A non-invasive strategy to recover the capacity of used battery by induction heating and pressure

Abstract

Non-invasive battery storage capacity recovery is achieved by performing induction heating of an assembled battery cell [100] positioned within a central region of a coil electrical conductor [102]. The induction heating is performed applying an alternating current through the coil electrical conductor to generate an alternating magnetic field [104] within the assembled battery cell [100] to induce eddy currents [106] within the assembled battery cell. The alternating current has a frequency from 50 Hz to 30 MHz, and the alternating magnetic field has a mean magnetic field strength from 5 mT to 100 mT.

Description

[0001] A NON-INVASIVE STRATEGY TO RECOVER THE CAPACITY OF USED BATTERY BY INDUCTION HEATING AND PRESSURE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to electrical batteries. More specifically, it relates to methods for restoring storage capacity of used electrical battery cells.

[0004] BACKGROUND OF THE INVENTION

[0005] Electric batteries are currently one of the world's most frequently used electrochemical storage devices, with many applications from powering small household electronics to electric vehicles (EVs). The drastic rise in the use of batteries has raised environmental concerns, and proper handling of spent batteries is urgently needed. Currently, there are three treatment options for batteries at the end-of-life stage: remanufacturing, repurposing, and recycling.

[0006] Remanufacturing, mostly used for EV lithium-ion batteries, is a refurbishing process that replaces the inferior cells in a pack so that the pack can be reutilized again in its original application. This option involves partial disassembly, replacement, and reassembly of the batteries and requires the batteries to meet strict requirements. Using EV as an example, the remanufactured batteries must have a capacity that is over 80% of the original rated value. When such a restriction is not economically favorable or impossible to meet, repurposing becomes an option.

[0007] In the repurposing process, the substandard batteries are also replaced, but instead of having the pack deployed in the original application, batteries are used in alternative applications such as energy storage systems. Although the batteries have been given a second life, extra steps need to be established, such as a new battery management system, different battery designs, and performance evaluation metrics, which could make repurposing options less economically beneficial when compared to new and cheap batteries.

[0008] Both manufacturing and repurposing options extend the battery life by replacing substandard cells with new cells. The replaced substandard cells can be recycled through either pyrometallurgy, hydrometallurgy, or a direct recycling process. Pyrometallurgy and hydrometallurgy have been used at industrial levels focusing mainly on recovering expensive metallic components of batteries. Both methods are invasive requiring pretreatment of the batteries (crashing, shredding, and disassembly) which has augmented economic costs. High CO2 emissions and wastewater generation from these recycling processes have also raised serious concerns. The direct recycling method is a relatively simple process that recovers the cathode of the battery. Compared to the other two recycling processes, it generates significantly lower pollution. However, rigorous battery classification and careful dissembling based on battery chemistry are necessary. Additionally, there is no guarantee that the recovered cathode can be recovered to a pristine state to meet strict industrial standards. Thus, so far, the direct recycling process has remained on a laboratory scale only.

[0009] The current end-of-life treatments for batteries are all invasive focusing on replacing substandard batteries for recovery and recycling of valuable metallic parts while neglecting the other major portion of the batteries due to the high environmental and economic cost. With these deficiencies in battery recovery and recycling methods, there is a substantial need to construct new battery recovery and recycling strategies.

[0010] SUMMARY OF THE INVENTION

[0011] Disclosed herein is a non-invasive, and cost-effective battery end-of-life treatment that reverses battery degradation effectively by recovering decayed battery storage capacity, elevating battery performance, and giving the battery a second life. This treatment method involves no replacement of battery parts, no dissembling of the battery cell, and no cell destruction. Consequently, this method will lower economic and environmental costs compared to other destructive or invasive approaches. The treatment is a thermal treatment method utilizing induction heating of the fully assembled battery cell. This induction heating treatment method melts porous plated lithium for lithium densification enabling more homogenous lithium stripping. It melts dendric lithium for reconnection with plated lithium enables more homogenous lithium stripping. It melts dead lithium for reconnection with plated lithium for battery capacity recovery. It increases lithium fluoride intensity of solid electrolyte interface for more uniform deposition of lithium. The thermal treatment method may also include pressurizing battery treatment. The combined thermal and pressure treatment allows rapid cooling of a heated battery for increased induction heating treatment efficiency, and it facilitates reconnection of melted porous plated lithium, dendric lithium, and dead lithium which escalates battery capacity recovery and further extends battery life.

[0012] In one aspect, the invention provides a method for non-invasive battery storage capacity recovery by performing induction heating of an assembled battery cell positioned within a central region of a coil electrical conductor. The induction heating comprises applying an alternating current through the coil electrical conductor to generate an alternating magnetic field within the assembled battery cell to induce eddy currents within the assembled battery cell. Preferably, the alternating current has a frequency in a range from 50 Hz to 30 MHz, or more preferably in a range from 10 kHz to 1 MHz. Preferably, the alternating magnetic field has a mean magnetic field strength in a range from 5 mT to 100 mT.

[0013] In some implementations, the induction heating comprises repeatedly alternating between a heating cycle and a cooling cycle. Preferably, the induction heating comprises repeatedly alternating N times between a heating cycle and a cooling cycle, where N ranges from 10 to 1000. Preferably, the heating cycle has a duration in the range from 100 ms to 5 s, or more preferably in the range from 0.5 s to 5 s. Preferably, the cooling cycle has a duration in the range from 2 s - 60 s, or more preferably 5 s to 60 s. In one implementation, the assembled battery cell is a coin battery cell, the alternating magnetic field has a mean magnetic field strength in a range from 5 to 20 mT, the heating cycle duration is less than 2 s, and the cooling cycle duration is in the range from 5 to 60 s.

[0014] In another implementation, the assembled battery cell is a cylindrical-shaped cell, the alternating magnetic field has a mean magnetic field strength in a range from 10 to 40 mT, the heating cycle duration is in the range from 0.5 to 2 s, the cooling cycle duration is in the range from 10 to 60 s, and the alternating current has a frequency in a range from 50 Hz to 50 kHz.

[0015] In another implementation, the assembled battery cell is a pouch cell, the alternating magnetic field has a mean magnetic field strength in a range from 5 to 15 mT, the heating cycle duration is in the range from 2 to 5 s, the cooling cycle duration is in the range from 5 to 30 s, and the alternating current has a frequency in a range from 50 Hz to 50 kHz.

[0016] The cooling cycle may cool the assembled battery cell using air flow generated by a fan and / or heat sinks in contact with the assembled battery cell. The heat sinks may be composed of silicon carbide, aluminum oxide, or beryllium oxide.

[0017] In some implementations, the method includes performing a pressurization treatment of the assembled battery cell during the induction heating by applying a mechanical compression force to the assembled battery cell. Preferably, applying the mechanical compression force to the assembled battery cell produces a pressure in the range from 40 kPa to 2000 kPa. In some implementations, applying the mechanical compression force to the assembled battery cell produces a pressure that varies during the pressurization treatment. In some implementations, the mechanical compression force is applied using heat sinks.

[0018] In some implementations, the induction heating comprises moving the coil electrical conductor to allow programmable heating of a battery pack. The assembled battery cell may be a lithium-ion battery cell, a lithium metal battery cell, or a solid state battery cell.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Fig. 1 is a schematic diagram showing induction heating of coin cell battery.

[0021] Fig. 2 is a series of scanning electron microscope images of plated lithium comparing surface morphology of non-heated lithium and induction heated lithium batteries.

[0022] Fig. 3 is a series of scanning electron microscope images of plated lithium comparing surface morphology of non-heated control battery and impulse induction heated batteries.

[0023] Fig. 4 are focused ion beam cross-section images comparing porosity of plated lithium of non-heated control battery and impulse induction heated battery.

[0024] Fig. 5 is a graph of Coulombic efficiency vs number of charge-discharge cycles, comparing non-heated control battery and impulse induction heated battery.

[0025] Fig. 6 is a graph of battery capacity vs number of charge-discharge cycles, comparing nonheated control battery and impulse induction heated full-cell battery.

[0026] Fig. 7 is a schematic diagram depicting induction heating of a battery pack of cylinder batteries using a movable coil.

[0027] Fig. 8 is a schematic diagram depicting an induction heating battery setup with heat sink pressurizing a battery from top and bottom surfaces.

[0028] Fig. 9 is a graph of Coulombic efficiency vs number of charge-discharge cycles, comparing non-heated control battery and impulse induction heated battery.

[0029] Fig. 10 is a graph of Coulombic efficiency vs number of charge-discharge cycles, comparing non-heated control battery and impulse induction heated and pressurized batteries.

[0030] DETAILED DESCRIPTION

[0031] As the needs for batteries continue to grow rapidly, the waste generated by spent batteries raises serious material depletion and environmental corners. The state-of-the-art end-of- life treatments of batteries work either by replacing substandard batteries with new ones for increased battery pack capacity or breaking down the spent batteries for valuable material extraction. The current treatments are all invasive, requiring the disassembly of batteries, which is not environmentally or economically ideal. Considering these challenges, we have developed a non-invasive strategy utilizing induction heating and pressure to recover battery loss, enabling lithium reconnection and densification which leads to battery capacity recovery and extends battery life.

[0032] One major reason for battery decay is lithium plating. Instead of having lithium ion intercalate with the negative electrode, metallic lithium is formed on the surface of the negative electrode causing plating which happens during fast charging or happens for lithium metal batteries. The metallic lithium reacts with electrolyte forming an SEI layer that is capable of isolating lithium forming non-recoverable dead lithium. The formation of additional SEI and dead lithium consumes lithium inventory which lowers battery capacity. Moreover, the plating process can also lead to dendrite growth that can cause a short circuit if penetrates the separator. The formed dendrite can lead to additional formation of dead lithium during the inhomogeneous stripping(discharging) resulting in capacity decay and shortened battery life.

[0033] To reverse lithium plating induced battery degradation, we have developed a thermal treatment utilizing induction heating to melt and merge plated and dendric lithium forming dense lithium on the anode. Induction heating, being a fast, reliable, and precise non-contact method that allows heat to be generated inside conductive material, is especially beneficial for lithium melting purposes as the plated lithium and dead lithium are electrically conductive. Thus, under induction heating, the lithium acts as a heat source that heats itself. In addition, the majority of the battery such as the current collector and cathode are also heated up and assist in heating lithium allowing for ultrafast heating, melting, and merging of plated and dead lithium. The dead lithium rejoins the lithium inventory which recovers the capacity loss of the battery. The melting and remerging of dead lithium densifies lithium layer which enables more homogenous lithium stripping during battery discharge which reduces or prevents dead lithium formation. The densification is elevated with the addition of pressure and is shown to bring the battery back to a pristine cell condition. Additionally, an increasing in lithium fluoride intensity of SEI layers in induction heating treated batteries is observed which enables more uniform lithium deposition that inhibits dendrite lithium growth.

[0034] In a preferred embodiment, a method for non-invasive battery storage capacity recovery performs induction heating of an assembled battery cell positioned within a central region of a coil electrical conductor. The induction heating is performed by applying an alternating current through the coil electrical conductor to generate an alternating magnetic field within the assembled battery cell to induce eddy currents within the assembled battery cell. Preferably, the induction heating is performed by repeatedly alternating between a heating cycle and a cooling cycle. This thermal treatment may be combined with a pressurization treatment of the assembled battery cell during the induction heating.

[0035] Treatment parameters include the alternating current frequency used to generate the alternating magnetic field, the mean magnetic field strength, the number of heating and cooling cycles, the duration of each heating cycle and cooling cycle, the pressure applied to the cell during treatment, variation of the pressure, and movement of the induction heating coil during treatment. Preferred treatment parameters depend primarily on the size and composition of the battery. Different types of batteries are subjected to different heating, cooling and pressurized conditions. Once these parameters are chosen, they could remain the same throughout the entire induction heating process, or vary. In some embodiments, for example, a strategy to speed up the treatment process is to pre-heat the battery for a duration of time to bring the battery temperature up and then initiate the impulse heating process of alternating heating and cooling cycles.

[0036] Generally, parameters are selected to keep the battery from overheating but still heat the battery to a high enough temperature during the heating process to melt the plated, dendritic, and dead lithium. We can apply a high-magnitude magnetic field for fast heating and at the same time decrease the heating duration to prevent the cell from overheating. As for cooling time, it cannot be too short such that accumulated heat cannot be dissipated fast enough which causes battery damage. Cooling time cannot be too long such that heat completely dissipates away during the cooling process in which the battery cannot be heated to a high enough temperature to have capacity recovery. As for the number of heating-cooling cycles used in the treatment, an increased number of cycles leads to increased capacity recovery. However, too many heating-cooling cycles may lead to battery damage. For pressure selection, increased pressure would help with lithium reconnection, but the pressure cannot be too high causing battery damage. It is beneficial to have pressure uniformly applied on the battery to ensure uniform densification of lithium for homogenous lithium stripping.

[0037] Examples

[0038] For a coin battery cell, the pressure may be applied on the anode by longitudinally compressing positive and negative cases. The heat sinks placed in contact with the cases are used to apply pressure. The coin cell battery is squeezed between two heat sinks so pressure is applied. Ideally, the pressure should remain the same throughout treatment. However, the applied pressure could vary due to the thermal expansion of parts or the melting of plated lithium. The pressure tolerance preferably is ± 20 kPa.

[0039] For coin cell batteries, the expected magnetic field strength ranges from 5 to 20 mT. The heating duration should be within 2 s and the cooling condition ranges from 5 to 60 s depending on the cooling condition.

[0040] For cylindrical-shaped lithium-ion batteries like 18650 batteries that are larger, the applied strength should range from 10 to 40 mT with a heating time ranging from 0.5 to 2 s and a cooling time ranging from 10 to 60 s. The field frequency should be in the range 50 Hz to 50 kHz so the heating can penetrate better inside the battery and heat the inner layers of the cell. The number of heating-cooling cycles should preferably range from 10 to 500.

[0041] For pouch cells that are flat and thin, a heating time from 2 to 5 s should be utilized so that the heating region can be uniform throughout the battery. At the same time, the corresponding magnitude of the magnetic field should be 5 to 15 mT to prevent the cell from overheating since the heating time has been increased. The cooling time should be 5 to 30 s due to the large surface area of the pouch cell that will facilitate cooling. The frequency applied should be in the range 50 Hz to 50 kHz due to the large size of the cell. The heatingcooling cycles should preferably range from 10 to 500.

[0042] Fig. 1 shows a schematic of an induction heating setup for a coin cell battery according to one embodiment of the invention. The battery 100 is placed inside a helix coil 102 with high-frequency alternating current (AC) running through the coil generating an alternating magnetic field 104 that heats the coin cell through eddy currents 106 generating resistive heat 108 inside the cell 100.

[0043] The lithium melting concept is first verified by induction heating copper current collectors with plated lithium under varying amounts of time of 0, 5, 10, 25, and 50 s under an alternating magnetic field with amplitude B = 19.3 mT and frequency f= 54 kHz. The scanning electron microscopic images of these plated lithium surfaces are shown in Fig. 2. The images show plated lithium surface morphology comparison of a control non-heated lithium 200 and induction heated lithium that are heated under B = 17.7 mT, / = 54 kHz for various durations. Images 202, 204, 206, 208, 210, show plated lithium that has been inductively heated for 2 s, 5 s, 10 s, 25 s, and 50 s, respectively.

[0044] It can be observed that for the control cell 200 that is not induction heated, the plated lithium appears to be slender dendric lithium showing high porosity. For the cells 202, 204, 206, 208, 210 that are subjected to induction heating, the plated lithium shows less porosity and pores appear to decrease in size and number with increased heating time.

[0045] Since batteries are made of varied materials and structures, the induction heating conditions for the battery depend on its assembly. It is key to note that when specifying the heating condition for a cell, the heat generated should not damage other plastic portions of the battery such as the separator. To prevent such damage while ensuring a recovery of battery capacity, an impulse heating strategy is used, i.e., alternating between heating and cooling cycles. The battery is controlled using a set of parameters (X1-X2-X3-X4): the battery is thermally treated using an alternating magnetic field of magnitude xi, where each heating cycle lasts X2 seconds, each cooling cycle lasts X3 seconds, and the heating-cooling cycles are repeated X4 times. The idea is to utilize the advantage of induction heat that heat comes from inside of conductive material to heat the lithium itself to melting temperature and allows the battery to cool to prevent the heat of another polymer component such as a separator. Impulse heating strategies of 1 s heating and 60 s cooling repeated 200, 400, 500, and 600 times under B = 17.7 mT, f= 54 kHz are applied on lithium metal half-cells. The impulse heating condition is referred to as 17.7-1-60-200, 400, 500, 600 for convenience of writing. Fig. 3 shows plated lithium surface morphology of a non-heated control battery 300 and impulse induction heated batteries 302, 304, 306, 308, that have gone through 200, 400, 500, 600 heating-cooling cycles, respectively. In each case, each heating-cooling cycle has heating that lasts for 1 s under B = 17.7 mT, / = 54 kHz, and cooling that lasts for 60 s. With increased heating and cooling numbers, the plated lithium shows a similar morphology change with the increased continuous heating time test mentioned previously. After heating and cooling 500 times, the plated lithium appears to be merged showing a relatively flat surface with very few pores to be seen.

[0046] Fig. 4 shows focused ion beam cross-section images comparing porosity of plated lithium of non-heated control battery 400 and impulse induction heated battery 402 that is heated for 1 s under B = 17.7 mT, / = 54 kHz, and cooled for 60 s. The heating and cooling process is repeated 500 times (17.7-1-60-500). These focused ion beam (FIB) images showing crosssection cuts of plated lithium of induction heated and non-heated lithium metal half-cell batteries also reinforce the idea of induction heating induced lithium densification. For the non-heated control battery 400, the FIB image shows a porosity of 37.4% whereas for the 17.7-1-60-500 heated battery 402, the porosity has decreased to 28.3% indicating densified plated lithium.

[0047] Induction heating generated battery recovery is best represented by the increase in coulombic efficiency (CE). Fig. 5 is a graph of Coulombic efficiency comparison between non-heated control battery and impulse induction heated battery that is heated for 1 s under B = 17.7 mT, / = 54 kHz, and cooled for 60 s. The heating and cooling process is repeated 500 times (17.7-1-60-500). The CE of the induction heated (17.7-1-60-500) battery (originally decayed to 60% CE) displays an approximate increase to 400% CE for the first charge- discharge cycle after heating, showing a great contrast to the non-heated control cell. It is also noticeable that the battery charge-discharge cycles (i.e., running cycles) after heating generally operate at a higher CE compared to the non-heated cell.

[0048] The same induction heating treatment is applied to a full-cell lithium metal battery decayed to 60% CE. Fig. 6 is a graph comparing storage capacity between non-heated control battery and impulse induction heated full-cell battery that is heated for 1 s under B = 17.7 mT, f= 54 kHz, and cooled for 60 s. The heating and cooling process is repeated 500 times (17.7- 1-60-500). The induction heated full-cell lithium metal battery shows almost no capacity decay for 15 battery running cycles after heating whereas the non-heated cell rapidly decays to almost 0 capacity after 15 battery running cycles. When comparing the total number of battery running cycles before reaching 0 CE, the induction heat treatment has extended the full-cell battery life for approximately 20 battery running cycles compared to non-heated cells demonstrating that induction heating treatment of batteries is a valid way of extending the lifetime of batteries. It is important to note that battery decay to any CE can be subjected to induction heating to recover capacity, not just 60% CE.

[0049] It is important to note that the battery induction heating mechanism is not restricted to coin cells. The induction heating strategy can also apply to other types of cells with varying shapes or sizes and is not restricted to treating a single cell but also can be utilized in treating battery packs. For example, a schematic depicting the induction heating of a pack 700 of cylinder batteries (e.g., cell 702) is shown in Fig. 7. By special designing the coil 704 to be moveable from cell to cell in the pack, and tuning the applied magnetic field, the entire degraded battery pack can be induction heated altogether for entire pack capacity recovery. It is important to note that the coil structure is not restricted to helical but can be altered to accommodate different battery structures.

[0050] The battery heating conditions (applied alternating magnetic field, heat time, cool time, and number of heating-cooling cycles) are important in determining the battery capacity recovery and are directly associated with the time cost of the treatment process. To minimize the time cost while maintaining a good recovery performance, the induction heating setup is optimized focusing on reducing the required battery cooling time to reduce the treatment time cost. Serval cooling strategies can be implemented. For example, the cooling time can be reduced by having fans blowing at the battery for faster heat dispassion. Moreover, heat sinks can be added to the heating system and placed directly in contact with the battery for improved cooling efficiency. Fig. 8 illustrates an induction heating battery setup with heat sinks 800, 802 contacting the top and bottom surface of a battery cell 804. The battery is positioned in the central region of induction coil 806.

[0051] It is important to note that the heat sinks should not be made of electrically conductive materials as they will be induction heated together with the battery contrary to the goal of faster cooling. The ideal material for the heat sink should be semiconductors or electrical insulators that have high thermal conductivity such as silicon carbide (Si C), aluminum oxide, or Beryllium oxide. Using SiC as an example, the silicon carbide blocks are placed in direct contact with the battery, facilitating heat dispassion. With this setup, the cooling time required for the battery to achieve capacity recovery while not damaging the cell is decreased from 60 s to 10 s. Fig. 9 is a graph of Coulombic efficiency comparison between non-heated control battery and impulse induction heated battery that is heated for 1 s under B = 17.7 mT, / = 54 kHz, and cooled for 10 s with SiC blocks as heat sinks. The heating and cooling process is repeated 500 times (17.7-1-10-500). The induction heated lithium metal half-cell with SiC blocks as heat sinks show a —200% capacity recovery at the first battery running cycle after heating and shows small to no CE decay for battery cycling after treatment. In contrast, the non-treated cell does not display significant capacity recovery and its CE gradually decays as the cell continues to go through running cycles.

[0052] The reversing of battery degradation can be further enhanced by pressurizing the cell during the induction heating process. The applied pressure forces melted lithium to merge to a greater extent compared to heating alone. The heat sinks may be utilized to apply the compression force on the battery to pressurize the cell and at the same time dissipate heat efficiently as they are in good contact with the cell. By firmly compressing the heat sink on the coin cell battery, the cooling time of the induction heated (17.7-1-8-500) battery is further reduced to 8 s. The CE of heating and pressurized lithium metal half-cell versus battery running cycles are shown in Fig. 10, which is a graph of Coulombic efficiency comparison between non-heated control battery and impulse induction heated and pressurized batteries that are heated for 1 s under B = 17.7 mT, / = 54 kHz, and cooled for 8 s with SiC blocks as heat sinks. The batteries are pressurized with SiC blocks compressing against them. For each heated battery, the heating and cooling process is repeated 500 times (17.7-1-60-500).

[0053] The initial battery running cycle after heating and pressurization treatment shows significant capacity recovery with the CE gradually increasing and remaining at a high value (>0.8 CE) as the battery cycles. In contrast, the non-heated control cell shows rapid decay in CE. The induction heating coupled with pressure treatment has been shown to not only be able to recover battery capacity but also elevate its performance gradually to close to pristine battery condition.

[0054] For purposes of illustration, the examples discussed above are focused on lithium-ion battery cell. However, the principles of the present invention are also applicable to other types of battery cells, including lithium metal battery cells and solid-state battery cells.

[0055] For lithium metal battery cells, the techniques and mechanism are the same as with lithium ion battery cells. The induction heating will melt the dendrite lithium which merges with the plated lithium to recover the lost capacity. The pressure can help densify the melted lithium (reduce the pores) which is why the treatment is able to bring back the capacity of lithium metal battery and have the battery cycling at high efficiency.

[0056] For solid state battery cells, the mechanism is the same, while the motivation is different. For solid state battery cells, the interface between lithium and solid-state electrolyte is key for the battery to perform stably. However, since both lithium and electrolyte are solid, the interface (i.e., how well the two parts are connected) is not well established. To improve the contact, we can use induction heating to melt the lithium to molten lithium and use pressure to force a better contact with the solid state electrolyte. This process can increase the contact between lithium and solid-state electrolyte. This treatment can be applied before the solid state battery is used or after the interface has grown poor due to battery cycling.

Claims

CLAIMS1. A method for non-invasive battery storage capacity recovery, the method comprising: performing induction heating of an assembled battery cell positioned within a central region of a coil electrical conductor, wherein the induction heating comprises applying an alternating current through the coil electrical conductor to generate an alternating magnetic field within the assembled battery cell to induce eddy currents within the assembled battery cell.

2. The method of claim 1, wherein the alternating current has a frequency in a range from50 Hz to 30 MHz, or more preferably in a range from 10 kHz to 1 MHz.

3. The method of claim 1, wherein the alternating magnetic field has a mean magnetic field strength in a range from 5 mT to 100 mT.

4. The method of claim 1, wherein the induction heating comprises repeatedly alternating between a heating cycle and a cooling cycle.

5. The method of claim 4, wherein the induction heating comprises repeatedly alternating N times between a heating cycle and a cooling cycle, where N ranges from 10 to 1000.

6. The method of claim 4, wherein the heating cycle has a duration in the range from 100 ms to 5 s, or more preferably in the range from 0.5 s to 5 s.

7. The method of claim 4, wherein the cooling cycle has a duration in the range from 2 s -60 s, or more preferably 5 s to 60 s.

8. The method of claim 4, wherein the assembled battery cell is a coin battery cell, wherein the alternating magnetic field has a mean magnetic field strength in a range from 5 to20 mT, wherein the heating cycle duration is less than 2 s, and wherein the cooling cycle duration is in the range from 5 to 60 s.

9. The method of claim 4, wherein the assembled battery cell is a cylindrical-shaped cell, wherein the alternating magnetic field has a mean magnetic field strength in a range from 10 to 40 mT, wherein the heating cycle duration is in the range from 0.5 to 2 s, wherein the cooling cycle duration is in the range from 10 to 60 s, and wherein the alternating current has a frequency in a range from 50 Hz to 50 kHz.

10. The method of claim 4, wherein the assembled battery cell is a pouch cell, wherein the alternating magnetic field has a mean magnetic field strength in a range from 5 to 15 mT, wherein the heating cycle duration is in the range from 2 to 5 s, wherein the cooling cycle duration is in the range from 5 to 30 s, and wherein the alternating current has a frequency in a range from 50 Hz to 50 kHz.

11. The method of claim 4, wherein the cooling cycle cools the assembled battery cell using air flow generated by a fan and / or heat sinks in contact with the assembled battery cell.

12. The method of claim 11, wherein the heat sinks are composed of silicon carbide, aluminum oxide, or beryllium oxide.

13. The method of claim 1, further comprising performing a pressurization treatment of the assembled battery cell during the induction heating by applying a mechanical compression force to the assembled battery cell.

14. The method of claim 13, wherein applying the mechanical compression force to the assembled battery cell produces a pressure in the range from 40 kPa to 2000 kPa.

15. The method of claim 13, wherein applying the mechanical compression force to the assembled battery cell produces a pressure that varies during the pressurization treatment.

16. The method of claim 13, wherein the mechanical compression force is applied using heat sinks.

17. The method of claim 1, wherein the induction heating comprises moving the coil electrical conductor to allow programmable heating of a battery pack.

18. The method of claim 1, wherein the assembled battery cell is a lithium-ion battery cell.

19. The method of claim 1, wherein the assembled battery cell is a lithium metal battery cell.

20. The method of claim 1, wherein the assembled battery cell is a solid state battery cell.

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