JPH07326386A - Secondary battery - Google Patents

Abstract

PURPOSE:To restrain a drop in high output capacity as well as in low output capacity, even when a negative electrode formed out of powder compact has small thickness. CONSTITUTION:Regarding a secondary battery using a positive electrode, a negative electrode and a nonaqueous electrolyte, the ratio p (sigma/eta, [10<-3>S/cm/ cPoise]) of the conductivity sigma [10<-3>S/cm] to the viscosity eta [cPoise] of the nonaqueous electrolyte is set to satisfy a relationship of 3<=p. Also, in a secondary battery using a positive electrode, a negative electrode and a nonaqueous electrolyte, a pulverized carbon material formed out of finely broken carbon fiber is used for the negative electrode.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a secondary battery using a positive electrode, a negative electrode and a non-aqueous electrolyte.

[0002]

2. Description of the Related Art In recent years, with the widespread use of portable devices such as video cameras and notebook computers, demand for small and high capacity secondary batteries has increased. Most of the secondary batteries currently used are nickel-cadmium batteries using an alkaline electrolyte, but the battery voltage is low at about 1.2 V, and it is difficult to improve the energy density. Therefore, in order to improve the voltage, a secondary battery using lithium metal for the negative electrode has been studied.

However, in a secondary battery in which lithium metal is used as the negative electrode, lithium tends to grow into dendrites due to repeated charging / discharging, resulting in short circuits and shortened life. Therefore, a secondary battery has been proposed in which various carbon materials are used for the negative electrode and the lithium ion is used by inserting and extracting lithium ions. Japanese Patent Application Laid-Open No. 57-2080 discloses a secondary battery including a negative electrode that utilizes the absorption and desorption of lithium ions in such a carbon material.
79, JP-A-58-93176, JP-A-5
8-192266, JP-A-62-90863, JP-A-62-122066, and JP-A-3-66.
Japanese Patent Publication No. 856 is known. The negative electrode of these secondary batteries is made of a powder molded body of a carbon material capable of inserting and extracting lithium. Further, as the electrolytic solution, a nonaqueous electrolytic solution such as an organic solvent is used because an aqueous solution cannot be used as the electrolytic solution because of its high voltage.

[0004]

However, when the thickness of the negative electrode or the positive electrode is increased, particularly when the electrode is formed of a powder molded body, the weight of the negative electrode active material when discharged at a high output current is high. Discharge capacity (mAh / g
) Has a problem that the discharge capacity is remarkably reduced as compared with the discharge capacity when discharged at a low output current. That is, if the discharge capacity when discharged with a high output current is a high output capacity and the discharge capacity when discharged with a low output current is a low output capacity, the high output capacity / low output capacity is small, and in the present invention, Aims to provide a secondary battery whose decrease in this value is small.

[0005]

The present invention has the following constitution in order to solve the above problems.

[1] In a secondary battery using a positive electrode, a negative electrode and a non-aqueous electrolyte, the conductivity of the non-aqueous electrolyte is σ [10 ⁻³ S /
cm] and the viscosity η [cPoise] ratio p (σ / η, [10 ^-3
S / cm / cPoise]) satisfies the relation of 3 ≦ p.

(2) A secondary battery using a positive electrode, a negative electrode, and a nonaqueous electrolytic solution, wherein a powdery carbon material obtained by finely cutting carbon fibers is used for the negative electrode. The secondary battery of the present invention relates to a secondary battery using a negative electrode, a positive electrode, and a non-aqueous electrolytic solution, and the structure of the secondary battery and its manufacturing method are not particularly limited.

The negative electrode and the positive electrode used in the present invention are not particularly limited, and electrodes generally used as electrodes can be used. When this electrode is made of a powder compact, especially when the compact is thick,
The discharge capacity at high output current decreases, but it is presumed that this is because the movement of ions in the electrolytic solution in the minute gaps of the electrode molded body is poor. Therefore, as a result of intensive studies, the inventors have considered that the ionic conductivity and viscosity of the electrolytic solution are important in order to improve the movement of ions in the fine gaps between the electrodes. Then, the relationship between the high output capacity / low output capacity and the electric conductivity or viscosity of the electrolytic solution was examined, but they were not related by themselves. However, by taking the ratio of conductivity and viscosity of this electrolyte,
It was found that high output capacity / low output capacity was improved. In other words, it has been found that when the ratio between the electric conductivity and the viscosity of the non-aqueous electrolyte is in the above-mentioned specific range, it is possible to suppress the decrease in high output capacity / low output capacity.

Materials used for the negative electrode of the present invention include:
Although not particularly limited, for example, a carbon material or the like is preferable because it has a good lithium ion storage / release property. The raw material and manufacturing method of the carbon material can be used without particular limitation. Examples of raw materials include coke and pitch such as petroleum and coal, plants such as wood, low molecular weight organic compounds such as natural gas and lower hydrocarbons, polyacrylonitrile, synthetic polymers such as phenol resin and furfuryl alcohol resin. Then, a carbon material is obtained through a treatment called carbonization or graphitization in which these are fired at 700 to 3000 ° C. depending on the raw material and application. Natural graphite can also be used. The properties of the carbon material include density, crystal thickness (Lc), crystal face spacing (d002),
The electrical resistance, strength, elastic modulus, etc. may be mentioned, but these should be appropriately determined according to the intended electrode characteristics of the secondary battery, and are not particularly limited.

A preferred embodiment is also a case where the above-mentioned carbon material is in the form of powder obtained by finely cutting carbon fibers. In the case of using the powdery one obtained by finely cutting the carbon fiber as described above, the voids increase in the electrode as compared with the case of using the carbon fiber as the long fiber, and thus the high output capacity / low capacity which is the object of the present invention is obtained. It is possible to preferably obtain a secondary battery having a large output capacity. Furthermore, when a powdery carbon material is used, a solvent can be added together with a binder and a conductive agent to form a slurry, and the slurry can be applied to easily form an electrode. The powdery carbon material preferably has an average length of 5 mm or less,
Furthermore, 0.1 mm or less and 0.05 mm or less are more preferable. The "average length" here is, for example, SEM
It is possible to obtain the value by measuring the length in the fiber axis direction for 20 or more powdery carbon materials by observing the above. Further, the method of “cutting” is not particularly limited, and a method such as cutting or crushing is used. As the carbon fiber, PAN-based carbon fiber obtained from polyacrylonitrile (PAN), pitch-based carbon fiber obtained from pitch of coal or petroleum, cellulose-based carbon fiber obtained from cellulose, gas obtained from gas of low molecular weight organic substance Examples of the carbon fiber include phase-grown carbon fiber, but in addition, carbon fiber obtained by firing polyvinyl alcohol, lignin, polyvinyl chloride, polyamide, polyimide, phenol resin, furfuryl alcohol, etc. may be used. Among these carbon fibers, a carbon fiber satisfying the characteristics is appropriately selected according to the characteristics of the negative electrode and the battery used, and the PAN-based carbon fiber,
Pitch-based carbon fibers and vapor grown carbon fibers are preferable. In particular, PAN-based carbon fibers and pitch-based carbon fibers are preferable in terms of good occlusion and release of lithium ions,
Among these, PAN-based carbon fibers such as "Torayca" T series or "Torayca" M series manufactured by Toray Industries, Inc. and pitch-based carbon fibers obtained by firing mesophase pitch coke are more preferably used.

The particle diameter or fiber diameter of the carbon material used in the present invention is not limited, but is 0.1-10.
0 μm is preferable, and 1 to 20 μm is particularly preferably used.

In the negative electrode used in the present invention, it is also preferable to add a binder to the active material in order to improve moldability. The binder is not particularly limited in addition to polymer compounds such as polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile, polyimide, polyethylene, polypropylene, epoxy resin and phenol resin. These binders are used as a powder by being mixed with the active material, and are dissolved in a solvent or dispersed as an emulsion to be used as a slurry with the active material. The form of use is not particularly limited. .

In the negative electrode used in the present invention, a current collector is used to conduct electricity from the negative electrode to the terminal. As such a current collector, metals such as copper, stainless steel, nickel, titanium tan, and platinum can be used in the form of foil, mesh, lath, etc., but these are not particularly limited. Absent. Further, also as a method of bringing the negative electrode into contact with the current collector, a fibrous or powdery mixture containing the negative electrode active material is directly pressed onto the current collector, and a slurry containing the negative electrode active material is applied to the current collector. There is no particular limitation on the manufacturing method, such as pressing after drying the solvent. Further, the distance from the current collector corresponding to the thickness of the negative electrode to the surface of the negative electrode is not particularly limited, but is 20 μm.
When it is m or more, the effect of the non-aqueous electrolyte of the present invention is great.

In addition to the above carbon material active material, it is also preferable to add a conductive agent to the negative electrode used in the present invention in order to improve electron conductivity. By adding a conductive agent, the resistance in the electrode is lowered, so that it is effective in improving the battery capacity, and it is particularly effective not only in improving the low output capacity but also in improving the high output capacity. As such a conductive agent, a metal, a semiconductor, or a semimetal, which is a material having a low electric resistance, is used, but a carbonaceous material or a carbon material such as graphite or carbon black is particularly preferably used. The shape of the conductive agent is not particularly limited, such as powder and fibrous, but in the case of powder, the particle size is 0.1 to 100.
It is preferable that it is μm, more preferably 1 to 50 μm. The amount of the conductive agent added is 0.01 to the carbon active material.
It is preferably 50%, more preferably 0.1 to 20%.

The solvent component of the non-aqueous electrolytic solution used in the present invention is not particularly limited as long as it satisfies the electric conductivity-viscosity ratio p of the above claims, but it is not limited thereto. And the like are used. As the high dielectric constant solvent, propylene carbonate, ethylene carbonate, cyclic carbonate such as butylene carbonate,
Cyclic esters such as γ-butyrolactone, tetramethylsulfolane, dimethylsulfoxide, N-methylpyrrolidone, dimethylformamide and their derivatives are not particularly limited. As a low viscosity solvent,
Chain ethers such as dimethoxyethane, ethoxymethoxyethane and diethoxyethane, cyclic ethers such as tetrahydrofuran, dioxolane and dioxane, chain carbonates such as dimethyl carbonate, ethylmethyl carbonate and diethyl carbonate and derivatives thereof are used, but especially It is not limited. The composition ratio of the high-dielectric-constant solvent and the low-viscosity solvent is also not particularly limited, and the electric conductivity-viscosity ratio p of the electrolytic solution is appropriately determined so as to fall within the scope of the above claims. . The solvent of the non-aqueous electrolytic solution used in the present invention is a preferred embodiment even when other components than the above-mentioned solvent are added as trace components up to 5% by volume. The additives used in this case can include various organic compounds or inorganic compounds.

The electrolyte contained in the non-aqueous electrolytic solution used in the present invention can be used without particular limitation, and examples thereof include LiClO ₄ , LiBF ₄ , LiPF ₆ , and LiPF ₆ .
_{CF 3 SO 3, LiAsF 6,} LiSCN, LiI, and the like LiAlO _4. Particularly, LiClO ₄ , LiBF ₄ , and LiPF ₆ are preferably used.

The electric conductivity and viscosity of the non-aqueous electrolytic solution used in the present invention may be values measured using a commercially available electric conductivity meter or rotational viscometer. The measurement is performed at 20 ° C.

The positive electrode used in the present invention is not particularly limited, and an electrode generally used as a positive electrode can be used. For example, a molding made of a mixture containing a powdered active material and a binder. The body is preferably used.
The active material is not particularly limited, but examples thereof include transition metal oxides such as lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium niobate, and lithium vanadate, molybdenum sulfide, and titanium sulfide. Transition metal chalcogen, or a mixture thereof, or a disulfide compound such as mercaptothiadiazole, or a polyalkylene oxide or polyalkylene sulfide, polyaniline, polythiophene, heteropolymer such as polypyrrole, polyacetylene, polydiacetylene, polyparaphenylene, polyphenylene vinylene or the like. A conjugated polymer compound is used. The above-mentioned substances capable of occluding and releasing lithium ions or anions are preferably used as the positive electrode active material without limitation, and the oxidation potential of these is preferably 2.5 V or more with respect to lithium. The particle size of this positive electrode active material powder is preferably 0.1 to 100 μm, and more preferably 1 to 50 μm.

It is also preferable to add a binder to the active material and the conductive agent in the positive electrode used in the present invention in order to improve the moldability. A compound similar to the negative electrode is used,
The use form is not particularly limited.

A current collector is used to connect the positive electrode used in the present invention to the terminal. As such a current collector, metals such as aluminum, titanium, platinum, and nickel can be used in the form of foil, mesh, lath, etc., but they are not particularly limited.
Also, as a method of contacting the positive electrode with the current collector, the powder mixture containing the positive electrode active material is directly pressure-bonded to the current collector, the slurry containing the positive electrode active material is applied to the current collector and solvent-dried and then pressure-bonded. The manufacturing method is not particularly limited. Further, the distance from the collector corresponding to the thickness of the positive electrode to the surface of the positive electrode is not particularly limited, but the effect of the non-aqueous electrolytic solution of the present invention is great when the distance is 20 μm or more.

The secondary battery of the present invention is widely used in portable small electronic devices such as video cameras, personal computers, word processors, radio-cassettes, mobile phones, etc. by utilizing the features of being lightweight, having high capacity and having high energy density. It is possible.

[0022]

EXAMPLES Specific embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 (1) Preparation of carbon negative electrode Powder of commercially available pitch coke "LPC-A" (manufactured by Nippon Steel Chemical Co., Ltd.) and Teflon powder were mixed in a weight ratio of 90/10. Then, 10 mg of the negative electrode of carbon material was obtained by pressure molding together with the nickel mesh of the collecting electrode. The negative electrode had a diameter of 1.6 cm and a thickness of 20 μm.

(2) Preparation of positive electrode Commercially available lithium carbonate (Li ₂ CO ₃ ) and basic cobalt carbonate
(2CoCO ₃ .3Co (OH) ₂ ) was weighed so that the molar ratio was Li / Co = 1/1, mixed in a ball mill, and heat-treated at 900 ° C. for 20 hours to obtain LiCoO ₂ . This is crushed with a ball mill, artificial graphite is used as the conductive material, and Teflon (PTF) is used as the binding material.
E) with LiCoO ₂ / artificial graphite / PTFE = 80/15 /
The mixture was mixed so as to be 5 and pressure-molded together with the nickel mesh of the collecting electrode to obtain 20 mg of a positive electrode.

(3) Preparation of secondary battery The negative electrode obtained in (2) above was prepared in (1) above via a porous polypropylene film (Celguard # 2500, manufactured by Daicel Chemical Industries, Ltd.) as a separator. The positive electrode thus prepared was overlaid to prepare a coin-type secondary battery. The electrolyte is propylene carbonate / dimethoxyethane containing 1M lithium perchlorate (volume ratio 30/70).
Was used.

(4) Evaluation The conductivity of the above-mentioned electrolyte was 12 × 10 ⁻³ S / cm when measured at 20 ° C. using a personal SC meter (Model SC82 manufactured by Yokogawa Electric Co., Ltd.). there were. The viscosity of this electrolytic solution was 2.3 c when measured at 20 ° C. using a rotational viscometer (Tokyo Keiki Co., Ltd., B-type viscometer BL).
It was Poise. The conductivity-viscosity ratio of this electrolyte is p =
It was 5.4 [10 ⁻³ S / cm / cPoise].

Further, the secondary battery obtained in (2) above was charged at a constant potential of 4.1 V at a current of 4 mA for 5 hours and then discharged at a constant current of 0.4 mA per negative electrode. The discharge capacity of was set as the low output capacity. On the other hand, under the same charging condition, the discharge capacity per negative electrode at the time of discharging at 8 mA low current was defined as the high output capacity. Then, high output capacity / low output capacity was obtained as a high output capacity ratio. This high output capacity ratio was 0.70, and the decrease in capacity at high output current was suppressed.

Comparative Example 1 A secondary battery was prepared and evaluated in the same manner as in Example 1 except that propylene carbonate containing 1M lithium perchlorate was used as the electrolytic solution. The conductivity of the electrolyte is 4.8 × 10 ^-3
S / cm, viscosity is 10 cPoise, ratio of conductivity to viscosity p =
At 0.47 [10 ^-3 S / cm / cPoise], the high output capacity ratio was 0.05, and the capacity decrease at high output was large.

Example 2 (1) Preparation of Carbon Negative Electrode Pitch coke "M-coke" (manufactured by Nippon Mining Co., Ltd.) powder and polyvinylidene fluoride (PVdF) powder in a weight ratio of 90/10. And mixed with N-methylpyrrolidone to give a slurry. This slurry was applied to a copper foil, dried, and pressed. The negative electrode had a diameter of 1.6 cm and a thickness of 20 μm. (2) Preparation of positive electrode LiCoO ₂ was synthesized in the same manner as in Example 1 and, after crushing, artificial graphite as a conductive material and polyvinylidene fluoride (as a binder) ( P
VDF) and LiCoO ₂ / artificial graphite / PVDF =
80/15/5 were mixed, and N-methylpyrrolidone was used as a solvent to form a slurry. This slurry was applied on an aluminum foil of a collecting electrode, dried and then pressed to obtain a molded positive electrode.

(3) Preparation and Evaluation of Secondary Battery A coin type secondary battery was prepared and evaluated in the same manner as in Example 1. The electrolyte has an electric conductivity of 13 × 10 ⁻³ S / cm, a viscosity of 10 cPoise, and a ratio of electric conductivity to viscosity p = 4.6 [10 ^−3]
S / cm / cPoise]. The high output capacity ratio of the secondary battery was 0.40, and the capacity decrease at high output was suppressed.

Comparative Example 2 A secondary battery was prepared and evaluated in the same manner as in Example 2 except that propylene carbonate / dimethoxyethane (volume ratio 70/30) containing 1M lithium perchlorate was used as the electrolytic solution. The electrolyte has an electric conductivity of 12 × 10 ⁻³ S / cm, a viscosity of 4.3 cPoise, and a ratio of electric conductivity to viscosity p = 2.9 [1.
0 ^-3 S / cm / cPoise]. High output capacity ratio is
It was 0.30, and the decrease in capacity was large.

Comparative Example 3 A secondary battery was prepared and evaluated in the same manner as in Example 2 except that propylene carbonate / ethylene carbonate containing 1M lithium perchlorate (volume ratio 50/50) was used as the electrolytic solution. . The conductivity of this electrolyte is 6.4 × 10 ^-3 S
/ Cm, viscosity is 15 cPoise, ratio of conductivity to viscosity p =
It was 0.43 [10 ⁻³ S / cm / cPoise]. The high output capacity ratio of this secondary battery was 0, and high output capacity was not obtained. Example 3 A secondary battery was prepared and evaluated in the same manner as in Example 2 except that the electrolyte solution was ethylene carbonate / dimethoxyethane (volume ratio 30/70) containing 1M lithium perchlorate. The electrolyte has an electric conductivity of 17 × 10 ⁻³ S / cm, a viscosity of 2.2 cPoise, and a ratio of electric conductivity to viscosity p = 7.8 [10].
^-3 S / cm / cPoise]. The high output capacity ratio of this secondary battery was 0.41, and the capacity decrease at high output was suppressed.

Example 4 Propylene carbonate / dimethoxyethane (volume ratio 30/70) containing 1M lithium tetrafluoroboron as the electrolytic solution
A secondary battery was prepared and evaluated in the same manner as in Example 2 except that was used. The conductivity of this electrolyte is 9.4 × 10 ^-3 S
/ Cm, viscosity is 1.7 cPoise, ratio of conductivity to viscosity p =
It was 5.4 [10 ⁻³ S / cm / cPoise]. The high output capacity ratio of this secondary battery was 0.45, and the reduction in capacity at high output was suppressed.

Example 5 Propylene carbonate / ethoxymethoxyethane containing 1M lithium perchlorate (volume ratio 20/80)
A secondary battery was prepared and evaluated in the same manner as in Example 2 except that was used. The conductivity of this electrolyte is 8.3 × 10 ^-3 S
/ Cm, the viscosity is 2.7 cPoise, the ratio of electric conductivity and viscosity p =
It was 3.1 [10 ^-3 S / cm / cPoise]. The high output capacity ratio of this secondary battery was 0.40.

Example 6 A secondary battery was used in the same manner as in Example 2 except that natural graphite was used as the negative electrode carbon material and ethylene carbonate / dimethoxyethane containing 1M lithium perchlorate (volume ratio 30/70) was used as the electrolytic solution. Was created and evaluated. The conductivity of this electrolyte is 1
The viscosity was 7 × 10 ⁻³ S / cm, the viscosity was 7.8 cPoise, and the ratio of electric conductivity to viscosity was p = 7.8 [10 ⁻³ S / cm / cPoise]. The high output capacity ratio of this secondary battery was 0.50.

Example 7 Carbon fiber (T300 manufactured by Toray) was used as the negative electrode carbon material in an amount of 30 μm.
A secondary battery was prepared and evaluated in the same manner as in Example 2 except that the powdered product that was cut into was used. High output capacity ratio is 0.4
It was 3.

Example 8 (1) Preparation of Positive Electrode Commercially available lithium carbonate (Li ₂ Co ₃ ) and basic cobalt carbonate
_{(2CoCO 3 · 3Co (OH)} 2) and, in a molar ratio Li / Co = 1 /
Weigh to 1 and mix in ball mill, then 900 ℃
Then, heat treatment was performed for 20 hours to obtain LiCoO ₂ . This is crushed with a ball mill, artificial graphite is used as the conductive material, and Teflon (PTFE) is used as the binder, and mixed so that the weight ratio is LiCoO ₂ / artificial graphite / PTFE = 80/15/5, and the collector electrode 20m positive electrode by pressure molding with nickel mesh
g was obtained. This positive electrode material has a diameter of 1.6 cm and a thickness of 50 μ.
It was m.

(2) Preparation of secondary battery 10 mg of commercially available PAN-based carbon fiber "Torayca" T-300 (manufactured by Toray Industries, Inc.) was uniaxially arranged and placed on a nickel mesh of a current collector as a negative electrode. And A coin-type secondary battery was prepared by superimposing the positive electrode prepared in (1) above on a porous polypropylene film (Celguard # 2500, manufactured by Daicel Chemical Industries, Ltd.) as a separator. The electrolyte used was propylene carbonate / dimethoxyethane (volume ratio 30/70) containing 1M lithium perchlorate.

(3) Evaluation The conductivity of the above-mentioned electrolytic solution was 20 ° C. using a personal SC meter (Model SC82 manufactured by Yokogawa Electric Co., Ltd.).
It was 12 × 10 ⁻³ S / cm when measured by
The viscosity of this electrolytic solution was measured at 20 ° C. using a rotational viscometer (B-type viscometer BL manufactured by Tokyo Keiki Co., Ltd.), which was 2.3.
It was cPoise. The conductivity-viscosity ratio of this electrolyte is p
= 5.4 [10 ^-3 S / cm / cPoise].

Further, the secondary battery obtained in the above (2) was charged for 5 hours at a constant potential up to 4.1 V at a current of 4 mA, and then discharged at a constant current of 0.4 mA per positive electrode. The discharge capacity of was set as the low output capacity. On the other hand, under the same charging condition, the discharge capacity per positive electrode when discharging at a low current of 8 mA was defined as the high output capacity. Then, high output capacity / low output capacity was obtained as a high output capacity ratio. This high output capacity ratio was 0.80, and the decrease in capacity at high output current was suppressed.

Comparative Example 4 A secondary battery was prepared and evaluated in the same manner as in Example 1 except that propylene carbonate containing 1M lithium perchlorate was used as the electrolytic solution. The conductivity of the electrolyte is 4.8 × 10 ^-3
S / cm, viscosity is 10 cPoise, ratio of conductivity to viscosity p =
At 0.47 [10 ^-3 S / cm / cPoise], the high output capacity ratio was 0.05, and the capacity decrease at high output was large.

Example 9 Powdered carbon fibers having an average length of 30 μm, carbon black (acetylene black) and polyvinylidene fluoride powder were mixed in a weight ratio of 80: 15: 5 as in Example 7. Then, N-methylpyrrolidone was added to form a slurry. A negative electrode and a positive electrode were prepared in the same manner as in Example 2 except that this slurry was used. A coin battery was prepared in the same manner as in Example 2 except that an electrolytic solution obtained by dissolving LiBF ₄ in ethylene carbonate / dimethyl carbonate / γ-butyrolactone at a ratio of 1 mol / l was used as the electrolytic solution. The high output capacity ratio was 0.51, and the capacity decrease at high output was suppressed. In Example 9, not only the high output capacity ratio was improved as compared with Example 7, but the discharge capacity itself at low output was also improved from 230 mAh / g of Example 7 to 330 mAh / g.

[0043]

According to the present invention, it is possible to suppress a decrease in high output capacity / low output capacity even when the thickness of the negative electrode made of a powder molded body is large.

Claims (17)

[Claims] 1. In a secondary battery using a positive electrode, a negative electrode and a non-aqueous electrolyte, the conductivity of the non-aqueous electrolyte is σ [10 ⁻³ S / cm].
And viscosity η [cPoise] ratio p (σ / η, [10 ^-3 S / c
m / cPoise]) satisfies the relation of 3 ≦ p. 2. The secondary battery according to claim 1, wherein the negative electrode is a powder molded body. 3. The secondary battery according to claim 1, wherein the positive electrode is a powder molded body. 4. The secondary battery according to claim 1, wherein a cyclic carbonate and a chain ether are contained as a solvent component of the non-aqueous electrolytic solution. 5. The secondary battery according to claim 1, wherein a cyclic carbonate and a chain carbonate are contained as a solvent component of the non-aqueous electrolytic solution. 6. The secondary battery according to claim 1, wherein a cyclic carbonate and a cyclic ether are included as a solvent component of the non-aqueous electrolytic solution. 7. The secondary battery according to claim 1, wherein the electrolyte of the non-aqueous electrolytic solution is a lithium salt. 8. The secondary battery according to claim 1, wherein the positive electrode contains at least a transition metal compound capable of inserting and extracting lithium ions. 9. The negative electrode contains at least a carbon material capable of inserting and extracting lithium ions.
The secondary battery according to any one of to 8. 10. The secondary battery according to claim 9, wherein the carbon material is carbon fiber. 11. The secondary battery according to claim 10, wherein the carbon fiber is a fired product of polyacrylonitrile. 12. The secondary battery according to claim 1, wherein the negative electrode is a structure selected from a unidirectional molded body made of carbon fiber, a cloth and a felt. 13. The positive electrode is a molded body obtained by laminating a mixture of a fiber metal compound powder capable of occluding and releasing lithium ions, a conductive agent powder and a binder on a current collector. The secondary battery according to 1. 14. A secondary battery using a positive electrode, a negative electrode and a non-aqueous electrolyte, wherein a powdery carbon material obtained by finely cutting carbon fibers is used for the negative electrode. 15. The powder carbon material has an average length of 0.1.
The secondary battery according to claim 14, wherein the secondary battery has a size of not more than mm. 16. The powder carbon material has an average length of 0.0.
The secondary battery according to claim 14, wherein the secondary battery has a length of 5 mm or less. 17. The secondary battery according to claim 14, wherein a conductive agent is used for the negative electrode.