Energy storage sodium-ion battery, negative electrode, preparation method and preparation device

Abstract

The present invention belongs to the technical field of energy storage batteries. Disclosed are a low-cost and long-cycle-life sodium-ion energy storage battery, a negative electrode, a preparation method and a preparation device. The preparation method comprises: adding a sodium-ion negative electrode material, a conductive agent and a binder to a high-speed shearing mixer for dry mixing; adding the mixed materials to a double-shaft hot roller, and extruding same into a membrane, wherein the thickness of the membrane is controlled to be 90-350 μm, the temperature of the double-shaft hot roller is controlled to be 100-180°C, and the pressure is controlled to be 18-35 T; attaching the membrane onto aluminum foil having a thickness of 8-20 μm, the surface of which has been subjected to gluing treatment, wherein an adhesive layer of the glued aluminum foil has a thickness of 2-6 μm, and the adhesive layer contains 65 wt% of conductive carbon and 35 wt% of polymer glue; and hot-pressing the complex at 85-130°C, so as to form a sodium-ion battery negative electrode. The sodium-ion energy storage battery comprises an aluminum-plastic film shell, a separator, an electrolyte, a positive electrode and a negative electrode. In the whole manufacturing process of the sodium-ion energy storage battery negative electrode, the energy consumption is reduced, the environment is protected, and the manufacturing cost of the whole battery is reduced.

Description

Energy storage sodium ion battery and negative electrode, preparation method, and preparation device Technical Field

[0001] The present invention belongs to the technical field of energy storage batteries, and in particular relates to a sodium ion battery and a method for preparing a negative electrode. Background Art

[0002] High-quality development of human society is inseparable from the efficient use of energy. With the implementation of China's dual carbon policy, China's energy consumption structure will undergo major changes. The continuous development of new energy has become a general trend. This will be of great strategic significance for accelerating the establishment and improvement of a green, low-carbon circular economic development system, promoting the comprehensive green transformation of the social economy, and achieving the established goals of carbon peak and carbon neutrality.

[0003] As a supplement and effective alternative to lithium-ion batteries, a new type of energy storage device called "Sodium Ion Battery (SIB)" has attracted widespread attention from all walks of life by taking a differentiated competitive development path. Its energy density is comparable to that of lithium iron phosphate batteries, but its theoretical cost can be as low as 70%. It is highly anticipated for its application in low-speed electric vehicles, 5G communication base stations, data centers, industrial and commercial, and ultra-large energy storage power stations.

[0004] The electrode, known as the heart of a battery, is a crucial component that determines its performance. Currently, sodium-ion batteries utilize the NMP slurrying process (referred to as the "wet process") in their electrode manufacturing process. Besides energy consumption and environmental issues, this process's biggest challenge is the difficulty in increasing electrode compaction density due to the introduction of solvents during electrode manufacturing. Compared to the wet process, the dry process, through dry mixing, can improve electrode compaction by over 10%, thereby increasing the overall battery energy density. Furthermore, the formed electrode exhibits crack-free microstructures, unobstructed electronic and ionic conductive networks, and strong contact with the current collector, significantly enhancing electrochemical performance and cycle durability. Dry process electrode technology was first introduced in the supercapacitor industry, and some companies in the lithium battery industry have also gradually adopted it. The introduction of dry process electrode technology into the sodium-ion battery manufacturing process is timely and necessary, but currently, due to limitations in battery technology development, wet process electrode manufacturing is still widely used. This process significantly increases battery manufacturing costs, failing to effectively meet the low cost requirements of industrialization. Technical issues

[0005] Through the above analysis, the problems and defects of the existing technology are: 1) The existing wet electrode manufacturing technology of sodium ion batteries limits the further improvement of their energy density; 2) The existing electrode manufacturing technology pushes up the overall manufacturing cost of sodium ion batteries; 3) The existing electrode process limits the cycle stability of sodium ion batteries; 4) The existing process leads to environmental problems in the product production and manufacturing process.

[0006] One existing related technology uses hard carbon as the negative electrode for sodium-ion batteries. This method also uses hard carbon as the primary negative electrode material, supplemented with a conductive agent and a binder. However, this technology typically uses a wide range of hard carbon particle sizes, pore size distributions, and specific surface areas, and the binder type and degree of polymerization are not specifically limited.

[0007] 1) Physical properties of hard carbon: Existing technologies have a wide range of pore size distribution and specific surface area. This results in inconsistent sodium ion diffusion rates during battery charge and discharge, impacting charge and discharge efficiency and battery cycle life. Furthermore, the particle size of hard carbon used in existing technologies is not strictly controlled, which affects the battery's energy density.

[0008] 2) Conductive agent selection: Numerous types of conductive agents are currently available, with no clear recommendation for use. Different conductive agents vary in their conductivity mechanisms, properties, stability, and compatibility with hard carbon, which can affect the overall performance of the battery.

[0009] 3) Binder Issues: Prior art lacks clear regulations on binder selection and its degree of polymerization, which can affect the stability of the battery's physical structure. The quality and performance of the binder directly impact the electrode sheet's fabrication process, mechanical strength, and battery cycle performance.

[0010] The present invention provides a new method for preparing a negative electrode for a sodium ion battery. By precisely controlling the physical properties of hard carbon, conductive agents, and binders, combined with innovative negative electrode process equipment, it can solve some problems existing in the prior art and achieve better battery performance and longer cycle life. Technical Solutions

[0011] In response to the problems existing in the prior art, the present invention provides a low-cost, long-cycle energy storage sodium ion battery and a method for preparing a negative electrode.

[0012] The present invention is achieved by providing a low-cost, long-cycle energy storage sodium ion battery negative electrode preparation method, wherein the negative electrode comprises a negative electrode material, a conductive agent, and a binder, and the mass ratio of the negative electrode material, the conductive agent, and the binder is: 90-95:1.0-3.0:3.0-8.0.

[0013] Furthermore, the negative electrode material is hard carbon, preferably biomass hard carbon; the pore size distribution is 8-30 nm, preferably the pore size range is 10-25 nm.

[0014] Furthermore, the median particle size of the hard carbon is 2.0-12.0 μm and the specific surface area is 3-10 m2 / g;

[0015] The preferred particle size of the hard carbon is 3.0-7.0 μm;

[0016] The high particle size of the hard carbon particles D90≤23um;

[0017] The hard carbon particles have a low particle size D10 of ≥0.9 μm.

[0018] Furthermore, the conductive agent is a Point to Point (PtP) type carbon-containing material, preferably Super P type conductive carbon black, 200GS type conductive carbon black and ECP type Ketjen black.

[0019] Furthermore, the binder is a fiberizable polytetrafluoroethylene polymer and its modified material, preferably expandable polytetrafluoroethylene with a polymerization degree of 1.7 to 4.6×10 4 .

[0020] Furthermore, the negative electrode preparation method specifically includes the following steps:

[0021] Step 1: Add the negative electrode material, conductive agent and binder into a high-speed shear mixer and mix them. Set the mixing speed to 6000-12000 rpm and the mixing time to 30-60 minutes.

[0022] Step 2: Add the pre-mixed materials to the biaxial hot rolling rollers and extrude them into a film. The thickness of the film is controlled at 90-350 μm. The temperature of the biaxial hot rolling rollers is controlled at 100-180°C and the pressure is controlled at 18-35°C.

[0023] Step 3: Mechanically bond the membrane obtained in step 2 to an 8-20 μm aluminum foil with an adhesive treatment on its surface to form a composite body, wherein the adhesive layer of the aluminum foil is 2-6 μm and contains 65 wt% conductive carbon and 35% polymer glue;

[0024] Step 4: hot-pressing the composite obtained in step 3 at 85-130° C. to form a negative electrode for a sodium ion battery.

[0025] Furthermore, the optimal temperature for hot pressing the composite is 105°C.

[0026] Another object of the present invention is to provide an energy storage sodium ion battery, comprising an aluminum-plastic film shell, a separator, an electrolyte, a positive electrode and a negative electrode, wherein the negative electrode is the sodium ion battery negative electrode prepared by the above method.

[0027] Another object of the present invention is to provide a sodium ion battery negative electrode preparation device for the above method, characterized in that it comprises:

[0028] a) a high-speed shear mixer for mixing the negative electrode material, conductive agent, and binder. The mixing speed of the mixer is set to 6000-12000 rpm and the mixing time is 30-60 minutes;

[0029] b) A pair of biaxial hot rolling rollers, used to extrude the pre-mixed materials into a film. The thickness of the film is controlled at 90-350 μm. The temperature of the biaxial hot rolling rollers is controlled at 100-180°C and the pressure is controlled at 18-35°F.

[0030] c) a mechanical laminating device for laminating the membrane obtained in step b to an 8-20 μm aluminum foil with an adhesive-treated surface to form a composite, wherein the adhesive layer of the aluminum foil is 2-6 μm and contains 65 wt% conductive carbon and 35% polymer glue;

[0031] d) a hot pressing composite device, used to hot press the composite obtained in step c at 85-130° C., wherein the optimal temperature for hot pressing the composite is 105° C., to form a negative electrode for a sodium ion battery. Beneficial effects

[0032] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0033] First, in the manufacturing process of the negative electrode of the energy storage sodium ion battery of the present invention, the electrode materials are dry-mixed and then directly hot-rolled and hot-pressed to form a dense and high-density negative electrode. On the one hand, this increases the effective load per unit volume of the electrode, thereby improving the electrode specific capacity; on the other hand, it avoids the increase in battery internal resistance caused by the traditional wet process due to the voids generated by heating to remove the solvent remaining in the electrode.

[0034] The energy storage sodium ion battery negative electrode prepared by the present invention reduces energy consumption during the entire manufacturing process, protects the environment, and reduces the manufacturing cost of the entire battery.

[0035] This method for preparing negative electrodes for sodium-ion energy storage batteries also brings the following significant technological advances:

[0036] 1) Higher energy storage efficiency: The optimized microporous structure in hard carbon can effectively store sodium ions, thereby improving the energy storage efficiency of the battery; and the precise control of parameters such as the pore size and particle size of the hard carbon makes the insertion / deintercalation process of sodium ions smoother, making the sodium-ion battery have a more stable power output.

[0037] 2) Optimized material utilization: The performance indicators of hard carbon are optimized according to specific needs, and the utilization efficiency of materials is improved by selecting different hard carbon sources (such as biomass, resin or coal).

[0038] 3) Environmental protection and sustainability: Especially when using biomass hard carbon, it utilizes renewable resources, reduces dependence on mineral resources, helps achieve sustainable development, and also reduces the impact on the environment during battery manufacturing.

[0039] 4) Improve battery stability: By precisely controlling the upper and lower limits of the hard carbon particle size (D90 and D10), the stability and cycle life of the battery during the charge and discharge process can be guaranteed, thereby improving the reliability and service life of the battery.

[0040] 5) Improve production efficiency: By precisely controlling the mass ratio of hard carbon, conductive agent, and binder, the negative electrode material can be prepared quickly and efficiently, providing technical support for large-scale production.

[0041] Second, the sodium ion negative electrode materials obtained by the present invention are evenly distributed and dense, the active materials are tightly bonded, and the prepared electrode microstructure is free of cracks, which helps improve the efficient transmission capacity of electrons and ions during battery operation and reduce the overall internal resistance of the battery;

[0042] The present invention adopts the dry-process negative electrode preparation technology solution described in the present invention, which can load more active materials in the limited electrode space, thereby improving the energy density of the energy storage sodium ion battery;

[0043] The present invention adopts the technical solution described in the present invention, which effectively reduces the overall manufacturing cost of energy storage sodium ion batteries by more than 10%.

[0044] Third, as auxiliary evidence of the inventiveness described in the claims of the present invention, it is also reflected in the following important aspects:

[0045] (1) The expected benefits and commercial value of the technical solution of the present invention after transformation are as follows: The economic benefits and commercial value of the technical solution of the present invention after transformation are obvious, and more and more manufacturers will introduce this technical solution.

[0046] (2) The technical solution of the present invention fills the technical gap in the industry at home and abroad: This technical solution is an original technical solution, and no such technical solution has been published at home or abroad.

[0047] (3) The technical solution of the present invention solves a technical problem that people have always wanted to solve but have never been able to solve successfully: the organic integration of high performance, low cost and environmental protection.

[0048] Fourth, in terms of the method for preparing the negative electrode of the energy storage sodium ion battery, the embodiments of the present invention have brought significant technical progress in many aspects:

[0049] 1. High stability and long life

[0050] By selecting hard carbon with a median particle size and specific surface area within a specific range, the stability and cycle life of the battery are effectively improved. In addition, by controlling the particle size distribution (such as the limits of D90 and D10), the structure and performance of the battery are further optimized.

[0051] 2. High energy density and high power density

[0052] The mass ratios (hard carbon, conductive agent, and binder) are carefully designed to achieve a balance of high energy and power density.

[0053] 3. Production costs and scalability

[0054] Due to the relatively flexible design in terms of mass ratio, this negative electrode material preparation method can not only obtain high-performance batteries, but also has good production cost control and engineering scalability.

[0055] The embodiments of the present invention not only optimize various performance indicators of energy storage sodium ion batteries, but also have high practical value and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0057] FIG1 is a flow chart of a method for preparing a negative electrode for an energy storage sodium ion battery according to an embodiment of the present invention;

[0058] FIG2 is a 0.5C cycle life test curve diagram of the energy storage sodium ion battery of Example 1 of the present invention. Modes for Carrying Out the Invention

[0059] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0060] In response to the problems existing in the prior art, the present invention provides an energy storage sodium ion battery and a method for preparing a negative electrode.

[0061] An embodiment of the present invention provides a method for preparing a negative electrode for an energy storage sodium ion battery, wherein the negative electrode comprises hard carbon, a conductive agent, and a binder, wherein the mass ratio of the hard carbon, the conductive agent, and the binder is: 90-95:1.0-3.0:3.0-8.0.

[0062] The hard carbon provided in the embodiment of the present invention has a median particle size of 2.0-12.0 μm and a specific surface area of ​​3-10 m2 / g;

[0063] The preferred particle size of the hard carbon is 3.0-7.0 μm;

[0064] The high particle size of the hard carbon particles D90≤23um;

[0065] The hard carbon particles have a low particle size D10 of ≥0.9 μm.

[0066] Furthermore, the conductive agent is a PtP type carbon-containing material, preferably Super P type conductive carbon black, 200GS type conductive carbon black and ECP type Ketjen black.

[0067] Furthermore, the binder is a fiberizable polytetrafluoroethylene polymer and its modified material, preferably expandable polytetrafluoroethylene with a polymerization degree of 1.7 to 4.6×10 4 .

[0068] As shown in FIG1 , the positive electrode preparation method provided by the embodiment of the present invention specifically includes the following steps:

[0069] Step 1: Add the hard carbon material, conductive agent and binder into a high-speed shear mixer and mix them in sequence. Set the mixing speed to 6000-12000 rpm for 30-60 minutes.

[0070] Step 2: Add the mixed materials to the biaxial hot rolling rollers and extrude them into a film. The thickness of the film is controlled at 90-350 μm. The temperature of the biaxial hot rolling rollers is controlled at 100-180°C and the pressure is controlled at 18-35°C.

[0071] Step 3: Laminating the film obtained in step 2 onto an 8-20 μm aluminum foil with an adhesive treatment on the surface, wherein the adhesive layer of the adhesive aluminum foil is 2-6 μm; the adhesive layer contains 65 wt% conductive carbon and 35% polymer glue;

[0072] Step 4: hot-press the composite obtained in step 3 at 100-180° C. to form a negative electrode for a sodium ion battery.

[0073] The optimal temperature for hot pressing the composite provided by the embodiment of the present invention is 105°C.

[0074] An energy storage sodium ion battery comprises an aluminum-plastic film shell, a diaphragm, an electrolyte, a positive electrode and a negative electrode, wherein the negative electrode is the sodium ion battery negative electrode prepared above.

[0075] Example 1

[0076] A low-cost, long-cycle energy storage sodium-ion battery comprises an aluminum-plastic film casing, a separator, an electrolyte, a positive electrode and a negative electrode.

[0077] The negative electrode comprises hard carbon, a conductive agent and a binder, wherein the mass ratio of the negative electrode, the conductive agent and the binder is 94:1.0:5.0;

[0078] The hard carbon is bamboo-based biomass hard carbon with a particle size (D50) of 5.4 μm and a specific surface area of ​​6 m2 / g;

[0079] The conductive agent is 200GS and has a specific surface area of ​​55m2 / g;

[0080] The binder is a fiberizable expandable polytetrafluoroethylene with a polymerization degree of 1.17×10 4 .

[0081] 1) Add hard carbon, conductive agent and binder to a high-speed shear mixer and mix them in sequence. Set the mixing speed to 7500 rpm and premix for 35 minutes.

[0082] 2) The pre-mixed electrode material is added to a pair of biaxial hot rolling rollers and pressed into a film. The thickness of the film is controlled at 125 μm. The temperature of the biaxial hot rolling rollers is controlled at 155°C and the pressure is controlled at 23°F.

[0083] 3) Mechanically bonding the membrane obtained in step 2) to a 12 μm aluminum foil with an adhesive treatment on its surface to form an electrode membrane / current collector composite, wherein the adhesive layer of the aluminum foil is 3 μm; the adhesive layer contains 65 wt% conductive carbon and 35% polymer glue;

[0084] 4) The composite obtained in step 3) is hot-pressed at 105° C. to form the negative electrode of the present invention.

[0085] The soft-pack sodium-ion energy storage battery produced under the above conditions was subjected to electrochemical charge-discharge tests and cycle durability tests. The experimental results showed that the sodium-ion battery of Example 1 had a capacity of 20.3 Ah at 0.5C, a corresponding specific energy of 180 Wh / kg, and a capacity retention rate of 93.65% after 1,000 cycles. Its specific energy, rate performance, and cycle durability were significantly better than those of existing technologies.

[0086] Example 2

[0087] A low-cost, long-cycle energy storage sodium-ion battery comprises an aluminum-plastic film casing, a separator, an electrolyte, a positive electrode and a negative electrode.

[0088] The negative electrode comprises hard carbon, a conductive agent and a binder, wherein the mass ratio of the negative electrode, the conductive agent and the binder is 95:0.5:4.5;

[0089] The hard carbon is resin hard carbon with a particle size (D50) of 5.9 μm and a specific surface area of ​​7 m2 / g;

[0090] The conductive agent is SP, with a specific surface area of ​​61m2 / g;

[0091] The binder is a fiberized modified polytetrafluoroethylene with a polymerization degree of 1.23×10 4 .

[0092] 1) Add hard carbon, conductive agent and binder to a high-speed shear mixer and mix them in sequence. Set the mixing speed to 8200 rpm and premix for 30 minutes.

[0093] 2) Add the pre-mixed electrode material to a pair of biaxial hot rolling rollers and extrude them into a film. The thickness of the film is controlled at 128 μm. The temperature of the biaxial hot rolling rollers is controlled at 175°C and the pressure is controlled at 32°C.

[0094] 3) Mechanically bonding the membrane obtained in step 2) to a 12 μm aluminum foil with an adhesive treatment on its surface to form an electrode membrane / current collector composite, wherein the adhesive layer of the aluminum foil is 3 μm; the adhesive layer contains 65 wt% conductive carbon and 35% polymer glue;

[0095] 4) The composite obtained in step 3) is hot-pressed at 105° C. to form the negative electrode of the present invention.

[0096] Example 3

[0097] A low-cost, long-cycle energy storage sodium-ion battery comprises an aluminum-plastic film casing, a separator, an electrolyte, a positive electrode and a negative electrode.

[0098] The negative electrode comprises hard carbon, a conductive agent and a binder, wherein the mass ratio of the negative electrode, the conductive agent and the binder is 93:1.5:5.5;

[0099] The hard carbon is coal-based hard carbon with a particle size (D50) of 6.8 μm and a specific surface area of ​​9 m2 / g;

[0100] The conductive agent is SP, with a specific surface area of ​​61m2 / g;

[0101] The binder is a fiberizable expandable polytetrafluoroethylene with a polymerization degree of 1.32×10 4 .

[0102] 1) Add hard carbon, conductive agent and binder to a high-speed shear mixer and mix them in sequence. Set the mixing speed to 6500 rpm and premix for 40 minutes.

[0103] 2) The pre-mixed electrode material is added to a pair of biaxial hot rolling rollers and pressed into a film. The thickness of the film is controlled at 117 μm. The temperature of the biaxial hot rolling rollers is controlled at 145°C and the pressure is controlled at 18°F.

[0104] 3) Mechanically bonding the membrane obtained in step 2) to a 12 μm aluminum foil with an adhesive treatment on its surface to form an electrode membrane / current collector composite, wherein the adhesive layer of the aluminum foil is 3 μm; the adhesive layer contains 65 wt% conductive carbon and 35% polymer glue;

[0105] 4) The composite obtained in step 3) is hot-pressed at 85° C. to form the negative electrode of the present invention.

[0106] Example 4

[0107] The same procedures as in Example 1 were followed except that the negative electrode active material was resin hard carbon, the mixing time was 5900 rpm, and the mixing time was 45 minutes.

[0108] Example 5

[0109] The same procedures as in Example 1 were followed except that coal-based hard carbon was used as the negative electrode active material, the mixing time was 9000 rpm, and the mixing time was 30 minutes.

[0110] Example 6

[0111] Except that the conductive agent is SP and the specific surface area is 61 m2 / g, the rest is the same as in Example 1.

[0112] Example 7

[0113] In addition to the binder, the fiberized modified polytetrafluoroethylene with a polymerization degree of 1.29×10 4 Other than that, the same as in Example 1.

[0114] Example 8

[0115] Except that the thickness of the membrane is controlled at 135 μm, the temperature of the biaxial hot rolling roller is controlled at 180° C., and the pressure is controlled at 32° C., the rest is the same as in Example 1.

[0116] Comparative Example 1

[0117] An energy storage sodium ion battery comprises an aluminum-plastic film shell, a diaphragm, an electrolyte, a positive electrode and a negative electrode.

[0118] The negative electrode comprises conventional hard carbon, a conductive agent and a binder. The negative electrode is prepared using an NMP oil-based wet coating process;

[0119] The positive electrode and subsequent preparation were the same as in Example 1.

[0120] Comparative Example 2

[0121] An energy storage sodium ion battery comprises an aluminum-plastic film shell, a diaphragm, an electrolyte, a positive electrode and a negative electrode.

[0122] The negative electrode comprises conventional hard carbon, a conductive agent and a binder. The negative electrode is prepared using a water-based wet coating process;

[0123] The positive electrode and subsequent preparation were the same as in Example 1.

[0124] The energy storage sodium ion battery prepared in the above embodiment and the energy storage battery prepared in the comparative embodiment were subjected to electrochemical basic performance, rate and 1000-cycle tests. The results are shown in Table 1.

[0125] From the data in FIG2 and Table 1, it can be analyzed that the energy storage sodium ion battery prepared by the present invention is better than the existing oily and water-based wet coating electrode preparation process technologies in terms of specific energy and cycle durability.

[0126] Table 1 Energy storage specific energy, rate and 1000 cycle performance of the above examples and comparative examples

[0127] Content Negative electrode method Capacity specific energy (Wh / kg) Internal resistance (mΩ) 1000 cycles Capacity retention rate (%) Example 1 Dry rolling 20.31800.6193.65 Example 2 Dry rolling 19.81770.5994.18 Example 3 Dry rolling 19.11740.6691.17 Example 4 Dry rolling 19.51760.6492.26 Example 5 Dry rolling Example 6 Dry rolling 19.31750.6290.88 Example 7 Dry rolling 19.21730.6789.53 Example 8 Dry rolling 20.81820.6792.18 Comparative Example 1 Oily coating 18.11600.7383.74 Comparative Example 2 Water-based coating 17.411520.8378.68

[0128] The following are four specific examples and implementation plans for preparing negative electrodes for sodium-ion energy storage batteries:

[0129] Application Example 1

[0130] 1. Select biomass hard carbon as the negative electrode material. First, biomass hard carbon is prepared from corn straw: corn straw is pyrolyzed at high temperature to generate hard carbon.

[0131] 2. The pore size distribution of the obtained hard carbon is 10-25nm, the median particle size is 5um, the specific surface area is 7m2 / g, the upper particle size D90 is 20um, and the lower particle size D10 is 1um.

[0132] 3. Based on this, 95 parts of hard carbon, 2 parts of conductive agent (such as graphite) and 3 parts of binder (such as polyvinyl fluoride) are mixed evenly to obtain the battery negative electrode.

[0133] Application Example 2

[0134] 1. Select resin-based hard carbon as the negative electrode material, for example, hard carbon obtained by high-temperature pyrolysis of phenolic resin.

[0135] 2. The pore size distribution of the obtained hard carbon is 15-30nm, the median particle size is 3um, the specific surface area is 9m2 / g, the upper particle size D90 is 22um, and the lower particle size D10 is 1.2um.

[0136] 3. Accordingly, 94 parts of hard carbon, 1.5 parts of a conductive agent (such as carbon black) and 4.5 parts of a binder (such as sodium polyacrylate) are mixed evenly to obtain a negative electrode for the battery.

[0137] Application Example 3

[0138] 1. Select coal-based hard carbon as the negative electrode material, for example, hard carbon obtained by pyrolysis of coal.

[0139] 2. The pore size distribution of the obtained hard carbon is 5-35nm, the median particle size is 7um, the specific surface area is 5m2 / g, the upper particle size D90 is 21um, and the lower particle size D10 is 1.5um.

[0140] 3. Based on this, 90 parts of hard carbon, 3 parts of conductive agent (such as graphite) and 7 parts of binder (such as polytetrafluoroethylene) are mixed evenly to obtain the battery negative electrode.

[0141] Application Example 4

[0142] 1. Select biomass hard carbon as the negative electrode material, preferably using bamboo as the biomass source. Prepare the hard carbon by pyrolyzing bamboo.

[0143] 2. The pore size distribution of the obtained hard carbon is 10-25nm, the median particle size is 4um, the specific surface area is 8m2 / g, the upper particle size D90 is 23um, and the lower particle size D10 is 0.9um.

[0144] 3. Accordingly, 93 parts of hard carbon, 2 parts of a conductive agent (such as carbon nanotubes) and 5 parts of a binder (such as sodium polyacrylate) are mixed evenly to obtain a negative electrode of the battery.

[0145] The above embodiments are merely implementation schemes, and the specific implementation needs to be adjusted and optimized according to the actual situation. Any matters not covered shall be handled according to common knowledge.

[0146] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A sodium ion energy storage battery negative electrode, characterized in that: The negative electrode comprises hard carbon, a conductive agent and a binder, and the mass ratio of the hard carbon, the conductive agent and the binder is: 90-95: 1.0-3.0: 3.0-8.

0.

2. The sodium ion energy storage battery negative electrode according to claim 1, characterized in that: The hard carbon is one or more of resin, coal-based or biomass-based.

3. The sodium ion energy storage battery negative electrode according to claim 1, characterized in that: The hard carbon is preferably biomass hard carbon; the pore size distribution is 8-30nm, preferably the pore size range is 10-25nm; The median particle size of the hard carbon is 2.0-12.0 μm, and the specific surface area is 3-10 m2 / g; The preferred particle size of the hard carbon is 3.0-7.0 um; The high particle size of the hard carbon particle size D90≤23um; The hard carbon particle size has a low particle size D10 ≥ 0.9 um.

4. The negative electrode of the sodium ion energy storage battery according to claim 1, characterized in that: The conductive agent is a point to point carbon-containing material, preferably one or more of Super P conductive carbon black, 200GS conductive carbon black and ECP Ketjen black.

5. The sodium ion energy storage battery negative electrode according to claim 1, characterized in that: The binder is a fiberizable polytetrafluoroethylene polymer and its modified material, preferably expandable polytetrafluoroethylene with a polymerization degree of 1.7 to 4.6×10 4 .

6. A method for preparing a negative electrode for a sodium ion energy storage battery as claimed in claim 1, characterized in that: The negative electrode preparation method specifically comprises the following steps: Step 1: Add the negative electrode material, conductive agent and binder into a high-speed shear mixer for mixing, set the mixing speed to 6000-12000 rpm, and the mixing time to 30-60 minutes; Step 2: Add the premixed materials to the biaxial hot rolling rollers to extrude into a film, the thickness of the film is controlled at 90-350um, the temperature of the biaxial hot rolling rollers is controlled at 100-180°C, and the pressure is controlled at 18-35°C; Step 3, mechanically bonding the film obtained in step 2 to an 8-20um aluminum foil with an adhesive treatment on the surface to form a composite body, wherein the adhesive layer of the adhesive aluminum foil is 2-6um; the adhesive layer contains 65wt% conductive carbon and 35% polymer glue; Step 4: hot-press the composite obtained in step 3 at 85-130° C. to form a negative electrode for a sodium ion battery.

7. A sodium ion energy storage battery, comprising an aluminum-plastic film housing, a diaphragm, an electrolyte, a positive electrode and a negative electrode, characterized in that: The negative electrode is the negative electrode of the sodium ion battery prepared according to claim 6.

8. A sodium ion battery negative electrode preparation device for the method according to claim 6, characterized in that: include: a) a high-speed shear mixer, used to mix the negative electrode material, the conductive agent and the binder, the mixing speed of the mixer is set to 6000-12000 rpm, and the mixing time is 30-60 minutes; b) A pair of biaxial hot rolling rollers, used to extrude the pre-mixed materials into a film, the thickness of the film is controlled at 90-350um, the temperature of the biaxial hot rolling rollers is controlled at 100-180℃, and the pressure is controlled at 18-35T; c) a mechanical bonding device, used to bond the film obtained in step b to an 8-20um aluminum foil with an adhesive surface to form a composite body, wherein the adhesive layer of the adhesive aluminum foil is 2-6um; the adhesive layer contains 65wt% conductive carbon and 35% polymer glue; d) a hot pressing device, used for hot pressing the composite obtained in step c at 85-130° C., wherein the optimal temperature for hot pressing the composite is 105° C., to form a negative electrode for a sodium ion battery.

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