A positive electrode slurry for lithium primary batteries, a method for preparing the same, and use thereof

Abstract

The application discloses a preparation method and application of a lithium primary battery positive electrode slurry. First, a binder is added into an organic solvent for dissolution, and carbon nanofibers are added to prepare a conductive glue solution; meanwhile, carbon fluoride and manganese dioxide are dry-mixed to obtain a dry-mixed material; then, the conductive glue solution is added into the dry-mixed material for mud-like kneading stirring; conductive carbon black slurry is added twice for stirring and mixing; finally, the viscosity is adjusted by adding an organic solvent, and vacuum degassing is performed to complete the preparation of the slurry. Through the design of the adding sequence and adding mode of the materials, and through the selection of specific conductive agents and the control of the adding mode of the conductive agents, the dispersibility of the materials is remarkably improved, the agglomeration problems among the carbon fluoride, the conductive agents and the binder are avoided, and the poor sedimentation stability problem caused by the large difference between the physical and chemical properties of the carbon fluoride and the manganese dioxide is avoided, so that the prepared positive electrode slurry is uniform and stable, and the rate discharge performance of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a method for preparing and applying a positive electrode slurry for primary lithium batteries. Background Technology

[0002] Lithium-ion primary batteries are disposable batteries using metallic lithium or lithium alloys as the negative electrode. They possess advantages such as high specific energy, high operating voltage, wide operating temperature range, excellent storage performance, convenient use and portability, and maintenance-free operation. With the development of lithium battery technology and battery material technology, there is a growing demand for high specific energy and high power in lithium batteries. Lithium / carbon fluoride primary batteries are a type of solid-state lithium battery with a theoretical specific energy of approximately 2189 Wh / kg (currently, the actual specific energy can reach 600–800 Wh / kg), making it the battery system with the highest specific energy among solid-state cathode systems. However, current lithium / carbon fluoride primary batteries still suffer from problems such as voltage lag, poor high-current discharge capability, high heat generation, and high cost.

[0003] Lithium / manganese dioxide primary batteries possess a series of advantages, including high plateau voltage, no significant voltage hysteresis, good rate performance, low heat generation, and low cost. Currently, the main approach to addressing the existing technical problems and difficulties of lithium / carbon fluoride primary batteries is to incorporate materials such as manganese dioxide into the positive electrode material, fluoride, to achieve a certain degree of improvement. However, due to differences in the physicochemical properties of the raw materials, such as the particle size (2–4 μm) and specific surface area (400–600 m²) of fluoride... 2 / g), tap density (0.8~1g / m³) 3 The particle size (20–30 μm) and specific surface area (20–30 m²) of manganese dioxide are compared with those of manganese dioxide. 2 / g), tap density (2~2.5g / m³) 3 The significant differences between these two materials make it difficult to achieve good dispersion with conductive agents during the slurry mixing process. This leads to agglomeration of the cathode material, poor sedimentation stability of the slurry, and ultimately, a severe impact on the battery's electrical performance. Therefore, it is necessary to develop a method for preparing a slurry for a carbon fluoride and manganese dioxide cathode composite system to improve the battery's electrical performance. Summary of the Invention

[0004] To address the problem in existing technologies where fluorinated carbon and manganese dioxide cannot be fully mixed with conductive agents during the slurry mixing process, resulting in poor battery performance, this invention provides a method for preparing and applying a positive electrode slurry for primary lithium batteries. By controlling the order of material addition, the mixing method, and selecting specific conductive agents in the slurry mixing process, this invention improves the dispersion effect between active materials such as fluorinated carbon and manganese dioxide and the conductive agent, forming a stable conductive network within the electrode. This improves the precipitation stability of the slurry, thereby facilitating the full utilization of the capacity of the fluorinated carbon material and the final battery performance.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a positive electrode slurry for a primary lithium battery, comprising the following steps:

[0007] S1, add the adhesive to the first part of the organic solvent and mix evenly to obtain the pre-adhesive solution; add carbon nanofibers to the pre-adhesive solution and mix evenly to obtain the conductive adhesive solution;

[0008] S2, mix fluorinated carbon and manganese dioxide evenly to obtain a dry mixture;

[0009] S3, the dry mixture is added to the conductive adhesive liquid in batches, and after each batch of dry mixture is mixed evenly, high-speed mud-like stirring is performed to obtain conductive mud.

[0010] S4. Add the conductive carbon black slurry to the conductive clay in batches, mix evenly, add the second part of organic solvent to adjust to the preset viscosity, and defoam under vacuum to obtain the lithium primary battery positive electrode slurry.

[0011] Compared with existing technologies, the method for preparing lithium primary battery cathode slurry provided by this invention has the following beneficial effects:

[0012] 1. Select carbon nanofibers, which have good compatibility with fluorinated carbon with small particle size, as a conductive agent, and pre-disperse and mix the carbon nanofibers with the binder evenly. This is beneficial for the subsequent full coating of fluorinated carbon materials and avoids the agglomeration of small-diameter fluorinated carbon particles. In addition, carbon nanofibers can also form conductive bridges and wires in the positive electrode slurry, which helps to reduce the resistance of the electrode sheet and improve the discharge performance of the battery.

[0013] 2. Since fluorinated carbon and manganese dioxide have significantly different physicochemical properties, physical dry mixing can be used to fully mix the two materials, thereby improving the uniformity of the two materials in the slurry system.

[0014] 3. Fluorocarbon has a small particle size and a high specific surface area, making it prone to agglomeration with binders and conductive agents. By dry mixing fluorocarbon with manganese dioxide and then adding it in batches to the conductive adhesive containing carbon nanofibers, the agglomeration of fluorocarbon is reduced. Furthermore, by adding only a portion of organic solvent to S1, the entire dry mixture can be mixed with the conductive adhesive to form a high-solids-content mud-like material. The shear force of high-speed mud-like stirring breaks up the agglomerated fluorocarbon material. Under high-speed mud-like stirring, fluorocarbon, carbon dioxide, and conductive agents are fully mixed and dispersed evenly, which is conducive to maximizing the capacity efficiency of fluorocarbon materials.

[0015] 4. Carbon nanofibers are pre-mixed with manganese dioxide and fluorinated carbon to form uniform conductive bridges in the system. Then, conductive carbon black slurry is added in batches, allowing the conductive carbon black to distribute conductive nodes within the conductive bridges formed by the carbon nanofibers, thereby forming a conductive network. This effectively improves the electron migration rate of the positive electrode slurry, thus significantly improving the rate performance of the battery. At the same time, adding the conductive carbon black in batches can prevent agglomeration between the conductive carbon black and carbon nanofibers, fluorinated carbon, etc., ensuring that the conductive carbon black is uniformly dispersed in the slurry system, thereby effectively reducing the resistance of the electrode sheet and improving the rate discharge performance of the battery.

[0016] Furthermore, the adhesive is polyvinylidene fluoride.

[0017] Furthermore, the organic solvent is N-methylpyrrolidone.

[0018] Furthermore, the lithium primary battery positive electrode slurry comprises the following raw material components in the following mass percentages: 20%–26% fluorinated carbon, 20%–26% manganese dioxide, 1.4%–1.6% conductive carbon black, 0.235%–0.26% carbon nanofibers, 2.2%–2.3% binder, and the balance being organic solvent, with the total mass content of all components being 100%.

[0019] Furthermore, in S1, the binder and the first part of the organic solvent are mixed evenly by a stirring method of first low speed and then high speed. The low speed has a general speed of 10 rpm to 15 rpm, a self speed of 500 rpm to 1000 rpm, and a stirring time of 10 min to 15 min. The high speed has a general speed of 35 rpm to 50 rpm, a self speed of 3500 rpm to 5000 rpm, and a stirring time of 4 h to 6 h.

[0020] Furthermore, in S1, the pre-adhesive solution and carbon nanofibers are mixed evenly by first using a vacuum high-speed and then a vacuum low-speed stirring method. The vacuum high-speed stirring method has a common rotation speed of 35 rpm to 50 rpm, a self-rotation speed of 3500 rpm to 5000 rpm, and a stirring time of 2 h to 3 h. The vacuum low-speed stirring method has a common rotation speed of 10 rpm to 15 rpm, a self-rotation speed of 0 rpm, and a stirring time of 30 min to 40 min.

[0021] The preferred stirring and mixing method is beneficial for the uniform dispersion of carbon nanofibers in the organic solvent, which in turn facilitates the subsequent coating of fluorinated carbon particles by the carbon nanofibers and reduces the agglomeration problem of fluorinated carbon particles.

[0022] Furthermore, in S1, the amount of the first portion of organic solvent added is 9 to 16 times the mass of the binder.

[0023] The optimal amount of organic solvent added is beneficial for achieving mud-like kneading and mixing under high solid content in step S3. This allows the shear force of the mud-like material under mixing conditions to break up the already agglomerated fluorinated carbon material, promoting the full dispersion of fluorinated carbon, manganese dioxide, and carbon nanofibers, and improving the mixing uniformity of the material.

[0024] Further, S2 specifically involves adding fluorinated carbon and manganese dioxide into a dry mixer, stirring at 1000 rpm to 2000 rpm for 3 to 5 minutes, and then stirring at 3000 rpm to 4500 rpm for 10 to 15 minutes to obtain a dry mixture.

[0025] Preferably, an EL5 high-power mixer is used to mix fluorinated carbon and manganese dioxide dry powders, which can fully stir the fluorinated carbon and manganese dioxide and improve the mixing degree of the two dry powders.

[0026] Furthermore, in step S3, the dry mix is ​​added to the conductive adhesive in 2 to 3 portions, with an interval of 5 to 10 minutes between each addition.

[0027] For example, in S3, the dry mix is ​​added in two parts, with the first addition amount being 30% to 50% of the total mass of the dry mix.

[0028] For example, in S3, the dry mix is ​​added in three batches, with the amounts added in the three batches being 30% to 45%, 30% to 45%, and 10% to 40% of the total mass of the dry mix, respectively.

[0029] Furthermore, in S3, the mixing speed of each batch of dry mixture is 10 rpm to 15 rpm, the stirring speed is 0 rpm, and the mixing time is 5 min to 10 min.

[0030] Furthermore, in S3, the high-speed mud-like stirring has a common rotational speed of 40 rpm to 50 rpm, a free rotational speed of 500 rpm to 1000 rpm, and a high-speed mud-like stirring time of 45 min to 60 min.

[0031] The preferred mixing method of conductive adhesive liquid and dry mix can improve the dispersion uniformity among fluorinated carbon, manganese dioxide and carbon nanofibers, and improve the sedimentation stability of the mixed material.

[0032] It should be noted that the conductive carbon black slurry described in this invention can be a commercially available conductive carbon black slurry, and its solvent is the same as the organic solvent described in step S1, such as a commercially available 10% concentration conductive carbon black slurry. The conductive carbon black slurry can also be prepared by oneself.

[0033] Further, in S4, the method for preparing the conductive carbon black slurry includes the following steps: adding conductive carbon black to the third part of the organic solvent, mixing evenly to obtain a conductive carbon black slurry with a mass concentration of 8% to 12%.

[0034] Furthermore, in S4, the conductive carbon black slurry is added to the conductive putty in two parts, with the first addition amount being 50wt% to 70wt% of the total amount of the conductive carbon black slurry.

[0035] Adding the conductive carbon black slurry in two stages, with the first addition being 50wt% to 70wt% of the conductive carbon black slurry, allows the slurry system to maintain a high solids content. Mixing a portion of the conductive carbon black slurry with conductive putty under this high solids content condition also allows the materials to fully break up the agglomerated materials under the shear force of the stirring conditions, thereby improving the dispersibility between the materials.

[0036] Furthermore, in S4, the process of adding each batch of conductive carbon black slurry and the second part of organic solvent is carried out by vacuum high-speed stirring to mix the materials. The general speed of the vacuum high-speed stirring is 40 rpm to 50 rpm, and the speed of the stirring wheel is 3000 rpm to 5000 rpm.

[0037] Based on the above, the stirring time after adding the first batch of conductive carbon black slurry is 60 min to 90 min, the stirring time after adding the second batch of conductive carbon black slurry is 45 min to 60 min, and the stirring time after adding the third part of organic solvent is 30 min to 60 min.

[0038] Furthermore, in S4, low-speed vacuum stirring is performed during the vacuum degassing process, wherein the general speed of the low-speed vacuum stirring is 10 rpm to 15 rpm, the self speed is 0 rpm, and the stirring time is 15 min to 30 min.

[0039] Furthermore, in S4, the preset viscosity is 8000 mPa·s to 12000 mPa·s.

[0040] It should be noted that the pressure of the vacuum state described in this invention can be set to -80KPa to -90KPa to avoid the generation of bubbles in the slurry during the stirring process.

[0041] Secondly, the present invention provides a lithium primary battery cathode slurry, which is prepared by the method for preparing lithium primary battery cathode slurry described in any of the above claims.

[0042] This invention significantly improves the dispersibility of materials by redesigning the order and method of adding each material and by selecting specific conductive agents and controlling their addition method. This avoids the agglomeration problem between fluorinated carbon and conductive agents / binders, as well as the problem of poor sedimentation stability caused by the large difference in physicochemical properties between fluorinated carbon and manganese dioxide. As a result, the prepared positive electrode slurry is uniform and stable, which helps to improve the rate discharge performance of the battery.

[0043] Thirdly, the present invention provides a positive electrode, comprising the above-mentioned lithium primary battery positive electrode slurry.

[0044] Furthermore, the positive electrode includes a current collector and a positive electrode active material layer coated on at least one surface of the current collector, the positive electrode active material layer being obtained by coating and drying the positive electrode slurry described above.

[0045] Fourthly, the present invention provides a primary lithium battery comprising the aforementioned positive electrode.

[0046] The positive electrode slurry prepared by this invention has good dispersibility, stability, and consistency, which can effectively reduce the resistance of the electrode sheet and improve the rate discharge performance of lithium primary batteries. It solves the problems of uneven dispersion and poor consistency of positive electrode slurry in current lithium primary batteries and has broad application prospects in the field of lithium primary batteries. Attached Figure Description

[0047] Figure 1 The curves showing the backscattering intensity and transmittance of the positive electrode slurry prepared in Example 1 of the present invention as a function of time are shown.

[0048] Figure 2 This is a graph showing the change of the instability index (TSI) of the positive electrode slurry prepared in Example 1 of the present invention over time. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0050] To better illustrate the present invention, further examples are provided below.

[0051] In the following examples and comparative examples, the mass percentages of each raw material in the positive electrode slurry system are as follows: fluorinated carbon 23%, manganese dioxide 23%, conductive carbon black 1.5%, carbon nanofibers 0.25%, polyvinylidene fluoride 2.25%, and N-methylpyrrolidone 50%.

[0052] The conductive carbon black slurry used in the following examples and comparative examples is a commercially available conductive carbon black slurry with a mass concentration of 10%, and the solvent is N-methylpyrrolidone (the amount of conductive carbon black slurry added is calculated based on the above-mentioned conductive carbon black content of 1.5%); the high-strength dry mixer used is an EL5 type dry mixer.

[0053] Example 1

[0054] This embodiment provides a method for preparing a positive electrode slurry for a primary lithium battery, comprising the following steps:

[0055] S1. Polyvinylidene fluoride (PVDF) is added to N-methylpyrrolidone at 11.5 times its mass. The mixture is first stirred at low speed (10 rpm revolution speed, 500 rpm rotation speed) for 15 min, and then stirred at high speed (50 rpm revolution speed, 5000 rpm rotation speed) for 4 h to obtain a pre-resin. Carbon nanofibers are added to the pre-resin, and the mixture is stirred at high speed (40 rpm revolution speed, 4000 rpm rotation speed) for 2 h under -85 kPa conditions, and then stirred at low speed (10 rpm revolution speed, 0 rpm rotation speed) for 30 min to obtain a conductive adhesive.

[0056] S2, add fluorinated carbon and manganese dioxide into a high-power dry mixer, stir at 1000 rpm for 5 min, then stir at 3500 rpm for 13 min, and let stand for 15 min to obtain dry mixture;

[0057] S3. Add 45% of the dry mix to the conductive adhesive liquid and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Then add another 45% of the dry mix and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Finally, add the remaining dry mix and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Then knead and stir at high speed (40 rpm, 500 rpm) for 60 minutes to obtain conductive clay.

[0058] S4. Add 60% of the conductive carbon black slurry to the above conductive mortar and stir at high speed (50 rpm revolution speed and 5000 rpm rotation speed) for 60 min under -85 kPa conditions. Then add the remaining conductive carbon black slurry and continue to stir at high speed for 45 min under the same conditions.

[0059] S5. Add N-methylpyrrolidone to the slurry obtained in the above steps, and stir at high speed (40 rpm revolution speed and 4000 rpm rotation speed) for 30 min under -85 kPa conditions to adjust the viscosity to 10000 mPa·s.

[0060] S6. The slurry obtained in the above steps is stirred at low speed (12 rpm for the common rotation speed and 0 rpm for the auto-rotation speed) for 20 minutes under -85 kPa conditions to remove bubbles under vacuum, thereby obtaining the positive electrode slurry for lithium primary batteries.

[0061] Example 2

[0062] This embodiment provides a method for preparing a positive electrode slurry for a primary lithium battery, comprising the following steps:

[0063] S1. Polyvinylidene fluoride (PVDF) is added to N-methylpyrrolidone in 9 times its mass. The mixture is first stirred at low speed (15 rpm revolution speed, 1000 rpm rotation speed) for 10 min, and then stirred at high speed (40 rpm revolution speed, 4500 rpm rotation speed) for 5 h to obtain a pre-resin. Carbon nanofibers are added to the pre-resin and stirred at high speed (50 rpm revolution speed, 5000 rpm rotation speed) for 3 h under -90 kPa conditions, and then stirred at low speed (15 rpm revolution speed, 0 rpm rotation speed) for 30 min to obtain a conductive adhesive.

[0064] S2, add fluorocarbon and manganese dioxide into a high-power dry mixer, stir at 1500 rpm for 4 min, then stir at 4500 rpm for 12 min, let stand for 10 min to obtain dry mixture;

[0065] S3, add 30% of the dry mix to the conductive adhesive liquid, stir at low speed (12 rpm, 0 rpm) for 7 minutes, then add another 30% of the dry mix, stir at low speed (12 rpm, 0 rpm) for 7 minutes, finally add the remaining dry mix, stir at low speed (12 rpm, 0 rpm) for 7 minutes, then knead and stir at high speed (45 rpm, 800 rpm) for 55 minutes to obtain conductive clay;

[0066] S4. Add 50% of the conductive carbon black slurry to the above conductive mortar and stir at high speed (45 rpm revolution speed, 4000 rpm rotation speed) for 70 min under -90 kPa conditions. Then add the remaining conductive carbon black slurry and continue to stir at high speed for 50 min under the same conditions.

[0067] S5. Add N-methylpyrrolidone to the slurry obtained in the above steps, and stir at high speed (50 rpm revolution speed and 5000 rpm rotation speed) for 30 min under -90 kPa conditions to adjust the viscosity to 8700 mPa·s.

[0068] S6. The slurry obtained in the above steps is stirred at low speed (10 rpm for the common rotation speed and 0 rpm for the auto-rotation speed) for 30 minutes under -90 kPa conditions to remove bubbles under vacuum, thereby obtaining the positive electrode slurry for lithium primary batteries.

[0069] Example 3

[0070] This embodiment provides a method for preparing a positive electrode slurry for a primary lithium battery, comprising the following steps:

[0071] S1. Polyvinylidene fluoride (PVDF) was added to N-methylpyrrolidone at 15.6 times its mass. The mixture was first stirred at low speed (12 rpm revolution speed, 700 rpm rotation speed) for 12 min, and then stirred at high speed (35 rpm revolution speed, 3500 rpm rotation speed) for 6 h to obtain a pre-resin. Carbon nanofibers were added to the pre-resin, and the mixture was stirred at high speed (35 rpm revolution speed, 3500 rpm rotation speed) for 3 h under -88 kPa conditions, and then stirred at low speed (12 rpm revolution speed, 0 rpm rotation speed) for 35 min to obtain a conductive adhesive.

[0072] S2, add fluorocarbon and manganese dioxide into a high-power dry mixer, stir at 2000 rpm for 3 minutes, then stir at 4000 rpm for 10 minutes, and let stand for 10 minutes to obtain a dry mixture;

[0073] S3. Add 50% of the dry mix to the conductive adhesive liquid and stir at low speed (15 rpm for the revolution and 0 rpm for the spindle) for 5 minutes. Then add the remaining dry mix and stir at low speed (15 rpm for the revolution and 0 rpm for the spindle) for 5 minutes. Then knead and stir at high speed (50 rpm for the revolution and 1000 rpm for the spindle) for 45 minutes to obtain conductive clay.

[0074] S4. Add 70% of the conductive carbon black slurry to the above conductive mortar and stir at high speed (40 rpm revolution speed, 3000 rpm rotation speed) for 90 min under -88 kPa conditions. Then add the remaining conductive carbon black slurry and continue to stir at high speed for 60 min under the same conditions.

[0075] S5. Add N-methylpyrrolidone to the slurry obtained in the above steps, and stir at high speed (revolution speed 40 rpm, rotation speed 3000 rpm) for 60 min under -88 kPa conditions to adjust the viscosity to 11000 mPa·s.

[0076] S6. The slurry obtained in the above steps is stirred at low speed (15 rpm for the common rotation speed and 0 rpm for the auto-rotation speed) for 15 min under -88 kPa conditions to remove bubbles under vacuum, thus obtaining the positive electrode slurry for lithium primary batteries.

[0077] Example 4

[0078] This embodiment provides a method for preparing a positive electrode slurry for a primary lithium battery, comprising the following steps:

[0079] S1. Polyvinylidene fluoride (PVDF) is added to N-methylpyrrolidone in 13 times its mass. The mixture is first stirred at low speed (14 rpm, 900 rpm) for 13 min, and then stirred at high speed (40 rpm, 4000 rpm) for 5 h to obtain a pre-resin. Carbon nanofibers are added to the pre-resin, and the mixture is stirred at high speed (45 rpm, 4500 rpm) for 2.5 h under -86 kPa conditions, and then stirred at low speed (11 rpm, 0 rpm) for 40 min to obtain a conductive adhesive.

[0080] S2, add fluorocarbon and manganese dioxide into a high-power dry mixer, stir at 1000 rpm for 5 min, then stir at 3000 rpm for 15 min, and let stand for 15 min to obtain dry mixture;

[0081] S3, add 30% of the dry mix to the conductive adhesive liquid, stir at low speed (revolution speed 13 rpm, rotation speed 0 rpm) for 8 minutes, then add the remaining dry mix, stir at low speed (revolution speed 13 rpm, rotation speed 0 rpm) for 8 minutes, then knead and stir at high speed (revolution speed 40 rpm, rotation speed 700 rpm) for 50 minutes to obtain conductive clay.

[0082] S4, add 55% of the conductive carbon black slurry to the above conductive mortar, and stir at high speed (45 rpm revolution speed, 4500 rpm rotation speed) for 80 min under -86 kPa conditions, then add the remaining conductive carbon black slurry, and continue to stir at high speed for 55 min under the same conditions as above.

[0083] S5. Add N-methylpyrrolidone to the slurry obtained in the above steps, and stir at high speed (revolution speed 45 rpm, rotation speed 4000 rpm) for 50 min under -86 kPa conditions to adjust the viscosity to 9000 mPa·s.

[0084] S6. The slurry obtained in the above steps is stirred at low speed (11 rpm for the common rotation speed and 0 rpm for the auto-rotation speed) for 25 minutes under -86 kPa conditions to remove bubbles under vacuum, thereby obtaining the positive electrode slurry for lithium primary batteries.

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing a positive electrode slurry for a lithium primary battery. The only difference from Example 1 is that conductive carbon black slurry and carbon nanofibers are added together in step S1. The specific steps are as follows:

[0087] S1. Polyvinylidene fluoride (PVDF) is added to N-methylpyrrolidone at 11.5 times its mass. The mixture is first stirred at low speed (10 rpm revolution speed, 500 rpm rotation speed) for 15 min, and then stirred at high speed (50 rpm revolution speed, 5000 rpm rotation speed) for 4 h to obtain a pre-resin. Carbon nanofibers and conductive carbon black slurry are added to the pre-resin. Under -85 kPa conditions, the mixture is first stirred at high speed (40 rpm revolution speed, 4000 rpm rotation speed) for 2 h, and then stirred at low speed (10 rpm revolution speed, 0 rpm rotation speed) for 30 min to obtain a conductive resin.

[0088] S2, add fluorinated carbon and manganese dioxide into a high-power dry mixer, stir at 1000 rpm for 5 min, then stir at 3500 rpm for 13 min, and let stand for 15 min to obtain dry mixture;

[0089] S3. Add 45% of the dry mix to the conductive adhesive liquid and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Then add another 45% of the dry mix and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Finally, add the remaining dry mix and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Then knead and stir at high speed (40 rpm, 500 rpm) for 60 minutes to obtain conductive clay.

[0090] S4. Add N-methylpyrrolidone to the conductive putty and stir at high speed (40 rpm revolution speed, 4000 rpm rotation speed) for 30 min under -85 kPa conditions to adjust the viscosity to 10000 mPa·s.

[0091] S5. The slurry obtained in the above steps is stirred at low speed (12 rpm for the common rotation speed and 0 rpm for the auto-rotation speed) for 20 minutes under -85 kPa conditions to remove bubbles under vacuum, thereby obtaining the positive electrode slurry for lithium primary batteries.

[0092] Comparative Example 2

[0093] This comparative example provides a method for preparing a positive electrode slurry for a primary lithium battery. The only difference from Example 1 is that carbon nanofibers are dry-mixed with fluorinated carbon and manganese dioxide. The specific steps are as follows:

[0094] S1. Add polyvinylidene fluoride to N-methylpyrrolidone at 11.5 times its mass, stir at low speed (10 rpm revolution speed, 500 rpm rotation speed) for 15 min, then stir at high speed (50 rpm revolution speed, 5000 rpm rotation speed) for 4 h, and then stir at low speed (10 rpm revolution speed, 0 rpm rotation speed) for 30 min under -85 kPa conditions to obtain conductive adhesive solution.

[0095] S2, add fluorinated carbon, manganese dioxide and carbon nanofibers into a high-performance dry mixer, stir at 1000 rpm for 5 min, then stir at 3500 rpm for 13 min, and let stand for 15 min to obtain dry mixture;

[0096] S3. Add 45% of the dry mix to the conductive adhesive liquid and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Then add another 45% of the dry mix and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Finally, add the remaining dry mix and stir at low speed (10 rpm, 0 rpm) for 10 minutes. Then knead and stir at high speed (40 rpm, 500 rpm) for 60 minutes to obtain conductive clay.

[0097] S4. Add 60% of the conductive carbon black slurry to the above conductive mortar and stir at high speed (50 rpm revolution speed and 5000 rpm rotation speed) for 60 min under -85 kPa conditions. Then add the remaining conductive carbon black slurry and continue to stir at high speed for 45 min under the same conditions.

[0098] S5. Add N-methylpyrrolidone to the slurry obtained in the above steps, and stir at high speed (40 rpm revolution speed and 4000 rpm rotation speed) for 30 min under -85 kPa conditions to adjust the viscosity to 10000 mPa·s.

[0099] S6. The slurry obtained in the above steps is stirred at low speed (12 rpm for the common rotation speed and 0 rpm for the auto-rotation speed) for 20 minutes under -85 kPa conditions to remove bubbles under vacuum, thereby obtaining the positive electrode slurry for lithium primary batteries.

[0100] Comparative Example 3

[0101] This comparative example provides a method for preparing a positive electrode slurry for a primary lithium battery. The only difference from Example 1 is that the conductive adhesive is directly added to the dry mixture without being added in batches. The specific steps are as follows:

[0102] S1. Polyvinylidene fluoride (PVDF) is added to N-methylpyrrolidone at 11.5 times its mass. The mixture is first stirred at low speed (10 rpm revolution speed, 500 rpm rotation speed) for 15 min, and then stirred at high speed (50 rpm revolution speed, 5000 rpm rotation speed) for 4 h to obtain a pre-resin. Carbon nanofibers are added to the pre-resin, and the mixture is stirred at high speed (40 rpm revolution speed, 4000 rpm rotation speed) for 2 h under -85 kPa conditions, and then stirred at low speed (10 rpm revolution speed, 0 rpm rotation speed) for 30 min to obtain a conductive adhesive.

[0103] S2, add fluorinated carbon and manganese dioxide into a high-power dry mixer, stir at 1000 rpm for 5 min, then stir at 3500 rpm for 13 min, and let stand for 15 min to obtain dry mixture;

[0104] S3. Add all the conductive adhesive liquid to the dry mixture, stir at low speed (10 rpm, 0 rpm) for 30 minutes, then knead and stir at high speed (40 rpm, 500 rpm) for 60 minutes to obtain conductive clay.

[0105] S4. Add 60% of the conductive carbon black slurry to the above conductive mortar and stir at high speed (50 rpm revolution speed and 5000 rpm rotation speed) for 60 min under -85 kPa conditions. Then add the remaining conductive carbon black slurry and continue to stir at high speed for 45 min under the same conditions.

[0106] S5. Add N-methylpyrrolidone to the slurry obtained in the above steps, and stir at high speed (40 rpm revolution speed and 4000 rpm rotation speed) for 30 min under -85 kPa conditions to adjust the viscosity to 10000 mPa·s.

[0107] S6. The slurry obtained in the above steps is stirred at low speed (12 rpm for the common rotation speed and 0 rpm for the auto-rotation speed) for 20 minutes under -85 kPa conditions to remove bubbles under vacuum, thereby obtaining the positive electrode slurry for lithium primary batteries.

[0108] Application examples

[0109] 1. Slurry stability

[0110] The positive electrode slurry prepared in Example 1 was subjected to stability testing using a slurry stability analyzer, and the results are as follows: Figures 1-2As shown in the figure, the intensity of transmitted and backscattered light in the cathode slurry prepared in Example 1 remained essentially unchanged over time, indicating that no particle agglomeration occurred in the slurry, and the slurry exhibited good dispersibility and stability. Regarding the overall dynamic stability of the slurry, after one day of storage, the measured TSI index (instability index) changed within 0.05, demonstrating good overall stability. This indicates that the cathode slurry prepared in this embodiment of the invention exhibits good stability in terms of storage and subsequent coating surface density.

[0111] 2. Resistance

[0112] The positive electrode slurries prepared in Example 1 and Comparative Examples 1-3 were coated onto electrode sheets using the same process. The prepared positive electrode sheets were subjected to film resistance testing, and the results are shown in Table 1.

[0113] Table 1

[0114] Case Electrode thickness μm <![CDATA[Compaction density mg / cm 3 > Membrane resistance (Ω·cm) Example 1 175 1.4 1.83 Comparative Example 1 175 1.4 2.17 Comparative Example 2 175 1.4 2.11 Comparative Example 3 175 1.4 2.04

[0115] By comparison, it can be found that the resistance of the positive electrode sheet obtained by coating the positive electrode slurry prepared in Example 1 is significantly lower than that of Comparative Examples 1-3, indicating that the preparation method of the positive electrode slurry in the present invention can make the conductive agent and each component mix more evenly, thereby effectively reducing the overall resistance of the electrode sheet.

[0116] 3. Discharge performance test

[0117] The positive electrode slurries prepared in Examples 1 and 1-3 were used to prepare 18650 batteries using the same process. The processes included coating, rolling, slitting, winding, welding, electrolyte injection, and sealing. Each process is a standard operation in the art and will not be described in detail here. Ten batteries were made from each positive electrode slurry. The prepared 18650 batteries included a positive electrode of manganese dioxide, a negative electrode of lithium metal, a separator, an electrolyte, metal tabs, and a casing.

[0118] The prepared 18650 batteries were subjected to constant current discharge at a rate of 0.2C. The experimental results showed that the battery prepared in Example 1 had an initial minimum hysteresis voltage of 2.86V and a discharge capacity of 4.18Ah; the battery prepared in Comparative Example 1 had an initial minimum hysteresis voltage of 2.50V and a discharge capacity of 3.71Ah; the battery prepared in Comparative Example 2 had an initial minimum hysteresis voltage of 2.55V and a discharge capacity of 3.76V; and the battery prepared in Comparative Example 3 had an initial minimum hysteresis voltage of 2.63V and a discharge capacity of 3.88Ah. The comparison of battery discharge performance shows that the battery prepared in Example 1 significantly outperforms Comparative Examples 1-3, indicating that the method for preparing the positive electrode slurry in this invention can significantly improve the agglomeration problem of fluorinated carbon and increase its capacity. Furthermore, the specific combination of two conductive agents and the order in which the conductive agents are added also significantly improve the battery's conductivity and increase the operating voltage platform.

[0119] Examples 2-4 can all achieve technical effects that are basically equivalent to those of Example 1.

[0120] Other positive electrode slurry system formulations defined in this invention, prepared according to the methods of the above embodiments, can achieve technical effects that are basically equivalent to those of the embodiments.

[0121] In summary, the method for preparing the positive electrode slurry provided by this invention can improve the dispersibility and stability of the slurry, effectively reduce the resistance of the electrode sheet, and improve the rate discharge performance of the lithium primary battery, thus having high practical value in lithium primary batteries.

[0122] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a positive electrode slurry for a primary lithium battery, characterized in that, Includes the following steps: S1, add the adhesive to the first part of the organic solvent and mix evenly to obtain the pre-adhesive solution; add carbon nanofibers to the pre-adhesive solution and mix evenly to obtain the conductive adhesive solution; S2, mix fluorinated carbon and manganese dioxide evenly to obtain a dry mixture; S3, the dry mixture is added to the conductive adhesive liquid in batches, and after each batch of dry mixture is mixed evenly, high-speed mud-like stirring is performed to obtain conductive mud. S4. Add the conductive carbon black slurry to the conductive clay in batches, mix evenly, add the second part of organic solvent to adjust to the preset viscosity, and defoam under vacuum to obtain the lithium primary battery positive electrode slurry. The adhesive is polyvinylidene fluoride; the organic solvent is N-methylpyrrolidone. The lithium primary battery cathode slurry comprises the following raw material components by mass percentage: fluorinated carbon 20%~26%, manganese dioxide 20%~26%, conductive carbon black 1.4%~1.6%, carbon nanofibers 0.235%~0.26%, binder 2.2%~2.3%, and the balance being organic solvent, with the total mass content of all components being 100%. In step S1, the binder and the first part of the organic solvent are mixed evenly by stirring at a low speed first and then at a high speed. The low speed has a common speed of 10 rpm to 15 rpm, a speed of 500 rpm to 1000 rpm, and a stirring time of 10 min to 15 min. The high speed has a common speed of 35 rpm to 50 rpm, a speed of 3500 rpm to 5000 rpm, and a stirring time of 4 h to 6 h. In S1, the pre-adhesive solution and carbon nanofibers are mixed evenly by first using a vacuum high-speed stirring method followed by a vacuum low-speed stirring method. The vacuum high-speed stirring method has a general rotation speed of 35 rpm to 50 rpm and a self-rotation speed of 3500 rpm to 5000 rpm, with a stirring time of 2 h to 3 h. The vacuum low-speed stirring method has a general rotation speed of 10 rpm to 15 rpm and a self-rotation speed of 0 rpm, with a stirring time of 30 min to 40 min.

2. The method for preparing the positive electrode slurry for a primary lithium battery as described in claim 1, characterized in that, In S1, the amount of the first portion of organic solvent added is 9 to 16 times the mass of the binder; and / or S2 specifically involves adding fluorinated carbon and manganese dioxide to a dry mixer, stirring at 1000-2000 rpm for 3-5 minutes, then stirring at 3000-4500 rpm for 10-15 minutes to obtain a dry mixture; and / or In step S3, the dry mix is ​​added to the conductive adhesive in 2-3 portions, with an interval of 5-10 minutes between each addition; and / or In S3, the mixing speed of each batch of dry mixture is 10 rpm to 15 rpm, the rotation speed is 0 rpm, and the mixing time is 5 min to 10 min; and / or In S3, the high-speed mud-forming stirring has a common rotational speed of 40 rpm to 50 rpm, a free rotational speed of 500 rpm to 1000 rpm, and a high-speed mud-forming stirring time of 45 min to 60 min.

3. The method for preparing the positive electrode slurry for a primary lithium battery as described in claim 1 or 2, characterized in that, In S3, the dry mixture is added in two stages, with the first addition being 30% to 50% of the total mass of the dry mixture; or In S3, the dry mix is ​​added in three batches, with the amounts added in the three batches being 30%~45%, 30%~45%, and 10%~40% of the total mass of the dry mix, respectively.

4. The method for preparing the positive electrode slurry for a primary lithium battery as described in claim 1, characterized in that, In S4, the preparation method of the conductive carbon black slurry includes the following steps: adding conductive carbon black to the third organic solvent, mixing evenly to obtain a conductive carbon black slurry with a mass concentration of 8%~12%; and / or In S4, the conductive carbon black slurry is added to the conductive putty in two parts. The amount added in the first part is 50wt% to 70wt% of the total amount of the conductive carbon black slurry.

5. The method for preparing the positive electrode slurry for a primary lithium battery as described in claim 1, characterized in that, In S4, the addition of each batch of conductive carbon black slurry and the second part of the organic solvent are all carried out by vacuum high-speed stirring to mix the materials. The general speed of the vacuum high-speed stirring is 40 rpm to 50 rpm, and the automatic speed is 3000 rpm to 5000 rpm; and / or In S4, low-speed vacuum stirring is performed during the vacuum degassing process, wherein the general rotational speed of the low-speed vacuum stirring is 10 rpm to 15 rpm, the free rotational speed is 0 rpm, and the stirring time is 15 min to 30 min; and / or In S4, the preset viscosity is 8000 mPa·s to 12000 mPa·s.

6. A lithium primary battery positive electrode slurry, characterized in that, It is prepared by the method for preparing the positive electrode slurry of a primary lithium battery according to any one of claims 1 to 5.

7. A positive electrode, characterized in that, Includes the lithium primary battery cathode slurry as described in claim 6.

8. A primary lithium battery, characterized in that, Includes the positive electrode as described in claim 7.

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