or "deintercalation" or lithium alloying / dealloying during the discharge process of the electrochemical cell). Such electrochemically active negative electrode materials can be selected from: silicon, alloys containing silicon, alloys containing tin, and combinations thereof. By way of example, silicon-containing electroactive material particles may include silicon or binary and ternary alloys containing silicon and / or alloys containing tin, such as Si-Sn, SiSnFe, SiSnAl, SiFeCo, SnO2, etc. According to various aspects of the present teachings, negative electroactive materials can be incorporated into the negative electrode of an electrochemical cell.

[0097] Furthermore, in a typical manufacturing process, a negative electrode material that does not contain any lithium is incorporated into an electrochemical cell. The positive electrode has lithium and after cycling the electrochemical cell, the lithium enters the negative electrode and lithiates the negative electrode. However, in a negative electroactive material that includes silicon, for example, after the first lithiation cycle, a portion of the lithium may not circulate back to the positive electrode through the electrolyte, but may remain at the negative electrode. This may be due to, for example, the formation of Li on the negative electrode. xSi and / or solid electrolyte interface (SEI) layer, and the ongoing lithium loss due to the continuous solid electrolyte interface (SEI) rupture. The solid electrolyte interface (SEI) layer can be formed on the surface of the negative electrode (anode), which is usually generated by the reaction products of the anode material, electrolyte reduction and / or lithium ion reduction. This permanent loss of lithium ions can lead to a decrease in specific energy and power in the battery pack, which is caused by the increased positive electrode mass that does not participate in the reversible operation of the battery pack. For example, a lithium-ion battery pack may experience an irreversible capacity loss of greater than or equal to about 5% to less than or equal to about 40% after the first cycle. More specifically, silicon oxide (SiOx) can consume up to 40% of the total capacity due to the conversion reaction of the first cycle. Silicon electrodes, depending on the specific surface area, have a capacity loss of about 20 to 40% due to SEI formation.

[0098] Lithiation of electroactive materials prior to incorporation into an electrochemical cell, such as pre-lithiation, can compensate for this lithium loss during cycling. However, common lithiation methods, such as electrochemical methods, direct contact methods, and lamination methods can be inefficient and often require half-cell fabrication and disassembly and / or high temperature chemical processes. In addition, it can be difficult to control the degree of lithiation that occurs during these methods. The present disclosure provides improved electroactive materials and electrode materials and methods of making the same that can address these challenges.

[0099] In various aspects, by pre-lithiating an electroactive material (or an electrode incorporating an electroactive material) before forming an electrode, the present disclosure provides advantages, including reducing mechanical stress in the negative electrode. Significantly, the electroactive material or an electrode incorporating an electroactive material can be coated and pre-lithiated with a protective coating in a continuous process in a single reactor having multiple separate reaction chambers. Therefore, active lithium loss during the formation cycle can be significantly reduced by the present technology. In addition, according to certain aspects of the present disclosure, the cycle life performance of a lithium-ion battery pack incorporating a negative electrode having a negative electroactive material is improved, and the negative electroactive material comprises pre-lithiated silicon with a mechanical protective coating.

[0100] Thus, according to certain aspects of the present disclosure, methods of making electrode materials for electrochemical cells that cycle lithium ions, such as negative electrode materials comprising silicon, are provided.

[0101] In certain aspects, a method for manufacturing an electrode material for an electrode in an electrochemical cell for cycling lithium ions is contemplated, which involves applying a protective coating selected from: an oxide-based coating, a fluoride-based coating, and a nitride-based coating to an electrode precursor material. The method also includes lithiation of the electrode precursor material. The application and lithiation of the protective coating are performed in a continuous process in a reactor having a first reaction chamber and a second reaction chamber to form a lithiated electrode material comprising the coating. In certain variations, the electrode precursor material may be a negative electrode precursor comprising silicon, binary and ternary alloys containing silicon, and / or an alloy containing tin. As will be discussed in more detail below, the electrode precursor material treated by the method may be a plurality of particles of an electroactive material that are lithiated in a continuous process in a reactor and a protective coating is applied, or may be a preformed electrode comprising an electroactive material (e.g., in a preformed composite electrode in which the electroactive material is distributed in a polymer matrix).

[0102] For example, Figure 2 As shown in FIG. 1 , a negatively electroactive particle 100 comprising a material containing silicon forms a core region 110 that is capable of undergoing significant volume expansion during lithium cycling, such as during lithium ion insertion or lithium alloying. In an initial state before any lithium ion insertion or reaction, the core region 110 is in a first contracted state. After lithium ion insertion / intercalation or alloying, the particle 100 will be in a second expanded state (not shown) having a much larger volume. For example, if the core region 110 is a silicon particle (Si) in the first contracted state, after lithium ion insertion, it forms a Li 4.4 Si (corresponding to the second expanded state). In the second expanded state after lithium insertion, the volume of the silicon particles defining the core region 110 may be up to three (3) times (300%) the volume of the silicon particles in the first contracted state. As will be appreciated, the first contracted state may correspond to the volume of the core region 110 before lithium insertion or after lithium extraction. For conventional silicon electroactive materials, the degree of volume expansion that occurs may cause the silicon particles to mechanically degrade and break into many smaller fragments or pieces. When the particles break into smaller fragments, these fragments or smaller fragments may no longer maintain the performance of the electrochemical cell.

[0103] By way of non-limiting example, the electroactive particles comprising silicon that comprise core region 110 may have an average particle size (D50) in a shrunken state of greater than or equal to about 10 nm to less than or equal to about 50 μm, optionally greater than or equal to about 50 nm to less than or equal to about 10 μm, and in certain variations, greater than or equal to about 150 nm to less than or equal to about 5 μm.

[0104] Negatively electroactive particle 100 includes core region 110 having surface 112. It should be noted that Figure 2The features in are not necessarily shown to scale, but are provided for illustration purposes only. A protective coating 120 is disposed on the surface 112, which, as will be further described below, may have continuous surface coverage. In various aspects, the protective coating 120 is a thin continuous layer applied to the surface 112 of the negative electroactive material particle 100 to provide sufficient coverage, thereby protecting the underlying electroactive material during the volume size change process to minimize or avoid cracking, rupture, and burning of the electroactive material during lithium cycling, and thereby minimize capacity loss and poor cycle life. The application of the protective coating 120 can help to enhance mechanical integrity at the electrode level, inhibit electrolyte decomposition, and promote charge transfer. In addition, the presence of the protective coating can better passivate the electrode after pre-lithiation occurs and help minimize the increase in surface roughness. In certain aspects, the continuous protective coating 120 can cover greater than or equal to about 90% to less than or equal to about 100% of the exposed surface area of ​​the electroactive material, and in certain aspects, optionally greater than or equal to about 95% to less than or equal to about 100%, and optionally greater than or equal to about 99% to less than or equal to about 100% of the exposed surface area of ​​the electroactive material.

[0105] The protective coating 120 may be formed of a material selected from the group consisting of an oxide-based coating, a fluoride-based coating, and a nitride-based coating. In certain aspects, as will be further described below, the protective coating 120 comprises a metal. In certain variations, the protective coating 120 comprises a metal selected from the group consisting of aluminum (Al), titanium (Ti), tin (Sn), zirconium (Zr), vanadium (V), hafnium (Hf), zinc (Zn), silicon (Si), lithium (Li), and combinations thereof. The protective coating 120 can minimize or prevent cracking of the negative electrode material 100 during lithium ion cycling. The protective coating 120 may be selected from the group consisting of aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin oxide (SnO2), zinc oxide (ZnO), lithium fluoride (LiF), aluminum fluoride (AlF3), aluminum oxyfluoride (AlFO), aluminum nitride (AlN), silicon nitride (SiN), and combinations thereof. In certain variations, the protective coating 120 may have a thickness of greater than or equal to about 1 nm to less than or equal to about 25 nm; optionally greater than or equal to about 2 nm to less than or equal to about 20 nm, and in certain variations, optionally greater than or equal to about 3 nm to less than or equal to about 10 nm, for example, about 5 nm.

[0106] The lithiated layer 130 is disposed on the protective coating 120 on the surface 112. It should be noted that the lithiated layer 130 may actually move into the pores of the surface 112 of the negatively electroactive particle 100 beneath the protective coating 120 to react with the silicon. Thus, the treated negatively electroactive particle 100 may not necessarily have the layers delineated as shown, but may actually have a hybridized and treated surface 112 in which a portion of the lithium has moved beneath the protective coating 120 to react and form an alloy with the silicon at the surface and penetrate into the core region 110.

[0107] In certain variations, the present disclosure contemplates methods of making electrode materials, such as negative electrode materials, for electrochemical cells that cycle lithium ions. The methods may be used in Figure 3 The reactor 140 shown in FIG. 1 is carried out in the reactor 140 shown in FIG. The reactor 140 includes a first reaction chamber 142 and a second reaction chamber 144, which allow materials to be transferred between them (e.g., via a conveyor or a roll-to-roll process). In the first reaction chamber 142, a coating is applied to an electrode precursor, such as a precursor containing silicon. The coating can be selected from: an oxide-based coating, a fluoride-based coating, and a nitride-based coating.

[0108] In some variants, the application of the surface coating can be performed by atomic layer deposition (ALD). The atomic layer deposition (ALD) method can coat the electrode material with a conformal layer containing a protective layer, such as aluminum oxide (Al2O3). ALD is a self-limiting process for chemical deposition or growth of ultra-thin films on a substrate. ALD generally involves applying a self-saturated surface reaction to the target substrate. The surface reaction can be performed sequentially and / or in an alternating manner, depending on the composition and structure of the desired film. In some other alternative variants, the protective surface coating can be synthesized on the electrode material by other methods, such as physical vapor deposition (PVD) (e.g., magnetron sputtering), chemical vapor deposition (CVD) or thermal methods, chemical vapor infiltration and other known conventional methods for continuously applying such coatings to solid materials.

[0109] like Figure 3 As shown in FIG. 1 , the first reaction chamber 142 is used to perform an ALD process to apply a protective coating. Figure 3An example of a roll-to-roll continuous process is shown, wherein an electrode precursor material 150 is unwound from a first roll or spool 152, introduced into a reactor 140, conveyed through first and second reaction chambers 142, 144 to a second spool 154 where it is rewound. As will be appreciated, the electrode precursor material 150 may be an elongated sheet of a preformed electrode material that may be wound and unwound as shown, or may be a non-continuous sheet conveyed on a conveyor, or a plurality of electroactive material particles conveyed on a belt that may be distributed onto a conveyor and collected after processing in the reactor 140. The first reaction chamber 142 includes first regions 156 and second regions 158 that are arranged in an alternating manner in the first reaction chamber 142. A gas or vapor containing an oxidant, such as oxygen or water, is introduced into each first region 156. One or more ALD precursors, as will be further discussed herein, are introduced into each second region 158. Each first region 156 and second region 158 together define a deposition zone 160. As the electrode precursor material 150 passes through a first region 156 in a deposition zone 160 and then enters a second region 158, a first layer of a protective first coating 162 is applied to the electrode precursor material 150. As will be appreciated by those skilled in the art, the number of deposition zones 160 having alternating first and second regions 156, 158 determines the thickness of the deposited coating, with a greater number of deposition zones producing a thicker first coating 162. Thus, the number of deposition zones 160 in the first reaction chamber 142 will depend on the desired number of ALD cycles (and the desired thickness of the coating). For example, as shown, five cycles corresponding to five deposition zones can provide a protective first coating 162 having a desired thickness within the ranges discussed above.

[0110] In certain variations, the protective first coating 162 is an oxide-based surface coating that is applied with a precursor to form a coating containing an oxide. In certain embodiments, the oxide-based surface coating is selected from: aluminum oxide (Al2O3), titanium oxide (TiO2), vanadium oxide (V2O5), silicon oxide (e.g., silicon dioxide (SiO2)), and aluminum oxyfluoride (AlFO). Such an oxide-based surface coating can be formed by using one or more precursors of aluminum oxide (Al2O3), titanium oxide (TiO2), vanadium oxide (V2O5), and / or silicon oxide (SiO2) materials. In certain other embodiments, the oxide-based surface coating comprises the material aluminum oxide (Al2O3). Such an oxide-based surface coating can be formed by using one or more precursors of an aluminum oxide (Al2O3) coating.

[0111] In other variations, the protective first coating 162 on the electrode material or electrode material particles comprises a fluoride-based coating or a nitride-based coating. A fluoride-based coating refers to a coating applied with a precursor to form a fluoride-containing coating. In certain embodiments, a fluoride-based coating may comprise, for example, lithium fluoride (LiF), aluminum fluoride (AlF3), or aluminum fluoride oxide (AlFO). Such a concept is similarly applicable to a nitride-based coating, which may also contain an oxide-containing species. In certain embodiments, a nitride-based coating may comprise aluminum nitride (AlN) or silicon nitride (SiN).

[0112] In various aspects, such a protective first coating 162 is applied to the electrode material by an atomic layer deposition (ALD) process, which can coat the electrode material with a conformal layer comprising an oxide-based layer, such as aluminum oxide (Al2O3). ALD is typically performed in an apparatus having a vacuum deposition chamber (which has a substrate holder or conveyor), at least one vapor source (called a precursor), which can be introduced into the reactor through a port, and various controls by which the vapor source can be applied to the substrate alone. Such controls may include heaters, coolers, flow routing, and valves to control the amount of exposure of the substrate to the vapor source, which are not shown. Figure 3 The area to be coated with electrode material may be pre-treated, for example by plasma treatment.

[0113] The ALD method for depositing a surface coating onto an electrode material region involves the reaction of the surface in a deposition chamber with a single vapor of a precursor material or the reaction of the surface with multiple vapors introduced sequentially and having a surface coating precursor. Suitable precursors may include organic and inorganic metal compounds, such as trimethylaluminum (TMA). The vapor may be pulsed on a carrier gas into a vacuum deposition chamber and may be rapidly purged, for example by vacuum pumping or flushing with an inert gas. Such vapor pulses and systematic purging may be performed to control the dose of precursor vapor to which the substrate is exposed.

[0114] Typically, the ALD process is performed at elevated temperatures and reduced pressures. The temperature of the deposition chamber is ideally high enough to allow reactions between the substrate and the precursor in the vapor to occur while also preventing the vapor from condensing onto the surface. As a non-limiting example, the reaction space in the deposition chamber (first reaction chamber 142) may be heated to between about 150°C and about 600°C, and the operating pressure may be about 7.5x10 -2 Torr to about 4 Torr (about 1 Pa to about 5000 Pa).

[0115] Due to the ALD method and the surface reaction, a monoatomic layer of the surface coating material is bonded to the electrode surface, thereby providing a monoatomic coating. In the case of sequential or alternating reactions, a composite layer can be formed. In addition, additional atomic monolayers can be generated on the monoatomic layer, thereby forming a surface coating with a greater thickness.

[0116] The ALD method can be exemplified by the formation of aluminum oxide (Al2O3) coatings on silicon-based electrode materials, as in Figure 3 In the illustrated method shown in . The electrode precursor material 150 containing silicon has a surface, which can first be pretreated with oxygen plasma or peroxide (H2O2) to form a plurality of hydroxyl groups (OH) on the surface. Although not shown, the reactor can have another reaction chamber for performing plasma or peroxide pretreatment. The presence of hydroxyl groups on the surface of the electrode material substrate provides a suitable reactant species to deposit aluminum-containing species on preselected areas of the surface. The hydroxyl groups can be protected in an argon atmosphere, and excess plasma or peroxide can be removed by an argon gas flow. The electrode precursor material 150 can be placed in a suitable first reaction chamber 142 for a step-by-step conformal coating method.

[0117] The precursor and accompanying gas (such as argon) can be introduced into the second region 158. A predetermined amount of aluminum (in the form of a suitable volatile precursor compound, such as trimethylaluminum (TMA ((CH3)3Al))) is introduced as a vapor (e.g., at a temperature of about 50°C) and flowed into contact with the exposed surface of the electrode precursor material 150. It is preferred to provide a stoichiometric excess of TMA relative to the hydroxyl or reactive groups on the surface. TMA chemisorbs onto the oxygen / hydroxyl groups on the surface of the electrode precursor material 150. Methane (CH4) is released as a byproduct. Typically, the reaction of the aluminum-containing material with the surface groups of the electrode precursor material 150 is completed within a short time frame, such as on the order of a few seconds.

[0118] Next, in the first zone, water vapor (H2O) or oxygen (O2) is introduced to flow across the exposed surface of the electrode precursor material 150. Water (H2O) further reacts with TMA and forms methane (CH4). In this manner, a first conformal layer of aluminum oxide (Al2O3) is formed on the surface of the electrode precursor material 150. Excess reactants and byproducts (not shown) may be removed from the first reaction chamber 142. Figure 3 In the next second reaction zone 158, TMA is introduced again and then exposed to water or oxygen in the next first reaction zone 156 to form another aluminum oxide layer. The ALD process is repeated in each deposition zone 160 to generate an Al2O3 film layer by layer on the surface of the electrode precursor material 150. As generally shown, due to the presence of five deposition zones 160, five Al2O3 atomic monolayers are formed.

[0119] The ALD method is an illustration of a technique for forming an aluminum oxide (Al2O3) coating on a silicon-based electrode material, but as a non-limiting example, the method can also be used to form other coatings. For example, other oxide-based, nitride-based or fluoride-based coatings can be formed on graphite-based electrode materials by the ALD method. In some aspects, the oxide-based coating can be selected from aluminum oxide (Al2O3), titanium oxide (TiO2), silicon oxide (SiO2), vanadium oxide (VnO5), zirconium oxide (ZrO2) or zinc oxide (ZnO). For titanium oxide coating (TiO2), the precursor material can be, for example, tetrakis (diethylamido) titanium (IV), tetrakis (dimethylamido) titanium (IV) and / or isopropoxide titanium (IV). For vanadium oxide coating (V2O5), the metal precursor can be, for example, triisopropoxide vanadium (V). For zirconium oxide coating (ZrO2), the precursor can be zirconium tetrachloride (ZrCl4) and oxygen (O2). For zinc oxide coating (ZnO), the precursor material may be methyl zinc isopropoxide. For silicon oxide coating, the precursor material may be, for example, silicon tetrachloride, tetraethoxysilane and / or tri(tert-butyloxy)silanol. For fluoride-based coatings, suitable precursor materials may be lithium fluoride (LiF), aluminum fluoride (AlF3), etc. For nitride-based coatings, suitable precursor materials may be ammonia (NH3), ammonium hydroxide (NH4OH), titanium nitride (TiN), vanadium nitride (VN), aluminum nitride ((AlN), where the precursors are TMA and ammonia) and tungsten hexafluoride (WF6) combined with ammonia (NH3), silicon tetrachloride (SiCl4) or dichlorosilane (SiH2Cl2), etc.

[0120] In certain variations, the surface coating can be applied by atomic layer deposition (ALD) using a precursor selected from the following: trimethylaluminum (TMA ((CH3)3Al)), tetrakis(diethylamido)titanium(IV), tetrakis(dimethylamido)titanium(IV), titanium(IV)isopropoxide, vanadium(V)triisopropoxide, silicon tetrachloride, tetraethoxysilane, tri(tert-butoxy)silanol, lithium fluoride (LiF), aluminum fluoride (AlF3), ammonia (NH3), ammonium hydroxide (NH4OH), titanium nitride (TiN), vanadium nitride (VN), aluminum nitride ((AlN), where the precursors are TMA and ammonia), tungsten hexafluoride (WF6) and ammonia (NH3), silicon tetrachloride (SiCl4) and ammonia (NH3) or dichlorosilane (SiH2Cl2) combined with ammonia (NH3), lithium fluoride (LiF), aluminum fluoride (AlF3), etc. Furthermore, in alternative variations, Al2O3 or other coatings can be readily obtained by using different precursors and deposition methods.

[0121] After the protective first coating 162 is applied in the first reaction chamber 142, the electrode precursor material 150 leaves the first reaction chamber 142 and then enters the second reaction chamber 144. In the second reaction chamber 144, the electrode precursor material 150 is lithiated. For example, the lithiation can be performed by thermal evaporation. In the thermal evaporation method, a vacuum pump (not shown) can be used to maintain the pressure in the second reaction chamber 144. Thermal evaporation uses the increase in vapor pressure with the temperature of the material to evaporate the material source and then condense the layer on the substrate (here, the electrode precursor material 150) which is usually significantly cooler than the source 166 material. For example, in the thermal evaporation method, the metal can be placed in a vacuum (e.g., <10 -3 The method of the present invention is to place the liquid metal in a crucible under a support and heat the liquid metal to a point where it becomes a vapor (>50°C above its melting point), which will be deposited on the surface of the solid electroactive material or electrode. When thermal evaporation is used, the thickness of the applied layer can be greater than or equal to about 1 micrometer (μm) less than or equal to about 50 μm, optionally greater than or equal to about 2 μm to less than or equal to about 20 μm, and in certain variations, optionally greater than or equal to about 3 nm less than or equal to about 10 μm of lithium metal.

[0122] In certain aspects, the lithiation of silicon by direct reaction can be expressed as: 4.4 x Li + Si → Li 4.4x Si, where 0 ≤ x ≤ 1, while for electrochemical lithiation of silicon, it can be expressed as 4.4 x Li + + 4.4 x e –+ Si → Li 4.4x In certain variations, the pre-lithiated electroactive material according to certain aspects of the present disclosure may form a material comprising Li 4.4x Si represents the surface layer of lithium silicon alloy, where 0 ≤ x ≤ approximately 0.85.

[0123] Therefore, the heater 164 is placed under the lithium metal source 166 to heat it. As the temperature of the lithium metal in the source 166 increases, the lithium metal evaporates or volatilizes and directs lithium molecules 168 to the electrode precursor material 150. Therefore, a second coating 170 of lithium metal or a coating containing lithium is formed on the protective first coating 162 and the electrode precursor material 150. After the first and second coatings 162, 170 are applied to the electrode precursor material 150, the electrode precursor material 150 is wound onto the second reel 154 and can be taken out of the reactor 140. Therefore, a continuous process can be performed in a single reactor 140, where there is no need to evacuate the chamber and adjust the temperature and pressure conditions during the process. Therefore, the pressure in the first and second reaction chambers 142, 144 can be maintained at a steady-state level for each deposition method. As will be appreciated by those skilled in the art, different designs of the continuous ALD process can be integrated with thermal evaporation to provide simultaneous protective coating deposition and electrode materials, such as lithiation of electrode precursor materials containing silicon.

[0124] Significantly, the advantage of applying the protective first coating 162 followed by the lithiation process is that any potential physical damage that may occur due to volume expansion of the electrode precursor during the initial lithiation process is reduced. In addition, the protective first coating 162 present prior to lithiation helps reduce the surface roughness increase that may otherwise occur during the initial lithiation process of the silicon-containing electrode precursor.

[0125] In one example, the deposition temperature of the Al2O3 coating is about 200°C. Trimethylaluminum is used as the aluminum (Al) precursor and H2O is used as the oxygen (O) precursor. Both precursors are heated to about 80°C during the deposition process. The exposure time and pump down time of each precursor are about 10 seconds and 20 seconds, respectively.

[0126] Figure 4 Shows methods that have been subject to certain aspects of the present disclosure, such as in Figure 3 A prefabricated electrode of the method described in the case of the negative electrode 200 includes a current collector 210 and an active layer 220. Many negatively electroactive particles 230 include a core region 232 and a multilayer coating 234, wherein the multilayer coating 234 includes a protective first coating 236 and a second layer 238 containing lithium (e.g., lithiated). Many negatively electroactive particles 230 are distributed in a porous matrix 240 (pores are not shown). The porous matrix 240 can be formed by one or more polymer binders. The active layer also includes many conductive particles 244 distributed in the porous matrix 240.

[0127] In this embodiment, the binder may be a conventional binder, such as those described in the case of the positive electrode 24. Suitable binders include polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), ethylene propylene diene monomer (EPDM) rubber or carboxymethyl cellulose (CMC), nitrile rubber (NBR), styrene-butadiene rubber (SBR), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, etc. Many conductive particles 244 may include carbon-based materials, powdered nickel or other conductive metal particles, or conductive polymers. Carbon-based materials may include, for example, graphite, acetylene black (such as KETCHEN TM Black or DENKA TM Black), carbon fiber and nanotubes, graphene and the like. Examples of conductive polymers include polyaniline, polythiophene, polyacetylene, polypyrrole and the like. In certain aspects, a mixture of such conductive materials may be used.

[0128] The negative electrode 200 may include a plurality of negative electroactive particles 230 of greater than or equal to about 50 wt % to less than or equal to about 90 wt %, and in some aspects, optionally greater than or equal to about 60 wt % to less than or equal to about 80 wt %. The negative electrode 200 may include a plurality of negative electroactive particles 230 of greater than or equal to about 1 wt % to less than or equal to about 40 wt %, and in some aspects, optionally greater than or equal to about 10 wt % to less than or equal to about 35 wt % of a polymer binder forming a polymer matrix. The negative electrode 200 may include a plurality of conductive particles 244 of greater than or equal to about 0.5 wt % to less than or equal to about 25 wt %, and in some aspects, optionally greater than or equal to about 10 wt % to less than or equal to about 15 wt %.

[0129] The negative electrode 200 can be made by mixing a negative electroactive material, such as silicon-containing particles, with a polymer binder compound, a non-aqueous solvent, an optional plasticizer, and (if necessary) optional conductive particles into a slurry. The slurry can be mixed or agitated and then thinly coated onto a substrate with the aid of a doctor blade. The substrate can be a removable substrate or a functional substrate, such as a current collector (such as a metal grid or mesh layer) attached to one side of the electrode film. In one variation, heat or radiation can be applied to evaporate the solvent from the electrode film, leaving a solid residue. The electrode film can be further consolidated, where heat and pressure are applied to the film to sinter and calender it. In other variations, the film can be dried at a moderate temperature to form a self-supporting film. If the substrate is removable, it is then removed from the electrode film, and the electrode film is then further laminated to the current collector. For either type of substrate, residual plasticizers may have to be extracted or removed before being incorporated into a battery cell.

[0130] Figure 5A Showing that the method according to certain aspects of the present disclosure (such as in Figure 3254 is a prefabricated electrode 250 on a current collector 252 (described in the case of FIG. 25). Notably, a simplified version of the prefabricated electrode is shown in which the porous polymer matrix and the conductive particles are omitted. The prefabricated electrode 250 is subjected to a continuous process in which it is simultaneously lithiated and coated with a protective coating. Thus, a coating 254 is applied to the prefabricated electrode comprising a plurality of electroactive particles 256. Since the coating 254 is applied after the electroactive particles 256 are assembled in the prefabricated electrode 250, the electrons generally have a direct path between the individual electroactive particles 256 and therefore have a lower impedance and internal resistance in the prefabricated electrode 250.

[0131] on the other hand, Figure 5B Electrode 270 is shown made by first treating negative electroactive material particles (e.g., treated silicon-containing particles 272 to which a lithium-containing coating and protective coating 274 are applied), followed by a molding process to produce electrode 270. Thus, in Figure 3 In the method described in the case of , the electrode precursor material can be a plurality of particles (e.g., powder) that are processed in a continuous process in a single reactor. After forming the treated silicon-containing particles 272 having the lithiated and protective coating 274, they can be made into electrodes 270 by casting them in a slurry together with a polymer binder compound, a non-aqueous solvent, an optional plasticizer, and (if necessary) optional conductive particles. The slurry is cast onto a current collector 280. Since the coating 274 is applied to the electroactive material before the electrode 270 is formed, the electrons entering the active layer 282 of the electrode 270 from the current collector 280 encounter the coating 274 between the individual electroactive particles 272. Therefore, the electrode 270 can have a relatively Figure 5A The variant shown in has a slightly higher internal resistance.

[0132] It should be noted that various arrangements of coating individual electroactive material particles with an ALD coating and pre-lithiating the material are also contemplated by the present disclosure. For example, individual electroactive material particles can be coated with an ALD coating, the electroactive particles with the ALD protective coating can be made into electrodes (e.g., into electrode rolls in a conventional roll-to-roll process), and then lithiated as an electrode either as part of a production line or separately.

[0133] Thus, a battery pack can be assembled by laminating a cell structure, which includes an anode layer (in the form of a negative electrode, such as Figure 5A 250 or Figure 5B 270 in), a cathode layer and an electrolyte / separator between the anode and cathode layers. The anode and cathode layers each include a current collector. The negative electrode current collector can be a copper current collector foil, which can be in the form of an open grid or a thin film. The current collector can be connected to an external current collector tab.

[0134] For example, in some variations, an electrode film, such as an anode film, comprises an electrode active material (e.g., coated lithiated silicon-containing particles) dispersed in a polymer binder matrix on a current collector. A separator can then be placed on the negative electrode element, which is covered with a positive electrode film comprising a composition, which is a finely divided lithium insertion compound in a polymer binder matrix. A positive current collector, such as an aluminum current collector foil or mesh, completes the assembly. The tabs of the current collector element form the terminals of the battery pack. A protective bagging material covers the battery and prevents air and moisture from penetrating. In such a bag, a liquid electrolyte suitable for transporting lithium ions can be injected into the separator (and possibly absorbed into the positive and / or negative electrode). In some aspects, the laminated battery pack is further hermetically sealed before use.

[0135] A protective surface coating (e.g., an oxide-based coating) applied to a negative electroactive material comprising a lithiated silicon-containing electroactive material according to certain aspects of the present technology can be formed over the entire exposed surface and thus act as an artificial solid electrolyte interface layer that can prevent the electrode from reacting with a liquid electrolyte. In various aspects, the electroactive material comprising a lithium-silicon alloy can have a surface coating that provides certain advantages, such as a high cutoff voltage (e.g., a cutoff potential relative to a lithium metal reference potential), which ideally minimizes or avoids SEI formation. In certain aspects, a lithium-ion battery incorporating a reinforced negative electroactive material (which has a lithiated silicon-containing electroactive material with a protective coating) substantially maintains (e.g., operates within a preselected range or other targeted high-capacity application) at least about 1,000 hours of battery operation, optionally greater than or equal to about 1,500 hours of battery operation, optionally greater than or equal to about 2,500 hours or more of battery operation, and in certain aspects, optionally greater than or equal to about 5,000 hours or more (active cycling) of charge capacity.

[0136] In certain aspects, lithium-ion batteries incorporating negative electroactive / electrode materials having lithiated silicon-containing electroactive materials with protective coatings prepared according to certain methods of the present disclosure maintain charge capacity and are therefore capable of operating within 20% of a target charge capacity for durations of greater than or equal to about 2 years (including storage and active cycling time under ambient conditions), optionally greater than or equal to about 3 years, optionally greater than or equal to about 4 years, optionally greater than or equal to about 5 years, optionally greater than or equal to about 6 years, optionally greater than or equal to about 7 years, optionally greater than or equal to about 8 years, optionally greater than or equal to about 9 years, and in certain aspects, optionally greater than or equal to about 10 years.

[0137] In other aspects, lithium-ion batteries incorporating lithiated silicon-containing electroactive materials with protective coatings prepared according to certain methods of the present disclosure are capable of operating for a duration of at least about 100 deep discharge cycles, optionally at least about 200 deep discharge cycles, optionally at least about 500 deep discharge cycles, optionally at least about 1,000 deep discharge cycles at less than or equal to about 30% variation of a preselected target charge capacity (thus with minimal charge capacity fade), optionally at less than or equal to about 20%, optionally at less than or equal to about 15%, optionally at less than or equal to about 10%, and in certain variations optionally at less than or equal to about 5% variation in charge capacity.

[0138] In other words, in certain aspects, a lithium ion battery or electrochemical cell incorporating an electrode having a lithiated silicon-containing electroactive material having a protective coating prepared according to certain methods of the present disclosure substantially retains a charge capacity and is capable of operating for at least about 1,000 deep discharge cycles, optionally greater than or equal to about 2,000 deep discharge cycles, optionally greater than or equal to about 3,000 deep discharge cycles, optionally greater than or equal to about 4,000 deep discharge cycles, and in certain variations, optionally greater than or equal to about 5,000 deep discharge cycles.

[0139] Figure 6 Another variation of a single reactor 300 is shown in which a method of making an electrode material, such as a negative electrode material, for an electrochemical cell that cycles lithium ions according to certain aspects of the present disclosure can be performed. Figure 3 ; however, the process of lithiation and application of a protective coating on the electrode precursor material 302 is reversed. Therefore, for the sake of brevity, common aspects of the method and reactor will not be described here. The reactor 300 includes a first reaction chamber 312 and a second reaction chamber 314, which allow material, i.e., the electrode precursor material 302, to be transferred therebetween (e.g., via a conveyor or a roll-to-roll process). In particular, the electrode precursor material 302 is unwound from a first roll or reel 320, introduced into the reactor 300, conveyed through the first and second reaction chambers 312, 314 to the second reel 322, where it is rewound. As in Figure 3 As discussed in the case of , the electrode material precursor 302 can be in a variety of different forms, although not shown, including a plurality of electroactive material particles conveyed on a belt, which can be distributed on a conveyor and collected after processing in the reactor 300.

[0140] In the first reaction chamber 312, the electrode precursor material 302 is lithiated. For example, the lithiation can be performed by a thermal evaporation method. In the thermal evaporation method, a vacuum pump (not shown) can be used to maintain the pressure in the first reaction chamber 312. A heater 330 is placed under the lithium metal source 332 to heat it. As the temperature of the lithium metal in the source 332 increases, the lithium metal evaporates or volatilizes and directs molecules 334 to the electrode precursor material 302. Thus, a first coating 336 of lithium metal is formed on the surface of the electrode precursor material 302.

[0141] After applying the first coating 336 containing lithium in the first reaction chamber 312, the electrode precursor material 302 is allowed to leave the first reaction chamber 312 and then enter the second reaction chamber 314. In the second reaction chamber 314, a second protective coating 338 is applied on the first coating 336. The second protective coating 338 can be selected from: oxide-based coatings, such as aluminum oxide (Al2O3), fluoride-based coatings, and nitride-based coatings. In some variations, as described above, the application of the surface coating can be performed by atomic layer deposition (ALD).

[0142] The second reaction chamber 314 includes first regions 340 and second regions 342, which are arranged in an alternating manner in the second reaction chamber 314. A gas or vapor containing an oxidant, such as oxygen or water, is introduced into each first region 340. One or more ALD precursors are introduced into each second region 342. Each first region 340 and second region 342 together define a deposition zone 344. When the electrode precursor material 302 passes through a first region 340 in a deposition zone 344 and then passes through a second region 342, a second protective coating 338 is applied on the first lithiation layer 336 on the electrode precursor material 302. Those skilled in the art will recognize that the number of deposition zones 344 having alternating first and second regions 340, 342 determines the thickness of the deposited coating, wherein a greater number of deposition zones produces a thicker second coating 338. As discussed above, five deposition zones 344 are shown, corresponding to five deposition cycles capable of providing a second protective coating 338 having a desired thickness within the range discussed above.

[0143] Thus, a second protective coating 338 is formed on the first lithium metal coating 336 on the electrode precursor material 302. After the first and second coatings 336, 338 are applied to the electrode precursor material 302, the electrode precursor material 302 is wound onto the second reel 322 and can be taken out of the reactor 300. Thus, a continuous process can be performed in a single reactor 300, wherein there is no need to evacuate these chambers and adjust the temperature and pressure conditions during processing. Thus, the pressure in the first and second reaction chambers 312, 314 can be maintained at a steady-state level for each deposition method to bring about an efficient process.

[0144] Thus, in various aspects, the present disclosure contemplates methods for making robust lithiated silicon electroactive materials in a continuous process in a single reactor. In certain aspects, a continuous process is used to make an ALD coating on a silicon-containing electrode precursor, wherein lithium is subsequently evaporated onto the silicon-containing electrode precursor to pre-lithiate the electrode. Pre-lithiation is particularly important for electroactive materials used in lithium-ion battery chemistries associated with large first cycle capacity losses, which, as discussed above, may include silicon-containing electroactive materials such as silicon oxide (SiOx) or elemental silicon electrodes, as non-limiting examples.

[0145] In various aspects, the method can perform subsequent processing of the electrode precursor without exposing the electrode / electrode precursor to the external atmosphere, which avoids evacuating the reactor and saves time while improving the quality of the electrode. In certain aspects, the design of the ALD method can produce a relatively thick coating (e.g., ≥ 1 nm) on the electrode by increasing the path length of the electrode precursor in the ALD reaction chamber or enabling the electrode to pass through the ALD reaction chamber multiple times. The amount of Li pre-lithiation is combined with an appropriate negative electrode capacity / positive electrode capacity ratio (N / P ratio) to control the silicon electrochemical potential within an appropriate window to improve the cycle stability of the battery pack. For example, pre-lithiation can drive the silicon potential down according to the N / P ratio and the amount of pre-lithiated Li. When the present method is used to form an electroactive material / electrode, the protective ALD coating can mitigate the mechanical degradation of SEI / silicon-containing electroactive materials by enhancing mechanical integrity, inhibiting electrolyte decomposition, and promoting charge transfer at the electrode level. In addition, the ALD protective coating can better passivate the electrode after pre-lithiation.

[0146] In an alternative variation, Figure 3 Reactor 140 or Figure 6 The reaction chamber for performing ALD in the reactor 300 (ie, the first reaction chamber 142 in the reactor 140 or the second reaction chamber 314 in the reactor 300) may instead have a Figure 7The design shown in . An ALD reaction chamber 350 is contemplated herein for continuously processing an electrode precursor material 360. The ALD reaction chamber 350 has a relatively long path length for the electrode precursor material 360 as it passes alternately between a plurality of upper rollers 362 and a plurality of lower rollers 364. A precursor for the ALD process is fed into an inlet 370 and can be pumped out of an outlet 372. Because the path length of the electrode precursor material 360 within the ALD reaction chamber 350 is longer, multiple deposition cycles can be performed (by alternately introducing the ALD precursor and an oxidant, such as oxygen or water, into the inlet 370) to apply multiple layers of the ALD coating to the electrode precursor material 360 while the electrode precursor material 360 remains therein. As will be appreciated by those skilled in the art, the path length within the ALD reaction chamber 350 can be predetermined based on the length of each deposition cycle (and how many deposition cycles are required to achieve a predetermined coating thickness) and the speed at which the electrode precursor material 360 travels within the ALD reaction chamber 350. In this manner, Figure 7 The ALD reaction chamber 350 in is integrated into a continuous production line (combined with an upstream or downstream reaction chamber for thermal evaporation of lithium).

[0147] In another alternative embodiment, Figure 3 Reactor 140 or Figure 6 The reactor 300 in Figure 8 400. In such a reactor 400, there is only a single reaction chamber, which can be separated from the continuous production line. The reactor 400 has an inlet 402 and an outlet 404. The electrode precursor material 410 is conveyed in the reactor 400 by means of rollers 412. However, the process can be a stop-start batch type process as will be described herein. In one variation, the ALD process can first be carried out in a region of the electrode precursor material 410 in the reactor 400. By alternately introducing the ALD precursor and an oxidant, such as oxygen or water, into the inlet 402, multiple ALD deposition cycles can be carried out while the electrode precursor material 410 is in the reactor 400. For multiple ALD deposition cycles, excess reactant and byproduct gases can be intermittently vented through the outlet 404 of the reactor 400 while the electrode precursor material 410 remains therein. In this way, multiple layers of the ALD coating can be applied to the electrode precursor material 410 to form a predetermined coating thickness. After all ALD reactants are evacuated from the chamber of reactor 400, thermal evaporation of lithium may be performed.

[0148] A heater 420 is placed below a lithium metal source 422. When the heater 420 is activated, the temperature of the lithium metal in the source 422 increases to direct volatilized lithium molecules 424 toward the electrode precursor material 410. A second lithium-containing coating is thus formed on the first ALD coating of the electrode precursor material 410. After the first protective ALD coating and the second lithium-containing coating are applied to the electrode precursor material 410, the electrode precursor material 410 can be removed from the reactor 400. As will be appreciated by those skilled in the art, the application of the ALD coating and the lithium-containing coating can be reversed so that thermal evaporation of lithium occurs first, followed by the ALD deposition process described above.

[0149] In certain aspects, the present disclosure provides methods for pre-lithiating electrode materials to provide an appropriate lithium content for a balanced cell. Figure 1 The battery pack 20 illustrated in FIG. 1 is cycled to determine the required amount of lithiation. At the beginning of the first charge, the positive electrode can be fully lithiated. For example, the initial lithium concentration at the positive electrode It can be expressed as:

[0150]

[0151] in is the mass of the positively active material (g / cm 2 )and is the initial specific capacity of the positive electroactive material (mAh / g). During the first charge, all lithium is removed from the positive electrode. However, due to, for example, the formation of the solid electrolyte interface (SEI) layer and other electrolyte reactions, only a portion of the removed lithium is embedded in the negative electrode or alloyed with the negative electrode. The lithium concentration at the negative electrode (mAh / cm 2 ) It can be expressed as:

[0152]

[0153] in is the mass of the negatively active material (g / cm 2 ),and is the initial specific capacity of the negatively charged material (mAh / g). First cycle or reversible capacity loss It can be expressed as:

[0154]

[0155] in is the first cycle efficiency of the negative electrode.

[0156] In various aspects, as highlighted above, lithiation of the negative electrode can compensate for such first cycle capacity loss. Represents the amount of lithium (mAh / cm 2),and represents the degree of lithiation. For example, It can be defined as:

[0157]

[0158] Recyclable lithium , including the lithium embedded in the negative electrode at the end of the first charge, can be expressed as:

[0159]

[0160] in is the ratio of N to P based on the first cycle capacity, for example expressed as:

[0161]

[0162] In this way, lithium can be recycled It can be roughly expressed in detail as the lithium concentration at the positive electrode First cycle or reversible capacity loss The difference plus the lithium The maximum possible lithiation of the negative electrode It can be expressed as:

[0163]

[0164] After the first discharge, the active sites of the cathode are lost due to the first cycle capacity loss. For example, the first cycle efficiency of the cathode is It can be expressed as:

[0165]

[0166] in is the reversible specific capacity of the positive electrode, and is the initial specific capacity of the positive electroactive material as shown above.

[0167] Reversible capacity of positive electrode It can be expressed as:

[0168]

[0169] When the positive electrode has enough cyclable lithium capacity, The negative electrode maintains substantially the same number of active sites. The reversible capacity of the negative electrode is the same as the initial capacity of the negative electrode. In this regard, the reversible capacity of the electrochemical cell is It can be expressed as:

[0170]

[0171] in .

[0172] In this case, the maximum lithium occupancy at the cathode is It can be expressed as

[0173]

[0174] If the positive electrode does not have enough cyclable lithium capacity , then the reversible battery capacity can be expressed as:

[0175]

[0176] And the maximum lithium occupancy at the positive electrode can be 1 In this case, the residual lithium can be expressed as

[0177]

[0178] Residual lithium cannot be deintercalated or de-alloyed from the negative electrode, and in this regard, the lithium occupancy is minimized. It can be expressed as:

[0179]

[0180] or

[0181]

[0182] With respect to charge, Q is the amount of lithium removed from the positive electrode to make

[0183]

[0184] and

[0185]

[0186] From this we can determine:

[0187]

[0188] and

[0189]

[0190] At the start of discharge:

[0191]

[0192] and

[0193]

[0194] To make

[0195]

[0196] The detailed process for determining the appropriate lithium content for a balanced cell is outlined below:

[0197]

[0198] In certain aspects, an electrochemical cell incorporating a lithiated electroactive material with a protective coating prepared according to certain methods of the present disclosure can have an N / P ratio (negative electrode capacity of lithium / positive electrode capacity) of greater than or equal to about 1.5 to less than or equal to about 2. By controlling the N / P ratio with pre-lithiation, the voltage window of silicon-based electrodes can be fine-tuned and optimized. For example, the voltage window of silicon can be about 0.465V to about 0.076V.

[0199] Example 1

[0200] A silicon negative electrode formed of 80 wt % active material (uncoated Si or lithiated and ALD coated Si), 10 wt % carbon black and 10 wt % binder was prepared. Super P was used as carbon black and polyimide was used as binder. The active material and carbon black were first mixed using a standard electrode mixing machine, and then mixed with the binder solution using a mixer. The electrode slurry was then coated on Cu foil and dried overnight at 250 ° C under vacuum.

[0201] ALD coating was performed directly on the silicon electrode. The deposition temperature of the Al2O3 coating was 200°C. Trimethylaluminum was used as the Al precursor and H2O was used as the O precursor. Both precursors were heated at 80°C during the deposition process. The exposure time and pump down time of each precursor were 10 seconds and 20 seconds, respectively.

[0202] Both the comparative uncoated silicon anode and the silicon anode with Al2O3 ALD coating were electrochemically pre-lithiated.

[0203] A coin cell half-cell (2032) was fabricated in an argon-filled glove box using an electroactive material containing silicon as the working electrode and lithium (Li) foil as the counter electrode. The electrolyte contained 1 M LiPF6 in fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) (FEC:EMC = 1:4 weight ratio), and Celgard TM 2320 separator. A silicon working electrode was formed, which contained electroactive particles containing silicon mixed with a polyimide binder and Super P carbon black in a weight ratio of 80:10:10.

[0204] The battery half-cells were then tested to determine the capacity retention over various charge / discharge cycles. More specifically, galvanostatic cycling was performed using an Arbin cycler, which included 2 formation cycles at a charge / discharge rate of C / 20, followed by cycling at C / 5. The galvanostatic voltage cutoffs were 3.0 V and 4.2 V vs. Li / Li+ for the formation cycles, and 3.0 V and 4.2 V vs. Li / Li+ for the C / 5 cycles. For the silicon electrode combining the ALD-coated Al2O3 coating and the pre-lithiation process according to certain aspects of the present disclosure, the N / P ratio was 2.

[0205] Fig. 9 Comparative full cell data showing a combination of ALD Al2O3 coating and pre-lithiation of Si electrodes, demonstrating that ALD coating can achieve ideal specific areal capacities (>4 mAh / cm 2 ) significantly improved the cycling stability. The discharge capacity (mAh / cm2) on the y-axis 450 is shown as a comparison of the cycle number / index (460) on the x-axis. 2 ) and discharge capacity retention (%) performance on the y-axis 452. More specifically, the performance of a negative electrode 470 having a comparative uncoated silicon and a negative electrode 472 treated with silicon particles 472 having an ALD coating prepared according to certain aspects of the present disclosure (both samples were pre-lithiated prior to cell assembly) in a half-cell is shown.

[0206] As can be seen, the uncoated comparative silicon-containing electrode 470 has a rapid drop in discharge capacity and only 35% capacity retention after 270 cycles. For the electrode incorporating the treated silicon-containing electroactive material particles 472 that have been subjected to an ALD step and lithiation according to certain aspects of the present disclosure, the capacity retention is approximately 70% at 270 cycles, which is a significant improvement over the comparative example.

[0207] The above description of the embodiments is provided for the purpose of illustration and description. It is not intended to be exhaustive or to limit the present disclosure. Each element or factor of a particular embodiment is generally not limited to that particular embodiment, but is interchangeable and can be used for a selected embodiment where applicable, even if not explicitly shown or described. The same content can also be changed in many ways. Such changes should not be considered as departing from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure.

Claims

1. A continuous method for manufacturing a negative electrode material for an electrochemical cell for cycling lithium ions, the method comprising: applying a protective coating onto a negative electrode precursor by atomic layer deposition (ALD) in a first reaction chamber of a reactor, wherein the negative electrode precursor comprises silicon; and transferring the negative electrode precursor to a second reaction chamber of the reactor and lithiating the negative electrode precursor to form a negative electrode material comprising a protective coating and a coating containing lithium; wherein said lithiation occurs in a continuous process conducted in a reactor having a first reaction chamber and a second reaction chamber; wherein lithiation is carried out by thermal evaporation; and The protective coating is selected from the group consisting of: aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin oxide (SnO2), zinc oxide (ZnO), lithium fluoride (LiF), aluminum fluoride (AlF3), aluminum oxyfluoride (AlFO), aluminum nitride (AlN), silicon nitride (SiN) and combinations thereof.

2. The method of claim 1, wherein the protective coating comprises aluminum oxide (Al2O3). The method of claim 1 , wherein the first reaction chamber defines a plurality of deposition zones.

4. The method of claim 3, wherein each of the plurality of deposition zones comprises a first region for introducing an oxidant and a second region for introducing one or more ALD precursors. The method of claim 1 , wherein the reactor is a vacuum chamber defining a first reaction chamber and a second reaction chamber. The method according to claim 1 , wherein the protective coating layer has a thickness of greater than or equal to 1 nm and less than or equal to 25 nm. 7 . The method according to claim 1 , wherein the thickness of the coating layer containing lithium is greater than or equal to 1 μm and less than or equal to 50 μm.

8. The method of claim 1, wherein the method is performed continuously in a roll-to-roll process.

9. A continuous method for manufacturing an electrode material for an electrode in an electrochemical cell for cycling lithium ions, the method comprising: Applying a protective coating to an electrode precursor material by atomic layer deposition (ALD) in a continuous process conducted in a reactor having a first reaction chamber and a second reaction chamber, and lithiating the electrode precursor material to form a lithiated electrode material including the protective coating; the method comprising applying the protective coating to the electrode precursor material in the first reaction chamber; and lithiating the electrode precursor material in a second reaction chamber; wherein the electrode precursor material comprises silicon; wherein lithiation is carried out by thermal evaporation; and The protective coating is selected from the group consisting of: aluminum oxide (Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium pentoxide (V2O5), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), tin oxide (SnO2), zinc oxide (ZnO), lithium fluoride (LiF), aluminum fluoride (AlF3), aluminum oxyfluoride (AlFO), aluminum nitride (AlN), silicon nitride (SiN) and combinations thereof.

10. The method of claim 9, wherein the protective coating comprises aluminum oxide (Al2O3).

11. The method of claim 9, wherein the first reaction chamber defines a plurality of deposition zones, each of which includes a first region for introducing an oxidant and a second region for introducing one or more ALD precursors.

12. The method of claim 9, wherein the reactor is a vacuum chamber defining a first reaction chamber and a second reaction chamber. 13 . The method according to claim 9 , wherein the protective coating layer has a thickness of greater than or equal to 1 nm and less than or equal to 25 nm.

14. The method of claim 9, wherein the method is performed continuously in a roll-to-roll process.

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