CA1290805C - Rechargeable organic electrolyte cell - Google Patents
Rechargeable organic electrolyte cellInfo
- Publication number
- CA1290805C CA1290805C CA000550431A CA550431A CA1290805C CA 1290805 C CA1290805 C CA 1290805C CA 000550431 A CA000550431 A CA 000550431A CA 550431 A CA550431 A CA 550431A CA 1290805 C CA1290805 C CA 1290805C
- Authority
- CA
- Canada
- Prior art keywords
- organic electrolyte
- limn2o4
- cell
- electrolyte cell
- rechargeable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G45/00—Compounds of manganese
- C01G45/12—Manganates manganites or permanganates
- C01G45/1221—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof
- C01G45/1242—Manganates or manganites with a manganese oxidation state of Mn(III), Mn(IV) or mixtures thereof of the type [Mn2O4]-, e.g. LiMn2O4, Li[MxMn2-x]O4
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/581—Chalcogenides or intercalation compounds thereof
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/74—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by peak-intensities or a ratio thereof only
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
Abstract
ABSTRACT OF THE DISCLOSURE
A rechargeable organic electrolyte cell is disclosed which is superior in charge-discharge cycle characteristics.
The cell comprises an anode containing lithium, a cathode formed of LiMn2O4 and organic electrolyte. The LiMn2O4 is preferably such material that has a full width at half maximum between 1.1 and 2.1° of a peak at 2.THETA. equals to 46.1°
by X ray diffraction analysis using FeK.alpha. ray.
A rechargeable organic electrolyte cell is disclosed which is superior in charge-discharge cycle characteristics.
The cell comprises an anode containing lithium, a cathode formed of LiMn2O4 and organic electrolyte. The LiMn2O4 is preferably such material that has a full width at half maximum between 1.1 and 2.1° of a peak at 2.THETA. equals to 46.1°
by X ray diffraction analysis using FeK.alpha. ray.
Description
,S d' ~ P,~ ~ c /1 ~
~9080S
Rechargeable Organic Electrolyte Cell BACKGROUND OF T~E INVENTION
This invention relates to a rechargeable organic electrolyte cell expected to be used as a power source for a variety of small sized electronic apparatuses.
So-called organic electrolyte cells, making use of lithium as the anode active material and an organic electrolyte as the electrolyte, are low in self-discharging, high in voltage and excellent in shelf life, so that they may be used with high operational reliability for a prolonged period of five to ten years. For this rèason, they are used at present extensively in electronic `time pieces or as a variety of memory backup power sources.
However, the presently used organic electrolyte cells are primary cells, such that their service life is terminated when used once so that they leave a lot to be desired especially from economic considerations.
; For this reason, with the rapid progress in a variety of electronic apparatuses, a strong demand has been raised for rechargeable organic electrolyte cells that can be used conveniently and economically for a prolonged time, and many researches are being conducted for developing this type of cells.
In general, me~al lithium, lithium alloys, such as Li-Al alloys, electroconductive polymer materials, such as ~ 2~308~;
polyacetylene or polypyrrole, doped with lithium ions, or intercalation compounds with lithium ions mixed into crystals thereof, are used as the anodic material of the cell, while an organic electrolytic solution is used as the electrolyte thereof.
On the other hand, various materials have been proposed as the cathodic active material. Examples of these materials include TiS2, ~oS2, NbSe2 or V205, as disclosed in the Japanese Laid-open Patent Publication No. 54836/1975.
The discharging reaction of the cell making use of these materials proceeds as the lithium ions of the anode are intercalated into the spacings between these materials, whereas the charging reaction proceeds as the lithium ions are deintercalated from these spacings towards the anode. In other words, the charging and discharging proceeds by a repetition of the reactions in which the lithium ions of the anode make entrance into and exit from -the interlayer spaeings of the cathode aetive material. For example, when using TiS2 as the eathode active material, the charging and discharging reaction may be represented by the formula disehaxgingTiS2 ~ xLi ~ e C ~LiXTiS2 (I) charging With the conventional cathodic material, charging and diseharging proeeeds by the above reaction. However, the eonventional cathodic material has a defieiency that, with ;.:,, ~ ~oao~
the repetition of the charging and discharging reactions, the discharge capacity thereof is decreased gradually. It is because the lithium ions, once having made an entrance into the cathode active material, tend to exit therefrom only with i~ .
increased difficulties, such that only a limited fraction of the lithium ions having made an entrance into the cathode active material by discharging are returned towards the anode by the charging reaction. In other words, the lithium ions are caused-to rernain in the cathode in the form of LiXTiS2 so that the number of the lithium ions taking part in the ensuing charging reaction is decreased. The result is that the discharge capacity of the cell af`ter the charging is decreased and the cyclic service life characteristics of the cell are correspondingly lowered.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved rechargeable organic electrolyte cell.
It is another object of the present invention to provide a rechargeable organic electrolyte cell superior in charge-discharge cycle characteristics.
It is another object of the present invention to provide a rechaxgeable organic electrolyte cell which is charged and discharge up to nearly full capacity of the active material contained in the cell.
~ ccording to one aspect of the present inven-tion, there ~290~305i is provided a rechargeable organic electrolyte cell which comprises an anode containing Li, a cathode formed of LiMn204 and an organic electrolyte. The LiMn204 preferable has a full width at half maximum between 1.1 and 2.1 of a peak at 2~ equal to 46.1 by X-ray diffraction analysis using FeK~
ray.
BRIEF DE~CRIPTION OF THE DRAWINGS
Fig. 1 is a chart showing charging and discharging cycle characteristics of a rechargeable organic electrolyte secondary cell making use of TiS2 and MoS2 as the cathode material.
Fig. 2 is a diagrammatic sectional view showing an exemplary rechargeable organic electrolyte secondary cell.
Fig. 3 is a char-t showing the result of an X-ray diffraction analysis of LiMn204 syntheslzed from electrolytic manganese dioxide and lithium carbonate.
Fig. 4 is a chart showing discharging characteristics of an rechargeable organic electrolyte secondary cell according to the present invention.
Fig. 5 is a chart showing charging characteristics of an organic electrolyte secondary celi according to the present invention.
Fig. 6 is a chart showing charge-discharge cycle characteristics of an organic electrolyte secondary cell according to the present invention.
~L290805 Fig. 7 is a chart showing the result of an X-ray diffraction analysis of LiMn204 synthesized from electrolytic manganese dioxide and lithium carbonate.
Fig. 8 is a chart showing the difference in the discharging characteristics caused by the difference in the full width at half maximum of the diffraction peak of LiMn204 employed in the cell.
Fig. 9 is a chart showing the difference in the charging characteris-tics caused by the difference in the full width half maximum of the diffraction peak of LiMnO4 employed in the cell.
Fig. 10 is a chart showing the r~elation between the discharging capacity of the non-aqueous electrolyte cell and the sintering temperature of LiMn204.
Fig. 11 is a chart showing the result of an X-ray diffraction analysis of LiMn204 synthesized from electrolytic manganese dioxide and lithium carbonate.
Fig~ 12 is a chart showing an X-ray diffraction spectrum of LiMn204 obtained by sinterinig manganese dioxide and lithium iodide at 300 C.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With a view towards achieving the above objects, the present inventors conducted various and repeated investigations into Einding a material less subject to deterioration in the intercalation of the lithium ions so as lX9~)8g)5 to be used as the cathode active material. As a result thereof, we have obtained an information that a compound LiMn2O4 having the splnel structure gives favorable results.
On the basis of such information, the present invention is characterized in that it comprises an anode containing lithium, a cathode formed essentially of LiMn2O4, and an organic electrolyte~
The compound LiMn2O4 employed as the cathode active material of the organic electrolyte cell according to the present rechargeable invention may be easily obtained by reacting lithium carbonate Li2CO3 and manganese dioxide MnO2 by heating in 400 C or by reactin`g lithium iodide LiI
and manganese dioxide MnO2 by heati`ng in a nitrogen atmosphere at 300 C. The compound LiMn2O4 itself is shown for example in the United States Patent No. 4246253 as the starting material for producing MnO2. However, when a cell is prepared by using LiMn2O4 obtained in accordance with the teaching of the United States Patent No. 4246253, that is, by a method including sintering lithium carbonate and manganese dioxide at a temperature of 800 to 900 C, as the cathode active material of the cell, the capacity of the order of only about 30 percent of the theoretical charging and discharging capacity of the cell is obtained.
Above all, by using LiMn2O4 in which the full width at half maximum of a diffraction peak at a diffraction angle of s 46.1 in the case of in X-ray diffraction analysis using FeK~
rays is in the range between 1.1 and 2.1, as the cathode active material of the rechargeable organic electrolyte cell, the charging and discharging capacity nearly equal to the theoretical capacity may be obtainèd. While LiMn204 may be prepared by sintering lithium carbonate and manganese dioxide in air, the full width at half maximum value of the diffraction peak observed upon X-ray diffraction analysis is changed by adjusting the sintering temperature. According to the present invention, the compound LiMn204 in which the full width at half maximum of the diffràction peak at the diffraction angle of 46.1 in the` case of an X-ray diffraction analysis using FeK~ rays is in the range of 1.1 and 2.1, is selectively employed. When the full width at half maximum value is less than the above range, the desired discharging are not achieved.
Lithium iodide may be used in place of lithium carbonate, while the sintering may be performed in an inert gas, such as nitrogen, instead of in air.
As the lithium containing material, employed as the anode material, metal lithium, lithium alloys, such as LiAl, LiPb, LiSn, LiBi or LiCd, electroconductive polymer materials, such as polyacetylene or polypyrrole, doped with lithium ions, or intercalation compounds with lithium ions mixed into crystals thereof, such as TiS2 or MoS2 containing lithium in the intercalation spacings thereof, may be employed.
As the electrolyte solution, non-aqueous organic electrolytes may be employed in which a lithium salt is used as an electrolyte and dissolved in an organic solvent.
Example of the organic solvent may include one or a mixture of two or more of 1,2-dimethoxyethane, 1,2-diethoxyethane, ~ -butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane or 4-methyl-1,3-dioxolane.
Examples of the electrolyte may incIude one or a mixture of two or more of LiCl04, LiAsF6, LiPF6,`LiBF4 or Li~(C6~5)4.
By using LiMnO4 as the cathode act~ve material of the rechargeable organic electrolyte cell, the lithium ions that have migrated towards the cathode by the discharging reaction may be optimally deintercalated during the charging reaction.
In addition, when LiMn204 in which the full width at half maximum of the diffraction peak at a diffraction angle of 46.1 in case of an X-ray diffraction analysis using FeK~
rays is in the range between 1.1 and 2.1, is selectively employed as the cathode active material of the non-aqueous electrolyte cell, it hecomes possible to procure a charging and discharging capacity of not less than 90 percent the theoretical charging capacity of the material.
The description with reference to specific test examples . ^ -:: '' ' .' ~ .
~2~0~(35 is given below. It is -to be understood that these examples are for illustration only and are not intended to limit the scope of the present invention.
OMPARATIVE EXAMPLE
The cycle characteristic of the Li/TiS2 or Li/MoS2 rechargeable organic electrolyte cell, making use of TiS2 or MoS2 as the cathode active material, were investigated. The results are shown in Fig. 1, from which it is seen that, wi-th the rechargeable organic electrolyte cell making use of TiS2 or MoS2 as the cathode active material, the discharge capacity of the cell is rapidly decreased after the repetition of about ten charge-dischar`ge cycles, such that the discharge current is only one half the`~original discharge capacity of the cell. It is also seen that the discharge capacity ~is continuously decreased with a further repetition of the charge-discharge cycles.
; In accordance with the following production steps, a button type cell shown in Fig. 2 was produced.
87 grams and 26 grams each of marketed manganese dioxide and lithium carbonate were thoroughly mixed in a mortar and the resulting mixture was heat-treated on an alumina boat in a nitrogen gas at 400 C Eor 10 hours. The product obtained after cooliny was subjected to an X-ray analysis, whereby a chart of the X-ray analysis as shown in Fig. 3 was obtained.
~9~8~5 In comparison with the material represented by the formula LiMn204 in the ASTM card, the chart was found to be coincident completely with the X-ray diffraction chart for LiMn204. Thus the material obtained by the above described process could be identified to be LiMn204.
Then, 88.9 parts by weight of LiMn204 produced by the above described process were admixed with 9.3 parts by weight of graphite and then with 1.8 parts by weight of polytetrafluoroethylene as the binder. The resulting mixture was then press-formed into a pellet of 15.5 mm in diameter and 0.3 mm in thickness under application of a pressure of 3 tons/cm2. The pellet thus produced was dried in vacuum at 300 C for five hours to a cathode pellet 5.
On the other hand, an aluminum foil of 0.3 mm in thickness was punched to a disk shaped piece of 15.5 mm in diameter, which was then spot welded to an anodic can 2. A
lithium foil of 0.3 mm in thickness was punched to a disk shaped piece of 15 mm in diameter, which was then press bonded onto the aluminum foil piece to form an anodic pellet 1 to be used as an anode.
On this anode was placed a non-woven propylene cloth as a separator 3 and propylene carbonate with LiCl04 dissloved therein at a rate of 1 mol/liter was added as an electrolyte solution. A gasket 4 formed of a suitable synthetic material was press fitted to the anode and the previously obtained ~;~90~305 cathode pellet 5 was placed on the separator 3. A cathodic can 6 was placed over the cathode pellet and caulk for hermetically sealing an openlng that may be present between it and the gasket 4 to form an rechargeable organic electrolyte cell having an outside diameter of 20 mm and a thickness of 1.6 mm.
The sample cell obtained as above was subjected to a discharge test through a resistor of 1 kiloohm. The discharge curve shown in Fig. 4 was obtained.
The discharge reaction may be expressed by the following reaction formula Li+ + LiMn204 ~ e ~ 2LiM O
The completely discharged sample cel`l was then charged with a current of 2 mA with the upper voltage setting of 3.1 V. The results are shown in Fig. 5. It is seen from this figure that the charging voltage curve is extremely flat.
This possibly implies that deintercalation of lithium ions in the charging reaction shown by the formula 2LiMnO2 ~ LiMn2O4 + Li+ ~ e has proceeded smoothly.
The sample cell showing the charging and discharging characteristics as described above was charged and discharged repeatedly for investigating into cyclic charge-discharge characteristics of the sample cell. It was seen that, as shown in Fig. 6, deterioration in the discharge capacity due 129~80s to the cyclic charging and discharging was not observed in the least and the obtained rechargeable cell had truely superior properties.
EXAMPLE 2 a In the present Example 2, various LiMn2O4 samples were prepared using various sintering temperatures and so-called button-type cells were prepared with the use of -these samples to investigate into the charge-discharge characteristics of th~se cells.
First, in order -to produce LiMn2O4 having favorable properties as the cathode active material of the organic electrolyte cell, the sintering temperatures of LiMn2O4 were changed variously to investigate into changes in the X-ray diffraction peaks and in discharge capacities cause by these changes in the sintering temperatures.
For producing the LiMn2O4 sample, 86.9 grams (1 mol) and 18.5 grams (0.25 mol) each of marketed manganese dioxide and lithium carbonate were mixed while being ground thoroughly in a mortar. The resulting mixture was sintered in air for one hour on an alumina boat at a sintering temperature of 430 to 900 C.
The product was cooled and analyzed by the X-ray di~fraction analysis using FeK~ rays and the measurement conditions including the tube voltage of 30 kV, tube current of 15 mA, measurement range of 2000 cps, scanning speed of ,:
., .
' ' ~' ., ,~
.. . . .
: . -: ,.. ~........... . . ;.
... ..
1/min., chart speed of 5 mmlmin., diffusion slit width of 1 and the light slit width of 0.6 mm. On collation with the card index of the American Society for Testing Materials (ASTM), the product could be identified to be LiMn2O4. Fig.
7 shows an X-ray diffraction spectrum of LiMn2O4 obtained at a sintering temperature of 460 C, a~ an example. The full width at half maximum oE the diffxaction peak at a diffractlon angle of ~6.1 is 2.08, which is larger than that of LiMn204 obtained by sintering at 800 to 900 C in accordance with the conventional production process thereof.
The full width at half maximum data for LiMn2O4 obtained by sintering at various other sintering temperatures are summarized in Table 1.
Then, using the LiMn2O4 s~mples obtained at the respective sintering temperatures as described above, organic electrolyte cells such as shown in cross-section in Fig. 2 were prepared. 86.4 parts by weight of LiMn2O4 were thus admixed with 8.6 parts by weight of graphite and 5 parts by weight of polytetrafluoroethylene (Teflont m ) to a cathodlc composition which was then formed a cathodic pellet 5 of 15.5 mm in diameter and 0.44 mm in thickness and having a weight of 0.213 gram.
A marketed aluminum plate of 0.3 mm in thickness was punched to a disk shaped piece of 15 mm in diameter and bonded to an anodic can 2 by spot welding. A lithium foil of ~; .... . , ,1 : `:
0.18 mm in thickness was punehed to a disk shaped piece of15 mm in diameter and press bonded to the aluminum piece to an anodic pellet 1 to form an anode.
Then a separator 3 was applied to the anode and a gasket 4 formed of a suitable synthetie material was fitted thereto.
Then, an eleetrolyte solution mixture of 1,2-dimethoxyethane and propylene earbonate with LiCl04 dissolved therein at a rate oE 1 mol/liter was introduced. The previously produced cathodic pellet 5 was applied to the separator 3 and then eovered by a cathodic ean 6, whieh was then eaulked for hermetically sealing an opening or gap between it and the anode to produce a so-called button type organic electrolyte cell having a diameter of 20 mm and a thickness of 1.6 mm.
Using the LiMn204 samples prepared in this manner at the various sintering temperatures, organic eleetrolyte cells A, B, C, D, E, F, G, H, I, J and K were produeedO In Table 1, these eell appellations are entered in assoeiation with the sintering temperatures for the LiMn204 samples used in the cells.
Investigations were made into charging and diseharging eharaeteristies of the thus produeed organie eleetrolyte eells A through K.
8~
_ .
full width at -ells sintering discharge half maximum at a temperature capacity X-ray diffraction angle of 46.1 _ A 430 C 24.0 mAH 1.80 B 450 25.9 2.10 C 460 25.6 2.08 D 480 24.9 1.91 E 500 23.5 1.55 F 520 20.3 1.10 G 550 17.4 0.93 ll 600 14.6 0.78 I 700 12.4 0.57 J 800 10.0 0.35 K 900 7.5 0.26 .
These organic electrolyte cells were respectively connected to resistances of 1 kiloohm,and the discharge characteristics were measured with the terminal voltage of 2.0 V. The results are shown in Table 8, wherein the cell voltage V and the discharge time Hr are plotted on the ordinate and the absissa, respectively. From this figure, the mean discharge voltage may be read and converted into the mean discharge current which may then be multiplied by the duration of discharging until reaching the terminal voltage to give the discharge capacity in terms of the ampere-hour capacity, which is given herein by units of mAH since the resistnace of 1 ]ciloohm is used in the present measurement system. The discharge capacities obtained in this manner are also shown in Table 1.
Then, with the terminal voltage being set to 3.1 V, the ~29~305 current of 4 mA was caused to flow through each of the thus discharged cells, for measuring the charging characteristics.
The results are shown in Fig. 9, wherein the cell voltage V
and the charging time Hr are plotted on the ordinate and the abscissa, respectively. The organic electrolyte cell according to the present invention has extremely stable charge discharge characteristics, as may be seen from Figs. 8 and 9 showing that the major portions of the curve for each cell are flat, that is, do not show voltage changes with -the charging time. This is an indication that intercalation and deintercalation of lithium ions into and from the spacings between the adjoining LiP~n2O4 layers occùr extremely promptly and thus LiMn2O4 obtained in the above described manner has superio properties as the cathode active material.
In Fig. 10, the relation between the discharge capacity and the sintering temperature shown in Table 1 is shown. In Flg. 10, the discharging capacity in mAH is shown on the ordinate and the sintering temperature in C is shown on the abscissa. It is seen from Table 1 and Figs. 8 and 10 that the cells A, B, C, D, E and F have the excellent discharging capacity of not less than 20 mAH and hence are may meet practical demands and that the full width at half maximum values of LiMn2O4 as the cathode active material of these cells at an X-ray diEEraction angle of 46.1 are all within the range of between 1.1 and 2.1. The full width half maximum values may be controlled by changing the sintering temperature of LiMn2O4, with the optimum sintering temperature range being 430 to 520. It has been found that the discharging capacity is gradually lowered when the sintering temperature higher than the above range is employed. The discharge capacity is similarly lowered when the sintering temperature lower than the above range is employed, such that, with the cell L making use of LiMn2O4 obtained by sintering at 400 C, the discharging capacity was lowered to 19.1 mA~, as shown in Fig. 10. The X-ray diffraction spectrum for this LiMn2O4 sample is as shown in Fig. 11. It is found from this figure that, with the lower sintering temperature of 400 C, parts of lithium carbonate and manganese dioxide remain unreacted, so that desired characteristics are not attained.
In the present Example, in preparing LiMn2O4, lithium iodide was used in place of lithium carbonate shown in the Example 1, while the sintering was performed in a nitrogen atmosphere instead of in air.
50 grams (0.57 mol), 39 grams (0.29 mol) and 5.2 grams each of marketed manganese dioxide, lithium iodide and graphite were thoroughly mixed while being ground in a mortar and the resulting mixture was press molded into a pellet under a pressure of 3 tons/cm2. This pellet was placed on an 9V8~5 alumina boat and sintered in a nitrogen atmosphere at 300 C
for six hours. After sintered, the product was cooled and washed with ethyleneglycol dimethylether. The product was analyzed by X-ray diffraction analysis under the conditions specified in the Example 2, and was identified to be LiMn2O4 on collation with the card index of ASTM. The X-ray diffraction spectrum for this product is shown in Fig. 12.
The full width at half maximum value of a peak at a diffraction angle of 46.1 was 1.57. In this figure, the peak corresponding to graphite may also be seen in addition to the peaks appearing in Fig. 7.
Then, to 95 parts by weight of L`iMn2O4 were added 5 parts by weight of polytetrafluoroethy`lene ~Teflon) as a binder to give a cathodic composition. The ensuing assemblying of the organic electrolyte cell was performed in accordance with the method described in Example 2 to produce the cell sample M. The discharge capacity of the cell sample M was tested by a method according to the Example 2 and found to be as high as 23.1 mAH.
In the present Example 4, LiMn2O4 was prepared by sintering in a nitrogen atmosphere, as in Example 3, instead of in air.
86.9 grams (1 mol) and 1~.5 grams (0.25 mol) each of marketed manganese dioxide and lithium carbonate were ~.29~S
thoroughly mixed while being ground in a mortar. The produced mixture was placed on an alumina boat and sintered in a nitrogen atmosphere at 450 C for one hour. The product was analyzed by the X-ray diffraction analysis under the conditions stated in the Example 1 and thereby identified to be LiMn2O4. The full width at half maximum value of the peak at a diffraction angle of 46.1 was 1.60.
The ensuing assembling of the organic electrolyte cell was performed by the method according to the Example 2 to produce the cell sample N. The discharge capacity of the cell sample was tested by a method according to the Example 2 and found to be as high as 22.9 mAH.
From the foregoing it is seen that,~ by using LiMn2O4 as the cathode active material of the rechargeable organic electrolyte cell, the lithium ions once migrated towards the cathode during the discharging reaction may be optimally deintercalated during the charging reaction, with the result that the charge-discharge cycle life properties of the rechargeable organic electrolyte cell may be lmproved significantly.
In this manner there is provided an rechargeable organic electrolyte cell suffering from only limited deterioration in the cell capacity caused by repeated charge-discharge cycles and hence superior in cyclic life characteristics.
When LiMn2O4 used as the cathode active material of the rechargeable organic electrolyte cell has a specified full width at half maximum of the diffraction peak at a dlffraction angle of 46.1 in the range of 1.1 to 2.1, it is possible to elevate the charge-discharge characteristics of the cell obtained by using such cathode active material to higher than 90 percent its theoretical capacity.
Since LiMn2O4 is a less costly material, it is not only excellent from economic considerations as compared to conven-tional cathode active materials, such as TiS2, MoS2, NbSe~ or V2O5, but also contributes to energy saving in the production process of the organic electrclyte cell.
. ' ' .
~9080S
Rechargeable Organic Electrolyte Cell BACKGROUND OF T~E INVENTION
This invention relates to a rechargeable organic electrolyte cell expected to be used as a power source for a variety of small sized electronic apparatuses.
So-called organic electrolyte cells, making use of lithium as the anode active material and an organic electrolyte as the electrolyte, are low in self-discharging, high in voltage and excellent in shelf life, so that they may be used with high operational reliability for a prolonged period of five to ten years. For this rèason, they are used at present extensively in electronic `time pieces or as a variety of memory backup power sources.
However, the presently used organic electrolyte cells are primary cells, such that their service life is terminated when used once so that they leave a lot to be desired especially from economic considerations.
; For this reason, with the rapid progress in a variety of electronic apparatuses, a strong demand has been raised for rechargeable organic electrolyte cells that can be used conveniently and economically for a prolonged time, and many researches are being conducted for developing this type of cells.
In general, me~al lithium, lithium alloys, such as Li-Al alloys, electroconductive polymer materials, such as ~ 2~308~;
polyacetylene or polypyrrole, doped with lithium ions, or intercalation compounds with lithium ions mixed into crystals thereof, are used as the anodic material of the cell, while an organic electrolytic solution is used as the electrolyte thereof.
On the other hand, various materials have been proposed as the cathodic active material. Examples of these materials include TiS2, ~oS2, NbSe2 or V205, as disclosed in the Japanese Laid-open Patent Publication No. 54836/1975.
The discharging reaction of the cell making use of these materials proceeds as the lithium ions of the anode are intercalated into the spacings between these materials, whereas the charging reaction proceeds as the lithium ions are deintercalated from these spacings towards the anode. In other words, the charging and discharging proceeds by a repetition of the reactions in which the lithium ions of the anode make entrance into and exit from -the interlayer spaeings of the cathode aetive material. For example, when using TiS2 as the eathode active material, the charging and discharging reaction may be represented by the formula disehaxgingTiS2 ~ xLi ~ e C ~LiXTiS2 (I) charging With the conventional cathodic material, charging and diseharging proeeeds by the above reaction. However, the eonventional cathodic material has a defieiency that, with ;.:,, ~ ~oao~
the repetition of the charging and discharging reactions, the discharge capacity thereof is decreased gradually. It is because the lithium ions, once having made an entrance into the cathode active material, tend to exit therefrom only with i~ .
increased difficulties, such that only a limited fraction of the lithium ions having made an entrance into the cathode active material by discharging are returned towards the anode by the charging reaction. In other words, the lithium ions are caused-to rernain in the cathode in the form of LiXTiS2 so that the number of the lithium ions taking part in the ensuing charging reaction is decreased. The result is that the discharge capacity of the cell af`ter the charging is decreased and the cyclic service life characteristics of the cell are correspondingly lowered.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved rechargeable organic electrolyte cell.
It is another object of the present invention to provide a rechargeable organic electrolyte cell superior in charge-discharge cycle characteristics.
It is another object of the present invention to provide a rechaxgeable organic electrolyte cell which is charged and discharge up to nearly full capacity of the active material contained in the cell.
~ ccording to one aspect of the present inven-tion, there ~290~305i is provided a rechargeable organic electrolyte cell which comprises an anode containing Li, a cathode formed of LiMn204 and an organic electrolyte. The LiMn204 preferable has a full width at half maximum between 1.1 and 2.1 of a peak at 2~ equal to 46.1 by X-ray diffraction analysis using FeK~
ray.
BRIEF DE~CRIPTION OF THE DRAWINGS
Fig. 1 is a chart showing charging and discharging cycle characteristics of a rechargeable organic electrolyte secondary cell making use of TiS2 and MoS2 as the cathode material.
Fig. 2 is a diagrammatic sectional view showing an exemplary rechargeable organic electrolyte secondary cell.
Fig. 3 is a char-t showing the result of an X-ray diffraction analysis of LiMn204 syntheslzed from electrolytic manganese dioxide and lithium carbonate.
Fig. 4 is a chart showing discharging characteristics of an rechargeable organic electrolyte secondary cell according to the present invention.
Fig. 5 is a chart showing charging characteristics of an organic electrolyte secondary celi according to the present invention.
Fig. 6 is a chart showing charge-discharge cycle characteristics of an organic electrolyte secondary cell according to the present invention.
~L290805 Fig. 7 is a chart showing the result of an X-ray diffraction analysis of LiMn204 synthesized from electrolytic manganese dioxide and lithium carbonate.
Fig. 8 is a chart showing the difference in the discharging characteristics caused by the difference in the full width at half maximum of the diffraction peak of LiMn204 employed in the cell.
Fig. 9 is a chart showing the difference in the charging characteris-tics caused by the difference in the full width half maximum of the diffraction peak of LiMnO4 employed in the cell.
Fig. 10 is a chart showing the r~elation between the discharging capacity of the non-aqueous electrolyte cell and the sintering temperature of LiMn204.
Fig. 11 is a chart showing the result of an X-ray diffraction analysis of LiMn204 synthesized from electrolytic manganese dioxide and lithium carbonate.
Fig~ 12 is a chart showing an X-ray diffraction spectrum of LiMn204 obtained by sinterinig manganese dioxide and lithium iodide at 300 C.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With a view towards achieving the above objects, the present inventors conducted various and repeated investigations into Einding a material less subject to deterioration in the intercalation of the lithium ions so as lX9~)8g)5 to be used as the cathode active material. As a result thereof, we have obtained an information that a compound LiMn2O4 having the splnel structure gives favorable results.
On the basis of such information, the present invention is characterized in that it comprises an anode containing lithium, a cathode formed essentially of LiMn2O4, and an organic electrolyte~
The compound LiMn2O4 employed as the cathode active material of the organic electrolyte cell according to the present rechargeable invention may be easily obtained by reacting lithium carbonate Li2CO3 and manganese dioxide MnO2 by heating in 400 C or by reactin`g lithium iodide LiI
and manganese dioxide MnO2 by heati`ng in a nitrogen atmosphere at 300 C. The compound LiMn2O4 itself is shown for example in the United States Patent No. 4246253 as the starting material for producing MnO2. However, when a cell is prepared by using LiMn2O4 obtained in accordance with the teaching of the United States Patent No. 4246253, that is, by a method including sintering lithium carbonate and manganese dioxide at a temperature of 800 to 900 C, as the cathode active material of the cell, the capacity of the order of only about 30 percent of the theoretical charging and discharging capacity of the cell is obtained.
Above all, by using LiMn2O4 in which the full width at half maximum of a diffraction peak at a diffraction angle of s 46.1 in the case of in X-ray diffraction analysis using FeK~
rays is in the range between 1.1 and 2.1, as the cathode active material of the rechargeable organic electrolyte cell, the charging and discharging capacity nearly equal to the theoretical capacity may be obtainèd. While LiMn204 may be prepared by sintering lithium carbonate and manganese dioxide in air, the full width at half maximum value of the diffraction peak observed upon X-ray diffraction analysis is changed by adjusting the sintering temperature. According to the present invention, the compound LiMn204 in which the full width at half maximum of the diffràction peak at the diffraction angle of 46.1 in the` case of an X-ray diffraction analysis using FeK~ rays is in the range of 1.1 and 2.1, is selectively employed. When the full width at half maximum value is less than the above range, the desired discharging are not achieved.
Lithium iodide may be used in place of lithium carbonate, while the sintering may be performed in an inert gas, such as nitrogen, instead of in air.
As the lithium containing material, employed as the anode material, metal lithium, lithium alloys, such as LiAl, LiPb, LiSn, LiBi or LiCd, electroconductive polymer materials, such as polyacetylene or polypyrrole, doped with lithium ions, or intercalation compounds with lithium ions mixed into crystals thereof, such as TiS2 or MoS2 containing lithium in the intercalation spacings thereof, may be employed.
As the electrolyte solution, non-aqueous organic electrolytes may be employed in which a lithium salt is used as an electrolyte and dissolved in an organic solvent.
Example of the organic solvent may include one or a mixture of two or more of 1,2-dimethoxyethane, 1,2-diethoxyethane, ~ -butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane or 4-methyl-1,3-dioxolane.
Examples of the electrolyte may incIude one or a mixture of two or more of LiCl04, LiAsF6, LiPF6,`LiBF4 or Li~(C6~5)4.
By using LiMnO4 as the cathode act~ve material of the rechargeable organic electrolyte cell, the lithium ions that have migrated towards the cathode by the discharging reaction may be optimally deintercalated during the charging reaction.
In addition, when LiMn204 in which the full width at half maximum of the diffraction peak at a diffraction angle of 46.1 in case of an X-ray diffraction analysis using FeK~
rays is in the range between 1.1 and 2.1, is selectively employed as the cathode active material of the non-aqueous electrolyte cell, it hecomes possible to procure a charging and discharging capacity of not less than 90 percent the theoretical charging capacity of the material.
The description with reference to specific test examples . ^ -:: '' ' .' ~ .
~2~0~(35 is given below. It is -to be understood that these examples are for illustration only and are not intended to limit the scope of the present invention.
OMPARATIVE EXAMPLE
The cycle characteristic of the Li/TiS2 or Li/MoS2 rechargeable organic electrolyte cell, making use of TiS2 or MoS2 as the cathode active material, were investigated. The results are shown in Fig. 1, from which it is seen that, wi-th the rechargeable organic electrolyte cell making use of TiS2 or MoS2 as the cathode active material, the discharge capacity of the cell is rapidly decreased after the repetition of about ten charge-dischar`ge cycles, such that the discharge current is only one half the`~original discharge capacity of the cell. It is also seen that the discharge capacity ~is continuously decreased with a further repetition of the charge-discharge cycles.
; In accordance with the following production steps, a button type cell shown in Fig. 2 was produced.
87 grams and 26 grams each of marketed manganese dioxide and lithium carbonate were thoroughly mixed in a mortar and the resulting mixture was heat-treated on an alumina boat in a nitrogen gas at 400 C Eor 10 hours. The product obtained after cooliny was subjected to an X-ray analysis, whereby a chart of the X-ray analysis as shown in Fig. 3 was obtained.
~9~8~5 In comparison with the material represented by the formula LiMn204 in the ASTM card, the chart was found to be coincident completely with the X-ray diffraction chart for LiMn204. Thus the material obtained by the above described process could be identified to be LiMn204.
Then, 88.9 parts by weight of LiMn204 produced by the above described process were admixed with 9.3 parts by weight of graphite and then with 1.8 parts by weight of polytetrafluoroethylene as the binder. The resulting mixture was then press-formed into a pellet of 15.5 mm in diameter and 0.3 mm in thickness under application of a pressure of 3 tons/cm2. The pellet thus produced was dried in vacuum at 300 C for five hours to a cathode pellet 5.
On the other hand, an aluminum foil of 0.3 mm in thickness was punched to a disk shaped piece of 15.5 mm in diameter, which was then spot welded to an anodic can 2. A
lithium foil of 0.3 mm in thickness was punched to a disk shaped piece of 15 mm in diameter, which was then press bonded onto the aluminum foil piece to form an anodic pellet 1 to be used as an anode.
On this anode was placed a non-woven propylene cloth as a separator 3 and propylene carbonate with LiCl04 dissloved therein at a rate of 1 mol/liter was added as an electrolyte solution. A gasket 4 formed of a suitable synthetic material was press fitted to the anode and the previously obtained ~;~90~305 cathode pellet 5 was placed on the separator 3. A cathodic can 6 was placed over the cathode pellet and caulk for hermetically sealing an openlng that may be present between it and the gasket 4 to form an rechargeable organic electrolyte cell having an outside diameter of 20 mm and a thickness of 1.6 mm.
The sample cell obtained as above was subjected to a discharge test through a resistor of 1 kiloohm. The discharge curve shown in Fig. 4 was obtained.
The discharge reaction may be expressed by the following reaction formula Li+ + LiMn204 ~ e ~ 2LiM O
The completely discharged sample cel`l was then charged with a current of 2 mA with the upper voltage setting of 3.1 V. The results are shown in Fig. 5. It is seen from this figure that the charging voltage curve is extremely flat.
This possibly implies that deintercalation of lithium ions in the charging reaction shown by the formula 2LiMnO2 ~ LiMn2O4 + Li+ ~ e has proceeded smoothly.
The sample cell showing the charging and discharging characteristics as described above was charged and discharged repeatedly for investigating into cyclic charge-discharge characteristics of the sample cell. It was seen that, as shown in Fig. 6, deterioration in the discharge capacity due 129~80s to the cyclic charging and discharging was not observed in the least and the obtained rechargeable cell had truely superior properties.
EXAMPLE 2 a In the present Example 2, various LiMn2O4 samples were prepared using various sintering temperatures and so-called button-type cells were prepared with the use of -these samples to investigate into the charge-discharge characteristics of th~se cells.
First, in order -to produce LiMn2O4 having favorable properties as the cathode active material of the organic electrolyte cell, the sintering temperatures of LiMn2O4 were changed variously to investigate into changes in the X-ray diffraction peaks and in discharge capacities cause by these changes in the sintering temperatures.
For producing the LiMn2O4 sample, 86.9 grams (1 mol) and 18.5 grams (0.25 mol) each of marketed manganese dioxide and lithium carbonate were mixed while being ground thoroughly in a mortar. The resulting mixture was sintered in air for one hour on an alumina boat at a sintering temperature of 430 to 900 C.
The product was cooled and analyzed by the X-ray di~fraction analysis using FeK~ rays and the measurement conditions including the tube voltage of 30 kV, tube current of 15 mA, measurement range of 2000 cps, scanning speed of ,:
., .
' ' ~' ., ,~
.. . . .
: . -: ,.. ~........... . . ;.
... ..
1/min., chart speed of 5 mmlmin., diffusion slit width of 1 and the light slit width of 0.6 mm. On collation with the card index of the American Society for Testing Materials (ASTM), the product could be identified to be LiMn2O4. Fig.
7 shows an X-ray diffraction spectrum of LiMn2O4 obtained at a sintering temperature of 460 C, a~ an example. The full width at half maximum oE the diffxaction peak at a diffractlon angle of ~6.1 is 2.08, which is larger than that of LiMn204 obtained by sintering at 800 to 900 C in accordance with the conventional production process thereof.
The full width at half maximum data for LiMn2O4 obtained by sintering at various other sintering temperatures are summarized in Table 1.
Then, using the LiMn2O4 s~mples obtained at the respective sintering temperatures as described above, organic electrolyte cells such as shown in cross-section in Fig. 2 were prepared. 86.4 parts by weight of LiMn2O4 were thus admixed with 8.6 parts by weight of graphite and 5 parts by weight of polytetrafluoroethylene (Teflont m ) to a cathodlc composition which was then formed a cathodic pellet 5 of 15.5 mm in diameter and 0.44 mm in thickness and having a weight of 0.213 gram.
A marketed aluminum plate of 0.3 mm in thickness was punched to a disk shaped piece of 15 mm in diameter and bonded to an anodic can 2 by spot welding. A lithium foil of ~; .... . , ,1 : `:
0.18 mm in thickness was punehed to a disk shaped piece of15 mm in diameter and press bonded to the aluminum piece to an anodic pellet 1 to form an anode.
Then a separator 3 was applied to the anode and a gasket 4 formed of a suitable synthetie material was fitted thereto.
Then, an eleetrolyte solution mixture of 1,2-dimethoxyethane and propylene earbonate with LiCl04 dissolved therein at a rate oE 1 mol/liter was introduced. The previously produced cathodic pellet 5 was applied to the separator 3 and then eovered by a cathodic ean 6, whieh was then eaulked for hermetically sealing an opening or gap between it and the anode to produce a so-called button type organic electrolyte cell having a diameter of 20 mm and a thickness of 1.6 mm.
Using the LiMn204 samples prepared in this manner at the various sintering temperatures, organic eleetrolyte cells A, B, C, D, E, F, G, H, I, J and K were produeedO In Table 1, these eell appellations are entered in assoeiation with the sintering temperatures for the LiMn204 samples used in the cells.
Investigations were made into charging and diseharging eharaeteristies of the thus produeed organie eleetrolyte eells A through K.
8~
_ .
full width at -ells sintering discharge half maximum at a temperature capacity X-ray diffraction angle of 46.1 _ A 430 C 24.0 mAH 1.80 B 450 25.9 2.10 C 460 25.6 2.08 D 480 24.9 1.91 E 500 23.5 1.55 F 520 20.3 1.10 G 550 17.4 0.93 ll 600 14.6 0.78 I 700 12.4 0.57 J 800 10.0 0.35 K 900 7.5 0.26 .
These organic electrolyte cells were respectively connected to resistances of 1 kiloohm,and the discharge characteristics were measured with the terminal voltage of 2.0 V. The results are shown in Table 8, wherein the cell voltage V and the discharge time Hr are plotted on the ordinate and the absissa, respectively. From this figure, the mean discharge voltage may be read and converted into the mean discharge current which may then be multiplied by the duration of discharging until reaching the terminal voltage to give the discharge capacity in terms of the ampere-hour capacity, which is given herein by units of mAH since the resistnace of 1 ]ciloohm is used in the present measurement system. The discharge capacities obtained in this manner are also shown in Table 1.
Then, with the terminal voltage being set to 3.1 V, the ~29~305 current of 4 mA was caused to flow through each of the thus discharged cells, for measuring the charging characteristics.
The results are shown in Fig. 9, wherein the cell voltage V
and the charging time Hr are plotted on the ordinate and the abscissa, respectively. The organic electrolyte cell according to the present invention has extremely stable charge discharge characteristics, as may be seen from Figs. 8 and 9 showing that the major portions of the curve for each cell are flat, that is, do not show voltage changes with -the charging time. This is an indication that intercalation and deintercalation of lithium ions into and from the spacings between the adjoining LiP~n2O4 layers occùr extremely promptly and thus LiMn2O4 obtained in the above described manner has superio properties as the cathode active material.
In Fig. 10, the relation between the discharge capacity and the sintering temperature shown in Table 1 is shown. In Flg. 10, the discharging capacity in mAH is shown on the ordinate and the sintering temperature in C is shown on the abscissa. It is seen from Table 1 and Figs. 8 and 10 that the cells A, B, C, D, E and F have the excellent discharging capacity of not less than 20 mAH and hence are may meet practical demands and that the full width at half maximum values of LiMn2O4 as the cathode active material of these cells at an X-ray diEEraction angle of 46.1 are all within the range of between 1.1 and 2.1. The full width half maximum values may be controlled by changing the sintering temperature of LiMn2O4, with the optimum sintering temperature range being 430 to 520. It has been found that the discharging capacity is gradually lowered when the sintering temperature higher than the above range is employed. The discharge capacity is similarly lowered when the sintering temperature lower than the above range is employed, such that, with the cell L making use of LiMn2O4 obtained by sintering at 400 C, the discharging capacity was lowered to 19.1 mA~, as shown in Fig. 10. The X-ray diffraction spectrum for this LiMn2O4 sample is as shown in Fig. 11. It is found from this figure that, with the lower sintering temperature of 400 C, parts of lithium carbonate and manganese dioxide remain unreacted, so that desired characteristics are not attained.
In the present Example, in preparing LiMn2O4, lithium iodide was used in place of lithium carbonate shown in the Example 1, while the sintering was performed in a nitrogen atmosphere instead of in air.
50 grams (0.57 mol), 39 grams (0.29 mol) and 5.2 grams each of marketed manganese dioxide, lithium iodide and graphite were thoroughly mixed while being ground in a mortar and the resulting mixture was press molded into a pellet under a pressure of 3 tons/cm2. This pellet was placed on an 9V8~5 alumina boat and sintered in a nitrogen atmosphere at 300 C
for six hours. After sintered, the product was cooled and washed with ethyleneglycol dimethylether. The product was analyzed by X-ray diffraction analysis under the conditions specified in the Example 2, and was identified to be LiMn2O4 on collation with the card index of ASTM. The X-ray diffraction spectrum for this product is shown in Fig. 12.
The full width at half maximum value of a peak at a diffraction angle of 46.1 was 1.57. In this figure, the peak corresponding to graphite may also be seen in addition to the peaks appearing in Fig. 7.
Then, to 95 parts by weight of L`iMn2O4 were added 5 parts by weight of polytetrafluoroethy`lene ~Teflon) as a binder to give a cathodic composition. The ensuing assemblying of the organic electrolyte cell was performed in accordance with the method described in Example 2 to produce the cell sample M. The discharge capacity of the cell sample M was tested by a method according to the Example 2 and found to be as high as 23.1 mAH.
In the present Example 4, LiMn2O4 was prepared by sintering in a nitrogen atmosphere, as in Example 3, instead of in air.
86.9 grams (1 mol) and 1~.5 grams (0.25 mol) each of marketed manganese dioxide and lithium carbonate were ~.29~S
thoroughly mixed while being ground in a mortar. The produced mixture was placed on an alumina boat and sintered in a nitrogen atmosphere at 450 C for one hour. The product was analyzed by the X-ray diffraction analysis under the conditions stated in the Example 1 and thereby identified to be LiMn2O4. The full width at half maximum value of the peak at a diffraction angle of 46.1 was 1.60.
The ensuing assembling of the organic electrolyte cell was performed by the method according to the Example 2 to produce the cell sample N. The discharge capacity of the cell sample was tested by a method according to the Example 2 and found to be as high as 22.9 mAH.
From the foregoing it is seen that,~ by using LiMn2O4 as the cathode active material of the rechargeable organic electrolyte cell, the lithium ions once migrated towards the cathode during the discharging reaction may be optimally deintercalated during the charging reaction, with the result that the charge-discharge cycle life properties of the rechargeable organic electrolyte cell may be lmproved significantly.
In this manner there is provided an rechargeable organic electrolyte cell suffering from only limited deterioration in the cell capacity caused by repeated charge-discharge cycles and hence superior in cyclic life characteristics.
When LiMn2O4 used as the cathode active material of the rechargeable organic electrolyte cell has a specified full width at half maximum of the diffraction peak at a dlffraction angle of 46.1 in the range of 1.1 to 2.1, it is possible to elevate the charge-discharge characteristics of the cell obtained by using such cathode active material to higher than 90 percent its theoretical capacity.
Since LiMn2O4 is a less costly material, it is not only excellent from economic considerations as compared to conven-tional cathode active materials, such as TiS2, MoS2, NbSe~ or V2O5, but also contributes to energy saving in the production process of the organic electrclyte cell.
. ' ' .
Claims (8)
1. A rechargeable organic electrolyte cell comprising an anode containing Li, a cathode mainly composed of LiMn2O4 having a full width at half maximum of a diffraction peak at a diffraction angle of 2.theta. equal to 46.1° in the range between 1.1° and 2.1°, upon an X-ray diffraction analysis using FeK.alpha., and an organic electrolyte.
2. A rechargeable organic electrolyte cell according to claim 1, wherein LiMn2O4 is obtained by sintering manganese dioxide and lithium carbonate.
3. A rechargeable organic electrolyte cell according to claim 1, wherein LiMn2O4 is obtained by sintering manganese dioxide and lithium iodide.
4. A rechargeable organic electrolyte cell according to claim 1, wherein LiMn2O4 is obtained by sintering manganese dioxide and lithium carbonate at a temperature between 430 °C
and 520 °C.
and 520 °C.
5. A rechargeable organic electrolyte cell comprising an anode containing Li, a cathode mainly composed of a lithium and manganese complex oxide corresponding to a chart of LiMn2O4 in ASTM card upon X-ray diffraction analysis having a full width at half maximum of a diffraction peak at a diffraction angle of 2.theta.
equal to 46.1° in the range between 1.1° and 2.1°, upon an X-ray diffraction analysis using FeKa, and an organic electrolyte.
equal to 46.1° in the range between 1.1° and 2.1°, upon an X-ray diffraction analysis using FeKa, and an organic electrolyte.
6. A rechargeable organic electrolyte cell according to claim 5 wherein the cathode material is obtained by sintering manganese dioxide and lithium carbonate.
7. A rechargeable organic electrolyte cell according to claim 5 wherein the cathode material is obtained by sintering manganese dioxide and lithium iodide.
8. A rechargeable organic electrolyte cell according to claim 5 wherein the cathode material is obtained by sintering manganese dioxide and lithium carbonate at a temperature between approximately 430° C. to about 520° C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP257479/86 | 1986-10-29 | ||
| JP61257479A JPH0821431B2 (en) | 1986-10-29 | 1986-10-29 | Organic electrolyte secondary battery |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1290805C true CA1290805C (en) | 1991-10-15 |
Family
ID=17306871
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000550431A Expired - Lifetime CA1290805C (en) | 1986-10-29 | 1987-10-28 | Rechargeable organic electrolyte cell |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0821431B2 (en) |
| CA (1) | CA1290805C (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2627314B2 (en) * | 1988-08-25 | 1997-07-02 | 三洋電機株式会社 | Non-aqueous secondary battery and method for producing its positive electrode active material |
| JPH0834101B2 (en) * | 1989-05-12 | 1996-03-29 | 富士電気化学株式会社 | Non-aqueous electrolyte secondary battery |
| US5807646A (en) * | 1995-02-23 | 1998-09-15 | Tosoh Corporation | Spinel type lithium-mangenese oxide material, process for preparing the same and use thereof |
| JPH09320603A (en) * | 1996-03-28 | 1997-12-12 | Aichi Steel Works Ltd | Manufacture of pulverized active material for lithium secondary battery |
| FR2997795B1 (en) * | 2012-11-02 | 2014-11-21 | Renault Sa | LITHIUM BATTERY |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPS61257479A (en) * | 1985-05-10 | 1986-11-14 | Agency Of Ind Science & Technol | Method for plating inorganic powder by electroless plating |
-
1986
- 1986-10-29 JP JP61257479A patent/JPH0821431B2/en not_active Expired - Lifetime
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1987
- 1987-10-28 CA CA000550431A patent/CA1290805C/en not_active Expired - Lifetime
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| Publication number | Publication date |
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| JPS63114065A (en) | 1988-05-18 |
| JPH0821431B2 (en) | 1996-03-04 |
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