CN110828898B

CN110828898B - Method for preparing diaphragm-free lithium ion battery by in-situ synthesis of inorganic particles

Info

Publication number: CN110828898B
Application number: CN201810897217.5A
Authority: CN
Inventors: 付冬; 简为
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-08-08
Filing date: 2018-08-08
Publication date: 2022-04-05
Anticipated expiration: 2038-08-08
Also published as: CN110828898A

Abstract

The invention relates to a method for preparing a diaphragm-free lithium ion battery by in-situ synthesis of inorganic particles. The invention particularly relates to the field of lithium ion batteries, and discloses a method for preparing a diaphragm-free lithium ion battery by in-situ synthesis of inorganic particles and a diaphragm-free lithium ion battery prepared by the method. The battery comprises a positive pole piece and a negative pole piece, wherein the surface of at least one of the positive pole piece and the negative pole piece is provided with an inorganic material film. The inorganic material film is formed in situ from a coating material including inorganic material particles, a binder, a catalyst, a solvent, and an auxiliary agent. The whole process flow is simplified, the production cost is greatly reduced, zero emission is realized in the whole process flow, and the environment-friendly process is realized. Meanwhile, the manufactured lithium ion battery does not contain a diaphragm, so that not only can the energy density of the lithium ion battery be improved, but also the stability and the safety of the lithium ion battery can be improved.

Description

Method for preparing diaphragm-free lithium ion battery by in-situ synthesis of inorganic particles

Technical Field

The invention relates to a method for preparing a diaphragm-free lithium ion battery by in-situ synthesis of inorganic particles. Specifically, the invention relates to the field of lithium ion batteries, and discloses a method for preparing a diaphragm-free lithium ion battery by directly synthesizing inorganic particles and a lithium ion battery prepared by the same, and more specifically, the invention relates to a method for preparing a diaphragm-free lithium ion battery by directly synthesizing inorganic particles in slurry and a lithium ion battery prepared by the same.

Background

In a lithium ion battery, a separator mainly plays a role in preventing contact between a positive electrode and a negative electrode and allowing lithium ions to conduct, and is an important component of the battery. At present, polyolefin diaphragm materials with a microporous structure, such as single-layer or multi-layer films of Polyethylene (PE) and Polypropylene (PP), are mainly used in commercial lithium ion batteries. The polyolefin separator may provide sufficient mechanical strength and chemical stability for a lithium ion battery, but exhibits greater thermal shrinkage under high temperature conditions. The thermal contraction causes the contact and short circuit of the positive electrode and the negative electrode, and a large amount of heat is rapidly accumulated, so that safety accidents such as fire, combustion and even explosion are caused.

Therefore, people mostly adopt inorganic ceramic powder to carry out ceramic coating modification on the polyolefin diaphragm material of the lithium ion battery, and the good high-temperature thermal stability of ceramic is utilized, so that the thermal stability of the diaphragm is improved. Meanwhile, the better electrolyte wettability of the ceramic is utilized, the service performance of the battery, such as the service life and the discharge efficiency of the battery, can be improved, and the method is the main direction for modifying the polyolefin diaphragm material.

However, in the course of research, the present inventors found that the lithium ion battery in the prior art has the following disadvantages: the separator does not contribute to the battery capacity, and a battery having a smaller size, a thinner size, and a lighter weight is required in accordance with the trend toward a smaller size and a lighter weight of the portable electronic device. Due to the limitation of a diaphragm manufacturing process and certain requirements on the tensile strength of the diaphragm in the production process of the lithium ion battery, the diaphragm is very thin and difficult to manufacture. The thinnest lithium ion battery separator is about 8 microns at present, but the use is limited due to strength problems. The thickness of a diaphragm commonly used in the lithium ion battery industry is 12-30 micrometers. In such a battery, the separator occupies a large volume and weight of the lithium ion battery, resulting in a limitation in volumetric and gravimetric energy densities of the lithium ion battery. In the use process of the power battery for the electric automobile, the battery often needs short-time heavy current discharge, a large amount of heat can be generated, and if the heat dissipation is not timely, the temperature of the battery is easily overhigh. Due to the limitation of the thermal shrinkage resistance of the separator material, excessive temperatures may cause the separator to shrink, resulting in short-circuiting of the battery and a safety problem. Ceramic coating, while improving separator performance, can increase separator cost. And the diaphragm occupies the volume and the weight of the lithium ion battery, so that the diaphragm does not directly contribute to the energy of the battery, and the volume energy density and the weight energy density of the lithium ion battery are reduced.

In order to solve the above technical problems, a method of directly coating inorganic material particles on a lithium ion battery electrode sheet instead of a separator is proposed, for example, CN 104916811a discloses a lithium ion battery without a separator, which includes a current collector coated with a ceramic layer on the front and back surfaces thereof. However, the ceramic layer is generally formed of finished ceramic particles, and it is necessary to overcome agglomeration among the ceramic particles by a long-time ball milling or the like to uniformly disperse in a solvent. This method is time consuming and energy consuming, is costly and the slurry is highly susceptible to contamination by the fine debris milled off in the ball mill.

CN 104396048A discloses another integrated electrode separator assembly for lithium ion batteries, which comprises at least one electrode having directly adhered thereto a porous fluoropolymer separator layer comprising interconnected fluoropolymer particles, wherein the electrode coating may contain an inorganic material. According to this invention, inorganic material powder is added to fluoropolymer to form fluoropolymer slurry. This method requires the purchase or preparation of an inorganic material powder that is then added to the fluoropolymer. A large number of inorganic material powder options are listed in this application, among which fumed silica powder is mentioned as one of the large number of options. However, taking silicon dioxide powder as an example, the existing silicon dioxide powder is generally prepared by burning silicon tetrachloride or precipitating sodium silicate with acid, and is like countless peanuts with shells pressed together in the appearance of an electron microscope, and is not monodisperse spheres. Alternatively, spherical silica is commercially available, such as nano-or submicron-sized spherical silica sold under the trade names KH570 and KH550 by golden nanotechnology materials ltd, but such commercially available silica is very expensive. Therefore, the method in the prior art is complex in process and high in cost.

Disclosure of Invention

The technical problems in the prior art are successfully solved by the following technical solutions and preferred embodiments thereof.

The invention provides a method for directly synthesizing nano particles in coating slurry, which avoids the problems of energy consumption, time consumption, easy pollution and the like of dispersing solid particles in the slurry, and can improve the energy density of a battery, thereby improving the performance of the lithium battery.

In particular, the inorganic material particles obtained by in situ synthesis in the coating slurry do not require drying and there is substantially no agglomeration between the inorganic material particles. The dry inorganic material powder used in the prior art is very serious in agglomeration and needs to be subjected to ball milling and other treatments for a long time when being dispersed in a solvent, but the particles synthesized in situ do not need the treatment step. And the particle size of the spherical inorganic material particles can be adjusted by adjusting the in-situ synthesis formula. Finally, a uniform coating slurry containing spherical inorganic particles having an adjustable particle size can be obtained, thereby greatly simplifying the manufacturing process and reducing the cost, and is environmentally friendly since the solvent can be recovered during the manufacturing process and there is substantially no pollutant discharge. Particularly in terms of cost, compared with the prior art of inorganic spherical particles obtained by commercial or ex-situ synthesis, the method has remarkable economic benefit and can save the cost by more than 50 percent.

According to one aspect of the present invention, there is provided a method of preparing a separator-free lithium ion battery, the method comprising the steps of:

providing a positive pole piece and a negative pole piece,

providing a coating slurry, and

curing to form an inorganic material film by applying the coating slurry on a surface of at least one of the positive electrode tab and the negative electrode tab,

wherein the coating slurry comprises inorganic material particles, a binder, a catalyst, a solvent and an auxiliary agent,

wherein the particles of inorganic material are predominantly silica particles,

characterized in that the silica particles are synthesized in situ in the coating slurry by hydrolysis of the organosilicon compound, i.e. the silica particles are synthesized directly in the coating slurry by hydrolysis of the organosilicon compound.

According to another aspect of the present invention, there is provided a lithium ion battery without a separator, comprising a positive electrode sheet and a negative electrode sheet, wherein at least one of the positive electrode sheet and the negative electrode sheet has an inorganic material film provided on a surface thereof, the inorganic material film being formed by curing a coating slurry, the coating slurry comprising inorganic material particles, a binder, a catalyst, a solvent and an auxiliary agent, the inorganic material particles being mainly silica particles, characterized in that the silica particles are synthesized in situ in the coating slurry by hydrolysis of an organosilicon compound.

In the lithium ion battery, the lithium ion positive electrode active material of the positive electrode tab and the lithium ion negative electrode active material of the negative electrode tab may be laminated oppositely, i.e., laminated in a manner of facing each other. The inorganic material film is arranged on the surface of at least one of the positive electrode and the negative electrode, and the inorganic material film is formed by curing the coating slurry. The coating slurry comprises inorganic material powder, an adhesive, a solvent and an auxiliary agent.

The inorganic material powder is mainly silica particles. The silicon dioxide particles are synthesized in situ by adopting the hydrolysis of an organic silicon compound. The organosilicon compound is preferably selected from the group consisting of silicates.

In a preferred embodiment of the present invention, the coating slurry is prepared from the following ingredients:

5 to 30 wt%, preferably 10 to 20 wt% of an organosilicon compound,

1 to 20 wt%, preferably 5 to 15 wt%,

0.1 to 5 wt%, preferably 0.5 to 3 wt%,

0.1 to 30% by weight, preferably 1 to 20% by weight, of a binder, and

30 to 95 wt%, preferably 40 to 80 wt%,

wherein the organosilicon compound is preferably a silicate ester, such as tetraethyl orthosilicate.

It is to be noted that in the present description of the formulation of the ingredients, although the content proportions are given in weight%, since the material density of some ingredients is close to 1g/ml, these content proportions may also be expressed in volume%, wherein in some cases they are given in volume%.

5 to 30 wt%, preferably 10 to 20 wt%,

1 to 20 wt%, preferably 5 to 15 wt% of concentrated ammonia water,

1 to 20 wt%, preferably 5 to 15 wt% of deionized water,

0.1 to 5 wt%, preferably 0.5 to 3 wt%,

0.1 to 30% by weight, preferably 1 to 20% by weight, of a binder, and

30 to 95 wt%, preferably 40 to 80 wt% of ethanol,

one example of such a silicate is tetraethyl orthosilicate.

The catalyst can be an acidic catalyst or a basic catalyst, preferably a basic catalyst, and a particularly preferred catalyst is concentrated ammonia.

The adhesive is selected from acrylonitrile multipolymer adhesive, polyvinyl fluoride adhesive, hydrosol adhesive and the combination of two or more of the acrylonitrile multipolymer adhesive, the polyvinyl fluoride adhesive and the hydrosol adhesive. The acrylonitrile multipolymer type adhesive is selected from acrylonitrile multipolymer, polymethyl methacrylate-butyl acrylate emulsion, polystyrene-butyl acrylate emulsion and a combination of two or more of the acrylonitrile multipolymer, the polyvinyl fluoride type adhesive is selected from polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion, vinylidene fluoride-hexafluoropropylene copolymer and a combination of two or more of the polyvinylidene fluoride emulsion, the hydrosol type adhesive is selected from carboxymethyl cellulose, gelatin, sodium alginate and a combination of two or more of the sodium alginate.

Optionally, the binder is selected from the group consisting of polymethylmethacrylate-butyl acrylate emulsion, polystyrene-butyl acrylate emulsion, polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion, vinylidene fluoride-hexafluoropropylene copolymer, carboxymethylcellulose, acrylonitrile multipolymer, gelatin, sodium alginate, and combinations of two or more thereof.

The solvent is selected from the group consisting of water, methanol, ethanol, N-propanol, isopropanol, acetone, N-methylpyrrolidone, and combinations of two or more thereof.

The adjuvant is selected from the group consisting of non-ionic adjuvants and ionic adjuvants, and combinations thereof. Wherein the nonionic auxiliary agent is selected from tertiary alkyl polyhydric alcohol polyvinyl ether, polyether modified silicone oil, polypropylene glycol-ethylene oxide, polyether stearate dimethyl siloxane, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene glycerol ether, polyoxyethylene polyoxypropylene amine ether, polyvinyl alcohol and a combination of two or more of the above, and the ionic auxiliary agent is selected from sodium diisooctyl sulfonate, alkyl naphthalene sulfonate and a combination of the above.

Optionally, the adjuvant is selected from the group consisting of tertiary alkyl polyol polyvinyl ethers, sodium diisooctyl sulfonate, alkyl naphthalene sulfonates, polyether modified silicone oils, polypropylene glycol-ethylene oxide, polyether stearate dimethyl siloxanes, polyoxyethylene polyoxypropylene pentaerythritol ethers, polyoxyethylene glycerol ethers, polyoxyethylene polyoxypropylene amine ethers, polyvinyl alcohol, and combinations of two or more thereof.

The silicon dioxide particles are prepared by a method of directly synthesizing an organic silicon compound, preferably silicate ester through hydrolysis, a series of problems caused by directly using silicon dioxide powder are avoided, such as agglomeration of inorganic material powder, difficulty in dispersion in a coating slurry solvent, long-time ball milling, time and energy consumption, and increased risk of pollution of the coating slurry. Furthermore, the invention can control the particle size of the silicon dioxide particles by changing the proportion of each component in the formula, and can better adapt to the requirements of different lithium ion batteries on the particle size of the coating slurry particles. The prepared silica particles contain pores inside, and the pores can increase the porosity of the inorganic material film. The liquid absorption rate of the inorganic material film to the electrolyte can be increased because the internal pore channels help to absorb the electrolyte better. Meanwhile, the pore channels in the silicon dioxide particles can reduce the apparent density of the silicon dioxide particles, and are beneficial to improving the energy density of the lithium battery. Because the inorganic material film is directly coated on the pole piece, the self-supporting diaphragm does not need certain tensile strength, can be very thin and is also beneficial to improving the energy density of the lithium battery.

According to a preferred embodiment of the invention, the organosilicon compound is chosen from silicates, preferably from silicates of formula 1:

wherein R is¹、R²、R³And R⁴Independently of one another in each occurrence are straight-chain or branched, preferably straight-chain alkyl radicals having 1 to 5, preferably 1 to 4, more preferably 1 to 3, particularly preferably 1 or 2C atoms.

Preferably, R¹、R²、R³And R⁴In each occurrence independently of one another from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, n-pentyl, sec-pentyl and neopentyl, preferably in each occurrence independently of one another from methyl, ethyl, n-propyl, isopropyl, n-butyl and n-pentyl, particularly preferably in each occurrence independently of one another from methyl, ethyl, n-propyl, isopropyl and n-butyl.

According to a preferred embodiment of the invention, R¹、R²、R³And R⁴The same at each occurrence.

According to a preferred embodiment of the invention, wherein the silicate is tetramethyl orthosilicate, tetraethyl orthosilicate or tetrapropyl orthosilicate.

In an exemplary embodiment of the invention, the silicate is tetraethyl orthosilicate.

According to the invention, the positive plate lithium ion positive active material and the negative plate lithium ion negative active material are oppositely laminated, wherein a diaphragm is not arranged independently, and an integrated inorganic material film coated on the surfaces of the positive plate and the negative plate replaces the diaphragm, so that the volume utilization rate of the battery cell is obviously improved, and the volume energy density of the lithium ion battery is improved.

The inorganic material film has higher porosity, and the inside of the silicon dioxide particles also has channels, so that the weight is lighter, the apparent density is lower, and the weight and the energy density of the lithium ion battery can be further improved. The silica particles have good insulation and heat resistance, and the inorganic material film of the battery cell does not shrink or melt at high temperature. The inorganic material used in the invention is an inorganic porous material, has good wettability to the electrolyte, and can reduce the internal resistance, thereby improving the battery performance.

By the scheme, the diaphragm-free lithium ion battery is realized, the battery preparation process is further simplified, the battery cost is further reduced, and meanwhile, the coated diaphragm is more tightly combined with the pole piece, so that the safety performance and the electrochemical performance of the battery are improved, the battery is more suitable for being used as a power battery for an electric automobile, and the development of the electric automobile using the lithium ion battery as power is greatly promoted.

According to the present invention, the inorganic material film is cured from the coating slurry.

In a preferred embodiment, polyvinylidene fluoride copolymer is used as a binder, and the solvent is a mixture of acetone and N-methyl pyrrolidone, wherein the ratio of the acetone to the N-methyl pyrrolidone is 1-100: 100.

In a preferred embodiment, vinylidene fluoride-hexafluoropropylene copolymer is used as a binder, and the solvent is a mixture of acetone and N-methyl pyrrolidone, wherein the ratio of the acetone to the N-methyl pyrrolidone is 100: 1-100, preferably 100: 1-30, and more preferably 100: 1-10.

In a preferred embodiment, one or more of polymethyl methacrylate-butyl acrylate emulsion, polystyrene-butyl acrylate emulsion, polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion, vinylidene fluoride-hexafluoropropylene copolymer, carboxymethyl cellulose, acrylonitrile multipolymer, gelatin and sodium alginate are used as a binding agent, a solvent is a mixture of ethanol and water, and the ratio of the ethanol to the water is 1-50: 100.

After the raw materials react, the coating slurry containing silica particles is generated.

Preferably, the size of the silica particles can be controlled to be 1-3000 nm, preferably 10-3000 nm, more preferably 10-500 nm, for example 100-300 nm, by adjusting the proportion in the ingredients.

In a preferred embodiment of the present invention, the coating slurry is obtained by centrifuging the reaction product of the above-mentioned raw materials. Deionized water may be added to the coating slurry obtained by the above centrifugation to adjust the slurry to a desired viscosity.

According to the invention, the composition of the obtained coating slurry comprises 20-80 parts by weight, preferably 30-80 parts by weight of silicon dioxide particles, 0.5-20 parts by weight, preferably 1-10 parts by weight of binder, 10-80 parts by weight, preferably 30-70 parts by weight of solvent and 0.1-10 parts by weight, preferably 1-5 parts by weight of auxiliary agent.

According to the present invention, the prepared coating slurry may be applied to the surface of the pole piece by a conventional method known to those skilled in the art, for example, the prepared coating slurry may be applied to the surface of the pole piece by slot die coating, curtain coating, flood coating, dip coating, spray coating, spin coating, printing, and the like. In an exemplary embodiment of the present invention, the prepared coating slurry is applied to the surface of the pole piece by coating with a coater.

In a preferred embodiment of the present invention, after the prepared coating slurry is applied to the surface of the pole piece, for example, by coating with a coater, the coated slurry may be cured by conventional methods known to those of ordinary skill in the art, such methods including, but not limited to, baking, infrared radiation, microwave radiation, and the like. In an exemplary embodiment of the present invention, the inorganic material film is provided on at least one of the surface and/or reverse of the positive electrode sheet and the surface and/or reverse of the negative electrode sheet by baking the coated electrode sheet at a temperature of 60 to 100 degrees celsius, for example, for 0.5 to 12 hours, to cure the coated slurry.

Preferably, the thickness of the single layer of the inorganic material film is 1-50 microns, preferably 1-30 microns, more preferably 1-20 microns, and most preferably 1-10 microns.

Preferably, the inorganic material film layer has a porosity of 30-70%.

By the above method, the inorganic material film is bonded to at least one of the surface and/or the reverse surface of the positive electrode tab and the surface and/or the reverse surface of the negative electrode tab.

In a preferred embodiment of the present invention, the positive electrode current collector is an aluminum foil coated with a lithium ion positive electrode active material coating, and the negative electrode sheet is a copper foil, metallic lithium or a lithium alloy and a copper foil coated with a lithium ion negative electrode active material coating.

Compared with the prior art, the invention has the beneficial effects that:

1. the silicon dioxide particles in the coating slurry used by the invention are directly synthesized in the slurry, and finished silicon dioxide powder is replaced, so that the preparation process of the coating slurry is simplified, and the time and the cost are saved. The cost of the lithium ion battery diaphragm is about 3-10 yuan/square meter, the cost of the inorganic material film of the lithium ion battery is lower than that of the diaphragm because the lithium ion battery is not provided with the diaphragm independently, which is beneficial to reducing the cost of the lithium ion battery, wherein, the cost of the inorganic material film for replacing the diaphragm can be reduced to 0.5-3 yuan/square meter, such as 0.8-2.5 yuan/square meter.

2. According to the present invention, the particle size of the spherical inorganic material particles can be adjusted by adjusting the in-situ synthesis formulation. Finally, uniform coating slurry containing spherical inorganic particles with adjustable particle size can be obtained, thereby greatly simplifying the operation process, reducing the cost, and having the characteristics of obvious zero emission because the solvent can be recovered in the production process and basically no pollutant is discharged, thereby being environment-friendly.

3. The silicon dioxide particles directly synthesized in the slurry contain pore channels, so that the apparent density of the silicon dioxide particles is reduced, and the energy density of the battery is further improved. The pore channels in the silicon dioxide particles are also beneficial to improving the liquid absorption rate of the battery electrolyte, reducing the internal resistance of the lithium battery and improving the battery performance.

4. The lithium ion battery is not provided with a diaphragm independently, and the inorganic material film is directly coated on the anode or cathode pole piece, so that the tensile strength of the whole pole piece is borne by the current collector copper foil or aluminum foil in the pole piece, and the inorganic material film does not bear tensile force and has no requirement on the tensile strength, so that the inorganic material film can be made very thin, for example, 1-10 microns. The inner pore channels of the silicon dioxide particles also contribute to improving the liquid absorption rate of the battery electrolyte, so that a thinner inorganic material film layer can be used, and the thickness and the weight of the isolating layer can be further reduced. The characteristics can further improve the weight utilization rate and the space utilization rate of the interior of the lithium ion battery cell, so that the weight energy density and the volume energy density of the lithium ion battery are improved.

Drawings

Fig. 1 is a schematic view of a coating paste preparation process according to an embodiment of the present invention.

Fig. 2 is a schematic view of porous silica particles obtained in the coating slurry according to an embodiment of the present invention.

Fig. 3 is a schematic structural diagram of embodiment 1 of the present invention, wherein the reference numbers are: 1. the negative pole piece comprises a negative pole current collector, in this case, a copper foil, 2, a negative pole material layer coated on the surface of the copper foil, 3, an inorganic material film coated on the surface of the negative pole material layer, 4, a positive pole material layer coated on the surface of an aluminum foil, and 5, a positive pole current collector, in this case, the aluminum foil.

FIG. 4 is an electron microscope image of the surface of the coating layer of example 1 of the present invention.

Fig. 5 is a battery capacity test of example 1 and comparative example 1 of the present invention, in which a solid line is the battery of example 1 and a dotted line is the battery of comparative example 1 of example 1 except that finished silica is used, and the steps and materials are the same.

FIG. 6 is an electron microscope image of the surface of the coating layer of example 2 of the present invention.

Fig. 7 is a battery capacity test of example 2 and comparative example 2 of the present invention, in which a solid line is the battery of example 2 and a dotted line is the battery of comparative example 2 of example 2 except that finished silica is used, and other steps and materials are the same.

FIG. 8 is an electron microscope image of the surface of the coating layer of example 3 of the present invention.

FIG. 9 is an electron microscope image of the surface of the coating layer of example 4 of the present invention.

Detailed Description

The invention will be further described with reference to embodiments with reference to the drawings. The following examples are intended only to illustrate the present invention specifically and are not intended to limit the present invention.

Example 1

Preparation of coating slurry for example 1: add 4 g of acrylonitrile multipolymer emulsion into 100 ml of ethanol and stir for 0.5 hour. Adding 3 ml of concentrated ammonia water, 3 ml of deionized water and 2 ml of 1 percent tertiary alkyl polyhydric alcohol polyvinyl ether aqueous solution, and then stirring for 0.5 hour. Then, 6 ml of tetraethyl orthosilicate was added, stirred at normal temperature for 2 hours, and centrifuged. And adding a small amount of deionized water into the prepared coating slurry according to the situation, stirring, adjusting the viscosity, coating the surface of the negative pole piece by using a coating machine, and baking the negative pole piece for 1 hour at 80 ℃. Fig. 4 shows an electron microscope image of the coating layer surface of this embodiment. And cutting the prepared negative pole piece, and forming a battery by using the cut positive pole piece. The inorganic material film had a thickness of 10 μm and a porosity of 45%.

Fig. 3 shows a schematic structural diagram of this embodiment, in which:

the negative current collector is copper foil, and the negative material is graphite; the conductive agent of the negative electrode is conductive carbon black; the adhesive of the negative electrode is polyvinylidene fluoride; the positive current collector is an aluminum foil, and the positive material is lithium cobaltate; the conductive agent of the positive electrode is conductive carbon black; the adhesive of the positive electrode is polyvinylidene fluoride; the electrolyte is LiPF with the concentration of 1mol/L₆As a solute, EC: EMC: DMC ═ 1:1:1 was used as a solvent.

Comparative example 1

Comparative example 1 was prepared in the same manner as in example 1 except that a finished silica, a nano-or submicron spherical silica sold under the trade name KH570 from golden nano-technical materials ltd, was used therein. Wherein, 6 g of silicon dioxide powder is added into 20 ml of ethanol, the mixture is ground in a ball mill for 10 hours, 4 g of acrylonitrile multipolymer emulsion and 2 ml of deionized water are added, and the grinding is continued for 2 hours. And (4) after the slurry is taken out, adding a small amount of deionized water according to the situation, stirring and adjusting the viscosity.

Fig. 5 shows the results of the battery capacity test of example 1 and comparative example 1, in which the solid line is the battery of example 1 and the dotted line is the battery of comparative example 1. As is clear from fig. 5, the battery capacity of example 1 is significantly improved as compared with the battery capacity of comparative example 1.

More importantly, from a comparison of example 1 and comparative example 1, it can be seen that the process of the present invention is time consuming, cost savings of at least 50% are achieved using direct in situ synthesis over the use of the finished silica nanoparticles, and only conventional stirring is required, without long ball milling, due to in situ synthesis in solution. And because the silicon dioxide particles are not dry powder, the agglomeration of the nano silicon dioxide particles can be effectively inhibited, and the uniform dispersion of the silicon dioxide particles can be easily realized without ball milling.

Example 2

Preparation of coating slurry for example 2: 4 g of polyvinylidene fluoride-hexafluoropropylene copolymer were dissolved in 100 ml of a mixture (1:1) of acetone and N-methylpyrrolidone. Adding 3 ml of concentrated ammonia water, 3 ml of deionized water and 2 ml of 1 percent tertiary alkyl polyhydric alcohol polyvinyl ether aqueous solution, and stirring for 0.5 hour. 8 ml of tetraethyl orthosilicate was added and stirred at room temperature for 2 hours. And (4) centrifugal separation. And adding a small amount of deionized water into the prepared coating slurry according to the situation, stirring, adjusting the viscosity, coating the prepared coating slurry on the surface of the negative pole piece by using a coating machine, and then baking the negative pole piece for 1 hour at 80 ℃. Fig. 6 shows an electron microscope image of the coating layer surface of this example.

And cutting the prepared negative pole piece, and forming a battery by using the cut positive pole piece. The inorganic material film had a thickness of 8 microns and a porosity of 40%.

The negative current collector is copper foil, and the negative material is graphite; the conductive agent of the negative electrode is conductive carbon black; the adhesive of the negative electrode is polyvinylidene fluoride; the positive current collector is an aluminum foil, and the positive material is lithium cobaltate; the conductive agent of the positive electrode is conductive carbon black; the adhesive of the positive electrode is polyvinylidene fluoride; the electrolyte takes LiPF6 with the concentration of 1mol/L as a solute and EC EMC DMC 1:1:1 as a solvent.

Comparative example 2

Comparative example 2 was prepared in the same manner as in example 2 except that a finished silica, a nano-or submicron spherical silica sold under the trade name KH550 from golden nano-technical materials ltd, was used therein. Wherein 6 g of nano-silica is added into a mixture (1:1) of acetone and N-methyl pyrrolidone 20 ml to dissolve 4 g of polyvinylidene fluoride-hexafluoropropylene copolymer. Milling was carried out in a ball mill for 20 hours. After the slurry is taken out, a small amount of mixture of acetone and N-methyl pyrrolidone is added according to the situation, and the mixture is stirred to adjust the viscosity.

Fig. 7 shows the results of the battery capacity test of example 2 and comparative example 2, in which the solid line is the battery of example 2 and the dotted line is the battery of comparative example 2. As is clear from fig. 7, the battery capacity of example 2 is significantly improved as compared with that of comparative example 2.

More importantly, from a comparison of example 2 and comparative example 2, it can be seen that the process of the present invention is less time consuming, can cost effectively be saved by at least 50% using direct in situ synthesis over the use of the finished silica nanoparticles, and requires only conventional agitation due to in situ synthesis in solution. And because the silicon dioxide particles are not dry powder, the agglomeration of the nano silicon dioxide particles can be effectively inhibited, and the uniform dispersion of the silicon dioxide particles can be easily realized without ball milling.

Example 3 and comparative example 3

Example 3 is the same as example 1 except that the binder carboxymethyl cellulose is substituted for the acrylonitrile copolymer emulsion. As a result, excellent technical effects similar to those of example 1 were obtained, in which the thickness of the obtained inorganic material film was 10 μm and the porosity was 40%.

Comparative example 3 is the same as comparative example 1 except that carboxymethyl cellulose as a binder is substituted for the acrylonitrile copolymer emulsion. Through the test, the battery capacity of example 3 was 103% of the battery capacity of comparative example 3.

Example 4 and comparative example 4

Example 4 is the same as example 1 except that the adjuvant sodium diisooctyl sulfoate is substituted for the tertiary alkyl polyol polyvinyl ether. As a result, excellent technical effects similar to those of example 1 were obtained, in which the obtained inorganic material film had a thickness of 12 μm and a porosity of 45%.

Comparative example 4 is the same as comparative example 1 except that the adjuvant sodium diisooctyl sulfoate is substituted for the tertiary alkyl polyol polyvinyl ether. Through the test, the battery capacity of example 4 was 102% of the battery capacity of comparative example 4.

The raw materials and equipment used in the invention are common raw materials and equipment in the field if not specified; the methods used in the present invention are conventional in the art unless otherwise specified.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any modifications, alterations, and equivalents of the above embodiments according to the technical spirit of the present invention are still within the scope of the claims of the present application.

Claims

1. A method of making a separator-free lithium ion battery, the method comprising the steps of:

providing a positive pole piece and a negative pole piece,

providing a coating slurry, and

wherein the coating slurry comprises inorganic material particles, a binder, a basic catalyst, a solvent and an auxiliary agent,

wherein the particles of inorganic material are predominantly silica particles,

characterized in that the silica particles are synthesized in situ in the coating slip by hydrolysis of an organosilicon compound,

wherein the preparation ingredients of the coating slurry comprise:

5 to 30% by weight of an organosilicon compound,

1 to 20 wt% of a basic catalyst,

0.1 to 5 weight percent of auxiliary agent,

0.1 to 30% by weight of a binder, and

30 to 95 wt% of a solvent, and

wherein the binder is selected from the group consisting of acrylonitrile multipolymer based binders, polyvinyl fluoride based binders, and hydrosol based binders, and combinations of two or more thereof.

2. The method of claim 1, wherein the acrylonitrile multipolymer based binder is selected from the group consisting of acrylonitrile multipolymers, polymethyl methacrylate-butyl acrylate emulsions, polystyrene-butyl acrylate emulsions, and combinations of two or more thereof.

3. The method of claim 1, wherein the polyvinyl fluoride based binder is selected from the group consisting of polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion, vinylidene fluoride-hexafluoropropylene copolymer, and combinations of two or more thereof.

4. The method of claim 1, wherein the hydrosol-based binder is selected from the group consisting of carboxymethylcellulose, gelatin, sodium alginate, and combinations of two or more thereof.

5. The method of claim 1, wherein the solvent is selected from the group consisting of water, methanol, ethanol, N-propanol, isopropanol, acetone, N-methylpyrrolidone, and combinations of two or more thereof.

6. The method of claim 1, wherein the adjuvant is selected from the group consisting of non-ionic adjuvants and ionic adjuvants, and combinations thereof.

7. The method of claim 6, wherein the non-ionic coagent is selected from the group consisting of tertiary alkyl polyol polyvinyl ethers, polyether modified silicone oils, polypropylene glycol-ethylene oxide, polyether stearate dimethyl siloxanes, polyoxyethylene polyoxypropylene pentaerythritol ethers, polyoxyethylene glycerol ethers, polyoxyethylene polyoxypropylene amine ethers, polyvinyl alcohols, and combinations of two or more thereof.

8. The method of claim 6 wherein the ionic adjuvant is selected from the group consisting of sodium diisooctyl sulfonate and alkyl naphthalene sulfonate and combinations thereof.

9. The method according to claim 1, wherein the lithium ion positive active material of the positive electrode sheet is laminated opposite to the lithium ion negative active material of the negative electrode sheet.

10. The method according to any one of claims 1 to 9, wherein the organosilicon compound is selected from silicates of formula 1:

wherein R is¹、R²、R³And R⁴Independently of one another in each occurrence are straight-chain or branched alkyl groups having 1 to 5C atoms.

11. The method of claim 10, wherein R¹、R²、R³And R⁴Independently of one another in each occurrence, is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, and n-pentyl.

12. The process according to any one of claims 1 to 9, wherein the basic catalyst is concentrated ammonia.

13. A method according to any one of claims 1 to 9, wherein the size of the silica particles is controlled to be in the range 1 to 3000 nm by adjusting the proportions in the furnish.

14. The method according to any one of claims 1 to 9, wherein the composition of the coating slurry comprises 20 to 80 parts by weight of silica particles, 0.5 to 20 parts by weight of a binder, 10 to 80 parts by weight of a solvent, and 0.1 to 10 parts by weight of an auxiliary.

15. The method of any one of claims 1 to 9, wherein the inorganic material film is provided on at least one of a surface and/or a reverse surface of the positive electrode tab and a surface and/or a reverse surface of the negative electrode tab.

16. The method of any one of claims 1 to 9, wherein the positive electrode sheet is an aluminum foil coated with a lithium ion positive active material coating and the negative electrode sheet is a copper foil coated with a lithium ion negative active material coating or metallic lithium and copper foil.

17. A lithium ion battery without a diaphragm comprises a positive pole piece and a negative pole piece, wherein the surface of at least one of the positive pole piece and the negative pole piece is provided with an inorganic material film, the inorganic material film is formed by curing coating slurry, the coating slurry comprises inorganic material particles, a bonding agent, an alkaline catalyst, a solvent and an auxiliary agent, the inorganic material particles are mainly silica particles, and the lithium ion battery is characterized in that the silica particles are synthesized in situ in the coating slurry by hydrolyzing an organic silicon compound,

wherein the preparation ingredients of the coating slurry comprise:

5 to 30% by weight of an organosilicon compound,

1 to 20 wt% of a basic catalyst,

0.1 to 5 weight percent of auxiliary agent,

0.1 to 30% by weight of a binder, and

30 to 95 wt% of a solvent, and

18. The lithium ion battery of claim 17, wherein the acrylonitrile multipolymer based binder is selected from the group consisting of acrylonitrile multipolymers, polymethyl methacrylate-butyl acrylate emulsions, polystyrene-butyl acrylate emulsions, and combinations of two or more thereof.

19. The lithium ion battery of claim 17, wherein the polyfluoroethylene-based binder is selected from the group consisting of polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion, vinylidene fluoride-hexafluoropropylene copolymer, and combinations of two or more thereof.

20. The lithium ion battery of claim 17, wherein the hydrosol-based binder is selected from the group consisting of carboxymethylcellulose, gelatin, sodium alginate, and combinations of two or more thereof.

21. The lithium ion battery of claim 17, wherein the solvent is selected from the group consisting of water, methanol, ethanol, N-propanol, isopropanol, acetone, N-methylpyrrolidone, and combinations of two or more thereof.

22. The lithium ion battery of claim 17, wherein the adjunct is selected from the group consisting of non-ionic and ionic adjuncts and combinations thereof.

23. The lithium ion battery of claim 22, wherein the non-ionic adjunct is selected from the group consisting of tertiary alkyl polyol polyvinyl ethers, polyether modified silicone oils, polypropylene glycol-ethylene oxide, polyether stearate dimethyl siloxanes, polyoxyethylene polyoxypropylene pentaerythritol ethers, polyoxyethylene glycerol ethers, polyoxyethylene polyoxypropylene amine ethers, polyvinyl alcohols, and combinations of two or more thereof.

24. The lithium ion battery of claim 22 wherein the ionic adjuvant is selected from the group consisting of sodium diisooctyl sulfonate and alkyl naphthalene sulfonate and combinations thereof.

25. The lithium ion battery of claim 17, wherein the lithium ion positive active material of the positive electrode tab is laminated opposite the lithium ion negative active material of the negative electrode tab.

26. The lithium ion battery of any of claims 17-25 wherein the organosilicon compound is selected from silicates of formula 1:

27. The lithium ion battery of claim 26, wherein R¹、R²、R³And R⁴Independently of one another in each occurrence, is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, and n-pentyl.

28. The lithium ion battery of any of claims 17-25 wherein the silica particles are 1-3000 nanometers in size.

29. The lithium ion battery according to any one of claims 17 to 25, wherein the composition of the coating paste comprises 20 to 80 parts by weight of silica particles, 0.5 to 20 parts by weight of a binder, 10 to 80 parts by weight of a solvent, and 0.1 to 10 parts by weight of an assistant.

30. The lithium ion battery of any of claims 17-25, wherein a monolayer thickness of the inorganic material film is 1-10 microns.

31. The lithium ion battery of any one of claims 17 to 25, wherein the inorganic material film is provided on at least one of a surface and/or a reverse surface of the positive electrode tab and a surface and/or a reverse surface of the negative electrode tab.

32. The lithium ion battery of any one of claims 17 to 25, wherein the positive electrode sheet is an aluminum foil coated with a lithium ion positive active material coating and the negative electrode sheet is a copper foil coated with a lithium ion negative active material coating or metallic lithium and copper foil.