Porous negative electrode material and preparation method thereof, negative electrode plate, secondary battery and electric device

Abstract

The invention relates to a porous negative electrode material and a preparation method thereof, a negative electrode plate, a secondary battery and an electric device, the porous negative electrode material comprises secondary particles with internal pore structures, the secondary particles comprise a plurality of primary particles, the primary particles comprise a carbon-based material, porous hard carbon is filled between adjacent primary particles, and the carbon-based material is a carbon-based material. Porous hard carbon contained in the secondary particles forms a net-shaped structure, and the porosity of the porous negative electrode material is 15-28%. The porous negative electrode material is internally porous and loose, and also has a relatively high graphitization degree, so that a buffer region is provided for volume expansion of the carbon-based material, the stability of the internal and surface structures of particles is facilitated, and the development of the gram volume is facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a porous negative electrode material and a preparation method thereof, a negative electrode plate, a secondary battery, and an electrical device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] In recent years, as the application scope of lithium-ion batteries has become increasingly wider, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0004] During the charging process of lithium-ion batteries, the graphite anode inevitably expands in volume due to the intercalation of lithium ions. During cycling, this repeated volume expansion causes the SEI film to thicken continuously, while also causing increased stress to accumulate within the anode material particles, ultimately leading to particle breakage and capacity degradation. Reducing the degree of graphitization, thereby reducing the proportion of graphite involved in the lithium intercalation reaction, is an effective way to mitigate this volume expansion, but it can also negatively impact the battery's ability to intercalate lithium and reduce specific capacity.

[0005] Therefore, how to improve the volume expansion of the negative electrode of carbon-based materials without reducing the gram capacity of carbon-based materials is a key issue facing lithium-ion batteries. Summary of the Invention

[0006] The present application provides a porous negative electrode material and a preparation method thereof, a negative electrode sheet, a secondary battery and an electrical device that can improve the volume expansion of a graphite negative electrode while taking into account the specific capacity of graphite.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a porous negative electrode material, which includes secondary particles with an internal pore structure, the secondary particles contain multiple primary particles, the primary particles contain carbon-based materials, and porous hard carbon is filled between adjacent primary particles. The porous hard carbon contained in the secondary particles forms a network structure, and the porosity of the porous negative electrode material is 15%-28%.

[0008] Therefore, the porous negative electrode material in the present application includes secondary particles with an internal pore structure, and the porous hard carbon filled between the multiple primary particles forming the secondary particles forms a network structure, and the porosity of the porous negative electrode material is 15%-28%; therefore, the porous and loose hard carbon structure inside the porous negative electrode material not only provides a buffer area for the volume expansion of the carbon-based material, but also helps to stabilize the internal and surface structure of the particles, and does not affect the gram capacity of the negative electrode material. Furthermore, the internal pore structure of the porous negative electrode material cannot be in direct contact with the electrolyte, so that the loss of active lithium due to the formation of the SEI film will not be caused, thereby reducing the loss of coulombic efficiency and gram capacity. In addition, the specific surface area of ​​the porous negative electrode material including the secondary particles is reduced, which is conducive to improving its coulombic efficiency. At the same time, because the secondary particles are more compact, their compaction density is significantly higher than that of the primary particles, thereby improving the energy density of the material.

[0009] In some embodiments of the present application, the porosity of the porous negative material is 18%-27%.

[0010] In some embodiments of the present application, the average pore diameter of the internal pore structure contained in the porous negative electrode material is 2.8 nm-5.2 nm, and can be optionally 3.0 nm-4.5 nm.

[0011] In some embodiments of the present application, the porous negative electrode material contains an internal pore structure including micropores with a pore size of less than 2 nm, mesopores with a pore size of 2 nm to 50 nm, and macropores with a pore size of more than 50 nm;

[0012] Optionally, the micropores account for 55%-70% of the internal pore structure, and optionally 58%-68%;

[0013] Optionally, the mesopores account for 20%-35% of the internal pore structure, and optionally 22%-32%;

[0014] Optionally, the macropores account for 3%-10% of the internal pore structure, and optionally 4%-8%.

[0015] In some embodiments of the present application, the porous negative electrode material contains an internal pore structure with a pore volume of 0.05 cm 3 / g-0.35cm 3 / g, optional 0.08cm 3 / g-0.32cm 3 / g.

[0016] In some embodiments of the present application, the volume average particle size Dv50 of the porous negative electrode material is 15 μm-25 μm, and can be optionally 16 μm-24 μm.

[0017] In some embodiments of the present application, the mass ratio of the porous hard carbon to the carbon-based material contained in the porous negative electrode material is 1:(5-50), and can be optionally 1:(20-35).

[0018] In some embodiments of the present application, the carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon and soft carbon; optionally, the carbon-based material includes artificial graphite.

[0019] The second aspect of the present application provides a method for preparing the porous negative electrode material of the first aspect of the present application, comprising the following steps:

[0020] The carbon-based material precursor and the hard carbon precursor are mixed and then crushed to prepare a mixed material;

[0021] pyrolyzing and granulating the mixed material to prepare an intermediate;

[0022] The intermediate is post-processed to prepare the porous negative electrode material.

[0023] Therefore, the present application is to mix a carbon-based material precursor with a hard carbon precursor, and after crushing and pyrolysis granulation, the hard carbon precursor is attached to the surface of the carbon-based material precursor particles, and the primary particles with smaller particle size are aggregated together to form secondary particles, and the hard carbon precursor is converted into hard carbon during pyrolysis granulation and subsequent heat treatment, and the released gas causes it to form porous hard carbon. This preparation method does not increase the specific surface area of ​​the particles, and thus does not increase the active sites to cause a decrease in coulomb efficiency and an increase in lithium consumption. The prepared porous negative electrode material with an internal porous structure can take into account the gram capacity while alleviating volume expansion, and has a high compaction density, high energy density and high coulomb efficiency. In addition, this preparation method does not need to improve the carbon-based material after molding, but only improves the processing process of forming the carbon-based material, and directly obtains the negative electrode material with an internal porous structure, which greatly reduces the cost.

[0024] In some embodiments of the present application, the hard carbon precursor includes one or more of a resin, an organic polymer, a biomass, and a carbohydrate;

[0025] Optionally, the resin includes one or more of phenolic resin, epoxy resin and polyfurfuryl alcohol resin;

[0026] Optionally, the organic polymer includes one or more of polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride and asphalt;

[0027] Optionally, the biomass comprises one or more of cellulose and lignin;

[0028] Optionally, the carbohydrates include one or more of sucrose and glucose.

[0029] In some embodiments of the present application, a crushing machine is used to perform the crushing process;

[0030] Optionally, the rotation speed of the pulverizer is 10000rpm-25000rpm, optionally 12000rpm-25000rpm;

[0031] Optionally, the crushing process takes 5 minutes to 10 minutes, or 8 minutes to 10 minutes.

[0032] In some embodiments of the present application, the mass ratio of the hard carbon precursor to the carbon-based material precursor is 1:(5-50), and can be optionally 1:(20-35).

[0033] In some embodiments of the present application, the carbon-based material precursor includes one or more of activated carbon, coke, carbon black, charcoal, biocoke and coal coke.

[0034] In some embodiments of the present application, the post-treatment includes graphitization;

[0035] Optionally, the graphitization temperature is 2000°C-3300°C, optionally 2500°C-3200°C;

[0036] Optionally, the graphitization time is 300h-800h, optionally 500h-800h.

[0037] In some embodiments of the present application, the post-treatment includes carbonization;

[0038] Optionally, the temperature of the carbonization treatment is 1500° C.-2000° C.;

[0039] Optionally, the carbonization treatment time is 15h-40h.

[0040] In some embodiments of the present application, the carbon-based material includes one or more of flake graphite and microcrystalline graphite.

[0041] In some embodiments of the present application, the post-processing includes spheroidization;

[0042] Optionally, the rotation speed of the spheroidization treatment is 2000 rpm-8000 rpm;

[0043] Optionally, the spheroidization treatment time is 5 min-15 min;

[0044] Optionally, the spheroidization treatment is performed by at least one of air flow milling and mechanical milling.

[0045] In some embodiments of the present application, the carbon-based material includes one or more of asphalt, paraffin, biomass, biomass extracts, and artificial organic high molecular polymers.

[0046] In some embodiments of the present application, the post-treatment includes carbonization;

[0047] Optionally, the temperature of the carbonization treatment is 800°C-1600°C;

[0048] Optionally, the carbonization treatment time is 2h-15h.

[0049] In some embodiments of the present application, the temperature of the pyrolysis granulation is 600° C.-1600° C., optionally 800° C.-1200° C.; and / or

[0050] The pyrolysis granulation time is 0.5h-6h, and can be optionally 2h-5h.

[0051] The third aspect of the present application provides a negative electrode plate, comprising:

[0052] negative electrode current collector; and

[0053] The negative electrode active material layer is located on at least one side of the negative electrode current collector, and the negative electrode active material layer comprises the porous negative electrode material of the first aspect of the present application or the porous negative electrode material prepared by the preparation method of the second aspect of the present application.

[0054] In some embodiments of the present application, the compaction density of the negative electrode sheet is 1.4 g / cm 3 -1.65g / cm 3 .

[0055] In some embodiments of the present application, the negative electrode active material layer further includes a conductive agent, a dispersant, and a binder;

[0056] Optionally, the conductive agent includes one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene and carbon nanotubes;

[0057] Optionally, the dispersant includes one or more of sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide and polyvinyl pyrrolidone;

[0058] Optionally, the binder includes one or more of polyimide resin, acrylic resin, polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose and styrene-butadiene rubber;

[0059] Optionally, the porous negative electrode material accounts for 95.5% to 97% by mass in the negative electrode active material layer;

[0060] Optionally, the conductive agent accounts for 0.8% to 1.2% by mass in the negative electrode active material layer;

[0061] Optionally, the mass proportion of the dispersant in the negative electrode active material layer is 0.5%-1%;

[0062] Optionally, the binder accounts for 1.2%-1.8% by mass in the negative electrode active material layer.

[0063] The fourth aspect of the present application provides a secondary battery, comprising the negative electrode sheet of the third aspect of the present application.

[0064] The fifth aspect of the present application provides an electrical device comprising the secondary battery of the fourth aspect of the present application. The secondary battery of the present application comprises the porous negative electrode material of the present application, has excellent coulombic efficiency and gram capacity, and has high energy density.

[0065] The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.

[0066] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0068] Figure 1 This is a schematic structural diagram of a porous negative electrode material according to one embodiment of the present application.

[0069] Figure 2 This is a schematic diagram of a battery cell according to one embodiment of the present application.

[0070] Figure 3 for Figure 2 FIG. 1 is an exploded view of a battery cell according to an embodiment of the present application.

[0071] Figure 4 This is a schematic diagram of a battery module according to one embodiment of the present application.

[0072] Figure 5 Schematic diagram of a battery pack according to one embodiment of the present application.

[0073] Figure 6 for Figure 5 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0074] Figure 7 Schematic diagram of an electrical device using a secondary battery as a power source according to one embodiment of the present application.

[0075] Description of reference numerals:

[0076] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Battery cell; 5. Casing; 5. Electrode assembly; 5. Cover; 6. Electrical device. DETAILED DESCRIPTION

[0077] Below, some embodiments of the porous negative electrode material and its preparation method, negative electrode sheet, secondary battery and electric device of the present application are described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0078] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0079] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0080] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0081] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0082] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0083] In this application, in the open technical features or technical solutions described with words such as "contain", "include", and "include", unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions that also include additional members in addition to the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" and the feature or solution of "A includes not only a1, a2, and a3, but also other members". In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0084] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0085] Improving the volume expansion of graphite anodes without reducing their specific capacity is a key issue facing current lithium-ion batteries. Pore formation in graphite is an effective method for reducing this volume expansion. While creating pores on the surface of graphite particles increases porosity and surface area, when used as a lithium-ion battery anode material, this porous surface provides an excessive number of active sites, consuming more active lithium, resulting in a decrease in coulombic efficiency and a thickening of the SEI film.

[0086] If pores are created inside graphite particles, it not only provides a buffer area for the volume expansion of graphite, which helps to stabilize the internal and surface structure of the particles, but also prevents the internal pore structure from directly contacting the electrolyte, thereby preventing the formation of SEI film and causing loss of active lithium.

[0087] Based on this, the present application improves the pretreatment step in the preparation process of carbon-based materials. A hard carbon precursor is added in the pretreatment step, and the primary particles of the carbon-based material precursor are bonded into secondary particles by the hard carbon precursor. During the pyrolysis and granulation process, the hard carbon precursor is carbonized into a hard carbon structure at high temperature, and the released gas makes the hard carbon have a porous structure. Finally, a porous negative electrode material with an internal pore structure is prepared, and the porous negative electrode material has a high degree of graphitization. While alleviating the volume expansion of the carbon-based material, it can take into account the gram capacity, and at the same time has a high compaction density, high energy density and high coulombic efficiency.

[0088] The first aspect of the present application provides a porous negative electrode material, which includes secondary particles with an internal pore structure, the secondary particles contain multiple primary particles, the primary particles contain carbon-based materials, and porous hard carbon is filled between adjacent primary particles. The porous hard carbon contained in the secondary particles forms a network structure, and the porosity of the porous negative electrode material is 15%-28%.

[0089] It should be noted that "internal pore structure" refers to the pore structure located inside the secondary particles and does not extend to the surface of the secondary particles. The secondary particles of the porous negative electrode material mentioned above only have a pore structure located inside them, and the surface of the secondary particles does not have a pore structure.

[0090] Understandably, the porous negative electrode material in the present application includes secondary particles with an internal pore structure, and the porous hard carbon filled between the multiple primary particles forming the secondary particles forms a network structure, and the porosity of the porous negative electrode material is 15%-28%; therefore, the porous negative electrode material has a porous and loose hard carbon structure inside, which not only provides a buffer area for the volume expansion of the carbon-based material and helps to stabilize the internal and surface structure of the particles, but also does not affect the gram capacity of the negative electrode material. Furthermore, the internal pore structure of the porous negative electrode material cannot be in direct contact with the electrolyte, so that the loss of active lithium due to the formation of the SEI film will not be caused, thereby reducing the loss of coulombic efficiency and gram capacity. In addition, the specific surface area of ​​the porous negative electrode material including the secondary particles is reduced, which is conducive to improving its coulombic efficiency. At the same time, because the secondary particles are more compact, their compaction density is significantly higher than that of the primary particles, thereby improving the energy density of the material.

[0091] It should be noted that the gaps between adjacent primary particles in the secondary particles can be partially filled with porous hard carbon or completely filled with porous hard carbon. Figure 1 This is a schematic diagram of the structure of the porous negative electrode material provided in one embodiment of the present application, referring to Figure 1 The gaps between adjacent primary particles (blue parts in the figure) formed by carbon-based materials are completely filled with porous hard carbon (dark gray parts), and the porous hard carbon contained in the secondary particles forms a network structure.

[0092] As an example, the porosity of the porous negative electrode material may be, but is not limited to, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, or a range between any two of the foregoing values. When the porosity of the porous negative electrode material is within the foregoing range, the volume expansion of the carbon-based material can be effectively mitigated while also taking into account the coulombic efficiency of the porous negative electrode material.

[0093] As a possible implementation, the porosity of the porous negative electrode material is 18%-27%.

[0094] As an example, the porosity of the porous anode material mentioned above can be measured using mercury intrusion porosimetry. The specific method is as follows: the porous anode material is cut into small pieces, placed in a sample container, and a glass cone probe is used as the sample container. Pressure is applied to the sample for measurement. The mercury intrusion porosimeter parameters are set to: a pressure of approximately 0.6 to 50 PSI (corresponding to a pore diameter ranging from 355 to 4 microns) in the low-pressure station (LP), and a pressure of approximately 20 to 60,000 PSI (corresponding to a pore diameter ranging from 10 to 0.004 microns) in the high-pressure station (HP). The mercury intrusion porosimeter can be a US PoreMaster 60GT mercury intrusion porosimeter.

[0095] In some embodiments, the porous negative electrode material comprises an internal pore structure having an average pore diameter of 2.8 nm to 5.2 nm; for example, but not limited to, 2.8 nm, 3 nm, 3.2 nm, 3.4 nm, 3.6 nm, 3.8 nm, 4 nm, 4.2 nm, 4.4 nm, 4.6 nm, 4.8 nm, 5 nm, 5.2 nm, or a range between any two of the foregoing pore diameters. When the average pore diameter of the internal pore structure of the porous negative electrode material is within the above range, it is beneficial to effectively mitigate the volume expansion of the carbon-based material and to improve the stability of the particle structure of the porous negative electrode material.

[0096] In some optional embodiments, the porous negative electrode material comprises an internal pore structure having an average pore size of 3.0 nm to 4.5 nm.

[0097] In some optional embodiments, the porous negative electrode material contains an internal pore structure including micropores with a pore size less than 2 nm, mesopores with a pore size of 2 nm-50 nm, and macropores with a pore size greater than 50 nm.

[0098] As a possible embodiment, the number of micropores in the internal pore structure accounts for 55%-70%, for example, but not limited to 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, or a range between any two of the above values. Optionally, the number of micropores in the internal pore structure accounts for 58%-68%.

[0099] As a possible embodiment, the number of mesopores in the internal pore structure accounts for 20%-35%, for example, but not limited to 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or a range between any two of the above values. Optionally, the number of mesopores in the internal pore structure accounts for 22%-32%.

[0100] As a possible embodiment, the number of macropores in the internal pore structure accounts for 3%-10%, for example, but not limited to 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range between any two of the above values. Optionally, the number of macropores in the internal pore structure accounts for 4%-8%.

[0101] When the proportions of micropores, mesopores, and macropores in the internal pore structure of the porous negative electrode material are respectively within the above ranges, it is beneficial to the mechanical strength inside the secondary particles while alleviating the volume expansion of the carbon-based material.

[0102] It should be noted that the pore size of the internal pore structure of the porous negative electrode material mentioned above and the ratio of micropores, mesopores and macropores can be measured using a nitrogen adsorption curve. Specifically, the following method can be used:

[0103] The test sample is placed in a sample tube and first degassed by vacuum. The entire system is then brought to the desired vacuum level. The sample tube is then immersed in a liquid nitrogen bath and filled with a known amount of gas. Adsorption of the gas by the adsorbent causes a pressure drop. After adsorption equilibrium is reached, the equilibrium pressure is measured, and the adsorbed amount is calculated based on the pressure change before and after adsorption. The adsorption-desorption isotherm is measured by gradually increasing the amount of adsorbate gas in the system and changing the pressure. The BJH model (Barret-Joyner-Halenda) is then used to equivalently determine the pore size distribution of the test sample.

[0104] In some embodiments, the porous negative electrode material comprises an internal pore structure with a pore volume of 0.05 cm 3 / g-0.35cm 3 / g; for example, but not limited to 0.05cm 3 / g, 0.07cm 3 / g, 0.1cm 3 / g, 0.13cm 3 / g, 0.15cm 3 / g, 0.18cm 3 / g, 0.2cm 3 / g, 0.23cm 3 / g, 0.25cm 3 / g, 0.28cm 3 / g, 0.3cm 3 / g, 0.33cm 3 / g, 0.35cm 3 / g or the range between any two of the above pore volumes. When the pore volume of the internal pore structure is within the above range, it is beneficial to the mechanical strength of the secondary particles while alleviating the volume expansion of the carbon-based material. Optionally, the porous negative electrode material contains an internal pore structure with a pore volume of 0.08cm 3 / g-0.32cm 3 / g.

[0105] As an example, the pore volume of the internal pore structure mentioned above can be measured using a nitrogen adsorption curve. Specifically, the following method can be used:

[0106] The test sample is placed in a sample tube and first degassed by vacuum. The entire system is then brought to the desired vacuum level. The sample tube is then immersed in a liquid nitrogen bath and filled with a known amount of gas. Adsorption of the gas by the adsorbent causes a pressure drop. After adsorption equilibrium is reached, the equilibrium pressure is measured, and the adsorbed amount is calculated based on the pressure change before and after adsorption. The adsorption-desorption isotherm is measured by gradually increasing the amount of adsorbate gas in the system and changing the pressure. The BJH model (Barret-Joyner-Halenda) is then used to equivalently determine the pore volume of the test sample.

[0107] In some embodiments, the volume average particle size Dv50 of the porous negative electrode material is 15 μm-25 μm; for example, it can be, but is not limited to, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, or a range between any two of the above particle sizes. Optionally, the volume average particle size Dv50 of the porous negative electrode material is 16 μm-24 μm.

[0108] The Dv50 of a material is well known in the art and can be measured using methods known in the art. For example, it can be measured using a laser particle size analyzer (such as the Malvern Master Size 3000) in accordance with standard GB / T 19077-2016. The physical definition of Dv50 is as follows:

[0109] Dv50: The particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%.

[0110] In some embodiments, the mass ratio of the porous hard carbon and the carbon-based material contained in the porous negative electrode material is 1:(5-50); for example, it can be but not limited to 1:5, 1:7, 1:10, 1:13, 1:15, 1:18, 1:20, 1:23, 1:25, 1:28, 1:30, 1:33, 1:35, 1:38, 1:40, 1:43, 1:45, 1:48, 1:50 or a range between any two of the above ratios. When the mass ratio of the porous hard carbon and the carbon-based material is within the above range, it is more conducive to the porous hard carbon to play an internal bonding role, so that the porous negative electrode material finally obtained has a suitable particle size. Optionally, the mass ratio of the porous hard carbon and the carbon-based material contained in the porous negative electrode material is 1:(20-35).

[0111] As a possible implementation, the carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon and soft carbon.

[0112] In some alternative embodiments, the carbon-based material comprises artificial graphite.

[0113] The second aspect of the present application provides a method for preparing a porous negative electrode material of the first aspect of the present application, comprising the following steps: mixing a carbon-based material precursor and a hard carbon precursor and then crushing them to prepare a mixed material; pyrolyzing and granulating the mixed material to prepare an intermediate; and post-processing the intermediate to prepare a porous negative electrode material.

[0114] The hard carbon precursor used in this application contains a large number of heteroatoms such as H, O, and N, which hinder the formation of crystalline regions during the heat treatment process, making it difficult to graphitize even at high temperatures above 2500°C; therefore, the hard carbon precursor added in this application not only has the function of a binder, but can also aggregate the primary particles of the carbon-based material precursor into secondary particles at room temperature or high temperature; at the same time, the hard carbon precursor cannot be completely graphitized at ultra-high temperatures (above 2500°C), and eventually forms a hard carbon structure, and the other released internal porous structures form porous hard carbon.

[0115] The microstructure of porous hard carbon is characterized by short-range ordered microdomains stacked with curved graphite-like sheets. These randomly and disorderly stacks leave a large number of nanopores. Compared to graphite, porous hard carbon has shorter graphene layers, approximately 1 nm in diameter, which can be single layers or composed of two or three layers. Compared to soft carbon (graphitizable carbon), porous hard carbon has a more disordered structure, a higher defect concentration, a higher heteroatom content, a larger distance between graphene layers, and a more closed pore structure.

[0116] Understandably, the present application is achieved by mixing a carbon-based material precursor with a hard carbon precursor, and subjecting the mixture to a crushing process and pyrolysis granulation, wherein the hard carbon precursor is attached to the surface of the carbon-based material precursor particles, and the primary particles with smaller particle sizes are aggregated together to form secondary particles. The hard carbon precursor is converted into hard carbon during pyrolysis granulation and subsequent heat treatment, and the released gas causes it to form porous hard carbon. This preparation method does not increase the specific surface area of ​​the particles, and thus does not increase the active sites to cause a decrease in coulombic efficiency and an increase in lithium consumption. The obtained porous negative electrode material with an internal porous structure can take into account gram capacity while alleviating volume expansion, and has high compaction density, high energy density and high coulombic efficiency. In addition, this preparation method does not require improvement of the carbon-based material after molding, but only improves the processing process of forming the carbon-based material, and directly obtains the negative electrode material with an internal porous structure, which greatly reduces the cost.

[0117] In some embodiments, the hard carbon precursor includes one or more of a resin, an organic polymer, a biomass, and a carbohydrate.

[0118] In some optional embodiments, the resin includes one or more of phenolic resin, epoxy resin and polyfurfuryl alcohol resin. As a possible embodiment, the organic polymer includes one or more of polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride and asphalt.

[0119] In some exemplary embodiments, the biomass includes one or more of cellulose and lignin. For example, the biomass includes cellulose and lignin contained in plant residues and shells.

[0120] In some embodiments thereof, the carbohydrate comprises one or more of sucrose and glucose.

[0121] In some embodiments, the hard carbon precursor includes high-temperature pyrolytic carbon with a pyrolytic carbonization temperature between 1000° C. and 1400° C. and low-temperature pyrolytic carbon with a pyrolytic carbonization temperature between 500° C. and 1000° C., depending on the pyrolytic carbonization temperature.

[0122] As a possible implementation method, a crusher is used for crushing, which is helpful for breaking up large particles and making the carbon-based material precursor and the hard carbon precursor into dry fine powder.

[0123] In some optional embodiments, during the crushing process, the rotational speed of the pulverizer is 10,000 rpm-25,000 rpm; for example, it can be, but is not limited to, 10,000 rpm, 11,000 rpm, 12,000 rpm, 13,000 rpm, 14,000 rpm, 15,000 rpm, 16,000 rpm, 17,000 rpm, 18,000 rpm, 19,000 rpm, 20,000 rpm, 21,000 rpm, 22,000 rpm, 23,000 rpm, 24,000 rpm, 25,000 rpm, or a range between any two of the above rotational speeds. When the rotational speed of the pulverizer is within the above range, it is more conducive to obtaining uniformly sized and appropriately crushed particles. Alternatively, during the crushing process, the rotational speed of the pulverizer is 12,000 rpm-25,000 rpm.

[0124] As a possible embodiment, the crushing process lasts for 5-10 minutes; for example, it can be, but is not limited to, 5, 6, 7, 8, 9, 10 minutes, or a range between any two of the above times. Crushing processes within the above ranges are more conducive to obtaining crushed particles of uniform and appropriate size. Optionally, the crushing process lasts for 8-10 minutes.

[0125] In some embodiments, the carbon-based material precursor and the hard carbon precursor are mixed by stirring so that the carbon-based material precursor and the hard carbon precursor are evenly mixed. As an example, the form of the agitator used can be, but is not limited to, a turbine type, a paddle type, a propeller type, a screw type or a planetary type. The stirring speed is 10rpm-300rpm; for example, it can be, but is not limited to, 10rpm, 30rpm, 50rpm, 70rpm, 100rpm, 130rpm, 150rpm, 180rpm, 200rpm, 230rpm, 250rpm, 280rpm, 300rpm or a range between any two of the above speeds. The stirring time is 0.25h-12h; for example, it can be, but is not limited to, 0.25h, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or a range between any two of the above times.

[0126] In some embodiments, the mass ratio of the hard carbon precursor to the carbon-based material precursor is 1:(5-50); for example, it can be, but is not limited to, 1:5, 1:7, 1:10, 1:13, 1:15, 1:18, 1:20, 1:23, 1:25, 1:28, 1:30, 1:33, 1:35, 1:38, 1:40, 1:43, 1:45, 1:48, 1:50, or a range between any two of the above ratios. When the mass ratio of the hard carbon precursor to the carbon-based material precursor is within the above range, it is more conducive to the internal bonding of the porous hard carbon, so that the porous negative electrode material finally obtained has a suitable particle size. Optionally, the mass ratio of the hard carbon precursor to the carbon-based material precursor is 1:(20-35).

[0127] As a possible embodiment, the carbon-based material precursor includes one or more of activated carbon, coke, carbon black, charcoal, bio-coke, and coal coke. Accordingly, the carbon-based material in the prepared porous negative electrode material is artificial graphite or soft carbon.

[0128] In some optional embodiments, when the carbon-based material in the porous negative electrode material is artificial graphite, the post-treatment during the preparation of the porous negative electrode material includes graphitization.

[0129] In some optional embodiments, the graphitization temperature is 2000°C-3300°C; for example, it can be, but is not limited to, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, 2500°C, 2600°C, 2700°C, 2800°C, 2900°C, 3000°C, 3100°C, 3200°C, 3300°C, or a range between any two of the above temperatures. Optionally, the graphitization temperature is 2200°C-3200°C; further optionally, the graphitization temperature is 2500°C-3200°C; more optionally, the graphitization temperature is 2600°C-3000°C.

[0130] In some optional embodiments, the graphitization time is 300 hours to 800 hours, for example, but not limited to, 300 hours, 350 hours, 400 hours, 450 hours, 500 hours, 550 hours, 600 hours, 650 hours, 700 hours, 750 hours, 800 hours, or a range between any two of the above times. Optionally, the graphitization time is 500 hours to 800 hours.

[0131] In some embodiments, when the carbon-based material in the porous negative electrode material is soft carbon, the post-treatment during the preparation of the porous negative electrode material includes carbonization treatment.

[0132] As a possible embodiment, when the carbon-based material in the porous negative electrode material is soft carbon, the temperature of the carbonization treatment during the preparation of the porous negative electrode material is 1500℃-2000℃; for example, it can be but not limited to 1500℃, 1600℃, 1700℃, 1800℃, 1900℃, 2000℃ or a range between any two of the above temperatures.

[0133] As a possible implementation manner, when the carbon-based material in the porous negative electrode material is soft carbon, the carbonization treatment time during the preparation of the porous negative electrode material is 15h-40h; for example, it can be but is not limited to 15h, 18h, 20h, 23h, 25h, 28h, 30h, 33h, 35h, 37h, 40h or a range between any two of the above times, etc.

[0134] In some embodiments, the carbon-based material includes one or more of flake graphite and microcrystalline graphite. Accordingly, the carbon-based material in the prepared porous negative electrode material is natural graphite.

[0135] In some optional embodiments, when the carbon-based material in the porous negative electrode material is natural graphite, the post-treatment during the preparation of the porous negative electrode material includes a spheroidization treatment.

[0136] In some exemplary embodiments, the rotation speed of the spheroidization treatment is 2000 rpm-8000 rpm; for example, it can be but not limited to 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm or a range between any two of the above rotation speeds.

[0137] In some optional embodiments, the spheroidization treatment time is 5 min-15 min; for example, it can be but not limited to 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min or a range between any two of the above times.

[0138] As a possible implementation, at least one of air flow milling and mechanical milling is used for spheroidization.

[0139] In some embodiments, the carbon-based material comprises one or more of asphalt, paraffin, biomass, biomass extracts, and artificial organic polymers. Accordingly, the carbon-based material in the prepared porous negative electrode material is hard carbon.

[0140] In some optional embodiments, when the carbon-based material in the porous negative electrode material is hard carbon, the post-treatment during the preparation of the porous negative electrode material includes carbonization treatment.

[0141] As a possible embodiment, when the carbon-based material in the porous negative electrode material is hard carbon, the temperature of the carbonization treatment during the preparation of the porous negative electrode material is 800℃-1600℃; for example, it can be but not limited to 800℃, 900℃, 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, 1500℃, 1600℃ or a range between any two of the above temperatures.

[0142] In some exemplary embodiments, when the carbon-based material in the porous negative electrode material is hard carbon, the time of carbonization treatment during the preparation of the porous negative electrode material is 2h-15h; for example, it can be but is not limited to 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or a range between any two of the above times, etc.

[0143] In some embodiments, the temperature of pyrolysis granulation is 600°C-1600°C; for example, it can be, but is not limited to, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C, 1500°C, 1600°C, or a range between any two of the above temperatures. Optionally, the temperature of pyrolysis granulation is 800°C-1200°C.

[0144] As an example, when performing pyrolysis granulation, the heating method includes at least one of continuous heating and step heating.

[0145] As a possible embodiment, the pyrolysis granulation time is 0.5h-6h; for example, it can be but not limited to 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or a range between any two of the above times. Optionally, the pyrolysis granulation time is 2h-5h.

[0146] In some embodiments, when the carbon-based material in the porous negative electrode material is artificial graphite, the method for preparing the porous negative electrode material comprises the following steps:

[0147] S1. A carbon-based material precursor and a hard carbon precursor are mixed in a stirring manner and then crushed to prepare a mixed material. The hard carbon precursor includes one or more of resins, organic polymers, biomass and carbohydrates. The carbon-based material precursor includes one or more of activated carbon, coke, carbon black, charcoal, biocoke and coal coke. The mass ratio of the hard carbon precursor to the carbon-based material precursor is 1:(5-50). The agitator used may be in the form of, but not limited to, turbine, paddle, propeller, screw or planetary type. The stirring speed is 10rpm-300rpm, and the stirring time is 0.25h-12h. A pulverizer is used for the crushing process; the speed of the pulverizer is 10000rpm-25000rpm; and the crushing time is 5min-10min.

[0148] S2. The mixed material is pyrolyzed and granulated to prepare an intermediate; the pyrolysis and granulation temperature is 600° C. to 1600° C. and the pyrolysis and granulation time is 0.5 h to 5 h.

[0149] S3. Graphitizing the intermediate to prepare a porous negative electrode material. The graphitization temperature is 2000° C. to 3300° C., and the graphitization time is 300 hours to 800 hours.

[0150] In some embodiments, when the carbon-based material in the porous negative electrode material is soft carbon, the method for preparing the porous negative electrode material comprises the following steps:

[0151] S1. A carbon-based material precursor and a hard carbon precursor are mixed in a stirring manner and then crushed to prepare a mixed material. The hard carbon precursor includes one or more of resins, organic polymers, biomass and carbohydrates. The carbon-based material precursor includes one or more of activated carbon, coke, carbon black, charcoal, biocoke and coal coke. The mass ratio of the hard carbon precursor to the carbon-based material precursor is 1:(5-50). The agitator used may be in the form of, but not limited to, turbine, paddle, propeller, screw or planetary type. The stirring speed is 10rpm-300rpm, and the stirring time is 0.25h-12h. A pulverizer is used for the crushing process; the speed of the pulverizer is 10000rpm-25000rpm; and the crushing time is 5min-10min.

[0152] S2. The mixed material is pyrolyzed and granulated to prepare an intermediate; the pyrolysis and granulation temperature is 600° C. to 1600° C. and the pyrolysis and granulation time is 0.5 h to 5 h.

[0153] S3. Carbonizing the intermediate to prepare a porous negative electrode material. The carbonization temperature is 1500° C. to 2000° C., and the carbonization time is 15 hours to 40 hours.

[0154] In some embodiments, when the carbon-based material in the porous negative electrode material is hard carbon, the method for preparing the porous negative electrode material comprises the following steps:

[0155] S1. A carbon-based material precursor and a hard carbon precursor are mixed in a stirring manner and then crushed to prepare a mixed material. The hard carbon precursor includes one or more of resins, organic polymers, biomass and carbohydrates. The carbon-based material precursor includes one or more of asphalt, paraffin, biomass, biomass extracts and artificial organic high molecular polymers. The mass ratio of the hard carbon precursor to the carbon-based material precursor is 1: (5-50). The agitator used may be in the form of, but not limited to, turbine, paddle, propeller, screw or planetary type. The stirring speed is 10rpm-300rpm, and the stirring time is 0.25h-12h. A crushing machine is used for the crushing process; the speed of the crusher is 10000rpm-25000rpm; and the crushing time is 5min-10min.

[0156] S2. The mixed material is pyrolyzed and granulated to prepare an intermediate; the pyrolysis and granulation temperature is 600° C. to 1600° C. and the pyrolysis and granulation time is 0.5 h to 6 h.

[0157] S3. Carbonizing the intermediate to prepare a porous negative electrode material. The carbonization temperature is 800° C. to 1600° C., and the carbonization time is 2 hours to 15 hours.

[0158] In some embodiments, when the carbon-based material in the porous negative electrode material is natural graphite, the method for preparing the porous negative electrode material comprises the following steps:

[0159] S1. A carbon-based material precursor and a hard carbon precursor are mixed in a stirring manner and then crushed to prepare a mixed material. The hard carbon precursor includes one or more of resin, organic polymer, biomass and carbohydrate. The carbon-based material precursor includes one or more of flake graphite and microcrystalline graphite. The mass ratio of the hard carbon precursor to the carbon-based material precursor is 1:(5-50). The agitator used may be in the form of, but not limited to, turbine, paddle, propeller, screw or planetary type. The stirring speed is 10rpm-300rpm, and the stirring time is 0.25h-12h. A pulverizer is used for the crushing process; the rotation speed of the pulverizer is 10000rpm-25000rpm; and the crushing time is 5min-10min.

[0160] S2. The mixed material is pyrolyzed and granulated to prepare an intermediate; the pyrolysis and granulation temperature is 600° C. to 1600° C. and the pyrolysis and granulation time is 0.5 h to 5 h.

[0161] S3. Spheroidize the intermediate to prepare a porous negative electrode material. The spheroidization process is performed at a rotation speed of 2000 rpm to 8000 rpm for a time of 5 min to 15 min. The spheroidization process is performed using at least one of a jet mill and a mechanical mill.

[0162] In addition, the secondary battery and the electric device of the present application will be described below with reference to the drawings as appropriate.

[0163] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0164] The secondary battery of the present application includes the porous negative electrode material of the present application, has excellent coulombic efficiency and gram capacity, and has high energy density.

[0165] Negative electrode

[0166] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector. The negative electrode active material layer includes the porous negative electrode material of the first aspect of the present application or the porous negative electrode material prepared by the preparation method of the second aspect of the present application.

[0167] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0168] In some embodiments, the compacted density of the negative electrode sheet is 1.4 g / cm 3 -1.65g / cm 3 For example, it can be but not limited to 1.4g / cm 3 , 1.42g / cm 3 , 1.45g / cm 3 , 1.47g / cm 3 , 1.5g / cm 3 , 1.52g / cm 3 , 1.55g / cm 3 、1.57g / cm 3 , 1.6g / cm 3 , 1.62g / cm 3 , 1.65g / cm 3 Or the range between any two of the above compacted densities, etc.

[0169] In some optional embodiments, the mass proportion of the porous negative electrode material in the negative electrode active material layer is 95.5%-97%. For example, it can be, but is not limited to, 95.5%, 95.8%, 96%, 96.3%, 96.5%, 96.8%, 97%, or a range between any two of the above values. Optionally, the mass proportion of the porous negative electrode material in the negative electrode active material layer is 96%-97%.

[0170] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0171] In some embodiments, the negative electrode active material layer may also include other negative electrode active materials for batteries that are well known in the art. As non-limiting examples, the negative electrode active material may also include one or more of the following materials: silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0172] In some embodiments, the negative electrode active material layer may further include a binder. Optionally, the binder includes one or more of polyimide resin, acrylic resin, polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose, and styrene-butadiene rubber. The binder may further include one or more of sodium polyacrylate (PAAS), polyacrylamide (PAM), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0173] In some embodiments, the mass proportion of the binder in the negative electrode active material layer is 1.2%-1.8%; for example, it can be but not limited to 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8% or a range between any two of the above values.

[0174] In some embodiments, the negative electrode active material layer may further include a conductive agent. Optionally, the conductive agent may include one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0175] In some optional embodiments, the mass proportion of the conductive agent in the negative electrode active material layer is 0.8%-1.2%; for example, it can be but not limited to 0.8%, 0.9%, 1%, 1.1%, 1.2% or a range between any two of the above values.

[0176] In some embodiments, the negative electrode active material layer may further include a dispersant. Optionally, the dispersant may include one or more of sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide, and polyvinyl pyrrolidone.

[0177] In some optional embodiments, the mass proportion of the dispersant in the negative electrode active material layer is 0.5%-1%; for example, it can be but not limited to 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1% or a range between any two of the above values.

[0178] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0179] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt%-60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000mPa·s-10000mPa·s. When coating the negative electrode slurry, the coating unit area density on a dry weight basis (excluding the solvent) can be 0.05-0.18g / 1540.25mm 2 The compaction density of the negative electrode can be 1.0g / cm 3 -1.8g / cm 3 .

[0180] Positive electrode

[0181] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0182] As a non-limiting example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0183] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the positive electrode current collector, non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0184] In some embodiments, the positive electrode active material may further include one or more of a ternary material and a lithium manganese iron phosphate material; wherein the ternary material includes Li x (Ni a Co b Mn c )1-dM d O2-yA y (x is 0.2-1.2) and / or Li x A a (Ni a Co b Mn c )1-dM d O2-yA y (x+a is 0.2-1.2); lithium manganese iron phosphate materials include Li a Mn 1-y B y P 1-z C z O 4-n D n (a is 0-1.1) and / or Li a A x Mn 1-y B y P 1-z C z O 4-n D n (a+x is 0-1.1).

[0185] It should be noted that the above definition of x includes the molar content of Li in different charge and discharge states of the battery (usually the battery voltage is between 2-5V).

[0186] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0187] In the examples of positive electrode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0188] In some embodiments, the positive electrode active material may also use other positive electrode active materials for batteries that are well known in the art. As non-limiting examples, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.80 Co 0.15 Al 0.05O2.

[0189] In some embodiments, the positive electrode active material layer may further optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0190] In some embodiments, the positive electrode active material layer may further include a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0191] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, cold pressing, and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The surface of the positive electrode current collector coated with the positive electrode slurry can be on a single surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt%-80wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000mPa·s-25000mPa·s. When applying the positive electrode slurry, the coating unit area density based on dry weight (excluding solvent) can be 0.2-0.45g / 1540.25mm 2 The compaction density of the positive electrode can be 3.0g / cm 3 -3.6g / cm 3 , optional 3.3g / cm 3 -3.5g / cm 3 .

[0192] electrolytes

[0193] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0194] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0195] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorodioxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0196] In some embodiments, the solvent may include ethylene carbonate (EC, ), propylene carbonate (PC, ), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate One or more of fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0197] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0198] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0199] Isolation film

[0200] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0201] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0202] In some embodiments, the isolation film has a thickness of 6 μm-20 μm, and optionally 10-16 μm.

[0203] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0204] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0205] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0206] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0207] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0208] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 2 The battery cell 5 is a square structure as an example.

[0209] In some of these embodiments, reference Figure 3 The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0210] The secondary battery may be a battery module 4 or a battery pack 1 .

[0211] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0212] Figure 4 4 is an example of a battery module. Figure 4 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0213] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0214] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0215] Figure 5 and Figure 6 The battery pack 1 is used as an example. Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0216] In addition, the present application also provides an electrical device, which includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can include, but is not limited to, mobile devices, electric vehicles, electric trains, ships, satellites, energy storage systems, etc. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to these.

[0217] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0218] Figure 7 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0219] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0220] Example

[0221] Below, the embodiment of the present application is described. The embodiment described below is exemplary, is only used to explain the present application, and is not to be construed as limiting the present application. Where the technology or conditions are not specified in the embodiment, the technology or conditions described in the literature in this area or the product instructions are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0222] 1. Preparation of porous anode materials

[0223] Example 1

[0224] A turbine agitator was used to evenly mix needle coke (as a carbon-based material precursor) and lignin (as a hard carbon precursor) to obtain a mixture, in which the mass ratio of lignin to needle coke was 1:30; the mixture was then crushed using a pulverizer with a rotation speed of 15,000 rpm and a crushing time of 8 minutes.

[0225] The crushed mixture was pyrolyzed and granulated at 1000°C for 5 hours to obtain an intermediate.

[0226] The intermediate is graphitized to obtain a porous negative electrode material. The graphitization temperature is 3000° C. and the graphitization time is 800 hours.

[0227] Example 2-16

[0228] The preparation methods of Examples 2-16 are similar to those of Example 1, and the differences are detailed in Table 1.

[0229] Comparative Example 1

[0230] The preparation methods of Comparative Example 1 and Example 1 are similar, except that no lignin is added when preparing the porous negative electrode material in Comparative Example 1, and all other conditions are the same; see Table 1 for details.

[0231] Comparative Example 2

[0232] The preparation methods of Comparative Example 2 and Example 2 are similar, except that no lignin is added when preparing the porous negative electrode material in Comparative Example 2, and all other conditions are the same; see Table 1 for details.

[0233] Comparative Example 3

[0234] The preparation methods of Comparative Example 3 and Example 3 are similar, except that no lignin is added when preparing the porous negative electrode material in Comparative Example 3, and all other conditions are the same; see Table 1 for details.

[0235] Comparative Example 4

[0236] The preparation methods of Comparative Example 4 and Example 4 are similar, except that no lignin is added when preparing the porous negative electrode material in Comparative Example 4, and all other conditions are the same; see Table 1 for details.

[0237] The preparation parameters of the above embodiments and comparative examples are shown in Table 1.

[0238] Table 1

[0239]

[0240] In Table 1, n represents the mass ratio of the hard carbon precursor to the carbon-based material precursor. Porosity refers to the porosity of the porous negative electrode material; and average pore size refers to the average pore size of the internal pore structure contained in the porous negative electrode material.

[0241] The porosity of the porous negative electrode material mentioned above is measured by the following method: the porous negative electrode material is cut into small pieces, placed in a sample container, a cone probe made of glass is used as the sample container, pressure is applied to the sample, and measurement is performed; wherein the parameters of the mercury intrusion instrument are set to: the pressure applied in the low pressure station (LP) is about 0.6 to 50 PSI (corresponding to a pore diameter of 355-4 microns), and the pressure applied in the high pressure station (HP) is about 20 to 60,000 PSI (corresponding to a pore diameter of 10-0.004 microns). The mercury intrusion instrument can be a US PoreMaster 60GT mercury intrusion instrument.

[0242] The average pore size of the porous negative electrode material mentioned above is measured by the following method:

[0243] The test sample is placed in a sample tube and first degassed by vacuum. The entire system is then brought to the desired vacuum level. The sample tube is then immersed in a liquid nitrogen bath and filled with a known amount of gas. Adsorption of the gas by the adsorbent causes a pressure drop. After adsorption equilibrium is reached, the equilibrium pressure is measured, and the adsorbed amount is calculated based on the pressure change before and after adsorption. The adsorption-desorption isotherm is measured by gradually increasing the amount of adsorbate gas in the system and changing the pressure. The BJH model (Barret-Joyner-Halenda) is then used to equivalently determine the pore size distribution of the test sample.

[0244] 2. Preparation of Secondary Batteries

[0245] 1. Preparation of positive electrode sheet

[0246] Lithium iron phosphate, conductive carbon black SP, and binder PVDF were dispersed in a solvent N-methylpyrrolidone at a weight ratio of 96:2:2 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on both sides of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained, wherein the coating amount per unit area on both sides was 0.30 g / 1540.25 mm 2 .

[0247] 2. Preparation of negative electrode sheet

[0248] The porous negative electrode material, dispersant sodium carboxymethyl cellulose, binder styrene butadiene rubber, and conductive agent acetylene black were mixed in a mass ratio of 97:1:1:1, and deionized water was added to obtain a negative electrode slurry under the action of a vacuum mixer; the negative electrode slurry was evenly coated on both sides of the copper foil; the copper foil was dried at room temperature and then transferred to a 120°C oven for drying for 1 hour, and then cold pressed and cut to obtain a negative electrode sheet, wherein the coating amount per unit area on both sides was 0.15g / 1540.25mm 2 .

[0249] 3. Isolation film

[0250] A 12μm thick polyethylene isolation film was selected.

[0251] 4. Preparation of Electrolyte

[0252] The organic solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), with a volume ratio of 3:7. In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt LiPF6 is dissolved in the organic solvent. 2 wt% fluoroethylene carbonate (FEC) is added and mixed thoroughly to obtain an electrolyte solution. The lithium salt concentration is 1 mol / L.

[0253] 5. Preparation of Cells

[0254] The positive electrode sheet, separator, and negative electrode sheet are stacked or wound in this order to form a cell. The bare cell is then placed in an outer package, injected with the aforementioned electrolyte, and sealed. After standing, hot and cold pressing, formation, clamping, and capacity separation, a secondary battery is obtained. The formation process is: charging at 0.04C to 30% remaining capacity (SOC).

[0255] 3. Secondary Battery Performance Test

[0256] 1. First effect test

[0257] The secondary battery is charged at a constant current of 0.33C to 3.65V, then charged at a constant voltage of 3.65V to 0.05C. The total charge capacity at this point is recorded as C0. It is then discharged at a constant current of 0.33C to 2.5V, and then discharged at a constant current of 0.04C to 2.0V. The total discharge capacity at this point is recorded as D0. D0 / C0 is the first effect.

[0258] 2. Cycle test

[0259] The secondary battery is charged at a constant current of 0.33C to 3.65V, and then discharged at a constant current of 0.33C to 2.5V. This process is repeated for multiple cycles until the discharge capacity of the battery decays to 0.9D0. The number of cycles at this time is the number of cycles required to decay to 90% SOH.

[0260] 3. Negative electrode rebound rate test

[0261] Measure the thickness d0 of the negative electrode after cold pressing. After the cell performance decays to 90% SOH, disassemble the cell and soak the electrode in DMC for 10 minutes to remove residual electrolyte. Then, dry it in an 80°C oven under vacuum for 10 minutes. The thickness d1 at this point is then recorded. (d1 - d0) / d0 is the electrode rebound rate at this point.

[0262] The test results of the above embodiments and comparative examples are shown in Table 2.

[0263] Table 2

[0264]

[0265] From the comparison of the results in Table 2, it can be seen that compared with comparative examples 1-6, the overall rebound rate of the negative electrode sheets of Examples 1-16 is significantly reduced, and the overall battery cycle life is significantly increased while taking into account the first effect of the battery; this shows that the porous negative electrode material provided in the present application can effectively alleviate the volume expansion of the carbon-based material while taking into account the first effect, and has excellent cycle performance.

[0266] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced to each other and will not be repeated herein for the sake of brevity.

[0267] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A porous negative electrode material, characterized in that The porous negative electrode material includes secondary particles with an internal pore structure, the secondary particles contain multiple primary particles, the primary particles contain carbon-based materials, porous hard carbon is filled between adjacent primary particles, the porous hard carbon contained in the secondary particles forms a network structure, and the porosity of the porous negative electrode material is 15%-28%.

2. The porous negative electrode material according to claim 1, wherein The porosity of the porous negative material is 18%-27%.

3. The porous negative electrode material according to any one of claims 1 to 2, characterized in that The porous negative electrode material has an internal pore structure with an average pore diameter of 2.8 nm to 5.2 nm, and can optionally be 3.0 nm to 4.5 nm.

4. The porous negative electrode material according to any one of claims 1 to 3, characterized in that The porous negative electrode material contains an internal pore structure comprising micropores with a pore diameter of less than 2 nm, mesopores with a pore diameter of 2 nm to 50 nm, and macropores with a pore diameter of more than 50 nm; Optionally, the micropores account for 55%-70% of the internal pore structure, and optionally 58%-68%; Optionally, the mesopores account for 20%-35% of the internal pore structure, and optionally 22%-32%; Optionally, the macropores account for 3%-10% of the internal pore structure, and optionally 4%-8%.

5. The porous negative electrode material according to any one of claims 1 to 4, characterized in that The porous negative electrode material has an internal pore structure with a pore volume of 0.05 cm 3 / g-0.35cm 3 / g, optional 0.08cm 3 / g-0.32cm 3 / g.

6. The porous negative electrode material according to any one of claims 1 to 5, characterized in that The volume average particle size Dv50 of the porous negative electrode material is 15 μm-25 μm, and can be optionally 16 μm-24 μm.

7. The porous negative electrode material according to any one of claims 1 to 6, characterized in that The mass ratio of the porous hard carbon to the carbon-based material contained in the porous negative electrode material is 1:(5-50), and can be optionally 1:(20-35).

8. The porous negative electrode material according to any one of claims 1 to 7, characterized in that The carbon-based material includes one or more of artificial graphite, natural graphite, hard carbon and soft carbon; optionally, the carbon-based material includes artificial graphite.

9. A method for preparing the porous negative electrode material according to any one of claims 1 to 8, characterized in that: The steps include: The carbon-based material precursor and the hard carbon precursor are mixed and then crushed to prepare a mixed material; pyrolyzing and granulating the mixed material to prepare an intermediate; The intermediate is post-processed to prepare the porous negative electrode material.

10. The method for preparing a porous negative electrode material according to claim 9, wherein: The hard carbon precursor includes one or more of a resin, an organic polymer, a biomass, and a carbohydrate; Optionally, the resin includes one or more of phenolic resin, epoxy resin and polyfurfuryl alcohol resin; Optionally, the organic polymer includes one or more of polyacrylonitrile, polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl chloride, polyvinylidene fluoride and asphalt; Optionally, the biomass comprises one or more of cellulose and lignin; Optionally, the carbohydrates include one or more of sucrose and glucose.

11. The method for preparing a porous negative electrode material according to any one of claims 9 to 10, characterized in that: Using a crusher to perform the crushing process; Optionally, the rotation speed of the pulverizer is 10000rpm-25000rpm, optionally 12000rpm-25000rpm; Optionally, the crushing process takes 5 minutes to 10 minutes, or 8 minutes to 10 minutes.

12. The method for preparing a porous negative electrode material according to any one of claims 9 to 11, wherein: The mass ratio of the hard carbon precursor to the carbon-based material precursor is 1:(5-50), and can be optionally 1:(20-35).

13. The method for preparing a porous negative electrode material according to any one of claims 9 to 12, wherein: The carbon-based material precursor includes one or more of activated carbon, coke, carbon black, charcoal, biocoke and coal coke.

14. The method for preparing a porous negative electrode material according to claim 13, wherein: The post-treatment includes graphitization; Optionally, the graphitization temperature is 2000°C-3300°C, optionally 2500°C-3200°C; Optionally, the graphitization time is 300h-800h, optionally 500h-800h.

15. The method for preparing a porous negative electrode material according to claim 13, wherein: The post-treatment includes carbonization treatment; Optionally, the temperature of the carbonization treatment is 1500° C.-2000° C.; Optionally, the carbonization treatment time is 15h-40h.

16. The method for preparing a porous negative electrode material according to any one of claims 9 to 12, wherein: The carbon-based material includes one or more of flake graphite and microcrystalline graphite.

17. The method for preparing a porous negative electrode material according to claim 16, wherein: The post-processing includes spheroidization; Optionally, the rotation speed of the spheroidization treatment is 2000 rpm-8000 rpm; Optionally, the spheroidization treatment time is 5 min-15 min; Optionally, the spheroidization treatment is performed by at least one of air flow milling and mechanical milling.

18. The method for preparing a porous negative electrode material according to any one of claims 9 to 12, wherein: The carbon-based material includes one or more of asphalt, paraffin, biomass, biomass extracts and artificial organic high molecular polymers.

19. The method for preparing a porous negative electrode material according to claim 18, wherein: The post-treatment includes carbonization treatment; Optionally, the temperature of the carbonization treatment is 800°C-1600°C; Optionally, the carbonization treatment time is 2h-15h.

20. The method for preparing a porous negative electrode material according to any one of claims 9 to 19, wherein: The temperature of the pyrolysis granulation is 600°C-1600°C, optionally 800°C-1200°C; and / or The pyrolysis granulation time is 0.5h-6h, and can be optionally 2h-5h.

21. A negative electrode plate, characterized in that: include: negative electrode current collector; and A negative electrode active material layer is located on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises the porous negative electrode material according to any one of claims 1 to 8 or the porous negative electrode material prepared by the preparation method according to any one of claims 9 to 20.

22. The negative electrode sheet according to claim 21, wherein: The compaction density of the negative electrode sheet is 1.4 g / cm 3 -1.65g / cm 3 .

23. The negative electrode sheet according to any one of claims 21 to 22, characterized in that: The negative electrode active material layer further includes a conductive agent, a dispersant and a binder; Optionally, the conductive agent includes one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene and carbon nanotubes; Optionally, the dispersant includes one or more of sodium tripolyphosphate, sodium hexametaphosphate, sodium pyrophosphate, sodium lauryl sulfate, methyl amyl alcohol, cellulose derivatives, polyacrylamide and polyvinyl pyrrolidone; Optionally, the binder includes one or more of polyimide resin, acrylic resin, polyvinylidene fluoride, polyvinyl alcohol, sodium carboxymethyl cellulose and styrene-butadiene rubber; Optionally, the porous negative electrode material accounts for 95.5% to 97% by mass in the negative electrode active material layer; Optionally, the conductive agent accounts for 0.8% to 1.2% by mass in the negative electrode active material layer; Optionally, the mass proportion of the dispersant in the negative electrode active material layer is 0.5%-1%; Optionally, the binder accounts for 1.2%-1.8% by mass in the negative electrode active material layer.

24. A secondary battery, characterized in that: Comprising the negative electrode sheet according to any one of claims 21 to 23.

25. An electrical device, characterized in that: A secondary battery according to claim 24 is included.

Images