JP2012227035A - Method of manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a nonaqueous electrolytic secondary battery capable of forming a film on a surface of a negative electrode mixture layer appropriately in a short time.SOLUTION: An initial charging step of a battery includes an auxiliary charging step D1, a charge and discharge repeating step D2, and a constant current charging step D3. At the auxiliary charging step D1, the battery is charged until a voltage of the battery becomes within a range of a film formation voltage region R where an SEI film is formed on a surface of a negative electrode mixture layer. At the charge and discharge repeating step D2, charge and discharge are repeated within the range of the film formation voltage region R. That is, when the voltage of the battery reaches an upper limit voltage VU of the film formation voltage region R, charge is stopped, and discharge is started. When the voltage of the battery reaches a lower limit voltage VL of the film formation voltage region R, discharge is stopped, and charge is started. At the constant current charging step D3, the voltage of the battery is charged until the voltage of the battery reaches a full-charge voltage.

Description

  The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery capable of suitably forming a film on the surface of an electrode.

  Batteries are used in various fields such as electronic devices such as mobile phones and personal computers, vehicles such as hybrid vehicles and electric vehicles. Of these, assembled batteries in which single cells are connected in series or in parallel are generally mounted on vehicles and large electronic devices.

  As such a battery, there is a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte. Non-aqueous electrolyte secondary batteries include lithium ion secondary batteries in which lithium ions are responsible for electrical conduction. In a lithium ion secondary battery, a carbon-based material is generally used as an active material on the negative electrode side. When a carbon-based material is used as the active material on the negative electrode side, the carbon-based material on the surface of the negative electrode mixture layer reacts with the electrolytic solution. As a result, a SEI (Solid Electrolyte Interface) film is formed on the surface of the negative electrode mixture layer.

  This SEI coating is indispensable for allowing the carbon-based material of the negative electrode mixture layer to occlude and release lithium ions. Therefore, a technique for suitably forming an SEI film has been developed. For example, Patent Literature 1 discloses an initial charging method including a first charging step of forming a film on the surface of the negative electrode mixture layer and a second charging step of charging to a full charge voltage (Patent Literature). 1 paragraph [0019] and FIG. 2 etc.). Thereby, a small amount of a stable coating can be formed on the surface of the negative electrode mixture layer (see paragraph [0011] and the like of Patent Document 1).

JP 2001-325988 A

  However, in the initial charging method described in Patent Document 1, it takes a long time to form a film. This is because the charging current value is as small as 0.1 C or less (see paragraph [0049], etc. of Patent Document 1). Under these conditions, it takes 1 to 2 hours to form the coating (see paragraph [0017] of FIG. 2 and FIG. 2 etc.). This has a long cycle time. In other words, productivity is not high.

  The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide a method for producing a non-aqueous electrolyte type secondary battery that can form a film on the surface of the negative electrode mixture layer in a short time.

  In order to solve this problem, a method for manufacturing a non-aqueous electrolyte type secondary battery according to an aspect of the present invention includes a non-aqueous electrolysis method in which an electrode body is housed in a battery container and a non-aqueous electrolyte is injected. This is a method including a battery assembly process for forming a liquid secondary battery and an initial charging process for charging the nonaqueous electrolyte secondary battery. In addition, the initial charging step includes a charge / discharge repetition step in which charging and discharging of the nonaqueous electrolyte type secondary battery are repeated. In the charge / discharge repetition step, the voltage of the non-aqueous electrolyte secondary battery is within the range of the film formation voltage region in which the SEI film is formed on at least a part of the electrode body. In such a non-aqueous electrolyte secondary battery manufacturing method, an SEI film can be suitably formed on the surface of the negative electrode of the non-aqueous electrolyte secondary battery. The time required to form this SEI film is sufficiently short.

  In the non-aqueous electrolyte secondary battery manufacturing method described above, in the charge / discharge repetition step, when the voltage of the non-aqueous electrolyte secondary battery reaches a predetermined upper limit voltage, charging is stopped. When the discharge is started and the voltage of the nonaqueous electrolyte secondary battery reaches a predetermined lower limit voltage, the discharge is stopped and the charging is started. This is because the charge capacity and discharge capacity from the lower limit voltage to the upper limit voltage can be evaluated for each cycle.

  In the method for manufacturing a non-aqueous electrolyte secondary battery described above, in the charge / discharge repetition step, the upper limit voltage of the film formation voltage region is used as the predetermined upper limit voltage, and the film formation is performed as the predetermined lower limit voltage. A lower limit voltage in the voltage region may be used. This is because the charge / discharge repetition process can be performed by effectively utilizing the voltage region within the film formation voltage region.

  In the method for manufacturing a non-aqueous electrolyte secondary battery described above, in the charge / discharge repetition step, the charge capacity when charging from the lower limit voltage to the upper limit voltage is less than or equal to a predetermined charge capacity threshold value. It is preferable to end the discharge repetition process. On the other hand, when the charge capacity when charging from the lower limit voltage to the upper limit voltage is larger than a predetermined charge capacity threshold, the charge / discharge repetition process is continued. This is because the charge / discharge repetition process can be completed after the SEI film is suitably formed on the surface of the negative electrode. Therefore, it is possible to suppress variation in the degree of formation of the SEI film that may occur for each lot of the non-aqueous electrolyte secondary battery.

  In the non-aqueous electrolyte secondary battery manufacturing method described above, the charge / discharge efficiency when charging / discharging is performed within a range from the lower limit voltage to the upper limit voltage in the charge / discharge repetition step is a predetermined charge / discharge. When it is equal to or higher than the efficiency threshold, the charge / discharge repetition process may be terminated. On the other hand, when the charge / discharge efficiency when the charge / discharge is performed within the range from the lower limit voltage to the upper limit voltage is less than a predetermined charge / discharge efficiency threshold, the charge / discharge repetition process is continuously performed. This is because the charge / discharge repetition process can be completed after the SEI film is suitably formed on the surface of the negative electrode. Therefore, it is possible to suppress variation in the degree of formation of the SEI film that may occur for each lot of the non-aqueous electrolyte secondary battery.

  In the method for manufacturing a non-aqueous electrolyte type secondary battery described above, a pre-charging step for charging the non-aqueous electrolyte type secondary battery to the upper limit voltage in the film forming voltage region is included before the charge / discharge repetition step. Good. And it is good to start a charging / discharging repetition process from discharge of a non-aqueous electrolyte type secondary battery. This is because the charge / discharge repetition process can be suitably started.

  In the method for producing a non-aqueous electrolyte type secondary battery described above, a precharging step of charging the non-aqueous electrolyte type secondary battery to a lower limit voltage in a film forming voltage region is included before the charge / discharge repetition step. Good. And it is good to start a charging / discharging repetition process from charge of a non-aqueous electrolyte type secondary battery. This is because the charge / discharge repetition process can be suitably started.

  In the method for manufacturing a non-aqueous electrolyte type secondary battery described above, the initial charging step is a charging step of charging the non-aqueous electrolyte type secondary battery with a current value of 2C or more and less than 5C after the charge / discharge repetition step. Even better. This is because the time required for the initial charging step can be shortened without reducing the battery capacity.

  In the method for manufacturing a non-aqueous electrolyte secondary battery described above, charging and discharging may be performed at a constant current in the charge / discharge repetition step. This is because it is easy to control charging and discharging.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the nonaqueous electrolyte type secondary battery which can form a film suitably on the surface of a negative electrode compound-material layer in a short time is provided.

It is a perspective view for demonstrating schematic structure of the battery pack which concerns on embodiment. It is sectional drawing for demonstrating schematic structure of the battery which concerns on embodiment. It is a perspective view for demonstrating the winding electrode body of the battery which concerns on embodiment. It is an expanded view for demonstrating the winding structure of the winding electrode body of the battery which concerns on embodiment. It is a perspective sectional view for explaining the sectional structure of the positive electrode plate (negative electrode plate) of the battery according to the embodiment. It is a graph for demonstrating the initial stage charge process in the manufacturing method of the battery which concerns on 1st Embodiment. It is a graph for demonstrating the initial stage charge process in the manufacturing method of the conventional battery. It is a graph (the 1) for demonstrating another initial charge process in the manufacturing method of the battery which concerns on 1st Embodiment. It is a graph (the 2) for demonstrating another initial charge process in the manufacturing method of the battery which concerns on 1st Embodiment. It is a graph (the 3) for demonstrating another initial charge process in the manufacturing method of the battery which concerns on 1st Embodiment. It is a graph which compares the electric current value and battery capacity of the constant current charge process in the manufacturing method of the battery which concerns on 1st Embodiment. It is a graph which shows the relationship between the charging / discharging repetition frequency | count (cycle number) in a charging / discharging repeating process which concerns on 2nd Embodiment, and charging capacity or discharge capacity. It is a graph which shows the relationship between the repetition frequency (cycle number) of charge and discharge in the charging / discharging repetition process which concerns on 2nd Embodiment, and charging / discharging efficiency.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is embodied in a method for manufacturing a lithium ion secondary battery that is a non-aqueous electrolyte secondary battery.

(First embodiment)
1. Battery structure 1-1. Battery Pack The battery pack BP of this embodiment is an assembled battery in which batteries 100 are connected in series as shown in FIG. The battery 100 is a rectangular unit cell. In the battery pack BP, as shown in FIG. 1, the positive terminal of the battery 100 and the negative terminal of the battery 100 adjacent to the battery 100 are fastened via a bus bar 190. This fastening is made with bolts and nuts.

1-2. Battery Cell A schematic configuration of the battery 100 is shown in a sectional view of FIG. FIG. 2 shows the battery 100 taken out from the battery pack BP shown in FIG. The battery 100 has a flat wound electrode body 10 shown in FIG. As shown in FIG. 2, the battery container 110 includes a battery container main body 120 and a sealing plate 130. A wound electrode body 10 is disposed inside the battery container 110. The wound electrode body 10 is a power generation element that actually contributes to power generation. The sealing plate 130 is for closing the opening of the battery container main body 120. Therefore, it is joined to the battery container body 120.

  An electrolyte is injected into the battery container 110. This electrolytic solution is obtained by dissolving an electrolyte in an organic solvent. Examples of organic solvents include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 1,2-dimethoxyethane, 1,2-diethoxyethane. , Tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, acetonitrile, propionitrile, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide, sulfolane, γ-butyrolactone, etc. A solvent or a combination of these can be used.

Further, as a salt that is an electrolyte, lithium perchlorate (LiClO ₄ ), lithium borofluoride (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAsF ₆ ), LiCF ₃ SO _{3 , LiC 4 F 9 SO 3,} LiN (CF 3 SO 2) 2, LiC (CF 3 SO 2) 3, can be used a lithium salt such as LiI.

  As shown in FIG. 2, the battery 100 includes a positive terminal 50, a negative terminal 60, an insulating member 150, and an insulating member 160. The insulating member 150 is a member for insulating the positive electrode terminal 50 and the sealing plate 130. The insulating member 160 is a member for insulating the negative electrode terminal 60 and the sealing plate 130.

  As shown in FIG. 2, a liquid injection hole 140 is provided in the sealing plate 130. The liquid injection hole 140 is a through hole that penetrates the sealing plate 130. Then, the electrolytic solution is injected into the battery container 110. The lid 170 is a liquid injection hole lid for closing the liquid injection hole 140 of the sealing plate 130. Therefore, the lid body 170 covers the opening portion of the liquid injection hole 140. The lid 170 is welded to the sealing plate 130 from the outside of the sealing plate 130.

1-3. FIG. 3 is a perspective view showing the wound electrode body 10. As shown in FIG. 3, the wound electrode body 10 has a flat shape. A positive electrode end portion 30 projects from one end portion of the wound electrode body 10. As will be described later, the positive electrode end 30 is a portion where the positive electrode core material of the positive electrode plate protrudes. A negative electrode end 40 protrudes from the other end of the wound electrode body 10. The negative electrode end 40 is a portion where the negative electrode core material of the negative electrode plate protrudes, as will be described later.

  FIG. 4 is a development view showing a wound structure of the wound electrode body 10. As shown in FIG. 4, the wound electrode body 10 is wound in a state where the positive electrode plate P, the separator S, the negative electrode plate N, and the separator T are stacked in this order from the inside. That is, the wound electrode body 10 is configured such that the positive plates P and the negative plates N are alternately arranged with the separators S and T interposed therebetween.

The positive electrode plate P is obtained by applying a composite material containing a positive electrode active material capable of inserting and extracting lithium ions to an aluminum foil as a positive electrode core material. As the positive electrode active material, lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), and lithium iron phosphate (LiFePO ₄ ) are used. The negative electrode plate N is obtained by applying a composite material containing a negative electrode active material capable of occluding and releasing lithium ions to a copper foil as a negative electrode core material. As the negative electrode active material, carbon-based materials such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, and graphite are used.

  As shown in FIG. 4, the positive electrode plate P has a positive electrode coating part P1 and a positive electrode non-coating part P2. The positive electrode coating part P1 is a place where a positive electrode mixture layer containing a positive electrode active material or the like is formed on a positive electrode core material. The positive electrode non-coated portion P2 is a portion where the positive electrode mixture layer is not formed on the positive electrode core material. The negative electrode plate N includes a negative electrode coating portion N1 and a negative electrode non-coating portion N2. The negative electrode coating portion N1 is a portion where a negative electrode mixture layer containing a negative electrode active material or the like is formed on a negative electrode core material. The negative electrode non-coated portion N2 is a portion where the negative electrode mixture layer is not formed on the negative electrode core material.

  An arrow A in FIG. 4 indicates the width direction (lateral direction in FIG. 3) of the positive electrode plate P, the negative electrode plate N, and the separators S and T. An arrow B in FIG. 4 indicates the longitudinal direction of the positive electrode plate P, the negative electrode plate N, the separators S and T (the circumferential direction of the wound electrode body 10 in FIG. 3).

  The separators S and T are porous films such as polyethylene and polypropylene. The thicknesses of the separators S and T are about 10 to 50 μm. Here, the separator S and the separator T are made of the same material. For the understanding of the above winding order, only the codes are distinguished as S and T.

  FIG. 5 is a perspective sectional view of the positive electrode plate P (or the negative electrode plate N). In FIG. 5, each symbol outside the parentheses indicates each part in the case of the positive electrode, and each symbol in the parenthesis indicates each part in the case of the negative electrode. The direction indicated by the arrow A in FIG. 5 is the same as the direction indicated by the arrow A in FIG. That is, it is the width direction of the positive electrode plate P (or the negative electrode plate N). The direction indicated by arrow B in FIG. 5 is the same as the direction indicated by arrow B in FIG. That is, it is the longitudinal direction of the positive electrode plate P (or the negative electrode plate N).

  As shown in FIG. 5, the positive electrode plate P is obtained by forming a positive electrode mixture layer PA on a part of both surfaces of a strip-like positive electrode core material PB. On the left side in FIG. 5, the positive electrode non-coated portion P2 of the positive electrode plate P protrudes in the width direction. The positive electrode non-coated portion P2 is formed in a strip shape. The positive electrode non-coated portion P2 is a region where the positive electrode active material is not applied to both surfaces of the positive electrode core material PB. Therefore, in the positive electrode non-coating portion P2, the positive electrode core material PB is still exposed. On the other hand, there is no protrusion corresponding to the positive electrode non-coated portion P2 on the right side in FIG. In the positive electrode coating part P1, the positive electrode mixture layer PA is formed with a uniform thickness on both surfaces of the positive electrode core material PB.

The positive electrode mixture layer PA is formed by applying a composite material including a conductive material, a binder, and a thickener in addition to the positive electrode active material capable of occluding and releasing lithium ions to the aluminum foil as the positive electrode core material PB. Layer. As the positive electrode active material, lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), and lithium iron phosphate (LiFePO ₄ ) are used.

  Carbon materials such as carbon powder and carbon fiber can be used as the conductive material for the positive electrode. For example, carbon powder such as acetylene black, furnace black, ketjen black, etc., graphite powder, etc.

  The binder for the positive electrode is preferably a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the positive electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the positive electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), hydroxypropylmethylcellulose phthalate (HPMCP) or the like is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. In addition, N-methyl-2-pyrrolidone (NMP, hereinafter referred to as NMP) may be used. Other lower alcohols and lower ketones can also be used.

  As indicated by the reference numerals in parentheses in FIG. 5, the negative electrode plate N is obtained by forming a negative electrode mixture layer NA on a part of both surfaces of a strip-shaped negative electrode core material NB. On the left side in FIG. 5, a negative electrode non-coated portion N2 of the negative electrode plate N protrudes in the width direction. The negative electrode non-coated portion N2 is formed in a strip shape. The negative electrode non-coated portion N2 is a region where the negative electrode active material is not applied to both surfaces of the negative electrode core material NB. Therefore, in the negative electrode non-coating portion N2, the negative electrode core material NB is still exposed. On the other hand, there is no protrusion corresponding to the negative electrode non-coated portion N2 on the right side in FIG. In the negative electrode coating portion N1, the negative electrode mixture layer NA is formed with a uniform thickness on both surfaces of the negative electrode core material NB. However, as shown in FIG. 4, at the time of winding, the positive electrode non-coated portion P2 and the negative electrode non-coated portion N2 are wound in a state of protruding to the opposite side.

  The negative electrode mixture layer NA is a layer obtained by applying a mixture containing a negative electrode active material, a binder, and a thickener to a copper foil as the negative electrode core material NB and drying it. The negative electrode active material is a material that can occlude and release lithium ions. As the negative electrode active material, a carbon-based material containing a graphite structure at least partially is used. For example, amorphous carbon, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), graphite (graphite), or a carbon material having a combination thereof can be used.

  The binder for the negative electrode may be a polymer that is insoluble (or hardly soluble) in the electrolyte and is dispersed in the solvent used for the negative electrode paste. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoro Fluorine resin such as ethylene copolymer (ETFE), vinyl acetate copolymer, styrene butadiene rubber (SBR), acrylic acid-modified SBR resin (SBR latex), rubber such as gum arabic can be used. Alternatively, a combination of these may be used. The binder is not necessarily limited to the above polymer.

  As the thickener for the negative electrode, cellulose such as carboxymethylcellulose (CMC), methylcellulose (MC), cellulose acetate phthalate (CAP), hydroxypropylmethylcellulose (HPMC), and hydroxypropylmethylcellulose phthalate (HPMCP) is used. However, it is not necessarily limited to cellulose as described above, and can be used.

  An example of the solvent is water. NMP may be used. Other lower alcohols and lower ketones can also be used.

2. Initial Charging Process The battery manufacturing method according to the present embodiment has a feature in the initial charging process. Therefore, the initial charging step in the battery manufacturing method of this embodiment will be described. This initial charging step is a step of performing initial charging on the assembled battery 100. At that time, an SEI film is formed on the surface of the negative electrode mixture layer NA. Therefore, the initial charging process may cause a difference in battery performance.

  As shown in FIG. 6, the initial charging step in this embodiment includes (D-1) a preliminary charging step, (D-2) a charge / discharge repetition step, and (D-3) a constant current charging step. Here, the preliminary charging step is a step of charging the battery 100 up to a voltage region (film formation voltage region R) where the charge / discharge repetition step is performed. The charging / discharging repeating step is a step of repeating charging and discharging within the range of the film forming voltage region R. By this charge / discharge repeating step, an SEI film is formed on the surface of the negative electrode mixture layer NA. The constant current charging step is a step of charging the battery 100 on which the SEI film has been formed to the full charge voltage VF.

2-1. Film Formation Voltage Region First, the film formation voltage region R will be described. This is a voltage region suitable for forming an SEI film on the surface of the negative electrode mixture layer NA. When the voltage of the battery 100 is within the range of the film forming voltage region R, the SEI film is preferably formed.

  Therefore, when the battery 100 on which the SEI film has not yet been formed is charged in the film forming voltage region R, a part of the charging energy is used for charging the battery 100 itself. The remainder of the charging energy is mainly used for forming the SEI film. Alternatively, other reactions may occur and gas may be generated inside the battery container 110.

  This SEI film is formed on the surface of the negative electrode mixture layer NA. However, the film forming voltage region R differs depending on the type of the positive electrode active material contained in the positive electrode mixture layer PA. Therefore, an example is shown below.

2-1-1. When the LiCoO ₂ positive electrode active material includes a lithium cobalt composite oxide in which a part of LiCoO ₂ or Co is substituted with another element, the film forming voltage region R is 3.1 to 3.7 V ( (See paragraph [0052] of Patent Document 1).
Lower limit voltage VL of film formation voltage region R: 3.1V
Upper limit voltage VU of film formation voltage region R: 3.7V

2-1-2. When the LiMn ₂ O ₄ -based or LiNiO ₂ -based positive electrode active material includes LiMn ₂ O ₄ , LiNiO _2, or a lithium composite oxide in which a part of Mn or Ni is substituted with another element, the film forming voltage region R Is 2.8 to 3.6 V (see paragraph [0053] of Patent Document 1).
Lower limit voltage VL of film formation voltage region R: 2.8V
Upper limit voltage VU of film formation voltage region R: 3.6V

2-1-3. When the LiFePO ₄ -based positive electrode active material includes an olivine-based composite oxide in which a part of LiFePO ₄ or Fe is substituted with another element, the film forming voltage region R is 2.5 to 2.9 V ( (See paragraph [0054] of Patent Document 1).
Lower limit voltage VL of film formation voltage region R: 2.5V
Upper limit voltage VU of film formation voltage region R: 2.9V

  Thus, the lower limit voltage VL and the upper limit voltage VU of the film forming voltage region R are determined according to the positive electrode active material. The initial charging process of this embodiment is performed as follows according to the film forming voltage region R.

2-2. (D-1) Preliminary charging step At this stage, the battery 100 itself is assembled. However, the SEI film is not yet formed on the surface of the negative electrode mixture layer NA. Therefore, first, the battery 100 is charged with a constant current. This is a preliminary charge for performing the charge / discharge repetition process. The constant current at this time is 0.1C. As a result, the voltage of the battery 100 gradually increases. Then, as shown in FIG. 6, the voltage of the battery 100 is raised to the upper limit voltage VU of the film formation voltage region R.

  The time required for this preliminary charging is about 10 minutes. Here, a constant current of 0.1 C is applied, but other values may be used. However, since the SEI film has not yet been formed, it is better not to set a very large current value. Although a constant current is used here, it is not necessarily required to have a constant current value. For example, a slightly smaller value may be used as the initial current value in the preliminary charging step.

2-3. (D-2) Charging / Discharging Repeating Step Next, the battery 100 is subjected to a charging / discharging repeating step of repeating constant current charging and constant current discharging. In FIG. 6, the discharge starts. In this step, the voltage of the battery 100 is within the film forming voltage region R. That is, when the voltage of the battery 100 reaches the upper limit voltage VU of the film formation voltage region R, the constant current charging is stopped and the battery 100 is started to discharge the constant current. The current value of constant current discharge at this time is, for example, 1C. Due to this constant current discharge, the voltage of the battery 100 drops. When the voltage of the battery 100 reaches the lower limit voltage VL of the film forming voltage region R, the constant current discharge is stopped and the battery 100 is started to be charged with a constant current. The current value of constant current charging at this time is, for example, 1C. Due to this constant current charging, the voltage of the battery 100 increases. When the voltage of the battery 100 reaches the upper limit voltage VU again, constant current discharge is performed again.

  Thus, every time the upper limit voltage VU and the lower limit voltage VL of the film forming voltage region R are reached, the constant current charging and the constant current discharging are alternately switched. As a result, the voltage of the battery 100 repeatedly rises and falls as shown in the area (D-2) of FIG. Then, after repeating these constant current charging and constant current discharging a predetermined number of times, this charging / discharging repeating step is terminated.

  By repeating this constant current charging and constant current discharging alternately, an SEI film is formed on the surface of the negative electrode mixture layer NA. That is, the SEI film is formed on at least a part of the wound electrode body 10. In addition, the time required for this charge / discharge repetition process is about 15 to 45 minutes. This required time varies depending on the number of times constant current charging and constant current discharging are repeated. Of course, this also changes when the constant current value 1C is changed.

2-4. (D-3) Constant current charging step Subsequently, constant current charging is performed. At this stage, the SEI film has been formed on the surface of the negative electrode mixture layer NA. Therefore, even if high-speed charging is performed at a slightly high current value, the formation of the SEI film is not affected. As shown in FIG. 6, the initial voltage in this step is the upper limit voltage VU of the film forming voltage region R. Accordingly, the battery 100 is charged with a constant current. The current value of constant current charging at this time is, for example, 2C. Of course, other current values may be used. Although a constant current is used here, it is not necessarily required to have a constant current value.

  As a result, the battery 100 reaches the full charge voltage VF. That is, the battery 100 having the SEI film and the full charge voltage VF is manufactured. The time required for this constant current charging process is about 30 minutes. Therefore, the time required for the initial charging process in this embodiment is about 55 to 70 minutes.

2-5. Comparison with prior art 2-5-1. (E-1) Preliminary Charging Step Here, a comparison between the initial charging step in this embodiment and the conventional initial charging step will be described. A conventional initial charging process will be described with reference to FIG. In the prior art, first, constant current charging is performed as shown in FIG. The current value at this time is about 0.1C. Thereby, the voltage of the battery 100 enters the film forming voltage region R. Then, when the voltage of the battery 100 becomes a voltage in the vicinity of the median value in the range of the film formation voltage region R, the preliminary charging is finished.

2-5-2. (E-2) Constant Voltage Charging Step Next, the battery 10 is charged with a constant voltage. Thereby, an SEI film is formed. However, this process takes about 1 to 2 hours (see paragraph [0017] of FIG. 2 and FIG. 2). This is sufficiently longer than this embodiment.

2-5-3. (E-3) Constant current charging step After this, constant current charging is performed. The current value at this time is about 1C. The time required for this step is about one hour. Thus, the time required for the conventional initial charging process is about 2 to 3 hours. This is sufficiently longer than this embodiment.

3. Battery Manufacturing Method Here, a battery manufacturing method according to the present embodiment will be described. The battery manufacturing method of the present embodiment includes the following steps. The battery manufacturing method of this embodiment is a method characterized by performing the above-described initial charging step.
(A) Electrode plate creation process (B) Electrode body creation process (C) Battery assembly process (D) Initial charging process (D-1) Pre-charging process (D-2) Charging / discharging repeating process (D-3) Constant current Charging process

3-1. (A) Electrode plate preparation process First, the positive electrode coating liquid is applied to the aluminum foil that is the positive electrode core material PB to form a positive electrode paste layer. This positive electrode coating solution is obtained by kneading the above positive electrode active material or the like in a solvent. Next, the positive electrode paste layer on which the positive electrode paste layer is formed is dried while being conveyed into the drying furnace. Thereby, the positive electrode mixture layer PA is formed on the positive electrode core material PB. The positive electrode mixture layer PA is a layer containing a positive electrode active material. The positive electrode mixture layer PA is preferably formed on both surfaces of the positive electrode core material PB. Thereby, the positive electrode plate P is created. The same applies to the negative electrode plate N. The positive electrode plate P and the negative electrode plate N may be appropriately subjected to a slitting process or a pressing process.

3-2. (B) Electrode body creation process Subsequently, the wound electrode body 10 is created. At that time, as shown in FIG. 4, the positive electrode plate P and the negative electrode plate N are wound with separators S and T interposed therebetween. Thereby, a cylindrical wound electrode body is created. By compressing the cylindrical wound electrode body from the cylindrical side surface direction, a flat wound electrode body 10 as shown in FIG. 3 is created.

3-3. (C) Battery Assembly Step Next, the positive electrode terminal 50 and the negative electrode terminal 60 are welded to the positive electrode end 30 and the negative electrode end 40 of the wound electrode body 10, respectively. Then, the welded wound electrode body 10 is accommodated in the battery container main body 120. Next, the sealing plate 130 is welded to the battery container main body 120. Subsequently, the non-aqueous electrolyte is injected into the battery container 110 from the liquid injection hole 140. Then, the lid 170 is welded to the sealing plate 130. Thereby, the battery 100 is assembled. However, as described above, at this stage, the SEI film is not yet formed on the surface of the negative electrode mixture layer NA.

3-4. (D) Initial Charging Step Next, the assembled battery 100 is initially charged. As described above, the (D-1) preliminary charging step, the (D-2) charging / discharging repeating step, and the (D-3) constant current charging step are performed in this order. Thereby, an SEI film is formed on the surface of the negative electrode mixture layer NA and the battery 100 is charged. Thereafter, a high temperature aging process or the like may be performed. Further, various other inspection processes may be performed. The battery 100 of this embodiment is manufactured through the above steps. Thereafter, the battery 100 may be combined as needed to form the battery pack BP.

3-5. Manufactured Battery As described above, in the manufacturing method of this embodiment, the time required for the initial charging process is shorter than the time required for the conventional initial charging process. That is, the cycle time is short. Further, in the battery 100 manufactured by the battery manufacturing method according to this embodiment, the SEI film is suitably formed on the surface of the negative electrode mixture layer NA. Therefore, the battery performance of the battery 100 is good.

4). Modified example 4-1. Start of Charging / Discharging Repeat Process from Charging In this embodiment, as shown in FIG. 6, the charging / discharging repeating process is started from discharging. However, as shown in FIG. 8, it may be started from charging. In that case, when the voltage of the battery 100 reaches the lower limit voltage VL of the film forming voltage region R, the preliminary charging process may be terminated. That is, the charging / discharging repetition process may be started by charging from the lower limit voltage VL of the film forming voltage region R.

  FIG. 8 shows a case where constant current charging and constant current discharging are repeated for three cycles. In this case, the constant voltage charging process also starts from the lower limit voltage VL of the film forming voltage region R. Even in this case, the SEI film is preferably formed on the surface of the negative electrode mixture layer NA.

4-2. Charging / discharging other than constant current In this embodiment, charging and discharging are performed at a constant current in the charge / discharge repetition process. However, the current is not necessarily constant. If charging and discharging are repeated, the current value may be changed in the middle. For example, a small value can be set as the current value at the beginning and end of charging and discharging. In that case, as shown in FIG. 9, the voltage of the battery 100 changes more smoothly.

4-3. Switching upper limit voltage and switching lower limit voltage In this embodiment, the upper limit voltage VU and the lower limit voltage VL of the film forming voltage region R are adopted as voltages for switching between charging and discharging. As described above, the upper limit voltage VU and the lower limit voltage VL have values determined by the type of the positive electrode active material. In this embodiment, the upper limit voltage VU and the lower limit voltage VL are selected as voltages for switching between charging and discharging.

  However, a predetermined upper limit voltage and lower limit voltage for switching between charging and discharging may be voltages other than the upper limit voltage VU and the lower limit voltage VL in the film forming voltage region R. That is, the switching lower limit voltage V1 shown in FIG. 10 can be used as the predetermined lower limit voltage. Similarly, the switching upper limit voltage V2 can be used as the predetermined upper limit voltage. However, as shown in FIG. 10, the switching lower limit voltage V1 and the switching upper limit voltage V2 are preferably within the range of the film forming voltage region R. Even in this case, charging and discharging are repeated within the film forming voltage region R. That is, the SEI film is suitably formed.

4-4. No upper limit voltage and lower limit voltage In the above-described modification, the switching upper limit voltage V2 and the switching lower limit voltage V1 are determined. However, even if charging and discharging are repeated without using the switching upper limit voltage V2 and the switching lower limit voltage V1, the SEI film can be formed. For example, if the voltage of the battery 100 is within the film forming voltage region R, the charging time and the discharging time may be determined in advance. Even if it does in this way, it does not change that a SEI film can be formed suitably.

4-5. Rapid Charging Process In this embodiment, charging is performed at a current value of 2C in the charge / discharge repetition process. However, it may be charged with a larger constant current. This is because the SEI film has already been formed. Of course, charging time is shortened by charging with a large constant current.

  FIG. 11 is a graph showing the relationship between the current value of the constant current employed in the constant current charging step and the battery capacity. As can be seen from FIG. 11, when the battery is charged with a current value of 5 C or more, the battery capacity is reduced. Therefore, it is preferable to charge at a current value of 2C or more and less than 5C. This is because it can be charged quickly without adversely affecting the battery performance. For example, charging may be performed with a current value of 4C. In that case, of course, charging can be performed in about half the time required for charging at 2C.

4-6. Combination Of course, the above modifications may be freely combined and applied.

5. Summary As described above in detail, in the battery manufacturing method according to the present embodiment, in the initial charging step, a charge / discharge repetition step of repeating charging and discharging at a predetermined current value is performed. In the charging / discharging repeating step, charging and discharging are repeated, so that the voltage of the battery 100 increases or decreases. However, this voltage is within the range of the film formation voltage region R. Thereby, the SEI film can be formed on the surface of the negative electrode mixture layer NA in a short time. Therefore, a battery manufacturing method that can perform initial charging of the battery in a short time has been realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the battery is not limited to having a flat wound electrode body 10. The present invention can also be applied to a cylindrical battery having a cylindrical electrode body. Further, the present invention can also be applied to a battery using an electrode body in which a positive electrode plate and a negative electrode plate are stacked without winding. These also remain the stacked electrode bodies. In the case of using flatly stacked electrode bodies, a step of winding the electrode plate or the like, or a pressing step of flattening the wound cylindrical electrode body is not essential.

  Further, the point that the range of the film forming voltage region R differs depending on the type of the positive electrode active material has been described. Of course, regardless of this difference, the battery manufacturing method of this embodiment can be applied.

(Second Embodiment)
A second embodiment will be described. In the first embodiment, the number of repetitions of charging and discharging in the charge / discharge repetition process is determined in advance. In this embodiment, the charge / discharge repetition process is terminated according to the degree of formation of the SEI film. Therefore, only the differences will be described.

1. Charge / Discharge Repeat Step and Degree of Film Formation In the first embodiment, constant current charge and constant current discharge are repeated a predetermined number of times in the charge / discharge repeat step. However, it is assumed that the same number of repetitions of the charge / discharge process is performed on different lots. In that case, the degree of formation of the SEI film varies among lots. Therefore, it is preferable to suppress the variation between the lots.

  Therefore, in this embodiment, after it is determined that the SEI film is sufficiently formed, the charge / discharge repetition process is terminated. This is because the variation in the degree of formation of the SEI film between lots can be reduced.

2. In this embodiment, the charge / discharge efficiency value measured in the charge / discharge repetition process is set as the end condition of the charge / discharge repetition process. Here, the charge / discharge efficiency is the ratio of the discharge capacity to the charge capacity.
Charging / discharging efficiency = Discharge capacity / Charge capacity (1)

  The charge capacity used at this time is the charge capacity when the battery 100 is charged from the lower limit voltage VL to the upper limit voltage VU in the film forming voltage region R. On the other hand, the discharge capacity is a discharge capacity when the battery 100 is discharged from the upper limit voltage VU to the lower limit voltage VL in the film forming voltage region R. These charge capacity and discharge capacity can be easily measured. However, when using the switching upper limit voltage V2 and the switching lower limit voltage V1 in the first embodiment, the charging capacity or discharging capacity charged or discharged between these switching upper limit voltage V2 and the switching lower limit voltage V1 is used.

  FIG. 12 is a graph showing the relationship between the number of repetitions (number of cycles) performed in the charge / discharge repetition step and the charge capacity and discharge capacity. This is a result when 1C constant current charging and 1C constant current discharging are repeated within the range from the lower limit voltage VL to the upper limit voltage VU in the film formation voltage region R. This is an example of a certain lot, and another lot may deviate from the graph of FIG. The horizontal axis in FIG. 12 is the number of cycles. The vertical axis in FIG. 12 represents the charge capacity or discharge capacity value. In drawing the graph of FIG. 12, the value of the discharge capacity at the third cycle was used as a reference (100%).

  As shown in FIG. 12, the discharge capacity is almost constant regardless of the number of cycles. On the other hand, the charge capacity decreases as the number of cycles increases. When the number of cycles is large, there is almost no difference between the charge capacity and the discharge capacity. The charge capacity in the first cycle is about four times the discharge capacity in the third cycle. In the third cycle, since the charge capacity and the discharge capacity are almost the same, it can be said that the charge capacity in the first cycle is very large.

  As described above, in the initial stage of the charge / discharge repetition process, the SEI film is formed during charging. That is, in the first cycle in FIG. 12, it is considered that a part of the charging energy supplied to the battery 100 was used for forming the SEI film. Therefore, extra energy is supplied to the battery 100 during the charge / discharge repetition process.

  In this case, the relationship between the number of repetitions (cycle number) performed in the charge / discharge repetition step and the charge / discharge efficiency is as shown in the graph of FIG. This is an example of a certain lot, and another lot may deviate from the graph of FIG. The horizontal axis in FIG. 13 is the number of cycles. The vertical axis in FIG. 13 is the charge / discharge efficiency. As shown in FIG. 13, the charge / discharge efficiency increases as the number of cycles increases. This is because the value of the charge capacity is large at the initial number of cycles (see equation (1)).

  Therefore, the value of the charge / discharge efficiency can be used as the end condition of the charge / discharge repetition process. That is, when the charge / discharge efficiency value in the charge / discharge repetition process is equal to or greater than a predetermined charge / discharge efficiency threshold, the charge / discharge repetition process may be terminated. Of course, when the value of the charge / discharge efficiency in the charge / discharge repetition process is less than a predetermined charge / discharge efficiency threshold, the charge / discharge repetition process is continued.

  When 70% is employed as the charge / discharge efficiency threshold, the charge / discharge repetition process is completed with two cycles. When 80% is adopted as the charging / discharging efficiency threshold value, the charging / discharging repetition process is completed in three cycles. Thus, it is preferable to repeat the charging and discharging for 3 cycles or more in forming the SEI film. However, the cycle time is longer accordingly. However, the cycle time is sufficiently short compared to the above-described prior art.

3. Modification 3-1. Charging capacity threshold In this embodiment, the end condition of the charging / discharging repetition process is determined by a predetermined charging / discharging efficiency threshold. However, instead of the charge / discharge efficiency, the value of the charge capacity may be used as a reference. As is clear from FIG. 12, excess energy is supplied during the formation of the SEI film. As the number of cycles increases, the charge capacity approaches a constant value.

  Therefore, in this embodiment, a value slightly larger than the certain value is set as a predetermined charge capacity threshold value. If the charge capacity when the battery 100 is charged from the lower limit voltage VL to the upper limit voltage VU in the film forming voltage region R is equal to or less than a predetermined charge capacity threshold value, the charge / discharge repetition process is terminated. Good. On the other hand, when the charge capacity when the battery 100 is charged from the lower limit voltage VL to the upper limit voltage VU in the film forming voltage region R is larger than a predetermined charge capacity threshold, the charge / discharge repetition process is continued.

  Even in this case, the SEI film can be suitably formed on the negative electrode mixture layer NA. In this case, it is not necessary to measure the discharge capacity. Therefore, the charge / discharge repetition process can be completed by charging. For example, in FIG. 8, the discharge is performed at the end of the charge / discharge repetition process, but this discharge need not be performed. Therefore, the cycle time is shorter. In this case, the number of times of charging in the charge / discharge repetition process is one more than the number of discharges.

  Alternatively, the difference between the charge capacity at the Nth cycle and the charge capacity at the (N-1) th cycle may be used as the threshold value. Alternatively, the difference between the charge capacity at the Nth cycle and the discharge capacity at the Nth cycle is used as the threshold value.

5. Summary As described above in detail, in the battery manufacturing method according to the present embodiment, in the initial charging step, a charge / discharge repetition step of repeating charging and discharging at a predetermined current value is performed. In the charging / discharging repeating step, charging and discharging are repeated, so that the voltage of the battery 100 increases or decreases. However, this voltage is within the range of the film formation voltage region R. Thereby, the SEI film can be formed on the surface of the negative electrode mixture layer NA in a short time. The charge / discharge repetition process is terminated depending on the degree of formation of the SEI film. Therefore, a battery manufacturing method is realized in which the battery is initially charged in a short time and the degree of formation of the SEI film hardly varies.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the battery is not limited to having a flat wound electrode body 10. The present invention can also be applied to a cylindrical battery having a cylindrical electrode body. Further, the present invention can also be applied to a battery using an electrode body in which a positive electrode plate and a negative electrode plate are stacked without winding. These also remain the stacked electrode bodies. In the case of using flatly stacked electrode bodies, a step of winding the electrode plate or the like, or a pressing step of flattening the wound cylindrical electrode body is not essential.

  Further, the point that the range of the film forming voltage region R differs depending on the type of the positive electrode active material has been described. Of course, regardless of this difference, the battery manufacturing method of this embodiment can be applied.

DESCRIPTION OF SYMBOLS 10 ... Winding electrode body 50 ... Positive electrode terminal 60 ... Negative electrode terminal 100 ... Battery 110 ... Battery container 120 ... Battery container main body 130 ... Sealing plate 140 ... Injection hole 150 ... Insulating member 160 ... Insulating member 170 ... Cover BP ... Battery Pack P ... Positive electrode plate P1 ... Positive electrode coating part P2 ... Positive electrode non-coating part N ... Negative electrode plate N1 ... Negative electrode coating part N2 ... Negative electrode non-coating part S, T ... Separator R ... Film forming voltage region V1 ... Switching lower limit Voltage V2 ... Switching upper limit voltage VL ... Lower limit voltage VU ... Upper limit voltage VF ... Fully charged voltage

Claims (9)

A battery assembly process in which an electrode body is housed in a battery container and a nonaqueous electrolyte is injected to form a nonaqueous electrolyte secondary battery;
An initial charging step of charging the non-aqueous electrolyte type secondary battery,
The initial charging step includes
A charge / discharge repeating step of repeating charging and discharging in the non-aqueous electrolyte type secondary battery;
In the charge / discharge repeating step,
The non-aqueous electrolyte type secondary battery has a voltage within the range of a film forming voltage region in which an SEI film is formed on at least a part of the electrode body. Method. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 1,
In the charge / discharge repeating step,
When the voltage of the non-aqueous electrolyte type secondary battery reaches a predetermined upper limit voltage,
Stop charging and start discharging,
When the voltage of the non-aqueous electrolyte secondary battery reaches a predetermined lower limit voltage,
A method for producing a non-aqueous electrolyte type secondary battery, characterized by stopping discharging and starting charging. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 2,
In the charge / discharge repeating step,
While using the upper limit voltage of the film formation voltage region as the predetermined upper limit voltage,
A method for producing a non-aqueous electrolyte secondary battery, wherein a lower limit voltage in the film forming voltage region is used as the predetermined lower limit voltage. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 2 or claim 3,
In the charge / discharge repeating step,
When the charge capacity when charging from the lower limit voltage to the upper limit voltage is not more than a predetermined charge capacity threshold,
End the charge / discharge repetition step,
When the charge capacity when charging from the lower limit voltage to the upper limit voltage is greater than a predetermined charge capacity threshold,
A method for producing a non-aqueous electrolyte secondary battery, wherein the charge / discharge repeating step is continuously performed. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 2 or claim 3,
In the charge / discharge repeating step,
When the charge / discharge efficiency when charging / discharging within the range from the lower limit voltage to the upper limit voltage is equal to or higher than a predetermined charge / discharge efficiency threshold,
End the charge / discharge repetition step,
When the charge / discharge efficiency when performing charge / discharge within the range from the lower limit voltage to the upper limit voltage is less than a predetermined charge / discharge efficiency threshold,
A method for producing a non-aqueous electrolyte secondary battery, wherein the charge / discharge repeating step is continuously performed. A method for manufacturing a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5,
Before the charge / discharge repetition step, the non-aqueous electrolyte type secondary battery has a precharge step of charging up to the upper limit voltage of the film forming voltage region,
The method for producing a non-aqueous electrolyte secondary battery, characterized in that the charge / discharge repeating step is started from the discharge of the non-aqueous electrolyte secondary battery. A method for manufacturing a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5,
Before the charge / discharge repetition step, the non-aqueous electrolyte type secondary battery has a precharge step of charging to the lower limit voltage of the film forming voltage region,
The method for producing a non-aqueous electrolyte secondary battery, wherein the charge / discharge repeating step is started from charging of the non-aqueous electrolyte secondary battery. A method for manufacturing a non-aqueous electrolyte type secondary battery according to any one of claims 1 to 7,
The initial charging step includes
A method for producing a non-aqueous electrolyte secondary battery, comprising a charging step of charging the non-aqueous electrolyte secondary battery with a current value of 2C or more and less than 5C after the charge / discharge repeating step. A method for manufacturing a non-aqueous electrolyte type secondary battery according to any one of claims 1 to 8,
In the charge / discharge repeating step,
A method for producing a non-aqueous electrolyte type secondary battery, wherein charging and discharging are performed at a constant current.

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