A method for preparing conductive carbon black, the conductive carbon black, and a positive electrode paste containing the same

Abstract

The present disclosure relates to a method for preparing conductive carbon black, which is used in lithium-ion secondary batteries; the method includes the following steps: Step 1: Provide a carbon black raw material, and treat the carbon black raw material with nitric acid to obtain Intermediate I; Step 2: Treat Intermediate I with an organic acid to obtain Intermediate II; Step 3: Treat Intermediate II with boric acid to obtain Intermediate III; Step 4: Perform post-treatment on Intermediate III to obtain conductive carbon black; The lithium-ion secondary battery using the conductive carbon black provided by the present disclosure has good electrochemical cycling performance.

Description

Technical Field

[0001] The present disclosure relates to the technical field of carbon materials, and in particular, to a method for preparing conductive carbon black, the conductive carbon black, and a positive electrode paste containing the same. Background Art

[0002] Lithium-ion secondary batteries are widely used as power sources for small electronic devices such as smart phones and tablet computers. A lithium-ion secondary battery generally includes an electrode, a separator, and an electrolyte. For the electrode, it is manufactured by coating a composite material paste obtained by dispersing an active material, a conductive agent, an adhesive, etc. in a dispersion medium on a current collector metal plate and drying to form a composite material layer.

[0003] Since 1872, people have started the industrial production of carbon black, and the term "Carbon Black" has officially appeared. In the development of more than one hundred years, it has been rapidly applied to various fields such as rubber tires, plastics, and coatings. Modern carbon black refers to a carbon material generated by the thermal decomposition of carbon-rich hydrocarbon substances in an anaerobic or aerobic environment. Available raw materials include coal tar, soft pitch, distillate oil, cracked oil, etc. While lithium-ion secondary batteries have become the most widely used batteries currently, conductive additives also play an important role in lithium-ion secondary batteries. It improves the conductivity of the electrode sheet by forming a conductive network in the electrode, and at the same time, its structure also affects the dispersion and lithium storage mechanism of the electrode material, thus affecting the performance of the battery. As one of the earliest discovered conductive additives, conductive carbon black still occupies the largest share in the market of commercial conductive additives due to its significant advantages such as low price, good dispersibility, simple production process, and strong conductivity.

[0004] The conductivity of conductive carbon black is affected by factors such as its specific surface area, porosity, structure, surface composition, and microstructure; therefore, by improving the preparation process, conductive carbon black with better conductive performance can be obtained. Summary of the Invention

[0005] The present disclosure provides a method for preparing conductive carbon black, the conductive carbon black, and a positive electrode paste containing the same to solve the deficiencies in the related art.

[0006] According to the first aspect of the embodiments of the present disclosure, a method for preparing conductive carbon black is provided. The conductive carbon black is used for lithium-ion secondary batteries, and the method includes the following steps:

[0007] Step 1: Provide a carbon black raw material, and treat the carbon black raw material with nitric acid to obtain Intermediate Product I;

[0008] Step 2: Treat Intermediate Product I with an organic acid to obtain Intermediate Product II;

[0009] Step 3: Treat the intermediate II with boric acid to obtain intermediate III;

[0010] Step 4: Perform post-treatment on the intermediate III to obtain the conductive carbon black.

[0011] In one aspect of the present disclosure, in Step 1, the treatment is as follows: Place the carbon black raw material in nitric acid with a concentration of 4 - 7 mol / L, and treat it at 120°C - 180°C for 4 - 8 h. Specifically, in Step 1, the treatment is as follows: Place the carbon black raw material in nitric acid with a concentration of 6 mol / L, and treat it at 150°C for 5 h.

[0012] In one aspect of the present disclosure, in Step 2, the treatment is as follows: Place the intermediate I in an organic acid solution with a concentration of 0.8 - 1.8 mol / L, and treat it at 150°C - 220°C for 3 - 7 h. Specifically, in Step 2, the treatment is as follows: Place the intermediate I in an organic acid solution with a concentration of 1.2 - 1.5 mol / L, and treat it at 200°C for 4 h.

[0013] In one aspect of the present disclosure, in Step 2, the organic acid solution contains at least one of tartaric acid, succinic acid, citric acid, oxalic acid, or ascorbic acid.

[0014] In one aspect of the present disclosure, the organic acid solution is tartaric acid with a concentration of 1.2 - 1.5 mol / L.

[0015] In one aspect of the present disclosure, in Step 3, the treatment is as follows: Under the atmosphere of a hydrogen / argon mixed gas, mix the intermediate II with boric acid, and treat it at 700°C - 900°C for 3 - 6 h.

[0016] In one aspect of the present disclosure, in Step 3, the mass ratio of the carbon black raw material to boric acid is selected from 1:(0.1 - 0.2). Specifically, the mass ratio of the carbon black raw material to boric acid is selected from 1:0.1, 1:0.12, 1:0.15, 1:0.18, or 1:0.2.

[0017] In one aspect of the present disclosure, between Step 1 and Step 2, a washing and drying process is further included.

[0018] In one aspect of the present disclosure, between Step 2 and Step 3, a washing and drying process is further included.

[0019] In one aspect of the present disclosure, in Step 4, the post-treatment includes a washing and drying process.

[0020] In one aspect of the present disclosure, in step 4, the post-treatment includes a calcination process carried out in an atmosphere of carbon dioxide. The temperature of the calcination is 800°C - 1200°C, and the time of the calcination is 1 - 3 h.

[0021] In one aspect of the present disclosure, the method includes the following steps:

[0022] Step 1: Provide a carbon black raw material, and treat the carbon black raw material with 4 - 7 mol / L nitric acid at 120°C - 180°C for 4 - 8 h to obtain Intermediate I;

[0023] Step 2: Treat Intermediate I with an organic acid solution of 0.8 - 1.8 mol / L at 150°C - 220°C for 3 - 7 h to obtain Intermediate II; wherein, the organic acid solution contains at least one of tartaric acid, succinic acid, citric acid, oxalic acid, or ascorbic acid;

[0024] Step 3: Mix Intermediate II with boric acid in an atmosphere of hydrogen / argon mixture, and treat at 700°C - 900°C for 3 - 6 h to obtain Intermediate III;

[0025] Step 4: Wash and dry Intermediate III to obtain the conductive carbon black.

[0026] In one aspect of the present disclosure, the method includes the following steps:

[0027] Step 1: Provide a carbon black raw material, and treat the carbon black raw material with 4 - 7 mol / L nitric acid at 120°C - 180°C for 4 - 8 h to obtain Intermediate I; and wash and dry Intermediate I;

[0028] Step 2: Treat Intermediate I with an organic acid solution of 0.8 - 1.8 mol / L at 150°C - 220°C for 3 - 7 h to obtain Intermediate II; and wash and dry Intermediate II; wherein, the organic acid solution contains at least one of tartaric acid, succinic acid, citric acid, oxalic acid, or ascorbic acid;

[0029] Step 3: Mix Intermediate II with boric acid in an atmosphere of hydrogen / argon mixture, and treat at 700°C - 900°C for 3 - 6 h to obtain Intermediate III;

[0030] Step 4: Wash and dry Intermediate III to obtain the conductive carbon black.

[0031] In one aspect of the present disclosure, the method includes the following steps:

[0032] Step 1: Provide carbon black raw material, and treat the carbon black raw material with 4 - 7 mol / L nitric acid at 120°C - 180°C for 4 - 8 h to obtain Intermediate I; and wash and dry the Intermediate I;

[0033] Step 2: Treat the Intermediate I with 0.8 - 1.8 mol / L organic acid solution at 150°C - 220°C for 3 - 7 h to obtain Intermediate II; and wash and dry the Intermediate II; wherein, the organic acid solution contains at least one of tartaric acid, succinic acid, citric acid, oxalic acid, or ascorbic acid;

[0034] Step 3: Mix the Intermediate II with boric acid under the atmosphere of hydrogen / argon mixture, and treat at 700°C - 900°C for 3 - 6 h to obtain Intermediate III;

[0035] Step 4: Wash and dry the Intermediate III, and then calcine it under the atmosphere of carbon dioxide, the calcination temperature is 800°C - 1200°C, and the calcination time is 1 - 3 h; to obtain the conductive carbon black.

[0036] According to the second aspect of the embodiments of the present disclosure, there is provided a conductive carbon black, which is prepared by the foregoing method.

[0037] According to the third aspect of the embodiments of the present disclosure, there is provided a positive electrode paste, which includes a positive electrode active material, a binder, and the foregoing conductive carbon black.

[0038] In one aspect of the present disclosure, based on the total weight of the positive electrode paste, the mass percentage of the conductive carbon black is selected from 1% - 20%, and the mass percentage of the binder is selected from 1% - 20%.

[0039] In one aspect of the present disclosure, based on the total weight of the positive electrode paste, the mass percentage of the conductive carbon black is selected from 5% - 20%, and the mass percentage of the binder is selected from 5% - 20%.

[0040] According to the fourth aspect of the embodiments of the present disclosure, there is provided a lithium - ion secondary battery, which includes a positive electrode plate, a negative electrode plate, and an electrolyte; the positive electrode plate includes a positive electrode current collector and a positive electrode paste coated on the positive electrode current collector.

[0041] The technical solutions provided by the embodiments of the present disclosure may include the following beneficial effects: The lithium - ion secondary battery using the conductive carbon black provided by the present disclosure has good electrochemical cycling performance.

[0042] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. Detailed Embodiments

[0043] Exemplary embodiments will be described in detail below. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure.

[0044] The terms used in the present disclosure are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. The singular forms "a", "the", and "said" used in the present disclosure and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0045] In this document, the term "comprising", "including" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or apparatus. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising the element.

[0046] Unless otherwise specified, the terms used in the present disclosure have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in the present disclosure can be measured by various commonly used measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of the present disclosure).

[0047] The list of items connected by the terms "at least one of", "at least one in", "at least one kind in" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0048] In some embodiments of the present disclosure, the conductive carbon black provided by the present disclosure is applied to secondary batteries, and the secondary batteries provided by the present disclosure include a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, etc.

[0049] Positive electrode sheet:

[0050] In some embodiments of the present disclosure, the secondary battery provided by the present invention includes a positive electrode, the positive electrode includes a current collector and a positive electrode material disposed on the current collector, and the positive electrode material is obtained by drying the positive electrode paste provided by the present disclosure. The positive electrode paste provided by the present disclosure includes a positive electrode active material, a binder, and the aforementioned conductive carbon black. The positive electrode active material includes a compound that reversibly intercalates and deintercalates lithium ions. In some embodiments of the present disclosure, the positive electrode active material includes at least one of lithium cobaltate, lithium nickel manganese cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganate, spinel-type lithium nickel manganate, and lithium titanate.

[0051] In some embodiments of the present invention, the thickness of the positive electrode active material layer in the positive electrode sheet provided by the present invention is selected from 30 - 400 μm, such as 30 μm, 40 μm, 50 μm, 80 μm, 110 μm, 200 μm, 300 μm, 400 μm, and preferably 50 - 110 μm.

[0052] In some embodiments of the present disclosure, non-limiting examples of the binder include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0053] In some embodiments of the present disclosure, the conductive carbon black is obtained through the following steps, but is not limited thereto:

[0054] Step 1: Provide a carbon black raw material, and treat the carbon black raw material with 4 - 7 mol / L nitric acid at 120°C - 180°C for 4 - 8 h to obtain Intermediate I; and wash and dry Intermediate I;

[0055] Step 2: Treat Intermediate I with 0.8 - 1.8 mol / L organic acid solution at 150°C - 220°C for 3 - 7 h to obtain Intermediate II; and wash and dry Intermediate II; wherein the organic acid solution contains at least one of tartaric acid, succinic acid, citric acid, oxalic acid, or ascorbic acid;

[0056] Step 3: Mix Intermediate II with boric acid in an atmosphere of hydrogen / argon mixture, and treat at 700°C - 900°C for 3 - 6 h to obtain Intermediate III;

[0057] Step 4: Wash and dry Intermediate III to obtain the conductive carbon black.

[0058] In the present disclosure, the carbon black raw material is selected from any one of carbon black N134, carbon black N110, carbon black N115, carbon black N121, carbon black N166, carbon black N219, carbon black N220, carbon black N231, carbon black N234, carbon black N242, carbon black N270, carbon black N285, carbon black N293, carbon black N294, carbon black N299, carbon black N326, carbon black N330, carbon black N332, carbon black N339, carbon black N347, carbon black N351, carbon black N356, carbon black N358, carbon black N363 or carbon black N375; preferably, the carbon black raw material used in the present disclosure is selected from carbon black N134.

[0059] In some embodiments of the present disclosure, the positive electrode tab includes a positive current collector. Exemplarily, the positive current collector may be aluminum (Al), but is not limited thereto.

[0060] Negative electrode tab:

[0061] In some embodiments of the present disclosure, the negative electrode tab includes a negative current collector and a negative active material layer provided on the negative current collector.

[0062] In the present disclosure, the specific types of the negative active material are not specifically limited and can be selected according to requirements. Specifically, the negative active material is selected from natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, spinel-structured lithiated TiO2-Li4Ti5O 12 , Li-Al alloy, or one or more of them. Non-limiting examples of carbon materials include crystalline carbon, amorphous carbon, and mixtures thereof. Crystalline carbon may be amorphous or in the form of flakes, small flakes, spheres, or fibers of natural graphite or artificial graphite. Amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, etc.

[0063] In some embodiments of the present disclosure, the negative active material layer may include a binder; the binder improves the binding between the negative active material particles and the binding between the negative active material and the current collector.

[0064] In some embodiments of the present disclosure, non-limiting examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0065] In some embodiments of the present disclosure, the negative electrode active material layer includes a conductive agent, thereby making the electrode conductive. The conductive agent can include any conductive material as long as it does not cause chemical changes. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., such as copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0066] In some embodiments of the present disclosure, the negative electrode sheet of the present application includes a negative electrode active material, a binder, and a conductive agent.

[0067] In some embodiments of the present disclosure, the negative electrode active material of the present application may also be selected from other materials that can electrochemically occlude and release metal ions such as lithium ions. Specifically, it can be selected from carbonaceous materials, silicon-based materials, alloy-based materials, lithium-containing metal composite oxide materials, etc. They can be used alone or in any combination of two or more.

[0068] In some embodiments of the present disclosure, the negative electrode current collector can be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0069] Electrolyte:

[0070] In some embodiments of the present disclosure, the electrolyte includes a lithium salt and a solvent.

[0071] In some embodiments of the present disclosure, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalato)borate LiB(C2O4)2 (LiBOB), or lithium difluorooxalate borate LiBF2(C2O4) (LiDFOB).

[0072] In some embodiments of the present disclosure, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0073] Separator:

[0074] In some embodiments of the present disclosure, a separator is provided between the positive electrode plate and the negative electrode plate of the lithium-ion secondary battery to prevent short circuit. There are no particular limitations on the material and shape of the separator used in the secondary battery, and it can be any technology disclosed in the prior art.

[0075] In some embodiments of the present disclosure, the separator may include a base material layer and a surface treatment layer. The base material layer is a non-woven fabric, film or composite film having a porous structure, and the material of the base material layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected. A surface treatment layer is provided on at least one surface of the base material layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from one or more combinations of alumina, silica, magnesia, titania, hafnium dioxide, tin dioxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from one or more combinations of polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinyl pyrrolidone, polyethylene ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate salt, polyvinyl pyrrolidone, polyethylene ether, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene).

[0076] Lithium-ion secondary battery:

[0077] In some embodiments of the present disclosure, the lithium-ion secondary battery involved in the present disclosure can be made by laminating the above positive and negative electrode sheets.

[0078] In some embodiments of the present disclosure, the lithium-ion secondary battery involved in the present disclosure may include an outer package, and the outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the lithium-ion secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as one or several of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0079] In some embodiments of the present disclosure, the present disclosure also provides a battery module. The battery module includes the above lithium-ion secondary battery. Since the battery module adopts the above lithium-ion battery, it has at least the same advantages as the above lithium-ion secondary battery. The number of lithium-ion secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0080] In some embodiments of the present disclosure, the present disclosure also provides a battery pack, which includes the above battery module. The number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0081] The present invention will be further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0082] Embodiment 1:

[0083] Embodiment 1 includes the following steps:

[0084] 1. Preparation of conductive carbon black:

[0085] Provide carbon black raw material N134, treat carbon black N134 with 6 mol / L nitric acid at 160 °C for 5 h to obtain intermediate product I; wash and dry intermediate product I; then treat intermediate product I with 1.5 mol / L tartaric acid at 200 °C for 4 h to obtain intermediate product II; wash and dry intermediate product II; in an atmosphere of hydrogen / argon mixture, mix intermediate product II with boric acid, and the mass of boric acid is 10 wt% of carbon black N134, then calcine, with a heating rate of 3 °C / min, keep the temperature at 800 °C for 4 h, and then naturally cool to room temperature to obtain intermediate product III; wash and dry intermediate product III to obtain the conductive carbon black of Embodiment 1.

[0086] 2. Preparation of the positive electrode sheet:

[0087] The cathode active material lithium cobalt oxide (LiCoO₂), the conductive carbon black of Example 1 prepared above, and polyvinylidene fluoride (PVDF) are stirred and mixed evenly in an appropriate amount of N-methylpyrrolidone (NMP) according to a weight ratio of 96:2:2, then coated on the aluminum foil of the cathode current collector, dried, and cold-pressed to obtain the cathode active material layer. Then, after cutting, slitting, and welding the tab, the cathode plate is obtained.

[0088] 3. Prepare the anode plate:

[0089] Artificial graphite, conductive agent superconducting carbon black, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are stirred and mixed evenly in an appropriate amount of deionized water solvent according to a weight ratio of 95.0:1.5:1.5:2 to form a uniform anode slurry. This slurry is coated on the copper foil of the anode current collector, dried, and cold-pressed to obtain the anode active material layer. Then, after cutting, slitting, and welding the tab, the anode plate is obtained.

[0090] 4. Prepare the lithium-ion secondary battery:

[0091] The prepared cathode plate, anode plate, and separator (composed of a 9-μm PE polyethylene film with a 2-μm boehmite ceramic coating coated on both sides) are stacked in sequence, and the separator is placed between the cathode plate and the anode plate to play a role in isolation, and then wound to obtain a bare battery cell; the bare battery cell is placed in an outer packaging aluminum-plastic film, and the electrolyte (50% EMC + 30% EC + 20% DEC + 1.1 M LiPF₆ + 1% LiPO₂F₂ + 1% VC (vinylene carbonate) + 1% FEC) is injected into the dried bare battery cell. After processes such as vacuum packaging, standing, formation, shaping, and capacity testing, the preparation of the lithium-ion secondary battery of Example 1 is completed.

[0092] Example 2:

[0093] Example 2 includes the following steps:

[0094] 1. Prepare the conductive carbon black:

[0095] Carbon black raw material N134 is provided. At 160 °C, carbon black N134 is treated with 6 mol / L nitric acid for 5 h to obtain intermediate product I; and intermediate product I is washed and dried; then at 200 °C, intermediate product I is treated with 1.5 mol / L tartaric acid for 4 h to obtain intermediate product II; and intermediate product II is washed and dried; in an atmosphere of hydrogen / argon mixed gas, intermediate product II is mixed with boric acid, and the mass of boric acid is 5 wt% of carbon black N134, and then calcined at a heating rate of 3 °C / min. At 800 °C, it is kept warm for 4 h, and then naturally cooled to room temperature to obtain intermediate product III; intermediate product III is washed and dried to obtain the conductive carbon black of Example 2.

[0096] 2. Preparation of the positive electrode plate:

[0097] The positive electrode active material lithium cobaltate (LiCoO2), the conductive carbon black of Example 2 prepared above, and polyvinylidene fluoride (PVDF) are fully stirred and mixed evenly in an appropriate amount of N-methylpyrrolidone (NMP) according to a weight ratio of 96:2:2, and then coated on the positive electrode current collector aluminum foil, dried, cold-pressed to obtain the positive electrode active material layer, and then through processes such as slicing, slitting, and welding the tab, the positive electrode plate is obtained.

[0098] 3. Preparation of the negative electrode plate:

[0099] Artificial graphite, conductive agent superconducting carbon black, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are fully stirred and mixed in an appropriate amount of deionized water solvent according to a weight ratio of 95.0:1.5:1.5:2 to form a uniform negative electrode slurry. This slurry is coated on the negative electrode current collector copper foil, dried and cold-pressed to obtain the negative electrode active material layer, and then through processes such as slicing, slitting, and welding the tab, the negative electrode plate is obtained.

[0100] 4. Preparation of the lithium-ion secondary battery:

[0101] The positive electrode plate, negative electrode plate, and separator (composed of a 9-μm PE polyethylene film with a 2-μm boehmite ceramic coating coated on both sides) prepared above are stacked in sequence, and the separator is placed between the positive electrode plate and the negative electrode plate to play a role in isolation, and then wound to obtain a bare battery cell; the bare battery cell is placed in an outer packaging aluminum-plastic film, and the electrolyte (50% EMC + 30% EC + 20% DEC + 1.1 M LiPF6 + 1% LiPO2F2 + 1% VC (vinylene carbonate) + 1% FEC) is injected into the dried bare battery cell, and through processes such as vacuum packaging, standing, formation, shaping, and capacity testing, the preparation of the lithium-ion secondary battery of Example 2 is completed.

[0102] Example 3:

[0103] The steps of Example 3 are the same as those of Example 1, except that in the process of preparing conductive carbon black, the mass of boric acid selected is 20 wt% of carbon black N134.

[0104] Example 4:

[0105] The steps of Example 4 are the same as those of Example 1, except that in the process of preparing conductive carbon black, the mass of boric acid selected is 30 wt% of carbon black N134.

[0106] Example 5:

[0107] The steps of Example 5 are the same as those of Example 1, except that in the process of preparing conductive carbon black, carbon black N134 is treated with 6 mol / L nitric acid for 9 h.

[0108] Comparative Example 1:

[0109] Comparative Example 1 includes the following steps:

[0110] 1. Select conductive carbon black:

[0111] Commercial carbon black superp is used as the conductive agent in Comparative Example 1.

[0112] 2. Prepare the positive electrode plate:

[0113] The positive electrode active material lithium cobalt oxide (LiCoO2), commercial carbon black super p, and polyvinylidene fluoride (PVDF) are fully stirred and mixed evenly in an appropriate amount of N-methylpyrrolidone (NMP) according to a weight ratio of 96:2:2, and then coated on the positive electrode current collector aluminum foil, dried, cold-pressed to obtain the positive electrode active material layer, and then through cutting, slitting, and welding the tab, the positive electrode plate is obtained.

[0114] 3. Prepare the negative electrode plate:

[0115] Artificial graphite, conductive agent superconducting carbon black, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) are fully stirred and mixed in an appropriate amount of deionized water solvent according to a weight ratio of 95.0:1.5:1.5:2 to form a uniform negative electrode slurry. This slurry is coated on the negative electrode current collector copper foil, dried and cold-pressed to obtain the negative electrode active material layer, and then through cutting, slitting, and welding the tab, the negative electrode plate is obtained.

[0116] 4. Prepare the lithium-ion secondary battery:

[0117] The prepared positive electrode sheet, negative electrode sheet, and separator (composed of a 9-μm PE polyethylene film with a 2-μm boehmite ceramic coating on each side) are stacked in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wound to obtain a bare battery cell. The bare battery cell is placed in an outer packaging aluminum-plastic film, and the electrolyte (50% EMC + 30% EC + 20% DEC + 1.1 M LiPF6 + 1% LiPO2F2 + 1% VC (vinyl carbonate) + 1% FEC) is injected into the dried bare battery cell. After processes such as vacuum packaging, standing, formation, shaping, and capacity testing, the preparation of the lithium-ion secondary battery of Comparative Example 1 is completed.

[0118] Comparative Example 2:

[0119] Comparative Example 2 includes the following steps:

[0120] 1. Preparation of conductive carbon black:

[0121] Provide carbon black raw material N134, treat carbon black N134 with 6 mol / L nitric acid at 160 °C for 5 h to obtain Intermediate I; in an atmosphere of hydrogen / argon mixture, mix Intermediate I with boric acid, where the mass of boric acid is 10 wt% of carbon black N134, and then conduct calcination with a heating rate of 3 °C / min. Keep the temperature at 800 °C for 4 h, and then naturally cool to room temperature to obtain Intermediate III-2; wash and dry Intermediate III-2 to obtain the conductive carbon black of Comparative Example 2.

[0122] 2. Preparation of positive electrode sheet:

[0123] Mix the positive active material lithium cobaltate (LiCoO2), the conductive carbon black of Comparative Example 2 prepared above, and polyvinylidene fluoride (PVDF) in a weight ratio of 96:2:2, stir and mix them evenly in an appropriate amount of N-methylpyrrolidone (NMP), coat them on a positive current collector aluminum foil, dry, and cold press to obtain a positive active material layer. Then, through processes such as slicing, slitting, and welding the tab, a positive electrode sheet is obtained.

[0124] 3. Preparation of negative electrode sheet:

[0125] Mix artificial graphite, conductive agent superconducting carbon black, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a weight ratio of 95.0:1.5:1.5:2, stir and mix them evenly in an appropriate amount of deionized water solvent to form a uniform negative electrode slurry. Coat this slurry on a negative current collector copper foil, dry, and cold press to obtain a negative active material layer. Then, through processes such as slicing, slitting, and welding the tab, a negative electrode sheet is obtained.

[0126] 4. Preparation of lithium-ion secondary battery:

[0127] Stack the prepared positive electrode sheet, negative electrode sheet, and separator (composed of a 9-μm PE polyethylene film with a 2-μm boehmite ceramic coating on each side) in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then wind to obtain a bare battery cell. Place the bare battery cell in an outer packaging aluminum-plastic film, and inject the electrolyte (50% EMC + 30% EC + 20% DEC + 1.1 M LiPF6 + 1% LiPO2F2 + 1% VC (vinyl carbonate) + 1% FEC) into the dried bare battery cell. After processes such as vacuum packaging, standing, formation, shaping, and capacity testing, the preparation of the lithium-ion secondary battery of Comparative Example 2 is completed.

[0128] Comparative Example 3:

[0129] Comparative Example 3 includes the following steps:

[0130] 1. Prepare conductive carbon black:

[0131] Provide carbon black raw material N134, treat carbon black N134 with 6 mol / L nitric acid at 160 °C for 5 h to obtain Intermediate I; wash and dry Intermediate I; then treat Intermediate I with 1.5 mol / L tartaric acid at 200 °C for 4 h to obtain Intermediate II, wash and dry Intermediate II to obtain the conductive carbon black of Comparative Example 3.

[0132] 2. Prepare the positive electrode sheet:

[0133] Mix the positive electrode active material lithium cobalt oxide (LiCoO2), the conductive carbon black of Comparative Example 3 prepared above, and polyvinylidene fluoride (PVDF) in a weight ratio of 96:2:2 in an appropriate amount of N-methylpyrrolidone (NMP), stir well and mix evenly, then coat it on the positive electrode current collector aluminum foil, dry, and cold press to obtain the positive electrode active material layer. Then, after cutting, slitting, and welding the tab, the positive electrode sheet is obtained.

[0134] 3. Prepare the negative electrode sheet:

[0135] Mix artificial graphite, conductive agent superconducting carbon black, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a weight ratio of 95.0:1.5:1.5:2 in an appropriate amount of deionized water solvent, stir well to form a uniform negative electrode slurry. Coat this slurry on the negative electrode current collector copper foil, dry and cold press to obtain the negative electrode active material layer. Then, after cutting, slitting, and welding the tab, the negative electrode sheet is obtained.

[0136] 4. Prepare the lithium-ion secondary battery:

[0137] Stack the prepared positive electrode sheet, negative electrode sheet, and separator (composed of a 9-μm PE polyethylene film with a 2-μm boehmite ceramic coating on each side) in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an insulating role, and then wind to obtain a bare battery cell. Place the bare battery cell in an outer packaging aluminum-plastic film, and inject the electrolyte (50% EMC + 30% EC + 20% DEC + 1.1 M LiPF6 + 1% LiPO2F2 + 1% VC (vinylene carbonate) + 1% FEC) into the dried bare battery cell. After processes such as vacuum packaging, standing, formation, shaping, and capacity testing, the preparation of the lithium-ion secondary battery of Comparative Example 3 is completed.

[0138] Comparative Example 4:

[0139] Comparative Example 4 includes the following steps:

[0140] 1. Prepare conductive carbon black:

[0141] Provide carbon black raw material N134, and treat the carbon black raw material N134 with 1.5 mol / L tartaric acid at 200 °C for 4 h to obtain intermediate product II-2; wash and dry intermediate product II-2; in an atmosphere of hydrogen / argon mixed gas, mix intermediate product II-2 with boric acid, and the mass of boric acid is 10 wt% of carbon black N134, then carry out calcination, with a heating rate of 3 °C / min, keep the temperature at 800 °C for 4 h, and then naturally cool to room temperature to obtain intermediate product III; wash and dry intermediate product III to obtain the conductive carbon black of Comparative Example 4.

[0142] 2. Prepare a positive electrode sheet:

[0143] Mix the positive active material lithium cobaltate (LiCoO2), the conductive carbon black of Comparative Example 4 prepared above, and polyvinylidene fluoride (PVDF) in a weight ratio of 96:2:2, stir and mix evenly in an appropriate amount of N-methylpyrrolidone (NMP), coat it on a positive current collector aluminum foil, dry it, and cold press it to obtain a positive active material layer, and then through processes such as cutting, slitting, and welding the tab, a positive electrode sheet is obtained.

[0144] 3. Prepare a negative electrode sheet:

[0145] Mix artificial graphite, conductive agent superconducting carbon black, thickening agent sodium carboxymethyl cellulose (CMC), and binder styrene-butadiene rubber (SBR) in a weight ratio of 95.0:1.5:1.5:2, stir and mix evenly in an appropriate amount of deionized water solvent to form a uniform negative electrode slurry. Coat this slurry on a negative current collector copper foil, dry it and cold press it to obtain a negative active material layer, and then through processes such as cutting, slitting, and welding the tab, a negative electrode sheet is obtained.

[0146] 4. Preparation of Lithium-Ion Secondary Battery:

[0147] Stack the prepared positive electrode sheet, negative electrode sheet, and separator (composed of a 9-μm PE polyethylene film with a 2-μm boehmite ceramic coating on each side) in sequence, with the separator placed between the positive electrode sheet and the negative electrode sheet to play an isolation role, and then wind to obtain a bare battery cell; place the bare battery cell in an outer packaging aluminum-plastic film, and inject the electrolyte (50% EMC + 30% EC + 20% DEC + 1.1 M LiPF6 + 1% LiPO2F2 + 1% VC (vinyl carbonate) + 1% FEC) into the dried bare battery cell. After processes such as vacuum packaging, standing, formation, shaping, and capacity testing, the preparation of the lithium-ion secondary battery in Comparative Example 4 is completed.

[0148] Experimental Example 1: Measurement of Specific Surface Area and Porosity:

[0149] For the conductive carbon blacks and carbon black N134 obtained in Examples 1-4 and Comparative Examples 1-4, use an ASAP 2460 specific surface area and porosity analyzer to characterize the specific surface area and pore distribution of the carbon black. Take about 300 mg of the dried carbon black sample, set the degassing temperature and time to 300 °C and 2 h respectively, and place it in a liquid nitrogen environment for testing after degassing; the test results are shown in Table 1:

[0150] Table 1:

[0151]

[0152]

[0153] It can be seen that treating with nitric acid can significantly increase the values of specific surface area and porosity; by comparing Examples 1-4 and Comparative Example 3, it can be seen that whether to treat with boric acid has little effect on specific surface area and porosity; by comparing Examples 1-4 and Comparative Examples 2 and 4, it can be seen that treating with tartaric acid can further increase the value of porosity, and the increase in specific surface area is not very significant.

[0154] Experimental Example 2: Measurement of Conductivity:

[0155] For the conductive carbon blacks and carbon black N134 obtained in Examples 1-4 and Comparative Examples 1-4, use an RTS-8 digital four-probe resistance meter to measure the conductivity of the carbon black; press the carbon black into a thin disc (pressure is 15 MPa) in a cylindrical mold with a bottom diameter of 13 mm, and measure its actual thickness (about 2 mm) with a digital display thickness gauge. Then place the carbon black disc on the four-probe resistance meter platform to measure its conductivity. Press 2 discs for each group of carbon black samples, measure the conductivity of each disc 10 times, and take the average value as the final result; the test results are shown in Table 2:

[0156] Table 2:

[0157] Example Conductivity (S / cm) Example 1 5.89 Example 2 6.21 Example 3 5.76 Example 4 5.55 Example 5 5.99 Comparative Example 1 (superp) 3.52 Comparative Example 2 5.37 Comparative Example 3 6.38 Comparative Example 4 2.63 N134 1.35

[0158] It can be seen that as the specific surface area increases, the conductivity also increases; the relatively high surface area of carbon black increases the electrical contact area with the active phase particles, which is beneficial to the construction of the conductive network. By comparing Examples 1-4, it can be seen that due to the introduction of boron element, the conductivity of the conductive carbon black decreases.

[0159] Example 6:

[0160] The steps of Example 6 are the same as those of Example 1, except that in the process of preparing conductive carbon black, succinic acid is used instead of tartaric acid.

[0161] Example 7:

[0162] The steps of Example 7 are the same as those of Example 1, except that in the process of preparing conductive carbon black, citric acid is used instead of tartaric acid.

[0163] Example 8:

[0164] The steps of Example 8 are the same as those of Example 1, except that in the process of preparing conductive carbon black, oxalic acid is used instead of tartaric acid.

[0165] Example 9:

[0166] The steps of Example 9 are the same as those of Example 1, except that in the process of preparing conductive carbon black, ascorbic acid is used instead of tartaric acid.

[0167] Experimental Example 3: Test of discharge capacity retention rate and cycle life:

[0168] The discharge capacity retention rate and cycle life of Examples 1-9 and Comparative Examples 1-4 were tested;

[0169] Test of 2C discharge capacity retention rate: In a normal temperature environment (25 °C), after charging the battery cell to 4.2V at 2C and then switching to constant voltage charging with a cut-off current of 0.05C, the capacity at this time is C0; the fully charged battery is discharged to 3.0V at the required rate (2C), and the measured capacity is C1. C1 / C0 is the 2C discharge capacity retention rate.

[0170] Test of cycle life: In a constant temperature environment of 25 °C, in the voltage range of 2.5V to 4.2V, after charging at a constant current of 1C to 4.2V and then with a cut-off current of 0.05C, the charge and discharge cycle life was tested with a discharge current of 1C. The test cut-off condition was that the capacity decayed to 80% of the initial capacity. The test results are shown in Table 3:

[0171] Table 3:

[0172] Example 2C Discharge Capacity Retention Rate Number of Cycles for Capacity to Decay to 80% Example 1 96％ 850 Example 2 92％ 770 Example 3 94％ 820 Example 4 91％ 720 Example 5 87％ 700 Example 6 94％ 820 Example 7 93％ 810 Example 8 94％ 810 Example 9 94％ 800 Comparative Example 1 (superp) 92％ 480 Comparative Example 2 92％ 620 Comparative Example 3 91％ 660 Comparative Example 4 85％ 510

[0173] By comparing Examples 1-5 with Comparative Example 3, it can be seen that although the introduction of boron element will lead to a decrease in conductivity, for carbon black with a relatively high specific surface area, it often has a relatively large defect density. In the positive electrode, more carbon atom defects can provide a large number of reaction sites for the electrolyte, resulting in more side reactions, thereby accelerating capacity decay. The introduction and combination of boron element can reduce the exposed carbon atom defects, thus reducing side reactions. From the results of Example 4, it can be seen that too much boron element content not only leads to a decrease in conductivity, but also the boron element itself can cause electrochemical side reactions. By comparing Example 1 with Examples 6-9, it can be seen that using tartaric acid for the treatment in Step 2 can further improve the porosity compared with other organic acids under the condition of little change in specific surface area (i.e., little change in defect density), thereby improving the conductivity of conductive carbon black and the performance of the battery.

[0174] Other embodiments of the present disclosure will be readily contemplated by those skilled in the art upon considering the specification and practice of the disclosure herein. The present disclosure is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include known common knowledge or conventional technical means in the technical field not disclosed herein. The specification and examples are only to be considered exemplary.

Claims

1. A method for preparing conductive carbon black, wherein the conductive carbon black is used for lithium ion secondary batteries; characterized in that: The method comprises the following steps: Step 1: providing a carbon black raw material, and treating the carbon black raw material with nitric acid to obtain an intermediate product I; Step 2: treating the intermediate I with an organic acid to obtain an intermediate II; the organic acid solution is tartaric acid with a concentration of 1.2-1.5 mol / L; Step 3: treating the intermediate II with boric acid to obtain an intermediate III; the treatment comprises: mixing the intermediate II with boric acid in an atmosphere of a hydrogen / argon mixed gas, treating at 700° C.-900° C. for 3-6 hours, and the mass ratio of the carbon black raw material to the boric acid is selected from 1:(0.1-0.2); Step 4: Post-treating the intermediate product III to obtain the conductive carbon black.

2. The method according to claim 1, characterized in that In step 1, the treatment is: placing the carbon black raw material in 4-7 mol / L nitric acid at 120° C.-180° C. for 4-8 hours.

3. The method according to claim 1, characterized in that The method satisfies at least one of the following conditions: (1) Between step 1 and step 2, a washing and drying process is also included; (2) Between step 2 and step 3, a washing and drying process is also included; (3) In step 4, the post-treatment includes washing and drying processes; (4) In step 4, the post-treatment includes a calcination process in a carbon dioxide atmosphere, the calcination temperature is 800° C.-1200° C., and the calcination time is 1-3 hours.

4. A conductive carbon black, characterized in that The conductive carbon black is prepared by the method according to any one of claims 1 to 3.

5. A positive electrode slurry, characterized in that: The positive electrode slurry comprises a positive electrode active material, a binder and the conductive carbon black according to claim 4.

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