CN112447979A - Porous current collector and preparation method thereof, lithium negative electrode and lithium ion battery - Google Patents

Porous current collector and preparation method thereof, lithium negative electrode and lithium ion battery Download PDF

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Publication number
CN112447979A
CN112447979A CN201910815224.0A CN201910815224A CN112447979A CN 112447979 A CN112447979 A CN 112447979A CN 201910815224 A CN201910815224 A CN 201910815224A CN 112447979 A CN112447979 A CN 112447979A
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current collector
conductive porous
lithium
porous
framework
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胡志鹏
史刘嵘
洪晔
长世勇
董海勇
胡倩倩
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Guangzhou Automobile Group Co Ltd
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Guangzhou Automobile Group 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
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M4/134—Electrodes based on metals, Si or alloys
    • 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
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/80—Porous plates, e.g. sintered carriers
    • 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
    • H01M2004/027—Negative electrodes
    • 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

In order to overcome the problem of low lithium affinity of the existing porous framework, the invention provides a porous current collector which comprises a conductive porous framework, wherein a plurality of micropores are formed in the conductive porous framework, and copper oxide layers are formed on the surface of the conductive porous framework and the inner walls of the micropores. Meanwhile, the invention also discloses a preparation method of the porous current collector, a lithium cathode and a lithium ion battery. The porous current collector provided by the invention improves the specific surface area of the conductive porous framework, and effectively reduces nucleation overpotential of lithium deposition, so that lithium is uniformly deposited on the surfaces of micropores of the conductive porous framework in the embedding process, thereby reducing the generation probability of lithium dendrite.

Description

Porous current collector and preparation method thereof, lithium negative electrode and lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a porous current collector, a preparation method of the porous current collector, a lithium cathode and a lithium ion battery.
Background
With the popularization of energy storage base stations, electric vehicles and portable electronic products in daily life, people increasingly demand energy storage devices with high safety, high energy density and long service life, and the demand depends on the further development of anode and cathode materials in lithium ion batteries to a great extent. Among the negative electrode materials of many lithium ion batteries, lithium metal is due to its ultra-high specific mass energy (3860mAh g)-1) And the lowest voltage platform (-3.04V vs SHE) becomes the next generation lithium ion battery cathode material with the most potential to replace the traditional carbon material. However, the lithium metal negative electrode has a great obstacle to practical application, on one hand, lithium dendrite is easily generated in the lithium metal negative electrode in the charging and discharging process, a diaphragm is pierced to cause short circuit, and a great safety hidden range is caused; on the other hand, in the process of deposition and dissolution of lithium metal, along with huge volume change, the generated deformation stress can continuously break an SEI film on the surface of an electrode, exposed lithium metal contacts with an electrolyte to form a new SEI film, so that irreversible consumption of lithium is caused, and the coulombic efficiency of the battery is seriously attenuated. Therefore, how to inhibit the generation of lithium dendrites in the charging and discharging process, reduce the volume change of the lithium metal electrode and improve the coulombic efficiency of the lithium metal electrode is the key to the application of the lithium metal negative electrode.
In recent years, a three-dimensional porous current collector having high conductivity and high toughness is considered as a more ideal lithium metal carrier, and the higher specific surface area thereof can effectively reduce the current density on the surface of an electrode, thereby inhibiting the generation of lithium dendrites; while the internal voids help to counteract the volume change of the lithium metal. The metal lithium is usually deposited on the three-dimensional porous current collector by means of electrodeposition, but the commonly used three-dimensional porous current collectors, such as copper foam, nickel foam, graphene foam and the like, have weak affinity with lithium, and lithium metal cannot be uniformly deposited on the surface of the current collector, so that the coulombic efficiency is low and the polarization voltage is high. In addition, the method for preparing the lithium metal negative electrode by pouring the metal lithium into the three-dimensional porous current collector by using a melting method has a good application prospect, and the affinity of the three-dimensional porous current collector to the lithium metal also limits the combination between the metal lithium and the three-dimensional porous current collector.
In the prior art, as described in patent CN 109244374 a, the surface of the stainless steel net is treated with nitrogen to improve the lithium affinity of the stainless steel net. Or, as described in patent CN109546153A, the surface of the porous copper current collector is subjected to a sulfurization reaction and an oxidation heat treatment to suppress the formation and growth of negative dendrites. Or, as disclosed in patent CN109755476A, a layer of tin oxide is uniformly coated on the conductive metal skeleton by a water bath method to improve the affinity with the metal lithium.
The proposal for carrying out surface treatment on the porous metal framework has higher requirements on the material of the porous metal framework and is difficult to adapt to the treatment of other metals or other non-metallic conductive materials; the surface tin oxide produced by the water bath method has a limited affinity for lithium, and the bonding strength between the tin oxide layer and the porous metal skeleton is low, so that the tin oxide layer is easy to fall off.
Disclosure of Invention
Aiming at the problem of low lithium affinity of the existing porous framework, the invention provides a porous current collector and a preparation method thereof, a lithium cathode and a lithium ion battery.
The technical scheme adopted by the invention for solving the technical problems is as follows:
in one aspect, the present invention provides a porous current collector, including a conductive porous skeleton, a plurality of micropores formed inside the conductive porous skeleton, and copper oxide layers formed on a surface of the conductive porous skeleton and on inner walls of the micropores.
Optionally, the conductive porous skeleton comprises one or more of nickel foam, aluminum foam and carbon fiber cloth.
Optionally, the conductive porous skeleton is a sheet structure, and the thickness of the conductive porous skeleton is 0.05-0.8 mm.
Optionally, the thickness of the copper oxide layer is between 10 nm and 1000 nm.
Optionally, the pore volume in the conductive porous framework is 50% to 90%.
Optionally, the pore diameter of the micropores is between 10 and 700 μm.
In another aspect, the present invention provides a method for preparing a porous current collector as described above, comprising the following steps:
electroplating: placing the conductive porous framework in a copper salt solution, and electroplating by taking the conductive porous framework as a cathode, wherein copper layers are formed on the surface of the conductive porous framework and the inner wall of each micropore;
and (3) heat treatment: and carrying out heat treatment on the conductive porous framework to oxidize the copper layer into copper oxide.
Optionally, before the electroplating operation, the conductive porous skeleton is subjected to hydrochloric acid soaking treatment, and then is subjected to ultrasonic cleaning by an organic polar solvent, and the cleaned conductive porous skeleton is dried in vacuum.
Optionally, the concentration of the hydrochloric acid is 0.1-1 mol/L, and the soaking time is 5-60 min; the organic polar solvent is acetone and/or ethanol, the cleaning frequency is 1-3 times, and the cleaning time is 5-30 min; the vacuum drying temperature is 50-80 ℃, and the time is 1-6 h.
Optionally, the copper salt solution includes a soluble copper salt and a non-strong oxidizing acid, the concentration of the soluble copper salt is 0.01 to 1mol/L, and the concentration of the non-strong oxidizing acid is 0.1 to 2 mol/L.
Optionally, the soluble copper salt comprises CuSO4And CuCl2Including one or more of sulfuric acid and hydrochloric acid.
Optionally, in the electroplating operation, electroplating is performed under the condition of direct current constant voltage, and the current density is 0.1-0.5A/dm2The electroplating time is 5-30 min.
Optionally, after the "electroplating" operation, the conductive porous framework is cleaned and dried.
Optionally, in the heat treatment operation, the heat treatment temperature is 200-450 ℃ and the heat treatment time is 0.5-5 h.
In another aspect, the present invention provides a lithium negative electrode comprising the porous current collector as described above and metallic lithium supported on the porous current collector.
In another aspect, the invention provides a lithium ion battery comprising a positive electrode, an electrolyte, and a lithium negative electrode as described above.
According to the porous current collector provided by the invention, a buffer space can be provided for the lithium metal in the de-intercalation process of charging and discharging through the micropores formed on the conductive porous framework, so that the volume change of the lithium negative electrode in the charging and discharging process is avoided, the stability of the whole lithium negative electrode is facilitated, in order to improve the affinity between the conductive porous framework and the lithium metal, a lithium-philic copper oxide layer is formed on the surface of the conductive porous framework and in the micropores, the specific surface area of the conductive porous framework is improved, the nucleation overpotential of lithium deposition is effectively reduced, lithium is uniformly deposited on the surface of the micropores of the conductive porous framework in the intercalation process, and the probability of lithium dendrite generation is reduced.
Drawings
Fig. 1 is a schematic structural view of a porous current collector provided by the present invention;
fig. 2 is an electron micrograph of the micro-morphology of the porous current collector provided in example 1 of the present invention;
fig. 3 is a graph of the cyclic coulombic efficiency of a lithium anode provided in example 1 of the present invention;
FIG. 4 is a plot of the cycling voltage of an asymmetric cell according to example 2 of the present invention (current density of 0.5 mA/cm)2The circulation capacity is 1mAh g-1)；
FIG. 5 is a plot of the cycling voltage of an asymmetric cell according to example 2 of the present invention (current density of 2 mA/cm)2The circulation capacity is 1mAh g-1)；
FIG. 6 is a plot of the cycling voltage of a symmetrical cell provided in example 2 of the present invention (current density of 5 mA/cm)2The circulation capacity is 1mAh g-1)。
Fig. 7 is a graph of the cyclic coulombic efficiency of the lithium negative electrode provided in comparative example 1 of the present invention;
the reference numbers in the drawings of the specification are as follows:
1. an electrically conductive porous skeleton; 2. a copper oxide layer.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, an embodiment of the present invention provides a porous current collector, including a conductive porous skeleton, a plurality of micropores formed inside the conductive porous skeleton, and a copper oxide layer formed on a surface of the conductive porous skeleton and on inner walls of the micropores.
The multiple micropores formed on the conductive porous framework can provide buffer space for the de-intercalation process of the metal lithium in the charging and discharging process, so that the volume change of the lithium negative electrode in the charging and discharging process is avoided, the overall stability of the lithium negative electrode is facilitated, in order to improve the affinity between the conductive porous framework and the metal lithium, a lithium-philic copper oxide layer is formed on the surface of the conductive porous framework and in the micropores, the specific surface area of the conductive porous framework is improved, the nucleation overpotential of lithium deposition is effectively reduced, lithium is uniformly deposited on the surface of the micropores of the conductive porous framework in the intercalation process, and the generation probability of lithium dendrites is reduced.
In some embodiments, the electrically conductive porous skeleton comprises one or more of nickel foam, aluminum foam, and carbon fiber cloth.
The foamed nickel, foamed aluminum and carbon fiber cloth all have better electric conductivity, can play the effect of supporting skeleton and the mass flow body of load metal lithium simultaneously, are favorable to improving the holistic energy density of lithium negative pole.
The conductive porous skeleton can be set into different shape structures according to requirements. In some embodiments, the conductive porous skeleton is a sheet structure, and the thickness of the conductive porous skeleton is 0.05-0.8 mm, and more preferably 0.3 mm.
The thickness of the conductive porous skeleton can be adaptively adjusted as required by those skilled in the art, and when the thickness of the conductive porous skeleton is too thin, a three-dimensional space for metal lithium deintercalation is difficult to form, and a large volume change rate is caused in the process of deintercalating metal lithium, thereby affecting the stability of an SEI film on the surface of an electrode.
In some embodiments, the thickness of the copper oxide layer is between 10 nm and 1000nm, and more preferably, the thickness of the copper oxide layer is between 10 nm and 500 nm.
When the thickness of the copper oxide layer is too thin, the improvement of the lithium affinity performance of the conductive porous framework is limited, and meanwhile, the preparation conditions are difficult to control; when the thickness of the copper oxide layer is too thick, the surface resistance of the conductive porous skeleton is increased, and the internal resistance of the lithium negative electrode is increased.
In some embodiments, the conductive porous framework has a pore volume in the range of 50% to 90%, more preferably a pore volume of 75%.
The pore volume range is a preferable range of the inventor, when the pore volume in the conductive porous framework is too small, the connectivity before each micropore is poor, the ionic conductivity is poor, and meanwhile, the supported metal lithium is less under the same volume, which is not beneficial to improving the capacity of the battery; when the pore volume of the conductive porous skeleton is too large, the strength of the conductive porous skeleton is affected.
In some embodiments, the pore size of the micropores is between 10 and 700 μm, and more preferably 300 μm.
Another embodiment of the present invention provides a method for preparing a porous current collector as described above, comprising the following steps:
electroplating: placing the conductive porous framework in a copper salt solution, and electroplating by taking the conductive porous framework as a cathode, wherein copper layers are formed on the surface of the conductive porous framework and the inner wall of each micropore;
and (3) heat treatment: and carrying out heat treatment on the conductive porous framework to oxidize the copper layer into copper oxide.
In the embodiment, the copper layers are formed on the inner surface and the outer surface of the conductive porous framework in an electroplating mode, compared with the modes of vapor deposition, plasma deposition and the like, the uniformity of the copper layers on the conductive porous framework can be ensured by adopting the electroplating mode, thereby improving the copper layer adhered on the inner wall of the micropores of the conductive porous framework, simultaneously the bonding strength of the copper layer formed by electroplating and the conductive porous framework is high, avoiding falling off, by oxidizing the copper layer into copper oxide, the affinity of the internal micropores of the conductive porous skeleton to the metallic lithium is improved, the nucleation overpotential of lithium deposition is reduced, the generation of lithium dendrites is inhibited, and the copper oxide layer increases the roughness of the surface of the micropores of the conductive porous framework, increases the specific surface area of the porous current collector, reduces the current density, further inhibits the generation of lithium dendrites, and improves the service life and the safety of the battery.
The preparation method provided by the invention has no special limitation on the material of the conductive porous framework, and is suitable for metal materials or non-metal conductive materials.
In some embodiments, prior to the "electroplating" operation, the conductive porous skeleton is subjected to a hydrochloric acid soaking treatment, and then the washed conductive porous skeleton is subjected to ultrasonic cleaning by an organic polar solvent, and vacuum drying is performed on the washed conductive porous skeleton.
Oxide on the conductive porous framework can be effectively removed and the surface of the conductive porous framework can be activated through hydrochloric acid soaking, if the conductive porous framework is made of a metal material, holes can be etched on the conductive porous framework through hydrochloric acid, and the bonding strength of a copper layer plated subsequently and the conductive porous framework is improved.
The organic polar solvent is used for removing oil stains on the surface of the conductive porous framework, and plays a role in promoting the dispersion of the oil stains through ultrasonic cleaning.
In some embodiments, the concentration of the hydrochloric acid is 0.1-1 mol/L, and the soaking time is 5-60 min; more preferably, the solution is soaked in 0.5mol/L hydrochloric acid for 30 min.
The organic polar solvent is acetone and/or ethanol, the cleaning frequency is 1-3 times, and the cleaning time is 5-30 min; the vacuum drying temperature is 50-80 ℃, and the time is 1-6 h. More preferably, the conductive porous framework is respectively washed twice by acetone and ethanol, the washing time is 20min, the vacuum drying temperature is 60 ℃, and the drying time is 4 h.
In some embodiments, the copper salt solution comprises a soluble copper salt and a non-strong oxidizing acid, wherein the concentration of the soluble copper salt is 0.01-1 mol/L, and the concentration of the non-strong oxidizing acid is 0.1-2 mol/L. More preferably, the concentration of the soluble copper salt is 0.1mol/L and the concentration of the non-strong oxidizing acid is 0.5mol/L
Non-strong oxidizing acids are capable of ionizing large amounts of H in said copper salt solutions+The method is favorable for remarkably reducing the resistance of the copper salt solution, increasing the conductivity of the solution, preventing the copper ions from hydrolyzing to form cuprous oxide and improving the electroplating effect.
In some embodiments, the soluble copper salt comprises CuSO4And CuCl2Including one or more of sulfuric acid and hydrochloric acid.
In some embodiments, the "electroplating" operation is performed under DC constant voltage conditions with a current density of 0.1-0.5A/dm2The electroplating time is 5-30 min. More preferably, the current density is 0.3A/dm2Electroplating time of 10min
The electroplating conditions are in the preferable range of the embodiment, and exceeding the preferable range can cause the copper layer to be too thin or too thick, which is not beneficial to the performance improvement of the porous current collector.
In some embodiments, after the "electroplating" operation, the conductive porous skeleton is washed to remove the copper salt solution attached to the conductive porous skeleton, and dried.
Specifically, the electroplated conductive porous framework is taken out, the conductive porous framework is washed twice by distilled water and ethanol respectively, and then the conductive porous framework is placed into an oven to be dried, wherein the drying temperature is 50-90 ℃, and the drying time is 2-12 hours. More preferably, the drying temperature is 60 ℃ and the drying time is 6 hours.
In some embodiments, the "heat treatment" operation is performed at a temperature of 200 to 450 ℃ for 0.5 to 5 hours. More preferably, the heat treatment temperature is 300 ℃ and the heat treatment time is 2 hours.
When the heat treatment time is too short or the heat treatment temperature is too low, the copper layer on the conductive porous skeleton is difficult to be completely oxidized into copper oxide; when the heat treatment time is too long or the heat treatment temperature is too high, the self material of the conductive porous framework is oxidized, and the internal resistance of the porous current collector is further improved.
Another embodiment of the present invention provides a lithium negative electrode including the porous current collector as described above and metallic lithium supported on the porous current collector.
The metal lithium is loaded on the porous current collector through a melting method, and the porous current collector has good lithium affinity and large specific surface area, so that the lithium cathode prepared by the porous current collector has the characteristics of high safety and long service life, and can be applied to a secondary battery to be used as a cathode.
Another embodiment of the present invention provides a lithium ion battery including a positive electrode, an electrolyte, and a lithium negative electrode as described above.
The lithium negative electrode of the lithium ion battery can be kept stable in the long-term charge and discharge process, lithium dendrites are avoided, and the lithium ion battery has good cycle stability and coulombic efficiency.
In other embodiments, the porous current collector may be used as a positive electrode of a battery as a support for a positive active material.
The present invention will be further illustrated by the following examples.
Example 1
This example is used to illustrate the porous current collector and the preparation method thereof disclosed in the present invention, and includes the following steps:
1) and (4) pretreating the conductive porous framework.
Selecting foamed nickel with proper specification as a conductive porous framework, wherein the pore volume is 75%, the pore diameter is 300 mu m, and the thickness is 0.3 mm. Soaking the foamed nickel in 0.5mol/L hydrochloric acid for 30min, then ultrasonically cleaning the foamed copper with acetone for 2 times for 20min, and finally drying the foamed nickel in vacuum at the drying temperature of 60 ℃ for 4 h.
2) And (5) carrying out surface copper plating treatment.
The electroplating solution is 0.1mol/LCuSO4，0.5mol/LH2SO4The mixed aqueous solution of (1). With titanium-platinum netThe anode is adopted, the conductive porous framework in the step 1) is adopted as the cathode, the two electrodes are respectively connected with a power supply and are placed in electroplating solution, the distance between the two electrodes is 30mm, electroplating is carried out under the constant current condition, and the current density is 0.3A/dm2The plating time was 10 min. After the treatment is finished, the foam nickel plated with copper on the surface is respectively cleaned for 2 times by distilled water and ethanol, and then the foam nickel is placed into a drying oven for drying at the drying temperature of 70 ℃ for 6 hours.
3) And (5) surface oxidation treatment.
And (3) putting the foamed nickel plated with copper on the surface in the step 2) into a muffle furnace for heat treatment at the temperature of 300 ℃ for 2h to obtain the porous current collector of the foamed nickel with the surface covered with copper oxide. Further observing the microstructure of the porous current collector through fig. 2, it is found that the surface of the nickel foam is covered by a coral-shaped copper oxide layer, and this modified layer not only improves the lithium affinity of the current collector, but also further improves the specific surface area of the porous current collector.
4) And assembling and testing the asymmetric battery.
And (2) assembling the button cell by taking the prepared porous current collector as a positive electrode and a lithium sheet as a negative electrode, wherein the diaphragm is a polypropylene microporous membrane, the electrolyte is a 1mol/L lithium bistrifluoromethanesulfonylimide (LiTFSI) solution as an electrolyte, the electrolyte solvent is a mixed system (volume ratio is 1:1) of 1, 3-Dioxolane (DOL) and ethylene glycol dimethyl ether (DME), and the additive is 0.1mol/L LiNO3. The coulomb efficiency of the battery is tested by using a blue charge-discharge test cabinet, and 0.5mA/cm is firstly used2Is discharged for 2h at a current density of 0.5mA/cm2And charging for 2h, and setting the upper limit of the charging voltage to be 1V. As shown in fig. 3, the coulombic efficiency of the battery reaches 99% or more after 10 cycles, and the coulombic efficiency of the battery still remains 98.5% or more after 200 cycles, showing excellent stability.
Example 2
This example is used to illustrate the porous current collector, the lithium negative electrode and the preparation method thereof disclosed in the present invention, and includes the following steps:
1) and (4) pretreating the conductive porous framework.
Selecting foamed nickel with proper specification as a conductive porous framework, wherein the pore volume is 75%, the pore diameter is 300 mu m, and the thickness is 0.3 mm. Soaking the foamed nickel in 0.5mol/L hydrochloric acid for 30min, then ultrasonically cleaning the foamed nickel with acetone for 2 times for 20min, and finally drying the foamed nickel in vacuum at the drying temperature of 60 ℃ for 4 h.
2) And (5) carrying out surface copper plating treatment.
The electroplating solution is 0.1mol/LCuSO4，0.5mol/LH2SO4The mixed aqueous solution of (1). Taking a titanium-platinum net as an anode and the conductive porous framework in the step 1) as a cathode, respectively connecting the two electrodes with a power supply, placing the two electrodes in electroplating solution with the distance of 30mm, and electroplating under the constant current condition with the current density of 0.3A/dm2The plating time was 10 min. After the treatment is finished, the foam nickel plated with copper on the surface is respectively cleaned for 2 times by distilled water and ethanol, and then the foam nickel is placed into a drying oven for drying at the drying temperature of 70 ℃ for 6 hours.
3) And (5) surface oxidation treatment.
And (3) putting the foamed nickel plated with copper on the surface in the step 2) into a muffle furnace for heat treatment at the temperature of 300 ℃ for 2h to obtain the porous current collector of the foamed nickel with the surface covered with copper oxide.
4) And (4) preparing a lithium negative electrode.
Transferring the prepared porous current collector into a glove box filled with argon, wherein the oxygen content of water in the glove box is 0.1 ppm; heating a certain amount of lithium metal in a container in a glove box to ensure that the lithium metal has certain fluidity, wherein the heating temperature is 300 ℃; clamping one end of the prepared porous current collector by using tweezers, enabling the other end of the prepared porous current collector to be in contact with molten metal lithium, enabling the molten metal lithium to be automatically adsorbed to the gaps and the surface of the porous current collector, controlling the contact time for 5s, and obtaining the porous current collector with the capacity density of 15mAh/cm2The lithium negative electrode of (1); and (3) cooling the metal lithium loaded on the porous current collector, and pressing the lithium negative electrode to the thickness of 0.4 mm.
5) And assembling and testing the symmetrical battery.
Assembling the prepared lithium cathode into a button-type symmetrical battery, wherein a diaphragm is a polypropylene microporous membrane, a lithium bistrifluoromethanesulfonylimide (LiTFSI) solution with an electrolyte of 1mol/L is used as the electrolyte, and a solvent of the electrolyte is used as a solvent of the electrolyteIs a mixed system of 1, 3-Dioxolane (DOL) and ethylene glycol dimethyl ether (DME) (the volume ratio is 1:1), and the additive is 0.1mol/L LiNO3. The blue charge-discharge test cabinet is utilized to carry out cycle performance test on the battery under different current densities, and the current densities are respectively 0.5mA/cm2，2mA/cm2And 5mA/cm2The circulation capacity is 1mAh/cm2. The test results are respectively shown in fig. 4-6, the symmetric battery always maintains a lower polarization voltage (the polarization voltage increases with the increase of the current density) in the cycle process, and a short circuit phenomenon caused by penetration of a lithium dendrite through the diaphragm does not occur, which indicates that the three-dimensional porous structure of the porous current collector and the surface copper oxide lithium-philic layer have the functions of guiding uniform deposition of lithium and inhibiting generation of the lithium dendrite.
Example 3
This example is used to illustrate the porous current collector and the preparation method thereof disclosed in the present invention, and includes the following steps:
1) and (4) pretreating the conductive porous framework.
Foamed aluminum with proper specification is selected as a conductive porous framework, the pore volume of the conductive porous framework is 50 percent, the pore diameter is 10 mu m, and the thickness is 0.05 mm. Soaking foamed aluminum in 0.1mol/L hydrochloric acid for 5min, ultrasonically cleaning foamed copper with ethanol for 1 time for 5min, and vacuum drying foamed aluminum at 50 deg.C for 6 h.
2) And (5) carrying out surface copper plating treatment.
The electroplating solution is 0.01mol/LCuCl20.1 mol/LHCl. Taking a titanium-platinum net as an anode and the conductive porous framework in the step 1) as a cathode, respectively connecting the two electrodes with a power supply, placing the two electrodes in electroplating solution with the distance of 30mm, and electroplating under the constant current condition with the current density of 0.1A/dm2The plating time was 5 min. After the treatment is finished, the foamed aluminum with copper plated on the surface is respectively cleaned for 1 time by distilled water and ethanol, and then the foamed aluminum is placed into a drying oven for drying, wherein the drying temperature is 60 ℃, and the drying time is 12 hours.
3) And (5) surface oxidation treatment.
And (3) putting the foamed aluminum plated with copper on the surface in the step 2) into a muffle furnace for heat treatment at the temperature of 200 ℃ for 5 hours to obtain the porous current collector of the foamed aluminum with the surface covered with copper oxide.
Example 4
This example is used to illustrate the porous current collector and the preparation method thereof disclosed in the present invention, and includes the following steps:
1) and (4) pretreating the conductive porous framework.
Selecting carbon fiber cloth with proper specification as a conductive porous framework, wherein the pore volume is 90%, the pore diameter is 700 mu m, and the thickness is 0.8 mm. Soaking the carbon fiber cloth with 1mol/L hydrochloric acid for 60min, then ultrasonically cleaning the carbon fiber cloth with acetone or ethanol for 3 times for 30min, and finally drying the carbon fiber cloth in vacuum at the drying temperature of 80 ℃ for 1 h.
2) And (5) carrying out surface copper plating treatment.
The electroplating solution is 1mol/LCuSO4，2mol/LH2SO4The mixed aqueous solution of (1). Taking a titanium-platinum net as an anode and the conductive porous framework in the step 1) as a cathode, respectively connecting the two electrodes with a power supply, placing the two electrodes in electroplating solution with the distance of 30mm, and electroplating under the constant current condition with the current density of 0.5A/dm2The plating time was 30 min. After the treatment is finished, the carbon fiber cloth with the copper plated surface is respectively washed for 4 times by distilled water and ethanol, and then is put into a drying oven for drying, wherein the drying temperature is 90 ℃, and the drying time is 2 hours.
3) And (5) surface oxidation treatment.
And (3) putting the carbon fiber cloth plated with copper on the surface in the step 2) into a muffle furnace for heat treatment at the temperature of 450 ℃ for 0.5h to obtain the porous current collector of the carbon fiber cloth covered with copper oxide on the surface.
Comparative example 1
The comparative example is used for comparative illustration of the porous current collector, the lithium negative electrode and the preparation method thereof disclosed by the invention, and comprises the following operation steps:
1) and (4) pretreating the conductive porous framework.
Selecting foamed nickel with proper specification as a conductive porous framework, wherein the pore volume is 75%, the pore diameter is 300 mu m, and the thickness is 0.3 mm. Soaking the foamed nickel in 0.5mol/L hydrochloric acid for 30min, then ultrasonically cleaning the foamed nickel with acetone for 2 times, wherein the time is 20min, and finally, drying the foamed nickel in vacuum at the drying temperature of 60 ℃ for 4h to obtain the porous current collector.
2) And assembling and testing the asymmetric battery.
And (2) assembling the button cell by taking the prepared porous current collector as a positive electrode and a lithium sheet as a negative electrode, wherein the diaphragm is a polypropylene microporous membrane, the electrolyte is a 1mol/L lithium bistrifluoromethanesulfonylimide (LiTFSI) solution as an electrolyte, the electrolyte solvent is a mixed system (volume ratio is 1:1) of 1, 3-Dioxolane (DOL) and ethylene glycol dimethyl ether (DME), and the additive is 0.1mol/L LiNO3. The coulomb efficiency of the battery is tested by using a blue charge-discharge test cabinet, and 0.5mA/cm is firstly used2Is discharged for 2h at a current density of 0.5mA/cm2And charging for 2h, and setting the upper limit of the charging voltage to be 1V. As shown in fig. 7, after the battery is cycled for 10 cycles, the coulombic efficiency can only reach 97.5%, and shows a fluctuation sign along with the increase of the cycle number, which shows that the copper oxide layer on the surface of the conductive porous skeleton in example 1 can reduce the nucleation barrier of lithium metal and improve the charging and discharging efficiency of the battery.
According to the test results of the embodiment and the comparative example, the porous current collector provided by the invention has good metal lithium affinity, and can be used as the current collector of a lithium cathode to effectively reduce the probability of generation of lithium dendrites and reduce the polarization voltage, so that the cycle performance of the lithium ion battery is effectively improved, the service life of the lithium ion battery is prolonged, and the safety performance is improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (16)

1. The porous current collector is characterized by comprising a conductive porous framework, wherein a plurality of micropores are formed inside the conductive porous framework, and copper oxide layers are formed on the surface of the conductive porous framework and the inner walls of the micropores.
2. The porous current collector of claim 1, wherein the electrically conductive porous skeleton comprises one or more of nickel foam, aluminum foam, and carbon fiber cloth.
3. The porous current collector of claim 1, wherein the conductive porous skeleton is a sheet structure, and the thickness of the conductive porous skeleton is 0.05-0.8 mm.
4. The porous current collector of claim 1, wherein the copper oxide layer has a thickness of between 10 nm and 1000 nm.
5. The porous current collector of claim 1, wherein the pore volume in the electrically conductive porous framework is from 50% to 90%.
6. The porous current collector of claim 1, wherein the pores have a diameter of 10-700 μm.
7. The method for preparing a porous current collector according to any one of claims 1 to 6, comprising the following operating steps:
electroplating: placing the conductive porous framework in a copper salt solution, and electroplating by taking the conductive porous framework as a cathode, wherein copper layers are formed on the surface of the conductive porous framework and the inner wall of each micropore;
and (3) heat treatment: and carrying out heat treatment on the conductive porous framework to oxidize the copper layer into copper oxide.
8. The method for preparing the porous current collector of claim 7, wherein before the electroplating operation, the conductive porous framework is subjected to hydrochloric acid soaking treatment, then the conductive porous framework is subjected to ultrasonic cleaning by an organic polar solvent, and the cleaned conductive porous framework is dried in vacuum.
9. The method for preparing the porous current collector of claim 8, wherein the concentration of the hydrochloric acid is 0.1-1 mol/L, and the soaking time is 5-60 min; the organic polar solvent is acetone and/or ethanol, the cleaning frequency is 1-3 times, and the cleaning time is 5-30 min; the vacuum drying temperature is 50-80 ℃, and the time is 1-6 h.
10. The method for preparing the porous current collector of claim 7, wherein the copper salt solution comprises a soluble copper salt and a non-strong oxidizing acid, the concentration of the soluble copper salt is 0.01-1 mol/L, and the concentration of the non-strong oxidizing acid is 0.1-2 mol/L.
11. The method of preparing the porous current collector of claim 10, wherein the soluble copper salt comprises CuSO4And CuCl2Including one or more of sulfuric acid and hydrochloric acid.
12. The method for preparing a porous current collector according to claim 7, wherein the electroplating is performed under a DC constant voltage condition in the electroplating operation, and the current density is 0.1-0.5A/dm2The electroplating time is 5-30 min.
13. The method for preparing a porous current collector according to claim 7, wherein the "electroplating" operation is followed by washing the conductive porous skeleton and drying.
14. The method for preparing the porous current collector of claim 7, wherein in the heat treatment operation, the heat treatment temperature is 200 to 450 ℃ and the heat treatment time is 0.5 to 5 hours.
15. A lithium negative electrode comprising the porous current collector according to any one of claims 1 to 6 and metallic lithium supported on the porous current collector.
16. A lithium ion battery comprising a positive electrode, an electrolyte, and the lithium negative electrode of claim 15.
CN201910815224.0A 2019-08-30 2019-08-30 Porous current collector and preparation method thereof, lithium negative electrode and lithium ion battery Pending CN112447979A (en)

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