JP5867364B2 - Method for producing non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a method for producing a nonaqueous electrolyte secondary battery having an electrolyte solution to which a redox shuttle agent is added.

  Conventionally, a technique related to a non-aqueous electrolyte secondary battery in which a redox shuttle agent (oxidation-reduction reagent) is added to an electrolytic solution for overcharge protection of the battery is known (see, for example, Patent Document 1).

  In Patent Document 1, a predetermined organic compound is used as the redox shuttle agent, and the molecular weight of the redox shuttle agent is regulated (500 or less) from the relationship between the concentration and diffusion rate of the redox shuttle agent in the electrolyte solution. A battery is disclosed.

JP-A-7-302614

  However, like the non-aqueous electrolyte secondary battery described in Patent Document 1, even if the molecular weight of the redox shuttle agent is defined, the effect of adding the redox shuttle agent may not be exhibited well depending on the addition amount. Further, in a non-aqueous electrolyte secondary battery, during overcharging, metal ions that are released from the positive electrode body and should be inserted or occluded in the negative electrode body are not deposited by the negative electrode body, but are deposited as metal. It may not contribute to the discharge reaction. For example, in a lithium ion secondary battery in which the metal ion is Li ion, Li may be deposited on the negative electrode body during overcharge. Since Li deposited on the negative electrode body can no longer contribute to the charge / discharge reaction of the battery, there is a problem that the battery capacity decreases when Li deposition increases by repeating the overcharge state.

  Then, this invention is made | formed in view of the said subject, and it aims at providing the manufacturing method of the nonaqueous electrolyte secondary battery which suppressed the capacity | capacitance fall by metal precipitation, such as Li at the time of overcharge. .

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1,
In a method for producing a non-aqueous electrolyte secondary battery that is mounted on a vehicle as a vehicle driving power source and has an electrolyte solution to which a redox shuttle agent is added,
Input of the same voltage range as the oxidation-reduction potential of the redox shuttle agent to the non-aqueous electrolyte secondary battery within 1 second after the accelerator is turned off at the maximum speed assumed for actual traveling of the vehicle (current × time [ The numerical value A [A · s] corresponding to A · s]) is calculated , and the redox shuttle agent of A / 96500 [mol] or more and 2.5A / 96500 [mol] or less is added to the electrolytic solution. It is a manufacturing method of a water electrolyte secondary battery.

In claim 2,
The lower limit value of the oxidation-reduction potential of the redox shuttle agent is a method for producing a non-aqueous electrolyte secondary battery that is equal to or higher than the upper limit value of a specified charging voltage of the non-aqueous electrolyte secondary battery.

In claim 4,
The redox shuttle agent has a redox potential of 4.2 to 4.4 V in the method for producing a non-aqueous electrolyte secondary battery.

In claim 5,
The redox shuttle agent is a method for producing a non-aqueous electrolyte secondary battery that is biphenyl or a biphenyl derivative.

  According to the present invention, it is possible to suppress a decrease in battery capacity due to metal deposition such as Li during overcharge.

The perspective view which shows the whole structure of the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention. Similarly, front sectional drawing which shows the inside of a nonaqueous electrolyte secondary battery. The figure which shows the vehicle carrying a nonaqueous electrolyte secondary battery. The figure which shows the flow of the manufacturing method of a nonaqueous electrolyte secondary battery. Explanatory drawing for demonstrating the principle of Li precipitation tolerance improvement by biphenyl addition amount and an electron transfer reaction. The graph which shows the capacity | capacitance maintenance factor of the battery in biphenyl addition amount. The graph which shows the capacity | capacitance maintenance factor of the battery in biphenyl addition amount.

Next, embodiments of the invention will be described.
First, the configuration of a battery 10 to which a method for manufacturing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention is applied will be described with reference to FIGS. 1 and 2. The battery 10 is a non-aqueous electrolyte secondary battery (in this embodiment, a lithium ion secondary battery) configured to be chargeable / dischargeable, and is mounted on a vehicle 100 (see FIG. 3) as a vehicle driving power source. It is a non-aqueous electrolyte secondary battery having an electrolyte solution 11 to which a redox shuttle agent is added. The battery 10 is a power source for driving a motor (electric motor) mounted on the vehicle as a drive source of the vehicle such as a hybrid vehicle or an electric vehicle. Hereinafter, the battery 10 will be specifically described.

  As shown in FIGS. 1 and 2, the battery 10 includes a charge / discharge element 1, a battery case 2 that houses the charge / discharge element 1 therein, a pair of external terminals 3, 3 that protrude from the upper surface of the battery case 2, and the like. And mainly.

  The charge / discharge element 1 is an electrode body in which a positive electrode and a negative electrode are stacked via a separator and wound a plurality of times. The laminated part of the positive electrode and the negative electrode carries a positive electrode active material or a mixture containing a negative electrode active material, respectively. An electrolytic solution 11 is immersed in the charge / discharge element 1 (see FIG. 2). The charge / discharge element 1 is charged / discharged by a chemical reaction between the positive electrode and the negative electrode in the laminated portion.

  The positive electrode is prepared by mixing a positive electrode active material capable of inserting and extracting lithium ions with a conductive material, a binder, a thickener, and other electrode materials using a dispersion solvent to prepare a paste mixture, It is applied to the surface of a sheet-like current collector made of metal foil (for example, aluminum foil), and after drying the current collector coated with the positive electrode mixture, the current collector is pressed to form a positive electrode active material. Manufactured through a roll press that increases density.

As the positive electrode active material, a positive electrode active material such as a lithium transition metal composite oxide can be used. As the positive electrode active material, for example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , and a lithium transition metal composite oxide in which a part thereof is substituted with another element can be used.

  The conductive material is for ensuring the electrical conductivity of the positive electrode. As the conductive material, carbon material powders such as natural graphite, artificial graphite, acetylene black (AB), and carbon black can be used.

  The binder (binder) plays a role of holding the particles of the positive electrode active material, the particles of the conductive material, and the like, and includes polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and styrene-butadiene. A copolymer (SBR), a fluorine-containing resin such as fluororubber, or a thermoplastic resin such as polypropylene can be used.

The thickener is for imparting viscosity to the positive electrode active material paste and the negative electrode active material paste. As the thickener, for example, polyethylene oxide (PEO), polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and the like are used.
The thickener is used when it is desired to give the positive electrode active material paste or the negative electrode active material paste viscous, and may be used as appropriate.

  The negative electrode is not particularly limited as long as it can use a negative electrode active material having the characteristics of occluding lithium ions during charging and releasing lithium ions during discharging. Examples of the material having such characteristics include lithium metal, carbon materials such as graphite and amorphous carbon, and the like. Among them, it is preferable to use a carbon material having a relatively large voltage change with charging / discharging of lithium ions, and it is more preferable to use a carbon material made of natural graphite or artificial graphite having high crystallinity. The particles of the negative electrode active material are held together using the binder as described above. The negative electrode is made of a metal foil (for example, copper foil), etc., prepared by mixing a negative electrode active material, a binder, a thickener, and other electrode materials using a dispersion solvent to prepare a paste. The current collector is coated on the surface of a sheet-like current collector, and after the current collector coated with the negative electrode mixture is dried, the current collector is pressed to increase the density of the negative electrode active material.

  The separator is for electrically insulating the positive electrode and the negative electrode and holding the non-aqueous electrolyte. Examples of the material constituting the separator include a porous synthetic resin film, particularly a porous film such as a polyolefin-based polymer (polyethylene, polypropylene).

  The battery case 2 is a rectangular parallelepiped metal member that houses the charge / discharge element 1 therein. The battery case 2 is formed as a rectangular battery container by the case body 2a, the lid body 2b, and the like.

  The case body 2a is a bottomed rectangular tube-shaped member having one surface (the upper surface in FIG. 1) opened, and the charge / discharge element 1 is accommodated therein.

The lid 2b is a flat plate member having a shape corresponding to the opening surface of the case body 2a (in the present embodiment, a substantially rectangular shape in plan view), and is a member for closing the opening surface of the case body 2a. The lid 2b includes a safety valve 6 at a substantially central portion thereof. In the lid 2b, a liquid injection hole 4 is formed between the safety valve 6 and one of the external terminals 3 and 3. The lid 2b is joined to the case body 2a by laser welding or the like with the opening surface of the case body 2a closed. Examples of the material constituting the case main body 2a and the lid body 2b include aluminum and aluminum alloys.
In addition, although the battery 10 of the present embodiment is configured as a prismatic battery in which the case body 2a is formed in a bottomed rectangular tube shape, the present invention is not limited to this. For example, the case body has a bottomed shape. It is also possible to apply to a cylindrical battery formed in a cylindrical shape.

  One of the external terminals 3 and 3 is a positive terminal, and the other is a negative terminal. The external terminals 3 and 3 are electrode terminals serving as connection paths for charging / discharging with the outside of the battery 10. As for the external terminals 3 and 3, a part of the external terminals 3 and 3 protrudes outward from the battery case 2. As shown in FIG. 2, the external terminals 3 and 3 are electrically connected to the positive electrode or the negative electrode of the charge / discharge element 1 through the current collecting terminals 7 and 7. The external terminals 3 and 3 are fixed to the lid body 2b through an insulating member.

  The liquid injection hole 4 is a through hole that penetrates the lid body 2b in the thickness direction of the lid body 2b. The liquid injection hole 4 is used for injecting the electrolytic solution 11 into the battery case 2 in which the charge / discharge element 1 is accommodated in advance. After the electrolyte solution 11 is injected through the injection hole 4, the injection hole 4 is sealed by the sealing member 5.

The electrolytic solution 11 is prepared as a solution in which a predetermined amount of a solute serving as an electrolyte and a predetermined redox shuttle agent are dissolved in a non-aqueous solvent (organic solvent). As the non-aqueous solvent, carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), propylene carbonate (PC), vinylene carbonate (VC) are used. Although preferable, it is not limited to these. Moreover, a non-aqueous solvent can also be used individually by 1 type, or can also be used as a mixed solvent combining 2 or more types. As the electrolyte, lithium salts such as LiPF ₆ , LiClO ₄ , and LiBF ₄ can be used. The redox shuttle agent is added to the electrolyte solution 11 in a predetermined addition amount.

The redox shuttle agent suppresses the battery voltage (potential difference between positive and negative electrodes) from exceeding the predetermined value (specifically, the reaction potential of the redox shuttle agent) due to the redox shuttle reaction of the redox shuttle agent itself. It is a compound which has the function to do. The redox shuttle agent is added to the electrolyte 11 of the battery 10 in a predetermined amount, thereby causing the redox shuttle agent to undergo an oxidation-reduction reaction when the battery 10 is overcharged, and the battery energy (overcharge current input) in the overcharged state. ) And the overcharge of the battery 10 can be suppressed. That is, the redox shuttle agent is oxidized (donation of electrons) at the positive electrode when the battery voltage becomes equal to or higher than the reaction potential of the redox shuttle agent during charging, and the oxidized redox shuttle agent moves from the positive electrode to the negative electrode and is reduced at the negative electrode. (Reception of electrons), the reduced redox shuttle agent moves from the negative electrode to the positive electrode. Thus, the redox shuttle agent consumes overcharge current by repeating the oxidation-reduction reaction and the movement (reciprocation) between the positive electrode and the negative electrode in the electrolytic solution 11 (this is called an electron transfer reaction or a redox shuttle reaction). The overcharge of the battery 10 can be continuously suppressed.
The redox shuttle agent according to the present invention utilizes the redox shuttle reaction of the redox shuttle agent (reversible reaction between an oxidation reaction and a reduction reaction), and the redox shuttle agent dissolved in the electrolytic solution 11 contains the redox shuttle agent. It has a function of performing an electron transfer reaction (redox shuttle reaction) between the redox shuttle agent and the positive and negative electrodes by applying a redox potential specific to the redox shuttle agent.

  As the redox shuttle agent, an organic compound which can be dissolved in a predetermined electrolytic solution and can perform a redox shuttle reaction as described above can be appropriately used. However, the redox shuttle agent needs to be appropriately selected according to the upper limit value of the prescribed charging voltage of the battery 10 (hereinafter referred to as the upper limit charging voltage). Specifically, when a redox shuttle agent is selected for a non-aqueous electrolyte secondary battery having an arbitrary battery voltage, the lower limit value of the oxidation-reduction potential of the redox shuttle agent is the specified charging voltage of the battery 10. It is preferable that the upper limit value or more. For example, in the case of a 4V class non-aqueous electrolyte secondary battery, when the upper limit charging voltage is set to 4.2 V, as described above, the redox shuttle agent is used as a redox shuttle agent in order to consume the overcharge current by the redox shuttle reaction. It is necessary to have a redox potential of 2V or higher.

  Examples of the redox shuttle agent include aromatic compounds, heterocyclic complexes, metallocene complexes such as ferrocene, Ce compounds, and radical compounds. Depending on the magnitude of the redox potential, the redox shuttle agent is a 3V class non-aqueous electrolyte secondary battery if the redox potential is about 3V, and 4V class non-aqueous if the redox potential is about 4V. It is preferably used for an electrolyte secondary battery. Moreover, a redox shuttle agent can also be used individually by 1 type, or can also be used in combination of 2 or more type.

  For example, biphenyl (BP) or a biphenyl derivative is preferable as a redox shuttle agent made of an aromatic compound that can be applied to a 4V class non-aqueous electrolyte secondary battery. That is, biphenyl or a biphenyl derivative has an oxidation-reduction potential of about 4 V, and can be suitably used for a 4 V class secondary battery as a redox shuttle agent. For example, since the oxidation-reduction potential of biphenyl is about 4.2 to 4.4 V, biphenyl can be used as a redox shuttle agent for a 4 V class non-aqueous electrolyte secondary battery. In this case, if the upper limit charging voltage is set to 4.2 V in the 4 V class non-aqueous electrolyte secondary battery, it is an overcharged state of 4.2 V or more which is the upper limit charging voltage during charging, and the range of the charging voltage is When an overcharged state of about 4.2 to 4.4 V is reached, the redox shuttle reaction is started as described above, and the overcharge current is consumed, thereby suppressing the battery 10 from being overcharged to 4.2 V or more. And the overcharge suppression effect which is a function of a redox shuttle agent can be acquired. In order to obtain a particularly effective overcharge suppression effect by adding the redox shuttle agent to the electrolyte solution 11, it is necessary to set a suitable addition amount of the redox shuttle agent to the electrolyte solution 11. However, a suitable addition amount of the redox shuttle agent will be described later.

Further, in order to appropriately set the oxidation-reduction potential of biphenyl with respect to the upper limit charging voltage of the battery 10 or to obtain solubility according to the electrolytic solution 11 to be used, biphenyl derivatives obtained by appropriately adding various substituents to biphenyl. It is also possible to use.
In addition, as an aromatic compound suitable as a redox shuttle agent, it is not limited to biphenyl or a biphenyl derivative. For example, it is possible to use an aromatic compound having 2 to 5 benzene rings due to the structure of the redox shuttle agent. Furthermore, an aromatic compound having at least one functional group R on the benzene ring and having a straight chain of 2 or less can also be used.

  Next, the configuration of the vehicle 100 according to the embodiment of the present invention will be described. The vehicle 100 is a hybrid vehicle on which an assembled battery 23 including a plurality of batteries 10 is mounted. Hereinafter, the vehicle 100 will be described.

  As shown in FIG. 3, the vehicle 100 includes an engine 20, a motor (electric motor) 21, a generator (generator) 22, an assembled battery 23, an inverter 24, a power split mechanism 25, a speed reducer 26, an accelerator position sensor 27, and driving wheels. 28, a hybrid control device 29, a vehicle body 30, and the like. The engine 20, the motor 21, and the generator 22 are connected to the speed reducer 26 and the drive wheels 28 via the power split mechanism 25. The vehicle 100 has an engine 20 and a motor 21 as its drive source, and can travel with power from the engine 20 or the motor 21.

  The engine 20 is an internal combustion engine that outputs power using fuel such as gasoline. The engine 20 can drive the vehicle 100 and also drive the generator 22.

  The motor 21 is driven by electric power supplied by the assembled battery 23 (battery 10), and is an electric motor mainly for assisting the output of the engine 20. The motor 21 also functions as a generator that generates regenerative power using regenerative energy generated when the vehicle 100 is braked. Driving of the engine 20 and the motor 21 is controlled by a hybrid control device 29.

  The generator 22 is a generator that is driven by the power of the engine 20 and generates electric power to be supplied to the motor 21. The electric power generated by the generator 22 is supplied to the assembled battery 23 via the inverter 24.

  The assembled battery 23 is configured by arranging a plurality of batteries 10 in a rectangular box-shaped case. The plurality of batteries 10 are connected in series to each other via a bus bar (not shown). The assembled battery 22 has a function of charging power generated by the motor 21 and the generator 22 and supplying the charged power to the motor 21. As described above, the assembled battery 23 (battery 10) uses a carbon material such as graphite for the negative electrode and a lithium compound such as lithium cobaltate for the positive electrode, and reversibly moves lithium ions between the electrodes. This is a secondary battery that is charged and discharged. As will be described in detail later, in the assembled battery 23 (battery 10), since the lithium metal is deposited on the negative electrode surface when the charging voltage becomes too high, the redox shuttle agent as described above is used so that the charging voltage does not become too high. Controlled.

  The inverter 24 is a device that converts a direct current supplied from the assembled battery 23 into an alternating current and supplies the alternating current to the motor 21. The inverter 24 is a device that converts alternating current generated by the generator 22 or regeneratively generated by the motor 21 into direct current. The converted direct current is supplied to the assembled battery 23, and the assembled battery 23 (battery 10) is Charged.

  The power split mechanism 25 is a mechanism that is coupled to the engine 20, the motor 21, and the generator 22 and splits the power among them.

  The speed reducer 26 decelerates the power transmitted from the engine 20 and the motor 21 and transmits the decelerated power to the drive wheels 28.

  The accelerator position sensor 27 is means for detecting the accelerator opening (the amount of operation of the accelerator) of an accelerator (not shown) that the vehicle 100 has. The accelerator position sensor 27 can detect the accelerator opening numerically in the range of 0 to 100%. When the accelerator opening is 100%, the accelerator is depressed most when the accelerator is depressed, and when the accelerator opening is 0%, the accelerator is depressed when the accelerator is not depressed.

  The hybrid control device 29 is connected to the engine 20, the motor 21, the generator 22, the inverter 24, and the accelerator position sensor 27, and has a function of comprehensively controlling a hybrid system including these components. The hybrid control device 29 mainly includes a microcomputer including a CPU, a ROM, a RAM, and the like, and controls the hybrid system by executing a control program for controlling the hybrid system by the microcomputer. When the driver drives the vehicle 100, the hybrid control device 29 reduces the accelerator opening so that the driver has a driving feeling equivalent to that of an engine vehicle equipped with only an engine as a drive source. Control is performed to decelerate the vehicle in the same manner as engine braking occurs in an engine vehicle. At that time, the hybrid control device 29 regenerates the motor 21 interlocked with the drive wheels 28 to generate electric energy, and the assembled battery 23 (battery 10) is charged with this electric energy.

  For example, when the vehicle 100 as described above is traveling in a state where the accelerator opening is high, if the accelerator is suddenly turned off and the motor 21 is shifted to the regenerative operation, an excessive charging current is generated at the beginning of regeneration. 23 (battery 10). Specifically, when the vehicle 100 is traveling at the maximum speed assumed as actual traveling (for example, about 100 km / h in Japan), the accelerator 21 is suddenly turned off and the motor 21 is shifted to the regenerative operation. At the beginning of regeneration, the most excessive charging current flows to the assembled battery 23 (battery 10). Thus, when an excessive charging current flows through the assembled battery 23 (battery 10), metallic lithium is deposited on the negative electrode of the battery 10, and the battery capacity of the battery 10 is reduced. Therefore, a method for manufacturing a non-aqueous electrolyte secondary battery in which a decrease in battery capacity due to lithium deposition during overcharge will be described below.

  Next, the manufacturing method of the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention is demonstrated using FIG. The manufacturing method of the nonaqueous electrolyte secondary battery is a manufacturing method of the battery 10 that is mounted on the vehicle 100 as a vehicle driving power source and includes the electrolytic solution 11 to which the redox shuttle agent is added. The manufacturing method of the non-battery 10 is a process for preparing the electrolytic solution 11 used when the battery 10 is manufactured.

  As shown in FIG. 4, the manufacturing method of the battery 10 includes a calculation step S10 and an addition step S20.

  In the calculation step S10, the input of the same voltage range as the oxidation-reduction potential of the redox shuttle agent to the battery 10 within 1 second after the accelerator is turned off at the maximum speed assumed as the actual traveling of the vehicle 100 (current × time [A This is a step of calculating a numerical value A [A · s] corresponding to s]). Here, the “maximum speed assumed as the actual driving of the vehicle” is not the maximum speed (maximum speed as the vehicle specifications) that can be obtained from the performance of the vehicle, but actually on a highway having a legal speed, etc. The maximum speed as the upper limit of the speed that can be delivered. For example, on a highway in Japan, the legal maximum speed is currently 100 km / h, and this speed is used as a reference for the maximum speed. In calculating the numerical value A, an error margin of the vehicle speed detection value is taken into consideration, and a value obtained by adding the error margin to the numerical value A corresponding to the maximum speed 100 km / h (when the error margin is considered as 10%, A numerical value A) corresponding to a vehicle speed of 110 km / h may be used. When the motor 21 is shifted to the regenerative operation after the accelerator is off (in a state where the accelerator opening is 0%) at the maximum speed assumed for actual traveling of the vehicle 100, the vehicle 100 can be considered as the vehicle 100 in one second at the beginning of regeneration. An excessive charging current flows to each battery 10 of the assembled battery 23, and each battery 10 is in the most excessive overcharged state.

  Further, the lower limit value of the redox potential of the redox shuttle agent may be set to be equal to or higher than the upper limit value of the specified charging voltage of the battery 10. By setting in this way, when the battery 10 is overcharged, the redox shuttle reaction by the redox shuttle agent can be immediately advanced.

  In the calculation step S10, assuming that each battery 10 is in the most excessive overcharge state as described above, the input to the battery 10 in this case is calculated in advance as a numerical value A [A · s]. The numerical value A indicates the charging current (overcharge current) [A] in the same voltage range as the redox shuttle redox potential and the input time (charging time) [s] (specifically, the elapsed time after the accelerator is turned off. It is expressed as a product of (one second).

  The adding step S20 is a step of adding A / 96500 [mol] or more redox shuttle agent to the electrolytic solution 11. In other words, the numerical value A [A · s] is the amount of electricity A [C] that flows when each battery 10 is in an overcharged state (A [A · s] = A [C]). When this numerical value A is divided by the Faraday constant (the amount of electricity held by 1 mol of electrons) 96500 [C / mol], the number of moles B [mol] of electrons flowing in each battery 10 can be calculated.

Specifically, when biphenyl (BP) is used as the redox shuttle agent, when the battery voltage is 4.2 V or more, which is the lower limit value of the biphenyl oxidation-reduction potential during charging, as shown in FIG. Oxidized at the positive electrode (donation of electron e ⁻ ), this oxidized biphenyl (electron acceptor) moves from the positive electrode to the negative electrode, and reduced at the negative electrode (acceptance of electron e ⁻ ), and this reduced biphenyl (electron acceptor) The donor) moves from the negative electrode to the positive electrode. Thus, when the charging voltage in the overcharged state of the battery 10 enters the voltage range of the biphenyl oxidation-reduction potential (4.2 to 4.4 V), the biphenyl delivers one electron per molecule, and the electron transfer reaction. I think that. Therefore, in order to continuously advance the electron transfer reaction as shown in FIG. 5, at least biphenyl having the number of moles B [mol] described above may be added to the electrolytic solution 11 of the battery 10 in advance. That is, in the case where the electron transfer reaction by the transfer of one electron is continuously performed by the redox shuttle agent, theoretically, the redox shuttle of at least A [A · s] / 96500 [C / mol] = B [mol]. If an agent is added to the electrolyte solution 11, an overcharge current is consumed by an electron transfer reaction (redox shuttle reaction) of the redox shuttle agent, and a decrease in battery capacity due to Li deposition due to overcharge of the battery 10 is suppressed. Can do.

  After completion of the addition step S20, the electrolyte solution 11 to which the redox shuttle agent has been added as described above is injected into the battery case 2 from the injection hole 4, and the injection hole 4 is further sealed into the sealing member 5. The battery 10 is manufactured by sealing the battery case 2 and sealing the battery case 2.

[Li precipitation durability test (accelerator on / off test)]
Next, biphenyl (BP) was added to the electrolyte solution 11 of the battery 10 described above, and an evaluation test of the capacity retention rate of the battery 10 was performed assuming that the accelerator was on / off. Specifically, the dependence of the capacity retention rate of the battery 10 on the amount of biphenyl (BP) added was tested using the amount of biphenyl (BP) added.

(Evaluation battery)
Batteries 10 with different amounts of biphenyl added were prepared as evaluation batteries. Hereinafter, a specific configuration of the battery 10 used as the evaluation battery will be described.

The positive electrode of the battery 10 has a positive electrode active material layer disposed on the surface (both sides) of a strip-shaped aluminum foil. The positive electrode active material layer is formed as a layer containing positive electrode active material particles made of LiCoO ₂ , a conductive material made of acetylene black, and a binder made of polyvinylidene fluoride (PVDF).
On the other hand, the negative electrode has a negative electrode active material layer disposed on the surface (both sides) of a strip-like copper-made copper foil. The negative electrode active material layer is formed as a layer containing negative electrode active material particles made of graphite and a binder made of polyvinylidene fluoride (PVDF).

The electrolyte solution 11 is an electrolyte solution containing LiPF ₆ as an electrolyte in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (mixed solvent having a volume ratio of about 1: 1) at a concentration of about 1 mol / liter. Used.
In addition, each battery 10 which is a battery for evaluation in this example uses an electrolytic solution in which a predetermined addition amount of biphenyl is added and dissolved as a redox shuttle agent in addition to LiPF ₆ which is an electrolyte. .

As a redox shuttle agent, 3.35 × 10 ⁻⁴ , 5.00 × 10 ⁻⁴ , 1.00 × 10 ⁻³ , 1.20 × 10 ⁻³ , 1.50 × 10 ⁻³ , 1.75 × 10 ^-3 , 2.00 × 10 ⁻³ , 2.25 × 10 ⁻³ , 2.50 × 10 ⁻³ , 2.75 × 10 ⁻³ in moles [mol] are added to the electrolyte solution 11. Thus, batteries 10 having different amounts of biphenyl added were produced as evaluation batteries. Moreover, in order to compare with the battery for evaluation which added biphenyl to the electrolyte solution 11, the battery 10 which did not add the redox shuttle agent to the electrolyte solution 11 was also manufactured as an evaluation battery.

In this embodiment, it is necessary to calculate in advance that the above-described numerical value A [A · s] is 125 [A · s] (= 125 [C]), and use this to add at least to the electrolytic solution 11. In terms of the number of moles of a redox shuttle agent [mol],
It is estimated that A [A · s] / 96500 [C / mol] = 125 [C] / 96500 [C / mol] ≈1.00 × 10 ⁻³ . In the present embodiment than this, which is the amount of biphenyl that at least it is necessary to add in order to obtain the effect of the present invention 1.00 × 10 ^-3 [mol] as a reference, the amount of the biphenyl around this reference Thus, the dependency of the volume dependency on the amount of biphenyl added was verified.

(Evaluation method of accelerator on / off test (capacity maintenance rate))
First, the battery capacity of each of the 11 evaluation batteries was measured. Specifically, each evaluation battery was charged to 4.1 V with a current value of 1.0 A, and then the current value was gradually decreased while maintaining the voltage in a temperature environment of 25 ° C. Hold for a minute (constant current-constant voltage charge). Further, for each of these evaluation batteries, constant current discharge was performed at a current value of 0.33 A to 3.0 V under a temperature environment of 25 ° C., and the discharged battery capacity was measured. In addition, each battery capacity at this time was made into the initial capacity (1C) of each battery for evaluation. For each evaluation battery for which the above measurement was performed, a charging test in which a charging current of 10 C was applied for 0.5 seconds was repeated 10,000 times. Note that this test condition (10C charging current is charged for 0.5 seconds) is when the vehicle 100 is running at the maximum speed assumed as the actual running of the vehicle 100, and the accelerator 21 is turned off to regenerate the motor 21. It is simulated that an excessive charging current flows to the assembled battery 23 (battery 10) when the operation is shifted. Thereafter, the battery capacity of each evaluation battery was measured in the same manner as described above. And the capacity maintenance rate of each battery for evaluation after a charge test was computed. This capacity maintenance ratio is obtained by dividing the value of the battery capacity after the charge test by the initial initial capacity before the charge test.
Under the above test conditions (10C charging current is charged for 0.5 seconds), when the vehicle 100 is driven with the accelerator opening in the vicinity of 100%, the accelerator 21 is turned off (accelerator opening 0%) and the motor 21 is driven. It can be said that an excessive charging current flows through the assembled battery 23 (battery 10) when the battery is shifted to the regenerative operation.

FIG. 6 and FIG. 7 show bar graphs of capacity retention rates of the batteries for evaluation at the respective amounts of biphenyl added after the charge test. The graph of FIG. 6 shows the evaluation battery to which 1.00 × 10 ⁻³ mol of biphenyl was added as the addition amount of biphenyl which is necessary to be added at least in order to obtain the effect of the present invention as described above, and biphenyl. The capacity retention rates of the evaluation batteries that were not added (0.00 × 10 ⁻³ [mol] in FIG. 6) were compared. From the results shown in FIG. 6, in the battery for evaluation to which 1.00 × 10 ⁻³ mol of biphenyl was added, the electron transfer reaction of biphenyl (redox shuttle reaction) in an overcharged state (charge voltage: 4.2 to 4.4 V). It is considered that the Li precipitation was significantly suppressed as a result of the progress of the battery as compared with the battery for evaluation to which biphenyl was not added. The graph in FIG. 7 compares the capacity retention rates of the evaluation batteries with the biphenyl addition amount based on the biphenyl addition amount of 1.00 × 10 ⁻³ mol. From the results shown in FIG. 7, when the amount of biphenyl added to the electrolytic solution 11 is 1.00 × 10 ⁻³ mol or more and 2.50 × 10 ⁻³ mol or less, the capacity retention rate of the evaluation battery is 80 to 100%. It is a neighborhood. 1.00 × 10 ^-3 mol of less than biphenyl battery for evaluation was added in ^{(3.35 × 10 -4 mol, 5.00} × 10 -4 mol), added biphenyl 1.00 × 10 ^-3 mol Compared to the evaluation battery, the capacity maintenance rate is about 20% lower. This is because the battery for evaluation to which 1.00 × 10 ⁻³ mol of biphenyl was added added the amount of biphenyl theoretically required when the above-described electron transfer reaction was continuously performed. It is thought that.

Thus, according to the above-described theory, 1/96500 [mol] of the redox shuttle agent can move 1 [A · s] of electrons, so that it is input to the battery 10 during overcharge (current × time) 1 It can be said that 1/96500 [mol] per [A · s] is the optimum value of the addition amount of biphenyl and the lower limit value. On the other hand, it can be seen that in the evaluation battery to which 2.75 × 10 ⁻³ mol of biphenyl larger than 2.50 × 10 ⁻³ mol was added, the capacity retention rate was less than 80%. This is probably because the addition of a large amount of biphenyl slows the speed of the electron transfer reaction (redox shuttle reaction) of biphenyl that moves between the electrodes. That is, it is considered that in the evaluation battery to which 2.75 × 10 ⁻³ mol of biphenyl was added, the speed of the electron transfer reaction was remarkably slow, and the effects of the present invention could not be obtained sufficiently. Therefore, by setting the amount of biphenyl added to 2.5 × 10 ⁻³ mol or less, it is possible to prevent a decrease in capacity maintenance rate accompanying a decrease in the rate of the electron transfer reaction due to an increase in the amount of added biphenyl. From the above, the optimum range of the amount of biphenyl added for obtaining the effects of the present invention is preferably 1.00 × 10 ⁻³ mol or more and 2.50 × 10 ⁻³ mol or less, and more preferably 1 It is 0.000 × 10 ⁻³ mol or more and 2.25 × 10 ⁻³ mol or less. As described above, by adding the addition amount of biphenyl to the electrolyte solution 11 within the above optimal range, it is possible to suppress a decrease in battery capacity due to Li metal deposition during overcharge.

  Further, from the result of this example, the same voltage as the redox potential of the redox shuttle agent to the non-aqueous electrolyte secondary battery within 1 second after the accelerator is turned off at the maximum speed assumed as the actual running of the vehicle. A numerical value A [A · s] corresponding to a range input (current × time [A · s]) is calculated, and the electrolyte solution has an A / 96500 [mol] or more and 2.5 A / 96500 [mol] or less. It may be desirable to add a redox shuttle agent.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the battery capacity resulting from metal precipitation, such as Li at the time of overcharge, can be suppressed by adding a redox shuttle agent with a suitable addition amount to electrolyte solution. Moreover, according to this invention, the fall of the battery capacity resulting from metal precipitation, such as Li at the time of overcharge, can be suppressed, without requiring special control and an apparatus.

10 Battery 11 Electrolyte 100 Vehicle

Claims (4)

In a method for producing a non-aqueous electrolyte secondary battery that is mounted on a vehicle as a vehicle driving power source and has an electrolyte solution to which a redox shuttle agent is added,
Input of the same voltage range as the oxidation-reduction potential of the redox shuttle agent to the non-aqueous electrolyte secondary battery within 1 second after the accelerator is turned off at the maximum speed assumed for actual traveling of the vehicle (current × time [ A / s]) is calculated, and A / 96500 [mol] or more and 2.5 A / 96500 [mol] or less of the redox shuttle agent is added to the electrolytic solution. A method for producing a non-aqueous electrolyte secondary battery.   2. The nonaqueous electrolyte secondary battery according to claim 1, wherein a lower limit value of the redox potential of the redox shuttle agent is equal to or higher than a predetermined upper limit value of a charging voltage of the nonaqueous electrolyte secondary battery. Manufacturing method. The method for producing a non-aqueous electrolyte secondary battery according to claim 1 or 2 , wherein the redox shuttle agent has an oxidation-reduction potential of 4.2 to 4.4V. The redox shuttle agent, method of manufacturing a non-aqueous electrolyte secondary battery as claimed in any one of claims 3, characterized in that the biphenyl or biphenyl derivatives.

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