CN109390585B - Liquid metal-based protective film for inhibiting lithium dendrites and preparation method thereof - Google Patents
Liquid metal-based protective film for inhibiting lithium dendrites and preparation method thereof Download PDFInfo
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- CN109390585B CN109390585B CN201811133179.2A CN201811133179A CN109390585B CN 109390585 B CN109390585 B CN 109390585B CN 201811133179 A CN201811133179 A CN 201811133179A CN 109390585 B CN109390585 B CN 109390585B
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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Abstract
The invention discloses a protective film for inhibiting lithium dendrite based on liquid metal, which is used for protecting a lithium metal electrode by introducing the liquid metal to prepare the protective film. The preparation method of the protective film comprises the following steps: firstly, mixing liquid metal and a viscoelastic body according to a certain proportion; secondly, coating the mixture obtained in the first step on a smooth substrate to form a film; and thirdly, solidifying the sample film to finish the preparation based on the liquid metal protective film. The protective film prepared by the invention can be combined with the self-healing property of liquid metal and the high toughness of viscoelastic body, effectively inhibit the growth of lithium dendrite in a lithium metal battery in a synergic manner, can withstand higher current density and still maintain better circulation stability. The invention can be applied to the field of lithium metal batteries and is beneficial to realizing the commercialization of the lithium metal batteries.
Description
Technical Field
The invention belongs to the technical field of energy storage batteries, and particularly relates to a protective film for inhibiting lithium dendrites based on liquid metal and a preparation method thereof.
Background
Lithium metal has low electrode potential (-3.040V) and high specific capacity (3860mAh g)─1) Has received much attention and is considered as one of the most promising candidates for the next generation of high-energy secondary batteries. However, in the process of charge and discharge cycles of the lithium metal battery, moss-shaped or dendritic lithium dendrite structures are easily formed on the surface of the electrode due to the uneven deposition of lithium ions, so that the problems of low coulombic efficiency, poor cycle stability, dry-up of electrolyte and the like of the lithium metal battery are caused. The further growth of the lithium dendrites is likely to puncture the diaphragm, so that the positive and negative electrodes of the battery are contacted, and the battery is short-circuited or even exploded. Therefore, the lithium dendrite problem is one of the major obstacles to commercialization of lithium metal batteries.
In recent years, aiming at the problem of lithium dendrite, many methods are tried to prolong the cycle life of the lithium metal battery, for example, a three-dimensional current collector is introduced, and the nucleation stage at the initial stage of lithium deposition is influenced, so that the lithium deposition behavior is effectively improved; adding an additive into the electrolyte to form a stable and uniform solid electrolyte layer in the circulating process and inhibit the growth of lithium dendrites; introducing high-hardness solid electrolyte to achieve growth without dendrite; in addition, an artificial protective film is directly coated on the surface of the lithium metal electrode, the stress of dendritic crystal growth is released by utilizing the mechanical property of the protective film, the original solid electrolyte membrane is prevented from being damaged, and the effect of inhibiting the lithium dendritic crystal is further achieved. Although these methods have achieved some breakthrough, they all have some limitations. Only improving lithium ion nucleation is not suitable for large-rate current density, and long-time stable circulation is difficult to achieve; the electrolyte additive is easily limited by a specific system and has low universality; the high-hardness solid electrolyte is difficult to solve the problem of overlarge impedance between the electrode and the electrolyte; the flexible protective film has a limited effect in suppressing lithium dendrites. Therefore, it is still a great challenge to achieve 100% suppression of lithium dendrites. (Xin-Bing Cheng; Chong Yan; Xiao Chen; Chao Guan; Jia-Qi Huang; Hong-Jie Pen; RuiZhang; Shu-pointing Yang; and Qiang Zhang, Implantable Solid Electrolyte Interphasein Lithium-Metal Batteries, Chem 2017,2,258)
The liquid metal is a low-melting-point intrinsic self-healing material, has the characteristics of both fluid and metal, and has good ionic conductivity, flow ductility and chemical stability. The liquid property of the low melting point of the metal enables the liquid metal to be regarded as a good soft conductor and can be used for preparing flexible or telescopic electronic devices; the self-healing property is embodied in that once its integrity is mechanically destroyed, its flow properties ensure that it will naturally tend to self-heal. Research shows that when the liquid metal is applied to the silicon particle electrode, the liquid metal is used as a soft conductor with flowing and self-healing characteristics, which is beneficial to the interconnection between silicon particles and the retention of the original appearance of the electrode, and greatly slows down the problem of volume expansion of the silicon electrode in the charging and discharging process. It is with these special properties that liquid metals are increasingly gaining wide attention.
Therefore, the special properties of the liquid metal are introduced, and the protective film is prepared by combining the viscoelastic material, so that the liquid metal can be used for melting the lithium dendrite, the stress of the dendrite can be relieved by combining the flexible protective layer, and the growth of the lithium dendrite can be effectively inhibited.
Disclosure of Invention
The invention provides a protective film for inhibiting lithium dendrite based on liquid metal and a preparation method thereof. The invention can effectively inhibit the problem of lithium dendrite generated in the charge-discharge cycle process of the lithium metal battery and improve the cycle stability of the battery.
The invention is realized by the following technical scheme:
a method for suppressing lithium dendrites based on a liquid metal protective film, at least comprising the steps of:
(1) selecting a proper amount of liquid metal;
(2) soaking the liquid metal selected in the step (1) by using a low-concentration acid solution or an alkali solution to remove surface oxides;
(3) carrying out heat treatment on the liquid metal with the oxide layer removed, which is obtained in the step (2), so that the liquid metal is melted into a liquid state;
(4) adding a proper amount of viscoelastic body into the metal in the liquid state obtained in the step (3);
(5) mixing the liquid metal and the viscoelastic mixture to uniformly disperse the mixture;
(6) smearing the uniform mixture of the step (5) on a smooth substrate;
(7) and drying and heating in vacuum, and curing the mixture to form a film so as to obtain the liquid metal-based protective film.
The liquid metal in the present invention generally refers to a low melting point metal having a melting point of 200 ℃ or lower, which becomes liquid when heated to the melting point. The liquid metal is easily oxidized by oxygen in the air and loses the surface metal luster, but an oxide film is formed on the surface of the liquid metal to further prevent the oxidation, so that the liquid metal has stable chemical properties in the air. Research has revealed that: the liquid metal placed in the electrolyte may form an alloy by absorbing the metal, and thus the present invention is based on the fact that the prepared liquid metal protective film is applied to a lithium metal battery for charge and discharge cycles, it is expected that the liquid metal in the protective film can absorb and ablate lithium dendrites formed by the uneven deposition of lithium, and the effective combination of the liquid metal and the polymer provides the protective film with excellent toughness, thereby ensuring the safety and cycle life of the lithium metal battery.
The liquid metal in the invention is selected from one or more of gallium, rubidium, cesium, bismuth, tin, cadmium, lead, indium and the like, preferably one or more of gallium, rubidium, cesium, bismuth, tin and indium.
The liquid metal itself is a liquid with metallic luster, but when in air, the metal surface is oxidized by oxygen and forms a layer of gray oxide film to prevent further oxidation of the liquid metal. The oxide film on the surface of the liquid metal is generally removed before the liquid metal is used.
The acid solution for removing the oxide layer on the surface of the liquid metal is selected from nitric acid, sulfuric acid, hydrochloric acid, carbonic acid, formic acid, acetic acid and bisulfate, and the alkali solution is selected from one of solutions of sodium hydroxide, calcium hydroxide, barium hydroxide, potassium hydroxide, ammonia water, sodium bicarbonate, sodium sulfide and carbonates. Preferably, the acid or alkali solution is selected from one of nitric acid, sulfuric acid, hydrochloric acid, carbonic acid, sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium bicarbonate and sodium sulfide.
The concentration of the acid or alkali solution in the step (2) is selected from 0.01-3 mol.L–1. Preferably, the concentration of the acid or alkali solution is selected from 0.1-0.8 mol.L–1Any concentration of (a).
The liquid metal has a large surface tension in a liquid state, such as a gallium-indium alloy which is a solid solution alloy formed by eutectic melting of gallium metal and indium metal and is in a liquid state at room temperature, and the surface tension is 500mN · m–1. Due to the existence of larger surface tension, the gallium-indium eutectic alloy can present a spherical liquid drop shape on a horizontal plane without the influence of external environmental force, and spontaneous film formation is difficult unless external stimulation (such as an electric field and a magnetic field) is introduced. For example, under the stimulation of a micro current, the spherical liquid metal can be spread on a plane to form a film, but once the electric field is removed, the liquid metal immediately restores the original shape, and the film is difficult to maintain for a long time. On the basis of the above, one or more mediums are required to assist the film formation of the liquid metal.
The invention introduces aromatic amines, amido amines, rubbers, organic silicon compounds, organic glass, polyolefin elastomer, ethylene-vinyl acetate copolymer, polyvinylidene fluoride and other organic viscoelastic bodies, utilizes the characteristics of small surface tension, chemical stability, flexibility, high and low temperature resistance, corrosion resistance, no toxicity and the like, can be well fused with liquid metal to assist film formation, and still keeps better stability in the air.
Preferably, the viscoelastic body in step (4) of the present invention is selected from any one or more of aromatic amines (including m-xylylenediamine and m-aminomethane), organic silicon compounds (including polydimethylsiloxane), organic glass, polyolefin elastomer, ethylene-vinyl acetate copolymer, and polyvinylidene fluoride.
When the liquid metal and the viscoelastic body are mixed in the step (4), the physical properties of the prepared liquid metal protective film can be influenced by different component proportions. Research shows that when the gallium-indium eutectic alloy is mixed with the organic viscoelastic body, the gallium-indium eutectic alloy with different proportions has great influence on the tensile fracture energy of the prepared flexible film. (Navid Kazem; Michael D.Bartlett; and Carmel Majidi, Extreme Toughening of Soft Materials with liquid Metal, adv.Mater.2018,30,1706594). The mixing ratio of the liquid metal and the viscoelastic body is 5-95% by mass, and the preferred mixing ratio is 20-80%.
The method for mixing the liquid metal and the viscoelastic body in the step (5) comprises any one of processing means such as a microwave ultrasonic method, a mechanical grinding method, a tip ultrasonic method, a magnetic stirring method and the like. Preferably, the mixing method is selected from any one of a microwave ultrasonic method, a mechanical milling method, and a tip ultrasonic method.
The degree of mixing is one of the important factors that can affect the physical properties of a mixture, and the mixing time is the critical factor for the degree of mixing of the liquid metal and the viscoelastic body. The mixing treatment method can realize that the liquid metal drop in the viscoelastic body is less than 10 mu m after the liquid metal and the viscoelastic body are fully mixed. The mixing time is 1-300 min, and the preferable time is 20-70 min.
The film coating is one of the important steps in the formation of the protective film, and factors such as the quality and thickness of the film coating directly influence the subsequent battery performance, so the selection of the film coating mode is important. The coating mode in the step (6) is selected from one of the group consisting of flow coating equipment, automatic coating machine, silk screen coating equipment, spin coating equipment, lifting coating equipment, manual scraper coating and four-side preparation equipment coating. Preferably, the apparatus used for coating the film is selected from one of an automatic coater, a spin coating apparatus, a manual blade coating, a four-side preparer coating apparatus.
According to the invention, by selecting the coating equipment, the coating film forming mode is optimized, and the film forming quality based on the liquid metal protective film is improved. The thickness of the film plays an important role in better performing the physicochemical properties of the protective film. When the film is too thick, the conduction of lithium ions in the charging and discharging process is easily obstructed, so that the problems of low coulombic efficiency, large internal resistance and the like are caused; when the film is too thin, it is difficult to have a good effect of suppressing lithium dendrites during long-term cycling. Therefore, the selection of the proper film thickness has a very important influence on the effectiveness of the liquid metal protective film. The thickness of the coating film is 5-200 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 50 μm, 75 μm, 100 μm, 150 μm and 200 μm, preferably 5-100 μm.
In the step (7), the protective film based on the liquid metal can be obtained by drying and heating the mixture in a vacuum oven to solidify the mixture into a film. The temperature of the heating protective film is 30-200 ℃, such as: 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃ and the like. The preferable heating temperature is 50-150 ℃. The time for heating the protective film is 2-24 h, such as 2.0h, 2.5h, 3.0h, 3.5h, 4.0h, 4.5h, 5.0h, 5.5h, 6.0h, 6.5h, 7.0h, 7.5h, 8h, etc., preferably 3-12 h.
And after heating, cooling to room temperature to obtain the liquid metal-based flexible protective film. And obtaining a protective film membrane with a proper size by an electrode plate punching machine, and applying the protective film membrane to the lithium metal battery to play a role of inhibiting lithium dendrite.
The invention is unique in that it provides a simple and effective method for introducing liquid metal to obtain a flexible lithium metal protective film. Firstly, the existence of the viscoelastic body can help to form a flexible film with certain tensile strength, and stress can be released through corresponding deformation when the flexible film is stressed by lithium dendrite; more importantly, during the charging and discharging of the lithium metal battery, the liquid metal can absorb and ablate lithium dendrites by alloying with lithium.
The invention has the beneficial effects that:
(1) the liquid metal protective film prepared by the simple and easy-to-operate method can keep stable physical properties in the air for a long time;
(2) the protective film based on the liquid metal has the transplantable characteristic, can be taken off from a smooth substrate of a coating film to be decorated on the surface of an electrode, and has certain universality;
(3) the liquid metal protective film prepared by the invention can locally release stress generated by lithium dendrite by utilizing the characteristic of the viscoelastic body flexible substrate, and meanwhile, in the charging and discharging processes, the lithium dendrite formed on the surface of the lithium metal can be absorbed and ablated through the alloying-dealloying reaction of the liquid metal to play the role of the protective film, and the liquid metal protective film and the liquid metal are mutually cooperated to jointly inhibit the formation of the lithium dendrite.
Drawings
FIG. 1 is a schematic representation of a liquid metal-based protective film prepared in example 1;
FIG. 2 is an optical microscope photograph of a liquid metal-based protective film prepared in example 1;
FIG. 3 is a top view of a scanning electron microscope based on a liquid metal protective film prepared in example 1 after cycling;
FIG. 4 is a scanning electron microscope side view of the protective liquid metal-based film prepared in example 1 after cycling;
fig. 5 is a graph of electrochemical performance of the liquid metal-based protective film prepared in example 1.
Detailed Description
To better illustrate the invention and to facilitate an understanding of the technical solutions of the invention, typical but non-limiting examples of the invention are provided herein below.
Example 1
(1) Taking 0.1g of solid gallium-indium eutectic alloy;
(2) carrying out surface oxidation removal treatment on the liquid metal selected in the step (1) by using 0.7M sodium hydroxide solution, namely soaking 0.1g of gallium-indium eutectic alloy in the sodium hydroxide solution for about 5min until the gray color of the surface of the gallium-indium alloy fades and silvery-white metallic luster appears again;
(3) placing the gallium-indium eutectic alloy with the oxide layer removed, obtained in the step (2), on a hot table, and heating at 80 ℃ to melt the gallium-indium eutectic alloy into a liquid state;
(4) adding 0.9g of polyolefin elastomer into the liquid metal obtained in the step (3) to form a mixed colloidal substance of gallium-indium eutectic alloy with the mass ratio of 10%;
(5) placing the mixture of the gallium-indium eutectic alloy and the polyolefin elastomer into a 2mL micro centrifuge tube of a micro ball mill, and stirring to uniformly disperse the mixture, wherein the stirring parameters are as follows: the rotating speed is 300rpm, the stirring time is 3min each time, and the total stirring times are 15 times;
(6) coating the uniform mixture obtained in the step (5) on a smooth organic glass substrate by using an automatic coating machine, wherein the coating thickness is 5 mu m;
(7) and (3) placing the obtained gallium-indium eutectic alloy protective film with the thickness of 5 microns in a vacuum oven, heating for 24 hours at 100 ℃ in a vacuum state, and curing the mixture to form a film so as to obtain the gallium-indium eutectic alloy based protective film.
Example 2
(1) 0.05g of gallium indium tin eutectic alloy in a solid state is taken;
(2) carrying out surface oxidation removal treatment on the liquid metal selected in the step (1) by using 0.3M sodium hydroxide solution, namely soaking 0.05g of gallium indium tin eutectic alloy in the sodium hydroxide solution for about 5min until the gray color of the surface of the gallium indium tin alloy fades, and reappearing silvery white metallic luster;
(3) placing the gallium indium tin eutectic alloy with the oxide layer removed obtained in the step (2) in a beaker, and then placing the beaker and the gallium indium tin eutectic alloy on a heating table together for heating at a constant temperature of 70 ℃ to ensure that the gallium indium tin eutectic alloy is converted into a liquid state;
(4) adding 0.95g of organic glass into the liquid metal obtained in the step (3) to form a gallium indium tin eutectic alloy mixed colloidal substance with the mass ratio of 5%;
(5) placing a beaker mixed with the gallium indium tin eutectic alloy and the organic glass on a hot table, and keeping the temperature of the beaker and the internal mixture constant at 160 ℃, and continuously stirring for 1min by using a glass rod to uniformly mix the beaker and the internal mixture;
(6) coating the uniform mixture obtained in the step (5) on a smooth acrylic plate by using a four-side preparation device, wherein the coating thickness is 100 mu m;
(7) and (3) placing the obtained gallium indium tin eutectic alloy protective film with the thickness of 100 mu m in a vacuum oven, heating for 24h at 100 ℃ in a vacuum state, and curing the mixture to form a film so as to obtain the gallium indium tin eutectic alloy based protective film.
Example 3
(1) Taking 0.4g of low-melting-point metal indium in a solid state;
(2) removing surface oxidation treatment on the liquid metal selected in the step (1) by using 0.1M potassium hydroxide solution, namely soaking 0.4g of metal indium in hydrochloric acid solution for about 5min until the surface of the metal indium is gray and faded, and reappearing metal luster;
(3) placing the metal indium obtained in the step (2) with the oxide layer removed in a beaker, and heating the metal indium on a heating table at 150 ℃ to melt the metal indium into liquid state;
(4) adding 0.6g of organic glass into the liquid metal obtained in the step (3) to form a metal indium mixed colloidal substance with the mass ratio of 40%;
(5) manually stirring the beaker mixed with the metal indium and the organic glass by using a glass rod for 20 min;
(6) coating the uniform mixture obtained in the step (5) on a smooth acrylic plate by using a four-side preparation device, wherein the coating thickness is 40 mu m;
(7) and placing the obtained metal indium protective film with the thickness of 40 mu m in a vacuum oven, heating for 4 hours at 80 ℃ in a vacuum state, and curing the mixture to form a film so as to obtain the metal indium-based protective film.
Example 4
(1) Taking 0.5g of liquid metal gallium in a solid state;
(2) carrying out surface oxidation removal treatment on the liquid metal selected in the step (1) by using 0.6M hydrochloric acid solution, namely soaking 0.5g of liquid metal gallium in the hydrochloric acid solution for about 5min until the grey color of the surface of the liquid metal gallium fades, and reappearing silvery white metallic luster;
(3) placing the gallium metal without the oxide layer obtained in the step (2) into a 2mL centrifuge tube, and placing the centrifuge tube on a hot table for heating treatment at 50 ℃ to melt the gallium metal into a liquid state;
(4) adding 0.5g of m-xylylenediamine to the liquid metal obtained in the step (3) to form a gallium metal mixed colloidal substance with a mass ratio of 50%;
(5) placing a centrifugal tube mixed with metal gallium and m-xylylenediamine in a 2mL miniature centrifugal tube of a miniature ball mill, and stirring to uniformly disperse the centrifugal tube, wherein stirring parameters are as follows: the rotating speed is 300rpm, the stirring time is 3min each time, and the total stirring times are 15 times;
(6) coating the uniform mixture obtained in the step (5) on a smooth glass plate by using a manual scraper, wherein the coating thickness is 30 microns;
(7) and placing the obtained metal gallium protective film with the thickness of 30 microns in a vacuum oven, heating for 11 hours at 110 ℃ in a vacuum state, and curing the mixture to form a film so as to obtain the metal gallium-based protective film.
Example 5
(1) Taking 0.7g of bismuth-tin-indium alloy in a solid state;
(2) carrying out surface oxidation removal treatment on the liquid metal selected in the step (1) by using 0.5M potassium hydroxide solution, namely soaking 0.7g of bismuth-tin-indium alloy in the potassium hydroxide solution for about 5min until the gray color of the surface of the bismuth-tin alloy fades and the metal luster reappears;
(3) placing the bismuth-tin-indium alloy with the oxide layer removed, which is obtained in the step (2), in a beaker, and heating the beaker and the bismuth-tin-indium alloy together in an oven at 100 ℃ to melt the bismuth-tin-indium alloy into a liquid state;
(4) adding 0.3g of beta-polyvinylidene fluoride into the liquid metal obtained in the step (3) to form a bismuth-tin-indium alloy mixed colloidal substance with the mass ratio of 70%;
(5) sealing the beaker mixed with the bismuth-tin-indium alloy and the polyvinylidene fluoride by using tin foil paper, placing the beaker in a tip ultrasonic instrument, and carrying out ultrasonic treatment for 300min to uniformly disperse the beaker;
(6) coating the uniform mixture obtained in the step (5) on a smooth acrylic plate by using a four-side preparation device, wherein the coating thickness is 200 mu m;
(7) and (3) placing the obtained bismuth-tin-indium alloy protective film with the thickness of 200 mu m in a vacuum oven, heating for 4h at 30 ℃ in a vacuum state, and curing the mixture to form a film so as to obtain the protective film based on the bismuth-tin-indium alloy.
Example 6
(1) Taking 0.95g of solid state bismuth-tin alloy;
(2) carrying out surface oxidation removal treatment on the liquid metal selected in the step (1) by using 0.2M sulfuric acid solution, namely soaking 0.95g of bismuth-tin alloy in the sulfuric acid solution for about 5min until the grey color of the surface of the bismuth-indium alloy fades and the metallic luster reappears;
(3) placing the bismuth-tin alloy with the oxide layer removed, which is obtained in the step (2), in a beaker, and heating the beaker and the bismuth-tin alloy on a heating table at 135 ℃ to melt bismuth and tin into liquid;
(4) adding 0.05g of polydimethylsiloxane into the liquid metal obtained in the step (3) to form a bismuth-tin alloy mixed colloidal substance with the mass ratio of 95%;
(5) placing the mixture mixed with the bismuth-tin alloy and the polydimethylsiloxane on a hot table, keeping the temperature of the beaker and the internal mixture constant at 130 ℃, adding a magnetic stirrer, rotating at 200 revolutions per minute, and magnetically stirring for 30min to uniformly mix the mixture;
(6) coating the uniform mixture obtained in the step (5) on a smooth copper foil by using a four-side preparation device, wherein the coating thickness is 40 mu m;
(7) and placing the obtained bismuth-tin alloy protective film with the thickness of 40 microns in a vacuum oven, heating for 2 hours at 200 ℃ in a vacuum state, and curing the mixture to form a film so as to obtain the protective film based on the bismuth-tin alloy.
Example 7
Test of Performance of protective film based on liquid Metal prepared in example 1
And (3) testing tensile property: FIG. 1 shows the stretching of the protective film under the action of external force. As can be seen from the figure, the protective film has excellent tensile properties under the action of external force. Fig. 2 is a structure under an optical microscope, and it can be seen from fig. 2(a) that liquid metal droplets are uniformly distributed inside a polyolefin elastomer, and the internal state of the protective film when being stretched is as shown in fig. 2(b), and the liquid metal can also be deformed correspondingly along the stress direction, and this unique structure not only can improve the tensile property of the protective film, but also is beneficial to relieving the stress generated by lithium dendrites, and further inhibits the lithium dendrites.
And (3) testing the inhibition effect on lithium dendrites: and assembling the obtained gallium-indium eutectic alloy protective film into a lithium metal button cell, circulating for 20 circles, disassembling the cell, and observing by using a scanning electron microscope. Fig. 3 and 4 are a top view and a side view, respectively, of a scanning electron microscope, and it can be seen from the figures that dendritic or moss-like lithium dendrites are not found on the surface of the protective film, indicating that the protective film can effectively suppress the formation of lithium dendrites.
And (3) testing the cycling stability: the obtained protective film is assembled into a Li/Li symmetrical battery to carry out current density of 1mA cm–2The cycle time of the cycle test (2) is 450 h. Fig. 5 shows a voltage-current curve, from which it can be seen that the voltage remains stationary after a cycle test of 450h, indicating that the protective film has a good inhibitory effect on the inhibition of lithium dendrites.
Comparative example 1
To better illustrate the effect of the invention, a comparative example of the invention is provided here as a control, i.e. a Li/Li symmetrical cell is assembled under the same conditions without the addition of a protective film based on a liquid metal and at 1mA · cm–2Comparative cycling tests were performed at current densities of (a).
Application example 1
The liquid metal protective films prepared in examples 1 to 6 were applied to lithium batteries and the cycle life thereof was tested in comparison with that of comparative example 1
The application method comprises the following steps: in order to further verify that the protective film based on the liquid metal prepared by the invention has an obvious inhibition effect on the growth of lithium dendrites, the obtained protective film is assembled into a Li/Li symmetrical battery for application, and the protective and stable effect of the liquid metal protective film on the lithium metal is verified by observing the stability of a voltage-current curve in the deposition/separation process of lithium.
The cycle life testing method comprises the following steps: in the blue electrochemical test system (LAND CT 2001A), the current density was measured at 0.5, 1, 2, 4 mA-cm, respectively–2The current density of the voltage-current curve is tested circularly, and the time for stabilizing the voltage-current curve is counted and compared.
The cycle life test results are shown in table 1, from which it can be seen that: the cycle life tests of the protective films prepared in the embodiments 1-6 are all over 400h, while the comparative example shows a large unstable phenomenon in a voltage-current curve when the cycle time reaches 120h, which proves that obvious lithium dendrite formation exists in the battery without the protection of the protective film, and further proves that the protective film based on liquid metal has a good inhibition effect on the formation of the lithium dendrite and plays a role in protecting a lithium electrode.
TABLE 1 cycle life test
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.
Claims (10)
1. A method for preparing a protective film for lithium dendrite suppression based on a liquid metal, comprising the steps of:
(1) weighing liquid metal, and placing the liquid metal in an acid or alkali solution to remove an oxide layer;
(2) mixing the liquid metal obtained in the step (1) with a viscoelastic body to obtain a mixture;
(3) coating the mixture of the step (2) on a smooth substrate to form a film;
(4) and (4) putting the film obtained in the step (3) into a vacuum drying oven for full drying to obtain the liquid metal-based protective film.
2. The method of claim 1, wherein the liquid metal is selected from the group consisting of gallium, rubidium, cesium, bismuth, tin, cadmium, lead, and indium in any combination thereof.
3. The method of claim 1, wherein: the viscoelastic body in the step (2) is selected from aromatic amines, amido amines, rubbers, organic silicon compounds, polyolefin elastomers, ethylene-vinyl acetate copolymers and alpha, beta, gamma and crystal polyvinylidene fluoride.
4. The method of claim 1 or 2, wherein: the mass ratio of the liquid metal to the total amount of the mixture is 5-95%.
5. The method of claim 1 or 2, wherein: the mixing method of the liquid metal and the viscoelastic body comprises any one of a microwave ultrasonic method, a mechanical grinding method, a tip ultrasonic method and a magnetic stirring method.
6. The method of claim 1, wherein: and (3) mixing for 1-300 min in the step (2).
7. The method of claim 1, wherein: and (4) the thickness of the film in the step (3) is 5-200 mu m.
8. The method of claim 1, wherein: the vacuum drying temperature in the step (4) is 30-200 ℃; the drying time is 2-24 h.
9. A liquid metal-based protective film for lithium dendrite suppression prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the liquid metal-based protective film prepared by the preparation method according to any one of claims 1 to 8 for suppressing lithium dendrites generated during charge and discharge cycles of a lithium metal battery.
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| CN112420978B (en) * | 2019-08-22 | 2022-12-09 | 比亚迪股份有限公司 | Composite negative electrode, solid-state lithium battery and preparation method of solid-state lithium battery |
| CN110911689A (en) * | 2019-10-31 | 2020-03-24 | 南方科技大学 | Current collector and preparation method thereof, electrode plate and secondary battery |
| CN110752375A (en) * | 2019-10-31 | 2020-02-04 | 山东大学 | Lithium battery for inhibiting growth of lithium dendrite by using liquid metal and preparation method and application thereof |
| CN111509211A (en) * | 2020-04-29 | 2020-08-07 | 广西师范大学 | Preparation method of L M/L i composite material |
| CN111755699B (en) * | 2020-07-08 | 2022-08-19 | 山东大学 | High-stability long-life metal lithium negative electrode material and preparation method and application thereof |
| CN112838212A (en) * | 2021-01-04 | 2021-05-25 | 江汉大学 | Self-healing artificial interface layer for protecting lithium metal, preparation method thereof and battery |
| CN112768695A (en) * | 2021-01-13 | 2021-05-07 | 山东大学 | High-safety dendrite-free lithium metal battery and preparation method and application thereof |
| CN113540587B (en) * | 2021-06-18 | 2022-09-23 | 江苏智蓝电源科技有限公司 | Method for improving compounding degree of gallium in polymer film |
| CN115172992A (en) * | 2022-07-01 | 2022-10-11 | 云南中宣液态金属科技有限公司 | Liquid metal coating battery diaphragm and preparation method thereof and lithium ion battery |
| CN115084780B (en) * | 2022-07-01 | 2024-02-13 | 云南中宣液态金属科技有限公司 | Battery diaphragm, preparation method thereof and lithium ion battery containing diaphragm |
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