CN110993954B - Negative current collector of lithium metal secondary battery and preparation method thereof - Google Patents

Negative current collector of lithium metal secondary battery and preparation method thereof Download PDF

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CN110993954B
CN110993954B CN201911101589.3A CN201911101589A CN110993954B CN 110993954 B CN110993954 B CN 110993954B CN 201911101589 A CN201911101589 A CN 201911101589A CN 110993954 B CN110993954 B CN 110993954B
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current collector
lithium
lithium metal
secondary battery
parts
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CN110993954A (en
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谢嫚
位广玲
吴锋
夏信德
蒋文全
周佳辉
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Guangzhou Great Power Energy & Technology Co ltd
Beijing Institute of Technology BIT
GRIMN Engineering Technology Research Institute Co Ltd
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Guangzhou Great Power Energy & Technology Co ltd
Beijing Institute of Technology BIT
GRIMN Engineering Technology Research Institute Co Ltd
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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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • 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
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to a negative current collector of a lithium metal secondary battery and a preparation method thereof, belonging to the technical field of lithium metal secondary batteries. The current collector consists of three layers of ZnO/graphene/carbon nano tubes, the content of ZnO is gradually reduced from the bottom layer to the top layer, and accordingly, the lithium affinity is gradually weakened from the bottom layer to the top layer, so that the uniform deposition of metal lithium from the bottom layer to the top layer is facilitated, and the problem of the deposition of the metal lithium on the top layer is solved; in addition, the framework of the current collector is of a high-conductivity porous lamellar structure, the larger specific surface area is favorable for reducing the actual current density and relieving the growth of dendrites, and the problem of volume expansion in the circulation process can be limited by more pores; moreover, the preparation process of the current collector is simple and easy to control, and provides a new opportunity for the practical application of the lithium metal secondary battery.

Description

Negative current collector of lithium metal secondary battery and preparation method thereof
Technical Field
The invention relates to a negative current collector of a lithium metal secondary battery and a preparation method thereof, belonging to the technical field of lithium metal secondary batteries.
Background
Lithium ion secondary batteries have been developed for a long time and are widely used in the fields of portable electronic devices and new energy electric vehicles. However, with the continuous development of various high-performance devices, especially new energy electric vehicles, the requirement of people on the energy density of lithium ion batteries is continuously increased, and the traditional lithium ion secondary batteries are increasingly difficult to meet the requirements of people on the energy density, the safety performance and the like. The high specific energy battery is developed based on high specific energy materials, and the lithium metal negative electrode has the highest theoretical specific capacity (3860mAh g)-1) Lowest reduction potential (-3.04V) and lower density (0.59g cm)-3) It is one of the most promising negative electrode materials for lithium secondary batteries.
However, the lithium metal secondary battery needs to overcome the safety problem and the cyclability problem to be commercially applied. These problems arise essentially from dendritic growth at the surface of the lithium metal negative electrode due to the constant deposition-deintercalation of lithium during electrochemical cycling. When the copper foil is used as a negative electrode current collector of the lithium metal battery, lithium metal is deposited in a dendritic shape when being deposited on the surface of the copper foil, and the growth of the lithium dendritic crystal consumes extra electrolyte and even pierces a diaphragm to cause short circuit of the battery. In addition, the lithium metal negative electrode has no framework structure, so that huge volume change can be generated in the circulation process, repeated volume expansion and contraction can further cause further capacity attenuation, the service life of the battery is shortened, and the further development and application of the lithium metal secondary battery are limited.
In order to solve the problem of dendritic growth of the lithium metal negative electrode, researchers commonly adopt methods such as using advanced electrolytes, constructing artificial protective layers, and developing highly conductive three-dimensional current collectors. Li et al use lithium polysulphides (Li)2S8) And lithium nitrate (LiNO)3) As an additive for ether-based electrolytes, use is made of the additive Li2S8And the stable and uniform SEI is formed on the lithium surface by the synergistic effect of the reaction between the lithium and the SEI film formed by the lithium and the electrolyteLayer, preventing dendrite formation (Li W, Yao H, Yan K, et al. the synthetic effect of lithium polysufide and lithium nitrate to prior lithium dendrite growth [ J]Nature communications.2015,6: 7436.). Liang et al in situ synthesis of a protective layer consisting of LiCl and a lithium-rich alloy on Li at room temperature for protection of metallic lithium negative electrodes, the lithium alloy enabling rapid migration of lithium ions and effectively mitigating dendrite growth (Liang X, Pang Q, Kochetkov I R, et al]Nature energy.2017,2: 17119.). The above studies improve the stability of the SEI film to some extent and inhibit the growth of dendrites, but the problem of volume change of the lithium metal negative electrode is not solved. Although researchers have utilized highly conductive three-dimensional current collectors to limit the volume expansion of lithium metal negative electrodes during electrochemical cycling, these inter-linked highly conductive three-dimensional materials are prone to forming equipotentials, so that lithium metal is deposited first on the top layer, rather than uniformly from bottom to top.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a negative current collector for a lithium metal secondary battery, the current collector is composed of a three-layer ZnO/graphene/carbon nanotube composite material, and the ZnO content gradually decreases from the bottom layer to the top layer, and accordingly, the lithium affinity gradually decreases from the bottom layer to the top layer, which is beneficial for uniform deposition of metal lithium from the bottom layer to the top layer, thereby solving the problem of deposition of metal lithium on the top layer; in addition, the framework of the current collector is of a high-conductivity porous lamellar structure, the larger specific surface area is favorable for reducing the actual current density and relieving the growth of dendrites, and the problem of volume expansion in the circulation process can be limited by more pores.
The invention also aims to provide a preparation method of the negative current collector of the lithium metal secondary battery, which is prepared by simple suction filtration, disordered freezing, freeze drying and calcination and is simple to operate.
The purpose of the invention is realized by the following technical scheme.
The current collector is a three-layer composite structure with gradient lithium affinity, each layer consists of ZnO, graphene and carbon nano tubes, the content of ZnO in the bottom layer contacting with the lithium metal of the negative electrode is highest, the content of ZnO in the middle layer is next to that of ZnO, and the content of ZnO in the top layer is lowest.
The ZnO and the graphene are respectively generated by calcining water-soluble zinc salt and graphene oxide, the content of the graphene in three layers is the same, the content of the carbon nano tube in the three layers is the same, the mass ratio of the graphene oxide used in each layer to the carbon nano tube is 5-10: 1, and the mass ratio of the zinc ion in the water-soluble zinc salt used in the bottom layer, the middle layer and the top layer to the graphene oxide used in each layer is 2.8-3.8: 1, 1.4-1.8: 1 and 0.7-1.0: 1.
The negative current collector of the lithium metal secondary battery is prepared by adopting the following method,
to three parts of Zn respectively2+Adding equal amount of carbon nano tubes into zinc salt aqueous solution with different contents, then stirring and carrying out ultrasonic treatment, and uniformly mixing to obtain three parts of carbon nano tube suspension; correspondingly mixing three parts of the same graphene oxide aqueous solution with three parts of the carbon nanotube suspension liquid one by one, stirring and ultrasonically treating, and uniformly mixing to obtain three parts of mixed suspension liquid; according to Zn2+Sequentially carrying out suction filtration on three parts of mixed suspension liquid from high to low, placing solid products collected by suction filtration at the temperature of-4 ℃ to-20 ℃ for disordered freezing for 30min to 60min, transferring the solid products to the temperature of-50 ℃ to-100 ℃ for freeze drying, and finally calcining to obtain the lithium metal secondary battery cathode current collector with the ZnO content from high to low from the bottom layer to the top layer.
Further, the size of the graphene oxide sheet in the aqueous solution of graphene oxide is 20 to 50 μm.
Further, the length of the carbon nanotube is 0.5 μm to 2 μm.
Further, the zinc salt is zinc acetate, zinc nitrate or zinc chloride.
Further calcining for 2-4 h at 400-800 ℃.
When the negative electrode current collector of the lithium metal secondary battery is applied to the negative electrode of the lithium metal secondary battery, the used electrolyte is preferably an ether electrolyte.
Has the advantages that:
(1) the current collector is formed by compounding three layers of ZnO/graphene/carbon nano tubes with different ZnO contents, the bottom layer has the highest ZnO content and the strongest lithium affinity, the top layer has the lowest ZnO content and the weakest lithium affinity, the middle layer has the ZnO content between the bottom layer and the top layer, and the phenomenon of lithium metal layering caused by the large lithium affinity difference between the bottom layer and the top layer can be buffered; the bottom layer with the strongest lithium affinity is easy to be tightly combined with the metal lithium, and the top layer with the weakest lithium affinity has relatively weaker bonding force with the metal lithium, so that the uniform deposition of the metal lithium from the bottom layer to the top layer is facilitated, and the problem of the deposition of the metal lithium on the top layer is solved; meanwhile, the high-conductivity porous skeleton structure composed of the carbon nano tube and the graphene has a larger specific surface area, so that the actual current density is reduced, the growth of dendrites is relieved, and the problem of volume expansion in the circulation process can be limited by more pores. Therefore, when the current collector is applied to the negative electrode of the lithium metal secondary battery, the current collector has higher coulombic efficiency and excellent cycle stability, and provides new opportunities for the practical application of the lithium metal secondary battery;
(2) the current collector is prepared by suction filtration, disordered freezing, freeze drying and calcination, and the process is simple to operate and easy to control.
Drawings
Fig. 1 is a side Scanning Electron Microscope (SEM) image of the current collector prepared in example 1 at 1000 times magnification.
Fig. 2 is a side SEM image of the current collector prepared in example 1 at magnification of 80000 times.
FIG. 3 shows the current collector of CR 2016 button cell at 0.5mA/cm assembled as obtained in example 12Voltage-capacity plot at current density.
FIG. 4 shows CR 2016 cells assembled at 0.5mA/cm using the current collectors obtained in example 12Graph of cycling efficiency at current density.
FIG. 5 shows the current collector of CR 2016 button cell at 1mA/cm assembled as obtained in example 12Voltage-capacity plot at current density.
FIG. 6 shows the current collector of CR 2016 button cell at 1mA/cm assembled as obtained in example 12Graph of cycling efficiency at current density.
FIG. 7 shows the current collector of CR 2016 button cell at 1mA/cm assembled as obtained in example 12SEM image of the surface of the current collector after 100 weeks of cycling at current density.
Fig. 8 is a graph of the cycle efficiency of the assembled lithium copper half cell of comparative example 1.
FIG. 9 shows the assembled lithium copper half cell of comparative example 1 at 1mA/cm2SEM images of the surface of the copper sheet after 100 weeks of cycling at current density.
Detailed Description
The invention is further illustrated by the following figures and detailed description, wherein the process is conventional unless otherwise specified, and the starting materials are commercially available from a public disclosure without further specification.
In the following examples:
and (4) SEM test: using a field emission scanning electron microscope (FEI, quandata 200f), the acceleration voltage was 20 kV;
assembling a CR 2016 button cell: cutting the current collector prepared in the embodiment into a wafer with the diameter of 11mm as a negative current collector, taking metal lithium as a negative electrode, taking a diaphragm as a Celgard diaphragm, taking 1, 3-Dioxolane (DOL)/ethylene glycol dimethyl ether (DME) based lithium bis (trifluoromethyl sulfonic acid) imide (LiTFSI) as electrolyte, and assembling the diaphragm into a half cell in an argon glove box; wherein the concentration of LiTFSI in the electrolyte is 1mol/L, and the volume ratio of DOL to DME is 1: 1.
Electrochemical performance test: electrochemical testing of the assembled CR 2016 coin cell was performed using a Land battery testing system.
Example 1
(1) Adding a graphene oxide solution containing 10mg of graphene oxide sheets with the size of 20-50 microns and the concentration of 10mg/mL into 4mL of deionized water, magnetically stirring for 30min, and then carrying out ultrasonic treatment for 120min to form a graphene oxide aqueous solution, wherein the same graphene oxide aqueous solution is prepared into three parts;
(2) adding 80mg, 40mg and 20mg zinc acetate into three parts of 5mL deionized water in a one-to-one correspondence manner, respectively adding 2mg carbon nano tubes with the length of 0.5-2 mu m into three parts of zinc acetate aqueous solution, magnetically stirring for 30min, and then performing ultrasonic treatment for 120min to obtain three parts of carbon nano tube suspension;
(3) correspondingly mixing three parts of the aqueous solution of graphene oxide and three parts of the carbon nanotube suspension liquid one by one, magnetically stirring for 30min, and then performing ultrasonic treatment for 60min to obtain three parts of mixed suspension liquid;
(4) sequentially carrying out suction filtration on three parts of mixed suspension according to the sequence of zinc acetate content from top to bottom (namely, firstly carrying out suction filtration on the mixed suspension with the highest zinc acetate content to form a bottom layer precursor, then carrying out suction filtration on the mixed suspension with the second zinc acetate content to form a middle layer precursor, and finally carrying out suction filtration on the mixed suspension with the lowest zinc acetate content to form a top layer precursor on the middle layer precursor), placing solid products collected by suction filtration at minus 10 ℃ for disordered freezing for 30min, transferring to minus 50 ℃ for freeze drying for 24h, and finally calcining at 800 ℃ for 2h to obtain the lithium metal secondary battery cathode current collector with the ZnO content from bottom layer to top layer from high to low.
As can be seen from the SEM images with different magnifications in fig. 1 and fig. 2, the current collector prepared in this embodiment has a three-dimensional layered porous structure, the graphene sheet layers and the carbon nanotubes are uniformly distributed, and the ZnO particles grow on the graphene sheet layers and the carbon nanotubes, so as to form a three-dimensional conductive structure with a porous morphology.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 0.5mA/cm2The constant current charge and discharge performance test is carried out under the current density. As can be seen from the voltage-capacity graph of fig. 3, the overpotential of the battery did not change significantly after 50 weeks, 100 weeks, and 150 weeks of cycling, and the stability was good. As can be seen from the cycle efficiency graph of fig. 4, the cycle efficiency of the battery after 200 cycles was not substantially reduced, and remained at 98%, and the cycle stability of the battery was good.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charge and discharge performance test is carried out under the current density. As can be seen from the voltage-capacity diagram of FIG. 5, the overpotential of the battery after 50, 100 and 150 cyclesNo obvious change, which indicates that the stability of the battery is good. As can be seen from the cycle efficiency graph of fig. 6, after 200 cycles, the cycle efficiency of the battery was not substantially decreased, and was maintained at 98%, which was excellent in cycle stability.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charging and discharging performance test is carried out under the current density, and the appearance representation of the current collector in the battery is carried out after 100 weeks of circulation. As can be seen from the SEM image of fig. 7, the surface of the current collector is relatively flat, and no significant lithium dendrite growth is observed, which indicates that the current collector prepared in this embodiment can significantly inhibit the lithium dendrite growth when used in a lithium metal negative electrode.
Example 2
(1) Adding a graphene oxide solution containing 10mg of graphene oxide sheets with the size of 20-50 microns and the concentration of 10mg/mL into 4mL of deionized water, magnetically stirring for 30min, and then carrying out ultrasonic treatment for 120min to form a graphene oxide aqueous solution, wherein the same graphene oxide aqueous solution is prepared into three parts;
(2) adding 100mg, 50mg and 25mg zinc acetate into three parts of 5mL deionized water in a one-to-one correspondence manner, respectively adding 2mg carbon nano tubes with the length of 0.5-2 mu m into three parts of zinc acetate aqueous solution, magnetically stirring for 30min, and then performing ultrasonic treatment for 120min to obtain three parts of carbon nano tube suspension;
(3) correspondingly mixing three parts of the aqueous solution of graphene oxide and three parts of the carbon nanotube suspension liquid one by one, magnetically stirring for 30min, and then performing ultrasonic treatment for 60min to obtain three parts of mixed suspension liquid;
(4) and sequentially carrying out suction filtration on the three parts of mixed suspension according to the sequence of zinc acetate content from top to bottom, placing solid products collected by suction filtration at minus 10 ℃ for disordered freezing for 30min, transferring to minus 50 ℃ for freeze drying for 24h, and finally calcining at 800 ℃ for 2h to obtain the lithium metal secondary battery cathode current collector with ZnO content from bottom to top from high to low.
The current collector prepared by the embodiment has a three-dimensional layered porous structure, the graphene sheet layer and the carbon nano tube are uniformly distributed, and ZnO particles grow on the graphene sheet layer and the carbon nano tube to form a three-dimensional conductive structure with a porous appearance.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 0.5mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, and the capacity retention performance is excellent.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, the cycle stability is good, and the capacity retention performance is excellent. According to the SEM images of the tests, the surface of the current collector in the battery was relatively flat after 100 cycles, and no obvious lithium dendrite was observed, indicating that the current collector prepared in this example can significantly inhibit the growth of lithium dendrite when used in a lithium metal negative electrode.
Example 3
(1) Adding a graphene oxide solution containing 10mg of graphene oxide sheets with the size of 20-50 microns and the concentration of 10mg/mL into 4mL of deionized water, magnetically stirring for 30min, and then carrying out ultrasonic treatment for 120min to form a graphene oxide aqueous solution, wherein the same graphene oxide aqueous solution is prepared into three parts;
(2) adding 80mg, 40mg and 20mg zinc acetate into three parts of 5mL deionized water in a one-to-one correspondence manner, respectively adding 1mg carbon nano tubes with the length of 0.5-2 mu m into three parts of zinc acetate aqueous solution, magnetically stirring for 30min, and then performing ultrasonic treatment for 120min to obtain three parts of carbon nano tube suspension;
(3) correspondingly mixing three parts of the aqueous solution of graphene oxide and three parts of the carbon nanotube suspension liquid one by one, magnetically stirring for 30min, and then performing ultrasonic treatment for 60min to obtain three parts of mixed suspension liquid;
(4) and sequentially carrying out suction filtration on the three parts of mixed suspension according to the sequence of zinc acetate content from top to bottom, placing solid products collected by suction filtration at minus 10 ℃ for disordered freezing for 30min, transferring to minus 50 ℃ for freeze drying for 24h, and finally calcining at 800 ℃ for 2h to obtain the lithium metal secondary battery cathode current collector with ZnO content from bottom to top from high to low.
The current collector prepared by the embodiment has a three-dimensional layered porous structure, the graphene sheet layer and the carbon nano tube are uniformly distributed, and ZnO particles grow on the graphene sheet layer and the carbon nano tube to form a three-dimensional conductive structure with a porous appearance.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 0.5mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, and the capacity retention performance is excellent.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, the cycle stability is good, and the capacity retention performance is excellent. According to the SEM images of the tests, the surface of the current collector in the battery was relatively flat after 100 cycles, and no obvious lithium dendrite was observed, indicating that the current collector prepared in this example can significantly inhibit the growth of lithium dendrite when used in a lithium metal negative electrode.
Example 4
(1) Adding a graphene oxide solution containing 10mg of graphene oxide sheets with the size of 20-50 microns and the concentration of 10mg/mL into 4mL of deionized water, magnetically stirring for 30min, and then carrying out ultrasonic treatment for 120min to form a graphene oxide aqueous solution, wherein the same graphene oxide aqueous solution is prepared into three parts;
(2) adding 80mg, 40mg and 20mg zinc acetate into three parts of 5mL deionized water in a one-to-one correspondence manner, respectively adding 2mg carbon nano tubes with the length of 0.5-2 mu m into three parts of zinc acetate aqueous solution, magnetically stirring for 30min, and then performing ultrasonic treatment for 120min to obtain three parts of carbon nano tube suspension;
(3) correspondingly mixing three parts of the aqueous solution of graphene oxide and three parts of the carbon nanotube suspension liquid one by one, magnetically stirring for 30min, and then performing ultrasonic treatment for 60min to obtain three parts of mixed suspension liquid;
(4) and sequentially carrying out suction filtration on the three parts of mixed suspension according to the sequence of zinc acetate content from top to bottom, placing solid products collected by suction filtration at minus 10 ℃ for disordered freezing for 60min, transferring to minus 50 ℃ for freeze drying for 24h, and finally calcining at 800 ℃ for 2h to obtain the lithium metal secondary battery cathode current collector with ZnO content from bottom to top from high to low.
The current collector prepared by the embodiment has a three-dimensional layered porous structure, the graphene sheet layer and the carbon nano tube are uniformly distributed, and ZnO particles grow on the graphene sheet layer and the carbon nano tube to form a three-dimensional conductive structure with a porous appearance.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 0.5mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, and the capacity retention performance is excellent.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency chart, the cycle efficiency of the battery is not substantially attenuated after 200 weeks of cycle, and the cycle efficiency is still maintainedThe content is maintained at 98%, the circulation stability is good, and the capacity retention performance is excellent. According to the SEM images of the tests, the surface of the current collector in the battery was relatively flat after 100 cycles, and no obvious lithium dendrite was observed, indicating that the current collector prepared in this example can significantly inhibit the growth of lithium dendrite when used in a lithium metal negative electrode.
Example 5
(1) Adding a graphene oxide solution containing 10mg of graphene oxide sheets with the size of 20-50 microns and the concentration of 10mg/mL into 4mL of deionized water, magnetically stirring for 30min, and then carrying out ultrasonic treatment for 120min to form a graphene oxide aqueous solution, wherein the same graphene oxide aqueous solution is prepared into three parts;
(2) adding 80mg, 40mg and 20mg zinc acetate into three parts of 5mL deionized water in a one-to-one correspondence manner, respectively adding 1mg carbon nano tubes with the length of 0.5-2 mu m into three parts of zinc acetate aqueous solution, magnetically stirring for 30min, and then performing ultrasonic treatment for 120min to obtain three parts of carbon nano tube suspension;
(3) correspondingly mixing three parts of the aqueous solution of graphene oxide and three parts of the carbon nanotube suspension liquid one by one, magnetically stirring for 30min, and then performing ultrasonic treatment for 60min to obtain three parts of mixed suspension liquid;
(4) and sequentially carrying out suction filtration on the three parts of mixed suspension according to the sequence of zinc acetate content from top to bottom, placing solid products collected by suction filtration at minus 10 ℃ for disordered freezing for 30min, transferring to minus 50 ℃ for freeze drying for 36h, and finally calcining at 800 ℃ for 2h to obtain the lithium metal secondary battery cathode current collector with ZnO content from bottom to top from high to low.
The current collector prepared by the embodiment has a three-dimensional layered porous structure, the graphene sheet layer and the carbon nano tube are uniformly distributed, and ZnO particles grow on the graphene sheet layer and the carbon nano tube to form a three-dimensional conductive structure with a porous appearance.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 0.5mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the testThe cycle efficiency chart shows that the cycle efficiency of the battery after 200 cycles is almost not attenuated, and the battery still maintains 98%, and has excellent capacity retention performance.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, the cycle stability is good, and the capacity retention performance is excellent. According to the SEM images of the tests, the surface of the current collector in the battery was relatively flat after 100 cycles, and no obvious lithium dendrite was observed, indicating that the current collector prepared in this example can significantly inhibit the growth of lithium dendrite when used in a lithium metal negative electrode.
Example 6
(1) Adding a graphene oxide solution containing 10mg of graphene oxide sheets with the size of 20-50 microns and the concentration of 10mg/mL into 4mL of deionized water, magnetically stirring for 30min, and then carrying out ultrasonic treatment for 120min to form a graphene oxide aqueous solution, wherein the same graphene oxide aqueous solution is prepared into three parts;
(2) adding 80mg, 40mg and 20mg zinc acetate into three parts of 5mL deionized water in a one-to-one correspondence manner, respectively adding 1mg carbon nano tubes with the length of 0.5-2 mu m into three parts of zinc acetate aqueous solution, magnetically stirring for 30min, and then performing ultrasonic treatment for 120min to obtain three parts of carbon nano tube suspension;
(3) correspondingly mixing three parts of the aqueous solution of graphene oxide and three parts of the carbon nanotube suspension liquid one by one, magnetically stirring for 30min, and then performing ultrasonic treatment for 60min to obtain three parts of mixed suspension liquid;
(4) and sequentially carrying out suction filtration on the three parts of mixed suspension according to the sequence of zinc acetate content from top to bottom, placing solid products collected by suction filtration at minus 10 ℃ for disordered freezing for 30min, transferring to minus 50 ℃ for freeze drying for 24h, and finally calcining at 800 ℃ for 2h to obtain the lithium metal secondary battery cathode current collector with ZnO content from bottom to top from high to low.
The current collector prepared by the embodiment has a three-dimensional layered porous structure, the graphene sheet layer and the carbon nano tube are uniformly distributed, and ZnO particles grow on the graphene sheet layer and the carbon nano tube to form a three-dimensional conductive structure with a porous appearance.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 0.5mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, and the capacity retention performance is excellent.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, the cycle stability is good, and the capacity retention performance is excellent. According to the SEM images of the tests, the surface of the current collector in the battery was relatively flat after 100 cycles, and no obvious lithium dendrite was observed, indicating that the current collector prepared in this example can significantly inhibit the growth of lithium dendrite when used in a lithium metal negative electrode.
Example 7
(1) Adding a graphene oxide solution containing 10mg of graphene oxide sheets with the size of 20-50 microns and the concentration of 10mg/mL into 4mL of deionized water, magnetically stirring for 30min, and then carrying out ultrasonic treatment for 120min to form a graphene oxide aqueous solution, wherein the same graphene oxide aqueous solution is prepared into three parts;
(2) adding 80mg, 40mg and 20mg zinc acetate into three parts of 5mL deionized water in a one-to-one correspondence manner, respectively adding 1mg carbon nano tubes with the length of 0.5-2 mu m into three parts of zinc acetate aqueous solution, magnetically stirring for 30min, and then performing ultrasonic treatment for 120min to obtain three parts of carbon nano tube suspension;
(3) correspondingly mixing three parts of the aqueous solution of graphene oxide and three parts of the carbon nanotube suspension liquid one by one, magnetically stirring for 30min, and then performing ultrasonic treatment for 60min to obtain three parts of mixed suspension liquid;
(4) and sequentially carrying out suction filtration on the three parts of mixed suspension according to the sequence of zinc acetate content from top to bottom, placing solid products collected by suction filtration at minus 10 ℃ for disordered freezing for 30min, transferring to minus 50 ℃ for freeze drying for 24h, and finally calcining at 400 ℃ for 4h to obtain the lithium metal secondary battery cathode current collector with ZnO content from bottom to top from high to low.
The current collector prepared by the embodiment has a three-dimensional layered porous structure, the graphene sheet layer and the carbon nano tube are uniformly distributed, and ZnO particles grow on the graphene sheet layer and the carbon nano tube to form a three-dimensional conductive structure with a porous appearance.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 0.5mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, and the capacity retention performance is excellent.
The current collector prepared by the embodiment is assembled into a CR 2016 button cell at 1mA/cm2The constant current charge and discharge performance test is carried out under the current density. According to the voltage-capacity diagram of the test, after 50 weeks, 100 weeks and 150 weeks of cycling, the overpotential of the battery is not obviously changed, and the stability of the battery is good. According to the tested cycle efficiency graph, the cycle efficiency of the battery is not attenuated basically after 200 weeks of cycling, the cycle efficiency is still maintained at 98%, the cycle stability is good, and the capacity retention performance is excellent. After the current collector is cycled for 100 weeks under the condition, the surface of the current collector in the battery is relatively flat, and no obvious lithium dendrite is observed, which shows that the current collector prepared by the embodiment can obviously inhibit the growth of the lithium dendrite when being used for a lithium metal negative electrode.
Comparative example 1
Using a CR 2016 battery case, cutting a copper foil into 16mm round pieces as a current collector, using metal lithium as a negative electrode, using a Celgard diaphragm as a diaphragm, using DOL/DME-based LiTFSI as an electrolyte (the concentration of the LiTFSI is 1mol/L, and the volume ratio of the DOL to the DME is 1:1), and assembling the lithium-copper half-cell in an argon glove box.
The assembled lithium copper half cell is at 1mA/cm2The result of the constant current charge and discharge performance test is shown in fig. 8, the battery cycle is quite unstable, and very obvious capacity attenuation occurs after 50 weeks of cycle; the surface topography of the copper current collector after 100 cycles is shown in fig. 9, and a large number of dendritic lithium dendrites appear on the surface of the copper current collector, which impairs the cycle stability of the battery.
In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (6)

1. A lithium metal secondary battery negative current collector, characterized in that: the current collector is of a three-layer composite structure with gradient lithium affinity, each layer consists of ZnO, graphene and carbon nanotubes, the content of ZnO in the bottom layer contacting with the negative metal lithium is highest, the content of ZnO in the middle layer is next highest, and the content of ZnO in the top layer is lowest;
the ZnO and the graphene are respectively generated by calcining water-soluble zinc salt and graphene oxide, the content of the graphene in three layers is the same, the content of the carbon nano tube in the three layers is the same, the mass ratio of the graphene oxide used in each layer to the carbon nano tube is 5-10: 1, and the mass ratio of the zinc ion in the water-soluble zinc salt used in the bottom layer, the middle layer and the top layer to the graphene oxide used in each layer is 2.8-3.8: 1, 1.4-1.8: 1 and 0.7-1.0: 1;
the current collector is prepared by the following method, the steps of the method are as follows,
to three parts of Zn respectively2+Adding equal amount of carbon nano tube into zinc salt water solution with different content, stirring and ultrasonic processing, mixing uniformlyObtaining three parts of carbon nano tube suspension liquid after homogenizing; correspondingly mixing three parts of the same graphene oxide aqueous solution with three parts of the carbon nanotube suspension liquid one by one, stirring and ultrasonically treating, and uniformly mixing to obtain three parts of mixed suspension liquid; according to Zn2+Sequentially carrying out suction filtration on three parts of mixed suspension liquid from high to low, placing solid products collected by suction filtration at the temperature of-4 ℃ to-20 ℃ for disordered freezing for 30min to 60min, transferring the solid products to the temperature of-50 ℃ to-100 ℃ for freeze drying, and finally calcining to obtain the lithium metal secondary battery cathode current collector with the ZnO content from high to low from the bottom layer to the top layer.
2. A negative electrode current collector for a lithium metal secondary battery according to claim 1, wherein: the size of the graphene oxide sheet in the aqueous solution of the graphene oxide is 20-50 μm.
3. A negative electrode current collector for a lithium metal secondary battery according to claim 1, wherein: the length of the carbon nano tube is 0.5-2 μm.
4. A negative electrode current collector for a lithium metal secondary battery according to claim 1, wherein: the zinc salt is zinc acetate, zinc nitrate or zinc chloride.
5. A negative electrode current collector for a lithium metal secondary battery according to claim 1, wherein: calcining for 2-4 h at 400-800 ℃.
6. Use of the negative electrode current collector for lithium metal secondary batteries according to claim 1, characterized in that: when the lithium metal secondary battery negative electrode current collector is applied to a lithium metal secondary battery negative electrode, the electrolyte is ether electrolyte.
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