Conductive agent with core-shell structure of carbon nanotube coated supported low-silicon X molecular sieve microspheres as well as continuous preparation device and method of conductive agent

Abstract

The invention discloses a conductive agent with a core-shell structure formed by carbon nanotube coated supported low-silicon X molecular sieve microspheres and an industrial continuous production device and method thereof. The conductive agent has a core-shell structure formed by coating supported low-silicon X molecular sieve microspheres with carbon nanotubes, the shell is formed by the carbon nanotubes, the core is formed by the supported low-silicon X molecular sieve microspheres, the thickness of the shell is 50-300 nm, preferably 80-200 nm, the particle size of the core is 0.5-1.5 [mu] m, and the weight ratio of the shell to the core is controlled to be 1: 5-5: 1. The conductive agent can give full play to the excellent conductivity of CNTs, overcomes the agglomeration problem of CNTs, improves the overall performance of the lithium battery, reduces the damage of the lithium battery in the charging and discharging process, improves the cycle stability of the battery, and prolongs the service life of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive agent materials, and in particular to a conductive agent having a core-shell structure of carbon nanotube-coated loaded low-silicon X molecular sieve microspheres and a continuous preparation device and method thereof. Background Art

[0002] Carbon nanotubes (CNTs) have remarkable properties. In terms of electrical properties, they have excellent conductivity and the current density can reach 1GA / cm 2 , which is 100 times more conductive than copper, and even more conductive than silver, and its electron migration rate is 70 times that of silicon. In terms of mechanical properties, its hardness is comparable to that of diamond, and it also has good flexibility, with a mechanical tensile strength between 50 and 70 GPa, which is 100 times that of steel. As for thermodynamic properties, its thermal conductivity is in the range of 2000 to 3000 W / mk, which is 10 times that of copper and 3 times that of diamond. These outstanding qualities give CNTs great development potential in the application field of lithium battery electrode materials. However, there are still some problems with single CNTs in practical applications, such as easy agglomeration when preparing electrode materials, which affects the full performance of their performance.

[0003] Porous materials have unique advantages in the field of lithium batteries. Porous structures can provide more active sites, which is conducive to the storage and transmission of lithium ions. During the charge and discharge process, lithium ions can diffuse rapidly in the pores of porous materials, thereby increasing the charge and discharge rate of the battery. In addition, porous materials can also alleviate the volume changes caused by the insertion and extraction of lithium ions, reduce the structural damage of electrode materials, and improve the cycle stability of batteries. The core-shell structure also shows significant advantages in the preparation of lithium battery electrode materials. With CNTs as the shell, it is possible to use its good conductivity to build an efficient electron transport network, so that electrons can be quickly transmitted inside the electrode, reduce resistance, reduce polarization, and improve the rate performance of the battery. The core structure derived from low-silicon X molecular sieve as a porous base material can not only inhibit the agglomeration of CNTs, but also further increase the specific surface area of ​​the material, providing more storage locations for lithium ions. At the same time, the core-shell structure can effectively buffer the stress of lithium ions on the electrode material during the insertion and extraction of lithium ions. The CNTs shell structure protects the internal core and maintains the stability of the electrode structure, thereby significantly improving the cycle life and overall performance of the negative electrode material of lithium batteries.

[0004] In addition, N doping is of great significance to the improvement of the performance of carbon nanotubes. The introduction of N atoms will change the electronic structure of carbon nanotubes and introduce additional electronic states into their original conjugated system. In terms of electrical properties, this further optimizes the conductivity of carbon nanotubes and makes electron transmission smoother, which can effectively reduce the resistance of the electrode, improve the performance of the battery at high-rate charge and discharge, and reduce energy loss. In terms of chemical activity, the surface activity of N-doped carbon nanotubes is enhanced, and the adsorption and desorption capacity of lithium ions is significantly improved, which is conducive to the rapid embedding and extraction of lithium ions in electrode materials, thereby accelerating the charge and discharge rate of the battery. At the same time, N doping can also enhance the synergistic effect between carbon nanotubes and other electrode materials, promote the uniform distribution of electrons and ions in composite electrode materials, and improve the overall utilization rate of electrode materials, thereby improving the cycle stability and capacity retention rate of the battery to a certain extent, and providing strong support for the high performance of lithium batteries.

[0005] The present invention aims to combine the advantages of nitrogen-doped CNTs and porous material core-shell structure to provide a new type of CNTs@low-silicon X molecular sieve microsphere core-shell structure conductive agent and its preparation device to meet the demand of lithium batteries for high-performance conductive agents. Summary of the invention

[0006] The purpose of the present invention is to provide a conductive agent having a core-shell structure formed by carbon nanotubes coating supported low-silicon X molecular sieve microspheres and an industrial continuous production device and method thereof, which can give full play to the excellent conductive properties of CNTs, while overcoming their agglomeration problem and improving the overall performance of lithium batteries.

[0007] According to one aspect of the present invention, an object of the present invention is to provide a conductive agent, which has a core-shell structure formed by carbon nanotubes coating supported low-silicon X molecular sieve microspheres, wherein the shell is formed by carbon nanotubes, and the core is formed by supported low-silicon X molecular sieve microspheres, wherein the thickness of the shell is 50-300nm, preferably 80-200nm, the particle size of the core is 0.5 to 1.5μm, and the weight ratio of the shell to the core is controlled to be between 1:5-5:1, preferably 1:3-3:1.

[0008] According to another aspect of the present invention, an object of the present invention is to provide a method for preparing the conductive agent, the method comprising the following steps:

[0009] 1) Dissolve NaOH and KOH in deionized water, add water glass and low-alkalinity sodium aluminate in sequence under strong stirring, and continue stirring for 30 minutes to obtain a milky white uniform synthetic system;

[0010] 2) transferring the synthesis system of step 1) into a closed hydrothermal reactor, aging at 30-120° C. for 3-12 h under static conditions, and then crystallizing at 80-100° C. for 1-6 h;

[0011] 3) The crystallized product is filtered, washed to a pH of 8 to 9, and dried at 120° C. to obtain a low-silicon X molecular sieve;

[0012] 4) adding 0.15 parts by weight of metal salt to anhydrous ethanol for ultrasonic dispersion to obtain a mixed liquid precursor liquid, and then adding 3.0 parts by weight of the low-silicon X molecular sieve obtained in step 3) to the mixed liquid, ultrasonically dispersed, and then magnetically stirred in a water bath at 80° C. until the aqueous solution evaporates without obvious moisture, and then placed in a drying oven and dried overnight at 80° C. for 12 hours to obtain a supported metal salt / X molecular sieve catalyst precursor;

[0013] 5) reacting the supported metal salt / X-type molecular sieve catalyst precursor prepared in step 4) with a reducing gas through a fluidized bed reactor to reduce the metal salt therein to a single metal to form a supported metal salt / X-type molecular sieve catalyst as a core, the reduction temperature being 300-500° C. and the reaction pressure being 0.1-1 MPa;

[0014] 6) transporting the reduced supported metal salt / X-type molecular sieve catalyst prepared in step 5) to a fluidized bed reactor, then introducing an inert carrier gas and a raw gas for reaction, in situ growing carbon nanotubes on the surface of the reduced supported metal salt / X-type molecular sieve catalyst, and generating a final conductive agent material having a core-shell structure of carbon nanotube-coated supported low-silicon X-type molecular sieve microspheres, wherein the volume ratio of the raw gas to the inert carrier gas is 2:1 to 6:1, the linear velocity of the mixed gas is controlled at 1.6 to 2.4 m / s, the reaction temperature is 600-900° C., the reaction pressure is normal pressure, and the reaction time is 150-600 min.

[0015] Preferably, in step 1), the molar ratio of water glass and low-alkalinity sodium aluminate is 2.05:1 based on SiO2, Al2O3, Na2O and K2O; the molar ratio of the total amount of NaOH and KOH to SiO2 is 3.25:1; the molar ratio of deionized water to the total amount of NaOH and KOH is 17:1; and the molar ratio of KOH to the total amount of NaOH and KOH is 0.23:1.

[0016] Preferably, the metal salt in step 4) is selected from nitrates, sulfates, sulfites, hydrochlorides, acetates or ferrocene of Fe, Co, Ni and Mo, preferably ferrocene, ferrous sulfate, cobalt acetate and nickel sulfate.

[0017] Preferably, the reducing gas in step 5) is hydrogen or carbon monoxide.

[0018] Preferably, the raw material gas in step 6) is a mixed organic matter of at least one selected from benzene, toluene, and cyclohexane and at least one selected from triethylamine, n-butylamine, di-n-propylamine, N-methylpyrrolidine, benzylamine, tri-n-butylamine, N-ethylcyclohexylamine, dibenzylamine, and N,N-dimethylaniline, wherein the molar ratio of the two is 1:1 to 5:1.

[0019] Preferably, the inert carrier gas is selected from nitrogen or argon.

[0020] According to another aspect of the present invention, an object of the present invention is to provide a device for preparing the conductive agent, the device mainly comprising: a catalyst tank, a catalyst reduction and activation fluidized bed reactor, a carbonization fluidized bed reactor, and a vibrating screen; wherein:

[0021] The catalyst tank is used to store the prepared supported metal salt / X-type molecular sieve catalyst precursor, and to input the catalyst precursor into the catalyst reduction activation fluidized bed reactor through a pipeline;

[0022] The catalyst reduction and activation fluidized bed reactor is used to make the catalyst precursor and the reducing gas undergo a reduction reaction. It is provided with a reducing gas inlet at the bottom for inputting a mixed gas of an inert carrier gas and a reducing gas into the reactor. A cyclone separator, an upper gas distributor and a lower gas distributor are provided inside the reactor for making the catalyst precursor and the reducing gas in the reactor fully contact and react. A reduced gas outlet is provided at the top.

[0023] The carbonization fluidized bed reactor is arranged downstream of the catalyst reduction activation fluidized bed reactor, and is connected through a pipeline to receive the activated catalyst from the catalyst reduction activation fluidized bed reactor. The carbonization fluidized bed reactor is provided with raw gas and inert carrier gas inlets for respectively introducing the raw gas and loosening gas into the reactor. A cyclone separator, an upper gas distributor, and a lower gas distributor are arranged inside the carbonization fluidized bed reactor for allowing the activated catalyst inside the reactor to fully contact and react with the raw gas to form large particles of conductive agent material. A carbonization reaction cracking gas outlet is arranged at the top of the carbonization fluidized bed reactor.

[0024] The vibrating screen is located at the lower part of the carbonization fluidized bed reactor, receives the large particles of the conductive agent material obtained after the reaction, and collects the final conductive agent material that meets the requirements through vibration screening.

[0025] Preferably, the preparation device further comprises a heat exchanger for heat exchange of feed gas, carbonization reaction cracking gas, inert carrier gas and the like.

[0026] Preferably, each cyclone separator and gas distributor in the catalyst reduction and activation fluidized bed reactor and the carbonization fluidized bed reactor is single-stage or multi-stage.

[0027] According to another aspect of the present invention, an object of the present invention is to provide use of the conductive agent as a negative electrode material for a battery.

[0028] According to another aspect of the present invention, an object of the present invention is to provide a lithium battery, wherein the lithium battery uses the conductive agent as the conductive agent material of the lithium battery.

[0029] Beneficial Effects

[0030] 1. Structural advantages: The core-shell structure design adopted by the present invention uses nitrogen-doped CNTs as the shell to provide a good conductive skeleton, effectively improving the electron transfer rate of the material. The microsphere core structure derived from low-silicon X molecular sieve as a porous carrier material can not only inhibit the agglomeration of CNTs, but also increase the specific surface area of ​​the material, providing more active sites for the storage and transmission of lithium ions.

[0031] 2. Performance improvement: In terms of electrochemical performance, when this conductive material is used in lithium-ion batteries, due to its special structure, it can increase the diffusion rate of lithium ions and enhance the charge and discharge performance of the battery. The network woven by nitrogen-doped CNTs provides a high-speed channel for electron transmission and improves the charge and discharge efficiency. At the same time, the shell structure can alleviate the volume change of lithium ions during the insertion and extraction process, and protect the Na + and K + The co-doped core structure reduces its damage during the charge and discharge process and prolongs the battery life. In addition, in lithium-ion battery electrodes, an important role of the conductive agent is to connect the active electrode materials to form a good conductive network. The doping of Na and K elements can enhance the adhesion between the conductive agent and the electrode material and improve the cycle stability of the battery.

[0032] Compared with the existing single CNTs conductive agent, the N-CNTs@loaded X molecular sieve microsphere core-shell structure conductive material of the present invention has higher cycle stability and better rate performance, can meet the needs of high-performance lithium-ion batteries, and is expected to be widely used in the new energy field. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 is a schematic structural diagram of a preparation device according to the present invention;

[0035] Figure 2 is a low-magnification SEM image of the conductive agent material prepared according to Example 1;

[0036] Figure 3 is a high-magnification SEM image of the conductive agent material prepared according to Example 1;

[0037] Figure 4 TEM image of carbon nanotubes on the surface of conductive agent particles prepared according to Example 1;

[0038] Figure 5 2 is the charge-discharge curve when SP is added as a conductive agent according to Comparative Example 1;

[0039] Figure 6 The charge-discharge curves are shown in Example 1 when a core-shell structure conductive agent is added;

[0040] Figure 7 The charge-discharge curves are based on the core-shell structure conductive agent in Example 2;

[0041] Figure 8 The charge-discharge curves are shown in Example 3 when a core-shell structure conductive agent is added;

[0042] Fig. 9 The charge-discharge curves are shown in Example 4 when a core-shell structure conductive agent is added;

[0043] Fig.10 1 is the charge and discharge curve according to Comparative Example 2 when only N-CNTs are used as the conductive agent.

[0044] Reference numerals:

[0045] 101-catalyst reduction activation fluidized bed reactor;

[0046] 102-carbonization fluidized bed reactor;

[0047] 103-vibrating screen;

[0048] 104-catalyst tank;

[0049] 105-heating furnace;

[0050] 106-raw gas / carbonization reaction cracking gas heat exchanger;

[0051] 1- Reducing gas;

[0052] 2- activated catalyst;

[0053] 3-reduced gas;

[0054] 4- Raw gas;

[0055] 5-Loose air;

[0056] 6-Carbonization reaction cracking gas;

[0057] 7-Large particles of conductive material;

[0058] 8- Finished conductive agent material;

[0059] 9- unreacted catalyst after sieving;

[0060] 10- inert carrier gas;

[0061] 1011-Catalyst reduction activation reactor cyclone separator;

[0062] 1012- upper gas distributor of catalyst reduction activation reactor;

[0063] 1013-catalyst reduction activation reactor lower gas distributor;

[0064] 1021-Carbonization reactor cyclone separator;

[0065] 1022-Carbonization reactor upper gas distributor;

[0066] 1023-Carbonization reactor lower gas distributor. DETAILED DESCRIPTION

[0067] Hereinafter, the preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be interpreted as limited to the general and dictionary meanings, but should be interpreted based on the principle of allowing the inventor to appropriately define the terms for the best interpretation, based on the meaning and concept corresponding to the technical level of the present invention. Therefore, the description herein is only a preferred example for illustrative purposes, and is not intended to limit the scope of the present invention, so it should be understood that other equivalent implementations and modifications can be made without departing from the spirit and scope of the present invention.

[0068] In this document, the terms "include", "including", "have", "contain" or any other similar terms are open conjunctions, which are intended to cover non-exclusive inclusions. For example, a composition or product containing multiple elements is not limited to the elements listed herein, but may also include other elements that are not explicitly listed but are generally inherent to the composition or product. In addition, unless otherwise explicitly stated, the term "or" refers to an inclusive "or" rather than an exclusive "or". For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and A and B are both true (or exist). In addition, in this document, the interpretation of the terms "include", "including", "have", and "contain" should be considered to have been specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as "consisting of" and "consisting essentially of".

[0069] In this article, all features or conditions defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be deemed to have covered and specifically disclosed all possible secondary ranges and individual values ​​within the range, especially integer values. For example, the range description of "1 to 8" should be deemed to have specifically disclosed all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., especially secondary ranges defined by all integer values, and should be deemed to have specifically disclosed individual values ​​such as 1, 2, 3, 4, 5, 6, 7, 8, etc. within the range. Unless otherwise specified, the above interpretation method applies to all contents of the entire present invention, regardless of whether the range is broad or not.

[0070] If the quantity or other numerical value or parameter is expressed as a range, a preferred range or a series of upper and lower limits, it should be understood that all ranges consisting of any upper limit or preferred value of the range and the lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, if a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0071] In this document, under the premise of achieving the purpose of the invention, numerical values ​​should be understood to have the accuracy of the number of significant digits of the numerical value. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0072] In order to clarify the present invention, parts irrelevant to the description are omitted in the drawings, and the same or similar components are denoted by the same reference numerals throughout the specification.

[0073] In addition, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of explanation, and thus the present invention is not necessarily limited to those shown in the drawings.

[0074] Throughout the specification, when it is mentioned that a certain element is “connected” to another element, it includes not only “direct connection” but also “indirect connection” between other components. In addition, when it is mentioned that a certain element “includes” a certain component, it means that the element may further include other components rather than excluding other components, unless explicitly described to the contrary.

[0075] The supported conductive agent of the present invention is formed by coating low-silicon X molecular sieve microspheres with carbon nanotubes to form a core-shell structure, and the thickness of the shell is controlled within 50-300nm, preferably 80-200nm. When controlled within this range, it can ensure that the carbon nanotubes form a good conductive network, and can better coat the core structure, while avoiding problems such as excessive agglomeration, and the conductive agent forms an effective conductive network between the current collectors inside the battery.

[0076] The main function of the core is to provide a porous structure, increase lithium ion storage sites and inhibit carbon nanotube agglomeration; the shell is responsible for building a conductive network. In order to balance the functions of the two, the weight ratio of the shell and the core can be controlled between 1:5-5:1, preferably 1:3-3:1, according to the preparation process. When the weight ratio of the two is controlled within this range, it can not only ensure that the porous core structure provides sufficient lithium ion storage space, but also utilize an appropriate amount of carbon nanotube shell layer to achieve efficient electron transmission and improve the overall performance of the battery. If the shell accounts for too high a proportion, it may lead to a decrease in the specific surface area of ​​the material and insufficient lithium ion storage sites; if the core accounts for too high a proportion, the electron transmission efficiency may be affected.

[0077] The preparation method and device of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0078] The method for preparing the conductive agent according to the present invention comprises the following steps:

[0079] 1) Dissolve NaOH and KOH in deionized water, add water glass and low-alkalinity sodium aluminate in sequence under strong stirring, and continue stirring for 30 minutes to obtain a milky white uniform synthetic system;

[0080] 2) transferring the synthesis system of step 1) into a closed hydrothermal reactor, aging at 30-120° C. for 3-12 h under static conditions, and then crystallizing at 80-100° C. for 1-6 h;

[0081] 3) The crystallized product is filtered, washed to a pH of 8 to 9, and dried at 120° C. to obtain a low-silicon X molecular sieve;

[0082] 4) adding 0.15 parts by weight of metal salt to anhydrous ethanol for ultrasonic dispersion to obtain a mixed liquid precursor liquid, and then adding 3.0 parts by weight of the low-silicon X molecular sieve obtained in step 3) to the mixed liquid, ultrasonically dispersed, and then magnetically stirred in a water bath at 80° C. until the aqueous solution evaporates without obvious moisture, and then placed in a drying oven and dried overnight at 80° C. for 12 hours to obtain a supported metal salt / X molecular sieve catalyst precursor;

[0083] 5) reacting the supported metal salt / X-type molecular sieve catalyst precursor prepared in step 4) with a reducing gas through a fluidized bed reactor to reduce the metal salt therein to a single metal to form a supported metal salt / X-type molecular sieve catalyst as a core, the reduction temperature being 300-500° C. and the reaction pressure being 0.1-1 MPa;

[0084] 6) The reduced supported metal salt / X-type molecular sieve catalyst prepared in step 5) is transported to a fluidized bed reactor, and then an inert carrier gas and a raw gas are introduced for reaction, and carbon nanotubes are in situ grown on the surface of the reduced supported metal salt / X-type molecular sieve catalyst to generate a conductive agent material having a core-shell structure of carbon nanotube-coated supported low-silicon X-type molecular sieve microspheres, wherein the volume ratio of the raw gas to the inert carrier gas is 2:1 to 6:1, the material space velocity of the mixed gas is controlled at 1.6 to 2.4 m / s, the reaction temperature is 600-900° C., the reaction pressure is normal pressure, and the reaction time is 150-600 min.

[0085] Wherein steps 5) and 6) are performed using the preparation device according to the present invention, wherein: the device mainly comprises: a catalyst tank 104, a catalyst reduction activation fluidized bed reactor 101, a carbonization fluidized bed reactor 102, and a vibrating screen 103; wherein:

[0086] The catalyst tank 104 is used to store the prepared supported metal salt / X-type molecular sieve catalyst precursor, and to input the catalyst precursor into the catalyst reduction activation fluidized bed reactor 101 through a pipeline;

[0087] The catalyst reduction and activation fluidized bed reactor 101 is used to make the catalyst precursor and the reducing gas 1 undergo a reduction reaction. A reducing gas inlet is provided at the bottom for inputting a mixed gas of an inert carrier gas and a reducing gas into the reactor 101. A cyclone separator 1011, an upper gas distributor 1012 and a lower gas distributor 1013 are provided inside the reactor 101 for making the catalyst precursor and the reducing gas in the reactor 101 fully contact and react. A reduced gas outlet 3 is provided at the top.

[0088] For example, the reducing gas 1 is continuously introduced into the bottom of the catalyst reduction and activation fluidized bed reactor 101, and the reducing gas 1 is initially distributed through the lower gas distributor 1013, and then evenly distributed again through the upper gas distributor 1012, so that the catalyst bed is formed into a dispersed fluidized state. The reduced gas 3 generated by the reaction is treated by the cyclone separator 1011 and then discharged, and the recovered catalyst particles are returned to the catalyst bed through the pipeline. The cyclone separator 1011 can be one-stage or multi-stage.

[0089] The carbonization fluidized bed reactor 102 is arranged downstream of the catalyst reduction activation fluidized bed reactor 101, and is connected through a pipeline to receive the activated catalyst 2 from the catalyst reduction activation fluidized bed reactor. The carbonization fluidized bed reactor 102 is provided with raw gas and inert carrier gas inlets for respectively introducing the raw gas 4 and loosening gas 5 into the reactor. A cyclone separator 1021, an upper gas distributor 1022, and a lower gas distributor 1023 are arranged inside the carbonization fluidized bed reactor 102, which are used to make the activated catalyst 2 inside the reactor 102 fully contact and react with the raw gas 4 to form large particles of conductive agent material. The top of the carbonization fluidized bed reactor 102 is provided with a carbonization reaction cracking gas 6 outlet.

[0090] For example, the raw gas 4 is preheated by the raw gas / carbonization reaction cracking gas heat exchanger 106, and after heat exchange with the carbonization reaction cracking gas 6, it enters the carbonization fluidized bed reactor 102 in two streams, and is distributed through the upper gas distributor 1022 and the lower gas distributor 1023 respectively. The activated catalyst 2 enters the carbonization fluidized bed reactor 102 through the flow control of the slide valve. Under the action of suitable temperature, pressure and catalyst, the raw gas 4 is carbonized. As the reaction proceeds, large particles of carbon nanotube aggregates are continuously screened out from the fluidized bed layer and settle at the conical bottom of the carbonization fluidized bed reactor 102. A small amount of inert gas is introduced into the side of the conical bottom of the carbonization fluidized bed reactor 102 as loosening gas 5 to maintain the fluidity of the particles at the outlet. The carbonization reaction cracking gas 6 produced by the reaction is processed by the cyclone separator 1021 and then discharged. The unreacted catalyst 9 particles after screening are transported back to the catalyst tank 104 through the pipeline. The cyclone separator 1021 can be one-stage or multi-stage. During the catalytic cracking process, the raw gas 4 and the activated catalyst 2 meet in the carbonization fluidized bed reactor 102 and undergo a catalytic cracking process. In this process, in addition to the generation of carbon nanotubes on the surface of the catalyst particles, cracked gas hydrogen is also generated. However, hydrogen and catalyst constitute dust pollution and cannot be directly discharged into the air. Therefore, the cyclone separator 1021 is added to separate the catalyst particles and hydrogen. Some catalyst particles are returned to the catalyst tank 104 through the pipeline, and the hydrogen is separated and discharged through the cyclone separator 1021. In order to ensure that the raw gas reacts fully, the activated catalyst 2 is excessive relative to the raw gas 4 during the reaction. Therefore, the above-mentioned part of the catalyst particles are returned to the catalyst tank 104 and then continue to react, and finally the surface of most of the catalyst is covered with a carbon nanotube shell.

[0091] The vibration screen 103 is located at the lower part of the carbonization fluidized bed reactor 102, receives the large particles 7 of the conductive material obtained after the reaction, and collects the final conductive material that meets the requirements through vibration screening.

[0092] Preferably, the preparation device further comprises a heat exchanger 106 and a heating furnace 105 for heat exchange of the raw gas 4, the carbonization reaction cracking gas 6, the inert carrier gas 5, 10 and the like.

[0093] Preferably, the inner and outer diameters d / D of the reduction activation bed reactor 101 are 0.2-0.6, and the ratio of the outlet inner diameters of the lower gas distributor 1013 and the catalyst reduction activation fluidized bed reactor 101 is 0.6-1.

[0094] Preferably, the diameter of the upper gas distributor 1022 is larger than the diameter of the lower gas distributor 1023, and the diameter ratio d1022 / d1023 is 0.5-1.

[0095] The following examples are only listed as examples of embodiments of the present invention and do not constitute any limitation to the present invention. It can be understood by those skilled in the art that modifications within the scope of the essence and concept of the present invention fall within the scope of protection of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are all commercially available products.

[0096] The performance test of the conductive agent of the present invention as a negative electrode material can be carried out according to the conventional battery preparation method. For example, a CR2032 button battery is assembled. The slurry is prepared with an oil-based needle coke negative electrode material (purchased from Shangdu Xuyang), a conductive agent prepared according to the present invention, and polyvinylidene fluoride (PVDF) in a mass ratio of 80:10:10. After sufficient grinding and stirring, the slurry is evenly coated on a copper foil and placed in an oven at 100°C for 4 hours. The average active material loaded on the electrode is about 1.5 mg / cm -2 . The battery assembly was carried out in an argon-filled glove box (Braun MB-Labstar 1500 / 780 model) with water and oxygen content below 0.1 ppm. For lithium-ion batteries (LIBs), a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) containing 1 mol lithium hexafluorophosphate (LiPF6) was used as the electrolyte, and Celgard 2300 was used as the separator material. The battery charge and discharge performance and charge and discharge efficiency were tested using a NEWARE-BTS-4008 multi-channel battery cycler.

[0097] The experimental drugs used in the present invention are all from MacLean's reagent, and the scanning electron microscopy (SEM) is obtained by field emission SU-70 microscope, and the transmission electron microscopy TEM analysis is performed using JEOL JEM2010 electron microscope at 200 kV.

[0098] The performance test method of the conductive agent as a battery material is a conventional test method in the art, for example, it can be performed as follows:

[0099] The slurry is made of oil-based needle coke negative electrode material (purchased from Shangdu Xuyang), conductive agent and polyvinylidene fluoride (PVDF) in a mass ratio of 80:10:10. After sufficient grinding and stirring, the slurry is evenly coated on the copper foil and placed in an oven at 100°C for 4 hours. The average active material loaded on the electrode is about 1.5 mg / cm 2. The battery assembly was carried out in an argon-filled glove box (Braun MB-Labstar 1500 / 780 model), and the water and oxygen content in the glove box was less than 0.1 ppm. For lithium-ion batteries (LIBs), a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) containing 1 mol lithium hexafluorophosphate (LiPF6) was used as the electrolyte, and Celgard2300 was used as the separator material. The battery charge and discharge performance and charge and discharge efficiency were tested using a NEWARE-BTS-4008 multi-channel battery cycler.

[0100] Example 1

[0101] (1) Preparation of ferrocene / X-type molecular sieve catalyst

[0102] 0.15g of ferrocene was added to 20ml of anhydrous ethanol and ultrasonically dispersed for 15min to obtain a mixed liquid precursor. Then 3.0g of X-type molecular sieve was added to the mixed liquid and ultrasonically dispersed for 15min. After that, it was magnetically stirred in a water bath at 80℃ until the aqueous solution evaporated without obvious water. Then it was placed in a drying oven and dried overnight at 80℃ for 12h to obtain a supported ferrocene / X-type molecular sieve catalyst precursor.

[0103] (2) reacting the supported ferrocene / X-type molecular sieve catalyst precursor prepared in step (1) with a reducing gas through a fluidized bed reactor to reduce the metal salt therein to a single metal to form a supported metal salt / X-type molecular sieve catalyst as a core, the reduction temperature being 500° C. and the reaction pressure being 1 MPa;

[0104] (3) transporting the reduced supported metal salt / X-type molecular sieve catalyst prepared in step (2) to a fluidized bed reactor, then introducing an inert carrier gas and a raw gas for reaction, in situ growing carbon nanotubes on the surface of the reduced supported metal salt / X-type molecular sieve catalyst, and generating a conductive agent material having a core-shell structure of carbon nanotube-coated supported low-silicon X-type molecular sieve microspheres, wherein the volume ratio of the raw gas to the inert carrier gas is 3:1, the linear velocity of the mixed gas is controlled at 2.1 m / s, the reaction temperature is 700° C., the reaction pressure is normal pressure, the reaction time is 500 min, the raw gas is a mixed organic matter of toluene and n-butylamine, the molar ratio of the two is 2:1, and nitrogen is used as the loosening gas.

[0105] By low magnification SEM ( Figure 2 ) and high magnification SEM ( Figure 3) It can be seen that the prepared conductive agent has a spherical structure, and its surface is covered with carbon nanotube structures (CNTs). At high temperatures, the catalytic metal particles have a certain fluidity and solubility. The carbon atoms produced by cracking dissolve in the metal particles with a certain solubility and diffuse under the action of the concentration gradient. When the carbon atoms diffused to the other side of the metal particles reach a supersaturated state, they will precipitate and grow in the form of nanotubes. During the whole process, the metal particles play a role in guiding the arrangement of carbon atoms and promoting the migration of carbon atoms, allowing carbon atoms to orderly construct nanotube structures. Through TEM ( Figure 4 ) It can be seen that there are catalytic metal particles at the tips of CNTs on the surface of the prepared conductive agent.

[0106] In order to further verify its electrochemical performance, the conductive agent was used as the negative electrode material to assemble a CR2032 button battery and perform charge and discharge tests. Figure 6 It can be seen that the conductive agent sample has good cycle stability. For example, the charge and discharge efficiencies are 94.63%, 99.41%, 99.62%, 99.69% and 99.73% during cycles 1-5 respectively.

[0107] Example 2

[0108] The conductive agent material is prepared in the same manner as Example 1, except that in the preparation process of step (3), the volume ratio of the raw gas to the inert carrier gas is 4:1, the linear velocity of the mixed gas is controlled at 1.8 m / s, the reaction temperature is 700°C, the reaction pressure is normal pressure, the reaction time is 400 min, the raw gas is a mixed organic matter of toluene and triethylamine, the molar ratio of the two is 4:1, and nitrogen is used as the loosening gas.

[0109] In order to further verify its electrochemical performance, the conductive agent was used as the negative electrode material to assemble a CR2032 button battery and perform charge and discharge tests. Figure 7 As shown: Electrochemical tests show that the conductive agent sample has good cycle stability. For example, the charge and discharge efficiencies are 94.47%, 99.19%, 99.41%, 99.52% and 99.56% during cycles 1-5 respectively.

[0110] Example 3

[0111] The conductive agent material is prepared in the same manner as Example 1, except that in the preparation process of step (3), the volume ratio of the raw gas to the inert carrier gas is 2:1, the linear velocity of the mixed gas is controlled at 1.6 m / s, the reaction temperature is 700°C, the reaction pressure is normal pressure, the reaction time is 260 min, the raw gas is a mixed organic matter of cyclohexane and di-n-propylamine, the molar ratio of the two is 3:1, and nitrogen is used as the loosening gas.

[0112] In order to further verify its electrochemical performance, the conductive agent was used as the negative electrode material to assemble a CR2032 button battery and perform charge and discharge tests. Figure 8 As shown: Electrochemical tests show that the conductive agent sample has good cycle stability. For example, the charge and discharge efficiencies are 93.59%, 99.01%, 99.27%, 99.38% and 99.48% during cycles 1-5 respectively.

[0113] Example 4

[0114] The conductive agent material is prepared in the same manner as Example 1, except that in the preparation process of step (3), the volume ratio of the raw gas to the inert carrier gas is 6:1, the linear velocity of the mixed gas is controlled at 1.9 m / s, the reaction temperature is 700°C, the reaction pressure is normal pressure, the reaction time is 300 min, the raw gas is a mixed organic matter of toluene and N-methylpyrrolidine, the molar ratio of the two is 5:1, and nitrogen is used as the loosening gas.

[0115] In order to further verify its electrochemical performance, the conductive agent was used as the negative electrode material to assemble a CR2032 button battery and perform charge and discharge tests. Fig. 9 As shown: Electrochemical tests show that the conductive agent sample has good cycle stability. For example, the charge and discharge efficiencies are 93.71%, 98.81%, 99.13%, 99.31% and 99.45% during cycles 1-5 respectively.

[0116] Comparative Example 1

[0117] Carbon black (SP, SP purchased from TIMCAL, Switzerland: (high purity carbon black SUPER P Li)) was used as the conductive agent, and the conductive agent product prepared by the present invention was not added. The electrochemical test was carried out in the same manner as in Example 1. Figure 5 As shown, the test results show that under the same conditions, the sample has poor cycle stability and large fluctuations in charge and discharge efficiency. For example, the charge and discharge efficiency is 91.63%, 97.75%, 96.61%, 93.94% and 91.37% when cycled 1-5 times, respectively.

[0118] Comparative Example 2

[0119] like Fig.10As shown: The difference between this comparative example and Example 1 is that ferrocene is used as a catalyst and the porous substrate material X molecular sieve is not added. Carbon nanotubes (N-CNTs) are prepared through a subsequent carbonization reaction stage and a post-treatment process. The N-CNTs are used as a conductive additive and an electrochemical test is performed in the same manner as Example 1. The test results show that under the same conditions, the sample with only CNTs added has poor cycle stability and large fluctuations in charge and discharge efficiency. The charge and discharge efficiencies are 94.67%, 98.52%, 98.30%, 97.81%, and 97.09% when the cycles are 1-5, respectively.

[0120] By comparing the performance of different conductive agents, the fluctuation of the charge and discharge efficiency data is analyzed by variance. For example, by comparing the charge and discharge efficiency data of Examples 1 and 2 and the 1-5 cycles in Example 1, by calculating the variance, the data is shown in Table 1 below, which can more intuitively judge the stability of the charge and discharge efficiency of different conductive agents. If the variance of the charge and discharge efficiency data of a conductive agent is small, it indicates that its performance is stable and the fluctuation is small; conversely, a large variance means that the performance is unstable and the fluctuation is large.

[0121] Table 1

[0122] variance Variance value Variance value*10^6 Example 1 0.000039 39 Comparative Example 1 0.00066148 661.48 Comparative Example 2 0.00019414 194.14

[0123] By comparison, the data of Comparative Example 1 and Comparative Example 2 prove that the charging and discharging efficiency fluctuates significantly and is not stable enough, while the charging and discharging efficiency of the product of Example 1 fluctuates little and has stable performance.

[0124] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A conductive agent having a core-shell structure formed by carbon nanotubes coating supported low-silicon X molecular sieve microspheres, wherein the shell is formed by carbon nanotubes, and the core is formed by supported low-silicon X molecular sieve microspheres, wherein the thickness of the shell is 50-300 nm, preferably 80-200 nm, the particle size of the core is 0.5 to 1.5 μm, and the weight ratio of the shell to the core is controlled to be between 1:5 and 5:1, preferably 1:3-3:

1.

2. The method for preparing the conductive agent according to claim 1, comprising the following steps: 1) Dissolve NaOH and KOH in deionized water, add water glass and low-alkalinity sodium aluminate in sequence under strong stirring, and continue stirring for 30 minutes to obtain a milky white uniform synthetic system; 2) transferring the synthesis system of step 1) into a closed hydrothermal reactor, aging at 30-120° C. for 3-12 h under static conditions, and then crystallizing at 80-100° C. for 1-6 h; 3) The crystallized product is filtered, washed to a pH of 8 to 9, and dried at 120° C. to obtain a low-silicon X molecular sieve; 4) adding 0.15 parts by weight of metal salt to anhydrous ethanol for ultrasonic dispersion to obtain a mixed liquid precursor liquid, and then adding 3.0 parts by weight of the low-silicon X molecular sieve obtained in step 3) to the mixed liquid, ultrasonically dispersed, and then magnetically stirred in a water bath at 80° C. until the aqueous solution evaporates without obvious moisture, and then placed in a drying oven and dried overnight at 80° C. for 12 hours to obtain a supported metal salt / X molecular sieve catalyst precursor; 5) reacting the supported metal salt / X-type molecular sieve catalyst precursor prepared in step 4) with a reducing gas through a fluidized bed reactor to reduce the metal salt therein to a single metal to form a supported metal salt / X-type molecular sieve catalyst as a core, the reduction temperature being 300-500° C. and the reaction pressure being 0.1-1 MPa; 6) transporting the reduced supported metal salt / X-type molecular sieve catalyst prepared in step 5) to a fluidized bed reactor, then introducing an inert carrier gas and a raw gas for reaction, in situ growing carbon nanotubes on the surface of the reduced supported metal salt / X-type molecular sieve catalyst, and generating a final conductive agent material having a core-shell structure of carbon nanotube-coated supported low-silicon X-type molecular sieve microspheres, wherein the volume ratio of the raw gas to the inert carrier gas is 2:1 to 6:1, the linear velocity of the mixed gas is controlled at 1.6 to 2.4 m / s, the reaction temperature is 600-900° C., the reaction pressure is normal pressure, and the reaction time is 150-600 min.

3. The preparation method according to claim 2, characterized in that: In step 1), the molar ratio of water glass to low-basicity sodium aluminate is 2.05:1 based on SiO2, Al2O3, Na2O and K2O; the molar ratio of the total amount of NaOH and KOH to SiO2 is 3.25:1; the molar ratio of deionized water to the total amount of NaOH and KOH is 17:1; the molar ratio of KOH to the total amount of NaOH and KOH is 0.23:1; Preferably, the metal salt in step 4) is selected from nitrates, sulfates, sulfites, hydrochlorides, acetates or ferrocene of Fe, Co, Ni and Mo, preferably ferrocene, ferrous sulfate, cobalt acetate and nickel sulfate; Preferably, the reducing gas in step 5) is hydrogen or carbon monoxide; Preferably, the raw material gas in step 6) is a mixed organic matter of at least one selected from benzene, toluene, and cyclohexane and at least one selected from triethylamine, n-butylamine, di-n-propylamine, N-methylpyrrolidine, benzylamine, tri-n-butylamine, N-ethylcyclohexylamine, dibenzylamine, and N,N-dimethylaniline, wherein the molar ratio of the two is 1:1 to 5:1; Preferably, the inert carrier gas is selected from nitrogen or argon.

4. The conductive agent preparation device according to claim 1, wherein the device mainly comprises: Catalyst tank, catalyst reduction and activation fluidized bed reactor, carbonization fluidized bed reactor, vibrating screen; among which: The catalyst tank is used to store the prepared supported metal salt / X-type molecular sieve catalyst precursor, and to input the catalyst precursor into the catalyst reduction activation fluidized bed reactor through a pipeline; The catalyst reduction and activation fluidized bed reactor is used to make the catalyst precursor and the reducing gas undergo a reduction reaction. It is provided with a reducing gas inlet at the bottom for inputting a mixed gas of an inert carrier gas and a reducing gas into the reactor. A cyclone separator, an upper gas distributor and a lower gas distributor are provided inside the reactor for making the catalyst precursor and the reducing gas in the reactor fully contact and react. A reduced gas outlet is provided at the top. The carbonization fluidized bed reactor is arranged downstream of the catalyst reduction and activation fluidized bed reactor, and is connected through a pipeline to receive the activated catalyst from the catalyst reduction and activation fluidized bed reactor. The carbonization fluidized bed reactor is provided with a raw gas and an inert carrier gas inlet, which are used to respectively introduce the raw gas and the loose gas into the reactor. A cyclone separator, an upper gas distributor, and a lower gas distributor are arranged inside the carbonization fluidized bed reactor, which are used to make the activated catalyst inside the reactor fully contact and react with the raw gas to form large particles of conductive agent material. The top of the carbonization fluidized bed reactor is provided with a carbonization reaction cracking gas outlet; The vibrating screen is located at the lower part of the carbonization fluidized bed reactor, receives the large particles of the conductive agent material obtained after the reaction, and collects the final conductive agent material that meets the requirements through vibration screening.

5. The preparation device according to claim 4, characterized in that: The preparation device also includes a heat exchanger for heat exchange between the raw gas, the carbonization reaction cracking gas, the inert carrier gas, etc.; Preferably, each cyclone separator and gas distributor in the catalyst reduction and activation fluidized bed reactor and the carbonization fluidized bed reactor is single-stage or multi-stage.

6. Use of the conductive agent according to claim 1 as a negative electrode material for a battery.

7. A lithium battery, wherein the conductive agent according to claim 1 is used as the conductive agent material of the lithium battery.

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