Electroactive materials for metal-ion batteries

Abstract

To provide electrochemical materials should have sufficient structural strength alongside high electrochemical storage capacity and high reversible capacity retention.SOLUTION: This invention relates to particulate electroactive materials consisting only of a plurality of composite particles, where the composite particles comprise: (a) a porous carbon framework including micropores and mesopores having a total volume of 0.4 cm3 / g to 0.75 cm3 / g, where the micropore volume fraction is in the range from 0.5 to 0.85 based on the total volume of micropores and mesopores; and (b) silicon located at least within the micropores of the porous carbon framework in a defined amount relative to the volume of the micropores and mesopores.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates generally to electroactive materials suitable for use in electrodes for rechargeable metal-ion batteries, and more particularly to particulate materials having high electrochemical capacity suitable for use as anode active materials in rechargeable metal-ion batteries. [Background technology]

[0002] Rechargeable metal-ion batteries are widely used in portable electronic devices such as mobile phones and laptops, and are increasingly being used in electric or hybrid vehicles. Rechargeable metal-ion batteries generally include an anode layer, a cathode layer, an electrolyte that transports metal ions between the anode and cathode layers, and an electrically insulating porous separator disposed between the anode and cathode. The cathode typically includes a metal current collector with a layer of metal ion-containing metal oxide-based composite, and the anode typically includes a metal current collector with a layer of electroactive material, defined herein as a material capable of inserting and releasing metal ions during charging and discharging of the battery. For the avoidance of doubt, the terms "cathode" and "anode" are used herein to mean a battery under load such that the cathode is the positive electrode and the anode is the negative electrode. When a metal-ion battery is charged, metal ions are transported from the metal-ion-containing cathode layer through the electrolyte to the anode and inserted into the anode material. The term "battery" is used herein to refer to both devices containing a single anode and a single cathode, and devices containing multiple anodes and / or multiple cathodes.

[0003] There is growing interest in improving the gravimetric and / or volumetric capacity of rechargeable metal-ion batteries. The use of lithium-ion batteries has already provided considerable improvements compared to other battery technologies, but there is room for further development. To date, commercially available lithium-ion batteries have been primarily limited to the use of graphite as the anode active material. Upon charging a graphite anode, lithium is intercalated between the graphite layers, forming a compound with the empirical formula Lix C6 (where x is greater than 0 and less than or equal to 1). As a result, graphite has a maximum theoretical capacity of 372 mAh / g in lithium-ion batteries, with practical capacities somewhat lower (approximately 340 mAh / g to 360 mAh / g). Other materials, such as silicon, tin, and germanium, can intercalate lithium at significantly higher capacities than graphite, but are not yet in widespread commercial use due to the difficulty of maintaining sufficient capacity over many charge-discharge cycles.

[0004] In particular, silicon has been recognized as a promising alternative to graphite in the production of rechargeable metal-ion batteries with high gravimetric and volumetric capacities due to its extremely high capacity relative to lithium (see, for example, Non-Patent Document 1). Silicon has a theoretical maximum specific capacity of about 3600 mAh / g (Li ) in lithium-ion batteries at room temperature. 15 However, the use of silicon as an anode material is complicated by its large volume change during charging and discharging.

[0005] When lithium is intercalated into bulk silicon, the volume of the silicon material increases significantly, up to 400% of its original volume when silicon is lithiated to its maximum capacity. Repeated charge-discharge cycles then create significant mechanical stresses in the silicon material, leading to fracture and delamination of the silicon anode material. The volumetric shrinkage of silicon particles during delithiation can result in loss of electrical contact between the anode material and the current collector. To make matters even more difficult, the solid electrolyte interface (SEI) layer that forms on the silicon surface is not mechanically durable enough to accommodate the expansion and contraction of the silicon. As a result, new The exposed silicon surface leads to further electrolyte decomposition, an increase in the thickness of the SEI layer, and irreversible lithium consumption. Collectively, these failure mechanisms result in unacceptable electrochemical capacity loss over successive charge-discharge cycles.

[0006] Numerous approaches have been proposed to overcome the problems associated with the volume changes observed during charging of silicon-containing anodes. The most widespread approach to addressing irreversible capacity loss in silicon-containing anodes is the use of some form of microstructured silicon as the electroactive material. It has been reported that fine silicon structures with cross sections less than about 150 nm, such as silicon films and silicon nanoparticles, are more resistant to volume changes during charge and discharge than silicon particles in the micron size range. However, neither of these is particularly suitable for commercial-scale applications without morphological modification. Nanoscale particles are difficult to manufacture and handle, and silicon films do not provide sufficient bulk capacitance. For example, nanoscale particles tend to form agglomerates, making it difficult to effectively disperse the particles within the anode material matrix. Furthermore, the formation of nanoscale particle agglomerates results in unacceptable capacity loss during repeated charge-discharge cycles.

[0007] Ohara et al. (Non-Patent Document 2) have reported that silicon is deposited as a thin film on a nickel foil current collector. and the use of this structure as an anode in a lithium-ion battery. While this approach provides good capacity retention, the thin film structure does not provide a useful amount of capacity per unit area, and any improvement is eliminated as the film thickness increases.

[0008] Patent Document 1 discloses that capacity retention can be improved by using silicon particles with a high aspect ratio, i.e., the ratio of the maximum dimension to the minimum dimension of the particle. The small cross-section of such particles reduces the structural stress on the material due to volume changes during charge and discharge. However, such particles can be difficult and expensive to manufacture and can be fragile. In addition, the large surface area can lead to the formation of excessive SEI, resulting in excessive capacity loss during the first charge-discharge cycle.

[0009] It is also generally known that electroactive materials such as silicon can be deposited within the pores of a porous carrier material such as an activated carbon material. These composite materials provide some of the beneficial charge and discharge characteristics of nanoscale silicon particles while avoiding the difficulties of handling nanoparticles. For example, Guo et al. (Non-Patent Document 3) disclose a silicon-carbon composite material that provides a conductive skeleton comprising silicon nanoparticles uniformly distributed and deposited within the pore structure of the substrate. The formation of the SEI in the first charge cycle is limited to the remaining pore volume so that the remaining silicon is not exposed to the electrolyte in subsequent charge cycles. Although this composite material improves the capacity retention rate over multiple charge cycles, it has been shown that the initial capacity of the composite material in mAh / g is significantly lower than the capacity for silicon nanoparticles. The first charge cycle SEI formation is limited to the remaining pore volume so that the remaining silicon is not exposed to the electrolyte in subsequent charge cycles. Although this composite material improves the capacity retention rate over multiple charge cycles, it has been shown that the initial capacity of the composite material in mAh / g is significantly lower than the capacity for silicon nanoparticles.

[0010] Patent Document 2 discloses an active material comprising a carbon-based scaffold having small pores branching from a few larger pores. The electroactive material (e.g., silicon) is randomly located on the walls of both the large and small pores and on the outer surface of the carbon-based scaffold.

[0011] Silicon suboxide materials (e.g., SiO x (where 0 < x < 2)) have been used in "hybrid" electrodes mainly containing graphite as the active material. However, since SiO x expands during lithiation and the irreversible lithium loss is relatively large in the first charge cycle, the maximum filling amount of SiO x is typically about 10% by weight based on the total electroactive material in the electrode. When the filling amount of SiO x is larger, it causes excessive electrode expansion and irreversible damage to the electrode. Therefore, there is a need for a high-capacity electrode material that has a lithiation capacity equivalent to silicon suboxide, while reducing expansion and reducing the capacity loss in the first charge cycle. This allows a high-capacity material to be used for SiO xThis allows for higher loadings than [Prior art documents] [Patent documents]

[0012] [Patent Document 1] International Publication No. 2007 / 083155 [Patent Document 2] JP 2003-100284 A [Non-patent literature]

[0013] [Non-Patent Document 1] Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M. et al. in Adv. Mater. 1998, 10, No. 10 [Non-patent document 2] Journal of Power Sources 136 (2004) 303-306 [Non-patent document 3] Journal of Materials Chemistry A, 2013, pp. 14075-14079 Summary of the Invention [Problem to be solved by the invention]

[0014] The desirable expansion characteristics of electrode materials must be achieved along with other important properties. In particular, commercially viable alternative electrode materials must offer the benefits of high lithiation capacity along with high capacity retention over multiple charge-discharge cycles. It is also important that new electroactive materials be easily substituted for known materials in conventional electrode fabrication processes. These processes typically rely on calendering the electrode material onto a current collector to densify the electrode layer and improve space utilization within the battery design. Porous materials are prone to fracture during electrode fabrication, leading to reduced electrochemical performance. Therefore, new electrochemical materials must possess sufficient structural strength along with high electrochemical storage capacity and high reversible capacity retention. [Means for solving the problem]

[0015] The inventors have discovered that the mechanical performance of composites comprising a porous carbon skeleton and an electroactive material located within the porous carbon skeleton can be improved by using a porous carbon skeleton with a specific pore structure, a carefully controlled pore size distribution, and a controlled loading of the electroactive material within the pores of the porous carbon skeleton. Locating the electroactive material within the carbon skeleton also reduces contact with the electrolyte solvent in the cell, minimizing chemical side reactions that lead to irreversible lithium loss during the first and subsequent charge cycles.

[0016] In a first aspect, the present invention provides a particulate material consisting solely of a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework containing micropores and mesopores, The micropores and mesopores have a total pore volume measured by gas adsorption of P 1 cm 3 / g, where P 1 represents a natural number having a value between 0.4 and 0.75, and a porous carbon skeleton in which the volume ratio of micropores to the total volume of micropores and mesopores is in the range of 0.5 to 0.85; (b) multiple nanoscale elemental silicon domains located within the pores of the porous carbon skeleton; Including, The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.9×P 1 ]:1.

[0017] The present invention relies in particular on the use of a porous carbon skeleton with relatively low porosity to provide a strong framework to accommodate the electroactive silicon domains. In particular, the upper porosity limit is set to 0.75 cm. 3 / g, the fracture resistance of the porous carbon skeleton under compressive stress is very high.

[0018] The porous carbon skeleton comprises a three-dimensionally interconnected open pore network including micropores and mesopores. The porous carbon skeleton may optionally further comprise a small amount of macropores. Following conventional IUPAC terminology, the term "micropore" is used herein to refer to pores less than 2 nm in diameter, the term "mesopore" is used herein to refer to pores between 2 nm and 50 nm in diameter, and the term "macropore" is used herein to refer to pores greater than 50 nm in diameter.

[0019] The total volume of the micropores and mesopores in the porous carbon framework is 0.4 cm 3 / g~0.75cm 3 For the avoidance of doubt, references herein to the pore volume of a porous carbon skeleton (unless expressly stated to the contrary) relate to the pore volume of the porous carbon skeleton when measured alone, i.e., in the absence of any electroactive material (or other material) occupying the pores of the porous carbon skeleton.

[0020] As used herein, the total volume of micropores and mesopores (i.e., the total pore volume of pores with diameters in the range of 0 nm to 50 nm) is defined as P 1 cm 3 / g, where P 1 represents a dimensionless natural number with a value between 0.4 and 0.75.1 The value of is used to correlate the effective pore volume in the porous carbon skeleton with the weight ratio of silicon to the porous carbon skeleton, as explained below.

[0021] Elemental silicon is located within the pore network of the porous carbon skeleton. As such, the silicon is in the form of a plurality of nanoscale silicon domains. As used herein, the term "nanoscale silicon domains" refers to nanoscale bodies of silicon having dimensions determined by the location of the silicon within the micropores and / or mesopores of the porous carbon skeleton.

[0022] Microporous carbon frameworks offer the advantage that the electroactive material is located within the micropore network in the form of small domains with dimensions on the order of a few nanometers or less. These fine electroactive structures are less resistant to elastic deformation and more fracture-resistant than larger electroactive structures, allowing them to be lithiated and delithiated without excessive structural stress. Thus, the microporosity of the porous carbon framework not only provides improved mechanical strength for the particles, but also ensures that the electroactive material itself is sufficiently resilient to withstand repeated volume changes over multiple charge-discharge cycles without significant capacity loss.

[0023] To provide a material with sufficiently high gravimetric and volumetric capacities, the pore volume of the porous carbon skeleton is small, so a relatively high pore volume occupancy by silicon is required. The weight ratio of silicon to porous carbon skeleton is [0.9×P 1 ~1.9×P 1 ]:1. 1 By specifying the weight ratio of silicon based on the value of [0.9×P], the volume occupancy rate of the pore volume by silicon is controlled within a specific limit. 1 ~1.9×P 1 ]:1, this corresponds to the volume of silicon being approximately 40% to 82% of the total volume of the micropores and mesopores.

[0024] It has been found that the required weight ratio of silicon to porous carbon skeleton can only be obtained by controlling the pore size distribution of the porous carbon skeleton within certain limits. High porosity skeletons developed by the applicant in another application have high porosity, containing multiple pathways to the innermost pores. While low-porosity frameworks have a highly interconnected pore network, low-porosity frameworks have much fewer interconnections within the pore network. To preferentially deposit silicon within the pores rather than on the outer surface of the porous carbon framework, a relatively high microporosity is required in the porous carbon framework, since silicon deposition into the micropores is kinetically favored. However, it has been found that if the microporosity is too high, silicon deposits substantially on the outer surface of the porous carbon framework. This is believed to be because the initial silicon deposits form obstacles in the pore network. The availability of alternative pathways through the pore network is a function of the total pore volume. In low-porosity materials, the relative lack of alternative pathways through the pore network means that such obstacles can render part of the pore volume inaccessible to silicon precursors. Therefore, ensuring internal silicon deposition in low-porosity carbon frameworks is a particular challenge that has been addressed by the present inventors. In summary, it has been found that achieving electroactive materials with the required properties of high compressive strength, limited expansion, high electrochemical capacity, and high capacity retention depends on a combination of total pore volume, pore size distribution, and the extent of pore occupation by silicon.

[0025] Another factor related to the interconnectivity of the pore network in low-porosity scaffolds is particle size. Larger particles necessarily have a longer path through the pore network to the innermost pores, and so the larger the particles, the more difficult it is to obtain the required internal silicon loading at the required weight ratio. Therefore, in preferred embodiments of the present invention, the median particle diameter (D 50) is also carefully controlled. Control of particle size distribution not only contributes additionally to particle strength, but also allows for improved close packing of the composite particles in the electrode active layer, thereby reducing the need for excessive calender pressure.

[0026] The highly microporous carbon skeleton of the composite materials of the present invention has a high tensile fracture strength, allowing it to accommodate within its pore volume a significant amount of expansion of the electroactive material without fracture. When the electroactive material is fully lithiated, the composite as a whole may undergo some external expansion, but the amount of external expansion is limited by the controlled total pore volume and, therefore, the maximum weight ratio of silicon to porous carbon skeleton. While this high-strength porous carbon skeleton is less susceptible to elastic deformation under stress than higher-porosity skeletons, controlling the ratio of silicon to porous carbon skeleton ensures that the expansion stress on the porous carbon skeleton during maximum lithiation remains below the level required to cause fracture.

[0027] Yet another factor in the exceptional performance of the composite materials of the present invention is the minimization of SEI formation. Because the electroactive material is located within a pore network, only a small area of ​​the electroactive material's surface is accessible to the electrolyte, limiting the formation of SEI on the surface of the electroactive material, thereby minimizing irreversible lithium loss during the first charge cycle. Further exposure of the electroactive material during subsequent charge / discharge cycles is also substantially prevented, so that SEI formation is not a significant failure mechanism leading to capacity loss. This is in contrast to the excessive SEI formation characteristic of the materials disclosed by Guo, for example. This is in stark contrast to (see above).

[0028] As a result of the unique particle structure of the particulate material of the present invention, the composite particles are x The particulate materials of the present invention have technology-improving electrochemical performance. In particular, the particulate materials of the present invention have higher electrochemical capacity, less overall expansion, and comparable reversible capacity retention than previously achieved, potentially allowing for higher loadings of high-capacity electroactive materials.

[0029] Any reference herein to the volume of micropores, mesopores, and macropores within a porous carbon skeleton, as well as to the pore volume distribution within a porous carbon skeleton, refers to the porous carbon skeleton alone (i.e., without any electroactive material or other material occupying some or all of the pore volume). It refers to the internal pore volume of the framework.

[0030] P 1 Preferably, the value of P is at least 0.42, more preferably at least 0.45, more preferably at least 0.47, more preferably at least 0.5. A higher porosity scaffold is advantageous because it can accommodate a greater amount of silicon within the pore structure without compromising the resistance of the porous carbon skeleton to fracture under compressive stresses during electrode fabrication or under expansion stresses due to silicon lithiation. As noted above, P 1 The value of is limited to a value that maintains high compressive strength of the particles. 1 The value of can be up to 0.75. However, P 1 The value of P may more preferably be at most 0.72, more preferably at most 0.7, more preferably at most 0.67, more preferably at most 0.65, more preferably at most 0.62, more preferably at most 0.6. 1 can optionally have a value less than 0.6.

[0031] P 1is in the range of 0.42 to 0.75, or in the range of 0.42 to 0.72, or in the range of 0.42 to 0.7, or in the range of 0.42 to 0.67, or in the range of 0.42 to 0.65, or in the range of 0.42 to 0.62, or in the range of 0.42 to 0.6, or in the range of less than 0.42 to 0.6, or in the range of 0.45 to 0.75, or in the range of 0.45 to 0.72, or in the range of 0.45 to 0.7, or in the range of 0.45 to 0.67, or in the range of 0.45 to 0.65, or in the range of 0.45 to 0.62, or in the range of 0.45 to 0.6, or in the range of less than 0.45 to 0.6, Alternatively, it may be in the range of 0.47 to 0.75, or in the range of 0.47 to 0.72, or in the range of 0.47 to 0.7, or in the range of 0.47 to 0.67, or in the range of 0.47 to 0.65, or in the range of 0.47 to 0.62, or in the range of 0.47 to less than 0.6, or in the range of 0.5 to 0.75, or in the range of 0.5 to 0.72, or in the range of 0.5 to 0.7, or in the range of 0.5 to 0.67, or in the range of 0.5 to 0.65, or in the range of 0.5 to 0.62, or in the range of 0.5 to 0.6, or in the range of 0.5 to less than 0.6.

[0032] As used herein, the term "micropore volume ratio" refers to the ratio of the volume of micropores to the total volume of micropores and mesopores. In other words, the micropore volume ratio is the volume ratio of pores having a diameter of 2 nm or less to the total volume of pores having a diameter of up to 50 nm. As described above, the volume ratio of micropores to the total volume of micropores and mesopores must be carefully controlled to be within the range of 0.5 to 0.85. Preferably, the volume ratio of micropores to the total volume of micropores and mesopores is at least 0.55, or at least 0.56, or at least 0.58, or at least 0.6, or at least 0.62, or at least 0.64, or at least 0.65. Preferably, the volume ratio of micropores to the total volume of micropores and mesopores is at most 0.84, or at most 0.82, or at most 0.8, or at most 0.78, or at most 0.76, or at most 0.75.

[0033] The volume ratio of micropores to the total volume of micropores and mesopores is optionally in the range of 0.5 to 0.84, or in the range of 0.5 to 0.82, or in the range of 0.5 to 0.8, or in the range of 0.5 to 0.78, or in the range of 0.5 to 0.76, or in the range of 0.5 to 0.75, or in the range of 0.55 to 0.84, or in the range of 0.55 to 0.82, or in the range of 0.55 to 0.8, or in the range of 0.55 to 0.78, or in the range of 0.55 to 0.76, or in the range of 0.5 to 0.75. It can be in the range of 0.55 to 0.75, or in the range of 0.6 to 0.84, or in the range of 0.6 to 0.82, or in the range of 0.6 to 0.8, or in the range of 0.6 to 0.78, or in the range of 0.6 to 0.76, or in the range of 0.6 to 0.75, or in the range of 0.65 to 0.84, or in the range of 0.65 to 0.82, or in the range of 0.65 to 0.8, or in the range of 0.65 to 0.78, or in the range of 0.65 to 0.76, or in the range of 0.65 to 0.75.

[0034] Microporosity within these ranges allows silicon nanostructures to withstand over-lithiation. The pore size is small enough to prevent excessive stress, while also being large enough to allow high levels of silicon to be deposited (e.g., by chemical vapor infiltration) within the pore structure of the porous carbon skeleton in acceptable processing times. Higher microporosity can cause the silicon to form plugs and / or caps upon deposition, particularly at higher deposition rates, which can result in pockets of inaccessible pore volume that cannot be filled by silicon, leading to excess silicon deposition on the outer surface of the particle.

[0035] PD of porous carbon frameworks 90 The pore size is preferably at most 20 nm, more preferably at most 15 nm, more preferably at most 12 nm, more preferably at most 10 nm, more preferably at most 8 nm, more preferably at most 6 nm, more preferably at most 5 nm.

[0036] As used herein, "PD" 90The term "pore size" refers to the 90th percentile pore size on a volume basis relative to the total volume of micropores and mesopores. 90 The term "pore size" refers to the size of the pores less than the P 1 For the avoidance of doubt, any macropore volume (pore diameters greater than 50 nm) is not included in the PD 90 It is not taken into account for the purpose of calculating the value.

[0037] Preferably, PD 95 The pore size is at most 20 nm, or at most 15 nm, or at most 12 nm, or at most 10 nm, or at most 8 nm. 95 "Pore size" refers to the 95th percentile pore size on a volume basis.

[0038] A small volume fraction of pores with diameters in the larger mesopore range can be advantageous because it facilitates electrolyte access to the silicon. Thus, pores with diameters in the 10 nm to 50 nm range (i.e., larger mesopores) can optionally comprise at least 1%, at least 2%, at least 5%, or at least 10% of the total micropore and mesopore volume of the porous carbon skeleton.

[0039] The pore size distribution of the porous carbon skeleton 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 the porous carbon skeleton. A bimodal or multimodal pore size distribution may be preferred because the proximity of micropores to larger diameter pores provides the advantage of efficient ion transport through the porous network to the silicon. Thus, the particulate material has high ion diffusivity, resulting in improved rate performance.

[0040] The total volume of micropores and mesopores, as well as the pore size distribution of micropores and mesopores, are determined using nitrogen gas adsorption at 77 K using quenched solid-state density functional theory (QSDFT) according to standard methodologies specified in ISO 15901-2 and ISO 15901-3. Nitrogen gas adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas within the pores of a solid. As the pressure is increased, the gas initially condenses within the smallest diameter pores until the saturation point is reached, at which point all pores are filled with liquid. The nitrogen gas pressure is then gradually reduced to evaporate the liquid from the system. Analysis of the adsorption and desorption isotherms and the hysteresis between them allows the pore volume and pore size distribution to be determined. Suitable instruments for measuring pore volume and pore size distribution by nitrogen gas adsorption include the TriStar II Porosity Analyzer and TriStar II Plus Porosity Analyzer available from Micromeritics Instrument Corporation, USA.

[0041] Nitrogen gas adsorption is effective for measuring pore volume and pore size distribution for pores with diameters up to 50 nm, but becomes less reliable for pores with much larger diameters. For clarity purposes, nitrogen adsorption is used to determine the pore volume and pore size distribution of only pores with diameters up to 50 nm. 1 The value of is determined by considering only pores with diameters up to 50 nm (i.e., only micropores and mesopores), and similarly, PD 90 and PD 95 The value of and the microporosity are determined relative to the total volume of micropores and mesopores only.

[0042] Given the limitations of available analytical techniques, it is not possible to measure the pore volume and pore size distribution across the entire range of micropores, mesopores, and macropores using a single technique. When a porous carbon skeleton contains macropores, the volume of pores in the range above 50 nm and up to 100 nm is referred to herein as P 2 cm 3It is specified in terms of the value of / g and is measured by mercury intrusion porosimetry. 2 The value relates to the pore volume of the porous carbon skeleton when measured alone, i.e., in the absence of silicon or other material occupying the pores of the porous carbon skeleton.

[0043] To avoid any misunderstanding, P 2 The value of P only considers pores with diameters greater than 50 nm and up to 100 nm. 2 The value of P includes only the volume of macropores up to 100 nm in diameter. Any pore volume measured by mercury porosimetry with pore diameters of 50 nm or less is included in the P 2 (As discussed above, nitrogen adsorption is used to characterize mesopores and micropores.) The pore volume measured above 100 nm by mercury porosimetry is assumed to be interparticle porosity for the purposes of this invention, and P 2 This pore volume is also not taken into account when determining the value of .

[0044] Mercury intrusion porosimetry is a technique for characterizing the porosity and pore size distribution of a material by applying various levels of pressure to a sample of the material immersed in mercury. The pressure required to force mercury into the pores of the sample is inversely proportional to the pore size. Mercury intrusion values ​​reported herein were obtained according to ASTM UOP578-11, assuming a surface tension γ of 480 mN / m and a contact angle φ of 140° for mercury at room temperature. The density of mercury at room temperature is 13.5462 g / cm. 3 Many high-precision mercury intrusion instruments are commercially available, such as the AutoPore IV series of automated mercury intrusion porosimetry instruments available from Micromeritics Instrument Corporation, USA. For a complete review of mercury intrusion techniques, see P.A. Webb and C. Orr. “Analytical Methods in Fine Particle Technology, 1997, Micromeritics Instrument Corporation" (ISBN 0-9656783-0).

[0045] The macropore volume (i.e., P 2 The value of ) is preferably determined by the volume of micropores and mesopores (i.e., P 1 Although some macropores may be useful for facilitating electrolyte access to the pore network, the benefits of the present invention are achieved substantially by containing silicon in the micropores and smaller mesopores.

[0046] Thus, according to the present invention, the total volume of macropores in the porous carbon skeleton is determined by mercury intrusion porosimetry (P 2 cm 3 / g, where P 2 is preferably up to 0.2 x P 1 , or maximum 0.1 x P 1 , or maximum 0.05 x P 1 , or maximum 0.02 x P 1 , or maximum 0.01 x P 1 , or maximum 0.005 x P 1 It has a value of

[0047] It will be understood that intrusion techniques such as gas adsorption and mercury porosimetry are only valid for determining the pore volume of pores accessible to nitrogen or mercury from the exterior of the porous carbon skeleton. The porosity values ​​(P 1 and P 2 ) should be understood to refer to the volume of open pores, i.e., pores accessible to fluids from outside the porous carbon skeleton. Completely enclosed pores that cannot be identified by nitrogen adsorption or mercury porosimetry shall not be considered in defining porosity values ​​herein. Similarly, any pore volume located within pores small enough to be below the detection limit by nitrogen adsorption shall not be considered in defining porosity values ​​herein. 1 To determine the value of This is not taken into consideration.

[0048] The porous carbon skeleton can comprise crystalline or amorphous carbon, or a mixture of amorphous and crystalline carbon. The porous carbon skeleton can be either a hard or soft carbon skeleton and can be suitably obtained by known procedures including pyrolysis of carbon-containing materials, including organic materials, resins, and polymers. Porous carbon materials can also be obtained by other processes, for example, from carbide-containing precursors.

[0049] The porous carbon skeleton preferably has an elemental composition comprising at least 90% by weight carbon, more preferably at least 95% by weight carbon, and more preferably at least 98% by weight carbon. Optionally, the porous carbon skeleton may contain small amounts of other elements, such as oxygen, nitrogen, sulfur, and hydrogen. The elemental composition of the porous carbon skeleton may be determined by conventional elemental analysis in the absence of silicon.

[0050] As used herein, the term "hard carbon" refers to a carbon atom in which the carbon atoms are primarily distributed in nanoscale polyaromatic domains. 2 It refers to a disordered carbon matrix that adopts a hybridized (three-way bond) state, in which the polyaromatic domains are cross-linked by chemical bonds, e.g., COC bonds.

[0051] Because the polycyclic aromatic domains are chemically cross-linked, the hard carbon cannot be converted to graphite at high temperatures. -1 ), hard carbons have graphite-like properties. However, the high D band (approximately 1350 cm) in the Raman spectrum -1 ), carbon is not completely graphite-like.

[0052] The term "soft carbon" as used herein also refers to carbon atoms that are primarily dispersed in polyaromatic domains with dimensions in the range of 5 nm to 200 nm. 2It refers to a disordered carbon matrix that adopts a hybridized state (three-way bonding). In contrast to hard carbon, the polyaromatic domains in soft carbon are not cross-linked by chemical bonds but are held together by intermolecular forces. That is, at high temperatures, soft carbon can be graphitized. The porous carbon skeleton preferably has at least 50% sp as measured by XPS. 2 For example, the porous carbon skeleton preferably contains 50% to 98% sp 2 Hybrid carbon, 55% to 95% sp 2 Hybrid carbon, 60%-90% sp 2 Hybrid carbon, or 70% to 85% sp 2 It may contain hybridized carbon.

[0053] A variety of different materials can be used to create suitable porous carbon skeletons. Examples of organic materials that can be used include plant biomass, including lignocellulosic materials (such as coconut shells, rice husks, and wood), and fossil carbon sources such as coal. Examples of resins and polymeric materials that form porous carbon skeletons upon pyrolysis include phenolic resins, novolac resins, pitch, melamine, polyacrylates, polystyrene, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylates, styrene, α-olefins, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the starting materials and the conditions of the pyrolysis process, a variety of different hard carbon materials are available in the art.

[0054] To increase the mesopore and micropore volume, the porous carbon framework can be subjected to a chemical or gas activation process. Suitable activation processes include contacting the pyrolyzed carbon with one or more of oxygen, steam, CO, CO2, and KOH at temperatures ranging from 600°C to 1000°C.

[0055] Mesopores can be removed by thermal or chemical means after pyrolysis or activation. They can also be obtained by known templating processes using extractable pore formers such as MgO and other colloidal or polymeric templates.

[0056] The amount of silicon in the composite particles of the present invention is selected so that the silicon occupies at least about 40% and up to about 78% of the internal pore volume of the porous carbon skeleton (in the uncharged state). The silicon preferably occupies about 50% to about 75% of the internal pore volume of the porous carbon skeleton, more preferably about 55% to 70% of the internal pore volume of the porous carbon skeleton. Within these preferred ranges, the pore volume of the porous carbon skeleton is effective to accommodate the expansion of the silicon during charging and discharging, while excess pore volume that does not contribute to the volumetric capacity of the particulate material is avoided. However, the amount of silicon is also not so great as to prevent effective lithiation due to insufficient metal ion diffusion rate or insufficient expansion volume, which results in mechanical resistance to lithiation.

[0057] As mentioned above, the amount of silicon in the porous carbon skeleton is determined by the weight ratio of silicon to the porous carbon skeleton being [0.9 × P 1 ~1.9×P 1 This can be correlated to the effective pore volume by the requirement that the silicon weight ratio be in the range of [0.9×P 1 ~1.8×P 1 ]:1, which indicates that approximately 40% to 78% of the pore volume is occupied.

[0058] Preferably, the weight ratio of silicon to porous carbon skeleton is at least 0.95×P 1 , or at least 1×P 1 , or at least 1.05 × P 1 , or at least 1.1 × P 1 , or at least 1.15 × P 1 , or at least 1.2 × P1 is.

[0059] Preferably, the weight ratio of silicon to porous carbon skeleton is at most 1.85×P 1 , or up to 1.8 x P 1 , or up to 1.75 x P 1 , or up to 1.7 x P 1 , or up to 1.65 x P 1 , or up to 1.6 x P 1 is.

[0060] For example, the weight ratio of silicon to the porous carbon skeleton is [0.95 × P 1 ~1.85×P 1 ]:1 range, or [0.95×P 1 ~1.8×P 1 ]:1 range, or [1×P 1 ~1.8×P 1 ]:1 range, or [1.05×P 1 ~1.75×P 1 ]:1 range, or [1.1×P 1 ~1.7×P 1 ]:1 range, or [1.15×P 1 ~1.7×P 1 ]:1 range, or [1.2×P 1 ~1.65×P 1 ]:1 range, or [1.25×P 1 ~1.65×P 1 ]:1 range, or [1.3×P 1 ~1.6×P 1 ]:1 range, or [1.35×P 1 ~1.6×P 1 ]:1 range, or [1.4×P 1 ~1.55×P 1 ]:1.

[0061] The composite particles preferably contain less than 10 wt% oxygen, more preferably less than 5 wt% oxygen, more preferably less than 2 wt% oxygen, based on the total weight of the composite particle. Preferably, silicon and carbon together constitute at least 90 wt% of the composite particle, more preferably at least 95 wt% of the composite particle.

[0062] The composite particles may optionally include pores that are completely enclosed by silicon to prevent electrolyte access to the voids.

[0063] Preferably at least 80% by weight of the silicon in the composite particles is located on the outer surface of the composite particles, more preferably at least 85% by weight, more preferably at least 90% by weight, more preferably at least 95% by weight, and Preferably, at least 98% by weight is located within the interior pore volume of the porous carbon skeleton.

[0064] The particulate materials of the present invention can be further characterized by their performance by thermogravimetric analysis (TGA) in air: preferably no more than 10%, more preferably no more than 5%, more preferably no more than 2% of the silicon content of the particulate material is unoxidized at 800°C when the particulate material is analyzed by TGA in air at a temperature ramp rate of 10°C / min.

[0065] The amount of unoxidized silicon is determined by derivation from TGA traces specific to these materials. A mass increase between about 300°C and 500°C corresponds to the initial oxidation of silicon to SiO2, followed by a mass loss between about 500°C and 600°C as carbon is oxidized to CO2 gas. Above about 600°C, there is a further mass increase corresponding to the continued conversion of silicon to SiO2, increasing toward an asymptotic value above 1000°C as the oxidation of silicon is completed.

[0066] For the purposes of this analysis, any mass increase above 800°C corresponds to the oxidation of silicon to SiO2, and the total mass at the completion of oxidation is assumed to be SiO2. This allows the fraction of unoxidized silicon at 800°C to be determined as a percentage of the total amount of silicon according to the following formula: Z = 1.875 × [(M f -M 800 ) / M f ]×100% (where Z is the proportion of unoxidized silicon at 800°C, and M f is the mass of the sample at the completion of oxidation, and M 800 is the mass of the sample at 800°C).

[0067] Without being bound by theory, it is understood that because the diffusion of oxygen atoms through the oxide layer is thermally activated, the temperature at which silicon oxidizes under TGA roughly corresponds to the length scale of the oxide film on the silicon. The size of the silicon nanostructures and their location limit the length scale of the oxide film thickness. Therefore, it is understood that silicon deposited in micropores and smaller mesopores oxidizes at lower temperatures than silicon deposits on particle surfaces because the oxide film present on these structures is necessarily thinner. Therefore, preferred materials according to the present invention exhibit substantially complete oxidation of silicon at low temperatures, consistent with the smaller length scale of the silicon nanostructures located in the micropores and smaller mesopores.

[0068] The total volume of micropores and optionally mesopores in the composite particles (i.e., in the presence of silicon), as measured by nitrogen gas adsorption, is preferably at most 0.15×P 1 , or maximum 0.10 x P 1 , or maximum 0.05 x P 1 , or maximum 0.02 x P 1 is.

[0069] The weight ratio of silicon to the porous carbon skeleton can be determined by elemental analysis. Elemental analysis is used to determine the weight fraction of both silicon and carbon in the composite particles. Optionally, the amounts of hydrogen, nitrogen, and oxygen can also be determined by elemental analysis. Preferably, elemental analysis is also used to determine the weight fraction of carbon (and optionally hydrogen, nitrogen, and oxygen) in the porous carbon skeleton alone. Determining the weight fraction of carbon in the porous carbon skeleton alone takes into account the possibility that the porous carbon skeleton may contain small amounts of heteroatoms within its molecular framework. By performing both measurements together, the weight fraction of silicon relative to the entire porous carbon skeleton can be reliably determined.

[0070] The silicon content is preferably determined by ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy). ICP-OES analyzers available from ThermoFisher Scientific Many ICP-OES instruments are commercially available, such as the iCAP™ 7000 series from Electron Microscopy, Inc. The carbon content (and optionally hydrogen, nitrogen, and oxygen content) in the composite particles and the porous carbon skeleton alone is preferably determined by IR absorption. A suitable instrument for determining elemental and oxygen content is the TruSpec™ Micro elemental analyzer available from LECO Corporation.

[0071] The composite particles preferably have a low total oxygen content. Oxygen may be present in the composite particles, for example, as part of the porous carbon skeleton or as an oxide layer on any exposed silicon surfaces. The total oxygen content of the composite particles is preferably less than 15 wt%, more preferably less than 10 wt%, more preferably less than 5 wt%, for example, less than 2 wt%, or less than 1 wt%, or less than 0.5 wt%.

[0072] The silicon can 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 wt. % or less, based on the total amount of silicon and dopant(s).

[0073] For the avoidance of doubt, the term "particle size" as used herein refers to the equivalent spherical diameter (esd), i.e., the diameter of a sphere having the same volume as a particle, where the volume of the particle is understood to include the volume of the pores within the particle. 50 " and "D 50 The term "particle size" refers to the median particle size on a volume basis, i.e., the diameter below which 50% by volume of the particle population lies. 10 " and "D 10 The term "particle size" refers to the 10th percentile median particle diameter on a volume basis, i.e., the diameter below which 10% by volume of the particle population lies. 90 " and "D 90 The term "particle size" refers to the 90th percentile median particle size on a volume basis, i.e., the diameter below which 90% of the particle population by volume lies.

[0074] As used herein to define particle size distribution, "D n The term "PD" is used herein to define the pore size distribution, as described above. n " should be distinguished from the term "

[0075] Particle size and size distribution can be determined by conventional laser diffraction techniques in accordance with ISO 13320:2009. Laser diffraction is based on the principle that particles scatter light at angles that vary depending on the size of the particle, and that a collection of particles produces a scattered light pattern defined by intensity and angle that can be correlated to particle size distribution. Many laser diffraction instruments are commercially available for quickly and reliably determining particle size distribution. Unless otherwise specified, particle size distribution measurements specified or reported herein are based on conventional laser diffraction instruments manufactured by Malvern Instruments. Measurements were made using a Malvern Mastersizer™ 3000 particle size analyzer. The Malvern Mastersizer™ 3000 particle size analyzer works by projecting a helium-neon gas laser beam through a transparent cell containing particles of interest suspended in an aqueous solution. Light striking the particles is scattered at angles inversely proportional to the particle size, and a photodetector array measures the light intensity at several predetermined angles. The measured intensities at various angles are processed by a computer using standard theoretical principles to determine the particle size distribution. Laser diffraction values ​​reported herein are obtained using a wet dispersion of particles in distilled water. The refractive index of the particles is assumed to be 3.50 and the refractive index of the dispersant is assumed to be 1.330. The particle size distribution is calculated using the Mie scattering model.

[0076] The composite particles are D in the range of 1 μm to 30 μm. 50 Optionally, D 50 The particle size 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. 50 The particle size may be up to 20 μm, or up to 18 μm, or up to 16 μm, or up to 14 μm, or up to 12 μm, or up to 10 μm.

[0077] For example, the composite particles may have a D in the range of 1 μm to 20 μm, or 1 μm to 18 μm, or 1 μm to 16 μm, or 2 μm to 16 μm, or 2 μm to 14 μm, or 3 μm to 12 μm, or 4 μm to 10 μm.50 Particles within these size ranges and having the porosities and pore size distributions described herein are ideally suited for use in metal-ion battery anodes because they are suitable for forming dense electrode layers that are dispersible in slurries, have structural integrity, retain capacity over repeated charge-discharge cycles, and have a uniform thickness in the conventional range of 20 μm to 50 μm.

[0078] D of composite particles 10 The particle size 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 Maintaining particle size above 0.5 μm reduces the likelihood of undesired agglomeration of submicron-sized particles, improving dispersibility of the particulate matter and improving volume retention.

[0079] D of composite particles 90 The particle size is preferably at most 50 μm, or at most 40 μm, or at most 30 μm, or at most 25 μm, or at most 20 μm. The presence of very large particles leads to uneven particle packing in the electrode active layer, which hinders the formation of a dense electrode layer, especially an electrode layer having a thickness in the range of 20 μm to 50 μm. Therefore, D 90 Preferably the particle size is up to 40 μm, and even smaller is more preferred.

[0080] The composite particles preferably have a narrow particle size distribution span. For example, the particle size distribution span (D 90 -D 10 ) / D 50 (defined as) 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 particle size distribution span, efficient packing of particles into a dense electrode layer can be more easily achieved.

[0081] The composite particles can have a spheroidal shape. As defined herein, spheroidal particles can include both spherical and spheroidal particles, and the shape of the composite particles of the present invention can be preferably defined by reference to the sphericity and aspect ratio of the particles of the present invention. Spheroidal particles have been found to be particularly suitable for dispersion in slurries without forming agglomerates. Additionally, the use of porous spheroidal particles has surprisingly been found to provide further strength improvements when compared to irregularly shaped porous particles and porous particle fragments.

[0082] The sphericity of an object is conventionally defined as the ratio of the surface area of ​​the object to the surface area of ​​a sphere, where the object and the sphere have the same volume. However, in practice, it is difficult to measure the surface area and volume of individual micron-scale particles. However, by scanning electron microscopy (SEM) and dynamic image analysis, in which the shadows cast by the particles are recorded using a digital camera, highly accurate two-dimensional projection images of micron-scale particles can be obtained. The term "sphericity" as used herein shall be understood as the ratio of the area of ​​the particle projection to the area of ​​a circle, where the particle projection and the circle have the same circumference. Thus, for an individual particle, the sphericity S is defined as follows:

number

number

[0083] As used herein, the term "spheroidal" as applied to the composite particles of the present invention shall be understood to refer to materials having an average sphericity of at least 0.70. The porous spheroidal particles of the present invention preferably have an average sphericity of at least 0.85, more preferably at least 0.90, more preferably at least 0.92, more preferably at least 0.93, more preferably at least 0.94, and more preferably at least 0.95. The porous spheroidal particles can optionally have an average sphericity of at least 0.96, or at least 0.97, or at least 0.98, or at least 0.99.

[0084] It will be understood that the circumference and area of ​​a two-dimensional particle projection image will depend on the particle orientation for any particle that is not perfectly spheroidal. However, the effect of particle orientation can be offset by reporting sphericity and aspect ratio as average values ​​obtained from multiple particles with random orientation. Many SEM instruments and dynamic image analyzers are commercially available that can quickly and reliably determine the sphericity and aspect ratio of particulate matter. Unless otherwise specified, sphericity values ​​specified or reported herein are measured using a CamSizer XT particle analyzer manufactured by Retsch Technology GmbH. The CamSizer XT is a dynamic image analyzer capable of obtaining highly accurate size and shape distributions of particulate matter in sample volumes between 100 mg and 100 g, allowing properties such as average sphericity and aspect ratio to be directly calculated using this instrument.

[0085] The composite particles of the present invention preferably have a particle size of up to 100 m 2 / g, or up to 80m 2 / g, or up to 60m 2 / g, or up to 50m 2 / g, or up to 40m 2 / g, or up to 30m 2 / g, or up to 25m 2 / g, or up to 20m 2 / g, or up to 15m 2 / g, or up to 10m 2The BET surface area is preferably at least 0.1 m / 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 onto a solid surface using the Brunauer-Emmett-Teller theory according to ISO 9277. Typically, a small BET surface area is preferred to minimize the formation of a solid electrolyte interfacial (SEI) layer on the surface of the composite particles during the first charge-discharge cycle of an anode comprising the particulate material of the present invention. However, an excessively small BET surface area can lead to unacceptably low charge rates and capacity limitations due to the inaccessibility of most of the electroactive material to metal ions in the surrounding electrolyte. For example, the BET surface area is preferably at least 0.1 m / g. 2 / g, or at least 1m 2 / g, or at least 2m 2 / g, or at least 5m 2 / g. For example, the BET surface area is 2 / g~25m 2 / g, more preferably 2m 2 / g~15m 2 / g.

[0086] The particulate materials of the present invention typically have a specific charge capacity of 1200 mAh / g to 2000 mAh / g upon initial lithiation. Preferably, the particulate materials of the present invention have a specific charge capacity of at least 1400 mAh / g upon initial lithiation.

[0087] The composite particles of the present invention are preferably prepared by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous carbon skeleton. As used herein, CVI refers to the process in which a gaseous silicon-containing precursor is thermally decomposed on a surface to produce elemental silicon and gaseous by-products on the surface. Refers to the process by which a product is formed.

[0088] 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, more commonly, as a dilute mixture with an inert carrier gas such as nitrogen or argon. For example, the silicon-containing precursor can be used in an amount ranging from 0.5% to 20% by volume, or from 1% to 10% by volume, or from 1% to 5% by volume, based on the total volume of the silicon-containing precursor and the inert carrier gas. The CVI process is preferably carried out at a total pressure of 101.3 kPa (i.e., 1 atm), with a low partial pressure of the silicon precursor, and the remaining partial pressure maintained at atmospheric pressure using an inert padding gas such as hydrogen, nitrogen, or argon. Deposition temperatures in the range of 400°C to 700°C, for example, 450°C to 550°C, or 450°C to 500°C, are used. The CVI process is suitably carried out in a fixed bed reactor, a rotary kiln, or a fluidized bed reactor (including an entrained bed reactor).

[0089] As an example of a fixed-bed reactor method, 1.8 g of particulate porous scaffold was placed on a stainless steel plate at a constant thickness of 1 mm along its length. The plate was then placed inside a 60 mm outer diameter stainless steel tube, and the gas inlet and outlet lines were placed in the hot zone of a retort furnace. The furnace tube was purged with nitrogen gas for 30 minutes at room temperature, after which the sample temperature was increased to 450-500 °C. The nitrogen gas flow rate was adjusted to ensure a gas residence time of at least 90 seconds in the furnace tube and maintained at that rate for 30 minutes. The gas supply was then switched from nitrogen to a mixture of monosilane in nitrogen at a concentration of 1.25% by volume. The monosilane charge was carried out over a 5-hour period, maintaining the reactor pressure at 101.3 kPa (1 atm). After charge completion, the gas flow rate was kept constant while nitrogen was used to purge the silane from the furnace. The furnace was purged under nitrogen for 30 minutes, and then cooled to room temperature over several hours. The atmosphere is then gradually switched to air over a period of 2 hours by switching the gas flow from nitrogen to air from a compressed air supply.

[0090] The particulate material of the present invention may optionally include a conductive carbon coating. Preferably, the conductive carbon coating is obtained by chemical vapor deposition (CVD). CVD is a methodology known in the art and involves the thermal decomposition of a volatile carbon-containing gas (e.g., ethylene) on the surface of the particulate material. Alternatively, the carbon coating may be formed by depositing a solution of a carbon-containing compound on the surface of the particulate material, followed by thermal decomposition. The conductive carbon coating has sufficient permeability to allow lithium access to the interior of the composite particle without excessive resistance so as not to degrade the rate performance of the composite particle. For example, the thickness of the carbon coating may preferably be in the range of 2 nm to 30 nm. The carbon coating may optionally be porous and / or may only partially cover the surface of the composite particle.

[0091] The carbon coating smooths out any surface imperfections and removes the remaining microporosity of the surface. The carbon coating has the advantage of further reducing the BET surface area of ​​the particulate material, thereby further reducing first cycle loss. The carbon coating also improves the surface conductivity of the composite particles, reducing the need for conductive additives in the electrode composition, and also improves the surface for the formation of a stable SEI layer, improving capacity retention during cycling.

[0092] According to the first aspect of the present invention, there are further provided particulate materials according to the following aspects 1-1 to 1-25.

[0093] Aspect 1-1: (i) the volume fraction of micropores is in the range of 0.55 to 0.85; (ii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9× P 1 ~1.8×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0094] Aspect 1-2: (i)P 1is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0095] Aspects 1-3: (i)P 1 is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0096] Aspects 1-4: (i)P 1 is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0097] Aspects 1-5: (i)P 1 is in the range of 0.5 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0098] Aspects 1-6: (i)P 1 is in the range of 0.5 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0099] Aspects 1-7: (i)P 1 is in the range of 0.5 to 0.75, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0100] Aspects 1-8: (i)P 1 is in the range of 0.5 to 0.7, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0101] Aspects 1-9: (i)P 1 is in the range of 0.5 to 0.7, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0102] Aspects 1-10: (i)P 1 is in the range of 0.5 to 0.7, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0103] Aspects 1-11: (i)P 1 is in the range of 0.45 to less than 0.6, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0104] Aspects 1-12: (i)P 1 is in the range of 0.45 to less than 0.6, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P 1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0105] Aspects 1-13: (i)P 1 is in the range of 0.45 to less than 0.6, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P1 ~1.6×P 1 ]:1, A particulate material according to a first aspect of the present invention.

[0106] Aspects 1-14: (i)P 1 is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0107] Aspects 1-15: (i)P 1 is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0108] Aspects 1-16: (i)P 1 is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0109] Aspect 1-17: (i)P 1 is in the range of 0.5 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0110] Aspect 1-18: (i)P 1 is in the range of 0.5 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0111] Aspect 1-19: (i)P 1 is in the range of 0.5 to 0.75, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0112] Aspect 1-20: (i)P 1is in the range of 0.5 to 0.7, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0113] Aspect 1-21: (i)P 1 is in the range of 0.5 to 0.7, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0114] Aspect 1-22: (i)P 1 is in the range of 0.5 to 0.7, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0115] Aspect 1-23: (i)P 1 is in the range of 0.45 to less than 0.6, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0116] Aspect 1-24: (i)P 1 is in the range of 0.45 to less than 0.6, (ii) the volume fraction of micropores is in the range of 0.55 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0117] Aspect 1-25: (i)P 1 is in the range of 0.45 to less than 0.6, (ii) the volume fraction of micropores is in the range of 0.6 to 0.75; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.5×P 1 ]:1, (iv)PD 90 The pore size is up to 10 nm. A particulate material according to a first aspect of the present invention.

[0118] Aspect 1-26: (i)P 1 is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.8×P 1]:1, (iv)PD 90 The pore size is up to 8 nm. A particulate material according to a first aspect of the present invention.

[0119] Aspect 1-27: (i)P 1 is in the range of 0.45 to 0.75, (ii) the volume fraction of micropores is in the range of 0.55 to 0.8; (iii) The weight ratio of silicon to the porous carbon skeleton in the composite particles is [1×P 1 ~1.8×P 1 ]:1, (iv)PD 90 The pore size is up to 6 nm. A particulate material according to a first aspect of the present invention.

[0120] According to the present invention, the first aspect of the present invention, which falls within the scope of the above-mentioned aspects 1-1 to 1-27, It should be understood that preferred / optional features disclosed herein with respect to embodiments should also be considered preferred / optional features of embodiments 1-1 through 1-27. Similarly, any features of dependent claims that fall within the scope of the above-mentioned embodiments 1-1 through 1-27 should be construed as if those claims are dependent on embodiments 1-1 through 1-27.

[0121] In a second aspect of the present invention, there is provided a composition comprising a particulate material according to the first aspect of the present invention and at least one other component. In particular, there is provided a composition 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 thus be used to form an active layer on an electrode.

[0122] The particulate material used to make the composition of the second aspect of the invention may have any of the features described as preferred or optional in relation to the first aspect of the invention.

[0123] The composition may be a hybrid electrode composition comprising the particulate material according to the 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. The at least one additional particulate electroactive material is most preferably graphite.

[0124] When a hybrid electrode composition, the composition preferably comprises 15% to 60% by weight, or 20% to 50% by weight, or 30% to 50% by weight of the particulate material according to the first aspect of the present invention, based on the total dry weight of the composition.

[0125] The at least one additional particulate electroactive material is suitably present in an amount of from 20% to 70% by weight, or from 25% to 65% by weight, or from 30% to 60% by weight of the at least one additional particulate electroactive material.

[0126] The at least one additional particulate electroactive material preferably has a D in the range of 10 μm to 50 μm, preferably 10 μm to 40 μm, more preferably 10 μm to 30 μm, most preferably 10 μm to 25 μm, for example 15 μm to 25 μm. 50 It has a particle size.

[0127] D of at least one additional particulate electroactive material 10 The particle size is preferably at least 5 μm, more preferably at least 6 μm, more preferably at least 7 μm, more preferably at least 8 μm, more preferably at least 9 μm, and even more preferably at least 10 μm.

[0128] D of at least one additional particulate electroactive material 90 The particle size is preferably at most 100 μm, more preferably at most 80 μm, more preferably at most 60 μm, more preferably at most 50 μm, most preferably at most 40 μm.

[0129] The at least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles, and / or hard carbon particles, wherein the graphite particles and hard carbon particles have a D in the range of 10 μm to 50 μm. 50 More preferably, the at least one additional particulate electroactive material is selected from graphite particles, wherein the graphite particles have a D in the range of 10 μm to 50 μm. 50 It has a particle size.

[0130] The composition may be a non-hybrid (i.e., "highly loaded") electrode composition that is substantially free of additional particulate electroactive material. In this context, the term "substantially free of additional particulate electroactive material" should be interpreted to mean that the composition contains less than 15 wt. %, preferably less than 10 wt. %, preferably less than 5 wt. %, preferably less than 2 wt. %, more preferably less than 1 wt. %, and more preferably less than 0.5 wt. % of any additional electroactive material (i.e., additional material capable of inserting and releasing metal ions during charging and discharging of the battery), based on the total dry weight of the composition.

[0131] Such "highly loaded" electrode compositions preferably comprise 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 invention, based on the total dry weight of the composition.

[0132] 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 can be used in accordance with the present invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, carboxymethyl cellulose (CMC), modified carboxymethyl cellulose (mCMC), sodium carboxymethyl cellulose (Na-CMC), polyvinyl alcohol (PVA), alginates and their alkali metal salts, styrene-butadiene rubber (SBR), and polyimides. The composition may contain a mixture of binders. Preferably, the binder comprises a polymer selected from polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0133] The binder may suitably be present in an amount of from 0.5% to 20% by weight, preferably from 1% to 15% by weight, preferably from 2% to 10% by weight, most preferably from 5% to 10% by weight, based on the total dry weight of the composition.

[0134] The binder may optionally 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.

[0135] The composition may optionally contain one or more conductive additives. Preferred conductive additives are non-electroactive materials that are included to improve electrical conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. The conductive additive may be suitably selected from carbon black, carbon fiber, carbon nanotubes, graphene, acetylene black, ketjen black, metal fiber, metal powder, and conductive metal oxide. Preferred conductive additives include carbon black and carbon nanotubes.

[0136] The one or more conductive additives may suitably be present in a total amount of from 0.5% to 20% by weight, preferably from 1% to 15% by weight, preferably from 2% to 10% by weight, most preferably from 5% to 10% by weight, based on the total dry weight of the composition.

[0137] In a third aspect, the present invention provides an electrode comprising a particulate material as defined with reference to the first aspect of the invention in electrical contact with a current collector. The particulate material used to make the electrode of the third aspect of the invention may have any of the features described as preferred or optional in relation to the first aspect of the invention.

[0138] The term current collector, as used herein, refers to any conductive substrate capable of conducting current to or from the electroactive particles in the composition. Examples of 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 typically have the form of a foil or mesh having a thickness of 3 μm to 500 μm. The particulate material of the present invention can be applied to one or both sides of the current collector, preferably in a thickness ranging from 10 μm to 1 mm, e.g., 20 μm to 500 μm, or 50 μm to 200 μm.

[0139] Preferably, the electrode comprises a composition as defined with reference to the second aspect of the invention in electrical contact with a current collector, the composition may have any of the features described as preferred or optional in relation to the second aspect of the invention.

[0140] The electrode of the third aspect of the present invention can be suitably prepared by combining the particulate material of the present invention (optionally in the form of a composition of the present invention) with a solvent and, optionally, one or more viscosity-adjusting 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 calendaring the electrode layer, can optionally be performed. The electrode layer suitably 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.

[0141] Alternatively, the slurry can be formed into a free-standing film or mat comprising the particulate material of the present invention, for example, by casting the slurry onto a suitable casting template, removing the solvent, and then removing the casting template. The resulting film or mat has the form of a free-standing agglomerate, which can then be adhered to a current collector by known methods.

[0142] The electrode of the third aspect of the invention can be used as the anode of a metal-ion battery. Thus, in a fourth aspect, the invention provides a rechargeable metal-ion battery comprising an anode comprising an electrode as described above, a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions, and an electrolyte between the anode and the cathode.

[0143] The metal ions are preferably lithium ions. More preferably, the rechargeable metal ion batteries of the present invention are lithium ion batteries, and the cathode active material is capable of releasing and accepting lithium ions.

[0144] The cathode active material is preferably a metal oxide composite. Examples of suitable cathode active materials include LiCoO, LiCo 0.99 Al 0.01 O2, LiNiO2, LiMnO2, LiCo 0.5 Ni0.5 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, LiNi 0.4 Co 0.3 Mn 0.3 O2 and LiNi 0.33 Co 0.33 Mn 0.34 Examples of materials that can be used as cathode current collectors include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0145] 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, a non-aqueous electrolyte, a solid electrolyte, and an inorganic solid electrolyte. Examples of non-aqueous electrolytes that can be used include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, and the like. Examples of suitable aprotic organic solvents include toluene, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, sulfolane, methylsulfolane, and 1,3-dimethyl-2-imidazolidinone.

[0146] 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 ionically dissociable groups.

[0147] Examples of inorganic solid electrolytes include nitrides, halides, and sulfides of lithium salts such as Li5NI2, Li3N, LiI, LiSiO4, Li2SiS3, Li4SiO4, LiOH, and Li3PO4.

[0148] The lithium salt is preferably soluble in the selected solvent or mixture of solvents. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO, LiBF, LiBCO, LiPF, LiCFSO, LiAsF, LiSbF, LiAlCl, CHSOLi, and CFSOLi.

[0149] When the electrolyte is a non-aqueous organic solution, the metal-ion battery preferably includes a separator inserted between the anode and the cathode. The separator is typically formed of an insulating material with high ion permeability and high mechanical strength. The separator typically has a pore size of 0.01 μm to 100 μm and a thickness of 5 μm to 300 μm. An example of a suitable electrode separator is a microporous polyethylene film.

[0150] The separator can 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.

[0151] In a fifth aspect, the present invention provides the use of a particulate material as defined with reference to the first aspect of the invention as an anode active material. Preferably, the particulate material has the form of a composition as defined with reference to the second aspect of the invention, and most preferably the composition comprises one or more additional particulate electroactive materials as defined above. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0152] The porous carbon skeletons C1 to C5 used in the following examples have the properties shown in Table 1.

[0153] [Table 1]

[0154] Example 1 - Preparation of composite particles in a fixed bed reactor Silicon-carbon composite particles were fabricated by depositing 1.8 g of a particulate porous scaffold with the properties listed in Table 1 onto a stainless steel plate at a constant thickness of 1 mm along its length. The plate was then placed inside a 60 mm outer diameter stainless steel tube, and the gas inlet and outlet lines were placed in the hot zone of a retort furnace. The furnace tube was purged with nitrogen gas at room temperature for 30 minutes, after which the sample temperature was increased to 450-500 °C. The nitrogen gas flow rate was adjusted to ensure a gas residence time of at least 90 seconds within the furnace tube and maintained at that rate for 30 minutes. The gas supply was then switched from nitrogen to a mixture of monosilane in nitrogen at a concentration of 1.25% by volume. The monosilane charge was carried out over a 5-hour period, maintaining the reactor pressure at 101.3 kPa (1 atm). After charge completion, the gas flow rate was kept constant while nitrogen was used to purge the silane from the furnace. The furnace was purged under nitrogen for 30 minutes, after which it was allowed to cool to room temperature over several hours. The atmosphere is then gradually switched to air over a period of 2 hours by switching the gas flow from nitrogen to air from a compressed air supply.

[0155] The composite material prepared according to Example 1 has the properties shown in Table 2 below.

[0156] [Table 2]

[0157] The data show that the porous carbon framework must have a carefully controlled pore size distribution to allow efficient infiltration of silicon into the micropores.

[0158] TGA analysis of sample S3 reveals that when the microporosity is too high, silicon cannot penetrate the pores of the porous carbon skeleton and instead deposits on the surface of the porous carbon skeleton. This is evidenced by the high levels of coarse silicon measured by TGA analysis. This is likely due to the initial silicon deposition rapidly blocking the open pores and preventing silane gas from accessing the interior pore space. Therefore, a minimum amount of mesoporosity is required to ensure sufficient transport of silane gas into the micropores. However, TGA analysis of sample S4 reveals that when the microporosity is too low, excessive amounts of coarse silicon are again obtained. It is likely that the micropore volume is rapidly depleted, leading to the formation of larger silicon deposits both within the mesopores and on the surface of the porous carbon skeleton.

[0159] In contrast, TGA analysis of Samples S1, S2, S5, and S6 revealed a very low content of coarse silicon, indicating that all of the silicon was essentially present in the form of fine silicon nanostructures located within the micropores and smaller mesopores. These fine silicon nanostructures have lower resistance to deformation and higher fracture resistance than the coarse silicon structures, making them more suitable for use as electroactive materials in lithium-ion batteries.

[0160] Example 2 - Preparation of composite particles in a rotary tube furnace reactor Silicon-carbon composite particles were prepared by placing 5 g of particulate porous scaffolds with the properties listed in Table 1 into a quartz tube (11.4 cm long) equipped with a spherical section. The quartz tube was then placed inside a rotary tube furnace reactor equipped with a heating zone approximately 15 cm x 20 cm (L x D), with the gas inlet and outlet lines positioned approximately 29 cm from the furnace hot zone. The quartz tube inside the furnace was rotated approximately 315° clockwise and then counterclockwise, thereby continuously moving / rotating the porous carbon. The furnace tube was purged with nitrogen gas at room temperature for 30 minutes, after which the sample temperature was increased to 450°C-500°C. The nitrogen gas flow rate was adjusted to ensure a gas residence time of at least 90 seconds in the furnace tube and maintained at that rate for 30 minutes. The gas supply was then switched from nitrogen to a mixture of monosilane in nitrogen at a concentration of 1.25% by volume. The monosilane charge is carried out over a 5-hour period, maintaining the reactor pressure at 101.3 kPa (1 atm). After the charge is complete, the gas flow rate is held constant while nitrogen is used to purge the silane from the furnace. The furnace is purged under nitrogen for 30 minutes and then cooled to room temperature over several hours. The atmosphere is then gradually switched to air over a 2-hour period by switching the gas flow from nitrogen to air from a compressed air supply.

[0161] Composites made according to Example 2 have the properties shown in Table 3 below.

[0162] [Table 3]

[0163] Example 3 - Electrode Preparation Anodes and test cells incorporating the particulate Si-C composites of Table 1 were fabricated using the following method.

[0164] Test coin cells were fabricated using a negative electrode containing the silicon-based material prepared as described above. A dispersion of Carbon Super P (conductive carbon) and CMC binder was mixed in a Thinky™ mixer. The silicon-based material was added to this mixture and mixed in the Thinky™ mixer for 30 minutes. SBR binder was then added to achieve a CMC:SBR ratio of 1:1, resulting in a slurry with a silicon-based material:CMC / SBR:conductive carbon weight ratio of 70%:16%:14%. The slurry was mixed in the Thinky™ mixer for an additional 30 minutes and then coated onto a 10 μm-thick copper substrate (current collector). The coating was dried at 50°C for 10 minutes and then further dried at 110°C for 12 hours to form an electrode with an active layer on the copper substrate.

[0165] Example 4 - Full Cell Preparation and Cycling A full coin cell was fabricated using a circular negative electrode with a radius of 0.8 cm cut from the electrode of Example 3, along with a porous polyethylene separator and a nickel manganese cobalt (NMC532) positive electrode. The positive and negative electrodes were designed to form a balanced pair so that the target capacity ratio of these electrodes was approximately 0.9. An electrolyte containing 1 M LiPF6 in a 7:3 EMC / FEC (ethyl methyl carbonate / fluoroethylene carbonate) solution containing 3 wt% vinylene carbonate was then added to the cell before sealing.

[0166] For each composite, three coin cells were fabricated.

[0167] The full coin cells were cycled as follows: The anode was lithiated by applying a constant current at a rate of C / 25 with a cutoff voltage of 4.3 V. Once the cutoff voltage was reached, a constant voltage of 4.3 V was applied until a cutoff current of C / 100 was reached. The cells were then allowed to rest in the lithiation state for 10 minutes. The anode was then delithiated at a constant current of C / 25 with a cutoff voltage of 2.75 V. The cells were then allowed to rest for 10 minutes. After this initial cycle, the anode was lithiated at a constant current of C / 2 with a cutoff voltage of 4.3 V, followed by a constant voltage of 4.3 V with a cutoff current of C / 40 and a 5-minute rest period. The anode was then delithiated at a constant current of C / 2 with a cutoff voltage of 2.75 V. This was then repeated the desired number of cycles. Each sample was charged and discharged. Capacity was tracked up to 1000 cycles, and the capacity retention (CR100, CR300, and CR500) at the 100th and 300th cycles was determined. In the case of S2, CR1000 was also determined. This data is shown in Table 4, along with the first lithiation capacity, first delithiation capacity, and first cycle loss (FCL) for each sample.

[0168] The charge (lithiation) capacity and discharge (delithiation) capacity for each cycle are calculated per unit mass of silicon-carbon composite, and the capacity retention is calculated for each discharge capacity as a percentage of the second cycle discharge capacity. The first cycle loss (FCL) is (1 - (first delithiation capacity / first lithiation capacity)) x 100%. Values ​​averaged across three coin cells for each sample are shown in Table 4.

[0169] Table 4 below shows that cells formed from materials according to the present invention have high initial capacity, consistent cycling performance, and high capacity retention. The S2 material, which has a lower crude silicon content (4.8 wt%), shows higher capacity retention at high cycle counts than the S7 material, which has a higher crude silicon content (10.1 wt%).

[0170] [Table 4]

[0171] Example 5 - Fabrication of a half cell Half-coin cells were fabricated using a 0.8 cm radius circular electrode cut from the electrode of Example 3 with a porous polyethylene separator, lithium foil as the counter electrode, and an electrolyte containing 1 M LiPF in a 1:5:14 FEC / EC / EMC (fluoroethylene carbonate / ethylene carbonate / ethyl methyl carbonate, v / v / v) solution containing 3 wt% vinylene carbonate.

[0172] These half-cells were used to measure the initial volumetric energy density (VED1), first cycle loss (FCL), and first delithiation capacity of the active layer. The relevant values ​​are shown in Table 4. The half-cells were tested as follows: A constant current of C / 25 (where "C" represents the specific capacity of the electrode in mAh, and "25" refers to 25 hours) was applied at a cutoff voltage of 10 mV to lithiate the electrode containing the porous particles. Once the cutoff voltage was reached, a constant voltage of 10 mV was applied at a cutoff current of C / 100. The cell was then allowed to rest for 1 hour in the lithiated state. The electrode was then delithiated at a constant current of C / 25 at a cutoff voltage of 1 V, and the cell was then allowed to rest for 1 hour. The cell was then lithiated a second time at a constant current of C / 25 at a cutoff voltage of 10 mV, followed by a constant voltage of 10 mV at a cutoff current of C / 100. The values ​​averaged across three cells for each sample are shown in Table 5.

[0173] [Table 5]

Claims

1. A particulate material consisting of a plurality of composite particles, the composite particles comprising: (a) a porous carbon framework containing micropores and mesopores, The micropores and the mesopores have a total pore volume measured by gas adsorption of P １ cm ３ / g, where P １ represents a natural number having a value between 0.4 and 0.75, and a porous carbon skeleton having a micropore volume ratio to the total volume of micropores and mesopores in the range of 0.5 to 0.85; (b) a plurality of nanoscale elemental silicon domains located within the pores of the porous carbon skeleton; Including, The weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P １ ~1.9 x P １ ]:1, particulate material.

2. The volume fraction of the micropores is in the range of 0.55 to 0.85, and the weight ratio of silicon to the porous carbon skeleton in the composite particles is [0.9×P １ ~1.8 x P １ ]:

1.

3. P １ 3. The particulate material of claim 1 or 2, wherein σ has a value of at least 0.42, or at least 0.45, or at least 0.47, or at least 0.

5.

4. P １ 4. A particulate material according to any one of claims 1 to 3, wherein σ has a value of at most 0.72, or at most 0.7, or at most 0.67, or at most 0.65, or at most 0.62, or at most 0.

6.

5. P １ 5. The particulate material of claim 4, wherein R has a value of less than 0.

6.

6. 6. A particulate material according to any one of claims 1 to 5, wherein the volume ratio of micropores to the total volume of micropores and mesopores is at least 0.55, or at least 0.56, or at least 0.58, or at least 0.6, or at least 0.62, or at least 0.64, or at least 0.

65.

7. 7. A particulate material according to any one of claims 1 to 6, wherein the volume ratio of the micropores to the total volume of the micropores and mesopores is at most 0.84, or at most 0.82, or at most 0.8, or at most 0.78, or at most 0.76, or at most 0.

75.

8. PD ９０ 8. A particulate material according to any one of claims 1 to 7, wherein the pore size is at most 20 nm, or at most 15 nm, or at most 12 nm, or at most 10 nm, or at most 8 nm, or at most 6 nm, or at most 5 nm.

9. A particulate material according to any one of claims 1 to 8, wherein the porous carbon skeleton has a bimodal or multimodal pore size distribution.

10. The total volume of pores having diameters in the range of more than 50 nm to 100 nm is defined as P ２ cm ３ / g, P ２ However, the maximum is 0.2 x P １ , or maximum 0.1 x P １ , or maximum 0.05 x P １ , or maximum 0.02 x P １ , or maximum 0.01 x P １ , or a maximum of 0.005 x P １ 10. The particulate material according to any one of claims 1 to 9, wherein

11. The weight ratio of silicon to carbon is at least 0.95×P １ , or at least 1×P １ , or at least 1.05×P １ , or at least 1.1 × P １ , or at least 1. 15 x P １ , or at least 1.2×P １ The particulate material according to any one of claims 1 to 10, wherein

12. The weight ratio of silicon to carbon is up to 1.85 x P １ , or up to 1.8 x P １ , or 1.75 × P １ , or up to 1.7 x P １ , or maximum 1.65 x P １ , or up to 1.6 x P １ 12. The particulate material according to any one of claims 1 to 11, wherein

13. 13. A particulate material according to any preceding claim, wherein at least some of the micropores and / or mesopores comprise voids completely surrounded by silicon.

14. 14. A particulate material according to any one of the preceding claims, wherein at least 80%, or at least 85%, or at least 90%, or at least 95%, or at least 98% by weight of the silicon in the composite particles is located in the interior pore volume of the porous carbon skeleton.

15. 15. A particulate material according to any one of claims 1 to 14, wherein when the particulate material is analysed by TGA in air at a temperature ramp rate of 10°C / min, not more than 10%, preferably not more than 5%, more preferably not more than 2% of the silicon content of the particulate material is unoxidized at 800°C.

16. The composite particles have a D in the range of 1 μm to 30 μm. ５０ A particulate material according to any one of claims 1 to 15, having a particle size.

17. The composite particles have a D of at least 2 μm, or at least 3 μm, or at least 4 μm, or at least 5 μm. ５０ 17. The particulate material of claim 16, having a particle size.

18. The composite particles have a D of at most 20 μm, or at most 18 μm, or at most 16 μm, or at most 14 μm, or at most 12 μm, or at most 10 μm. ５０ 18. The particulate material of claim 16 or 17, having a particle size.

19. The composite particles have a D of 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 A particulate material according to any one of claims 1 to 18, having a particle size.

20. The composite particles have a D of at most 50 μm, or at most 40 μm, or at most 30 μm, or at most 25 μm, or at most 20 μm. ９０ 20. The particulate material of any one of claims 1 to 19, having a particle size.

21. 21. The particulate material of any one of claims 1 to 20, wherein the composite particles have a particle size distribution span of 5 or less, or 4 or less, or 3 or less, or 2 or less, or 1.5 or less.

22. The composite particles have a maximum diameter of 100 m ２ / g, or up to 80m ２ / g, or up to 60m ２ / g, or up to 50m ２ / g, or up to 40m ２ / g, or up to 30m ２ / g, or up to 25m ２ / g, or up to 20m ２ / g, or up to 15m ２ / g, or up to 10 m ２ 22. The particulate material of any one of claims 1 to 21, having a BET surface area of ​​1 / g.

23. The composite particles are at least 0.1 m ２ / g, or at least 1 m ２ / g, or at least 2m ２ / g, or at least 5m ２ 23. The particulate material of any one of claims 1 to 22, having a BET surface area of ​​1 / g.

24. The volume of micropores and mesopores in the composite particles in the presence of silicon, as measured by nitrogen gas adsorption, is at most 0.15×P １ , or maximum 0.10 x P １ , or maximum 0.05 x P １ , or maximum 0.02 x P １ 24. The particulate material according to any one of claims 1 to 23, wherein

25. A particulate material according to any one of claims 1 to 24, wherein the composite particles are obtained by chemical vapor infiltration (CVI) of a silicon-containing precursor into the pore structure of a porous carbon skeleton.

26. A composition comprising a particulate material according to any one of claims 1 to 25 and at least one other ingredient.

27. 27. The composition of claim 26, comprising at least one additional particulate electroactive material.

28. 28. The composition of claim 27, comprising from 15% to 60%, or from 20% to 50%, or from 30% to 50% by weight of the particulate material of any one of claims 1 to 25, based on the total dry weight of the composition.

29. 29. The composition of claim 27 or 28, comprising 20% ​​to 70% by weight, or 25% to 65% by weight, or 30% to 60% by weight of the at least one additional particulate electroactive material.

30. 30. The composition of any one of claims 27 to 29, wherein the at least one additional particulate electroactive material is selected from graphite, hard carbon, silicon, tin, germanium, aluminum, and lead.

31. 27. The composition of claim 26, which is substantially free of additional particulate electroactive material.

32. 32. The composition of claim 31, comprising at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90% by weight of the particulate material of any one of claims 1 to 25, based on the total dry weight of the composition.

33. The composition of any one of claims 26 to 32, comprising a binder.

34. 34. The composition of claim 33, comprising from 0.5% to 20% by weight, or from 1% to 15% by weight, or from 2% to 10% by weight, or from 5% to 10% by weight of the binder, based on the total dry weight of the composition.

35. The composition of any one of claims 26 to 34, comprising one or more conductive additives.

36. 36. The composition of claim 35, comprising 0.5 wt % to 20 wt %, or 1 wt % to 15 wt %, or 2 wt % to 10 wt %, or 5 wt % to 10 wt %, of the one or more conductive additives, based on the total dry weight of the composition.

37. 26. An electrode comprising the particulate material of any one of claims 1 to 25 in electrical contact with a current collector.

38. 38. An electrode according to claim 37, wherein the particulate material has the form of a composition according to any one of claims 26 to 36.

39. (i) an anode comprising the electrode of claim 37 or 38; (ii) a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions; (iii) an electrolyte between the anode and the cathode; Rechargeable metal ion battery including:

40. Use of a particulate material according to any one of claims 1 to 25 as an anode active material.

41. 41. Use according to claim 40, wherein the particulate material has the form of a composition according to any one of claims 26 to 36.

Images