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EP-4191727-B1 - NON-AQUEOUS ELECTROLYTE SOLUTION AND POWER STORAGE DEVICE USING SAME

EP4191727B1EP 4191727 B1EP4191727 B1EP 4191727B1EP-4191727-B1

Inventors

  • KIDO, Taiki
  • KURIHARA, Yoshiki
  • SETOGUCHI, HIROYUKI
  • SHIMAMOTO, KEI

Dates

Publication Date
20260506
Application Date
20210730

Claims (13)

  1. A nonaqueous electrolytic solution for an energy storage device, which is the nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution comprising: a phosphonate represented by the following general formula (I): wherein, in formula (I), R 1 represents an alkenyl group having 2 to 6 carbon atoms or an alkynyl group having 3 to 6 carbon atoms, and R 2 and R 3 each independently represent an alkynyl group having 3 to 6 carbon atoms, wherein the electrolyte salt comprises one or more lithium salts (b) selected from the group consisting of LiPF 6 , LiBF 4 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , and LiN(SO 2 F) 2 [LiFSI], and wherein the nonaqueous solvent comprises one or more selected from the group consisting of a saturated cyclic carbonate, a linear ester, a lactone, an ether, and an amide.
  2. The nonaqueous electrolytic solution for an energy storage device according to claim 1, wherein a content of the phosphonate represented by the general formula (I) is 0.001% by mass or more and 5% by mass or less.
  3. The nonaqueous electrolytic solution for an energy storage device according to claim 1 or 2, wherein R 1 in the general formula (I) is a vinyl group, an allyl group, a 1-methylallyl group, a 2-methylallyl group, a crotyl group, a butenyl group, or a propynyl group.
  4. The nonaqueous electrolytic solution for an energy storage device according to any one of claims 1 to 3, wherein R 2 and R 3 in the general formula (I) each independently represent a 2-propynyl group, a 2-butynyl group, a 3-butynyl group, a 1-methyl-2-propynyl group, a 1,1-dimethyl-2-propynyl group, a 1-ethyl-1-methyl-2-propynyl group, or a 4-pentynyl group.
  5. The nonaqueous electrolytic solution for an energy storage device according to any one of claims 1 to 4, wherein the nonaqueous electrolytic solution further comprises one or more lithium salts (a) selected from the group consisting of a lithium salt having a phosphoric acid structure and a lithium salt having an S(=O) group.
  6. The nonaqueous electrolytic solution for an energy storage device according to claim 5, wherein a content of the lithium salt (a) is 0.01% by mass or more and 8% by mass or less.
  7. The nonaqueous electrolytic solution for an energy storage device according to any one of claims 1 to 6, wherein a content of the lithium salt (b) is 4% by mass or more and 28% by mass or less.
  8. The nonaqueous electrolytic solution for an energy storage device according to any one of claims 1 to 7, wherein the phosphonate comprises one or more selected from the group consisting of di-2-propynyl vinylphosphonate, di-2-propynyl allylphosphonate, di-2-propynyl 1-methylallylphosphonate, di-2-propynyl 2-methylallylphosphonate, di-2-propynyl crotylphosphonate, di-2-propynyl butenylphosphonate, and di-2-propynyl propynylphosphonate.
  9. The nonaqueous electrolytic solution for an energy storage device according to any one of claims 1 to 8, wherein the nonaqueous solvent comprises a saturated cyclic carbonate and a linear ester, and a ratio (mass ratio) of the cyclic carbonate to the linear ester is 10:90 to 50:50.
  10. The nonaqueous electrolytic solution for an energy storage device according to any one of claims 1 to 9, further comprising at least one of a cyclic carbonate having an unsaturated bond and a cyclic carbonate having a fluorine atom.
  11. The nonaqueous electrolytic solution for an energy storage device according to claim 10, wherein a content of the cyclic carbonate having an unsaturated bond is 0.05% by mass or more and 8% by mass or less.
  12. An energy storage device comprising: a positive electrode; a negative electrode; and a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, wherein the nonaqueous electrolytic solution is the nonaqueous electrolytic solution according to any one of claims 1 to 11.
  13. The energy storage device according to claim 12, wherein a proportion of an atomic concentration of Ni to an atomic concentration of all transition metal elements in a positive electrode active material in the positive electrode is 50 atomic% or more.

Description

Technical Field The present invention relates to a nonaqueous electrolytic solution and an energy storage device using the same. Background Art An energy storage device, especially a lithium secondary battery, has been widely used recently for a power source of a small-sized electronic device, such as a mobile telephone and a notebook personal computer, and a power source for an electric vehicle or electric power storage. There is a possibility that such an electronic device or a vehicle is used in a wide temperature range, such as a high temperature in midsummer and an extremely low temperature. Therefore, the energy storage device is required to improve electrochemical characteristics in a wide temperature range in a well-balanced manner. In particular, it is urgently necessary to reduce a CO2 emission amount in order to prevent global warming, and among eco-friendly vehicles equipped with an energy storage apparatus that includes an energy storage device, such as a lithium secondary battery and a capacitor, hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV) are required for early popularization. Since the vehicles travel a long distance, there is a possibility that the vehicles are used in regions with a wide temperature range, from a very hot tropical region to an extremely cold region. Therefore, in particular, these on-board energy storage devices are required to have electrochemical characteristics that do not worsen even when used in a wide temperature range from a high temperature to a low temperature. In the present specification, the term "lithium secondary battery" is used as a concept including a so-called lithium ion secondary battery. A lithium secondary battery mainly contains a positive electrode and a negative electrode, each containing a material capable of absorbing and releasing lithium ions, and a nonaqueous electrolytic solution containing a lithium salt and a nonaqueous solvent. A carbonate, such as ethylene carbonate (EC) and propylene carbonate (PC), is used as the nonaqueous solvent. In addition, metal lithium, a metal compound capable of absorbing and releasing lithium ions (e.g., an elemental metal, a metal oxide, and an alloy with lithium), a carbon material, and the like are known in the negative electrode. In particular, a lithium secondary battery using a carbon material capable of absorbing and releasing lithium ions, such as coke, artificial graphite, and natural graphite, is widely put into practical use. For example, in a lithium secondary battery using a highly crystallized carbon material, such as natural graphite and artificial graphite, as the negative electrode material, a solvent in a nonaqueous electrolytic solution is reductively decomposed on a negative electrode surface during charging. It is known that decomposed products and generated gases generated by the reductive decomposition inhibit a desirable electrochemical reaction of the battery, and therefore, cycle properties of the lithium secondary battery are worsened. In addition, when the decomposed products of the nonaqueous solvent are accumulated, the absorbing and releasing of lithium ions from and into the negative electrode cannot be smoothly performed, and electrochemical characteristics in the case of using the battery in a wide temperature range are apt to be worsened. Further, it is known that a lithium secondary battery using metal lithium or an alloy thereof, an elemental metal, such as tin and silicon, or a metal oxide thereof as the negative electrode material has a high initial capacity, but micronized powdering of the material is promoted during cycles, which brings about accelerated reductive decomposition of the nonaqueous solvent, and large worsening in battery performance, such as a battery capacity and cycle properties, as compared with the negative electrode formed of a carbon material. In addition, when the negative electrode material is subjected to micronized powdering or the decomposed products of the nonaqueous solvent are accumulated, the absorbing and releasing of lithium ions from and into the negative electrode cannot be smoothly performed, and the electrochemical characteristics are apt to be worsened in the case of using the battery in a wide temperature range. Meanwhile, in a lithium secondary battery using, for example, LiCoO2, LiMn2O4, LiNiO2, or LiFePO4 in the positive electrode, a part of a nonaqueous solvent in a nonaqueous electrolytic solution is oxidized and decomposed locally at an interface between the positive electrode material and the nonaqueous electrolytic solution in a charged state. It is known that decomposed products and generated gases generated by the oxidative decomposition inhibit a desirable electrochemical reaction of the battery, and therefore, electrochemical characteristics of the lithium secondary battery are worsened in the case of using the battery in a wide temperature range. As describ