Silicon negative electrode slurry based on supramolecular interaction as well as preparation method and application of silicon negative electrode slurry

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses silicon negative electrode slurry based on supramolecular interaction as well as a preparation method and application of the silicon negative electrode slurry. The silicon negative electrode slurry is prepared from the following raw materials: a water-soluble polymer, metal nitrate, hydroxylated silicon powder and water. According to the silicon negative electrode slurry provided by the invention, the polymer and the metal ions form a polymer-metal compound through a coordination reaction, the polymer-metal compound and hydroxylated silicon particles are self-assembled through hydrogen bonds, and a polymer-metal coating is formed on the surface of the polymer-metal compound, so that huge volume expansion / shrinkage stress of silicon in an electrochemical reaction process is relieved step by step; in the process of charging and discharging, metal ions in the coating are reduced into nanoscale metal particles, the sites for conducting lithium ions and electrons are constructed, the continuity of an internal interface structure of the silicon negative electrode and electrode reaction kinetics are enhanced, and the performance of the electrode is improved. And the electron conduction and ion conduction capabilities of the electrode are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and in particular to a silicon negative electrode slurry based on supramolecular action, and a preparation method and application thereof. Background Art

[0002] Developing high-energy-density, high-safety energy storage devices is one of the effective ways to alleviate the energy crisis. Among various electrochemical energy storage technologies, lithium-ion batteries (LIBs) have been widely researched and applied due to their high energy density, high operating voltage, and long cycle life. The rapid development of artificial intelligence and new energy vehicle industries has placed higher demands on the energy density of lithium-ion batteries.

[0003] Currently, the commercial negative electrode material is mainly graphite, and its actual specific capacity is close to the theoretical value (372mAh / g). Among the many alternative negative electrode materials to graphite, silicon (Si) has a high mass specific capacity (Li 15 Si4, 3579mAh / g), abundant crustal reserves (the second most abundant element) and low delithiation potential (~0.4V vs Li / Li + ) and is considered one of the most promising anode materials. However, during charge-discharge cycling, silicon undergoes a significant volume change (>300%), causing active silicon particles to shatter and fall off the current collector, leading to rapid capacity decay. Furthermore, silicon's low intrinsic electronic and ionic conductivity results in poor reaction kinetics in silicon electrodes, resulting in low output capacity at high current densities. Therefore, improving the interfacial stability and conductivity of silicon particles is crucial for the development and application of silicon electrodes in energy storage.

[0004] For silicon anodes, coating construction is one of the most commonly used modification methods. Constructing a robust, conductive and ion-conducting coating can effectively improve the structural stability of silicon anodes and reduce the energy barrier for lithium ion and electron migration within the electrode. Common silicon anode coating technologies include carbon coating, polymer coating, silicon oxide coating, and metal coating. Among them, polymer coating has attracted much attention due to its unique structural and performance advantages.

[0005] The advantages of polymer coatings are mainly reflected in: ① The excellent viscoelastic properties of polymer materials enable them to form stable interfacial contact with silicon and effectively adapt to the volume expansion of silicon particles during charging and discharging; ② The good solution processing properties of polymers enable silicon particles to be dispersed at the nanoscale in the solvent, thereby obtaining a uniform coating effect; ③ The microstructure of the polymer can be customized and regulated, and the polymer molecular structure can be grafted and modified according to needs.

[0006] However, existing polymer coatings still have defects such as low intrinsic electronic and ionic conductivity, and generally low ionic and thermal conductivity. These defects may lead to increased electrode polarization and local heat accumulation, thereby affecting the cycle stability and safety of the battery. Summary of the Invention

[0007] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, one of the purposes of the present invention is to provide a silicon negative electrode slurry.

[0008] A second object of the present invention is to provide a method for preparing the silicon negative electrode slurry.

[0009] A third object of the present invention is to provide a silicon negative electrode plate.

[0010] A third object of the present invention is to provide a lithium ion battery.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A first aspect of the present invention provides a silicon negative electrode slurry, which is prepared from the following raw materials: a water-soluble polymer, a metal nitrate, hydroxylated silicon powder, and water.

[0013] In some embodiments of the present invention, in the silicon negative electrode slurry, the mass ratio of the water-soluble polymer to the metal ions in the metal nitrate is 1:(0.2-5).

[0014] In some specific embodiments of the present invention, in the silicon negative electrode slurry, the mass ratio of the water-soluble polymer to the metal ions in the metal nitrate is 1:(0.5-3).

[0015] In some embodiments of the present invention, in the silicon negative electrode slurry, the ratio of the total mass of the water-soluble polymer and the metal ions in the metal nitrate to the mass of the hydroxylated silicon powder is 1:(3-10).

[0016] In some specific embodiments of the present invention, in the silicon negative electrode slurry, the ratio of the total mass of the water-soluble polymer and the metal ions in the metal nitrate to the mass of the hydroxylated silicon powder is 1:(3-6).

[0017] In some embodiments of the present invention, the water-soluble polymer is selected from at least one of polyacrylic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt.

[0018] In some embodiments of the present invention, the metal nitrate includes silver nitrate, or silver nitrate and at least one of copper nitrate, zinc nitrate, aluminum nitrate, and indium nitrate.

[0019] In some embodiments of the present invention, the particle size of the hydroxylated silicon powder is 30 nm-3 μm.

[0020] In some specific embodiments of the present invention, the particle size of the hydroxylated silicon powder is 50 nm-2 μm.

[0021] In some embodiments of the present invention, the hydroxylated silicon powder is obtained by hydroxylating silicon powder; the hydroxylation treatment is carried out by at least one method selected from air oxidation, concentrated sulfuric acid oxidation, concentrated nitric acid oxidation, and hydrogen peroxide oxidation.

[0022] The second aspect of the present invention provides a method for preparing the silicon negative electrode slurry according to the first aspect of the present invention, comprising the following steps:

[0023] S1. dissolving a water-soluble polymer in water to obtain solution A, and dissolving a metal nitrate in water to obtain solution B;

[0024] S2, mixing the solution A and the solution B, reacting to obtain a composite solution C;

[0025] S3. Mixing the composite solution C with hydroxylated silicon powder to obtain the silicon negative electrode slurry.

[0026] In some embodiments of the present invention, in step S1, the concentration of solution A is 10 wt%-50 wt%.

[0027] In some specific embodiments of the present invention, in step S1, the concentration of solution A is 20 wt%-40 wt%.

[0028] In some embodiments of the present invention, in step S1, the concentration of solution B is 0.1-0.5 mol / L.

[0029] In some specific embodiments of the present invention, in step S1, the concentration of the solution B is 0.1-0.3 mol / L.

[0030] In some embodiments of the present invention, in step S2, the reaction temperature is 20-100° C., and the reaction time is 10-360 min.

[0031] In some specific embodiments of the present invention, in step S2, the reaction temperature is 50-80° C., and the reaction time is 10-60 min.

[0032] In some embodiments of the present invention, in step S3, the mixing time is 30-360 min.

[0033] In some specific embodiments of the present invention, in step S3, the mixing time is 30-60 minutes.

[0034] In some embodiments of the present invention, in step S3, the mixing method is selected from at least one of magnetic stirring, ultrasonic dispersion, vibration ball milling, high-energy ball milling, and manual grinding.

[0035] A third aspect of the present invention provides a silicon negative electrode plate, which includes a current collector and the silicon negative electrode slurry described in the first aspect of the present invention coated on the surface thereof.

[0036] In some embodiments of the present invention, the current collector is selected from a copper foil current collector, a nickel current collector or a stainless steel current collector.

[0037] In some embodiments of the present invention, the silicon negative electrode plate is prepared by a method comprising the following steps:

[0038] The silicon negative electrode slurry is coated on a current collector, in-situ etched, and dried to obtain the silicon negative electrode sheet.

[0039] In some embodiments of the present invention, the in-situ etching is performed at a temperature of 20-90° C. and for a time of 10-120 min.

[0040] In some specific embodiments of the present invention, the temperature of the in-situ etching is 20-50° C., and the time is 10-30 minutes.

[0041] In some embodiments of the present invention, the drying temperature is 50-100° C. and the drying time is 2-15 hours.

[0042] In some specific embodiments of the present invention, the drying temperature is 50-80° C. and the drying time is 10-12 hours.

[0043] In some embodiments of the present invention, the drying method is selected from at least one of vacuum drying, natural air drying, and forced air drying.

[0044] In some embodiments of the present invention, the active material loading of the silicon negative electrode plate is 0.2-3.0 mg / cm 2 .

[0045] In some specific embodiments of the present invention, the active material loading of the silicon negative electrode plate is 0.2-2.0 mg / cm 2 .

[0046] A fourth aspect of the present invention provides a lithium-ion battery, comprising the silicon negative electrode sheet according to the third aspect of the present invention.

[0047] In some embodiments of the present invention, the lithium-ion battery includes a lithium sheet counter electrode.

[0048] In some embodiments of the present invention, the specific capacity of the lithium-ion battery under the test conditions of a potential window of 0.01-2.0 V and a current density of 200-1000 mA / g is 1000-3000 mAh / g.

[0049] The basic principles of the present invention are described as follows:

[0050] 1) The present invention uses a water-soluble polymer and a metal nitrate as raw materials for preparing a silicon negative electrode slurry. After the two are formed into aqueous solutions and mixed for reaction, the polymer and the metal ions form a polymer-metal system through coordination. Since the selected water-soluble polymers such as polyacrylic acid, poly (2-acrylamide-2-methylpropanesulfonic acid), acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer and poly (4-styrenesulfonic acid-co-maleic acid) sodium salt contain rich polar groups (such as carboxyl groups, sulfonic acid groups, amide groups, etc.), after the hydroxylated silicon powder is dispersed in the polymer-metal system, the polar groups of the water-soluble polymer and the hydroxyl groups of the hydroxylated silicon powder interact through hydrogen bonds, so that the polymer-metal system spontaneously assembles on the surface of the silicon particles (supramolecular self-assembly) and forms a polymer-metal coating of uniform thickness on the surface of the silicon particles, thereby obtaining a uniform silicon negative electrode slurry;

[0051] 2) The polymer-metal coating in the silicon anode slurry helps gradually alleviate the huge volume expansion / contraction stress of silicon during the electrochemical reaction. With the elasticity and reversibility of hydrogen bonds, it can play a buffering role when the silicon volume changes. At the same time, during the charge and discharge process, the metal ions in the coating are reduced to nano-scale metal particles, forming an alloy with lithium, creating sites that conduct lithium ions and electrons, and enhancing the continuity of the internal interface structure of the silicon anode and the electrode reaction kinetics.

[0052] 3) The present invention coats a silicon negative electrode slurry on a current collector, and obtains a silicon negative electrode sheet through in-situ etching and drying. During the in-situ etching process, the metal ions in the slurry undergo a replacement / redox reaction with the metal in the current collector, and the metal ions are reduced to metal elements and attached to the surface of the current collector, which changes the surface morphology / properties of the current collector and enhances its binding force with the active substance. After drying to remove moisture, the interaction between polymer molecules and between the polymer and silicon powder and metal ions is enhanced, forming a stable electrode structure, which is beneficial to more efficient transmission of electrons between the current collector and the active substance during the battery charging and discharging process, reducing the contact resistance of the electrode and improving the electrochemical performance of the battery.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1) The silicon negative electrode slurry provided by the present invention uses a water-soluble polymer, a metal nitrate, and hydroxylated silicon powder as raw materials. The polymer and the metal ions in the metal nitrate form a polymer-metal complex through a coordination reaction, and then self-assemble with the hydroxylated silicon particles through hydrogen bonds to form a polymer-metal coating on the surface of the silicon particles. This can effectively alleviate the huge volume expansion / contraction stress of silicon during the electrochemical reaction and reduce the shedding of silicon particles on the current collector;

[0055] 2) The method for preparing the silicon negative electrode slurry provided by the present invention has simple steps, mild reaction conditions, and is suitable for industrial use;

[0056] 3) The silicon negative electrode plate provided by the present invention is prepared by in-situ etching of a current collector with a silicon negative electrode slurry. In-situ etching can change the surface morphology of the current collector and increase the adhesion between the current collector and the silicon particles. The surface of the silicon particles on the silicon negative electrode plate has a polymer-metal coating, which can not only reduce the shedding of silicon particles and alleviate capacity decay, but also enable the in-situ electrochemical reduction of metal ions into nanoparticles during the charge and discharge cycle, which serve as active centers for electrical conduction and ionization.

[0057] 4) The lithium-ion battery provided by the present invention adopts a silicon negative electrode plate, which effectively improves the interface structure continuity and electrode reaction kinetics of the silicon negative electrode, has a higher mass specific capacity and better cycle stability, and can better meet the market demand for high energy density batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a transmission electron microscope image of the powder obtained from the silicon negative electrode plate after cycling in Example 1;

[0059] Figure 2 This is a cyclic voltammetry test diagram of a button cell assembled with the silicon negative electrode piece in Example 1;

[0060] Figure 3 This is a constant current charge and discharge diagram of the button battery assembled with the silicon negative electrode piece in Example 1;

[0061] Figure 4 This is a constant current charge and discharge diagram of the button battery assembled with the silicon negative electrode piece in Example 2;

[0062] Figure 5 This is a constant current charge and discharge diagram of the button battery assembled with the silicon negative electrode piece in Example 3;

[0063] Figure 6 This is a comparison chart of the cycle performance of batteries assembled with silicon negative electrode sheets in Example 1, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0064] The present invention is further described in detail below using specific examples. Unless otherwise specified, the raw materials, reagents, and apparatus used in the examples and comparative examples are available from conventional commercial sources or by conventional methods. Unless otherwise specified, all experimental or testing methods are conventional in the art.

[0065] Example 1

[0066] In this embodiment, a silicon negative electrode slurry is prepared and used to prepare a silicon negative electrode plate, and the steps are as follows:

[0067] Preparation of silicon anode slurry:

[0068] S11, weighing an appropriate amount of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer and dissolving it in water to obtain a solution A with a concentration of 30 wt%, and weighing an appropriate amount of silver nitrate and dissolving it in water to obtain a solution B with a concentration of 0.25 mol / L;

[0069] S21, adding an appropriate amount of solution B to solution A, reacting at 80°C for 10 minutes to obtain a composite solution C, wherein the mass ratio of metal ions to polymer is 1:1;

[0070] S31. Weigh hydroxylated silicon powder with a size of 50 nm, which is prepared by exposing silicon powder to air for a long time, and disperse it in composite solution C. Vibration ball milling is performed for 30 minutes to obtain a uniform silicon negative electrode slurry, wherein the ratio of the total mass of the polymer and the metal ions to the mass of the hydroxylated silicon powder is 1:4.

[0071] Preparation of silicon negative electrode:

[0072] The silicon anode slurry was quickly coated on the copper foil current collector, and the copper foil was in situ etched at 30 ° C for 10 min, and then vacuum dried at 80 ° C for 12 h to obtain an active material loading of 0.5 mg / cm -2 Silicon negative electrode.

[0073] Among them, active material loading = (mass of silicon negative electrode piece - mass of blank electrode piece) * active material ratio.

[0074] Example 2

[0075] In this embodiment, a silicon negative electrode slurry is prepared and used to prepare a silicon negative electrode plate, and the steps are as follows:

[0076] Preparation of silicon anode slurry:

[0077] S11, weighing an appropriate amount of poly(2-acrylamide-2-methylpropanesulfonic acid) and dissolving it in water to obtain a solution A with a concentration of 40 wt %, weighing appropriate amounts of silver nitrate and zinc nitrate and dissolving them in water to obtain a solution B with a concentration of 0.3 mol / L, wherein the mass ratio of the metal ions silver and zinc in solution B is 1:1;

[0078] S21, adding an appropriate amount of solution B to solution A, reacting at 60°C for 40 minutes to obtain a composite solution C, wherein the mass ratio of metal ions to polymer is 1:3;

[0079] S31. Weigh hydroxylated silicon powder with a size of 50 nm, which is obtained by oxidizing silicon powder with concentrated sulfuric acid, and disperse it in composite solution C. Ultrasonic dispersion is performed for 50 minutes to obtain a uniform silicon negative electrode slurry, wherein the ratio of the total mass of the polymer and the metal ions to the mass of the hydroxylated silicon powder is 1:4.

[0080] Preparation of silicon negative electrode:

[0081] The silicon anode slurry was quickly coated on the copper foil current collector, and the copper foil was in situ etched at 40 ° C for 10 min, and then vacuum dried at 80 ° C for 12 h to obtain an active material loading of 1.0 mg / cm -2 Silicon negative electrode.

[0082] Example 3

[0083] In this embodiment, a silicon negative electrode slurry is prepared and used to prepare a silicon negative electrode plate, and the steps are as follows:

[0084] Preparation of silicon anode slurry:

[0085] S11. Weigh an appropriate amount of polyacrylic acid and dissolve it in water to obtain a solution A with a concentration of 20 wt %. Weigh an appropriate amount of silver nitrate and dissolve it in water to obtain a solution B with a concentration of 0.15 mol / L.

[0086] S21, adding an appropriate amount of solution B to solution A, reacting at 50°C for 60 minutes to obtain a composite solution C, wherein the mass ratio of metal ions to polymer is 1:1;

[0087] S31. Weigh hydroxylated silicon powder with a size of 1 μm, which is obtained by oxidizing silicon powder with concentrated sulfuric acid, and disperse it in composite solution C. Manually grind it for 60 minutes to obtain a uniform silicon negative electrode slurry, wherein the ratio of the total mass of the polymer and the metal ions to the mass of the hydroxylated silicon powder is 1:4.

[0088] Preparation of silicon negative electrode:

[0089] The silicon anode slurry was quickly coated on the copper foil current collector, and the copper foil was in situ etched at 50 ° C for 10 min, and then vacuum dried at 80 ° C for 12 h to obtain an active material loading of 1.5 mg / cm -2 Silicon negative electrode.

[0090] Comparative Example 1

[0091] In this comparative example, a silicon negative electrode slurry was prepared. The difference from Example 1 was that silver nitrate was not used. The slurry was used to prepare a silicon negative electrode sheet. The steps were as follows:

[0092] Preparation of silicon anode slurry:

[0093] S11, weighing an appropriate amount of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer and dissolving it in water to obtain a solution A with a concentration of 30 wt%;

[0094] S31. Weigh hydroxylated silicon powder with a size of 50 nm, which is prepared by exposing silicon powder to air for a long time, and disperse it in solution A. Vibration ball milling is performed for 30 minutes to obtain a uniform silicon negative electrode slurry.

[0095] Preparation of silicon negative electrode:

[0096] The silicon negative electrode slurry was quickly coated on the copper foil current collector, and the copper foil was in-situ etched at 30°C for 10 minutes, and then vacuum dried at 80°C for 12 hours to obtain a silicon negative electrode sheet.

[0097] Comparative Example 2

[0098] This comparative example prepares a silicon negative electrode slurry. The difference from Example 1 is that copper nitrate, silver nitrate, zinc nitrate, aluminum nitrate and indium nitrate are used simultaneously, and the slurry is used to prepare a silicon negative electrode sheet. The steps are as follows:

[0099] S11. Weigh an appropriate amount of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer and dissolve it in water to obtain a 30 wt% solution A. Weigh appropriate amounts of copper nitrate, silver nitrate, zinc nitrate, aluminum nitrate, and indium nitrate and dissolve them in water to obtain a 0.25 mol / L solution B, wherein the mass ratio of the metal ions copper, silver, zinc, aluminum, and indium in solution B is 1:1:1:1:1;

[0100] S21, adding an appropriate amount of solution B to solution A, reacting at 80°C for 10 minutes to obtain a composite solution C, wherein the mass ratio of metal ions to polymer is 1:1;

[0101] S31. Weigh hydroxylated silicon powder with a size of 50 nm, which is prepared by exposing silicon powder to air for a long time, and disperse it in composite solution C. Vibration ball milling is performed for 30 minutes to obtain a uniform silicon negative electrode slurry, wherein the ratio of the total mass of the polymer and the metal ions to the mass of the hydroxylated silicon powder is 1:4.

[0102] Preparation of silicon negative electrode:

[0103] The silicon negative electrode slurry was quickly coated on the copper foil current collector, and the copper foil was in-situ etched at 30°C for 10 minutes, and then vacuum dried at 80°C for 12 hours to obtain a silicon negative electrode sheet.

[0104] Performance Testing

[0105] The silicon negative electrode sheets prepared in Examples 1-3 and Comparative Examples 1 and 2 were respectively assembled with lithium counter electrodes into button batteries for electrochemical testing.

[0106] 1. Cyclic voltammetry was performed on the battery assembled with the silicon negative electrode sheet in Example 1, with a potential window of 0.01-2.0 V and a scan rate of 0.1 mV / s:

[0107] Figure 1 This is a transmission electron microscope image of the powder obtained from the silicon negative electrode plate in Example 1 after cycling. Figure 1 It can be seen that the dark small particles in the transmission electron microscope image are silver nanoparticles, which intuitively show that during the charging and discharging process, the metal ions (silver ions) in the coating are reduced to nanoscale metal particles. These silver nanoparticles improve the ion and electron conductivity of the silicon electrode, provide more conductive pathways and active sites for electrode reactions, and help improve battery performance.

[0108] Figure 2 This is the cyclic voltammetry test diagram of the button battery assembled with the silicon negative electrode piece in Example 1. Figure 2 It can be seen that the cyclic voltammetry curve shows that the electrode material in Example 1 has obvious lithiation and delithiation redox characteristic peaks attributable to silicon, indicating that the electrode reaction kinetics is good.

[0109] 2. The battery assembled with the silicon negative electrode pieces in Examples 1-3 was subjected to constant current charge and discharge tests, with a potential window of 0.01-2.0 V and a current density of 200 mA / g:

[0110] Figure 3 This is the constant current charge and discharge diagram of the button battery assembled with the silicon negative electrode piece in Example 1. Figure 3 It can be seen that the specific capacity of the button battery assembled with the silicon negative electrode sheet in Example 1 is 1247 mAh / g.

[0111] Figure 4 This is the constant current charge and discharge diagram of the button battery assembled with the silicon negative electrode piece in Example 2. Figure 4 It can be seen that the specific capacity of the button battery assembled with the silicon negative electrode sheet in Example 1 is 1198 mAh / g.

[0112] Figure 5 This is the constant current charge and discharge diagram of the button battery assembled with the silicon negative electrode piece in Example 3. Figure 5 It can be seen that the specific capacity of the button battery assembled with the silicon negative electrode sheet in Example 1 is 2720 mAh / g.

[0113] It can be seen from the constant current charge and discharge test results that the specific capacity of the silicon negative electrode sheets prepared in Examples 1-3 is much higher than that of the graphite negative electrode, which means that under the same mass or volume, the battery using the silicon negative electrode provided by the present invention can store more electricity, thereby significantly improving the energy density of the battery, and better meeting the needs of artificial intelligence, new energy vehicles and other fields for high energy density batteries and lightweight products.

[0114] 3. A long-term cycle test was conducted on the batteries assembled with the silicon negative electrode sheets in Example 1, Comparative Example 1 and Comparative Example 2. The charge and discharge cycles were performed 150 times at a current density of 1000 mA / g, with the 10th cycle capacity as the initial value.

[0115] Figure 6 The comparison chart of the cycle performance of the battery assembled with silicon negative electrode pieces in Example 1, Comparative Example 1 and Comparative Example 2 is shown in FIG. Figure 6 It can be seen that, taking the 10th cycle capacity as the initial value, after 150 charge and discharge cycles at a current density of 1000 mA / g, the capacity retention rate of the battery assembled with the silicon negative electrode plate in Example 1 is 93.8%, which is much higher than that of Comparative Example 1 (43.4%). This shows that compared with a single polymer coating, the silicon negative electrode plate provided by the present invention comprising a polymer-metal coating forms multi-level hydrogen bonds with the surface of the silicon particles due to the polar groups of the polymer, thereby alleviating the expansion of the silicon particles and reducing the irreversible crushing of the silicon particles, so that the silicon interface structure remains stable. At the same time, the metal ions also form nanoparticles in situ during the charge and discharge process, thereby improving the electron and ion conductivity of the electrode, which is more conducive to maintaining the cycle stability of the battery.

[0116] In contrast, the capacity retention rate of the battery assembled with the silicon negative electrode in Comparative Example 2 is only 53.8%. This is presumably because it contains multiple metal ions at the same time, and the chemical properties and coordination abilities of different metal ions are different. In the coordination process with the polymer, there is mutual competition, which easily destroys the originally relatively ordered coordination structure. In addition, in the subsequent charging and discharging process, the reduction potentials of the metal ions are different, and the simultaneous presence of multiple metal ions will make the reduction process complicated and chaotic, making it difficult to form uniform and stable nano-metal particles. However, in this case, its capacity retention rate is still higher than that of Comparative Example 1 (43.4%), which once again proves that the silicon negative electrode with a polymer-metal coating performs better in terms of cycle stability.

Claims

1. A silicon negative electrode slurry, characterized in that: The invention is prepared from the following raw materials: water-soluble polymer, metal nitrate, hydroxylated silicon powder and water.

2. The silicon negative electrode slurry according to claim 1, characterized in that In the silicon negative electrode slurry, the mass ratio of the water-soluble polymer to the metal ions in the metal nitrate is 1:(0.2-5); And / or, in the silicon negative electrode slurry, the ratio of the total mass of the water-soluble polymer and the metal ions in the metal nitrate to the mass of the hydroxylated silicon powder is 1:(3-10).

3. The silicon negative electrode slurry according to claim 1 or 2, characterized in that: The water-soluble polymer is selected from at least one of polyacrylic acid, poly(2-acrylamide-2-methylpropanesulfonic acid), acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt; And / or, the metal nitrate includes silver nitrate, or silver nitrate and at least one of copper nitrate, zinc nitrate, aluminum nitrate, and indium nitrate; And / or, the particle size of the hydroxylated silicon powder is 30 nm-3 μm.

4. The method for preparing the silicon negative electrode slurry according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. dissolving a water-soluble polymer in water to obtain solution A, and dissolving a metal nitrate in water to obtain solution B; S2, mixing the solution A and the solution B, reacting to obtain a composite solution C; S3. Mixing the composite solution C with hydroxylated silicon powder to obtain the silicon negative electrode slurry.

5. The preparation method according to claim 4, characterized in that In step S2, the reaction temperature is 20-100° C., and the reaction time is 10-360 min; And / or, in step S3, the mixing time is 30-360 minutes.

6. A silicon negative electrode plate, characterized in that: The present invention comprises a current collector and the silicon negative electrode slurry according to any one of claims 1 to 3 coated on the surface of the current collector.

7. The silicon negative electrode sheet according to claim 6, characterized in that: The silicon negative electrode plate is prepared by a method comprising the following steps: The silicon negative electrode slurry is coated on a current collector, in-situ etched, and dried to obtain the silicon negative electrode sheet.

8. The silicon negative electrode plate according to claim 7, characterized in that: The in-situ etching temperature is 20-90°C and the time is 10-120 minutes; And / or, the drying temperature is 50-100° C. and the drying time is 2-15 hours.

9. The silicon negative electrode sheet according to any one of claims 6 to 8, characterized in that: The active material loading of the silicon negative electrode plate is 0.2-3.0 mg / cm 2 .

10. A lithium ion battery, characterized in that: Including the silicon negative electrode sheet as described in any one of claims 6-9.

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