An aqueous cathode slurry for lithium ion batteries and its preparation method

Abstract

The present invention belongs to the technical field of lithium-ion battery slurries, and specifically relates to a lithium-ion battery aqueous positive electrode slurry and a preparation method thereof. The components include 50-60 parts of positive electrode active material, 6-10 parts of carbon nanotube dispersion, 1-5 parts of conductive agent, 1-3 parts of aqueous binder, and 40-50 parts of deionized water. In the present invention, deionized water is used as a solvent to increase the fluidity of carbon nanotubes (CNTs), reduce the viscosity of CNTs, and reduce environmental pollution. Then, a certain proportion of polyisobutenyl succinimide and α-olefin sulfonate are added to improve the dispersion stability of CNTs, reduce the fluidity of the slurry, increase the friction coefficient of the dispersion axis, and prevent CNTs from adhering to the binder and forming agglomerates. The prepared lithium-ion battery aqueous positive electrode slurry has good consistency, high stability, and is not prone to sedimentation.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery slurries, and particularly relates to an aqueous cathode slurry for lithium-ion batteries and a preparation method thereof. Background Art

[0002] In recent years, due to the pressure of environmental pollution and energy shortage, countries have been forced to strive to find new green, environmentally friendly, and sustainable energy sources. The green high-energy environmentally friendly lithium-ion battery that emerged in the 1990s has become one of the most prominent power sources due to its high energy density, long cycle life, high working voltage, and other advantages. A lithium-ion battery is a secondary rechargeable battery that mainly relies on the movement of lithium ions between the positive electrode and the negative electrode to work. That is, during the charging and discharging process, Li + intercalates and deintercalates between the two electrodes back and forth: during charging, Li + deintercalates from the positive electrode and intercalates into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; during discharging, it is the opposite.

[0003] The positive electrode is one of the most important components of a lithium-ion battery, which determines the core electrochemical performance of the battery. The battery cell of a lithium-ion battery requires the positive electrode sheet to have excellent electrical conductivity. At present, battery manufacturers all add conductive agents such as carbon black, graphite, or carbon nanofibers to the cathode slurry to improve the electrical conductivity between the active substances and between the active substances and the current collector. Carbon nanotubes (CNT) are emerging conductive agents in recent years. It generally has a diameter of about 5 nanometers and a length of 10 - 20 micrometers. It can not only act as a "wire" in the conductive network, but also has a double-layer capacitance effect, exerting the high-rate characteristics of a supercapacitor; in addition, its good thermal conductivity is also beneficial to the heat dissipation of the lithium battery during charging and discharging, reducing the polarization of the battery, improving the high and low temperature performance of the battery, and extending the battery life. However, CNT has a large specific surface area and is prone to agglomeration, and it is not easy to disperse uniformly in the solvent.

[0004] A reasonable cathode formula and its preparation process are also the primary conditions for the performance of a lithium battery to be exerted. At present, according to the type of solvent and processing technology in the cathode formula slurry, the positive electrode can be divided into an oil-based system (using NMP as the solvent) and an aqueous system (using deionized water as the solvent). The aqueous system process is favored by most lithium battery cell factories because it does not involve solvent recovery and environmental pollution problems, and has the advantages of low price and less environmental restriction on homogenization. However, solid substances such as conductive agents and cathode active substances in the aqueous cathode slurry are not easy to disperse uniformly, resulting in poor consistency and low stability of the aqueous cathode slurry, and easy sedimentation, thus leading to a small reversible capacity of the battery and poor cycle performance, greatly affecting the battery capacity and cycle life. Especially after adding carbon nanotubes, the carbon nanotubes are extremely prone to agglomeration and are difficult to disperse in deionized water.

[0005] Therefore, it is necessary to develop a method in this field to uniformly mix each component to obtain a long-life lithium battery cathode slurry with excellent performance. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies of the prior art and provide an aqueous cathode slurry with uniformly dispersed carbon nanotubes, good consistency and high stability.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] An aqueous cathode slurry for lithium-ion batteries, comprising 50-60 parts of a cathode active material, 6-10 parts of a carbon nanotube dispersion, 1-5 parts of a conductive agent, 1-3 parts of an aqueous binder, and 40-50 parts of deionized water.

[0009] Preferably, the cathode active material is selected from one of lithium cobaltate, lithium iron phosphate and lithium manganate.

[0010] Preferably, the components of the carbon nanotube dispersion include carbon nanotubes, polyisobutenyl succinimide and α-olefin sulfonate, and the mass concentration of the carbon nanotube dispersion is 5.2% wt.

[0011] Preferably, the content ratio of the carbon nanotubes, polyisobutenyl succinimide and α-olefin sulfonate is 86-98:0.5-1.5:0.01-0.5.

[0012] Preferably, the carbon nanotube dispersion is prepared by dispersing each raw material component and purified water in an ultrasonic homogenizer at room temperature.

[0013] Preferably, the conductive agent is a composition mixture of graphene, Ketjen black and Super-P, wherein the content ratio of the graphene, Ketjen black and Super-P is 45-65:15-25:20-30.

[0014] Preferably, the aqueous binder is a composite composed of sodium polyacrylate, styrene-butadiene latex and LA132, wherein the content ratio of the sodium polyacrylate, styrene-butadiene latex and LA132 is 25-35:30-40:25-35.

[0015] Based on a general inventive concept, another object of the present invention is to provide a preparation method of the above-mentioned aqueous cathode slurry for lithium-ion batteries, comprising the following steps:

[0016] (1) Add the aqueous binder and 1 / 2 of the deionized water to a double planetary mixer and stir for 20-40 min. The dispersion speed of the double planetary mixer is 500 ± 2 rpm and the revolution speed is 20 ± 1 rpm;

[0017] (2) Add the positive electrode active material, carbon nanotube dispersion, and 1 / 2 of the conductive agent to the mixed material in step (1) and stir for 20 - 40 min;

[0018] (3) Add the remaining 1 / 2 of the conductive agent to the mixed material in step (2). The double planetary mixer first stirs at a low speed with a dispersion speed of 350 rpm and a revolution speed of 5 rpm for 10 - 20 min, then stirs at a high speed with a dispersion speed of 1050 rpm and a revolution speed of 35 rpm for 20 - 30 min, and then stirs at a dispersion speed of 4000 rpm and a revolution speed of 25 rpm for 3 - 5 h;

[0019] (4) Add the remaining 1 / 2 of deionized water to the mixed material in step (3) to make the solid content in the material 50 - 60%, and stir at a dispersion speed of 4000 ± 10 rpm and a revolution of 25 ± 1 rpm for 20 - 40 min to make the viscosity of the material 5200 - 6800 Mpa·s;

[0020] (5) Turn off the high - speed dispersion stirring, stir at a low - speed positive and reverse rotation of 10 ± 1 rpm, and at the same time evacuate the inner barrel to a vacuum and keep the pressure for 5 - 10 min, then let it stand for 30 - 50 min to defoam, and obtain the aqueous positive electrode slurry.

[0021] In the present invention, deionized water is used as a solvent to increase the fluidity of carbon nanotubes CNT, reduce the viscosity of CNT, and reduce environmental pollution. Then, a certain proportion of polyisobutylene succinimide and α - olefin sulfonate are added to improve the dispersion stability of carbon nanotubes CNT, reduce the fluidity of the slurry, increase the friction coefficient of the dispersion shaft, and prevent CNT from adhering to the binder to form agglomerates; the carbon nanotubes and the mixed conductive agent form a long - and short - range conductive network, improving the conductivity and reducing the dosage of the conductive agent; in addition, in the preparation method of the present invention, a double planetary mixer is used to batch - stir and mix the materials, achieving a short stirring time and uniform mixing, so that CNT is evenly dispersed in the aqueous slurry, thereby improving the conductivity of the slurry.

[0022] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0023] (1) Small environmental pollution and low production cost. The lithium - ion battery prepared with this aqueous positive electrode slurry of lithium - ion battery has good energy density and cycle performance;

[0024] (2) The process steps are simple, highly feasible, and suitable for large - scale industrial production;

[0025] (3) The prepared aqueous positive electrode slurry of lithium - ion battery has good consistency, high stability, and is not easy to settle. Detailed implementation mode

[0026] To make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in conjunction with specific embodiments. However, the present invention is not limited to these embodiments. It should be noted that, on the premise of non-conflict, the following-described embodiments or technical features may be arbitrarily combined to form new embodiments. In the present invention, unless otherwise specified, all parts and percentages are in mass units, and the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following embodiments are conventional methods in the art unless otherwise specified.

[0027] As used herein, the terms "comprising", "including", "containing" or any other variation thereof are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article or apparatus containing the recited elements is not necessarily limited to those elements but may include other elements not expressly listed or elements inherent to such composition, step, method, article or apparatus.

[0028] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the ranges are separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted to include the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0029] Example 1

[0030] An aqueous cathode slurry for a lithium-ion battery comprises components in the following parts by content: 55 parts of a cathode active material, 8 parts of a carbon nanotube dispersion, 3 parts of a conductive agent, 2 parts of an aqueous binder, and 45 parts of deionized water.

[0031] The cathode active material is lithium iron phosphate.

[0032] The components of the carbon nanotube dispersion include carbon nanotubes, polyisobutenyl succinimide, and α-olefin sulfonate, and the mass concentration of the carbon nanotube dispersion is 5.2% wt.

[0033] The content parts ratio among the carbon nanotubes, polyisobutenyl succinimide, and α-olefin sulfonate is 92:1.0:0.1.

[0034] The carbon nanotube dispersion is prepared by dispersing each raw material component and purified water in an ultrasonic homogenizer at room temperature of 25°C.

[0035] The conductive agent is a composition mixture of graphene, Ketjen black, and Super-P. Among them, the content ratio of graphene, Ketjen black, and Super-P is 55:20:25.

[0036] The aqueous binder is a composite composed of sodium polyacrylate, styrene-butadiene latex, and LA132. Among them, the content ratio of sodium polyacrylate, styrene-butadiene latex, and LA132 is 30:35:30.

[0037] The preparation method of the above-mentioned aqueous cathode slurry for lithium-ion batteries includes the following steps:

[0038] (1) Add the aqueous binder and 1 / 2 deionized water to a double planetary mixer and stir for 30 min. The dispersion speed of the double planetary mixer is 500 ± 2 rpm, and the revolution speed is 20 ± 1 rpm;

[0039] (2) Add the cathode active material, carbon nanotube dispersion, and 1 / 2 conductive agent to the mixed material in step (1) and stir for 30 min;

[0040] (3) Add the remaining 1 / 2 conductive agent to the mixed material in step (2). The double planetary mixer first stirs at a low speed of 350 rpm for the dispersion speed and 5 rpm for the revolution speed for 15 min, then stirs at a high speed of 1050 rpm for the dispersion speed and 35 rpm for the revolution speed for 25 min, and then stirs at a dispersion speed of 4000 rpm and a revolution speed of 25 rpm for 4 h;

[0041] (4) Add the remaining 1 / 2 deionized water to the mixed material in step (3) to make the solid content in the material 55%, and stir at a dispersion speed of 4000 ± 10 rpm and a revolution of 25 ± 1 rpm for 30 min to make the viscosity of the material 6000 Mpa·s;

[0042] (5) Turn off the high-speed dispersion stirring, stir at a low speed of 10 ± 1 rpm for the revolution and rotation, and at the same time evacuate the inner barrel to a vacuum (vacuum degree: -80 KPa), keep the pressure for 8 min, and then let it stand for 40 min to defoam, to obtain the aqueous cathode slurry.

[0043] Example 2

[0044] An aqueous cathode slurry for a lithium-ion battery, including 60 parts of cathode active material, 6 parts of carbon nanotube dispersion, 5 parts of conductive agent, 1 part of aqueous binder, and 50 parts of deionized water.

[0045] The cathode active material is lithium cobaltate.

[0046] The components of the carbon nanotube dispersion include carbon nanotubes, polyisobutenyl succinimide, and α-olefin sulfonate. The mass concentration of the carbon nanotube dispersion is 5.2% wt.

[0047] The content parts ratio among the carbon nanotubes, polyisobutenyl succinimide and α-olefin sulfonate is 98∶0.5∶0.5.

[0048] The carbon nanotube dispersion is made by dispersing each raw material component and purified water in an ultrasonic homogenizer at normal temperature of 25°C.

[0049] The conductive agent is a composition mixture of graphene, Ketjen black and Super-P, wherein the content parts ratio of the graphene, Ketjen black and Super-P is 65∶15∶30.

[0050] The aqueous binder is a composite composed of sodium polyacrylate, styrene-butadiene latex and LA132, wherein the content parts ratio of the sodium polyacrylate, styrene-butadiene latex and LA132 is 35∶30∶35.

[0051] The preparation method of the above-mentioned aqueous positive electrode paste for lithium-ion battery includes the following steps:

[0052] (1) Add the aqueous binder and 1 / 2 deionized water to a double planetary mixer and stir for 40 min. The dispersion speed of the double planetary mixer is 500±2 rpm and the revolution speed is 20±1 rpm;

[0053] (2) Add the positive electrode active material, carbon nanotube dispersion and 1 / 2 conductive agent to the mixed material in step (1) and stir for 20 min;

[0054] (3) Add the remaining 1 / 2 conductive agent to the mixed material in step (2). The double planetary mixer first stirs at a low speed of 350 rpm for the dispersion speed and 5 rpm for the revolution speed for 20 min, then stirs at a high speed of 1050 rpm for the dispersion speed and 35 rpm for the revolution speed for 20 min, and then stirs at a dispersion speed of 4000 rpm and a revolution speed of 25 rpm for 5 h;

[0055] (4) Add the remaining 1 / 2 deionized water to the mixed material in step (3) to make the solid content in the material 50%. Stir at a dispersion speed of 4000±10 rpm and a revolution of 25±1 rpm for 40 min to make the viscosity of the material 5200 Mpa·s;

[0056] (5) Turn off the high-speed dispersion stirring, stir at a low speed of 10±1 rpm for the revolution and rotation, and at the same time evacuate the inside of the inner barrel to a vacuum (vacuum degree is -80 KPa), keep the pressure for 10 min, and then let it stand for 30 min to defoam, and obtain the aqueous positive electrode paste.

[0057] Example 3

[0058] An aqueous cathode slurry for a lithium-ion battery, comprising 50 parts of a cathode active material, 10 parts of a carbon nanotube dispersion, 1 part of a conductive agent, 3 parts of an aqueous binder, and 40 parts of deionized water.

[0059] The cathode active material is lithium cobalt manganese oxide.

[0060] The components of the carbon nanotube dispersion include carbon nanotubes, polyisobutenyl succinimide, and α-olefin sulfonate, and the mass concentration of the carbon nanotube dispersion is 5.2% wt.

[0061] The content ratio of the carbon nanotubes, polyisobutenyl succinimide, and α-olefin sulfonate is 86:1.5:0.01.

[0062] The carbon nanotube dispersion is prepared by dispersing each raw material component and purified water in an ultrasonic homogenizer at room temperature of 25°C.

[0063] The conductive agent is a composition mixture of graphene, Ketjen black, and Super-P, wherein the content ratio of the graphene, Ketjen black, and Super-P is 45:25:20.

[0064] The aqueous binder is a composite composed of sodium polyacrylate, styrene-butadiene latex, and LA132, wherein the content ratio of the sodium polyacrylate, styrene-butadiene latex, and LA132 is 25:40:25.

[0065] The preparation method of the above-mentioned aqueous cathode slurry for a lithium-ion battery comprises the following steps:

[0066] (1) Add the aqueous binder and 1 / 2 of the deionized water to a double planetary mixer and stir for 20 min. The dispersion speed of the double planetary mixer is 500 ± 2 rpm, and the revolution speed is 20 ± 1 rpm;

[0067] (2) Add the cathode active material, the carbon nanotube dispersion, and 1 / 2 of the conductive agent to the mixed material in step (1) and stir for 40 min;

[0068] (3) Add the remaining 1 / 2 of the conductive agent to the mixed material in step (2). The double planetary mixer first stirs at a low speed of 350 rpm for the dispersion speed and 5 rpm for the revolution speed for 10 min, then stirs at a high speed of 1050 rpm for the dispersion speed and 35 rpm for the revolution speed for 30 min, and then stirs at a dispersion speed of 4000 rpm and a revolution speed of 25 rpm for 3 h;

[0069] (4) Add the remaining 1 / 2 of the deionized water to the mixed material in step (3) to make the solid content in the material 60%. Stir at a dispersion speed of 4000 ± 10 rpm and a revolution of 25 ± 1 rpm for 20 min to make the viscosity of the material 6800 Mpa·s;

[0070] (5) Turn off the high-speed dispersion stirring, stir at a low speed of 10 ± 1 rpm in both forward and reverse directions, and at the same time evacuate the inner barrel to a vacuum (vacuum degree: -80 KPa) and keep the pressure for 5 min, then let it stand for 50 min to defoam, and obtain the aqueous positive electrode paste.

[0071] Comparative Example 1

[0072] The component of the carbon nanotube dispersion is carbon nanotubes, and the mass concentration of the carbon nanotube dispersion is 5.2% wt; other conditions and preparation methods are the same as those in Example 1.

[0073] Comparative Example 2

[0074] The components of the carbon nanotube dispersion include carbon nanotubes and polyisobutenyl succinimide, the mass concentration of the carbon nanotube dispersion is 5.2% wt, and the content ratio between the carbon nanotubes and polyisobutenyl succinimide is 92:1.0; other conditions and preparation methods are the same as those in Example 1.

[0075] Comparative Example 3

[0076] The components of the carbon nanotube dispersion include carbon nanotubes and α-olefin sulfonate, the mass concentration of the carbon nanotube dispersion is 5.2% wt, and the content ratio between the carbon nanotubes and α-olefin sulfonate is 92:0.1; other conditions and preparation methods are the same as those in Example 1.

[0077] Comparative Example 4

[0078] The components of the carbon nanotube dispersion include carbon nanotubes, polyisobutenyl succinimide and α-olefin sulfonate, and the mass concentration of the carbon nanotube dispersion is 5.1% wt; other conditions and preparation methods are the same as those in Example 1.

[0079] Comparative Example 5

[0080] The components of the carbon nanotube dispersion include carbon nanotubes, polyisobutenyl succinimide and α-olefin sulfonate, and the mass concentration of the carbon nanotube dispersion is 5.3% wt; other conditions and preparation methods are the same as those in Example 1.

[0081] Comparative Example 6

[0082] The conductive agent is a composition mixture of Ketjen black and Super-P, wherein the content ratio of Ketjen black to Super-P is 60:40, and other conditions and preparation methods are the same as those in Example 1; other conditions and preparation methods are the same as those in Example 1.

[0083] Comparative Example 7

[0084] The aqueous binder is a composite composed of sodium polyacrylate and styrene-butadiene latex. Among them, the content ratio of sodium polyacrylate to styrene-butadiene latex is 30:65; other conditions and preparation methods are the same as those in Example 1.

[0085] Comparative Example 8

[0086] The aqueous binder is a composite composed of sodium polyacrylate and LA132. Among them, the content ratio of sodium polyacrylate to LA132 is 30:60; other conditions and preparation methods are the same as those in Example 1.

[0087] Comparative Example 9

[0088] The aqueous binder is a composite composed of styrene-butadiene latex and LA132. Among them, the content ratio of styrene-butadiene latex to LA132 is 45:40; other conditions and preparation methods are the same as those in Example 1.

[0089] Comparative Example 10

[0090] An aqueous cathode slurry for a lithium-ion battery comprises the following components in parts by content: 55 parts of a cathode active material, 8 parts of a carbon nanotube dispersion, 3 parts of a conductive agent, 2 parts of an aqueous binder, and 45 parts of deionized water.

[0091] The cathode active material is lithium iron phosphate.

[0092] The components of the carbon nanotube dispersion include carbon nanotubes, polyisobutenyl succinimide, and α-olefin sulfonate, and the mass concentration of the carbon nanotube dispersion is 5.2% wt.

[0093] The content ratio among the carbon nanotubes, polyisobutenyl succinimide, and α-olefin sulfonate is 92:1.0:0.1.

[0094] The carbon nanotube dispersion is prepared by dispersing each raw material component and purified water in an ultrasonic homogenizer at room temperature of 25°C.

[0095] The conductive agent is a composition mixture of graphene, Ketjenblack, and Super-P. Among them, the content ratio of graphene, Ketjenblack, and Super-P is 55:20:25.

[0096] The aqueous binder is a composite composed of sodium polyacrylate, styrene-butadiene latex, and LA132. Among them, the content ratio of sodium polyacrylate, styrene-butadiene latex, and LA132 is 30:35:30.

[0097] The preparation method of the above-mentioned aqueous cathode slurry for a lithium-ion battery comprises the following steps:

[0098] (1) Add the carbon nanotube dispersion, conductive agent, and 1 / 5 deionized water to a double planetary mixer and stir for 30 min. The dispersion speed of the double planetary mixer is 500 ± 2 rpm, and the revolution speed is 20 ± 1 rpm;

[0099] (2) Add 3 / 5 of the positive electrode active material to the mixed material in step (1) and stir for 30 min. Then add the remaining positive electrode active material and 1 / 5 deionized water and stir for 30 min;

[0100] (3) Add an aqueous binder to the mixed material in step (2). The double planetary mixer first stirs at a low speed of 350 rpm for the dispersion speed and 5 rpm for the revolution speed for 15 min, then stirs at a high speed of 1050 rpm for the dispersion speed and 35 rpm for the revolution speed for 25 min, and then stirs at a dispersion speed of 4000 rpm and a revolution speed of 25 rpm for 4 h;

[0101] (4) Add the remaining deionized water to the mixed material in step (3) to make the solid content in the material 55%. Stir at a dispersion speed of 4000 ± 10 rpm and a revolution of 25 ± 1 rpm for 30 min to make the viscosity of the material 6000 Mpa·s;

[0102] (5) Turn off the high-speed dispersion stirring, stir at a low-speed revolution and rotation of 10 ± 1 rpm, and at the same time evacuate the inner barrel to a vacuum (vacuum degree of -80 KPa), keep the pressure for 8 min, and then let it stand for 40 min to defoam to obtain an aqueous positive electrode slurry.

[0103] After testing the aqueous positive electrode slurries of lithium-ion batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 10 after standing for 48 h, the solid content of the slurries was used to characterize the stability of the slurries. It was found that after 48 h, the change rate of the solid content of the slurries in Examples 1 to 3 was less than 2.5%, while the change rate of the solid content of the slurries in Comparative Examples 1 to 10 was greater than 10%. Therefore, the aqueous positive electrode slurry of the lithium-ion battery of the present invention is relatively stable and can meet the application requirements.

[0104] The aqueous positive electrode slurries of lithium-ion batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 10 were made into positive electrode sheets according to the conventional lithium battery positive electrode production process, through coating, drying, rolling, and slitting. Then they were assembled with negative electrode sheets, separators, electrolytes, and battery casings, and 10 Ah batteries were obtained after charge and discharge activation. The energy density, high-temperature life (2C / 2C), and capacity retention rate after 350 charge and discharge cycles of the prepared batteries were tested. The test results are shown in Table 1.

[0105] Table 1 Test results of energy density, high-temperature life (2C / 2C), and capacity retention rate

[0106]

[0107] As can be seen from Table 1, the positive electrode paste prepared by the present invention enables the obtained lithium battery to have an energy density as high as 158.2 Wh / kg, a capacity retention rate of more than 92.5%, and good high-temperature performance. When the mass percentage of specific components in the positive electrode paste is limited outside the scope of the present invention, the performance of the obtained battery is significantly lower than that of the battery prepared by the present invention.

[0108] The above embodiments are only the preferred embodiments of the present invention. Any simple modification, modification and alternative change made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. An aqueous cathode slurry for a lithium-ion battery, characterized in that, 50 - 60 parts of positive electrode active material, 6 - 10 parts of carbon nanotube dispersion, 1 - 5 parts of conductive agent, 1 - 3 parts of water-based binder, 40 - 50 parts of deionized water; the components of the carbon nanotube dispersion include carbon nanotubes, polyisobutylene succinimide and α-olefin sulfonate, and the mass concentration of the carbon nanotube dispersion is 5.2%wt; the content ratio of carbon nanotubes, polyisobutylene succinimide and α-olefin sulfonate is 86 - 98∶0.5 - 1.5∶0.01 - 0.5; The conductive agent is a composition mixture of graphene, Ketjen black and Super-P, wherein the content ratio of graphene, Ketjen black and Super-P is 45 - 65∶15 - 25∶20 - 30; The water-based binder is a composite composed of sodium polyacrylate, styrene-butadiene latex and LA132, wherein the content ratio of sodium polyacrylate, styrene-butadiene latex and LA132 is 25 - 35∶30 - 40∶25 - 35; The preparation method of the water-based positive electrode slurry of the lithium-ion battery includes the following steps: (1) Add the water-based binder and 1 / 2 of the deionized water into a double planetary mixer and stir for 20 - 40 min. The dispersion speed of the double planetary mixer is 500 ± 2 rpm and the revolution speed is 20 ± 1 rpm; (2) Add the positive electrode active material, carbon nanotube dispersion and 1 / 2 of the conductive agent to the mixed material in step (1) and stir for 20 - 40 min; (3) Add the remaining 1 / 2 of the conductive agent to the mixed material in step (2). The double planetary mixer first stirs at a low speed of 350 rpm for the dispersion speed and 5 rpm for the revolution speed for 10 - 20 min, then stirs at a high speed of 1050 rpm for the dispersion speed and 35 rpm for the revolution speed for 20 - 30 min, and then stirs at a dispersion speed of 4000 rpm and a revolution speed of 25 rpm for 3 - 5 h; (4) Add the remaining 1 / 2 of the deionized water to the mixed material in step (3) to make the solid content in the material 50 - 60%, and stir at a dispersion speed of 4000 ± 10 rpm and a revolution of 25 ± 1 rpm for 20 - 40 min to make the viscosity of the material 5200 - 6800 Mpa·s; (5) Turn off the high-speed dispersion stirring, stir at a low speed of revolution and rotation of 10 ± 1 rpm, and at the same time evacuate the inner barrel to vacuum and keep the pressure for 5 - 10 min, then let it stand for 30 - 50 min to remove foam, and obtain the water-based positive electrode slurry.

2. The aqueous cathode slurry for a lithium-ion battery according to claim 1, wherein, The positive electrode active material is selected from one of lithium cobaltate, lithium iron phosphate and lithium manganate.

3. The water-based cathode slurry for a lithium-ion battery according to claim 1, wherein The carbon nanotube dispersion is prepared by dispersing each raw material component and purified water at room temperature in an ultrasonic homogenizer.

4. The preparation method of an aqueous cathode slurry for a lithium-ion battery according to any one of claims 1 to 3, characterized in that, Including the following steps: (1) Add the water-based binder and 1 / 2 of the deionized water into a double planetary mixer and stir for 20 - 40 min. The dispersion speed of the double planetary mixer is 500 ± 2 rpm and the revolution speed is 20 ± 1 rpm; (2) Add the positive electrode active material, carbon nanotube dispersion and 1 / 2 of the conductive agent to the mixed material in step (1) and stir for 20 - 40 min; (3) Add the remaining 1 / 2 of the conductive agent to the mixed material in step (2). The double planetary mixer first stirs at a low speed with a dispersion speed of 350 rpm and a revolution speed of 5 rpm for 10 to 20 minutes, then stirs at a high speed with a dispersion speed of 1050 rpm and a revolution speed of 35 rpm for 20 to 30 minutes, and then stirs at a dispersion speed of 4000 rpm and a revolution speed of 25 rpm for 3 to 5 hours; (4) Add the remaining 1 / 2 of the deionized water to the mixed material in step (3) to make the solid content in the material 50 to 60%. Stir at a dispersion speed of 4000 ± 10 rpm and a revolution of 25 ± 1 rpm for 20 to 40 minutes to make the viscosity of the material 5200 to 6800 Mpa·s; (5) Turn off the high-speed dispersion stirring, stir at a low speed with a forward and reverse rotation of 10 ± 1 rpm, and at the same time evacuate the inner barrel to a vacuum and hold the pressure for 5 to 10 minutes, and then let it stand for 30 to 50 minutes to remove the foam to obtain the aqueous positive electrode slurry.

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