JPS63276873A - Nonaqueous solvent secondary battery - Google Patents

Abstract

PURPOSE:To enhance the charge/discharge cycle characteristic and prolong the life by using alkali metal containing Li as active substance, and by using as bearer a one which has a specific H/C value, G-value corresponding to the measure for the degree of graphitization, size of surface spacing Lc of (002) faces by X-rays wide-angle diffraction method, volume average particle size, and specific surface area. CONSTITUTION:Li or an al-metal containing Li is used as active material in this negative electrode body. An aggregate containing a carbonaceous material particles with specific property as a component unit is used as bearer. That is, H/C value is below 0.15, the G value indicated by Eq. I in Raman spectrum analysis using argon ion laser beam having a wave length of 5145Angstrom is no greater than 2.5, the surface spacing of the (002) face by X-rays wide-angle diffraction method is over 3.37Angstrom , size of crystallite in the C-axis direction is no greater than 150Angstrom , and the volume average particle size is no greater than 500Angstrom . The specific surface area of this aggregate shall be over 1 m<2>/g.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a non-aqueous solvent secondary battery, and more specifically, to a non-aqueous solvent secondary battery that is small in size, has a long charge/discharge cycle life, and has a stable high capacity. Related to non-aqueous solvent secondary batteries.

(Prior art) The main component of the positive electrode body is TiS2. Efforts are being made to commercialize nonaqueous solvent secondary batteries, which are chalcogen compounds of transition metals such as MoS2, and whose negative electrodes are Li or an alkali metal mainly composed of Li, because they have high energy density.

(Problems to be Solved by the Invention) However, in such a nonaqueous solvent secondary battery, a problem arises due to the fact that the negative electrode body is an Lf foil or an alkali metal foil mainly composed of Lf itself.

That is, when the battery is discharged, Li from the negative electrode body becomes Li ions and moves into the electrolyte solution, and during charging, these Li ions become metal L+ and are deposited on the negative electrode body again, but this charge-discharge cycle is repeated. As a result, the metal Li deposited becomes dendrite-like. This dendrite LX
is an extremely active substance, it decomposes the electrolyte,
As a result, a disadvantage arises in that the charge/discharge cycle characteristics of the battery deteriorate. As they grow further, a problem arises in that the dendrite-like metal Li deposits eventually penetrate the separator and reach the positive electrode body, causing a short circuit phenomenon. In other words, the problem is that the charge/discharge cycle life is short.

In order to avoid such problems, attempts have been made to construct the negative electrode body by using a carbonaceous material obtained by calcining various organic compounds as a carrier, and supporting Li or an alkali metal mainly composed of Li. It is being

By using such a negative electrode body, the separation t8 of Li dendrites has been prevented, but on the other hand, a battery incorporating this negative electrode body has a lower discharge capacity than a primary battery of the same size. Very small, about 1/Zoo,
Furthermore, there are various practical problems, such as large self-discharge, very short operating period of equipment equipped with this battery, and inability to discharge large currents, which limit its use.

The present invention solves the above-mentioned disadvantages in a non-aqueous solvent secondary battery equipped with a negative electrode body using a carbonaceous material as a carrier.
．． The purpose of this invention is to provide a non-aqueous solvent secondary battery.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the problem 1), the present inventors have conducted extensive research on negative electrode bodies, and as a result, the above-mentioned carrier has been developed using a carbonaceous material having the parameters described below. The inventors discovered that the non-aqueous solvent secondary battery of the present invention is effective in achieving the objective when the non-aqueous solvent is composed of particles.

That is, the nonaqueous solvent secondary battery of the present invention is a nonaqueous solvent secondary battery equipped with a negative electrode body consisting of an active material and a carrier supporting the active material, in which (A) the active material is lithium or (B) the carrier is an alkali metal mainly composed of lithium; (1) the hydrogen/carbon atomic ratio is less than 0.15;
) In Raman spectrum analysis using argon ion laser light with a wavelength of 5145, the following formula: The G value indicated by the integrated value of the spectral intensity in the wave number region of 1360 ± 100 cm-' is less than 2.5; (iii) X-ray The interplanar spacing (d 002) of the (002) plane by wide-angle diffraction method is 3.37 A or more, and the crystallite size in the C-axis direction (L c) is 150 A or less: The volume average particle diameter is 500 Å or less; The structural unit is carbonaceous material particles, and the specific surface area is 1.
m″/g or more.

The battery of the present invention is characterized in that the negative electrode body has the above-described configuration, and other elements may be the same as conventional non-aqueous solvent secondary batteries.

In the negative electrode body according to the present invention, the active material is Li or Li
This active material, which is mainly an alkali metal, moves back and forth between the positive electrode body and the negative electrode body in response to charging and discharging of the battery.

The carrier of the present invention has carbonaceous material particles having the characteristics described below as a constituent unit, and is formed as an aggregate of these units.

The carbonaceous material particles do not need to be composed only of carbon; for example, the content of other atoms such as nitrogen and halogen is 7 mol% or less, preferably 4 mol% or less.

More preferably, it may be contained in an amount of 2 mol% or less.

For each parameter that specifies carbonaceous material particles, first,
H/C is required to be 0.15 or less, preferably less than 0.10, more preferably less than 0.07, particularly preferably less than 0.05.

Further, the G value needs to be less than 0.25, preferably less than 2.0. More preferably 0.1 to 1.5. Particularly preferably 0.2 to 1.2.

Here, the G value means a wavelength of 5145A for this carbonaceous material.
In the spectral intensity curve recorded on the chart when performing Raman spectrum analysis using argon ion laser light, the integral value (area intensity) of the spectral intensity within the range of wave number 1580 ± 100 cm-' is calculated as wave number 13
It refers to the value divided by the area intensity within the range of 60±100 CI', and corresponds to a measure of the degree of graphitization of the carbonaceous material.

That is, this carbonaceous material has a crystalline portion and an amorphous portion, and the G value is a parameter indicating the ratio of the crystalline portion in this carbonaceous structure.

Furthermore, when measured by X-ray wide-angle diffraction, d002 must be 3.37 Å or more and Lc must be 150 Å or less, preferably dQ (123,39 to 3.75, Lc
5 to 150A, more preferably d0023.41 to
3.70A, Lo 10-80 people, particularly preferably 12-70A.

Further, the volume average particle diameter of the carbonaceous material particles needs to be 500 Å or less, preferably 300 Å or less, and more preferably 200 Å or less. Note that the volume average particle size here is the volume-weighted average particle size, and the cross section of the carbonaceous material particles is photographed using an electron microscope, and the carbonaceous material particles (
This can be determined by measuring the size of the primary particles that make up the secondary particles.

Among these parameters that specify carbonaceous material particles, H
If any of /C, d002 and Le are out of the above range, the overvoltage at the negative electrode during charging and discharging will increase, and as a result, gas will be generated from the negative electrode, significantly reducing the safety of the battery. be damaged. Moreover, the charge/discharge cycle and cycle characteristics are unsatisfactory.

In addition, if the G value is 2.5 or more, the carbonaceous material is in a highly graphitized state, and the amount of active material that can exist inside the carbonaceous material particles decreases and becomes unstable. As a result, the capacity of the battery decreases.

Furthermore, it is desirable that the carbonaceous material satisfies the following conditions, that is, in X-ray wide-angle diffraction analysis (
110) Distance ao twice the interplanar spacing d110 (=
2clllO), preferably 2.38 to 2.47 people,
More preferably 2.39 to 2.46λ; crystallite size La in the a-axis direction is preferably 10 Å or more, still more preferably 15 to 150, particularly preferably 19 to 70.

In addition, if the volume average particle size of the carbonaceous material particles is larger than 500, the ability to support the active material is insufficient and a large amount of active material cannot be supported, resulting in an increase in the electrode capacity of the negative electrode body. I can't force it.

The carrier of the present invention has the above-mentioned carbonaceous material particles as its constituent units, and is an aggregate formed by aggregating these units. And this carrier has a specific surface area of 1rr? /g or more, preferably 10rn'/g or more, more preferably 1
00rrr'/g or more. When the specific surface area deviates from the J2 range, the battery capacity decreases and the battery performance deteriorates.

The structural unit of the carbonaceous material according to the present invention can be produced as follows.

First, one or more of the following organic polymer compounds, condensed polycyclic hydrocarbon compounds, and polycyclic heterocyclic compounds are calcined and
It can be prepared by pyrolysis and carbonization. An important factor in this carbonization process is the heat treatment temperature,
If this temperature is too low, carbonization will not proceed, and if it is too high, the carbonaceous state will be converted to graphite and the G value will become large. Although it varies depending on the starting source used, the heat treatment temperature is usually set in the range of 800 to 3000°C.

Examples of starting sources of carbonaceous materials include cellulose resins; phenolic resins; acrylic resins such as polyacrylonitrile and poly(α-halogenated acrylonitrile); halogenated vinyl resins such as polyvinyl chloride, polyvinylidene chloride, and polychlorinated vinyl chloride. : Boryamideimide resin;
Polyamide resin; Any organic polymer compound such as conjugated resin such as polyacetylene, poly(p-phenylene); For example, naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene.

naphthacene, vicene, perylene, pentaphene.

A condensed polycyclic hydrocarbon compound formed by condensing two or more monocyclic hydrocarbon compounds with three or more members such as pentacene,
Or carboxylic acid, carboxylic acid anhydride of the above compound,
Derivatives such as carboxylic acid imides, various pitches based on mixtures of the above compounds; for example, indoles,
Isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine.

A fused heterocyclic compound formed by at least two heteromonocyclic compounds having 3 or more members such as phenazine and zenatridine bonded to each other or to one or more monocyclic hydrocarbon compounds having 3 or more members.

Carboxylic acids and carboxylic acid anhydrides of each of the above compounds.

derivatives such as carboxylic acid imides, as well as benzene 1.
Examples include 2,4.5-tetracarboxylic acid, its dianhydride, or its diimide.

In this case, each of the above-mentioned parameters can be adjusted to an appropriate range by subjecting the starting source of the carbonaceous material to a pretreatment such as crosslinking treatment, and by appropriately selecting carbonization conditions.

The obtained carbonaceous material has various forms such as powder and block, but in any case, its constituent units are specified by the above parameters. In these forms, the constituent units aggregate with each other to form secondary particles.

In this case, when the volume average particle diameter of the structural unit is 500 Å or less, that of the secondary particles is usually 0.05 to 300 J.
It becomes iIM. In the present invention, it is preferable that the volume average particle diameter of the secondary particles is 100μ or less,
Furthermore, it is preferably 50 microns or less, particularly 20 microns or less.

A desired carrier is manufactured by molding such carbonaceous material particles. That is, the carbonaceous material obtained by firing is pulverized by an appropriate means to form a powder with a predetermined particle size, and this powder and a binder (for example, a powder of a polyolefin thermoplastic polymer such as polyethylene) are mixed in a predetermined amount. They are kneaded at a ratio of 98 to 80:2 to 20 (for example, former: latter = 98 to 80: 2 to 20 by weight), and the mixed material is formed into pellets, sheets, etc. to form a porous body.

Alternatively, the above-mentioned starting source may be previously shaped into an arbitrary shape and then carbonized under the above conditions, and this may be used as a support.

Note that the specific surface area of the support may be adjusted by applying an activation treatment using an oxidizing gas such as water vapor or carbon dioxide gas, for example.

The negative electrode body of the present invention is manufactured by making the above-mentioned carrier support Li or an alkali metal mainly composed of Li.

Supporting methods at this time include chemical methods, electrochemical methods, and physical methods. A method can be applied in which a certain carrier is immersed and electrolytically impregnated using lithium as a counter electrode and the carrier as an anode. By doing so, Li ions or alkali metal ions are doped between the layers of the carrier and supported therein. Note that the active material may be supported not only on the carrier but also on the supporting body of the positive electrode body or on both electrodes.

In the secondary battery of the present invention, for example, a doping phenomenon of Li ions occurs in the negative electrode body during charging, and a dedoping phenomenon of Li ions supported on the negative electrode body occurs during discharging, resulting in reversible electrochemical oxidation. Since the reduction reaction progresses with charging and discharging, the formation of dendrite-shaped deposits that occur on the surface of the negative electrode when it is made of Li foil disappears. Therefore, self-discharge is reduced and charge-discharge cycle characteristics can be significantly improved.

Next, in FIG. 0, which describes the structure of the non-aqueous solvent secondary battery of the present invention with reference to FIG. ) is installed and stored at the bottom.

This positive electrode body is not particularly limited, but for example, V20
5, MoO3, WO3, TiS2, CuS, NrP
A transition metal chalcogen compound such as Ss, FePS3, or VSe2 is used as an active material, and this active material, carbon powder, nickel powder, and a binder are mixed to form a sheet metal core (
Those obtained by integrating with a current collector) are used.

and.

On the positive electrode body (2), the negative electrode body (
4) are laminated.

The separator (3) that holds the electrolyte is made of a material with excellent liquid retention properties, such as a nonwoven fabric made of polyolefin resin. This separator (3) contains LiC 04+ in an aprotic organic solvent such as propylene carbonate, 1,2-dimethoxyethane, or γ-butyl lactone.
LiA sentence On, Li BF4, T, i
It is impregnated with a non-aqueous electrolyte of a predetermined concentration in which an electrolyte such as PFs or LiAsF6 is dissolved.

The negative electrode body (4) is made by bonding and molding a carbonaceous material carrier having the above-mentioned characteristics of the present invention to support Li as an active material, and is placed in a negative electrode can (5) which also serves as a negative electrode terminal. It has been installed.

These positive electrode bodies (2), separators (non-aqueous electrolyte) (3)
, and the negative electrode body (4) constitute a power generation element as a whole. This power generation element is then connected to a positive electrode can (1) and a negative electrode can (
5) The battery is assembled into a battery container.

6 is an insulating backing that separates the positive and negative electrode bodies, and the battery is sealed by bending the opening of the positive electrode can (1) inward.

(Embodiments of the Invention) (1) Manufacture of positive electrode body ■ A mixture of 9 g of 205 powder and 2.5 g of WO3 powder (17.9% with respect to VzOs)' Ft mixture was melted at 1100° C. for 4 hours. The resulting melt was cooled with dry ice and poured onto a copper plate for rapid cooling, and then ground to an average particle size of 3 μm.

5 g of this solid solution powder and 0.5 g of powdered polytetrafluoroethylene were kneaded, and the resulting kneaded product was roll-formed to form a sheet with a thickness of 0.4 mm.

One side of this sheet is a current collector with a wire diameter of 0.1 am, 60
It was crimped onto a mesh stainless steel net to form a positive electrode body.

(2) Manufacture of negative electrode body 108 g of orthocresol, 32 g of rose formaldehyde
After the completion of the reaction, 240 g of ethyl cellosolve and 240 g of ethyl cellosolve were reacted with Log sulfuric acid at 115°C.
It was neutralized by adding 17 g of COs and 30 g of water. Then, the reaction solution was poured into 2 fL of water while stirring at high speed, and the precipitated product was separated and dried to obtain 115 g of a linear high molecular weight novolak resin. The number average molecular weight of this resin was measured by vapor pressure method (in methyl ethyl ketone, 40°C) and was found to be 2,600.

2.25g of the obtained novolak resin and 0.2g of hexamine
After melting and kneading 5g with a roll, the kneaded product was placed in a glass container in a nitrogen atmosphere, and 25g was melted in a nitrogen atmosphere.
Heat treatment was performed at 0°C for 2 hours.

The obtained heat-treated product was placed in an electric furnace and heated in a concentrated air stream.
The temperature was raised to 1900°C at a heating rate of 0°C/min and held for 1 hour. A black carbonaceous material was obtained. This is designated as sample a.

The H/C of this sample is 0.04. dQQ2 is 3.6OA,
Lc was 16 people, 2dlIO was 2.42A, La was 23 people, and G value was 0.68.

Further, an electron micrograph was taken for sample a, and the volume average particle diameter was calculated based on this photograph. That is, a square section of 2 cm on a side is arbitrarily selected in the photograph, the particle size (di) of the particles present there is measured, and Σ(di)'/
The particle size was calculated from the formula ``(di)'' and determined as an average value in three sections. As a result, the volume average particle size was 300 Å or less.

Sample a was pulverized to form a particle group with a volume average particle size of 14 units. The specific surface area of this particle group was measured by the BET method and was found to be 18 m''7 g.

Next, 9.5 g of this powder and 085 g of polyethylene powder were mixed, and 50 mg of this mixture was pressure-molded to a thickness of 0.
It was made into 5mi+ pellets.

Next, this pellet was immersed in a Li ion electrolyte solution having a concentration of 1 mol/mole, and subjected to an electrolytic treatment using the pellet as an anode and Li as a cathode. The electrolytic conditions were a bath temperature of 20°C and a current density of 0.5 mA/c. The electrolysis time was 15 hours. Through such treatment, the carrier (pellet) has a capacity of 1,
A negative electrode body supporting OmAh of Li was obtained.

(3) Assembly of the battery The above-mentioned positive electrode body was installed in a stainless steel positive electrode can with the current collector facing down, and after placing a polypropylene nonwoven fabric as a separator on top of it, Li CfLO was placed thereon.
It was impregnated with a non-aqueous electrolyte prepared by dissolving << in propylene carbonate at a concentration of 1 mol/l. Then, the negative electrode body was placed thereon to form a power generation element.

In addition, the positive electrode body should also be prepared at a concentration of 1 mol/min before being incorporated into the battery.
immersed in LI ion electrolyte of 1 ml, using the positive electrode body as an anode,
It was subjected to electrolytic treatment using lithium as a cathode. The electrolytic conditions are
Bath temperature 20°C, current density 0, 5mA/cm2. "i!The opening time was 15 hours. Through this treatment, Li with a capacity of 8.0 mAh was supported on the positive electrode body.

In this way, a button-shaped secondary battery as shown in FIG. 1 was manufactured.

For comparison, a battery similar to that in Example except that the negative electrode body was made of Li foil itself was fabricated, and this was used as Comparative Example 1.
It was used as a battery.

In addition, a battery similar to that of the example was manufactured, except that the structural parameters and physical properties of the tg carrier were as shown in Table 1, and this was used as a comparative example 2 battery.

Table 1 Note that for the constituent units of this support, electron micrographs were taken in the same manner as in Examples, and the volume average particle diameter was calculated, and it was found to be larger than 500 particles.

(4) Characteristics of each battery For these batteries, constant voltage charging between 3 and 2V -20
Ω constant resistance discharge was repeated, and the capacity retention rate (%: initial capacity is taken as lOO) of the battery in each cycle was measured. The results are shown in Figure 2.

Also, 3.5 to 2. Overcharge cycle evaluation was performed by repeating constant voltage charging at -20Ω and constant resistance discharging between OV and measuring the capacity retention rate of the battery in each cycle. The results are shown in Figure 3.

Furthermore, a self-discharge evaluation experiment during storage at 20° C. was conducted to measure the capacity retention rate relative to the capacity before storage, and the results are shown in FIG.

As is clear from each figure, the battery of the present invention can be discharged in all cases of charge/discharge cycle evaluation, overcharge cycle evaluation, and self-discharge evaluation, and its capacity deteriorates slowly and the charge/discharge cycle life is significantly shortened. It turned out to be long.

[Effects of the Invention] As is clear from the above explanation, the secondary battery of the present invention has a long charge/discharge cycle life without being affected by overcharging, and also uses the active material Li or Ll during charging. Since the main alkali metal can be stably fixed on the carrier, stable high capacity, that is, large current discharge is possible, and the battery has good self-discharge characteristics and is highly reliable. The value is great.

Although the explanation has been given regarding a secondary battery having a button-shaped structure, the technical idea of the present invention is not limited to this structure, and for example, non-aqueous solvents having a cylindrical, flat, or square shape may be used. It can also be applied to secondary batteries.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a button-shaped non-aqueous solvent secondary battery according to an embodiment of the present invention. 1... Positive electrode can, 2... Positive electrode body. 3...Separator (non-aqueous electrolyte). 4... Negative electrode body, 5... Each negative electrode. 6... Insulating backing 7... Current collector FIGS. 2 and 3 are diagrams showing the relationship between charge/discharge cycles and capacity retention rates of batteries in Examples and Comparative Examples of the present invention. Figure 4 shows the state of self-discharge during storage at 20° C. in terms of the capacity retention rate versus the number of days that have passed. Figure 1 0 50 too 150
200 skins (electronic “Suikuru R”)

Claims (1)

[Claims] (1) In a non-aqueous solvent secondary battery equipped with a negative electrode body consisting of an active material and a carrier supporting the active material, (A) the active material is lithium or an alkali metal mainly composed of lithium; B) The support has (i) a hydrogen/carbon atomic ratio of less than 0.15; (ii) Raman spectrum analysis using argon ion laser light with a wavelength of 5145 Å, as determined by the following formula: 1580 ± 100 cm^-^1 Integral value of spectral intensity in the wave number range of /1360±100cm^-^1 ▲Mathematical formula, chemical formula,
There are tables, etc. ▼ G value shown by is less than 2.5; (iii) Interplanar spacing (d_0_0_2) of (002) plane by X-ray wide-angle diffraction method is 3.37 Å or more, crystallite size in C-axis direction (Lc) is 150 Å or less; (iv) the volume average particle diameter is 500 Å or less; and the specific surface area is 1
A non-aqueous solvent secondary battery characterized in that it is m^2/g or more.