WO2013076958A1

WO2013076958A1 - Positive electrode material for nonaqueous electrolyte secondary batteries, nonaqueous electrolyte secondary battery, and method for producing positive electrode material for nonaqueous electrolyte secondary batteries

Info

Publication number: WO2013076958A1
Application number: PCT/JP2012/007417
Authority: WO
Inventors: 一仁川澄; 淳一丹羽; 正孝仲西; 中川　敏; 友哉佐藤; 琢寛幸; 敏勝小島; 境　哲男
Original assignee: 株式会社豊田自動織機; 独立行政法人産業技術総合研究所
Priority date: 2011-11-24
Filing date: 2012-11-19
Publication date: 2013-05-30
Also published as: JP5754606B2; JPWO2013076958A1

Abstract

The purpose of the present invention is to provide a positive electrode material for nonaqueous electrolyte secondary batteries, which contains a sulfur-modified polyacrylonitrile as a positive electrode active material and has excellent electrical conductivity. The present invention relates to: positive electrode material particles for nonaqueous electrolyte secondary batteries, which have particle diameters of 2 μm or less and use sulfur-modified polyacrylonitrile particles and a conductive assistant, said positive electrode material particles being obtained by crushing a sulfur-modified polyacrylonitrile in the form of aggregates, having the conductive assistant adhere to the thus-obtained sulfur-modified polyacrylonitrile particles, and causing the sulfur-modified polyacrylonitrile to aggregate again, as a starting material for the positive electrode material for nonaqueous electrolyte secondary batteries, after the addition of the conductive assistant; and a method for producing the positive electrode material particles for nonaqueous electrolyte secondary batteries.

Description

Positive electrode material for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery, and method of manufacturing positive electrode material for non-aqueous electrolyte secondary battery

The present invention relates to non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries, lithium secondary batteries, sodium secondary batteries and the like.

Lithium secondary batteries and lithium ion secondary batteries, which are a type of non-aqueous electrolyte secondary battery, are batteries with large charge and discharge capacities, and are mainly used as batteries for portable electronic devices. In addition, lithium ion secondary batteries are also expected as batteries for electric vehicles. A sodium secondary battery and a sodium ion secondary battery, which are a type of non-aqueous electrolyte secondary battery, have the advantage that they can be provided at low cost because sodium is used instead of lithium and is readily available. Although sodium has a standard redox potential 0.33 V lower and a density about 80% higher than lithium, it is considered that 70-80% performance of a lithium ion secondary battery can be expressed in the whole cell.

As a positive electrode active material of these non-aqueous electrolyte secondary batteries, those containing rare metals such as cobalt and nickel are generally used. However, since these metals have low flow rates and are expensive, in recent years, positive electrode active materials using materials that replace these rare metals are being sought.

A technology using sulfur as a positive electrode active material of a lithium ion secondary battery is known. By using sulfur as a positive electrode active material, the charge and discharge capacity of the lithium ion secondary battery can be increased. However, in a lithium ion secondary battery using elemental sulfur as a positive electrode active material, a compound of sulfur and lithium is formed during discharge. The compound of sulfur and lithium is soluble in the non-aqueous electrolyte solution (for example, ethylene carbonate, dimethyl carbonate, etc.) of the lithium ion secondary battery. For this reason, a lithium ion secondary battery using sulfur as a positive electrode active material has a problem that when charge and discharge are repeated, the elution of the sulfur into the electrolytic solution gradually deteriorates and the battery capacity decreases. That is, a lithium ion secondary battery using sulfur as a positive electrode active material is inferior in cycle characteristics.

The inventors of the present invention invented a positive electrode active material obtained by heat-treating a mixture of polyacrylonitrile (PAN) and sulfur as a result of intensive studies (see Patent Document 1). By using a sulfur-based positive electrode active material (hereinafter abbreviated as sulfur-modified PAN) made of PAN and sulfur as a positive electrode active material, the charge / discharge capacity of the lithium ion secondary battery is increased, and the cycle characteristics are also increased. improves.

By the way, although sulfur-modified PAN has a high charge / discharge capacity per mass, it is bulky because the mass density (bulk density) is small. For this reason, in order to produce a battery having high volumetric energy density (for example, 2 times or 3 times the conventional battery ratio), a positive electrode mixture containing sulfur-modified PAN is coated on a current collector to a thickness of 150 μm or more There is a need to. When the positive electrode mixture is thickly coated in this manner, the electrode surface and the current collector surface are largely separated, which may increase the electrical resistance. If the electrical resistance is excessive, there is a concern that the battery characteristics may be degraded.

Therefore, in order to suppress an increase in electrical resistance even when the positive electrode mixture is thickly coated, a positive electrode material containing sulfur-modified PAN and having excellent conductivity is desired.

WO 2010/044437

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a positive electrode material for a non-aqueous electrolyte secondary battery which contains sulfur-modified PAN as a positive electrode active material and is excellent in conductivity.

As a result of intensive studies, the inventors of the present invention have obtained that sulfur-modified PAN is present in the form of aggregates, and crush the aggregate-like sulfur-modified PAN to obtain small-diameter sulfur-modified PAN particles. By attaching the conductive aid to the surface of the particles, the conductive aid can be highly dispersed in the positive electrode material as compared with the case where the conductive aid is directly attached to the aggregate sulfur-modified PAN. Found out.

That is, the manufacturing method of the non-aqueous electrolyte secondary battery of the present invention which solves the above-mentioned subject decomposes a sulfur system positive electrode active material which consists of a carbon frame originating in polyacrylonitrile, the carbon frame and sulfur (S). Crushing process,
An auxiliary agent addition step of causing a conductive auxiliary agent to adhere to the surface of the crushed sulfur-based positive electrode active material;
And a reaggregation step of reaggregating the sulfur-based positive electrode active material after the auxiliary agent addition step.

Further, the positive electrode material for a non-aqueous electrolyte secondary battery of the present invention obtained by such a method is a positive electrode material for a non-aqueous electrolyte secondary battery,
Using a carbon skeleton derived from polyacrylonitrile, a sulfur-based positive electrode active material consisting of the carbon skeleton and sulfur (S), and a conductive aid,
In the particle size distribution of the sulfur-based positive electrode active material, 50 frequency% or more of the whole particles are particles having a particle diameter of 2 μm or less.

The non-aqueous electrolyte secondary battery of the present invention for solving the above-mentioned problems is characterized in that the positive electrode material for a non-aqueous electrolyte secondary battery of the present invention is contained in the positive electrode.

The non-aqueous electrolyte secondary battery of the present invention can be preferably used as a non-aqueous electrolyte secondary battery for vehicles.

Hereinafter, unless otherwise noted, the positive electrode material for a non-aqueous electrolyte secondary battery of the present invention is simply abbreviated as the positive electrode material of the present invention, and the method for producing a positive electrode material for non-aqueous electrolyte secondary battery of the present invention is simply referred to as the present invention. Abbreviated as manufacturing method.

The sulfur-modified PAN is present in a state of aggregation of many sulfur-modified PAN particles (secondary particles). For this reason, when the conductive aid is directly attached to such aggregate-like sulfur-modified PAN, the conductive aid adheres only to the surface of the aggregate-like sulfur-modified PAN, and the sulfur located at the center of the aggregate The modified PAN particles are largely separated from the conductive aid. For this reason, there is a problem that it is difficult to greatly improve the conductivity of the positive electrode material unless a large amount of the conductive additive is added. According to the production method of the present invention, the conductive aid is attached to the surface of each sulfur-modified PAN particle by attaching the conductive aid to the sulfur-modified PAN which has been crushed once (that is, broken into fine particles). Adhere to. For this reason, even if the sulfur-modified PAN particles reaggregate, a conductive aid is present inside the aggregate. In other words, the conductive aid is dispersed at a very small distance in the positive electrode material, and the distance between the conductive aid and the sulfur-modified PAN particles located inside the aggregate is small. Therefore, in the positive electrode material of the present invention obtained by such a manufacturing method of the present invention, the conductivity derived from the conductive auxiliary is sufficiently exhibited. That is, according to the manufacturing method of the present invention, a positive electrode material having excellent conductivity can be manufactured.

In addition, as described later, in the particle size distribution of the pulverized sulfur-modified PAN, 50% or more of all particles are particles having a particle diameter of 2 μm or less. That is, in the particle size distribution of the sulfur-modified PAN which is a raw material of the positive electrode material of the present invention, 50% by frequency or more of the whole particles are particles having a particle diameter of 2 μm or less. When the conductive auxiliary agent is attached to the small-diameter sulfur-modified PAN particles in this manner, the conductive auxiliary agent is highly dispersed in the positive electrode material. For this reason, the distance from the conductive additive to the center of the sulfur-modified PAN particles is reduced, and the distance between the conductive additives in the positive electrode material is also reduced. If these distances are small, the conductivity of the positive electrode material is necessarily improved, and the increase in electrical resistance can be suppressed even when the positive electrode mixture containing the positive electrode material is thickly coated.

6 is a graph showing the results of X-ray diffraction of sulfur-modified PAN and sulfur-modified PAN. It is a graph showing the result of having carried out the Raman spectrum analysis of sulfur-modified PAN. It is a graph. It is explanatory drawing which represents typically the reaction apparatus used with the manufacturing method of sulfur-modified PAN of an Example. It is explanatory drawing which represents typically sulfur-modified PAN used by the manufacturing method of the positive electrode material of an Example. It is explanatory drawing which represents typically the sulfur-modified PAN particle | grains obtained at the crushing process in the manufacturing method of the positive electrode material of an Example. It is explanatory drawing which represents typically the water dispersion of the sulfur-modified PAN particle and the conductive support agent obtained at the auxiliary agent addition process in the manufacturing method of the positive electrode material of an Example. It is explanatory drawing which represents typically the positive electrode material obtained by the reaggregation process in the manufacturing method of the positive electrode material of an Example. It is explanatory drawing which represents typically sulfur-modified PAN used by the manufacturing method of the positive electrode material of a comparative example. It is explanatory drawing which represents typically the positive electrode material obtained by the manufacturing method of the positive electrode material of a comparative example. It is a graph and table showing the particle size distribution of sulfur modification PAN before crushing. It is a graph and table showing the particle size distribution of sulfur-modified PAN after disintegration. It is a SEM image of sulfur-modified PAN before crushing. It is a SEM image of the positive electrode material of an Example. It is a graph showing the discharge characteristic of the nonaqueous electrolyte secondary battery of an example. It is a graph showing the discharge characteristic of the nonaqueous electrolyte secondary battery of a comparative example.

(Positive electrode active material)
The positive electrode active material in the non-aqueous electrolyte secondary battery of the present invention is the above-described sulfur-modified PAN, which comprises a carbon skeleton derived from PAN and sulfur (S).

Sulfur-modified PAN is similar to that disclosed in the above-mentioned Patent Document 1. PAN as a material for sulfur-modified PAN is preferably in the form of powder, and the mass average molecular weight is preferably about 10 ⁴ to 3 × 10 ⁵ . In addition, the particle diameter of PAN is preferably about 0.5 to 50 μm, more preferably about 1 to 10 μm, as observed by an electron microscope. If the molecular weight and the particle size of PAN are within these ranges, the contact area between PAN and sulfur can be increased, and PAN and sulfur can be reacted with high reliability. Therefore, the elution of sulfur into the electrolyte can be suppressed more reliably.

By using sulfur-modified PAN as the positive electrode active material of the non-aqueous electrolyte secondary battery, the high capacity inherent in sulfur can be maintained, and elution of sulfur into the electrolytic solution can be suppressed, thereby greatly improving cycle characteristics. . It is considered that this is because sulfur is not present as a single substance in sulfur-modified PAN but in a stable state incorporated in the structure of PAN. In the manufacturing method disclosed in Patent Document 1, sulfur is heat-treated together with PAN. When PAN is heated, it is believed that PAN bridges three-dimensionally and forms a condensed ring (mainly a six-membered ring) while closing the ring. For this reason, sulfur is considered to be present in the structure with closed ring PAN. In sulfur-modified PAN, sulfur is present in a stable state in which it is combined with PAN, or although sulfur is present as a single substance, it is confined in a crosslinked structure when PAN is ring-closed by heating, and It is considered to be in a state where it is difficult to contact, and even if it contacts with the electrolytic solution, the reaction product is difficult to elute. By this, elution of sulfur to the electrolytic solution can be suppressed, and cycle characteristics can be improved.

By the way, a lithium ion secondary battery having an electrode in which a single inorganic sulfur is used as an active material has a large initial capacity, but when charging and discharging are repeated, soluble Li ₂ S _x is generated in the electrolytic solution. When this Li ₂ S _x elutes in the electrolyte, the battery performance represented by the cycle characteristics is rapidly degraded.

Even when an organic sulfide in which sulfur is fixed by —C—S bond is used as an active material, when the —C—S bond is cleaved, Li ₂ S _x is generated and eluted in the electrolytic solution. In addition, the once-cut -CS bond is hard to return. Therefore, also in this case, deterioration of the cycle characteristics is inevitable.

Furthermore, even when using a sulfur-based active material in which sulfur is fixed in the pores of the carbon material, the sulfur inlet / outlet remains in the pores, and the sulfur easily contacts the electrolyte, so Li ₂ S _x It will elute into the electrolyte.

However, all lithium ion secondary batteries using sulfur-modified PAN have excellent cycle characteristics, and maintain high capacity even after repeated charge and discharge. This is considered to be an effect due to suppression of sulfur desorption from the positive electrode or the negative electrode. That is, in the lithium ion secondary battery using sulfur-modified PAN, it is considered that the contact between sulfur and the electrolytic solution is suppressed.

That is, in the case of sulfur-modified PAN, since PAN and sulfur coexist at a temperature at which the ring closure reaction of PAN occurs, sulfur is incorporated into the crosslinked structure of PAN, and sulfur is trapped in the pore without outlet. It is thought that Therefore, the direct contact of the electrolytic solution with sulfur is suppressed, and the elution of Li ₂ S _x is prevented, so that the battery using the sulfur-modified PAN is considered to be excellent in the cycle characteristics. Even if part of the sulfur can be in direct contact with the electrolyte, stable charge-discharge capacity is maintained after the sulfur is eluted into the electrolyte as Li ₂ S _x at the first charge / discharge.

The sulfur used for the sulfur-modified PAN, like PAN, is preferably in powder form. The particle size of sulfur is not particularly limited, but when it is classified using a sieve, those which do not pass through a sieve with a sieve opening of 40 μm and which have a size within a 150 μm sieve are preferable. It is more preferable not to pass through a sieve with a sieve opening of 40 μm and in the size range of passing through a 100 μm sieve.

The compounding ratio of PAN powder to sulfur powder used for sulfur-modified PAN is not particularly limited, but it is preferably 1: 0.5 to 1:10 by mass ratio, 1: 0.5 to 1: 7. It is more preferable to be present, and more preferable to be 1: 2 to 1: 5.

Sulfur-modified PAN can be produced by the following method.

The mixed raw material which mixed PAN powder and sulfur powder is heated (heat treatment process). The mixed material may be mixed by a general mixing device such as a mortar or a ball mill. As the mixed raw material, one obtained by simply mixing sulfur and PAN may be used, but for example, the mixed raw material may be formed into a pellet and used. The mixed raw material may be composed only of PAN and sulfur, or may be blended with a general material (such as a conductive additive) that can be blended in the positive electrode active material.

By heating the mixed raw material in the heat treatment step, sulfur contained in the mixed raw material is incorporated into the structure of PAN. The heat treatment step may be performed in a closed system or an open system, but in order to suppress the dissipation of sulfur vapor, the closed system is preferable. The heat treatment step is not particularly limited as to which atmosphere to carry out, but it is preferable to carry out in an atmosphere which does not prevent the incorporation of sulfur into PAN (for example, an atmosphere containing no hydrogen, a non-oxidative atmosphere). For example, when hydrogen is present in the atmosphere, sulfur in the reaction system reacts with hydrogen to form hydrogen sulfide, which may result in loss of sulfur in the reaction system. Further, it is considered that by heat treatment in a non-oxidative atmosphere, sulfur in the vapor state reacts with PAN simultaneously with the ring closure reaction of PAN, and PAN modified with sulfur is obtained. The non-oxidative atmosphere referred to here includes a reduced pressure state where the oxygen concentration is low to such an extent that the oxidation reaction does not proceed, an inert gas atmosphere such as nitrogen and argon, a sulfur gas atmosphere and the like.

There is no particular limitation on a specific method for making a non-oxidative atmosphere in a sealed state, for example, the mixed raw material is put in a container in which the sealing property is maintained to the extent that the sulfur vapor does not dissipate, and the pressure in the container is reduced. Alternatively, heating may be performed in an inert gas atmosphere. In addition, you may heat in the state vacuum-packed with the material (for example, aluminum laminate film etc.) which is hard to react with a sulfur raw material. In this case, for example, the packaged raw material is placed in a pressure container such as an autoclave containing water and heated so that the packaging material is not damaged by the generated sulfur vapor, and the generated steam is added from the outside of the packaging material It is preferable to press. According to this method, since the steam is pressurized by steam from the outside of the packaging material, the sulfur vapor prevents the packaging material from being blown and broken.

The heating time of the mixed raw material in the heat treatment step may be appropriately set according to the heating temperature, and is not particularly limited. The above-described preferable heating temperature may be a temperature at which incorporation of sulfur into PAN proceeds and the conductive material is not deteriorated. Specifically, the heating temperature is preferably 250 or more and 500 ° C. or less, more preferably 250 or more and 400 ° C. or less, and still more preferably 250 or more and 300 ° C. or less.

In the heat treatment step, sulfur is preferably refluxed. In this case, the mixed material may be heated so that a part of the mixed material becomes a gas and a part becomes a liquid. In other words, the temperature of the mixed raw material may be a temperature higher than the temperature at which sulfur is vaporized. The term "vaporization" as used herein refers to phase change of sulfur from liquid or solid to gas, which may be boiling, evaporation or sublimation. For reference, the melting point of alpha sulfur (orthogonal sulfur, which is the most stable structure around normal temperature) is 112.8 ° C, the melting point of beta sulfur (monoclinic sulfur) is 119.6 ° C, gamma sulfur (monoclinic sulfur) The melting point of) is 106.8 ° C. The boiling point of sulfur is 444.7.degree. By the way, since the vapor pressure of sulfur is high, when the temperature of the mixed raw material reaches 150 ° C. or more, the generation of sulfur vapor can be visually confirmed. Therefore, if the temperature of the mixed raw material is 150 ° C. or more, sulfur reflux is possible. In addition, what is necessary is just to reflux sulfur using the reflux apparatus of known structure, when refluxing sulfur in a heat treatment process.

Even when the blending amount of sulfur in the mixed raw material is excessive, sufficient amount of sulfur can be taken into PAN in the heat treatment step. For this reason, when mix | blending sulfur with respect to PAN excessively, the bad influence by the single-piece | unit sulfur mentioned above can be suppressed by removing single-piece | unit sulfur from the to-be-processed object after a heat treatment process. Specifically, when the blending ratio of PAN and sulfur in the mixed raw material is 1: 2 to 1:10 in mass ratio, the object to be treated after the heat treatment step is heated at 200 ° C. to 250 ° C. while reducing pressure. By the (single sulfur removing step), it is possible to suppress an adverse effect due to the remaining single sulfur while taking a sufficient amount of sulfur into PAN. When the single sulfur removing step is not performed on the object to be treated after the heat treatment step, the object to be treated may be used as the sulfur-modified PAN as it is. When the single sulfur removing step is performed on the target after the heat treatment step, the target after the single sulfur removing step may be used as the sulfur-modified PAN. The time for the single sulfur removal step is not particularly limited, but is preferably about 1 to 6 hours.

Sulfur-modified PAN contains carbon, nitrogen, and sulfur as a result of elemental analysis, and may further contain small amounts of oxygen and hydrogen. In addition, as shown in FIG. 1, as a result of X-ray diffraction of sulfur-modified PAN with CuKα rays, only a broad peak having a peak position near 25 ° was confirmed in the diffraction angle (2θ) range of 20 ° to 30 °. The For reference, X-ray diffraction measurement was performed using a powder X-ray diffractometer (manufactured by MAC Science, model number: M06XCE) using a CuKα ray. The measurement conditions were: voltage: 40 kV, current: 100 mA, scan rate: 4 ° / min, sampling: 0.02 °, number of integrations: 1 measurement range: diffraction angle (2θ) 10 ° to 60 °.

Furthermore, the mass loss by thermogravimetric analysis at the time of heating sulfur-modified PAN from a room temperature to 900 ° C. at a temperature rising rate of 20 ° C./min is 10% or less at 400 ° C. On the other hand, when a mixture of sulfur powder and PAN powder is heated under the same conditions, a mass loss is recognized from around 120 ° C., and at 200 ° C. or more, a large mass loss due to the disappearance of sulfur is recognized.
That is, in sulfur-modified PAN, it is considered that sulfur is not present as a simple substance, but is present in the state of being taken up in the ring-closed PAN.

An example of a Raman spectrum of sulfur-modified PAN is shown in FIG. In the Raman spectrum shown in FIG. 2, there are major peak near 1331cm ^-1 of Raman shift, ^{^and, 1548cm} -1 in the range of ^{^{^{200cm -1 ~ 1800cm -1, 939cm -1}}} , 479cm -1, 381cm -1, A peak is present around 317 cm ^-1 . The peak of the above-mentioned Raman shift is observed at the same position even when the ratio of elemental sulfur to PAN is changed. Therefore, these peaks are characteristic of sulfur-modified PAN. Each peak mentioned above exists in the range of about ± 8 cm ⁻¹ centered on the peak position mentioned above. In addition, in this specification, a "main peak" refers to the peak which peak height becomes the largest among all the peaks which appeared in the Raman spectrum.

For reference, the above-mentioned Raman shift is measured by RMP-320 (excitation wavelength λ = 532 nm, grating: 1800 gr / mm, resolution: 3 cm ⁻¹ ) manufactured by JASCO Corporation. Note that the peaks of the Raman spectrum may change in number or the position of the peak top may be shifted depending on the wavelength of incident light or the difference in resolution. Therefore, when the Raman spectrum of the positive electrode of the present invention using sulfur-modified PAN as the positive electrode active material is measured, the same peak as the above peak or a peak slightly different in number or peak top position from the above peak is confirmed Ru.

(Positive material for non-aqueous electrolyte secondary batteries)
The positive electrode material for a non-aqueous electrolyte secondary battery of the present invention contains a sulfur-modified PAN as a positive electrode active material and a conductive aid. The sulfur-modified PAN has been described above.

As a conductive support agent, vapor grown carbon fiber (VGCF), carbon powder, carbon black (CB), acetylene black (AB), ketjen black (KB), graphite, positive electrode such as aluminum or titanium For example, fine powders of metals stable at potentials are exemplified.

The particle diameter of the conductive aid is preferably 0.005 μm to 1 μm, and more preferably 0.01 μm to 0.1 μm. When the compounding amount of the conductive aid is the same, the smaller the particle diameter of the conductive aid is, the more conductive paths can be formed in the positive electrode.
(Method of manufacturing positive electrode material)
The manufacturing method of the present invention for manufacturing the positive electrode material described above comprises a crushing step, an auxiliary agent adding step, and a re-aggregation step.

[Crushing process]
The crushing step is a step of crushing the sulfur-modified PAN. As described later, the sulfur-modified PAN before crushing is generally present as an aggregate having a particle diameter (median diameter) of about 10 μm. In the crushing step, the aggregate is crushed to obtain a sulfur-modified PAN having a small diameter. The crushing step may be carried out by any known method as long as it is possible to loosen the aggregated sulfur-modified PAN. For example, an apparatus such as a ball mill, bead mill, air jet mill, in-liquid collision apparatus or the like may be used, or grinding may be performed using a mortar or the like. As described above, the sulfur-modified PAN particles after crushing should be "50 frequency% or more of the total particles have a particle diameter of 2 μm or less". The particle size of the sulfur-modified PAN particles can be measured by a laser diffraction scattering particle size distribution measuring apparatus. Furthermore, the median diameter of the sulfur-modified PAN particles as measured by a laser diffraction / scattering particle size distribution measuring apparatus is preferably 4 μm or less, and more preferably 2 μm or less. The crushing step may be carried out in the atmosphere or under an inert gas atmosphere or in a liquid medium, but in order to prevent reaggregation of the broken sulfur-modified PAN particles, it is carried out in a liquid medium Is preferred. A dispersing agent such as Tween 20 (polyoxyethylene sorbitan monolaurate) may also be used. As the liquid medium, a known medium such as water or an organic solvent may be used.

[Auxiliary agent addition process]
The auxiliary agent addition step is a step of adhering a conductive auxiliary agent to the surface of the crushed sulfur-modified PAN. In the auxiliary addition step, the conductive auxiliary may be attached to the surface of the sulfur-modified PAN particles by a known method. For example, the sulfur-modified PAN particles and the conductive auxiliary may be simply mixed, or the sulfur-modified PAN may be used. And the conductive aid may be bound by a binder resin or the like. In any case, it is preferable to carry out in the liquid medium in the same manner as the crushing step in order to attach the conductive aid to the surface while preventing reaggregation of the crushed sulfur-modified PAN particles. In addition, an auxiliary agent addition process may be performed after the crushing process mentioned above, and you may carry out simultaneously with the crushing process. Alternatively, only a part of the conductive additive may be added at the time of the crushing step, and the remaining part may be added at the time of preparation of the positive electrode mixture described later.

[Reaggregation process]
The reaggregation step is a step of reaggregating the sulfur-modified PAN (i.e., the sulfur-modified PAN to which the conductive auxiliary is attached) after the above-described auxiliary agent addition step. As described above, since the conductive auxiliary adheres to the surface of the sulfur-modified PAN particles in the auxiliary addition step, in the aggregate obtained in the reaggregation step, the conductive auxiliary is present not only on the surface but also inside . The particle size of the aggregate obtained in the reaggregation step is not particularly limited, but is preferably about 1 to 10 μm (median diameter). Moreover, it is preferable that the particle size of the aggregate obtained in a reaggregation process is uniform. In order to obtain aggregates of uniform or substantially uniform particle size, it is desirable to reaggregate the sulfur-modified PAN by a method such as spray drying, fluidized bed granulation, or the like that can control the particle size of the aggregates. If the method of crushing in a liquid medium and simultaneously performing drying and aggregation such as spray drying in the reaggregation step is not used, the sulfur modification after the auxiliary agent addition step before the reaggregation step A step of drying the PAN is required. This drying step may be a known method according to the liquid medium such as heat drying, vacuum drying and the like.

(Non-aqueous electrolyte secondary battery)
Hereinafter, the configuration of the non-aqueous electrolyte secondary battery of the present invention will be described.

[Positive electrode]
The positive electrode in the non-aqueous electrolyte secondary battery of the present invention can have the same structure as that of a general non-aqueous electrolyte secondary battery positive electrode except for the positive electrode material. For example, the positive electrode in the non-aqueous electrolyte secondary battery of the present invention can be manufactured by applying a positive electrode mixture prepared by mixing the above-described positive electrode material, a binder, and a solvent to a current collector. As another method, a mixture of the above-mentioned positive electrode material and binder is kneaded with a mortar or press and made into a film, and the film-like mixture is pressure-bonded to a current collector with a press or the like to produce a positive electrode. You can also

As a binder, polyvinylidene fluoride (PolyVinylidene DiFluoride: PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyimide (PI), polyamidoimide (PAI), carboxymethylcellulose (CMC), polychlorinated Examples include vinyl (PVC), methacrylic resin (PMA), polyacrylonitrile (PAN), modified polyphenylene oxide (PPO), polyethylene oxide (PEO), polyethylene (PE), polypropylene (PP) and the like.

Examples of the solvent include N-methyl-2-pyrrolidone, N, N-dimethylformaldehyde, alcohol, water and the like. These conductive aids, binders and solvents may be used in combination of two or more. There are no particular limitations on the amounts of these materials, but it is preferable to blend, for example, about 5 to 100 parts by mass of the conductive additive and 5 to 20 parts by mass of the binder with respect to 100 parts by mass of the sulfur-modified PAN.

What is generally used for the positive electrode for nonaqueous electrolyte secondary batteries may be used as a collector. For example, as a current collector, aluminum foil, aluminum mesh, punching aluminum sheet, aluminum expanded sheet, stainless steel foil, stainless steel mesh, punching stainless steel sheet, stainless steel expanded sheet, foamed nickel, nickel non-woven fabric, copper foil, copper mesh , Punched copper sheet, copper expanded sheet, titanium foil, titanium mesh, carbon paper (non-woven fabric / woven fabric) and the like. Among them, a carbon paper current collector made of carbon having a high degree of graphitization does not contain hydrogen and has low reactivity with sulfur, so it is suitable as a current collector for a positive electrode in the non-aqueous electrolyte secondary battery of the present invention. It is. As a raw material of carbon fiber having a high degree of graphitization, various kinds of pitch (that is, by-products such as petroleum, coal, coal tar, etc.), PAN fiber, etc. can be used as a material of carbon fiber.

[Negative electrode]
As a negative electrode active material for the non-aqueous electrolyte secondary battery of the present invention, an element compound capable of absorbing and releasing lithium ions and having an element capable of alloying with lithium and / or an element capable of alloying with lithium Are preferably used. Alternatively, it is preferable to use an element compound which is capable of storing and releasing sodium ions and which has an element capable of alloying with sodium and / or an element capable of alloying with atrium. For example, as elements that can be alloyed with lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si, At least one selected from Ge, Sn, Pb, Sb, and Bi can be mentioned. Among these, it is particularly preferable to use silicon (Si) or tin (Sn). The elemental compound having an element capable of alloying reaction with lithium is preferably a silicon compound or a tin compound. Examples of the silicon compound include SiO _x (0.5 ≦ x ≦ 1.5). Examples of tin compounds include tin alloys (Cu-Sn alloys, Co-Sn alloys, etc.), tin alloys (Cu-Sn alloys, Co-Sn alloys, etc.), and the like. In addition, known carbon-based materials such as metallic lithium, metallic sodium and graphite can also be used. When metallic lithium is used as the negative electrode active material, the non-aqueous electrolyte secondary battery of the present invention is a lithium secondary battery. When metallic sodium is used as the negative electrode active material, the non-aqueous electrolyte secondary battery of the present invention is a sodium secondary battery (so-called sodium-sulfur battery). When a material containing no lithium, for example, a carbon-based material, a silicon-based material, an alloy-based material or the like among the above-mentioned negative electrode materials is used as the negative electrode material, short circuit between positive and negative electrodes due to generation of dendrite hardly occurs It is advantageous in point. However, when these negative electrode materials not containing lithium are used in combination with the positive electrode material of the present invention, neither the positive electrode nor the negative electrode contains lithium. Therefore, a lithium pre-doping process is required in which lithium is inserted in advance into one or both of the negative electrode and the positive electrode. A known method may be used as the lithium pre-doping method. For example, when the negative electrode is doped with lithium, a method of inserting lithium by an electrolytic doping method in which metal lithium is used as a counter electrode to form a half cell and electrochemically dopes lithium, or a metal lithium foil is attached to an electrode After that, there is a method of inserting lithium by a sticking pre-doping method of leaving in an electrolytic solution and doping using diffusion of lithium to the electrode. In addition, the above-described electrolytic doping method can be used also in the case of pre-doping lithium to the positive electrode.

As the negative electrode material not containing lithium, particularly, a silicon-based material which is a high capacity negative electrode material is preferable, and among them, thin film silicon which has a thin electrode thickness and is advantageous in capacity per volume is more preferable.

As a current collector for the negative electrode, aluminum foil, aluminum mesh, punching aluminum sheet, aluminum expanded sheet, stainless steel foil, stainless steel mesh, punching stainless steel sheet, stainless steel expanded sheet, foamed nickel, nickel non-woven fabric, copper foil, Examples thereof include copper mesh, punched copper sheet, copper expanded sheet, titanium foil, titanium mesh, carbon paper (nonwoven fabric / woven fabric) and the like.

〔Electrolytes〕
As an electrolyte used for a non-aqueous electrolyte secondary battery, what melt | dissolved the alkali metal salt which is electrolyte in an organic solvent can be used. As the organic solvent, it is preferable to use at least one selected from non-aqueous solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl ether, isopropyl methyl carbonate, vinylene carbonate, γ-butyrolactone and acetonitrile. . When lithium is used as the negative electrode active material, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiI, LiClO ₄ or the like can be used as the electrolyte. When using sodium as the negative electrode active material, it is selected from NaPF ₆ , NaBF ₄ , NaClO ₄ , NaAsF ₆ , NaSbF ₆ , NaCF ₃ SO ₃ , NaN (SO ₂ CF ₃ ) ₂ , lower fatty acid sodium salt, NaAlCl ₄ etc. One or more of these can be used. Among them, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , NaPF ₆ , NaBF ₄ , NaAsF ₆ , NaSbF ₆ , NaSbF ₆ , NaCF ₃ SO ₃ , NaN (SO ₂ CF ₃ ) ₂ etc. contain fluorine (F) Are preferably used. The concentration of the electrolyte may be about 0.5 mol / L to 1.7 mol / L. The electrolyte is not limited to liquid, and may be solid (for example, polymer gel).

[Others]
The non-aqueous electrolyte secondary battery may include members such as a separator in addition to the above-described negative electrode, positive electrode, and electrolyte. The separator is interposed between the positive electrode and the negative electrode, allows movement of ions between the positive electrode and the negative electrode, and prevents an internal short circuit between the positive electrode and the negative electrode. If the non-aqueous electrolyte secondary battery is a closed type, the separator is also required to have a function of holding the electrolytic solution. As the separator, it is preferable to use a thin, microporous or non-woven membrane made of polyethylene, polypropylene, PAN, aramid, polyimide, cellulose, glass or the like. The shape of the non-aqueous electrolyte secondary battery is not particularly limited, and various shapes such as a cylindrical shape, a laminated shape, and a coin shape can be used.
Hereinafter, the non-aqueous electrolyte secondary battery of the present invention and a method of manufacturing the same will be specifically described.

(Example)
The non-aqueous electrolyte secondary battery of the example is a lithium ion secondary battery. The nonaqueous electrolyte secondary battery of the example was produced as follows.

<Sulfur-modified PAN>
[1] Mixed raw material As a sulfur powder, when it classified using a sieve, the thing used as a particle size of 50 micrometers or less was prepared. As a PAN powder, one having a particle diameter in the range of 0.2 μm to 2 μm as prepared by an electron microscope was prepared. 5 parts by mass of sulfur powder and 1 part by mass of PAN powder were mixed and pulverized in a mortar to obtain a mixed raw material.

[2] Device As shown in FIG. 3, the reaction device 1 comprises a reaction vessel 2, a lid 3, a thermocouple 4, an alumina protective tube 40, two alumina tubes (gas inlet tube 5, gas outlet tube 6), argon gas It has a piping 50, a gas tank 51 containing argon gas, a trap piping 60, a trap tank 62 containing an aqueous sodium hydroxide solution 61, an electric furnace 7, and a temperature controller 70 connected to the electric furnace.

As the reaction vessel 2, a bottomed cylindrical glass tube (made of quartz glass) was used. The mixed raw material 9 was accommodated in the reaction container 2 in the heat treatment process mentioned later. The opening of the reaction vessel 2 was closed by a glass lid 3 having three through holes. An alumina protective tube 40 (alumina SSA-S, manufactured by Nikkato Co., Ltd.) containing a thermocouple 4 was attached to one of the through holes. A gas introduction pipe 5 (alumina SSA-S, manufactured by Nikkato Co., Ltd.) was attached to the other one of the through holes. A gas exhaust pipe 6 (alumina SSA-S, manufactured by Nikkato Co., Ltd.) was attached to the remaining one of the through holes. The reaction vessel 2 had an outer diameter of 60 mm, an inner diameter of 50 mm, and a length of 300 mm. The alumina protective tube 40 had an outer diameter of 4 mm, an inner diameter of 2 mm, and a length of 250 mm. The gas introduction pipe 5 and the gas discharge pipe 6 had an outer diameter of 6 mm, an inner diameter of 4 mm, and a length of 150 mm. The tips of the gas introduction pipe 5 and the gas discharge pipe 6 were exposed to the outside of the lid 3 (in the reaction vessel 2). The length of this exposed portion was 3 mm. The tips of the gas introduction pipe 5 and the gas discharge pipe 6 become almost 100 ° C. or less in the heat treatment step described later. For this reason, the sulfur vapor generated in the heat treatment step does not flow out from the gas introduction pipe 5 and the gas discharge pipe 6 and is returned (refluxed) to the reaction vessel 2.

The tip of the thermocouple 4 placed in the alumina protective tube 40 indirectly measured the temperature of the mixed raw material 9 in the reaction vessel 2. The temperature measured by the thermocouple 4 was fed back to the temperature controller 70 of the electric furnace 7.

An argon gas pipe 50 was connected to the gas introduction pipe 5. The argon gas pipe 50 was connected to a gas tank 51 containing argon gas. One end of a trap pipe 60 was connected to the gas discharge pipe 6. The other end of the trap pipe 60 was inserted into the sodium hydroxide aqueous solution 61 in the trap tank 62. The trap pipe 60 and the trap tank 62 are traps of hydrogen sulfide gas generated in a heat treatment process described later.

[3] Heat Treatment Step The reaction vessel 2 containing the mixed raw material 9 was housed in an electric furnace 7 (crucible furnace, opening width φ 80 mm, heating height 100 mm). At this time, argon was introduced into the reaction vessel 2 through the gas introduction pipe 5. The flow rate of argon gas at this time was 100 ml / min. Ten minutes after the start of the introduction of the argon gas, heating of the mixed material 9 in the reaction vessel 2 was started while continuing the introduction of the argon gas. The temperature rising rate at this time was 5 ° C./min. When the mixed material 9 reached 100 ° C., the introduction of argon gas was stopped while continuing to heat the mixed material 9. When the mixed material 9 reached about 200 ° C., gas was generated. Heating was stopped when the mixed material 9 reached 360 ° C. After the heating was stopped, the temperature of the mixed material 9 rose to 400 ° C. and then dropped. Therefore, the mixed raw material 9 was heated to 400 ° C. in this heat treatment step. Thereafter, the mixed raw material 9 was naturally cooled, and when the mixed raw material 9 was cooled to room temperature (about 25 ° C.), the product (that is, the object to be treated after the heat treatment step) was taken out from the reaction vessel 2. The heating time at this time was about 10 minutes at 400 ° C., and sulfur was refluxed.

[4] Single Sulfur Removal Step In order to remove single sulfur (free sulfur) remaining on the object to be treated after the heat treatment step, the following steps were carried out.

The object to be treated after the heat treatment step was crushed in a mortar. 2 g of the pulverized material was placed in a glass tube oven and heated at 200 ° C. for 3 hours while vacuum suction was performed. The temperature rising temperature at this time was 10 ° C./min. In this step, the elemental sulfur remaining on the object to be treated after the heat treatment step is evaporated and removed to obtain sulfur-modified PAN containing (or substantially not containing) elemental sulfur.

<Positive material>
[1] Crushing Step As shown in FIG. 4A, the sulfur-modified PAN 80 obtained in the above step is in the form of an aggregate in which primary particles 81 of the sulfur-modified PAN particles are aggregated. In the crushing step, this aggregate-like sulfur-modified PAN 80 is dispersed in water, and subjected to collision crushing in liquid using a Starburst Lab HJP-25005 (oblique collision chamber, pressurized at 245 MPa) manufactured by Sugino Machine Co., Ltd. The sulfur-modified PANs 80 in aggregate form were allowed to collide with each other in water. As shown in FIG. 4B, this step yielded sulfur-modified PAN particles 82 in which aggregate-like sulfur-modified PAN 80 was crushed.

[2] Auxiliary Agent Addition Step After one cycle of the crushing step was completed, acetylene black (AB) as the conductive auxiliary agent 83 was added to the sample tank of the above-mentioned crushing apparatus. The blending amount of AB was 6 parts by mass with respect to 100 parts by mass of the sulfur-modified PAN. The particle diameter of this AB was 0.02 μm (median value). As shown in FIG. 4C, after the addition of the conductive aid 83, the crushing cycle was repeated four cycles to adhere the conductive aid 83 to the surface of the sulfur-modified PAN particles 82.

[3] Reaggregation Step The aqueous dispersion of the sulfur-modified PAN particles 82 and the conductive auxiliary agent 83 obtained in the auxiliary agent addition step was spray-dried using a spray dryer MDL-050B manufactured by Fujisaki Electric. By this process, water was evaporated and aggregates having a substantially constant particle size were obtained. This aggregate is the positive electrode material 84 of the example. As shown in FIG. 4D, in the positive electrode material 84 of the embodiment, the conductive auxiliary agent 83 exists on the surface and inside of the positive electrode material 84.

[1] Positive Electrode A slurry was prepared by mixing 80 parts by mass of the positive electrode material obtained in the above step, 20 parts by mass of polyimide (PI), and N-methyl-2-pyrrolidone (NMP).

On the other hand, a current collector made of carbon paper (Toray; TGP-H-030) punched out to a diameter of 11 mm was prepared, filled with the above slurry, and dried at 200 ° C. for 2 hours under reduced pressure to prepare a positive electrode. .

[2] Negative Electrode As a negative electrode, a metal lithium foil punched out to a size of 11 mm in diameter was used.

[3] Electrolyte A non-aqueous electrolyte in which LiPF ₆ was dissolved in propylene carbonate was used as the electrolyte. The concentration of LiPF ₆ in the electrolyte was 1.0 mol / L.

[4] Battery A coin battery was produced using the positive electrode, the negative electrode and the electrolyte obtained in the above [1], [2] and [3]. Specifically, in a dry room, a separator (made of “Celgard 2400” Celgard) made of a 25 μm-thick polypropylene microporous film and a 500 μm-thick glass non-woven filter are sandwiched between a positive electrode and a negative electrode. As an electrode body battery. The electrode battery was housed in a battery case (CR2032 type coin battery member manufactured by Takasen Co., Ltd.) consisting of a stainless steel container. The electrolytic solution obtained in [3] was injected into the battery case. The battery case was sealed with a caulking machine to obtain the non-aqueous electrolyte secondary battery of the example.

(Comparative example)
The positive electrode material for a non-aqueous electrolyte secondary battery of the comparative example is the same as the positive electrode material for a non-aqueous electrolyte secondary battery of the example except that the conductive auxiliary is directly attached to the sulfur-modified PAN aggregate before crushing. It is a thing. The positive electrode material for a non-aqueous electrolyte secondary battery of Comparative Example was obtained by mixing the sulfur-modified PAN aggregate before crushing and the conductive additive in an agate mortar. As shown in FIG. 5A, the sulfur-modified PAN 80 used in the comparative example is in the form of aggregates. When the conductive auxiliary agent 83 is directly attached to the aggregate-like sulfur-modified PAN 80, the conductive auxiliary agent 83 is attached only to the surface of the aggregate-like sulfur-modified PAN 80 as shown in FIG. 5B. The non-aqueous electrolyte secondary battery of the comparative example is the same as the non-aqueous electrolyte secondary battery of the example except for the positive electrode material.

<Particle size distribution of sulfur-modified PAN>
The particle size distributions of the sulfur-modified PAN before crushing and the sulfur-modified PAN after crushing were measured. As the sulfur-modified PAN after crushing, a sulfur-modified PAN aqueous dispersion after the same crushing step as in the example was collected from a sample tank of a crushing apparatus.

The particle size distribution of each sulfur-modified PAN was measured by a laser diffraction scattering particle size distribution method using a particle size distribution analyzer LA-910W manufactured by Horiba, Ltd. The measurement results are shown in FIG. 6, FIG. 7 and Table 1. Specifically, FIG. 6 shows the particle size distribution of the sulfur-modified PAN before crushing, and FIG. 7 shows the particle size distribution of the sulfur-modified PAN after crushing.

As shown in FIG. 6, FIG. 7 and Table 1, small-sized sulfur-modified PAN particles having a median diameter of 2 μm or less can be obtained from large-sized sulfur-modified PAN aggregates having a median diameter of 10 μm or more by the crushing step. Further, sulfur-modified PAN particles having a substantially uniform particle diameter can be obtained by the crushing step. In the sulfur-modified PAN aggregate before the crushing step, particles having a particle diameter of 2 μm or less are less than 1% (about 0.6 frequency%) of the whole, while in the sulfur-modified PAN particles after the crushing step, Particles having a particle size of 2 μm or less are 50% or more of the whole (about 70% by frequency).

In the positive electrode material of the example in which the conductive support agent is attached to the surface of such sulfur-modified PAN particles, the conductive support agent is dispersed and disposed at intervals of the particle diameter of the sulfur-modified PAN particles. As described above, in the particle size distribution of the sulfur-modified PAN particles after crushing, particles having a particle diameter of 2 μm or less account for about 70% of the whole. For this reason, in the positive electrode material of the example, the region where the conductive support agent is not present in the range of 2 μm or more is less than 30% of the entire positive electrode material. That is, when the positive electrode material is analyzed, if the region in which the conductive additive is not present in the range of 2 μm or more is less than 30% of the entire positive electrode material, the positive electrode material of the example (that is, the positive electrode material of the present invention) It can be determined that there is. In other words, it can be judged that the positive electrode material of the present invention is a region in which adjacent conductive assistants are separated by 2 μm or more from less than 30% of the entire positive electrode material.
<Observation of positive electrode material by SEM>

The surface of the positive electrode material of the example and the sulfur-modified PAN before crushing were observed with a scanning electron microscope (SEM; Scanning Electron Microscope). The acceleration voltage at this time was 5 kV and the magnification was 5000 times. The SEM image of sulfur-modified PAN before crushing is shown in FIG. 8, and the SEM image of the positive electrode material of the example is shown in FIG.

As shown in FIGS. 8 and 9, the positive electrode material of the example has a smaller diameter than the sulfur-modified PAN before crushing. In addition, particles of acetylene black, which is a conductive additive, can be observed on the surface of the sulfur-modified PAN having a reduced diameter.

<Charge / discharge characteristics>
The charge and discharge characteristics of the non-aqueous electrolyte secondary batteries of Examples and Comparative Examples were measured. Specifically, charge and discharge were repeatedly performed in each non-aqueous electrolyte secondary battery. The discharge rate at this time was 0.1 C, and the cut-off voltage was 3.0 V to 1.0 V. The temperature was 25-30 ° C. Among the charge and discharge characteristic tests, the results of the second cycle discharge test are shown in FIG. 10 and FIG. FIG. 10 relates to the nonaqueous electrolyte secondary battery of the example, and FIG. 11 relates to the nonaqueous electrolyte secondary battery of the comparative example.

In the nonaqueous electrolyte secondary battery (FIG. 11) of the comparative example, the battery voltage immediately after the start of discharge was 2.68 V. On the other hand, in the non-aqueous electrolyte secondary battery (FIG. 10) of the example, the battery voltage immediately after the start of discharge was 2.53 V. From these results, it can be seen that the internal resistance of the non-aqueous electrolyte secondary battery of the example is lower than that of the non-aqueous electrolyte secondary battery of the comparative example. This indicates that the positive electrode material of the example is more conductive than the positive electrode material of the comparative example. That is, when the conductive auxiliary is attached to the crushed sulfur-modified PAN, the conductivity is the same even with the same amount of conductive auxiliary as compared to the case where the conductive auxiliary is attached to the sulfur-modified PAN before the crushing. Can be improved.

1: Reactor 2: Reaction vessel 3: Lid 4: Thermocouple 5: Gas inlet tube 6: Gas outlet tube 7: Electric furnace 80: Aggregate-like sulfur-modified PAN 81: Primary particles 82 of sulfur-modified PAN particles: Sulfur Modified PAN particle 83: conductive aid 84: positive electrode material

Claims

A positive electrode material for a non-aqueous electrolyte secondary battery,
Using a carbon skeleton derived from polyacrylonitrile, a sulfur-based positive electrode active material consisting of the carbon skeleton and sulfur (S), and a conductive aid,
What is claimed is: 1. A positive electrode material for a non-aqueous electrolyte secondary battery, wherein 50% by frequency or more of the particles in the particle size distribution of the sulfur-based positive electrode active material is particles having a particle diameter of 2 μm or less.
In the Raman spectrum of the sulfur-based positive active material, there is a main peak near 1331cm -1 of Raman shift, and, 1548cm -1 in the range of 200cm -1 ~ 1800cm -1, 939cm -1 , 479cm -1, The positive electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein peaks are present respectively at 381 cm -1 and 317 cm -1 .
3. The positive electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein 70% or more of the particles in the particle size distribution of the sulfur-based positive electrode active material are particles having a particle diameter of 2 μm or less.
A non-aqueous electrolyte secondary battery comprising the positive electrode material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3 in a positive electrode.
A method for producing a positive electrode material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3,
A crushing step of crushing a sulfur-based positive electrode active material comprising a carbon skeleton derived from polyacrylonitrile and the carbon skeleton and sulfur (S);
An auxiliary agent addition step of causing a conductive auxiliary agent to adhere to the surface of the crushed sulfur-based positive electrode active material;
A method for producing a positive electrode material for a non-aqueous electrolyte secondary battery, comprising: a reaggregation step of reaggregating the sulfur-based positive electrode active material after the auxiliary agent addition step.
The method for producing a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the crushing step is performed in a liquid medium.
The method for producing a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the auxiliary agent addition step is performed in a liquid medium.
The method for producing a positive electrode material for a non-aqueous electrolyte secondary battery according to any one of claims 5 to 7, wherein the auxiliary agent addition step is performed simultaneously with the crushing step.
The method for producing a positive electrode material for a non-aqueous electrolyte secondary battery according to claim 7, wherein the reaggregation step is performed by spray drying or fluidized bed granulation.