Method of activating secondary battery

Abstract

Disclosed is an activation method for a secondary battery. The method comprises activating a preformed cell by a number of activation cycles (Nac), 5 < Nac ≤ 50, each activation cycle comprising: charging the preformed cell by charging from SOCa1 to SOCa2 at a rate of Ca1 and discharging from SOCa2 to SOCa1 at Ca2, leading to an activated cell, wherein Ca2 has a value no greater than a critical value (Ccr). In some embodiments, Ca1 has a value no greater than 0.8C. In some embodiments, Ca2 has a value in a range from 0.01C to 0.8C.

Description

METHOD OF ACTIVATING SECONDARY BATTERY CROSS-REFERENCE[00011 The present application claims priority of US Serial No. 63 / 725,705, filed November 27, 2024, the entire content of which is incorporated herein by reference into this application.FIELD

[0002] The present disclosure is generally related to a method of activating or manufacturing a secondary battery such as lithium ion battery (LIB) and lithium metal batteries.BACKGROUND

[0003] An electrode assembly of a secondary battery comprises a cathode, an anode and a separator between the cathode and the anode. A cathode comprises a cathode active material layer on one or both sides of a cathode current collector. An anode comprises an anode active material layer on one or both sides of an anode current collector. An electrode assembly is usually prepared by inserting a separator into a space between a cathode and an anode. After the electrode assembly is placed into a container such as a hard case or pouch, an electrolyte is introduced into the space between either electrode and separator, thus obtaining a battery assembly of a secondary battery. To stabilize the battery structure and form a solid electrolyte interface (SEI) film, a couple of initial charge / discharge cycles and / or degassing steps (usually 1-5 cycles) are usually performed after electrode and separator are impregnated by the electrolyte. These steps are part of battery formation and manufacturing and are referred to as formation steps or activation steps. However, a secondary battery after such conventional formation steps does not show desirable low temperature performance and / or rate performance for practical applications such as electric vehicle, drone, or electric vertical take-off and landing (eVTOL) aircraft. Thus, there remains a need for new activation methods for a secondary battery.SUMMARY

[0004] The present disclosure provides an activation method for a secondary battery. The method comprises activating a preformed cell (pre-formed cell) by a number of activation cycles (Nac), each activation cycle comprising: charging the preformed cell from SOCai to SOCa2 at a rate of Cai and discharging from SOCa2 to SOCai at a rate of Ca2, leading to an activated cell, wherein Ca2 has a value no greater than a critical value (Ccr).

[0005] In some embodiments, Cai has a value no greater than 0.8C.|0006] In some embodiments, CCThas a value of 1.0C.

[0007] In some embodiments, 5 < Nac < 50. In some embodiments, 6 < Nac < 50.

[0008] The following terms shall be used to describe the present disclosure. In the absence of a specific definition set forth herein, the terms used to describe the present disclosure shall be given their common meaning as understood by those of ordinary skill in the art.

[0009] A preformed (pre-formed) cell or battery refers to an electrochemical device prepared by applying a number of formation cycles (Nfm) (Nfm < 5) to a cell, wherein each formation cycle comprises charging the cell from SOCfi to SOC12 at a rate of Cfi and discharging from SOC12 to SOCn at a rate of Ci2. In some embodiments, Cfi < 0.33 C. In some embodiments, Ci2 < 1.0 C.BRIEF DESCRIPTION OF THE FIGURES

[0010] 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.

[0011] Fig. 1 shows a typical structure of a battery according to one embodiment of the present disclosure.

[0012] Fig. 2 shows the discharge capacity of pre-formed cell and activated cell according to some embodiments of the present disclosure. The cells were fully charged then discharged at a rate of 8C (24 mA / cm2) to 2.8 V.

[0013] Figs. 3A and 3B show the surface morphology of anode before and after activation, respectively, according to some embodiments of the present disclosure.

[0014] Fig. 4 shows the discharge capacity of preformed cell and activated cell at -20 °C according to some embodiments of the present disclosure.DETAILED DESCRIPTION10015] In one aspect, a battery comprises cathode (1), anode (2), electrolyte (3) and separator (4) as shown in Fig. 1. The cathode (1) comprises a cathode current collector (10) and a cathode active layer (11). The anode (2) comprises an anode current collector (20) and an anode active layer (21). The electrolyte (3) is located between the separator (4) and either electrode, i.e., either the cathode (1) or the anode (2). In some embodiments, the separator is soaked with the electrolyte. In some embodiments, the battery comprises an anode comprising an alkali metal such as lithium metal or lithium alloy. In some embodiments, the battery is anode free, wherein the anode only comprises the anode current collector. In some embodiments, a battery may comprise a cathode, an anode and electrolyte without separator. In some embodiments, the electrolyte is nonaqueous.

[0016] The present disclosure provides an activation method for a secondary battery. The method comprises activating a pre-formed cell by a number of activation cycles (Nac), each activation cycle comprising: charging the pre-formed cell from SOCai to SOCa2 at a rate of Cai and discharging from SOCa2 to SOCai at a rate of Ca2, leading to an activated cell, wherein Ca2 has a value no greater than a critical value (Ccr). A battery's C rate is a relative measurement of how quickly it can be charged or discharged. It's calculated by dividing the charge or discharge current in amps by the battery's full capacity in ampere-hours. A battery’s SOC, or state of charge, is the battery’s remaining capacity divided by the battery’s full capacity.

[0017] In some embodiments, Cai has a value no greater than 0.8C.

[0018] In some embodiments, Ccr has a value of 1.0C. In some embodiments, Ca2 has a value no greater than 0.8C. In some embodiments, Ca2 has a value of at least 0.01C. In some embodiments, Ca2 has a value of at least 0.01C and no greater than 0.8C.

[0019] In some embodiments, the number of activation cycles (Nac) is greater than 5. In some embodiments, the number of activation cycles (Nac) is equal to 50 or less. In some embodiments, 5 < Nac < 50. In some embodiments, 6 < Nac < 50.

[0020] In some embodiments, the C rate is a constant C rate or an average C rate.

[0021] In some embodiments, SOCai has a value of at least 0%. In some embodiments, SOCai has a value of less than 50%. In some embodiments, SOCai has a value of 45% or less. In some embodiments, SOCai has a value of 40% or less. In some embodiments, SOCai has a value of 35% or less. In some embodiments, SOCai has a value of 30% or less. In some embodiments, SOCai has a value of 25% or less. In some embodiments, SOCai has a value of 20% or less. In some embodiments, SOCai has a value of 15% or less.

[0022] In some embodiments, SOCa2 has a value of at least 5%, at least 10%, at least 15%, at least 20%, at least 30%, or at least 40%. In some embodiments, SOCa2 has a value of no greater than 40%, no greater than 50%, no greater than 60%, no greater than 70%, no greater than 80%, no greater than 90%, or no greater than 100%. In some embodiments, 5% < SOCa2 < 100%.

[0023] In some embodiments, the preformed cell is prepared by applying a number of formation cycles (Nfm) to a cell, wherein each formation cycle comprises charging a cell from SOCfi to SOC12 at a rate of Cfi and discharging from SOC12 to SOCfi at a rate of Ci2.

[0024] In some embodiments, SOCfi is 0%. In some embodiments, SOC12 is 100%.

[0025] In some embodiments, 1 < Nfm< 5. In some embodiments, the total cycle numbers, i.e., Nfm + Nac, have a value greater than 6, i.e., Nfm + Nac > 6. In some embodiments, 6 < Nfm + Nac < 51. In some embodiments, 7 < Nfm + Nac < 52. In some embodiments, 8 < Nfm + Nac < 53. In some embodiments, 9 < Nfm + Nac < 54. In some embodiments, 10 < Nfm + Nac < 55.

[0026] In some embodiments, Cfi < 0.33 C.

[0027] In some embodiments, Cf2 < 1.0 C.

[0028] Rate performance of a cell can be characterized by discharge capacity retention at a high C rate in comparison to that at a low C rate. In some embodiments, the discharge capacity retention at a high C rate is the discharge capacity of a fully charged cell at a rate in a range from 4C to 10C (e.g., from 12 mA / cm2to 30 mA / cm2) divided by the discharge capacity at 0.33C multiplied by 100%. In one embodiment, the capacity retention at 8C is the discharge capacity at 8C divided by the discharge capacity at 0.33C multiplied by 100%.

[0029] Low temperature performance of a cell can be characterized by discharge capacity retention at a low temperature in comparison to that at 25 °C. In some embodiments, the discharge capacity retention at a low temperature is the discharge capacity of a fully charged cell after storing at a temperature in a range from -30 °C to 0 °C divided by the discharge capacity of a fully charged cell at 25 °C multiplied by 100%. In one embodiment, low temperature performance of a cell can be characterized by capacity retention at -20 °C, which is the discharge capacity of a fully charged cell after storing at -20 °C for 6 hours divided by the discharge capacity of a fully charged cell after storing at 25 °C multiplied by 100%. The storage of a fully charged cell at -20 °C for 6 hours is to ensure that a fully charged cell is cooled to a desired low temperature for at least beginning of the discharge.

[0030] In some embodiments, an activated cell refers to a cell with a discharge capacity retention at a high rate such as 8C at least 20% greater than that of the preformed cell, a discharge capacity retention at a low temperature such as -20 °C at least 20% greater than that of the preformed cell, or both.|0031] In some embodiments, an activated cell refers to a cell with a bulk resistance of at least 30% lower than that of a preformed cell without activation. In some embodiments, an activated cell refers to a cell with an anode resistance of at least 30% lower than that of a preformed cellwithout activation. In some embodiments, an activated cell refers to a cell with a cathode resistance of at least 30% lower than that of a preformed cell without activation.Cathode

[0032] In one embodiment, the cathode active material layer in the cathode layer of an electrochemical device comprises a cathode electroactive material. In one embodiment, 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 some embodiments, the cathode comprises an electroactive material including one or more selected from the group consisting of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate, lithium metal oxide, lithium manganese oxide, lithium cobalt oxide, and lithium iron phosphate.

[0033] In some embodiments, the cathode active material contains a sulfur-based compound comprising at least one selected from the group consisting of elemental sulfur (S8), Li2Sn (n > 1), an organosulfur compound, and a carbon-sulfur polymer ((C2Sx)n (x=2.5-50, and n > 2). In some embodiments, the cathode active material comprises a polyacrylonitrile-sulfur (SPAN) composite produced by reacting polyacrylonitrile (PAN) with sulfur (S). In some embodiments, the SPAN material has sulfur-carbon bonds which can bond polysulfides to the SPAN polymer matrix.

[0034] In one embodiment, the cathode active material contains at least one of Fe, and P. In some embodiments, the cathode active material is substantially free of LiFePCU.Anode

[0035] In some embodiments, the anode layer comprises an anode active material layer and an anode current collector. In some embodiments, the anode layer comprises an anode current collector with or without the anode active material layer. In some embodiments, an anode active material layer is assembled into a secondary battery prior to the first charge. In some embodiments, an anode active material layer is formed after the first charge.

[0036] In some embodiments, the anode active material layer comprises an anode active material such as alkali metal. In some embodiments, the alkali metal includes lithium (Li,), sodium (Na) and potassium (K). In some embodiments, the anode active material is 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.

[0037] In some embodiments, the anode is a carbon anode, Li anode, Si anode, alloy anode, LiMisOn, or made from conversion anode materials. In some embodiments, the carbon anode comprises graphite, soft carbon, hard carbon, or combinations of thereof. In some embodiments, the Li anode comprises Li metal foil, Li metal on Cu, Ni, or stainless steel. In some embodiments, the Si anode comprises Si, Si / Carbon composite, SiOx (0<x<2), SiOx (0<x<2) / carbon composite or a combination thereof. In some embodiments, the alloy anode comprises Sn, SnCh, Sb, Al, Mg, Bi, In, As, Zn, Ga, B, or a combination thereof. In some embodiments, the conversion anode materials comprise MaXb, M is Mn, Fe, Co, Ni, or Cu, X is O, S, Se, F, N, or P, a and b are respectively 1 to 4. In some embodiments, the anode is Li metal foil or Li metal on Cu, Ni, or stainless steel.

[0038] In some embodiments, the anode active material layer also includes a carbon-based conductive material. In some embodiments, the carbon-based conductive material comprises at least one selected from the group consisting of carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, natural graphite and artificial graphite. Separator

[0039] In some embodiments, the separator is a porous polymer separator. In some embodiments, the porous polymer separator is made of a polyolefin such as polyethylene (PE), polypropylene (PP) or combinations thereof.

[0040] In some embodiments, the separator is a composite separator comprising a polyolefin and an inorganic particle distributed within the polyolefin so that it can achieve a desirable thermal stability. In some embodiments, the separator is a multiple layered structure comprising a layer of polyolefin and an inorganic coating such as ceramic coating on one or both sides of the polyolefin layer. In some embodiments, the separator comprises two layers of polyolefin and an inorganic layer sandwiched between the two layers of polyolefin.|004l] In some embodiments, the inorganic coating or layer in the separator comprises at least one selected from the group consisting of AI2O3, B2O3, NbO, NbCh, Nb2Os, TiCh, BaO, PbO, ZrO2, BaTiCh, SrTiCh, CeO2, MgO, CaO, SiC, Caio(PO4)6(OH)2, Caio(PO4)6(OH)2, Caio(P04)e(OH)2-2xF2x, lithium phosphate (LisPC ), lithium titanium phosphate (LixTiy(PO4)3, 0<x<2, 0<y<3), lithium aluminum titanium phosphate (LixAlyTiz(PO4)3, 0<x<2, 0<y<l, 0<z<3), (LiAlTiP)xOytype glass (0<x<4, 0<y<13) such as 14Li2O-9AhO3-38TiO2-39P2O5, lithium lanthanum titanate (LixLayTiO3, 0<x<2, 0<y<3), lithium nitrides(LixNy, 0<x<4, 0<y<2) such as LisN, SiS2type glass (LixSiySz, 0<x<3, 0<y<2, 0<z<4) such as LisPC — IA2S — SiS2, Y2O3, iron oxides, boehmite (Al(O)OH), barium sulfate (BaSC ), aluminum nitride, calcium fluoride, barium fluoride, zeolite, kaoline, mullite, spinel, olivine, mica, calcined clay, titanium nitride, boron nitride, talc, dickite, nacrite, halloysite, pyrophyllite, montmorillonite, sericite, amesite, bentonite, asbestos, zeolite, diatomaceous earth, quartz sand, and mixtures thereof.

[0042] In some embodiments, the separator has a thickness in a range from 5 pm to 30 pm, from 5 pm to 25 pm, from 5 pm to 20 pm, from 5 pm to 15 pm, from 5 pm to 10 pm, from 7.5 pm to 30 pm, from 7.5 pm to 25 pm, from 7.5 pm to 20 pm, from 7.5 pm to 15 pm, from 7.5 pm to 10 pm, from 10 pm to 30 pm, from 10 pm to 25 pm, from 10 pm to 20 pm, from 10 pm to 15 pm, or all and any ranges and subranges therebetween.Solvent in Electrolyte

[0043] In some embodiments, the electrolyte is nonaqueous, i.e., the electrolyte is substantially free of water. In some embodiments, the solvent in the electrolyte comprises at least oneselected from the group consisting of diethyl ether, dimethoxy methane, diethoxy methane, dimethoxy ethane, 1,2-di ethoxy ethane, 1,1 -di ethoxy ethane, 1,1 -dipropoxy ethane, 1,2- dipropoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, tetrahydrofuran, dioxolane, tetrahydropyran, 1,4-di oxane, 1,3 -di oxane, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, fluoroethylene carbonate, vinylene carbonate, succinonitrile, glutaronitrile, hexanenitrile, malononitrile, dimethyl sulfoxide, 1,3 -propane sultone, sulfolane, dimethyl sulfone, ethyl methyl sulfone, ethyl vinyl sulfone, vinyl sulfone, methyl vinyl sulfone, phenyl vinyl sulfone, 7V-propyl-7V-methylpyrrolidinium bis(fluorosulfonyl)imide, 7V-butyl-7V-methylpyrrolidinium bis(fluorosulfonyl)imide, A-propyl- 7V-methylpiperidinium bis(fluorosulfonyl)imide, 1 -methyl- 1 -(2-methoxyethyl)pyrrolidinium bis(fluorosulfonyl)imide, l-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, trimethyl phosphate, triethyl phosphate, poly(ethylene oxide), and a combination thereof.

[0044] In some embodiments, the solvent has a weight percentage in a range from 10.0 wt % to 90 wt % in the electrolyte.

[0045] In some embodiments, the solvent is substantially free of ester-based solvent, carbonate-based solvent, and nitrile-based solvent.

[0046] In some embodiments, the solvent comprises a fluorinated ether, fluorine-free ether, or a mixture thereof.

[0047] In some embodiments, the fluorine-free ether comprises at least one selected from the group consisting of 1,2-di ethoxy ethane, 1,1 -di ethoxy ethane, 1,1 -dipropoxy ethane, 1,2- dipropoxy ethane, 1,2-dibutoxy ethane, dibutyl ether, di -tert-butyl ether, tert-butyl ethyl ether, tert-butyl methyl ether, 1,3 -di oxolane, 1,4-di oxane and mixtures thereof.

[0048] In some embodiments, the fluorinated ether comprises one or more of bis(2,2,2- trifluoroethoxy)m ethane (BTFM), 1,1, 1 ,3 ,3 ,3 -hexafluoro-2-( 1,1,1 ,3 ,3 ,3 -hexafluoropropan-2- yloxymethoxy)propane, bis(3,3,3-trifluoropropoxy)methane, l,l,l-trifluoro-3-[(2,2,2- trifluoroethoxy)methoxy]propane, bis(2,2,3,3,3-pentafluoropropoxy)methane, 1, 1, 1,2,2- pentafluoro-3-((2,2,2-trifluoroethoxy)methoxy)propane, l,l,2,2-tetrafluoroethyl-2,2,3,3- tetrafluoropropyl ether (TTE), lH,lH,5H-octafluoropentyl-l,l,2,2-tetrafluoroethyl ether (OTE), bis(2,2,2-trifluoroethyl) ether, 1H, 1H, 2 ’H-Perfluorodi propyl ether, 2,2,2- Trifluoroethyl 1,1,2,2-tetrafluoroethyl ether, 1,2-(1,1,2,2-Tetrafluoroethoxy)ethane (TFEE), tris(2,2,2-trifluoroethyl)orthoformate (TFEO) and mixtures thereof.

[0049] In some embodiments, the fluorine-free ether and the fluorinated ether are present in a weight ratio of 1 :20 to 20: 1, 1 : 10 to 10: 1, 1 :5 to 10: 1, 1 :3 to 8: 1, or 1 : 1 to 3: 1. In some embodiments, the fluorine-free ether and the fluorinated ether are present in a weight ratio in a range from 1 :3 to 8: 1 or from 1 : 1 to 3 : 1.

[0050] In some embodiments, the solvent has a boiling point of at least 100 °C at 1 atm. In some embodiments, the solvent has a boiling point of at least 110 °C at 1 atm, at least 120 °C at 1 atm, at least 130 °C at 1 atm, or at least 140 °C at 1 atm.

[0051] In some embodiments, each component in the electrolyte has a boiling point of at least 100 °C, at least 110 °C, at least 120 °C, at least 130 °C or at least 140 °C at 1 atm. In some embodiments, the electrolyte does not include any component with a boiling point lower than 100 °C, 110 °C, 120 °C, 130 °C, or 140 °C at 1 atm to ensure stability and safety.Electrolyte Salt in Electrolyte

[0052] The electrolyte salt may be, for example, a lithium salt, or other salts such as sodium, potassium, magnesium, calcium salts, and the like.

[0053] In some embodiments, the electrolyte salt comprises a lithium salt. In some embodiments, the electrolyte salt includes one or more of lithium perchlorate (LiCICU), lithium hexafluorophosphate (LiPFe), lithium nitrate (LiNCh), lithium borofluoride (LiBF4), lithiumhexafluoroarsenide (LiAsFe), lithium trifluoromethanesulfonate (LiCFsSCh), lithium bisperfluoro-ethysulfonylimide (LiBETI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SC>2)2, LiTFSI), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiBF2C2C>4, LiDFOB), lithium fluoroalkyl- phosphates (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 (LiC4POsF2), and lithium tetrafluoro oxalato phosphate (LiC2PC>4F4), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SC>2)3), LiF, LiCl, LiBr, Lil, Li2SC>4, LisPCU, Li2CC>3, lithium acetate, lithium trifluoromethyl acetate, and lithium oxalate.

[0054] In some embodiments, the electrolyte salt comprises LiFSI, LiTFSI or both.

[0055] In some embodiments, the electrolyte salt is present in a weight percentage in a range from about 5 wt% to about 85 wt% based on the total weight of the electrolyte. For example, the electrolyte salt has a weight percentage in a range from about 10 wt% to about 75 wt%, from about 15 wt% to about 75 wt%, from about 25 wt% to about 75 wt%, from about 30 wt% to about 70 wt%, from about 40 wt% to about 60 wt%, from about 15 wt% to about 50 wt%, or from about 10 wt% to about 30 wt%, based on the total weight of the electrolyte. In some embodiments, the electrolyte salt can be present in the electrolyte in an amount of about 40 wt% to about 60 wt%, based on the total weight of the electrolyte composition. In some embodiments, the electrolyte salt is present in the electrolyte in an amount of about 10 wt% to about 40 wt%, based on the total weight of the electrolyte composition.

[0056] In addition, certain embodiments are directed to compositions for use with electrolytes, batteries, or other electrochemical devices including same, and methods for producing same.

[0057] In one aspect, the present disclosure is generally directed to an activated electrochemical cell including an electrolyte herein.Polymer in Electrolyte

[0058] In some embodiments, the electrolyte comprises a polymer in an amount of about 0.02 wt% to about 40 wt%, based on the total weight of the electrolyte composition.

[0059] In some cases, the electrolyte composition may include a crosslinked polymer obtained from a crosslinking reaction of a composition comprising one or more monomers, wherein at least one of the monomers comprises two or more polymerizable groups. In some embodiments, at least one of the monomers comprises three or more polymerizable groups.

[0060] In certain embodiments, a monomer for preparing the polymer has three or four polymerizable or crosslinkable arms, wherein each arm has a polymerizable or crosslinkable terminal covalently connected to a center. In some embodiments, the center can be an element of C, Si, N, P, B, or a cyclic ring. In some embodiments, each polymerizable or crosslinkable terminal is covalently connected to the center directly or via a spacer chain or group. In some embodiments, each arm is the same or different from each other.

[0061] In certain embodiments, the polymerizable or crosslinkable terminals are independently selected from the group consisting of C2-20 alkenyl, C2-20 alkynyl, epoxy, amino, hydroxyl, carboxylic acid, or any substituted form thereof.

[0062] In certain embodiments, the monomer with three or more polymerizable or crosslinkable terminals is a tri-acrylate, tetra-acrylate, modified tri-acrylate, modified tetraacrylate, silane, siloxane or triazinane-trione (triazine-trione).

[0063] In certain embodiments, modified tri-acrylates and tetra-acrylates include tri-acrylates and tetra-acrylates with substituted groups such as -CN, -SO2H, -CO2H, -CO2-, F, Cl, Br, or I.

[0064] In certain embodiments, the monomer with three or more terminals is a silane or siloxane.|0065] In certain embodiments, one of the monomers comprises one or more functional groups including without limitation:an

[0066] 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 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.EXAMPLE 1Preparation of pre-formed cell

[0067] A battery comprises Li metal on Cu foil as anode, microporous membrane as separator, NMC811 on Al foil as cathode, and electrolytes were assembled according to some embodiments of the present disclosure. The battery was subjected to a conventional Formation Protocol: 1) charge from OCV (0% SOC) to 4.25 V (100% SOC) at a rate of 0.05 C, discharge to 2.8 V (0% SOC) at a rate of 1C; 2) charge to 4.25 V at a rate of 0.1 C, discharge to 2.8 V at a rate of 1C, repeat once (twice in total); and 3) charge to 4.25 V at a rate of 0.1 C , 0.33C discharge to 2.8 V at a rate of 0.33 C. The total cycle number of the Formation Protocol is 4 cycles. After the conventional Formation Protocol, a pre-formed cell was obtained.Preparation of activated cell

[0068] The pre-formed cell was subjected to a representative Activation Protocol A: 1) charge to 4.25 V (100% SOC) at a rate of 0.33 C, discharge to 2.8 V (0% SOC) at a rate of 0.33 C; 2) repeat step 1) for a total of 20 cycles. Thus, an activated cell was obtained.

[0069] As shown in Table 1 and Fig. 2, a fully charged pre-formed cell can only deliver a discharge capacity of 14.3 mAh or a discharge capacity retention of 2.0% at 8C (24 mA / cm2) to 2.8 V. In contrast, an activated cell can deliver a discharge capacity of 557.5 mAh or adischarge capacity retention of 79.6% at 8C (24 mA / cm2) to 2.8 V. The Activation Protocol significantly improved the rate capability of the battery.Table 1. 8C discharge capacity for pre-formed cell and activated cell by Activation Protocol Aa: the capacity retention at 8C is the discharge capacity at 8C divided by the discharge capacity at 0.33C multiplied by 100%.

[0070] The resistances of the cell were measured by electrochemical impedance spectroscopy (EIS). The bulk resistance, anode resistance, and cathode resistance are listed in Table 2. All resistances decreased significantly after activation. The bulk resistance of the activated cell was only 34% of that of the pre-formed cell. The anode resistance of the activated cell was only 14% of the anode resistance of the pre-formed cell. The cathode resistance of the activated cell was only 28% of that of the pre-formed cell. A lower resistance is critical for better rate capability. Table 2. Bulk resistance, anode resistance, and cathode resistance of pre-formed cell and activated cell

[0071] The surface morphology of the anode was evaluated by scanning electron microscopy (SEM). The anode surface of the activated cell (Fig. 3B) is more porous and has a much higher surface area than the pre-formed cell (Fig. 3 A).EXAMPLE 2

[0072] In this example the pre-formed cell and activated cell were prepared by using the same formation protocol and activation protocol as described in Example 1. The cells were chargedto 4.25 V at a rate of 0.1C at 25 °C, then stored in a -20 °C chamber for 6 h before discharging to 2.8 V at a rate of 0.33C. The usable discharge capacity and capacity retention are shown in Table 3 and Fig. 4. The pre-formed cell has a capacity retention of less than 1% at -20 °C while the activated cell has a capacity retention of around 80.8%. The activation protocol significantly improved the low temperature performance of the cell.Table 3. -20 °C discharge capacity for pre-formed cell and activated cellb: the capacity retention at -20 °C is the discharge capacity of a fully charged cell after stored at -20 °C for 6 hours divided by the discharge capacity of a fully charged cell at 25 °C multiplied by 100%. A storage at -20 °C for 6 hours was to ensure the cell temperature was at -20 °C for at least at the beginning of discharge.EXAMPLE 3

[0073] In this example the pre-formed cell was prepared by using the same formation protocol as described in example 1. The activated cell was prepared using Activation Protocol B: 1) charge to 4.25 V at a rate of 0.1 C, discharge to 2.8 V at a rate of 0.1 C; 2) repeat step 1) for a total of 25 cycles, thereby obtaining an activated cell. The influence of the C rate and number of the activation cycles on activation was investigated. The present disclosure discovered that the number of activation cycles depends on the C rate of activation cycles. When the total number of cycles was 20 cycles or less, the cell could not be activated using Activation Protocol B.

[0074] As shown in Table 4, a fully charged activated cell prepared using Activation Protocol B can deliver a discharge capacity of 557.7 mAh or a discharge capacity retention of 79.7% at 8C (24 mA / cm2). The Activation Protocol significantly improved the rate capability of the battery.Table 4. 8C discharge capacity for pre-formed cell and activated cell by Activation Protocol BEXAMPLE 4

[0075] In this example the pre-formed cell was prepared by using the same formation protocol as described in example 1. The activated cell was prepared using Activation Protocol C: 1) charge to 4.25 V at a rate of 0.33 C, discharge to an SOC of 40% at a rate of 0.33 C, followed by discharge to 2.8 V at a rate of 1C (the average discharge C rate is 0.6C); 2) repeat step 1) for a total of 16 cycles. The SOC of 40% is defined as the remaining capacity of the cell is 40% of total discharge capacity when the cell is discharged to 2.8 V at a rate of 0.33C.

[0076] As shown in Table 5, a fully charged activated cell prepared using Activation Protocol C can deliver a discharge capacity of 534.1 mAh or a discharge capacity retention of 76.3% when discharging at a current density of 8C (24 mA / cm2) to 2.8 V. The Activation Protocol significantly improved the rate capability of the battery.Table 5. 8C discharge capacity for pre-formed cell and activated cell by Activation Protocol CEXAMPLE 5

[0077] In this example the pre-formed cell was prepared by using the same formation protocol as described in example 1. The pre-formed cell was subjected to Control Protocol A: 1) charge to 4.25 V at a rate of 0.33 C, discharge to 2.8 V at a rate of 1.0 C; 2) repeat step 1) for a totalof 80 cycles. The 8C discharge capacity was checked every 20 cycles. As shown in Table 6,The cell can only deliver < 20% capacity after 80 cycles. Thus, the cell was not activated.Table 6. 8C discharge capacity for the cell by Control Protocol AEXAMPLE 6|0078] In this example the pre-formed cell was prepared by using the same formation protocol as described in Example 1. The activated cell was prepared using Activation Protocol D: 1) charge to 50% SOC at a rate of 0.33C, discharge to 0% SOC at a rate of 0.33C; 2) repeat step 1) for a total of 20 cycles. The control cell was prepared by charging the pre-formed cell to 50% SOC at a rate of 0.33C then the cell was subjected to Control Protocol B: 1) charge to 100% SOC (4.25 V) at a rate of 0.33C, discharge to 50% SOC at a rate of 0.33C; 2) repeat step 1) for a total of 20 cycles.

[0079] As shown in Table 7, a fully charged activated cell prepared using Activation Protocol D can deliver 65.6% discharge capacity when discharging at a current density of 8C (24 mA / cm2) to 2.8 V. A fully charged control cell using Control protocol B can only deliver 6.3% discharge capacity when discharging at a current density of 8C. The SOC range is critical to the success of activation.Table 7. 8C discharge capacity retention for activated cell prepared by Activation Protocol D and control cell prepared by Control Protocol BEXAMPLE 7

[0080] In this example the pre-formed cell was prepared by using the same formation protocol as described in example 1. The activated cell was prepared using Activation Protocol A as described in example 1. The control cell was prepared using pre-formed cell and Control Protocol C: 1) charge to 4.25 V at a rate of 0.33 C, discharge to 2.8 V at a rate of 0.33 C; 2) repeat step 1) for a total of 5 cycles. The cells were charged to 4.25 V at a rate of 0.1C at 25 °C, then stored in a -30 °C chamber for 6 h before discharging to 2.8 V at a rate of 0.33C. The discharge capacity retention is shown in Table 8. The control cell has a capacity retention of 2.1% at -30 °C while the activated cell has a capacity retention of 77.8%. The number of activation cycles is critical to the success of activation.Table 8. -30 °C discharge capacity retention for control cell and activated cellAspects

[0081] In a first aspect, the present disclosure provides a method for preparing an activated cell, comprising:• activating a preformed cell by a number of activation cycles (Nac), each activation cycle comprising charging the preformed cell from SOCai to SOCa2 at a rate of Cai and discharging from SOCa2 to SOCai at a rate of Ca2, leading to an activated cell, wherein Ca2 has a value no greater than a critical rate (Ccr).

[0082] In a second aspect according to the first aspect, Cai < 0.8C.

[0083] In a third aspect according to the first or second aspect, Ccr is 1.0C.

[0084] In a fourth aspect according to any preceding aspect, Nac is an integer greater than 5, i.e., 5 < Nac < 50.

[0085] In a fifth aspect according to any preceding aspect, 0.01C < Ca2 < 0.8 C

[0086] In a sixth aspect according to any preceding aspect, 0% < SOCai < 50%, and 20% < SOCa2 < 100%. In some embodiments, 0% < SOCai < 40%. In some embodiments, 0% < SOCai < 35%. In some embodiments, 0% < SOCai < 30%. In some embodiments, 0% < SOCai < 25%. In some embodiments, 0% < SOCai < 20%. In some embodiments, 0% < SOCai < 15%. In some embodiments, 0% < SOCai < 10%.

[0087] In a seventh aspect according to any preceding aspect, the activated cell comprises an anode comprising lithium metal or lithium alloy.

[0088] In an eighth aspect according to any preceding aspect, the anode exhibits a porous morphology.

[0089] In a nineth aspect according to any preceding aspect, the activated cell exhibits a bulk resistivity of at least 30% lower than that of the preformed cell.

[0090] In a tenth aspect according to any preceding aspect, the activated cell exhibits a capacity retention at least 20% higher than that of the preformed cell at a temperature in a range from - 30 °C to 0 °C.

[0091] In an eleventh aspect according to any preceding aspect, the activated cell exhibits a capacity retention at least 20% higher than that of the preformed cell at a rate in a range from 4C to 10C. In some embodiments, the preformed cell is prepared by applying a number of formation cycles (Nfm) to a cell, wherein each formation cycle comprises charging a cell from SOCfi to SOCf2 at a rate of Cfi and discharging from SOC12 to SOCfi at a rate of Cf2. In some embodiments, 1 < Nfm < 5, Cfi < 0.33C, and Cf2 < 1.0C.

[0092] In a twelfth aspect, the present disclosure provides a lithium metal secondary battery comprising:1) an assembly comprising a cathode, an anode and a separator interposed between the cathode and anode, wherein the anode comprises anode current collector and an anodeactive material layer comprising lithium metal or lithium alloy on at least one surface of the anode current collector,2) a non-aqueous electrolyte impregnating the assembly, and3) a housing receiving the assembly and the non-aqueous electrolyte, wherein a number of formation cycles (Nfm) are applied to the assembly in the housing, leading to a pre-formed lithium metal secondary battery, and a number of activation cycles (Nac) are applied to the pre-formed lithium metal secondary battery, thereby obtaining an activated lithium metal secondary battery, wherein each formation cycle comprises charging the assembly from SOCfi to SOCf2 at a rate of Cfi and discharging from SOC12 to SOCfi at a rate of Cf2, and each activation cycle comprises charging the pre-formed lithium metal secondary battery by charging from SOCai to SOCa2 at a rate of Cai and discharging from SOCa2 to SOCai at Ca2 with a value no greater than a critical rate (Ccr).

[0093] In a thirteenth aspect according to the twelfth aspect, 1 < Nfm < 5, 5 < Nac <50, 0.01C < Cai < 0.8C, Ccr is 1.0C, and 0.01C < Ca2< 0.8C.

[0094] In a fourteenth aspect according to the twelfth aspect, the activated lithium metal secondary battery exhibits a capacity retention at least 20% higher than that of the pre-formed lithium metal secondary battery at a temperature in a range from -30 °C to 0 °C.

[0095] In a fifteenth aspect according to the twelfth aspect, the activated lithium metal secondary battery exhibits a capacity retention at least 20% higher than that of the pre-formed lithium metal secondary battery at a rate in a range from 4C to 10C.

[0096] 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.

[0097] 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.

[0098] 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

1. We claim:

1. A method for preparing an activated cell, comprising:• activating a pre-formed cell by a number of activation cycles (Nac), each activation cycle comprising charging the pre-formed cell from SOCai to SOCa2 at a rate of Cai and discharging from SOCa2 to SOCai at a rate of Ca2, leading to an activated cell, wherein Ca2 has a value no greater than a critical rate (Ccr).

2. The method of claim 1, wherein Cai < 0.8C.

3. The method of claim 1, wherein Ccr is 1.0C.

4. The method of claim 1, wherein 5 < Nac < 50.

5. The method of claim 1, wherein 0.01C < Ca2 < 0.8C.

6. The method of claim 1, wherein 0% < SOCai < 50%, and 20% < SOCa2 < 100%.

7. The method of claim 1, wherein the activated cell comprises an anode comprising lithium metal or lithium alloy.

8. The method of claim 7, wherein the anode of the activated cell exhibits a porous morphology.

9. The method of claim 1, wherein the activated cell exhibits a bulk resistivity of at least 30% lower than that of the pre-formed cell.

10. The method of claim 1, wherein the activated cell exhibits a capacity retention at least 20 % higher than that of the pre-formed cell at a temperature in a range from -30 °C to 0 °C.

11. The method of claim 1, wherein the activated cell exhibits a capacity retention at least 20% higher than that of the pre-formed cell at a rate in a range from 4C to 10C.

12. An activated lithium metal secondary battery, comprising: a. an assembly comprising a cathode, an anode and a separator interposed between the cathode and anode, wherein the anode comprises anode current collector and an anode active material layer comprising lithium metal or lithium alloy on at least one surface of the anode current collector, b. a non-aqueous electrolyte impregnating the assembly, and c. a housing receiving the assembly and the non-aqueous electrolyte, wherein a number of formation cycles (Nfm) are applied to the assembly in the housing, leading to a pre-formed lithium metal secondary battery, and a number of activation cycles (Nac) are applied to the pre-formed lithium metal secondary battery, thereby obtaining an activated lithium metal secondary battery, wherein each formation cycle comprises charging the assembly from SOCfi to SOCf2 at a rate of Cfi and discharging from SOC12 to SOCfi at a rate of Cf2, and each activation cycle comprises charging the pre-formed lithium metal secondary battery by charging from SOCai to SOCa2 at a rate of Cai and discharging from SOCa2 to SOCai at Ca2 with a value no greater than a critical rate (Ccr).

13. The activated lithium metal secondary battery of claim 12, wherein 1 < Nfm< 5, 5 < Nac< 50, 0.01C < Cai< 0.8C and 0.01 C < Ca2< 0.8C.

14. The activated lithium metal secondary battery of claim 12, wherein the activated lithium metal secondary battery exhibits a capacity retention at least 20% higher than that of the pre-formed lithium metal secondary battery at a temperature in a range from -30 °C to 0 °C.

15. The activated lithium metal secondary battery of claim 12, wherein the activated lithium metal secondary battery exhibits a capacity retention at least 20% higher than that of the pre-formed lithium metal secondary battery at a rate in a range from 4C to 10C.

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