CN113629235A - Lithium battery cathode stable structure, lithium battery cathode and preparation method thereof, and lithium battery - Google Patents
Lithium battery cathode stable structure, lithium battery cathode and preparation method thereof, and lithium battery Download PDFInfo
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Abstract
The invention discloses a lithium battery cathode stable structure, a lithium battery cathode, a preparation method thereof and a lithium battery, wherein the lithium battery cathode stable structure comprises 44-71% of a silicon/tin-based cathode material, 5-10% of graphite oxide, 15-28% of polyacrylonitrile and 9-27% of a binder by weight percentage. According to the invention, the lithium battery cathode is prepared from various components according to a specific ratio, the problem of volume expansion of the silicon/tin-based cathode material in a circulation process is solved, the conductivity of the silicon/tin-based cathode material is improved, the structural stability of the silicon/tin-based cathode material is enhanced, and the electrochemical performance of the lithium battery cathode is improved.
Description
Technical Field
The invention relates to the technical field of lithium battery cathode materials, in particular to a lithium battery cathode stable structure, a lithium battery cathode, a preparation method of the lithium battery cathode and a lithium battery.
Background
In recent years, with the rapid development of multifunctional portable and high-energy electronic equipment in the information age and the urgent need of energy and environmental crises for the development of electric vehicles, the development of novel lithium ion battery cathode materials with high specific capacity, high stability, high safety, long service life and low cost is urgent. Silicon-based and tin-based negative electrode materials increasingly become another research hotspot in the field of negative electrode materials of lithium ion batteries due to the advantages of high lithium intercalation capacity, low voltage platform, rich raw materials, environmental friendliness and the like. However, the silicon/tin-based material undergoes a large volume change during lithium intercalation and deintercalation, resulting in structural pulverization during cycling, loss of electrical contact with a current collector and a conductive agent, and thus cycle degradation of battery capacity. In addition, poor conductivity is detrimental to the good rate capability of such materials.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a stable structure of a lithium battery cathode, a preparation method of the lithium battery cathode and a lithium battery, wherein the stable structure of the lithium battery cathode, the lithium battery cathode and the preparation method of the lithium battery cathode are used for improving the conductivity of a silicon/tin-based cathode material and solving the problems of structural pulverization, poor conductivity and the like caused by volume expansion in the circulation process.
In order to achieve the above object, a first aspect of the present invention provides a stable structure of a negative electrode of a lithium battery, which includes, by weight, 44% to 71% of a silicon/tin-based negative electrode material, 5% to 10% of graphite oxide, 15% to 28% of polyacrylonitrile, and 9% to 27% of a binder.
Further, the silicon/tin-based negative electrode material comprises SnO2、Si、SiO、SiO/C、SiOx、SiOxAny one of the above-mentioned groups.
Further, the binder includes polyvinylidene fluoride and/or polytetrafluoroethylene.
A second aspect of the present invention provides a method for manufacturing a negative electrode for a lithium battery, including:
1) preparing a silicon/tin-based negative electrode material, graphite oxide, polyacrylonitrile and a binder according to the proportion of the stable structure of the negative electrode of the lithium battery in the first aspect;
2) dispersing graphite oxide in N-methyl pyrrolidone in a cell crusher to form a graphite oxide solution;
3) adding polyacrylonitrile into a graphite oxide solution, heating and stirring for 1-5 h, adding a silicon/tin-based negative electrode material and a binder, uniformly stirring until the mixture is viscous, and coating the mixture on a copper foil;
4) and after drying, keeping the temperature at a first preset temperature for 2-6 h at a preset temperature rising rate in a protective atmosphere, and then rising to a second preset temperature for 1-10 h to obtain the lithium battery cathode.
Further, the concentration of the graphite oxide solution in the step 1) is 1-10 mg/mL.
Further, the preset heating rate in the step 4) is 1-10 ℃/min.
Further, the first preset temperature is 200-350 ℃, and the second preset temperature is 450-800 ℃.
Further, the protective atmosphere in the step 4) is Ar or Ar/H2。
The third aspect of the invention provides a negative electrode for a lithium battery produced by the production method according to the second aspect.
The invention also provides a lithium battery negative electrode, which comprises a copper matrix and the lithium battery negative electrode stable structure as described in the first aspect.
A fourth aspect of the invention provides a lithium battery comprising a positive electrode for a lithium battery and a negative electrode for a lithium battery as described in the third aspect.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
According to the invention, the lithium battery cathode is prepared from various components according to a specific ratio, the problem of volume expansion of the silicon/tin-based cathode material in a circulation process is solved, the conductivity of the silicon/tin-based cathode material is improved, the structural stability of the silicon/tin-based cathode material is enhanced, and the electrochemical performance of the lithium battery cathode is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 shows the structure of the negative electrode of the lithium ion battery after cycling.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a lithium battery cathode stable structure, which comprises, by weight, 44% -71% of a silicon/tin-based cathode material, 5% -10% of graphite oxide, 15% -28% of polyacrylonitrile and 9% -27% of a binder.
Graphite oxide is dispersed in N-methyl pyrrolidone in a cell crusher to form a graphite oxide solution; adding polyacrylonitrile into a graphite oxide solution, heating and stirring for 1-5 h, adding a silicon/tin-based negative electrode material and a binder, uniformly stirring until the mixture is viscous, and coating the mixture on a copper foil; and after drying, keeping the temperature at a first preset temperature for 2-6 h at a preset temperature rising rate in a protective atmosphere, and then rising to a second preset temperature for 1-10 h to obtain the lithium battery cathode. The silicon/tin-based anode particles are embedded in porous carbon and are sandwiched together in graphene sheets. The design of this structure can avoid the direct and electrolyte contact of negative pole granule to graphite alkene is as the buffer layer of negative pole granule, can alleviate silicon/tin-based negative electrode material's volume expansion effectively. In addition, the porous carbon matrix formed by carbonizing polyacrylonitrile and a binder can further relieve the volume expansion of the negative electrode material in the charge and discharge processes. The conducting network formed by the two-dimensional graphene and the porous carbon matrix can buffer the strain of the cathode particles between the interlayers, so that the insulation of the cathode particles in the circulation process is avoided. The graphene has good conductivity, and forms a conductive network with the porous carbon substrate, so that the conductivity of the composite electrode can be greatly improved. The graphene is used as a buffer layer of the negative electrode particles to relieve volume expansion in the charging and discharging process, pulverization and falling of the negative electrode material are prevented, the structural stability of the electrode is guaranteed, and the composite electrode has the advantages of high ionic conductivity of the graphene and porous carbon, large specific surface area, nanoscale diffusion length and the like, and has excellent cycle and rate performance.
Optionally, the silicon/tin-based negative electrode material comprises SnO2、Si、SiO、SiO/C、SiOx、SiOxAny one of the above-mentioned groups.
Optionally, the binder comprises polyvinylidene fluoride and/or polytetrafluoroethylene.
A second object of the present invention is to provide a method for manufacturing a negative electrode for a lithium battery, including:
1) according to the proportion of the stable structure of the lithium battery cathode, silicon/tin-based cathode material, graphite oxide, polyacrylonitrile and binder are prepared. The proportions of the components in the stable structure of the negative electrode of the lithium battery are described in detail above, and are not described herein again.
2) Graphite oxide is dispersed in N-methyl pyrrolidone in a cell disruptor to form a graphite oxide solution.
3) Adding polyacrylonitrile into a graphite oxide solution, heating and stirring for 1-5 h, adding a silicon/tin-based negative electrode material and a binder, uniformly stirring until the mixture is viscous, and coating the mixture on a copper foil.
4) And after drying, keeping the temperature at a first preset temperature for 2-6 h at a preset temperature rising rate in a protective atmosphere, and then rising to a second preset temperature for 1-10 h to obtain the lithium battery cathode.
The method for manufacturing the lithium battery cathode comprises the steps of 1) preparing raw materials according to a specific formula and a specific proportion, then 2) mixing the raw materials, and then drying and sintering the raw materials in the step 4) to obtain the lithium battery cathode.
Optionally, the concentration of the graphite oxide solution in the step 1) is 1-10 mg/mL.
Optionally, the preset heating rate in the step 4) is 1-10 ℃/min.
Optionally, in the step 4), the first predetermined temperature is 200 to 350 ℃, and the second predetermined temperature is 450 to 800 ℃.
Optionally, the protective atmosphere in the step 4) is Ar or Ar/H2。
The third object of the present invention is to provide a negative electrode for a lithium battery, which is obtained by the above-mentioned manufacturing method. The structure of the prepared lithium battery negative electrode after circulation is shown in figure 1, and it can be seen from the figure that negative electrode particles are still distributed among graphene sheet layers after the prepared lithium battery negative electrode is circulated, and the phenomena of agglomeration, pulverization and electrode structure collapse do not occur. In the lithium battery cathode prepared by the invention, silicon/tin-based cathode particles are embedded in porous carbon and are clamped in a graphene sheet layer together. The design of this structure can avoid the direct and electrolyte contact of negative pole granule to graphite alkene is as the buffer layer of negative pole granule, can alleviate silicon/tin-based negative electrode material's volume expansion effectively. In addition, the porous carbon matrix formed by carbonizing polyacrylonitrile and a binder can further relieve the volume expansion of the negative electrode material in the charge and discharge processes. The conducting network formed by the two-dimensional graphene and the porous carbon matrix can buffer the strain of the cathode particles between the interlayers, so that the insulation of the cathode particles in the circulation process is avoided.
The invention also provides a lithium battery cathode, which comprises a copper matrix and the lithium battery cathode stable structure. The combination of the copper matrix and the stable structure of the negative electrode of the lithium battery can adopt the preparation method as described above, and can also adopt other possible methods, such as changing the parameters of the sintering temperature after drying, the protective atmosphere or the heating rate, and the like, and the invention is not limited by the method.
A fifth object of the present invention is to provide a lithium battery comprising a positive electrode of the lithium battery and a negative electrode of the lithium battery as described above.
Example 1:
(1) lithium battery cathode stable structure
Lithium batteryThe pool cathode stable structure comprises 44% of silicon/tin-based cathode material, 10% of graphite oxide, 28% of polyacrylonitrile and 18% of binder. Wherein, the silicon/tin-based cathode material can be SnO2Si, SiO/C, SiOx/C, the binder can be polyvinylidene fluoride and/or polytetrafluoroethylene.
(2) Method for manufacturing negative electrode of lithium battery
A method of making a negative electrode for a lithium battery, comprising:
1) according to the weight percentage, 44% of silicon/tin-based negative electrode material, 10% of graphite oxide, 28% of polyacrylonitrile and 18% of binder are prepared. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxIn any of the above embodiments, the binder may be polyvinylidene fluoride and/or polytetrafluoroethylene.
2) Graphite oxide was dispersed in N-methylpyrrolidone in a cell disruptor to form a 3mg/mL graphite oxide solution.
3) Adding polyacrylonitrile into the graphite oxide solution, heating and stirring for 2h, adding the silicon/tin-based negative electrode material and the binder, stirring uniformly to proper viscosity, and coating on a copper foil.
4) Drying in protective atmosphere Ar or Ar/H2And (4) keeping the temperature at 300 ℃ for 2h at the temperature rise rate of 2 ℃/min, and then keeping the temperature at 350 ℃ for 4h to obtain the lithium battery cathode.
(3) Negative electrode for lithium battery
The lithium battery cathode in the embodiment is prepared by the manufacturing method.
(4) Lithium battery
The lithium battery of the present embodiment includes a lithium battery positive electrode and the above lithium battery negative electrode.
Example 2:
(1) lithium battery cathode stable structure
The lithium battery negative electrode stable structure comprises 44% of silicon/tin-based negative electrode material, 10% of graphite oxide, 28% of polyacrylonitrile and 18% of binder. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxAny one of/C, the binder may be polyvinylidene fluoride and/or polytetrafluoroVinyl fluoride.
(2) Method for manufacturing negative electrode of lithium battery
A method of making a negative electrode for a lithium battery, comprising:
1) according to the weight percentage, 44% of silicon/tin-based negative electrode material, 10% of graphite oxide, 28% of polyacrylonitrile and 18% of binder are prepared. Wherein, the silicon/tin-based cathode material can be SnO2Si, SiO/C, SiOx/C, the binder can be polyvinylidene fluoride and/or polytetrafluoroethylene.
2) Graphite oxide was dispersed in N-methylpyrrolidone in a cell disruptor to form a 5mg/mL graphite oxide solution.
3) Adding polyacrylonitrile into the graphite oxide solution, heating and stirring for 2h, adding the silicon/tin-based negative electrode material and the binder, stirring uniformly to proper viscosity, and coating on a copper foil.
4) Drying in protective atmosphere Ar or Ar/H2And (4) keeping the temperature at 250 ℃ for 4h at the heating rate of 10 ℃/min, then keeping the temperature at 600 ℃ for 4h, and obtaining the lithium battery cathode.
(3) Negative electrode for lithium battery
The lithium battery cathode in the embodiment is prepared by the manufacturing method.
(4) Lithium battery
The lithium battery of the present embodiment includes a lithium battery positive electrode and the above lithium battery negative electrode.
Example 3:
(1) lithium battery cathode stable structure
The stable structure of the lithium battery negative electrode comprises 71% of silicon/tin-based negative electrode material, 5% of graphite oxide, 15% of polyacrylonitrile and 9% of binder. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxIn any of the above embodiments, the binder may be polyvinylidene fluoride and/or polytetrafluoroethylene.
(2) Method for manufacturing negative electrode of lithium battery
A method of making a negative electrode for a lithium battery, comprising:
1) preparing 71 percent of silicon/tin-based negative electrode material, 5 percent of graphite oxide and 1 percent of polyacrylonitrile according to weight percentage5% and 9% of a binder. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxIn any of the above embodiments, the binder may be polyvinylidene fluoride and/or polytetrafluoroethylene.
2) Graphite oxide was dispersed in N-methylpyrrolidone in a cell disruptor to form a 5mg/mL graphite oxide solution.
3) Adding polyacrylonitrile into the graphite oxide solution, heating and stirring for 5h, adding the silicon/tin-based negative electrode material and the binder, stirring uniformly to proper viscosity, and coating on a copper foil.
4) Drying in protective atmosphere Ar or Ar/H2And (4) keeping the temperature at 250 ℃ for 4h at the temperature rise rate of 5 ℃/min, and then keeping the temperature at 800 ℃ for 10h to obtain the lithium battery cathode.
(3) Negative electrode for lithium battery
The lithium battery cathode in the embodiment is prepared by the manufacturing method.
(4) Lithium battery
The lithium battery of the present embodiment includes a lithium battery positive electrode and the above lithium battery negative electrode.
Example 4:
(1) lithium battery cathode stable structure
The stable structure of the lithium battery negative electrode comprises 53% of silicon/tin-based negative electrode material, 5% of graphite oxide, 15% of polyacrylonitrile and 27% of binder. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxIn any of the above embodiments, the binder may be polyvinylidene fluoride and/or polytetrafluoroethylene.
(2) Method for manufacturing negative electrode of lithium battery
A method of making a negative electrode for a lithium battery, comprising:
1) 53% of silicon/tin-based negative electrode material, 5% of graphite oxide, 15% of polyacrylonitrile and 27% of binder are prepared according to weight percentage. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxIn any of the above embodiments, the binder may be polyvinylidene fluoride and/or polytetrafluoroethylene.
2) Graphite oxide was dispersed in N-methylpyrrolidone in a cell disruptor to form a 5mg/mL graphite oxide solution.
3) Adding polyacrylonitrile into the graphite oxide solution, heating and stirring for 5h, adding the silicon/tin-based negative electrode material and the binder, stirring uniformly to proper viscosity, and coating on a copper foil.
4) Drying in protective atmosphere Ar or Ar/H2And (4) keeping the temperature at 250 ℃ for 4h at the temperature rise rate of 5 ℃/min, and then keeping the temperature at 800 ℃ for 10h to obtain the lithium battery cathode.
(3) Negative electrode for lithium battery
The lithium battery cathode in the embodiment is prepared by the manufacturing method.
(4) Lithium battery
The lithium battery of the present embodiment includes a lithium battery positive electrode and the above lithium battery negative electrode.
Example 5:
(1) lithium battery cathode stable structure
The stable structure of the lithium battery negative electrode comprises 50% of silicon/tin-based negative electrode material, 8% of graphite oxide, 15% of polyacrylonitrile and 27% of binder. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxIn any of the above embodiments, the binder may be polyvinylidene fluoride and/or polytetrafluoroethylene.
(2) Method for manufacturing negative electrode of lithium battery
A method of making a negative electrode for a lithium battery, comprising:
1) according to the weight percentage, 50 percent of silicon/tin-based negative electrode material, 8 percent of graphite oxide, 15 percent of polyacrylonitrile and 27 percent of binder are prepared. Wherein, the silicon/tin-based cathode material can be SnO2、Si、SiO、SiO/C、SiOx、SiOxIn any of the above embodiments, the binder may be polyvinylidene fluoride and/or polytetrafluoroethylene.
2) Graphite oxide was dispersed in N-methylpyrrolidone in a cell disruptor to form a 5mg/mL graphite oxide solution.
3) Adding polyacrylonitrile into the graphite oxide solution, heating and stirring for 4h, adding the silicon/tin-based negative electrode material and the binder, stirring uniformly to proper viscosity, and coating on a copper foil.
4) Drying in protective atmosphere Ar or Ar/H2And (4) keeping the temperature at 300 ℃ for 4h at the temperature rise rate of 5 ℃/min, and then keeping the temperature at 500 ℃ for 10h to obtain the lithium battery cathode.
(3) Negative electrode for lithium battery
The lithium battery cathode in the embodiment is prepared by the manufacturing method.
(4) Lithium battery
The lithium battery of the present embodiment includes a lithium battery positive electrode and the above lithium battery negative electrode.
Referring to fig. 1 after the lithium battery negative electrode prepared by the above embodiment is cycled, it can be seen from the figure that negative electrode particles are still distributed between graphene sheet layers after the prepared lithium battery negative electrode is cycled, and the phenomena of agglomeration, pulverization and electrode structure collapse do not occur. In the lithium battery cathode prepared by the invention, silicon/tin-based cathode particles are embedded in porous carbon and are clamped in a graphene sheet layer together. The design of this structure can avoid the direct and electrolyte contact of negative pole granule to graphite alkene is as the buffer layer of negative pole granule, can alleviate silicon/tin-based negative electrode material's volume expansion effectively. In addition, the porous carbon matrix formed by carbonizing polyacrylonitrile and a binder can further relieve the volume expansion of the negative electrode material in the charge and discharge processes. The conducting network formed by the two-dimensional graphene and the porous carbon matrix can buffer the strain of the cathode particles between the interlayers, so that the insulation of the cathode particles in the circulation process is avoided.
It can be seen from the above embodiments that the lithium battery cathode prepared by the formulation and the method provided by the invention solves the problem of volume expansion of the silicon/tin-based cathode material in the circulation process, improves the conductivity of the silicon/tin-based cathode material, enhances the structural stability of the silicon/tin-based cathode material, and improves the electrochemical performance of the lithium battery cathode.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
It will be understood that the invention is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (10)
1. The lithium battery cathode stable structure is characterized by comprising, by weight, 44% -71% of a silicon/tin-based cathode material, 5% -10% of graphite oxide, 15% -28% of polyacrylonitrile and 9% -27% of a binder.
2. The lithium battery negative electrode stabilization structure of claim 1, wherein the silicon/tin-based negative electrode material comprises SnO2、Si、SiO、SiO/C、SiOx、SiOxAny one of the above-mentioned groups.
3. The lithium battery negative electrode stabilization structure of claim 1, wherein the binder comprises polyvinylidene fluoride and/or polytetrafluoroethylene.
4. A method for manufacturing a negative electrode for a lithium battery, comprising:
1) preparing a silicon/tin-based negative electrode material, graphite oxide, polyacrylonitrile and a binder in a proportion of the stable structure of the negative electrode for the lithium battery as claimed in any one of claims 1 to 3;
2) dispersing graphite oxide in N-methyl pyrrolidone in a cell crusher to form a graphite oxide solution;
3) adding polyacrylonitrile into a graphite oxide solution, heating and stirring for 1-5 h, adding a silicon/tin-based negative electrode material and a binder, uniformly stirring until the mixture is viscous, and coating the mixture on a copper foil;
4) and after drying, keeping the temperature at a first preset temperature for 2-6 h at a preset temperature rising rate in a protective atmosphere, and then rising to a second preset temperature for 1-10 h to obtain the lithium battery cathode.
5. The method according to claim 4, wherein the concentration of the graphite oxide solution in the step 1) is 1 to 10 mg/mL.
6. The method according to claim 4, wherein the predetermined temperature rise rate in the step 4) is 1 to 10 ℃/min.
7. The method of claim 4, wherein the first predetermined temperature is 200 to 350 ℃ and the second predetermined temperature is 450 to 800 ℃.
8. The method according to claim 4, wherein the protective atmosphere in the step 4) is Ar or Ar/H2。
9. A negative electrode for a lithium battery, characterized in that it is produced by the production method according to any one of claims 4 to 8.
10. A lithium battery comprising a positive electrode for a lithium battery and a negative electrode for a lithium battery as claimed in claim 9.
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