Electroactive composite particles

Abstract

The present invention relates to a method for preparing a composite particle comprising depositing a plurality of electroactive material domains in pores of a porous particle wherein the porous particle comprises micropores and mesopores and has a D1 particle size of at least 0.5 m and a D50 particle size in the range of 1 to 20 m.

Description

[0001] Introduction

[0002] The present invention relates to a method for preparing composite particles comprising an electroactive material deposited into pores of a porous particle backbone. The method of the present invention particularly relates to a method for preparing composite particles using a porous particle feedstock having a controlled particle size and pore size distribution. The present invention also relates to composite particles comprising a porous particle backbone and a plurality of electroactive domains located within pores of the porous particle backbone, wherein the composite particles have a controlled particle size and pore size distribution. Background Art

[0003] Lithium ion batteries (LIBs) typically comprise an anode, a cathode, and a lithium-containing electrolyte. The anode typically comprises a metal current collector having a layer of electroactive material, which is defined herein as a material capable of intercalating and releasing lithium ions during charging and discharging of the battery. When an LIB is charged, lithium ions are transported from the cathode to the anode via the electrolyte and intercalate into the electroactive material of the anode as intercalated lithium atoms. Thus, the terms "cathode" and "anode" are used herein in the sense that the battery is connected to a load such that the anode is the negative electrode. The term "battery" is used herein to refer both to a device comprising a single lithium ion battery cell and to a device comprising a plurality of interconnected lithium ion battery cells.

[0004] LIBs were developed in the 1980s and 1990s and have since found wide use in portable electronic devices. The recent development of electric or hybrid vehicles has created a large new market for LIBs, and renewable energy has further created a need for grid-connected energy storage, which the LIB market can at least partially meet. Overall, the global production of LIBs is expected to grow from approximately 290 GWh in 2018 to more than 2,000 GWh in 2028.

[0005] While the total storage capacity is increasing, there is a strong interest in improving the weight and / or volume capacity of rechargeable metal ion batteries such that the same energy storage is achieved with less battery mass and / or less battery volume. Conventional LIBs use graphite as the anode electroactive material. Graphite anodes can accommodate at most one lithium atom per six carbon atoms, resulting in a maximum theoretical specific capacity of 372 mAh / g for lithium ion batteries, while the actual capacity is slightly lower (about 340 to 360 mAh / g).

[0006] Silicon has emerged as a promising graphite alternative due to its very high lithium capacity (see, e.g., Insertion Electrode Materials for Rechargeable Lithium Batteries, Winter, M. et al., Adv. Mater. 1998, 10, issue 10). Silicon has a theoretical maximum specific capacity of approximately 3,600 mAh / g in a lithium-ion battery (based on Li 15 Si 4 ). However, such a high ratio of intercalated lithium to silicon results in a swelling of the silicon material up to 400% of its original volume. Repeated charge and discharge cycles impose significant mechanical stress on the silicon material, leading to cracking and structural damage. Additionally, charging of the anode in a LIB results in the formation of a solid electrolyte interface (SEI) layer. This SEI layer is an ion-conductive but insulating layer that is formed by the reductive decomposition of the electrolyte on the exposed electrode surface during the initial charge. In a graphite anode, this SEI layer is relatively stable during subsequent charge / discharge cycles. However, the swelling and shrinking of a silicon anode result in the cracking and delamination of the SEI layer and the exposure of fresh silicon surfaces, leading to further electrolyte decomposition, an increase in the SEI layer thickness, and irreversible lithium consumption. These degradation mechanisms together result in unacceptable electrochemical capacity loss during successive charge and discharge cycles.

[0007] The present inventors have previously reported the development of a class of electroactive materials with a composite structure in which an electroactive material (such as silicon) is deposited into the pore network of highly porous particles (such as porous carbon materials) with a carefully controlled pore size distribution. For example, WO 2020 / 095067 and WO 2020 / 128495 report that the improved electrochemical performance of these materials can be attributed to the way in which the electroactive material forms small domains on the order of a few nanometers or less in size within the pore network of the porous particles, such that the porous particles act as a scaffold for the composite particles. The fine electroactive structures are thought to have lower tolerance to elastic deformation and higher fracture resistance compared to larger electroactive structures, and thus are able to lithiate and delithiate without excessive structural stress. As a result, the electroactive material exhibits good reversible capacity retention over multiple charge-discharge cycles. Secondly, by controlling the loading of silicon within the porous carbon scaffold such that only a portion of the pore volume is occupied by silicon in the uncharged state, the unoccupied pore volume of the porous carbon scaffold can internally accommodate a significant amount of silicon swelling. The excessive swelling is restricted by the particle scaffold. Additionally, only small areas of the electroactive material surface are accessible to the electrolyte, thus substantially preventing SEI formation.

[0008] In WO 2022 / 029422, the applicant reported further progress, where control of the distribution of electroactive silicon within the pore network of the particle framework led to a further improvement in the electrochemical properties of the composite particles. Specifically, the applicant has demonstrated that when the length dimensions of the individual silicon structures in the composite particles are minimized such that a large proportion of the silicon atoms are located in the surface region of the silicon structures and a relatively smaller proportion of the silicon atoms are located inside the bulk / crude silicon structures, the electrochemical properties are optimized. The applicant has determined an optimized pore structure of the porous particle framework and a set of conditions for depositing silicon onto the porous particle framework, which can increase the proportion of this so-called "surface silicon" while also ensuring that a large total amount of silicon is incorporated into the composite particles to meet the overall volumetric energy density requirements.

[0009] There is still a need in the art for further improvement of electroactive composite particles of the above type to provide improvements in the electrochemical properties and lifespan of the material during multiple charge-discharge cycles. Summary of the Invention

[0010] In a first aspect, the present invention provides a method for preparing composite particles, the method comprising the following steps:

[0011] (a) providing a plurality of porous particles, the porous particles comprising micropores and mesopores,

[0012] wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is 0.4 to 2.0 cm 3 / g, and

[0013] wherein the porous particles have a D 1 particle size of at least 0.5 µm and a D 50 particle size in the range of 1 to 20 µm;

[0014] (b) contacting the porous particles with a precursor of an electroactive material at a temperature effective to cause deposition of a plurality of electroactive material domains within the pores of the porous particles.

[0015] Accordingly, the present invention generally relates to a method for preparing composite particles, wherein a plurality of nano-sized silicon domains are deposited into a pore network of a porous particle including micropores and mesopores by thermal decomposition of a silicon-containing precursor material. This type of deposition process is referred to as chemical vapor infiltration (CVI). Thus, the composite particles prepared according to the method of the present invention comprise: a first component in the form of a porous particle skeleton, which is derived from the porous particle provided in step (a); and a second component in the form of a plurality of nano-sized silicon domains, which are deposited in the pore structure of the porous particle skeleton in step (b). As used herein, the term "nano-sized silicon domain" refers to a nano-sized elemental silicon body having a defined maximum size by positioning silicon within the micropores and / or mesopores of a porous particle.

[0016] The method of the present invention further develops on the basis of the applicant's previous disclosures, recognizing that the presence of fine particles has a particularly adverse effect on the product properties. Previous work in the art has focused on the definition of composite particles (and the porous particle skeletons used to prepare them) in terms of their D 10 particle size, D 50 particle size, and D 90 particle size. However, the presence of fine particles and their impact on the preparation and use of composite particles of the type disclosed herein have received little attention. Even in the case of specifying the D 10 value of the particles, the fines still constitute up to 10% by volume of the total particle volume, and due to the small particle size of the fines, they account for a larger proportion in the particle number distribution and the external particle surface area.

[0017] The problems associated with the use of fine particles mainly depend on two factors: cohesiveness (or called cohesiveness) and surface area, which are related to both particle size and pore size distribution. As the particle size decreases, particle cohesion becomes an increasingly important factor. This is because as the surface area increases, attractive forces (such as van der Waals forces) increase. This is relevant during the manufacture of composite particles, especially in the case of thermal infiltration and deposition manufacturing processes where solid-gas contact behavior is a key factor, not only because excessive cohesiveness makes the handling of porous particle raw materials more difficult, but also because it has a negative impact on the uniform distribution of the particles within the reaction vessel. This in turn results in a sub-optimal distribution of the deposited electroactive material in the composite particle product.

[0018] Similarly, the presence of over-sized particles has received little attention in the art. Even in the case of specifying the D 90In the case of the value, extra-large-sized particles still constitute up to 10 volume % of the total particle volume and have a disproportionate impact on performance. It has been found that even a small amount of over-sized particles remaining in the composite particle population can significantly reduce the performance of the electrode composition. The over-sized composite particles cannot be filled efficiently, thus creating non-uniformities in the electrode layer. These non-uniformities affect the connectivity between particles, have different charging behaviors, and are more prone to cracking.

[0019] It has also been found that maintaining a tight distribution between the D 98 particle size and the D 1 particle size is important for ensuring the uniform distribution of the porous particles within the reaction vessel during the vapor deposition of the electromagnetic material onto the porous particles, ensuring both a uniform distribution of the mass of the electromagnetic material per particle and also a good distribution of the electromagnetic material within the particles, thereby avoiding excessive deposition on the outer surface of the porous particles.

[0020] The present invention specifically relates to composite particles and a method for their preparation, where the particle size distribution, total pore volume, and pore size distribution are carefully adjusted to achieve a fine electroactive structure in the form of small domains on the order of a few nanometers or less in size. The morphology of the electroactive material can be analyzed by thermogravimetric analysis (TGA). Atoms at or near the surface of the electroactive nanostructure are oxidized at lower temperatures compared to atoms in the bulk phase (Reference: Bardet et al., Phys. Chem. Chem. Phys. (2016), 18, 18201). By plotting the weight gain versus temperature, the environment of the atoms of the electroactive material in the sample can be distinguished and quantified.

[0021] As described above, WO 2022 / 029422 uses the term "surface silicon" to refer to silicon atoms in the surface region of a silicon nanostructure and the term "coarse bulk silicon" to refer to silicon atoms located inside a bulk / coarse silicon nanostructure. It has been found that optimal performance is achieved when there is a high ratio of "surface silicon" to "coarse bulk silicon". WO 2022 / 029422 determined an optimized pore structure for the porous particle framework and a set of conditions for depositing silicon onto the porous particle framework, which can increase this so-called proportion of "surface silicon", while also ensuring that a total large amount of silicon is incorporated into the composite particles to meet the overall volume energy density requirements.

[0022] The present applicant has now determined that the distribution of electroactive material between the coarse nanostructure and the fine nanostructure depends on the presence of fines. Without being bound by theory, it is believed that agglomeration of the particles creates interstitial spaces where the coarse electroactive structure can form. Elimination of fines from the porous particle feedstock correspondingly reduces the tendency for the formation of the coarse electroactive material structure. In addition, the possibility of the agglomerated particles moving during electrode fabrication or during the first charge of the electrode results in increased exposure of the silicon surface, which may oxidize and / or form a SEI layer, and / or reduce conductivity. Together, these mechanisms result in a loss of total capacity of the composite particles.

[0023] As described above, the surface area of the material is particularly sensitive to the presence of fines because the smaller particles contribute disproportionately to the surface area. Thus, small variations in the amount of fines between batches can result in large variability in the processing parameters. This means that despite using feedstock with a controlled surface area, deviations in the surface area of the composite particles after deposition of the electroactive material can occur due to variations in the contribution of the fines to the total surface area. This is in addition to any effects caused by the cohesion / agglomeration of the fine particles. Variations in the surface area of the composite particles have an impact on the further processing of the composite particles into electrodes, particularly with respect to the binder content of the electrode composition.

[0024] It has thus been found that removing fines from the porous particle feedstock provides better reproducibility during deposition of the electroactive material to form the composite particles. It also prevents cohesion and thus reduces the formation of the coarse electroactive material during deposition of the electroactive material, and correspondingly increases the proportion of the fine electroactive material structure. Removal of the fines also reduces the formation of the SEI layer and thus reduces the irreversible capacity loss that occurs during the first charge / discharge cycle, thereby increasing the recyclability of the electrodes containing the composite particles.

[0025] In a second aspect, the present invention provides a particulate material comprising a plurality of composite particles, wherein the composite particles comprise:

[0026] (a) a porous particle backbone comprising micropores and mesopores,

[0027] wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is from 0.4 to 2.0 cm 3 / g, and

[0028] (b) a plurality of nano-sized electroactive material domains located within the pores of the porous particle backbone,

[0029] wherein the composite particles have a D 1 particle size of at least 0.5 µm and a D 50 particle size in the range of 1 to 20 µm.

[0030] In a third aspect, the present invention provides a composition comprising the particulate material of the second aspect and at least one other component.

[0031] In a fourth aspect, the present invention provides an electrode comprising the particulate material of the second aspect or the composition of the third aspect.

[0032] In a fifth aspect, the present invention provides a rechargeable metal ion battery comprising the electrode of the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Shows the TGA trace of the particulate material according to the present invention, the particulate material comprising a high content level of surface silicon and a low content level of bulk coarse silicon.

[0034] Figure 2 Shows the TGA trace of the particulate material comprising a low content level of surface silicon and a high content level of bulk coarse silicon.

[0035] Figure 3 Shows the transient flow function of the sample from Example 2.

[0036] Figure 4 Shows the transient flow function of the sample from Example 3. DETAILED DESCRIPTION

[0037] The method of the first aspect of the present invention comprises the following steps:

[0038] (a) Providing a plurality of porous particles comprising micropores and mesopores,

[0039] wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is 0.4 to 2.0 cm 3 / g, and

[0040] wherein the porous particles have a D 1 particle size of at least 0.5 µm and a D 50 particle size in the range of 1 to 20 µm;

[0041] (b) Contacting the porous particles with a precursor of an electroactive material at a temperature effective to cause deposition of a plurality of electroactive material domains in the pores of the porous particles.

[0042] The porous particles serve as a skeleton for the electroactive material, which is generally deposited in the form of multiple electroactive material domains. The term "electroactive material domain" refers to a body of electroactive material having a maximum size determined by the size of the micropores and / or mesopores of the porous particles in which they are located, such as elemental silicon. Thus, the electroactive domains can be described as nano-sized electroactive domains, where the term "nano-sized" is understood to generally refer to a size less than 100 nm. However, due to the size of the micropores and mesopores, the maximum size of the electroactive material domains in any direction is less than 50 nm, and is typically significantly less than 50 nm. The domains can, for example, take the form of regular or irregular particles or bounded layers or regions of a coating.

[0043] The method of the present invention is characterized by using a porous particle feedstock having a D 1 particle size of at least 0.5 µm in combination with a carefully controlled pore volume and pore size distribution. Generally speaking, these factors ensure the obtaining of composite particles with a high content of "surface silicon" as compared to using a feedstock in which fines of the porous particles are present in the porous particle feedstock. Preferably, the D 1 particle size of the porous particles is at least 0.8 µm, or at least 1.0 µm, or at least 1.2 µm, or at least 1.4 µm, or at least 1.5 µm, or at least 1.6 µm, or at least 1.8 µm, or at least 2.0 µm, or at least 2.2 µm, or at least 2.4 µm, or at least 2.5 µm, or at least 2.6 µm, or at least 2.8 µm, or at least 3.0 µm.

[0044] Generally, the D 50 particle size of the porous particles is in the range of 1 to 20 µm. Preferably, the D 50 particle size of the porous particles is at least 1.5 µm, or at least 2 µm, or at least 2.5 µm, or at least 3 µm. Preferably, the D 50 particle size of the porous particles does not exceed 18 µm, or does not exceed 15 µm, or does not exceed 12 µm, or does not exceed 10 µm, or does not exceed 8 µm. For example, the D 50 particle size of the porous particles can be in the range of 1.5 to 18 µm, or in the range of 1.5 to 15 µm, or in the range of 2 to 12 µm, or in the range of 2 to 10 µm, or in the range of 2.5 to 8 µm, or in the range of 3 to 8 µm.

[0045] The D 90 particle size of the porous particles preferably does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 18 µm, or does not exceed 15 µm, or does not exceed 13 µm, or does not exceed 12 µm.

[0046] Preferably, D 1 has a particle size in the range of 0.8 to 5.0 µm, and D 90 has a particle size in the range of 6 to 15 µm, preferably D 1 has a particle size in the range of 1.0 to 5.0 µm, and D 90 has a particle size in the range of 7.5 to 15 µm, preferably D 1 has a particle size in the range of 1.5 to 4.5 µm, and D 90 has a particle size in the range of 9 to 15 µm, preferably where D 1 has a particle size in the range of 2 to 4 µm, and D 90 has a particle size in the range of 10 to 14 µm, preferably where D 1 has a particle size in the range of 2.5 to 3.5 µm, and D 90 has a particle size in the range of 11 to 13 µm.

[0047] The D of the porous particles 98 preferably has a particle size not exceeding 35 µm, or not exceeding 30 µm, or not exceeding 25 µm, or not exceeding 20 µm, or not exceeding 18 µm, or not exceeding 16 µm, or not exceeding 15.5 µm, or not exceeding 15 µm, or not exceeding 12 µm.

[0048] The D of the porous particles 100 preferably has a particle size not exceeding 40 µm, or not exceeding 35 µm, or not exceeding 30 µm, or not exceeding 25 µm, or not exceeding 20 µm, or not exceeding 16 µm.

[0049] Depositing the electroactive material into overly large porous particles may be less efficient because the precursor molecules must diffuse through the pore structure over a longer distance to reach the innermost pores. Depositing the electroactive material into pores closer to the particle surface may prevent the precursor molecules from accessing the innermost pores, resulting in insufficient particle filling and thus non-uniform deposition of the electroactive material among particles of different sizes. Additionally, as discussed above, the extra-large particles are also filled less efficiently, thus hindering the formation of an electrode layer with a uniform structure and composition.

[0050] Preferably, the D of the porous particles 98 particle size and D 1 the difference between the particle sizes (D 98 - D 1 ) does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 14 µm, or does not exceed 13 µm, or does not exceed 12 µm. As described above, simultaneously controlling the D 1 particle size and D 98The particle size provides a solution to problems associated with both fine particles and extra-large sized particles. In particular, by maintaining a small particle size distribution between the D 1 particle size and the D 98 particle size, the present invention provides a plurality of composite particles that can be efficiently packed in an electrode layer and also provides efficient and uniform heat penetration and deposition behavior during the manufacture of the composite particles.

[0051] Preferably, the ratio of the D 98 particle size of the porous particles to the D 1 particle size (D 98 / D 1 ) does not exceed 12, or does not exceed 10, or does not exceed 8, or does not exceed 6, or does not exceed 5.

[0052] Preferably, (D 98 - D 1 ) / D 50 does not exceed 2.2, or does not exceed 2, or does not exceed 1.9, or does not exceed 1.8, or does not exceed 1.7, or does not exceed 1.6.

[0053] Preferably, the difference (D 90 - D 1 ) between the D 90 particle size and the D 1 particle size of the porous particles does not exceed 12.0 µm, or does not exceed 10.0 µm, or does not exceed 9.0 µm, or does not exceed 8.0 µm.

[0054] Preferably, the ratio of the D 90 particle size of the porous particles to the D 1 particle size (D 90 / D 1 ) does not exceed 12.0, or does not exceed 10.0, or does not exceed 9.0, or does not exceed 8.0, or does not exceed 7.0, or does not exceed 6.0, or does not exceed 5.0.

[0055] Preferably, (D 90 - D 1 ) / D 50 does not exceed 2.2, or does not exceed 2, or does not exceed 1.9, or does not exceed 1.8, or does not exceed 1.7, or does not exceed 1.6.

[0056] The porous particles preferably have a narrow particle size distribution span. For example, the particle size distribution span (defined as (D 90 - D 10 ) / D 50 ) is preferably 3 or less, more preferably 2 or less, still more preferably 1.5 or less, and most preferably 1.2 or less. By maintaining a narrow particle size distribution span, it is possible to more easily achieve efficient packing of particles into a dense powder bed.

[0057] D of the porous particles 50 Particle size and D 1 Ratio of particle size to D 50 (D 1 ) is preferably not more than 10.0, or not more than 8.0, or not more than 7.0, or not more than 6.0, or not more than 5.0, or not more than 4.0, or not more than 3.0, or not more than 2.5. For example, D of the porous particles 50 Particle size and D 1 Ratio of particle size to D is in the range of 2.0 to 10.0, or 2.0 to 8.0, or 2.0 to 5.0, or 2.0 to 4.0.

[0058] D of the porous particles 100 Particle size and D 50 Ratio of particle size to D is preferably not more than 3, or not more than 2.5, or not more than 2.

[0059] Preferred porous particles include those in which D 1 Particle size is at least 1.0 µm and D 50 Particle size and D 1 Ratio of particle size to D is not more than 5.0, or not more than 4.0, or not more than 3.0.

[0060] Preferred porous particles further include those in which D 1 Particle size is at least 1.0 µm and D of the porous particles 90 Particle size and D 1 Ratio of particle size to D 90 (D 1 / D 1

[0061] Preferred porous particles further include those in which D 90 Particle size is at least 1.0 µm and D of the porous particles 1 Particle size and D 90 Difference between particle sizes(D 1 -D 1

[0062] Preferred porous particles further include those in which D 98 Particle size is at least 1.0 µm and D of the porous particles 1 Particle size and D 98 Ratio of particle size to D(D 1 / D

[0063] Preferred porous particles further include those in which D 1 has a particle size of at least 1.0 µm and the D of the porous particles 98 particle size and D 1 the difference between the particle sizes (D 98 -D 1 ) is not more than 15 µm, or not more than 14 µm, or not more than 13 µm, or not more than 12 µm.

[0064] Preferred porous particles further include those in which D 1 has a particle size of at least 1.0 µm and (D 98 -D 1 ) / D 50 is not more than 2, or not more than 1.9, or not more than 1.8, or not more than 1.7, or not more than 1.6.

[0065] Preferred porous particles include those in which D 1 has a particle size of at least 1.5 µm and the D 50 particle size ratio to D 1 is not more than 6.0, or not more than 5.0, or not more than 4.0, or not more than 3.0.

[0066] Preferred porous particles further include those in which D 1 has a particle size of at least 1.5 µm and the D of the porous particles 90 particle size ratio to D 1 (D 90 / D 1 ) is not more than 10.0, or not more than 9.0, or not more than 8.0, or not more than 7.0, or not more than 6.0, or not more than 5.

[0067] Preferred porous particles further include those in which D 1 has a particle size of at least 1.5 µm and the D of the porous particles 90 particle size and D 1 the difference between the particle sizes (D 90 -D 1 ) is not more than 10.0 µm, or not more than 9 µm, or not more than 8.0 µm.

[0068] Preferred porous particles further include those in which D 1 has a particle size of at least 1.5 µm and the D of the porous particles 98 particle size ratio to D 1 (D 98 / D 1 ) is not more than 12, or not more than 10, or not more than 8.

[0069] Preferred porous particles further include those in which D1 Those having a particle size of at least 1.5 µm and a D of the porous particles 98 Particle size and D 1 The difference between the particle sizes (D 98 -D 1 ) that does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 14 µm, or does not exceed 13 µm, or does not exceed 12 µm.

[0070] Preferred porous particles further include those in which D 1 has a particle size of at least 1.5 µm and (D 98 -D 1 ) / D 50 does not exceed 2, or does not exceed 1.9, or does not exceed 1.8, or does not exceed 1.7, or does not exceed 1.6.

[0071] The porous particles preferably have a positive skew in the volume-based distribution, e.g., such that the volume-based distribution is asymmetric with a longer tail on the right-hand side. A positive skew in the volume-based particle size distribution is advantageous because the natural packing factor will be higher than in the case where all particles are of the same size, thus reducing the need for calendering or other physical densification processes when forming an electrode layer from the composite particles. Preferably, D 50 particle size is less than the volume average (D[4.3]) of the particle size distribution. Preferably, the skewness of the particle size distribution (measured by a Malvern Mastersizer TM 3000 analyzer) does not exceed 5, or does not exceed 3, preferably does not exceed 2. Preferably, the skewness is at least 0.2, or at least 0.3, or at least 0.4.

[0072] The particle size distribution of the porous particles can be unimodal, bimodal or multimodal. Preferably, the particle size distribution is unimodal.

[0073] The average sphericity of the porous particles (as defined herein) can exceed 0.5. Preferably, their average sphericity is at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85. Preferably, the average sphericity of the porous particles is at least 0.90, or at least 0.92, or at least 0.93, or at least 0.94, or at least 0.95. Spherical particles are considered to contribute to the uniformity of deposition and at the same time facilitate denser packing in a batch pressure reactor and in the final product when incorporated into an electrode.

[0074] Highly accurate two-dimensional projections of micron-scale particles can be obtained by scanning electron microscopy (SEM) or by dynamic image analysis, where a digital camera is used to record the shadow of the particle projection. As used herein, the term "sphericity" should be understood as the ratio of the area of the particle projection (obtained by such imaging techniques) to the area of a circle, where the particle projection and the circle have the same perimeter. Thus, for an individual particle, the sphericity S can be defined as:

[0075]

[0076] where A m is the measured area of the particle projection, and C m is the measured perimeter of the particle projection. The average sphericity S of multiple particles as used herein av is defined as:

[0077]

[0078] where n represents the number of particles in the population. The average sphericity of the particle population is preferably calculated from two-dimensional projections of at least 50 particles.

[0079] Porous particles typically comprise a three-dimensional interconnected open pore network, the three-dimensional interconnected open pore network comprising micropores and / or mesopores and optionally a small volume of macropores. According to conventional IUPAC terminology, the term "micropore" is used herein to refer to pores with a diameter of less than 2 nm, the term "mesopore" is used herein to refer to pores with a diameter of 2 - 50 nm, and the term "macropore" is used to refer to pores with a diameter greater than 50 nm.

[0080] The volume of micropores, mesopores, and macropores in the porous particles mentioned herein and any mention of the distribution of the pore volume within the porous particles relate to the internal pore volume of the porous particles, which is used as the starting material in step (a) of the claimed method (i.e., before depositing the electroactive material into the pore volume in step (b)).

[0081] The porous particles can be characterized by the total volume of micropores and mesopores (i.e., the total pore volume in the pore diameter range of 0 to 50 nm). Typically, the porous particles contain both micropores and mesopores. However, it is not excluded that porous particles comprising micropores without mesopores or comprising mesopores without micropores can be used.

[0082] The total volume of micropores and mesopores in the porous particles is preferably at least 0.45 cm 3 / g, or at least 0.5 cm 3 / g, or at least 0.55 cm 3 / g, or at least 0.6 cm 3 / g, or at least 0.65 cm3 / g, or at least 0.7 cm 3 / g, or at least 0.75 cm 3 / g, or at least 0.8 cm 3 / g. The use of higher porosity particles can be advantageous as it enables a larger amount of electroactive material to be accommodated within the pore volume.

[0083] The internal pore volume of the porous particles is suitably limited to a value at which the increased brittleness of the particle structure outweighs the advantage of the increased pore volume for accommodating a larger amount of electroactive material. Preferably, the total volume of micropores and mesopores in the porous particles does not exceed 2.0 cm 3 / g, or does not exceed 1.8 cm 3 / g, or does not exceed 1.7 cm 3 / g, or does not exceed 1.6 cm 3 / g, or does not exceed 1.55 cm 3 / g, or does not exceed 1.5 cm 3 / g, or does not exceed 1.45 cm 3 / g, or does not exceed 1.4 cm 3 / g, or does not exceed 1.35 cm 3 / g, or does not exceed 1.3 cm 3 / g, or does not exceed 1.25 cm 3 / g, or does not exceed 1.2 cm 3 / g, or does not exceed 1.15 cm 3 / g, or does not exceed 1.1 cm 3 / g.

[0084] Preferably, the total volume of micropores and mesopores in the porous particles is in the range of 0.4 to 1.8 cm 3 / g, or 0.4 to 1.7 cm 3 / g, or 0.5 to 1.6 cm 3 / g, or 0.5 to 1.55 cm 3 / g, or 0.6 to 1.5 cm 3 / g, or 0.6 to 1.45 cm 3 / g, or 0.65 to 1.4 cm 3 / g, or 0.65 to 1.35 cm 3 / g, or 0.7 to 1.3 cm 3 / g, or 0.7 to 1.25 cm 3 / g, or 0.75 to 1.2 cm 3 / g, or 0.75 to 1.1 cm 3 / g, or 0.8 to 1.15 cm3 / g, or in the range of 0.8 to 1.1 cm 3 per gram.

[0085] As used herein, the term "particle size" refers to the equivalent spherical diameter (ESD), i.e., the diameter of a sphere having the same volume as a given particle, where the particle volume is understood to include the volume of any pores within the particle. As used herein, the term "D n particle size" and "D n particle diameter" refer to the volume median diameter at the nth percentile, i.e., the diameter at which n% of the volume of the particle population is measured to be below a certain diameter. For example, as used herein, the terms "D 50 " and "D 50 particle diameter" refer to the volume median diameter, i.e., the diameter at which 50% of the volume of the particle population is measured to be below a certain diameter.

[0086] Particle size and particle size distribution can be determined by standard laser diffraction techniques in accordance with ISO 13320:2009. Laser diffraction relies on the principle that particles will scatter light at an angle that varies according to the size of the particles, and a collection of multiple particles will produce a scattering light pattern defined by the intensity and angle that can be correlated with the particle size distribution. Many commercially available laser diffraction instruments are available for the rapid and reliable determination of particle size distribution. Unless otherwise stated, the particle size distribution measurements specified or reported herein are made using a conventional Malvern Mastersizer TM from Malvern Instruments TM 3000 particle size analyzer. The Malvern Mastersizer TM 3000 particle size analyzer operates by projecting a helium-neon gas laser beam through a transparent cell containing the particles of interest suspended in an aqueous solution. The light impinging on the particles is scattered at an angle inversely proportional to the particle size, and a photodetector array measures the intensity of the light at multiple predetermined angles, and the intensities measured at different angles are processed by a computer using standard theoretical principles to determine the particle size distribution. The laser diffraction values reported herein are obtained using a wet dispersion of particles with 5 vol% surfactant SPAN TM -40 (sorbitan monopalmitate) in 2-propanol. The particle refractive index of porous particles is considered to be 2.68, and the particle refractive index of composite particles is considered to be 3.50, and the refractive index of the dispersant is considered to be 1.378. The Mie scattering model is used to calculate the particle size distribution.

[0087] The general term "PD n"Pore diameter" as used herein refers to the pore diameter at the nth percentile of the volume based on the total volume of micropores and mesopores. For example, as used herein, the term "PD" 50 "pore diameter" refers to the pore diameter at which 50% of the measured total micropore and mesopore volume is lower than a certain pore diameter. To avoid ambiguity, for determining the PD n value, any macropore volume (pore diameter greater than 50 nm) is not considered.

[0088] The PD 50 pore diameter of the porous particles is preferably not more than 10 nm, or not more than 8 nm, or not more than 6 nm. More preferably, the PD 50 pore diameter of the porous particles is not more than 5 nm, or not more than 4 nm, or not more than 3 nm, or not more than 2.5 nm, or not more than 2 nm, or not more than 1.9 nm, or not more than 1.8 nm, or not more than 1.7 nm, or not more than 1.6 nm.

[0089] The PD 90 pore diameter of the porous particles is preferably not more than 20 nm, or not more than 15 nm, or not more than 12 nm, or not more than 10 nm, or not more than 8 nm, or not more than 6 nm, or not more than 5 nm, or not more than 4 nm. Preferably, the PD 90 pore diameter of the porous particles is at least 1.5 nm, or at least 2 nm, or at least 3 nm, or at least 3.2 nm, or at least 3.5 nm, or at least 3.8 nm, or at least 4 nm. For example, the PD 90 pore diameter of the porous particles is preferably in the range of 1.5 to 20 nm, or 2 to 20 nm, or 3.2 to 20 nm, or 3.5 to 15 nm, or 3.8 to 10 nm, or 4 to 8 nm, or 1.5 to 5 nm, or 2 to 5 nm, or 3 to 5 nm.

[0090] Based on the total volume of micropores and mesopores in the porous particles, the micropore volume fraction is preferably at least 0.35, or at least 0.4, or at least 0.45, or at least 0.5, or at least 0.55, or at least 0.6, or at least 0.61.

[0091] Based on the total volume of micropores and mesopores in the porous particles, the micropore volume fraction is preferably not more than 0.98, or not more than 0.95, or not more than 0.90, or not more than 0.85, or not more than 0.8, or not more than 0.79.

[0092] Most preferably, the micropore volume fraction can be in the range of 0.35 to 0.98, or in the range of 0.4 to 0.95, or in the range of 0.4 to 0.90, or in the range of 0.4 to 0.85, or in the range of 0.45 to 0.85, or in the range of 0.5 to 0.8, or in the range of 0.55 to 0.8, or in the range of 0.6 to 0.8, or in the range of 0.61 to 0.79, based on the total volume of micropores and mesopores in the porous particles.

[0093] In some other embodiments, the porous particles can be highly microporous, for example such that the micropore fraction is in the range of 0.7 to 0.98, or in the range of 0.7 to 0.95, or in the range of 0.8 to 0.98, or in the range of 0.35 to 0.55, or in the range of 0.35 to 0.5.

[0094] In some other embodiments, the porous particles may have a low microporosity, for example such that the micropore fraction is in the range of 0.3 to 0.6, or in the range of 0.35 to 0.55, or in the range of 0.4 to 0.5.

[0095] The pore size distribution of the porous particles may be unimodal, bimodal or multimodal. As used herein, the term "pore size distribution" relates to the distribution of pore sizes of the porous particles relative to the cumulative total internal pore volume. Bimodal or multimodal pore size distributions may be preferred because the close proximity between micropores and pores with larger diameters provides the advantage of efficient ion transport from the porous network to the electroactive material.

[0096] The quenched solid density functional theory (QSDFT) was used according to the standard method described in ISO 15901-2 and ISO 15901-3, using nitrogen adsorption at 77 K down to 0.8 × 10 -6 Relative pressure p / p 0 to determine the total volume of micropores and mesopores and the pore size distribution of micropores and mesopores. Nitrogen adsorption is a technique for characterizing the porosity and pore size distribution of a material by condensing a gas in the pores of a solid. As the pressure increases, the gas condenses first in the pores with the smallest diameter, and the pressure increases until a saturation point is reached, at which all pores are filled with liquid. The nitrogen pressure is then gradually reduced to allow the liquid to evaporate from the system. Analysis of the adsorption and desorption isotherms and the hysteresis between them enables the pore volume and pore size distribution to be determined. Instruments suitable for measuring pore volume and pore size distribution by nitrogen adsorption include the AutosorbIq Porosity Analyzer, which is available from Quantachrome Instruments.

[0097] Nitrogen adsorption is effective for measuring the pore volume and pore size distribution of pores with a maximum diameter of 50 nm, but is less reliable for measuring the pore size distribution in a wider and higher pore size range. For the purposes of the present invention, therefore, nitrogen adsorption is used only for pores with a maximum diameter of 50 nm (including 50 nm) (i.e., only for micropores and mesopores) to determine the pore volume and pore size distribution. The PD n value is also determined only relative to the total volume of micropores and mesopores.

[0098] Given the limitations of available analytical techniques, it is not possible to measure the pore volume and pore size distribution over the entire range of micropores, mesopores, and macropores using a single technique. In the case where the porous particles include macropores, the volume of pores with diameters in the range greater than 50 nm up to and including 100 nm can be measured by mercury intrusion porosimetry, and is preferably not more than 0.3 cm 3 / g, or not more than 0.2 cm 3 / g, or not more than 0.1 cm 3 / g, or not more than 0.05 cm 3 / g. Although a small fraction of macropores can be useful for facilitating the entry of electrolyte into the pore network, the advantages of the present invention are obtained substantially by accommodating electroactive material in micropores and smaller mesopores.

[0099] Any pore volume of pores with a pore diameter below 50 nm measured by mercury intrusion porosimetry is not considered (as described above, nitrogen adsorption is used to characterize mesopores and micropores). For the purposes of the present invention, the pore volume above 100 nm measured by mercury intrusion porosimetry is assumed to be the interparticle porosity and is ignored.

[0100] Mercury intrusion porosimetry is a technique for characterizing the porosity and pore size distribution of a material sample by applying different 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 size of the pores. The values obtained by mercury intrusion porosimetry reported herein are obtained according to ASTM UOP578-11, where for mercury at room temperature, the surface tension γ is taken as 480 mN / m, and the contact angle φ is taken as 140°. The density of mercury at room temperature is taken as 13.5462 g / cm 3A variety of high-precision mercury intrusion porosimetry instruments are commercially available, such as the AutoPore IV series of automated mercury porosimeters, which can be obtained from Micromeritics Instrument Corporation in the United States. For a complete overview of mercury intrusion porosimetry, reference can be made to "Analytical Methods in Fine Particle Technology" by P.A. Webb and C. Orr, 1997, Micromeritics Instrument Corporation, ISBN 0-9656783-0.

[0101] It should be understood that intrusion techniques such as gas adsorption and mercury intrusion porosimetry are only effective for determining the pore volume of pores accessible to nitrogen or mercury from the outside of the porous particles. The porosity values specified herein should be understood to refer to the volume of open pores (i.e., pores accessible to fluid from the outside of the porous particles). In this article, when determining porosity values, completely encapsulated pores that cannot be identified by nitrogen adsorption or mercury intrusion porosimetry should not be considered. Similarly, any pore volume located in pores smaller than the detection limit of nitrogen adsorption is not considered.

[0102] The BET surface area of the porous particles is preferably at least 500 m 2 / g, or at least 750 m 2 / g, or at least 1,000 m 2 / g, or at least 1,250 m 2 / g, or at least 1,500 m 2 / g. As used herein, the term "BET surface area" should be considered to refer to the surface area per unit mass calculated from the measurement results of the physical adsorption of gas molecules on the solid surface according to ISO 9277 using the Brunauer–Emmett–Teller principle. Preferably, the BET surface area of the porous particles does not exceed 4,000 m 2 / g, or does not exceed 3,500 m 2 / g, or does not exceed 3,250 m 2 / g, or does not exceed 3,000 m 2 / g, or does not exceed 2,500 m 2 / g, or does not exceed 2,000 m 2 / g. For example, the BET surface area of the porous particles can be between 500 m 2 / g and 4,000 m 2 / g, or between 750 m 2 / g and 3,500 m 2 / g, or between 1,000 m 2 / g and 3,250 m2 / g, or 1,000 m 2 / g to 3,000 m 2 / g, or 1,000 m 2 / g to 2,500 m 2 / g, or 1,000 m 2 / g to 2,000 m 2 within the range of / g.

[0103] The particle density of the porous particles is preferably at least 0.35 and preferably less than 3 g / cm 3 and more preferably less than 2 g / cm 3 and even more preferably less than 1.5 g / cm 3 and most preferably 0.35 to 1.2 g / cm 3 . As used herein, the term "particle density" refers to the "apparent particle density" measured by mercury intrusion porosimetry (i.e., the mass of the particles divided by the particle volume, where the particle volume is considered the sum of the volume of the solid material and any enclosed or blind pores ("blind pores" are pores that are too small to be measured by mercury intrusion porosimetry). Preferably, the particle density of the porous particles is at least 0.4 g / cm 3 or at least 0.45 g / cm 3 or at least 0.5 g / cm 3 or at least 0.55 g / cm 3 or at least 0.6 g / cm 3 or at least 0.65 g / cm 3 or at least 0.7 g / cm 3 . Preferably, the particle density of the porous particles does not exceed 1.15 g / cm 3 or does not exceed 1.1 g / cm 3 or does not exceed 1.05 g / cm 3 or does not exceed 1 g / cm 3 or does not exceed 0.95 g / cm 3 or does not exceed 0.9 g / cm 3 .

[0104] The tapped density of the porous particles is preferably at least 0.3 g / cm 3 or at least 0.35 g / cm 3 or at least 0.4 g / cm 3 or at least 0.5 g / cm 3 .

[0105] Preferably, the porous particles have:

[0106] (i) at 0.4 to 1.8 cm 3Total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.5 to 1.6 cm³ / g;

[0107] (ii) PD not exceeding 4 nm 50 pore diameter, and preferably PD not exceeding 10 nm 90 pore diameter;

[0108] (iii) D in the range of 1 to 20 µm 50 particle size;

[0109] (iv) D of at least 1.0 µm 1 particle size; and

[0110] (v) ratio D not exceeding 5 50 / D 1 .

[0111] More preferably, the porous particles have:

[0112] (i) Total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.5 to 1.6 cm³ / g; 3 Total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.5 to 1.6 cm³ / g;

[0113] (ii) PD not exceeding 4 nm 50 pore diameter, and preferably PD not exceeding 10 nm 90 pore diameter;

[0114] (iii) D in the range of 2 to 12 µm 50 particle size;

[0115] (iv) D of at least 1.0 µm 1 particle size; and

[0116] (v) ratio D not exceeding 4 50 / D 1 .

[0117] More preferably, the porous particles have:

[0118] (i) Total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.6 to 1.5 cm³ / g; 3 Total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.6 to 1.5 cm³ / g;

[0119] (ii) PD not exceeding 3 nm 50 pore diameter, and preferably PD not exceeding 8 nm 90 pore diameter;

[0120] (iii) D in the range of 2 to 12 µm 50 particle size;

[0121] (iv) D of at least 1.0 µm 1Particle size;

[0122] (v) A ratio D not exceeding 3 50 / D 1 .

[0123] More preferably, the porous particles have:

[0124] (i) A total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.65 to 1.4 cm 3 / g;

[0125] (ii) A PD pore diameter not exceeding 2.5 nm, and preferably a PD pore diameter not exceeding 8 nm 50 ; 90 pore diameter;

[0126] (iii) A D particle size in the range of 2 to 10 µm 50 particle size;

[0127] (iv) A D particle size of at least 1.0 µm 1 particle size; and

[0128] (v) A ratio D not exceeding 3 50 / D 1 .

[0129] Preferably, the porous particles have:

[0130] (i) A total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.4 to 1.8 cm 3 / g;

[0131] (ii) A PD pore diameter not exceeding 4 nm, and preferably a PD pore diameter not exceeding 10 nm 50 ; 90 pore diameter;

[0132] (iii) A D particle size in the range of 1 to 20 µm 50 particle size;

[0133] (iv) A D particle size of at least 1.0 µm 1 particle size;

[0134] (v) Preferably a D particle size not exceeding 16 µm 98 particle size; and

[0135] (vi) A ratio D not exceeding 10 98 / D 1 .

[0136] More preferably, the porous particles have:

[0137] (i) In the range of 0.5 to 1.6 cm 3The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 1 / g;

[0138] (ii) PDs not exceeding 4 nm 50 pore size, and preferably no more than 10 nm PD 90 Aperture;

[0139] (iii) D in the range of 2 to 12 µm 50 Particle size;

[0140] (iv) D of at least 1.0 µm 1 Particle size;

[0141] (v) preferably not more than 16 µm D 98 Particle size; and

[0142] (vi) Ratio D not exceeding 8 98 / D 1 .

[0143] More preferably, the porous particles have:

[0144] (i) 0.6 to 1.5 cm 3 The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 1 / g;

[0145] (ii) PDs not exceeding 3 nm 50 pore size, and preferably no more than 8 nm PD 90 Aperture;

[0146] (iii) D in the range of 2 to 10 µm 50 Particle size;

[0147] (iv) D of at least 1.0 µm 1 Particle size;

[0148] (v) preferably not more than 16 µm D 98 Particle size; and

[0149] (vi) Ratio D not exceeding 6 98 / D 1 .

[0150] Preferably, the porous particles have:

[0151] (i) 0.4 to 1.8 cm 3 The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 1 / g;

[0152] (ii) PDs not exceeding 4 nm 50 pore size, and preferably no more than 10 nm PD 90Pore diameter;

[0153] (iii) D in the range of 1 to 20 µm 50 Particle size;

[0154] (iv) D of at least 1.0 µm 1 Particle size;

[0155] (v) Preferably, D not exceeding 16 µm 98 Particle size; and

[0156] (vi) D not exceeding 15 µm 98 -D 1 .

[0157] More preferably, the porous particles have:

[0158] (i) The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.5 to 1.6 cm 3 / g;

[0159] (ii) PD not exceeding 4 nm 50 Pore diameter, and preferably PD not exceeding 10 nm 90 Pore diameter;

[0160] (iii) D in the range of 2 to 12 µm 50 Particle size;

[0161] (iv) D of at least 1.0 µm 1 Particle size;;

[0162] (v) Preferably, D not exceeding 16 µm 98 Particle size; and

[0163] (vi) D not exceeding 13 µm 98 -D 1 .

[0164] More preferably, the porous particles have:

[0165] (i) The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.6 to 1.5 cm 3 / g;

[0166] (ii) PD not exceeding 3 nm 50 Pore diameter, and preferably PD not exceeding 8 nm 90 Pore diameter;

[0167] (iii) D in the range of 2 to 10 µm 50 Particle size;

[0168] (iv) D of at least 1.0 µm1 Particle size;

[0169] (v) A D that is preferably not more than 16 µm 98 Particle size; and

[0170] (vi) A D that is not more than 12 µm 98 -D 1 .

[0171] More preferably, the porous particles have:

[0172] (i) A total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.7 to 1.3 cm 3 / g;

[0173] (ii) A PD that is not more than 4 nm 50 pore diameter, and preferably a PD that is not more than 8 nm 90 pore diameter;

[0174] (iii) A D in the range of 2 to 10 µm 50 particle size;

[0175] (iv) A D of at least 1.5 µm 1 particle size; and

[0176] (v) A ratio D that is preferably not more than 5 50 / D 1 .

[0177] More preferably, the porous particles have:

[0178] (i) A total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.75 to 1.2 cm 3 / g;

[0179] (ii) A PD that is not more than 3 nm 50 pore diameter, and preferably a PD that is not more than 6 nm 90 pore diameter;

[0180] (iii) A D in the range of 2 to 10 µm 50 particle size; and

[0181] (iv) A D of at least 1.8 µm 1 particle size; and

[0182] (v) A ratio D that is preferably not more than 4 50 / D 1 .

[0183] More preferably, the porous particles have:

[0184] (i) The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.8 to 1.2 cm 3 / g;

[0185] (ii) A PD 50 pore diameter not exceeding 2 nm, and preferably a PD 90 pore diameter not exceeding 5 nm;

[0186] (iii) A D 50 particle size in the range of 2.5 to 8 µm; and

[0187] (iv) A D 1 particle size of at least 2 µm; and

[0188] (v) A ratio D 50 / D 1 preferably not exceeding 3.

[0189] More preferably, the porous particles have:

[0190] (i) The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.7 to 1.3 cm 3 / g;

[0191] (ii) A PD 50 pore diameter not exceeding 4 nm, and preferably a PD 90 pore diameter not exceeding 8 nm;

[0192] (iii) A D 50 particle size in the range of 2 to 10 µm;

[0193] (iv) A D 1 particle size of at least 1.5 µm;

[0194] (v) A D 98 particle size preferably not exceeding 16 µm; and

[0195] (vi) A ratio D 98 / D 1 not exceeding 10.

[0196] Even more preferably, the porous particles have:

[0197] (i) The total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.75 to 1.2 cm 3 / g;

[0198] (ii) A PD 50 pore diameter not exceeding 3 nm, and preferably a PD 90 pore diameter not exceeding 6 nm;

[0199] (iii) D within the range of 2 to 10 µm 50 Particle size;

[0200] (iv) D of at least 1.8 µm 1 Particle size;

[0201] (v) Preferably, D not exceeding 16 µm 98 Particle size; and

[0202] (vi) Ratio D not exceeding 8 98 / D 1 .

[0203] More preferably, the porous particles have:

[0204] (i) Total pore volume of micropores and mesopores measured by nitrogen adsorption within the range of 0.8 to 1.2 cm 3 / g;

[0205] (ii) PD not exceeding 2 nm 50 Pore diameter, and preferably PD not exceeding 5 nm 90 Pore diameter;

[0206] (iii) D within the range of 2.5 to 8 µm 50 Particle size;

[0207] (iv) D of at least 2 µm 1 Particle size;

[0208] (v) Preferably, D not exceeding 16 µm 98 Particle size; and

[0209] (vi) Ratio D not exceeding 6 98 / D 1 .

[0210] Even more preferably, the porous particles have:

[0211] (i) Total pore volume of micropores and mesopores measured by nitrogen adsorption within the range of 0.7 to 1.3 cm 3 / g;

[0212] (ii) PD not exceeding 4 nm 50 Pore diameter, and preferably PD not exceeding 8 nm 90 Pore diameter;

[0213] (iii) D within the range of 2 to 10 µm 50 Particle size;

[0214] (iv) D of at least 1.5 µm 1 Particle size;

[0215] (v) D preferably not exceeding 16 µm 98 particle size; and

[0216] (Vi) (D 98 - D 1 ) / D 50 value.

[0217] More preferably, the porous particles have:

[0218] (i) a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.75 to 1.2 cm 3 / g;

[0219] (ii) a PD 50 pore diameter not exceeding 3 nm, and preferably a PD 90 pore diameter not exceeding 6 nm;

[0220] (iii) a D 50 particle size in the range of 2 to 10 µm;

[0221] (iv) a D 1 particle size of at least 1.8 µm;

[0222] (v) D preferably not exceeding 16 µm 98 particle size; and

[0223] (Vi) (D 98 - D 1 ) / D 50 value.

[0224] More preferably, the porous particles have:

[0225] (i) a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.8 to 1.2 cm 3 / g;

[0226] (ii) a PD 50 pore diameter not exceeding 2 nm, and preferably a PD 90 pore diameter not exceeding 5 nm;

[0227] (iii) a D 50 particle size in the range of 2.5 to 8 µm;

[0228] (iv) a D 1 particle size of at least 2 µm;

[0229] (v) D preferably not exceeding 16 µm 98 particle size; and

[0230] (Vi) The value of (D 98 -D 1 ) / D 50 not exceeding 1.8.

[0231] The step of providing a plurality of porous particles (step (a)) may include the following steps:

[0232] (i) Providing a population of precursors of porous particles comprising micropores and mesopores, wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is 0.4 to 2.0 cm 3 / g, and

[0233] (ii) Classifying the population of precursors of the particles to obtain the plurality of porous particles as defined herein for use in step (a).

[0234] A suitable classification device is a dynamic air classifier, such as the Alpine TTD Ultra-Fine Air Classifier from Hosokawa Micron Powder Systems.

[0235] Optionally, the removal of fine particles is carried out in a step different from the removal of oversized particles. Optionally, the oversized particles can be removed by sieving.

[0236] The flowability (ff c ) of the porous particles is preferably at least 4, preferably at least 4.5, preferably at least 5, preferably at least 6, more preferably at least 7, where ff c is defined as σ 1 / σ c , where σ 1 is the consolidation stress, and σ c is the unconfined yield strength, which is measured according to ASTM-D6773-16 using a Schulze ring shear tester (e.g., Brookfield TM powder flow tester), and where the flowability is measured at σ 1 = 5 kPa.

[0237] The flowability of the porous particles is closely related to the particle size distribution, because compared with larger particles, fine particles contribute more to the cohesiveness of the particles. Reducing the cohesiveness of the porous particles directly contributes to the improved deposition of the electroactive material in the composite particle product by ensuring the uniform distribution of the porous particles during the deposition process. The free movement of the porous particles within the CVI reactor ensures the efficient and uniform penetration of the precursor into the pores of the porous particles. It also ensures the thermal uniformity within the CVI reactor, thus ensuring the controlled and uniform deposition of the electroactive material.

[0238] The porous particles preferably contain a conductive material. The use of conductive porous particles is advantageous because the porous particles form a conductive framework within the composite particles, which facilitates the flow of electrons between the lithium atoms / ions embedded in the electroactive material and the current collector.

[0239] A preferred conductive porous particle is a particle containing or consisting of a conductive carbon-based material, which is referred to herein as a conductive porous carbon particle.

[0240] The conductive porous carbon particles preferably contain at least 80% by weight of carbon, more preferably at least 85% by weight of carbon, more preferably at least 90% by weight of carbon, more preferably at least 95% by weight of carbon, and optionally at least 98% by weight or at least 99% by weight of carbon. The ash content of the conductive porous carbon particles preferably does not exceed 0.5% by weight, more preferably does not exceed 0.4% by weight, or does not exceed 0.3% by weight, or does not exceed 0.2% by weight, or does not exceed 0.15% by weight. The carbon can be crystalline carbon or amorphous carbon, or a mixture of amorphous carbon and crystalline carbon. The porous carbon particles can be hard carbon particles or soft carbon particles. Preferably, the porous carbon particles are hard carbon particles.

[0241] As used herein, the term "hard carbon" refers to a disordered carbon matrix in which the carbon atoms are found mainly in the sp 2 hybridization state (trigonal bond) in nano-sized polyaromatic domains. The polyaromatic domains are cross-linked by chemical bonds such as C-O-C bonds. Due to the chemical cross-linking between the polyaromatic domains, hard carbon cannot be converted to graphite at high temperatures. Hard carbon has graphite-like characteristics, which are demonstrated by a large G band (~1600 cm -1 ) in the Raman spectrum. However, the carbon is not completely graphitic, which is demonstrated by an obvious D band (~1350 cm -1 ) in the Raman spectrum.

[0242] As used herein, the term "soft carbon" also refers to a disordered carbon matrix in which the carbon atoms are found mainly in the sp 2 hybridization state (trigonal bond) in polyaromatic domains in the size range of 5 to 200 nm. Compared with hard carbon, the polyaromatic domains in soft carbon are associated by intermolecular forces rather than cross-linked by chemical bonds. This means that they will be graphitized at high temperatures. The porous carbon particles preferably contain at least 50% of sp 2 hybrid carbon (measured by XPS). For example, the porous carbon particles can suitably contain 50% to 98% of sp 2 hybrid carbon, 55% to 95% of sp 2 hybrid carbon, 60% to 90% of sp 2 hybrid carbon, or 70% to 85% of sp 2Hybrid carbon.

[0243] Preferably, the ratio (I D / I G ) of the relative intensities of the D-band peak and the G-band peak of the porous carbon particles measured by Raman spectroscopy is ≤ 2.0 or ≤ 1.8. Preferably, the I D / I G of the optimized particulate porous carbon framework can be ≥ 1 or ≥ 1.05. For example, the I D / I G of the optimized particulate porous carbon framework can be in the range of 1.0 to 1.7, or in the range of 1.0 to 1.5. A higher I D / I G value indicates a higher degree of disorder in the carbon structure.

[0244] Suitable porous carbon particles can be prepared by pyrolysis using a variety of different materials. Examples of organic materials that can be used include: plant biomass, which includes lignocellulosic materials (such as coconut shells, rice husks, hardwoods and softwoods, and products derived therefrom, including bark and sawdust, etc.), and fossil carbon sources such as coal. Examples of resin and polymer materials that form porous carbon particles upon pyrolysis include: phenolic resins, novolac resins, pitch, melamine-based materials, polyacrylate-based materials, polystyrene-based materials, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and various copolymers containing monomer units of acrylate monomers, styrene monomers, α-olefins, vinylpyrrolidone, and other ethylenically unsaturated monomers. Depending on the raw materials and conditions of the pyrolysis process, various different carbon materials can be obtained in the art. Porous carbon particles of various different specifications are available from commercial suppliers.

[0245] The porous carbon particles can be subjected to a chemical or gas activation process to increase the volume of mesopores and micropores. Suitable activation processes include: contacting the pyrolytic carbon with one or more of oxygen, steam, CO, CO 2 , boric acid, and KOH at a temperature in the range of 600 to 1000 °C.

[0246] Mesopores can also be obtained by a known templating process using removable pore formers such as MgO and other colloidal or polymeric templates (which can be removed by thermal or chemical means after pyrolysis or activation).

[0247] Alternatives to the carbon-based conductive particles include porous particles comprising: titanium nitride (TiN), titanium carbide (TiC), silicon carbide (SiC), nickel oxide (NiOx), titanium silicon nitride (TiSiN), nickel nitride (Ni 3 N), molybdenum nitride (MoN), titanium oxynitride (TiO x N 1-x)、silicon oxide, silicon oxycarbide (SiOC), boron nitride (BN), or vanadium nitride (VN). Preferably, the porous particles comprise titanium nitride (TiN), silicon oxycarbide (SiOC), or boron nitride (BN).

[0248] The electroactive material is preferably deposited by chemical vapor infiltration (CVI) of a gaseous precursor of the electroactive material into the pore structure of the porous particles. As used herein, CVI refers to a process in which a gaseous precursor is thermally decomposed on a surface to form an electroactive material and gaseous by-products at the surface. Thus, the precursor of the electroactive material is preferably a gaseous precursor. The term "gaseous precursor" shall be construed herein to mean a molecule that is capable of thermally decomposing to form an electroactive material and is in the gas phase under the conditions of the deposition reaction.

[0249] The gaseous precursor in step (b) can be used in pure form (or substantially pure form), or as a mixture diluted with an inert carrier such as nitrogen or argon. Preferably, step (b) comprises: contacting the porous particles with a gas comprising a precursor of the electroactive material that is at least 30 vol%, or at least 40 vol%, or at least 50 vol%, or at least 60 vol%, or at least 70 vol%, or at least 80 vol%, or at least 90 vol%, or at least 95 vol%, or at least 97 vol%, or at least 99 vol% based on the total volume of the gas.

[0250] The electroactive material deposited in step (b) is preferably selected from silicon, tin, germanium, aluminum, and mixtures and alloys thereof. Preferably, the electroactive material deposited in step (b) is silicon.

[0251] Suitable gaseous silicon-containing precursors include: silane (SiH 4 )), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), tetrasilane (Si 4 H 10 ), methylsilane (CH 3 SiH 3 ), dimethylsilane ((CH 3 ) 2 SiH 2 ), or chlorosilanes such as trichlorosilane (HSiCl 3 ), or methylchlorosilanes such as methyltrichlorosilane (CH 3 SiCl 3 ), or dimethyldichlorosilane ((CH 3 ) 2 SiCl 2 ). Preferably, the silicon-containing precursor is selected from the group consisting of silane (SiH 4 ), disilane (Si2 H 6 )), silane (Si 3 H 8 ), disilane (Si 4 H 10 ). A particularly preferred silicon precursor is silane.

[0252] Suitable tin precursors include: bis[bis(trimethylsilyl)amino]tin(II) ([[(CH 3 ) 3 Si] 2 N] 2 Sn), tetraallyltin ((H 2 C=CHCH 2 ) 4 Sn), tetra(diethylamino)tin(IV) ([(C 2 H 5 ) 2 N] 4 Sn), tetra(dimethylamino)tin(IV) ([(CH 3 ) 2 N] 4 Sn), tetramethyltin (Sn(CH 3 ) 4 ), tetravinyltin (Sn(CH=CH 2 ) 4 ), acetylacetonatotin(II) (C 10 H 14 O 4 Sn), trimethyl(phenylethynyl)tin (C 6 H 5 C≡CSn(CH 3 ) 3 ) and trimethyl(phenyl)tin (C 6 H 5 Sn(CH 3 ) 3 ). A preferred tin precursor is tetramethyltin.

[0253] Suitable aluminum precursors include: tris(2,2,6,6-tetramethyl-3,5-heptanedionato)aluminum (Al(OCC(CH 3 ) 3 CHCOC(CH 3 ) 3 ) 3 ), trimethylaluminum ((CH 3 ) 3 Al) and tris(dimethylamino)aluminum(III) (Al(N(CH 3 ) 2 ) 3)。A preferred aluminum precursor is trimethylaluminum.

[0254] Suitable germanium precursors include: germane (GeH 4 ), hexamethyldigermane ((CH 3 ) 3 GeGe(CH 3 ) 3 ), tetramethylgermane ((CH 3 ) 4 Ge), tributylgermanium hydride ([CH 3 (CH 2 ) 3 3 GeH), triethylgermanium hydride ((C 2 H 5 ) 3 GeH) and triphenylgermanium hydride ((C 6 H 5 ) 3 GeH). A preferred germanium precursor is germane.

[0255] In the case where the precursor is a chlorine-containing compound such as a chlorosilane, the precursor is used in admixture with hydrogen, preferably at an atomic ratio of hydrogen to chlorine of at least 1:1.

[0256] Optionally, the precursor is chlorine-free. Chlorine-free means that the precursor contains less than 1 wt%, preferably less than 0.1 wt%, preferably less than 0.01 wt% of chlorine-containing compounds.

[0257] In accordance with the usual procedures for working in an inert atmosphere, the presence of oxygen in step (b) should be avoided to prevent inappropriate oxidation of the deposited electroactive material. Preferably, based on the total volume of the gases used in step (b), the oxygen content is less than 0.01% by volume, more preferably less than 0.001% by volume.

[0258] The temperature in step (b) is preferably in the range of 340 to 500 °C, or 350 to 480 °C, or 350 to 450 °C, or 350 to 420 °C, or 350 to less than 400 °C, or 355 to 395 °C, or 360 to 390 °C, or 360 to 385 °C, or 360 to 380 °C.

[0259] The pressure in step (b) is preferably in the range of 1 to 5000 kPa.

[0260] ​Optionally, the pressure in step (b) is from 20 to 500 kPa, or from 40 to 200 kPa, or from 50 to 150 kPa, or from 60 to 120 kPa, or from 80 to 100 kPa. Preferably, the pressure in step (b) is maintained not to exceed 200 kPa, or not to exceed 150 kPa, or not to exceed 120 kPa, or not to exceed 110 kPa, or not to exceed 100 kPa, or not to exceed 90 kPa, or not to exceed 80 kPa.

[0261] More preferably, the pressure in step (b) is in the range of 50 to 15000 kPa, or 100 to 10000 kPa, or 150 to 5000 kPa, or 200 to 2000 kPa, or 500 to 1800 kPa, or 800 to 1500 kPa, or 1000 to 1400 kPa.

[0262] The pressure mentioned in any step of the claimed method refers to the absolute pressure in the reaction zone, which may comprise any suitable form of reaction vessel.

[0263] The deposition of electroactive material by CVI results in the elimination of by-products, in particular by-product gases such as hydrogen. Step (b) preferably further comprises separating the by-products from the particles formed in step (b). Separation of the by-products can be achieved by flushing the reactor with an inert gas and / or by reducing the pressure to evacuate the reactor. For example, separation of the by-products from the particles formed in step (b) can be achieved by evacuating the reactor to a pressure below 100 kPa, or below 80 kPa, or below 60 kPa, or below 40 kPa, or below 20 kPa, or below 10 kPa, or below 5 kPa, or below 2 kPa, or below 1 kPa. Evacuating the reactor to a low pressure can not only effectively remove the by-products in the gas phase, but also effectively desorb any by-products that may be adsorbed on the surface of the deposited silicon.

[0264] The composite particles obtained by the method according to the invention preferably comprise at least 26% by weight of electroactive material, or at least 28% by weight of electroactive material, or at least 30% by weight of electroactive material, or at least 32% by weight of electroactive material, or at least 34% by weight of electroactive material, or at least 36% by weight of electroactive material, or at least 38% by weight of electroactive material, or at least 40% by weight of electroactive material, or at least 42% by weight of electroactive material, or at least 44% by weight of electroactive material. Preferably, the electroactive material is silicon.

[0265] The amount of electroactive material (such as silicon) in the composite particles is preferably selected such that at least 20% to 90% of the internal pore volume of the porous particles is occupied by the electroactive material after step (c). For example, the electroactive material can occupy 20% to 80%, or 25% to 75%, or 30% to 70%, or 35% to 65%, or 40% to 60%, or 45% to 55% of the internal pore volume of the porous particles. Within these preferred ranges, the remaining pore volume of the porous particles effectively accommodates the expansion of the electroactive material during charging and discharging without a large excess pore volume, which is not conducive to the volumetric capacity of the particulate particles. However, due to insufficient metal ion diffusion rate or insufficient expansion volume resulting in mechanical resistance to lithiation, the amount of electroactive material is not so high as to hinder effective lithiation.

[0266] In the case where the electroactive material is silicon, by requiring the mass ratio of silicon to the porous particles to be in the range of [0.5×P 1 to 1.9×P 1 :1, the amount of silicon in the composite particles can be related to the available pore volume in the porous particles, where P 1 is a dimensionless quantity representing the magnitude of the total pore volume (expressed in cm 3 / g) of the micropores and mesopores in the porous particles (for example, if the total volume of the micropores and mesopores of the porous particles is 1.2 cm 3 / g, then P 1 = 1.2). This relationship takes into account the density of silicon and the pore volume of the porous particles to define the weight ratio of silicon at which the occupied pore volume is approximately 20% to 82%. Preferably, the weight ratio of the silicon deposited in step (b) to the porous particles is in the range of [0.6×P 1 to 1.8×P 1 :1, or [0.7×P 1 to 1.7×P 1 :1, or [0.8×P 1 to 1.6×P 1 :1.

[0267] The amount of silicon in the composite particles can be determined by elemental analysis. Preferably, elemental analysis is used to determine the elemental composition of the individual porous particles and the composition of the composite particles.

[0268] The silicon content is preferably determined by ICP - OES (Inductively Coupled Plasma - Optical Emission Spectroscopy). A variety of ICP - OES instruments are commercially available, such as the ICP - OES analyzer of the iCAP® 7000 series (available from ThermoFisher Scientific). The carbon content (and if necessary, the hydrogen content, nitrogen content, and oxygen content) of the composite particles and the porous carbon particles themselves is preferably determined by IR absorption. A suitable instrument for determining the carbon content, hydrogen content, nitrogen content, and oxygen content is the TruSpec® Micro elemental analyzer (available from Leco Corporation).

[0269] Preferably at least 90 wt%, more preferably at least 95 wt%, and even more preferably at least 98 wt% of the electroactive material in the composite particles is located within the internal pore volume of the porous particles, such that no or very little electroactive material is located on the outer surface of the composite particles. As discussed above, the deposition of the electroactive material during the CVI process occurs on the surface of the porous particles. Given the very high internal surface area of the porous particles, the reaction kinetics of the CVI process ensure that the deposition of the electroactive material occurs almost entirely within the pores of the porous particles. The internal deposition of the electroactive material is further improved by requiring that the pressure in step (b) be maintained below 200 kPa or within the more preferred pressure range discussed above.

[0270] The method of the present invention optionally further comprises the following step:

[0271] (c) heat - treating the particles from step (b) at a temperature of at least 400 °C and in the presence of an inert gas.

[0272] The heat - treatment in step (c) is believed to promote the elimination of hydrogen and the solid - state rearrangement of atoms of the electroactive material (such as silicon), thereby reducing the density of unstable and reactive M - H bonds and promoting the formation of more thermodynamically stable M - M bonds (where M = electroactive material, such as Si, Sn, Al, Ge, etc.). This is believed to contribute to the improved stability of the electroactive material during charging and discharging, and thus to the improvement of the cycle life of the metal - ion battery containing the composite particles.

[0273] The temperature in step (c) is generally higher than the temperature in step (b). Preferably, the temperature in step (c) is at least 20 °C, or at least 40 °C, or at least 60 °C, or at least 80 °C, or at least 100 °C, or at least 120 °C, or at least 140 °C, or at least 150 °C higher than the temperature in step (b).

[0274] Step (c) is carried out in the presence of an inert gas. An inert gas herein refers to any gas that does not react under the conditions of step (c). Preferably, the inert gas is selected from nitrogen and noble gases, especially argon. Optionally, the inert gas may contain hydrogen. The inert gas may be selected from the group consisting of nitrogen, argon, helium, and combinations thereof. Step (c) may be carried out in the presence of hydrogen and a gas selected from the group consisting of nitrogen, argon, helium, and combinations thereof.

[0275] The method of the present invention optionally further comprises the following step:

[0276] (d) contacting the surface of the particles from step (b) or step (c) with a passivating agent.

[0277] In the case where the method of the present invention includes step (c), step (d) may be carried out before or after step (c).

[0278] As defined herein, a passivating agent is a compound or mixture of compounds capable of reacting with the surface of the silicon deposited in step (b) to form a modified surface. In particular, a passivating agent as defined herein is a material capable of reacting with the surface of an electroactive material to further reduce its surface energy.

[0279] Preferably, step (d) is carried out after step (c). One effect of step (c) is to reopen the pore space previously blocked or capped by the electroactive material nanostructures, such that the pore space is accessible to the passivating gas, thereby allowing for more extensive passivation of the electroactive material surface and reduction or elimination of the hydrogen-terminated electroactive material surface.

[0280] One type of passivation layer is a native oxide layer. The native oxide layer can be formed, for example, by exposing the surface of the electroactive material to a passivating agent selected from air or other oxygen-containing gases (such as water vapor or CO 2 )). The passivation layer may comprise an oxide of the formula MO x where 0 < x ≤ 2. The oxide is preferably amorphous. The formation of the native oxide layer is exothermic, so careful process control is required to prevent overheating or even combustion of the particulate material. In the case where the passivating agent is an oxygen-containing gas, step (c) may include: cooling the material formed in step (b) to a temperature below 300 °C, preferably below 200 °C, optionally below 100 °C, before contacting the surface of the electroactive material with the oxygen-containing gas.

[0281] Another type of passivation layer is a nitride layer formed, for example, by exposing the surface of the electroactive material to a passivating agent selected from ammonia or other nitrogen-containing molecules. The passivation layer may comprise a nitride of the formula MN xa nitride, where 0 < x ≤ 4 / 3. The nitride is preferably amorphous. The nitride layer can be formed by contacting the surface of the electroactive material with ammonia at a temperature in the range of 200 to 700 °C, preferably 400 to 700 °C, more preferably 400 to 600 °C. Then, the temperature can be raised to the range of 500 to 1,000 °C if necessary to form the nitride surface. Nitride passivation can be superior to oxide passivation. Since sub-stoichiometric nitrides (such as SiN x , where 0 < x ≤ 4 / 3) are conductive, the nitride passivation layer can act as a conductive network that allows for faster charging and discharging of the electroactive material. As a phosphorus analogue of ammonia, phosphine can also be used as a passivating agent.

[0282] Another type of passivation layer is, for example, an oxynitride layer formed by exposing the surface of the electroactive material to a passivating agent containing ammonia (or other nitrogen-containing molecules) and oxygen. The passivation layer can contain an electroactive material oxynitride of the formula MO x N y , where 0 < x < 2, 0 < y < 4 / 3, and 0 < (2x + 3y) ≤ 4). The oxynitride is preferably amorphous.

[0283] Another type of passivation layer is a carbide layer. The passivation layer can contain a carbide of the formula MC x , where 0 < x ≤ 1. The carbide is preferably amorphous. The carbide layer can be formed by contacting the surface of the electroactive material with a passivating agent selected from carbon-containing precursors (such as methane or ethylene) at a high temperature in the range of 250 to 700 °C. At lower temperatures, covalent bonds are formed between the surface of the electroactive material and the carbon-containing precursor, which transforms into a crystalline carbide monolayer as the temperature increases. The carbide can include silicon carbide of the formula SiCx, where 0 < x ≤ 1.

[0284] Other suitable passivating agents include: compounds containing olefin, alkyne, or carbonyl functional groups, more preferably terminal olefins, terminal alkynes, aldehyde groups, or ketone groups.

[0285] Preferred passivating agents include one or more compounds having the following formula:

[0286] (i) R 1 -CH=CH-R 1 ;

[0287] (ii) R 1 -C≡C-R 1 ; and

[0288] (iii) O=CR 1 R 1 ;

[0289] where each R1 independently represent H or an unsubstituted or substituted aliphatic or aromatic hydrocarbon group having 1 to 20 carbon atoms, or two of the R 1 groups form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring.

[0290] Particularly preferred passivating agents include one or more compounds having the following formula:

[0291] (i)CH 2 =CH-R 1 ; and

[0292] (ii)HC≡C-R 1 ;

[0293] wherein R 1 is as defined above. Preferably, R 1 is unsubstituted.

[0294] Examples of suitable passivating agents include: ethylene, propylene, 1-butene, butadiene, 1-pentene, 1,4-pentadiene, 1-hexene, 1-octene, styrene, divinylbenzene, acetylene, phenylacetylene, norbornene, norbornadiene, and bicyclo[2.2.2]oct-2-ene. Optionally, a mixture of different passivating agents can also be used.

[0295] It is believed that passivating agents containing olefinic, acetylenic or carbonyl groups undergo an insertion reaction with M-H groups (such as Si-H groups) on the silicon surface to form a covalently passivated surface resistant to air oxidation. For example, thus, the passivation reaction between the silicon surface and the passivating agent can be understood as a form of hydrosilylation, as schematically shown below.

[0296]

[0297] Other suitable passivating agents include compounds containing active hydrogen atoms bonded to oxygen, nitrogen, sulfur or phosphorus. For example, the passivating agent can be an alcohol, an amine, a thiol or a phosphine. The reaction of the group -XH with the hydride group on the electroactive material silicon surface is understood to result in the elimination of H 2 and the formation of a direct bond between X and the electroactive material surface.

[0298] Suitable passivating agents in this category include compounds having the following formula:

[0299] (iv)HX-R 2 , and

[0300] (v)HX-C(O)-R 1 ,

[0301] wherein X represents O, S, NR1 or PR 1 ; each R 1 is independently defined as above; and R 2 represents an unsubstituted or substituted aliphatic or aromatic hydrocarbon group having 1 to 20 carbon atoms, or R 1 and R 2 together form an unsubstituted or substituted ring structure containing 3 to 8 carbon atoms in the ring.

[0302] Preferably, X represents O or NH.

[0303] Preferably, R 2 represents an optionally substituted aliphatic or aromatic group having 2 to 10 carbon atoms. An amino group can also be incorporated into a 4- to 10-membered aliphatic or aromatic ring structure, such as in pyrrolidine, pyrrole, imidazole, piperazine, indole or purine.

[0304] The contact of the electroactive material with the passivating agent in step (d) can be carried out at a temperature in the range of 25 to 500 °C, preferably in the range of 50 to 450 °C, more preferably 100 to 400 °C.

[0305] The method of the present invention optionally further comprises the following step:

[0306] (e) depositing a lithium ion permeable material into the pores and / or outer surface of the composite particles from step (b), (c) or step (d).

[0307] In the case where the method of the present invention includes step (c) and / or step (d), steps (c), (d) and (e) can be carried out in any order. In the case of including step (c), step (e) is preferably carried out after step (c). In the case of including step (d), step (e) is preferably carried out after step (d). In the case of including steps (c) and (d), step (e) is preferably carried out after step (d).

[0308] Preferably, the lithium ion permeable material is a pyrolytic carbon material, and step (e) includes: combining the particles from step (b), (c) or step (d) with a pyrolytic carbon precursor; and heating the pyrolytic carbon precursor to a temperature effective to cause the deposition of a conductive pyrolytic carbon material into the pores and / or outer surface of the composite particles.

[0309] The pyrolytic carbon precursor is preferably a hydrocarbon. Suitable hydrocarbons include polycyclic hydrocarbons containing 10 to 25 carbon atoms and optionally 1 to 3 heteroatoms, optionally where the polycyclic hydrocarbons are selected from naphthalene, substituted naphthalenes (such as dihydroxynaphthalene), anthracene, tetracene, pentacene, fluorene, acenapthene, phenanthrene, fluoranthene, pyrene, chrysene, perylene, coronene, fluorenone, anthraquinone, anthrone, and their alkyl-substituted derivatives. Suitable pyrolytic carbon precursors also include bicyclic monoterpenes, optionally where the bicyclic monoterpenes are selected from camphor, borneol, eucalyptol, camphene, careen, sabinene, limonene, and pinene. Other suitable pyrolytic carbon precursors include C 2 -C 10 hydrocarbons, optionally where the hydrocarbons are selected from alkanes, alkenes, alkynes, cycloalkanes, cycloalkenes, and aromatic hydrocarbons, such as methane, ethylene, propylene, limonene, styrene, cyclohexane, cyclohexene, α-terpinene, and acetylene. Other suitable pyrolytic carbon precursors include phthalocyanine, sucrose, starch, graphene oxide, reduced graphene oxide, pyrene, perhydropyrene, 9,10-benzophenanthrene, tetracene, benzopyrene, perylene, coronene, and chrysene. A preferred carbon precursor is acetylene.

[0310] The temperature suitable for the deposition of the pyrolytic carbon material in step (e) is in the range of 300 to 800 °C, or 400 to 700 °C. For example, the temperature can be not more than 680 °C, or not more than 660 °C, or not more than 640 °C, or not more than 620 °C, or not more than 600 °C, or not more than 580 °C, or not more than 560 °C, or not more than 540 °C, or not more than 520 °C, or not more than 500 °C. The minimum temperature will depend on the type of carbon precursor used. Preferably, the temperature is at least 300 °C, or at least 350 °C, or at least 400 °C, or at least 450 °C, or at least 500 °C.

[0311] The carbon precursor used in step (e) can be used in pure form or as a mixture diluted with an inert carrier gas such as nitrogen or argon. For example, the usage amount of the carbon precursor can be in the range of 0.1 vol% to 100 vol%, or 0.5 vol% to 20 vol%, or 1 vol% to 10 vol%, or 1 vol% to 5 vol% based on the total volume of the precursor and the inert carrier gas.

[0312] In the case of depositing a pyrolytic carbon material in step (e), the same compound can serve simultaneously as the passivating agent in step (d) and the pyrolytic carbon precursor in step (e). For example, if styrene is selected as the pyrolytic carbon precursor, styrene will also serve as a passivating agent in the case where the particles from step (b) are not exposed to other passivating agents prior to contact with styrene. In this case, passivation and deposition of the conductive carbon material in some steps can be carried out simultaneously, for example, at a temperature in the range of 300 to 700 °C. Alternatively, passivation and deposition of the conductive carbon material can be carried out sequentially, using the same material as the passivating agent and the pyrolytic carbon precursor, but where step (e) is carried out at a temperature higher than the passivation in step (d) after the passivation in step (d). For example, the passivation in step (d) can be carried out at a temperature in the range of 25 °C to below 300 °C, while the deposition of pyrolytic carbon can be carried out at a temperature in the range of 300 to 700 °C. These two steps can be suitably carried out sequentially by raising the temperature while maintaining contact with the compound that serves simultaneously as the passivating agent and the pyrolytic carbon precursor. At the lower temperature (for example, in the range of 25 °C to <300 °C), passivation will be the main process. As the temperature increases (for example, up to 300 to 700 °C), deposition of pyrolytic carbon will then occur.

[0313] The method of the present invention optionally further comprises the following steps:

[0314] (f) A step of deagglomerating the particles from step (b), (c), (d) or (e) to reduce the presence of agglomerated particles.

[0315] The method of the present invention optionally further comprises the following steps:

[0316] (g) Classifying the composite particles from step (b), (c), (d), (e) or (f) such that the D 1 particle size is at least 0.5 µm.

[0317] Classification of the composite particles can be suitably carried out by dynamic air classification as described above. Alternative classification methods can be used, including hydrocyclone classification, gravity separation or other known methods.

[0318] The composite particles obtained by the method of the present invention can be characterized by their performance under thermogravimetric analysis (TGA) in air. This analytical method relies on the principle that an increase in weight is observed when the electroactive material is oxidized in air and at an elevated temperature.

[0319] As defined herein, "surface silicon" is calculated from the initial mass increment in the TGA trace from the minimum mass between 150 °C and 500 °C to the maximum mass measured in the temperature range of 550 °C to 650 °C, where the TGA is performed in air at a heating rate of 10 °C / min. This mass increment is considered to be due to the oxidation of surface silicon, thus enabling the percentage of surface silicon to be determined as the proportion of the total silicon according to the following formula:

[0320] Y = 1.875 × [(M max – M min ) / M f × 100%

[0321] where Y is the percentage of surface silicon (proportion of the total silicon in the sample), M max is the maximum mass of the sample measured in the temperature range between 550 °C and 650 °C, M min is the minimum mass of the sample above 150 °C and below 500 °C, and M f is the mass of the sample at the completion of oxidation at 1400 °C. For completeness, it should be understood that 1.875 is the molar mass ratio of SiO 2 to O 2 (i.e., the mass ratio of the SiO 2 formed to the mass increment due to the addition of oxygen). Typically, the TGA analysis is performed using a sample amount of 10 mg ± 2 mg.

[0322] It has been found that when the surface silicon determined by the above TGA method is at least 20 wt% of the total amount of silicon in the material, the reversible capacity retention rate after multiple charge / discharge cycles is significantly improved. Preferably, determined by thermogravimetric analysis (TGA), at least 22 wt%, or at least 25 wt%, at least 30 wt% of silicon, or at least 35 wt% of silicon, or at least 40 wt% of silicon, or at least 45 wt% of silicon is surface silicon.

[0323] In addition to the surface silicon content, determined by TGA, the silicon-containing composite particles obtained by the method of the present invention preferably have a low content of bulk-phase silicon. Bulk-phase silicon is defined herein as the silicon that is oxidized at temperatures above 800 °C as determined by TGA, where the TGA is performed in air at a heating rate of 10 °C / min. Thus, the bulk-phase silicon content is determined according to the following formula:

[0324] Z = 1.875 × [(M f - M 800 ) / M f × 100%

[0325] where Z is the percentage of silicon that is not oxidized at 800 °C, M800 is the mass of the sample at 800 °C, and M f is the mass of the ash at the completion of oxidation at 1400 °C. For the purposes of this analysis, it is assumed that any mass increase above 800 °C corresponds to the oxidation of silicon to SiO 2 , and the total mass at the completion of oxidation is SiO 2 .

[0326] Silicon oxidized above 800 °C is less desirable. Preferably, by TGA measurement, no more than 10 wt%, or no more than 8 wt%, or no more than 6 wt%, or no more than 5 wt%, or no more than 4 wt%, or no more than 3 wt%, or no more than 2 wt%, or no more than 1.5 wt% of the silicon is bulk-phase silicon.

[0327] Preferably, at least 30 wt% of the silicon is surface silicon and no more than 10 wt% of the silicon is bulk-phase silicon, both determined by TGA. More preferably, at least 35 wt% of the silicon is surface silicon and no more than 8 wt% of the silicon is bulk-phase silicon, both determined by TGA. More preferably, at least 40 wt% of the silicon is surface silicon and no more than 5 wt% of the silicon is bulk-phase silicon, both determined by TGA. More preferably, at least 45 wt% of the silicon is surface silicon and no more than 2 wt% of the silicon is bulk-phase silicon, both determined by TGA.

[0328] The BET surface area of the composite particles obtained by the method according to the invention is preferably no more than 100 m 2 / g, or no more than 80 m 2 / g, or no more than 60 m 2 / g, or no more than 40 m 2 / g, or no more than 30 m 2 / g, or no more than 25 m 2 / g, or no more than 20 m 2 / g, or no more than 15 m 2 / g, or no more than 10 m 2 / g, or no more than 5 m 2 / g. Generally, a low BET surface area is preferred to minimize the formation of the solid electrolyte interface (SEI) layer at the surface of the composite particles during the first charge-discharge cycle of the anode. However, an overly low BET surface area results in unacceptably low charge rates and capacities due to the inaccessibility of the bulk of the electroactive material to metal ions in the surrounding electrolyte. The BET surface area is preferably at least 0.1 m 2 / g, or at least 1 m 2 / g, or at least 2 m 2 / g, or at least 5 m 2 / g. For example, the BET surface area of the composite particles can be in the range of 0.1 to 100 m 2 / g, or 0.1 to 80 m 2 / g, or 0.5 to 60 m 2 / g, or 0.5 to 40 m 2 / g, or 1 to 30 m 2 / g, or 1 to 25 m 2 / g, or 2 to 20 m 2 / g.

[0329] The reaction process can be carried out using any reactor capable of bringing solids and gases into contact at high temperatures. The porous particles and the formed composite particles preferably exist in the reactor in the form of a stirred bed of particles.

[0330] The second aspect of the present invention provides a particulate material composite particle composed of a plurality of composite particles, wherein the composite particles include:

[0331] (a) A porous particle framework including micropores and mesopores,

[0332] wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is 0.4 to 2.0 cm 3 / g, and

[0333] (b) A plurality of nano-sized electroactive material domains located within the pores of the porous particle framework,

[0334] wherein the composite particles have a D 1 particle size of at least 0.5 µm, a D 50 particle size in the range of 1 to 20 µm, and a BET surface area of not more than 50 m 2 / g.

[0335] Preferably, the D 1 particle size of the composite particles is at least 0.8 µm, or at least 1.0 µm, or at least 1.2 µm, or at least 1.4 µm, or at least 1.5 µm, or at least 1.6 µm, or at least 1.8 µm, or at least 2.0 µm, or at least 2.2 µm, or at least 2.4 µm, or at least 2.5 µm, or at least 2.6 µm, or at least 2.8 µm, or at least 3.0 µm.

[0336] Generally, the D 50 particle size of the composite particles is in the range of 1 to 20 µm. Preferably, the D 50 particle size of the composite particles is at least 1.5 µm, or at least 2 µm, or at least 2.5 µm, or at least 3 µm. Preferably, the D 50The particle size does not exceed 18 µm, or does not exceed 15 µm, or does not exceed 12 µm, or does not exceed 10 µm, or does not exceed 8 µm. For example, the D of the composite particles 50 The particle size can be in the range of 1.5 to 18 µm, or in the range of 1.5 to 15 µm, or in the range of 2 to 12 µm, or in the range of 2 to 10 µm, or in the range of 2.5 to 8 µm, or in the range of 3 to 8 µm.

[0337] The D of the composite particles 90 The particle size of the composite particles preferably does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 12 µm.

[0338] Preferably, the D of the composite particles 1 The particle size is in the range of 1.5 to 4.5 µm, and the D 90 The particle size is in the range of 9 to 15 µm. Preferably, the D of the composite particles 1 The particle size is in the range of 2 to 4 µm, and the D 90 The particle size is in the range of 10 to 14 µm. Preferably, the D of the composite particles 1 The particle size is in the range of 2.5 to 3.5 µm, and the D 90 The particle size is in the range of 11 to 13 µm.

[0339] The D of the composite particles 98 The particle size of the composite particles preferably does not exceed 35 µm, or does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 12 µm.

[0340] The D of the composite particles 100 The particle size of the composite particles preferably does not exceed 40 µm, or does not exceed 35 µm, or does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm.

[0341] Preferably, the D of the composite particles 98 The difference (D 1 -D 98 -D 1 ) between the particle sizes does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 14 µm, or does not exceed 13 µm, or does not exceed 12 µm.

[0342] Preferably, the ratio (D 98 of the particle size to D 1 of the particle size (D 98 / D1 ) Not exceeding 12, or not exceeding 10, or not exceeding 8, or not exceeding 6, or not exceeding 5.

[0343] Preferably, the (D 98 -D 1 ) / D 50 Not exceeding 2.2, or not exceeding 2, or not exceeding 1.9, or not exceeding 1.8, or not exceeding 1.7, or not exceeding 1.6.

[0344] Preferably, the D 90 particle size and D 1 particle size difference (D 90 -D 1 ) does not exceed 12.0 µm, or does not exceed 10.0 µm, or does not exceed 9.0 µm, or does not exceed 8.0 µm.

[0345] Preferably, the ratio of the D 90 particle size to D 1 particle size (D 90 / D 1 ) does not exceed 12.0, or does not exceed 10.0, or does not exceed 9.0, or does not exceed 8.0, or does not exceed 6.0, or does not exceed 5.0.

[0346] Preferably, the (D 90 -D 1 ) / D 50 does not exceed 2.2, or does not exceed 2, or does not exceed 1.9, or does not exceed 1.8, or does not exceed 1.7, or does not exceed 1.6.

[0347] The composite particles preferably have a narrow particle size distribution span. For example, the particle size distribution span (defined as (D 90 -D 10 ) / D 50 ) is preferably 3 or less, more preferably 2 or less, and most preferably 1.5 or less. By maintaining a narrow particle size distribution span, it is possible to more easily achieve efficient filling of particles into a dense powder bed.

[0348] The ratio of the D 50 particle size to D 1 particle size is preferably not exceeding 10.0, or not exceeding 8.0, or not exceeding 7.0, or not exceeding 6.0, or not exceeding 5.0, or not exceeding 4.0, or not exceeding 3.0. For example, the ratio of the D 50 particle size to D 1 particle size is in the range of 2.0 to 10.0, or 2.0 to 8.0, or 2.0 to 5.0.

[0349] The D100 The particle size and D 50 The ratio of the particle size to D is preferably not more than 3, or not more than 2.5, or not more than 2.

[0350] Preferred composite particles include those in which D 1 The particle size is at least 1.0 µm and D 50 The ratio of the particle size to D 1 is not more than 5, or not more than 4, or not more than 3.

[0351] Preferred composite particles also include those in which D 1 The particle size is at least 1.0 µm and the D of the composite particle 90 The ratio of the particle size to D 1 The ratio of the particle size (D 90 / D 1 ) is not more than 9.0, or not more than 8.0, or not more than 7.0, or not more than 6.0, or not more than 5.0.

[0352] Preferred composite particles also include those in which D 1 The particle size is at least 1.0 µm and the D of the composite particle 90 The particle size and D 1 The difference between the particle sizes (D 90 -D 1 ) is not more than 10.0 µm, or not more than 9 µm, or not more than 8 µm.

[0353] Preferred composite particles also include those in which D 1 The particle size is at least 1.0 µm and the D of the composite particle 98 The ratio of the particle size to D 1 The ratio of the particle size (D 98 / D 1 ) is not more than 10, or not more than 8.

[0354] Preferred composite particles also include those in which D 1 The particle size is at least 1.0 µm and the D of the composite particle 98 The particle size and D 1 The difference between the particle sizes (D 98 -D 1 ) is not more than 15 µm, or not more than 14 µm, or not more than 13 µm, or not more than 12 µm.

[0355] Preferred composite particles also include those in which D 1 The particle size is at least 1.0 µm and the (D 98 -D 1 ) / D 50Those not exceeding 2, or not exceeding 1.9, or not exceeding 1.8, or not exceeding 1.7, or not exceeding 1.6.

[0356] Preferred composite particles include those in which D 1 The particle size is at least 1.5 µm and D 50 The particle size and D 1 Those with a ratio of particle sizes not exceeding 6.0, or not exceeding 5.0, or not exceeding 4.0, or not exceeding 3.0.

[0357] Preferred composite particles further include those in which D 1 The particle size is at least 1.5 µm and the D of the composite particle 90 The particle size and D 1 The ratio of the particle sizes (D 90 / D 1 ) not exceeding 10.0, or not exceeding 9.0, or not exceeding 8.0, or not exceeding 7.0, or not exceeding 6.0, or not exceeding 5.0.

[0358] Preferred composite particles further include those in which D 1 The particle size is at least 1.5 µm and the D of the composite particle 90 The particle size and D 1 The difference between the particle sizes (D 90 -D 1 ) not exceeding 10.0 µm, or not exceeding 9.0 µm, or not exceeding 8.0 µm.

[0359] Preferred composite particles further include those in which D 1 The particle size is at least 1.5 µm and the D of the composite particle 98 The particle size and D 1 The ratio of the particle sizes (D 98 / D 1 ) not exceeding 12, or not exceeding 10, or not exceeding 8.

[0360] Preferred composite particles further include those in which D 1 The particle size is at least 1.5 µm and the D of the composite particle 98 The particle size and D 1 The difference between the particle sizes (D 98 -D 1 ) not exceeding 18 µm, or not exceeding 16 µm, or not exceeding 15 µm, or not exceeding 14 µm, or not exceeding 13 µm, or not exceeding 12 µm.

[0361] Preferred composite particles further include those in which D 1 The particle size is at least 1.5 µm and the (D of the composite particle 98 -D 1 ) / D50 Those not exceeding 2, or not exceeding 1.9, or not exceeding 1.8, or not exceeding 1.7, or not exceeding 1.6.

[0362] The composite particles preferably have a positive skew in the volume-based particle size distribution. Preferably, D 50 The diameter is less than the volume-based average particle size. Preferably, the skew of the composite particle size distribution (measured by a Malvern Mastersizer TM 3000 analyzer) does not exceed 4, or does not exceed 3, or does not exceed 2, or does not exceed 1.5. Preferably, the skew is at least 0.2, or at least 0.3, or at least 0.4. The particle size distribution of the composite particles can be unimodal, bimodal or multimodal. Preferably, it is unimodal.

[0363] The average sphericity (as defined herein) of the composite particles can exceed 0.5. Preferably, their average sphericity is at least 0.55, or at least 0.6, or at least 0.65, or at least 0.7, or at least 0.75, or at least 0.8, or at least 0.85. Preferably, the average sphericity of the composite particles is at least 0.90, or at least 0.92, or at least 0.93, or at least 0.94, or at least 0.95.

[0364] The total pore volume of the micropores and mesopores in the porous particle skeleton is preferably at least 0.45 cm 3 / g, or at least 0.5 cm 3 / g, or at least 0.55 cm 3 / g, or at least 0.6 cm 3 / g, or at least 0.65 cm 3 / g, or at least 0.7 cm 3 / g, or at least 0.75 cm 3 / g, or at least 0.8 cm 3 / g. Preferably, the total pore volume of the micropores and mesopores in the porous particle skeleton does not exceed 1.8 cm 3 / g, or does not exceed 1.7 cm 3 / g, or does not exceed 1.6 cm 3 / g, or does not exceed 1.55 cm 3 / g, or does not exceed 1.5 cm 3 / g, or does not exceed 1.45 cm 3 / g, or does not exceed 1.4 cm 3 / g, or does not exceed 1.35 cm 3 / g, or does not exceed 1.3 cm 3 / g, or does not exceed 1.25 cm 3 / g, or not exceeding 1.2 cm 3 / g, or not exceeding 1.15 cm 3 / g, or not exceeding 1.1 cm 3 / g.

[0365] Preferably, the total volume of micropores and mesopores in the porous particle framework is in the range of 0.4 to 1.8 cm 3 / g, or 0.4 to 1.7 cm 3 / g, or 0.5 to 1.6 cm 3 / g, or 0.5 to 1.55 cm 3 / g, or 0.6 to 1.5 cm 3 / g, or 0.6 to 1.45 cm 3 / g, or 0.65 to 1.4 cm 3 / g, or 0.65 to 1.35 cm 3 / g, or 0.7 to 1.3 cm 3 / g, or 0.7 to 1.25 cm 3 / g, or 0.75 to 1.2 cm 3 / g, or 0.75 to 1.1 cm 3 / g, or 0.8 to 1.15 cm 3 / g, or 0.8 to 1.1 cm 3 / g.

[0366] The PD of the porous particle framework 50 The pore diameter of the porous particle framework is preferably not exceeding 10 nm, or not exceeding 8 nm, or not exceeding 6 nm, or not exceeding 5 nm, or not exceeding 4 nm, or not exceeding 3 nm, or not exceeding 2.5 nm, or not exceeding 2 nm, or not exceeding 1.9 nm, or not exceeding 1.8 nm, or not exceeding 1.7 nm, or not exceeding 1.6 nm.

[0367] The PD of the porous particle framework 90 The pore diameter of the porous particle framework is preferably not exceeding 20 nm, or not exceeding 15 nm, or not exceeding 12 nm, or not exceeding 10 nm, or not exceeding 8 nm, or not exceeding 6 nm, or not exceeding 5 nm. Preferably, the PD of the porous particle framework 90 The pore diameter is at least 3.2 nm, or at least 3.5 nm, or at least 3.8 nm, or at least 4 nm. For example, the PD of the porous particle framework 90 The pore diameter is preferably in the range of 3.2 to 20 nm, or 3.5 to 15 nm, or 3.8 to 10 nm, or 4 to 8 nm.

[0368] Based on the total volume of micropores and mesopores, the micropore volume fraction of the porous particle framework is preferably at least 0.4, or at least 0.45, or at least 0.5, or at least 0.55, or at least 0.6.

[0369] Based on the total volume of micropores and mesopores, the micropore volume fraction of the porous particle framework is preferably not more than 0.85, or not more than 0.8.

[0370] The pore size distribution of the porous particle framework can be unimodal, bimodal or multimodal.

[0371] The BET surface area of the porous particle framework can be in the range of 100 m 2 / g to 4,000 m 2 / g, or 500 m 2 / g to 4,000 m 2 / g, or 750 m 2 / g to 3,500 m 2 / g, or 1,000 m 2 / g to 3,250 m 2 / g, or 1,000 m 2 / g to 3,000 m 2 / g, or 1,000 m 2 / g to 2,500 m 2 / g, or 1,000 m 2 / g to 2,000 m 2 / g.

[0372] To avoid ambiguity, the pore volume, pore size distribution and BET surface area of the porous particle framework mentioned herein relate to the porous particle framework measured separately, i.e., the porous particle framework measured in the absence of an electroactive material or any other material occupying the pores of the porous particle framework.

[0373] The porous particle framework preferably contains a conductive material. A preferred type of conductive porous particle framework contains or consists of a conductive carbon material. The conductive porous carbon particle framework preferably contains at least 80 wt% carbon, more preferably at least 85 wt% carbon, more preferably at least 90 wt% carbon, more preferably at least 95 wt% carbon, and optionally at least 98 wt% or at least 99 wt% carbon. The carbon can be crystalline carbon or amorphous carbon, or can be a mixture of amorphous carbon and crystalline carbon. The porous carbon particle framework can be hard carbon or soft carbon.

[0374] The porous carbon particle framework can contain any of the materials described herein with respect to the porous particles used according to the first aspect of the invention.

[0375] The composite particles of the present invention can suitably be obtained by chemical vapor infiltration (CVI) of a gaseous precursor of an electroactive material into the pore structure of porous particles.

[0376] The electroactive material is preferably selected from silicon, tin, germanium, aluminum, and mixtures and alloys thereof. Preferably, the electroactive material is silicon.

[0377] The composite particles preferably contain at least 26 wt% of the electroactive material, or at least 28 wt% of the electroactive material, or at least 30 wt% of the electroactive material, or at least 32 wt% of the electroactive material, or at least 34 wt% of the electroactive material, or at least 36 wt% of the electroactive material, or at least 38 wt% of the electroactive material, or at least 40 wt% of the electroactive material, or at least 42 wt% of the electroactive material, or at least 44 wt% of the electroactive material.

[0378] The amount of the electroactive material (such as silicon) in the composite particles is preferably selected such that at least 20% and at most 90% of the internal pore volume of the porous particle skeleton is occupied by the electroactive material after step (c). For example, the electroactive material can occupy 20% to 80%, or 25% to 75%, or 30% to 70%, or 35% to 65%, or 40% to 60%, or 45% to 55% of the internal pore volume of the porous particle skeleton.

[0379] In the case where the electroactive material is silicon, by requiring the mass ratio of silicon to the porous particles to be in the range of [0.5×P 1 to 1.9×P 1 :1, the amount of silicon in the composite particles can be related to the available pore volume in the porous particles, where P 1 is a dimensionless quantity representing the magnitude of the total pore volume (expressed in cm 3 / g) of the micropores and mesopores in the porous particles (for example, if the total volume of the micropores and mesopores of the porous particles is 1.2 cm 3 / g, then P 1 =1.2). This relationship takes into account the density of silicon and the pore volume of the porous particles to define the weight ratio of silicon at which the occupied pore volume is approximately 20% to 82%. Preferably, the weight ratio of the silicon deposited in step (b) to the porous particles is in the range of [0.6×P 1 to 1.8×P 1 :1, or [0.7×P 1 to 1.7×P 1 :1, or [0.8×P 1 to 1.6×P 1 :1.

[0380] Preferably, at least 90 wt%, more preferably at least 95 wt%, even more preferably at least 98 wt% of the electroactive material in the composite particles is located within the internal pore volume of the porous particle skeleton.

[0381] Preferably, the electroactive material is silicon, and as determined by TGA according to the above method, at least 22 wt%, or at least 25 wt%, at least 30 wt%, or at least 35 wt%, or at least 40 wt%, or at least 45 wt% of the silicon is surface silicon.

[0382] Preferably, the electroactive material is silicon, and as determined by TGA according to the above method, no more than 10 wt%, or no more than 8 wt%, or no more than 6 wt%, or no more than 5 wt%, or no more than 4 wt%, or no more than 3 wt%, or no more than 2 wt%, or no more than 1.5 wt% of the silicon is bulk-phase silicon.

[0383] Preferably, at least 30 wt% of the silicon is surface silicon and no more than 10 wt% of the silicon is bulk-phase silicon, both determined by TGA. More preferably, at least 35 wt% of the silicon is surface silicon and no more than 8 wt% of the silicon is bulk-phase silicon, both determined by TGA. More preferably, at least 40 wt% of the silicon is surface silicon and no more than 5 wt% of the silicon is bulk-phase silicon, both determined by TGA. More preferably, at least 45 wt% of the silicon is surface silicon and no more than 2 wt% of the silicon is bulk-phase silicon, both determined by TGA.

[0384] The BET surface area of the composite particles is preferably no more than 100 m 2 / g, or no more than 80 m 2 / g, or no more than 60 m 2 / g, or no more than 50 m 2 / g, or no more than 40 m 2 / g, or no more than 30 m 2 / g, or no more than 25 m 2 / g, or no more than 20 m 2 / g, or no more than 15 m 2 / g, or no more than 10 m 2 / g, or no more than 5 m 2 / g. Generally, a low BET surface area is preferred to minimize the formation of the solid electrolyte interface (SEI) layer at the surface of the composite particles during the first charge-discharge cycle of the anode. However, an overly low BET surface area results in unacceptably low charge rates and capacities due to the inaccessibility of the bulk phase of the electroactive material to metal ions in the surrounding electrolyte. The BET surface area is preferably at least 0.1 m 2 / g, or at least 1 m2 / g, or at least 2 m 2 / g, or at least 5 m 2 / g. For example, the BET surface area of the composite particles can be in the range of 0.1 to 100 m 2 / g, or 0.1 to 80 m 2 / g, or 0.5 to 60 m 2 / g, or 0.5 to 40 m 2 / g, or 1 to 30 m 2 / g, or 1 to 25 m 2 / g, or 2 to 20 m 2 / g.

[0385] The total pore volume of the gas-accessible micropores and mesopores of the composite particles is preferably not more than 0.1 cm 3 / g, or not more than 0.05 cm 3 / g, or not more than 0.02 cm 3 / g, or not more than 0.01 cm 3 / g, or not more than 0.008 cm 3 / g.

[0386] The composite particles of the present invention may include a passivation layer on the surface of the nanostructured electroactive material domain, and / or a lithium-permeable material (preferably a pyrolytic carbon material) deposited into the pores and / or outer surface of the particles. Methods suitable for forming the passivation layer and depositing the lithium-permeable material are described above.

[0387] Preferably, the composite particles are non-agglomerated and non-aggregated particles. As used herein, the term "aggregated" refers to particles that have grown together and / or are connected together by covalent bonds during their manufacture. Agglomerates refer to a cluster of primary particles or aggregates that are loosely bound together, for example, by van der Waals interactions or hydrogen bonds. Agglomerates can be easily broken into aggregates or primary particles by conventional kneading and dispersion processes. However, aggregates are bound by more durable bonding interactions and cannot be easily broken into primary particles. The presence of porous particles in the form of aggregates, agglomerates or discrete particles can be visualized, for example, by means of conventional scanning electron microscopy (SEM).

[0388] The flowability (ff c ,) of the composite particles is preferably at least 4, preferably at least 4.5, preferably at least 5, preferably at least 6, more preferably at least 7, where ff c is defined as σ 1 / σ c , where σ 1 is the consolidation stress, and σ cis the unrestricted yield strength, which is measured using a Schulze ring shear tester (e.g., Brookfield TM powder flow tester) according to ASTM-D6773-16, and wherein the flowability is measured at σ 1 = 5 kPa.

[0389] The flowability of the composite particles is an important factor in electrode coating manufacture because electrode materials with excessive adhesiveness have a significant impact on the ease of preparing a high-quality, uniform electrode coating from a slurry on a current collector. If the powder is adhesive and does not flow easily, an uneven and poor coating may result. Compared to comparative materials, the composite particles of the present invention provide a powder with greater flowability.

[0390] The tapped density of the composite particles is preferably greater than 0.7 g / cm 3 , or at least 0.8 g / cm 3 , or at least 0.85 g / cm 3 , or at least 0.9 g / cm 3 , said tapped density being measured using a Quantachrome TM Autotap according to ISO 3953 and ISO 787 (Determination of tamped volume and apparent density after tamping). The drop height of the instrument is 3 mm, and the tapping frequency of the instrument is fixed at 250 to 265 taps / minute. The sample is tapped at least 5,000 times. If a change in sample volume is still observed after 5,000 taps, an additional increment of 1,250 taps is applied until no further volume change is observed.

[0391] Preferably, in the composite particles of the present invention:

[0392] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.4 to 1.8 cm 3 / g; a PD 50 pore diameter of not more than 10 nm; and preferably a PD 90 pore diameter of not more than 20 nm;

[0393] (ii) The electroactive material is silicon;

[0394] (iii) Z is not more than 10%, and preferably Y is at least 30%;

[0395] (iv) D 50 particle size is in the range of 1 to 20 µm;

[0396] (v) D 1 The particle size is at least 1.0 µm;

[0397] (vi) The ratio D 50 / D 1 is not more than 5; and

[0398] (vii) The BET surface area is not more than 25 m 2 / g.

[0399] More preferably, in the composite particles of the present invention:

[0400] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.5 to 1.6 cm 3 / g; a PD 50 pore diameter not exceeding 8 nm; and preferably a PD 90 pore diameter not exceeding 15 nm;

[0401] (ii) The electroactive material is silicon;

[0402] (iii) Z is not more than 10%, and preferably Y is at least 30%;

[0403] (iv) D 50 The particle size is in the range of 2 to 12 µm;

[0404] (v) D 1 The particle size is at least 1.0 µm;

[0405] (vi) The ratio D 50 / D 1 is not more than 4; and

[0406] (vii) The BET surface area is not more than 25 m 2 / g.

[0407] More preferably, in the composite particles of the present invention:

[0408] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.6 to 1.5 cm 3 / g; a PD 50 pore diameter not exceeding 6 nm; and preferably a PD 90 pore diameter not exceeding 12 nm;

[0409] (ii) The electroactive material is silicon;

[0410] (iii) Z is not more than 8%, and preferably Y is at least 35%;

[0411] (iv) D 50 has a particle size in the range of 2 to 12 µm;

[0412] (v) D 1 has a particle size of at least 1.0 µm;

[0413] (vi) The ratio D 50 / D 1 is not more than 3; and

[0414] (vii) The BET surface area is not more than 20 m 2 / g.

[0415] More preferably, in the composite particles of the present invention:

[0416] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.65 to 1.4 cm 3 / g; a PD 50 pore diameter of not more than 2.5 nm; and preferably a PD 90 pore diameter of not more than 10 nm;

[0417] (ii) The electroactive material is silicon;

[0418] (iii) Z is not more than 8%, and preferably Y is at least 35%;

[0419] (iv) D 50 has a particle size in the range of 2 to 10 µm;

[0420] (v) D 1 has a particle size of at least 1.0 µm;

[0421] (vi) The ratio D 50 / D 1 is not more than 3; and

[0422] (vii) The BET surface area is not more than 20 m 2 / g.

[0423] Preferably, in the composite particles of the present invention:

[0424] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.4 to 1.8 cm 3 / g; a PD 50 pore diameter of not more than 10 nm; and preferably a PD 90 pore diameter of not more than 20 nm;

[0425] (ii) The electroactive material is silicon;

[0426] (iii) Z does not exceed 10%, and preferably Y is at least 30%;

[0427] (iv) D 50 has a particle size in the range of 1 to 20 µm;

[0428] (v) D 1 has a particle size of at least 1.0 µm;

[0429] (vi) The ratio D 98 / D 1 does not exceed 10; and

[0430] (vii) The BET surface area does not exceed 25 m 2 / g.

[0431] More preferably, in the composite particles of the present invention:

[0432] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.5 to 1.6 cm 3 / g; a PD 50 pore diameter not exceeding 8 nm; and preferably a PD 90 pore diameter not exceeding 15 nm;

[0433] (ii) The electroactive material is silicon;

[0434] (iii) Z does not exceed 10%, and preferably Y is at least 30%;

[0435] (iv) D 50 has a particle size in the range of 2 to 12 µm;

[0436] (v) D 1 has a particle size of at least 1.0 µm;

[0437] (vi) The ratio D 98 / D 1 does not exceed 8; and

[0438] (vii) The BET surface area does not exceed 25 m 2 / g.

[0439] More preferably, in the composite particles of the present invention:

[0440] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.6 to 1.5 cm 3 / g; a PD 50 pore diameter not exceeding 6 nm; and preferably a PD 90 pore diameter not exceeding 12 nm;

[0441] (ii) The electroactive material is silicon;

[0442] (iii) Z is not more than 8%, and preferably Y is at least 35%;

[0443] (iv) D 50 has a particle size in the range of 2 to 12 µm;

[0444] (v) D 1 has a particle size of at least 1.0 µm;

[0445] (vi) The ratio D 98 / D 1 is not more than 6; and

[0446] (vii) The BET surface area is not more than 20 m 2 / g.

[0447] Preferably, in the composite particles of the present invention:

[0448] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.4 to 1.8 cm 3 / g; a PD 50 pore diameter not exceeding 10 nm; and preferably a PD 90 pore diameter not exceeding 20 nm;

[0449] (ii) The electroactive material is silicon;

[0450] (iii) Z is not more than 10%, and preferably Y is at least 30%;

[0451] (iv) D 50 has a particle size in the range of 1 to 20 µm;

[0452] (v) D 1 has a particle size of at least 1.0 µm;

[0453] (vi) Preferably D 98 has a particle size not exceeding 16 µm;

[0454] (vii) D 98 -D 1 is not more than 15 µm; and

[0455] (viii) The BET surface area is not more than 25 m 2 / g.

[0456] More preferably, in the composite particles of the present invention:

[0457] (i) The porous particle framework has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.5 to 1.6 cm 3 / g; a PD 50 pore diameter of not more than 8 nm; and preferably a PD 90 pore diameter of not more than 15 nm;

[0458] (ii) The electroactive material is silicon;

[0459] (iii) Z is not more than 10%, and preferably Y is at least 30%;

[0460] (iv) D 50 has a particle size in the range of 2 to 12 µm;

[0461] (v) D 1 has a particle size of at least 1.0 µm;

[0462] (vi) Preferably, D 98 has a particle size of not more than 16 µm;

[0463] (vii) D 98 -D 1 is not more than 13 µm; and

[0464] (viii) The BET surface area is not more than 25 m 2 / g.

[0465] More preferably, in the composite particles of the present invention:

[0466] (i) The porous particle framework has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.6 to 1.5 cm 3 / g; a PD 50 pore diameter of not more than 6 nm; and preferably a PD 90 pore diameter of not more than 12 nm;

[0467] (ii) The electroactive material is silicon;

[0468] (iii) Z is not more than 8%, and preferably Y is at least 35%;

[0469] (iv) D 50 has a particle size in the range of 2 to 12 µm;

[0470] (v) D 1 has a particle size of at least 1.0 µm;

[0471] (vi) Preferably, D 98 has a particle size of not more than 16 µm;

[0472] (vii) D 98 -D 1 not exceeding 12 µm; and

[0473] (viii) the BET surface area not exceeding 20 m 2 / g.

[0474] More preferably, in the composite particles of the present invention:

[0475] (i) the porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.7 to 1.3 cm 3 / g; a PD pore diameter not exceeding 4 nm; and preferably a PD pore diameter not exceeding 8 nm 50 ; 90 pore diameter;

[0476] (ii) the electroactive material is silicon;

[0477] (iii) Z does not exceed 5%, and preferably Y is at least 40%;

[0478] (iv) D 50 particle size in the range of 2 to 10 µm;

[0479] (v) D 1 particle size of at least 1.5 µm;

[0480] (vi) the ratio D 50 / D 1 is preferably not more than 5; and

[0481] (vii) the BET surface area not exceeding 15 m 2 / g.

[0482] More preferably, in the composite particles of the present invention:

[0483] (i) the porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.75 to 1.2 cm 3 / g; a PD pore diameter not exceeding 3 nm; and preferably a PD pore diameter not exceeding 6 nm 50 ; 90 pore diameter;

[0484] (ii) the electroactive material is silicon;

[0485] (iii) Z does not exceed 5%, and preferably Y is at least 40%;

[0486] (iv) D 50 particle size in the range of 2 to 10 µm;

[0487] (v) D1 The particle size is at least 1.8 µm;

[0488] (vi) Ratio D 50 / D 1 is preferably not more than 4; and

[0489] (vii) The BET surface area is not more than 15 m 2 / g.

[0490] More preferably, in the composite particles of the present invention:

[0491] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.8 to 1.2 cm 3 / g; a PD 50 pore diameter not exceeding 2 nm, and preferably a PD 90 pore diameter not exceeding 5 nm;

[0492] (ii) The electroactive material is silicon;

[0493] (iii) Z does not exceed 2%, and preferably Y is at least 45%;

[0494] (iv) D 50 The particle size is in the range of 2.5 to 8 µm; and

[0495] (v) D 1 The particle size is at least 2 µm;

[0496] (vi) Ratio D 50 / D 1 is preferably not more than 3; and

[0497] (vii) The BET surface area is not more than 10 m 2 / g.

[0498] More preferably, in the composite particles of the present invention:

[0499] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.7 to 1.3 cm 3 / g; a PD 50 pore diameter not exceeding 4 nm; and preferably a PD 90 pore diameter not exceeding 8 nm;

[0500] (ii) The electroactive material is silicon;

[0501] (iii) Z does not exceed 5%, and preferably Y is at least 40%;

[0502] (iv) D 50The particle size is in the range of 2 to 10 µm;

[0503] (v) D 1 The particle size is at least 1.5 µm;

[0504] (vi) Ratio D 98 / D 1 Preferably not exceeding 10; and

[0505] (vii) The BET surface area does not exceed 15 m 2 / g.

[0506] More preferably, in the composite particles of the present invention:

[0507] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.75 to 1.2 cm 3 / g; a PD 50 pore diameter not exceeding 3 nm; and preferably a PD 90 pore diameter not exceeding 6 nm;

[0508] (ii) The electroactive material is silicon;

[0509] (iii) Z does not exceed 5%, and preferably Y is at least 40%;

[0510] (iv) D 50 The particle size is in the range of 2 to 10 µm;

[0511] (v) D 1 The particle size is at least 1.8 µm;

[0512] (vi) Ratio D 98 / D 1 Preferably not exceeding 8; and

[0513] (vii) The BET surface area does not exceed 15 m 2 / g.

[0514] More preferably, in the composite particles of the present invention:

[0515] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.8 to 1.2 cm 3 / g; a PD 50 pore diameter not exceeding 2 nm, and preferably a PD 90 pore diameter not exceeding 5 nm;

[0516] (ii) The electroactive material is silicon;

[0517] (iii) Z does not exceed 2%, and preferably Y is at least 45%;

[0518] (iv) D 50 has a particle size in the range of 2.5 to 8 µm; and

[0519] (v) D 1 has a particle size of at least 2 µm;

[0520] (vi) The ratio of D 98 / D 1 is preferably not more than 6; and

[0521] (vii) The BET surface area does not exceed 10 m 2 / g.

[0522] More preferably, in the composite particles of the present invention:

[0523] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.7 to 1.3 cm 3 / g; a PD 50 pore diameter not exceeding 4 nm; and preferably a PD 90 pore diameter not exceeding 8 nm;

[0524] (ii) The electroactive material is silicon;

[0525] (iii) Z does not exceed 5%, and preferably Y is at least 40%;

[0526] (iv) D 50 has a particle size in the range of 2 to 10 µm;

[0527] (v) D 1 has a particle size of at least 1.5 µm;

[0528] (vi) Preferably, the particle size of D 98 does not exceed 16 µm;

[0529] (vii) The value of (D 98 -D 1 ) / D 50 does not exceed 2; and

[0530] (viii) The BET surface area does not exceed 15 m 2 / g.

[0531] More preferably, in the composite particles of the present invention:

[0532] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.75 to 1.2 cm 3Total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of / g; PD not exceeding 3 nm 50 Pore diameter; and preferably PD not exceeding 6 nm 90 Pore diameter;

[0533] (ii) The electroactive material is silicon;

[0534] (iii) Z does not exceed 5%, and preferably Y is at least 40%;

[0535] (iv) D 50 Particle size in the range of 2 to 10 µm;

[0536] (v) D 1 Particle size is at least 1.8 µm;

[0537] (vi) Preferably D 98 Particle size does not exceed 16 µm;

[0538] (vii) (D 98 -D 1 ) / D 50 The value does not exceed 1.8; and

[0539] (viii) BET specific surface area does not exceed 15 m 2 / g.

[0540] More preferably, in the composite particles of the present invention:

[0541] (i) The porous particle skeleton has a total pore volume of micropores and mesopores measured by nitrogen adsorption in the range of 0.8 to 1.2 cm 3 / g; PD not exceeding 2 nm 50 Pore diameter, and preferably PD not exceeding 5 nm 90 Pore diameter;

[0542] (ii) The electroactive material is silicon;

[0543] (iii) Z does not exceed 2%, and preferably Y is at least 45%;

[0544] (iv) D 50 Particle size in the range of 2.5 to 8 µm; and

[0545] (v) D 1 Particle size is at least 2 µm;

[0546] (vi) Preferably D 98 Particle size does not exceed 16 µm;

[0547] (vii) (D 98 -D1 ) / D 50 The value does not exceed 1.8; and

[0548] (viii) The BET surface area does not exceed 10 m 2 / g.

[0549] The composite particles of the second aspect of the present invention can be obtained by the method of the first aspect of the present invention. Alternatively, the composite particles of the second aspect of the present invention can be obtained by the following method: providing a plurality of composite particles according to any one of the previous disclosures of the present applicant (see, for example, WO 2022 / 029422), and classifying the plurality of composite particles to obtain D 1 a particle population having a particle size of at least 0.5 µm and a D 50 particle size in the range of 1 to 20 µm.

[0550] In a third aspect of the present invention, there is provided a composition comprising the composite particles of the second aspect of the present invention and at least one other component. In particular, there is provided a composition comprising the composite particles of the second 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 third aspect of the present invention can be used as an electrode composition and can therefore be used to form the active layer of an electrode.

[0551] The composition can be a mixed-type electrode composition comprising the composite particles and at least one additional particulate electroactive material. Without being bound by theory, it is believed that the carefully controlled particle size distribution of the composite particles of the present invention is advantageous for use in a mixed-type electrode composition because it provides improved compatibility with at least one additional particulate electroactive material.

[0552] Examples of the additional particulate electroactive material include graphite, hard carbon, silicon, tin, germanium, aluminum, and lead. At least one additional particulate electroactive material is preferably selected from graphite and hard carbon, and most preferably, at least one additional particulate electroactive material is graphite.

[0553] In the case of a mixed-type electrode composition, based on the total dry weight of the composition, the composition can comprise at least 5 wt%, or at least 8 wt%, or at least 10 wt%, or at least 12 wt%, or at least 15 wt% of the composite particles according to the second aspect of the present invention. Optionally, based on the total dry weight of the composition, the mixed-type electrode composition can comprise at most 60 wt%, or at most 50 wt%, or at most 40 wt%, or at most 30 wt%, or at most 25 wt% of the composite particles according to the second aspect of the present invention.

[0554] Preferably, based on the total dry weight of the composition, the hybrid electrode composition comprises from 3 wt% to 60 wt%, or from 3 wt% to 50 wt%, or from 5 wt% to 40 wt%, or from 10 wt% to 30 wt%, or from 15 wt% to 25 wt% of the composite particles according to the second aspect of the present invention.

[0555] At least one additional particulate electroactive material is suitably present in an amount of from 20 wt% to 95 wt%, or from 25 wt% to 90 wt%, or from 30 wt% to 75 wt% of at least one additional particulate electroactive material.

[0556] The D 50 particle size of at least one additional particulate electroactive material is preferably in the range of 10 to 50 µm, preferably 10 to 40 µm, more preferably 10 to 30 µm, and most preferably 10 to 25 µm, for example in the range of 15 to 25 µm.

[0557] The D 10 particle size of at least one additional particulate electroactive material 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 still more preferably at least 10 µm.

[0558] The D 90 particle size of at least one additional particulate electroactive material is preferably at most 100 µm, more preferably at most 80 µm, more preferably at most 60 µm, more preferably at most 50 µm, and most preferably at most 40 µm.

[0559] At least one additional particulate electroactive material is preferably selected from carbon-containing particles, graphite particles and / or hard carbon particles, wherein the D 50 particle size of the graphite particles and the hard carbon particles is in the range of 10 to 50 µm. Still more preferably, at least one additional particulate electroactive material is selected from graphite particles, wherein the D 50 particle size of the graphite particles is in the range of 10 to 50 µm.

[0560] The composition may also be a non-hybrid (or "high loading") electrode composition that is substantially free of additional particulate electroactive materials. In this case, the term "substantially free of additional particulate electroactive materials" should be interpreted to mean that, based on the total dry weight of the composition, 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%, still more preferably less than 0.5 wt% of any additional electroactive material (i.e., additional material capable of intercalating and releasing metal ions during charging and discharging of the battery).

[0561] Based on the total dry weight of the composition, this type of "high loading" electrode composition preferably comprises at least 50 wt%, or at least 60 wt%, or at least 70 wt%, or at least 80 wt%, or at least 90 wt% of the composite particles according to the second aspect of the present invention.

[0562] The composition may optionally comprise a binder. The binder serves to adhere the composition to the current collector and maintain the integrity of the composition. Examples of binders that can be used according to the present invention include polyvinylidene fluoride (PVDF), polyacrylic acid (PAA) and its alkali metal salts, modified polyacrylic acid (mPAA) and its alkali metal salts, 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 polyimide. The composition may comprise a mixture of multiple binders. Preferably, the binder comprises a polymer selected from the following: polyacrylic acid (PAA) and its alkali metal salts, and modified polyacrylic acid (mPAA) and its alkali metal salts, SBR, and CMC.

[0563] The binder may suitably be present in an amount of 0.5 wt% to 20 wt%, preferably 1 wt% to 15 wt%, preferably 2 wt% to 10 wt%, and most preferably 5 wt% to 10 wt% based on the total dry weight of the composition.

[0564] 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.

[0565] The composition may optionally comprise one or more conductive additives. Preferred conductive additives are non-electroactive materials that are included to improve the conductivity between the electroactive components of the composition and between the electroactive components of the composition and the current collector. The conductive additives may be selected from carbon black, carbon fiber, carbon nanotubes, graphene, acetylene black, Ketjen black, metal fibers, metal powders, and conductive metal oxides. Preferred conductive additives include carbon black and carbon nanotubes.

[0566] One or more conductive additives may suitably be present in a total amount of 0.5 wt% to 20 wt%, preferably 1 wt% to 15 wt%, preferably 2 wt% to 10 wt%, and most preferably 5 wt% to 10 wt% based on the total dry weight of the composition.

[0567] In a fourth aspect, the present invention provides an electrode comprising the composite particles according to the second aspect of the present invention in electrical contact with a current collector. The particulate material for preparing the electrode of the fourth aspect of the present invention may be in the form of the composition according to the third aspect of the present invention.

[0568] As used herein, the term current collector refers to any conductive substrate capable of carrying current to and 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. The current collector is typically in the form of a foil or mesh with a thickness of 3 to 500 μm. The particulate material of the present invention can be applied to one or both surfaces of the current collector to a thickness preferably in the range of 10 μm to 1 mm, such as 20 to 500 μm, or 50 to 200 μm.

[0569] The electrode of the fourth aspect of the present invention can be prepared by combining the particulate material of the present invention with a solvent and optionally one or more viscosity-modifying additives to form a slurry. The slurry is then cast onto the surface of the current collector, and the solvent is removed to form an electrode layer on the surface of the current collector. Additional steps, such as heat treatment for curing any binder and / or calendering of the electrode layer, can be carried out as appropriate. The thickness of the electrode layer is suitably 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, preferably 20 µm to 50 µm.

[0570] 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 is in the form of a sticky, free-standing object, which can then be bonded to the current collector by known methods.

[0571] The electrode of the fourth aspect of the present invention can be used as the anode of a metal ion battery. Thus, in a fifth aspect, the present invention provides a rechargeable metal ion battery comprising the electrode of the fourth aspect as the anode.

[0572] The metal ion is preferably a lithium ion. More preferably, the rechargeable metal ion battery of the present invention is a lithium ion battery, and the cathode active material is capable of releasing and accepting lithium ions.

[0573] The cathode of a rechargeable metal ion battery generally comprises a current collector and a cathode active material capable of releasing and reabsorbing metal ions. The cathode active material is preferably a metal oxide-based composite material. Examples of suitable cathode active materials include LiCoO 2 , LiCo 0.99 Al 0.01 O 2 , LiNiO 2 , LiMnO 2 , LiCo 0.5 Ni0.5 O 2 , LiCo 0.7 Ni 0.3 O 2 , LiCo 0.8 Ni 0.2 O 2 , LiCo 0.82 Ni 0.18 O 2 , LiCo 0.8 Ni 0.15 Al 0.05 O 2 , LiNi 0.4 Co 0.3 Mn 0.3 O 2 and LiNi 0.33 Co 0.33 Mn 0.34 O 2 . The cathode current collector typically has a thickness of 3 to 500 μm. Examples of materials that can be used as the cathode current collector include aluminum, stainless steel, nickel, titanium, and sintered carbon.

[0574] Suitable electrolytes are non-aqueous electrolytes containing metal salts (such as lithium salts), and can include but are not limited to non-aqueous electrolytic solutions, solid electrolytes, and inorganic solid electrolytes. Examples of non-aqueous electrolyte solutions that can be used include: aprotic organic solvents such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, sulfolane, methylsulfolane, and 1,3-dimethyl-2-imidazolidinone.

[0575] Examples of organic solid electrolytes include polyethylene derivatives, poly(ethylene oxide) derivatives, poly(propylene oxide) derivatives, phosphate esters polymers, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ion dissociating groups.

[0576] Examples of inorganic solid electrolytes include nitrides, halides, and sulfides of lithium salts, such as Li 5 NI 2 , Li 3 N, LiI, LiSiO 4 , Li 2 SiS 3 , Li 4 SiO 4 , LiOH and Li 3 PO 4 .

[0577] The lithium salt is suitably soluble in the selected solvent or solvent mixture. Examples of suitable lithium salts include LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiBC 4 O 8 , LiPF 6 , LiCF 3 SO 3 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li and CF 3 SO 3 Li.

[0578] In the case where the electrolyte is a non-aqueous organic solution, the metal ion battery is preferably provided with a separator interposed between the anode and the cathode. The separator is typically formed of an insulating material having a high ion permeability and a high mechanical strength. The separator typically has a pore size of 0.01 to 100 μm and a thickness of 5 to 300 μm. Examples of suitable electrode separators include microporous polyethylene membranes.

[0579] The separator can be replaced with a polymer electrolyte material, and in such a case, the polymer electrolyte material can be 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.

[0580] Example 1: General procedure for silicon deposition

[0581] A 5.0 L stirred pressure reactor was filled with 300 g of porous carbon particles. The reactor was sealed and slowly placed under vacuum (10 mbar) to remove air, and then filled with dry nitrogen or argon free of oxygen. This process was repeated three times to expel all air from the porous carbon particles. The reactor was heated to 340 °C, evacuated again, and filled with silane to a pressure of 1.2 MPa. Then the reactor was heated to 400 °C at a heating rate of 10 °C / min and held at 400 °C for 30 minutes. Then the reactor was cooled to 340 °C and slowly depressurized. Then the reactor was filled with silane again to 1.2 MPa and heated to 400 °C again at 10 °C / min and held under these conditions for another 30 minutes. The steps of cooling and refilling were repeated for a total of 6 cycles. The reactor was depressurized and filled with nitrogen or argon and then cooled to below 30 °C. Then, the composite particle product was passivated with air by evacuating the reactor and filling it with a gas mixture of 10% air in nitrogen to a pressure of 0.1 MPa and allowing the reactor to stand for 15 minutes. This process was repeated 3 times with a gas mixture of 10% air in nitrogen, 3 times with 25% air in nitrogen, once with 50% air in nitrogen, once with 75% air in nitrogen, and finally with 100% air.

[0582] Example 2

[0583] The porous particle skeletons having the properties listed in Table 1 were infiltrated according to the procedure of Example 1. Sample A was an unclassified porous particle skeleton with a skewness of 2.9. Sample B was a porous particle skeleton with a skewness of 1.3 obtained by pneumatically classifying Sample A to remove fines.

[0584] Table 1

[0585]

[0586] * PV represents the total volume of micropores and mesopores measured by nitrogen adsorption; MPF represents the micropore volume fraction based on the total volume of micropores and mesopores in the porous particles; BET represents the BET surface area of the porous particles.

[0587] The properties of the silicon-carbon composite particles are provided in Table 2. Sample C with a skewness of 1.9 was obtained by infiltrating Sample A (without classification). Sample D with a skewness of 1.0 was obtained according to the method of the present invention.

[0588] Table 2

[0589]

[0590] *Si represents the silicon content as a percentage of the mass of the composite particles; coarse Si represents the content of "bold-phase silicon" determined by TGA according to the method defined herein; surface Si represents the "surface silicon" determined by TGA according to the method defined herein.

[0591] The results in Table 2 demonstrate that the formation of bold-phase silicon is significantly reduced and the formation of surface silicon is increased when preparing composite particles according to the method of the present invention. This demonstrates that the fine particles make a significant contribution to the formation of the coarse silicon structure. As described above, it is known that the presence of bold-phase silicon results in poor capacity retention when using composite particles in a lithium-ion battery.

[0592] The adhesiveness of Samples A to D was also tested, and the results are shown in Figure 3 It was found that a significant reduction in adhesiveness (increase in the instantaneous fluidity function) was observed for both the classified porous particles and the classified composite particles. This demonstrates the advantages for both the processing of porous particles during the production of composite particles and the processing of composite particles during the production of electrodes.

[0593] Example 3

[0594] A porous particle skeleton (Sample E) having the properties listed in Table 3 was infiltrated according to the procedure of Example 1. The product was analyzed before and after air classification to remove fine particles. The properties of the silicon-carbon composite particles are provided in Table 4. Sample F with a skewness of 2.8 was obtained by infiltrating unclassified Sample E. Sample G with a skewness of 1.3 was obtained after air classification of Sample F.

[0595] Table 3

[0596]

[0597] Table 4

[0598]

[0599] The results in Table 4 demonstrate that bold-phase silicon is mainly formed on the fine portions of the porous particles. Therefore, classification of the composite particle product provides a product with a reduced bold-phase silicon content and an increased surface silicon content, and thus this product is expected to have improved reversible capacity retention in a lithium-ion battery.

[0600] The adhesiveness (fluidity) of Samples E to G was also tested, and the results are shown in Figure 4 Once again, a significant reduction in adhesiveness was observed for the classified composite particles.

[0601] Example 4

[0602] The Si-C composite particles of Sample D, F (comparison), and G were used to prepare the negative electrode (anode), and the reversible capacity retention rate of the negative electrode in a single-layer pouch cell was tested.

[0603] To fabricate the electrode, a dispersion of carbon black in a PAA binder was mixed in a Thinky TM mixer. Electrochemically active graphite was added to the dispersion and mixed for 15 minutes. Then the Si-C composite particle sample was added and mixed for 15 minutes. The ratio of the active materials in the electrode was as follows: graphite: Si-C composite material was 74 wt%: 15 wt%. The remaining 11 wt% consisted of 4 wt% carbon black (conductive additive) and 7 wt% PAA binder. The slurry was coated onto a 10 μm thick copper substrate (current collector), dried at 50 °C for 10 minutes, then dried at 80 °C for 10 minutes, and subsequently calendared. An additional drying step was carried out at 110 °C for 12 hours to form a negative electrode with a coating density of 1.5 g / cm3 ± 0.5 g / cm 3 of the negative electrode.

[0604] Using this electrode as the negative electrode and a porous polyethylene separator and a nickel manganese cobalt (NMC532) positive electrode to prepare a full pouch cell. The positive electrode and the negative electrode were designed to form a balanced pair such that the capacity ratio of the positive electrode to the negative electrode was 0.9. Then, before sealing, an electrolyte was added to the cell, and the electrolyte contained 1M LiPF 6 in solution, and the solution was a solution of fluoroethylene carbonate, ethylene carbonate, and ethyl methyl carbonate containing 3 wt% vinylene carbonate.

[0605] The single-layer pouch cell was cycled as follows: a constant current was applied at a rate of C / 10 to lithiate the anode, and the cut-off voltage was 4.2 V. When the cut-off voltage was reached, a constant voltage of 4.2 V was applied until the cut-off current of C / 40 was reached. Then the cell was allowed to stand in the lithiated state for 2 minutes. Then the anode was delithiated at a constant current of C / 10, and the cut-off voltage was 3.0 V. Then the cell was allowed to stand for 2 minutes. Then this charge-discharge cycle was repeated 500 times. The capacity retention rates at 100 cycles (CR100), at 500 cycles (CR500), at 680 cycles (CR680), and at 1000 cycles (CR1000) were calculated and given in Table 5.

[0606] Table 5

[0607]

[0608] * Comparative sample

[0609] As can be seen from Table 5, compared with the comparative sample F, sample D (manufactured by CVI into the porous particle framework of air classification) and sample G (classified composite particle product) have significantly improved cycling performance. For example, before its capacity drops to 80% of its initial charge capacity, the cycle duration of the battery containing sample D is twice that of the battery containing the comparative sample F (>1000 cycles for D versus ~500 cycles for F). The battery containing sample G reaches a capacity retention rate of 80% at 920 cycles.

Claims

1. A method for preparing composite particles, the method comprising the steps of: (a) providing a plurality of porous particles comprising micropores and mesopores, wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is 0.4 to 2.0 cm 3 / g, and wherein the porous particles have a D of at least 0.5 µm 1 particle size and a D in the range of 1 to 20 µm 50 particle size; (b) contacting the porous particles with a precursor of an electroactive material at a temperature effective to cause deposition of a plurality of electroactive material domains within the pores of the porous particles.

2. The method according to claim 1, wherein the D of the porous particles 1 particle size is at least 0.8 µm, or at least 1.0 µm, or at least 1.2 µm, or at least 1.4 µm, or at least 1.5 µm, or at least 1.6 µm, or at least 1.8 µm, or at least 2.0 µm, or at least 2.2 µm, or at least 2.4 µm, or at least 2.5 µm, or at least 2.6 µm, or at least 2.8 µm, or at least 3.0 µm.

3. The method according to claim 1 or claim 2, wherein the D of the porous particles 50 particle size ranges from 1.5 to 18 µm, or from 1.5 to 15 µm, or from 2 to 12 µm, or from 2 to 10 µm, or from 2.5 to 8 µm, or from 3 to 8 µm.

4. The method according to any one of the preceding claims, wherein the D of the porous particles 90 particle size does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 18 µm, or does not exceed 15 µm, or does not exceed 13 µm, or does not exceed 12 µm.

5. The method according to any one of the preceding claims, wherein the D 1 particle size is in the range of 0.8 to 5.0 µm, and the D 90 particle size is in the range of 6 to 15 µm, preferably wherein the D 1 particle size is in the range of 1.0 to 5.0 µm, and the D 90 particle size is in the range of 7.5 to 15 µm, preferably wherein the D 1 particle size is in the range of 1.5 to 4.5 µm, and the D 90 particle size is in the range of 9 to 15 µm, preferably wherein the D 1 particle size is in the range of 2 to 4 µm, and the D 90 particle size is in the range of 10 to 14 µm, preferably wherein the D 1 particle size is in the range of 2.5 to 3.5 µm, and the D 90 particle size is in the range of 11 to 13 µm.

6. The method according to any one of the preceding claims, wherein the D of the porous particles 98 particle size does not exceed 35 µm, or does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 12 µm.

7. The method according to any one of the preceding claims, wherein the D of the porous particles 100 particle size does not exceed 40 µm, or does not exceed 35 µm, or does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 16 µm.

8. The method according to any one of the preceding claims, wherein the difference (D 98 particle size and D 1 particle size (D 98 - D 1 ) is not more than 18 µm, or not more than 16 µm, or not more than 15 µm, or not more than 14 µm, or not more than 13 µm, or not more than 12 µm.

9. The method according to any one of the preceding claims, wherein the ratio of the D 98 particle size to the D 1 particle size (D 98 / D 1 ) is not more than 12, or not more than 10, or not more than 8, or not more than 6, or not more than 5.

10. The method according to any one of the preceding claims, wherein (D 98 -D 1 ) / D 50 is not more than 2.2, or not more than 2, or not more than 1.9, or not more than 1.8, or not more than 1.7, or not more than 1.

6.

11. The method according to any one of the preceding claims, wherein the difference (D 90 particle size and D 1 particle size (D 90 - D 1 ) does not exceed 12.0 µm, or does not exceed 10.0 µm, or does not exceed 9.0 µm, or does not exceed 8.0 µm.

12. The method according to any one of the preceding claims, wherein the D of the porous particles 90 particle size and the D 1 particle size ratio (D 90 / D 1 ) is not more than 12.0, or not more than 10.0, or not more than 9.0, or not more than 8.0, or not more than 7.0, or not more than 6.0, or not more than 5.

0.

13. The method according to any one of the preceding claims, wherein (D 90 -D 1 ) / D 50 is not more than 2.2, or not more than 2, or not more than 1.9, or not more than 1.8, or not more than 1.7, or not more than 1.

6.

14. The method according to any one of the preceding claims, wherein the D of the porous particles 50 particle size and the D 1 particle size ratio (D 50 / D 1 ) is not more than 10.0, or not more than 8.0, or not more than 7.0, or not more than 6.0, or not more than 5.0, or not more than 4.0, or not more than 3.0, or not more than 2.

5.

15. The method according to any one of the preceding claims, wherein the particle size distribution of the porous particles has a positive skewness.

16. The method according to any one of the preceding claims, wherein the total pore volume of the micropores and mesopores in the porous particles, measured by gas adsorption, is in the range of 0.4 to 1.8 cm 3 / g, or 0.4 to 1.7 cm 3 / g, or 0.5 to 1.6 cm 3 / g, or 0.5 to 1.55 cm 3 / g, or 0.6 to 1.5 cm 3 / g, or 0.6 to 1.45 cm 3 / g, or 0.65 to 1.4 cm 3 / g, or 0.65 to 1.35 cm 3 / g, or 0.7 to 1.3 cm 3 / g, or 0.7 to 1.25 cm 3 / g, or 0.75 to 1.2 cm 3 / g, or 0.75 to 1.1 cm 3 / g, or 0.8 to 1.15 cm 3 / g, or 0.8 to 1.1 cm 3 / g.

17. The method according to any one of the preceding claims, wherein the PD 50 pore diameter of the porous particles does not exceed 10 nm, or does not exceed 8 nm, or does not exceed 6 nm, or does not exceed 5 nm, or does not exceed 4 nm, or does not exceed 3 nm, or does not exceed 2.5 nm, or does not exceed 2 nm, or does not exceed 1.9 nm, or does not exceed 1.8 nm, or does not exceed 1.7 nm, or does not exceed 1.6 nm.

18. The method according to any one of the preceding claims, wherein the PD 90 pore diameter of the porous particles is in the range of 1.5 to 20 nm, or 2 to 20 nm, or 3.2 to 20 nm, or 3.5 to 15 nm, or 3.8 to 10 nm, or 4 to 8 nm.

19. The method according to any one of the preceding claims, wherein the micropore volume fraction is in the range of 0.35 to 0.98, or in the range of 0.4 to 0.95, or in the range of 0.4 to 0.90, or in the range of 0.4 to 0.85, or in the range of 0.45 to 0.85, or in the range of 0.5 to 0.8, or in the range of 0.55 to 0.8, or in the range of 0.6 to 0.8, or in the range of 0.61 to 0.

79.

20. The method according to any one of the preceding claims, wherein the BET surface area of the porous particles is in the range of 500 m 2 / g to 4,000 m 2 / g, or 750 m 2 / g to 3,500 m 2 / g, or 1,000 m 2 / g to 3,250 m 2 / g, or 1,000 m 2 / g to 3,000 m 2 / g, or 1,000 m 2 / g to 2,500 m 2 / g, or 1,000 m 2 / g to 2,000 m 2 / g.

21. The method according to any one of the preceding claims, wherein step (a) comprises sizing the porous particles to provide a plurality of porous particles having a specified D 1 value and a D 50 value.

22. The method according to claim 21, wherein step (a) comprises: (i) Provide a precursor population of porous particles comprising micropores and mesopores, wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is 0.4 to 2.0 cm 3 / g, and (ii) classifying a population of precursors of the particles to obtain the plurality of porous particles as defined herein for use in step (a).

23. The method according to any one of the preceding claims, wherein the porous particles are electrically conductive porous particles, preferably electrically conductive porous carbon particles, more preferably electrically conductive porous carbon particles comprising at least 80 wt%, or at least 85 wt%, or at least 90 wt%, or at least 95 wt% carbon.

24. The method according to any one of the preceding claims, wherein the precursor of the electroactive material is a gaseous precursor.

25. The method according to claim 24, wherein step (b) comprises: contacting the porous particles with a gas comprising at least 30 vol%, or at least 40 vol%, or at least 50 vol%, or at least 60 vol%, or at least 70 vol%, or at least 80 vol%, or at least 90 vol%, or at least 95 vol%, or at least 97 vol%, or at least 99 vol% of the precursor of the electroactive material based on the total volume of the gas.

26. The method according to any one of the preceding claims, wherein the electroactive material deposited in step (b) is selected from silicon, tin, germanium, aluminum and mixtures and alloys thereof, preferably wherein the electroactive material deposited in step (b) is silicon, preferably wherein the precursor of the electroactive material is selected from silane, disilane, trisilane, tetrasilane, methylsilane, dimethylsilane and chlorosilane.

27. The method according to any one of the preceding claims, wherein the particles formed in step (b) comprise at least 26% by weight of the electroactive material, or at least 28% by weight of the electroactive material, or at least 30% by weight of the electroactive material, or at least 32% by weight of the electroactive material, or at least 34% by weight of the electroactive material, or at least 36% by weight of the electroactive material, or at least 38% by weight of the electroactive material, or at least 40% by weight of the electroactive material, or at least 42% by weight of the electroactive material, or at least 44% by weight of the electroactive material, preferably wherein the electroactive material is silicon.

28. The method according to claim 26 or claim 27, wherein the weight ratio of the silicon deposited in step (b) to the porous particles is in the range of [0.50×P 1 to 1.9×P 1 :1, or [0.6×P 1 to 1.8×P 1 :1, or [0.7×P 1 to 1.7×P 1 :1, or [0.8×P 1 to 1.6×P 1 :1, where P 1 is a dimensionless number whose value is the same as the total pore volume in cm 3 / g measured by gas adsorption of the micropores and mesopores in the porous particles.

29. The method according to any one of the preceding claims, the method further comprising one or more of the following steps (c) to (g): (c) Heat-treating the particles from step (b) at a temperature of at least 400 °C and in the presence of an inert gas; (d) Contacting the surface of the particles from step (b) or step (c) with a passivating agent; (e) Depositing a lithium-ion permeable material into the pores and / or outer surface of the composite particles from step (b), (c) or step (d); (f) Performing a deagglomeration step on the particles from step (b), (c), (d) or (e) to reduce the presence of agglomerated particles; (g) Classify the composite particles from step (b), (c), (d), (e) or (f) such that the D 1 particle size of the classified particles is at least 0.5 µm.

30. A particulate material composed of a plurality of composite particles, wherein the composite particles comprise: (a) A porous particle skeleton including micropores and mesopores, wherein the total pore volume of the micropores and mesopores measured by nitrogen adsorption is 0.4 to 2.0 cm 3 / g, and (b) A plurality of nano-sized electroactive material domains located within the pores of the porous particle skeleton, wherein the composite particles have a D of at least 0.5 µm 1 particle size and a D in the range of 1 to 20 µm 50 particle size, and a BET surface area of not more than 50 m 2 / g.

31. The particulate material according to claim 30, wherein the D of the composite particles 1 particle size is at least 0.8 µm, or at least 1.0 µm, or at least 1.2 µm, or at least 1.4 µm, or at least 1.5 µm, or at least 1.6 µm, or at least 1.8 µm, or at least 2.0 µm, or at least 2.2 µm, or at least 2.4 µm, or at least 2.5 µm, or at least 2.6 µm, or at least 2.8 µm, or at least 3.0 µm.

32. The particulate material according to claim 30 or claim 31, wherein the D of the composite particles 50 particle size is in the range of 1.5 to 18 µm, or in the range of 1.5 to 15 µm, or in the range of 2 to 12 µm, or in the range of 2 to 10 µm, or in the range of 2.5 to 8 µm, or in the range of 3 to 8 µm.

33. The particulate material according to any one of claims 30 to 32, wherein the D of the composite particles 90 particle size does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 12 µm.

34. The particulate material according to claim 33, wherein the D of the composite particles 1 particle size is in the range of 1.5 to 4.5 µm, and D 90 particle size is in the range of 9 to 15 µm, preferably wherein the D of the composite particles 1 particle size is in the range of 2 to 4 µm, and D 90 particle size is in the range of 10 to 14 µm, preferably wherein the D of the composite particles 1 particle size is in the range of 2.5 to 3.5 µm, and D 90 particle size is in the range of 11 to 13 µm.

35. The particulate material according to any one of claims 30 to 34, wherein the D of the composite particles 98 particle size does not exceed 35 µm, or does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm, or does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 12 µm.

36. The particulate material according to any one of claims 30 to 35, wherein the D 100 particle size of the composite particles does not exceed 40 µm, or does not exceed 35 µm, or does not exceed 30 µm, or does not exceed 25 µm, or does not exceed 20 µm.

37. The particulate material according to any one of claims 30 to 36, wherein the difference (D 98 particle size and D 1 particle size (D 98 - D 1 ) does not exceed 18 µm, or does not exceed 16 µm, or does not exceed 15 µm, or does not exceed 14 µm, or does not exceed 13 µm, or does not exceed 12 µm.

38. The particulate material according to any one of claims 30 to 37, wherein the D 98 particle size of the composite particles and the D 1 particle size ratio (D 98 / D 1 ) is not more than 12, or not more than 10, or not more than 8, or not more than 6, or not more than 5.

39. The particulate material according to any one of claims 30 to 38, wherein (D 98 - D 1 ) / D 50 does not exceed 2.2, or does not exceed 2, or does not exceed 1.9, or does not exceed 1.8, or does not exceed 1.7, or does not exceed 1.

6.

40. The particulate material according to any one of claims 30 to 39, wherein the difference (D 90 particle size and D 1 particle size (D 90 - D 1 ) does not exceed 12.0 µm, or does not exceed 10.0 µm, or does not exceed 9.0 µm, or does not exceed 8.0 µm.

41. The particulate material according to any one of claims 30 to 40, wherein the D 90 particle size of the composite particles and the D 1 particle size ratio (D 90 / D 1 ) is not more than 12.0, or not more than 10.0, or not more than 9.0, or not more than 8.0, or not more than 7.0, or not more than 6.0, or not more than 5.

0.

42. The particulate material according to any one of claims 30 to 41, wherein (D 90 - D 1 ) / D 50 does not exceed 2.2, or does not exceed 2, or does not exceed 1.9, or does not exceed 1.8, or does not exceed 1.7, or does not exceed 1.

6.

43. The particulate material according to any one of claims 30 to 42, wherein the D of the composite particles 50 particle size and the D 1 particle size ratio is not more than 10.0, or not more than 8.0, or not more than 7.0, or not more than 6.0, or not more than 5.0, or not more than 4.0, or not more than 3.

0.

44. The particulate material according to any one of claims 30 to 43, wherein the particle size distribution of the composite particles has a positive skewness.

45. The particulate material according to any one of claims 30 to 44, wherein the total pore volume of the micropores and mesopores in the porous particle framework, measured by nitrogen adsorption, is in the range of 0.4 to 1.8 cm 3 / g, or 0.4 to 1.7 cm 3 / g, or 0.5 to 1.6 cm 3 / g, or 0.5 to 1.55 cm 3 / g, or 0.6 to 1.5 cm 3 / g, or 0.6 to 1.45 cm 3 / g, or 0.65 to 1.4 cm 3 / g, or 0.65 to 1.35 cm 3 / g, or 0.7 to 1.3 cm 3 / g, or 0.7 to 1.25 cm 3 / g, or 0.75 to 1.2 cm 3 / g, or 0.75 to 1.1 cm 3 / g, or 0.8 to 1.15 cm 3 / g, or 0.8 to 1.1 cm 3 / g.

46. The particulate material according to any one of claims 30 to 45, wherein the PD 50 pore diameter of the porous particle framework does not exceed 10 nm, or does not exceed 8 nm, or does not exceed 6 nm, or does not exceed 5 nm, or does not exceed 4 nm, or does not exceed 3 nm, or does not exceed 2.5 nm, or does not exceed 2 nm, or does not exceed 1.9 nm, or does not exceed 1.8 nm, or does not exceed 1.7 nm, or does not exceed 1.6 nm.

47. The particulate material according to any one of claims 30 to 46, wherein the PD 90 pore diameter of the porous particle framework is in the range of 3.2 to 20 nm, or 3.5 to 15 nm, or 3.8 to 10 nm, or 4 to 8 nm.

48. The particulate material according to any one of claims 30 to 47, wherein based on the total volume of the micropores and mesopores, the micropore volume fraction of the porous particle skeleton is at least 0.4, or at least 0.45, or at least 0.5, or at least 0.55, or at least 0.

6.

49. The particulate material according to any one of claims 30 to 48, wherein based on the total volume of the micropores and mesopores, the micropore volume fraction of the porous particle skeleton does not exceed 0.85, or does not exceed 0.

8.

50. The particulate material according to any one of claims 30 to 49, wherein the BET surface area of the porous particle framework is in the range of 100 m 2 / g to 4,000 m 2 / g, or 500 m 2 / g to 4,000 m 2 / g, or 750 m 2 / g to 3,500 m 2 / g, or 1,000 m 2 / g to 3,250 m 2 / g, or 1,000 m 2 / g to 3,000 m 2 / g, or 1,000 m 2 / g to 2,500 m 2 / g, or 1,000 m 2 / g to 2,000 m 2 / g.

51. The particulate material according to any one of claims 30 to 50, wherein the porous particle skeleton is a conductive porous particle skeleton, preferably a conductive porous carbon particle skeleton, more preferably a conductive porous carbon particle skeleton comprising at least 80% by weight of carbon, or at least 85% by weight of carbon, or at least 90% by weight of carbon, or at least 95% by weight of carbon.

52. The particulate material according to any one of claims 30 to 51, wherein the electroactive material is selected from silicon, tin, germanium, aluminum, and mixtures and alloys thereof, preferably wherein the electroactive material is silicon.

53. The particulate material according to any one of claims 30 to 52, wherein the particulate material comprises at least 26 wt% of the electroactive material, or at least 28 wt% of the electroactive material, or at least 30 wt% of the electroactive material, or at least 32 wt% of the electroactive material, or at least 34 wt% of the electroactive material, or at least 36 wt% of the electroactive material, or at least 38 wt% of the electroactive material, or at least 40 wt% of the electroactive material, or at least 42 wt% of the electroactive material, or at least 44 wt% of the electroactive material, preferably wherein the electroactive material is silicon.

54. The particulate material according to claim 52, wherein the weight ratio of silicon to the porous particle framework is in the range of 1 from 0.50×P 1 to 1.9×P 1 :1, or from 0.6×P 1 to 1.8×P 1 :1, or from 0.7×P 1 to 1.7×P 1 :1, or from 0.8×P 1 to 1.6×P 1 :1, where P 3 represents a dimensionless number whose value is the same as the total pore volume in cm 3 / g measured by gas adsorption of the micropores and mesopores in the porous particle framework.

55. The particulate material according to any one of claims 52 to 54, wherein at least 22 wt%, or at least 25 wt%, or at least 30 wt%, or at least 35 wt%, or at least 40 wt%, or at least 45 wt% of the silicon in the composite particles is surface silicon as determined by thermogravimetric analysis (TGA).

56. The particulate material according to any one of claims 52 to 55, wherein no more than 10 wt%, or no more than 8 wt%, or no more than 6 wt%, or no more than 5 wt%, or no more than 4 wt%, or no more than 3 wt%, or no more than 2 wt%, or no more than 1.5 wt% of the silicon in the composite particles is bulk-phase silicon as determined by thermogravimetric analysis (TGA).

57. The particulate material according to any one of claims 30 to 56, wherein the BET surface area of the composite particles does not exceed 100 m 2 / g, or does not exceed 80 m 2 / g, or does not exceed 60 m 2 / g, or does not exceed 50 m 2 / g, or does not exceed 40 m 2 / g, or does not exceed 30 m 2 / g, or does not exceed 25 m 2 / g, or does not exceed 20 m 2 / g, or does not exceed 15 m 2 / g, or does not exceed 10 m 2 / g, or does not exceed 5 m 2 / g.

58. The particulate material according to any one of claims 30 to 57, wherein the particulate material further comprises a passivation layer, a conductive carbon layer, a conductive metal layer, or a lithium-ion permeable solid electrolyte layer formed on the surface of the nano-sized electroactive material domain.

59. The particulate material according to any one of claims 30 to 58, wherein the composite particles are non-agglomerated and non-aggregated particles.

60. A composition comprising the particulate material according to any one of claims 30 to 59 and at least one other component.

61. An electrode comprising the particulate material according to any one of claims 30 to 59 or the composition according to claim 60.

62. A rechargeable metal-ion battery comprising the electrode according to claim 61.

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