A positive electrode slurry, a method for preparing the same, and an application thereof

Abstract

The present application relates to a kind of positive electrode slurry and its preparation method and application, the positive electrode slurry includes solid component and solvent, the solid component includes positive electrode active material, conductive agent, binder and dispersant;The functional group in the dispersant includes amino, sulfonate group and ether bond.The dispersant in the positive electrode slurry provided by the present application contains amino, ether bond and sulfonate group, multiple functional groups in dispersant synergize with each other, improve the dispersibility and dispersion stability of positive electrode slurry, and enhance the adhesion between positive electrode material and current collector, thereby effectively solve the problem of lithium ion fast charging battery positive electrode slurry dispersion difficulty, while improving the electrochemical performance of battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a positive electrode slurry, its preparation method, and its application. Background Technology

[0002] With the increasing global demand for clean and renewable energy, lithium-ion batteries, as efficient and environmentally friendly energy storage devices, have been widely used in electric vehicles, portable electronic devices, and energy storage systems. To meet the demands for higher energy density, longer cycle life, and better safety performance, the materials science and technology of lithium-ion batteries are constantly advancing.

[0003] In the manufacturing process of lithium-ion batteries, the performance of the cathode material plays a crucial role in the overall performance of the battery. Cathode materials, represented by lithium iron phosphate, are typically composed of micron- or nano-sized particles. These particles are prone to agglomeration during slurry preparation, leading to decreased uniformity and stability of the slurry. Agglomerated particles not only affect the electrode density and conductivity but also reduce lithium-ion transport efficiency, thereby impacting the battery's electrochemical performance.

[0004] To address these issues, dispersants are widely used in the preparation of lithium-ion battery cathode materials. Common cathode dispersants include polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), or polyvinyl alcohol (PVA). CN109167068A discloses a lithium battery cathode slurry and its processing technology. The raw material composition and mass percentage of each raw material in the cathode slurry are as follows: 47%-52% cathode active material, 46%-50% solvent, 0.7%-1.5% binder, 0.6%-1.2% conductive agent, and 1.5%-2% dispersant, wherein the dispersant is polyvinylpyrrolidone.

[0005] However, the use of common dispersants such as polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), or polyvinyl alcohol (PVA) typically involves additions of more than 0.2 wt% of the solid component, which reduces the content of the cathode material and is not conducive to improving the energy density of the battery. Moreover, with the development of materials science, cathode material particles are moving towards the nanoscale, and the proportion of carbon coating on the material surface is also increasing, gradually increasing the difficulty of dispersion.

[0006] Therefore, how to provide a dispersant for use in cathode slurry to solve the problem of difficult dispersion of cathode material particles, while improving the electrochemical performance of lithium-ion batteries, has become an urgent problem to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a positive electrode slurry, its preparation method, and its application. The dispersant in the positive electrode slurry provided by the present invention contains amino, ether, and sulfonate groups. These various functional groups synergistically enhance the dispersibility and dispersion stability of the positive electrode slurry, as well as strengthen the adhesion between the positive electrode material and the current collector. This effectively solves the problem of difficult dispersion of positive electrode slurry in lithium-ion fast-charging batteries, while simultaneously improving the electrochemical performance of the battery.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a positive electrode slurry comprising a solid component and a solvent, wherein the solid component comprises a positive electrode active material, a conductive agent, a binder, and a dispersant; and the functional groups in the dispersant include amino, sulfonate, and ether groups.

[0010] The present invention introduces specific dispersants into the positive electrode slurry. These dispersants possess multiple functional groups, including amino, sulfonate, and ether groups. The amino groups in the dispersant exhibit polarity and alkalinity, providing additional charge within the dispersant molecules and promoting the stability of the dispersion system. Furthermore, the amino groups can form coordination bonds with metal ions on the current collector surface, thereby enhancing the adhesion between the positive electrode material and the current collector. The ether groups introduced into the dispersant enhance the flexibility of the dispersant molecules, allowing them to better adapt to particles of different shapes and sizes, thus improving the dispersion effect. The sulfonate groups introduced into the dispersant provide a large amount of negative charge, enhancing the charge shielding effect of the dispersant and further improving the stability of the dispersant system. Through the interaction of the various specific functional groups of the dispersant introduced into the positive electrode slurry, the dispersibility and dispersion stability of the positive electrode slurry are improved, as well as the adhesion between the positive electrode material and the current collector is enhanced, effectively solving the problem of difficult dispersion of positive electrode slurries in lithium-ion fast-charging batteries, while simultaneously improving the electrochemical performance of the battery.

[0011] Preferably, the general chemical formula of the dispersant is as shown in formula (1):

[0012]

[0013] R1 is a substituent containing an amino group.

[0014] Preferably, the dispersant comprises Any one or at least two of them.

[0015] The present invention selects the above three specific chemical formula molecules as further preferred dispersants, which can more significantly improve the dispersibility and dispersion stability of the positive electrode slurry, as well as enhance the adhesion between the positive electrode material and the current collector, thereby more effectively solving the problem of difficult dispersion of positive electrode slurry in lithium-ion fast charging batteries, and further improving the electrochemical performance of the battery.

[0016] Preferably, based on a solid component mass percentage of 100 wt% in the positive electrode slurry, the mass percentage of the dispersant is 0.05-0.15 wt%, for example, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, 0.10 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, or 0.15 wt%.

[0017] The positive electrode slurry provided by this invention selects specific substances as dispersants, which ensures the dispersant's dispersion effect on the positive electrode slurry while avoiding the dispersant crowding out the content of positive electrode active materials, thereby effectively improving the energy density of lithium-ion batteries.

[0018] Preferably, the initial viscosity of the positive electrode slurry is 8000-20000 mPa·s, such as 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 11000 mPa·s, 12000 mPa·s, 13000 mPa·s, 14000 mPa·s, 15000 mPa·s, 16000 mPa·s, 17000 mPa·s, 18000 mPa·s, 19000 mPa·s, or 20000 mPa·s.

[0019] In this invention, the "initial viscosity of the positive electrode slurry" refers to the viscosity of the prepared positive electrode slurry before it has been allowed to stand, that is, the viscosity of the positive electrode slurry after standing for 0 hours.

[0020] The viscosity of the cathode slurry with the specific dispersant introduced in this invention is within a specific range, which can further improve the dispersion effect of the dispersant on the cathode slurry.

[0021] Preferably, the positive electrode active material includes lithium iron phosphate and / or lithium manganese iron phosphate.

[0022] Preferably, the particle size D50 of the positive electrode active material is 400-500nm, such as 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm or 500nm.

[0023] Preferably, based on a solid component mass percentage of 100 wt% in the positive electrode slurry, the mass percentage of the positive electrode active material is 95-98 wt%, such as 95.0 wt%, 95.2 wt%, 95.4 wt%, 95.6 wt%, 95.8 wt%, 96.0 wt%, 96.2 wt%, 96.4 wt%, 96.6 wt%, 96.8 wt%, 97.0 wt%, 97.2 wt%, 97.4 wt%, 97.6 wt%, 97.8 wt%, or 98.0 wt%.

[0024] Preferably, the conductive agent includes any one or a combination of at least two of conductive carbon black, conductive graphite, carbon nanotubes, graphene, or carbon fiber, with a preferred combination of conductive carbon black and carbon nanotubes.

[0025] Preferably, the mass ratio of the conductive carbon black to the carbon nanotubes is (0.2-0.5):(0.3-0.5), wherein the mass fraction of the conductive carbon black is selected from "0.2-0.5", for example, 0.20, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, or 0.50, etc.; the mass fraction of the carbon nanotubes is selected from "0.3-0.5", for example, 0.30, 0.32, 0.34, 0.36, 0.38, 0.40, 0.42, 0.44, 0.46, 0.48, or 0.50, etc.

[0026] Preferably, based on a mass percentage of 100 wt% of the solid components in the positive electrode slurry, the mass percentage of the conductive agent is 0.5-1 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%.

[0027] Preferably, the adhesive comprises any one or a combination of at least two of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, sodium carboxymethyl cellulose, or styrene-butadiene rubber.

[0028] Preferably, based on a solid component mass percentage of 100 wt% in the positive electrode slurry, the binder mass percentage is 1-2 wt%, such as 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, or 2.0 wt%.

[0029] Preferably, the solvent comprises N-methylpyrrolidone.

[0030] Preferably, in the positive electrode slurry, the mass ratio of the solid component to the solvent is 1:(3-5), for example, 1:3.0, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4.0, 1:4.2, 1:4.4, 1:4.6, 1:4.8 or 1:5.0, etc.

[0031] In a second aspect, the present invention provides a method for preparing the positive electrode slurry according to the first aspect, the method comprising the following steps:

[0032] (1) The binder and solvent are mixed for the first time to obtain a first dispersion;

[0033] (2) The first dispersion, the conductive agent and the dispersant are mixed in a second mixture to obtain a second dispersion;

[0034] The functional groups in the dispersant include amino, sulfonate, and ether groups;

[0035] (3) The second dispersion and the positive electrode active material are mixed in a third way to obtain the positive electrode slurry.

[0036] In the method for preparing the positive electrode slurry provided by this invention, the binder and solvent are first mixed to pre-expand the binder molecules, enabling them to be effectively adsorbed onto the surface of the conductive agent and active material. This prevents particle agglomeration through steric hindrance and maintains the stability of the slurry. Next, the dispersion formed by the binder and solvent is mixed with the conductive agent and a specific dispersant. This aims to utilize the coating effect of the polymer chains of the binder to uniformly disperse the conductive agent and form a conductive network. The various functional groups, including amino, ether, and sulfonate groups, contained in the dispersant work synergistically to improve the dispersibility and dispersion stability of the positive electrode slurry, as well as enhance the adhesion between the positive electrode material and the current collector. Finally, the positive electrode active material is added to the dispersion to stabilize the viscosity of the slurry.

[0037] Preferably, the first mixture, the second mixture, and the third mixture are independently selected from vacuum stirring and / or dispersion.

[0038] Preferably, during the first mixing, the second mixing, and the third mixing processes, the vacuum stirring is performed first, followed by the dispersion.

[0039] Preferably, during the first mixing, the second mixing, and the third mixing processes, the rotation speed of the vacuum stirring is independently selected from 150-350 rpm, such as 150 rpm, 160 rpm, 180 rpm, 200 rpm, 220 rpm, 240 rpm, 260 rpm, 280 rpm, 300 rpm, 320 rpm, 340 rpm, or 350 rpm.

[0040] Preferably, during the first mixing, the second mixing, and the third mixing processes, the vacuum stirring time is 30-40 minutes, such as 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes, or 40 minutes.

[0041] Preferably, during the first mixing, the second mixing, and the third mixing processes, the dispersion speed is independently selected from 1000-2000 rpm, such as 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, or 2000 rpm.

[0042] Preferably, during the first mixing, the second mixing, and the third mixing processes, the dispersion time is independently selected from 30-50 min, such as 30 min, 32 min, 34 min, 36 min, 38 min, 40 min, 42 min, 44 min, 46 min, 48 min, or 50 min.

[0043] Preferably, a solvent is also added during the third mixing process.

[0044] Preferably, the solvent added during the third mixing process includes N-methylpyrrolidone.

[0045] Preferably, the mass ratio of the solvent added in the first mixture to the solvent added in the third mixture is (93-97):(3-7), for example, 93:7, 94:6, 95:5, 96:4 or 97:3, etc.

[0046] Thirdly, the present invention provides a positive electrode sheet, which is prepared using the positive electrode slurry as described in the first aspect.

[0047] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode sheet described in the third aspect.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] The dispersant in the positive electrode slurry provided by this invention contains amino, ether bonds and sulfonate groups. The various functional groups in the dispersant work synergistically to improve the dispersibility and dispersion stability of the positive electrode slurry, as well as enhance the adhesion between the positive electrode material and the current collector, thereby effectively solving the problem of difficult dispersion of positive electrode slurry in lithium-ion fast charging batteries, and improving the electrochemical performance of the battery. Detailed Implementation

[0050] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0051] The dispersants used in the following examples The CAS number is 68179-90-8.

[0052] The dispersants used in the following examples The CAS number is 883732-10-3.

[0053] The dispersants used in the following examples The CAS number is 883731-80-4.

[0054] The dispersants used in the following comparative examples The CAS number is 25289-73-0.

[0055] The dispersants used in the following comparative examples The CAS number is 72674-70-5.

[0056] The dispersants used in the following comparative examples The CAS number is 61017-18-3.

[0057] Example 1

[0058] This embodiment provides a positive electrode slurry, specifically comprising a solid component and an organic solvent in a mass ratio of 15:65. The organic solvent is N-methylpyrrolidone. The solid component includes lithium iron phosphate, conductive carbon black, carbon nanotubes, polyvinylidene fluoride (PVDF), and a dispersant. The lithium iron phosphate has a particle size D50 of 450 nm. Based on a 100 wt% mass percentage of the solid component in the positive electrode slurry, the mass percentages are: lithium iron phosphate 97.80 wt%, conductive carbon black 0.2 wt%, carbon nanotubes 0.4 wt%, PVDF 1.5 wt%, and dispersant 0.1 wt%. The chemical structural formula of the dispersant is as follows:

[0059] This embodiment provides a method for preparing the above-mentioned positive electrode slurry, including the following steps:

[0060] (1) Polyvinylidene fluoride and N-methylpyrrolidone were stirred under vacuum according to the formula amount. The stirring speed was 250 rpm and the stirring time was 30 min. Then, the mixture was dispersed for 40 min at a speed of 1500 rpm to obtain the first dispersion.

[0061] (2) The first dispersion, conductive carbon black, carbon nanotubes and dispersant were stirred under vacuum according to the formula amount. The stirring speed was 250 rpm and the stirring time was 30 min. Then, the dispersion was carried out for 40 min at a speed of 1500 rpm to obtain the second dispersion.

[0062] (3) The second dispersion was stirred with lithium iron phosphate and N-methylpyrrolidone under vacuum according to the formula amount. The mass ratio of N-methylpyrrolidone added in step (3) to N-methylpyrrolidone added in step (1) was 5:95. The vacuum stirring speed was 250 rpm and the vacuum stirring time was 30 min. Then, the dispersion was carried out for 40 min at a speed of 1500 rpm to obtain the positive electrode slurry.

[0063] Example 2

[0064] This embodiment provides a positive electrode slurry, specifically comprising solid components and an organic solvent in a mass ratio of 15:65. The organic solvent is N-methylpyrrolidone. The solid components include lithium manganese iron phosphate, conductive carbon black, carbon nanotubes, polytetrafluoroethylene (PTFE), and a dispersant. The particle size D50 of the lithium manganese iron phosphate is 400 nm. Based on a 100 wt% mass percentage of solid components in the positive electrode slurry, the mass percentages are: lithium manganese iron phosphate 98 wt%, conductive carbon black 0.4 wt%, carbon nanotubes 0.4 wt%, PTFE 1.15 wt%, and dispersant 0.05 wt%. The chemical structural formula of the dispersant is as follows:

[0065] This embodiment provides a method for preparing the above-mentioned positive electrode slurry, including the following steps:

[0066] (1) Polytetrafluoroethylene and N-methylpyrrolidone were stirred under vacuum according to the formula amount. The stirring speed was 150 rpm and the stirring time was 30 min. Then, the mixture was dispersed for 30 min at a speed of 2000 rpm to obtain the first dispersion.

[0067] (2) The first dispersion, conductive carbon black, carbon nanotubes and dispersant are stirred under vacuum according to the formula amount. The stirring speed is 200 rpm and the stirring time is 30 min. Then, the dispersion is carried out for 35 min at a speed of 1500 rpm to obtain the second dispersion.

[0068] (3) The second dispersion was stirred with lithium manganese iron phosphate and N-methylpyrrolidone under vacuum according to the formula amount. The mass ratio of N-methylpyrrolidone added in step (3) to N-methylpyrrolidone added in step (1) was 7:93. The vacuum stirring speed was 300 rpm and the vacuum stirring time was 30 min. Then, the dispersion was carried out for 30 min at a speed of 1500 rpm to obtain the positive electrode slurry.

[0069] Example 3

[0070] This embodiment provides a positive electrode slurry with a viscosity of [viscosity value missing]. Specifically, it comprises a solid component and an organic solvent in a mass ratio of 15:65. The organic solvent is N-methylpyrrolidone. The solid component includes lithium iron phosphate, conductive carbon black, carbon nanotubes, polyacrylic acid, and a dispersant. The lithium iron phosphate has a particle size D50 of 500 nm. Based on a 100 wt% mass percentage of solid components in the positive electrode slurry, the mass percentages are: lithium iron phosphate 96.85 wt%, conductive carbon black 0.5 wt%, carbon nanotubes 0.5 wt%, polyacrylic acid 2 wt%, and dispersant 0.15 wt%. The chemical structural formula of the dispersant is [chemical formula missing].

[0071] This embodiment provides a method for preparing the above-mentioned positive electrode slurry, including the following steps:

[0072] (1) Polyacrylic acid and N-methylpyrrolidone were stirred under vacuum according to the formula amount. The stirring speed was 350 rpm and the stirring time was 30 min. Then, the mixture was dispersed for 40 min at a speed of 1000 rpm to obtain the first dispersion.

[0073] (2) The first dispersion, conductive carbon black, carbon nanotubes and dispersant are stirred under vacuum according to the formula amount. The stirring speed is 350 rpm and the stirring time is 30 min. Then, the dispersion is carried out for 40 min at a speed of 1000 rpm to obtain the second dispersion.

[0074] (3) The second dispersion was stirred with lithium iron phosphate and N-methylpyrrolidone under vacuum according to the formula amount. The mass ratio of N-methylpyrrolidone added in step (3) to N-methylpyrrolidone added in step (1) was 3:97. The vacuum stirring speed was 350 rpm and the vacuum stirring time was 30 min. Then, the dispersion was carried out for 40 min at a speed of 1000 rpm to obtain the positive electrode slurry.

[0075] Example 4

[0076] The only difference between this embodiment and Example 1 is that, based on a 100wt% mass percentage of solid components in the positive electrode slurry, the mass percentage of lithium iron phosphate is 97.85wt%, the mass percentage of conductive carbon black is 0.2wt%, the mass percentage of carbon nanotubes is 0.4wt%, the mass percentage of polyvinylidene fluoride is 1.5wt%, and the mass percentage of dispersant is 0.05wt%. All other contents are the same as in Example 1.

[0077] Example 5

[0078] The only difference between this embodiment and Example 1 is that, based on a 100wt% mass percentage of solid components in the positive electrode slurry, the mass percentage of lithium iron phosphate is 97.75wt%, the mass percentage of conductive carbon black is 0.2wt%, the mass percentage of carbon nanotubes is 0.4wt%, the mass percentage of polyvinylidene fluoride is 1.5wt%, and the mass percentage of dispersant is 0.15wt%. All other contents are the same as in Example 1.

[0079] Example 6

[0080] The only difference between this embodiment and Embodiment 1 is that the dispersant is... The rest of the content is the same as in Example 1.

[0081] Example 7

[0082] The only difference between this embodiment and Embodiment 1 is that the dispersant is... The rest of the content is the same as in Example 1.

[0083] Example 8

[0084] The only difference between this embodiment and Example 1 is that, based on a 100wt% mass percentage of solid components in the positive electrode slurry, the mass percentage of lithium iron phosphate is 97.88wt%, the mass percentage of conductive carbon black is 0.2wt%, the mass percentage of carbon nanotubes is 0.4wt%, the mass percentage of polyvinylidene fluoride is 1.5wt%, and the mass percentage of dispersant is 0.02wt%. All other contents are the same as in Example 1.

[0085] Example 9

[0086] The only difference between this embodiment and Example 1 is that, based on a 100wt% mass percentage of solid components in the positive electrode slurry, the mass percentage of lithium iron phosphate is 97.70wt%, the mass percentage of conductive carbon black is 0.2wt%, the mass percentage of carbon nanotubes is 0.4wt%, the mass percentage of polyvinylidene fluoride is 1.5wt%, and the mass percentage of dispersant is 0.2wt%. All other contents are the same as in Example 1.

[0087] Example 10

[0088] The only difference between this embodiment and Embodiment 1 is that the vacuum stirring process in steps (1), (2), and (3) of the positive electrode slurry preparation method in this embodiment is omitted, and the dispersion process is carried out directly. All other contents are the same as in Embodiment 1.

[0089] Example 11

[0090] The only difference between this embodiment and Embodiment 1 is that the dispersion process in steps (1), (2), and (3) of the positive electrode slurry preparation method in this embodiment is omitted, and only the vacuum stirring process is performed. All other contents are the same as in Embodiment 1.

[0091] Example 12

[0092] The only difference between this embodiment and Example 1 is that in the preparation method of the positive electrode slurry, lithium iron phosphate, conductive carbon black, carbon nanotubes, polyvinylidene fluoride, dispersant, and N-methylpyrrolidone are directly stirred under vacuum at a speed of 250 rpm for 30 minutes, followed by dispersion for 40 minutes at a speed of 1500 rpm to obtain the positive electrode slurry. All other aspects are the same as in Example 1.

[0093] Comparative Example 1

[0094] The only difference between this comparative example and Example 1 is that the chemical formula of the dispersant is: The rest of the content is the same as in Example 1.

[0095] Comparative Example 2

[0096] The only difference between this comparative example and Example 1 is that the chemical formula of the dispersant is: The rest of the content is the same as in Example 1.

[0097] Comparative Example 3

[0098] The only difference between this comparative example and Example 1 is that the chemical formula of the dispersant is: The rest of the content is the same as in Example 1.

[0099] Comparative Example 4

[0100] The only difference between this comparative example and Example 1 is that the dispersant is polyvinyl alcohol. All other aspects are the same as in Example 1.

[0101] Comparative Example 5

[0102] The only difference between this comparative example and Example 1 is that the dispersant is omitted. All other aspects are the same as in Example 1.

[0103] Performance testing

[0104] (1) Viscosity test: The positive electrode slurry provided in the above examples and comparative examples was subjected to viscosity tests at time intervals of 0h, 4h and 24h.

[0105] (2) Peel force test of electrode: The positive electrode slurry provided in the above examples and comparative examples is coated on aluminum foil and made into positive electrode sheets. The cold-pressed electrode sheets are then subjected to peel force test using a universal tensile testing machine.

[0106] The test results are as follows:

[0107] Table 1

[0108]

[0109] The positive electrode slurries provided in the above examples and comparative examples were coated onto aluminum foil to form positive electrode sheets. These sheets were then assembled with negative electrode sheets containing artificial graphite as the active material, a separator, and an electrolyte solution of 1 mol / L LiPF6 dissolved in EC and DMC solvents (volume ratio 3:7) to form a lithium-ion battery. The energy density and fast-charging performance of the prepared lithium-ion batteries were tested using the following testing process:

[0110] The assembled lithium-ion battery was fully charged at 0.5C constant current and constant voltage to 3.65V, then discharged at 0.5C constant current to 2.5V, for 3 cycles. The discharge capacity of the last cycle was taken as Q0, and the discharge energy as W0. Then, it was fully charged at 0.5C and discharged at 1C constant current to 2.5V, with a discharge capacity of Q1. Then, it was fully charged at 0.5C and discharged at 2C constant current to 2.5V, with a discharge capacity of Q2. Finally, it was fully charged at 0.5C and discharged at 3C constant current to 2.5V, with a discharge capacity of Q3. The cell weight is m0, energy density = W0 / m0, capacity retention rate at 1C = Q1 / Q0, and capacity retention rate at 3C = Q3 / Q0.

[0111] The test results are shown in Table 2.

[0112] Table 2

[0113]

[0114]

[0115] The test results show that:

[0116] (1) As can be seen from Examples 1 to 7, the dispersant in the positive electrode slurry provided by the present invention contains amino, ether bonds and sulfonate groups. The various functional groups in the dispersant work together to improve the dispersibility and dispersion stability of the positive electrode slurry and enhance the adhesion between the positive electrode material and the current collector, thereby effectively solving the problem of difficult dispersion of positive electrode slurry in lithium-ion fast charging battery and improving the electrochemical performance of the battery.

[0117] (2) By comparing Examples 1 and Examples 8-9, it can be seen that if the mass ratio of the dispersant is too low, the dispersion and dispersion stability of the positive electrode slurry will decrease, the peeling force of the positive electrode sheet will decrease, and the electrochemical performance of the battery will decrease; if the mass ratio of the dispersant is too high, the conductivity will be reduced, and too much dispersant will crowd out the content of the positive electrode active material, thereby affecting the electrical performance.

[0118] (3) By comparing Example 1 and Example 10-11, it can be seen that if the vacuum stirring process of steps (1)-(3) is omitted in this invention, water will be introduced, which will affect the performance of the slurry; if the dispersion process is omitted, uneven dispersion will occur, which will affect the performance of the slurry.

[0119] (4) By comparing Example 1 and Example 12, it can be seen that if the solid components of the positive electrode slurry and the solvent are directly mixed together, the dispersion effect of the positive electrode slurry will be worse and the electrochemical performance of the obtained positive electrode sheet will decrease.

[0120] (5) As can be seen from the comparison between Example 1 and Comparative Examples 1-5, the dispersant of the present invention has amino, ether, and sulfonate groups, and has a better dispersion effect and dispersion stability. If any functional group of amino, ether, or sulfonate groups is omitted, or directly replaced with conventional polyvinyl alcohol dispersant, or even the addition of dispersant is omitted, the dispersibility and dispersion stability of the positive electrode slurry will decrease, the peeling force of the electrode sheet will decrease significantly, and the electrochemical performance of the assembled lithium-ion battery will deteriorate.

[0121] In summary, the positive electrode slurry provided by this invention introduces specific dispersants with multiple functional groups, including amino, sulfonate, and ether groups. The amino groups in the dispersant possess a certain degree of polarity and alkalinity, providing additional charge within the dispersant molecules and promoting the stability of the dispersion system. Furthermore, the amino groups can form coordination bonds with metal ions on the current collector surface, thereby enhancing the adhesion between the positive electrode material and the current collector. The ether groups introduced into the dispersant enhance the flexibility of the dispersant molecules, allowing them to better adapt to particle surfaces of different shapes and sizes, thus improving the dispersion effect. The sulfonate groups introduced into the dispersant provide a large amount of negative charge, enhancing the charge shielding effect of the dispersant and further improving the stability of the dispersant system. Through the interaction of the various specific functional groups of the dispersant introduced into the positive electrode slurry, the dispersibility and dispersion stability of the positive electrode slurry are jointly improved, as well as the adhesion between the positive electrode material and the current collector is enhanced, effectively solving the problem of difficult dispersion of positive electrode slurries for fast-charging lithium-ion batteries, while simultaneously improving the electrochemical performance of the battery.

[0122] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A positive electrode slurry, characterized in that, The positive electrode slurry comprises a solid component and a solvent. The solid component includes a positive electrode active material, a conductive agent, a binder, and a dispersant. The functional groups in the dispersant include amino, sulfonate, and ether groups. The dispersant includes , or Any one or at least two of them.

2. The positive electrode slurry according to claim 1, characterized in that, Based on a solid component mass percentage of 100 wt% in the positive electrode slurry, the dispersant mass percentage is 0.05-0.15 wt%.

3. The positive electrode slurry according to claim 1, characterized in that, The initial viscosity of the positive electrode slurry is 8000~20000 mPa·s.

4. The positive electrode slurry according to claim 1, characterized in that, The positive electrode active material includes lithium iron phosphate and / or lithium manganese iron phosphate.

5. The positive electrode slurry according to claim 1, characterized in that, The particle size D50 of the positive electrode active material is 400-500 nm.

6. The positive electrode slurry according to claim 1, characterized in that, Based on a solid component mass percentage of 100 wt% in the positive electrode slurry, the positive electrode active material mass percentage is 95-98 wt%.

7. The positive electrode slurry according to claim 1, characterized in that, The conductive agent includes any one or a combination of at least two of conductive carbon black, conductive graphite, carbon nanotubes, graphene, or carbon fiber.

8. The positive electrode slurry according to claim 7, characterized in that, The conductive agent is a combination of conductive carbon black and carbon nanotubes.

9. The positive electrode slurry according to claim 8, characterized in that, The mass ratio of the conductive carbon black to the carbon nanotubes is (0.2-0.5):(0.3-0.5).

10. The positive electrode slurry according to claim 1, characterized in that, With the solid component in the positive electrode slurry having a mass percentage of 100 wt%, the conductive agent has a mass percentage of 0.5-1 wt%.

11. The positive electrode slurry according to claim 1, characterized in that, The adhesive includes any one or a combination of at least two of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, sodium carboxymethyl cellulose, or styrene-butadiene rubber.

12. The positive electrode slurry according to claim 1, characterized in that, With the solid component in the positive electrode slurry having a mass percentage of 100 wt%, the binder has a mass percentage of 1-2 wt%.

13. The positive electrode slurry according to claim 1, characterized in that, The solvent includes N-methylpyrrolidone.

14. The positive electrode slurry according to claim 1, characterized in that, In the positive electrode slurry, the mass ratio of the solid component to the solvent is 1:(3-5).

15. A method for preparing a positive electrode slurry according to any one of claims 1-14, characterized in that, The preparation method includes the following steps: (1) The binder and solvent are mixed for the first time to obtain a first dispersion; (2) The first dispersion, the conductive agent, and the dispersant are mixed for the second time to obtain a second dispersion; The functional groups in the dispersant include amino, sulfonate, and ether groups; (3) The second dispersion and the positive electrode active material are mixed for the third time to obtain the positive electrode slurry.

16. The preparation method according to claim 15, characterized in that, The first mixture, the second mixture, and the third mixture each independently include vacuum stirring and / or dispersion.

17. The preparation method according to claim 16, characterized in that, During the first mixing, the second mixing, and the third mixing processes, the rotational speed of the vacuum stirring is independently selected from 150-350 rpm.

18. The preparation method according to claim 16, characterized in that, During the first mixing, the second mixing, and the third mixing processes, the dispersion rotation speed is independently selected from 1000-2000 rpm.

19. A positive electrode plate, characterized in that, The positive electrode sheet is prepared using the positive electrode slurry as described in any one of claims 1-14.

20. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet as described in claim 19.

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