Nonaqueous electrolyte and electricity storing device in which same is used
10164293 ยท 2018-12-25
Assignee
Inventors
Cpc classification
H01G11/62
ELECTRICITY
Y02T10/70
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02E60/10
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02E60/13
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
International classification
H01G11/62
ELECTRICITY
H01G11/06
ELECTRICITY
Abstract
Disclosed are a non-aqueous electrolytic solution, which can improve cycle characteristics when a power storage device is used at high temperature and high voltage, and a power device using the same. The non-aqueous electrolytic solution according to the present invention comprises, in addition to a non-aqueous solvent and an electrolyte salt dissolved therein, a compound represented by the following formula (I): ##STR00001## wherein n is an integer of 1 or 2; and when n is 1, L represents a straight or branched unsaturated hydrocarbon group of which at least one hydrogen atom is optionally substituted by a halogen atom, a cycloalkyl group of which at least one hydrogen atom is optionally substituted by a halogen atom, or an aryl group of which at least one hydrogen atom is optionally substituted by a halogen atom; and when n is 2, L represents a saturated or unsaturated divalent hydrocarbon group which optionally contains ether bond(s), or an arylene group.
Claims
1. A non-aqueous electrolytic solution comprising at least a non-aqueous solvent, an electrolyte salt dissolved in the non-aqueous solvent, and a compound represented by general formula (I): ##STR00031## wherein n is an integer of 1 or 2; and when n is 1, L represents a straight or branched unsaturated hydrocarbon group that has 2 to 10 carbon atoms and of which at least one hydrogen atom is optionally substituted by a halogen atom, a cycloalkyl group that has 3 to 10 carbon atoms and of which at least one hydrogen atom is optionally substituted by a halogen atom, or an aryl group having 6 to 20 carbon atoms and of which at least one hydrogen atom is optionally substituted by a halogen atom; and when n is 2, L represents a saturated or unsaturated divalent hydrocarbon group that has 2 to 12 carbon atoms and optionally contains ether bond(s), or an arylene group that has 6 to 20 carbon atoms.
2. The non-aqueous electrolytic solution according to claim 1, wherein a content of the compound represented by general formula (I) is 0.001 to 10% by mass.
3. The non-aqueous electrolytic solution according to claim 1, wherein n is 1 and L represents a straight or branched C2-C10 alkenyl group, a straight or branched C2-10 alkynyl group, or a C3-10 cycloalkyl group, wherein these groups are optionally substituted by one or more halogen atoms selected from the group consisting of fluorine, chlorine, bromine, and iodine.
4. The non-aqueous electrolytic solution according to claim 1, wherein n is 1 and L represents a phenyl group which is optionally substituted by one or more straight or branched alkyl groups, wherein hydrogen atom(s) on a benzene ring of the phenyl group and hydrogen atom(s) on an alkyl group substituted on the benzene ring are optionally substituted by one or more halogen atoms selected from the group consisting of fluorine, chlorine, bromine, and iodine.
5. The non-aqueous electrolytic solution according to claim 1, wherein n is 2 and L represents a straight or branched C2-12 alkylene group, a straight or branched C2-12 alkenylene group, and a C2-12 alkynylene group, wherein these groups may contain ether bond(s).
6. The non-aqueous electrolytic solution according to claim 1, wherein n is 2 and L represents a cycloalkylene group having 2 to 12 carbon atoms.
7. The non-aqueous electrolytic solution according to claim 1, wherein n is 2 and L represents a phenylene group, a tolylene group (methylphenylene group), a dimthylphenylene group, a xylylene group (phenylene-bis-methylene group), a biphenylylene group, a naphthylene group, an anthrylene group, or a phenanthrylene group.
8. The non-aqueous electrolytic solution according to claim 1, wherein n is 2 and L represents a phenylene group or a naphthylene group which is optionally substituted by one or more straight or branched alkyl groups.
9. The non-aqueous electrolytic solution according to claim 1, wherein the non-aqueous solvent comprises one or at least two selected from the group consisting of cyclic carbonates and chain esters.
10. The non-aqueous electrolytic solution according to claim 9, wherein the cyclic carbonates is one or at least two selected from the group consisting of ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 4-fluoro-1,3-dioxolan-2-one, trans- or cis-4,5-difluoro-1,3-dioxolan-2-one, vinylene carbonate, and vinylethylene carbonate.
11. The non-aqueous electrolytic solution according to claim 9, wherein the chain esters is one or at least two selected from the group consisting of asymmetric chain carbonates, symmetric chain carbonates, and chain carboxylic acid esters.
12. The non-aqueous electrolytic solution according to claim 11, wherein the asymmetric chain carbonates is one or at least two selected from the group consisting of methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, and ethyl propyl carbonate; the symmetric chain carbonate is one or at least two selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, and dibutyl carbonate; and the linear carboxylic acid ester is one or at least two selected from the group consisting of pivalic acid esters such as methyl pivalate, ethyl pivalate, propyl pivalate, and the like, methyl propionate, ethyl propionate, methyl acetate, and ethyl acetate.
13. The non-aqueous electrolytic solution according to claim 9, wherein the chain esters is one or at least two methyl-containing chain esters selected from the group consisting of methyl ethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, methyl butyl carbonate, dimethyl carbonate, methyl propionate, methyl acetate, and ethyl acetate.
14. The non-aqueous electrolytic solution according to claim 1, wherein the electrolyte salt contains one or at least two selected from LiPF.sub.6, LiPO.sub.2F.sub.2, Li.sub.2PO.sub.3F, LiBF.sub.4, LiN(SO.sub.2CF.sub.3).sub.2, LiN(SO.sub.2C.sub.2F.sub.5).sub.2, LiN(SO.sub.2F).sub.2, lithium difluorobis[oxalate-O,O]phosphate, and lithium tetrafluoro[oxalate-O,O]phosphate.
15. The non-aqueous electrolytic solution according to claim 1, which is used as a non-aqueous electrolytic solution for a power storage device comprising a positive electrode, a negative electrode, and a non-aqueous electrolytic solution containing an electrolyte salt dissolved in a non-aqueous solvent.
16. The non-aqueous electrolytic solution according to claim 15, wherein the power storage device is a lithium ion rechargeable battery.
17. The non-aqueous electrolytic solution according to claim 15, wherein the negative electrode comprises, as a negative electrode active material, one or at least two materials selected from lithium metal, lithium alloys, carbon materials capable of occluding and releasing lithium, tin, tin compounds, silicon, silicon compounds, and lithium titanate compounds.
18. The non-aqueous electrolytic solution according to claim 15, wherein the negative electrode is one comprising a carbon material.
19. The non-aqueous electrolytic solution according to claim 15, wherein the positive electrode is one comprising, as a positive electrode active material, a composite metal oxide of one or more metals selected from cobalt, manganese, and nickel with lithium, or lithium-containing olivine form of phosphoric acid salts containing one or more metals selected from iron, cobalt, nickel, and manganese.
20. A power storage device comprising at least a positive electrode, a negative electrode, and a non-aqueous electrolytic solution containing an electrolyte salt dissolved in a non-aqueous solvent, wherein the non-aqueous electrolytic solution is a non-aqueous electrolytic solution according to claim 1.
Description
EXAMPLES
(1) The present invention will be further described in detail with reference to the following examples, but the present invention is not limited to these examples.
Examples 1 to 18 and Comparative Examples 1 to 3
(2) [Preparation of Lithium Ion Rechargeable Battery]
(3) LiNi.sub.1/3Mn.sub.1/3CO.sub.1/3O.sub.2 (94% by mass) and acetylene black (conductive agent) (3% by mass) were mixed together, and the mixture was added to and mixed with a solution previously prepared by dissolving polyvinylidene fluoride (binder) (3% by mass) in 1-methyl-2-pyrrolidone to prepare a positive electrode mixture paste. The positive electrode mixture paste was coated on one surface of an aluminum foil (current collector). The coating was dried and pressed, followed by cutting into a predetermined size to prepare a strip-shaped positive electrode sheet. The density of the positive electrode excluding the current collector was 3.6 g/cm.sup.3. Further, silicon (simple substance) (10% by mass), an artificial graphite (d.sub.0.02=0.335 nm, negative electrode active material) (80% by mass), and acetylene black (conductive agent) (5% by mass) were mixed together, and the mixture was added to and mixed with a solution previously prepared by dissolving polyvinylidene fluoride (binder) (5% by mass) in 1-methyl-2-pyrrolidone to prepare a negative electrode mixture paste. The negative electrode mixture paste was coated on one surface of a copper foil (current collector), and the coating was dried and pressed, followed by cutting into a predetermined size to prepare a negative electrode sheet. The density of the negative electrode excluding the current collector was 1.5 g/cm.sup.3. The electrode sheet was analyzed by X-ray diffractometry. As a result, the ratio of a peak intensity of (110) face, i.e. l(110), to a peak intensity of (004) face, i.e. l(004), of graphite crystal [l(110)/l(004)] was 0.1. The positive electrode sheet, a microporous polyethylene film separator, and the negative electrode sheet were stacked in that order. Further, a non-aqueous electrolytic solution having a composition described in Table 1 and Table 2 was added to prepare a laminate type battery.
(4) [Evaluation of High-Temperature Cycle Characteristics]
(5) The battery prepared by the above method was charged in a thermostatic chamber of 65 C. at a constant current of 1 C and a constant voltage for 3 hours to an end voltage of 4.3 V, and the battery was discharged under a constant current of 1 C to a discharge voltage of 3.0 V. This process was taken as one cycle, and the process was repeated for 100 cycles. Then, a capacity retention ratio after cycling was determined according to the following formula:
Capacity retention ratio(%)=(discharge capacity after the 100th cycle)/(discharge capacity after the 1.sup.st cycle)100
(6) The preparation conditions and battery characteristics were as shown in Tables 1 and 2.
(7) TABLE-US-00001 TABLE 1 Compound (I) Content in non- Capacity Composition of electrolyte salt aqueous retention ratio Composition of non-aqueous electrolytic after high- electrolytic solution solution temperature (volume ratio of solvents) formula % by mass) cycling (%) Ex. 1 1M LiPF6 EC/PC/MEC/DEC (20/10/30/40)
(8) TABLE-US-00002 TABLE 2 Compound (I) Capacity Composition of electrolyte salt Content in non- retention ratio Composition of non-aqueous aqueous electrolytic after high- electrolytic solution solution temperature (volume ratio of solvents) formula (% by mass) cycling (%) Ex. 8 1M LiPF6 EC/PC/VC/MEC/DEC (20/9/1/30/40)
Example 19 and Comparative Example 4
(9) A positive electrode sheet was prepared in the same manner as in Example 1 and Comparative Example 1 except that, instead of the positive electrode active material used therein, LiNi.sub.1/2Mn.sub.3/2O.sub.4 (positive electrode active material) was used. There were mixed 94% by mass of LiNi.sub.1/2Mn.sub.3/2O.sub.4 coated with amorphous carbon and 3% by mass of acetylene black (conductive agent), and the mixture was added to and mixed with a solution prepared beforehand by dissolving 3% by mass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone to prepare a positive electrode mixture paste. A laminate type battery was prepared and evaluation of the battery was conducted in the same manner as in Example 1 and Comparative Example 1 except that the above positive electrode mixture paste was coated on one surface of an aluminum foil (current collector), that the coated material was dried and subjected to a pressure treatment, and the material was cut into a predetermined size to prepare a positive electrode sheet, that the charge end voltage and the discharge end voltage at the time of battery evaluation were set at 4.9 V and 2.7 V, respectively, and that the composition of the non-aqueous electrolytic solution was changed to a specified one. The results were as shown in Table 3.
(10) TABLE-US-00003 TABLE 3 Composition of electrolyte salt Compound (I) Composition of non- Content in non- Capacity aqueous electrolytic aqueous retention ratio Amount of gas solution electrolytic after high- generation after (volume ratio of solution temperature high-temperature solvents) formula (% by mass) cycling (%) cycling (%) Ex. 19 1M LiPF6 FEC/MTFEC (35/65)
Example 20 and Comparative Example 5
(11) A negative electrode sheet was prepared in the same manner as in Example 1 except that, instead of the negative electrode active material used therein, lithium titanate Li.sub.4Ti.sub.5O.sub.12 (negative electrode active material) was used. There were mixed 80% by mass of lithium titanate Li.sub.4Ti.sub.5O.sub.12 and 15% by mass of acetylene black (conductive agent), and the mixture was added to and mixed with a solution prepared beforehand by dissolving 5% by mass of polyvinylidene fluoride (binder) in 1-methyl-2-pyrrolidone to prepare a negative electrode mixture paste. A laminate type battery was prepared and evaluation of the battery was conducted in the same manner as in Example 1 except that the above negative electrode mixture paste was coated on a copper foil (current collector), that the coated material was dried and subjected to a pressure treatment, and the material was cut into a predetermined size to prepare a negative electrode sheet, that the charge end voltage and the discharge end voltage at the time of battery evaluation were set at 2.8 V and 1.2 V, respectively, and that the composition of the non-aqueous electrolytic solution was changed to a specified one. The results were as shown in Table 4.
(12) TABLE-US-00004 TABLE 4 Composition of electrolyte salt Compound (I) Composition of non- Content in non- Capacity aqueous electrolytic aqueous retention ratio Amount of gas solution electrolytic after high- generation after (volume ratio of solution temperature high-temperature solvents) formula (% by mass) cycling (%) cycling (%) Ex. 20 1M LiPF6 PC/DEC (30/70)
(13) All the lithium ion rechargeable batteries of Examples 1 to 18 are improved in cycle characteristics at high temperature compared to the following lithium ion rechargeable batteries where, in the non-aqueous electrolytic solution of the present invention, the compound represented by general formula (I) is not added (Comparative Example 1), a compound described in the Patent Literature 1 is added (Comparative Example 2), and a compound described in the Patent Literature 2 is added (Comparative Example 3). Further, the same effect can be seen when lithium nickel manganate (LiNi.sub.1/2Mn.sub.3/2O.sub.4) is used for the positive electrode from comparison of Example 19 and Comparative Example 4, and also when lithium titanate is used for the negative electrode from comparison of Example 20 and Comparative Example 4. Accordingly, it is evident that the effect of the present invention is not dependent upon specific positive electrode and negative electrode.
(14) From the above, it has become clear that the effect obtained when the power storage device of the present invention is used at high temperature and high pressure is an effect characteristic of a case where the compound represented by general formula (I) is contained in the non-aqueous electrolytic solution.
(15) Furthermore, the non-aqueous electrolytic solution of the present invention also has an effect of improving discharge characteristics when the lithium primary battery is used at high voltage.