Negative pole piece, secondary battery and device

Abstract

The invention discloses a negative pole piece, a secondary battery and a device, the negative pole piece comprises a negative current collector and a negative material layer located on the negative current collector, the negative material layer comprises a carbon-based material, a silicon-based material and a dispersant, and the dispersant accounts for 0.03%-1.7% of the mass of the negative material. The negative electrode material disclosed by the invention has the advantages of high solid content, high stability and good coating effect. Moreover, through the preparation method of the negative electrode material, the active material, the conductive agent and other solid substances can be uniformly and stably dispersed in the deionized water, the operation is convenient, and large-scale production can be realized.

Description

Technical Field

[0001] The present invention relates to a negative electrode plate, and particularly to a negative electrode plate, a secondary battery and a device, belonging to the field of batteries. Background Art

[0002] At present, the capacity of graphite has approached the theoretical capacity value. One of the effective methods to further improve the capacity of the negative electrode of lithium batteries is to add a certain proportion of nano-silicon / silicon oxide / silicon-carbon composite material to graphite. However, the current graphite used is micron-sized particles, and the particle size Dv50 is concentrated at 5-20 microns, while the nano-silicon / silicon oxide / silicon-carbon composite is basically nano-sized particles. It is very difficult for these two kinds of negative electrode active materials with extremely different particle sizes to be uniformly dispersed in the electrode slurry at the same time and maintain the stability of the slurry viscosity. In addition, the current silicon-graphite mixed negative electrode material has problems such as insufficient dispersion, low solid content, resulting in many dark marks during coating, and serious floating of the binder.

[0003] Therefore, there is an urgent need to develop a novel negative electrode plate. Summary of the Invention

[0004] In order to overcome the problems of serious floating of the binder during coating drying due to the low solid content of the existing negative electrode material and uneven dispersion due to the large difference in the particle sizes of the negative electrode active materials, the present invention provides a negative electrode plate, a secondary battery and a device.

[0005] In the first aspect of the present invention, a negative electrode plate is provided, which includes a negative electrode current collector and a negative electrode material layer located on the negative electrode current collector. Among them, the negative electrode material layer includes a coating layer formed by a negative electrode slurry. Among them, the negative electrode material layer includes a carbon-based material, a silicon-based material and a dispersant, and the mass content of the dispersant in the negative electrode material layer is 0.03% - 1.7%.

[0006] In some embodiments, the mass content of the carbon-based material in the negative electrode material layer is 55% - 97%. In some embodiments, the mass content of the carbon-based material in the negative electrode material is 70% - 95%.

[0007] In some embodiments, the mass content of the silicon-based material in the negative electrode material layer is 1.0% - 35%; in some embodiments, the mass content of the silicon-based material in the negative electrode material is 2% - 32%.

[0008] In some embodiments, the mass content of the dispersant in the negative electrode material layer is 0.05% - 1.5%.

[0009] In some embodiments, the negative electrode material further includes a binder, a conductive agent, and a thickening agent. Among them, the mass content of the binder in the negative electrode material is 0.5% to 5.0%. In some embodiments, the mass content of the binder in the negative electrode material layer is 1.0% to 3.0%.

[0010] In some embodiments, the mass content of the conductive agent in the negative electrode material layer is 0.1% to 4.0%. In some embodiments, the mass content of the conductive agent in the negative electrode material is 0.5% to 3.5%.

[0011] In some embodiments, the mass content of the thickening agent in the negative electrode material layer is 0.3% to 2.5%. In some embodiments, the mass content of the thickening agent in the negative electrode material layer is 0.5% to 2.0%.

[0012] In some embodiments, the dispersant includes at least one of polyacrylate dispersants and phosphate ester dispersants. In some embodiments, the dispersant includes phosphate ester dispersants. In some embodiments, the polyacrylate dispersant includes DCS308. In some embodiments, the phosphate ester dispersant includes BYK-LPN25432. In some embodiments, the dispersant further includes 2-amino-2-methyl-1-propanol.

[0013] In some embodiments, the conductive agent includes at least one of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, and carbon nanotubes.

[0014] In some embodiments, the silicon-based material includes at least one of nanoscale silicon, silicon oxides, and silicon carbide compounds. In some embodiments, the silicon oxide includes SiOx, where 0.5 ≤ x ≤ 1.5. In some embodiments, the silicon oxide includes SiOx, where 0.7 ≤ x ≤ 1.0. In some embodiments, the silicon oxide includes SiOx, where 0.8 ≤ x ≤ 0.9. In some embodiments, the D V 50 of the silicon-based material is 0.1 μm to 9 μm.

[0015] In some embodiments, the thickening agent includes at least one of lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, and carboxymethyl cellulose. In some embodiments, the binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), and lithium polyacrylate (PAA-Li). In some embodiments, the carbon-based material includes at least one of natural graphite, artificial graphite, mesophase microcarbon microspheres, hard carbon, and soft carbon. In some embodiments, the D V 50 of the carbon-based material is 2 μm to 25 μm.

[0016] In some embodiments, the preparation of the negative electrode paste includes the following steps:

[0017] (a) Predispersing 20% - 60% deionized water, a dispersant, a conductive agent, 30% - 60% thickener, and a silicon-based material to obtain a first mixture; (b) Mixing a carbon-based material and the remaining thickener to obtain a second mixture; (c) Mixing the remaining deionized water and the second mixture to obtain a third mixture; (d) Mixing the first mixture and the third mixture to obtain a fourth mixture; (e) Mixing a binder and the fourth mixture to obtain the negative electrode paste.

[0018] In some embodiments, the viscosity value of the negative electrode paste is 3000 mPa·s - 15000 mPa·s; in some embodiments, the solid content of the negative electrode paste is 50 wt% - 62 wt%.

[0019] In some embodiments, the compaction density of the negative electrode plate is 1.45 g / cm 3 ~1.70 g / cm 3 ; in some embodiments, the double-sided areal density of the negative electrode plate is 160 g / m 2 ~220 g / m 2 .

[0020] The third aspect of the present invention provides a secondary battery, which includes the above-mentioned negative electrode plate and positive electrode plate.

[0021] The fourth aspect of the present invention provides a device, which includes the above-mentioned secondary battery.

[0022] The negative electrode material of the present invention has advantages such as high solid content, high stability, and good coating effect. And by adopting the preparation method of the negative electrode material of the present invention, the negative electrode active material, conductive agent, etc. can be uniformly and stably dispersed in the solvent, which is convenient to operate and can be produced on a large scale. Specific Embodiments

[0023] For the sake of simplicity, the present application only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0024] Unless otherwise specified, the terms used in this application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various common measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0025] The list of items connected by the term "at least one of" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0026] The term "D V 50" refers to the particle size corresponding to when the cumulative particle size volume distribution percentage reaches 50%.

[0027] In the first aspect of the present invention, a negative electrode sheet is provided, which includes a negative electrode current collector and a negative electrode material layer located on the negative electrode current collector. Among them, the negative electrode material layer includes a coating layer formed by a negative electrode slurry. Among them, the negative electrode material layer includes a carbon-based material, a silicon-based material, and a dispersant, and the mass content of the dispersant in the negative electrode material layer is 0.03% to 1.7%. The dispersant is mainly used to uniformly and stably disperse and suspend nano-scale particles in deionized water. Due to the interaction between the functional groups in the dispersant and the nano-scale particles and the solvent, if the mass content of the dispersant in the negative electrode material is too small, the dispersion effect is weak; if the mass content of the dispersant is too large, the proportion of the active material is too low, affecting the energy density. In some embodiments, the mass content of the dispersant in the negative electrode material layer is 0.03% to 1.7%. In some embodiments, the mass content of the dispersant in the negative electrode material layer is 0.05% to 1.5%. In some embodiments, the mass content of the dispersant in the negative electrode material layer is 0.03%, 0.09%, 0.15%, 0.17%, 0.19%, 0.21%, 0.23%, 0.25%, 0.27%, 0.29%, 0.31%, 0.33%, 0.35%, 0.39%, 0.44%, 0.49%, 0.53%, 0.58%, 0.63%, 0.73%, 0.88%, 1.03%, 1.18%, 1.38%, 1.70% or any range between them.

[0028] In some embodiments, the mass content of the carbon-based material in the negative electrode material layer is 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 97% or any range therebetween.

[0029] In some embodiments, the mass content of the silicon-based material in the negative electrode material layer is 1%, 6%, 11%, 16%, 21%, 26%, 31%, 35% or any range therebetween.

[0030] In some embodiments, the mass content of the binder in the negative electrode material layer is 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% or any range therebetween.

[0031] In some embodiments, the mass content of the conductive agent in the negative electrode material layer is 0.1%, 0.6%, 1.1%, 1.6%, 2.1%, 2.6%, 3.1%, 4.0% or any range therebetween.

[0032] In some embodiments, the mass content of the thickening agent in the negative electrode material layer is 0.3%, 0.8%, 1.3%, 1.8%, 2.1%, 2.5% or any range therebetween. The thickening agent is used to coat the silicon-based material and the carbon-based material, thereby improving the wettability of the silicon-based material and the carbon-based material with water. At the same time, the coated thickening agent plays a role in preventing the re-agglomeration between the silicon-based material and the carbon-based material particles, thereby achieving the effect of suspension stability.

[0033] In some embodiments, the DV50 of the silicon-based material is 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or any interval therebetween.

[0034] In some embodiments, the DV50 of the carbon-based material is 2 μm, 7 μm, 12 μm, 17 μm, 22 μm, 25 μm or any interval therebetween.

[0035] In the present invention, the nanoscale silicon-based material is first sanded and depolymerized with a dispersant, a binder, a part of the solvent and a part of the thickening agent, and coated to prevent polymerization, and then mixed with the carbon-based material, so as to pre-disperse the relatively difficult-to-disperse nanoparticles into a uniform and stable slurry, which can effectively solve the problem that it is difficult to uniformly disperse two or more active materials with extremely different particle sizes in the electrode slurry when using the existing negative electrode materials. In addition, while improving the mixing and dispersion uniformity of the negative electrode active material, the solid content of the slurry is increased, thereby solving the problems of coating dark marks and particle scratches caused by uneven dispersion, and serious floating of the binder during coating drying caused by low solid content.

[0036] The method for preparing the negative electrode paste of the present invention comprises the following steps: (a) adding 20-60% deionized water, a dispersant, a conductive agent, 30-60% thickener, and a silicon-based material to a sand mill in sequence for pre-dispersion to obtain a first mixture; (b) stirring and mixing a carbon-based material and the remaining thickener to obtain a second mixture; (c) dispersing and stirring the remaining deionized water and the above-mentioned second mixture to obtain a third mixture with a solid content of 65-80 wt%; (d) dispersing and stirring the above-mentioned first mixture and the above-mentioned third mixture to obtain a fourth mixture; (e) stirring and mixing a binder and the above-mentioned fourth mixture to obtain a negative electrode material with a solid content of 50-62 wt% and a viscosity value of 3000-15000 mPa·s.

[0037] In some embodiments, in step (a), the filling rate of zirconium beads in the sand mill is 30% - 80%. In some embodiments, in step (a), the particle sizes of the zirconium beads include at least one of 0.5 mm, 2 mm, 5 mm, 10 mm, and 20 mm. In some embodiments, in step (a), the rotation speed of the sand mill is 300 rmp - 3000 rmp. In some embodiments, in step (a), the sanding time is 15 min - 60 min. In some embodiments, in step (a), the sanding temperature is 15°C - 60°C. In some embodiments, in step (b), the stirring speed is 0 rmp - 500 rmp. In some embodiments, in step (b), the mixing time is 5 min - 30 min. In some embodiments, in step (c), the revolution speed of the mixer is 10 rmp - 30 rmp. In some embodiments, in step (c), the dispersion speed is 0 rmp - 500 rmp. In some embodiments, in step (c), the stirring time is 30 min - 90 min. In some embodiments, in step (c), the stirring temperature is 15°C - 60°C. In some embodiments, in step (d), the revolution speed of the mixer is 10 rmp - 30 rmp. In some embodiments, in step (d), the dispersion speed is 500 rmp - 3000 rmp. In some embodiments, in step (d), the stirring time is 30 min - 120 min. In some embodiments, in step (d), the stirring temperature is 15°C - 45°C. In some embodiments, in step (d), the vacuum degree is lower than -80 kPa. In some embodiments, in step (e), the revolution speed of the mixer is 10 rmp - 30 rmp. In some embodiments, in step (e), the dispersion speed is 500 rmp - 1500 rmp. In some embodiments, in step (e), the stirring time is 15 min - 60 min. In some embodiments, in step (e), the stirring temperature is 15°C - 45°C. In some embodiments, in step (e), the vacuum degree is lower than -80 kPa.

[0038] The characteristic parameters of the slurry and the performance measurement methods of the negative electrode sheet in the following examples and comparative examples are as follows:

[0039] 1. Measurement method of slurry viscosity

[0040] a) Take 450 ml of the stirred negative electrode material using a 500 ml beaker; b) Set the parameters of the rotational viscometer to a #4 rotor and a rotation speed of 12 rpm; c) Place the beaker containing 450 ml of the slurry directly below the rotor of the viscometer, and rotate the lift knob of the viscometer so that the groove in the middle of the rotor is just submerged in the slurry liquid level; d) Press the "start" button for viscosity testing, and read the slurry viscosity data after the test data is stable.

[0041] 2. Measurement Method of Slurry Solids Content

[0042] a) Set the parameters of the infrared solids content instrument as follows: baking temperature 120°C, test mode automatic (stop when the weight decreases by 1 mg in 30S); b) Take a copper foil of about 4mmX4mm, fold it into a bowl shape, put it into the infrared solids content instrument and press the test button to automatically tare; c) Take out the copper foil, and use a stainless steel sampling spoon to take 3 - 5 g of the negative electrode material and smear it inside the bowl-shaped copper foil; d) Put the bowl-shaped copper foil coated with the negative electrode material into the infrared solids content instrument and press the test button; e) After the test is completed and the data is stable, read the solids content data.

[0043] 3. Measurement of DV50 of Silicon-based Materials and Carbon-based Materials

[0044] 1) Put the selected powder sample into the sample cup in the instrument, and place the sample cup at the measurement position of the laser particle size analyzer.

[0045] 2) Turn on the power of the laser particle size analyzer and start the measurement program. In the program interface, different measurement modes can be selected according to needs, such as single measurement, continuous measurement, etc.

[0046] 3) During the measurement, it is necessary to keep the sample cup stable and avoid vibration or shaking. At the same time, parameters of the measurement program need to be set, such as the measurement range, measurement time, volume distribution, etc.

[0047] 4) After starting the measurement, the laser particle size analyzer will start to measure the powder sample. By analyzing the scattered light intensity of the powder sample, the particle size volume distribution data of the powder sample can be obtained.

[0048] 5) After the measurement is completed, the experimental data needs to be recorded and analyzed. The particle size distribution of the powder sample can be shown by plotting the particle size distribution curve, and the DV50 of the silicon-based material and the carbon-based material can be obtained.

[0049] 4. Measurement Method of Negative Electrode Sheet Areal Density

[0050] a) Use a sampler with a fixed area (1540.25 mm2) to cut out small round pieces of the electrode sheet; b) Weigh the cut small round pieces of the electrode sheet using an analytical balance; c) Divide the weight of the small round piece by the area of the small round piece to obtain the areal density of the electrode sheet including the foil, and then subtract the areal density of the foil to obtain the coating areal density of the electrode sheet.

[0051] 5. Test Method for Compaction Density of Negative Electrode Sheet

[0052] a) Use a sampler with a fixed area (1540.25 mm2) to cut the rolled electrode into small round pieces; b) Weigh the cut small round pieces of the electrode using an analytical balance; c) Measure the thickness of the small round pieces using a micrometer or a ten-thousandth micrometer, and then subtract the thickness of the foil to obtain the coating thickness; d) Divide the weight of the small round pieces by the coating thickness of the small round pieces to obtain the compaction density of the electrode.

[0053] Examples and Comparative Examples

[0054] Example 1

[0055] A negative electrode sheet includes a negative current collector and a negative electrode material layer located on the negative current collector. Among them, the negative electrode material layer includes a coating layer formed by a negative electrode slurry, and the negative electrode material layer includes the following components: by mass percentage, natural graphite 65%; nano-silicon oxide compound (commercially available) 30%; dispersant 0.05%; binder (SBR) 2.45%; conductive agent SP 0.9%; conductive agent CNT 0.4%; thickener (CMC-Na) 1.2%.

[0056] Among them, the dispersant is composed of a polyacrylate dispersant (DCS308 (Shenzhen Haodian Technology)) and a phosphate ester dispersant (BYK-LPN25432 (BYK Germany)), and the mass ratio of DCS308:BYK-LPN25432 is 50:50.

[0057] Preparation of the negative electrode sheet

[0058] (1) Preparation of the negative electrode slurry

[0059] (a) Add 23% deionized water, dispersant, conductive agent (SP), conductive agent (CNT), 50% thickener (CMC-Na) and nano-silicon oxide compound (commercially available) to a sand mill in sequence for pre-dispersion to obtain a first mixed slurry. Among them, the D V 50 of this nano-silicon oxide compound is 1.3 μm, the rotation speed of the sand mill is 2000 rmp, the sanding time is 30 min, the sanding temperature is 15°C to 60°C, the filling rate of zirconium beads in the sand mill is 70%, and the particle sizes of the zirconium beads are 0.5 mm and 10 mm (where the volume of zirconium beads with a particle size of 0.5 mm accounts for 30%, and the volume of zirconium beads with a particle size of 10 mm accounts for 70%);

[0060] (b) Add natural graphite particles and the remaining 50% of CMC-Na to a double planetary mixer in sequence and dry mix for 10 min to obtain a dry mixed mixture. Among them, the D V 50 of this natural graphite is 5 μm; the revolution speed of the mixer is 20 rmp, and the dispersion speed is 100 rmp;

[0061] (c) Add the remaining 77% deionized water to the dry mixed mixture obtained in step (b), and conduct high-viscosity kneading and stirring to obtain a second mixed slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 20 rmp, the dispersion speed is 0 rmp, the stirring time is 60 min, and the stirring temperature is 15°C to 60°C;

[0062] (d) Add the first mixed slurry obtained in step (a) to the second mixed slurry obtained in step (c), and conduct stirring at a high-speed dispersion speed to obtain a third mixed slurry. Among them, the revolution speed of the mixer is 25 rmp, the dispersion speed is 1200 rmp, the stirring time is 90 min, the stirring temperature is 15°C to 45°C, and the vacuum degree is lower than -80 kPa;

[0063] (e) Add the binder (SBR) to the third mixed slurry obtained in step (d) and conduct stirring to obtain a negative electrode slurry with a solid content of 50 wt% and a viscosity value of 6000 mPa·s to 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp, the dispersion speed is 800 rmp, the stirring time is 30 min, the stirring temperature is 15°C to 45°C, and the vacuum degree is lower than -80 kPa.

[0064] (2) Preparation of the negative electrode sheet

[0065] Coat the negative electrode slurry obtained above on both sides of the copper foil by extrusion coating or transfer coating, and after drying in a coating oven, wind it into a coated electrode roll. The coated electrode roll is roll-pressed at a certain compaction density and then cut into negative electrode sheets of the required size. Among them, the coating surface density (both sides) of the negative electrode sheet (i.e., the coated electrode roll) is 180 g / m 2 , and the compaction density of the electrode sheet roll-pressing is 1.6 g / cm 3 .

[0066] Example 2

[0067] The steps of Example 2 are the same as those in Example 1. The difference is that in Example 2, the composition of the negative electrode material layer and the preparation of the negative electrode sheet are as follows:

[0068] (1) Composition of the negative electrode material layer

[0069] The negative electrode material includes the following components: by mass percentage, artificial graphite 95%; nano-silicon 2.5%; dispersant 0.05%; binder (PAA) 1%; conductive agent (CNT) 0.5%; thickener (CMC-Li) 0.95%.

[0070] Among them, the dispersant is a phosphate ester dispersant (BYK-LPN25432 (BYK of Germany)).

[0071] (2) Preparation of the negative electrode sheet

[0072] (a) 23% deionized water, 100% dispersant, 100% conductive agent (CNT), 50% thickener (CMC-Li), and 100% nanosilicon (nanoscale silicon particles) were added to a sand mill in sequence for pre-dispersion to obtain a first mixed slurry. Among them, the D V 50 of the nanosilicon is 0.3 μm, the sand mill rotation speed is 2000 rmp, the sanding time is 30 min, the sanding temperature is 15°C to 60°C, the filling rate of zirconium beads in the sand mill is 70%, and the zirconium bead diameters are 0.5 mm and 10 mm (where the volume of zirconium beads with a diameter of 0.5 mm accounts for 30%, and the volume of zirconium beads with a diameter of 10 mm accounts for 70%);

[0073] (b) 100% artificial graphite and the remaining 50% of CMC were added to a double planetary mixer and dry mixed for 10 min to obtain a dry mixed mixture. Among them, the D V 50 of the graphite is 13 μm; the revolution speed of the mixer is 20 rmp, and the dispersion speed is 100 rmp;

[0074] (c) The remaining 77% deionized water was added to the dry mixed mixture prepared in step (b) for high-viscosity kneading and stirring to obtain a second mixed slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 20 rmp, the dispersion speed is 0 rmp, the stirring time is 60 min, and the stirring temperature is 15°C to 60°C;

[0075] (d) The first mixed slurry prepared in step (a) was added to the second mixed slurry prepared in step (c) for stirring at a high-speed dispersion speed to obtain a third mixed slurry. Among them, the revolution speed of the mixer is 25 rmp, the dispersion speed is 1200 rmp, the stirring time is 90 min, the stirring temperature is 15°C to 45°C, and the vacuum degree is lower than -80 kPa;

[0076] (e) Binder (PAA) was added to the third mixed slurry prepared in step (d) for stirring to obtain a mixed negative electrode slurry with a solid content of 62 wt% and a viscosity value of 6000 mPa·s to 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp, the dispersion speed is 800 rmp, the stirring time is 30 min, the temperature is 15 to 45°C, and the vacuum degree is lower than -80 kPa.

[0077] (f) Preparation of the negative electrode plate

[0078] The above-prepared anode material is coated on both sides of a copper foil by extrusion coating or transfer coating, and after being dried in a coating oven, it is wound into a coated anode roll. The coated anode roll is roll-pressed at a certain compaction density and then cut into anode sheets of the required size. Among them, the coating areal density (both sides) of the anode sheet (i.e., the coated anode roll) is 160 g / m 2 , and the compaction density of the roll-pressed anode sheet is 1.70 g / cm 3 .

[0079] Example 3

[0080] The steps of Example 3 are the same as those in Example 1, except that in Example 3, the composition of the anode material layer and the preparation of the anode sheet are as follows:

[0081] (1) Composition of the anode material layer

[0082] The anode material layer includes the following components: by mass percentage, 65% of mesophase carbon microspheres; 23% of nano-silicon oxide compound (commercially available); 1.5% of dispersant; 2% of binder (SBR); 3% of binder (PAA); 3% of conductive agent (SP); 2% of thickener (CMC).

[0083] Among them, the dispersant is a polyacrylate dispersant (DCS308 (Shenzhen Haodian Technology)).

[0084] (2) Preparation of the anode sheet

[0085] (a) 23% of deionized water, dispersant, conductive agent (SP), 50% of CMC thickener, and nano-silicon oxide compound (commercially available) are sequentially added to a sand mill for pre-dispersion to obtain a first mixed slurry. Among them, the D V 50 of this nano-silicon oxide compound is 7.0 μm, the rotation speed of the sand mill is 2000 rmp, the sanding time is 30 min, and the sanding temperature is 15 - 60 °C; the filling rate of zirconium beads in the sand mill is 70%; the particle sizes of the zirconium beads are 0.5 mm and 10 mm (wherein, the volume of zirconium beads with a particle size of 0.5 mm accounts for 30%, and the volume of zirconium beads with a particle size of 10 mm accounts for 70%);

[0086] (b) 100% of mesophase micro-carbon spheres and the remaining 50% of CMC are sequentially added to a double planetary mixer and dry-mixed for 10 min to obtain a dry-mixed mixture. Among them, the D V 50 of this graphite is 20 μm; the revolution speed of the mixer is 20 rmp, and the dispersion speed is 100 rmp;

[0087] (c) Add the remaining 77% deionized water to the dry-mixed mixture obtained in step (b) and perform high-viscosity kneading and stirring to obtain a second mixed slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 20 rmp, the dispersion speed is 0 rmp, the stirring time is 60 min, and the stirring temperature is 15°C to 60°C;

[0088] (d) Add the first mixed slurry obtained in step (a) to the second mixed slurry obtained in step (c) and perform high-speed dispersion stirring to obtain a third mixed slurry. Among them, the revolution speed of the mixer is 25 rmp, the dispersion speed is 1200 rmp, the stirring time is 90 min, the stirring temperature is 15 - 45°C, and the vacuum degree is lower than -80 kPa;

[0089] (e) Add the binders (SBR and PAA) to the third mixed slurry obtained in step (d) and stir to obtain a negative electrode slurry with a solid content of 50 wt% and a viscosity value of 6000 mPa·s to 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp, the dispersion speed is 800 rmp, the stirring time is 30 min, the stirring temperature is 15 - 45°C, and the vacuum degree is lower than -80 kPa.

[0090] (f) By extrusion coating or transfer coating, coat the above-prepared negative electrode material on both sides of the copper foil, dry it in a coating oven, and then wind it into a coated electrode roll. The coated electrode roll is roll-pressed at a certain compaction density and then cut into negative electrode sheets of the required size. Among them, the coating surface density (double-sided) of the negative electrode sheet (i.e., the coated electrode roll) is 220 g / m 2 and the compaction density of the electrode sheet roll-pressing is 1.65 g / cm 3 .

[0091] Example 4

[0092] The steps of Example 4 are the same as those in Example 1, except that in Example 4, the composition of the negative electrode material layer and the preparation of the electrode sheet are as follows:

[0093] (1) Composition of the negative electrode material layer

[0094] The negative electrode material layer includes the following components: by mass percentage, 80% hard carbon; 16.3% nano-silicon oxide compound (commercially available); 0.5% dispersant; 2% binder (PAA); 0.8% conductive agent (SP); 0.2% conductive agent (CNT); 1.2% thickener (CMC).

[0095] Among them, the dispersant is composed of a polyacrylate dispersant (DCS308 (Shenzhen Haodian Technology Co., Ltd.)) and a phosphate dispersant (BYK-LPN25432 (BYK Chemie GmbH)), and the mass ratio of DCS308:BYK-LPN25432 is 80:20.

[0096] (2) Preparation of the negative electrode sheet

[0097] (a) 23% deionized water, a dispersant, a conductive agent (SP), a conductive agent (CNT), 50% thickener (CMC), and nano-silicon oxide particles (commercially available) are sequentially added to a sand mill for pre-dispersion to obtain a first mixed slurry. Among them, the D V 50 of this nano-silicon oxide is 2 μm, the rotational speed of the sand mill is 2000 rmp, the sanding time is 30 min, and the sanding temperature is 15 - 60 °C; the filling rate of zirconium beads in the sand mill is 70%; the particle sizes of the zirconium beads are 0.5 mm and 10 mm (where the volume of zirconium beads with a particle size of 0.5 mm accounts for 30%, and the volume of zirconium beads with a particle size of 10 mm accounts for 70%);

[0098] (b) 100% hard carbon and the remaining 50% of CMC are sequentially added to a double planetary mixer and dry-mixed for 10 min to obtain a dry-mixed mixture. Among them, the D V 50 of this graphite is 8 μm; the revolution speed of the mixer is 20 rmp, and the dispersion speed is 100 rmp;

[0099] (c) The remaining 77% deionized water is added to the dry-mixed mixture prepared in step (b) for high-viscosity kneading and stirring to obtain a second mixed slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 20 rmp; the dispersion speed is 0 rmp; the stirring time is 60 min; the stirring temperature is 15 - 60 °C;

[0100] (d) The first mixed slurry prepared in step (a) is added to the second mixed slurry prepared in step (c) for high-speed dispersion and stirring to obtain a third mixed slurry. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 1200 rmp; the stirring time is 90 min; the stirring temperature is 15 - 45 °C; the vacuum degree is lower than -80 kPa;

[0101] (e) A binder (PAA) is added to the third mixed slurry prepared in step (d) for stirring to obtain a mixed negative electrode slurry with a solid content of 55 wt% and a viscosity value of 6000 mPa·s - 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 800 rmp; the stirring time is 30 min; the stirring temperature is 15 °C - 45 °C; the vacuum degree is lower than -80 kPa.

[0102] (f) By extrusion coating or transfer coating, the above-prepared negative electrode material is coated on both sides of a copper foil, dried in a coating oven, and then wound into a coated electrode roll. The coated electrode roll is rolled at a certain compaction density and then cut into negative electrode sheets of the required size. Among them, the coating surface density (both sides) of the negative electrode sheet (i.e., the negative electrode coated roll) is 180 g / m 2 , and the compaction density of the electrode sheet rolling is 1.45 g / cm 3 .

[0103] Example 5

[0104] The steps of Example 5 are the same as those in Example 1. The difference is that in Example 5, the composition of the negative electrode material layer and the preparation of the electrode sheet are as follows:

[0105] (1) Composition of the negative electrode material layer

[0106] The negative electrode material includes the following components: by mass percentage, 70% of soft carbon; 26.3% of nano-silicon oxide compound (commercially available); 0.5% of dispersant; 2% of binder (SBR); 1% of conductive agent (SP); and 1.2% of thickener (CMC).

[0107] Among them, the dispersant is a phosphate ester dispersant (BYK-LPN25432 (BYK of Germany)).

[0108] (2) Preparation of the negative electrode sheet

[0109] (a) 23% of deionized water, dispersant, conductive agent (SP), 50% of thickener (CMC), and nano-scale silicon oxide compound particles (commercially available) are sequentially added to a sand mill for pre-dispersion to obtain a first mixed slurry. Among them, the D V 50 of this nano-silicon oxide is 3.3 μm, the rotation speed of the sand mill is 2000 rmp; the sanding time is 30 min; the sanding temperature is 15°C to 60°C; the filling rate of zirconium beads in the sand mill is 70%; the particle size of the zirconium beads is 0.5 mm and 10 mm (wherein, the volume of zirconium beads with a particle size of 0.5 mm accounts for 30%, and the volume of zirconium beads with a particle size of 10 mm accounts for 70%);

[0110] (b) 100% of soft carbon and the remaining 50% of CMC are sequentially added to a double planetary mixer and dry-mixed for 10 min to obtain a dry-mixed mixture. Among them, the D V 50 of this graphite is 18 μm; the revolution speed of the mixer is 20 rmp; the dispersion speed is 100 rmp;

[0111] (c) Add the remaining 77% deionized water to the dry-mixed mixture prepared in step (b), and perform high-viscosity kneading and stirring to obtain a second mixed slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 20 rmp; the dispersion speed is 0 rmp; the stirring time is 60 min; the stirring temperature is 15 - 60 °C;

[0112] (d) Add the first mixed slurry prepared in step (a) to the second mixed slurry prepared in step (c), and perform high-speed dispersion stirring to obtain a third mixed slurry. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 1200 rmp; the stirring time is 90 min; the stirring temperature is 15 - 45 °C; the vacuum degree is lower than -80 kPa;

[0113] (e) Add the binder SBR to the third mixed slurry prepared in step (d) and stir to obtain a negative electrode slurry with a solid content of 54 wt% and a viscosity value of 6000 mPa·s - 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 800 rmp; the stirring time is 30 min; the stirring temperature is 15 °C - 45 °C; the vacuum degree is lower than -80 kPa.

[0114] (f) By extrusion coating or transfer coating, coat the negative electrode material prepared above on both sides of the copper foil, dry it in a coating oven, and then wind it into a coated electrode roll. The coated electrode roll is roll-pressed at a certain compaction density and then cut into negative electrode sheets of the required size. Among them, the coating surface density (double-sided) of the negative electrode sheet (i.e., the coated electrode roll) is 200 g / m 2 , and the compaction density of the electrode sheet roll-pressing is 1.55 g / cm 3 .

[0115] Example 6

[0116] The steps of Example 6 are the same as those in Example 1. The difference is that in Example 5, the composition and preparation of the negative electrode material layer are as follows:

[0117] (1) Composition of the negative electrode material layer

[0118] The negative electrode material layer includes the following components: by mass percentage, artificial graphite 65%; nano-silicon oxide compound (commercially available) 31%; dispersant 0.5%; binder (SBR) 1%, binder (PAA) 1%; conductive agent (SP) 1%; thickener (CMC) is 0.5%.

[0119] Among them, the dispersant is a polyacrylate dispersant (DCS308 (Shenzhen Haodian Technology)).

[0120] (2) Preparation of the negative electrode sheet

[0121] (a) Add 23% deionized water, a dispersant, a conductive agent (SP), 50% thickener (CMC), and nanosilicon oxide particles (commercially available) to a sand mill in sequence for pre-dispersion to obtain a first mixed slurry. Among them, the D V 50 of this nanosilicon oxide is 7.3 μm, the rotational speed of the sand mill is 2000 rmp; the sanding time is 30 min; the sanding temperature is 15 °C to 60 °C; the filling rate of zirconium beads in the sand mill is 70%; the zirconium bead diameters are 0.5 mm and 10 mm (wherein, the volume of zirconium beads with a diameter of 0.5 mm accounts for 30%, and the volume of zirconium beads with a diameter of 10 mm accounts for 70%);

[0122] (b) Add 100% artificial graphite and the remaining 50% of CMC to a double planetary mixer in sequence and dry mix for 10 min to obtain a dry-mixed mixture. Among them, the D V 50 of this graphite is 11 μm; the revolution speed of the mixer is 20 rmp; the dispersion speed is 100 rmp;

[0123] (c) Add the remaining 77% deionized water to the dry-mixed mixture prepared in step (b) for high-viscosity kneading and stirring to obtain a second mixed slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 20 rmp; the dispersion speed is 0 rmp; the stirring time is 60 min; the stirring temperature is 15 °C to 60 °C;

[0124] (d) Add the first mixed slurry prepared in step (a) to the second mixed slurry prepared in step (c) for high-speed dispersion and stirring to obtain a third mixed slurry. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 1200 rmp; the stirring time is 90 min; the stirring temperature is 15 °C to 45 °C; the vacuum degree is lower than -80 kPa;

[0125] (e) Add a binder (SBR and PAA) to the third mixed slurry prepared in step (d) for stirring to obtain a negative electrode slurry with a solid content of 52 wt% and a viscosity value of 6000 mPa·s to 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 800 rmp; the stirring time is 30 min; the stirring temperature is 15 °C to 45 °C; the vacuum degree is lower than -80 kPa.

[0126] (f) By extrusion coating or transfer coating, coat the above-prepared negative electrode slurry on both sides of a copper foil, dry it in a coating oven, and then wind it into a coated electrode roll. The coated electrode roll is roll-pressed at a certain compaction density and then cut into negative electrode sheets of the required size. Among them, the coating surface density (double-sided) of the negative electrode sheet (i.e., the coated electrode roll) is 160 g / m 2 , and the compaction density of the electrode roll pressing is 1.65 g / cm 3 .

[0127] Comparative Example 1

[0128] The steps of Comparative Example 1 are the same as those in Example 1, except that in Comparative Example 1, the composition of the negative electrode material layer and the preparation of the electrode sheet are as follows:

[0129] (1) Composition of the negative electrode material layer

[0130] The negative electrode material includes the following components: by mass percentage, 65% graphite; 30% nano-silicon oxide compound (commercially available); 0% dispersant; 2.45% binder (SBR); 0.9% conductive agent (SP); 0.4% conductive agent (CNT); 1.25% thickener (CMC).

[0131] (2) Preparation of the negative electrode sheet

[0132] (a) Graphite, nano-silicon oxide compound particles (commercially available), conductive agent (SP); conductive agent (CNT) and 50% of the thickener (CMC) were sequentially added to a double planetary mixer and dry mixed for 10 min to obtain the first dry mixed particles. Among them, the D V 50 of this nano-silicon oxide compound is 1.3 μm, and the D V 50 of this graphite is 5 μm; the revolution speed of the mixer is 20 rmp; the dispersion speed is 100 rmp;

[0133] (b) 21% deionized water was added to the first dry mixed particles prepared in step (a), and kneading and stirring were carried out to obtain a second kneaded slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 15 rmp; the dispersion speed is 0 rmp; the stirring time is 60 min; the stirring temperature is 15 - 60 °C;

[0134] (c) The remaining 50% thickener powder and 79% deionized water were added to the second kneaded slurry prepared in step (b) for high-speed dispersion stirring to obtain a third mixed slurry. Among them, the revolution speed of the double mixer is 25 rmp; the dispersion speed is 1200 rmp; the stirring time is 90 min; the stirring temperature is 15 °C - 45 °C; the vacuum degree is lower than -80 kPa;

[0135] (d) The binder SBR was added to the third mixed slurry prepared in step (c) for stirring to obtain a negative electrode material with a solid content of 44 wt% and a viscosity value of 6000 mPa·s - 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 800 rmp; the stirring time is 30 min; the stirring temperature is 15 °C - 45 °C; the vacuum degree is lower than -80 kPa.

[0136] Among them, the coating areal density (both sides) of the negative electrode coating pole roll is 160 g / m2, and the compaction density of the pole piece after rolling is 1.55 g / cm3.

[0137] Comparative Example 2

[0138] The steps of Comparative Example 2 are the same as those in Example 1, except that in Comparative Example 2, the composition of the negative electrode material layer and the preparation of the pole piece are as follows:

[0139] (1) Composition of the negative electrode material layer

[0140] The negative electrode material includes the following components: by mass percentage, artificial graphite 65%; nano silicon oxide compound (commercially available) 31%; dispersant 0.02%; binder (SBR) 1%, binder (PAA) 1%; conductive agent (SP) 1%; thickener (CMC) 0.5%.

[0141] The dispersant is polyvinylpyrrolidone.

[0142] (2) Preparation of the negative electrode pole piece

[0143] (a) 23% deionized water, dispersant, conductive agent (SP), 50% thickener (CMC) and nano silicon oxide compound (commercially available) are added to a sand mill in sequence for pre-dispersion to obtain a first mixed slurry. Among them, the D V 50 of this nano silicon oxide compound is 1.3 μm, the rotation speed of the sand mill is 2000 rmp; the sand milling time is 30 min; the sand milling temperature is 15 - 60 °C; the filling rate of zirconium beads in the sand mill is 70%; the particle sizes of the zirconium beads are 0.5 mm and 10 mm (wherein, the volume of zirconium beads with a particle size of 0.5 mm accounts for 30%, and the volume of zirconium beads with a particle size of 10 mm accounts for 70%);

[0144] (b) Graphite and the remaining 50% of CMC are added to a double planetary mixer in sequence for dry mixing for 10 min to obtain a dry mixed mixture. Among them, the D V 50 of this graphite is 20 μm; the revolution speed of the mixer is 20 rmp; the dispersion speed is 100 rmp;

[0145] (c) The remaining 77% deionized water is added to the dry mixed mixture prepared in step (b) for high-viscosity kneading and stirring to obtain a second mixed slurry with a solid content of 70 wt%. Among them, the revolution speed of the mixer is 20 rmp; the dispersion speed is 0 rmp; the stirring time is 60 min; the stirring temperature is 15 °C - 60 °C;

[0146] (d) Add the first mixed slurry prepared in step (a) to the second mixed slurry prepared in step (c) and carry out high-speed dispersion stirring to obtain a third mixed slurry. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 1200 rmp; the stirring time is 90 min; the stirring temperature is 15 - 45 °C; the vacuum degree is lower than -80 kPa;

[0147] (e) Add binders (SBR and PAA) to the third mixed slurry prepared in step (d) and stir to obtain a negative electrode slurry with a solid content of 48 wt% and a viscosity value of 6000 mPa·s - 8000 mPa·s. Among them, the revolution speed of the mixer is 25 rmp; the dispersion speed is 800 rmp; the stirring time is 30 min; the stirring temperature is 15 °C - 45 °C; the vacuum degree is lower than -80 kPa.

[0148] Among them, the coating surface density (both sides) of the negative electrode coating pole roll is 180 g / m2, and the compaction density of the pole piece rolling is 1.58 g / cm3.

[0149] Although some exemplary embodiments of the present application have been described and illustrated, the present application is not limited to the disclosed embodiments. On the contrary, those of ordinary skill in the art will recognize that some modifications and changes can be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims

1. A negative electrode plate, comprising a negative electrode current collector and a negative electrode material layer located on the negative electrode current collector, wherein, The negative electrode material layer includes a coating layer formed from a negative electrode slurry. Among them, the negative electrode material layer includes a carbon-based material, a silicon-based material, and a dispersant. Among them, the mass content of the dispersant in the negative electrode material layer is 0.03% to 1.7%.

2. The negative electrode sheet according to claim 1, wherein The mass content of the carbon-based material in the negative electrode material layer is 55% to 97%; and / or The mass content of the silicon-based material in the negative electrode material layer is 1.0% to 35%; and / or The mass content of the dispersant in the negative electrode material layer is 0.05% to 1.5%.

3. The negative electrode sheet according to claim 1, characterized in that, The negative electrode material further includes a binder, a conductive agent, and a thickening agent. Among them, The mass content of the binder in the negative electrode material layer is 0.5% to 5.0%; and / or The mass content of the conductive agent in the negative electrode material layer is 0.1% to 4.0%; and / or The mass content of the thickening agent in the negative electrode material layer is 0.3% to 2.5%; and / or The dispersant includes at least one of polyacrylate dispersants and phosphate ester dispersants; and / or The silicon-based material includes at least one of silicon, silicon oxides, and silicon carbide compounds; and / or The carbon-based material includes at least one of natural graphite, artificial graphite, mesophase microcarbon microspheres, hard carbon, and soft carbon; and / or The D of the silicon-based material V 50 is 0.1 μm to 9 μm. The D of the carbon-based material V 50 is 2 μm to 25 μm.

4. The negative electrode tab according to claim 3, wherein The thickening agent includes at least one of lithium carboxymethyl cellulose, sodium carboxymethyl cellulose, and carboxymethyl cellulose; and / or The binder includes at least one of styrene-butadiene rubber, polyacrylic acid, and lithium polyacrylate; and / or The conductive agent includes at least one of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, and carbon nanotubes.

5. The negative electrode sheet according to claim 1, characterized in that, The preparation of the negative electrode slurry includes the following steps: (a) Pre-disperse 20% to 60% of deionized water, a dispersant, a conductive agent, 30% to 60% of a thickening agent, and a silicon-based material to obtain a first mixture; (b) Mix the carbon-based material and the remaining thickening agent to obtain a second mixture; (c) Mix the remaining deionized water and the second mixture to obtain a third mixture; (d) Mix the first mixture and the third mixture to obtain a fourth mixture; (e) Mix the binder and the fourth mixture to obtain a negative electrode slurry.

6. The negative electrode sheet according to claim 5, wherein, The viscosity value of this negative electrode slurry is 3000 mPa·s to 15000 mPa·s; and / or The solid content of this negative electrode slurry is 50 wt% to 62 wt%.

7. A secondary battery, which includes the negative electrode tab according to any one of claims 1-6 and a positive electrode tab.

8. A device, which includes the secondary battery according to claim 7.