Three-dimensional porous material, negative electrode composite material and use

Abstract

Provided in the present invention are a three-dimensional porous material, a negative electrode composite material and the use. The three-dimensional porous material has a specially designed opening size distribution, wherein the volume proportion of openings having an opening size smaller than or equal to 2 nm is greater than or equal to 70%, and the volume proportion of openings having an opening size of 1-2 nm is larger than or equal to 50%; therefore, the proportion of effective deposition pores in the three-dimensional porous material is relatively high, the opening size distribution has a relatively high degree of concentration, and a relatively good threshold limiting effect can be achieved. The three-dimensional porous material can be used for providing a negative electrode composite material having both a high gram capacity and a relatively high structural stability.

Description

Three-dimensional porous materials, negative electrode composite materials and their applications

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 27, 2023, with application number 202311282907.7 and application name “Three-dimensional porous materials, negative electrode composite materials and applications”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to three-dimensional porous materials, negative electrode composite materials and their applications. Background Art

[0003] Currently, the industry mostly uses carbon materials (e.g., graphite) as negative electrode materials for secondary batteries. However, the low specific capacity of carbon materials seriously restricts the energy density of secondary batteries. To cater to the market's pursuit of high-energy-density batteries, high-performance electrode materials with high specific capacity (e.g., silicon negative electrode materials) have gradually attracted attention. However, the volume change rate of such high-performance electrode materials before and after the deintercalation / intercalation of active ions is usually very large, which seriously affects the performance of the battery and shortens the cycle life of the battery.

[0004] To address these issues, the industry often deposits high-performance electrode materials within three-dimensional porous materials to limit their expansion. However, existing three-dimensional porous materials have a wide pore size distribution, which is not conducive to the deposition of high-performance electrode materials. Furthermore, this results in poor structural uniformity in the resulting negative electrode material, which in turn hinders battery performance.

[0005] Summary of the Invention

[0006] In view of this, the embodiments of the present application provide a three-dimensional porous material, a negative electrode composite material and an application. The three-dimensional porous material has a specially designed opening diameter distribution of the openings, a high proportion of effective deposition holes, and a high concentration of the opening diameter distribution of the openings, thereby achieving a better threshold limiting effect on the deposited material, and can be used to provide a negative electrode material with both high gram capacity and high structural stability.

[0007] In a first aspect, an embodiment of the present application provides a three-dimensional porous material comprising a plurality of openings. Based on the total opening volume of the three-dimensional porous material, the volume of openings with an opening diameter ≤2 nm accounts for ≥70%, and the volume of openings with an opening diameter in the range of 1 nm-2 nm accounts for ≥50%.

[0008] The opening diameter distribution concentration of the openings with an opening diameter ≤ 2 nm in the above-mentioned three-dimensional porous material is relatively high, and the volume proportion of the openings with an opening diameter in the range of 1 nm-2 nm is ≥50%, so that the opening diameter distribution of the three-dimensional porous material is relatively narrow and the effective deposition pore proportion is large, which can improve the adsorption deposition efficiency of active material particles (particles that can be used to form positive electrode active materials or negative electrode active materials, such as silane, etc.) in the three-dimensional porous material and the deposition utilization rate of the openings, and has a good limiting effect on the particle size of the deposited active material, which is conducive to the formation of extremely small nanoparticles. At the same time, the above-mentioned three-dimensional porous material has good uniformity, thereby improving the concentration and uniformity of the particle size of the deposited active material. Therefore, when the deposited material is a silicon-containing material, a phosphorus-containing material, etc., it can further alleviate its volume expansion during the battery charge and discharge cycle, and the problem of uneven distribution of mechanical stress caused by its volume expansion.

[0009] In some embodiments of the present application, based on the total open pore volume of the three-dimensional porous material, the volume of pores with an opening diameter of 2 nm or less accounts for ≥85%. This can further improve the uniformity of the three-dimensional porous material and further limit the average particle size of the deposited active material when depositing the active material within the three-dimensional porous material.

[0010] In some embodiments of the present application, based on the total open pore volume of the three-dimensional porous material, the volume of pores with an opening diameter of less than 1 nm accounts for ≤40%. This ensures a high proportion of effective deposition in the three-dimensional porous material. In some specific embodiments, based on the total open pore volume of the three-dimensional porous material, the volume of pores with an opening diameter of less than 1 nm accounts for ≤38%. In this way, when depositing active materials in the three-dimensional porous material, the mass proportion of deposited active materials in the final composite material can be increased.

[0011] In some embodiments of the present application, the volume of pores with an opening diameter greater than 5 nm accounts for less than 1%. When depositing active materials in a three-dimensional porous material, the average particle size of the deposited active materials can be further limited.

[0012] In some embodiments of the present application, the total pore volume of the three-dimensional porous material is greater than 0.5 cm 3 / g. Under the distribution of opening diameters of three-dimensional porous materials, the total pore volume is controlled to be >0.5cm 3 / g can make the number of effective deposition pores in the three-dimensional porous material more appropriate, thereby being used to provide a composite material with better comprehensive performance.

[0013] In some embodiments of the present application, the material of the three-dimensional porous material includes at least one of conductive carbon, conductive ceramic or metal.

[0014] The second aspect of an embodiment of the present application provides a negative electrode composite material, comprising the three-dimensional porous material provided in the first aspect of the present application and a plurality of nanoparticles located in the openings; the material of the nanoparticles comprises at least one of a silicon-containing material, a phosphorus-containing material or a tin-containing material.

[0015] Based on the unique structural design of the three-dimensional porous material, the nanoparticles have a small average particle size, which can effectively reduce the expansion rate of the negative electrode composite material during the charge and discharge cycle. At the same time, the multiple nanoparticles in the negative electrode composite material are highly concentrated within a small particle size range (the negative electrode composite material has better uniformity), which can improve the uniformity of the internal mechanical stress distribution of the negative electrode composite material during battery cycling, reduce the risk of rupture of the negative electrode composite material, and thus improve the battery's cycle performance. In addition, based on the inherent properties of silicon-containing materials, phosphorus-containing materials, and tin-containing materials, the above-mentioned negative electrode composite material has a high reversible capacity.

[0016] In some embodiments of the present application, the size of the nanoparticles in at least one direction is ≤ 2 nm, which is more conducive to suppressing the volume change of the negative electrode composite material during battery cycling.

[0017] In some embodiments of the present application, the negative electrode composite material further includes a coating layer coated on the surface of the three-dimensional porous material; the coating layer includes a carbon coating layer and / or a fast ion conductor coating layer, or a composite coating layer; wherein the composite coating layer includes a carbon material and a fast ion conductor material; the thickness of the coating layer is ≤20nm. The carbon coating layer can improve the electronic conductivity of the negative electrode composite material, and the fast ion conductor coating layer can improve the ionic conductivity of the negative electrode composite material, thereby both improving the rate performance of the battery; the composite coating layer can simultaneously improve the electronic conductivity and ionic conductivity of the negative electrode composite material. In addition, the above-mentioned coating layer can also serve as a physical barrier, effectively reducing the risk of silicon-containing materials, phosphorus-containing materials, and tin-containing materials being exposed to the surface of the negative electrode composite material, thereby improving the interface stability of the negative electrode composite material and being more conducive to the performance of the battery.

[0018] In some embodiments of the present application, the carbon coating layer is further formed in the openings, thereby further improving the electronic conductivity of the negative electrode composite material.

[0019] In some embodiments of the present application, the negative electrode composite material contains a doping element, and the doping element is at least one of N, P, or S. Doping the negative electrode composite material can improve the electronic conductivity and stability of the negative electrode composite material.

[0020] In some embodiments of the present application, the nanoparticles contain the doping element, which is beneficial for improving the electronic conductivity and stability of the negative electrode composite material.

[0021] In some embodiments of the present application, the three-dimensional porous material contains the doping element. This helps improve the electronic conductivity of the negative electrode composite material. In some specific embodiments of the present application, both the three-dimensional porous material and the nanoparticles contain the doping element. This further improves the overall performance of the negative electrode composite material.

[0022] In some embodiments of the present application, the weight percentage of the doping element in the negative electrode composite material is less than 10%. In this way, both the electronic conductivity and the reversible capacity of the negative electrode composite material can be taken into account.

[0023] In some embodiments of the present application, the mass of the plurality of nanoparticles accounts for 30%-80% of the total mass of the negative electrode composite material.

[0024] In a third aspect of the embodiments of the present application, a negative electrode plate is provided, comprising a current collector and a negative electrode material layer disposed on the surface of the current collector, wherein the negative electrode material layer comprises the negative electrode composite material provided in the second aspect of the embodiments of the present application. Due to the use of the negative electrode composite material provided in the embodiments of the present application, the negative electrode plate has a low volume expansion rate after battery cycling and can provide a high reversible capacity, thereby being used to provide a secondary battery with both high energy density and excellent cycle performance. The negative electrode plate can be a negative electrode plate used in a lithium secondary battery, or a negative electrode plate used in a sodium secondary battery.

[0025] A fourth aspect of the present application provides a secondary battery, comprising a negative electrode sheet, a positive electrode sheet, and an electrolyte positioned between the positive electrode sheet and the negative electrode sheet. Due to the use of the negative electrode sheet provided in the third aspect of the present application, the secondary battery can have both high energy density and excellent cycle performance. The secondary battery can be a lithium secondary battery or a sodium secondary battery.

[0026] In some embodiments of the present application, the secondary battery is a liquid battery.

[0027] In some embodiments of the present application, the secondary battery is a solid-state battery.

[0028] A fifth aspect of the embodiments of the present application provides an electrical device, including the secondary battery provided in the fourth aspect of the embodiments of the present application. In some embodiments of the present application, the electrical device includes, but is not limited to, 3C electronic products, such as mobile phones, laptops, tablet computers, drones, wearable electronic devices, etc. In other embodiments of the present application, the electrical device includes a powered vehicle, such as a new energy vehicle, an electric bicycle, etc.

[0029] A sixth aspect of the present application provides an energy storage system, including the secondary battery provided in the fourth aspect of the present application. Due to the use of the secondary battery provided in the present application, the energy storage system can have a higher energy density.

[0030] In some embodiments of the present application, the energy storage system includes an electrically connected energy storage device and a power converter, and the energy storage device includes a receiving cavity and the secondary battery received in the receiving cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG1 is a schematic structural diagram of a cross section of a three-dimensional porous material provided in one embodiment of the present application;

[0032] FIG2 is a schematic diagram showing the cross-section of a negative electrode composite material provided in one embodiment of the present application;

[0033] FIG3A is a schematic structural diagram of a cross section of a negative electrode composite material provided in another embodiment of the present application;

[0034] FIG3B is a schematic structural diagram of a cross section of a negative electrode composite material provided in another embodiment of the present application;

[0035] FIG4 is an X-ray diffraction (XRD) spectrum of the negative electrode composite material SC1 provided in an embodiment of the present application and the negative electrode composite material DSC2 of a comparative example;

[0036] FIG5 is a scanning electron microscope (SEM) photograph of the negative electrode composite material SC1 provided in an embodiment of the present application and a corresponding silicon element distribution diagram measured by an energy dispersive spectrometer (EDS);

[0037] FIG6 is an SEM image of the negative electrode composite material DSC2 of the comparative example and the corresponding EDS silicon element distribution diagram;

[0038] FIG7 is a transmission electron microscope (TEM) photograph of the negative electrode composite material SC1 provided in an embodiment of the present application.

[0039] Explanation of the accompanying figures: 1-three-dimensional porous material; 10-micropore; 11-first type of pore; 12-second type of pore; 20-third type of pore; 100-negative electrode composite material; 30-nanoparticles; 40-coating layer. DETAILED DESCRIPTION

[0040] With the advancement of electronic products, the market demand for higher energy density in batteries is increasing. The development of high-performance anode materials, such as silicon-based, phosphorus-containing, and tin-based anode materials, has become a key technology path. However, these high-performance electrode materials experience significant volume changes before and after the deintercalation and insertion of active ions. For example, in lithium-ion batteries with silicon-based anodes, the volume expansion of silicon particles during the deintercalation and insertion process can reach as high as 300%. This can easily lead to anode material particle rupture, exacerbating battery side reactions (e.g., thickening of the solid electrolyte interface membrane), resulting in irreversible loss of active ions, and even cracking of the anode electrode sheet, causing separation of the anode material layer from the current collector, severely impacting battery cycle performance.

[0041] Taking silicon negative electrode materials as an example, in order to suppress the expansion of silicon negative electrode materials during battery cycling, the industry often deposits silicon-containing active materials (for example, silicon element) in the open pores of three-dimensional porous materials, and generally adopts a vapor deposition process to prepare them, specifically including: placing the three-dimensional porous material in silane gas, silane adsorbed in its open pores and deposited into silicon particles, to obtain a composite negative electrode material. However, the pore size distribution of the three-dimensional porous materials in the prior art is wide, which not only affects the adsorption and deposition of silane by the open pores, but also the particle size distribution of the silicon particles in the composite negative electrode material finally obtained is also relatively wide, which will result in a large number of silicon particles with large particle size differences having large differences in volume expansion effects during battery cycling. As a result, the three-dimensional porous material has limited inhibitory effect on the expansion of silicon particles, and causes uneven distribution of mechanical stress of the composite negative electrode material particles. The risk of rupture of the composite negative electrode material particles during the charge and discharge cycle is still high, affecting the battery cycle performance. However, the growth of silicon particles in the composite negative electrode material and the final particle size distribution are significantly affected by the pore size distribution of the three-dimensional porous material. Therefore, providing a three-dimensional porous material with a special pore size distribution design is one of the keys to overcoming the above technical problems.

[0042] In view of this, for the convenience of description, hereinafter, openings with an opening diameter ≤ 2nm are collectively referred to as "micropores", openings with an opening diameter in the range of 1nm-2nm are collectively referred to as "first-class pores", and openings with an opening diameter <1nm are collectively referred to as "second-class pores". In other words, micropores include first-class pores and second-class pores; openings with an opening diameter > 5nm are collectively referred to as "third-class pores". Referring to Figure 1, an embodiment of the present application provides a three-dimensional porous material 1. Based on the total open pore volume of the three-dimensional porous material 1, the volume proportion of openings with an opening diameter ≤ 2nm (micropores 10) is ≥ 70%, and the volume proportion of openings with an opening diameter in the range of 1nm-2nm (first-class pores 11) is ≥ 50%.

[0043] In the embodiment of the present application, the opening diameter and the distribution of the opening diameter in the three-dimensional porous material 1 are measured by gas adsorption and desorption test. Based on the principle of gas adsorption and desorption test (closed pores cannot be measured), the opening diameter of each opening measured specifically refers to the opening diameter measured by the gas adsorption and desorption test, which can be considered as the "maximum lateral dimension of the opening of the opening". Specifically, the shape of the micropores 10 can be spherical, quasi-spherical, long strip, irregular, etc. Among them, the gas used in the above-mentioned gas adsorption and desorption test can be, but is not limited to, nitrogen, carbon dioxide, argon, etc.

[0044] Specifically, the three-dimensional porous material 1 is placed in a gas adsorption-desorption tester, such as a nitrogen adsorption-desorption test. During the test, the degassing time is maintained at ≥30 min and the degassing temperature is maintained at ≥100°C to obtain the adsorption-desorption curve of the three-dimensional porous material 1, thereby obtaining the opening diameter distribution of the three-dimensional porous material 1.

[0045] In some specific embodiments of the present application, a small number of closed pores (pores into which gas cannot enter, not shown in the figure) may exist in the three-dimensional porous material 1. It should be noted that in the embodiments of the present application, the volume of the closed pores is not included in the total open pore volume of the above-mentioned three-dimensional porous material 1.

[0046] Understandably, the distribution of pores in three-dimensional porous materials is intricate. Generally, solid substances are prepared in their pores by deposition, and the above-mentioned deposition includes but is not limited to chemical vapor deposition, sputtering deposition, etc. For porous materials, there are differences in the adsorption capacity of pores with different opening diameters for particles (e.g., gas molecules, atoms, ions, etc.): under the superposition effect of the interaction potential energy between the pore walls, the adsorption capacity of pores with an opening diameter ≤ 2nm for particles is stronger, and its threshold limiting effect is better, which is more conducive to limiting the particle size of the deposited material in the pore, and is more conducive to limiting the particle size distribution of the deposited material. More importantly, the inventors have found that the adsorption capacity of pores with an opening diameter in the range of 1nm-2nm for active material particles (particles that can be used to form positive active materials or negative active materials, such as silane, etc.) is stronger than that of pores with other opening diameters, and the threshold limiting effect on the deposited material is better. The opening diameter distribution of the pores in the three-dimensional porous material 1 provided in the embodiment of the present application is concentrated in the range of ≤2nm, and the sum of the volume percentages of the first type of pores 11 (i.e., openings with an opening diameter of 1nm-2nm) is ≥50%. The opening diameter distribution is narrow and the proportion of effective deposition pores is large (the proportion of openings that can effectively adsorb particles and deposit them to form deposited materials is large). Therefore, the adsorption and deposition efficiency of active material particles in the three-dimensional porous material 1 and the deposition utilization rate of the openings can be improved, so that the composite material can achieve a higher active material deposition load. In particular, when the deposited material is a high-performance electrode material, the gram capacity of the final composite material can be increased. At the same time, the uniformity of the above-mentioned three-dimensional porous material 1 is good, which can increase the concentration of the particle size of the active material finally deposited in its openings; and the above-mentioned three-dimensional porous material 1 has a good limiting effect on the particle size of the deposited active material, which is conducive to the formation of extremely small nanoparticles. In the embodiment of the present application, extremely small nanoparticles refer to "nanoparticles with a size of at least one dimension ≤2nm". Therefore, when the deposited active material is a high-performance electrode material such as a silicon-containing material, a phosphorus-containing material, or a tin-containing material, the three-dimensional porous material 1 can better inhibit its volume expansion during the charge and discharge cycle, and improve the problem of uneven distribution of mechanical stress and rupture of the three-dimensional porous material 1 caused by its volume expansion.

[0047] In the embodiments of the present application, based on the total open pore volume of the three-dimensional porous material 1, the volume percentage of the plurality of micropores 10 may be, but is not limited to, 70%, 75%, 80%, 85%, 88%, 90%, 92%, 95%, 98%, 99%, 100%, etc. If the volume percentage of the micropores 10 is too low, the volume percentage of pores with an opening diameter greater than 2 nm will increase, which is not conducive to the subsequent adsorption and deposition of other materials and the particle size control of the active material. When the deposited active material is a high-performance electrode material such as the aforementioned silicon-containing material, the effect on its volume expansion during the charge-discharge cycle is still limited.

[0048] In the embodiment of the present application, based on the total open pore volume of the three-dimensional porous material 1, the volume percentage of the plurality of first-type pores 11 may be, but is not limited to, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 80%, 85%, 90%, 95%, etc. If the volume percentage of the micropores 10 is ≥ 70%, but the volume percentage of the first-type pores 11 is too low, it will make it difficult to effectively deposit a large number of subsequent open pores. When the deposited active material is a high-performance electrode material such as the aforementioned silicon-containing material, the specific capacity of the resulting composite material will be too low.

[0049] In some embodiments of the present application, based on the total open pore volume of the three-dimensional porous material 1, the volume proportion of the plurality of micropores 10 is ≥85%. In some specific embodiments, the volume proportion of the plurality of micropores 10 is ≥87%, for example, 87%-92%. Further increasing the volume proportion of the micropores 10 in the three-dimensional porous material 1 and reducing the volume proportion of the openings with an opening diameter of >2nm, the uniformity of the three-dimensional porous material 1 is better, thereby increasing the probability that the deposited active material is an extremely small nanoparticle. When the deposited active material is a high-performance electrode material such as a silicon-containing material, the volume expansion rate of the final composite material during the battery cycle can be further reduced, thereby reducing the problem of uneven distribution of mechanical stress inside the final composite material, and further reducing the risk of composite material rupture.

[0050] In some embodiments of the present application, based on the total open pore volume of the three-dimensional porous material 1, the volume proportion of the plurality of second-type pores 12 is ≤40%. Openings with an opening diameter of <1 nm are more difficult to adsorb particles (for example, silane gas molecules). When the proportion of micropores 10 is high, controlling the volume proportion of the second-type pores 12 to ≤40% can increase the proportion of effective deposition pores, which is beneficial to increasing the mass proportion of the deposited active material in the final composite material. In addition, when the second-type pores 12 exist in the three-dimensional porous material 1, the probability of the second-type pores 12 existing as "empty pores" in the final composite material is high, or in other words, because adsorption is difficult, the particle size of the active material deposited in the final second-type pores 12 is very small and few, and the remaining second-type pores 12 form "empty pores". Therefore, when the deposited active material is the aforementioned high-performance negative electrode material such as silicon-containing material, the second-type pores 12 can serve as a buffer space for the expansion of the high-performance electrode material in other openings, thereby reducing the overall expansion rate of the composite material. Specifically, the volume proportion of the plurality of second type holes 12 may be 40%, 38%, 36%, 35%, 32%, 30%, 25%, 22%, 20%, 15%, 10%, 5%, 1%, etc.

[0051] In some embodiments of the present application, based on the total open pore volume of the three-dimensional porous material 1, the volume proportion of the plurality of second-type pores 12 is ≤ 38%, for example, 34%-38%. This allows for a certain expansion buffer space to be retained within the final composite material while further increasing the mass proportion of deposited material in the composite material.

[0052] In some embodiments of the present application, based on the total open pore volume of the three-dimensional porous material 1, the volume proportion of the plurality of third-type pores 20 is <1% (the volume proportion of the pores with an opening diameter > 5 nm is <1%). During the preparation process of the three-dimensional porous material 1, third-type pores 20 with an opening diameter > 5 nm may be formed. Their ability to adsorb particles is slightly weaker than that of the micropores 10, and their effect on limiting the particle size of the deposited negative active material is also slightly weaker. By controlling the volume proportion of the third-type pores 20 to <1%, the probability of the appearance of active materials with larger particle sizes in the final composite material can be reduced, thereby further enhancing the threshold limiting effect of the three-dimensional porous material 1 on the deposited material. When the deposited material is the aforementioned high-performance electrode material such as a silicon-containing material, the expansion rate of the composite material during the charge and discharge cycle can be further reduced, and the problem of uneven distribution of its internal mechanical stress can be further improved. Specifically, the volume proportion of the plurality of third-type pores 20 is ≤0.7%, for example, 0.5%-0.7%.

[0053] In some embodiments of the present application, the total pore volume of the three-dimensional porous material 1 is greater than 0.5 cm 3 In the embodiment of the present application, the volume ratio of the micropores 10 and the first type of pores 11 of the three-dimensional porous material 1 has been defined, and the total pore volume is controlled to be greater than 0.5 cm 3 / g can make the number of effective deposition pores in the three-dimensional porous material 1 more appropriate, thereby being used to provide a composite material with better comprehensive performance. Specifically, the total pore volume of the three-dimensional porous material 1 can be, but is not limited to, 0.55 cm 3 / g, 0.60cm 3 / g, 0.65cm 3 / g, 0.70cm 3 / g, 0.75cm 3 / g, 0.80cm 3 / g, 0.85cm 3 / g, 0.90cm 3 / g, etc. Further, the total pore volume of the three-dimensional porous material 1 is greater than 0.80 cm 3 / g, for example, 0.80cm 3 / g-0.90cm 3 In the embodiment of the present application, the total pore volume of the three-dimensional porous material 1 is also measured by gas adsorption-desorption test.

[0054] In some embodiments of the present application, the D50 of the three-dimensional porous material 1 is in the range of 2μm-15μm. In some specific embodiments, the D50 of the three-dimensional porous material 1 is in the range of 7μm-8μm. Specifically, the D50 of the three-dimensional porous material 1 can be, but is not limited to, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc. When the three-dimensional porous material 1 is used to provide a negative electrode composite material, when the D50 of the negative electrode composite material is within the above range, the length of the deintercalation path of the active ions can be controlled within a reasonable range, which is beneficial to the electrochemical performance of the battery. In the embodiments of the present application, the above-mentioned D50 refers to the particle size corresponding to when the cumulative particle size distribution percentage of the three-dimensional porous material 1 reaches 50%, and the D50 of the three-dimensional porous material 1 is tested using a laser particle size analyzer.

[0055] In some embodiments of the present application, the material of the three-dimensional porous material 1 includes at least one of conductive carbon, conductive ceramic, or metal. Those skilled in the art can select the material according to application requirements.

[0056] In some embodiments of the present application, the material of the three-dimensional porous material 1 is conductive carbon. In some specific embodiments, the material of the three-dimensional porous material 1 is amorphous carbon. At this time, the true density of the three-dimensional porous material 1 is in the range of 1.0g / cc-2.3g / cc. In the embodiments of the present application, the true density of the three-dimensional porous material 1 is tested by the gas volume method. In addition, in some cases, there are closed pores in the three-dimensional porous material 1. At this time, limiting its true density also limits the volume ratio of the closed pores in the three-dimensional porous material 1 to a suitable range to a certain extent. Specifically, the true density of the three-dimensional porous material 1 can be, but is not limited to, 1.0g / cc, 1.2g / cc, 1.5g / cc, 1.8g / cc, 2.0g / cc, 2.1g / cc, 2.2g / cc, 2.3g / cc, etc.

[0057] In some embodiments of the present application, the material of the three-dimensional porous material 1 is conductive carbon. Furthermore, the material of the three-dimensional porous material 1 is amorphous carbon. Taking into account the preparation process and raw materials of the three-dimensional porous material 1, the three-dimensional porous material 1 (i.e., conductive carbon) also includes some heteroatoms, such as oxygen, hydrogen, nitrogen, sulfur, etc. The carbon content of the three-dimensional porous material 1 is greater than 90wt.%. Specifically, the carbon content of the three-dimensional porous material 1 can be, but is not limited to, 91wt.%, 92wt.%, 95wt.%, 98wt.%, etc. The carbon content of the three-dimensional porous material 1 can be measured using a carbon-sulfur analyzer.

[0058] Accordingly, in some embodiments of the present application, the preparation of the three-dimensional porous material 1 may include: providing a base material, and forming pores in the base material to obtain the three-dimensional porous material 1 provided in the embodiments of the present application. The base material includes, but is not limited to, a carbon precursor, a ceramic precursor, and a metal precursor.

[0059] In some embodiments of the present application, the above-mentioned base material is a carbon precursor. In this case, the preparation of the three-dimensional porous material 1 may include:

[0060] S01. Placing a carbon precursor in a reaction chamber, maintaining the temperature at a first temperature for a first time, cooling to room temperature, and then sequentially washing, drying, and crushing to obtain a three-dimensional porous material 1. The above preparation method is simple in steps, has high process reliability, and can be implemented for large-scale industrial production. In some specific embodiments of the present application, the material obtained after the first maintenance time is naturally cooled to room temperature.

[0061] In some embodiments of the present application, the carbon precursor includes, but is not limited to, at least one of coke, a biomass carbon raw material, or a chemical organic polymer material. The coke includes, but is not limited to, coal coke, petroleum coke, etc. The biomass carbon raw material includes, but is not limited to, at least one of coconut shell, bamboo, apricot shell, starch, or lignin. The organic polymer material includes, but is not limited to, at least one of phenolic resin, epoxy resin, polyethylene, polycarbonate, polyphenylene ether, or rubber.

[0062] In some embodiments of the present application, when the carbon precursor is coke, the method further includes mixing the coke with an alkaline activator and then subjecting the mixture to a heat preservation treatment at a first temperature. The alkaline activator includes but is not limited to at least one of sodium hydroxide, potassium hydroxide, or potassium carbonate.

[0063] In some specific embodiments of the present application, the carbon precursor is coke. In this case, the first temperature is 500°C-1200°C, and the first time is 1 hour-48 hours. Specifically, the first temperature may be, but is not limited to, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, etc. Specifically, the first time may be, but is not limited to, 1 hour, 2 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, 25 hours, 28 hours, 30 hours, 32 hours, 35 hours, 38 hours, 40 hours, 42 hours, 45 hours, 48 ​​hours, etc. Specifically, coke and an alkaline activator are mixed in a mass ratio of 1:(1-20) and kept at 500°C-1200°C for 1-48 hours. In some specific embodiments, coke and an alkaline activator are mixed in a mass ratio of 1:(2-5) and kept at 500°C-1200°C for 1-48 hours. This is more conducive to regulating the opening diameter and distribution of the three-dimensional porous material 1. Specifically, the mass ratio of coke to activator can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, etc.

[0064] In some specific embodiments of the present application, the carbon precursor is at least one of a biomass carbon raw material or an organic polymer material. In this case, in step S01, the first temperature is 500°C-1200°C, and the first time is 0.5h-5h. Furthermore, before the heat preservation treatment at the first temperature, the biomass carbon raw material and / or the organic polymer material is carbonized. Furthermore, during the heat preservation treatment at the first temperature, an activation agent is introduced into the reaction chamber. The activation agent includes, but is not limited to, at least one of water vapor, carbon dioxide, or water gas. Specifically, when the carbon precursor is a biomass carbon raw material and / or an organic polymer material, the first temperature is but not limited to 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, etc.; the first insulation time can be but not limited to 0.5h, 1.0h, 1.5h, 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h, etc.

[0065] In some specific embodiments, the above step S01 includes: placing the biomass carbon raw material and / or the organic polymer material in a reaction chamber and keeping it at 300℃-1000℃ for 0.5h-10h to carbonize it, then introducing an activating agent into the reaction chamber and keeping it at 500℃-1200℃ for 0.5h-5h to form pores on the carbonized biomass carbon raw material and / or the carbonized organic polymer material, and after cooling, drying and crushing, obtaining a three-dimensional porous material 1. Wherein, when the activating agent is introduced into the reaction chamber, the gas flow rate of the activating agent is in the range of 1mL / min-20mL / min. Specifically, the gas flow rate of the activating agent can be, but is not limited to, 1mL / min, 2mL / min, 3mL / min, 5mL / min, 8mL / min, 10mL / min, 12mL / min, 15mL / min, 18mL / min, 20mL / min, etc.

[0066] In some specific embodiments of the present application, when the carbon precursor is an organic polymer material such as a thermosetting phenolic resin, a cross-linking and curing treatment is also performed on it before the carbonization treatment. For example, the thermosetting phenolic resin is mixed with phenol formaldehyde and heat-insulated at 50°C-200°C to cure the thermosetting phenolic resin, thereby making it more conducive to the subsequent carbonization treatment. Those skilled in the art can select the type of carbon precursor of the three-dimensional porous material 1 according to actual needs and select a suitable preparation process for the selected carbon precursor.

[0067] In some embodiments of the present application, step S02 is further included: in a protective atmosphere, the product obtained after the crushing in step S01 is subjected to a heat preservation treatment at a second temperature to obtain a three-dimensional porous material 1; wherein the second temperature is in the range of 400°C-2000°C. In this way, impurity functional groups (for example, hydroxyl groups, carboxyl groups, oxygen atoms, nitrogen atoms, etc.) in the three-dimensional porous material 1 can be removed, thereby increasing the carbon content of the three-dimensional porous material 1 and preventing the impurity functional groups from affecting the adsorption and deposition of particles during the application of the three-dimensional porous material 1. Specifically, the second temperature can be, but is not limited to, 400°C, 500°C, 800°C, 1000°C, 1200°C, 1500°C, 1800°C, 2000°C, etc.

[0068] Referring to Figure 2 , this embodiment of the present application also provides a negative electrode composite material 100, comprising the three-dimensional porous material 1 provided in this embodiment of the present application and a plurality of nanoparticles 30 located within the pores of the three-dimensional porous material 1. The nanoparticles 30 are made of at least one of a silicon-containing material, a phosphorus-containing material, or a tin-containing material. In this embodiment of the present application, the material of the nanoparticles 30 can be either crystalline or amorphous, depending on the application.

[0069] In the embodiment of the present application, the negative electrode composite material 100 is pretreated to release the nanoparticles 30 from the three-dimensional porous material 1, thereby obtaining the three-dimensional porous material 1. A gas adsorption-desorption test is then performed to determine the opening diameter distribution of the three-dimensional porous material 1. In the embodiment of the present application, an energy dispersive spectrometer (EDS) test can be used to characterize the distribution of the nanoparticles 30 in the negative electrode composite material 100.

[0070] The materials of the aforementioned nanoparticles 30 are all high-performance electrode active materials. Due to their inherent properties, they can provide a high reversible capacity for the battery. Furthermore, due to the special opening diameter and distribution design of the three-dimensional porous material 1, the average particle size of the nanoparticles 30 is relatively small, which can effectively reduce the expansion rate of the negative electrode composite material 100 during the charge-discharge cycle. At the same time, the concentration of the multiple nanoparticles 30 within the negative electrode composite material 100 is relatively high within a relatively small particle size range (the negative electrode composite material 100 has better uniformity). This can improve the uniformity of the internal mechanical stress distribution of the negative electrode composite material 100 during battery cycling, reduce the risk of rupture of the negative electrode composite material 100, and thus improve the battery's cycling performance.

[0071] In the embodiments of the present application, the silicon-containing material includes but is not limited to silicon, silicon dioxide (SiOx), and silicon-carbon composites; the phosphorus-containing material includes but is not limited to phosphorus; and the tin-containing material includes but is not limited to tin and tin alloys.

[0072] In some embodiments of the present application, the nanoparticles 30 are located in the pores of the three-dimensional porous material 1 with an opening diameter ≥ 1 nm. Thanks to the deposition and adsorption characteristics of the three-dimensional porous material 1 provided in the embodiments of the present application, the nanoparticles 30 are more easily deposited in the pores with an opening diameter ≥ 1 nm. In addition, this characteristic can also allow the negative electrode composite material 100 to have "empty pores" (openings that do not contain nanoparticles 30). In this way, a buffer space can be provided for the expansion of the nanoparticles 30 in the negative electrode composite material 100, thereby reducing the volume change of the negative electrode composite material 100 during the battery cycle, which is more conducive to the final battery cycle performance. In some cases, nanoparticles 30 may also exist in the openings (second type pores 12) with an opening diameter < 1 nm. At this time, the particle size of the nanoparticles 30 in the second type pores 12 is very small and the content is very small.

[0073] In some embodiments of the present application, the size of the nanoparticles 30 in at least one direction is ≤ 2 nm. This is more conducive to suppressing the volume change of the negative electrode composite material 100 during battery cycling. Furthermore, in some embodiments, the particle size of the nanoparticles 30 is ≤ 2 nm.

[0074] In some embodiments of the present application, in the negative electrode composite material 100, the volume of the plurality of micropores 10 accounts for ≥85% of the total open pore volume of the three-dimensional porous material 1. This further reduces the average particle size of the nanoparticles 30 in the negative electrode composite material 100 and improves the particle size uniformity within the negative electrode composite material 100, thereby further reducing the expansion rate of the negative electrode composite material 100 during battery cycling and improving the uniformity of the negative electrode composite material 100.

[0075] In some embodiments of the present application, in the negative electrode composite material 100, the volume of the plurality of third-type pores 20 accounts for less than 1% of the total open pore volume of the three-dimensional porous material 1. Limiting the proportion of the third-type pores 20 helps reduce the average particle size of the nanoparticles 30, thereby optimizing the electrochemical performance of the negative electrode composite material 100.

[0076] In some embodiments of the present application, in the negative electrode composite material 100, the volume proportion of the plurality of second-type pores 12 is ≤ 40% based on the total open pore volume of the three-dimensional porous material 1. This increases the mass proportion of the nanoparticles 30 in the negative electrode composite material 100, thereby increasing the reversible capacity of the negative electrode composite material 100 and, consequently, the energy density of the battery.

[0077] In some embodiments of the present application, the mass of the plurality of nanoparticles 30 accounts for 30%-80% of the total mass of the negative electrode composite material 100. In some specific embodiments, the mass of the plurality of nanoparticles 30 accounts for 40%-50% of the total mass of the negative electrode composite material 100. In combination with the special structural design of the negative electrode composite material 100 provided in the embodiments of the present application, by controlling the mass proportion of the nanoparticles 30 (i.e., the high-performance electrode material) within the above range, the negative electrode composite material 100 can achieve both a high reversible capacity and a low expansion rate, thereby providing a battery with both high energy density and excellent cycle performance. Specifically, the mass of the nanoparticles 30 may account for 30%, 32%, 35%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, etc. of the total mass of the negative electrode composite material 100. In the embodiment of the present application, a thermogravimetric analysis (TGA), an X-ray fluorescence spectrometer (XRF), or an energy dispersive spectrometer (EDS) may be used to test the mass proportion of the plurality of nanoparticles 30 in the negative electrode composite material 100.

[0078] In some embodiments of the present application, when the three-dimensional porous material is made of amorphous carbon and the nanoparticles 30 are doped or undoped silicon, the true density of the negative electrode composite material 100 is within the range of 1.85g / cc-2.30g / cc. In the embodiments of the present application, the true density of the three-dimensional porous material is tested using a gas volumetric method. In addition, in some cases, closed pores are present in the negative electrode composite material 100. In this case, limiting its true density also limits the volume fraction of closed pores in the negative electrode composite material 100 to a suitable range to a certain extent. The true density of the negative electrode composite material 100 may be, but is not limited to, 1.50 g / cc, 1.55 g / cc, 1.60 g / cc, 1.65 g / cc, 1.70 g / cc, 1.75 g / cc, 1.80 g / cc, 1.85 g / cc, 1.88 g / cc, 1.89 g / cc, 1.90 g / cc, 1.91 g / cc, 1.92 g / cc, 1.93 g / cc, 1.94 g / cc, 1.95 g / cc, 2.00 g / cc, 2.05 g / cc, 2.05 g / cc, 2.10 g / cc, 2.15 g / cc, 2.20 g / cc, 2.25 g / cc, 2.30 g / cc, and the like.

[0079] In some embodiments of the present application, see Figures 3A and 3B. The negative electrode composite material 100 also includes a coating layer 40 formed on the surface of the three-dimensional porous material 1. The coating layer 40 includes a carbon coating layer and / or a fast ion conductor coating layer, or the coating layer 40 is a composite coating layer, and the material of the composite coating layer includes a carbon material and a fast ion conductor material. The carbon coating layer can improve the electronic conductivity of the negative electrode composite material 100 and contribute to the capacity. The fast ion conductor coating layer can improve the ionic conductivity of the negative electrode composite material 100, thereby improving the rate performance of the battery and improving the fast charging performance of the battery; the composite coating layer can simultaneously improve the electronic conductivity and ionic conductivity of the composite material. In addition, the coating layer 40 can serve as a physical isolation, effectively reducing the risk of silicon-containing materials, phosphorus-containing materials, and tin-containing materials being exposed to the surface of the negative electrode composite material 100, thereby reducing side reactions during the battery cycle (for example, side reactions between silicon-containing materials and electrolytes in liquid batteries), thereby improving the interface stability of the negative electrode composite material 100 and better promoting the performance of the battery. Furthermore, the three-dimensional porous material containing nanoparticles 30 is equivalent to the "core" of the negative electrode composite material 100. At this time, the coating layer on the surface of the three-dimensional porous material can also inhibit the expansion of the "core", thereby further reducing the expansion rate of the negative electrode composite material 100 during the charge and discharge cycle.

[0080] In some embodiments of the present application, a carbon coating layer and a fast ion conductor coating layer are sequentially formed on the surface of the three-dimensional porous material 1, or a fast ion conductor coating layer and a carbon coating layer are sequentially formed on the surface of the three-dimensional porous material 1. Those skilled in the art can select the appropriate coating layer based on actual application.

[0081] In the embodiment of the present application, the material of the fast ion conductor coating layer (fast ion conductor material) can be any fast ion conductor material known in the art. For example, the fast ion conductor material for lithium ion batteries includes but is not limited to Li3N, Li 14 Zn, etc. Taking fast ion conductors for sodium ion batteries as an example, they include but are not limited to Na3Zr2Si2PO 12 , Na2O·Al2O3, etc.

[0082] In some specific embodiments of the present application, the material (carbon material) of the carbon coating layer includes amorphous carbon. The amorphous carbon coating layer can be characterized using a transmission electron microscope (TEM), as shown in FIG7 , which is a TEM image of the negative electrode composite material 100 provided in one embodiment of the present application, showing a clear amorphous carbon coating layer.

[0083] In some embodiments of the present application, the coating layer 40 has a thickness of ≤20 nm. Controlling the thickness within the above range can achieve physical isolation and shorten the diffusion path of ions or electrons in the negative electrode composite material 100, thereby ensuring better rate performance of the final battery. Specifically, the thickness of the coating layer 40 can be, but is not limited to, 1 nm, 2 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, etc.

[0084] In the embodiment of the present application, the fast ion conductor coating layer can be formed on the surface of the three-dimensional porous material 1 (ie, the negative electrode composite material 100 ) by any process known in the art, such as ball milling.

[0085] In the embodiment of the present application, the carbon coating layer can be formed on the surface of the three-dimensional porous material 1 (ie, the negative electrode composite material 100 ) by any process known in the art, such as vapor deposition and ball milling.

[0086] In some embodiments of the present application, see FIG3B , the carbon coating layer 40 is also formed in the pores of the three-dimensional porous material 1. The carbon coating layer formed in the pores of the three-dimensional porous material 1 may include the following situations: (1) The carbon coating layer is formed in the pores where the nanoparticles 30 are deposited. In some specific embodiments, the carbon coating layer is also fully or partially coated on the surface of the nanoparticles 30. (2) The carbon coating layer is formed in the pores that do not contain the nanoparticles 30 and is attached to the inner wall of the pores of the three-dimensional porous material 1; in some specific embodiments, the carbon coating layer also partially fills or completely fills the pores. In this case, the voids in the negative electrode composite material 100 can be reduced, and the contact between the nanoparticles 30 and the three-dimensional porous material can be increased, thereby facilitating the transmission of electrons and ions in the negative electrode composite material 100, further suppressing the expansion of the nanoparticles 30, and contributing to a portion of the reversible capacity.

[0087] In some embodiments of the present application, a carbon coating layer can be formed in the pores of the three-dimensional porous material 1 by vapor deposition. It is understood that the vapor deposition process can also simultaneously form a carbon coating layer on the surface of the three-dimensional porous material. That is, in some embodiments, a carbon coating layer is formed on both the surface of the three-dimensional porous material 1 and in the pores of the three-dimensional porous material 1.

[0088] In some embodiments of the present application, the negative electrode composite material 100 contains a doping element, wherein the doping element is at least one of N, P, or S. Doping can improve the electrochemical performance of the negative electrode composite material 100 .

[0089] In some embodiments of the present application, the nanoparticles 30 contain the above-mentioned doping elements. Doping is beneficial to the charge transfer and ion diffusion of the nanoparticles 30, and can also improve the stability of the material of the nanoparticles 30, thereby improving the electrochemical performance of the negative electrode composite material 100. Specifically, when the nanoparticles 30 are silicon-containing materials, the nanoparticles 30 include but are not limited to silicon elemental doped with N, silicon elemental doped with P, silicon elemental doped with S, etc.; when the nanoparticles 30 are phosphorus-containing materials, the nanoparticles 30 include but are not limited to phosphorus elemental doped with S atoms; when the nanoparticles 30 are tin-containing materials, the nanoparticles 30 include but are not limited to Si-N alloys. The above is just an enumeration and does not limit the elemental composition of the negative electrode composite material 100 provided in the embodiments of the present application.

[0090] In some embodiments of the present application, the three-dimensional porous material 1 contains the above-mentioned doping elements. In this way, at least the electrical conductivity of the negative electrode composite material 100 can be improved. Specifically, when the material of the three-dimensional porous material 1 is conductive carbon, the doping element can be at least one of N, S or P. Specifically, for example: the negative electrode composite material 100 can be an N-doped phosphorus / carbon composite material, and the phosphorus nanoparticles are located in the N-doped three-dimensional porous carbon; the negative electrode composite material 100 can be a P-doped tin / carbon composite material, and the tin nanoparticles are located in the P-doped three-dimensional porous carbon. The above is just an example and does not limit the composition of the negative electrode composite material 100 provided in the embodiment of the present application. Those skilled in the art can make a choice according to actual application.

[0091] In some embodiments of the present application, the three-dimensional porous material 1 and the nanoparticles 30 simultaneously contain the aforementioned doping elements. For example, the negative electrode composite material 100 is an N-doped silicon / carbon composite material, wherein the N-doped silicon nanoparticles are located within the N-doped three-dimensional porous carbon. Another example is an S-doped phosphorus / carbon composite material, wherein the S-doped silicon nanoparticles are located within the S-doped three-dimensional porous carbon. The above is merely illustrative and does not limit the composition of the negative electrode composite material 100 provided in the embodiments of the present application. Those skilled in the art may select the appropriate composition based on actual application.

[0092] In some embodiments of the present application, the three-dimensional porous material 1, the nanoparticles 30 and the carbon coating layer all contain the above-mentioned doping elements. Those skilled in the art can select them according to application needs.

[0093] In some embodiments of the present application, the mass proportion of the above-mentioned doping elements in the negative electrode composite material 100 is less than 10%. In this way, the electronic conductivity and reversible capacity of the negative electrode composite material can be taken into account. Specifically, the mass proportion of the above-mentioned doping elements in the negative electrode composite material 100 can be 0.1%, 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 9.5%, 9.8%, etc. In the embodiments of the present application, XRF or EDS can be used to test the mass proportion of the doping elements in the negative electrode composite material.

[0094] In some embodiments of the present application, the D50 of the negative electrode composite material 100 is in the range of 2μm-15μm. In some specific embodiments, the D50 of the negative electrode composite material 100 is in the range of 7μm-8μm. Specifically, the D50 of the negative electrode composite material 100 can be, but is not limited to, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc. When the D50 of the negative electrode composite material 100 is within the above range, the length of the deintercalation path of the active ions can be controlled within a reasonable range, which is beneficial to the performance of the battery. In the embodiments of the present application, the above-mentioned D50 refers to the particle size corresponding to when the cumulative particle size distribution percentage of the negative electrode composite material 100 reaches 50%, and the D50 of the negative electrode composite material 100 is tested using a laser particle size analyzer.

[0095] In some embodiments of the present application, the preparation of the negative electrode composite material 100 includes: S01, depositing nanoparticles in the three-dimensional porous material 1 provided in the embodiments of the present application. This preparation method features a simple process, strong controllability, high production efficiency, and is suitable for large-scale industrial production. Furthermore, the mass fraction of nanoparticles in the negative electrode composite material can be adjusted by adjusting parameters in the deposition process. For example, the mass fraction of nanoparticles can be adjusted by adjusting the holding time. For another example, when the deposition raw material is in a gaseous state, the mass fraction of nanoparticles can be adjusted by adjusting the flow rate of the deposition raw material.

[0096] In some embodiments of the present application, the above-mentioned deposition can be vapor deposition or sputtering deposition, and those skilled in the art can select the appropriate process based on the actual application. The raw material of the nanoparticles can be selected based on the actual application.

[0097] It should be noted that since the above-mentioned negative electrode composite material is prepared by depositing nanoparticles 30 in the three-dimensional porous material 1, in some embodiments of the present application, nanoparticle material is also deposited on the surface of the three-dimensional porous material 1 (not shown in the figure). Specifically, the above-mentioned nanoparticle material can be distributed in the form of particles on the surface of the three-dimensional porous material 1 in a dotted manner, and / or partially coated on the surface of the three-dimensional porous material 1 in the form of a continuous phase.

[0098] The following is a brief description of step S01 using the example of the nanoparticles 30 being made of silicon and the three-dimensional porous material 1 being made of amorphous carbon: the three-dimensional porous material 1 is placed in a reaction chamber, a protective gas (e.g., nitrogen) is introduced to expel the air, and the three-dimensional porous material 1 is preheated to 400°C-500°C under the protective atmosphere. Then, monosilane gas is introduced into the reaction chamber and kept warm for 2h-3h to achieve the deposition of silicon nanoparticles. The temperature is then naturally lowered to room temperature, and the material is discharged to obtain the negative electrode composite material 100. In some cases, after the temperature in the reaction chamber drops to room temperature, a mixed gas of oxygen and nitrogen (the oxygen content in the mixed gas is <10%) is introduced into the reaction chamber to pre-oxidize and passivate the negative electrode composite material 100 to prevent it from suddenly coming into contact with air and causing oxidation and exothermic combustion of the silicon nanoparticles, thereby improving the stability of the negative electrode composite material. It should be noted that, in some specific embodiments, granular silicon is deposited on the surface of the negative electrode composite material 100 (ie, the surface of the three-dimensional porous material 1 ), and / or a silicon layer is formed on part of the surface of the negative electrode composite material 100 .

[0099] In some embodiments of the present application, the preparation of the negative electrode composite material 100 further includes step S02: forming a coating layer on the surface of the three-dimensional porous material on which the nanoparticles are deposited. Specifically, the coating layer can be formed on the surface of the three-dimensional porous material on which the nanoparticles are deposited using any process known in the art, including but not limited to ball milling.

[0100] In some cases, the three-dimensional porous material 1 on which the nanoparticles 30 are deposited can be placed together with a carbon material in a ball milling device to obtain a negative electrode composite material 100 having a carbon coating layer on its surface. In other cases, the three-dimensional porous material 1 on which the nanoparticles 30 are deposited can be placed together with a fast ion conductor material in a ball milling device to obtain a negative electrode composite material 100 having a fast ion conductor coating layer on its surface. In still other cases, the three-dimensional porous material 1 on which the nanoparticles 30 are deposited, a carbon material, and a fast ion conductor material can be placed together in a ball milling device to obtain a negative electrode composite material 100 having a composite coating layer on its surface.

[0101] In other embodiments of the present application, step S02 is: simultaneously forming a carbon coating layer on the surface and in the pores of the three-dimensional porous material 1 on which the nanoparticles 30 are deposited. In some specific embodiments, the three-dimensional porous material 1 on which the nanoparticles 30 are deposited is placed in a reaction chamber (a reaction chamber free of air), and a carbon source is introduced at 600°C-800°C. The temperature is maintained for 0.5-4 hours to allow the carbon material to be deposited in the pores of the three-dimensional porous material 1 to form a carbon coating layer. The material is then naturally cooled to room temperature to obtain the negative electrode composite material 100. The carbon source includes, but is not limited to, methane, ethane, acetylene, benzene, amines, and the like.

[0102] Some embodiments of the present application further include step S03: doping the material obtained in step S01 with an element, or doping the material obtained in step S02 with an element. Specifically, doping is performed on the three-dimensional porous material 1 deposited with nanoparticles 30, or on the three-dimensional porous material 1 deposited with nanoparticles 30 and having a coating layer 40. The doping process can be any known process in the art, and those skilled in the art can select one based on the actual application.

[0103] In some specific embodiments of the present application, the preparation of the negative electrode composite material includes the following steps:

[0104] S01, placing the three-dimensional porous material 1 in a reaction chamber, introducing nitrogen gas to expel the air in the reaction chamber, and preheating the three-dimensional porous material to 400° C.-500° C. under a nitrogen atmosphere; then introducing monosilane gas into the reaction chamber and maintaining the temperature at 400° C.-500° C. for 2 h-3 h;

[0105] S02, cut off the monosilane gas, and raise the temperature to 600℃-800℃, introduce a gaseous carbon source into the reaction chamber, and keep it at 600℃-800℃ for 0.5h-4h;

[0106] S03. Replace the gaseous carbon source with nitrogen, keep the temperature at 600-800°C for 0.5-2 hours, cool naturally to room temperature, and discharge the material to obtain a N-doped silicon / carbon negative electrode composite material.

[0107] The present invention also provides a negative electrode plate, comprising a current collector and a negative electrode material layer disposed on a surface of the current collector, wherein the negative electrode material layer comprises the negative electrode composite material 100 provided in the present invention. Due to the use of the negative electrode composite material 100 provided in the present invention, the negative electrode plate has a low volume expansion rate after battery cycling and can provide a high reversible capacity, thereby providing a secondary battery with both high energy density and excellent cycling performance.

[0108] In the embodiments of the present application, the above-mentioned current collector is selected from any known negative electrode current collector for secondary batteries in the field, and the present application does not impose any limitation on this.

[0109] In some embodiments of the present application, the negative electrode active material layer includes the above-mentioned negative electrode composite material, a binder, and an optional conductive agent. The binder can be selected from any binder known in the art. The conductive agent can also be selected from any conductive agent known in the art.

[0110] In some embodiments of the present application, the negative electrode active material layer may further include other negative electrode materials commonly used in the field. That is, a mixture of the negative electrode composite material provided in the embodiments of the present application and other negative electrode materials commonly used in the field is used as the negative electrode active material.

[0111] The present invention also provides a secondary battery comprising a negative electrode, a positive electrode, and an electrolyte disposed between the positive electrode and the negative electrode. Due to the use of the negative electrode provided in the present invention, the secondary battery can have both high energy density and excellent cycle performance.

[0112] In the embodiment of the present application, the secondary battery may be a lithium-ion battery, a sodium-ion battery, etc., but is not limited thereto.

[0113] In some embodiments of the present application, the secondary battery is a liquid battery, which includes a negative electrode sheet, a positive electrode sheet, and a separator and an electrolyte located between the positive electrode sheet and the negative electrode sheet.

[0114] In some embodiments of the present application, the secondary battery is a liquid battery, which includes a negative electrode sheet, a positive electrode sheet, and a solid electrolyte located between the positive electrode sheet and the negative electrode sheet.

[0115] In some other embodiments of the present application, the secondary battery is a semi-solid-state battery.

[0116] The present application also provides an electrical device comprising the secondary battery provided in the present application. The electrical device includes, but is not limited to, consumer electronics products such as cell phones, laptops, tablet computers, drones, and wearable electronic devices. The electrical device may also include powered vehicles such as new energy vehicles and electric bicycles.

[0117] The present invention also provides an energy storage system including the secondary battery provided in the present invention. Due to the use of the secondary battery provided in the present invention, the energy storage system can have a higher energy density.

[0118] In some embodiments of the present application, the energy storage system includes an electrically connected energy storage device and a power converter, the energy storage device includes a accommodating cavity and the secondary battery accommodated in the accommodating cavity, the power converter is used to perform power conversion processing on the voltage and / or current, and input the changed voltage and / or current into the energy storage device, so that the energy storage device can meet the power requirements of the electrical equipment.

[0119] The technical solutions of the embodiments of the present application are described in detail below in multiple embodiments.

[0120] Example 1

[0121] The three-dimensional porous material prepared in the embodiment of the present application has a carbon content of >90 wt.% and a total pore volume of 0.87 cm 3 / g, based on the total open pore volume of the three-dimensional porous material, the volume proportion of micropores (opening diameter ≤ 2nm) is 91%, the volume proportion of the first type of pores (opening diameter 1nm-2nm) is 57%, the volume proportion of the second type of pores (opening diameter <1nm) is 34%, and the volume proportion of the third type of pores (opening diameter >5nm) is 0.5%.

[0122] Example 2

[0123] The difference from the three-dimensional porous material in Example 1 is that the total pore volume is 0.86 cm 3 / g, based on the total open pore volume of the three-dimensional porous material, the volume proportion of micropores (pores with an opening diameter ≤ 2nm) is 89%, the volume proportion of the first type of pores (pores with an opening diameter of 1nm-2nm) is 51%, the volume proportion of the second type of pores (pores with an opening diameter <1nm) is 38%, and the volume proportion of the third type of pores (pores with an opening diameter >5nm) is 0.6%.

[0124] Example 3

[0125] The difference from the three-dimensional porous material in Example 1 is that the total pore volume is 0.84 cm 3 / g, based on the total open pore volume of the three-dimensional porous material, the volume proportion of micropores (opening diameter ≤ 2nm) is 87%, the volume proportion of the first type of pores (opening diameter 1nm-2nm) is 50%, the volume proportion of the second type of pores (opening diameter <1nm) is 37%, and the volume proportion of the third type of pores (opening diameter >5nm) is 0.7%.

[0126] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0127] Comparative Example 1

[0128] Provided is a three-dimensional porous material with a carbon content >90 wt.% and a total pore volume of 0.85 cm 3 / g, based on the total open pore volume of the three-dimensional porous material, the volume of micropores (opening diameter ≤ 2nm) accounts for 86%, the volume of the first type of pores (opening diameter 1nm-2nm) accounts for 33%, the volume of the second type of pores (opening diameter <1nm) accounts for 53%, and the volume of the third type of pores (opening diameter >5nm) accounts for 1.8%.

[0129] Comparative Example 2

[0130] Provided is a three-dimensional porous material with a carbon content >90 wt.% and a total pore volume of 0.86 cm 3 / g, based on the total open pore volume of the three-dimensional porous material, the volume of micropores (openings with an opening diameter ≤ 2nm) accounts for 74%, the volume of the first type of pores (openings with an opening diameter of 1nm-2nm) accounts for 38%, the volume of the second type of pores (openings with an opening diameter <1nm) accounts for 36%, and the volume of the third type of pores (openings with an opening diameter >5nm) accounts for 9.8%.

[0131] It should be noted that the opening diameter distribution of the three-dimensional porous materials of the above-mentioned embodiments and comparative examples was determined by a nitrogen elution gas adsorption-desorption test: the three-dimensional porous materials of the above-mentioned embodiments and comparative examples were placed in a gas adsorption-desorption tester and degassed at 200°C for 16 hours to obtain the opening diameter distribution and calculate the specific surface area. The specific surface area results are summarized in Table 1. For ease of reading, the opening diameter distribution of the three-dimensional porous materials of the embodiments and comparative examples is also summarized in Table 1.

[0132] The carbon content of the three-dimensional porous materials of the above-mentioned embodiments and comparative examples was measured by a carbon-sulfur analyzer.

[0133] Deposition of silicon nanoparticles in three-dimensional porous materials

[0134] The three-dimensional porous materials provided in the above embodiments and comparative examples were placed in a rotary tube furnace, nitrogen gas was passed through the furnace for 1 hour to expel the air in the rotary tube furnace, and the three-dimensional porous materials were preheated to 420° C. under a nitrogen atmosphere. Monosilane gas was then passed into the rotary tube furnace and the temperature was maintained at 420° C. for 2 hours.

[0135] After cooling to room temperature, a mixture of oxygen and nitrogen was introduced into the rotary tube furnace, where the oxygen content in the mixture was less than 10%. After 30 minutes, the material was discharged. The negative electrode composite materials prepared from the three-dimensional porous materials of each example were designated S1-S3, respectively. The negative electrode composite materials prepared from the three-dimensional porous materials of each comparative example were designated DS1 and DS2, respectively.

[0136] Preparation of negative electrode composite materials with carbon coating layer

[0137] The three-dimensional porous materials provided in the above embodiments and comparative examples were placed in a rotary tube furnace, nitrogen gas was passed through the furnace for 1 hour to expel the air in the rotary tube furnace, and the three-dimensional porous materials were preheated to 420° C. under a nitrogen atmosphere. Monosilane gas was then passed into the rotary tube furnace and the temperature was maintained at 420° C. for 2 hours.

[0138] The monosilane gas was shut off, and the temperature was raised to 650°C. A gaseous carbon source was introduced into the rotary tube furnace and maintained at 650°C for 3 hours. The furnace was then naturally cooled to room temperature and discharged. The negative electrode composite materials prepared from the three-dimensional porous materials of the respective examples were designated SC1-SC3, respectively. The negative electrode composite materials prepared from the three-dimensional porous materials of the respective comparative examples were designated DSC1 and DSC2, respectively.

[0139] Preparation of N-doped anode composite materials with carbon coating

[0140] The three-dimensional porous material of Example 1 was placed in a rotary tube furnace, nitrogen gas was passed through the furnace for 1 hour to expel the air from the furnace, and the three-dimensional porous material was preheated to 420° C. under a nitrogen atmosphere. Monosilane gas was then passed through the furnace and the temperature was maintained at 420° C. for 2 hours.

[0141] Cut off the monosilane gas, raise the temperature to 650°C, introduce a gaseous carbon source (specifically methane) into the rotary tube furnace, keep the temperature at 650°C for 3 hours, cool naturally to room temperature, and discharge;

[0142] The temperature was kept constant, methane was replaced with nitrogen, and the mixture was kept warm for 0.5 h, and then naturally cooled to room temperature. The negative electrode composite material prepared from the three-dimensional porous material in Example 1 was recorded as SCN1.

[0143] Changing the deposition time of monosilane to prepare negative electrode composite materials with different silicon contents from SC1

[0144] Case SC1-2

[0145] The three-dimensional porous material provided in Example 1 was placed in a rotary tube furnace, nitrogen gas was passed through the furnace for 1 hour to expel the air in the rotary tube furnace, and the three-dimensional porous material was preheated to 420° C. under a nitrogen atmosphere; monosilane gas was then passed through the rotary tube furnace, and the temperature was maintained at 420° C. for 1.9 hours;

[0146] The monosilane gas was cut off, and the temperature was raised to 650° C. A gaseous carbon source was introduced into the rotary tube furnace, and the temperature was kept at 650° C. for 3 h. The furnace was naturally cooled to room temperature and discharged to obtain the negative electrode composite material SC1-2.

[0147] Case SC1-3

[0148] The only difference from Case SC1-2 is that monosilane gas was introduced into the rotary tube furnace and kept at 420°C for 1.8 hours to obtain the negative electrode composite material SC1-3.

[0149] Structural parameters and electrochemical performance characterization

[0150] 1) Structural parameter characterization

[0151] ① X-ray fluorescence scattering analyzer was used to test the mass proportion of silicon element in each negative electrode composite material in S1-S3, DS1, DS2 and SC1-SC3, DSC1, DSC2, SCN1 and SC1-1 to SC1-3. The results are summarized in Tables 2 to 5 respectively.

[0152] ② The D50 of S1-S3, DS1, DS2, SC1-SC3, DSC1, DSC2 and SCN1 were tested using a laser particle size analyzer. The results are summarized in Tables 2 to 5 respectively.

[0153] ③ The true densities of S1-S3, DS1, DS2, SC1-SC3, DSC1, DSC2, SCN1, and SC1-1 to SC1-3 were tested using a fully automatic gas replacement method true density tester. The results are summarized in Tables 2 to 5 respectively.

[0154] ④ The powder resistivity of S1-S3, DS1, DS2, SC1-SC3, DSC1, DSC2, SCN1, and SC1-1 to SC1-3 was tested using a powder resistivity tester. The results are summarized in Tables 2 to 5, respectively.

[0155] ⑤ The specific surface areas of S1-S3, DS1, DS2, SC1-SC3, DSC1, DSC2, SCN1, and SC1-1 to SC1-3 were determined by nitrogen adsorption-desorption test, and the results are summarized in Tables 2 to 5 respectively.

[0156] ⑥ Thermogravimetric analysis (TGA) was used to determine the silicon content in S1-S3, DS1, DS2, SC1-SC3, DSC1, DSC2, SCN1, and SC1-1 to SC1-3. The results are summarized in Tables 2 to 5, respectively.

[0157] ⑦ TEM was used to observe SC1-SC3, DSC1, and DSC2. The TEM image of SC1 is shown in Figure 7, where a clear amorphous carbon coating layer can be seen.

[0158] ⑧ X-ray diffraction (XRD) was used to test the negative electrode composite material SC1 and the comparative negative electrode composite material DSC2. The XRD patterns of SC1 and DSC2 are shown in FIG4 , showing clear characteristic peaks of amorphous carbon.

[0159] ⑨ The morphology of the negative electrode composite material SC1 and the comparative negative electrode composite material DSC2 and the distribution of silicon elements at corresponding positions were observed using a scanning electron microscope (SEM)-energy dispersive spectrometer (EDS); the SEM photos of SC1 and DSC2 and the corresponding EDS silicon element distribution maps are summarized in Figures 5 and 6, respectively.

[0160] 2) Electrochemical performance characterization

[0161] ① Prepare test cells of each negative electrode composite material separately:

[0162] S1-S3, DS1, DS2, SC1-SC3, DSC1, DSC2, SCN1, and SC1-2 to SC1-3 were added to water with a conductive agent (specifically Super P) and a binder (specifically sodium carboxymethyl cellulose) at a mass ratio of 8:1:1, and stirred evenly to obtain a negative electrode slurry; each of the above negative electrode slurries was coated on a negative electrode current collector (specifically copper foil), vacuum dried at 110°C for 12 hours, and then rolled and cut to obtain each negative electrode sheet;

[0163] In an argon-protected glove box, a metallic lithium sheet was used as the counter electrode. The negative electrode sheet, the diaphragm (specifically a commercial polyethylene diaphragm) and the above counter electrode were stacked in sequence, encapsulated and filled with electrolyte to obtain a 2032-type button cell. The electrolyte was a 1 mol / L LiPF6 solution, and the electrolyte solvent was ethylene carbonate and diethyl carbonate in a volume ratio of 1:1.

[0164] ② Each test battery prepared as described above was placed in an electrochemical test cabinet, and at 25°C, discharged at a constant current of 0.1C to 0.005V, allowed to stand for 5 minutes, and then discharged at a constant current of 0.02C to 0.005V and allowed to stand for 5 minutes. Then, it was charged to 1V at a constant current of 0.1C for cycle testing. The reversible capacity, first coulombic efficiency, and cycle capacity retention rate of the negative electrode composite material after 100 cycles were calculated. The results are summarized in Tables 2 to 5.

[0165] ③ At 25°C, measure the initial thickness of each newly produced negative electrode sheet. Then, take the button cell produced in step ①, charge it to 0.05V to fully lithiumize the negative electrode, disassemble it, measure the thickness of the negative electrode sheet, record the thickness increase, and calculate the expansion rate of the negative electrode sheet. The expansion rate of the negative electrode sheet = thickness increase of the negative electrode sheet / initial thickness of the negative electrode sheet × 100%. The results are summarized in Tables 2-5.

[0166] Table 1

[0167] Table 2

[0168] Table 3

[0169] Table 4

[0170] Table 5

[0171] Combining the data in Tables 1 and 2, it can be seen that, given similar total pore volumes of the three-dimensional porous materials, the negative electrode composite materials S1-S3 prepared from the three-dimensional porous materials provided in the examples of the present application have significantly higher silicon contents than those of the comparative examples DS1-DS2, and their reversible capacities are even more significantly higher, indicating that the three-dimensional porous materials of the examples of the present application contain a higher content of effective deposited pores. Furthermore, because the opening diameters of the pores in the three-dimensional porous materials provided in the examples of the present application are more uniformly distributed, the resulting negative electrode composite materials exhibit low expansion characteristics and good cycling performance while maintaining high reversible capacity.

[0172] Combining the data in Tables 2 and 3, we can see that carbon coating can significantly increase the electronic conductivity of the negative electrode composite material, improve cycling performance, further reduce the expansion rate of the negative electrode composite material, and slightly increase the reversible capacity. Furthermore, the specific surface area of ​​the negative electrode composite material decreases significantly after carbon coating, indicating that the carbon coating layer is also formed in the open pores of the three-dimensional porous material.

[0173] Furthermore, combining the data in Tables 3 and 4, it can be seen that N doping further improves the electronic conductivity and reversible capacity of the negative electrode composite material, and further optimizes the cycle performance, indicating that its doping can also improve the stability of the negative electrode composite material.

[0174] It is not difficult to see from the data in Table 5 that by adjusting the silicon content in the negative electrode composite material, the changing trends of the cycle performance and the reversible capacity are opposite, and the changing trends of the cycle performance and the negative electrode expansion rate are opposite. Ordinary technicians in this field can flexibly adjust the silicon content (that is, the content of nanoparticles) in the negative electrode composite material according to actual needs.

[0175] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A three-dimensional porous material, characterized in that: The three-dimensional porous material includes a plurality of openings. Based on the total opening volume of the three-dimensional porous material, the volume of openings with an opening diameter ≤ 2 nm accounts for ≥ 70%, and the volume of openings with an opening diameter in the range of 1 nm-2 nm accounts for ≥ 50%.

2. The three-dimensional porous material according to claim 1, characterized in that: Based on the total open pore volume of the three-dimensional porous material, the volume of open pores with an opening diameter of ≤2 nm accounts for ≥85%.

3. The three-dimensional porous material according to claim 1 or 2, characterized in that: Based on the total open pore volume of the three-dimensional porous material, the volume of open pores with an opening diameter of less than 1 nm accounts for ≤40%.

4. The three-dimensional porous material according to claim 3, characterized in that: Based on the total open pore volume of the three-dimensional porous material, the volume proportion of open pores with an opening diameter of less than 1 nm is ≤38%.

5. The three-dimensional porous material according to any one of claims 1 to 4, characterized in that: Based on the total open pore volume of the three-dimensional porous material, the volume of open pores with an opening diameter of >5 nm accounts for <1%.

6. The three-dimensional porous material according to any one of claims 1 to 5, characterized in that: The total pore volume of the three-dimensional porous material is greater than 0.5 cm 3 / g.

7. The three-dimensional porous material according to any one of claims 1 to 6, characterized in that: The material of the three-dimensional porous material includes at least one of conductive carbon, conductive ceramic or metal.

8. A negative electrode composite material, characterized in that: The negative electrode composite material comprises the three-dimensional porous material according to any one of claims 1 to 7 and a plurality of nanoparticles located in the open pores; The material of the nanoparticles includes at least one of a silicon-containing material, a phosphorus-containing material or a tin-containing material.

9. The negative electrode composite material according to claim 8, characterized in that: The size of the nanoparticles in at least one direction is ≤2 nm.

10. The negative electrode composite material according to any one of claims 8 to 9, characterized in that: The negative electrode composite material further includes a coating layer formed on the surface of the three-dimensional porous material; The coating layer comprises a carbon coating layer and / or a fast ion conductor coating layer, or a composite coating layer; wherein the material of the composite coating layer comprises a carbon material and a fast ion conductor material; The thickness of the coating layer is ≤20nm.

11. The negative electrode composite material according to claim 10, characterized in that: The carbon coating layer is also formed in the open pores of the three-dimensional porous material.

12. The negative electrode composite material according to any one of claims 8 to 11, characterized in that: The negative electrode composite material contains a doping element; the doping element is at least one of N, P or S.

13. The negative electrode composite material according to claim 12, characterized in that: The nanoparticles contain the doping element.

14. The negative electrode composite material according to claim 12 or 13, characterized in that: The three-dimensional porous material contains the doping element.

15. The negative electrode composite material according to any one of claims 12 to 14, characterized in that: The mass proportion of the doping element in the negative electrode composite material is less than 10%.

16. The negative electrode composite material according to any one of claims 8 to 15, characterized in that: The mass of the plurality of nanoparticles accounts for 30%-80% of the total mass of the negative electrode composite material.

17. A negative electrode plate, characterized in that: It comprises a current collector and a negative electrode material layer arranged on the surface of the current collector, wherein the negative electrode material layer comprises the negative electrode composite material according to any one of claims 8 to 16.

18. A secondary battery, characterized in that: The secondary battery comprises the negative electrode sheet and the positive electrode sheet as claimed in claim 17, and an electrolyte located between the negative electrode sheet and the positive electrode sheet.

19. An electrical equipment, characterized in that: The electric device comprises the secondary battery as claimed in claim 18.

20. An energy storage system, characterized in that: The energy storage system comprises the secondary battery as claimed in claim 18.

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