Manufacturing method of electrode active material

Abstract

To provide a manufacturing method of electrode active material capable of reducing the battery resistance while reducing the amount of by-products.SOLUTION: The manufacturing method of electrode active material including porous Si includes: a filtration step of filtering slurry including the electrode active material; and before the filtration step, a cleaning step of washing the electrode active material with organic solvents.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing an electrode active material. [Background technology]

[0002] Various techniques have been proposed for porous Si used as an electrode active material as disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-022554 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional techniques, by-products (oxides, etc.) adhere to the surface of the electrode active material during the manufacturing process, which may increase the resistance of the battery.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and has as its main object to provide a method for producing an electrode active material that can reduce the amount of by-products and reduce the resistance of a battery. [Means for solving the problem]

[0006] That is, the present disclosure includes the following aspects. <1> A method for producing an electrode active material containing porous Si, a step of filtering the slurry containing the electrode active material, The method for producing an electrode active material comprises, before the filtering step, a washing step of washing the electrode active material with an organic solvent. [Effects of the Invention]

[0007] The method for producing an electrode active material according to the present disclosure can reduce the amount of by-products and reduce the resistance of the battery. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a flowchart showing an example of a method for producing an electrode active material according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described. It should be noted that matters other than those specifically mentioned in this specification that are necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of electrode active materials that do not characterize the present disclosure) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The present disclosure can be implemented based on the contents disclosed in this specification and common general technical knowledge in the relevant field. In the present disclosure, unless otherwise specified, the average particle size of particles is the median diameter (D50) value, which is the particle size at 50% of the cumulative value in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0010] The present disclosure provides a method for producing an electrode active material containing porous Si, comprising: a step of filtering the slurry containing the electrode active material, The method for producing an electrode active material further comprises a washing step of washing the electrode active material with an organic solvent before the filtration step.

[0011] In the present disclosure, after synthesis of the electrode active material, washing of the electrode active material in the form of a slurry before filtration can reduce by-products (reduce residual oxygen, etc.) and cell resistance.

[0012] FIG. 1 is a flowchart showing an example of a method for producing an electrode active material according to the present disclosure. In the example shown in Figure 1, fine particles of Si and metallic Li are prepared, then alloyed to obtain a LiSi alloy. The LiSi alloy is then de-Li (porous) using mesitylene (1,3,5-trimethylbenzene), ethanol, and acetic acid. The resulting slurry containing nanoporous Si particles is washed, and the washed slurry is pressure filtered to obtain nanoporous Si (powder). The nanoporous Si is then vacuum dried to obtain the electrode active material.

[0013] The method for producing an electrode active material according to the present disclosure is a method for producing an electrode active material containing porous Si. The method for producing an electrode active material according to the present disclosure includes at least a filtration step and a washing step, and may include an alloying step, a delithiation step, etc. before the washing step, and may include a drying step after the filtration step.

[0014] [Alloying process] The alloying step is a step of producing a LiSi alloy (precursor) by mixing silicon and lithium before the cleaning step. The silicon may be Si particles. The lithium may be Li foil. The mixing may be carried out using a mortar or a bead mill. The mixing conditions are not particularly limited. The LiSi alloy may be LiSi alloy particles.

[0015] [Li removal process] The delithiation process is a process performed after the alloying process and before the washing process. The LiSi alloy is added to a dispersion medium, and a Li extractant such as ethanol is added dropwise under an Ar gas atmosphere to remove Li from the LiSi alloy, thereby obtaining porous Si (porous Si). The dispersion medium may be one that does not react with the alloy and is compatible with the Li extractant, such as 1,3,5-trimethylbenzene.

[0016] [Cleaning process] The washing step is a step of washing the electrode active material with an organic solvent before the filtration step. An organic solvent is used for washing. Examples of the organic solvent include alcohols such as ethanol, methanol, isopropyl alcohol (IPA), and normal propyl alcohol (NPA), and acetone. A mixed solvent containing two or more of these may also be used, or a mixed solvent of methanol and isopropyl alcohol may also be used. The mixture ratio of methanol and isopropyl alcohol may be methanol:isopropyl alcohol=95 wt %:5 wt %.

[0017] [Filtration process] The filtration step is a step of filtering the slurry containing the electrode active material. The electrode active material includes porous Si. The electrode active material may be electrode active material particles. The average particle size of the electrode active material particles is not particularly limited and may be 1 nm or more and less than 1000 nm. That is, the porous Si may be nanoporous Si. The filtration may be suction filtration, and the slurry may be separated into a liquid and a solid reactant (negative electrode active material) by suction filtration.

[0018] [Drying process] The drying step is a step of drying the electrode active material obtained after the filtration step. Drying may be performed by vacuum drying.

[0019] The electrode active material of the present disclosure may be used as a negative electrode active material in a negative electrode of a battery. The battery comprises a positive electrode, an electrolyte layer, and a negative electrode. The type of battery is not particularly limited, but examples include lithium ion batteries. The battery may be a primary battery or a secondary battery. The battery may be a liquid battery using an electrolytic solution as an electrolyte, or a solid battery. In the present disclosure, a solid-state battery refers to a battery containing a solid electrolyte. The solid-state battery may be a semi-solid-state battery that contains a solid electrolyte and a liquid-based material, or an all-solid-state battery that does not contain a liquid-based material. Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, the battery may be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery may also be used as a power source for mobile objects other than vehicles (for example, trains, ships, and aircraft), and as a power source for electrical appliances such as information processing devices. [Example]

[0020] (Comparative Example 1) [Synthesis of negative electrode active material] 0.65 g of Si particles (particle size 5 μm, manufactured by Kojundo Chemical Co., Ltd.) and 0.60 g of Li metal (manufactured by Honjo Metal Co., Ltd.) were mixed in an agate mortar under an Ar atmosphere to obtain a LiSi precursor. In a glass reactor under an Ar atmosphere, 12.0 g of the LiSi precursor and 400 ml of a dispersion medium (1,3,5-trimethylbenzene, manufactured by Nacalai Tesque) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). The LiSi precursor dispersion obtained after mixing was cooled to 0°C, and 400 ml of ethanol (manufactured by Nacalai Tesque) was added dropwise and reacted for 120 minutes. After the reaction, 600 ml of acetic acid (manufactured by Nacalai Tesque) was added dropwise and reacted for 60 minutes. [Filtration process] After the reaction, the liquid and the solid reaction product (negative electrode active material) were separated by suction filtration. The resulting solid reaction product was vacuum dried at 120° C. for 2 hours to recover the negative electrode active material.

[0021] [Synthesis of solid electrolyte] 0.550 g of Li2S (Furuuchi Chemical Co., Ltd.), 0.887 g of P2S5 (Aldrich Co., Ltd.), 0.285 g of LiI (Nippo Chemical Co., Ltd.), and 0.277 g of LiBr (Kojundo Chemical Co., Ltd.) were mixed in an agate mortar for 5 minutes. 4 g of n-heptane (dehydrated grade, Kanto Chemical Co., Ltd.) was added to the resulting mixture, and mechanical milling was performed for 40 hours using a planetary ball mill to obtain a solid electrolyte.

[0022] [Preparation of positive electrode mixture] LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 A cathode active material was obtained by surface-treating LiNbO3 (manufactured by Nichia Corporation) with LiNbO3. 1.5 g of this cathode active material, 0.023 g of a conductive additive (VGCF, manufactured by Showa Denko), 0.239 g of the solid electrolyte, 0.011 g of a binder (PVdF, manufactured by Kureha), and 0.8 g of butyl butyrate (manufactured by Kishida Chemical Co., Ltd.) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation) to obtain a cathode composite.

[0023] [Preparation of negative electrode mixture] 1.0 g of the synthesized negative electrode active material, 0.04 g of a conductive additive (VGCF, manufactured by Showa Denko), 0.776 g of the solid electrolyte, 0.02 g of a binder (PVdF, manufactured by Kureha), and 1.7 g of butyl butyrate (manufactured by Kishida Chemical Co., Ltd.) were mixed using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation) to obtain a negative electrode composite.

[0024] [Preparation of evaluation battery] 1cm 2 0.065 g of the above solid electrolyte was placed in a ceramic mold at 1 ton / cm 2 The separator layer (solid electrolyte layer) was prepared by pressing the separator with a pressure of 1 ton / cm. 0.018 g of the positive electrode mixture was placed on one side of the separator. 2 0.0054 g of the negative electrode mixture was placed on the opposite side of the positive electrode layer at a pressure of 4 ton / cm. 2 The negative electrode layer was fabricated by pressing. Aluminum foil was used for the positive electrode current collector, and copper foil for the negative electrode current collector. This resulted in the fabrication of an evaluation battery (all-solid-state battery).

[0025] Example 1 A battery for evaluation was produced in the same manner as in Comparative Example 1, except that in the above [Synthesis of negative electrode active material], the negative electrode active material was synthesized by the following method. A LiSi precursor was obtained by mixing 0.65 g of Si particles (5 μm diameter, manufactured by Kojundo Chemical Co., Ltd.) and 0.60 g of Li metal (manufactured by Honjo Metal Co., Ltd.) in an agate mortar under an Ar atmosphere. 12.0 g of the LiSi precursor was mixed with 400 ml of a dispersion medium (1,3,5-trimethylbenzene, manufactured by Nacalai Tesque) in a glass reactor under an Ar atmosphere using an ultrasonic homogenizer (UH-50, manufactured by SMT Corporation). The LiSi precursor dispersion obtained after mixing was cooled to 0°C, and 400 ml of ethanol (manufactured by Nacalai Tesque) was added dropwise and reacted for 120 minutes. After the reaction, 600 ml of acetic acid (manufactured by Nacalai Tesque) was added dropwise and reacted for 60 minutes. [Cleaning process] The slurry after the reaction was placed in a rotary ceramic filter (DyF152 / S) (manufactured by Mitsubishi Chemical Industries, Ltd.), and filtered using 1600 ml of acetone while rotating the ceramic filter in the pressure chamber at high speed (1000 rpm). This concentrated the slurry and washed the negative electrode active material particles while preventing clogging of the filter. [Filtration process] The resulting slurry was separated into a liquid and a solid reactant (negative electrode active material) by suction filtration. The resulting solid reaction product was vacuum dried at 120° C. for 2 hours to recover the negative electrode active material.

[0026] Examples 2 to 7 A negative electrode active material was obtained in the same manner as in Example 1, except that the solvent used for washing in the above [Washing step] was changed to the solvent shown in Table 1, and a battery for evaluation was fabricated in the same manner as in Comparative Example 1.

[0027] [Table 1]

[0028] [Residual oxygen and carbon measurement] The amounts of residual oxygen and residual carbon in each of the negative electrode active materials obtained in Comparative Example 1 and Examples 1 to 7 were measured. The residual oxygen was measured by a melting-infrared absorption method. Residual carbon was measured by combustion-infrared absorption method. The results of these measurements are shown in Table 1.

[0029] It is clear that the negative electrode active materials obtained in Examples 1 to 7 have reduced amounts of residual oxygen and residual carbon compared to the negative electrode active material obtained in Comparative Example 1 due to the washing step. Furthermore, the negative electrode active materials obtained in Examples 2 to 7 had lower amounts of residual oxygen and carbon than the negative electrode active material obtained in Example 1, which indicates that using alcohols as a solvent in the washing step is more effective in reducing the amounts of residual oxygen and carbon. Since alcohols have OH groups, it is presumed that they can more efficiently remove by-products (such as lithium silicate).

[0030] [Resistance measurement] The resistances of the evaluation batteries fabricated in Comparative Example 1, and Examples 1 to 2, 5, and 7 were measured. The results are shown in Table 1. It can be seen that the resistance of the evaluation batteries fabricated in Examples 1 to 2, 5, and 7 is lower than that of the evaluation battery fabricated in Comparative Example 1.

Claims

[Claim 1] A method for producing an electrode active material containing porous Si, a step of filtering the slurry containing the electrode active material, The method for producing an electrode active material comprises, before the filtering step, a washing step of washing the electrode active material with an organic solvent.

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