CN114927778A - Positive electrode lithium supplement additive and preparation method and application thereof - Google Patents
Positive electrode lithium supplement additive and preparation method and application thereof Download PDFInfo
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- CN114927778A CN114927778A CN202210653630.3A CN202210653630A CN114927778A CN 114927778 A CN114927778 A CN 114927778A CN 202210653630 A CN202210653630 A CN 202210653630A CN 114927778 A CN114927778 A CN 114927778A
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
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- H01M10/05—Accumulators with non-aqueous electrolyte
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Abstract
The invention relates to the technical field of lithium ion batteries, in particular to a positive electrode lithium supplement additive and a preparation method and application thereof. The anode lithium supplement additive provided by the invention is a porous material and has a core-shell structure, wherein the core material is submicron lithium oxide, and the shell material is a nano-carbon nanotube; nitrogen and Li are adsorbed in the gaps among the core-shell structures and the carbon nano tube layers 3 And N is added. The additive provided by the invention can effectively reduce the interface impedance of the anode material through the interaction of the material structure and the components, and simultaneously can improve the first charge-discharge efficiency of the battery, the capacity, the cycle performance and the service life of the battery, reduce the expansion rate of a battery core and enable the battery to have more excellent performance.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a positive electrode lithium supplement additive and a preparation method and application thereof.
Background
The lithium ion battery comprises a positive electrode material, a negative electrode material and electrolyte, wherein the negative electrode material mainly comprises silicon base, carbon base and silicon carbon base, and the electrolyte usually comprises a cyclic and linear carbonate solvent and solvated lithium salt. The electrolyte can be irreversibly decomposed at a low potential (0.8-2.0V vs. Li/Li +), and finally a thin SEI film is formed on the surface of the electrode. SEI has very important influence on the performance of the battery and can be continuously formed along with the circulation, but a large amount of lithium consumption mainly occurs in the first circulation, so that the first irreversible coulombic efficiency is reduced, and the performance of the battery is obviously reduced.
The pre-lithiation can effectively avoid collapse of an electrode structure and falling of an electrode material in the subsequent cyclic charge and discharge process of the battery, and is beneficial to improving the cycle performance of the battery. Meanwhile, the SEI film can be generated in advance, a more stable SEI film is formed through manual regulation, the consumption of electrolyte is reduced, the loss of active ions of the cathode material is reduced, and the first coulombic efficiency of the lithium ion battery is improved.
The existing lithium supplement technology is mainly divided into negative electrode lithium supplement and positive electrode lithium supplement. The common lithium supplement technology for the negative electrode mainly comprises a lithium powder doping lithium supplement technology, an ultrathin lithium belt rolling lithium supplement technology, a polymer-coated metal lithium pre-lithiation technology, and a chemical pre-lithiation technology for the negative electrode by the reaction of the metal lithium and a complexing agent. The cathode pre-lithiation can significantly improve the first coulomb efficiency of the cathode material, thereby improving the energy efficiency of the battery. However, the use of metal lithium brings certain safety problems, and the technical process of lithium supplement of the negative electrode is complicated, the environmental requirement is high, and the cost is high. After lithium is supplemented, a layer of metal lithium exists on the surface of the negative electrode, symmetrical chain carbonate such as dimethyl carbonate (DMC) and diethyl carbonate (DEC), acid ester such as Propyl Propionate (PP) and the metal lithium can generate side reaction, and the phenomena of solution discoloration and metal lithium dissolution can occur when lithium sheets enter the solution, so that the problems of non-uniform SEI film, active lithium consumption and battery impedance increase are caused. Therefore, the related technology of lithium supplement of the negative electrode is relatively large, but is rarely applied to actual production.
The positive electrode lithium supplement is generally to add a small amount of positive electrode lithium supplement additive in the positive electrode size mixing process, and the existing positive electrode lithium supplement additive such as Li 5 FeO 4 The lithium source can be provided during the first charging, lithium consumed by the SEI film formation is compensated, and the first coulombic efficiency is improved. However, the lithium pre-charging efficiency of the conventional positive electrode lithium supplement additive is low, the improvement on the first charging and discharging efficiency is limited, the impedance of a positive electrode material is increased, and the gram capacity exertion of the positive electrode material is reduced.
Disclosure of Invention
In order to overcome the defects that the conventional positive electrode lithium supplement additive has a limited effect of improving the first charge-discharge efficiency of a battery, can increase the impedance of a positive electrode material and reduce the gram volume exertion of the material, the positive electrode lithium supplement additive and the preparation method and application thereof are further provided.
In order to achieve the purpose, the invention adopts the following technical scheme:
the additive for supplementing lithium to the positive electrode is a mixture of more than oneThe porous material is of a core-shell structure, the core material is submicron lithium oxide, and the shell material is a nano-scale carbon nanotube; nitrogen and Li are adsorbed in the gaps among the core-shell structures and among the carbon nano tube layers 3 And N is added. As can be understood, the core of the additive material is submicron lithium oxide, a gap is formed between the core and the shell, and the shell material is a nano carbon nanotube; nitrogen and Li are adsorbed in the gaps among the core-shell structures and among the carbon nano tube layers 3 N。
Preferably, the lithium oxide accounts for 30.76-66.67% of the mass of the additive, the carbon nano tubes account for 33.33-69.24% of the mass of the additive, the nitrogen accounts for 0.7-1.5% of the volume of the additive, and the Li 3 N accounts for 0.01-0.05% of the mass of the additive.
Preferably, the particle size of the lithium oxide is 0.1-0.5 μm, and the particle size of the carbon nano tube is 10-15 nm.
The submicron lithium oxide is obtained by calcining micron lithium carbonate with the particle size of 2-5 mu m. Optionally, the calcination temperature is 1200-1600 ℃, the heating rate is 3-5 ℃/min, and the calcination time is 6-10 h.
The invention also provides a preparation method of the positive electrode lithium supplement additive, which comprises the following steps:
1) mixing the nano-scale carbon nano-tube, the polar organic solvent, the dispersing agent and the non-polar organic solvent, carrying out ball milling, then adding micron-scale lithium carbonate, continuing ball milling, and drying to obtain a dried mixed material;
2) and calcining the dried mixed material in a high-pressure nitrogen atmosphere, wherein the nitrogen pressure is not lower than 70kPa, so as to obtain the anode lithium supplement additive.
Preferably, the mass ratio of the nanoscale carbon nanotube to the polar organic solvent to the dispersing agent to the non-polar organic solvent is (8-12): 100: (0.4-1): (0.8-1.4);
optionally, the mass ratio of the nanoscale carbon nanotube to the polar organic solvent to the dispersing agent to the non-polar organic solvent is 10: 100: 0.6: 1.0;
the mass ratio of the nano-scale carbon nano-tubes to the micro-scale lithium carbonate is (0.2-0.9): 1. The invention can further ensure that the battery adopting the additive material has more excellent performance and reduces the battery impedance by controlling the mass ratio of the nano-scale carbon nano tube to the micro-scale lithium carbonate to be (0.2-0.9): 1; if the carbon nanotube ratio is too low, the content of Li on the carbon nanotube layer is too high, the quantity of lithium ions provided in the process of deintercalation of metallic lithium is increased suddenly, the thickness of a battery SEI film is increased, the battery impedance is increased, and the performance of the battery efficiency is influenced; preferably, the mass ratio of the nano-scale carbon nanotubes to the micro-scale lithium carbonate is 0.6: 1.
Preferably, the ball milling temperature is 21-29 ℃, the ball milling time is 2-6h, and the continuous ball milling time is not more than 8 h. Optionally, the continuous ball milling time is 1-8 h. The invention controls the ball milling temperature to be 21-29 ℃ and the ball milling time to be 2-6 h. The carbon nano tubes can be uniformly dispersed in the slurry, and the phenomenon that the carbon atoms at the fracture part can irreversibly react with Li + to cause the electrochemical performance of the lithium ion battery to be poor due to the damage to the structure of the carbon nano tubes caused by overlong grinding time can also be avoided.
The drying temperature is 80-100 ℃, and the drying time is 8-10 h;
the calcination temperature is 1200-1600 ℃, the heating rate is 3-5 ℃/min, and the calcination time is 6-10 h; preferably, the calcination temperature is 1400 ℃, and the calcination time is 8 h. The invention is beneficial to Li by controlling the calcination temperature and the calcination time 2 CO 3 Decomposition at high temperature to form Li 2 O and CO 2 The method is favorable for improving the diffusion of metal Li atoms into the carbon nanotube material layer and enhancing the adhesion with the metal Li, and the generation of gas enables the lithium ion battery anode lithium supplement additive to have the structural characteristic of porosity and looseness, is favorable for shortening the migration path and the interface impedance of Li + ions, and is convenient for the Li + ions to migrate and continuously supplement a lithium source for the lithium ion battery, thereby promoting the first effect of the lithium ion battery.
The nitrogen pressure is 70-74 kPa;
the grain size of the nano-scale carbon nano-tube is 10-15nm, and the grain size of the micron-scale lithium carbonate is 2-5 mu m;
after the calcining and sintering, the steps of crushing, grinding and sieving the calcined material are also included;
the types of the polar organic solvent, the dispersing agent and the nonpolar organic solvent are not particularly limited, and the preferred polar organic solvent is N-methylpyrrolidone, the dispersing agent is polyvinylpyrrolidone and the nonpolar organic solvent is toluene. The invention can promote the uniform dispersion of the carbon nano tube and avoid the agglomeration of the carbon nano tube by the polyvinylpyrrolidone and the toluene.
The invention is not limited to the ball milling media, and the object of the invention can be achieved by the conventional ball milling media in the field. Optionally, the ball milling medium can be zirconium silicate beads or zirconium oxide beads with the diameter of 1.0-1.2 mm.
The invention also provides a lithium ion battery anode material which comprises an anode active substance, the anode lithium supplement additive, a conductive agent and a binder, wherein the amount of the anode lithium supplement additive accounts for 0.1-10% of the total mass of the anode material.
The composition of the positive electrode active material is not specifically limited in the present invention, and optionally, the positive electrode active material is selected from one or more of a lithium cobaltate positive electrode material, a lithium nickel manganese aluminate positive electrode material, a lithium manganese oxide positive electrode material, a lithium nickel manganese oxide positive electrode material, a lithium iron phosphate positive electrode material, a lithium manganese phosphate positive electrode material, and a lithium manganese iron phosphate positive electrode material, but is not limited to the above listed species, and other positive electrode active materials containing transition metals commonly used in the art are also applicable to the present invention.
The invention does not specifically limit the types of the conductive agent and the binder, and optionally, the conductive agent is one or more of Super P, acetylene black, Ketjen black, conductive graphite and graphene.
The binder is one or more of PVDF (polyvinylidene fluoride), LA132, LA133, CMC (carboxymethyl cellulose) and SBR (styrene butadiene rubber). Wherein LA132, LA133 are commercially available binders conventional in the art.
The invention also provides a lithium ion battery which comprises a positive electrode containing the lithium ion battery positive electrode material. The lithium ion battery also comprises a negative electrode material, wherein the negative electrode material comprises one or more of graphite, silicon carbon and silicon oxygen. Among them, negative electrode materials having low coulombic efficiency for the first time, such as silicon carbon and silicon oxygen, are preferable.
The invention has the beneficial effects that:
1. the anode lithium supplement additive provided by the invention is a porous material and has a core-shell structure, wherein the core material is submicron lithium oxide, and the shell material is a nano-carbon nanotube; nitrogen and Li are adsorbed in the gaps among the core-shell structures and the carbon nano tube layers 3 And N is added. The nano-carbon nanotube is used as a shell material, the excellent conductivity of the nano-carbon nanotube is favorable for reducing the interface impedance of the anode material, the porous structure of the additive is favorable for the adsorption and the layering of metal Li, and the Li + ion migration is convenient for continuously supplementing a lithium source to the lithium ion battery, so that the first effect of the lithium ion battery is promoted, and meanwhile, the nano-carbon nanotube shell material increases submicron Li 2 The surface activity of O is reduced, the Gibbs free energy of O is reduced, the migration of Li + ions can be promoted, and the interlayer structure of the carbon nano tube provides an attachment site for metal lithium, so that more metal lithium is allowed to diffuse and be embedded into the interlayer structure of the carbon nano tube under the action of high temperature; meanwhile, nitrogen and Li are adsorbed in the gaps between the core-shell structures and the carbon nano tube layers 3 N, in the using process of the lithium ion battery, lithium between the carbon nano tube layers is firstly subjected to deintercalation, and submicron grade Li 2 The O inner core is finally subjected to de-intercalation to supplement the metallic lithium between the carbon nano tube layers, so that Li + ions are continuously provided for the lithium ion battery, and meanwhile, Li 3 N can realize an electrochemical reaction between 0.01V and 4.5V under the catalytic action of metal in the anode material, and promote the anode and the electrolyte to form a compact CEI film layer, nitrogen between layers is easy to react with lithium element to obtain lithium nitride in actual work, the consumed lithium nitride is further supplemented, and the catalytic action is continuously exerted; meanwhile, the positive electrode potential of the additive material obtained by the invention is high in the charging process, and the higher potential can promote Li + to enter the negative electrode side and enter the negative electrode material at the lower potential, so that the additive material canThe method realizes the prelithiation of various cathode materials, and meanwhile, the submicron lithium oxide and the nanoscale carbon nano tube can realize uniform and compact contact with electrode material particles, thereby greatly improving the efficiency of the prelithiation process. According to the invention, through a specific core-shell structure, the core material is submicron lithium oxide, and the shell material is a nano carbon nanotube; nitrogen and Li are adsorbed in the gaps between the core-shell structures and the carbon nano tube layers 3 And N, through interaction of a material structure and components, the impedance of a positive electrode material can be effectively reduced, the first charge-discharge efficiency of the battery can be improved, the capacity, the cycle performance and the service life of the battery can be improved, the expansion rate of a battery cell is reduced, and the battery has more excellent performance.
2. The preparation method of the positive electrode lithium supplement additive provided by the invention comprises the steps of mixing the nano-scale carbon nano tube, the polar organic solvent, the dispersing agent and the non-polar organic solvent, carrying out ball milling, then adding the micron-scale lithium carbonate, continuing ball milling, and drying to obtain a dried mixed material; and then calcining the dried mixed material in a high-pressure nitrogen atmosphere to obtain the anode lithium supplement additive. The invention forms micron lithium carbonate mixed material coated by nanometer carbon nanometer tube by mixing and ball milling nanometer carbon nanometer tube and micron lithium carbonate, then calcinates under high pressure nitrogen, Li 2 CO 3 Decomposition at high temperature to form Li 2 O and CO 2 The generation of gas is beneficial to opening the passage of the shell material, and the Li of the nuclear material is reduced + Migration resistance during the charging and discharging process of the battery enables the additive to have a porous structural characteristic; moreover, the carbon nano tubes are microscopically ordered in short distance, so that the adsorption and layering of metal Li are facilitated, Li + can be rapidly transferred to electrolyte to participate in the charging and discharging process, and the first effect of the lithium ion battery is further promoted. In addition, the material is calcined in a high-pressure nitrogen atmosphere, so that partial Li atoms can be promoted to diffuse into the carbon nanotube layer; meanwhile, the formation of the porous shell structure promotes high-pressure nitrogen to enter the core-shell structure, which is favorable for the absorption of N in the gaps between the core-shell structures and the carbon nano tube layers 2 And Li 3 And (4) forming N. Meanwhile, micron-sized lithium carbonate forms submicron particles in the calcining processLithium oxide of the meter level, the reduction of size can form certain space between the lithium oxide nuclear structure and the carbon nanotube layer of cladding at the surface, and Li + migrates fast, and then promotes the battery performance. The additive material prepared by the method has a specific core-shell structure, wherein the core material is submicron lithium oxide, and the shell material is a nanoscale carbon nanotube; nitrogen and Li are adsorbed in the gaps among the core-shell structures and the carbon nano tube layers 3 And N, through interaction of a material structure and components, the impedance of the anode material can be effectively reduced, the first charge-discharge efficiency of the battery can be improved, the capacity, the cycle performance and the service life of the battery can be improved, the expansion rate of the battery cell is reduced, and the battery has more excellent performance.
Meanwhile, the method provided by the invention does not need to change the original production process and has lower cost; the prepared material not only avoids the direct use of metal lithium, but also obviously improves the safety and the reliability compared with the prior negative electrode lithium supplement; and the lithium source can be provided during the first charging, the lithium consumed by the SEI film formed by the negative electrode material is compensated, the first coulombic efficiency of the lithium ion battery and the battery capacity and other performances are improved, and the lithium ion battery has important significance for the commercial application of carbon-based negative electrode materials, silicon-based negative electrode materials and silicon-carbon negative electrode materials.
Detailed Description
The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.
The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.
Example 1
The embodiment provides a preparation method of a positive electrode lithium supplement additive, which comprises the following steps:
1) adding 10g of carbon nanotubes (the particle size is 12nm) into 100g of N-methyl pyrrolidone, adding 0.6g of polyvinylpyrrolidone and 1.0g of toluene, carrying out ball milling on the mixed slurry by adopting a high-energy ball mill at the ball milling temperature of 25 ℃ for 4h, using zirconium oxide beads with the diameter of 1.0-1.2mm as a ball milling medium, then adding lithium carbonate (the particle size of the lithium carbonate is 3 mu m, and the mass ratio of the carbon nanotubes to the lithium carbonate is 0.9:1), continuing ball milling for 6h to fully mix the lithium carbonate in the slurry, and after finishing ball milling, putting the slurry into a forced air drying oven to dry at 90 ℃ for 9h to obtain a dried mixed material;
2) placing the dried mixed material in a tubular heating furnace to calcine under the high-pressure nitrogen atmosphere (the nitrogen pressure is 70kPa), the calcining temperature is 1400 ℃, the heating rate is 3 ℃/min, the calcining time is 8h, crushing, grinding, sieving and vacuum storing are carried out on the material after calcining and sintering, the anode lithium supplement additive is obtained, the obtained anode lithium supplement additive is a porous material and has a core-shell structure, the core material is lithium oxide with the particle size of 0.2 mu m, the shell material is carbon nano tubes with the particle size of 12nm, nitrogen and Li are adsorbed in gaps between the core-shell structures and among the carbon nano tube layers 3 N, wherein the lithium oxide accounts for 37.657% of the mass of the additive, the carbon nano tubes account for 62.325% of the mass of the additive, the nitrogen accounts for 0.842% of the volume of the additive, and Li 3 N accounts for 0.018 wt% of the additive.
Example 2
The embodiment provides a preparation method of a positive electrode lithium supplement additive, which comprises the following steps:
1) adding 8g of carbon nanotubes (the particle size is 13nm) into 100g of N-methyl pyrrolidone, adding 0.4g of polyvinylpyrrolidone and 1.4g of toluene, carrying out ball milling on the mixed slurry by using a high-energy ball mill at the ball milling temperature of 25 ℃ for 4h, using zirconia beads with the diameter of 1.0-1.2mm as a ball milling medium, then adding lithium carbonate (the particle size of the lithium carbonate is 3 mu m, and the mass ratio of the carbon nanotubes to the lithium carbonate is 0.8:1), continuing ball milling for 6h to fully mix the lithium carbonate in the slurry, and after the ball milling is finished, placing the slurry in a forced air drying oven to dry at 85 ℃ for 9h to obtain a dried mixed material;
2) placing the dried mixed material in a tubular heating furnace to calcine under high-pressure nitrogen atmosphere (the nitrogen pressure is 71kPa), the calcining temperature is 1300 ℃, the heating rate is 4 ℃/min, the calcining time is 9h, crushing, grinding, sieving and vacuum storing are carried out on the material after calcining and sintering, the anode lithium supplement additive is obtained, the obtained anode lithium supplement additive is a porous material and has a core-shell structure, the core material is lithium oxide with the particle size of 0.2 mu m, the shell material is carbon nano tubes with the particle size of 13nm, and nitrogen and Li are adsorbed in gaps between the core-shell structures and among carbon nano tube layers 3 N, wherein the lithium oxide accounts for 42.840% of the mass of the additive, the carbon nano tubes account for 57.129% of the mass of the additive, the nitrogen accounts for 0.891% of the volume of the additive, and Li 3 N accounts for 0.031% of the mass of the additive.
Example 3
The embodiment provides a preparation method of a positive electrode lithium supplement additive, which comprises the following steps:
1) adding 12g of carbon nanotubes (the particle size is 14nm) into 100g of N-methyl pyrrolidone, adding 1g of polyvinylpyrrolidone and 0.8g of toluene, carrying out ball milling on the mixed slurry by using a high-energy ball mill, wherein the ball milling temperature is 25 ℃, the ball milling time is 4h, a ball milling medium adopts zirconia beads with the diameter of 1.0-1.2mm, then adding lithium carbonate (the particle size of the lithium carbonate is 3 mu m, and the mass ratio of the carbon nanotubes to the lithium carbonate is 0.8:1), continuing ball milling for 6h, fully mixing the lithium carbonate in the slurry, and after the ball milling is finished, putting the slurry into an air-blowing drying oven to dry for 8h at the temperature of 100 ℃ to obtain a dried mixed material;
2) placing the dried mixed material in a tubular heating furnace to be calcined in a high-pressure nitrogen atmosphere (the nitrogen pressure is 72kPa), the calcining temperature is 1600 ℃, the heating rate is 3 ℃/min, the calcining time is 6h, crushing, grinding, sieving and vacuum storing are carried out on the material after calcining, and the anode lithium supplement additive is obtained, is a porous material and has a core-shell structure, the core material is lithium oxide with the particle size of 0.2 mu m, the shell material is a carbon nano tube with the particle size of 14nm, and the anode lithium supplement additive is prepared by the steps ofNitrogen and Li are adsorbed in the gaps between the core-shell structures and among the carbon nano tube layers 3 N, wherein lithium oxide accounts for 40.712% of the mass of the additive, carbon nano tubes accounts for 59.251% of the mass of the additive, nitrogen accounts for 0.843% of the volume of the additive, and Li 3 N accounts for 0.037 percent of the mass of the additive.
Example 4
This example provides a method for preparing a positive electrode lithium supplement additive, which is different from example 1 in that the mass ratio of carbon nanotubes to lithium carbonate in step 1) is 0.6: 1.
The prepared positive electrode lithium supplement additive is a porous material and has a core-shell structure, wherein the core material is lithium oxide with the particle size of 0.2 mu m, the shell material is a carbon nano tube with the particle size of 12nm, and nitrogen and Li are adsorbed in gaps among the core-shell structures and among carbon nano tube layers 3 N, wherein the lithium oxide accounts for 50.345% of the mass of the additive, the carbon nano tubes account for 49.613% of the mass of the additive, the nitrogen accounts for 0.957% of the volume of the additive, and Li 3 N accounts for 0.042 percent of the mass of the additive.
Example 5
This example provides a method for preparing a positive electrode lithium supplement additive, which is different from example 1 in that the mass ratio of carbon nanotubes to lithium carbonate in step 1) is 0.4: 1.
The prepared positive electrode lithium supplement additive is a porous material and has a core-shell structure, wherein the core material is lithium oxide with the particle size of 0.2 mu m, the shell material is a carbon nano tube with the particle size of 12nm, and nitrogen and Li are adsorbed in gaps among the core-shell structures and among carbon nano tube layers 3 N, wherein the lithium oxide accounts for 58.394% of the mass of the additive, the carbon nano tube accounts for 41.563% of the mass of the additive, the nitrogen accounts for 0.984% of the volume of the additive, and Li 3 N accounts for 0.043 percent of the mass of the additive.
Example 6
This example provides a method for preparing a positive electrode lithium supplement additive, which is different from example 1 in that the mass ratio of carbon nanotubes to lithium carbonate in step 1) is 0.2: 1.
The prepared anode lithium supplement additive is a porous materialThe composite material has a core-shell structure, wherein the core material is lithium oxide with the particle size of 0.2 mu m, the shell material is a carbon nano tube with the particle size of 12nm, and nitrogen and Li are adsorbed in gaps among the core-shell structure and among carbon nano tube layers 3 N, wherein the lithium oxide accounts for 65.810% of the mass of the additive, the carbon nano tube accounts for 34.141% of the mass of the additive, the nitrogen accounts for 1.108% of the volume of the additive, and Li 3 N accounts for 0.049 percent of the mass of the additive.
Comparative example 1
The positive electrode lithium supplement additive provided by the comparative example is the carbon nano tube with the particle size of 12 nm.
Comparative example 2
The comparative example provides a method for preparing a positive electrode lithium supplement additive, comprising the following steps:
1) adding 10g of carbon nanotubes (the particle size is 12nm) into 100g of N-methyl pyrrolidone, adding 0.6g of polyvinylpyrrolidone and 1.0g of toluene, carrying out ball milling on the mixed slurry by using a high-energy ball mill at the ball milling temperature of 25 ℃ for 4h, using zirconia beads with the diameter of 1.0-1.2mm as a ball milling medium, and after the ball milling is finished, placing the slurry in a forced air drying oven to dry for 9h at the temperature of 90 ℃ to obtain a dried mixed material;
2) and (3) placing the dried mixed material in a tubular heating furnace to calcine under the high-pressure nitrogen atmosphere (the nitrogen pressure is 70kPa), the calcining temperature is 1400 ℃, the heating rate is 3 ℃/min, the calcining time is 8h, and crushing, grinding, sieving and vacuum storing are carried out on the material after calcining and sintering to obtain the anode lithium supplement additive.
Comparative example 3
The comparative example provides a preparation method of a positive electrode lithium supplement additive, and compared with the embodiment 1, the difference is that in the step 2), the dried mixed material is placed in a tubular heating furnace to be calcined in a normal-pressure nitrogen atmosphere, the calcination temperature is 1400 ℃, the heating rate is 3 ℃/min, the calcination time is 8h, and after calcination, the material is crushed, ground, sieved and stored in vacuum, so that the positive electrode lithium supplement additive is obtained. The prepared anode lithium supplement additive is a porous material with a core-shell structure, the core material is lithium oxide with the grain diameter of 0.5 mu m,the shell material is carbon nano tube with the particle size of 15nm, and CO which is not desorbed is adsorbed between the layers of the carbon nano tube 2 Gases, which increase Li + migration resistance, reducing the performance of the additive; wherein lithium oxide accounts for 30.76% of the mass of the additive, carbon nano tubes account for 69.24% of the mass of the additive, nitrogen is adsorbed on the surface of the carbon nano tube shell in trace, and no Li is detected 3 N production, indicating that nitrogen at atmospheric pressure hardly promotes N 2 Molecules enter the gaps of the core-shell structure of the material to participate in the reaction.
Test example
Manufacture of lithium ion batteries
1) Preparing a positive pole piece: using LiNi 0.65 Mn 0.35 O 2 Taking the material as a positive electrode active substance, homogenizing the positive electrode active substance, the positive electrode lithium supplement additive provided by the embodiment or the comparative example and polyvinylidene fluoride according to the mass ratio of 96% to 2.5% to 1.5%, and preparing slurry; the prepared slurry was uniformly coated on an aluminum foil 12 μm thick with a double-side coating weight of 50mg/cm 2 And then drying, rolling, die cutting and punching to obtain the positive pole piece.
2) Preparation of the electrolyte
An equal volume of ethylene carbonate was dissolved in ethyl methyl carbonate and then an appropriate amount of LiPF was added 6 Uniformly dissolving the electrolyte in the mixed solvent to form 1mol/L electrolyte for later use.
3) Negative pole piece
The negative plate is made of a silicon-carbon negative electrode material (the silicon-carbon negative electrode material contains 6.8 wt% of Si), the silicon-carbon negative electrode material, styrene butadiene rubber, sodium carboxymethylcellulose and a conductive agent Super P (superconducting carbon black) are mixed according to the mass ratio of 95 wt%: 2.2 wt%: 1.8 wt%: 1 wt%, deionized water is used for homogenization, the viscosity of slurry is adjusted to 3000 plus or minus 5000cP (the temperature standard of the tested slurry is 25 +/-2 ℃), the solid content is 50 +/-2%), the prepared slurry is uniformly coated on copper foil with the thickness of 6 mu m, and the coating weight of the two surfaces of the copper foil is 30mg/cm 2 And then drying, rolling, die cutting and punching into the negative pole piece.
4) And (3) isolation film: the PET isolation film is selected and has a thickness of 16 μm.
5) Preparing a battery:
and stacking the positive plate, the isolating film and the negative plate in sequence, packaging into a soft package battery, baking, injecting liquid, pre-charging, forming, sealing and manufacturing into the battery cell.
Test example
The electrochemical performance of the prepared batteries is tested respectively, and the specific test is as follows:
the test method for 1C initial discharge capacity is as follows: and charging to 4.2V at constant current and constant voltage with 1C rate, and then discharging to 2.7V at 1C rate (the recorded discharge capacity is 1C initial discharge capacity).
The first charge-discharge efficiency (first effect) was tested as follows: discharging to 2.7V at 1C rate, and constant-current and constant-voltage charging to 4.2V at 1C rate (recording charge capacity C) 0 ) 1C rate discharge to 2.7V (recording discharge capacity C) 1 ) (ii) a First charge-discharge efficiency/% (C) 1 /C 0 )*100％。
The capacity retention rate was tested as follows: charging to 4.2V at constant current and constant voltage of 1C rate, and discharging to 2.7V at 1C rate (recording discharge capacity C) 1 ) Recording and playing capacitance C after 200 cycles of circulation 200 (ii) a Capacity retention rate/% (C) 200 /C 1 )*100％。
The impedance DCIR was tested as follows: discharging for 10 seconds at constant current with the current I as 300A, and recording the voltage change value delta V; DCIR ═ Δ V/I.
The calendar life test method is as follows: the capacity retention (%) of the battery at 100% SOC (4.2V) for 60 days was tested under an environment of 55 ℃.
The method for testing the cell expansion rate comprises the following steps: the method comprises the following steps of flatly placing a battery cell on a horizontal desktop, measuring the horizontal height of the highest point of the center of the battery cell (namely H1) by using a laser range finder, then charging the battery cell to 4.2V at a constant current and a constant voltage with a 1C multiplying power, then discharging the battery cell to 2.7V with a 1C multiplying power, flatly placing the battery cell on the horizontal desktop again after circulating for 200 circles, measuring the horizontal height of the highest point of the center of the battery cell (namely H2) by using the laser range finder, and measuring the battery cell expansion rate/% (H2-H1)/H1) after circulation by 100%;
the method comprises the steps of flatly placing a battery cell on a horizontal desktop, measuring the horizontal height of the highest point of the center of the battery cell (namely H1) by using a laser range finder, storing the battery cell at 100% SOC (4.2V) for 60 days in an environment with the temperature of 55 ℃, flatly placing the battery cell on the horizontal desktop again, measuring the horizontal height of the highest point of the center of the battery cell (namely H2) by using the laser range finder, and measuring the battery cell expansion rate/% (H2-H1)/H1) 100% after storage.
The test results are shown in table 1.
TABLE 1
As can be seen from comparative examples 1 and 2, the performance of the carbon nanotubes in the lithium ion battery is deteriorated by ball milling and high temperature treatment alone. Compared with the embodiment 1, the lithium ion battery anode lithium supplement additive disclosed by the invention is beneficial to Li + ion migration and can be used for continuously supplementing a lithium source for a lithium ion battery, so that the first effect of the lithium ion battery is promoted, and the performances such as the capacity of the lithium ion battery are improved. Compared with the embodiment 1, the lithium ion battery positive electrode lithium supplement additive is obtained by calcining in a high-pressure nitrogen atmosphere, so that nitrogen and Li are adsorbed in the gaps among the core-shell structures and the carbon nanotube layers 3 And N, through interaction of a material structure and components, the impedance of the anode material can be effectively reduced, the first charge-discharge efficiency of the battery can be improved, the capacity, the cycle performance and the service life of the battery can be improved, the expansion rate of the battery cell is reduced, and the battery has more excellent performance.
The lithium ion battery anode lithium supplement additive provided by the invention can effectively promote the formation of an SEI film, improve the first effect of a battery and reduce the impedance of the battery. The positive electrode lithium supplement additive can provide sufficient lithium ions, surplus Li + provided in the first charging process is obviously enough to compensate Li + lost by an SET film formed on the surface of a negative electrode, and the formation of a more uniform and compact SEI film is facilitated, so that the first effect is improved, the impedance of a positive electrode material can be effectively reduced, the capacity, the cycle performance and the service life of the battery can be improved, the expansion rate of a battery cell is reduced, and the battery has more excellent performance.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (10)
1. The anode lithium supplement additive is characterized in that the additive is a porous material and has a core-shell structure, wherein the core material is submicron lithium oxide, and the shell material is a nano-scale carbon nano tube; nitrogen and Li are adsorbed in the gaps among the core-shell structures and among the carbon nano tube layers 3 N。
2. The positive electrode lithium supplement additive according to claim 1, wherein the lithium oxide accounts for 30.76-66.67% of the mass of the additive, the carbon nanotubes accounts for 33.33-69.24% of the mass of the additive, the nitrogen accounts for 0.7-1.5% of the volume of the additive, and the Li 3 N accounts for 0.01-0.05% of the mass of the additive.
3. The additive for supplementing lithium to the positive electrode according to claim 1 or 2, wherein the particle size of the lithium oxide is 0.1 to 0.5 μm, and the particle size of the carbon nanotube is 10 to 15 nm.
4. The positive electrode lithium supplement additive according to any one of claims 1 to 3, wherein the submicron lithium oxide is obtained by calcining micron lithium carbonate with a particle size of 2 to 5 μm.
5. The method for preparing the lithium supplement additive for the positive electrode as claimed in any one of claims 1 to 4, comprising the steps of:
1) mixing the nano-scale carbon nano-tube, the polar organic solvent, the dispersing agent and the non-polar organic solvent, carrying out ball milling, then adding micron-scale lithium carbonate, continuing ball milling, and drying to obtain a dried mixed material;
2) and calcining the dried mixed material in a high-pressure nitrogen atmosphere, wherein the nitrogen pressure is not lower than 70kPa, so as to obtain the anode lithium supplement additive.
6. The preparation method of the positive lithium supplement additive according to claim 5, wherein the mass ratio of the nanoscale carbon nanotubes to the polar organic solvent to the dispersing agent to the non-polar organic solvent is (8-12): 100: (0.4-1): (0.8-1.4);
the mass ratio of the nano-scale carbon nano-tubes to the micro-scale lithium carbonate is (0.2-0.9): 1.
7. The preparation method of the positive electrode lithium supplement additive according to claim 5 or 6, wherein the ball milling temperature is 21-29 ℃, the ball milling time is 2-6h, and the continuous ball milling time is not more than 8 h;
the drying temperature is 80-100 ℃, and the drying time is 8-10 h;
the calcination temperature is 1200-1600 ℃, the heating rate is 3-5 ℃/min, and the calcination time is 6-10 h;
the nitrogen pressure is 70-74 kPa;
the grain size of the nano-scale carbon nano-tube is 10-15nm, and the grain size of the micron-scale lithium carbonate is 2-5 mu m;
after the calcining and sintering, the steps of crushing, grinding and sieving the calcined material are also included;
the polar organic solvent is N-methyl pyrrolidone, the dispersing agent is polyvinylpyrrolidone, and the nonpolar organic solvent is toluene.
8. The positive electrode material of the lithium ion battery is characterized by comprising a positive electrode active material, the positive electrode lithium supplement additive as defined in any one of claims 1 to 4, a conductive agent and a binder, wherein the amount of the positive electrode lithium supplement additive accounts for 0.1 to 10 percent of the total mass of the positive electrode material.
9. The positive electrode material of claim 8, wherein the positive active material is selected from one or more of a lithium cobaltate positive electrode material, a lithium nickel manganese aluminate positive electrode material, a lithium manganese oxide positive electrode material, a lithium nickel manganese oxide positive electrode material, a lithium iron phosphate positive electrode material, a lithium manganese phosphate positive electrode material, and a lithium manganese iron phosphate positive electrode material.
10. A lithium ion battery comprising a positive electrode comprising the lithium ion battery positive electrode material of claim 8 or 9.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115621461A (en) * | 2022-10-13 | 2023-01-17 | 江苏正力新能电池技术有限公司 | Positive electrode lithium supplement agent, preparation method thereof, positive electrode piece and battery |
| CN115764010A (en) * | 2022-10-25 | 2023-03-07 | 江苏正力新能电池技术有限公司 | Positive electrode lithium supplement agent, positive electrode lithium supplement pole piece prepared from positive electrode lithium supplement agent and lithium ion battery |
| CN117936757A (en) * | 2024-03-21 | 2024-04-26 | 瑞浦兰钧能源股份有限公司 | Lithium supplementing material, lithium supplementing diaphragm and preparation method of lithium supplementing diaphragm |
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2022
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115621461A (en) * | 2022-10-13 | 2023-01-17 | 江苏正力新能电池技术有限公司 | Positive electrode lithium supplement agent, preparation method thereof, positive electrode piece and battery |
| CN115764010A (en) * | 2022-10-25 | 2023-03-07 | 江苏正力新能电池技术有限公司 | Positive electrode lithium supplement agent, positive electrode lithium supplement pole piece prepared from positive electrode lithium supplement agent and lithium ion battery |
| CN115764010B (en) * | 2022-10-25 | 2024-09-27 | 江苏正力新能电池技术股份有限公司 | Positive electrode lithium supplementing agent, positive electrode lithium supplementing pole piece prepared from same and lithium ion battery |
| CN117936757A (en) * | 2024-03-21 | 2024-04-26 | 瑞浦兰钧能源股份有限公司 | Lithium supplementing material, lithium supplementing diaphragm and preparation method of lithium supplementing diaphragm |
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