U.S. patent application number 10/619005 was filed with the patent office on 2004-01-22 for non-aqueous electrolytic solution and lithium battery.
This patent application is currently assigned to UBE INDUSTRIES, LTD.. Invention is credited to Abe, Koji, Hattori, Takayuki, Matsumori, Yasuo.
Application Number | 20040013946 10/619005 |
Document ID | / |
Family ID | 30447647 |
Filed Date | 2004-01-22 |
United States Patent
Application |
20040013946 |
Kind Code |
A1 |
Abe, Koji ; et al. |
January 22, 2004 |
Non-aqueous electrolytic solution and lithium battery
Abstract
A non-aqueous electrolytic solution comprising a non-aqueous
solvent and an electrolyte, which further contains a combination of
a nitrile compound and an S.dbd.O group-containing compound (or a
dinitrile compound) in an amount of 0.001 to 10 wt. % imparts
improved cycle performance and storage property to a lithium
battery, particularly a lithium secondary battery.
Inventors: |
Abe, Koji; (Yamaguchi,
JP) ; Hattori, Takayuki; (Yamaguchi, JP) ;
Matsumori, Yasuo; (Yamaguchi, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
401 9TH STREET, NW
SUITE 900
WASINGTON
DC
20004-2128
US
|
Assignee: |
UBE INDUSTRIES, LTD.
Yamaguchi
JP
|
Family ID: |
30447647 |
Appl. No.: |
10/619005 |
Filed: |
July 15, 2003 |
Current U.S.
Class: |
429/326 ;
429/231.8; 429/330; 429/339; 429/340 |
Current CPC
Class: |
H01M 2004/027 20130101;
H01M 4/625 20130101; H01M 4/661 20130101; H01M 10/0568 20130101;
H01M 2300/004 20130101; H01M 4/525 20130101; H01M 2300/0037
20130101; H01M 4/1391 20130101; H01M 4/587 20130101; Y02E 60/10
20130101; H01M 4/133 20130101; H01M 2300/0028 20130101; H01M 50/411
20210101; H01M 4/0471 20130101; H01M 6/168 20130101; H01M 10/052
20130101; H01M 4/0404 20130101; H01M 2220/30 20130101; H01M 4/043
20130101; H01M 10/0569 20130101; H01M 4/131 20130101; H01M 10/0525
20130101; H01M 4/1393 20130101; H01M 4/623 20130101; H01M 50/417
20210101; H01M 2004/028 20130101; H01M 4/505 20130101; H01M 4/485
20130101; H01M 10/0567 20130101 |
Class at
Publication: |
429/326 ;
429/339; 429/340; 429/330; 429/231.8 |
International
Class: |
H01M 010/40; H01M
004/58 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2002 |
JP |
2002-205560 |
Nov 11, 2002 |
JP |
2002-326391 |
Claims
What is claimed is:
1. A non-aqueous electrolytic solution comprising a non-aqueous
solvent and an electrolyte, which further contains a nitrile
compound and an S.dbd.O group-containing compound.
2. The electrolytic solution of claim 1, wherein the nitrile
compound is a mononitrile compound.
3. The electrolytic solution of claim 2, wherein the mononitrile
compound is acetonitrile, propionitrile, butylonitrile,
valeronitrile, hexanenitrile, octanenitrile, undecanenitrile,
decanenitrile, cyclohexanecarbonitrile, benzonitrile, or
phenylacetonitrile.
4. The electrolytic solution of claim 1, wherein the nitrile
compound is a dinitrile compound.
5. The electrolytic solution of claim 4, wherein the dinitrile
compound is succinonitrile, glutaronitrile, adiponitrile,
1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane,
1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane,
1,12-dicyanododecane, tetramethylsuccinonitrile,
2-methylglutaronitrile, 2,4-dimethylglutaronitrile,
2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane,
2,5-dimethyl-2,5-hexanedicarbonitrile, 2,6-dicyanoheptane,
2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane,
1,2-dicyanobenzene, 1,3-dicyanobenzene, or 1,4-dicyanobenzene.
6. The electrolytic solution of claim 1, wherein the S.dbd.O
group-containing compound is dimethylsulfite, diethylsulfite,
ethylenesulfite, propylenesulfite, vinylenesulfite,
dimethylsulfone, diethylsulfone, methylethylsulfone,
divinylsulfone, sulforane, sulforene, methyl methanesulfonate,
ethylmethanesulfonate, propargyl methanesulfonate, methyl
benzenesulfonate, 1,3-propanesultone, 1,4-butanesultone, dimethyl
sulfate, diethyl sulfate, ethyleneglycol sulfate, or
1,2-propanediol sulfate.
7. The electrolytic solution of claim 1, wherein the nitrile
compound is contained in an amount of 0.001 to 10 wt. %.
8. The electrolytic solution of claim 1, wherein the S.dbd.O
group-containing compound is contained in an amount of 4 wt. % or
less.
9. The electrolytic solution of claim 1, wherein the nitrile
compound and the S.dbd.O group-containing compound are contained in
a weight ratio of 1:99 to 99:1.
11. The electrolytic solution of claim 1, wherein the non-aqueous
solvent comprises at least one compound selected from the group
consisting of a cyclic carbonate, a cyclic ester, a linear
carbonate, and an ether.
12. The electrolytic solution of claim 1, wherein the non-aqueous
solvent comprises a cyclic carbonate and a linear carbonate in a
volume ratio of 1:9 to 9:1.
13. The electrolytic solution of claim 1, wherein the non-aqueous
solvent comprises a cyclic carbonate and an ether in a volume ratio
of 1:9 to 9:1.
14. The electrolytic solution of claim 1, wherein the non-aqueous
solvent comprises a cyclic carbonate and a cyclic ester in a volume
ratio of 1:99 to 99:1.
15. A non-aqueous electrolytic solution comprising a non-aqueous
solvent and an electrolyte, which further contains a dinitrile
compound in an amount of 0.001 to 10 wt. %.
16. The electrolytic solution of claim 15, wherein the dinitrile
compound is succinonitrile, glutaronitrile, adiponitrile,
1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane,
1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane,
1,12-dicyanododecane, tetramethylsuccinonitrile,
2-methylglutaronitrile, 2,4-dimethylglutaronitrile,
2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane,
2,5-dimethyl-2,5-hexanedicarbonitrile, 2,6-dicyanoheptane,
2,7-dicyanooctane, 2,8-dicyanononane, 1,6-dicyanodecane,
1,2-dicyanobenzene, 1,3-dicyanobenzene, or 1,4-dicyanobenzene.
17. The electrolytic solution of claim 15, wherein the non-aqueous
solvent comprises at least one compound selected from the group
consisting of a cyclic carbonate, a cyclic ester, a linear
carbonate, and an ether.
18. The electrolytic solution of claim 15, wherein the non-aqueous
solvent comprises a cyclic carbonate and a linear carbonate in a
volume ratio of 1:9 to 9:1.
19. The electrolytic solution of claim 15, wherein the non-aqueous
solvent comprises a cyclic carbonate and an ether in a volume ratio
of 1:9 to 9:1.
20. The electrolytic solution of claim 15, wherein the non-aqueous
solvent comprises a cyclic carbonate and a cyclic ester in a volume
ratio of 1:99 to 99:1.
21. A lithium battery comprising a positive electrode, a negative
electrode comprising a carbonaceous material of a graphite crystal
structure having a lattice distance of lattice surface (002) of
0.34 nanometer or less and a non-aqueous electrolytic solution of
claim 1.
22. A lithium battery comprising a positive electrode, a negative
electrode comprising a carbonaceous material of a graphite crystal
structure having a lattice distance of lattice surface (002) of
0.34 nanometer or less and a non-aqueous electrolytic solution of
claim 14.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a non-aqueous electrolytic
solution favorably employable for a lithium battery such as a
lithium primary battery or a lithium secondary battery. The
invention further relates to a lithium battery showing improved
battery performances, particularly, to a lithium primary battery
having a high energy density and a low self-discharge ratio and a
lithium secondary battery showing good cycle performance, high
electric capacity and good storage endurance.
BACKGROUND OF THE INVENTION
[0002] At present, a non-aqueous secondary battery is generally
employed as an electric source for driving small electronic
devices. The non-aqueous secondary battery comprises a positive
electrode, a negative electrode, and a non-aqueous electrolytic
solution. The non-aqueous lithium secondary battery generally
comprises a positive electrode of lithium complex oxide such as
LiCoO.sub.2, LiMn.sub.2O.sub.4 or LiNiO.sub.2, a non-aqueous
electrolytic solution such as a solution of electrolyte in a
carbonate solvent such as ethylene carbonate (EC), propylene
carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC),
or methyl ethyl carbonate (MEC), and a negative electrode of
carbonaceous material or lithium metal.
[0003] Also known is a lithium primary battery comprising a
positive electrode of, for instance, manganese dioxide and a
negative electrode of, for instance, lithium metal and showing a
high energy density.
[0004] The non-aqueous secondary battery preferably has good
battery performances such as large electric discharge capacity and
high electric discharge retention (i.e., good cycle
characteristics). However, there are observed certain problems in
the known non-aqueous secondary battery. For instance, in the
non-aqueous lithium ion secondary battery using a positive
electrode of LiCoO.sub.2, LiMn.sub.2O.sub.4, or LiNiO.sub.2,
oxidative decomposition of a portion of the non-aqueous
electrolytic solution undergoes in the electric charging stage. The
decomposition product disturbs electrochemical reaction so that the
electric discharge capacity decreases. It is considered that the
oxidative decomposition is caused in the non-aqueous solvent of the
non-aqueous electrolytic solution on the interface between the
positive electrode and the electrolytic solution.
[0005] Moreover, in the non-aqueous lithium secondary battery
particularly using negative electrode of carbonaceous material of
high crystallinity such as natural graphite or artificial (or
synthetic) graphite, reductive decomposition of the solvent of the
non-aqueous electrolytic solution undergoes on the surface of the
negative electrode in the charging stage. The reductive
decomposition on the negative electrode undergoes after repeated
charging-discharging procedures even in the case of using ethylene
carbonate (EC) which is generally employed in the electrolytic
solution.
[0006] JP-A-3-289062 proposes to incorporate 0.2 to 10 vol. % of
1,4-dimethoxybenzene compound into a non-aqueous solvent comprising
a high permittivity solvent such as ethylene carbonate (EC) or
propylene carbonate (PC) and a low permittivity solvent such as
tetrahydrofuran (THF) so that the cycle characteristics can be
improved.
[0007] U.S. Pat. No. 5,256,504 and No. 5,474,862 propose to
incorporate ethyl propionate into a combination of ethylene
carbonate and diethyl carbonate (DEC) so that the cycle
characteristics can be improved.
[0008] JP-A-9-161845 proposes a lithium secondary battery which
employs a combination of a high activity solvent having a donor
number of 14 to 20 and a low activity solvent having a donor number
of 10 or lower. This patent publication describes the use of a
negative electrode comprising a carbonaceous material of a graphite
crystal structure having a lattice distance (d.sub.002) of lattice
surface (002) of 0.3365 nanometer or more. The patent publication
further describes that the high activity solvent can be a cyclic
carbonate ester, a cyclic ester, a linear esher, a cyclic ether, a
linear ether, or a nitrile. The nitrile can be a dinitrile such as
glutaronitrile or adiponitrile. It is noted that in Example 6 the
glutaronitrile is employed in an amount of 19 vol. % in a
non-aqueous solvent for preparing a electrolytic solution.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a
non-aqueous electrolytic solution which is favorably employable for
producing a lithium battery showing improved battery performances
such as good cycle performance, a high electric capacity, good
storage endurance, and a high electric conductivity.
[0010] It is another object of the invention to provide a lithium
primary or secondary battery showing improved battery performances
such as good cycle performance, a high electric capacity, good
storage endurance, and a high electric conductivity.
[0011] The invention resides in a non-aqueous electrolytic solution
comprising a non-aqueous solvent and an electrolyte, which further
contains a nitrile compound and an S.dbd.O group-containing
compound.
[0012] The invention further resides in a non-aqueous electrolytic
solution comprising a non-aqueous solvent and an electrolyte, which
further contains a dinitrile compound in an amount of 0.001 to 10
wt. %.
[0013] The invention furthermore resides in a lithium battery
comprising a positive electrode, a negative electrode comprising a
carbonaceous material of a graphite crystal structure having a
lattice distance of lattice surface (002) of 0.34 nanometer or less
and one of the above-mentioned non-aqueous electrolytic solution of
the invention.
DETAILS DESCRIPTION OF THE INVENTION
[0014] In the non-aqueous solvent employed for producing a
non-aqueous electrolytic solution of the invention, a mononitrile
compound or a dinitrile compound is contained. The mononitrile
compound preferably has a linear or branched alkyl chain having 1
to 12 carbon atoms which may have one or more substituents or an
aromatic group and can be acetonitrile, propionitrile,
butylonitrile, valeronitrile, hexanenitrile, octanenitrile,
undecanenitrile, decanenitrile, cyclohexanecarbonitrile,
benzonitrile, or phenylacetonitrile.
[0015] The dinitrile compound preferably has a linear or branched
alkylene chain having 1 to 12 carbon atoms which may have one or
more substituents or an aromatic group and can be succinonitrile,
glutaronitrile, adiponitrile, 1,5-dicyanopentane,
1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane,
1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane,
tetramethylsuccino-nitrile, 2-methylglutaronitrile,
2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile,
1,4-dicyanopentane, 2,5-dimethyl-2,5-hexanedicarbonitrile,
2,6-dicyanoheptane, 2,7-dicyanooctane, 2,8-dicyanononane,
1,6-dicyanodecane, 1,2-dicyanobenzene, 1,3-dicyanobenzene, or
1,4-dicyanobenzene.
[0016] In the invention, the mononitrile compound should be used in
combination with an S.dbd.O group-containing compound.
[0017] The dinitrile compound can be used not in combination with
the S.dbd.O group-containing compound, under the condition that the
dinitrile compound should be contained in the electrolytic solution
in such a small amount as 0.001 to 10 wt. %, preferably 0.01 to 5
wt. %, more preferably 0.01 to 3 wt. %, most preferably 0.01 to 2
wt. %.
[0018] The incorporation of a dinitrile compound into an
electrolytic solution is effective to reduce erosion of a metallic
inner surface of a battery case. If an S.dbd.O group-containing
compound is incorporated in the electrolytic solution in
combination with a dinitrile compound, the effect to reduce the
erosion of a metallic inner surface of a battery case becomes more
prominent.
[0019] The S.dbd.O group-containing compound can be a cyclic
compound or a linear compound and can be dimethylsulfite,
diethylsulfite, ethylenesulfite, propylenesulfite, vinylenesulfite,
dimethylsulfone, diethylsulfone, methylethylsulfone,
divinylsulfone, sulforane, sulforene, methyl methanesulfonate,
ethylmethanesulfonate, propargyl methanesulfonate, methyl
benzenesulfonate, 1,3-propanesultone, 1,4-butanesultone, dimethyl
sulfate, diethyl sulfate, ethyleneglycol sulfate, or
1,2-propanediol sulfate.
[0020] When the electrolytic solution contains a nitrile compound
and an S.dbd.O group-containing compound in combination, the
nitrile compound is preferably contained in the electrolytic
solution in an amount of 0.001 to 10 wt. %, more preferably 0.01 to
5 wt. %, more preferably 0.01 to 3 wt. %, most preferably 0.01 to 2
wt. %. The S.dbd.O group-containing compound is preferably
contained in an amount of 4 wt. % or less, more preferably in the
range of 0.2 to 3 wt. %. The nitrile compound and the S.dbd.O
group-containing compound are contained preferably in a weight
ratio of 1:99 to 99:1, more preferably 9:1 to 1:9, 9:1 to 3:7.
[0021] The non-aqueous solvent of the electrolytic solution of the
invention preferably comprises at least one compound selected from
the group consisting of a cyclic carbonate, a cyclic ester, a
linear carbonate, and an ether.
[0022] Preferred examples of the cyclic carbonates include ethylene
carbonate (EC), propylene carbonate (PC), butylene carbonate (BC),
and vinylene carbonate (VC).
[0023] Preferred examples of the cyclic esters include lactones
such as .gamma.-butyrolactone (GBL).
[0024] Preferred examples of the linear carbonates include dimethyl
carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate
(DEC), dipropyl carbonate (DPC), and dibutyl carbonate (DBC).
[0025] Preferred examples of the ethers include cyclic ethers such
as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), and
1,4-dioxane (1,4-DOX) and linear ethers such as 1,2-dimethoxyethane
(DME), 1,2-diethoxyethane (DEE), and 1,2-dibutoxyethane (DBE).
[0026] In the solvent, these compounds can be used singly or in any
combinations. Moreover, one or more of other solvents such as other
esters, e.g., methyl propionate, ethyl pivalate, butyl pivalate,
hexyl pivalate, octyl pivalate, or dodecyl pivalate, can be used in
combination.
[0027] When a cyclic carbonate and a linear carbonate is employed
in combination, they are preferably employed in a volume ratio of
1:9 to 9:1 (cyclic carbonate:linear carbonate), more preferably 1:4
to 1:1.
[0028] When a cyclic carbonate and an ether is employed in
combination, they are preferably employed in a volume ratio of 1:9
to 9:1 (cyclic carbonate:ether), more preferably 1:4 to 1:1.
[0029] When a cyclic carbonate and a cyclic ester is employed in
combination, they are preferably employed in a volume ratio of 1:99
to 99:1 (cyclic carbonate:cyclic ester), more preferably 1:9 to
9:1, most preferably 1:4 to 1:1.
[0030] Examples of the electrolytes to be incorporated into the
non-aqueous solvent include LiPF.sub.6, LiBF.sub.4, LiAsF.sub.6,
LiClO.sub.4, LiOSO.sub.2CF.sub.3, LiN (SO.sub.2CF.sub.3) 2,
LiN(SO.sub.2C.sub.2F.sub.5) 2, LiC(SO.sub.2CF.sub.3).sub.3,
LiPF.sub.4(CF.sub.3) 2, LiPF.sub.3(CF.sub.3) 3,
LiPF.sub.3(C.sub.2F.sub.5- ).sub.3, LiPF.sub.5(iso-C.sub.3F.sub.7),
LiPF.sub.4(iso-C.sub.3F.sub.7) 2 and LiBF.sub.3(C.sub.2F5). The
electrolytes can be employed singly or in combination. Generally,
the electrolyte can be incorporated into the non-aqueous solvent in
such an amount to give an electrolytic solution of 0.1 M to 3 M,
preferably 0.5 M to 1.5 M.
[0031] A non-aqueous secondary battery of the invention comprises a
positive electrode and a negative electrode in addition to the
non-aqueous electrolytic solution.
[0032] The positive electrode generally comprises a positive
electrode active material and an electro-conductive binder
composition.
[0033] The positive electrode active material for a lithium
secondary battery preferably is a complex metal oxide containing
one metal element selected from the group consisting of cobalt,
manganese, nickel, chromium, iron, and vanadium and a lithium
element. Examples of the complex metal oxides include LiCoO.sub.2,
LiMn.sub.2O.sub.4, LiNiO.sub.2 and LiCO.sub.1-xNi.sub.xO.sub.2
(0.01<x<1).
[0034] The positive electrode active material for a lithium primary
battery preferably is an oxide of one or more metals or a calcogen
compound such as CuO, Cu.sub.2O, Ag.sub.2O, Ag.sub.2CrO.sub.4, CuS,
CuSO.sub.4, TiO.sub.2, TiS.sub.2, SiO.sub.2, SnO, V.sub.2O.sub.5,
V.sub.6O.sub.12, VO.sub.x, Nb.sub.2O.sub.5, Bi.sub.2O.sub.3,
Bi.sub.2Pb.sub.2O.sub.5, Sb.sub.2O.sub.3, CrO.sub.3,
Cr.sub.2O.sub.3, MoO.sub.3, WO.sub.3, SeO.sub.2, MnO.sub.2,
MnO.sub.3, Fe.sub.2O.sub.3, FeO, Fe.sub.3O.sub.4, Ni.sub.2O.sub.3,
NiO, CoO.sub.3, or CoO, a sulfur compound such a SO.sub.2 or
SOCl.sub.2, or carbon fluoride having a formula of
(CF.sub.x).sub.n. Preferred are MnO.sub.2, V.sub.2O.sub.5, and
carbon fluoride.
[0035] The electro-conductive binder composition can be produced by
a mixture of an electro-conductive material such as acetylene black
or carbon black, a binder such as poly(tetrafluoroethylene) (PTFE),
poly(vinylidene fluoride) (PVDF), styrene-butadiene copolymer
(SBR), acrylonitrile-butadiene copolymer (NBR) or
carboxymethylcellulose (CMC), and a solvent. For the preparation of
a positive electrode, the mixture is coated on a metal plate such
as aluminum foil or stainless plate, dried, and pressed for
molding. The molded product is then heated in vacuo at a
temperature of approx. 50 to 250.degree. C. for approx. 2 hours, to
give the desired positive electrode.
[0036] The negative electrode comprises a negative electrode active
material such as a lithium metal, a lithium alloy, carbonaceous
material having a graphite-type crystalline structure which can
absorb and release lithium ion, or a complex tin oxide. Examples of
the carbonaceous materials include thermally decomposed
carbonaceous materials, cokes, graphites (e.g., artificial graphite
and natural graphite), fired organic polymer materials, and carbon
fibers. Preferred are carbonaceous materials having a graphite-type
crystalline structure in which the lattice distance of lattice
surface (002), namely, d.sub.002, is 0.34 nm (nanometer) or less,
preferably 0.336 nm or less.
[0037] The negative electrode active material in the powdery form
such as carbonaceous powder is preferably used in combination with
a binder such as ethylene propylene diene terpolymer (EPDM),
polytetrafluoroethylene (PTFE), poly(vinylidene fluoride) (PVDF),
styrene-butadiene copolymer (SBR), acrylonitrile-butadiene
copolymer (NBR) or carboxymethylcellulose (CMC).
[0038] There are no specific limitations with respect to the
structure of the non-aqueous lithium battery of the invention. For
instance, the non-aqueous secondary battery can be a battery of
coin type comprising a positive electrode, a negative electrode,
and single or plural separators, or a cylindrical or prismatic
battery comprising a positive electrode, a negative electrode, and
a separator roll. The separator can be a known microporous
polyolefin film, woven fabric, or non-woven fabric.
[0039] The present invention is further described by the following
non-limiting examples.
[0040] [Incorporation of Dinitrile Compound into Electrolytic
Solution for Lithium Secondary Battery]
[EXAMPLE A-1]
[0041] 1) Preparation of Non-Aqueous Electrolytic Solution
[0042] In a non-aqueous mixture of ethylene carbonate and methyl
ethyl carbonate [EC:MEC=3:7, volume ratio] was dissolved LiPF.sub.6
to give a non-aqueous electrolytic solution of 1 M concentration.
To the electrolytic solution was added adiponitrile in an amount of
0.01 wt. % (based on the amount of the electrolytic solution).
[0043] 2) Preparation of Lithium Secondary Battery and Measurement
of its Battery Characteristics
[0044] LiCoO.sub.2 (positive electrode active material, 90 wt. %),
acetylene black (electro-conductive material, 5 wt. %), and
poly(vinylidene fluoride) (binder, 5 wt. %) were mixed. To the
resulting mixture was further added 1-methyl-2-pyrrolidone
(solvent). Thus produced positive electrode mixture was coated on
aluminum foil, dried, molded under pressure, and heated to give a
positive electrode.
[0045] A natural graphite (negative electrode active material,
doo.sub.2=0.3354 nm, 90 wt. %) and poly(vinylidene fluoride)
(binder, 10 wt. %) were mixed. To the resulting mixture was further
added 1-methyl-2-pyrrolidone (solvent). Thus produced negative
electrode mixture was coated on copper foil, dried, molded under
pressure, and heated to give a negative electrode.
[0046] The positive and negative electrodes, a microporous
polypropylene film separator, and the non-aqueous electrolytic
solution were combined to give a coin-type battery (diameter: 20
mm, thickness: 3.2 mm).
[0047] The coin-type battery was charged at room temperature
(20.degree. C.) with a constant electric current (0.8 mA, per
electrode area) to reach 4.2 V and then the charging was continued
under a constant voltage of 4.2 V. In total, the charging was
performed for 5 hours. Subsequently, the battery was discharged to
give a constant electric current (0.8 mA). The discharge was
continued to give a terminal voltage of 2.7 V. The charge-discharge
cycle was repeated 100 times.
[0048] The initial discharge capacity was 1.00 time as much as that
measured in a battery using an EC/MEC (3/7) solvent mixture
(containing 1M LiPF.sub.6 but no adiponitrile) [see Comparison
Example A-1].
[0049] After the 100 cycle charge-discharge procedure was complete,
the discharge capacity became 86.2% of the initial discharge
capacity.
[0050] The preparation and evaluation of the battery are summarized
in Table 1.
[0051] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[EXAMPLE A-2]
[0052] The procedures of Example A-1 were repeated except that
adiponitrile was incorporated into the electrolytic solution in an
amount of 0.05 wt. %, to prepare a coin-type battery.
[0053] The initial discharge capacity was 0.99 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 87.9% of the initial discharge capacity.
[0054] The preparation and evaluation of the battery are summarized
in Table 1.
[EXAMPLE A-3]
[0055] The procedures of Example A-1 were repeated except that
adiponitrile was incorporated into the electrolytic solution in an
amount of 0.1 wt. %, to prepare a coin-type battery.
[0056] The initial discharge capacity was 1.01 times as much as
that measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 89.0% of the initial discharge capacity.
[0057] The preparation and evaluation of the battery are summarized
in Table 1.
[EXAMPLE A-4]
[0058] The procedures of Example A-1 were repeated except that
adiponitrile was incorporated into the electrolytic solution in an
amount of 0.2 wt. %, to prepare a coin-type battery.
[0059] The initial discharge capacity was 1.02 times as much as
that measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 89.2% of the initial discharge capacity.
[0060] The preparation and evaluation of the battery are summarized
in Table 1.
[0061] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[EXAMPLE A-5]
[0062] The procedures of Example A-1 were repeated except that
adiponitrile was incorporated into the electrolytic solution in an
amount of 0.5 wt. %, to prepare a coin-type battery.
[0063] The initial discharge capacity was 0.99 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 88.8% of the initial discharge capacity.
[0064] The preparation and evaluation of the battery are summarized
in Table 1.
[EXAMPLE A-6]
[0065] The procedures of Example A-1 were repeated except that
adiponitrile was incorporated into the electrolytic solution in an
amount of 1 wt. %, to prepare a coin-type battery.
[0066] The initial discharge capacity was 0.98 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 85.6% of the initial discharge capacity.
[0067] The preparation and evaluation of the battery are summarized
in Table 1.
[COMPARISON EXAMPLE A-1]
[0068] The procedures of Example A-1 were repeated except that no
adiponitrile was incorporated into the electrolytic solution, to
prepare a coin-type battery.
[0069] After the 100 cycle charge-discharge procedure was complete,
the discharge capacity became 82.6% of the initial discharge
capacity.
[0070] The preparation and evaluation of the battery are summarized
in Table 1.
[0071] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had no glossy inner surface like that
observed before the electrolytic solution was placed. Microscopic
observation revealed that the inner surface had eroded spots.
[COMPARISON EXAMPLE A-2]
[0072] The procedures of Example A-1 were repeated except that
adiponitrile was incorporated into the electrolytic solution in an
amount of 13 wt. %, to prepare a coin-type battery.
[0073] The initial discharge capacity was 0.95 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 72.3% of the initial discharge capacity.
[0074] The preparation and evaluation of the battery are summarized
in Table 1.
[EXAMPLE A-7]
[0075] The procedures of Example A-1 were repeated except that
glutaronitrile was incorporated in place of adiponitrile into the
electrolytic solution in an amount of 0.2 wt. %, to prepare a
coin-type battery.
[0076] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 88.9% of the initial discharge capacity.
[0077] The preparation and evaluation of the battery are summarized
in Table 1.
[COMPARISON EXAMPLE A-3
Trace of Example 6 of JP-A-9-161845]
[0078] The procedures of Example A-1 were repeated except that the
non-aqueous solvent composition was replaced with a combination of
glutaronitrile and dimethyl carbonate (19:81, volume ratio), to
prepare a coin-type battery.
[0079] The initial discharge capacity was 1.01 times as much as
that measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 64.7% of the initial discharge capacity.
[0080] The preparation and evaluation of the battery are summarized
in Table 1.
[COMPARISON EXAMPLE A-4]
[0081] The procedures of Example A-1 were repeated except that
adiponitrile was replaced with 0.2 wt. % of propionitrile, to
prepare a coin-type battery.
[0082] The initial discharge capacity was 0.96 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 82.4% of the initial discharge capacity.
[0083] The preparation and evaluation of the battery are summarized
in Table 1.
1TABLE 1 Initial Discharge Nitrile discharge capacity Example
compound (wt. %) capacity (R.V.) retention (%) A-1 Adiponitrile
(0.01) 1.00 86.2 A-2 Adiponitrile (0.05) 0.99 87.9 A-3 Adiponitrile
(0.1) 1.01 89.0 A-4 Adiponitrile (0.2) 1.02 89.2 A-5 Adiponitrile
(0.5) 0.99 88.8 A-6 Adiponitrile (1) 0.98 85.6 A-7 Glutaronitrile
(0.2) 1.00 88.9 Comparison A-1 None 1 82.6 A-2 Adiponitrile (13)
0.95 72.3 A-3 [Glutaronitrile (19)] 1.01 64.7 A-4 Propionitrile
(0.2) 0.96 82.4 Remarks: Comparison Example A-3 uses
glutaronitrile/methyl carbonate (19:81, vol. ratio) and 1 mol/L
LIPF.sub.6. R.V. means "Relative Value".
[EXAMPLE A-8]
[0084] 1) Preparation of Non-Aqueous Electrolytic Solution
[0085] In a non-aqueous mixture of ethylene carbonate and
.gamma.-butyrolactone [EC:GBL=3:7, volume ratio] was dissolved
LiBF.sub.4 to give a non-aqueous electrolytic solution of 1.5 M
concentration. To the electrolytic solution were added n-butyl
pivalate (separator-wetting improver) and adiponitrile in amounts
of 5 wt. % and 0.2 wt. % (based on the amount of the electrolytic
solution), respectively.
[0086] 2) Preparation of Lithium Secondary Battery and Measurement
of its Battery Characteristics
[0087] The procedures of Example A-1 were repeated except that the
above-prepared electrolytic solution was used, to prepare a
coin-type battery.
[0088] The initial discharge capacity was 0.96 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 70.1% of the initial discharge capacity.
[0089] The preparation and evaluation of the battery are summarized
in Table 2.
[EXAMPLE A-9]
[0090] 1) Preparation of Non-Aqueous Electrolytic Solution
[0091] In a non-aqueous .gamma.-butyrolactone solvent was dissolved
LiBF.sub.4 to give a non-aqueous electrolytic solution of 1.5 M
concentration. To the electrolytic solution were added n-butyl
pivalate (separator-wetting improver) and adiponitrile in amounts
of 5 wt. % and 0.2 wt. % (based on the amount of the electrolytic
solution), respectively.
[0092] 2) Preparation of Lithium Secondary Battery and Measurement
of its Battery Characteristics
[0093] The procedures of Example A-1 were repeated except that the
above-prepared electrolytic solution was used, to prepare a
coin-type battery.
[0094] The initial discharge capacity was 0.98 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 67.3% of the initial discharge capacity.
[0095] The preparation and evaluation of the battery are summarized
in Table 2.
[COMPARISON EXAMPLE A-5]
[0096] 1) Preparation of Non-Aqueous Electrolytic Solution
[0097] In a non-aqueous mixture of ethylene carbonate and
.gamma.-butyrolactone [EC:GBL=3:7, volume ratio] was dissolved
LiBF.sub.4 to give a non-aqueous electrolytic solution of 1.5 M
concentration. To the electrolytic solution was added n-butyl
pivalate (separator-wetting improver) in an amount of 5 wt. %
(based on the amount of the electrolytic solution), but added no
dinitrile compound.
[0098] 2) Preparation of Lithium Secondary Battery and Measurement
of its Battery Characteristics
[0099] The procedures of Example A-1 were repeated except that the
above-prepared electrolytic solution was used, to prepare a
coin-type battery.
[0100] The initial discharge capacity was 0.97 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 61.4% of the initial discharge capacity.
[0101] The preparation and evaluation of the battery are summarized
in Table 2.
[COMPARISON EXAMPLE A-6]
[0102] 1) Preparation of Non-Aqueous Electrolytic Solution
[0103] In a non-aqueous .gamma.-butyrolactone solvent was dissolved
LIBF.sub.4 to give a non-aqueous electrolytic solution of 1.5 M
concentration. To the electrolytic solution was added n-butyl
pivalate (separator-wetting improver) in an amount of 5 wt. %
(based on the amount of the electrolytic solution), but added no
dinitrile compound.
[0104] 2) Preparation of Lithium Secondary Battery and Measurement
of its Battery Characteristics
[0105] The procedures of Example A-1 were repeated except that the
above-prepared electrolytic solution was used, to prepare a
coin-type battery.
[0106] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example A-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 59.5% of the initial discharge capacity.
[0107] The preparation and evaluation of the battery are summarized
in Table 2.
2TABLE 2 Initial Discharge Nitrile discharge capacity Example
compound (wt. %) capacity (R.V.) retention (%) A-8 Adiponitrile
(0.2) 0.96 70.1 A-9 Adiponitrile (0.2) 0.98 67.3 Comparison A-5
None 0.97 61.4 A-6 None 1.00 59.5 Remarks: Example A-8 and
Comparison Example A-5 use EC/GBL (3:7) solvent, and Example A-9
and Comparison Example A-6 use GBL solvent.
[Summary of Evaluations]
[0108] The results of Examples A-1 to A-6 and Comparison Examples
A-1 and A-2 indicate that the use of the electrolytic solution
containing an appropriate amount of a dinitrile compound gives a
favorably effect to a lithium secondary battery (enhancement of a
discharge capacity retention without lowering the initial discharge
capacity after a long term charge-discharge cycles) as compared
with an electrolytic solution containing no dinitrile compound. The
results of Comparison Examples A-2 and A-3 indicate that the use of
a dinitrile compound in an excessive amount gives an adverse effect
to the battery performances. The results of Comparison Example A-4
indicate that the use of a mononitrile compound in place of a
dinitrile compound give almost no favorable effect to the discharge
capacity retention.
[0109] In summary, the incorporation of an appropriate amount of a
dinitrile compound into a non-aqueous electrolytic solution gives
favorably effects to battery performances such as discharge
capacity retention by forming a protective film on metallic
supports of the positive and negative electrodes and a battery case
and hence keeping conductivity between the electrode active
material and metallic support from lowering.
[0110] [Incorporation of Dinitrile Compound into Electrolytic
Solution for Lithium Primary Battery]
[EXAMPLE B-1]
[0111] 1) Preparation of Non-Aqueous Electrolytic Solution
[0112] In a non-aqueous mixture of propylene carbonate and
1,2-dimethoxyethane [PC:DME=1:1, volume ratio] was dissolved
LiOSO.sub.2CF.sub.3 to give a non-aqueous electrolytic solution of
1.0 M concentration. To the electrolytic solution was added
adiponitrile in an amount of 0.2 wt. % (based on the amount of the
electrolytic solution).
[0113] 2) Preparation of Lithium Primary Battery and Measurement of
its Battery Characteristics
[0114] MnO.sub.2 (positive electrode active material, 85 wt. %),
acetylene black (electro-conductive material, 10 wt. %), and
poly(vinylidene fluoride) (binder, 5 wt. %) were mixed. To the
resulting mixture was further added 1-methyl-2-pyrrolidone
(solvent). Thus produced positive electrode mixture was coated on
aluminum foil, dried, molded under pressure, and heated to give a
positive electrode.
[0115] A lithium metal foil (negative electrode material) having a
thickness of 0.2 mm was punched out to give a disc which was then
pressed on a negative electrode collector to give a negative
electrode.
[0116] The positive and negative electrodes, a microporous
polypropylene film separator, and the non-aqueous electrolytic
solution were combined to give a coin-type battery (diameter: 20
mm, thickness: 3.2 mm).
[0117] The prepared coin-type battery was subjected to the
following capacity test and high temperature storage test.
[0118] [Capacity Test]
[0119] The coin-type battery was charged at room temperature
(20.degree. C.) with a constant electric current (0.5 mA per an
electrode area) to reach 3.5 V. Subsequently, the battery was
discharged to give a constant electric current (1.0 mA). The
discharge was continued to give a terminal voltage of 2.4 V, to
measure a discharge capacity.
[0120] [High Temperature Storage Test]
[0121] The coin-type battery was charged at room temperature
(20.degree. C.) with a constant electric current (0.5 mA per
electrode area) to reach 3.5 V. Subsequently, the battery was kept
in a thermostat at 60.degree. C. for 20 days. Then, the battery was
discharged to give a constant electric current (1.0 mA). The
discharge was continued to give a terminal voltage of 2.4 V, to
measure a discharge capacity. A self discharge ratio in the high
temperature storage was calculated from thus measured discharge
capacity and the discharge capacity measured at room
temperature.
[0122] The discharge capacity was 1.04 time as much as that
measured in a battery using a PC/DME (1/1) solvent mixture
(containing 1.0M LiOSO.sub.2CF.sub.3, but no adiponitrile) [see
Comparison Example B-1]. The self-discharge ratio in the high
temperature storage was 6.2 w.
[0123] The preparation and evaluation of the battery are summarized
in Table 3.
[0124] After the high temperature storage evaluation was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[COMPARISON EXAMPLE B-1]
[0125] The procedures of Example B-1 were repeated except that no
adiponitrile was incorporated in the electrolytic solution, to
prepare a coin-type battery.
[0126] The prepared coin-type battery was subjected to the capacity
test and high temperature storage test. The self-discharge ratio in
the high temperature storage was 10.5%.
[0127] The preparation and evaluation of the battery are summarized
in Table 3.
[0128] After the high temperature storage evaluation was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had no glossy inner surface like that
observed before the electrolytic solution was placed. Microscopic
observation revealed that the inner surface had eroded spots.
[COMPARISON EXAMPLE B-2]
[0129] The procedures of Example B-1 were repeated except that
adiponitrile was incorporated into the electrolytic solution in an
amount of 13 wt. %, to prepare a coin-type battery.
[0130] The prepared coin-type battery was subjected to the capacity
test and high temperature storage test.
[0131] The discharge capacity was 0.92 time as much as that
measured in Comparison Example B-1. The self-discharge ratio in the
high temperature storage was 22.8%.
[0132] The preparation and evaluation of the battery are summarized
in Table 3.
[0133] After the high temperature storage evaluation was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
3TABLE 3 Initial High temperature Nitrile discharge self-discharge
Example compound (wt. %) capacity (R.V.) ratio (%) B-1 Adiponitrile
(0.2) 1.04 6.2 Comparison B-1 None 1 10.5 B-2 Adiponitrile (13)
0.92 22.8
[0134] [Incorporation of Nitrile Compound and S.dbd.O
Group-Containing Compound into Electrolytic Solution for Lithium
Secondary Battery]
[EXAMPLE C-1]
[0135] 1) Preparation of Non-Aqueous Electrolytic Solution
[0136] In a non-aqueous mixture of ethylene carbonate, vinylene
carbonate, and methyl ethyl carbonate [EC:VC:MEC=28:2:70, volume
ratio] was dissolved LiPF.sub.6 to give a non-aqueous electrolytic
solution of 1 M concentration. To the electrolytic solution were
added 1,4-dicyanobenzene and ethylene sulfite in amounts of 2 wt. %
and 2 wt. % (based on the amount of the electrolytic solution),
respectively.
[0137] 2) Preparation of Lithium Secondary Battery and Measurement
of its Battery Characteristics
[0138] A coin-type battery was prepared using the above-obtained
electrolytic solution in the same manner as described in Example
A-1, and the battery performances were measured in the same
manner.
[0139] The initial discharge capacity was 1.00 time as much as that
measured in a battery using an EC/VC/MEC (28/2/70) solvent mixture
(containing 1M LiPF.sub.6 but neither 1,4-dicyanobenzene nor
ethylene sulfite) [see Comparison Example C-1].
[0140] After the 100 cycle charge-discharge procedure was complete,
the discharge capacity became 88.9% of the initial discharge
capacity.
[0141] The preparation and evaluation of the battery are summarized
in Table 4.
[0142] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[COMPARISON EXAMPLE C-1]
[0143] The procedures of Example C-1 were repeated except that
neither 1,4-dicyanobenzene nor ethylene sulfite was incorporated
into the electrolytic solution, to prepare a coin-type battery.
After the 100 cycle charge-discharge procedure was complete, the
discharge capacity became 83.7% of the initial discharge
capacity.
[0144] The preparation and evaluation of the battery are summarized
in Table 4.
[0145] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had no glossy inner surface like that
observed before the electrolytic solution was placed. Microscopic
observation revealed that the inner surface had eroded spots.
[EXAMPLE C-2]
[0146] The procedures of Example C-1 were repeated except that
1,4-dicyanobenzene was replaced with adiponitrile, to prepare a
coin-type battery.
[0147] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example C-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 90.2% of the initial discharge capacity.
[0148] The preparation and evaluation of the battery are summarized
in Table 4.
[0149] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[EXAMPLE C-3]
[0150] The procedures of Example C-2 were repeated except that 1M
of LiPF.sub.6 was replaced with a combination of 0.9M of LiPF.sub.6
and 0.1M of LiN(SO.sub.2CF.sub.3).sub.2, to prepare a coin-type
battery.
[0151] After the 100 cycle charge-discharge procedure was complete,
the discharge capacity became 89.4% of the initial discharge
capacity.
[0152] The preparation and evaluation of the battery are summarized
in Table 4.
[0153] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[EXAMPLE C-4]
[0154] The procedures of Example C-2 were repeated except that 1M
of LiPF.sub.6 was replaced with a combination of 0.9M of LiPF.sub.6
and 0.1M of LiBF.sub.4, to prepare a coin-type battery.
[0155] After the 100 cycle charge-discharge procedure was complete,
the discharge capacity became 89.7% of the initial discharge
capacity.
[0156] The preparation and evaluation of the battery are summarized
in Table 4.
[0157] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[EXAMPLE C-5]
[0158] The procedures of Example C-2 were repeated except that
ethylene sulfite was replaced with 1,3-propanesultone, to prepare a
coin-type battery.
[0159] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example C-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 89.8% of the initial discharge capacity.
[0160] The preparation and evaluation of the battery are summarized
in Table 4.
[0161] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[EXAMPLE C-6]
[0162] The procedures of Example C-2 were repeated except that 2
wt. % of ethylene sulfite was replaced with 0.3 wt. % of
divinylsulfone, to prepare a coin-type battery.
[0163] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example C-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 89.4% of the initial discharge capacity.
[0164] The preparation and evaluation of the battery are summarized
in Table 4.
[0165] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[EXAMPLE C-7]
[0166] The procedures of Example C-2 were repeated except that 2
wt. % of ethylene sulfite was replaced with 0.5 wt. % of propargyl
methanesulfonate, to prepare a coin-type battery.
[0167] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example C-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 89.3% of the initial discharge capacity.
[0168] The preparation and evaluation of the battery are summarized
in Table 4.
[0169] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had the same glossy inner surface as that
observed before the electrolytic solution was placed.
[COMPARISON EXAMPLE C-2]
[0170] The procedures of Example C-2 were repeated except that no
1,4-cyanobenzene was used, to prepare a coin-type battery.
[0171] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example C-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 84.2% of the initial discharge capacity.
[0172] The preparation and evaluation of the battery are summarized
in Table 4.
[0173] After the evaluation on battery performances was complete,
the battery was disassembled to observe the inner surface of the
battery case. The case had no glossy inner surface like that
observed before the electrolytic solution was placed. Microscopic
observation revealed that the inner surface had eroded spots.
[EXAMPLE C-8]
[0174] The procedures of Example C-1 were repeated except that
1,4-dicyanobenzene was replaced with propionitrile, to prepare a
coin-type battery.
[0175] The initial discharge capacity was 1.00 time as much as that
measured in a battery of Comparison Example C-1. After the 100
cycle charge-discharge procedure was complete, the discharge
capacity became 88.2% of the initial discharge capacity.
[0176] The preparation and evaluation of the battery are summarized
in Table 4.
4TABLE 4 Initial Discharge Electrolytic solution discharge capacity
Nitrile compound (wt. %) capacity retention Example
SO.sub.2-containing compound (wt. %) (R.V.) (%) C-1 1 M LiPF.sub.6
in EC/VC/MEC 1.00 88.9 1,4-Dicyanobenzene (2) Ethylene sulfite (2)
C-2 1 M LIPF.sub.6 in EC/VC/MEC 1.00 90.2 Adiponitrile (2) Ethylene
sulfite (2) C-3 0.9 M LiPF.sub.6 + 0.1 M 1.00 89.4
LiN(SO.sub.2CF.sub.3).sub.2 in EC/VC/MEC Adiponitrile (2) Ethylene
sulfite (2) C-4 0.9 M LiPF.sub.6 + 0.1 M 1.00 89.7 LiBF.sub.4 in
EC/VC/MEC Adiponitrile (2) Ethylene sulfite (2) C-5 1 M LiPF.sub.6
in EC/VC/MEC 1.00 89.8 Adiponitrile (2) 1,3-Propanesultone (2) C-6
1 M LiPF.sub.6 in EC/VC/MEC 1.00 89.4 Adiponitrile (2)
Divinylsulfone (0.3) C-7 1 M LiPF.sub.6 in EC/VC/MEC 1.00 89.3
Adiponitrile (2) Propargyl methanesulfonate (0.5) C-8 1 M
LiPF.sub.6 in EC/VC/MEC 1.00 88.2 Propionitrile (2) Ethylene
sulfite (2) Comparison C-1 1 M LiPF.sub.6 in EC/VC/MEC 1.00 83.7
None None Comparison C-2 1 M LiPF.sub.6 in EC/VC/MEC 1.00 84.2 None
Ethylene sulfite (2)
* * * * *