CN117790763B - Composite positive electrode material, preparation method thereof, positive electrode plate, secondary battery and application - Google Patents
Composite positive electrode material, preparation method thereof, positive electrode plate, secondary battery and application Download PDFInfo
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- CN117790763B CN117790763B CN202410219223.0A CN202410219223A CN117790763B CN 117790763 B CN117790763 B CN 117790763B CN 202410219223 A CN202410219223 A CN 202410219223A CN 117790763 B CN117790763 B CN 117790763B
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 94
- 239000002131 composite material Substances 0.000 title claims abstract description 79
- 238000002360 preparation method Methods 0.000 title abstract description 13
- 239000000463 material Substances 0.000 claims abstract description 94
- 239000011247 coating layer Substances 0.000 claims abstract description 50
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 34
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 33
- 239000011248 coating agent Substances 0.000 claims abstract description 23
- 238000000576 coating method Methods 0.000 claims abstract description 23
- 239000011734 sodium Substances 0.000 claims abstract description 23
- 229910052596 spinel Inorganic materials 0.000 claims abstract description 4
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- 239000010410 layer Substances 0.000 claims description 36
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- YPPMLCHGJUMYPZ-UHFFFAOYSA-L sodium;iron(2+);sulfate Chemical compound [Na+].[Fe+2].[O-]S([O-])(=O)=O YPPMLCHGJUMYPZ-UHFFFAOYSA-L 0.000 claims description 25
- 238000010438 heat treatment Methods 0.000 claims description 21
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- 238000000034 method Methods 0.000 claims description 19
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- 238000007499 fusion processing Methods 0.000 claims description 3
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- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 abstract description 6
- 229910052708 sodium Inorganic materials 0.000 abstract description 6
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 abstract description 5
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical group [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229910015872 LiNi0.8Co0.1Mn0.1O2 Inorganic materials 0.000 description 3
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 description 3
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- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical compound [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 description 3
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- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
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- 229910002991 LiNi0.5Co0.2Mn0.3O2 Inorganic materials 0.000 description 1
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- 229910003005 LiNiO2 Inorganic materials 0.000 description 1
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- NDPGDHBNXZOBJS-UHFFFAOYSA-N aluminum lithium cobalt(2+) nickel(2+) oxygen(2-) Chemical compound [Li+].[O--].[O--].[O--].[O--].[Al+3].[Co++].[Ni++] NDPGDHBNXZOBJS-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- Battery Electrode And Active Subsutance (AREA)
Abstract
The application relates to a composite positive electrode material and a preparation method thereof, a positive electrode plate, a secondary battery and application, wherein the composite positive electrode material comprises a core and a coating layer for coating at least part of the surface of the core, the material of the core comprises a lithium-containing positive electrode material with at least one of a layered structure and a spinel structure, the material of the coating layer comprises sodium ferric sulfate, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the core is 10-50, so that the rate performance, the cycle performance and the safety performance of the composite positive electrode material are effectively improved.
Description
Technical Field
The application relates to the technical field of batteries, in particular to a composite positive electrode material, a preparation method thereof, a positive electrode plate, a secondary battery and application.
Background
The lithium ion battery has the advantages of high working voltage, small self-discharge, environmental protection and the like, and is widely applied to the fields of electric automobiles, portable electronic products, energy storage systems and the like. Lithium nickel cobalt manganese oxide is a ternary material, and lithium ion batteries using lithium nickel cobalt manganese oxide as the positive electrode material are also referred to as ternary lithium ion batteries. The cycle life of the traditional ternary lithium ion battery is not ideal, and the multiplying power performance and the safety performance are also to be improved, so that the further application of the traditional ternary lithium ion battery is restricted, and therefore, a technical scheme for solving the problems is needed.
Disclosure of Invention
The application provides a composite positive electrode material, a preparation method thereof, a positive electrode plate, a secondary battery and application, and aims to improve the rate capability, the cycle performance and the safety performance of the composite positive electrode material.
According to a first aspect of the application, a composite positive electrode material is provided, the composite positive electrode material comprises a core and a coating layer coating at least part of the surface of the core, the material of the core comprises a lithium-containing positive electrode material with at least one of a layered structure and a spinel structure, the material of the coating layer comprises sodium iron sulfate, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the core is 10-50.
In some embodiments, the specific surface area of the material of the coating layer is 10m 2/g~20m2/g.
In some embodiments, the specific surface area of the material of the inner core is 0.4m 2/g~1m2/g.
In some embodiments, the mass ratio of the sodium iron sulfate in the composite positive electrode material is 12% -30%.
In some embodiments, the lithium-containing cathode material accounts for 70% -88% of the composite cathode material by mass.
In some embodiments, the lithium-containing positive electrode material includes one or more of a material having a chemical formula of LiNi xMyXzO2 and a material having a chemical formula of LiMn 2O4, wherein 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z < 1, and x+y+z=1, m includes one or more of Co and Fe, and X includes one or more of Mn and Al.
In some embodiments, the sodium iron sulfate comprises a material having the chemical formula Na mFe(SO4)n, where 1.ltoreq.m.ltoreq.3, n= (m+2)/2.
In some embodiments, the material of the coating layer further comprises a carbon material that coats at least a portion of a surface of the sodium iron sulfate, the carbon material comprising one or more of carbon nanotubes, graphene, carbon black, and graphite.
In a second aspect of the present application, there is provided a method for preparing the composite positive electrode material according to the first aspect of the present application, comprising the steps of:
Mechanically fusing the material of the inner core and the material of the coating layer in a first protective atmosphere;
and carrying out heat treatment on the materials obtained by mechanical fusion in a second protective atmosphere to form the coating layer.
In some embodiments, the mechanical fusion process conditions include: the rotating speed of the blade is 100 rpm-2000 rpm, and the mechanical fusion time is 0.5 h-5 h.
In some embodiments, the process conditions of the heat treatment include: the heat treatment temperature is 200-800 ℃, and the heat treatment time is 1-48 h.
In some embodiments, the first protective atmosphere and the second protective atmosphere each independently comprise one or more of nitrogen and argon.
In a third aspect of the present application, there is provided a positive electrode sheet comprising at least one of the composite positive electrode material according to the first aspect of the present application and the composite positive electrode material produced by the production method according to the second aspect of the present application.
In a fourth aspect of the present application, there is provided a secondary battery comprising the positive electrode sheet, the negative electrode sheet, and the separator provided between the positive electrode sheet and the negative electrode sheet according to the third aspect of the present application.
In some embodiments, the negative electrode sheet includes a negative electrode current collector, and a first negative electrode film layer and a second negative electrode film layer sequentially stacked on at least one surface of the negative electrode current collector, wherein the first negative electrode film layer contains hard carbon, the second negative electrode film layer contains graphite, and the mass ratio of the hard carbon to the total mass of the graphite is 0.01% -20%.
In some embodiments, the membrane has an average pore size of 0.01 μm to 0.02 μm.
In some embodiments, the secondary battery further includes an electrolyte including an electrolyte salt including a lithium salt and a sodium salt, the sodium salt being present in the electrolyte salt in a molar ratio of 0.1% -20%.
In a fifth aspect of the present application, there is provided an electric device comprising the secondary battery according to the fourth aspect of the present application.
Compared with the prior art, the composite positive electrode material and the preparation method thereof, the positive electrode plate, the secondary battery and the application have at least the following advantages:
(1) A coating layer containing sodium ferric sulfate is arranged on the surface of an inner core containing a lithium-containing positive electrode material, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is controlled to be 10-50, so that the inner core can be better coated by the coating layer, side reactions between the lithium-containing positive electrode material and electrolyte are reduced, and the cycle performance and the safety performance of the composite positive electrode material can be improved;
(2) The lithium-containing positive electrode material and the sodium iron sulfate have similar working voltage intervals and voltage platforms, so that Na + in the sodium iron sulfate and Li + in the lithium-containing positive electrode material can participate in charge-discharge reaction together to provide capacity, the composite positive electrode material can be ensured to have high working voltage, and meanwhile, the battery can have higher energy density; in addition, the radius of Na + is larger than that of Li +, and in the process of charge and discharge cycle, na + which is partially deintercalated from sodium iron sulfate can be embedded into the structure of the lithium-containing positive electrode material, the interlayer spacing of the material is increased, and subsequent embedding and deintercalation of Li + are relatively easy, so that the high-rate charge and discharge capacity of the composite positive electrode material is effectively improved.
Detailed Description
The following detailed description of the present application will provide further details in order to make the above-mentioned objects, features and advantages of the present application more comprehensible. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.
In the present application, "first aspect", "second aspect", "third aspect", etc. are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or quantity, nor as implying an importance or quantity of the indicated technical features. Moreover, "first," "second," "third," etc. are for non-exhaustive list description purposes only, and it should be understood that no closed limitation on the number is made.
In the present application, "optional" means optional or not, that is, means any one selected from two parallel schemes of "with" or "without". If multiple "alternatives" occur in a technical solution, if no particular description exists and there is no contradiction or mutual constraint, then each "alternative" is independent.
In the present application, the numerical ranges are referred to as continuous, and include the minimum and maximum values of the ranges, and each value between the minimum and maximum values, unless otherwise specified. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
In the application, the technical characteristics described in an open mode comprise a closed technical scheme composed of the listed characteristics and also comprise an open technical scheme comprising the listed characteristics.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items. The term "plurality" in the present application means at least two, for example, two, three, etc., unless specifically defined otherwise.
The lithium nickel cobalt manganese oxide or the lithium nickel cobalt aluminum oxide is called a ternary material, and the proportion of the molar quantity of nickel atoms in the ternary material accounting for more than or equal to 60 percent of the total molar quantity of non-lithium metal atoms can be called a high-nickel ternary material.
The traditional high-nickel ternary positive electrode material has poor safety performance, the problem of the interface between the positive electrode and the electrolyte is always a main factor for restricting the safety performance of the high-nickel ternary material, the electrolyte is seriously decomposed under a high-nickel system, so that surface transition metal is dissolved out, the structure is damaged, a passivation layer is generated on the surface, and the multiplying power performance, the cycle performance and the safety performance of the material are affected.
Based on the above, an embodiment of the present application provides a composite positive electrode material, including an inner core and a coating layer coating at least part of the surface of the inner core, where the material of the inner core includes a positive electrode material containing lithium and having at least one of a layered structure and a spinel structure, the material of the coating layer includes sodium iron sulfate, and a ratio of a specific surface area of the material of the coating layer to a specific surface area of the material of the inner core is 10-50.
The working voltage of the sodium ferric sulfate is 2V-4.5V vs. Na +/Na, compared with the lithium-containing positive electrode material, the sodium ferric sulfate has a relatively stable structure, and the crystal structure has small volume change and no phase change in the process of embedding and extracting Na +, so that the sodium ferric sulfate has good long-term circulation stability, high safety and the same advantages of low-temperature performance and rate capability.
In the above embodiment, a coating layer containing sodium iron sulfate is disposed on the surface of the inner core containing the lithium-containing cathode material, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is controlled within the above range, so that the coating layer can better coat the inner core, and side reactions between the lithium-containing cathode material and the electrolyte are reduced, thereby improving the cycle performance and the safety performance of the composite cathode material; the lithium-containing positive electrode material and the sodium iron sulfate have similar working voltage intervals and voltage platforms, so that Na + in the sodium iron sulfate and Li + in the lithium-containing positive electrode material can participate in charge-discharge reaction together to provide capacity, the composite positive electrode material can be ensured to have high working voltage, and meanwhile, the battery can have higher energy density; in addition, the radius of Na + is larger than that of Li +, and in the process of charge and discharge cycle, na + which is partially deintercalated from sodium iron sulfate can be embedded into the structure of the lithium-containing positive electrode material, the interlayer spacing of the material is increased, and subsequent embedding and deintercalation of Li + are relatively easy, so that the high-rate charge and discharge capacity of the composite positive electrode material is effectively improved.
When the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is too small, the coating effect of the coating layer on the inner core is poor, and when the ratio is too large, the composite positive electrode material particles are easy to agglomerate in the dispersion process, are unfavorable for forming a thin layer with the conductive agent particles to disperse into a conductive network, are unfavorable for interlocking and connecting the composite positive electrode material particles on the current collector in a large amount, influence the homogenate coating effect of the positive electrode slurry, and deteriorate the multiplying power performance and the cycle performance of the composite positive electrode material. In conclusion, the ratio of the specific surface areas of the material of the inner core to the material of the coating layer is controlled within the range, so that the multiplying power performance, the cycle performance and the safety performance of the composite positive electrode material can be cooperatively improved. It is understood that the ratio of the specific surface area of the material of the cladding layer to the specific surface area of the material of the core includes, but is not limited to: 10. 20, 30, 40, 50.
The iron ions in the sodium iron sulfate are ferrous ions.
In some embodiments, the specific surface area of the material of the coating layer is 10m 2/g~20m2/g. Therefore, the coating effect of the material of the coating layer on the material of the inner core can be improved, and the dispersion of the composite anode material in the homogenizing process is facilitated. It is understood that the specific surface area of the material of the coating layer includes, but is not limited to ：10m2/g、11m2/g、12m2/g、13m2/g、14m2/g、15m2/g、16m2/g、17m2/g、18m2/g、19m2/g、20m2/g.
In some embodiments, the specific surface area of the material of the core is 0.4m 2/g~1m2/g. Therefore, the coating effect of the material of the coating layer on the material of the inner core can be improved, and the dispersion of the composite anode material in the homogenizing process is facilitated. It is understood that the specific surface area of the material of the coating layer includes, but is not limited to ：0.4m2/g、0.5m2/g、0.6m2/g、0.7m2/g、0.8m2/g、0.9m2/g、1m2/g.
In some embodiments, the mass ratio of the sodium iron sulfate in the composite positive electrode material is 12% -30%. Therefore, the multiplying power performance, the cycle performance and the safety performance of the composite positive electrode material are further improved. The mass ratio of the sodium iron sulfate in the composite positive electrode material comprises, but is not limited to: 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%.
In some embodiments, the lithium-containing cathode material comprises 70% -88% by mass of the composite cathode material. Therefore, the multiplying power performance, the cycle performance and the safety performance of the composite positive electrode material are further improved. The mass ratio of the lithium-containing positive electrode material in the composite positive electrode material includes, but is not limited to: 70%, 73%, 75%, 78%, 80%, 85%, 88%.
In some embodiments, the lithium-containing positive electrode material includes one or more of a material having a chemical formula of LiNi xMyXzO2 and a material having a chemical formula of LiMn 2O4, wherein 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0.ltoreq.z < 1, and x+y+z=1, m includes one or more of Co and Fe, and X includes one or more of Mn and Al. It is understood that the lithium-containing positive electrode material includes, but is not limited to, ：LiNi0.8Co0.1Mn0.1O2、LiNi0.6Co0.2Mn0.2O2、LiNi0.5Co0.2Mn0.3O2、LiNi0.8Co0.1Al0.1O2、LiCoO2、LiNiO2、LiMn2O4 and one or more of its respective modified compounds. The above-mentioned modifying compound means doping modification of a part of elements to the lithium-containing positive electrode material.
In some embodiments, sodium iron sulfate comprises a material having the formula Na mFe(SO4)n, where 1.ltoreq.m.ltoreq.3, n= (m+2)/2. It is understood that sodium iron sulfate includes, but is not limited to: na 2Fe(SO4)2.
In some embodiments, the material of the coating layer further comprises a carbon material that coats at least a portion of the surface of the sodium iron sulfate. The carbon material in the coating layer can improve the coating effect of the sodium iron sulfate on the lithium-containing positive electrode material, and the carbon material can improve the intrinsic conductivity, sodium storage kinetics and lithium storage kinetics of the sodium iron sulfate, and the formed conductive network can reduce the phase change of the lithium-containing positive electrode material under high voltage, so that the multiplying power performance, the circulating performance and the safety performance of the composite positive electrode material are further improved. Optionally, the carbon material comprises one or more of carbon nanotubes, graphene, carbon black, and graphite. The carbon material has excellent conductivity, and the formed three-dimensional conductive network can promote Na + and Li + to be rapidly embedded and separated, so that the composite positive electrode material is favorable for high-rate charge and discharge, and meanwhile, the cycle performance and the safety performance of the composite positive electrode material can be further improved. Further alternatively, the carbon material at least includes carbon nanotubes, and the carbon material containing the carbon nanotubes can further enhance the coating effect of the lithium-containing cathode material.
Another embodiment of the present application provides a method for preparing the above composite positive electrode material, including the steps of:
mechanically fusing the material of the inner core and the material of the coating layer in a first protective atmosphere;
And carrying out heat treatment on the materials obtained by mechanical fusion in a second protective atmosphere to form the inner core and the coating layer.
In the embodiment, the mechanical fusion ensures that the material of the inner core and the material of the coating layer are subjected to the action of compression and shearing force for a plurality of times, so that the coating effect of the coating layer on the inner core can be improved, and the multiplying power performance, the circulating performance and the safety performance of the composite positive electrode material are further improved.
In some embodiments, the process conditions of mechanical fusion include: the rotating speed of the blade is 100 rpm-2000 rpm, and the mechanical fusion time is 0.5 h-5 h. The adoption of the mechanical fusion process condition is beneficial to further improving the coating effect of the coating layer on the inner core, so that the multiplying power performance, the cycle performance and the safety performance of the composite anode material can be further improved. It is understood that the rotational speed of the blade includes, but is not limited to: 100rpm, 300rpm, 500rpm, 700rpm, 1000rpm, 1300rpm, 1500rpm, 1700rpm, 2000rpm. The time of mechanical fusion includes, but is not limited to: 0.5h, 1h, 2h, 3h, 4h, 5h.
In some embodiments, the process conditions of the heat treatment include: the heat treatment temperature is 200-800 ℃, and the heat treatment time is 1-48 h. It is understood that the temperature of the heat treatment includes, but is not limited to: 200 ℃, 300 ℃, 400 ℃, 500 ℃, 600 ℃, 700 ℃, 800 ℃; the heat treatment time includes, but is not limited to: 1h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 48h.
In some embodiments, the first protective atmosphere and the second protective atmosphere each independently comprise one or more of nitrogen and argon.
In still another embodiment, the present application provides a positive electrode sheet, which includes at least one of the above-described composite positive electrode material of the present application and the composite positive electrode material prepared by the above-described preparation method of the present application. Therefore, the positive electrode sheet of the present application has excellent rate performance, cycle performance and safety performance. It is understood that the composite positive electrode material may be used as a positive electrode active material.
In some embodiments, the positive electrode sheet further comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer contains at least one of the composite positive electrode material of the present application and the composite positive electrode material prepared by the preparation method of the present application. Optionally, the positive electrode film layer further includes a conductive agent and a binder. The conductive agent and the binder may be those commonly used in the art.
Still another embodiment of the present application provides a secondary battery including the above positive electrode sheet, the negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet.
The secondary battery of the present application includes the above-described positive electrode sheet of the present application, and thus has at least the same advantages as the positive electrode sheet. Therefore, the secondary battery of the present application has excellent rate performance, cycle performance and safety performance.
In some embodiments, the negative electrode sheet includes a negative electrode current collector, and a first negative electrode film layer and a second negative electrode film layer sequentially stacked on at least one surface of the negative electrode current collector, wherein the first negative electrode film layer contains hard carbon, the second negative electrode film layer contains graphite, and the mass ratio of the hard carbon to the total mass of the graphite is 0.01% -20%.
In the above embodiment, the first negative electrode film layer and the second negative electrode film layer are sequentially stacked in a direction away from the negative electrode current collector. The graphite in the second negative electrode film layer can relieve the characteristic of unstable high temperature of hard carbon in the first negative electrode film layer, so that the high-temperature cycle performance of the secondary battery can be improved. It is understood that the ratio of the mass of hard carbon to the total mass of hard carbon to graphite includes, but is not limited to: 0.01%, 0.1%, 1%, 3%, 5%, 7%, 10%, 12%, 15%, 17%, 20%.
In some embodiments, the positive and negative electrode sheets satisfy the following conditions: 1.01-1.1 (N W×NA×Ng) /(PW×PA XPg), wherein N W is the mass ratio of the anode active material in the anode film layer, N A is the coating surface density of the anode active material, N g is the reversible gram capacity of the anode active material, P W is the mass ratio of the cathode active material in the cathode film layer, P A is the coating surface density of the cathode active material, and P g is the reversible gram capacity of the cathode active material. The negative electrode active material includes hard carbon and graphite, and the positive electrode active material includes a composite positive electrode material. It is understood that the anode film layer may include the first anode film layer and the second anode film layer described above.
In some embodiments, the membrane has an average pore size of 0.01 μm to 0.02 μm. In this way, li + can preferentially insert Na + into the anode active material, and a solid electrolyte interface film (SEI film) formed by lithium ions is superior to that formed by sodium ions in thermal stability, so that the high-temperature cycle stability of the secondary battery can be further improved. Further, by combining the design of the first negative electrode film layer and the second negative electrode film layer in the negative electrode plate, li + is preferentially embedded in graphite by Na + and most Na + is embedded in hard carbon in the charging process of the battery, so that the structural stability of the negative electrode plate can be improved, and the cycle performance of the secondary battery can be further improved; in the discharging process of the battery, li + is preferentially embedded in sodium iron sulfate by Na +, so that Na + is embedded in the structure of the lithium-containing positive electrode material, and the rate capability of the secondary battery is further improved.
In some embodiments, the separator is made of one or more of polypropylene (PP) and Polyethylene (PE).
In some embodiments, the secondary battery further comprises an electrolyte solution comprising an electrolyte salt, the electrolyte salt comprising a lithium salt and a sodium salt, the sodium salt comprising 0.1% -20% by mole of the electrolyte salt. Controlling the molar ratio of the sodium salt in the electrolyte salt within the above range can further improve the rate performance of the secondary battery. Alternatively, the lithium salt includes, but is not limited to, lithium hexafluorophosphate (LiPF 6). Alternatively, the sodium salt includes, but is not limited to, sodium hexafluorophosphate (NaPF 6). It is understood that the molar ratio of sodium salt in the electrolyte salt includes, but is not limited to: 0.1%, 1%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 20%.
In some embodiments, the electrolyte further comprises an organic solvent and an additive.
The application further provides an electric device comprising the secondary battery. The above-mentioned power utilization device may include any device or apparatus using a secondary battery as a driving source, such as a mobile phone, a notebook computer, an electric vehicle, a ship, a satellite, an energy storage device, an intelligent home appliance, etc., but is not limited thereto.
In order to further illustrate the present application, the following describes the technical scheme of the present application in detail with reference to specific embodiments. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Example 1
(1) Preparation of composite cathode material
(1.1) Putting a lithium-containing positive electrode material NCM811 (LiNi 0.8Co0.1Mn0.1O2) and an NFS (Na 2Fe(SO4)2) material into a mechanical fusion machine, and coating in an argon atmosphere, wherein the mass ratio of the NCM811 to the NFS is 80:20; wherein, the blade rotating speed of the mechanical fusion machine is 500rpm, and the mechanical fusion time is 5h.
Transferring the mixed material obtained in the step (1.1) into a box furnace, performing heat treatment under the protective atmosphere of argon, and then crushing the heat-treated product into powder to obtain a composite anode material, wherein the heat treatment temperature is 300 ℃, and the heat treatment time is 3 hours; the specific surface area of NCM811 in the composite positive electrode material is 0.6m 2/g, the specific surface area of NFS is 12m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is 20.
(2) Preparation of positive plate
96.6Wt% of composite positive electrode material, 1.6wt% of binder PVDF (polyvinylidene fluoride), 0.6wt% of conductive agent SP (conductive carbon black) and 1.2wt% of conductive agent MWCNT (multi-wall carbon nano tube) are adopted, and NMP (N-methylpyrrolidone) is used as a solvent; the raw materials are uniformly stirred and then coated on the surface of a positive electrode current collector (carbon-coated aluminum foil) with the thickness of 13 mu m, the positive electrode is baked at 85 ℃ and then rolled and die-cut, the compacted density of a positive electrode sheet is 2.0g/m 3-3 g/m3, and the pole sheet is baked for 12 hours at 100 ℃ after die-cutting and powder brushing.
(3) Preparation of negative electrode sheet
The preparation method comprises the steps of carrying out homogenate by using 94.5wt% of anode active material hard carbon, 1.5wt% of conductive agent SP, 2.8wt% of binder SBR (styrene butadiene rubber) and 1.2wt% of binder CMC (carboxymethyl cellulose) under the condition of taking deionized water as a solvent, coating the slurry on 6 mu m copper foil, carrying out rolling and die cutting after baking at 85 ℃ to ensure that the compaction density is 0.9g/m 3-1.2 g/m3, and carrying out die cutting and powder brushing on a pole piece after baking at 100 ℃ for 12 hours. After the pole piece is rolled, spraying graphite slurry on the pole piece, and drying to form a hard carbon graphite negative pole piece, wherein the proportion of the graphite slurry is 96wt% of negative pole active material hard carbon, 1wt% of conductive agent SP, 1.8wt% of binder SBR (styrene butadiene rubber) and 1.2wt% of binder CMC (carboxymethyl cellulose). The hard carbon and graphite in the negative electrode sheet are negative electrode active materials, and the mass ratio of the hard carbon to the total mass of the hard carbon and graphite (the mass of the negative electrode active materials) is 20%.
When preparing the negative plate and the positive plate, the following conditions are satisfied: the mass ratio of the anode active material in the anode film layer is multiplied by the coating surface density of the anode active material multiplied by the reversible gram capacity of the anode active material/(the mass ratio of the mass of the composite cathode material in the cathode film layer multiplied by the coating surface density of the composite cathode material multiplied by the reversible gram capacity of the composite cathode material) =1.08; the negative electrode film layer is a film layer where hard carbon and graphite are located, and the positive electrode film layer is a film layer where a composite positive electrode material is located.
(4) Diaphragm
The PE separator was used, and the average pore diameter of the PE separator was 0.01. Mu.m.
(5) Electrolyte solution
The electrolyte consists of an organic solvent, electrolyte salt and an additive; wherein the concentration of the electrolyte salt is 1mol/L, the electrolyte salt is lithium hexafluorophosphate and sodium hexafluorophosphate with the molar ratio of 8:2, and the molar ratio of the organic solvent, the electrolyte salt and the additive is 4.5:4.5:1, the organic solvent is EC (ethylene carbonate): EMC (methylethyl carbonate): DEC (diethyl carbonate) =4.5:4.5:1 (mass ratio).
(6) Preparation of a Battery
And sequentially stacking the negative electrode plate, the diaphragm and the positive electrode plate by using a lamination machine to prepare a bare cell, wherein the diaphragm is positioned between the positive electrode plate and the negative electrode plate to play a role in isolation, and then the battery is prepared by welding, top side sealing, liquid injection, formation, two sealing and capacity division processes, the production environment is required to be controlled in the lamination process, and the dew point requirement of a workshop is less than-45 ℃.
Example 2
Substantially the same as in example 1, the difference is that: in step (1.1), the mass ratio of NCM811 to NFS is 70:30.
Example 3
Substantially the same as in example 1, the difference is that: in step (1.1), the mass ratio of NCM811 to NFS is 88:12.
Example 4
Substantially the same as in example 1, the difference is that: in the step (1.2), the heat treatment temperature was 400 ℃.
Example 5
Substantially the same as in example 1, the difference is that: in the step (1.2), the specific surface area of NCM811 in the composite positive electrode material is 1m 2/g, the specific surface area of NFS is 10m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the core is 10.
Example 6
Substantially the same as in example 1, the difference is that: in the step (1.2), the specific surface area of NCM811 in the composite positive electrode material is 0.4m 2/g, the specific surface area of NFS is 20m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the core is 50.
Example 7
Substantially the same as in example 1, the difference is that: step (1.1) and step (1.2) are different;
(1.1) mixing NFS and carbon nanotubes in a mass ratio of 95:5, so that part of the carbon nanotubes are coated on the surface of the NFS to obtain an NFS coating material; putting a lithium-containing positive electrode material NCM811 (LiNi 0.8Co0.1Mn0.1O2) and an NFS coating material into a mechanical fusion machine, and coating in an argon atmosphere, wherein the mass ratio of the NCM811 to the NFS coating material is 80:20; wherein, the blade rotating speed of the mechanical fusion machine is 500rpm, and the mechanical fusion time is 5h.
Transferring the mixed material obtained in the step (1.1) into a box furnace, performing heat treatment under the protective atmosphere of argon, and then crushing the heat-treated product into powder to obtain a composite anode material, wherein the heat treatment temperature is 300 ℃, and the heat treatment time is 3 hours; the specific surface area of NCM811 in the composite positive electrode material is 0.6m 2/g, the specific surface area of the NFS coating material is 7.2m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is 12.
Example 8
Substantially the same as in example 1, the difference is that: when the negative electrode sheet is prepared in the step (3), hard carbon and graphite are mixed to be used as a negative electrode active material, and the mass ratio of the hard carbon in the mass of the negative electrode active material is 20%.
The negative electrode active material of 95wt%, the conductive agent SP of 1.2wt%, the binder SBR (styrene butadiene rubber) of 2wt% and the binder CMC (carboxymethyl cellulose) of 1.8wt% are adopted to carry out homogenization under the condition of deionized water as a solvent, the slurry is coated on a copper foil of 6 mu m, and the copper foil is baked at the temperature of 85 ℃ and then rolled and die-cut to have the compaction density of 0.9g/m 3-1.2 g/m3, and then baked at the temperature of 100 ℃ for 12 hours.
Example 9
Substantially the same as in example 1, the difference is that: the average pore diameter of the PE separator in the step (4) was 0.03. Mu.m.
Example 10
Substantially the same as in example 1, the difference is that: the average pore diameter of the PE separator in the step (4) was 0.005. Mu.m.
Example 11
Substantially the same as in example 1, the difference is that: the lithium-containing cathode material in step (1.1) is replaced with LiCoO 2; the specific surface area of LiCoO 2 in the composite positive electrode material of the step (1.2) is 0.6m 2/g, the specific surface area of NFS is 12m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is 20.
Example 12
Substantially the same as in example 1, the difference is that: the lithium-containing positive electrode material in the step (1.1) is replaced by LiMn 2O4; the specific surface area of LiCoO 2 in the composite positive electrode material of the step (1.2) is 0.6m 2/g, the specific surface area of NFS is 12m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is 20.
Comparative example 1
Substantially the same as in example 1, the difference is that: when the positive electrode sheet is prepared in the step (2), the NCM811 raw material in example 1 is directly used as a composite positive electrode material.
Comparative example 2
Substantially the same as in example 1, the difference is that: in the step (1.2), the specific surface area of NCM811 in the composite positive electrode material is 0.8m 2/g, the specific surface area of NFS is 5.6m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is 7.
Comparative example 3
Substantially the same as in example 1, the difference is that: in the step (1.2), the specific surface area of NCM811 in the composite positive electrode material is 0.4m 2/g, the specific surface area of NFS is 21.2m 2/g, and the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the inner core is 53.
Comparative example 4
Substantially the same as in example 11, the difference is that: in the step (2), the LiCoO 2 raw material in example 11 was directly used as a composite positive electrode material when preparing a positive electrode sheet.
Comparative example 5
Substantially the same as in example 12, the difference is that: when the positive plate is prepared in the step (2), the LiMn 2O4 raw material in the example 12 is directly used as a composite positive electrode material.
Performance testing
(1) Rate capability test
Testing the multiplying power performance of the battery at room temperature (25+/-5 ℃), wherein the tested voltage interval is 2.75-4.3V, and charging by using 1C current and discharging by using 1C current; then charged with 1C current and discharged with 5C current. Then, 5C discharge capacity/1C discharge capacity was calculated.
Testing the multiplying power performance of the battery at room temperature (25+/-5 ℃), wherein the tested voltage interval is 2.75-4.3V, and charging by using 1C current and discharging by using 1C current; then charged with 1C current and discharged with 3C current. Then, 3C discharge capacity/1C discharge capacity was calculated.
(2) Normal temperature cycle performance test
Testing the cycle performance of the battery at room temperature (25 ℃ plus or minus 5 ℃), wherein the tested voltage interval is 3V-4.2V, charging by using 1C current, and discharging by using 1C current, thus being one cycle; the capacity retention after 2000 cycles of the battery was calculated by repeating 2000 cycles.
(3) High temperature cycle performance test
Testing the cycle performance of the battery at 45 ℃, wherein the tested voltage interval is 3V-4.2V, charging is carried out by using 1C current, and discharging is carried out by 1C current, so that one cycle is realized; the capacity retention after 1000 cycles of the battery was calculated by repeating 1000 cycles.
(4) Safety performance test
1. 1C constant-current and constant-voltage charging to 4.3V, stopping current at 0.05C, testing by a 5mm needle, and monitoring the temperature of the anode lug, the cathode lug and the center;
2. Penetrating from the direction perpendicular to the electrode plate of the battery cell at the speed of (25+/-5) mm by using a high-temperature resistant steel needle (the conical angle of the needle point is 45-60 degrees, the surface of the steel needle is smooth and clean and has no rust, oxide layer and oil stain), the penetrating position is preferably close to the geometric center of the penetrated surface, and the steel needle stays in the battery cell;
3. the reaction was observed for 1h.
TABLE 1
From the data in table 1, it can be seen that:
From the comparison of examples 1 to 10 and comparative examples 1 to 3, the comparison of examples 11 and comparative example 4, and the comparison of examples 12 and comparative example 5, it is known that the 5C discharge capacity/1C discharge capacity, 3C discharge capacity/1C discharge capacity, capacity retention rate of 2000 cycles at normal temperature and capacity retention rate of 1000 cycles at 45 ℃ of the batteries of examples 1 to 12 are higher than those of the corresponding comparative examples, and the batteries of examples 1 to 12 can be demonstrated by the needling experiments that the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the core in the composite cathode material of examples 1 to 12 is controlled to be 10 to 50, and the rate performance, cycle performance and safety performance of the composite cathode material can be effectively improved.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. The scope of the application is, therefore, indicated by the appended claims, and the description may be intended to interpret the contents of the claims.
Claims (12)
1. The composite positive electrode material is characterized by comprising a core and a coating layer coating at least part of the surface of the core, wherein the material of the core comprises a lithium-containing positive electrode material with at least one of a layered structure and a spinel structure, the material of the coating layer comprises sodium iron sulfate, the ratio of the specific surface area of the material of the coating layer to the specific surface area of the material of the core is 10-50, and the specific surface area of the material of the coating layer is 10m 2/g~20m2/g.
2. The composite positive electrode material of claim 1, wherein the composite positive electrode material has one or more of the following characteristics:
(1) The specific surface area of the material of the inner core is 0.4m 2/g~1m2/g;
(2) The mass ratio of the sodium iron sulfate in the composite anode material is 12% -30%;
(3) The mass ratio of the lithium-containing positive electrode material in the composite positive electrode material is 70% -88%.
3. The composite positive electrode material of claim 2, wherein the composite positive electrode material has one or more of the following characteristics:
(1) The lithium-containing positive electrode material comprises one or more of a material with a chemical formula of LiNi xMyXzO2 and a material with a chemical formula of LiMn 2O4, wherein X is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, x+y+z=1, M comprises one or more of Co and Fe, and X comprises one or more of Mn and Al;
(2) The sodium iron sulfate comprises a material with a chemical formula of Na mFe(SO4)n, wherein m is more than or equal to 1 and less than or equal to 3, and n= (m+2)/2.
4. The composite positive electrode material according to claim 1 or 2, wherein the material of the coating layer further comprises a carbon material that coats at least part of the surface of the sodium iron sulfate, the carbon material comprising one or more of carbon nanotubes, graphene, carbon black, and graphite.
5. The method for producing a composite positive electrode material according to any one of claims 1 to 4, comprising the steps of:
Mechanically fusing the material of the inner core and the material of the coating layer in a first protective atmosphere;
And carrying out heat treatment on the materials obtained by mechanical fusion in a second protective atmosphere to form the inner core and the coating layer.
6. The method of manufacture of claim 5, wherein the method of manufacture satisfies one or more of the following conditions:
(1) The mechanical fusion process conditions comprise: the rotating speed of the blade is 100 rpm-2000 rpm, and the mechanical fusion time is 0.5 h-5 h;
(2) The process conditions of the heat treatment include: the heat treatment temperature is 200-800 ℃, and the heat treatment time is 1-48 h;
(3) The first protective atmosphere and the second protective atmosphere each independently include one or more of nitrogen and argon.
7. A positive electrode sheet comprising at least one of the composite positive electrode material according to any one of claims 1 to 4 and the composite positive electrode material produced by the production method according to any one of claims 5 to 6.
8. A secondary battery comprising the positive electrode sheet, the negative electrode sheet, and the separator provided between the positive electrode sheet and the negative electrode sheet according to claim 7.
9. The secondary battery according to claim 8, wherein the negative electrode sheet includes a negative electrode current collector, and a first negative electrode film layer and a second negative electrode film layer which are sequentially stacked on at least one surface of the negative electrode current collector, the first negative electrode film layer containing hard carbon therein, the second negative electrode film layer containing graphite therein, and a mass ratio of the hard carbon to a total mass of the graphite is 0.01% -20%.
10. The secondary battery according to claim 8 or 9, wherein the average pore diameter of the separator is 0.01 μm to 0.02 μm.
11. The secondary battery according to claim 8 or 9, further comprising an electrolyte solution including an electrolyte salt including a lithium salt and a sodium salt, wherein the molar ratio of the sodium salt in the electrolyte salt is 0.1% -20%.
12. An electric device comprising the secondary battery according to any one of claims 8 to 11.
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| CN115986073A (en) * | 2022-12-02 | 2023-04-18 | 宁波容百新能源科技股份有限公司 | Positive active material and preparation method and application thereof |
| CN116354405A (en) * | 2023-04-06 | 2023-06-30 | 北京理工大学 | In-situ carbon-coated sodium ferrous sulfate composite positive electrode material, preparation and sodium ion battery |
| CN116581274A (en) * | 2023-06-15 | 2023-08-11 | 中国科学院深圳先进技术研究院 | Sodium ion battery positive electrode material and preparation method and application thereof |
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