JP2019061874A - Method of manufacturing power storage element - Google Patents

Abstract

To provide a method of manufacturing a power storage element in which swelling of the power storage element containing a lithium excess type positive electrode active material is suppressed, a good discharge capacity is obtained, and an initial charge time is shortened.SOLUTION: A CPU of a control unit of a power storage element manufacturing apparatus performs constant current charging on a power storage element including a lithium excess type positive electrode active material until potential of a positive electrode becomes predetermined potential (S1). Then, the CPU performs constant voltage charging, and when it is determined that a current value is less than a predetermined value B (CmA) (S3: YES), ends the constant voltage charging.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method of manufacturing a storage element including a lithium excess type positive electrode active material.

  Storage devices such as lithium ion secondary batteries have been used as power supplies for mobile devices such as notebook computers and mobile phones. In recent years, it has been used in a wide range of fields such as power supplies for EV (electric vehicles), HEVs (hybrid electric vehicles), PHEVs (plug-in hybrid electric vehicles), and lithium ion secondary batteries are required to have higher capacity. There is. Until now, various studies and improvements have been made, and it is difficult to realize a further increase in capacity only by improving the electrode structure and the like. Therefore, development of a positive electrode material having a higher capacity than current materials is in progress.

Conventionally, a lithium transition metal complex oxide having an α-NaFeO ₂ type crystal structure has been studied as a positive electrode active material for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, and a non-aqueous electrolyte ₂ using LiCoO ₂ The secondary battery has been widely put to practical use. The discharge capacity of LiCoO ₂ was about 120 to 130 mAh / g.
When the lithium transition metal complex oxide is represented by LiMeO ₂ (Me is a transition metal), it has been desired to use Mn as Me. When Mn is contained as Me, when the molar ratio of Mn in Me exceeds 0.5, structural change occurs to the spinel type upon charging, and the crystal structure can not be maintained, so charge and discharge The cycle performance is extremely poor.
Various LiMeO ₂ -type active materials have been proposed and put to practical use, in which the molar ratio Mn / Me of Mn in Me is 0.5 or less and the molar ratio Li / Me relative to Me is approximately 1. The positive electrode active material containing LiNi _1/2 Mn _1/2 O ₂ and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ which are lithium transition metal composite oxides has a discharge capacity of 150 to 180 mAh / g. Have.

A lithium transition metal complex oxide in which the molar ratio Mn / Me of Mn in Me to LiMeO _{2 type} active material exceeds 0.5, and the composition ratio Li / Me of Li to the ratio of transition metal (Me) is more than 1 So-called excessive lithium type active materials are also known.
As the above-mentioned high-capacity positive electrode material, an Li ₂ MnO ₃ -based active material which is a lithium excess type is being studied.

  In a battery having a lithium excess type positive electrode active material, in order to develop a high capacity of the positive electrode, it is necessary to perform initial charging so that the upper limit charging potential of the positive electrode is equal to or higher than a predetermined value on the basis of Li.

In Patent Document 1, reduction of the discharge voltage is intended to be suppressed by setting the charge potential of the positive electrode to 4.55 V or more with respect to the pair Li at the first charge. By performing the initial charge at a high voltage, it is considered that Li in the positive electrode active material can be taken out more largely, and Li usable for charge and discharge from the next time can be increased. However, when the initial charge is performed at a high voltage, the crystal structure of the positive electrode active material may collapse with release of Li ions, and oxygen may be released from the inside of the crystal. When this oxygen reaches the negative electrode, Li ₂ O or the like precipitates on the negative electrode surface, which causes a problem of inhibiting the negative electrode reaction.

  Patent Document 2 discloses that initial charging is performed at a temperature of 40 ° C. to 70 ° C. and the potential of the positive electrode becomes 4.5 V or more in order to solve the above-mentioned problems. By charging at high temperature, the solubility of oxygen in the electrolytic solution is reduced, and the movement of oxygen to the negative electrode side is suppressed.

  In Patent Document 3, in a lithium ion secondary battery including a positive electrode active material represented by a predetermined composition formula and having a metal compound deposited on the surface, the upper limit potential is converted to a lithium counter electrode to be 4.4 V or more and 5.0 V A charge and discharge pretreatment is performed to set the lower limit potential to a lithium counter electrode of 2.0 V or more and less than 3.6 V. This improves the cycle characteristics at high temperatures.

  Patent Document 4 includes a positive electrode active material represented by a predetermined composition formula, and the upper limit voltage during charging is 4.0 V or more and less than 4.9 V with respect to the Li reference electrode, and the lower limit voltage during discharge is 2.0 V The constant potential control is performed to the voltage range of 3.5 V or more and the initial charging time is performed. Processing time of initial charge is shortened.

Unexamined-Japanese-Patent No. 2015-084303 Unexamined-Japanese-Patent No. 2010-282874 JP, 2013-206688, A JP, 2012-186035, A

  When a battery with a lithium excess type positive electrode active material performs constant current (CC) charging followed by constant voltage (CV) charging, the discharge capacity may increase, but the thickness of the battery may also increase . When the battery swells, the battery performance decreases due to, for example, an increase in resistance. With the initial charge method of the above-mentioned patent documents 1-4, the swelling of a battery can not be suppressed. In addition, in the case of only CC charging, charging unevenness may occur in the thickness direction of the electrode due to the influence of coating weight variation of the electrode and the like, and the charging state may be uneven.

  An object of the present invention is to provide a method of manufacturing a storage element capable of suppressing swelling of a storage element containing a lithium excess type positive electrode active material, obtaining a good discharge capacity, and shortening the time of initial charge. Do.

  A method of manufacturing a storage element according to the present invention is a method of manufacturing a storage element including a lithium excess type positive electrode active material, wherein constant current charging is performed so that the potential of the positive electrode reaches a predetermined potential, and the current value is predetermined. The constant voltage charging is performed until the current value decreases.

  The method of manufacturing an electricity storage device according to the present invention is a method of manufacturing an electricity storage device including a lithium excess type positive electrode active material, wherein constant current charging is performed so that the potential of the positive electrode reaches a predetermined potential. The constant voltage charging is performed until the absolute value of the amount of change of V decreases to a predetermined value.

  In the present invention, the swelling of the storage element is suppressed, a good discharge capacity is obtained, and the time of initial charge is shortened.

FIG. 1 is a cross-sectional view showing a lithium ion secondary battery according to an embodiment. FIG. 2 is a block diagram showing a battery, a control unit provided in the battery manufacturing apparatus, and a current sensor. It is a graph which shows the relationship between charge time, an electric current value, and a thickness increase amount. It is a graph which shows the relationship between charge time, an electric current value, and the absolute value (| (DELTA) I / (DELTA) t |) of the variation of the electric current value with respect to time. It is a flowchart which shows the procedure of the initial stage charge process which concerns on the manufacturing method of the battery of embodiment. It is a flowchart which shows the procedure of the initial stage charge process which concerns on the manufacturing method of the other battery of embodiment. It is a graph which shows the relationship between a cut current value, discharge capacity, and the amount of thickness increase. It is a graph which shows the relation between | ΔI / Δt | and the discharge capacity and the increase in thickness.

Hereinafter, the present invention will be specifically described based on the drawings showing the embodiments thereof. Hereinafter, although the case where the storage element is a lithium ion secondary battery will be described, the storage element is not limited to the lithium ion secondary battery.
FIG. 1 is a cross-sectional view showing a lithium ion secondary battery as a storage element according to the embodiment. In FIG. 1, 1 is a rectangular lithium ion secondary battery (hereinafter referred to as battery), 2 is an electrode group, 3 is a negative electrode, 4 is a positive electrode, 5 is a separator, 6 is a battery case, 7 is a case lid, 8 is a case lid A safety valve, 9 is a negative electrode terminal, 10 is a negative electrode lead, 11 is a positive electrode lead, and 12 is an insulating member. The electrode group 2 is obtained by winding the negative electrode 3 and the positive electrode 4 in a flat shape via the separator 5. The electrode group 2 and the non-aqueous electrolyte are housed in a battery case 6. The opening of the battery case 6 is sealed by laser welding a case lid 7 provided with a safety valve 8. The negative electrode terminal 9 has a head and a leg that is L-shaped in side view, and is provided so as to penetrate the case lid 7 in a state where the leg is covered by the insulating member 12. The negative electrode terminal 9 is connected to the negative electrode 3 through the negative electrode lead 10, and the positive electrode 4 is connected to the inner surface of the case lid 7 through the positive electrode lead 11.
The battery 1 may be cylindrical, and the electrode group 2 may be one in which the negative electrode 3 and the positive electrode 4 are alternately stacked via the separator 5.

In the case of producing the positive electrode 4, first, a positive electrode active material of a Li excess type, a conductive support agent, and a binder are mixed at a predetermined mass ratio to obtain a positive electrode mixture.
As the positive electrode active material, LiMeO ₂ -Li ₂ MnO ₃ solid solution described above, Li ₂ O-LiMeO ₂ solid solution, Li ₃ NbO ₄ -LiMeO ₂ solid solution, Li ₄ WO ₅ -LiMeO ₂ solid solution, Li ₄ TeO ₅ -LiMeO ₂ solid solution, Li ₃ SbO ₄ -LiFeO ₂ solid solution, Li ₂ RuO ₃ -LiMeO ₂ solid solution, and a Li-excess active material such as Li ₂ RuO ₃ -Li ₂ MeO ₃ solid solution.
As a conductive support agent, natural graphite (scaly graphite, flake graphite, earthy graphite etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver) , Gold, etc. 1) or 2 or more of conductive materials such as powder, metal fibers and conductive ceramic materials.
Binders include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene and polypropylene, ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), 1 type, or 2 or more types, such as polymers which have rubber elasticity, such as fluororubber, are mentioned.

  A paste is obtained by dispersing the positive electrode mixture in an organic solvent such as N-methyl-2-pyrrolidone or toluene. The paste is uniformly applied to a current collector made of aluminum or the like having a predetermined thickness and dried, and then compression molding is performed by a roll press to obtain the positive electrode 4.

When producing the negative electrode 3, first, a negative electrode active material and a binder are mixed, distilled water is appropriately added and dispersed, and a slurry is prepared.
Examples of the negative electrode active material include graphite, hard carbon, metals such as Si, Sn, Cd, Zn, Al, Bi, Pb, Ge, Ag and the like, and alloys. The slurry is uniformly applied to a current collector made of copper or the like having a predetermined thickness, dried, and compression molded by a roll press to obtain the negative electrode 3.

  As the separator 5, it is preferable to use, alone or in combination, a porous film, a non-woven fabric or the like exhibiting excellent high-rate discharge performance. Examples of the material of the separator 5 include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-perfluorovinyl ether Copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride -Ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluorope Pyrene copolymer, vinylidene fluoride - ethylene - tetrafluoroethylene copolymer, and the like.

  As a non-aqueous solvent used for the non-aqueous electrolyte, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, 4-fluoroethylene carbonate, vinylene carbonate and the like; cyclic resins such as γ-butyrolactone and γ-valerolactone Esters; Linear carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate; Linear esters such as methyl formate, methyl acetate, methyl butyrate; Tetrahydrofuran or derivatives thereof; 1,3-Dioxane, 1,4-dioxane Ethers such as 1,2-dimethoxyethane, 1,4-dibutoxyethane and methyl diglyme; Nitriles such as acetonitrile and benzonitrile; Dioxolane or derivatives thereof; Ethylene sulfide Examples thereof include, but are not limited to, sulfolane, sultone or a derivative thereof alone or a mixture of two or more thereof.

  FIG. 2 is a block diagram showing the battery 1, the control unit 13 provided in the battery 1 manufacturing apparatus, and the current sensor 19.

The control unit 13 includes a central processing unit (CPU) 15 that controls the operation of each component, and the CPU 15 is connected to the storage unit 16, the timer unit 17, and the I / F 18 via a bus.
The battery 1 and the current sensor 19 are connected to the control unit 13 via the I / F 18.

The storage unit 16 stores a control program for performing initial charging according to the present embodiment. Further, various data generated by the arithmetic processing of the CPU 15 are temporarily stored.
The timer unit 17 starts clocking at the start of the initial charging. The control unit 13 obtains the current value flowing from the current sensor 19 to the battery 1 at predetermined time intervals. In addition, | ΔI / Δt |, which will be described later, is obtained by clocking.

  In the method of manufacturing the battery 1 according to the present embodiment, after the battery 1 is assembled, initial charging is performed. Constant current charging (CC charging) is performed so that the potential of the positive electrode 4 reaches a predetermined potential, and then constant voltage charging (CV charging) is performed. The predetermined potential is preferably nobler than the plateau potential. The plateau potential means a region where the potential change is relatively flat, which appears in the positive electrode potential-charge charge quantity curve.

When the current value for terminating constant voltage charging is 0.04 CmA or more, the discharge capacity is high, the increase in battery thickness is small, and the charge time is also short. The lower limit value of the current value is preferably 0.05 CmA. The upper limit value of the current value is preferably 0.08 CmA, and more preferably 0.07 CmA.
The current value for terminating constant voltage charging is set in consideration of the desired discharge capacity and the allowable amount of increase in battery thickness.

The constant voltage charging may be performed until the absolute value (| ΔI / Δt |) of the change amount of the current value with respect to time reaches a predetermined value. At that time, it is preferable that Δt be a constant interval. The unit of | ΔI / Δt | is not particularly limited, and any unit such as mA / min, A / min, mA / sec, CmA / min can be used. Above all, mA / min is easy to apply. For example, in the case where the interval of Δt is 1 min and the unit of | ΔI / Δt | is mA / min, it is preferable to be 0.9 mA / min or more. When | ΔI / Δt | is 0.9 mA / min or more, the discharge capacity is high, the increase in battery thickness is small, and the charge time is also short. The lower limit value of | ΔI / Δt | is preferably in the order of 0.98 mA / min, 1 mA / min and 1.1 mA / min. The upper limit of | ΔI / Δt | is preferably in the order of 3 mA / min, 2.9 mA / min, and 2.5 mA / min.
The predetermined value is set in consideration of a desired discharge capacity and an allowable amount of increase in battery thickness.

FIG. 3 is a graph showing the relationship between the charging time and the current value and the amount of increase in battery thickness. The horizontal axis is time (h), the vertical axis on the left is current value I (mA), and the vertical axis on the right is thickness increase amount (mm) of the battery 1.
As shown in FIG. 3, in the initial charging, first, CC charging is performed.
A schematic cross-sectional view of the positive electrode 4 at the time of completion of the CC charging is also shown in FIG. Lithium ions are inserted between the carbon crystal layers of the negative electrode 3 (not shown) from the upper separator side of the mixture of FIG. 3. As shown in a schematic cross-sectional view, charging unevenness exists in the thickness direction. Due to the weight variation at the time of application of the mixture of the positive electrode 4, the charge state also varies among the batteries 1.

For this reason, constant voltage charging (CV charging) is subsequently performed. The current value gradually decreases during constant voltage charging.
By continuing CV charge, charge advances so that nonuniformity may be eliminated, as shown in the typical sectional view by the side of the inside of FIG.
Since the charge on the separator side still proceeds, the charge level exceeds a certain level as the constant voltage charge time increases, as shown in the lower schematic cross-sectional view of FIG. In this case, the amount of generated gas such as carbon dioxide rapidly increases, and the battery 1 is expanded.

FIG. 4 is a graph showing the relationship between the charging time, the current value, and the absolute value (| ΔI / Δt |) of the amount of change in the current value with respect to time. The horizontal axis represents time (sec), the left vertical axis represents | ΔI / Δt | (mA / min), and the right vertical axis represents current value I (mA).
After the electrolyte was injected and the battery 1 was assembled, CC charging was performed at 0.1 CmA for 3 hours as preliminary charging, and aging was performed for 48 hours. By aging, the gas accumulated in the battery 1 is dissolved and absorbed in the electrolytic solution. After that, CC charge and CV charge were performed.
As shown in FIG. 4, when performing CV charging after CC charging, both the | ΔI / Δt | and the current value decrease as the time of CV charging increases.
Although precharging and aging are performed after the battery 1 is assembled, it is not necessary to perform precharging and aging before the initial charging process according to the present embodiment.

  As described above, in the present embodiment, the indicator for terminating the CV charging is the current value or | ΔI / Δt |.

FIG. 5 is a flowchart showing the procedure of the initial charging process according to the method of manufacturing the battery 1 of the embodiment. After the battery 1 is assembled, an initial charging process is performed.
First, CC charging is performed by the CPU 15 (S1). The current value is preferably 0.05 CmA or more and 3 CmA or less.
CC charging is performed until the potential of the positive electrode reaches a predetermined potential higher than the plateau potential. The plateau potential of the positive electrode active material according to the present embodiment is around 4.5 V (vs. Li ^/ Li ⁺ ). Therefore, it is preferable to perform CC charging until the potential of the positive electrode becomes about 4.6V. When converted to cell voltage, it is approximately 4.5V. Thereby, Li in the positive electrode active material can be taken out largely. The upper limit value of the current value and the positive electrode potential is determined based on the constituent material of the battery 1, the required discharge capacity, and the like.

After the potential of the positive electrode reaches a predetermined potential, the CPU 15 performs CV charging in a state in which the predetermined potential is maintained (S2).
The CPU 15 determines whether the current value is less than B (C mA) (S3). B is preferably 0.04 CmA.
When the CPU 15 determines that the current value is not less than B (C mA) (S3: NO), the determination process is repeated.
When the CPU 15 determines that the current value is less than B (CmA) (S3: YES), the initial charging process is ended.
In addition, the threshold value of the electric current value which complete | finishes a constant voltage charge is not limited to above-mentioned 0.04 CmA.
A plurality of batteries 1 subjected to the initial charging process as described above are housed in the case in a state of being electrically connected, whereby a power storage device is configured. A battery pack is configured by including the power storage device and a BMW (Battery Management Unit) that controls charging and discharging of the battery 1.

FIG. 6 is a flowchart showing the procedure of another initial charging process according to the method of manufacturing the other battery 1 of the embodiment. After battery assembly, an initial charging process is performed.
First, CC charging is performed by the CPU 15 in the same manner as described above (S11).

After the potential of the positive electrode reaches a predetermined potential, the CPU 15 performs CV charging in a state in which the predetermined potential is maintained (S12).
The CPU 15 determines whether or not | ΔI / Δt | (mA / min) is less than the lower limit value A (S13). When the CPU 15 determines that the current value is not less than the lower limit value A (S13: NO), the determination process is repeated. The lower limit value A is preferably 0.9 (mA / min).
When it is determined that | ΔI / Δt | is less than the lower limit value A (S13: YES), the CPU 15 ends the initial charging process.
The lower limit value A is not limited to 0.9 (mA / min) described above.

After performing CC charging, the relationship between | ΔI / Δt | and current values, and battery characteristics and battery swelling when performing CV charging was examined.
First, the battery 1 was assembled. The composition of the material of the battery 1 is as follows. The positive electrode composite material of the positive electrode 4 was obtained by mixing 94 parts by mass of an Li-rich positive electrode active material, 4.5 parts by mass of acetylene black, and 1.5 parts by mass of polyvinylidene fluoride (PVDF). The positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to obtain a paste. The paste was uniformly applied to a current collector made of aluminum and dried, and then compression molding was performed by a roll press to obtain a positive electrode 4.
The mixture of the negative electrode 3 was obtained by mixing 96.7 parts by mass of graphite, 1.2 parts by mass of CMC (carboxymethylcellulose), and 2.1 parts by mass of SBR. The paste was uniformly applied to a copper current collector and dried, and then compression molding was performed by a roll press to obtain a negative electrode 3.
As the separator 5, a microporous polyethylene film was used.
The electrolyte solution was prepared by dissolving 1.2 mol / L of LiPF ₆ in a mixed solvent of 4-fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) at a volume ratio of 5:95, and using 1,3-propene sultone (PRS) ) Was used with 2% by mass added to the total mass of the non-aqueous electrolyte.

  After the assembly of the battery, initial charging of Experimental Examples 1 to 5 and Comparative Examples 1 and 2 was performed under the following conditions. Table 1 shows the conditions.

  In Table 1, "cut current value" is a current value when CV charging is finished.

[Experimental Example 1]
After performing CC charging at 0.1 CmA until reaching 4.5 V as a battery voltage, CV charging was performed at 4.5 V, and CV charging was ended when the current value reached 0.04 CmA. After that, CC discharge was performed to 2.0 V at 0.1 C mA. The interval of Δt at the time of calculation of | ΔI / Δt | is 1 min. At the end of CV charging, | ΔI / Δt | is 0.98 mA / min.
[Experimental Example 2]
When the current value reached 0.05 CmA, CCCV charging of Experimental Example 2 was performed in the same manner as Experimental Example 1 except that CV charging was terminated. At the end of CV charging, | ΔI / Δt | is 1.16 mA / min.
[Experimental Example 3]
When the current value reached 0.06 CmA, CCCV charging of Experimental Example 3 was performed in the same manner as Experimental Example 1 except that CV charging was finished. At the end of CV charging, | ΔI / Δt | is 1.46 mA / min.
[Experimental Example 4]
When the current value reached 0.07 CmA, CCCV charging of Experimental Example 4 was performed in the same manner as Experimental Example 1 except that CV charging was finished. At the end of CV charging, | ΔI / Δt | is 2.17 mA / min.

[Experimental Example 5]
When the current value reached 0.08 CmA, CCCV charging of Experimental Example 5 was performed in the same manner as in Experimental Example 1 except that CV charging was finished. At the end of CV charging, | ΔI / Δt | is 2.99 mA / min.

Comparative Example 1
When the current value reached 0.02 CmA, CCCV charging of Comparative Example 1 was performed in the same manner as in Experimental Example 1 except that CV charging was finished. At the end of CV charging, | ΔI / Δt | is 0.14 mA / min.
Comparative Example 2
CC charge was performed to 4.5 V at 0.1 C mA.

With respect to the batteries 1 of Experimental Examples 1 to 5 and the batteries of Comparative Examples 1 and 2, the charge amount, discharge capacity, battery thickness increase amount, charge time, and gas amount were determined as follows.
(Amount of charge)
The amount of charge in the initial charge was determined.
(Discharge capacity)
The discharge capacity at the initial charge was determined.
(Battery thickness increase)
Before and after the initial charge and after the initial charge, respectively, the thickness of the battery 1 was measured by sandwiching the central portion of the long side of the battery 1 with a vernier caliper from the vertical direction with respect to the long side. The amount of increase in battery thickness (mm) before and after the initial charge was calculated.
(charging time)
The charge time was measured by the timer unit 17.
(Measurement of gas amount)
With the battery placed in a closed container equipped with a syringe, the battery case was opened, and the amount of gas released was checked on the scale of the syringe.

FIG. 7 is a graph showing the relationship between the cut current value and the discharge capacity and the increase in thickness. The horizontal axis is a current value (CmA), the left vertical axis is a discharge capacity (mAh / g), and the right vertical axis is a thickness increase amount (mm). In FIG. 7, ● is a graph showing the relationship between the cut current value and the discharge capacity, and ▪ is a graph showing the relationship between the cut current value and the increase in thickness.
From FIG. 7 and Table 1, it is understood that as the CV charge time becomes longer and the cut current value becomes smaller, the discharge capacity is improved and the battery thickness increase amount is increased.
In the case of the battery 1 of Experimental Examples 1 to 5 having a cut current value of 0.04 CmA or more, the discharge capacity is 255.5 mAh / g or more, the increase in battery thickness is 0.30 mm or less, and the charge time is 12 hours It is below.
In the case of the battery of Comparative Example 1, the increase in battery thickness is 0.39 mm. In the case of the battery of Comparative Example 2, the discharge capacity is 254.1 mAh / g. In the case of the battery of Comparative Example 2, since CV charging is not performed, charging is insufficient and the discharge capacity is small.
The lower limit value of the cut current value is preferably 0.05 CmA. The upper limit of the cut current value is preferably 0.08 CmA, and more preferably 0.07 CmA.

FIG. 8 is a graph showing the relationship between | ΔI / Δt | and the discharge capacity and the increase in thickness. The horizontal axis is | ΔI / Δt | (mA / min), the vertical axis on the left is the discharge capacity (mAh / g), and the vertical axis on the right is the thickness increase (mm). In FIG. 8, ● is a graph showing the relationship between | ΔI / Δt | and the discharge capacity, and ▪ is a graph showing the relationship between | ΔI / Δt | and the amount of increase in thickness.
From FIG. 9 and Table 1, it is understood that as the CV charge time becomes longer and | ΔI / Δt | becomes smaller, the discharge capacity is improved and the battery thickness increase amount is increased.
It is understood that | ΔI / Δt | is preferably 0.9 mA / min or more. When | ΔI / Δt | is 0.9 mA / min or more, the discharge capacity is 255.5 mAh / g or more, the increase in battery thickness is 0.3 mm or less, and the charge time is 12 hours or less. The lower limit value of | ΔI / Δt | is preferably in the order of 0.98 mA / min, 1.0 mA / min and 1.1 mA / min. The upper limit value of | ΔI / Δt | is preferably in the order of 3.0 mA / min, 2.9 mA / min and 2.5 mA / min.

From the above, by performing CV charge so that the current value at the end of CV charge is 0.04 CmA or more, the swelling of battery 1 is favorably suppressed, battery 1 has a good discharge capacity, and the charge time is It was confirmed to be short.
Further, by performing CV charging so that | ΔI / Δt | at the end of CV charging is equal to or more than a predetermined value, the swelling of battery 1 is favorably suppressed, battery 1 has a good discharge capacity, and the charging time is It was confirmed to be short.

  The above manufacturing method of a storage element is a method of manufacturing a storage element including a lithium excess type positive electrode active material, wherein constant current charging is performed so that the potential of the positive electrode reaches a predetermined potential, and the current value is a predetermined current Perform constant voltage charging until it drops to the value.

  According to the above configuration, the swelling of the storage element can be well suppressed, a good discharge capacity can be obtained, and the time of initial charge can be shortened.

  In the method of manufacturing the storage element described above, the predetermined current value is preferably 0.04 CmA or more.

  According to the above configuration, the swelling of the storage element can be suppressed better.

  Another method of manufacturing a storage element is a method of manufacturing a storage element including a lithium excess type positive electrode active material, wherein constant current charging is performed so that the potential of the positive electrode reaches a predetermined potential, and a change in current value with respect to time Constant voltage charging is performed until the absolute value of the amount decreases to a predetermined value.

  According to the above configuration, the swelling of the storage element can be well suppressed, a good discharge capacity can be obtained, and the time of initial charge can be shortened.

  In the manufacturing method of the above-mentioned electrical storage element, it is preferable that the predetermined value is 0.9 mA / min or more.

  According to the above configuration, the swelling of the storage element can be suppressed better.

  The present invention is not limited to the contents of the embodiments described above, and various modifications can be made within the scope of the claims. That is, an embodiment obtained by combining technical means appropriately modified within the scope of the claims is also included in the technical scope of the present invention.

REFERENCE SIGNS LIST 1 battery 2 electrode group 3 negative electrode 4 positive electrode 5 separator 6 battery case 7 case lid 8 safety valve 9 negative electrode terminal 10 negative electrode lead 11 positive electrode lead 12 insulating member 13 control unit 15 CPU
19 current sensor

Claims (4)

A method of manufacturing a storage element including a lithium excess type positive electrode active material,
Constant current charging so that the positive electrode potential reaches a predetermined potential,
A manufacturing method of a storage element characterized in that constant-voltage charging is performed until the current value decreases to a predetermined current value.   The method according to claim 1, wherein the predetermined current value is 0.04 CmA or more. A method of manufacturing a storage element including a lithium excess type positive electrode active material,
Constant current charging so that the positive electrode potential reaches a predetermined potential,
A manufacturing method of a storage element characterized in that constant voltage charging is performed until an absolute value of a change amount of a current value with respect to time decreases to a predetermined value.   The method according to claim 3, wherein the predetermined value is 0.9 mA / min or more.