A sodium ion battery hard carbon prepared by using apple pruning waste branches and method

Abstract

The present invention belongs to the field of waste resource utilization and sodium ion battery technology, and relates to a sodium ion battery hard carbon and method prepared by using apple pruning waste branches, including: 1) pre-treating the apple pruning waste branches to obtain a pre-carbonized product and a dry distillation liquid; 2) heating the pre-carbonized product to reflux, calcining, and washing to obtain a hard carbon precursor; 3) mixing the hard carbon precursor with an organic small molecule compound, calcining in an inert gas atmosphere, and cooling to obtain a sodium ion battery hard carbon. The sodium ion battery hard carbon prepared by the present invention not only has a high specific capacity and a high first charge and discharge efficiency, but also realizes the deep reuse of apple pruning waste branches.

Description

Technical Field

[0001] The invention belongs to the technical field of waste resource utilization and sodium ion battery, and relates to a sodium ion battery hard charcoal prepared by utilizing apple pruning waste branches and a method thereof. Background Art

[0002] Sodium-ion batteries have become an excellent alternative to lithium-ion batteries because of their similar physical and chemical properties, lower cost, and higher safety. Hard carbon has become an extremely excellent negative electrode material for sodium-ion batteries due to its excellent performance and low cost. Hard carbon can be divided into biomass-based hard carbon and organic polymer-based hard carbon. The former is obtained by thermal treatment of biomass, and the latter organic polymer is obtained by artificial synthesis. However, most organic compounds will produce harmful gases during the pyrolysis process. Due to the different bio-based sources, their repeatability is poor and further processing is required. In addition, hard carbon negative electrode materials also face problems such as low first coulomb efficiency and poor rate performance.

[0003] In order to ensure that the branches of apple trees are reasonable, nutritious, and high and stable, apple trees must be pruned every year. The amount of waste branches cut off is large and needs to be treated. The existing treatment method is: incineration treatment, but it is highly polluting, easy to cause fire, and has safety hazards. Another treatment is crushing and composting treatment. Although the waste branches can be used as fertilizers to achieve recycling treatment, the deep value of apple waste branches has not yet been brought into play; in recent years, with the rapid development of electronic products, apple waste branches are carbonized to generate biochar, which is used as a solid fuel in electronic products, which deepens the application space of apple waste branches. However, the current carbonization adopts a pyrolysis process. The rapid pyrolysis product of biomass is mainly liquid bio-oil, which is a polar substance with poor chemical stability and corrosiveness. There are certain problems in its application as a high-grade energy. Therefore, it is necessary to develop an efficient treatment method that can achieve the deep reuse of apple waste branches in hard carbon negative electrode materials. Summary of the invention

[0004] The purpose of the present invention is to provide a sodium ion battery hard carbon prepared by using apple pruning waste branches and a method thereof. The prepared sodium ion battery hard carbon not only has a high specific capacity and a high initial charge and discharge efficiency, but also realizes the deep recycling of apple pruning waste branches.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing sodium ion battery hard carbon using apple pruning waste branches, comprising the following steps:

[0007] 1) Pre-carbonized products and dry distillation liquid are obtained by pre-treating waste apple branches;

[0008] 2) mixing the pre-carbonized product and the dry distillation liquid, and obtaining a hard carbon precursor by heating, refluxing, calcining, and washing;

[0009] 3) Mixing the hard carbon precursor with an organic small molecule compound, calcining and cooling in an inert gas atmosphere to obtain hard carbon for a sodium ion battery.

[0010] Furthermore, the step 1) specifically includes:

[0011] 1.1) Crush the apple pruning waste branches into small pieces with a particle size of 0.5 cm to 1 cm;

[0012] 1.2) The small pieces of waste branches are subjected to pre-carbonization treatment by dry distillation to obtain pre-carbonized products and dry distillation liquid.

[0013] Furthermore, in the step 1.2), the process conditions of the dry distillation pre-carbonization are: a heating rate of 5°C / min, a dry distillation temperature of 300-700°C, and a dry distillation time of 2-5h; the yield of the pre-carbonized product is 300 g / 1kg of small waste branches; the output of the dry distillation liquid is 300 ml / 1kg of small waste branches, and the pH of the dry distillation liquid is 4-5.

[0014] Furthermore, the step 2) specifically includes:

[0015] 2.1) The pre-carbonized product of step 1) is subjected to primary heating reflux with the dry distillation liquid of step 1) at a ratio of 1 g: 6-20 ml, and filtered to obtain a primary solid and a primary liquid;

[0016] 2.2) In an inert gas atmosphere, the primary solid is calcined and cooled to obtain a secondary solid;

[0017] 2.3) The secondary solid is subjected to secondary heating reflux with the dry distillation liquid of step 1) at a ratio of 1 g:4-10 ml, and is subjected to secondary filtration to obtain a tertiary solid and a secondary liquid;

[0018] 2.4) The tertiary solid is washed with boiling water and filtered three times to obtain a quaternary solid and a tertiary liquid. The quaternary solid is a hard carbon precursor.

[0019] Furthermore, the conditions of the primary heating reflux in step 2.1) and the conditions of the secondary heating reflux in step 2.3) are: heating temperature is 100°C to 120°C, reflux for 0.5h; the calcination temperature in step 2.2) is 1000°C to 1600°C, and calcination time is 2h to 4h.

[0020] Furthermore, the step 2.4) further includes a step 2.5), which is specifically:

[0021] 2.5) The primary liquid of step 2.1), the secondary liquid of step 2.3) and the tertiary liquid of step 2.4) are mixed to obtain a mixed liquid, and the pH of the mixed liquid is adjusted to 4-5 with the dry distillation liquid of step 1) to obtain an organic liquid fertilizer matrix.

[0022] Furthermore, in the step 3), the calcination temperature is 200° C. to 400° C., the calcination time is 2 h to 4 h; and the mass ratio of the hard carbon precursor to the organic small molecule compound is 1:1-1:5.

[0023] Furthermore, in step 3), the organic small molecule compound is one or more of imidazole, thiophene, quinoline, thiourea, imidazole derivatives, thiophene derivatives, quinoline derivatives and thiourea derivatives.

[0024] A method for preparing sodium ion battery hard carbon by utilizing waste apple pruning branches to obtain sodium ion battery hard carbon.

[0025] Furthermore, the sodium ion battery hard carbon is assembled in a sodium ion half-cell, with a specific capacity of up to 480 mAh / g and a first charge and discharge efficiency of up to 91%.

[0026] The beneficial effects of the present invention are:

[0027] 1. The present invention adopts apple pruning waste branches as raw materials to prepare sodium ion battery hard carbon. The sodium ion battery hard carbon provided by the present invention has a specific capacity of up to 480 mAh / g, and the first charge and discharge efficiency is 88% at this time; the first charge and discharge efficiency is up to 91%, and the specific capacity is 368 mAh / g at this time; the excellent performance has developed a new way for the deep reuse of apple waste branches.

[0028] 2. The present invention undergoes a pre-carbonization treatment by dry distillation, and the pre-carbonization product is refluxed with dry distillation liquid to obtain a primary solid; the primary solid is calcined at high temperature in an inert gas atmosphere, and a secondary solid is obtained after cooling; the dry distillation liquid is heated and refluxed, and filtered to obtain a tertiary solid, which is then washed to obtain a fourth solid, i.e., a hard carbon precursor, and the hard carbon precursor is further mixed with an organic small molecule compound, calcined, and cooled to prepare a sodium ion battery hard carbon. The entire preparation condition is mild, avoids the use of toxic, harmful and corrosive reagents, and has good safety.

[0029] 3. In the present invention, the hard carbon precursor is mixed with the organic small molecule compound and the calcination temperature is 200°C to 400°C. This low-temperature calcination is used to coat the obtained product, thereby reducing the specific surface area and adjusting the pore structure, thereby improving the performance of the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a scanning electron microscope photograph of the hard carbon negative electrode material for a sodium ion battery prepared in Example 1 of the present invention;

[0031] Figure 2 This is the first charge and discharge curve of the hard carbon negative electrode material for a sodium ion battery prepared in Example 1 of the present invention;

[0032] Figure 3 This is the first charge and discharge curve of the hard carbon negative electrode material for a sodium ion battery prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0033] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] The method for preparing sodium ion battery hard carbon by using apple pruning waste branches of the present invention comprises the following steps:

[0035] 1) Apple pruning waste branches were pretreated to obtain pre-carbonized products and distillation liquid.

[0036] Step 1) specifically includes:

[0037] 1.1) Crush the apple pruning waste branches into small pieces with a particle size of 0.5 to 1 cm.

[0038] 1.2) The above-mentioned small waste branches are subjected to pre-carbonization treatment by dry distillation to obtain pre-carbonization products and dry distillation liquid.

[0039] In step 1.2), the process conditions of dry distillation pre-carbonization are: heating rate of 5°C / min, dry distillation temperature of 300°C-700°C, and dry distillation time of 2-5h; the yield of pre-carbonized product is 300 g / 1kg small waste branch; the output of dry distillation liquid is 300 ml / 1kg small waste branch, and the pH of the dry distillation liquid is 4-5.

[0040] 2) Mixing the pre-carbonized product and the dry distillation liquid, heating and refluxing, calcining, and washing to obtain a hard carbon precursor. The process specifically includes the following steps.

[0041] 2.1) The pre-carbonized product of step 1.2) is subjected to primary heating reflux with the dry distillation liquid obtained in step 1.2) at a ratio of 1 g: 6-20 ml, and then filtered to obtain a primary solid and a primary liquid.

[0042] 100 g of pre-carbonized product and 0.6-2 L of dry distillation liquid are mixed in a ratio of 100 g:0.6-2 L, heated at 100-120° C., and refluxed for 0.5 h.

[0043] 2.2) Under an inert gas atmosphere, the primary solid is calcined and cooled in sequence to obtain a secondary solid.

[0044] The calcination temperature is 1000°C to 1600°C, and the calcination time is 2 to 4 hours.

[0045] 2.3) The secondary solid is treated with the dry distillate of step 1) at a ratio of 1 g:4-10 ml by secondary heating reflux and secondary filtration to obtain a tertiary solid and a secondary liquid.

[0046] The secondary solid is 100 g, the dry distillation liquid is 0.4-1 L, the solid-liquid ratio is 100 g:0.4-1 L, the heating temperature is 100-120°C, and the reflux is 0.5 h.

[0047] 2.4) The tertiary solid is washed with boiling water and filtered to obtain a quaternary solid and a tertiary liquid. The quaternary solid is the hard carbon precursor.

[0048] 3) Mixing the hard carbon precursor with an organic small molecule compound, calcining and cooling in an inert gas atmosphere to obtain hard carbon for a sodium ion battery.

[0049] In this step, the calcination temperature is 200° C.-400° C., the calcination time is 2-4 hours, and the mass ratio of the hard carbon precursor to the organic small molecule compound is 1:1-1:5.

[0050] In this step, the organic small molecule compound is one or more of imidazole, thiophene, quinoline, thiourea, imidazole derivatives, thiophene derivatives, quinoline derivatives and thiourea derivatives.

[0051] The present invention is described in detail below with reference to several groups of specific embodiments, but they cannot be used as limitations on the technical solutions protected by the present invention.

[0052] Example 1

[0053] The method for preparing sodium ion battery hard carbon using apple pruning waste branches provided in this embodiment includes the following steps.

[0054] 1) Apple pruning waste branches were pretreated to obtain pre-carbonized products and distillation liquid.

[0055] 1.1) Crush the apple pruning waste branches into small pieces with a particle size of 0.5 cm.

[0056] 1.2) The crushed small waste branches are subjected to pre-carbonization treatment by dry distillation to obtain pre-carbonized products and dry distillation liquid.

[0057] The process conditions of carbonization pre-carbonization are as follows: heating rate of 5°C / min, carbonization temperature of 500°C, and carbonization time of 2h.

[0058] In this embodiment, the yield of the pre-carbonized product is 300 g / 1 kg of small waste branches; the yield of the dry distillation liquid is 300 ml / 1 kg of small waste branches, and the pH of the dry distillation liquid is 4-5.

[0059] 2) The pre-carbonized product is heated to reflux, calcined and washed to obtain a hard carbon precursor.

[0060] 2.1) The pre-carbonized product of step 1.2) was subjected to primary heating reflux at a ratio of 1 g:10 ml with the dry distillation liquid obtained in step 1.2) at a temperature of 120° C. for 0.5 h, and filtered to obtain a solid and a liquid.

[0061] 2.2) In an inert gas atmosphere, the primary solid is calcined at 1400° C. for 2 h and then cooled to obtain a secondary solid.

[0062] 2.3) The secondary solid was subjected to secondary heating reflux at a ratio of 1 g:10 ml with the dry distillation liquid obtained in step 1) at 120° C. for 0.5 h, and filtered to obtain a tertiary solid and a secondary liquid.

[0063] 2.4) The tertiary solid is washed with boiling water and filtered to obtain a quaternary solid and a tertiary liquid. The quaternary solid is the hard carbon precursor.

[0064] 3) The hard carbon precursor and the organic small molecule compound are fully mixed in a mass ratio of 1:1, and calcined at 300° C. for 4 h in an inert gas atmosphere to obtain sodium ion battery hard carbon.

[0065] In this embodiment, the organic small molecule compound is imidazole.

[0066] In this embodiment, the primary liquid of step 2.1), the secondary liquid of step 2.3) and the tertiary liquid of step 2.4) are mixed to obtain a mixed liquid, and the pH of the mixed liquid is adjusted to 4-5 with the dry distillation liquid of step 1) to obtain an organic liquid fertilizer matrix.

[0067] Embodiment 2 to Embodiment 4

[0068] The preparation methods of Examples 2 to 4 are the same as those of Example 1, except that the reaction conditions of each step are different, see Table 1 for details.

[0069] Table 1 Comparison of reaction conditions in Examples 2 to 4

[0070]

[0071] Comparative Example

[0072] The difference between the comparative example and Example 3 is that no organic small molecules are used, and the hard carbon precursor is calcined in an inert gas atmosphere to obtain the sodium ion battery hard carbon.

[0073] The sodium ion battery hard carbon obtained in this comparative example was measured for specific capacity and initial charge and discharge efficiency according to the test method of Verification 2, as shown in Table 1.

[0074] Furthermore, the advantages of the preparation method of the present invention were verified using the sodium ion battery hard carbon prepared in Example 1.

[0075] Verification 1 Scanning electron microscope test

[0076] Experimental steps: A Hitachi SU-70 scanning electron microscope was used to scan the hard carbon group obtained in Example 1. The test results are shown in Figure 1 shown.

[0077] from Figure 1 It can be seen that the hard carbon product obtained from apple pruning waste branches under the preparation process conditions described in Example 1 has fewer surface pores and only a small number of larger pores, indicating that after the coating effect of small molecule compounds, the pore structure of the apple branch raw material is filled and coated, so that the specific surface area is reduced.

[0078] Verification 2 Chemical Properties

[0079] Test samples: sodium ion hard carbon prepared in Examples 1 to 4, sodium ion hard carbon prepared in Comparative Example 1

[0080] Test process:

[0081] The sodium ion hard carbon sample prepared by the process of the present invention is crushed to less than 200 mesh, mixed with conductive carbon and PVDF in a ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added. After mixing and stirring on a stirrer for 24 hours, the slurry is evenly coated on the aluminum foil current collector with an applicator. After the coated aluminum foil is vacuum dried at 120 degrees Celsius for 24 hours, it is cut into discs with a diameter of 1 cm for standby use with a puncher. In a glove box filled with argon (the oxygen content and moisture content are both less than 0.1ppm), the electrode sheet cut and weighed as above is used as the negative electrode, the sodium sheet is used as the positive electrode, the sodium hexafluorometaphosphate solution is used as the electrolyte, and the diaphragm uses a glass fiber diaphragm to assemble into a button half-cell test. The test equipment is a blue battery tester, and the test conditions are a voltage of 0.005-2.5v and a 0.2C rate charge and discharge test cycle of 1000 times.

[0082] Test results: The results of the sodium ion battery hard carbon prepared in Example 1 are shown in Figure 2 and Table 2, the results of sodium ion battery hard carbon prepared in Example 2 are shown in Figure 3 and Table 2; the results of the sodium ion battery hard carbon prepared in Example 3, Example 4 and the comparative example are shown in Table 2.

[0083] Table 2 Performance comparison of the hard carbon of the present invention and the comparative example

[0084]

[0085]

[0086] Depend on Figure 2 , Figure 3As shown in Table 2, the sodium ion battery hard carbon prepared under the process conditions of Examples 1 to 4 has a specific capacity of 480mAh / g, 368mAh / g, 470mAh / g and 440mAh / g under the charge and discharge conditions of 0.2C, and the first charge and discharge efficiency is 88%, 91%, 86% and 81% respectively. The maximum specific capacity is 480mAh / g, and the first charge and discharge efficiency is as high as 91%, which meets the performance requirements of sodium ion hard carbon and is used in sodium ion batteries.

[0087] Analyzing Example 3 and the comparative example, the comparative example did not use organic small molecules, and the obtained sodium ion hard carbon had a specific capacity of 275 mAh / g and an initial charge and discharge efficiency of up to 75%. Compared with the comparative example, Example 3 had a specific capacity increased by 245 mAh / g and an initial charge and discharge efficiency increased by 11%. This indicates that the use of organic small molecules can greatly improve the specific capacity and initial charge and discharge efficiency of sodium ion hard carbon negative electrode materials.

[0088] Specific capacity refers to the amount of electricity that can be discharged by a unit mass of a battery or active material.

[0089] In addition, the performance of the sodium ion hard carbon prepared by the present invention is compared with commercially available products. The results are shown in Table 3.

[0090] Table 3 Performance comparison of the hard carbon of the present invention and related commercial products

[0091] serial number product Specific capacity First charge and discharge efficiency raw materials 1 Domestic A manufacturer's products on the market 194mAh / g 82.3％ anthracite 2 Domestic B manufacturer's products on the market 305mAh / g 89％ Cellulose 3 Products from foreign manufacturers on the market 302mAh / g 89.2％ Resin 4 Product of Example 1 of the present invention 480mAh / g 88％ Apple branch 5 Product of Example 2 of the present invention 368mAh / g 91％ Apple branch

[0092] It can be seen from Table 3 that the present invention uses apple pruning waste branches as raw materials to prepare sodium ion battery hard carbon, with a specific capacity of up to 480 mAh / g and an initial charge and discharge efficiency of 88%, which is significantly better than commercially available products and has developed a new approach for the deep recycling of apple waste branches.

Claims

1. A method for preparing sodium ion battery hard carbon using waste apple pruning branches, characterized in that: The following steps are involved: 1) Apple pruning waste branches are pretreated to obtain pre-carbonized products and dry distillation liquid; 2) Step 1) The pre-carbonized product is heated, refluxed, and calcined to obtain a hard carbon precursor; Step 2) specifically includes: 2.1) The pre-carbonized product of step 1) is subjected to primary heating reflux with the dry distillation liquid of step 1) at a ratio of 1 g: 6-20 ml, and filtered to obtain a primary solid and a primary liquid; 2.2) In an inert gas atmosphere, the primary solid is calcined and cooled to obtain a secondary solid; 2.3) The secondary solid is subjected to secondary heating reflux with the dry distillation liquid of step 1) at a ratio of 1 g:4-10 ml, and is subjected to secondary filtration to obtain a tertiary solid and a secondary liquid; 2.4) The tertiary solid is washed with boiling water and filtered three times to obtain a quaternary solid and a tertiary liquid. The quaternary solid is a hard carbon precursor; 3) Mixing the hard carbon precursor with an organic small molecule compound, calcining and cooling in an inert gas atmosphere to obtain hard carbon for sodium ion batteries; In the step 3), the calcination temperature is 200°C to 400°C, the calcination time is 2h to 4h; the mass ratio of the hard carbon precursor to the organic small molecule compound is 1:1-1:5; The step 1) specifically includes: 1.1) Crush the apple pruning waste branches into small pieces with a particle size of 0.5cm~1cm; 1.2) Pre-carbonizing the small waste branches by dry distillation to obtain pre-carbonized products and dry distillation liquid; In the step 1.2), the process conditions of the carbonization pre-carbonization are: the heating rate is 5°C / min, the carbonization temperature is 300-700°C, and the carbonization time is 2-5h; the yield of the pre-carbonization product is 300g / 1kg of small waste branches; the yield of the carbonization liquid is 300ml / 1kg of small waste branches, and the pH of the carbonization liquid is 4-5; The conditions of the first-stage heating reflux in step 2.1) and the conditions of the second-stage heating reflux in step 2.3) are: the heating temperature is 100°C to 120°C, and the reflux time is 0.5h; the calcination temperature in step 2.2) is 1000°C to 1600°C, and the calcination time is 2h to 4h; In the step 3), the organic small molecule compound is one or more of imidazole, thiophene, quinoline, thiourea, imidazole derivatives, thiophene derivatives, quinoline derivatives and thiourea derivatives.

2. The method for preparing sodium ion battery hard carbon using apple pruning waste branches according to claim 1, characterized in that: The step 2.4) also includes step 2.5), which is specifically: 2.5) The primary liquid of step 2.1), the secondary liquid of step 2.3) and the tertiary liquid of step 2.4) are mixed to obtain a mixed liquid, and the pH of the mixed liquid is adjusted to 4-5 with the dry distillation liquid of step 1) to obtain an organic liquid fertilizer matrix.

3. A sodium ion battery hard carbon obtained by the method for preparing sodium ion battery hard carbon using apple pruning waste branches as described in any one of claims 1-2.

4. The sodium ion battery hard carbon according to claim 3, characterized in that The sodium ion battery hard carbon is assembled in a sodium ion half-cell, with a specific capacity of up to 480 mAh / g and a first charge and discharge efficiency of up to 91%.

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