JPS63226882A - Nonaqueous solvent secondary cell - Google Patents

Abstract

PURPOSE:To make a secondary cell small-sized and high capacity and improve the charge and discharge cycle characteristic and the overcharge and discharge characteristic by specifying the Li quantity contained in a positive electrode at the charged state or the discharged state respectively in the cell incorporating a negative electrode and the positive electrode with the preset component. CONSTITUTION:In a cell incorporating a positive electrode using noncrystalline V2O3 as the main component and a negative electrode using a carbon material with the G value of less than 2.5 shown by the equation I in the Raman spec trum analysis using argon ion laser rays with the H/C atom ratio of less than 0.15, the face spacing (d002) of the (002) plane by the X-ray wide angle diffraction method of 3.37Angstrom or more, the crystallite size (Lc) in the C-axis direction of 150Angstrom or less, and the wavelength of 5145Angstrom , the Li quantity contained in the positive electrode is set to 0.4-0.8 mol against 1.0mol of V2O5. The Li quantity contained in the positive electrode is set to 1.4-1.8 mol against 1.0 mol of V2O5 when the cell voltage is less than 2.0V.

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, the present invention relates to a non-aqueous solvent secondary battery that can be discharged regardless of overcharging and discharging, and that reduces capacity deterioration. The present invention relates to a small, stable, high-capacity non-aqueous solvent battery that has a significantly long charge/discharge cycle life.

(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.

An example of such a secondary battery is shown in FIG.

The figure is a longitudinal cross-sectional view of a button-shaped non-aqueous solvent secondary battery.

In the figure, 1 is a positive electrode body. The positive electrode body l is.

A mixture of the metal chalcogen compound powder as described above and a binder such as polytetrafluoroethylene is formed into pellets or sheets.

2 is a separator, for example, a porous polypropylene thin film,
It is made of a liquid-retentive material such as polypropylene nonwoven fabric, and is placed on the positive electrode body 1 . This separator 2 contains LiC in an aprotic organic solvent such as propylene carbonate or 1,2-dimethoxyethane.
Cross04+LiAlO4, LiBF4. LiPF6. Li
AsF.

It is impregnated with a non-aqueous electrolyte of a predetermined strength in which an electrolyte such as the following is dissolved.

Reference numeral 3 denotes a negative electrode body placed on the positive electrode body through the separator 2, and is made of Li foil or an alkali metal foil mainly composed of Li.

These positive electrode body 1, separator (non-aqueous electrolyte) 2, and negative electrode body 3 constitute a power generation element as a whole. Then, this power generation element is housed in a battery container consisting of a positive electrode can 4 and a negative electrode can 5, and a battery is assembled. 6 is an insulating backing, and 7 is a current collector interposed between the positive electrode body 1 and the positive electrode can 4. This current collector 7 is usually made of nickel net,
It is composed of a stainless steel wire mesh, punched metal, or foam metal, and is crimped onto one side of a pelletized or sheeted positive electrode body l.

(Problems to be Solved by the Invention) In the secondary battery having the conventional structure as described above, the following problems have occurred, and improvement thereof is required.

This is a problem based on the fact that the negative electrode body is a Li foil or an alkali metal foil mainly composed of Li. In other words, when the battery is discharged, Li from the negative electrode body becomes Li ions and moves to the electrolyte, and during charging, these Li ions become metal Li and are deposited on the negative electrode body again, but if this charge-discharge cycle is repeated, Along with this, the metal Li deposited becomes dendrite-like and grows, and finally, this dendrite-shaped metal Li deposit penetrates the separator and reaches 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 having Li or an alkali metal mainly composed of Li supported on a carbonaceous material support made by firing various organic compounds.

By using such a negative electrode body, the precipitation of Li dendrites has been prevented, but on the other hand, this battery has a very low discharge capacity of about 1/Zoo compared to a primary battery of the same size. There are various problems in practical use, such as the small size and large self-discharge, and the operating period of equipment equipped with this battery is very short and large current discharge is impossible.

In addition, as for the positive electrode body, since it is mainly composed of metal chalcogen compounds, as the depth of charge and discharge increases, the metal chalcogen compounds become inactivated rapidly, and as a result, after several charge and discharge cycles. There is also the problem that battery capacity decreases significantly with repeated use.

As a result, the practical application of this type of secondary battery has been delayed.

The present invention solves the above-mentioned problems and has a small size and high capacity.
The purpose of the present invention is to provide a nonaqueous solvent secondary battery that has excellent charge/discharge cycle characteristics and overcharge/discharge characteristics, has low self-discharge, and is capable of large current discharge.

[Structure of the Invention] (Means for Solving the Problems) The non-aqueous solvent battery of the present invention has an H/C atomic ratio of less than 0.15; Surface spacing (d 002) is 3
．． 37 Å or more, the crystallite size in the C-axis direction (L c) is 150 λ or less, and the wavelength is 5145. In line spectrum analysis using argon laser light, linear equation: 1380 ±
A negative electrode body made of a fired organic material having a G value of less than 2.5 as an integral value of spectral intensity in a wavenumber region of 100 cm; a positive electrode body mainly composed of amorphous V2O; and an active material. Lj; A non-aqueous solvent secondary battery having a battery voltage of 2. OV or more, the positive electrode body contains 0.4 to 0.8 molar amount of Li per 1 molar amount of V2O, and when the battery voltage is 2.0v or less, the positive electrode body contains V2O, Li is 1.8 per mol amount
It is characterized in that it is contained in an amount of ~1.4 mol.

In the battery of the present invention, the active material is Li, and this active material moves back and forth between the above-described negative electrode body and positive electrode body in response to charging and discharging operations of the battery.

First, the negative electrode body has a hydrogen/carbon (H/C) atomic ratio of 0.1.
Less than 5; Interplanar spacing of (OO2) plane (d 00
2) is 3.37 Å or more; and the crystallite size L c) in the C-axis direction is 150 Å or less; in Raman spectrum analysis using an argon ion laser beam with a wavelength s l of 45 A, the following formula: 1360 ± 100 c layer degree The organic material fired body (carbonaceous material) has a G value expressed as an integral value of spectral intensity in a wave number region of 1, which is less than 2.5.

Here, the G value is the wave number 1580±l OOc+s-' in the spectral intensity curve recorded on the chart when Raman spectrum analysis was performed on this carbonaceous material using argon ion laser light with a wavelength of 5145.
It refers to the value obtained by dividing the integral value of the spectral intensity (area intensity) within the range of 1380±100 cm' by the area intensity within the wave number range of 1380±100 cm', and corresponds to a measure of the degree of graphitization of the carbonaceous material.

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

Any of these parameters, especially H/C and d002. If any of Lc deviates from the above range, the overvoltage at the negative electrode body during charging and discharging will increase, and as a result, gas will be generated from the negative electrode body, significantly impairing the safety of the battery. Furthermore, the charge/discharge cycle characteristics are also unsatisfactory.

Furthermore, the carbonaceous material of this support preferably has an H/C of 0.
．． It is less than 0.01, more preferably less than 0.07, particularly preferably less than 0.05.

d 002 is preferably 3.39 to 3.75 people, more preferably 3.41 to 3.70 people; LC is preferably 8 to 100 people, still more preferably 10 to 70 people.

Furthermore, the G value is preferably 0.1 to 2.0 or less, more preferably 0.2 to 1.5.

Moreover, it is preferable that this organic substance fired body satisfies the following conditions in addition to the above conditions.

That is, the crystallite size La) in the a-axis direction determined by wide-angle X-ray diffraction is preferably 10 Å or more, more preferably 15 Å or more and 150 Å or less, and particularly preferably 18 Å or more and 70 Å or less.

Also, it is also found in X-ray wide-angle diffraction (110)
The distance fll a is twice the interplanar spacing dllO.

("2 d 110) is preferably 2.38 A or more,
More preferably, it is 2.39 Å or more and 2.46 Å or less.

A carbonaceous material having such parameters is prepared by carbonizing one or more of the following organic polymer compounds, fused polycyclic hydrocarbon compounds, and polycyclic heterocyclic compounds by calcining ψ thermal decomposition. be able to. 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 convert to graphite and the G value will increase. It is. Although it varies depending on the starting source used, the heat treatment temperature is usually set in the range of 800 to 3000°C.

Starting sources for carbon purchases include, for example, cellulose resins; phenolic resins; acrylic resins such as polyacrylonitrile and poly(alpha-halogenated acrylonitrile); halogenated vinyl resins such as polyvinyl chloride, polyvinylidene chloride, and polychlorinated vinyl chloride. ;Polyamideimide 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, kime + sarin, phthalazine, carbazole, acridine.

A fused heterocyclic compound formed by at least two or more 3-membered ring or more heterocyclic compounds such as phenazine or zenatridine bonded to each other or bonded to one or more 3-membered or more monocyclic hydrocarbon compounds; Examples include derivatives of each compound such as carboxylic acid, carboxylic acid anhydride, and carboxylic acid imide, as well as 1,2,4,5-tetracarboxylic acid of benzene, its dianhydride, or its diimide.

For example, the carbonaceous material prepared in this way has an average particle size of 5
The powder is pulverized into a powder of ~10μ, mixed with a predetermined amount of a binder such as polyethylene, and then pelletized and formed into a sheet to form a negative electrode carrier.

When this is incorporated into a battery as a negative electrode body, it is subjected to the treatment described below to make it support a predetermined amount of Li.

The positive electrode body in the battery of the present invention has an amorphous main component.
It is 20S. P2O as a subcomponent.

These subcomponents, which may include WO, B2o, etc., are useful for promoting and stabilizing the amorphization of v20s during the production of the positive electrode body. The content of these subcomponents is V2
It is preferable that the amount is in the range of 3 to 30 mol% based on 1 mol of os. If it exceeds 30 mol%, the capacity of the obtained battery will be significantly reduced, and if it is less than 3 mol%, it will become amorphous. This is because the cost is too high and it is not suitable for industrial use.

This positive electrode body is made by blending a predetermined amount of each of the above-mentioned components, melting the mixture at a predetermined temperature, and then rapidly cooling the melt to form an amorphous body.
The powder obtained by crushing this amorphous material is mixed with a conductive material such as carbon powder or nickel powder, and a binder such as polytetrafluoroethylene, and then formed into sheets or pellets. can do.

When assembling a battery, a predetermined amount of Li is supported on the negative electrode body and/or the positive electrode body. Various methods such as chemical methods, electrochemical methods, and physical methods can be applied as the supporting method. For example, the above-mentioned negative electrode body (or positive electrode body ) is immersed, and metal Li is used as the counter electrode,
Electrolytic impregnation treatment may be performed using the former as the (+) electrode. In this way, Li ions are supported in the amorphous portion between the layers of the negative electrode body (or positive electrode body).

In this case, the amount of Li ions supported on the negative electrode body and/or the positive electrode body is defined as follows.

That is, in a battery incorporating the above negative electrode body and positive electrode body, the battery voltage is 2.0 V or more (when in a charged state).
When the amount of Li contained in the positive electrode body is V2O,1
The amount of Li contained in the positive electrode body is 0.4 to 0.8 molar amount relative to the molar amount, and when the battery voltage is less than 2.0 V (in the discharge state), the amount of Li contained in the positive electrode body is 1 molar amount per v20s1.
．． It is supported in an amount of 4 to 1.8 moles.

For example, even in a fully charged state where the charging voltage of the battery is constant, the V, O, and Lt of the positive electrode body are 0.4 to 0.
It is preferable that Li is contained in an amount of 8 mol, and in a completely discharged state or an over-discharged state, Li is contained in an amount of V2O5
It is preferably contained in an amount of 1.4 to 1.8 moles per 1 mole.

When in a charging state of 2.0■ or more, V2O.

If Lil is less than 0.4 mole per mole,
Surface deterioration of the positive electrode body progresses, and conversely, if the amount exceeds 0.8 mol, the battery capacity decreases, causing practical problems, which is disadvantageous. Further, in a discharge state, if the amount of Li is less than 1.4 mol per 72051 mol, the amount of Li that moves from the positive electrode body to the negative electrode body during charging is small and the battery capacity decreases.

On the other hand, if the amount is more than 1.8 mol, it is disadvantageous because it causes physical destruction of the positive electrode body during the progress of the discharge cycle or during overdischarge.

During such charging and discharging, L contained in the positive electrode body
The amount of i is regulated by calculating the amount of Li to be supported according to the weight and volume of the positive electrode body (or negative electrode body) when Li is supported by the method described above, and then,
The electrolytic impregnation treatment can be carried out by appropriately selecting conditions such as bath temperature, current density, and electrolysis time.

(Embodiments of the invention) (1) Manufacture of negative electrode Phenol resin powder was heated to 1800°C in N2 gas.
Baked for 1 hour. The obtained fired body powder was pulverized to obtain a powder with an average particle size of 70p1. Next, 9.4 g of this powder and 0.6 g of polyethylene powder were mixed, and 50 g of the mixed powder was mixed.
mg was pressure-molded into pellets with a thickness of 0.5 mm.

The above fired body (7) H/C ratio, d002. The L[ and G values were measured and the results are shown in Table 1. A Raman spectrum diagram is shown in FIG.

Table 2 Note that the dimensions and weight of the pellet are determined by the amount of Li contained in the positive electrode body in the fully charged state of the battery after assembly.
The amount is regulated to be 0.8 to 0.4 mol per 1 mol of zO.

(2) Manufacture of positive electrode body v205 powder 9g, (NH,)3PO4 fist 3H20f
15.0 g (1.23 (-L%) of V2O3) was mixed and the mixture was melted at 800 DEG C. for 4 hours. The resulting melt was quenched by flowing down onto a copper plate cooled with dry ice.

The quenched product was then ground into powder with an average particle size of 10 μm.

This powder was identified by X-ray diffraction and was found to be amorphous.

5 g of this amorphous powder and 0.0 g of polytetrafluoroethylene.
Knead 5g and roll form the obtained kneaded product to a thickness of 0.
．． It was made into a 4 mm sheet. One side of this sheet has a wire diameter of 0.
A 1 mm, 60 mesh stainless steel net was crimped as a current collector to form a positive electrode body.

(3) Assembling the battery The button type battery shown in FIG. 4 was assembled. That is, the above-mentioned positive electrode body 1 was attached to a stainless steel positive electrode can 4 via a current collector 7, and a polypropylene nonwoven fabric was placed thereon as a separator 2, and then L t CQ
An electrolytic solution containing 04 dissolved in propylene carbonate at a concentration of 1 molar was injected. Then, a stainless steel negative electrode 5 having the negative electrode body 3 crimped thereon was attached.

In addition, before assembling the positive electrode body 1, the positive electrode body is immersed in an Lf electrolyte solution with a concentration of 1 molar, and this is used as the (+) electrode and the metal Li
Electrolytic impregnation treatment was performed using the electrode as the (-) electrode. The electrolytic conditions at this time were: bath temperature 20°C, current density 0, 5mA/cm"
, the electrolysis time was 15 hours.

Through this treatment, the positive electrode body has a capacity of 6. Omah.

This means that 1.7 mol of Li was supported per 1 mol of VzO.

For comparison, a battery similar to that of the example was produced, except that the negative electrode body was made of Li foil itself, and this was designated as Comparative Example 1 battery.

In addition, the negative electrode body is H/CO, 01, dH23, 39 people,
A battery similar to that of the example was manufactured and used as a comparative example, except that the fired body had a Li of 2.45 people and a G value of 5 or more. It was used as a battery.

Furthermore, in a fully charged state, the amount of Li in VzO, t mol is 0.
．． A battery was manufactured in the same manner as in the example except that a cathode body was used that carried Li so that the amount of Li was 1.2 mol per 1 mol of VzO in a fully discharged state. This was used as Comparative Example 3 battery.

(4) Characteristics of each battery These batteries were repeatedly charged with a constant voltage of 3 to 2V and discharged with a constant resistance of -15Ω, and the capacity retention rate (%; initial capacity was assumed to be 100) of the battery in each cycle. ) was measured. The results are shown in Figure 1.

In addition, constant voltage charging and -15 Ω constant resistance discharging were repeated between 3 V and OV, and the capacity retention rate of the battery in each cycle was measured to perform deep discharge evaluation.

The results are shown in Figure 2.

Furthermore 3.6v~2. Similar charging and discharging is performed between Ov,
The capacity retention rate was measured and overcharge evaluation was performed, and the results are shown in FIG.

As is clear from the figure, it was found that the battery of the present invention can be discharged regardless of overcharging and discharging, and its capacity deterioration is small and its charge/discharge cycle life is significantly longer.

[Effects of the Invention] As is clear from the above explanation, the nonaqueous solvent secondary battery of the present invention is not affected by overcharging or overdischarging, and has a long charge/discharge cycle life. It has high capacity and high reliability, and its industrial value is great.

Although the explanation was given regarding a secondary battery with a button-shaped structure, the battery of the present invention is not limited to this type, and can also be applied to non-aqueous solvent secondary batteries with shapes such as cylindrical, flat, and square. can.

[Brief explanation of the drawing]

Both FIG. 1 and FIG. 2 are diagrams showing the characteristics of the battery of the present invention. FIG. 3 is a chart of Raman spectrum analysis of the negative electrode body of the example battery. FIG. 4 is a longitudinal sectional view of a non-aqueous solvent battery having a button-shaped structure. 1... Positive electrode body 2... Separator (non-aqueous electrolyte)
3... Negative electrode body 4... Positive electrode can 5... Each negative electrode 6... Insulating backing 7... Current collector cycle (times) □ Figure 1 Figure 2 Figure 5 Friend sail (cm-') □ Figure 4

Claims (1)

[Claims] The hydrogen/carbon atomic ratio is less than 0.15; the interplanar spacing (d_0_0_2) of the (002) plane determined by X-ray wide-angle diffraction is 3.
37 Å or more, crystallite size (Lc) in the C-axis direction is 15
In Raman spectrum analysis using an argon laser beam of 0 Å or less and a wavelength of 5145 Å, the following formula: Integral value of spectral intensity in the wave number range of 1580 ± 100 cm^-^1 G = Spectrum in the wave number range of 1380 ± 100 cm^-^2 A non-aqueous negative electrode body comprising a fired organic material having a G value expressed as an integral value of strength of less than 2.5; a positive electrode body mainly composed of amorphous vanadium pentoxide; and lithium as an active material. In a solvent secondary battery, when the battery voltage is 2.0 V or more, lithium is 0.4 to 0 per 1 mole of vanadium pentoxide in the positive electrode body.
．． When the battery voltage is 2.0 V or less, lithium is contained in an amount of 1.8 to 1.4 moles per mole of vanadium pentoxide in the positive electrode body. Non-aqueous solvent secondary battery.