JP5618385B2 - Method for producing lithium polymer battery - Google Patents

Description

  The present invention relates to a method for producing a lithium polymer battery, and more particularly to a method for producing a lithium polymer battery in which an organic compound that improves battery characteristics is contained in a gel electrolyte.

  Lithium polymer batteries are attracting attention as power sources for mobile devices because they can be thinned, have a high degree of freedom in shape selection, and have a high level of safety by not using an electrolyte. Recently, with the increase in the functions of mobile devices used, higher energy and improved battery characteristics have become the goals of technological development.

  Among these, one of the important technical issues is improvement of cycle characteristics. The cycle characteristics have been improved by devising various polymer materials to be used. In patent document 1, the improvement by mixing a physical crosslinkable polymer and a chemical crosslinkable gel electrolyte is proposed. In patent document 2, the improvement about the impregnation property of a pregel solution is proposed by modifying the separator surface to be used. In Non-Patent Document 1, for secondary batteries using a gel electrolyte, electrode materials (for example, artificial graphite (bulk graphite) that is expensive for the negative electrode material but has an effect of suppressing battery swelling), battery shape, etc. Investigations have been made, and battery swelling suppression and improvement of cycle characteristics are described. In addition, proposals have been made to improve battery characteristics by using an additive added to the electrolytic solution and a charging method. Patent Document 3 proposes that a film made of an additive can be efficiently produced by maintaining a voltage at which the main solvent is not decomposed and the additive is decomposed during the initial charge (also referred to as initial charge).

JP 2002-100406 A JP 2003-257490 A JP 2001-325988 A

Supervised by Satoshi Kanamura, latest polymer battery technology II, p. 242-247, CM Publishing (2003)

  However, during initial charging, gas is generated due to decomposition of the additive. In the lithium polymer battery, since the electrolyte is solid, the influence of the generated gas is larger than that of the secondary battery using the electrolytic solution, and the cycle characteristics are inferior. In the case of a lithium polymer battery that is polymerized using a peroxide, gas is also generated by the decomposition of the peroxide during the polymerization. Therefore, addition of a degassing step after gel electrolyte polymerization or initial charging, or initial charging in an opened state is performed.

  The inventors of the present invention have previously proposed an additive that decomposes at a lower voltage than a commonly used additive to produce a good film. (Japanese Patent Application No. 2007-195663) In a lithium polymer battery using a gel electrolyte, not only the material of the gel electrolyte but also the selection of the electrode material, battery shape, battery preparation conditions, electrolyte material, and the like are extremely important.

  The present invention has been made in view of the above problems. The object of the present invention is to apply characteristics of lithium polymer batteries, in particular, cycle characteristics, in a simple manner against the deterioration of characteristics caused by gas generated during gel electrolyte polymerization and initial charging when the gel electrolyte is applied to a lithium polymer battery. An object of the present invention is to provide a method for producing a lithium polymer battery that improves the battery.

  In order to solve the above-mentioned problems, a method for producing a lithium polymer battery of the present invention is shown in Chemical Formula 1 which is decomposed at a lower voltage than at least a positive electrode, a negative electrode, a solvent, a cross-linked polymer, a polymerization initiator, and the solvent. A step of encapsulating the organic compound or the gel electrolyte containing the cyclic disulfonic acid ester in the exterior body, and charging the organic compound or the cyclic disulfonic acid ester represented by Chemical Formula 1 to a voltage higher than or equal to the decomposition voltage and lower than a full charge voltage. Having a first charging step, a step of removing the generated gas by opening the exterior body after the first charging step, a step of sealing the exterior body, and a second charging step of charging until full charge. Features.

However, in Chemical formula 1, Z is a halogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a polyfluoroalkyl group, a substituted or unsubstituted cyclic hydrocarbon having 4 to 20 carbon atoms, or XR ₅ ( Here, X represents an oxygen atom, a sulfur atom or NR ₆ , R ₆ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and R ₅ represents a substituted or unsubstituted carbon atom having 4 to 4 carbon atoms. Represents 20 cyclic hydrocarbons). n represents an integer of 0 to 4. A ₁ and A ₂ are each independently an oxygen atom, a sulfur atom, or A ₁ is NR ₇ and A ₂ is NR ₈ (where R ₇ and R ₈ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted atom) Represents an alkyl group having 1 to 10 carbon atoms, a polyfluoroalkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted cyclic hydrocarbon having 4 to 20 carbon atoms, and R ₇ and R ₈ are bonded to each other. A ring structure may be formed). L represents a methylene group or a single bond. M represents boron or phosphorus. B ₁ and B ₂ each independently represent a carbonyl group, a substituted or unsubstituted alkylene group or a polyfluoroalkylene group. m represents an integer of 1 to 3 (provided that 2m + n = 4 when M is boron, and 2m + n = 6 when M is phosphorus).

  In the method for producing a lithium polymer battery of the present invention, it is preferable that the lowest empty orbit energy (LUMO) of the organic compound represented by Chemical Formula 1 is −1.5 (eV) or more and 0 (eV) or less.

  In the method for producing a lithium polymer battery of the present invention, the cyclic disulfonate is preferably at least one selected from methylene methane disulfonate, ethylene methane disulfonate, and propylene methane disulfonate.

  In the method for producing a lithium polymer battery according to the present invention, it is preferable that the ultimate voltage in the first charging step is equal to or higher than a discharge lower limit voltage.

  In the method for producing a lithium polymer battery of the present invention, the gel electrolyte includes a solvent, a cross-linked polymer, a polymerization initiator, 0.1 to 3.0% by mass of vinylene carbonate or a derivative thereof, and 0.1 to 3. 0% by mass of an organic compound represented by Chemical Formula 2 or Chemical Formula 3, or at least one selected from methylene methane disulfonate, ethylene methane disulfonate, and propylene methane disulfonate may be contained.

  Further, in the method for producing a lithium polymer battery of the present invention, the positive electrode contains lithium manganate or lithium cobaltate as an active material, the cross-linked polymer is composed of an acrylic polymer, and the polymerization initiator is peroxidized. Preferably, the solvent contains at least a chain carbonate and a cyclic carbonate, the negative electrode contains graphite as an active material, and the exterior material is made of a laminate material.

  In a lithium polymer battery using a polymerization initiator, gas is generated from the polymerization initiator during the polymerization of the polymer in addition to gas generation due to decomposition of the additive during initial charging. Since the electrolyte is solid, the influence of a minute gap between the electrodes due to the gas is larger than that of a battery using a normal electrolytic solution. Therefore, degassing is required in the process after polymerization. Even in a battery using a normal electrolytic solution, in order to remove the influence of the generated gas, initial charging in an opened state, cell opening in a fully charged state after initial charging, and the like are performed. In this process, the possibility of ignition cannot be denied, and there is a big problem in terms of safety. As described in the present invention, after polymer polymerization, charging is performed to an extent that exceeds the voltage at which the additive is decomposed during initial charging, and then degassing is performed, thereby decomposing the additive during polymerization and initial charging in one step. The gas can be easily removed, and since the charging capacity is very small, the risk of ignition when opened is very small.

  According to the present invention, at least a positive electrode, a negative electrode, a solvent, a crosslinkable polymer, a polymerization initiator, a gel containing an organic compound represented by Chemical Formula 1 decomposed at a lower voltage than the solvent, or a cyclic disulfonic acid ester A step of encapsulating the electrolyte in the outer package, a first charging step of charging the organic compound represented by Chemical Formula 1 or a voltage at which the cyclic disulfonic acid ester is decomposed, and opening the outer package to remove the generated gas By having a process, a step of sealing the exterior body, and a second charging step of charging until full charge, charging in an unsealed state having a problem in the manufacturing process or opening the exterior body in a fully charged state In addition, the gas generated during gel electrolyte polymerization and the decomposition gas of the additive during initial charging can be easily removed in one step. At this time, in the first charging process of the first stage, it is not necessary to hold for a certain time at a predetermined voltage, and the normal initial charging process is interrupted at a predetermined voltage, and the outer casing is opened to remove the generated gas. It is effective enough just to add.

The figure explaining the structure of the positive electrode of a lithium polymer battery. The figure explaining the structure of the negative electrode of a lithium polymer battery. Sectional drawing explaining the structure of the battery element after winding of a lithium polymer battery. The figure explaining the exterior | packing process of a lithium polymer battery.

  The positive electrode used in the method for producing a lithium polymer battery of the present invention is obtained by applying a positive electrode active material layer to a current collector made of a metal such as an aluminum foil, and compressing and molding the dried material. A negative electrode active material is applied to a current collector made of a metal such as a foil, and a dried product is compressed and molded. A separator will not be specifically limited if it is generally used with lithium polymer batteries, such as a nonwoven fabric and a polyolefin microporous film. A positive electrode and a negative electrode are stacked via a separator to produce a laminated body, or a positive electrode and a negative electrode are wound flatly via a separator to form a wound body, and the laminated body or the wound body is laminated material, etc. A lithium polymer battery is prepared by injecting and treating the gel electrolyte after being put in the outer packaging material.

  As the gelling component contained in the gel electrolyte, for example, a monomer having two or more polymerizable groups capable of thermal polymerization per molecule, an oligomer, a copolymer oligomer, or the like can be given. As this gelling component, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, propylene diacrylate, dipropylene diacrylate, tripropylene diacrylate, which forms an acrylic polymer, Bifunctional acrylates such as 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and trifunctional acrylates such as trimethylolpropane triacrylate and pentaerythritol triacrylate, In addition, tetrafunctional acrylates such as ditrimethylolpropane tetraacrylate and pentaerythritol tetraacrylate, and the above-mentioned methacrylate. Tomonoma and the like. In addition to these, monomers such as urethane acrylate and urethane methacrylate, copolymer oligomers thereof, and copolymer oligomers with acrylonitrile are exemplified, but not limited thereto.

  In addition, polymers that can be dissolved in a plasticizer and gelled, such as polyvinylidene fluoride, polyethylene oxide, and polyacrylonitrile can also be used.

  The gel component is not limited to the above-described monomer, oligomer, or polymer, and any gel component that can be gelled can be used. Further, the gelation is not limited to one kind of monomer, oligomer or polymer, and it can be used by mixing 2 to several kinds of gel components as required.

  Solvents contained in the gel electrolyte include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), Chain carbonates such as ethyl methyl carbonate (EMC) and dipropyl carbonate (DPC), aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate, γ-lactones such as γ-butyrolactone, Chain ethers such as 2-ethoxyethane (DEE) and ethoxymethoxyethane (EME), cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, acetami Dimethylformamide, dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl A mixture of one or more aprotic organic solvents such as 2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ethyl ether, 1,3-propane sultone, anisole, N-methylpyrrolidone, fluorinated carboxylate, etc. However, the present invention is not limited to these.

Examples of the organic compound represented by Chemical Formula 1 contained in the gel electrolyte include the organic compounds represented by Chemical Formulas 2 and 3 and the organic compounds shown in Table 1 as Compound Nos. 1 to 6, but the present invention includes these compounds. It is not limited.

  Examples of the cyclic disulfonic acid ester contained in the gel electrolyte include methylene methane disulfonate, ethylene methane disulfonate, and propylene methane disulfonate, but the present invention is not limited to these.

  In particular, when using scaly graphite as the negative electrode active material, it has an active site, unlike artificial graphite, which causes gas generation each time charging / discharging occurs, causing battery swelling and capacity reduction. In a battery composed only of a liquid, vinylene carbonate (hereinafter referred to as VC), 1,3-propane sultone (hereinafter referred to as PS) or the like is generally used as a countermeasure. For example, PS has a minimum orbital energy (LUMO) of 0.07 eV, and decomposes to form a film before EC (LUMO: 1.18 eV) or DEC (LUMO: 1.26 eV), where PS is a solvent molecule. It is possible. As a result, decomposition of solvent molecules is suppressed, and suppression of battery swelling due to gas generation and improvement of rate characteristics can be expected. When dispersed in a polymer gel as in the system of the present invention, since the gel has a high resistance, the above-described VC and PS are unlikely to form a decomposition film on the negative electrode. (Minimum empty orbit energy (LUMO): PS (0.07 (eV)), VC: 0.09 (eV)). Therefore, a molecular additive having a LUMO smaller than that of PS or VC is desirable, and those having −1.5 (eV) or more and 0 (eV) or less are optimal. For example, the organic compound represented by Chemical Formula 1 is considered to form a decomposition film on the electrode of the lithium ion secondary battery. For example, the minimum empty orbit energy (LUMO) of the organic compound represented by Chemical formula 2 is −1.21 eV, and EC (LUMO: 1.18 eV) or DEC (LUMO: 1) in which the organic compound represented by Chemical formula 2 is a solvent molecule. .26 eV) to decompose and form a film. As a result, decomposition of solvent molecules is suppressed, and suppression of battery swelling due to gas generation and improvement of rate characteristics can be expected. Further, the minimum empty orbit energy (LUMO) of the organic compound represented by Chemical formula 3 is −0.24 eV. For example, when lithium manganate is included in the positive electrode, Mn eluted in the gel is prevented from adsorbing on the negative electrode surface by adding an organic compound represented by chemical formula 2 or chemical formula 3, and as a result, rate characteristics due to an increase in resistance. This is considered to be effective for suppressing the decrease in the cycle and improving the cycle characteristics.

  In the present invention, it is effective to stabilize the film formed of the organic compound represented by Chemical Formula 1 or the cyclic disulfonic acid ester by appropriately containing VC or a derivative thereof in the gel electrolyte. VC is particularly effective when lithium cobaltate is used for the positive electrode, and the concentration of VC contained is preferably 0.1% by mass or more and 3.0% by mass or less, and particularly preferably 0.1% by mass or more and 1% by mass. 0.0 mass% or less.

  The concentration of the organic compound represented by Chemical Formula 1 or cyclic disulfonic acid ester contained in these gel electrolytes is not particularly limited, but a secondary battery using a positive electrode containing lithium manganate as the positive electrode active material In this case, it is preferably 0.1% by mass or more and 5.0% by mass or less, more preferably 0.5% by mass or more and 2.0% by mass or less. If it is less than 0.1% by mass, a sufficient film is not formed on the electrode surface, and the effect of improving cycle characteristics and rate characteristics is small. If it exceeds 5.0% by mass, the resistance increases and the rate characteristics deteriorate.

  When lithium cobaltate is used as the positive electrode active material, the concentration of the organic compound represented by Chemical Formula 2 or Chemical Formula 3 or cyclic disulfonic acid ester contained in the gel electrolyte is not particularly limited. 5 mass% or more and 5.0 mass% or less are preferable. If it is less than 0.5% by mass, a sufficient film is not formed on the electrode surface, and the effect of improving cycle characteristics and rate characteristics is small. If it exceeds 5.0% by mass, the resistance increases and the rate characteristics deteriorate.

The supporting salt contained in the gel electrolyte is not particularly limited, but electrolytes generally used for lithium polymer batteries such as LiPF ₆ , LiBF ₄ , LiAsPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ can be used. .

  In the present invention, benzoins, peroxides, and the like can be used as thermal polymerization initiators as necessary, but are not limited thereto.

Further, as the positive electrode active material, for example, complex oxides such as LiCoO ₂ , LiNi _1-x Co _x O ₂ , LiMn ₂ O ₄ , LiNi _x Mn _2−x O ₄ (0 ≦ X ≦ 1) can be used. It is not limited to these.

  Examples of the negative electrode active material include, but are not limited to, graphite, amorphous carbon, silicon, silicon oxide, metallic lithium, and alloys thereof.

  The separator may be a polyolefin such as polypropylene or polyethylene, or a porous film such as a fluororesin, but is not limited thereto.

  In the present invention, the charging voltage in the first charging step is not particularly limited as long as it is equal to or higher than the discharge lower limit voltage of the battery, but when a Co-based or Mn-based positive electrode whose discharge lower limit voltage is usually 3.0 V is used. The voltage is preferably about 3.2 to 3.6V.

  The present invention will be described in detail by way of examples with reference to the drawings.

  FIG. 1 is a diagram for explaining the configuration of the positive electrode of the lithium polymer battery, FIG. 2 is a diagram for explaining the configuration of the negative electrode of the lithium polymer battery, and FIG. 3 shows the configuration of the battery element after winding of the lithium polymer battery. FIG. 4 is a diagram illustrating an exterior process of a lithium polymer battery.

Example 1
First, the production of the positive electrode will be described with reference to FIG. A mixture of 85% by mass of LiMn ₂ O ₄ , 7% by mass of acetylene black as a conductive auxiliary and 8% by mass of polyvinylidene fluoride as a binder is added to N-methylpyrrolidone and further mixed to prepare a positive electrode slurry. did. This was applied to both surfaces of a 20 μm thick Al foil 2 serving as a current collector by a doctor blade method so that the thickness after the roll press treatment was 160 μm, thereby forming a positive electrode active material coating portion 3. In addition, the positive electrode active material non-application part 4 in which the positive electrode active material is not apply | coated to either surface is provided in both ends, and one positive electrode active material non-application part in which the positive electrode active material single-side application part 5 was provided subsequently 4 was provided with a positive electrode conductive tab 6 to obtain a positive electrode 1.

  Next, the production of the negative electrode will be described with reference to FIG. 90% by mass of graphite and 10% by mass of polyvinylidene fluoride as a binder were mixed, and N-methylpyrrolidone was added and further mixed to prepare a negative electrode slurry. This was applied to both surfaces of a 10 μm-thick Cu foil 8 serving as a current collector so that the thickness after the roll press treatment was 120 μm to form a negative electrode active material coating portion 9. In addition, the negative electrode active material one-side application part 10 and the negative electrode active material non-application part 11 in which the negative electrode active material was not apply | coated are provided in one end surface of both ends, and the negative electrode conductive tab 12 was attached to make the negative electrode 7.

  The production of the battery element will be described with reference to FIG. Two separators 13 made of polyethylene having a film thickness of 12 μm and a porosity of 35% are welded and cut, and the cut portion is fixed to the core of the winding device and wound, and the tips of the positive electrode 1 and the negative electrode 7 are attached. Introduce. The positive electrode 1 and the negative electrode 7 are arranged such that the side on which the electrode active material layer is formed on both sides is the tip side, the negative electrode is placed between the two separators, and the positive electrode is placed on the upper surface of the separator. Turned to form a battery element (hereinafter referred to as jelly roll (J / R)).

  This J / R was housed in an embossed laminate outer package as shown in FIG. 4, the sides of the laminate outer body were folded, and heat fusion was performed leaving a portion for injecting the gel electrolyte.

The pregel solution used as the gel electrolyte is an organic compound represented by Chemical Formula 2 with respect to an electrolytic solution composed of 30% by mass of ethylene carbonate (EC) and 58% by mass of diethyl carbonate (DEC) and 12% by mass of LiPF ₆ as a lithium salt. After adding 1% by mass of 3.8% by mass and 1% by mass of triethylene glycol diacrylate and trimethylolpropane triacrylate as gelling agents respectively, and mixing well, t-butyl peroxypi It was prepared by mixing 0.5% by mass of valerate.

  Next, the pregel solution was injected from the injection portion and vacuum impregnation was performed to obtain a lithium polymer battery. The discharge lower limit voltage of this battery is 3.0V.

  As a first charging step, the obtained lithium polymer battery is charged to a battery voltage of 3.2 V (charging current: 0.2 C, CC charging), opened once, and then vacuum-sealed again to form a second charging As a process, the battery voltage was charged to 4.2 V (charging current: 0.2 C, CC-CV charging, charging time: 6.5 hours). Thereafter, CC discharge was performed at 0.2 C to a battery voltage of 3.0 V, and the discharge capacity at that time was defined as the initial capacity.

  The rate characteristics of the obtained lithium polymer battery were as follows: a battery charged to a battery voltage of 4.2V was discharged at 0.2C to a battery voltage of 3.0V, and the discharge capacity was 100, and discharged at a discharge rate (1C). It was shown in Table 2 by the ratio with the obtained discharge capacity.

  The battery volume change rate after cycling of the obtained lithium polymer battery was shown in Table 2 as the ratio of the battery volume after initial charging to 1 and the battery volume after cycling. The cycle conditions were as follows: charge: upper limit voltage 4.2V, current: 1C, time 2.5H, discharge: lower limit voltage 3.0V, current: 1C. The capacity retention rate was expressed as a ratio of the discharge capacity (1C) at the 100th cycle to the discharge capacity (1C) at the first cycle.

(Example 2)
A battery was prepared and evaluated in the same manner as in Example 1 except that the charging voltage in the first charging step was set to 3.0V.

Example 3
A battery was prepared and evaluated in the same manner as in Example 1 except that the charging voltage in the first charging step was 3.4V.

Example 4
A battery was prepared and evaluated in the same manner as in Example 1 except that the charging voltage in the first charging step was 3.6V.

(Example 5)
A battery was prepared and evaluated in the same manner as in Example 1 except that the charging voltage in the first charging step was 3.8V.

(Example 6)
A battery was prepared and evaluated in the same manner as in Example 1 except that the charging voltage in the first charging step was 2.8V.

(Comparative Example 1)
A battery was fabricated and evaluated in the same manner as in Example 1 except that the first charging step was not performed and the gas removal step was performed in a fully charged state after performing initial charging to 4.2V.

(Comparative Example 2)
A battery was produced and evaluated in the same manner as in Example 1 except that the first charging step and the gas removal step were not performed.

  In the lithium polymer battery of the present invention, as shown in Examples 1 to 5 and Comparative Example 1 of Table 2, the first stage charging voltage is set to the discharge lower limit voltage or more, and the degassing step is performed, thereby performing two stages. It was found that the battery exhibited the same characteristics as a battery that was not charged and degassed in a fully charged state. Thereby, a process can be advanced in a safer state. Further, from Example 6 and Comparative Example 1 in Table 2, it was found that when the charge voltage at the first stage was lower than the discharge lower limit voltage, relatively good characteristics were exhibited although the characteristics were slightly inferior.

  Moreover, in the lithium polymer battery of the present invention, as shown in Examples 1 to 5 and Comparative Example 2 in Table 2, by setting the first stage charging voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, It has been found that the characteristics are better than batteries without two-stage charging and degassing. Further, from Example 6 and Comparative Example 2 in Table 2, it was found that the characteristics were better than the battery that did not perform two-stage charging and degassing even when the first stage charging voltage was lower than the discharge lower limit voltage.

(Example 7)
A battery was prepared and evaluated in the same manner as in Example 1 except that the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2.

(Example 8)
A battery was prepared and evaluated in the same manner as in Example 2 except that the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2.

Example 9
A battery was prepared and evaluated in the same manner as in Example 3 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Example 10)
A battery was prepared and evaluated in the same manner as in Example 4 except that the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2.

(Example 11)
A battery was prepared and evaluated in the same manner as in Example 5 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Example 12)
A battery was prepared and evaluated in the same manner as in Example 6 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Comparative Example 3)
A battery was prepared and evaluated in the same manner as in Comparative Example 1 except that the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2.

(Comparative Example 4)
A battery was prepared and evaluated in the same manner as in Comparative Example 2 except that the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2.

  Table 3 shows the rate characteristics, capacity retention rate, and battery volume change rate for Examples 7 to 12 and Comparative Examples 3 and 4.

(Example 13)
A battery was prepared and evaluated in the same manner as in Example 1 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 14)
A battery was prepared and evaluated in the same manner as in Example 2 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 15)
A battery was prepared and evaluated in the same manner as in Example 3 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 16)
A battery was prepared and evaluated in the same manner as in Example 4 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 17)
A battery was prepared and evaluated in the same manner as in Example 5 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 18)
A battery was prepared and evaluated in the same manner as in Example 6 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Comparative Example 5)
A battery was prepared and evaluated in the same manner as in Comparative Example 1 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Comparative Example 6)
A battery was prepared and evaluated in the same manner as in Comparative Example 2 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

  Table 4 shows the rate characteristics, capacity retention rate, and battery volume change rate for Examples 13 to 18 and Comparative Examples 5 and 6.

  In the lithium polymer battery of the present invention, as shown in Examples 7 to 11 and Comparative Example 3 in Table 3, even when the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2, It was found that by setting the one-stage charging voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, the characteristics equivalent to those of the battery degassed in the fully charged state without performing the two-stage charging were shown. Further, from Example 12 and Comparative Example 3 in Table 3, it was found that, when the charge voltage at the first stage was equal to or lower than the discharge lower limit voltage, although the characteristics were slightly inferior, relatively good characteristics were exhibited.

  Furthermore, in the lithium polymer battery of the present invention, as shown in Examples 13 to 17 and Comparative Example 5 in Table 4, when methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2, It was found that by setting the stage charge voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, the characteristics were better than those of the battery not performing two-stage charge and degassing. Further, from Example 18 and Comparative Example 6 in Table 4, it was found that the characteristics were better than the battery that did not perform two-stage charging and degassing even when the first-stage charging voltage was lower than the discharge lower limit voltage.

(Example 19)
The positive electrode in this example using lithium cobaltate as the positive electrode active material was produced as follows. N-methylpyrrolidone was added to and mixed with 87% by mass of LiCoO ₂ , 5% by mass of acetylene black as a conductive auxiliary material, and 8% by mass of polyvinylidene fluoride as a binder to prepare a positive electrode slurry. Otherwise, a positive electrode and a negative electrode were produced in the same manner as in Example 1 to produce a battery. Moreover, the pregel solution produced and evaluated the battery similarly to Example 1 except having set the mass of the organic compound shown by VC: 0.5 mass% and chemical formula 2 to 1.0 mass%.

(Example 20)
A battery was prepared and evaluated in the same manner as in Example 19 except that the charging voltage in the first charging step was set to 3.0V.

(Example 21)
A battery was produced and evaluated in the same manner as in Example 19 except that the charging voltage in the first charging step was 3.4 V.

(Example 22)
A battery was fabricated and evaluated in the same manner as in Example 19 except that the charging voltage in the first charging step was 3.6V.

(Example 23)
A battery was produced and evaluated in the same manner as in Example 19 except that the charging voltage in the first charging step was 3.8V.

(Example 24)
A battery was produced and evaluated in the same manner as in Example 19 except that the charging voltage in the first charging step was 2.8V.

(Comparative Example 7)
A battery was prepared and evaluated in the same manner as in Example 19 except that the two-stage charging was not performed and the degassing step was performed in a fully charged state after the initial charging to 4.2V.

(Comparative Example 8)
A battery was prepared and evaluated in the same manner as in Example 19 except that the two-stage charging and degassing steps were not performed.

Table 5 shows the rate characteristics, capacity retention ratio, and battery volume change rate for Examples 19 to 24 and Comparative Examples 7 and 8.

  In the lithium polymer battery of the present invention, as shown in Examples 19 to 23 and Comparative Example 7 in Table 5, the first stage charging voltage is set to the discharge lower limit voltage or more, and the degassing step is performed, so that two steps are performed. It was found that the battery exhibited the same characteristics as a battery that was not charged and degassed in a fully charged state. Thereby, a process can be advanced in a safer state. Further, from Example 24 and Comparative Example 7 in Table 5, it was found that when the charge voltage at the first stage was equal to or lower than the discharge lower limit voltage, although the characteristics were slightly inferior, relatively good characteristics were exhibited.

  Moreover, in the lithium polymer battery of the present invention, as shown in Examples 19 to 23 of Table 5 and Comparative Example 8, by setting the first stage charging voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, It has been found that the characteristics are better than batteries without two-stage charging and degassing. In addition, from Example 24 and Comparative Example 8 in Table 5, it was found that the characteristics were better than the battery that did not perform two-stage charging and degassing even when the first-stage charging voltage was lower than the discharge lower limit voltage.

(Example 25)
A battery was prepared and evaluated in the same manner as in Example 19 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Example 26)
A battery was prepared and evaluated in the same manner as in Example 20 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Example 27)
A battery was prepared and evaluated in the same manner as in Example 21 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Example 28)
A battery was prepared and evaluated in the same manner as in Example 22 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Example 29)
A battery was prepared and evaluated in the same manner as in Example 23 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Example 30)
A battery was prepared and evaluated in the same manner as in Example 24 except that the organic compound represented by Chemical formula 3 was used instead of the organic compound represented by Chemical formula 2.

(Comparative Example 9)
A battery was prepared and evaluated in the same manner as in Comparative Example 7 except that the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2.

(Comparative Example 10)
A battery was prepared and evaluated in the same manner as in Comparative Example 8 except that the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2.

  Table 6 shows the rate characteristics, capacity retention rate, and battery volume change rate for Examples 25 to 30 and Comparative Examples 9 and 10.

(Example 31)
A battery was prepared and evaluated in the same manner as in Example 19 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 32)
A battery was prepared and evaluated in the same manner as in Example 20 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 33)
A battery was prepared and evaluated in the same manner as in Example 21 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 34)
A battery was prepared and evaluated in the same manner as in Example 22 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 35)
A battery was prepared and evaluated in the same manner as in Example 23 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Example 36)
A battery was prepared and evaluated in the same manner as in Example 24 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Comparative Example 12)
A battery was prepared and evaluated in the same manner as in Comparative Example 7 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

(Comparative Example 13)
A battery was prepared and evaluated in the same manner as in Comparative Example 8 except that methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2.

  Table 7 shows the rate characteristics, capacity retention rate, and battery volume change rate for Examples 31 to 36 and Comparative Examples 12 and 13.

  In the lithium polymer battery of the present invention, as shown in Examples 25 to 29 and Comparative Example 10 in Table 6, even when the organic compound represented by Chemical Formula 3 was used instead of the organic compound represented by Chemical Formula 2, It was found that by setting the one-stage charging voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, the characteristics equivalent to those of the battery degassed in the fully charged state without performing the two-stage charging were shown. Further, from Example 30 and Comparative Example 10 in Table 6, it was found that when the charge voltage at the first stage was lower than the discharge lower limit voltage, relatively good characteristics were exhibited although the characteristics were slightly inferior.

  Further, in the lithium polymer battery of the present invention, as shown in Examples 25 to 29 of Table 6 and Comparative Example 11, by setting the first stage charging voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, It has been found that the characteristics are better than batteries without two-stage charging and degassing. Further, from Example 30 and Comparative Example 11 in Table 6, it was found that the characteristics were better than the battery that did not perform two-stage charging and degassing even when the first stage charging voltage was lower than the discharge lower limit voltage.

  Further, in the lithium polymer battery of the present invention, as shown in Examples 31 to 35 and Comparative Example 12 in Table 7, even when methylenemethane disulfonate was used instead of the organic compound represented by Chemical Formula 2, It was found that by setting the stage charge voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, the characteristics were better than those of the battery not performing two-stage charge and degassing. Further, from Example 36 and Comparative Example 13 in Table 7, it was found that the characteristics were better than the battery that did not perform two-stage charging and degassing even when the first stage charging voltage was lower than the discharge lower limit voltage.

  Further, in the lithium polymer battery of the present invention, as shown in Examples 31 to 35 and Comparative Example 13 in Table 7, by setting the first stage charging voltage to be equal to or higher than the discharge lower limit voltage and performing the degassing step, It has been found that the characteristics are better than batteries without two-stage charging and degassing. Further, from Example 36 and Comparative Example 13 in Table 5, it was found that the characteristics were better than the battery that did not perform two-stage charging and degassing even when the first stage charging voltage was lower than the discharge lower limit voltage.

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Al foil 3 Positive electrode active material application part 4 Positive electrode active material non-application part 5 Positive electrode active material single side application part 6 Positive electrode conductive tab 7 Negative electrode 8 Cu foil 9 Negative electrode active material application part 10 Negative electrode active material single side application part 11 Negative electrode active Substance non-applied portion 12 Negative electrode conductive tab 13 Separator 14 Battery

Claims (7)

At least a positive electrode, a negative electrode, a step of enclosing a solvent and an electrolyte containing an additive consisting of organic compounds in the exterior body and a voltage more than the additive is decomposed, first to charge to less than the full-charge voltage charging process and the steps of removing a generated gas and opening the exterior body after said first charging step and, and processes for sealing the exterior body, have a second charging step of charging to the full charge,
The organic compound is at least one selected from the compounds represented by the compound numbers 1 to 6 of Chemical Formula 1, Chemical Formula 2 and Chemical Formula 3, or at least one selected from methylenemethane disulfonate, ethylenemethane disulfonate and propylenemethane disulfonate. A method for producing a lithium secondary battery, which is a cyclic disulfonic acid ester ;

.   2. The method of manufacturing a lithium secondary battery according to claim 1, wherein a minimum empty orbit energy (LUMO) of the additive is −1.5 (eV) or more and 0 (eV) or less.   The method for producing a lithium secondary battery according to claim 1, wherein the ultimate voltage in the first charging step is equal to or higher than a discharge lower limit voltage.   The method for producing a lithium secondary battery according to claim 1, wherein the solvent contains at least a chain carbonate and a cyclic carbonate.   The method for producing a lithium secondary battery according to claim 4, wherein the chain carbonate and the cyclic carbonate contain ethylene carbonate (EC) and diethyl carbonate (DEC), respectively. The negative electrode is a method for manufacturing a lithium secondary battery according to any one of claims 1 to 5, characterized in that it contains graphite as an active material. Method for producing a lithium secondary battery according to any one of claims 1 to 6 wherein said outer body is characterized by comprising the laminated material.

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