CN115312772A - Composite lithium supplement material and preparation method and application thereof - Google Patents
Composite lithium supplement material and preparation method and application thereof Download PDFInfo
- Publication number
- CN115312772A CN115312772A CN202210536962.3A CN202210536962A CN115312772A CN 115312772 A CN115312772 A CN 115312772A CN 202210536962 A CN202210536962 A CN 202210536962A CN 115312772 A CN115312772 A CN 115312772A
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- China
- Prior art keywords
- lithium supplement
- composite
- composite lithium
- carbon
- supplement material
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 225
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 224
- 239000013589 supplement Substances 0.000 title claims abstract description 201
- 239000002131 composite material Substances 0.000 title claims abstract description 147
- 239000000463 material Substances 0.000 title claims abstract description 146
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 119
- 239000002041 carbon nanotube Substances 0.000 claims abstract description 89
- 229910021393 carbon nanotube Inorganic materials 0.000 claims abstract description 89
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- 229910052723 transition metal Inorganic materials 0.000 claims abstract description 40
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- 239000002243 precursor Substances 0.000 claims description 12
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- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 4
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- YWJVFBOUPMWANA-UHFFFAOYSA-H [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Li+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O YWJVFBOUPMWANA-UHFFFAOYSA-H 0.000 description 2
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The application provides a composite lithium supplement material and a preparation method and application thereof. The composite lithium supplement material comprises an inner core and a shell layer growing on the surface of the inner core in situ, wherein the inner core comprises a doped lithium supplement agent, and the shell layer comprises amorphous carbon and carbon nano tubes dispersed in the amorphous carbon; wherein the doped lithium supplement agent contains transition metal elements. The carbon nano tube and the amorphous carbon which grow and wrap the surface of the core material can isolate the influence of external environmental factors on the core material, so that the composite lithium supplement material has the characteristic of stable existence in the processes of storage and battery technology. In addition, the carbon nano tube has regular crystal form and good conductivity, and can further improve the conductivity of the composite lithium supplement material, thereby improving the capacity of the battery, reducing the using amount of a conductive agent in an electrode plate, reducing the internal resistance of the battery and prolonging the cycle life of the battery.
Description
Technical Field
The application relates to the technical field of batteries, in particular to a composite lithium supplement material and a preparation method and application thereof.
Background
With the development of new energy industry, the energy density of lithium batteries in the market is higher and higher, and the development of lithium batteries with large capacity, long service life and high safety performance is imperative. In the first charge-discharge process of the lithium battery, active Li can be caused along with the formation of an SEI film on the surface of an electrode pole piece + Irreversible loss of (b), resulting in overall active Li + The amount is reduced and the capacity and performance of the electrode active material cannot be sufficiently exerted, resulting in a loss of battery capacity and a reduction in battery life. At present, the industry often solves the problems by supplementing lithium in the active materials of the positive electrode and the negative electrode, and the lithium supplementation of the positive electrode has better safety and simpler process than the lithium supplementation of the negative electrode. However, the anode lithium-supplement material has high residual alkali value and poor stability, and is very easy to react with moisture and CO in the air 2 The reaction takes place. The stability of the lithium-doped material of the positive electrode is generally improved by doping or providing a coating layer, but the improvement effect is limited.
Disclosure of Invention
In view of this, the present application provides a composite lithium supplement material, and a preparation method and an application thereof. The composite lithium supplement material has the characteristic of stable existence in the process of storage and battery technology. In addition, the carbon nano tube in the shell layer has regular crystal form and good conductivity, and the conductivity of the composite lithium supplement material can be further improved.
The first aspect of the present application provides a composite lithium supplement material, which comprises an inner core and a shell layer grown in situ on the surface of the inner core, wherein the inner core comprises a doped lithium supplement agent, and the shell layer comprises amorphous carbon and carbon nanotubes dispersed in the amorphous carbon; wherein the doped lithium supplement agent contains transition metal elements.
The carbon nano tube and the amorphous carbon which grow and wrap the surface of the core material can isolate the influence of external environmental factors on the core material, so that the composite lithium supplement material has the characteristic of stable existence in the processes of storage and battery technology. In addition, the carbon nano tube has regular crystal form and good conductivity, and can further improve the conductivity of the composite lithium supplement material, thereby improving the capacity of the battery, reducing the using amount of a conductive agent in an electrode plate, reducing the internal resistance of the battery and prolonging the cycle life of the battery.
The second aspect of the present application provides a method for preparing a composite lithium supplement material, comprising the following steps:
(1) Mixing a lithium supplement source with a doping source to prepare a doping type lithium supplement precursor;
(2) Mixing the doped lithium supplement agent precursor with an organic carbon source, and calcining in an inert atmosphere to grow a carbon nanotube and amorphous carbon to obtain a composite lithium supplement material; the composite lithium supplement material comprises an inner core and a shell, wherein the inner core comprises a doped lithium supplement agent, the shell comprises amorphous carbon and carbon nanotubes dispersed in the amorphous carbon, and the doped lithium supplement agent contains transition metal elements.
The third aspect of the present application provides a positive electrode composite material, which includes the composite lithium supplement material provided in the first aspect of the present application or the composite lithium supplement material prepared by the preparation method provided in the second aspect of the present application.
The positive electrode composite material has good lithium supplement performance and good processing performance, and can be used for providing a battery with higher first charge-discharge coulombic efficiency and longer cycle service life.
The fourth aspect of the present application provides a positive electrode plate having the positive electrode composite material provided by the third aspect of the present application.
The positive pole piece has a good lithium supplementing effect, and can be used for providing a battery with high first charge-discharge coulombic efficiency and long cycle service life.
In a fifth aspect, the present application provides a battery with the positive electrode plate provided in the fourth aspect of the present application.
The battery has high first charge-discharge coulombic efficiency and long cycle service life.
Drawings
Fig. 1 is a schematic structural diagram of a composite lithium supplement material according to an embodiment of the present disclosure;
fig. 2A and 2B are Scanning Electron Microscope (SEM) photographs of the composite lithium supplement material prepared in example 1 of the present application at different magnifications.
Detailed Description
The technical scheme of the application is described in detail in the following with reference to the accompanying drawings.
Referring to fig. 1, the composite lithium supplement material 100 includes an inner core 10 and a shell layer 11 in-situ grown on a surface of the inner core 10, wherein the inner core 10 includes a doped lithium supplement agent, and the shell layer 11 includes amorphous carbon 110 and carbon nanotubes 111 dispersed in the amorphous carbon 110; wherein the doped lithium supplement agent contains transition metal elements.
The transition metal element in the doped lithium supplement agent can catalyze carbon atoms in the organic carbon source to generate carbon nano tubes 111 on the surface of the doped lithium supplement agent in situ, amorphous carbon 110 is continuously separated out, and the carbon nano tubes and the amorphous carbon are coated on the surface of the doped lithium supplement agent to form the composite lithium supplement material 100 with the core-shell structure. The carbon nanotube 111 has high crystal form regularity and good conductivity, and the in-situ grown carbon nanotube 111 inherits the dispersion position of the doping element in the doping type lithium supplement agent and can be uniformly dispersed in the composite lithium supplement material 100, so that the phenomenon of carbon nanotube agglomeration which is easy to occur in the traditional coating method can be avoided, the transmission of electrons is facilitated, and the conductivity of the composite lithium supplement material 100 can be further improved.
In addition, the shell layer 11 directly grown on the surface of the core 10 has good interface bonding force with the core 10, and can improve the structural stability of the composite lithium supplement material 100. Moreover, the carbon nanotube 111 is not hydrophilic and oleophilic, the performance of isolating moisture is better than that of the amorphous carbon 110, and the compact shell 11 formed by the two can effectively prevent the doped lithium supplement agent in the core 10 and moisture and CO in the air 2 The components react, so that the storage stability of the composite lithium supplement material 100 in the air environment can be remarkably improved, and the phenomena that the composite lithium supplement material 100 is easy to react with moisture and the like to cause anode slurry gelation, difficult stirring, incapability of batching and the like in the preparation process of the anode slurry can be effectively avoided. Furthermore, the doped lithium supplement agent has a higher gram capacity, and the structural stability of the core 10 can be further improved by the electrostatic interaction between the doping elements. Therefore, the composite lithium supplement material 100 has the characteristics of high gram capacity, good environmental stability, stable structure and good conductivity, and is beneficial to promoting the exertion of the capacity and performance of the positive active material, so that the first charge-discharge coulombic efficiency, the energy density and the cycle capacity retention rate of the lithium battery can be improved, and the service life of the battery can be prolonged.
In the present application, the carbon nanotube 111 may be a multi-walled carbon nanotube or a single-walled carbon nanotube.
In some embodiments of the present application, the transition metal element in the doped lithium supplement agent includes, but is not limited to, at least one of Fe, co, ni, mn, mo, and Cu.
In the present application, the undoped lithium supplement agent may contain a transition metal element or may not contain a transition metal element. For better distinction, the transition metal element in the lithium supplement body is marked as the transition metal element A, and the transition metal element A is doped no matter whether the body contains the transition metal element A or not, and the doped element can be the transition metal element, so that the doped lithium supplement containing the transition metal element is obtained.
In some embodiments of the present application, in the doped lithium supplement agent, the doped element includes, but is not limited to, at least one of Fe, co, ni, mn, mo, and Cu. In this case, the undoped lithium supplement agent phase may contain the transition metal element a or may not contain the transition metal element a. In the present application, the doped element may be doped in the lithium supplement agent in a simple substance form, or may be doped in the lithium supplement agent in a metal oxidized form. The selection can be made by one skilled in the art according to the actual production needs and the catalytic effect of the doping element. The doped element also belongs to a transition metal element, and for convenience of distinction, the doped transition metal element is marked as a transition metal element M. The transition metal element a and the transition metal element M may be the same or different, and those skilled in the art can select them according to actual production needs. In the preparation process of the composite lithium supplement material, the doped simple substance or oxide of the transition metal element M is a high-quality active center, and can catalyze the cracking of an organic carbon source and the rearrangement of carbon atoms to generate a carbon nano tube and amorphous carbon, so that the composite lithium supplement material provided by the embodiment of the application can be smoothly prepared. In addition, the doping of the transition metal element M can improve the gram capacity of the lithium supplement agent.
In some embodiments of the present application, the molar percentage of the doped element in the doped lithium supplement agent in the core 10 is in a range of 1% to 50%. Illustratively, the mole percentage of the doped element in the core 10 may be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. In some embodiments, the mole percentage of the doped element in the core 10 is in the range of 1% to 10%. Controlling the content of the doped elements within the above range is beneficial to ensuring that the grown shell layer 11 has proper thickness and density, so that the composite lithium supplement material 100 has good environmental stability and ion transmission rate, and the existence of a proper amount of doped elements is beneficial to improving the gram capacity and structural stability of the composite lithium supplement material 100.
In some embodiments of the present application, the doped lithium supplement agent is doped with a second element, and the second element includes Al and/or Mg. The second element can be doped in the lithium supplement agent in the form of a simple substance and/or an oxide. In this case, the undoped lithium supplement material phase needs to contain the transition metal element a, and the transition metal element a in the lithium supplement material phase on the surface of the core 10 needs to be reduced in the preparation process of the composite lithium supplement material 100. The Al and/or Mg can improve the catalytic activity of the transition metal simple substance or the oxide, so that the doped Al and/or Mg and the reduced transition metal simple substance cooperate to catalyze the growth of the carbon nano tube and the amorphous carbon, thereby smoothly preparing the composite lithium supplement material 100. At this time, the mole percentage of the second element in the core 10 is 1% to 25%. The proper proportion of the two is beneficial to promoting the high-efficiency growth of the carbon nano tube.
In some embodiments of the present application, the doped lithium supplement agent may be doped with the transition metal element M and the second element at the same time. In this case, there is no limitation on whether or not the undoped lithium supplement agent contains the transition metal element a in the phase. The second element can be cooperated with the doped transition metal element M to form a binary or even ternary catalyst to efficiently catalyze the growth of the carbon nano tube. Illustratively, the doped transition metal element M and the second element may constitute a Co/MgO catalyst, an Fe-based catalyst (Fe-Mo/MgO), a Ni-based catalyst (Ni-Mo/MgO), or the like.
In some embodiments, the mass percentage of the carbon nanotube 111 in the shell 11 is in the range of 0.1% to 10%. Illustratively, the mass percentage of the carbon nanotube 111 in the shell layer 11 may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. In some embodiments, the mass percentage of the carbon nanotubes 111 in the shell 11 is in the range of 0.1% to 5%. The appropriate amount of carbon nanotubes can improve the conductivity and environmental stability of the composite lithium supplement material 100, and the appropriate amount of amorphous carbon is beneficial to ensuring the compactness of the shell layer 11, so that the composite lithium supplement material 100 has good environmental stability and better conductivity at the same time.
In some embodiments of the present application, at least a portion of the carbon nanotubes 111 are in contact with the inner core 10. In the preparation process of the composite lithium supplement material 100, most of the active centers are still doped in the doping type lithium supplement agent, and the in-situ grown carbon nanotubes 111 inherit the dispersed positions of the active centers, so that most of the carbon nanotubes 111 grow from the inner core and extend towards the shell layer 11. The carbon nanotubes 111 may be grown from the inside of the core or from the interface between the core 10 and the shell 11. That is, the carbon nanotubes 111 are interspersed in the amorphous carbon and in contact with the core 10. At this time, the interfacial bonding force between the shell layer 11 and the core 10 may be significantly improved, and thus the structural stability of the composite lithium supplement material 100 may be significantly improved.
In some embodiments of the present application, there is a portion of the carbon nanotubes 111 that is not in contact with the inner core 10. In the preparation process of the composite lithium supplement material 100, under the action of high temperature, a small amount of doping elements can migrate to the amorphous carbon 110 or dope in the newly generated carbon nanotube 111, and the doping elements can catalyze the carbon nanotube 111 to directly grow in the shell layer, so that part of the carbon nanotube 111 is not in contact with the inner core 10.
In some embodiments, at least a portion of the carbon nanotubes 111 form a three-dimensional conductive network on the surface of the inner core 10. When the content of the carbon nanotubes 111 is high, the carbon nanotubes 111 are arranged in a staggered manner, so that a three-dimensional conductive network can be formed on the surface of the core 10, and the conductivity of the composite lithium supplement material 100 can be further improved.
In some embodiments, the diameter of the carbon nanotubes 111 is in the range of 5nm to 100 nm. Illustratively, the tube diameter of the carbon nanotube 111 may be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, 85nm, 90nm, 95nm, 100nm, or the like. In some embodiments, the diameter of the carbon nanotubes 111 is in the range of 5nm to 20 nm. Further preferably, the tube diameter of the carbon nanotube 111 may be 9nm to 11nm. The conductivity of the carbon nano tube is related to the size of the tube diameter of the carbon nano tube, the carbon nano tube with the proper tube diameter has better conductivity, and the performance of the composite lithium supplement material 100 is better exerted.
In some embodiments of the present disclosure, the carbon nanotubes 111 have a wall thickness in the range of 0.05nm to 2 nm. Illustratively, the wall thickness of the carbon nanotubes 111 may be 0.05nm, 0.1nm, 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 2nm, and the like. In some embodiments, the carbon nanotubes 111 have a wall thickness in the range of 0.5nm to 1.5 nm.
In some embodiments of the present application, the carbon nanotubes 111 have a length in the range of 3 μm to 50 μm. Illustratively, the carbon nanotubes may have a length of 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, and the like. In some embodiments, the length of the carbon nanotubes 111 is in the range of 5 μm to 30 μm. In this case, the carbon nanotubes form a conductive network, so that the conductivity of the composite lithium supplement material 100 can be further improved.
In some embodiments of the present application, the aspect ratio of the carbon nanotubes 111 is in the range of 50 to 10000. In some embodiments, the aspect ratio of the carbon nanotubes 111 is in the range of 50 to 5000. The high length-diameter ratio can improve the conductivity of the carbon nano tube, thereby being beneficial to improving the conductivity of the composite lithium supplement material.
In some embodiments of the present application, the average thickness of the shell layer 11 is in the range of 3nm to 100 nm. Illustratively, the average thickness of shell 11 may be 3nm-8nm, 10nm-15nm, 15nm-20nm, 20nm-30nm, 30nm-40nm, 40nm-50nm, 50nm-60nm, 60nm-70nm, 70nm-80nm, 80nm-90nm, 90nm-100nm, 3nm, 5nm, 6nm, 7nm, 8nm, 15nm, 20nm, 25nm, 30mn, 35nm, 40nm, 45nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, and the like. The thickness of the shell layer 11 is controlled within a proper range, which is beneficial to ensuring the stability of the composite lithium supplement material 100 in the air and in the battery preparation process and controlling the short path of ion transmission, thereby being beneficial to realizing high-efficiency lithium supplement.
In some embodiments of the present disclosure, the mass percentage of the shell layer 11 in the composite lithium supplement material 100 is 1.0% to 5.5%. Illustratively, the mass percentage of the shell layer 11 in the composite lithium supplement material 100 may be 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, and the like. The mass percent of the shell layer 11 is controlled within the range, the thickness of the shell layer 11 can be further controlled, so that the environmental stability and the conductivity can be favorably ensured, the over-thick shell layer can be prevented from reducing the lithium supplementing gram capacity of the composite lithium supplementing material and the conductivity of the composite lithium supplementing material to lithium ions in the battery charging process, and the high-efficiency lithium supplementing can be favorably realized.
In some embodiments of the present application, the diameter of the inner core 10 is in the range of 0.05 μm to 100 μm. Illustratively, the diameter of the core 10 may be 0.05 μm-3 μm, 5 μm-10 μm, 10 μm-20 μm, 25 μm-30 μm, 30 μm-40 μm, 40 μm-50 μm, 50 μm-60 μm, 60 μm-70 μm, 70 μm-80 μm, 80 μm-100 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 80 μm, 90 μm, and the like. In some embodiments, the diameter of inner core 10 is in the range of 0.05 μm to 30 μm. The diameter of the inner core 10 is controlled within a proper range, so that the size of the composite lithium supplement material 100 can be effectively promoted to be within a proper range, and the performance of the lithium supplement performance is facilitated.
In some embodiments of the present application, the doped transition metal element may also react with an organic carbon source to generate a carbide in the preparation process of the composite lithium supplement material 100, which not only can improve the combination stability and tightness between the shell 11 and the core 10, but also the newly generated carbide can be further used as an active catalytic center to better promote the growth of amorphous carbon and carbon nanotubes, and improve the coating degree and quality of the amorphous carbon and carbon nanotubes on the surface of the core 10.
In some embodiments of the present application, the composite lithium supplement material 100 further has an encapsulation layer coated on the outer surface of the shell layer 11. The encapsulation layer includes, but is not limited to, at least one of an isolation sub-packaging layer, an ion-conducting sub-layer, and an electronic conductor encapsulation layer. The packaging layers can effectively improve the electronic and ionic conduction performance of the lithium supplement agent in the core 10 and improve the removal rate of active lithium in the charging process; the composite lithium supplement material 100 can also play a certain role in isolating moisture, improve the stability and realize a stable lithium supplement effect. In addition, the stability, the uniformity of dispersion and the good processability of the composite lithium supplement material 100 in the electrode active slurry and the active layer for lithium supplement can be further improved. Specifically, the isolation packaging layer plays a further role in protecting the composite lithium supplement material, and further reduces water and CO in the inner core and the environment 2 The risk of contact; the electron conductor packaging layer can enhance the electron conductivity of the shell layer, thereby enhancing the electron conductivity of the composite lithium supplement material 100 and reducing the internal electrode areaThe impedance of the section; the ion conductor encapsulation layer can enhance the ionic conductivity of the composite lithium supplement material 100, so that the ionic conductivity of the composite lithium supplement material 100 is enhanced, and the outward transportation of lithium ions in the core is facilitated.
In some embodiments, the encapsulation layer may be a separate isolation encapsulation layer, which fully covers the core 10 and the shell 11, so as to protect the core 10 and further improve the stability of the core 10. Or a composite laminated structure of an isolation packaging layer and an electronic conductor packaging layer, wherein the isolation packaging layer is coated on the outer surface of the shell layer, and the electronic conductor packaging layer is coated on the outer surface of the isolation packaging layer. Or a composite laminated structure of an isolation packaging layer and an ion conductor packaging layer, wherein the isolation packaging layer is coated on the outer surface of the shell layer, and the ion conductor packaging layer is coated on the outer surface of the isolation packaging layer. The composite laminated structure of the isolation packaging layer, the electronic conductor packaging layer and the ion conductor packaging layer can also be adopted. The preferred structure is that the isolation packaging layer is coated on the outer surface of the shell layer, the ion conductor packaging layer is coated on the outer surface of the isolation packaging layer, and the electron conductor packaging layer is coated on the outer surface of the ion conductor packaging layer; or the isolation packaging layer is coated on the outer surface of the shell layer, the electronic conductor packaging layer is coated on the outer surface of the isolation packaging layer, and the ion conductor packaging layer is coated on the outer surface of the electronic conductor packaging layer.
In some embodiments, the material of the isolation encapsulation layer includes, but is not limited to, at least one of a ceramic, a high molecular polymer, and a carbon material. In some embodiments, the ceramic includes, but is not limited to, al 2 O 3 、SiO 2 Boehmite, si 3 N 4 At least one of SiC and BN. In some embodiments, the polymer includes, but is not limited to, poly (vinyl chloride) [ C ] 6 H 7 O 6 Na] n An organic polymer having the structure [ C ] 6 H 7 O 2 (OH) 2 OCH 2 COONa] n An organic polymer having the structure [ C ] 3 H 4 O 2 ] n An organic polymer of structure [ C ] 3 H 3 O 2 M a ] n An organic polymer having the structure [ sic ], [C 3 H 3 N] n Organic polymers of structure, containing- [ CH ] 2 -CF 2 ] n Organic Polymer having-Structure containing- [ NHCO ]]An organic polymer having a structure of (i) an imide ring- [ CO-N-CO ] in the main chain]At least one of an organic polymer of structure and polyvinylpyrrolidone, wherein M is a Is an alkali metal element. Specifically, the polymer includes, but is not limited to, at least one of polyvinylidene fluoride, sodium alginate, sodium carboxymethylcellulose, polyacrylic acid, polyacrylate, polyacrylonitrile, polyamide, polyimide, polyvinylpyrrolidone, polyethylene oxide (PEO), polypyrrole (PPy), polytetrafluoroethylene (PTFE), and Polyurethane (PU). Further, the polymer includes, but is not limited to, at least one of sodium carboxymethylcellulose and polyacrylic acid. The sodium carboxymethylcellulose and the polyacrylic acid are two-dimensional surface type high molecular polymers, have good bonding effect, and can effectively coat the doped lithium supplement core, so that the contact between the core material and air is avoided, and the stability of the composite lithium supplement material 100 is improved. In some embodiments, the molecular weight of the polymer is greater than or equal to 10 ten thousand. Illustratively, the molecular weight of the polymer can be 10, 15, 20, 30, 50, 100, etc. ten thousand. The larger the molecular weight of the polymer, the higher the compactness and structural strength of the polymer layer, and the more beneficial the protection of the core material is. In some specific embodiments, the carbon material includes, but is not limited to, at least one of graphene, carbon nanotubes, amorphous carbon, graphite, and carbon black.
In some embodiments, the isolation encapsulation layer has a thickness in the range of 5nm to 200 nm. Further preferably, the thickness of the isolation encapsulation layer is in the range of 5nm-50 nm. The water and CO barrier can be further improved by adjusting the material and thickness of the isolation packaging layer 2 And the lithium-doped lithium-supplementing material is contacted with a doped lithium-supplementing agent in the kernel, so that the stability of the composite lithium-supplementing material 100 is improved.
In some embodiments, the material of the electronic conductor encapsulation layer includes, but is not limited to, at least one of a carbon material, a conductive polymer, and a conductive oxide. In some embodiments, carbon materials include, but are not limited to, mesoporous carbon, carbon nanotubes, graphite, carbon black, andat least one of graphene, conductive polymers including but not limited to those contained In the isolation encapsulation layer above, conductive oxides including but not limited to In 2 O 3 ZnO and SnO 2 At least one of (1).
In some embodiments, the electronic conductor encapsulation layer has a thickness in the range of 5nm to 200 nm; it is further preferred that the thickness of the electron conductor encapsulation layer is in the range of 5nm to 50 nm. The electronic conductivity of the composite lithium supplement material 100 can be further improved by adjusting the thickness of the electronic conductor encapsulation layer.
In some embodiments, the material of the ion conductor encapsulation layer includes, but is not limited to, at least one of a perovskite-type, NA SICON-type, garnet-type, or polymer-type solid electrolyte. In some embodiments, the perovskite type includes, but is not limited to, li 3x La 2/3-x TiO 3 (LLTO), in particular Li 0.5 La 0.5 TiO 3 、Li 0.33 La 0.57 TiO 3 、Li 0.29 La 0.57 TiO 3 、Li 0.33 Ba 0.25 La 0.39 TiO 3 、(Li 0.33 La 0.56 ) 1.005 Ti 0.99 Al 0.01 O 3 And Li 0.5 La 0.5 Ti 0.95 Zr 0.05 O 3 At least one of; NASICON types include, but are not limited to, li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 (LATP). Garnet types including but not limited to Li 7 La 3 Zr 2 O 12 (LLZO、Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 And Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 At least one of (a); the polymeric solid electrolyte includes, but is not limited to, at least one of PEO/PPO/PVDF dissolved with lithium salt.
In some embodiments, the ion conductor encapsulation layer has a thickness in the range of 5nm to 200 nm. Further preferably, the thickness of the ion conductor encapsulation layer is in the range of 5nm-50 nm. The ionic conductivity of the composite lithium supplement material 100 can be further improved by adjusting the thickness and material of the ion conductor encapsulation layer.
Correspondingly, the embodiment of the application also provides a preparation method of the composite lithium supplement material, which can be used for preparing the composite lithium supplement material 100 provided by the embodiment of the application. The preparation method comprises the following steps:
(1) Mixing a lithium supplement source with a doping source to prepare a doping type lithium supplement precursor;
(2) Mixing the doped lithium supplement precursor with an organic carbon source, and calcining in an inert atmosphere to grow a carbon nanotube and amorphous carbon to obtain a composite lithium supplement material; the composite lithium supplement material comprises an inner core and a shell layer, wherein the inner core comprises a doped lithium supplement agent, the shell layer comprises amorphous carbon and carbon nano tubes dispersed in the amorphous carbon, and the doped lithium supplement agent contains transition metal elements.
Carbon atoms in the organic carbon source can perform carbon rearrangement reaction on the surface of the doped lithium supplement agent, so that the carbon source grows carbon nanotubes and amorphous carbon on the surface of the core material to form the composite lithium supplement material with a shell-core structure.
The preparation method has simple process and is suitable for large-scale industrial production.
In the present application, the inert gas atmosphere may be at least one of nitrogen, helium and argon.
In some embodiments of the present application, in step (2), the calcination conditions are: preserving the heat for 30min to 90min under the nitrogen environment at the temperature of 500 ℃ to 750 ℃. The specific calcining temperature and the heat preservation time can be determined according to actual conditions, and the suitable temperatures for generating the carbon nano tubes by catalysis of different elements are different. The proper calcination condition is beneficial to the growth of the carbon nano tube and the amorphous carbon, thereby being beneficial to ensuring the good performance of the composite lithium supplement material.
In some embodiments of the present application, the doping source includes at least one of nitrate, sulfate, carbonate, hydroxide, and ammonium salt of the doping element. The doping element includes the transition metal element M, which includes but is not limited to at least one of Fe, co, ni, mn, mo, and Cu.
In some embodiments of the present application, the doping source includes at least one of nitrate, sulfate, carbonate, hydroxide, and ammonium salt of the doping element. Such doping elements include, but are not limited to, al and/or Mg. It is to be noted that, if the transition metal element a is present in the lithium dopant source phase, the dopant source may be only at least one of nitrate, sulfate, carbonate, hydroxide and ammonium salt of Al and/or Mg. If the lithium supplement source does not contain the transition metal element a, the dopant source must also contain at least one of the nitrate, sulfate, carbonate, hydroxide, and ammonium salt of the transition metal element M.
The doping sources are easy to reduce into simple substances or be oxidized into oxides, and other elements are volatilized and removed in a gaseous state and are not easy to remain.
In some embodiments of the present application, the organic carbon source includes, but is not limited to, at least one of alcohols, aldehydes, alkanes, alkenes, alkynes, and benzene hydrocarbons. Illustratively, the organic carbon source may be polypropylene, polyethylene, ethanol, benzene, toluene, polyaniline, and the like.
In the present application, the organic carbon source may be in a gaseous state or a liquid state.
In the present application, the lithium supplement source may be a material known to those of ordinary skill in the art. Illustratively, such sources of lithium-supplementing agents include, but are not limited to, li 4 FeO 5 Lithium cobaltate, lithium aluminate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl fluorophosphate, lithium titanate, lithium nickelate, lithium nickel cobalt aluminate, and the like.
In some embodiments of the present application, after step (2), further comprising step (3): and forming an encapsulation layer on the surface of the shell layer. The encapsulation layer includes, but is not limited to, at least one of an isolation sub-packaging layer, an ion-conducting sub-layer, and an electronic conductor encapsulation layer. The preparation method of the packaging layer includes but is not limited to chemical deposition, magnetron sputtering, atomic layer deposition and the like.
In some embodiments, when the material of the encapsulation layer is a ceramic layer, the step of preparing the ceramic encapsulation layer may employ a magnetron sputtering method to sputter a ceramic target on the surface of the shell layer to deposit a ceramic ion encapsulation layer, wherein the magnetron sputtering condition is adjusted according to the specific target property.
In some embodiments, when the material of the encapsulation layer is a polymer layer, the step of forming the polymer isolation encapsulation layer may be: and (3) dispersing the composite lithium supplement material prepared in the step (2) in a solution containing a high molecular polymer, and then performing vacuum drying on the solution to form a compact polymer packaging layer on the surface of a shell layer. Wherein the solvent of the solution is a solvent capable of uniformly dispersing or dissolving the high molecular polymer, such as one or more of N-methylpyrrolidone, methanol, ethanol, isopropanol, acetone, tetrahydrofuran and diethyl ether.
In some embodiments, when the material of the encapsulation layer is a carbon material layer, the method of forming the carbon material isolation encapsulation layer comprises the steps of: and (3) dispersing the composite lithium supplement material prepared in the step (2) in a solution containing a carbon source, drying, and then carbonizing to form a compact carbon packaging layer on the surface of the shell layer. The carbon source may be, but is not limited to, PEO, and may be other carbon sources. Any carbon source coating layer can be formed on the composite lithium supplement material. Specifically, the carbon-coated lithium supplement material and PEO are mixed uniformly, the mixture is treated at 300 ℃ to ensure that the PEO in a molten state is coated on the surface of the shell layer uniformly, and the coated material is sintered for 6 hours at 600 ℃ in an inert atmosphere.
The embodiment of the application also provides a positive electrode composite material, and the positive electrode composite material comprises the composite lithium supplement material provided by the embodiment of the application or the composite lithium supplement material prepared by the preparation method provided by the embodiment of the application.
The positive electrode composite material has good lithium supplement performance and good processing performance, and can be used for providing a battery with higher first charge-discharge coulombic efficiency and longer cycle service life.
In some embodiments of the present application, the positive electrode composite material further includes a positive electrode active material, and the mass percentage of the composite lithium supplement material in the positive electrode composite material is in a range of 0.1% to 10%. Illustratively, the above compoundingThe mass percentage of the lithium supplement material in the positive electrode composite material may be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. Can be determined according to the lithium supplement requirement of the actual battery. The content of the composite lithium supplement material is controlled within the range, so that the active Li of the battery in the first charging process can be effectively compensated + The loss of the battery can improve the first charging and discharging coulombic efficiency of the battery, and is beneficial to improving the energy density and the capacity retention rate of the battery.
In the present application, the above-mentioned positive electrode active material is a material well known to those skilled in the art. Specifically, the above-mentioned cathode active material includes, but is not limited to, at least one of a phosphate cathode active material, a ternary cathode active material, and a lithium transition metal oxide. Illustratively, the above-described positive electrode active material may be lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium vanadium fluorophosphate, lithium titanate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or the like.
The embodiment of the application also provides a positive pole piece, and the positive pole piece is provided with the positive pole composite material provided by the embodiment of the application. The positive pole piece has a good lithium supplement effect, and can be used for providing a battery with high first charge-discharge coulomb efficiency and long cycle service life.
In this application, above-mentioned positive pole piece includes the mass flow body and sets up the anodal active material layer on the at least one side surface of above-mentioned mass flow body.
In some embodiments of the present invention, the positive electrode current collector includes, but is not limited to, any one of a copper foil and an aluminum foil.
In some embodiments of the present application, the positive active layer may further include a conductive agent, a binder, and other components, which are well known to those skilled in the art, and the suitable material may be selected according to the actual application requirement.
In some embodiments of the present application, the mass percentage of the binder in the positive electrode active layer is in a range of 2% to 4%. Illustratively, the mass percentage of the binder in the positive electrode active layer may be 2%, 3%, 4%, etc. Illustratively, the binder includes at least one of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropylmethyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan, and chitosan derivative.
In some embodiments of the present application, the mass percentage of the conductive agent in the positive electrode active layer is in a range of 3% to 5%. Illustratively, the mass percentage of the conductive agent in the positive electrode active layer may be 3%, 4%, 5%, etc. Illustratively, the conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fibers, C60, and carbon nanotubes.
In the present application, the preparation process of the positive electrode plate may include the following steps:
mixing a positive electrode active material, a composite lithium supplement material, a conductive agent, a binder and a solvent to obtain positive electrode slurry;
and coating the positive electrode slurry on a current collector, and drying, rolling, die cutting and the like to prepare the positive electrode piece.
The embodiment of the application also provides a battery, and the battery is provided with the positive pole piece provided by the embodiment of the application. The battery has higher first charge-discharge coulomb efficiency and longer cycle service life.
The technical solution of the present application is described in detail with reference to specific embodiments.
Example 1
(1) Reacting LiOH with CS 2 (CS 2 For providing Li + Complex anions), and a doping source-Cu (NO) 3 ) 2 And (2) mechanically crushing and uniformly stirring the mixture according to a molar ratio of 4.
(2) Firstly, uniformly mixing benzene and a doped lithium supplement precursor, placing the mixture in a muffle furnace, and sintering the mixture for 1.5 hours at 700 ℃ in a nitrogen atmosphere to obtain the composite lithium supplement material provided by the embodiment of the application.
Wherein the average thickness of the shell layer is 6nm, and the average particle size of the core is 10 μm. The mass percentage of the shell layer is 1.75 percent, and the carbon number in the shell layerThe mass percent of the rice tube is 0.15%. The diameter of the obtained carbon nano tube is in the range of 30-50nm, and the length of the carbon nano tube is in the range of 3-8 mu m. The chemical formula of the core can be expressed as Li 2 S0.5 CuO. Wherein Cu is a doping element, cuO is a catalyst and can catalyze the growth of a carbon nano tube and amorphous carbon in the preparation process of the composite lithium supplement material, and Li 2 S as a lithium supplement to provide Li + 。
Example 2
(1) Mixing Li 2 O and Ni (OH) 2 Mechanically crushing according to a molar ratio of 1:1, uniformly stirring, sintering at 700 ℃ for 10 hours in a nitrogen atmosphere, crushing, and sieving to obtain a lithium supplement source-Li 2 NiO 2 。
(2) Adding a lithium-supplementing agent source-Li 2 NiO 2 And a doping source- (NH) 4 ) 2 MoO 4 Uniformly mixing the components according to the proportion of 1.
(3) Ethanol and a doped lithium supplement agent precursor are uniformly mixed, then the mixture is placed in a tube furnace, and the reaction is carried out for 0.5h at 650 ℃ in a nitrogen atmosphere, so as to obtain the composite lithium supplement material provided by the embodiment of the application.
Wherein the average thickness of the shell layer is 5nm, and the average particle size of the core is 3 μm. The mass percent of the shell layer is 1.98 percent, and the mass percent of the carbon nano tube in the shell layer is 0.5 percent. The obtained carbon nanotube has a tube diameter of 20-30nm and a length of 5-10 μm. The chemical formula of the core can be expressed as Li 2 NiO 2 0.05Mo, wherein Mo is doped in Li in the form of a simple substance 2 NiO 2 In (C), mo catalyzes the growth of carbon nanotubes and amorphous carbon, li 2 NiO 2 Provision of Li as a lithium-supplementing agent + 。
Example 3
(1) Mixing Li 2 CO 3 And Fe (OH) 3 Mechanically crushing the mixture according to a molar ratio of 2.6 5 FeO 4 。
(2) Adding a lithium-supplementing agent source-Li 5 FeO 4 And doping source-Al (NO) 3 ) 3 Uniformly mixing 1:1 in proportion, sintering for 3h at 550 ℃ in a mixed atmosphere of hydrogen and nitrogen, crushing, and sieving to obtain a doped lithium supplement precursor, wherein the hydrogen reduces Fe element in the surface layer of the lithium supplement source.
(3) The composite lithium supplement material provided by the embodiment of the application is obtained by crushing the polypropylene waste plastic, uniformly mixing the crushed polypropylene waste plastic with the doped lithium supplement precursor, placing the mixture in a box-type furnace, and reacting for 1h at 600 ℃ in a nitrogen atmosphere.
Wherein the average thickness of the shell layer is 3nm, and the average particle size of the core is 4 μm. The mass percent of the shell layer is 1.23 percent, and the mass percent of the carbon nano tube in the shell layer is 0.4 percent. The obtained carbon nano tube has the tube diameter within the range of 10nm-20nm and the length within the range of 10 mu m-15 mu m. The chemical formula of the doping type lithium supplement agent can be expressed as Li 5 FeO 4 ·0.1Fe·Al 2 O 3 Wherein the reduced Fe simple substance is positioned on the surface of the core material, and is mixed with the doped Al 2 O 3 Catalyzing the growth of carbon nanotubes and amorphous carbon together, while Li inside the core material 5 FeO 4 Then Li is supplied as a lithium-supplementing agent + 。
Example 4
(1) Mixing Li 2 CO 3 And Fe (OH) 3 Mechanically crushing the mixture according to a molar ratio of 2.5 5 FeO 4 。
(2) Adding a lithium-supplementing agent source-Li 5 FeO 4 And a doping source- (NH) 4 ) 2 MoO 4 And Al (NO) 3 ) 3 The weight ratio of 1:0.05:1, sintering for 2h at 450 ℃ in the atmosphere, crushing, and sieving to obtain the doped lithium supplement precursor.
(3) And uniformly mixing ethanol and the doped lithium supplement agent precursor, placing the mixture in a tubular furnace, and reacting for 0.5h at 650 ℃ in a nitrogen atmosphere to obtain the composite lithium supplement material provided by the embodiment of the application.
Wherein the average thickness of the shell layer is 3nm, and the average particle size of the core is 2 μm. ShellThe mass percent of the layer is 1.48 percent, and the mass percent of the carbon nano tube in the shell layer is 0.2 percent. The obtained carbon nano tube has the tube diameter within the range of 25nm-40nm and the length within the range of 5 mu m-10 mu m. The chemical formula of the core can be expressed as Li 5 FeO 4 ·0.05Mo·Al 2 O 3 . Wherein, mo simple substance and Al 2 O 3 Doped in Li 5 FeO 4 In (C), mo and Al 2 O 3 Concerted catalysis of growth of carbon nanotubes and amorphous carbon, li 2 NiO 2 Provision of Li as a lithium-supplementing agent + 。
Example 5
The differences from example 1 are: the obtained carbon nanotube has a tube diameter of 9-11 nm and a length of 20-30 μm.
Example 6
The differences from example 1 are: the content of benzene in example 1 was adjusted so that the mass percentage of the shell layer in the composite lithium-supplement material was 3.5%.
Example 7
The differences from example 1 are: the benzene content in example 1 was adjusted so that the average thickness of the shell layer was 10nm.
Example 8
The differences from example 1 are: the surface of the inner core has a three-dimensional conductive network.
Comparative example 1
(1) LiNO is reacted with 3 And Fe 2 O 3 Mechanically crushing according to a molar ratio of 5:1, uniformly stirring, sintering at 850 ℃ for 8 hours in a nitrogen atmosphere, crushing, and sieving to obtain a lithium supplement source-Li 5 FeO 4 。
(2) Dissolving polyaniline in N-pyrrolidone, and adding Li as lithium source 5 FeO 4 After being mixed evenly, the mixture is placed in a reaction kettle, reacts for 1h at the temperature of 250 ℃ under the atmosphere of nitrogen, and is dried in vacuum to obtain the composite lithium supplement material.
Wherein the shell layer of the composite lithium supplement material is only composed of amorphous carbon, the average thickness of the shell layer is 7nm, and the average grain diameter of the core is 30 μm. The mass percentage of the shell layer is 0.95%.
Comparative example 2
(1) Mixing Li 2 CO 3 And anion source-CS 2 Mechanically crushing and stirring uniformly according to a molar ratio of 2:1, sintering for 10 hours at 780 ℃ in a nitrogen atmosphere, crushing and sieving to obtain a lithium supplement source-Li 2 S。
(2) Toluene and lithium-supplement agent source-Li 2 And S is uniformly mixed, then is placed in a muffle furnace, and is sintered for 1.5h at 600 ℃ in a nitrogen atmosphere, so as to obtain the composite lithium supplement material.
Wherein the shell layer of the composite lithium supplement material is only composed of amorphous carbon, the average thickness of the shell layer is 10nm, and the average grain diameter of the core is 20 μm. The mass percent of the shell layer is 0.83 percent.
Comparative example 3
(1) Mixing LiOH and Ni (OH) 2 Mechanically crushing according to a molar ratio of 2:1, uniformly stirring, sintering at 900 ℃ for 6 hours in a nitrogen atmosphere, crushing, and sieving to obtain a lithium supplement source-Li 2 NiO 2 。
(2) Acetone and lithium supplementing agent source-Li 2 NiO 2 And after uniformly mixing, placing the mixture into a reaction kettle, reacting for 2 hours at 300 ℃ in a nitrogen atmosphere, and then drying in vacuum to obtain the composite lithium supplement material.
Wherein the shell layer of the composite lithium supplement material is only composed of amorphous carbon, the average thickness of the shell layer is 8nm, and the average grain diameter of the core is 25 μm. The mass percentage of the shell layer is 1.02%.
Comparative example 4
(1) Mixing Li 2 CO 3 And Fe (OH) 3 Mechanically crushing the mixture according to a molar ratio of 2.5 5 FeO 4 。
(2) Adding a lithium-supplementing agent source-Li 5 FeO 4 And a doping source-Al (NO) 3 ) 3 Uniformly mixing 1:1 in proportion, placing the mixture into a reaction kettle, reacting for 2 hours at 300 ℃ in a nitrogen atmosphere, drying in vacuum, mixing with crushed polypropylene waste plastic, placing the mixture into a box-type furnace, and reacting for 1 hour at 600 ℃ in the nitrogen atmosphere to obtain the composite lithium supplement material.
In this case, the Fe element cannot catalyze the growth of the carbon nanotube together with Al as a catalyst, and thus the shell layer of the composite lithium supplement material is composed of amorphous carbon only and does not contain the carbon nanotube. The average thickness of the shell layer was 3nm, and the average particle size of the core was 15 μm. The mass percent of the shell layer is 0.92%.
The following tests were performed on the composite lithium supplement materials prepared in the examples and comparative examples of the present application:
(1) And (3) morphology characterization: the composite lithium supplement material prepared in example 1 was subjected to SEM test to observe the surface morphology thereof.
(2) And (3) gram capacity test: the composite lithium supplement materials prepared in the above examples and comparative examples are respectively prepared into a positive electrode and an assembled lithium ion battery according to the following methods:
positive pole piece: mixing the composite lithium supplementing material with lithium cobaltate according to a certain mass ratio to obtain a target material, mixing the target material with a conductive agent-super-P: mixing, ball-milling and stirring the binder-PVDF for 60min according to the mass ratio of 95; the rotation speed is set to 30HZ: respectively preparing the anode pieces by homogenizing, coating, drying and cutting, and baking the anode pieces in a vacuum oven at 100 ℃ to remove trace water;
negative pole piece: manufacturing a lithium metal sheet with the diameter of 16 mm;
and alternately laminating the prepared negative pole piece, the diaphragm and the positive pole piece to obtain the dry battery core. Wherein the positive pole piece and the negative pole piece are alternately isolated by a diaphragm. And (3) placing the dry electric core in an aluminum plastic film outer package, injecting electrolyte, vacuumizing and sealing, standing at 60 ℃ for 48 hours, pressurizing at 60 ℃, packaging for the second time, exhausting, and grading to obtain the composite lithium supplement material-lithium ion battery. Wherein, the electrolyte comprises the following components: 1mol/L LiPF 6 A solution, wherein the solvent consists of Ethylene Carbonate (EC) and diethyl carbonate (DEC) according to a volume ratio of 1:1; the diaphragm is a polypropylene micropore diaphragm.
The first charge-discharge specific capacity of each composite lithium supplement material-lithium ion battery prepared by the method is tested according to the following method:
charging to 4.5V at 0.05C, and keeping the voltage at 4.5V until the current is less than 0.01C; discharging to 2.5V at 0.05C, and testing the first charge-discharge specific capacity. The results are summarized in table 1.
(3) The composite lithium supplement materials prepared in the above examples and comparative examples were added to a positive electrode active material to prepare a secondary battery.
a) Preparing a positive pole piece: and mixing the composite lithium supplement material prepared in each embodiment and the comparative example with a positive active material lithium iron phosphate to obtain the positive composite material. And uniformly mixing the positive electrode composite material with the binder-PVDF and the conductive agent super-p, dissolving the mixture in water, and uniformly stirring to obtain positive electrode slurry. The mass ratio of the composite lithium supplement material to the positive active material lithium iron phosphate is 2:98, the mass ratio of the positive electrode composite material, the binder and the conductive agent is 95. And coating the obtained positive electrode slurry on a positive electrode current collector-aluminum foil, and drying and die-cutting to obtain the positive electrode piece.
b) Preparing a negative pole piece: 100g of graphite negative electrode active material is added into water and uniformly mixed to obtain negative electrode slurry. And uniformly coating the negative electrode slurry on the surface of a negative electrode current collector-copper foil. And (4) drying, and tabletting by using a roller press to obtain the negative pole piece. And obtaining the negative pole piece.
c) Preparation of secondary battery: and (3) alternately stacking the positive pole pieces, the negative pole pieces and the diaphragms obtained in the steps, and preparing the battery in a lamination mode, wherein the positive pole pieces and the negative pole pieces are alternately arranged, and the adjacent positive pole pieces and the adjacent negative pole pieces are separated by the diaphragms, so that the dry battery core is obtained. And (3) placing the dry electric core in an aluminum plastic film outer package, injecting electrolyte, vacuumizing, sealing, standing at 60 ℃ for 48 hours, pressurizing at 60 ℃, performing secondary packaging, exhausting and capacity grading to obtain the full battery.
Wherein, the batteries with the positive pole pieces of the composite lithium supplement materials provided by the examples 1 to 8 are respectively marked as S1 to S8, and the batteries with the positive pole pieces of the composite lithium supplement materials provided by the comparative examples are respectively marked as DS1 to DS4.
The electrochemical performance of each battery is tested, and the batteries are respectively charged to 4.3V at 0.05C and are charged at a constant voltage of 4.3V until the current is less than 0.01C. The batteries were tested for first charge gram capacity and cycle capacity retention after 100 weeks of battery cycling. The results are summarized in Table 2.
TABLE 1 carbon content and gram Capacity test results for composite lithium supplement materials prepared in each example and comparative example
Table 2 electrochemical performance test results of the batteries manufactured in the respective examples and comparative examples
As is apparent from the SEM images (see fig. 2A and 2B) of the composite lithium supplement material prepared in example 1, the composite lithium supplement material has carbon nanotubes, and a portion of the carbon nanotubes is wound around the surface of the composite lithium supplement material, and there are also carbon nanotubes having a portion of the carbon nanotubes extending from the interior of the composite lithium supplement material.
Furthermore, as can be seen from the data in table 1, under the condition of the same material composition, the capacity of 0h gram at 25% humidity of the composite lithium supplement material provided by the examples is slightly better than that of the comparative example, but the environmental stability of the composite lithium supplement material provided by all the examples is obviously better than that of the comparative example. In addition, the gram capacity of the secondary battery with the composite lithium supplement material provided by the embodiment of the application and the capacity retention rate of the secondary battery after 100 weeks of circulation are both obviously superior to those of the comparative battery.
The foregoing are illustrative embodiments of the present application and it should be noted that those skilled in the art may make numerous modifications and enhancements without departing from the principles of the present application and which are also considered to be within the scope of the present application.
Claims (17)
1. The composite lithium supplement material is characterized by comprising an inner core and a shell layer growing on the surface of the inner core in situ, wherein the inner core comprises a doped lithium supplement agent, and the shell layer comprises amorphous carbon and carbon nano tubes dispersed in the amorphous carbon; wherein the doped lithium supplement agent contains transition metal elements.
2. The composite lithium supplement material of claim 1, wherein the mass percentage of the carbon nanotubes in the shell layer is in the range of 0.1-10%.
3. The composite lithium supplement material of claim 1, wherein at least a portion of the carbon nanotubes are in contact with the inner core.
4. The composite lithium supplement material of claim 1, wherein at least a portion of the carbon nanotubes form a three-dimensional conductive network at the surface of the inner core.
5. The composite lithium supplement material according to claim 1, wherein the tube diameter of the carbon nanotube is in the range of 5nm to 100 nm.
6. The composite lithium supplement material of claim 1, wherein the carbon nanotubes have a length in the range of 3 μ ι η to 50 μ ι η.
7. The composite lithium supplement material of claim 1, wherein the transition metal element comprises at least one of Fe, co, ni, mn, mo, and Cu.
8. The composite lithium supplement material of claim 1, wherein the doped element in the doped lithium supplement agent comprises at least one of Fe, co, ni, mn, mo, and Cu.
9. The composite lithium supplement material of claim 8, wherein the molar percentage of the doped element in the doped lithium supplement agent in the inner core is in the range of 1-50%.
10. The composite lithium supplement material of claim 1, wherein the doped element comprises a second element comprising Al and/or Mg.
11. The composite lithium supplement material as claimed in claim 1, wherein the mass percentage of the shell layer in the composite lithium supplement material is 1.0-5.5%.
12. The composite lithium supplementing material according to claim 1, wherein the diameter of the inner core is in the range of 0.05 μm to 100 μm, and the average thickness of the shell layer is in the range of 3nm to 100 nm.
13. The composite lithium supplement material of any one of claims 1-12, wherein the composite lithium supplement material has a delta attenuation of not greater than 25% in gram capacity stored for 24 hours at an ambient humidity of 25% relative to gram capacity stored for 0 hours.
14. The preparation method of the composite lithium supplement material is characterized by comprising the following steps of:
(1) Mixing a lithium supplement source with a doping source to prepare a doping type lithium supplement precursor;
(2) Mixing the doped lithium supplement precursor with an organic carbon source, and calcining in an inert atmosphere to grow a carbon nanotube and amorphous carbon to obtain a composite lithium supplement material; the composite lithium supplement material comprises an inner core and a shell layer, wherein the inner core comprises a doped lithium supplement agent, the shell layer comprises amorphous carbon and carbon nanotubes dispersed in the amorphous carbon, and the doped lithium supplement agent contains transition metal elements.
15. A positive electrode composite material, characterized in that the positive electrode composite material comprises the composite lithium supplement material according to any one of claims 1 to 13 or the composite lithium supplement material prepared by the preparation method according to claim 14.
16. A positive electrode sheet having the positive electrode composite material according to claim 15.
17. A battery having the positive electrode tab of claim 16 incorporated therein.
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| CN116864837A (en) * | 2023-09-04 | 2023-10-10 | 宁德时代新能源科技股份有限公司 | Secondary battery and electricity utilization device |
| CN117776273A (en) * | 2024-02-23 | 2024-03-29 | 江苏维锂新能源材料有限公司 | Lithium supplementing agent, lithium iron phosphate battery repair material and preparation method thereof |
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| CN116864837A (en) * | 2023-09-04 | 2023-10-10 | 宁德时代新能源科技股份有限公司 | Secondary battery and electricity utilization device |
| CN117776273A (en) * | 2024-02-23 | 2024-03-29 | 江苏维锂新能源材料有限公司 | Lithium supplementing agent, lithium iron phosphate battery repair material and preparation method thereof |
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