Hard carbon negative electrode material and preparation method and application thereof

Abstract

The invention provides a hard carbon negative electrode material as well as a preparation method and application thereof, and relates to the technical field of negative electrode materials, and the preparation method comprises the following steps: mixing lignin with resin, acid and zinc salt for carbonization, enabling the lignin and the resin to be subjected to cross-linking compounding, activating, pore-forming and sintering at the same time, and obtaining the hard carbon negative electrode material with high compaction density and high capacity. Compared with a traditional biomass-based material, the hard carbon negative electrode material disclosed by the invention has higher compaction density, and compared with resin-derived hard carbon, the hard carbon negative electrode material disclosed by the invention has higher sodium storage capacity, the overall energy density of a hard carbon negative electrode is improved, the specific capacity is high, and the technical problem that the existing hard carbon material is difficult to effectively consider high compaction density and high capacity is solved.

Description

Technical Field

[0001] This invention relates to the technical field of anode materials, and in particular to a hard carbon anode material, its preparation method, and its application. Background Technology

[0002] With the accelerated global energy structure transformation, sodium-ion batteries have become a key technology for large-scale energy storage due to their abundant resources and low cost. As a core component, hard carbon anode materials have been extensively studied due to their excellent sodium storage capacity (300mAh / g-350mAh / g) and structural stability. Biomass hard carbon, due to its low cost, has become the mainstream commercial hard carbon technology.

[0003] However, hard carbon materials have a low compaction density (3T powder compaction is generally <1.0 g / cm³). 3 This severely restricts the volumetric energy density of batteries, especially in space-constrained scenarios such as electric vehicles and portable devices. Improving compaction density has become an essential industry requirement.

[0004] Traditional biomass-based hard charcoal 3T powder has a compacted density of only 0.95 g / cm³. 3 -1.0g / cm 3 This results in a low volumetric energy density for the entire battery; biomass hard char (coconut shell / straw) has a capacity >300mAh / g, but a low compaction density (3T powder compaction ≤1.0g / cm³). 3 ); High-compact density coal-based / resin-based hard carbon 3T powder with a compaction density >1g / cm³ 3 However, the capacity is less than 250mAh / g and the cost is high.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] One of the objectives of this invention is to provide a method for preparing hard carbon anode material, which enables hard carbon to maintain a high capacity while having a high compaction density.

[0007] The second objective of this invention is to provide a hard carbon anode material that has a higher compaction density compared to traditional biomass-based materials and a higher sodium storage capacity compared to resin-derived hard carbon, thereby improving the overall energy density and specific capacity of the hard carbon anode.

[0008] The third objective of this invention is to provide an application of hard carbon anode material that is beneficial to improving the performance of sodium-ion batteries.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, a method for preparing a hard carbon anode material includes the following steps: Lignin is mixed with resin, acid and zinc salt and carbonized to crosslink and composite the lignin with the resin, while activating pore formation. The mixture is then sintered to obtain the hard carbon anode material.

[0010] Furthermore, the preparation method includes the following steps: (a) First, lignin and resin are mixed to obtain a matrix, and then acid and zinc salt are added to the matrix and mixed to obtain a pretreated raw material; (b) Carbonize the pretreated raw material to crosslink and composite the lignin and resin, while activating pore formation and sintering to obtain the hard carbon anode material.

[0011] Furthermore, the mixing temperature is 50℃-100℃.

[0012] Furthermore, the resin includes at least one of polyethylene, polypropylene, polystyrene, polyamide, phenolic resin, epoxy resin, and polyurethane; Preferably, the acid includes at least one selected from hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid, phosphoric acid, carbonic acid, oxalic acid, and citric acid; Preferably, the zinc salt includes at least one of zinc sulfate, zinc chloride, zinc carbonate, zinc nitrate, zinc acetate, and zinc gluconate.

[0013] Furthermore, the mass ratio of the lignin to the resin is 1:10 to 2:1; Preferably, the mass ratio of the substrate to the acid is 1:0.3 to 1:0.02; Preferably, the mass ratio of the substrate to the zinc salt is 1:0.8 to 1:0.02.

[0014] Furthermore, the carbonization temperature is 400℃-800℃, and the carbonization time is 0.5h-5h; Preferably, the carbonization is carried out under an inert atmosphere.

[0015] Furthermore, the carbonization process also includes a step of pulverizing the carbonized product; Preferably, the carbonization product is pulverized to D 50 The range is 2μm-20μm; Preferably, the sintering temperature is 1000℃-1500℃, and the sintering time is 1h-10h; Preferably, the sintering is carried out under an inert atmosphere.

[0016] Secondly, a hard carbon anode material prepared by any of the above-described preparation methods.

[0017] Furthermore, the compacted density of the 3T powder of the hard carbon anode material is ≥1.0 g / cm³. 3Sodium storage capacity ≥350mAh / g, initial coulombic efficiency >90%.

[0018] Thirdly, the application of the aforementioned hard carbon anode material in the anode of a sodium-ion battery.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention provides a method for preparing hard carbon anode material by compounding lignin with resin. The resulting hard carbon product has a higher compaction density compared with traditional biomass-based materials and a higher sodium storage capacity compared with resin-derived hard carbon, thereby improving the overall energy density of the hard carbon anode. At the same time, acid and zinc salt are used as additives, which can improve the degree of crosslinking between lignin and resin during carbonization, promote the homogenization of lignin and resin components, play an activating role during carbonization, and act as template agents during sintering. Together, they result in a hard carbon product with a high specific capacity.

[0020] The hard carbon anode material provided by this invention has a higher compaction density compared with traditional biomass-based materials, and a higher sodium storage capacity compared with resin-derived hard carbon, thereby improving the overall energy density and specific capacity of the hard carbon anode.

[0021] The application of the hard carbon anode material provided by this invention is beneficial to improving the performance of sodium-ion batteries. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a performance characterization diagram of the hard carbon anode material provided in Embodiment 1 of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] After direct carbonization of biomass such as coconut shells and straw, the compacted density of 3T powder is difficult to exceed 1.0 g / cm³ due to its rich mesoporous structure and disordered arrangement of microcrystals. 3Post-treatment pore-filling methods, which use acid anhydride to plug pores or asphalt coating, can increase density, but they also block ion channels, leading to a sharp drop in capacity (≤250mAh / g). In view of this, the technical solution of this invention is proposed.

[0026] According to a first aspect of the present invention, a method for preparing a hard carbon anode material is provided, comprising the following steps: Lignin is mixed with resin, acid and zinc salt for carbonization, which cross-links and composites the lignin with the resin, while activating pore formation. The mixture is then sintered to obtain a hard carbon anode material.

[0027] In this invention, lignin and resin are compounded to obtain a hard carbon product with higher compaction density compared to traditional biomass-based materials and higher sodium storage capacity compared to resin-derived hard carbon, thereby improving the overall energy density of the hard carbon anode. At the same time, acid and zinc salt are used as additives, which can improve the degree of crosslinking between lignin and resin during carbonization, promote the homogenization of lignin and resin components, play an activating role during carbonization, and act as template agents during sintering. Together, they result in a hard carbon product with a high specific capacity.

[0028] It should be noted that acids and zinc salts can effectively promote the homogenization of the lignin and resin mixture during the carbonization process, while also promoting their cross-linking, so that the finished product has both the physical and electrochemical characteristics of lignin-based hard carbon and resin-based hard carbon. If acids are not added, the activation of the carbonization step will be insufficient, and the degree of cross-linking between lignin and resin will also decrease. If zinc salts are not added, the sodium storage capacity will decrease. The metallic zinc after the decomposition of zinc salts can act as a template agent in the carbonized material. During sintering, zinc evaporates, leaving uniform micropores and increasing the sodium storage capacity. The combined effect of acids and zinc salts not only catalyzes the cross-linking of lignin and resin, but also activates pore formation during the carbonization process, increasing the proportion of micropores with sodium storage activity.

[0029] In a preferred embodiment, the preparation method of the present invention includes the following steps: (a) First, lignin and resin are mixed to obtain a matrix, and then acid and zinc salt are added to the matrix and mixed to obtain a pretreated raw material; (b) The pretreated raw material is carbonized to crosslink and composite the lignin and resin, while activating pore formation and sintering to obtain hard carbon anode material.

[0030] Lignin (ash content ≤0.5%) and resin are uniformly mixed at 50℃-100℃ to obtain a matrix. Then, acid and zinc salt are added within the softening temperature and thoroughly stirred to obtain a pretreated raw material. The pretreated raw material is then carbonized to cross-link the lignin and resin, simultaneously activating pore formation. After further pulverization and sintering, a high compaction density (≥1.0 g / cm³ for 3T powder) is obtained. 3Hard carbon anode material with high sodium storage capacity (≥350mAh / g) and initial coulombic efficiency >90%.

[0031] In a preferred embodiment, the resin includes, but is not limited to, at least one of polyethylene, polypropylene, polystyrene, polyamide, phenolic resin, epoxy resin, and polyurethane.

[0032] In a preferred embodiment, the acid includes, but is not limited to, at least one of hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid, phosphoric acid, carbonic acid, oxalic acid, and citric acid.

[0033] In a preferred embodiment, the zinc salt includes, but is not limited to, at least one of zinc sulfate, zinc chloride, zinc carbonate, zinc nitrate, zinc acetate, and zinc gluconate.

[0034] In a preferred embodiment, the mass ratio of lignin to resin can be 1:10 to 2:1, with typical but non-limiting ratios such as 1:10, 1:8, 1:6, 1:4, 1:2, 1:1, and 2:1. This is more conducive to giving the hard carbon anode material a higher sodium storage capacity and a higher initial coulombic efficiency, while also having a higher compaction density. If the lignin ratio is too high, it will result in a low compaction density of the 3T powder; if the resin ratio is too high, it will result in a decrease in capacity.

[0035] In a preferred embodiment, the mass ratio of the substrate to the acid mixture can be 1:0.3 to 1:0.02, with typical but non-limiting ratios such as 1:0.3, 1:0.2, 1:0.1, 1:0.08, 1:0.06, 1:0.04, and 1:0.02. This is more conducive to promoting the homogenization of the lignin and resin mixture during the carbonization process, while also promoting the cross-linking of the two, so that the finished product has both the physical and electrochemical characteristics of lignin-based hard carbon and resin-based hard carbon.

[0036] In a preferred embodiment, the mass ratio of the substrate to the zinc salt can be 1:0.8 to 1:0.02, with typical but non-limiting ratios such as 1:0.8, 1:0.6, 1:0.4, 1:0.2, 1:0.05, and 1:0.02. This is more conducive to promoting the homogenization of the lignin and resin mixture during the carbonization process, while also promoting the cross-linking of the two, so that the finished product has both the physical and electrochemical characteristics of lignin-based hard carbon and resin-based hard carbon.

[0037] In a preferred embodiment, carbonization can be carried out in an inert atmosphere (such as nitrogen or argon) at a rate of 0.5℃ / min-10℃ / min to 400℃-800℃ and held for 0.5h-5h. The equipment used includes, but is not limited to, tube furnaces, atmosphere muffle furnaces, static carbonization furnaces, rotary kilns or roller kilns.

[0038] In a preferred embodiment, carbonization is followed by a step of pulverizing the carbonized product; the carbonized product can be pulverized to a density of D. 50 The particle size is 2μm-20μm; the pulverization method includes, but is not limited to, at least one of grinding, ball milling, air jet milling, roller milling and wet fine grinding.

[0039] In a preferred embodiment, the carbonized product can be pulverized and then sintered in an inert atmosphere (such as nitrogen or argon) at 1000℃-1500℃ for 1h-10h. The sintering equipment includes, but is not limited to, high-temperature tube furnace, high-temperature box furnace, high-temperature sintering furnace, roller kiln, graphitization furnace or rotary kiln.

[0040] According to a second aspect of the present invention, a hard carbon anode material prepared by any of the above-described preparation methods is provided.

[0041] Compared with traditional biomass-based materials, the hard carbon anode material of this invention has a higher compaction density and a higher sodium storage capacity compared with resin-derived hard carbon, thereby improving the overall energy density and specific capacity of the hard carbon anode.

[0042] In this invention, the compacted density of the 3T powder of the hard carbon anode material is ≥1.0 g / cm³. 3 Sodium storage capacity ≥350mAh / g, initial coulombic efficiency >90%.

[0043] According to a third aspect of the present invention, the application of the hard carbon anode material described above in the anode of a sodium-ion battery is provided.

[0044] The application of the hard carbon anode material provided by this invention is beneficial to improving the performance of sodium-ion batteries.

[0045] The present invention will be further illustrated below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0046] Example 1 A method for preparing a hard carbon anode material includes the following steps: (1) Take 100g of phenolic resin, melt the phenolic resin at 80℃, add 50g of lignin, stir thoroughly to obtain the substrate; Add 15 mL of industrial hydrochloric acid and 10 g of zinc acetate to the substrate, and control the mass ratio of substrate, hydrochloric acid and zinc acetate to 150:15:10. Stir and mix thoroughly to obtain the pretreated raw material. (2) The pretreated raw material is placed in an atmosphere tube furnace and heated to 700℃ at a rate of 0.5℃ / min under nitrogen atmosphere and held for 1h to obtain carbonized product. The carbonized products were ball-milled to D using a planetary ball mill.50 It is 7μm; (3) The carbonized product after ball milling was placed in a high-temperature tube furnace and sintered at 1400℃ for 5 hours under a nitrogen atmosphere at a rate of 2℃ / min to obtain a hard carbon anode material with a 3T powder compaction density of 1.03 g / cm³. 3 Performance characterization can be found in Figure 1 It has a reversible capacity of 367.5 mAh / g and an initial coulombic efficiency of 92.1%.

[0047] Example 2 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of phenolic resin used is 25g; The mass ratios of the substrate, hydrochloric acid, and zinc acetate remain unchanged. The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0048] Example 3 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of phenolic resin used is 50g; The mass ratios of the substrate, hydrochloric acid, and zinc acetate remain unchanged. The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0049] Example 4 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of phenolic resin used is 150g; The mass ratios of the substrate, hydrochloric acid, and zinc acetate remain unchanged. The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0050] Example 5 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of phenolic resin used is 250g; The mass ratios of the substrate, hydrochloric acid, and zinc acetate remain unchanged. The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0051] Example 6 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of phenolic resin used is 500g; The mass ratios of the substrate, hydrochloric acid, and zinc acetate remain unchanged. The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0052] Example 7 The only difference between this embodiment and Embodiment 1 is that, in step (1), phenolic resin is replaced with polyethylene in equal amounts; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0053] Example 8 The only difference between this embodiment and Embodiment 1 is that in step (1), phenolic resin is replaced with an equal amount of polypropylene; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0054] Example 9 The only difference between this embodiment and Embodiment 1 is that, in step (1), phenolic resin is replaced with an equal amount of polystyrene. The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0055] Example 10 The only difference between this embodiment and Embodiment 1 is that, in step (1), phenolic resin is replaced with polyamide in equal amounts; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0056] Example 11 The only difference between this embodiment and embodiment 1 is that in step (1), phenolic resin is replaced with epoxy resin in equal amounts; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0057] Example 12 The only difference between this embodiment and Embodiment 1 is that, in step (1), phenolic resin is replaced with an equal amount of polyurethane; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0058] Example 13 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of zinc acetate used is 5g; The mass ratio of the substrate, hydrochloric acid, and zinc acetate is 150:15:5; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0059] Example 14 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of zinc acetate used is 15g; The mass ratio of the substrate, hydrochloric acid, and zinc acetate is 150:15:15; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0060] Example 15 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of zinc acetate used is 20g; The mass ratio of the substrate, hydrochloric acid, and zinc acetate is 150:15:20; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0061] Example 16 The only difference between this embodiment and Embodiment 1 is that, in step (1), the amount of zinc acetate used is 30g; The mass ratio of the substrate, hydrochloric acid, and zinc acetate is 150:15:30; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0062] Example 17 The only difference between this embodiment and Embodiment 1 is that, in step (1), zinc acetate is replaced with an equal amount of zinc sulfate; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0063] Example 18 The only difference between this embodiment and Embodiment 1 is that, in step (1), zinc acetate is replaced with an equal amount of zinc carbonate; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0064] Example 19 The only difference between this embodiment and Embodiment 1 is that, in step (1), zinc acetate is replaced with an equal amount of zinc gluconate; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0065] Example 20 The only difference between this embodiment and Embodiment 1 is that, in step (1), hydrochloric acid is replaced with an equal amount of nitric acid; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0066] Example 21 The only difference between this embodiment and Embodiment 1 is that, in step (1), hydrochloric acid is replaced with an equal amount of oxalic acid; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0067] Example 22 The only difference between this embodiment and embodiment 1 is that in step (2), the temperature is raised to 400℃ and held for 5 hours to carry out carbonization, thereby obtaining carbonized products; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0068] Example 23 The only difference between this embodiment and embodiment 1 is that in step (2), the temperature is raised to 600°C and held for 3 hours to carbonize, thereby obtaining carbonized products; The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0069] Example 24 The only difference between this embodiment and embodiment 1 is that in step (2), the temperature is raised to 800℃ and held for 0.5h to carry out carbonization, and carbonized products are obtained. The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0070] Comparative Example 1 The only difference between this comparative example and Example 1 is that phenolic resin was not added in step (1); The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0071] Comparative Example 2 The only difference between this comparative example and Example 1 is that lignin was not added in step (1); The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0072] Comparative Example 3 The only difference between this comparative example and Example 1 is that hydrochloric acid was not added in step (1); The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0073] Comparative Example 4 The only difference between this comparative example and Example 1 is that zinc acetate was not added in step (1); The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0074] Comparative Example 5 The only difference between this comparative example and Example 1 is that the carbonization step was not performed in step (2); The rest is the same as in Example 1, and a hard carbon anode material is obtained.

[0075] Test case The hard carbon anode materials of Examples 1-24 and Comparative Examples 1-5 were tested, and the results are shown in Table 1.

[0076] Half-cell test: The hard carbon anode materials of Examples 1-24 and Comparative Examples 1-5 were respectively made into anodes and assembled into sodium-ion batteries for testing.

[0077] Battery fabrication method: The specific button cell electrode sheet is prepared using a method known in the art: hard carbon negative electrode material, conductive agent, and binder are mixed at a mass ratio of 91:3:6, adjusted to a solid content of 50% with deionized water, and mixed evenly. The mixture is then coated onto a copper foil current collector, vacuum dried, and rolled to achieve an areal density of 5.5 ± 0.5 mg / cm³. 2 The negative electrode sheet is obtained by cutting it into 14mm pieces using a punch.

[0078] Button cell fabrication: Using a 16mm sodium sheet as the counter electrode, 1M NaPF6 in DMC:EC:EMC as the electrolyte, glass fiber as the separator, and a 2032 button cell casing, a button half cell is assembled.

[0079] Battery testing method: In a 25℃ constant temperature chamber, constant current discharge: discharge at a constant rate of 0.1C to 1mV, then discharge at a current of 50uA to 1mV, and then discharge at a current of 10uA to 1mV; constant current charging: charge at a constant current rate of 0.1C to 2V.

[0080] Table 1. Performance of Hard Carbon Anode Materials

[0081] By comparing the test data of Example 1 and Comparative Example 1, it can be found that the compaction density of Example 1 is higher than that of Comparative Example 1, while the specific capacity is lower than that of Comparative Example 1. This may be because no resin material was added, which reduced the compaction density caused by the original structure of the substrate. Therefore, the compaction density of Example 1 is higher. Pure lignin is more easily activated, so the specific capacity of Comparative Example 1 is higher than that of Example 1. However, the volumetric specific capacity of Example 1 is much higher than that of Comparative Example 1.

[0082] By comparing the test data of Example 1 and Comparative Example 2, it can be found that the compaction density of Example 1 is lower than that of Comparative Example 2, while the specific capacity is higher. This may be because lignin was not added. Since the original compaction density of the resin is higher, the compaction density of Comparative Example 2 is higher than that of Example 1. However, the activation effect of the resin is lower than that of lignin, so the specific capacity of Comparative Example 2 is lower than that of Example 1. But from the perspective of volumetric capacity, the volumetric capacity of Example 1 is much higher than that of Comparative Example 2.

[0083] By comparing the test data of Example 1 and Comparative Examples 3-4, it can be found that the compaction density of Example 1 is lower than that of Comparative Examples 3-4. This may be because the amount of activator added is insufficient, the activation effect is poor, the activation and pore-forming effect is weak, and the volumetric specific capacity is lower than that of Example 1. At the same time, due to the insufficient degree of pore-forming, there are fewer bulk pore structures and the compaction density is higher.

[0084] By comparing the test data of Example 1 and Comparative Example 5, it can be found that the compaction density and specific capacity of Example 1 are higher than those of Comparative Example 5. The reason may be that after omitting the carbonization step, the activation process is missing, the activation is insufficient, and the specific capacity is low. At the same time, the hard carbon holding time is insufficient during the heating process, the overall structural shrinkage process is too short, and the compaction density is low.

[0085] Comparing the test data from Examples 1 and 2-6 reveals that, while maintaining the acid and zinc salt ratio, controlling the amount of resin added allows for a compaction density of 0.87 g / cm³ for the hard carbon material.3 -1.08g / cm 3 The specific capacity can be adjusted within the range of 326.7mAh / g-386.2mAh / g. The higher the amount of resin added, the higher the compaction density and the lower the specific capacity.

[0086] By comparing the test data of Examples 1 and Examples 7-12, it can be found that by controlling the type of resin added while keeping the formula ratio unchanged, hard carbon materials can have different compaction densities and specific capacities. The addition of different types of resins results in hard carbon materials having different volumetric specific capacities.

[0087] Comparing the test data of Example 1 and Examples 13-16 reveals that, while keeping the proportions of other raw materials constant, controlling the proportion of zinc acetate can result in different activation levels in the hard carbon material, achieving a compaction density of 0.98 g / cm³. 3 -1.04g / cm 3 The specific capacity can be adjusted within the range of 356.6mAh / g-382.0mAh / g. The higher the amount of zinc acetate added, the lower the compaction density and the higher the specific capacity.

[0088] By comparing the test data of Example 1 and Examples 17-19, it can be found that, while keeping the formula ratio unchanged, controlling the type of zinc salt added can make the hard carbon material have different compaction densities and specific capacities. The addition of different types of zinc salts makes the hard carbon material have different volumetric specific capacities.

[0089] By comparing the test data of Example 1 and Examples 20-21, it can be found that, while keeping the formula ratio unchanged, controlling the type of acid added can make the hard carbon material have different compaction densities and specific capacities. The addition of different types of acids makes the hard carbon material have different volumetric specific capacities.

[0090] Comparing the test data of Examples 1 and 22-24 reveals that, while maintaining the same raw material formulation, controlling the carbonization temperature allows for different activation levels in the hard carbon material, resulting in a compaction density of 1.01 g / cm³. 3 -1.04g / cm 3 The capacity can be adjusted within the range of 360.8 mAh / g to 370.9 mAh / g.

[0091] In summary, Examples 1-24 of this invention, by mixing lignin and resin and adding acid and zinc salt for carbonization, cross-link and composite the lignin and resin, while simultaneously activating pore formation and sintering, achieve a compaction density of ≥1.0 g / cm³ for the 3T powder of the hard carbon anode material. 3With a sodium storage capacity of ≥350mAh / g and an initial coulombic efficiency of >90%, it solves the technical problem that hard carbon materials are difficult to effectively balance high compaction density and high capacity.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a hard carbon anode material, characterized in that, Includes the following steps: Lignin is mixed with resin, acid and zinc salt and carbonized to crosslink and composite the lignin with the resin, while activating pore formation. The mixture is then sintered to obtain the hard carbon anode material.

2. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (a) First, lignin and resin are mixed to obtain a matrix, and then acid and zinc salt are added to the matrix and mixed to obtain a pretreated raw material; (b) Carbonize the pretreated raw material to crosslink and composite the lignin and resin, while activating pore formation and sintering to obtain the hard carbon anode material.

3. The preparation method according to claim 2, characterized in that, The mixing temperature is 50℃-100℃.

4. The preparation method according to any one of claims 1-3, characterized in that, The resin includes at least one of polyethylene, polypropylene, polystyrene, polyamide, phenolic resin, epoxy resin, and polyurethane; Preferably, the acid includes at least one selected from hydrochloric acid, sulfuric acid, hydrofluoric acid, nitric acid, phosphoric acid, carbonic acid, oxalic acid, and citric acid; Preferably, the zinc salt includes at least one of zinc sulfate, zinc chloride, zinc carbonate, zinc nitrate, zinc acetate, and zinc gluconate.

5. The preparation method according to claim 2, characterized in that, The mass ratio of lignin to resin is 1:10-2:1; Preferably, the mass ratio of the substrate to the acid is 1:0.3 to 1:0.02; Preferably, the mass ratio of the substrate to the zinc salt is 1:0.8 to 1:0.

02.

6. The preparation method according to claim 2, characterized in that, The carbonization temperature is 400℃-800℃, and the carbonization time is 0.5h-5h; Preferably, the carbonization is carried out under an inert atmosphere.

7. The preparation method according to claim 6, characterized in that, The carbonization process also includes a step of pulverizing the carbonized product. Preferably, the carbonization product is pulverized to D 50 The range is 2μm-20μm; Preferably, the sintering temperature is 1000℃-1500℃, and the sintering time is 1h-10h; Preferably, the sintering is carried out under an inert atmosphere.

8. A hard carbon anode material prepared by the preparation method according to any one of claims 1-7.

9. The hard carbon anode material according to claim 8, characterized in that, The compacted density of the 3T powder of the hard carbon anode material is ≥1.0 g / cm³. 3 Sodium storage capacity ≥350mAh / g, initial coulombic efficiency >90%.

10. The application of the hard carbon anode material according to claim 8 or 9 in the anode of a sodium-ion battery.

Images