Electroactive composite particles

Abstract

The present invention relates to a particulate material consisting only of a plurality of composite particles, each comprising a porous particle framework and a plurality of nanoscale elemental silicon domains located within the pores of the porous particle framework. The porous particle framework includes micropores and mesopores, and the total volume of the micropores and mesopores in the porous particle framework measured by gas adsorption is 0.5 to 1.8 cm 3 / g. The composite particles contain 30 to 70% by weight of silicon, and at least 30% by weight of the silicon is surface silicon determined by thermogravimetric analysis (TGA). Hydrogen is 1.2 wt% or less; the weight ratio of oxygen to silicon is 0.15 or less. The BET surface area of the composite particles is 40 m 2 / g or less.

Description

[Technical Field]

[0001] Introduction This invention relates to composite particles suitable for use as an anode active material in lithium-ion batteries. The composite particles comprise a porous particle framework and a plurality of silicon domains located within the pores of the porous particle framework. The dimensions and chemical composition of the silicon domains are controlled for optimal electrochemical performance. [Background technology]

[0002] A lithium-ion battery (LIB) generally comprises an anode, a cathode, and a lithium-containing electrolyte. The anode generally comprises a metal current collector with a layer of electroactive material, as defined herein, a material capable of inserting and releasing lithium ions during charging and discharging of the battery. When the LIB is charged, lithium ions are transported from the cathode through the electrolyte to the anode and inserted into the electroactive material of the anode as intercalated lithium atoms. Thus, the terms “cathode” and “anode” are used herein in the sense that the battery is positioned across a load such that the anode is the negative electrode. The term “battery” is used herein to refer to both a device containing a single lithium-ion cell and a device containing multiple connected lithium-ion cells.

[0003] Lithium-ion batteries (LIBs) were developed in the 1980s and 1990s and have since found a wide range of applications in portable electronic devices. Recent developments in electric or hybrid vehicles have created significant new markets for LIBs, and renewable energy sources have generated further demand for on-grid energy storage, which can be at least partially met by LIB farms. Overall, global LIB production is projected to increase from approximately 290 GWh in 2018 to over 2,000 GWh in 2028.

[0004] In addition to increasing total storage capacity, there is considerable interest in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries so that the same energy storage can be achieved with less battery mass and / or less battery volume. Conventional LIBs use graphite as the anode electroactive material. A graphite anode can accommodate up to one lithium atom for every six carbon atoms, resulting in a maximum theoretical relative capacity of 372 mAh / g in lithium-ion batteries, while the practical capacity is somewhat lower (approximately 340-360 mAh / g).

[0005] Silicon is a promising alternative to graphite due to its much higher capacity compared to lithium (see, for example, Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M. et al. in Adv. Mater. 1998, 10, No. 10). Silicon is used in lithium-ion batteries (Li 15 In a Si4-based LIB, the theoretical maximum specific capacity is approximately 3,600 mAh / g. However, such a high ratio of intercalated lithium to silicon results in expansion of the silicon material up to 400% of its original volume. Repeated charge-discharge cycles cause significant mechanical stress on the silicon material, leading to fracture and structural failure. Furthermore, charging the anode in a LIB results in the formation of a solid electrolyte interface (SEI) layer. This SEI layer is an ionic conductive but insulating layer formed by the reductive decomposition of the electrolyte on the electrode surface exposed during the initial charge. In a graphite anode, this SEI layer remains relatively stable during subsequent charge / discharge cycles. However, the expansion and contraction of the silicon anode leads to fracture and delamination of the SEI layer and exposure of a fresh silicon surface, resulting in further electrolyte decomposition, increased SEI layer thickness, and irreversible lithium consumption. These failure mechanisms collectively result in unacceptable electrochemical capacity loss over consecutive charge-discharge cycles.

[0006] The inventors have previously reported the development of certain electroactive materials having a composite structure in which an electroactive material such as silicon is deposited within the pore network of highly porous particles with a carefully controlled pore size distribution, such as porous carbon materials. For example, International Publication Nos. 2020 / 095067 and International Publication Nos. 2020 / 128495 report that the improved electrochemical performance of these materials may be due to the way in which the electroactive material forms small domains with dimensions on the order of a few nanometers or less within the pore network of the porous particles, and thus functions as a framework for the composite particles. Fine electroactive structures are thought to have lower resistance to elastic deformation and higher resistance to fracturing than larger electroactive structures, and therefore can be lithiated and delithiated without excessive structural stress. As a result, the electroactive materials exhibit good reversible capacity retention over multiple charge-discharge cycles. Secondly, by controlling the amount of silicon filling within the porous particle framework so that only a portion of the pore volume is occupied by uncharged silicon, the unoccupied pore volume of the porous particle framework can accommodate a considerable amount of silicon expansion internally. Excessive expansion is constrained by the particle framework. Furthermore, the area of ​​the electroactive material surface accessible to the electrolyte is very small, and therefore SEI formation is substantially prevented.

[0007] In International Publication No. 2022 / 029422, the applicant reported further developments in controlling the distribution of electroactive silicon within the pore network of a particle framework, leading to further improvements in the electrochemical performance of composite particles. Specifically, the applicant demonstrated that the electrochemical performance is optimized when the length scale of individual silicon structures in the composite particles is minimized, with the majority of silicon atoms located in the surface region of the silicon structure and a relatively small proportion of silicon atoms located inside the bulky / coarse silicon structure. The applicant identified a set of conditions for the optimized pore structure of the porous particle framework and for the deposition of silicon onto the porous particle framework, enabling an increase in the proportion of this so-called "surface silicon" while ensuring that a large amount of silicon is incorporated into the composite particles in total to meet the overall volumetric energy density requirements. Nanoscale silicon domains formed by the thermal decomposition of silicon-containing precursors are considered to be in the form of nanoclusters of silicon atoms substantially terminated by silicon-hydrogen bonds (Si-H).

[0008] Further improvements to the above-described type of electroactive composite particles remain necessary in the art to improve the electrochemical performance and lifespan of materials over multiple charge-discharge cycles. Here, it has been found that improved electrochemical properties can be obtained by modifying the surface functionalities of nanoscale silicon domains. [Overview of the project]

[0009] In a first aspect, the present invention relates to a particulate material consisting only of a plurality of composite particles, wherein the composite particles are (a) A porous particle framework comprising micropores and mesopores, When measured by gas adsorption, the total volume of micropores and mesopores in the porous particle framework is 0.5–1.8 cm³. 3 A porous particle framework that is / g, (b) Multiple nanoscale elemental silicon domains located within the pores of a porous particle framework, (i) The composite particles contain 30-70% by weight of silicon, (ii) When determined by thermogravimetric analysis (TGA), at least 30% by weight of silicon is surface silicon, (iii) The hydrogen content of the composite particles is 1.2% by weight or less, (iv) The weight ratio of oxygen to silicon in the composite particles is 0.15 or less. (v) The BET surface area of ​​the composite particles is 40 m 2 It is less than or equal to / g. Multiple nanoscale elemental silicon domains, The present invention provides particulate materials containing [the specified element].

[0010] Accordingly, the present invention generally relates to composite particles comprising multiple nanoscale silicon domains into a pore network of porous particles, including micropores and mesopores. As used herein, the term “nanoscale silicon domain” refers to a nanoscale body of elemental silicon having a maximum dimension determined by the position of silicon within the micropores and mesopores of the porous particle.

[0011] The deposition of nanoscale silicon domains in mesoporous and microporous particles is kinetically controlled so that thermal deposition preferentially occurs on the internal pore surfaces of the porous particles. In International Publication No. 2022 / 029422, the applicant previously demonstrated a method for obtaining composite particles containing a large proportion of so-called "surface silicon," which, as herein, refers to silicon located in the surface region of a silicon microstructure. The silicon in the surface region of a silicon microstructure can be quantified by TGA measurement, thus providing a measure of the fineness of the silicon microstructure.

[0012] Nanoscale silicon domains formed by the thermal decomposition of silicon-containing precursors are considered to be nanoclusters of silicon atoms having a series of different bonding interactions on their surfaces, between silicon atoms, and between silicon atoms and the porous particle framework, as well as silicon atoms terminated by silicon-hydrogen bonds (Si-H). The surfaces of these silicon nanoclusters are highly reactive as a result of these unbalanced bonding interactions of silicon atoms on the surface of the silicon nanoclusters. In particular, silicon surfaces terminated by silicon-hydrogen bonds (Si-H) are highly reactive in Li-ion batteries when lithium insertion occurs. Therefore, improved stability can be achieved if the composite particles have a high proportion of "surface silicon," but the Si-H bonds are reduced and the Si-Si bonds are maximized. Accordingly, the present invention provides a particulate material as defined above, in which at least 30% by weight of silicon is surface silicon and the hydrogen content of the composite particles is less than 1.2% by weight. In this way, silicon maintains a desirable length scale for effective electrochemical performance while reducing the surface reactivity of silicon.

[0013] In preferred embodiments of the present invention, the oxygen content of the composite particles is 10% by weight or less. If the oxygen content of the composite particles is too high, too much silicon is trapped as Si-O bonds. Although this is less inert than Si-H bonds, it can increase the resistivity of the electroactive material and undergo irreversible lithium insertion, potentially reducing the efficiency of the electroactive material in the Li-ion battery.

[0014] Therefore, the particulate materials are based on the applicant's previous disclosures, which identified the performance advantages achieved by composite particles containing a high proportion of surface silicon by identifying further beneficial structural features of the composite particles. This has been shown to improve the stability of the electroactive material during charging and discharging, and to improve the cycle life of lithium-ion batteries containing particulate materials as anode active materials.

[0015] In a second aspect, the present invention provides a composition comprising the particulate material of the first aspect and at least one other component.

[0016] In a third aspect, the present invention provides an electrode comprising the particulate material of the first aspect or the composition of the second aspect.

[0017] In a fourth aspect, the present invention provides a rechargeable metal-ion battery including the electrode of the third aspect. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 shows the TGA trace of the particulate material according to the present invention, which includes a high level of surface silicon and a low level of bulk crude silicon. [Figure 2] Figure 2 shows the TGA trace of particulate material containing low levels of surface silicon and high levels of bulk crude silicon. [Modes for carrying out the invention]

[0019] Detailed description of the invention The composite particles of the present invention contain multiple nanoscale elemental silicon domains located within the pores of a porous particle framework. The length scale of the nanoscale silicon domains in the particulate material of the present invention is quantified using TGA analysis. This analytical method relies on the principle that a weight increase is observed when silicon is oxidized to silicon dioxide (SiO2) in air and at high temperatures. The mechanism of silicon oxidation is temperature-dependent. Silicon atoms on the surface of silicon nanostructures are oxidized at lower temperatures than silicon atoms in the bulk of the silicon nanostructure (Reference: Bardet et al., Phys. Chem. Chem. Phys. (2016), 18, 18201). By plotting the weight increase against temperature, it is possible to distinguish and quantify bulk silicon and surface silicon in a sample.

[0020] The amount of unoxidized surface silicon is determined from the property TGA traces of these materials, as shown in Figures 1 and 2. Following an initial mass loss up to approximately 300°C, a significant increase in mass is observed from approximately 400°C (shown as a mass decrease from (a) to (b) in Figures 1 and 2), peaking between 550°C and 650°C (shown as a mass increase from (b) to (c) in Figures 1 and 2). Subsequently, as the porous particle framework is oxidized to CO2 gas, a mass decrease is observed (mass decrease from (c)), and then above approximately 800°C, a mass increase is again observed corresponding to the continuous conversion of silicon to SiO2, which increases towards an asymptotic value above 1000°C as silicon oxidation becomes complete (mass increase from (d) to (e)). The temperature at which the weight increase occurs is related to the structure of the silicon, with surface silicon oxidizing at lower temperatures and bulk silicon oxidizing at higher temperatures. Therefore, the coarser the silicon domains, the more oxidation is observed at higher temperatures.

[0021] Since already oxidized silicon does not cause a mass increase in TGA analysis, any naturally occurring oxides already formed on a silicon surface exposed to air do not affect the TGA analysis. Therefore, the less surface silicon is observed by TGA, the more the silicon surface can react with air to form naturally occurring oxides. Thus, to avoid misunderstanding, the calculation of "surface silicon" takes into account only silicon that has not been oxidized at the start of the TGA analysis after the material has been passivated with air or another surface passivating agent described herein (i.e., particulate material is not kept under any special inert conditions prior to the TGA analysis).

[0022] As defined herein, “surface silicon” is calculated from the initial mass increase of the TGA trace from a minimum value between 150°C and 500°C to a maximum mass measured in the temperature range between 550°C and 650°C, where the TGA is performed in air at a temperature gradient rate of 10°C / min. This mass increase is assumed to be due to oxidation of the surface silicon, and therefore the percentage of surface silicon as a percentage of the total amount of silicon can be determined according to the following formula. Y=1.875×[(Mmax-Mmin) / Mf]×100%

[0023] In the formula, Y is the percentage of surface silicon as the proportion of total silicon in the sample, Mmax is the maximum mass of the sample measured in the temperature range of 550°C to 650°C (mass (c) in Figures 1 and 2), Mmin is the minimum mass of the sample between 150°C and 500°C (mass (b) in Figures 1 and 2), and Mf is the mass of the sample at 1400°C when oxidation is complete (mass (e) in Figures 1 and 2). For completeness, it should be understood that 1.875 is the molar mass ratio of SiO2 to O2 (i.e., the mass ratio of formed SiO2 to the mass increase due to the addition of oxygen). Typically, TGA analysis is performed using a sample size of 10 mg ± 2 mg.

[0024] It has been found that when the surface silicon, as determined by the TGA method described above, is at least 30% by weight of the total silicon in the material, an optimal reversible capacity retention rate is obtained over multiple charge / discharge cycles. Preferably, as determined by thermogravimetric analysis (TGA), at least 32% by weight, or at least 35% by weight, or at least 38% by weight, or at least 40% by weight, or at least 42% by weight, or at least 45% by weight, or at least 48% by weight, or at least 50% by weight of the silicon is surface silicon.

[0025] In addition to the surface silicon content, the particulate material of the present invention preferably has a low content of crude bulk silicon determined by TGA. Crude bulk silicon is defined herein as silicon that undergoes oxidation above 800°C, as determined by TGA, which is carried out in air at a temperature gradient rate of 10°C / min. This is shown in Figures 1 and 2 as the mass increase from (d) to (e). Thus, the crude bulk silicon content is determined according to the following formula: Z = 1.875 × [(M f -M 800 ) / M f ] × 100%

[0026] In the formula, Z is the percentage of unoxidized silicon at 800 °C, and M 800 is the mass of the sample at 800 °C (mass (d) in FIGS. 1 and 2), and M f is the mass of the ash at the completion of oxidation at 1400 °C (mass (e) in FIGS. 1 and 2). For the purpose of this analysis, any mass increase above 800 °C is assumed to correspond to the oxidation of silicon to SiO2, and the total mass at the completion of oxidation is SiO2.

[0027] Preferably, silicon of 6 wt% or less, or 5 wt% or less, or 4 wt% or less, or 3.5 wt% or less, or 3 wt% or less, or 2.5 wt% or less, or 2 wt% or less, or 1.5 wt% or less is the crude bulk silicon determined by TGA.

[0028] Preferably, at least 35 wt% of the silicon is surface silicon, and 6 wt% or less of the silicon, more preferably 5 wt% or less of the silicon, is the crude bulk silicon, both determined by TGA as defined herein. More preferably, at least 40 wt% of the silicon is surface silicon, and 5 wt% or less of the silicon, more preferably 4 wt% or less of the silicon, is the crude bulk silicon, both determined by TGA as defined herein. More preferably, at least 45 wt% of the silicon is surface silicon, and 4 wt% or less of the silicon, more preferably 3 wt% or less of the silicon, is the crude bulk silicon, both determined by TGA as defined herein. More preferably, at least 50 wt% of the silicon is surface silicon, and 3 wt% or less of the silicon, more preferably 2 wt% or less of the silicon, is the crude bulk silicon, both determined by TGA as defined herein.

[0029] The total volume of micropores and mesopores in the porous particle framework (i.e., the total pore volume of pores having diameters in the range of 0 to 50 nm) is 0.5 to 1.8 cm 3The value is / g. To avoid misunderstanding, references to the pore volume of porous particle frameworks in this specification refer to the pore volume of the porous particle framework taken alone (unless otherwise indicated), i.e., measured in the absence of electroactive material (or any other material) occupying the pores of the porous particle framework.

[0030] Preferably, the total volume of micropores and mesopores in the porous particle framework is at least 0.55 cm³. 3 / g, or at least 0.6cm 3 / g, or at least 0.65cm 3 / g, or at least 0.7cm 3 / g, or at least 0.75cm 3 It is / g.

[0031] A high pore volume can be advantageous because it allows for the accommodating of larger amounts of silicon within the pore structure without compromising the porous particle framework's resistance to crushing under compressive stress during electrode manufacturing or expansion stress due to silicon lithiation. However, if the pore volume is too high, it becomes impossible to achieve the high level of surface silicon that characterizes the present invention. Therefore, the total volume of micropores and mesopores in the porous particle framework is preferably 1.6 cm³. 3 Less than / g, or 1.4cm 3 Less than / g, or 1.3cm 3 Less than / g, or 1.2cm 3 Less than / g, or 1.1cm 3 It is less than / g.

[0032] For example, the total volume of micropores and mesopores in the porous particle framework is preferably 0.55 to 1.6 cm³. 3 / g, or 0.6-1.4cm 3 / g, or 0.65-1.3cm 3 / g, or 0.7-1.2cm 3 / g, or 0.75-1.1cm 3 It is within the range of / g.

[0033] Common term "PD"n In this specification, "pore diameter" refers to the nth percentile pore diameter on a volume basis of a porous particle framework, based on the total volume of micropores and mesopores. For example, as used herein, "PD 50 The term "pore diameter" refers to pore diameters below which 50% of the total micropore and mesopore volume is found. To avoid misunderstanding, PD n For the purpose of determining the value, macropore volume (pore diameters greater than 50 nm) is not considered.

[0034] Porous particle framework PD 90 The pore diameter is preferably 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 4 nm or less. Preferably, PD 90 The pore diameter is at least 3 nm. PD 90 If the value is too high, excessive deposition of crude silicon and / or excessive native oxide formation will lower the surface silicon content. However, PD 90 If the pressure is too low, the penetration of silicon precursors into the pore volume is hindered, and instead, silicon deposits on the outer surface of the porous particle framework.

[0035] Porous particle framework PD 50 The pore diameter is preferably 2 nm or less, or 1.9 nm or less, or 1.8 nm or less, or 1.7 nm or less, or 1.6 nm or less. Preferably, the PD of the porous particle framework. 50 The pore diameter is at least 1 nm, or at least 1.1 nm, or at least 1.2 nm. For example, PD of a porous particle framework. 50 The pore diameter is preferably in the range of 1-2 nm, 1-1.9 nm, 1.1-1.8 nm, 1.1-1.7 nm, or 1.2-1.6 nm.

[0036] As used herein, the micropore volume fraction refers to the volume of micropores expressed as a fraction of the total volume of micropores and mesopores. In other words, the micropore volume fraction is the volume fraction of pores with a diameter of 2 nm or less relative to the total volume of pores with a diameter of up to 50 nm. Preferably, the micropore volume fraction of the porous particle framework is selected within the range of 0.45 to 0.95 in order to obtain the required high level of surface silicon content in the composite particles.

[0037] Preferably, the micropore volume fraction is at least 0.45, or at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, and optionally at least 0.75. Preferably, the micropore volume fraction is 0.9 or less, or 0.85 or less, and optionally 0.8 or less.

[0038] The micropore volume fraction may, depending on the case, be in the range of 0.5 to 0.9, or 0.5 to 0.85, or 0.55 to 0.80, or 0.55 to 0.75, or 0.6 to 0.7.

[0039] The total volume of micropores in the porous particle framework (determined using nitrogen gas adsorption at 77K as described herein) is preferably at least 0.32 cm³. 3 / g, or at least 0.36cm 3 / g, or at least 0.38cm 3 / g, at least 0.40cm 3 / g, at least 0.42cm 3 / g, or at least 0.5cm 3 / g, or at least 0.6cm 3 The value is / g. Since silicon located within micropores has a smaller length scale, a higher total micropore volume allows a higher proportion of surface silicon to be contained within the porous particle framework, thus enabling higher gravimetric and volumetric capacity of the composite particles.

[0040] The total volume of micropores and mesopores in the porous particle framework is 0.7-1.2 cm³. 3 When the values ​​are within the range of / g, the total volume of micropores is preferably in the range of 0.4 to 0.9.

[0041] Any pore volume within the mesopore range is preferably substantially within the smaller range of mesopores. Therefore, the fractional volume of pores having a pore diameter of 5 nm or less is preferably at least 0.8, or at least 0.82, or at least 0.84, or at least 0.86, or at least 0.88, or at least 0.9, based on the total volume of micropores and mesopores. Preferably, the fractional volume of pores having a pore diameter of 10 nm or less is preferably at least 0.9, or at least 0.92, or at least 0.94, or at least 0.96, based on the total volume of micropores and mesopores. Preferably, the fractional volume of pores having a pore diameter of 20 nm or less is preferably at least 0.94, or at least 0.96, or at least 0.98, based on the total volume of micropores and mesopores.

[0042] Pore ​​portions with diameters in the larger mesopore range may be advantageous in facilitating electrolyte access to silicon domains. Thus, pores with diameters in the range of 10–50 nm (i.e., larger mesopores) may, in some cases, constitute 2% or less, 4% or less, or 6% or less of the total micropore and mesopore volume of the porous particle framework.

[0043] The pore size distribution of a porous particle framework is preferably bimodal or multimodal. As used herein, the term “pore size distribution” refers to the distribution of pore sizes relative to the cumulative total internal pore volume of a porous particle framework. A bimodal or multimodal pore size distribution may be preferred because the proximity between micropores and larger diameter pores provides the advantage of efficient ion transport to silicon through the porous network. As a result, the particulate material has high ion diffusivity and therefore improved velocity performance.

[0044] The total volume of micropores and mesopores, as well as the pore size distribution of micropores and mesopores, were determined using quenched solid density functional theory (QSDFT) according to the standard methods described in ISO 15901-2 and ISO 15901-3. -6 This is determined using nitrogen gas adsorption at 77K up to a relative pressure p / p0. Nitrogen gas adsorption is a technique for characterizing the porosity and pore diameter distribution of a material by condensing a gas within the pores of a solid. As the pressure increases, the gas first condenses in the smallest diameter pores, and the pressure increases until a saturation point is reached where all pores are filled with liquid. Then, the pressure of the nitrogen gas is gradually reduced to evaporate the liquid from the system. Analysis of adsorption and desorption isotherms, as well as the hysteresis between them, makes it possible to determine the pore volume and pore diameter distribution. Suitable instruments for measuring pore volume and pore diameter distribution by nitrogen gas adsorption include the TriStar II and TriStar II Plus porosity analyzers available from Micromeritics Instrument Corporation, USA, and the Autosorb IQ porosity analyzer available from Quantachrome Instruments.

[0045] Nitrogen gas adsorption is effective for measuring pore volume and pore size distribution of pores with diameters up to 50 nm, but it is unreliable for pores with much larger diameters. Therefore, for the purposes of this invention, nitrogen adsorption is used to determine pore volume and pore size distribution only for pores with diameters of 50 nm or less.

[0046] If the porous particle framework contains macropores, the pore volume in the range of over 50 nm to 100 nm is measured by mercury porosimetry. As described above, this parameter relates to the pore volume of the porous particle framework when measured alone, i.e., in the absence of silicon or any other material occupying the pores of the porous particle framework. The pore volume measured by mercury porosimetry beyond 100 nm is assumed, for the purposes of this invention, to be the porosity between particles.

[0047] Mercury porosimetry is a technique for characterizing the porosity and pore diameter distribution of a material by applying varying levels of pressure to a sample of the material immersed in mercury. The pressure required to penetrate the pores of the sample with mercury is inversely proportional to the pore size. The values ​​obtained by mercury porosimetry described herein are obtained according to ASTM UOP578-11, with a surface tension γ assumed to be 480 mN / m and a contact angle φ assumed to be 140° for mercury at room temperature. The density of mercury is 13.5462 g / cm³ at room temperature. 3 Numerous high-precision mercury porosimetry instruments are commercially available, such as the AutoPoreIV series of automated mercury porosimetry instruments from Micromeritics Instrument Corporation in the United States. For a complete review of mercury porosimetry, see PAWebb and C. Orr, "Analytical Methods in Fine Particle Technology," 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0.

[0048] The volume of macropores is preferably smaller than the volumes of micropores and mesopores. While the smaller portion of macropores may be useful for facilitating electrolyte access to the pore network, the advantages of the present invention are substantially obtained by accommodating silicon in micropores and even smaller mesopores.

[0049] Therefore, according to the present invention, the total volume of macropores in the porous particle framework in the range of over 50 nm to 100 nm is preferably 0.2 × P 1 The following, or 0.1 × P 1 The following, or 0.05 × P 1 The following, or 0.02 × P 1 The following, or 0.01 × P 1 The following, or 0.005 × P 1 The following is P 1 This represents the total volume of micropores and mesopores in the porous particle framework defined above.

[0050] It will be understood that intrusion techniques such as gas adsorption and mercury porosimetry are effective only for determining the pore volume of pores that allow access to nitrogen or mercury from outside the porous particle framework. The porosity value (P) specified herein 1 and P 2 Porosity should be understood to refer to the volume of open pores, i.e., pores that are accessible to fluid from outside the porous particle framework. Completely enclosed pores that cannot be identified by nitrogen adsorption or mercury porosimetry are not considered herein when specifying porosity values. Similarly, pore volumes located within pores small enough to be undetectable by nitrogen adsorption are not considered when determining porosity values.

[0051] The porous particle framework is preferably 1200-3000 m 2 It has a BET surface area of ​​1 / g. Preferably, the porous particle framework has at least 1500m 2 / g, or at least 1700m 2 It has a BET surface area of ​​1 / g. Preferably, the porous particle framework is 2500m 2 / g or less, or 2000m 2 It has a BET surface area of ​​less than or equal to / g. The term "BET surface area" as used herein should be interpreted as referring to the surface area per unit mass calculated from measurements of the physical adsorption of gas molecules on a solid surface using the Brunauer-Emmett-Teller theory, in accordance with ISO 9277.

[0052] The porous particle framework preferably contains at least 0.35, preferably 3 g / cm³ of particles. 3 Less than 2 g / cm³, more preferably 2 g / cm³ 3 Less than 1.5 g / cm³, more preferably 1.5 g / cm³ 3 Less than 0.35 to 1.2 g / cm³ 3The particles have a particle density of . As used herein, the term “particle density” means “apparent particle density” as measured by mercury porosimetry (i.e., the mass of the particles divided by the particle volume, where the particle volume is considered to be the sum of the volume of the solid material and any closed or blind pores (“blind pores” are pores too small to be measured by mercury porosimetry)). Preferably, the porous particles have a particle density of at least 0.4 g / cm³ 3 , or at least 0.45 g / cm³ 3 , or at least 0.5 g / cm³ 3 , or at least 0.55 g / cm³ 3 , or at least 0.6 g / cm³ 3 , or at least 0.65 g / cm³ 3 , or at least 0.7 g / cm³ 3 It has a particle density of 1.15 g / cm³. Preferably, the porous particles have a density of 1.15 g / cm³. 3 The following, or 1.1 g / cm³ 3 The following, or 1.05 g / cm³ 3 The following, or 1 g / cm³ 3 The following, or 0.95 g / cm³ 3 The following, or 0.9 g / cm³ 3 It has the following particle density.

[0053] The porous particle framework preferably includes a conductive material. The use of a conductive porous particle framework is advantageous because the conductive framework within the composite particles facilitates the flow of electrons between the lithium atoms / ions inserted into the electroactive material and the current collector.

[0054] A preferred type of conductive porous particle framework comprises, or consists solely of, a conductive carbon material, which is referred to herein as a conductive porous carbon particle framework.

[0055] The conductive porous carbon particle framework preferably comprises at least 80% by weight of carbon, more preferably at least 85% by weight of carbon, more preferably at least 90% by weight of carbon, more preferably at least 95% by weight of carbon, and optionally at least 98% by weight or at least 99% by weight of carbon. The carbon may be crystalline carbon, amorphous carbon, or a mixture of amorphous and crystalline carbon. The porous carbon particle framework may be either a hard carbon or a soft carbon particle framework.

[0056] As used herein, the term “hard carbon” refers to carbon atoms that are primarily sp-coupled in nanoscale polycyclic aromatic domains. 2 This refers to the disordered carbon matrix found in a hybridized state (three-way bonding). Polycyclic aromatic domains are cross-linked by chemical bonds, such as COC bonds. Due to the chemical cross-linking between polycyclic aromatic domains, hard carbon cannot be converted to graphite at high temperatures. Hard carbon is found in the large G band (approximately 1600 cm⁻¹) of the Raman spectrum. -1 It has graphite-like characteristics, as evidenced by ). However, carbon has a significant D band in the Raman spectrum (approximately 1350 cm⁻¹). -1 As evidenced by ), it is not entirely graphite.

[0057] As used herein, the term "soft carbon" also refers to polycyclic aromatic domains in which carbon atoms are primarily sp-containing, with dimensions ranging from 5 to 200 nm. 2 This refers to a disordered carbon matrix found in a hybridized state (three-way bonding). In contrast to hard carbon, polycyclic aromatic domains in soft carbon are associated by intermolecular forces but are not cross-linked by chemical bonds. This means that they graphitize at high temperatures. Porous carbon particles preferably have at least 50% sp, as measured by XPS. 2 Contains mixed carbon. For example, porous carbon particles are appropriately 50% to 98% sp 2 Hybrid carbon, 55%~95% sp 2 Hybrid carbon, 60%~90% sp2 Mixed carbon, or 70%-85% sp 2 It can contain hybrid carbon.

[0058] Suitable porous carbon particles can be prepared by pyrolysis using a variety of different materials. Examples of organic materials that can be used include plant biomass, such as lignocellulose materials (e.g., coconut shells, rice husks, wood, etc.), and fossil carbon sources such as coal. Examples of resins and polymer materials that form porous carbon particles by pyrolysis include phenolic resins, novolac resins, pitch, melamine, polyacrylate, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylate, styrene, α-olefin, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the starting materials and the conditions of the pyrolysis process, a variety of different carbon materials are available in the art. Porous carbon particles of various different specifications are available from commercial suppliers.

[0059] Porous carbon particles can undergo chemical or gaseous activation processes to increase the volume of mesopores and micropores. A suitable activation process involves contacting pyrolysis carbon with one or more of oxygen, vapor, CO, CO2, and KOH at temperatures ranging from 600 to 1000°C.

[0060] Mesopores can also be obtained by known template processes using extractable pore-forming agents such as MgO and other colloidal or polymer templates, which can be removed by thermal or chemical means after thermal decomposition or activation.

[0061] Alternatives to carbon-based conductive particles include titanium nitride (TiN), titanium carbide (TiC), silicon carbide (SiC), nickel oxide (NiOx), titanium silicon nitride (TiSiN), nickel nitride (Ni3N), molybdenum nitride (MoN), and titanium oxynitride (TiO2). x N 1-xExamples include porous particles containing titanium nitride (TiN), silicon oxycarbide (SiOC), boron nitride (BN), or vanadium nitride (VN). Preferably, the porous particles contain titanium nitride (TiN), silicon oxycarbide (SiOC), or boron nitride (BN).

[0062] The elemental composition of the composite particles can be determined by elemental analysis. Elemental analysis is used to determine the weight percentages of silicon, hydrogen, and carbon in the composite particles. In some cases, the amounts of nitrogen and oxygen may also be determined by elemental analysis.

[0063] The silicon content is preferably determined by ICP-OES (inductively coupled plasma emission spectroscopy). Several ICP-OES instruments are commercially available, such as the iCAP® 7000 series ICP-OES analyzers available from ThermoFisher Scientific. The carbon content (and, if necessary, hydrogen, nitrogen, and oxygen content) of composite particles and porous particle frameworks alone is preferably determined by combustion and infrared (IR) absorption techniques. A suitable instrument for measuring the carbon, hydrogen, nitrogen, and oxygen content is the TruSpec® Micro elemental analyzer available from LECO Corporation.

[0064] The composite particles contain 30 to 70% by weight of silicon. Preferably, the composite particles contain at least 32% by weight of silicon, or at least 35% by weight of silicon, or at least 38% by weight of silicon, or at least 40% by weight of silicon, or at least 42% by weight of silicon, or at least 44% by weight of silicon, or at least 46% by weight of silicon, or at least 48% by weight of silicon, or at least 50% by weight of silicon. In some cases, the composite particles may contain up to 68% by weight of silicon, or up to 65% by weight of silicon, or up to 60% by weight of silicon, or up to 58% by weight of silicon, or up to 55% by weight of silicon. For example, the composite particles may contain 32 to 68% by weight of silicon, or 35 to 66% by weight of silicon, or 38 to 64% by weight of silicon, or 40 to 62% by weight of silicon, or 42 to 60% by weight of silicon, or 44 to 58% by weight of silicon.

[0065] A minimum amount of silicon is required to ensure that particulate materials have sufficient volumetric measurement capacity for commercial use. However, excessive amounts of silicon deposit silicon into larger pores and / or surfaces of the porous particle framework, reducing the surface silicon content and degrading its performance as an electroactive material.

[0066] The amount of silicon in the composite particles of the present invention is selected such that at least about 20% to a maximum of about 78% of the internal pore volume of the porous particle framework (based on micropores and mesopores) is occupied by silicon (in an uncharged state). Generally, the higher the microporosity of the porous particle framework, the greater the amount of silicon that can be used without reducing the percentage of surface silicon.

[0067] Preferably, silicon occupies from about 20% to about 78% of the internal pore volume of the porous particle framework, such as from about 23% to 75%, or from about 26% to 72%, or from about 28% to 70%, or from about 30% to 70%, or from about 35% to 68%, or from about 40% to 65%, or from about 45 to 60% of the internal pore volume of the porous particle framework. Within these preferred ranges, the pore volume of the porous particle framework is effective to accommodate the expansion of silicon during charge and discharge, while avoiding excessive pore volume that does not contribute to the volumetric capacity of the particulate material. However, the amount of silicon is also not so high as to prevent effective lithiation due to insufficient metal ion diffusion rate or insufficient expansion volume resulting in mechanical resistance to lithiation.

[0068] The amount of silicon in the porous particle framework can be correlated with the available pore volume by the requirement that the weight ratio of silicon to the porous particle framework is in the range of [0.50×P 1 ~1.9×P 1 :1, where P 1 represents the total volume of micropores and mesopores in the porous particle framework defined above. This relationship defines the weight ratio of silicon that is estimated to occupy from about 20% to 78% of the pore volume, taking into account the density of silicon and the pore volume of the porous particle framework. Preferably, the weight ratio of silicon to the porous particle framework is in the range of [0.7×P 1 ~1.8×P 1 :1, which indicates that the pore volume is occupied from about 30% to 78%.

[0069] Preferably, the weight ratio of silicon to the porous particle framework is at least 0.50×P 1 or at least 0.55×P 1 or at least 0.6×P 1 or at least 0.65×P 1 or 0.7×P 1 or at least 0.75×P 1 or at least 0.8×P 1 or at least 0.85×P1 , or at least 0.9 × P 1 , or at least 0.95 × P 1 , or at least 1 × P 1 Preferably, the weight ratio of silicon to the porous particle framework is 1.85 × P 1 The following, or 1.8 × P 1 The following, or 1.75 × P 1 The following, or 1.7 × P 1 The following, or 1.65 × P 1 The following, or 1.6 × P 1 The following, or 1.55 × P 1 The following, or 1.5 × P 1 The following applies:

[0070] The composite particles of the present invention contain less than 1.2% by weight of hydrogen. Preferably, the composite particles contain at least 0.1% by weight of hydrogen, or at least 0.15% by weight of hydrogen, or at least 0.2% by weight of hydrogen. Preferably, the composite particles contain 1.1% by weight or less of hydrogen, or 1% by weight or less of hydrogen, or 0.95% by weight or less of hydrogen, or 0.9% by weight or less of hydrogen, or 0.85% by weight or less of hydrogen, or 0.8% by weight or less of hydrogen, or 0.75% by weight or less of hydrogen. For example, the composite particles may contain 0.1 to 0.9% by weight of hydrogen, more preferably 0.15 to 0.85% by weight of hydrogen, more preferably 0.15 to 0.8% by weight of hydrogen, and more preferably 0.2 to 0.8% by weight of hydrogen.

[0071] Preferably, the ratio of hydrogen to silicon (H wt% / Si wt% × 100%) is in the range of 1.0 to 3.0 wt%, more preferably 1.4 to 2.8 wt%.

[0072] The composite particles preferably have a low total oxygen content, as determined by elemental analysis. Oxygen may be present in the composite particles, for example, as part of the porous particle framework or as an oxide layer on the exposed silicon surface. Preferably, the composite particles contain 6% by weight or less of oxygen, or 5.5% by weight or less of oxygen, or 5% by weight or less of oxygen, or 4.5% by weight or less of oxygen, for example, 4% by weight or less of oxygen, or 3% by weight or less of oxygen, or 2% by weight or less of oxygen, or 1% by weight or less of oxygen, or 0.5% by weight or less of oxygen.

[0073] Preferably, the weight ratio of oxygen to silicon in the composite particles is 0.14 or less, or 0.12 or less, or 0.1 or less, or 0.09 or less, or 0.08 or less.

[0074] Preferably, silicon and carbon together constitute at least 90% by weight of the composite particles, more preferably at least 95% by weight of the composite particles.

[0075] The silicon may optionally contain small amounts of one or more dopants. Suitable dopants include boron and phosphorus, other n-type or p-type dopants, nitrogen, or germanium. Preferably, the dopants are present in a total amount of 2% by weight or less based on the total amount of silicon and dopants.

[0076] Preferably, the total volume of micropores and mesopores in the composite particles (i.e., in the presence of silicon), as measured by nitrogen gas adsorption, is 0.15 × P 1 The following, or 0.10 × P 1 up to, or 0.05 × P 1 up to, or 0.02 × P 1 That is the end.

[0077] Preferably, the total volume of micropores and mesopores in the composite particles (i.e., in the presence of silicon), as measured by nitrogen gas adsorption, is 0.2 cm³. 3 Less than / g, or 0.15cm 3 Less than / g, or 0.12cm 3 Less than / g, or 0.1cm3 Less than / g, or 0.09cm 3 Less than / g, or 0.08cm 3 Less than / g, or 0.07cm 3 Less than / g, or 0.06cm 3 Less than / g, or 0.05cm 3 It is less than / g.

[0078] Preferably, the total volume of micropores and mesopores in the composite particles, as measured by nitrogen gas adsorption, is 0.2 cm³. 3 Less than 0.15 cm / g, preferably 0.15 cm 3 Less than / g, or 0.1cm 3 Less than / g, or 0.08cm 3 Less than / g, or 0.06cm 3 Less than / g, or 0.04cm 3 Less than / g, or 0.02cm 3 Less than / g, or 0.015cm 3 Less than / g, or 0.012cm 3 Less than / g, or 0.010cm 3 Less than / g, or 0.008cm 3 It is less than / g.

[0079] As used herein, the term “particle diameter” refers to the equivalent spherical diameter (esd), i.e., the diameter of a sphere having the same volume as a given particle, and the particle volume is understood to include the volume of any pores within the particle. 50 " and "D 50 The term “particle diameter” refers to the median particle diameter on a volume basis, i.e., the diameter of less than 50% by volume of the particle population. 10 " and "D 10 The term “particle diameter” refers to the median particle diameter on a volume basis at the 10th percentile, i.e., the diameter of less than 10% by volume of the particle population. 90 " and "D 90 The term "particle diameter" refers to the median particle diameter based on the 90th percentile volume, i.e., the diameter of less than 90% of the particle population by volume.

[0080] The term "D" used herein to define the particle diameter distribution n The term "PD" is used herein to define the pore diameter distribution, as described above. n This term should be distinguished from the term "...".

[0081] Particle diameter and particle size distribution can be determined by routine laser diffraction techniques in accordance with ISO 13320:2009. Unless otherwise specified, particle size distribution measurements specified or reported herein are measured using a conventional Malvern Mastersizer® 3000 particle size analyzer manufactured by Malvern Instruments. The Malvern Mastersizer® 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing the target particles suspended in an aqueous solution. The light beam striking the particles is scattered at angles inversely proportional to the particle size, and a photodetector array measures the intensity of the light at several predetermined angles. The intensities measured at different angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values ​​described herein are obtained using a wet dispersion of particles in 2-propanol with 5 volume% of the surfactant SPAN®-40 (sorbitan monopalmitate) added. The particle refractive index is assumed to be 2.68 for porous particle framework particles and 3.50 for composite particles, and the dispersant index is assumed to be 1.378. The particle size distribution is calculated using the Mie scattering model.

[0082] The composite particles are D in the range of 1 to 30 μm. 50 It may have a particle diameter. Preferably, the composite particle has a diameter of D 50 The particle diameter may be at least 1 μm, or at least 2 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm. Depending on the case, D 50 The particle diameter may be 20 μm or less, or 18 μm or less, or 16 μm or less, or 14 μm or less, or 12 μm or less, or 10 μm or less, or 8 μm or less.

[0083] For example, composite particles are in the range of 1-20 μm, or 1-18 μm, or 1-16 μm, or 2-16 μm, or 2-14 μm, or 2-12 μm, or 2-10 μm, or 2-8 μm. 50 Particles may have a particle diameter. Particles within these size ranges and having the porosity and pore diameter distribution described herein are ideally suited for use in the anode of metal-ion batteries due to their dispersibility in slurries, structural robustness, capacity retention over repeated charge-discharge cycles, and suitability for forming high-density electrode layers with a uniform thickness in the conventional range of 20-50 μm.

[0084] D of composite particles 10 The particle diameter is preferably at least 0.5 μm, or at least 0.8 μm, or at least 1 μm, or at least 1.5 μm, or at least 2 μm. 10 By maintaining a particle diameter of 0.5 μm or larger, the possibility of submicron-sized particles undesiringly agglomerating is reduced, improving the dispersibility of particulate materials and enhancing volume retention.

[0085] The D1 particle size of the composite particles is preferably at least 0.5 μm, or at least 0.8 μm, or at least 1.0 μm, or at least 1.2 μm, or at least 1.4 μm, or at least 1.5 μm.

[0086] D of composite particles 90 The particle diameter is preferably 50 μm or less, or 40 μm or less, or 30 μm or less, or 25 μm or less, or 20 μm or less, or 15 μm or less. The presence of very large particles leads to the non-uniform formation and packing of particles in the electrode active layer, and therefore disrupts the formation of a high-density electrode layer, especially an electrode layer having a thickness in the range of 20 to 50 μm. Therefore, D 90 The particle diameter is preferably up to 40 μm, and even smaller is more preferable.

[0087] The composite particles preferably have a narrow size distribution span. For example, a particle size distribution span ((D 90 -D 10 ) / D 50) is preferably 5 or less, more preferably 4 or less, more preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow size distribution span, efficient filling of particles into the high-density electrode layer can be more easily achieved.

[0088] The composite particles preferably have positive asymmetry in their volume-based distribution, for example, such that the volume-based distribution is asymmetrical with a longer tail on the right side. Positive asymmetry in the volume-based particle size distribution is advantageous because it provides a higher density electrode, resulting in a higher spontaneous filling rate than when all particles are the same size, thereby reducing the need for calendering or other physical densification processes. Preferably, D 50 The composite particle diameter is less than the volume-based mean of the particle diameter distribution (D[4.3]). Preferably, the asymmetry of the composite particle size distribution (measured by a Malvern Mastersizer® 3000 analyzer) is 5 or less, or 3 or less.

[0089] The composite particles may have an average sphericity (as defined herein) of at least 0.5, or at least 0.55. Preferably, the average sphericity is at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8.

[0090] High-precision two-dimensional projections of micron-scale particles can be obtained by scanning electron microscopy (SEM) or dynamic image analysis using a digital camera to record the shadow projected by the particle. As used herein, the term "sphericity" is understood as the ratio of the area of ​​the particle projection (obtained from such imaging techniques) to the area of ​​a circle, where the particle projection and the circle have the same circumference. Therefore, for individual particles, sphericity S can be defined as follows:

number

number

[0091] The composite particles of the present invention are preferably 35m 2 / g or less, or 30m 2 / g or less, or 25m 2 / g or less, or 20m 2 / g or less, or 15m 2 / g or less, or 10m 2 It has a BET surface area of ​​less than or equal to / g.

[0092] Generally, a low BET surface area is preferred to minimize the formation of a solid electrolyte interface (SEI) layer on the surface of composite particles during the first charge-discharge cycle of an anode containing the particulate material of the present invention. However, if the BET surface area is excessively small, the bulk of the electroactive material cannot access the metal ions in the surrounding electrolyte, resulting in unacceptably low charging speed and capacity limitations. For example, the BET surface area is preferably at least 0.1 m². 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 2 It is / g. For example, the BET surface area is 1m 2 / g~25m 2 Range of / g, more preferably 2-15m 2 The range of / g is also acceptable.

[0093] The composite particles were measured using Quantachrome® Autotap according to ISO 3953 and ISO 787 (measurement of tamping volume and apparent density after tamping), yielding a result of 0.7 g / cm³. 3 exceeding, or at least 0.8 g / cm³ 3, or at least 0.85 g / cm³ 3 , or at least 0.9 g / cm³ 3 It is preferable to have a tap density of . The drop height of the instrument is 3 mm, and the tap frequency of the instrument is fixed at 250-265 taps / min. The sample is tapped at least 5,000 times. If a change in sample volume is still observed after 5,000 taps, a further increment of 1,250 taps is applied until no further volume change is observed.

[0094] The particulate material of the present invention typically has a specific charge capacity of 900 to 2300 mAh / g upon initial lithiation. Preferably, the particulate material of the present invention has a specific charge capacity of at least 1200 mAh / g, or at least 1400 mAh / g, upon initial lithiation.

[0095] The particulate material of the present invention may optionally include a silicon surface treated with a passivating agent. As will be described in more detail below, a passivating agent is defined herein as a compound that can modify the surface of an electroactive material to inhibit or prevent the formation of surface oxides.

[0096] The composite particles of the present invention may optionally be coated with a lithium-ion permeable coating. The coating may at least partially cover the outer surface of the particles, and preferably completely cover them. As used herein, the term “lithium-ion permeable” refers to an ion-conductive material that allows the transport of lithium ions from outside the composite particles to nanoscale electroactive material domains. Preferably, the lithium-ion permeable coating is impermeable to liquids, such as solvents in liquid electrolytes. Preferably, the lithium-ion permeable filler material is Li / Li + It is electrochemically stable at less than 0.1V.

[0097] In some cases, the coating may be a conductive carbon coating. Suitablely, the conductive carbon coating can be obtained by chemical vapor deposition (CVD), a method well known in the art, which involves the thermal decomposition of a volatile carbon-containing gas (e.g., ethylene) onto the surface of particulate material. Alternatively, the carbon coating may be formed by depositing a solution of a carbon-containing compound onto the surface of particulate material, followed by thermal decomposition. The conductive carbon coating has sufficient permeability to allow lithium access to the interior of the composite particles without excessive resistance, so as not to degrade the velocity performance of the composite particles. For example, the thickness of the carbon coating may be suitablely in the range of 2 to 50 nm, for example, 2 to 30 nm. In some cases, the carbon coating may be porous and / or only partially cover the surface of the composite particles.

[0098] Alternatively, the coating may include a lithium-ion permeable solid electrolyte. Examples of suitable lithium-permeable solid electrolytes include garnet-type solid electrolytes (Li7La3Zr2O 12 and Li 6.5 La3C 0.5 Zr 1.5 O 12 Includes "LLZO" electrolytes such as; Perovskite-type solid electrolytes (Li 0.33 La 0.57 Includes "LLTO" electrolytes such as TiO3; LISICON type solid electrolyte, NaSICON type solid electrolyte (Li 1.3 Al 0.3 Ti 1.7 (PO4)3 etc); Lithium oxynitride phosphate (LiPON) solid electrolyte; Li3N type solid electrolyte; Lithium phosphate (Li3PO4) solid electrolyte, Lithium titanate (Li4Ti5O 12 Examples include solid electrolytes; lithium tantalate (LiTaO3) solid electrolytes; sulfide-type solid electrolytes; alginate-type solid electrolytes; and anti-perovskite-type solid electrolytes. Variations (e.g., including dopants) and combinations of these electrolyte types are also included.

[0099] The coating has the advantage of further reducing the BET surface area of ​​the particulate material by smoothing any surface defects and filling any remaining surface micropores, thereby further reducing the first cycle loss. The use of conductive coatings, such as carbon coatings, is particularly advantageous because it improves the conductivity of the composite particle surface, improves the kinetic performance of the particulate material when used as an electroactive material in lithium-ion batteries, and / or reduces the need for conductive additives in the electrode composition, creates an improved surface for the formation of a stable SEI layer, and improves the capacity retention rate during cycling. When the composite particle includes a coating, the silicon content of the particle in wt% is determined based on the weight of the particle including the coating.

[0100] The preferred particulate material according to the present invention, when measured by gas adsorption, has a total volume of micropores and mesopores in the porous particle framework of 0.6 to 1.4 cm³. 3 The composition is such that the micropore volume fraction relative to the total volume of micropores and mesopores in the porous particle framework is 0.5 to 0.9, the silicon content of the composite particles is 40 to 70% by weight, at least 30% by weight of the silicon is surface silicon as determined by thermogravimetric analysis (TGA), and 5% by weight or less of the silicon is crude bulk silicon as determined by thermogravimetric analysis (TGA), and the hydrogen content of the composite particles is 0.4 to 0.9% by weight.

[0101] A more preferred particulate material according to the present invention, when measured by gas adsorption, has a total volume of micropores and mesopores in the porous particle framework of 0.65 to 1.3 cm³. 3 The composition is such that the micropore volume fraction relative to the total volume of micropores and mesopores in the porous particle framework is 0.55 to 0.9, the silicon content of the composite particles is 42 to 68% by weight, at least 35% by weight of the silicon is surface silicon as determined by thermogravimetric analysis (TGA), and 4% or less by weight of the silicon is crude bulk silicon as determined by thermogravimetric analysis (TGA), and the hydrogen content of the composite particles is 0.45 to 0.85% by weight.

[0102] A more preferred particulate material according to the present invention, when measured by gas adsorption, has a total volume of micropores and mesopores in the porous particle framework of 0.7 to 1.2 cm³. 3 The composition is such that the micropore volume fraction relative to the total volume of micropores and mesopores in the porous particle framework is 0.6 to 0.85, the silicon content of the composite particles is 44 to 66% by weight, at least 40% by weight of the silicon is surface silicon as determined by thermogravimetric analysis (TGA), and 3% or less by weight of the silicon is crude bulk silicon as determined by thermogravimetric analysis (TGA), and the hydrogen content of the composite particles is 0.5 to 0.8% by weight.

[0103] A more preferred particulate material according to the present invention, when measured by gas adsorption, has a total volume of micropores and mesopores in the porous particle framework of 0.75 to 1.1 cm³. 3 The composition is such that the micropore volume fraction relative to the total volume of micropores and mesopores in the porous particle framework is 0.65 to 0.85, the silicon content of the composite particles is 46 to 64% by weight, at least 45% by weight of the silicon is surface silicon as determined by thermogravimetric analysis (TGA), and 2% by weight or less of the silicon is crude bulk silicon as determined by thermogravimetric analysis (TGA), and the hydrogen content of the composite particles is 0.55 to 0.75% by weight.

[0104] The composite particles of the present invention are appropriately prepared by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous particle framework. As used herein, CVI refers to the process by which a gaseous silicon-containing precursor is thermally decomposed on a surface to form elemental silicon and gaseous by-products on the surface.

[0105] The preferred CVI process is: (a) A step of providing a plurality of porous particles in a pressure reactor, (b) A step of continuously introducing silicon precursor gas into a pressure reactor, (c) A step of providing a composite particle comprising a porous particle framework and elemental silicon in the pores of the porous particle framework by contacting a plurality of porous particles with a silicon precursor gas under conditions effective for depositing silicon in the pores of the porous particles, (d) The process includes drawing in effluent gas from the pressure reactor during the contact.

[0106] Operating the pressure reactor under these conditions means that CVI deposition proceeds under conditions where fresh silicon precursor is added before by-products are completely removed from the system. Therefore, when silicon precursor gas is continuously added to the reactor, it mixes with the by-products, resulting in a consistent concentration of silicon precursor. Compared to systems operated by batch loading of silicon precursor gas, porous particles come into contact with a more consistent concentration of silicon precursor throughout the deposition.

[0107] This process is continuous with respect to the silicon precursor gas and operated in batches with respect to the porous particles. Therefore, the process operates as a semi-continuous process.

[0108] The term "continuous" is used herein to distinguish it from batch operations. In batch operations, batches of starting materials (porous particles and silicon-containing precursors) are added to the reactor in the first step, the reaction is allowed to proceed for a specific period, and then a batch of the product (composite particles) is removed from the reactor along with the by-products. In semi-continuous operations, the introduction of the starting materials (silicon precursors) into the reactor, and optionally the removal of the product (flue gas), are carried out continuously with the ongoing reaction.

[0109] In principle, continuous operation does not eliminate the possibility of uneven flow rates of silicon precursor gas into the reactor or gas effluent from the reactor. For example, a continuous reactor can operate in pulsed mode. For instance, the flow rate of silicon precursor gas into the pressure reactor can be reduced to facilitate the removal of gas effluent from the pressure reactor. Alternatively, the silicon precursor gas may be introduced into the pressure reactor at a constant pressure.

[0110] The removal of effluent gas may be operated continuously so that both the supply of silicon precursor gas and the removal of effluent gas from the reactor occur continuously and simultaneously with the ongoing reaction.

[0111] Alternatively, the removal of effluent gas from the pressure reactor may be operated semi-continuously. Here, semi-continuous means that the effluent gas is removed intermittently.

[0112] Semi-continuous extraction of effluent gas from a pressure reactor can be achieved by oscillating at least one gas outlet of the pressure reactor between an open and closed state at a predetermined frequency, such as at least 1 min⁻¹ or 2 min⁻¹.

[0113] Suitable gaseous silicon-containing precursors include silane (SiH4), silane derivatives (e.g., disilane, trisilane, and tetrasilane), and trichlorosilane (SiHCl3). The silicon-containing precursor can be used in pure form or as a diluted mixture with a carrier gas, the carrier gas being selected from nitrogen or an inert gas such as nitrogen or argon.

[0114] Preferably, the concentration of the silicon-containing precursor in the diluted mixture in the feed stream to the CVI reaction vessel is at least 60% by volume, or at least 70% by volume, or at least 80% by volume, or at least 90% by volume, or at least 95% by volume, or at least 98% by volume, or at least 99% by volume, based on the total amount of silicon-containing precursor gas and inert carrier gas. Preferably, the concentration of the silicon-containing precursor gas is 100% (i.e., no inert carrier gas is used).

[0115] Preferably, the silicon-containing precursor is chlorine-free. Chlorine-free means that the silicon-containing precursor contains less than 1% by weight, preferably less than 0.1% by weight, and preferably less than 0.01% by weight of a chlorine-containing compound.

[0116] Suitable temperatures for the CVI process are in the range of 350–500°C, for example, 350–450°C, 360–430°C, 370–420°C, or 370–400°C. Preferably, the specified temperature is maintained throughout the CVI process, as temperature fluctuations can cause non-uniformity of the product.

[0117] The pressure in the pressure reactor during step (c) is preferably in the range of 50 to 15000 kPa, or 100 to 10000 kPa, or 150 to 5000 kPa, or 200 to 2000 kPa, or 500 to 1800 kPa, or 800 to 1500 kPa, or 1000 to 1400 kPa. Operating at high pressure has the advantage of reducing the limitation on mass transfer relative to the reaction rate and promoting the penetration of silicon precursor gas into the pore network of porous particles. Operating at higher pressures also increases the residence time of the silicon precursor gas, and therefore increases the conversion of the silicon precursor. To prevent uncontrolled reactions, it is preferable that the temperature in the pressure reactor decreases as the pressure increases. In particular, when the pressure inside the pressure reactor exceeds 100 kPa, the reaction temperature inside the pressure reactor is preferably 450°C or lower, more preferably 430°C or lower, more preferably 420°C or lower, more preferably 410°C or lower, more preferably 400°C or lower, and more preferably 395°C or lower.

[0118] During step (c), the mole fraction of the silicon precursor in the pressure reactor may be in the range of 0.2 to 0.8 in terms of the total number of moles of gaseous compounds in the pressure reactor, or 0.3 to 0.7, or 0.4 to 0.6 in terms of the total number of moles of gaseous compounds in the pressure reactor.

[0119] The conditions within the CVI reactor should also be as uniform as possible. Stirring or fluidizing the porous carbon particles ensures that the silicon precursor gas can penetrate the particles uniformly and that the temperature within the reactor is uniform across the particle bed. Thus, by carefully selecting porous particles in conjunction with the use of the controlled CVI conditions described herein, particulate materials with a very high surface silicon content and a low crude bulk silicon content can be obtained, indicating that a high proportion of silicon exists in the form of ultrafine silicon nanostructures.

[0120] During the aforementioned contact, the ratio of the flow rate of silicon in the silicon precursor gas per gram per minute to the mass of porous particles in the pressure reactor per gram may be in the range of 0.006 to 0.7.

[0121] During the aforementioned contact, the ratio of the flow rate of silicon in the silicon precursor gas per gram per minute to the mass of porous particles in the pressure reactor per gram may be in the range of 0.006 to 0.008. These ratios have the advantage of a higher conversion rate of the silicon precursor compared to higher ratios. A high level of conversion of the silicon precursor is thought to help obtain composite particles with less coarse silicon formation. However, at lower ratios, the reaction time is unacceptably long.

[0122] Alternatively, during the contact, the ratio of the flow rate of silicon in the silicon precursor gas per gram per minute to the mass of porous particles in the pressure reactor per gram may be in the range of 0.01 to 0.7. These ratios have the advantage of maintaining an excess of silicon precursor in the pressure reactor. In the equilibrium between the silicon precursor and silicon + byproducts, a higher silicon precursor concentration pushes the equilibrium toward silicon deposition. As mentioned above, higher pressures in the pressure reactor reduce the silicon deposition rate. Maintaining an excess of silicon precursor in the pressure reactor compensates for the decrease in silicon deposition rate at higher pressures, thus providing the advantage of operation at higher pressures while maintaining the silicon deposition rate. This also helps to shorten the synthesis time.

[0123] During the aforementioned contact, the ratio of the flow rate of silicon in the silicon precursor gas per gram per minute to (mass of porous particles in the pressure reactor in grams × internal free volume of the reactor in liters) may be in the range of 0.0002 to 0.025. During the aforementioned contact, the ratio of the flow rate of silicon in the silicon precursor gas per gram per minute to (mass of porous particles in the pressure reactor in grams × internal free volume of the reactor in liters) may be in the range of 0.0002 to 0.0003. Alternatively, during the aforementioned contact, the ratio of the flow rate of silicon in the silicon precursor gas per gram per minute to (mass of porous particles in the pressure reactor in grams × internal free volume of the reactor in liters) may be in the range of 0.0004 to 0.025. The internal free volume of the reactor refers to the volume excluding internal elements.

[0124] The flow rate of silicon in the silicon precursor gas to the mass of porous particles in the pressure reactor and / or the ratio of the flow rate of silicon in the silicon precursor gas per minute in grams to (mass of porous particles in the pressure reactor in grams × internal free volume of the reactor in liters) can be maintained throughout step (c).

[0125] Alternatively, the process further (i) the ratio of the flow rate of silicon in the silicon precursor gas per gram to the mass of porous particles in the pressure reactor per gram, and / or (ii) The ratio of the flow rate of silicon in grams per minute in silicon precursor gas to (mass of porous particles in the pressure reactor in grams × internal free volume of the reactor in liters) This may include a process for adjusting the settings.

[0126] This process, after a predetermined period, during the contact, (i) the ratio of the flow rate of silicon in the silicon precursor gas per gram to the mass of porous particles in the pressure reactor per gram, and / or (ii) The ratio of the flow rate of silicon in grams per minute in silicon precursor gas to (mass of porous particles in the pressure reactor in grams × internal free volume of the reactor in liters) This may include a process for adjusting the settings.

[0127] The composite particles provided in step (c) may contain a target amount of silicon that accounts for 20% to 95% of the internal pore volume of the porous particle framework, and a predetermined period may occur after the composite particles have contained an amount of silicon that accounts for 50% to 95%, or 60% to 95%, or 70% to 95%, or 80% to 95%, or 90% to 95% of the target amount. The target amount of silicon may account for 20% to 80%, or 20% to 70%, or 30% to 70%, or 30% to 60% of the internal pore volume of the porous particle framework.

[0128] The ratio can be adjusted throughout process (c), for example, by adjusting the flow rate of the silicon precursor gas. For example, process (c) may be operated for a period of time when the ratio of the flow rate of silicon in the silicon precursor gas to the mass of porous particles in the pressure reactor is outside the range of 0.006 to 0.7. Thereafter, in process (c), the ratio of the flow rate of silicon in the silicon precursor gas to the mass of porous particles in the pressure reactor may be adjusted to be within the range of 0.006 to 0.7.

[0129] Preferably, the pressure reactor is operated such that the silicon precursor consumption rate is at least 20%, preferably at least 50%, preferably at least 60%, preferably at least 80%, and preferably at least 90%. Alternatively, the pressure reactor may be operated in a low-conversion mode such that the silicon precursor consumption rate is 20% or less, preferably 10% or less, and more preferably 5% or less.

[0130] The composite particles extracted from the pressure reactor may contain 0.2 to 1.8 grams of silicon per gram of the porous particle framework.

[0131] Depending on the circumstances, step (c) may include two or more deposition steps in which the supply of silicon-containing precursor gas is interrupted and by-products are removed from the reactor volume. By-product removal may include flushing the reactor volume with an inert gas and / or hydrogen gas. More preferably, by-product removal includes reducing the pressure in the pressure reactor to less than 50 kPa, or less than 40 kPa, or less than 30 kPa, or less than 20 kPa, or less than 10 kPa, or less than 5 kPa, or less than 3 kPa, or less than 2 kPa, or less than 1 kPa. Thereafter, the supply of silicon-containing precursor gas is resumed and silicon deposition is continued. Preferably, the number of deposition steps is 5 or less, more preferably 3 or less.

[0132] The surface of electroactive materials deposited by CVI is reactive to oxygen and forms a native oxide layer when exposed to atmospheric oxygen. Therefore, particles formed by CVI can be brought into contact with a passivator before the particles are exposed to atmospheric oxygen. A passivator is defined herein as a compound that can modify the surface of the electroactive material to inhibit or prevent the formation of surface oxides. Suitable passivators and passivation conditions are disclosed in the applicant's International Publication No. 2022 / 029422. Optionally, an intermediate passivation step may be performed during the silicon deposition stage if silicon deposition is interrupted as described above.

[0133] The hydrogen content of the composite particles can be adjusted by heat treatment (annealing) in the presence of an inert gas at a temperature of at least 400°C. This heat treatment of the composite particles is thought to promote hydrogen desorption and solid rearrangement of silicon atoms, thereby reducing the density of unstable and reactive Si-H bonds and promoting the formation of more thermodynamically stable Si-Si bonds.

[0134] Rearranging of silicon atoms further contributes to the volumetric contraction of silicon domains. One consequence of this is the reopening of pore spaces previously blocked or sealed by silicon nanostructures, allowing passivation gases and other functional gases to access the remaining pore volume. Increased access of passivation gases to residual pore spaces enables more extensive passivation of the silicon surface, while the removal of hydrogen from silicon nanostructures in previously inaccessible pore spaces reduces hydrogen generation during charging and discharging.

[0135] The inert gas can, in principle, be any gas that does not react during the heat treatment (annealing) of the composite particles. Preferably, the inert gas is selected from nitrogen and noble gases, particularly argon. In some cases, the inert gas may include hydrogen.

[0136] The temperature of the heat treatment step may be at least 450°C, or at least 500°C, or at least 510°C, or at least 520°C, or at least 540°C, or at least 560°C, or at least 580°C, or at least 600°C. Preferably, the temperature of the heat treatment step is 800°C or less, or 750°C or less, or 700°C or less, or 680°C or less, or 660°C or less, or 650°C or less. For example, a suitable heat treatment temperature may be in the range of 510°C to 800°C, or 520°C to 750°C, or 540°C to 700°C, or 560°C to 680°C, or 580°C to 660°C, or 600°C to 650°C.

[0137] The duration of step (c) is preferably at least 1 minute, or at least 2 minutes, or at least 5 minutes, or at least 10 minutes, or at least 15 minutes, or at least 20 minutes, or at least 30 minutes, or at least 45 minutes, or at least 1 hour, or at least 2 hours. Preferably, the duration of step (c) is 72 hours or less, or 48 hours or less, or 24 hours or less, or 12 hours or less, or 6 hours or less, or 5 hours or less, or 4 hours or less, or 3 hours or less.

[0138] A second aspect of the present invention provides a composition comprising a particulate material according to the first aspect of the present invention and at least one other component. In particular, a composition is provided comprising a particulate material according to the first aspect of the present invention and at least one other component selected from (i) a binder, (ii) a conductive additive, and (iii) an additional particulate electroactive material. The composition according to the second aspect of the present invention is useful as an electrode composition and can be used to form the active layer of an electrode.

[0139] The particulate material used to prepare the composition according to the second aspect of the present invention may have any of the features described as preferred or optional with respect to the first aspect of the present invention.

[0140] The composition may be a hybrid electrode composition comprising a particulate material according to a first aspect of the present invention and at least one additional particulate electroactive material. Examples of the additional particulate electroactive material include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. The at least one additional particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably the at least one additional particulate electroactive material is graphite.

[0141] In the case of a hybrid electrode composition, the composition may contain at least 5% by weight, or at least 8% by weight, or at least 10% by weight, or at least 12% by weight, or at least 15% by weight of composite particles according to the second aspect of the present invention, based on the total dry weight of the composition. Optionally, the hybrid electrode composition may contain up to 60% by weight, or up to 50% by weight, or up to 40% by weight, or up to 30% by weight, or up to 25% by weight of composite particles according to the second aspect of the present invention, based on the total dry weight of the composition.

[0142] Preferably, the hybrid electrode composition contains 3 to 60% by weight, or 3 to 50% by weight, or 5 to 40% by weight, or 10 to 30% by weight, or 15 to 25% by weight, of particulate material according to the first embodiment of the present invention, based on the total dry weight of the composition.

[0143] At least one additional particulate electroactive material is present, preferably in an amount of 20–95% by weight, or 25–90% by weight, or 30–75% by weight.

[0144] At least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles and / or hard carbon particles, wherein the graphite and hard carbon particles are in the range of 10 to 50 μm. 50 The particle has a diameter. More preferably, at least one additional particulate electroactive material is selected from graphite particles, the graphite particles having a diameter in the range of 10 to 50 μm. 50 It has a particle diameter.

[0145] The composition may also be a non-hybrid (or “high-load”) electrode composition substantially free of additional particulate electroactive material. In this context, the term “substantially free of additional particulate electroactive material” should be interpreted as meaning that the composition contains less than 15% by weight, preferably less than 10% by weight, preferably less than 5% by weight, preferably less than 2% by weight, more preferably less than 1% by weight, and more preferably less than 0.5% by weight of any additional electroactive material (i.e., additional material that can insert and release metal ions during charging and discharging of the battery) based on the total dry weight of the composition.

[0146] This type of "high-load" electrode composition preferably comprises, based on the total dry weight of the composition, at least 50% by weight, or at least 60% by weight, or at least 70% by weight, or at least 80% by weight, or at least 90% by weight of particulate material according to the first aspect of the present invention.

[0147] The composition may optionally contain a binder. The binder functions to adhere the composition to the current collector and maintain the integrity of the composition. Examples of binders that may be used according to the present invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethylcellulose (CMC), modified carboxymethylcellulose (mCMC), sodium carboxymethylcellulose (Na-CMC), polyvinyl alcohol (PVA), alginates and their alkali metal salts, styrene-butadiene rubber (SBR), and polyimide. The composition may contain a mixture of binders. Preferably, the binder includes polyacrylic acid (PAA) and its alkali metal salts, as well as polymers selected from modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0148] The binder may be appropriately present in an amount of 0.5 to 20% by weight, preferably 1 to 15% by weight, preferably 2 to 10% by weight, and most preferably 5 to 10% by weight, based on the total dry weight of the composition.

[0149] The binder may, if applicable, be present in combination with one or more additives that modify the properties of the binder, such as crosslinking promoters, coupling agents, and / or adhesion promoters.

[0150] The composition may optionally contain one or more conductive additives. Preferred conductive additives are non-electroactive materials included to improve conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. Conductive additives can be appropriately selected from carbon black, carbon fibers, carbon nanotubes, graphene, acetylene black, Ketjenblack, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

[0151] One or more conductive additives may be present in a total amount of 0.5 to 20% by weight, preferably 1 to 15% by weight, preferably 2 to 10% by weight, and most preferably 5 to 10% by weight, based on the total dry weight of the composition.

[0152] In a third aspect, the present invention provides an electrode comprising a particulate material as defined by reference to a first aspect of the present invention. Generally, the electrode comprises the particulate material as an electroactive material and a current collector, the particulate material being in electrical contact with the current collector. The particulate material used to prepare the electrode of the third aspect of the present invention may have any of the features described as preferred or optional with respect to a first aspect of the present invention.

[0153] As used herein, the term current collector refers to any conductive substrate that can conduct electric current with respect to electroactive particles in the composition. Materials that can be used as current collectors include copper, aluminum, stainless steel, nickel, titanium, and sintered carbon. Copper is a preferred material. Current collectors are typically in the form of foils or meshes having a thickness between 3 and 500 μm. The particulate material of the present invention may be coated on one or both sides of the current collector to a thickness preferably in the range of 10 μm to 1 mm, for example, 20 to 500 μm, or 50 to 200 μm.

[0154] Preferably, the electrode is in electrical contact with the current collector and contains a composition defined with reference to a second aspect of the present invention. The composition may have any of the features described as preferred or optional with reference to a second aspect of the present invention.

[0155] An electrode according to a third aspect of the present invention can be appropriately manufactured by combining the particulate material of the present invention (or optionally in the form of a composition of the present invention) with a solvent and optionally one or more viscosity-modifying additives to form a slurry. The slurry is then cast onto the surface of a current collector, and the solvent is removed to form an electrode layer on the surface of the current collector. Further steps, such as heat treatment to cure any binder and / or calendering of the electrode layer, can be performed as needed. The electrode layer preferably has a thickness in the range of 20 μm to 2 mm, preferably 20 μm to 1 mm, preferably 20 μm to 500 μm, preferably 20 μm to 200 μm, preferably 20 μm to 100 μm, and preferably 20 μm to 50 μm.

[0156] Alternatively, the slurry may be formed into a separate film or mat containing the particulate material of the present invention by, for example, casting the slurry onto a suitable mold, removing the solvent, and then removing the casting mold. The resulting film or mat is then in the form of aggregated, self-supporting lumps that can be bonded to a current collector by known methods.

[0157] The electrode of a third aspect of the present invention may be used as an anode of a metal-ion battery. Accordingly, in a fourth aspect, the present invention provides a rechargeable metal-ion battery comprising the electrode of the third aspect of the present invention. In particular, the present invention provides a rechargeable metal-ion battery comprising an anode, the anode comprising the electrode as described above, the cathode comprising a cathode active material capable of releasing and reabsorbing metal ions, and an electrolyte between the anode and the cathode.

[0158] The metal ions are preferably lithium ions. More preferably, the rechargeable metal ion battery of the present invention is a lithium ion battery, and the cathode active material is capable of releasing and receiving lithium ions.

[0159] The cathode active material is preferably a metal oxide composite. Examples of suitable cathode active materials include LiCoO2, LiCo 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni 0.5 O2, LiCo 0.7 Ni 0.3 O2, LiCo 0.8 Ni 0.2 O2, LiCo 0.82 Ni 0.18 O2, LiCo 0.8 Ni 0.15 Al 0.05 O2, LiLiLi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 O2 is one example. The cathode current collector generally has a thickness between 3 and 500 μm. Materials that can be used as cathode current collectors include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0160] The electrolyte is preferably a non-aqueous electrolyte containing a metal salt, such as a lithium salt, and may include, but is not limited to, non-aqueous electrolyte solutions, solid electrolytes, and inorganic solid electrolytes. As the non-aqueous electrolyte solution, aprotic organic solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methylformate, methyl acetate, triester phosphate, trimethoxymethane, sulfolane, methylsulfolane, and 1,3-dimethyl-2-imidazolidinone can be used.

[0161] Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups.

[0162] Examples of inorganic solid electrolytes include nitrides, halides, and sulfides of lithium salts such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4.

[0163] Lithium salts are appropriately soluble in selected solvents or mixtures of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, LiBC4O8, LiPF6, LiCF3SO3, LiAsF6, LiSbF6, LiAlCl4,CH3SO3Li, and CF3SO3Li.

[0164] When the electrolyte is a non-aqueous organic solution, metal-ion batteries preferably include a separator between the anode and the cathode. The separator is typically formed from an insulating material having high ion permeability and high mechanical strength. The separator typically has a pore diameter between 0.01 and 100 μm and a thickness between 5 and 300 μm. Examples of suitable electrode separators include microporous polyethylene films.

[0165] The separator may be replaced with a polymer electrolyte material, in which case the polymer electrolyte material is present in both the composite anode layer and the composite cathode layer. The polymer electrolyte material can be a solid polymer electrolyte or a gel-type polymer electrolyte. [Examples]

[0166] Example 1 Composite particles were prepared using a porous particle framework having the characteristics shown in Table 1. [Table 1]

[0167] To evaluate the influence of various composite particle properties on electrochemical performance, composite particles were prepared under various CVI reaction conditions. The composite particles according to the present invention were prepared according to the preferred reaction conditions disclosed above. Comparative composite particles were prepared under modified reaction conditions including one or more of the following: increased CVI reaction temperature (resulting in decreased surface silicon content, increased crude silicon content, and increased hydrogen content), reduced particle stirring or a static bed (resulting in increased coarse silicon and hydrogen content), and faster air passivation (resulting in higher oxygen content, higher BET, and decreased chemical stability of the particle surface).

[0168] Example 2 - Electrochemical Test A test coin cell was fabricated using a negative electrode containing the composite particles shown in Table 2 below. A dispersion of Carbon Super P (conductive carbon) in the CMC binder was mixed using a Thinky™ mixer. The composite particles were added to the mixture and mixed for 30 minutes. After further mixing this slurry in a Thinky™ mixer for another 30 minutes, it was applied to a 10 μm thick copper substrate (current collector), dried at 50°C for 10 minutes, and then dried at 110°C for 12 hours to form an electrode containing an active layer on the copper substrate.

[0169] A coin-type half-cell was fabricated using a porous polyethylene separator, lithium foil as a counter electrode, and a circular electrode with a radius of 0.8 cm cut from an electrode having an electrolyte containing 1 M LiPF6 in a 7:3 EC / FEC (ethylene carbonate / fluoroethylene carbonate) solution containing 3 wt% vinylene carbonate.

[0170] These half-cells were used to measure the first lithiation capacity (DC0) and first lithium desorption capacity (DC1: also called the first discharge capacity) of the active layer, as well as the first cycle loss (FCL), where DC0 and DC1 are defined in units of mAh per gram of electroactive material in the electrode, and FCL is defined as (1 - (DC1 / DC0)) × 100%. The half-cells were tested by lithiating the electrode containing porous particles with a cutoff voltage of 10 mV by applying a constant current of C / 25 (where "C" represents the specific capacity of the electrode in units of mAh, and "25" refers to 25 hours). Upon reaching the cutoff, a constant voltage of 10 mV was applied with a cutoff current of C / 100. The cell was then left to rest in the lithiated state for 10 minutes. The electrode was then delithiated with a constant current of C / 25 with a cutoff voltage of 1 V, and the cell was then left to rest for 10 minutes. Next, a constant current of C / 25 is applied, and the cell is lithium-ionized a second time with a cutoff voltage of 10mV. Then, a constant voltage of 10mV is applied with a cutoff current of C / 100, and it is left for 5 minutes.

[0171] The effects of the present invention are shown in Table 2. Specifically, it was found that if the composite particles lack one or more of the properties described in claim 1, the first discharge capacity (DC1) decreases and the first cycle loss (FCL) of the active material increases. [Table 2]

Claims

1. A particulate material consisting only of multiple composite particles, wherein the composite particles are (a) A porous particle framework comprising micropores and mesopores, When measured by gas adsorption, the total volume of micropores and mesopores in the porous particle framework is 0.5 to 1.8 cm³. ３ A porous particle framework that is / g, (b) A plurality of nanoscale elemental silicon domains located within the pores of the porous particle framework, (i) The composite particles contain 30 to 70% by weight of silicon, (ii) When determined by thermogravimetric analysis (TGA), at least 30% by weight of the silicon is surface silicon, the TGA is performed in air with a temperature gradient rate of 10°C / min, and the percentage of surface silicon is determined according to the following formula: Y=1.875×[(M ｍａｘ -M ｍｉｎ ) / M ｆ ]×100% In the formula, Y is the percentage of surface silicon as the proportion of total silicon in the sample, and M ｍａｘ This is the maximum mass of the sample measured in the temperature range of 550°C to 650°C, and M ｍｉｎ This is the minimum mass of the sample between 150°C and 500°C, M ｆ This is the mass of the sample when oxidation is complete at 1400°C. (iii) The hydrogen content of the composite particles is 1.2% by weight or less, (iv) The weight ratio of oxygen to silicon in the composite particles is 0.15 or less. (v) The BET surface area of ​​the composite particles is 40 m ２ It is less than or equal to / g. Multiple nanoscale elemental silicon domains, A particulate material containing [the specified element].

2. The particulate material according to claim 1, wherein, as determined by thermogravimetric analysis (TGA), at least 32% by weight of the silicon, or at least 35% by weight of the silicon, or at least 38% by weight of the silicon, or at least 40% by weight of the silicon, or at least 42% by weight of the silicon, or at least 45% by weight of the silicon, or at least 48% by weight of the silicon, or at least 50% by weight of the silicon is surface silicon.

3. When determined by thermogravimetric analysis (TGA), crude bulk silicon is 6% by weight or less, or 5% by weight or less, or 4% by weight or less, or 3.5% by weight or less, or 3% by weight or less, or 2.5% by weight or less, or 2% by weight or less, or 1.5% by weight or less of the silicon, and the TGA is performed in air at a temperature gradient rate of 10°C / min, and the percentage of crude bulk silicon is determined according to the following formula: Z=1.875×[(M ｆ -M ８００ ) / M ｆ ]×100% In the formula, Z is the percentage of crude bulk silicon, and M ８００ This is the mass of the sample at 800°C, M ｆ This is the mass of ash when oxidation is complete at 1400°C. The particulate material according to claim 1 or claim 2.

4. When measured by gas adsorption, the total volume of micropores and mesopores in the porous particle framework is at least 0.55 cm³. ３ / g, or at least 0.6cm ３ / g, or at least 0.65 cm ３ / g, or at least 0.7cm ３ / g, or at least 0.75 cm ３ The particulate material according to claim 1 or 2, wherein the amount is / g.

5. When measured by gas adsorption, the total volume of micropores and mesopores in the porous particle framework is 1.6 cm³. ３ Less than or equal to 1.4 cm / g ３ Less than or equal to 1.3 cm ３ Less than or equal to 1.2 cm / g ３ Less than or equal to 1.1 cm / g ３ The particulate material according to claim 1 or 2, wherein the amount is less than or equal to / g.

6. PD of the porous particle framework ９０ The pore diameter is 12 nm or less, or 10 nm or less, or 8 nm or less, or 6 nm or less, or 4 nm or less, and the PD ９０ The particulate material according to claim 1 or 2, wherein the pore diameter is the 90th percentile pore diameter based on the volume of the porous particle framework, which is determined by the total volume of micropores and mesopores.

7. PD of the porous particle framework ５０ The pore diameter is 2 nm or less, or 1.9 nm or less, or 1.8 nm or less, or 1.7 nm or less, or 1.6 nm or less, and the PD ５０ The particulate material according to claim 1 or 2, wherein the pore diameter is the 50th percentile pore diameter based on the volume of the porous particle framework, which is determined by the total volume of micropores and mesopores.

8. PD of the porous particle framework ５０ The pore diameter is at least 1 nm, or at least 1.1 nm, or at least 1.2 nm, and the PD ５０ The particulate material according to claim 1 or 2, wherein the pore diameter is the 50th percentile pore diameter based on the volume of the porous particle framework, which is determined by the total volume of micropores and mesopores.

9. The particulate material according to claim 1 or 2, wherein the micropore volume fraction of the porous particle framework is at least 0.45, or at least 0.5, or at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, based on the total volume of micropores and mesopores.

10. The particulate material according to claim 1 or 2, wherein the micropore volume fraction of the porous particle framework is 0.95 or less, or 0.9 or less, or 0.85 or less, or 0.8 or less, based on the total volume of micropores and mesopores.

11. The total volume of micropores in the porous particle framework is at least 0.36 cm³. ３ / g, or at least 0.38 cm ３ / g, at least 0.40 cm ３ / g, at least 0.42 cm ３ The particulate material according to claim 1 or 2, wherein the amount is / g.

12. The particulate material according to claim 1 or 2, wherein the porous particle framework has a bimodal or multimodal pore size distribution.

13. The total volume of pores with a diameter in the range of over 50 nm to 100 nm is 0.2 × P １ The following, or 0.1 × P １ The following, or 0.05 × P １ The following, or 0.02 × P １ The following, or 0.01 × P １ The following, or 0.005 × P １ The following is P １ The particulate material according to claim 1 or 2, wherein the volume of micropores and mesopores in the porous particle framework represents the total volume of micropores and mesopores in the porous particle framework.

14. The porous particle framework is 1200 to 3000 m ２ The particulate material according to claim 1 or 2, having a BET surface area of ​​1 / g.

15. The particulate material according to claim 1 or 2, wherein the porous particle framework is a conductive porous particle framework.

16. The particulate material according to claim 15, wherein the conductive porous particle framework is a conductive porous carbon particle framework.

17. The particulate material according to claim 16, wherein the conductive porous carbon particle framework comprises at least 80% by weight of carbon, or at least 85% by weight of carbon, or at least 90% by weight of carbon, or at least 95% by weight of carbon.

18. The particulate material according to claim 1 or 2, wherein the composite particles contain at least 32% by weight of silicon, or at least 35% by weight of silicon, or at least 38% by weight of silicon, or at least 40% by weight of silicon, or at least 42% by weight of silicon, or at least 44% by weight of silicon, or at least 46% by weight of silicon, or at least 48% by weight of silicon, or at least 50% by weight of silicon.

19. The particulate material according to claim 1 or 2, comprising up to 68% by weight of silicon, or up to 65% by weight of silicon, or up to 60% by weight of silicon, or up to 58% by weight of silicon, or up to 55% by weight of silicon.

20. The particulate material according to claim 1 or 2, wherein the composite particles contain at least 0.1% by weight of hydrogen, or at least 0.15% by weight of hydrogen, or at least 0.2% by weight of hydrogen.

21. The particulate material according to claim 1 or 2, wherein the composite particles contain 1.1% by weight or less of hydrogen, or 1% by weight or less of hydrogen, or 0.95% by weight or less of hydrogen, or 0.9% by weight or less of hydrogen, or 0.85% by weight or less of hydrogen, or 0.8% by weight or less of hydrogen, or 0.75% by weight or less of hydrogen.

22. The particulate material according to claim 1 or 2, wherein the composite particles contain 6% by weight or less of oxygen, or 5.5% by weight or less of oxygen, or 5% by weight or less of oxygen, or 4.5% by weight or less of oxygen.

23. The particulate material according to claim 1 or 2, wherein the weight ratio of oxygen to silicon in the composite particles is 0.14 or less, or 0.12 or less, or 0.1 or less, or 0.09 or less, or 0.08 or less.

24. The composite particles are at least 1 μm, or at least 2 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm of D ５０ A particulate material according to claim 1 or 2, having a particle diameter.

25. The composite particles are 20 μm or less, or 18 μm or less, or 16 μm or less, or 14 μm or less, or 12 μm or less, or 10 μm or less, or 8 μm or less. ５０ A particulate material according to claim 1 or 2, having a particle diameter.

26. The composite particles are at least 0.5 μm, or at least 0.8 μm, or at least 1 μm, or at least 1.5 μm, or at least 2 μm of D １０ A particulate material according to claim 1 or 2, having a particle diameter.

27. The composite particles are at least 0.5 μm, or at least 0.8 μm, or at least 1.0 μm, or at least 1.2 μm, or at least 1.4 μm, or at least 1.5 μm of D １ A particulate material according to claim 1 or 2, having particle size.

28. The composite particles are 30 μm or less, or 25 μm or less, or 20 μm or less, or 15 μm or less D ９０ A particulate material according to claim 1 or 2, having a particle diameter.

29. The composite particles are 35m ２ / g or less, or 30m ２ / g or less, or 25m ２ / g or less, or 20m ２ / g or less, or 15m ２ / g or less, or 10m ２ The particulate material according to claim 1 or 2, having a BET surface area of ​​less than or equal to / g.

30. The composite particles are at least 0.1 m ２ / g, or at least 1m ２ / g, or at least 2m ２ / g, or at least 5m ２ The particulate material according to claim 1 or 2, having a BET surface area of ​​1 / g.

31. The particulate material according to claim 1 or 2, wherein the composite particles are obtained by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous carbon framework.

32. A composition comprising the particulate material described in claim 1 and at least one other component.

33. An electrode comprising the particulate material according to claim 1 or 2 or the composition according to claim 32.

34. A rechargeable metal-ion battery comprising the electrode described in claim 33.

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