JP6941535B2 - Manufacturing method of lithium ion secondary battery - Google Patents

Description

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

As a power source for driving a motor of an electric vehicle (EV) or a hybrid electric vehicle (HEV), a lithium ion secondary battery that can be repeatedly charged and discharged is being actively developed.

A lithium ion secondary battery is an electrolytic solution containing a power generation element in which a positive electrode having a positive electrode active material layer containing a positive electrode active material and a negative electrode having a negative electrode active material layer containing a negative electrode active material are laminated via a separator. After being sealed inside the exterior body, it is manufactured through the initial charging process.

In connection with this, in Patent Document 1 below, a lithium ion secondary battery in which an additive (non-aqueous solvent) that is reduced and decomposed at a potential higher than that of the main solvent is added to the electrolytic solution is charged for the first time. A method for charging the secondary battery has been proposed. In the charging method of Patent Document 1, the negative electrode potential is maintained at a potential where the additive in the electrolytic solution is reduced and decomposed and the main solvent is not reduced and decomposed, and then the lithium ion secondary battery is charged until it is fully charged. According to such a configuration, the additive is reduced and decomposed before the main solvent is reduced and decomposed, so that a stable film can be formed on the particle surface of the negative electrode active material with a minimum amount of electricity.

By the way, as the negative electrode active material of the lithium ion secondary battery, a material containing silicon (hereinafter, also referred to as “silicon-based material”) can be used in addition to a carbon-based material such as hard carbon. If a silicon-based material is used as the negative electrode active material, the battery capacity can be increased.

Japanese Unexamined Patent Publication No. 2010-212253

However, according to the study by the present inventors, when the binder content is small in the negative electrode active material layer containing a silicon-based material as the negative electrode active material, sufficient battery performance such as initial capacity and discharge rate characteristics can be obtained. It turns out that it may not be.

The present invention has been made to solve the above-mentioned problems. Therefore, an object of the present invention is to provide a means capable of improving the battery performance of a lithium ion secondary battery having a negative electrode containing a silicon-based material as a negative electrode active material and having a negative electrode active material layer having a low binder content. It is to be.

The above object of the present invention is achieved by the following means.

The method for manufacturing a lithium ion secondary battery according to the present invention is a method for manufacturing a lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte layer, and includes a first charging step, a resting step, and a second charging step. It has an initial charging process. The positive electrode includes a positive electrode active material layer containing a positive electrode active material capable of occluding and releasing lithium ions. The negative electrode includes a negative electrode active material layer which is a non-bonded body of the negative electrode active material containing silicon. The electrolyte layer has an electrolytic solution containing a non-aqueous solvent. In the first charging step, the lithium ion secondary battery reaches a predetermined battery voltage set in a range in which the negative electrode potential of the lithium ion secondary battery is maintained at a potential noble than the reduction decomposition potential of the electrolytic solution. To charge. In the pause step, when the lithium ion secondary battery is charged to the predetermined battery voltage, the charging of the lithium ion secondary battery is paused for a predetermined time. In the second charging step, when the predetermined time elapses, charging of the lithium ion secondary battery is restarted, and charging of the lithium ion secondary battery is continued.
_{Here, the predetermined battery voltage is in a range smaller than the battery voltage (V H} ) when the negative potential of the lithium ion secondary battery is equal to the reduction decomposition potential of the electrolytic solution and larger than the battery voltage ( _VL). Set,
The battery voltage ( _VL ) is calculated by the following mathematical formula (1):
_{V L = V I + 0.3 ×} (V H -V I) ... (1)
(In the above equation (1), V _I is the battery voltage of the lithium ion secondary battery at the start of charging)
It is represented by.

According to the present invention, the battery performance of a lithium ion secondary battery having a negative electrode containing a silicon-based material as the negative electrode active material and having a negative electrode active material layer having a low binder content is improved.

It is a figure which shows the schematic structure of the charging device to which the manufacturing method of the lithium ion secondary battery which concerns on one Embodiment of this invention is applied. It is sectional drawing which shows typically the basic structure of the lithium ion secondary battery. It is a flowchart which shows the procedure of the charging process executed by a charging device. It is a figure which shows typically the structure of the negative electrode active material layer before the 1st charging process. It is a figure which shows typically the structure of the negative electrode active material layer after the 1st charging step. It is a figure which shows typically the structure of the negative electrode active material layer after a rest process. It is a figure which shows the relationship between the positive electrode and negative electrode potential of a lithium ion secondary battery, and the charge amount. It is a figure which shows the change of the battery voltage of the lithium ion secondary battery in the initial charging process. It is a figure which shows the relationship between the discharge capacity of a lithium ion secondary battery, and a C rate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the figure, the same reference numerals are used for similar members. In addition, the dimensional ratios in the drawings may be exaggerated for convenience of explanation and may differ from the actual ratios.

FIG. 1 is a diagram showing a schematic configuration of a charging device to which the method for manufacturing a lithium ion secondary battery according to an embodiment of the present invention is applied. The charging device 100 according to the present embodiment is electrically connected to the lithium ion secondary battery 200 to charge the secondary battery 200 for the first time.

As shown in FIG. 1, the charging device 100 includes a voltage sensor 110, a current sensor 120, a power supply 130, and a control unit 140.

The voltage sensor 110 is connected in parallel to the secondary battery 200 and detects the battery voltage of the secondary battery 200. The voltage value obtained by detecting the battery voltage of the secondary battery 200 by the voltage sensor 110 is transmitted to the control unit 140.

The current sensor 120 is provided between the secondary battery 200 and the power supply 130, and detects the current flowing from the power supply 130 to the secondary battery 200. The current value obtained by detecting the current with the current sensor 120 is transmitted to the control unit 140.

The power supply 130 is connected in parallel to the secondary battery 200 to supply electric power to the secondary battery 200. The power supply 130 is a DC power supply, and supplies power to the lithium ion secondary battery 200 at a predetermined current value or voltage value.

The control unit 140 controls the operation of the power supply 130. The control unit 140 includes a CPU and various memories, and controls the operation of the power supply 130 according to a program.

Next, the lithium ion secondary battery 200 charged by the charging device 100 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view schematically showing the basic configuration of a lithium ion secondary battery. The lithium ion secondary battery 200 according to the present embodiment is a bipolar secondary battery. The secondary battery 200 has a structure in which a substantially rectangular power generation element 210 through which the charge / discharge reaction actually proceeds is sealed inside the battery exterior 220.

As shown in FIG. 2, in the power generation element 210 of the secondary battery 200, the positive electrode active material layer 212 is formed on one surface of the current collector 211, and the negative electrode active material layer 213 is formed on the other surface of the current collector 211. It has a plurality of bipolar electrodes 215 configured to be formed. The negative electrode active material layer 213 of the present embodiment includes, for example, a carbon-based negative electrode active material, a silicon-based negative electrode active material, and a conductive auxiliary agent. Further, the negative electrode active material layer 213 is a non-bonded body of the negative electrode active material. In addition, in this specification, "non-binding body" means that active materials are not bound to each other by a binder, and not only when the electrode active material layer does not contain a binder, but also. The case where the electrode active material layer contains a small amount of binder is also included in the present invention. A detailed description of the materials constituting the secondary battery 200 will be described later.

Each bipolar electrode 215 is laminated via the electrolyte layer 216 to form a power generation element 210. The electrolyte layer 216 has a structure in which the electrolytic solution is held by a separator as a base material. The electrolytic solution is, for example, a solution in which LiFSI (lithium bis (fluorosulfonyl) imide) is dissolved in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC). At this time, the positive electrode active material layer 212 of the one bipolar electrode 215 and the negative electrode active material layer 213 of the other bipolar electrode 215 adjacent to the one bipolar electrode 215 face each other via the electrolyte layer 216. The bipolar electrodes 215 and the electrolyte layer 216 are alternately laminated. That is, the electrolyte layer 216 is sandwiched between the positive electrode active material layer 212 of the one bipolar electrode 215 and the negative electrode active material layer 213 of the other bipolar electrode 215 adjacent to the one bipolar electrode 215. ing.

The adjacent positive electrode active material layer 212, electrolyte layer 216, and negative electrode active material layer 213 constitute one cell cell layer 217. Therefore, it can be said that the secondary battery 200 has a configuration in which the single battery layers 217 are laminated. The number of stacked cell layers 217 is adjusted according to the desired voltage. Further, for the purpose of preventing liquid leakage due to leakage of the electrolytic solution from the electrolyte layer 216, a seal portion 218 is arranged on the outer peripheral portion of the cell cell layer 217.

The positive electrode active material layer 212 is formed on only one side of the outermost layer current collector 211a on the positive electrode side, which is located in the outermost layer of the power generation element 210. Further, the negative electrode active material layer 213 is formed on only one side of the outermost layer current collector 211b on the negative electrode side located in the outermost layer of the power generation element 210.

Further, in the secondary battery 200, the positive electrode current collector plate 221 is arranged so as to be adjacent to the outermost layer current collector 211a on the positive electrode side, and this is extended and derived from the exterior body 220. On the other hand, the negative electrode current collector plate 222 is arranged so as to be adjacent to the outermost layer current collector 211b on the negative electrode side, and is similarly extended and derived from the exterior body 220. The voltage sensor 110 of the charging device 100 detects the voltage between the positive electrode and the negative electrode current collector plates 221 and 222 derived from the exterior body 220 as the battery voltage of the secondary battery 200.

Next, with reference to FIG. 3, the operation of the charging device 100 that initially charges the lithium ion secondary battery 200 will be described in detail.

FIG. 3 is a flowchart showing the procedure of the charging process executed by the charging device.

First, the charging device 100 starts constant current charging of the secondary battery 200 (step S101). More specifically, the control unit 140 of the charging device 100 controls the power supply 130 with a constant current, and starts charging the secondary battery 200 with a current of, for example, 0.1C.

Then, the charging device 100 determines whether the battery voltage of the secondary battery 200 has reached the resting voltage _{V S} (step S102). More specifically, the control unit 140 of the charging apparatus 100, by referring to the output value of the voltage sensor 110, the battery voltage of the secondary battery 200 and determines whether it has reached a predetermined quiescent voltage V _S. Here, resting voltage V _S is the battery voltage as a reference for resting the charging of the secondary battery 200, kept at a noble potential than the reduction decomposition potential of the negative electrode potential electrolyte secondary battery 200 It is set in the range to be used. Resting voltage _{V S} is set to, for example, a value obtained by multiplying the 3.0V to stacking number of the single cell layers 217. The invention is not limited to this embodiment, whether or not the battery voltage of the secondary battery 200 has reached the resting voltage V _S, may be determined based on the amount of charge of the secondary battery 200 (SOC).

If it is determined that the battery voltage of the secondary battery 200 has not reached the resting voltage _{V S} (step S102: NO), the charging apparatus 100, until the battery voltage of the secondary battery 200 reaches the resting voltage _{V S,} the secondary Continue constant current charging of the battery 200.

On the other hand, if it is determined that the battery voltage of the secondary battery 200 has reached the resting voltage _{V S} (step S102: YES), the charging device 100 to pause the charging of the secondary battery 200 (step S103). More specifically, the control unit 140 of the charging device 100 controls the power supply 130 to temporarily stop charging the secondary battery 200.

Next, the charging device 100 determines whether or not a predetermined time T has elapsed after the charging of the secondary battery 200 is stopped (step S104). Here, the predetermined time T is a reference time when resuming charging of the secondary battery 200, and is preferably set to 1 hour or more (for example, 24 hours).

When it is determined that the predetermined time T has not elapsed (step S104: NO), the charging device 100 waits until the predetermined time T elapses.

On the other hand, when it is determined that the predetermined time T has elapsed (step S104: YES), the charging device 100 restarts the constant current charging of the secondary battery 200 (step S105). More specifically, the control unit 140 of the charging device 100 controls the power supply 130 with a constant current, and restarts charging of the secondary battery 200 with a current of, for example, 0.1C.

Then, the charging device 100 determines whether the battery voltage of the secondary battery 200 has reached the final voltage _{V E} (step S106). More specifically, the control unit 140 of the charging apparatus 100, by referring to the output value of the voltage sensor 110, the battery voltage of the secondary battery 200 and determines whether it has reached a predetermined end voltage V _E. Here, the final voltage _VE is a battery voltage that serves as a reference when the charging method of the secondary battery 200 is switched from constant current charging to constant voltage charging, and is set to a value corresponding to a fully charged state. The final voltage _VE is set to, for example, a value obtained by multiplying the number of stacked cell layers 217 by 4.2 V.

When the battery voltage of the secondary battery 200 is determined not to reach the final voltage _{V E} (Step S106: NO), the charging apparatus 100, until the battery voltage of the secondary battery 200 reaches the end voltage _{V E,} the secondary Continue constant current charging of the battery 200.

On the other hand, if it is determined that the battery voltage of the secondary battery 200 has reached the final voltage _{V E} (Step S106: YES), the charging apparatus 100 starts the constant voltage charging of the secondary battery 200 (step S107). More specifically, the control unit 140 of the charging device 100, a power supply 130 and a constant voltage control to start charging of the secondary battery 200 at the stop voltage _{V E.}

Next, the charging device 100 determines whether or not the current value of the current flowing from the power supply 130 to the secondary battery 200 is equal to or less than the _{termination current value IE (step S108).} More specifically, whether or not the control unit 140 of the charging device 100 refers to the output value of the current sensor 120 and the current value of the current flowing through the secondary battery 200 is equal to or less than the _{predetermined termination current value IE.} To judge. Here, the termination current value _IE is a reference current value when stopping the constant voltage charging of the secondary battery 200, and is, for example, a value (0.001C) of 1% of the current value in the above constant current charging. ) Is set.

When it is determined that the current value is _{not equal to or less than the termination current value IE} (step S108: NO), the charging device 100 charges the secondary battery 200 at a constant voltage until the _{current value becomes equal to or less than the termination current value IE.} To continue.

On the other hand, _{when it is determined that the current value is equal to or less than the termination current value IE} (step S108: YES), the charging device 100 stops charging the secondary battery 200 (step S109), and ends the process. More specifically, the control unit 140 of the charging device 100 controls the power supply 130 to stop charging the secondary battery 200.

As described above, according to the processing of the flowchart shown in FIG. 3, first, a predetermined battery voltage (1) set in a range in which the negative electrode potential of the secondary battery 200 is maintained at a potential noble than the reduction / decomposition potential of the electrolytic solution ( resting voltage) to V _S, the first charging step of charging the secondary battery 200 is performed. Then, the secondary battery 200 to a predetermined battery voltage V _S is when it is charged, pause step of resting the predetermined time T the charge of the secondary battery 200 is performed. After that, when the predetermined time T elapses, the second charging step of restarting the charging of the secondary battery 200 is performed, and the secondary battery 200 is fully charged. According to such a configuration, when the secondary battery 200 is charged for the first time, the reductive decomposition reaction of the electrolytic solution due to the expansion of the particles of the silicon-based material contained in the negative electrode active material is suppressed, and the battery performance of the secondary battery 200 is suppressed. (Initial capacity, discharge rate characteristics, etc.) are improved.

In the embodiment described above, if the positive electrode and the voltage between the negative electrode terminal plate 221 and 222 of the lithium ion secondary battery 200 is detected as the battery voltage, the battery voltage reaches a quiescent voltage V _S, the secondary battery 200 Charging was suspended. However, unlike the present embodiment, the voltage of each cell layer 217 of the lithium ion secondary battery 200 may be detected as the battery voltage. In this case, when the battery voltage of each cell layer 217 reaches a predetermined battery voltage (for example, 3.0 V), or when the battery voltage of one cell layer 217 reaches a predetermined battery voltage, two Charging of the next battery 200 is suspended.

Next, the behavior of the negative electrode active material in the initial charging step of the secondary battery 200 will be described with reference to FIGS. 4A to 4C. As described above, the first charge step of the present embodiment, the secondary first charging step of charging the battery 200 to a predetermined battery voltage V _S, resting step of resting the predetermined time T the charge of the secondary battery 200, and secondary It includes a second charging step of resuming charging of the battery 200.

FIG. 4A is a diagram schematically showing the configuration of the negative electrode active material layer before the first charging step, and FIG. 4B is a diagram schematically showing the configuration of the negative electrode active material layer after the first charging step. FIG. 4C is a diagram schematically showing the configuration of the negative electrode active material layer after the resting step.

As shown in FIG. 4A, the negative electrode active material layer 213 of the present embodiment includes, for example, carbon-based active material particles 250 and silicon-based active material particles 260 as negative electrode active materials. Further, the negative electrode active material layer 213 preferably contains conductive carbon particles 270 as a conductive auxiliary agent. Here, the average particle size of the carbon-based active material particles 250 is, for example, about 10 μm, and the average particle size of the silicon-based active material particles 260 is, for example, about 1 μm. The average particle size of the conductive carbon particles 270 is, for example, about 100 nm. Further, the negative electrode active material layer 213 of the secondary battery 200 according to the present embodiment is a non-bonded body of the active material particles 250 and 260, and the carbon-based active material particles 250 and the silicon-based active material particles 260 are easy to move. It exists on the current collector 211 in the state.

As described above, according to the method for manufacturing a lithium ion secondary battery according to the present embodiment, there is an effect that the secondary battery 200 having excellent battery performance can be obtained. The mechanism by which such an effect is obtained has not been completely clarified, but the following mechanism has been presumed. The mechanism shown below is based on speculation, and the correctness of the following mechanism does not affect the technical scope of the present invention.

The particles of the silicon-based material expand greatly when lithium ions are occluded. Therefore, when the negative electrode is charged for the first time with a lithium ion secondary battery containing a silicon-based material, if the negative electrode active material layer 213 is a non-bonded body of the negative electrode active material, as the silicon-based active material particles 260 expand, The carbon-based active material particles 250 and the silicon-based active material particles 260 move. When the active material particles 250 and 260 move, the surfaces of the active material particles 250 and 260 that were not exposed to the electrolytic solution at the start of charging are newly exposed to the electrolytic solution. In a general initial charging step in which charging of the secondary battery is not interrupted, the surface of particles exposed to the electrolyte continues to increase while the secondary battery is being charged. As a result, the reductive decomposition reaction of the electrolytic solution becomes active, and the SEI (solid electrolyte interface) coating formed on the surfaces of the active material particles 250 and 260 becomes thick. In the conventional technique, it is considered that this thick SEI coating causes a decrease in battery performance.

On the other hand, also in the method for manufacturing a lithium ion secondary battery according to the present embodiment, the silicon-based active material particles 260 occlude lithium ions and expand while the secondary battery 200 is charged in the first charging step. As a result, as shown in FIG. 4B, the carbon-based active material particles 250 and the silicon-based active material particles 260 moved, and the surfaces of the active material particles 250 and 260 that were not exposed to the electrolytic solution before the start of charging were exposed. , It will be newly exposed to the electrolytic solution. However, in the first charging step, the negative electrode potential of the secondary battery 200 is maintained at a potential noble than the reduction / decomposition potential of the electrolytic solution, so that the reduction / decomposition reaction of the electrolytic solution does not occur.

In the method for manufacturing a lithium ion secondary battery according to the present embodiment, charging of the secondary battery 200 is suspended for a predetermined time after the first charging step. In the resting step, as shown in FIG. 4C, the particles contained in the negative electrode active material layer 213 are rearranged. Specifically, the carbon-based active material particles 250 and the silicon-based active material particles 260 slowly move toward the current collector 211 side, and the active material particles 250 and 260 come into contact with each other. In addition, the conductive carbon particles 270 move to the surface of the active material particles 250, 260 and cover a part of the surface of the active material particles 250, 260. As a result, a part of the surface of the active material particles 250 and 260 that were exposed to the electrolytic solution at the end of the first charging step is not exposed to the electrolytic solution.

Therefore, according to the method for manufacturing a lithium ion secondary battery according to the present embodiment, the surfaces of the active material particles 250 and 260 exposed to the electrolytic solution are reduced in the resting step during the initial charging step. Therefore, in the second charging step in which charging of the secondary battery 200 is restarted and the negative electrode potential of the secondary battery 200 takes a lower potential than the reduction / decomposition potential of the electrolytic solution, the reduction / decomposition reaction of the electrolytic solution occurs. It is suppressed. As a result, the SEI film is formed thinner on the surfaces of the active material particles 250 and 260 as compared with the case where the charging of the secondary battery is not stopped. If the SEI coating is thin, the ionic conductivity of the secondary battery 200 increases and the internal resistance decreases. Then, it is considered that the battery performance of the secondary battery 200 is improved.

When the electrolytic solution is composed of a plurality of non-aqueous solvents, the most noble reduction-decomposition potential among the reduction-decomposition potentials of the plurality of non-aqueous solvents is the reduction-decomposition potential of the electrolytic solution. Further, as described above, in the suspension step, since the active material particles 250 and 260 move slowly, it is preferable to suspend the charging of the secondary battery 200 for 1 hour or more. If the rest time is 1 hour or more, even if the secondary battery 200 is placed under atmospheric pressure and the active material particles 250 and 260 move slowly, the rearrangement of the particles surely occurs. Therefore, the surfaces of the active material particles 250 and 260 exposed to the electrolytic solution can be reliably reduced, and the reduction decomposition reaction of the electrolytic solution can be reliably suppressed.

Further, the method for charging the secondary battery shown in Patent Document 1 described above is a lithium ion secondary battery that does not contain a silicon-based material as the negative electrode active material and that the negative electrode active material layer contains a sufficient binder. It is the one to be charged for the first time. Therefore, in the technique of Patent Document 1, the point of suppressing the movement of the particles of the negative electrode active material and the active reduction and decomposition reaction of the electrolytic solution is not taken into consideration.

Next, with reference to FIG. 5, the relationship between the battery voltage of the lithium ion secondary battery 200 and the reduction decomposition potential of the electrolytic solution will be described.

FIG. 5 is a diagram showing the relationship between the positive electrode and negative electrode potentials of the lithium ion secondary battery and the charge amount. The vertical axis of FIG. 5 shows the positive electrode and negative electrode potentials of the secondary battery 200 based on lithium metal, and the horizontal axis shows the charge amount of the secondary battery 200. The solid line in FIG. 5 indicates the change in the positive electrode potential, and the broken line indicates the change in the negative electrode potential. The potential difference between the positive electrode potential and the negative electrode potential corresponds to the battery voltage. In the following, for convenience of explanation, the unit cell layer 217 of the secondary battery 200 will be used as a reference.

For example, when the electrolytic solution is a solution in which LiFSI is dissolved in a mixed solvent of EC and PC, the reduction decomposition potential of _PC V PC becomes the reduction decomposition potential of the electrolytic solution. In FIG. 5, it is assumed that _{the reduction decomposition potential V PC} of the PC is about 0.4 V (vs. Li ^{/ Li +).}

As indicated by a broken line in FIG. 5, at the charge start time of the secondary battery 200 (charge amount of 0%), the negative electrode potential of the secondary battery 200 takes a noble potential than the reduction decomposition potential V _PC of the electrolyte. Then, as the process proceeds the charging of the secondary battery 200, the negative electrode potential of the secondary battery 200 is reduced, so that take lower potential than the reduction decomposition potential V _PC of the electrolyte.

As described above, in the method for manufacturing a lithium ion secondary battery according to the present embodiment, in the first charging step, the negative electrode potential of the secondary battery 200 is set to a range that is noble than the reduction decomposition potential of the electrolytic solution. was up to a predetermined battery voltage V _S, the secondary battery 200 is charged. Accordingly, the predetermined battery voltage V _S, is set to a smaller voltage than the battery voltage V _H when the negative electrode potential of the secondary battery 200 is equal to the reduction decomposition potential V _PC of the electrolytic solution _(e.g., about 3.5 V) ..

On the other hand, reliably suppressing standpoint reductive decomposition reaction of the electrolytic solution, the predetermined battery voltage V _S, preferably set to a voltage higher than the battery voltage V _L which is represented by the following equation (1).

_{V L = V I + 0.3 ×} (V H -V I) ... (1)
Here, V _I is the battery voltage at the start of charging the secondary battery 200.

If the predetermined battery voltage V _S is greater than the battery voltage V _L, the negative electrode active conductive carbon particles 270 in the gap material layer 213 caused by the expansion of the silicon-based active material particles 260 penetrate reliably. Therefore, the surfaces of the carbon-based active material particles 250 and the silicon-based active material particles 260 are surely covered with the conductive carbon particles 270, and the reduction decomposition reaction of the electrolytic solution is surely suppressed. On the other hand, if the predetermined battery voltage V _S is smaller than the battery voltage V _L, the negative electrode active conductive carbon particles 270 in the gap material layer 213 is not easily enter that occurs with the expansion of the silicon-based active material particles 260, the electrolyte It becomes difficult to suppress the reduction decomposition reaction of.

When the lithium ion secondary battery 200 is charged from a charge amount of 0% to a charge amount of 100%, the silicon-based active material particles 260 theoretically expand about 4 times in volume and about 1.6 times in length. Therefore, when the silicon-based active material particles 260 having a particle size of about 1 μm are charged from a charge amount of 0% to a charge amount of 100%, the particle size becomes about 1.6 μm and expands by about 600 nm (in other words, the charge amount is 10). Expands about 60 nm per%). Then, assuming the amount of charge corresponding to the voltage difference between the _(V H -V _I) and about 20%, the change in the charge amount corresponding to 0.3 × _(V H -V _I) is, 36 nm ( It causes expansion of silicon-based active material particles 260 (about 0.3 × 120 nm). When the silicon-based active material particles 260 expand by 36 nm, a similar gap is formed in the negative electrode active material layer 213. If the average particle size of the conductive carbon particles 270 is 100 nm or less, some of the conductive carbon particles 270 will enter the gap of about 36 nm. Therefore, the conductive carbon particles 270 cover the surfaces of the carbon-based active material particles 250 and the silicon-based active material particles 260, and the reduction decomposition reaction of the electrolytic solution is suppressed.

The above reductive decomposition potential _{V PC,} the battery voltage _V H, the value of the charge amount and the like corresponding to the voltage difference between _{V I} and, _(V H -V _I) is of a material constituting the lithium ion secondary battery 200 It changes according to the type, concentration, size, etc. Therefore, the specific numerical values described herein do not limit the present invention.

As described above, according to the method for manufacturing a lithium ion secondary battery according to the present embodiment, in the initial charging step of the lithium ion secondary battery, charging is temporarily suspended while the secondary battery 200 is charged. As a result, the initial capacity and discharge rate characteristics of the secondary battery 200 are improved. In addition, the initial coulombic efficiency of the secondary battery 200 is improved, and the cycle life characteristics of the secondary battery 200 are also improved.

Hereinafter, the main components of the lithium ion secondary battery 200 will be described.

[Current collector]
The current collector 211 has a function of mediating the movement of electrons from one surface in contact with the positive electrode active material layer 212 to the other surface in contact with the negative electrode active material layer 213. The material constituting the current collector 211 is not particularly limited, and for example, a metal or a resin having conductivity may be adopted.

Specific examples of the metal include aluminum, nickel, iron, stainless steel (SUS), titanium, copper and the like. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, a plating material of a combination of these metals, and the like can be preferably used. Further, the foil may be a metal surface coated with aluminum. Of these, aluminum, nickel, stainless steel (SUS), and copper are preferable from the viewpoint of electron conductivity, battery operating potential, and the like.

Examples of the latter resin having conductivity include a resin in which a conductive filler is added to a conductive polymer material as needed, or a resin in which a conductive filler is added to a non-conductive polymer material. Be done. Examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyoxadiazole and the like. Since such a conductive polymer material has sufficient conductivity without adding a conductive filler, it is advantageous in terms of facilitating the manufacturing process or reducing the weight of the current collector 211.

Examples of the non-conductive polymer material include polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), and polyimide. (PI), Polyethyleneimide (PAI), Polyethylene (PA), Polytetrafluoroethylene (PTFE), Styrene-butadiene rubber (SBR), Polyacrylonitrile (PAN), Polymethylacrylate (PMA), Polymethylmethacrylate (PMMA) , Polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), polystyrene (PS) and the like. Such non-conductive polymer materials can have excellent potential resistance or solvent resistance.

The conductive filler can be used without particular limitation as long as it is a conductive substance. For example, as a material having excellent conductivity, potential resistance, or lithium ion blocking property, metal, conductive carbon, and the like can be mentioned. The metal is not particularly limited, but at least one metal selected from the group consisting of nickel, titanium, aluminum, copper, platinum, iron, chromium, tin, zinc, indium, antimony, and potassium, or at least one of these metals. It is preferable to contain an alloy containing, or a metal oxide. Further, the conductive carbon is not particularly limited. Preferably, from the group consisting of acetylene black, vulcan (registered trademark), black pearl (registered trademark), carbon nanofiber, Ketjen black (registered trademark), carbon nanotube (CNT), carbon nanohorn, carbon nanoballoon, and fullerene. It is preferable to include at least one selected.

The amount of the conductive filler added is not particularly limited as long as it can impart sufficient conductivity to the current collector 211, and is generally about 5 to 35% by volume.

The current collector 211 may have a single-layer structure made of a single material, or may have a laminated structure in which layers made of these materials are appropriately combined. From the viewpoint of reducing the weight of the current collector, it is preferable to include a conductive resin layer made of at least a conductive resin. Further, from the viewpoint of blocking the movement of lithium ions between the cell cell layers 217, a metal layer may be provided as a part of the current collector.

[Electrode active material layer (positive electrode active material layer, negative electrode active material layer)]
The electrode active material layer (positive electrode active material layer 212, negative electrode active material layer 213) contains an electrode active material (positive electrode active material or negative electrode active material). Further, the electrode active material layer (positive electrode active material layer 212, negative electrode active material layer 213) may contain a conductive auxiliary agent, a conductive member, a binder, a coating resin, and the like, if necessary.

(Positive electrode active material)
Examples of the positive electrode active material include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni-Mn-Co) O ₂ , and lithium such as those in which some of these transition metals are replaced by other elements. Examples thereof include −transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more kinds of positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. More preferably, a composite oxide containing lithium and nickel is used. More preferably, Li (Ni-Mn-Co) O ₂ and a part of these transition metals are substituted with other elements (hereinafter, also simply referred to as "NMC composite oxide"), or lithium-nickel-cobalt. -Aluminum composite oxide (hereinafter, also simply referred to as "NCA composite oxide") or the like is used. The NMC composite oxide has a layered crystal structure in which a lithium atomic layer and a transition metal (Mn, Ni, and Co are arranged in an orderly manner) atomic layer are alternately stacked via an oxygen atomic layer. Then, one Li atom is contained in each transition metal atom, and the amount of Li that can be taken out is twice that of the spinel-based lithium manganese oxide, that is, the supply capacity is doubled, and a high capacity can be obtained.

(Negative electrode active material)
The negative electrode active material indispensably contains a silicon-based material. Examples of the silicon-based material include Si alone, SiO ₂ , silicon oxides such as SiO, and silicon alloys. The silicon alloy is preferably at least a ternary system of Si, Sn, and M (transition metal), and M is preferably titanium (Ti). Examples of other negative electrode active materials include carbon materials such as graphite, soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), and metal materials (tin). , Lithium alloy-based negative electrode materials (for example, lithium-aluminum alloy, lithium-aluminum-manganese alloy, etc.) and the like. In some cases, two or more kinds of negative electrode active materials may be used in combination. Preferably, in addition to the silicon-based material, a carbon material, a lithium-transition metal composite oxide, and a lithium alloy-based negative electrode material are used as the negative electrode active material from the viewpoint of capacity and output characteristics. Needless to say, a negative electrode active material other than the above may be used. Further, the coating resin has a property of being particularly easy to adhere to a carbon material. Therefore, from the viewpoint of providing a structurally stable electrode material, it is preferable to use a carbon material as another negative electrode active material.

(Conductive aid)
The conductive auxiliary agent can contribute to the improvement of the output characteristics of the battery at a high rate by forming an electron conduction path in the electrode active material layer and reducing the electron transfer resistance of the electrode active material layer.

Conductive aids include, for example, metals such as aluminum, stainless steel (SUS), silver, gold, copper, titanium, alloys or metal oxides containing these metals; graphite, carbon fibers (specifically, vapor phase growth). Examples include carbon such as carbon fiber (VGCF), carbon nanotube (CNT), carbon black (specifically, acetylene black, Ketjen black (registered trademark), furnace black, channel black, thermal lamp black, etc.). However, it is not limited to these. Further, a particulate ceramic material or a resin material coated with the above metal material by plating or the like can also be used as a conductive auxiliary agent. Among these conductive auxiliaries, it is preferable to contain at least one selected from the group consisting of aluminum, stainless steel (SUS), silver, gold, copper, titanium, and carbon from the viewpoint of electrical stability. It is more preferable to contain at least one selected from the group consisting of aluminum, stainless steel (SUS), silver, gold, and carbon, and it is further preferable to contain at least one kind of carbon. Only one kind of these conductive auxiliaries may be used alone, or two or more kinds thereof may be used in combination.

The shape of the conductive auxiliary agent is preferably particulate or fibrous. When the conductive auxiliary agent is in the form of particles, the shape of the particles is not particularly limited, and may be any shape such as powder, sphere, rod, needle, plate, columnar, indefinite, flint, and spindle. It doesn't matter. When the conductive auxiliary agent is in the form of particles, the average particle size (primary particle size) is preferably 100 nm or less. In the present specification, the “particle size” means the maximum distance L among the distances between any two points on the contour line of the conductive auxiliary agent. The value of the "average particle size" is the average value of the particle size of the particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

(Conductive member)
The conductive member has a function of forming an electron conduction path in the electrode active material layer. In particular, at least a part of the conductive member forms a conductive passage that electrically connects the two main surfaces of the electrode active material layer (in the present embodiment, it contacts the electrolyte layer 216 side of the electrode active material layer). It is preferable to form a conductive passage that electrically connects the first main surface to the second main surface in contact with the current collector 211 side). By having such a form, the electron transfer resistance in the thickness direction in the electrode active material layer is further reduced, so that the output characteristics at a high rate of the battery can be further improved. Whether or not at least a part of the conductive member forms a conductive passage that electrically connects the two main surfaces of the electrode active material layer is determined by using an SEM or an optical microscope in cross section of the electrode active material layer. Can be confirmed by observing.

The conductive member is preferably a conductive fiber having a fibrous form. Specifically, carbon fibers such as PAN-based carbon fibers and pitch-based carbon fibers, conductive fibers in which a metal having good conductivity or graphite is uniformly dispersed in synthetic fibers, and a metal such as stainless steel (SUS). Examples thereof include metal fibers made of fibers, conductive fibers in which the surface of organic fibers is coated with metal, and conductive fibers in which the surface of organic fibers is coated with a resin containing a conductive substance. Of these, carbon fiber is preferable because it has excellent conductivity and is lightweight.

(Binder)
Examples of the binder include solvent-based binders such as polyvinylidene fluoride (PVdF) and water-based binders such as styrene-butadiene rubber (SBR). The binder content in the negative electrode active material layer 213 is 1% by mass or less, preferably 0% by mass, based on 100% by mass of the total solid content contained in the negative electrode active material layer 213.

(Coating resin)
The coating resin exists on the surface of the electrode active material and has a function of absorbing and holding the electrolytic solution. Thereby, in the electrode active material layer, an ion conduction path from the surface of the electrode active material to the electrolyte layer can be formed. The material of the coating resin is not particularly limited, but from the viewpoint of flexibility and liquid absorbency, it consists of a group consisting of (A) polyurethane resin and (B) polyvinyl resin (for example, (meth) acrylate-based copolymer, etc.). It is preferable to include at least one selected.

Further, the above-mentioned conductive auxiliary agent may be dispersed in the coating resin. With such a configuration, in the electrode active material layer, an ion conduction path from the surface of the electrode active material to the electrolyte layer and an electron conduction path from the surface of the electrode active material to the current collector can be secured.

In the lithium ion secondary battery 200 of the present embodiment, the thickness of the electrode active material layer is preferably 150 to 1500 μm, more preferably 180 to 950 μm, and further preferably 200 for the positive electrode active material layer 212. It is ~ 800 μm. The thickness of the negative electrode active material layer 213 is preferably 150 to 1500 μm, more preferably 180 to 1200 μm, and even more preferably 200 to 1000 μm. When the thickness of the electrode active material layer is at least the above-mentioned lower limit value, the energy density of the battery can be sufficiently increased. On the other hand, if the thickness of the electrode active material layer is a value equal to or less than the above-mentioned upper limit value, the structure of the electrode active material layer can be sufficiently maintained.

[Electrolyte layer]
As the electrolyte used for the electrolyte layer 216, a liquid electrolyte (electrolyte solution) containing a non-aqueous solvent or a gel polymer electrolyte having a host polymer holding the electrolyte solution is used.

The electrolytic solution has a form in which a lithium salt is dissolved in a non-aqueous solvent. Examples of the non-aqueous solvent include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate. The lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6 LiClO 4, Li [(FSO 2) 2 N] (LiFSI) lithium salts of inorganic acids such _{as, LiN (CF 3 SO 2)} 2, LiN ( Examples thereof include lithium salts (ionic liquids) of organic acids such as C ₂ F ₅ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) _3.

The gel polymer electrolyte has a structure in which an electrolytic solution is injected into a matrix polymer (host polymer) made of an ionic conductive polymer. Examples of the ionic conductive polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVdF-HEP), and polymethyl methacrylate (polymethyl methacrylate). PMMA), and copolymers thereof and the like.

A separator may be further used for the electrolyte layer 216. The separator has a function of holding an electrolytic solution and ensuring lithium ion conductivity between the positive electrode and the negative electrode, and a function as a partition wall between the positive electrode and the negative electrode. Examples of the form of the separator include a porous sheet separator made of a polymer or fiber that absorbs and retains an electrolytic solution, a non-woven fabric separator, and the like.

[Positive current collector plate and negative electrode current collector plate]
The material constituting the current collector plates 221 and 222 is not particularly limited, and a known highly conductive material conventionally used as a current collector plate for a lithium ion secondary battery can be used. As the constituent materials of the current collector plates 221,222, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. The same material may be used or different materials may be used for the positive electrode current collector plate 221 and the negative electrode current collector plate 222.

[Seal part]
The seal portion 218 has a function of preventing contact between the current collectors 211 and a short circuit at the end portion of the cell cell layer 217. The material constituting the sealing portion 218 may have insulating property, sealing property against falling off of solid electrolyte, sealing property against moisture permeation from the outside (sealing property), heat resistance under battery operating temperature, and the like. Just do it. For example, acrylic resin, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber (ethylene-propylene-diene rubber: EPDM) and the like can be used. Further, an isocyanate-based adhesive, an acrylic resin-based adhesive, a cyanoacrylate-based adhesive, or the like may be used, or a hot melt adhesive (urethane resin, polyamide resin, polyolefin resin) or the like may be used. Among them, polyethylene resin and polypropylene resin are preferably used as constituent materials of the insulating layer from the viewpoints of corrosion resistance, chemical resistance, ease of production (film formation), economy, etc., and the main component is non-crystalline polypropylene resin. It is preferable to use a resin obtained by copolymerizing ethylene, propylene, and butene.

[Exterior body]
As the exterior body 220, a bag-shaped case using a laminated film containing aluminum can be used, or a known metal can case can be used. As the laminate film, for example, a laminate film having a three-layer structure in which polypropylene (PP), aluminum, and nylon are laminated in this order can be used, but the laminate film is not limited thereto. A laminated film is desirable from the viewpoint of high output and excellent cooling performance, and can be suitably used for batteries for large devices for EVs and HEVs. Further, the exterior body 220 is more preferably an aluminumate laminate because the group pressure applied to the power generation element 210 from the outside can be easily adjusted and the thickness of the desired electrolyte layer 216 can be easily adjusted.

As described above, the present embodiment described has the following effects.

(A) first charge step, the first charging step of charging the secondary battery 200 to a predetermined battery voltage V _S, resting step of resting the predetermined time T the charge of the secondary battery 200, and the charging of the secondary battery 200 Includes a second charging step to resume. Therefore, in the resting step, the particles of the negative electrode active material are rearranged, and the reduction decomposition reaction of the electrolytic solution is suppressed. As a result, the SEI film formed on the surface of the particles of the negative electrode active material becomes thin, and the battery performance is improved.

(B) In the pause step, it is preferable that the charging of the secondary battery 200 is paused for 1 hour or more. According to such a configuration, even when the secondary battery 200 is placed under atmospheric pressure, the particles of the negative electrode active material are surely rearranged, and the reduction decomposition reaction of the electrolytic solution can be surely suppressed. ..

(C) a predetermined battery voltage V _S is the battery voltage V _H negative electrode potential of the secondary battery 200 is in the reduction decomposition potential and equipotential of the electrolyte, the battery voltage V _L represented by the above formula (1) It is preferable that it is set between and. According to such a configuration, the conductive auxiliary agent surely enters the gap generated in the negative electrode active material layer due to the expansion of the silicon-based active material particles, and the reduction decomposition reaction of the electrolytic solution is surely suppressed.

(D) The electrolytic solution is preferably a solution in which LiFSI is dissolved in a mixed solvent of PC and EC. According to such a configuration, the battery output and the cycle life characteristics can be improved.

As described above, the method for manufacturing the lithium ion secondary battery according to the present invention has been described in the described embodiment. However, it goes without saying that the present invention can be appropriately added, modified, and omitted by those skilled in the art within the scope of the technical idea.

For example, in the above-described embodiment, the charging of the secondary battery is stopped only once in the initial charging step of the secondary battery 200. However, charging of the secondary battery 200 may be suspended a plurality of times. In this case, charging of the secondary battery 200 is stopped at a plurality of battery voltages set in a range in which the negative electrode potential of the secondary battery 200 is maintained at a potential noble than the reduction / decomposition potential of the electrolytic solution. For example, charging is stopped when the secondary battery 200 is charged to the first battery voltage, and after resuming charging, charging is stopped again when the secondary battery 200 is charged to the second battery voltage.

Further, in the above-described embodiment, the state in which the secondary battery 200 is connected to the charging device 100 is maintained in the pause step of suspending the charging of the secondary battery 200 for a predetermined time. However, in the pause process, the secondary battery 200 may be electrically disconnected from the charging device 100, and the secondary battery 200 may be reconnected to the charging device 100 when charging is resumed. Further, the first charging step and the second charging step do not have to be executed by the same charging device 100, and may be executed by different charging devices 100.

Further, in the above-described embodiment, the case where the lithium ion secondary battery 200 is a bipolar secondary battery has been described as an example. However, in a lithium ion secondary battery, a positive electrode having a positive electrode active material layer formed on a positive electrode current collector and a negative electrode having a negative electrode active material layer formed on a negative electrode current collector are formed via an electrolyte layer. It may be a general secondary battery constructed by stacking.

The effects of the present invention will be described with reference to the following examples and comparative examples. Unless otherwise stated, each operation is performed at room temperature (25 ° C.).

(Example)
(1) Assembly of Lithium Ion Secondary Battery LiFSI was dissolved in an equal volume mixed solvent of ethylene carbonate and propylene carbonate so that the supporting salt concentration was 2 mol / L to prepare an electrolytic solution. Also, of NCA composite oxide (LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) (94% by mass), acetylene black (5.8% by mass), and carbon nanofibers (0.2% by mass). An electrolytic solution was added to the mixture to prepare a slurry for a positive electrode. Similarly, hard carbon (70.4% by mass), Si alloy (Si ₅₅ Sn ₁₅ Ti ₃₀ (atomic ratio is mass ratio)) (17.6% by mass), acetylene black (10% by mass), and carbon nanofibers. An electrolytic solution was added to the mixture (2.0% by mass) to prepare a slurry for a negative electrode. Then, a positive electrode was produced by applying a positive electrode slurry on an aluminum current collector foil to form a positive electrode active material layer (thickness 354 μm). Similarly, a negative electrode was produced by applying a negative electrode slurry on a copper current collector foil to form a negative electrode active material layer (thickness 256 μm). Then, the positive electrode and the negative electrode are laminated via a separator (Celguard 3501 manufactured by Cellguard) so that the active material layers face each other, and an electrolytic solution is added to vacuum-seal the inside of the aluminumate laminated exterior body. Assembled a lithium ion secondary battery composed of one cell cell layer. In addition, it was confirmed by linear sweep voltammetry measurement that the battery voltage of the lithium ion secondary battery in which the reduction decomposition reaction of the electrolytic solution occurs was about 3.5 V.

(2) Initial Charging Step of Lithium Ion Secondary Battery The assembled secondary battery was subjected to the initial charging step to complete the lithium ion secondary battery. Specifically, first, the lithium ion secondary battery was constantly charged with a current of 0.1 C, and when the charge amount reached 10% (battery voltage: about 3.0 V), charging was suspended for 24 hours. After 24 hours, constant current charging was restarted with a current of 0.1 C, and then, when the battery voltage reached 4.2 V, the charging method was switched to constant voltage charging. Then, charging was terminated when the current flowing through the lithium ion secondary battery reached 0.001 C.

(Comparison example)
The lithium ion secondary battery assembled in the same manner as the lithium ion secondary battery according to the embodiment was subjected to a general initial charging step to complete the secondary battery. Specifically, the lithium ion secondary power was charged with a constant current of 0.1 C without pausing the charging, and when the battery voltage reached 4.2 V, the charging method was switched to the constant voltage charging. Then, charging was terminated when the current flowing through the lithium ion secondary battery reached 0.001 C.

[Evaluation item]
(Evaluation of initial capacity)
FIG. 6 shows changes in the battery voltage of the lithium ion secondary batteries according to the examples and the comparative examples. The vertical axis of FIG. 6 shows the battery voltage of the secondary battery, and the horizontal axis shows the charge capacity of the secondary battery. The solid line in FIG. 6 shows the change in the battery voltage of the secondary battery according to the embodiment, and the broken line shows the change in the battery voltage of the secondary battery according to the comparative example.

As shown in FIG. 6, the lithium ion secondary battery according to the embodiment has been charged when the charging capacity is about 200 mAh. On the other hand, the lithium ion secondary battery according to the comparative example has been charged when the charging capacity is about 180 mAh.

Therefore, it was confirmed that the initial capacity of the lithium ion secondary battery is increased according to the method for manufacturing the secondary battery according to the present embodiment. In the embodiment, it can be seen that the battery voltage of the secondary battery is slightly reduced while the charging of the lithium ion secondary battery is stopped.

(Evaluation of discharge rate characteristics)
The lithium ion secondary batteries according to Examples and Comparative Examples were discharged by changing the discharge rate, and the discharge rate characteristics were evaluated. The evaluation results are shown in FIG. The vertical axis of FIG. 7 shows the discharge capacity of the secondary battery, and the horizontal axis shows the C rate at the time of discharge. The white circles in FIG. 7 indicate the characteristics of the secondary battery according to the embodiment, and the black circles indicate the characteristics of the secondary battery according to the comparative example.

As shown in FIG. 7, the secondary battery according to the embodiment shows a larger discharge capacity than the secondary battery according to the comparative example at all C rates. Then, it can be seen that the discharge rate characteristics of the secondary battery according to the embodiment are improved as compared with the secondary battery according to the comparative example. Therefore, it was confirmed that the discharge rate characteristics of the lithium ion secondary battery are improved according to the method for manufacturing the secondary battery according to the present embodiment.

100 charging device,
110 voltage sensor,
120 current sensor,
130 power supply,
140 control unit,
200 lithium ion secondary battery,
210 power generation element,
211 current collector,
212 Positive electrode active material layer,
213 Negative electrode active material layer,
215 bipolar electrode,
216 Electrolyte layer,
217 Single battery layer,
218 Seal part,
220 exterior,
250 carbon-based active material particles,
260 Silicon-based active material particles,
270 Conductive carbon particles.

Claims (3)

A positive electrode having a positive electrode active material layer containing a positive electrode active material capable of storing and releasing lithium ions, a negative electrode having a negative electrode active material layer which is a non-bonded body of a negative electrode active material containing silicon, and a non-aqueous solvent. A method for manufacturing a lithium ion secondary battery having an electrolyte layer having an electrolytic solution containing the electrolyte.
The first charging step of charging the lithium ion secondary battery to a predetermined battery voltage set in a range in which the negative electrode potential of the lithium ion secondary battery is maintained at a potential noble than the reduction decomposition potential of the electrolytic solution. When,
When the lithium ion secondary battery is charged to the predetermined battery voltage, a pause step of suspending the charging of the lithium ion secondary battery for a predetermined time and a pause step.
When the predetermined time has elapsed, the second charging step of restarting the charging of the lithium ion secondary battery and continuing the charging of the lithium ion secondary battery, and
Have a first charge process, including,
The predetermined battery voltage is set in a range _{smaller than the battery voltage (V H} ) when the negative potential of the lithium ion secondary battery is equal to the reduction decomposition potential of the electrolytic solution and larger than the battery voltage ( _VL).
The battery voltage ( _VL ) is calculated by the following mathematical formula (1):
_{V L = V I + 0.3 ×} (V H -V I) ... (1)
(In the above equation (1), V _I is the battery voltage of the lithium ion secondary battery at the start of charging)
In represented Ru, method for manufacturing a lithium ion secondary battery. The method for manufacturing a lithium ion secondary battery according to claim 1, wherein in the pause step, charging of the lithium ion secondary battery is suspended for 1 hour or more. The electrolytic solution is a solution in which lithium bis (fluorosulfonyl) imide is dissolved in a mixed solvent of propylene carbonate and ethylene carbonate.
The method for producing a lithium ion secondary battery according to claim 1 or 2 , wherein the reduction decomposition potential of the electrolytic solution is the reduction decomposition potential of propylene carbonate.

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