Manufacturing method of porous structure for lithium battery and porous structure for lithium battery

Abstract

The invention relates to a method for manufacturing a porous structure for a lithium battery, a porous structure for a lithium battery manufactured according to the said method, a negative electrode for a lithium battery including the said porous structure for a lithium battery, and a lithium battery including the same. In one embodiment, the method for manufacturing a porous structure for a lithium battery is performed through welding and etching processes via a bottom-up method. Since this allows for the control of physical properties such as conductivity and lithium affinity, as well as microscopic structures such as porosity, pore size, and surface area, and macroscopic structures such as the thickness and width of the electrode, it has the advantage of accurately realizing pore sizes in the hundreds of nanometer range or realizing high porosity. Accordingly, a lithium battery negative electrode comprising a porous structure for a lithium battery manufactured according to a method for manufacturing a porous structure for a lithium battery according to one embodiment has the advantage of suppressing the dendrite-shaped growth of lithium or suppressing thickness changes by inducing lithium electrodeposition inside the pores, because the conductivity is relatively lowered compared to a conventional negative electrode by appropriately including a binder in the porous structure for a lithium battery, so that lithium can be electrodeposited inside the porous structure during charging and discharging.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a porous structure for a lithium battery, a porous structure for a lithium battery manufactured according to the said method, a negative electrode for a lithium battery comprising the said porous structure for a lithium battery, and a lithium battery comprising the same. Background Technology

[0002] Due to the rapid depletion of fossil fuels, the acceleration of environmental pollution, and increasing energy demand, research and development of sustainable, eco-friendly energy sources and energy storage / conversion devices utilizing electrochemical mechanisms are emerging. Among these, lithium batteries are excellent energy conversion devices with high energy and power densities; they are used as core components not only in small electronic devices but also in eco-friendly electric vehicles, possessing the potential to replace conventional internal combustion engines.

[0003] Lithium metal is a next-generation lithium battery anode material with high conductivity and capacity, but there were problems with reduced battery life due to cell short circuits, the formation of lithium surface SEI in every cycle, and the generation of dead lithium caused by the electrodeposition of lithium in the form of dendrites during the charging / discharging process.

[0004] Accordingly, a solution was being proposed to disperse current density and nucleation sites by securing a high electrochemically active surface area using porous structures.

[0005] However, due to the low porosity and high weight of the structure, the capacity per weight / volume is low, and there is still a problem in that dendrite growth cannot be effectively suppressed because the pore diameter, surface area, and electrical properties cannot be accurately controlled.

[0006] To improve such porous structures, there is a demand for fabricating porous structures capable of freely controlling porosity, pore diameter, surface area, thickness, and electrical properties. However, conventional support development has relied on a top-down approach using metal foils, meshes, and foams, which makes it difficult to precisely control these factors and presents complex fabrication methods. Furthermore, accurately realizing pore diameters in the hundreds of nanometer range or achieving high porosity has been challenging, resulting in a lack of support fabrication technology for the practical improvement of lithium metal anode performance.

[0007] Furthermore, in the case of highly conductive meshes and foams, since the composite resistance, including material transport resistance, is minimized at the electrode surface, lithium deposition is concentrated on the electrode surface rather than in the internal pores, making it difficult to increase electrode thickness and suppress lithium dendrite formation.

[0008] Therefore, there was a need for a method to manufacture a porous structure for lithium batteries that can improve lifespan and performance through a new manufacturing method while solving the aforementioned problems. Prior art literature

[0009] Republic of Korea Registered Patent Publication No. 10-0855595 The problem to be solved

[0010] The purpose of solving the above problem is as follows.

[0011] The purpose is to provide a bottom-up method for manufacturing a porous structure for a lithium battery, comprising the steps of: preparing a precursor by mixing metal nanoparticles, additional organic or inorganic nanoparticles, and a binder; heat-treating the precursor to weld the metal nanoparticles together; and etching the additional nanoparticles within the heat-treated precursor.

[0012] In addition, the invention aims to provide a porous structure for a lithium battery having a specific porosity and pore size manufactured by the above-described manufacturing method, a negative electrode for a lithium battery comprising the same, and a lithium battery employing the said negative electrode. means of solving the problem

[0013] A method for manufacturing a porous structure for a lithium battery according to one aspect comprises the steps of: preparing a precursor by mixing metal nanoparticles and additional nanoparticles; heat-treating the precursor; and etching additional nanoparticles in the heat-treated precursor.

[0014] The above precursor can be prepared by further mixing in a binder.

[0015] The content of the binder may be 3% to 50% by weight based on 100% by weight of the total precursor.

[0016] After preparing the above precursor, the step of producing a precursor sheet by calendering it may be further included.

[0017] The above metal nanoparticles may include one or more selected from the group consisting of metals that can be alloyed with lithium and conductive metals.

[0018] The above-mentioned metals that can be alloyed with lithium may include one or more selected from the group consisting of silver (Ag), zinc (Zn), gold (Au), aluminum (Al), magnesium (Mg), tin (Sn), silicon (Si), and carbon (C).

[0019] The conductive metal may include one or more selected from the group consisting of copper (Cu), iron (Fe), titanium (Ti), and nickel (Ni).

[0020] The mass ratio of the above metal nanoparticles to additional nanoparticles may be 1:0.3 to 1:1.2.

[0021] The above additional nanoparticles may include one or more selected from the group consisting of organic nanoparticles and inorganic nanoparticles.

[0022] The above organic nanoparticles may include one or more selected from the group consisting of PMMA, PEO, cellulose, and polystyrene.

[0023] The above inorganic nanoparticles may include one or more selected from the group consisting of silica, titania (TiO2), zirconia (ZrO2), and alumina (Al2O3).

[0024] The above heat treatment step may be a step of welding the metal nanoparticles together by heat treating from room temperature to a temperature of 240°C to 260°C at a heating rate of 30°C / min or less.

[0025] The above etching step can remove additional nanoparticles by treating the heat-treated precursor with an acid solution.

[0026] The above acid solution may include one or more selected from the group consisting of a hydrofluoric acid (HF) solution and a mixed solution of alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol.

[0027] A porous structure for a lithium battery according to another aspect comprises metal nanoparticles and is characterized by having a porosity of 30% to 90%.

[0028] The pore size of the pores included in the porous structure for the lithium battery above may be 30 nm to 5000 nm.

[0029] The thickness of the porous structure for the lithium battery above may be 10 μm to 100 μm.

[0030] According to another aspect, the negative electrode for a lithium battery comprises lithium metal disposed on the porous structure for the lithium battery.

[0031] A lithium battery according to another aspect employs the negative electrode for the lithium battery described above. Effects of the invention

[0032] In one embodiment, the method for manufacturing a porous structure for a lithium battery is performed through welding and etching processes via a bottom-up method, so as to control physical properties such as conductivity and lithium affinity, as well as microscopic structures such as porosity, pore size, and surface area, and macroscopic structures such as the thickness and width of the electrode, it has the advantage of accurately realizing pore sizes in the hundreds of nanometer range or realizing high porosity.

[0033] In addition, a lithium battery negative electrode comprising a porous structure for a lithium battery manufactured according to a method for manufacturing a porous structure for a lithium battery according to one embodiment has the advantage of suppressing the dendrite-shaped growth of lithium or suppressing thickness changes by inducing lithium electrodeposition inside the pores, because the conductivity is relatively lowered compared to a conventional negative electrode by appropriately including a binder in the porous structure for a lithium battery, so that lithium can be electrodeposited inside the porous structure during charging and discharging. Brief explanation of the drawing

[0034] Figures 1a and 1b are graphs showing the charge / discharge efficiency results according to Manufacturing Example 1 (Figure 1a) or Comparative Manufacturing Example 1 (Figure 1b), respectively. Figures 2a and 2b are scanning electron microscope images showing the top view of Manufacturing Example 1 (Figure 2a) or Comparative Manufacturing Example 1 (Figure 2b), respectively, during charging and discharging. Figures 3a and 3b are scanning electron microscope images showing a cross-section view of Preparation Example 1 (Fig. 3a) or Comparative Preparation Example 1 (Fig. 3b), respectively, during charging and discharging. Figure 4 is a graph showing the Coulomb efficiency results according to Manufacturing Example 1, Manufacturing Example 2, and Comparative Manufacturing Example 1, respectively. FIG. 5 shows 1 mA cm of a lithium battery according to Example 1 and Comparative Example 1. -2 This is a graph measuring the capacity retention rate of a lithium battery after charging and discharging at a current density. FIGS. 6 to 8 show 1 mA cm² of lithium batteries according to Comparative Example 2 (Fig. 6), Comparative Example 3 (Fig. 7), and Example 1 (Fig. 8). -2 This is an optical microscope image showing the degree of lithium electrodeposition over time after charging and discharging at a current density. Specific details for implementing the invention

[0035] The above objectives, other objectives, features, and advantages will be readily understood through the following preferred embodiments associated with the accompanying drawings. However, the embodiments described herein are not limited to those described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and that the technical concept is sufficiently conveyed to a person skilled in the art.

[0036] In describing each drawing, similar reference numerals have been used for similar components. In the attached drawings, the dimensions of the structures are depicted enlarged from their actual size for clarity of the invention. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the invention, the first component may be named the second component, and similarly, the second component may be named the first component. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0037] In this specification, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "immediately below" the other part, but also the case where there is another part in between.

[0038] Unless otherwise specified, all numbers, values, and / or expressions used herein to represent amounts of ingredients, reaction conditions, polymer compositions, and formulations should be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among other things. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including said maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to said maximum value including said maximum value, unless otherwise indicated.

[0039] In this specification, where a range is described for a variable, it will be understood that the variable includes all values ​​within the described range, including the described endpoints of the range. For example, the range “5 to 10” will be understood to include not only the values ​​5, 6, 7, 8, 9, and 10, but also any sub-ranges such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, etc., and any values ​​between integers valid for the category of the described range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, and 6.5 to 9. Also, for example, the range “10% to 30%” will be understood to include all integers including values ​​such as 10%, 11%, 12%, 13%, etc. and up to 30%, as well as any sub-range such as 10% to 15%, 12% to 18%, 20% to 30%, etc., and any value between valid integers within the stated range category such as 10.5%, 15.5%, 25.5%, etc.

[0041] In conventional lithium batteries, the lithium metal used as the negative electrode has problems such as cell short circuits and the formation of dead lithium due to the electrodeposition of lithium in the form of dendrites during the charging / discharging process, which leads to a decrease in battery life. Therefore, a solution has been proposed to secure a high electrochemically active surface area by using a porous structure to disperse current density and nucleation sites.

[0042] However, conventional support development has relied on a top-down approach using metal foils, meshes, and foams, which makes it difficult to precisely control relevant factors and presents complex fabrication methods. Furthermore, accurately realizing pore sizes in the hundreds of nanometer range or achieving high porosity has been challenging, resulting in a lack of support fabrication technology for the practical improvement of lithium metal anode performance. Additionally, in the case of highly conductive meshes and foams, the composite resistance, including material transport resistance, is minimized at the electrode surface; consequently, lithium deposition is concentrated on the surface rather than in internal pores, making it difficult to increase electrode thickness and suppress lithium dendrite formation.

[0043] Therefore, there was a need for a method to manufacture a porous structure for lithium batteries that can improve lifespan and performance through a new manufacturing method while solving the aforementioned problems.

[0044] Accordingly, the inventors, having conducted diligent research to solve the above problem, have prepared a precursor by mixing metal nanoparticles, additional organic or inorganic nanoparticles, and a binder; and a step of heat-treating the precursor to weld the metal nanoparticles together. The present invention was completed by discovering that when a porous structure for a lithium battery is manufactured using a bottom-up method comprising the step of etching additional nanoparticles within the heat-treated precursor, not only microscopic structures such as porosity, pore size, and surface area, but also macroscopic structures such as the thickness and width of the electrode can be accurately controlled, and furthermore, physical properties such as conductivity and lithium affinity can be controlled, thereby enabling the accurate realization of pore sizes in the hundreds of nanometer range or the realization of high porosity, and consequently, a negative electrode for a lithium battery containing a porous structure for a lithium battery manufactured according to this method can suppress the dendrite-shaped growth of lithium or induce lithium electrodeposition inside the pores to suppress changes in thickness.

[0046] A method for manufacturing a porous structure for a lithium battery according to one embodiment is a method performed through welding and etching processes via a bottom-up method, specifically comprising the steps of: preparing a precursor by mixing metal nanoparticles and additional nanoparticles; heat-treating the precursor; and etching the additional nanoparticles within the heat-treated precursor.

[0047] The above bottom-up method refers to a manufacturing method in which copper particles and silica particles of a fixed particle size are mixed with a binder, followed by a welding process to introduce electrical contact between the copper particles, and then etching the silica. That is, the method for manufacturing a porous structure for a lithium battery according to one embodiment has the advantage of being able to more precisely control material properties such as pore diameter, porosity, and conductivity by manufacturing the porous structure for a lithium battery through a bottom-up method instead of the conventional top-down method.

[0048] The step of preparing the above precursor can be performed by mixing metal nanoparticles and additional nanoparticles.

[0049] At this time, the metal nanoparticles are a material that forms the framework of a porous structure for a lithium battery to be manufactured thereafter. Specifically, the metal nanoparticles may include one or more selected from the group consisting of metals alloyable with lithium and conductive metals. By including one or more selected from the group consisting of metals alloyable with lithium and conductive metals in the metal nanoparticles, it is possible to increase the electrochemically active surface area of ​​the electrode, thereby providing the advantage of suppressing current concentration.

[0050] In particular, the metal alloyable with lithium according to one embodiment may include one or more selected from the group consisting of silver (Ag), zinc (Zn), gold (Au), aluminum (Al), magnesium (Mg), tin (Sn), silicon (Si), and carbon (C).

[0051] In addition, the conductive metal according to one embodiment may include one or more selected from the group consisting of copper (Cu), iron (Fe), titanium (Ti), and nickel (Ni).

[0052] Meanwhile, the additional nanoparticles are particles that can be removed in a subsequent etching step to form pores, and specifically, may include one or more selected from the group consisting of organic nanoparticles and inorganic nanoparticles that can be etched by an acid solution, etc. In particular, there is a feature that the pore size of the porous structure for a lithium battery, which is the final product, can be controlled by controlling the size of the additional nanoparticles.

[0053] In particular, the organic nanoparticles according to one embodiment may include one or more selected from the group consisting of PMMA, PEO, cellulose, and polystyrene, and the inorganic nanoparticles may include one or more selected from the group consisting of silica (SiO2), titania (TiO2), zirconia (ZrO2), and alumina (Al2O3).

[0054] At this time, there is an advantage in that the porosity of the porous structure for a lithium battery, which is the final product, can be controlled by adjusting the mass ratio of the metal nanoparticles and the additional nanoparticles. Specifically, according to one embodiment, the mass ratio of metal nanoparticles to additional nanoparticles may be 1:0.3 to 1:1.2, and preferably 1:0.5 to 1:1. Outside of the above range, if the mass of the additional nanoparticles is too low, there is a disadvantage that the energy density and specific energy are reduced because there is less space for lithium to be electrodeposited and the weight of the structure is heavy; and if the mass of the additional nanoparticles is too high, there is a disadvantage that the mechanical properties of the structure are reduced because the porosity becomes too high.

[0055] In addition, the step of preparing the precursor can be further prepared by mixing in a binder. At this time, the binder added not only improves the binding strength of the metal nanoparticles but also has the advantage of suppressing the dendrite-shaped growth of lithium or inducing lithium electrodeposition inside the pores, thereby suppressing thickness changes, because the binder is appropriately incorporated into the porous structure for the final product, which is a lithium battery, so that the conductivity is relatively lowered and lithium can be electrodeposited inside the porous structure during charging and discharging.

[0056] A binder according to one embodiment may include one or more selected from the group consisting of PTFE, PEO, PAA, PAN, PVA, and PVDF.

[0057] In particular, according to one embodiment, the content of the binder can be adjusted to 3% to 50% by weight based on 100% by weight of the total precursor, and preferably to 5% to 20% by weight. If the content of the binder is too low outside of the above range, the conductivity of the electrode becomes too high, resulting in a predominance of surface electrodeposition and a decrease in mechanical strength, and if the content of the binder is too high, the resistance increases, resulting in an increase in overvoltage.

[0058] In addition, the method may further include a step of preparing the aforementioned precursor and then calendering it to produce a precursor sheet. This offers the advantage of enabling precise control of the macroscopic structure of the final product, a porous structure for a lithium battery.

[0059] A calendering process according to one embodiment can be performed at a temperature of 30°C or lower with a thickness of 20 to 80 μm. If the temperature is too high outside the above condition range, the electrode may dry out and crack may occur during the calendering process; if the thickness is too high, there is a disadvantage of lowering the energy density of the battery; and if the thickness is too low, there is a disadvantage of failing to meet the areal capacity of the electrode.

[0060] The step of preparing the aforementioned precursor and then heat-treating the precursor is a step of welding the metal nanoparticles together to improve bonding strength. By welding the metal nanoparticles together to improve bonding strength through the heat treatment step, there is an advantage of enhancing the conductivity and mechanical strength of the electrode.

[0061] Specifically, the step of heat-treating the precursor according to one embodiment may be performed at a heating rate of 30°C / min or less from room temperature to a temperature of 240°C to 260°C, thereby allowing the metal nanoparticles to be welded together. If the heat treatment temperature is too low outside of this range, melting between the metal nanoparticles does not occur, resulting in no electrical connection and a decrease in mechanical strength. If the heat treatment temperature is too high, the binder decomposes, resulting in a decrease in mechanical strength. Additionally, if the heating rate is too fast, the electrode may shrink rapidly, which may cause cracks.

[0062] After the heat treatment step, the step of etching the heat-treated precursor is a step of treating the heat-treated precursor with an acid solution to remove additional nanoparticles and forming pores of the final product, a porous structure for a lithium battery. That is, through the etching step, the pore size and porosity of the final product, a porous structure for a lithium battery, can be finally and precisely controlled.

[0063] Specifically, according to one embodiment, the acid solution processed may include one or more selected from the group consisting of a solution in which a hydrofluoric acid (HF) solution is mixed with methyl alcohol, ethyl alcohol, isopropyl alcohol, etc.

[0064] In addition, the concentration of the acid solution according to one embodiment may be 1 wt.% to 20 wt.%, and the treatment conditions may be carried out with a solution that combines degassing using an inert gas at 30°C or lower. If the above range is exceeded, there are disadvantages such as damage to the structure due to gas generated by a rapid etching reaction or oxidation of metal nanoparticles by dissolved oxygen and water.

[0065] That is, in one embodiment, a method for manufacturing a porous structure for a lithium battery is performed through welding and etching processes via a bottom-up method, thereby not only controlling physical properties such as conductivity and lithium affinity, but also precisely controlling microscopic structures such as porosity, pore size, and surface area, as well as macroscopic structures such as the thickness and width of the electrode, so that it has the advantage of accurately realizing pore sizes in the hundreds of nanometer range or realizing high porosity.

[0067] In addition, a porous structure for a lithium battery manufactured according to a method for manufacturing a porous structure for a lithium battery according to one embodiment has the advantage of being able to accurately achieve a pore size of several hundred nanometers or achieve a high porosity depending on specific conditions of the manufacturing method. At this time, the porous structure for a lithium battery may include content that substantially overlaps with the content regarding the method for manufacturing a porous structure for a lithium battery described above, and the description of the overlapping parts may be omitted.

[0068] Specifically, the porous structure for the lithium battery comprises metal nanoparticles and may additionally comprise a binder.

[0069] The porous structure for the lithium battery described above can control the porosity by adjusting the mass ratio of metal nanoparticles and additional nanoparticles in the manufacturing method. Specifically, the porous structure for the lithium battery according to one embodiment is characterized by having a porosity of 30% to 90%, and preferably, 50% to 90%. If the porosity is too low outside of the above range, the weight of the electrode relative to the volume of lithium that can be stored becomes too high, which has the disadvantage of lowering the specific energy and energy density; and if the porosity is too high, the mechanical strength is reduced.

[0070] In addition, the porous structure for the lithium battery can have its pore size controlled by controlling the size of additional nanoparticles in the manufacturing method. Specifically, the porous structure for the lithium battery according to one embodiment may have a pore size of 30 nm to 5000 nm, and preferably 500 nm to 2000 nm. If the pore size is too small outside of the above range, there is a disadvantage that ion penetration is slow and surface electrodeposition becomes dominant, and if the pore size is too large, there is a disadvantage that dendrite-shaped growth cannot be suppressed and the surface area is reduced.

[0071] In addition, the thickness of the porous structure for the lithium battery can be controlled through a calendering process in the manufacturing method. Specifically, the porous structure for the lithium battery according to one embodiment may have a thickness of 10 μm to 100 μm, and preferably, 20 μm to 80 μm. If the thickness is too thin outside the above range, there is a disadvantage that it does not satisfy the capacity per electrode area required for a secondary battery, and if the thickness is too thick, there is a disadvantage that it lowers the energy density.

[0072] Accordingly, the weight of the porous structure for a lithium battery according to one embodiment is 0.9 mg / cm² per 10 μm thickness. 2 It can be reduced to below, preferably, 1.2 mg / cm² 2 to 0.8 mg / cm² 2It can be reduced to the weight of.

[0074] Accordingly, a lithium battery can be manufactured by employing a negative electrode for a lithium battery in which lithium metal is disposed on a porous structure for a lithium battery manufactured according to a method for manufacturing a porous structure for a lithium battery according to one embodiment.

[0075] At this time, the manufactured lithium battery may include a negative electrode for the lithium battery, a positive electrode, and an electrolyte located between the negative electrode and the positive electrode for the lithium battery.

[0076] First, the anode may include an anode active material, a binder, a conductive agent, etc.

[0077] The above-mentioned positive electrode active material may include one or more selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and combinations thereof. However, the above-mentioned positive electrode active material is not limited to these, and any positive electrode active material available in the relevant technical field may be used.

[0078] The above binder is a component that assists in the bonding of the positive active material and the conductive agent, and the bonding to the current collector, and may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, various copolymers, etc.

[0079] The above conductive agent is not particularly limited as long as it is conductive without causing chemical changes in the battery, and may include, for example, graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0080] In addition, the above electrolyte may include an electrolyte, a lithium salt, and an organic fluorine compound as a component responsible for the movement of lithium ions between the cathode and the anode.

[0081] The above electrolyte is a type of organic solvent and is not limited to any solvents that can be used in a lithium secondary battery, and may include, for example, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluoroethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethylene glycol dimethyl ether, trimethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, succinonitrile, sulforaine, dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, adiponitrile, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, dimethylacetamide, etc.

[0082] The above lithium salt is not limited to any type that can be used in a lithium secondary battery and may include, for example, LiNO3, LiPF6, LiBF6, LiClO4, LiCF3SO3, LiBr, LiI, etc.

[0083] The above organic fluorine compound may be a type of additive that reacts with the lithium metal of the above cathode (10) to form a protective layer (20). The above organic fluorine compound spontaneously chemically reacts with the lithium metal to form a protective layer (20) containing lithium fluoride (LiF).

[0084] The above organic fluorine compound may include a compound represented by the following chemical formula 1.

[0085] [Chemical Formula 1]

[0086] CF3(CF2) n (CH2) m X

[0087] In the above chemical formula 1, X comprises at least one selected from the group consisting of Cl, Br, I, and combinations thereof, and 1 n≤10 and 0≤m≤2 may be satisfied. Preferably, the organic fluorine compound may include CF3(CF2)2I.

[0089] That is, the above lithium battery includes a negative electrode for a lithium battery comprising a porous structure for a lithium battery manufactured according to a method for manufacturing a porous structure for a lithium battery according to one embodiment, so it is possible to accurately implement a pore size of several hundred nanometers or achieve a high porosity, and furthermore, since a binder is appropriately included in the porous structure for a lithium battery, the conductivity is relatively lower compared to a conventional negative electrode, so lithium can be electrodeposited inside the porous structure during charging and discharging, thereby having the advantage of suppressing the dendrite-shaped growth of lithium or inducing lithium electrodeposition inside the pores to suppress changes in thickness.

[0091] The present invention will be explained in more detail through the following examples. The following manufacturing examples and examples are merely illustrative to aid in understanding the present invention and do not limit the scope of the present invention.

[0093] Preparation Example 1: Preparation of a porous structure for a lithium battery

[0094] As additional nanoparticles, 500 nm silica (SiO2) nanoparticles (prepared via the Stober method), which are inorganic nanoparticles, and copper nanoparticles, a conductive metal, are added in a 1:1 mass ratio and mixed via ball milling. Subsequently, a binder is added at a ratio of 10 wt% based on 100 wt% of the total precursor, and a precursor sheet is fabricated by calendering. Next, the material is heat-treated from room temperature to 250°C at a heating rate of 25°C / min to induce physical welding between the metal nanoparticles. Finally, the silica (SiO2) is removed by etching in hydrofluoric acid (HF) solvent, resulting in a final material with a porosity of 91%, a pore size of 500 nm, a thickness of 80 µm, and a weight of 7.0 mg / cm³. 2 A porous structure for lithium batteries is manufactured.

[0096] Preparation Example 2: Preparation of a porous structure for a lithium battery

[0097] A porous structure for a lithium battery was prepared in the same manner as in Preparation Example 1, except that copper nanoparticles, which are metal nanoparticles, and silica (SiO2) nanoparticles, which are additional nanoparticles, were added in a mass ratio of 1:0.5 compared to Preparation Example 1, and finally, the porosity was 68%, the pore size was 500 nm, the thickness was 80 μm, and the weight was 23.2 mg / cm³. 2 A porous structure for lithium batteries is manufactured.

[0099] Comparative Manufacturing Example 1: Preparation of a porous structure for a lithium battery

[0100] A porous structure for a lithium battery was prepared in the same manner as in Preparation Example 1, except that 500 nm silica (SiO2) nanoparticles, which are inorganic nanoparticles, were not used as additional nanoparticles compared to Preparation Example 1, and finally, the porosity was 35%, the pore size was 30 nm, the thickness was 80 µm, and the weight was 53.9 mg / cm³ 2 A porous structure for lithium batteries is manufactured.

[0102] Example 1: A lithium battery prepared using a negative electrode for a lithium battery comprising a porous structure for a lithium battery according to Preparation Example 1

[0103] As a cathode, 1 mA h cm in the porous structure for a lithium battery according to Preparation Example 1 -2 A negative electrode is prepared by electrodepositing a certain amount of lithium. Additionally, a LiNi5Co2Mn3 cathode material is prepared as the positive electrode. Furthermore, Celgard #2400 is prepared as a separator between the negative electrode and the positive electrode. Additionally, a 1M LiPF6EC:DEC + 10 wt% FEC electrolyte is prepared to finally manufacture a lithium battery.

[0105] Comparative Example 1: A lithium battery manufactured using only lithium foil as the negative electrode for a lithium battery

[0106] A lithium battery is manufactured in the same manner as in Example 1, except that only lithium foil is used as the negative electrode compared to Example 1.

[0108] Comparative Example 2: A lithium battery manufactured using only copper foil as the negative electrode for a lithium battery

[0109] A lithium battery is manufactured in the same manner as in Example 1, except that only copper foil is used for the negative electrode compared to Example 1.

[0111] Comparative Example 3: A lithium battery manufactured using only copper mesh as the negative electrode for a lithium battery

[0112] A lithium battery is manufactured in the same manner as in Example 1, except that only copper mesh is used for the negative electrode compared to Example 1.

[0114] Experimental Example 1: Analysis of Charge / Discharge Efficiency of Lithium Battery Anode According to the Presence of Additional Nanoparticles

[0115] A 160 μm thick layer of lithium was stacked on a porous structure for a lithium battery prepared according to Preparation Example 1 and Comparative Preparation Example 1 and used as a counter electrode and a reference electrode, and the porous structure for a lithium battery was used as a working electrode to achieve 1 mA cm⁻¹ -2 The charge / discharge efficiency was analyzed at the current density.

[0116] At this time, the electrolyte used for electrochemical analysis was prepared by dissolving the LiPF6 salt in a solvent containing 10% (weight percent) of FEC (fluoroethylene carbonate) with a volume ratio of EC (ethylene carbonate) / DEC (diethyl carbonate) of 1:1 to a concentration of 1 M.

[0117] The results of the charge / discharge efficiency and scanning electron microscope images resulting therefrom are shown in Figures 1a to 3b.

[0118] Specifically, FIGS. 1a and 1b are graphs showing the charge / discharge efficiency results according to Manufacturing Example 1 (Fig. 1a) or Comparative Manufacturing Example 1 (Fig. 1b), respectively; FIGS. 2a and 2b are scanning electron microscope images showing the top view of Manufacturing Example 1 (Fig. 2a) or Comparative Manufacturing Example 1 (Fig. 2b), respectively, during charging and discharging; and FIGS. 3a and 3b are scanning electron microscope images showing the cross-section view of Manufacturing Example 1 (Fig. 3a) or Comparative Manufacturing Example 1 (Fig. 3b), respectively, during charging and discharging.

[0119] Referring to the above Figures 1a, 2a, and 3a, it was confirmed that when the pore size and porosity are sufficiently high, electrodeposition occurs internally, increasing Coulomb efficiency, which can reduce energy loss and improve the lifespan of the battery.

[0120] On the other hand, referring to Figures 1b, 2b, and 3b, it can be seen that when the pore size and porosity are small, lithium is not electrodeposited inside but is electrodeposited on the surface, and the Coulomb efficiency is also low at 83%.

[0122] Experimental Example 2: Analysis of Coulomb Efficiency According to Pore Size and Porosity

[0123] A 160 μm thick layer of lithium was stacked on a porous structure for a lithium battery prepared according to Preparation Example 1, Preparation Example 2, and Comparative Preparation Example 1 and used as a counter electrode and a reference electrode, and the porous structure for a lithium battery was used as a working electrode to achieve 1 mA cm⁻¹ -2 The Coulomb efficiency was analyzed at the current density.

[0124] At this time, the electrolyte used for electrochemical analysis was prepared by dissolving the LiPF6 salt in a solvent containing 10% (weight percent) of FEC (fluoroethylene carbonate) with a volume ratio of EC (ethylene carbonate) / DEC (diethyl carbonate) of 1:1 to a concentration of 1 M.

[0125] The results of the analysis of Coulomb efficiency based on this are shown in Figure 4.

[0126] Specifically, FIG. 4 is a graph showing the Coulomb efficiency results according to Manufacturing Example 1, Manufacturing Example 2, and Comparative Manufacturing Example 1, respectively.

[0127] Referring to FIG. 4, when comparing the Coulomb efficiency results of Preparation Example 1, Preparation Example 2, and Comparative Preparation Example 1, it can be seen that the Coulomb efficiency increases as the pore diameter and porosity increase. Since an increase in Coulomb efficiency can lead to an increase in battery life, there is an advantage in that the battery life of a lithium battery manufactured using a porous structure for a lithium battery manufactured by the method for manufacturing a porous structure for a lithium battery according to one embodiment can be improved.

[0129] Experimental Example 3: Analysis of Capacity Retention Rate and Lithium Electrodeposition of a Conventional Anode and an Anode Using a Porous Structure for Lithium Batteries

[0130] A lithium battery according to Example 1 and Comparative Example 1 was prepared, and 1 mA cm⁻¹ -2 The capacity retention rate of the lithium battery after charging and discharging at a current density was measured, and the results are shown in Figure 5.

[0131] Specifically, FIG. 5 shows 1 mA cm of a lithium battery according to Example 1 and Comparative Example 1. -2 This is a graph measuring the capacity retention rate of a lithium battery after charging and discharging at a current density.

[0132] Referring to Figure 5 above, it was confirmed that the capacity retention rate of the lithium battery according to Example 1 was improved by using a porous structure for lithium batteries.

[0133] In addition, FIGS. 6 to 8 show the 1 mA cm² of a lithium battery according to Comparative Example 2 (FIG. 6), Comparative Example 3 (FIG. 7), and Example 1 (FIG. 8). -2 This is an optical microscope image showing the degree of lithium electrodeposition over time after charging and discharging at a current density.

[0134] First, referring to Fig. 6, in the case of a lithium battery using a commercially available copper foil with high conductivity as the negative electrode, it was confirmed that lithium dendrite shapes were clearly observed as charging and discharging progressed. Additionally, referring to Fig. 7, in the case of a lithium battery using a copper mesh with high conductivity as the negative electrode, it was confirmed that lithium electrodeposition on the mesh surface was dominant and thickness changes were also observed as charging and discharging progressed. On the other hand, referring to Fig. 8, in the case of a lithium battery using a copper porous structure with artificially lowered conductivity containing a binder as the negative electrode, the thickness change was minimal and it was confirmed that lithium was electrodeposited inside the pores.

[0135] That is, since the method for manufacturing a porous structure for a lithium battery according to one embodiment is performed through welding and etching processes via a bottom-up method, it is possible to control not only physical properties such as conductivity and lithium affinity, but also microscopic structures such as porosity, pore size, and surface area, and macroscopic structures such as the thickness and width of the electrode, so it has the advantage of accurately realizing pore sizes in the hundreds of nanometer range or realizing high porosity.

[0136] Accordingly, it can be confirmed that the negative electrode for a lithium battery containing a porous structure for a lithium battery manufactured by the above manufacturing method has a binder appropriately included in the porous structure for a lithium battery, thereby relatively lowering the conductivity compared to conventional negative electrodes, so that lithium can be electrodeposited inside the porous structure during charging and discharging, thereby suppressing the dendrite-shaped growth of lithium or inducing lithium electrodeposition inside the pores to suppress changes in thickness.

Claims

Claim 1 A method for manufacturing a negative electrode for a lithium battery, comprising: a step of preparing a precursor by mixing metal nanoparticles and additional nanoparticles; a step of heat-treating the precursor; a step of etching additional nanoparticles within the heat-treated precursor; and a step of placing lithium metal on a porous structure. Claim 2 A method for manufacturing a negative electrode for a lithium battery according to claim 1, wherein the precursor is prepared by further mixing a binder. Claim 3 A method for manufacturing a negative electrode for a lithium battery according to claim 2, wherein the content of the binder is 3% to 50% by weight based on 100% by weight of the total precursor. Claim 4 A method for manufacturing a negative electrode for a lithium battery according to claim 1, further comprising the step of preparing the precursor and then calendering it to produce a precursor sheet. Claim 5 A method for manufacturing a negative electrode for a lithium battery according to claim 1, wherein the metal nanoparticle comprises one or more selected from the group consisting of a metal alloyable with lithium and a conductive metal. Claim 6 A method for manufacturing a negative electrode for a lithium battery according to claim 5, wherein the metal alloyable with lithium comprises one or more selected from the group consisting of silver (Ag), zinc (Zn), gold (Au), aluminum (Al), magnesium (Mg), tin (Sn), silicon (Si), and carbon (C). Claim 7 A method for manufacturing a negative electrode for a lithium battery according to claim 5, wherein the conductive metal comprises one or more selected from the group consisting of copper (Cu), iron (Fe), titanium (Ti), and nickel (Ni). Claim 8 A method for manufacturing a negative electrode for a lithium battery according to claim 1, wherein the mass ratio of the metal nanoparticles to additional nanoparticles is 1:0.3 to 1:1.

2. Claim 9 A method for manufacturing a negative electrode for a lithium battery according to claim 1, wherein the additional nanoparticles comprise one or more selected from the group consisting of organic nanoparticles and inorganic nanoparticles. Claim 10 A method for manufacturing a negative electrode for a lithium battery according to claim 9, wherein the organic nanoparticle comprises one or more selected from the group consisting of PMMA, PEO, cellulose, and polystyrene. Claim 11 A method for manufacturing a negative electrode for a lithium battery according to claim 9, wherein the inorganic nanoparticles comprise one or more selected from the group consisting of silica, titania (TiO2), zirconia (ZrO2), and alumina (Al2O3). Claim 12 A method for manufacturing a negative electrode for a lithium battery according to claim 1, wherein the heat treatment step is a step of welding the metal nanoparticles together by heating from room temperature to a temperature of 240℃ to 260℃ at a heating rate of 30℃ / min or less. Claim 13 A method for manufacturing a porous structure for a lithium battery according to claim 1, wherein the etching step involves treating the heat-treated precursor with an acid solution to remove additional nanoparticles. Claim 14 A method for manufacturing a negative electrode for a lithium battery according to claim 13, wherein the acid solution comprises one or more selected from the group consisting of a hydrofluoric acid (HF) solution and a mixed solution of alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol. Claim 15 A negative electrode for a lithium battery comprising: a porous structure for a lithium battery characterized by including metal nanoparticles and having a porosity of 30% to 90%; and a lithium metal disposed on the porous structure. Claim 16 A negative electrode for a lithium battery having a pore size of 30 nm to 5000 nm, according to claim 15. Claim 17 In claim 15, a negative electrode for a lithium battery having a thickness of 10 μm to 100 μm. Claim 18 delete Claim 19 A lithium battery employing a negative electrode according to paragraph 15.

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