JPH063745B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery in which a carbon body capable of reversibly absorbing and releasing a light metal such as lithium and sodium is used as a negative electrode.

<Prior Art> For the negative electrode of a non-aqueous electrolyte secondary battery, a light metal such as lithium or sodium is used alone or a light metal alloy such as a low melting point alloy represented by lithium-aluminum alloy or wood alloy, and the other positive electrode. For this purpose, metal oxides such as vanadium pentoxide and chromium trioxide, chalcogen compounds such as titanium disulfide, organic polymers and the like are mainly used.

In such a conventional non-aqueous electrolyte secondary battery system,
There is known a so-called negative electrode dominant type (negative electrode limited type) in which the charge and discharge capacity of the positive electrode is set larger than that of the negative electrode in order to improve reliability or cycle characteristics.

This is because a positive electrode-dominated (positive electrode limited) secondary battery in which the charge and discharge capacity of the negative electrode is larger than that of the positive electrode causes the breakdown of the positive electrode when deeply discharged, making it impossible to perform subsequent charge and discharge. To do. Therefore, in order to solve this problem, by making the charge and discharge capacity of the positive electrode larger than that of the negative electrode,
Even when the capacity of the negative electrode is fully charged / discharged, the positive electrode is prevented from reaching its limit so as to prevent the positive electrode from being broken and improve reliability or cycle characteristics. Also,
By adopting the negative electrode dominant type, there is an advantage that the selection range of the positive electrode material can be widened.

However, it has been revealed that the negative electrode-dominant secondary battery also has a defect due to the limited depth of discharge of the negative electrode.

That is, when a light metal simple substance such as lithium or sodium is used as the negative electrode, a metal dendrite that causes an internal short circuit of the battery is generated due to frequent repeated dissolution and precipitation processes of the metal. In addition, when a lithium-aluminum alloy is used as the negative electrode, the lithium concentration decreases, and the electrode becomes brittle, which causes a decrease in capacity. Further, in a low melting point alloy typified by wood alloy, when the electric potential is made extremely base, melting of alloy components causing deterioration of characteristics occurs. When the negative electrode is discharged to a deep discharge depth such as complete discharge due to such a cause, some change occurs in the negative electrode, which adversely affects battery performance such as reliability and cycle characteristics.

In short, it has been clarified that, even in a negative electrode-dominated secondary battery, when a deep discharge is carried out similarly to the positive electrode-dominated battery, a similar problem still occurs due to a problem on the negative electrode side.

<Object of the Invention> Therefore, the present invention is a so-called negative electrode-dominant secondary battery in which the charge and discharge capacity of the positive electrode is set to be larger than that of the negative electrode. It is an object of the present invention to provide a non-aqueous electrolyte type secondary battery that does not have any adverse effect on the battery performance.

<Structure of Invention> In order to achieve the above-mentioned object, the present invention, for example, as a negative electrode of a secondary battery using a non-aqueous organic solution as an electrolytic solution, vapor phase deposition from a hydrocarbon compound by low temperature pyrolysis at 1500 ° C. or lower. By using a carbon body containing carbon as a main component, which has a slightly disordered structure and has a selectively oriented structure as compared with the carbon having a highly oriented graphite structure formed by the method (pyrolysis CVD), It is characterized by a negative electrode-dominated battery in which the capacity of the negative electrode is smaller than that of the positive electrode.

Here, the hydrocarbon compound means benzene, naphthalene,
Examples include anthracene, hexamethylbenzene, 1,2-dibromoethylene, 2-butyne, acetylene, biphenyl and diphenylacetylene. The concentration and temperature for low-temperature pyrolysis vary depending on the hydrocarbon compound material used as the starting material, but are usually controlled at a concentration of several milmol percent and a temperature of about 1000 ° C. Further, as the vaporizing method, there are a bubbler method using hydrogen and / or argon as a carrier gas, an evaporation method, a sublimation method and the like.

In addition, as a result of analyzing the carbon bodies used in the present invention by various means, carbon having a slightly disordered structure and a carbon having a selectively oriented structure than carbon having a highly oriented graphite structure was found. The carbon body as the main component is defined as follows, for example. That is, the plane spacing of the plane mesh hexagonal ring surface of the carbon body is a value determined by the X-ray diffraction method.
It is from 0.337 nm to 0.355 nm. Also, the diffraction peak has a full width at half maximum, for example, 2θ = 1.62 °, which is considerably wider than that found in graphite. Regarding the graphitization degree of the carbon body, the result obtained by the Raman scattering method is 1580.
The carbon body has a ratio of Raman intensity of 1360 cm ^-1 to Raman intensity of cm ^-1 in the range of 0.4 to 1.0.

It is a carbon body in which the size of the crystallite in the C-axis direction of the plane hexagonal ring surface determined from the half width of the X-ray diffraction peak is in the range of 2.00 nm to 100.00 nm.

The orientation of the plane net-like hexagonal ring surface in the C-axis direction is a value determined by the reflection high-energy electron diffraction method, and the relative inclination in the C-axis direction between crystallites is within ± 75 degrees. It is preferably within ± 60 degrees. Further, it is a carbon body in which the reflection high-speed electron beam diffraction pattern is not uniform and has a broad ring shape such as an arc shape or a broad spot.

Non-aqueous electrolytes include dimethyl sulfoxide, gamma-butyl lactone, propylene carbonate sulfolane,
Tetrahydrofuran, 2-methyltetrahydrofuran,
Using an alkali metal ion such as lithium perchlorate, lithium hexafluoroarsenate, lithium borofluoride, or lithium trifluoromethanesulfonate as an electrolyte in an organic solvent such as 1,2-dimethoxyethane or 1,3-dioxolane as an electrolyte A single solution or a mixed solution obtained by dissolving a salt is used.

For the positive electrode, vanadium pentoxide, niobium pentoxide, bismuth trioxide, antimony trioxide, chromium trioxide, chromium trioxide, molybdenum trioxide, tungsten trioxide, selenium dioxide, tellurium dioxide, manganese dioxide, iron sesquioxide, tetraoxide Oxides of nickel trioxide, nickel oxide, cobalt trioxide, cobalt oxide, etc., titanium sulfide, zirconium sulfide, hafnium sulfide, tantalum sulfide, molybdenum sulfide, tungsten sulfide, titanium selenide, zirconium selenide, hafnium selenide, selenide vanadium,
A single or complex compound or mixture of chalcogen compounds such as niobium selenide, tantalum selenide, molybdenum selenide, and tungsten selenide is used.

<Examples> In the following, a carbon body formed by a low temperature pyrolysis method using benzene as a starting material is used as a negative electrode active material, various oxides and chalcogen compounds are used as a positive electrode active material, and 1M lithium perchlorate is used as an electrolytic solution. The present invention will be described in more detail with reference to a non-aqueous electrolyte type secondary battery using propylene carbonate in which is dissolved as an example.

The carbon body as the negative electrode active material was produced using the reaction apparatus shown in FIG. That is, argon gas was supplied from an argon gas supplier 2 into a container 1 containing benzene which had been dehydrated and then subjected to a distillation and purification operation by vacuum transfer, and benzene was bubbled through a glass tube 3 made by Pyrex. Benzene is fed to the quartz reaction tube 4.
At this time, the temperature was kept constant by heating the container 1 by the amount of heat absorbed by the evaporation of benzene, and the amount of benzene was optimized by the needle valves 5 and 6. The reaction tube 4 is provided with a holder 7 on which a three-dimensional structure made of foamed nickel and having a diameter of 15φ and a thickness of 1.5 mm is placed.
A heating furnace 8 is provided around the outside of the reaction tube 4. With this heating furnace 8, the holder 7 and the three-dimensional structure are
Maintaining the temperature at 0 ° C., benzene supplied from the Pyrex glass tube 3 is thermally decomposed and deposited as a carbon body on the three-dimensional structure. The gas remaining in the reaction tube 4 after the thermal decomposition reaction is removed through the exhaust equipment 9 and 10. The three-dimensional structure in which the carbon body is deposited in this manner is molded by a press machine to form the negative electrode of the battery of this example.

The X-ray diffraction diagram of the carbon body obtained here by CuKα ray is shown in FIG. 2, and the Raman spectrum diagram is shown in FIG. From this figure, the average spacing of the carbon material of the present embodiment is 0.342Nm, the ratio of the Raman intensity of 1360 cm ^-1 for the Raman intensity of 1580 cm ^-1 by Raman spectrum is found to be 0.75.

The size of the crystallite in the C-axis direction determined from the half width of the diffraction peak was 4.86 nm. Further, the orientation of the carbon body deposited on the nickel plate placed on the holder 7 in the same manner as the three-dimensional structure was examined. The diffraction pattern obtained by reflection high-energy electron diffraction was an arc-shaped broad ring. Regarding the crystallite orientation determined from this diffraction pattern, the relative inclination of each crystallite in the C-axis direction was within ± 35 degrees, and it was confirmed that the crystallite had a high orientation.

When natural graphite (made in Madagascar) was investigated by X-ray diffraction and Raman scattering, the average spacing was 0.336 nm.
, And the ratio of the Raman intensity of 1360 cm ^-1 for the Raman intensity of 1580 cm ^-1 by Raman spectrum was 0.1.

As described above, even if there is no great difference in the average interplanar spacing, there is a large difference in the Raman band reflected in the disorder of the crystal structure of 1360 cm ⁻¹ obtained by the laser Raman method. It can be seen that it has a slightly disordered structure compared to.

Chromium trioxide is heat-treated in a pressure vessel at a temperature of 230 ° C. to obtain an oxide having a composition of Cr ₃ O ₈ . This oxide 100
A mixture of 20 parts by weight of powdered polyethylene and 10 parts by weight of acetylene black is prepared with respect to parts by weight, and the mixture is heated to 120 ° C
And a pressure of 300 kgcm ^-2 to form a positive electrode.

The separator composed of the positive electrode, the negative electrode and the polyethylene nonwoven fabric was vacuum dried at 120 ° C. for 8 hours and dehydrated. When the capacity was examined in a glove box using 1 M propylene carbonate containing lithium perchlorate as an electrolytic solution, the capacity was 18 mAh for the positive electrode and 7.0 mAh for the negative electrode. FIG. 4 is a sectional view of a battery composed of the positive electrode, the negative electrode and the separator described above. 11 and 12 are stainless steel positive,
It is a negative electrode canister, and both are separated by an insulating packing 13 made of polypropylene. Reference numeral 14 is a positive electrode using Cr ₃ O ₈ as an active material, and is pressed against a positive electrode current collector 15 fixed to the inner bottom surface of the positive electrode can 11. Reference numeral 16 denotes a negative electrode having a carbon body as an active material, which is spot-welded to the negative electrode can 12. Reference numeral 17 is a separator, and a propylene carbonate solution containing 1 M lithium perchlorate as a solute was impregnated as an electrolytic solution. The battery assembled as described above is referred to as battery A.

Further, as shown in Table 1 below, batteries obtained by using various oxides and chalcogen compounds as the positive electrode and the carbon body of this example as the negative electrode were designated as B to E.

FIG. 5 shows a charge / discharge cycle characteristic diagram of these batteries. The charging and discharging conditions were a charging current density of 1 mAcm ^-2 for 4 hours, and a discharge current density of 1 mAcm ^-2 and a discharge end voltage of 2.0 V.

<Comparative Example> A battery A similar to Examples A to E was used, in which a negative electrode 16 in FIG. 4 was pressed with a negative electrode current collector fixed to the inner surface of the negative electrode can 12 using a rolled lithium plate punched with 15φ. Tables 2 and 3 show comparative examples "-E".

FIG. 6 shows a charge / discharge cycle characteristic diagram of the batteries of these comparative examples. The charging and discharging conditions were a charging current density of 1 mAcm ^-2 for 4 hours, and a discharge current density of 1 mAcm ^-2 and a discharge termination voltage of 2.0V.

<Effects of the Invention> As described above, in the present invention, in the non-aqueous electrolyte secondary battery in which the chargeable / dischargeable capacity of the positive electrode is set to be larger than that of the negative electrode, the negative electrode contains a light metal element. A carbon body having a planar network hexagonal ring structure capable of forming an electrochemically reversible intercalation compound, having an average spacing of 0.337 nm.
To 0.355 nm range and 136 for a Raman intensity of 1580 cm ^{-1 in} the Raman spectrum.
Since a carbon body having a Raman intensity ratio of 0 cm ⁻¹ in the range of 0.4 to 1.0 is used as an active material, it is possible to completely discharge the negative electrode in a negative electrode-dominated secondary battery. Even if deep discharge is performed up to the deep discharge depth, no adverse effect occurs on the negative electrode. As a result, it is possible to provide a non-aqueous electrolyte secondary battery having excellent characteristics such as reliability and cycle characteristics.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a carbon body producing apparatus used for explaining one example of the present invention. FIG. 2 is an X-ray diffraction diagram by a CuKα ray of a carbon body according to one example of the present invention. FIG. 3 is a Raman spectrum diagram of a carbon body according to one example of the present invention. FIG. 4 is a sectional view of a secondary battery showing one embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the chargeable / dischargeable capacity and the number of cycles of the batteries A to E of this example. FIG. 6 is a diagram showing the relationship between the chargeable / dischargeable capacity and the number of cycles of the comparative batteries A ′ to E ′. 1 ... Bubble container, 2 ... Argon gas supply device, 3 ... Pyrex glass tube, 4 ... Reaction tube, 5, 6 ... Needle valve, 7
... sample holder, 8 ... heating furnace, 11 ... positive electrode canister, 13 ... insulating packing, 14 ... positive electrode, 15 ... positive electrode current collector, 16 ...
Negative electrode, 17 ... Separator.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-60-182670 (JP, A) JP-A-55-62671 (JP, A) JP-A-57-103274 (JP, A) JP-A-58- 93176 (JP, A) JP 61-111907 (JP, A) JP 60-36315 (JP, A)

Claims (3)

[Claims] 1. A non-aqueous electrolyte secondary battery in which the chargeable / dischargeable capacity of the positive electrode is set to be larger than that of the negative electrode, wherein the negative electrode is an electrochemically reversible intercalation compound with a light metal element. A carbon body having a planar net-like hexagonal ring structure capable of forming a sphere having an average interplanar spacing of 0.337 nm to 0.355 n.
m range and 15 in the Raman spectrum
Nonaqueous electrolyte secondary batteries, characterized in that the ratio of the Raman intensity of 1360 cm ^-1 for the Raman intensity of 80 cm ^-1 to the active material carbon body in the range of 0.4 to 1.0. 2. A carbon body having a planar net-like hexagonal ring structure, which is a carbon body mainly having a graphite structure having a slightly disordered structure and a selectively oriented structure. Non-aqueous electrolyte secondary battery. 3. A carbon body having a plane network hexagonal ring structure is vapor-deposited by thermal decomposition from a hydrocarbon or a hydrocarbon compound obtained by adding or substituting another characteristic group to a part of the hydrocarbon as a starting material. The non-aqueous electrolyte secondary battery according to claim 1, which is a carbon body.