JP6100473B2 - Electrochemical devices - Google Patents

Description

  The present invention relates to electrochemical devices such as lithium ion capacitors and lithium ion secondary batteries.

  Examples of the electrochemical device having a chargeable / dischargeable battery function include an electric double layer capacitor and a lithium ion secondary battery. A hybrid type capacitor such as a lithium ion capacitor constituted by a positive electrode of an electric double layer capacitor and a negative electrode of a lithium ion secondary battery is also known.

  Such electrochemical devices are required to have higher energy density, lower resistance, and lower cost in application to energy sources and energy regeneration applications.

  For the negative electrode of these electrochemical devices, graphitizable carbon or non-graphitizable carbon is used depending on the application, and the non-graphitizable carbon is characterized by excellent high output characteristics and cycle characteristics.

  Conventionally, in an electrochemical device using non-graphitizable carbon as a negative electrode, by using an electrolyte containing ethylene carbonate, the surface of the negative electrode is subjected to SEI (Solid electrolyte interface) by initial charge and discharge. A film is formed. This SEI film is mainly composed of a Li-containing inorganic substance or a Li-containing organic substance. By forming the SEI film, the decomposition of the electrolytic solution is suppressed, the insertion of lithium ions into the negative electrode (hereinafter referred to as “dope”) and the elimination are facilitated, and the cycle characteristics are improved.

Patent Document 1 discloses that a film is formed on the surface of a negative electrode using a solution obtained by dissolving LiPF _{6 in} a mixed solution of ethylene carbonate, propylene carbonate, and dimethyl carbonate as an electrolytic solution.

JP 2001-126760 A

  However, an electrochemical device using an electrolytic solution as disclosed in Patent Document 1 has a tendency that the SEI film grows and the film is formed thick by repeating charge and discharge. When the thickness of the SEI film formed on the surface of the negative electrode is increased, there is a problem that diffusion of lithium ions is inhibited and internal resistance is increased.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electrochemical device in which the growth of the SEI film is suppressed and the resistance is reduced.

  A positive electrode having a positive electrode active material made of activated carbon or an oxide containing lithium, a negative electrode having a negative electrode active material made of a non-graphitizable carbon material that can be doped or dedoped with lithium, and at least propylene carbonate and ethylene carbonate And an electrolytic solution composed of a solution obtained by dissolving a lithium salt in a solvent of a mixed solution containing a chain carbonate, and a lithium ion supply source for doping the lithium into the negative electrode, The ethylene carbonate content is 0.01 vol% or more and less than 5.00 vol%, the propylene carbonate content is 60.00 vol% or more and 99.90 vol% or less, and the chain carbonate content is 0 to 35.00 vol% of electrochemical data A chair.

  The chain carbonate is preferably at least one selected from diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate.

The lithium salt is preferably at least one selected from LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiSbF ₅ , LiN (C ₂ F ₅ SO ₂ ) ₂ and LiClO ₄ .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the electrochemical device which suppressed the growth of the SEI film and aimed at low resistance.

Sectional drawing which shows the electrochemical device of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

  The electrochemical device of the present embodiment includes a positive electrode, a negative electrode, an electrolytic solution, and a lithium ion supply source. The positive electrode has a positive electrode active material made of activated carbon or an oxide containing lithium, and the negative electrode has a negative electrode active material made of a non-graphitizable carbon material that can be doped or dedoped with lithium. Moreover, the electrolytic solution of the present embodiment is a solution in which a lithium salt is dissolved in a solvent of a mixed solution containing at least propylene carbonate and ethylene carbonate and further containing a chain carbonate. In this solvent, the ethylene carbonate content is 0.01 vol% or more and less than 5.00 vol%, the propylene carbonate content is more than 60.00 vol% and 99.90 vol% or less, and the chain carbonate content is Is 0 or more and 35.00 vol% or less.

  FIG. 1 is a view showing an electrochemical device of the present invention. In this embodiment, a lithium ion capacitor will be described as an example of an electrochemical device.

  As shown in FIG. 1, the electrochemical device of the present embodiment includes a positive electrode 11, a negative electrode 12, and an electrolytic solution 13. The positive electrode 11 includes a positive electrode current collector 14 and a positive electrode active material layer 15 in which a positive electrode active material is formed on one surface or both surfaces of the positive electrode current collector 14. The negative electrode 12 includes a negative electrode current collector 16 and a negative electrode active material layer 17 in which a negative electrode active material is formed on one surface or both surfaces of the negative electrode current collector 16. A separator 18 is disposed so as to face the positive electrode 11 and the negative electrode 12.

  The positive electrode 11 and the negative electrode 12 are alternately stacked via the separator 18 to form an electrode body 101. At this time, the electrode body 101 is preferably laminated so that the outermost layer of the electrode body 101 becomes the negative electrode 12. A lithium ion supply source 19 is disposed on at least a part of the outer side of the electrode body 101 so as to face the electrode body 101.

  The electrode body 101 is housed in the exterior material 20 together with the lithium ion supply source 19 and is impregnated in the electrolytic solution 13. In this state, lithium ions are doped into the negative electrode active material layer 17 from the lithium ion supply source 19. In the present embodiment, the means for doping the negative electrode active material layer 17 with lithium ions is not particularly limited. For example, a method of electrochemically doping the negative electrode active material layer 17 with lithium ions, The lithium ion source 19 can be physically short-circuited and doped.

  The number of positive electrodes 11 and negative electrodes 12 constituting the electrode body 101 can be appropriately set according to the desired capacity and resistance. The quantity of the lithium ion supply source 19 can also be set as appropriate in consideration of the lithium ion doping amount and the doping time. Further, the position of the lithium ion supply source 19 can be laminated not only on the upper and lower surfaces and side surfaces of the electrode body 101 which is the outside of the electrode body 101 but also on the central portion of the electrode body 101.

  As the electrolytic solution 13 of the present embodiment, a solution in which a lithium salt is dissolved in a solvent of a mixed solution containing at least propylene carbonate (PC) and ethylene carbonate (EC) is used. This solvent may further contain a chain carbonate.

  In the said solvent, the content rate of ethylene carbonate is 0.01 vol% or more and less than 5.00 vol%, the content rate of propylene carbonate is more than 60.00 vol% and 99.90 vol% or less, and the content rate of chain carbonate However, it is 0 or more and 35.00 vol% or less. In the present embodiment, by setting the content of the solvent within the above range, it becomes possible to form the SEI film on the surface of the negative electrode, and to suppress the growth of the SEI film even when charging and discharging are repeated. The resistance of chemical devices can be reduced.

  In the above-mentioned solvent, it is not always necessary to contain a chain carbonate, but an electrolyte solution containing ethylene carbonate generally has a high viscosity, so that the effect of lowering the viscosity of the electrolyte solution can be obtained by containing a chain carbonate. . As the chain carbonate, diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and the like can be preferably used.

  Moreover, it is also possible to add additives, such as vinylene carbonate (VC), ethylene sulfite (ES), and fluoroethylene carbonate (FEC), within the range of the above solvent. By adding these additives, it becomes possible to form the SEI film more smoothly, and an improvement in cycle characteristics can be expected.

The lithium salt dissolved in the solvent may be any one that ionizes to generate lithium ions, such as LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiSbF ₅ , LiN (C ₂ F ₅ SO ₂ ) ₂ and It is preferably at least one selected from LiClO ₄ .

  As the material of the negative electrode current collector 16, various materials generally used for lithium ion secondary batteries and the like, that is, stainless steel, copper, nickel and the like can be used. The same material can be used for the current collector of the lithium ion supply source 19. For these current collectors, rolled foil, electrolytic foil, penetrating foil with holes penetrating the front and back surfaces, net-like porous lath foil such as expanded metal, and the like can be used.

The negative electrode active material that is the main component of the negative electrode active material layer 17 is formed of a material that can be reversibly doped with lithium ions, and is made of a non-graphitizable carbon material. Among non-graphitizable carbon materials, the C-axis direction plane distance d ₀₀₂ value obtained by the X-ray diffraction method is 0.341 nm or more and 0.339 nm or less, and the crystal size (Lc) in the C axis direction is An amorphous carbon material having a thickness of 0.5 to 18 nm is preferable in consideration of characteristics such as energy density. In addition, the specific surface area of the negative electrode active material layer 17 is preferably about 1 to 40 m ² / g because output characteristics such as energy density can be expected to be improved.

  Aluminum, stainless steel, or the like can be used for the positive electrode current collector 14. In order to reduce the resistance and the cost, it is preferable to use an aluminum etching foil generally used for an aluminum electrolytic capacitor or an electric double layer capacitor. Since the aluminum etching foil increases the specific surface area by etching aluminum, the contact area with the positive electrode active material layer 15 is increased, the resistance is reduced, and the output characteristics are improved. Moreover, since it is a general-purpose product, low cost can be expected. The etching treatment of the aluminum etching foil can be any of rolled foil and electrolytic foil. Various rolled foils, electrolytic foils, and porous lath foils used for lithium ion secondary batteries can also be used.

  The positive electrode active material that is the main component of the positive electrode active material layer 15 is formed of a material that can reversibly carry anions or cations. For example, carbon materials such as polarizable phenol resin activated carbon, coconut shell activated carbon, petroleum coke activated carbon, and polyacene can be used. Moreover, the positive electrode material etc. of a lithium ion secondary battery can also be used.

  A conductive additive and a binder are added to the positive electrode active material layer 15 and the negative electrode active material layer 17 as necessary. Examples of the conductive assistant include graphite, carbon black, ketjen black, vapor-grown carbon, and carbon nanotube, and carbon black and graphite are particularly preferable. As the binder, for example, a rubber-based binder such as styrene-butadiene rubber (SBR), a fluorine-containing resin such as polytetrafluoroethylene or polyvinylidene fluoride, or a thermoplastic resin such as polypropylene or polyethylene can be used.

  The lithium ion supply source 19 may be a material that can supply lithium ions, such as metallic lithium or a lithium-aluminum alloy. The thickness of the lithium ion supply source 19 can be changed depending on the doping amount of lithium ions, but is preferably 5 μm or more and 400 μm or less. When the thickness is 5 μm or more, workability is improved, and when the thickness is 400 μm or less, it is possible to suppress the remaining lithium ion supply source 19. The lithium ion supply source 19 may have a current collector for taking out electric charges.

  As mentioned above, although this Embodiment was demonstrated taking the case of the lithium ion capacitor as an example, it is also possible to apply a lithium ion secondary battery as an electrochemical device of this invention.

  However, in general, a lithium ion secondary battery uses a Li transition metal oxide as a positive electrode active material, and initial charge to the negative electrode (dope of lithium ions) is supplied from the positive electrode active material. For this reason, in a lithium ion secondary battery, when a non-graphitizable carbon material having a large irreversible capacity is used as the negative electrode active material, it is necessary to increase the thickness (weight) of the positive electrode active material layer, resulting in a low energy density. There is. Therefore, in general, a graphitizable carbon material having a small irreversible capacity is often used for the negative electrode active material of the lithium ion secondary battery. The present invention can also be applied to a lithium ion secondary battery using a non-graphitizing material. In addition, the lithium ion secondary battery is repeatedly destroyed and regenerated in the SEI film except for a part due to charge and discharge, whereas the lithium ion capacitor does not break the SEI film. When a lithium ion capacitor is used, the effects of the present invention can be obtained more remarkably.

Example 1
92 parts by mass of a phenol-based activated carbon powder having a specific surface area of 1500 m ² / g, which is a positive electrode active material, and 8 parts by mass of graphite as a conductive agent, 3 parts by mass of styrene butadiene rubber as a binder and 3 parts by mass of carboxymethyl cellulose And 200 parts by mass of water as a solvent and kneaded to obtain a slurry. Next, an aluminum foil having a thickness of 20 μm whose both surfaces are roughened by etching treatment is used as a positive electrode current collector, and the slurry is uniformly applied to both sides thereof, then dried and rolled and pressed. A positive electrode active material layer of 30 μm was formed to obtain a positive electrode. The thickness of this positive electrode was 80 μm. Further, an extension part in which the current collector is extended in a tab shape is formed from a part of the end face of the positive electrode, and the negative electrode active material layer is not formed on both surfaces of the current collector of the extension part, and the aluminum foil Was exposed and connected to an external terminal so that charges could be taken out. In addition, the positive electrode collector used the plain foil in which the through-hole was not provided.

For the powder obtained by mixing 88 parts by mass of the non-graphitizing material powder having a specific surface area of 20 m ² / g as the negative electrode active material and 6 parts by mass of acetylene black as a conductive agent, 5 parts by mass of styrene butadiene rubber and 4 parts by mass of carboxymethyl cellulose are used as binders. The solvent was added to 200 parts by mass of water and kneaded to obtain a slurry. Next, a copper foil having a thickness of 10 μm is used as a negative electrode current collector, and the slurry is uniformly applied on both sides thereof, then dried and rolled and pressed to form a negative electrode active material layer having a thickness of 20 μm on both sides, thereby forming a negative electrode Got. The thickness of this negative electrode was 50 μm. Further, an extension part in which the current collector is extended in a tab shape is formed from a part of the end face of the negative electrode, and the negative electrode active material layer is not formed on both surfaces of the current collector of the extension part, and the copper The foil was exposed and connected to an external terminal so that charges could be taken out. The negative electrode current collector used was a plain foil without a through hole.

  As a separator, a thin plate of a natural cellulose material having a thickness of 35 μm was used. The size and shape of this separator was configured to be slightly larger than the positive electrode and the negative electrode.

  Subsequently, these three members were laminated in the order of a separator, a negative electrode, a separator, a positive electrode, and a separator to obtain an electrode body. One separator was arranged on each of the uppermost part and the lowermost part of the electrode body. In this example, four positive electrodes, five negative electrodes, and ten separators were stacked per sample, and the dimensions excluding the extension were 53 mm x 70 mm for the positive electrode and 55 mm for the negative electrode. X 72 mm, separator was 57 mm x 74 mm. Moreover, the extension part formed in each electrode extended from the same short side of each electrode, and the dimension of the extension part was 9 mm x 12 mm, respectively.

  Next, the extending portions of the positive electrode and the negative electrode extending from the electrode body were bundled and collectively fixed to the end portions of the external terminals by ultrasonic welding. In addition, a lithium ion supply source was prepared by laminating metal lithium to the copper foil, and an external terminal of the lithium ion supply source was fixed to the extension part extending from a part of the copper foil by ultrasonic welding. The produced lithium ion supply source was disposed on the upper surface of the electrode body so that the metallic lithium faced the electrode body. Thereafter, the electrode body is wrapped with two exterior materials, and the peripheral edge of the three sides including the side where the positive electrode, the negative electrode, and the external terminal of the lithium ion supply source are arranged is thermocompression bonded, and the heat formed on the inner surface of the exterior material The plastic resin layer was joined to form a bag. The thermoplastic resin layer on the inner surface of the exterior material is made of an acid-modified polyolefin resin, and its thickness is 40 μm.

Further, an electrolytic solution was injected into a bag-shaped exterior material containing the electrode body. The electrolyte solution in this example was prepared to a concentration of 1.0 mol / l by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate was mixed at a ratio of 0.01 vol% and propylene carbonate at a ratio of 99.99 vol%. I used something.

  After injecting the electrolytic solution, the remaining one side of the two exterior members was sealed by thermocompression bonding in a vacuum atmosphere. Further, lithium ions were doped from the lithium ion source to the negative electrode active material of the negative electrode by an electrochemical method. The dope amount was 400 mAh / g with respect to the mass of the negative electrode active material.

(Example 2)
The electrolyte solution of Example 2 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of 0.05 vol% ethylene carbonate and 99.95 vol% propylene carbonate to prepare a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Example 3)
The electrolytic solution of Example 3 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate was mixed at a ratio of 0.10 vol% and propylene carbonate 99.90 vol% to a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

Example 4
The electrolyte solution of Example 4 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of ethylene carbonate 0.50 vol% and propylene carbonate 99.50 vol% to a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Example 5)
The electrolyte solution of Example 5 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of ethylene carbonate 1.00 vol% and propylene carbonate 99.00 vol% to a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Example 6)
The electrolyte solution of Example 6 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of ethylene carbonate of 3.00 vol% and propylene carbonate of 97.00 vol% to a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Example 7)
The electrolyte solution of Example 7 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of ethylene carbonate 4.50 vol% and propylene carbonate 95.50 vol% to a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

( Reference example )
The electrolyte solution of the reference example was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of 4.90 vol% ethylene carbonate and 95.10 vol% propylene carbonate and adjusting the concentration to 1.0 mol / l. did. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Comparative Example 1)
The electrolytic solution of Comparative Example 1 was prepared by dissolving LiPF ₆ in a solvent containing only propylene carbonate without containing ethylene carbonate, and adjusting the concentration to 1.0 mol / l. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Comparative Example 2)
The electrolytic solution of Comparative Example 2 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of ethylene carbonate 6.00 vol% and propylene carbonate 94.00 vol% to a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Comparative Example 3)
The electrolytic solution of Comparative Example 3 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of ethylene carbonate 40.00 vol% and propylene carbonate 60.00 vol% to a concentration of 1.0 mol / l. used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

Example 9
The electrolyte solution of Example 9 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate was mixed at a ratio of 3.00 vol%, propylene carbonate 96.00 vol%, and diethyl carbonate 1.00 vol%. What was adjusted to the density | concentration of was used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Example 10)
The electrolyte solution of Example 10 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution obtained by mixing ethylene carbonate at 3.00 vol%, propylene carbonate at 77.00 vol%, and diethyl carbonate at 20.00 vol%. What was adjusted to the density | concentration of was used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Example 11)
The electrolyte solution of Example 11 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate was mixed at a ratio of 3.00 vol%, propylene carbonate 62.00 vol%, and diethyl carbonate 35.00 vol%. What was adjusted to the density | concentration of was used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Comparative Example 4)
The electrolytic solution of Comparative Example 4 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate was mixed at a ratio of 3.00 vol%, propylene carbonate 59.00 vol%, and diethyl carbonate 38.00 vol%. What was adjusted to the density | concentration of was used. Except for the configuration of this electrolytic solution, it was the same as Example 1.

(Example 12)
In Example 12, a lithium ion secondary battery was produced as an electrochemical device. Lithium cobalt oxide was used as the positive electrode active material, and a polyethylene separator was used as the separator.

In addition, the electrolyte solution of Example 12 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate was mixed at a ratio of 3.00 vol% and propylene carbonate at 97.00 vol% to a concentration of 1.0 mol / l. I used something.

  Except for the configuration of the positive electrode active material, the separator, and the electrolytic solution, it was the same as Example 1.

(Example 13)
The electrolyte solution of Example 13 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution mixed at a ratio of ethylene carbonate 4.50 vol%, propylene carbonate 85.50 vol%, diethyl carbonate 10.00 vol%, and 1.0 mol / l. What was adjusted to the density | concentration of was used. Except for the configuration of the electrolytic solution, the same procedure as in Example 12 was performed.

(Example 14)
The electrolyte solution of Example 14 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate was mixed at a ratio of 4.50 vol%, propylene carbonate 85.50 vol%, and ethyl methyl carbonate 10.00 vol%. What was prepared to the density | concentration of 1 was used. Except for the configuration of the electrolytic solution, the same procedure as in Example 12 was performed.

(Example 15)
The electrolytic solution of Example 15 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution in which ethylene carbonate 4.50 vol%, propylene carbonate 85.50 vol%, and dimethyl carbonate 10.00 vol% were mixed, and 1.0 mol / l. What was adjusted to the density | concentration of was used. Except for the configuration of the electrolytic solution, the same procedure as in Example 12 was performed.

(Comparative Example 5)
The electrolyte solution of Comparative Example 5 was prepared by dissolving LiPF _{6 in} a solvent of a mixed solution obtained by mixing ethylene carbonate at 5.00 vol%, propylene carbonate at 50.00 vol%, and diethyl carbonate at 45.00 vol%. What was adjusted to the density | concentration of was used. Except for the configuration of the electrolytic solution, the same procedure as in Example 12 was performed.

  Twenty electrochemical devices were produced by the above method. The produced electrochemical device was charged at a constant current and a constant voltage at 3.8 V for 1 hour, and discharged at 80 mV until the voltage reached 2.2 V. The direct current resistance (DC-R) was calculated from the voltage drop during discharge, and the average value of 20 was obtained. As an initial characteristic, in the lithium ion capacitor, a value of 5% or less of the average value of Comparative Example 3 was determined to be acceptable with reference to Comparative Example 3 which is a conventional technique. Moreover, in the lithium ion secondary battery, the value of 5% or less of the average value of the comparative example 5 and the pass were determined based on the comparative example 5.

  Moreover, the float test and the cycle test were implemented as an endurance test. In the float test, in a lithium ion capacitor, DC-R was measured at room temperature after 2000 hours in a state where a voltage of 3.8 V was applied in an environment of 70 ° C. In a lithium ion secondary battery, DC-R was measured at room temperature after 2000 hours in a state where a voltage of 4.2 V was applied in an environment of 60 ° C.

  In the cycle test, for a lithium ion capacitor, charge and discharge were repeated 5000 cycles in an environment at 70 ° C., and then the capacity and DC-R were measured at room temperature. In the lithium ion secondary battery, charging / discharging was repeated 1000 cycles in an environment of 60 ° C., and then the capacity and DC-R were measured at room temperature.

  In the float test and the cycle test, the rate of change of DC-R was calculated from the average value of the measured values before and after the test. In the float test, the change rate was determined to be within 20%, and in the cycle test, the change rate was determined to be within 50%.

  Table 1 shows the evaluation results of the initial characteristics and durability tests of the examples and comparative examples.

  As shown in Table 1, in the examples of the present invention, the initial characteristics are maintained at the same level as in the conventional comparative example, and in the durability test, the rate of change of DC-R is greatly improved and the increase in DC-R Can be suppressed. Therefore, the electrochemical device in which the growth of the SEI film is suppressed and the resistance is reduced is obtained by the configuration of the present invention.

  As described above, the present invention has been described using the embodiment and the examples. However, the present invention is not limited to these, and even if there is a design change or the like without departing from the gist of the present invention, the present invention is not limited thereto. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

DESCRIPTION OF SYMBOLS 11 Positive electrode 12 Negative electrode 13 Electrolytic solution 14 Positive electrode collector 15 Positive electrode active material layer 16 Negative electrode collector 17 Negative electrode active material layer 18 Separator 19 Lithium ion supply source 20 Exterior material 101 Electrode body

Claims (7)

A positive electrode having a positive electrode active material made of activated carbon or an oxide containing lithium, a negative electrode having a negative electrode active material made of a non-graphitizable carbon material that can be doped or dedoped with lithium, and at least propylene carbonate and ethylene carbonate DOO comprising an electrolyte solution in a solvent mixture consisting of a solution obtained by dissolving a lithium salt you containing a lithium ion supply source to dope the lithium into the negative electrode, and
The content of the ethylene carbonate is 0.01 vol% or more and 4.50 vol% or less,
The propylene carbonate content is more than 60.00 vol% and not more than 99.99 vol%,
An electrochemical device having a chain carbonate content of 0 or more and 35.00 vol% or less. 2. The electrochemical device according to claim 1, wherein the content of the chain carbonate is 1.00 vol% or more and 35.00 vol% or less. The linear carbonate electrochemical device according to claim 1 or 2, characterized in that at least one selected diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate. The lithium _{salt, LiPF 6, LiBF 4, LiCF} 3 SO 3, LiSbF 5, LiN (C 2 F 5 SO 2) 2 and claims 1-3, characterized in that at least one selected from LiClO ₄ The electrochemical device according to any one of the above. The solvent has a total content of ethylene carbonate and propylene carbonate of 65 vol% or more,
The electrochemical device according to any one of claims 1 to 4 , wherein a volume ratio (EC / PC) of ethylene carbonate (EC) to propylene carbonate (PC) is 0.01 / 99.99 to 3/62. The electrochemical device according to claim 5 , wherein the electrochemical device is a lithium ion capacitor, and the positive electrode has activated carbon as the positive electrode active material. The electrochemical device according to any one of claims 1 to 4 , wherein the electrochemical device is a lithium ion capacitor, and the positive electrode includes activated carbon as the positive electrode active material.

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