JP2015185459A - electrode manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an electrode whose deterioration is suppressed due to great suppression of expansion and contraction even if occlusion and discharge of Li are repeated.SOLUTION: An electrode material 21 in a state where Li is occluded and expanded is finely crushed to produce finely crushed materials from which stress is removed, the finely crushed materials in the state where the stress is removed are mixed with each other to make arrangements of Li uniform, thereby manufacturing a negative electrode 12.

Description

  The present invention relates to an electrode manufacturing method for manufacturing a negative electrode of a secondary battery.

  A secondary battery such as a lithium secondary battery is used as a battery for driving a motor mounted on an electric vehicle such as an electric vehicle or a plug-in hybrid vehicle. When the secondary battery is charged, lithium is released from the positive electrode and stored in the negative electrode, and during discharge, lithium is released from the negative electrode and stored in the positive electrode.

  In the negative electrode of the secondary battery, lithium is occluded and expanded during charging, and lithium is released and contracted during discharging. For this reason, by repeating charging and discharging, there is a possibility that a portion where expansion and contraction are repeated and the structure becomes weak may occur. That is, the amount of lithium that can be occluded (amount of charge) is reduced, and there is a limit to the number of times that lithium can be stored and released repeatedly.

  Since the battery capacity is determined by the amount of lithium moving due to the reversible reaction between the positive electrode and the negative electrode, for example, a material that can occlude a large amount of lithium has been studied as an electrode material constituting the negative electrode. A material that can occlude a large amount of lithium has a high expansion rate. Therefore, it is conceivable that the rate of decrease in the charge amount is increased due to repeated expansion and contraction, and there is a risk of deterioration.

  As a method for producing a negative electrode, a technique for forming a negative electrode using a material containing lithium (carbonaceous material, silicon oxide powder) has been conventionally known (see, for example, Patent Documents 1 and 2). The techniques disclosed in Patent Documents 1 and 2 are such that lithium is fixed to the negative electrode material in advance, so that when the lithium released from the positive electrode is occluded by the negative electrode, the occluded lithium is not fixed to the negative electrode. It is ensured to be discharged during discharge.

  In other words, a conventionally known technique is a technique for pre-doping lithium into the negative electrode and suppressing the fixation of lithium occluded during charging to the electrode material. In the negative electrode, the amount of lithium occluded during charging is reduced. On the other hand, this is a technique for preventing the amount of lithium released during discharge from decreasing.

  For this reason, the technologies disclosed in Patent Documents 1 and 2 are technologies that can effectively utilize lithium moving by reversible reaction in battery capacity, and are different from technologies that suppress deterioration due to expansion and contraction of the negative electrode. Therefore, deterioration of the negative electrode cannot be suppressed.

JP-A-6-44958 JP2013-114820A

  The present invention has been made in view of the above circumstances, and provides an electrode manufacturing method capable of manufacturing a negative electrode in which expansion and contraction are greatly suppressed and deterioration is suppressed even when lithium insertion and extraction are repeated. For the purpose.

  In order to achieve the above object, the electrode manufacturing method of the present invention according to claim 1 is an electrode manufacturing method for manufacturing a negative electrode of a secondary battery that performs charge and discharge by inserting and extracting lithium by a reversible reaction between the positive electrode and the negative electrode. A method is characterized in that lithium to be released is occluded in an electrode material serving as a negative electrode, the electrode material in a state where lithium is occluded is pulverized, and a negative electrode is produced using the pulverized product.

  In the present invention according to claim 1, by pulverizing the electrode material in an expanded state with occlusion of lithium, a pulverized product from which stress has been removed is obtained, and the pulverized product from which stress has been removed is mixed. Thus, the negative electrode can be manufactured with a uniform lithium arrangement. For this reason, the produced negative electrode becomes an electrode having a uniform and strong lithium arrangement, lithium is released in a strong state, and lithium is occluded in a strong state.

  Therefore, even when lithium insertion and extraction is repeated, a negative electrode in which the expansion and contraction are significantly suppressed and deterioration is suppressed can be manufactured.

  The electrode manufacturing method of the present invention according to claim 2 is the electrode manufacturing method according to claim 1, wherein the pulverized electrode material contains a predetermined amount of lithium. .

  In the present invention according to claim 2, since a predetermined amount of lithium is contained in the electrode material to be pulverized, the electrode material in which a sufficient amount of lithium is occluded is pulverized to make the arrangement of lithium uniform. be able to. The predetermined amount of lithium is, for example, the amount of lithium in a fully charged state, and the determination that the predetermined amount of lithium is contained can be determined by, for example, the lithium storage time (charging time).

  According to a third aspect of the present invention, in the electrode manufacturing method of the second aspect, the determination that the predetermined amount of lithium is contained is made by the expansion of the electrode material. It is characterized by that.

  In the present invention according to claim 3, it is determined that a predetermined amount of lithium is contained due to expansion of the electrode material. The determination of the expansion of the electrode material can be made by measuring the state of the expansion coefficient.

  The electrode manufacturing method of the present invention according to claim 4 is the electrode manufacturing method according to any one of claims 1 to 3, wherein lithium to be discharged is charged from a positive electrode of a secondary battery. It contains lithium transferred by the above.

  In the present invention according to claim 4, since the lithium occluded in the electrode material of the negative electrode includes lithium transferred from the positive electrode of the secondary battery by charging, the battery is paired with the positive electrode from which lithium has been released by charging. Can be configured.

  Incidentally, Japanese Patent Application No. 11-307129 discloses a method for producing a secondary battery by detaching lithium ions from a positive electrode member and occluding the separated lithium ions in a negative electrode member. By occluding lithium ions, a secondary battery with little deterioration is obtained by suppressing the expansion of the negative electrode member more than necessary. However, since it is not a technique of a manufacturing method for suppressing deterioration of the negative electrode member itself, it is a technique different from the electrode manufacturing method of the present invention.

  The electrode manufacturing method of the present invention according to claim 5 is the electrode manufacturing method according to any one of claims 1 to 4, wherein the electrode material is made of at least one of silicon, tin, and aluminum. It is characterized by including.

  In this invention which concerns on Claim 5, even if it uses a material with a large expansion | swelling ratio as an electrode material, expansion | swelling and shrinkage | contraction can be suppressed significantly.

  The electrode production method of the present invention makes it possible to produce a negative electrode in which expansion and contraction are greatly suppressed and deterioration is suppressed even when lithium insertion and extraction are repeated.

It is a conceptual diagram of an electric vehicle. It is sectional drawing which illustrates notionally the structure of a lithium secondary battery. It is process explanatory drawing of the electrode preparation method which concerns on one Example of this invention. It is explanatory drawing which represents typically the process of the electrode preparation method which concerns on one Example of this invention. It is explanatory drawing which compares the expansion process of a negative electrode. It is a graph showing the relationship between the capacity | capacitance of the electrode produced with the electrode production method which concerns on one Example of this invention, and the frequency | count of charging / discharging. It is explanatory drawing of the relationship with the positive electrode in electrode preparation.

  The state of the lithium secondary battery (secondary battery) will be described with reference to FIGS.

  FIG. 1 conceptually illustrates an electric vehicle on which a secondary battery including a negative electrode manufactured by an electrode manufacturing method according to an embodiment of the present invention is mounted, and FIG. 2 conceptually illustrates the configuration of the secondary battery. A cross section is shown.

  As shown in FIG. 1, an in-vehicle battery pack 1 is mounted under the floor of an electric vehicle 2 and supplies power to a traveling motor or the like of the electric vehicle 2. In the battery pack 1, a large number of lithium secondary batteries (secondary batteries) 3 are modularized and accommodated.

  As shown in FIG. 2, in the secondary battery 3, a negative electrode body 6 and a positive electrode body 7 are housed in a case 5, and the electrode bodies 6 and 7 are immersed in an electrolytic solution 8. In the negative electrode body 6, a negative electrode material is applied to a current collector foil 11 to form a negative electrode (negative electrode) 12, and the current collector foil 11 is connected to a negative electrode terminal 13. The positive electrode body 7 has a current collector foil 15 coated with a positive electrode material to form an electrode (positive electrode) 16, and the current collector foil 15 is connected to a positive electrode terminal 17.

  As the electrode material 12 (negative electrode), for example, an alloy-based electrode material containing silicon (Si), tin (Sn), aluminum (Al), or the like is used. An alloy-based electrode material containing Si, Sn, Al, or the like can store a large amount of lithium (Li) by expansion, and can be a large-capacity battery.

  In addition, as an electrode material of the negative electrode 12, for example, an amorphous carbon material such as graphite (artificial or natural), soft carbon, or hard carbon, or an oxide-based negative electrode material can be applied.

  Since the battery capacity of the secondary battery 3 is determined by the amount of lithium moving due to the reversible reaction between the positive electrode and the negative electrode, an alloy-based electrode material containing Si, Al, Sn, or the like that can absorb a large amount of Li is used as the electrode material of the negative electrode 12. It is used. An electrode material that can occlude a large amount of Li has a high rate of expansion. Therefore, when the expansion and contraction are repeated, the rate of decrease in the charge amount increases and the deterioration tends to occur.

  For this reason, the negative electrode 12 is produced by a production method capable of producing an electrode in which the expansion and contraction are greatly suppressed and deterioration is suppressed even when the insertion and extraction of Li are repeated.

  An electrode manufacturing method according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 3 shows a schematic situation of an electrode manufacturing method according to an embodiment of the present invention, FIG. 4 schematically shows a process of an electrode manufacturing method according to an embodiment of the present invention, and FIG. Is a situation schematically showing the expansion process of the electrode (negative electrode) compared with the conventional preparation method, and FIG. 6 illustrates suppression of deterioration of the electrode produced by the electrode production method according to one embodiment of the present invention. Therefore, the relationship between the capacity of the negative electrode and the number of charge / discharge cycles is shown, and FIG. 7 shows the situation explaining the aspect of the relationship with the positive electrode in electrode fabrication.

  The electrode manufacturing process will be specifically described with reference to FIGS.

  As shown in FIG. 3, for example, Li is occluded in an alloy-based electrode material 21 containing silicon (Si), tin (Sn), aluminum (Al), and the like, and is charged to form a battery. Then, the expansion rate is measured. For example, when it is determined that the battery is fully charged, the battery-made electrode material 21 is crushed.

  That is, as shown in FIG. 4, the electrode material 21 and the electrode 16 (positive electrode 16) to be the positive electrode are prepared (a), and the Li stored in the positive electrode 16 is released by the charging operation, and a predetermined amount of Li is released. The electrode material 21 is occluded and charged (b). When Li is occluded in the electrode material 21, the electrode material 21 expands and stress is applied. Then, the electrode material 21 in a state where Li is occluded and expands and stress is applied is pulverized (c).

  The determination as to whether a predetermined amount of Li has been occluded, that is, the determination that a predetermined amount of Li is contained, is made by measuring the state of the expansion rate of the electrode material 21. In the measurement, for example, the state of expansion is detected by bringing a contact of the measuring device into contact.

  In this case, it is possible to determine that a predetermined amount of Li has been contained by detecting expansion corresponding to the state of the SOC, which is the ratio of the remaining charge to the charge capacity of the battery. For example, it is determined that a predetermined amount of Li is contained when a ratio defined as full charge (for example, SOC is 80%) is detected by measurement of an expansion state.

  As shown in FIG. 3, the powder of the electrode material 21 occluded with a predetermined amount of Li that has been pulverized and released in the expanded state is mixed, and formed into an electrode shape, or the kneaded material is collected. It is applied to a foil or a metal plate to form a negative electrode 12 to produce an electrode.

  That is, as shown in FIG. 4, the electrode material 21 in a state where Li is occluded and expanded and stress is applied is pulverized into a powder from which stress is removed in the expanded state (c), and is kneaded and collected. An electrode is produced, for example, by being applied to an electric foil or a metal plate, and becomes the negative electrode 12 (d).

  In the negative electrode 12, the electrode material 21 in a state where it is expanded and stressed is pulverized and kneaded, so that the arrangement of Li is uniform and the stress is removed in the expanded state. (D). Then, the positive electrode 16 and the negative electrode 12 from which Li is released are paired to form the secondary battery 3 (e).

  The negative electrode 12 produced by the above-described electrode preparation method is pulverized from the stress removed by pulverizing the electrode material 21 in an expanded state by absorbing Li, and the pulverized material from which the stress has been removed is mixed. Continuously, the negative electrode 12 can be manufactured by making the arrangement of Li uniform.

  For this reason, the produced negative electrode 12 becomes an electrode in which the arrangement of Li is uniform and strong, Li is released in a strong state at the time of discharging, and Li is occluded while remaining in a strong state at the time of charging. There is almost no expansion beyond the state. Therefore, even when Li occlusion and release are repeated, it is possible to produce the negative electrode 12 in which expansion and contraction are significantly suppressed and deterioration is suppressed.

  A situation where expansion and contraction are greatly suppressed will be described with reference to FIG.

  FIG. 5A is a conceptual diagram of charging / discharging of the negative electrode 12 produced by the method of the present invention, and FIG. 5B is a conceptual diagram of charging / discharging of a general negative electrode.

  As shown in FIG. 5B, in the general electrode (negative electrode) 31, during charging, Li is occluded in the contracted electrode material to become the negative electrode 31a. In the negative electrode 31a, Li is occluded and expands from a contracted state to become an electrode having a soft structure, and the arrangement of Li is in a non-uniform state.

  At the time of discharging, Li arranged unevenly is released, and the negative electrode 31b is left in a state where a soft structure remains (shrinkage). And the negative electrode 31b has a thin site | part in the wall part between the parts 31c after Li escapes, and the frequency | count which can endure repetition of occlusion and discharge | release of Li will be limited.

  As shown in FIG. 5 (a), the negative electrode 12 produced by the method of the present invention uses a pulverized electrode material in a state where Li is occluded and expanded, so that the state of charge in a state where Li is uniformly arranged is used. This is the negative electrode 12. That is, Li is occluded by an electrode material having a strong structure, not a negative electrode in which the contracted material expands and Li is occluded.

  For this reason, even if Li is released, it does not contract (expand), maintains a strong structure, does not repeat expansion and contraction, and deterioration is suppressed even if Li is occluded and released repeatedly.

  Based on FIG. 6, the deterioration state of the negative electrode 12 produced by the method of the present invention and the general negative electrode 31 will be described.

  As shown by the solid line in FIG. 6, since the negative electrode 12 produced by the method of the present invention is suppressed from being deteriorated, the capacity of the battery hardly decreases even when the number of times of charge / discharge increases. For this reason, in order to maintain the performance of the required capacity Q over a long period of time, the negative electrode 12 having a capacity Q1 slightly larger than the required capacity Q may be used.

  As shown by a dotted line in FIG. 6, the general negative electrode 31 deteriorates as the number of charge / discharge increases, and the battery capacity decreases. For this reason, in order to maintain the performance of the required capacity Q over a long period of time, it is necessary to use the negative electrode 31 having a capacity Q2 that is significantly larger than the required capacity Q.

  As shown in FIG. 6, it can be seen that the negative electrode 12 produced by the method of the present invention has almost no decrease in capacity and the deterioration is suppressed.

  Based on FIG. 7, the relationship with the positive electrode in producing the negative electrode 12 of the method of the present invention will be described and the situation of producing a battery will be described. In the figure, the hatched portion indicates a state where Li is occluded.

  As shown in FIG. 7A, when the negative electrode 12 is produced, an electrode material 21 that is an electrode and an electrode 16 that is a positive electrode of the battery are used. Li stored in the electrode 16 is released and stored in the electrode material 21, and pulverized and kneaded to prepare the negative electrode 12. A battery is formed by using the electrode 16 from which Li is released as a positive electrode with respect to the negative electrode 12. For this reason, the electrode 16 can be produced in the process of manufacturing the battery.

  As shown in FIG. 7B, an electrode material 21 to be an electrode and an electrode 41 to be a positive electrode of the battery are used. The electrode 41 stores more Li than the storage amount of the electrode material 21. A part of Li occluded in the electrode 41 is released, occluded in the electrode material 21, and pulverized and kneaded to produce the negative electrode 12. Li is left in the electrode 41. A battery is formed by using the electrode 41 in which Li is left as a positive electrode with respect to the negative electrode 12.

  Since a part of Li is fixed to the positive electrode of the battery, if the amount of Li stored in the negative electrode 12 is stored, the battery capacity may not be sufficiently secured. By using the electrode 41 in which more Li is occluded than the amount of occlusion in the electrode material 21 to occlude Li in the electrode material 21, the electrode 41 in a state in which Li to be fixed is occluded in advance is used as a positive electrode. A battery can be configured in combination with the negative electrode 12.

  As shown in FIG. 7C, an electrode material 21 to be an electrode is used, Li from an Li source other than the positive electrode, such as an electrolytic solution, is occluded in the electrode material 21, and pulverized and kneaded to produce the negative electrode 12. A battery is configured using the electrode 16 in a state where Li is released or 41 in a state where a part of Li is left as a positive electrode with respect to the negative electrode 12.

  In the configuration example shown in FIG. 7, it is possible to configure a battery using another electrode as a positive electrode without using the electrodes 16 and 41 from which Li is released.

  The combination of the negative electrode 12 and the positive electrode is arbitrary, and the amount of Li that is occluded and the amount of Li that is moved during recharging by reversible reaction are also arbitrary. In other words, the negative electrode 12 and various positive electrodes can be combined depending on the performance of the battery, and the battery can be configured using an electrode or the like having an arbitrary Li occlusion state.

  In the electrode manufacturing method of the present invention, the electrode material 21 in an expanded state by occluding Li is pulverized to obtain a pulverized product from which stress has been removed, and the pulverized product from which stress has been removed is mixed to form Li Since the negative electrode 12 was produced in a uniform state, the electrode was in a strong state, Li was released in a strong state at the time of discharging, and Li was occluded while remaining in a strong state at the time of charging. Will not expand beyond.

  Therefore, even when Li occlusion and release are repeated, it is possible to manufacture the negative electrode 12 in which expansion and contraction are significantly suppressed and deterioration is suppressed.

  INDUSTRIAL APPLICATION This invention can be utilized in the industrial field | area of the electrode preparation method for producing the negative electrode of a secondary battery.

DESCRIPTION OF SYMBOLS 1 Battery pack 2 Electric vehicle 3 Lithium secondary battery (secondary battery)
5 Case 6, 7 Electrode body 8 Electrolyte solution 11, 15 Current collector foil 12 Electrode (negative electrode)
13 Negative terminal 16, 41 Electrode (positive electrode)
17 Positive terminal 21 Electrode material 31 Negative electrode

Claims (5)

An electrode production method for producing a negative electrode of a secondary battery that performs charge and discharge by inserting and extracting lithium by a reversible reaction between a positive electrode and a negative electrode,
A method for producing an electrode, characterized in that lithium to be released is occluded in an electrode material serving as a negative electrode, the electrode material in which lithium is occluded is pulverized, and a negative electrode is produced using the pulverized product. The electrode manufacturing method according to claim 1,
The electrode material to be pulverized contains a predetermined amount of lithium. The electrode manufacturing method according to claim 2,
The determination that the predetermined amount of lithium is contained is made by the expansion of the electrode material. In the electrode manufacturing method according to any one of claims 1 to 3,
The lithium for release includes lithium transferred by charging from the positive electrode of the secondary battery. In the electrode manufacturing method according to any one of claims 1 to 4,
The electrode material includes at least one of silicon, tin, and aluminum.

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