JP2019121499A - Composite particles for lithium ion battery and method for producing the same - Google Patents

Abstract

To provide composite particles for a lithium ion battery including a solid electrolyte part having a novel structure, and a method for producing the same including a solid electrolyte portion substantially free of LiS and having the novel structure.SOLUTION: Composite particles 1 for a lithium ion battery include: an active material portion 10 containing an active material; and a solid electrolyte portion 20 disposed on a surface of the active material portion 10. The electrolyte portion 20 contains thio-LISICON and made of a covering portion 22 covering the surface of the active material portion 10 and a thin portion 24 extending from the covering portion 22 to an outside thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite particle for lithium ion battery suitable as a material for forming an electrode of a lithium ion battery, and a method for producing the same.

BACKGROUND ART In recent years, development of lithium ion batteries, sodium ion batteries, and further multivalent ion batteries represented by magnesium secondary batteries has been energetically promoted as batteries realizing high energy density.
The lithium ion battery is a secondary battery having a structure in which lithium is desorbed as ions from the positive electrode during charging, moves to the negative electrode, and is occluded, and lithium ions are inserted from the negative electrode to the positive electrode and returned during discharging. Since this lithium ion battery has features such as high energy density and long life, conventionally, household electric appliances such as personal computers and cameras, portable electronic devices such as mobile phones or communication devices, and power tools Are widely used as power sources for electric tools and the like, and recently, they are also applied to large batteries mounted on electric vehicles (EVs), hybrid electric vehicles (HEVs), and the like.
In such lithium ion batteries, it is known that not only simplification of the safety device can be achieved but also excellent in manufacturing cost, productivity, etc. if a solid electrolyte is used instead of the electrolytic solution containing the flammable organic solvent. ing. In addition, it is said that a solid electrolyte composed of sulfide has high conductivity (lithium ion conductivity) and is useful for achieving high output of a battery, and it is an all solid type using this sulfide solid electrolyte Development of lithium ion batteries is in active.
By the way, since the liquid electrolyte has high permeability and penetrates to every corner of the electrode and contacts with each of the filled active materials at its interface, the path of continuous ion conduction from the negative electrode to the positive electrode is facilitated It can be formed. On the other hand, since the solid electrolyte is less fluid than the liquid electrolyte and does not enter the electrode as it is, the electrode is formed using a composition in which the solid electrolyte is mixed with the active material in order to conduct ions to the inside of the electrode. It is formed.

In addition, in order to bring the active material and the solid electrolyte into good contact with each other and to increase the contact area, there is known a technique of improving the ion conductivity by a complex in which the active material is coated with the solid electrolyte. For example, in Patent Document 1, Li ₂ S-M _x S _y (M is selected from P, Si, Ge, B, Al and Ga, and x and y are stoichiometric ratios according to the type of M. A solution for forming a layer containing a solid electrolyte of an all-solid lithium secondary battery, comprising: a solid electrolyte represented by the formula: and a organic solvent capable of dissolving the solid electrolyte is disclosed. The composite obtained by applying and drying the positive electrode active material to the positive electrode active material is described as being suitable for all solid lithium secondary batteries. Furthermore, Patent Document 2 discloses a composite active material particle obtained by coating active material particles with a sulfide-based solid electrolyte, a fibrous conductive material, and a sulfide-based solid having an average particle diameter smaller than that of the composite active material particles. An electrode mixture comprising electrolyte particles is disclosed. Then, the composite active material particles are produced by dry-kneading the obtained composite particles and the sulfide-based solid electrolyte particles after the active material particles are coated with the oxide-based solid electrolyte to form composite particles. ing.

JP, 2014-191899, A JP, 2016-207418, A

In Example 1 of Patent Document 1, after mechanical milling of a predetermined ratio of Li ₂ S and P ₂ S ₅ to prepare a glassy solid electrolyte, it is obtained by dissolving it in N-methyl formamide (NMF). The described solution is described. And it is described that the precipitate obtained by vacuum-drying this solution contains Li ₂ S crystals and Li ₃ PS ₄ crystals. Therefore, applying a solution of the glassy solid electrolyte to positive electrode active material, when dry, complexes containing Li 2 _S crystal and Li ₃ PS ₄ crystal surface. Li ₂ S has low stability in the atmosphere, reacts easily with water to generate hydrogen sulfide which is a toxic gas, etc. There is room for improvement in terms of use safety in the manufacture of lithium ion batteries. The Furthermore, once the sulfide-based solid electrolyte is dissolved in a solvent and then reprecipitated, a raw material of the sulfide-based solid electrolyte precipitates, and so on. The composition often differs from the sulfide-based solid electrolyte before dissolution. There was a problem that it would become In addition, according to the analysis of the present inventors, the ion conductivity of the dissolved and precipitated Li ₃ PS ₄ crystal was found to be extremely low, and was mainly changed to γ-Li ₃ PS ₄ I believe.
Furthermore, as described above, Patent Document 2 describes a method for producing composite particles by dry kneading, but since active material particles usually have irregularities on the surface, mechanical dry kneading is preferable. There is a problem that the adhesion of the sulfide-based solid electrolyte to the surface of the active material particles can not be sufficiently secured.

An object of the present invention is a composite particle including an active material portion including an active material and a solid electrolyte portion disposed on the surface of the active material portion, wherein the lithium is provided with a solid electrolyte portion having a novel structure. It is providing the composite particle for ion batteries. Another object of the present invention is to produce a composite particle for a lithium ion battery having a solid electrolyte portion substantially free of Li ₂ S and having the above-described novel structure and having a suppressed interfacial resistance. It is to provide a method.

The inventors of the present invention have intensively studied a method of forming a solid electrolyte layer having high adhesiveness over the entire surface of active material particles, and as a result, found composite particles having a novel structure.
The present invention is shown below.
[1] A composite particle including an active material portion containing an active material and a solid electrolyte portion provided on the surface of the active material portion, wherein the solid electrolyte portion contains thiolicicon, and the active material portion A composite particle for a lithium ion battery, comprising: a coated portion for coating the surface of the thin film; and a thin portion extending from the coated portion to the outside thereof.
[2] The composite particle for a lithium ion battery according to the above [1], wherein the thiolysicon contains β-Li ₃ PS ₄ .
[3] The composite particle for a lithium ion battery according to the above [1], wherein the thiolysicon contains Li ₇ P ₂ S ₈ I.
[4] The composite particle for a lithium ion battery according to any one of the above [1] to [3], wherein the above thiolicicon is a glass ceramic.
[5] The mass ratio of the above-mentioned active material portion and the above-mentioned solid electrolyte portion is 70 to 99 mass% and 1 to 30 mass%, respectively, when the total of these is 100 mass%. 4] The composite particle for lithium ion batteries as described in any one of 4).
[6] The composite particle for lithium ion battery according to any one of the above [1] to [5], wherein the active material is a positive electrode active material comprising a composite oxide containing Li element.
[7] In any one of the above-mentioned [1] to [6], the above-mentioned active material is a negative electrode active material consisting of at least one selected from graphite, silicon, lithium titanate, tin dioxide and molybdenum trioxide Composite particle for lithium ion batteries as described.
[8] A method for producing the composite particle for lithium ion battery according to any one of [1] to [7] above,
Among the solvents for dissolving the second sulfide, using a raw material containing the first composite particle to which the first sulfide is attached and the second sulfide, on the surface of the particle containing the active material, A method of producing composite particles for a lithium ion battery, comprising the steps of: reacting the first sulfide and the second sulfide to form thiolysicon.
[9] The method for producing a composite particle for lithium ion battery according to the above [8], wherein the first sulfide contains Li ₂ S, and the second sulfide contains a compound represented by the following general formula (1) .
_{a (Li 2 S) -b (} P 2 S 5) -c (LiX) (1)
(Wherein, X is a halogen atom, a is a number of 0 or more, c is a number of 0 or more, b = a + c, a + c> 0)
[10] The method for producing a composite particle for lithium ion battery according to the above [8] or [9], wherein the solvent contains at least one selected from saturated fatty acid ester and dialkyl carbonate.
[11] An electrode for a lithium ion battery, comprising the composite particle for a lithium ion battery according to any one of the above [1] to [7].
[12] A lithium ion battery comprising the lithium ion battery electrode according to the above [11].

The composite particle for lithium ion battery of the present invention is suitable as a material for forming an electrode of a lithium ion battery, and it is possible to use a conventionally known mixture of an active material and a solid electrolyte or a composite disclosed in the above patent document In comparison, the ion conduction path is comprehensively and continuously formed, the ion conductivity between the active material portion and the solid electrolyte portion becomes better, and an electrode with reduced interface resistance can be provided. . In addition, since the solid electrolyte portion does not substantially contain Li ₂ S, it is suitable for manufacturing a lithium ion battery in which hydrogen sulfide is not generated. Furthermore, since the adhesion between the active material portion and the solid electrolyte portion is excellent, in the case of a lithium ion battery provided with an electrode containing the composite particle for lithium ion batteries of the present invention, the solid electrolyte portion It is thought that it suitably follows the volume change of the active material portion during discharge.
According to the method for producing composite particles for lithium ion batteries of the present invention, lithium ion is provided with a solid electrolyte portion which is excellent in the adhesion between the active material portion and the solid electrolyte portion, contains thiolithicon and does not substantially contain Li ₂ S. Composite particles for battery can be efficiently obtained.

It is a schematic sectional drawing which shows the structure of the composite particle for lithium ion batteries of this invention. It is the schematic which shows the principal part cross section of a lithium ion battery provided with the electrode for lithium ion batteries. It is an image by a scanning electron microscope of composite particles (p1) for lithium ion batteries obtained in Example 1. It is the other image by the scanning electron microscope of composite particle (p1) for lithium ion batteries obtained in Example 1. FIG. It is a mapping image by EDS elemental analysis of composite particle (p1) for lithium ion batteries of FIG. 4, (A) is distribution of P element, (B) is an image which shows distribution of S element. It is the image by the transmission electron microscope which shows the surface layer of composite particle (p1) for lithium ion batteries obtained in Example 1, "LPS" shows a coating | coated part, "NMC" shows an active material part. It is a limited field electron diffraction image of LPS (cover part) in FIG. It is a figure which shows the X-ray-diffraction pattern of LPS (coated part) produced based on FIG. It is an image by a scanning electron microscope of composite particles (p2) for lithium ion batteries obtained in Example 2. It is a mapping image by EDS elemental analysis of the composite particle (p2) for lithium ion batteries of FIG. 9, (A) is distribution of P element, (B) is distribution of S element, and (C) is distribution of I element. Is an image showing It is the image by the transmission electron microscope which shows the surface layer of composite particle (p2) for lithium ion batteries obtained in Example 2, "LPSI" shows a coating | coated part, "NMC" shows an active material part. It is a limited field electron diffraction image of LPSI (cover part) in FIG. It is a figure which shows the X-ray-diffraction pattern of LPSI (coated part) produced based on FIG. It is a schematic sectional drawing which shows the structure of the all-solid-state lithium ion battery produced by [Example]. FIG. 16 is a graph showing charge and discharge characteristics of the all solid state lithium ion battery in Example 3. FIG. It is a graph which shows the charge / discharge characteristic by the all-solid-state lithium ion battery in Comparative Example 1.

  The composite particle for lithium ion batteries according to the present invention is a composite particle including an active material portion containing an active material and a solid electrolyte portion provided on the surface of the active material portion, and the solid electrolyte portion is It is characterized in that it comprises a coated portion which contains thiolicicon and covers the surface of the active material portion, and a thin portion which extends from the coated portion to the outside. That is, the composite particle for lithium ion batteries of the present invention is not a particle only having a coating portion including a solid electrolyte on the surface of the active material portion, but a thin portion extending to the outside while forming a continuous phase from the coating portion It is a modified particle comprising

The composite particles for lithium ion batteries of the present invention have a schematic cross section shown in FIG. That is, the composite particle 1 for lithium ion battery of FIG. 1 includes the active material portion 10 and the solid electrolyte portion 20, and the solid electrolyte portion 20 includes the coated portion 22 that covers the surface of the active material portion 10; 22 consists of a thin portion 24 extending outwardly from 22; The covering portion 22 substantially covers the entire surface so as to follow the outer shape (surface unevenness) of the active material portion 10, and the thin portion 24 is generally formed locally.
In the composite particles used in the lithium ion battery, it is considered preferable that the solid electrolyte is adsorbed over the entire surface of the active material from the viewpoint of ion conductivity. From the viewpoint of the battery capacity, it is desirable that the amount of the active material loaded in the electrode is large. Therefore, it is preferable that the amount of the solid electrolyte adsorbed to the active material be smaller. However, when the amount of solid electrolyte adsorbed to the active material is reduced, the ion conduction path may be broken, or the active material may be easily broken by press molding at the time of electrode formation.
Here, since the composite particles for lithium ion batteries according to the present invention are irregularly shaped particles, it is intended to secure ion conductivity and reduce the amount of adhesion of solid electrolyte in the covering portion 22 formed on the entire surface of the active material. In addition, the locally formed thin-walled portion 24 can have an action of relieving stress during press molding.

The active material constituting the active material portion may be either a positive electrode active material or a negative electrode active material.
As the positive electrode active material, MoO _x , WO _x , VO _x , Li _x CoO _y (LiCoO ₂ etc.), Li _x MnO _y (LiMnO ₂ , LiMn ₂ O ₄ etc.), Li _x NiO _y (LiNiO ₂ etc.), Li _x VO _y (LiVO _{2, etc.), Li x Mn y Ni z} Co w O (LiNi 1/3 Co 1/3 Mn 1/3 O 2 , _{etc.), Li x FeP x O y} (LiFePO 4 , etc.), Li Oxides (complex oxides) based materials such as _x MnP _x O _y (LiMnPO ₄ etc.), Li _x NiP _x O _y (LiNiPO ₄ etc.), Li _x CuP _x O _y (LiCuPO ₄ etc.); (MoS _x , _{CuS x, TiS x, WS x} ), Li x S y, Li x P y S z sulfide-based materials such as; selenide-based materials and the like. Among these, composite oxides containing Li element are preferable.
Also, as the negative electrode active material, carbon materials such as graphite; metals such as lithium, indium, aluminum, silicon or alloys containing these; lithium titanate (Li ₄ Ti ₅ O ₁₂ ), Sn _x O _y (SnO ₂ etc. And MoO _x (MoO _{3 and the} like), WO _{x and the} like. Among these, graphite, silicon, lithium titanate, tin dioxide, molybdenum trioxide and the like are preferable.

  The shape and size of the active material portion are not particularly limited. The active material portion is usually granular, and the surface thereof may be smooth or may have asperities. The particle diameter of the active material portion is preferably 0.5 to 20 μm, more preferably 3 to 10 μm.

Next, the solid electrolyte portion is composed of a covering portion covering the surface of the active material portion and a thin portion extending from the covering portion to the outer side, both of which contain thiolicon.
The above thiolicicon has a general formula: mLi _4-x M ¹ _1-x M ² _x S _4- n LiX (wherein, M ¹ and M ² are atoms selected from P, Ge, Si, Al and Ga) And X is a halogen atom, m is 1 to 2 and n is 0 to 1). In the present invention, compounds in which M ¹ is a P atom are preferred. Such _{compounds, β-Li 3 PS 4,} Li 7 P 2 S 8 I, such as _Li 7 P _{3 S 11} and the like. Among the above-mentioned thiolicones, there are crystalline compounds and amorphous compounds, and in the present invention, regardless of the crystallinity, it is suitable as a constituent material of composite particles for lithium ion batteries. Moreover, it is preferable that it is glass ceramics from the viewpoint of ion conductivity.
The thiolicicon contained in the above-mentioned solid electrolyte part may be only one kind, or two or more kinds.

  The thickness of the covering portion 22 constituting the solid electrolyte portion is extremely thin. The thickness of the covering portion 22 is not particularly limited, but the lower limit is preferably 50 nm, more preferably 10 nm from the viewpoint of improving the filling amount of the active material in the electrode regardless of the size of the active material portion 10.

The thin portion 24 constituting the solid electrolyte portion is a portion extending outward from the covering portion 22. Preferably, the length, width and thickness are not particularly limited. Face plate shape) (see FIG. 1). The thin portion 24 is preferably thicker than the covering portion 22 from the viewpoint of stress relaxation at the time of electrode formation, preferably 10 times or more, more preferably 20 times or more. Moreover, as a structure of the said thin part 24, it can be set as the structure to which several thin part 24 condenses except being shown in FIG. 1 (not shown).
The position and number of the base portions of the thin portion 24 in the covering portion 22 and the extending direction of the thin portion 24 are not particularly limited. The composite particles for lithium ion batteries according to the present invention are obtained by the method for producing composite particles for lithium ion batteries according to the other present invention described later, and the shape and size of the thin portion and the position of the base portion in the covering portion Since the shape and size of one thin-walled portion and the shape and size of the other thin-walled portion are usually different, it is not possible to control the number and number and the extension direction of the thin-walled portion. The position and number of foundations and the position and number of other foundations are again different.

  In the composite particle for lithium ion battery of the present invention, the mass ratio of the active material portion and the solid electrolyte portion is 100% by mass of the total of these in view of battery characteristics in the case of using an electrode including composite particle for lithium ion battery. When it is, it is respectively preferably 70 to 99% by mass and 1 to 30% by mass, more preferably 85 to 95% by mass and 5 to 15% by mass.

  The composite particles for lithium ion batteries of the present invention are suitable as constituent materials of electrodes for lithium ion batteries. Specifically, it is suitable as a constituent material of the positive electrode 31 or the negative electrode 33 of the lithium ion battery 30 shown in FIG.

  Another invention of the present invention is a method of producing composite particles for lithium ion batteries according to the invention described above, comprising: first composite particles in which a first sulfide is attached to the surface of particles containing an active material; A step of reacting the first sulfide and the second sulfide in a solvent for dissolving the second sulfide using a raw material containing the sulfide and producing thiolicicon (hereinafter referred to as “reaction step”) A method for producing composite particles for lithium ion batteries (hereinafter referred to as “the production method of the present invention”). The production method of the present invention can further comprise the step of removing the solvent from the reaction solution obtained by the reaction step.

  The first composite particle used in the reaction step is a particle in which the first sulfide is attached to the surface of a particle containing an active material (hereinafter referred to as "active material particle"), and the structure thereof is particularly limited I will not. The first composite particles preferably have a structure in which the first sulfide covers the entire surface of the active material particles. The thickness of the first sulfide coated portion is not particularly limited.

  The active material particles constituting the first composite particles may be made of either a positive electrode active material or a negative electrode active material. The positive electrode active material and the negative electrode active material are as exemplified above.

  The shape and size of the active material particles are not particularly limited. The active material particle may have a shape such as a sphere, an ellipsoid, a polyhedron, or an indeterminate shape, and the surface thereof may be smooth or may have asperities. In the present invention, regardless of the surface roughness of the active material particles, the attached first sulfide acts as a base point, reacts with the second sulfide, and the entire surface of the active material particles (including the inner surface of the recess) It is possible to efficiently form a coating layer containing thiolicicon. Moreover, the particle size of the said active material particle becomes like this. Preferably it is 0.5-20 micrometers, More preferably, it is 3-10 micrometers.

The first sulfide attached to the surface of the active material particle depends on the structure of the composite particle for lithium ion battery, but is preferably a lithium compound, particularly preferably Li ₂ S.

  The mass ratio of the active material particles constituting the first composite particles to the first sulfide attached to the active material particles is not particularly limited, but the content ratio of the first sulfide is the lithium ion obtained. From the viewpoint of battery characteristics in the case of using an electrode containing composite particles for battery, the active material particle is preferably 0.25 to 10 parts by mass, and more preferably 1 to 5 parts by mass, when it is 100 parts by mass. Therefore, the thickness of the attachment portion of the first sulfide to the active material particles is extremely thin, and the shape and size of the first composite particles are substantially equivalent to those of the active material particles, and the particle size is Preferably it is 0.5-20 micrometers, More preferably, it is 3-10 micrometers.

  The method of preparing the first composite particle is not particularly limited, but as the method of preparing the first composite particle having a structure in which the first sulfide covers the entire surface of the active material particles, which is the preferred embodiment, A method of removing an organic solvent in a mixed solution after mixing a first sulfide solution obtained by dissolving a first sulfide in an organic solvent and active material particles, dissolving the first sulfide in an organic solvent And the like. There is a method of spraying an active first sulfide solution onto active material particles and then removing an organic solvent.

In the reaction step, using a raw material containing the first composite particles and the second sulfide, the first sulfide and the second sulfide are reacted in a solvent that dissolves the second sulfide, To generate
The solvent is a compound that dissolves the second sulfide, but is preferably a compound that does not dissolve the thiolicicon that does not dissolve the first sulfide (insoluble or poorly soluble) and does not dissolve (insoluble). In the present invention, composite particles for lithium ion batteries, which are irregularly shaped particles, can be efficiently produced by using a sulfide that dissolves in a solvent and a sulfide that does not dissolve in the same solvent in combination.
The above solvents are preferably saturated fatty acid esters and dialkyl carbonates. The saturated fatty acid ester is preferably a propionate ester, and examples of this propionate ester include methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. Examples of dialkyl carbonates include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and the like.

The second sulfide is not particularly limited as long as it reacts with the first sulfide to generate thiolysicon, but is preferably a compound represented by the following general formula (1). The compound may be a complex sulfide containing P ₂ S ₅ among Li ₂ S, P ₂ S ₅ and LiX, or a mixture containing only P ₂ S ₅ or P ₂ S ₅ It may be.
_{a (Li 2 S) -b (} P 2 S 5) -c (LiX) (1)
(Wherein, X is a halogen atom, a is a number of 0 or more, c is a number of 0 or more, b = a + c, a + c> 0)

In the general formula (1), the halogen atom X can be a fluorine atom, a chlorine atom, a bromine atom or an iodine atom, but is preferably an iodine atom.
Examples of the compound represented by the general formula _{(1), Li 2 S-} P 2 S 5 ( aka _{Li 2 P 2 S 6),} Li 2 P 2 S 6 LiI , and the like.

  In the above reaction step, a reaction system containing a first composite particle, a second sulfide, and a solvent is used, but as long as the first sulfide and the second sulfide are reacted in the solvent, The preparation method is not particularly limited. As a preferable preparation method, (1) a method using a first composite particle, a second sulfide, and a solvent, and (2) at least a second sulfide which is dissolved in the solvent is formed by contacting with the solvent. Method using a solution obtained by mixing two types of compounds (hereinafter referred to as “compound for forming second sulfide”) and a solvent (hereinafter referred to as “second sulfide solution”), and a first composite particle Etc.

In the case of the above method (2), each second sulfide forming compound is not particularly limited as long as it is a compound which reacts in the above solvent to form a second sulfide solution. Each of the second sulfide-forming compounds may be independently dissolved in the solvent or may not be dissolved.
Examples of the second sulfide forming compound include Li ₂ S and P ₂ S ₅ . Further, as the second sulfide-forming compound, a compound not containing a sulfur atom, for example, LiX (lithium halide) can be used in combination.
Among the compounds for forming the second sulfide, the compounds which are independently soluble in the above-mentioned saturated fatty acid ester or dialkyl carbonate include LiX (lithium halide) and the like, and the above-mentioned saturated fatty acid ester or dialkyl carbonate solvent alone Li ₂ S, P ₂ S _{5 and the} like can be mentioned as compounds which do not dissolve in water. When P ₂ S ₅ coexists with Li ₂ S so that the molar ratio is 1: 1, the solubility in various solvents is improved. Further, in the second sulfide compound for forming the latter, as the compound is soluble in the solvent be used in conjunction with LiX (lithium halide) include P ₂ S ₅ or the like.

The amount of the first composite particles and the second sulfide used in the above reaction step is appropriately selected depending on the configuration of the first sulfide contained in the first composite particles, but the composite obtained for lithium ion batteries From the viewpoint of battery characteristics in the case of using an electrode containing particles, the mass ratio of the active material contained in the first composite particle and the thiosilicon (solid electrolyte) formed in the reaction step is 100% by mass of the total of both When selected, preferably 70 to 99% by mass and 1 to 30% by mass, more preferably 85 to 95% by mass and 5 to 15% by mass, respectively. When the first composite particles and the second sulfide contain Li ₂ S, it is preferable to set the reaction molar ratio so that the Li ₂ S is consumed.
The amount of the solvent used is selected so that the solid content concentration of the total amount of the first composite particles and the second sulfide is preferably 20 to 70% by mass, more preferably 30 to 50% by mass. Ru.

In the above reaction step, thiolicicon is generated with the first sulfide attached to the surface of the active material particle constituting the first composite particle as a base point, and a solid electrolyte portion is formed on the surface of the active material particle. Composite particles for lithium ion batteries are obtained. This reaction step is preferably a step of contacting and reacting the first sulfide constituting the first composite particle and the second sulfide in a solvent, for example, the first composite particle and the second sulfide. After the substance and the solvent are contained in a container, a method of dynamically mixing this slurry-like mixture with a stirrer, a stirrer, beads, balls, a homogenizer, etc. can be applied.
The atmosphere of the reaction system in the reaction step is not particularly limited, and may be made of nitrogen gas, an inert gas such as argon gas, dry air or the like.
The reaction time in the reaction step may depend on the method of the catalytic reaction, and is not particularly limited, but is usually 1 hour or more, preferably 6 hours or more.
In addition, depending on the composition of the second sulfide or the compound for forming a second sulfide to be used, thiolicicon may be formed in the absence of the first sulfide, so in the reaction step using the first composite particles. In some cases, it is thought that the thiolicicon is produced while being released without using the first sulfide attached to the surface of the active material particles as a base point, but as the contact reaction proceeds, the solid is finally solid. It is estimated that it contributes to formation of the thin part in an electrolyte part.

According to the above reaction step, a dispersion (suspension) having a solid content concentration of the reaction product of preferably 2 to 10% by mass, more preferably 3 to 5% by mass can be obtained. The reaction product is a composite particle provided with a solid electrolyte portion having a coated portion and a thin portion formed on the surface of the active material particle, ie, the composite particle for a lithium ion battery of the present invention. Therefore, the composite particle for lithium ion batteries can be isolated by the solvent removal process which removes a solvent from the obtained reaction liquid after a reaction process. In the solvent removal step, conventionally known methods such as decantation, filtration, evaporation and the like can be applied.
In the reaction step according to the present invention, even when Li ₂ S is used as one of the raw materials in forming the solid electrolyte part, Li ₂ S remains in the reaction product, or after reaction, separately There is no precipitation. That is, unlike the method in which the solid electrolyte is deposited on the surface of the active material particles using a solution obtained by dissolving the solid electrolyte in a solvent, the aspect of the thiolicicon is maintained. In other words, the highly conductive solid electrolyte portion can be adsorbed on the surface of the active material particles. Therefore, when the composite particles for lithium ion battery obtained are used to form a lithium ion battery etc., hydrogen sulfide is not generated due to Li ₂ S. In addition, since composite particles for lithium ion batteries in which the formation of a resistive phase with extremely low ion conductivity such as Li ₂ S or Li ₂ S—P ₂ S ₅ (γ phase) is suppressed, use thereof And a lithium ion battery having good ion conductivity.

Still another electrode for a lithium ion battery of the present invention is characterized by including the composite particles for a lithium ion battery of the present invention. The positive electrode includes composite particles for a lithium ion battery including an active material portion made of a positive electrode active material, and the negative electrode includes composite particles for a lithium ion battery including an active material portion made of a negative electrode active material.
The lithium ion battery electrode of the present invention can contain a binder, a conductive additive, another solid electrolyte, and the like.
Examples of the binder include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), polyvinylidene fluoride (PVdF) and vinylidene fluoride / hexafluoropropylene copolymer; and polyolefins such as polypropylene and polyethylene And ethylene-propylene-non-conjugated diene-based rubber (EPDM etc.), sulfonated EPDM, natural butyl rubber (NBR) and the like.
Examples of the conductive aid include carbon materials (plate-like conductive substances such as graphene; linear conductive substances such as carbon nanotubes and carbon fibers; carbon blacks such as ketjen black, acetylene black, thermal black and channel black, graphite Particulate conductive substances, etc.), metals, metal compounds and the like.

  The lithium ion battery electrode of the present invention is usually a molded body of a predetermined shape obtained by subjecting a mixture containing the above-mentioned materials to a conventionally known method such as press molding.

Still another lithium ion battery is characterized by comprising the above-mentioned electrode for lithium ion battery of the present invention. The lithium ion battery of the present invention preferably comprises a positive electrode 31 including composite particles for lithium ion battery comprising an active material portion comprising a positive electrode active material and an active material portion comprising a negative electrode active material, as shown in FIG. A negative electrode 33 containing composite particles for lithium ion battery, an electrolyte layer 35 disposed between the positive electrode 31 and the negative electrode 33, a positive electrode current collector 37 for collecting current from the positive electrode 31, and a negative electrode for collecting current from the negative electrode 35 It has a current collector 39 and a battery case (not shown) for housing these members.
The electrolyte layer may contain an electrolytic solution, a gel electrolyte, a solid electrolyte, and the like.
Each of the positive electrode current collector and the negative electrode current collector is preferably a foil, a plate or a mesh containing aluminum, stainless steel, nickel, iron, titanium or the like.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to the examples unless the gist of the present invention is exceeded.

1. Production and Evaluation of Composite Particles for Lithium Ion Battery Example 1
In an argon atmosphere, 0.0638 g of Li ₂ S powder ("Li ₂ S" manufactured by Mitsuwa Chemical Co., Ltd., purity 99%, particle diameter 53 μm) is added to 5 ml of ethanol and stirred at 50 ° C. for 30 minutes. _A 2S solution was obtained.
Then, the Li ₂ S solution and positive electrode active material particles to the surface of the particle of lithium nickel manganese cobalt oxide _LiNi 1/3 _Co 1/3 _Mn 1/3 _{O 2} is LiNbO ₃ covers (particle size 3 The mixture was mixed with 10 μm, 2.25 g of “NMC” hereinafter, and stirred at 50 ° C. for 1 hour. And this liquid mixture is vacuum-dried at 170 ° C. for 2 hours, ethanol is evaporated, and N ₂ C-Li ₂ S composite particles (first composite particles) in which Li ₂ S is adsorbed on the surface of the positive electrode active material particles. Got).
On the other hand, Li ₂ S powder and P ₂ S ₅ powder ("P ₂ S ₅ " manufactured by Aldrich, purity 99%, particle diameter 100 μm) such that Li ₂ S and P ₂ S ₅ become equimolar And, P ₂ S ₅ was weighed such that it had a molar ratio of 1/3 to the total Li ₂ S containing Li ₂ S contained in the NMC-Li ₂ S composite particles, and these powders were mixed. . Then, this mixture was added to 10 ml of ethyl propionate and subjected to ultrasonic treatment for 1 hour to obtain a solution in which Li ₂ S-P ₂ S ₅ (second sulfide) was dissolved.
Thereafter, this solution and the NMC-Li ₂ S composite particles obtained above are mixed, and stirred at 50 ° C. for 6 hours to form a composite particle in which a solid electrolyte is closely attached to the surface of the positive electrode active material particles. A dispersion (suspension) of (p1) was obtained.
The dispersion was then dried under vacuum at 170 ° C. for 2 hours, and ethyl propionate was evaporated to isolate composite particles (p1). Note that the _Li 3 PS ₄ for generating the NMC powder, charged amount of the raw material is set so that the mass ratio of 90:10.

  The composite particles (p1) were observed at an accelerating voltage of 10 kV with a field emission scanning electron microscope “SU8000 TYPE II” (type name) manufactured by Hitachi High-Technologies Corporation, and the images shown in FIGS. 3 and 4 were obtained. In each case, it was found that a coated portion and a thin portion made of a solid electrolyte were formed on the surface of the positive electrode active material particles. The covering portion is formed in a thin thickness of about 10 nm along the irregularities of the surface of the positive electrode active material particle, and the thin portion is mostly in the form of a plate having a thickness of 200 to 300 nm and is outside the covering portion Overhang at random. Moreover, when the elemental analysis by EDS was performed with respect to the inside of the square frame of an image about the composite particle (p1) of FIG. 4, as shown to FIG. 5 (A) and (B), phosphorus element (P) is each. And elemental sulfur (S) were detected across the surface of the composite particle (p1). From this, it was found that this composite particle (p1) has a covering portion and a thin portion made of a compound containing a phosphorus element and a sulfur element on the surface of a positive electrode active material particle not containing a phosphorus element and a sulfur element.

The composite particles (p1) were observed at an accelerating voltage of 200 kV with a field emission type transmission electron microscope “JEM-2100F” (type name) manufactured by JEOL. FIG. 6 is an image in the vicinity of the surface of a positive electrode active material particle, which includes a covering portion (indicated as “LPS” in the figure) made of a solid electrolyte. EDS elemental analysis of the coated portion showed that elements derived from active material particles were not detected except for Li. Further, based on the image of FIG. 6, by performing the electron beam diffraction of the coating portion, was obtained a X-ray diffraction pattern in the following manner, the solid electrolyte is composed of β-Li ₃ PS ₄ is a glass ceramic It was found to contain thiolicone (see Figure 8). Furthermore, since no diffraction peaks attributable to Li ₂ S were observed at 2θ = 27 ° and 31 °, it was found that this composite particle (p1) did not contain Li ₂ S.
Converting the crystal structure into a one-dimensional profile by integrating the intensities of the electron diffraction pattern (FIG. 7) obtained by electron beam diffraction (FIG. 7) with respect to the radial direction, and then plotting on the horizontal axis 2θ The X-ray diffraction pattern of FIG. 8 was obtained.

Example 2
In an argon atmosphere, Li ₂ S powder, P ₂ S ₅ powder, and LiI powder ("LiI" manufactured by Aldrich, purity 99% or more, particle diameter 100 mesh or less), Li ₂ S, P ₂ S ₅ And LiI is equimolar, and so that P ₂ S ₅ has a molar ratio of 1/3 to the total Li ₂ S including Li ₂ S contained in the NMC-Li ₂ S composite particles Weighed and mixed these powders. Then, the mixture was poured into ethyl propionate 10 ml, sonicated performed 1 _{hour, Li 2 S-P 2 S} 5 -LiI ( second sulfide) to obtain a solution comprising dissolved.
Thereafter, this solution and the same NMC-Li ₂ S composite particles as in Example 1 are mixed, and the mixture is stirred at 50 ° C. for 6 hours to form a composite in which the solid electrolyte is closely attached to the surface of the positive electrode active material particles. A dispersion (suspension) of particles (p2) was obtained.
The dispersion was then dried under vacuum at 170 ° C. for 2 hours, and ethyl propionate was evaporated to isolate composite particles (p2).

  The composite particle (p2) was observed with the scanning electron microscope to obtain an image shown in FIG. 9, and a coated portion and a thin portion formed of a solid electrolyte were formed on the surface of the positive electrode active material particle. I understand. The covering portion is formed at a thin thickness of about 10 nm along the irregularities of the surface of the positive electrode active material particle, and the thin portion has a thickness of 200 to 300 nm, and does not protrude outward from the covering portion , Was formed to cover the covering portion. Further, when elemental analysis by EDS was performed on the composite particle (p2) of FIG. 9, it was found that as shown in FIGS. 10 (A), (B) and (C), phosphorus element (P) and sulfur element (element S) and elemental iodine (I) were detected across the surface of the composite particle (p2). From this, this composite particle (p2) has a covering portion and a thin portion made of a compound containing phosphorus element, sulfur element and iodine element on the surface of positive electrode active material particle not containing phosphorus element, sulfur element and iodine element. I understand.

Moreover, about the said composite particle (p2), the observation by the said transmission electron microscope was performed. FIG. 11 is an image in the vicinity of the surface of a positive electrode active material particle, which includes a covering portion (indicated as “LPSI” in the figure) made of a solid electrolyte. EDS elemental analysis of the coated portion showed that elements derived from active material particles were not detected except for Li. In addition, electron beam diffraction of the coated portion was performed based on the image of FIG. 11, and an X-ray diffraction pattern was obtained in the same manner as in Example 1 using the obtained electron diffraction pattern (FIG. 12) ( Figure 13). In FIG. 13, two regions (circled numbers 1 and 2) surrounded by two dotted lines respectively correspond to the halo pattern of the inner diameter and the halo pattern of the outer diameter in FIG. 12, respectively. It was found from FIG. 13 that most of the solid electrolyte was amorphous. Here, when X-ray diffraction measurement was performed on a solid electrolyte synthesized by the same method without using positive electrode active material particles, it was a thiolithicon which is also amorphous and composed of Li ₇ P ₂ S ₈ I. I found that. Therefore, the solid electrolyte portion constituting the composite particles (p2) is estimated to include a Chiorishikon consisting Li 7 _P 2 _S 8 _I is a glass ceramic. Further, in FIG. 13, no diffraction peaks attributable to Li ₂ S were observed at 2θ = 27 ° and 31 °, so that it was found that this composite particle (p2) did not contain Li ₂ S.

2. Production and evaluation of all solid state lithium ion battery Example 3
Under an argon atmosphere, 0.3827 g of lithium sulfide powder and 0.6174 g of phosphorus pentasulfide powder were weighed to a total of 1 g so as to have a molar ratio of 3: 1, and lightly mixed using an agate mortar. Next, this mixture, 20 ml of ethyl propionate and zirconia balls with a diameter of 4 mm (21.6 g in total) are placed in a test tube type resin container (inner volume 45 ml) with an inner diameter of 28 mm and a length of 116 mm. C., amplitude was about 1 cm, and shaking was performed under mild conditions of about 1500 times / minute, and contact reaction was performed for 6 hours to obtain a suspension. Thereafter, the solid was collected from this suspension, under reduced pressure, 170 ° C., subjected to heat treatment for 2 hours to obtain β-Li ₃ PS ₄ is a solid electrolyte.
Next, 80 mg of the solid electrolyte prepared above is filled into a tubular body made of polyetheretherketone (PEEK), and pressed for 1 minute at 180 MPa with a uniaxial press for preforming, and an electrolyte layer molded body I got Then, in a state in which the molded body for electrolyte layer is accommodated in the inside of a cylindrical body, 10 mg of the composite particles (p1) produced in Example 1 is filled in the whole of one surface side thereof, for 30 minutes at 500 MPa. Press molding was performed. Furthermore, a circular indium foil (thickness 0.1 mm, diameter 0.8 cm) is attached to the other surface of the electrolyte layer molding and pressurized at 180 MPa to obtain a composite (all-solid-state lithium ion battery) did. The stainless steel-nickel conductive parts were respectively inserted from both sides of the cylindrical body accommodating the composite, and fixed with a jig to obtain a measurement cell shown in FIG. Then, the entire measurement cell was sealed in a glass container, and the gas in the glass container was replaced with argon gas, and a charge / discharge test was performed.
The charge / discharge test was performed under the conditions of 2-3.8 V vs. In-Li, C rate: 0.1 C, and the number of cycles: 20. The results are shown in FIG.

Comparative Example 1
The NMC powder used in Example 1 and the β-Li ₃ PS ₄ powder obtained above were weighed so as to have a mass ratio of 90:10, and mixed in a mortar for 15 minutes to obtain a mixed powder. The A positive electrode composite was produced using this mixed powder, and an all solid lithium ion battery was produced by the same method as in Example 3 to obtain a measurement cell. Then, a charge and discharge test was performed. The results are shown in FIG.

  As is clear from FIGS. 15 and 16, the all-solid-state lithium ion battery of Example 3 is superior to the all-solid-state lithium ion battery of Comparative Example 1 in both discharge capacity and cycle characteristics.

Further, with respect to the all-solid-state lithium ion battery of Example 3 and the all-solid-state lithium ion battery of Comparative Example 1, the potentio / galvanostat “SI1287” (type name) manufactured by Solartron and the impedance analyzer manufactured by Solartron Electrochemical impedance measurement is performed in the frequency range of 10 ^{6 to} 0.1 Hz using “1255 B” (model name), and in the obtained Nyquist diagram, it corresponds to the interface resistance between the positive electrode active material and the solid electrolyte The sizes of half circles (interface resistance values) were compared. The all-solid-state battery of Comparative Example 1 was about 56 Ω, and the all-solid-state battery of Example 3 was about 41 Ω. From this, it can be seen that in the composite particle for a lithium ion battery of the present invention, the active material portion and the solid electrolyte portion are in close contact, and a good interface is formed.

  The composite particles for lithium ion batteries according to the present invention can be used in household appliances such as personal computers and cameras, power storage devices, portable electronic devices such as mobile phones or communication devices, power supplies such as electric tools such as power tools, and electricity. It is suitable as a constituent material of a lithium ion battery which constitutes a large battery mounted on a car (EV), a hybrid electric vehicle (HEV) or the like, for example, a constituent material of an electrode for a lithium ion battery.

1: Composite particle 10 for lithium ion battery 10: Active material portion 20: Solid electrolyte portion 22: Coating portion 24: Thin portion 30: All solid lithium ion battery 31: Positive electrode 33: Negative electrode 35: Electrolyte layer 37: Positive electrode current collector 39: Negative electrode current collector 40: Measurement cell 41: Press plate 43: Press pin 45: Tightening screw 47: Kapton (registered trademark) tape

Claims (12)

A composite particle comprising: an active material portion containing an active material; and a solid electrolyte portion provided on the surface of the active material portion,
The composite particle for a lithium ion battery according to claim 1, wherein the solid electrolyte portion includes thiolicicon, and a coated portion covering the surface of the active material portion and a thin portion extending from the coated portion to the outside. The composite particle for a lithium ion battery according to claim 1, wherein the thiolisicon comprises β-Li ₃ PS ₄ . The composite particle for a lithium ion battery according to claim 1, wherein the thiolithicon comprises Li ₇ P ₂ S ₈ I.   The composite particle for a lithium ion battery according to any one of claims 1 to 3, wherein the thiolithicon is a glass ceramic.   The mass ratio of the said active material part and the said solid electrolyte part is 70-99 mass% and 1-30 mass%, respectively, when the sum total is made into 100 mass%. The composite particle for lithium ion batteries as described in a term.   The composite particle for a lithium ion battery according to any one of claims 1 to 5, wherein the active material is a positive electrode active material composed of a complex oxide containing Li element.   The lithium ion battery according to any one of claims 1 to 6, wherein the active material is a negative electrode active material composed of at least one selected from graphite, silicon, lithium titanate, tin dioxide and molybdenum trioxide. Composite particles. It is a method of manufacturing the composite particle for lithium ion batteries as described in any one of Claims 1 thru | or 7, Comprising:
In a solvent for dissolving the second sulfide, using a raw material containing the first composite particle having the first sulfide attached to the surface of the particle containing the active material, and the second sulfide, A method of producing composite particles for a lithium ion battery, comprising the steps of: reacting the first sulfide and the second sulfide to form thiolysicon. The method for producing composite particles for a lithium ion battery according to claim 8, wherein the first sulfide contains Li ₂ S, and the second sulfide contains a compound represented by the following general formula (1).
_{a (Li 2 S) -b (} P 2 S 5) -c (LiX) (1)
(Wherein, X is a halogen atom, a is a number of 0 or more, c is a number of 0 or more, b = a + c, a + c> 0)   The method for producing composite particles for a lithium ion battery according to claim 8 or 9, wherein the solvent contains at least one selected from saturated fatty acid esters and dialkyl carbonates.   An electrode for a lithium ion battery comprising the composite particle for a lithium ion battery according to any one of claims 1 to 7.   A lithium ion battery comprising the lithium ion battery electrode according to claim 11.