Glucuronate-derived hard carbon negative electrode material, preparation method thereof, negative electrode and lithium ion battery

Abstract

The application relates to the field of batteries, and discloses a gluconate-derived hard carbon negative electrode material, a preparation method thereof, a negative electrode and a lithium ion battery. The hard carbon negative electrode material is obtained by the following steps: after a first heat treatment of gluconate in an inert gas atmosphere, the intermediate is obtained by soaking in an acid solution; and the intermediate is subjected to a second heat treatment in an inert gas atmosphere. The first heat treatment process comprises a first-step heat treatment and a second-step heat treatment, the temperature of the first-step heat treatment is 400-600 DEG C, the time is 1-2 h, and the temperature of the second-step heat treatment is higher than that of the first-step heat treatment. The second heat treatment process comprises a third-step heat treatment and a fourth-step heat treatment, the temperature of the third-step heat treatment is higher than that of the second-step heat treatment and lower than that of the fourth-step heat treatment, the temperature of the fourth-step heat treatment is 1300-1500 DEG C, and the time is 50-150 min. The method is simple, the cost is low, and the prepared negative electrode material has a higher lithium storage capacity in an ether-based electrolyte.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a gluconate-derived hard carbon negative electrode material, a preparation method thereof, a negative electrode and a lithium ion battery. BACKGROUND

[0002] With the rapid development of global economy, people gradually realize that fossil fuels are increasingly depleted and harmful to the environment, and developing green and pollution-free renewable energy is an effective way to solve energy and environmental problems. In recent years, lithium ion batteries have been widely used in portable electronic devices, electric vehicles and other fields due to their high capacity, long cycle life and other advantages. Since the development of lithium ion batteries, various positive electrode material systems have been developed. In the history of the birth and development of lithium ion batteries, carbon negative electrode materials have played a significant role in improving battery energy storage performance, safety, and cost reduction, and have triggered a research and development boom among global academic and industrial institutions. Currently, the negative electrode of commercial lithium ion batteries is mainly graphite-based material. According to the lithium storage mechanism of LiC6 between graphite layers, its theoretical specific capacity is only 372 mAh / g, and the space for improvement is very limited. Moreover, the lithium diffusion between the graphite layers also restricts its rate performance. Therefore, with the increasing demand for battery energy and power performance in downstream applications, pure graphite-based negative electrode materials have become insufficient. Hard carbon, as a new type of negative electrode material, has similar lithium potential and higher specific capacity to graphite. More importantly, hard carbon is composed of graphite-like microcrystalline structure and open angular microcrystalline structure. This unique microcrystalline structure not only provides more lithium storage sites, but also facilitates lithium ion intercalation / deintercalation between graphite layers. Therefore, hard carbon has a very broad development prospect as a new generation of lithium ion battery negative electrode material.

[0003] In recent years, significant progress has been made in the research of hard carbon negative electrode materials, but many challenges / bottlenecks still exist: 1) the lithium storage capacity of most hard carbon materials is still low; 2) the rate performance and cycle performance need to be improved. SUMMARY

[0004] The purpose of the present application is to overcome the above problems existing in the prior art, and to provide a gluconate-derived hard carbon negative electrode material, a preparation method thereof, a negative electrode and a lithium ion battery. The hard carbon negative electrode material provided by the present application has excellent charge specific capacity and cycle coulombic efficiency.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a preparation method of a hard carbon negative electrode material, wherein a gluconate is subjected to a first heat treatment in an inert gas atmosphere, then soaked with an acidic solution to remove metal elements to obtain an intermediate, and the intermediate is subjected to a second heat treatment in an inert gas atmosphere to obtain a hard carbon negative electrode material.

[0006] The first heat treatment process comprises a first step heat treatment and a second step heat treatment in sequence, wherein the temperature of the first step heat treatment is 400-600 DEG C, and the time is 1-2h, the temperature of the second step heat treatment is higher than that of the first step heat treatment.

[0007] The second heat treatment process comprises a third step heat treatment and a fourth step heat treatment in sequence, wherein the temperature of the third step heat treatment is higher than that of the second step heat treatment, and lower than that of the fourth step heat treatment, the temperature of the fourth step heat treatment is 1300-1500 DEG C, and the time is 50-150min.

[0008] The second aspect of the present application provides a hard carbon negative material, wherein the preparation method is prepared according to the first aspect of the present application.

[0009] The third aspect of the present application provides a negative electrode, wherein the hard carbon negative material prepared by the preparation method of the first aspect of the present application or the hard carbon negative material of the second aspect of the present application is included.

[0010] The fourth aspect of the present application provides a lithium ion battery, wherein the negative electrode of the third aspect of the present application is included.

[0011] The present application introduces abundant pore structure into the material by carbonizing in stages and removing metal elements in the material by pickling during the two carbonizing processes, increases lithium storage sites, and a part of the introduced pores form closed pore structure during the second carbonizing process, which is beneficial to improve the electrochemical performance.

[0012] Compared with commercial graphite, the hard carbon material prepared by the present application has higher lithium storage capacity in ether-based electrolyte. In addition, the present application only comprises two steps of carbonization and washing, and the process is simple, safe and low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The figure is an SEM image of the hard carbon negative material prepared in example 1 (the scale is 10um);

[0014] Figure 2 The figure is an SEM image of the hard carbon negative material prepared in example 1 (the scale is 1um);

[0015] Figure 3 The figure is an EDS image of the hard carbon negative material prepared in example 1;

[0016] Figure 4 The figure is a first cycle charge-discharge curve of the hard carbon negative material prepared in example 1 under 0.01V-1.5V voltage window and 0.1C (1C=300mAh / g) current density;

[0017] Figure 5 This is a cycle curve of 1C current density in a voltage window of 0.01V~1.5V after the hard carbon negative electrode material prepared in Example 1 is assembled into a battery. DETAILED DESCRIPTION

[0018] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0019] The terms "first", "second", etc. are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein. The objects distinguished by "first", "second", etc. are generally of the same type, and the number of objects is not limited. For example, the first object can be one or more.

[0020] In addition, the term "and / or" in the specification and claims is used to describe an association relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0021] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0022] A first aspect of the present invention provides a method for preparing a hard carbon negative electrode material, wherein gluconate is subjected to a first heat treatment under an inert gas atmosphere, then soaked in an acidic solution to remove metal elements to obtain an intermediate, and the intermediate is subjected to a second heat treatment under an inert gas atmosphere to obtain the hard carbon negative electrode material;

[0023] The first heat treatment process comprises a first step heat treatment and a second step heat treatment in sequence, wherein the temperature of the first step heat treatment is 400-600 DEG C, the time is 1-2h, the temperature of the second step heat treatment is higher than that of the first step heat treatment.

[0024] The second heat treatment process comprises a third step heat treatment and a fourth step heat treatment in sequence, wherein the temperature of the third step heat treatment is higher than that of the second step heat treatment and lower than that of the fourth step heat treatment, the temperature of the fourth step heat treatment is 1300-1500 DEG C, the time is 50-150min.

[0025] In some embodiments, preferably, the temperature difference between the second step heat treatment and the first step heat treatment is not less than 200 DEG C.

[0026] In some embodiments, preferably, the temperature difference between the third step heat treatment and the second step heat treatment is not less than 100 DEG C.

[0027] In some embodiments, preferably, the temperature difference between the fourth step heat treatment and the third step heat treatment is not less than 100 DEG C.

[0028] In some embodiments, preferably, the temperature of the second step heat treatment is 800-1000 DEG C, the time is 1-2h.

[0029] In some embodiments, preferably, the temperature of the third step heat treatment is 900-1200 DEG C, the time is 1-2h.

[0030] In some embodiments, preferably, the heating rate of the first step heat treatment is 5-15 DEG C / min.

[0031] In some embodiments, preferably, the heating rate of the fourth step heat treatment is 1-5 DEG C / min.

[0032] In some embodiments, preferably, the heating rate of the second step heat treatment is 5-15 DEG C / min.

[0033] In some embodiments, preferably, the heating rate of the third step heat treatment is 5-10 DEG C / min.

[0034] The heat treatment temperature, time and heating rate of different stages are directly related to the carbonization degree of the material, the amount of introduced pores and the increase of lithium storage sites, and the heat treatment time and temperature of each stage provided by the application can further improve the above performance.

[0035] The temperature of the first heat treatment can be any value within a value range formed by any two of 400℃, 450℃, 500℃, 550℃, 600℃; the time of the first heat treatment can be any value within a value range formed by any two of 1h, 1.5h, 2h; the heating rate of the first heat treatment can be any value within a value range formed by any two of 5℃ / min, 7℃ / min, 9℃ / min, 11℃ / min, 13℃ / min, 15℃ / min.

[0036] The temperature of the second heat treatment can be any value within a value range formed by any two of 800℃, 850℃, 900℃, 950℃, 1000℃; the time of the second heat treatment can be any value within a value range formed by any two of 1h, 1.5h, 2h; the heating rate of the second heat treatment can be any value within a value range formed by any two of 5℃ / min, 7℃ / min, 9℃ / min, 11℃ / min, 13℃ / min, 15℃ / min.

[0037] The temperature of the third heat treatment can be any value within a value range formed by any two of 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃; the time of the third heat treatment can be any value within a value range formed by any two of 1h, 1.5h, 2h; the heating rate of the third heat treatment can be any value within a value range formed by any two of 5℃ / min, 7℃ / min, 9℃ / min, 10℃ / min.

[0038] The temperature of the fourth heat treatment can be any value within a value range formed by any two of 1300℃, 1350℃, 1400℃, 1450℃, 1500℃; the time of the fourth heat treatment can be any value within a value range formed by any two of 50min, 70min, 900min, 110min, 130min, 150min; the heating rate of the fourth heat treatment can be any value within a value range formed by any two of 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min.

[0039] In some embodiments, preferably, the concentration of the acidic solution is 0.5-1.5mol / L. There is no particular requirement for the kind of the acidic solution, which can be hydrochloric acid, and the concentration of the acidic solution can be any value within a value range formed by any two of 0.5mol / L, 1mol / L, 1.5mol / L.

[0040] There is no particular requirement for the kind of the inert gas, which can be argon.

[0041] The room temperature of the present application is 20-25℃.

[0042] In some embodiments, preferably, the gluconate is selected from one or more of zinc gluconate, calcium gluconate, sodium gluconate, ferrous gluconate, and magnesium gluconate. The above raw materials are inexpensive and easy to obtain, which is conducive to reducing costs.

[0043] In some embodiments, preferably, the preparation method further comprises: performing ultrasonic treatment while performing the soaking, and the soaking time is 0.5-2h. The use of ultrasonic treatment during soaking can improve the removal speed and efficiency of metal elements. The ultrasonic intensity of the ultrasonic treatment is not particularly limited, and can be, for example, 30W, 40W, etc. The ultrasonic treatment time can be any value within a range formed by any two values selected from 0.5h, 1h, 1.5h, and 2h.

[0044] In some embodiments, preferably, the preparation method further comprises: after the fourth step of heat treatment, washing the collected material with deionized water to neutral, and drying to obtain the hard carbon negative electrode material.

[0045] The second aspect of the present application provides a hard carbon negative electrode material, wherein the preparation method according to the first aspect of the present application is used.

[0046] The third aspect of the present application provides a negative electrode, wherein the hard carbon negative electrode material prepared by the preparation method according to the first aspect of the present application or the hard carbon negative electrode material according to the second aspect of the present application is included.

[0047] The fourth aspect of the present application provides a lithium ion battery, wherein the negative electrode according to the third aspect of the present application is included.

[0048] The present application introduces a large number of pore structures into the prepared hard carbon negative electrode material by stage carbonization and acid pickling, and part of the pore structures form closed pore structures. The prepared hard carbon negative electrode material exhibits excellent cycle performance. In the first cycle of charge and discharge under the condition of 0.1C, the charge specific capacity is not less than 320mAh / g. Under the condition of 1C, the reversible specific capacity of the prepared hard carbon negative electrode material is not less than 250mAh / g after 300 cycles, and the cycle performance is stable, and the cycle coulombic efficiency is not less than 99%, close to 100%.

[0049] The present application will be described in detail below through examples. In the following examples and comparative examples, if no specific manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased on the market. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used.

[0050] The constant current charge-discharge test of the battery was performed by Land CT2001A of Wuhan Blue Electric Co., Ltd.

[0051] Example 1

[0052] (1) 10 g of zinc gluconate was weighed into a porcelain boat, and argon was passed through the boat for 30 minutes in a tube furnace. After heating from room temperature to 400°C at a heating rate of 10°C / min under the argon flow, the temperature was maintained for 1 h, then the temperature was continuously increased to 900°C at a heating rate of 10°C / min, and then maintained for 1 h, and then naturally cooled to room temperature to obtain a precursor.

[0053] (2) The precursor was crushed and ground into powder in a mortar while hot, then soaked in a 1M HCl solution, and the soaking was assisted by ultrasonic treatment (ultrasonic intensity 30W). After 1 h, the mixture was filtered, then washed with deionized water until neutral, washed with ethanol three times, and then vacuum dried at 110°C for 12 h to obtain an intermediate.

[0054] (3) The intermediate dried in step 2 was heated from room temperature to 1100°C at a heating rate of 5°C / min under the argon flow, and maintained for 2 h, then continuously heated to 1500°C at a heating rate of 2°C / min, and maintained for 100 min, and then naturally cooled to room temperature.

[0055] (4) The material collected in step 3 was washed with deionized water and ethanol three times, and then vacuum dried at 80°C for 12 h to obtain a zinc gluconate-derived hard carbon negative electrode material, denoted as A1.

[0056] The SEM image of the material prepared in this example is shown in Figure 1 and 2 It can be seen that the prepared hard carbon negative electrode material has an irregular porous structure, and the SED image thereof is shown in Figure 3 It can be seen that the prepared hard carbon negative electrode material no longer contains zinc element, but mainly contains C and O elements, and the C and O elements are uniformly distributed, indicating that the hard carbon is successfully obtained by the method, and the sample does not contain other impurities, and the ZnO nanoparticles are successfully removed, leaving a large number of pores.

[0057] The first cycle charge-discharge curve of the prepared hard carbon negative electrode material at a current density of 0.1C (1C=300mAh / g) in a voltage window of 0.01V~1.5V is shown in Figure 4 The cycle diagram at a current density of 1C in a voltage window of 0.01V~1.5V is shown in Figure 5 Figure 4 and Figure 5 ​It can be seen that the hard carbon negative material prepared in the embodiment exhibits excellent cycle performance. In the first week of charge and discharge cycle under the condition of 0.1C, the specific charge capacity is as high as 338.94 mAh / g. Under the condition of 1C rate, the reversible specific capacity of the prepared hard carbon is maintained at 272.2 mAh / g after 300 cycles, and the cycle performance is stable, and the cycle coulombic efficiency is close to 100%.

[0058] Example 2

[0059] (1) 10 g of magnesium gluconate was weighed into a porcelain boat, and argon was passed for 30 minutes in a tube furnace. After being heated to 600 DEG C at a heating rate of 5 DEG C / min from room temperature under the flow of argon, it was kept for 1.5 h, then it was continuously heated to 800 DEG C at a heating rate of 5 DEG C / min, and then kept for 1.5 h, and then naturally cooled to room temperature to obtain a precursor.

[0060] (2) The precursor was crushed and ground into powder in a mortar while hot, then soaked in a 0.5 M HCl solution, and the soaking was assisted by ultrasonic treatment (ultrasonic intensity 30 W). After 2 h, it was filtered, then washed with deionized water until neutral, washed with ethanol three times, and then vacuum dried at 110 DEG C for 12 h to obtain an intermediate.

[0061] (3) The intermediate dried in step 2 was heated to 900 DEG C at a heating rate of 7 DEG C / min from room temperature under the flow of argon, and kept for 1.5 h, then it was continuously heated to 1300 DEG C at a heating rate of 1 DEG C / min, and kept for 150 min, and then naturally cooled to room temperature.

[0062] (4) The material collected in step 3 was washed with deionized water and ethanol three times in turn, and then vacuum dried at 80 DEG C for 12 h to obtain a zinc gluconate-derived hard carbon negative material, which is denoted as A2.

[0063] Example 3

[0064] (1) 10 g of calcium gluconate was weighed into a porcelain boat, and argon was passed for 30 minutes in a tube furnace. After being heated to 500 DEG C at a heating rate of 15 DEG C / min from room temperature under the flow of argon, it was kept for 2 h, then it was continuously heated to 1000 DEG C at a heating rate of 15 DEG C / min, and then kept for 2 h, and then naturally cooled to room temperature to obtain a precursor.

[0065] (2) The precursor was crushed and ground into powder in a mortar while hot, then soaked in a 1.5 M HCl solution, and the soaking was assisted by ultrasonic treatment (ultrasonic intensity 30 W). After 0.5 h, it was filtered, then washed with deionized water until neutral, washed with ethanol three times, and then vacuum dried at 110 DEG C for 12 h to obtain an intermediate.

[0066] (3) The intermediate dried in step 2 was heated to 1200°C at a heating rate of 10°C / min from room temperature under argon flow, and kept for 1 h, then heated to 1400°C at a heating rate of 5°C / min, and kept for 50 min, and then naturally cooled to room temperature.

[0067] (4) The material collected in step 3 was washed with deionized water and ethanol for 3 times, respectively, and then vacuum dried at 80°C for 12 h to obtain a zinc gluconate-derived hard carbon negative electrode material, denoted as A3.

[0068] Example 4

[0069] It was carried out in the same manner as in Example 1, except that the temperature of the second heat treatment was 600°C, and the obtained sample was denoted as A4.

[0070] Example 5

[0071] It was carried out in the same manner as in Example 1, except that the temperature of the second heat treatment was 600°C, and the temperature of the third heat treatment was 700°C, and the obtained sample was denoted as A5.

[0072] Example 6

[0073] It was carried out in the same manner as in Example 1, except that the heating rate of the first heat treatment was 2°C / min, and the obtained sample was denoted as A6.

[0074] Example 7

[0075] It was carried out in the same manner as in Example 1, except that the heating rate of the first heat treatment was 20°C / min, and the obtained sample was denoted as A7.

[0076] Example 8

[0077] It was carried out in the same manner as in Example 1, except that the heating rate of the second heat treatment was 2°C / min, and the obtained sample was denoted as A8.

[0078] Example 9

[0079] It was carried out in the same manner as in Example 1, except that the heating rate of the second heat treatment was 20°C / min, and the obtained sample was denoted as A9.

[0080] Example 10

[0081] It was carried out in the same manner as in Example 1, except that the heating rate of the third heat treatment was 2°C / min, and the obtained sample was denoted as A10.

[0082] Example 11

[0083] The procedure of Example 1 was followed, except that the temperature ramp rate for the third heat treatment was 15°C / min, and the sample obtained was designated A11.

[0084] Example 12

[0085] The procedure of Example 1 was followed, except that the temperature ramp rate for the fourth heat treatment was 8°C / min, and the sample obtained was designated A12.

[0086] Example 13

[0087] The procedure of Example 1 was followed, except that the soak time for the first heat treatment was 3.5 h, and the sample obtained was designated A13.

[0088] Example 14

[0089] The procedure of Example 1 was followed, except that the soak time for the second heat treatment was 3.5 h, and the sample obtained was designated A14.

[0090] Example 15

[0091] The procedure of Example 1 was followed, except that the soak time for the third heat treatment was 3.5 h, and the sample obtained was designated A15.

[0092] Example 16

[0093] The procedure of Example 1 was followed, except that the soak time for the fourth heat treatment was 20 min, and the sample obtained was designated A16.

[0094] Example 17

[0095] The procedure of Example 1 was followed, except that the soak time for the fourth heat treatment was 200 min, and the sample obtained was designated A17.

[0096] Comparative Example 1

[0097] The procedure of Example 1 was followed, except that the temperature for the first heat treatment was 300°C, and the sample obtained was designated D1.

[0098] Comparative Example 2

[0099] The procedure of Example 1 was followed, except that the temperature for the first heat treatment was 700°C, and the sample obtained was designated D2.

[0100] Comparative Example 3

[0101] The procedure of Example 1 was followed, except that the temperature for the second heat treatment was 400°C, and the sample obtained was designated D3.

[0102] Comparative Example 4

[0103] The procedure of Example 1 was followed except that the temperature of the third heat treatment was 900°C, and the sample obtained was designated D4.

[0104] Comparative Example 5

[0105] The procedure of Example 1 was followed except that the temperature of the fourth heat treatment was 1200°C, and the sample obtained was designated D5.

[0106] Comparative Example 6

[0107] The procedure of Example 1 was followed except that the temperature of the fourth heat treatment was 1600°C, and the sample obtained was designated D6.

[0108] Comparative Example 7

[0109] (1) 10 g of zinc gluconate was placed in a porcelain boat, and argon gas was passed for 30 minutes in a tube furnace. The precursor was obtained by heating from room temperature to 600°C at a heating rate of 10°C / min under argon flow, and then maintaining the temperature for 2 h, and naturally cooling to room temperature.

[0110] (2) The precursor was crushed and ground into powder in a mortar while hot, and then soaked in a 1 M HC1 solution, while ultrasonic treatment (ultrasonic intensity 30 W) was assisted. After 1 h, filtration was performed, and then deionized water was used for washing until neutral, and ethanol was used for cleaning three times, and then vacuum drying at 110°C for 12 h to obtain the intermediate.

[0111] (3) The intermediate after drying in step 2 was heated to 1300°C from room temperature at a heating rate of 5°C / min under argon flow, and then maintaining the temperature for 3.6 h, and naturally cooling to room temperature.

[0112] (4) The material collected in step 3 was cleaned with deionized water and ethanol three times, and then vacuum drying at 80°C for 12 h to obtain the zinc gluconate-derived hard carbon negative electrode material, designated as D7.

[0113] The materials obtained in the above Examples 1-17 and Comparative Examples 1-7 were subjected to battery assembly and testing, and the specific operation was as follows:

[0114] According to the sample material (Examples 1-17 and Comparative Examples 1-7): the slurry obtained by mixing Super P:PAA (binder, polyacrylic acid aqueous solution) at a mass ratio of 8:1:1 was coated on a copper foil using a 125 μm doctor blade to form an electrode sheet, a metal sodium sheet was used as a counter electrode, a 1M LiPF6 solution in diethylene glycol dimethyl ether was used as an electrolyte (the solvent was diethylene glycol dimethyl ether and the solute was LiPF6), and a 2032 type button cell was assembled in an argon glove box. Then the cell was left to stand for 10 h, and then tested at a temperature of 30°C, a test voltage range of 0.01V-1.5V, and a 0.1C (1C=300mA / g) current density, and then cycled at a 1C rate to 300 cycles after 5 cycles, and the test results are shown in Table 1.

[0115] Table 1 Test results

[0116]

[0117] As can be seen from the results in Table 1, the first cycle coulombic efficiency and the charge specific capacity of the hard carbon material prepared by the present application are significantly improved, and still have a high reversible specific capacity after 300 cycles at 1C.

[0118] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A method for preparing a hard carbon negative electrode material, characterized by, The intermediate is obtained by removing metal elements from the intermediate after the first heat treatment of the gluconate under an inert gas atmosphere and then soaking in an acidic solution, and the hard carbon negative electrode material is obtained by the second heat treatment of the intermediate under an inert gas atmosphere; wherein the first heat treatment process comprises: first step heat treatment and second step heat treatment in sequence, wherein the temperature of the first step heat treatment is 400-600 DEG C, the time is 1-2h, and the temperature of the second step heat treatment is higher than that of the first step heat treatment; The second heat treatment process comprises: third step heat treatment and fourth step heat treatment in sequence, wherein the temperature of the third step heat treatment is higher than that of the second step heat treatment, and lower than that of the fourth step heat treatment, and the temperature of the fourth step heat treatment is 1300-1500 DEG C, and the time is 50-150 min.

2. The production method according to claim 1, wherein, The difference between the temperature of the second step heat treatment and the temperature of the first step heat treatment is not less than 200 DEG C; And / or, the difference between the temperature of the third step heat treatment and the temperature of the second step heat treatment is not less than 100 DEG C; And / or, the difference between the temperature of the fourth step heat treatment and the temperature of the third step heat treatment is not less than 100 DEG C.

3. The production method according to claim 1 or 2, wherein, The temperature of the second step heat treatment is 800-1000 DEG C, and the time is 1-2h; And / or, the temperature of the third step heat treatment is 900-1200 DEG C, and the time is 1-2h.

4. The production method according to claim 1 or 2, wherein The heating rate of the first step heat treatment is 5-15 DEG C / min; And / or, the heating rate of the fourth step heat treatment is 1-5 DEG C / min.

5. The production method according to claim 3, wherein The heating rate of the first step heat treatment is 5-15 DEG C / min; And / or, the heating rate of the fourth step heat treatment is 1-5 DEG C / min.

6. The production process according to claim 1, 2 or 5, wherein, The heating rate of the second heat treatment is 5-15 DEG C / min; And / or, the heating rate of the third step heat treatment is 5-10 DEG C / min.

7. The production method according to claim 3, wherein The heating rate of the second heat treatment is 5-15 DEG C / min; And / or, the heating rate of the third step heat treatment is 5-10 DEG C / min.

8. The production method according to claim 4, wherein The heating rate of the second heat treatment is 5-15 DEG C / min; And / or, the heating rate of the third step heat treatment is 5-10 DEG C / min.

9. The production method according to any one of claims 1, 2, 5, 7 and 8, wherein, The concentration of the acidic solution is 0.5-1.5 mol / L; And / or, the gluconate is selected from one and more than two of zinc gluconate, calcium gluconate, sodium gluconate, ferrous gluconate and magnesium gluconate.

10. The production method according to claim 3, wherein, The concentration of the acidic solution is 0.5-1.5 mol / L; And / or, the gluconate is selected from one and more than two of zinc gluconate, calcium gluconate, sodium gluconate, ferrous gluconate and magnesium gluconate.

11. The production method according to any one of claims 1, 2, 5, 7, 8, and 10, wherein, The preparation method further comprises: ultrasonic treatment is carried out at the same time as the soaking, and the soaking time is 0.5-2h; And / or, the preparation method further comprises: the collected material is washed to neutral with deionized water after the fourth step heat treatment, and the hard carbon negative electrode material is obtained by drying.

12. The production method according to claim 9, wherein The preparation method further comprises: ultrasonic treatment is carried out at the same time as the soaking, and the soaking time is 0.5-2h; And / or, the preparation method further comprises: the collected material is washed to neutral with deionized water after the fourth step heat treatment, and the hard carbon negative electrode material is obtained by drying. And / or, the preparation method further comprises: after the fourth step of heat treatment, washing the collected material with deionized water to neutral, and drying to obtain the hard carbon negative electrode material.

13. A hard carbon negative electrode material, characterized in that, The hard carbon negative electrode material is prepared by the preparation method according to any one of claims 1-12.

14. A negative electrode characterized by comprising: The hard carbon negative electrode material prepared by the preparation method according to any one of claims 1-12 or the hard carbon negative electrode material according to claim 13.

15. A lithium-ion battery, characterized by, The negative electrode according to claim 14. The negative electrode according to claim 14.

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