Graphene-containing metalized silicon oxide composite materials

Abstract

This invention relates to active material composite particles, electrodes comprising such composite particles, lithium-ion secondary batteries comprising such electrodes, and methods for forming the same, wherein each of the composite particles comprises a core particle comprising an alkali metal or alkaline earth metal silicate and a coating disposed on the surface of the core particle. The coating comprises a turbine layer carbon having a Raman spectrum having the following: a D band having a peak intensity (ID) at wavenumbers between 1330 cm⁻¹ and 1360 cm⁻¹; a G band having a peak intensity (IG) at wavenumbers between 1580 cm⁻¹ and 1600 cm⁻¹; and a 2D band having a peak intensity (I²D) at wavenumbers between 2650 cm⁻¹ and 2750 cm⁻¹, wherein the ID / IG ratio is in the range of greater than zero to about 1.1, and the I²D / IG ratio is in the range of about 0.4 to about 2.

Description

Technical Field

[0001] The present invention relates to a graphite-metallized silicon oxide composite active material, a negative electrode therein, and a battery including the negative electrode. Prior Technology

[0002] Lithium (Li)-ion electrochemical batteries typically require materials capable of achieving high energy density, high power density, and high cycle stability. Lithium-ion batteries are commonly used in a variety of applications, including consumer electronics, wearable computing devices, military mobile devices, satellite communications, spacecraft, and electric vehicles, and are particularly prevalent in large-scale energy applications such as low-emission electric vehicles, renewable power plants, and stationary power grids. Furthermore, lithium-ion batteries are at the forefront of next-generation wireless and portable communication applications. One or more lithium-ion batteries can be configured as a power source for any of these applications. However, due to the increasing demand for high-energy applications, research into lithium-ion batteries with higher energy density, higher power density, faster charge / discharge rates, and longer cycle life is accelerating. Moreover, with the increasing adoption of lithium-ion technology and the migration of applications towards higher current requirements, longer operating times, wider and higher power ranges, and smaller form factors, there is a growing need to expand the latest energy and power densities.

[0003] Silicon or silicon alloy anode materials are currently included in most long-term lithium-ion technology adoption blueprints as a practical means of achieving higher energy and power densities. Silicon is the required negative electrode active material for lithium-ion electrochemical battery applications, possessing a theoretical gravimetric capacity of approximately 4,200 mAh / g and a volumetric capacity of approximately 9,786 mAh / cm³ when fully lithiated. Silicon is also a desirable alternative to current graphite-based anodes because its high lithium storage capacity exceeds that of graphite by 7 times. The market has adopted silicon-based anodes for lithium-ion batteries; however, this has been challenged by rapidly decreasing cycle life, poor charge / discharge rate capability under high power demands, and low-load, defective coulombic efficiency, all of which can result from extreme anode volume changes during charging and discharging (up to 400% volume expansion has been noted). Cycle life degradation in silicon-based alloys is well understood and can be broken down into two basic mechanisms: (1) electrical disconnection and (2) unstable solid electrolyte interface (SEI), leading to lithium-ion consumption and impedance growth. High-rate capability and coulombic efficiency are also impaired by these mechanisms. Electrical disconnection occurs during charging and discharging due to significant volume fluctuations caused by the large volume changes following lithiation and delithiation.

[0004] These large volume changes can cause the fragmentation of silicon particles (pressure-induced fracture and breakage) and the loss of electrical contacts between these active silicon particles. The result is an electrochemical cell with low power capability and rapid capacity decay. The fracture and breakage introduced in mechanism (1) further degrades the battery performance by subsequently promoting mechanism (2) (unstable SEI). Because the fracture and breakage expose the new Si surface to the electrolyte solvent, further SEI formation occurs, and lithium compounds are deposited on the new Si surface. During charge / discharge cycles, the insulating SEI layer also grows thicker, further reducing the capacity and cycle stability of the Si anode, and impairing charge / discharge rate capability and coulombic efficiency.

[0005] The continuous growth and new formation of the SEI layer gradually depletes the available Li+, and the amount of electrolyte available is also depleted due to side reactions with the electrolyte solvent and salts (one or more), thereby reducing the overall electrochemical cell performance. Therefore, the use of silicon-based anodes in applications requiring high electrochemical cell charge / discharge rates is severely limited due to the high ohmic resistance and ion contribution to polarization resulting from these mechanisms.

[0006] Therefore, there is a need for silicon-based electrode materials with improved first-cycle efficiency and cycle life.

[0007] Therefore, there is a need for an advanced anode active material for electrochemical batteries, which is a carbon material with defined quality characteristics that advantageously influence the cycle performance of electrochemical batteries. More specifically, there is a need for advanced silicon-based composite anode materials comprising low-defect turbine layer carbon, which enables lithium-ion electrochemical batteries to achieve cycle life stability, energy density, and rate performance. Summary of the Invention

[0008] According to various embodiments of this disclosure, the active material composite particles comprise a core particle including an alkali metal or alkaline earth metal silicate and a coating disposed on the surface of the core particle. The coating comprises a turbine layer carbon having a Raman spectrum having the following: a D band having a peak intensity (ID) at a wavenumber between 1330 cm⁻¹ and 1360 cm⁻¹; a G band having a peak intensity (IG) at a wavenumber between 1580 cm⁻¹ and 1600 cm⁻¹; and a 2D band having a peak intensity (I²D) at a wavenumber between 2650 cm⁻¹ and 2750 cm⁻¹, wherein the ID / IG ratio ranges from greater than zero to about 1.1, and the I²D / IG ratio ranges from about 0.4 to about 2.

[0009] According to various embodiments of this disclosure, a method for forming active material composite particles includes: forming a mixture comprising core particles, the core particles comprising an alkali metal or alkaline earth metal silicate and a turbine layer carbon; and spray drying the mixture to form composite particles comprising core particles coated with a turbine layer carbon. The turbine layer carbon has a Raman spectrum having: a D band with a peak intensity (ID) at wavenumbers between 1330 cm⁻¹ and 1360 cm⁻¹; a G band with a peak intensity (IG) at wavenumbers between 1580 cm⁻¹ and 1600 cm⁻¹; and a 2D band with a peak intensity (I²D) at wavenumbers between 2650 cm⁻¹ and 2750 cm⁻¹. The ID / IG ratio ranges from greater than zero to about 1.1, and the I²D / IG ratio ranges from about 0.4 to about 2.

[0010] Other key features and advantages of the invention will become apparent to those skilled in the art when examined in light of the following drawings, embodiments and the appended claims. Simple Explanation of the Diagram

[0011] Figure 1A is a scanning electron microscope (SEM) image of the active material composite particles according to various embodiments of the present disclosure, and Figures 1B-1D are cross-sectional views of the core particles that may be included in the composite particles of Figure 1A.

[0012] Figures 2A, 2B, and 2C show the Raman spectra of graphite and various graphene-based materials.

[0013] Figure 3 is a bar chart comparing the ID / IG ratio of Raman spectra of typical carbon materials and low-defect turbine layer carbon.

[0014] Figures 4A, 4B, and 4C show the Raman spectra of an electrode active material containing SiOx core particles encapsulated by amorphous carbon, reduced graphene oxide (rGO), and low-defect turbine layer carbon, respectively.

[0015] Figure 5 is a diagram illustrating the cycle life of exemplary and comparative half-cells containing lithium metallized SiO (LM-SiO) according to various embodiments of the present disclosure.

[0016] Figure 6 is a diagram showing the X-ray diffraction results of the control material compared with the material of Example 1 according to the embodiment of this disclosure.

[0017] Figure 7 is a graph showing the cycling characteristics of a half-cell containing magnesium metallized SiO (MM-SiO) and the capacity retention of a control half-cell.

[0018] Figure 8 is a diagram showing the anode capacity of the half-cell in Figure 7. Implementation

[0019] Various embodiments will be described in detail with reference to the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. Reference to specific examples and embodiments is for illustrative purposes and is not intended to limit the scope of the invention or the claims.

[0020] It should be understood that when a component or layer is referred to as "on another component or layer" or "connected to another component or layer," it may be directly on or directly connected to the other component or layer, or an intervening component or layer may be present. In contrast, when a component is referred to as "directly on another component or layer" or "directly connected to another component or layer," no intervening component or layer exists. It will be understood that, for the purposes of this disclosure, "at least one of X, Y, and Z" may be considered as only X, only Y, only Z, or any combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ, ZZ).

[0021] When providing value ranges, it should be understood that this invention covers all intermediate values ​​between the upper and lower limits of the range (unless the context clearly indicates otherwise, up to one-tenth of the lower limit unit) and any other stated or intermediate values ​​within the stated range. The upper and lower limits of these smaller ranges may be independently included within the smaller range and are also covered within this invention, subject to any specific exclusions within the stated range. When a stated range includes one or both of the limits, the range excluding any or both of the included limits is also included in this invention. It should also be understood that the term "about" may refer, for example, a small measurement error of + / - 5% to 10%.

[0022] Words such as “after which,” “following,” and “then” are not necessarily intended to limit the order of steps; such words may be used to guide the reader through the description of the method. Furthermore, any reference to an element in the claims that is in the singular form (e.g., the use of the words “a” or “the”) should not be construed as limiting the element to the singular form.

[0023] "Electrode material" is defined as a material that can be configured for use as an electrode in an electrochemical battery (such as a lithium-ion rechargeable battery). "Electrode" is defined as the anode or cathode of an electrochemical battery. "Composite electrode material" is also defined as an active material particle that is combined with particles, sheets, spheres, flakes, plates, tubes, fibers, or combinations thereof and has the characteristics of a conductive material. Particles, sheets, spheres, flakes, plates, tubes, fibers, or combinations thereof may further be flat, wrinkled, pleated, layered, woven, braided, or combinations thereof.

[0024] Conductive materials may be selected from the group consisting of: conductive carbon-based materials, conductive polymers, graphite, metal powders, nickel, aluminum, titanium, stainless steel, and any combination thereof. Conductive carbon-based materials may further include graphite, graphene, diamond, pyrolytic graphite, carbon black, low-defect turbine layer carbon, fullerenes, or combinations thereof. "Electrode material mixture" is defined as a combination of materials such as: material particles (electrochemically active, conductive, composites, or combinations thereof), one or more binders, non-crosslinked and / or crosslinked polymers or polymers, mixed together to form an electrode for use in an electrochemical battery. "Electrochemically active material," "electrode active material," or "active material" is defined herein as a material that inserts and releases ions (such as ions in an electrolyte) to store and release potential. The term "insertion and release" can be further understood as the insertion and deintercalation or lithiation and delithiation of ions. Therefore, it should also be understood that the process of inserting and releasing ions is insertion and deintercalation or lithiation and delithiation. Therefore, "active materials" or "electrochemically active materials" or "active material particles" are defined as materials or particles that can be repeatedly inserted and extracted into ions or lithiated and delithiated.

[0025] A "defect" is defined as any feature that disrupts the hexagonal lattice symmetry of carbon atoms in a given carbon sheet. According to this definition, defects can include vacancies, substituted atoms, edges, grain boundaries, or variations in carbon hybridization. "Hybridization" refers to the mixing of standard atomic orbitals to form new orbitals, which can be used to describe bonds in molecules. Hybridization of standard atomic orbitals typically occurs with sp2 and sp3 orbitals.

[0026] Defect density is defined as the amount of symmetry-breaking features (defects) per unit area of ​​a carbon plane. This value is often estimated as the average distance between two defects. Defect density can be estimated using the ID / IG ratio via Raman spectroscopy.

[0027] "Composite particles" may comprise one or more core particles, which include an electrochemically active material and a coating disposed on the surface of the core particles. The coating may comprise carbon materials, such as turbine layer carbon, carbon nanotubes, activated carbon, or any combination thereof.

[0028] According to various embodiments of this disclosure, the core particles are at least partially encapsulated (e.g., covered) by a coating. For example, the coating and / or turbine layer carbon may cover approximately 10% to approximately 100% of the surface of each core particle, such as approximately 20% to approximately 90%, approximately 25% to approximately 80%, approximately 30% to approximately 70%, or approximately 40% to approximately 60%. In some embodiments, the coating may be in the form of a membrane or shell that at least partially or completely encapsulates one or more of the core particles.

[0029] In some embodiments, the coating may have a wrinkled morphology. The term "wrinkle" is defined as a body or mass exhibiting the distribution of creases, ripples, folds, wrinkles, and ridges. The term "wrinkle" is also defined as causing or bending. The term "morphology" is defined as the structure and one or more features of a surface. Specifically, "morphology" refers to the structure and features of the outer surface of the particles or macroparticles of the electrode material.

[0030] As defined herein, a secondary electrochemical cell is a rechargeable electrochemical cell or battery. "Capacity" is defined herein as a measure of the charge stored in the cell, determined by the mass of the active material contained within the cell, representing the maximum amount of energy, in ampere-hours (Ah), that can be extracted from the cell at its rated voltage. Capacity can also be defined by the following equation: Capacity = Energy / Voltage or Current (A) × Time (h). "Energy" is mathematically defined by the following equation: Energy = Capacity (Ah) × Voltage (V). "Specific capacity" is defined herein as the amount of charge that can be delivered per unit mass or unit volume of active electrode material for a specified time. Specific capacity can be measured in units of weight, such as (Ah) / g, or in units of volume, such as (Ah) / cc. Specific capacity is defined mathematically by the formula: Specific capacity (Ah / kg) = Capacity (Ah) / Mass (kg). "Rate capacity" is the ability of an electrochemical cell to receive or deliver the amount of energy within a specified time period. Alternatively, "rate capacity" refers to the maximum continuous or pulsed energy that a battery can provide per unit time.

[0031] "C-rate" is defined in this paper as a measure of the rate at which a battery discharges relative to its maximum rated capacity. For example, a 1C current rate means that the discharge current will discharge the entire battery in 1 hour; a C / 2 current rate means that the battery will be fully discharged in 2 hours, and a 2C rate means that the battery will be fully discharged in 0.5 hours. "Power" is defined as the rate of energy transfer over time, measured in watts (W). Power is the product of the voltage (V) passing through the battery or cell and the current (A) passing through the battery or cell. Mathematically, "C-rate" is defined as C-rate (reverse time) = current (A) / capacity (Ah) or C-rate (reverse time) = 1 / discharge time (h). Power is defined by the mathematical equation: Power (W) = Energy (Wh) / Time (h) or Power (W) = Current (A) × Voltage (V). Coulombic efficiency is the efficiency of charge transfer within an electrochemical cell. Coulombic efficiency is the ratio of the battery's output charge to its input charge.

[0032] [Active Material Composite Particles] [] Silicon and silicon alloys can significantly increase battery capacity when incorporated into the electrodes of electrochemical cells. Silicon and silicon alloys are typically incorporated into electrodes containing graphite, graphene, or other carbon-based active materials. Examples of electrodes containing carbon-based materials and silicon are provided in U.S. Patents 8,551,650, 8,778,538, and 9,728,773 to Kung et al., and U.S. Patents 10,135,059 and 10,135,063 to Huang et al., all of which are incorporated herein by reference in their entirety.

[0033] In this article, "SiO materials" generally refers to silicon- and oxygen-containing materials. SiO materials have attracted attention for use as anode electrodes in lithium-ion batteries due to their high theoretical energy and power density. However, the utilization rate of current commercial SiO materials (such as silicon oxide (e.g., SiOx, where x is in the range of 0.8 to 1.2, such as 0.9 to 1.1) is limited by their low first-cycle efficiency and high irreversibility. This low first-cycle efficiency is attributed to the highly irreversible Li+ reaction with the silicon oxide matrix.

[0034] To reduce the irreversible Li+ reaction with silicon oxide, various embodiments include metallized SiO materials (M-SiO). Hereinafter, M-SiO material can refer to an active material that reacts directly with a metal-containing precursor (such as an alkali-containing precursor and / or an alkaline earth-containing precursor, such as a lithium-containing precursor and / or a magnesium-containing precursor) to form a metallized silicon and an oxygen-containing phase before being used as an active material and / or in a battery undergoing charge and discharge reactions. In one embodiment, all or part of the metallized metal may remain in the active material and not be intercalated (i.e., not inserted) or deintercalated during battery charge and discharge. Therefore, M-SiO material can refer to lithium metallized SiO (LM-SiO) material and / or Mg metallized SiO (MM-SiO) material. However, in some embodiments, M-SiO material may include SiO material metallized to include other suitable alkali metals and / or alkaline earth metals, such as sodium, potassium, calcium, or the like. For example, in some embodiments, the M-SiO material may be metallized to include magnesium, lithium, sodium, potassium, calcium, or any combination thereof.

[0035] Electrode materials incorporating M-SiO active materials have been found to offer increased first-cycle efficiency (FCE) compared to non-metallized SiO materials. Unfortunately, M-SiO materials have been found to exhibit severe electrical disconnection and rapid capacity loss, often resulting in over 90% capacity decay within 20 cycles. Coating M-SiO materials with carbon and / or other materials, and / or doping M-SiO materials with graphite, has been found to slightly reduce electrical disconnection and capacity loss of the active material, delaying capacity decay by over 50% to approximately 50 cycles, but this still represents highly unsatisfactory cycle stability for commercial applications. Overall, current M-SiO materials do not exhibit sufficient electrical stability for commercial use.

[0036] Figure 1A is a scanning electron microscope (SEM) image of the active material composite particle 100 according to various embodiments of the present disclosure, and Figures 1B-1D are cross-sectional views of the core particles 102A-102C that may be included in the composite particle 100 of Figure 1A. Referring to Figures 1A and 1B, the composite particle 100 includes: a core particle 102 containing an electrochemically active material; and a graphene-containing coating 110 coated on and / or encapsulating the core particle 102.

[0037] In a preferred embodiment, the active material of the core particle 102 comprises M-SiO material. Therefore, the composite particle 100 is described below with respect to the core particle 102 comprising M-SiO material.

[0038] The average particle size of the composite particles 100 and / or the core particles 102 can be in the range of about 1 µm to about 20 µm, such as for example about 2 µm to about 15 µm, about 3 µm to about 10 µm, about 3 µm to about 7 µm, or about 5 µm. The core particles 102 can include an M-SiO material, which includes a metallized silicon substance and silicon (such as crystalline and / or amorphous silicon). The metallized silicon substance can include metallized silicides and metallized silicates. In some embodiments, the M-SiO material can also include silicon oxide (SiOx, where x is in the range of 0.8 to 1.2, such as between 0.9 and 1.1). In various embodiments, the M-SiO material can include a lithiated silicon substance. As used herein, "lithiated silicon substance" can include lithium silicides (LixSi, 0 < x < 4.4) and / or one or more lithium silicates (such as Li2Si2O, Li2SiO3, and / or Li4SiO4, etc.).

[0039] Referring to FIG. 1B, in some embodiments, the composite particles 100 can include a heterogeneous core particle 102A, which includes an M-SiO material that includes multiple silicon-containing material phases 104, 106, 108. For example, the phases 104, 106, 108 can independently include crystalline silicon, silicon oxide (such as SiOx, where x is in the range of 0.8 to 1.2, such as 0.9 to 1.1), and / or a lithiated silicon substance. However, in some embodiments, the core particles 102 can be substantially homogeneous particles that lack different phases but include silicon, oxygen, and lithium.

[0040] Referring to FIG. 1C, in some embodiments, the composite particles 100 can include a core particle 102B, which includes a primary phase 120 in which crystalline silicon domains 122 are dispersed in a secondary phase. For example, the primary phase 120 can include a lithiated silicon substance, such as a lithium silicate substance, and in particular Li2Si2O, In other embodiments, the primary phase 120 can include a metallized magnesium silicon substance, a magnesium silicate substance, and in particular MgSiO3, Mg2SiO4, or a combination thereof. The crystalline silicon domains 122 can include crystalline silicon nanoparticles with a particle size less than 100 nm. For example, the crystalline silicon domains 122 can have an average particle size in the range of about 3 nm to about 60 nm. In one embodiment, most of the crystalline silicon domains 122 can have an average particle size in the range of about 5 nm to about 10 nm, and the remaining crystalline silicon domains 122 can have an average particle size of about 10 nm to about 50 nm.

[0041] Referring to Figure 1D, in some embodiments, the composite particle 100 may include a core particle 102C comprising a primary phase 120 containing M-SiO material and crystalline silicon domains 122 and SiOx domains 124 (e.g., SiOx, where x is in the range of 0.8 to 1.2, such as 0.9 to 1.1) dispersed as secondary phases within the primary phase 120. For example, the primary phase 120 may include lithium silicate species, such as lithium silicate, and more specifically Li₂Si₂O₅; the crystalline silicon domains 122 may include crystalline silicon nanoparticles; and the SiOx domains 124 may include the SiOx phase and / or nanoparticles. The crystalline silicon domains 122 and SiOx domains 124 may have a particle size of less than about 100 nm. For example, the crystalline silicon domains 122 and SiOx domains 124 may have an average particle size in the range of about 3 nm to about 60 nm (such as about 5 nm to about 50 nm).

[0042] In various embodiments, core particle 102 may comprise about 80 wt% to about 99.5 wt% of the total weight of composite particles 100, such as about 90 wt% to about 99 wt%, including about 90 wt% to 95 wt%. In some embodiments, the M-SiO material may comprise about 40 at% to about 5 at%, such as 20 at% to about 10 at% or about 15 at% of lithium-ion silicon. In some embodiments, the M-SiO material of core particle 102A may comprise about 60 at% to about 95 at%, such as about 80 at% to about 90 at% or about 85 at% silicon and SiOx. The M-SiO material of core particle 102 may have a silicon-oxygen atomic weight ratio in the range of about 1.25:1 to about 1:1.25, such as about 1.1:1 to about 1:1.1, or about 1:1. In some embodiments, the M-SiO material of core particle 102 may comprise approximately equal atomic weights of crystalline silicon and SiOx.

[0043] During the initial charging reaction and / or subsequent charging reactions, the composition of the M-SiO material of the core particle 102A can be altered by lithiation and / or other reactions. For example, Si and SiOx can be lithilated to form LixSi domains. In addition, some SiOx can form inactive substances such as lithium silicate and Li₂O.

[0044] In various embodiments, coating 110 may be in the form of a shell that completely encapsulates the core particles 102, as shown in Figures 1B-1D. However, in some embodiments, coating 110 may only partially encapsulate some or all of the core particles 102. In some embodiments, coating 110 may constitute from about 0.5 wt% to about 20 wt% of the total weight of the composite particles 100, such as from about 1 wt% to about 10 wt% or from about 5 wt% to about 10 wt%.

[0045] In some embodiments, coating 110 may comprise a flexible, highly conductive graphene material, such as graphene, graphene oxide, partially reduced graphene oxide, or combinations thereof. For example, coating 110 may preferably comprise a flexible, highly conductive graphene material having low-defect turbine layer characteristics, which may be referred to as turbine layer carbon. The low-defect turbine layer carbon may be in the form of a sheet comprising one to about 10 layers of graphene material, such as graphene, graphene oxide, or reduced graphene oxide. In some embodiments, the low-defect turbine layer carbon may comprise at least 90 wt%, such as about 90 wt% to about 100 wt% graphene. The graphene material may further comprise powder, particles, monolayer sheets, multilayer sheets, layers, flakes, strips, quantum dots, tubes, fullerenes (hollow graphene spheres), or combinations thereof.

[0046] The turbine layer carbon can be in the form of partially overlapping sheets or flakes to simulate a larger monolithic structure. In some embodiments, the flakes have more than one or more layers of graphene-based material. In some embodiments, the flakes can have an average sheet size of ≤15 µm. In some embodiments, the flakes can have an average sheet size of ≤1 µm. In some embodiments, the turbine layer carbon-based material flakes can have a lower thickness. In some embodiments, the lower thickness of the turbine layer carbon-based material flakes can be ≤1 µm on average. In some embodiments, the lower thickness of the turbine layer carbon-based material flakes can be ≤100 nm on average.

[0047] In addition to graphene materials, coating 110 may contain one or more additives, such as polymers, carbon nanotubes, activated carbon, and / or surfactants. In various embodiments, coating 110 may also contain lithium-containing substances (e.g., LiF or its analogues), alkali metal substances, polymeric coating substances, amorphous carbon, and / or other conductive additives or reagents. For example, conductive additives or reagents may include carbon black, KETJENBLACK, Super-P carbon black, low-defect turbine layer carbon, acetylene black, channel black, furnace black, lamp black, thermal black, graphite, natural graphite, synthetic graphite, graphite oxide, partially reduced graphite, flake graphite, exfoliated graphite, thin sheet graphite, or combinations thereof. Conductive reagents may also include one of the following: conductive fibers, carbon fibers, metal fibers, carbon nanotubes (CNTs), single-walled CNTs, double-walled CNTs, multi-walled CNTs, metal powders, fluorocarbon powders, aluminum powders, nickel powders; nickel sheets, conductive whiskers, zinc oxide whiskers, potassium titanate whiskers, conductive metal oxides, titanium oxide, conductive organic compounds, conductive polyphenylene derivatives, conductive polymers, or combinations thereof.

[0048] For example, in some embodiments, the composite particles 100 may include about 0.5 wt% to about 19 wt%, such as about 1 wt% to about 10 wt%, or about 5 wt% to about 10 wt% of turbine layer carbon, and 0 wt% to about 2 wt%, such as about 0.25 wt% to about 1 wt%, or about 1 wt% of carbon nanotubes, based on the total weight of the composite particles 100.

[0049] Due to its conductive properties, coating 110 ensures that the M-SiO material of core 102 circulates uniformly in all three dimensions (the movement of electrons and Li-ions into and out of the structure), thereby minimizing the stress applied to and by the core particles and minimizing particle breakage. Furthermore, in the event of core M-SiO material breakage, the flexible coating 110 can operate to electrically connect the broken M-SiO material while maintaining the overall integrity of the composite particles 100, thereby resulting in significantly improved electrochemical performance.

[0050] For example, as discussed in detail below, it has been found that the graphite-containing coating 110 improves the electrical stability of the M-SiO material and increases its cycling performance to >300 cycles. Furthermore, it has been found that coating 110 provides significantly improved conductivity and a higher first-cycle efficiency value for the M-SiO material compared to pristine (e.g., uncoated) M-SiO material or M-SiO material coated with graphite and carbon black. In some embodiments, the electrode material including the composite particles 100 can retain more than 90% of its usable capacity after twenty cycles, providing an increase of more than nine times in usable cycle life.

[0051] [Turbine layer carbon] [] Figures 2A, 2B, and 2C show the Raman spectra of graphite and various graphene-based materials. Graphite and graphene materials are known to have characteristic peaks at approximately 1340 cm⁻¹, 1584 cm⁻¹, and 2700 cm⁻¹. The peak at 1340 cm⁻¹ is shown in Figure 2C and is characterized as the D band. The peak at 1584 cm⁻¹ is shown in the spectra of Figures 2A and 2C and is characterized as the G band, which is generated by vibrational modes representing the stretching of C=C bonds in all sp² hybrid carbon atom pairs. The D band originates from hybrid vibrational modes associated with the edges of graphene and indicates the presence of defects or broken symmetries in the graphene structure. The peak at 2700 cm⁻¹ is shown in Figure 2B and is characterized as the 2D band, which is attributed to a double resonance process resulting from the interaction between stacked graphene layers. The appearance of double peaks at 2D wavenumbers disrupts the symmetry of the peaks and indicates the AB stacking order between graphene planes in graphite and graphite derivatives (such as nanosheets). When the AB stacking order in turbine multilayer graphene particles is broken, the 2D1 peak shown in Figure 1B is suppressed. The positions of the G and 2D bands are used to determine the number of layers in the material system. Therefore, Raman spectroscopy provides scientific clarity and definition for carbon material additives in electrochemical batteries, providing a fingerprint for the correct selection of additives in active material electrode compositions. As will be shown, a fingerprint of the low-defect turbine layer carbon used in this application is defined herein. It is precisely because of this low-defect turbine layer carbon that, when used as an additive in electrochemical battery electrode active material mixtures, it provides excellent electrochemical battery performance.

[0052] Figure 3 shows the ID / IG ratio of carbon additives typically used in prior art electrode active material mixtures (i.e., reduced graphene oxide or amorphous carbon) compared to the low-defect turbine layer carbon of this application.

[0053] Reduced graphene oxide (rGO) is a carbon variant commonly referred to in the industry as graphene, yet it is unique in its final structure and manufacturing process. Graphene oxide is typically first manufactured using a modified Hummers process, in which graphite material is oxidized and exfoliated into monolayers or sheets containing several layers of carbon, which may contain various functional groups, including but not limited to hydroxyl, epoxide, carboxyl, and hydroxyl groups. These functional groups are then removed by chemical or thermal treatment to convert insulating graphene oxide into conductive reduced graphene oxide. This reduced graphene oxide is similar to graphene in that it consists of a monolayer of carbon atom lattice, but differs in that it has a mixture of sp2 and sp3 atoms, residual functional groups, and an increased defect density typically resulting from the manufacturing and reduction processes. As shown in the first line of Figure 3, reduced graphene oxide has an ID / IG ratio of 0.9.

[0054] Amorphous carbon is commonly used as an additive or surface coating in both anode and cathode material mixtures in electrochemical cells to enhance electrode conductivity. Typically, amorphous carbon is produced using chemical vapor deposition (CVD), in which hydrocarbon feedstock gases flow into a sealed container and carbonize at high temperatures onto the surface of the desired powder material. This thermal decomposition process can provide relatively thin amorphous carbon coatings of a few nanometers in thickness, lacking any sp2 blending found in crystalline graphene-based materials. As shown in Figure 3, amorphous carbon has an ID / IG ratio >1.2.

[0055] Low-defect turbine layer carbon, also known as graphene, possesses unique properties resulting from its manufacturing process. A common method for producing this material is via plasma-based CVD, in which hydrocarbon feedstock gases are fed through an inert gas plasma in the presence of a catalyst that allows graphene-like carbon structures to nucleate. By controlling production parameters, carbon materials with multiple layers and no AB stacking order between crystal lattices can be produced. These carbon materials are typically highly ordered sp2 carbon lattices with low defect density.

[0056] The low-defect turbine layer carbon of this disclosure is shown in Figure 3, paragraph 2. The Raman spectra of the low-defect turbine layer carbon additive of this application are derived from the intensity ratio of the D band to the G band (ID / IG) and the intensity ratio of the 2D band to the G band (I²D / IG). ID, I²D, and IG are represented by their respective integrated intensities. A low ID / IG ratio indicates a low-defect material. As determined by Raman spectroscopy, the low-defect turbine layer carbon material of this invention has an ID / IG ratio greater than zero and less than or equal to about 0.8, where IG is in the wavenumber range between 1580 and 1600 cm⁻¹, and ID is in the wavenumber range between 1330 and 1360 cm⁻¹, measured using an incident laser wavelength of 532 nm. Furthermore, the low-defect turbine layer carbon material of this disclosure exhibits an I²D / IG ratio of about 0.4 or higher. As a reference for the I²D / IG ratio, an I²D / IG ratio of approximately 2 is generally associated with monolayer graphene. An I²D / IG ratio less than approximately 0.4 is generally associated with bulk graphene composed of numerous AB-stacked graphene layers. Therefore, for the low-defect turbine layer carbon material of this disclosure, an I²D / IG ratio of approximately 0.4 or higher indicates a low layer count ≤ 10. Low-defect turbine layer carbon materials with low layer counts further lack AB stacking order between graphene layers (i.e., turbine layers). This lack of turbine layer properties or AB stacking in the graphene planes is indicated by the symmetry of the I²D peak. It is precisely the symmetry of the 2D peak that distinguishes turbine layer graphene layered materials from AB-stacked graphene layered materials and indicates rotational stacking disorder versus layered stacking order.

[0057] Carbon materials with high AB stacking order will still exhibit 2D peaks; however, these 2D peaks exhibit doublets that break peak symmetry. This symmetry breaking is present in both multi-layer AB stacked graphene and multilayer graphite. Therefore, 2D peaks (which are a very strong indicator of the presence of stacking order, regardless of the number of graphene layers present in the material) are important when selecting graphene or graphene-based additives. The rotational disorder of the low-defect turbine layer carbon in this disclosure distinguishes it from all other graphene or graphene-based additives. This is because the rotational disorder of the low-defect turbine layer carbon stack in this application provides flexibility to the carbon-based particles, enabling these carbon-based particles to provide and maintain contact with the active core particles of the composite particles containing the electrodes of the electrochemical cell. The result is an electrochemical cell with increased cycle life, better cycle life stability, enhanced energy density, and excellent high-rate performance.

[0058] Figures 4A-4C show the Raman spectra of active material mixtures containing SiOx core particles encapsulated or coated with carbon material. Figure 4A is a schematic diagram of the Raman spectrum of an active material mixture containing SiOx core particles coated with amorphous carbon material. Figure 4B is a schematic diagram of the Raman spectrum of an active material mixture containing SiOx core particles encapsulated by rGO. Figure 4C is a schematic diagram of the Raman spectrum of an active material mixture containing SiOx core particles encapsulated by a low-defect turbine layer of carbon. The spectra differ due to different layer thicknesses (size, shape, and position of the 2D peak at approximately 2700 cm⁻¹) and disorder (size of the D peak at approximately 1340 cm⁻¹).

[0059] Sample preparation for Raman analysis involves obtaining small aliquots of powders such as active material powders, composite material powders, and carbon material powders, and placing these powders separately in clean glass vials. The sample powders are rinsed with methanol. The powder / methanol solution is then briefly vortexed and sonicated for approximately 10 minutes. The suspension is then transferred to a microscope slide using a micropipette. The slide is then allowed to air dry completely before analysis.

[0060] Raman spectroscopy analysis of this application was performed using confocal Raman spectroscopy on a Bruker Senterra Raman system under the following test conditions: 532 nm laser, 0.02 mW, 50x objective lens, 90 sec integration time, and three co-additions (three Raman spectroscopy sample runs) using a 50 × 1000 μm aperture and 9-18 cm⁻¹ resolution. As a reference point, the D band is inactive in Raman scattering of ideal crystals. Due to defect-induced double-resonance Raman scattering involving π-π electronic transitions, the D band becomes Raman active in defective graphite materials. The intensity of the D band relative to the G band increases with the amount of disorder. The intensity ID / IG ratio can thus be used to characterize graphene materials.

[0061] The intensities of the D and G bands of amorphous carbon shown in Figure 4A are higher than those of reduced graphene oxide (rGO) in Figure 4B or turbine layer carbon in Figure 4C. Amorphous carbon also exhibits a significantly higher ID / IG ratio (1.25) than rGO and turbine layer carbon. Compared to the intensity of the D band, the suppression intensity of the G band of amorphous carbon reflects the lack of crystallinity (also known as its graphitic properties) within its carbon structure. The higher D peak intensity than the G peak intensity is caused by the large number of defects in the amorphous carbon network. Therefore, compared to the larger crystallinity of carbons such as graphene, graphene oxide, and rGO, the spectrum of amorphous carbon exhibits low crystallinity and a much higher degree of disorder in its graphitic network. Furthermore, the higher intensity of the rGO D peak compared to its G peak and its higher ID / IG ratio (almost twice) compared to the turbine layer carbon D and G peak intensities and ID / IG ratio indicate that rGO has more defects than the turbine layer carbon of this application.

[0062] Table 1 below provides details of the Raman spectra of Figures 4A-4C. Table 1 rGO D G 2D ID / IG I2D / IG Cm-1 1346.98 1597.82 -- strength 9115.5 10033.3 -- .91 -- Low-defect turbine layer carbon D G 2D ID / IG I2D / IG Cm-1 1346.92 1581.32 2691.9 strength 2915.3 5849.98 6009.4 0.5 1.03 Amorphous carbon D G 2D ID / IG I2D / IG Cm-1 1344.93 1589.40 2695.4 strength 6194.8 4908.2 5238.5 1.25 1.07

[0063] Careful observation of these spectra revealed that the D-band broadened and the relative intensities of the bands changed with increasing disorder. For the amorphous carbon-coated sample, the high intensity (6194.8) and broad D-peak indicated a large number of defects. The lower intensity of the G-peak (4908.2), followed by the D-peak (6194.8), indicated the absence of crystallinity. The D-peak intensities (9115.5) and G-peak intensities (10033.3) of the rGO-encapsulated sample were remarkably similar. However, note that the D-peak intensity (9115.5) of the rGO sample was significantly higher than that of the turbine layer carbon sample (2915.3), indicating that the defect density of the rGO sample was significantly higher than that of the turbine layer carbon sample. It is also noteworthy that the G-band of the amorphous carbon and rGO samples shifted to the right of wavelength 1584 cm⁻¹ to wavelengths of 1589.4 cm⁻¹ and 1597.82 cm⁻¹, respectively, while the G-band of the turbine layer carbon sample was slightly to the left of wavelength 1581.32 cm⁻¹ at 1584 cm⁻¹. Importantly, unlike the amorphous carbon and rGO samples, the turbine layer carbon (in this case, the graphene sample) did not show much (if any) displacement in position, reflecting its low defect rate. Therefore, the turbine layer carbon sample is the closest to a near-ideal turbine layer carbon material.

[0064] [Complex particle formation] According to various embodiments, active material composite particles can be formed by forming a composite mixture containing core particles of active materials, such as M-SiO active materials, graphene materials, and one or more additives, such as CNTs, dispersants, binders, etc., as appropriate.

[0065] Specifically, the composite mixture may initially comprise a composite suspension formed by mixing a first suspension comprising core particles dispersed in a polar solvent (such as water or ethanol) and a second suspension comprising graphene material dispersed in a polar solvent. The graphene material may include turbine layer carbon, such as turbine layer graphene. In various embodiments, the graphene material may include graphene, graphene oxide, partially reduced graphene oxide, or any combination thereof.

[0066] In some embodiments, the mixture may be subjected to mixing and / or sonication until the mixture is visibly homogeneous and stable. For example, the first mixture may be sonicated or subjected to high-shear mixing for about 30 minutes to about 90 minutes, such as about 60 minutes, to improve the stability of the suspension.

[0067] Based on the total weight of the first suspension, the first suspension may include about 0.5 wt% to about 10 wt%, such as about 1 wt% to about 5 wt% or about 2 wt% M-SiO particles and the remaining solvent. Based on the total weight of the second suspension, the second suspension may include about 0.5 wt% to about 10 wt%, such as about 1 wt% to about 5 wt% or about 2 wt% graphene material and the remaining solvent.

[0068] The amounts of the first and second suspensions used to form the composite mixture can be selected such that the composite mixture can have a core particle to carbon weight ratio in the range of about 80:20 to about 95:05, such as about 90:10 to about 95:05. The composite mixture can be subjected to sonic treatment or high-shear mixing for about 30 minutes to about 90 minutes, such as about 60 minutes, to improve the stability of the suspension.

[0069] In some embodiments, CNTs may be added to either the first or second suspension, or directly to the composite mixture. For example, the amount of CNTs may be selected such that the composite mixture has a core particle to CNT weight ratio of about 100:0 to about 95:3, such as about 99.9:0.1 to about 99:1 or about 99:1.

[0070] The composite mixture can be processed such that the core particles are coated with graphene material and, where appropriate, CNTs. For example, the mixture can be dried using various methods, such as spray drying, to evaporate the solvent and produce a powder containing composite particles, which include core particles coated with carbon (e.g., turbine layer carbon, or turbine layer graphene). Specifically, the composite mixture can be fed via a heated aerosol evaporator to evaporate the solvent and form composite particles. This process can transform the graphene material into a wrinkled structure with numerous wrinkles, bends, and twists that do not loosen over time by isotropically compressing it with fully wrinkled capillary forces.

[0071] Depending on the final powder particle requirements, process parameters can vary. For example, wrinkled spherical composite particles are formed by aerosolizing droplets and then rapidly drying them in a heated chamber. For instance, an atomizer atomizes a material suspension to form aerosol droplets. The atomization step requires sufficient spray parameters to allow the particles within the droplets to become ordered before aerosol evaporation begins. For turbine layer carbon materials, particles within the droplets migrate to the droplet surface to form a coating on the M-SiO particles after drying. Because this structure overcomes the strong interparticle van der Waals forces that cause the carbon material sheets to re-stacking, complicating solution processability and reducing the particle access surface area, the coating minimizes particle aggregation and agglomeration. This structure is also stable relative to unfolding or folding.

[0072] Once the evaporation process is complete, the composite particles can be collected in powder form. After collection, the powder can be heat-treated in an inert atmosphere such as argon to carbonize any remaining surfactants or dispersants. Specifically, the powder can be heated at temperatures ranging from about 600°C to about 800°C, such as from about 650°C to about 750°C or about 700°C. The heating rate can range from about 5°C / min to about 20°C / min, such as about 10°C / min. The resulting dried composite active material powder can then be sorted by sieving or filtration to achieve the desired particle size distribution for a given application.

[0073] In an alternative approach, the composite mixture can be formed by dispersing the core particles in a liquid solvent (such as water or ethanol) to create a first suspension. A polyelectrolyte, such as polydiallyldimethylammonium chloride (PDDA), polyacrylic acid (PAA), or sodium polystyrene sulfonate (PSS), can be added to the solvent before or after the addition of the active material particles to form a first surface charge on the active material particles, thereby stabilizing the active material particles in the solvent. A second suspension can be formed by dispersing carbon materials (e.g., turbine layer graphene powder) in a solvent such as water or ethanol. A polyelectrolyte with an opposite charge can be added to the solvent before or after the addition of graphene to form a second surface charge on the graphene, thereby stabilizing the graphene in the solvent. The first and second surface charges can be different surface charges, one positive and one negative.

[0074] In some embodiments, the composite mixture can be formed by combining a first and a second suspension, such that graphene is attracted to the surface of the core particles due to the charge difference between them, thereby forming composite particles comprising graphene-coated active material particles. The polyelectrolytes on the graphene and the active material particles can neutralize each other, making the composite particles essentially uncharged.

[0075] In various embodiments, the composite mixture may alternatively be formed by forming a dry mixture comprising carbon material (e.g., turbine layer graphene powder) and core particles but excluding a liquid solvent (i.e., where the composite mixture is not a suspension). A binder material may be added to the mixture, followed by a mechanical melting process. Specifically, the binder material may be physically mixed with the graphene powder and core particles, such that the core particles are coated with graphene using a binder to form composite particles.

[0076] Non-limiting bonding materials may include polymethyl methacrylate, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene terephthalate, polyacrylonitrile, polydiallyl dimethyl ammonium chloride, polyacrylic acid, lithium-ionized polyacrylic acid (LiPAA), sodium polystyrene sulfonate, polyvinylpyrrolidone, polyethylene glycol, polyoxyethylene, nylon, carboxymethyl cellulose, polysiloxane, polyarylamine, polyamide, polyimide, polyacrylate, polycarbonate, polyurethane, polyacetylene, etc. Polypyrrole, polyphenylene sulfide, poly(3,4-ethylenedioxythiophene), poly(1,3-dioxane), polyphenylenevinylene, polythiophene, polyaniline, polypyrene, polypyrene, petroleum coke, coal tar pitch, carbon black, carbon nanotubes, sucrose, silicon dioxide, indium tin oxide, aluminum-doped zinc oxide, lithium hydroxide, lithium acetate, lithium perchlorate, lithium fluoride, lithium nitride, lithium nitrate, lithium hexafluorophosphate, LiTFSI, LiFSI, NASICON, LISICON, LIPON, Li3PO4, Li7P3S11, perovskite, garnet, polymeric ionic liquids or any combination thereof.

[0077] In various embodiments, the amounts of other embodiments, the particles of M-SiO material, and the carbon material including the low-defect turbine layer carbon can be dry-mixed at a dry weight ratio between 7:3 and 99:1. In some embodiments, CNTs can be added to the dry mixture. For example, M-SiO material, carbon material, and CNTs selected as appropriate can be combined to form a dry mixture excluding liquid solvents, or formed in a wetted mixture including liquid solvents. For example, in some embodiments, M-SiO material and carbon material can be suspended in a polar liquid solvent (such as water or ethanol) by high-shear mixing or ultrasonic treatment. Some material suspensions can also be promoted by using surfactants and / or binders. Importantly, the high conductivity achieved by the low-defect turbine layer structure compared to other carbon additives allows for mixing of lower ratios of material (<90:10 and as low as 99:1) with electrochemically active materials to achieve comparable conductivity enhancement.

[0078] [Electrodes and Electrochemical Cells] According to various embodiments, composite particles can be used as active materials for electrodes (such as anodes). For example, composite particles can be mixed with conductive reagents, binders, and / or solvents to form a slurry. The slurry can be coated onto a current collector to form an electrode.

[0079] Conductive reagents may include low-defect turbine layer carbon materials, carbon black, graphite, graphite oxide, graphene, exfoliated graphite or graphene, graphene oxide, rGO, partially reduced GO, carbon nanotubes (CNTs) such as single-walled, double-walled or multi-walled, graphene sheets, nanosheets or nanoparticles, nanosheets or nanoparticles containing graphene sheets or several graphene sheets, or combinations thereof.

[0080] The electrode may comprise a composite material mixture capable of providing 100% anode lithium capacity or may be mixed with other lithium active materials such as graphite, graphene oxide, graphene oxide, rGO, and partially reduced GO in a mixture ranging from 0% to 100%. If the electrode includes a binder to hold the electrode materials together, the binder may comprise polymeric materials such as polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), CMC / SBR, polyacrylic acid (PAA), lithium polyacrylate (LiPAA), or combinations thereof. The electrode material components are then mixed into a polar solvent (such as water or N-methyl-2-pyrrolidone (NMP)) at a solids loading ranging from about 20 wt% to about 60 wt% to form an electrode slurry.

[0081] Mixing is typically achieved using a planetary mixer and high-shear dispersion blades. The electrode slurry is then coated onto a metal substrate (typically copper or aluminum) at an appropriate mass load to balance the lithium capacity of the anode with that of the selected cathode. Various devices can be used for coating, such as blade coaters, comma coaters, gravure coaters, and dip coaters. After coating, the slurry is dried under forced air between room temperature and approximately 120°C. Final electrode processing steps prior to battery assembly include pressing the electrodes to reduce internal porosity and cutting them into appropriate geometries. Typical anode pressing densities range from approximately 1.0 g / cc to approximately 1.7 g / cc, depending on the electrode composition and target application. Cathode pressing densities range from approximately 2.7 g / cc to approximately 4.7 g / cc.

[0082] In various embodiments, the electrode is the anode electrode of an electrochemical cell, which also includes a cathode and a non-aqueous electrolyte containing a lithium salt. The anode comprises a metalloid or metal oxide material. The anode further comprises a low-defect turbine layer carbon material. The anode may comprise composite particles. The composite particles may further comprise a wrinkled spherical structure, wherein the wrinkled structure comprises a low-defect turbine layer carbon material encapsulating a metalloid or metal oxide material within its core. The anode may alternatively comprise a mixture of anode materials having particles comprising a metalloid or metal oxide material and particles comprising turbine layer carbon material. The turbine layer carbon material may comprise low-defect turbine layer carbon sheets surrounding and / or bonded to at least some of the core particles comprising the metalloid or metal oxide material. The cathode may comprise a carbon-based material. In addition to conventional carbon-based materials used in the cathode electrode of an electrochemical cell, the low-defect turbine layer carbon material of this application can also be used as an additive for the cathode electrode of an electrochemical cell.

[0083] The construction of an electrochemical cell involves the pairing of a coated anode substrate and a coated cathode substrate, which are electronically isolated from each other by a polymeric and / or ceramic electrical insulator. The electrode assembly is hermetically sealed in a housing, which can have various structures, such as (but not limited to) coin cells, pouch cells, or can cells, and contains a non-aqueous ion-conductive electrolyte operatively associated with the anode and cathode. The electrolyte comprises an inorganic salt dissolved in a non-aqueous solvent, and more preferably comprises an alkali metal salt dissolved in a mixture of a low-viscosity solvent and a high-conductivity solvent, the low-viscosity solvents including organic esters, ethers, and dialkyl carbonates, and the high-conductivity solvents including cyclic carbonates, cyclic esters, and cyclic amides. Non-limiting examples of electrolytes can include lithium hexafluorophosphate (LiPF6) or lithium bis(fluorosulfonyl)imide (LiFSi) salts in an organic solvent, the organic solvent comprising one of the following: ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), or a combination thereof. Additional solvents suitable for embodiments of the present invention include dialkyl carbonates such as tetrahydrofuran (THF), methyl acetate (MA), diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), 1-ethoxy-2-methoxyethane (EME), ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, and combinations thereof. Also suitable are high-dielectric-constant solvents including cyclic carbonates, cyclic esters, and cyclic amides such as propylene carbonate (PC), butylene carbonate, acetonitrile, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, γ-valerolactone, γ-butyrolactone (GBL), N-methyl-2-pyrrolidone (NMP), and combinations thereof. The electrolyte serves as a medium for the migration of lithium ions between the anode and cathode during the electrochemical reactions of the battery, particularly during battery discharge and recharge. The electrochemical cell can also have a positive terminal and a negative terminal and / or contact structures.

[0084] [Experimental Example] [(] [Li] [Metallization] [SiO] [)] [] The following examples relate to anodes formed using various embodiments of the present disclosure, including anodic active materials (e.g., composite particles) and comparative anodic active material particles, and are given by way of illustration rather than limitation. In the examples, % refers to weight percentage, g to grams, CE to coulombic efficiency, and mAh / g to capacity. Furthermore, the M-SiO active material used in the following formulations 1-4, examples 1-4, and comparative examples includes lithium metallized SiO (LM-SiO).

[0085] [Ingredients] [:] [1] The composite active material of Formula 1 was synthesized by suspending 2 grams of LM-SiO in 98 grams of water to form a 2 wt% suspension. The LM-SiO suspension was sonicated for 60 minutes to improve its stability. After sonication, 11.11 grams of a 2 wt% graphene suspension was added to the LM-SiO suspension to form a uniform 2 wt% composite suspension. The ratio of LM-SiO to graphene suspensions was chosen to achieve a mass ratio of 90:10 LM-SiO:graphene. The composite suspension was then sonicated again for 60 minutes. After sonication, the composite suspension was fed into a heated aerosol evaporator to evaporate water and generate graphene-coated LM-SiO particles. After collecting the powder, the material was then heat-treated at 700°C for 1 hour (heating at 10°C / min) under an argon atmosphere to remove residual water and carbonize the surfactant present in the stable graphene suspension. Next, collect the composite active material obtained from the formulation 1.

[0086] [Ingredients] [:] [2] The composite active material of Formula 2 was synthesized by suspending 2 grams of LM-SiO in 98 grams of water to form a 2 wt% suspension. The LM-SiO suspension was sonicated for 60 minutes to improve its stability. After sonication, 11.11 grams of a 2 wt% graphene oxide (GO) suspension was added to the LM-SiO suspension to form a uniform 2 wt% composite suspension. The ratio of LM-SiO to GO suspensions was chosen to achieve a mass ratio of 90:10 LM-SiO:reduced graphene oxide. The composite suspension was then sonicated again for 60 minutes. After sonication, the composite suspension was subsequently fed into a heated aerosol evaporator to evaporate water and generate graphene-coated LM-SiO particles. After collecting the powder, the material was then heat-treated at 700°C for 1 hour (heating at 10°C / min) under an argon atmosphere to remove residual water and carbonize the surfactant present in the stable graphene suspension. Next, collect the composite active material obtained from the formulation 2.

[0087] [Ingredients] [:] [3] The composite active material of Formula 3 was synthesized by suspending 2 grams of LM-SiO in 98 grams of water to form a 2 wt% suspension. The LM-SiO suspension was acoustically treated for 60 minutes to improve its stability. After acoustic treatment, 10.78 grams of a 2 wt% graphene suspension and 6.66 mg of carbon nanotubes (CNTs) were added to the LM-SiO suspension to form a homogeneous 2 wt% composite suspension. The ratio of LM-SiO to graphene suspension was chosen to achieve a mass ratio of 90:9.7:0.3 (LM-SiO:graphene:CNT). The composite suspension was then acoustically treated again for 60 minutes. After acoustic treatment, the composite suspension was subsequently fed into a heated aerosol evaporator to evaporate water and generate graphene-coated LM-SiO particles. After collecting the powder, the material was then subjected to heat treatment at 700°C for 1 hour (heating at 10°C / min) under an argon atmosphere to remove residual water and carbonize the surfactant present in the stable graphene suspension. The resulting composite active material from formulation 3 was then collected.

[0088] [Ingredients] [:] [4] The composite active material of Formula 4 was synthesized by suspending 2 g of LM-SiO in 98 g of water to form a 2 wt% LM-SiO suspension. Additionally, 0.1 g of polymer dispersant was added to the suspension to improve stability. The LM-SiO suspension was acoustically treated for 60 minutes to further improve its stability. After acoustic treatment, 11.11 g of a 2 wt% graphene suspension was added to the LM-SiO suspension to form a uniform 2 wt% composite suspension. The ratio of LM-SiO to graphene suspensions was selected to achieve a mass ratio of 90:10 LM-SiO:graphene. The composite suspension was then acoustically treated again for 60 minutes. Following acoustic treatment, the composite suspension was subsequently fed into a heated aerosol evaporator to evaporate water and generate graphene-coated LM-SiO particles. After collecting the powder, the material was then subjected to heat treatment at 700°C for 1 hour (heating at 10°C / min) under an argon atmosphere to remove residual water and carbonize the surfactant present in the stable graphene suspension. The resulting composite active material from formulation 4 was then collected.

[0089] [Control formulation] A control anode active material was generated by combining 0.5 g of LM-SiO anode active material with 1.3 g of graphite, 0.04 g of conductive reagent (C65 carbon black), 7.72 g of aqueous binder (CMC 1.1 wt%), and 0.1875 g of 40 wt% SBR in a small mixing tank. The combined materials were then subjected to rigorous mixing in a planetary mixer for 30 minutes to form a control formulation slurry.

[0090] [Comparison with Examples] [] A control anode slurry was coated onto a copper foil with a loading of 3 mAh / cm² and an electrode density of 1.3 g / cc. The coating was dried and rolled to a porosity of 40–45%. The electrode coatings were assembled into a half-cell (excess relative electrode material = lithium metal), and 100 µL of electrolyte was injected into the cell. The cell was electrochemically "formed" under C / 20, C / 10, and C / 5 charge-discharge cycles. The resulting half-cell was then characterized under a standard C / 2 charge-discharge scheme until the anode capacity was 80% of its initial capacity.

[0091] [Example] [1] Anode material was generated by combining 0.5 g of Compound 1 composite anode active material with 1.3 g of graphite, 0.04 g of conductive reagent (C65 carbon black), 7.72 g of aqueous binder (carbon methyl cellulose (CMC) 1.1 wt%), and 0.1875 g of 40 wt% SBR in a small mixing vessel. The combined materials were then subjected to a 30-minute rigorous mixing process in a planetary mixer. An anode slurry was coated onto copper foil with a loading of 3 mAh / cm² and an electrode density of 1.3 g / cc. The coating was dried and calendered to a porosity of 40-45%. The electrode coatings were assembled into a half-cell (excess relative electrode material = lithium metal), and 100 µL of electrolyte was injected into the cell. The cell underwent electrochemical "formulation" under C / 20, C / 10, and C / 5 charge-discharge cycles. The resulting half-cell was then characterized under a standard C / 2 charge / discharge scheme until the anode capacity was 80% of its initial capacity.

[0092] [Example] [2] Anode material was generated by combining 0.5 g of Compound 2 composite anode active material with 1.3 g of graphite, 0.04 g of conductive reagent (C65 carbon black), 7.72 g of aqueous binder (CMC 1.1 wt%), and 0.1875 g of 40 wt% SBR in a small mixing vessel. The combined materials were then subjected to a planetary mixer for 30 minutes of intense mixing. An anode slurry was coated onto copper foil with a loading of 3 mAh / cm² and an electrode density of 1.3 g / cc. The coating was dried and calendered to a porosity of 40–45%. The electrode coatings were assembled into a half-cell (excess relative electrode material = lithium metal), and 100 µL of electrolyte was injected into the cell. The cell was electrochemically "formed" under C / 20, C / 10, and C / 5 charge-discharge cycles. The resulting half-cell was then characterized under a standard C / 2 charge-discharge scheme until the anode capacity reached 80% of its initial capacity.

[0093] [Example] [3] Anode material was generated by combining 0.5 g of formulation 3 composite anode active material with 1.3 g of graphite, 0.04 g of conductive reagent (C65 carbon black), 7.72 g of aqueous binder (CMC 1.1 wt%), and 0.1875 g of 40 wt% SBR in a small mixing vessel. The combined materials were then subjected to a planetary mixer for 30 minutes of intense mixing. An anode slurry was coated onto copper foil with a loading of 3 mAh / cm² and an electrode density of 1.3 g / cc. The coating was dried and calendered to a porosity of 40–45%. The electrode coatings were assembled into a half-cell (excess relative electrode material = lithium metal), and 100 µL of electrolyte was injected into the cell. The cell was electrochemically "formed" under C / 20, C / 10, and C / 5 charge-discharge cycles. The resulting half-cell was then characterized under a standard C / 2 charge-discharge scheme until the anode capacity reached 80% of its initial capacity.

[0094] [Example] [4] Anode material was generated by combining 0.5 g of Compound 4 composite anode active material with 1.3 g of graphite, 0.04 g of conductive reagent (C65 carbon black), 7.72 g of aqueous binder (CMC 1.1 wt%), and 0.1875 g of 40 wt% SBR in a small mixing vessel. The combined materials were then subjected to a 30-minute rigorous mixing process in a planetary mixer. An anode slurry was coated onto copper foil with a loading of 3 mAh / cm² and an electrode density of 1.3 g / cc. The coating was dried and calendered to a porosity of 40–45%. The electrode coatings were assembled into a half-cell (excess relative electrode material = lithium metal), and 100 µL of electrolyte was injected into the cell. The cell was electrochemically "formed" under C / 20, C / 10, and C / 5 charge-discharge cycles. The resulting half-cell was subsequently characterized under a standard C / 2 charge-discharge scheme until the anode capacity reached 80% of its initial capacity.

[0095] Figure 5 is a diagram showing the electrochemical cycling performance of half-cells formed using the control formulation (control) and formulations 1-4 (Examples 1-4). As discussed in detail below, the anode of the control half-cell included 25 wt% bare LM-SiO material, and the anode of the Example 1-4 half-cells included 25 wt% graphene-coated LM-SiO material of formulations 1-4. The anodes of the control and Example 1-4 half-cells also included 65 wt% graphite, 2 wt% C65, 4.25 wt% CMC, and 3.75 wt% styrene-butadiene rubber (SBR).

[0096] Table 2 below includes the electrochemical cycling performance of the half-cell shown in Figure 5. Table 2 [Active Materials] [LM] [-] [SiO] [Comparison] [(] [original] [)] [LM] [-] [SiO] [+]

[10] [%] Graphene [ , ] [(] [Ingredients] [1] [)] [LM] [-] [SiO] [+]

[10] [%] Graphene [ , ] [(] [Ingredients] [2] [)] [LM] [-] [SiO] [+]

[10] [%] Graphene [ , ] [(] [Ingredients] [3] [)] [LM] [-] [SiO] [+]

[10] [%] Graphene [ , ] [(] [Ingredients] [4] [)] 1st CE (%) 86.9% 87.3% 88.1% 88.6% 88.4% 1st DC (mAh / g) 656 672 628 639 647 1 CC (mAh / g) 570 586 553 567 571 Maximum C / 2 (mAh / g) 337 540 528 560 531 Average CE, 10-50 cycles 99.2% 99.3% 99.5% 99.6% 99.4% 1st CE (%) (LD-SiO only) 83.6% 84.3% 85.6% 87.0% 86.1% 1st DC (mAh / g) (LD-SiO only) 1637 1714 1503 1556 1594 1st CC (mAh / g) (LD-SiO only) 1368 1445 1286 1354 1373

[0097] Table 3 below includes the electrochemical cycle values ​​of the half-cell shown in Figure 5. Table 3 [Material] [Initial Capacity] [(] [mAh] [ / ] [g] [)] [Capacity retention rate] [(] [No.]

[50] [cycle] [)] [Increased retention rate] [(] [No.]

[50] [cycle] [)] Control (25% LM-SiO) 570 43% --- Compound 1 (25% LM-SiO) 586 72% 67% Compound 2 (25% LM-SiO) 553 79% 84% Compound 3 (25% LM-SiO) 567 84% 95% Compound 4 (25% LM-SiO) 571 74% 72%

[0098] As shown in Figure 5 and Tables 2 and 3, compared with the half-cell containing the control material, after 50 charge / discharge cycles, the half-cell containing formulation 1 material showed a 67% increase in cycle life, the half-cell containing formulation 2 material showed an 84% increase in cycle life, the half-cell containing formulation 3 material showed a 95% increase in cycle life, and the half-cell containing formulation 4 material showed a 72% increase in cycle life.

[0099] Therefore, the composite particles of this invention unexpectedly and significantly increase the usable cycle life of LM-SiO materials for commercial lithium-ion battery applications. This improved usable cycle life is attributed to the unexpected and non-obvious ability of graphene to stabilize lithium-containing SiO active materials to electrochemical cycling. Usable cycle life is defined as the number of cycles (cycle n) during which a battery can cycle while maintaining at least 80% of its initial capacity (i.e., the first cycle). For example, formulation 4 shows a half-cell cycle life of approximately 50 cycles (n=50) to 80% capacity retention (approximately 600 mAh / g initial capacity in the first cycle, therefore 480 mAh / g = 80% capacity retention). In contrast, the control material exhibits a half-cell cycle life of only 5 cycles to 80% capacity retention.

[0100] According to an embodiment, the battery has a 50-cycle capacity retention of at least 72%, such as 80% to 84%, and a first-cycle efficiency of at least 87%, such as 87% to 88.6%.

[0101] Figure 6 is a diagram showing the X-ray diffraction results of the control material (shown in gray) and the material of Example 1 (shown in black). As can be seen in Figure 6, the lack of observed particle crystallinity and structure is attributed to the changes in graphene addition and treatment.

[0102] [Experimental Examples] [(] [MG] [Metalization] [SiO] [)] [] The following examples relate to anodes formed using various embodiments of the present disclosure of anodic active materials (e.g., composite particles) and comparative anodic active material particles, and are given by way of illustration and not limitation. In the examples, % refers to weight percentage, g refers to grams, CE refers to coulombic efficiency, and mAh / g refers to capacity. Furthermore, the M-SiO active material used in the following formulation 5, example 5, and comparative examples includes magnesium metallized SiO (MM-SiO).

[0103] [Ingredients] [5] The composite active material of Formula 5 was synthesized by suspending 2 grams of MM-SiO (magnesium-containing silicon oxide) in 98 grams of water to form a 2 wt% suspension. The MM-SiO suspension was sonicated for 60 minutes to improve its stability. After sonication, 5.05 grams of a 2 wt% graphene suspension and 4.21 mg of carbon nanotubes (CNTs) were added to the MM-SiO suspension to form a uniform 2 wt% composite suspension. The ratio of MM-SiO to graphene suspension was chosen to achieve a mass ratio of 95:4.8:0.2 MM-SiO:graphene:CNT. The composite suspension was then sonicated again for 60 minutes. After sonication, the composite suspension was subsequently fed into a heated aerosol evaporator to evaporate water and generate graphene-coated MM-SiO particles. After collecting the powder, the material was then subjected to heat treatment at 700°C for 1 hour (heating at 10°C / min) under an argon atmosphere to remove residual water and carbonize the surfactant present in the stable graphene suspension. The resulting composite active material from formulation 5 was then collected.

[0104] [Example] [5] Anode material was generated by combining 0.5 g of formulation 5 composite anode active material, 0.033 g of conductive reagent (C65 carbon black), and 1.33 g of aqueous binder (LiPAA, 10 wt%) in a small mixing vessel. The combined materials were then subjected to a planetary mixer for 30 minutes of intense mixing. An anode slurry was coated onto copper foil with a loading of 3 mAh / cm² and an electrode density of 1.3 g / cc. The coating was dried and calendered to a porosity of 40–45%. The electrode coatings were assembled into a half-cell (excess relative electrode material = lithium metal), and 100 µL of electrolyte was injected into the cell. The cell was electrochemically "formed" under C / 20, C / 10, and C / 5 charge-discharge cycles. The resulting half-cell was then characterized under a standard C / 2 charge-discharge scheme until the anode capacity reached 80% of its initial capacity.

[0105] [MM] [-] [SiO] [Comparison with Examples] Anode material was generated by combining 0.5 g of MM-SiO anode active material, 0.033 g of conductive reagent (C65 carbon black), and 1.33 g of aqueous binder (LiPAA, 10 wt%) in a small mixing vessel. The combined materials were then subjected to a planetary mixer for 30 minutes of intense mixing. The anode slurry was coated onto copper foil with a loading of 3 mAh / cm² and an electrode density of 1.3 g / cc. The coating was dried and calendered to a porosity of 40–45%. The electrode coatings were assembled into a half-cell (excess relative electrode material = lithium metal), and 100 µL of electrolyte was injected into the cell. The cell was electrochemically "formed" under C / 20, C / 10, and C / 5 charge-discharge cycles. The resulting half-cell was then characterized under a standard C / 2 charge-discharge scheme until the anode capacity reached 80% of its initial capacity.

[0106] Figure 7 is a diagram showing the capacity retention of a cycled half-cell, which includes the MM-SiO material of formulation 5 and a control example of MM-SiO. Figure 8 is a diagram showing the anode capacity of the cycled half-cell of Figure 7. Referring to Figures 7 and 8, it can be seen that formulation 5 provides significantly better anode capacity and capacity retention compared to the MM-SiO control example.

[0107] While the foregoing describes particularly preferred embodiments, it should be understood that the invention is not limited thereto. Those skilled in the art will recognize that various modifications can be made to the disclosed embodiments, and such modifications are intended to be within the scope of the invention. All publications, patent applications, and patents cited herein are incorporated herein by reference in their entirety.

[0108] 100: Composite particles 102, 102A, 102B, 102C: Core particles 104, 106, 108: Phase 110: Coating 120:First appearance 122: Crystalline silicon domain 124: SiOx domain

Claims

1. A composite particle of active material for lithium-ion secondary batteries, each composite particle comprising: a core particle comprising an alkali metal or alkaline earth metal silicate; and a coating disposed on the surface of the core particle, the coating comprising turbostratic carbon having a Raman spectrum having: a D band having a peak intensity (ID) at a wavenumber between 1330 cm⁻¹ and 1360 cm⁻¹; a G band having a peak intensity (IG) at a wavenumber between 1580 cm⁻¹ and 1600 cm⁻¹; and a 2D band having a peak intensity (I₂D) at a wavenumber between 2650 cm⁻¹ and 2750 cm⁻¹, wherein: The ID / IG ratio is in the range of 0.3 to 0.7; and the I2D / IG ratio is in the range of about 0.4 to about 2, wherein at least a portion of the core particles are completely encapsulated by the corresponding coatings.

2. The composite particle as described in request item 1, wherein: The core particle accounts for about 80 wt% to about 99.5 wt% of the total weight of the composite particles; the coating accounts for about 0.5 wt% to about 20 wt% of the total weight of the composite particles; and the turbine layer carbon accounts for about 1 wt% to about 10 wt% of the total weight of the composite particles.

3. The composite particles of claim 1, wherein about 90 wt% to about 100 wt% of the turbine layer carbon is in the form of a sheet containing 1 to 10 sheets of graphene, and wherein the coating further comprises about 0.1 wt% to about 1 wt% carbon nanotubes (CNTs) by the total weight of the composite particles.

4. The composite particles of claim 1, wherein the average particle size of such composite particles is about 3 µm to about 10 µm.

5. The composite particle of claim 1, wherein the core particle comprises: an initial phase comprising Li2Si2O5, Li2SiO3, Li4SiO4 or any combination thereof; and crystalline silicon domains dispersed in the initial phase.

6. The composite particle of claim 5, wherein the core particle further comprises SiOx domains dispersed in the primary phase, wherein x is in the range of 0.8 to 1.

2.

7. The composite particle as described in claim 5, wherein: The primary phase contains Li2Si2O5; and the average particle size of these crystalline silicon domains is less than 100 nm.

8. The composite particle of claim 1, wherein the core particle comprises: an initial phase comprising MgSiO3, Mg2SiO4 or a combination thereof; and crystalline silicon domains dispersed in the initial phase.

9. A composite particle of active material for lithium-ion secondary batteries, each composite particle comprising: a core particle comprising an alkali metal or alkaline earth metal silicate; and a coating disposed on the surface of the core particle, the coating comprising turbostratic carbon having a Raman spectrum having: a D band having a peak intensity (ID) at a wavenumber between 1330 cm⁻¹ and 1360 cm⁻¹; a G band having a peak intensity (IG) at a wavenumber between 1580 cm⁻¹ and 1600 cm⁻¹; and a 2D band having a peak intensity (I₂D) at a wavenumber between 2650 cm⁻¹ and 2750 cm⁻¹, wherein: The ID / IG ratio is greater than zero and in the range of about 1.1; wherein at least a portion of the core particles are completely encapsulated by the corresponding coatings, wherein: the I2D / IG ratio is in the range of 0.8 to 1.2; ID is at a wavenumber of about 1340 cm⁻¹; IG is at a wavenumber of about 1584 cm⁻¹; and I2D is at a wavenumber of about 2700 cm⁻¹.

10. An electrode comprising: composite particles as claimed in claim 1; and an adhesive.

11. The electrode of claim 10, wherein the adhesive comprises polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(acrylic acid), polyethylene tetrafluoroethylene (ETFE), polyamide and polyimide, polyethylene (UHMW), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), or mixtures thereof; and further comprises conductive additives selected from the group consisting of: carbon black, carbon nanotubes, conductive polymers, graphite, metal powders, and any combination thereof.

12. The electrode of claim 10, wherein the adhesive comprises polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(acrylic acid), polyethylene tetrafluoroethylene (ETFE), polyamide and polyimide, polyethylene (UHMW), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), lithium polyacrylate (LiPAA), or mixtures thereof; and further comprises conductive additives selected from the group consisting of nickel, aluminum, titanium, stainless steel, and any combination thereof.

13. A lithium secondary battery comprising: an anode including an electrode as claimed in claim 10; a cathode; a housing housing the anode and the cathode; and an electrolyte disposed between the anode and the cathode, wherein the battery has a 50th cycle capacity retention of at least 72% and a first cycle efficiency of at least 87%.

14. A method for forming active material composite particles, the method comprising: forming a mixture comprising core particles, the core particles comprising an alkali metal or alkaline earth metal silicate and a turbine layer carbon; and processing the mixture to form composite particles comprising the core particles coated with the turbine layer carbon, wherein at least a portion of the core particles is completely encapsulated by the turbine layer carbon; wherein the turbine layer carbon has a Raman spectrum having: a D band having a peak intensity (ID) at a wavenumber between 1330 cm⁻¹ and 1360 cm⁻¹; a G band having a peak intensity (IG) at a wavenumber between 1580 cm⁻¹ and 1600 cm⁻¹; and a 2D band having a peak intensity (I²D) at a wavenumber between 2650 cm⁻¹ and 2750 cm⁻¹, an ID / IG ratio in the range of 0.3 to 0.7, and an I²D / IG ratio in the range of about 0.4 to about 2.

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