JP2008300188A - Manufacturing method of electrode material, electrode material, and non-aqueous system lithium-ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of reducing as much as possible a residual sulfur content in an electrode material. <P>SOLUTION: When composing an active material such as vanadium oxide in which lithium ion is doped, a lithium compound which does not contain sulfur is used in place of lithium sulfide as a conventional lithium ion source. By using such substance as the lithium ion source, compared with the conventional case of using lithium sulfide, the sulfur residue is reduced and improvement in characteristics such as capacity characteristics can be realized. Other than lithium azide, for example, lithium amide, lithium cyanide, and lithium cyanate etc. may be used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery technology such as a lithium ion secondary battery, and in particular, when a compound containing no sulfur is used as a lithium ion source for the purpose of reducing the residual sulfur content when using vanadium oxide as an active material. It is an effective technology.

  The technology described below has been studied by the present inventors in completing the present invention, and the outline thereof is as follows.

  Conventional non-aqueous lithium ion secondary batteries use lithium cobaltate, lithium manganate, or lithium nickelate as the positive electrode, and the capacity should theoretically exceed 137 mAh / g, 148 mAh / g, 198 mAh / g, and 200 mAh / g. There was no.

  Therefore, the application of vanadium pentoxide materials having a large number of valences and a high capacity potential to batteries has been promoted. However, since such a material does not contain lithium ions, it is necessary to use lithium for the negative electrode, and its use is limited to a primary battery or a secondary battery with a very low current amount.

  Furthermore, when crystalline vanadium pentoxide is used as the positive electrode material, the use of low-valence vanadium to extract high capacity causes the crystal structure to collapse with charge / discharge, so the charge / discharge cycle is repeated. The problem is a decrease in capacity.

  In order to solve this, Patent Document 1 proposes a method of making a crystal structure amorphous with an organic sulfur material or the like. Moreover, in this invention, by inserting an organic sulfur material such as a sulfur-containing conductive polymer between layers of an insulating layered compound such as vanadium pentoxide, the crystal structure of the layered compound is fixed to some extent to suppress phase transformation. It is described that it can. It is stated that the capacity characteristics of the layered compound can be maximized by such a method.

Further, in such a configuration, an insulating (non-conductive) organic sulfur compound that expands the discharge potential range is also inserted between the layers. For example, a situation in which protons of a mercapto group are reduced on the negative electrode to generate hydrogen gas. It is said that high cycle characteristics can be achieved at the same time.
JP 2005-285376 A

  The inventor of the present invention uses a vanadium oxide such as vanadium pentoxide, which is a novel layered crystalline material containing fine crystal grains having a short layer length at a predetermined ratio, as a positive electrode active material, thereby providing a lithium ion secondary material. The inventors have found that the improvement of battery characteristics is remarkably improved and filed an application earlier.

  While a layered crystalline material containing such fine crystal grains in a predetermined ratio is used as an active material to further improve the characteristics of the lithium ion secondary battery, sulfur residue is mixed in the layered crystalline material of the active material. It has been found that the charging / discharging cycle or the capacity is lowered, and further, the cause of the variation in the material characteristics is caused.

  Thus, since the amount of sulfur residue leads to halving the effect of the novel layered crystalline material, the present inventor has determined that the sulfur residue in the layered crystalline material used as such an electrode active material. I thought it was necessary to develop technology to reduce the risk.

  The objective of this invention is providing the technique which can reduce the quantity of the sulfur residue in an electrode material as much as possible.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Incidentally, the present invention is an invention aimed at effectively removing the sulfur residue, taking into account the amount of sulfur residue in the active material to be produced. The details of the entity are not clear.

  That is, whether the sulfur content that lowers the initial capacity and cycle characteristics is a simple sulfur, a sulfur compound, or a compound represented by a molecular formula containing a sulfur atom is under investigation, but honestly The details are still unclear. Therefore, in this specification, the sulfur content that reduces the initial capacity, cycle characteristics, and the like is expressed as “sulfur residue”. However, it is true that the initial capacity, cycle characteristics, and the like are reduced as sulfur is detected in the analysis, and this is clearly confirmed.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows. That is, a sulfur-free compound was used as a lithium ion source added as a raw material for the active material.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  By using a sulfur-free compound as the lithium ion source, it was possible to eliminate any sulfur residue derived from the lithium ion source. Therefore, even when a sulfur-containing compound other than the lithium ion source is used in the production, the amount of sulfur residue in the obtained active material can be sufficiently reduced, and the characteristics of the original active material such as vanadium pentoxide can be reduced. I was able to make full use of it.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention relates to an electrode material and the like. In particular, the present invention relates to an active material that can be used as a positive electrode material used in a non-aqueous lithium ion secondary battery, and is a technique that can reduce a sulfur residue in the production of an active material. Such a sulfur residue could be reduced by using a lithium compound that does not contain sulfur without using the conventionally used lithium sulfide as a lithium ion source.

  For example, it is obtained by dissolving crystalline vanadium pentoxide in an aqueous solution containing a lithium ion source and a conductive organic material, simultaneously performing chemical lithium ion pre-doping and mixing of a conductive material, and drying the solution. Amorphized layered crystalline active material can be produced. When synthesizing the vanadium-type lithium ion secondary battery positive electrode material that has been made amorphous and contains lithium ions, a sulfide is not used as a lithium ion source, and an unnecessary sulfur content filtering step is omitted. In addition, when such an active material is used as an electrode material to form an electrode, higher capacity and higher cycle characteristics can be stably obtained.

  For example, vanadium oxide such as crystalline vanadium pentoxide is dissolved in an alkaline aqueous solution containing lithium ions and a conductive organic material, and chemical lithium doping and a conductive material are mixed simultaneously, and the solution is dried. It solidified while making it amorphous. When synthesizing such amorphized vanadium lithium ion secondary battery positive electrode material containing lithium ions, without using sulfide as a lithium ion source, the amount of sulfur residue as a by-product is suppressed, for example unnecessary. It is supposed that the filtration process of a sulfur content can be omitted. Moreover, in a battery in which such an active material is used as an electrode material for an electrode, higher capacity and higher cycle characteristics can be stably obtained.

  The lithium ion source used in the present invention does not generate a quantifiable amount of sulfur based on the analysis of the produced electrode material when producing the electrode material together with a doped compound that can be doped and dedoped with lithium ion. A compound. That is, the amount of sulfur exceeding the analysis limit is not generated. For example, preferred examples of such a compound include lithium azide. Such lithium azide is water-soluble, and when dissolved in water, nitrogen is easily removed as a gas, so there is no concern that byproducts such as lithium nitride based on nitrogen are formed.

  By using lithium azide as the lithium ion source as described above, the amount of sulfur residue in the active material can be considerably reduced. Moreover, if the use of the sulfur-containing organic substance that has been used together with the conventional lithium ion source can be reduced, the sulfur residue in the active material can be further reduced.

  As also shown in the examples described later, the capacity characteristics are sufficient even when the residual sulfur content is 0 without using any sulfur-containing organic material other than the lithium ion source used in the production of the active material. It has been confirmed that the correct value can be obtained.

  As the non-sulfur-containing lithium ion source, in addition to lithium azide, for example, lithium amide, lithium cyanide, lithium cyanate and the like can be used. Such a substance is a substance that exhibits alkalinity by hydrolysis when converted into an aqueous solution. In the case where such a material uses a doped compound that can be doped with lithium ions and a lithium compound that becomes a lithium ion source as raw materials, the chemical formula representing the lithium compound does not contain a sulfur atom.

  As an active material used together with such a non-sulfur-containing lithium compound such as lithium azide, a compound to be doped capable of doping and dedoping lithium ions can be used, and the following can be mentioned. For example, as an active material of a compound to be doped that can be used as a positive electrode material of a non-aqueous lithium ion secondary battery, at least one metal element selected from Group V elements and Group VI elements in the periodic table is widely used. The thing containing an oxide is mentioned. Examples of the metal oxide include vanadium oxide (vanadium oxide) and niobium oxide. In particular, vanadium pentoxide is preferable. The lithium ion-doped compound to be doped does not contain a sulfur atom in its chemical formula.

Further, even in such vanadium oxide, for example, vanadium pentoxide (V ₂ O ₅ ) forms a single layer by spreading a pentahedral unit having VO ₅ as one unit in a two-dimensional direction by a covalent bond. . By laminating these layers, a layered structure is formed as a whole.

  Such a layered crystalline material of vanadium pentoxide is made macroscopically amorphous while maintaining a layered crystal structure, so that the layer length of the layered crystalline material is shortened (miniaturized). For example, a layered crystal state having a long layer length is divided and a layered crystal state having a short layer length appears.

  Such a state is a structure that cannot be realized if all are in an amorphous state, and by stopping the progress of amorphization halfway, the above state, that is, a layered crystal state with a short layer length can exist. .

  Here, macroscopic amorphization means that the state of the layered crystalline substance is only a crystal structure having a layer length of 30 nm or less, or such a crystal structure, from a microscopic viewpoint that enables observation on the order of nm or less. A coexisting state with an amorphous structure is confirmed, but when viewed from a macro perspective where only a micrometer order larger than nm can be observed, an amorphous structure with randomly arranged crystal structures can be obtained. It shall mean the observed state.

  More specifically, as schematically shown in FIG. 1, the layer length L1 of the so-called short-period structure fine crystal grains having a short layer length does not include 0, but preferably falls within the range of 1 nm or more and 30 nm or less. It only has to be.

  In the layered crystal state, when the layered crystal is less than 1 nm from the viewpoint of entering and exiting lithium ions between layers, it is difficult to dope and dedope lithium ions, and it is difficult to take out a high capacity. On the other hand, if it exceeds 30 nm, the crystal structure collapses due to charge / discharge, resulting in poor cycle characteristics. Therefore, the layer length may be 30 nm or less not including 0, preferably 1 nm or more and 30 nm or less, more preferably 5 nm or more and 25 nm or less. In this way, the path related to the entry / exit of lithium ions between layers is shortened to facilitate the entry / exit of lithium ions between vanadium oxide layers, and the discharge capacity, cycle characteristics, etc. are improved. is there. As shown in FIG. 2, when the layer length L2 of the so-called long-period structure with a long layer length is long, it is difficult for lithium ions to enter and exit between the layers as compared with the case of the short-period structure with a short layer length L1. .

  Note that the layered crystal structure of 30 nm or less in which the fine crystal grains of vanadium oxide do not contain 0 may occupy an area ratio of 30% or more in the cross section of the vanadium oxide. When the area ratio is 100%, the amorphous state does not already exist, and only the layered crystal state is obtained. Of course, the layered crystal of 30 nm or less not containing 0 may have an area ratio of 100%.

  Moreover, lithium ions are doped in metal oxides such as vanadium pentoxide having the above layered crystal structure. Lithium ions are preferably doped at a molar ratio of 0.1 to 10 with respect to the metal oxide, more preferably 0.1 to 6. If the doping amount of lithium ions is less than 0.1 in terms of molar ratio, the doping effect is not sufficiently exerted, and if the doping amount of lithium ions exceeds 10, the metal oxide may be reduced to metal. Therefore, it is not preferable.

  In the present invention, dope means occlusion, support, adsorption or insertion, and means a phenomenon in which lithium ions enter an electrode active material such as a positive electrode.

  In the present invention, as described above, a non-sulfur-containing lithium compound is used for the lithium ion source. In addition, in the production of the active material, a sulfur-containing conductive polymer may be included as a sulfur-containing organic substance. Absent. Such a sulfur-containing conductive polymer has redox activity and contains sulfur. For example, if 3,4-ethylenedioxythiophene having the structural formula shown in FIG. 3 is used as a raw material as a monomer, a polythiophene compound of a sulfur-containing conductive polymer as poly (3,4-ethylenedioxythiophene) is synthesized. Good.

  Although details are unknown, when a monomer corresponding to the sulfur-containing conductive polymer is present in the reaction system, this monomer acts as an oxygen inhibitor, and the oxygen concentration of the reaction system is kept constant, and the resulting lithium ion-doped amorphous metal oxidation It is thought to control the structure of things. However, since the sulfur-containing conductive polymer at the end of the reaction lowers the performance as an active material, the performance of the active material is improved by removing the final product by vacuum concentration or the like.

  In the active material of the positive electrode material for a non-aqueous lithium ion secondary battery to which the manufacturing technology of the present invention is applied, the X-ray diffraction pattern of the metal oxide contained is in the range where the metal oxide has a diffraction angle 2θ = 5 to 15 °. Has a peak.

  The active material thus obtained is mixed with a binder such as polyvinylidene fluoride (PDVF), preferably with conductive particles, to form a positive electrode material, which is coated on a conductive substrate to produce a positive electrode. be able to. The layer of the positive electrode material for non-aqueous lithium ion secondary batteries is preferably formed to a thickness of, for example, 10 to 100 μm.

  The conductive particles include conductive carbon (conductive carbon such as ketjen black), copper, iron, silver, nickel, palladium, gold, platinum, indium, tungsten and other metals, indium oxide, tin oxide. Conductive metal oxides such as can be used. Such conductive particles may be contained at a ratio of 1 to 30% of the weight of the metal oxide.

  Furthermore, a conductive substrate that exhibits conductivity at least on the surface in contact with the positive electrode material is used as the base (current collector) that supports the positive electrode material layer. Such a substrate can be formed of a conductive material such as metal, conductive metal oxide, or conductive carbon. In particular, it is preferable to form with copper, gold | metal | money, aluminum, those alloys, or conductive carbon. Alternatively, the base may have a configuration in which a base body formed of a non-conductive material is covered with a conductive material.

  An active material that can be used as a positive electrode material for such a non-aqueous lithium ion secondary battery can be manufactured through the following manufacturing process. That is, first, an active material for a positive electrode material of a non-aqueous lithium ion secondary battery, a metal oxide such as vanadium pentoxide, a non-sulfur-containing lithium compound as a lithium ion source, and, if necessary, a sulfur-containing organic substance Is mixed with water and heated to reflux for a predetermined time for synthesis.

  The active material suspension for the positive electrode material thus synthesized is concentrated by a method such as concentration under reduced pressure, and further dried under vacuum to solidify. The drying temperature may be 30 ° C. or more and less than 250 ° C. If it is less than 30 degreeC, it cannot be dried substantially. Further, at 250 ° C. or higher, the crystal structure changes, and the layered crystal state having a short layer length cannot be obtained. After solidification, the powder is pulverized to a predetermined particle size by a ball mill or the like, sieved, and classified to produce an active material powder as a positive electrode material.

  By forming a positive electrode using such an active material, a non-aqueous lithium ion secondary battery can be configured. The non-aqueous lithium ion secondary battery includes the positive electrode, the negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode.

  In the non-aqueous lithium ion secondary battery having such a configuration, the negative electrode can be formed of a commonly used lithium material. Such lithium-based materials include lithium-based metal materials such as metallic lithium and lithium alloys (for example, Li-Al alloys), intermetallic compound materials of metals such as tin and silicon and lithium metals, and lithium such as lithium nitride. Examples thereof include carbon materials that can be doped or dedoped with a compound or lithium ion.

As electrolytes, lithium salts such as CF ₃ SO ₃ Li, C ₄ F ₉ SO ₈ Li, (CF ₃ SO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, LiBF ₄ , LiPF ₆ , LiClO _4, etc. Can be used. The solvent that dissolves the electrolyte is a non-aqueous solvent.

  Examples of non-aqueous solvents include chain carbonates, cyclic carbonates, cyclic esters, nitrile compounds, acid anhydrides, amide compounds, phosphate compounds, amine compounds, and the like. Furthermore, specific examples of the non-aqueous solvent include ethylene carbonate, diethyl carbonate (DEC), propylene carbonate, dimethoxyethane, γ-butyrolactone, n-methylpyrrolidinone, N, N′-dimethylacetamide, acetonitrile, or propylene carbonate. A mixture of dimethoxyethane, a mixture of sulfolane and tetrahydrofuran, and the like. The molar concentration in the electrolytic solution is preferably at least 0.1 mol / l or more, and more preferably in the range of 0.5 to 1.5 mol / l, in order to reduce the internal resistance due to the electrolytic solution.

  The electrolyte layer interposed between the positive electrode and the negative electrode may be a solution of the electrolyte in a non-aqueous solvent or a polymer gel (polymer gel electrolyte) containing the electrolyte solution.

  An example of such a lithium ion secondary battery is a configuration as shown in FIG. That is, in the non-aqueous lithium ion secondary battery 10, the positive electrode 11 and the negative electrode 12 are opposed to each other through the electrolyte layer 13. The positive electrode 11 includes a positive electrode active material 11a having a predetermined amount of a layered crystal structure and a base 11b that functions as a current collector. As shown in FIG. 4, a layer of the positive electrode active material 11a is provided on the surface of the base 11b.

  Similarly, the negative electrode 12 includes a negative electrode active material 12a and a base 12b as a current collector, and a layer of the negative electrode active material 12a is provided on the surface of the base 12b. The positive electrode 11 and the negative electrode 12 are opposed to each other with the electrolyte layer 13 interposed therebetween.

  Hereinafter, based on an Example, this invention is demonstrated in detail. In the following examples, the case where vanadium oxide doped with lithium ions is used as an active material will be described as an example, but the present invention is not limited to the following examples, and the gist of the present invention is described. It goes without saying that it can be used as appropriate for other active materials, other batteries, and the like, as long as it does not fall out.

Example 1
In this example, 2.0 g of vanadium pentoxide (V ₂ O ₅ ), 0.13 g of lithium azide of a third with respect to such vanadium pentoxide, and 0.6 mol of 3,4 of with respect to vanadium pentoxide. -1.0 g of ethylenedioxythiophene (see Fig. 3) was suspended in 50 ml of water and heated under reflux with stirring for 24 hours. The suspended solution was concentrated under reduced pressure at 75 ° C. and a pressure of 21.3 kPa to obtain a black solid. Then, this solid was vacuum-dried at 100 degreeC.

  As a result of X-ray diffraction of this solid, as shown in FIG. 5, a peak was observed in the vicinity of 2θ = 10 °, and it was confirmed that the solid was amorphized. It was also confirmed by the ICP analysis that lithium ions were incorporated into the amorphized product. Further, as shown in FIG. 6, the sulfur amount based on the sulfur residue in the active material is obtained by using a fully automatic elemental analyzer (VarioELIII: manufactured by elementar) to convert the active material into a helium atmosphere to which oxygen is added. After oxidizing and burning in a catalyst tube and separating it as sulfur dioxide gas with an adsorption tube, it was desorbed and quantified with a detector. From the quantitative result by this method, it was found that 0.08% by weight was contained.

  The active material obtained as described above, when observed with a transmission electron microscope, confirmed that fine crystal grains having a layer length of 5 nm or more and 25 nm or less were obtained in an area ratio of 99%. . The positive electrode material powder made of such an active material was pulverized and subsequently classified by sieving.

  The vanadium oxide of the active material thus produced was mixed with 20 wt% of conductive carbon black and 10 wt% of polyvinylidene fluoride (PVDF), and made into a slurry using N-methylpyrrolidone (NMP) as a solvent. The slurry was coated on an Al foil by a doctor blade method to produce a positive electrode.

  Using this positive electrode, a secondary battery was assembled using 1M LiBF4 / EC: DEC = 1: 3 mixed solvent as the electrolyte and metallic lithium as the negative electrode. Charging was performed with a constant current-constant voltage (CC-CV) charging method of 4.2 V at 0.1 C charging, and discharging was performed with a constant current (CC) method of 1.5 V cutting at 0.1 C. FIG. 6 shows the results of the discharge capacity per active material and the capacity retention rate after 10 cycles.

(Example 2)
In this example, except that 3,4-ethylenedioxythiophene, which is a sulfur-containing organic substance, is not used, a non-sulfur-containing lithium compound is used as a lithium ion source in the same manner as in Example 1 above. Manufactured. That is, 2.0 g of vanadium pentoxide (V ₂ O ₅ ) and 0.13 g of lithium azide (Li ₃ N) in one-third molar amount with respect to the vanadium pentoxide are suspended in 50 ml of water and applied. The suspension solution was heated to reflux with stirring for 24 hours, and then vacuum dried in the same manner as in Example 1 to synthesize an active material. The layered crystal structure of the synthesized active material was the same as in Example 1.

  The amount of sulfur based on the sulfur residue in the active material was measured by elemental analysis, and it was confirmed that it was not contained as shown in FIG. The positive electrode material powder made of such an active material was pulverized and subsequently classified by sieving.

  The vanadium oxide of the active material was mixed with 20% by weight of conductive carbon black and 10% by weight of polyvinylidene fluoride (PVDF), and slurried using N-methylpyrrolidone (NMP) as a solvent. The slurry was coated on an Al foil by a doctor blade method to produce a positive electrode. Using such a positive electrode, a secondary battery was assembled using 1M LiBF4 / EC: DEC = 1: 3 mixed solvent as an electrolytic solution and metallic lithium as a negative electrode, and subjected to charge / discharge evaluation by 0.1 C discharge. The results are shown in FIG.

(Comparative Example 1)
In this comparative example, unlike Examples 1 and 2, lithium sulfide was used for the lithium ion source without using lithium azide. Moreover, the sulfur residue of the active material was adjusted by the concentration at the time of vacuum concentration.

That is, vanadium pentoxide (V ₂ O ₅ ), 0.3 g of lithium sulfide (Li ₂ S) in a half molar amount with respect to vanadium pentoxide, and 0.6 mol of 3,4-ethylenedioxy with respect to vanadium pentoxide. Thiophene was suspended in 50 ml of water and stirred with heating for 24 hours. The solution was filtered to remove the generated sulfur residue, and the filtrate was concentrated under reduced pressure at 9.33 kPa and 75 ° C. to obtain a black solid.

  This product was then treated in the same manner as in Example 1 to obtain an active material having a layered crystal structure similar to that in Example 1. As a result of elemental analysis, as shown in FIG. 6, it was confirmed that the sulfur content was 0.15 wt%. Furthermore, the positive electrode material powder made of such an active material was pulverized and subsequently classified by sieving to produce a positive electrode in the same manner as in Example 1 and subjected to charge / discharge evaluation. The result is shown in FIG.

(Comparative Example 2)
In this comparative example, an active material was produced by processing in the same manner as in comparative example 1. However, only the pressure during vacuum concentration was changed. That is, vanadium pentoxide (V ₂ O ₅ ), a half molar amount of lithium sulfide (Li ₂ S) 0.3 g, and 0.6 mol of 3,4-ethylenedioxythiophene (EDOT: FIG. 1) with respect to vanadium pentoxide. The mixture was suspended in 50 ml of water, heated and stirred for 24 hours, the solution was filtered, and the generated sulfur residue was removed.

  The filtrate was concentrated under reduced pressure at 21.3 kPa and 75 ° C. to obtain a black solid. As a result of elemental analysis, as shown in FIG. 6, it was confirmed that 1.6 wt% sulfur was contained. Thereafter, an active material was prepared in the same manner as in Example 1, a positive electrode was prepared using the active material, and was subjected to charge / discharge evaluation. The result is shown in FIG.

(Comparative Example 3)
In this comparative example, an active material was produced by processing in the same manner as in comparative example 1. However, the pressure during vacuum concentration was 24.00 kPa. As a result of elemental analysis, it was confirmed that sulfur contained 1.9 wt%. Others produced a positive electrode in the same manner as in Example 1 using the active material, and were subjected to a charge / discharge test. The result is shown in FIG.

  As shown in FIG. 6, from Examples 1 and 2 and Comparative Examples 1 to 3, the case where lithium azide was used as the lithium ion source was clearly more than the case where lithium sulfide was used as the lithium ion source. It can be seen that the sulfur residue can be reduced. In addition, when the sulfur residue is small, the amount of sulfur based on the sulfur residue is naturally reduced, and the initial capacity of the battery configured using the active material having a small amount of sulfur residue is 10th cycle capacity maintenance rate. It can confirm that it has improved.

  Furthermore, from the comparison of Examples 1 and 2, when lithium azide is used as the lithium ion source, it is the initial state when the battery is configured not to mix other sulfur-containing organic substances such as 3,4-ethylenedioxythiophene. It can also be confirmed that the capacity retention rate at the 10th cycle is improved.

  From the comparison of Examples 1 and 2, the initial capacity and cycle capacity maintenance rate are suppressed by mixing the sulfur-containing organic material such as 3,4-ethylenedioxythiophene to suppress the structure of the lithium ion-doped amorphous metal oxide. The effect of improving the initial capacity and cycle capacity retention rate is not greater than the effect of increasing the initial capacity and cycle capacity retention rate by suppressing the amount of sulfur residue and preventing the decrease in the initial capacity and cycle capacity retention rate. I think. The assertive opinion on this point requires further experimentation, but at least it can be interpreted as such.

  Further, as shown in Example 2, when a non-sulfur-containing lithium compound such as lithium azide is used for the lithium ion source and no other sulfur-containing organic substance is used, the remaining sulfur is removed in the middle. For this reason, there is an advantage that the filtration process is basically not required, the labor of the process can be saved, and the production cost can be reduced.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  In the above-described embodiments and examples, vanadium pentoxide in a layered crystal state mainly when the layer length is 30 nm or less has been described. Of course, the present invention is also applicable to a layered crystal material having a layer length of more than 30 nm. It goes without saying that we can do it.

  INDUSTRIAL APPLICABILITY The present invention can be effectively used in a field where a lithium compound containing no sulfur is used as a lithium ion source in a battery such as a lithium ion secondary battery.

It is explanatory drawing which showed typically the layered crystal structure with a short layer length. It is explanatory drawing which showed typically the layered crystal structure with a long layer length. It is explanatory drawing which shows the structural formula of an example of a sulfur containing organic substance. 1 is a diagram showing a schematic configuration of a non-aqueous lithium ion secondary battery to which the present invention can be applied. It is explanatory drawing which shows the result of the X-ray crystal diffraction of positive electrode material. It is explanatory drawing which shows the effect of this invention in a table form.

Explanation of symbols

10 Nonaqueous Lithium Ion Secondary Battery 11 Positive Electrode 11a Positive Electrode Active Material 11b Base (Current Collector)
12 Negative electrode 12a Negative electrode active material 12b Substrate (current collector)
13 Electrolyte layer
L1 layer length
L2 layer length

Claims (11)

A method for producing an electrode material using as a raw material a compound to be doped and dedoped with lithium ions and a lithium compound as a lithium ion source,
The chemical formula showing the said to-be-doped compound and the chemical formula showing the said lithium compound do not contain a sulfur atom, The manufacturing method of the electrode material characterized by the above-mentioned. In the manufacturing method of the electrode material of Claim 1,
The method for producing an electrode material, wherein the lithium compound is at least one compound selected from the group consisting of lithium azide, lithium amide, lithium cyanide, and lithium cyanate. In the manufacturing method of the electrode material of Claim 1 or 2,
The method for producing an electrode material, wherein the doped compound is an oxide of at least one metal element selected from Group V elements and Group VI elements of the Periodic Table. In the manufacturing method of the electrode material of Claim 3,
The method of manufacturing an electrode material, wherein the metal oxide is a layered crystal substance capable of doping and dedoping lithium ions between layers. In the manufacturing method of the electrode material of Claim 4,
The method for producing an electrode material, wherein the layered crystal substance capable of doping and dedoping lithium ions between the layers is vanadium oxide. In the manufacturing method of the electrode material of Claim 7,
The method for producing an electrode material, wherein the vanadium oxide is vanadium pentoxide. In the manufacturing method of the electrode material of any one of Claims 1-6,
In addition to the compound to be doped and the lithium compound, a sulfur-containing organic material is used for the production of the electrode material. An electrode material using a doped compound that can be doped and dedoped with lithium ions and a lithium compound that is a lithium ion source as raw materials,
The electrode material according to claim 1, wherein a sulfur concentration of the electrode material is 0.1% by weight or less including 0. The electrode material according to claim 8,
The electrode material is a vanadium oxide doped with lithium ions. The electrode material according to claim 9,
The vanadium oxide is a layered crystalline material having a layer length of 1 nm or more and 30 nm or less. A positive electrode having a doped compound doped with lithium ions is a non-aqueous lithium ion secondary battery facing a negative electrode via a non-aqueous electrolyte,
It has the said positive electrode using the electrode material manufactured by the manufacturing method of the electrode material of any one of Claims 1-7, or the electrode material of any one of Claims 8-11. A non-aqueous lithium ion secondary battery.

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