Method for producing all-solid-state batteries and method for restoring the capacity of all-solid-state batteries
By charging all-solid-state batteries at a higher voltage during a capacity recovery process after storage, the method addresses energy waste issues in existing recovery methods, effectively restoring battery capacity for efficient use.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-11-25
- Publication Date
- 2026-06-04
AI Technical Summary
Existing methods for recovering the capacity of all-solid-state batteries after storage result in energy waste due to the need for discharging stored energy, which is inefficient and wasteful.
A method involving charging the all-solid-state battery at a first voltage during production, followed by storage, and then charging it at a higher second voltage during a capacity recovery process to maintain that voltage for a predetermined period, thereby restoring the battery's capacity while minimizing energy waste.
The method effectively recovers the capacity of all-solid-state batteries after storage, reducing energy waste by utilizing the stored power for subsequent use, particularly during transportation.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a method for producing an all-solid-state battery and a method for recovering the capacity of an all-solid-state battery.
Background Art
[0002] Japanese Patent Application Laid-Open No. 2023-135693 (Patent Document 1) discloses a method for recovering the capacity of an all-solid-state battery. In Patent Document 1, while superimposing a ripple current, the voltage is discharged at a constant current and voltage to 0 [V], and the voltage is held at 0 [V] for a predetermined time or longer to recover the capacity of the all-solid-state battery.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] When an all-solid-state battery is stored for a relatively long period of time due to transportation or the like, the SOC (State Of Charge) decreases after storage due to the self-discharge of the all-solid-state battery. Therefore, after storing the all-solid-state battery, in the capacity recovery method disclosed in Patent Document 1, after charging the all-solid-state battery to full charge once, the voltage is discharged at a constant current and voltage to 0 [V] while superimposing a ripple current, and further, the voltage needs to be held at 0 [V] for a predetermined time or longer. Therefore, a step of discharging the electric power stored by charging is required, and there is a concern that energy may be wasted depending on the discharge environment.
[0005] An object of the present disclosure is to make it possible to recover the capacity of an all-solid-state battery after storage while suppressing waste of energy.
Means for Solving the Problems
[0006] The production method for a solid-state battery according to the present disclosure includes a charging step of charging the solid-state battery at a constant voltage with a first voltage, a storage step of the solid-state battery after the completion of the charging step, and a capacity recovery step of charging the stored solid-state battery at a constant voltage with a second voltage higher than the first voltage and maintaining the second voltage for a predetermined period of time.
[0007] According to this method, the all-solid-state battery is charged at a constant voltage (a first voltage) during the charging process and then stored. During storage, the state of charge (SOC) decreases and the capacity of the all-solid-state battery decreases due to self-discharge. The battery is then charged at a constant voltage (a second voltage higher than the first voltage) and maintained at this voltage for a predetermined period in a capacity recovery process, thereby restoring its capacity. The restored capacity of the solid-state battery can then be used with the power stored during the capacity recovery process, thus reducing energy waste.
[0008] Preferably, the process of storing the solid-state battery may include transporting the solid-state battery or an article containing the solid-state battery. The capacity lost during transport of the solid-state battery can be recovered when the solid-state battery is used.
[0009] Preferably, the constant voltage charging in the capacity recovery process may be constant current constant voltage charging. By performing constant current constant voltage charging, the charging time can be shortened.
[0010] The capacity recovery method for a solid-state battery disclosed herein is a method for recovering the capacity of a solid-state battery that has been stored after being charged at a constant voltage at a first voltage. The capacity recovery method includes charging the solid-state battery at a second voltage higher than the first voltage, and maintaining the solid-state battery that has been charged at a constant voltage at the second voltage for a predetermined period of time.
[0011] According to this method, a solid-state battery that has been charged at a constant voltage of a first voltage and then stored is charged at a second voltage higher than the first voltage, held at the second voltage for a predetermined period, and its capacity is restored. The fully restored capacity of the solid-state battery can then use the power stored during the capacity restoration process for discharging to a load, etc., thereby suppressing energy waste. [Effects of the Invention]
[0012] According to this disclosure, it is possible to recover the capacity of all-solid-state batteries after storage while suppressing energy waste. [Brief explanation of the drawing]
[0013] [Figure 1] This is a flowchart illustrating the general outline of the production method for all-solid-state batteries according to this embodiment. [Figure 2] This is a flowchart illustrating the control of the capacity recovery method during the capacity recovery process. [Figure 3] This diagram illustrates the results of capacity recovery in an all-solid-state battery. [Figure 4] This diagram illustrates the capacity retention rate during capacity recovery due to differences in the set voltage. [Modes for carrying out the invention]
[0014] Embodiments of this disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.
[0015] In this embodiment, the all-solid-state battery 100 (see Figure 2) is, for example, an NCA-LTO-based all-solid-state lithium-ion battery. The positive electrode active material of the positive electrode layer may include lithium nickelate, for example, NCA (LiNixCoyAlzO2). 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 an all-solid-state battery element, in which a positive electrode current collector, positive electrode layer, solid electrolyte layer, negative electrode layer, and negative electrode current collector are stacked in this order, within an outer casing. Multiple all-solid-state battery elements may be stacked electrically in series and housed within the outer casing.
[0016] Figure 1 is a flowchart illustrating the general method for producing a solid-state battery 100 according to this embodiment. In step 10 (hereinafter, steps are abbreviated as "S"), the prepared solid-state battery is charged by constant current, constant voltage (CCCV) charging. In S10, the constant voltage value for CCCV charging is VB, and is hereinafter also referred to as the set voltage VB. Constant current charging (CC (Constant Current) charging) is performed until the voltage of the solid-state battery reaches the set voltage VB. The C rate may be, for example, 1C. The set voltage VB may be, for example, 2.7[V] when the solid-state battery 100 has one solid-state battery element.
[0017] When the voltage of the solid-state battery 100 reaches the set voltage VB, constant voltage charging (CV (Constant Voltage) charging) is performed. While maintaining the charging voltage at the set voltage VB, when the charging current falls below a predetermined value, for example, when it falls below 0.02C, charging of the solid-state battery 100 is terminated. Charging may also be terminated when the CV charging time exceeds a predetermined time. When charging of the solid-state battery 100 is completed in the charging process of S10, the process proceeds to S20.
[0018] In S20, the solid-state battery 100, after charging is complete, is stored. The storage period may be arbitrary. For example, it may be the period during which a vehicle equipped with the solid-state battery 100 after charging is transported by ship, and may be 3 to 6 months. S20 is the process of storing the solid-state battery 100.
[0019] In the subsequent S30, the capacity of the stored solid-state battery is restored. The stored solid-state battery 100 has a reduced capacity due to self-discharge, etc. In this embodiment, the capacity of the solid-state battery 100 is restored by the capacity recovery process in S30.
[0020] Figure 2 is a flowchart for explaining a 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 for which capacity recovery is to be performed is obtained. The pre-storage holding voltage is the set voltage VB in S10 of FIG. 1. The set voltage VB corresponds to an example of the "first voltage" of the present disclosure. For example, the set voltage VB is obtained from the history information of the all-solid-state battery 100 using a control device or a reading device not shown. The history information of the all-solid-state battery 100 may be read from a two-dimensional code or an RFID (Radio Frequency Identification) tag attached to the all-solid-state battery 100. The history information includes information on the set voltage VB. Also, the set voltage VB may be obtained from a server that manages the data of the set voltage VB based on the identification ID of the all-solid-state battery 100 read from the two-dimensional code or the RFID (Radio Frequency Identification) tag.
[0021] The barcode or FRID tag may be attached to the battery pack including the all-solid-state battery 100. When the all-solid-state battery 100 is mounted on a vehicle, the set voltage VB (pre-storage holding voltage) of the all-solid-state battery 100 may be obtained from the management server based on the identification number of the vehicle (for example, the vehicle body number).
[0022] In S32, the all-solid-state battery 100 is charged by CCCV charging using the charging device 200. In S32, the constant voltage value of the CCCV charging is VR, which is 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 corresponds to the "second voltage" of the present disclosure. In S32, CC charging is performed until the voltage of the all-solid-state battery 100 reaches the set voltage VR. The C rate may be, for example, 0.5C. When the all-solid-state battery has one all-solid-state battery element, the set voltage VR may be, for example, 3.15 [V]. When the voltage of the all-solid-state battery reaches the set voltage VR, CV charging is performed. In this CV charging, the voltage (charging voltage) supplied from the charging device 200 to the all-solid-state battery 100 is maintained at the set voltage VR regardless of the decrease in the charging current.
[0023] In S33, it is determined whether a predetermined period has elapsed since CV charging at the set voltage VR. The predetermined period may be, for example, 7 days. If the predetermined period has not elapsed, the voltage supplied from the charging device 200 to the solid-state battery 100 is maintained at the set voltage VR. Once the predetermined period has elapsed, the process proceeds to S34, where charging is terminated and the capacity recovery process is completed.
[0024] Figure 3 illustrates the results of capacity recovery for all-solid-state battery 100. In Figure 3, the vertical axis represents discharge capacity [Ah], and the horizontal axis represents time. The scale of the horizontal axis is √day (number of days raised to the power of 0.5). In Figure 3, the solid line shows the change in discharge capacity of an all-solid-state battery that was stored from time t0 to time t1 after undergoing an energizing endurance evaluation by performing CCCV charging at a set voltage V1 after the manufacturing of the all-solid-state battery. The dashed line shows the change in discharge capacity of an all-solid-state battery that was stored from time t0 to time t1 after undergoing an energizing endurance evaluation by performing CCCV charging at a set voltage V2 after the manufacturing of the all-solid-state battery. 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].
[0025] In Figure 3, the CCCV charge (current endurance evaluation) before storage is performed in a 60°C environment, with CC charging at 1C until the set voltage is reached, at which point it switches to CV charging at the set voltage. The set voltage is then maintained for 7 days. The discharge capacity is determined by discharging the all-solid-state battery. The discharge temperature is 25°C, and the discharge is performed at a C rate of 0.5C. When the discharge current reaches 0.02C, the discharge is terminated, and the discharge capacity is calculated from the integrated value of the discharge current.
[0026] Figure 3 shows five energization endurance tests (CCCV charging). The discharge capacity from time t0 to time t1 corresponds to the fully charged capacity of the solid-state battery. At time t1, after the fifth energization endurance test was completed, the battery was fully charged using CCCV charging at a set voltage, and then stored. The storage period is from time t1 to time t2. The storage period is 6 months.
[0027] At the end of storage (time t2), the discharge capacity of the all-solid-state battery stored after CCCV charging at the set voltage V1 (hereinafter also referred to as the "V1 all-solid-state battery") decreased from C[Ah] at the start of storage (time t1) to A[Ah]. The discharge capacity of the all-solid-state battery stored after CCCV charging at the set voltage V2 (hereinafter also referred to as the "V2 all-solid-state battery") decreased from D[Ah] at the start of storage (time t1) to approximately C[Ah].
[0028] At time t2 (end of storage), the V1 and V2 solid-state batteries were subjected to current-continuity endurance evaluation by CCCV charging at a set voltage V2. CCCV charging was performed in a 60°C environment with 1C CC charging until the set voltage V2 was reached. Upon reaching the set voltage V2, the charging switched to CV charging at the set voltage V2, and this state was maintained for 7 days. The discharge capacity of the V1 and V2 solid-state batteries was then determined. The current-continuity endurance evaluation (CCCV charging at set voltage V2) after the end of storage was performed multiple times.
[0029] As shown in Figure 3, in the V1 all-solid-state battery, the discharge capacity increased to approximately D [Ah] during the current-conducting endurance evaluation using CCCV charging at a set voltage V2. In the V2 whole-solid-state battery, there was no increase in discharge capacity during the current-conducting endurance evaluation using CCCV charging at a set voltage V2, and the capacity continued to decrease.
[0030] In Figure 3, the dashed line for the V1 all-solid-state battery shows the discharge capacity when the V1 all-solid-state battery underwent an endurance test using CCCV charging at a set voltage V1. In the V1 all-solid-state battery, there was no increase in discharge capacity during the endurance test using CCCV charging at a set voltage V1, and the capacity continued to decrease.
[0031] As shown in Fig. 3, when the V1 all-solid-state battery is charged by CCCV at the set voltage V2, the discharge capacity increases and the capacity of the V1 all-solid-state battery is restored. When the V2 all-solid-state battery is charged by CCCV at the set voltage V2, and when the V1 all-solid-state battery is charged by CCCV at the set voltage V1, the discharge capacity does not increase and the capacity is not restored. It is speculated that when the set voltage is higher than the set voltage of the CCCV charge before storage and CCCV charging is performed after storage, more lithium ions are desorbed from the positive electrode of the all-solid-state battery than before storage, and the capacity is restored.
[0032] Fig. 4 is a diagram for explaining the capacity retention rate during capacity recovery due to the difference in the set voltage. In Fig. 4, the vertical axis represents the capacity retention rate, and the horizontal axis represents time. The scale of the horizontal axis is √day (square root of the number of days). In Fig. 4, the capacity retention rate is shown based on the capacity at the end of storage (time t2 in Fig. 3) (the capacity retention rate at the end of storage is set to 100 [%]). CCCV charging is performed with the set voltages Va to Vd, and when the set voltages Va to Vd are reached, the state of holding at that set voltage is continued. The horizontal axis is the time of CCCV charging, which approximately corresponds to the time of holding at the set voltage. The magnitudes of the set voltages are "Va < Vb < Vc < Vd". The set voltage Va is higher than the set voltage of the CCCV charge before storage. The set voltage Vd is set to a voltage at which the all-solid-state battery does not become overcharged.
[0033] As shown in Fig. 4, in the capacity recovery process, the set voltage of the CCCV charge is preferably higher than the voltage of the CCCV charge before storage and is a higher voltage within the range where the all-solid-state battery does not become overcharged. Also, it is preferable to hold the set voltages Va to Vd for 7 days or more.
[0034] According to this embodiment, the all-solid-state battery 100 is charged via CCCV at a set voltage VB (first voltage) during the charging process (S10), and then stored (S20). Due to self-discharge during storage, the state of charge (SOC) decreases and the capacity of the all-solid-state battery 100 decreases. The capacity of the all-solid-state battery 100 is recovered by a capacity recovery process (S30, S31-34) in which it is charged via CCCV at a set voltage VR (second voltage) higher than the set voltage VB and held at the set voltage VR for a predetermined period. The all-solid-state battery 100 whose capacity has been recovered can then be used using the power stored in the capacity recovery process, thereby suppressing energy waste.
[0035] The process of storing the solid-state battery 100 may include transporting the solid-state battery 100 or an item containing the solid-state battery. The capacity lost during the transport of the solid-state battery 100 can be recovered when the solid-state battery 100 is used.
[0036] According to this embodiment, the all-solid-state battery 100, which has been charged via CCCV at a set voltage VB (first voltage) and then stored, is charged via CCCV at a set voltage VR (second voltage) that is higher than the set voltage VB. The CCCV-charged all-solid-state battery 100 is then held at the set voltage VR for a predetermined period (S32, S33), and its capacity is restored. The all-solid-state battery 100, whose capacity has been restored, can use the power stored in the capacity recovery process for discharging to a load, etc., thereby suppressing energy waste.
[0037] In the above embodiment, CCCV charging was performed in the charging process (S10) and the capacity recovery process (S30, S32). However, CV charging may also be performed in the charging process and the capacity recovery process. In this case, CV charging is performed by a set voltage VB in the charging process, and CV charging is performed by a set voltage VR in the capacity recovery process.
[0038] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]
[0039] 100 Solid-state batteries, 200 Charging devices.
Claims
1. A charging process in which an all-solid-state battery is charged at a constant voltage with a first voltage, After the completion of the charging process, the process involves storing the all-solid-state battery, A method for producing an all-solid-state battery, comprising: a capacity recovery step of charging the stored all-solid-state battery with a second voltage higher than the first voltage, and maintaining the second voltage for a predetermined period of time.
2. The method for producing an all-solid-state battery according to claim 1, wherein the step of storing the all-solid-state battery includes transporting the all-solid-state battery or an article on which the all-solid-state battery is installed.
3. The method for producing an all-solid-state battery according to claim 1 or claim 2, wherein the constant-voltage charging in the capacity recovery step is constant-current constant-voltage charging.
4. A method for restoring the capacity of an all-solid-state battery that has been stored after being charged at a constant voltage with a first voltage, The all-solid-state battery is charged at a constant voltage with a second voltage higher than the first voltage, A method for restoring the capacity of a solid-state battery, comprising: maintaining the solid-state battery, which has been charged at a constant voltage, at the second voltage for a predetermined period of time.
5. The method for restoring the capacity of an all-solid-state battery according to claim 4, wherein the constant voltage charging by the second voltage is constant current constant voltage charging.