A hard carbon anode material for sodium-ion batteries prepared from traditional Chinese medicine residues and method thereof

Abstract

The present invention belongs to the technical fields of waste resource utilization and sodium-ion battery, and relates to a hard carbon anode material for sodium-ion battery prepared from traditional Chinese medicine residue and a method therefor, comprising the following steps: 1) Pretreatment: drying the traditional Chinese medicine residue and obtaining a pretreated product through pretreatment; 2) Freeze drying: freeze drying the pretreated product in step 1) to obtain a solid product; 3) Pre-carbonization: subjecting the solid product to pre-carbonization to obtain a pre-carbonized product and a dry distillate; 4) Preparing the hard carbon anode material: treating the pre-carbonized product by alternately heating under reflux and calcining to obtain the hard carbon anode material for sodium-ion battery. The hard carbon for sodium-ion battery prepared from traditional Chinese medicine residue by the present invention not only has a very high specific capacity and a very high first charge-discharge efficiency, but also realizes the efficient resource development and utilization of traditional Chinese medicine residue.

Description

Technical Field

[0001] The present invention belongs to the technical fields of waste resource utilization and sodium-ion battery technology, and relates to a hard carbon for sodium-ion batteries prepared from traditional Chinese medicine residues and a method therefor. Background Art

[0002] Hard carbon for sodium-ion batteries can be used as a negative electrode material. Since hard carbon has a stable structure, a long charge-discharge cycle life, and a carbon-lithium potential higher than 0.2V, its safety performance is better. It can overcome the problem that graphitized carbon has a high reaction activity during the charging process to form lithiated graphite. Once an internal short circuit occurs, it will cause a serious exothermic reaction and pose a risk of explosion. It is mainly used in new energy vehicles, low-speed electric vehicles, and energy storage fields.

[0003] In the prior art, the technical barrier of the negative electrode material for sodium batteries is relatively high. At present, the domestic market demand is mainly met by imports. However, due to the high price of imported products, the cost is high, which is not conducive to the development of the sodium-ion battery industry. In addition, there are also problems in hard carbon for sodium-ion batteries, such as large variation of the discharge voltage with the capacity and lower first charge-discharge efficiency than graphitized carbon. Therefore, the modification research on hard carbon materials is one of the important ways to improve the performance of hard carbon as a negative electrode material for lithium-ion batteries.

[0004] In the pharmaceutical field, a large amount of traditional Chinese medicine is used. However, after the traditional Chinese medicine is decocted, the active ingredients in the traditional Chinese medicine are basically decocted out, and the remaining traditional Chinese medicine residues have little use. Generally, they are directly discarded as wet garbage. However, the residues usually contain relatively high drug residues and pollutants, and need to be treated safely and environmentally to meet the requirements of the green resource environment. Usually, the treatment methods for the residues include incineration treatment, composting treatment, and crushing and landfill treatment. However, these methods are likely to cause environmental pollution. Therefore, by simply converting them into value-added products, such as carbonizing the residues, which refers to the process of pyrolyzing the residues to convert them into biomass carbon. However, there are the following problems in carbonization: Currently, the pyrolysis method is generally adopted, and most of the generated biochar is used for agricultural fertilizers and sewage treatment agents. The performance of the carbonized products generated by the existing residue conversion methods is generally average, which greatly limits the efficient conversion of the residues. In addition, due to the presence of toxic and harmful substances in the residues, the process requirements for carbonization are relatively high to avoid environmental pollution. Therefore, finding an efficient conversion route for traditional Chinese medicine residues is of great significance for realizing the effective value of the residues, reducing environmental pollution, and maintaining ecological balance. Summary of the Invention

[0005] The object of the present invention is to provide a hard carbon for sodium-ion batteries prepared from traditional Chinese medicine residues and a method therefor. The prepared hard carbon for sodium-ion batteries not only has a very high specific capacity and a very high first charge-discharge efficiency, but also realizes the efficient resource development and utilization of traditional Chinese medicine residues.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a hard carbon anode material for a sodium-ion battery using traditional Chinese medicine residues, comprising the following steps:

[0008] 1) Pretreatment

[0009] After drying the traditional Chinese medicine residues, a pretreatment product is obtained through pretreatment;

[0010] 2) Freeze-drying

[0011] The pretreatment product in step 1) is freeze-dried to obtain a solid product;

[0012] 3) Pre-carbonization

[0013] The solid product undergoes pre-carbonization to obtain a pre-carbonized product and a dry distillate;

[0014] 4) Preparation of the hard carbon anode material

[0015] The pre-carbonized product is treated by alternately heating under reflux and calcining to obtain the hard carbon anode material for the sodium-ion battery.

[0016] Furthermore, step 1) specifically includes:

[0017] 1.1) After drying the traditional Chinese medicine residues, they are soaked in wood vinegar, and then successively pulped, filtered, washed, and dried to obtain solid residues;

[0018] 1.2) The solid residues are dispersed in a saturated potassium carbonate solution, allowed to stand, and then pulped to obtain the pretreatment product.

[0019] Furthermore, in step 1), the dosage of the traditional Chinese medicine residues and wood vinegar is 1 g: 2 - 8 ml, and the dosage ratio of the pulped residues to the saturated potassium carbonate solution is 1 g: 2 - 5 ml; the wood vinegar is a wine-red liquid obtained during the dry distillation process of the material, and the material is straw, corn cob, Xanthoceras sorbifolia shell, wild jujube kernel shell, almond shell, bamboo, or wood; the traditional Chinese medicine residues are Astragalus membranaceus, Glycyrrhiza uralensis, Salvia miltiorrhiza, Polygala tenuifolia, Chinese date, or a mixed residue.

[0020] Furthermore, in step 2), the freezing temperature is -40°C to -80°C.

[0021] Furthermore, in step 3), the conditions for dry distillation pre-carbonization are: the heating rate is 5°C / min, the dry distillation temperature is 300°C to 700°C, and the dry distillation time is 2 h to 5 h; the dry distillate includes wood acetic acid and wood tar.

[0022] Furthermore, step 4) is specifically:

[0023] The pre-carbonized product is successively subjected to first-stage heating reflux, first-stage calcination, second-stage heating reflux, second-stage calcination, and third-stage heating reflux treatments to obtain a hard carbon negative electrode material for a sodium-ion battery; the temperature of the second-stage calcination is lower than that of the first-stage calcination.

[0024] Further, step 4) includes the following steps:

[0025] 4.1) Take the pre-carbonized product of step 3), perform first-stage heating reflux with the wood vinegar liquid of step 3), and then perform first-stage calcination in an inert gas atmosphere to obtain a primary solid product;

[0026] 4.2) Take the primary solid product, perform second-stage heating reflux with the wood vinegar liquid of step 3) to obtain a secondary solid product;

[0027] 4.3) Disperse the secondary solid in the wood tar of step 3), and perform second-stage calcination in an inert gas atmosphere to obtain a tertiary solid product;

[0028] 4.4) Take the tertiary solid product, perform third-stage heating reflux with the wood vinegar liquid of step 3) to obtain a secondary solid product, and further perform drying and pulverization treatments to obtain hard carbon for a sodium-ion battery.

[0029] Further, the conditions for the first-stage calcination are: temperature is 1100 °C to 1400 °C, and time is 2 h; the conditions for the first-stage heating reflux, second-stage heating reflux, and third-stage heating reflux are all: temperature is 100 to 120 °C, and time is 0.5 h to 2 h; the conditions for the second-stage calcination are: temperature is 700 °C to 900 °C, and time is 2 to 3 h.

[0030] A hard carbon negative electrode material for a sodium-ion battery obtained by a method for preparing a hard carbon negative electrode material for a sodium-ion battery using traditional Chinese medicine residues.

[0031] Further, the specific capacity of the hard carbon negative electrode material for the sodium-ion battery is at most 578 mAh / g, and the first charge-discharge efficiency is at most 91%.

[0032] The beneficial effects of the present invention are:

[0033] 1. The present invention uses traditional Chinese medicine residues as raw materials to prepare hard carbon for a sodium-ion battery. The hard carbon for a sodium-ion battery provided by the present invention is assembled as a negative electrode in a battery, and the specific capacity can reach at most 578 mAh / g, and the first charge-discharge efficiency can reach at most 91%. The performance is excellent, realizing the full-component utilization of traditional Chinese medicine residues, and developing a new way for the resource utilization of traditional Chinese medicine residues.

[0034] 2. After the traditional Chinese medicine residue is pretreated and pre-carbonized in the present invention, the obtained pre-carbonized product is heated and refluxed with wood vinegar liquid, calcined at the first stage, and then heated and refluxed again; then it is mixed and coated with wood tar and calcined again, and finally heated and refluxed with wood vinegar liquid, filtered, washed and dried to obtain hard carbon for sodium-ion batteries. The whole preparation condition of the present invention is mild, the use of toxic, harmful and corrosive reagents is avoided, and the safety is good.

[0035] 3. When pretreating the medicine residue in the present invention, it is soaked with saturated potassium carbonate solution. Potassium carbonate can be used as a pore-forming agent, with low cost and small corrosiveness. By soaking, the specific capacity and the first charge-discharge efficiency of the hard carbon for sodium-ion batteries are improved.

[0036] 4. The present invention adopts wood vinegar liquid for multi-stage heating and reflux, which can remove the ash and other impurities in the product. This operation replaces the hydrochloric acid washing procedure in the conventional production method, reduces the production cost, reduces the corrosion of the equipment, and reduces the pollution to the environment caused by the waste liquid of hydrochloric acid used in the conventional production method; the purpose of mixing and calcining with wood tar is to coat the carbonized product of wood tar on the surface of the hard carbon, reduce the specific surface area of the product, adjust the pore structure of the product, and is beneficial to improving the specific capacity and the first charge-discharge performance of the product. Description of the Drawings

[0037] Figure 1 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the astragalus medicine residue in Example 1;

[0038] Figure 2 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the astragalus medicine residue in Comparative Example 1;

[0039] Figure 3 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the licorice medicine residue in Example 2;

[0040] Figure 4 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the licorice medicine residue in Comparative Example 2;

[0041] Figure 5 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the salvia miltiorrhiza medicine residue in Example 3;

[0042] Figure 6 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the salvia miltiorrhiza medicine residue in Comparative Example 3;

[0043] Figure 7 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the polygonatum sibiricum medicine residue in Example 4;

[0044] Figure 8 It is the first charge-discharge performance diagram of the hard carbon for sodium-ion batteries of the polygonatum sibiricum medicine residue in Comparative Example 4;

[0045] Figure 9Figure of the first charge-discharge performance of the hard carbon of Polygala tenuifolia residue for Example 5;

[0046] Figure 10 Figure of the first charge-discharge performance of the hard carbon of Polygala tenuifolia residue for Comparative Example 5;

[0047] Figure 11 Figure of the first charge-discharge performance of the hard carbon of Ziziphus jujuba residue for Example 6;

[0048] Figure 12 Figure of the first charge-discharge performance of the hard carbon of Ziziphus jujuba residue for Comparative Example 6;

[0049] Figure 13 Figure of the first charge-discharge performance of the hard carbon of mixed residue for Example 7;

[0050] Figure 14 Figure of the first charge-discharge performance of the hard carbon of mixed residue for Comparative Example 7. Detailed implementation manners

[0051] The present invention will be described in detail below in conjunction with the accompanying drawings and examples.

[0052] The method for preparing hard carbon for sodium-ion batteries using traditional Chinese medicine residues in the present invention includes the following steps.

[0053] 1) Pretreatment

[0054] After drying the traditional Chinese medicine residues, a pretreatment product is obtained through pretreatment.

[0055] Step 1) of the present invention specifically includes:

[0056] 1.1) After drying the traditional Chinese medicine residues, soak them in wood vinegar liquid, and then successively carry out pulping, filtration, washing, and drying to obtain solid residues;

[0057] 1.2) Disperse the solid residues into a saturated potassium carbonate solution, let it stand, and carry out pulping to obtain a pretreatment product.

[0058] The liquids generated during filtration and washing in step 1.1) are combined to obtain a primary liquid.

[0059] In the present invention, the dosage ratio of the traditional Chinese medicine residues to the wood vinegar liquid is 1 g: 2 - 10 ml, and the dosage ratio of the pulpy residues to the saturated potassium carbonate solution is 1 g: 2 - 10 ml.

[0060] Wood vinegar liquid is a wine-red liquid obtained during the dry distillation process of materials. The materials are straw, corn cob, Xanthoceras sorbifolia shell, wild jujube kernel shell, almond shell, bamboo or wood.

[0061] The traditional Chinese medicine residues are Astragalus membranaceus, Glycyrrhiza uralensis, Salvia miltiorrhiza, Polygala tenuifolia, Ziziphus jujuba or mixed residues.

[0062] 2) Freeze-drying

[0063] The pre-treated product in step 1) is freeze-dried to obtain a solid product; the freezing temperature is -40°C to -80°C.

[0064] 3) Pre-carbonization

[0065] The solid product is pre-carbonized to obtain a pre-carbonized product, wood vinegar and wood tar; the conditions for dry distillation pre-carbonization are: the heating rate is 5°C / min, the dry distillation temperature is 300°C to 700°C, and the dry distillation time is 2h to 5h.

[0066] 4) Preparation of hard carbon anode material

[0067] Take the pre-carbonized product, heat and reflux it with the dry distillate, and then calcine it to obtain the hard carbon anode material for sodium-ion batteries.

[0068] Step 4) specifically includes the following steps:

[0069] 4.1) Add the wood vinegar in step 3) to the pre-carbonized product in step 3) and mix them according to a ratio of 1:2 to 1:10 (g / ml). After primary heating reflux and primary filtration, the obtained filtered product is calcined at the first stage in an inert gas atmosphere to obtain a primary solid product.

[0070] In step 4.1), the primary reflux temperature is 100 - 120°C, and the primary reflux time is 0.5h - 2h; the conditions for the first-stage calcination are that the temperature is 1100°C - 1400°C and the time is 2h.

[0071] 4.2) Add the wood vinegar in step 3) to the primary solid again and mix them according to a ratio of 1:2 to 1:10 (g / ml). After secondary heating reflux, secondary filtration, and washing and drying, a secondary solid product is obtained. The secondary reflux temperature is 100 - 120°C, and the secondary reflux time is 0.5h - 2h.

[0072] 4.3) Disperse the tertiary solid in the wood tar in step 3). The ratio of the tertiary solid to the wood tar is 2:1 to 5:1 (g / ml). Under an inert gas atmosphere, it is calcined at the second stage to obtain a tertiary solid product.

[0073] In step 4.3), the conditions for the second-stage calcination are that the temperature is 700°C - 900°C and the time is 2 - 3h.

[0074] 4.4) Mix the tertiary solid product with the wood vinegar in step 3) according to a ratio of 1:2 to 1:10 (g / ml), carry out tertiary heating reflux, and then through suction filtration, washing, drying, and pulverization, the hard carbon for sodium-ion batteries is obtained.

[0075] In this step, the tertiary reflux temperature is 100°C - 120°C, and the tertiary reflux time is 0.5h - 2h.

[0076] The specific capacity of the hard carbon negative electrode material for sodium-ion batteries prepared by the present invention is 578 mAh / g, and the highest initial charge-discharge efficiency is 91%.

[0077] In the present invention, the primary liquid generated in step 1), the secondary liquid in step 4.1), the tertiary liquid in step 4.2), and the quaternary liquid in step 4.4) are collected together. After mixing, the pH is adjusted to 4 - 5 with the dry distillate obtained by pre-carbonization in step 3) to obtain an organic liquid fertilizer matrix rich in potassium ions.

[0078] Since both the soaking liquid and the reflux liquid used in the preparation process of the present invention are wood vinegar liquid, and water washing is used for washing without the addition of other organic reagents, the obtained organic liquid fertilizer matrix rich in potassium ions can be used in crops and is safe.

[0079] During the preparation process of the present invention, unless otherwise specified, conventional operation methods in the art are adopted.

[0080] The following describes the present invention in detail with several specific examples, but it cannot be used as a limitation to the technical solutions protected by the present invention.

[0081] Example 1

[0082] The preparation method of the hard carbon negative electrode material for sodium-ion batteries prepared from Chinese medicine residues provided in this example includes the following steps.

[0083] 1) Pretreatment of drying Chinese medicine residues

[0084] 1.1) Thoroughly dry the Astragalus membranaceus residues after extracting the active ingredients;

[0085] 1.2) Soak the Astragalus membranaceus residues in step 1.1) with wood vinegar liquid at a ratio of 1 g:5 ml, let it stand, swell and soften, and then beat it into a uniform slurry;

[0086] 1.3) Filter the Astragalus membranaceus residues in the form of slurry obtained in step 1.2), wash the filter residue with water repeatedly, and dry it to obtain solid residues. Combine all the filtrates to obtain the primary liquid;

[0087] 1.4) Disperse the solid residues obtained in step 1.3) into a saturated potassium carbonate solution at a ratio of 1 g:5 ml, let it stand, swell and soften, and then beat it again to form a homogeneous slurry.

[0088] 2) Freeze-drying

[0089] Freeze-dry the slurry obtained in step 4) at -60 °C to remove moisture and obtain a solid product.

[0090] 3) Pre-carbonization treatment

[0091] The solid product obtained in step 2) is subjected to dry distillation pre-carbonization at 500 °C for 2 h, and the dry distillation liquid is collected. The dry distillation liquid is allowed to stand and layer to obtain the upper-layer wood vinegar liquid and the lower-layer wood tar.

[0092] 4) Preparation of hard carbon anode material

[0093] 4.1) The pre-carbonized product after cooling is mixed with the wood vinegar liquid obtained in step 3) at a ratio of 1:10 (g / ml), and then subjected to first-stage heating reflux at a reflux temperature of 120 °C for 0.5 h. After first-stage filtration, a filtered product and a secondary liquid are obtained. The solid of the filtered product is placed in a high-temperature furnace and calcined at 1400 °C for 2 h in an inert gas atmosphere to obtain a primary solid product.

[0094] 4.2) The primary solid product obtained from the first-stage calcination is mixed with the wood vinegar liquid obtained in step 3) at a ratio of 1:10 (g / ml), and then subjected to second-stage heating reflux at a reflux temperature of 120 °C for 0.5 h. After second-stage filtration, the surface wood vinegar liquid is washed off with water, and after drying, a secondary solid product is obtained. The filtrates are combined to obtain a tertiary liquid.

[0095] 4.3) The secondary solid product is dispersed in the wood tar obtained in step 3), and the secondary solid product and the wood tar are fully mixed and stirred evenly at a ratio of 2:1 (g / ml). Then, it is subjected to second-stage calcination at 700 °C for 2 h in an inert gas atmosphere in a high-temperature furnace to obtain a tertiary solid product.

[0096] 4.4) The tertiary solid product is mixed with the wood vinegar liquid obtained in step 3) at a ratio of 1:10 (g / ml) and then subjected to third-stage heating reflux at a reflux temperature of 120 °C for 0.5 h. After suction filtration, the surface wood vinegar liquid is washed off with water, and after drying and pulverization, the hard carbon anode material for sodium-ion batteries is obtained; the filtrates are combined to obtain a quaternary liquid.

[0097] The primary liquid in step 1.3), the secondary liquid in step 4.1), the tertiary liquid in step 4.2), and the quaternary liquid in step 4.4) are combined. After mixing, the pH is adjusted to 4.5 with the dry distillation liquid from the pre-carbonization in step 3) to obtain an organic liquid fertilizer matrix rich in potassium ions.

[0098] Examples 2 to 7

[0099] The preparation methods of the hard carbon anode materials for sodium-ion batteries prepared from the traditional Chinese medicine residue provided in Examples 2 to 7 are the same as those in Example 1, except that the types of traditional Chinese medicine residue used are different, and the raw material dosages and reaction parameters in each step are different. For details, see Table 1.

[0100] Table 1 Comparison of preparation process conditions in Examples 2 to 7

[0101]

[0102] The following are several comparative examples, with different preparation methods from the examples, and the performances are compared.

[0103] Comparative Example 1

[0104] The difference between this comparative example and the example is that in step 4), only primary heating reflux, primary calcination, and secondary heating reflux are adopted, and wood tar coating calcination and tertiary heating reflux are not adopted.

[0105] The preparation method provided by this comparative example specifically includes the following steps:

[0106] 1) Dry pretreatment of traditional Chinese medicine residues

[0107] 1.1) Thoroughly dry the astragalus residues after extracting the active ingredients;

[0108] 1.2) Immerse the astragalus residues in step 1.1) in wood vinegar solution at a ratio of 1 g: 5 ml, soak, stand, swell and soften them, and then beat them into a uniform slurry;

[0109] 1.3) Filter the astragalus residues in the form of slurry, wash the filter residue with water repeatedly, and dry to obtain solid residues. Combine all the filtrates to obtain the primary liquid;

[0110] 1.4) Disperse the solid residues obtained in step 1.3) into a saturated potassium carbonate solution at a ratio of 1 g: 5 ml, stand, swell and soften them, and then beat them again to form a uniform slurry.

[0111] 2) Freeze-drying

[0112] Remove the moisture from the slurry obtained in step 1.4) by freeze-drying to obtain a solid product.

[0113] 3) Pre-carbonization treatment

[0114] Carry out dry distillation pre-carbonization on the solid product obtained in step 2) at 500 °C for 2 h, collect the dry distillate, and let the dry distillate stand and separate into the upper-layer wood vinegar and the lower-layer wood tar.

[0115] 4) Preparation of hard carbon anode material

[0116] 4.1) After the pre-carbonization product is cooled, mix it with the wood vinegar obtained in step 3) at a ratio of 1:10 (g / ml), carry out primary heating reflux at a reflux temperature of 120 °C and a reflux time of 0.5 h, perform primary filtration to obtain a filtered product and a secondary liquid, place the solid of the obtained filtered product in a high-temperature furnace, and carry out primary calcination at 1400 °C for 2 h in an inert gas atmosphere to obtain a primary solid product.

[0117] 4.2) The primary solid product is mixed with the wood vinegar liquor obtained in step 3) at a ratio of 1:10 (g / ml), followed by secondary heating under reflux at a temperature of 120 °C for 0.5 h. After secondary filtration, the surface wood vinegar liquor is washed off with water, and after drying, a secondary solid product is obtained. After drying and pulverization, the hard carbon anode material for sodium-ion batteries is obtained, and the filtrates are combined to obtain a tertiary liquid.

[0118] The primary liquid from step 1.3), the secondary liquid from step 4.1), and the tertiary liquid from step 4.2) are combined, and the pH is adjusted to 4.5 with the dry distillate obtained in step 3) to obtain an organic liquid fertilizer matrix rich in potassium ions.

[0119] Comparative Example 2

[0120] The difference between Comparative Example 2 and Example 2 lies in that in step 4), only primary heating under reflux, primary calcination, and secondary heating under reflux are employed.

[0121] The preparation method of the hard carbon anode material for sodium-ion batteries provided by this control includes the following steps.

[0122] 1) Dry pretreatment of traditional Chinese medicine residues

[0123] 1.1) The licorice residues after extracting the active ingredients are fully dried.

[0124] 1.2) The licorice residues in step 1.1) are mixed with wood vinegar liquor at a ratio of 1:5 (g / ml), fully soaked, allowed to stand, and swollen and softened before pulping to form a uniform slurry.

[0125] 1.3) The licorice residues in the form of slurry are filtered by suction, the filter residue is repeatedly washed with water, and after drying, a solid residue is obtained, and all the filtrates are combined to obtain a primary liquid.

[0126] 1.4) The solid residue obtained in step 1.3) is dispersed in a saturated potassium carbonate solution and mixed at a ratio of 1:10 (g / ml), allowed to stand, swollen and softened, and then pulped again to form a homogeneous slurry, which is the pretreatment product.

[0127] 2) Freeze-drying

[0128] The slurry obtained in step 1.4) is freeze-dried to remove moisture to obtain a solid product.

[0129] 3) Pre-carbonization treatment

[0130] The solid product obtained in step 2) is subjected to dry distillation pre-carbonization at 500 °C for 1.5 h, and the dry distillate is collected. The dry distillate is allowed to stand and layer to obtain the upper-layer wood vinegar liquor and the lower-layer wood tar.

[0131] 4) Preparation of hard carbon anode material

[0132] 4.1) The pre-carbonized product after cooling is placed in a high-temperature furnace and calcined at 1400 °C for 2 h in an inert gas atmosphere. The primary solid product is obtained after the primary calcination.

[0133] 4.2) The secondary solid product is dispersed in the wood tar obtained in step 3). The secondary solid product and the wood tar are fully mixed and stirred evenly according to the ratio of 4:1 (g / ml), and then calcined at 700 °C for 2 h in an inert gas atmosphere in a high-temperature furnace to obtain the tertiary solid product. After pulverization, the hard carbon anode material for sodium-ion batteries is obtained.

[0134] In step 1.3), the pH of the primary liquid is adjusted to 4.5 with the dry distillate obtained in step 3) to obtain an organic liquid fertilizer matrix rich in potassium ions.

[0135] Comparative Example 3

[0136] The difference between Comparative Example 3 and Example 3 is that after the medicinal residues are dried, they are not subjected to wood vinegar soaking, potassium carbonate soaking, and freeze-drying treatments, and the dried medicinal residues are directly subjected to subsequent treatments such as pre-carbonization.

[0137] The preparation method of the hard carbon anode material for sodium-ion batteries provided by this comparative example includes the following steps.

[0138] 1) Drying pretreatment of traditional Chinese medicine residues

[0139] The Salvia miltiorrhiza residues after extracting the active ingredients are fully dried.

[0140] 2) Pre-carbonization treatment

[0141] The dried Salvia miltiorrhiza residues obtained in step 1) are subjected to dry distillation pre-carbonization at 400 °C for 3 h, and the dry distillate is collected. The dry distillate is allowed to stand and layer to obtain the upper-layer wood vinegar and the lower-layer wood tar.

[0142] 3) Preparation of hard carbon anode material

[0143] 3.1) After the pre-carbonized product after cooling is mixed with the wood vinegar obtained in step 2) according to the ratio of 1:10 (g / ml), it is subjected to primary heating reflux at a reflux temperature of 120 °C for 0.5 h, and then primary filtration is carried out to obtain the filtration product and the secondary liquid. The solid of the obtained filtration product is placed in a high-temperature furnace and calcined at 1200 °C for 2 h in an inert gas atmosphere to obtain the primary solid product.

[0144] 3.2) The calcined primary solid product is subjected to secondary heating reflux and secondary filtration with the wood vinegar obtained in step 2) according to the ratio of 1:10 (g / ml), the surface wood vinegar is washed off with water, and after drying, the secondary solid product is obtained, and the filtrates are combined to obtain the tertiary liquid.

[0145] 3.3) The secondary solid product is dispersed in the wood tar obtained in step 2), and they are thoroughly mixed and stirred evenly according to the ratio of 4:1 (g / ml), and then subjected to secondary calcination at 600 °C in an inert gas atmosphere in a high-temperature furnace for 2 h to obtain a tertiary solid product.

[0146] 3.4) The tertiary solid product is subjected to tertiary heating reflux with the wood vinegar obtained in step 2) according to the ratio of 1:10 (g / ml). The reflux temperature is 120 °C and the reflux time is 2 h. After filtration by suction, the surface wood vinegar is washed off with water, dried, and pulverized to obtain the hard carbon anode material for sodium-ion batteries; the filtrates are combined to obtain a fourth liquid.

[0147] The secondary liquid in step 3.1), the tertiary liquid in step 3.2) and the fourth liquid in step 3.4) are combined, and the pH is adjusted to 4.5 with the dry distillate in step 2) to obtain an organic liquid fertilizer matrix rich in potassium ions.

[0148] Comparative Example 4

[0149] The difference between Comparative Example 4 and Example 4 is that direct high-temperature calcination is carried out after pre-carbonization treatment.

[0150] The preparation method for preparing the hard carbon anode material for sodium-ion batteries from Chinese medicine residues provided in this example includes the following steps.

[0151] 1) Dry pretreatment of Chinese medicine residues

[0152] 1.1) Thoroughly dry the polygonatum odoratum residues after extracting the active ingredients.

[0153] 1.2) The polygonatum odoratum residues in step 1.1) are fully soaked with wood vinegar according to the ratio of 1:6 (g / ml), allowed to stand, and swollen and softened, and then pulped to form a uniform slurry.

[0154] 1.3) The polygonatum odoratum residues forming a paste are filtered by suction, the filter residue is repeatedly washed with water, dried to obtain solid residues, and all the filtrates are combined to obtain a first liquid.

[0155] 1.4) The solid residues obtained in step 1.3) are dispersed in a saturated potassium carbonate solution and mixed and allowed to stand according to the ratio of 1:8 (g / ml), swollen and softened, and then pulped again and homogenized to form a uniform slurry, which is the pretreatment product.

[0156] 2) Freeze-drying

[0157] The slurry obtained in step 1.4) is dehydrated by freeze-drying to obtain a solid product.

[0158] 3) Pre-carbonization treatment

[0159] The solid product obtained in step 2) is subjected to dry distillation pre-carbonization at 600 °C for 2 h, and the dry distillation liquid is collected. The dry distillation liquid is allowed to stand and layer to obtain the upper-layer wood vinegar liquid and the lower-layer wood tar.

[0160] 4) Preparation of hard carbon anode material

[0161] The pre-carbonized product after cooling is subjected to first-stage calcination at 1100 °C in an inert gas atmosphere for 2 h to obtain a primary solid product; after drying and pulverizing, the hard carbon anode material for sodium-ion batteries is obtained.

[0162] Comparative Example 5

[0163] The difference between Comparative Example 5 and Example 5 is that after the medicinal residues are dried, they are not subjected to potassium carbonate soaking treatment.

[0164] The preparation method for preparing the hard carbon anode material for sodium-ion batteries from the traditional Chinese medicine residues provided in this example includes the following steps.

[0165] 1) Dry pretreatment of traditional Chinese medicine residues

[0166] 1.1) Sufficiently dry the polygala tenuifolia medicinal residues after extracting the active ingredients;

[0167] 1.2) The polygala tenuifolia medicinal residues in step 1) are fully soaked with wood vinegar liquid at a ratio of 1:9 (g / ml), allowed to stand, and swollen and softened, and then pulped to form a uniform slurry;

[0168] 1.3) The polygala tenuifolia medicinal residues forming a paste are filtered by suction, the filter residue is repeatedly washed with water and dried to obtain solid medicinal residues, and all the filtrates are combined to obtain a primary liquid.

[0169] 2) Freeze-drying

[0170] The solid medicinal residues obtained in step 1.3) are dehydrated by freeze-drying to obtain a solid product.

[0171] 3) Pre-carbonization treatment

[0172] The solid product obtained in step 2) is subjected to dry distillation pre-carbonization at 300 °C for 2 h; and the dry distillation liquid is collected. The dry distillation liquid is allowed to stand and layer to obtain the upper-layer wood vinegar liquid and the lower-layer wood tar.

[0173] 4) Preparation of hard carbon anode material

[0174] 4.1) After the pre-carbonized product after cooling is mixed with the wood vinegar liquid obtained in step 3) at a ratio of 1:10 (g / ml), it is subjected to first-stage heating reflux at a reflux temperature of 120 °C for 0.5 h, first-stage filtration, and a filtered product and a secondary liquid are obtained. The solid of the obtained filtered product is placed in a high-temperature furnace and subjected to first-stage calcination at 1400 °C in an inert gas atmosphere for 2 h to obtain a primary solid product.

[0175] 4.2) The calcined primary solid product is subjected to secondary heating reflux with the wood vinegar liquid obtained in step 3) at a ratio of 1:10 (g / ml), the reflux temperature is 120 °C, the reflux time is 2 h, followed by secondary filtration. The surface wood vinegar liquid is washed off with water, and after drying, a secondary solid product is obtained. The filtrates are combined to obtain a tertiary liquid.

[0176] 4.3) The secondary solid product is dispersed in the wood tar obtained in step 3) and thoroughly mixed and stirred evenly at a ratio of 6:1 (g / ml). It is subjected to secondary calcination at 900 °C in an inert gas atmosphere in a high-temperature furnace for 3 h to obtain a tertiary solid product.

[0177] 4.4) The tertiary solid product is subjected to tertiary heating reflux with the wood vinegar liquid obtained in step 3) at a ratio of 1:10 (g / ml), the reflux temperature is 120 °C, the reflux time is 0.5 h, and then it is subjected to suction filtration. The surface wood vinegar liquid is washed off with water, dried, and pulverized to obtain the hard carbon anode material for sodium-ion batteries; the filtrates are combined to obtain a quaternary liquid.

[0178] The primary liquid in step 1.3), the secondary liquid in step 4.1), the tertiary liquid in step 4.2), and the quaternary liquid in step 4.4) are combined, and the pH is adjusted to 4.5 with the dry distillate obtained in step 3) to obtain an organic liquid fertilizer matrix rich in potassium ions.

[0179] Comparative Example 6

[0180] The difference between Comparative Example 6 and Example 6 is that after the medicinal residues are dried, they are not subjected to the wood vinegar liquid soaking treatment.

[0181] The preparation method for preparing the hard carbon anode material for sodium-ion batteries from traditional Chinese medicine residues provided in this example includes the following steps:

[0182] 1) Pretreatment of drying traditional Chinese medicine residues

[0183] 1.1) The jujube medicinal residues after extracting the active ingredients are fully dried;

[0184] 1.2) The solid medicinal residues obtained in step 3) are dispersed in a saturated potassium carbonate solution at a ratio of 1:7 (g / ml), allowed to stand, swell and soften, and then beaten into a slurry and homogenized to form a uniform slurry, i.e., the pretreatment product.

[0185] 2) Freeze-drying

[0186] The slurry obtained in step 1.2) is dehydrated by freeze-drying to obtain a solid product.

[0187] 3) Pre-carbonization treatment

[0188] The solid product obtained in step 2) is subjected to dry distillation pre-carbonization at 600 °C for 3 h, and the dry distillation liquid is collected. The dry distillation liquid is allowed to stand and layer to obtain the upper-layer wood vinegar liquid and the lower-layer wood tar.

[0189] 4) Preparation of hard carbon anode material

[0190] 4.1) After the cooled pre-carbonized product is mixed with the wood vinegar liquid obtained in step 3) at a ratio of 1:4 (g / ml), it is subjected to first-stage heating reflux at a reflux temperature of 120 °C for 1 h, followed by first-stage filtration to obtain a solid filtration product and a secondary liquid. The obtained solid filtration product is placed in a high-temperature furnace and calcined at 1100 °C in an inert gas atmosphere for 2 h to obtain a primary solid product.

[0191] 4.2) The calcined primary solid product is subjected to second-stage heating reflux with the wood vinegar liquid obtained in step 3) at a ratio of 1:7 (g / ml), the reflux temperature is 120 °C, the reflux time is 1 h, followed by second-stage filtration. The surface wood vinegar liquid is washed off with water, and after drying, a secondary solid product is obtained. The filtrates are combined to obtain a tertiary liquid.

[0192] 4.3) The secondary solid product is dispersed in the wood tar obtained in step 3), and is thoroughly mixed and stirred evenly at a ratio of 7:2 (g / ml). It is then subjected to second-stage calcination at 700 °C in an inert gas atmosphere in a high-temperature furnace for 2 h to obtain a tertiary solid product.

[0193] 4.4) The tertiary solid product is subjected to third-stage heating reflux with the wood vinegar liquid obtained in step 3) at a ratio of 1:7 (g / ml), the reflux temperature is 120 °C, the reflux time is 1 h, and then it is subjected to suction filtration. The surface wood vinegar liquid is washed off with water, dried, and pulverized to obtain the hard carbon anode material for sodium-ion batteries; the filtrates are combined to obtain a quaternary liquid.

[0194] The secondary liquid in step 4.1), the tertiary liquid in step 4.2), and the quaternary liquid in step 4.4) are combined, and the pH is adjusted to 4.5 with the dry distillation liquid obtained in step 3) to obtain an organic liquid fertilizer matrix rich in potassium ions.

[0195] Comparative Example 7

[0196] The difference between Comparative Example 7 and Example 7 is that after the medicinal residues are dried, they are directly pre-carbonized and then directly subjected to high-temperature calcination treatment.

[0197] The preparation method of the hard carbon anode material for sodium-ion batteries provided by this comparative example includes the following steps.

[0198] 1) Dry pretreatment of traditional Chinese medicine residues

[0199] 1) The mixed medicinal residues after extracting the active ingredients are thoroughly dried.

[0200] 2) Pre-carbonization treatment

[0201] The solid product obtained in step 1) is subjected to dry distillation pre-carbonization at 500 °C for 2 h to obtain a pre-carbonized product, and the dry distillation liquid is collected. The dry distillation liquid is allowed to stand and layer to obtain the upper-layer wood vinegar liquid and the lower-layer wood tar.

[0202] 3) Preparation of hard carbon anode material

[0203] The pre-carbonized product is placed in a high-temperature furnace and calcined at 1400 °C for 2 h in an inert gas atmosphere to obtain a solid product. After drying and pulverizing, the hard carbon anode material for sodium-ion batteries is obtained.

[0204] Comparative Example 8

[0205] The difference between the preparation method of this comparative example and that of Example 1 is that freeze-drying is not used.

[0206] Verify the performance of the hard carbon for sodium-ion batteries prepared in the examples and comparative examples.

[0207] Verification 1 Electrochemical performance test of the hard carbon anode material for sodium-ion batteries prepared from Astragalus residue

[0208] Conduct an electrochemical performance test on the hard carbon anode materials for sodium-ion batteries prepared in Example 1 and Comparative Example 1. The specific test process is as follows.

[0209] 1) Mix the above-prepared active substance powder in a ratio of active substance: conductive agent: binder = 8:1:1, add an appropriate amount of NMP, and mix well to form a slurry. Then, uniformly coat the slurry on the aluminum foil and dry it in a vacuum environment at 120 °C. After thorough drying, cut it into circular pieces with a diameter of 10 mm for use in assembling the battery.

[0210] 2) Assemble a button battery in a glove box filled with argon (the water and oxygen content < 0.1 ppm). Use metallic sodium as the counter electrode, use a solution of 1 mol of sodium hypochlorite dissolved in 1 L of a mixed solution of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1 and added with 1 wt% of fluoroethylene carbonate as the electrolyte, and use a glass fiber membrane as the separator to assemble a CR2032 button battery.

[0211] 3) Use a rate charge-discharge test to detect the electrochemical performance of the button battery. Conduct a rate charge-discharge test at a charge-discharge rate of 0.2C, and set the charge-discharge voltage to 0.01V to 2.5V.

[0212] The first charge-discharge curves of the hard carbon anode materials for sodium-ion batteries prepared in Example 1 and Comparative Example 1 are as shown in Appendix Figure 1 、 Figure 2 and Table 2.

[0213] As shown in Table 2, Figure 1and Figure 2 It can be seen that the specific capacity of the sodium ion battery hard carbon negative electrode prepared by using Astragalus residue as raw material and not using wood tar coating method is 410 mAh / g, and the first charge and discharge efficiency is 59.2%; the specific capacity of the sodium ion battery hard carbon negative electrode prepared by the present invention using wood tar coating is 578 mAh / g, and the first charge and discharge efficiency is as high as 85.1%. Compared with Comparative Example 1, the specific capacity of the present invention is increased by 168 mAh / g, and the first charge and discharge efficiency is increased by 25.9%.

[0214] It is explained that the present invention uses Astragalus root residue to prepare sodium ion battery hard carbon negative electrode material, and then coats it with wood tar and performs secondary calcination, which can greatly improve the specific capacity and initial charge and discharge efficiency of the product.

[0215] Verification 2 Electrochemical performance test of hard carbon anode material for sodium ion battery prepared from licorice residue

[0216] The electrochemical performance of the sodium ion battery hard carbon negative electrode materials prepared in Example 2 and Comparative Example 2 was tested. The specific test process is as follows.

[0217] 1. Mix the prepared active material powder in the ratio of active material: conductive agent: binder = 8:1:1, add appropriate amount of NMP, and mix thoroughly to form slurry. Then evenly apply the slurry on aluminum foil and dry it in a vacuum environment at 120°C. After thorough drying, cut it into discs with a diameter of 10 mm for battery assembly.

[0218] 2. Assemble button cells in an argon-filled glove box (water and oxygen content <0.1ppm). Use metallic sodium as the counter electrode, dissolve 1 mol of sodium hypochlorite in 1L of ethylene carbonate and diethyl carbonate solution with a volume ratio of 1:1, add 1wt% of fluoroethylene carbonate solution as the electrolyte, and use glass fiber membrane as the diaphragm to assemble a CR2032 button cell.

[0219] 3. Use rate charge and discharge test to detect the electrochemical performance of button batteries. Perform rate charge and discharge test at 0.2C, and set the charge and discharge voltage to 0.01V to 2.5V.

[0220] The first charge and discharge curves of the sodium ion battery hard carbon negative electrode materials prepared in Example 2 and Comparative Example 2 are shown in the attached figure. Figure 3 , Figure 4 And as shown in Table 2.

[0221] Depend on Figure 3 , Figure 4As can be seen from Table 2, the specific capacity of the hard carbon anode for sodium-ion batteries prepared from licorice residue by using low-temperature pre-carbonization, high-temperature calcination carbonization, and wood tar coating calcination without using the method of fractional reflux of wood vinegar is 266 mAh / g, and the first charge-discharge efficiency is 81.2%; the specific capacity of the hard carbon anode for sodium-ion batteries prepared by the present invention is 370 mAh / g, and the first charge-discharge efficiency is as high as 91.3%.

[0222] It can be seen that the process of the present invention for preparing the hard carbon anode material for sodium-ion batteries from licorice residue can greatly improve the specific capacity and the first charge-discharge efficiency of the product compared with the process without using fractional reflux of wood vinegar.

[0223] Verification 3 Electrochemical performance test of the hard carbon anode material for sodium-ion batteries prepared from Salvia miltiorrhiza residue

[0224] The electrochemical performance of the hard carbon anode materials for sodium-ion batteries prepared in Example 3 and Comparative Example 3 was tested. The specific test process is as follows.

[0225] 1. The prepared active material powder was mixed in a ratio of active material: conductive agent: binder = 8:1:1, and an appropriate amount of NMP was added and mixed well to form a slurry. Then the slurry was evenly coated on the aluminum foil and dried in a vacuum environment at 120 °C. After thorough drying, it was cut into circular pieces with a diameter of 10 mm for use in assembling the battery.

[0226] 2. The button battery was assembled in a glove box filled with argon (the water and oxygen content < 0.1 ppm). Using metallic sodium as the counter electrode, a solution of 1 mol of sodium hypochlorite dissolved in 1 L of a mixed solution of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1 and adding 1 wt% of fluoroethylene carbonate as the electrolyte, and using a glass fiber membrane as the separator to assemble a CR2032 button battery.

[0227] 3. The rate charge-discharge test was used to detect the electrochemical performance of the button battery. The rate charge-discharge test was carried out at a charge-discharge capacity of 0.2C, and the charge-discharge voltage was set from 0.01V to 2.5V.

[0228] The first charge-discharge curves of the hard carbon anode materials for sodium-ion batteries prepared in Example 3 and Comparative Example 3 are as shown in the appendix Figure 5 、 Figure 6 and Table 2.

[0229] From Figure 5 、 Figure 6 and Table 2, it can be seen that the specific capacity of the hard carbon anode for sodium-ion batteries prepared from Salvia miltiorrhiza residue by using direct pre-carbonization, high-temperature carbonization, pickling, and coating methods is 267 mAh / g, and the first charge-discharge efficiency is 63.6%; the specific capacity of the hard carbon anode for sodium-ion batteries prepared by the present invention is 401 mAh / g, and the first charge-discharge efficiency is as high as 87.4%.

[0230] It can be seen that the process of the present invention uses liquorice residue to prepare sodium ion battery hard carbon negative electrode materials, and adopts a pretreatment method of swelling and pulping the residue and using potassium carbonate as a catalyst, which can greatly improve the specific capacity and initial charge and discharge efficiency of the product.

[0231] Verification 4 Electrochemical performance test of sodium ion battery hard carbon negative electrode material prepared from Polygonatum sibiricum residue

[0232] The electrochemical performance of the sodium ion battery hard carbon negative electrode materials prepared in Example 4 and Comparative Example 4 was tested. The specific test process is as follows.

[0233] 1. Mix the prepared active material powder in the ratio of active material: conductive agent: binder = 8:1:1, add appropriate amount of NMP, and mix thoroughly to form slurry. Then evenly apply the slurry on aluminum foil and dry it in a vacuum environment at 120°C. After thorough drying, cut it into discs with a diameter of 10 mm for battery assembly.

[0234] 2. Assemble button cells in an argon-filled glove box (water and oxygen content <0.1ppm). Use metallic sodium as the counter electrode, dissolve 1 mol of sodium hypochlorite in 1L of ethylene carbonate and diethyl carbonate solution with a volume ratio of 1:1, add 1wt% of fluoroethylene carbonate solution as the electrolyte, and use glass fiber membrane as the diaphragm to assemble a CR2032 button cell.

[0235] 3. Use rate charge and discharge test to detect the electrochemical performance of button batteries. Perform rate charge and discharge test at 0.2C, and set the charge and discharge voltage to 0.01V to 2.5V.

[0236] The first charge and discharge curves of the sodium ion battery hard carbon negative electrode materials prepared in Example 4 and Comparative Example 4 are shown in the attached figure. Figure 7 , Figure 8 And as shown in Table 2.

[0237] Depend on Figure 7 , Figure 8 As shown in Table 2, the specific capacity of the sodium ion battery hard carbon negative electrode prepared by using the Polygonatum sibiricum residue as raw material and not using the method of wood vinegar fractional reflux and wood tar coating is 270 mAh / g, and the first charge and discharge efficiency is 75.9%; the specific capacity of the sodium ion battery hard carbon negative electrode prepared by the present invention is 403 mAh / g, and the first charge and discharge efficiency is as high as 84.6%.

[0238] It can be seen that the process of the present invention uses liquorice residue to prepare sodium ion battery hard carbon negative electrode material, which is then refluxed by wood vinegar and coated with wood tar in batches, and can greatly improve the specific capacity and initial charge and discharge efficiency of the product.

[0239] Verification of the Electrochemical Performance Test of the Hard Carbon Anode Material for Sodium-Ion Batteries Prepared from Polygala tenuifolia Residue

[0240] The electrochemical performance of the hard carbon anode materials for sodium-ion batteries prepared in Example 5 and Comparative Example 5 was tested. The specific test process is as follows.

[0241] 1. The prepared active material powder was mixed in a ratio of active material: conductive agent: binder = 8:1:1, and an appropriate amount of NMP was added and thoroughly mixed to form a slurry. Subsequently, the slurry was evenly coated on the aluminum foil and dried in a vacuum environment at 120 °C. After thorough drying, it was cut into circular pieces with a diameter of 10 mm for use in assembling the battery.

[0242] 2. The coin-type battery was assembled in a glove box filled with argon (the water and oxygen content < 0.1 ppm). Using metallic sodium as the counter electrode, a solution of 1 mol of sodium hypochlorite dissolved in 1 L of a mixed solution of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1 and added with 1 wt% of fluoroethylene carbonate was used as the electrolyte, and a glass fiber membrane was used as the separator to assemble a CR2032 coin-type battery.

[0243] 3. The rate charge and discharge test was used to detect the electrochemical performance of the coin-type battery. The rate charge and discharge test was carried out at a charge and discharge capacity of 0.2C, and the charge and discharge voltage was set at 0.01V to 2.5V.

[0244] The first charge and discharge curves of the hard carbon anode materials for sodium-ion batteries prepared in Example 5 and Comparative Example 5 are as shown in the appendix Figure 9 、 Figure 10 and Table 2.

[0245] From Figure 9 、 Figure 10 and Table 2, it can be seen that for the hard carbon anode of the sodium-ion battery prepared from Polygala tenuifolia residue without using potassium carbonate as the pore-forming agent, the specific capacity is 277 mAh / g and the first charge and discharge efficiency is 23.8%; for the hard carbon anode of the sodium-ion battery prepared by the present invention, the specific capacity is 423 mAh / g and the first charge and discharge efficiency is as high as 85.5%.

[0246] It can be seen that the process of the present invention for preparing the hard carbon anode material for sodium-ion batteries from Polygala tenuifolia residue can greatly improve the specific capacity and the first charge and discharge efficiency of the product through the action of potassium carbonate.

[0247] Verification of the Electrochemical Performance Test of the Hard Carbon Anode Material for Sodium-Ion Batteries Prepared from Jujube Residue

[0248] The electrochemical performance of the hard carbon anode materials for sodium-ion batteries prepared in Example 6 and Comparative Example 6 was tested. The specific test process is as follows.

[0249] 1. Mix the prepared active material powder in a ratio of active material: conductive agent: binder = 8:1:1, add an appropriate amount of NMP, and mix well to form a slurry. Then, evenly coat the slurry on the aluminum foil and dry it in a vacuum environment at 120 °C. After thorough drying, cut it into circular pieces with a diameter of 10 mm for use in assembling the battery.

[0250] 2. Assemble the coin cell in a glove box filled with argon (with water and oxygen content < 0.1 ppm). Use metallic sodium as the counter electrode, a solution of 1 mol of sodium hypochlorite dissolved in 1 L of a mixed solution of ethylene carbonate and diethyl carbonate with a volume ratio of 1:1 and added with 1 wt% of fluoroethylene carbonate as the electrolyte, and a glass fiber membrane as the separator to assemble a CR2032 coin cell.

[0251] 3. Use rate charge-discharge testing to detect the electrochemical performance of the coin cell. Conduct rate charge-discharge testing at a charge-discharge rate of 0.2C, and set the charge-discharge voltage to 0.01V to 2.5V.

[0252] The first charge-discharge curves of the hard carbon negative electrode materials of the sodium-ion batteries prepared in Example 6 and Comparative Example 6 are as shown in the appendix Figure 11 、 Figure 12 and Table 2.

[0253] From Figure 11 、 Figure 12 and Table 2, it can be seen that for the hard carbon negative electrode of the sodium-ion battery prepared from jujube residue without using the method of pretreating the residue with wood vinegar, the specific capacity is 291 mAh / g and the first charge-discharge efficiency is 83%; for the hard carbon negative electrode of the sodium-ion battery prepared by the present invention, the specific capacity is 508 mAh / g and the first charge-discharge efficiency is as high as 83.8%.

[0254] It can be seen that the process of the present invention uses wood vinegar to pretreat the residue first when preparing the hard carbon negative electrode material of the sodium-ion battery from licorice residue, which can greatly improve the specific capacity of the product.

[0255] Verification 7 Electrochemical performance test of the hard carbon negative electrode material of the sodium-ion battery prepared from the mixed residue

[0256] Conduct electrochemical performance tests on the hard carbon negative electrode materials of the sodium-ion batteries prepared in Example 7 and Comparative Example 7. The specific test process is as follows.

[0257] 1. Mix the prepared active material powder in a ratio of active material: conductive agent: binder = 8:1:1, add an appropriate amount of NMP, and mix well to form a slurry. Then, evenly coat the slurry on the aluminum foil and dry it in a vacuum environment at 120 °C. After thorough drying, cut it into circular pieces with a diameter of 10 mm for use in assembling the battery.

[0258] 2. Assemble the coin cell in a glove box filled with argon (water and oxygen content < 0.1 ppm). Use metallic sodium as the counter electrode, a solution of 1 mol of sodium hypochlorite dissolved in 1 L of a 1:1 volume ratio of ethylene carbonate and diethyl carbonate solution with 1 wt% of fluoroethylene carbonate added as the electrolyte, and a glass fiber membrane as the separator to assemble a CR2032 coin cell.

[0259] 3. Use rate charge-discharge tests to detect the electrochemical performance of the coin cell. Conduct rate charge-discharge tests at a charge-discharge rate of 0.2C, and set the charge-discharge voltage to 0.01V to 2.5V.

[0260] The first charge-discharge curves of the hard carbon anode materials for sodium-ion batteries prepared in Example 7 and Comparative Example 7 are as shown in the appendix Figure 13 、 Figure 14 and Table 2.

[0261] From Figure 13 、 Figure 14 and Table 2, it can be seen that for the hard carbon anode of the sodium-ion battery prepared from the mixed medicinal residues by the traditional pyrolysis method, the specific capacity is 244 mAh / g and the first charge-discharge efficiency is 55%; for the hard carbon anode of the sodium-ion battery prepared by the present invention, the specific capacity is 375 mAh / g and the first charge-discharge efficiency is as high as 86%.

[0262] It can be seen that compared with the traditional process, the process of the present invention for preparing the hard carbon anode material for sodium-ion batteries from licorice medicinal residues can greatly improve the specific capacity and the first charge-discharge efficiency of the product.

[0263] Verification 8

[0264] Conduct electrochemical performance tests on the hard carbon anode materials for sodium-ion batteries prepared in Example 1 and Comparative Example 8. The specific test process is the same as that in Verification 1, and the results are shown in Table 2.

[0265] From Table 2, it can be seen that for the hard carbon anode material for sodium-ion batteries obtained in Comparative Example 8, the specific capacity is 472 mAh / g and the first charge-discharge efficiency is 75%. For the hard carbon anode material for sodium-ion batteries prepared in Example 1, the specific capacity is increased by 106 mAh / g and the first charge-discharge efficiency is increased by 10.1%.

[0266] The results show that after freeze-drying, the specific capacity and the first charge-discharge efficiency of the obtained hard carbon anode material for sodium-ion batteries are both improved.

[0267] Test results of the electrochemical performance of the hard carbon anode for sodium-ion batteries prepared from medicinal residues in Table 2

[0268]

[0269]

Claims

1. A method for preparing a hard carbon anode material for a sodium-ion battery using traditional Chinese medicine residue, characterized in that, it includes the following steps: 1) Pretreatment After drying the traditional Chinese medicine residue, a pretreatment product is obtained through pretreatment; The specific steps of step 1) include: 1.1) After drying the traditional Chinese medicine residue, soak it in wood vinegar liquid, and then successively carry out beating, filtering, washing, and drying to obtain solid residue; 1.2) Disperse the solid residue into a saturated potassium carbonate solution, let it stand and beat to obtain a pretreatment product; 2) Freeze-drying Freeze-dry the pretreatment product of step 1) to obtain a solid product; 3) Pre-carbonization The solid product undergoes pre-carbonization to obtain a pre-carbonized product and a dry distillate; In step 3), the conditions for dry distillation pre-carbonization are: the heating rate is 5 °C / min, the dry distillation temperature is 300 °C to 700 °C, and the dry distillation time is 2 h to 5 h; the dry distillate includes wood vinegar liquid and wood tar; 4) Preparation of hard carbon anode material 4.1) Take the pre-carbonized product of step 3), and carry out first-stage heating reflux with the wood vinegar liquid of step 3), and then carry out first-stage calcination in an inert gas atmosphere to obtain a primary solid product; 4.2) Take the primary solid product, and carry out second-stage heating reflux with the wood vinegar liquid of step 3) to obtain a secondary solid product; 4.3) Disperse the secondary solid in the wood tar of step 3), and carry out second-stage calcination in an inert gas atmosphere to obtain a tertiary solid product; 4.4) Take the tertiary solid product, and carry out third-stage heating reflux with the wood vinegar liquid of step 3) to obtain a secondary solid product, and further carry out drying and pulverization treatment to obtain hard carbon for sodium-ion battery; The conditions for the first-stage calcination are: the temperature is 1100 °C to 1400 °C, and the time is 2 h; the conditions for the first-stage heating reflux, second-stage heating reflux, and third-stage heating reflux are all: the temperature is 100 to 120 °C, and the time is 0.5 h to 2 h; the conditions for the second-stage calcination are: the temperature is 700 °C to 900 °C, and the time is 2 to 3 h.

2. The method for preparing a hard carbon anode material for a sodium-ion battery using traditional Chinese medicine residue according to claim 1, characterized in that, in step 1), the dosage ratio of the traditional Chinese medicine residue to the wood vinegar liquid is 1 g: 2 - 8 ml, and the dosage ratio of the solid residue to the saturated potassium carbonate solution is 1 g: 2 - 5 ml; the wood vinegar liquid is a wine-red liquid obtained during the dry distillation process of materials, and the materials are straw, corn cob, Xanthoceras sorbifolia shell, wild jujube kernel shell, almond shell, bamboo or wood; the traditional Chinese medicine residue is astragalus membranaceus, licorice, salvia miltiorrhiza, polygala tenuifolia, jujube or mixed residue.

3. The method for preparing a hard carbon anode material for a sodium-ion battery using traditional Chinese medicine residue according to claim 1, characterized in that, in step 2), the freezing temperature is -40 °C to -80 °C.

4. A hard carbon anode material for a sodium-ion battery obtained by the method for preparing a hard carbon anode material for a sodium-ion battery using traditional Chinese medicine residue according to any one of claims 1 - 3.

5. The hard carbon anode material for a sodium-ion battery according to claim 4, characterized in that, the highest specific capacity of the hard carbon anode material for a sodium-ion battery is 578 mAh / g, and the highest first charge-discharge efficiency is 91%.

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