Hard carbon negative electrode material, preparation method thereof and battery

Abstract

The application provides a hard carbon negative electrode material, a preparation method thereof and a battery. The hard carbon negative electrode material comprises a hard carbon base material, the hard carbon base material has a pore structure, and nano-scanium oxide is fixed in the pore structure. In the application, the nano-scanium oxide is fixed in the pore structure of the hard carbon base material as a support, which on one hand improves the compaction density of the hard carbon negative electrode material, and on the other hand forms an inlaid conductive network structure, and improves the electrochemical performance of the hard carbon negative electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and relates to a hard carbon negative electrode material, a preparation method thereof and a battery, in particular to a hard carbon negative electrode material for a sodium ion battery, a preparation method thereof and the sodium ion battery. BACKGROUND

[0002] Lithium ion batteries are widely used in 3C consumer electronics, new energy electric vehicles and renewable energy storage fields. Limited lithium resources, unbalanced distribution and high cost are not conducive to the large-scale application of lithium ion batteries in the energy storage field. At the same time, the graphite negative electrode of the commercialized lithium ion battery hinders the further improvement of the cycle performance and rate performance of the battery due to its structural characteristics. Sodium ion batteries have similar energy storage mechanisms as lithium ion batteries, and are expected to replace lithium ion battery products due to their advantages of abundant resources and low cost.

[0003] Hard carbon has randomly oriented graphite domains, and the disordered structure of high carbon layer spacing and some residual heteroatoms (mainly oxygen functional groups) can provide more ion diffusion paths and ion storage sites, especially sodium ion diffusion paths and sodium ion storage sites, which are currently the more preferred negative electrode materials for sodium ion batteries.

[0004] Hard carbon materials are usually obtained by high-temperature heat treatment of organic precursor in a protective gas atmosphere. In the high-temperature pyrolysis process, the carbon precursor material decomposes to release volatile gases, and the released gases form pores in the hard carbon material, resulting in high specific surface area, high porosity and low bulk density of the hard carbon material, which brings problems such as low compaction density, low first coulombic efficiency and poor cycle performance of the hard carbon material; and the irregular morphology causes the breakage of the current collector under high compaction conditions, leading to internal short circuit, thermal runaway, fire and explosion and other safety problems of the battery.

[0005] Therefore, how to improve the compaction density and electrochemical performance of the hard carbon material is a technical problem to be solved. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a hard carbon negative electrode material, a preparation method thereof and a battery. In the present application, nano-scanium oxide is fixed in the pore structure of the hard carbon matrix material, which on the one hand improves the compaction density of the hard carbon negative electrode material, and on the other hand forms an inlaid conductive network structure, thereby improving the electrochemical performance of the hard carbon negative electrode material.

[0007] To achieve the purpose of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides a hard carbon negative electrode material, which comprises a hard carbon base material, wherein the hard carbon base material has a pore structure, and nano-scaled scandium oxide is fixed in the pore structure.

[0009] The hard carbon negative electrode material provided by the present application has nano-scaled scandium oxide with high conductivity, which can promote selective adsorption of ester groups and carbonyl groups in a sodium ion electrolyte, thereby inhibiting the occurrence of side reactions between the hard carbon and the electrolyte, reducing the generation of SEI films, allowing more sodium ions to participate in the reversible embedding and de-embedding process, and thus improving the initial efficiency of the hard carbon; the nano-scaled scandium oxide is also fixed in the pore structure of the hard carbon base material as a support, forming an inlaid conductive network structure, which can effectively prevent the aggregation and loss of scandium oxide particles, so that the hard carbon particles are uniformly distributed, and electrons can be quickly transmitted in the electrode material even under high-rate charging and discharging.

[0010] Meanwhile, the high specific surface area of the nano-scaled scandium oxide allows it to have more contact points with the hard carbon particles, generating van der Waals forces, which help to pull the hard carbon particles towards each other during the pressing process, so that they are more tightly bonded together, improving the compaction density of the material; furthermore, the nano-particles have a larger specific surface area and more surface atoms, and these surface atoms have higher chemical activity, thereby becoming potential active sites, which can chemically react with functional groups (such as carboxyl groups and hydroxyl groups) on the surface of the hard carbon to form chemical bonds, and the chemical bond effect can enhance the connection strength between the hard carbon particles, so that the hard carbon particles are less likely to have relative displacement during the compaction process, thereby being able to withstand higher pressure and achieving higher compaction density.

[0011] That is, the hard carbon negative electrode material provided by the present application has high compaction density and excellent electrochemical performance, and when used in a sodium ion battery, the initial efficiency and rate performance of the battery are greatly improved.

[0012] In the present application, if the scandium oxide is micron-sized, due to its larger particle size, it cannot effectively fill the gaps like nano-scaled scandium oxide, resulting in less significant improvement in the mechanical properties of the hard carbon material than nano-scaled scandium oxide.

[0013] The following is a preferred technical solution of the present application, but is not a limitation on the technical solution provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0014] Preferably, the surface of the nano-scaled scandium oxide is modified with an oxygen bridge bond.

[0015] It should be noted that the oxygen bridge bond in the present application is Sc-O-Sc, which is formed through nucleophilic addition between the hard carbon precursor and the scandium oxide and subsequent elimination of water.

[0016] In the present application, the surface of the nano scandium oxide is modified by an oxygen bridge bond, which can better promote the selective adsorption of the ester group and the carbonyl group of the sodium ion electrolyte, thereby inhibiting the occurrence of the side reaction of the hard carbon and the electrolyte, reducing the generation of the SEI film, allowing more sodium ions to participate in the reversible embedding and de-embedding process, and further improving the initial efficiency of the sodium ion battery.

[0017] Preferably, the median particle size D50 of the nano scandium oxide is 5-250 nm, such as 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, or 250 nm, etc.

[0018] In the present application, the median particle size D50 of the nano scandium oxide is adjusted to 5-250 nm, which is more conducive to the high specific surface area of the scandium oxide, thereby providing more active sites for the hard carbon material, and further improving the electrochemical performance of the battery.

[0019] Preferably, the hard carbon matrix material includes a resin-based hard carbon matrix material.

[0020] The resin-based hard carbon matrix material, i.e., the hard carbon material obtained by taking resin as a raw material, consumes a large amount of electrolyte and sodium ions to generate an SEI (solid electrolyte interface) film during the first charging process, thereby leading to a decrease in the initial coulombic efficiency. The contact resistance exists between the hard carbon particles, and a good conductive network is not formed during the material preparation process. In high-rate charging and discharging, electrons cannot be quickly transmitted in the electrode material. At the same time, the resin-based hard carbon particles usually have irregular shapes, such as blocky, flaky, or complex polyhedral structures. This irregularity makes it difficult for the particles to form a close arrangement when they are stacked, which leads to a low proportion of solid parts in the hard carbon material under the same volume, i.e., a low compaction density.

[0021] The hard carbon matrix material in the present application is selected from a resin-based hard carbon matrix material, which cooperates with the nano scandium oxide to further improve the initial efficiency. The nano scandium oxide can promote the selective adsorption of the electrolyte, inhibit the side reaction, reduce the generation of the SEI film, and improve the initial efficiency. The nano scandium oxide and the hard carbon material form an inlaid conductive network structure to prevent the loss of particle aggregation, thereby improving the compaction density of the hard carbon material.

[0022] Preferably, the porosity of the hard carbon matrix material is 20%-55%, such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 55%, etc.

[0023] Preferably, the D50 of the hard carbon negative electrode material is 5-10 μm, such as 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, or 10 μm, etc.

[0024] In a second aspect, the present application provides a preparation method of the hard carbon negative electrode material according to the first aspect, the preparation method comprising the following steps:

[0025] Mixing the nano-scaled scandium oxide, the hard carbon precursor material and the binder solution, compacting, carbonizing, to obtain the hard carbon negative electrode material.

[0026] The preparation method provided by the present application uniformly mixes the nano-scaled scandium oxide and the hard carbon precursor material under the action of the binder, effectively improves the compacting density of the material through subsequent compacting treatment, and fixes the nano-scaled scandium oxide as a support in the pore structure of the hard carbon matrix material through subsequent carbonizing treatment, so that the hard carbon negative electrode material has excellent compacting density and electrochemical performance; and the preparation method is simple to operate and does not require a complex process, and is suitable for commercial production.

[0027] In the present application, if the binder is not added, the nano-scaled scandium oxide and the hard carbon precursor material cannot form a stable and uniform mixed system during the mixing process; and if the compacting treatment is not performed, the particles cannot be forced to move and fill into the gaps between adjacent particles, and there are gaps between the particles, which is not conducive to the improvement of the compacting density of the material; that is, the addition of the binder and the subsequent compacting treatment are cooperated to realize that the prepared hard carbon negative electrode material has high compacting density.

[0028] Preferably, the preparation method of the nano-scaled scandium oxide comprises:

[0029] Mixing and dispersing the scandium salt solution and the precipitator solution, performing a co-precipitation reaction, sintering, to obtain the nano-scaled scandium oxide.

[0030] It should be noted that the present application does not specially limit the specific method of mixing and dispersing, and any method that can realize uniform mixing of raw materials is applicable to the present application; for example, ultrasonic dispersion can be performed, and the time of ultrasonic dispersion can be 0.5-1.5 h (such as 0.5 h, 1 h or 1.5 h, etc.).

[0031] Further, the scandium salt includes but is not limited to at least one of scandium sulfate, scandium acetate, scandium chloride or scandium citrate, etc.; and the precipitator includes but is not limited to at least one of sodium oxalate, sodium carbonate, sodium hydrogen phosphate or sodium dihydrogen phosphate, etc.

[0032] The present application prepares the nano-scaled scandium oxide material, which is more conducive to the compounding with the hard carbon precursor material.

[0033] Preferably, the mixing and dispersing process further comprises a surfactant solution.

[0034] In the preparation process of nano scandium oxide, the size of the crystal nucleus gradually increases due to the continuous collision and aggregation of the scandium salt precipitate in the system in the initial nucleation stage. When the crystal nucleus reaches a certain size, its growth becomes uncontrollable. The addition of a surfactant can form an interfacial film on the surface of the solution, preventing the agglomeration of nanoparticles, so that the prepared nanoparticles have good dispersibility and uniform particle size of nano-level scandium oxide material is obtained.

[0035] Preferably, the surfactant comprises any one or a combination of at least two of glycerol, polyethylene glycol, Span or Tween.

[0036] Preferably, the molar ratio of the scandium salt, the precipitant and the surfactant is 1:(1-5):(0.5-1.5), such as 1:1:0.5, 1:1:0.8, 1:1:1, 1:1:1.3, 1:1:1.5, 1:2:0.5, 1:2:0.8, 1:2:1, 1:2:1.3, 1:2:1.5, 1:3:0.5, 1:3:0.8, 1:3:1, 1:3:1.3, 1:3:1.5, 1:4:0.5, 1:4:0.8, 1:4:1, 1:4:1.3, 1:4:1.5, 1:5:0.5, 1:5:0.8, 1:5:1, 1:5:1.3 or 1:5:1.5, etc.

[0037] Preferably, the concentration of the scandium salt solution is 0.5-3.5 mol / L, such as 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, etc.

[0038] Preferably, the concentration of the precipitant solution is 1-6 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or 6 mol / L, etc.

[0039] Preferably, the concentration of the surfactant solution is 0.1-1.5 mol / L, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L or 1.5 mol / L, etc.

[0040] Preferably, the pH value of the co-precipitation reaction is 8-10, such as 8, 8.3, 8.5, 8.8, 9, 9.3, 9.5, 9.8 or 10, etc.

[0041] In the present application, the method for adjusting the pH value during the co-precipitation reaction is not limited, and any method that can adjust the pH value without affecting the normal progress of the reaction is applicable, for example, ammonia water can be added to adjust the pH value in the system.

[0042] Preferably, the reaction solution after the co-precipitation reaction is freeze-dried.

[0043] Preferably, the freeze-drying time is 6-36h, for example, 6h, 10h, 12h, 15h, 18h, 20h, 24h, 25h, 27h, 30h, 33h, 35h or 36h, etc.

[0044] Preferably, the sintering temperature is 450-850℃, for example, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃ or 850℃, etc.

[0045] Preferably, the sintering time is 0.5-2h, for example, 0.5h, 1h, 1.5h or 2h, etc.

[0046] Preferably, the amount of nano-scanium oxide added is 0.5%-5% of the mass of the hard carbon precursor material, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc.

[0047] In the present application, the amount of nano-scanium oxide added is 0.5%-5% of the mass of the hard carbon precursor material, which can better achieve good transmission of sodium ions during charging and discharging.

[0048] Preferably, the amount of binder added is 5%-10% of the mass of the hard carbon precursor material, for example, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%, etc.

[0049] In the present application, the amount of binder added is 5%-10% of the mass of the hard carbon precursor material, which can better improve the porosity of the hard carbon material; if a large amount of binder is added, it will fill the pores of the hard carbon material, and after spray drying, the binder will solidify and occupy the space originally belonging to the pores, greatly reducing the porosity of the hard carbon material.

[0050] Preferably, the hard carbon precursor material comprises a resin.

[0051] It should be noted that in addition to the resin, the hard carbon precursor material in the application can also select biomass carbon source and coke carbon source, etc., and further preferably the resin, and the specific selection of the resin in the application is a conventional technical solution, for example, the resin includes at least one of phenolic resin, urea-formaldehyde resin, epoxy resin, melamine resin or lignin phenolic resin, etc.

[0052] Preferably, the binder includes any one or a combination of at least two of paraffin, polyvinyl alcohol, polymethyl methacrylate or polyurethane.

[0053] Preferably, the concentration of the binder solution is 1-10 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, etc.

[0054] Preferably, the mixed solution is subjected to spray drying, and then is subjected to compaction forming treatment.

[0055] In the application, by the method of spray drying, the nano scandium oxide can be uniformly dispersed in the hard carbon precursor material. In the process of droplet formation and drying, the nano scandium oxide particles can be fully mixed with the hard carbon precursor material. With rapid evaporation of the solvent, the nano scandium oxide with high conductivity is fixed in the pore structure of the hard carbon as a support, forming an inlaid conductive network structure. This structure can effectively prevent the aggregation and loss of scandium oxide particles, avoid the agglomeration problem of the hard carbon precursor material, thereby improving the rate performance of the hard carbon material. Compared with the traditional solid-phase mixing, the spray drying can also control the morphology and structure of the hard carbon material, so that the hard carbon material with regular structure and more uniform pore structure and uniform pore size is obtained. At the same time, if micron-sized scandium oxide is used in the spray drying process, the problem of uneven mixing or agglomeration of the slurry in the subsequent spray drying process will occur due to the large particle size and low surface energy of the micron-sized scandium oxide.

[0056] Preferably, the inlet air temperature of the spray drying is 120-300℃, for example, 120℃, 150℃, 175℃, 200℃, 225℃, 250℃, 275℃ or 300℃, etc.

[0057] Preferably, the outlet air temperature of the spray drying is 100-200℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃.

[0058] Preferably, the rotation speed of the atomizer of the spray drying is 10000-30000r / min, such as 10000r / min, 15000r / min, 20000r / min, 25000r / min or 30000r / min, etc.

[0059] In the present application, by adjusting the process parameters of the spray drying, such as the feeding speed, the rotation speed of the atomizer, the drying temperature, etc., the hard carbon material with more uniform pore structure can be obtained.

[0060] Preferably, the pressure applied in the compaction forming process is 5-10MPa, such as 5MPa, 6MPa, 7MPa, 8MPa, 9MPa or 10MPa, etc.

[0061] Preferably, the carbonization method comprises microwave sintering carbonization.

[0062] In the present application, by the method of microwave sintering carbonization, the hard carbon negative electrode material with more uniform grain and higher density can be obtained.

[0063] Specifically, first, the surface of the material after compaction forming is activated by inert atmosphere, then the material absorbs microwave energy by the dielectric loss in the microwave electromagnetic field, and further converts into the kinetic energy and potential energy of the particles in the material, so that the whole is heated to the sintering temperature to realize the densification of the material. Compared with the traditional atmosphere furnace sintering, the microwave sintering can make the material absorb the microwave and heat uniformly, the internal temperature gradient is small, low-temperature rapid sintering can be realized, and no additional heat source is needed, which is high efficient and energy saving.

[0064] Preferably, the carbonization temperature is 1200-1650℃, such as 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, 1600℃ or 1650℃, etc.

[0065] Preferably, the carbonization time is 10-30min, such as 10min, 15min, 20min, 25min or 30min, etc.

[0066] It can be understood that the specific atmosphere of carbonization in the present application is not different from the conventional carbonization process, and it can be carried out in a protective atmosphere, such as nitrogen atmosphere and / or inert gas atmosphere, etc.

[0067] It should be further pointed out that in the process of microwave sintering carbonization in the present application, the specific parameters of microwave sintering can be selected and adjusted by the person skilled in the art according to the difference of the microwave instruments used.

[0068] For example, the power of the microwave sintering carbonization can be 1-10 kW, such as 1 kW, 2 kW, 3 kW, 4 kW, 5 kW, 6 kW, 7 kW, 8 kW, 9 kW or 10 kW, etc.

[0069] In a third aspect, the present application further provides a battery, which comprises the hard carbon negative electrode material according to the first aspect or the hard carbon negative electrode material prepared by the preparation method according to the second aspect.

[0070] Preferably, the battery comprises a sodium ion battery.

[0071] The hard carbon negative electrode material provided by the present application has high compacted density and excellent electrochemical performance, and when used in a sodium ion battery, the initial efficiency and rate performance of the sodium ion battery are significantly improved.

[0072] However, it can be understood that the hard carbon negative electrode material in the present application can be used in a lithium ion battery in addition to a sodium ion battery, and those skilled in the art can make adaptive selection and adjustment according to actual needs.

[0073] For simplicity, only some numerical ranges are explicitly disclosed in the present application. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, although not explicitly recited, every point or individual number between the range endpoints is included in the range. Thus, each point or individual number can be combined with any other point or individual number to form a range not explicitly recited, or combined with other lower limits or upper limits to form a range not explicitly recited.

[0074] Compared with the prior art, the present application has the following beneficial effects:

[0075] (1) The hard carbon negative electrode material provided by the application has high conductivity of nano scandium oxide, which can promote selective adsorption of ester groups and carbonyl groups of sodium ion electrolyte, thereby inhibiting the occurrence of side reactions of hard carbon and electrolyte, reducing the generation of SEI film, allowing more sodium ions to participate in the reversible embedding and de-embedding process, thereby improving the initial efficiency of hard carbon; nano scandium oxide is also fixed in the pore structure of the hard carbon matrix material as a support, forming a inlaid conductive network structure, which can effectively prevent the aggregation and loss of scandium oxide particles, so that the hard carbon particles are uniformly distributed, and electrons can be quickly transmitted in the electrode material even under high rate charging and discharging; at the same time, the high specific surface area of nano scandium oxide enables it to have more contact points with hard carbon particles, generating van der Waals force, which helps to pull hard carbon particles towards each other during the pressing process, so that they are more closely bonded together, thereby improving the compaction density of the material. Furthermore, nano particles have a larger specific surface area and more surface atoms, and these surface atoms have higher chemical activity, thereby becoming potential active sites, which can chemically react with functional groups (such as carboxyl groups and hydroxyl groups) on the surface of hard carbon to form chemical bonds. The chemical bond effect can enhance the connection strength between hard carbon particles, so that they are less likely to undergo relative displacement during the compaction process, thereby being able to withstand higher pressure and achieve higher compaction density.

[0076] (2) The preparation method provided by the application uniformly mixes nano scandium oxide and hard carbon precursor material under the action of a binder, effectively improves the compaction density of the material after subsequent compaction molding treatment, and fixes nano scandium oxide as a support in the pore structure of the hard carbon matrix material after subsequent carbonization treatment, so as to have excellent compaction density and electrochemical performance; and the preparation method is simple to operate and does not require complex processing process, and is suitable for commercial production. BRIEF DESCRIPTION OF DRAWINGS

[0077] Figure 1 The SEM image of the hard carbon negative electrode material provided for Example 1 of the application. DETAILED DESCRIPTION

[0078] The technical solutions of the application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the application and should not be regarded as specific limitations on the application.

[0079] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the application; the terms "include" and "have" and any variations thereof in the application are intended to cover non-exclusive inclusion.

[0080] Embodiment 1

[0081] The embodiment provides a hard carbon negative electrode material, which comprises a resin-based hard carbon matrix material, wherein the resin-based hard carbon matrix material has a pore structure, and nano-scanium oxide is fixed in the pore structure.

[0082] The nano-scanium oxide has a median particle size of 100 nm, and the surface of the nano-scanium oxide is modified with an oxygen bridge bond; the resin-based hard carbon material has a porosity of 40%; and the hard carbon negative electrode material has a median particle size D50 of 5 μm.

[0083] The hard carbon negative electrode material is prepared by the following method:

[0084] (1) A sodium oxalate solution with a concentration of 3 mol / L is added to a scandium sulfate solution with a scandium ion concentration of 2 mol / L and is ultrasonically treated to be fully dispersed, and then a soluble surfactant glycerol solution with a concentration of 1 mol / L is rapidly added to the suspension, and a co-precipitation reaction is performed, wherein the molar ratio of scandium sulfate, sodium oxalate and glycerol is 1:2:1, and the pH value in the co-precipitation reaction process is 8.3-8.5; the reaction liquid after the co-precipitation reaction is rapidly frozen by liquid nitrogen and is placed in a freeze dryer for freeze drying for 20 h, and finally is ground, and nano-scanium oxide with a median particle size of 100 nm is obtained by sintering at 650 ℃;

[0085] (2) The nano-scanium oxide, phenolic resin and polyvinyl alcohol (with a concentration of 5 mol / L) are mixed into a slurry, the addition amount of the nano-scanium oxide is 2.5% of the mass of the phenolic resin, and the addition amount of the polyvinyl alcohol is 8% of the mass of the phenolic resin, and spray drying is performed, wherein the parameters of the spray drying are as follows: the inlet air temperature is 200 ℃, the outlet air temperature is 150 ℃, and the rotating speed of the atomizer is 20000 r / min;

[0086] The particles obtained by the spray drying are compacted and formed in a mold under a pressure of 10 MPa, and then are placed in a graphite crucible to perform microwave sintering high-temperature carbonization at 1400 ℃ under a nitrogen atmosphere for 20 min, wherein the power of the microwave is 5 kw; after cooling, the particles are crushed and sieved, and the hard carbon negative electrode material is obtained.

[0087] Figure 1 An SEM image of the hard carbon negative electrode material provided by Embodiment 1 of the application is shown.

[0088] Embodiment 2

[0089] The embodiment provides a hard carbon negative electrode material, which comprises a resin-based hard carbon matrix material, wherein the resin-based hard carbon matrix material has a pore structure, and nano-scanium oxide is fixed in the pore structure.

[0090] The median particle size of the nano-scanium oxide is 5 nm, and the nano-scanium oxide is modified with oxygen bridge bonds on the surface; the porosity of the resin-based hard carbon material is 30%; and the D50 of the hard carbon negative electrode material is 5 μm.

[0091] The preparation method of the hard carbon negative electrode material is as follows:

[0092] (1) A sodium oxalate solution with a concentration of 1 mol / L is added to a scandium sulfate solution with a scandium ion concentration of 0.5 mol / L and is ultrasonically treated to be fully dispersed, and then a soluble surfactant glycerol solution with a concentration of 0.1 mol / L is quickly added to the suspension, the molar ratio of scandium sulfate, sodium oxalate and glycerol being 1:1:0.5, and a coprecipitation reaction is performed, the pH value during the coprecipitation reaction being 8.8-9, the reaction liquid after the coprecipitation reaction is quickly frozen with liquid nitrogen and is placed in a freeze dryer for freeze drying for 6 h, and finally grinding is performed, and nano-scanium oxide with a median particle size of 5 nm is obtained by sintering at 450 ℃;

[0093] (2) The nano-scanium oxide, phenolic resin and polymethyl methacrylate (with a concentration of 1 mol / L) are mixed into a slurry, the addition amount of the nano-scanium oxide being 0.5% of the mass of the phenolic resin, and the addition amount of the polyvinyl alcohol being 5% of the mass of the phenolic resin, and spray drying is performed, the parameters of the spray drying being: the inlet air temperature 120 ℃, the outlet air temperature 100 ℃, and the rotation speed of the atomizer 10,000 r / min;

[0094] The particles obtained by the spray drying are compacted and formed in a mold at a pressure of 10 MPa, and then are placed in a graphite crucible to be subjected to microwave sintering high-temperature carbonization at 1650 ℃ under a nitrogen atmosphere for 10 min, the power of the microwave being 10 kW; after cooling, crushing and sieving are performed, and the hard carbon negative electrode material is obtained.

[0095] Example 3

[0096] The present embodiment provides a hard carbon negative electrode material, which comprises a resin-based hard carbon matrix material, the resin-based hard carbon matrix material having a pore structure, and nano-scanium oxide being fixed in the pore structure.

[0097] The median particle size of the nano-scanium oxide is 250 nm, and the nano-scanium oxide is modified with oxygen bridge bonds on the surface; the porosity of the resin-based hard carbon material is 50%; and the D50 of the hard carbon negative electrode material is 10 μm.

[0098] The preparation method of the hard carbon negative electrode material is as follows:

[0099] (1) adding a precipitant sodium oxalate solution with a concentration of 3 mol / L into a scandium sulfate solution with a scandium ion concentration of 2 mol / L and ultrasonic treatment to make it fully dispersed, then rapidly adding a soluble surfactant glycerol solution with a concentration of 1 mol / L into the above suspension, the molar ratio of scandium sulfate, sodium oxalate and glycerol being 1:5:1.5, carrying out a co-precipitation reaction, the pH value during the co-precipitation reaction being 9.5-9.8, rapidly freezing the reaction liquid after the co-precipitation reaction by pouring liquid nitrogen and placing it in a freeze dryer for freeze drying for 35 h, and finally grinding to obtain nanometer scandium oxide with a median particle size of 250 nm, which is sintered at 850 ℃;

[0100] (2) mixing nanometer scandium oxide, phenolic resin and polymethyl methacrylate (concentration of 5 mol / L) into a slurry, the addition amount of nanometer scandium oxide being 5% of the mass of the phenolic resin, and the addition amount of polyvinyl alcohol being 10% of the mass of the phenolic resin, carrying out spray drying, the parameters of the spray drying being: inlet air temperature 300 ℃, outlet air temperature 200 ℃, and the rotation speed of the atomizer 30000 r / min;

[0101] compacting and forming the particles obtained by the spray drying into a mold at a pressure of 5 MPa, then placing it in a graphite crucible to carry out microwave sintering high-temperature carbonization at 1200 ℃ under a nitrogen atmosphere for 30 min, the power of the microwave being 10 kw, crushing and sieving after cooling to obtain the hard carbon negative electrode material.

[0102] Example 4

[0103] The difference between this example and Example 1 is that the hard carbon precursor material in this example is coconut shell.

[0104] The rest of the preparation methods and parameters remain the same as those in Example 1.

[0105] Example 5

[0106] The difference between this example and Example 1 is that the D50 of the nanometer scandium oxide in this example is 300 nm.

[0107] In the preparation method, the molar ratio of the scandium salt, the precipitant and the surfactant is 1:5:0.5.

[0108] The rest of the preparation methods and parameters remain the same as those in Example 1.

[0109] Example 6

[0110] The difference between this example and Example 1 is that the addition amount of nanometer scandium oxide in this example is 0.1% of the mass of the phenolic resin.

[0111] The rest of the preparation methods and parameters remain the same as those in Example 1.

[0112] Example 7

[0113] The difference between this example and Example 1 is that the amount of nano- scandium oxide added in this example is 6% of the mass of the phenolic resin.

[0114] The rest of the preparation method and parameters are consistent with Example 1.

[0115] Example 8

[0116] The difference between this example and Example 1 is that the amount of polyvinyl alcohol added in this example is 3% of the mass of the phenolic resin.

[0117] The rest of the preparation method and parameters are consistent with Example 1.

[0118] Example 9

[0119] The difference between this example and Example 1 is that the amount of polyvinyl alcohol added in this example is 12% of the mass of the phenolic resin.

[0120] The rest of the preparation method and parameters are consistent with Example 1.

[0121] Example 10

[0122] The difference between this example and Example 1 is that the slurry after mixing in step (2) is not spray dried, but is directly placed in a drying oven for drying treatment.

[0123] The rest of the preparation method and parameters are consistent with Example 1.

[0124] Comparative Example 1

[0125] The difference between this example and Example 1 is that the hard carbon negative electrode material provided in this example does not contain nano-scandium oxide.

[0126] In the preparation method, step (1) is not performed.

[0127] The rest of the preparation method and parameters are consistent with Example 1.

[0128] Comparative Example 2

[0129] The difference between this example and Example 1 is that the scandium oxide in this example is a commercially available product, and the median particle size is 1.3 μm.

[0130] In the preparation method, the nano-sized scandium oxide is directly replaced by micron-sized scandium oxide.

[0131] The rest of the preparation method and parameters are consistent with Example 1.

[0132] Comparative Example 3

[0133] The difference between the present comparative example and Example 1 is that the preparation method of the present comparative example does not contain a binder polyvinyl alcohol.

[0134] The remaining preparation method and parameters remain the same as those of Example 1.

[0135] Comparative Example 4

[0136] The difference between the present comparative example and Example 1 is that the present comparative example performs carbonization treatment between the particles after spray drying, and does not perform the process of compaction molding.

[0137] The remaining preparation method and parameters remain the same as those of Example 1.

[0138] The hard carbon negative electrode materials provided by Examples 1-10 and Comparative Examples 1-4 were tested for compaction density, with the test conditions being that a compaction powder resistance meter was used to detect the compaction density of the hard carbon negative electrode materials, the test range being 50-200 Mpa, and the test using material mass being 0.5 g. The test results are shown in Table 1.

[0139] Table 1

[0140]

[0141]

[0142] [Preparation and performance testing of sodium-ion batteries]

[0143] Sodium-ion battery preparation:

[0144] The hard carbon negative electrode materials, conductive agent Super P and polyvinylidene fluoride provided by the examples and comparative examples were respectively adjusted into a slurry in a ratio of 8:1:1 using N-methyl pyrrolidone (NMP), stirred for 24 h, coated on a carbon-coated copper foil, dried in an 80°C oven for 24 h, and the dried electrode sheet was cut into 12 mm round pieces with a loading of 1.24 mg / cm 2 .

[0145] A sodium foil was used as the counter electrode, glass fiber (GF / A) was used as the separator, and 1 mol / L NaFP6 was dissolved in a mixed solvent of EC and DMC as the electrolyte, with the volume ratio of EC to EMC being 1:1.

[0146] The hard carbon negative electrode, the separator and the sodium foil were stacked, and the electrolyte was injected to assemble a 2032 type button cell in a glove box.

[0147] Performance testing:

[0148] (a) the first efficiency: using the blue electric test cabinet to test at 25 DEG C, the current density is 30 mA / g, the nominal specific capacity is set to 300 mAh / g, the charging cut-off voltage is 2.0 V, the discharging cut-off voltage is 0 V, and the first coulombic efficiency (the first efficiency) can be calculated by the ratio of the first charge specific capacity to the first discharge specific capacity. The specific formula is: the first efficiency = the first charge specific capacity / the first discharge specific capacity*100%.

[0149] (b) the rate performance: the rate charging and discharging method adopted is to perform charging and discharging successively at 5 different current densities, which are 30 mA / g, 60 mA / g, 100 mA / g, 300 mA / g and 600 mA / g respectively, each current density is performed for 5 cycles of charging and discharging, and after the end, the current density is returned to 30 mA / g to perform long cycle charging and discharging, the capacity of the test battery in the large rate charging and discharging test is tested, and the capacity at 600 mA / g is taken as the test result.

[0150] The test results of the above tests are shown in Table 2.

[0151] Table 2

[0152]

[0153]

[0154] In summary, in the present application, the nano scandium oxide is fixed in the pore structure of the hard carbon matrix material as a support, which on the one hand improves the compaction density of the hard carbon negative electrode material, and on the other hand forms an inlaid type conductive network structure, and improves the electrochemical performance of the hard carbon negative electrode material.

[0155] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by any person skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A hard carbon negative electrode material, characterized in that, The hard carbon negative electrode material comprises a hard carbon base material having a pore structure in which nano scandium oxide is fixed; The nano scandium oxide has a median particle size D50 of 5-250 nm; The hard carbon negative electrode material is prepared by a preparation method comprising the following steps: The nano scandium oxide, a hard carbon precursor material and a binder solution are mixed, the mixed solution is spray dried, and then compacted and formed, and carbonized to obtain the hard carbon negative electrode material; The nano scandium oxide is added in an amount of 0.5%-5% of the mass of the hard carbon precursor material; the binder is added in an amount of 5%-10% of the mass of the hard carbon precursor material; and the binder comprises any one or a combination of at least two of paraffin, polyvinyl alcohol, polymethyl methacrylate or polyurethane. 2.The hard carbon negative electrode material of claim 1, characterized in that, The nano scandium oxide is surface modified with an oxygen bridge. 3.The hard carbon negative electrode material of claim 1, characterized in that, The hard carbon base material comprises a resin-based hard carbon base material. 4.The hard carbon negative electrode material of claim 1, characterized in that, The hard carbon base material has a porosity of 20%-55%. 5.The hard carbon negative electrode material of claim 1, wherein, The hard carbon negative electrode material has a median particle size D50 of 5-10 μm.

6. A method for preparing the hard carbon negative electrode material according to any one of claims 1-5, characterized in that, The preparation method comprises the following steps: The nano scandium oxide, a hard carbon precursor material and a binder solution are mixed, the mixed solution is spray dried, and then compacted and formed, and carbonized to obtain the hard carbon negative electrode material; The nano scandium oxide is added in an amount of 0.5%-5% of the mass of the hard carbon precursor material; the binder is added in an amount of 5%-10% of the mass of the hard carbon precursor material; and the binder comprises any one or a combination of at least two of paraffin, polyvinyl alcohol, polymethyl methacrylate or polyurethane.

7. The preparation method according to claim 6, characterized in that, The preparation method of the nano scandium oxide comprises: The scandium salt solution and the precipitant solution are mixed and co-precipitated, and then sintered to obtain the nano scandium oxide.

8. The preparation method according to claim 7, characterized in that, The mixing and dispersing process further comprises a surfactant solution.

9. The production method according to claim 8, characterized by, The surfactant comprises any one or a combination of at least two of glycerol, polyethylene glycol, Span or Tween.

10. The preparation method according to claim 8, characterized in that, The molar ratio of the scandium salt, the precipitant and the surfactant is 1:(1-5):(0.5-1.5).

11. The preparation method according to claim 7, characterized in that, The concentration of the scandium salt solution is 0.5-3.5 mol / L.

12. The method of claim 7, wherein, The concentration of the precipitant solution is 1-6 mol / L.

13. The preparation method according to claim 8, characterized in that, The concentration of the surfactant solution is 0.1-1.5 mol / L.

14. The method of claim 7, wherein, The pH value of the co-precipitation reaction is 8-10.

15. The method of claim 7, wherein the method further comprises, The reaction liquid after the co-precipitation reaction is freeze-dried.

16. The method of claim 15, wherein, The freeze-drying time is 6-36 h.

17. The method of claim 7, wherein the method further comprises, The sintering temperature is 450-850 ℃, and the sintering time is 0.5-2 h.

18. The method of claim 6, wherein, The hard carbon precursor material comprises a resin.

19. The method of claim 6, wherein, The concentration of the binder solution is 1-10 mol / L.

20. The method of claim 6, wherein, The spray drying inlet temperature is 120-300 ℃, the spray drying outlet temperature is 100-200 ℃, and the spray drying atomizer rotation speed is 10,000-30,000 r / min.

21. The method of claim 6, wherein, The carbonization method comprises microwave sintering carbonization.

22. The method of claim 6, wherein, The carbonization temperature is 1,200-1,650 ℃, and the carbonization time is 10-30 min.

23. A battery, characterized by The battery comprises the hard carbon negative electrode material according to any one of claims 1-5 or the hard carbon negative electrode material prepared by the preparation method according to any one of claims 6-22.

24. The battery of claim 23, wherein, The battery comprises a sodium ion battery.

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