CN115863589B - Silicon composite material, material preparation method, electrode plate and battery - Google Patents
Silicon composite material, material preparation method, electrode plate and battery Download PDFInfo
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- CN115863589B CN115863589B CN202211638385.5A CN202211638385A CN115863589B CN 115863589 B CN115863589 B CN 115863589B CN 202211638385 A CN202211638385 A CN 202211638385A CN 115863589 B CN115863589 B CN 115863589B
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Abstract
The application provides a silicon composite material, a material preparation method, an electrode plate and a battery, relates to the technical field of batteries, and solves the technical problem that the current covalent organic framework is poor in effect of inhibiting the volume expansion of a silicon nano material. The silicon composite material comprises silicon nanoparticles, a covalent organic framework and lithium salt; wherein the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework.
Description
Technical Field
The application relates to the technical field of batteries, in particular to a silicon composite material, a material preparation method, an electrode plate and a battery.
Background
Silicon (Si) is considered to be one of the most promising negative electrode materials for lithium ion batteries due to its higher theoretical capacity. However, silicon is susceptible to volume expansion during intercalation and deintercalation, thereby causing pulverization of silicon particles, resulting in rapid degradation of battery capacity.
To overcome the above problems, the related art generally mixes a silicon nanomaterial with a covalent organic framework material, and suppresses the volume expansion of the silicon nanomaterial using the covalent organic framework. However, the covalent organic frameworks have poor stability in an electrolyte solution and are easily subject to structural breakdown, so that the covalent organic frameworks have poor effect of inhibiting the volume expansion of the silicon nanomaterial.
Disclosure of Invention
The application provides a silicon composite material, a material preparation method, an electrode slice and a battery, which can be used for solving the technical problem that the current covalent organic framework has poor effect of inhibiting the volume expansion of a silicon nano material.
In a first aspect, embodiments herein provide a silicon composite comprising silicon nanoparticles, a covalent organic framework, and a lithium salt;
wherein the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework.
Optionally, in one embodiment, the covalent organic framework is grown on the surface of the silicon nanoparticle to encapsulate the silicon nanoparticle.
Alternatively, in one embodiment, the covalent organic framework is COF-5.
Optionally, in one embodiment, the silicon nanoparticles have a particle size of 20nm to 100nm.
Optionally, in one embodiment, the lithium salt comprises lithium chloride and/or lithium acetate.
In a second aspect, an embodiment of the present application provides a method for preparing a silicon composite material provided in the first aspect of the present application, where the method includes:
mixing the first composite material with lithium salt to obtain a mixture;
Carbonizing the mixture to obtain the silicon composite material with lithium salt filled between the covalent organic framework pores and the lamellar layers;
the first composite material comprises silicon nanoparticles and a covalent organic framework, wherein the covalent organic framework is coated on the surface of the silicon nanoparticles.
Alternatively, in one embodiment, where the covalent organic framework is grown on the surface of the silicon nanoparticle, the first composite material is prepared by:
adding silicon nano particles and 1, 4-phenyldiboronic acid into a first solvent to obtain a solution A;
adding hexahydroxybenzophenanthrene into a first solvent to obtain a solution B;
and mixing the solution A and the solution B, heating, and filtering to obtain the first composite material.
Optionally, in one embodiment, the mass ratio of the first composite material to the lithium salt is 1: (2-10), wherein the mass ratio of the silicon nano particles to the 1, 4-phenyldiboronic acid to the hexahydroxybenzophenanthrene is 8: (1-3): (1-4).
In a third aspect, embodiments of the present application provide an electrode sheet, the electrode sheet including: a binder, a conductive agent, a current collector, and a silicon composite material provided in the first aspect of the present application;
Wherein the binder, the conductive agent and the silicon composite material are mixed to form a negative electrode slurry, and the negative electrode slurry is coated on the current collector.
In a fourth aspect, embodiments of the present application provide a battery including a positive electrode sheet and an electrode sheet provided in the third aspect of the present application.
The beneficial effects brought by the embodiment of the application are as follows:
by adopting the scheme provided by the embodiment of the application, the silicon composite material comprises silicon nano particles, covalent organic frameworks and lithium salt; wherein the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework. The lithium salt is filled between the pores and the sheets of the covalent organic frameworks, so that the covalent organic frameworks can be supported, and the collapse of the covalent organic frameworks is prevented, and the volume expansion of the silicon nanomaterial can be effectively inhibited.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. In the drawings:
Fig. 1 is a schematic flow chart of a method for preparing a silicon composite material according to an embodiment of the present application;
FIG. 2 is a schematic flow chart of another method for preparing a silicon composite material according to an embodiment of the present disclosure;
fig. 3 is a schematic view of the rate performance of the battery according to the embodiment of the present application.
Detailed Description
For the purposes, technical solutions and advantages of the present application, the technical solutions of the present application will be clearly and completely described below with reference to specific embodiments of the present application and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
As described in the background of the present application, when the covalent organic framework is utilized to inhibit the volume expansion of the silicon nanomaterial, structural collapse is liable to occur due to poor stability of the covalent organic framework in the electrolyte solution, resulting in poor effect of the covalent organic framework in inhibiting the volume expansion of the silicon nanomaterial.
In view of this, the embodiment of the application provides a silicon composite material, which can be used as a negative electrode material of a battery, in particular, can be used as a negative electrode material of a lithium ion battery. The silicon composite may include silicon nanoparticles, covalent organic frameworks, and lithium salts; the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework.
The particle size of the silicon nanoparticle can be set according to the pore diameter of the covalent organic framework selected.
In the embodiment of the application, in order to enhance the transmission rate of lithium ions during the charge and discharge process, the covalent organic framework may specifically be COF-5. Compared with other types of covalent organic frameworks, the COF-5 has larger pore diameter, so that lithium ions can be better transmitted through the pore canal when charge and discharge are carried out.
In the case where the covalent organic framework is specifically COF-5, the particle size of the silicon nanoparticle may be 20nm to 100nm. The particle size of the silicon nano particles is set to be 20-100 nm, so that the silicon nano particles can be better matched with the structure of the COF-5, the escape of the silicon nano particles from the frame caused by the fact that the silicon nano particles are too small can be avoided, and the fact that the silicon nano particles cannot be completely coated due to the fact that the silicon nano particles are too large can be avoided. Therefore, the COF-5 has better coating effect on the silicon nano particles. In particular implementations, the silicon nanoparticles may have a particle size of 20nm, 30nm, 40nm, 50nm, 60nm, 75nm, 90nm, 100nm, or other values between 20nm and 100nm. For ease of explanation of the scheme of the present application, the following exemplary explanation will be made with the particle size of the silicon nanoparticles being 50 nm; it will be appreciated that in practical applications, some of the silicon nanoparticles used in the synthesis of the silicon composite may have a particle size of less than 50nm and/or some of the silicon nanoparticles may have a particle size of greater than 50nm.
In embodiments of the present application, the lithium salt may include lithium chloride (LiCl) and/or lithium acetate (LiOAc). It should be understood that the selection of lithium chloride and/or lithium acetate as the lithium salt to be filled between the pores and the sheets of the covalent organic framework is merely exemplary and not meant to be unduly limiting, and that in practical applications other lithium salts suitable for such filling may be selected as appropriate.
The lithium salt is filled between the pores and the sheet layers of the covalent organic framework, and particularly can be in a form of compounding lithium ions in the lithium salt with active groups on the surface of the covalent valuable framework to realize the filling. It can be appreciated that, compared with a simple physical filling manner, the manner of filling by compounding lithium ions with the covalent valuable framework surface active groups enables lithium salt to be stably filled between the pores and the sheets of the covalent organic framework, and further can play a longer-term and more stable supporting role on the covalent organic framework.
It can be appreciated that with the silicon composite provided by embodiments of the present application, the silicon composite includes silicon nanoparticles, a covalent organic framework, and a lithium salt; wherein the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework. The lithium salt is filled between the pores and the sheet layers of the covalent organic framework, so that the covalent organic framework can be supported, and the structure of the covalent organic framework is prevented from collapsing, so that the volume expansion of the silicon nanomaterial can be effectively inhibited, and the cycle performance of the battery can be improved.
Moreover, the silicon composite material provided by the embodiment of the application fills the lithium salt between the pores and the sheets of the covalent organic framework, so that the lithium salt can be combined with the covalent organic framework. Further, in the process of charging and discharging the battery, the covalent organic framework combined with lithium salt can be used as an artificial SEI film, and the SEI film naturally formed on the surface of the negative electrode of the battery in the related art is replaced by the artificial SEI film. Compared with the method for obtaining lithium ions from electrolyte to form SEI film in the related art, the method for forming SEI film by using the covalent organic framework combined with lithium salt as the artificial SEI film can greatly reduce the consumption of lithium ions in electrolyte, thereby improving the first efficiency of the battery.
In order to further improve the stability of the covalent organic framework structure, the inhibition effect on the volume expansion of the silicon nano material is further improved. In embodiments of the present application, the covalent organic framework may specifically be a carbonized covalent organic framework.
After carbonization, the covalent organic framework structure is more compact and stable, so that the inhibition effect on the volume expansion of the silicon nano material can be further improved. In addition, after carbonization, the distance between covalent organic framework layers is reduced, the conductivity of lithium ions is correspondingly increased, and the lithium ion transmission effect is better.
On the other hand, in the related art, when the covalent organic frameworks are used to suppress the volume expansion of the silicon nanomaterial, it is common to simply physically mix the silicon nanoparticles and the covalent organic frameworks, which makes the relationship between the silicon nanoparticles and the covalent organic frameworks mostly: the silicon nanoparticles are attached to the surface of the covalent organic framework lamellae. This results in the covalent organic frameworks not confining the silicon nanoparticles well within the "cages" of the covalent organic frameworks, which in turn also results in the covalent organic frameworks having poor effect of inhibiting the volume expansion of the silicon nanomaterial. In the examples of the present application, the relationship between the silicon nanoparticle and the covalent organic framework is: the covalent organic framework is coated on the surface of the silicon nano-particle, so that the covalent organic framework can well limit the silicon nano-particle in a 'cage' of the covalent organic framework, and further the inhibition effect on the volume expansion of the silicon nano-material can be improved.
In order to enable the covalent organic framework to coat the surface of the silicon nanoparticle, in one embodiment, the covalent organic framework is grown on the surface of the silicon nanoparticle to coat the silicon nanoparticle.
In the specific implementation, a mode of adding the silicon nano particles in the process of synthesizing the covalent organic frameworks can be adopted, so that the covalent organic frameworks are grown on the surfaces of the silicon nano particles, and further a coating-like structure is formed on the surfaces of the silicon nano particles, so that the silicon nano particles are wrapped. The covalent organic framework coating is grown on the surface of the silicon nano particle, so that the silicon nano particle can be better bound by the covalent organic framework, and the inhibition effect of the covalent organic framework on the volume expansion of the silicon nano material can be further improved.
Based on the silicon composite material provided in the foregoing embodiments of the present application, the embodiments of the present application further provide a preparation method of the silicon composite material, as shown in fig. 1, where the preparation method may include:
step 101, mixing a first composite material with lithium salt to obtain a mixture; the first composite material comprises silicon nanoparticles and a covalent organic framework, wherein the covalent organic framework is coated on the surface of the silicon nanoparticles.
In order to make the mixing effect of the first composite material and the lithium salt better, the lithium salt can be dissolved in an organic solvent first, and then the first composite material is added for mixing.
The organic solvent for dissolving the lithium salt can be selected from any one or more of methanol, ethanol and acetone.
In order that the covalent organic framework may bind more lithium salt, the mass ratio of the first composite material to lithium salt may be 1: (2-10).
And 102, carbonizing the mixture to obtain the silicon composite material with lithium salt filled between the covalent organic framework pores and the sheets.
Wherein, in order to avoid residual organic solvent of dissolved lithium salt, resulting in inclusion of impurities after carbonization, the mixture may be dried to remove the organic solvent therein before carbonization treatment.
In the embodiment of the present application, the step 102 of carbonizing the mixture may specifically be: the mixture is heat treated in a tube furnace under a protective gas atmosphere. By performing the heat treatment process under a protective gas atmosphere, oxygen and the covalent organic frameworks can be prevented from side reactions. The shielding gas may be argon.
The temperature of the heat treatment may be 500 to 800 c for better carbonization. At this carbonization temperature, the lithium salt is generally in a molten state because of its low melting point, and thus can be more favorably filled between the pores and the sheets of the covalent organic framework.
It can be appreciated that with the method for preparing a silicon composite material provided by the embodiments of the present application, a silicon composite material comprising silicon nanoparticles, a covalent organic framework, and a lithium salt can be formed; wherein the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework. The lithium salt is filled between the pores and the sheets of the covalent organic frameworks, so that the covalent organic frameworks can be supported, and the collapse of the covalent organic frameworks is prevented, and the volume expansion of the silicon nanomaterial can be effectively inhibited.
To further enable the lithium salt to more stably fill between the pores and the lamellae of the covalent organic framework, the method for preparing a silicon composite provided in embodiments of the present application may further include, after carbonizing the mixture in step 102: the solid powder obtained by the heat treatment was washed with a hydrochloric acid solution.
In the process of washing the solid powder by using hydrochloric acid solution, boric acid ester bonds on the surface of the covalent organic framework are hydrolyzed, boron is removed, and active groups of hydroxyl groups are formed on the surface of the covalent organic framework. The hydroxyl groups may be further complexed with lithium ions in the lithium salt, thereby enabling the lithium salt to more stably fill in between the pores and the lamellae of the covalent organic framework. The mass fraction of the hydrochloric acid solution may be 10%.
The above-described hydrochloric acid washing process may be repeated a plurality of times in order that the covalent organic framework may bind more lithium ions.
Further, after washing the solid powder obtained by the heat treatment with the hydrochloric acid solution, the preparation method of the silicon composite material provided in the embodiment of the application may further include: excess lithium salt in the silicon composite is removed.
Wherein removal of excess lithium salt is understood to be removal of lithium salt that fails to bind to the covalent organic framework.
In practice, the material may be washed with water to remove excess lithium salt. In order to optimize the washing effect, warm water at 50-80 ℃ can be used for stirring and washing the material, and the stirring time can be 20-24 hours. The washing process may also be repeated a number of times in order to remove as much excess lithium salt as possible.
After the washing process is completed, the final silicon composite material can be obtained through vacuum drying.
In order to enable the covalent organic framework to coat the surface of the silicon nanoparticle, in one embodiment, in the case that the covalent organic framework grows on the surface of the silicon nanoparticle, the first composite material is prepared by the following process:
in step 201, silicon nanoparticles and 1, 4-phenyldiboronic acid are added to a first solvent to obtain a solution a.
Among them, 1, 4-phenyldiboronic acid (BDBA) is a raw material for preparing covalent organic frameworks. The first solvent may be used to dissolve 1, 4-benzenediboronic acid. The first solvent may specifically be a mixed solvent of dioxane and mesitylene.
Step 202, adding hexahydroxytriphenylene to the first solvent to obtain solution B.
Among them, hexahydroxybenzophenanthrene (HHTP) is a starting material for the preparation of covalent organic frameworks. The first solvent may be used to dissolve hexahydroxytriphenylene. The first solvent may be the same as the first solvent in step 201. In the case that the first solvent is a mixed solvent of dioxane and mesitylene, the volume ratio of dioxane to mesitylene can be 1:1-3:1, so that the dissolution effect of 1, 4-phenyldiboronic acid and hexahydroxybenzophenanthrene is better.
The execution sequence of step 201 and step 202 is not limited, and solution a may be prepared first and then solution B may be prepared; alternatively, solution B may be prepared first, followed by solution A; still alternatively, solution a and solution B may be prepared simultaneously in two reaction vessels, respectively.
In order to make the final silicon composite material have both energy density and volume expansion inhibition effect, the mass ratio of the silicon nanoparticles to the 1, 4-phenyldiboronic acid to the hexahydroxybenzophenanthrene can be 8: (1-3): (1-4).
And 203, mixing the solution A and the solution B, heating, and filtering to obtain the first composite material.
Wherein, to be able to successfully synthesize the covalent organic framework, step 203 mixes the solution a and the solution B to heat, which may specifically include: solution a, solution B and glacial acetic acid (HOAc) were mixed, degassed by freeze-pump-thaw cycles and then heated.
Through the above process, under weak acid condition, 1, 4-benzene diboronic acid and hexahydroxy benzophenanthrene can undergo condensation reaction, so as to synthesize covalent organic framework. Oxygen can be removed by freeze-pump-thaw cycle degassing, thereby avoiding oxygen affecting the synthesis of covalent organic frameworks.
After filtration, the primary product obtained by filtration may be washed and dried to obtain the first composite material.
In specific implementation, the initial product can be washed by water, an organic solvent C and an organic solvent D in sequence; wherein the polarity of the organic solvent C is greater than that of the organic solvent D, and the boiling point of the organic solvent C is higher than that of the organic solvent D. Washing with water can remove the residual inorganic impurities in the initial product. Washing with organic solvent C to remove residual organic impurities such as unreacted 1, 4-benzene diboronic acid and hexahydroxybenzophenanthrene; the organic solvent C with higher polarity is used for washing, so that more organic impurities can be dissolved, and the washing effect is better. Washing with an organic solvent D can remove the organic solvent C which remains in the initial product after washing with the organic solvent C; and finally, the organic solvent D with a lower boiling point is used for washing, so that the drying and purification of the initial product are facilitated. The organic solvent C may be N, N-dimethylformamide and/or dimethylsulfoxide. The organic solvent D may be selected from any one or more of ethanol, acetone and chloroform.
In order to enable the subsequent covalent organic frameworks to be combined with more lithium salt, after the first composite material is obtained through drying, the first composite material can be subjected to vacuum degassing so as to remove plugs in the covalent organic framework pore channels, and the pore channels are emptied. Thus, allowing the subsequent covalent organic framework to bind more lithium salt.
In particular, to enhance the removal of plugs from covalent organic framework channels, vacuum degassing may be carried out at 200-300 ℃ overnight.
It can be appreciated that by adopting the scheme, the covalent organic framework is made to grow on the surface of the silicon nanoparticle by adding the silicon nanoparticle in the process of synthesizing the covalent organic framework, and a coating-like structure is formed on the surface of the silicon nanoparticle, so that the silicon nanoparticle is wrapped. The covalent organic framework coating is grown on the surface of the silicon nano particle, so that the silicon nano particle can be better bound by the covalent organic framework, and the inhibition effect of the covalent organic framework on the volume expansion of the silicon nano material can be further improved.
Based on the silicon composite material provided in the above embodiments of the present application, the embodiments of the present application further provide an electrode sheet, where the electrode sheet includes: a binder, a conductive agent, a current collector, and a silicon composite material according to any of the above embodiments; the binder, the conductive agent and the silicon composite material are mixed to form a negative electrode slurry, and the negative electrode slurry is coated on the current collector.
The electrode sheet may be a negative electrode sheet, and the current collector may be a copper foil.
The binder may be sodium carboxymethyl cellulose and the conductive agent may be carbon black. It should be understood that the binder is sodium carboxymethyl cellulose, which is only an example, and the binder may be selected according to the actual situation, and the conductive agent is the same.
In specific implementation, after the binder, the conductive agent and the silicon composite material provided by the embodiment of the application are mixed to form the negative electrode slurry, the negative electrode slurry is coated on the current collector, and the negative electrode sheet can be further obtained through drying and rolling.
It can be appreciated that the electrode sheet provided by the embodiments of the present application is adopted, and the electrode sheet is obtained based on the silicon composite material provided by the embodiments of the present application, wherein the silicon composite material comprises silicon nanoparticles, a covalent organic framework and lithium salt; the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework. The lithium salt is filled between the pores and the sheet layers of the covalent organic framework, so that the covalent organic framework can be supported, and the structure of the covalent organic framework is prevented from collapsing, so that the volume expansion of the silicon nanomaterial can be effectively inhibited, and the cycle performance of the battery can be improved. The covalent organic frameworks are coated on the surfaces of the silicon nanoparticles, so that a coating-like structure is formed on the surfaces of the silicon nanoparticles, the covalent organic frameworks can well limit the silicon nanoparticles in the 'cage' of the covalent organic frameworks, the silicon nanoparticles can be better bound by the covalent organic frameworks, and further, the inhibition effect on the volume expansion of the silicon nanomaterial can be further improved.
Based on the silicon composite material provided in the above embodiment of the present application, the embodiment of the present application further provides a battery, where the battery includes a positive electrode plate and an electrode plate provided in the above embodiment of the present application, that is, includes the positive electrode plate and the negative electrode plate provided in the above embodiment of the present application.
Wherein, the battery can be a lithium ion battery or a sodium ion battery.
Taking the battery as a lithium ion battery as an example, the battery can further comprise electrolyte, a diaphragm and the like besides the positive electrode plate and the electrode plate provided by the embodiment of the application.
It can be understood that, with the battery provided in the embodiment of the present application, since the negative electrode sheet in the battery is the electrode sheet provided in the embodiment of the present application, and the negative electrode sheet is obtained based on the silicon composite material provided in the embodiment of the present application, the silicon composite material includes silicon nanoparticles, a covalent organic framework, and a lithium salt; the covalent organic framework is coated on the surface of the silicon nanoparticle, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic framework. The lithium salt is filled between the pores and the sheet layers of the covalent organic framework, so that the covalent organic framework can be supported, and the structure of the covalent organic framework is prevented from collapsing, so that the volume expansion of the silicon nanomaterial can be effectively inhibited, and the cycle performance of the battery can be improved. The covalent organic frameworks are coated on the surfaces of the silicon nanoparticles, so that a coating-like structure is formed on the surfaces of the silicon nanoparticles, the covalent organic frameworks can well limit the silicon nanoparticles in the 'cage' of the covalent organic frameworks, the silicon nanoparticles can be better bound by the covalent organic frameworks, and further, the inhibition effect on the volume expansion of the silicon nanomaterial can be further improved.
In order to facilitate the explanation of the technical effects of the silicon composite material, the material preparation method, the electrode sheet and the battery provided in the embodiments of the present application, the following description is made with reference to specific examples and corresponding test data.
Example 1
80mg of Si nanoparticles (wherein 99% of the particles have a particle diameter of approximately 50 nm) and 20mg of 1, 4-phenyldiboronic acid are dispersed in 3mL of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and subjected to ultrasonic treatment for 15 minutes to obtain a solution A.
25mg of hexahydroxybenzophenanthrene was dispersed in 3ml of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene: 2:1), and sonicated for 15 minutes to obtain solution B.
Solution a and solution B were added to Pyrex tubes, then 1.5mL of 6M HOAc was added, after 10 minutes of sonication, the reaction mixture was flash frozen under liquid nitrogen and degassed by three freeze-pump-thaw cycles. Then, the Pyrex tube was sealed and heated at 110 ℃ for 48 hours. The precipitate was collected by filtration and washed with deionized water, N-dimethylformamide and ethanol in that order. The precipitate is dried in vacuum at 60 ℃ for 8 hours to obtain a first composite material, the first composite material comprises silicon nano particles and covalent organic frameworks, the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and a similar coating structure is formed on the surfaces of the silicon nano particles.
10mg of the first composite material was degassed overnight at 250 ℃ under vacuum and then mixed with 80mg of lithium chloride in 5mL of acetone uniformly, i.e. the mass ratio of the first composite material to lithium chloride was 1:8. after the mixture was dried, it was heat-treated in a tube furnace at 600℃for 3 hours under an Ar atmosphere. The solid powder obtained was first washed 3 times with 10% HCl solution and then with stirring in water at 70 ℃ for 24 hours. And repeating the washing step twice, and vacuum drying the sample to obtain the silicon composite material.
Silicon composite material, conductive carbon black (Super P), binder sodium carboxymethyl cellulose (CMC) according to 8:1:1, mixing the materials into slurry in deionized water, coating the slurry on copper foil, and drying the slurry in vacuum at 80 ℃ to obtain the negative electrode plate. The electrolyte is 1mol/L lithium perchlorate, the solvent is Ethyl Carbonate (EC) and diethyl carbonate (DMC), and the volume ratio of EC to DMC is 1:1. assembled into a button cell in a glove box.
And (3) carrying out electrochemical test on the lithium ion battery assembled by the steps by adopting an electrochemical tester, wherein the test temperature is 25 ℃. The battery tester of the Wuhan blue CT2001A type is used for 0.1C charge and discharge, the test voltage range is 0.01V-1.0V, and the capacity and the first efficiency are tested.
Lithium iron phosphate is used as an anode, and electrolyte is 1M LiPF 6 The solvent is EC+DEC, and the volume ratio of EC to DEC is 1: and 1, assembling the battery into a full battery, and testing the cycle capacity retention rate under the charging and discharging conditions of different multiplying powers.
Example 2
80mg of Si nanoparticles (wherein 99% of the particles have a particle diameter of approximately 50 nm) and 10mg of 1, 4-phenyldiboronic acid are dispersed in 3mL of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and subjected to ultrasonic treatment for 15 minutes to obtain a solution A.
15mg of hexahydroxybenzophenanthrene was dispersed in 3ml of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene: 2:1), and sonicated for 15 minutes to obtain solution B.
Solution a and solution B were added to Pyrex tubes, then 1.5mL of 6M HOAc was added, after sonication for 30 minutes, the reaction mixture was flash frozen under liquid nitrogen and degassed by three freeze-pump-thaw cycles. Then, the Pyrex tube was sealed and heated at 110 ℃ for 72 hours. The precipitate was collected by filtration and washed with deionized water, N-dimethylformamide and ethanol in that order. The precipitate is dried in vacuum at 60 ℃ for 8 hours to obtain a first composite material, the first composite material comprises silicon nano particles and covalent organic frameworks, the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and a similar coating structure is formed on the surfaces of the silicon nano particles.
10mg of the first composite material was degassed overnight at 250 ℃ under vacuum and then mixed with 50mg of lithium acetate in 5mL of acetone uniformly, i.e. the mass ratio of the first composite material to lithium acetate was 1:5. after the mixture was dried, it was heat-treated in a tube furnace at 500℃for 3 hours under an Ar atmosphere. The solid powder obtained was first washed 3 times with 10% hcl solution and then with stirring in water at 70 ℃ for 24 hours. And repeating the washing step twice, and vacuum drying the sample to obtain the silicon composite material.
Silicon composite material, conductive carbon black (Super P), binder sodium carboxymethyl cellulose (CMC) according to 8:1:1, mixing the materials into slurry in deionized water, coating the slurry on copper foil, and drying the slurry in vacuum at 80 ℃ to obtain the negative electrode plate. The electrolyte is 1mol/L lithium perchlorate, the solvent is Ethyl Carbonate (EC) and diethyl carbonate (DMC), and the volume ratio of EC to DMC is 1:1. assembled into a button cell in a glove box.
And (3) carrying out electrochemical test on the lithium ion battery assembled by the steps by adopting an electrochemical tester, wherein the test temperature is 25 ℃. The battery tester of the Wuhan blue CT2001A type is used for 0.1C charge and discharge, the test voltage range is 0.01V-1.0V, and the capacity and the first efficiency are tested.
Lithium iron phosphate is used as an anode, and electrolyte is 1M LiPF 6 The solvent is EC+DEC, and the volume ratio of EC to DEC is 1: and 1, assembling the battery into a full battery, and testing the cycle capacity retention rate under the charging and discharging conditions of different multiplying powers.
Example 3
80mg of Si nanoparticles (wherein 99% of the particles have a particle diameter of approximately 50 nm) and 30mg of 1, 4-phenyldiboronic acid are dispersed in 3mL of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and subjected to ultrasonic treatment for 15 minutes to obtain a solution A.
37.5mg of hexahydroxybenzophenanthrene was dispersed in 3ml of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and sonicated for 15 minutes to obtain solution B.
Solution a and solution B were added to Pyrex tubes, then 1.5mL of 6M HOAc was added, after sonication for 20 minutes, the reaction mixture was flash frozen under liquid nitrogen and degassed by three freeze-pump-thaw cycles. Then, the Pyrex tube was sealed and heated at 100 ℃ for 48 hours. The precipitate was collected by filtration and washed with deionized water, dimethyl sulfoxide and acetone in that order. The precipitate is dried in vacuum at 60 ℃ for 8 hours to obtain a first composite material, the first composite material comprises silicon nano particles and covalent organic frameworks, the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and a similar coating structure is formed on the surfaces of the silicon nano particles.
10mg of the first composite material was degassed overnight at 250 ℃ under vacuum and then mixed with 60mg of lithium acetate in 5mL of acetone uniformly, i.e. the mass ratio of the first composite material to lithium acetate was 1:6. after the mixture was dried, it was heat-treated in a tube furnace at 500℃for 3 hours under an Ar atmosphere. The solid powder obtained was first washed 3 times with 10% hcl solution and then with stirring in water at 70 ℃ for 24 hours. And repeating the washing step twice, and vacuum drying the sample to obtain the silicon composite material.
Silicon composite material, conductive carbon black (Super P), binder sodium carboxymethyl cellulose (CMC) according to 8:1:1, mixing the materials into slurry in deionized water, coating the slurry on copper foil, and drying the slurry in vacuum at 80 ℃ to obtain the negative electrode plate. The electrolyte is 1mol/L lithium perchlorate, the solvent is Ethyl Carbonate (EC) and diethyl carbonate (DMC), and the volume ratio of EC to DMC is 1:1. assembled into a button cell in a glove box.
And (3) carrying out electrochemical test on the lithium ion battery assembled by the steps by adopting an electrochemical tester, wherein the test temperature is 25 ℃. The battery tester of the Wuhan blue CT2001A type is used for 0.1C charge and discharge, the test voltage range is 0.01V-1.0V, and the capacity and the first efficiency are tested.
Lithium iron phosphate is used as an anode, and electrolyte is 1M LiPF 6 The solvent is EC+DEC, and the volume ratio of EC to DEC is 1: and 1, assembling the battery into a full battery, and testing the cycle capacity retention rate under the charging and discharging conditions of different multiplying powers.
Example 4
80mg of Si nanoparticles (wherein 99% of the particles have a particle diameter of approximately 50 nm) and 15mg of 1, 4-phenyldiboronic acid are dispersed in 3mL of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and subjected to ultrasonic treatment for 15 minutes to obtain a solution A.
25mg of hexahydroxybenzophenanthrene was dispersed in 3ml of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene: 2:1), and sonicated for 15 minutes to obtain solution B.
Solution a and solution B were added to Pyrex tubes, then 1.5mL of 6M HOAc was added, after sonication for 30 minutes, the reaction mixture was flash frozen under liquid nitrogen and degassed by three freeze-pump-thaw cycles. Then, the Pyrex tube was sealed and heated at 110 ℃ for 48 hours. The precipitate was collected by filtration and washed with deionized water, dimethyl sulfoxide and acetone in that order. The precipitate is dried in vacuum at 60 ℃ for 10 hours to obtain a first composite material, the first composite material comprises silicon nano particles and covalent organic frameworks, the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and a similar coating structure is formed on the surfaces of the silicon nano particles.
10mg of the first composite material was degassed overnight at 300 ℃ under vacuum and then mixed with 20mg of lithium acetate in 5mL of acetone uniformly, i.e. the mass ratio of the first composite material to lithium acetate was 1:2. after the mixture was dried, it was heat-treated in a tube furnace at 600℃for 4 hours under an Ar atmosphere. The solid powder obtained was first washed 3 times with 10% hcl solution and then with stirring in water at 80 ℃ for 24 hours. And repeating the washing step twice, and vacuum drying the sample to obtain the silicon composite material.
Silicon composite material, conductive carbon black (Super P), binder sodium carboxymethyl cellulose (CMC) according to 8:1:1, mixing the materials into slurry in deionized water, coating the slurry on copper foil, and drying the slurry in vacuum at 80 ℃ to obtain the negative electrode plate. The electrolyte is 1mol/L lithium perchlorate, the solvent is Ethyl Carbonate (EC) and diethyl carbonate (DMC), and the volume ratio of EC to DMC is 1:1. assembled into a button cell in a glove box.
And (3) carrying out electrochemical test on the lithium ion battery assembled by the steps by adopting an electrochemical tester, wherein the test temperature is 25 ℃. The battery tester of the Wuhan blue CT2001A type is used for 0.1C charge and discharge, the test voltage range is 0.01V-1.0V, and the capacity and the first efficiency are tested.
Lithium iron phosphate is used as an anode, and electrolyte is 1M LiPF 6 The solvent is EC+DEC, and the volume ratio of EC to DEC is 1:1, assembling into a full battery, and testing under the condition of charging and discharging with different multiplying powersIs a cyclic capacity retention rate of (a).
Example 5
80mg of Si nanoparticles (wherein 99% of the particles have a particle diameter of approximately 50 nm) and 15mg of 1, 4-phenyldiboronic acid are dispersed in 3mL of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and subjected to ultrasonic treatment for 15 minutes to obtain a solution A.
25mg of hexahydroxybenzophenanthrene was dispersed in 3ml of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene: 2:1), and sonicated for 15 minutes to obtain solution B.
Solution a and solution B were added to Pyrex tubes, then 1.5mL of 6M HOAc was added, after sonication for 30 minutes, the reaction mixture was flash frozen under liquid nitrogen and degassed by three freeze-pump-thaw cycles. Then, the Pyrex tube was sealed and heated at 120 ℃ for 60 hours. The precipitate was collected by filtration and washed with deionized water, dimethyl sulfoxide and ethanol in that order. The precipitate is dried in vacuum at 60 ℃ for 8 hours to obtain a first composite material, the first composite material comprises silicon nano particles and covalent organic frameworks, the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and a similar coating structure is formed on the surfaces of the silicon nano particles.
10mg of the first composite material was degassed overnight at 250 ℃ under vacuum and then mixed with 100mg of lithium chloride in 5mL of acetone uniformly, i.e. the mass ratio of the first composite material to lithium chloride was 1:10. after the mixture was dried, it was heat-treated in a tube furnace at 700℃for 3 hours under an Ar atmosphere. The solid powder obtained was first washed 3 times with 10% HCl solution and then with stirring in water at 60 ℃ for 24 hours. And repeating the washing step twice, and vacuum drying the sample to obtain the silicon composite material.
Silicon composite material, conductive carbon black (Super P), binder sodium carboxymethyl cellulose (CMC) according to 8:1:1, mixing the materials into slurry in deionized water, coating the slurry on copper foil, and drying the slurry in vacuum at 80 ℃ to obtain the negative electrode plate. The electrolyte is 1mol/L lithium perchlorate, the solvent is Ethyl Carbonate (EC) and diethyl carbonate (DMC), and the volume ratio of EC to DMC is 1:1. assembled into a button cell in a glove box.
And (3) carrying out electrochemical test on the lithium ion battery assembled by the steps by adopting an electrochemical tester, wherein the test temperature is 25 ℃. The battery tester of the Wuhan blue CT2001A type is used for 0.1C charge and discharge, the test voltage range is 0.01V-1.0V, and the capacity and the first efficiency are tested.
Lithium iron phosphate is used as an anode, and electrolyte is 1M LiPF 6 The solvent is EC+DEC, and the volume ratio of EC to DEC is 1: and 1, assembling the battery into a full battery, and testing the cycle capacity retention rate under the charging and discharging conditions of different multiplying powers.
Example 6
80mg of Si nanoparticles (wherein 99% of the particles have a particle diameter of approximately 50 nm) and 30mg of 1, 4-phenyldiboronic acid are dispersed in 3mL of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and subjected to ultrasonic treatment for 15 minutes to obtain a solution A.
35mg of hexahydroxybenzophenanthrene was dispersed in 3ml of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene: 2:1), and sonicated for 15 minutes to obtain solution B.
Solution a and solution B were added to Pyrex tubes, then 1.5mL of 6M HOAc was added, after 10 minutes of sonication, the reaction mixture was flash frozen under liquid nitrogen and degassed by three freeze-pump-thaw cycles. Then, the Pyrex tube was sealed and heated at 100 ℃ for 72 hours. The precipitate was collected by filtration and washed with deionized water, dimethyl sulfoxide and acetone in that order. The precipitate is dried in vacuum at 60 ℃ for 10 hours to obtain a first composite material, the first composite material comprises silicon nano particles and covalent organic frameworks, the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and a similar coating structure is formed on the surfaces of the silicon nano particles.
10mg of the first composite material was degassed overnight at 200 ℃ under vacuum and then mixed with 80mg of lithium chloride in 5mL of acetone uniformly, i.e. the mass ratio of the first composite material to lithium chloride was 1:8. after the mixture was dried, it was heat-treated in a tube furnace at 650℃for 4 hours under an Ar atmosphere. The solid powder obtained was first washed 3 times with 10% hcl solution and then with stirring in water at 70 ℃ for 24 hours. And repeating the washing step twice, and vacuum drying the sample to obtain the silicon composite material.
Silicon composite material, conductive carbon black (Super P), binder sodium carboxymethyl cellulose (CMC) according to 8:1:1, mixing the materials into slurry in deionized water, coating the slurry on copper foil, and drying the slurry in vacuum at 80 ℃ to obtain the negative electrode plate. The electrolyte is 1mol/L lithium perchlorate, the solvent is Ethyl Carbonate (EC) and diethyl carbonate (DMC), and the volume ratio of EC to DMC is 1:1. assembled into a button cell in a glove box.
And (3) carrying out electrochemical test on the lithium ion battery assembled by the steps by adopting an electrochemical tester, wherein the test temperature is 25 ℃. The battery tester of the Wuhan blue CT2001A type is used for 0.1C charge and discharge, the test voltage range is 0.01V-1.0V, and the capacity and the first efficiency are tested.
Lithium iron phosphate is used as an anode, and electrolyte is 1M LiPF 6 The solvent is EC+DEC, and the volume ratio of EC to DEC is 1: and 1, assembling the battery into a full battery, and testing the cycle capacity retention rate under the charging and discharging conditions of different multiplying powers.
Example 7
80mg of Si nanoparticles (wherein 99% of the particles have a particle diameter of approximately 50 nm) and 15mg of 1, 4-phenyldiboronic acid are dispersed in 3mL of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene is 2:1), and subjected to ultrasonic treatment for 15 minutes to obtain a solution A.
25mg of hexahydroxybenzophenanthrene was dispersed in 3ml of a mixed solvent of dioxane and mesitylene (the volume ratio of dioxane to mesitylene: 2:1), and sonicated for 15 minutes to obtain solution B.
Solution a and solution B were added to Pyrex tubes, then 1.5mL of 6M HOAc was added, after 10 minutes of sonication, the reaction mixture was flash frozen under liquid nitrogen and degassed by three freeze-pump-thaw cycles. Then, the Pyrex tube was sealed and heated at 120 ℃ for 48 hours. The precipitate was collected by filtration and washed with deionized water, dimethyl sulfoxide and acetone in that order. The precipitate is dried in vacuum at 60 ℃ for 8 hours to obtain a first composite material, the first composite material comprises silicon nano particles and covalent organic frameworks, the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and a similar coating structure is formed on the surfaces of the silicon nano particles.
10mg of the first composite material was degassed overnight at 300 ℃ under vacuum and then mixed with 70mg of lithium chloride in 5mL of acetone uniformly, i.e. the mass ratio of the first composite material to lithium chloride was 1:7. after the mixture was dried, it was heat-treated in a tube furnace at 700℃for 4 hours under an Ar atmosphere. The solid powder obtained was first washed 3 times with 10% hcl solution and then with stirring in water at 70 ℃ for 24 hours. And repeating the washing step twice, and vacuum drying the sample to obtain the silicon composite material.
Silicon composite material, conductive carbon black (Super P), binder sodium carboxymethyl cellulose (CMC) according to 8:1:1, mixing the materials into slurry in deionized water, coating the slurry on copper foil, and drying the slurry in vacuum at 80 ℃ to obtain the negative electrode plate. The electrolyte is 1mol/L lithium perchlorate, the solvent is Ethyl Carbonate (EC) and diethyl carbonate (DMC), and the volume ratio of EC to DMC is 1:1. assembled into a button cell in a glove box.
And (3) carrying out electrochemical test on the lithium ion battery assembled by the steps by adopting an electrochemical tester, wherein the test temperature is 25 ℃. The battery tester of the Wuhan blue CT2001A type is used for 0.1C charge and discharge, the test voltage range is 0.01V-1.0V, and the capacity and the first efficiency are tested.
Lithium iron phosphate is used as an anode, and electrolyte is 1M LiPF 6 The solvent is EC+DEC, and the volume ratio of EC to DEC is 1: and 1, assembling the battery into a full battery, and testing the cycle capacity retention rate under the charging and discharging conditions of different multiplying powers.
Example 8
In comparison with example 1, the silicon nanoparticles were modified without adding 1, 4-phenyldiboronic acid and hexahydroxybenzophenanthrene, i.e., without adding COF-5 in example 8. It is understood that example 8 resulted in Si nanoparticles.
Example 9
In comparison with example 1, 50mg of 1, 4-benzenediboronic acid and 75mg of hexahydroxybenzophenanthrene are added in example 9. Namely, adding excessive COF-5 to modify the silicon nano-particles; the rest of the experimental conditions were the same as in example 1.
Example 10
In comparison with example 1, the first composite material obtained after vacuum drying in example 10 was not subjected to subsequent operations of filling with lithium salt and carbonization; the rest of the experimental conditions were the same as in example 1.
Electrochemical test data of the lithium ion battery assembled by the above examples are shown in table 1:
table 1 results of electrochemical performance tests for examples
As can be seen from table 1, the silicon composite materials prepared in examples 1 to 7 were more excellent in both cycle performance and specific capacity performance than those prepared in examples 8 and 10. Therefore, the silicon composite material comprising the silicon nano-particles, the covalent organic frameworks and the lithium salt, which is provided by the embodiment of the application, is adopted, wherein the covalent organic frameworks are coated on the surfaces of the silicon nano-particles, a coating-like structure is formed on the surfaces of the silicon nano-particles, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic frameworks, so that the cycle performance and the specific capacity performance of the battery can be remarkably improved. The silicon composites prepared in examples 1-7 exhibited higher specific capacities than example 9. This demonstrates that the specific capacity, cycle performance, and other properties can be achieved by using the silicon composite material comprising silicon nanoparticles, covalent organic frameworks, and lithium salt provided in the above examples of the present application.
The full cell obtained in example 1 and the full cell obtained in example 8 are shown in fig. 3 for the cycle capacity retention under different rate charge and discharge conditions.
As can be seen from table 1 and fig. 3, since the covalent organic framework combined with lithium salt in the silicon composite material provided in the embodiment of the present application can be used as an artificial SEI film, and has excellent lithium ion conductivity, the silicon composite material provided in the embodiment of the present application has more excellent rate capability compared with the example 8 pure Si nanoparticle negative electrode. At 500 mA.g -1 The lithium ion capacity at the current density of (2) was 2890 mAh.g -1 At 5000 mA.g -1 The lithium ion capacity at the extremely high current density of (3) is 1107 mAh.g -1 . When the current is restored to the original 500 mA.g -1 When the capacity is restored to 2860 mAh.g -1 The silicon composites provided by the examples of the present application exhibit good electrochemical reversibility (-98.3%). Compared with the silicon composite material provided by the embodiment of the application, the negative electrode of the Si nano particle of example 8 is 500 mA.g -1 The lithium ion capacity at the current density of (3) was 2919 mAh.g -1 At 5000 mA.g -1 Only 371 mAh.g was shown below -1 About 33% of the lithium capacity of the silicon composite provided in the examples herein). Therefore, the covalent organic framework combined with lithium salt in the silicon composite material provided by the embodiment of the application can be used as an excellent artificial SEI layer, and the artificial SEI layer has better lithium intercalation/deintercalation kinetic performance.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises the element.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. which are within the spirit and principles of the present application are intended to be included within the scope of the claims of the present application.
Claims (10)
1. A silicon composite material, characterized in that the silicon composite material comprises silicon nanoparticles, a covalent organic framework, and a lithium salt; the covalent organic frameworks are coated on the surfaces of the silicon nano particles, and the lithium salt is filled between the pores and the lamellar layers of the covalent organic frameworks so as to support the covalent organic frameworks, and the covalent organic frameworks are subjected to carbonization treatment.
2. The silicon composite of claim 1, wherein the covalent organic framework grows on the surface of the silicon nanoparticle to encapsulate the silicon nanoparticle.
3. The silicon composite of claim 1, wherein the covalent organic framework is COF-5.
4. A silicon composite material according to claim 3, wherein the silicon nanoparticles have a particle diameter of 20nm to 100nm.
5. The silicon composite according to claim 1, wherein the lithium salt comprises lithium chloride and/or lithium acetate.
6. A method of preparing a silicon composite material according to any one of claims 1 to 5, comprising: mixing the first composite material with lithium salt to obtain a mixture; carbonizing the mixture to obtain the silicon composite material with lithium salt filled between the covalent organic framework pores and the lamellar layers; the first composite material comprises silicon nanoparticles and a covalent organic framework, wherein the covalent organic framework is coated on the surface of the silicon nanoparticles.
7. The method according to claim 6, wherein in the case where the covalent organic framework grows on the surface of the silicon nanoparticle, the first composite material is prepared by: adding silicon nano particles and 1, 4-phenyldiboronic acid into a first solvent to obtain a solution A; adding hexahydroxybenzophenanthrene into a first solvent to obtain a solution B; and mixing the solution A and the solution B, heating, and filtering to obtain the first composite material.
8. The method of claim 7, wherein the mass ratio of the first composite material to the lithium salt is 1: (2-10), wherein the mass ratio of the silicon nano particles to the 1, 4-phenyldiboronic acid to the hexahydroxybenzophenanthrene is 8: (1-3): (1-4).
9. An electrode sheet, characterized in that the electrode sheet comprises: a binder, a conductive agent, a current collector, and the silicon composite of any one of claims 1-5; wherein the binder, the conductive agent and the silicon composite material are mixed to form a negative electrode slurry, and the negative electrode slurry is coated on the current collector.
10. A battery comprising a positive electrode sheet and the electrode sheet of claim 9.
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