Production methods and capacity recovery methods for all-solid-state batteries

Abstract

In the charging process, the all-solid-state battery undergoes CCCV charging at a set voltage VB, followed by storage. In the recovery process, the stored all-solid-state battery undergoes CCCV charging at a set voltage VR higher than the set voltage VB, and is maintained at the set voltage VR for a specified period. If CCCV charging is performed after storage using a set voltage VR that is higher than the original set voltage VB, then lithium ions exceeding the original set voltage VB will detach from the positive electrode of the all-solid-state battery, and its capacity will be restored.

Description

Technical Field

[0001] This disclosure relates to a method for producing all-solid-state batteries and a method for restoring the capacity of all-solid-state batteries. Background Technology

[0002] Japanese Patent Application Publication No. 2023-135693 discloses a method for restoring the capacity of an all-solid-state battery. In this method, a constant current voltage is discharged to 0V while a pulsating current is applied, and the voltage is maintained at 0V for a specified time to restore the capacity of the all-solid-state battery. Summary of the Invention

[0003] Solid-state batteries are sometimes stored for extended periods, often during transportation or other processes. Due to self-discharge, their State of Charge (SOC) decreases after storage. Therefore, in the capacity recovery method disclosed in Japanese Patent Application Laid-Open No. 2023-135693, after storing a solid-state battery, it is necessary to temporarily charge the battery to full charge, then discharge it to 0V while simultaneously applying a pulsating current, maintaining the voltage at 0V for a specified time or longer. This process of discharging the electricity accumulated during charging can potentially lead to energy waste, depending on the discharge environment.

[0004] The purpose of this disclosure is to restore the capacity of a stored all-solid-state battery while suppressing energy waste.

[0005] The method for producing an all-solid-state battery disclosed herein includes: a charging step, wherein the all-solid-state battery is charged at a constant voltage with a first voltage; a storage step, wherein the all-solid-state battery is stored after the charging step is completed; and a capacity recovery step, wherein the stored all-solid-state battery is charged at a constant voltage with a second voltage higher than the first voltage, and maintained at the second voltage for a specified period.

[0006] According to this method, the all-solid-state battery is charged at a constant voltage with a first voltage during the charging process, and then stored. Due to self-discharge during storage, the state of charge (SOC) decreases and the capacity diminishes. The battery is then charged at a constant voltage with a second voltage higher than the first voltage, and its capacity is restored through a capacity recovery process that maintains the second voltage for a specified period. The restored solid-state battery can then utilize the electricity stored in the capacity recovery process, thus suppressing energy waste.

[0007] Preferably, the process of storing the all-solid-state battery may include transporting the all-solid-state battery or an article carrying the all-solid-state battery. The capacity lost during transport of the all-solid-state battery can be restored when it is used.

[0008] Preferably, the constant voltage charging in the capacity recovery process can be constant current constant voltage charging. By performing constant current constant voltage charging, the charging time can be shortened.

[0009] The capacity recovery method for an all-solid-state battery disclosed herein is a method for recovering the capacity of an all-solid-state battery after it has been stored following constant-voltage charging at a first voltage. The capacity recovery method includes: charging the all-solid-state battery at a second voltage higher than the first voltage; and maintaining the all-solid-state battery at the second voltage for a specified period after constant-voltage charging.

[0010] According to this method, a solid-state battery that has been stored after constant-voltage charging at a first voltage is charged at a second voltage higher than the first voltage, and maintained at the second voltage for a specified period, thus restoring its capacity. The restored solid-state battery can then use the electricity stored during the capacity restoration process for discharging to a load, thereby suppressing energy waste.

[0011] According to this disclosure, it is possible to restore the capacity of a stored solid-state battery while suppressing energy waste. Attached Figure Description

[0012] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will now be described in conjunction with the accompanying drawings, wherein the same reference numerals denote the same elements.

[0013] Figure 1 This is a flowchart illustrating a general method for producing the all-solid-state battery according to this embodiment.

[0014] Figure 2 This is a flowchart illustrating the control of the capacity recovery method in the capacity recovery process.

[0015] Figure 3 This is a graph illustrating the capacity recovery results of an all-solid-state battery.

[0016] Figure 4 This is a graph illustrating the capacity retention rate during capacity recovery based on the difference in set voltage. Detailed Implementation

[0017] The embodiments of this disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same or equivalent parts are labeled with the same reference numerals, and their descriptions are not repeated.

[0018] In this embodiment, the all-solid-state battery 100 (refer to...) Figure 2 For example, there are all-solid-state lithium-ion batteries based on the NCA-LTO system. The positive electrode active material in the positive electrode layer can contain lithium nickel oxide, such as NCA (LiNiO2). x Co y Al zO2). The negative electrode active material of the negative electrode layer may include lithium titanate (LTO). The solid electrolyte layer may be a sulfide-based solid electrolyte. The all-solid-state battery 100 is manufactured by housing all-solid-state battery elements, which are sequentially stacked with a positive current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative current collector, in an outer packaging component. Multiple all-solid-state battery elements may be electrically stacked in series and housed in the outer packaging component.

[0019] Figure 1 This is a flowchart outlining the general method for producing the all-solid-state battery 100 according to this embodiment. In step (hereinafter, step S) 10, the prepared all-solid-state battery is charged by constant current constant voltage (CCCV) charging. In S10, the constant voltage value of CCCV charging is VB, hereinafter also referred to as the set voltage VB. Constant current charging (CC) is performed until the voltage of the all-solid-state battery reaches the set voltage VB. The C rate can be, for example, 1C. When the all-solid-state battery element of the all-solid-state battery 100 is one, the set voltage VB can be, for example, 2.7V.

[0020] When the voltage of the all-solid-state battery 100 reaches the set voltage VB, constant voltage (CV) charging is performed. While maintaining the charging voltage at the set voltage VB, charging of the all-solid-state battery 100 ends when the charging current falls below a predetermined value, for example, below 0.02 C. Charging can also end when the CV charging time exceeds a predetermined time. In the charging process of S10, when charging of the all-solid-state battery 100 ends, the process proceeds to S20.

[0021] In S20, the solid-state battery 100 is stored after charging is completed. The storage period can be arbitrary. For example, it can be the period during which a vehicle carrying the solid-state battery 100 after charging is transported by ship, or it can be 3 to 6 months. S20 is the process of storing the solid-state battery 100.

[0022] In the next step, S30, the capacity of the stored solid-state battery is restored. The stored solid-state battery 100 experiences a capacity reduction due to self-discharge, etc. In this embodiment, the capacity of the solid-state battery 100 is restored through the capacity restoration step in S30.

[0023] Figure 2 This is a flowchart illustrating the capacity recovery method in the capacity recovery process of S30. First, in S31, the pre-storage holding voltage of the all-solid-state battery 100 undergoing capacity recovery is obtained. The pre-storage holding voltage is... Figure 1The setting voltage VB in S10. The setting voltage VB is an example of the "first voltage" of this disclosure. For example, the setting voltage VB can be obtained from the historical information of the all-solid-state battery 100 using a control device or a reading device not shown. The historical information of the all-solid-state battery 100 can also be read from a QR code or RFID (Radio Frequency Identification) tag affixed to the all-solid-state battery 100. The historical information includes information about the setting voltage VB. Alternatively, the setting voltage VB can also be obtained from a server that manages the data of the setting voltage VB based on the identification ID of the all-solid-state battery 100 read from the QR code or RFID (Radio Frequency Identification) tag.

[0024] QR codes and RFID tags can be affixed to the battery pack containing the all-solid-state battery 100. When the all-solid-state battery 100 is installed in a vehicle, the set voltage VB (pre-storage voltage) of the all-solid-state battery 100 can also be obtained from the management server based on the vehicle's identification number (e.g., vehicle identification number).

[0025] In step S32, the all-solid-state battery 100 is charged by the charging device 200 using CCCV charging. In step S32, the constant voltage value for CCCV charging is VR, hereinafter also referred to as the set voltage VR. The set voltage VR is a voltage higher than the set voltage VB. The set voltage VR is equivalent to the "second voltage" of this disclosure. In step S32, CC charging is performed until the voltage of the all-solid-state battery 100 reaches the set voltage VR. The C rate can be, for example, 0.5C. When the all-solid-state battery 100 has only one all-solid-state element, the set voltage VR can be, for example, 3.15 [V]. When the voltage of the all-solid-state battery 100 reaches the set voltage VR, CV charging is performed. During this CV charging, regardless of the decrease in charging current, the voltage (charging voltage) supplied from the charging device 200 to the all-solid-state battery 100 is maintained at the set voltage VR.

[0026] In step S33, it is determined whether the CV charging based on the set voltage VR has elapsed for a predetermined period. The predetermined period could be, for example, 7 days. If the predetermined period has not elapsed, the voltage supplied from the charging device 200 to the all-solid-state battery 100 continues to be maintained at the set voltage VR. When the predetermined period has elapsed, step S34 is entered, charging ends, and the capacity recovery process concludes.

[0027] Figure 3 This is a graph illustrating the capacity recovery results of the all-solid-state battery 100. In Figure 3 In the graph, the vertical axis represents the discharge capacity [Ah], and the horizontal axis represents time. The scale of the horizontal axis is √days (days to the power of 0.5). Figure 3In the diagram, the solid line represents the change in discharge capacity of the all-solid-state battery stored from time t1 to time t2 after a power-on endurance evaluation performed with a set voltage V1 during CCCV charging following manufacturing. The dashed line represents the change in discharge capacity of the all-solid-state battery stored from time t1 to time t2 after a power-on endurance evaluation performed with a set voltage V2 during CCCV charging following manufacturing. The set voltage V2 is a higher voltage than the set voltage V1. For example, the set voltage V2 is 3.15 [V], and the set voltage V1 is 2.7 [V].

[0028] exist Figure 3 Before storage, the CCCV charging (power-on durability evaluation) was performed at 60°C with a 1C CC charge until the set voltage was reached. Upon reaching the set voltage, the charging was switched to CV charging at the set voltage. This state was then maintained at the set voltage for 7 days. The discharge capacity was determined by discharging the all-solid-state battery. The discharge temperature was 25°C, and the discharge rate was 0.5C. Discharge was then stopped when the discharge current reached 0.02C, and the discharge capacity was calculated based on the cumulative discharge current.

[0029] exist Figure 3 Five power-on durability tests (CCCV charging) were performed. The discharge capacity from time t0 to time t1 was equivalent to the full-charge capacity of the all-solid-state battery. At time t1, at the end of the fifth power-on durability test, the battery was fully charged via CCCV charging at a set voltage. Afterward, the all-solid-state battery was stored. Time t1 to time t2 constituted the storage period, which was 6 months.

[0030] At the end of storage (time t2), the discharge capacity of the all-solid-state battery (hereinafter referred to as "V1 all-solid-state battery") stored after being charged with a set voltage V1 using CCCV decreased from C[Ah] at the start of storage (time t1) to A[Ah]. The discharge capacity of the all-solid-state battery (hereinafter referred to as "V2 all-solid-state battery") stored after being charged with a set voltage V2 using CCCV decreased from D[Ah] at the start of storage (time t1) to approximately C[Ah].

[0031] At time t2 (end of storage), a power-on durability evaluation based on a set voltage V2 and a CCCV charge was performed on the V1 and V2 all-solid-state batteries. CCCV charging was performed at 1C at 60°C until the set voltage V2 was reached. Upon reaching V2, the charging was switched to CV charging at V2. This state was then maintained at V2 for 7 days, and the discharge capacity of the V1 and V2 all-solid-state batteries was calculated. The power-on durability evaluation (CCCV charging at set voltage V2) was performed multiple times after the storage period ended.

[0032] like Figure 3 As shown, in the V1 all-solid-state battery, the discharge capacity increases to approximately D[Ah] in the endurance evaluation of CCCV charging based on a set voltage V2. In the V2 all-solid-state battery, the discharge capacity does not increase in the endurance evaluation of CCCV charging based on a set voltage V2, and the capacity continues to decrease.

[0033] It should be noted that, in Figure 3 In the diagram, the dashed line in the V1 all-solid-state battery represents the discharge capacity during a power-on durability evaluation performed using CCCV charging based on a set voltage V1. In the V1 all-solid-state battery, the discharge capacity did not increase during the power-on durability evaluation using CCCV charging based on the set voltage V1; instead, the capacity continuously decreased.

[0034] like Figure 3 As shown, if the V1 all-solid-state battery is charged with a set voltage V2 using CCCV charging, the discharge capacity increases, and the capacity of the V1 all-solid-state battery is restored. However, when the V2 all-solid-state battery is charged with a set voltage V2 using CCCV charging, and when the V1 all-solid-state battery is charged with a set voltage V1 using CCCV charging, the discharge capacity does not increase, and the capacity is not restored. This is presumably because, by using a set voltage higher than the CCCV charging voltage before storage, when performing CCCV charging after storage, more lithium ions than those before storage are removed from the positive electrode of the all-solid-state battery, thus restoring the capacity.

[0035] Figure 4 This is a graph illustrating the capacity retention rate during capacity recovery based on the difference in set voltage. Figure 4 In the graph, the vertical axis represents capacity maintenance rate, and the horizontal axis represents time. The scale of the horizontal axis is √days (days to the power of 0.5). Figure 4 In the middle, at the end of storage ( Figure 3 The capacity retention rate (with the capacity retention rate at the end of storage set to 100%) is shown based on the capacity at time t2. CCCV charging is performed at set voltages Va to Vd, and the battery continues to maintain these set voltages after reaching them. The horizontal axis represents the CCCV charging time, which is approximately equivalent to the time maintained at the set voltage. The set voltage is defined as "Va < Vb < Vc < Vd". The set voltage Va is higher than the set voltage of the CCCV charging before storage. The set voltage Vd is set to the voltage at which the all-solid-state battery will not be overcharged.

[0036] like Figure 4 As shown, preferably, the set voltage of the CCCV charge in the capacity recovery process is higher than the CCCV charge voltage before storage, and is a higher voltage within the range where the all-solid-state battery will not be overcharged. Furthermore, it is preferable to maintain the set voltages Va to Vd for more than 7 days.

[0037] According to this embodiment, the all-solid-state battery 100 is charged with a set voltage VB (first voltage) using a CCCV method during the charging process (S10), and then stored (S20). Due to self-discharge during storage, the all-solid-state battery 100, whose SOC has decreased and capacity has reduced, is charged with a set voltage VR (second voltage) that is higher than the set voltage VB using a CCCV method. Through a capacity recovery process (S30, S31-34) that maintains the set voltage VR for a predetermined period, the capacity is recovered. After capacity recovery, the all-solid-state battery 100 can then use the electricity stored in the capacity recovery process, thus suppressing energy waste.

[0038] The process of storing the all-solid-state battery 100 may include transporting the all-solid-state battery 100 or an article carrying the all-solid-state battery 100. The capacity lost during transport of the all-solid-state battery 100 can be restored when the all-solid-state battery 100 is used.

[0039] According to this embodiment, the all-solid-state battery 100, after being stored following CCCV charging at a set voltage VB (first voltage), is CCCV charged at a set voltage VR (second voltage) that is higher than the set voltage VB. The all-solid-state battery 100 after CCCV charging is maintained at the set voltage VR for a predetermined period (S32, S33), and its capacity is restored. The all-solid-state battery 100, after capacity restoration, can use the electricity accumulated during the capacity restoration process for discharging to a load, etc., thus suppressing energy waste.

[0040] In the above embodiment, CCCV charging is performed in the charging step (S10) and the capacity recovery step (S30, S32). However, CV charging can also be performed in both the charging step and the capacity recovery step. In this case, CV charging is performed by setting a voltage VB in the charging step, and CV charging is performed by setting a voltage VR in the capacity recovery step.

[0041] The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects. The scope of the invention is defined not by the description of the embodiments above, but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A method for producing an all-solid-state battery, comprising: The charging process involves constant-voltage charging of the all-solid-state battery using a first voltage. The process of storing the all-solid-state battery after the charging process is completed; as well as The capacity recovery process involves charging the stored solid-state battery at a constant voltage using a second voltage that is higher than the first voltage, and maintaining the second voltage for a specified period.

2. The method for producing the all-solid-state battery according to claim 1, wherein, The process of storing the all-solid-state battery includes conveying the all-solid-state battery or an article containing the all-solid-state battery.

3. The method for producing the all-solid-state battery according to claim 1 or 2, wherein, The constant voltage charging in the capacity recovery process is constant current constant voltage charging.

4. A method for capacity recovery of an all-solid-state battery, comprising: The all-solid-state battery is charged at a constant voltage using a second voltage that is higher than the first voltage. as well as The all-solid-state battery, after constant voltage charging, is maintained at the second voltage for a specified period.

5. The capacity recovery method for an all-solid-state battery according to claim 4, wherein, Constant voltage charging based on the second voltage is constant current constant voltage charging.

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