Wood / Bamboo-derived Carbon Self-Supported 3D Anode Material and Its Preparation Method and Application

Abstract

The present invention discloses a wood / bamboo-derived carbon self-supporting 3D anode material, its preparation method and application. The preparation method includes: obtaining a wood / bamboo original sheet with a smooth cross-section of wood / bamboo, pre-treating the wood / bamboo original sheet and then placing it in an inert atmosphere for high-temperature carbonization treatment. The obtained high-temperature carbonized wood / bamboo sheet is subjected to quality control and flatness adjustment of its cross-section with fine sandpaper to obtain a wood / bamboo-derived carbon self-supporting 3D anode material with appropriate quality. This material is applied in lithium-sodium secondary batteries. The battery preparation operation process is simple, and it has both high sodium storage capacity and initial Coulombic efficiency. The material of the present invention utilizes the abundant wood or bamboo resources in nature, has a wide range of raw material sources, and by the innovative means of directly using the whole carbonized wood block or bamboo block as the battery anode sheet, it avoids the influence of conductive agents, binders, etc., improves the loading amount of active substances and the energy density of the battery, and can be widely applied in the field of secondary batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy and biomass materials, and particularly relates to a wood / bamboo-derived carbon self-supporting 3D anode material, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid consumption of fossil energy and the increasingly prominent environmental pollution problems, secondary battery technology has developed rapidly and has become an important direction for the development of energy science and technology. Lithium and sodium ion batteries in secondary batteries have become the mainstream of current applications, and the anode materials in secondary batteries are mainly carbon materials. Biomass-derived carbon materials have received increasing attention due to their superior resources. The traditional preparation process of carbon anodes for secondary batteries usually involves uniformly mixing active materials, conductive agents, and binders in a certain proportion, and then coating them on a current collector. This traditional anode preparation process is time-consuming, complex in process, and may even bring uncontrollable factors to the instability of battery performance. In particular, the additional adhesives, conductive agents, etc. will limit the loading amount of active materials and the energy density of the battery. Therefore, it is particularly important to avoid the negative effects of additives such as adhesives and conductive agents on the anode material. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art. In particular, aiming at the technical defects such as the non-renewability of mineral carbon, and the powder carbon needs to be mixed with a conductive agent and a binder and then coated on a current collector to be used as an anode sheet, with complex process and long anode preparation time, etc., the present invention provides a wood / bamboo-derived carbon self-supporting 3D anode material with high capacity, excellent rate performance, and can be directly used as an anode sheet, a preparation method thereof, and an application thereof.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions.

[0005] A preparation method of a wood / bamboo-derived carbon self-supporting 3D anode material, comprising the following steps:

[0006] S1. Process natural wood or bamboo into a wood / bamboo original sheet with uniform thickness, the two cross-sections of the wood / bamboo original sheet are smooth, and the cell fractures of the two cross-sections are flat without cutting and tearing; (The original sheet refers to a thin sheet)

[0007] S2. Pretreat the wood / bamboo original sheet obtained in step S1 to clean the internal channels of the wood / bamboo to obtain a pretreated 3D wood / bamboo self-supporting precursor;

[0008] S3. Heat the 3D wood / bamboo self-supporting precursor obtained in step S2 to 1000 - 1600 °C under a protective gas atmosphere for pyrolytic carbonization treatment to obtain carbonized wood / bamboo slices. Take out and polish the cross-section of the carbonized wood / bamboo slices to control the weight and cross-section flatness of the carbonized wood / bamboo slices, and then wash and dry them to obtain the wood / bamboo-derived carbon self-supporting 3D anode material.

[0009] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S3, the mass of the wood / bamboo-derived carbon self-supporting 3D anode material ≤ 5 mg.

[0010] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S1, the cross-sectional size of the original material slice is 1 cm - 3 cm × 1 cm - 3 cm, and the thickness size is 0.1 cm - 0.5 cm.

[0011] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S3, the mass of the wood / bamboo-derived carbon self-supporting 3D anode material is 1 mg - 5 mg.

[0012] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S3, the heating rate of the pyrolytic carbonization treatment is 2 °C / min - 20 °C / min, and the heat preservation time of the pyrolytic carbonization treatment is 1 h - 5 h.

[0013] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S2, the pretreatment is to immerse the original wood / bamboo slice in a H2SO4 solution with a concentration of 6 mol / L - 12 mol / L for 2 h - 48 h, then take it out and wash, filter by suction, and dry.

[0014] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S2, the ratio of the mass (m) of the immersed original material slice to the volume (V) of the H2SO4 solution m / V ≤ 1∶8.

[0015] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S2, the immersion includes one or several of atmospheric pressure immersion, vacuum immersion, and pressure immersion, and the immersion temperature is 20 °C - 80 °C.

[0016] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S2, the drying temperature is 40 °C - 60 °C, the drying time is 24 h - 48 h, and during the drying process, observe and discard the warped and deformed wood / bamboo slices.

[0017] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S3, the grinding is carried out using sandpaper, the grit size of the sandpaper is above 600 mesh, and the sanding surface is the cross-section of the carbonized wood / bamboo slices.

[0018] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S3, the cleaning is carried out by ultrasonic cleaning, the washing solution is a methanol solution and / or an ethanol solution with a volume concentration of 40% to 100%, and the ultrasonic cleaning time is 2 s to 120 s.

[0019] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S3, the drying temperature is 40°C to 100°C, and the drying time is 1 h to 24 h.

[0020] For the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material, preferably, in step S1, the cross-section leveling and size error adjustment of the wood / bamboo original slices are carried out using a sliding microtome.

[0021] As a general technical concept, the present invention also provides a wood / bamboo-derived carbon self-supporting 3D anode material prepared by the above preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material.

[0022] As a general technical concept, the present invention also provides the application of the above wood / bamboo-derived carbon self-supporting 3D anode material in secondary batteries, and the secondary battery is a lithium-ion battery or a sodium-ion battery.

[0023] For the above application, preferably, the sodium-ion battery uses the wood / bamboo-derived carbon self-supporting 3D anode material as the negative electrode sheet, does not require a binder or a conductive agent, uses a metal sodium sheet as the counter electrode, uses a solution of NaPF6 dissolved in diglyme as the electrolyte, and uses a glass microfiber filter membrane as the separator.

[0024] Wood / bamboo, as an easily accessible natural renewable resource, has a unique pore structure. After being processed in the present invention, its pores are retained and its mechanical properties are stabilized, and it is prepared into a self-supporting negative electrode, which does not require additional binders, conductive agents, and current collectors and can be directly used as an electrode; the wood / bamboo-derived carbon self-supporting 3D negative electrode has a higher specific capacity and energy density. Using natural plant biomass materials to prepare self-supporting electrodes, the raw material sources are wide, the resources are renewable, and the wood / bamboo-derived carbon self-supporting 3D negative electrode has the characteristics of being green, environmentally friendly, renewable, and having high performance at the same time.

[0025] Compared with the prior art, the advantages of the present invention are as follows:

[0026] (1) The preparation method of the present invention makes full use of the natural multi-level void structure of wood / bamboo materials, and uses renewable, green and environmentally friendly wood / bamboo materials as substrate precursors for high-temperature pyrolysis and carbonization treatment. The obtained carbonized wood / bamboo materials have good mechanical properties and interconnected pores with low curvature, which can meet the mechanical property requirements of negative electrode materials during battery assembly. The pore channels can ensure the efficient passage of lithium and sodium ions and shorten the transmission length of metal ions. It has a larger discharge specific capacity and excellent rate performance than general hard carbon negative electrode materials, and has great potential in the research and application fields of electrochemistry and energy materials. More importantly, the present invention solves the problems of many raw materials and complex processes in the traditional carbon negative electrode material pulping method. Specifically, by strictly controlling the flatness and smoothness of the cross section of the wood / bamboo slice, the wood / bamboo material is carbonized as a whole to obtain a wood / bamboo derived carbon self-supporting 3D negative electrode material of a specific mass (such as the mass used in sodium ion button batteries is usually ≤5mg). No additional binder, conductive agent and current collector are required, and it can be directly used as a negative electrode sheet to assemble energy storage batteries. It completely avoids the adverse effects of additives such as adhesives and conductive agents, greatly simplifies the overall process of making energy storage batteries, and increases the loading amount of active substances. The widely abundant and easily renewable raw materials avoid the use of a large amount of hazardous chemicals or fossil raw materials. The overall preparation process of the present invention is simple and efficient, green and environmentally friendly, and is very suitable for industrialization and large-scale promotion.

[0027] (2) The wood / bamboo derived carbon self-supporting 3D negative electrode material of the present invention is prepared by subjecting a wood / bamboo original sheet with a smooth cross section to high temperature carbonization under a protective atmosphere, and then polishing the wood / bamboo derived carbon sheet to control the weight and cross-sectional flatness, thereby obtaining the wood / bamboo derived carbon self-supporting 3D negative electrode material. The negative electrode material uses easily renewable, green, widely available, and inexpensive wood or bamboo as raw materials, and has a simple preparation process, eliminating many processes for current mineral carbon negative electrode assembly, and also saving raw material costs. The negative electrode material has good mechanical properties, high capacity, and excellent rate performance, and can be used for lithium and sodium secondary batteries. The present invention can give easily renewable and inexpensive wood / bamboo materials new functions and high value, and can provide a new solution for the preparation of self-supporting negative electrode materials for secondary batteries.

[0028] (3) The application of the wood / bamboo derived carbon self-supporting 3D negative electrode material in the secondary battery of the present invention, using the wood / bamboo derived carbon self-supporting 3D negative electrode material directly as the negative electrode sheet to assemble the energy storage battery, can completely avoid the adverse effects of additives such as adhesives and conductive agents, and also greatly simplify the overall process of making energy storage batteries, save raw material costs, and increase the loading amount of active substances. The process steps of this application are simple, efficient, and environmentally friendly, and are suitable for industrial promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1Process flow diagram of the preparation method and application method of the wood / bamboo-derived carbon self-supporting 3D anode material of the present invention.

[0030] Figure 2 Digital photos of basswood, rosewood, poplar, ekki and Chinese fir wood (corresponding to Figures a - e in sequence) and bamboo (f) before and after pretreatment in Examples 1 and 2 of the present invention.

[0031] Figure 3 SEM images of the cross-sections of the wood / bamboo original slices before and after pretreatment in Examples 1 and 2 of the present invention. Among them, the SEM images of basswood before and after pretreatment are shown in Figures a and b, rosewood in Figures c and d, Chinese fir in Figures e and f, poplar in Figures i and j, ekki in Figures k and l, and bamboo in Figures g and h. The magnification of all the pictures is ×100.

[0032] Figure 4 XRD patterns of the wood / bamboo-derived carbon self-supporting 3D anode materials in Examples 1 and 2 of the present invention. Among them, the wood-derived carbon self-supporting 3D anode materials in Example 1 are abbreviated as carbonized basswood, carbonized rosewood, carbonized Chinese fir, carbonized poplar, and carbonized ekki respectively, and the bamboo-derived carbon self-supporting 3D anode material in Example 2 is abbreviated as carbonized bamboo.

[0033] Figure 5 TEM images of the wood / bamboo-derived carbon self-supporting 3D anode materials in Examples 1 and 2 of the present invention. Basswood, rosewood, poplar, ekki, Chinese fir and bamboo correspond to Figures a - f in sequence.

[0034] Figure 6 First charge-discharge curves of the wood / bamboo-derived carbon self-supporting 3D anode materials in Examples 1 and 2 of the present invention at a current density of 30 mA / g.

[0035] Figure 7 Rate performance graphs of the wood / bamboo-derived carbon self-supporting 3D anode materials in Examples 1 and 2 of the present invention.

[0036] Figure 8 SEM images of the cross-sections of the wood / bamboo-derived carbon anode materials of Comparative Example 1. Basswood, rosewood, poplar, ekki, Chinese fir and bamboo correspond to Figures a - f in sequence.

[0037] Figure 9 First charge-discharge curve of the basswood-derived carbon anode material of Comparative Example 1 at a current density of 30 mA / g.

[0038] Figure 10 First charge-discharge curves of the wood / bamboo-derived carbon anode materials of Comparative Example 2 at a current density of 30 mA / g. Basswood, rosewood, poplar, ekki, Chinese fir and bamboo correspond to Figures a - f in sequence. Detailed implementation manners

[0039] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. In the following embodiments, unless otherwise specified, the raw materials and instruments used are commercially available, and the obtained data are the averages of more than three repeated experiments.

[0040] A method for preparing a wood / bamboo-derived carbon self-supporting 3D negative electrode material of the present invention includes the following steps:

[0041] S1. Select wood / bamboo without any defects, and process it into a raw sheet with a uniform thickness using equipment with a sharp blade. The cross-sectional size is 1 cm to 3 cm × 1 cm to 3 cm, and the thickness size is 0.1 cm to 0.5 cm. The cross-section of the raw sheet must be smooth, and the cross-sectional cell fracture of the wood / bamboo observed under a microscope is flat without cutting and tearing; the cross-section of the wood / bamboo raw sheet can be trimmed and the dimensional error adjusted on a sliding microtome.

[0042] S2. Immerse the wood / bamboo raw sheet in a concentrated H2SO4 solution (pressure impregnation, vacuum impregnation, pressure impregnation). The concentration of the H2SO4 solution is 6 mol / L to 12 mol / L, the temperature during impregnation is 20°C to 80°C, and the impregnation time is 2 h to 48 h. The ratio of the mass (m) of the wood / bamboo during impregnation to the volume (V) of the H2SO4 solution is m / V ≤ 1:8; after impregnation, wash, filter by suction, and dry with distilled water. The drying temperature is 40°C to 60°C, and the drying time is 24 h to 48 h. During the drying process, pay attention to observing that the pre-treated raw sheet of wood / bamboo does not warp or deform, and discard the pre-treated raw sheet of wood / bamboo with serious deformation.

[0043] S3. Perform high-temperature carbonization of the pre-treated wood / bamboo sheet at 1000°C to 1600°C under the protection of an inert gas. The heating rate of the carbonization temperature is 2°C / min to 20°C / min, and the holding time is 1 h to 5 h; take out the carbonized wood / bamboo sheet, and polish the cross-section with fine sandpaper with a particle size of more than 600 mesh to control the weight and cross-sectional flatness of the carbonized wood / bamboo sheet; then clean it in an ultrasonic cleaner filled with methanol or ethanol solution. The volume concentration of the methanol or ethanol solution is 40% to 100%, and the ultrasonic time is 2 s to 120 s. After ultrasonic cleaning, take it out and dry. The drying temperature of the carbonized wood sheet is 40°C to 100°C, and the drying time is 1 h to 24 h; thus, a wood / bamboo-derived carbon self-supporting 3D negative electrode material with a mass of 1 mg to 5 mg is obtained.

[0044] Example 1:

[0045] As Figure 1 shown, a method for preparing a wood-derived carbon self-supporting 3D negative electrode material includes the following steps:

[0046] S1. Cut natural wood such as basswood, rosewood, poplar, azobe, and fir without any defects into wood chips with a thickness of about 0.3 cm and uniform along the growth direction using equipment with a sharp blade. Observe the cell fractures of the two cross-sections of the wood chips under a microscope, and ensure that the fractures are flat without cutting or tearing. Then cut the wood chips into small blocks with a length and width of 1.5 cm. The cross-section of the small blocks must be smooth. Put 10 g of the cut blocks into an 80 °C water bath and soak for 4 days for softening. Use a sliding microtome to flatten the cross-section of the wood chips and adjust the dimensional error to obtain the original wood slices.

[0047] S2. Immerse the original wood slices in 60 mL of 6 mol / L H2SO4 solution at normal temperature and pressure for 8 h. Wash with distilled water and filter by suction. Slowly dry at 40 °C for 36 h to obtain the pretreated 3D wood self-supporting precursor.

[0048] S3. Heat the 3D wood self-supporting precursor obtained in step S2 to 1300 °C at a rate of 5 °C / min under argon protection and hold for 2 h for pyrolytic carbonization to obtain carbonized wood chips. Polish the cross-section of the carbonized wood chips with 1000-mesh fine sandpaper, and stop polishing in time when the mass reaches 2 mg. Immerse the polished carbonized wood chips in ethanol with a volume concentration of 100% and ultrasonicate at 100 W for 10 s. Then dry in an oven at 60 °C for 12 h to obtain the wood-derived carbon self-supporting 3D anode material.

[0049] Digital photos of the original basswood, rosewood, poplar, azobe, and fir wood slices prepared in this example after pretreatment are shown in Figure 2 (a - e). It can be seen that after sulfuric acid treatment, the wood surface turns black significantly, indicating an oxidation reaction has occurred.

[0050] Scanning electron microscope images (SEM) of the original wood slices prepared in this example before and after sulfuric acid treatment are shown in Figure 3 . Among them, a - b are basswood (Bass-SHC), c - d are rosewood (Rose-SHC), e - f are fir (Fir-SHC), i - j are poplar (Pop-SHC), and k - l are azobe (Azo-SHC). The wood itself has a natural porous structure. In addition, after sulfuric acid treatment, the wood channels become more unobstructed. This microscopic morphology is beneficial for the storage of lithium or sodium ions, and it is conducive to improving the charge-discharge capacity and rate performance of lithium or sodium ion batteries when applied to them in the future.

[0051] XRD patterns of the 5 wood-derived carbon self-supporting 3D anode materials prepared in this example are shown in Figure 4 , and TEM images are shown in Figure 5 as a - e in it, indicating that the 5 wood-derived carbon self-supporting 3D anode materials are all amorphous structures.

[0052] Application of a wood-derived carbon self-supporting 3D anode material prepared in this embodiment. The specific application process includes the following steps:

[0053] Take 2 mg of self-supporting 3D anode materials of Tilia wood, Rosewood, Poplar, ekki wood, and Chinese fir prepared in this embodiment as the negative electrode sheets respectively. Then, use a sodium metal sheet (which can be rolled and cut by oneself) as the counter electrode, and use a solution of solute NaPF6 dissolved in DIGLYME (diethylene glycol dimethyl ether) as the electrolyte. In the electrolyte, the concentration of NaPF6 is 1 mol / L. Use Whatman GF / C glass microfiber filter membrane as the separator to assemble a button battery.

[0054] It is measured that when the charge-discharge current of the self-supporting 3D anode material of Tilia wood in this embodiment is 30 mA / g, the initial discharge specific capacity is up to 383.1 mAh / g at most, and the initial Coulomb efficiency is 92.4%. The initial charge-discharge curve is as Figure 6 , it can be seen that the voltage hysteresis effect between the charge curve and the discharge curve is small, as Figure 7 shown, and the rate performance is excellent, which can meet the requirements of sodium-ion batteries for high energy density. The specific data is shown in Table 1.

[0055] Example 2:

[0056] A preparation method of a bamboo-derived carbon self-supporting 3D anode material, including the following steps:

[0057] S1. Cut the natural bamboo along the growth direction into bamboo slices with a thickness of about 0.3 cm and uniform thickness using equipment with a sharp blade. Observe the cell fractures of the two cross-sections of the bamboo slices under a microscope to be flat without cutting and tearing. Then cut them into small bamboo blocks with a length and width of 1.5 cm each. Put 10 g of the cut bamboo blocks into an 80 °C water bath for 4 days to soften them. Use a sliding microtome to level the cross-section of the bamboo slices and adjust the dimensional error to obtain the original bamboo slices.

[0058] S2. Put the original bamboo slices into 60 mL of H2SO4 solution with a concentration of 6 mol / L at normal temperature and pressure for impregnation for 8 h. Wash with distilled water and filter by suction, and slowly dry at 40 °C for 3 days to obtain a pretreated 3D bamboo self-supporting precursor.

[0059] S3. Heat-treat and carbonize the 3D bamboo self-supporting precursor obtained in step S2 under argon protection by heating to 1300 °C at a rate of 5 °C / min and holding for 2 h to obtain carbonized bamboo slices. Polish the cross-section of the carbonized bamboo with 1000-mesh fine sandpaper, and stop polishing in time when the weight reaches 2 mg. Place the polished carbonized bamboo slices in ethanol with a volume concentration of 100% and ultrasonicate them at 100 W for 10 s, and then dry them in an oven at 60 °C for 12 h to obtain the bamboo-derived carbon self-supporting 3D anode material.

[0060] In fact, the difference between this embodiment and Embodiment 1 is only that the raw material is natural bamboo, and the preparation method of the corresponding bamboo-derived carbon self-supporting 3D anode material is the same as that of Embodiment 1.

[0061] Photos before and after pretreatment of the bamboo slices in this embodiment are shown in Figure 2 (f), and the scanning electron microscope images are shown in Figure 3 (g - h). The XRD pattern of the bamboo-derived carbon self-supporting 3D anode material is shown in Figure 4 , and the TEM images are shown in Figure 5 .

[0062] Take the bamboo-derived carbon self-supporting 3D anode material prepared in this embodiment and assemble it into a button battery according to the application method in Embodiment 1. It is measured that the first discharge specific capacity of the bamboo-derived carbon self-supporting 3D anode material prepared in this embodiment is 364.9 mAh / g under the condition of a charge-discharge current of 30 mA / g, and the first Coulombic efficiency is 87.5%. The first charge-discharge curve is as shown in Figure 6 , and the specific data is shown in Table 1. It can be seen that the voltage hysteresis effect between the charge curve and the discharge curve is small, and the rate performance is as shown in Figure 7 , which can meet the requirements of sodium-ion batteries for high energy density.

[0063] Table 1 - First charge / discharge capacity and corresponding XRD layer spacing of wood / bamboo-derived carbon self-supporting 3D anode materials in Embodiments 1 and 2 at a current density of 30 mA / g

[0064]

[0065] Table 1 is a table showing the first charge / discharge capacity and corresponding XRD layer spacing of wood / bamboo-derived carbon self-supporting 3D anode materials in Embodiments 1 and 2 of the present invention at a current density of 30 mA / g. The layer spacing of the derived carbon self-supporting 3D anode materials of different woods is different, which will then affect the performance of the assembled battery. The first Coulombic efficiency of basswood is the largest. It can be seen from Table 1 that the electrical properties of the anode materials prepared from 5 kinds of woods including basswood, rosewood, poplar, ekki, and Chinese fir in Embodiment 1 and bamboo in Embodiment 2 are different due to the different material types. The first discharge specific capacity and charge specific capacity are both above 300 mA h / g under the condition of a charge-discharge current of 30 mA / g, with the highest reaching 439.4 A h / g. The first Coulombic efficiency is generally above 86%, with the highest reaching 92.4%.

[0066] Comparative Example 1:

[0067] A preparation method of a wood / bamboo-derived carbon negative electrode material is basically the same as that of Examples 1 and 2, except that in step S1, the cutting of the original wood slices of basswood, rosewood, poplar, ekki, fir and the original bamboo slices is not flat enough. When observing the cell fractures of the two cross-sections of the wood slices and bamboo slices under a microscope, the fractures are uneven, and there are occasional cutting tears.

[0068] The scanning electron microscope (SEM) images of the basswood, rosewood, poplar, ekki, fir wood, and bamboo-derived carbon negative electrode materials prepared in this comparative example are as Figure 8 (a - f) shown. It can be seen from the figure that there are cutting tears.

[0069] Referring to the application method in Example 1, the basswood-derived carbon negative electrode material prepared in this comparative example was assembled into a button battery. It was measured that the battery capacity of the basswood-derived carbon negative electrode material prepared in this comparative example was relatively low under the condition of a charge-discharge current of 30 mA / g, and the capacity decay was also very obvious, as Figure 9 shown in the test results of three groups of tests of the basswood-derived carbon negative electrode material prepared in this comparative example. By comparing the electrical properties of the negative electrode materials in Comparative Example 1 with those in Examples 1 and 2, it can be seen that the flatness of the wood surface is crucial for the electrical properties of the negative electrode material. The battery capacity of the derived carbon negative electrode material prepared from basswood with an unsmoothed surface is much lower than that of the derived carbon negative electrode material prepared from smoothed and polished basswood under the same conditions.

[0070] Comparative Example 2:

[0071] A preparation method of a wood / bamboo-derived carbon negative electrode material is basically the same as that of Examples 1 and 2, except that in step S3, the carbonized wood slices and carbonized bamboo slices are not polished and weight-reduced. The mass of the obtained derived carbon negative electrode material > 5 mg. When carbonizing a wooden block with a length, width and height of 1.5 cm × 1.5 cm × 2 mm without polishing and weight-reducing, the corresponding thickness will > 1 mm.

[0072] Referring to the application method in Example 1, the basswood, rosewood, poplar, ekki, fir wood-derived carbon negative electrode materials and bamboo-derived carbon negative electrode materials prepared in this comparative example were respectively assembled into button batteries. It was measured that the short-circuit phenomenon of each derived carbon negative electrode material prepared in this comparative example was very obvious under the condition of a charge-discharge current of 30 mA / g and could not be used normally as a battery negative electrode sheet, as Figure 10As shown. By comparing the electrical properties of the negative electrode materials in Comparative Example 2 with those in Examples 1 and 2, it can be seen that the quality of the negative electrode material has a great influence on its electrical properties and needs to be controlled within an appropriate mass. For example, when used in sodium-ion button batteries, the mass is usually ≤ 5 mg, and the thickness of the negative electrode material will vary depending on the type of wood and the wood density. The above are only preferred embodiments of the present invention and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent changes, without departing from the spirit and technical solution of the present invention. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of a wood / bamboo-derived carbon self-supporting 3D anode material, characterized in that, It includes the following steps: S1. Process natural wood or bamboo into wood / bamboo original sheets with uniform thickness. The two cross-sections of the wood / bamboo original sheets are smooth, and the cell fractures of the two cross-sections are flat without cutting and tearing. S2. Pretreat the wood / bamboo original sheets obtained in step S1 to clean the internal channels of the wood / bamboo, and obtain a pretreated 3D wood / bamboo self-supporting precursor. The pretreatment is to immerse the wood / bamboo original sheets in an H2SO4 solution with a concentration of 6 mol / L to 12 mol / L for 2 h to 48 h, then take them out, wash, filter by suction, and dry. S3. Heat the 3D wood / bamboo self-supporting precursor obtained in step S2 to 1000 °C to 1600 °C in a protective gas atmosphere for pyrolytic carbonization treatment to obtain carbonized wood / bamboo sheets. Take out and polish the cross-section of the carbonized wood / bamboo sheets to reduce the weight, then wash and dry to obtain a wood / bamboo-derived carbon self-supporting 3D negative electrode material. The mass of the wood / bamboo-derived carbon self-supporting 3D negative electrode material ≤ 5 mg.

2. The preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material according to claim 1, wherein: In step S1, the cross-section size of the wood / bamboo original sheet is 1 cm to 3 cm × 1 cm to 3 cm, and the thickness size is 0.1 cm to 0.5 cm.

3. The preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material according to claim 1, wherein: In step S3, the heating rate of the pyrolytic carbonization treatment is 2 °C / min to 20 °C / min, and the heat preservation time of the pyrolytic carbonization treatment is 1 h to 5 h.

4. The preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material according to claim 1, characterized in that: In step S2, the drying temperature is 40 °C to 60 °C, the drying time is 24 h to 48 h, and the warped and deformed wood / bamboo sheets are observed and discarded during the drying process. And / or, in step S2, the ratio of the mass m of the immersed wood / bamboo original sheets to the volume V of the H2SO4 solution, m / V ≤ 1:

8.

5. The preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material according to claim 1, characterized in that: In step S3, the polishing is carried out with sandpaper, and the sand grain size of the sandpaper is above 600 mesh.

6. The preparation method of the wood / bamboo-derived carbon self-supporting 3D anode material according to claim 1, characterized in that: In step S3, the cleaning is carried out by ultrasonic cleaning. The washing solution is a methanol solution and / or an ethanol solution with a volume concentration of 40% to 100%, and the ultrasonic cleaning time is 2 s to 120 s. And / or, in step S3, the drying temperature is 40 °C to 100 °C, and the drying time is 1 h to 24 h.

7. A wood / bamboo-derived carbon self-supporting 3D negative electrode material prepared by the preparation method of the wood / bamboo-derived carbon self-supporting 3D negative electrode material according to any one of claims 1 to 6.

8. Use of the wood / bamboo-derived carbon self-supporting 3D anode material according to claim 7 in a secondary battery, characterized in that: The secondary battery is a lithium-ion battery or a sodium-ion battery.

9. The application according to claim 8, characterized in that: The sodium-ion battery uses the wood / bamboo-derived carbon self-supporting 3D negative electrode material as the negative electrode sheet, does not require a binder or a conductive agent, uses a metal sodium sheet as the counter electrode, uses a solution with NaPF6 as the solute dissolved in diglyme as the electrolyte, and uses a glass microfiber filter membrane as the separator.

Images