JP4456449B2 - Battery positive electrode material containing sulfur and / or sulfur compound having S—S bond and method for producing the same - Google Patents

Description

  The present invention relates to a battery positive electrode material composed of sulfur containing carbon particles and / or a sulfur compound having an S—S bond, and more particularly to a positive electrode material constituting a lithium battery having extremely high energy density and power density.

  In recent years, communication devices and OA devices have become portable, and competition for weight reduction and downsizing of these devices has been developed. High energy density is required for such various devices or batteries used as power sources for electric vehicles and the like. Among them, lithium batteries have been attracting attention in the past because it is not necessary to consider the decomposition voltage of water, and the voltage can be increased by appropriately selecting the positive electrode material. A typical positive electrode material for this type of battery is a metal oxide. Among these, manganese dioxide is one of the most practical positive electrode materials because manganese is abundant in nature and inexpensive.

  However, a lithium battery using manganese dioxide as a positive electrode material has a problem that the capacity is small. In order to solve such a problem, a battery using a mixture of manganese dioxide and a predetermined ratio as a positive electrode has been proposed (Patent Document 1).

On the other hand, in order to obtain a battery having a high energy density, it is preferable to use an active material having a large capacity density. For example, as a battery material for a positive electrode, sulfur is known to have the largest capacity density as a known material. ing. That is, as shown in FIG. 1, when S ₈ is completely reduced to Li ₂ S (utilization rate 100%), the theoretical capacity density per weight of the material is 1675 Ah / kg, which is larger than any chemical species. It shows.
A battery having a positive electrode using sulfur having a high capacity as an active material has been studied using such characteristics of sulfur (Patent Document 2).

In recent years, in addition to active sulfur, some studies have focused on sulfur, and include polycarbon sulfide and organic disulfide compounds. The theoretical capacity density of these two typical sulfur compounds is also 3 times higher than that of common conductive polymers and various lithium metal oxides, and 13 times as high. The present inventors have proposed "a novel compound design method characterized by combining an increase in theoretical capacity density with an increase in disulfide sites and polysulfidation when designing an energy storage device material from a heterocyclic organic sulfur compound". And we have already filed an international application (Patent Document 3).
JP-A-8-213018 US Patent No. 5523179 WO 02/082569

Since the electronic conductivity of sulfur compounds having sulfur and / or S—S bonds is as low as about 5 × 10 ⁻³⁰ S · cm ⁻¹ at room temperature, it is necessary to contain a large amount of conductive auxiliary. Usually, the upper limit of the ratio of sulfur in the electrode is 50 to 60% by weight. Moreover, it is known that the capacity utilization of sulfur is about 50 to 70%. For example, when the content of sulfur in the positive electrode material is 50%, the capacity density of sulfur takes into account the sulfur content in the electrode (50%) and the upper limit of the capacity utilization of sulfur (70%). 600Ah / kg is the upper limit, and only about 35% of the theoretical capacity can be obtained. In order to further increase the capacity, it is necessary to increase the content of sulfur or sulfur compounds.

  However, since the electron conductivity of sulfur is poor, an excessive conduction auxiliary agent (substance with conductivity) is necessary to obtain a sufficient electron recovery route. In other particle composite methods such as a wet method, The sulfur content was limited to about 50% by weight at most.

  In addition, in the wet method, the viscosity of sulfur increases at the time of mixing, so that re-aggregation easily occurs and the processability is difficult, and the content rate cannot be increased.

  Furthermore, since the oxidation-reduction reaction of sulfur is slow and the resistance of the electrode reaction is high, there is a disadvantage that only a low voltage of 2 V or less can be obtained even when a battery using a metal lithium negative electrode is operated at room temperature.

  In view of the above problems, the present invention uses sulfur having a large capacity density as an active material without containing a large amount of a conductive auxiliary agent (substance having conductivity) while taking advantage of the characteristic of having the largest capacity density of sulfur. An object of the present invention is to provide a positive electrode material for a positive electrode material, that is, a battery having a high energy density.

The gist of the present invention is the battery positive electrode material of the following (1) to (4).
(1) Sulfur compound particles having sulfur and / or S—S bonds and a composite fine particle layer formed by compositing fine particles of a conductive material by mechano-fusion and in which the fine particles are biting into the particles. Using the composite material as a starting material, the composite material is heated to a temperature higher than the melting point, a physical stress by stirring or stretching is applied to the heated composite material, cooled to room temperature, and the resulting fibrous intermediate composite material is pulverized. From the conductive fibrous composite material having a three-dimensional network structure derived from the fine particles of the conductive material on the surface of the fibrous intermediate composite material formed by combining the fine particles of the conductive material with the mechanofusion. A battery positive electrode material characterized by comprising.
(2) The composite material as the starting material is a composite fine particle layer in which sulfur and / or a sulfur compound particle having an S—S bond is used as a nucleus and the surface is provided with a sufficient electron / ion conduction path. The battery positive electrode material according to (1) above, wherein is formed.
(3) The battery according to (1) or (2) above, wherein the three-dimensional network structure derived from the fine particles of the conductive material in the conductive fibrous composite material is such that the fine particles of the conductive material form a network structure in a bead shape. Positive electrode material.
(4) The conductive fibrous composite material has a sulfur content of 73% or more and an electrical conductivity of 10 ⁰ to 10 ¹ S · cm ⁻¹ or more (1), ( Battery positive electrode material of 2) or (3).

Moreover, this invention makes the summary the manufacturing method of the battery positive electrode material of following (5)-(9).
(5) Sulfur and / or sulfur compound particles containing 70% by weight or more of sulfur and conductive fine particles are used as raw materials, and these particles are mechano-fused. First step of producing a composite material of sulfur and / or a sulfur compound and a conductive material, in which a composite fine particle layer is formed with both sufficient electron / ion conduction paths secured, and the composite material exceeds the melting point Obtained by the second step of heating the composite material, the third step of applying physical stress by stirring or stretching to the heated composite material, the fourth step of cooling the composite material to room temperature, and the fourth step. The fifth step of pulverizing the fibrous intermediate composite material, the pulverized fibrous intermediate composite material is further mechanofused with conductive fine particles, the fibrous intermediate composite material is used as a core, and the conductive material is formed on the surface. Method for producing a battery positive electrode material characterized by comprising a sixth step of obtaining a conductive fibrous composite material having a three-dimensional network structure derived from particles.
(6) The method for producing a battery positive electrode material according to (5), wherein the fourth step is rapid cooling to near room temperature at 50 ° C. to 200 ° C. per minute by natural air cooling or a cooling medium / heat sink.
(7) In the first step, the battery positive electrode material according to (5) or (6) above, wherein a raw material mixture containing 70% by weight or more of sulfur and / or sulfur compound particles having an S—S bond as sulfur is used. Production method.
(8) In the first step, a raw material mixture of sulfur compound particles having a particle size of 75 μm or less and / or a sulfur compound having an S—S bond and fine particles of a conductive material which is carbon fine particles having a primary particle size of 30 nm to 50 nm is used. The method for producing a battery positive electrode material according to any one of the above (5) to (7).
(9) The method for producing a battery positive electrode material according to any one of (5) to (8), wherein the carbon fine particles have a hollow structure with a porosity of 60 vol% or more and 80 vol% or less.

  The present invention increases the current density by ensuring both sufficient electron and ion conduction paths even if the content of the conductive material is small, and also changes the operating voltage by changing the structure of sulfur or sulfur compounds. Therefore, it is possible to provide a lithium ion battery having a high energy density and an extremely high power density.

  Moreover, since it manufactures with a dry construction method, it is possible to raise the content rate of sulfur compared with a wet construction method, and it is excellent in the workability at the time of electrode formation.

  Furthermore, since the carbon fine particles and sulfur particles used as materials are inexpensive and excellent in cost, it is possible to provide batteries with high energy density and high output density at low cost.

  In the present invention, examples of sulfur compounds having sulfur and / or S—S bonds include sulfur, polycarbon sulfide, and organic disulfide compounds. The theoretical capacity density of these three typical sulfur compounds is also three times higher than that of common conductive polymers and various lithium metal oxides, and 13 times as high. Fig. 1 shows the theoretical capacity density (Ah / kg) per weight of materials that have been considered as lithium battery positive electrodes. The theoretical capacity density is obtained from the ratio (n / Mw) of the number of reaction electrons (n) to the molecular weight (Mw). Lithium transition metal oxide, which is the cathode material of current lithium ion secondary batteries, is 130-280 Ah / kg, conductive polymer is 70-100 Ah / kg, while sulfur compounds are 300-1675 Ah / kg. Because of this value, higher capacity can be expected.

In the positive electrode of the present invention, elemental sulfur having a cyclic structure (S ₈ ) or organic sulfur compound having an organic skeleton (-(-RS _n -R-) _m- : n is 2 or more and 8 or less, m is 2 or more and 10 or less ) And the like. Both have disulfide bonds (-SS-) or polysulfide bonds (-S _n- ) in which disulfide bonds are linked. Sulfur is electrochemically active elemental sulfur. For sulfur-based positive electrodes, sulfur (S ₈ ) reacts with lithium to produce Li ₂ S. This capacity density is very high at 1675 Ah / kg, and if the voltage is 2 V, the energy density is 3340 Wh kg ^-1 , an attractive substance that is 17 times that of LiCoO ₂ 137 Wh kg ^-1 It is. As shown in FIG. 2, elemental sulfur changes from S ₈ to Li ₂ S ₈ , Li ₂ S ₄ , Li ₂ S ₂ , and Li ₂ S by a reduction reaction. The number of reaction electrons obtained by the reaction at that time is 16 electrons. That is, when sulfur or a sulfur compound is used for the positive electrode of a lithium battery, the elemental sulfur is changed from S ₈ to 8Li ₂ S by a reduction reaction, and the number of electrons used in the reaction is 16, compared with other materials. The ratio of the number of reaction electrons to the amount of active material is large. However, the electron conductivity of simple sulfur is about 5 × 10 ⁻³⁰ S · cm ⁻¹ at room temperature (25 ° C.), and the electron conductivity of other positive electrode materials (lithium transition metal oxides of current positive electrode materials: 10 ⁻² ˜10 ⁻¹ S · cm ⁻¹ ), which is extremely low and cannot be used as a positive electrode material as it is.

Examples of sulfur-based compounds, (SRS) R is polycarbonate Nsu sulfide compound is carbon (C) of _n [(CS _{x) n]} is charged and discharged while maintaining the state of the polymer, at least 680 Ah / kg The energy density can be expected to be twice or more that of a general oxide electrode. Various polycarbon sulfide compounds are known. Of course, the larger the y / x value of C _x S _y , the more advantageous the energy density.

As for organic disulfide compounds, disulfide bonds (-SS-) are formed when an organic sulfur compound (mercaptan or thiol) having a mercapto group (-SH group) in the molecule is oxidized, and again converted into thiols when reduced. The redox reaction of returning can be applied to energy storage. The formation of SS bond by oxidation reaction is applied to battery charging, and the cleavage of SS bond by reduction reaction is applied to discharge, and organic sulfur compounds become the positive electrode material for lithium secondary batteries. The theoretical energy density is 650 to 1240 Wh kg ^-1 , which is an order of magnitude higher than that of lead-acid batteries and nickel-cadmium batteries. In addition, it has high potential as a high energy density secondary battery material in terms of material price and low toxicity. I can say that.

  2,5-dimercapto-1,3,4-thiadiazole (DMcT), trithiocyanuric acid (TTCA), 5-methyl-1,3,4-thiadiazole-2-thiol (MTT) with a carbon atom in the α-position The disulfide, trisulfide, and tetrasulfide compounds are typical organic disulfide compounds. A major disadvantage of using organic disulfide compounds as positive electrode materials for lithium batteries is that they are insulators and therefore must be provided with a conductive additive, which reduces the capacity density, which is a major feature. .

Explain the discharge reaction of lithium / sulfur batteries. Lithium metal (Li ⁰ ) is used for the negative electrode. For the positive electrode, elemental sulfur (S ₈ ) having a cyclic structure or organic sulfur compound having an organic skeleton (-(-RS _n -R-) _m- : n is 2 to 8 and m is 2 to 10) Sulfur compounds are used. Both have disulfide bonds (-SS-) or polysulfide bonds (-S _n- ) in which disulfide bonds are linked. As shown in FIG. 3, an oxidation reaction (dissolution reaction) occurs at the negative electrode during discharge and changes from Li ⁰ to Li ⁺ . The positive electrode during discharge, as shown in FIG. 3 reduction reaction occurs (cleavage reaction of a disulfide bond) from -SS- 2S ^- changes to.

Conventionally, elemental sulfur or the like requires a carbon material called carbon black or acetylene black, which is a large amount of a conductive auxiliary agent, in order to collect and donate (redox) electrons from low electron conductivity. In the present invention, carbon or metal-supported carbon having a catalytic effect can be used as the conductive material used as a raw material for producing the composite material. What is marketed as carbon black has high conductivity and is excellent in handling.
The carbon fine particles are preferably those having a primary particle diameter of 30 nm to 50 nm and a hollow structure having a porosity of 60 Vol% or more and 80 Vol% or less, and these carbon fine particles are commercially available as Ketjen Black (registered trademark). FIG. 4 is a photograph of Ketjen Black (registered trademark) taken with a transmission electron microscope (TEM).

Usually, the conductive auxiliary carbon material has a spherical shape with primary particles of about 30-40 nm, and simple sulfur is a particle with primary particles of about 70-100 μm. In the present invention, it is preferable to use a sulfur or sulfur compound having a particle size of 75 μm or less. By forming a very thin layer of carbon fine particles on the particle surface, the content of sulfur or sulfur compound is 72.9. and the weight% or more, electric conductivity becomes possible to manufacture a battery cathode material is 10 ⁰ ~10 ¹ S · cm ^-1 or more.

In order to use sulfur or a sulfur compound as a battery positive electrode material, it is ideal to have a structure as shown in FIG. 2 that covers the conductive auxiliary agent around the single sulfur particles. For example, a composite material of simple sulfur and a conductive auxiliary carbon material is mixed with an organic solvent such as n-methylpyrrolidone, ink is made, applied onto a copper or aluminum sheet as a current collector, dried, and then dried. Thus, an electrode is formed on the current collector so that the conductive auxiliary carbon material is uniformly coated around the elemental sulfur. What is necessary for the electrode preparation is the formation of fine particles of sulfur, homogenization of the particles, optimization of the addition amount of the carbon material for assisting conduction, and uniform dispersion.

Therefore, the present invention is to reduce the content of the conductive auxiliary agent as much as possible (addition of an optimal amount), sulfur or sulfur compound in order to fully utilize the material characteristics of sulfur and / or sulfur compounds having an S—S bond. The above-mentioned problems are solved by making the particles uniformly fine particles and by uniformly dispersing the composite material. The present inventors have succeeded in forming a very thin conductive material layer on the surface of sulfur or sulfur compound particles by mechanofusion. Raw material sulfur and / or sulfur compound particles having an S—S bond and conductive fine particles are mechano-fused to form a composite fine particle layer in which the fine particles are biting into the particles.
By uniformly dispersing the composite particles obtained by this method, both the electron and ion conduction paths are ensured and a large amount of energy can be stored even when the content of the conductive material is small.

  Mechanofusion is a dry-mechanical composite technology that creates new materials by adding mechanical energy to multiple different material particles to cause mechanochemical reactions. In recent years, it has become clear that when a certain kind of mechanical energy is applied to a plurality of different material particles, a reaction occurs and mechano-fusion (surface fusion) occurs, thereby creating a new material. . This method is characterized by a simple process and a much wider range of combinations than other particle compositing methods such as a wet method. The mechanochemical reaction refers to a chemical interaction with surrounding substances in a highly excited state of a solid by mechanical energy.

  In other words, the stage where foreign particles adhere to the surface of the core particles activated by mechanical action, and after the foreign particles adhere to the surface of the core particles to some extent, the fine particles are further laminated and the fine particle layer itself is consolidated to form a composite By passing through the stage in which the fine particle layer is formed, composite particles having a strong bonding interface can be produced.

In the present invention, as shown in FIG. 5, by forming a layer of a conductive material nano-ordered on the surface of the sulfur fine particles, both the electron and ion conduction paths are secured, thereby increasing the capacity. Made it possible. The composite fine particle layer formed by mechano-fusion is in a state where fine particles of a conductive substance are biting into sulfur compound particles having sulfur and / or S—S bonds. That is, as shown in FIG. 5, a composite material in which Ketjen Black (registered trademark) is coated on a sulfur-based compound thinly and uniformly in a nano size is provided. Nanocomposite of ketjen black (registered trademark) and sulfur-based compounds is a novel composite material that imparts both electron and ion conduction paths to sulfur-based compounds with ketjen black (registered trademark). As shown in FIG. 5, Ketjen Black (registered trademark) is thinly and uniformly coated with a sulfur compound to form an electron conduction path, and the electrolyte solution is formed by nano-sized voids due to the hollow structure of Ketjen Black (registered trademark). The structure soaks well, and the electrolyte solution soaks well due to the micro-sized voids of the ketjen black (registered trademark) bead-like structure.
The composite fine particle layer will be described in more detail. FIG. 6 is a scanning electron microscope (SEM) photograph of the composite particles composited by raw material sulfur and mechanofusion. In the raw material sulfur (see FIG. 7), there are particles having a diameter of about 20 to 50 μm, but in the composite material, the particle diameter is as small as about 5 to 10 μm, and the shape becomes spherical when compounded by mechanofusion.

  FIG. 8 shows the pore volume distribution of Ketjen Black (registered trademark) obtained by mercury porosimetry, and FIG. 9 shows the pore volume distribution of the composite material. Mercury porosimetry is a measurement in which surface area, pore distribution, and pore volume can be estimated by injecting and discharging mercury into a sample by pressure. You can see the state of the powder by looking at the mercury injection / discharge route. In the measurement with Ketjen Black (registered trademark) alone, the path of the pore volume change differential value does not coincide with the pore diameter at the time of mercury injection. This is because aggregates in which primary particles are gathered scattered during mercury injection. On the other hand, in the composite material, the path of the pore volume change differential value of the pore diameter of 20 nm or less matches. This means that primary particles of Ketjenblack (registered trademark) or aggregates thereof are present without scattering. That is, it can be seen that the composite particles composited by mechanofusion form a composite fine particle layer in which Ketjen Black (registered trademark) is intruded into sulfur.

However, in the above production method, the sulfur content was able to be 73% or more, but as shown in FIG. 10, a phenomenon was observed in which the discharge capacity was lowered as the sulfur content was increased. This is probably because a sufficient electron / ion conduction path could not be secured due to a decrease in the content of the conductive auxiliary agent.

Therefore, the inventor made it possible to secure a sufficient electron / ion conduction path even with a smaller content of the conductive auxiliary agent by adding the following steps.
That is, mechanofusion of sulfur or sulfur compound particles and conductive fine particles to produce a composite material, a second step of heating the composite material produced in the first step to a temperature higher than the melting point of sulfur or sulfur compound A third step of applying a physical stress by stirring or stretching to the composite material in a heated state, a fourth step of cooling the composite material to room temperature to produce a fibrous intermediate composite material, the fibrous intermediate composite material A fibrous composite material that secures sufficient electron / ion conduction paths by passing through the fifth step of pulverizing the material, and the sixth step of mechanofusion of the pulverized fibrous intermediate composite material and conductive fine particles Can do it. This is schematically shown in FIG.
In the fourth step, since the internal structure of the sulfur or sulfur compound changes in the phase change temperature range near 100 to 120 ° C., in order to suppress this as much as possible, natural air cooling or a cooling medium / heat sink is used. It is preferable to rapidly cool to near room temperature at 50 ° C. to 200 ° C. per minute.

It is thought that a change occurs in the structure of sulfur through the above process. That is, as shown in FIG. 12, the sulfur having the structure of S ₈ is usually polymerized, so that a discharge characteristic with a high operating voltage can be obtained, and a battery having this as a positive electrode can have a high energy density. .
In addition, through the third step, the carbon particles inside the molten sulfur or sulfur compound are mixed at the nano level to form a network structure. As a result, a sufficient ion / electron conduction path is formed inside the composite, so that a discharge with a larger current is possible, and the battery can have a high output density.

  FIG. 13 shows an example of a method for producing a fibrous intermediate composite material. The composite material is heated to 160-165 ° C. When the temperature is maintained at 160 to 165 ° C., the composite material becomes fluid. Stretching is performed by stirring the fibrous intermediate composite material in a fluidized state. The composite material in a fluid state is cooled at room temperature after stretching. Next, the surface of the prepared fibrous composite material and the form of the cut surface were observed with a scanning electron microscope. Further, the obtained fibrous composite material was pulverized, and the particles were observed with a scanning electron microscope.

FIG. 14 shows a scanning electron microscope (SEM) photograph (200 times) of the fibrous intermediate composite material. The obtained fibrous intermediate composite material had a diameter of about 2 μm.
FIG. 15 shows a scanning electron microscope (SEM) photograph (magnified 2000 times) of the fibrous intermediate composite material. A vein-like pattern was visible on the surface.
FIG. 16 shows a scanning electron microscope (SEM) photograph (25000 times) of the fibrous intermediate composite material. A single sulfur mass of about 10 μm was visible. A three-dimensional network structure of carbon derived from Ketjen Black (registered trademark) was confirmed.
Figures 17 and 18 show scanning electron microscope (SEM) photographs (70000 times) of the fibrous intermediate composite material. A three-dimensional network structure of carbon derived from Ketjen Black (registered trademark) was confirmed.
FIG. 19 shows a scanning electron microscope (SEM) photograph (800 times) in the cross-sectional direction of the fibrous intermediate composite material.
FIG. 20 shows a scanning electron microscope (SEM) photograph (magnified 35,000 times) in the cross-sectional direction of the fibrous intermediate composite material. Also in the cross-sectional direction, a single sulfur mass of 2 μm or less and a three-dimensional network structure of carbon derived from Ketjen Black (registered trademark) were confirmed.

FIG. 21 shows a scanning electron microscope (SEM) photograph (18000 times) of particles obtained by pulverizing the fibrous intermediate composite material. Even after pulverization, a single sulfur mass of 2 μm or less and a three-dimensional network structure of carbon derived from Ketjen Black (registered trademark) were confirmed.
As shown in FIG. 22, the fibrous intermediate composite material produced in FIG. 13 was pulverized into particles, and Ketjen Black (registered trademark) was further added to the carbon ratio of the composite material. The fiber intermediate composite material formed into particles by pulverization and Ketjen Black (registered trademark) are added and mixed by a ball mill (manufactured by Lecce), and the resulting composite material is used as a fibrous composite material.

  In addition, it is also possible to increase the operating voltage by using an organic polysulfide compound instead of elemental sulfur. Further, by using microwave irradiation and organic polysulfide in combination, a higher operating voltage can be achieved. The voltage at the time of discharge of the battery using simple sulfur is about 2.0 to 2.3 V. However, in a battery using both microwave irradiation and polysulfidation, discharge can be performed at an operating voltage of 3.3 to 3.6 V.

  Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following embodiment is only a preferred embodiment of the present invention, and the present invention is not limited to the following embodiment.

  In Example 1, positive electrodes C and D composed of a composite material of sulfur and a conductive additive generated by mechanofusion, a step of heating the intermediate composite material to apply physical stress, a step of cooling to room temperature The positive electrode E composed of the fibrous composite material obtained through the pulverizing step and the mechanofusion step with the conductive auxiliary agent was subjected to a discharge capacity comparison test.

1． Materials Used The positive electrode C is composed of 73 wt% sulfur and 27 wt% carbon fine particles, and the positive electrodes D and E are composed of 84 wt% sulfur and 16 wt% carbon fine particles. Commercially available Ketjen Black (registered trademark) was used as the carbon fine particles of the positive electrodes C to E.

2． Manufacture of Positive Electrode Material The positive electrodes C and D are manufactured by introducing sulfur and carbon fine particles into a rotating container as shown in FIG. 23, and applying a strong shearing force, compression and breaking stress between the inner roll and the container wall surface. In addition, it was compounded by mechanochemical reaction. Thus, positive electrode materials C and D in which carbon fine particles were thinly coated and combined on the surface of the sulfur particles were obtained. The diameter of each produced positive electrode material was about 10 μm.

  The positive electrode E is manufactured in the first step of mixing 99.1% by weight of sulfur and 0.9% by weight of Ketjen Black (registered trademark) by mechanofusion, and the composite material produced in the first step is above the melting point of sulfur or a sulfur compound. A second step of heating to 160 to 165 ° C., a third step of applying physical stress by stirring to the heated composite material, a fourth step of rapidly cooling the composite material, and a second step of pulverizing the composite material And a sixth step in which the composite material is mixed by mechanofusion at a ratio of 84.8% by weight of sulfur and 15.2% by weight of Ketjen Black (registered trademark).

3． Identification of Composite Materials C and D and Fibrous Composite Material E Composite materials C and D are obtained by combining Ketjen Black (registered trademark) on the surface of sulfur particles by mechanofusion. A material obtained by pulverizing a fibrous intermediate composite material as shown in -19, and coating the surface with Ketjen Black (registered trademark), a conductive material, by mechanofusion.
Four. Measurement Method Electrode performance evaluation of the positive electrode materials C, D, and E was performed in a coin-type battery cell as shown in FIG. Ethylene in which 1M lithium tetrafluoroborate (manufactured by Kishida Chemical Co., Ltd.) is dissolved as an electrolyte in a lithium metal (manufactured by Honjo Metal Co., Ltd.) and a separator of 150 μm thickness (manufactured by Nippon Kogyo Paper Industries Co., Ltd.) as the negative electrode A mixed solvent of carbonate and 1,2-dimethoxyethane (manufactured by Kishida Chemical Co., Ltd.) (1: 1) was used.

  1,3-dioxolane mixed with a volume ratio of 1: 1, in which lithium tetrafluoroborate was dissolved in 1M, using 10 mg of the above positive electrode materials C, D and E as positive electrode materials, lithium metal having a thickness of 0.3 mm as a negative electrode material, A battery having a diameter of 20 mm was formed by impregnating a separator layer with a nonwoven fabric having a thickness of 150 μm using 0.1 ml of a mixed solvent of 2-dimethoxyethane as an electrolyte. These batteries were discharged in a range of 3 to 0 V at a constant current of 0.7 mA at a room temperature of 20 ° C.

Five. Measurement Results FIG. 25 is a comparison result of discharge capacity per weight. Both the composite material D and the fibrous composite material E were 84% by weight of sulfur, but the fibrous composite material E had a discharge capacity about 1.6 times that of the composite material D.

  FIG. 26 shows a comparison result of discharge capacity per volume. In the same volume, the fibrous composite material E was able to obtain an electric capacity approximately 1.8 times that of the composite material D, and a discharge capacity approximately 1.7 times that of the composite material C.

It is a graph of the theoretical capacity density of the positive electrode material for current lithium ion batteries. It is a schematic diagram of the mixing state of ideal sulfur and a conductive support agent. It is explanatory drawing of the discharge reaction of a lithium / sulfur type battery. It is the photograph which image | photographed Ketjen Black (trademark) with the transmission electron microscope. It is a schematic diagram of the sulfur particle which coat | covered the nano carbon particle on the surface. It is the photograph (1000 times) which image | photographed the composite material of this invention with the scanning electron microscope. It is the photograph (1000 times) which image | photographed the sulfur particle with the scanning electron microscope. It is the pore volume distribution of Ketjen Black (registered trademark) alone. It is pore volume distribution of the composite material of this invention. It is the discharge capacity of the composite material at different sulfur amounts. It is a schematic diagram of the manufacturing process of a fibrous composite material. It is explanatory drawing of the composition change of sulfur in a heating-cooling process. It is an example of the preparation method of a fibrous intermediate composite material. It is the photograph which image | photographed the fibrous intermediate composite material before a grinding | pulverization by 200 time with the scanning electron microscope. It is the photograph which image | photographed 2000 times by the scanning electron microscope about the fibrous intermediate composite material before a grinding | pulverization. It is the photograph which image | photographed 25,000 times with the scanning electron microscope the fibrous intermediate composite material before a grinding | pulverization. It is the photograph which image | photographed the fibrous intermediate composite material before a grinding | pulverization by 70000 times with the scanning electron microscope. It is the photograph which image | photographed the fibrous intermediate composite material before a grinding | pulverization by 70000 times with the scanning electron microscope. It is the photograph which image | photographed 800 times by the scanning electron microscope from the cross-sectional direction the fibrous intermediate substance after a grinding | pulverization. It is the photograph which image | photographed 35,000 times with the scanning electron microscope the fibrous intermediate substance after a grinding | pulverization. It is the photograph which image | photographed 18,000 times with the scanning electron microscope the fibrous intermediate substance after a grinding | pulverization. It is a schematic diagram of the preparation process of a fibrous composite material. It is a schematic diagram of the compounding apparatus for performing a mechanochemical reaction. 1 is a configuration diagram of a comparative measurement battery according to Example 1. FIG. 3 is a comparison result of discharge capacity per weight according to Example 1. FIG. 3 is a comparison result of discharge capacity per volume according to Example 1. FIG.

Claims (8)

Mechano particles of sulfur compounds particle size 75μm or less of sulfur and / or containing more than 70% by weight of sulfur with an S-S bond, and, fine particles of conductive material is carbon particles of from a primary particle diameter of 30 nm 50 nm Starting with a composite material formed by fusion and having a composite fine particle layer in which the fine particles are encroaching on the particles, the composite material is heated to the melting point or higher and stirred or stretched to the heated composite material. Applying physical stress by cooling, cooling to room temperature, pulverizing the obtained fibrous intermediate composite material, and using the fibrous intermediate composite material formed by combining fine particles of conductive material and mechanofusion as the core, Battery positive electrode material comprising a conductive fibrous composite material having a three-dimensional network structure derived from fine particles of a conductive material on the surface .   The composite material, which is a starting material, has a composite fine particle layer formed with sulfur and / or a sulfur compound particle having an S—S bond as a nucleus and a sufficient electron / ion conduction path secured on the surface thereof. 2. The battery positive electrode material according to claim 1, wherein   3. The battery positive electrode material according to claim 1, wherein the three-dimensional network structure derived from the fine particles of the conductive material in the conductive fibrous composite material has a bead-like shape and the fine particles of the conductive material form a network structure. The battery according to claim 1, 2 or 3, wherein the conductive fibrous composite material has a sulfur content of 73% or more and an electric conductivity of 10 ⁰ to 10 ¹ S · cm ^-1 or more. Positive electrode material. Over 70 wt% particle size 75μm or less of sulfur and / or containing a sulfur as a raw material fine particles of conductive material is carbon particles of particles and primary particle size 30nm to 50nm sulfur compound having an S-S bond, Sulfur and / or sulfur compounds formed by mechanofusion of these particles, with the particles as nuclei, and a composite fine particle layer of the particles and fine particles consolidated on the surface in a state where both sufficient electron and ion conduction paths are secured A first step of producing a composite material of conductive materials,
A second step of heating the composite material above its melting point;
A third step of applying physical stress to the composite material in the heated state by stirring or stretching;
A fourth step of cooling the composite material to room temperature;
A fifth step of pulverizing the fibrous intermediate composite material obtained in the fourth step,
The pulverized fibrous intermediate composite material is further mechanofused with the conductive fine particles, and the fibrous intermediate composite material has a three-dimensional network structure derived from the fine particles of the conductive material on the surface of the fibrous intermediate composite material. A method for producing a battery positive electrode material comprising the sixth step of obtaining   6. The method for producing a battery positive electrode material according to claim 5, wherein the fourth step is rapid cooling to near room temperature at 50 ° C. to 200 ° C. per minute by natural air cooling or a cooling medium / heat sink.   7. The method for producing a battery positive electrode material according to claim 5, wherein in the first step, a raw material mixture containing 70% by weight or more of sulfur and / or sulfur compound particles having an S—S bond as sulfur is used. The above carbon fine particles, porosity 60 vol% or more, the production method of claims 5 to 7 or the battery cathode material used having a hollow structure below 80 vol%.