Preparation method of silicon nanowire@carbon negative electrode material for lithium battery, product and application thereof

Abstract

The application provides a preparation method of a silicon nanowire@carbon negative electrode material for lithium batteries, a product and application thereof. The preparation method comprises the following steps: mixing silicon nanowires with an aqueous solution of a surfactant to obtain solution A; then mixing solution A obtained in step (1) with an aqueous solution of a carbon source to obtain solution B; finally sintering solution B obtained in step (2) to obtain the silicon nanowire@carbon negative electrode material for lithium batteries; the sintering comprises a first temperature rising stage, a first temperature holding stage, a second temperature rising stage, a second temperature holding stage, a third temperature rising stage and a third temperature holding stage in sequence; the sintering is carried out in a protective atmosphere, and the temperature range of the sintering is 250-1000 DEG C. The preparation method is simple in process, and the obtained silicon nanowire@carbon negative electrode material for lithium batteries can be applied to the preparation of lithium batteries, so that the batteries have excellent discharge performance and cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a method for preparing silicon nanowire@carbon anode material for lithium batteries, its products, and applications. Background Technology

[0002] Lithium-ion batteries have been widely used in portable electronic products and electric vehicles. Currently, commercially available lithium-ion batteries mainly use graphite-based anode materials. However, graphite's theoretical specific capacity is 372 mAh / g, and the specific capacity of existing graphite-based anode materials is already close to its theoretical value. Therefore, the development potential of graphite-based anode materials is currently very limited, making it difficult to meet the miniaturization needs of various portable electronic devices and the widespread demand for high-energy-density and high-power-density lithium-ion batteries in electric vehicles. Silicon, however, has a high energy storage capacity (theoretical specific capacity of 4200 mAh / g), more than ten times that of graphite, and is considered one of the ideal candidate materials for developing next-generation high-energy-density and high-power-density lithium-ion battery anode materials. However, silicon undergoes a volume change of up to 300% during cycling, resulting in poor first-efficiency and cycle performance. Therefore, modifying silicon before using it as a battery anode material is currently a key research focus and hot topic.

[0003] CN107785095A discloses a porous silicon conductive paste doped with copper and graphene, comprising porous silicon, copper, graphene, stabilizer, dispersant, and organic carrier. The resulting porous silicon conductive paste doped with copper and graphene exhibits good conductivity, high stability, and is not prone to agglomeration. However, the introduction of copper only provides the function of a conductive agent; the conductivity and stability of silicon are not effectively improved.

[0004] CN108598452A discloses a silicon-based anode material for lithium batteries and its preparation method. The silicon-based anode material comprises nano-silicon particles and a first organic small molecule layer, a second organic small molecule layer, and a conductive polymer layer sequentially coated on the nano-silicon particles. This effectively maintains the morphology of the solid electrolyte interface film and suppresses the formation of lithium dendrites, resulting in higher specific capacity and better cycle performance in the lithium battery. However, the capacity retention rate of the lithium battery decreases significantly after 50 cycles, requiring further improvement.

[0005] Based on the above research, it can be seen that there are many studies on modifying silicon materials and applying them to lithium batteries. However, problems still exist, such as poor electrochemical performance of silicon materials themselves or poor cycle performance of lithium batteries. Therefore, finding an effective method to modify silicon materials to improve their conductivity and stability, thereby improving the specific capacity and cycle performance of lithium batteries, is an urgent problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies and practical needs, the present invention aims to provide a method for preparing silicon nanowire@carbon anode materials for lithium batteries, as well as the resulting products and applications. The silicon nanowire@carbon anode material obtained using the described method can be used to prepare lithium batteries, improving their specific capacity and cycle life.

[0007] To achieve this objective, the present invention employs the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing silicon nanowires@carbon anode materials for lithium batteries, the preparation method comprising the following steps:

[0009] (1) Mix silicon nanowires with an aqueous solution of a surfactant to obtain solution A;

[0010] (2) Mix solution A obtained in step (1) with an aqueous solution of carbon source to obtain solution B;

[0011] (3) Sinter the solution B obtained in step (2) to obtain the silicon nanowire@carbon anode material;

[0012] The sintering process includes, in sequence, a first heating stage, a first holding stage, a second heating stage, a second holding stage, a third heating stage, and a third holding stage.

[0013] The sintering is carried out in a protective gas atmosphere, and the sintering temperature range is 250-1000℃.

[0014] The 250-1000℃ range can be 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, or 1000℃, etc.

[0015] Other point values ​​within the above range can be selected, and will not be elaborated on here.

[0016] This invention employs an aqueous solution of surfactant to wet silicon nanowires, followed by a one-step, multi-temperature-range carbonization process to obtain silicon nanowire@carbon anode materials for lithium batteries. The entire process is simple and easy to implement, requires minimal equipment investment and floor space, and uses inexpensive raw materials, facilitating industrialization and commercialization.

[0017] It should be noted that the present invention uses an aqueous solution of surfactant to wet the silicon nanowires, which ensures more uniform dispersion of the silicon nanowires and better contact between the aqueous solution of the carbon source and the silicon nanowires, thereby achieving a better carbon coating effect. Furthermore, the present invention employs a one-step multi-temperature carbonization process during sintering, which allows for better carbon coating of the silicon nanowires.

[0018] In this invention, the mass ratio of the surfactant to the silicon nanowire is (0.5-1):1.

[0019] The ratio (0.5-1):1 can be 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1, 0.95:1, or 1:1, etc.

[0020] Other point values ​​within the above range can be selected, and will not be elaborated on here.

[0021] In this invention, the surfactant includes any one or a combination of at least two of hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium carboxymethyl cellulose, or trisodium citrate, preferably a combination of hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate.

[0022] The combination of at least two can be a combination of hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate or a combination of sodium dodecylbenzenesulfonate and sodium carboxymethyl cellulose, etc. Any other combination can be selected, and will not be described in detail here.

[0023] The present invention preferably uses a combination of hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate as a surfactant because both are small molecules with low solution viscosity, which is more conducive to the dispersion of silicon nanowires.

[0024] Preferably, the mass ratio of hexadecyltrimethylammonium bromide to sodium dodecylbenzenesulfonate is (2-3):1.

[0025] The ratio (2-3):1 can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1, etc.

[0026] Other point values ​​within the above range can be selected, and will not be elaborated on here.

[0027] In this invention, the carbon source includes any one or a combination of at least two of starch, glucose, chitosan, polyvinyl alcohol, polyvinylpyrrolidone, or hydroxypropyl cellulose, preferably starch.

[0028] The combination of at least two can be a combination of starch and glucose or a combination of glucose and chitosan, etc. Any other combination can be selected, which will not be described in detail here.

[0029] The present invention prefers starch as the carbon source because starch is biomass carbon and is more abundant.

[0030] Preferably, the mass ratio of the silicon nanowire to the carbon source is 1:(3-5).

[0031] The 1:(3-5) can be 1:3, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4.0, 1:4.2, 1:4.4, 1:4.6, 1:4.8 or 1:5, etc.

[0032] Other point values ​​within the above range can be selected, and will not be elaborated on here.

[0033] In this invention, the mixing method in step (2) is stirring, the stirring rate is 180-250 r / min, and the stirring time is 1.5-2.5 h.

[0034] The 180-250 r / min can be 180 r / min, 190 r / min, 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, or 250 r / min, etc.

[0035] The 1.5-2.5h can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h, or 2.5h, etc.

[0036] Other point values ​​within the above range can be selected, and will not be elaborated on here.

[0037] In this invention, the temperature is raised to 250-350°C during the first heating stage.

[0038] The 250-350℃ can be 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, or 350℃, etc.

[0039] The first heating stage of this invention raises the temperature to 250-350°C because this temperature range ensures that the volatile components can reach their volatilization temperature.

[0040] In this invention, the duration of the first heat preservation stage is 80-100 minutes.

[0041] The first heat preservation stage of this invention lasts for 80-100 minutes to ensure complete evaporation.

[0042] The 80-100min can be 80min, 82min, 84min, 86min, 88min, 90min, 92min, 94min, 96min, 98min, or 100min, etc.

[0043] In this invention, the second heating stage involves heating to 450-550°C.

[0044] The 450-550℃ can be 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, or 550℃, etc.

[0045] In this invention, the second heating stage heats the temperature to 450-550°C, achieving spherical shrinkage within this temperature range.

[0046] In this invention, the second heat preservation stage lasts for 50-70 minutes.

[0047] The 50-70 min can be 50 min, 52 min, 54 min, 56 min, 58 min, 60 min, 62 min, 64 min, 66 min, 68 min, or 70 min, etc.

[0048] In this invention, the second heat preservation stage lasts for 50-70 minutes to ensure that spheroidization shrinkage is completed.

[0049] In this invention, the third heating stage raises the temperature to 850-1000℃.

[0050] The 850-1000℃ can be 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, or 1000℃, etc.

[0051] In this invention, the third heating stage raises the temperature to 850-1000℃, and carbonization is achieved within this temperature range.

[0052] In this invention, the duration of the third heat preservation stage is 2-4 hours.

[0053] The 2-4h can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3.0h, 3.2h, 3.4h, 3.6h, 3.8h, or 4h, etc.

[0054] In this invention, the third heat preservation stage lasts for 2-4 hours to ensure complete carbonization.

[0055] In a second aspect, the present invention provides a silicon nanowire@carbon anode material for lithium batteries, wherein the silicon nanowire@carbon anode material for lithium batteries is prepared by the preparation method described in the first aspect.

[0056] The lithium battery silicon nanowire@carbon anode material is composed of silicon nanowires and a carbon layer coated on the surface of the silicon nanowires.

[0057] Preferably, the silicon nanowires in the silicon nanowire@carbon anode material for lithium batteries have a mass content of 5-40 wt%.

[0058] The 5-40wt% can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, or 40wt%, etc.

[0059] Preferably, the carbon layer in the silicon nanowire@carbon anode material for lithium batteries has a mass content of 60-95 wt%.

[0060] The 60-95wt% can be 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, or 95wt%, etc.

[0061] Thirdly, the present invention provides an application of the silicon nanowire@carbon anode material for lithium batteries described in the second aspect in the preparation of lithium batteries.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] (1) The raw materials in the preparation method of silicon nanowire@carbon anode material for lithium battery provided by the present invention are inexpensive, have obvious cost advantages, and are easy to industrialize and commercialize.

[0064] (2) The preparation method of silicon nanowires@carbon anode material for lithium batteries provided by the present invention has a simple process. The silicon nanowires@carbon anode material can be obtained by mechanically stirring the raw materials at room temperature and carbon coating in one step. The equipment investment cost is small, the floor space is small, and the process cost advantage is obvious.

[0065] (3) The battery obtained by using the silicon nanowire@carbon anode material for lithium battery provided by the present invention has excellent cycle performance, rate charge and discharge performance and safety performance. Its initial reversible specific capacity is more than 1200mAh / g, and the capacity retention rate after 50 cycles is more than 97%, with a maximum of 97.6%. Attached Figure Description

[0066] Figure 1 This is an electron microscope image of the silicon nanowire@carbon anode material for lithium batteries obtained in Example 1;

[0067] Figure 2 This is a cycle performance graph of the battery obtained from Example 1. Detailed Implementation

[0068] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0069] The sources of the materials and raw materials used in the following preparation examples, embodiments, and comparative examples are as follows:

[0070] Starch was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; acetylene black from Sinopharm Chemical Reagent Co., Ltd.; and polyvinylidene fluoride from Sinopharm Chemical Reagent Co., Ltd. Unless otherwise specified, all other materials and raw materials were obtained from other commercial sources.

[0071] Preparation Example 1

[0072] This preparation example provides a silicon nanowire, prepared by the following method:

[0073] In an argon protective atmosphere (flow rate of 200 mL / min), zinc powder was placed in the middle of a quartz tube. When the temperature reached 900℃, silicon tetrachloride gas was introduced into the quartz tube through an argon carrier. After reacting for 1 hour, the quartz tube was cooled to 100℃ to obtain silicon nanowires.

[0074] Example 1

[0075] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries, and its preparation method is as follows:

[0076] (1) Weigh 1.5g of cetyltrimethylammonium bromide and 0.6g of sodium dodecylbenzenesulfonate, dissolve them in 100mL of deionized water, add 3g of silicon nanowires obtained in Example 1 after complete dissolution, mix well to obtain solution A;

[0077] (2) Weigh 10g of starch and dissolve it in 50mL of deionized water. Then mix the solution A obtained in step (1) with the starch aqueous solution and stir at 200r / min for 2h to obtain solution B.

[0078] (3) The solution B obtained in step (2) is placed in a crucible and transferred to a sintering furnace. In an argon atmosphere of 200 mL / min, the first heating stage, the first holding stage, the second heating stage, the second holding stage, the third heating stage and the third holding stage are carried out in sequence to finally obtain the silicon nanowire@carbon anode material for lithium batteries.

[0079] The process involves three stages: the first stage involves heating from 25°C to 300°C at a rate of 5°C / min, and holding at this temperature for 90 minutes; the second stage involves heating from 300°C to 500°C at a rate of 3°C / min, and holding at this temperature for 60 minutes; and the third stage involves heating from 500°C to 900°C at a rate of 5°C / min, and holding at this temperature for 3 hours.

[0080] The electron microscopy results of the silicon nanowire@carbon anode material for lithium batteries are as follows: Figure 1As shown, silicon nanowires can be well coated with carbon.

[0081] Example 2

[0082] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries, and its preparation method is as follows:

[0083] (1) Weigh 1.5g of cetyltrimethylammonium bromide, 0.5g of sodium dodecylbenzenesulfonate and 0.5g of sodium carboxymethyl cellulose respectively, dissolve them in 100mL of deionized water, add 2.5g of silicon nanowires obtained in Example 1 after complete dissolution, mix evenly to obtain solution A;

[0084] (2) Weigh 8g of starch and 2g of glucose respectively, dissolve them in 50mL of deionized water, and then mix the solution A obtained in step (1) with the aqueous solution containing starch and glucose. Stir at 250r / min for 1.5h to obtain solution B.

[0085] (3) The solution B obtained in step (2) is placed in a crucible and transferred to a sintering furnace. In an argon atmosphere of 350 mL / min, the first heating stage, the first holding stage, the second heating stage, the second holding stage, the third heating stage and the third holding stage are carried out in sequence to finally obtain the silicon nanowire@carbon anode material for lithium batteries.

[0086] The process involves three stages: the first stage involves heating from 25°C to 350°C at a rate of 6°C / min and holding at this temperature for 80 minutes; the second stage involves heating from 350°C to 550°C at a rate of 4°C / min and holding at this temperature for 50 minutes; and the third stage involves heating from 550°C to 1000°C at a rate of 8°C / min and holding at this temperature for 2 hours.

[0087] Example 3

[0088] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries, and its preparation method is as follows:

[0089] (1) Weigh 2g of cetyltrimethylammonium bromide and 1g of sodium carboxymethyl cellulose, dissolve them in 100mL of deionized water, add 5g of silicon nanowires obtained in Example 1 after complete dissolution, mix well to obtain solution A;

[0090] (2) Weigh 10g of starch and 5g of glucose respectively, dissolve them in 50mL of deionized water, and then mix the solution A obtained in step (1) with the aqueous solution containing starch and glucose. Stir at 180r / min for 2.5h to obtain solution B.

[0091] (3) The solution B obtained in step (2) is placed in a crucible and transferred to a sintering furnace. In an argon atmosphere of 150 mL / min, the first heating stage, the first holding stage, the second heating stage, the second holding stage, the third heating stage and the third holding stage are carried out in sequence to finally obtain the silicon nanowire@carbon anode material for lithium batteries.

[0092] The process involves three stages: the first stage involves heating from 25°C to 250°C at a rate of 4°C / min and holding at this temperature for 100 min; the second stage involves heating from 250°C to 450°C at a rate of 4°C / min and holding at this temperature for 70 min; and the third stage involves heating from 450°C to 850°C at a rate of 5°C / min and holding at this temperature for 4 h.

[0093] Example 4

[0094] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Example 1 is that in step (1), only 2.1g of hexadecyltrimethylammonium bromide is weighed and dissolved in 100mL of deionized water. The other parameters are the same as in Example 1. The preparation method is the same as in Example 1.

[0095] Example 5

[0096] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Example 1 is that in step (1), only 2.1g of sodium dodecylbenzenesulfonate is weighed and dissolved in 100mL of deionized water. The other parameters are the same as in Example 1. The preparation method is the same as in Example 1.

[0097] Example 6

[0098] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Example 1 is that starch is replaced with an equal amount of glucose; all other parameters remain the same as in Example 1. The preparation method is the same as in Example 1.

[0099] Example 7

[0100] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Embodiment 1 is that the first heating stage is heated to 300°C and held at this temperature for 70 minutes. All other parameters remain the same as in Embodiment 1. The preparation method is the same as in Embodiment 1.

[0101] Example 8

[0102] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Embodiment 1 is that the first heating stage is heated to 300°C and held at this temperature for 110 minutes. All other parameters remain the same as in Embodiment 1. The preparation method is the same as in Embodiment 1.

[0103] Example 9

[0104] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Embodiment 1 is that the second heating stage is heated to 500°C and held at this temperature for 40 minutes. All other parameters remain the same as in Embodiment 1. The preparation method is the same as in Embodiment 1.

[0105] Example 10

[0106] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Embodiment 1 is that the second heating stage is heated to 500°C and held at this temperature for 80 minutes. All other parameters remain the same as in Embodiment 1. The preparation method is the same as in Embodiment 1.

[0107] Example 11

[0108] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Embodiment 1 is that the second heating stage is heated to 500°C and held at this temperature for 1.8 hours. All other parameters remain the same as in Embodiment 1. The preparation method is the same as in Embodiment 1.

[0109] Example 12

[0110] This embodiment provides a silicon nanowire@carbon anode material for lithium batteries. The only difference from Embodiment 1 is that the second heating stage is heated to 500°C and held at this temperature for 4.2 hours. All other parameters remain the same as in Embodiment 1. The preparation method is the same as in Embodiment 1.

[0111] Comparative Example 1

[0112] This comparative example provides a silicon nanowire@carbon anode material for lithium batteries, and its preparation method is as follows:

[0113] (1) Weigh 3g of the silicon nanowires obtained in Example 1 and dissolve them in 100mL of deionized water to obtain solution A;

[0114] (2) Weigh 10g of starch and dissolve it in 50mL of deionized water. Then mix the solution A obtained in step (1) with the starch aqueous solution and stir at 200r / min for 2h to obtain solution B.

[0115] (3) The solution B obtained in step (2) is placed in a crucible and transferred to a sintering furnace. In an argon atmosphere, the first heating stage, the first holding stage, the second heating stage, the second holding stage, the third heating stage and the third holding stage are carried out in sequence to finally obtain the silicon nanowire@carbon anode material for lithium batteries.

[0116] The process involves three stages: the first stage involves heating from 25°C to 300°C at a rate of 5°C / min, and holding at this temperature for 90 minutes; the second stage involves heating from 300°C to 500°C at a rate of 3°C / min, and holding at this temperature for 60 minutes; and the third stage involves heating from 500°C to 900°C at a rate of 5°C / min, and holding at this temperature for 3 hours.

[0117] Comparative Example 2

[0118] This comparative example provides a silicon nanowire@carbon anode material for lithium batteries, and its preparation method is as follows:

[0119] (1) Weigh 1.5g of cetyltrimethylammonium bromide and 0.6g of sodium dodecylbenzenesulfonate, dissolve them in 100mL of deionized water, add 3g of silicon nanowires obtained in Example 1 after complete dissolution, mix well to obtain solution A;

[0120] (2) Weigh 10g of starch and dissolve it in 50mL of deionized water. Then mix the solution A obtained in step (1) with the starch aqueous solution and stir at 200r / min for 2h to obtain solution B.

[0121] (3) Place the solution B obtained in step (2) into a crucible and transfer it to a sintering furnace. In an argon atmosphere, perform the first heating stage, the first holding stage, the second heating stage and the second holding stage in sequence to finally obtain the silicon nanowire@carbon anode material for lithium batteries.

[0122] The first heating stage involves raising the temperature from 25°C to 500°C at a rate of 5°C / min and holding it at this temperature for 70 minutes; the second heating stage involves raising the temperature from 500°C to 900°C at a rate of 5°C / min and holding it at this temperature for 3 hours.

[0123] Comparative Example 3

[0124] This comparative example provides a silicon nanowire@carbon anode material for lithium batteries, and its preparation method is as follows:

[0125] (1) Weigh 1.5g of cetyltrimethylammonium bromide and 0.6g of sodium dodecylbenzenesulfonate, dissolve them in 100mL of deionized water, add 3g of silicon nanowires obtained in Example 1 after complete dissolution, mix well to obtain solution A;

[0126] (2) Weigh 10g of starch and dissolve it in 50mL of deionized water. Then mix the solution A obtained in step (1) with the starch aqueous solution and stir at 200r / min for 2h to obtain solution B.

[0127] (3) Place the solution B obtained in step (2) into a crucible and transfer it to a sintering furnace. In an argon atmosphere, perform the first heating stage, the first holding stage, the second heating stage and the second holding stage in sequence to finally obtain the silicon nanowire@carbon anode material for lithium batteries.

[0128] The first heating stage involves raising the temperature from 25℃ to 300℃ at a rate of 5℃ / min and holding it at this temperature for 90 minutes; the second heating stage involves raising the temperature from 300℃ to 900℃ at a rate of 5℃ / min and holding it at this temperature for 3.5 hours.

[0129] Comparative Example 4

[0130] This comparative example provides a silicon nanowire@carbon anode material for lithium batteries, and its preparation method is as follows:

[0131] (1) Weigh 1.5g of cetyltrimethylammonium bromide and 0.6g of sodium dodecylbenzenesulfonate, dissolve them in 100mL of deionized water, add 3g of silicon nanowires obtained in Example 1 after complete dissolution, mix well to obtain solution A;

[0132] (2) Weigh 10g of starch and dissolve it in 50mL of deionized water. Then mix the solution A obtained in step (1) with the starch aqueous solution and stir at 200r / min for 2h to obtain solution B.

[0133] (3) The solution B obtained in step (2) is placed in a crucible and transferred to a sintering furnace. In an argon atmosphere, the temperature is increased from 25°C to 900°C at a rate of 5°C / min and held at this temperature for 3.5 hours. Finally, the silicon nanowire@carbon anode material for lithium batteries is obtained.

[0134] Application Example 1-12

[0135] 2g of the silicon nanowire@carbon anode material for lithium batteries obtained in Examples 1-12, 0.3g of acetylene black, and 0.4g of polyvinylidene fluoride were weighed and dissolved in 20mL of N-methylpyrrolidone (NMP) to obtain a mixed slurry. The slurry was then uniformly coated onto copper foil and dried at 110℃ for 30h to obtain a laboratory battery electrode. A CR2032 coin cell was prepared using a 1mol / L electrolyte with ethyl carbonate and dimethyl carbonate as solvents, a lithium sheet as the corresponding electrode, and a Legard 2400 separator.

[0136] Compare and contrast examples 1-4

[0137] 2g of silicon nanowire@carbon anode material for lithium batteries obtained in Comparative Examples 1-4, 0.3g of acetylene black, and 0.4g of polyvinylidene fluoride were weighed and dissolved in 20mL of N-methylpyrrolidone (NMP) to obtain a mixed slurry. The slurry was then uniformly coated onto copper foil and dried at 110℃ for 30h to obtain a laboratory battery electrode. A CR2032 coin cell was prepared using a 1mol / L electrolyte with ethyl carbonate and dimethyl carbonate as solvents, a lithium sheet as the corresponding electrode, and a Legard 2400 separator.

[0138] Test Example 1

[0139] This test case examines the specific capacity and cycle performance of the CR2032 coin cells obtained from test cases 1-12 and comparative examples 1-4. The test method is as follows:

[0140] The constant current charge-discharge test was conducted using the Xinwei BTS battery testing system. The CR2032 coin cell was charged and discharged using a current of 0.1C at a test temperature of 25℃.

[0141] The test results are shown in Table 1 below:

[0142] Table 1

[0143]

[0144]

[0145] The data in the table above shows that the battery prepared using the silicon nanowire@carbon anode material for lithium batteries provided by this invention exhibits excellent discharge and cycle performance. Data from Application Examples 4-5 shows that the choice of surfactant type affects battery performance. Data from Application Example 6 shows that the choice of carbon source type affects battery performance. Data from Application Examples 7-12 shows that the duration of different holding stages in the multi-temperature carbonization process during sintering affects battery performance. Comparing the data from Application Examples 1-4 shows that the absence of surfactant or the absence of any one of the three heating stages in the sintering process negatively impacts battery performance.

[0146] The cycle performance results of the battery obtained from Example 1 are as follows: Figure 2 As shown, the battery's discharge specific capacity remains stable with minimal fluctuations during 50 consecutive cycles, and the initial discharge specific capacity reaches 1273 mAh / g. This indicates that the battery prepared using the silicon nanowire@carbon anode material provided by this invention exhibits excellent discharge and cycle performance.

[0147] In summary, the preparation method of silicon nanowire@carbon anode material for lithium batteries provided by this invention has a simple process. The silicon nanowire@carbon anode material can be obtained by mechanically stirring the raw materials at room temperature and then carbon coating in one step. The equipment investment cost is small, the footprint is small, the process cost advantage is obvious, and the raw material cost is low. The battery obtained by using the silicon nanowire@carbon anode material for lithium batteries provided by this invention has excellent cycle performance, rate charge and discharge performance and safety performance. Its initial reversible specific capacity is over 1200 mAh / g, and the capacity retention rate after 50 cycles is over 97%, with a maximum of 97.6%.

[0148] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing silicon nanowires@carbon anode material for lithium batteries, characterized in that, The preparation method includes the following steps: (1) Mix silicon nanowires with an aqueous solution of a surfactant to obtain solution A; (2) Mix solution A obtained in step (1) with an aqueous solution of carbon source to obtain solution B; (3) Sinter the solution B obtained in step (2) to obtain the silicon nanowire@carbon anode material for lithium batteries; The sintering process includes, in sequence, a first heating stage, a first holding stage, a second heating stage, a second holding stage, a third heating stage, and a third holding stage. The first heating stage raises the temperature to 250-350℃, and the first holding stage lasts for 80-100 minutes. The second heating stage involves heating to 450-550℃, and the second holding stage lasts for 50-70 minutes. The third heating stage raises the temperature to 850-1000℃, and the third heat preservation stage lasts for 2-4 hours. The sintering is carried out in a protective gas atmosphere.

2. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 1, characterized in that, The mass ratio of the surfactant to the silicon nanowire is (0.5-1):

1.

3. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 1, characterized in that, The surfactants include hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, Sodium carboxymethyl cellulose or trisodium citrate, or a combination of at least two of them.

4. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 3, characterized in that, The surfactant is a combination of hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate.

5. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 4, characterized in that, The mass ratio of hexadecyltrimethylammonium bromide to sodium dodecylbenzenesulfonate is (2-3):

1.

6. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 1, characterized in that, The carbon source includes any one or a combination of at least two of starch, glucose, chitosan, polyvinyl alcohol, polyvinylpyrrolidone, or hydroxypropyl cellulose.

7. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 6, characterized in that, The carbon source is starch.

8. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 1, characterized in that, The mass ratio of the silicon nanowires to the carbon source is 1:(3-5).

9. The method for preparing silicon nanowires@carbon anode material for lithium batteries according to claim 1, characterized in that, The mixing method in step (2) is stirring, the stirring rate is 180-250 r / min, and the stirring time is 1.5-2.5 h.

10. A silicon nanowire@carbon anode material for lithium batteries, characterized in that, The silicon nanowire@carbon anode material for lithium batteries is prepared by the preparation method described in any one of claims 1-9; The lithium battery silicon nanowire@carbon anode material is composed of silicon nanowires and a carbon layer coated on the surface of the silicon nanowires.

11. The silicon nanowire@carbon anode material for lithium batteries according to claim 10, characterized in that, The silicon nanowires in the silicon nanowire@carbon anode material for lithium batteries have a mass content of 5-40 wt%.

12. The silicon nanowire@carbon anode material for lithium batteries according to claim 10, characterized in that, The carbon layer in the silicon nanowire@carbon anode material for lithium batteries has a mass content of 60-95 wt%.

13. The application of silicon nanowires@carbon anode material for lithium batteries according to any one of claims 10-12 in the preparation of lithium batteries.

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