Biomass hard carbon sodium battery negative electrode material with expanded interlayer spacing, preparation method and application

Abstract

The present application belongs to the technical field of biomass hard carbon, and particularly relates to a biomass hard carbon sodium electric negative electrode material with expanded interlayer spacing, a preparation method and application. The preparation method comprises the following steps: washing and drying biomass raw materials to obtain pretreated materials; crushing the pretreated materials to obtain crushed materials; soaking the crushed materials in a nitrate solution while stirring, and drying after soaking to obtain soaked materials; pre-carbonizing the soaked materials in a protective atmosphere to obtain pre-carbonized materials; adding an additive to the pre-carbonized materials, performing acid washing and water washing to remove ash, and finally performing suction filtration and drying to obtain purified materials; uniformly mixing the purified materials with a modifier, and then performing high-temperature carbonization in a protective atmosphere to obtain the material after removing iron through sieving. The application includes a negative electrode sheet and a battery. The present application expands the interlayer spacing of the biomass hard carbon sodium electric negative electrode material, and improves the charge and discharge capacity of the biomass hard carbon negative electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of biomass hard carbon, and particularly relates to a biomass hard carbon sodium electric negative electrode material with expanded interlayer spacing, a preparation method and application. BACKGROUND

[0002] Due to rich sodium resource reserves, wide distribution and low development cost on the earth, sodium and lithium are in the same main group in the periodic table, and have similar physical and chemical properties, and sodium ion batteries have similar deintercalation mechanism with lithium ion batteries in the charging and discharging process. + The standard potential of Na + / Li is about 0.3V higher than that of Li Compared with lithium ion batteries, the commercial graphite widely used in lithium ion batteries cannot be applied to sodium ion batteries, mainly because the interlayer spacing of graphite is small, only 0.335nm, while larger sodium ions need larger interlayer pores and cannot be quickly inserted and deintercalated. Biomass as a rich renewable energy source has wide sources and low cost, and the synthesized carbon-based material has a large specific surface area, an interlayer spacing of 0.36-0.38nm, and controllable pores and high conductivity, so that it has attracted more and more attention as a sodium ion battery negative electrode material.

[0003] The biomass hard carbon has a large specific surface area and a large number of defects, resulting in low first coulombic efficiency and charge and discharge capacity. SUMMARY

[0004] The first object of the application is to provide a biomass hard carbon sodium electric negative electrode material with expanded interlayer spacing, the second object of the application is to provide a preparation method of the biomass hard carbon sodium electric negative electrode material with expanded interlayer spacing, the third object of the application is to provide a negative electrode sheet, and the fourth object of the application is to provide a battery.

[0005] The application expands the interlayer spacing of the biomass hard carbon sodium electric negative electrode material, and improves the charge and discharge capacity of the biomass hard carbon negative electrode material.

[0006] To achieve the above objects and other related objects, the application provides the following technical solutions.

[0007] In a first aspect, the application provides a preparation method of a biomass hard carbon sodium electric negative electrode material with expanded interlayer spacing, comprising the following steps,

[0008] Pretreatment: washing and drying biomass raw materials to obtain pretreated materials;

[0009] Crushing: crushing the pretreated materials to obtain crushed materials;

[0010] Soaking: the crushed material is added to a nitrate solution for soaking, stirring is carried out at the same time, and after soaking, drying is carried out, to obtain soaked material;

[0011] Pre-carbonization: the soaked material is pre-carbonized under a protective atmosphere, to obtain pre-carbonized material;

[0012] Purification: an additive is added to the pre-carbonized material, acid washing, water washing and ash removal are carried out, and finally, suction filtration and drying are carried out, to obtain purified material;

[0013] Coated carbonization: the purified material is uniformly mixed with a modifier, and then high-temperature coated carbonization is carried out under a protective atmosphere, and after removing iron through sieving, a biomass hard carbon sodium electrode material with expanded interlayer spacing is obtained.

[0014] In the prior art, the disordered structure of the hard carbon material is also difficult to eliminate under high temperature, and the high temperature condition also causes the interlayer spacing of the hard carbon material to decrease. In view of the objective defects, in the present application, the biomass crushed material is first soaked with a nitrate, and then the nitrate is added in the pre-carbonization to expand the interlayer spacing and form pores during decomposition, so that the acid washing and purification can be more fully reacted with the inorganic components to reduce the ash content, and the additive added during the purification can be doped into the holes formed in the pre-carbonization process, so that during the high-temperature coated carbonization process, on the one hand, the specific surface area can be reduced, and on the other hand, the residual phosphoric acid group and the additive added during the purification can produce a synergistic effect to further expand the interlayer spacing, thereby improving the first coulombic efficiency and the charge and discharge capacity. In view of the foregoing, the present application is also different from the prior art, and the acid washing in the prior art is generally used to remove impurities, and the present application also does not need secondary pore formation.

[0015] In an embodiment of the present application, in the pretreatment, the biomass raw material includes at least one of Phyllostachys edulis and Phyllostachys nigra, the biomass raw material is first cleaned with tap water, and then is placed in a blast drying oven for drying, the drying temperature of the blast drying oven is 60-200 DEG C, and the drying time is 6-48h.

[0016] In an embodiment of the present application, in the crushing, the crushing equipment is at least one of a mechanical crusher, a roller pressure powder crusher and an air flow crusher, and the particle size of the crushed material is controlled to be 3-17um.

[0017] In an embodiment of the present application, in the soaking, the crushed material is added to a nitrate solution for soaking, the soaking time is 0.5h-3h, the solid-liquid ratio is 1:0.2-2, stirring is carried out at the same time, the stirring speed is 100-150rpm, and after soaking, the material is placed in a blast drying oven for drying, the drying temperature of the blast drying oven is 80-150 DEG C, and the drying time is 6-48h, to obtain soaked material;

[0018] The nitrate solution comprises at least one of cobalt nitrate, iron nitrate and nickel nitrate; the concentration of the nitrate solution is 0.01-0.1 mol / L.

[0019] In an embodiment of the present application, in the pre-carbonization, the protective atmosphere comprises at least one of nitrogen, argon and helium, and the pre-carbonization conditions comprise a heating rate of 2-10℃ / min, a pre-carbonization temperature of 350-800℃, and a holding time of 1-3h, and the pre-carbonization is performed in an atmosphere carbonization furnace.

[0020] In an embodiment of the present application, in the purification, the additive comprises at least one of hydroxyethylidene diphosphonic acid, (1-hydroxyethylidene) diphosphonic acid and histamine phosphate, and the mass of the additive accounts for 0.1-10wt% of the total mass of the pre-carbonized material; the acid for pickling comprises at least one of hydrochloric acid, nitric acid, hydrofluoric acid and sulfuric acid; the concentration of the acid in the pickling is 0.5-5 mol / L; the reaction temperature of the pickling is 60-120℃; the solid-liquid mass ratio of the pickling is 1:0.7-5.5; and the pickling time is 6-24h.

[0021] The specific process of the water washing and ash removal comprises multiple deionized water washing until the filtrate is close to neutral, then suction filtration, and drying at a temperature of 80-150℃ for 6-48h.

[0022] In an embodiment of the present application, in the coating carbonization, the modifier comprises at least one of pitch and resin; the mass of the modifier accounts for 1-10wt% of the mass of the purified material; the mixing time is 0.5-3h; the high-temperature carbonization conditions comprise a heating rate of 2-10℃ / min, a high-temperature carbonization temperature of 1200-1800℃, and a holding time of 2-6h, and the high-temperature carbonization is performed in an atmosphere carbonization furnace; the protective atmosphere of the coating carbonization comprises at least one of nitrogen, argon and helium; and the mesh number of the vibration screening machine used for sieving is 200-400 mesh.

[0023] In a second aspect, the present application provides a biomass hard carbon sodium battery negative electrode material with expanded interlayer spacing, which is prepared by the above-mentioned method for preparing a biomass hard carbon sodium battery negative electrode material with expanded interlayer spacing.

[0024] In a third aspect, the present application provides a negative electrode sheet, which uses the biomass hard carbon sodium battery negative electrode material with expanded interlayer spacing as an active substance of a battery negative electrode material.

[0025] The preparation method of the negative electrode sheet comprises the following steps:

[0026] The binder, the additive, the biomass hard carbon sodium battery negative electrode material with expanded interlayer spacing and the polymer are mixed in proportion to a uniform paste, which is uniformly coated on a carrier, dried, and a negative electrode sheet is prepared.

[0027] In an embodiment of the present application, the binder includes CMC (sodium carboxymethyl cellulose), sodium polyacrylate, polyvinylidene fluoride, the additive includes conductive carbon black, and the polymer includes SBR (styrene butadiene rubber) and PAA (acrylic acid homopolymer).

[0028] In an embodiment of the present application, the mass ratio of the binder, the additive, the biomass hard carbon sodium electrode material with expanded interlayer spacing, and the polymer is 1-2.0%:2-4.0%:92.0-95%:1-2.0%.

[0029] In an embodiment of the present application, the carrier includes copper foil.

[0030] In an embodiment of the present application, the drying conditions include a drying temperature of 100-120°C and a drying time of 10-25 min.

[0031] In an embodiment of the present application, the specific preparation steps of the negative electrode tab include:

[0032] According to a mass ratio of 2.0%:4.0%:92.0%:2.0%, 0.2 g of CMC (sodium carboxymethyl cellulose), 0.4 g of conductive carbon black, 9.2 g of hard carbon material, and 0.5 g of SBR (styrene butadiene rubber, solid content 40%) are weighed, an appropriate amount of deionized water is added, stirring is performed for 20 min until a uniform slurry is obtained, a 100 μm doctor blade is used to uniformly coat the slurry on the surface of the copper foil, drying is performed in a 105°C air drying oven for 2 h, the copper foil with the active material is cut into a circular negative electrode tab, and the negative electrode tab is immediately transferred to a glove box for standby.

[0033] In a fourth aspect, the present application provides a battery, which is a sodium ion battery, the sodium ion battery including a negative electrode, a positive electrode, a separator, and an electrolyte, the negative electrode including the negative electrode tab, and the sodium ion battery having an interlayer spacing of 0.411-0.420 nm, a first charge specific capacity of 320-340 mAh / g, a first discharge specific capacity of 350-380 mAh / g, and a first efficiency of 90-95% when performing charge-discharge tests at a current density of 0.1 C.

[0034] In an embodiment of the present application, the preparation steps of the sodium ion battery include simulating the assembly of the battery in a glove box in a protective atmosphere, using the prepared biomass hard carbon sodium electrode material with expanded interlayer spacing as the negative electrode tab, and using an electrolyte and a counter electrode to form a button cell.

[0035] In an embodiment of the present application, the protective atmosphere includes Ar.

[0036] In an embodiment of the present application, the electrolyte includes at least one of NaPF6, EC, and DMC.

[0037] In an embodiment of the present application, the counter electrode comprises a Na metal sheet.

[0038] In an embodiment of the present application, the specific preparation steps of the sodium ion battery include: the assembly of the battery is carried out in an Ar atmosphere glove box, a prepared biomass hard carbon sodium electrode material negative electrode sheet with expanded interlayer spacing is used as the negative electrode, a 1.0 mol / L commercial electrolyte, the commercial electrolyte is prepared as follows: the V:V of NaPF6 / EC:DMC is 1:1, a Na metal sheet is used as the counter electrode, a CR2032 type button cell is assembled, and then a constant current charge and discharge mode is used to carry out charge and discharge test at a current density of 0.1C.

[0039] The negative electrode sheet and the battery described above are applications of the biomass hard carbon sodium electrode material with expanded interlayer spacing.

[0040] The present application has the following beneficial effects:

[0041] The biomass hard carbon has a large specific surface area and a large number of defects, thereby causing low first coulombic efficiency and charge and discharge capacity. In view of the problems faced by the biomass hard carbon material and in combination with the sodium storage mechanism of the hard carbon, reasonable control of the defects and interlayer spacing of the biomass hard carbon negative electrode material and reduction of the specific surface area can effectively improve the coulombic efficiency and charge and discharge capacity. Therefore, the present application provides a biomass hard carbon sodium electrode material with expanded interlayer spacing and a preparation method thereof. In the present application, the biomass crushed material is first soaked with a nitrate salt, and then the nitrate salt doped in the pre-carbonization can expand the interlayer spacing and form pores during decomposition, so that the acid washing purification can more fully react with the inorganic components to reduce the ash content, and the additive added during purification can be doped into the cavities formed in the pre-carbonization process, so that during the high-temperature carbonization process, on the one hand, the specific surface area can be reduced, and on the other hand, the residual phosphoric acid group and the additive added during purification can produce a synergistic effect to further expand the interlayer spacing, thereby improving the first coulombic efficiency and charge and discharge capacity. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings are included to provide a further understanding of the present application, and constitute a part of the specification, illustrate the present application together with the embodiments thereof, and explain the present application, but do not constitute a limitation of the present application. In the drawings:

[0043] Fig. 1 is an XRD comparison diagram of the biomass hard carbon negative electrode material of Example 1 and Comparative Examples 1-3 of the present application;

[0044] Fig. 2 is a TEM diagram of the biomass hard carbon negative electrode material of Example 1 of the present application with expanded interlayer spacing;

[0045] Fig. 3 is a TEM diagram of the biomass hard carbon negative electrode material of Comparative Example 1 of the present application;

[0046] Fig. 4 is a TEM image of the biomass hard carbon negative electrode material of Comparative Example 2 of the present application;

[0047] Fig. 5 is a TEM image of the biomass hard carbon negative electrode material of Comparative Example 3 of the present application;

[0048] Fig. 6 is a comparison chart of charge-discharge curves of the biomass hard carbon negative electrode materials of Example 1 and Comparative Example 1 of the present application under the condition of 0.1C. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0050] The equipment and materials used in the embodiments can be easily obtained from commercial companies if not specifically stated.

[0051] Phenol formaldehyde resin (AR, aladdin reagent).

[0052] A preparation method of a biomass hard carbon sodium battery negative electrode material with expanded interlayer spacing, comprising the following steps:

[0053] Pretreatment: the biomass raw material is first cleaned with tap water, and then dried in a blast drying oven to obtain pretreated material. The biomass raw material is at least one of Phyllostachys pubescens and Phyllostachys nigra. The drying temperature of the blast drying oven is 60-200°C, and the drying time is 6-48h.

[0054] Pulverization: the pretreated material is pulverized to obtain a pulverized material. The equipment used for pulverization is a mechanical pulverizer, a roller grinding pulverizer or an air flow pulverizer, and the particle size is controlled to be 3-17um.

[0055] Soaking: after pulverization, the pulverized material is added to a nitrate solution for soaking, and stirring is performed at the same time. The stirring speed is 100-150rpm. After soaking, the material is dried in a blast drying oven. The drying temperature of the blast drying oven is 80-150°C, and the drying time is 6-48h. The material after soaking is obtained. The nitrate solution is at least one of cobalt nitrate, iron nitrate and nickel nitrate. The concentration of the nitrate is 0.01-0.1mol / L. The soaking time is 0.5h-3h. The solid-liquid ratio is 1:0.2-2.

[0056] Pre-carbonization: the soaked material is pre-carbonized under a protective atmosphere to obtain pre-carbonized material. The protective atmosphere is at least one of nitrogen, argon, and helium. The pre-carbonization conditions are: a heating rate of 2-10°C / min, a pre-carbonization temperature of 350-800°C, a holding time of 1-3h, and the pre-carbonization is performed in an atmosphere carbonization furnace.

[0057] Purification: an additive is added to the pre-carbonized material, which is then subjected to acid pickling, water washing, and finally filtered and dried to obtain purified material. The additive is at least one of hydroxyethylidene diphosphonic acid (C2H8O7P2), (1-hydroxyethylidene) diphosphonic acid, and histamine phosphate (C5H 15 N3O8P2). The mass of the additive accounts for 0.1-10wt% of the total mass of the pre-carbonized material. The acid used for acid pickling is at least one of hydrochloric acid, nitric acid, hydrofluoric acid, and sulfuric acid. The concentration of the acid is 0.5-5mol / L. The reaction temperature for acid pickling is 60-120°C. The solid-liquid mass ratio for acid pickling is 1:0.7-5.5. The acid pickling time is 6-24h. The specific process for water washing and ash removal is to wash with multiple times of deionized water until the filtrate is close to neutral, and then to filter. The drying temperature is 80-150°C, and the drying time is 6-48h.

[0058] Coated carbonization: the purified material is mixed with a modifier using a VC machine, and then subjected to high-temperature coated carbonization under a protective atmosphere to obtain a biomass hard carbon sodium anode material with expanded interlayer spacing after iron removal. The modifier is at least one of pitch and resin. The mass of the modifier accounts for 1-10wt% of the mass of the purified material. The mixing time is 0.5-3h. The high-temperature carbonization conditions are: a heating rate of 2-10°C / min, a high-temperature carbonization temperature of 1200-1800°C, a holding time of 2-6h, and the high-temperature carbonization is performed in an atmosphere carbonization furnace. The protective atmosphere is at least one of nitrogen, argon, and helium. The mesh number of the vibrating screen machine used for sieving is 200-400 mesh.

[0059] The biomass hard carbon material prepared above is used as an active substance of a battery anode material for a sodium ion battery. The preparation method is:

[0060] CMC (sodium carboxymethyl cellulose) 0.2g, conductive carbon black 0.4g, hard carbon material 9.2g, and SBR (styrene-butadiene rubber, solid content 40%) 0.5g are weighed according to a mass ratio of 2.0%:4.0%:92.0%:2.0%, and an appropriate amount of deionized water is added, stirred for 20min to form a uniform slurry, and then coated on the surface of a copper foil using a 100μm doctor blade. The coated copper foil is dried in a 105°C air drying oven for 2h, and then cut into a circular negative electrode sheet, which is immediately transferred to a glove box for standby.

[0061] The assembly of the simulation battery was carried out in an Ar atmosphere glove box, using the prepared biomass hard carbon pole piece as the negative electrode, 1.0 mol / L commercial electrolyte, the commercial electrolyte was prepared as follows: the V:V of NaPF6 / EC:DMC was 1:1, Na metal sheet as the counter electrode, assemble CR2032 type button cell, and then use constant current charge and discharge mode, at 0.1C current density, charge and discharge test.

[0062] Example 1

[0063] A preparation method of a biomass hard carbon sodium electric negative electrode material with expanded interlayer spacing, comprising the following steps:

[0064] Step 1: pretreatment, the raw material of bamboo is cleaned with tap water, dried, then placed in a forced air drying oven, the drying temperature is 120℃, the drying time is 24h, the water is removed by drying, and the pretreated material is obtained;

[0065] Step 2: crushing, the dried bamboo (i.e. pretreated material) is crushed by roller grinding mill, the particle size D50 in the crushed particles is controlled at about 10um, and the crushed material is obtained;

[0066] Step 3: soaking, 0.05mol / L cobalt nitrate is added to the crushed material, the solid-liquid ratio of the crushed material to cobalt nitrate is 1:1.2, the material is soaked while stirring, the stirring speed is 120rpm, after soaking for 2h, it is placed in a drying oven, the drying temperature is 120℃, and the drying time is 24h, and the soaked material is obtained;

[0067] Step 4: pre-carbonization, the soaked material is placed in a nitrogen atmosphere carbonization furnace, heated to 600℃ at a heating rate of 5℃ / min under nitrogen atmosphere, and pre-carbonized for 2h, and the pre-carbonized material is obtained;

[0068] Step 5: purification, the pre-carbonized material is placed in a 2mol / L HCl aqueous solution, the solid-liquid mass ratio is 1:3, 5wt% hydroxyethylidene diphosphonic acid is added to the solution, and the acid pickling is carried out under the conditions of a temperature of 90℃ and a holding time of 12h, the filtrate is washed with deionized water for multiple times until it is close to neutral, then filtered and placed in a forced air drying oven, the drying temperature is 120℃, and the drying time is 24h, and the purified material is obtained;

[0069] Step 6: coating carbonization, the obtained purified material and phenolic resin are uniformly mixed at room temperature by a VC machine, the amount of phenolic resin is controlled to be 5wt% of the total mass of the purified material, the mixture is placed in a carbonization furnace after mixing for 2h, and high-temperature coating carbonization is carried out at a nitrogen atmosphere, the temperature is raised to 1400℃ at a heating rate of 5℃ / min, the carbonization time is 4h, after completion, the coated carbonized material is placed in a vibrating screen machine for screening, the mesh number of the vibrating screen machine is 325 meshes, and an expanded biomass hard carbon sodium electric negative electrode material is obtained after removing iron;

[0070] Step 7: The biomass hard carbon material prepared above is used as an active material for a sodium-ion battery as a negative electrode material. The preparation method is as follows:

[0071] According to a mass ratio of 2.0%:4.0%:92.0%:2.0%, CMC 0.2 g, conductive carbon black 0.4 g, hard carbon material 9.2 g, and SBR (solid content 40%) 0.5 g are weighed, and a proper amount of deionized water is added dropwise, and stirred for 20 min to form a uniform slurry. A 100-μm doctor blade is used to uniformly coat the slurry on the surface of a copper foil, and the copper foil is dried in a 105°C air drying oven for 2 h. The Cu foil with active material is cut into a circular negative electrode sheet, which is then transferred to a glove box for standby.

[0072] The assembly of the simulated battery is carried out in an Ar atmosphere glove box, the prepared biomass hard carbon electrode sheet is used as the negative electrode, 1.0 mol / L commercial electrolyte, the commercial electrolyte is prepared as follows: NaPF6 / EC:DMC V:V is 1:1, Na metal sheet is used as the counter electrode, CR2032 type button cell is assembled, and then the constant current charge and discharge mode is used for charge and discharge test at 0.1C current density, the first charge capacity is 364.11 mAh / g, the first discharge capacity is 336.76 mAh / g, and the first coulombic efficiency is 92.49%.

[0073] Example 2

[0074] A preparation method of a biomass hard carbon sodium battery negative electrode material with expanded interlayer spacing, comprising the following steps:

[0075] Step 1: Pretreatment, the raw material of the cibotium is washed clean with tap water, filtered and dried, and then placed in a blast drying oven, the drying temperature is 120°C, and the drying time is 24 h, the water is removed by drying, and the pretreated material is obtained;

[0076] Step 2: Pulverization, the dried cibotium (i.e. pretreated material) is pulverized by a roller grinding mill, the particle size D50 in the pulverized particles is controlled at about 10 um, and the pulverized material is obtained;

[0077] Step 3: Soaking, 0.05 mol / L cobalt nitrate is added to the pulverized material, the solid-liquid ratio of the pulverized material to cobalt nitrate is 1:1.2, and the soaking is carried out while stirring at a stirring speed of 120 rpm. After soaking for 2 h, the material is placed in a drying oven, the drying temperature is 120°C, and the drying time is 24 h, and the soaked material is obtained;

[0078] Step 4: Pre-carbonization, the soaked material is placed in a gas atmosphere carbonization furnace, heated to 600°C at a heating rate of 5°C / min under a nitrogen atmosphere, and pre-carbonized for 2 h to obtain a pre-carbonized material;

[0079] Step 5: purification, the pre-carbonization material is placed in a 2 mol / L HCl aqueous solution, the solid-liquid mass ratio is 1:3, 5wt% hydroxyethylidene diphosphonic acid is added to the solution, the temperature is 90℃, the holding time is 12h, the acid pickling is carried out, the filtrate is washed with deionized water for multiple times until the filtrate is close to neutral, then the material is filtered and placed in a blast drying oven, the drying temperature is 120℃, the drying time is 24h, and the purified material is obtained;

[0080] Step 6: carbonization coating, the obtained purified material is uniformly mixed with phenolic resin at room temperature by using a VC machine, the amount of phenolic resin is controlled to be 5wt% of the total mass of the purified material, the mixture is placed in a carbonization furnace after being mixed for 2h, the temperature is raised to 1400℃ at a rate of 5℃ / min under a nitrogen atmosphere, and high-temperature carbonization coating is performed for 4h, then the carbonized and coated material is placed in a vibrating screen machine for screening, the mesh number of the vibrating screen machine is 325 mesh, and a biomass hard carbon sodium electrode material with expanded interlayer spacing is obtained after iron removal;

[0081] Step 7: the biomass hard carbon material prepared in the above is used as an active material of a battery negative electrode material for a sodium ion battery. The preparation method is as follows:

[0082] According to a mass ratio of 2.0%:4.0%:92.0%:2.0%, CMC 0.2g, conductive carbon black 0.4g, hard carbon material 9.2g, and SBR (solid content 40%) 0.5g are weighed, and a proper amount of deionized water is added dropwise, and stirred for 20min to form a uniform slurry. A 100μm doctor blade is used to uniformly coat the slurry on the surface of a copper foil. The copper foil is dried in a blast drying oven at 105℃ for 2h. The Cu foil with the active material is cut into a circular negative electrode sheet, which is then transferred to a glove box for standby.

[0083] The assembly of the simulation battery is carried out in an Ar atmosphere glove box. The prepared biomass hard carbon electrode sheet is used as the negative electrode, 1.0mol / L commercial electrolyte, the commercial electrolyte is prepared as follows: NaPF6 / EC:DMC V:V is 1:1, Na metal sheet is used as the counter electrode, CR2032 type button cell is assembled, and then the constant current charge and discharge mode is used for charge and discharge test at a current density of 0.1C.

[0084] According to the above examples 1-2, it can be seen that the raw material of the preparation method of the application can be at least one of the raw materials of the bamboo and the raw materials of the bamboo.

[0085] Example 3

[0086] A preparation method of a biomass hard carbon sodium electrode material with expanded interlayer spacing, comprising the following steps:

[0087] Step 1: Pretreatment, the raw material of bamboo is cleaned with tap water, dried, and then placed in a forced air drying oven, the drying temperature is 60℃, the drying time is 6h, the water is removed by drying, and the pretreated material is obtained;

[0088] Step 2: Pulverization, the dried bamboo (i.e. pretreated material) is pulverized by roller grinding mill, the particle size D50 in the pulverized particles is controlled at about 3um, and the pulverized material is obtained;

[0089] Step 3: Soaking, iron nitrate with a concentration of 0.01mol / L is added to the pulverized material, the solid-liquid ratio of the pulverized material to the iron nitrate is 1:0.2, and the soaking is stirred at a stirring speed of 100rpm. After soaking for 0.5h, it is placed in a drying oven with a drying temperature of 80℃ and a drying time of 6h to obtain the soaked material;

[0090] Step 4: Pre-carbonization, the soaked material is placed in an atmosphere carbonization furnace, heated to 350℃ at a heating rate of 2℃ / min under argon atmosphere, and pre-carbonized for 1h to obtain the pre-carbonized material;

[0091] Step 5: Purification, the pre-carbonized material is placed in a 0.5mol / L HNO3 aqueous solution with a solid-liquid mass ratio of 1:0.7, 0.1wt% (1-hydroxyethylidene) diphosphonic acid is added to the solution, and the acid washing is carried out at a temperature of 60℃ for 6h. After washing with deionized water for multiple times until the filtrate is close to neutral, it is filtered and placed in a forced air drying oven with a drying temperature of 80℃ and a drying time of 6h to obtain the purified material;

[0092] Step 6: Coated carbonization, the purified material is mixed with phenolic resin at room temperature using a VC machine, the amount of phenolic resin is controlled at 1wt% of the total mass of the purified material, and the mixture is placed in a carbonization furnace after mixing for 0.5h. The furnace is heated to 1200℃ at a heating rate of 2℃ / min under argon atmosphere for high-temperature coated carbonization, and the carbonization time is 2h. After completion, the coated carbonized material is screened in a vibrating screen machine with a mesh size of 200 meshes to obtain a biomass hard carbon sodium electrode material with expanded interlayer spacing after iron removal;

[0093] Step 7: The biomass hard carbon material prepared above is used as an active material for the negative electrode of a sodium ion battery. The preparation method is as follows:

[0094] According to the mass ratio of 2.0%:4.0%:92.0%:2.0%, CMC 0.2g, conductive carbon black 0.4g, hard carbon material 9.2g, SBR (solid content 40%) 0.5g are weighed, and appropriate amount of deionized water is added, stirred for 20min to form a uniform slurry, and then coated on the surface of the copper foil using a 100μm doctor blade. Dry in a 105℃ forced air drying oven for 2h. Cut the Cu foil with active material into a circular negative electrode sheet, and then transfer it to a glove box for standby.

[0095] The assembly of the simulated battery was carried out in a glove box in an argon atmosphere, using the prepared biomass hard carbon pole piece as the negative electrode, 1.0 mol / L commercial electrolyte, the commercial electrolyte was prepared as follows: the V:V of NaPF6 / EC:DMC was 1:1, a piece of Na metal was used as the counter electrode, a CR2032 type button cell was assembled, and then a constant current charge and discharge mode was used to carry out charge and discharge test at a current density of 0.1C.

[0096] Example 4

[0097] A preparation method of a biomass hard carbon sodium electric negative electrode material with expanded interlayer spacing, comprising the following steps:

[0098] Step 1: pretreatment, the raw material of bamboo was cleaned with tap water, dried by filtration, and then placed in a forced air drying oven, the drying temperature was 200℃, the drying time was 48h, the water was removed by drying, and the pretreated material was obtained;

[0099] Step 2: crushing, the dried bamboo (i.e. pretreated material) was crushed by a roller grinding mill, the particle size D50 in the crushed particles was controlled at about 17um, and the crushed material was obtained;

[0100] Step 3: soaking, 0.1 mol / L nickel nitrate was added to the crushed material, the solid-liquid ratio of the crushed material to nickel nitrate was 1:2, the material was soaked while stirring, the stirring speed was 150rpm, after soaking for 3h, the material was placed in a drying oven, the drying temperature was 150℃, and the drying time was 48h, and the soaked material was obtained;

[0101] Step 4: pre-carbonization, the soaked material was placed in a gas atmosphere carbonization furnace, heated to 800℃ at a heating rate of 10℃ / min under a helium atmosphere, and pre-carbonized for 3h, and the pre-carbonized material was obtained;

[0102] Step 5: purification, the pre-carbonized material was placed in a 5mol / L HF aqueous solution, the solid-liquid mass ratio was 1:5.5, 10wt% histamine phosphate was added to the solution, the solution was acid washed under the conditions of a temperature of 120℃ and a holding time of 24h, the filtrate was washed with deionized water until it was close to neutral, then filtered and placed in a forced air drying oven, the drying temperature was 150℃, and the drying time was 48h, and the purified material was obtained;

[0103] Step 6: carbonization, the obtained purified material is mixed with phenolic resin at room temperature by VC machine, the amount of phenolic resin is controlled to be 10wt% of the total mass of the purified material, after mixing for 3h, the mixture is placed in a carbonization furnace, heated to 1800℃ at a heating rate of 10℃ / min under helium atmosphere, and high-temperature carbonization is carried out for 6h, after completion, the carbonized material is placed in a vibrating screen machine for screening, the mesh number of the vibrating screen machine is 400 meshes, and after removing iron, a biomass hard carbon sodium electrode material with expanded interlayer spacing is obtained;

[0104] Step 7: the biomass hard carbon material prepared above is used as an active material of a battery negative electrode for a sodium ion battery. The preparation method is as follows:

[0105] According to a mass ratio of 2.0%:4.0%:92.0%:2.0%, CMC 0.2g, conductive carbon black 0.4g, hard carbon material 9.2g, SBR (solid content 40%) 0.5g are weighed, and an appropriate amount of deionized water is added dropwise, stirred for 20min to form a uniform slurry, and then a 100μm doctor blade is used to uniformly coat the slurry on the surface of a copper foil, and the copper foil is dried in a 105℃ air drying oven for 2h. The Cu foil with active material is cut into a circular negative electrode sheet, which is then transferred to a glove box for standby.

[0106] The assembly of the simulation battery is carried out in an Ar atmosphere glove box, the prepared biomass hard carbon electrode sheet is used as the negative electrode, 1.0mol / L commercial electrolyte, the commercial electrolyte is prepared as follows: NaPF6 / EC:DMC V:V is 1:1, Na metal sheet is used as the counter electrode, CR2032 type button cell is assembled, and then constant current charge and discharge mode is used for charge and discharge test at 0.1C current density.

[0107] Comparative Example 1

[0108] A biomass hard carbon sodium electrode material, comprising the following steps:

[0109] Step 1: pretreatment, the raw material of bamboo is cleaned with tap water, filtered and dried, and then placed in a forced air drying oven, the drying temperature is 120℃, and the drying time is 24h, the water is removed by drying, and a pretreated material is obtained;

[0110] Step 2: crushing, the dried bamboo (i.e. pretreated material) is crushed by a roller grinding mill, and the particle size D50 in the crushed particles is controlled to be about 10um, and a crushed material is obtained;

[0111] Step 3: pre-carbonization, the crushed material is placed in a gas atmosphere carbonization furnace, heated to 600℃ at a heating rate of 5℃ / min under nitrogen atmosphere, and pre-carbonized for 2h, and a pre-carbonized material is obtained;

[0112] Step 4: purification, the pre-carbonization material is placed in a 2 mol / L HCl aqueous solution, the solid-liquid mass ratio is 1:3, 5% wt of hydroxyethylidene diphosphonic acid is added to the solution, the temperature is 90℃, the holding time is 12h, the acid pickling is carried out under the condition, the filtrate is washed with deionized water for multiple times until it is close to neutral, then it is filtered and placed in a blast drying oven, the drying temperature is 120℃, the drying time is 24h, and the purified material is obtained.

[0113] Step 5: carbonization, the obtained purified material is uniformly mixed with phenolic resin at room temperature by using a VC machine, the amount of phenolic resin is controlled to be 5% wt of the total mass of the purified material, after mixing for 2h, the material is placed in a carbonization furnace, the temperature is raised to 1400℃ at a rate of 5℃ / min under a nitrogen atmosphere, and high-temperature carbonization is carried out for 4h, after completion, the carbonized material is placed in a vibrating screen machine for screening, the mesh number of the vibrating screen machine is 325 mesh, and a biomass hard carbon sodium negative electrode material is obtained after removing iron;

[0114] Step 6: the biomass hard carbon material prepared above is used as an active material of a battery negative electrode for a sodium ion battery. The preparation method is as follows:

[0115] According to a mass ratio of 2.0%:4.0%:92.0%:2.0%, CMC 0.2g, conductive carbon black 0.4g, hard carbon material 9.2g, and SBR (solid content 40%) 0.5g are weighed, and an appropriate amount of deionized water is added dropwise, stirred for 20min to form a uniform slurry, and a 100μm doctor blade is used to uniformly coat the surface of the copper foil in a 105℃ blast drying oven for 2h. The Cu foil with active material is cut into a circular negative electrode sheet, which is then transferred to a glove box for standby.

[0116] The assembly of the simulation battery is carried out in an Ar atmosphere glove box, the prepared biomass hard carbon electrode sheet is used as the negative electrode, 1.0mol / L commercial electrolyte, the commercial electrolyte is prepared as follows: NaPF6 / EC:DMC V:V is 1:1, Na metal sheet is used as the counter electrode, CR2032 type button cell is assembled, and then the constant current charge and discharge mode is used for charge and discharge test at 0.1C current density.

[0117] Comparative Example 2

[0118] A biomass hard carbon sodium negative electrode material, comprising the following steps:

[0119] Step 1: pretreatment, the raw material of bamboo is cleaned with tap water, filtered and dried, then placed in a blast drying oven, the drying temperature is 120℃, the drying time is 24h, and the water is removed by drying to obtain a pretreated material;

[0120] Step 2: Pulverization, the dried bamboo (i.e. pretreated material) is pulverized by a roller mill, and the particle size D50 in the pulverized particles is controlled at about 10 um, to obtain a pulverized material;

[0121] Step 3: Soaking, 0.05 mol / L cobalt nitrate is added to the pulverized material, the solid-liquid ratio of the pulverized material to cobalt nitrate is 1:1.2, and the soaking is carried out while stirring at a stirring speed of 120 rpm. After soaking for 2 h, the material is placed in a drying oven at a drying temperature of 120℃ for 24 h to obtain a soaked material.

[0122] Step 4: Pre-carbonization, the soaked material is placed in a gas atmosphere carbonization furnace, heated to 600℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, and pre-carbonized for 2 h to obtain a pre-carbonized material.

[0123] Step 5: Purification, the pre-carbonized material is placed in a 2 mol / L HCl aqueous solution with a solid-liquid mass ratio of 1:3, and acid washing is carried out at a temperature of 90℃ for 12 h. The material is washed with deionized water multiple times until the filtrate is nearly neutral, then filtered and placed in a forced air drying oven at a drying temperature of 120℃ for 24 h to obtain a purified material.

[0124] Step 6: Coated carbonization, the purified material is mixed with phenolic resin at room temperature using a VC machine, and the amount of phenolic resin is controlled at 5wt% of the total mass of the purified material. After mixing for 2 h, the mixture is placed in a carbonization furnace under a nitrogen atmosphere, heated to 1400℃ at a heating rate of 5℃ / min for high-temperature coated carbonization, and carbonized for 4 h. After completion, the coated carbonized material is screened in a vibrating screen machine with a mesh size of 325 mesh to obtain a biomass hard carbon sodium negative electrode material after iron removal.

[0125] Step 7: The biomass hard carbon material prepared above is used as an active material for a sodium ion battery as a battery negative electrode material. The preparation method is as follows:

[0126] According to a mass ratio of 2.0%:4.0%:92.0%:2.0%, CMC 0.2g, conductive carbon black 0.4g, hard carbon material 9.2g, and SBR (solid content 40%) 0.5g are weighed, and an appropriate amount of deionized water is added, stirred for 20 min to form a uniform slurry, and then coated on the surface of a copper foil using a 100 um doctor blade. The coated copper foil is dried in a 105℃ air drying oven for 2 h, and then cut into a circular negative electrode sheet and transferred to a glove box for standby.

[0127] The assembly of the simulation battery was carried out in an Ar atmosphere glove box, using the prepared biomass hard carbon pole piece as the negative electrode, 1.0 mol / L commercial electrolyte, the commercial electrolyte was prepared as follows: the V:V of NaPF6 / EC:DMC was 1:1, Na metal sheet as the counter electrode, assemble CR2032 type button cell, and then use constant current charge and discharge mode, at 0.1C current density, charge and discharge test.

[0128] Comparative example 3

[0129] A biomass hard carbon sodium electric negative electrode material, comprising the following steps:

[0130] Step 1: pretreatment, the raw material of moso bamboo is cleaned with tap water, filtered and dried, then placed in a forced air drying oven, the drying temperature is 120℃, the drying time is 24h, the water is removed by drying, and the pretreated material is obtained;

[0131] Step 2: crushing, the dried moso bamboo (i.e. pretreated material) is crushed with a ring roller mill, the particle size D50 in the crushed particles is controlled at about 10um, and the crushed material is obtained;

[0132] Step 3: purification, the crushed material is placed in a 2mol / L HCl aqueous solution, the solid-liquid mass ratio is 1:3, the temperature is 90℃, the holding time is 12h, and the acid pickling is carried out, then washed with deionized water for several times until the filtrate is close to neutral, then filtered and placed in a forced air drying oven, the drying temperature is 120℃, the drying time is 24h, and the purified material is obtained;

[0133] Step 4: coating and carbonization, the obtained purified material is mixed with phenolic resin at room temperature by VC machine, the amount of phenolic resin is controlled to be 5wt% of the total mass of the purified material, after mixing for 2h, it is placed in a carbonization furnace, heated to 1400℃ at a heating rate of 5℃ / min under nitrogen atmosphere for high-temperature coating and carbonization, the carbonization time is 4h, after completion, the coated and carbonized material is placed in a vibrating screen machine for screening, the mesh number of the vibrating screen machine is 325 mesh, and an biomass hard carbon sodium electric negative electrode material is obtained after removing iron.

[0134] Step 5: the biomass hard carbon material prepared above is used as the active substance of the battery negative electrode material for sodium ion battery. The preparation method is as follows:

[0135] According to the mass ratio of 2.0%:4.0%:92.0%:2.0%, CMC 0.2g, conductive carbon black 0.4g, hard carbon material 9.2g, SBR (solid content 40%) 0.5g are weighed, and appropriate amount of deionized water is added, stirred for 20min to form a uniform slurry, and then a 100μm doctor blade is used to uniformly coat the surface of the copper foil, and then dried in a 105℃ air drying oven for 2h. The Cu foil with active material is cut into a circular negative electrode pole piece, and then transferred to a glove box for standby.

[0136] The assembly of the simulated battery was carried out in a glove box in an argon atmosphere, using the prepared biomass pole piece as the negative electrode, 1.0 mol / L commercial electrolyte, the commercial electrolyte was prepared as follows: the V:V of NaPF6 / EC:DMC was 1:1, a Na metal piece was used as the counter electrode, a CR2032 type button cell was assembled, and then a constant current charge-discharge mode was used to carry out charge-discharge test at a current density of 0.1C.

[0137] The seven biomass hard carbon negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to TEM test and assembled into sodium ion button cells for electrochemical performance test, and the test results are shown in Table 1, combined with Figs. 1-6 .

[0138] Table 1 Electrochemical performance of sodium ion battery

[0139]

[0140] As can be seen from Table 1, the interlayer spacing of the biomass hard carbon negative electrode material obtained by Examples 1-4 is greater than that of Comparative Examples 1-3, and the interlayer spacing of Examples 1-4 can reach 1.1 times that of Comparative Examples 1-3; the initial efficiency, the initial efficiency of Examples 1-4 and Comparative Examples 1-3 can differ by 5.55%. Therefore, the biomass hard carbon sodium battery negative electrode material has high initial discharge specific capacity, initial charge specific capacity and initial efficiency.

[0141] Referring to Fig. 1 , the XRD patterns of the biomass hard carbon negative electrode materials of Example 1 and Comparative Examples 1-3 were compared, the peak positions of Comparative Examples 1-3 and Example 1 were the same, the intensities were different, the intensity of Example 1 was higher, and the crystal form was better.

[0142] Referring to Fig. 6 , the charge-discharge curves of the biomass hard carbon negative electrode materials of Example 1 and Comparative Example 1 under the condition of 0.1C were compared, and it can be directly seen that the charge-discharge capacity of Example 1 is better.

[0143] The raw materials of Example 1 and Example 2 are different, the interlayer spacing of Example 1 is greater than that of Example 2, and the initial efficiency of Example 2 is slightly higher. It is shown that according to actual needs, the raw materials of Phyllostachys pubescens / Phyllostachys nigra can be selected in combination with the preparation method of the present application.

[0144] Comparing Example 1 and Examples 3-4, the interlayer spacing of Example 4 is larger, and the initial efficiency of Example 3 is higher, which shows that according to actual needs, the parameter conditions can be selected in Examples 1 and Examples 3-4 in combination with the preparation method of the present application.

[0145] Comparative Example 1 does not contain the soaking step, Comparative Example 2 changes the purification conditions, and no additive is added; Comparative Example 3 does not contain soaking, pre-carbonization, and no additive is added in the purification. It is found that the interlayer spacing of Comparative Example 3 is the smallest, and the first discharge specific capacity and the first charge specific capacity are the lowest, and the first efficiency of Comparative Example 1 is the lowest.

[0146] This is mainly because in Examples 1-4, the biomass crushed material is first soaked with nitrate, and in the pre-carbonization process, in addition to the cross-linking rearrangement of the biomass raw material itself, the nitrate is incorporated into the precursor to expand the interlayer spacing and form pores of about 500 nm when decomposed, so that the acid washing purification can more fully react with the inorganic components to reduce the ash content, and the additive added during purification can be incorporated into the pores formed during pre-carbonization, so that during high-temperature carbonization, on the one hand, the specific surface area can be reduced, and on the other hand, the residual nitrate groups can produce a synergistic effect with the phosphate additive added during purification, further expanding the interlayer spacing, and ultimately improving the first coulombic efficiency and charge-discharge capacity.

[0147] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a biomass hard carbon sodium anode material with expanded interlayer spacing, characterized in that, Includes the following steps, Pretreatment: The biomass raw material is washed and dried to obtain pretreated feed. Crushing: The pretreated material is crushed to obtain crushed material; Soaking: The pulverized material is added to a nitrate solution for soaking while stirring. After soaking, it is dried to obtain the soaked material; wherein the concentration of the nitrate solution is 0.01-0.1 mol / L. Pre-carbonization: The soaked material is pre-carbonized under a protective atmosphere to obtain pre-carbonized material; wherein, the pre-carbonization temperature is 350-800℃; Purification: Additives are added to the pre-carbonized material, followed by acid washing, water washing and deashing, and finally filtration and drying to obtain purified material; the additives include at least one of hydroxyethylidene diphosphonic acid and histamine phosphate; Coating carbonization: The purified raw material is mixed evenly with the modifier, and then coated carbonization is carried out at high temperature under a protective atmosphere. After iron removal by sieving, a biomass hard carbon sodium electrode material with expanded interlayer spacing is obtained; wherein, the high temperature carbonization temperature is 1200~1800℃.

2. The method for preparing the biomass hard carbon sodium anode material with increased interlayer spacing according to claim 1, characterized in that, In the pretreatment, the biomass raw material includes at least one of moso bamboo and green bamboo. The biomass raw material is first washed with tap water and then placed in a forced-air drying oven for drying. The drying temperature of the forced-air drying oven is 60-200℃ and the drying time is 6-48h.

3. The method for preparing the biomass hard carbon sodium anode material with increased interlayer spacing according to claim 1, characterized in that, In the pulverization process, the pulverizing equipment used is at least one of a mechanical pulverizer, a roller mill, or an air jet mill, and the particle size of the pulverized material is controlled between 3 and 17 μm.

4. The method for preparing the biomass hard carbon sodium anode material with increased interlayer spacing according to claim 1, characterized in that, In the soaking process, the pulverized material is added to a nitrate solution for soaking for 0.5h to 3h, with a solid-liquid ratio of 1:0.2 to 2. The material is stirred during soaking at a speed of 100 to 150 rpm. After soaking, the material is placed in a forced-air drying oven at a drying temperature of 80 to 150℃ for 6 to 48h to obtain the soaked material. The nitrate solution includes at least one of cobalt nitrate, ferric nitrate, and nickel nitrate.

5. The method for preparing the biomass hard carbon sodium anode material with increased interlayer spacing according to claim 1, characterized in that, In the pre-carbonization, the protective atmosphere includes at least one of nitrogen, argon, and helium. The pre-carbonization conditions include a heating rate of 2 to 10 °C / min and a holding time of 1 to 3 h. The pre-carbonization is carried out in an atmosphere carbonization furnace.

6. The method for preparing the biomass hard carbon sodium anode material with increased interlayer spacing according to claim 1, characterized in that, In the purification process, the additive accounts for 0.1-10% wt% of the total mass of the pre-carbonized material; the acid used for pickling includes at least one of hydrochloric acid, nitric acid, hydrofluoric acid, and sulfuric acid; the concentration of the acid during pickling is 0.5-5 mol / L; the reaction temperature for pickling is 60-120℃; the solid-liquid mass ratio for pickling is 1:0.7-5.5; and the pickling time is 6-24 h. The specific process of water washing and deashing includes washing with deionized water multiple times until the filtrate is close to neutral, then filtration, drying at a temperature of 80-150℃, and drying time of 6-48 hours.

7. The method for preparing the biomass hard carbon sodium anode material with increased interlayer spacing according to claim 1, characterized in that, In the coating carbonization process, the modifier includes at least one of asphalt and resin; the mass of the modifier accounts for 1 to 10% wt% of the mass of the purified material. The mixing time is 0.5 to 3 hours; the conditions for high-temperature carbonization include: a heating rate of 2 to 10 °C / min, a holding time of 2 to 6 hours, and high-temperature carbonization is carried out in an atmosphere carbonization furnace; the protective atmosphere for coating carbonization includes at least one of nitrogen, argon, and helium; the mesh size of the vibrating sieve used for sieving is 200 to 400 mesh.

8. A biomass hard carbon sodium electrode anode material with increased interlayer spacing, characterized in that, It is prepared according to the method for preparing biomass hard carbon sodium anode material with increased interlayer spacing according to any one of claims 1 to 7.

9. A negative electrode sheet, characterized in that, The negative electrode sheet uses the biomass hard carbon sodium electrode material with expanded interlayer spacing as described in claim 8 as the active material of the battery negative electrode material.

10. A battery, characterized in that, This battery is a sodium-ion battery, which includes a negative electrode, a positive electrode, a separator, and an electrolyte. The negative electrode includes the negative electrode sheet of claim 9. The battery is tested for charge and discharge at a current density of 0.1C. The interlayer spacing of the sodium-ion battery is 0.411~0.420nm, the initial charge specific capacity is 320~340mAh / g, the initial discharge specific capacity is 350~380 mAh / g, and the initial efficiency is 90~95%.

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