JPH0544143B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a nonaqueous solvent secondary battery, and more particularly, to a nonaqueous solvent secondary battery that is small, has a long charge/discharge cycle life, and has a stable high capacity. . (Prior art) The main part of the positive electrode body is a transition metal chalcogen compound such as TiS ₂ or MoS ₂ , and the negative electrode body is made of Li or
Efforts are being made to commercialize non-aqueous solvent secondary batteries, which are made of alkali metals mainly consisting of Li, and have a high energy density. (Problems to be Solved by the Invention) However, in such a non-aqueous solvent secondary battery, a problem arises due to 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 is removed from the negative electrode body.
They become ions and move into the electrolyte, and during charging, these Li ions turn into metallic Li and are deposited on the negative electrode body again. However, when this charge/discharge cycle is repeated, the deposited metallic Li becomes dendrite-like. becomes.
Since this dendrite-like Li is an extremely active substance, it decomposes the electrolyte, resulting in the disadvantage that the charge/discharge cycle characteristics of the battery deteriorate. As these grow further, in the end,
This dendrite-like metallic Li deposit penetrates the separator and reaches the positive electrode body, causing a problem in that a short circuit phenomenon occurs. 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 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. There is. By using such a negative electrode body, the precipitation of Li dendrites has been prevented, but on the other hand, a battery incorporating this negative electrode body has a discharge capacity of 1% compared to a primary battery of the same size. /100, it has a large self-discharge rate, and the operating period of devices equipped with this battery is very short, and large current discharge is impossible.There are various problems in practical use. Its use is limited. The present invention aims to provide a non-aqueous solvent secondary battery that eliminates the above-mentioned disadvantages in a non-aqueous solvent secondary battery equipped with a negative electrode body using a carbonaceous material as a carrier. [Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present inventors have conducted intensive research on negative electrode bodies, and as a result, the above-mentioned carriers are carbonaceous particles having the parameters described below. The inventors have discovered that the configuration is effective in achieving the objective, and have developed the non-aqueous solvent secondary battery of the present invention. That is, the non-aqueous solvent secondary battery of the present invention is a non-aqueous 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 an alkali metal mainly composed of lithium; (B) the support has (i) a hydrogen/carbon atomic ratio of less than 0.15; (ii) in Raman spectrum analysis using argon ion laser light with a wavelength of 5145 Å; The following formula; G = integral value of spectral intensity in the wave number region of 1580 ± 100 cm ^-1 / integral value of spectral intensity in the wave number region of 1360 ± 100 cm ^-1 The G value is less than 2.5; (iii) X-ray wide-angle diffraction carbonaceous material particles whose interplanar spacing (d ₀₀₂ ) of the (002) plane by the method is 3.37 Å or more, the crystallite size (Lc) in the C-axis direction is 150 Å or less; (iv) the volume average particle diameter is 500 Å or less; as a constituent unit, and has a specific surface area of 1 m ² /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 an alkali metal mainly composed of Li, and this active material 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, they may contain other atoms such as nitrogen or halogen in an amount of 7 mol% or less, preferably 4 mol% or less, and more preferably 2 mol% or less. Good too. In each parameter that specifies carbonaceous material particles, first, H/C must be 0.15 or less, preferably less than 0.10, more preferably less than 0.07, and 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, and particularly preferably 0.2 to 1.2. Here, the G value is the wavelength for this carbonaceous material.
In the spectrum intensity curve recorded in the chart when performing Raman spectrum analysis using 5145 Å argon ion laser light, the wave number 1580
It refers to the value obtained by dividing the integrated value of the spectral intensity (area intensity) within the range of ±100 cm ^-1 by the area intensity within the wave number range of 1360 ± 100 cm ^-1 , 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, d ₀₀₂ when measured by X-ray wide-angle diffraction method is
3.37 Å or more, Lc must be 150 Å or less,
Preferably d ₀₀₂ is 3.39 to 3.75 Å, Lc is 5 to 150 Å, more preferably d ₀₀₂ is 3.41 to 3.70 Å, Lc is 10 to 80 Å, particularly preferably 12 to 70 Å. In addition, the volume average particle diameter of this carbonaceous material particle is 500
It is necessary to have a thickness of Å or less, preferably 300 Å or less, and more preferably 200 Å or less. Note that the volume average particle size here refers to the volume-weighted average particle size, and the size of the primary particles constituting the carbonaceous material particles (secondary particles) is determined by photographing the cross section of the carbonaceous material particles using an electron microscope. This can be determined by measuring the Among these parameters that specify carbonaceous material particles, if any of H/C, d ₀₂₂ , and Lc deviate from the above range, the overvoltage during charging and discharging in the negative electrode body will increase, and as a result, the negative electrode body Gas is emitted from the battery, significantly compromising the safety of the battery. Moreover, the charge/discharge 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, the distance a _p (=2d ₁₁₀ ), which is twice the interplanar spacing d ₁₁₀ of the (110) plane in X-ray wide-angle diffraction analysis, is preferably 2.38 to 2.47 Å, more preferably 2.39 to 2.46 Å; The crystallite size La is preferably 10 Å or more, more preferably 15 to 150 Å, particularly preferably 19 to 70 Å. In addition, if the volume average particle diameter of the carbonaceous material particles is larger than 500 Å, the ability to support the active material is insufficient and a large amount of the active material cannot be supported, resulting in an increase in the electrode capacity of the negative electrode body. I can't. 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. This support has a specific surface area of 1
m ² /g or more, preferably 10 m ² /g or more, more preferably 100 m ² /g or more. If the specific surface area deviates from the above range, the battery capacity will decrease.
Battery performance deteriorates. The structural unit of the carbonaceous material according to the present invention can be produced as follows. First, one or two of the following organic polymer compounds, fused polycyclic hydrocarbon compounds, and polycyclic heterocyclic compounds are used.
It can be prepared by firing, pyrolyzing, and carbonizing a species or more. 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. Examples of starting sources of carbonaceous materials include cellulose resin; phenolic resin; polyacrylonitrile,
Acrylic resins such as poly(α-halogenated acrylonitrile); halogenated vinyl resins such as polyvinyl chloride, polyvinylidene chloride, and polychlorinated vinyl chloride; polyamideimide resins; polyamide resins; polyacetylene, poly(p-phenylene), etc. Any organic polymer compound such as conjugated resin; for example, naphthalene, phenanthrene, anthracene, triphenylene, pyrene, chrysene,
naphthacene, picene, 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 acids, carboxylic acid anhydrides, and carboxylic acid imides of the above compounds. derivatives, various pitches containing mixtures of the above compounds as main components; for example, indole, isoindole, quinoline, isoquinoline, quinoxaline,
At least two or more heteromonocyclic compounds having 3 or more members such as phthalazine, carbazole, acridine, phenazine, and phenatridine are bonded to each other, or to one or more monocyclic hydrocarbon compounds having 3 or more members. fused heterocyclic compounds, derivatives of the above compounds such as carboxylic acids, carboxylic acid anhydrides, and carboxylic acid imides;
Examples include 2,4,5-tetracarboxylic acid, its dianhydride, or its diimide; and the like. 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. and,
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 μm. In the present invention, it is preferable that the volume average particle diameter of the secondary particles is 100 μm or less, and further,
It is preferably 50 μm or less, particularly 20 μm 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 in a ratio of 98 to 80 to 2 to 20 (for example, the former:latter by weight), and the kneaded product 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 support support Li or an alkali metal mainly composed of Li. The supporting methods at this time include chemical methods,
There are electrochemical methods, physical methods, etc., but for example, the support which is the powder compact described above is immersed in an electrolytic solution containing Li ions or alkali metal ions at a predetermined concentration, and lithium is used as a counter electrode. A method of electrolytic impregnation using the carrier as an anode can be applied. In this way, Li ions or alkali metal ions are doped between the layers of the carrier and supported therein. Note that such support of the active material may be carried out not only on the carrier but also on the carrier of the positive electrode body or 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. As the reduction reaction progresses with charging and discharging, the negative electrode body
This eliminates the formation of dendrite-shaped deposits that occur on the surface of foil. Therefore, self-discharge is reduced and charge-discharge cycle characteristics can be significantly improved. Next, the structure of the non-aqueous solvent secondary battery of the present invention will be explained with reference to FIG. In the figure, a positive electrode body 2 is placed inside a positive electrode can 1 that also serves as a positive electrode terminal.
It is installed and stored at the bottom of the. This positive electrode body is not particularly limited, but includes, for example, V ₂ O ₅ , MoO ₃ ,
A transition metal chalcogen compound such as WO ₃ , TiS ₂ , CuS, NiPS ₃ , FePS ₃ , VSe ₂ is used as an active material, and this active material is mixed with carbon powder, nickel powder, and a binder to form a sheet metal core ( Those obtained by integrating with a current collector) are used. and,
A negative electrode body 4 is laminated on the positive electrode body 2 with a separator 3 in between. The separator 3 that holds the electrolyte is made of a material with excellent liquid retention properties, such as a nonwoven fabric of polyolefin resin. This separator 3 contains LiCO ₄ , LiAO ₄ , LiBF ₄ , LiPF ₆ in an aprotic organic solvent such as propylene carbonate, 1,2-dimethoxyethane, or γ-butyl lactone.
Alternatively, it is impregnated with a non-aqueous electrolyte of a predetermined concentration in which an electrolyte such as LiAsF ₆ is dissolved. The negative electrode body 4 is made by binding and molding a carbonaceous material carrier having the above-mentioned characteristics of the present invention, and using Li as an active material.
It is mounted in a negative electrode can 5 which also serves as a negative electrode terminal. These positive electrode bodies 2, separators (non-aqueous electrolyte)
3 and the negative electrode body 4 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 1 and a negative electrode can 5, and a battery is assembled. 6 is an insulating packing that separates the positive and negative electrode bodies, and the battery is sealed by bending the opening of the positive electrode can 1 inward. (Example of the invention) (1) Manufacture of positive electrode body 9 g of V ₂ O ₅ powder and 2.5 g of WO ₃ powder (17.9 mol % based on V ₂ O ₅ ) were mixed, and this mixture was melted at 1100°C for 4 hours. . The resulting melt was rapidly cooled by flowing down onto a copper plate cooled with dry ice, 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 mm.
It was crimped onto a 60 mesh stainless steel net to form a positive electrode body. (2) Manufacture of negative electrode body 108 g of orthocresol, 32 g of paraformaldehyde, and 240 g of ethyl cellosolve were reacted together with 10 g of sulfuric acid at 115°C. After the reaction is finished, here
It was neutralized by adding 17 g of NaHCO ₃ and 30 g of water. Then,
The above reaction solution was poured into water 2 while stirring at high speed, and the precipitated product was dried in an oven to obtain 115 g of a linear high molecular weight novolac resin. The number average molecular weight of this resin was determined by vapor pressure method (40% in methyl ethyl ketone).
It was 2600 when measured at ℃). 2.25g of the obtained novolac resin and hexamine
After melting and kneading 0.25 g with a roll, the kneaded product was placed in a glass container in a nitrogen atmosphere and heat-treated at 250° C. for 2 hours in a nitrogen atmosphere. The obtained heat-treated product was placed in an electric furnace, and the temperature was raised to 1900°C at a temperature increase rate of 20°C/min in a nitrogen stream, and maintained for 1 hour. A black carbonaceous material was obtained. This is designated as sample a. The H/C of this sample is 0.04, d ₀₀₂ is 3.60Å, and Lc is
16 Å, 2d ₁₁₀ is 2.42 Å, La is 23 Å, and the G value is
It 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 the particle size is calculated from the formula Σ (di) ⁴ / (di) ³ . It was calculated as the average value in the section. As a result, the volume average particle diameter was 300 Å or less. Sample a was pulverized to form a particle group with a volume average particle diameter of 14 μm. BET the specific surface area of this particle group
When measured by method, it was 18 m ² /g. Next, 9.5 g of this powder and 0.5 g of polyethylene powder were mixed, and 50 mg of this mixture was pressure-molded to give a thickness.
It was made into 0.5mm pellets. Next, this pellet was immersed in a Li ion electrolyte solution with a concentration of 1 mol/mole, and the Li was used as an anode.
It was subjected to electrolytic treatment using as a cathode. The electrolysis conditions were a bath temperature of 20° C., a current density of 0.5 mA/cm ² , and an electrolysis time of 15 hours. Through this treatment, the carrier (pellet)
A negative electrode body supporting Li with a capacity of 1.0 mAh was obtained. (3) Battery assembly The above-mentioned positive electrode was placed in a stainless steel positive electrode can with the current collector facing down, and a polypropylene nonwoven fabric was placed on top of it as a separator _. It was impregnated with a non-aqueous electrolyte dissolved in propylene carbonate at 1 mol/mol. Then, the negative electrode body was placed thereon to form a power generation element. Note that, before being incorporated into a battery, the positive electrode body was also immersed in a Li ion electrolyte solution with a concentration of 1 mol/min, and subjected to an electrolytic treatment using the positive electrode body as an anode and lithium as a cathode. Electrolysis conditions are bath temperature 20℃, current density 0.5mA/
cm ² and electrolysis time was 15 hours. Through such treatment, Li with a capacity of 6.0 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 of the example was manufactured, except that the negative electrode body was made of Li foil itself, and this was designated as Comparative Example 1 battery. In addition, a battery similar to that of the example was manufactured, except that the structural parameters and physical properties of the carrier were as shown in Table 1, and this was used as a comparative example 2 battery.

[Table] Regarding the structural units of this support, electron micrographs were taken in the same manner as in the examples, and the volume average particle size was calculated, and it was found to be larger than 500 Å. (4) Characteristics of each battery For these batteries, constant voltage charging and 20kΩ constant resistance discharging were repeated between 3 and 2V, and the capacity retention rate of the battery in each cycle (%: initial capacity is 100) ) was measured. The results are shown in Figure 2. In addition, overcharge cycle evaluation was performed by repeating constant voltage charging and 20 kΩ constant resistance discharging between 3.5 and 2.0 V, and measuring the capacity retention rate of the battery in each cycle. The results are shown in Figure 3. Furthermore, we conducted a self-discharge evaluation experiment during storage at 20℃ and measured the capacity retention rate relative to the capacity before storage.
The results are shown in Figure 4. 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 is an active material during charging.
Since Li or an alkali metal mainly composed of Li can be fixed on the carrier in a stable manner, stable high capacity, that is, large current discharge is possible.
Furthermore, since it is a highly reliable battery with good self-discharge characteristics, its industrial 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... Negative electrode can,
6... Insulating packing, 7... Current collector. Figures 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, and Figure 4 shows the progress of self-discharge during storage at 20°C. It is expressed as a value of capacity maintenance rate against the number of days.

Claims (1)

[Scope of Claims] 1. A non-aqueous solvent secondary battery equipped with a negative electrode body consisting of an active material and a carrier supporting the active material, wherein (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) the following formula in Raman spectrum analysis using argon ion laser light with a wavelength of 514 Å; G = 1580 ± 100 cm Integral value of spectral intensity in wavenumber region of ^-1 /1360±100cm G value expressed as integral value of spectral intensity in wavenumber region of ^-1 is less than 2.5; (iii) Surface of (002) plane by X-ray wide-angle diffraction method A carbonaceous material particle having a spacing (d ₀₀₂ ) of 3.37 Å or more and a crystallite size (Lc) in the C-axis direction of 150 Å or less; (iv) a volume average particle diameter of 500 Å or less; and a specific surface area of 1 m ² /g or more.