A sodium ion battery hard carbon material and preparation method thereof and a sodium ion battery using the hard material

Abstract

The present invention discloses a sodium ion battery hard carbon material, a preparation method thereof, and a sodium ion battery using the hard carbon material. The hard carbon material is a composite porous material inlaid with hollow porous spheres and porous carbon sheets. Compared with the prior art, the advantages of the present invention are: a method for preparing sodium ion hard carbon materials from concentrated papermaking black liquor in a short process using spray pyrolysis, using spray pyrolysis to construct a precursor material with a hollow porous spherical structure; using an aqueous solution to collect the precursor material, and removing impurities through solid-liquid separation and washing; and then further regulating the microstructure of the carbon material through two-stage heat treatment to obtain a hard carbon negative electrode material with high specific capacity, excellent rate performance, and cycle stability. Using the hard carbon material as the negative electrode, a high-energy-density sodium ion battery is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ions and battery materials thereof, and in particular to a sodium ion battery hard carbon material and a preparation method thereof, and a sodium ion battery using the hard material. Background Art

[0002] Sodium-ion batteries are a type of green and environmentally friendly battery with electrical properties closest to those of lithium-ion batteries. In addition to having the characteristics of high operating voltage, high specific energy and long cycle life, they also have the advantages of abundant resources, good low-temperature performance, over-discharge resistance and low cost. They have great potential in large-scale energy storage and have developed rapidly in recent years. Hard carbon negative electrode materials are key materials for sodium-ion batteries. Their microstructure and morphology, pore structure and pore size distribution significantly affect their performance. Common precursors for preparing hard carbon materials include biomass, synthetic polymers and fossil fuels.

[0003] Lignin is second only to cellulose in content in the plant kingdom. It is a natural macromolecular organic compound with abundant resources. It has a unique and complex aromatic and aliphatic main chain structure and functional groups suitable for functionalization. After treatment, it can become an important chemical raw material and energy material. Papermaking black liquor is a dark brown wastewater containing a large amount of lignin produced by the alkaline pulping process. It also contains some hemicellulose, residual alkali, etc. Black liquor concentrates almost 90% of the pollutants discharged by papermaking. Direct discharge into water bodies will cause serious pollution.

[0004] Spray pyrolysis is a new technology for preparing solid particulate materials in a short process, in which a solution is atomized into tiny droplets through a spray device, and the droplets are rapidly evaporated and the solute is thermally decomposed under high temperature.

[0005] This project aims to efficiently utilize high-molecular organic matter such as lignin and hemicellulose in papermaking black liquor, directly prepare high-performance hard carbon negative electrode materials through spray pyrolysis, realize short-process and high-value application of papermaking black liquor, and use this hard carbon material as the negative electrode to prepare high-energy density sodium ion batteries. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a sodium ion battery hard carbon material and a preparation method thereof, and a sodium ion battery using the hard material, in response to the above-mentioned technical summary of the problems of sodium ion battery hard carbon material and papermaking black liquor treatment.

[0007] In order to solve the above technical problems, the present invention provides a technical solution: a hard carbon material for sodium ion batteries, wherein the hard carbon material is a composite porous material inlaid with hollow porous balls and porous carbon sheets, wherein the diameter of the hard carbon microspheres is about 0.3-3 μm, the wall thickness is about 30-100 nm, and the (002) crystal plane interlayer spacing (d 002 ) is 0.36-0.38nm, and the average thickness along the c-axis direction (Lc ) is 0.6-0.75nm, and the average width along the a-axis (L a ) is 11-14nm.

[0008] The preparation method of sodium ion battery hard carbon material is to obtain sodium ion hard carbon negative electrode material by spray pyrolysis and high temperature heat treatment of papermaking black liquor. The specific steps include:

[0009] Step 1: Preparation of precursor materials by spray pyrolysis. Papermaking black liquor is atomized, and an inert gas is used as a carrier gas. The atomized droplets and the inert gas enter a protective atmosphere furnace, where they undergo high-temperature pyrolysis. After the spray pyrolysis is complete, the collected carbon material is washed and dried to obtain the precursor material.

[0010] Step 2: High-temperature heat treatment to adjust composition and microstructure. The precursor material prepared above is placed in a protective atmosphere furnace for high-temperature heat treatment, and then cooled to obtain a hard carbon negative electrode material.

[0011] As an improvement, the total dissolved solids (including lignin, hemicellulose and their derivatives, sodium salts, residual alkali, etc.) in the papermaking black liquor is 50-600 g / L, the total carbon content (TOC) is 10-100 g / L, and the hydroxide (OH) - ) content is 2-30g / L, and the sodium (Na) content is 10-100g / L.

[0012] As an improvement, the precursor material has a spherical porous structure, and some carbon spheres are collapsed, which is a porous spherical material rich in mesoporous structure.

[0013] As an improvement, the water partial pressure in the atmosphere protection furnace in step 1 is 0.1-0.5 atm.

[0014] As an improvement, in the step 1, the temperature of the papermaking black liquor during atomization is 40-70°C, the atomization method includes ultrasonic atomization and centrifugal atomization, and the high-temperature pyrolysis temperature is 550-750°C.

[0015] As an improvement, the high temperature heat treatment in step 2 includes two stages of heat treatment, namely, first heating to 450-600°C at 5-20°C / min and keeping the temperature constant for 1-12 hours, then heating to 1300-1600°C at 1-5°C / min and keeping the temperature constant for 1-12 hours.

[0016] As an improvement, preferably, one or more of polyaziridine, ethylenediamine, and diethylenetriamine are added to the papermaking black liquor in step 1. A nitrogen-doped spherical porous structure precursor material and a composite porous material comprising nitrogen-doped hollow porous spheres embedded in porous carbon sheets are prepared. The nitrogen atoms in the precursor and hard carbon material range from 0.1 to 0.5 wt%.

[0017] A sodium ion battery using a hard carbon material is prepared. The hard carbon material is used as the negative electrode material, a high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide is used as the positive electrode material, the electrolyte is a 1-1.3 mol / LNaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution (volume ratio is x:1-x, where x=0.15-0.35) and 0.5%-3% propylene sulfite (PS) and 1%-5% fluoroethylene carbonate (FEC) additives are added. The prepared high-voltage soft-pack sodium ion battery can be charged and discharged between 1.5V and 4.15V, and has an energy density of 160-180Wh / kg.

[0018] After adopting the above structure, the present invention has the following advantages:

[0019] (1) Spray pyrolysis is used to prepare sodium ion hard carbon materials from concentrated papermaking black liquor in a short process, which can be used as negative electrode materials for sodium ion batteries, thus realizing the short process and high value utilization of papermaking black liquor.

[0020] (2) Spray pyrolysis was used to construct a precursor material with a hollow porous spherical structure. The resulting precursor had a spherical porous structure, with some carbon spheres in a collapsed state, indicating a porous spherical material rich in mesoporous structure.

[0021] (3) The solid material and tail gas after pyrolysis are introduced into a collector containing a dilute sodium hydroxide solution, thereby achieving the purposes of sealing the atmosphere protection furnace, collecting the porous carbon material, absorbing and treating the pyrolysis tail gas, and removing soluble impurities.

[0022] (4) The precursor material with a hollow porous spherical structure is subjected to two-stage heat treatment to further regulate the microstructure of the carbon material. The low-temperature heat treatment makes the precursor material more completely pyrolyzed and stabilizes the morphology and pore structure of the precursor material; the high-temperature heat treatment further regulates the crystal structure and functional groups of the material to obtain a high-performance hard carbon negative electrode material.

[0023] (5) In combination with the characteristics of the reaction system, nitrogen-containing compounds such as polyaziridine, ethylenediamine, and diethylenetriamine were added to the papermaking black liquor to obtain in situ nitrogen-doped spherical porous structure precursor materials with uniform molecular distribution and composite porous materials inlaid with nitrogen-doped hollow porous spheres and porous carbon sheets, which significantly improved the electrochemical properties of hard carbon materials.

[0024] (6) The hard carbon material of the present invention is used as the negative electrode material, the high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide is used as the positive electrode material, the electrolyte is a PC / EMC solution of NaPF6 and PS and FEC additives are added, and the prepared high-voltage soft-pack sodium ion battery has a high energy density (160-180Wh / kg). BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a SEM image of the pyrolyzed hard carbon material of the present invention;

[0026] Figure 2 is a SEM image of the pyrolyzed hard carbon material of the present invention;

[0027] Figure 3 is a TEM image of the pyrolyzed hard carbon material of the present invention;

[0028] Figure 4 is a TEM image of the pyrolyzed hard carbon material of the present invention;

[0029] Figure 5 This is a charge and discharge curve diagram of the sodium ion battery using pyrolysis hard carbon material in the present invention. DETAILED DESCRIPTION

[0030] The present invention will be described in further detail below with reference to the accompanying drawings.

[0031] Combined with attachment Figure 1-5 A hard carbon material for sodium ion batteries, wherein the hard carbon material is a composite porous material inlaid with hollow porous balls and porous carbon sheets, wherein the diameter of the hard carbon microspheres is about 0.3-3 μm, the wall thickness is about 30-100 nm, and the (002) crystal plane interlayer spacing (d 002 ) is 0.36-0.38nm, and the average thickness along the c-axis direction (L c ) is 0.6-0.75nm, and the average width along the a-axis (L a ) is 11-14nm.

[0032] The sodium ion hard carbon negative electrode material is obtained by spray pyrolysis and high-temperature heat treatment of papermaking black liquor. The specific steps include:

[0033] Step 1: Preparation of precursor material by spray pyrolysis. Papermaking black liquor is atomized, and an inert gas is used as a carrier gas. The atomized droplets and the inert gas enter an atmosphere protection furnace, where they undergo high-temperature pyrolysis. After the spray pyrolysis is completed, the collected carbon material is washed and dried to obtain the precursor material.

[0034] Step 2: High-temperature heat treatment to adjust composition and microstructure. The precursor material prepared above is placed in a protective atmosphere furnace for high-temperature heat treatment, and then cooled to obtain a hard carbon negative electrode material.

[0035] The total dissolved solids (including lignin, hemicellulose and their derivatives, sodium salts, residual alkali, etc.) in the papermaking black liquor are 50-600 g / L, the total carbon content (TOC) is 10-100 g / L, and the hydroxide (OH) -) content is 2-30g / L, and the sodium (Na) content is 10-100g / L. The precursor material has a spherical porous structure, and some carbon balls are collapsed. It is a porous spherical material rich in mesoporous structure. The water partial pressure in the atmosphere protection furnace in the step one is 0.1-0.5atm. The temperature of the papermaking black liquor during atomization in the step one is 40-70°C, and the atomization method includes ultrasonic atomization and centrifugal atomization. The high-temperature pyrolysis temperature is 550-750°C. The high-temperature heat treatment in the step two includes two-stage heat treatment, namely, first heating to 450-600°C at 5-20°C / min and keeping the temperature constant for 1-12h, and then heating to 1300-1600°C at 1-5°C / min and keeping the temperature constant for 1-12h. Preferably, one or more of polyaziridine, ethylenediamine, and diethylenetriamine are added to the papermaking black liquor in step one. A nitrogen-doped spherical porous structure precursor material and a composite porous material inlaid with nitrogen-doped hollow porous spheres and porous carbon sheets are prepared. The nitrogen atoms in the precursor and the hard carbon material account for 0.1 to 0.5 wt%.

[0036] The hard carbon material is used as the negative electrode material, a high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide is used as the positive electrode material, the electrolyte is a 1-1.3 mol / LNaPF6 propylene carbonate (PC) / ethyl methyl carbonate (EMC) solution (volume ratio is x:1-x, where x=0.15-0.35) and 0.5%-3% propylene sulfite (PS) and 1%-5% fluoroethylene carbonate (FEC) additives are added to prepare a high-voltage soft-pack sodium ion battery that can be charged and discharged between 1.5V and 4.15V, with an energy density of 160-180Wh / kg.

[0037] Specific Example 1: Preparation of Hollow Porous Spheres by Spray Pyrolysis Precursor: Papermaking Black Liquor (Total Dissolved Solids 60 g / L, TOC 10 g / L, OH - 5g / L, Na10g / L) were heated to 40℃ and then ultrasonically atomized. Nitrogen was used as carrier gas. The atomized droplets and nitrogen (3L / min) were sent into the atmosphere protection furnace. H2O =0.4atm) at 700 ° C., and the obtained carbon material and tail gas are introduced into a collector filled with a dilute sodium hydroxide solution. After the spray pyrolysis is completed, it is filtered, washed, and dried to obtain a precursor material.

[0038] High-temperature heat treatment to regulate the microstructure: the porous spherical precursor material prepared above was placed in a nitrogen protective atmosphere furnace, first heated to 500°C at a rate of 10°C / min, kept constant at this temperature for 2 hours, then heated to 1400°C at a rate of 5°C / min, kept constant at this temperature for 2 hours, and then cooled with the furnace to obtain a hard carbon negative electrode material inlaid with hollow porous spheres and porous carbon sheets.

[0039] The obtained hard carbon material is a composite porous material inlaid with hollow porous balls and porous carbon sheets. The diameter of the hard carbon microspheres is about 0.3-2 μm, the wall thickness is about 30-100 nm, and the interlayer spacing d is about 0. 002 The average thickness along the c-axis is L c The average width L along the a-axis is 0.72nm. a The resulting hard carbon negative electrode material was used as the active material to make an electrode, which was then assembled with a metal lithium sheet, a separator, and an electrolyte into a button cell. Charge and discharge at a current density of 0.1C (30mA / g) between 0-1.5V resulted in a reversible capacity of 342mAh / g, and after 300 cycles at 0.5C (150mA / g), the capacity retention rate was 97.5%.

[0040] The hard carbon material prepared in this example was used as the negative electrode material, a high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide was used as the positive electrode material, the electrolyte was a 1 mol / L NaPF6 PC / EMC (volume ratio of x:1-x, where x=0.3) solution and 1% PS and 3% FEC additives were added. The prepared soft-pack sodium ion battery was charged and discharged between 1.5 V and 4.15 V, with an energy density of 165 Wh / kg.

[0041] Specific Example 2: Preparation of Hollow Porous Spheres by Spray Pyrolysis Precursor: Papermaking Black Liquor (Total Dissolved Solids 120 g / L, TOC 21 g / L, OH - 5.5g / L, Na20g / L) were heated to 50℃ and then ultrasonically atomized. Nitrogen was used as the carrier gas. The atomized droplets and nitrogen (5L / min) were sent into the atmosphere protection furnace together. H2O =0.2atm) at 550 ° C., and the obtained carbon material and tail gas are introduced into a collector filled with a dilute sodium hydroxide solution. After the spray pyrolysis is completed, it is filtered, washed, and dried to obtain a precursor material.

[0042] High-temperature heat treatment to regulate the microstructure: the porous spherical precursor material prepared above was placed in a nitrogen protective atmosphere furnace, first heated to 450°C at a rate of 20°C / min, kept constant at this temperature for 12 hours, then heated to 1300°C at a rate of 5°C / min, kept constant at this temperature for 12 hours, and then cooled with the furnace to obtain a hard carbon negative electrode material inlaid with hollow porous spheres and porous carbon sheets.

[0043] The obtained hard carbon material is a composite porous material inlaid with hollow porous balls and porous carbon sheets. The diameter of the phenolic resin-based hard carbon microspheres is about 0.3-3 μm, the wall thickness is about 30-100 nm, and the interlayer spacing d is about 0. 002 The average thickness along the c-axis is L c The average width L along the a-axis is 0.61 nm.a The resulting hard carbon negative electrode material was used as the active material to make an electrode, which was then assembled with a metal lithium sheet, a separator, and an electrolyte into a button cell. Charge and discharge at a current density of 0.1C (30mA / g) between 0-1.5V resulted in a reversible capacity of 342mAh / g, and after 300 cycles at 0.5C (150mA / g), the capacity retention rate was 98.1%.

[0044] The hard carbon material prepared in this example was used as the negative electrode material, a high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide was used as the positive electrode material, the electrolyte was a 1.3 mol / L NaPF6 PC / EMC (volume ratio of x:1-x, where x = 0.35) solution, and 0.5% PS and 5% FEC additives were added. The prepared soft-pack sodium ion battery was charged and discharged between 1.5 V and 4.15 V, with an energy density of 162 Wh / kg.

[0045] Specific Example 3: Preparation of Hollow Porous Spheres by Spray Pyrolysis Precursor: Papermaking Black Liquor (Total Dissolved Solids 595 g / L, TOC 98 g / L, OH - 29g / L, Na98g / L) were heated to 65℃ and centrifugally atomized. Nitrogen was used as carrier gas. The atomized droplets and nitrogen (10L / min) were fed into the atmosphere protection furnace. H2O =0.1atm) at 750 ° C., and the obtained carbon material and tail gas are introduced into a collector filled with a dilute sodium hydroxide solution. After the spray pyrolysis is completed, it is filtered, washed, and dried to obtain a precursor material.

[0046] High-temperature heat treatment to regulate the microstructure: the porous spherical precursor material prepared above was placed in a nitrogen protective atmosphere furnace, first heated to 500°C at 20°C / min, kept constant at this temperature for 2 hours, then heated to 1400°C at 1°C / min, kept constant at this temperature for 2 hours, and then cooled with the furnace to obtain a hard carbon negative electrode material inlaid with hollow porous spheres and porous carbon sheets.

[0047] The obtained hard carbon material is a composite porous material inlaid with hollow porous spheres and porous carbon sheets. The diameter of the hard carbon microspheres is about 0.5-3 μm, the wall thickness is about 30-100 nm, and the interlayer spacing d is 0. 002 The average thickness along the c-axis is L c The average width L along the a-axis is 0.75 nm. a The resulting hard carbon negative electrode material was used as the active material to make an electrode, which was then assembled with a metal lithium sheet, a separator, and an electrolyte into a button cell. Charge and discharge at a current density of 0.1C (30mA / g) between 0-1.5V resulted in a reversible capacity of 348mAh / g, and after 300 cycles at 0.5C (150mA / g), the capacity retention rate was 98.0%.

[0048] The hard carbon material prepared in this example was used as the negative electrode material, a high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide was used as the positive electrode material, the electrolyte was a 1.2 mol / L NaPF6 PC / EMC (volume ratio of x:1-x, where x = 0.15) solution, and 3% PS and 1% FEC additives were added. The prepared soft-pack sodium ion battery was charged and discharged between 1.5 V and 4.15 V, with an energy density of 167 Wh / kg.

[0049] Specific Example 4: Preparation of Hollow Porous Ball Precursor by Spray Pyrolysis: In papermaking black liquor (total dissolved solids 120 g / L, TOC 21 g / L, OH - 5.5g / L, Na20g / L) was added with 2% polyaziridine, heated to 70℃ and then ultrasonically atomized, with nitrogen as carrier gas, the atomized droplets and nitrogen (3L / min) were sent into the atmosphere protection furnace together, and the atmosphere protection furnace (p H2O =0.4atm) at 650 ° C., and the obtained carbon material and tail gas are introduced into a collector filled with a dilute sodium hydroxide solution. After the spray pyrolysis is completed, it is filtered, washed, and dried to obtain a nitrogen-doped precursor material.

[0050] High-temperature heat treatment to regulate the microstructure: the porous spherical precursor material prepared above was placed in a nitrogen-protected atmosphere furnace, first heated to 500°C at a rate of 20°C / min, kept constant at that temperature for 3 hours, then heated to 1400°C at a rate of 2°C / min, kept constant at that temperature for 2 hours, and then cooled with the furnace to obtain a nitrogen-doped hard carbon negative electrode material inlaid with hollow porous spheres and porous carbon sheets.

[0051] The obtained hard carbon material is a composite porous material inlaid with hollow porous balls and porous carbon sheets. The diameter of the hard carbon microspheres is about 0.3-3 μm, the wall thickness is about 30-100 nm, and the interlayer spacing d is about 0. 002 The average thickness along the c-axis is L c The average width L along the a-axis is 0.71 nm. a The resulting hard carbon negative electrode material was used as the active material to make an electrode, which was then assembled with a metal lithium sheet, a separator, and an electrolyte into a button cell. Charge and discharge at a current density of 0.1C (30mA / g) between 0-1.5V resulted in a reversible capacity of 380mAh / g, and after 300 cycles at 0.5C (150mA / g), the capacity retention rate was 97.6%.

[0052] The hard carbon material prepared in this example is used as the negative electrode material, the high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide is used as the positive electrode material, the electrolyte is a 1.1 mol / LNaPF6 PC / EMC (volume ratio of x:1-x, where x=0.25) solution and 1.5% PS and 2% FEC additives are added. The prepared soft-pack sodium ion battery is charged and discharged between 1.5V and 4.15V, and the energy density is 180Wh / kg.

[0053] Specific Example 5: Preparation of Hollow Porous Ball Precursor by Spray Pyrolysis: In papermaking black liquor (total dissolved solids 60 g / L, TOC 10 g / L, OH - 5g / L, Na10g / L) was added with 5% ethylenediamine, heated to 40℃ and then ultrasonically atomized, with nitrogen as carrier gas, the atomized droplets and nitrogen (3L / min) were fed into the atmosphere protection furnace. H2O =0.4atm) at 650 ° C., and the obtained carbon material and tail gas are introduced into a collector filled with a dilute sodium hydroxide solution. After the spray pyrolysis is completed, it is filtered, washed, and dried to obtain a nitrogen-doped precursor material.

[0054] High-temperature heat treatment to regulate the microstructure: the porous spherical precursor material prepared above was placed in a nitrogen-protected atmosphere furnace, first heated to 600°C at a rate of 20°C / min, kept constant at this temperature for 3 hours, then heated to 1400°C at a rate of 2°C / min, kept constant at this temperature for 2 hours, and then cooled with the furnace to obtain a nitrogen-doped hard carbon negative electrode material inlaid with hollow porous spheres and porous carbon sheets.

[0055] The obtained hard carbon material is a composite porous material inlaid with hollow porous balls and porous carbon sheets. The diameter of the hard carbon microspheres is about 0.3-3 μm, the wall thickness is about 30-100 nm, and the interlayer spacing d is about 0. 002 The average thickness along the c-axis is L c The average width L along the a-axis is 0.69 nm. a The resulting hard carbon negative electrode material was used as the active material to make an electrode, which was then assembled with a metal lithium sheet, a separator, and an electrolyte into a button cell. Charge and discharge at a current density of 0.1C (30mA / g) between 0-1.5V resulted in a reversible capacity of 370mAh / g, and after 300 cycles at 0.5C (150mA / g), the capacity retention rate was 97.8%.

[0056] The hard carbon material prepared in this example is used as the negative electrode material, the high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide is used as the positive electrode material, the electrolyte is a 1.2 mol / LNaPF6 PC / EMC (volume ratio of x:1-x, where x=0.25) solution and 1.5% PS and 2% FEC additives are added. The prepared soft-pack sodium ion battery is charged and discharged between 1.5V and 4.15V, and the energy density is 172Wh / kg.

[0057] Specific Example 6: Preparation of Hollow Porous Ball Precursor by Spray Pyrolysis: In papermaking black liquor (total dissolved solids 60 g / L, TOC 10 g / L, OH - 5g / L, Na10g / L) was added with 5% diethylenetriamine, heated to 50℃ and then ultrasonically atomized, with nitrogen as carrier gas, the atomized droplets and nitrogen (3L / min) were sent into the atmosphere protection furnace together, and the atmosphere protection furnace (p H2O =0.4atm) at 650 ° C., and the obtained carbon material and tail gas are introduced into a collector filled with a dilute sodium hydroxide solution. After the spray pyrolysis is completed, it is filtered, washed, and dried to obtain a nitrogen-doped precursor material.

[0058] High-temperature heat treatment to regulate the microstructure: the porous spherical precursor material prepared above was placed in a nitrogen-protected atmosphere furnace, first heated to 500°C at a rate of 20°C / min, kept constant at that temperature for 3 hours, then heated to 1400°C at a rate of 2°C / min, kept constant at that temperature for 2 hours, and then cooled with the furnace to obtain a nitrogen-doped hard carbon negative electrode material inlaid with hollow porous spheres and porous carbon sheets.

[0059] The obtained hard carbon material is a composite porous material inlaid with hollow porous balls and porous carbon sheets. The diameter of the hard carbon microspheres is about 0.3-3 μm, the wall thickness is about 30-100 nm, and the interlayer spacing d is about 0. 002 The average thickness along the c-axis is L c The average width L along the a-axis is 0.71 nm. a The resulting hard carbon negative electrode material was used as the active material to make an electrode, which was then assembled with a metal lithium sheet, a separator, and an electrolyte into a button cell. Charge and discharge at a current density of 0.1C (30mA / g) between 0-1.5V resulted in a reversible capacity of 375mAh / g, and after 300 cycles at 0.5C (150mA / g), the capacity retention rate was 97.7%.

[0060] The hard carbon material prepared in this example was used as the negative electrode material, a high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide was used as the positive electrode material, the electrolyte was a 1.1 mol / L NaPF6 PC / EMC (volume ratio of x:1-x, where x=0.25) solution, and 1.5% PS and 2% FEC additives were added. The prepared soft-pack sodium ion battery was charged and discharged between 1.5 V and 4.15 V, with an energy density of 174 Wh / kg.

[0061] The above description of the present invention and its embodiments is non-limiting, and the actual structure is not limited thereto. In short, if a person skilled in the art is inspired by the above, and does not deviate from the purpose of the invention, without creatively designing a structure and embodiment similar to the technical solution, they shall fall within the scope of protection of the present invention.

Claims

1. A hard carbon material for sodium ion batteries, characterized in that: The hard carbon material is a composite porous material in which hollow porous balls and porous carbon sheets are embedded. The diameter of the microspheres of the hard carbon material is 0.3-3 μm, the wall thickness is 30-100 nm, and the 002 crystal plane interlayer spacing d is 0. 002 The average thickness along the c-axis is L c The average width L along the a-axis is 0.6-0.75 nm. a 11-14 nm; The sodium ion hard carbon negative electrode material is obtained by spray pyrolysis and high-temperature heat treatment of papermaking black liquor. The specific steps include: Step 1: Preparation of precursor material by spray pyrolysis. Papermaking black liquor is atomized, and inert gas is used as carrier gas. The atomized droplets and the inert gas enter the atmosphere protection furnace together, and are subjected to high-temperature pyrolysis in the atmosphere protection furnace. The high-temperature pyrolysis temperature is 550-750°C. After the spray pyrolysis is completed, the collected carbon material is washed and dried to obtain the precursor material. Step 2: High-temperature heat treatment to adjust the composition and microstructure, the precursor material prepared above is placed in a protective atmosphere furnace for high-temperature heat treatment, and then cooled to obtain a hard carbon negative electrode material; The high temperature heat treatment in step 2 includes two stages of heat treatment, namely, firstly heating the temperature to 450-600°C at 5-20°C / min and holding the temperature for 1-12 hours, then heating the temperature to 1300-1600°C at 1-5°C / min and holding the temperature for 1-12 hours; The total dissolved solids in the papermaking black liquor are 50-600 g / L, the total carbon content is 10-100 g / L, the hydroxide content is 2-30 g / L, and the sodium content is 10-100 g / L. The total dissolved solids in the papermaking black liquor include lignin, hemicellulose and their derivatives, sodium salts and residual alkali.

2. The hard carbon material for sodium ion batteries according to claim 1, wherein: The precursor material has a spherical porous structure, and some carbon spheres are collapsed, and is a porous spherical material rich in mesoporous structure.

3. The hard carbon material for sodium ion batteries according to claim 1, characterized in that: In the step 1, the water partial pressure in the atmosphere protection furnace is 0.1-0.5 atm.

4. The hard carbon material for sodium ion batteries according to claim 1, wherein: In the step 1, the temperature of the papermaking black liquor during atomization is 40-70° C., and the atomization method includes ultrasonic atomization and centrifugal atomization.

5. The hard carbon material for sodium ion batteries according to claim 1, characterized in that: In step 1, one or more of polyaziridine, ethylenediamine, and diethylenetriamine are added to the papermaking black liquor to prepare a nitrogen-doped spherical porous structure precursor material and a composite porous material in which nitrogen-doped hollow porous spheres and porous carbon sheets are inlaid. The proportion of nitrogen atoms in the precursor and the hard carbon material is 0.1~0.5wt%.

6. A sodium ion battery using the hard carbon material of claim 1, characterized in that: The hard carbon material according to claim 1 is used as the negative electrode material, a high-voltage layered sodium-nickel-iron-manganese-copper-titanium composite oxide is used as the positive electrode material, the electrolyte is 1-1.3 mol / L NaPF6 propylene carbonate / ethyl methyl carbonate, the volume ratio is x:1-x, where x=0.15-0.35, and 0.5%-3% propylene sulfite and 1%-5% fluoroethylene carbonate additives are added to the solution to prepare a high-voltage soft-pack sodium ion battery with a charge and discharge range of 1.5V-4.15V and an energy density of 160-180Wh / kg.

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