Tumorous stem mustard-based hard carbon material as well as preparation method and application thereof

Abstract

The invention discloses a tumorous stem mustard-based hard carbon material as well as a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. The material takes tumorous stem mustard as a raw material and is of a porous structure, the specific surface area is 280-320 m < 2 > / g, the total pore volume is 0.36-0.45 cm < 3 > / g, and the d002 value is 0.31-0.39 nm. The preparation method comprises the steps of pre-carbonization, activation and secondary carbonization, wherein the secondary carbonization comprises primary carbonization and deep carbonization. The material has excellent electrochemical performance, the specific capacitance at 0.5 A / g is 258mAh / g, the coulombic efficiency of the first week is 82.4%, the capacity retention rate of 3000 cycles is 72.3%, and the capacity retention rate at-20 DEG C is 66.5%. The coconut shell-based hard carbon material can also be used for preparing a sodium ion battery negative electrode material and a sodium ion battery, the energy consumption is only about 53.6% of that of the coconut shell-based hard carbon material, the cost is low, and the performance is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion batteries, and particularly relates to a Brassica juncea var. tumida Tsen et Lee-based hard carbon material and a preparation method and application thereof. BACKGROUND

[0002] As a new generation of high specific energy battery negative electrode core material, the bio-based hard carbon material is prepared from natural biomass (such as coconut shell, fruit shell, etc.) as a precursor through high-temperature carbonization and activation. The disordered carbon layer structure and rich pore system (pore diameter 0.4-5 nm) can efficiently store lithium / sodium ions. However, the traditional raw materials have significant industrialization bottlenecks: high cost: the growth cycle of coconut shell needs 5-6 years, and the import price is more than 200,000 yuan / ton (including tariff and transportation cost), so that the large-scale supply cannot meet the demand of the energy storage market; insufficient structure regulation: the ratio of lignin / cellulose of coconut shell is about 1:2, the closed pore rate after carbonization is 35%-40%, and the interlayer spacing (d002) is low, which cannot adapt to the rapid embedding / extraction of sodium ions; large performance dispersion: affected by the production place and maturity, the specific surface area of the derived hard carbon fluctuates ±50 m 2 / g, resulting in a battery performance dispersion exceeding the industry standard (±5%).

[0003] Due to the high cost of traditional bio-based hard carbon and poor structure controllability, the traditional bio-based hard carbon cannot meet the demand of the energy storage industry for low-cost, high initial efficiency and long-life negative electrode materials, and it is urgent to develop a new type of biomass-based hard carbon material. SUMMARY

[0004] Therefore, the application provides a hard carbon material prepared from Brassica juncea var. tumida Tsen et Lee as a bio-based substrate. Through optimization of the preparation process, the hard carbon material has a larger specific surface area and total pore volume, a wider interlayer spacing (d002), and lower energy consumption compared with the hard carbon material prepared from coconut shell.

[0005] To achieve the above-mentioned purposes, the following technical solutions are adopted in the application:

[0006] On the one hand, a Brassica juncea var. tumida Tsen et Lee-based hard carbon material is provided, which satisfies the following characteristics: (i) prepared from Brassica juncea var. tumida Tsen et Lee as a raw material, and has a porous structure; (ii) the specific surface area is 280-320 m 2 / g, and the total pore volume is 0.36-0.45 cm 3 / g; (iii) the d002 value detected by XRD is 0.31-0.39 nm.

[0007] On the other hand, a preparation method of the Brassica juncea var. tumida Tsen et Lee-based hard carbon material is provided, and the preparation method comprises the following steps:

[0008] (1) pre-carbonizing Brassica juncea var. tumida Tsen et Lee at 300-500 ℃ to obtain a pre-carbonized material;

[0009] (2) mixing the pre-carbonized material with an alkali solution, and activating the pre-carbonized material by a hydrothermal reaction to obtain an activated material;

[0010] (3) secondary carbonization of the activated material: first primary carbonization at 300-500℃, and then deep carbonization at 700-900℃ to obtain a hard carbon material.

[0011] Preferably, the secondary carbonization satisfies one or more of the following conditions:

[0012] (a) the primary carbonization has a heating rate of 8-12℃ / min, and is kept at 300-500℃ for 25-35min;

[0013] (b) the deep carbonization has a heating rate of 4-6℃ / min, and is kept at 700-900℃ for 55-65min.

[0014] Preferably, the step (2) satisfies one or more of the following conditions:

[0015] (A) the alkali solution is a 1-3mol / L NaOH and / or KOH solution;

[0016] (B) the solid-liquid ratio of the pre-carbonized material to the alkali solution is 1:55-1:65.

[0017] In another aspect, a sodium ion battery negative electrode material is provided, which is prepared by growing Ni3V2O8@C nanoparticles with a thickness of 10-100nm on the surface of the hard carbon material of claim 1 by a hydrothermal method.

[0018] In another aspect, a preparation method of the above-mentioned sodium ion battery negative electrode material is provided, which comprises:

[0019] (1) dissolving ammonium metavanadate and nickel chloride hexahydrate in water to obtain a mixed solution;

[0020] (2) adding the hard carbon material to the mixed solution to perform a hydrothermal reaction, wherein the hydrothermal reaction is performed at a temperature of 170-190℃ for 2.5-3.5h;

[0021] (3) centrifuging, drying and calcining the reaction product to obtain the negative electrode material.

[0022] In another aspect, a sodium ion battery negative electrode is provided, which comprises the above-mentioned sodium ion battery negative electrode material or the above-mentioned hard carbon material.

[0023] In another aspect, a sodium ion battery is provided, which comprises the above-mentioned sodium ion battery negative electrode.

[0024] The beneficial effects of the present application are as follows:

[0025] (1) The specific surface area of the stem-nodulated Brassica juncea-based hard carbon material of the present application can reach 320 m 2 / g, the total pore volume can reach 0.45 cm 3 / g, the d002 value can reach 0.39 nm, the specific surface area and total pore volume are larger than those of the hard carbon material prepared from coconut shells, and the d002 value is wider.

[0026] (2) The sodium ion battery prepared based on the material has excellent electrochemical performance, the specific capacitance is 258 mAh / g at 0.5 A / g, the first cycle coulombic efficiency is 82.4%, the capacity retention rate after 3000 cycles is 72.3%, and the capacity retention rate at -20℃ is 66.5%.

[0027] (3) The preparation of the stem-nodulated Brassica juncea-based hard carbon material of the present application has low energy consumption, only 1500 kWh / ton, which is reduced by about 46.4% compared with 2800 kWh / ton of the coconut shell-based hard carbon material.

[0028] (4) The raw material of the stem-nodulated Brassica juncea-based hard carbon material of the present application is Fuling stem-nodulated Brassica juncea, the price of which is 600-700 yuan / ton, while in the existing biomass-based hard carbon material, traditional biomass such as coconut shell is commonly used as the preparation raw material, the import price is about > 200,000 yuan / ton, and the raw material cost in the present application is much lower than that in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the XRD image of the Ni3V2O8@C composite material;

[0030] Figure 2 is the SEM image of the Ni3V2O8@C composite material;

[0031] Figure 3 is the CV curve of the sodium ion battery prepared from the Ni3V2O8@C composite material.

[0032] Figure 4 is the charge-discharge curve (0.1 mA / g) of the sodium ion battery prepared from the Ni3V2O8@C composite material.

[0033] Figure 5 is the cycle performance curve of the sodium ion battery prepared from the Ni3V2O8@C composite material. DETAILED DESCRIPTION

[0034] The examples are given to better illustrate the present application, but are not the only embodiments of the present application, which are limited only by the following claims. Therefore, those skilled in the art can make non-essential improvements and adjustments to the embodiments according to the above description, which still belong to the protection scope of the present application.

[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. Unless otherwise defined, all terms of art used herein have the same meaning as commonly understood by one of ordinary skill in the art in the field of the disclosure. As used herein, it is also to be understood that the use of "a", "an", "the" or "said" herein does not exclude a plurality, and "comprising" does not exclude other steps. It is also to be understood that the terminology "comprising" is used herein to mean that other elements can also be present in the described embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0036] In the existing biomass-based hard carbon materials, traditional biomass such as coconut shell is often used as a raw material for preparation, but the traditional biomass such as coconut shell is expensive (import price is about > 200,000 yuan / ton); and the structural consistency is poor, the pore distribution is uneven, and the initial effect and cycle performance are insufficient. In addition, the energy consumption of coconut shell as a raw material for preparing hard carbon materials is high.

[0037] Based on this, the present application provides the following technical solutions:

[0038] In a first aspect, the present application provides a stem tumor mustard-based hard carbon material, which satisfies the following characteristics:

[0039] (i) prepared from stem tumor mustard as a raw material, in a porous structure;

[0040] (ii) the specific surface area is 280-320m 2 / g, and the total pore volume is 0.36-0.45cm 3 / g;

[0041] (iii) the d002 value detected by XRD is 0.31-0.39nm.

[0042] It should be noted that the stem tumor mustard-based hard carbon material in the present application has a large specific surface area, a large total pore volume, and a large d002 value detected by XRD. Specifically, a large d002 value (such as 0.37-0.39nm) indicates that the graphite layer spacing is expanded, which is beneficial to the embedding and extraction of sodium ions, and a larger d002 value is more suitable for sodium ions with a larger radius which can enhance the sodium storage capacity. In addition, the high specific surface area and abundant mesoporous / microporous structure provide more ion transmission channels and active sites, and the large pore volume and optimized pore distribution can relieve the volume expansion during charging and discharging.

[0043] In a second aspect, the present application provides a preparation method of the above-mentioned stem tumor mustard-based hard carbon material, which comprises:

[0044] (1) pre-carbonizing the stem tumor mustard at 300-500℃ to obtain a pre-carbonized material;

[0045] (2) mixing the pre-carbonized material with an alkali solution, and activating the pre-carbonized material through a hydrothermal reaction to obtain an activated material;

[0046] (3) performing secondary carbonization on the activated material: first performing primary carbonization at 300-500℃, and then performing deep carbonization at 700-900℃ to obtain a hard carbon material.

[0047] It should be noted that the stems and tubers in the present application can be leaves of stems and tubers, or rhizomes, which can be selected according to specific conditions.

[0048] It should be further noted that, compared with the hard carbon material prepared by using the commonly used coconut shell as a raw material, the hard carbon material prepared by using the stems and tubers as a raw material in the present application has more excellent electrochemical performance and lower energy consumption; in addition, the cost of the stems and tubers is much lower than that of the coconut shell. In addition, the hard carbon material prepared by using step-by-step carbonization for secondary carbonization after activation has more excellent electrochemical performance than the hard carbon material prepared by using one-step carbonization for secondary carbonization. It can be seen from the above that the preparation method in the present application is more suitable for stems and tubers.

[0049] It should be understood that the pre-carbonization temperature can be 300-500℃, for example, 350℃, 400℃ or 450℃, etc.; the primary carbonization temperature is 300-500℃, for example, 350℃, 400℃ or 450℃, etc.; and the deep carbonization temperature is 700-900℃, for example, 750℃, 800℃ or 850℃, etc.

[0050] In addition, the stems and tubers in the present application need to be cleaned and dried before pre-carbonization; preferably, the stems and tubers are broken after drying, which is more conducive to subsequent pre-carbonization. The particle size of the broken stems and tubers is less than 0.355 cm (i.e., the broken stems and tubers pass through a 0.355 cm screen).

[0051] In some specific examples, in the above preparation method, the stems and tubers can be selected from Fuling stems and tubers, and preferably stems and tubers with cellulose content ≥40%.

[0052] In some specific examples, the secondary carbonization satisfies one or more of the following conditions:

[0053] (a) the primary carbonization has a heating rate of 8-12℃ / min, and is kept at 300-500℃ for 25-35min; specifically, in the primary carbonization, the rate of heating to the primary carbonization temperature is 8℃ / min-12℃ / min, for example, 9℃ / min, 10℃ / min or 11℃ / min, etc.; and the primary carbonization time is 25min-35min, for example, 28min, 30min or 32min, etc.

[0054] (b) the deep carbonization temperature rising rate is 4-6℃ / min, and the temperature holding time is 700-900℃ for 55-65min; specifically, in the deep carbonization, the temperature rising rate to the deep carbonization temperature is 4-6℃ / min, such as 4.5℃ / min, 5℃ / min or 5.5℃ / min, etc.; the deep carbonization time is 55-65min, such as 57min, 60min or 63min, etc.

[0055] In some specific examples, the above step (2) satisfies one or more of the following conditions:

[0056] (A) the alkali solution is a 1-3mol / L NaOH and / or KOH solution; specifically, the alkali solution in the present application is well known in the art, such as sodium hydroxide solution and / or potassium hydroxide solution; the concentration can be 1-3mol / L, such as 1.5mol / L, 2mol / L or 2.5mol / L, etc.; in addition, the concentration of the alkali solution has an effect on the performance of the prepared hard carbon material, and preferably 2mol / L, the specific surface area of the prepared hard carbon material can reach 320m 2 / g, the first-week coulomb efficiency at 0.5A / g can reach 82.4%; while the specific surface area of the hard carbon material prepared by 1mol / L alkali solution can reach 280m 2 / g, the first-week coulomb efficiency at 0.5A / g can reach 78%; the specific surface area of the hard carbon material prepared by 3mol / L alkali solution can reach 310m 2 / g, the first-week coulomb efficiency at 0.5A / g can reach 75%(micropore collapse leads to first efficiency drop);

[0057] (B) the solid-liquid ratio of the pre-carbonized material to the alkali solution is 1:55-1:65, such as 1:58, 1:60 or 1:63, etc.; specifically, the solid-liquid ratio refers to the mass of the pre-carbonized material and the volume of the alkali solution, for example, the solid-liquid ratio of 1:60 means 1g of pre-carbonized material: 60mL of alkali solution, and so on.

[0058] It should be noted that the corrosion of the activation method in the present application can be reduced by 70% compared with the traditional activation method (such as 30% concentration KOH solution, solid-liquid ratio 1:10), and the pore distribution uniformity is also improved.

[0059] In a third aspect, the present application provides a sodium ion battery negative electrode material, which is prepared by growing Ni3V2O8@C nanoparticles on the surface of the hard carbon material of claim 1 by a hydrothermal method, and the thickness of the nanoparticles is 10-100nm, such as 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm or 90nm, etc.

[0060] It should be noted that the Ni3V3O8 nanoparticles can be grown on the stem and tumor mustard base hard carbon material in the present application, and the hard carbon material and the Ni3V3O8 nanoparticles can form a three-dimensional interconnected structure, thereby improving the ion diffusion rate (which can be improved by 45%, and the slope in the low frequency region of the EIS test is improved by 32%).

[0061] In a fourth aspect, the embodiments of the present application provide a preparation method of the above-mentioned sodium ion battery negative electrode material, which comprises:

[0062] (1) dissolving ammonium metavanadate and nickel chloride hexahydrate in water to obtain a mixed solution;

[0063] (2) adding hard carbon material to the mixed solution for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 170-190℃, and the time is 2.5-3.5h;

[0064] (3) centrifuging, drying and calcining the reaction product to obtain the negative electrode material.

[0065] It should be noted that in the preparation method of the above-mentioned sodium ion battery negative electrode material, the molar ratio of ammonium metavanadate to nickel chloride hexahydrate can be 1:(1-2), such as 1:1.2, 1:1.5 or 1:1.7, etc. In addition, it should be understood that the hydrothermal reaction in step (2) is well known in the art, for example, the reaction product can be obtained by hydrothermal reaction at a temperature of 170-190℃ for 2.5-3.5h.

[0066] In a fifth aspect, the embodiments of the present application provide a sodium ion battery negative electrode, which comprises the above-mentioned sodium ion battery negative electrode material or the above-mentioned hard carbon material.

[0067] It should be noted that the sodium ion battery negative electrode material or the above-mentioned hard carbon material in the present application can be prepared into a sodium ion battery negative electrode. It should be understood that the sodium ion battery negative electrode can also include conductive carbon black or PVDF (polyvinylidene fluoride) and the like. For example, the sodium ion battery negative electrode can include sodium ion battery negative electrode material, conductive carbon black or PVDF, and the mass ratio can be 8:1:1. For another example, the sodium ion battery negative electrode can include hard carbon material, conductive carbon black or PVDF, and the mass ratio can be 8:1:1.

[0068] In a sixth aspect, the embodiments of the present application provide a sodium ion battery, which comprises the above-mentioned sodium ion battery negative electrode.

[0069] It should be noted that the sodium ion battery negative electrode in the present application can be assembled into a sodium ion battery, and the positive electrode or electrolyte of the sodium ion battery is known in the art. For example, the electrolyte can be EC (ethylene carbonate): DEC (diethyl carbonate) (volume ratio) added with NaPF6 (sodium hexafluorophosphate, concentration of 1M). In addition, the hard carbon material in the present application can be prepared into the positive electrode of the sodium ion battery in the present application, specifically, the hard carbon material, conductive carbon black and PVDF can be prepared according to the mass ratio of 7:2:1.

[0070] In order to better understand the present application, the content of the present application will be further illustrated below in combination with specific examples, but the content of the present application is not limited to the following examples only.

[0071] In the following examples, the negative electrode sheet is prepared according to the following method: the raw materials are weighed according to the mass ratio of negative electrode material: conductive carbon black: PVDF (polyvinylidene fluoride) of 8:1:1; then the PVDF powder is dissolved in N-methyl-2-pyrrolidone to obtain a PVDF solution; the conductive carbon black is added to the PVDF solution to obtain a conductive slurry; the negative electrode material and the conductive slurry are mixed to obtain a negative electrode slurry; the negative electrode slurry is uniformly coated on one side of the negative electrode current collector (copper foil) by a coating machine, dried in an 80℃ oven for 1h, taken out and cooled to room temperature to obtain the negative electrode sheet.

[0072] In the following examples, the positive electrode is prepared according to the following method: the raw materials are weighed according to the mass ratio of nickel-iron-manganese sodium acid: conductive carbon black: PVDF of 7:2:1; then the PVDF powder is dissolved in N-methyl-2-pyrrolidone to obtain a PVDF solution; the conductive carbon black is added to the PVDF solution to obtain a conductive slurry; the nickel-iron-manganese sodium acid and the conductive slurry are mixed to obtain a positive electrode slurry; the positive electrode slurry is uniformly coated on one side of the positive electrode current collector (aluminum foil) by a coating machine, dried in an 80℃ oven for 1h, taken out and cooled to room temperature to obtain the positive electrode sheet.

[0073] I. Hard carbon material, sodium ion battery negative electrode material, and preparation of sodium ion battery

[0074] Example 1

[0075] The present application provides a kind of hard carbon material, and its preparation method is as follows:

[0076] (1) raw material processing: Fuling stem tumor mustard stem leaf is washed, and dried at 80 DEG C for 48 hours, and is broken to 0.355 cm sieve to obtain powder;

[0077] (2) pre-carbonization: the powder is placed in a tube furnace, nitrogen flow rate is 5L / min, with 5 DEG C / min to 400 DEG C, and is kept for 2h to obtain pre-carbonization product;

[0078] (3) KOH activation: 10 g of the pre-carbonized product was mixed with 600 mL of KOH solution (2 mol / L) (1:60 solid-liquid ratio), transferred to a polytetrafluoroethylene reactor, reacted at 180 °C for 18 h, and centrifuged and washed until neutral to obtain the activated pre-carbonized product;

[0079] (4) Step-by-step carbonization: The activated pre-carbonized product is carbonized step-by-step in a tube furnace under a continuous flow of argon gas, as follows:

[0080] Primary carbonization: The activated pre-carbonized product was subjected to primary carbonization: the temperature was raised to 400°C at a heating rate of 10°C / min and maintained at 400°C for 30 min to obtain the primary carbonized product;

[0081] Deep carbonization: The primary carbonization product is subjected to deep carbonization: the temperature is increased to 800°C at a heating rate of 5°C / min, and the temperature is maintained at 800°C for 60 minutes to obtain a hard carbon material.

[0082] Example 2 to Example 5

[0083] Examples 2 to 5 of the present invention provide a hard carbon material, and the preparation method thereof is substantially the same as that of Example 1, specifically as follows:

[0084] The difference between Examples 2 to 5 and Example 1 is that the initial carbonization parameters and deep carbonization parameters of step (4) in Examples 2 to 5 are different from those in Example 1, and the other steps are the same as in Example 1. Among them, the initial carbonization parameters and deep carbonization parameters of step (4) in Examples 1 to 5 are shown in Table 1 below.

[0085] Table 1 Primary carbonization parameters and deep carbonization parameters of Example 1 and Examples 2 to 5

[0086] Example Primary carbonization Deep carbonization Example 1 400℃×30min, heating rate 10℃ / min 800℃×60min, heating rate 5℃ / min Example 2 300℃×30min, heating rate 10℃ / min 800℃×60min, heating rate 5℃ / min Example 3 500℃×30min, heating rate 10℃ / min 800℃×60min, heating rate 5℃ / min Example 4 400℃×30min, heating rate 10℃ / min 700℃×60min, heating rate 5℃ / min Example 5 400℃×30min, heating rate 10℃ / min 900℃×60min, heating rate 5℃ / min

[0087] Example 6 to Example 7

[0088] Examples 6 and 7 of the present invention provide a hard carbon material, and the preparation method thereof is substantially the same as that of Example 1, specifically as follows:

[0089] The difference between Examples 6 and 7 and Example 1 is that the concentration of the KOH solution in step (3) of Examples 6 and 7 is different from that of Example 1. The other steps are the same as in Example 1 to prepare a hard carbon material. The concentrations of the KOH solution in step (3) of Example 1 and Examples 6 and 7 are shown in Table 2 below.

[0090] Table 2 KOH solution concentrations of Example 1 and Example 7 to Example 8

[0091] Example KOH solution concentration Example 1 2mol / L Example 6 1mol / L Example 7 3mol / L

[0092] Example 8

[0093] The embodiment of the present application provides a sodium ion battery negative material, and a preparation method thereof is as follows:

[0094] (1) NH4VO3 (ammonium metavanadate, 1.68 mmol) and NiCl2·6H2O (nickel chloride hexahydrate, 2.535 mmol) are dissolved in 60 mL of water, and stirring is performed at 80 DEG C until a nickel vanadate precursor is obtained;

[0095] (2) 1 g of the hard carbon material obtained in the step (1) is added into 1 g of the nickel vanadate precursor, and hydrothermal treatment is performed at 180 DEG C for 3 h; after centrifugal drying, calcination is performed at 350 DEG C for 3 h to obtain the sodium ion battery negative material (also referred to as a Ni3V2O8@C composite material).

[0096] Examples 9 to 14

[0097] The embodiment 9 to the embodiment 14 of the present application provide a sodium ion battery negative material, and a preparation method thereof is as follows:

[0098] The difference between the embodiment 9 to the embodiment 14 and the embodiment 8 is that the hard carbon material in the step (2) in the embodiment 9 to the embodiment 14 is the hard carbon material in the embodiment 2 to the embodiment 7 respectively, and other conditions are the same as the embodiment 8, so that the sodium ion battery negative material is prepared; specifically:

[0099] The embodiment 9 is the hard carbon material in the embodiment 2, which is used for preparing the sodium ion battery negative material;

[0100] The embodiment 10 is the hard carbon material in the embodiment 3, which is used for preparing the sodium ion battery negative material;

[0101] The embodiment 11 is the hard carbon material in the embodiment 4, which is used for preparing the sodium ion battery negative material;

[0102] The embodiment 12 is the hard carbon material in the embodiment 5, which is used for preparing the sodium ion battery negative material;

[0103] The embodiment 13 is the hard carbon material in the embodiment 6, which is used for preparing the sodium ion battery negative material;

[0104] The embodiment 14 is the hard carbon material in the embodiment 7, which is used for preparing the sodium ion battery negative material.

[0105] Example 15

[0106] The embodiment of the present application provides a sodium ion battery, and each component is as follows:

[0107] The negative sheet is the negative material in the embodiment 8, the conductive carbon black is PVDF (mass ratio) = 8:1:1;

[0108] The positive sheet is sodium nickel iron manganese acid, the conductive carbon black is PVDF (mass ratio) = 7:2:1.

[0109] Electrolyte: EC (ethylene carbonate): DEC (diethyl carbonate) (volume ratio) with NaPF6 (sodium hexafluorophosphate, concentration of 1M) added.

[0110] Examples 16 to 21

[0111] Examples 16 to 21 provide a sodium ion battery, each component of which is as follows:

[0112] Examples 16 to 21 are different from the negative electrode and the positive electrode in Example 15, and the others are the same as in Example 15, to prepare a sodium ion battery. Among them, the negative electrode and the positive electrode in Examples 15 to 21 are as shown in Table 3.

[0113] Table 3 Negative electrode and positive electrode in Examples 16 to 21

[0114]

[0115]

[0116] Comparative Example 1

[0117] Comparative Example 1 provides a hard carbon material, the preparation method of which is substantially the same as that of Example 1, and specifically as follows:

[0118] The difference between Comparative Example 1 and Example 1 is that step (4) in Comparative Example 1 is: carbonizing the pre-carbonized product, which includes: increasing the temperature to 800°C at a temperature increasing rate of 10°C / min, maintaining 800°C for 2h, and the other steps are the same as in Example 1, to prepare a hard carbon material.

[0119] Comparative Example 2

[0120] Comparative Example 2 provides a hard carbon material, the preparation method of which is substantially the same as that of Example 1, and specifically as follows:

[0121] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the Fuling stem tumor mustard stem leaves are replaced by coconut shells, and the other steps are the same as in Example 1, to prepare a hard carbon material.

[0122] Comparative Examples 3 to 4

[0123] Comparative Examples 3 and 4 provide a sodium ion battery negative electrode material, the preparation method of which is as follows:

[0124] The difference between Comparative Examples 3 and 4 and Example 8 is that the hard carbon material in step (2) in Comparative Examples 3 and 4 is the hard carbon material prepared in Comparative Examples 1 and 2, respectively, and the others are the same as in Example 8, to prepare an ion battery negative electrode material; specifically:

[0125] Comparative Example 3 is a sodium-ion battery negative electrode material prepared using the hard carbon material prepared in Comparative Example 1;

[0126] Comparative Example 4 is a sodium-ion battery negative electrode material prepared using the hard carbon material prepared in Comparative Example 2.

[0127] Comparative Example 5

[0128] Comparative Example 5 provides a sodium-ion battery (the negative electrode and the positive electrode in Comparative Example 5 are different from those in Example 15), and the components of the sodium-ion battery in Comparative Example 5 are as follows:

[0129] Negative electrode: Comparative Example 3 negative electrode material: conductive carbon black: PVDF (mass ratio) = 8:1:1;

[0130] Positive electrode: same as Example 15;

[0131] Electrolyte: same as Example 15.

[0132] Comparative Example 6

[0133] Comparative Example 6 provides a sodium-ion battery (the negative electrode and the positive electrode in Comparative Example 6 are different from those in Example 15), and the components of the sodium-ion battery in Comparative Example 6 are as follows:

[0134] Negative electrode: Comparative Example 4 negative electrode material: conductive carbon black: PVDF (mass ratio) = 8:1:1;

[0135] Positive electrode: same as Example 15;

[0136] Electrolyte: same as Example 15.

[0137] II. Characterization of the hard carbon material

[0138] The BET analysis method was used to test the specific surface area and total pore volume of the hard carbon materials prepared in Examples 1 to 9 and Comparative Example 1; in addition, the d002 value of each hard carbon material was also tested using the XRD method. The test results are shown in Table 4 below.

[0139] Table 4 Specific surface area, total pore volume and d002 value of the hard carbon materials prepared in the examples and comparative examples

[0140] Example Specific surface area (m 2 / g) Total pore volume (cm 3 / g) d002 value (nm) Example 1 320 0.45 0.39 Example 2 313 0.41 0.36 Example 3 315 0.42 0.35 Example 4 316 0.42 0.34 Example 5 317 0.43 0.37 Example 6 280 0.36 0.31 Example 7 310 0.39 0.33 Comparative Example 1 250 0.34 0.29 Comparative Example 2 220 0.27 0.25

[0141] From Table 4 above, it can be seen that:

[0142] Comparative Example and Comparative Example 1 can be seen that the specific surface area, total pore volume and d 002 value of the hard carbon material prepared by step-by-step carbonization in the present application are all greater than those of the hard carbon material prepared by one-step carbonization in Comparative Example 1, indicating that the performance of the hard carbon material prepared by step-by-step carbonization in the present application is more excellent than that of the hard carbon material prepared by one-step carbonization;

[0143] It can be seen from the comparative example and the comparative example 2 that the specific surface area, total pore volume and D 002 The values are all greater than those of the hard carbon material prepared by using coconut shell as the raw material in the comparative example 2, which indicates that the stem tumor mustard as the raw material is more suitable for preparing the hard carbon material than the coconut shell as the raw material, and the hard carbon material prepared by using the stem tumor mustard as the raw material has more excellent performance.

[0144] In addition, the X-ray diffraction analysis result of the Ni3V2O8@C composite material prepared in the example 8 is shown in Figure 1 The electron scanning electron microscope image is shown in Figure 2 .

[0145] In addition, the energy consumption of mass production of the hard carbon material prepared in the example 1 and the example 2 is tested, and the results are shown in the following table 5.

[0146] Table 5 Energy consumption of mass production of the hard carbon material prepared in the example 1 and the example 2

[0147] Example Mass production capacity consumption Example 1 1500kWh / ton Comparative Example 2 2800kWh / ton

[0148] III. Analysis of the electrochemical performance of the sodium ion battery

[0149] In the following analysis, the sodium ion button cell is prepared as follows: the negative electrode sheet is rolled by adjusting the rolling distance, and the rolled negative electrode sheet is cut to form a small round sheet with a diameter of 14 mm; the small round sheet is placed in a 80℃ oven for vacuum drying for 12h; the positive electrode sheet is also prepared into a small round sheet according to the above preparation method. The negative electrode small round sheet, the positive electrode small round sheet, the electrolyte and the glass fiber separator are assembled into a sodium ion button cell in a glove box with oxygen and water content less than 0.01ppm.

[0150] In the following analysis, the 0.5A / g specific capacity, 0.5A / g initial coulombic efficiency, 0.5A / g cycle capacity retention rate (3000 times) and-20℃ capacity retention rate (the sodium ion button cell is activated at 25℃ under 1C charging and discharging for 1 week, the discharge capacity A1 of 1C charging and discharging in the 2nd week is recorded, the cell is transferred to a-20℃ constant temperature box after 1C charging, and 1C discharging is carried out after 3h, the discharge capacity is recorded as A2, and the-20℃ capacity retention rate is A2 / A1x100%) of the sodium ion button cell at room temperature are tested by using the Shenzhen Xinwei battery test system.

[0151] The sodium ion batteries of Examples 15 to 21 and Comparative Examples 5 and 6 were prepared into sodium ion button cells according to the preparation method of the sodium ion button cell described above, and then the 0.5A / g specific capacity, 0.5A / g first-week coulombic efficiency, 0.5A / g cycle capacity retention rate (3000 times) and -20℃ capacity retention rate of the sodium ion button cells were tested according to the test method described above. The results are shown in Table 6 below.

[0152] Table 6 Electrochemical performance of sodium ion batteries assembled by examples and comparative examples

[0153]

[0154] It can be seen from Table 6 above that the electrochemical performance of the sodium ion batteries assembled by Examples 15 to 21 is much better than that of the sodium ion batteries assembled by Comparative Examples 5 and 6, that is, the electrochemical performance of the sodium ion batteries assembled by the hard carbon material prepared based on the stem tumor mustard as raw material and step-by-step carbonization is better than that of the sodium ion batteries assembled by the hard carbon material prepared based on the step-by-step carbonization of coconut shell and the one-step carbonization of stem tumor mustard. Among them, the electrochemical performance of the sodium ion battery assembled by the hard carbon material prepared by Example 1 is the best.

[0155] In addition, the sodium ion button cell prepared by the sodium ion battery of Example 15 was subjected to cyclic voltammetry test using a Shenzhen Xinwei battery test system, and the results are shown in Figure 3 .

[0156] At the same time, the sodium ion button cell prepared by the sodium ion battery of Example 15 was subjected to constant current charge-discharge test at a current density of 0.5A / g using a Shenzhen Xinwei battery test system, and the charge-discharge curve is shown in Figure 4 , and the cycle performance is shown in Figure 5 .

[0157] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A tumor-bearing mustard-based hard carbon material, characterized in that: Tuberculosis-based hard carbon materials meet the following characteristics: (i) Prepared from stem mustard as raw material, with a porous structure; (ii) Specific surface area of ​​280-320m 2 / g, with a total pore volume of 0.36-0.45cm 3 / g; (iii) The d002 value detected by XRD was 0.31-0.39 nm.

2. The method for preparing the tumor-bearing Brassica juncea-based hard carbon material according to claim 1, wherein: The preparation method comprises: (1) pre-carbonizing the stem mustard at 300-500° C. to obtain a pre-carbonized material; (2) mixing the pre-carbonized material with an alkaline solution and activating the mixture through a hydrothermal reaction to obtain an activated material; (3) Perform secondary carbonization on the activated material: first perform primary carbonization at 300-500°C, then perform deep carbonization at 700-900°C to obtain a hard carbon material.

3. The preparation method according to claim 2, wherein The secondary carbonization satisfies the following conditions: (a) The initial carbonization heating rate is 8-12°C / min, and the temperature is kept at 300-500°C for 25-35 min; (b) Deep carbonization heating rate is 4-6℃ / min, and the temperature is kept at 700-900℃ for 55-65min.

4. The preparation method according to claim 2 or 3, wherein Step (2) satisfies one or more of the following conditions: (A) The alkaline solution is a 1-3 mol / L NaOH and / or KOH solution; (B) The solid-to-liquid ratio of the pre-carbonized material to the alkaline solution is 1:55-1:

65.

5. A sodium ion battery negative electrode material, characterized in that The nanoparticles are prepared by growing Ni3V2O8@C nanoparticles on the surface of the hard carbon material according to claim 1 by a hydrothermal method, and the thickness of the nanoparticles is 10-100 nm.

6. The method for preparing the negative electrode material according to claim 5, wherein: The preparation method comprises: (1) dissolving ammonium metavanadate and nickel chloride hexahydrate in water to obtain a mixed solution; (2) adding hard carbon material to the mixed solution for hydrothermal reaction at a temperature of 170-190° C. for 2.5-3.5 h; (3) The reactants are centrifuged, dried, and then calcined to obtain the negative electrode material.

7. A sodium ion battery negative electrode, characterized in that: Contains the hard carbon material according to claim 1 or the negative electrode material according to claim 5.

8. A sodium ion battery, characterized in that: The sodium ion battery negative electrode according to claim 7 is included.

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