JP2012084322A - Method for producing lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a lithium ion secondary battery prepared with an electrolyte containing a difluorophosphate in which the duration of a cell-voltage rise after the start of discharge is short in a second self-discharge step.SOLUTION: A cell 100 satisfying at least one of the following requirements (1) to (4), is manufactured in an assembly step. (1) A positive electrode active material 137 is LiMO, where 1.04≤X≤1.15. (2) The BET specific surface area of the grains of a negative electrode active material 127 is in the range of 2.8 to 5.2 m/g. (3) The grains of the negative electrode active material 127 are composed of graphite and amorphous carbon, and the percentage of amorphous carbon in the grains of the negative electrode active material is in the range of 2.5 to 7.1 wt%. (4) The concentration of a difluorophosphate in an electrolyte 160 is in the range of 0.01 to 0.076 mol/L.

Description

  The present invention relates to a method for manufacturing a lithium ion secondary battery.

In recent years, lithium ion secondary batteries have been used as driving power sources for portable electronic devices such as hybrid vehicles, notebook computers, and video camcorders.
Patent Document 1 proposes a lithium ion secondary battery using an electrolytic solution containing difluorophosphate. It is described that low temperature discharge characteristics (low temperature output characteristics) and the like are improved by using an electrolytic solution containing difluorophosphate.

JP 2006-143572 A

  By the way, a lithium ion secondary battery using an electrolytic solution containing difluorophosphate is manufactured as follows, for example. First, in the assembling step, a battery in which an electrode body having a positive electrode active material and a negative electrode active material and an electrolytic solution containing difluorophosphate is housed in a battery case is manufactured. Next, in the initial charging step, the battery after the assembly step is initially charged. Thereafter, in the aging process, the battery that has finished the initial charging process is aged at a predetermined temperature for a fixed time. Next, in the first self-discharge process, the battery that has finished the aging process is left to stand for a predetermined period to be self-discharged. Thereafter, in the capacity measurement step, the battery capacity (part or all) of the battery that has finished the self-discharge step is measured. Next, in the internal resistance measurement step, the internal resistance of the battery that has finished the capacity measurement step is measured.

Next, in the battery row restraint step, a plurality of batteries having undergone the internal resistance measurement step are prepared, and these batteries are arranged in one row or a plurality of rows to form one or a plurality of battery rows. Then, it is held in a restrained state by being sandwiched by pressing jigs from both ends. Thereafter, in the second self-discharge step, the batteries in the battery array are self-discharged by leaving the battery array in a restrained state.
In the second self-discharge process, the battery voltage value before and after being left is measured for each battery in the battery array, and it is determined whether or not an internal short circuit has occurred in each battery based on the battery voltage difference before and after being left. To do. A battery with an internal short circuit has a larger self-discharge amount due to neglected than a battery with no internal short circuit (normal battery), so the battery voltage value is smaller, and the battery voltage difference before and after leaving is greater. It is considered to be. Therefore, it is possible to determine whether or not an internal short circuit has occurred in the battery based on the battery voltage difference before and after being left.

  However, a lithium ion secondary battery using an electrolytic solution containing difluorophosphate has a tendency for the battery voltage to increase for a while after starting to stand in the second self-discharge process. For example, the battery voltage may increase for about a week after the start of standing, and then the battery voltage value may decrease. While the battery voltage value is rising, the self-discharge characteristics of the battery cannot be grasped (it cannot be distinguished from a battery that is not internally short-circuited), so wait for the battery voltage value to finish rising, After that, it was necessary to leave the battery array in a restrained state for a specified period and determine whether an internal short circuit occurred in the battery.

  Thus, when producing a lithium ion secondary battery using an electrolytic solution containing difluorophosphate, in the second self-discharge step, the battery voltage rises for a while after starting to stand, A long process time has been a problem. For this reason, in the 2nd self-discharge process, it was calculated | required to shorten as much as possible the battery voltage rise period after a leaving start.

  The present invention has been made in view of such problems, and in a method for manufacturing a lithium ion secondary battery using an electrolytic solution containing a difluorophosphate, after the start of standing in the second self-discharge step described above. An object of the present invention is to provide a method of manufacturing a lithium ion secondary battery that can shorten the battery voltage increase period.

One embodiment of the present invention is an assembly process for manufacturing a battery in which an electrode body having a positive electrode active material and a negative electrode active material, and an electrolytic solution containing a difluorophosphate is contained in a battery case, and the assembly process described above. An initial charging step for initial charging the finished battery, an aging step for aging the battery after the initial charging step for a predetermined time at a predetermined temperature, and the battery after the aging step for a predetermined time. A first self-discharge step for self-discharge by leaving for a period of time; a capacity measurement step for measuring part or all of the battery capacity of the battery that has finished the self-discharge step; and the battery that has finished the capacity measurement step. An internal resistance measurement step for measuring internal resistance and a plurality of the batteries after completion of the internal resistance measurement step are prepared, and one or a plurality of these batteries are arranged in one or a plurality of rows. The battery row is formed by holding the battery row in a restrained state by sandwiching the battery row from both ends with a pressing jig, and leaving the battery row in the restrained state. A second self-discharge step of self-discharging each of the batteries, wherein the second self-discharge step starts with leaving the battery array and the battery voltage If the value rises, the battery voltage value is set after the battery row in the constrained state is left for a specified period after the rising period of the battery voltage value elapses, or after the battery row is started to leave. Is a step of self-discharging the battery forming the battery row by leaving the battery row in the restrained state for the specified period after starting to leave the battery row. , The above assembly work In a method for manufacturing a lithium ion secondary battery to produce at least one condition is satisfied batteries of the following (1) to (4).
(1) The positive electrode active material is Li _x MO ₂ (M is Ni or Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mg in addition to Ni as the main component) , Ga, Zr, or Si), and satisfies 1.04 ≦ X ≦ 1.15.
(2) The BET specific surface area of the particles of the negative electrode active material is in the range of 2.8 to 5.2 m ² / g.
(3) The negative electrode active material particles are composed of graphite and amorphous carbon, and the ratio of the amorphous carbon in the negative electrode active material particles is in the range of 2.5 to 7.1 wt%. .
(4) The concentration of the difluorophosphate in the electrolytic solution is in the range of 0.01 to 0.076 mol / L.

In the above-described method for manufacturing a lithium ion secondary battery, a battery that satisfies at least one of the above conditions (1) to (4) is manufactured in the assembly process.
Specifically, (1) As a positive electrode active material, “Li _X MO ₂ (M is Ni or Al, Ti, V, Cr, Mn, Fe, Co, in addition to Ni as a main component, A positive electrode active material that includes at least one of Cu, Zn, Mg, Ga, Zr, and Si, and satisfies 1.04 ≦ X ≦ 1.15 ”.

As a result of investigation by the present inventor, as the value of X is increased in Li _X MO ₂ (the molar amount of Li with respect to M is increased), the battery voltage increase period after the start of standing in the second self-discharge process described above It was found that can be shortened. However, on the other hand, it has been found that the battery capacity decreases (specific capacity decreases) as the value of X increases. As a result of the investigation, by using Li _x MO ₂ satisfying 1.04 ≦ X ≦ 1.15 as the positive electrode active material, the battery voltage increase period after the start of standing in the second self-discharge process can be shortened, In addition, a sufficient battery capacity (specific capacity) can be maintained. The specific capacity is an electric capacity (mAh / g) per 1 g of the positive electrode active material.

Moreover, it is good to use the negative electrode active material whose (2) BET specific surface area of the particle | grains of a negative electrode active material exists in the range of 2.8-5.2 m < ² > / g as a negative electrode active material.
As a result of an investigation by the present inventor, it has been found that as the BET specific surface area of the particles of the negative electrode active material is increased, the battery voltage increase period after the start of standing in the second self-discharge process can be shortened. However, on the other hand, it has been found that, as the BET specific surface area of the particles of the negative electrode active material is increased, the high temperature durability of the battery decreases (the high temperature storage capacity retention rate decreases). As a result of the investigation, by using a negative electrode active material having a BET specific surface area of particles in the range of 2.8 to 5.2 m ² / g as the negative electrode active material, the battery voltage after the start of standing in the second self-discharge step The rising period can be shortened, and the high-temperature durability of the battery can be improved. The BET specific surface area is a specific surface area obtained by the BET method (for example, N ₂ gas adsorption method).

Further, (3) As the negative electrode active material, “the negative electrode active material particles are composed of graphite and amorphous carbon (for example, the surface of graphite is coated with amorphous carbon), and the negative electrode active material particles It is preferable to use a negative electrode active material in which the ratio of amorphous carbon (amorphous carbon content) is in the range of 2.5 to 7.1 wt%.
As a result of investigation by the present inventor, it is possible to shorten the battery voltage increase period after the start of the standing in the second self-discharge step as the ratio (content ratio) of the amorphous carbon in the negative electrode active material particles is reduced. found. However, if the ratio (content ratio) of amorphous carbon in the particles of the negative electrode active material is made too small, the low-temperature characteristics of the battery (particularly, the high-rate charge / discharge characteristics at low temperatures) are deteriorated (capacity reduction due to low-temperature pulse charge / discharge). Was found to be larger). As a result of the investigation, as the negative electrode active material, “the negative electrode active material particles consist of graphite and amorphous carbon, and the ratio (content ratio) of amorphous carbon in the negative electrode active material particles is 2.5 to 7. By using the negative electrode active material that is within the range of 1 wt%, the battery voltage increase period after the start of standing in the second self-discharge process can be shortened, and the low temperature characteristics of the battery (particularly, the high rate at low temperature) (Charge / discharge characteristics) can be improved (capacity reduction due to low-temperature pulse charge / discharge can be reduced).

Moreover, it is good to use the electrolyte solution (the density | concentration of the difluorophosphate in electrolyte solution is in the range of 0.01-0.076 mol / L) as electrolyte solution (4).
As a result of investigation by the present inventor, it was found that the battery voltage increase period after the start of standing in the second self-discharge step can be shortened as the concentration of difluorophosphate in the electrolytic solution is lowered. On the other hand, it was found that when the concentration of difluorophosphate in the electrolytic solution is too low, the battery internal resistance (particularly, internal resistance in a low temperature environment) increases. As a result of the investigation, by setting the concentration of difluorophosphate in the electrolyte within the range of 0.01 to 0.076 mol / L, the battery voltage increase period after the start of standing in the second self-discharge process is shortened. In addition, the internal resistance of the battery in a low temperature environment can be reduced.

Furthermore, a method for manufacturing a lithium ion secondary battery, wherein the lithium ion secondary battery is Li _x MO ₂ that satisfies 1.09 ≦ X ≦ 1.15 for the condition (1), Good.

By using Li _X MO ₂ satisfying 1.09 ≦ X ≦ 1.15 as the positive electrode active material, the battery voltage increase period after the start of standing in the second self-discharge process is further shortened (the increase period is substantially reduced). 0). In other words, by using Li _x MO ₂ satisfying 1.09 ≦ X ≦ 1.15 as the positive electrode active material, the battery voltage is quickly lowered after starting to stand in the second self-discharge process. Become. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

Furthermore, in any one of the above-described methods for producing a lithium ion secondary battery, the BET specific surface area of the negative electrode active material particles is in the range of 4.0 to 5.2 m ² / g with respect to the condition (2). It is good to use the manufacturing method of the lithium ion secondary battery used as an inside.

With respect to the above condition (2), by setting the BET specific surface area of the particles of the negative electrode active material within the range of 4.0 to 5.2 m ² / g, the battery voltage after the start of standing in the second self-discharge step The rising period can be zero. In other words, with the condition (2) described above, by leaving the range of the BET specific surface area of the negative electrode active material particles to 4.0 to 5.2 m ² / g, the second self-discharge process is left to stand. After that, the battery voltage decreases rapidly. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

  Furthermore, in any one of the above-described methods for producing a lithium ion secondary battery, the ratio of the amorphous carbon in the negative electrode active material particles is 2.5 to 4.6 wt% with respect to the condition (3). It is preferable to use a method for manufacturing a lithium ion secondary battery within the range of.

  With respect to the above condition (3), the ratio of the amorphous carbon in the negative electrode active material particles (amorphous carbon content) is set within the range of 2.5 to 4.6 wt%, so that the second self The battery voltage increase period after the start of standing in the discharging process can be made zero. In other words, with respect to the condition (3) described above, the ratio of amorphous carbon in the negative electrode active material particles is set in the range of 2.5 to 4.6 wt%, so that it is left in the second self-discharge step. When started, the battery voltage will quickly drop. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

  Furthermore, in the method for producing any one of the above lithium ion secondary batteries, the concentration of the difluorophosphate in the electrolytic solution is 0.01 to 0.015 mol / L under the condition (4). A method of manufacturing a lithium ion secondary battery within the range is preferable.

  Regarding the condition (4) described above, by setting the concentration of difluorophosphate in the electrolytic solution within the range of 0.01 to 0.015 mol / L, the battery voltage after the start of standing in the second self-discharge step The rising period can be made extremely short. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

  Furthermore, in any one of the above-described lithium ion secondary battery manufacturing methods, after the assembly process, before the initial charging process, the battery that has finished the assembly process is sandwiched between pressing jigs, and is constrained A battery restraining step, and after the internal resistance measuring step and before the battery row restraining step, a restraint releasing step for releasing the restraint of the battery performed in the battery restraining step, the initial charging step, In any of the aging process, the first self-discharge process, the capacity measurement process, and the internal resistance measurement process, the battery may be a method for manufacturing a lithium ion secondary battery in the restrained state.

  In the above-described manufacturing method, the initial charging step, the aging step, the first self-discharge step, the capacity measuring step, and the internal resistance measuring step are performed with the battery held in a restrained state by a pressing jig. By placing the battery in a restrained state with a pressing jig, the electrode body can be compressed, and unevenness in the distance between the positive electrode plate and the negative electrode plate can be reduced (made uniform). For this reason, in each said process, since the nonuniformity of a battery reaction (a charge reaction, a discharge reaction) can be made small, it is preferable.

It is a perspective view of the lithium ion secondary battery manufactured by the manufacturing method of embodiment. It is a perspective view of the positive electrode plate of the lithium ion secondary battery. It is a perspective view of the negative electrode plate of the lithium ion secondary battery. It is an expanded sectional view of the same negative electrode plate, and corresponds to the AA sectional view of FIG. It is a flowchart which shows the flow of the manufacturing method of the lithium ion secondary battery concerning embodiment. It is a perspective view which shows the state which pinched | interposed the battery which finished the assembly | attachment process in the battery restraint process, and was made into the restraint state. In a battery row | line | column restraint process, it is a figure which shows the state made into the restraint state by pinching | interposing a battery row | line | column with the pressing jig from the both ends. It is a graph which shows the relationship between the leaving period when leaving a battery row | line | column on the same conditions as a 2nd self-discharge process, and the variation | change_quantity of battery voltage (a normal battery which is not short-circuited internally, and a battery which is short-circuited internally). It is a graph showing the relationship between the battery voltage rising period at the X value and a second self-discharge process of the positive electrode active material (Li _X MO _2). It is a graph which shows the relationship between the value of the BET specific surface area of a negative electrode active material, and the battery voltage rise period in a 2nd self-discharge process. It is a graph which shows the relationship between the amorphous carbon content rate of a negative electrode active material, and the battery voltage rise period in a 2nd self-discharge process. It is a graph which shows the relationship between the density | concentration of the difluorophosphate in electrolyte solution, and the battery voltage rise period in a 2nd self-discharge process. It is a graph which shows the relationship between the capacity | capacitance ratio of a positive electrode and a negative electrode (opposing part), and the battery voltage rise period in a 2nd self-discharge process. It is a graph which shows the relationship between the thickness of the metal oxide insulating layer of a negative electrode plate, and the battery voltage rise period in a 2nd self-discharge process. It is a graph which shows the relationship between the thickness of the carbon layer of a positive electrode plate, and the battery voltage rise period in a 2nd self-discharge process.

First, the lithium ion secondary battery 100 manufactured by the manufacturing method of this embodiment will be described.
As illustrated in FIG. 1, the lithium ion secondary battery 100 includes an electrode body 110 and a battery case 180 that accommodates the electrode body 110. The electrode body 110 includes a positive electrode plate 130, a negative electrode plate 120, and a separator 150. The separator 150 is made of polyethylene, and is interposed between the positive electrode plate 130 and the negative electrode plate 120 to separate them. The separator 150 is impregnated with an electrolytic solution 160 having lithium ions.

  The battery case 180 is made of aluminum and has a rectangular parallelepiped shape. The battery case 180 has a battery case main body 181 and a sealing lid 182. Among these, the battery case main body 181 has a bottomed rectangular box shape. Note that an insulating film (not shown) made of a resin and bent in a box shape is interposed between the battery case main body 181 and the electrode body 110. The battery case 180 has a pair of wide side surfaces 180b and 180c facing away from each other. The wide side surface 180b is a surface facing the front side in FIG. 1, and the wide side surface 180c is a surface facing the back side in FIG. 1 (a surface located on the back side of the wide side surface 180b).

  The sealing lid 182 has a rectangular plate shape, closes the opening of the battery case body 181, and is welded to the battery case body 181. A rectangular plate-shaped safety valve 197 is sealed on the sealing lid 182.

  Further, a plate-like positive electrode current collecting member 191 bent in a crank shape is welded to the positive electrode plate 130 of the electrode body 110 (see FIG. 1). Further, a plate-like negative electrode current collecting member 192 bent in a crank shape is welded to the negative electrode plate 120. Of the positive electrode current collecting member 191 and the negative electrode current collecting member 192, the positive electrode terminal portion 191A and the negative electrode terminal portion 192A located at the respective tips penetrate the sealing lid 182 and protrude from the lid surface 182A. Insulating members 195 made of electrically insulating resin are interposed between the positive electrode terminal portion 191A and the sealing lid 182 and between the negative electrode terminal portion 192A and the sealing lid 182, respectively.

The electrolyte solution 160 is LiPF ₆ added as a solute to a mixed organic solvent in which ethylene carbonate (EC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC) are adjusted to a volume ratio of 3: 4: 3. Furthermore, it is a non-aqueous electrolyte to which difluorophosphate is added. The concentration of LiPF ₆ in the electrolytic solution 160 is 1 mol / L.

  The electrode body 110 is a wound type in which a belt-like positive electrode plate 130 and a negative electrode plate 120 are wound into a flat shape via a belt-like separator 150 (see FIG. 1). Specifically, the strip-shaped positive electrode plate 130, the negative electrode plate 120, and the separator 150 extending in the longitudinal direction DA are wound in the longitudinal direction DA to form a wound electrode body 110 (FIGS. 1 to 4). reference). In the electrode body 110, the positive electrode active material layer 131 of the positive electrode plate 130 and the negative electrode active material layer 121 of the negative electrode plate 120 face each other with the separator 150 interposed therebetween (see FIG. 4).

  As shown in FIG. 2, the positive electrode plate 130 has a belt-like shape extending in the longitudinal direction DA. The positive electrode current collector plate 138 made of aluminum foil and both main surfaces of the positive electrode current collector plate 138 extend in the longitudinal direction DA. It has two positive electrode active material layers 131 and 131 arranged in a strip shape. The positive electrode active material layer 131 includes a positive electrode active material 137, a conductive material made of acetylene black, PEO (polyethylene oxide), and CMC (carboxymethylcellulose) in a weight ratio of 88: 10: 1: 1. Yes.

Note that as the positive electrode active material 137, Li _x MO ₂ (M is Ni, or in addition to Ni as a main component, Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mg, (Including at least one of Ga, Zr, and Si). In addition, carbon layers 139 are provided on both surfaces of the aluminum foil forming the positive electrode current collector plate 138. The carbon layer 139 contains acetylene black and polyvinylidene fluoride in a weight ratio of 3: 7.

  Further, as shown in FIG. 3, the negative electrode plate 120 is formed on a negative electrode current collector plate 128 made of a copper foil in a strip shape extending in the longitudinal direction DA, and on both main surfaces 128 F and 128 F of the negative electrode current collector plate 128. It has two negative electrode active material layers 121 and 121 arranged in a strip shape extending in the direction DA. The negative electrode active material layer 121 includes the negative electrode active material 127, SBR (styrene butadiene rubber), CMC, and (carboxymethyl cellulose) in a weight ratio of 98: 1: 1.

  In addition, as the negative electrode active material 127, a material in which particles of the negative electrode active material are composed of graphite and amorphous carbon (for example, a surface of graphite covered with amorphous carbon) is used. A metal oxide insulating layer 129 is provided on the surface of the negative electrode active material layer 121. The metal oxide insulating layer 129 contains aluminum oxide (alumina) and polyvinylidene fluoride in a weight ratio of 95: 5.

  As shown in FIGS. 3 and 4 (AA cross-sectional view of FIG. 3), the negative electrode active material layer 121 includes a facing portion 122 that faces the positive electrode active material layer 131 through the separator 150, and a separator 150. It consists of a non-facing portion 123 where the facing positive electrode active material layer 131 does not exist. Specifically, the negative electrode active material layer 121 has a larger area than the positive electrode active material layer 131, and the non-opposing portion 123 is positioned around the opposing portion 122. Note that the position of the boundary between the non-facing portion 123 and the facing portion 122 in the negative electrode active material layer 121 is determined when the electrode body 110 is formed by winding the negative electrode plate 120, the separator 150, and the positive electrode plate 130. In FIG. 4, for reference, the positions of the positive electrode plate 130 and the separator 150 when the electrode body 110 is formed are indicated by a two-dot chain line.

Next, a manufacturing method of the lithium ion secondary battery according to the present embodiment will be described.
As shown in FIG. 5, in step S <b> 1 (assembly process), a battery in which the electrode body 110 and the electrolytic solution 160 are housed in the battery case 180 is manufactured. Specifically, first, the positive electrode active material 137, acetylene black, PEO (polyethylene oxide), and CMC (carboxymethylcellulose) are mixed at a weight ratio of 88: 10: 1: 1, and water (solvent) is mixed therewith. Were mixed to prepare a positive electrode slurry. Next, this positive electrode slurry was applied to the surface of a positive electrode current collector plate 138 made of aluminum foil (having a carbon layer 139 on the surface), dried, and then pressed. Thereby, the positive electrode plate 130 was obtained.

A carbon layer 139 is formed in advance on the surface of the aluminum foil that forms the positive electrode current collector plate 138. The carbon layer 139 contains acetylene black and polyvinylidene fluoride in a weight ratio of 3: 7. By providing the carbon layer 139 on the surface of the aluminum foil, when the positive electrode slurry is applied, contact between the positive electrode slurry (being alkaline) and the aluminum foil constituting the positive electrode current collector plate 138 can be prevented. Thereby, corrosion of the aluminum foil which comprises the positive electrode current collecting plate 138 can be prevented.
The thickness of the carbon layer 139 is preferably 1 to 5 μm. This is because the period required for the second self-discharge process (step S10) can be shortened as will be described later.

Further, as the positive electrode active material 137, Li _x MO ₂ (M is Ni, or in addition to Ni as the main component, Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mg, (Including at least one of Ga, Zr, and Si).
Note that as the positive electrode active material 137, Li _x MO ₂ satisfying a relationship of 1.04 ≦ X ≦ 1.15 is preferably used. In other words, it is preferable to use Li _x MO ₂ having a molar ratio between Li and M (molar amount of Li / molar amount of M) in the range of 1.04 to 1.15. This is because the period required for the second self-discharge process (step S10) can be shortened as will be described later.

  Moreover, the negative electrode active material 127, SBR (styrene butadiene rubber), CMC, and (carboxymethylcellulose) were mixed in water in the ratio of 98: 1: 1 (weight ratio), and the negative electrode slurry was produced. Next, this negative electrode slurry was applied on both main surfaces 128F of the negative electrode current collector plate 128 made of copper foil, dried, and then pressed. Thereby, the negative electrode plate 120 was obtained.

  In addition, as the negative electrode active material 127, a material in which the particles of the negative electrode active material are composed of graphite and amorphous carbon (the surface of graphite is coated with amorphous carbon) is used. This negative electrode active material 127 can be produced, for example, as follows. Spherical shaped graphite and pitch (petroleum pitch) are mixed and fired. By this firing, the pitch (petroleum pitch) becomes amorphous carbon. Thereafter, the fired body is pulverized, whereby the negative electrode active material 127 (graphite surface coated with amorphous carbon) can be obtained.

Note that as the negative electrode active material 127, it is preferable to use a negative electrode active material in which the ratio of amorphous carbon (amorphous carbon content) is in the range of 2.5 to 7.1 wt%. This is because the period required for the second self-discharge process (step S10) can be shortened as will be described later.
As the negative electrode active material 127, it is preferable to use a negative electrode active material in which the BET specific surface area of the negative electrode active material particles is in the range of 2.8 to 5.2 m ² / g. This is because the period required for the second self-discharge process (step S10) can be shortened as will be described later. In the present embodiment, the value of the specific surface area obtained by a known BET method (specifically, the N ₂ gas adsorption method) is adopted as the value of the BET specific surface area.

A metal oxide insulating layer 129 is formed on the surface of the negative electrode active material layer 121. Specifically, aluminum oxide (alumina) and polyvinylidene fluoride are mixed at a weight ratio of 95: 5, and a solvent is mixed with this to obtain a paste. The paste is applied to the surface of the negative electrode active material layer 121 and dried, whereby the metal oxide insulating layer 129 can be formed.
Note that the thickness of the metal oxide insulating layer 129 is preferably 2 to 8 μm. This is because the period required for the second self-discharge process (step S10) can be shortened as will be described later.

  Further, the capacity ratio (negative electrode capacity / positive electrode capacity) between the positive electrode capacity and the negative electrode capacity is preferably in the range of 1.4 to 1.9. This is because the period required for the second self-discharge process (step S10) can be shortened as will be described later. Note that the capacity ratio between the positive electrode capacity and the negative electrode capacity (the ratio of the negative electrode capacity to the positive electrode capacity) is the capacity ratio between the positive electrode active material layer 131 and the facing portion 122 of the negative electrode active material layer 121. This capacity ratio can be adjusted within the range of 1.4 to 1.9 by adjusting the thickness of the negative electrode active material layer 121 (opposing portion 122) (that is, the coating amount of the negative electrode slurry).

  Thereafter, the electrode body 110 is formed by winding the separator 150 between the negative electrode plate 120 and the positive electrode plate 130. Note that the separator 150, the negative electrode plate 120, the separator 150, and the positive electrode plate 130 are disposed so that the positive electrode active material layer 131 of the positive electrode plate 130 faces the facing portion 122 of the negative electrode active material layer 121 of the negative electrode plate 120 through the separator 150. The layers are wound in the order of (see FIG. 4).

  Thereafter, the negative electrode current collecting member 192 is welded to the negative electrode plate 120 (negative electrode current collecting plate 128), and the positive electrode current collecting member 191 is welded to the positive electrode plate 130 (positive electrode current collecting plate 138). Next, after the electrode body 110 welded to the negative electrode current collecting member 192 and the positive electrode current collecting member 191 is inserted into the battery case main body 181, the electrolytic solution 160 is injected. Thereafter, the sealing lid 182 and the battery case main body 181 are welded in a state where the opening of the battery case main body 181 is closed with the sealing lid 182 to complete the assembly of the lithium ion secondary battery.

Incidentally, the electrolytic solution 160, the ethylene carbonate (EC) and methyl ethyl carbonate (MEC) and dimethyl carbonate (DMC), 3 in volume ratio: 4: a mixed organic solvent was adjusted to 3, added LiPF ₆ as a solute Furthermore, it is a non-aqueous electrolyte to which difluorophosphate is added. The concentration of LiPF ₆ in the electrolytic solution 160 is 1 mol / L.
Moreover, it is preferable that the density | concentration of the difluorophosphate in the electrolyte solution 160 shall be in the range of 0.01-0.076 mol / L. This is because the period required for the second self-discharge process (step S10) can be shortened as will be described later. In this embodiment, LiPF ₂ O ₂ is used as the difluorophosphate.

  Next, the process proceeds to step S2 (battery restraint process) (see FIG. 5), and the lithium ion secondary battery 100 manufactured in the above assembly process (step S1) is sandwiched between the pressing jigs 30 and 40 to be in a restraint state. (See FIG. 6). Specifically, as illustrated in FIG. 6, the lithium ion secondary battery 100 is sandwiched between the pressing jigs 30 and 40 so that the wide side surfaces 180 b and 180 c of the battery case 180 are pressed by the pressing jigs 30 and 40. Then, the lithium ion secondary battery 100 is brought into a restrained state. Specifically, the pressing jig 30 disposed on the wide side surface 180 b side of the battery case 180 and the pressing jig 40 disposed on the wide side surface 180 c side are fastened using the cylindrical rod 51 and the nut 53. Then, the lithium ion secondary battery 100 is sandwiched between the pressing jigs 30 and 40, and the wide side surfaces 180 b and 180 c of the battery case 180 are pressed with the pressing jigs 30 and 40. Thus, a predetermined load (for example, 400 to 800 kgf) is applied to the battery case 180.

  As shown in FIG. 7, the pressing jig 30 includes a metal pressing main body portion 35 and a resin close contact pressing plate 36. The pressing jig 40 has a metal pressing main body 45 and a resin-made close pressing plate 46. The close-contact pressing plates 36 and 46 have a comb-shaped cross section (see FIG. 7).

  Next, it progresses to step S3 (initial charge process) (refer FIG. 5), and the lithium ion secondary battery 100 of the state (state shown in FIG. 6) restrained with the pressing jigs 30 and 40 is initially charged. The lithium ion secondary battery 100 can be activated by this initial charging. In addition, an SEI (film) can be formed on the surface of the negative electrode active material 127.

  Next, the process proceeds to step S4 (aging process), and the lithium ion secondary battery 100 in the restraint state (the state shown in FIG. 6) after the initial charge (the process of step S3) is completed at a predetermined temperature (for example, 50 ° C.). Aging at a fixed time (for example, 15 hours).

  By the way, in the assembly process (step S1), metal powder (such as Cu powder) may be mixed in the electrode body 110 by mistake. In such a battery, dendrite derived from metal powder is generated in the aging process, and an internal short circuit occurs (the positive electrode plate 130 and the negative electrode plate 120 that are electrically insulated by the separator 150 are electrically connected through the dendrite. Sometimes). For this reason, in step S5 (first self-discharge process) described later, a battery in which an internal short circuit has occurred is detected so as not to be shipped (removed as a defective product).

  In step S5 (first self-discharge process), the lithium ion secondary battery 100 in a restrained state (state shown in FIG. 6) after aging (the process of step S4) is kept in a temperature environment of 25 ° C. for a predetermined period ( For example, it is self-discharged by leaving it for 5 days. However, in step S5 (first self-discharge process), the battery voltage value V10 before leaving the lithium ion secondary battery 100 and the battery voltage value V11 after leaving the lithium ion secondary battery 100 for 5 days are measured. Then, the battery voltage difference ΔV1 (= V10−V11) is calculated.

  In a battery in which an internal short circuit has occurred, since the amount of self-discharge due to neglect is larger than a battery in which an internal short circuit has not occurred (normal battery), the battery voltage value becomes smaller, and the battery voltage difference ΔV1 before and after the neglect is also growing. Therefore, based on the battery voltage difference ΔV1 before and after being left, it can be determined whether or not an internal short circuit has occurred in the battery. Therefore, in step S5 (first self-discharge process), it is determined whether or not an internal short circuit has occurred in the lithium ion secondary battery 100 depending on whether or not the battery voltage difference ΔV1 is equal to or greater than a predetermined threshold T1. A battery determined to have an internal short circuit is removed as a defective product (for example, discarded). Note that the threshold T1 is, for example, a value between the battery voltage difference ΔV1 of both batteries, in which a battery voltage difference ΔV1 is investigated in advance for a battery in which an internal short circuit has occurred and a battery in which no internal short circuit has occurred. It ’s fine.

  Next, it progresses to step S6 (capacity | capacitance measurement process), and part of battery capacity is measured about the lithium ion secondary battery 100 determined that the internal short circuit has not arisen in step S5 (it is normal). Specifically, for example, when the lithium ion secondary battery 100 is discharged and the battery voltage value decreases from 4.0 V (SOC 90%) to 3.55 V (SOC 30%), the discharge electricity quantity Q1 (battery capacity) Part of). A battery whose discharge electricity quantity Q1 is outside the allowable range is removed as a defective product (for example, discarded).

Battery capacity is the amount of electricity discharged when battery 100 is discharged from SOC 100% to SOC 0%. Therefore, the amount of discharged electricity Q1 is a part of the battery capacity of the battery 100 (corresponding to 60% of the battery capacity).
In step S6 (capacity measurement step), the lithium ion secondary battery 100 remains in the state of being restrained by the pressing jigs 30 and 40 (the state shown in FIG. 6).
Also, SOC is an abbreviation for State Of Charge.

  Subsequently, it progresses to step S7 (internal resistance measurement process), and the internal resistance (IV resistance) is measured about the lithium ion secondary battery 100 of the restraint state (state shown in FIG. 6) which finished the capacity | capacitance measurement process (step S6). To do. Specifically, the lithium ion secondary battery 100 is charged, and the battery voltage value is set to 3.6 V (SOC 40%). Thereafter, the lithium ion secondary battery 100 is discharged at a constant current of 20 A for 4 seconds, and the battery voltage value Vb at the end of discharge (moment of completion) is measured. Next, a value (= ΔV / 20) obtained by dividing the battery voltage change amount ΔV (= 3.6-Vb) changed by the discharge by the current value 20A is acquired as an IV resistance value (internal resistance value). A battery whose IV resistance value is out of the allowable range is removed as a defective product (for example, discarded).

  Then, it progresses to step S8 (restraint cancellation | release process), and the restraint state of the lithium ion secondary battery 100 which finished the internal resistance measurement process (step S7) is cancelled | released. Specifically, the pressing jigs 30 and 40 that have been pressed with the lithium ion secondary battery 100 interposed therebetween are removed.

  Next, in step S9 (battery row restraint process), a plurality of lithium ion secondary batteries 100 that have finished the restraint release process (step S9) are prepared, and these batteries are put together into a restraint state. Specifically, first, a plurality (for example, 20) of lithium ion secondary batteries 100 that have finished the restraint releasing step (step S8) are prepared. Thereafter, for example, as shown in FIG. 7, these lithium ion secondary batteries 100 are arranged in a row to form a battery row 200. Further, the battery array 200 is held in a restrained state by being sandwiched between the pressing jigs 30 and 40 from both ends (left and right ends in FIG. 7). In the example shown in FIG. 7, the batteries 100 adjacent to each other in the row direction are arranged in a row with the wide side surfaces 180 b and 180 c of the battery case 180 in the opposite direction to form the battery row 200.

  Specifically, a battery case in which the close contact pressing plate 36 is disposed between the lithium ion secondary batteries 100 adjacent to each other in the row direction (left and right direction in FIG. 7) and is positioned at one end (right end in FIG. 7) of the battery row 200. The pressing jig 30 is arranged on the wide side surface 180c side (right end in FIG. 7) of 180, and the wide side surface 180c side (left end in FIG. 7) of the battery case 180 located at the other end (left end in FIG. 7) of the battery array 200. The pressing jig 40 is disposed on the surface. In this state, the pressing jig 30 and the pressing jig 40 are fastened by using the cylindrical rod 52 and the nut 53, whereby the battery row 200 is sandwiched between the pressing jigs 30 and 40 to form the battery row. The wide side surfaces 180b and 180c of the battery case 180 of each battery 100 to be pressed are pressed by the pressing jigs 30 and 40. As a result, a predetermined load (a larger load than the battery restraining step, for example, 2000 to 3000 kgf) is applied to the battery array 200.

  In the above example, the case where the battery row is one row has been described, but the battery row may be a plurality of rows (for example, two rows of battery rows in which 10 batteries are arranged in one row). good. Therefore, a plurality of battery rows may be put together into a restrained state.

  By the way, if the battery row 200 is brought into a restrained state in step S9 (battery row restraining step), a large compressive force is applied to the electrode bodies 110 of each lithium ion secondary battery 100 constituting the battery row 200, and each electrode body 110 is placed. Is compressed. If a metal foreign object is mixed in the electrode body 110 (for example, if a metal foreign object is mistakenly mixed in the electrode body 110 in the assembling process and the metal foreign object still remains), as described above. When the electrode body 110 is compressed, the metal foreign matter penetrates the separator 150 and an internal short circuit occurs (the positive electrode plate 130 and the negative electrode plate 120 electrically insulated by the separator 150 are electrically connected through the metal foreign matter. Connection). For this reason, in step S10 (second self-discharge process) described later, a battery in which an internal short circuit has occurred is detected so as not to be shipped (removed as a defective product).

  In step S10 (second self-discharge step), each of the lithium ion secondary batteries forming the battery array 200 is left by leaving the battery array 200 in a restrained state (the state shown in FIG. 7) in a temperature environment of 25 ° C. 100 is self-discharged. Further, in step S10 (second self-discharge step), each lithium ion secondary battery 100 is internally short-circuited based on the change in battery voltage of each lithium ion secondary battery 100 when self-discharged. It is determined whether or not.

  However, in step S10 (second self-discharge process), when the battery voltage value of each lithium ion secondary battery 100 increases after the battery array 200 is left unattended, the battery voltage value increase period has elapsed. Later, the battery array 200 in a restrained state is left for a specified period (for example, 3 days). On the other hand, when the battery voltage value of each lithium ion secondary battery 100 decreases without increasing after the start of leaving the battery array 200, the specified period (for example, 3) Days), the battery array 200 in a restrained state is left unattended.

  Further, in step S10 (second self-discharge step), the battery voltage value V20 of each lithium ion secondary battery 100 immediately before the battery array 200 is left for the specified period (for example, 3 days) and the battery array 200 are specified. The battery voltage value V21 immediately after being left for a period (for example, 3 days) is measured, and the battery voltage difference ΔV2 (= V20−V21) is calculated.

  A battery with an internal short circuit has a larger self-discharge amount due to neglected than a battery without normal internal short circuit (normal battery). The voltage difference ΔV2 also increases. Therefore, based on the battery voltage difference ΔV2, it can be determined whether or not an internal short circuit has occurred in the battery. Therefore, in step S10 (second self-discharge process), an internal short circuit occurs for each lithium ion secondary battery 100 constituting the battery array 200 depending on whether or not the battery voltage difference ΔV2 is equal to or greater than a predetermined threshold T2. It is determined whether or not. A battery determined to have an internal short circuit is removed as a defective product (for example, discarded). For example, the threshold value T2 is determined in advance by checking the battery voltage difference ΔV2 between the battery in which the internal short circuit has occurred and the battery in which the internal short circuit has not occurred. It ’s fine.

  In this way, each lithium ion secondary battery 100 constituting the battery array 200 is left to stand for a specified period (for example, 3 days) in which the battery voltage value is reliably reduced by self-discharge, and each lithium ion before and after the specified period is left. By determining whether or not each lithium ion secondary battery 100 is internally short-circuited based on the battery voltage difference ΔV <b> 2 of the secondary battery 100, appropriate internal short-circuit determination can be performed.

  Whether or not the battery voltage value of the lithium ion secondary battery 100 increases in step S10 (second self-discharge process), the length of the battery voltage increase period when the battery voltage value increases, and the internal short circuit The length of the specified period during which presence / absence can be properly determined is previously determined by a neglect test. Specifically, under the same conditions as in step S10 (second self-discharge process), the battery row 200 including the battery 100 in which the internal short circuit has occurred and the battery 100 in which the internal short circuit has not occurred is left to stand, A battery voltage value of 100 is measured. Based on this measurement result (see FIG. 8 to be described later), it is determined whether or not there is an internal short circuit when starting to leave the specified period in step S10 (second self-discharge step) (when measuring the battery voltage value V20). The value of the threshold value T2 is determined in advance when the predetermined period that can be discriminated at the end of the predetermined period and when the leaving of the specified period ends (when the battery voltage value V21 is measured). Note that a method for determining these values will be specifically described later with reference to FIG.

  If it is determined in step S10 (second self-discharge step) that no internal short circuit has occurred in any of the batteries 100 constituting the battery array 200, the assembled battery 300 (see FIG. 7) remains in the above-described restrained state. Will be shipped as. As shown in FIG. 7, the assembled battery 300 is configured such that the battery array 200 is sandwiched between pressing jigs 30 and 40 from both ends (left and right ends in FIG. 7).

  On the other hand, if it is determined in step S10 (second self-discharge step) that an internal short circuit has occurred in any of the batteries 100 constituting the battery array 200, the restraint state is once released and the internal short circuit is performed. Remove the battery 100. Then, the battery 100 determined not to be internally short-circuited is taken out from the other battery array 200 that has finished step S10 (second self-discharge process), and this battery 100 is replaced with the battery 100 that is internally short-circuited. Arrange. In this way, the battery array 200 is configured by only the batteries 100 that are determined not to have an internal short circuit, and then the battery array 200 is placed in a restrained state in the same manner as in step S9 (battery train restraining step). The battery is shipped as an assembled battery 300 (see FIG. 7).

  The battery 100 of this embodiment is used as the assembled battery 300 (in the state of the assembled battery 300). This assembled battery 300 is used, for example, as a driving power source for a hybrid vehicle or an electric vehicle.

Example 1
In the first embodiment, the lithium ion secondary battery 100 is manufactured as follows.
First, in step S1 (assembly process), a battery in which the electrode body 110 and the electrolytic solution 160 are housed in the battery case 180 is manufactured as described above.

In the first embodiment, the thickness of the carbon layer 139 of the positive electrode plate 130 is 2 μm.
Further, as the positive electrode active material 137, Li _X MO ₂ having an _X value of 1.08 is used. That is, Li _1.08 MO ₂ is used as the positive electrode active material 137. Specifically, Li _1.08 Ni _0.8 Co _0.15 Al _0.05 O ₂ is used as the positive electrode active material 137. As described above, in Example 1, “ _1.0 ” of Li _1.08 MO ₂ containing Co and Al in addition to Ni as the main component is used as the positive electrode active material 137.

Further, as the negative electrode active material 127, a negative electrode active material in which the ratio of amorphous carbon (amorphous carbon content) is 6 wt% and the BET specific surface area of the negative electrode active material particles is 3.3 m ² / g. Is used.
The thickness of the metal oxide insulating layer 129 of the negative electrode plate 120 is 4 μm.
The capacity ratio (negative electrode capacity / positive electrode capacity) between the positive electrode capacity and the negative electrode capacity is 1.5.
Moreover, the density | concentration of the difluorophosphate in the electrolyte solution 160 shall be 0.038 mol / L.

Next, as described above, steps S2 to S9 were performed. In the first embodiment, in step S4 (aging process), the lithium ion secondary battery 100 is aged at an environmental temperature of 50 ° C. for 15 hours.
Thereafter, as described above, the process of step S10 (second self-discharge process) is performed.

  However, as will be described later, the battery of Example 1 (battery manufactured in the assembly process as described above) has a battery voltage value of nearly two days after the start of leaving the battery array 200 (up to a maximum). 2 days) is known to rise. For this reason, in step S10 (second self-discharge process) of the first embodiment, the battery voltage value V20 of each lithium ion secondary battery 100 is measured two days after the start of leaving the battery array 200, Thereafter, the battery array 200 is left for a specified period, and when the specified period has elapsed, the battery voltage value V21 of each lithium ion secondary battery 100 is measured.

  Thereafter, for each lithium ion secondary battery 100, a battery voltage difference ΔV2 (= V20−V21), which is a difference value between the battery voltage value V20 and the battery voltage value V21, is calculated, and the battery voltage difference ΔV2 is greater than or equal to the threshold T2. It is determined whether or not there is. The lithium ion secondary battery 100 whose battery voltage difference ΔV2 is equal to or greater than the threshold value T2 determines that an internal short circuit has occurred. On the other hand, regarding the lithium ion secondary battery 100 with the battery voltage difference ΔV2 less than the threshold value T2, it is determined that an internal short circuit has not occurred.

  In the first embodiment, the “specified period” is 3 days. As will be described later, whether or not there is an internal short circuit appropriately based on the battery voltage difference ΔV2 after two days have passed since the start of leaving the battery array 200 and then left for another 3 days. This is because it is understood that it can be determined. Further, the threshold value T2 may be set to 0.5 mV, for example. As will be described later, from the result of the neglect test, in the battery 100 in which the internal short circuit has not occurred, the value of ΔV2 is about 0.3 mV, and in the battery 100 in which the internal short circuit has occurred, the value of ΔV2 is about 0.8 mV. I know that Therefore, by setting the threshold value T2 to a value between these values, it is possible to appropriately determine the presence or absence of an internal short circuit.

(Leave test)
Here, FIG. 8 shows the result of the standing test performed for determining each condition in step S10 (second self-discharge process) of Example 1. FIG. Specifically, the processes from Steps S1 to S9 were performed under the conditions of Example 1, and a plurality of batteries 100 in which an internal short circuit occurred and a plurality of batteries 100 in which no internal short circuit occurred were prepared. After that, under the same conditions as in step S10 (second self-discharge step), the battery train 200 including the battery 100 in which the internal short circuit has occurred and the battery 100 in which the internal short circuit has not occurred is left for 11 days, 100 battery voltage values were measured. In FIG. 8, among these measurement results, the measurement results of two batteries 100 (the battery 100 in which an internal short circuit has occurred and the battery 100 in which no internal short circuit has occurred) are used with reference to the battery voltage value at the time of starting to stand. The amount of change is shown.

  In FIG. 8, the change amount of the battery voltage of the battery 100 in which the internal short circuit has not occurred is indicated by ◯, and the change amount of the battery voltage of the battery 100 in which the internal short circuit has occurred is indicated by the Δ mark. Whether or not an internal short circuit has occurred is confirmed by disassembling each battery 100 after the 11-day standing test has been completed.

As shown in FIG. 8, the battery voltage values of the two batteries 100 have risen nearly two days after the battery array 200 has been left unattended. The other batteries 100 were almost the same, and it was found that the voltage increase period from the start of standing was 2 days at the longest.
Further, it can be seen that after the voltage increase period (2 days) has elapsed, the battery voltage value of the battery 100 in which the internal short circuit has occurred is greatly reduced as compared with the battery 100 in which the internal short circuit has not occurred. Then, after the voltage increase period (2 days) has elapsed, the battery 100 that has undergone internal short-circuiting and the battery 100 that has not undergone internal short-circuiting have been left for another 3 days. It can be seen that there is a large difference in the amount of change in battery voltage from

  Specifically, in the battery 100 in which no internal short circuit has occurred, the battery is a difference value between the battery voltage value when the voltage increase period (2 days) has elapsed and the battery voltage value when left for another 3 days thereafter. The voltage difference ΔV2 was about 0.3 mV. On the other hand, in the battery 100 in which the internal short circuit occurs, the battery voltage difference ΔV2 is about 0.8 mV, which is a considerably large value compared to the battery 100 in which the internal short circuit does not occur. If such a large difference occurs in the battery voltage difference ΔV2, it is possible to appropriately determine the presence or absence of an internal short circuit based on the battery voltage difference ΔV2. Therefore, the “specified period” in the second self-discharge process of Example 1 is set to 3 days.

  Therefore, in step S10 (second self-discharge step) of Example 1, the battery voltage value V20 of each lithium ion secondary battery 100 is measured two days after the start of leaving the battery array 200, and then The battery array 200 was left unattended for 3 days (specified period), and when the 3 days (specified period) passed, the battery voltage value V21 of each lithium ion secondary battery 100 was measured.

As described above, according to the manufacturing method of Example 1, in step S10 (second self-discharge step), the battery voltage increase period after the start of standing can be shortened to within 2 days (maximum 2 days). The entire period of the second self-discharge process can be shortened to 5 days. The reason is that in the assembly process, the carbon layer 139 of the positive electrode plate 130 has a thickness of 2 μm, Li _X MO ₂ having an _X value of 1.08 is used as the positive electrode active material 137, and the negative electrode active material 127 is used as the negative electrode active material 127. In addition, a negative electrode active material in which the ratio (content ratio) of amorphous carbon is 6 wt% and the negative electrode active material particles have a BET specific surface area of 3.3 m ² / g is used. The thickness of the material insulating layer 129 is 4 μm, the capacity ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.5, and the concentration of difluorophosphate in the electrolytic solution 160 is 0.00. This is because it is 038 mol / L.

(Preferable X value in Li _X MO ₂ )
Next, for the positive electrode active material 137 (Li _x MO ₂ ) used in the assembling step, a preferable value of X (molar ratio between Li and M) was investigated.
Specifically, first, a battery 100 was manufactured in the same manner as steps S1 to S9 in Example 1. However, for the positive electrode active material 137 (Li _X MO ₂ ), 11 types of positive electrode active materials having different X values are prepared, and for the positive electrode active material 137 (Li _X MO ₂ ), only the X value is different. 11 types were prepared (see FIG. 9). Thereafter, the above-mentioned leaving test (leaving as in the second self-discharge step) was performed, and the battery voltage increase period from the start of leaving was examined for each battery 100. The result is shown by a circle in FIG. 9 as the relationship between the value of X and the battery voltage increase period.

Further, the battery capacity of each of the 11 types of batteries 100 described above was measured. Specifically, for each battery 100, in a temperature environment of 25 ° C., from a state of SOC 100% (battery voltage value 4.1V) to a state of SOC 0% (battery voltage value 3.0V), 2A Discharge (CCCV discharge) was performed at a constant current, and the amount of electricity discharged at this time was obtained as the battery capacity. Based on this battery capacity, the specific capacity (electric capacity per gram of the positive electrode active material) was calculated for each battery 100. The result is shown by a Δ mark in FIG. 9 as the relationship between the X value of Li _X MO ₂ and the specific capacity.

As can be seen from FIG. 9, in Li _X MO ₂ , as the value of X is increased, the battery voltage increase period after the start of standing in the second self-discharge process can be shortened. However, as the value of X increases, the specific capacity decreases. If the specific capacity is too small, it is not preferable as battery characteristics. From the above results, by using Li _x MO ₂ satisfying the relationship of 1.04 ≦ X ≦ 1.15 as the positive electrode active material 137, the battery voltage increase period after the start of standing in the second self-discharge process is shortened. (Within 2.5 days) and a sufficient specific capacity can be obtained.

In particular, by using Li _x MO ₂ satisfying the relationship of 1.09 ≦ X ≦ 1.15, the battery voltage increase period after the start of standing in the second self-discharge process is further shortened (the voltage increase period is substantially reduced). 0). In other words, by using Li _x MO ₂ satisfying the relationship of 1.09 ≦ X ≦ 1.15, the battery voltage is quickly lowered after starting to stand in the second self-discharge process. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

For example, in the assembling process, Li _X MO ₂ having an _X value of 1.10 is used as the positive electrode active material 137, the thickness of the carbon layer 139 of the positive electrode plate 130 is 2 μm, and the negative electrode active material 127 is In addition, a negative electrode active material in which the ratio (content ratio) of amorphous carbon is 6 wt% and the negative electrode active material particles have a BET specific surface area of 3.3 m ² / g is used. The thickness of the material insulating layer 129 is 4 μm, the capacity ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.5, and the concentration of difluorophosphate in the electrolytic solution 160 is 0.00. By setting it to 038 mol / L, the battery voltage increase period in the second self-discharge process can be set to 0 (none). Thereby, a 2nd self-discharge period can be made into 3 days (only as for a regulation period).

On the other hand, the specific capacity can be particularly increased by using Li _x MO ₂ that satisfies the relationship of 1.04 ≦ X ≦ 1.08 as the positive electrode active material 137. Thereby, the battery 100 excellent in output characteristics can be obtained.

(Preferred value of BET specific surface area of negative electrode active material)
Next, the preferable value of the BET specific surface area was investigated about the negative electrode active material 127 used at an assembly | attachment process.
Specifically, first, a battery 100 was manufactured in the same manner as steps S1 to S9 in Example 1. However, as the negative electrode active material 127, 13 types of negative electrode active materials differing only in the value of the BET specific surface area were prepared, and 13 types of batteries 100 different in only the value of the BET specific surface area of the negative electrode active material 127 were prepared (see FIG. 10). Thereafter, the above-mentioned leaving test (leaving as in the second self-discharge step) was performed, and the battery voltage increase period from the start of leaving was examined for each battery 100. The result is shown by a circle in FIG. 10 as the relationship between the BET specific surface area and the battery voltage increase period.

  Moreover, the above-mentioned 13 types of batteries 100 were each subjected to a high temperature storage test, and the capacity retention rate was calculated based on the battery capacity before and after the high temperature storage test. Specifically, each battery 100 was allowed to stand (store) for 30 days in a temperature environment of 60 ° C. (in a constant temperature bath of 60 ° C.) with SOC of 80%. Before and after the storage test, the battery capacity of each battery 100 is measured, and the ratio (Q2 / Q1) × 100 (%) of the battery capacity Q2 after the storage test to the battery capacity Q1 before the storage test is used as the capacity maintenance rate. Calculated. The result is shown by Δ in FIG. 10 as the relationship between the BET specific surface area and the capacity retention rate.

As can be seen from FIG. 10, as the BET specific surface area of the particles of the negative electrode active material 127 is increased, the battery voltage increase period after the start of standing in the second self-discharge process can be shortened. However, as the BET specific surface area of the particles of the negative electrode active material 127 is increased, the high-temperature durability of the battery is reduced (the capacity retention rate is reduced). It is not preferable as the characteristics of the battery that the high-temperature durability is too low. From the above results, by using a negative electrode active material whose particle BET specific surface area is in the range of 2.8 to 5.2 m ² / g as the negative electrode active material 127, It can be said that the battery voltage increase period can be shortened (within 3 days) and the high-temperature durability of the battery can be improved.

In particular, by using a negative electrode active material having a BET specific surface area within the range of 4.0 to 5.2 m ² / g, the battery voltage increase period after the start of standing in the second self-discharge process is further shortened ( Voltage rise period can be reduced to zero). In other words, by using a negative electrode active material having a BET specific surface area in the range of 4.0 to 5.2 m ² / g, the battery voltage is quickly lowered after starting to stand in the second self-discharge process. It becomes like this. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

For example, in the assembly process, Li _X MO ₂ having an _X value of 1.08 is used as the positive electrode active material 137, the thickness of the carbon layer 139 of the positive electrode plate 130 is 2 μm, and the negative electrode active material 127 is A negative active material in which the proportion (content) of amorphous carbon is 6 wt% and the negative active material particles have a BET specific surface area in the range of 4.0 to 5.2 m ² / g; The thickness of the metal oxide insulating layer 129 of the negative electrode plate 120 is 4 μm, the capacity ratio of the positive electrode capacity to the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.5, and difluorophosphorus in the electrolyte 160 By setting the acid salt concentration to 0.038 mol / L, the battery voltage increase period in the second self-discharge step can be set to 0 (none). Thereby, a 2nd self-discharge period can be made into 3 days (only as for a regulation period).

On the other hand, as the negative electrode active material 127, BET specific surface area by using a negative electrode active material is in the range of less than 2.8 m ² / g or more 4.0 m ² / g, in particular, can enhance the capacity maintenance ratio ( (See FIG. 10). Thereby, the battery 100 excellent in high temperature durability can be obtained.

(Preferable value of the amorphous carbon content of the negative electrode active material)
Next, for the negative electrode active material 127 used in the assembling process, the preferred value of the amorphous carbon content was investigated.
Specifically, first, a battery 100 was manufactured in the same manner as steps S1 to S9 in Example 1. However, for the negative electrode active material 127, 12 types of negative electrode active materials that differ only in the value of the amorphous carbon content are prepared, and the battery 100 that differs only in the value of the amorphous carbon content of the negative electrode active material 127 is obtained. Twelve types were produced (see FIG. 11). Thereafter, the above-mentioned leaving test (leaving as in the second self-discharge step) was performed, and the battery voltage increase period from the start of leaving was examined for each battery 100. The result is shown by a circle in FIG. 11 as the relationship between the amorphous carbon content and the battery voltage increase period.

  In addition, each of the 12 types of batteries 100 described above was subjected to a pulse charge / discharge cycle test under a low temperature environment, and the capacity reduction rate was calculated based on the battery capacity before and after the cycle test. Specifically, 1200 cycles of pulse charge / discharge were performed under the temperature environment of 0 ° C. (within a constant temperature bath of 0 ° C.) with each battery 100 at SOC 60%. One cycle of pulse charging / discharging is a cycle in which charging is performed at a constant current of 100 A for 10 seconds, and then discharging is performed at a constant current of 10 A for 100 seconds.

  Before and after this cycle test, the battery capacity of each battery 100 was measured, and the capacity reduction rate was calculated. In addition, when the battery capacity before the cycle test is Q1, and the battery capacity after the cycle test is Q2, the capacity reduction rate is calculated as ((Q1-Q2) / Q1) × 100 (%). This result is indicated by Δ in FIG. 11 as the relationship between the amorphous carbon content and the capacity reduction rate.

  As can be seen from FIG. 11, as the proportion of amorphous carbon (amorphous carbon content) in the particles of the negative electrode active material 127 is reduced, the battery voltage increase period after the start of standing in the second self-discharge process is shortened. can do. However, if the proportion of amorphous carbon (amorphous carbon content) in the particles of the negative electrode active material 127 is too small, the low-temperature characteristics of the battery deteriorate (the capacity drop due to the low-temperature pulse charge / discharge cycle test increases). . The deterioration of the low temperature characteristics is not preferable as the characteristics of the battery. From the above results, by using a negative electrode active material having an amorphous carbon content in the range of 2.5 to 7.1 wt% as the negative electrode active material 127, the battery after the start of standing in the second self-discharge step is used. It can be said that the voltage rise period can be shortened (within 2.5 days), and the low-temperature characteristics of the battery can be improved.

  In particular, by using a negative electrode active material having an amorphous carbon content in the range of 2.5 to 4.6 wt%, the battery voltage increase period after the start of standing in the second self-discharge process is further shortened. (The voltage rise period can be set to 0). In other words, by using a negative electrode active material having an amorphous carbon content in the range of 2.5 to 4.6 wt%, the battery voltage quickly decreases after starting to stand in the second self-discharge process. Will come to do. Thereby, the period concerning a 2nd self-discharge process can be shortened very much. Moreover, the low-temperature characteristics of the battery are particularly good.

For example, in the assembly process, Li _X MO ₂ having an _X value of 1.08 is used as the positive electrode active material 137, the thickness of the carbon layer 139 of the positive electrode plate 130 is 2 μm, and the negative electrode active material 127 is A negative electrode active material in which the amorphous carbon content is in the range of 2.5 to 4.6 wt% and the negative electrode active material particles have a BET specific surface area of 3.3 m ² / g; The thickness of the metal oxide insulating layer 129 of the plate 120 is 4 μm, the capacity ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.5, and the difluorophosphate in the electrolyte 160 By making the density | concentration of 0.038 mol / L, the battery voltage increase period in a 2nd self-discharge process can be set to 0 (none). Thereby, a 2nd self-discharge period can be made into 3 days (only as for a regulation period).

(Preferred value of difluorophosphate concentration in electrolyte)
Next, the preferable value of the difluorophosphate concentration in the electrolytic solution was investigated for the electrolytic solution 160 used in the assembly process.
Specifically, first, a battery 100 was manufactured in the same manner as steps S1 to S9 in Example 1. However, for the electrolytic solution, nine types of electrolytic solutions that differ only in the difluorophosphate concentration were prepared, and nine types of batteries 100 that differed only in the difluorophosphate concentration in the electrolytic solution were prepared (then, described above). A standing test (same as in the second self-discharge process) was performed, and the battery voltage increase period from the start of the stand was investigated for each battery 100. The result was calculated as a result of the difluorophosphate concentration and the battery voltage increase period. The relationship is indicated by a circle in Fig. 12. Note that LiPF ₂ O ₂ is used as the difluorophosphate.

  Further, the internal resistance (IV resistance) of each of the nine types of batteries 100 described above was measured. Specifically, each battery 100 is charged (or discharged) to set each battery voltage value to 3.6 V (SOC 40%). Thereafter, each battery 100 is discharged at a constant current of 40 A for 2 seconds in a low temperature environment of −40 ° C., and the battery voltage value Vb at the end of discharge (moment of completion) is measured. Next, a value (= ΔV / 40) obtained by dividing the battery voltage change ΔV (= 3.6-Vb) changed by the discharge by the current value 40A was obtained as an IV resistance value (internal resistance value). These results are shown as Δ in FIG. 12 as the relationship between the difluorophosphate concentration in the electrolyte and the internal resistance (IV resistance) of the battery.

  As can be seen from FIG. 12, as the concentration of difluorophosphate in the electrolytic solution is lowered, the battery voltage increase period after the start of standing in the second self-discharge step can be shortened. However, if the concentration of difluorophosphate in the electrolytic solution is too low, the internal resistance of the battery (particularly the internal resistance in a low temperature environment) increases. A battery having a large internal resistance is not preferable. From the above results, by setting the concentration of difluorophosphate in the electrolyte within the range of 0.01 to 0.076 mol / L, the battery voltage increase period after the start of standing in the second self-discharge process is shortened. It can be said that the battery internal resistance in a low temperature environment can be reduced.

  In particular, by setting the concentration of difluorophosphate in the electrolyte within the range of 0.01 to 0.015 mol / L, the battery voltage increase period after the start of standing in the second self-discharge process is extremely shortened. (The voltage rise period can be set to 0). In other words, by using the electrolytic solution 160 having a difluorophosphate concentration of 0.01 to 0.015 mol / L, the battery voltage is quickly lowered after starting to stand in the second self-discharge process. Become. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

For example, in the assembly process, Li _X MO ₂ having an _X value of 1.08 is used as the positive electrode active material 137, the thickness of the carbon layer 139 of the positive electrode plate 130 is 2 μm, and the negative electrode active material 127 is A negative electrode active material in which the amorphous carbon content is in the range of 6 wt% and the negative electrode active material particles have a BET specific surface area of 3.3 m ² / g; The thickness of the insulating layer 129 is 4 μm, the capacity ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.5, and the concentration of difluorophosphate in the electrolytic solution 160 is 0.01. By setting it to ˜0.015 mol / L, the battery voltage increase period in the second self-discharge process can be set to 0 (none). Thereby, a 2nd self-discharge period can be made into 3 days (only as for a regulation period).

  On the other hand, by setting the concentration of difluorophosphate in the electrolytic solution within the range of 0.018 to 0.076 mol / L, particularly the internal resistance of the battery (particularly the internal resistance in a low temperature environment) is reduced. (See the Δ mark in FIG. 12). Thereby, the battery 100 excellent in output characteristics (particularly, output characteristics in a low temperature environment) can be obtained.

(Preferred value of positive / negative electrode capacity ratio)
Next, for the positive electrode plate 130 and the negative electrode plate 120 used in the assembling process, the preferred capacity ratio (negative electrode capacity / positive electrode capacity) value was investigated. Note that this capacity ratio (ratio of the negative electrode capacity to the positive electrode capacity) is a capacity ratio between the positive electrode active material layer 131 and the facing portion 122 of the negative electrode active material layer 121.

  Specifically, first, a battery 100 was manufactured in the same manner as steps S1 to S9 in Example 1. However, as for the negative electrode plate, eight types of negative electrode plates were prepared which differed only in the thickness of the negative electrode active material layer (opposing portion) (that is, the amount of application of the negative electrode slurry). As a result, eight types of negative electrode plates differing only in negative electrode capacity were prepared. Then, using these negative electrode plates, eight types of batteries 100 differing only in the positive / negative electrode capacity ratio (negative electrode capacity / positive electrode capacity) were produced. In the eight types of batteries 100, equivalent positive plates are used. Thereafter, the above-mentioned leaving test (leaving as in the second self-discharge step) was performed, and the battery voltage increase period from the start of leaving was examined for each battery 100. The result is shown by a circle in FIG. 13 as the relationship between the positive / negative electrode capacity ratio and the battery voltage increase period.

  Further, the battery capacity of each of the eight types of batteries 100 described above was measured. Specifically, for each battery 100, in a temperature environment of 25 ° C., from a state of SOC 100% (battery voltage value 4.1V) to a state of SOC 0% (battery voltage value 3.0V), 2A Discharge (CCCV discharge) was performed at a constant current, and the amount of electricity discharged at this time was obtained as the battery capacity. This result is shown by Δ in FIG. 13 as the relationship between the positive / negative electrode capacity ratio and the battery capacity.

  As can be seen from FIG. 13, as the positive / negative electrode capacity ratio (negative electrode capacity / positive electrode capacity) is increased, the battery voltage increase period after the start of standing in the second self-discharge process can be shortened. However, as the positive / negative electrode capacity ratio (negative electrode capacity / positive electrode capacity) increases, the battery capacity decreases. It is not preferable that the battery capacity is reduced. From the above results, by setting the positive / negative electrode capacity ratio (negative electrode capacity / positive electrode capacity) within the range of 1.4 to 1.9, the battery voltage increase period after the start of standing in the second self-discharge process is shortened. (Within 2.5 days) and sufficient battery capacity can be ensured.

  In particular, by setting the positive / negative electrode capacity ratio (negative electrode capacity / positive electrode capacity) within the range of 1.7 to 1.9, the battery voltage increase period after the start of standing in the second self-discharge step is extremely shortened ( Within a day). In other words, by setting the positive / negative electrode capacity ratio (negative electrode capacity / positive electrode capacity) within the range of 1.7 to 1.9, the battery voltage is quickly reduced after starting to stand in the second self-discharge process. It becomes like this. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

For example, in the assembly process, Li _X MO ₂ having an _X value of 1.08 is used as the positive electrode active material 137, the thickness of the carbon layer 139 of the positive electrode plate 130 is 2 μm, and the negative electrode active material 127 is A negative electrode active material in which the amorphous carbon content is in the range of 6 wt% and the negative electrode active material particles have a BET specific surface area of 3.3 m ² / g; The thickness of the insulating layer 129 is 4 μm, the capacity ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.7 to 1.9, and the concentration of difluorophosphate in the electrolyte 160 By making 0.038 mol / L, the battery voltage increase period in the second self-discharge process can be made within one day. Thereby, the second self-discharge period can be made within 4 days.

  On the other hand, by setting the positive / negative electrode capacity ratio (negative electrode capacity / positive electrode capacity) within the range of 1.4 to 1.6, in particular, a decrease in battery capacity can be suppressed (see Δ in FIG. 13). ). Thereby, the battery 100 with a large battery capacity can be obtained.

(Preferred thickness of metal oxide insulating layer of negative electrode plate)
Next, the preferable thickness was investigated about the metal oxide insulating layer 129 of the negative electrode plate used at an assembly | attachment process. Note that the metal oxide insulating layer 129 contains aluminum oxide (alumina) and polyvinylidene fluoride in a weight ratio of 95: 5.

  Specifically, first, a battery 100 was manufactured in the same manner as steps S1 to S9 in Example 1. However, for the negative electrode plate 120, eight types of negative electrode plates differing only in the thickness of the metal oxide insulating layer 129 were prepared. Using these negative electrode plates, eight types of batteries 100 in which only the thickness of the metal oxide insulating layer 129 was different were produced. Thereafter, the above-mentioned leaving test (leaving as in the second self-discharge step) was performed, and the battery voltage increase period from the start of leaving was examined for each battery 100. The result is shown by a circle in FIG. 14 as the relationship between the thickness of the metal oxide insulating layer and the battery voltage increase period.

  Further, the internal resistance (IV resistance) of each of the eight types of batteries 100 described above was measured. Specifically, each battery 100 is charged, and each battery voltage value is set to 3.6 V (SOC 40%). Thereafter, each battery 100 is discharged at a constant current of 40 A for 2 seconds in a low temperature environment of −30 ° C., and the battery voltage value Vb at the end of discharge (moment of completion) is measured. Next, a value (= ΔV / 40) obtained by dividing the battery voltage change ΔV (= 3.6-Vb) changed by the discharge by the current value 40A was obtained as an IV resistance value (internal resistance value). These results are shown by Δ in FIG. 14 as the relationship between the thickness of the metal oxide insulating layer and the internal resistance (IV resistance) of the battery.

  As can be seen from FIG. 14, increasing the thickness of the metal oxide insulating layer of the negative electrode plate can shorten the battery voltage increase period after the start of standing in the second self-discharge step. However, as the thickness of the metal oxide insulating layer is increased, the internal resistance of the battery (in particular, the internal resistance in a low temperature environment) increases. A battery having a large internal resistance is not preferable. From the above results, by setting the thickness of the metal oxide insulating layer of the negative electrode plate within the range of 2 to 8 μm, the battery voltage increase period after the start of standing in the second self-discharge process is shortened (within 2 days) It can be said that the internal resistance of the battery in a low temperature environment can be reduced.

  In particular, by setting the thickness of the metal oxide insulating layer within the range of 7.5 to 8 μm, the battery voltage increase period after the start of standing in the second self-discharge process is extremely shortened (the voltage increase period is 1.. Within 5 days). In other words, by setting the thickness of the metal oxide insulating layer to be in the range of 7.5 to 8 μm, the battery voltage quickly decreases after starting to stand in the second self-discharge step. Thereby, the period concerning a 2nd self-discharge process can be shortened very much.

For example, in the assembly process, Li _X MO ₂ having an _X value of 1.08 is used as the positive electrode active material 137, the thickness of the carbon layer 139 of the positive electrode plate 130 is 2 μm, and the negative electrode active material 127 is A negative electrode active material in which the amorphous carbon content is in the range of 6 wt% and the negative electrode active material particles have a BET specific surface area of 3.3 m ² / g; The thickness of the insulating layer 129 is 7.5 to 8 μm, the capacity ratio between the positive electrode capacity and the negative electrode capacity (negative electrode capacity / positive electrode capacity) is 1.5, and the concentration of difluorophosphate in the electrolyte 160 By making 0.038 mol / L, the battery voltage increase period in the second self-discharge process can be made within 1.5 days.

  On the other hand, by setting the thickness of the metal oxide insulating layer within the range of 2 to 7 μm, in particular, the internal resistance of the battery (particularly, the internal resistance under a low temperature environment) can be reduced (Δ in FIG. 14). See the sign). Thereby, the battery 100 excellent in output characteristics (particularly, output characteristics in a low temperature environment) can be obtained.

(Preferred thickness of carbon layer of positive electrode plate)
Next, the preferable thickness was investigated about the carbon layer 139 of the positive electrode plate used at an assembly | attachment process. The carbon layer 139 contains acetylene black and polyvinylidene fluoride in a weight ratio of 3: 7.

  Specifically, first, a battery 100 was manufactured in the same manner as steps S1 to S9 in Example 1. However, as the positive electrode plate 130, eight types of positive electrode plates having different thicknesses of the carbon layer 139 were prepared. Using these positive electrode plates, eight types of batteries 100 in which only the thickness of the carbon layer 139 was different were produced. Thereafter, the above-mentioned leaving test (leaving as in the second self-discharge step) was performed, and the battery voltage increase period from the start of leaving was examined for each battery 100. The result is shown by a circle in FIG. 15 as the relationship between the thickness of the carbon layer and the battery voltage increase period.

  Further, the internal resistance (IV resistance) of each of the eight types of batteries 100 described above was measured. Specifically, each battery 100 is charged, and each battery voltage value is set to 3.6 V (SOC 40%). Thereafter, each battery 100 is discharged at a constant current of 40 A for 2 seconds under a temperature environment of 25 ° C., and the battery voltage value Vb at the end of discharge (the moment when it is finished) is measured. Next, a value (= ΔV / 40) obtained by dividing the battery voltage change ΔV (= 3.6-Vb) changed by the discharge by the current value 40A was obtained as an IV resistance value (internal resistance value). These results are shown by Δ in FIG. 15 as the relationship between the thickness of the carbon layer and the internal resistance (IV resistance) of the battery.

  As can be seen from FIG. 15, increasing the thickness of the carbon layer of the positive electrode plate can shorten the battery voltage increase period after the start of standing in the second self-discharge process. However, if the thickness of the metal oxide insulating layer is increased too much, the internal resistance of the battery increases. A battery having a large internal resistance is not preferable. From the above results, by setting the thickness of the carbon layer of the positive electrode plate within the range of 1 to 5 μm, the battery voltage increase period after the start of standing in the second self-discharge process is shortened (within 2 days). It can be said that the internal resistance of the battery can be reduced.

  In particular, by setting the thickness of the metal oxide insulating layer within the range of 1 to 3 μm, the battery internal resistance can be particularly reduced. Thereby, the battery 100 excellent in output characteristics can be obtained.

In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, although step S2 (battery restraint process) and step S8 (restraint release process) are provided in the embodiment, a lithium ion secondary battery may be manufactured without providing these processes. That is, you may make it perform the process of step S3-S7, without putting the lithium ion secondary battery 100 produced in the assembly | attachment process (step S1) between the pressing jigs 30 and 40, and making it a restraint state.

  In step S6 (capacity measurement step), a part (60%) of the battery capacity is measured for the battery 100, but the whole battery capacity may be measured. Specifically, first, the lithium ion secondary battery 100 is charged to an SOC of 100% (battery voltage value is 4.1 V), and then the battery 100 is discharged to have a battery voltage value of 4.1 V (SOC100 %) To 3.0 V (SOC 0%), the amount of discharged electricity (this corresponds to the battery capacity) is measured. A battery in which the amount of discharged electricity (battery capacity) is out of the allowable range is removed as a defective product (for example, discarded).

30, 40 Pressing jig 100 Lithium ion secondary battery (battery)
DESCRIPTION OF SYMBOLS 110 Electrode body 120 Negative electrode plate 121 Negative electrode active material layer 122 Opposing part 127 Negative electrode active material 128 Negative electrode current collecting plate 130 Positive electrode plate 131 Positive electrode active material layer 137 Positive electrode active material 138 Positive electrode current collecting plate 150 Separator 160 Electrolytic solution 180 Battery case 200 Battery Column

Claims (6)

An assembly process for producing a battery in which an electrode body having a positive electrode active material and a negative electrode active material and an electrolytic solution containing difluorophosphate are housed in a battery case;
An initial charging step for initially charging the battery after the assembly step;
An aging process in which the battery after the initial charging process is aged at a predetermined temperature for a fixed time; and
A first self-discharge step in which the battery that has finished the aging step is self-discharged by being left for a predetermined period;
A capacity measuring step for measuring part or all of the battery capacity of the battery after the self-discharge step;
An internal resistance measurement step of measuring the internal resistance of the battery after the capacity measurement step;
A plurality of the batteries having undergone the internal resistance measurement step are prepared, and these batteries are arranged in one or a plurality of rows to form one or a plurality of battery rows, and the battery row is pressed from both ends. A battery array restraining step to be in a restrained state sandwiched between tools,
A second self-discharge step of self-discharging each of the batteries constituting the battery row by leaving the battery row in the restrained state, and a method of manufacturing a lithium ion secondary battery,
The second self-discharge step is
If the battery voltage value rises after starting to leave the battery row, leave the battery row in the restrained state for a specified period after the rising period of the battery voltage value, or
If the battery voltage value decreases without increasing after starting to leave the battery row, leave the battery row in the restrained state for the specified period after starting to leave the battery row,
A step of self-discharging the battery forming the battery row;
In the assembling step, a method of manufacturing a lithium ion secondary battery that produces a battery that satisfies at least one of the following conditions (1) to (4).
(1) The positive electrode active material is Li _x MO ₂ (M is Ni or Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mg in addition to Ni as the main component) , Ga, Zr, or Si), and satisfies 1.04 ≦ X ≦ 1.15.
(2) The BET specific surface area of the particles of the negative electrode active material is in the range of 2.8 to 5.2 m ² / g.
(3) The negative electrode active material particles are composed of graphite and amorphous carbon, and the ratio of the amorphous carbon in the negative electrode active material particles is in the range of 2.5 to 7.1 wt%. .
(4) The concentration of the difluorophosphate in the electrolytic solution is in the range of 0.01 to 0.076 mol / L. It is a manufacturing method of the lithium ion secondary battery according to claim 1,
A manufacturing method of a lithium ion secondary battery using Li _x MO ₂ satisfying 1.09 ≦ X ≦ 1.15 under the condition (1). It is a manufacturing method of the lithium ion secondary battery according to claim 1 or 2,
Regarding the condition (2), a method for producing a lithium ion secondary battery in which the negative electrode active material particles have a BET specific surface area within a range of 4.0 to 5.2 m ² / g. It is a manufacturing method of the lithium ion secondary battery as described in any one of Claims 1-3,
Regarding the condition (3), a method for producing a lithium ion secondary battery in which the proportion of the amorphous carbon in the negative electrode active material particles is in the range of 2.5 to 4.6 wt%. It is a manufacturing method of the lithium ion secondary battery as described in any one of Claims 1-4, Comprising:
Regarding the condition (4) above, a method for producing a lithium ion secondary battery, wherein the concentration of the difluorophosphate in the electrolytic solution is in the range of 0.01 to 0.015 mol / L. It is a manufacturing method of the lithium ion secondary battery as described in any one of Claims 1-5, Comprising:
After the assembling step, before the initial charging step, the battery that has finished the assembling step is provided with a battery restraining step that is sandwiched between pressing jigs,
After the internal resistance measurement step, before the battery row restraint step, comprising a restraint release step of releasing the restraint of the battery performed in the battery restraint step,
In all of the initial charging step, the aging step, the first self-discharge step, the capacity measuring step, and the internal resistance measuring step, the battery is a method for manufacturing a lithium ion secondary battery in the restrained state.

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