Modified current collector for cathode-free metal battery as well as preparation method and application of modified current collector

Abstract

The invention relates to a modified current collector for a cathode-free metal battery and a preparation method and application thereof.The preparation method comprises the steps that an in-situ modification reaction is conducted on the surface of a copper current collector to obtain a current collector coated with a copper oxide nanometer material, and then selenium is introduced to the surface of the current collector coated with the copper oxide nanometer material through a partial in-situ substitution reaction to obtain the modified current collector coated with the copper oxide nanometer material. The preparation method comprises the following steps: preparing a copper selenide and copper oxide composite modified current collector, performing in-situ lithiation reaction through electrochemical deposition, and partially converting to generate corresponding lithiates, thereby obtaining the modified current collector for the non-anode metal battery. According to the invention, the functional artificial interface layer with lithium affinity, high stability and high ionic conductivity is constructed on the surface of the copper-based current collector in situ, so that the key problems of uneven metal deposition and unstable SEI layer on the surface of the negative electrode current collector in the current research of the metal secondary battery without the negative electrode are solved, the formation of dendritic crystals and the occurrence of side reactions are inhibited, and the service life of the metal secondary battery is prolonged. Therefore, the coulombic efficiency, the safety and the cycle life of the battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery negative electrode current collector materials, and in particular to a modified current collector for a negative electrode-free metal battery, and a preparation method and application thereof. Background Art

[0002] The development of lithium secondary batteries has strongly promoted the rapid transformation of global energy, playing a significant role in the fields of mobile phones, computers and new energy vehicles. However, due to the limitations of graphite anodes, which have reached their theoretical specific capacity, it has been difficult to increase the energy density of commercial lithium-ion secondary batteries. Battery technologies such as lithium-ion batteries (silicon-based anodes), solid-state batteries and lithium metal batteries have high theoretical energy densities and have become the hottest research areas for high-energy-density batteries. Constructing a new energy storage innovation system is essentially a breakthrough in high-energy-density energy storage systems and has become the core proposition for breaking through the bottleneck of the new energy industry.

[0003] Taking the negative electrode-free lithium metal battery as an example, this battery system abandons negative electrodes such as graphite, silicon and metallic lithium. The negative electrode-free design can maximize the proportion of active materials, and the theoretical energy density is as high as 423Whkg -1 and 1514WhL -1 , far exceeding the development plan and development needs of the lithium battery new energy industry. At the same time, it is highly compatible with existing lithium-ion battery production lines, saving more than 30% of the cost of negative electrode materials. At present, the negative electrode current collector of lithium secondary batteries is mainly copper foil. During the charging process, the poor binding energy between lithium and copper leads to two problems: (1) The lithium deposition overpotential on the surface of the copper current collector is high, inducing the growth of lithium dendrites and the accumulation of "dead lithium", leading to the risk of battery short circuit; (2) The solid electrolyte interface film (SEI layer) is easy to rupture and reorganize during the cycle, causing irreversible loss of active lithium, which seriously restricts the coulombic efficiency (<95%) and cycle life (<50 times).

[0004] In response to the problem of uneven deposition and stripping of lithium on the surface of copper foil current collector in anode-free lithium metal battery systems, research on the modification of copper foil current collectors has received widespread attention. It mainly includes two aspects: (1) improving the lithium affinity of the current collector, reducing the nucleation barrier of lithium on the surface of copper foil current collector, and promoting lithium deposition; (2) improving the stability of the SEI layer, mainly by increasing the inorganic components in the SEI components or designing an artificial SEI layer, improving the mechanical strength and ionic conductivity of the SEI layer, and ensuring the rapid transmission of lithium ions. Lithium-philic materials include gold, silver, and zinc oxide; high ionic conductivity materials mainly include lithium sulfide and lithium selenide. The introduction of these materials can alleviate the problem of undesirable lithium deposition on the surface of copper foil current collector in anode-free lithium metal batteries to a certain extent.

[0005] Introducing a functionalized artificial interface layer on the surface of the copper foil current collector is an effective method to improve the electrochemical performance of anode-free lithium metal batteries. However, high ionic conductivity interface layers, such as lithium sulfide and lithium selenide, have multi-component lithium-sulfur and lithium-selenium bonds that are easily broken, resulting in rapid failure during long-cycle charge and discharge, which is not conducive to the stable cycle of the battery. As for the research on lithiophilic interfaces, the overall ionic conductivity is low, which is not conducive to the rapid transport of lithium ions. Therefore, designing a multifunctional artificial interface layer with high ionic conductivity, lithiophilicity and cycle stability still faces huge challenges, and it also plays a vital role in the development of new high-energy-density anode-free lithium metal batteries. Summary of the Invention

[0006] To solve the above problems, the purpose of the present invention is to provide a modified current collector for a negative electrode metal-free battery and its preparation method and application. The modified current collector is a composite current collector modified with a multifunctional artificial interface layer.

[0007] The present invention provides a method for preparing a modified current collector for a negative electrode metal-free battery, which specifically comprises the following steps:

[0008] (1) Pre-treating the copper current collector;

[0009] (2) performing an in-situ modification reaction on the surface of the copper current collector obtained by pretreatment in step (1) to obtain a current collector coated with copper oxide (CuO or Cu2O) nanomaterial (i.e., a partially oxidized copper current collector);

[0010] (3) introducing selenium into the surface of the current collector coated with the copper oxide nanomaterial obtained in step (2), and subjecting it to an in-situ chemical reaction to obtain a modified current collector having a composite of copper selenide and copper oxide;

[0011] (4) The modified current collector composed of copper selenide and copper oxide obtained in step (3) is subjected to an in-situ lithiation reaction by electrochemical deposition to generate a corresponding lithium compound, thereby obtaining a modified current collector for a negative electrode metal-free battery.

[0012] Furthermore, in step (1), the copper current collector is one of copper foil, copper mesh and copper foam;

[0013] Furthermore, the pretreatment in step (1) specifically refers to first immersing the copper current collector in dilute hydrochloric acid and performing ultrasonic treatment, then washing it with anhydrous ethanol, and then drying it.

[0014] Furthermore, the in-situ modification in step (2) includes one of aqueous solution method, solvent thermal, electrochemistry, air oxidation, magnetron sputtering, and chemical vapor deposition.

[0015] Furthermore, in step (2), air oxidation is used to perform an in-situ modification reaction on the surface of the copper current collector to generate copper oxide nanomaterials. Specifically, the copper current collector is placed in a muffle furnace, and the heating rate is set to 1 to 10°C / min, more preferably 2°C / min; the reaction temperature is 100°C to 500°C, more preferably 300°C; the reaction time is 1 min to 120 min, more preferably 30 min, and after the reaction is completed, the reaction is naturally cooled to room temperature to obtain the copper oxide nanomaterial.

[0016] Furthermore, the in-situ chemical reaction in step (3) includes one of hydrothermal method, solvothermal method, electrochemistry, and chemical vapor deposition.

[0017] Furthermore, in step (3), a hydrothermal method is used to introduce selenium by in-situ chemical reaction on the surface of the current collector coated with the copper oxide nanomaterial. Specifically, sodium borohydride is first dissolved in 2 mL of deionized water, stirred, and allowed to stand for 2 minutes, then a selenium source is added, stirred until the solution becomes colorless, and finally 28 mL of deionized water is added. The resulting solution is transferred to a reactor, and the current collector coated with the copper oxide nanomaterial obtained in step (2) is placed in the reactor. The reactor is then placed in a thermostat for hydrothermal reaction at a reaction temperature of 60° C. to 200° C., more preferably 120° C., and a reaction time of 1 hour to 12 hours, more preferably 6 hours. After the hydrothermal reaction is completed, a modified current collector having a composite of copper selenide and copper oxide (i.e., a partially selenized and oxidized modified current collector) is obtained, which is dried and set aside.

[0018] Furthermore, the selenium source in step (3) includes one or more selenates such as selenium powder, sodium selenate, and sodium selenite, more preferably selenium powder;

[0019] Furthermore, in step (3), chemical vapor deposition is used to introduce selenium by in-situ chemical reaction on the surface of the current collector coated with copper oxide nanomaterials. Specifically, the selenium powder is evenly spread on the bottom of a porcelain boat, and the current collector coated with copper oxide nanomaterials obtained in step (2) is placed in the porcelain boat. The porcelain boat is then transferred to a chemical vapor deposition tube furnace. Before heating, the air in the tube furnace is extracted by a vacuum pump and an inert gas argon or nitrogen is introduced, with the argon or nitrogen flow rate controlled at 20 sccm / min. The heating parameters are: heating rate of 2°C / min, reaction temperature of 250°C, and reaction time of 10 minutes. After the reaction is completed, a modified current collector composed of copper selenide and copper oxide is obtained, which is placed in a vacuum drying oven for drying.

[0020] Furthermore, in step (3), the molar ratio of the selenium source to the copper oxide nanomaterial coated current collector is 1:99-99:1, preferably 1:30.

[0021] Furthermore, the specific process of in-situ lithiation by electrochemical deposition in step (4) includes: using the modified current collector of copper selenide and copper oxide obtained in step (3) as the positive electrode, the metal lithium sheet as the negative electrode, assembling the battery in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell, and performing charge and discharge lithiation treatment after assembly. The charge and discharge process is as follows: setting the discharge current density to 0.1-1 mA / cm 2 , preferably 0.1 mA / cm 2 , the cut-off voltage is 0V; after completion, continue to 2 The current density is discharged, and the discharge time is 1min-60min, preferably 5min. After the discharge is completed, the current density is 0.1mA / cm 2 The current density is set to 1V, and the cut-off voltage is set to 1V to complete the entire electrochemical deposition in-situ lithiation reaction process.

[0022] Furthermore, the battery assembly operation in step (4) is performed in a glove box filled with argon.

[0023] Furthermore, the separator in step (4) is Celgard 2400, and the formula of the electrolyte used in the battery is: the concentration is 1 mol / L, the electrolyte is lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), the solvent is 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME is 1:1, LiNO3 is used as an additive, and the mass content of LiNO3 in the electrolyte solution is 1%.

[0024] Furthermore, the metal lithium sheet negative electrode used in the assembled battery in step (4) is replaced with one of the negative electrode materials of K, Na, Zn, Ca, and Mg, which can achieve the corresponding potassium, sodium, zinc, calcium, and magnesium conversion reactions.

[0025] The present invention also provides a modified current collector obtained according to the above preparation method and the use of the modified current collector in a negative electrode-free metal battery (the negative electrode-free metal includes one of a negative electrode-free lithium battery, a negative electrode-free potassium battery, a negative electrode-free sodium battery, a negative electrode-free zinc battery, a negative electrode-free calcium battery, and a negative electrode-free magnesium battery).

[0026] The present invention solves the key problems of uneven metal deposition and unstable SEI layer on the surface of negative electrode current collector in current research on negative electrode metal-free secondary batteries by in-situ constructing a functional artificial interface layer with lithium affinity, high stability and high ionic conductivity on the surface of copper current collector, inhibiting the formation of dendrites and the occurrence of side reactions, thereby improving the coulombic efficiency, safety and cycle life of the battery.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention adopts a composite current collector covered with an artificial interface layer of a multifunctional component, which not only solves the problem of difficult deposition caused by the weak binding energy between lithium and copper, but also introduces a heterogeneous interface layer with high stability and high ionic conductivity to promote the rapid transmission of lithium ions, thereby synergistically solving the two key problems of uneven lithium deposition and unstable SEI layer.

[0029] (2) The raw materials of the present invention are widely available and inexpensive. In addition, the preparation process is relatively simple and has great potential for industrial application.

[0030] (3) The preparation of a modified negative electrode current collector for a negative electrode-free lithium metal battery provided by the present invention can also be applied to the research and application of various current negative electrode-free metal secondary batteries (Na, Zn, K, Mg, etc.), solving the key problems of uneven metal deposition and unstable SEI layer in the current research of various negative electrode-free metal secondary batteries, thereby inhibiting the formation of dendrites and the occurrence of side reactions, thereby improving the coulombic efficiency, safety and cycle life of the battery. Various negative electrode current collectors derived from this, as well as their application in the construction of high-safety, long-life, high-energy-density metal secondary batteries, are all within the scope of protection of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a scanning electron microscope image of the modified current collector obtained in step (4) of Example 1;

[0032] Figure 2 is a scanning electron microscope image of the modified current collector obtained in step (4) of Example 2;

[0033] Figure 3 This is a scanning electron microscope image of the modified current collector obtained in step (3) of Comparative Example 2;

[0034] Figure 4 This is a scanning electron microscope image of the modified current collector obtained in step (3) of Comparative Example 3;

[0035] Figure 5 Graph showing the capacity retention of negative electrode-free lithium metal full batteries assembled with the modified current collectors obtained in Example 1 and Example 2;

[0036] Figure 6 Graph showing the capacity retention of negative electrode-free lithium metal full batteries assembled with the modified current collectors obtained in Comparative Example 1, Comparative Example 2, and Comparative Example 3;

[0037] Figure 7 Graph showing the capacity retention of negative electrode-free lithium metal full batteries assembled with the modified current collectors obtained in Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0038] In order to better understand the content of the present invention, the present invention will be further described below in conjunction with specific examples and drawings. The following examples are implemented based on the technology of the present invention and provide detailed implementation methods and operating steps, but the scope of protection of the present invention is not limited to the following examples.

[0039] Example 1:

[0040] (1) A 200-mesh copper mesh with dimensions of 40 mm * 200 mm * 0.1 mm (length * width * thickness) was immersed in 0.1 mol / L dilute hydrochloric acid and ultrasonically treated for 10 min; then, it was washed three times with anhydrous ethanol; and then, it was placed in a vacuum drying oven for drying and used for later use;

[0041] (2) placing the copper mesh obtained in step (1) in a muffle furnace, setting the reaction temperature to 300° C., the heating rate to 2° C. / min, the reaction time to 1 h, and naturally cooling to room temperature after the reaction to obtain a partially oxidized copper mesh;

[0042] (3) 50 mg of sodium borohydride was dissolved in 2 mL of deionized water, stirred, and allowed to stand for 2 min, followed by the addition of 20 mg of selenium powder, and the stirring was continued until the solution was colorless. Finally, 28 mL of deionized water was added, and the above solution was transferred to a reactor. The partially oxidized copper mesh obtained in step (2) was then placed in the above reactor (i.e., the molar ratio of selenium powder to partially oxidized copper mesh in this embodiment was 1:30), and the reactor was placed in a thermostat for hydrothermal reaction. The reaction temperature was set to 120 ° C, and the reaction time was 6 h. After the hydrothermal reaction was completed, a partially selenized and oxidized modified copper mesh was obtained, which was placed in a vacuum drying oven for drying.

[0043] (4) The modified copper mesh obtained in step (3) was used as the positive electrode and the lithium sheet was used as the negative electrode. The battery was assembled in a glove box filled with argon in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell. The battery separator was Celgard 2400. The formula of the electrolyte was as follows: the electrolyte was lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a concentration of 1 mol / L, LiNO3 was used as an additive, wherein the mass content of LiNO3 in the electrolyte solution was 1%, and the solvent was 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME was 1:1; then, with the help of CT3001A equipment produced by Wuhan Landian Electronics Co., Ltd., the discharge current density was set to 0.1 mA / cm 2 First, the discharge cut-off voltage is 0V, and then the discharge voltage is 0.1mA / cm 2 The current density is discharged, and the discharge time is 5min. After the discharge is completed, the charging current density is set to 0.1mA / cm 2, and set the cutoff voltage to 1 V. After the program is completed, a lithiated modified copper mesh is obtained, and the lithiated modified copper mesh is a modified current collector for a negative electrode metal-free battery.

[0044] Example 2:

[0045] (1) A 200-mesh copper mesh with dimensions of 40 mm * 200 mm * 0.1 mm (length * width * thickness) was immersed in 0.1 mol / L dilute hydrochloric acid and ultrasonically treated for 10 min. The mesh was then washed three times with anhydrous ethanol and dried in a vacuum drying oven for later use.

[0046] (2) placing the copper mesh obtained in step (1) in a muffle furnace, setting the reaction temperature to 300° C., the heating rate to 2° C. / min, the reaction time to 1 h, and naturally cooling to room temperature after the reaction to obtain a partially oxidized copper mesh;

[0047] (3) Weigh 20 mg of selenium powder and spread it evenly on the bottom of a porcelain boat. Then, place the partially oxidized copper mesh obtained in step (2) in the porcelain boat (i.e., the copper mesh is located on top of the selenium powder. In this embodiment, the molar ratio of selenium powder to partially oxidized copper mesh is 1:30). Then, transfer the porcelain boat to a chemical vapor deposition tube furnace. Before heating, the air in the tube furnace is evacuated by a vacuum pump and inert argon gas is introduced. The argon flow rate is controlled at 20 sccm / min. The heating parameters are: heating rate of 2°C / min, reaction temperature of 250°C, and reaction time of 10 min. After the reaction is completed, a partially selenized and oxidized modified copper mesh is obtained, which is placed in a vacuum drying oven for drying.

[0048] (4) The modified copper mesh obtained in step (3) was used as the positive electrode, and the lithium sheet was used as the negative electrode. The battery was assembled in an argon-filled glove box in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell. The battery separator was Celgard 2400. The formula of the electrolyte was as follows: the electrolyte was lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a concentration of 1 mol / L, LiNO3 was used as an additive, wherein the mass content of LiNO3 in the electrolyte solution was 1%, and the solvent was 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME was 1:1; then, with the help of CT3001A equipment produced by Wuhan Blue Electric Electronics Co., Ltd., the discharge current density was set to 0.1 mA / cm 2 First, the discharge cut-off voltage is 0V, and then the discharge voltage is 0.1mA / cm 2 The current density is discharged, and the discharge time is 5min. After the discharge is completed, the charging current density is set to 0.1mA / cm 2 , and set the cutoff voltage to 1 V. After the program is completed, a lithiated modified copper mesh is obtained, and the lithiated modified copper mesh is a modified current collector for a negative electrode metal-free battery.

[0049] Example 3:

[0050] (1) A copper foil with a size of 40 mm * 200 mm * 0.01 mm (length * width * thickness) was immersed in 0.1 mol / L dilute hydrochloric acid and ultrasonically treated for 5 min; then, it was washed with anhydrous ethanol three times; and then, it was placed in a vacuum drying oven for drying and used for standby use;

[0051] (2) placing the copper foil obtained in step (1) in a muffle furnace, setting the reaction temperature to 250° C., the heating rate to 2° C. / min, the reaction time to 1 h, and naturally cooling to room temperature after the reaction to obtain a partially oxidized copper foil;

[0052] (3) Dissolve 10 mg of sodium borohydride in 2 mL of deionized water, stir, and let stand for 2 minutes, then add 5 mg of selenium powder, stir until the solution becomes colorless, and finally add 28 mL of deionized water. Transfer the above solution to a reactor, then put the partially oxidized copper foil obtained in step (2) into the above reactor (that is, the molar ratio of selenium powder to partially oxidized copper mesh in this embodiment is 1:30), and then put the reactor into a constant temperature box for hydrothermal reaction. Set the reaction temperature to 150°C and the reaction time to 2 hours. After the hydrothermal reaction is completed, a partially selenized and oxidized modified copper foil is obtained, which is placed in a vacuum drying oven for drying.

[0053] (4) The modified copper foil obtained in step (3) is used as the positive electrode, and the lithium sheet is used as the negative electrode. The battery is assembled in a glove box filled with argon in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell. The battery separator is Celgard 2400, and the formula of the electrolyte is as follows: the electrolyte is lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a concentration of 1 mol / L, LiNO3 is used as an additive, wherein the mass content of LiNO3 in the electrolyte solution is 1%, and the solvent is 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME is 1:1; then, with the help of CT3001A equipment produced by Wuhan Landian Electronics Co., Ltd., the discharge current density is set to 0.1 mA / cm 2 First, the discharge cut-off voltage is 0V, and then the discharge voltage is 0.1mA / cm 2 The current density is discharged, and the discharge time is 5min. After the discharge is completed, the charging current density is set to 0.1mA / cm 2 , set the cutoff voltage to 1V, and after the program is completed, a lithiated modified copper foil is obtained. The lithiated modified copper foil is a modified current collector for a negative electrode metal-free battery.

[0054] Comparative Example 1:

[0055] (1) A copper foil with a size of 40 mm * 200 mm * 0.01 mm (length * width * thickness) was immersed in 0.1 mol / L dilute hydrochloric acid and ultrasonically treated for 5 min; then, it was washed with anhydrous ethanol three times; and then, it was placed in a vacuum drying oven for drying and used for standby use;

[0056] (2) The copper foil obtained in step (1) is used as the positive electrode, and the lithium sheet is used as the negative electrode. The battery is assembled in a glove box filled with argon in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell. The battery separator is Celgard2400, and the formula of the electrolyte is as follows: the electrolyte is lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a concentration of 1 mol / L, LiNO3 is used as an additive, wherein the mass content of LiNO3 in the electrolyte solution is 1%, and the solvent is 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME is 1:1; then, with the help of CT3001A equipment produced by Wuhan Landian Electronics Co., Ltd., the discharge current density is set to 0.1 mA / cm 2 First, the discharge cut-off voltage is 0V, and then the discharge voltage is 0.1mA / cm 2 The current density is discharged, and the discharge time is 5min. After the discharge is completed, the charging current density is set to 0.1mA / cm 2 , set the cutoff voltage to 1V, and after the program is completed, a lithiated copper foil is obtained, which is a modified current collector.

[0057] Comparative Example 2:

[0058] (1) A copper foil with a size of 40 mm * 200 mm * 0.01 mm (length * width * thickness) was immersed in 0.1 mol / L dilute hydrochloric acid and ultrasonically treated for 5 min; then, it was washed with anhydrous ethanol three times; and then, it was placed in a vacuum drying oven for drying and used for standby use;

[0059] (2) placing the copper foil obtained in step (1) in a muffle furnace, setting the reaction temperature to 250° C., the heating rate to 2° C. / min, the reaction time to 1 h, and naturally cooling to room temperature after the reaction to obtain a partially oxidized copper foil;

[0060] (3) The partially oxidized copper foil obtained in step (2) was used as the positive electrode, and the lithium sheet was used as the negative electrode. The battery was assembled in an argon-filled glove box in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell. The battery separator was Celgard 2400. The formula of the electrolyte was as follows: the electrolyte was lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a concentration of 1 mol / L, LiNO3 was used as an additive, wherein the mass content of LiNO3 in the electrolyte solution was 1%, and the solvent was 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME was 1:1. Then, with the help of CT3001A equipment produced by Wuhan Landian Electronics Co., Ltd., the discharge current density was set to 0.1 mA / cm 2 First, the discharge cut-off voltage is 0V, and then the discharge voltage is 0.1mA / cm 2 The current density is discharged, and the discharge time is 5min. After the discharge is completed, the charging current density is set to 0.1mA / cm 2 , the cutoff voltage is set to 1V. After the program is completed, a lithiated modified copper foil is obtained, and the lithiated modified copper foil is a modified current collector.

[0061] Comparative Example 3:

[0062] (1) A copper foil with a size of 40 mm * 200 mm * 0.01 mm (length * width * thickness) was immersed in 0.1 mol / L dilute hydrochloric acid and ultrasonically treated for 5 min; then, it was washed with anhydrous ethanol three times; and then, it was placed in a vacuum drying oven for drying and used for standby use;

[0063] (2) 50 mg of sodium borohydride was dissolved in 2 mL of deionized water, stirred, and allowed to stand for 2 min, followed by the addition of 20 mg of selenium powder, which was stirred until the solution became colorless. Finally, 28 mL of deionized water was added, and the above solution was transferred to a reactor. The copper foil obtained in step (1) was then placed in the reactor (i.e., the molar ratio of selenium powder to partially oxidized copper mesh in this comparative example was 1:30). The reactor was then placed in a thermostat for hydrothermal reaction, with the reaction temperature set at 120° C. and the reaction time set at 6 h. After the hydrothermal reaction, the partially selenized modified copper foil was placed in a vacuum drying oven for drying.

[0064] (3) The modified copper foil obtained in step (2) is used as the positive electrode, and the lithium sheet is used as the negative electrode. The battery is assembled in a glove box filled with argon in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell. The battery separator is Celgard 2400. The formula of the electrolyte is: the electrolyte is lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a concentration of 1 mol / L, LiNO3 is used as an additive, wherein the mass content of LiNO3 in the electrolyte solution is 1%, and the solvent is 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME is 1:1. Then, with the help of CT3001A equipment produced by Wuhan Landian Electronics Co., Ltd., the discharge current density is set to 0.1 mA / cm 2 First, the discharge cut-off voltage is 0V, and then the discharge voltage is 0.1mA / cm 2 The current density is discharged, and the discharge time is 5min. After the discharge is completed, the charging current density is set to 0.1mA / cm 2 , the cutoff voltage is set to 1V. After the program is completed, a lithiated modified copper foil is obtained, and the lithiated modified copper foil is a modified current collector.

[0065] The modified current collectors prepared in Examples 1-3 and Comparative Examples 1-3 were respectively subjected to performance tests: a full lithium metal battery without a negative electrode was assembled: a commercial LiFeO4 electrode was used as the positive electrode, the separator was Celgard2400, the modified current collector was used as the counter electrode, and 1MLiTFSI (DOL:DME=1:1) + 1%LiNO3 was used as the electrolyte (i.e., the formula of the electrolyte was: the electrolyte was lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a concentration of 1 mol / L, LiNO3 was used as an additive, and the mass content of LiNO3 in the electrolyte solution was 1%, and the solvent was 1,3-dioxolane (DOL) / ethylene glycol dimethyl ether (DME), wherein the volume ratio of DOL to DME was 1:1). The charge and discharge cycle performance test was carried out at room temperature at a rate of 0.2C. The test results are shown in Table 1.

[0066] Table 1

[0067] Capacity retention rate after 20 cycles Capacity retention rate after 50 cycles Capacity retention rate after 100 cycles Example 1 98.1％ 95％ 85.2％ Example 2 98.3％ 95.6％ 88.7％ Example 3 97.5％ 94.1％ 83.5％ Comparative Example 1 15.8％ / / Comparative Example 2 42.5％ 15.6％ / Comparative Example 3 46.5％ 19.1％ /

[0068] As shown in Table 1, the copper current collectors that underwent a single-step oxidation or selenization treatment (Comparative Examples 2 and 3) exhibited improved electrochemical performance compared to the unmodified copper current collector in Comparative Example 1. Furthermore, the copper current collectors that underwent sequential partial oxidation and selenization (Examples 1-3) exhibited significant improvements in the performance of anode-free lithium metal batteries. Among them, Example 2 exhibited the best electrochemical performance. Therefore, this type of modified current collector can effectively improve the performance of anode-free lithium metal batteries.

[0069] Figure 13 is a scanning electron microscope image of the modified current collector obtained in Example 1. It can be seen from the image that the surface of the modified current collector is composed of nanoparticles with a diameter of about 200 nm. Figure 2 3 is a scanning electron microscope image of the modified current collector obtained in Example 2. It can be seen from the image that the surface of the modified current collector is composed of a nanosheet structure with a thickness of about 50 nm. Figure 3 This is a scanning electron microscope image of the modified current collector obtained in Comparative Example 2. It can be seen from the image that the surface of the modified current collector is composed of uneven nanomaterials. Figure 4 This is a scanning electron microscope image of the modified current collector obtained in Example 3. Figure 4 It can be seen that the surface of the modified current collector is composed of uneven nanosheet-like structured materials.

[0070] Figure 5 It is a capacity retention rate diagram of the negative electrode-free lithium metal full battery assembled with the modified current collectors obtained in Example 1 and Example 2. It can be seen that after 100 cycles of Example 2, the capacity retention rate is as high as 88.7%; after 100 cycles of Example 1, the capacity retention rate is 85.2%.

[0071] Figure 6 This is a capacity retention rate diagram of the negative electrode-free lithium metal full battery assembled with the modified current collectors obtained in Examples 1, 2 and 3. It can be seen that after 20 cycles of Comparative Example 1, the capacity retention rate is only 15.8%; after 20 cycles of Comparative Example 2, the capacity retention rate is only 42.5%, and after 50 cycles, the capacity retention rate is only 15.6%; after 20 cycles of Comparative Example 3, the capacity retention rate is only 46.5%, and after 50 cycles, the capacity retention rate is only 19.1%, and Comparative Examples 1-3 cannot be cycled for more than 100 cycles before the battery fails.

[0072] Figure 7 The capacity retention rate diagram of the negative electrode-free lithium metal full battery assembled with the modified current collectors obtained in Example 2 and Comparative Example 1 respectively shows that the battery cycle life and capacity retention rate of Example 2 are greatly improved compared with those of Comparative Example 1. The cycle life is increased from 20 cycles to 100 cycles, and the capacity retention rate is still as high as 88.7%.

[0073] The above description is merely an embodiment of the present invention and does not constitute any form of limitation to the present invention. The present invention may also have other forms of embodiments based on the above structures and functions, which are not listed here one by one. Therefore, any simple modification, equivalent changes, and modifications made to the above embodiments by any person skilled in the art in accordance with the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a modified current collector, characterized in that: The specific steps include: (1) Pre-treating the copper current collector; (2) performing an in-situ modification reaction on the surface of the copper current collector obtained by pretreatment in step (1) to obtain a current collector coated with a copper oxide nanomaterial; (3) introducing selenium into the surface of the current collector coated with the copper oxide nanomaterial obtained in step (2), and subjecting it to an in-situ chemical reaction to obtain a modified current collector having a composite of copper selenide and copper oxide; (4) The modified current collector composed of copper selenide and copper oxide obtained in step (3) is subjected to an in-situ lithiation reaction by electrochemical deposition to generate a corresponding lithium compound, thereby obtaining a modified current collector for a negative electrode metal-free battery.

2. The method for preparing the modified current collector according to claim 1, wherein: In step (1), the copper current collector is one of copper foil, copper mesh and foam copper; the pretreatment specifically refers to first immersing the copper current collector in dilute hydrochloric acid and performing ultrasound, then cleaning it with anhydrous ethanol, and then drying it; the in situ modification in step (2) includes one of aqueous solution method, solvent thermal, electrochemistry, air oxidation, magnetron sputtering, and chemical vapor deposition.

3. The method for preparing the modified current collector according to claim 2, wherein: When the in-situ modification in step (2) is air oxidation, specifically: place the copper current collector in a muffle furnace, set the heating rate to 1-10°C / min, the reaction temperature to 100°C-500°C, the reaction time to 1min-120min, and naturally cool to room temperature after the reaction is completed.

4. The method for preparing the modified current collector according to claim 1, wherein: The in-situ chemical reaction described in step (3) includes one of hydrothermal method, solvent thermal method, electrochemistry, and chemical vapor deposition.

5. The method for preparing the modified current collector according to claim 1, wherein: In step (3), a hydrothermal method is used to generate an in-situ chemical reaction on the surface of the current collector coated with the copper oxide nanomaterial to introduce selenium. Specifically, sodium borohydride is first dissolved in 2 mL of deionized water, stirred, and allowed to stand for 2 minutes, and then a selenium source is added and stirred until the solution becomes colorless. Finally, 28 mL of deionized water is added and the resulting solution is transferred to a reactor. The current collector coated with the copper oxide nanomaterial obtained in step (2) is then placed in the reactor, and the reactor is placed in a thermostat for a hydrothermal reaction at a reaction temperature of 60° C. to 200° C. for a reaction time of 1 hour to 12 hours. After the hydrothermal reaction is completed, a modified current collector having a composite of copper selenide and copper oxide is obtained, which is dried and set aside. The selenium source comprises one of selenium powder, sodium selenite, and selenate. The molar ratio of the selenium source to the current collector coated with the copper oxide nanomaterial is 1:99-99:

1.

6. The method for preparing the modified current collector according to claim 4, wherein: In step (3), chemical vapor deposition is used to cause an in-situ chemical reaction on the surface of the current collector coated with copper oxide nanomaterials to introduce selenium elements. Specifically, selenium powder is evenly spread on the bottom of a porcelain boat, and the current collector coated with copper oxide nanomaterials obtained in step (2) is placed in the porcelain boat. The porcelain boat is then transferred to a chemical vapor deposition tube furnace. Before heating, the air in the tube furnace is extracted by a vacuum pump, and inert gas argon or nitrogen is introduced, and the argon or nitrogen flow rate is controlled to be 20sccm / min; heating parameters are: heating rate of 2°C / min, reaction temperature of 250°C, reaction time of 10min, after the reaction is completed, a modified current collector composite of copper selenide and copper oxide is obtained, which is placed in a vacuum drying oven for drying treatment; wherein the molar ratio of selenium powder to the current collector coated with copper oxide nanomaterials is 1:99-99:

1.

7. The method for preparing the modified current collector according to claim 1, wherein: The specific process of in-situ lithiation by electrochemical deposition in step (4) includes: using the modified current collector of copper selenide and copper oxide obtained in step (3) as the positive electrode and the metal lithium sheet as the negative electrode, assembling the battery in the order of positive electrode shell-positive electrode-diaphragm-negative electrode-negative electrode shell, and performing charge and discharge lithiation treatment after assembly. The charge and discharge process is as follows: setting the discharge current density to 0.1-1 mA / cm 2 , the cut-off voltage is 0V; after completion, continue to 2 The current density is discharged, and the discharge time is 1min-60min; after the discharge is completed, the current is discharged at 0.1mA / cm 2 The current density is set to 1V, and the cut-off voltage is set to 1V to complete the entire electrochemical deposition in-situ lithiation reaction process.

8. The method for preparing the modified current collector according to claim 1, wherein: The battery assembly operation in step (4) is carried out in an argon-filled glove box; the diaphragm is Celgard 2400, and the electrolyte used in the battery has the following formula: a concentration of 1 mol / L, the electrolyte is lithium bis(trifluoromethylsulfonyl)imide, the solvent is DOL / DME, wherein the volume ratio of DOL to DME is 1:1, and the mass content of the additive LiNO3 in the electrolyte solution is 1%.

9. A modified current collector obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the modified current collector according to claim 9 in a negative electrode-free metal battery, wherein the negative electrode-free metal battery comprises one of a negative electrode-free lithium battery, a negative electrode-free potassium battery, a negative electrode-free sodium battery, a negative electrode-free zinc battery, a negative electrode-free calcium battery, and a negative electrode-free magnesium battery.

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