JP6038560B2 - Non-aqueous electrolyte battery storage or transport method, battery pack storage or transport method, and non-aqueous electrolyte battery charge state maintaining method - Google Patents

Description

  Embodiments described herein relate generally to a method for manufacturing a nonaqueous electrolyte battery, a method for manufacturing a battery pack, and a method for using a nonaqueous electrolyte battery.

  As a large-sized and large-capacity power source used for an electric vehicle (EV), a hybrid vehicle (HEV), an electric motorcycle, a forklift, etc., a non-aqueous electrolyte battery (for example, a lithium ion battery) having a high energy density has been attracting attention. Developments for increasing the size and capacity are being carried out while considering the lifetime and safety. As a large-capacity power supply, an assembled battery including a large number of batteries connected in series or in parallel has been developed in order to increase driving power.

  Nonaqueous electrolyte batteries include lithium ion batteries using a carbon material for the negative electrode and lithium batteries using lithium titanate.

  Batteries using a lithium titanate battery as the negative electrode are superior in life characteristics, safety and input / output characteristics, particularly rapid charge characteristics, because the negative electrode potential is higher than that of the carbon negative electrode.

  On the other hand, in non-aqueous electrolyte batteries using lithium titanate for the negative electrode, it is difficult to grow a film formed by decomposition of the electrolytic solution between the electrolytic solution and the negative electrode active material. There's a problem. Therefore, if a nonaqueous electrolyte battery using lithium titanate as a negative electrode is charged and then left to stand, the amount of electricity stored in the nonaqueous electrolyte battery decreases due to self-discharge.

  In an automobile equipped with a nonaqueous electrolyte battery in which the amount of stored electricity is significantly lower than the amount of charge, it is difficult to obtain the expected travel distance.

  In addition, when assembling an assembled battery by connecting a plurality of non-aqueous electrolyte batteries using lithium titanate as a negative electrode in series, there is a risk of variations in the storage state between the batteries due to the difference in self-discharge speed. . Variation in the storage state between the batteries can adversely affect the capacity of the battery pack including the assembled battery.

Japanese Patent Laid-Open No. 10-69922 JP 2000-12090 A JP 2007-87909 A

  The problem to be solved by the present invention is to provide a method for producing a nonaqueous electrolyte battery using lithium titanate as a negative electrode, in which self-discharge is suppressed.

According to one embodiment, a method for storing or transporting a non-aqueous electrolyte battery is provided. Storage or transport method of the nonaqueous electrolyte battery according to one embodiment, a negative electrode comprising lithium titanate, the positive electrode and the nonaqueous electrolyte and the method comprising: fully charged non-aqueous electrolyte batteries comprising, fully charged non-aqueous It includes discharging the electrolyte battery and storing or transporting the nonaqueous electrolyte battery . The negative electrode includes a negative electrode active material layer including a negative electrode active material made of lithium titanate, a conductive agent, and a binder. The compounding ratios of the negative electrode active material, the conductive agent, and the binder in the negative electrode active material layer are 70 to 96% by mass, 2 to 28% by mass, and 2 to 28% by mass, respectively. The discharging performed on the charged nonaqueous electrolyte battery is performed for 0.2 seconds or more at a rate of 5C or more so that the state of charge SOC of the nonaqueous electrolyte battery is 10 to 95%. In this way, the nonaqueous electrolyte battery having a state of charge SOC of 10 to 95% is stored or transported.

According to one embodiment, a method for storing or transporting a battery pack is provided. Storage or transport method of a battery pack according to one embodiment, a negative electrode comprising lithium titanate, and the positive electrode and, fully charging the battery pack which includes a non-aqueous electrolyte battery comprising a nonaqueous electrolyte, fully charged Discharging the battery pack and storing or transporting the battery pack . The negative electrode includes a negative electrode active material layer including a negative electrode active material made of lithium titanate, a conductive agent, and a binder. The compounding ratios of the negative electrode active material, the conductive agent, and the binder in the negative electrode active material layer are 70 to 96% by mass, 2 to 28% by mass, and 2 to 28% by mass, respectively. The discharge performed on the charged battery pack is performed at a rate of 5C or more for 0.2 seconds or more so that the state of charge SOC of each nonaqueous electrolyte battery is 10 to 95%. Thus, the battery pack in which the state of charge SOC of each non-aqueous electrolyte is 10 to 95% is stored or transported.

According to one embodiment, a method for maintaining the state of charge of a non-aqueous electrolyte battery is provided. The nonaqueous electrolyte battery is connected to the electronic device unit. The nonaqueous electrolyte battery includes a negative electrode containing lithium titanate, a positive electrode, and a nonaqueous electrolyte. The negative electrode includes a negative electrode active material layer including a negative electrode active material made of lithium titanate, a conductive agent, and a binder. The compounding ratios of the negative electrode active material, the conductive agent, and the binder in the negative electrode active material layer are 70 to 96% by mass, 2 to 28% by mass, and 2 to 28% by mass, respectively. A method for maintaining a charged state of a non-aqueous electrolyte battery according to an embodiment includes: cutting off power supply from the non-aqueous electrolyte battery to the electronic device unit; fully charging the non-aqueous electrolyte battery; and fully charged non-aqueous electrolyte battery On the other hand , by discharging at a rate of 5 C or more for 0.2 seconds or more, the non-aqueous electrolyte battery is brought to a state of charge of 10 to 95%, and then the discharge is stopped. Leave the non-aqueous electrolyte battery at ˜95% .

FIG. 1 shows an example of the relationship between the distance from the surface of the negative electrode current collector of the nonaqueous electrolyte battery that can be manufactured by the manufacturing method according to the first embodiment and the relative Li + ion concentration in the negative electrode active material layer. It is the schematic diagram shown schematically. FIG. 2 is a schematic view partially enlarging an electrode group included in the nonaqueous electrolyte battery that can be manufactured by the manufacturing method according to the first embodiment. FIG. 3 is an exploded perspective view of a nonaqueous electrolyte battery that can be manufactured by the manufacturing method according to the first embodiment. FIG. 4 is a block diagram showing an electric circuit of an example of a battery pack that can be manufactured by the manufacturing method according to the second embodiment. FIG. 5 is a schematic flowchart showing an example of a procedure that can be executed when the electric vehicle is turned off according to the method of use according to the third embodiment.

  Hereinafter, embodiments will be described with reference to the drawings. In the following description, constituent elements that exhibit the same or similar functions are denoted by the same reference numerals throughout the drawings, and redundant descriptions are omitted.

(First embodiment)
According to the first embodiment, a method for manufacturing a nonaqueous electrolyte battery is provided. A method for manufacturing a nonaqueous electrolyte battery according to a first embodiment includes assembling a nonaqueous electrolyte battery including a negative electrode including lithium titanate, a positive electrode, and a nonaqueous electrolyte, and charging the assembled nonaqueous electrolyte battery. And discharging the charged nonaqueous electrolyte battery. The discharging performed on the charged nonaqueous electrolyte battery is performed for 0.2 seconds or more at a rate of 5C or more so that the state of charge SOC of the nonaqueous electrolyte battery is 10 to 95%.

  Here, SOC is an abbreviation for “state of charge”, and “charge state SOC” of a battery indicates a percentage of the amount of electricity stored in the battery with respect to the amount of electricity in a fully charged state of the battery. .

  The purpose of discharging over 0.2 seconds or more at a rate of 5C or higher is such that the charged state SOC of the nonaqueous electrolyte battery is 10 to 95% with respect to the charged nonaqueous electrolyte battery. The purpose is to suppress the self-discharge of the water electrolyte battery.

  As described above, the nonaqueous electrolyte battery using lithium titanate for the negative electrode has a fast self-discharge. This is repeated, but in a non-aqueous electrolyte battery using lithium titanate for the negative electrode, it is difficult to form a film between the non-aqueous electrolyte and the negative electrode active material layer, which causes lithium ions to be inserted by charging. This is because lithium ions are easily released from the lithium titanate in a state.

  As a result of earnest research, the inventors charged a nonaqueous electrolyte battery having an electrode group including a negative electrode containing lithium titanate, and then charged with a large current, that is, a rate of 5 C or more for 2 seconds or more. By performing discharge over a portion of the negative electrode active material layer that is in contact with the non-aqueous electrolyte, a layer having a low lithium ion concentration, that is, a lithium ion-deficient layer can be formed. It was found that self-discharge can be suppressed.

FIG. 1 shows an example of the relationship between the distance from the surface of the negative electrode current collector of the nonaqueous electrolyte battery that can be manufactured by the manufacturing method according to the first embodiment and the relative Li ⁺ ion concentration in the negative electrode active material layer. The graph shown schematically is shown.

  In FIG. 1, the horizontal axis indicates the distance from the current collector surface, the distance 0 corresponds to the negative electrode current collector surface, and the distance L corresponds to the interface between the negative electrode active material layer and the nonaqueous electrolyte. . The curve (5C) shown in the graph of FIG. 1 shows that the nonaqueous electrolyte battery including the electrode group including the negative electrode containing lithium titanate is fully charged, and then the SOC is 50% over 6 minutes at a rate of 5C. The relative lithium ion concentration in the negative electrode active material layer immediately after forcibly discharging is shown. The curve (1C) shown in the graph of FIG. 1 shows that a nonaqueous electrolyte battery including an electrode group including a negative electrode containing lithium titanate is charged to SOC 100% and then forced to SOC 50% at a rate of 1C. 3 shows the relative lithium ion concentration in the negative electrode active material layer immediately after being discharged.

  As is clear from the graph of FIG. 1, in the nonaqueous electrolyte battery discharged under the condition of the curve (5C), the distance from the portion of the negative electrode active material layer that is away from the surface of the negative electrode current collector carrying it by the distance l The lithium ion concentration is close to 0 up to a portion separated by L, that is, to the interface with the nonaqueous electrolyte. That is, it can be confirmed from FIG. 1 that a lithium ion-deficient layer is formed in the vicinity of the interface between the negative electrode active material layer and the non-aqueous electrolyte in the charged non-aqueous electrolyte battery by the discharge.

  On the contrary, when discharging is performed at a low rate as in the condition of curve (1C), a lithium-deficient layer is not formed in the vicinity of the interface between the negative electrode active material and the nonaqueous electrolyte.

  Although not wishing to be bound by theory, the inventors consider the reason why such a lithium ion deficient layer is formed as follows as a result of intensive studies.

  First, the inventors consider that the lithium ion insertion reaction of lithium titanate is a heterogeneous two-phase reaction. Here, the lithium ion insertion reaction of lithium titanate, which is a heterogeneous two-phase reaction, means that lithium titanate has an intermediate lithium ion concentration state other than the state where the lithium ion is “full” and the state “empty”. It means that it is difficult to pick.

  In addition, the inventors have found that there is a large difference in electrical characteristics, that is, conductivity and ion conductivity, between lithium titanate in which lithium ions are “full” and lithium titanate in which lithium ions are “empty”. Therefore, it is considered that the negative electrode containing lithium titanate has “hysteresis characteristics” that greatly differ in their electrical characteristics depending on the previous charge / discharge history, that is, the last charge / discharge. The difference in the electrical characteristics is that lithium titanate with lithium ions in an “empty” state has lower conductivity and ion conductivity than that with lithium ions in a “full” state.

  When such a non-aqueous electrolyte battery using lithium titanate for the negative electrode is forcibly discharged with a large current, first, lithium ions are desorbed from the lithium titanate contained in the vicinity of the interface of the negative electrode active material layer with the non-aqueous electrolyte. To do. On the other hand, as described above, lithium titanate in which lithium ions are “empty” has low ion conductivity and is difficult to pass lithium ions. Uniformity of the lithium ion concentration in the negative electrode active material layer containing lithium titanate is unlikely to occur because the lithium ions need to pass through the “empty” lithium titanate. Therefore, if forced discharge with a large current is continued, the lithium ion concentration in the negative electrode active material layer does not progress so much, and lithium ions in the negative electrode active material layer start from lithium titanate close to the interface with the nonaqueous electrolyte. Continue to detach unilaterally. As a result, as shown in FIG. 1, a lithium ion deficient layer is formed in a portion of the negative electrode active material layer that is in contact with the nonaqueous electrolyte.

  Note that even in a non-aqueous electrolyte battery using carbon or the like for the negative electrode, a lithium ion deficient layer is formed in a portion of the negative electrode active material layer in contact with the non-aqueous electrolyte by forced discharge with a large current. However, since materials such as carbon have high ion conductivity even when the lithium ion concentration is low, in a negative electrode active material layer containing a material such as carbon, even if a lithium ion deficient layer is formed, lithium in the negative electrode active material The uniform ion concentration occurs rapidly, and as a result, the lithium ion deficient layer disappears.

  On the other hand, as described above, since lithium titanate has low ion conductivity in a state where the lithium ion concentration is low, it is difficult to make the lithium ion concentration uniform in the negative electrode active material. As a result, the negative electrode active material layer Can hold the lithium ion-deficient layer for a relatively long period of time.

  Next, the reason why the lithium ion deficient layer formed in the portion of the negative electrode active material layer in contact with the non-aqueous electrolyte can suppress the self-discharge of the non-aqueous electrolyte battery will be described in detail with reference to FIG.

  FIG. 2 is a schematic view partially enlarging an electrode group included in the nonaqueous electrolyte battery that can be manufactured by the manufacturing method according to the first embodiment.

  The manufacturing method according to the first embodiment can provide the nonaqueous electrolyte battery 1 shown in FIG.

  The details will be described with further reference to FIG. 3. The nonaqueous electrolyte battery 1 shown in FIG. 2 includes an electrode group 3 including a negative electrode 31, a positive electrode 32, and a separator 33 sandwiched between the negative electrode 31 and the positive electrode 32. To do. The separator 33 is impregnated with a non-aqueous electrolyte (not shown).

  In the non-aqueous electrolyte battery 1, during charging, the positive electrode active material layer 32 b included in the positive electrode 32 passes through the separator 33, that is, the negative electrode active material layer 31 b included in the negative electrode 31 through the non-aqueous electrolyte, that is, lithium in the direction (A). Ions move. On the other hand, in the nonaqueous electrolyte battery 1, during discharge, lithium ions move from the negative electrode active material layer 31b to the positive electrode active material layer 32b via the nonaqueous electrolyte, that is, in the direction of (B). Thus, charging / discharging of the non-aqueous electrolyte battery 1 involves the movement of lithium ions through the non-aqueous electrolyte.

  In the nonaqueous electrolyte battery 1 immediately after being charged, lithium titanate in which lithium ions are “full” exists in the vicinity of the interface of the negative electrode active material layer 31b with the nonaqueous electrolyte. In a non-aqueous electrolyte battery using lithium titanate for the negative electrode, a coating is unlikely to form at this interface. Therefore, in the nonaqueous electrolyte battery 1 in such a state, lithium ions are easily detached from lithium titanate in contact with the nonaqueous electrolyte. That is, the nonaqueous electrolyte battery 1 in such a state is easily discharged.

  On the other hand, in the battery that can be manufactured according to the manufacturing method according to the first embodiment, as described with reference to FIG. 1, the lithium ion deficient layer is formed in the portion of the negative electrode active material layer 31 b that is in contact with the nonaqueous electrolyte. Yes.

  Since the lithium ion deficient layer has very few lithium ions, the amount of lithium ions moving from the surface of the negative electrode active material layer 31b to the nonaqueous electrolyte is extremely small.

  In addition, as described above, lithium titanate has lower conductivity and ion conductivity in a state where the lithium ion concentration is low than in a state where lithium ions are high. Therefore, the amount of lithium ions that enter the non-aqueous electrolyte across the lithium ion-deficient layer from a portion that is relatively rich in lithium ions adjacent to the lithium ion-deficient layer is extremely small. That is, the lithium ion deficient layer in contact with the nonaqueous electrolyte of the negative electrode active material layer can suppress the movement of lithium ions passing through the layer to the nonaqueous electrolyte.

  Thus, the nonaqueous electrolyte battery including the electrode group including the negative electrode having the lithium ion-deficient layer at the interface with the nonaqueous electrolyte can suppress the movement of lithium ions from the negative electrode active material layer to the nonaqueous electrolyte. As a result, self-discharge can be suppressed.

  The charged nonaqueous electrolyte battery is discharged at a rate of 5 C or more for 0.2 seconds or longer, so that the state of charge SOC of the nonaqueous electrolyte battery is 10 to 95%. A sufficient distance between the non-aqueous electrolyte and the lithium-rich portion adjacent to the ion-deficient layer can be secured, thereby sufficiently suppressing the movement of lithium ions from the negative electrode active material layer to the non-aqueous electrolyte. Discharge can be suppressed.

  When the charged nonaqueous electrolyte battery is discharged at a rate of less than 5 C, the distance between the lithium-rich portion adjacent to the lithium ion-deficient layer of the negative electrode active material layer and the nonaqueous electrolyte is shortened, or lithium Since the ion-deficient layer is not formed, the migration of lithium ions from the negative electrode active material layer to the non-aqueous electrolyte cannot be sufficiently suppressed. For example, when the above discharge is performed at 25 ° C. at a rate of about 1 C as shown by the curve (1C) in FIG. 1, the negative electrode active material is independent of the distance from the interface between the negative electrode active material layer and the nonaqueous electrolyte. The lithium ion concentration in the layer is uniform and easy to do. That is, under such discharge conditions, it is difficult to form a lithium ion deficient layer.

  In addition, it is difficult to form a lithium ion deficient layer in the negative electrode active material that can sufficiently suppress the movement of lithium ions even when the charged nonaqueous electrolyte battery is discharged over a period of less than 0.2 seconds. is there.

  When the charged nonaqueous electrolyte battery is discharged over a period of 0.2 seconds or more and the state of charge SOC of the nonaqueous electrolyte battery is set to less than 10%, the resulting nonaqueous electrolyte battery is in a fully discharged state. Get closer. Such a nonaqueous electrolyte battery may be in an overdischarged state during long-term storage or transportation of the nonaqueous electrolyte battery.

  The rate of discharge performed on the charged nonaqueous electrolyte battery is preferably in the range of 7C to 100C. When the discharge rate for the charged non-aqueous electrolyte battery is set to 7C or more, the distance between the non-aqueous electrolyte and the relatively lithium-rich portion adjacent to the lithium ion-deficient layer of the negative electrode active material layer is further secured. Accordingly, the movement of lithium ions from the negative electrode active material layer to the non-aqueous electrolyte can be further sufficiently suppressed. In addition, discharging at a rate of 100 C or less does not require a large-scale cooling facility, so that the productivity of the nonaqueous electrolyte battery can be improved.

  The discharge performed on the charged nonaqueous electrolyte battery is preferably performed at a temperature of −30 ° C. or higher and 40 ° C. or lower. When the above discharge is performed within this temperature range, it is possible to further suppress the uniformity of the lithium ion concentration between the lithium-deficient layer and the adjacent portion. Therefore, when the above discharge is performed at a temperature of −30 ° C. or more and 40 ° C. or less, the interface between the lithium ion-deficient layer of the negative electrode active material layer and the relatively lithium-rich portion adjacent thereto can be further clarified, Thereby, the movement of lithium ions from the negative electrode active material layer to the nonaqueous electrolyte can be further sufficiently suppressed.

  It is more preferable that the discharging performed on the charged nonaqueous electrolyte battery is performed at a temperature of 0 ° C. or higher and 30 ° C. or lower. Since the discharge at a temperature within this range can be performed at a temperature closer to room temperature, the productivity of the nonaqueous electrolyte battery can be improved.

  Hereinafter, the manufacturing method of the nonaqueous electrolyte battery according to the first embodiment will be described in more detail with reference to the drawings.

  FIG. 3 is an exploded perspective view of a nonaqueous electrolyte battery that can be manufactured by the manufacturing method according to the first embodiment.

  According to the manufacturing method according to the first embodiment, for example, the nonaqueous electrolyte battery 1 having the structure shown in FIG. 3 is manufactured.

  A battery 1 shown in FIG. 3 includes a bottomed rectangular tube-shaped container 2a having an opening, a flat electrode group 3 housed in the container 2a, and a nonaqueous electrolyte (for example, non-aqueous electrolyte) impregnated in the flat electrode group 3. A water electrolyte (not shown) and a lid 2b fixed to the opening of the container 2a by welding, for example.

  As the container 2a, various materials can be used. Examples of materials that can be used as the container 2a will be described later.

  The flat electrode 3 includes a negative electrode 31 and a positive electrode 32 shown in FIG. 2 and a separator 33 sandwiched between the negative electrode 31 and the positive electrode 32.

  The negative electrode 31 includes, for example, a strip-shaped negative electrode current collector 31a made of metal foil, and a negative electrode active material-containing layer 31b supported on a part of the negative electrode current collector 31a. In the negative electrode current collector 31a, at least a part of the portion not supporting the negative electrode active material layer 31b functions as the negative electrode current collection tab 31c.

  The negative electrode active material layer 31b contains lithium titanate. As lithium titanate, for example, one having a spinel structure can be used. As the lithium titanate having a structure other than the spinel structure, a bronze structure lithium titanate can be considered. For example, a rutile type or anatase type lithium titanium oxide can also be used. From the viewpoint of life characteristics and internal resistance, it is preferable to use lithium titanate having a spinel structure.

  The positive electrode 32 includes a strip-shaped positive electrode current collector 32a made of, for example, a metal foil, and a positive electrode active material layer 32b supported on a part of the positive electrode current collector 32a. Materials that can be used for the positive electrode 32 will be described later. In the positive electrode current collector 32a, at least a part of the portion not supporting the positive electrode active material layer 32b functions as a positive electrode current collection tab 32c.

  Examples of materials that can be used as the separator 33 will be described later.

  The flat electrode group 3 has a structure in which a negative electrode 31, a separator 33, and a positive electrode 32 are stacked in this order. Moreover, in the flat electrode group 3, the negative electrode current collection tab 31c and the positive electrode current collection tab 32c protrude in the mutually opposite side in the winding axis direction. A method for producing the flat electrode group 3 will be further described later.

  Although the electrode group 3 shown in FIG. 3 has a flat shape, the shape of the electrode group 3 manufactured by the manufacturing method according to the first embodiment is not limited to the flat shape, and may be a cylindrical shape, a stacked type, or the like. Various shapes can be adopted.

  The flat electrode group 3 has two clamping members 4. The clamping member 4 includes a first clamping part 4a, a second clamping part 4b, and a connecting part 4c that couples the first and second clamping parts 4a and 4b. Since the negative electrode current collecting tab 31c and the positive electrode current collecting tab 32c are wound in a flat shape, the center of winding is a space. Of this space, the connecting portion 4c of one clamping member 4 is arranged in the space inside the negative electrode current collecting tab 31c, and the connecting portion 4c of the other holding member 4 is arranged in the space inside the positive electrode current collecting tab 32c. ing. With such an arrangement, each of the negative electrode current collecting tab 31c and the positive electrode current collecting tab 32c is sandwiched by the first sandwiching part 4a with the connecting part 4c as a boundary, and the negative electrode current collecting tab 31c or The other part facing the part across the space in the positive electrode current collecting tab 32c is sandwiched by the second sandwiching part 4b.

  Of the outermost periphery of the electrode group 3, the portion excluding the negative electrode current collecting tab 31 c and the positive electrode current collecting tab 32 c is covered with the insulating tape 5.

  The lid 2b has a rectangular shape. A liquid injection port (not shown) for injecting a non-aqueous electrolyte is opened in the lid 2b. The liquid injection port is sealed by a sealing lid (not shown) after the electrolytic solution is injected.

The battery shown in FIG. 3 further includes a negative electrode lead 6, a negative electrode terminal 7, a positive electrode lead 8, and a positive electrode terminal 9.
The negative electrode lead 6 has a connection plate 6a for electrical connection with the negative electrode terminal 7, a through hole 6b opened in the connection plate 6a, a bifurcated branch from the connection plate 6a, and a strip-like shape extending downward. And a current collector 6c. The two current collectors 6c of the negative electrode lead 6 sandwich the sandwiching member 4 sandwiching the anode current collecting tab 31c and the anode current collecting tab 31c therebetween, and are electrically connected to the sandwiching member 4 by welding.

  The positive electrode lead 8 has a connection plate 8a for electrically connecting to the positive electrode terminal 9, a through hole 8b opened in the connection plate 8a, a bifurcated branch from the connection plate 8a, and a strip-like shape extending downward. And a current collector 8c. The two current collectors 8c of the positive electrode lead 8 sandwich the sandwiching member 4 and the cathode current collector tab 32c that sandwich the cathode current collecting tab 32c therebetween, and are electrically connected to the sandwiching member 4 by welding.

  A method for electrically connecting the negative electrode lead 6 and the positive electrode lead 8 to the negative electrode current collecting tab 31c and the positive electrode current collecting tab 32c via the sandwiching member 4 is not particularly limited. And welding such as laser welding.

  The negative electrode terminal 7 is caulked and fixed to the lid 2b and the negative electrode lead 6 via an insulating member 7a. The positive electrode terminal 9 is caulked and fixed to the lid 2b and the positive electrode lead 8 via an insulating member 9a.

  Next, the manufacturing method of the nonaqueous electrolyte battery according to the first embodiment will be described in order.

  The manufacturing method according to the first embodiment includes producing a negative electrode 31 containing lithium titanate.

The lithium titanate preferably has a surface area of 1 to 10 m ² / g. By setting the surface area to 1 m ² / g or more, the effective area contributing to the electrode reaction can be increased, so that the large current discharge characteristics can be improved. By setting the surface area to 10 m ² / g or less, the amount of reaction with the electrolytic solution can be reduced, so that high charge / discharge efficiency and suppression of gas generation during storage can be achieved.

The negative electrode 31 can be produced as follows, for example.
First, a binder is added to lithium titanate which is a negative electrode active material, and these are suspended in a suitable solvent to obtain a suspension. As the binder, for example, polytetrafluoroethylene (PTEF), polyvinylidene fluoride (PVdF), fluorine rubber, or the like can be used.

  In order to increase conductivity, a conductive agent may be further added to the suspension. As the conductive agent, for example, acetylene black, carbon, graphite or the like can be used.

  Next, the suspension thus obtained is applied to one side or both sides of the belt-like current collector. As the current collector, for example, aluminum, copper, nickel, an aluminum alloy, a copper alloy, a nickel alloy, or the like can be used.

  Here, in the application of the suspension, in order to form the negative electrode current collector tab 31c, a portion where the suspension is not applied, for example, one end parallel to the long side of the strip-shaped current collector remains on the current collector. Do as follows.

  Thereafter, the current collector carrying the negative electrode active material on one side or both sides is pressed and dried to form a strip-like negative electrode 31.

  The compounding ratio of lithium titanate, conductive agent and binder in the negative electrode 31 is preferably in the range of 70 to 96% by weight of lithium titanate, 2 to 28% of conductive agent and 2 to 28% by weight of binder. If the amount of the conductive agent is less than 2% by weight, the large current characteristic may be deteriorated due to the lack of current collection. However, when the conductivity of lithium titanate is very high, a conductive agent may be unnecessary. In that case, the blending ratio is preferably 2 to 29% by weight of the binder. If the amount of the binder is less than 2% by weight, the cycle performance may be deteriorated due to lack of binding between the active material-containing layer and the current collector. On the other hand, from the viewpoint of increasing the capacity, the amount of the conductive agent and the binder is preferably 28% by weight or less.

  In the manufacturing method according to the first embodiment, for example, the negative electrode 31 produced as described above and the separately produced positive electrode 32 are wound with a separator 33 interposed therebetween, and then pressed into a flat shape. Forming the electrode group 3.

  The electrode group 3 includes, for example, the negative electrode 31, the separator 33, and the positive electrode 32. The negative electrode current collecting tab 31c projects from the separator 33 in the winding axis direction of the electrode group 3, and the positive electrode current collecting tab 32c extends in the opposite direction. It can be formed by winding the negative electrode 31 and the positive electrode 32 so that they protrude from the separator 6. The negative electrode 31, the positive electrode 32, and the separator 33 in the electrode group 3 may be integrated with the negative electrode 31, the positive electrode 32, and the separator 33 in the electrode group 3 using an adhesive polymer. After the production of the electrode group 3, the outermost periphery of the electrode group 3 is covered with the insulating tape 5.

  The manufacturing method according to the first embodiment includes housing the produced electrode group 3 in a container 2a.

  The housing of the electrode group 3 can be performed, for example, by the following method.

  First, the clamping member 4 is attached to each of the negative electrode current collecting tab 31c and the positive electrode current collecting tab 32c. On the other hand, as described with reference to FIG. 3, the negative electrode terminal 7 is caulked and fixed to the lid body 2b and the negative electrode lead 6 via the insulating member 7a, and the positive electrode terminal 9 is fixed to the lid body 2b and the positive electrode lead 8 with the insulating member 9a. Secure by caulking through.

  Thereafter, the negative electrode lead 6 is welded to the holding member 4 attached to the negative electrode current collecting tab 31 c of the electrode group 3, and the positive electrode lead 8 is welded to the holding member 4 attached to the positive electrode current collecting tab 32 c of the electrode group 3. Thereafter, the electrode group 3 is accommodated in the container 2a. After the electrode group 3 is housed in the container 2a, the lid 2b is welded to the opening of the container 2a.

  The manufacturing method according to the first embodiment includes housing a nonaqueous electrolyte in the container 2a. For storing the nonaqueous electrolyte, for example, the electrode group 3 is stored in the container 2a, the lid 2b is welded to the opening of the container 2a, and then the nonaqueous electrolyte is stored in the container from the liquid injection port (not shown) of the lid 2b. This can be done by injecting into 2a.

  The manufacturing method according to the first embodiment includes assembling the nonaqueous electrolyte battery 1 by sealing the electrode group 3 and the container 2a containing the nonaqueous electrolyte. The container 2a can be sealed by sealing the liquid injection port with a sealing lid after storing the nonaqueous electrolyte.

  The manufacturing method according to the first embodiment includes a step of charging the nonaqueous electrolyte battery 1 assembled in this way. This charging can be performed by a charging method that is normally performed in charging a nonaqueous electrolyte battery.

  In this charging, the nonaqueous electrolyte battery 1 can be brought into various charged state SOCs by changing the charging conditions.

  This charging can be performed multiple times. In addition, the manufacturing method according to the first embodiment can include processes generally performed in battery manufacturing, such as aging, capacity measurement, and resistance measurement. Therefore, the charging can be performed before, after, and / or between these steps.

  As described above, the manufacturing method according to the first embodiment discharges the charged nonaqueous electrolyte battery 1 at a rate of 5 C or more for 0.2 seconds or more, thereby providing a nonaqueous electrolyte battery. 1 to 10 to 95% of the state of charge SOC.

  Since this discharge is performed on the nonaqueous electrolyte battery 1 in a charged state, it can be performed after any charge that can be included in the manufacturing method according to the first embodiment. For example, the non-aqueous electrolyte battery 1 that has been initially charged may be discharged under the above conditions, or the non-aqueous electrolyte battery 1 that has been charged and ready for shipment may be discharged under the above conditions. May be performed. Or the discharge on the said conditions can also be performed in multiple times in the manufacturing method which concerns on 1st Embodiment. For example, the non-aqueous electrolyte battery 1 subjected to initial charge is discharged under the above conditions, and then the non-aqueous electrolyte battery 1 subjected to aging and capacity measurement is discharged under the above conditions. You can also.

  Before the non-aqueous electrolyte battery 1 is transported to the customer, the discharge is performed on the non-aqueous electrolyte battery 1 that has been charged to a charge state that is requested by the customer or that is equal to or higher than the nominal charge state of the non-aqueous electrolyte battery 1. To the nominal charge state SOC of the non-aqueous electrolyte battery 1 requested by the customer. Such discharge suppresses self-discharge during transport of the non-aqueous electrolyte battery 1 to the customer, so that the non-aqueous electrolyte that is requested by the customer or is in the nominal charge state of the non-aqueous electrolyte battery 1 is used. The electrolyte battery 1 can be delivered to the customer.

  The non-aqueous electrolyte battery 1 shown in FIG. 3 can be obtained by performing the above-described discharge at least in the final step.

  Hereinafter, the production method of the positive electrode 32, the positive electrode active material, the separator 33, the nonaqueous electrolyte, and the container 2a that can be used in the production method according to the first embodiment will be described.

<Method for producing positive electrode>
The positive electrode 32 that can be used in the first embodiment can be produced, for example, by the following method.

  First, a binder and optionally a conductive agent are added to the positive electrode active material, and these are suspended in a suitable solvent to obtain a suspension.

  The positive electrode active material that can be used will be described later. Moreover, as a binder and a electrically conductive agent, the material shown in the preparation example of the negative electrode 31, for example can be used.

  Next, the suspension thus obtained is applied to one side or both sides of the belt-like current collector. As the positive electrode current collector 32a, for example, aluminum, an aluminum alloy, or the like can be used.

  Here, the application of the suspension is such that a portion where the suspension is not applied, for example, one end parallel to the long side of the belt-like current collector 32a, is formed on the current collector so that the positive electrode current collecting tab 32c is formed. Do so to remain.

  Thereafter, the current collector 32 a carrying the positive electrode active material on one side or both sides is dried and pressed to form a strip-like positive electrode 32.

  The mixing ratio of the positive electrode active material, the conductive agent, and the binder in the positive electrode 32 can be set within the same range as that of the mixing ratio in the negative electrode.

<Positive electrode active material>
As the positive electrode active material of the positive electrode active material layer 32b of the positive electrode 32, a material that can be charged and discharged by a combination with lithium titanate that is a negative electrode active material can be used.

  As the positive electrode active material, it is desirable to use a mixture of the following two or more active materials from the viewpoint of cost and life.

The first positive electrode active material is LiNi _1-x M (a) _x O ₂ (M (a) is an element selected from the group consisting of Co, Al, Mn, Cr, Fe, Nb, Mg, B, and F) Including at least one kind, and X represents a range of 0 ≦ X ≦ 0.7).

  Here, when X is larger than 0.7, the capacity per cost decreases. A more preferable range of X is 0.3 ≦ X ≦ 0.6. If X is less than 0.3, the life characteristics are difficult.

The second positive electrode active material is LiCo _1-y M (b) _y O ₂ (M (b) is an element selected from the group consisting of Ni, Al, Mn, Cr, Fe, Nb, Mg, B and F) Including at least one kind, and Y represents a range of 0 ≦ Y <0.3).

Since it is thought that LiCoO ₂ in the charged state has the ability to treat the reducing gas by oxidation, if Y is 0.3 or more, the ability to treat the reducing gas generated from the negative electrode may be significantly reduced. There is.

  The mixing ratio of the first positive electrode active material and the second positive electrode active material is preferably a weight ratio of 95: 5 to 30:70. When the first positive electrode active material is larger than 95% by weight, the ability to treat the reducing gas generated from the negative electrode is remarkably lowered. When the first positive electrode active material is less than 30% by weight, the capacity per cost decreases.

<Separator>
As the separator 33, for example, a porous separator can be used. Examples of the porous separator include a porous film containing polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), and a synthetic resin nonwoven fabric. Among these, a porous film made of polyethylene or polypropylene or both is preferable because it can improve battery safety.

<Nonaqueous electrolyte>
A non-aqueous electrolyte can be used for the non-aqueous electrolyte. The nonaqueous electrolytic solution is prepared, for example, by dissolving an electrolyte in an organic solvent. Also, a room temperature molten salt containing lithium ions can be used as the non-aqueous electrolyte.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), and trifluorometa. Examples thereof include lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and lithium bistrifluoromethylsulfonylimide [LiN (CF ₃ SO ₂ ) ₂ ]. The electrolyte is preferably dissolved in the range of 0.5 to 2 mol / L with respect to the organic solvent.

  Examples of the organic solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC), chains such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC). Cyclic ethers such as linear carbonate, tetrahydrofuran (THF), and 2-methyltetrahydrofuran (2MeTHF), chain ethers such as dimethoxyethane (DME), γ-butyrolactone (BL), acetonitrile (AN), sulfolane (SL), etc. Can do. These organic solvents can be used alone or in the form of a mixture of two or more.

  The room temperature molten salt refers to a salt that is at least partially in a liquid state at room temperature, and the room temperature refers to a temperature range in which the power supply is assumed to normally operate. The temperature range in which the power supply is assumed to normally operate has an upper limit of about 120 ° C. and in some cases about 60 ° C., and a lower limit of about −40 ° C. and in some cases about −20 ° C.

The room temperature molten salt is composed of a combination of a lithium salt and an organic cation. As the lithium salt, a lithium salt having a wide potential window, which is generally used for lithium batteries, is used. For example, LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ), LiN (CF ₃ SC (C ₂ F ₅ SO ₂ ) ₃ ) However, it is not limited to these. These may be used alone or in combination of two or more.

  The lithium salt content is preferably 0.1 to 3.0 mol / L, and particularly preferably 1.0 to 2.0 mol / L. When the lithium salt content is 0.1 mol / L or more, the resistance of the electrolyte is reduced, and the large current / low temperature discharge performance is improved. By setting the content to 3.0 mol / L or less, the melting point of the electrolyte is lowered. Thus, it becomes possible to maintain a liquid state at room temperature.

<Container 2a>
As the container 2a, a metal can made of aluminum, aluminum alloy, iron, stainless steel or the like having a square shape can be used. The plate thickness of the container is preferably 0.5 mm or less, and more preferably 0.2 mm or less.

  As the container 2a, an exterior container made of a laminate film can be used instead of a metal can. As the laminate film, it is preferable to use a multilayer film in which a metal foil is coated with a resin film. Polymers such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used as the resin. The thickness of the laminate film is desirably 0.2 mm or less.

  The shape of the container 2a is not limited to a square shape, and may be a cylindrical shape, a thin shape, a coin shape, or the like.

  According to the manufacturing method of the nonaqueous electrolyte battery according to the first embodiment described above, the charged nonaqueous electrolyte battery is discharged at a rate of 5 C or more for 0.2 seconds or more, and the nonaqueous electrolyte battery is charged. By performing the SOC so as to be 10 to 95%, a lithium ion deficient layer can be formed in a portion of the negative electrode active material layer in contact with the nonaqueous electrolyte. As described above, the lithium ion-deficient layer formed in the portion of the negative electrode active material layer that is in contact with the nonaqueous electrolyte can suppress the movement of lithium from the negative electrode active material layer to the nonaqueous electrolyte. Therefore, according to the manufacturing method according to the first embodiment, it is possible to provide a nonaqueous electrolyte battery in which self-discharge is suppressed and lithium titanate is used for the negative electrode. Since such a non-aqueous electrolyte battery is prevented from self-discharging as described above, even if it is stored for a long period of time or transported over a long period of time, it is unlikely to be in an overdischarged state.

(Second Embodiment)
According to the second embodiment, a battery pack manufacturing method is provided. The battery pack includes a plurality of nonaqueous electrolyte batteries including a negative electrode containing lithium titanate, a positive electrode, and a nonaqueous electrolyte. The battery pack can be assembled by electrically connecting a plurality of nonaqueous electrolyte batteries to form an assembled battery. The battery pack manufacturing method according to the second embodiment includes charging the assembled battery pack and discharging the charged battery pack. Discharging is performed at a rate of 5C or more for 0.2 seconds or more so that the state of charge SOC of each nonaqueous electrolyte battery is 10 to 95%.

  FIG. 4 is a block diagram showing an electric circuit of an example of a battery pack that can be manufactured by the manufacturing method according to the second embodiment.

  A battery pack 10 shown in FIG. 4 includes a plurality of batteries 1 (unit cells). The plurality of batteries 1 can be manufactured, for example, by the nonaqueous electrolyte battery manufacturing method according to the first embodiment. However, as will be described in detail later, the battery 1 included in the battery pack 10 may not be discharged for 0.2 seconds or more at a rate of 5 C or more. The plurality of batteries 1 are connected in series to form an assembled battery 11.

  The battery pack 10 further includes a protection circuit 12, a thermistor 13, and a terminal 14 for energizing external devices.

  The assembled battery 11 is electrically connected to the protection circuit 12 by a negative electrode side wiring 15 and a positive electrode side wiring 16. The protection circuit 12 is electrically connected to the thermistor 13. Further, the protection circuit 12 is electrically connected to the energization terminal 14 by a minus side wiring 17 and a plus side wiring 18.

  The thermistor 13 is configured to detect the temperature of the plurality of batteries 1 or the assembled battery 11. A detection signal related to the temperature of the battery 1 or the assembled battery 11 is transmitted from the thermistor 13 to the protection circuit 12.

  The protection circuit 12 is configured to be able to block the minus side wiring 17 and the plus side wiring 18 between the protection circuit 12 and the energization terminal 14 under a predetermined condition. The predetermined condition is, for example, when the detected temperature of the thermistor 13 is equal to or higher than a predetermined temperature, or when overcharge, overdischarge, overcurrent, or the like of the battery 1 is detected. This detection method is performed for each individual battery 1 or the entire assembled battery 11. When detecting each individual battery 1, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. The entire assembled battery 11 can be detected by inserting a lithium electrode used as a reference electrode into each battery 1. In the case of the battery pack 10 of FIG. 4, a voltage detection wiring 19 is connected to each of the batteries 1, and a detection signal is transmitted to the protection circuit 12 through the wiring 19.

  Although the plurality of batteries 1 shown in FIG. 4 are connected in series, they can also be connected in parallel to increase the battery capacity. Of course, the assembled battery packs can be connected in series and in parallel.

  Moreover, the aspect of the battery pack 10 can be appropriately changed depending on the application.

  In the second embodiment, the discharge described in the first embodiment is performed on the assembled battery 11 incorporated in the battery pack 10 whose circuit diagram is shown in FIG. As described in the first embodiment, self-discharge of the charged nonaqueous electrolyte battery 1 can be suppressed by this discharge. Therefore, according to the second embodiment, the charged state of the charged nonaqueous electrolyte battery 1 is maintained even when the battery pack 10 is manufactured for a long period of time or the battery pack 10 is manufactured for a long period of time. And overdischarge of the nonaqueous electrolyte battery 1 can be prevented.

  By charging the assembled battery 11 and then discharging as described above, the state of charge SOC of the plurality of nonaqueous electrolyte batteries 1 constituting the assembled battery 11 can be made substantially uniform. . As described above, the battery pack 10 including the assembled battery 11 including the plurality of non-aqueous electrolyte batteries 1 having a substantially uniform state of charge SOC can supply power more stably.

  According to the method for manufacturing a battery pack according to the second embodiment described above, the charged state of the SOC of each non-electrolyte battery is determined by discharging the charged battery pack at a rate of 5 C or more for 0.2 seconds or more. By setting the content to 10 to 95%, a lithium ion deficient layer can be formed in a portion of the negative electrode active material layer in contact with the nonaqueous electrolyte. Therefore, according to the manufacturing method according to the second embodiment, it is possible to provide a battery pack including a nonaqueous electrolyte battery using lithium titanate as a negative electrode, in which self-discharge is suppressed. Since such a battery pack can suppress the self-discharge of the nonaqueous electrolyte battery included in the battery pack as described above, it is in an overdischarged state even if stored for a long period of time or transported over a long period of time. It is hard to become.

(Third embodiment)
According to the third embodiment, a method of using a nonaqueous electrolyte battery is provided. The nonaqueous electrolyte battery includes a negative electrode containing lithium titanate, a positive electrode, and a nonaqueous electrolyte. The method for using the nonaqueous electrolyte battery according to the third embodiment is to discharge the battery over a period of 0.2 seconds or more at a rate of 5C or more, thereby setting the state of charge SOC of the nonaqueous electrolyte battery to 10 to 95%. Stop the discharge.

  Examples of the electronic device in which the nonaqueous electrolyte battery is used include, but are not limited to, an electric vehicle and a mobile phone.

  An example of an electric vehicle that can be used in the usage method according to the third embodiment will be described.

  An electric vehicle of this example is electrically connected to a non-aqueous electrolyte battery including an electronic device unit including a drive unit that converts electric power into kinetic energy, an electrode group including a negative electrode including lithium titanate, and a non-aqueous electrolyte battery. It has a connected discharger and a controller. The discharger is configured to discharge the non-aqueous electrolyte battery at a rate of 5 C or more for 0.2 seconds or more so that the state of charge SOC of the non-aqueous electrolyte battery is 10 to 95%. The controller is configured to control power supply from the non-aqueous electrolyte battery to the electronic device unit and discharge to the non-aqueous electrolyte battery by the discharger, and supply power from the non-aqueous electrolyte battery to the electronic device unit. When shutting off, the discharger is configured to discharge the nonaqueous electrolyte battery.

  Examples of the drive unit that converts electric power included in the electric vehicle of this example into kinetic energy include a mechanism that contributes to traveling of the vehicle, such as a motor. As other examples of the drive unit, various drive units that can be provided in the automobile, such as a mechanism that contributes to the opening and closing of doors and / or windows, an air conditioning facility, and a mechanism that contributes to the operation of a wiper can be cited. .

  As an electronic device constituting the electric device unit included in the electric vehicle of this example, in addition to the drive unit, for example, a lighting device such as a front light, a brake lamp, a winker and an indoor lighting, a car audio, etc. There are various possible ones.

  The nonaqueous electrolyte battery included in the electric vehicle of this example includes an electrode group including a negative electrode containing lithium titanate. As such a nonaqueous electrolyte battery, for example, the nonaqueous electrolyte battery 1 that can be manufactured by the manufacturing method according to the first embodiment can be used.

  The nonaqueous electrolyte battery is electrically connected to the electric device unit described above, for example. Supply of electric power from the nonaqueous electrolyte battery to the electric equipment unit is controlled by a controller.

  Moreover, the nonaqueous electrolyte battery is electrically connected to a discharger. The discharger is configured to discharge the non-aqueous electrolyte battery at a rate of 5 C or more for 0.2 seconds or more, so that the state of charge SOC of the non-aqueous electrolyte battery is 10 to 95%. .

  The discharge by the discharger is controlled by the controller. Specifically, the controller is configured to cause the discharger to discharge the nonaqueous electrolyte battery when the supply of power from the nonaqueous electrolyte battery to the electrical device unit is interrupted.

  In the electric vehicle of this example, when power supply from the nonaqueous electrolyte battery to the electronic device unit is stopped, the nonaqueous electrolyte battery using lithium titanate as the negative electrode discharges at a rate of 5 C or more for 0.2 seconds or more. be able to. For example, when the power of an automobile is turned off, the nonaqueous electrolyte battery can be discharged at a rate of 5 C or more for 0.2 seconds or more.

  As described in the description of the first embodiment, the non-aqueous electrolyte battery is discharged at a rate of 5 C or more for 0.2 seconds or more so that the SOC of the non-electrolyte battery is 10 to 95%. A lithium ion deficient layer is formed in a portion of the negative electrode active material layer of the electrolyte battery that is in contact with the nonaqueous electrolyte. Since this lithium ion deficient layer can suppress the movement of lithium ions from the negative electrode active material to the nonaqueous electrolyte, the self discharge of the nonaqueous electrolyte battery can be suppressed. In addition, since the negative electrode active material layer can hold the lithium ion-deficient layer for a long period of time, the effect of suppressing the self-discharge of the nonaqueous electrolyte battery can be maintained for a long period of time.

  For this reason, the electric vehicle of this example can suppress self-discharge of the nonaqueous electrolyte battery for a long period of time by discharging at a rate of 5 C or more for 0.2 seconds or more to make the SOC of the nonelectrolyte battery 10 to 95%. It is possible to prevent the nonaqueous electrolyte battery from being overdischarged while this automobile is not used for a long time. That is, according to the usage method according to the third embodiment, it is possible to prevent the battery of the electric vehicle of this example from rising for a long period of time.

  Hereinafter, an exemplary procedure for turning off the electric vehicle according to the method of use according to the third embodiment will be described with reference to the drawings.

  FIG. 5 is a schematic flowchart showing an example of a procedure that can be executed when the electric vehicle is turned off according to the method of use according to the third embodiment.

  First, the driver parks the electric vehicle of the example described above at a predetermined position (start).

  Next, the driver or passenger presses the power switch of the electric vehicle (S1).

  By pressing the power switch, the controller cuts off the power supply from the nonaqueous electrolyte battery to the electric device unit (S2).

  Further, the controller cuts off the power supply from the nonaqueous electrolyte battery to the electrical equipment unit, and then causes the discharger to discharge the nonaqueous electrolyte battery at a rate of 5C or more for 0.2 seconds or more (S3). ). By this discharge, a lithium ion deficient layer is formed in a portion of the negative electrode active material layer of the nonaqueous electrolyte battery that is in contact with the nonaqueous electrolyte.

  After the discharge, the electric vehicle is turned off (finished).

  By following the above procedure, a lithium ion deficient layer is formed in the portion of the negative electrode active material layer of the nonaqueous electrolyte battery that is in contact with the nonaqueous electrolyte, thereby suppressing self-discharge of the nonaqueous electrolyte battery included in the electric vehicle. Can do. Further, the lithium ion deficient layer formed in the negative electrode active material layer is maintained for a long time. Therefore, even when the automobile is not operated for a long period of time, the battery of the automobile can be prevented from rising.

  According to the third embodiment described above, the negative electrode is made to have a non-aqueous electrolyte battery state of charge of 10 to 95% by performing discharge over 0.2 seconds at a rate of 5 C or more of the nonaqueous electrolyte battery. A lithium ion deficient layer can be formed in a portion of the active material layer in contact with the nonaqueous electrolyte. Therefore, according to the usage method according to the third embodiment, the self-discharge of the nonaqueous electrolyte battery can be suppressed. In addition, as described in the description of the first embodiment, since the lithium ion deficient layer formed in the negative electrode active material layer in this way is maintained for a long time, according to the third embodiment, the nonaqueous electrolyte is used. Even when the electric device including the battery is not used for a long period of time, overdischarge of the non-aqueous electrolyte battery can be prevented.

(Example)
Examples will be described below.

Example 1
In Example 1, a battery similar to the nonaqueous electrolyte battery 1 shown in FIG. 3 was produced.

(Preparation of negative electrode 31)
As the negative electrode active material, spinel type lithium titanate Li ₄ Ti ₅ O ₁₂ was used. This spinel type lithium titanate, graphite, and polyvinylidene fluoride (PVdF) were mixed at a weight ratio of 100: 5: 5, and these were added to N-methylpyrrolidone to form a slurry. The slurry thus obtained was applied on both sides to an aluminum foil 31a as a current collector. The coating amount of the negative electrode 31 was 100 g / m ² .

  The current collector 31a coated with the slurry was dried and then pressed to prepare the negative electrode 31.

(Preparation of positive electrode 32)
As the positive electrode active material, a positive electrode active material mixture in which LiNi _0.33 Co _0.33 Mn _0.33 O ₂ and LiCoO ₂ were mixed at 80:20 was prepared. This positive electrode active material mixture, carbon black, and PVdF were mixed at a weight ratio of 100: 5: 5, and these were added to N-methylpyrrolidone to form a slurry. The slurry thus obtained was applied on both sides to an aluminum foil as a current collector. The coating amount of the positive electrode 4 was 100 g / m ² .

  The positive electrode 32 was produced by drying and pressing the current collector 32a coated with the slurry.

(Separator 33)
As the separator 33, a separator made of polyethylene and having a thickness of 30 μm was used.

(Production of electrode group 3)
Using the positive electrode, the negative electrode, and the separator, a flat electrode group 3 having the same structure as the electrode group 3 shown in FIG. 3 was produced. Table 1 below shows the application length and width of the active material-containing slurry in the positive electrode and the negative electrode used for the production of the electrode group 3, and the length and width of the separator.

  The produced electrode group 3 was pressed to produce a flat electrode group 3.

(Storage of electrode group 3 in container 2a)
The negative electrode current collecting tab 31c of the produced electrode group 3 was clamped using the clamping member 4 in a state where the negative electrode current collecting tabs 31c were combined into one. Next, the holding member 4 holding the negative electrode current collecting tab 31c is sandwiched between the two current collecting parts 6c of the negative electrode lead 6, and the two current collecting parts 6c of the negative electrode lead 6 and the holding member 4 are joined by ultrasonic welding. did. Similarly, the positive electrode current collection tab 32c of the produced electrode group 3 was clamped using the clamping member 4 in the state which put together. Next, the holding member 4 holding the positive electrode current collecting tab 32c is sandwiched between the two current collecting portions 8c of the positive electrode lead 8, and the two current collecting portions 8c of the positive electrode lead 8 and the holding member 4 are joined by ultrasonic welding. did.

  After the electrode group 3 was housed in a rectangular aluminum can which is a container 2a, a lid 2b was attached to the opening of the can 2a by welding.

(Non-aqueous electrolyte injection)
A non-aqueous electrolyte was injected into the can 2a into the container 2a containing the electrode group 3 from the injection port of the lid 3b. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF ₆ as an electrolyte at a concentration of 1.5 mol / L in a non-aqueous solvent in which PC and MEC were mixed at a volume ratio of 1: 2 was used.

(Assembly of non-aqueous electrolyte battery 1)
After injecting the nonaqueous electrolyte, the liquid injection port was sealed with a sealing lid, whereby the assembly of the nonaqueous electrolyte secondary battery 1 was completed.

(First charge)
The assembled battery 1 was subjected to constant current and constant voltage (CCCV) charging for 10 hours up to 0.1 A and 2.7 V as initial charging.

(Capacity measurement)
The initially charged battery 1 was discharged to 1.5 V at 1.0 A. When the discharge capacity was measured, it was 1 Ah.

(Discharge)
The capacity-measured battery 1 was charged again. Thereafter, the battery 1 was discharged at a rate of 20 C for 90 seconds at 25 ° C., and the SOC was reduced to 50%.

(Measurement of self-discharge rate)
The discharged battery 1 was left at 35 ° C. for 4 weeks. Thereafter, the SOC of the battery 1 was measured.

  The self-discharge rate was determined by determining the difference between the SOC of the battery 1 before being left and the SOC of the battery 1 after being left. The self-discharge rate of the battery 1 of Example 1 was 1% / 4weak.

(Examples 2 to 4 and Comparative Examples 1 to 5)
In Examples 2 to 4 and Comparative Examples 1 to 4, the rate, discharge time, and adjusted SOC in the discharge performed after the first capacity measurement were set to the values shown in Table 2 below, and the same method as in Example 1 was used. A battery was produced. In Comparative Example 5, a battery was produced in the same manner as in Example 1 except that no discharge was performed after the first capacity measurement. The self-discharge rates of the batteries prepared in Examples 2 to 4 and Comparative Examples 1 to 5 were determined in the same manner as in Example 1. The results are shown in Table 2.

  As is clear from Table 1, the batteries 1 produced in Examples 1 to 4 exhibited lower self-discharge rates than the batteries produced in Comparative Examples 1 to 5. This is because the battery 1 produced in Examples 1 to 4 has a charge state SOC of the battery 1 of 10% to 95% by discharging at a rate of 5 C or more for 0.2 seconds or more. This is because a lithium ion deficient layer was formed in a portion of the active material layer in contact with the nonaqueous electrolyte, and the lithium ion deficient layer was able to suppress the self-discharge of the battery 1 for at least 4 weeks.

  On the other hand, the batteries of Comparative Examples 1 and 2 exhibited higher self-discharge rates than the batteries 1 produced in Examples 1 to 4. In Comparative Examples 1 and 2, discharge was performed at a rate of 5 C or more for 0.2 seconds or more, but the SOC of the adjusted battery 1 was 97% and 98%, respectively. This is presumably because the distance between the lithium-rich portion in contact with the lithium ion-deficient layer and the non-aqueous electrolyte was short, or the lithium ion-deficient layer was not formed, and thus the self-discharge of the battery 1 could not be suppressed. .

  In addition, the batteries of Comparative Examples 3 and 4 exhibited higher self-discharge rates than the battery 1 produced in Examples 1 to 4. This is because in Comparative Examples 3 and 4, the discharge was performed at a rate of less than 5C, so that the distance between the lithium-rich portion in contact with the lithium ion-deficient layer of the negative electrode active material layer and the nonaqueous electrolyte was short, or lithium ions It is assumed that the self-discharge of the battery 1 could not be suppressed because the deficient layer was not formed.

  Further, the battery of Comparative Example 5 exhibited an extremely high self-discharge rate. This is presumably because, in Comparative Example 5, the discharge was not performed after the first capacity measurement, and thus the self-discharge of the battery 1 could not be suppressed.

  That is, according to the nonaqueous electrolyte battery manufacturing method according to at least one embodiment and example described above, the charged nonaqueous electrolyte battery is discharged at a rate of 5C or more for 0.2 seconds or more. Since the state of charge SOC of the nonaqueous electrolyte battery is 10 to 95%, it is possible to provide a nonaqueous electrolyte battery using lithium titanate for the negative electrode in which self-discharge is suppressed.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.
The invention described in the scope of claims at the beginning of the application of the present application will be appended.
[1] Assembling a non-aqueous electrolyte battery including a negative electrode including lithium titanate, a positive electrode, and a non-aqueous electrolyte; charging the assembled non-aqueous electrolyte battery; and charging the charged non-aqueous electrolyte battery On the other hand, a non-aqueous electrolyte battery comprising: discharging at a rate of 5 C or more for 0.2 seconds or more to set the state of charge SOC of the non-aqueous electrolyte battery to 10 to 95%. Production method.
[2] The method for producing a nonaqueous electrolyte battery according to [1], wherein the discharge rate is in a range of 7C to 100C.
[3] The method for producing a nonaqueous electrolyte battery according to [2], wherein the discharging is performed at a temperature of −30 ° C. or higher and 40 ° C. or higher.
[4] Assembling a battery pack including a nonaqueous electrolyte battery including a negative electrode including lithium titanate, a positive electrode, and a nonaqueous electrolyte, charging the assembled battery pack, and the charged battery pack On the other hand, the battery pack includes: discharging at a rate of 5 C or more for 0.2 seconds or more to set the state of charge SOC of each of the nonaqueous electrolyte batteries to 10 to 95%. Manufacturing method.
[5] A method of using a non-aqueous electrolyte battery including a negative electrode containing lithium titanate, a positive electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte is discharged at a rate of 5 C or more for 0.2 seconds or more. A method for using a non-aqueous electrolyte battery, wherein the discharge is stopped after the state of charge SOC of the electrolyte battery is 10 to 95%.

  DESCRIPTION OF SYMBOLS 1 ... Nonaqueous electrolyte battery, 2a ... Container, 2b ... Cover body, 3 ... Flat electrode group, 31 ... Negative electrode, 31a ... Negative electrode collector, 31b ... Negative electrode active material layer, 31c ... Negative electrode current collection tab, 32 ... Positive electrode 32a ... positive electrode current collector, 32b ... positive electrode active material layer, 32c ... positive electrode current collector, 33 ... separator, 4 ... clamping member, 5 ... insulating tape, 6 ... negative electrode lead, 7 ... negative electrode terminal, 8 ... positive electrode lead , 9 ... Positive terminal, 10 ... Battery pack, 11 ... Battery pack, 12 ... Protection circuit, 13 ... Thermistor, 14 ... Terminal for energization, 15 ... Negative side wiring, 16 ... Positive side wiring, 17 ... Negative side wiring, 18 ... plus-side wiring, 19 ... wiring.

Claims (5)

Comprising a negative electrode containing a lithium titanate, a positive electrode, viewed contains a non-aqueous electrolyte, wherein the negative electrode includes a negative electrode active material composed of the lithium titanate, a conducting agent and a negative electrode active material layer containing a binder And the non-aqueous composition of the negative electrode active material, the conductive agent and the binder in the negative electrode active material layer is 70 to 96% by mass, 2 to 28% by mass, and 2 to 28% by mass, respectively. Fully charging the electrolyte battery;
Discharging the fully charged non-aqueous electrolyte battery at a rate of 5 C or more for 0.2 seconds or more to set the state of charge SOC of the non-aqueous electrolyte battery to 10 to 95% ;
Storage or transport method of the nonaqueous electrolyte battery characterized in that it comprises a <br/> and be stored or transported to a non-aqueous electrolyte batteries the state of charge SOC to 10% to 95%. The method for storing or transporting a nonaqueous electrolyte battery according to claim 1, wherein the discharge rate is set in a range of 7C to 100C. The method for storing or transporting a nonaqueous electrolyte battery according to claim 2, wherein the discharging is performed at a temperature of -30 ° C or higher and 40 ° C or higher. Comprising a negative electrode containing a lithium titanate, a positive electrode, viewed contains a non-aqueous electrolyte, wherein the negative electrode includes a negative electrode active material composed of the lithium titanate, a conducting agent and a negative electrode active material layer containing a binder And the non-aqueous composition of the negative electrode active material, the conductive agent and the binder in the negative electrode active material layer is 70 to 96% by mass, 2 to 28% by mass, and 2 to 28% by mass, respectively. and to fully charge the battery pack with an electrolyte batteries,
Discharging the fully charged battery pack at a rate of 5C or more for 0.2 seconds or more to set the state of charge SOC of each non-aqueous electrolyte battery to 10 to 95% ;
A battery pack storage or transport method comprising: storing or transporting a battery pack in which the state of charge SOC of each of the nonaqueous electrolyte batteries is 10 to 95% . A nonaqueous electrolyte battery which is connected to the electronics unit, a negative electrode containing a lithium titanate, a positive electrode, a nonaqueous seen electrolyte and containing said anode, a negative electrode active material composed of the lithium titanate, conductive A negative electrode active material layer containing an agent and a binder, and the mixing ratio of the negative electrode active material, the conductive agent and the binder in the negative electrode active material layer is 70 to 96% by mass, 2 A method for maintaining the state of charge of a nonaqueous electrolyte battery that is -28 mass% and 2-28 mass% ,
Shutting off the power supply from the non-aqueous electrolyte battery to the electronic device unit;
Fully charge the non-aqueous electrolyte battery,
Discharge is stopped after the charged state SOC of the nonaqueous electrolyte battery is 10 to 95% by discharging the fully charged nonaqueous electrolyte battery at a rate of 5C or more for 0.2 seconds or more. And
A method for maintaining a charged state of a nonaqueous electrolyte battery , wherein the nonaqueous electrolyte battery having a charged state SOC of 10 to 95% is left unattended .

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