Nanometer silicon negative electrode material for lithium ion battery and preparation method and application of nanometer silicon negative electrode material
The preparation of nano-silicon anode material with a porous frame structure by electrolytic method solves the problem of volume expansion and low first cycle efficiency in the charge and discharge process of silicon-based anode material in lithium-ion batteries, and significantly improves the cycle stability and electrochemical performance of the battery.
Patent Information
- Application Number
- CN202510154218.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-12
- Publication Date
- 2025-05-13
AI Technical Summary
The volume expansion and first cycle efficiency of the silicon-based negative electrode material in lithium-ion batteries during charging and discharging process, resulting in repeated formation/cracking of the solid electrolyte interface film on the surface of the electrode material, affecting the cycle life of the battery.
Nanosilicon negative electrode materials are prepared by electrolytic method. By electrolyzing the silicon plate as an electrode in an electrolyte containing metal ions, controlling the metal embedding and removal, nanosilicon materials with different microstructures are prepared to adapt to the volume changes in the charge and discharge process and improve cycle stability.
By preparing nano-silicon anode material with a porous frame structure, the cycle stability and electrochemical performance of lithium-ion batteries are significantly improved and the service life of the battery is extended.
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Figure CN119980390A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of batteries, and in particular to a nano silicon negative electrode material for lithium ion batteries, a preparation method thereof and an application thereof. Background Art
[0002] Graphite has excellent conductivity and stable layered structure. It is the main material for the negative electrode of lithium-ion batteries for new energy vehicles. Its actual reversible capacity has reached 360-365mAh g -1 , close to the theoretical reversible capacity of 372 mAh g -1 , which cannot meet the growing energy density requirements of electric vehicles and 3C products. Silicon-based negative electrode materials have high theoretical specific capacity (4200mAh g -1 ), low operating voltage, and abundant resources, making it a highly-regarded negative electrode material for power batteries.
[0003] However, silicon-based negative electrode materials have problems such as low conductivity and volume expansion during charging and discharging, which leads to repeated formation / rupture of the solid electrolyte interface (SEI) on the surface of the electrode material, and the crushing and pulverization of the negative electrode material particles, which ultimately affects the cycle life of the battery and hinders the commercialization of silicon-based negative electrode materials. In response to the defects in the performance of silicon-based negative electrode materials, researchers have designed the material structure and used a variety of methods to synthesize nano-silicon, prepare hollow or porous silicon, prepare amorphous silicon, and silicon-carbon composite materials to improve the volume expansion of silicon-based negative electrodes during charging and discharging.
[0004] Therefore, in view of the volume expansion and low first cycle efficiency of silicon-based negative electrode materials used in current lithium-ion batteries during charging and discharging, it is particularly important to develop a silicon-carbon negative electrode material and its preparation technology that can be mass-produced, has a stable structure, and has excellent cycle performance. Summary of the invention
[0005] In view of the above-mentioned shortcomings, the present invention provides a nano-silicon negative electrode material for lithium-ion batteries and a preparation method and application thereof. The porous silicon negative electrode prepared by the preparation method of the present invention can better adapt to the volume change during the charge and discharge process and improve the cycle stability of the silicon-based negative electrode material.
[0006] In order to achieve the above object, the present invention provides a method for preparing a nano-silicon negative electrode material for a lithium ion battery, comprising the following steps:
[0007] S1. inserting the silicon plates as cathode and anode into an electrolytic cell containing electrolyte, wherein the electrolyte contains metal ions;
[0008] S2, direct current is passed through, and electrolysis is performed in an inert atmosphere, and a silicon plate with metal attached is obtained at the cathode;
[0009] S3, reverse current is applied to the metal on the metal-attached silicon plate to return the metal to the electrolyte in the form of ions, and then the silicon plate after the metal is embedded and removed is taken out, crushed, and cleaned in turn to obtain a nano-silicon negative electrode material.
[0010] It should be noted that in step S2, the connection method between the DC power terminal and the silicon plate is at least one of point connection and wire winding; multiple silicon plates can be connected in parallel for large-scale production, and the parallel silicon plates can serve as cathodes / anodes at the same time.
[0011] It should be noted that, in step S2, the metal in the metal-attached silicon plate is combined with the silicon plate to form a metal-silicon alloy.
[0012] According to one aspect of the present invention, it also includes:
[0013] S4, changing the current direction of the electrolytic cell again, placing a new silicon plate as a cathode, and repeating steps S2 to S3 to obtain continuously large-scale generated nano-silicon negative electrode materials.
[0014] According to one aspect of the present invention, in step S1, the length of the silicon plate is 0.1-3 m, the width is 0.05-2 m, the thickness is 0.01-1 m, and the distance between two silicon plates is 0.01-0.1 m.
[0015] According to one aspect of the present invention, in step S1, the electrolyte is at least one of a molten salt containing metal ions, an aqueous solution containing metal ions, and an organic solution containing metal ions; the metal ions are at least one of lithium ions, sodium ions, magnesium ions, aluminum ions, calcium ions, iron ions, and nickel ions.
[0016] According to one aspect of the present invention, the purity of the silicon plate is 98% to 99.99999%; the electrolytic cell is an integrated electrolytic cell; the inner wall material of the electrolytic cell includes at least one of tantalum, tungsten, molybdenum, zirconium, heat-resistant stainless steel, and heat-resistant ceramics.
[0017] It should be noted that the purity of the silicon plate is 98% to 99.99999%; the silicon used as the electrode contains a small amount of metal impurities, the purpose of which is to improve the conductivity of the electrode. The metal impurities are at least one of lithium, sodium, magnesium, aluminum, calcium, iron, nickel and other metals.
[0018] According to one aspect of the present invention, the electrolyte further includes an additive, and the additive is at least one of sodium metasilicate, sodium chloride, potassium chloride, potassium fluoride, barium chloride, aluminum oxide, polyacrylamide, carboxymethyl cellulose, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate.
[0019] It should be noted that the additive acts on the silicon surface exposed when the metal in the metal silicon alloy is released, and is used to inhibit the growth and aggregation of nano-silicon and control the surface oxidation of nano-silicon.
[0020] According to one aspect of the present invention, in step S2, the electrolysis temperature is 25-1000°C, the time is 1-48h, and the current density is 0.1-5.0A / cm 2 .
[0021] It should be noted that changing the current density can change the distribution state of the metal in the cathode silicon plate; changing the electrolysis time can change the content of the metal in the cathode silicon plate; that is, changing both can regulate the final nano-silicon structure.
[0022] According to one aspect of the present invention, the inert atmosphere includes at least one of nitrogen, helium, and argon; the solvent used for cleaning is at least one of deionized water, sodium carbonate, carbon tetrachloride, acetone, toluene, petroleum ether, ethyl formate, ethyl acetate, ethylene carbonate, dimethyl carbonate, ethanol, and isopropanol.
[0023] Based on the same inventive concept, the present invention also provides a nano-silicon negative electrode material prepared by any of the above-mentioned preparation methods, wherein the nano-silicon negative electrode material is at least one of coral-shaped nano-silicon, nano-silicon with a porous framework, spherical nano-silicon with a porous framework, nano-wire silicon with a porous framework, and nano-silicon particles with a porous framework.
[0024] According to one aspect of the present invention, the coral-like length is 0.1 to 100 μm; the diameter of silicon in the nano-silicon with a porous framework is 10 nm to 10 μm, and the specific surface area is 10 to 1000 m 2 g -1 ; The length of the nanowire is 1 to 100 μm; the D50 of the spherical nanosilicon in the spherical nanosilicon is 5 to 1000 nm.
[0025] Based on the same inventive concept, the present invention also provides an application of a nano-silicon negative electrode material prepared by any of the above preparation methods in a lithium-ion battery.
[0026] Beneficial effects of the present invention:
[0027] (1) The present invention adopts an electrolysis method, using silicon plates as electrodes to electrolyze electrolytes containing different metal ions. By changing the current density, electrolysis time, and metal type, the metal embedding and extraction are controlled to prepare nano-silicon materials with different microstructures, such as nano-silicon balls, silicon nanowires, silicon nanosheets, porous nano-silicon frameworks, etc., which can better adapt to the volume changes during the charge and discharge process and improve the cycle stability of silicon-based negative electrode materials.
[0028] (2) The present invention realizes a nano-silicon preparation process that is easy to operate and can be continuously produced by building an integrated electrolytic cell with a detachable and replaceable cathode and anode. The electrolyte containing metal ions can be recycled as an intermediate carrier, which reduces the difficulty of operation and the cost of electrolysis and improves the preparation efficiency of nano-silicon. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 It is a diagram of an electrolysis device for the method for preparing nano-silicon by electrolysis according to the present invention;
[0030] Figure 2 is a SEM image of the silicon-based negative electrode material prepared in Example 1 of the present invention;
[0031] Figure 3 It is a cycle performance diagram of the silicon-based negative electrode material prepared in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION
[0032] To make the present invention easier to understand, the present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by professional and technical personnel in the field; unless otherwise specified, the raw materials and reagents involved in this article can be purchased from the market or prepared by known methods.
[0033] Example 1
[0034] A method for preparing a nano-silicon negative electrode material for a lithium-ion battery comprises the following steps:
[0035] (1) A lithium chloride-potassium chloride molten salt system was used. The length, width and height of the silicon plate were 0.5 m, 0.2 m and 0.02 m respectively. The distance between adjacent silicon plates was 0.05 m. The purity of the silicon plate was 99%. The plate was placed in an electrolytic cell with a tantalum metal inner wall and heated to 450°C in a N2 atmosphere.
[0036] (2) Add nano-alumina to the electrolytic cell and pass direct current with a current density of 0.15 A / cm 2 After 8 hours of electrolysis in a N2 atmosphere, the power is reversed, and the metal lithium on the silicon plate re-enters the electrolyte. After charging, the metal lithium returns to the molten salt in the form of ions. The silicon plate after the metal lithium is inserted and removed is taken out, broken and washed with dimethyl carbonate to obtain the nano-silicon negative electrode material. Among them, the electrolysis device is as follows Figure 1 shown.
[0037] (3) Place a new silicon plate, change the direction of the electrolytic cell current, and start a new round of electrolysis.
[0038] The nano-silicon negative electrode material prepared above was analyzed by scanning electron microscope, and the results are as follows: Figure 2 As shown. Figure 2 It can be seen that the nano silicon negative electrode material prepared in Example 1 of the present application is silicon with a coral-like porous framework. Porous silicon negative electrode sheet (porous silicon negative electrode material) surface density 2 mg cm -2 The electrolyte solute is LiPF6, the solvents are EC, DMC, and DEC, the volume ratio is 0.3:0.3:0.4, and the concentration of the solute is 1 mol L -1 . Perform half-cell test and charge and discharge test between 0.01 and 1.5 V (at a current density of 50 mA g -1 The first three charge and discharge tests were carried out at a current density of 200 mA g -1 The electrochemical performance is shown in Table 1.
[0039] Example 2
[0040] A method for preparing a nano-silicon negative electrode material for a lithium-ion battery comprises the following steps:
[0041] (1) A magnesium chloride molten salt system is used. The length, width and height of the silicon plate are 0.5m, 0.2m and 0.02m respectively. The distance between adjacent silicon plates is 0.05m. The purity of the silicon plate is 99%. It is placed in an electrolytic cell with tantalum metal as the inner wall and heated to 1000°C in a N2 atmosphere.
[0042] (2) Add nano-alumina to the electrolytic cell and pass direct current with a current density of 0.12 A / cm 2 After electrolysis in a N2 atmosphere for 10 hours, the power is reversed and the metallic magnesium on the silicon plate re-enters the electrolyte. After charging, the metallic magnesium returns to the molten salt in the form of ions. The silicon plate after the metallic magnesium is embedded and de-embedded is taken out, broken and cleaned with dimethyl carbonate to obtain a porous silicon negative electrode material.
[0043] (3) Place a new silicon plate, change the direction of the electrolytic cell current, and start a new round of electrolysis.
[0044] Nano silicon negative electrode sheet (nano silicon negative electrode material) surface density 2mg cm -2 The electrolyte solute is LiPF6, the solvents are EC, DMC, and DEC, the volume ratio is 0.3:0.3:0.4, and the concentration of the solute is 1 mol L -1 . Perform half-cell test and charge and discharge test between 0.01 and 1.5 V (at a current density of 50 mA g -1 The first three charge and discharge tests were carried out at a current density of 200 mAg-1 The electrochemical performance is shown in Table 2.
[0045] Example 3
[0046] A method for preparing a nano-silicon negative electrode material for a lithium-ion battery comprises the following steps:
[0047] (1) A sulfuric acid-ferrous sulfate aqueous solution system was used. The length, width and height of the silicon plate were 0.5 m, 0.2 m and 0.02 m respectively. The distance between adjacent silicon plates was 0.05 m. The purity of the silicon plate was 99%. The plate was placed in an electrolytic cell with a ceramic inner wall and heated to 80° C. in a N2 atmosphere.
[0048] (2) Add potassium chloride to the electrolytic cell and pass direct current with a current density of 0.20 A / cm 2 After 10 hours of electrolysis in a N2 atmosphere, the power was reversed and the metallic iron on the silicon plate re-entered the electrolyte. After charging, the metallic iron returned to the molten salt in the form of ions. The silicon plate after the metallic iron was embedded and removed was taken out, broken and cleaned with dimethyl carbonate.
[0049] (3) Place a new silicon plate, change the direction of the electrolytic cell current, and start a new round of electrolysis.
[0050] Nano silicon negative electrode sheet (nano silicon negative electrode material) surface density 2mg cm -2 The electrolyte solute is LiPF6, the solvents are EC, DMC, and DEC, the volume ratio is 0.3:0.3:0.4, and the concentration of the solute is 1 mol L -1 . Perform half-cell test and charge and discharge test between 0.01 and 1.5 V (at a current density of 50 mA g -1 The first three charge and discharge tests were carried out at a current density of 200 mAg -1 The electrochemical performance is shown in Table 3.
[0051] Comparative Example 1
[0052] The difference between this comparative example and Example 1 is that step (1) in Example 1 is changed, the metal molten salt is replaced by an aqueous solution, the temperature is raised to 50°C, the silicon plate is taken out and cleaned and crushed. The other steps and parameters are the same as Example 1. The obtained silicon powder is micron-sized particles without a porous structure.
[0053] Controlling other experimental conditions to be the same, the comparative example 1 assembled half-cell was tested, and the test mechanism was the same as that of Example 1. Its electrochemical performance is shown in Table 1 below, and its cycle performance is shown in Table 1 below. Figure 3 As shown:
[0054] Table 1 Performance comparison of silicon-based negative electrode materials prepared by electrolytes containing metal ions and electrolytes without metal ions
[0055]
[0056] From Table 1 and Figure 3 It can be seen that the silicon-based negative electrode material obtained by electrolysis of electrolyte containing metal ions has a better internal structure, the silicon in the negative electrode particles is distributed in a coral-like manner, the structure is more stable, and it can effectively resist the volume effect of silicon, so its electrochemical performance is better. The silicon-based negative electrode material obtained by direct electrolysis of aqueous solution has no special morphology, no porous structure inside, and serious volume expansion during charging and discharging, resulting in a decrease in cycle performance.
[0057] Comparative Example 2
[0058] The difference between this comparative example and Example 2 is that step (2) in Example 2 is changed and no additive is added. The other steps and parameters are the same as those in Example 2.
[0059] The other experimental conditions were controlled to be the same, and the half-cell assembled in Comparative Example 2 was tested. The test mechanism was the same as that in Example 2, and its electrochemical performance was shown in Table 2 below:
[0060] Table 2 Performance comparison of silicon-based negative electrode materials with and without additives
[0061]
[0062] It can be seen from Table 2 that the performance of the silicon-based negative electrode material obtained by electrolysis after adding an appropriate amount of additives is more excellent. The silicon-based negative electrode material without additives has a low reversible capacity and a decreased electrochemical performance due to the agglomeration of nanosilicon and poor conductivity of the internal porous structure.
[0063] Comparative Example 3
[0064] The difference between this comparative example and Example 3 is that step (3) in Example 3 is changed, and no washing is performed after crushing. The other steps and parameters are the same as those in Example 1. The other steps and parameters are the same as those in Example 3.
[0065] Table 3 Performance comparison of silicon-based negative electrode materials after cleaning and after crushing without cleaning
[0066]
[0067] As shown in Table 3, the performance of the silicon-based negative electrode material after crushing and cleaning is better. The porous silicon without cleaning after crushing has a relatively high content of metal impurities, and lithium dendrites are generated during the charge and discharge process, resulting in the rupture of the SEI film. Although the performance is similar in the early stage of the cycle, the nano-silicon particles crack and even pulverize in the later stage, and the reversible capacity and cycle retention rate deteriorate sharply.
[0068] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.
Claims
1. A method for preparing a nano-silicon negative electrode material for a lithium-ion battery, characterized in that: The following steps are involved: S1. inserting the silicon plates as cathode and anode into an electrolytic cell containing electrolyte, wherein the electrolyte contains metal ions; S2, direct current is passed through, and electrolysis is performed in an inert atmosphere, and a silicon plate with metal attached is obtained at the cathode; S3, reverse current is applied to the metal on the metal-attached silicon plate to return the metal to the electrolyte in the form of ions, and then the silicon plate after the metal is embedded and removed is taken out, crushed, and cleaned in turn to obtain a nano-silicon negative electrode material.
2. The method for preparing nano silicon negative electrode material for lithium ion battery according to claim 1, characterized in that: The following steps are also included: S4, changing the current direction of the electrolytic cell again, placing a new silicon plate as a cathode, and repeating steps S2 to S3 to obtain continuously large-scale generated nano-silicon negative electrode materials.
3. The method for preparing nano silicon negative electrode material for lithium ion battery according to claim 1, characterized in that: In step S1, the electrolyte is at least one of a molten salt containing metal ions, an aqueous solution containing metal ions, and an organic solution containing metal ions; the metal ions are at least one of lithium ions, sodium ions, magnesium ions, aluminum ions, calcium ions, iron ions, and nickel ions.
4. The method for preparing nano silicon negative electrode material for lithium ion battery according to claim 1, characterized in that: The purity of the silicon plate is 98% to 99.99999%; the electrolytic cell is an integrated electrolytic cell; the inner wall material of the electrolytic cell includes at least one of tantalum, tungsten, molybdenum, zirconium, heat-resistant stainless steel, and heat-resistant ceramics.
5. The method for preparing nano silicon negative electrode material for lithium ion battery according to claim 1, characterized in that: The electrolyte also includes an additive, and the additive is at least one of sodium metasilicate, sodium chloride, potassium chloride, potassium fluoride, barium chloride, aluminum oxide, polyacrylamide, carboxymethyl cellulose, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate.
6. The method for preparing nano silicon negative electrode material for lithium ion battery according to claim 1, characterized in that: In step S2, the electrolysis temperature is 25-1000°C, the time is 1-48h, and the current density is 0.1-5.0A / cm 2 .
7. The method for preparing nano silicon negative electrode material for lithium ion battery according to claim 1, characterized in that: The inert atmosphere includes at least one of nitrogen, helium and argon; the solvent used for cleaning is at least one of deionized water, sodium carbonate, carbon tetrachloride, acetone, toluene, petroleum ether, ethyl formate, ethyl acetate, ethylene carbonate, dimethyl carbonate, ethanol and isopropanol.
8. A nano-silicon negative electrode material prepared by the preparation method according to any one of claims 1 to 7, characterized in that: The nano-silicon negative electrode material is at least one of coral-shaped nano-silicon, nano-silicon with a porous framework, spherical nano-silicon with a porous framework, nano-wire-shaped silicon with a porous framework, and nano-silicon particles with a porous framework.
9. The nano-silicon negative electrode material according to claim 8, characterized in that: The length of the coral shape is 0.1 to 100 μm; the diameter of the silicon in the nano-silicon with a porous framework is 10 nm to 10 μm, and the specific surface area is 10 to 1000 m 2 g -1 ; The length of the nanowire is 1 to 100 μm; the D50 of the spherical nanosilicon in the spherical nanosilicon is 5 to 1000 nm.
10. Use of the nano-silicon negative electrode material prepared by the preparation method according to any one of claims 1 to 7 or the nano-silicon negative electrode material according to any one of claims 8 to 9 in a lithium-ion battery.