Anode Composition

Abstract

The present disclosure generally relates to an anode for a lithium-ion battery, and an anode composition thereof. Specifically, the anode of the present disclosure includes an anode composition comprising micro-silicon active material particles, the micro-silicon active material particles comprising low surface area and high purity. The present disclosure also relates to a method of incorporating the anode composition into an electrochemical cell.

Description

[Technical field]

[0001] The present disclosure generally relates to an anode for a lithium-ion battery, and an anode composition thereof. Specifically, the anode of the present disclosure includes an anode composition comprising micro-silicon active material particles, the micro-silicon active material particles comprising low surface area and high purity. The present disclosure also relates to a method of incorporating the anode composition into an electrochemical cell. [Background technology]

[0002] Conventional lithium-ion (Li-ion) batteries typically employ graphite-based anodes as the intercalation material for lithium. However, silicon-based anodes offer an improvement over graphite-based Li-ion batteries. 3.75 Si) has higher gravimetric (3579 mAh / g vs. 372 mAh / g for graphite) and volumetric capacity (in the fully lithiated state, about 750 mAh / cm for graphite). 3 Approximately 2194mAh / cm 3 In addition, silicon-based anodes exhibit both Li / Li + Silicon has a low lithiation / delithiation voltage plateau at about 0.3-0.4 V vs. , which allows for maintaining an open circuit potential that avoids undesirable Li plating and dendrite formation. Although silicon exhibits excellent electrochemical activity, it is difficult to achieve stable cycle life for silicon-based anodes due to the large volume change of silicon during lithiation and delithiation. Silicon active materials and regions can lose electrical contact from the anode, as the large volume change combined with its low electrical conductivity separates the silicon from the surrounding material in the anode.

[0003] In addition, the large silicon volume change aggravates the formation of the solid electrolyte interface (SEI), which may further lead to electrical insulation and therefore capacity loss. The expansion and contraction of silicon particles during charge-discharge cycling causes the pulverization of silicon particles, which increases their specific surface area. As the silicon surface area changes and increases during cycling, the SEI repeatedly decomposes and reforms. Thus, the SEI is continuously built up around the pulverized silicon regions during cycling, resulting in a thick electronically and ionically insulating layer. This accumulating SEI increases the impedance of the electrode, reduces the electrochemical reactivity of the electrode, and adversely affects the cycle life. Due to its high specific capacity, abundance, and low cost, silicon is a promising active material for Li-ion anodes. However, its large volume change during lithiation and delithiation (Li 3.75 The increase in the volume change (>280% for the Si1 phase) leads to mechanical degradation of the electrode and an unstable SEI, which leads to electrode swelling and poor cell cycle life.

[0004] Therefore, there is a need to provide new and alternative anode compositions for lithium ion batteries, especially anode compositions containing a majority of silicon active material, which can control the swelling effect of silicon and significantly extend the stability and / or cycle life of the anode. Summary of the Invention

[0005] The present disclosure provides an anode composition comprising micro-silicon active material particles, the silicon content being at least 60% by weight based on the total weight of the anode composition. The present disclosure also provides a method of incorporating an anode comprising the anode composition into an electrochemical cell and the electrochemical cell so formed, whereby the anode paired with the method of integration into the electrochemical cell can extend the stability and / or cycle life of the anode.

[0006] In one aspect, an anode composition is provided that includes microsilicon active material particles, the microsilicon active material particles having a particle size of less than about 0.1 m 2 / g~about 10m2 / g, (ii) a measured BET surface area of ​​about 0.1 μm to about 10 μm 50 and (iii) one or more of the following: (i) particle size; and (ii) D50:BET surface area ratio of about 0.1 to about 10, and the amount of microsilicon active material particles present in the anode composition is about 60% to about 95% by weight, based on the total weight percent of the anode composition. In some embodiments, the amount of microsilicon active material particles present in the anode composition can be about 70% to about 95% by weight, based on the total weight percent of the anode composition. In some embodiments, the purity of the microsilicon active material particles (oxygen free) can be at least 95% by weight.

[0007] In some embodiments, the anode composition may further include one or more binders. The amount of binder present in the anode composition may be from about 2.5% by weight to about 15% by weight, based on the total weight of the anode composition.

[0008] In some embodiments, the anode composition can further include one or more conductive materials. The amount of conductive material present in the anode composition can be from about 2.5% by weight to about 40% by weight, based on the total weight of the anode composition.

[0009] In some embodiments, the micro silicon active material particles and / or the anode composition may be prelithiated. The prelithiation level of the micro silicon active material particles and / or the anode composition may be from about 1% to about 30% silicon lithiation.

[0010] In another aspect, an electrochemical cell is provided that includes an anode, a cathode, an electrolyte, and a separator, the anode comprising an anode composition defined in any one or more of the embodiments or examples described herein, and the lithium uptake capacity of the anode is greater than the lithium release capacity of the cathode. In some embodiments, the lithium uptake capacity of the anode may not be fully utilized during charging of the lithium ion battery. In one example, the anode may be only partially lithiated in a fully charged state. In some embodiments, the degree of silicon lithiation may be limited to about 20% to about 80% of the theoretical maximum. In some embodiments, the capacity ratio (N / P ratio) of the anode and the cathode may be about 1.05 to about 7. In other embodiments, the lower cutoff voltage may be about 2.0V to 3.5V.

[0011] In some embodiments, the pre-lithiation level of the anode can be from about 1% to about 30% silicon lithiation. The cathode can be selected from the group including lithium nickel cobalt manganese oxide (NCM), lithium iron phosphate (LFP), lithium nickel manganese spinel (LNMO), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), and sulfur complexes. The electrolyte can be selected from non-aqueous electrolyte solutions including one or more lithium salts.

[0012] In some embodiments, the electrochemical cell can be an energy storage device. The energy storage device can be a battery, preferably a secondary battery. For example, the battery can be a lithium ion battery.

[0013] In another aspect, a method is provided for improving the cycling stability of a lithium-ion battery having an anode and a cathode, at least one electrolyte, and a separator, wherein the anode composition is defined according to any one or more of the embodiments or examples described herein. In some embodiments, the anode in the battery delivers a specific capacity of at least about 450 mAh / g, 500 mAh / g, 600 mAh / g, 800 mAh / g, 1000 mAh / g, 1200 mAh / g, or 1500 mAh / g and retains at least about 80% of its initial capacity after 100, 200, 400, 600, 800, 1000, or 1500 cycles of the battery.

[0014] In another aspect, there is provided a use of an anode composition in an electrochemical cell, the anode composition being at least partially applied to a current collector material, the anode composition being as defined by any one or more of the embodiments or examples described herein.

[0015] In another aspect, there is provided a process for preparing an anode for an electrochemical cell comprising: (i) preparing an anode slurry comprising microsilicon active material particles, optionally one or more further active materials, optionally one or more binders, optionally one or more conductive materials, optionally one or more additives, and a solvent system; and (ii) casting a layer of the anode slurry onto a current collector material to provide a wet anode composition layer on the current collector material.

[0016] In another aspect, there is provided an anode prepared as defined by the process in any one or more of the embodiments or examples described herein.

[0017] In another aspect, a process for assembling an electrochemical cell is provided, the process comprising the steps of: preparing an anode as defined by the process in any one or more of the embodiments or examples described herein, where the anode comprises an anode composition as defined in any one or more of the embodiments or examples described herein, and assembling the anode into an electrochemical cell. [Brief description of the drawings]

[0018] Preferred embodiments of the present disclosure will be further described and illustrated, by way of example only, with reference to the accompanying drawings, in which:

[0019] [Figure 1a] 13 is a series of graphs showing specific coating capacity (anode) at C / 2 (four micro silicon anode samples) in a full cell. [Figure 1b] FIG. 13 is a graph showing the discharge capacity retention of 30% capacity limited full cells at a rate of C / 2 (four micro silicon anode samples). [Diagram 2] 13 is a graph showing half-cell capacity retention data for four micro silicon anode samples. [Figure 3a] FIG. 13 is a graph showing the specific coating capacity of a full cell (anode) with limited capacity (at 35%, 51%, and 99% capacity limits) of 70 wt. % mSi (Elkem2) at C / 2. [Figure 3b] FIG. 13 is a graph showing the discharge capacity retention of capacity limited (at 35%, 51%, and 99% capacity limits) full cells of 70 wt. % mSi (Elkem2) at a rate of C / 2. [Figure 4a] FIG. 13 shows the specific coating capacity of full cells of pre-lithiated 70 wt. % mSi (Elkem2) anodes (at 0, 10, and 20% pre-lithiation) at a rate of C / 2. [Figure 4b]FIG. 13 is a graph showing discharge capacity retention at C / 2 (anode) of pre-lithiated 70 wt. % mSi (Elkem2) anodes at 0, 10, and 20% pre-lithiation. [Figure 5a] FIG. 13 shows the specific coating capacity of anodes of 70 wt. % mSi (Elkem2) with different binders (CMC / SBR vs. PAA) in a 30% limited capacity full cell at a rate of C / 2. [Figure 5b] FIG. 13 shows the discharge capacity retention of 70 wt. % mSi (Elkem2) anodes with different binders (CMC / SBR vs. PAA) in 30% limited capacity full cells at C / 2 rate. [Figure 6a] 13 is a graph showing the specific coating capacity for anodes of 70 wt. % mSi (Elkem2) with Li0.25PAA binder vs. Li0.95PAA binder with and without CNTs (anode) at C / 2. [Figure 6b] 13 is a graph showing discharge capacity retention for anodes of 70 wt. % mSi (Elkem2) with Li0.25PAA binder vs. Li0.95PAA binder with and without CNTs (anode) at C / 2. [Figure 7a] 13 is a graph showing the discharge capacity retention of limited capacity full cells with micro-Si with PAA copolymer at a rate of C / 2. [Figure 7b] 1 is a graph showing the specific coating capacity (anode) of micro-Si with PAA copolymer at a rate of C / 2. [Figure 8a] FIG. 13 is a graph showing specific coating capacity for anodes of 70 wt% vs. 90 wt% mSi (Elkem2) at C / 2. [Figure 8b] FIG. 13 is a graph showing discharge capacity retention of 70 wt. % vs. 90 wt. % mSi (Elkem2) anodes for limited capacity full cells at C / 2 rate. [Figure 9a]FIG. 13 is a graph showing the specific coating capacity for an anode of 70 wt. % mSi (Elkem2) with and without CNTs at C / 2. [Figure 9b] FIG. 13 shows the discharge capacity retention of anodes of 70 wt % mSi (Elkem2) in limited capacity full cells with and without CNTs at C / 2. [Figure 10a] 13 is a graph showing the specific coating capacity (anode) at C / 2 of a pre-lithiated (direct contact) 70 wt % mSi (Elkem2) anode via the direct contact method. [Figure 10b] FIG. 13 is a graph showing the discharge capacity retention of a pre-lithiated (direct contact) 70 wt % mSi (Elkem2) anode via a full cell of the direct contact method at a rate of C / 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] This disclosure describes the investigations conducted to identify alternative and improved anodes, including most microsilicon anode compositions for lithium ion batteries, optional methods of incorporating the anodes into electrochemical cells, electrochemical cells so formed, and the following various non-limiting examples of their uses.

[0021] General Definitions and Terminology In the following description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration several embodiments, It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure.

[0022] With respect to the definitions provided herein, unless otherwise stated or implied from the context, the defined terms and phrases include the meanings provided. In addition, unless otherwise expressly stated or clear from the context, the following terms and phrases do not exclude the meaning that the term or phrase would have acquired by one of ordinary skill in the relevant art. The definitions are provided to aid in describing certain embodiments and are not intended to limit the claimed invention, as the scope of the invention is limited only by the claims. Further, unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular.

[0023] All publications discussed and / or referenced herein are incorporated herein in their entirety.

[0024] Throughout this disclosure, unless specifically stated otherwise or unless the context requires otherwise, reference to a single step, composition of matter, group of steps, or group of compositions of matter is intended to encompass one and more than one (i.e., one or more) of that step, composition of matter, group of steps, or group of compositions of matter. Thus, as used herein, the singular forms "a," "an," and "the" include plural aspects unless the context clearly indicates otherwise. For example, reference to "a" includes the singular and two or more, reference to "an" includes the singular and two or more, reference to "the" includes the singular and two or more, etc.

[0025] Those skilled in the art will appreciate that the disclosure herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes, individually or collectively, all of the embodiments, steps, features, methods, compositions, and processes referred to or shown in this specification, and any and all combinations, or any two or more of such steps or features.

[0026] The term "and / or," e.g., "X and / or Y," shall be understood to mean either "X and Y" or "X or Y," and shall be interpreted as providing explicit support for both meanings or for either meaning.

[0027] Unless otherwise indicated, the terms "first," "second," and the like are used herein merely as labels, and are not intended to impose any sequential, positional, or hierarchical requirements on the items to which these terms refer. Moreover, a reference to a "second" item does not require or preclude the presence of a lower-numbered item (e.g., a "first" item) and / or a higher-numbered item (e.g., a "third" item).

[0028] As used herein, the phrase "at least one of," when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. The items may be specific objects, things, or categories. In other words, "at least one of" means that any combination or number of items from the list may be used, but not all of the items in the list may be required. For example, "at least one of item A, item B, and item C" may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, "at least one of item A, item B, and item C" may mean, for example, but not limited to, two of item A, one of item B, and ten of item C, four of item B, and seven of item C, or some other suitable combination.

[0029] It should be understood that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination.

[0030] Throughout this specification, various aspects and components of the invention can be presented in a range format. The range format is included for convenience and should not be construed as an inflexible limitation on the scope of the invention. Thus, the description of a range should be considered to have specifically disclosed all possible subranges and individual numerical values ​​within that range, unless specifically indicated otherwise. For example, the description of a range such as 1-5 should be considered to have specifically disclosed subranges such as 1-3, 1-4, 1-5, 2-4, 2-5, 3-5, etc., as well as individual and partial numbers within the recited range, such as 1, 2, 3, 4, 5, 5.5, and 6, unless an integer is required or is implied by context. This applies regardless of the breadth of the range disclosed. When specific values ​​are required, they are set forth herein.

[0031] Throughout this specification the word "comprise" or variations such as "comprises" or "comprising" will be understood to mean the inclusion of the specified elements, integers, or steps, or group of elements, integers, or steps, but not the exclusion of any other elements, integers, or steps, or group of elements, integers, or steps.

[0032] Throughout this specification, the term "consisting essentially of" is intended to exclude elements that would materially affect the properties of the claimed composition.

[0033] As used herein, the terms "comprising," "comprise," and "comprises" are intended to be optionally replaceable in all instances with the terms "consisting essentially of," "consist essentially of," "consist essentially of," "consisting of," "consist of," and "consists of," respectively.

[0034] As used herein, the term "about" encompasses a tolerance of 10% in any value or values ​​connected to the term.

[0035] As used herein, the term "weight percent" may be abbreviated as "wt.%."

[0036] Specific Terms As used herein, the term "lithiation" includes the lithiation of either the anode or the cathode and refers to the interaction of Li with the active material. + is intended to indicate the intercalation or alloying of

[0037] As used herein, the term "delithiation" includes delithiation of either the anode or the cathode, and refers to the dissociation of Li from the active material. + is intended to indicate the extraction or dealloying of

[0038] The term "charging" can be used in the context of full cells and half cells. In full cells, the term "charging" refers to the charging of Li + The term "charging" refers to the involuntary process of forcing Li from the cathode to the anode (initial pairing of the anode and cathode) and indicates a rise in cell voltage. In a half cell, the term "charging" refers to the transfer of Li from the working electrode to the anode. + It involves an involuntary process of extraction and deposition on the reference electrode (lithium metal foil) and shows an increase in the cell voltage.

[0039] The term "discharge" can be used in the context of full cells and half cells. In a full cell, the term "discharge" refers to the removal of Li from the anode. + It encompasses the optional process of extracting ions and transferring them from the anode to the cathode when assembled, which indicates a decrease in cell voltage. In a half cell, the term "discharge" refers to the removal of Li from the reference electrode (lithium metal foil). + Optional process of dissolution, and Li + into the working electrode, showing a decrease in cell voltage.

[0040] As used herein, the term "half cell" describes a reference test system used for research and development purposes consisting of a working electrode (the electrode of interest) and a reference electrode (e.g., lithium metal foil).

[0041] As used herein, the term "full cell" describes a conventional electrochemical cell system that pairs a commercially relevant anode (graphite, silicon, LTO) with a commercially relevant cathode (LFP, LCO, NCM, NCA, LMO).

[0042] The term "prelithiated" refers to the process of prelithiating a lithium battery with Li prior to pairing with the cathode electrode in a full-cell format. + into the anode or anode active material.

[0043] The term "N / P ratio" or "negative to positive ratio" refers to the mass balance between the anode (negative electrode) and the cathode (positive electrode). The mass balance is the mass of each electrode cm 2 The available area capacity per

[0044] The term "areal capacity" refers to the available capacity of an electrode (anode or cathode) per area. It depends on the type and weight % of active material in the coating, as well as mg / cm 2 (or g / m 2 ) can be determined by the amount of coating loading applied to the current collector substrate.2 The higher the load at cm 2 The capacity per unit area is increased.

[0045] Anode Composition The present disclosure is directed to providing improved anodes for lithium-ion batteries. The present disclosure spans various research and development efforts directed to identifying and better understanding the failure mechanisms of anodes, including most silicon anode compositions, and then optimizing their formulations so that solid electrolyte interface decomposition (e.g., cracking and delamination), silicon particle fracture, and instability can be controlled, reduced, or in some ways ameliorated, to improve the stability and cyclability of lithium-ion batteries.

[0046] Surprisingly, it has been found, at least according to some examples described herein, that most silicon anode compositions can exhibit significant anode stability and / or cycle life. Even more surprisingly, it has been found that most silicon anode compositions, paired with a method of integration into an electrochemical cell, can control the formation of the SEI, as well as the expansion and decomposition of the silicon, and thus significantly extend the anode stability and / or cycle life.

[0047] Also, according to at least some examples described herein, most silicon anode compositions for electrochemical cells (e.g., batteries) include: (a) Long-term cycling stability of lithium-ion (Li-ion) cells; (b) controlled expansion and contraction of silicon during charge and discharge cycling of Li-ion cells, minimizing silicon particle cracking, pulverization, and SEI growth; (c) reduced cell capacity fade during cycle life due to controlled silicon expansion / contraction and silicon anode voltage window; and / or (d) It has been found that the present invention may provide one or more additional advantages, such as high rate capability.

[0048] The anode compositions described herein may include microsilicon active material particles, which may be any of the following: (i) about 0.1 m 2 / g~about 10m 2 / g, (ii) a measured BET surface area of ​​about 0.1 μm to about 10 μm 50 particle size, and (iii) a D of about 0.1 to 10 50 :BET surface area ratios and the amount of silicon present in the anode composition is from about 60% by weight to about 95% by weight, based on the total weight percent of the anode composition.

[0049] The anode compositions described herein may include microsilicon active material particles, the microsilicon active material particles having an average particle size of (i) about 0.1 m 2 / g~about 10m 2 / g, and (ii) a D of about 0.1 μm to about 10 μm. 50 particle size, or (iii) a D of about 0.1 to 10 50 :BET surface area ratio, and the amount of silicon present in the anode composition is from about 60% by weight to about 95% by weight, based on the total weight percent of the anode composition.

[0050] The anode compositions described herein may comprise or consist of the microsilicon active material particles described herein, optionally one or more additional active materials, optionally one or more binders, optionally one or more conductive materials, and optionally one or more additives. In one example, the anode compositions described herein comprise microsilicon active material particles, the microsilicon active material particles having a density of less than or equal to: (i) about 0.1 m 2 / g~about 10m 2 / g, (ii) a measured BET surface area of ​​about 0.1 μm to about 10 μm 50 and (iii) a D of about 0.1 to about 10. 50% to about 95 wt. %, based on the total weight percent of the anode composition. In another example, the anode compositions described herein may comprise or consist of microsilicon active material particles having one or more of the following ratios of surface area to surface area: BET surface area, and the amount of microsilicon active material particles present in the anode composition is from about 60 wt. % to about 95 wt. %, based on the total weight percent of the anode composition. Optionally, one or more additional active materials, optionally one or more binders, optionally one or more conductive materials, and optionally one or more additives. In another example, the anode compositions described herein may comprise microsilicon active material particles, the microsilicon active material particles having a surface area of ​​about 0.1 m 2 / g~about 10m 2 / g, and (ii) a D of about 0.1 μm to about 10 μm. 50 particle size, or (iii) D of about 0.1 to about 10 50 % to about 95 wt %, based on the total weight % of the anode composition, and optionally one or more further active materials, optionally one or more binders, optionally one or more conductive materials, and optionally one or more additives.

[0051] In some embodiments or examples, the microsilicon active material particle content of the anode composition may be about 60% to about 95% by weight based on the total weight of the anode composition. It will be appreciated that further advantages may be exhibited when the microsilicon active material particle content of the anode composition is greater than 60% by weight, preferably greater than 70% by weight. The microsilicon active material particle content may be less than about 95% by weight, 90% by weight, 85% by weight, 80% by weight, 75% by weight, 70% by weight, 65% by weight, or 60% by weight. The microsilicon active material particle content may be at least about 60% by weight, 65% by weight, 70% by weight, 75% by weight, 80% by weight, 85% by weight, 90% by weight, or 95% by weight. The microsilicon active material particle content of the anode composition may be in a range provided by any two of these upper and / or lower amounts.

[0052] In some embodiments or examples, the thickness of the anode composition is substantially uniform and may be in the range of about 5 μm to about 70 μm. The thickness (μm) of the anode composition may be less than about 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5. The thickness (μm) of the anode composition may be at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70. The thickness of the anode composition may be in a range provided by any two of these upper and / or lower amounts.

[0053] In some embodiments or examples, the anode composition may be supported on a current collector material. In some embodiments or examples, the anode composition may be applied to the current collector material as a coating or film. It will be understood that the current collector may be at least partially coated with the anode composition. For example, the anode composition may be applied to only one side of the current collector material. The current collector material for the anode may be selected from the group including copper, aluminum, stainless steel, titanium, carbon, perforated metal foils, metal foams, and metal-coated polymer-based porous and non-porous films. It will be understood that the current collector material is of suitable dimensions, porosity, and pore size to include the above materials and act as a current collector. For example, the anode composition may be applied to a copper current collector material (e.g., copper foil). For example, an anode composition including or consisting of microsilicon active material particles, optionally one or more additional active materials, optionally one or more binders, optionally one or more conductive materials, and optionally one or more additives may be supported on a copper current collector material (e.g., copper foil). In some embodiments, the current collector material for the anode can have a thickness of about 4 μm to about 25 μm. The thickness (in μm) of the current collector can be less than about 25, 20, 15, 10, 8, 6, or 4. The thickness (in μm) of the current collector can be at least about 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, or 25. The thickness (in μm) of the current collector can be in a range provided by any two of these upper and / or lower amounts. In one example, the current collector material for the anode can be a copper foil having a thickness of about 6 μm to about 12 μm.

[0054] In some embodiments or examples, the anode composition can be an anode for a battery. For example, the anode composition can be an anode for a lithium ion battery.

[0055] Silicon particles The present invention relates to an anode composition comprising micro-silicon active material particles.

[0056] In some embodiments or examples, the microsilicon active material particles may include or be selected from the group consisting of metallurgical silicon, polycrystalline silicon, and single crystal silicon. In a preferred example, the microsilicon active material particles are metallurgical silicon.

[0057] It will be appreciated that the raw feedstock for elemental silicon of any kind is quartz sand (silicon dioxide (SiO2)). In conventional manufacturing processes, SiO2 is reacted with carbon in an arc furnace, which may be fed to the process in the form of coke, and high temperatures (about 1800°C) are applied to reduce the SiO2 to Si and CO according to the following reaction:

number

[0058] This reaction produces metallurgical grade silicon, which may contain impurities such as Al, Ca, Fe, Ti, P, Cu, Cr, K, V, Ni, Na, and others at levels ranging from hundreds to thousands of parts per million (ppm). Metallurgical silicon can be used in a variety of industrial applications, including steel production. However, due to the impurities, it cannot be used for electronic applications. The crystal structure of metallurgical silicon is well defined, but it is not as pure as single crystal silicon, nor is it as efficient at conducting electricity. Metallurgical silicon has a metallic crystal structure, characterized by its metallic bonds between atoms. In a metallic crystal structure, the atoms are arranged in a repeating pattern, but lacking order.

[0059] Metallurgical silicon requires further purification to reduce impurities to parts per billion (ppb). This process can result in semiconductor or electronic grade Si (also called polycrystalline silicon). The reaction between metallurgical silicon and dry HCl forms trichlorosilane (SiHCl3), a liquid with a boiling point of 32°C.

number

[0060] It will be appreciated that some chloride impurities may form, such as FeCl3, but due to the difference between the boiling points of these impurities and SiHCl3, the impurities can be separated using fractional distillation techniques. During this process, a mixture of SiHCl3 and chloride impurities is heated and the vapors are condensed in different distillation columns and held at the appropriate temperature. This allows the separation of pure SiHCl3 from the impurities. The reaction between SiHCl3 and H2 results in the formation of pure polycrystalline silicon.

number

[0061] The crystal structure of polycrystalline silicon is not well defined, and the small crystals (grains) that make up the material are randomly oriented and typically less than 100 micrometers in size. The grains are separated by grain boundaries and usually have a random crystallographic orientation. This results in a material that is weaker and less efficient at conducting electricity than single crystal silicon.

[0062] The Czochralski process is used to convert pure polycrystalline silicon to single crystal monocrystalline silicon. A seed crystal is required to grow a single crystal of material that acts as a template for the growth. The Czochralski process involves heating polycrystalline silicon in a quartz-lined graphite crucible by resistive heating to the melting point of Si (1412°C). The seed crystal is then lowered into the molten material and slowly raised, allowing a crystal to grow on the seed. During crystal growth, slow rotation is required to average out any temperature fluctuations that may result in uneven solidification.

[0063] The resulting single crystal silicon is often referred to as monocrystalline silicon. It is characterized by its regular and repeating arrangement of atoms in a three-dimensional lattice and consists of silicon that has no grain limits. Monocrystalline silicon can be treated as an intrinsic semiconductor consisting of only excessively pure silicon. Monocrystalline silicon is known for its high efficiency and high purity, making it ideal for use in electronic applications. Monocrystalline silicon can be p-type and n-type silicon by doping with other elements.

[0064] It is well known in the art that impurities may be present in any microsilicon active material particle. It is also well known that impurities may be selectively added to any microsilicon active material particle. In some embodiments, impurities selected from the group consisting of Al, Ca, Fe, Ti, P, Cu, Cr, K, V, Ni, and Na may be present in the microsilicon active material particle in a total or individual amount of, for example, less than about 5000 ppm, less than about 4500 ppm, less than about 4000 ppm, less than about 3500 ppm, or less than about 3000 ppm. In some embodiments, the total or individual impurities selected from the group consisting of Al, Ca, Fe, Ti, P, Cu, Cr, K, V, Ni, and Na may be present in the microsilicon active material particle in a range of about 0 ppm to about 5000 ppm, preferably about 0 ppm to about 4000 ppm, and more preferably about 0 ppm to about 3000 ppm.

[0065] In one embodiment, the microsilicon active material particles may exhibit any morphology, for example, they may take the form of flakes, aggregates, granules, powders, spheres, powdered materials, and the like, and combinations thereof. The microsilicon active material particles may have any desired shape, including, but not limited to, cubic, rod-like, plate-like, polyhedral, spherical or hemispherical, quasi-spherical, rounded or semi-rounded, angular, irregular, and the like. In one embodiment, the microsilicon active material particles have an aspect ratio (i.e., the ratio of length to width, where length and width are measured perpendicular to each other and length refers to the longest linearly measured dimension) of 1.0 to 10.0, or 1.0 to 5.0, or 1.0 to 4.0, or 1.0 to 2.0. In one embodiment, the microsilicon active material particles may have an aspect ratio of about 1.0 to 5.0, or about 1.0 to 4.0, or about 1.0 to about 3.0, or about 1.0 to about 2.0, for example, about 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0.

[0066] In some embodiments, the particle size (in μm) of the microsilicon active material particles may be at least about 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, or 30. In some embodiments, the particle size (in μm) of the microsilicon active material particles may be less than about 30, 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or 0.5. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, the particle size (in μm) of the microsilicon active material particles may be about 1 to about 10, about 2 to about 8, about 3 to about 6, or about 2 to about 5. The particle size is taken to be the longest cross-sectional diameter across the microsilicon active material particle. For non-spherical microsilicon active material particles, the particle size is taken to be the distance corresponding to the longest cross-sectional dimension across the particle.

[0067] The microsilicon active material particles may have a particle size distribution, with 90% (D 90) may have a particle size of less than about 34, 32, 30, 28, 24, 20, 18, 16, 14, 12, 10, 8, 6, 5, or 4 μm, or 50% of the microsilicon active material particles (D 50 ) have a particle size (in μm) of less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.8, 0.6, 0.4, 0.2, 0.1, or 10% of the microsilicon active material particles (D 10 ) has a particle size of less than about 4, 3, 2, or 1 μm. In some embodiments, the microsilicon active material particles have a (D 50 In some embodiments, the microsilicon active material particles have a particle size (in μm) of less than about 10, 9, 8, 7, 6, 5, 4, 3.5, 3, 2.5, 2, 1 (D 50 ) particle size (in μm). 0.9, 0.8, 0.7, 0.6, 0.5, 0.5, 0.4, 0.3, 0.2, or 0.1. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, the microsilicon active material particles have a (D 50 ) particle size (in μm).

[0068] One or more advantages of the present disclosure are provided by microsilicon active material particles having a low surface area. It has been found that the more charge / discharge cycles the microsilicon is subjected to, the higher the surface roughness of the microsilicon particles, resulting in a higher surface area. The higher the surface area, the higher the loss of Li-ions per cycle. This has a large impact on the cycle life of the anode. It has been found that starting with a low surface area can reduce this effect. In some embodiments or examples, the microsilicon active material particles have a surface area of ​​about 0.1 m 2 / g~about 10m 2 / g, for example, about 1m 2 / g~about 5m 2 The microsilicon active material particles may have a BET surface area in the range of at least about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 m / g. 2 / g BET surface area (m 2 In other embodiments or examples, the micro silicon active material particles may have a molecular weight of about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1 m 2 Surface area (m 2 Combinations of these surface area values ​​to form various ranges are also possible, for example, the microsilicon active material particles may have a surface area of ​​about 0.1 to about 10, about 0.1 to about 9, about 0.1 to about 8, about 0.1 to about 7, about 0.1 to about 6, about 0.1 to about 5, about 0.5 to about 10, about 0.5 to about 9, about 0.5 to about 8, about 0.5 to about 7, about 0.5 to about 6, about 0.5 to about 5, about 1 to about 10, about 1 to about 9, about 1 to about 8, about 1 to about 7, about 1 to about 6, or about 1 to about 5 m. 2 Surface area (m 2 / g).

[0069] The present inventors have surprisingly found that the D 50 Particle size (in μm) and BET surface area (m 2 / g) and the ratio of these parameters to the electrochemical performance of the anode. In some embodiments or examples, the D of the micro silicon active material particles 50 Particle size (in μm) and BET surface area (m 2 / g) may range from about 0.1 to about 10. In some embodiments or examples, the D 50 Particle size (in μm) and BET surface area (m 2 / g) may be at least about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10. In some embodiments or examples, the D of the micro silicon active material particles 50 Particle size (in μm) and BET surface area (m 2 / g) can be less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1. Combinations of these ratios to form various ranges are also possible, for example, the D of the microsilicon active material particles. 50 Particle size (in μm) and BET surface area (m 2 / g) can be in the range of about 0.1 to about 10, about 0.1 to about 9, about 0.1 to about 8, about 0.1 to about 7, about 0.1 to about 6, about 0.1 to about 5, about 0.5 to about 10, about 0.5 to about 9, about 0.5 to about 8, about 0.5 to about 7, about 0.5 to about 6, about 0.5 to about 5, about 1 to about 10, about 1 to about 9, about 1 to about 8, about 1 to about 7, about 1 to about 6, or about 1 to about 5. In one particular example, the ratio of about 2 μm to about 8 μm and about 1 m, respectively, can be in the range of about 0.1 to about 10, about 0.1 to about 9, about 0.5 to about 8, about 0.5 to about 7, about 0.5 to about 6, about 0.5 to about 5, about 1 to about 10, about 1 to about 9, about 1 to about 8, about 1 to about 7, about 1 to about 6, or about 1 to about 5. 2 / g~about 5m 2 / g D 50 and the D of the microsilicon active material particles in the range of about 0.1 to about 6 provided by the BET surface area range. 50 Particle size (in μm) and BET surface area (m 2 / g) improves the initial coulombic efficiency and capacity retention of the anode. 2 / g ~ approx. 3.5m 2 / g D 50 D of the microsilicon active material particles in the range of about 1.0 to about 3.5 provided by the particle size and BET surface area range 50 Particle size (in μm) and BET surface area (m 2 / g) advantageously provided the most improved capacity retention in the full cell configuration for the micro-silicon anode design. 50 It will be appreciated that when the particle size / BET surface area ratio is greater than 3.5 and less than 1.0, a gradual decrease in electrochemical performance is found. 50 D with particle size / BET surface area ratio of 0.1 to 2.0 μm 50 Particle size range and >5m 2 A dramatic decrease in ICE and capacity retention is found when the r is 0.01-0.10 due to the BET surface area of ​​1000 μm / g. Without wishing to be bound by theory, this phenomenon is likely due to the low surface reactivity of the microsilicon active material particles with the electrolyte forming a thinner and less resistive SEI layer.

[0070] Surprisingly, when various microsilicon anode grades were cycled in half-cell and full-cell designs, an inverse relationship of cycling stability was found to exist, which correlated with the respective particle size, BET surface area, and d 50 It was governed by the ratio between particle size and BET surface area.

[0071] In a half-cell format, where the micro-silicon anode is tested under fully lithiated conditions, d 50 >2.0μm, BET surface area <5m 2 / g, and d of 0.01 to more than 0.1 50A rapid capacity fade was evident for samples with particle size:BET surface area ratios. When microsilicon materials were tested in a limited capacity full cell design, the cycling stability observed from the half cell tests was reversed. High d 50 Particle size (preferably 2.0-8.0 μm), low BET surface area (preferably 1.0-5.0 m 2 / g), and high d 50 Microsilicon materials with particle size:BET surface area ratio (preferably 0.1-6.0) provide stable cycling performance with higher ICE and capacity retention.

[0072] The expansion and contraction of silicon particles during charge-discharge cycling causes the silicon particles to pulverize, which increases their specific surface area. + With an unlimited supply of ions, the loss of Li from the SEI formation reaction with the newly formed surface can be easily compensated for, and the Si anode can continue to be cycled until the silicon electrode is completely depleted. Thus, a low d 50 , high BET surface area, and d 50 Micro silicon particles with a particle size:BET surface area ratio <0.1 take longer to reach complete depletion of the silicon electrode due to the presence of larger silicon surface area, lower average particle size, and therefore reduced stress on the particles, resulting in relatively stable cycling performance.

[0073] In a full-cell design with a limited Li reservoir, d 50 <2.0μm, BET surface area>5m 2 / g and d 50 The increased reactivity of microsilicon particles with larger surface area, with particle size:BET surface area ratio <0.1, was observed with Li + This leads to accelerated consumption of , resulting in poor capacity retention and cycle life. Low surface reactivity and therefore high d during cycling 50 Particle size (preferably 2.0-8.0 μm), low BET surface area (preferably 1.0-5.0 m2 / g), and high d 50 Li in microsilicon material with particle size:BET surface area ratio (preferably 0.1-6.0) + The low irreversible consumption of ions extended the capacity retention and cycle life. 50 It has been found that a particular combination of and BET surface area can lead to exceptionally good performance in a full cell.

[0074] In limited capacity electrochemical full cells, the anode is designed such that its lithium uptake capacity is greater than the lithium release capacity of the cathode. This ensures that the lithium uptake capacity of the anode is not fully utilized, i.e., the silicon active material particles of the anode are only partially lithiated in the fully charged state, advantageously reducing or preventing the high volume change typically found in silicon anodes during lithiation / delithiation cycles that degrades the structure of the silicon anode and shortens the life of the battery. In other words, a high N / P ratio can limit the degree of lithiation of the microsilicon, since the amount of Li ions is fixed by the cathode during cell assembly. For example, the anode can be significantly oversized relative to the amount of lithium contained in the cell and provided by the cathode. As the degree of lithiation is limited by the oversized anode, so too is the level of expansion of the microsilicon active material particles and their decomposition.

[0075] In some embodiments or examples, the tap density of the micro silicon active material particles is about 0.5 g / cm 3 ~Approx. 1.5g / cm 3 The tap density of the micro silicon active material particles may be in the range of at least about 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.2, 1.3, or 1.5 g / cm. 3 In other embodiments or examples, the tap density of the micro silicon active material particles can be about 1.5, 1.4, 1.3, 1.2, 1.0, 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, or 0.5 g / cm3 Combinations of these density values ​​to form various ranges are also possible, for example, micro silicon active material particles may be less than about 0.5 g / cm 3 ~Approx. 1.2g / cm 3 The density can be measured by any standard method, for example, according to ASTM D7481-18.

[0076] Advantageously, the microsilicon active material particles of the present disclosure can be provided with high purity. In some embodiments or examples, the purity of the microsilicon active material particles (oxygen free) can be in the range of about 95 to about 99.9 (by weight %). The purity of the microsilicon active material particles (oxygen free) can be at least about 95, 96, 97, 98, 99, 99.5, or 99.9 (by weight %). The purity of the microsilicon active material particles (oxygen free) can be less than about 99.9, 99.5, 99, 98, 97, 96, or 95 (by weight %). The purity of the microsilicon active material particles (oxygen free) can be in the range provided by any lower and / or upper limits as previously described.

[0077] In some embodiments or examples, the purity of the microsilicon active particles (with oxygen) may range from about 79 to about 99.5 (by weight %). The purity of the microsilicon active particles (with oxygen) may be at least about 75, 80, 85, 90, 95, 96, 97, 98, 99, or 99.5 (by weight %). The purity of the microsilicon active particles (with oxygen) may be less than about 99.5, 99, 98, 97, 96, 95, 90, 85, 80, or 75 (by weight %). The purity of the microsilicon active particles (with oxygen) may be in a range provided by any lower and / or upper limits as previously described.

[0078] The combination of the novel and inventive features of the microsilicon active material particles according to the present disclosure and their use in an anode composition for an anode in a lithium-ion battery surprisingly leads to an improvement in battery cycling behavior. Unexpectedly, it has been shown that the lithium-ion battery described herein has a small irreversible capacity loss in the first charging cycle and a stable electrochemical behavior with minimal fading in subsequent cycles. Thus, the use of the microsilicon active material particles described herein can achieve a lower initial capacity loss and also a low continuous capacity loss in the lithium-ion battery. Overall, the lithium-ion battery described herein provides very good stability and cycle life. Thus, many cycles can be achieved with minimal fatigue as a result of, for example, mechanical destruction of the anode coating layer, the anode material, or the SEI formation.

[0079] Pre-lithiation The SEI layer is formed during the intercalation of lithium ions, and the organic electrolyte is reduced on the surface of the anode when the anode potential is less than about 1 V vs. Li+ / Li. The SEI layer is important to prevent the co-intercalation of electrolyte ions into the bulk electrode material by creating an electrically insulating but ionically conductive film. This prevents excessive ongoing decomposition of the electrolyte. However, during the formation of the SEI layer film on the surface of the anode active material, some lithium ions may be irreversibly trapped in the electrode, which leads to lithium ion consumption.

[0080] The initial irreversible lithium loss of the anode can be compensated for by adding lithium to the anode via prelithiation. Prelithiation methods can be broadly grouped into electrochemical prelithiation and chemical prelithiation. Electrochemical prelithiation can be further grouped into half-cell prelithiation or short circuit prelithiation. Chemical prelithiation can be further grouped into chemical synthesis, solution soaking, and mechanical process methods. Additional methods for prelithiation that can be utilized at the anode coating level of active material particles are represented by chemical vapor deposition (CVD) type methods and physical vapor deposition methods (PVD). Preferred methods for prelithiating the anode composition also include methods that preform the SEI layer and can be performed in a roll-to-roll process, which is inherently cost-effective. It will be understood that the preferred prelithiation method for prelithiating the active material particles prior to incorporation into the anode composition may differ from the method used to prelithiate the anode composition. It should be noted that the present disclosure is not limited to a particular method of prelithiation, and the most suitable method is selected to achieve the intended results.

[0081] Prelithiation may be applied to the anode electrode. For example, prelithiation may be applied to compensate for lithium lost in the first cycle, which constitutes one full charge and one full discharge of the electrochemical cell. If the amount of prelithiation is selected such that an SEI layer forms but the lithium is not intercalated or alloyed with the active material prior to assembly into a full cell, it is expected that the first cycle loss of the anode will be minimized and any further loss of lithium will be contributed from other sources, such as the cathode electrode, once incorporated into the full cell. As a result, the electrochemical cell will now cycle at a higher cell capacity since more lithium is available for subsequent cycles to pass back and forth between the anode and cathode during repeated charge and discharge cycles.

[0082] Prelithiation can also provide a lithium reservoir to the anode before assembly into a cell assembly, in addition to compensating for any lithium loss that occurs during the first cycle and more generally the initial formation cycle. The lithium reservoir can compensate for ongoing lithium loss over multiple cycles, thus reducing capacity fade and extending the useful life of the full cell. In other words, prelithiation can provide one or more advantages to silicon-containing anodes, particularly anodes that contain a high percentage of silicon. Providing a lithium reservoir to the anode using a method of applying an SEI layer to the active material can also maximize the first cycle efficiency of the cell.

[0083] Optionally, the anode composition may provide a prelithiated anode composition. Prelithiation may occur at the anode active material level prior to incorporation of the active material into the anode composition, or prelithiation may occur after the anode composition is prepared. One or more advantages of the present disclosure are provided by prelithiating anode compositions that can provide a lithium reservoir for the anode, thereby allowing ongoing Li ionization during charge / discharge cycling when incorporated into a full cell configuration. + By compensating for losses, its cycle life is extended.

[0084] In some embodiments, the microsilicon active material particles may be prelithiated microsilicon active material particles, where the prelithiation occurs prior to incorporating the active material into the anode composition. In other embodiments, the microsilicon active material particles may be prelithiated microsilicon active material particles, where the prelithiation occurs after incorporating the active material into the anode composition. The degree of prelithiation can be determined by whether the phase produced is Li0Si1 (0% prelithiation) or Li 3.75 Si1 or Li 4.40 LiSi1, Li 1.71 Si2, Li2Si1, Li 3.5 Si1, and Li 3.75Any phase composition therebetween, including Si1, may be desirable. In some embodiments or examples, the amount of pre-lithiation of the microsilicon active material particles and / or anode composition may be from about 1% to about 30%. The amount of pre-lithiation of the microsilicon active material particles and / or anode composition may be less than about 30%, 25%, 20%, 15%, 10%, 5%, or 1%. The amount of pre-lithiation of the microsilicon active material particles and / or anode composition may be at least about 1%, 5%, 10%, 15%, 20%, 25%, or 30%. The amount of pre-lithiation of the microsilicon active material particles and / or anode composition may be in a range provided by any two of these upper and / or lower amounts.

[0085] Pre-lithiation of the micro-silicon active material particles may be carried out via physical vapor deposition (PVD) or chemical vapor deposition (CVD), or via mechanical alloying, chemical or electrochemical processes. It will be appreciated that a range of suitable methods may be applied to create a silicon-lithium alloy phase prior to incorporating the pre-lithiated micro-silicon active material particles into an anode composition.

[0086] Further active materials The anode compositions described herein may further comprise one or more additional active materials. In some embodiments, the additional active material may be graphite or silicon, such as flake graphite, natural graphite, artificial graphite, silicon oxides with x=0.8-2 (SiOx), silicon carbon composites, silicon alloys, or any combination thereof.

[0087] Binder The anode compositions disclosed herein may further include one or more binders. The binder may be a polymer. In some embodiments, the polymer may be selected from the group consisting of gum arabic, carboxymethylcellulose (CMC) / citric acid, CMC / styrene-butadiene rubber (SBR), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(1-trimethylsilyl-1-propyne) (PTMSP), rubber binders such as gum arabic, xanthan gum, and guar gum, natural cellulosic binders, polysaccharides such as sodium carboxymethylcellulose, lithium carboxymethylcellulose, sodium alginate, polyacrylates, aliphatic polymers such as polyvinyl butyral, aromatic polymers such as styrene-butadiene rubber. For example, the polymer may be selected from the group consisting of polyvinylpyrrolidone, carboxymethylcellulose, polyacrylic acid (PAA), poly(methacrylic acid), maleic anhydride copolymers including poly(ethylene and maleic anhydride) copolymers, polyvinyl alcohol, carboxymethyl chitosan, natural polysaccharides, xanthan gum, alginates, polyimides, and PAA copolymers including one or several of the following polyvinyl alcohol (PVA), polyurethane (PU), polyimide (PI), or polyacrylonitrile (PAN), in one example, the binder is PAA. The binder may be dissolved in H2O or ethanol, or a mixture of H2O and ethanol or N,N' dimethylformamide, or any other solvent suitable for the intended purpose. Some binders may be in the form of a water-based emulsion.

[0088] In some embodiments or examples, the ratio of binder to microsilicon active particles may be about 1:40, 1:35, 1:32, 1:30, 1:25, 1:23, 1:20, 1:15, 1:10, 1:9, 1:6, or 1:4. The ratio of binder to microsilicon active particles may range from about 1:4 to about 1:32. The ratio of binder to microsilicon active particles may range from about 1:8 to about 1:23. The ratio of binder to microsilicon active particles may range from about 1:9 to about 1:15.

[0089] In some embodiments or examples, the binder (in weight %) may be present in the anode composition in a range of about 2.5 to 15. The binder (in weight %) may be present in the anode composition in an amount of less than about 15, 12, 10, 8, 5, or 2.5. The binder (in weight %) may be present in the anode composition in an amount of at least about 2.5%, 5%, 8%, 10%, 12%, or 15%. The binder (in weight %) may be present in the anode composition in a range provided by any two of these upper and / or lower amounts. For example, the binder (in weight %) may be present in the anode composition in a range of about 3 to about 8, or about 4 to about 8.

[0090] It has been found that the pH of the binder can affect the electrochemical performance of the anode composition. In some embodiments or examples, the pH of the binder can be less than 9, 8, 7, 6, 5, 4, 3, or 2. In some embodiments or examples, the pH of the binder can be at least 2, 3, 4, 5, 6, 7, 8, or 9. The pH of the binder can be in a range provided by any two of these upper and / or lower values. For example, the pH of the binder can be in the range of 4 to 8. Preferably, a binder pH of less than 7 can be beneficial to the electrochemical performance of the microsilicon anode, and can be due to (i) reduced corrosion of pure silicon in the acidic region, and / or (ii) greater affinity of silicon to interact with the binder, such as PAA.

[0091] Conductive Materials The anode compositions described herein may further comprise one or more conductive materials. In some embodiments or examples, the conductive material may be a carbon-based material. In some embodiments or examples, the carbon-based material may be nano-sized or micro-sized carbon particles or flakes, or a combination thereof. In some embodiments or examples, the carbon-based material may be selected from the group consisting of activated carbon, carbon nanoparticles, graphite, single-walled (SWCNT) or multi-walled (MWCNT) carbon nanotubes, branched carbon nanotubes, carbon nanofibers, graphene, graphene oxide, MXene, nano- or micro-sized hard carbon, nano- or micro-sized porous carbon, and conductive polymers. The carbon-based material may be selected from the group consisting of graphene, graphene oxide, graphite, single-walled (SWCNT) or multi-walled (MWCNT) carbon nanotubes, branched carbon nanotubes, carbon nanofibers, MXene, nano- or micro-sized hard carbon, nano- or micro-sized porous carbon, and conductive polymers. In one example, the carbon-based material may be a carbon nanotube.

[0092] In some embodiments or examples, the ratio of conductive material to microsilicon active particles may be about 1:50, 1:48, 1:45, 1:40, 1:35, 1:30, 1:25, 1:20, 1:18, 1:15, 1:10, 1:8, 1:6, 1:4, 1:3, 1:2, or 1:1.3. The ratio of conductive material to microsilicon active particles may range from about 1:2 to about 1:30. The ratio of conductive material to microsilicon active particles may range from about 1:2 to about 1:18. The ratio of conductive material to microsilicon active particles may range from about 1:2 to about 1:15.

[0093] In some embodiments or examples, the conductive material may be present in the anode composition in a range of about 2.5 to 40 weight percent (based on the total weight of the anode composition). The conductive material may be present in the anode composition in an amount of less than about 40 weight percent, 30 weight percent, 20 weight percent, 15 weight percent, 10 weight percent, 7 weight percent, 5 weight percent, or 2.5 weight percent (based on the total weight of the anode composition). The conductive material may be present in the anode composition in an amount of at least about 2.5 weight percent, 5 weight percent, 7 weight percent, 10 weight percent, 15 weight percent, 20 weight percent, 30 weight percent, or 40 weight percent (based on the total weight of the anode composition). The conductive material may be present in the anode composition in an amount provided by any two of these upper and / or lower amounts. For example, the conductive material may be present in the anode composition in an amount of about 7 weight percent to about 25 weight percent.

[0094] Electrochemical Cell The present disclosure is directed to providing an improved anode for an electrochemical cell. In some embodiments or examples, the present disclosure is directed to an anode for an electrochemical cell comprising an anode composition according to at least some embodiments or examples described herein.

[0095] In some embodiments or examples, an electrochemical cell can include a negative electrode, a positive electrode, at least one electrolyte, and a separator, where the anode comprises an anode composition as defined herein. For example, an electrochemical cell can include or consist of an anode, a cathode, at least one electrolyte including one or more electrolyte solvents, and a separator, where the anode comprises an anode composition as defined herein, where the lithium uptake capacity of the anode is greater than the lithium release capacity of the cathode.

[0096] One or more advantages of the present disclosure are provided by the arrangement of the anode and cathode in the electrochemical cell, which has been found to be of significant importance for increasing the stability and cycle life of the anode compositions described herein.

[0097] In some embodiments, the capacity limit may be considered in terms of mass loading or areal capacity. Mass loading or areal capacity refers to an electrochemical cell assembly where the capacity of the anode may be significantly over-sized relative to the cathode. The capacity limit may have the effect of limiting the capacity of the over-sized electrode (anode) only by allowing partial lithiation to occur, since the amount of lithium contained in the electrochemical cell is limited by the lithium contained in the cathode at the time of cell assembly. For example, in an electrochemical cell assembly where the anode has an areal capacity of x and the cathode has an areal capacity of y, the resulting estimated percentage capacity limit is calculated by y / x*100. It will be appreciated that this approach to capacity limit may be particularly useful in situations where the anode contains a high percentage of elemental silicon as an active material providing a specific capacity in excess of 3500 mAh / g.

[0098] Specific area capacity (mAh / cm 2 (in mg / cm) is the specific loading weight (in mg / cm) provided by the amount of anode composition applied to the current collector. 2 It will be understood that the specific loading weight (mg / cm 2 The specific areal capacity (in mAh / cm) is based on the total weight of the anode composition including the microsilicon active material particles, one or more optional additional active materials, one or more optional binders, and one or more optional conductive materials. 2 (in) depends on the thickness of the anode composition coating on the current collector, the silicon content in the anode composition, and the availability of silicon.

[0099] In some embodiments, the specific areal capacity (mAh / cm) corresponding to full utilization of the active material contained within the anode composition of the anode. 2 at 2.5mAh / cm 2 ~20mAh / cm 2 It could be.

[0100] In some embodiments, the specific loading weight (mg / cm) of the anode composition 2at 0.95 mg / cm 2 ~7.5mg / cm 2 It could be.

[0101] In some embodiments, the anode and cathode have a capacity of about 0.5 mAh / cm 2 ~about 6mAh / cm 2 and the anode can deliver about 1500 mAh / g, 1200 mAh / g, 1000 mAh / g, 800 mAh / g, 600 mAh / g, 500 mAh / g, or 400 mAh / g. In another embodiment, the anode and cathode are arranged in such a way that the cathode can deliver about 0.5 mAh / cm 2 ~about 6mAh / cm 2 can be delivered and positioned in such a way that the anode can be utilized up to about 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, or 20%.

[0102] In other embodiments, the capacity limit may be considered in terms of the phase composition of the LiSi alloy. 3.75 Si1 or Li 4.4 Si1 corresponds to the maximum accessible capacity of 3590 mAh / g, or the highest theoretical state of lithiation of 4200 mAh / g. It will be appreciated that this may translate to a specific phase composition of the LiSi alloy if the anode is of limited availability. The specific phase composition may also be translated to a specific capacity (mAh / g). For example, Li 1.71 Si1 can support a specific capacity of up to 1636 mAh / g, while Li 2.33 Si1 can support a specific capacity of up to 2227mAh / g, while Li 3.25 Si1 can support a specific capacity of up to 3101mAh / g, while Li 3.75 Si1 can support a specific capacity of up to 3579 mAh / g, while Li 4.4 Si1 can support a specific capacity of up to 4199 mAh / g.

[0103] In yet another embodiment, the capacity limit may be considered in terms of the voltage of the anode during charging and / or discharging. It will be appreciated that the amount of silicon lithiation after discharge may be accounted for by the discharge voltage of the anode.

[0104] For example, it will be appreciated that the N / P ratio balance between the anode and the cathode may be from about 1.05 to about 7, and / or the voltage range may be controlled with respect to the level of discharge of the electrochemical cell. In some embodiments or examples, the capacity of the lithium uptake capacity of the anode may not be fully utilized during charging of the lithium ion battery. In some embodiments or examples, the specific areal capacity of the anode may be greater than the specific areal capacity of the cathode. In other words, the anode is only partially lithiated at a fully charged state. Fully charged refers to the state of the electrochemical cell (e.g., Li-ion battery) in which the anode, specifically the microsilicon active material, has its highest degree of lithiation in accordance with the disclosures set forth herein. Partial lithiation of the anode means that the maximum lithium uptake capacity of the anode active material in the anode is not fully utilized. In some embodiments, the amount of lithium (mAh / cm) stored in the cathode may be greater than the specific areal capacity of the cathode. 2 ) is the lithium storage capacity of the anode (mAh / cm 2 ) may be at least two times smaller than the amount of lithium stored in the cathode (mAh / cm 2 ) is the lithium storage capacity of the anode (mAh / cm 2 ) may be in the range of 0.05 to 7 times smaller.

[0105] In some embodiments, the Li / Si ratio of an electrochemical cell (e.g., a Li-ion battery) can be set by the anode to cathode ratio (N / P). In some embodiments, the N / P ratio between the anode and cathode can be about 1.05 to about 7, about 2 to about 5, or about 3 to about 4. The N / P ratio can be greater than about 7, 6, 5, 4, 3, 2, or 1.05. The N / P ratio can be at least about 1.05, 2, 3, 4, 5, 6, or 7. The N / P ratio can be in a range provided by any two of these upper and / or lower values. For example, the N / P ratio between the anode and cathode can be about 1.5 to about 4, or about 1.8 to about 3.5.

[0106] In some embodiments, the capacity limit (in %) can be at least about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or 99. In some embodiments, the capacity limit (in %) can be less than about 99, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, or 20. The capacity limit (in %) can be in a range provided by any two of these upper and / or lower values. For example, the capacity limit (in %) can be from about 25 to about 90, or from about 30 to about 80.

[0107] The present disclosure advantageously provides an electrochemical cell designed such that the lithium uptake capacity of the anode is greater than the lithium release capacity of the cathode. This ensures that the lithium uptake capacity of the anode is not fully utilized, i.e., the silicon active material particles of the anode are only partially lithiated in the fully charged state, advantageously reducing or preventing the high volume change typically found in silicon anodes during lithiation / delithiation cycling that degrades the structure of the silicon anode and shortens the life of the battery. In other words, a high N / P ratio can limit the degree of lithiation of the microsilicon since the amount of Li ions is fixed by the cathode during cell assembly. For example, the anode can be significantly oversized relative to the amount of lithium contained in the cell and provided by the cathode. As the degree of lithiation is limited by the oversized anode, so too is the level of expansion of the microsilicon active material particles and their decomposition. In some embodiments or examples, the degree of silicon lithiation can be in the range of about 20% to about 80%. Unexpectedly, the degree of silicon lithiation in this range can have a stabilizing effect on electrochemical cell performance.

[0108] In another embodiment, the capacity of the electrochemical cell can be limited by limiting the lower cutoff voltage. In some embodiments or examples, the lower cutoff voltage can be about 2.5V to about 3.0V. For example, the lower cutoff voltage can be 2.8V to about 3.0V. It will be understood that the voltage limit can be applied by limiting the lower cutoff voltage. This can prevent complete delithiation of the microsilicon active material particles at each cycle and reduce their expansion, which reduces decomposition and therefore leads to an extended cycle life.

[0109] In another embodiment, the capacity of the electrochemical cell can be limited by limiting the upper cutoff voltage. In some embodiments or examples, the upper cutoff voltage can be between about 3.6V and about 4.25V.

[0110] It will be appreciated that both capacitive and voltage limiting may be used simultaneously.

[0111] It will be understood that the anode composition may be prelithiated as described in any one of more of the embodiments or examples described herein. In some embodiments, prelithiation may occur prior to incorporating the active material into the anode composition. In other embodiments, prelithiation may occur after incorporating the active material into the anode composition. Prelithiation may be carried out through direct contact between lithium metal in the electrolyte and the active anode material. Due to the potential difference between the lithium metal and the anode material, an electric field is formed, which allows electrons to move from a region of lower potential to a region of higher potential at the point of contact under the action of the electric field. In an electrically neutral environment, the Li metal releases lithium ions that pass through the electrolyte and are embedded in the anode material. For the direct contact prelithiation method, lithium metal powder or lithium metal foil may be used. During prelithiation, the lithium metal foil or powder self-discharges upon contact, which is a relatively simple and efficient process. In some embodiments or examples, the amount of prelithiation of the anode composition may be from about 1% to about 30%. The amount of pre-lithiation of the anode composition can be less than about 30%, 25%, 20%, 15%, 10%, 5%, or 1%. The amount of pre-lithiation of the anode composition can be at least about 1%, 5%, 10%, 15%, 20%, 25%, or 30%. The amount of pre-lithiation of the anode composition can be in a range provided by any two of these upper and / or lower amounts.

[0112] In some embodiments, the amount of lithium contained in the anode may be about 30% of its maximum storage capacity, while the cathode may contain 100% of its maximum storage capacity. In some embodiments, the amount of lithium contained in the anode may be about 20% of its maximum storage capacity, while the cathode may contain 100% of its maximum storage capacity. In some embodiments, the amount of lithium contained in the anode may be about 10% of its maximum storage capacity, while the cathode may contain 100% of its maximum storage capacity.

[0113] In one embodiment, a half-cell method may be used to perform electrochemical prelithiation. A silicon-containing electrode is assembled in a half-cell setup using a lithium foil reference electrode, and the degree of prelithiation is controlled by setting appropriate parameters in a galvanostatic charge / discharge cycle program. The half-cell goes through a first cycle by partially or fully lithiating the silicon-containing electrode, followed by full delithiation, to create a lithium reservoir of up to 30% lithium in the SEI layer and anode.

[0114] On the other hand, creating a lithium reservoir in the anode requires partial lithiation to the desired degree of lithium reservoir. According to the composition of the silicon-containing anode and the associated material properties, the first cycle loss can be estimated by testing the corresponding composition in a half cell against a lithium metal foil reference electrode and determining the first cycle loss of the anode composition as such. If the first cycle loss is estimated to be x%, then the initial lithiation step during the prelithiation process required to achieve a lithiation level of the silicon anode composition of z% to create a lithium reservoir of y% should account for x%+y%. In one particular embodiment, if the anode composition exhibits a first cycle loss of 10%, this loss should be taken into account when calculating the desired degree of prelithiation to obtain the resulting lithium reservoir. For example, to achieve a 10% lithium reservoir, the anode may be lithiated to 20% of its expected design capacity (mAh / g), where the initial approximately 10% is intended to compensate for irreversible lithium loss during the first cycle, and additional lithium is stored in the anode or silicon material, thus forming the desired lithium reservoir. It will be understood that higher levels of pre-lithiation may be applied to achieve other desired levels of lithium reservoir. The maximum desired level of lithium reservoir may be 30%.

[0115] It has been found that the pairing of prelithiation and capacity limiting can provide one or more additional advantages to the electrochemical cells of the present disclosure. For example, the capacity of the anode occupied by lithium provided by the cathode and stored in the anode in the first lithiation is the same with or without prelithiation, notwithstanding any loss of lithium in the first cycle, but the lithium reservoir in the anode can compensate for the gradual loss of lithium during repeated charge and discharge cycles over multiple cycles.

[0116] In some embodiments, the anode composition may be applied to a current collector material as a coating or film. The current collector material for the anode may be selected from the group including copper, aluminum, stainless steel, titanium, carbon, perforated metal foils, metal foams, and metal-coated polymer-based porous and non-porous films. For example, the anode composition may be applied to a copper current collector material (e.g., copper foil). It will be understood that the current collector material is of appropriate dimensions, porosity, and pore size to act as a current collector, including the above materials.

[0117] In some embodiments, the current collector material for the anode can have a thickness of about 4 μm to about 25 μm. The thickness (in μm) of the current collector can be less than about 25, 20, 15, 10, 8, 6, or 4. The thickness (in μm) of the current collector can be at least about 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, or 25. The thickness (in μm) of the current collector can be in a range provided by any two of these upper and / or lower amounts. In one example, the current collector material for the anode can be a copper foil having a thickness of about 6 μm to about 12 μm.

[0118] In some embodiments, the thickness of the anode composition is substantially uniform and can be in the range of about 5 μm to about 45 μm. The thickness (μm) of the anode composition can be less than about 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5. The thickness (μm) of the anode composition can be at least about 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70. The thickness of the anode composition can be in a range provided by any two of these upper and / or lower amounts.

[0119] It will be understood that the cathode active material is also applied to the current collector material. The current collector material for the cathode can be selected from the group including aluminum, stainless steel carbon, perforated metal foil, metal foam, and metal-coated polymer-based porous and non-porous membranes. It will be understood that the current collector material is of appropriate dimensions, porosity, and pore size to include the above materials and act as a current collector. For example, the cathode composition can be applied to an aluminum current collector material (e.g., aluminum foil).

[0120] In some embodiments, the current collector material for the cathode can have a thickness of about 10 μm to about 30 μm. The thickness (in μm) of the current collector can be less than about 30, 25, 20, 15, or 10. The thickness (in μm) of the current collector can be at least about 10, 12, 14, 16, 18, 20, 25, or 30. The thickness (in μm) of the current collector can be in a range provided by any two of these upper and / or lower amounts. In one example, the current collector material for the cathode can be an aluminum foil having a thickness of about 10 μm to about 30 μm.

[0121] In some embodiments, the cathode may be selected from the group consisting of lithium nickel cobalt manganese oxide (NCM), lithium iron phosphate (LFP), lithium nickel manganese spinel (LNMO), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), and sulfur or a sulfur composite comprising a sulfur and carbon mixture.

[0122] In some embodiments or examples, the electrolyte may be selected from a non-aqueous solution of one or more lithium salts (eg, in a Li-ion cell). The one or more lithium salts may be selected from the group including lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium bis(trifluorosulfonylimide), lithium trifluoromethanesulfonate, lithium fluoroalkylsulfonimide, lithium fluoroarylsulfonimide, lithium bis(oxalatoborate), lithium tris(trifluoromethylsulfonylimide)methide, lithium difluoromethanesulfonate, lithium trifluoromethanesulfonate salt (lithium triflate), lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate, lithium hexafluoroarsenate, lithium hexafluoroantimonate, 4,5-dyano-2-(trifluoromethyl)imidazolide (LiTDI), LiPF3(CF5)3 (LiFAP), LiBF3(CF5), lithium chloride, and combinations thereof. For example, the electrolyte can include lithium hexafluorophosphate.

[0123] In some embodiments or examples, the lithium salt can be dissolved in an organic solvent. The lithium salt can be dissolved in an organic solvent selected from ethers, esters, carbonates, and acetals. In one example, the solvent can be selected from dimethoxyethane, diglyme, triglyme, tetraglyme, ethylene carbonate, propylene carbonate, dimethyl carbonate, tetrahydrofuran, and dioxolane. In some embodiments or examples, the lithium salt may be dissolved in an organic solvent selected from the group including ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate, ethyl propyl carbonate, dipropyl carbonate, cyclopentanone, sulfolane, dimethyl sulfoxide, 3-methyl-1,3-oxazolidin-2-one, γ-butyrolactone, 1,2-diethoxymethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 1,2-dimethoxyethane, methyl acetate, ethyl acetate, nitromethane, 1,3-propane sultone, γ-valerolactone, methyl isobutyryl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, diethyl oxalate, ionic liquids, and any combination thereof. In some embodiments or examples, the lithium salt may be dissolved in an organic solvent selected from the group including ethylene carbonate, dimethyl carbonate, diethyl carbonate, and any combination thereof.

[0124] The electrolyte may include an additive selected from one or more alkali metal salts of LiPF6LiBF4, LiAsF6, LiSbF6, LiClO4, LiAlCl4, LiGaCl4, LiC(SO2CF3)3, LiN(SO2CF3)2, LiSCN, LiSO2CF2CF3, LiC6F5SO3, LiO2CCF3, LiSO3F, LiB(CH5)4, LiCF3SO3, LiNO3, and mixtures thereof. In other embodiments, the additive may be selected from one or more of fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), vinyl carbonate (VC), propylene carbonate (PC), ethyl methyl carbonate (EMC), propane sultone (PS), and mixtures thereof. The electrolyte additive may further improve certain characteristics of the cell. For example, an electrolyte (eg, lithium hexafluorophosphate) can include an additive (eg, fluoroethylene carbonate) dissolved in an organic solvent (eg, diethyl carbonate).

[0125] In some embodiments or examples, the lithium salt may be dissolved in one or more organic solvents described above, where the one or more organic solvents are present in a volume to volume ratio ranging from 10 to 1 to 1 to 10. For example, the lithium salt (e.g., 1M LiPF6) may be dissolved in FEC / DEC (2:8) vol%, FEC:EMC (3:7) w / w + 2 wt% VC, EC / EMC / DEC (3 / 5 / 2 vol%) + 1 wt% VC + 10 wt% FEC, or EC / EMC (3:7) wt% + 1 wt% VC.

[0126] In some embodiments or examples, the separator is used to electrically separate the anode from the cathode and allow free passage of lithium ions in the electrolyte. The separator may be selected from a variety of different porous polymer films. It will be understood that any porous polymer film may be selected for use as a separator having suitable porosity, tortuosity, and thickness. For example, a polymer film-based separator material may be selected. In some embodiments or examples, the separator may be selected from polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET). In another embodiment, a nonwoven fibrous material is selected as the separator, comprising fibers selected from nylon, polyethylene terephthalate (PET), cellulose, aramid, or polyacrylonitrile.

[0127] In some embodiments or examples, the electrochemical cell can be an energy storage device. The energy storage device can be a battery. For example, the battery can be a secondary battery. In one particular example, the battery can be a lithium ion battery (Li-ion battery).

[0128] Anode Compositions for Lithium-Ion Batteries In some embodiments or examples, the present disclosure also provides a method for improving the cycling stability of a battery having an anode and a cathode, at least one electrolyte, and optionally a separator, the anode comprising the anode composition described herein. It has been found that the anode comprising the anode composition provides a particularly effective anode for use in a battery (e.g., a Li-ion battery) that can maintain long-term capacity retention. In some embodiments or examples, the anode within the battery can have a discharge capacity of at least about 800 mAh / g for at least 100 cycles of the battery. In some embodiments or examples, the specific capacity (mAh / g) can be at least about 500, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 3000, or 3500. In some embodiments or examples, the specific capacity (mAh / g) may be less than about 3500, 3400, 3200, 3000, 2800, 2600, 2400, 2200, 2000, 1800, 1600, 1400, 1200, 1000, 800, 600, or 500. The specific capacity (mAh / g) may be in a range provided by any two of these upper and / or lower values. In some embodiments or examples, the number of cycles may be at least 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480, 500, 1000, or 1500.

[0129] The long-term cycling performance of electrochemical cells (e.g., Li-ion batteries) including the anode compositions can be tested for high silicon content anodes (i.e., about 70% silicon content) with various capacity limits. The initial discharge capacity of an anode including the anode compositions according to at least some embodiments or examples described herein can be at least about 600, 800, 1100, 1200, 1300, 1400, 1500, or 1600 (in mAh / g). According to at least some embodiments or examples, at least about 80% of the discharge capacity can be retained after 100, 200, 300, 400, 500, 800, 1000, or 1500 cycles.

[0130] It will be appreciated that galvanostatic charge-discharge cycling experiments can typically be used to evaluate the performance metrics of a battery: capacity, rate capability, coulombic efficiency, and capacity retention upon cycling.

[0131] In some embodiments or examples, the present disclosure is also directed to the use of an anode comprising the anode composition described herein in an electrochemical cell. For example, the electrochemical cell can be an energy storage device such as a battery, preferably a secondary battery. More specifically, the battery can be a lithium ion battery.

[0132] In some embodiments or examples, the present disclosure is also directed to an anode comprising the anode composition, which can be a battery anode. More particularly, a lithium ion battery anode.

[0133] It has been found that the anode composition, which may comprise or consist of microsilicon active material particles, optionally one or more binders, optionally one or more conductive materials, and optionally one or more additives, significantly reduces the effects exhibited by SEI formation and silicon expansion and decomposition, thus providing improved performance of Li-ion batteries. The anode composition provides high first cycle efficiency and provides the additional advantage of providing controlled silicon utilization, thereby improving the high current response and performance of the battery. For example, an electrochemical cell (e.g., Li-ion battery) comprising the anode composition described herein allows silicon utilization / lithiation in part, the specific capacity of the anode is reduced and controlled by the amount of lithium the cathode can supply, and provides an improved average coulombic efficiency (CE) of at least about 75, 80, 85, 90, 95, 98%, 99%, or 99.5%, or 99.8%, or 99.9 or more, or less than 100%, over at least 200 cycles. In another example, use of the anode composition as an anode provides improved performance of a Li-ion battery that exhibits cycling stability after at least 200 cycles at C / 2.

[0134] Moreover, it has been surprisingly found that when the N / P ratio for an anode containing a majority of microsilicon (e.g., >70%) is operated to a value greater than 3 (e.g., 3.3), it is possible to provide stable cycling of the anode, achieving more than 200 cycles with greater than 80% capacity retention. In other words, Li +The high N / P ratio limits the degree of lithiation of the microsilicon since the amount of N is fixed by the cathode during cell assembly. This leads to a degree of silicon lithiation of about 20% to about 80%, instead of 80% to 90% as found in conventional cell assemblies where the anode contains mostly graphite, which has a stabilizing effect on cell performance. It will be appreciated that the anode is significantly oversized relative to the amount of lithium contained in the cell and provided by the cathode. Advantageously, since the degree of lithiation is limited by the oversized anode, so too is the level of expansion of the silicon and its decomposition.

[0135] Preparation process In some embodiments or examples, the present disclosure is directed to a process for preparing an anode for an electrochemical cell. The process may be for preparing an anode according to any embodiment or example described herein. It will be understood that the anode prepared by the process may include an anode composition including micro-silicon active material particles. It will also be understood that the anode prepared by the process may include or consist of an anode composition including micro-silicon active material particles, optionally one or more additional active materials, optionally one or more binders, optionally one or more conductive materials, optionally one or more additives, and optionally a solvent. The micro-silicon active material particles, one or more additional active materials, one or more optional binders, one or more optional conductive materials, one or more optional additives, and one or more optional solvents may be selected from any one or more of the embodiments or examples described herein.

[0136] In some embodiments or examples, a process for preparing an anode for an electrochemical cell comprises: (i) preparing an anode slurry comprising microsilicon active material particles, optionally one or more further active materials, optionally one or more binders, optionally one or more conductive materials, optionally one or more additives, and a solvent system; and (ii) casting a layer of the anode slurry onto a current collector material to provide a wet anode composition layer on the current collector material.

[0137] In some embodiments or examples, the process may further include step (iii) solidifying the wet anode layer by solvent evaporation to provide a dry anode composition layer on the current collector material.

[0138] In some embodiments or examples, the solvent may be an organic solvent selected from aromatics, halogenated aromatics, halogenated aliphatic hydrocarbons, aliphatic hydrocarbons, glycols, ethers, glycol ethers, esters, alcohols, ketones, or combinations thereof. In some embodiments or examples, the solvent may be present in an amount (by weight % of the total anode composition) of about 40% to 90% by weight, about 40% to 70% by weight, or about 40% to 60% by weight. The solvent may be a low boiling organic solvent, or a mixture of one or more of such solvents. In some embodiments or examples, the solvent may be selected from the group including water, methanol, ethanol, n-propanol, isopropanol, tetrahydrofuran, methylene chloride, chloroform, diethyl ether, room temperature ionic liquids, ethylene glycol, glycerol, formamide, N-methylformamide, dimethylformamide, N-methylsydnone, aqueous solutions thereof, and any mixtures thereof. For example, the solvent may be water, ethanol, N,N' dimethylformamide, or a combination thereof.

[0139] In some embodiments or examples, the ratio of binder to microsilicon active particles may be about 1:40, 1:35, 1:32, 1:30, 1:25, 1:23, 1:20, 1:15, 1:10, 1:9, 1:6, or 1:4. The ratio of binder to microsilicon active particles may range from about 1:4 to about 1:32. The ratio of binder to microsilicon active particles may range from about 1:8 to about 1:23. The ratio of binder to microsilicon active particles may range from about 1:9 to about 1:15.

[0140] In some embodiments or examples, the binder (in weight %) may be present in the anode composition in a range of about 2.5 to 15. The binder (in weight %) may be present in the anode composition in an amount of less than about 15, 12, 10, 8, 5, or 2.5. The binder (in weight %) may be present in the anode composition in an amount of at least about 2.5%, 5%, 8%, 10%, 12%, or 15%. The binder (in weight %) may be present in the anode composition in a range provided by any two of these upper and / or lower amounts. For example, the binder (in weight %) may be present in the anode composition in a range of about 3 to about 8, or about 4 to about 8.

[0141] It has been found that the pH of the binder can affect the electrochemical performance of the anode composition. In some embodiments or examples, the pH of the binder can be less than 9, 8, 7, 6, 5, 4, 3, or 2. In some embodiments or examples, the pH of the binder can be at least 2, 3, 4, 5, 6, 7, 8, or 9. The pH of the binder can be in a range provided by any two of these upper and / or lower values. For example, the pH of the binder can be in the range of 4 to 8. Preferably, a binder pH of less than 7 can be beneficial to the electrochemical performance of the microsilicon anode, and can be due to (i) reduced corrosion of pure silicon in the acidic region, and / or (ii) greater affinity of silicon to interact with the binder, such as PAA.

[0142] In some embodiments or examples, the viscosity of the anode slurry may be in the range of about 10 mPas to 100,000 mPas. The viscosity (mPas) may be less than about 100,000, 90,000, 80,000, 70,000, 60,000, 50,000, 40,000, 30,000, 20,000, 10,000, 8000, 6000, 4000, 2000, 1000, 800, 600, 400, 200, 100, 50, or 10. The viscosity may be at least about 10, 20, 40, 60, 80, 100, 300, 500, 700, 900, 1000, 3000, 5000, 7000, 9000, 10,000, 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, or 100,000. The viscosity (mPas) of the anode slurry may be in a range provided by any two of these upper and / or lower amounts. For example, the viscosity (mPas) of the anode slurry may be in a range of about 2500 mPas to about 8000 mPas. All viscosity values ​​listed herein may be at a given shear rate. In embodiments, the shear rate may be that used in any art accepted standard testing approach.

[0143] In some embodiments or examples, the thickness of the dry anode composition may be in the range of about 5 μm to about 45 μm. The thickness (μm) of the dry anode composition may be less than about 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, 8, 6, or 5. The thickness (μm) of the dry anode composition may be at least about 5, 6, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70. The thickness (μm) of the dry anode composition may be in the range provided by any two of these upper and / or lower amounts.

[0144] In some embodiments or examples, the wet anode composition layer may be maintained at a temperature of about 40° C. to about 60° C. for about 30 seconds to about 5 minutes in step (iii)(a). The wet anode composition may be maintained at a temperature (° C.) less than about 60, 55, 50, 45, or 40. The wet anode composition may be maintained at a temperature (° C.) of at least about 40, 45, 50, 55, or 60. The wet anode composition may be maintained at a temperature (° C.) in the range provided by any two of these upper and / or lower amounts. The wet anode composition may be maintained at a temperature described herein for less than about 24 hours, 12 hours, 8 hours, 4 hours, 2 hours, 1 hour, 30 minutes, 5 minutes, 4 minutes, 3 minutes, 2 minutes, 1 minute, or 30 seconds. The wet anode composition can be maintained at a temperature described herein for at least about 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 10 hours, 12 hours, or 24 hours. The wet anode composition can be maintained at a temperature described herein for a time range provided by any two of these upper and / or lower amounts.

[0145] In some embodiments or examples, the wet anode composition may be maintained at a temperature of about 90° C. to about 180° C. for about 30 seconds to about 5 minutes in step (iii)(b). The wet anode composition may be maintained at a temperature (° C.) of less than about 180, 170, 160, 150, 140, 130, 120, 115, 110, 105, 100, 95, or 90. The wet anode composition may be maintained at a temperature (° C.) of at least about 90, 95, 100, 105, 110, 115, 120, 130, 140, 150, 160, 170, or 180. The wet anode composition may be maintained at a temperature (° C.) in the range provided by any two of these upper and / or lower amounts. The wet anode composition may be maintained at a temperature described herein for less than about 24 hours, 12 hours, 8 hours, 4 hours, 2 hours, 1 hour, 30 minutes, 5 minutes, 4 minutes, 3 minutes, 2 minutes, 1 minute, or 30 seconds. The wet anode composition may be maintained at a temperature described herein for at least about 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, 10 hours, 12 hours, or 24 hours. The wet anode composition may be maintained at a temperature described herein for a time range provided by any two of these upper and / or lower amounts.

[0146] In some embodiments or examples, the anode slurry may be homogenized to provide further advantages / improvements.

[0147] In some embodiments or examples, the present disclosure is directed to a process for assembling an electrochemical cell, the process may include preparing an anode as defined by at least one of the processes described herein, the anode may include an anode composition including microsilicon active material particles, and assembling the anode into an electrochemical cell. In some other embodiments or examples, the present disclosure is directed to a process for assembling an electrochemical cell, the process may include preparing an anode as defined by at least one of the processes described herein, the anode may include or consist of an anode composition including microsilicon active material particles, optionally one or more additional active materials, optionally one or more binders, and optionally one or more conductive materials, at least one of the processes described herein, and assembling the anode into an electrochemical cell.

[0148] Upon formation of the anode slurry, some or all of the solvent may be removed (e.g., by natural evaporation, forced evaporation, or under vacuum) to produce a solid or viscous anode slurry. The anode slurry may be formed or shaped into any desired shape, such as an anode.

[0149] In some embodiments or examples, the anode slurry may also be deposited onto a current collector material as defined herein to produce an anode. It will be understood that the anode is a combination of the current collector material and the anode composition, also referred to as the anode composition applied to the current collector material. The current collector material may be selected from any of the current collector materials mentioned herein.

[0150] During preparation of the anode, the anode composition may be applied to only a portion of the surface of the current collector material. In some embodiments or examples, the portion (%) may be less than about 100, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5. In some embodiments or examples, the anode composition may be applied by casting onto the current collector material (e.g., roll-to-roll processing).

[0151] It will be understood by those skilled in the art that numerous variations and / or modifications may be made to the above-described embodiments without departing from the broad general scope of the present disclosure, and the present embodiments are therefore considered in all respects to be illustrative and not restrictive. EXAMPLES

[0152] The present invention is further described by the following examples. It should be understood that the following descriptions are only for the purpose of describing specific embodiments, and are not intended to be limiting with respect to the above descriptions.

[0153] Example 1: General procedure for preparing the anode A variety of commercially available silicon materials can be used to prepare the anode compositions as described herein and further illustrated in the Examples. Examples of a select number of characteristics of such silicon materials, including their PSD, BET surface area, and measured impurities (measured via ICP-AES), are provided in Table 1 below. [Table 1]

[0154] It will be understood that impurities may be present in the silicon material, one such example being as shown above in Table 1. Such impurities may be present in the micro-silicon active material particles, preferably in an amount of less than about 3000 ppm total impurities.

[0155] To prepare the anode slurry, the binder solution and conductive material are combined using a planetary centrifugal mixer. The mixture is then incorporated at 2000 rpm for 2 minutes, mixed manually with a spatula, and then mixed for an additional 2 minutes. Microsilicon active material particles and the required amount of additional water are added and the mixing step is repeated. Activated graphite is added and the mixing step is repeated. Unless otherwise stated, a predetermined amount of the anode slurry is transferred to a Dispermat compatible container and mixed for 5 minutes at 6000 rpm using an overhead mixer (e.g., VMA-Getzmann Dispermat).

[0156] For full cell assembly, the slurry was cast on copper foil and dried at 60 °C before being cut for coin cell assembly. The electrodes (coated anode and commercial NCM523 cathode) were further dried at 110 °C for 12 h under vacuum. 150 μL of electrolyte (e.g., 1 M LiPF6 in FEC / DEC (2:8) vol.%) was used, and a separator (e.g., Whatman glass fiber) was used for coin cell (CR20232 type) assembly. For charge / discharge cycle test, the coin cell was activated at 0.05 C for one cycle and then cycled at 0.5 C for long-term stability test. The C rate was based on the mass of active materials (Si particles, graphite) in the electrode. The voltage range for charge / discharge cycle test was 4.2-2.5 V during formation and 4.2-3 V during cycling. Charge / discharge test was performed on a Neware multichannel battery tester controlled by a computer. Four replicate cells were prepared and tested for each condition.

[0157] For half-cell assembly, the slurry was cast on copper foil and dried at 60 °C before being cut for coin cell assembly. The electrodes were further dried at 110 °C under vacuum for 12 h. Lithium (Li) metal was used as the counter electrode. 150 μL of electrolyte (e.g., 1 M LiPF6 in FEC / DEC (2:8) vol.%) was used, and a separator (e.g., Celgard2500) was used for coin cell (CR2032 type) assembly. For charge / discharge cycle testing, the coin cells were activated at 0.05 C for one cycle, followed by 0.1 C for two cycles, and then cycled at 0.5 C for long-term stability testing. The C rate was based on the mass of active materials (Si particles, graphite) in the electrodes. The voltage range for charge / discharge testing was 0.005-1.50 V vs. Li. Charge / discharge testing was performed on a Neware multichannel battery tester controlled by a computer. Four replicate cells were prepared and tested for each condition.

[0158] Example 2: Surface area and particle size studies Example 2(a) Microsilicon-containing sample Each silicon material was tested using a micro-silicon anode composition as described in Example 1. The micro-silicon active material particle content is about 70%.

[0159] It will be understood that one (1) battery slurry is produced for each microsilicon sample.

[0160] For each silicon anode configuration assembled: a. Four (4) coin half cells (for metallic lithium) b. Four (4) coin full cells (for commercial grade NCM523 cathodes) i. Tested in a full cell design with limited volume ii. Anode capacity limit in full cells at 30-36%

[0161] All microsilicon-containing anodes were paired with NCM523 cathodes in a test setup with a limited capacity of 30-36%. The 30-36% capacity limit refers to the extent to which the anode is utilized. In practical terms, this means that the anode areal capacity is oversized compared to the cathode. Considering that the cathode contains the cell's lithium stock upon cell assembly, the areal capacity of both electrodes was chosen such that only a maximum of 30-36% anode lithiation was possible upon first charge.

[0162] Example 2(b) Specific Coating Capacity - Anode The specific coating capacity for the anode is 1 cm2 of the cathode when the full cell is 2 Volume delivered per 1cm 2 The cycling capacity was calculated by dividing by the weight of the anode coating in g per cell. The obtained cycling capacity values ​​(from the second cycle onwards) at a rate of C / 2 are within the target range of 600-700 mAh / g for all anode configurations. A cycle graph comparison based on the specific anode coating capacity is shown for the full cell in Figure 1a.

[0163] Example 2(c) Specific Coating Capacity - Cathode The specific coating capacity for the cathode is 1 cm of cathode when the full cell is 2 Volume delivered per 1cm 2 The capacity was calculated by dividing by the weight of the cathode coating in g per unit area. The obtained values ​​for all anode configurations are within the target range of 160-165 mAh / g. This capacity figure is expected considering the NCM523 cathode material being used.

[0164] Example 2(d) Electrode Composition An anode composition was prepared consisting of 70% microsilicon. The specific electrode composition used for all experiments in Example 2 is shown in Table 2 below. [Table 2]

[0165] Example 2(e) Slurry Preparation The amounts of materials specified in Table 2 were used in the slurry preparation process for micro silicon materials Elkem 1, 2, 3 and 4. The procedure in Example 1 was used to prepare the slurries.

[0166] Example 2.1 Surface Area and Particle Size Studies: Full Cell Tests Example 2.1(a) Test Setup for Full Cell The electrochemical test setup used for the full cells was as described in Example 1. The test program is detailed in Table 3 below. [Table 3]

[0167] The current densities used in the cycling tests were based on the electrode capacity achieved at the final delithiation step of the formation program. [Table 4]

[0168] Example 2.1(b) Summary of Key Findings for Full Cell Testing Elkem 1, 2, and 3 silicon materials showed superior electrochemical performance compared to Elkem 4, resulting in >89% ICE and higher capacity retention. At 95.3% capacity retention, Elkem 2 showed 24 more cycles compared to Elkem 1, 29 cycles compared to Elkem 3, and 131 cycles compared to Elkem 4.

[0169] Reducing the SSA leads to improved electrochemical behavior by increasing the ICE and extending the cycle life of the Si anode.

[0170] A summary of the limited capacity full cell electrochemical data is shown in Table 5 below. [Table 5]

[0171] The following table shows the D50 particle size, BET surface area, and D50 vs. BET surface area of ​​the microsilicon active material particles. 50 provides a ratio of [Table 6]

[0172] D in Table 6 50 Particle size, BET surface area, and D 50 A range for the ratio between particle size and BET surface area was defined as the representative range for the measurements obtained.

[0173] D 3.0~6.0μm 50 Particle size and 1.0~3.5m 2 D relative to the BET surface area due to the BET surface area range / g 50 Silicon materials with a particle size ratio of 1.0-3.5 have higher (6.0-8.0 μm) and lower (0.1-3.0 μm) D 50 Particle size and higher BET surface area (>3.5 m 2 / g) for the BET surface area. 50 It showed superior cycle life when compared with higher (3.5-6.0) or lower (0.01-1.0) ratios of particle size.

[0174] Example 2.2 Surface Area and Particle Size Studies: Half-Cell Tests Example 2.2(a) Test Setup for Half-Cell Testing The electrochemical test setup used for the half cells was as described in Example 1. The test program is detailed in Table 7 below. [Table 7]

[0175] The current densities used in the cycling tests were based on the electrode capacity achieved at the final delithiation step of the formation program. [Table 8]

[0176] Example 2.2(b) Summary of Key Findings for Half-Cell Studies All half-cells were tested under full lithiation conditions. Figure 2 shows that the cycling stability of the various silicon samples is governed by their respective particle size, surface area, and the ratio between particle size and surface area. As a result, the D of 3.0 to 6.0 μm 50 Particle size and 1.0~3.5m 2 / g BET surface area, resulting in a D for BET surface area of ​​1.0 to 3.5 50 Samples with particle size ratios of 0.1 to 2.0 μm showed the fastest volume loss. 50 Particle size and 35~50m 2 D for a BET surface area of ​​0.01 to 0.1 due to a BET surface area of ​​1.0 to 1.0 / g 50 The samples with the particle size ratio showed the most stable cycling performance. In half-cell tests with unlimited lithium supply, the small particle size and large surface area do not adversely affect the cycling performance.

[0177] The table below shows the D of micro silicon active material. 50 Particle size, BET surface area, D relative to BET surface area 50 A summary of particle size ratios and corresponding electrochemical data for half-cell measurements is provided. [Table 9]

[0178] Example 3. Levels of Capacity Restriction: 30%, 50%, and Full Capacity Each microsilicon-containing anode was paired with an NCM523 cathode in a test configuration of 30%, 50%, and full capacity. The degree of capacity limitation refers to the degree to which the anode is utilized. In practical terms, this means that the anode areal capacity is oversized compared to the cathode. Considering that the cathode contains the lithium stock of the cell upon cell assembly, the areal capacity of both electrodes was selected such that only the maximum capacity that would be converted to the selected degree of anode lithiation upon first charge would be utilized.

[0179] Example 3(a) Electrode Composition An anode composition was prepared consisting of 70% microcrystalline silicon. The specific electrode composition used for all experiments is shown in Table 10 below. [Table 10]

[0180] Example 3(b) Slurry Preparation First, polyacrylic acid (18.20 g) (PAA, 250 kDa, 25% neutralized) and conductive carbon black Super C65 (0.91 g) were combined using a Thinky Mixer ARE-250 CE planetary mixer. The mixture was incorporated at 2000 rpm for 2 minutes and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (24.20 g) and microsilicone (31.85 g) and the mixing step was repeated. Finally, flake graphite (9.10 g) was added and the mixing step was repeated. 64.81 g of this complete mixture was transferred to a Dispermat compatible container and mixed at 6000 rpm for 5 minutes.

[0181] Example 3(c) Electrochemical Test Program The full cell was assembled using the procedure described in Example 1. The cycle program is shown in Tables 3 and 4 above.

[0182] Example 3.2(d) Cyclic Study - Summary of Key Findings Increasing the capacity limit increases the stress on the tested anode compositions in the full cells, and the ICE increases with higher capacity utilization and decreases capacity retention. At the 99% capacity limit, the ICE was 0.4% higher than at the 35% capacity limit (Table 11). Restricting the capacity down to 35% extended the cycle life over 258 cycles and reached the same level of capacity retention as at the 99% capacity limit (Figure 3). At the 50% capacity limit, the ICE is only 0.3% less than at the 99% capacity limit, but capacity retention is still poor with a 20% capacity loss after 138 cycles. [Table 11]

[0183] Example 4 Prelithiation of micro-Si anodes Example 4.1 Electrochemical Prelithiation Example 4.1(a) Electrode Composition An anode composition was fabricated consisting of 70% microcrystalline silicon. The specific electrode composition used for all experiments is shown in Table 12 below. [Table 12]

[0184] Example 4.1(b) Slurry Preparation: First, polyacrylic acid (18.20 g) (PAA, 250 kDa, 25% neutralized) and conductive carbon black Super C65 (0.91 g) were combined using a Thinky Mixer ARE-250 CE planetary mixer. The mixture was incorporated at 2000 rpm for 2 minutes and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (24.20 g) and microsilicone (31.85 g) and the mixing step was repeated. Finally, flake graphite (9.10 g) was added and the mixing step was repeated. 64.81 g of this complete mixture was transferred to a Dispermat compatible container and mixed at 6000 rpm for 5 minutes.

[0185] Example 4.1(c) Prelithiation Step The electrochemical test program is set up as follows: · First cycle in half-cell setup: Partial formation cycle at C / 20 to a certain % based on expected capacity of the anode. The first lithiation is limited by a capacity (mAh / g) of up to 30% or 20% of the expected capacity of the anode (accounting for the approximately 10% lithium loss on the first cycle). [Table 13]

[0186] The slurry was cast on copper foil and dried at 60°C before being cut for coin cell assembly. The electrodes were further dried at 110°C under vacuum for 12 hours. Lithium (Li) metal was used as the counter electrode and a Celgard separator was used. 150 μL of 1M LiPF6 in FEC / DEC (2:8) vol% was used as the electrolyte for coin cell assembly. The coin cells were lithiated for one cycle at 0.05C and stopped when the capacity reached the required degree of prelithiation. The C-rate was based on the mass of active materials (Si particles, graphite) in the electrodes. Two replicate cells were made and tested for each condition.

[0187] Example 4.1(d) Post-Prelithiation Steps The coin cell was removed, introduced into a glove box (under Ar atmosphere) and disassembled for full cell preparation. The anode was washed with DMC and dried before assembly. The full cell was assembled using the procedure described in Example 1. See Tables 3 and 4 for the cycle program.

[0188] Example 4.1(e) Cycling Study - Summary of Key Findings Using similar capacity limits, pre-lithiated and non-lithiated full cells were compared, with initial coulombic efficiency increasing by an average of 1%, from 89% to a maximum of 90%.

[0189] The cycling capacity and average coulombic efficiency increased substantially. Negligible capacity loss was observed over the first 330 cycles. The 20% lithium reservoir reached 95% capacity retention at 260 cycles and 80% retention after 680 cycles (Figure 4). [Table 14]

[0190] Example 4.2 Direct Contact Prelithiation Example 4.2(a) Electrode Composition An anode composition was prepared consisting of 70% microcrystalline silicon. The specific electrode composition used for all experiments is shown in Table 15 below. [Table 15]

[0191] Example 4.2(b) Slurry Preparation: First, polyacrylic acid (19.24 g) (PAA, 250 kDa, 25% neutralized) and conductive carbon black Super C65 (0.94 g) were combined using a Thinky Mixer ARE-250 CE planetary mixer. The mixture was incorporated for 2 minutes at 2000 rpm and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (14.91 g) and microsilicon (33.67 g) and the mixing step was repeated. Next, flake graphite (9.62 g) was added and the mixing step was repeated. Finally, the pre-dispersed carbon nanotube solution (6.01 g) was added and the mixing step was repeated. 60.31 g of this complete mixture was transferred to a Dispermat compatible container and mixed for 5 minutes at 6000 rpm.

[0192] Example 4.2(c) Prelithiation Step and Electrochemical Test Program Direct contact experimental setup: [Table 16]

[0193] The slurry was cast on copper foil and dried at 60°C before cutting for coin cell assembly. The electrodes (coated anode and commercial NCM523) were further dried at 110°C under vacuum for 12 hours. The electrodes were then introduced inside an Ar glove box where the prelithiaton process was carried out. The silicon anode was placed in direct contact with the lithium foil for a specific time (Table 16) with an electrolyte medium (2.0 ml of 1M LiPF6 in FEC / DEC 2:8% by volume) between them. Pressure (certain weight) was applied to establish direct contact between the silicon and the lithium foil (Table 16), thereby initiating the prelithiaton process. The outcome of the prelithiaton process and the extent of prelithiaton depend on the contact duration, the applied pressure, and the homogeneity of the contact.

[0194] Based on thermodynamics, lithium metal foil spontaneously reacts with silicon (Si) to form a Li-Si alloy as follows: Net reaction 4.4Li+Si=Li 4.4 S Reduction 4.4Li+Si+4.4e-=Li 4.4 S Oxide 4.4Li-4.4e-=4.4Li+ ΔG=-nEF approx.-4.4*96500=-42kJmol -1 where ΔG is the Gibbs free energy of the overall reaction, E is the potential of the overall reaction, and F is the Faraday constant. E was assumed to be approximately 0.1 V according to experimental data.

[0195] The pre-lithiated electrodes were then assembled onto full cells using the procedure described in Example 1. See Tables 3 and 4 for the cycling program.

[0196] Example 4.2(d) Cyclic Study - Summary of Key Findings Direct contact prelithiation increased the ICE for all electrodes compared to the control. The percentage of lithiation that can be achieved is a factor of the contact time and the applied pressure. Table 17 shows the capacity retention of the cells at cycle 90, with both 200g / 5min and 100g / 5min (pressure / time) having the same capacity retention (98.9%), and the best performing samples, 200g / 10min and 100g / 15min, also having the same capacity retention (101%). It is clear that the degree of prelithiation can be controlled by controlling the contact time and the applied pressure. [Table 17]

[0197] Example 5 Micro-Si anode with CMC / SBR binder at 30% capacity limit 5(a) Electrode composition The specific electrode compositions used in this experiment are shown in Table 18 below. [Table 18]

[0198] Example 5(b) Slurry Preparation Example 5(b)(i) - 4% CMC, 4% SBR First, carboxymethyl cellulose binder (52.00 g, CMC) and conductive carbon black Super C65 (0.52 g) were combined using a Thinky Mixer ARE-250 CE planetary mixer. The mixture was incorporated for 2 minutes at 2000 rpm and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (18.30 g) and microsilicone (18.20 g) and the mixing step was repeated. Next, flake graphite (5.20 g) was added and the mixing step was repeated. Finally, styrene-butadiene rubber (2.08, SBR) was added and mixed for 2 minutes at 900 rpm and then repeated for another 2 minutes, during which manual mixing with a spatula was required. 72.47 g of this complete mixture was transferred to a Dispermat compatible container and mixed for 5 minutes at 900 rpm.

[0199] Example 5(b)(ii) – 8% LiPAA First, polyacrylic acid (18.20 g) (PAA, 250 kDa, 25% neutralized) and conductive carbon black Super C65 (0.91 g) were combined using a Thinky Mixer ARE-250 CE planetary mixer. The mixture was incorporated at 2000 rpm for 2 minutes and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (19.25 g) and microsilicon (31.85 g) and the mixing step was repeated. Finally, flake graphite (9.10 g) was added and the mixing step was repeated. 61.01 g of this complete mixture was transferred to a Dispermat compatible container and mixed at 3000 rpm. Additional water (3.81 g) was added dropwise to the mixture and the mixing speed was increased to 6000 rpm for 5 minutes.

[0200] Example 5(c) Electrochemical Test Program The full cell was assembled using the procedure described in Example 1. The cycle program was as shown in Tables 3 and 4 above.

[0201] Example 5(d) Cyclic Study - Summary of Key Findings [Table 19]

[0202] The full cell results using 8% PAA binder were used to compare the effect of binder on the electrochemical performance of the 70% micro-Si anode. The use of a CMC / SBR binder improves the ICE by 0.6% when compared to the PAA binder. However, the CMC / SBR full cell lost 20% capacity after only about 155 cycles, while the PAA full cell lost the same amount of capacity after 277 cycles (Figure 5).

[0203] Example 6 Effect of binder / binder pH The degree of PAA neutralization by LiOH, and therefore the resulting binder pH, showed a direct impact on the electrochemical performance of the micro-silicon anode. Results with a binder pH of 4-5 were found to be particularly beneficial, leading to improved capacity retention while requiring a lower amount of conductive additive for further enhancement of electrode performance. When the pH of the PAA binder exceeds 7, the capacity retention of the micro-silicon anode is significantly degraded. A high binder pH also leads to the requirement of a higher amount of conductive additive.

[0204] The gradually deteriorating electrochemical performance of microsilicon anodes at pH approaching or exceeding 7 may result from the exposure of Si particles to LiOH, which causes oxidation of Si. In addition, the reduced number of -COOH groups at pH above 7 may reduce the degree of esterification of siloxyl groups on the surface of Si particles, which allows the formation of strong bonds between polymer chains and Si. This makes the PAA binder less efficient in countering the effect of volume changes of Si particles in the electrode matrix. In addition, the difference in solid content to achieve a workable slurry viscosity based on the binder pH may affect the morphology of the microsilicon anode, further contributing to the variation in electrochemical performance.

[0205] Example 6.1 Comparison of 25% vs. 95% Neutralized PAA with and without CNTs Example 6.1(a) Electrode Composition An anode composition was prepared consisting of 70% Elkem2 microsilicon. The specific electrode composition used for all experiments in Example 6.1 is shown in Table 20 below. [Table 20]

[0206] Example 6.1(b) Slurry Preparation The material compositions listed in Table 20 were used to prepare the slurries.

[0207] A slurry without carbon nanotubes was prepared using the procedure described in Example 1. The final mixing step with Dispermat was performed using Li 0.95 Omitted only for slurries with PAA binder.

[0208] Li 0.25 PAA and Li 0.95 A carbon nanotube incorporated slurry with a PAA binder system was prepared using the procedure described in Example 4.2(b).

[0209] Example 6.1(c) Test Setup for Full Cell The full cell was assembled using the procedure described in Example 1. The cycle program was as shown in Tables 3 and 4 above.

[0210] Example 6.1(d) Cycling Testing - Summary of Key Findings for Full Cell Testing Overall, the addition of CNTs improves the ICE and extends the cycle life. For 25% neutralized PAA [Li0.25PAA], the addition of 0.05 wt% CNTs increases the cycle life by 80 cycles when compared to 0% CNTs. For the example of 95% neutralized PAA [Li0.95PAA], the addition of CNTs slightly increases the ICE but reduces the capacity retention by 26 cycles (Figure 6b). Based on electrochemical testing, Li0.25PAA produced better cycling results than the Li0.95PAA binder system. [Table 21] [Table 22]

[0211] Furthermore, the micro-silicon electrodes resulting from the anode formulation consisting of 95% neutralized PAA binder exhibited a relatively loosely packed morphology, which was prone to particle collapse and therefore electrical isolation during cycling, resulting in poor capacity retention. In contrast, a relatively densely packed electrode morphology resulted from the anode formulation consisting of 25% neutralized PAA binder, suggesting that the electrodes were less likely to suffer capacity loss due to electrical isolation of the Si particles.

[0212] Example 6.2 70% MicroSi with PAA Copolymer (hydrophilic portion) binder Example 6.2(a) Electrode Composition The specific electrode compositions used for all experiments are shown in Table 23 below. [Table 23]

[0213] Example 6.3(b) Slurry Preparation PAA copolymer with hydrophilic moieties (37.14 g, 9.8 wt% solution) and conductive carbon black Super C65 (0.91 g, Nanografi, Turkey) were combined using a Thinky Mixer ARE-250 CE (Thinky Corp, USA) centrifugal planetary mixer. The mixture was incorporated at 2000 rpm for 2 minutes and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (18.05 g) and microsilicone (31.85 g) and the mixing step was repeated. Finally, flake graphite (9.10 g, KS6L, Imerys, Malaysia) was added and the mixing step was repeated. 74.65 g of this complete mixture was transferred to a Dispermat compatible container and mixed at 3000 rpm using an overhead mixer (VMA-Getzmann Dispermat, Germany). 3.81 g of water was added dropwise (1-2 drops / sec) to the mixture. The speed was increased to 6000 rpm and allowed to mix for 5 minutes.

[0214] Example 6.2(c) Electrochemical Test Program The full cell was assembled using the procedure described in Example 1. The cycle program was as shown in Tables 3 and 4 above.

[0215] Example 6.2(d) Cyclic Study - Summary of Key Findings [Table 24]

[0216] The use of PAA copolymer (hydrophilic portion) binder showed discharge capacity of 165 mAh / g based on the weight of the cathode coating and 1357 mAh / g based on the weight of the anode coating at an ICE of 90.3% and a rate of C / 20. Figure 7a shows the capacity retention for 8% hydrophilic PAA copolymer cycling at a capacity limit of 60%, with the full cell losing 20% ​​cycling capacity after about 116 cycles. The initial discharge capacity of the anode shown in Figure 7b was 1357 mAh / g, and after about 170 cycles the capacity had decreased to 760 mAh / g.

[0217] Example 7: 70wt% vs. 90wt% microsilicon anode design The silicon-based anode design allows access to higher energy densities compared to commercial state-of-the-art anode formulations that contain silicon as an additive material. Although a 70 wt% microsilicon anode design is already a silicon-based system, a further increment in silicon content to 90 wt% reduces the degree of silicon utilization required to achieve the same capacity as a 70 wt% microsilicon anode design.

[0218] For example, if a 70 wt% microsilicon anode design can deliver 800 mAh / g of coating capacity at a capacity limit of 30%, 1000 mAh / g can be accessed by a 90 wt% microsilicon anode design at the same capacity limit. This allows for faster Li + It enables the design of thinner electrodes with ion diffusion capabilities, paving the way for new lightweight battery designs. In addition, the 90 wt% micro-silicon anode design can further increase the energy density and support high-rate capability.

[0219] Example 7(a) Electrode Composition Anode compositions consisting of 70% and 90% Elkem2 microsilicon were prepared. The specific electrode compositions used for all experiments are shown in Table 25 below. [Table 25]

[0220] Example 7(b) Slurry Preparation Slurries were prepared using the compositions in Table 25. The procedure described in Example 4.2(b) was used for the slurry preparation process.

[0221] Example 7(c) Test Cell Setup for Full Cell The full cell was assembled using the procedure described in Example 1. See Tables 3 and 4 for the cycle program.

[0222] Example 7(d) Cycling Testing - Summary of Key Findings for Full Cell Testing The effect of mSi content (70 and 90%) was investigated (FIG. 8). Although they have similar starting capacities, the 90% mSi anode has about 1% higher ICE than the 70% mSi anode. The 70% mSi anode showed better capacity retention than the 90% mSi system, reaching 80% capacity retention after 300 cycles, about 77 cycles more than that of the 90% mSi anode. [Table 26]

[0223] Example 8 Effect of carbon nanotube conductive additive CNTs have been found to improve conductivity for LIB electrodes when used as a conductive additive, which also provides an effective conductive network for Si anodes. Physical mixing is a simple and effective method to improve the conductivity of Si-based anodes, with the drawback of low homogeneity and therefore lack of consistency in cycling performance. The use of CNTs in physical mixing was found to affect the slurry viscosity without a direct effect on the slurry processability and anode structure. Fortunately, many benefits were observed after adding CNTs to the anode composition. It was concluded that the improvement of conductivity and charge transfer due to the reduction of resistance, and based on cycling tests, CNTs extend the life cycle by about 90 cycles.

[0224] Example 8(a) Electrode Composition (0% CNT) An anode composition was prepared consisting of 70% microcrystalline silicon. The specific electrode compositions used are shown in Table 27 below. [Table 27]

[0225] Example 8(b) Slurry Preparation First, polyacrylic acid (18.20 g) (PAA, 250 kDa, 25% neutralized) and conductive carbon black Super C65 (0.91 g) were combined using a Thinky Mixer ARE-250 CE planetary mixer. The mixture was incorporated for 2 minutes at 2000 rpm and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (19.25 g) and microsilicon (31.85 g) and the mixing step was repeated. Finally, flake graphite (9.10 g) was added and the mixing step was repeated. 61.01 g of this complete mixture was transferred to a Dispermat compatible container and mixed at 3000 rpm using an overhead mixer (VMA-Getzmann Dispermat). 3.81 g of water was added dropwise (1-2 drops / sec) to the mixture. The speed was increased to 6000 rpm and left to mix for 5 minutes.

[0226] Example 8(c) Electrode Composition (0.05% CNT) An anode composition consisting of 70% microcrystalline silicon was prepared. The specific electrode composition used for all experiments is shown in Table 28 below. [Table 28]

[0227] Example 8(d) Slurry Preparation First, polyacrylic acid (18.20 g) (PAA, 250 kDa, 25% neutralized) and conductive carbon black Super C65 (0.89 g) were combined using a Thinky Mixer ARE-250 CE planetary mixer. The mixture was incorporated for 2 minutes at 2000 rpm and then repeated for another 2 minutes, during which manual mixing with a spatula was required. This was followed by the addition of water (18.53 g) and microsilicon (31.85 g) and the mixing step was repeated. Next, flake graphite (9.10 g) was added and the mixing step was repeated. Finally, pre-dispersed carbon nanotube (CNT) solution (5.69 g) was added and the mixing step was repeated. 60.46 g of this complete mixture was transferred to a Dispermat compatible container and mixed for 5 minutes at 6000 rpm.

[0228] Example 8(e) Electrochemical Test Program The full cell was assembled using the procedure described in Example 1. The cycle program is as shown in Tables 3 and 4.

[0229] Example 8(f) Cycling Study - Summary of Key Findings The effect of CNT addition was investigated for a 70 wt% mSi anode and it was found that 0.05 wt% CNT increased the ICE by 0.3% and extended the cycle life to 85 cycles with 80% capacity retention when compared to 0% CNT (Figure 9). [Table 29]

Claims

1. an anode composition containing micro silicon active material particles, The micro silicon active material particles are as follows: (i) about 0.1 m 2 / g ~ approx. 10m 2 BET surface area measured per g, (ii) D approximately 0.1 μm to approximately 10 μm 50 Particle size, and (iii) D of approximately 0.1 to approximately 10 50 : Having one or more of the BET surface area ratios, An anode composition in which the amount of microsilicon active material particles present in the anode composition is about 60% by weight to about 95% by weight, based on the total weight percentage of the anode composition.

2. The anode composition according to claim 1, wherein the amount of microsilicon active material particles present in the anode composition is about 70% by weight to about 95% by weight, based on the total weight % of the anode composition.

3. The tap density of the aforementioned microsilicon active material particles is approximately 0.5 g / cm³. 2 ~Approx. 1.5g / cm 2 The anode composition according to claim 1.

4. The anode composition according to claim 1, wherein the purity of the microsilicon active material particles (without oxygen) is at least 95% by weight, preferably 98% by weight.

5. The D of the microsilicon active material particles 50 The anode composition according to claim 1, wherein the particle size is approximately 2 μm to approximately 8 μm.

6. The measured BET surface area of the micro-silicon active material particles is from about 1 m 2 / g to about 5 m 2 / g. The anode composition according to claim 1.

7. D of the microsilicon active material particles 50 The anode composition according to claim 1, wherein the ratio of BET surface area is about 0.1 to about 6.

8. The anode composition according to claim 1, wherein an impurity selected from the group consisting of Al, Ca, Fe, Ti, P, Cu, Cr, K, V, Ni, and Na is present in the microsilicon active material particles in an amount of less than approximately 5000 ppm, either individually or as a total impurity level.

9. The anode composition according to claim 1, wherein the anode composition further comprises one or more binders and / or one or more conductive materials.

10. The anode composition according to claim 1, wherein the microsilicon active material particles or anode composition are prelithitated.

11. The anode composition according to claim 10, wherein the pre-lithiation level of the microsilicon active material particles and / or the anode composition is about 1% to about 30%.

12. The anode composition according to claim 1, wherein the anode composition is a coating or film applied to the surface of a current collector material.

13. An electrochemical cell comprising an anode, a cathode, an electrolyte, and a separator, An electrochemical cell in which the anode comprises the anode composition according to any one of claims 1 to 12.

14. The electrochemical cell according to claim 13, wherein the lithium uptake capacity of the anode is greater than the lithium release capacity of the cathode.

15. The electrochemical cell according to claim 13, wherein the lithium uptake capacity of the anode is not fully utilized during charging of the lithium-ion battery.

16. The electrochemical cell according to claim 13, wherein the anode is partially lithium-ionized while fully charged.

17. The electrochemical cell according to claim 13, wherein the capacitance ratio (N / P ratio) of the anode and the cathode is about 1.05 to about 7.

18. The electrochemical cell according to claim 13, wherein the cathode is selected from the group comprising lithium nickel cobalt manganese oxide (NCM), lithium iron phosphate (LFP), lithium nickel manganese spinel (LNMO), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), and sulfur complexes.

19. A process for preparing an anode for an electrochemical cell, (i) A step of preparing an anode slurry comprising microsilicon active material particles, one or more optionally further active materials, one or more optionally binders, one or more optionally conductive materials, one or more optionally additives, and a solvent system. (ii) The step of casting the layer of the anode slurry onto a current collector material to provide a wet anode composition layer on the current collector material, The micro silicon active material particles are as follows: (i) about 0.1 m 2 / g ~ approx. 10m 2 BET surface area measured per g, (ii) D approximately 0.1 μm to approximately 10 μm 50 Particle size, and (iii) D of approximately 0.1 to approximately 10 50 A process having one or more of the BET surface area ratios.

20. The process according to claim 19, wherein the content of the binder in the anode slurry is about 2.5% by weight to about 15% by weight, based on the total weight of the anode composition.

21. The process according to claim 19, wherein the content of the conductive material in the anode slurry is about 2.5% by weight to about 40% by weight, based on the total weight of the anode composition.

22. The process according to claim 19, further comprising step (iii) (a) solvent evaporation and / or (b) heat treatment to solidify the wet anode layer to provide a dry anode composition layer coated on the current collector material.

23. The process according to claim 19, wherein the thickness of the dried anode composition layer is in the range of about 5 μm to about 70 μm.

24. The process according to claim 22, wherein the temperature for step (iii)(a) is about 40°C to 60°C, and / or the temperature for step (iii)(b) is about 90°C to 180°C.

Images