Silicon-based porous negative active material for electrochemical device, electrochemical device comprising same, and preparation method therefor

Abstract

The present invention relates to a silicon-based porous negative active material for an electrochemical device, an electrochemical device comprising same, and a preparation method therefor and, in particular, to a silicon-based porous negative active material for an electrochemical device, an electrochemical device comprising same, and a preparation method therefor, in which porous magnesium silicate particles are formed through a reaction between a silicate salt and a magnesium salt and reduced through heat treatment in a temperature range where thermal fusion between the particles and clogging of a porous structure in the particles do not occur, thereby preparing a silicon-based porous negative active material, and by minimizing a change in the volume of the silicon-based negative active material during charging / discharging of an electrochemical device, structural stability is ensured and excellent lifespan characteristics are exhibited.

Description

Silicon-based porous negative electrode active material for electrochemical devices, electrochemical devices containing the same, and manufacturing method thereof

[0001] This invention claims the benefit of Korean Patent Application No. 10-2023-0125725 filed with the Korean Intellectual Property Office on September 20, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a silicon-based porous negative electrode active material for an electrochemical device, an electrochemical device comprising the same, and a method for manufacturing the same. Specifically, the present invention relates to a silicon-based porous negative electrode active material, which is prepared by forming porous magnesium silicate particles by a reaction between a silicate salt and a magnesium salt, reducing the porous magnesium silicate particles through heat treatment, and then heat treating the particles so as to be reduced at a temperature in a range where thermal fusion between particles and closure of the porous structure within the particles do not occur, and to a silicon-based porous negative electrode active material for an electrochemical device having excellent life characteristics and minimizing volume change of the silicon-based negative electrode active material during a charge / discharge process of the electrochemical device, thereby ensuring structural stability, an electrochemical device comprising the same, and a method for manufacturing the same.

[0003] Lithium secondary batteries exhibit high energy density and operating potential, long cycle life, and low self-discharge rates. These characteristics have led to their widespread use in mobile information terminals such as cell phones, laptops, and smartphones. More recently, they have also become a common power source for electric vehicles. Lithium secondary batteries possess high voltage and energy density, enabling them to deliver the discharge capacity and cycle life characteristics required for electric vehicles. Therefore, demand for these batteries is expected to rapidly increase in the future.

[0004] Lithium secondary batteries consist of a cathode and an anode, each containing an active material capable of inserting and de-inserting lithium ions. An organic or polymer electrolyte is placed between the two electrodes to generate electricity. As lithium ions migrate between the anode and cathode, oxidation and reduction reactions occur, converting the chemical energy within the battery into electrical energy.

[0005] Lithium secondary batteries are composed of a cathode, an anode, and an electrolyte. The cathode active material is mainly an oxide composed of lithium and a transition metal that has a structure that allows lithium ion intercalation, such as LCO (LiCoO2 - lithium cobalt oxide), NCM (NiCoMn - nickel cobalt manganese oxide), NCA (NiCoAl - nickel cobalt aluminum oxide), and LMO (LiMn2O4 - lithium manganese oxide). In the past, various carbon-based materials have been used as anode active materials.

[0006] Among these, graphite is widely used due to its structure, which facilitates the insertion and de-insertion of lithium ions, and its stability, which remains unchanged even after long-term use. However, graphite's electrical capacity is 372 mAh / g per unit mass, which is currently close to its theoretical capacity, making it difficult to expect further capacity increases.

[0007] Silicon, tin, and aluminum, which form intermetallic compounds with lithium, are known to be suitable high-capacity anode active materials to replace graphite. Among them, silicon, which stores 4.4 lithium ions per silicon atom, has a specific capacity of 4,200 mAh / g, approximately 10 times higher than that of graphite, making it a promising new anode material for lithium secondary batteries.

[0008] There are high expectations for the application of silicon (Si) as an anode active material to increase the capacity of lithium secondary batteries. However, the silicon anode active material experiences significant volume changes when lithium ions are inserted or extracted, which reduces the structural stability of the battery and deteriorates its lifespan characteristics. Furthermore, it suffers from low initial charge / discharge efficiency and reduced ionic and electrical conductivity.

[0009] To solve this problem, various methods have been examined, such as nano-forming silicon particles, composites with carbon-based materials, conductive coating, metal coating, and alloys, but the problem caused by the above-mentioned silicon volume change has not been sufficiently resolved.

[0010] Therefore, there is a need to develop a negative electrode active material that has excellent structural stability, a long cycle life, and excellent charge / discharge capacity, as the volume change of silicon is not large even during repeated charge / discharge cycles.

[0011] The technical problem to be achieved by the present invention is to provide a silicon-based porous negative electrode active material for an electrochemical device, which can introduce a porous structure into a silicon-based negative electrode active material so as to minimize the volume change occurring during the charge and discharge process, and can reduce the manufacturing cost and improve the production speed by using a specific polymer and compound during the manufacturing process to introduce the porous structure, an electrochemical device including the same, and a method for manufacturing the same.

[0012] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0013] One embodiment of the present invention provides a method for producing a silicon-based porous negative electrode active material for an electrochemical device, comprising the steps of: preparing porous magnesium silicate particles by reacting a silicate salt and a magnesium salt; and heat-treating the porous magnesium silicate particles; wherein the step of producing the porous magnesium silicate particles further includes an additive in the process of reacting the silicate salt and the magnesium salt, and the additive includes at least one selected from the group consisting of sodium chloride, sodium sulfate, potassium chloride, potassium sulfate, and combinations thereof.

[0014] According to one embodiment of the present invention, the silicate salt may include at least one selected from the group consisting of sodium silicate, potassium silicate, zinc silicate, barium silicate, lithium silicate, calcium silicate, aluminum silicate, and combinations thereof.

[0015] According to one embodiment of the present invention, the magnesium salt may include at least one selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium carbonate, magnesium acetate, magnesium phosphate, magnesium hydroxide, and combinations thereof.

[0016] According to one embodiment of the present invention, the heat treatment step may be performed by further adding a reducing metal and a heat absorbent to the porous magnesium silicate particles.

[0017] According to one embodiment of the present invention, in the heat treatment step, the weight ratio of the porous magnesium silicate particles, the reducing metal, and the heat absorbent may be 1.0 to 5.0: 0.1 to 3.0: 0.1 to 8.0.

[0018] According to one embodiment of the present invention, the reducing metal may be at least one selected from the group consisting of magnesium, aluminum, copper, iron, lithium, sodium, germanium, potassium, calcium, titanium, zinc, nickel, zirconium, chromium, barium, rubidium, cesium, beryllium, strontium, and combinations thereof.

[0019] According to one embodiment of the present invention, the heat absorbent may be at least one selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, barium chloride, calcium chloride, and combinations thereof.

[0020] According to one embodiment of the present invention, the heat treatment step may be a heat treatment performed at a temperature of 300°C or higher and 1,200°C or lower in an inert gas atmosphere for 1 hour or longer and 24 hours or shorter.

[0021] According to one embodiment of the present invention, the method may further include a step of treating the heat-treated porous magnesium silicate particles with acid after the heat treatment step.

[0022] According to one embodiment of the present invention, the acid treatment step may be performed at a temperature of 10°C or higher and 100°C or lower.

[0023] According to one embodiment of the present invention, the acid may be at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, acetic acid, perchloric acid, chloric acid, chlorous acid, hypochlorous acid, iodic acid, and combinations thereof.

[0024] According to one embodiment of the present invention, the method may further include a step of providing a carbon layer on at least a portion of the surface of at least one of the heat-treated porous magnesium silicate particles or the acid-treated porous magnesium silicate particles.

[0025] According to one embodiment of the present invention, the step of providing the carbon layer may be heat treating at a temperature of 300°C or higher and 2,000°C or lower in an atmosphere containing one of an inert gas, hydrogen gas, and a combination thereof.

[0026] One embodiment of the present invention provides a silicon-based porous negative electrode active material for an electrochemical device manufactured by the above manufacturing method.

[0027] One embodiment of the present invention provides an electrochemical device comprising: a negative electrode including the silicon-based porous negative electrode active material for the electrochemical device; and a positive electrode; and a separator and an electrolyte interposed between the negative electrode and the positive electrode.

[0028] A method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to one embodiment of the present invention is advantageous for mass production and can improve economic feasibility.

[0029] The method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to one embodiment of the present invention is a method for manufacturing a silicon-based negative electrode active material by using naturally occurring magnesium silicate-based mineral particles using artificially manufactured magnesium silicate particles through a chemical synthesis method, and thus can ensure higher quality and uniformity when used in an electrochemical device with high quality sensitivity since the components, structure, size, etc. can be uniformly controlled.

[0030] A silicon-based porous negative electrode active material for an electrochemical device according to one embodiment of the present invention can realize uniform quality compared to a negative electrode active material manufactured from a mineral containing magnesium silicate, such as talc, olivine, pyroxene, and serpentine, which are naturally occurring magnesium silicate-based mineral particles.

[0031] A silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention has a porous structure, which, despite containing silicon that undergoes a large volume change during charge and discharge in a lithium secondary battery, can minimize volume change of the electrode during charge and discharge, and thus improve the life characteristics of the electrode by increasing the stability of the electrode structure.

[0032] An electrochemical device according to one embodiment of the present invention has excellent specific surface area and porosity, so that not only does it mitigate volume expansion during charging and discharging, but it also increases the contact area with the electrolyte and reduces the movement distance of lithium ions compared to existing silicon particles, thereby improving both life characteristics and speed performance.

[0033] It should be understood that the effects according to one embodiment of the present invention are not limited to the effects mentioned above, and include all effects that can be inferred from the following description.

[0034] Figure 1 is a flow chart of a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to one embodiment of the present invention.

[0035] FIG. 2 is a scanning electron microscope (SEM) photograph of Manufacturing Example 1, which is a porous magnesium silicate particle manufactured in a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to one embodiment of the present invention.

[0036] FIG. 3 is a scanning electron microscope (SEM) photograph of Manufacturing Example 2, which is a porous magnesium silicate particle manufactured in a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to one embodiment of the present invention.

[0037] FIG. 4 is a scanning electron microscope (SEM) photograph of Manufacturing Example 3, which is a porous magnesium silicate particle manufactured in a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to one embodiment of the present invention.

[0038] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0039] In this specification, “A and / or B” means “A and B, or A or B.”

[0040] In this specification, “porous” may mean having a porous structure.

[0041] The drawings attached to this specification illustrate preferred embodiments of the invention and, together with the description of the invention, serve to explain the principles of the invention, but are not intended to limit the scope of the invention. Furthermore, the shape, size, scale, or ratio of elements in the drawings included in this specification may be exaggerated for clarity.

[0042] Hereinafter, the present invention will be described in more detail.

[0043] Conventionally, it has been difficult to commercialize negative electrode materials containing silicon due to material deterioration caused by volume change during charge and discharge. Accordingly, the inventors of the present invention have studied to develop a technology that can improve life characteristics and rate performance while minimizing volume change during charge and discharge by manufacturing particles having a porous structure containing silicon and applying them to negative electrode materials in secondary batteries. As a result, magnesium silicate particles having a porous structure were first synthesized, and then, through heat treatment using alkali and alkaline earth metals, silicate, which is a silicon oxide, was converted into silicon (Si) and partially oxidized silicon (SiO). x, 0≤x<2) to enable charging and discharging of lithium ions, and by removing by-products present in the particle structure through acid treatment, silicon and partial oxidation (SiO) with a porous structure having excellent specific surface area and porosity are obtained by strengthening the porous structure. x , 0≤x<2) A silicon-based negative electrode active material for an electrochemical device having a porous structure of silicon particles was manufactured.

[0044] Through this, a method for manufacturing a silicon-based negative electrode active material for an electrochemical device having a porous structure with excellent charge / discharge capacity, life characteristics, and rate performance using an inexpensive method was discovered, and the present invention was completed.

[0045] One embodiment of the present invention provides a method for producing a silicon-based porous negative electrode active material for an electrochemical device, comprising the steps of: producing porous magnesium silicate particles by reacting a silicate salt and a magnesium salt (S10); and heat-treating the porous magnesium silicate particles (S30).

[0046] The method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention is advantageous for mass production and can improve economic feasibility. Furthermore, the method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention is a method for manufacturing a silicon-based negative electrode active material by using naturally occurring magnesium silicate mineral particles using artificially manufactured magnesium silicate particles through a chemical synthesis method, and thus can uniformly control the components, structure, size, etc., thereby ensuring higher quality and uniformity when used in an electrochemical device with high quality sensitivity.

[0047] Figure 1 is a flowchart illustrating a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention. Referring to Figure 1, a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention will be described in detail.

[0048] According to one embodiment of the present invention, the method comprises a step (S10) of producing porous magnesium silicate particles by reacting a silicate salt and a magnesium salt. Specifically, the step (S10) of producing porous magnesium silicate particles may be a step of synthesizing porous magnesium silicate particles by sequentially reacting a silicate salt, a magnesium salt, and an additive to be described later. By including the step (S10) of producing porous magnesium silicate particles by reacting a silicate salt and a magnesium salt as described above, the substrate itself can have a porous structure in the process of precipitation through spontaneous and violent reaction of the anionized silicate salt and the cationized magnesium in the aqueous solution, and the magnesium complex included in the porous magnesium silicate particles can be removed in the acid treatment (S50) step after the heat treatment (S30) step described below, thereby further increasing the porous structure of the silicon and silicon partial oxide structures. Through this, a silicon-based negative electrode active material for an electrochemical device having a porous structure, i.e., a silicon-based porous negative electrode active material for an electrochemical device, can be easily produced. In the present specification, “magnesium silicate composite” may mean porous magnesium silicate particles, and “magnesium composite” may mean a remaining material contained in porous magnesium silicate particles that cannot be synthesized into magnesium silicate.

[0049] According to one embodiment of the present invention, by selecting a silicate salt and a magnesium salt as synthetic precursor materials in the step of manufacturing the porous magnesium silicate particles, the magnesium silicate synthesis is quickly and easily implemented in an aqueous solution, and a porous structure can be easily formed in the porous magnesium silicate particles themselves, and in the subsequent heat treatment step and acid treatment step, the magnesium complex present in the porous magnesium silicate particles is removed, thereby removing silicon and silicon partial oxide (SiO). x , 0≤x<2) can further promote the porous structure in the particles.

[0050] According to one embodiment of the present invention, the step (S10) of manufacturing the porous magnesium silicate particles may be a reaction of a silicate salt and a magnesium salt in an aqueous dispersion environment. Specifically, the reaction, i.e., synthesis, may be performed in a state where the silicate salt and the magnesium salt are dissolved in water as a solvent, or in a state where the silicate salt and the magnesium salt are not dissolved but dispersed in water as a dispersion medium. As described above, the step (S10) of manufacturing the porous magnesium silicate particles may minimize environmental problems caused by the use of organic solvents, and may reduce manufacturing costs, since the silicate salt and the magnesium salt are reacted in an aqueous dispersion environment. Furthermore, the manufacturing process may be simplified since there is no need to continuously exchange the solvent using water in the subsequent reaction.

[0051] According to one embodiment of the present invention, after the step (S10) of producing the porous magnesium silicate particles, a step (S21) of separating the porous magnesium silicate particles may be further included. Specifically, the step (S21) of separating the porous magnesium silicate particles may be a step of filtering, wherein the porous magnesium silicate particles are separated using a filter. By further including the step (S21) of separating the porous magnesium silicate particles as described above, byproducts generated in the reaction can be removed.

[0052] According to one embodiment of the present invention, the process may further include a step (S23) of washing the porous magnesium silicate particles after the separation step (S21). Specifically, the process may include washing the porous magnesium silicate particles using a solvent, i.e., an organic solvent such as water or ethanol. By further including the step (S23) of washing the porous magnesium silicate particles as described above, the yield of the porous magnesium silicate particles can be improved.

[0053] According to one embodiment of the present invention, a step (S25) of drying the porous magnesium silicate particles may be further included after the washing step (S23). By further including the step (S25) of drying the porous magnesium silicate particles as described above, it is possible to prevent the porous magnesium silicate particles from being denatured by the solvent used in the washing process.

[0054] According to one embodiment of the present invention, after the step of drying the porous magnesium silicate particles (S25), a step of crushing the porous magnesium silicate particles (S27) may be further included. By further including the step of crushing the dried porous magnesium silicate particles (S27) as described above, the aggregated porous magnesium silicate particles are separated, thereby increasing the specific surface area and increasing the reduction efficiency in the heat treatment step (S30) to be performed thereafter. In addition, when included in an electrochemical device, high electrochemical performance and uniform quality can be realized.

[0055] According to one embodiment of the present invention, the step (S27) of crushing the porous magnesium silicate particles may be a mechanical crushing of the porous magnesium silicate particles. Specifically, the method of mechanically crushing the particles may include air jet milling, steam jet milling, high-speed impact mechanical crushing, agitator bead mill, grind mill, nano milling, and planetary ball mill.

[0056] According to one embodiment of the present invention, the separation step (S21), the washing step (S23), the drying step (S25), and the crushing step (S27) may be performed sequentially. As described above, by sequentially performing the separation step (S21), the washing step (S23), the drying step (S25), and the crushing step (S27), reaction by-products are removed from the porous magnesium silicate particles, thereby preventing side effects that may occur when applied to electrochemical devices.

[0057] According to one embodiment of the present invention, the temperature of the drying step (S25) may be 200°C or lower. By controlling the temperature of the drying step within the above-described range, changes in the physical properties of the porous magnesium silicate particles can be prevented.

[0058] According to one embodiment of the present invention, the average diameter of the porous magnesium silicate particles may be 0.0001 μm or more and 1000 μm or less. Specifically, the diameter of the porous magnesium silicate particles may be 0.0001 μm or more and 1000 μm or less. By controlling the average diameter of the porous magnesium silicate particles within the above-described range, the volume expansion reduction efficiency of the negative electrode material including the silicon-based porous negative electrode active material for an electrochemical device is prevented from deteriorating, the loading amount of the negative electrode active material in the electrode is easily controlled, the porosity control efficiency of the negative electrode material is easily controlled, and further, the charge / discharge efficiency of the negative electrode material is prevented from deteriorating, the structural stability is prevented from deteriorating, and the life characteristics are prevented from deteriorating.

[0059] According to one embodiment of the present invention, the method comprises a step (S30) of heat-treating the porous magnesium silicate particles. Specifically, the porous magnesium silicate particles may be heat-treated to reduce the porous magnesium silicate particles. The heat treatment may be a reduction heat treatment. As described above, by including the step (S30) of heat-treating the porous magnesium silicate particles, the silicate-based compound included in the porous magnesium silicate particles is reduced to form silicon metal and silicon partial oxide (SiO). x,By reducing the 0≤x<2) to reversibly alloy lithium ions during the charging and discharging process of a lithium secondary battery, charging of lithium ions is enabled, and the porous structure minimizes the expansion of the silicon-based negative electrode active material, thereby increasing the structural stability of the negative electrode active material and improving the life characteristics of the negative electrode material.

[0060] According to one embodiment of the present invention, the silicate salt may include at least one selected from the group consisting of sodium silicate, potassium silicate, zinc silicate, barium silicate, lithium silicate, calcium silicate, aluminum silicate, and combinations thereof. By selecting the silicate salt from the above, the electrochemical characteristics of the silicon-based negative electrode active material for an electrochemical device having the porous structure can be controlled, and the porous structure of the formed particles can be controlled. In addition, from an economical perspective, the manufacturing cost can be reduced, and the manufacturing time can be reduced by controlling the reaction rate, thereby improving the competitiveness of the product.

[0061] According to one embodiment of the present invention, the magnesium salt may include at least one selected from the group consisting of magnesium chloride (MgCl2), magnesium sulfate (MgSO4), magnesium nitrate (Mg(NO3)2), magnesium carbonate (MgCO3), magnesium acetate (Mg(CH3COO)2), magnesium phosphate (Mg3(PO4)2), magnesium hydroxide (Mg(OH2)2) and combinations thereof. By selecting the magnesium salt from the above, the electrochemical characteristics of the silicon-based porous negative electrode active material for the electrochemical device can be controlled, and the porous structure of the formed particles can be controlled. Additionally, from an economic perspective, it can reduce manufacturing costs and enhance product competitiveness by controlling reaction speed and reducing manufacturing time.

[0062] According to one embodiment of the present invention, the step (S10) of manufacturing the porous magnesium silicate particles further includes an additive in the process of reacting the silicate salt and the magnesium salt, and the additive may include at least one selected from the group consisting of sodium chloride (NaCl), sodium sulfate (Na2SO4), sodium carbonate (Na2CO3), potassium chloride (KCl), potassium sulfate (K2SO4), and combinations thereof. As described above, the step (S10) of manufacturing the porous magnesium silicate particles further includes an additive in the process of reacting the silicate salt and the magnesium salt, and by selecting the additive to include at least one selected from the group consisting of sodium chloride (NaCl), sodium sulfate (Na2SO4), sodium carbonate (Na2CO3), potassium chloride (KCl), potassium sulfate (K2SO4), and combinations thereof, the reaction of the porous magnesium silicate particles, i.e., the synthesis reaction, can be promoted and the yield can be improved.

[0063] According to one embodiment of the present invention, the heat treatment step (S30) may be to heat-treat the porous magnesium silicate particles by further adding a reducing metal and a heat absorbent. As described above, by implementing the heat treatment step (S30) by further adding a reducing metal and a heat absorbent to the porous magnesium silicate particles, the porous magnesium silicate particles are reduced to convert silicon dioxide into silicon metal and silicon metal oxide (SiO). x, 0≤x<2) and absorbs the heat generated during the reduction reaction process to minimize excessive reaction and prevent the pores of the porous structure from being closed by local melting of particles due to local high exothermic reaction.

[0064] According to one embodiment of the present invention, the heat treatment step (S30) converts the porous magnesium silicate particles into silicon metal and silicon metal oxide (SiO x , 0≤x<2) to form particles including silicon and partially oxidized silicon. As described above, the porous magnesium silicate particles may be formed by reducing the porous magnesium silicate particles to silicon metal and silicon metal oxide (SiO x , 0≤x<2) to form particles containing silicon and partially oxidized silicon, thereby strengthening the porous structure, thereby forming a porous structure with excellent specific surface area and porosity.

[0065] According to one embodiment of the present invention, in the heat treatment step (S30), the weight ratio of the porous magnesium silicate particles, the reducing metal, and the heat absorbent may be 1.0 to 5.0: 0.1 to 3.0: 0.1 to 8.0. By adjusting the weight ratio of the porous magnesium silicate particles, the reducing metal, and the heat absorbent in the heat treatment step (S30) within the above-described range, the magnesium silicate particles are reduced to convert silicon dioxide included in the particle structure into silicon metal and silicon partial oxide (SiO). x, 0≤x<2) and silicon dioxide is reduced to silicon metal and silicon partial oxide (SiO x,0≤x<2) enables the charging of lithium ions by reversibly alloying lithium ions during the charge / discharge process of a lithium secondary battery, and the charge capacity can be controlled by adjusting the weight ratio. In addition, by minimizing the expansion of the silicon-based negative electrode active material, the structural stability of the negative electrode active material can be increased, thereby improving the life characteristics of the negative electrode material. Furthermore, by adjusting the amount of the heat absorbent in the weight ratio, the heat generated during the reduction reaction process can be absorbed, thereby minimizing excessive reaction and preventing the closure of the pores of the porous structure due to local melting of particles caused by local high exothermic reaction.

[0066] According to one embodiment of the present invention, the reducing metal may be at least one selected from the group consisting of magnesium (Mg), aluminum (Al), copper (Cu), iron (Fe), lithium (Li), sodium (Na), germanium (Ge), potassium (K), calcium (Ca), titanium (Ti), zinc (Zn), nickel (Ni), zirconium (Zr), chromium (Cr), barium (Ba), rubidium (Rb), cesium (Cs), beryllium (Be), strontium (Sr), and combinations thereof. By selecting the reducing metal from the above, the manufacturing cost can be reduced and the reducing power can be improved.

[0067] According to one embodiment of the present invention, the heat absorbent may be at least one selected from the group consisting of sodium chloride (NaCl), potassium chloride (KCl), magnesium chloride (MgCl2), barium chloride (BaCl2), calcium chloride (CaCl2), and combinations thereof. By selecting the heat absorbent from the above, heat generated by the reduction reaction between the porous magnesium silicate particles and the reducing metal can be alleviated, thereby maintaining a constant and uniform temperature during the reduction reaction.

[0068] According to one embodiment of the present invention, the heat treatment step (S30) may be a heat treatment performed in an inert gas atmosphere at a temperature of 300°C or more and 1,200°C or less for 1 hour or more and 24 hours or less. Specifically, the heat treatment step (S30) is preferably performed at a temperature of 300°C or more and 1,200°C or less and for 1 hour or more and 24 hours or less, so that the porous magnesium silicate particles react with a reducing metal to induce reduction. As described above, by controlling the temperature and time of the heat treatment step, silicon dioxide is converted into silicon metal and silicon partial oxide (SiO). x, 0≤x<2) enables the charging of lithium ions by reversibly alloying lithium ions during the charge / discharge process of a lithium secondary battery, and the specific charge capacity of the material can be controlled by adjusting these control conditions. In addition, by controlling the reduction rate through adjusting the control conditions, the expansion of the silicon-based negative electrode active material can be minimized, thereby increasing the structural stability of the negative electrode active material, thereby improving the life characteristics of the negative electrode material. Furthermore, the charge capacity and life characteristics can be improved by preventing the collapse of the porous structure.

[0069] According to one embodiment of the present invention, the inert gas in the heat treatment step may be at least one selected from the group consisting of nitrogen gas, argon gas, neon gas, helium gas, and combinations thereof. By selecting the inert gas used in the heat treatment step from the above-described ones, side reactions occurring in the heat treatment step can be minimized, thereby improving the performance of the negative electrode active material.

[0070] According to one embodiment of the present invention, after the heat treatment step (S30), a step (S50) of treating the heat-treated porous magnesium silicate particles with acid may be further included. Specifically, the porosity may be increased by removing additional products in the matrix, i.e., the porous magnesium silicate particles reduced by the heat treatment. As described above, by further including a step (S50) of treating the heat-treated porous magnesium silicate particles with acid after the heat treatment step (S30), the magnesium complex included in the porous magnesium silicate particles is removed in the acid treatment step, so that the obtained target material is silicon metal and silicon partial oxide (SiO). x , 0≤x<2) can be increased, and the space of the removed magnesium composite forms pores, thereby further maximizing the porosity of the existing porous particles. Additionally, unreacted substances and / or reaction by-products can be removed, and thereby a purified and reduced silicon-based porous negative active material for an electrochemical device can be manufactured. In the present specification, the magnesium composite, the magnesium-based composite, the magnesium composite material and the magnesium-based composite material may refer to by-products remaining in the synthesis process of porous magnesium silicate particles or generated as side reactions.

[0071] According to one embodiment of the present invention, the acid treatment step (S50) may be performed at a temperature of 10°C or more and 100°C or less. By controlling the temperature in the acid treatment step within the above-described range, the removal efficiency of foreign substances remaining in the side reactions or unreacted reactors can be improved.

[0072] According to one embodiment of the present invention, the acid may be at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, acetic acid, perchloric acid, chloric acid, chlorous acid, hypochlorous acid, iodic acid, and combinations thereof. By selecting the acid from the above, oxides produced by oxidation of the metal can be effectively removed.

[0073] According to one embodiment of the present invention, the method may further include a step (S40, S60) of providing a carbon layer on at least a portion of the surface of at least one of the heat-treated porous magnesium silicate particles or the acid-treated porous magnesium silicate particles. Specifically, the method may further include a step (S40) of providing a carbon layer on at least a portion of the surface of the porous magnesium silicate particles after the heat treatment step (S30), or a step (S60) of providing a carbon layer on at least a portion of the surface of the porous magnesium silicate particles after the acid treatment step (S50), and may further include a step (S40, S60) of providing a carbon layer on at least a portion of the surface of the porous magnesium silicate particles for both the heat treatment step (S30) and the acid treatment step (S50), respectively. By further including a step of providing the carbon layer as described above, the surface electrical conductivity of the silicon-based porous negative electrode active material for the electrochemical device can be improved, and the formation of a stabilizing interface (SEI, Solid Electrolyte Interface) with the electrolyte of a lithium secondary battery can be minimized, thereby improving the electrochemical stability of the silicon-based electrochemical device.

[0074] According to one embodiment of the present invention, the step (S40, S60) of providing the carbon layer may be a heat treatment at 300°C or more and 2,000°C or less in an atmosphere containing one of an inert gas, hydrogen gas, and a combination thereof. As described above, by implementing the step (S40, S60) of providing the carbon layer as a heat treatment at 300°C or more and 2,000°C or less in an atmosphere containing one of an inert gas, hydrogen gas, and a combination thereof, the carbon layer can be easily formed.

[0075] One embodiment of the present invention provides a silicon-based porous negative electrode active material for an electrochemical device manufactured by the above manufacturing method.

[0076] According to one embodiment of the present invention, a silicon-based porous negative electrode active material for an electrochemical device can realize uniform quality compared to a negative electrode active material manufactured from a mineral containing magnesium silicate, such as talc, olivine, pyroxene, and serpentine, which are naturally occurring magnesium silicate-based mineral particles. Furthermore, according to one embodiment of the present invention, although the silicon-based porous negative electrode active material for an electrochemical device contains silicon, which undergoes a large volume change during charge and discharge in a lithium secondary battery, it has a porous structure, so that the volume change of the electrode can be minimized during charge and discharge, and the stability of the electrode structure is thus increased, so that the life characteristics of the electrode can be improved.

[0077] According to one embodiment of the present invention, the silicon-based porous negative electrode active material for an electrochemical device may not have a layer containing carbon on the inner surface of the porous structure. As described above, by implementing the silicon-based porous negative electrode active material for an electrochemical device as not having a layer containing carbon on the inner surface of the porous structure, the purity of the silicon-based porous negative electrode active material for an electrochemical device can be improved and the porosity can be improved.

[0078] According to one embodiment of the present invention, the silicon-based porous negative electrode active material for the electrochemical device comprises silicon (Si) and partially oxidized silicon (SiO x , 0 <x<2)을 포함하는 것일 수 있다. 상술한 것과 같이 상기 전기화학소자용 실리콘계 다공성 음극 활물질이 실리콘(Si) 및 부분 산화된 실리콘(SiO x , 0 <x<2)을 포함함으로써, 다공 구조를 강화할 수 있으며, 리튬이차전지의 충방전 과정에서 리튬이온을 가역적으로 합금화 함을 통해 리튬이온의 충전을 가능하게 하며, 상기 다공구조는 상기 실리콘계 음극 활물질의 팽창을 최소화하여, 음극 활물질의 구조적 안정성을 높여 음극재의 수명특성을 개선할 수 있다.

[0079] One embodiment of the present invention provides an electrochemical device comprising: a negative electrode including the silicon-based porous negative electrode active material for the electrochemical device; and a positive electrode; and a separator and an electrolyte interposed between the negative electrode and the positive electrode.

[0080] An electrochemical device according to one embodiment of the present invention has excellent specific surface area and porosity, so that not only does it mitigate volume expansion during charging and discharging, but it also increases the contact area with the electrolyte and reduces the movement distance of lithium ions compared to existing silicon particles, thereby improving both life characteristics and speed performance.

[0081] In one embodiment of the present invention, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept encompassing a primary battery and a secondary battery. In the present specification, the secondary battery is capable of charging and discharging, and refers to a lithium secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, etc. The lithium secondary battery uses lithium ions as an ion conductor, and examples thereof include, but are not limited to, a non-aqueous electrolyte secondary battery including a liquid electrolyte, an all-solid-state battery including a solid electrolyte, a lithium polymer battery including a gel polymer electrolyte, and a lithium metal battery using lithium metal as an anode.

[0082] According to one embodiment of the present invention, the positive electrode has a positive electrode current collector and a positive electrode active material layer including a positive electrode active material, a conductive material, and a binder resin on at least one surface of the positive electrode current collector. The positive electrode active material is a layered compound such as lithium manganese oxide (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); chemical formula LiMn 1-x M xA lithium manganese composite oxide represented by O2 (wherein, M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (wherein, M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; a disulfide compound; or a mixture of two or more of Fe2(MoO4)3.

[0083] According to one embodiment of the present invention, the negative electrode has a negative electrode current collector and a negative electrode active material layer including a negative electrode active material, a conductive material, and a binder resin on at least one surface of the current collector. The negative electrode necessarily includes a silicon-based negative electrode active material for an electrochemical device having the porous structure described above as the negative electrode active material. Furthermore, the negative electrode active material is carbon such as lithium metal oxide, non-graphitizable carbon, graphitic carbon; LixFe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, 및 Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료; 티타늄 산화물 중 선택된 1종 또는 2종 이상의 혼합물을 포함할 수 있다.

[0084] According to one embodiment of the present invention, the conductive material may be, for example, one selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials among these. More specifically, the conductive material may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials among these.

[0085] According to one embodiment of the present invention, the current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used.

[0086] According to one embodiment of the present invention, the binder resin may be a polymer commonly used in electrodes in the art. Non-limiting examples of such binder resins include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, polyethylhexyl acrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. Examples thereof include, but are not limited to, cellulose acetatepropionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose.

[0087] According to one embodiment of the present invention, an electrochemical device prepared as described above can be placed in an appropriate case and an electrolyte solution is injected to manufacture a battery.

[0088] According to one embodiment of the present invention, the electrolyte is A + B - As a salt with the same structure as A + is Li + , Na + , K + B containing an ion composed of an alkali metal cation or a combination thereof; - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - Salts containing anions such as or combinations thereof are dissolved or dissociated in organic solvents such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma butyrolactone (γ-butyrolactone) or mixtures thereof, but are not limited thereto.

[0089] One embodiment of the present invention provides a battery module including a battery including the electrochemical element as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0090] Hereinafter, the present invention will be described in detail using examples. However, the examples according to the present invention may be modified in various ways, and the scope of the present invention is not limited to the examples described below. The examples in this specification are provided to more fully explain the present invention to those of ordinary skill in the art.

[0091] <Manufacturing Example 1: Manufacturing of a silicon-based negative electrode active material for an electrochemical device having a porous structure>

[0092] In order to manufacture a silicon-based negative electrode active material for an electrochemical device having a porous structure, i.e., a silicon-based porous negative electrode active material for an electrochemical device, porous magnesium silicate particles were manufactured by reacting sodium silicate, a silicate salt, and magnesium chloride (MgCl2), a magnesium salt.

[0093] Specifically, a 1,000 mL round-bottom flask was equipped with a paddle stirrer, a thermometer, and a reflux condenser. 400 mL of deionized water (DIW) was added to the 1,000 mL round-bottom flask.

[0094] To form a silicate salt as a reactant, 28 g of sodium silicate and 4 g of sodium chloride (NaCl), an additive for promoting and stabilizing the reaction, were first added to each of the 1,000 mL round-bottom flasks, and then the solution was heated to 70°C and maintained at a stirring speed of 80 rpm for about 10 minutes to prepare a synthetic bed.

[0095] Afterwards, in order to prepare a magnesium salt solution separately from the above reactant, silicate salt, in the above 1,000 mL round bottom flask, 30 g of magnesium chloride (MgCl2) was dissolved in 200 mL of deionized water (DIW).

[0096] The above-prepared magnesium salt solution was added to the silicate salt contained in the 1,000 mL round-bottom flask at a rate of 2.5 g / min.

[0097] The above 1,000 mL round bottom flask was maintained at a stirring speed of 80 rpm and a temperature of 70°C until the magnesium salt solution was completely added, and was maintained for 180 minutes after the supply of the magnesium salt solution was completed.

[0098] After the reaction of the above silicate salt and the above magnesium salt was completed, the magnesium silicate particles were separated from the particles through a filter device, washed with deionized water (DIW) three or more times, and filtering was repeated to completely remove unreacted dispersions and obtain only the targeted porous magnesium silicate particles.

[0099] Afterwards, the porous magnesium silicate particles were placed in a dry oven and maintained at 85°C for 5 hours to completely remove moisture.

[0100] Afterwards, the porous magnesium silicate particles were mechanically ground for about 10 minutes using a planetary ball mill to reduce the size of the agglomerated powder and make it uniform.

[0101] 5 g of the porous magnesium silicate particles, 5 g of magnesium metal powder as a reducing metal, and 10 g of sodium chloride (NaCl) as a heat absorbent were ground in an agate mortar to form a uniform mixture. The mixture was filled into an alumina crucible, placed in a tubular furnace, and heated at a rate of 5 °C / min under an atmosphere of an inert gas mixture of argon (Ar) and 5 wt% hydrogen (H2), and maintained at 660 °C for 6 hours. The porous magnesium silicate particles and the magnesium powder as a metal were melted and sufficiently reacted, thereby heat-treating so that the silicon dioxide of the porous magnesium silicate particles was reduced to silicon metal and silicon partial oxide (SiOx, 0≤x<2), thereby manufacturing a silicon-based porous negative active material for an electrochemical device.

[0102] The silicon-based porous negative active material for electrochemical devices, which is a powder produced by the above heat treatment, was immediately dispersed in an ethanol / water mixture through magnetic stirring and ultrasonic treatment for 30 minutes, and then 1 M HCl, a hydrochloric acid solution, was added to the dispersed colloidal solution for acid treatment and mixed, and then ultrasonic treatment was performed at 80°C for 1 hour to completely remove reaction byproducts along with MgO and Mg2Si.

[0103] To increase the purity of the above acid-treated particles, the washing process with deionized water (DIW) was repeated 2 to 3 times to completely remove any remaining acidic substances and reaction by-products.

[0104] 10 g of the above silicon-based porous negative electrode active material for electrochemical devices was mixed with 15 g of pitch carbon, filled into an alumina crucible, placed in a tubular furnace, and heated to 900°C at a rate of 5°C / min under an argon (Ar) / 5 wt% hydrogen (H2) mixed gas atmosphere, and maintained for 6 hours, thereby manufacturing a silicon-based negative electrode active material for electrochemical devices having a porous structure with a carbon layer.

[0105] <Manufacturing Example 2>

[0106] In the manufacture of a silicon-based negative electrode active material according to the above Manufacturing Example 1, a silicon-based porous negative electrode active material for an electrochemical device was manufactured in the same manner as in Manufacturing Example 1, except that 14 g of sodium silicate was used to form a silicate salt as a reactant.

[0107] <Manufacturing Example 3>

[0108] In the manufacture of a silicon-based negative electrode active material according to the above Manufacturing Example 1, a silicon-based porous negative electrode active material for an electrochemical device was manufactured in the same manner as in Manufacturing Example 1, except that 60 g of magnesium chloride (MgCl2) was used to form a magnesium salt as a reactant.

[0109]

[0110] The types and contents of silicate salts and magnesium salts used in the above manufacturing examples 1 to 3 are summarized in Table 1 below.

[0111] Types of silicate saltsSilicate salt dosageTypes of magnesium saltsMagnesium salt dosagePreparation example 1Sodium silicate (Na₂SiO₃) 28gMagnesium chloride (MgCl2) 30gPreparation example 2Sodium silicate (Na₂SiO₃) 14gMagnesium chloride (MgCl2) 30gPreparation example 3Sodium silicate (Na₂SiO₃) 14gMagnesium chloride (MgCl2) 60g

[0112] <Comparative Manufacturing Example 1: Manufacturing of a Silicon-Based Negative Electrode Active Material for Electrochemical Devices Without a Porous Structure>

[0113] To manufacture a silicon-based negative electrode active material for electrochemical devices without a porous structure, a 1,000 mL round-bottom flask was equipped with a paddle stirrer, a thermometer, and a reflux condenser.

[0114] 600 ml of deionized water (DIW) was added to the 1,000 ml round-bottom flask, and 30 g of sodium silicate was added to form a reactant, a silicate salt, and stirred at 80 rpm for about 10 minutes at a temperature of 50 °C. Approximately 0.5 M hydrochloric acid (HCl) was added stepwise to adjust the pH of the dispersion until the pH reached 3 and maintained for 60 minutes to complete the reaction, thereby producing particles.

[0115] After the above reaction was completed, only the silicon dioxide (SiO2) particles were separated through a filter device, washed with deionized water (DIW) three or more times, and filtering was repeated to completely remove the reaction dispersion and obtain only the silicon dioxide (SiO2) particles.

[0116] Afterwards, the silicon dioxide (SiO2) particles were placed in a dry oven and maintained at 85°C for 5 hours to completely remove moisture.

[0117] Afterwards, the silicon dioxide (SiO2) particles were mechanically ground for about 10 minutes using a planetary ball mill to reduce the size of the agglomerated powder and make it uniform.

[0118] 5 g of the above-mentioned silicon dioxide (SiO2) particles, 5 g of magnesium metal powder as a reducing metal, and 10 g of sodium chloride (NaCl) as a heat absorbent were ground in an agate mortar to form a uniform mixture. The mixture was filled into an alumina crucible, placed in a tube-shaped furnace, and heated at a rate of 5 ℃ / min under an argon (Ar) / 5 wt% hydrogen (H2) mixed gas atmosphere to reach 660 ℃ and maintained for 6 hours, so that the silicon dioxide (SiO2) particles and the magnesium metal powder melted and sufficiently reacted, so that the silicon dioxide of the silicon dioxide particles was converted into silicon metal and silicon partial oxide (SiO). x, A silicon-based negative electrode active material for an electrochemical device without a porous structure was manufactured by heat treatment so that it is reduced to (0≤x<2).

[0119] The silicon-based negative electrode active material for electrochemical devices, which is a powder produced by the above heat treatment, was immediately dispersed in an ethanol / water mixture through magnetic stirring and ultrasonic treatment for 30 minutes, and then 1 M HCl hydrochloric acid solution was added to the dispersed colloidal solution for acid treatment, mixed, and then ultrasonic treatment was performed at 80°C for 1 hour to completely remove reaction byproducts along with MgO and Mg2Si.

[0120] To increase the purity of the above acid-treated particles, the washing process with deionized water (DIW) was repeated 2 to 3 times to completely remove any remaining acidic substances and reaction by-products.

[0121] 10 g of the silicon-based negative electrode active material for electrochemical devices without a porous structure was mixed with 15 g of pitch carbon, filled into an alumina crucible, placed in a tubular furnace, and heated to 900°C at a rate of 5°C / min under an argon (Ar) / 5% hydrogen (H2) mixed gas atmosphere, and maintained for 6 hours, thereby manufacturing a silicon-based negative electrode active material for electrochemical devices without a porous structure having a carbon layer.

[0122]

[0123] Manufacturing of lithium secondary batteries

[0124] <Example 1>

[0125] According to Manufacturing Example 1, the silicon-based negative electrode active material, Super P-Li (Timcal) and poly(acrylic acid) (PAA, weight average molecular weight = 250,000 g / mol, Sigma-Aldrich) were mixed in distilled water at a weight ratio of 60:20:20 using a DI planetary mixer (Thinky mixer, ARE310) to prepare a negative electrode slurry. Then, the prepared negative electrode slurry was cast on a Cu foil (thickness 10 μm) and an electrode was obtained through a two-step drying process.

[0126] Specifically, the Cu foil cast with the slurry for the cathode was dried for 45 to 60 minutes under atmospheric pressure and then dried for 120 to 480 minutes under vacuum to completely remove the solvent and moisture.

[0127] The electrolyte used was 1.3 M LiPF6 in ethylene carbonate / diethyl carbonate (EC / DEC, volume ratio = 3:7) containing 10 wt% fluoroethylene carbonate (FEC) additive. The separator used was a porous polyethylene film. The cathode used a lithium metal foil. After the separator was interposed between the cathode and the anode in an argon (Ar)-filled glove box with a moisture and oxygen content of less than 1 ppm, the electrolyte was injected to manufacture a coin-type lithium secondary battery.

[0128] <Example 2>

[0129] A coin-type lithium secondary battery was manufactured in the same manner as in Example 1, except that the silicon-based negative electrode active material according to Manufacturing Example 2 was used instead of the silicon-based negative electrode active material according to Manufacturing Example 1.

[0130] <Example 3>

[0131] A coin-type lithium secondary battery was manufactured in the same manner as in Example 1, except that the silicon-based negative electrode active material according to Manufacturing Example 3 was used instead of the silicon-based negative electrode active material according to Manufacturing Example 1.

[0132] <Comparative Example 1>

[0133] A coin-type lithium secondary battery was manufactured in the same manner as in Example 1, except that the silicon-based negative electrode active material according to Comparative Manufacturing Example 1 was used instead of the silicon-based negative electrode active material according to Manufacturing Example 1.

[0134] Battery performance evaluations of Examples 1 to 3 and Comparative Example 1 were performed.

[0135] <Experimental Example 1: Confirmation of particle shape>

[0136] Scanning electron microscope photographs were taken of each of the silicon-based porous negative electrode active materials for electrochemical devices manufactured in the manufacturing process of the silicon-based negative electrode active materials of Manufacturing Examples 1 to 3 above.

[0137] The surface of the silicon-based porous negative electrode active material for the electrochemical device was observed by coating each particle with 10 nm Pt and then photographing the surface using a scanning electron microscope (Field Emission Scanning Electron Microscopy, FE-SEM, TESCAN S8000).

[0138] FIG. 2 is a scanning electron microscope (SEM) photograph of Preparation Example 1, which is a porous magnesium silicate particle manufactured in a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention. FIG. 3 is a scanning electron microscope (SEM) photograph of Preparation Example 2, which is a porous magnesium silicate particle manufactured in a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention. FIG. 4 is a scanning electron microscope (SEM) photograph of Preparation Example 3, which is a porous magnesium silicate particle manufactured in a method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device according to an embodiment of the present invention. Specifically, the above scanning electron microscope (FE-SEM, Field Emission Scanning Electron Microscopy) photographs were taken at a magnification of 30,000 times at a scanning voltage of 25 keV for the particles of Manufacturing Examples 1 to 3.

[0139] Referring to the above Figures 2 to 4, it was confirmed that the individual particle size of the porous magnesium silicate particles manufactured by the above Manufacturing Examples 1 to 3 decreased as the amount of magnesium salt increased compared to the amount of silicate salt introduced.

[0140] <Experimental Example 2: Nitrogen Desorption / Adsorption Isotherm Analysis>

[0141] The silicon-based porous anode active materials for electrochemical devices manufactured in the manufacturing processes of the silicon-based anode active materials of Manufacturing Examples 1 to 3 and Comparative Manufacturing Example 1 in the lithium secondary batteries of Examples 1 to 3 and Comparative Example 1 were subjected to nitrogen adsorption / desorption isotherms (adsorption-desorption isotherms, Micrometrics ASAP2000) to measure the specific surface area, pore volume, and pore size. The Barrett-Joyner-Halenda (BJH) method was used from the nitrogen adsorption / desorption isotherm curve to calculate the pore size distribution and pore diameter. The Brunauer-EmmettTeller (BET) method was used from the nitrogen adsorption / desorption isotherm curve to measure the specific surface area. The specific surface area was typically calculated from the linear portion of the isotherm curve in ISO 9277:2010 (BET) and ISO 15901-2:2006 (gas adsorption / desorption).

[0142] <Experimental Example 3: Plate Expansion Rate>

[0143] The above Examples 1 to 3 and Comparative Example 1 were charged at 1.5 V, 0.5 C under constant current (CC) conditions at a temperature of 25°C, and then discharged at 0.5 C to 0.01 V under constant current (CC) conditions. One cycle was performed, and after 50 cycles, the percentage of increase with respect to the initial electrode thickness was calculated and summarized in Table 2 below.

[0144] <Experimental Example 4: Life Evaluation - Battery Capacity Retention Rate>

[0145] The above Examples 1 and 3 and Comparative Example 1 were charged to 1.5 V, 0.5 C under constant current (CC) conditions at a temperature of 25°C, and then discharged to 0.01 V, 0.5 C under constant current (CC) conditions. This was considered 1 cycle. After 100 cycles, the battery capacity retention rate, which is the percentage of the initial battery capacity, was calculated and summarized in Table 2 below.

[0146] Particle surface area (m 2 / g) pore volume (cm) 3 / g)Pore size (nm)Catalogue expansion rateBattery capacity retention rateExample 1450.80.4845.3535 %76 %Example 2475.00.4864.9533 %77 %Example 3530.70.6414.7723 %81 %Comparative example 1210.50.09518.5444 %71 %

[0147] Referring to Table 2 above, it was confirmed that Examples 1 to 3 having a porous structure had a plate expansion rate of 35% or less and a battery capacity retention rate of 76% or more. In contrast, it was confirmed that Comparative Example 1, which did not have a porous structure, had a reduced plate expansion rate and battery capacity retention rate.

[0148] Therefore, the porous silicon-based negative electrode active material for an electrochemical device according to one embodiment of the present invention, the electrochemical device including the same, and the method for manufacturing the same can manufacture porous magnesium silicate particles through the reaction of an aqueous solution of silicate salt and magnesium salt, and further remove the Mg compound present in the particles through thermal reduction and subsequent acid treatment, thereby further maximizing the porous structure, and the porous silicon metal and silicon partial oxide (SiO) manufactured by thermal reduction x , 0≤x<2) is applied as a lithium secondary battery negative electrode material to manufacture an electrochemical cell, the volume change according to the charge and discharge of the battery can be minimized, the structural stability can be increased, and the life characteristics of the battery can be improved.

[0149] [Explanation of symbols]

[0150] S10: Manufacturing step of porous magnesium silicate particles

[0151] S21: Separation stage

[0152] S23: Cleaning stage

[0153] S25: Drying stage

[0154] S27: Crushing stage

[0155] S30: Heat treatment stage

[0156] S40: Carbon layer preparation stage

[0157] S50: Acid treatment stage

[0158] S60: Carbon layer preparation stage

Claims

1. A step of producing porous magnesium silicate particles by reacting a silicate salt and a magnesium salt; and A step of heat treating the above porous magnesium silicate particles; The step of manufacturing the above porous magnesium silicate particles is to further include an additive in the process of reacting the silicate salt and the magnesium salt, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the additive comprises at least one selected from the group consisting of sodium chloride, sodium sulfate, potassium chloride, potassium sulfate, and combinations thereof.

2. In claim 1, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the silicate salt comprises at least one selected from the group consisting of sodium silicate, potassium silicate, zinc silicate, barium silicate, lithium silicate, calcium silicate, aluminum silicate, and combinations thereof.

3. In claim 1, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the magnesium salt comprises at least one selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium nitrate, magnesium carbonate, magnesium acetate, magnesium phosphate, magnesium hydroxide, and combinations thereof.

4. In claim 1, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the heat treatment step further adds a reducing metal and a heat absorbent to the porous magnesium silicate particles and performs heat treatment.

5. In claim 4, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the weight ratio of the porous magnesium silicate particles, the reducing metal, and the heat absorbent in the heat treatment step is 1.0 to 5.0: 0.1 to 3.0: 0.1 to 8.

0.

6. In claim 4, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the reducing metal is at least one selected from the group consisting of magnesium, aluminum, copper, iron, lithium, sodium, germanium, potassium, calcium, titanium, zinc, nickel, zirconium, chromium, barium, rubidium, cesium, beryllium, strontium, and combinations thereof.

7. In claim 4, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the heat absorbent is at least one selected from the group consisting of sodium chloride, potassium chloride, magnesium chloride, barium chloride, calcium chloride, and combinations thereof.

8. In claim 1, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the heat treatment step is performed at a temperature of 300°C or higher and 1,200°C or lower in an inert gas atmosphere for 1 hour or longer and 24 hours or shorter.

9. In claim 1, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, further comprising a step of treating the heat-treated porous magnesium silicate particles with acid after the heat treatment step.

10. In claim 9, A method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device, wherein the acid treatment step is performed at a temperature of 10°C or higher and 100°C or lower.

11. In claim 9, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, wherein the acid is at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, acetic acid, perchloric acid, chloric acid, chlorous acid, hypochlorous acid, iodic acid, and combinations thereof.

12. In claim 9, A method for producing a silicon-based porous negative electrode active material for an electrochemical device, further comprising a step of providing a carbon layer on at least a portion of the surface of at least one of the heat-treated porous magnesium silicate particles or the acid-treated porous magnesium silicate particles.

13. In claim 12, A method for manufacturing a silicon-based porous negative electrode active material for an electrochemical device, wherein the step of providing the carbon layer comprises heat treatment at a temperature of 300°C or higher and 2,000°C or lower in an atmosphere containing one of an inert gas, hydrogen gas, and a combination thereof.

14. A silicon-based porous negative electrode active material for an electrochemical device manufactured by the manufacturing method of claim 1.

15. An electrochemical device comprising a negative electrode including a silicon-based porous negative electrode active material for an electrochemical device according to claim 14; and a positive electrode; and a separator and an electrolyte interposed between the negative electrode and the positive electrode.

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