JP2006032321A - Active material, its manufacturing method, and nonaqueous electrolyte secondary battery containing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having high capacity by tremendously decreasing the adding amount of conductive auxiliaries by lowering the resistivity of an active material. <P>SOLUTION: Material represented by composition formula: Li<SB>x</SB>MeO<SB>y</SB>N<SB>z</SB>(wherein, 0≤x≤2; 0.1<y<2.2; 0<z<1.4; Me represents at least one element out of Ti, Co, Ni, Mn, Si, Ge, and Sn.) is used as the active material. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an active material used for a nonaqueous electrolyte secondary battery and a method for producing the same.

A lithium ion battery used as a main power source for mobile communication devices and portable electronic devices has a feature of high electromotive force and high energy density.
Examples of the positive electrode active material used in this lithium ion battery include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), manganese spinel (LiMn ₂ O ₄ ), and mixtures thereof. These positive electrode active materials have a voltage of 4 V or more with respect to lithium. A carbon material is generally used for the negative electrode, and a 4V class lithium ion battery is formed by combining with the above-described positive electrode.

Various techniques using titanium oxide as a negative electrode active material have also been reported.
For example, Patent Document 1 discloses a battery using titanium oxide as a negative electrode and spinel manganese oxide or LiCoO ₂ as a positive electrode. Patent Document 2 discloses a lithium-titanium oxide having a spinel structure. A non-aqueous electrolyte comprising a negative electrode using (Li _4/3 Ti _5/3 O ₄ ) as an active material, a positive electrode using Li ₂ MnO ₃ or LiMnO ₂ as an active material, and a non-aqueous electrolyte. A secondary battery is disclosed.
Patent Document 3 discloses a lithium secondary battery using Li ₂ Ti ₃ O ₇ as a negative electrode, and Patent Document 4 discloses a method of manufacturing a negative electrode using a preferable titanium oxide. Yes.

Unlike graphite used in the negative electrode, titanium oxide useful as an active material disclosed in Patent Documents 1 to 4 has low electronic conductivity. Further, even LiCoO ₂ having relatively good conductivity has a resistivity of about 1 × 10 ⁴ Ωcm.
Therefore, when the above titanium oxide is used in a battery, it is common to use a highly conductive material such as acetylene black or graphite as a conductive assistant.

On the other hand, Patent Document 5 discloses that a compound containing at least one of silicon, germanium, and tin, oxygen, and nitrogen is used as an active material for the negative electrode. This active material has a general formula: M _x N _y O _z (wherein M is at least one element of Si, Ge and Sn, and x, y and z are 1.4 <x <2.1, 1.. 4 <y <2.1, 0.9 <z <1.6.)
An object of the invention according to Patent Document 5 is to provide a high-capacity negative electrode active material. In the active material described in Patent Document 5, a pseudo-plane composed of a chair-type six-membered ring made of silicon and nitrogen spreads in a matrix, and a silicon-oxygen-silicon bond is bridged between the planes (interlayers). Exist to form a one-dimensional tunnel-like portion. This tunnel-like portion becomes a lithium doping / undoping site, and the obtained negative electrode material exhibits a large capacity.

Therefore, the negative electrode active material shown in the example of Patent Document 5 has a crystal structure as a matrix made of Si ₂ N ₂ O, Ge ₂ N ₂ O, or Sn ₂ N ₂ O, which is an oxygen nitride containing N is important. However, Patent Document 5 does not disclose or suggest the electronic conductivity of the negative electrode active material, and in the examples, a carbon material is simply mixed as a conductive additive.
Patent Document 6 discloses that Si _x N _y is obtained by baking SiO _x in a nitrogen stream.
Japanese Patent Laid-Open No. 06-275263 Japanese Patent Application Laid-Open No. 07-320784 Japanese Patent Laid-Open No. 11-283624 JP 2000-302547 A JP-A-11-102705 JP 2002-356314 A

As described above, when an oxide such as titanium oxide is used as an active material for a negative electrode, since the oxide has low electronic conductivity, a highly conductive material such as acetylene black or graphite is used in combination as a conductive aid. There is a need to. However, since these conductive assistants are not power generation elements, they cause a significant reduction in the capacity per unit volume of the battery.
Further, for example, TiO ₂ which is a titanium oxide is an insulating material having a resistivity of about 1 × 10 ¹⁴ Ωcm. When using a material with poor electron conductivity as an active material in this way, it is not sufficient to simply mix a conductive additive, increasing the specific surface area of the active material particles, or using a graphite material for the surface. It is necessary to devise such as coating. However, refinement by pulverization leads to a decrease in filling amount and a further decrease in capacity. Moreover, it leads to the cost increase of a manufacturing process.
In view of the above, an object of the present invention is to solve the above problems, to provide an active material that is mainly composed of oxides but has high conductivity, and to provide a high capacity non-aqueous electrolyte secondary battery.

In order to solve the above problems, the present invention proposes to use a nitrogen oxide having a resistivity of less than 1 × 10 ⁴ Ωcm as an active material.
The nitrogen oxide is preferably amorphous and has a composition formula: Li _x MeO _y N _z (where 0 ≦ x ≦ 2, 0.1 <y <2.2, 0 <z <1.4, Me is preferably represented by at least one selected from the group consisting of Ti, Co, Ni, Mn, Si, Ge, and Sn.

In the active material according to the present invention, an oxide having a resistivity of 1 × 10 ⁴ Ωcm or more is heated in a reducing atmosphere, and the heated oxide is reacted with ammonia gas to obtain a composition formula: Li _x MeO _y N _z (where 0 ≦ x ≦ 2, 0.1 <y <2.2, 0 <z <1.4, Me is from the group consisting of Ti, Co, Ni, Mn, Si, Ge and Sn) It can be produced by obtaining a nitrogen oxide having a resistivity of less than 1 × 10 ⁴ Ωcm, represented by at least one selected.

The gas constituting the reducing atmosphere may be at least one selected from the group consisting of argon, nitrogen, carbon monoxide and hydrogen, and the heating temperature may be 500 ° C to 1500 ° C.
In addition, after the reaction with the ammonia gas, the nitrogen oxide is preferably heated at a temperature of 400 ° C. or lower in a reducing atmosphere.

  ADVANTAGE OF THE INVENTION According to this invention, the addition amount of a conductive support agent can be drastically reduced by reducing the resistivity of an active material, and a high capacity nonaqueous electrolyte secondary battery can be provided.

(1) Synthesis of active material according to the present invention The active material according to the present invention comprises a nitrogen oxide having a resistivity of less than 1 × 10 ⁴ Ωcm, preferably 1 × 10 ³ Ωcm or less, and has a resistivity of 1 × 10. An oxide of ⁴ Ωcm or more is heated in a reducing atmosphere, the heated oxide is reacted with ammonia gas, and a composition formula: Li _x MeO _y N _z (where 0 ≦ x ≦ 2, 0. 1 <y <2.2, 0 <z <1.4, Me is at least one selected from the group consisting of Ti, Co, Ni, Mn, Si, Ge, and Sn) Can be synthesized.
Among these, the nitrogen oxide is preferably amorphous. If it is amorphous, the cycle life can be further improved, which is effective.

In the present invention, oxides such as metal oxides, transition metal oxides, lithium-containing metal oxides, and lithium-containing transition metal oxides (for example, TiO ₂ , LiNi _1/3 Mn _1/3 Co _1/3 , which are raw materials) O ₂ , LiCoO ₂ , LiNi _5/6 Co _1/6 O ₂ , LiMn ₂ O ₄ , LiVO ₂ , MnO ₂ , V ₂ O ₅ , SnO, SiO _y (y is preferably 1.0 to 1.5) Etc.) is heated in a reducing atmosphere such as ammonia gas or hydrogen gas at a temperature of 500 ° C. or higher and 1500 ° C. or lower to obtain a conductive material (the above nitrogen oxide).
In order to obtain an amorphous nitrogen oxide, it is preferable to use an amorphous oxide as a raw material.

If the temperature is less than 500 ° C., the reaction time is long. On the other hand, if the temperature exceeds 1500 ° C., the temperature becomes higher than necessary, and the cost increases in any case. In view of cost and the amount of nitrogen to be introduced, the temperature is preferably 500 to 1100 ° C.
Further, in order to obtain an amorphous nitrogen oxide easily and reliably, the temperature is preferably 500 to 900 ° C.

However, when the obtained conductive material is sintered by the above-described heating, it may be difficult to use the sintered body as an active material as it is for a secondary battery.
In this case, for example, if the sintered body is mechanically pulverized and dried in the presence of a solvent or the like, it can be easily used as an active material.
Alternatively, the raw material oxide may be reacted with ammonia gas after being converted into a low-order oxide in a hydrogen gas atmosphere.

  Furthermore, it is preferable to perform a post-process in which the nitrogen oxide obtained in the above process is heat-treated at a temperature of 400 ° C. or lower in a reducing atmosphere. The reducing atmosphere may be nitrogen gas. Further, for example, heat treatment is performed at 400 ° C. or lower in the presence of an organic reducing agent such as methanol or butanol, or in an atmosphere such as ammonia gas, and nitrogen derived from excess oxygen and ammonia gas on the particle surface. And adsorption species such as ammonia can be removed. Thereby, the resistivity of the obtained powdery active material falls. In this case, as the organic reducing agent, in addition to alcohols, ketones, esters, amines and the like may be used.

By introducing nitrogen atoms from the surface of the oxide, which is a raw material, by the above-described method, the oxygen arrangement on the surface of the oxide is changed, and the resistivity is increased by generating carriers involved in conduction. It is thought that it can be reduced.
As for the composition, various kinds of oxides and reaction conditions as raw materials to be used were analyzed, and the ratio of Me, O, and N was analyzed. As a result, in the above composition formula, 0.1 <y <2.2, 0 It was found that <z <1.4 was satisfied. Further, regarding Li, depending on the type and composition of raw materials, it is considered appropriate to satisfy 0 ≦ x ≦ 2 from the conventionally known LiMeO ₂ and Li ₂ MeO ₂ .

(2) Measurement of resistivity The resistivity referred to in the present invention is measured by the following method. That is, the raw material or the nitrogen oxide powder produced by the above method is quantitatively filled into a conductivity measurement mold. Then, pressure is applied to the filled powder, the strength is gradually increased, and the change in resistivity of the powder with pressure is measured. At this time, the resistivity of the powder decreases as the pressure increases, but the degree of decrease gradually decreases and approaches a certain value. This constant value is defined as the resistivity.

(3) Electrochemical measurement When measuring the electrochemical characteristics of the active material according to the present invention as a model, a cell for measuring electrochemical characteristics is prepared as follows.
First, 80 parts by weight of an active material, 10 parts by weight of acetylene black as a conductive additive, and 10 parts by weight of PVdF (polyvinylidene fluoride) as a binder are mixed to obtain a mixture. It is diluted with (N-methyl-2-pyrrolidone) and coated on an aluminum foil current collector. This is dried in vacuum at 60 ° C. for 30 minutes, then cut into 15 mm × 20 mm, and further dried in vacuum at 150 ° C. for 14 hours. The thickness of the obtained electrode is made between 120 μm and 190 μm.

As the counter electrode, for example, a material obtained by pressure bonding a lithium metal sheet on a stainless steel plate is used. As the separator, for example, using a polyethylene porous film, as the electrolyte solution, for example, EC (ethylene carbonate) and DMC (dimethyl carbonate) 3: 7 mixed solvent of a volume ratio of the LiPF ₆ of 1.0M Use the dissolved one. In the charge / discharge test, charge / discharge is repeated between predetermined voltage regions at a current density of 0.17 mA / cm ² , for example.

(4) Other members Here, as the separator, a polyolefin microporous film or a nonwoven fabric can be used. Polyester may be used. Generally, aluminum or aluminum alloy foil is used for the current collector for the positive electrode, and copper foil is used for the current collector for the negative electrode. The current collector in the present invention is selected according to the charge / discharge potential of each active material. For example, when the active material of the present invention made of, for example, a nitrogen atom-containing titanium oxide is used for the negative electrode, a thin film of aluminum or an aluminum alloy should be used as a current collector because it has a potential higher than the lithium occlusion potential of aluminum. Is possible.

FIG. 2 shows a schematic longitudinal sectional view of an example of a cylindrical battery obtained using the active material according to the present invention.
In FIG. 2, an electrode plate group 4 in which a positive electrode plate and a negative electrode plate are wound in a spiral shape through a separator is housed in a battery case 1. Then, the positive electrode lead 5 is drawn from the positive electrode plate and connected to the sealing plate 2, and the negative electrode lead 6 is drawn from the negative electrode plate and connected to the bottom of the battery case 1. For the battery case and the lead plate, a metal or an alloy having an organic electrolyte resistance and an electron conductivity can be used.
For example, a metal such as iron, nickel, titanium, chromium, molybdenum, copper, aluminum, or an alloy thereof. In particular, the battery case is most preferably a stainless steel plate or an Al—Mn alloy plate processed, the positive electrode lead is aluminum, and the negative electrode lead is most preferably nickel. In addition, various engineering plastics and a combination of these and a metal can be used for the battery case in order to reduce the weight.

Insulating rings 7 are respectively provided on the upper and lower portions of the electrode plate group 4. And electrolyte solution is inject | poured and a battery case is sealed using a sealing board. At this time, a safety valve can be provided on the sealing plate. In addition to the safety valve, various conventionally known safety elements may be provided.
For example, a fuse, bimetal, PTC element, or the like is used as the overcurrent prevention element. Moreover, as a countermeasure against the increase in the internal pressure of the battery case, a method of cutting the battery case, a gasket cracking method, a sealing plate cracking method, or a cutting method with a lead plate can be used. Further, the charger may be provided with a protection circuit incorporating measures against overcharge and overdischarge, or may be connected independently.

In addition, as a measure against overcharging, a method of cutting off current by increasing the battery internal pressure can be provided. At this time, a compound for increasing the internal pressure can be contained in the mixture or the electrolyte. Examples of the compound raising the internal pressure and carbonates such as _{Li 2 CO 3, LiHCO 3,} Na 2 CO 3, NaHCO 3, CaCO 3 and MgCO ₃ and the like.
As a welding method for the cap, the battery case, the sheet, and the lead plate, a known method (such as direct current or alternating current electric welding, laser welding, or ultrasonic welding) can be used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.

Although these elements can be combined to form the nonaqueous electrolyte secondary battery of the present invention, conventionally known materials are used as other materials used for producing the nonaqueous electrolyte secondary battery according to the present invention. That's fine. For example, polyvinylidene fluoride, styrene butadiene rubber, or the like may be used as a binder used when producing a positive electrode plate or a negative electrode plate.
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited only to these.

<< Experiment 1 >>
Titanium dioxide TiO ₂ has a resistivity of 1 × 10 ¹⁴ Ωcm and is almost an insulator. However, if an electrode obtained by adding a sufficient amount of a conductive additive and a binder to titanium dioxide is used, a battery that can be discharged at a discharge potential of about 1.7 V with respect to Li metal can be obtained. For example, LiCoO ₂ used for the positive electrode, the use of TiO ₂ in the negative electrode, it is possible to construct a lithium ion battery 2V grade.
However, since the conductivity of TiO ₂ is very low, the TiO ₂ particles are made finer and a larger amount of conductive aid is required, resulting in a battery with a small energy capacity and high cost. Moreover, when titanium dioxide is used for the positive electrode and Li metal is used for the negative electrode, a 1.7 V lithium battery can be constructed, but the above-mentioned problems remain similarly. Therefore, in this experimental example, an active material was produced from titanium dioxide TiO ₂ by the production method according to the present invention.

White titanium dioxide TiO ₂ powder was placed in a quartz reaction tube and heated to 800 ° C. in a nitrogen gas atmosphere. Thereafter, ammonia gas was allowed to flow through the reaction tube and reacted for 10 hours to obtain a nitrogen oxide.
After the reaction, since the obtained nitrogen oxide was found to be sintered, the nitrogen oxide was pulverized in water using a ball mill to obtain an active material 1 (TiO _1.7 N _0.3 ) according to the present invention. The volume resistivity of the obtained active material was measured as described above and shown in Table 1.

Further, methanol was added to the active material 1 produced above, and further reacted at 300 ° C. for 10 minutes in a nitrogen gas atmosphere to obtain an active material 2 according to the present invention.
Table 1 shows the volume resistivity of the active materials 1 and 2 according to the present invention thus obtained. For comparison, the value of untreated TiO ₂ (active material 3) was also measured and shown in Table 1.

As is clear from Table 1, it can be seen that the resistivity of TiO ₂ as an insulator is drastically lowered by introducing nitrogen atoms. Moreover, when the reduction process at a low temperature, which is a subsequent process, was added, a decrease in resistivity was further observed.
Here, the electrochemical characteristics of the active material 1 obtained above are shown in FIG. The electrochemical characteristics were measured by the method described above.

  That is, 80 parts by weight of an active material, 10 parts by weight of acetylene black as a conductive additive, and 10 parts by weight of PVdF (polyvinylidene fluoride) as a binder are mixed to obtain a mixture. The solution was diluted with (N-methyl-2-pyrrolidone) and coated on an aluminum foil current collector. The coated current collector was dried in vacuum at 60 ° C. for 30 minutes, then cut to 15 mm × 20 mm, and further dried in vacuum at 150 ° C. for 14 hours to obtain an electrode having a thickness of 120 μm.

Next, lithium metal is used as the counter electrode, a polyethylene porous film is used as the separator, and EC (ethylene carbonate) and DMC (dimethyl carbonate) are mixed in a volume ratio of 3: 7 as the electrolyte. It was used by dissolving LiPF ₆ of 1.0 M. And charging / discharging was repeated between predetermined voltage area | regions with the current density of 0.17mA / cm < ² >, discharging to 1.0V, and charging to 2.5V. First, the measurement was started from the discharge, and the results of the first charge / discharge are shown in FIG.

  FIG. 1 shows that this active material can be charged and discharged at substantially the same potential as the behavior of the oxide before introducing nitrogen atoms. In addition, the active material 2 obtained above also gave almost the same result as shown in FIG.

<< Experiment 2 >>
White titanium dioxide TiO ₂ powder was placed in a quartz reaction tube and heated to 700 ° C. in a nitrogen gas atmosphere. Thereafter, ammonia gas was allowed to flow through the reaction tube at a flow rate of 300 ml / min, and nitrogen gas was allowed to flow at a flow rate of 50 ml / min to react for 28 hours to obtain a nitrogen oxide. After the reaction, since sintering was observed in the obtained nitrogen oxide, the nitrogen oxide was pulverized in water using a ball mill.
Further, the pulverized nitrogen oxide was put in a quartz tube together with methyl ethyl ketone, heated at 300 ° C. for 20 minutes in a nitrogen atmosphere, and rapidly cooled to obtain an active material 4 (TiO _1.0 N _1.0 ) according to the present invention. When the volume resistivity of the obtained active material was measured as described above, it was 1.0 Ωcm.

Further, white titanium dioxide TiO ₂ powder was put in a quartz reaction tube and heated to 800 ° C. in a nitrogen gas atmosphere. Thereafter, ammonia gas was allowed to flow through the reaction tube at a water flow rate of 300 ml / min, and nitrogen gas was allowed to flow at a flow rate of 50 ml / min to react for 5 hours to obtain a nitrogen oxide.
After the reaction, since the obtained nitrogen oxide was found to be sintered, the nitrogen oxide was pulverized in water using a ball mill to obtain an active material 5 (TiO _1.89 N _0.11 ) according to the present invention. When the volume resistivity of the obtained active material was measured as described above, it was 10 Ωcm.

When surface elemental analysis of the active materials 4 and 5 obtained as described above was performed using ESCA, it was confirmed that the compositions were different in layers and gradually changed.
The surface layer is mainly composed of titanium nitride, and is composed of titanium oxynitride from the surface layer to the inside. The nitrogen content gradually decreases, while the oxygen content increases.
Further, in the active materials 4 and 5, particles (A) whose surface layer and inside are composed of titanium oxynitride and nitrogen are hardly observed, and the oxygen content is reduced from titanium dioxide. Particles (B) were also observed. The particles were not necessarily spherical but had various shapes.

In the active materials 1, 2, 4, and 5 according to the present invention obtained in the above experimental examples, there are particles having a single structure of either A or B, and both of A and B Particles with mixed structures were also observed. Thus, TiO _1.7 N _0.3 and TiO _1.89 N _0.11 (a = 0.3 or 1.0 in TiO _2-a N a) is obtained as the preferred active material, surface analysis of the results as described above can be obtained Therefore, the composition of a preferable active material was specified as Li _x MeO _y N _z (x = 0, 0.1 <y <2, 0 <z <1.4, Me is Ti). The values of y and z were determined in consideration of errors in analysis values. Further, regarding the lower limit of the degree of nitrogenation, since _a of TiO _2-a Na is 0.11 in the active material 5, it is considered that a part of oxygen is replaced with nitrogen. However, 0.1 <y <2 was specified in consideration of the fact that it is difficult to analyze strictly and that a is as small as 0.11.

<< Experimental Example 3 >>
Next, since the conductivity of the active material according to the present invention is improved, it can be expected to reduce the amount of the conductive auxiliary agent used in the case of constituting a battery using the active material. The capacity | capacitance accompanying the weight loss of a conductive support agent was compared using the obtained active material. The results are shown in Table 2.
As an evaluation, the above-described method for measuring electrochemical characteristics was performed by changing the amount of acetylene black as a conductive auxiliary agent to be added. The discharge capacity was shown as a comparative value with respect to 100 when the active material 1 was used and 10 parts by weight of a conductive additive was added to produce an electrode.

From Table 2, it was found that the active material according to the present invention can maintain the capacity even when the amount of the conductive auxiliary agent is drastically reduced. As a result, when this active material is applied to a non-aqueous electrolyte secondary battery, the capacity per volume can be increased by reducing the conductive additive.
In addition, it is clear that the active material according to the present invention can be used for the positive electrode, but by combining the active material with an active material such as LiCoO ₂ having a higher potential than the active material in the present invention, the active material for the negative electrode In this case, a 2V class battery can be realized.

<< Experimental Example 4 >>
In this experimental example, a lithium-containing transition metal oxide was used as a raw material, and a nitrogen atom was introduced to synthesize an active material according to the present invention. The resistivity of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , which is a transition metal oxide, is higher than that of TiO ₂ , but is about 1 × 10 ⁴ Ωcm. However, in the case where this transition metal oxide is used as an active material, at present, sufficient discharge characteristics as a practical battery cannot be obtained unless at least about 3% by weight of a conductive additive is added.

Therefore, nitrogen atoms are introduced into the raw material LiNi _1/3 Mn _1/3 Co _1/3 O ₂ in the same manner as in Experimental Example 1, and the active material 6 (LiNi _1/3 Mn _{1) according} to the present invention is introduced. _{/ 3} Co _1/3 O _1.9 N _0.1 ). The resistivity of the obtained active material was measured and found to be 2 × 10 ² Ωcm. In addition, the electrochemical characteristics of this active material were also evaluated in the same manner as described above. However, there was no significant difference in charge / discharge behavior before and after introduction of nitrogen atoms, and when lithium metal was used as the counter electrode, a 4V class active material was obtained. Operated as.

This active material can be used as a positive electrode in combination with graphite or the like, but can also be used as a negative electrode. When lithium metal was used for the counter electrode, the charge / discharge potential was 1 V to 1.5 V. Therefore, when LiCoO ₂ is used for the positive electrode, a battery of about 2V can be formed, and when a high potential LiNi _1/2 Mn _3/2 O ₄ is combined, a battery of about 3V can be formed. It was.

Here, in order to investigate the nitride ratio, the x value in LiNi _1/3 Mn _1/3 Co _1/3 O _2−x N _x was changed to the values shown in Table 3 by changing the synthesis conditions. As the synthesis conditions, heating was performed at 800 ° C. in a nitrogen gas atmosphere, and the reaction time was changed by flowing ammonia gas. In the post-process, methyl ethyl ketone was added and reacted at 300 ° C. in a nitrogen gas atmosphere, and the reaction time was changed.

In this experimental example, the volume resistivity was all 1 × 10 ² Ωcm.
Moreover, when the surface elemental analysis of the active materials 7-9 was performed using ESCA similarly to the above, it was confirmed that the composition is layered and gradually changed. The surface layer is mainly composed of titanium nitride, and is composed of titanium oxynitride from the surface layer to the inside. The nitrogen content gradually decreases, while the oxygen content increases. Further, particles (A) composed of titanium oxynitride both in the surface layer and inside, and particles (B) in which almost no nitrogen was observed and the oxygen content decreased from titanium dioxide were also observed. .

In the active materials 7 to 9 according to the present invention obtained in the above experimental examples, there are those having any one of these A or B structures, and both A and B structures are mixed. Some were also observed. From the above results, the preferable composition of the active material according to the present invention was specified as Li _x MeO _y N _z (0 ≦ x ≦ 0, 0.1 <y <2.2, 0 <z <1.4). .

<< Experimental Example 5 >>
Active material 10 (SiO _x N _y ) and active material 11 (SnO _x N _y ) according to the present invention were synthesized in the same manner as in Experimental Example 1 using SiO and SnO as raw materials.
When the obtained active material was subjected to X-ray diffraction, a pattern identified as Si ₂ N ₂ O as disclosed in JP-A-11-102705 was not confirmed. This is because, in the active material according to the present invention, nitrogen atoms are not introduced into the entire matrix, but nitrogen atoms are introduced into the active material surface, and the oxygen conductivity is changed by changing the oxygen arrangement. This is considered to be given. The resistivity of the active material 10 (SiO _x N _y ) and the active material 11 (SnO _x N _y ) was 1 × 10 ³ Ωcm and 1 × 10 ² Ωcm, respectively.

<< Experimental Example 6 >>
Active material 6 (LiNi _1/3 Mn _1/3 Co _1/3 O _1.9 N _0.1 ), active material 10 (SiO _x N _y ) and active material 11 (SnO _x N _y ) according to the present invention prepared in the above experimental example. ), The effect of reducing the conductive assistant was examined in the same manner as in Experimental Example 3. The results are shown in Table 4.
For comparison, the same evaluation was performed when LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , SiO, and SnO as raw materials in the present invention were used as the active material. In addition, the capacity | capacitance was shown by the ratio when the value at the time of adding 20 weight% of conductive support agents to each raw material was set to 100.

  From Table 4, it was found that the active material according to the present invention can maintain the capacity even when the conductive aid is drastically reduced. As a result, when this active material is applied to a non-aqueous electrolyte secondary battery, the capacity per volume can be increased by reducing the conductive additive.

<< Experimental Example 7 >>
In this experimental example, the cylindrical battery described above with reference to FIG. 2 was produced.
The negative electrode plate was produced as follows. 1 part by weight of carbon powder as a conductive agent and 3 parts by weight of polyvinylidene fluoride resin as a binder were mixed with 100 parts by weight of the powdered negative electrode active material (TiO _1.7 N _0.3 ) according to the present invention. The obtained mixture was dispersed in dehydrated N-methylpyrrolidinone to obtain a slurry, which was applied onto a current collector made of aluminum foil, dried and rolled, and then cut into a predetermined size to obtain a negative electrode.

The positive electrode plate was produced in the same manner as the negative electrode plate except that the active material was changed to LiNi _1/3 Mn _1/3 Co _1/3 O _2-x N _{x according} to the present invention.
As the separator, a polypropylene nonwoven fabric is used, and in the organic electrolyte, LiPF ₆ is dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) in a volume ratio of 1: 1 by 1.0 mol / liter. Used. The produced cylindrical battery had a diameter of 14.1 mm and a height of 50.0 mm.

The cylindrical battery thus produced was charged at a constant voltage of 3.0 V and discharged to 1 V at a constant current of 100 mA. The discharge capacity obtained at this time was 550 mAh. Similarly, a comparative battery constructed using LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as the positive electrode active material and TiO ₂ as the negative electrode active material had a low discharge capacity of 90 mAh.

<< Experimental Example 8 >>
Various oxides shown in Table 5 as raw materials were nitrided by the following method, and volume resistivity was measured in the same manner as described above.
Further, as shown in Experimental Example 6, the volume% when acetylene black (AB) was reduced to 1% by weight was similarly measured. In Table 5, [capacity ratio after nitrogenation (AB 1 wt%) / (capacity ratio before nitrogenation (AB 1 wt%)]] is shown as a value of the capacity increase rate.

  From Table 5, by nitriding a lithium-containing oxide or oxide known as a battery active material, the conductivity is dramatically improved, and the resulting battery capacity can be increased. I understand that.

<< Experimental Example 9 >>
Here, an active material (SiO _y N _z ) according to the present invention was synthesized using amorphous SiO _1.03 as a raw material. First, in FIG. 3, showing the XRD pattern of amorphous SiO _1.03. FIG. 3 shows that a clear (sharp) crystal peak pattern is not observed, and only a broad peak (broad diffraction) is observed, which is amorphous.
Amorphous SiO _1.03 powder (average particle size 8 μm) was placed in a quartz reaction tube and heated to 600 ° C. in a nitrogen gas atmosphere. Thereafter, ammonia gas was passed through the reaction tube and reacted for 8 hours to obtain a nitrogen oxide. The obtained nitrogen oxide was pulverized in water to obtain an active material 12 (amorphous SiO _x N _y ) of the present invention.
The volume resistivity of the obtained active material 12 of the present invention was measured in the same manner as in Experimental Example 1 and found to be 1 × 10 ³ Ωcm. Further, when an XRD analysis of the obtained active material 12 was performed, an amorphous pattern similar to the amorphous SiO _1.03 as a raw material was observed.

In addition, the above-mentioned amorphous SiO _1.03 powder (average particle size 8 μm) is put in a quartz reaction tube and heated to 1400 ° C. in a nitrogen gas atmosphere. The active material 13 (crystalline SiO _x N _y ) was pulverized to obtain an electrochemical measurement of the active materials 12 and 13 in the same manner as in Experimental Example 1. However, the electrodes were put in an aluminum laminate bag and heat sealed. Aluminum and nickel leads were attached to the electrode and counter electrode, respectively, to form terminals. In addition, assuming that SiO _y N _z is used as a negative electrode active material in an actual battery, charging / discharging (voltage region 0 to 1.5 V) was performed by charging to 0 V and discharging to 1.5 V. Assuming that the discharge capacity at the third cycle is 100, the ratio of the discharge capacity after 20 cycles is shown in Table 6.

  Table 6 shows that the cycle life is good when the amorphous active material 12 is used. Even if the crystal is present only in the vicinity of the surface of the active material, it is considered that the crystal part is destroyed by charge / discharge, thereby causing a decrease in cycle life.

<< Experimental Example 10 >>
Crystalline, which is considered to have an adverse effect on the electrochemical characteristics, is considered to be produced when the firing temperature becomes high. For the purpose of clarifying this temperature, in the method shown in Experimental Example 9, the temperature is set to 500 ° C. To 1400 ° C. at 100 ° C. increments.
While observing whether or not crystalline material appeared by XRD analysis, the same electrochemical measurement as in Experimental Example 9 was performed. The results are shown in Table 7.

  From Table 7, crystallization appeared from 1100 ° C., and the cycle life was reduced accordingly. Therefore, a preferable temperature is 1000 ° C. or less, and 500 to 1000 ° C. is preferable including the meaning of shortening the nitriding time.

  When the active material according to the present invention is used, a battery having a high electromotive force and a high energy density can be obtained, and the battery is suitable as a main power source for mobile communication devices and portable electronic devices.

Is a diagram showing a charge-discharge curve of the TiO _2-x N _x of the active material according to the present invention. It is a schematic longitudinal cross-sectional view of the cylindrical battery produced in the present Example. It is a figure which shows the XRD pattern of amorphous _SiO1.03 .

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulation packing 4 Electrode plate group 5 Positive electrode lead 6 Negative electrode lead 7 Insulation ring

Claims (9)

An active material made of a nitrogen oxide having a resistivity of less than 1 × 10 ⁴ Ωcm.   The active material according to claim 1, wherein the nitrogen oxide is amorphous. Composition formula: Li _x MeO _y N _z (where 0 ≦ x ≦ 2, 0.1 <y <2.2, 0 <z <1.4, Me is Ti, Co, Ni, Mn, Si, Ge And at least one selected from the group consisting of Sn and the active material according to claim 1 or 2. An oxide having a resistivity of 1 × 10 ⁴ Ωcm or higher is heated in a reducing atmosphere, and then the oxide is reacted with ammonia gas to obtain a composition formula: Li _x MeO _y N _z (where 0 ≦ x ≦ 2, 0.1 <y <2.2, 0 <z <1.4, Me is at least one selected from the group consisting of Ti, Co, Ni, Mn, Si, Ge and Sn) Obtaining a nitrogen oxide having a resistivity of less than 1 × 10 ⁴ Ωcm.   The method for producing an active material according to claim 4, wherein the nitrogen oxide is amorphous.   The method for producing an active material according to claim 4 or 5, wherein the gas constituting the reducing atmosphere is at least one selected from the group consisting of argon, nitrogen, carbon monoxide and hydrogen.   The method for producing an active material according to any one of claims 4 to 6, wherein the heating temperature is 500C to 1500C.   The method for producing an active material according to any one of claims 4 to 7, wherein after the reaction with the ammonia gas, the nitrogen oxide is heated at a temperature of 400 ° C or lower in a reducing atmosphere. A non-aqueous electrolyte secondary battery comprising a positive electrode and / or a negative electrode comprising the active material according to claim 1.

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