System and methods for determining lithium diffusion for dry-contact pre-lithiation time-dependent resistance change for lithium diffusion kinetics in prelithiated anodes

Abstract

Embodiments of the disclosure provided herein include systems and methods for characterizing lithium diffusion in energy storage devices. The system includes a plurality of flexible carriers including layers of lithium and a calendering unit to produce a prelithiated electrode. A film characterization device is disposed after the calendering unit. A controller configured to apply a voltage using the film characterization device to a prelithiated electrode measures a current value corresponding to the voltage used at the film characterization device, determines a measured resistance value of the prelithiated electrode using the current value and the voltage, determines whether the measured resistance value exceeds a predetermined threshold, and, upon determining that the measured resistance value exceeds the predetermined threshold, indicates that the prelithiated electrode has reached equilibrium.

Description

SYSTEM AND METHODS FOR DETERMINING LITHIUM DIFFUSION FOR DRYCONTACT PRE-LITHIATION TIME-DEPENDENT RESISTANCE CHANGE FOR LITHIUM DIFFUSION KINETICS IN PRELITHIATED ANODESBACKGROUNDField

[0001] Embodiments of the present invention generally relate to systems and methods for manufacturing energy storage devices.Description of the Related Art

[0002] Silicon (Si), as an anode material, exhibits rich natural abundance, low operational voltage, and high theoretical capacity greater than that of graphite. However, wide adoption of Si-based anodes is hindered by large volume change upon cycling of Si and poor chemical compatibility of the electrolyte solution at low potentials of the anodes. One resultant is a large amount of irreversible capacity loss (ICL) in the initial cycle of Si-based anodes. Substantial solid electrolyte interphase (SEI) formation results in low initial coulombic efficiency (CE) of 50-80%, which indicates 20-50% of battery capacity will be lost after the first cycle. Therefore, prelithiation, a strategy to add sacrificial lithium to the electrodes prior to cycling has been developed to compensate for the ICL in the initial cycle and improve the cyclable capacity in Si- based batteries.

[0003] Substrate independent direct transfer (SIDT) methods for prelithiation involve mechanically rolling to transfer lithium metal from polyethylene terephthalate (PET) onto anodes. This method offers high operating efficiency, ease for practical application, and no need for additional complicated devices. However, since lithium metal has been transferred onto the top of the electrodes, the lithium distribution and lithium diffusion kinetics in the prelithiated electrodes remain unknown.

[0004] Accordingly, there is a need for an improved approach to determine when prelithiated electrodes reach uniform lithium distribution.SUMMARY

[0005] Embodiments described herein generally relate to systems and methods used for manufacturing energy storage devices. More particularly, embodimentsherein provide for processes and methods to characterize lithium diffusion in energy storage devices to allow for improved lithium uniformity in the energy storage device.

[0006] In an embodiment, a substrate processing system is provided. The substrate processing system includes a first flexible carrier including a first layer of lithium, a second flexible carrier including a second layer of lithium, a calendering unit configured to transfer the first layer of lithium onto an upper surface of a flexible substrate and transfer the second layer of lithium onto a lower surface of the flexible substrate to produce a prelithiated electrode. A film characterization device is disposed after the calendering unit, as well as a substrate pickup roll configured to receive the flexible substrate after processing in the calendering unit. The substrate processing system also includes a controller having a processor and a memory, where the controller is configured to apply a voltage using the film characterization device to a prelithiated electrode, measure a current value corresponding to the voltage used at the film characterization device, determine a measured resistance value of the prelithiated electrode using the current value and the voltage, determine whether the measured resistance value exceeds a predetermined threshold, and, upon determining that the measured resistance value exceeds the predetermined threshold, indicate that the prelithiated electrode has reached equilibrium.

[0007] In another embodiment, a substrate processing system is provided. The substrate processing system includes a first flexible carrier including a first layer of lithium, a second flexible carrier including a second layer of lithium, a calendering unit configured to transfer the first layer of lithium onto an upper surface of a flexible substrate and transfer the second layer of lithium onto a lower surface of the flexible substrate to produce a prelithiated electrode. A film characterization device disposed after the calendering unit, as well as a substrate pickup roll configured to receive the flexible substrate after processing in the calendering unit. The substrate processing system includes a controller having a processor and a memory, where the controller configured to apply an electrolyte solution to a prelithiated electrode using the film characterization device, apply a voltage using the film characterization device to the prelithiated electrode, measure a current value received at the film characterization device corresponding to the voltage, determine a measured resistance value of the prelithiated electrode using the current value and the voltage, determine whether themeasured resistance value exceeds a predetermined threshold, and upon determining that the measured resistance value exceeds the predetermined threshold, indicate that the prelithiated electrode has reached equilibrium.

[0008] In yet another embodiment, a method of processing a substrate is provided. The method includes applying a voltage using a film characterization device to a prelithiated electrode, measuring a current value received corresponding to the voltage using the film characterization device, determining a measured resistance value of the prelithiated electrode using the current value and the voltage, determining whether the measured resistance value exceeds a predetermined threshold, and upon determining that the measured resistance value exceeds the predetermined threshold, indicating that the prelithiated electrode has reached equilibrium.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of the present disclosure and are therefore not to be considered limiting of the scope of the disclosure, as the disclosure may admit to other equally effective embodiments.

[0010] Figure 1 shows a side cross-sectional view of an exemplary flexible substrate processing system, according to some embodiments.

[0011] Figure 2 shows an exemplary prelithiated electrode after undergoing a substrate independent direct transfer process, according to some embodiments.

[0012] Figure 3 shows a flow diagram illustrating an exemplary film characterization method for determining the lithiation of an electrode, according to some embodiments.

[0013] Figure 4A shows a prelithiated electrode undergoing the method of Figure 3, according to some embodiments.

[0014] Figure 4B shows an exploded view of an exemplary cell assembly of the film characterization method of Figure 3, according to some embodiments.

[0015] Figure 5 shows a flow diagram illustrating an exemplary film characterization method for determining the lithiation of an electrode, according to some embodiments.

[0016] Figure 6A shows a prelithiated electrode undergoing the method of Figure 5, according to some embodiments.

[0017] Figure 6B shows a prelithiated electrode undergoing the method of Figure 5, according to some embodiments.

[0018] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0019] Embodiments herein are generally directed to systems and methods for manufacturing energy storage devices and, more particularly to systems and methods for electrode characterization. Embodiments provided herein include improved systems and methods for determining lithium distribution and diffusion within an anode.

[0020] Silicon is an attractive candidate for energy storage systems due to its high theoretical capacity and low cost. However, the large amount of solid electrolyte interphase (SEI) formation in the initial cycle results in substantial irreversible capacity loss and causes quick battery capacity decay. Substrate independent direct transfer (SIDT)-based prelithiation methods compensate for the initial capacity loss efficiently while allowing for scalability. However, the lithium distribution and lithium diffusion kinetics within the prelithiated electrodes following SIDT-based prelithiation remain unclear.

[0021] Accordingly, the present disclosure provides a technical solution to the problems described above by providing systems and methods for measuring lithium diffusion within a prelithiated electrode. The system and methods are resistancebased and reveal lithium diffusion kinetics in SIDT-prelithiated electrodes. During SIDT methods, lithium is transferred or calendered from one or more carrier films, such as polyethylene terephthalate (PET), onto one or both sides of an anode. Thedisclosed system and methods then measure the resistance and the rate of change of the resistance of the prelithiated electrode for a period of time to determine the diffusion state of the lithium into the anode.

[0022] Resistance measurements provide simple, in situ monitoring of the prelithiated electrodes. The resistance of the prelithiated electrode is closely related to the electrode resistance and electrode thickness which correspond to the lithium distribution within the electrodes. The measured resistance then corresponds to lithium diffusion thickness, and the rate of change in resistance indicates the rate of lithium diffusion. The present disclosure provides a promising tool to characterize lithium distribution and lithium diffusion kinetics in SIDT-prelithiated electrodes.

[0023] Figure 1 shows a side cross-sectional view of a flexible substrate processing system 100, according to one embodiment. The processing system 100 includes equipment for transferring lithium films on a first flexible carrier 110 and a second flexible carrier 120 to each side of a flexible substrate 130, so that the flexible substrate 130 with the lithium films can be used as an electrode (for example, anode) in a lithium- ion battery. The processing system 100 includes a calendering unit 140 to transfer the lithium films on the flexible carriers 110, 120 to the flexible substrate 130. The processing system 100 may include a cleaning unit (not shown) for cleaning the lithium films or a passivation unit (not shown) for passivating the newly exposed surfaces of the lithium films transferred onto the flexible substrate 130, or both.

[0024] The processing system 100 includes a first flexible carrier supply hub 115. A supply roll 111 of the first flexible carrier 110 is positioned on the first flexible carrier supply hub 115. In some embodiments, the first flexible carrier 110 can be formed of a polymer material, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), or combinations thereof. A lithium film 110A is positioned on the first flexible carrier 110 so that the lithium film 110A faces an upper surface 13011 of the flexible substrate 130 as the first flexible carrier 110 and the flexible substrate 130 are conveyed through the calendering unit 140. An upper surface 13011 of the flexible substrate 130 is on an opposite side relative to a lower surface 130L of the flexible substrate 130.

[0025] The processing system 100 includes a second flexible carrier supply hub 125. A supply roll 121 of the second flexible carrier 120 is positioned on the second flexible carrier supply hub 125. In some embodiments, the second flexible carrier 120 can be formed of a same material (for example, PET) as the first flexible carrier 110. A lithium film 120A is positioned the second flexible carrier 120 so that the lithium film 120A faces the lower surface 130L of the flexible substrate 130 as the second flexible carrier 120 and the flexible substrate 130 are conveyed through the calendering unit 140.

[0026] The lithium films on the first flexible carrier 110 and the second flexible carrier 120 may be formed of lithium, other alkali metals, or an alloy including an alkali metal.

[0027] A supply roll 131 of the flexible substrate 130 is positioned on a flexible substrate supply hub 135. In some embodiments, the flexible substrate 130 can be formed of one or more of graphite, silicon, silicon graphite, silicon oxide graphite, silicon, metalized plastic, or other materials.

[0028] The calendering unit 140 includes a first calender roller 141 and a second calender roller 142. The first flexible carrier 110, the second flexible carrier 120, and the flexible substrate 130 are arranged to be conveyed along a path that extends between the first calender roller 141 and the second calender roller 142. The flexible substrate 130 is positioned between the first flexible carrier 110 and the second flexible carrier 120 when the first flexible carrier 110, the second flexible carrier 120, and the flexible substrate 130 are conveyed between the first calender roller 141 and the second calender roller 142. The calender rollers 141 , 142 exert a sufficient amount of pressure on the flexible carriers 110, 120 and the flexible substrate 130 that causes the lithium film on each of the flexible carriers 110, 120 to be transferred to the flexible substrate 130.

[0029] The processing system 100 includes a first flexible carrier pickup hub 116 and a second flexible carrier pickup hub 126. A first pickup roll 112 of the first flexible carrier 110 is positioned on the first flexible carrier pickup hub 116. A second pickup roll 122 of the second flexible carrier 120 is positioned on the second flexible carrier pickup hub 126. As the lithium film was transferred to the flexible substrate 130 in thecalendering unit 140, the first flexible carrier 110 and the second flexible carrier 120 are bare.

[0030] The processing system 100 includes a flexible substrate pickup hub 136. A substrate pickup roll 132 positioned on the flexible substrate pickup hub 136 receives and winds the flexible substrate 130. The flexible substrate 130 includes a lithium film on each of the upper surface 130U and the lower surface 130L of the flexible substrate 130. These lithium films are transferred from the respective flexible carriers 110, 120 onto the flexible substrate 130 by the calendering unit 140.

[0031] The processing system 100 further includes a plurality of rollers 180 to assist in appropriate transportation of the flexible carriers 110, 120 through the processing system. In some embodiments, each of the plurality of rollers 180 may be passive rollers. Alternatively, one or more of the plurality of rollers 180 may be a bar configured to apply tension to the flexible carriers 110, 120 or the flexible substrate 130 during transportation.

[0032] The film may be characterized by a film characterization device 150 two- point probe, a four-point probe, or other resistance measuring device which may be a part of the roll-to-roll system or a sheet-by-sheet system (not shown). The film characterization device 150 is positioned after calendering at the end of the roll or as part of the wound substrate pickup roll 132. The film characterization device 150 may be coupled to a controller 105 of the processing system 100. The film characterization device 150 measures the resistance of the flexible substrate 130 including the lithium films. Alternatively, the film characterization device 150 may be configured for sheet- to-sheet use where a portion of a processed substrate sheet is probed or otherwise characterized by the film characterization device 150. As a further alternative, the film characterization device 150 may be used off-system, e.g., at another location apart from the calendering unit 140, such as in cell testing conditions (not shown) where a portion of the flexible substrate 130 along with the lithium films are converted into cells and characterized by the film characterization device 150.

[0033] The controller 105 is configured to control processes performed by the processing system 100. The controller 105 can be any type of controller used in an industrial setting, such as a programmable logic controller (PLC). The controller 105includes a processor 107, a memory 106, and input / output (I / O) circuits 108. The controller 105 can further include one or more of the following components (not shown), such as one or more power supplies, clocks, communication components (for example, network interface card), and user interfaces typically found in controllers for semiconductor equipment.

[0034] The memory 106 can include non-transitory memory. The non-transitory memory can be used to store the programs and settings described below. The memory 106 can include one or more readily available types of memory, such as read only memory (ROM) (for example, electrically erasable programmable read-only memory (EEPROM), flash memory, floppy disk, hard disk, or random access memory (RAM) (for example, non-volatile random access memory (NVRAM).

[0035] The processor 107 is configured to execute various programs stored in the memory 106 such as a program configured to execute methods described herein. During execution of these programs, the controller 105 can communicate to I / O devices through the I / O circuits 108. For example, during execution of these programs and communication through the I / O circuits 108, the controller 105 can control outputs (for example, the actuators connected to the different hubs and the calendering unit 140). The memory 106 can further include various operational settings used to control the processing system 100. For example, the settings can include speed settings for the actuators connected to the hubs as well as settings to control the film characterization device 150.

[0036] Figure 2 shows an exemplary prelithiated electrode 200 after undergoing an SIDT process. The prelithiated electrode 200 includes an anode 210, a first lithium layer 212, and a second lithium layer 214. As the prelithiated electrode 200 ages, each of the first lithium layer 212 and the second lithium layer 214 diffuse into the anode 210 until the lithium reaches a state of equilibrium within the anode 210. The anode 210 may be made of any suitable anode material, including graphite, silicon, silicon graphite, silicon oxide graphite, silicon, metalized plastic, or a combination thereof.

[0037] Figure 3 shows a flow diagram illustrating a method 300 for determining the lithiation of an anode (e.g., anode 210) after SIDT processing which may be performedby a controller, such as the controller 105 of Figure 1 , using a film characterization device, such as the film characterization device 150 of Figure 1. Figure 4A shows a prelithiated electrode 400 undergoing method 300.

[0038] In block 302 of method 300, an anode 410 is prelithiated using an SIDT method. For example, the anode 410 may be calendered with a first lithium layer 412 and a second lithium layer 414 using a substrate processing system, such as the processing system 100, to produce the prelithiated electrode 400. A current collector layer 416 may be disposed within the anode 410. The current collector layer 416 may comprise of copper or copper alloys.

[0039] In optional block 304, coin cell fabrication occurs as shown in Figure 4B. Coin cell fabrication may be used in applications outside of roll-to-roll SIDT processes, such as sheet-to-sheet SIDT processes. A coin cell 420 may be assembled using cases. For example, the coin cell 420 may include an anode case 422 and a cathode case 424. The anode case 422 and the cathode case 424 may be coated or plated by metals such as SUS3130L Nickel. The prelithiated electrode 400 is then pressed between a spacer 426 and the cathode case 424 without addition of a counter electrode and separator. A washer 428 is disposed between the spacer 426 and the anode case 422. The coin cell 420 is then pressed and sealed for a period of time, such as 1 second to 10 seconds, preferably between 2 second and 5 seconds, preferably 3 seconds, using a battery crimper after assembly.

[0040] In block 306, a voltage is applied to measure a current of the prelithiated electrode 400. For example, current-voltage characterization (IVC) is conducted using a film characterization device 150 coupled to a controller (e.g., controller 105). The film characterization device 150 may include a two-point probe 450 coupled to an outer surface 412A of the first lithium layer 412 and an outer surface 414A of the second lithium layer 414 simultaneously. Alternatively, the film characterization device 150 may include a four-point probe coupled to the outer surface 412a of the first lithium layer 412 and the outer surface 414A of the second lithium layer 414. The film characterization device 150 may then apply a voltage to the prelithiated electrode 400 through the two-point probe 450. For example, a linear potential sweep may be applied to measure the corresponding current value. The linear potential sweep may be from about -200 mV to about 200 mV, between about -150 mV and about 150 mV,between about -125 mV and about 125 mV, and between about -100 mV and about 100 mV at about 0.01 mV / s. The linear potential sweep may be repeated periodically, such as once a day, twice a day, once an hour, or every 30 minutes.

[0041] In block 308, the controller 105 stores the current measurement and supplied voltage data and determines measured current-voltage curves. The controller 105 performs an analysis (e.g., linear regression) to determine resistance values of the prel ithiated electrode 400 at the time of measurement.

[0042] In block 310, the measured resistance values of the prelithiated electrode 400 are then compared to a predetermined threshold to evaluate whether the lithium from the first lithium layer 412 and the second lithium layer 414 has reached equilibrium within the anode 410. If the measured resistance values exceed the predetermined threshold, the controller 105 may indicate that the prelithiated electrode is at equilibrium in block 312. If the measured resistance values do not exceed the predetermined threshold, the method 300 may return to block 306.

[0043] The predetermined threshold may be a user-determined resistance value, a decrease in a rate of change of resistance between measured resistance values, or a total resistance difference between the measured resistance and an initial resistance.

[0044] In a first example, a user may input into the controller 105 a desired resistance value per sample, per roll, per cell, or in batches. The user may also change the desired resistance value during the processing or between batches.

[0045] In a second example, the predetermined threshold may be a rate of change of resistance between measured resistance values, such as a percentage. If the difference between a first resistance measurement and a second resistance measurement falls below a desired percentage, such as about 1 % to 5%, the prelithiated electrode 400 is determined to have reached equilibrium and the resistance measurement within the film characterization device 150 is completed.

[0046] In a third example, the predetermined threshold may be a total resistance change from an initial resistance taken from the first resistance measurement. Once the measured resistance increases by a desired amount of ohms, such as 20 Ohms, from the initial resistance measurement, the prelithiated electrode 400 is determinedto have reached equilibrium and the resistance measurement process within the film characterization device 150 is completed.

[0047] Figure 5 shows a flow diagram illustrating method 500 for determining the lithiation of an anode (e.g., anode 210) after SIDT processing which may be performed by a controller, such as the controller 105 of Figure 1 , using a film characterization device, such as the film characterization device 150 of Figure 1. Figure 6A shows a prelithiated electrode 600 undergoing method 500.

[0048] In block 502 of method 500, an anode 610 is prelithiated using an SIDT method. For example, the anode 610 may be calendered with a first lithium layer 612 and a second lithium layer 614 using a substrate processing system, such as the processing system 100, to produce the prelithiated electrode 600.

[0049] In block 504A, an electrolyte solution 630 is applied to the prelithiated electrode 600. Adding electrolytes allows the lithium diffusion rate to increase because lithium ions can travel quickly between anode particles, such as silicon, within the electrolyte. The addition of electrolytes simulates the aging period after cell assembly, which is normally required during regular cell formation. If the lithium distribution can be accelerated to uniformity during the resting periods after cell assembly, cell production rate increases as long aging times in a dry room become less necessary.

[0050] Block 504B may be used in lieu of block 504A. In optional block 504B, coin cell fabrication occurs as shown in Figure 6B similar to that of the optional block 304 of the method 300. A coin cell 620 may be assembled using cases. For example, the coin cell 620 may include an anode case 622 and a cathode case 624. The anode case 622 and the cathode case 624 may be coated or plated by metals such as SUS3130L Nickel. An electrolyte solution 630 is applied to the prelithiated electrode 600 before it is pressed between a spacer 626 and the cathode case 624 without addition of a counter electrode and separator. A washer 628 is disposed between the spacer 626 and the anode case 622. The coin cell 620 is then pressed and sealed for a period of time, such as 1 second to 10 seconds, preferably between 2 second and 5 seconds, preferably 3 seconds, using a battery crimper after assembly.

[0051] In block 506, a voltage is applied to measure a current of the prelithiated electrode 600. For example, current-voltage characterization (IVC) is conducted using a film characterization device (e.g., film characterization device 150) coupled to a controller (e.g., controller 105). The film characterization device 150 may include a two-point probe 650 contacting an outer surface 612A of the first lithium layer 612 and an outer surface 614A of the second lithium layer 614 simultaneously. Alternatively, the film characterization device 150 may include a four-point probe coupled to the outer surface 612a of the first lithium layer 612 and the outer surface 614A of the second lithium layer 614. The film characterization device 150 may then apply a voltage to the prelithiated electrode 600 through the two-point probe 650. For example, a linear potential sweep may be applied to measure the corresponding current. The linear potential sweep may be from -200 mV to about 200 mV, between about -150 mV and about 150 mV, between about -125 mV and about 125 mV, and between about -100 mV and about 100 mV at about 0.01 mV / s. The linear potential sweep may be repeated periodically, such as once a day, twice a day, once an hour, or every 30 minutes.

[0052] In block 508, the controller 105 then stores the current measurement and supplied voltage data and determines measured current-voltage curves. The controller 105 performs an analysis (e.g., linear regression) to determine resistance values of the prelithiated electrode 600 at the time of measurement.

[0053] In block 510, the measured resistance values of the prelithiated electrode 600 are then compared to a predetermined threshold to evaluate whether the lithium from the first lithium layer 612 and the second lithium layer 614 has reached equilibrium within the anode 610. If the measured resistance values exceed the predetermined threshold, the controller 105 may indicate that the prelithiated electrode is at equilibrium in block 512. If the measured resistance values do not exceed the predetermined threshold, the method 500 may return to block 506.

[0054] The predetermined threshold may be a user-determined resistance value, a decrease in a rate of change of resistance between measured resistance values, or a total resistance difference between the measured resistance and an initial resistance.

[0055] In a first example, a user may input into the controller 105 a desired resistance value per sample, per roll, per cell, or in batches. The user may also change the desired resistance value during the processing or between batches.

[0056] In a second example, the predetermined threshold may be a rate of change of resistance between measured resistance values, such as a percentage. If the difference between a first resistance measurement and a second resistance measurement falls below a desired percentage, such as about 1% to 5%, the prelithiated electrode 600 is determined to have reached equilibrium and the resistance measurement within the film characterization device 150 is completed.

[0057] In a third example, the predetermined threshold may be a total resistance change from an initial resistance taken from the first measured resistance. Once the measured resistance increases by a desired amount of ohms, such as 20 Ohms, from the initial resistance measurement, the prelithiated electrode 600 is determined to have reached equilibrium and the resistance measurement process within the film characterization device 150 is completed.

[0058] The present disclosure provides systems and methods for measuring lithium diffusion within a prelithiated electrode. The disclosed system and methods measure the resistance and the rate of change of the resistance of the prelithiated electrode following an SIDT process for a period of time to determine the diffusion state of the lithium into the electrode. Resistance measurements provide simple, in situ monitoring of the prelithiated electrodes which correspond to the lithium distribution within the electrodes. The present disclosure provides a promising tool to characterize lithium distribution and lithium diffusion kinetics in SIDT-prelithiated electrodes.

[0059] When introducing elements of the present disclosure or exemplary aspects or embodiments thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements.

[0060] The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0061] The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B and objectB touches object C, the objects A and C may still be considered coupled to one another — even if objects A and C do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly in physical contact with the second object.

[0062] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:1 . A substrate processing system, comprising: a first flexible carrier comprising a first layer of lithium; a second flexible carrier comprising a second layer of lithium; a calendering unit configured to transfer the first layer of lithium onto an upper surface of a flexible substrate and transfer the second layer of lithium onto a lower surface of the flexible substrate to produce a prelithiated electrode; a film characterization device disposed after the calendering unit; a substrate pickup roll configured to receive the flexible substrate after processing in the calendering unit; and a controller comprising a processor and a memory, the controller configured to: apply a voltage using the film characterization device to a prelithiated electrode; measure a current value corresponding to the voltage used at the film characterization device; determine a measured resistance value of the prelithiated electrode using the current value and the voltage; determine whether the measured resistance value exceeds a predetermined threshold; and upon determining that the measured resistance value exceeds the predetermined threshold, indicate that the prelithiated electrode has reached equilibrium.

2. The substrate processing system of claim 1 , wherein the controller is configured to apply the voltage by applying a linear potential sweep repeated periodically.

3. The substrate processing system of claim 1 , wherein the film characterization device comprises a two-point probe.

4. The substrate processing system of claim 1 , wherein the film characterization device comprises a four-point probe.

5. The substrate processing system of claim 1 , wherein the predetermined threshold is a rate of change of resistance of the measured resistance value.

6. The substrate processing system of claim 1 , wherein the predetermined threshold is a total resistance change from a first measured resistance.

7. A substrate processing system, comprising: a first flexible carrier comprising a first layer of lithium; a second flexible carrier comprising a second layer of lithium; a calendering unit configured to transfer the first layer of lithium onto an upper surface of a flexible substrate and transfer the second layer of lithium onto a lower surface of the flexible substrate to produce a prelithiated electrode; a film characterization device disposed after the calendering unit; a substrate pickup roll configured to receive the flexible substrate after processing in the calendering unit; and a controller comprising a processor and a memory, the controller configured to: apply an electrolyte solution to a prelithiated electrode using the film characterization device; apply a voltage using the film characterization device to the prelithiated electrode; measure a current value received at the film characterization device corresponding to the voltage; determine a measured resistance value of the prelithiated electrode using the current value and the voltage; determine whether the measured resistance value exceeds a predetermined threshold; and upon determining that the measured resistance value exceeds the predetermined threshold, indicate that the prelithiated electrode has reached equilibrium.

8. The substrate processing system of claim 7, wherein the controller is configured to apply the voltage by applying a linear potential sweep repeated periodically.

9. The substrate processing system of claim 7, wherein the film characterization device comprises a two-point probe.

10. The substrate processing system of claim 7, wherein the film characterization device comprises a four-point probe.11 . The substrate processing system of claim 7, wherein the predetermined threshold is a rate of change of resistance of the measured resistance value.

12. The substrate processing system of claim 7, wherein the predetermined threshold is a total resistance change from a first measured resistance.

13. The substrate processing system of claim 7, wherein the flexible substrate comprises an anode.

14. A method of processing a substrate, comprising: applying a voltage using a film characterization device to a prelithiated electrode; measuring a current value received corresponding to the voltage using the film characterization device; determining a measured resistance value of the prelithiated electrode using the current value and the voltage; determining whether the measured resistance value exceeds a predetermined threshold; and upon determining that the measured resistance value exceeds the predetermined threshold, indicating that the prelithiated electrode has reached equilibrium.

15. The method of claim 14, further comprising: before applying the voltage to the prelithiated electrode, applying an electrolyte solution to the prelithiated electrode.

16. The method of claim 14, wherein applying a voltage comprises applying a linear potential sweep repeated periodically.

17. The method of claim 14, wherein the prelithiated electrode comprises an anode and a first layer of lithium.

18. The method of claim 14, wherein the film characterization device comprises a four-point probe.

19. The method of claim 14, wherein the predetermined threshold is a rate of change of resistance of the measured resistance value.

20. The method of claim 14, wherein the predetermined threshold is a total resistance change from a first measured resistance.

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