JP2005317389A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery in which swelling of a battery at the time of initial charging, deterioration of the battery capacity, and swelling of the battery at the time of repeated charge and discharge cycle are suppressed. <P>SOLUTION: In the non-aqueous electrolyte secondary battery 1 having a positive electrode 4, a negative electrode 3, and an electrolyte, the electrolyte contains ethane-1, 2-diol sulfonic acid or propane-1, 2-diol sulfonic acid, and the negative electrode 3 contains graphite of which a part or whole part of the surface is covered by a low crystalline carbon having 0.5 mass% or more and 20 mass% or less. And the electrolyte contains either ethylene glicol sulfate ester or one or both of propanediol sulfate ester and vinylene carbonate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and an electrolyte.

In recent years, portable electronic devices have been improved in performance and size and weight, and the use of non-aqueous electrolyte secondary batteries such as lithium ion batteries has increased as high-energy density batteries used in these electronic devices. Yes. A nonaqueous electrolyte secondary battery such as a lithium ion battery tends to have a reduced discharge capacity as charging and discharging are repeated. Therefore, in order to prevent a reduction in discharge capacity when charging and discharging are repeated, a chain diol sulfonic acid is added to the electrolyte (for example, see Patent Document 1).
JP 2003-308876 A

  However, in a non-aqueous electrolyte secondary battery in which a chain diol sulfonic acid is added to the electrolyte, gas is generated during initial charging, so that the battery internal pressure increases and the battery swells, and the generated gas is between the electrode plates. The battery capacity is reduced. In addition, when current concentrates at a portion other than the portion where the gas is accumulated, metallic lithium dendrite is deposited on the negative electrode, causing a short circuit between the positive electrode and the negative electrode, and reducing charge / discharge efficiency. Furthermore, although the reduction of the discharge capacity when charging / discharging is repeated can be suppressed, there is a problem that when the charging / discharging is repeated, the thickness of the negative electrode plate is increased and the swelling of the battery is increased.

  The present invention has been made in view of such circumstances, by using graphite having a surface coated with low crystalline carbon as a negative electrode active material, and adding a compound represented by Formula 1 described later to an electrolyte. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery capable of suppressing battery swelling during initial charging, battery capacity decrease when the charge / discharge cycle is repeated, and battery swelling.

  In addition, the present invention covers a part or all of the surface of graphite with 0.5% by mass or more and 20% by mass or less of low crystalline carbon, thereby repeating battery swelling and charge / discharge cycles during initial charging. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery that can more effectively suppress a decrease in battery capacity and battery swelling.

  In addition, the present invention further suppresses the swelling of the battery during initial charging and the swelling of the battery when the charge / discharge cycle is repeated by adding a compound represented by Formula 2 or vinylene carbonate described later to the electrolyte. Another object is to provide a non-aqueous electrolyte secondary battery that can be used.

  In addition, the present invention uses ethane-1,2-diol sulfonic acid or propane-1,2-diol sulfonic acid as the compound represented by Formula 1, so that the battery swells and charges and discharges during initial charging. Another object of the present invention is to provide a nonaqueous electrolyte secondary battery that can more effectively suppress a decrease in battery capacity and battery swelling when the above is repeated.

  In addition, the present invention uses ethylene glycol sulfate or propanediol sulfate as the compound represented by Formula 2, thereby reducing the battery capacity when the battery is repeatedly swollen and charged / discharged during initial charging. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery that can more effectively suppress battery swelling.

  In addition, the present invention further increases the swelling of the battery during initial charging and the swelling of the battery when repeated charging and discharging by adding 0.2% by mass or more and 2% by mass or less of vinylene carbonate to the electrolyte. Another object is to provide a non-aqueous electrolyte secondary battery that can be satisfactorily suppressed.

A nonaqueous electrolyte secondary battery according to a first aspect of the present invention is a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte. The electrolyte includes a compound represented by the following formula 1, wherein the negative electrode is a low crystal It is characterized by containing graphite in which part or all of the surface is coated with crystalline carbon.
A-R1-OH (1)
(In the formula, R1 is a hydrocarbon group which may contain an unsaturated bond, or a hydrocarbon group which may contain an unsaturated bond, part or all of which is substituted with a halogen element; Has a structure represented by the following formula A1, A2 or A3.)

  A nonaqueous electrolyte secondary battery according to a second invention is the non-aqueous electrolyte secondary battery according to the first invention, wherein the coated graphite is coated with a low crystalline carbon having a part or all of the surface of 0.5% by mass or more and 20% by mass or less. It is characterized by being.

A nonaqueous electrolyte secondary battery according to a third invention is characterized in that, in the first or second invention, the electrolyte contains a compound represented by the following formula 2.
R2-B-R3 (2)
(In the formula, R 2 and R 3 are each independently a hydrocarbon group which may contain an unsaturated bond, or a carbon atom which may contain an unsaturated bond, part or all of which is substituted with a halogen element. Represents a hydrogen group, or R2 and R3 are bonded to each other to form a cyclic structure with B, and B has a structure represented by the following formula B1, B2, B3, or B4.

  The nonaqueous electrolyte secondary battery according to a fourth aspect of the present invention is the non-aqueous electrolyte secondary battery according to any one of the first to third aspects, wherein the compound represented by the formula 1 is ethane-1,2-diol sulfonic acid or propane-1, It is 2-diol sulfonic acid.

  A nonaqueous electrolyte secondary battery according to a fifth invention is characterized in that, in the third invention, the compound represented by Formula 2 is ethylene glycol sulfate or propanediol sulfate.

  The nonaqueous electrolyte secondary battery according to a sixth aspect of the present invention is characterized in that, in any one of the first to fifth aspects, the electrolyte contains vinylene carbonate.

  A nonaqueous electrolyte secondary battery according to a seventh invention is characterized in that, in the sixth invention, the electrolyte contains 0.2% by mass or more and 2% by mass or less of vinylene carbonate.

  In 1st invention, the fall of the discharge capacity at the time of repeating charging / discharging can be suppressed by using the compound represented by the said Formula 1 for electrolyte. When the surface of graphite is coated with low crystalline carbon, the surface functional groups are removed by the coating process. The surface functional group is active with respect to the electrolytic solution, and itself reacts with lithium or reacts with the compound represented by the formula 1 so that gas is easily generated. However, since surface functional groups are removed, gas generation is suppressed. In general, because graphite has an exposed edge surface, co-insertion of the solvent between the graphite layers during charging is likely to occur, and the inter-graphite interlayer increases the graphite interlayer distance, and the graphite particles expand. Sometimes. When the surface of graphite is coated with low crystalline carbon, it becomes difficult for the solvent to co-insert between the graphite layers during charging, and the expansion of the graphite particles can be suppressed.

  In the second invention, when the graphite surface is coated with 0.5% by mass or more and 20% by mass or less of low crystalline carbon with respect to the mass of graphite, the battery capacity decreases when charging and discharging are repeated, and An increase in battery thickness when charging and discharging are repeated is favorably suppressed. When the surface of graphite is coated with low crystalline carbon of less than 0.5% by mass, the effect is small, and the battery thickness increases when charging and discharging are repeated. Moreover, when the surface of graphite is coated with more than 20% by mass of low crystalline carbon, the battery capacity at the time of repeated charge / discharge decreases, and the battery thickness at the time of repeated charge / discharge increases.

  In the third and sixth inventions, when the compound represented by Formula 2 or vinylene carbonate is added to the electrolyte, a stable negative electrode protective film is formed on the negative electrode. The SEI (solid electrolyte interface) formed by the compound represented by the formula 1 on the negative electrode has a property that the co-insertion of the solvent between the graphite layers easily occurs. When added to, the active material expands when the charge and discharge are repeated, and the negative electrode plate tends to expand. Further, the binding force of the binder is reduced by the compound represented by the formula 1 or the binder itself is expanded by the compound represented by the formula 1, so that the negative electrode plate expands and contracts due to charge / discharge. The electrode plate tends to expand easily. However, since a stable negative electrode protective film is formed on the negative electrode, the above-described expansion of the negative electrode plate due to the addition of Formula 1 can be suppressed.

  In the fourth aspect of the invention, when ethane-1,2-diol sulfonic acid or propane-1,2-diol sulfonic acid is used as the compound represented by formula 1, the battery swells and is charged and discharged during initial charging. A decrease in battery capacity and battery swelling when the cycle is repeated are satisfactorily suppressed.

  In the fifth invention, when ethylene glycol sulfate or propanediol sulfate is used as the compound represented by Formula 2, the battery swells during initial charging, and the battery capacity decreases when the charge / discharge cycle is repeated. In addition, the swelling of the battery is satisfactorily suppressed.

  In 7th invention, when 0.2-2 mass% vinylene carbonate is added to electrolyte, the swelling of the battery at the time of initial charge and the swelling of the battery at the time of repeating charging / discharging cycle are suppressed favorably. . When vinylene carbonate is added to the electrolyte in an amount of more than 2% by mass, the initial discharge capacity and the discharge capacity upon repeated charge / discharge decrease, and the initial battery thickness and the thickness increment upon repeated charge / discharge tend to increase. It is in. Moreover, when less than 0.2 mass of vinylene carbonate is added to electrolyte, an effect is small.

  According to the first invention, it is possible to suppress battery swelling during initial charging, battery capacity reduction and battery swelling when the charge / discharge cycle is repeated.

  According to the second, fourth, and fifth inventions, it is possible to more favorably suppress battery swelling during initial charging, battery capacity reduction and battery swelling when the charge / discharge cycle is repeated.

  According to the 3rd and 6th invention, the swelling of the battery at the time of initial charge and the swelling of the battery at the time of repeating a charging / discharging cycle can be suppressed further.

  According to the seventh aspect of the present invention, the swelling of the battery at the time of initial charge and the swelling of the battery when the charge / discharge cycle is repeated can be further suppressed satisfactorily.

  Hereinafter, the present invention will be specifically described with reference to the drawings illustrating the embodiments thereof, but the present invention is not limited to the embodiments in any way, and may be appropriately changed without departing from the scope of the present invention. Can be implemented.

(Example 1)
FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery (hereinafter referred to as a battery) according to the present invention. In FIG. 1, 1 is a battery, 2 is a flat wound electrode group, 3 is a negative electrode, 4 is a positive electrode, 5 is a separator, 6 is a battery case, 7 is a battery lid, 8 is a safety valve, 9 is a negative electrode terminal, and 10 is a negative electrode Lead. The flat wound electrode group 2 is obtained by winding a positive electrode 4 and a negative electrode 3 through a separator 5. The battery lid 7 has a negative electrode terminal 9 and a safety valve 8, the flat wound electrode group 2 is accommodated in the battery case 6, and the battery lid 7 and the battery case 6 are laser welded. The negative electrode terminal 9 is connected to the negative electrode lead 10, and the negative electrode 3 is connected to the battery case 6.

The positive electrode mixture was prepared by mixing 90% by mass of LiCoO ₂ as an active material, 5% by mass of acetylene black as a conductive additive, and 5% by mass of polyvinylidene fluoride (PVDF) as a binder, A paste was prepared by dispersing in N-methyl-2-pyrrolidone (NMP). The prepared paste was uniformly applied to an aluminum current collector with a thickness of 20 μm and dried, and then subjected to compression molding with a roll press to produce a positive electrode.

The negative electrode mixture was prepared by mixing 95% by mass of a carbon material as a negative electrode active material, 3% by mass of carboxymethyl cellulose and 2% by mass of styrene butadiene rubber as a binder, and adding and dispersing distilled water as appropriate to prepare a slurry. . The prepared slurry was uniformly applied to a 15 μm thick copper current collector, dried at 100 ° C. for 5 hours, and then compression-molded with a roll press so that the density of the negative electrode mixture layer was 1.4 g / cm ^3. As a result, a negative electrode was produced.

The carbon material is obtained by coating a part or all of the surface of natural graphite with low crystalline carbon having lower crystallinity than natural graphite (hereinafter referred to as coated graphite). The average plane spacing (d002) of the (002) plane by the diffraction method is 3.357 mm, and the intensity ratio (I1355 / I1580) of the peak near 1355 cm ^{−1 to} the peak near 1580 cm ⁻¹ by argon laser Raman is The crystallite size Lc and La obtained by X-ray diffraction by the Gakushin method was 100 nm or more. Further, the coated graphite, the peak intensity ratio of around 1355 cm ^-1 to a peak around 1580 cm ^-1 due to the argon laser Raman (hereinafter, referred to as Raman R value) is 1.03.

  The coated graphite is obtained by coating the surface of natural graphite with 10% by mass (hereinafter referred to as coating amount) of low crystalline carbon by a chemical vapor deposition method using toluene gas as a carbon raw material. Although it does not specifically limit as a chemical vapor deposition processing method, For example, it is possible to use a fluidized bed type chemical vapor deposition processing method or a stationary type fixed bed chemical vapor deposition processing method.

In the fluidized bed chemical vapor deposition method, first, graphite particles and an inert gas are supplied into a reactor, and flow of graphite particles having a bulk density (JIS K5101) of about 0.1 to 0.5 g / cm ^3. Form a layer. In this state, the temperature inside the reactor is raised and the inside of the reactor reaches a predetermined temperature, and then the surface of the graphite particles is coated with low crystalline carbon by supplying a carbon source into the reactor. The chemical vapor deposition temperature varies depending on the type of organic substance used as the carbon source. However, when the chemical vapor deposition temperature is less than 850 ° C., the deposition rate of pyrolytic carbon is low, and it takes a long time for the chemical vapor deposition, which is not preferable. The chemical vapor deposition temperature is not particularly limited, but is preferably 850 to 1200 ° C, more preferably 900 to 1200 ° C, and particularly preferably 950 to 1150 ° C.

  The carbon source is not particularly limited, but for example, one ring such as benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, biphenyl, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, etc. Organic substances such as ˜3-ring aromatic hydrocarbons, derivatives thereof, or mixtures thereof can be used. Also, aliphatic hydrocarbons such as gas light oil, creosote oil, anthracene oil, petroleum cracked oil, naphtha cracked tar oil, methane, ethane, propane, butane, pentane, hexane, etc., obtained in the coal tar distillation process , Alcohols that are derivatives of the above aliphatic hydrocarbons can be used alone or as a mixture, or organic substances having a double bond or triple bond such as ethylene, propylene, isopropylene, butadiene, acetylene, etc. can be used. It is.

  In the chemical vapor deposition process, it is preferable to supply the organic substance as a carbon source supplied into the reactor in the form of a mixed gas diluted with an inert gas. Although it does not specifically limit as an inert gas, Nitrogen or argon can be used. The molar concentration of the organic substance in the mixed gas is preferably 2 to 80%, more preferably 5 to 70%. If the molar concentration of the organic substance in the mixed gas is less than 2%, the chemical vapor deposition process takes a long time, which is not preferable. On the other hand, when the molar concentration of the organic substance in the mixed gas exceeds 80%, the low crystalline carbon tends to peel off from the carbon particle surface after the carbon particle surface is coated with the low crystalline carbon, which is not preferable. By appropriately selecting the above conditions and performing chemical vapor deposition, the surface of the graphite particles can be coated with low crystalline carbon. The amount of low crystalline carbon used for coating (coating amount) can be adjusted by the chemical vapor deposition time.

  In the stationary fixed bed chemical vapor deposition method, for example, graphite particles are allowed to stand on a graphite plate in a quartz tube, and a mixed gas composed of an organic substance serving as a carbon source and a dilution gas is supplied into the quartz tube. Heat above the thermal decomposition temperature of organic matter. In addition, the kind of organic substance used as a carbon source, the kind of dilution gas, the molar concentration of the organic substance in the mixed gas, and the treatment temperature are the same as those in the fluidized bed chemical vapor deposition method described above.

As the separator 5, a microporous polyethylene film having a thickness of about 20 μm was used. The electrolyte was prepared by dissolving 1.1 mol / l of LiPF _{6 in} a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3: 7, and the formula 1 (A-R1-OH However, R1 is a hydrocarbon group which may contain an unsaturated bond, or a hydrocarbon group which may contain an unsaturated bond, part or all of which is substituted with a halogen element, and A is A nonaqueous electrolyte to which 0.5% by mass of the compound C1 shown in Table 1 according to A1 or A2 or A3 shown in Table 1 was added was used. The battery 10 has a width of 30 mm, a thickness of 4.2 mm, a height of 50 mm, and a capacity of 600 mAh.

(Example 2)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of the compound C2 shown in Table 1 according to Formula 1 was added to the electrolyte.

Example 3
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of the compound C3 shown in Table 1 according to Formula 1 was added to the electrolyte.

(Example 4)
A battery was produced in the same manner as in Example 1 except that 0.5% by mass of the compound C4 shown in Table 1 according to Formula 1 was added to the electrolyte.

(Example 5)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of the compound C5 shown in Table 1 according to Formula 1 was added to the electrolyte.

(Example 6)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of Compound C6 shown in Table 2 according to Formula 1 was added to the electrolyte.

(Example 7)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of Compound C7 shown in Table 2 according to Formula 1 was added to the electrolyte.

(Example 8)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of Compound C8 shown in Table 2 according to Formula 1 was added to the electrolyte.

Example 9
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of Compound C9 shown in Table 2 according to Formula 1 was added to the electrolyte.

(Example 10)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of the compound C10 shown in Table 3 according to Formula 1 was added to the electrolyte.

(Example 11)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of the compound C11 shown in Table 3 according to Formula 1 was added to the electrolyte.

(Example 12)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of the compound C12 shown in Table 3 according to Formula 1 was added to the electrolyte.

(Example 13)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of Compound C13 shown in Table 3 according to Formula 1 was added to the electrolyte.

(Example 14)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of Compound C14 shown in Table 4 according to Formula 1 was added to the electrolyte.

(Example 15)
A battery was prepared in the same manner as in Example 1 except that 0.5% by mass of Compound C15 shown in Table 4 according to Formula 1 was added to the electrolyte.

(Example 16)
A battery was prepared in the same manner as in Example 1 except that 0.001% by mass of the compound C1 according to Formula 1 was added to the electrolyte.

(Example 17)
A battery was prepared in the same manner as in Example 1 except that 0.01% by mass of the compound C1 according to Formula 1 was added to the electrolyte.

(Example 18)
A battery was produced in the same manner as in Example 1 except that 0.1% by mass of the compound C1 according to Formula 1 was added to the electrolyte.

(Example 19)
A battery was produced in the same manner as in Example 1 except that 1.0% by mass of the compound C1 according to Formula 1 was added to the electrolyte.

(Example 20)
A battery was produced in the same manner as in Example 1 except that 2.0% by mass of the compound C1 according to Formula 1 was added to the electrolyte.

(Example 21)
A battery was prepared in the same manner as in Example 1 except that 3.0% by mass of the compound C1 according to Formula 1 was added to the electrolyte.

(Example 22)
A battery was produced in the same manner as in Example 1 except that 4.0% by mass of the compound C1 according to Formula 1 was added to the electrolyte.

(Example 23)
A battery was prepared in the same manner as in Example 2 except that 0.001% by mass of the compound C2 according to Formula 1 was added to the electrolyte.

(Example 24)
A battery was prepared in the same manner as in Example 2 except that 0.01% by mass of the compound C2 according to Formula 1 was added to the electrolyte.

(Example 25)
A battery was prepared in the same manner as in Example 2 except that 0.1% by mass of the compound C2 according to Formula 1 was added to the electrolyte.

(Example 26)
A battery was prepared in the same manner as in Example 2 except that 1.0% by mass of the compound C2 according to Formula 1 was added to the electrolyte.

(Example 27)
A battery was prepared in the same manner as in Example 2 except that 2.0% by mass of the compound C2 according to Formula 1 was added to the electrolyte.

(Example 28)
A battery was prepared in the same manner as in Example 2 except that 3.0% by mass of the compound C2 according to Formula 1 was added to the electrolyte.

(Example 29)
A battery was produced in the same manner as in Example 2 except that 4.0% by mass of the compound C2 according to Formula 1 was added to the electrolyte.

(Example 30)
A battery was produced in the same manner as in Example 3, except that 0.001% by mass of the compound C3 according to Formula 1 was added to the electrolyte.

(Example 31)
A battery was produced in the same manner as in Example 3, except that 0.01% by mass of the compound C3 according to Formula 1 was added to the electrolyte.

(Example 32)
A battery was prepared in the same manner as in Example 3 except that 0.1% by mass of the compound C3 according to Formula 1 was added to the electrolyte.

(Example 33)
A battery was prepared in the same manner as in Example 3 except that 1.0% by mass of the compound C3 according to Formula 1 was added to the electrolyte.

(Example 34)
A battery was prepared in the same manner as in Example 3 except that 2.0% by mass of the compound C3 according to Formula 1 was added to the electrolyte.

(Example 35)
A battery was produced in the same manner as in Example 3, except that 3.0% by mass of the compound C3 according to Formula 1 was added to the electrolyte.

(Example 36)
A battery was produced in the same manner as in Example 3, except that 4.0% by mass of the compound C3 according to Formula 1 was added to the electrolyte.

(Example 37)
A battery was produced in the same manner as in Example 5 except that 0.001% by mass of the compound C5 according to Formula 1 was added to the electrolyte.

(Example 38)
A battery was produced in the same manner as in Example 5 except that 0.01% by mass of the compound C5 according to Formula 1 was added to the electrolyte.

(Example 39)
A battery was prepared in the same manner as in Example 5 except that 0.1% by mass of Compound C5 according to Formula 1 was added to the electrolyte.

(Example 40)
A battery was produced in the same manner as in Example 5 except that 1.0% by mass of the compound C5 according to Formula 1 was added to the electrolyte.

(Example 41)
A battery was produced in the same manner as in Example 5 except that 2.0% by mass of the compound C5 according to Formula 1 was added to the electrolyte.

(Example 42)
A battery was produced in the same manner as in Example 5 except that 3.0% by mass of the compound C5 according to Formula 1 was added to the electrolyte.

(Example 43)
A battery was produced in the same manner as in Example 5 except that 4.0% by mass of the compound C5 according to Formula 1 was added to the electrolyte.

(Example 44)
A battery was produced in the same manner as in Example 7 except that 0.001% by mass of the compound C7 according to Formula 1 was added to the electrolyte.

(Example 45)
A battery was produced in the same manner as in Example 7 except that 0.01% by mass of the compound C7 according to Formula 1 was added to the electrolyte.

(Example 46)
A battery was prepared in the same manner as in Example 7 except that 0.1% by mass of Compound C7 according to Formula 1 was added to the electrolyte.

(Example 47)
A battery was produced in the same manner as in Example 7 except that 1.0% by mass of the compound C7 according to Formula 1 was added to the electrolyte.

(Example 48)
A battery similar to that of Example 7 was prepared, except that 2.0% by mass of Compound C7 according to Formula 1 was added to the electrolyte.

(Example 49)
A battery was produced in the same manner as in Example 7 except that 3.0% by mass of the compound C7 according to Formula 1 was added to the electrolyte.

(Example 50)
A battery was prepared in the same manner as in Example 7 except that 4.0% by mass of the compound C7 according to Formula 1 was added to the electrolyte.

(Example 51)
A battery was produced in the same manner as in Example 12 except that 0.001% by mass of the compound C12 according to Formula 1 was added to the electrolyte.

(Example 52)
A battery was prepared in the same manner as in Example 12 except that 0.01% by mass of the compound C12 according to Formula 1 was added to the electrolyte.

(Example 53)
A battery was prepared in the same manner as in Example 12 except that 0.1% by mass of the compound C12 according to Formula 1 was added to the electrolyte.

(Example 54)
A battery was produced in the same manner as in Example 12 except that 1.0% by mass of the compound C12 according to Formula 1 was added to the electrolyte.

(Example 55)
A battery was produced in the same manner as in Example 12 except that 2.0% by mass of the compound C12 according to Formula 1 was added to the electrolyte.

(Example 56)
A battery similar to that of Example 12 was prepared, except that 3.0% by mass of Compound C12 according to Formula 1 was added to the electrolyte.

(Example 57)
A battery was produced in the same manner as in Example 12 except that 4.0% by mass of the compound C12 according to Formula 1 was added to the electrolyte.

(Example 58)
A battery similar to that of Example 46 was produced, except that the amount of coating with low crystalline carbon in the coated graphite as the negative electrode active material was 0.5 mass%, and the Raman R value of the coated graphite was 0.48. .

(Example 59)
A battery was produced in the same manner as in Example 46 except that the coating amount of the low crystalline carbon in the coated graphite as the negative electrode active material was 1.0% by mass and the Raman R value of the coated graphite was 0.52. .

(Example 60)
A battery was produced in the same manner as in Example 46 except that the amount of coating with low crystalline carbon in the coated graphite as the negative electrode active material was 2.0 mass%, and the Raman R value of the coated graphite was 0.55. .

(Example 61)
A battery was produced in the same manner as in Example 46 except that the coating amount of low crystalline carbon in the coated graphite as the negative electrode active material was 5.0 mass%, and the Raman R value of the coated graphite was 0.80. .

(Example 62)
A battery was produced in the same manner as in Example 46 except that the coating amount of the low-crystalline carbon in the coated graphite as the negative electrode active material was 15% by mass and the Raman R value of the coated graphite was 1.23.

(Example 63)
A battery was produced in the same manner as in Example 46 except that the coating amount of the low-crystalline carbon in the coated graphite as the negative electrode active material was 20% by mass and the Raman R value of the coated graphite was 1.44.

(Example 64)
A battery was produced in the same manner as in Example 46 except that the coating amount of the low-crystalline carbon in the coated graphite as the negative electrode active material was 25% by mass and the Raman R value of the coated graphite was 1.64.

(Example 65)
In the electrolyte, 0.1% by mass of the compound C7 according to the formula 1 and the formula 2 (R2-B-R3, where R2 and R3 are each independently a hydrocarbon group optionally containing an unsaturated bond, Or a hydrocarbon group which may contain an unsaturated bond, part or all of which is substituted with a halogen element, or R2 and R3 are bonded to each other to form a cyclic structure with B; Prepared a battery similar to that of Example 61 except that 1% by mass of the compound D1 shown in Table 5 according to Formula B1, B2, B3, or B4 shown in Table 5 was added.

Example 66
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 1% by mass of the compound D2 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 67)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 1% by mass of the compound D3 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 68)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 1% by mass of the compound D4 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 69)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 1% by mass of the compound D5 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 70)
A battery was produced in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 1% by mass of the compound D6 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 71)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of compound C7 according to formula 1 and 0.1% by mass of compound D7 shown in Table 5 according to formula 2 were added to the electrolyte. .

(Example 72)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 0.2% by mass of the compound D7 shown in Table 5 according to Formula 2 were added to the electrolyte. .

(Example 73)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of compound C7 according to formula 1 and 0.5% by mass of compound D7 shown in Table 5 according to formula 2 were added to the electrolyte. .

(Example 74)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 1% by mass of the compound D7 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 75)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 2% by mass of the compound D7 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 76)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 3% by mass of the compound D7 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 77)
A battery was produced in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 5% by mass of the compound D7 shown in Table 5 according to Formula 2 were added to the electrolyte.

(Example 78)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of Compound C7 according to Formula 1 and 0.2% by mass of vinylene carbonate (VC) were added to the electrolyte.

(Example 79)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of compound C7 according to formula 1 and 0.5% by mass of vinylene carbonate (VC) were added to the electrolyte.

(Example 80)
A battery was produced in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 1% by mass of vinylene carbonate (VC) were added to the electrolyte.

(Example 81)
A battery was produced in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 2% by mass of vinylene carbonate (VC) were added to the electrolyte.

(Example 82)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of compound C7 according to formula 1 and 3% by mass of vinylene carbonate (VC) were added to the electrolyte.

(Example 83)
A battery was produced in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 5% by mass of vinylene carbonate (VC) were added to the electrolyte.

(Example 84)
A battery was prepared in the same manner as in Example 61 except that 0.1% by mass of the compound C7 according to Formula 1 and 7% by mass of vinylene carbonate (VC) were added to the electrolyte.

(Example 85)
The same as Example 61 except that 0.1% by mass of the compound C7 according to the formula 1, 1% by mass of the compound D7 according to the formula 2, and 1% by mass of vinylene carbonate (VC) were added to the electrolyte. A battery was produced.

(Example 86)
Example, except that 0.1% by mass of compound C7 according to formula 1, 0.5% by mass of compound D7 according to formula 2 and 0.5% by mass of vinylene carbonate (VC) were added to the electrolyte. A battery similar to 61 was produced.

(Example 87)
In an electrolyte obtained by dissolving 1.1 mol / l of LiPF _{6 in} a mixed solvent having a volume ratio of ethylene carbonate (EC) and diethyl carbonate (DEC) of 3: 7, 0.1% by mass of the compound C7 according to Formula 1; A battery was produced in the same manner as in Example 85 except that 1% by mass of compound D7 according to formula 2 and 1% by mass of vinylene carbonate (VC) were added.

(Example 88)
In an electrolyte prepared by dissolving 1.1 mol / l of LiPF _{6 in} a mixed solvent having a volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) of 3: 7, 0.1% by mass of the compound C7 according to the formula 1 is dissolved. A battery was produced in the same manner as in Example 85 except that 1% by mass of compound D7 according to formula 2 and 1% by mass of vinylene carbonate (VC) were added.

Example 89
An electrolyte in which 1.1 mol / l of LiPF ₆ is dissolved in a mixed solvent having a volume ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) of 3: 5: 2 is expressed by Formula 1. A battery was produced in the same manner as in Example 85 except that 0.1% by mass of compound C7, 1% by mass of compound D7 according to formula 2 and 1% by mass of vinylene carbonate (VC) were added.

(Example 90)
In an electrolyte in which 1.5 mol / l of LiPF ₆ was dissolved in a mixed solvent having a volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) of 3: 7, 0.1% by mass of compound C7 according to formula 1 A battery was produced in the same manner as in Example 85 except that 1% by mass of Compound D7 according to Formula 2 and 1% by mass of vinylene carbonate (VC) were added.

(Example 91)
In an electrolyte in which 0.7 mol / l of LiPF ₆ was dissolved in a mixed solvent having a volume ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) of 3: 7, 0.1% by mass of the compound C7 according to Formula 1 A battery was produced in the same manner as in Example 85 except that 1% by mass of Compound D7 according to Formula 2 and 1% by mass of vinylene carbonate (VC) were added.

(Example 92)
An electrolyte in which 1.1 mol / l of LiPF ₆ was dissolved in a mixed solvent having a volume ratio of ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) of 2: 1: 7 is expressed by Formula 1. A battery was produced in the same manner as in Example 85 except that 0.1% by mass of compound C7, 1% by mass of compound D7 according to formula 2 and 1% by mass of vinylene carbonate (VC) were added.

(Example 93)
A battery was prepared in the same manner as in Example 85 except that 70% by mass of coated graphite and 30% by mass of artificial graphite were used as the negative electrode active material.

(Example 94)
A battery was produced in the same manner as in Example 85 except that 50% by mass of coated graphite and 50% by mass of artificial graphite were used as the negative electrode active material.

(Example 95)
A battery was prepared in the same manner as in Example 85 except that 40% by mass of coated graphite and 60% by mass of artificial graphite were used as the negative electrode active material.

(Example 96)
A battery was produced in the same manner as in Example 85 except that 30% by mass of coated graphite and 70% by mass of artificial graphite were used as the negative electrode active material.

(Example 97)
A battery was produced in the same manner as in Example 85 except that 50% by mass of coated graphite and 50% by mass of mesophase-based graphite were used as the negative electrode active material.

(Example 98)
A battery was produced in the same manner as in Example 85 except that 60% by mass of coated graphite, 30% by mass of mesophase-based graphite, and 10% by mass of artificial graphite were used as the negative electrode active material.

Example 99
A battery was produced in the same manner as in Example 85 except that 40% by mass of coated graphite and 60% by mass of mesophase-based graphite were used as the negative electrode active material.

(Example 100)
A battery was prepared in the same manner as in Example 85 except that 98% by mass of coated graphite and 2% by mass of acetylene black (AB) were used as the negative electrode active material.

(Example 101)
A battery was produced in the same manner as in Example 85 except that 98% by mass of coated graphite and 2% by mass of vapor grown carbon (VGCF) were used as the negative electrode active material.

(Comparative Example 1)
A battery was produced in the same manner as in Example 1 except that natural graphite whose surface was not coated with low crystalline carbon was used as the negative electrode active material.

(Comparative Example 2)
Example 1 except that natural graphite not coated on the surface with low crystalline carbon was used as the negative electrode active material, and 0.5% by mass of compound C2 shown in Table 1 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 3)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, is used as the negative electrode active material, and 0.5% by mass of compound C3 shown in Table 1 according to Formula 1 is added to the electrolyte. A similar battery was produced.

(Comparative Example 4)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, is used as the negative electrode active material, and 0.5% by mass of compound C4 shown in Table 1 according to Formula 1 is added to the electrolyte. A similar battery was produced.

(Comparative Example 5)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, is used as the negative electrode active material, and 0.5% by mass of compound C5 shown in Table 1 according to Formula 1 is added to the electrolyte. A similar battery was produced.

(Comparative Example 6)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, was used as the negative electrode active material, and 0.5% by mass of compound C6 shown in Table 2 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 7)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, was used as the negative electrode active material, and 0.5% by mass of Compound C7 shown in Table 2 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 8)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, was used as the negative electrode active material, and 0.5% by mass of Compound C8 shown in Table 2 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 9)
Example 1 except that natural graphite not coated on the surface with low crystalline carbon was used as the negative electrode active material, and 0.5% by mass of Compound C9 shown in Table 2 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 10)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, is used as the negative electrode active material, and 0.5% by mass of compound C10 shown in Table 3 according to Formula 1 is added to the electrolyte. A similar battery was produced.

(Comparative Example 11)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, is used as the negative electrode active material, and 0.5% by mass of compound C11 shown in Table 3 according to Formula 1 is added to the electrolyte. A similar battery was produced.

(Comparative Example 12)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, was used as the negative electrode active material, and 0.5% by mass of compound C12 shown in Table 3 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 13)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, was used as the negative electrode active material, and 0.5% by mass of compound C13 shown in Table 3 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 14)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, is used as the negative electrode active material and 0.5% by mass of compound C14 shown in Table 4 according to Formula 1 is added to the electrolyte. A similar battery was produced.

(Comparative Example 15)
Example 1 except that natural graphite, the surface of which is not coated with low crystalline carbon, was used as the negative electrode active material, and 0.5% by mass of Compound C15 shown in Table 4 according to Formula 1 was added to the electrolyte. A similar battery was produced.

(Comparative Example 16)
A battery was prepared in the same manner as in Example 1 except that natural graphite whose surface was not coated with low crystalline carbon was used as the negative electrode active material, and the compound according to Formula 1 was not added to the electrolyte.

(Comparative Example 17)
A battery was prepared in the same manner as in Example 1 except that the compound according to Formula 1 was not added to the electrolyte.

(Comparative Example 18)
A battery was produced in the same manner as in Example 46, except that natural graphite whose surface was not coated with low crystalline carbon (Raman R value was 0.25) was used as the negative electrode active material.

  A charge / discharge cycle test and a battery thickness test were performed on the batteries of the respective Examples and Comparative Examples. First, 5 batteries of the same conditions were prepared for each example and each comparative example, and these batteries were charged at a constant current and a constant voltage for 3 hours to a voltage of 4.2 V at a current of 600 mA, and then a voltage of 3 V at a current of 600 mA. The initial discharge capacity and the initial battery thickness were measured. Thereafter, the same charge and discharge was repeated 500 cycles, the discharge capacity and battery thickness at the 500th cycle were measured, the capacity retention rate (%) and the thickness increment (mm) were calculated, and the average value of 5 cells was obtained. Here, the capacity retention is the ratio (%) of the discharge capacity at the 500th cycle to the initial discharge capacity, and the thickness increment is the difference (mm) obtained by subtracting the initial battery thickness from the battery thickness at the 500th cycle. is there. Test results are shown in Tables 6-14.

  Table 6 shows the test results of Examples 1 to 15 and Comparative Examples 1 to 16.

  As shown in Comparative Examples 1 to 16 in Table 6, the battery (Comparative Example 16) in which the compound C according to Formula 1 is not added to the electrolyte is compared to the battery (Comparative Examples 1 to 15) in which the battery is added. The initial discharge capacity and the initial battery thickness are not significantly different and the thickness increment after cycling is excellent, but the capacity retention after cycling is greatly inferior. Further, as shown in Examples 1 to 15 and Comparative Examples 1 to 15 in Table 6, batteries not using coated carbon as a negative electrode active material (Comparative Examples 1 to 15) are used (Examples 1 to 15). Compared with 15), the initial discharge capacity, the initial battery thickness, and the capacity retention after the cycle are slightly inferior, and the thickness increment after the cycle thickness is greatly inferior. When the compound C according to Formula 1 is added to the electrolyte, the capacity retention after the cycle is improved, and when the coated graphite is used as the negative electrode active material, the increase in thickness after the cycle is suppressed.

  The increase in the initial battery thickness is thought to be due to gas generation due to reductive decomposition of the electrolyte on the negative electrode. Graphite whose surface is not coated with low crystalline carbon has a large number of surface functional groups such as carboxyl groups or hydroxyl groups on the surface, and the surface hydroxyl groups are active against the electrolyte, and lithium or compound C according to Formula 1 It is presumed that gas is likely to be generated due to the reaction. When the surface of graphite is coated with low crystalline carbon, the surface functional groups are removed by the coating treatment, so that it is considered that the decomposition of the surface functional groups and the compound represented by Formula 1 during initial charging is suppressed. .

  Moreover, since the edge surface of graphite is exposed, co-insertion of the solvent between the graphite layers during charging is likely to occur. For example, when propylene carbonate (PC) is contained in the electrolyte, the graphite is inserted between the graphite layers of the PC. By co-insertion, the graphite interlayer distance increases, and the graphite particles expand, or when the PC-containing concentration is high, the graphite layers may peel off. Further, when the compound C according to the formula 1 is added to the electrolytic solution and charging / discharging is repeated, the SEI (solid electrolyte interface) formed on the negative electrode by the compound C according to the formula 1 is the co-solvent between the graphite layers. Has the property of facilitating insertion. Further, the binding force of the binder is reduced by the compound C according to the formula 1, and the binder itself is expanded by the compound C according to the formula 1, so that the electrode plate is expanded and contracted due to charge / discharge. Becomes easy to expand. When the graphite is coated with low crystalline carbon, it is considered that co-insertion of the solvent between the graphite layers at the time of charging hardly occurs, and the expansion of the graphite particles can be suppressed.

  Although R1 of the compound C of Example 1 and 5 and Example 2 and 6 is the same and A is different, the favorable test result is obtained in all. However, Examples 5 and 6 using A3 are superior in Example 1 using A1 and Example 2 using A2 in initial discharge capacity, initial battery thickness, and capacity retention after cycling. . This is presumably because A3 contains more oxygen than A1 or A2 in its structure, and thus the properties of the negative electrode film formed during initial charging become more stable.

  As in Examples 3, 4 and 8, R1 of Compound C according to Formula 1 may contain an unsaturated bond. When the unsaturated bond is included, it is considered that a negative electrode and a more stable film are formed. Further, as in Examples 4, 7, 8, 9, 10, 11, 12, the side chain of R1 of compound C according to Formula 1 may be lengthened or plural. When the side chain is made long or plural, the surface active effect is increased, so that the affinity between the separator and the electrolyte is improved, the electrolyte solution easily penetrates into the electrode plate, and the initial capacity is increased. However, if the side chain is lengthened, the viscosity of the electrolyte may increase when the compound C according to Formula 1 is added to the electrolyte, and the charge / discharge performance may be reduced. Therefore, the carbon number of the side chain of R1 is 8 The following is preferred.

  R1 of compound C according to Formula 1 may be halogenated. When an electron withdrawing halogen is added, it is difficult to oxidize and is easily reduced. Since it is difficult to oxidize, the oxidative decomposition reaction on the positive electrode is suppressed, and the decrease in charge / discharge cycle characteristics (capacity retention) due to the deposition of decomposition products on the positive electrode surface is suppressed. In addition, since it is easy to be reduced, a stable inorganic coating such as LiF or LiCl containing halogen is formed on the negative electrode. In order to suppress the reductive decomposition reaction of other electrolytes, the initial charge / discharge efficiency is improved, and the discharge The capacity is thought to increase.

  Tables 7 to 8 show the test results of Examples 1, 2, 3, 5, 7, 12, Examples 16 to 57, and Comparative Example 17.

  As shown in Tables 7 and 8, when Compound C was added (Examples 1, 2, 3, 5, 7, 12, and Examples 16 to 57), compared with the case where Compound C was not added (Comparative Example 17). The capacity retention after the cycle is improved, and the increase in thickness is suppressed. However, when the amount of compound C added is small, the capacity retention after the cycle is not sufficient, and when the amount added is large, the initial battery thickness and the increase in thickness after the cycle are not sufficiently suppressed. The addition amount of the compound C according to Formula 1 is preferably 0.1 to 2% by mass regardless of the type. When the amount of Compound C according to Formula 1 is large, it is considered that during initial charging, gas generation increases due to reductive decomposition on the negative electrode of Compound C according to Formula 1 and the battery thickness increases. In addition, it is considered that the generated gas is accumulated between the electrode plates, current is concentrated around the gas reservoir, metal lithium dendrite is deposited on the negative electrode, and charge / discharge efficiency is slightly reduced.

  Table 9 shows the test results of Examples 58 to 64 and Comparative Example 18.

  As shown in Table 9, when the natural graphite surface was coated with low crystalline carbon (Examples 46 and 58 to 64), the thickness increment after the cycle was larger than that when not coated (Comparative Example 18). It is suppressed. The increase in thickness after the cycle is well suppressed when the coating amount is 2% by mass or more. Further, when the coating amount is larger than 10% by mass, the capacity retention after the cycle tends to decrease, and the thickness increment after the cycle tends to increase. This is because when the coating amount is larger than 10% by mass, the particles become hard due to the low crystalline carbon covering the surface, and it becomes difficult to compress the negative electrode active material layer to a predetermined density, which is applied to the particles during compression processing. It is considered that because the stress was increased, the particles were destroyed and the inner surface of the uncoated active material was exposed. The coating amount is preferably 2 to 10% by mass.

  Table 10 shows the test results of Examples 61 and 65 to 77.

  As shown in Table 10, when 1% by mass of the compound D according to Formula 2 was added to the electrolyte (Examples 65 to 70, 74), compared to the case where it was not added (Example 61), after the cycle The capacity retention rate is improved and the thickness increment is suppressed. The compound D according to the formula 2 is effective regardless of the kind of B, and the compound D according to the formula 2 is also effective in the case of a chain like D5 and a ring like D6 or D7. In particular, in the case of D7, the initial discharge capacity, the initial battery thickness, the capacity retention after the cycle, and the thickness increment are all good. This is presumably because the cyclic sulfate ester containing B4 in the structure forms a good film at the initial charge.

  Moreover, when the addition amount of D7 was changed with 0.1-5 mass% (Examples 71-77), the effect was acquired more with the addition amount of 0.1-3 mass%, especially 0.5 mass. % And 3% by mass or less, the capacity retention after the cycle is greatly improved. However, when the addition amount is 3% by mass or more, the negative electrode film formed by D7 becomes thick and the film resistance increases, and metallic lithium is deposited on the negative electrode during charging. In addition, the thickness of the battery after the cycle increases because the metal lithium deposition proceeds intermittently even during the cycle. As for the addition amount of the compound D which concerns on Formula 2, 0.5-2 mass% is especially preferable.

  Table 11 shows the test results of Examples 61 and 78 to 84.

  As shown in Table 11, when the vinylene carbonate (VC) was added to the electrolyte (Examples 78 to 84), compared with the case where it was not added (Example 61), the generation of hydrogen gas was suppressed, and the initial battery The thickness and the thickness increase after the cycle are small. Further, the capacity retention after the cycle is equivalent or improved. However, when VC is added in an amount of 3% by mass or more, the initial discharge capacity and the capacity retention after the cycle tend to decrease, and the initial battery thickness and the thickness increment after the cycle tend to increase. When the amount of VC added is 3% by mass or more, the negative electrode film formed by VC becomes thick and the film resistance increases, so that metal lithium is deposited on the negative electrode during charging. Thus, the initial battery thickness is large, and since the lithium metal deposition proceeds intermittently even during the cycle, the thickness after the cycle also increases. Therefore, the amount of VC added to the electrolyte is preferably 0.2 to 2% by mass.

  Table 12 shows the test results of Examples 74, 80, and 85-86.

  As shown in Table 12, when both VC and D7 were added to the electrolyte (Examples 85 and 86), the capacity retention and thickness increment after the cycle were equal or improved compared to the case where only one was added. doing. By using a mixture of VC and D7, the effect more than that used alone can be obtained. This is because the reductive decomposition potential of D7 (potential with respect to Li / Li +) is 1.9 V, which is higher than the reductive decomposition potential of VC (1.5 V), so that a film of D7 was formed on the negative electrode. This is probably because a VC film was formed later, and each film showed better characteristics than the single film. In general, the same effect can be obtained for the compound D according to Formula 2 because the reductive decomposition potential is higher than that of VC.

  Table 13 shows the test results of Examples 85 and 87-92.

  As shown in Table 13, even when the composition or concentration of the electrolyte is changed, the effect of the present invention is not particularly changed, and good test results are obtained.

  Table 14 shows the test results of Examples 93 to 101.

  As shown in Examples 93 to 96 in Table 14, the capacity retention after the cycle is improved by mixing artificial graphite, preferably 30% by mass or less. When natural graphite is coated with low crystalline carbon, the coated natural graphite has low electron conductivity, and therefore, the conductivity between particles in the negative electrode mixture is lowered. By blending a suitable conductive assistant such as artificial graphite, acetylene black, or VGCF, it is possible to suppress a decrease in capacity due to a decrease in conductivity between active material particles due to expansion and contraction of the active material during charge and discharge. In addition, the thickness increment after the cycle can be reduced. As shown in Example 100 or 101 of Table 14, acetylene black or VGCF is more preferable because the conductivity imparting effect can be obtained even in a small amount, and the ratio of the negative electrode active material of the coated graphite can be increased. As shown in Examples 97 to 99 in Table 14, it is particularly preferable to mix coated graphite and mesophase-based graphite with a small increase in thickness during the charge / discharge cycle as the negative electrode active material. Since mesophase graphite is stable with respect to the electrolytic solution, cycle characteristics are improved because there is little depletion of the solution due to intermittent decomposition of the electrolytic solution during the charge / discharge cycle. Artificial graphite and mesophase graphite can be appropriately blended.

As mentioned above, although the Example which concerns on this invention was described, the graphite particle used for the active material of a negative electrode is not limited to the Example mentioned above, Natural graphite or artificial graphite is preferable, and the X-ray wide angle diffraction method (002) A natural graphite having an average surface separation (d002) of 3.354 to 3.4 mm, more preferably 3.354 to 3.38 mm, and a peak near 1355 cm ^{−1 with} respect to a peak near 1580 cm ⁻¹ by argon laser Raman. The intensity ratio (I1355 / I1580) is 0.40 or less, and the crystallite sizes Lc and La determined by X-ray diffraction by the Gakushin method are preferably 100 nm or more.

Further, the coated graphite in which a part or all of the surface of the graphite particles is coated with low crystalline carbon is not limited to the above-described embodiment, and the average spacing of (002) planes by the X-ray wide angle diffraction method ( It is preferable that d002) is 3.354 to 3.4 mm and the intensity ratio (I1355 / I1580) of the peak near 1355 cm ^{−1 to} the peak near 1580 cm ⁻¹ by argon laser Raman is 0.45 or more.

  The method for coating the graphite particles is not limited to the above-described embodiment, and a chemical vapor deposition method (all of gas phase, liquid phase, and solid phase) is preferable. Considering the uniformity or effectiveness of the coating, a fluidized bed chemical vapor deposition method is preferred. In addition, all those coated with gas phase, liquid phase, and solid phase materials can be used alone or in combination.

  In pitch coating in which graphite particles are immersed in pitch and heat-treated in an inert atmosphere, first, graphite particles are pitched at a temperature of about 10 to 300 ° C., preferably at about 100 to 200 ° C. for 5 to 60 minutes. Soak for about 10 minutes, preferably about 10 to 30 minutes. The pitch used in that case is not particularly limited as long as it is a residue oil obtained by distilling tar obtained by dry distillation of an organic substance such as coal, petroleum, or wood. For example, coal tar pitch or petroleum pitch is used. It is possible. Next, after separating the graphite particles from the pitch, an organic solvent is added and washing is performed at about 10 to 300 ° C., preferably about 10 to 100 ° C. And the graphite (coating graphite) by which the surface was coat | covered with the low crystalline carbon is obtained by carbonizing the pitch coat | covered on the graphite particle surface in inert atmosphere.

  Here, the organic solvent for cleaning is not particularly limited, and for example, toluene, methanol, acetone, hexane, benzene, xylene, methylnaphthalene, tar oil, and the like can be used. The amount of low crystalline carbon used for coating (coating amount) can be adjusted by the type of organic solvent used for cleaning, the cleaning time, the cleaning temperature, and the like. Although the temperature which carbonizes the pitch in an inert atmosphere is not specifically limited, For example, it is 600-1500 degreeC, Preferably it is 800-1200 degreeC, More preferably, it is 900-1000 degreeC. Also, the carbonization time is not particularly limited, but is about 1 to 20 hours, preferably about 3 to 12 hours.

  The coating amount of the low crystalline carbon in the coated graphite varies depending on the form of the coating or the graphite, but the effect of the present invention can be obtained by coating 0.5 mass% or more with respect to the mass of the graphite. The upper limit of the coating amount is not particularly limited. However, when the coating amount is large, the particles themselves are hardened by the low crystalline carbon used for coating, and the negative electrode filling property may be decreased, or the voltage behavior of charge / discharge may be changed. Therefore, the coating amount is preferably 20% by mass or less, and more preferably 2% by mass or more and 15% by mass or less.

  The content of the coated graphite contained in the negative electrode active material is preferably high, but can be appropriately selected according to the amount of the compound represented by Formula 1 or the required battery performance. Although content of the covering graphite in a negative electrode active material is not limited to the Example mentioned above, 40 mass% or more is preferable, and 50 mass% to 98 mass% is especially preferable.

  The negative electrode active material other than the coated graphite is not limited to the above-described examples, and preferably, natural graphite, artificial graphite, metal or metal oxide that absorbs and releases lithium can be used, and mesophase-based graphite ( MCMB or MCF) is particularly preferred.

  When the coating amount is 4% by mass or more, the conductivity between the active materials is lowered due to the low crystalline carbon. Therefore, it is preferable to add a conductive additive that improves the conductivity. As the conductive assistant, generally used graphite, carbon black (CB), acetylene black (AB), ketjen black, vapor grown carbon (VGCF), etc. can be used. Is considered to have an adverse effect on the compound represented by Formula 1, and therefore the amount used is preferably kept to the minimum necessary. A particularly preferable amount is 2% by mass to 20% by mass. More preferable as the conductive assistant is carbon black, acetylene black, or VGCF, which has lower crystallinity than graphite and has less interaction with the compound represented by Formula 1. The addition amount varies depending on the negative electrode active material or the binder to be used, but is generally preferably 0.5% by mass to 10% by mass and more preferably 2% by mass to 5% by mass in order to maintain conductivity.

  The binder of the negative electrode is not limited to the above-described embodiments, and considering adhesiveness or battery performance, polyvinylidene fluoride (PVDF), a part of PVDF carboxy-modified, styrene butadiene rubber, carboxymethyl cellulose, etc. Is preferred. In particular, when a mixture of styrene butadiene rubber and carboxymethyl cellulose, which is softer than PVDF and increases in thickness of the negative electrode accompanying expansion and contraction of the active material, is used, the effect of the present invention is great.

  Moreover, the compound D which concerns on Formula 2 (R2-B-R3) shown in Table 5 added to electrolyte is not limited to the Example mentioned above, Preferably the alkyl group which R2 and R3 can take is carbon number. 1 to 4 alkyl groups, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and the like can be used. As the aryl group serving as a substituent for the alkyl group, a phenyl group, a naphthyl group, an anthranyl group, and the like can be used, and a phenyl group is preferable. Moreover, as a halogen atom which becomes a substituent of an alkyl group, it is possible to use a fluorine atom, a chlorine atom, or a bromine atom. A plurality of these substituents may be substituted with an alkyl group, or both an aryl group and a halogen atom may be substituted.

The cyclic structure formed by combining R2 and R3 of Formula 2 together with -B- is a 4-membered ring or more and may contain a double bond or a triple bond. As coupling groups R2 and R3 is formed by bonding, for _{example, -CH 2 CH 2 -, -} CH 2 CH 2 CH 2 -, - CH 2 CH 2 CH 2 CH 2 -, - CH 2 CH 2 CH 2 _{CH 2 CH 2 -, - CH} = CH -, - CH = CHCH 2 -, - CH = CHCH 2 CH 2 -, - CH 2 CH = CHCH 2 -, - CH 2 CH 2 C≡CCH 2 CH 2 - and It is possible to use. These one or more hydrogen atoms may be substituted with an alkyl group, a halogen atom, an aryl group, or the like.

  Examples of the compound having a structure in which B in Formula 2 is represented by B1 include dimethyl sulfite, diethyl sulfite, ethyl methyl sulfite, methyl propyl sulfite, ethyl propyl sulfite, diphenyl sulfite, methyl phenyl sulfite, Chain sulfites such as ethyl sulfite, dibenzyl sulfite, benzyl methyl sulfite, and benzyl ethyl sulfite are used, ethylene sulfite, propylene sulfite, butylene sulfite, vinylene sulfite, phenylethylene sulfite, 1 -Cyclic sulfite such as methyl-2-phenylethylene sulfite or 1-ethyl-2-phenylethylene sulfite, or the chain sulfite or cyclic sulfite halide It is possible to use.

  Examples of the compound having a structure in which B in Formula 2 is represented by B2 include dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, ethylpropylsulfone, diphenylsulfone, methylphenylsulfone, ethylphenylsulfone, dibenzylsulfone. Chain sulfone such as benzyl methyl sulfone and benzyl ethyl sulfone, sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, 2-ethyl sulfolane, 3-ethyl sulfolane, 2,4-dimethyl sulfolane It is possible to use cyclic sulfones such as sulfolene, 3-methylsulfolene, 2-phenylsulfolane, 3-phenylsulfolane, the chain sulfone or the cyclic sulfone halide.

  Examples of the compound having a structure in which B in Formula 2 is represented by B3 include, for example, methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, propyl ethanesulfonate, and benzenesulfone. Methyl acetate, ethyl benzenesulfonate, propyl benzenesulfonate, phenyl methanesulfonate, phenyl ethanesulfonate, phenyl propanesulfonate, methyl benzylsulfonate, ethyl benzylsulfonate, propyl benzylsulfonate, benzyl methanesulfonate, ethanesulfone A chain sulfonic acid ester such as benzyl acid and benzyl propane sulfonate, 1,3-propane sultone, 1,4-butane sultone, 3-phenyl-1,3-propane sultone, 4-phenyl Or using a cyclic sulfonic acid esters such as 1,4-butane sultone, it is possible to use a halide of the chain sulfonic acid esters or cyclic sulfonic acid ester.

  Examples of the compound having a structure in which B in Formula 2 is represented by B4 include dimethyl sulfate, diethyl sulfate, ethyl methyl sulfate, methyl propyl sulfate, ethyl propyl sulfate, methyl phenyl sulfate, ethyl phenyl sulfate, phenyl propyl sulfate, benzyl sulfate. A chain sulfate such as methyl and benzylethyl sulfate is used, ethylene glycol sulfate, 1,2-propanediol sulfate, 1,3-propanediol sulfate, 1,2-butanediol sulfate, 1,3 A cyclic sulfate such as butanediol sulfate, 2,3-butadiol sulfate, phenylethylene glycol sulfate, methylphenylethylene glycol sulfate, ethylphenylethylene glycol sulfate, It is possible to use a halide of an ester or cyclic sulfate.

  These compounds represented by Formula 2 may be used by selecting only one type or by combining two or more types. It can also be used in combination with vinylene carbonate.

FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery according to the present invention.

Explanation of symbols

1 battery (non-aqueous electrolyte secondary battery)
2 Flat wound electrode group 3 Negative electrode 4 Positive electrode 5 Separator 6 Battery case 7 Battery lid 8 Safety valve 9 Negative electrode terminal 10 Negative electrode lead

Claims (7)

In a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte,
The electrolyte includes a compound represented by the following formula 1,
The non-aqueous electrolyte secondary battery, wherein the negative electrode includes graphite whose surface is partially or entirely coated with low crystalline carbon.
A-R1-OH (1)
(In the formula, R1 is a hydrocarbon group which may contain an unsaturated bond, or a hydrocarbon group which may contain an unsaturated bond, part or all of which is substituted with a halogen element; Has a structure represented by the following formula A1, A2 or A3.)

  2. The non-aqueous electrolyte secondary according to claim 1, wherein a part or all of the surface of the coated graphite is coated with low crystalline carbon of 0.5% by mass or more and 20% by mass or less. battery. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrolyte contains a compound represented by the following formula 2.
R2-B-R3 (2)
(In the formula, R 2 and R 3 are each independently a hydrocarbon group which may contain an unsaturated bond, or a carbon atom which may contain an unsaturated bond, part or all of which is substituted with a halogen element. Represents a hydrogen group, or R2 and R3 are bonded to each other to form a cyclic structure with B, and B has a structure represented by the following formula B1, B2, B3, or B4.

  The compound represented by Formula 1 is ethane-1,2-diol sulfonic acid or propane-1,2-diol sulfonic acid, according to any one of claims 1 to 3. Water electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 3, wherein the compound represented by Formula 2 is ethylene glycol sulfate or propanediol sulfate.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrolyte contains vinylene carbonate.   The non-aqueous electrolyte secondary battery according to claim 6, wherein the electrolyte contains 0.2% by mass or more and 2% by mass or less of vinylene carbonate.

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