Si / MXene / metal composite electrode material for all-solid-state battery as well as preparation method and application of Si / MXene / metal composite electrode material

Abstract

The invention discloses a Si / MXene / metal composite electrode material for an all-solid-state battery and a preparation method and application thereof, and the preparation method comprises the following steps: stirring micro-nano silicon powder and poly (diallyldimethylammonium chloride) in water for a set time, carrying out solid-liquid separation, adding a precipitate into deionized water, and uniformly stirring and mixing to obtain a suspension with positively charged silicon; carrying out ultrasonic dispersion on a negatively charged MXene solution, mixing the negatively charged MXene solution with the positively charged silicon suspension, carrying out ultrasonic treatment, stirring to generate flocculent precipitate, standing, carrying out solid-liquid separation, and drying to obtain a precursor Si / MXene; the preparation method comprises the following steps: uniformly dispersing a precursor Si / MXene in water to obtain a Si / MXene suspension, adding a metal salt solution into the Si / MXene suspension, and carrying out stirring reaction, solid-liquid separation and drying to obtain the modified silicon composite material Si / MXene / metal. MXene has reducibility, metal is grown on the surface of the Si / MXene precursor through in-situ reduction, the transport rate of Li < + > and electrons can be increased through high electron / ion conductivity of the metal, and reaction kinetics is accelerated.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials and relates to a Si / MXene / metal composite electrode material for all-solid-state batteries and a preparation method and application thereof. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] All-solid-state batteries have attracted great interest from academia and industry due to their potential high safety and power / energy density. Among all candidate materials, all-solid-state batteries using sulfide solid electrolytes and silicon anodes are considered to be one of the most promising systems. This is because silicon has a theoretical capacity comparable to lithium (4200mAh g -1 ), and is safer and cheaper than lithium, making it a promising candidate for anode materials in solid-state batteries. However, silicon forms an alloy with lithium during the lithiation process in all-solid-state battery systems (such as Li 22 Si5), resulting in a volume expansion rate of up to 300%, but it cannot return to its initial state after delithiation. Therefore, the cycle is prone to stress concentration, making the solid electrolyte interface (SEI) layer unstable, reducing the coulomb efficiency and cycle life. In addition, since silicon is a semiconductor, it has poor intrinsic conductivity and slow ion / electron conduction rate, which can easily cause Li on the electrode surface during the charge and discharge process. + Uneven concentration distribution leads to electrode polarization and shortens battery life. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a Si / MXene / metal composite electrode material for all-solid-state batteries, as well as its preparation method and application. The composite material is coated and doped with in situ reaction through electrostatic self-assembly technology, which improves the ion and electron transmission rate of the silicon negative electrode, thereby improving the kinetic performance of the electrode. At the same time, the coating structure also provides a buffer for the drastic volume expansion of Si, stabilizes the structure of the electrode, and improves the cycle stability of the battery.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery, comprising the following steps:

[0007] Stirring micro-nano silicon powder and polydiallyldimethylammonium chloride (PDDA) in water for a set time, separating the solid and liquid, and then adding the precipitate into deionized water and stirring to obtain a suspension of positively charged silicon;

[0008] The negatively charged MXene solution is ultrasonically dispersed and then mixed with a positively charged silicon suspension. The mixture is ultrasonically dispersed and stirred to form a flocculent precipitate. After standing, the solid-liquid separation is performed and the mixture is dried to obtain the precursor Si / MXene.

[0009] The precursor Si / MXene is uniformly dispersed in water to obtain a Si / MXene suspension, to which a metal salt solution is added, stirred for reaction, and solid-liquid separation and drying are performed to obtain a modified silicon composite material Si / MXene / metal.

[0010] By adding PDDA, silicon is made positively charged, and electrostatic self-assembly occurs with negatively charged MXene to obtain Si / MXene; the reducing property of MXene is used to make Si / MXene react with AgNO3 in situ to convert metal ions (such as Ag) into + ) is reduced to metal (Ag) particles that grow on the Si / MXene surface to obtain modified silicon composite materials (such as Si / MXene / Ag).

[0011] Coating MXene through electrostatic self-assembly technology and introducing metal (Ag) can accelerate the transmission of electrons and ions, alleviate the volume expansion of silicon, and effectively improve the electrochemical properties of the material.

[0012] The present invention can coat MXene on the surface of silicon through electrostatic self-assembly technology, thanks to the thin layer of Ti3C2T x The characteristics of fast mixing ion-electron conductor, this structure can accelerate the Si alloying reaction Li + The conduction of electrons in the electrode can alleviate the problems such as the gap in the electrode caused by volume change. The introduction of metal (Ag) through in-situ spontaneous reaction and the formation of Li-metal (Ag) alloy phase in the battery can reduce Li + Migration energy barrier, enhance electron delocalization at the interface, and increase Li + Adsorption capacity is beneficial to Li + diffusion, thus improving the electrode reaction kinetics.

[0013] In some embodiments, the mass ratio of micro-nano silicon powder to polydiallyldimethylammonium chloride is 3-8:2, preferably 5:2.

[0014] Preferably, the time for stirring the micro-nano silicon powder and polydiallyldimethylammonium chloride in water is 8-24 hours.

[0015] In some embodiments, the micro-nano silicon powder is micron silicon powder or nano silicon powder.

[0016] In some embodiments, the method further includes sintering the prepared Si / MXene precursor in an inert atmosphere at a temperature of 350-450° C. and a sintering time of 0.5-2 h.

[0017] The purpose of sintering is to remove excess functional groups on the surface of MXenes, so that the MXene coating is anchored on the surface of Si, reducing the occurrence of side reactions during subsequent charging and discharging.

[0018] Preferably, the heating rate during sintering is 1-6°C min -1 .

[0019] In some embodiments, in the modified silicon composite material Si / MXene / metal, the mass ratio of Si, MXene, and metal is 50-70:25-40:3-7.

[0020] In some embodiments, the metal salt solution is a salt solution of Ag, Cu, Ni, or Mg.

[0021] In a second aspect, the present invention provides a Si / MXene / metal composite electrode material for an all-solid-state battery, which is prepared by the preparation method.

[0022] In a third aspect, the present invention provides an all-solid-state battery negative electrode, comprising the Si / MXene / metal composite electrode material for the all-solid-state battery.

[0023] In a fourth aspect, the present invention provides an all-solid-state battery, whose negative electrode is the all-solid-state battery negative electrode.

[0024] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0025] (1) The present invention uses an electrostatic self-assembly coating method. MXene has some outstanding advantages: the surface contains rich functional groups (-F, =O and -OH, etc.), and specific surface chemical properties can be achieved by regulating the functional groups; and it has excellent Li + The electrostatic self-assembly method can be used to coat the silicon surface, and the lamellar structure can alleviate the volume expansion of silicon during the charge and discharge process to a certain extent. In addition, the excellent Li + The high electrical conductivity and electronic conductivity can make up for the disadvantage of low electrical conductivity of silicon, thereby improving the comprehensive electrochemical performance of silicon-based negative electrode materials.

[0026] (2) The present invention utilizes the reducing property of MXene to in-situ reduce and grow Ag on the surface of Si / MXene precursor, providing guidance for the doping of other metals in silicon materials. For example, the doping metal is replaced with copper (Cu), nickel (Ni), zinc (Zn), etc. The high electronic / ionic conductivity of silver can improve the Li +The method has a simple preparation process, low production cost and good practical application prospects.

[0027] (3) Experiments have shown that the modified silicon composite material prepared by the present invention as the negative electrode material of all-solid-state batteries has excellent rate performance and cycle stability.

[0028] (4) The preparation method of the present invention is simple, practical, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0030] Figure 1 This is the SEM of the modified silicon composite material prepared in Example 1 of the present invention;

[0031] Figure 2 This is a rate performance test chart of the modified silicon composite material prepared in Example 1 of the present invention as an anode material for an all-solid-state battery;

[0032] Figure 3 This is a test chart of the cycle performance of the modified silicon composite material prepared in Example 1 of the present invention as an all-solid-state battery negative electrode material. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0034] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0035] Example 1

[0036] 1) Material preparation method

[0037] Step 1: Preparation of MXene: This is achieved by selectively etching the Al layer in the MAX phase (Ti3AlC2). Take 15ml of concentrated hydrochloric acid and 5ml of deionized water and add them to the reactor. Stir at 200rpm. Weigh 2g of LiF and add it to the reactor all at once. HF is generated in situ during stirring. Then weigh 2g of MAX phase and add it to the reactor in small amounts over 10 minutes. Then cover the reactor, stir at 200rpm, and heat in a 38℃ water bath for 24 hours. After etching, transfer the etched black solution to a centrifuge tube and slowly rinse the remaining reactants in the reactor with deionized water. Centrifuge at 8000rpm three times for 10 minutes each time to collect the bottom precipitate. The precipitate was transferred to a solvent filter and filtered three times. The filtered precipitate was transferred to a beaker and dissolved in deionized water. After ice bath ultrasonication for 30 minutes, the upper black solution was transferred to a centrifuge tube and centrifuged at 3000 rpm for 30 minutes. The upper black solution was taken as the prepared MXene solution and used after calibration.

[0038] Step 2: Weigh 500 mg of micronized silicon powder, grind it, and dissolve it in deionized water. Then add 1 ml of PDDA solution and stir at 500 rpm for 12 hours. After sufficient reaction, centrifuge the solution at 8000 rpm three times for 10 minutes each time. Keep the bottom precipitate. After centrifugation, the precipitate is prepared into a positively charged Si suspension with deionized water and calibrated before use.

[0039] Step 3: Measure 100 mg of Si suspension into a beaker and dilute it to 0.5 mg ml with deionized water. -1 A 10% MXene:Si solution (MXene:Si, where MXene accounts for 10% of the mass of Si) was measured and added to the positively charged Si suspension after 30 seconds of sonication. The mixed solution was then sonicated for another 30 seconds and then subjected to electrostatic self-assembly at 200 rpm. Flocculent particles precipitated and gradually became clear and transparent. After the solution was allowed to stand for 1 hour, self-assembly was complete. The solution was then centrifuged at 5000 rpm for 10 minutes, and the precipitate at the bottom was collected and freeze-dried for 48 hours to obtain the Si / MXene precursor.

[0040] Step 4: Disperse 100 mg of Si / MXene in 80 ml of deionized water and sonicate for 30 minutes. Dissolve 25 mg of AgNO₃ in 20 ml of deionized water. Add the AgNO₃ solution to the Si / MXene suspension and stir at 200 rpm for 30 minutes. Centrifuge the solution at 8000 rpm for 10 minutes, collect the precipitate, and freeze-dry it for 48 hours to obtain the modified silicon composite material (Si / MXene / Ag).

[0041] 2) Electrochemical performance test method

[0042] Step 1: Grind Si / MXene / Ag and PVDF in a mortar at a mass ratio of 98:2 for 10 minutes to mix thoroughly. Transfer the material to a weighing bottle, add 3 drops of NMP, and stir for 10 hours. Apply the material to the polished surface of copper foil and dry it in a vacuum oven at 80°C for 8 hours. After drying, punch a 10mm hole into the negative electrode for later use.

[0043] Step 2: Weigh 100mg of solid electrolyte Li6PS5Cl into the mold battery and hold the pressure at 1 ton (127MPa) for 1 minute. Place the negative electrode sheet on the surface of the Li6PS5Cl and hold the pressure at 2-3 tons (254-381MPa) for 2-3 minutes. Remove the copper foil and place a pre-cut lithium sheet with a mass equal to 3 / 4 of the mass of the negative electrode active material. Then place a piece of stainless steel foil to complete the negative electrode side of the mold battery. Place 5mg of pre-rolled lithium cobalt oxide positive electrode film on the other side of the Li6PS5Cl and complete the positive electrode side of the mold battery.

[0044] Step 3: The mold was placed in an external pressurizing device and subjected to a stacking pressure of 254 MPa. Electrochemical testing was then performed at 60°C with a voltage range of 2.5-4.2 V.

[0045] The electrochemical performance of the all-solid-state battery prepared in Example 1 was tested, and the results were as follows: Figure 2 and Figure 3 As shown, it can be seen that Si / MXene / Ag exhibits excellent rate performance and cycle stability in the solid-state system.

[0046] Example 2

[0047] This embodiment is basically the same as embodiment 1, except that the silicon used is nano-silicon.

[0048] Example 3

[0049] This embodiment is basically the same as embodiment 1, except that the metal doped in the in-situ reaction is Cu, and a copper nitrate solution is used. The mass of the copper nitrate is the same as the silver nitrate in embodiment 1.

[0050] Example 4

[0051] This embodiment is basically the same as Example 1, except that the mass fraction of MXene is 20 wt% (MXene:Si).

[0052] Example 5

[0053] This embodiment is basically the same as embodiment 1, except that: after obtaining the Si / MXene precursor, a one-step sintering is performed: Si / MXene is placed in a tube furnace in an Ar atmosphere and sintered at 400°C for 1 h, with a heating rate of 5°C min -1 .

[0054] Comparative Example 1

[0055] The difference from Example 1 is that no MXene is added.

[0056] Comparative Example 2

[0057] The difference from Example 1 is that no metal particles are doped.

[0058] Table 1 is a summary of the discharge specific capacity and cycle capacity retention rate of the all-solid-state batteries prepared in Examples 1-6 and Comparative Examples 1-2 at various current densities.

[0059] Table 1

[0060]

[0061] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery, characterized in that: The steps include: Stirring micro-nano silicon powder and polydiallyldimethylammonium chloride in water for a set time, and after solid-liquid separation, adding the precipitate into deionized water and stirring to obtain a positively charged silicon suspension; The negatively charged MXene solution is ultrasonically dispersed and then mixed with a positively charged silicon suspension. The mixture is ultrasonically dispersed and stirred to form a flocculent precipitate. After standing, the solid-liquid separation is performed and the mixture is dried to obtain the precursor Si / MXene. The precursor Si / MXene is uniformly dispersed in water to obtain a Si / MXene suspension, to which a metal salt solution is added, stirred for reaction, and solid-liquid separation and drying are performed to obtain a modified silicon composite material Si / MXene / metal.

2. The method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery according to claim 1, wherein: The mass ratio of micro-nano silicon powder to polydiallyldimethylammonium chloride is 3-8:2, preferably 5:2; Preferably, the time for stirring the micro-nano silicon powder and polydiallyldimethylammonium chloride in water is 8-24 hours.

3. The method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery according to claim 1, wherein: The micro-nano silicon powder is micron silicon powder or nano silicon powder.

4. The method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery according to claim 1, wherein: The method further includes sintering the prepared Si / MXene precursor in an inert atmosphere at a temperature of 350-450° C. and a sintering time of 0.5-2 h.

5. The method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery according to claim 1, wherein: The heating rate during sintering is 1-6°C min -1 .

6. The method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery according to claim 1, wherein: In the modified silicon composite material Si / MXene / metal, the mass ratio of Si, MXene and metal is 50-70:25-40:3-7.

7. The method for preparing a Si / MXene / metal composite electrode material for an all-solid-state battery according to claim 1, wherein: The metal salt solution is a salt solution of Ag, Cu, Ni or Mg.

8. A Si / MXene / metal composite electrode material for all-solid-state batteries, characterized by: Prepared by the preparation method according to any one of claims 1 to 7.

9. An all-solid-state battery negative electrode, characterized in that: Including the Si / MXene / metal composite electrode material for all-solid-state batteries as described in claim 8.

10. An all-solid-state battery, characterized in that: The negative electrode is the all-solid-state battery negative electrode as claimed in claim 9.

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