CN111710865A - Lithium powder dispersion liquid and preparation method and application thereof - Google Patents
Lithium powder dispersion liquid and preparation method and application thereof Download PDFInfo
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- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
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Abstract
The invention discloses a lithium powder dispersion liquid and a preparation method and application thereof. The method for preparing the lithium powder dispersion liquid is characterized by comprising the following steps: mixing carbon nano tubes, a surfactant and an organic solvent to obtain a carbon nano tube colloidal solution; and mixing a stabilized lithium powder with the colloidal solution to obtain a lithium powder dispersion, wherein the stabilized lithium powder comprises lithium metal particles and a soluble lithium salt coating layer formed on the surfaces of the lithium metal particles. The method is simple in process, and when the prepared lithium powder dispersion liquid is used for the pre-lithiation of the negative plate, the initial efficiency can be improved, and a layer of ion fast channel can be constructed on the surface of the negative plate, so that the rate capability of the negative plate is obviously improved.
Description
Technical Field
The invention belongs to the field of lithium batteries, and particularly relates to a lithium powder dispersion liquid, and a preparation method and application thereof.
Background
Currently, lithium ion batteries have gradually merged into every part of life as mature energy storage units. In the daily life, electrical appliances such as mobile phones and notebooks use lithium ion batteries as their energy storage units, and in recent years, lithium ion batteries are also gradually used in power energy storage, such as electric vehicles. For a lithium ion battery, the most influential factors on its energy density should be the positive electrode material and the negative electrode material. At present, the commercial graphite cathode material for the lithium ion battery has lower theoretical capacity, so that the space for further improving the capacity is very small, and the demand of future high-capacity and long-service-life electronic equipment cannot be met. The metal and alloy materials are novel high-efficiency lithium storage negative electrode material systems which are researched more in recent years, wherein the silicon-oxygen material is concerned about due to the fact that the silicon-oxygen material has extremely high theoretical specific capacity, but the silicon-oxygen material can form some irreversible capacity byproducts during first charging, and therefore the first efficiency of the battery is far from reaching the application standard.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. To this end, an object of the present invention is to provide a lithium powder dispersion, a method for preparing the same, and applications thereof. The method for preparing the lithium powder dispersion liquid is simple in process, and when the prepared lithium powder dispersion liquid is used for the pre-lithiation of the negative plate, the initial efficiency can be improved, and a layer of ion fast channel can be constructed on the surface of the negative plate, so that the rate capability of the negative plate is obviously improved.
According to a first aspect of the present invention, a method of preparing a lithium powder dispersion is provided. According to an embodiment of the invention, the method comprises:
mixing carbon nano tubes, a surfactant and an organic solvent to obtain a carbon nano tube colloidal solution;
mixing stabilized lithium powder with the colloidal solution to obtain a lithium powder dispersion,
wherein the stabilized lithium powder includes lithium metal particles and a soluble lithium salt coating layer formed on the surfaces of the lithium metal particles.
The method for preparing the lithium powder dispersion liquid according to the above embodiment of the present invention has at least the following advantages: 1) the carbon nano tube, the surfactant and the organic solvent are mixed in advance to form a uniform and stable colloidal solution, so that the inert lithium powder can be uniformly and stably dispersed in the colloidal solution to form a long-term stable dispersion liquid; 2) the preparation method is simple in process, and the prepared lithium powder dispersion liquid can be widely used for pre-lithiation of the negative plate; 3) when the prepared lithium powder dispersion liquid is used for pre-lithiation, stable lithium powder and carbon nano tubes can be uniformly distributed on the surface of a negative plate, so that the initial efficiency of a battery cell can be improved, a layer of ion fast channel can be constructed on the surface of the negative plate, the multiplying power performance of the negative plate is obviously improved, meanwhile, a soluble lithium salt coating layer is dissolved in electrolyte to expose active metal to meet the lithium supplement requirement, the fire danger caused by excessive active lithium powder in the operation process can be reduced, and the safety risk is reduced.
In addition, the method of preparing the lithium powder dispersion according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the present invention, a method of preparing a lithium powder dispersion satisfies at least one of the following conditions: the carbon nano tube is a multi-wall carbon nano tube and/or a single-wall carbon nano tube; the surfactant is at least one selected from polyvinylpyrrolidone, polyethylene oxide, polypyrrole and polythiophene; the organic solvent is at least one selected from N, N-dimethyl pyrrolidone, toluene, N-dimethyl formamide and dimethyl carbonate; the soluble lithium salt coating layer is a LiF coating layer.
In some embodiments of the present invention, the stable lithium powder has a particle size of 10 to 30 μm, the soluble lithium salt coating layer has a thickness of 10 to 100nm, and the purity of the lithium metal particles is not less than 98 wt%.
In some embodiments of the invention, the colloidal solution has a viscosity of 500 to 1500mPa · s.
In some embodiments of the present invention, the mass ratio of the surfactant to the carbon nanotubes is (0.01-2.2): 1, the content of the carbon nano tube in the colloidal solution is 0.1-5 wt%.
In some embodiments of the invention, the solid-to-liquid ratio of the stabilized lithium powder to the colloidal solution is (2-5) g: 100 mL.
In some embodiments of the present invention, the carbon nanotubes, the surfactant and the organic solvent are mixed and stirred in a dry environment so as to obtain the carbon nanotube colloidal solution; mixing the stable lithium powder with the colloidal solution under stirring, and performing ultrasonic treatment to obtain the lithium powder dispersion liquid.
According to a second aspect of the present invention, there is provided a lithium powder dispersion liquid obtained by the above-mentioned preparation method. The dispersibility of lithium powder and carbon nanotube is better in this lithium powder dispersion, when it is used for lithiation in advance, can make stable lithium powder and carbon nanotube evenly distributed on negative pole piece surface, not only can improve the first efficiency of electric core from this, can also construct the quick passageway of one deck ion on the negative pole surface, thereby show the multiplying power performance that improves the negative pole piece, soluble lithium salt coating dissolves in electrolyte simultaneously and exposes active metal and satisfies the benefit lithium demand, can also reduce the danger of firing that the excessive arouses of active lithium powder in the operation process, reduce the safety risk.
According to a third aspect of the invention, a method of prelithiation is presented. According to an embodiment of the invention, the method comprises: and forming the lithium powder dispersion liquid and/or the lithium powder dispersion liquid obtained by the preparation method on a negative electrode sheet and drying the negative electrode sheet so as to form a pre-lithiation layer on the negative electrode sheet. Compared with the prior art, the method for pre-lithiation can meet the lithium supplement requirement of the negative plate and improve the rate capability of the negative plate, so that the first efficiency, the rate capability, the safety performance and the service life of the battery can be obviously improved, and the silicon-oxygen material is favorable for being used as the negative electrode to improve the energy density of the battery.
In some embodiments of the invention, the method of prelithiation further comprises: 10 to 80Kg/cm is adopted2The dried negative electrode sheet is rolled under the pressure of (2).
Optionally, the thickness of the pre-lithiation layer is 3 to 15 μm.
Optionally, the negative plate is SiOxX is more than or equal to 0.8 and less than or equal to 1.5.
Optionally, the lithium powder dispersion is formed on the negative electrode sheet by spraying or knife coating.
According to a fourth aspect of the present invention, the present invention provides a negative electrode sheet obtained by the above-mentioned prelithiation method. When the negative plate is used in a battery, the first efficiency, the rate capability, the safety performance, the service life, the capacity density and the like of the battery can be obviously improved.
According to a fifth aspect of the present invention, a battery is provided. According to an embodiment of the present invention, the battery has the above negative electrode sheet or the negative electrode sheet obtained by the above pre-lithiation method. Compared with the prior art, the battery has the advantages of high first-time efficiency, good rate capability and safety performance, long service life, high capacity density and the like.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a graph showing the stability of lithium powder dispersions prepared according to examples 1 and 2 of the present invention when they are left to stand for 0 to 10 min.
FIG. 2 is a graph showing the stability of lithium powder dispersions prepared according to comparative examples 1 and 2 of the present invention when they are left standing for 0 to 10 min.
FIG. 3 is a comparison graph of the first effect of button cell prepared by using the electrode plates obtained in examples 1-2 and comparative example 1 of the present invention.
Fig. 4 is a comparison graph of capacity utilization rate of button cells prepared by using the pole pieces obtained in example 1 and comparative example 4 of the present invention under different charging rates.
Detailed Description
The following describes embodiments of the present invention in detail. The following described embodiments are exemplary and are intended to be illustrative of the invention and are not to be construed as limiting the invention.
According to a first aspect of the present invention, a method of preparing a lithium powder dispersion is provided. According to an embodiment of the invention, the method comprises: mixing carbon nano tubes, a surfactant and an organic solvent to obtain a carbon nano tube colloidal solution; and mixing the stabilized lithium powder with the colloidal solution to obtain a lithium powder dispersion, wherein the stabilized lithium powder comprises lithium metal particles and a soluble lithium salt coating layer formed on the surfaces of the lithium metal particles. The method is simple in process, and when the prepared lithium powder dispersion liquid is used for the pre-lithiation of the negative plate, the initial efficiency can be improved, and a layer of ion fast channel can be constructed on the surface of the negative plate, so that the rate capability of the negative plate is obviously improved.
The method of preparing the lithium powder dispersion liquid of the above embodiment of the present invention is described in detail mainly from two aspects.
1. Mixing carbon nano tube, surfactant and organic solvent to obtain carbon nano tube colloidal solution
According to the embodiment of the invention, the colloidal solution with certain viscosity and certain solid content of the carbon nano tube can be obtained by mixing the carbon nano tube, the surfactant and the organic solvent, so that not only can a uniform and stable lithium powder dispersion liquid be obtained, but also the lithium powder dispersion liquid can be more favorably formed on the surface of the negative plate, and a pre-lithiation layer is formed on the surface of the negative plate, thereby realizing the lithium supplement effect.
According to an embodiment of the present invention, the dried carbon nanotube powder may be dispersed in an organic solvent in a dry environment with a dew point of not higher than-40 ℃ or an inert atmosphere with a water oxygen content of not higher than 0.1ppm, and simultaneously a surfactant is added, followed by stirring and sealing to obtain a uniform and stable carbon nanotube colloidal solution. Therefore, the stable lithium powder can be further effectively prevented from reacting with oxygen, nitrogen, water and the like in the subsequent mixing process.
According to still another embodiment of the present invention, the types of the carbon nanotubes, the surfactant and the organic solvent in the present invention are not particularly limited, and those skilled in the art can select them according to actual needs. For example, the carbon nanotubes may be multi-walled carbon nanotubes and/or single-walled carbon nanotubes; the surfactant may be at least one selected from polyvinylpyrrolidone, polyethylene oxide, polypyrrole, and polythiophene; the organic solvent may be at least one selected from the group consisting of N, N-dimethylpyrrolidone, toluene, N-dimethylformamide, and dimethyl carbonate; preferably, the surfactant may be polyvinylpyrrolidone, and the organic solvent may be N, N-dimethylpyrrolidone. Wherein the purity of each carbon nanotube/surfactant can be independently not less than 99.9%.
According to yet another embodiment of the present invention, the viscosity of the colloidal solution may be 500 to 1500mPa · s. The inventor finds that if the viscosity of the colloidal solution is too low, the lithium powder is easy to settle in the colloidal solution, which is not only unfavorable for forming a uniform and stable lithium powder dispersion liquid, but also unfavorable for forming a uniform pre-lithiation layer on the surface of the negative plate, and if the viscosity of the colloidal solution is too high, which is unfavorable for uniformly dispersing the lithium powder in the colloidal solution, the uniform and stable lithium powder dispersion liquid is difficult to obtain, and the pre-lithiation effect on the negative plate is influenced. In the invention, by controlling the viscosity range of the colloidal solution, not only can uniform and stable lithium powder dispersion liquid be obtained, but also the adhesive force of the lithium powder dispersion liquid on the negative plate can be increased, so that the pre-lithiation effect on the negative plate is obviously improved.
According to another embodiment of the present invention, the mass ratio of the surfactant to the carbon nanotubes may be (0.01 to 2.2): the amount of carbon nanotubes in the colloidal solution may be 0.1 to 5 wt%, for example, 0.1 to 0.4 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%. The inventor finds that if the dosage of the surfactant is too small, the carbon nano tubes are easy to agglomerate, and the uniformity of the colloidal solution is influenced, and if the dosage of the surfactant is too large, a thicker polymer film is formed on the surface of the pole piece active material, so that the charging and discharging performance of the battery is influenced; if the content of the carbon nano-tube in the colloidal solution is too low, the multiplying power of a battery system can be weakened, and the charge and discharge performance is influenced; if the content of the carbon nano tubes in the colloidal solution is too much, the pre-lithiation layer is too thick easily, the bonding strength between the pre-lithiation layer and the pole piece is affected, and the pre-lithiation layer falls off. According to the invention, by controlling the surfactant and the carbon nano tube within the above range, not only can a uniform and stable colloidal solution be formed, so that the dispersibility of the lithium powder in the colloidal solution is improved, but also a stable pre-lithiation layer can be formed on the surface of the negative electrode by the finally prepared lithium powder dispersion liquid, and an ion fast channel is constructed, so that the rate capability of the negative electrode plate is obviously improved.
2. Mixing the stabilized lithium powder with the colloidal solution to obtain a lithium powder dispersion
According to the embodiment of the invention, the stable lithium powder comprises lithium metal particles and a soluble lithium salt coating layer formed on the surfaces of the lithium metal particles, so that active metal is exposed by dissolving the soluble lithium salt coating layer in electrolyte, the lithium supplement requirement can be met, the first efficiency of a battery cell is improved, the fire risk caused by excessive active lithium in the operation process can be reduced, and the safety risk is reduced.
According to an embodiment of the present invention, the soluble lithium salt coating layer may be a LiF coating layer, thereby not only reducing the activity of the lithium powder, but also improving the safety during the operation.
According to another embodiment of the present invention, the particle size of the stabilized lithium powder may be 10 to 30 μm, for example, 10 μm, 13 μm, 16 μm, 19 μm, 22 μm, 25 μm, 28 μm, or 30 μm, etc., the thickness of the coating layer of the soluble lithium salt may be 10 to 100nm, for example, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, or 100nm, etc., and the purity of the lithium metal particles may be not less than 98 wt%. The inventor finds that the lithium metal particles have high reactivity, and if the particle size of the stable lithium powder is small, the particle size of the lithium metal particles is also small, the specific surface area is too large, and safety accidents are easily caused when the stable lithium powder is prepared; if the particle size of the stable lithium powder is too large, the particle size of the required lithium metal particles is too large, which directly results in that the addition amount of the stable lithium powder required during the pre-lithiation is reduced and the stable lithium powder cannot be uniformly distributed in a negative electrode material (such as a silicon-oxygen negative electrode), so that the kinetics of lithium metal ion extraction during the pre-lithiation is poor, and the pre-lithiation effect is influenced. If the thickness of the soluble lithium salt coating layer is too small, the capability of reducing the activity of the lithium powder is limited, safety accidents are easily caused, if the thickness of the soluble lithium salt coating layer is too large, the dissolution efficiency of the lithium powder is greatly reduced, and the effect of improving the first efficiency of the battery is not obvious. According to the invention, the pre-lithiation effect of the negative plate can be further improved by controlling the stable lithium powder to be within the parameter range.
According to another embodiment of the present invention, the solid-to-liquid ratio of the stable lithium powder to the colloidal solution may be (2-5) g: 100mL of L. The inventor finds that if the solid-liquid ratio is too small, the required pre-lithiation layer is too thick to achieve the same lithium supplement effect, and the pre-lithiation layer is easy to fall off and can weaken the comprehensive performance of the battery; if the solid-liquid ratio is too large, lithium in the pre-lithiation layer is relatively excessive, the problem of lithium precipitation occurs, and the safety performance of the battery is affected. According to the invention, by controlling the solid-to-liquid ratio range of the stable lithium powder and the colloidal solution, the uniformity of the stable lithium powder in the lithium powder dispersion liquid can be further improved, a good pre-lithiation effect on the negative plate is ensured, and the thickness of the pre-lithiation layer can be controlled, so that the first efficiency, the rate capability, the safety performance and the like of the battery can be obviously improved. Preferably, the solid-to-liquid ratio of the stable lithium powder to the colloidal solution may be (2-2.5) g: 100mL L, the inventor finds that the solid-to-liquid ratio of the stable lithium powder to the colloidal solution is different, so that the first efficiency of the full cell can be improved in different levels, and when the solid-to-liquid ratio is (2-2.5) g: the first efficiency of the full cell can be improved to 85-92% when the volume of the battery is 100 mL.
According to still another embodiment of the present invention, the carbon nanotubes, the surfactant and the organic solvent may be mixed and stirred in a dry environment to obtain a carbon nanotube colloidal solution; the stabilized lithium powder is mixed with the colloidal solution under stirring, and subjected to ultrasonic treatment to obtain a lithium powder dispersion liquid. Thereby, the uniformity and stability of the lithium powder dispersion can be further improved.
According to another embodiment of the invention, stable lithium powder with a predetermined proportion can be slowly added into the stirred carbon nanotube colloidal solution, sealed and stirred for 20-30 min, and then ultrasonic treatment is carried out for 10min, so as to form a lithium powder dispersion liquid which is uniformly dispersed and can stably exist for a long time.
In summary, the method for preparing the lithium powder dispersion liquid according to the above embodiment of the present invention has at least the following advantages: 1) the carbon nano tube, the surfactant and the organic solvent are mixed in advance to form a uniform and stable colloidal solution, so that the inert lithium powder can be uniformly and stably dispersed in the colloidal solution to form a long-term stable dispersion liquid; 2) the preparation method is simple in process, and the prepared lithium powder dispersion liquid can be widely used for pre-lithiation of the negative plate; 3) when the prepared lithium powder dispersion liquid is used for pre-lithiation, stable lithium powder and carbon nano tubes can be uniformly distributed on the surface of a negative plate, so that the initial efficiency of a battery cell can be improved, a layer of ion fast channel can be constructed on the surface of the negative plate, the multiplying power performance of the negative plate is obviously improved, meanwhile, a soluble lithium salt coating layer is dissolved in electrolyte to expose active metal to meet the lithium supplement requirement, the fire danger caused by excessive active lithium powder in the operation process can be reduced, and the safety risk is reduced.
According to a second aspect of the present invention, there is provided a lithium powder dispersion liquid obtained by the above-mentioned preparation method. The dispersibility of lithium powder and carbon nanotube is better in this lithium powder dispersion, when it is used for lithiation in advance, can make stable lithium powder and carbon nanotube evenly distributed on negative pole piece surface, not only can improve the first efficiency of electric core from this, can also construct the quick passageway of one deck ion on the negative pole surface, thereby show the multiplying power performance that improves the negative pole piece, soluble lithium salt coating dissolves in electrolyte simultaneously and exposes active metal and satisfies the benefit lithium demand, can also reduce the danger of firing that the excessive arouses of active lithium powder in the operation process, reduce the safety risk. It should be noted that the features and effects described for the above method for preparing a lithium powder dispersion liquid are also applicable to the lithium powder dispersion liquid, and are not described in detail herein.
According to a third aspect of the invention, a method of prelithiation is presented. According to an embodiment of the invention, the method comprises: and forming the lithium powder dispersion liquid and/or the lithium powder dispersion liquid obtained by the preparation method on a negative electrode sheet and drying the negative electrode sheet so as to form a pre-lithiation layer on the negative electrode sheet. Compared with the prior art, the method for pre-lithiation can meet the lithium supplement requirement of the negative plate and improve the rate capability of the negative plate, so that the first efficiency, the rate capability, the safety performance and the service life of the battery can be obviously improved, and the silicon-oxygen material is favorable for being used as the negative electrode to improve the energy density of the battery.
According to a specific embodiment of the present invention, the method of prelithiation may further comprise: 10 to 80Kg/cm is adopted2The dried negative electrode sheet is rolled under the pressure of (2). The uniformity of the prelithiation layer and the bonding strength with the negative electrode sheet can be further improved.
According to yet another embodiment of the present invention, the pre-lithiation layer may have a thickness of 3 to 15 μm. The inventor finds that if the thickness of the prelithiation layer is too small, the lithium supplementing effect on the negative plate is effective, the first efficiency is not obviously improved, and if the thickness of the prelithiation layer is too large, lithium ions are easily excessive, so that the lithium precipitation of the negative electrode easily affects the electrical property and safety. According to the invention, by controlling the thickness of the pre-lithiation layer to be in the range, the first efficiency of the battery can be obviously improved, and the cycle performance and energy density of the battery can be improved.
According to still another embodiment of the present invention, the negative electrode sheet may be SiOxX is more than or equal to 0.8 and less than or equal to 1.5. Wherein SiO isxthe/C is a core-shell structure, and the core material is a silica material SiOxAnd the shell layer is made of a C material, so that the energy density of the battery can be remarkably improved, and the stable electric conductivity of the negative plate can be ensured.
According to still another embodiment of the present invention, the method of forming the lithium powder dispersion on the negative electrode sheet in the present invention is not particularly limited, and may be selected by those skilled in the art according to actual needs. For example, the lithium powder dispersion may be formed on the negative electrode sheet by spray coating or knife coating.
It should be noted that the features and effects described for the lithium powder dispersion liquid and the method for preparing the lithium powder dispersion liquid are also applicable to the prelithiation method, and are not described in detail herein.
According to a fourth aspect of the present invention, the present invention provides a negative electrode sheet obtained by the above-mentioned prelithiation method. When the negative plate is used in a battery, the first efficiency, the rate capability, the safety performance, the service life, the capacity density and the like of the battery can be obviously improved. It should be noted that the features and effects described for the above-mentioned pre-lithiation method are also applicable to the negative electrode sheet, and are not described in detail here.
According to a fifth aspect of the present invention, a battery is provided. According to an embodiment of the present invention, the battery has the above negative electrode sheet or the negative electrode sheet obtained by the above pre-lithiation method. Compared with the prior art, the battery has the advantages of high first-time efficiency, good rate capability and safety performance, long service life, high capacity density and the like. It should be noted that the features and effects described for the negative electrode sheet and the negative electrode sheet obtained by the pre-lithiation method are also applicable to the battery, and are not described in detail here.
The scheme of the invention will be explained with reference to the examples. It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Example 1:
dispersing 0.011g of PVP (polyvinylpyrrolidone) in 10mL of NMP (N, N-dimethylpyrrolidone) as an organic solvent, sealing and magnetically stirring until the PVP is completely dissolved in the NMP solvent, then adding 0.53g of CNT (carbon nano tube) powder into the NMP solvent in batches and in small amount, operating in a dry environment (the humidity is less than or equal to 1%) or a glove box, sealing and magnetically stirring for 20-50 min after the addition is finished, weighing 0.22g of LiF-coated lithium powder after the CNT colloid is stabilized, slowly adding the LiF-coated lithium powder into the CNT colloid, carrying out ultrasonic treatment for 2h after sealing to obtain a stable and uniform lithium powder dispersion, statically storing the dispersion for 5min, 10min and 15min to observe the stable condition, and statically storing the system for 5min, 10min and 15min to observe the stable conditionNo obvious layering or sedimentation after 15 min; coating the lithium powder dispersion liquid on a prepared SiOx/C pole piece by using a four-side scraper with the thickness of 25 mu m, baking the lithium powder dispersion liquid for 10-40 min at the temperature of 60 ℃, and rolling the lithium powder dispersion liquid in a dry environment (the humidity is less than or equal to 1%), wherein the pressure is 10-80 kg/cm2(ii) a The obtained pole piece was used to prepare 2025 button cell and tested.
Example 2:
dispersing 0.011g of PVP in 10mL of organic solvent NMP, sealing and magnetically stirring until the PVP is completely dissolved in the NMP solvent, then adding 0.53g of CNT powder into the NMP solvent in batches and in a small amount, operating the process in a dry environment (the humidity is less than or equal to 1%) or a glove box, sealing and magnetically stirring for 20-50 min after the addition is finished, weighing 0.44g of LiF-coated lithium powder after the CNT colloid is stabilized, slowly adding the LiF-coated lithium powder into the CNT colloid, sealing, carrying out ultrasonic treatment for 2h to obtain a stable and uniform lithium powder dispersion liquid, statically storing the dispersion liquid for 0min, 5min and 10min to observe the stable condition, and statically storing the system for 10min without obvious layering or sedimentation; coating the lithium powder dispersion liquid on a prepared SiOx/C pole piece by using a four-side scraper with the thickness of 25 mu m, baking the lithium powder dispersion liquid for 10-40 min at the temperature of 60 ℃, and rolling the lithium powder dispersion liquid in a dry environment (the humidity is less than or equal to 1%), wherein the pressure is 10-80 kg/cm2(ii) a The obtained pole piece was used to prepare 2025 button cell and tested.
Comparative example 1
The difference from example 1 is that no surfactant is added.
Comparative example 2
The difference from example 1 is that dimethyl sulfoxide (DMSO) is used as the organic solvent, and no surfactant is added.
Comparative example 3
A button cell of 2025 was prepared using an non-prelithiated SiOx/C pole piece and tested.
Comparative example 4
The difference from example 1 is that 0.22g of LiF-coated lithium powder was weighed and slowly added to 10mL of organic solvent NMP, and after sealing, ultrasonic treatment was performed for 2 hours to obtain a lithium powder dispersion.
Evaluation:
1. the lithium powder dispersions obtained in comparative examples 1 to 2 and comparative examples 1 to 2 were stored still for 5min and 10 min. The comparison results are shown in fig. 1 and 2. As can be seen from fig. 1, the lithium powder dispersion prepared by the method of the above embodiment of the present invention does not significantly settle and delaminate after standing for 10min, and as can be seen from fig. 2, the lithium powder dispersion obtained without adding a surfactant and the lithium powder dispersion prepared by replacing an organic solvent with dimethyl sulfoxide without adding a surfactant both undergo significant delamination after 5min of storage, and the lithium powder dispersion of comparative example 2 is lighter in color and less stable after 10min of storage. Therefore, the lithium powder dispersion liquid prepared by the technical scheme of the invention has better stability.
2. Under the same conditions, preparing a button cell by using the pre-lithiated pole piece obtained in the embodiments 1-2 and the comparative examples 3-4, and testing, wherein the button cell is in a model number CR 2025; electrolyte solution: LiPF 6: EC (ethylene carbonate): DEC (diethyl carbonate): PP ═ 1:1.78:3.57: 1.4; and (3) negative electrode proportioning: PAA (polyacrylic acid) 3.0%, SP (superconducting carbon black) 1.0%, CMC (sodium carboxymethyl cellulose) 3.0%, and the counter electrode is a pure lithium sheet. The first efficiency of the batteries obtained in examples 1-2 and comparative example 3 was tested, and the rate performance of the batteries obtained in example 1 and comparative example 4 was tested. The test results are shown in fig. 3 and fig. 4, respectively, and table 1. As can be seen from fig. 3, the efficiency of the battery can be significantly improved by pre-lithiating the electrode sheet according to the technical scheme of the present invention. Fig. 4 is a comparison graph of discharge capacity ratios of the batteries obtained in example 1 and comparative example 4, which were charged at a rate of 0.2C, 0.5C, 1C, 1.5C, and 2C and discharged at a rate of 0.2C, respectively, and it is understood from table 1 and fig. 4 that the addition of carbon nanotubes to the lithium powder dispersion can further improve the capacity utilization rate of the battery and the rate performance of the battery.
Table 1 capacity utilization for example 1 and comparative example 4 at different charge rates
In conclusion, the lithium powder dispersion liquid prepared by the embodiment of the invention has better stability, and the application of the lithium powder dispersion liquid to the prelithiation can not only obviously improve the first efficiency of the battery, but also improve the rate capability of the battery.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A method of preparing a lithium powder dispersion, comprising:
mixing carbon nano tubes, a surfactant and an organic solvent to obtain a carbon nano tube colloidal solution;
mixing stabilized lithium powder with the colloidal solution to obtain a lithium powder dispersion,
wherein the stabilized lithium powder includes lithium metal particles and a soluble lithium salt coating layer formed on the surfaces of the lithium metal particles.
2. The method of claim 1, wherein at least one of the following conditions is satisfied:
the carbon nano tube is a multi-wall carbon nano tube and/or a single-wall carbon nano tube;
the surfactant is at least one selected from polyvinylpyrrolidone, polyethylene oxide, polypyrrole and polythiophene;
the organic solvent is at least one selected from N, N-dimethyl pyrrolidone, toluene, N-dimethyl formamide and dimethyl carbonate;
the soluble lithium salt coating layer is a LiF coating layer.
3. The method of claim 2, wherein the stable lithium powder has a particle size of 10 to 30 μm, the coating layer of the soluble lithium salt has a thickness of 10 to 100nm, and the lithium metal particles have a purity of not less than 98 wt%.
4. A method according to any one of claims 1 to 3, wherein the colloidal solution has a viscosity of 500 to 1500 mPa-s,
optionally, the mass ratio of the surfactant to the carbon nano tube is (0.01-2.2): 1, the content of the carbon nano-tube in the colloidal solution is 0.1-5 wt%,
optionally, the solid-to-liquid ratio of the stable lithium powder to the colloidal solution is (2-5) g: 100 mL.
5. The method of claim 4,
mixing and stirring the carbon nanotubes, the surfactant and the organic solvent in a dry environment to obtain the carbon nanotube colloidal solution;
mixing the stable lithium powder with the colloidal solution under stirring, and performing ultrasonic treatment to obtain the lithium powder dispersion liquid.
6. A lithium powder dispersion prepared by the method of any one of claims 1 to 5.
7. A method of prelithiation, comprising: forming the lithium powder dispersion liquid according to claim 6 and/or the lithium powder dispersion liquid prepared by the method according to any one of claims 1 to 5 on a negative electrode sheet and drying the same to form a prelithiation layer on the negative electrode sheet.
8. The method of claim 7, further comprising: 10 to 80Kg/cm is adopted2The dried negative electrode sheet is rolled under the pressure,
optionally, the thickness of the pre-lithiation layer is 3 to 15 μm,
optionally, the negative plate is SiOxX is more than or equal to 0.8 and less than or equal to 1.5,
optionally, the lithium powder dispersion is formed on the negative electrode sheet by spraying or knife coating.
9. A negative electrode sheet obtained by the prelithiation method of claim 7 or 8.
10. A battery comprising the negative electrode sheet according to claim 9 or a negative electrode sheet obtained by the prelithiation method according to claim 7 or 8.
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| CN114388790A (en) * | 2020-10-21 | 2022-04-22 | 比亚迪股份有限公司 | Battery prelithiation slurry, battery negative plate and lithium ion battery |
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