CN109994710B - Composite negative electrode material, preparation method thereof, negative electrode plate and battery - Google Patents
Composite negative electrode material, preparation method thereof, negative electrode plate and battery Download PDFInfo
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Abstract
The application provides a composite negative electrode material and a preparation method thereof, a negative electrode pole piece and a battery, wherein the composite negative electrode material comprises a negative electrode material center core and a coating layer coated on the surface of the negative electrode material center core, and the coating layer comprises an inorganic polymer or an organic derivative of the inorganic polymer. The negative electrode material can effectively inhibit the volume expansion of the negative electrode material in the charging and discharging process, inhibit the rebound of the negative electrode pole piece, and improve the electrochemical performance of the battery.
Description
Technical Field
The application relates to the field of batteries, in particular to a composite negative electrode material, a preparation method thereof, a negative electrode plate and a battery.
Background
The lithium ion secondary battery has the advantages of high capacity, long cycle, no memory effect, less self-discharge, wide use temperature range, high multiplying power and the like, and is widely applied to the fields of mobile phones, computers, electric bicycles, electric automobiles and the like. In the using process of the lithium ion secondary battery, due to the insertion and the separation of lithium ions, the positive and negative pole pieces can generate volume expansion, and the performance of the lithium ion secondary battery is influenced. The silicon-based negative electrode material has the advantages of high capacity, good cycle performance, good rate performance and the like, is more and more emphasized by research and development personnel, but has larger volume expansion in the charge and discharge process, seriously influences the use of the lithium ion secondary battery and limits the application of the lithium ion secondary battery.
In view of this, the present application is specifically made.
Disclosure of Invention
In view of the problems in the background art, an object of the present application is to provide a composite negative electrode material, a preparation method thereof, a negative electrode sheet, and a battery, which effectively inhibit the volume expansion of the negative electrode material during the charging and discharging process, inhibit the rebound of the negative electrode sheet, and improve the electrochemical performance of the battery.
In order to achieve the above objects, in a first aspect of the present application, there is provided a composite anode material comprising a center core of an anode material and a coating layer coated on a surface of the center core of the anode material, the coating layer comprising an inorganic polymer or an organic derivative of an inorganic polymer.
In a second aspect of the present application, there is provided a method for preparing a composite anode material, for preparing the composite anode material according to the first aspect of the present application, comprising the steps of: adding a negative electrode material and an optional conductive agent into a polymerizable micromolecular substance solution, adding a curing agent into the polymerizable micromolecular substance solution under the stirring condition for polymerization reaction, and drying to remove the solvent after the reaction is finished to obtain the composite negative electrode material.
In a third aspect of the present application, the present application provides a negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being located on a surface of the negative electrode current collector, the negative electrode active material layer comprising the composite negative electrode material according to the first aspect of the present application.
In a fourth aspect of the present application, there is provided a battery comprising a negative electrode tab according to the third aspect of the present application.
Compared with the prior art, the application at least comprises the following beneficial effects:
according to the preparation method, the inorganic polymer coating layer or the organic derivative coating layer of the inorganic polymer is formed on the surface of the negative electrode material in an in-situ polymerization manner, so that the adhesion of the negative electrode material can be obviously improved, the volume expansion of the negative electrode material in the charging and discharging process is effectively inhibited, the rebound of a negative electrode pole piece is inhibited, and the electrochemical performance of the battery is improved.
Detailed Description
The composite negative electrode material, the preparation method thereof, the negative electrode plate and the battery according to the application are described in detail below.
First, a composite anode material according to a first aspect of the present application is explained, which includes an anode material central core and a coating layer coated on a surface of the anode material central core, the coating layer including an inorganic polymer or an organic derivative of an inorganic polymer.
In the composite anode material of the first aspect of the present application, the inorganic polymer is one or more selected from a silicate inorganic polymer, a phosphate inorganic polymer, and an aluminosilicate inorganic polymer. The organic derivative of the inorganic polymer refers to that organic groups containing carbon atoms are introduced into the structure of the inorganic polymer.
In the composite anode material of the first aspect of the present application, the content of the coating layer in the composite anode material is not excessively high, which may affect the capacity exertion of the anode material. Specifically, in the composite anode material, the mass content of the coating layer is 40% or less, and preferably 20% or less.
In the composite anode material of the first aspect of the present application, the anode material central core may be selected from one or more of a silicon-based anode material and a tin-based anode material. Preferably, the silicon-based negative electrode material is selected from one or more of silicon, silicon oxide, silicon-carbon composite and silicon alloy. The silicon can be selected from one or more of silicon nanoparticles, silicon nanowires, silicon nanotubes, silicon thin films, 3D porous silicon and hollow porous silicon. The tin-based negative electrode material is selected from one or more of tin, tin oxide and tin alloy.
In the composite anode material of the first aspect of the present application, the anode material may be subjected to a surface hydroxylation treatment to facilitate coating of the coating layer.
In the composite negative electrode material of the first aspect of the present application, the coating layer may further contain a conductive agent, and the conductive agent may further improve the conductivity of the negative electrode material, such as a silicon-based negative electrode material and a tin-based negative electrode material, and may also prevent the formation of an excessively dense coating layer on the surface of the negative electrode material from affecting the electron transmission.
In the composite anode material of the first aspect of the present application, the coating layer is formed by in-situ polymerization of a polymerizable small-molecule substance on the surface of the anode material. When the polymerization process of the polymerizable micromolecule substance on the surface of the negative electrode material is in-situ polymerization, the inorganic polymer or the organic derivative of the inorganic polymer in the coating layer can be tightly attached to the negative electrode material, and the polymerizable micromolecule substance has the characteristics of high strength and good toughness, can tolerate the expansion and contraction of the negative electrode material in the process of lithium ion (or other ions) insertion and removal, ensures the high elasticity and toughness of the SEI film on the surface of the negative electrode material, reduces the lithium ion (or other ions) consumption in the circulating process, and obviously prolongs the service life of the battery. Particularly, the method is particularly suitable for the negative electrode materials with larger volume expansion in the charging and discharging processes of silicon-based negative electrode materials, tin-based negative electrode materials and the like, can effectively inhibit the volume expansion of the silicon-based negative electrode materials, the tin-based negative electrode materials and the like in the charging and discharging processes, can inhibit the rebound of a negative electrode pole piece, and can be helpful for obtaining the battery with high capacity, good cycle performance and good rate capability. Preferably, the polymerizable small molecular substance is selected from one or more of inorganic silicate, inorganic phosphate, inorganic aluminate, ethyl orthosilicate and kaolin. Among them, the kind of the cation portion in the inorganic silicate, the inorganic phosphate, and the inorganic aluminate is not limited, but is preferably an alkali metal or an alkaline earth metal, more preferably an alkali metal, and still more preferably sodium or potassium. The inorganic phosphate may in turn be orthophosphate, dihydrogen phosphate, sesquihydrogen phosphate or hydrogen phosphate. Further preferably, the inorganic silicate may be water glass.
Taking water glass as an example, the polymerization process is as follows:
the water glass is gradually hydrolyzed in aqueous solution to generate [ Si (OH) under the promotion of a curing agent4]Single molecules which polymerize at different rates, with the progressive formation of the more reactive Si (OH) in the form of monomers4Then combining with silicate polymer with low polymerization degree and hydroxyl on the surface of negative electrode material to form core point on the surface of negative electrode material, and gradually forming amorphous SiO2·nH2The reaction process of the coating layer in the O form is as follows:
next, a method for producing a composite anode material according to a second aspect of the present application, which is used for producing the composite anode material according to the first aspect of the present application, is described, including the steps of: adding a negative electrode material and an optional conductive agent into a polymerizable micromolecular substance solution, adding a curing agent into the polymerizable micromolecular substance solution under the stirring condition for polymerization reaction, and drying to remove the solvent after the reaction is finished to obtain the composite negative electrode material.
In the preparation method of the composite negative electrode material of the second aspect of the present application, the polymerizable small molecular substance is selected from one or more of inorganic silicate, inorganic phosphate, inorganic aluminate and ethyl orthosilicate. Among them, the kind of the cation portion in the inorganic silicate, the inorganic phosphate, and the inorganic aluminate is not limited, but is preferably an alkali metal or an alkaline earth metal, more preferably an alkali metal, and still more preferably sodium or potassium. The inorganic phosphate may in turn be orthophosphate, dihydrogen phosphate, sesquihydrogen phosphate or hydrogen phosphate.
In the preparation method of the composite anode material of the second aspect of the present application, the kind of the curing agent is not limited, and may be selected according to the requirement. The curing agent can be inorganic substances such as metal oxides, hydroxides and metal salts, and can also be organic substances such as silane coupling agents and ethyl acetate. Specifically, the curing agent may be one or more selected from magnesium oxide, calcium oxide, aluminum oxide, copper oxide, sodium hydroxide, magnesium hydroxide, calcium chloride, calcium nitrate, magnesium chloride, magnesium sulfate, aluminum chloride, hydrochloric acid, dilute sulfuric acid, nitric acid, acetic acid, citric acid, silane coupling agent, and ethyl acetate.
In the preparation method of the composite anode material according to the second aspect of the present application, the kind of the solvent used in the polymerizable small molecular substance solution is not limited, and may be selected according to the requirement, for example, deionized water, an organic solvent, or a mixed solution of deionized water and an organic solvent may be used. Wherein, preferably, the organic solvent can be one or more selected from ethanol, propylene glycol, N-methyl pyrrolidone and ethyl acetate.
In the preparation method of the composite negative electrode material according to the second aspect of the present application, preferably, the mass fraction of the active material is 70% to 95%, the mass fraction of the conductive agent is 0% to 10%, the mass fraction of the polymerizable small molecular substance is 3% to 25%, and the mass fraction of the curing agent is 1% to 15%. The proportion of the polymerizable micromolecule substances is small, so that a complete, uniform and compact coating layer is not formed; the proportion of the curing agent is small, and the system can not be effectively cured, so that a complete, uniform and compact coating layer is not formed.
A negative electrode sheet according to a third aspect of the present application is explained again, which includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being located on a surface of the negative electrode current collector, the negative electrode active material layer including the composite negative electrode material according to the first aspect of the present application.
In the negative electrode sheet of the third aspect of the present invention, in the negative electrode active material layer, only the composite negative electrode material of the first aspect of the present invention may be used as the negative electrode active material of the negative electrode sheet, or the composite negative electrode material of the first aspect of the present invention may be used in combination with other common negative electrode materials. Preferably, the negative electrode active material layer may further include other commonly used negative electrode materials, such as one or more of soft carbon, hard carbon, artificial graphite, natural graphite, mesocarbon microbeads, lithium titanate, and metals capable of forming an alloy with lithium.
In the negative electrode sheet of the third aspect of the present application, the negative electrode active material layer may further include a conductive agent and a binder. The kinds of the conductive agent and the binder are not limited and may be selected as required.
In the negative electrode sheet of the third aspect of the present application, the method for preparing the negative electrode sheet may include the steps of: adding a negative electrode material and an optional conductive agent into a polymerizable micromolecular substance solvent solution, adding a curing agent into the polymerizable micromolecular substance solvent solution under the stirring condition for polymerization reaction, continuously stirring the mixture for a period of time, then adding other common negative electrode materials, binders and conductive agents, and uniformly stirring the mixture to obtain negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying to obtain the negative electrode piece. Therefore, when the polymerizable micromolecule substance is cured in situ, the cohesive strength of the negative active substance layer can be enhanced, and the binding power between the negative active substance layer and the negative current collector can be improved.
Next, a battery according to a fourth aspect of the present application, which includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, and the like, is described, wherein the negative electrode sheet is the negative electrode sheet according to the third aspect of the present application.
The battery according to the fourth aspect of the present application may be a lithium ion secondary battery, a sodium ion secondary battery, a zinc ion secondary battery, or a magnesium ion secondary battery. In the present application, a lithium ion secondary battery is described in detail by way of example only, but the present application is not limited thereto.
In the lithium ion secondary battery, the positive active material may be selected from lithium transition metal complex oxides including one or more of lithium transition metal oxides (e.g., lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide), and compounds obtained by adding other transition metals or non-transition metals to these lithium transition metal oxides.
The present application is further illustrated below with reference to examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.
Comparative example 1
(1) Preparation of negative pole piece
And (3) fully stirring and uniformly mixing the negative active material, the conductive agent and the binder in a deionized water solvent system, coating the mixture on a Cu foil, and drying and cold-pressing the Cu foil to obtain the negative pole piece. The negative electrode active material is a mixture of artificial graphite and silicon monoxide (SiO), the conductive agent is acetylene black, the binder is polyacrylic acid, and the mass ratio of the artificial graphite to the silicon monoxide to the acetylene black to the polyacrylic acid is 76:20:2: 2.
(2) Preparation of positive pole piece
LiNi as positive electrode active material0.8Mn0.1Co0.1O2The positive pole piece is obtained by coating the mixture on an Al foil, drying and cold pressing the mixture after fully stirring and uniformly mixing the conductive agent acetylene black and the adhesive polyvinylidene fluoride in an N-methyl pyrrolidone solvent system according to the mass ratio of 94:3: 3.
(3) Preparation of the separator
The PE porous polymer film is used as a separation film.
(4) Preparation of the electrolyte
Carbonic acid at a mass ratio of 30:70Adding lithium salt LiPF into mixed solvent of ethylene ester and methyl ethyl carbonate6Uniformly mixing to obtain electrolyte, wherein LiPF is contained in the electrolyte6The concentration of (2) is 1 mol/L.
(5) Preparation of lithium ion secondary battery
And stacking the positive pole piece, the isolating membrane and the negative pole piece in sequence to enable the isolating membrane to be positioned between the positive pole piece and the negative pole piece to play an isolating role, and winding to obtain the bare cell. And placing the bare cell in an outer package, injecting the prepared electrolyte and packaging.
Comparative example 2
A lithium ion secondary battery was produced in the same manner as in comparative example 1, except that the silicon oxide used in the production of the negative electrode sheet was a silicon oxide coated with a layer of amorphous carbon.
Example 1
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative pole piece
Adding 70 parts by mass of silica, 1 part by mass of acetylene black and 25 parts by mass of an aqueous solution of sodium silicate (the mass fraction is 20%, "25 parts by mass" means 25 parts by mass of sodium silicate in the aqueous solution of sodium silicate, and the same shall apply to the following examples) to deionized water and mixing them uniformly; slowly dropwise adding 4 parts by mass of CaCl under the stirring condition2Aqueous solution (mass fraction is 10%, "4 parts by mass" means CaCl2CaCl in aqueous solution24 parts by mass, similar to the following examples); after the dropwise addition is finished, continuously stirring for 2 hours to form a silicate inorganic polymer on the surface of the silica; and then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, drying and cold pressing to obtain the negative pole piece, wherein the mass ratio of the artificial graphite, the silicon monoxide, the acetylene black (the acetylene black added for the second time) and the polyacrylic acid is 76:20:2: 2.
Example 2
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative pole piece
Adding 95 parts by mass of silicon monoxide, 1 part by mass of acetylene black and 3 parts by mass of sodium silicate aqueous solution (mass fraction is 20%) into deionized water, and uniformly mixing; slowly dripping 1 part by mass of CaCl under the condition of stirring2Aqueous solution (10% by mass); after the dropwise addition is finished, continuously stirring for 2 hours to form a silicate inorganic polymer on the surface of the silicon oxide; and then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, and drying and cold pressing to obtain the negative pole piece. Wherein the mass ratio of the artificial graphite, the silicon monoxide, the acetylene black (the acetylene black added for the second time) and the polyacrylic acid is 76:20:2: 2.
Example 3
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative pole piece
Pouring 75 parts by mass of silicon monoxide, 10 parts by mass of acetylene black and 10 parts by mass of sodium silicate aqueous solution (mass fraction is 20%) into deionized water, and uniformly mixing; slowly dropwise adding 5 parts by mass of CaCl under the stirring condition2Aqueous solution (10% by mass); after the dropwise addition is finished, continuously stirring for 2 hours to form a silicate inorganic polymer on the surface of the silica; and then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, and drying and cold pressing to obtain the negative pole piece. Wherein the mass ratio of the artificial graphite, the silicon monoxide, the acetylene black (the acetylene black added for the second time) and the polyacrylic acid is 76:20:2: 2.
Example 4
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative pole piece
Pouring 70 parts by mass of silicon monoxide, 10 parts by mass of acetylene black and 5 parts by mass of sodium silicate aqueous solution (mass fraction is 20%) into deionized water, and uniformly mixing; slowly dropwise adding 15 parts by mass of CaCl under the stirring condition2Aqueous solution (10% by mass); after the dropwise addition, stirring was continued for 2 hours to form a silicate inorganic on the surface of the silicaA polymer; and then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, and drying and cold pressing to obtain the negative pole piece. Wherein the mass ratio of the artificial graphite, the silicon monoxide, the acetylene black (the acetylene black added for the second time) and the polyacrylic acid is 76:20:2: 2.
Example 5
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative pole piece
Pouring 70 parts by mass of silicon monoxide and 25 parts by mass of sodium silicate aqueous solution (mass fraction is 20%) into deionized water, and uniformly mixing; slowly dropwise adding 5 parts by mass of CaCl under the stirring condition2Aqueous solution (10% by mass); after the dropwise addition is finished, continuously stirring for 2 hours to form a silicate inorganic polymer on the surface of the silicon oxide; and then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, and drying and cold pressing to obtain the negative pole piece. Wherein the mass ratio of the artificial graphite to the silicon monoxide to the acetylene black to the polyacrylic acid is 76:20:2: 2.
Example 6
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative pole piece
Pouring 70 parts by mass of silicon monoxide and 25 parts by mass of an aluminum phosphate aqueous solution (the mass fraction is 20%) into deionized water, and uniformly mixing; slowly adding 5 parts by mass of copper oxide powder under the stirring condition; after the addition is finished, stirring is continuously carried out for 2 hours to form a phosphate inorganic polymer on the surface of the silicon oxide; then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, drying and cold pressing to obtain the negative pole piece. Wherein the mass ratio of the artificial graphite to the silicon monoxide to the acetylene black to the polyacrylic acid is 76:20:2: 2.
Example 7
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative pole piece
Pouring 70 parts by mass of silicon monoxide and 25 parts by mass of sodium aluminosilicate aqueous solution (the mass fraction is 20%) into deionized water, and uniformly mixing; slowly dropwise adding 5 parts by mass of CaCl under the stirring condition2Aqueous solution (10% by mass); after the dropwise addition is finished, stirring is continuously carried out for 2 hours to form an aluminosilicate inorganic polymer on the surface of the silicon oxide; and then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, and drying and cold pressing to obtain the negative pole piece. Wherein the mass ratio of the artificial graphite to the silicon monoxide to the acetylene black to the polyacrylic acid is 76:20:2: 2.
Example 8
A lithium ion secondary battery was manufactured in the same manner as in comparative example 1, except that:
(1) preparation of negative electrode plate
Pouring 70 parts by mass of silicon monoxide and 25 parts by mass of ethyl orthosilicate into N-methylpyrrolidone, and uniformly mixing; slowly dropwise adding 5 parts by mass of NaOH aqueous solution (the mass fraction is 10%) under the stirring condition; after the dropwise addition, stirring is continuously carried out for 2 hours to form organic derivatives of silicate inorganic polymers on the surface of the silica; and then adding artificial graphite, acetylene black and polyacrylic acid, fully stirring and uniformly mixing, coating on a Cu foil, and drying and cold pressing to obtain the negative pole piece. Wherein the mass ratio of the artificial graphite, the silicon monoxide, the acetylene black and the polyacrylic acid is 76:20:2: 2.
Next, the performance of the lithium ion secondary battery was tested.
Testing one: first charge-discharge efficiency test of lithium ion secondary battery
The uncharged lithium ion secondary batteries obtained in comparative examples 1 to 2 and examples 1 to 8 were respectively charged at a constant current of 0.1C to 3.5V, then at a constant current of 0.3C to 4.2V, and further at a constant voltage to a current of less than 0.05C at normal temperature, and the charge capacity during the entire charging process was designated as C1Then, the discharge was carried out at a constant current of 0.5C to 2.8V, and the discharge capacity during the whole discharge was designated as D1。
Lithium ion secondary batteryFirst charge-discharge efficiency E ═ D1/C1×100％。
TABLE 1 results of first charge and discharge efficiency test of comparative examples 1-2 and examples 1-8
And (2) testing: rebound test of negative pole piece after charging
Thickness test of the negative pole piece in the initial state (i.e. after cold pressing): taking 3 negative pole pieces in comparative examples 1-2 and examples 1-8 respectively, testing the thickness of the negative pole piece in the initial state and marking as D0。
And (3) testing the thickness of the charged negative pole piece: the lithium ion secondary batteries of comparative examples 1 to 2 and examples 1 to 8 were each charged at 3 times at a constant current of 0.5C to 4.2V at normal temperature, and further charged at a constant voltage of 4.2V to a current of less than 0.05C to be in a fully charged state of 4.2V. Disassembling the fully charged lithium ion secondary battery, testing the thickness of the negative pole piece and recording the thickness as D1。
Thickness expansion rate of negative electrode piece after charging ═ D1-D0)/D0×100％。
TABLE 2 negative pole piece rebound test results for comparative examples 1-2 and examples 1-8
And (3) testing: discharge rate performance test of lithium ion secondary battery
The lithium ion secondary batteries obtained in comparative examples 1 to 2 and examples 1 to 8 were each charged at a constant current of 0.5C to 4.2V and at a constant voltage of 4.2V to a current of less than 0.05V at room temperature, and then discharged at different discharge rates (0.2C, 0.5C, 1.0C, 3.0C, 5.0C) to 2.8V, respectively, and the discharge capacity was measured, taking the discharge capacity obtained by 0.2C discharge as a reference value (i.e., 100%).
TABLE 3 discharge Rate Performance test results for comparative examples 1-2 and examples 1-8
And (4) testing: high temperature storage performance test of lithium ion secondary battery
The lithium ion secondary batteries obtained in comparative examples 1 to 2 and examples 1 to 8 were subjected to high-temperature storage performance tests, 3 each.
Charging the lithium ion secondary battery at constant current and constant voltage under the charging current of 1C at normal temperature until the upper limit voltage is 4.2V, and testing the thickness of the lithium ion secondary battery at the moment and recording the thickness as D0Then, the lithium ion secondary battery was placed in an incubator at 80 ℃ and taken out every 4 hours to be tested for thickness.
Thickness expansion rate after high-temperature storage of lithium ion secondary battery (thickness-D of lithium ion secondary battery at hour N)0)/D0×100％。
TABLE 4 results of the high temperature storage expansion test for comparative examples 1-2 and examples 1-8
| 0 hour | 4 hours | 8 hours | 12 hours | |
| Comparative example 1 | 0％ | 8.2％ | 14.9％ | 28.7％ |
| Comparative example 2 | 0％ | 6.1％ | 10.9％ | 20.2％ |
| Example 1 | 0％ | 5.2％ | 9.3％ | 13.6％ |
| Example 2 | 0％ | 7.3％ | 8.5％ | 15.7％ |
| Example 3 | 0％ | 6.3％ | 8.4％ | 14.7％ |
| Example 4 | 0％ | 6.4％ | 8.6％ | 15.5％ |
| Example 5 | 0％ | 5.5％ | 9.6％ | 13.9％ |
| Example 6 | 0％ | 5.9％ | 7.7％ | 14.2％ |
| Example 7 | 0％ | 6.1％ | 8.9％ | 13.3％ |
| Example 8 | 0％ | 6.0％ | 9.1％ | 14.9％ |
And testing five: cycle performance test of lithium ion secondary battery
The lithium ion secondary batteries obtained in comparative examples 1 to 2 and examples 1 to 8 were subjected to cycle performance tests, 3 each.
Respectively charging the lithium ion secondary battery at constant current and constant voltage under the charging current of 1C at normal temperature and 45 ℃ until the upper limit voltage is 4.2V, then discharging the lithium ion secondary battery at constant current under the discharging current of 0.5C until the final voltage is 2.75V, and recording the discharge capacity of the first cycle; and then 800 charge and discharge cycles were performed.
The cycle capacity retention ratio of the lithium ion battery was (discharge capacity at 800 th cycle/discharge capacity at first cycle) × 100%.
TABLE 5 results of cycle performance test for comparative examples 1-2 and examples 1-8
| Capacity retention rate at normal temperature for 800 cycles | Capacity retention rate at 45 ℃ for 800 cycles | |
| Comparative example 1 | 73.1％ | 68.8％ |
| Comparative example 2 | 76.2％ | 71.3％ |
| Example 1 | 78.1％ | 73.1％ |
| Example 2 | 77.5％ | 72.7％ |
| Example 3 | 80.8％ | 74.9％ |
| Example 4 | 80.1％ | 75.2％ |
| Example 5 | 78.6％ | 73.6％ |
| Example 6 | 78.0％ | 73.2％ |
| Example 7 | 81.3％ | 75.4％ |
| Example 8 | 80.6％ | 75.7％ |
From the test results in tables 1 and 2, it can be seen that the first charge-discharge efficiency of the battery can be improved by coating an inorganic polymer layer or an organic derivative layer of an inorganic polymer on the surface of the silicon oxide in situ, which indicates that the inorganic polymer layer or the organic derivative layer of an inorganic polymer has a certain effect of promoting the formation of the SEI film, and is also helpful for ensuring the high elasticity and toughness of the SEI film. The inorganic polymer layer can also inhibit the charge expansion of the silicon oxide, because the polymerization process of polymerizable micromolecule substances such as sodium silicate and the like on the surface of the silicon oxide is in-situ polymerization, the inorganic polymer or the organic derivative of the inorganic polymer can be tightly attached to the silicon oxide, and the inorganic polymer or the organic derivative of the inorganic polymer has the characteristics of high strength and good toughness and can tolerate the charge expansion of the silicon oxide.
From the test results in tables 3 to 5, it can be seen that the electrochemical performance of the battery can be improved by coating an inorganic polymer layer or an organic derivative layer of an inorganic polymer in situ on the surface of the oxidized silica, and the rate capability, the cycle performance and the storage performance of the battery are improved to different degrees. The inorganic polymer layer or the organic derivative layer of the inorganic polymer is coated on the surface of the silicon oxide in situ, so that the charge expansion of the silicon oxide can be tolerated, the structural stability of the silicon oxide in the charge and discharge processes is improved, the stability of an SEI (solid electrolyte interface) film on the surface of the silicon oxide is further ensured, and the effects of protecting the silicon oxide and reducing the probability of side reactions of electrolyte on the surface of the silicon oxide at high temperature are achieved. It can also be seen from the test results of examples 1-8 that the overall performance of the battery prepared in example 4 is better, which shows that the combination of proper amounts of the curing agent and the silicate can help to form an inorganic polymer layer with better quality on the surface of the silicon oxide, and the combination of proper amounts of the conductive agent can further help to improve the electron transport of the silicon oxide, and further improve the performance of the battery.
Claims (9)
1. The composite negative electrode material is characterized by comprising a negative electrode material central core and a coating layer coated on the surface of the negative electrode material central core, wherein the coating layer comprises an inorganic polymer, and the inorganic polymer is one or more selected from silicate inorganic polymers, phosphate inorganic polymers and aluminosilicate inorganic polymers; the coating layer also contains a conductive agent.
2. The composite anode material according to claim 1, wherein a mass content of the coating layer in the composite anode material is 40% or less.
3. The composite anode material according to claim 1, wherein the mass content of the coating layer in the composite anode material is 20%.
4. The composite anode material of claim 1, wherein the anode material central core is selected from one or more of silicon-based anode materials and tin-based anode materials.
5. A method for producing a composite anode material for use in producing the composite anode material according to any one of claims 1 to 4, comprising the steps of:
adding a negative electrode material and an optional conductive agent into a polymerizable micromolecular substance solution, adding a curing agent into the polymerizable micromolecular substance solution under the stirring condition for polymerization reaction, and drying to remove the solvent after the reaction is finished to obtain the composite negative electrode material.
6. The method for producing a composite anode material according to claim 5,
the polymerizable micromolecule substance is one or more selected from inorganic silicate, inorganic phosphate, inorganic aluminate, ethyl orthosilicate and kaolin.
7. A negative electrode sheet comprising:
a negative current collector; and
a negative electrode active material layer on a surface of the negative electrode current collector;
characterized in that the anode active material layer comprises the composite anode material according to any one of claims 1 to 4.
8. The negative electrode sheet according to claim 7, wherein the negative electrode active material layer further comprises a carbon-based negative electrode material, a conductive agent, and a binder.
9. A battery comprising a negative electrode tab according to any one of claims 7 to 8.
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| CN113013386A (en) * | 2019-12-19 | 2021-06-22 | 山西沃特海默新材料科技股份有限公司 | Composite negative electrode material and preparation method thereof |
| CN111384385B (en) * | 2020-03-25 | 2021-07-27 | 长沙矿冶研究院有限责任公司 | Silicon-containing material and preparation method and application thereof |
| US20210313578A1 (en) * | 2020-04-01 | 2021-10-07 | Enevate Corporation | Method and system for clay minerals as cathode, silicon anode, or separator additives in lithium-ion batteries |
| CN111916681B (en) * | 2020-06-23 | 2021-07-20 | 成都新柯力化工科技有限公司 | Method for simply producing silicon-carbon negative electrode plate of power lithium battery by spherical graphite |
| CN117012910A (en) * | 2022-04-29 | 2023-11-07 | 华为技术有限公司 | Composite material, preparation method and application thereof |
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