Fast charging protocol for lithium metal battery and apparatus

Abstract

Disclosed is a fast-charging protocol for a rechargeable battery such as solid-state battery and lithium metal battery. The fast-charging protocol includes a multi-step constant current (MSCC) charging protocol comprising at least a first charging step with a first constant current (I1), a second charging step with a second constant current (I2), and a third charging step with a third constant current (I3), wherein the constant currents in the first, second and third steps exhibit the following pattern I1 < I2 > I3; or I1 > I2 < I3. The battery charged by the MSCC charging protocol exhibits a cycle life of at least 10% longer than a battery charged by a charging protocol with a single constant current.

Description

FAST CHARGING PROTOCOL FOR LITHIUM METAL BATTERY AND APPARATUSCROSS-REFERENCE

[0001] The present application claims the benefit of US Serial No. 63 / 666,779, filed July 2, 2024, the entire content of which is incorporated herein by reference into this application.FIELD

[0002] Disclosed are fast-charging protocols for lithium metal batteries and apparatus for conducting the same.BACKGROUND

[0003] Various charging protocols or methods can be used to charge a battery. For example, a charging protocol may comprise charging the battery with a constant current until a predetermined voltage followed by charging with a constant voltage. In another example, a fast-charging protocol may comprise charging the battery with a high constant current when the state of charge (SOC) of the battery is in certain range such as 10% until the battery reaches a predetermined voltage or SOC and charging with a relatively lower current. However, such fast-charging protocol may deteriorate the cycle life of a battery. The cycle life may be further deteriorated for lithium metal batteries due to formation and growth of lithium dendrite, and changes of stress and temperature during charge and discharge. Thus, there remains a need for new fast-charging protocols without sacrificing the cycle life.SUMMARY

[0004] The present disclosure provides a fast-charging protocol for a rechargeable battery. The fast-charging protocol comprises charging the battery from a first threshold value of state of charge (SOCa) to a second threshold value (SOCb) following a multi-step constant current (MSCC), wherein the MSCC charging protocol comprises a first charging step with a first constant current (Ii), a second charging step with a second constant current (b), and a third charging step with a third constant current (I3), wherein the constant currents in the first, secondand third steps exhibit the following pattern Ii < I2 > I3; or Ii > I2 < I3. The battery charged by the MSCC charging protocol exhibits a cycle life of at least 10% longer than a battery charged by a charging protocol with a single constant current.BRIEF DESCRIPTION OF THE FIGURES[00051 Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure.

[0006] Fig. 1 illustrates an exemplary method for fast-charging protocol according to one embodiment of the present disclosure.

[0007] Figs. 2 and 3 illustrate two representative fast-charging protocols according to some embodiments of the present disclosure.

[0008] Figs. 4 and 5 illustrate two representative fast-charging protocols according to some embodiments of the present disclosure.

[0009] Fig. 6 illustrates a representative fast-charging protocol according to one embodiment of the present disclosure.

[0010] Fig. 7A illustrates a single step constant current charging protocol according to one embodiment of the present disclosure.

[0011] Fig. 7B illustrates a multi-step constant current charging protocol according to one embodiment of the present disclosure.

[0012] Fig. 8A shows the cycling performance of batteries charged by following a single constant current charging protocol and MSCC charging protocol.[0013| Fig. 8B shows the columbic efficiency (CE) of batteries charged by following a single constant current charging protocol and MSCC charging protocol.DETAILED DESCRIPTION[00141 Disclosed is a fast-charging protocol for a rechargeable battery. The fast-charging protocol comprises charging the battery from a first threshold value of state of charge (SOCa) to a second threshold value (SOCb) following a multi-step constant current (MSCC), wherein the MSCC charging protocol comprises a first charging step with a first constant current (Ii), a second charging step with a second constant current (I2), and a third charging step with a third constant current (I3), wherein the constant currents in the first, second and third steps exhibit the following pattern Ii < I2 > I3; or Ii > I2 < I3. The battery charged by the MSCC charging protocol exhibits a cycle life of at least 10% longer than a battery charged by a charging protocol with a single constant current.

[0015] In some embodiments, the method of charging a rechargeable battery comprises: detecting an initial value of state of charge (SOCi) of a rechargeable battery, and1) if SOCi is less than a first threshold value of SOC (SOCa), charging the battery with a low constant current (la) until SOC reaches SOCa, and then charging the battery with a multi-step constant current (MSCC) charging protocol comprising multiple charging steps,2) if SOCi is equal to or greater than a second threshold value of SOC (SOCb), charging the battery with a fixed constant current (lb), and3) when if SOCi is equal to or higher than SOCa but less than SOCb, charging the battery following a MSCC charging protocol comprising multiple charging steps, wherein the MSCC charging protocol comprises at least three steps: a) after a first condition is satisfied, charging the battery following a first charging step comprising charging the battery with a first constant current (Ii) higher than lb for a first duration,b) after a second condition is satisfied, changing from the first charging step to a second charging step, wherein the second charging step comprises charging the battery with a second constant current (I2) for a second duration, and c) after a third condition is satisfied, changing from the second charging step to a third charging step, wherein the third charging step comprises charging the battery with a third constant current (I3) for a third duration, wherein the constant currents in the first, second and third steps exhibit the following pattern: Ii < I2 > I3; or Ii > I2 < I3.

[0016] Cycle life is the number of cycles for the battery to reach a threshold value such as 80% of its original capacity or a threshold value such as 99.0% of its columbic efficiency (CE), whichever is earlier. Cycle life is usually used to measure the cycling performance of a secondary battery.

[0017] In some embodiments, the difference between SOCb and SOCa is at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, or at least 60%. In some embodiments, the difference between SOCb and SOCa is no greater than 90%, no greater than 80%, no greater than 70%, no greater than 60%, or no greater than 50%.

[0018] In some embodiments, the battery charged by the MSCC charging protocol exhibits a cycle life of at least 10%, at least 25%, at least 50%, at least 75%, at least 100%, at least 150%, at least 200%, at least 250%, or at least 300% longer than a battery charged by a charging protocol with a single constant current.

[0019] Without wishing to be bound by any theory, the elongated cycle life is ascribed to the stress and / or temperature change in a less dramatic way.

[0020] In some embodiments, SOCa and SOCb are each independently defined by a user or a program.[0021| In some embodiments, SOCa has a value in a range from 5% to 75%, from 5% to 70%, from 5% to 65%, from 5% to 60%, from 5% to 55%, from 5% to 55%, from 5% to 50%, from 5% to 45%, from 5% to 40%, from 5% to 35%, from 5% to 30%, from 5% to 25%, from 5% to 20%, from 5% to 15%, or from 5% to 10%.

[0022] In some embodiments, SOCb is greater than SOCa. In some embodiments, SOCb has a value in a range from 70% to 95%, from 70% to 90%, from 70% to 85%, from 70% to 80%, or from 70% to 75%.

[0023] In some embodiments, the total duration from SOCa to SOCb depends on the difference therebetween.

[0024] In some embodiments, when SOCi has a value of at least SOCa and less than SOCb, an MSCC charging protocol is selected from a set of MSCC charging protocols with different starting SOCs and one MSCC charging protocol with a starting SOC of SOCi would be selected. In some embodiments, SOCa is reassigned (or redefined) with a new value equal to SOCi. In some embodiments, a fixed battery may be charged by following MSCC charging protocols depending on SOCi it has prior to charging. For example, a battery may be charged with a first MSCC charging protocol with SOCa having a value of 10% in one cycle when SOCi is equal to or less than 10%. For the same battery but with an SOCi of 20%, it was charged with a second MSCC charging protocol wherein SOCa is re-assigned with a new value equal to SOCi.

[0025] As shown in Fig. 1, if a battery has an SOCi less than SOCa, the battery is first charged with a low fixed constant current (la) to SOCa, subsequently charged with an MSCC charging protocol until SOC and finally charged with a fixed constant current (lb) until a preset cutoff voltage (Vc).

[0026] As also shown in Fig. 1, if a battery has a high SOCi equal to or greater than SOCb, the battery will opt out MSCC charging protocol and directly enter a charging with a fixed constant current (lb) until a preset cutoff voltage (Vc).

[0027] If a battery has a SOCi greater than SOCa and less than SOCb, an eligibility is then determined based on the difference between SOCi and SOCb. In some embodiments, when the difference between SOCb and SOCi (SOCb - SOCi) is equal to or greater than a threshold value, such as 10% and 15%, the battery is eligible to be charged with an MSCC charging protocol, wherein SOCa is reassigned with a new value equal to SOCi.

[0028] If the difference between SOCb and SOCi is less than the threshold value, the battery will not be charged with an MSCC charging protocol and will be charged with a fixed constant current (lb) until a preset cutoff voltage (Vc), wherein SOCb is reassigned with a new value equal to SOCi which is close to SOCb.

[0029] Fig. 2 shows a representative charging profile of a battery with an SOCi lower than SOCa, wherein the MSCC charging starts a first step charging from SOCa.

[0030] Fig. 3 shows a representative charging profile of a battery with an SOCi greater than SOCa, wherein the MSCC charging starts a first step charging from SOCi, and SOCa is redefined with a new value equal to SOCi.

[0031] Figs. 2 and 3 show a pattern wherein Ii < I2 > I3. Figs. 4 and 5 show another pattern, wherein Ii > I2 < I3.

[0032] Fig. 4 shows a representative charging profile of a battery with an SOCi lower than SOCa, wherein the MSCC charging starts a first step charging from SOCa.

[0033] Fig. 5 shows a representative charging profile of a battery with an SOCi greater than SOCa, wherein the MSCC charging starts a first step charging from SOCi, and SOCa is redefined with a new value equal to SOCi.

[0034] Fig. 6 shows an exemplary charging profile of a battery with an MSCC charging protocol comprising at least four stages. From another perspective, Fig. 6 shows a pattern wherein Ii > I2 < I3 > I4. In some embodiments, the pattern can be Ii < I2 > I3 < I4.

[0035] In some embodiments, the condition for one charging step is satisfied when the SOC reaches a preset value for each step. In some embodiments, the preset value is calculated inview of the difference between SOCa and SOCb. In some embodiments, the preset value is expressed as percentage from SOCa to SOCb.

[0036] In some embodiments, the first condition is satisfied when the SOC reaches SOCa or SOCi has a value equal to or greater than SOCa. Upon the satisfaction of the first condition, the battery is charged with a first charging step with a first constant current (Ii). In some embodiments, the first condition is satisfied when one or more of the following conditions are met: 1) the SOC reaches SOCa, and 2) the open circuit voltage (OCV) of the battery reaches a value corresponding to SOCa.

[0037] In some embodiments, the second condition is satisfied the SOC reaches SOC2 and the battery is charged with a second charging step with a second constant current (I2). In some embodiments, the second condition is satisfied when one or more of the following conditions are met: 1) the SOC reaches SOC2, and 2) the open circuit voltage (OCV) of the battery reaches a value corresponding to SOC2.

[0038] In some embodiments, the third condition is satisfied the SOC reaches SOC3 and the battery is charged with a third charging step with a third constant current (I3). In some embodiments, the third condition is satisfied when one or more of the following conditions are met: 1) the SOC reaches SOC3, and 2) the open circuit voltage (OCV) of the battery reaches a value corresponding to SOC3.

[0039] In some embodiments, la has a value in a range from C / 10 to C / 2.

[0040] In some embodiments, lb has a value in a range from C / 5 to 1C.

[0041] In some embodiments, la < lb.

[0042] In some embodiments, each of Ii, I2 and I3 is greater than lb.

[0043] In some embodiments, Ii, I2 and I3 are different from each other.

[0044] In some embodiments, the MSCC charging protocol is not a pulse charge protocol

[0045] In some embodiments, each of the first, second and third charging steps is longer than a period in a pulse charging protocol.

[0046] In some embodiments, each of the first, second and third charging steps is longer than 10 seconds.

[0047] In some embodiments, the MSCC is free of resting steps between two adjacent steps.

[0048] In some embodiments, the MSCC is free of any constant voltage charging step.

[0049] In some embodiments, the MSCC charging protocol has a total duration from SOCa to SOCb in a range from 10 min to 20 min.

[0050] In some embodiments, the fast-charging protocol comprises a first, second, third and fourth steps, wherein the constant currents of the first through fourth steps exhibit the following pattern:• Ii < I2 > I3 < I4; or• Ii > I2 < I3 > 14.

[0051] In some embodiments, the fourth condition is satisfied when SOC reaches SOC4. In some embodiments, SOC4 has a value in a range from 35% to 95%.

[0052] In some embodiments, I4 is equal to or greater than lb.

[0053] In some embodiments, the fast-charging protocol comprises a first, second, third, fourth and fifth steps. The fifth step is triggered upon satisfaction of a fifth condition, wherein the fifth charging step comprises charging the battery with a fifth constant current (Is) for a fifth duration.

[0054] In some embodiments, Is has a value lower or greater than I4.

[0055] In some embodiments, the MSCC charging protocol comprises at least two steps.

[0056] In some embodiments, the battery comprises a cathode including a cathode active material. In some embodiments, the cathode active material contains Li, Ni, and Co. In one embodiment, the cathode active material contains Li, Ni, and Co and at least one of Mn and Al. In one embodiment, the cathode active material contains at least one of Fe, and P.

[0057] In one embodiment, the cathode active material layer of the battery comprises a cathode active material. In some embodiments, the battery has a relatively high cathode loading. Insome embodiments, the ASSB has a cathode loading of at least 5.0 mAh / cm2, at least 5.5 mAh / cm2, at least 6.0 mAh / cm2, at least 6.5 mAh / cm2, at least 6.8 mAh / cm2, at least 7.2 mAh / cm2, or at least 7.5 mAh / cm2. A high cathode loading is critical to achieve a high energy density. However, a battery with a high cathode loading may be subject to a relatively fast decay, which ultimately leads to a lower capacity retention. In some embodiments, the present disclosure provides a fast-charging protocol for a battery exhibiting both a high cathode loading and a good cycling performance.

[0058] In some embodiments, the anode of the battery comprises an anode active material layer comprising an anode active material such as lithium metal or a lithium alloy. In some embodiments, the anode active material comprises at least one selected from the group consisting of lithium, sodium, magnesium, aluminum, silicon, calcium, titanium, manganese, iron, cobalt, nickel, zinc, molybdenum, silver, indium, tin, and tungsten.

[0059] In some embodiments, the anode of the battery further comprises an anode current collector. In some embodiments, an anode active material layer is assembled into the battery prior to the first charge. In some embodiments, an anode active material layer is formed after the first charge.

[0060] In some embodiments, the battery comprises a liquid electrolyte, a polymer electrolyte or all-state electrolyte.

[0061] In some embodiments, the polymer electrolyte comprises an electrolyte salt, a solvent, and a polymer.

[0062] In some embodiments, the polymer is in situ polymerized after mixing the electrolyte salt, solvent and a polymer precursor (alternatively monomer).

[0063] In some embodiments, the monomer contains one or more polymerizable groups. In some embodiments, non-limiting specific polymerizable groups include vinyl (-CH=CH2), substituted vinyl (-CRI=CR2R3) and a combination thereof, wherein Ri, R2 and R3 areindependently hydrogen, halogen, -CN, -NO2, C1-6 alkyl, Ci-ehaloalkyl, Ci-ehydroxyalkyl, C1-6 aminoalkyl, C2-6 alkenyl, C2-6 alkynyl, Ce-14 aryl or any combination thereof.

[0064] In some embodiments, the polymer precursor is a monomer and comprises at least one selected from the group consisting of 2,2,3,3-tetrafluorobutane-l,4-diacrylate, 2, 2, 3, 3, 4, 4,5,5- octafluorohexane-l,6-diyl diacrylate, 2,2,3,3,4,4,5,5-octafhrorohexane-l,6-diyl bis(2- methylacrylate), polyethylene glycol) diacrylate (Mn=500-5000), triethylene glycol dimethacrylate (TEGDMA), diurethane dimethacrylate, tetraallyl silane (TAS), 2, 4,6,8- tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, triethoxyvinylsilane, allyltriethoxysilane, pentaerythritol tetraacrylate (PETA), pentaerythritol tetramethacrylate (PETMA), tris[2- (acryloyloxy)ethyl] isocyanurate (TAEI), di(trimethylolpropane) tetraacrylate (Di-TMPTA), trimethylolpropane propoxylate triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

[0065] In some embodiments, the polymer in the polymer electrolyte is a crosslinked polymer. In some embodiments, the precursor (or monomer) for a crosslinked polymer includes at least two or more polymerizable groups. In some embodiments, the precursor (or monomer) for a crosslinked polymer includes at least three or more polymerizable groups

[0066] In some embodiments, the electrolyte salt is selected from the group consisting of lithium perchlorate (LiCICh), lithium nitrate (LiNCh), lithium hexafluorophosphate (LiPFe), lithium borofluoride (LiBF4), lithium hexafluoroarsenide (LiAsFe), lithium trifluoromethanesulfonate (LiCFsSCh), lithium bis(perfluoroethanesulfonyl)imide (LiBETI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiDFOB), lithium fluoroalkylphosphates (Li[PFx(CyF2y+i-zHz)6-x]) (l<x<5, l<y<8, and 0<z<2y-l), lithium fluorophosphate (Li2PO3F), lithium difluorophosphate (LiDFP), lithium difluoro(bisoxalato)phosphate (LiC4PO8F2), lithium tetrafluoro oxalato phosphate (LiC2PO4F4), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SO2)3), LiF, LiCl, LiBr,Lil, Li2SO4, LisPCh, Li2COs, LiOH, lithium acetate, lithium trifluoromethyl acetate, lithium oxalate, and a mixture thereof.

[0067] In some embodiments, the battery charged by the MSCC charging protocol exhibits a cycle life of at least 10%, at least 25%, at least 50%, at least 75%, or at least 100% longer than a battery charged by a charging protocol with a single constant current.

[0068] In some embodiments, the battery exhibits an average CE of at least 95.0%, at least 96.0%, at least 97.0%, at least 98.0%, at least 99.0%, at least 99.25%, at least 99.50%, at least 99.75%, at least 99.80%, at least 99.85% or at least 99.90% after at least 50 cycles wherein each cycle is charged by following the MSCC charging protocol and discharged at a rate of 1C at 25 °C.

[0069] In some embodiments, the battery can be charged at a temperature in a range from -20 °C to 60 °C, from -10 °C to 60 °C, from 0 °C to 60 °C, from 10 °C to 60 °C, from 20 °C to 60 °C, from 30 °C to 60 °C, from -20 °C to 50 °C, from -10 °C to 50 °C, from 0 °C to 50 °C, from 10 °C to 50 °C, from 20 °C to 50 °C, from 30 °C to 50 °C, from -20 °C to 40 °C, from -10 °C to 40 °C, from 0 °C to 40 °C, from 10 °C to 40 °C, from 20 °C to 40 °C, or from 30 °C to 40 °C.

[0070] In some embodiments, the battery exhibits a capacity retention rate of at least 95.0%, at least 96.0%, at least 97.0%, at least 98.0%, at least 99.0%, at least 99.25%, or at least 99.50%, after at least 50 cycles wherein each cycle is charged by following the MSCC charging protocol and discharged at a rate of 1C at 25 °C.

[0071] In some embodiments, the battery is a lithium metal battery tested at a temperature of 25 °C under an external pressure in a range from 0.5 MPa to 5.0 MPa.

[0072] In one aspect, the present disclosure provides a battery charging apparatus comprising• a memory configured to store one or more instructions; and• a processor coupled to the memory, wherein, when executing the one or more instructions, the processor is configured to: operate a multi-step constant current (MSCC) charging protocol including multiplecharging steps, wherein it is determined whether a condition is satisfied in each of the multiple charging steps, the condition comprising whether a state of charge (SOC) of a battery is greater than or equal to a threshold value in each step, upon satisfaction of a first charging condition, charge the battery in a first charging step with a first constant charging current (Ii), upon satisfaction of a second charging condition, change from the first charging step to a second charging step with a second constant current (I2), and upon satisfaction of a third charging condition, change from the second charging step to a third charging step with a third constant current (I3), wherein the constant currents in the first, second and third steps exhibit the following pattern: Ii < I2 > I3; or Ii > I2 < I3.

[0073] In some embodiments, the battery is continually charged without any resting steps between adjacent two steps during MSCC charging.

[0074] In some embodiments, the first condition is satisfied when an initial SOC (SOCi) is equal to or greater than a first threshold value of SOC (SOCa) or when the SOCi is smaller than SOCi, the SOC reaches SOCa after charging at a low constant current (la). In some embodiments, la has a value in a range from C / 10 to C / 2.

[0075] In some embodiments, the second condition is satisfied when SOC reaches SOC2. In some embodiments, SOC2 has a value in a range from 15% to 85%.

[0076] In some embodiments, the third condition is satisfied when SOC reaches SOC3. In some embodiments, SOC3 has a value in a range from 30% to 95%.

[0077] In some embodiments, the battery opts out of the MSCC charging protocol to a slow charging step with a fixed constant current (lb) upon satisfaction of an opt condition. In some embodiments, lb has a value in a range from C / 5 to C.

[0078] In some embodiments, the process is further configured to measure or receive a voltage of the battery and determine whether the voltage is equal to or greater than a cut-off voltage(Vc). In some embodiments, the opt condition is satisfied when the voltage is equal to or greater than a cut-off voltage (Vc).

[0079] The disclosure will be better understood by reference to the Experimental Details which follow, but those skilled in the art will readily appreciate that the specific experiments detailed are only illustrative, and are not meant to limit the disclosure as described herein, as numerous variations and modifications of these exemplary embodiments are possible without undue experimentation. All such variations and modifications are within the scope of the teachings of this disclosure. It will be appreciated that the foregoing description and following examples, no matter how detailed they may appear in text, the disclosure may be practiced in many ways, and the disclosure should be construed in accordance with the appended claims and equivalents thereof.ExamplesExample 1

[0080] A pouch cell (0.75Ah) comprising Li metal as anode, microporous membrane as separator, NMC811 as cathode, and a polymer electrolyte as electrolyte was prepared and cycled between 2.8V to 4.25 V at 25 °C under an external pressure. In each cycle, the pouch cell was charged by following the MSCC charging protocol in Table 3 and discharged at 1C at 25 °C. In some embodiments, the external pressure is in a range from 0.5MPa to 5.0 MPa.Table 1 MSCC charging protocol of example 1[00811 Fig. 7A illustrates a conventional charging protocol with a single constant current of 2.8C wherein SOCa and SOCb were set as 10% and 80%, respectively. Fig. 7B illustrates an exemplary MSCC charging protocol as summarized in Table 1.[00821 A pouch cell was similarly prepared and cycled except that the cell was charged at a single constant current of 2.8C in each cycle from SOCa to SOCb.

[0083] Cycle life is the number of cycles for the battery to reach a threshold value such as 80% of its original capacity or a threshold value such as 98.0% of its columbic efficiency (CE), whichever is earlier. Cycle life is usually used to measure the cycling performance of a secondary battery. As shown in Figs. 8A, 8B and Table 2, the cell charged with the MSCC charging protocol exhibited a cycle life of more than 90 cycles, which is around 260% longer than that of the comparative example with a cycle life of 25 cycles.Table 2 Cycle life of cell charged with MSCC and single constant currentExample 2[00841 A multi-layer pouch cell (0.75Ah) comprising Li metal as anode, microporous membrane as separator, NMC811 as cathode, and a polymer electrolyte as electrolyte was cycled between 2.8V to 4.25 V at 25 °C under an external pressure. In some embodiments, the external pressure is in a range from 0.5MPa to 5.0 MPa. In each cycle, the pouch cell was charged by following the MSCC charging protocol in Table 3 and discharged at 1C at 25 °C.Table 3 MSCC charging protocol of example 2Example 3

[0085] A pouch cell (0.75Ah) comprising Li metal as anode, microporous membrane as separator, NMC811 as cathode, and a polymer electrolyte as electrolyte was prepared according to Example 1 and was cycled between 2.8V to 4.25 V at 25 °C under an external pressure. In each cycle, the pouch cell was charged by following the MSCC charging protocol in Table 4 and discharged at 1C at 25 °C.Table 4 MSCC charging protocol of example 3Aspects

[0086] In a first aspect, the present disclosure provides a method of charging a rechargeable battery, comprising:• obtaining an initial state of charge (SOCi) of a rechargeable battery, and1) if SOCi is less than a first threshold value of SOC (SOCa), charging the battery with a low constant current (la),2) if SOCi is equal to or greater than SOCb, charging the battery with a fixed constant current (lb), and3) if SOCi is equal to or higher than SOCa but less than SOCb, charging the battery following a multi-step constant current (MSCC) charging protocol comprising multiple charging steps, wherein the MSCC charging protocol comprises at least three steps: a) after a first condition is satisfied, charging the battery following a first charging step comprising charging the battery with a first constant current (Ii) for a first duration,b) after a second condition is satisfied, changing from the first charging step to a second charging step, wherein the second charging step comprises charging the battery with a second constant current (I2) for a second duration, and c) after a third condition is satisfied, changing from the second charging step to a third charging step, wherein the third charging step comprises charging the battery with a third constant current (I3) for a third duration, wherein the constant currents in the first, second and third steps exhibit the following pattern:• Ii < I2 > I3; or• Il > l2 < l3.

[0087] In a second aspect according to the first aspect, SOCb has a value greater than SOCa and the difference therebetween is equal to or greater than 10%. In some embodiments, SOCb has a value greater than SOCa and the difference therebetween is equal to or greater than 15%.

[0088] In a third aspect according to the first aspect, the battery charged by the MSCC charging protocol exhibits a cycle life of at least 10% longer than a battery charged by a charging protocol with a single constant current from SOCa to SOCb. In some embodiments, the battery exhibits a specific capacity greater than a battery charged by a charging protocol with a single constant current.

[0089] In a fourth aspect according to the first aspect, SOCa and SOCb are each independently defined by a user or a program.

[0090] In a fifth aspect according to the first aspect, SOCa has a value in a range from 5% to 75% and SOCb has a value in a range from 70% to 95%.

[0091] In a sixth aspect according to the first aspect, la has a value in a range from C / 10 to C / 2 and lb has a value in a range from C / 5 to 1C. In some embodiments, la has a value lower than lb.

[0092] In a seventh aspect according to the first aspect, each of Ii, I2 and I3 is greater than lb. In some embodiments, Ii, I2 and I3 are different from each other.In an eighth aspect according to any preceding aspect, the MSCC is not a pulse charge protocol and each duration of the first, second and third charging steps is longer than a period in a pulse charging protocol. In some embodiments, each duration of the first, second and third charging steps is longer than 10 seconds.

[0093] In a nineth aspect according to any preceding aspect, the MSCC is free of resting steps (or relaxation steps) between two adjacent steps. In some embodiments, the MSCC is free of any constant voltage charging step.

[0094] In a tenth aspect according to any preceding aspect, the MSCC charging protocol has a total duration in a range from 10 min to 60 min.

[0095] In an eleventh aspect according to the first aspect, the method further comprises a fourth charging step following the third charging step upon satisfaction of a fourth condition, wherein the fourth charging step comprises charging the battery with a fourth constant current (I4) for a fourth duration, wherein the constant currents of the first through fourth steps exhibit the following pattern:• Ii < I2 > I3 < I4; or• Ii > I2 < I3 > 14.

[0096] In a twelfth aspect according to the eleventh aspect, I4 is equal to or greater than lb.

[0097] In a thirteenth aspect according to the eleventh aspect, the method further comprises a fifth charging step following the fourth charging step upon satisfaction of a fifth condition, wherein the fifth charging step comprises charging the battery with a fifth constant current (Is) for a fifth duration, wherein Is has a value lower or greater than I4.

[0098] In a fourteenth aspect according to the first aspect, the battery comprises an anode comprising lithium metal or lithium alloy, a liquid electrolyte, a polymer electrolyte or all-state electrolyte.

[0099] In a fifteenth aspect according to the fourteenth aspect, the polymer electrolyte comprises an electrolyte salt, a solvent, and a polymer with a weight percentage in a range from 0.01wt% to 20wt% in the polymer electrolyte and the polymer is in situ polymerized after mixing the electrolyte salt, solvent and a polymer precursor. In some embodiments, the polymer precursor (monomer) comprises at least one selected from the group consisting of 2,2,3,3-tetrafluorobutane-l,4-diacrylate, 2,2,3,3,4,4,5,5-octafluorohexane-l,6-diyl diacrylate, 2,2,3,3,4,4,5,5-octafluorohexane-l,6-diyl bis(2-methylacrylate), poly(ethylene glycol) diacrylate (Mn=500-5000), triethylene glycol dimethacrylate (TEGDMA), diurethane dimethacrylate, tetraallyl silane (TAS), 2,4,6,8-tetramethyl-2,4,6,8- tetravinylcyclotetrasiloxane, triethoxyvinylsilane, allyltriethoxysilane, pentaerythritol tetraacrylate (PETA), pentaerythritol tetramethacrylate (PETMA), tris[2-(acryloyloxy)ethyl] isocyanurate (TAEI), di(trimethylolpropane) tetraacrylate (Di-TMPTA), trimethylolpropane propoxylate triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and dipentaerythritol hexaacrylate.

[0100] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0101] All transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively.

[0102] Various embodiments of the features of this disclosure are described herein. However, it should be understood that such embodiments are provided merely by way of example, and numerous variations, changes, and substitutions can occur to those skilled in the art without departing from the scope of this disclosure. It should also be understood that various alternative to the specific embodiments described herein are also within the scope of this disclosure.

Claims

What is claimed is:

1. A method of charging a rechargeable battery, comprising:• obtaining an initial state of charge (SOCi) of a rechargeable battery, and1) if SOCi is less than a first threshold value of SOC (SOCa), charging the battery with a low constant current (la),2) if SOCi is equal to or greater than SOCb, charging the battery with a fixed constant current (lb), and3) if SOCi is equal to or higher than SOCa but less than SOCb, charging the battery following a multi-step constant current (MSCC) charging protocol comprising multiple charging steps, wherein the MSCC charging protocol comprises at least three steps: a) after a first condition is satisfied, charging the battery following a first charging step comprising charging the battery with a first constant current (Ii) for a first duration, b) after a second condition is satisfied, changing from the first charging step to a second charging step, wherein the second charging step comprises charging the battery with a second constant current (I2) for a second duration, and c) after a third condition is satisfied, changing from the second charging step to a third charging step, wherein the third charging step comprises charging the battery with a third constant current (I3) for a third duration, wherein the constant currents in the first, second and third steps exhibit the following pattern:• Ii < I2 > I3; or• Il > l2 < l3.

2. The method of claim 1, wherein SOCb has a value greater than SOCa and the difference therebetween is equal to or greater than 10%.

3. The method of claim 1, wherein the battery charged by the MSCC charging protocol exhibits a cycle life of at least 10% longer than a battery charged by a charging protocol with a single constant current from SOCa to SOCb.

4. The method of claim 1, wherein SOCa and SOCb are each independently defined by a user or a program.

5. The method of claim 1, wherein SOCa has a value in a range from 5% to 75% and SOCb has a value in a range from 70% to 95%.

6. The method of claim 1, wherein Iahas a value in a range from C / 10 to C / 2 and lb has a value in a range from C / 5 to 1C.

7. The method of claim 1, wherein each of Ii, I2 and I3 is greater than lb.

8. The method of claim 1, wherein the MSCC is not a pulse charge protocol each duration of the first, second and third charging steps is longer than a period in a pulse charging protocol.

9. The method of claim 1, wherein the MSCC is free of resting steps between two adjacent steps.

10. The method of claim 1, wherein the MSCC charging protocol has a total duration in a range from 10 min to 60 min.

11. The method of claim 1, further comprising a fourth charging step following the third charging step upon satisfaction of a fourth condition, wherein the fourth charging step comprises charging the battery with a fourth constant current (I4) for a fourth duration, wherein the constant currents of the first through fourth steps exhibit the following pattern:• Ii < I2 > I3 < I4; or• Ii > I2 < I3 > I4.

12. The method of claim 11, wherein I4 is equal to or greater than lb.

13. The method of claim 11, further comprising a fifth charging step following the fourth charging step upon satisfaction of a fifth condition, wherein the fifth charging step comprises charging the battery with a fifth constant current (Is) for a fifth duration, wherein Is has a value lower or greater than I4.

14. The method of claim 1, wherein the battery comprises an anode comprising lithium metal or lithium alloy and the battery comprises a liquid electrolyte, a polymer electrolyte or an all-state electrolyte.

15. The method of claim 14, wherein the polymer electrolyte comprises an electrolyte salt, a solvent, and a polymer with a weight percentage in a range from 0.01wt% to 20wt% in the polymer electrolyte and the polymer is in situ polymerized after mixing the electrolyte salt, solvent and a polymer precursor.

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