Hybrid coating for lithium metal protection

Abstract

A method of forming a lithium ion battery, a lithium ion battery anode, and a lithium ion battery for a vehicle. The method includes exposing a first surface of the lithium layer to carbon dioxide gas and forming a lithium carbonate layer on the first surface of the lithium layer. The method further includes depositing a fluoropolymer layer on the second surface of the lithium carbonate layer to provide a lithium anode. The battery includes one or more battery cells including a negative electrode for a lithium ion battery. The negative electrode includes a lithium layer having a first surface and a hybrid coating disposed on the first surface, wherein the hybrid coating includes a plurality of lithium fluoride domains and a plurality of lithium carbonate domains within a carbonaceous matrix.

Description

Technical Field

[0001] The present invention relates to the automotive field, in particular, to a hybrid coating for lithium metal protection. Background Art

[0002] Electric vehicle and hybrid electric vehicle technology has been made possible by the development and application of rechargeable secondary batteries that replace or enhance internal combustion engines to provide energy for the power system. Secondary batteries include lithium-ion batteries, which generally include a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode provides lithium ions (Li + ) source, the negative electrode stores and releases lithium ions received from the positive electrode, and the separator prevents the positive and negative electrodes from contacting. The electrolyte provides a medium between the positive and negative electrodes through which the lithium ions move. The type and quality of the materials that form these battery components greatly affect the battery's capacity, number of charge and discharge cycles, and overall performance.

[0003] For example, the negative electrode chemistry must resist volume changes and dendrite growth to maintain battery performance, and various negative electrode chemistries have been studied to provide stable negative electrode materials. For example, lithium may be a favorable negative electrode material because it has a relatively low density, a low negative electrochemical potential, and a high theoretical specific capacity. However, lithium reacts with water, requiring the lithium negative electrode to be stored in a low humidity environment during formation, transportation, and assembly. Even in a dry indoor environment with a relative humidity of 1% and a dew point of -40°C, lithium may react with moisture in the air and carbon dioxide in the environment. Initially, lithium (Li) reacts with water (H2O) to form lithium hydroxide (LiOH), and lithium hydroxide (LiOH) reacts with carbon dioxide (CO2) to form lithium carbonate (Li2CO3). Although lithium carbonate forms a passivation layer, it is brittle and lithium is soft, and when lithium is bent, lithium carbonate breaks, which further exposes lithium to the environment and forms more lithium carbonate. In addition, lithium carbonate does not dissolve in the electrolyte after battery assembly, thereby reducing or even hindering the transfer of lithium.

[0004] The above factors may make the handling of lithium difficult when manufacturing lithium anodes. In view of these difficulties, other anode materials have been studied and adopted. For example, graphite is often used as anode due to its physical stability during charging and discharging. Silicon has also been identified as a useful material for lithium-ion battery anodes due to its stability compared to lithium and its relatively higher energy density compared to graphite.

[0005] Therefore, while existing secondary lithium ion battery negative electrodes achieve their intended purpose, there is still a need for new and improved secondary lithium ion battery negative electrodes. Summary of the invention

[0006] According to several aspects, the present disclosure relates to a method for forming a lithium ion battery. The method includes exposing a first surface of a lithium layer to carbon dioxide gas and forming a lithium carbonate layer on the first surface of the lithium layer. The method also includes depositing a fluoropolymer layer on a second surface of the lithium carbonate layer to provide a lithium negative electrode.

[0007] In embodiments, forming the lithium carbonate layer comprises forming the lithium carbonate layer to a thickness of less than 50 nanometers.

[0008] In any of the above embodiments, depositing the fluoropolymer layer comprises depositing a plurality of fluoropolymer fragments of the fluoropolymer using a physical deposition process, wherein the plurality of fluoropolymer fragments impinge the lithium carbonate layer. In other embodiments, depositing the fluoropolymer layer comprises depositing a fluoropolymer having a thickness in the range of 5 nanometers to 100 nanometers. In other embodiments, depositing the fluoropolymer layer comprises depositing a plurality of fluoropolymer fragments of at least one of polyvinyl fluoride (PVD), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene (TFE), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene perfluoromethylvinyl ether (methylfluoroalkoxy, MFA), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and ethylene chlorotrifluoroethylene (ECTFE).

[0009] In the above embodiments, the fluoropolymer layer is deposited using a physical deposition process, the physical deposition process comprising depositing the fluoropolymer layer by thermally evaporating the fluoropolymer from a fluoropolymer target. In alternative or additional embodiments, the fluoropolymer layer is deposited using a physical deposition process comprising depositing the fluoropolymer layer by sputtering the fluoropolymer from a fluoropolymer target.

[0010] In any of the above embodiments, the method further comprises forming a lithium layer by thermally evaporating lithium and depositing the lithium on a substrate. In embodiments, the substrate is a negative electrode current collector.

[0011] In any of the above embodiments, the method further comprises assembling the lithium negative electrode into a battery cell. In an embodiment, assembling the lithium negative electrode into a battery cell comprises positioning the separator between the positive electrode and the lithium negative electrode. In an embodiment, the positive electrode is formed on the positive electrode current collector, and the negative electrode is formed on the negative electrode current collector.

[0012] In other embodiments, the method further comprises defluorinating the fluoropolymer layer and forming a hybrid coating comprising a plurality of lithium fluoride domains and a plurality of lithium carbonate domains. In embodiments, the method further comprises forming a carbonaceous matrix around the plurality of lithium fluoride domains and the plurality of lithium carbonate domains. And, in other embodiments, the method comprises sealing the battery cell in a soft pack battery core shell and introducing the electrolyte into the battery cell.

[0013] According to various other aspects, the present disclosure relates to a negative electrode for a lithium ion battery. The negative electrode includes a lithium layer having a first surface. A lithium carbonate layer is provided on the first surface, wherein the lithium carbonate layer includes a second surface. In addition, a fluoropolymer layer is provided on the second surface. In an embodiment, the lithium carbonate layer presents a thickness of less than 50 nanometers. In any of the above embodiments, the fluoropolymer layer presents a thickness of 5 nanometers to 100 nanometers. In an embodiment, the fluoropolymer layer is formed by one or more of the following fluoropolymers: polyvinyl fluoride (PVD), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene (TFE), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene perfluoromethylvinyl ether (methylfluoroalkoxy, MFA), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), ethylene chlorotrifluoroethylene (ECTFE).

[0014] According to various other aspects, the present disclosure relates to a lithium-ion battery for a vehicle. The lithium-ion battery includes one or more battery cells, wherein each battery cell includes a positive electrode disposed on a positive current collector, a negative electrode disposed on a negative current collector, a porous separator between the positive electrode and the negative electrode, and an electrolyte that permeates the porous separator. The negative electrode includes a lithium layer having a first surface and a mixed coating disposed on the first surface. The mixed coating includes a plurality of lithium fluoride domains and a plurality of lithium carbonate domains within a carbonaceous matrix. The lithium-ion battery also includes a soft-pack battery core shell defining a volume for accommodating the battery cell, a negative electrode tab welded to a portion of the negative electrode collector extending from the soft-pack battery core shell, and a positive electrode tab welded to a portion of the positive electrode collector extending from the soft-pack battery core shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0016] Figure 1 A vehicle including a propulsion system utilizing a battery is shown according to various embodiments described herein.

[0017] Figure 2A According to various embodiments described herein, one or more Figure 2B A battery with a lithium-ion battery cell is shown.

[0018] Figure 2B A lithium-ion battery cell is shown according to various embodiments described herein.

[0019] Figure 3 Methods of forming a lithium negative electrode including a hybrid coating according to various embodiments described herein are shown.

[0020] Figure 4A A lithium layer including a lithium carbonate layer deposited on lithium is shown according to various embodiments described herein.

[0021] Figure 4B A lithium layer is shown according to various embodiments described herein and includes a fluoropolymer layer deposited on a lithium carbonate layer to form a hybrid coating on the lithium layer.

[0022] Figure 4C Shown is a hybrid coating after initiation of difluorination of the fluoropolymer according to various embodiments described herein.

[0023] Figure 5 A physical vapor deposition system according to various embodiments described herein is shown.

[0024] Figure 6 A plasma enhanced chemical vapor deposition system according to various embodiments described herein is shown.

[0025] Figure 7 Methods of forming a cell and initiating defluorination of a fluoropolymer according to various embodiments described herein are shown. DETAILED DESCRIPTION

[0026] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application or use. In addition, there is no intention to be bound by any express or implied theory presented in the previous background technology, the invention summary or the following detailed description. It should be understood that throughout the drawings, the same reference numerals indicate similar or corresponding parts and features.

[0027] Reference will now be made in detail to several embodiments of the present disclosure illustrated in the accompanying drawings. Whenever possible, the same or similar reference numerals are used in the drawings and description to refer to the same or similar parts or steps. The drawings are in simplified form and not drawn to exact scale.

[0028] The present disclosure relates to a hybrid coating for a lithium negative electrode used in a lithium-ion battery cell, a battery including such a battery cell, and a vehicle including such a battery, and a method for manufacturing a lithium negative electrode including a hybrid coating. As used herein, the term "vehicle" is not limited to an automobile. Although the present technology is described primarily in conjunction with electric vehicles herein, the technology is not limited to electric vehicles, but also includes hybrid electric vehicles. In addition, these concepts can be used in a variety of applications, such as in conjunction with components used in motorcycles, mopeds, locomotives, aircraft, ships and other vehicles and other applications using batteries, such as components used in portable power stations, for example, power stations for powering remote work sites and emergency backup power supplies, and permanent power stations associated with buildings and equipment, all of which can be powered by, for example, solar or wind turbine generator systems, power mains and fuel-based generators (such as gasoline or diesel generators) and heat engines.

[0029] Figure 1 The vehicle 100 is shown including a propulsion system 120. The propulsion system 120 generally includes an electric motor 124 and a secondary battery 126 for powering the electric motor 124. In many embodiments of the propulsion system 120, the propulsion system 120 includes an inverter 128 for changing power from DC (direct current) provided by the battery 126 to AC (alternating current) used by the electric motor 124. The inverter 128 may be included in a power electronics module 130 that includes, for example, transistors and diodes for switching power from DC to AC and vice versa.

[0030] The controller 132 is connected to the inverter 128 and is programmed to control and manage the operation of the motor 124 and related hardware including the inverter 128. The motor 124 is connected to a transmission (drive unit) 136 and a drive line 138, which transmits mechanical power and rotation to wheels 140 of the vehicle 100. The controller 132 includes one or more processors and tangible, non-transitory memory 134.

[0031] The electric motor 124, which is powered by the battery 126, includes a stator 142 and a rotor 144 arranged together with the stator 142. The stator 142 is the stationary part of the electric motor 124 and provides a rotating magnetic field that attempts to align with the stationary magnetic field of the rotor 144. This causes the rotor 144 to rotate in a so-called "electric" mode. In other applications, the rotating field of the rotor 144 (caused by physical rotation) generates current in the stator 142, and this operating mode is called a "generation" mode and the electric motor 124 used in this way is called a generator. In traction motor vehicle applications, the driving mode provides movement to the vehicle 100, while the generation mode recovers energy when the vehicle is in the process of stopping. The recovered energy is stored in the vehicle battery 126.

[0032] Figure 2A and 2B An embodiment of a secondary battery 126 for powering an electric vehicle 100 is shown. The battery 126 is connected to a load 148, such as an electric motor 124. The battery 126 discharges when a load is applied and recharges when an external power source is applied. The battery 126 includes one or more battery cells 150 assembled together. Each battery cell 150 generally includes a positive current collector 152, a negative current collector 154, a positive electrode 156, a negative electrode 158, a separator 160, and an electrolyte 162. During discharge, when the battery 126 powers the load 124, lithium ions (Li + ) moves from the negative electrode 158 through the electrolyte 162 through the separator 160 to the positive electrode 156. - ) moves from the positive electrode 156 to the negative electrode 158 through the circuit 146, providing a voltage to the load 124. When charging, when an external voltage is applied, the lithium ions move from the positive electrode 156 to the negative electrode 158 through the electrolyte 162 through the separator 160, and can be embedded in the negative electrode 158. The battery cell 150 is encapsulated in a volume defined by a soft-pack battery core case 168, which is sealed around the periphery of the positive electrode collector 152, the negative electrode collector 154, the positive electrode 156, the negative electrode 158, the separator 160 and the electrolyte 162. Figure 2B As shown, the battery cell 150 includes two negative current collectors 154 and one positive current collector 152. Alternatively, there may be two positive current collectors 152 and one negative current collector 154, or there may be one negative current collector 154 and one positive current collector 152. In addition, a portion of the positive current collector 152 extends from the soft-pack battery core case 168 and is welded to the positive electrode tab 172, and a portion of the negative current collector 154 extends from the soft-pack battery core case 168 and is welded to the negative electrode tab 174. The positive electrode tab 172 is connected to the positive bus bar 178, and the negative electrode tab 174 is connected to the negative bus bar 180.

[0033] The positive current collector 152 and the negative current collector 154 are formed of a conductive material. In an embodiment, the positive current collector 152 may include one or more of aluminum, nickel, and stainless steel; and the negative current collector 154 may include one or more of copper, nickel, stainless steel, and titanium. The current collectors 152, 154 are shown in the form of foil; however, it should be understood that other forms may be present. The positive current collector 152 and the negative current collector 154 are impermeable to moisture, thereby preventing moisture from entering from the current collector side of the positive electrode 156 and the negative electrode 158. In an embodiment, the positive current collector 152 presents a thickness in the range of 5 microns to 15 microns, including all values ​​and ranges therein, and the negative current collector 154 presents a thickness in the range of 5 microns to 15 microns, including all values ​​and ranges therein.

[0034] The positive electrode 156 includes a lithium ion (Li+ ) source and can undergo reversible insertion or embedding of lithium ions, thereby determining the capacity and average voltage of the battery. The positive electrode material includes an oxide or phosphate of lithium and one or more transition metals, such as cobalt oxide, manganese oxide, manganese phosphate, iron phosphate, and lithium nickel manganese cobalt oxide. The positive electrode 156 presents a thickness in the range of 20 to 200 microns, including all values ​​and ranges therein. In an embodiment, the positive electrode 156 is applied to the positive current collector 152 as a coating using a deposition process (such as a slurry-based process, a hot roll pressing process, extrusion, or additive manufacturing). The combined positive electrode 156 and the positive current collector 152 provide a positive electrode, as further mentioned in the present disclosure.

[0035] Negative electrode 158 includes a material capable of undergoing reversible insertion or intercalation of lithium ions at a lower electrochemical potential than the material of positive electrode 156 , such that an electrochemical potential difference exists between negative electrode 158 and positive electrode 156 . Figure 4C , which shows a negative electrode 158 according to an embodiment of the present invention. The negative electrode 158 includes a mixed coating 164 of lithium fluoride (LiF) domains and lithium carbonate (Li2CO3) domains (both designated as 196) in a carbonaceous matrix 198 disposed on a lithium layer 166. The negative electrode 158 exhibits a thickness in the range of 1 micron to 50 microns, including all values ​​and ranges therein. In an embodiment, the negative electrode 158 is applied to the negative current collector 154 using a lamination process or, alternatively, a process such as sputtering deposition, to form a coating on the negative current collector 154, or electron beam evaporation can be used to deposit the negative electrode 158. The combined negative electrode 158 and the negative current collector 154 provide a negative electrode, as further mentioned in the present disclosure.

[0036] The separator 160 is a porous material formed by an electrically insulating material, which can prevent the positive electrode 156 and the negative electrode 158 from contacting and potentially shorting the circuit. The separator 160 is sandwiched or at least partially surrounded between the positive electrode 156 and the negative electrode 158, allowing lithium ions and electrolyte 162 to pass through the pores of the separator 160. The separator 160 may include one or more of a composite material, a polymeric material, and a non-woven material. In an embodiment, the separator 160 is thermoplastic and includes at least one of polyethylene, polypropylene, polyamide, polytetrafluoroethylene, polyvinylidene fluoride, and polyvinyl chloride. In other embodiments, the separator 160 may be filled with a material such as glass fiber. The separator 160 may include one or more layers, wherein each layer is formed by one or more of the above materials. The separator 160 may be in the form of a film or a net, such as a woven net or a cut film. In an embodiment, the separator 160 presents a thickness in the range of 7 microns to 50 microns, including all values ​​and ranges therein.

[0037] The electrolyte 162 provides a medium through which lithium ions pass between the positive electrode 156 and the negative electrode 158. The medium may be a liquid, a gel, or a solid, and is capable of conducting lithium ions between the positive electrode 156 and the negative electrode 158. The electrolyte 162 permeates the porous separator 160 and wets the surfaces of the positive electrode 156 and the negative electrode 158 and the separator 160. In an embodiment, the electrolyte 162 is a non-aqueous organic solvent. In other embodiments, the electrolyte 162 is a non-aqueous aprotic organic solvent that includes one or more different alkyl carbonates, for example, cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), aliphatic carboxylates (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain structure ethers (e.g., 1,2-dimethoxyethane, 1-2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), 1,3-dioxolane).

[0038] In any of the above embodiments, the electrolyte 162 may include a lithium salt dissolved in one or more organic solvents. The lithium salt may include one or more of the following: lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate (LiB(C6H5)4), lithium bis(oxalato)borate (LiB(C2O4)2) (LiBOB), lithium difluorooxalatoborate (LiB F2(C2O4)), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethane)sulfonyl imide (LiN(CF3SO2)2), lithium bis(fluorosulfonyl)imide (LiN(FSO2)2)(LiSFI), lithium (triethylene glycol dimethyl 1 ether) bis(trifluoromethanesulfonyl)imide (Li(G3)(TFSI), lithium bis(trifluoromethanesulfonyl) azide (LiTFSA)). The lithium salt may be present in the electrolyte 162 at a concentration (moles of salt per liter of solvent) ranging from 1M to 4M, including all values ​​and ranges therein, such as 2M or 3M.

[0039] In addition, the electrolyte 162 may include a variety of additives, such as, but not limited to, ethylene carbonate, vinyl ethylene carbonate, propane sulfonate, and combinations thereof. Other additives may include diluents that do not coordinate with lithium ions but can reduce the viscosity of the electrolyte 162, such as bis(2,2,2-trifluoroethyl) ether (BTFE), and flame retardants, such as triethyl phosphate.

[0040] In an embodiment, the battery cells 150 are separated by a separator 160, which may at least partially wrap each battery cell 150. Alternatively or additionally, the battery cells 150 are heat sealed in a soft pack battery core case 168 and stacked in a housing 170. The soft pack battery core case 168 is formed of a non-conductive material, for example, a thermoplastic film coated with aluminum. In an embodiment, the thermoplastic film includes polyethylene or polypropylene.

[0041] In an embodiment, the positive current collectors 152 are joined together using one or more positive bus bars 178, and the negative current collectors 154 are joined together using one or more negative bus bars 180. The bus bars 178 and 180 extend out of the battery 126, or include connectors that extend out of the battery 126. The bus bars 178, 180 are then connected directly or indirectly to the load 148.

[0042] Reference Figure 3 , which shows an embodiment of a method 300 for forming a lithium negative electrode 158, wherein the lithium negative electrode 158 includes a mixed coating 164 of lithium fluoride (LiF) and lithium carbonate (Li2CO3) 196 in a carbonaceous matrix 198, and further reference FIG. 4A to FIG. 4B , which shows the lithium negative electrode 158 after applying the mixed coating, and reference Figure 4C , which shows the lithium negative electrode 158 after battery assembly.

[0043] At block 302, and with further reference to Figure 5 , which shows a physical vapor deposition system 500, optionally, the method 300 continues to form a lithium layer 166. The lithium layer 166 can be formed on a substrate 502 (such as a negative electrode current collector 154) by, for example, physical vapor deposition using a process such as thermal evaporation, sputtering, or laminating lithium onto the substrate 502. During deposition, the substrate 502 is placed in a first processing chamber 504, and the processing chamber 504 is evacuated using a vacuum pump system 510, which typically includes a multi-stage vacuum pump. A lithium source 506, such as a lithium target including solid lithium or lithium powder, is disposed opposite to the substrate 502 in the processing chamber 504. Lithium 508 is evaporated from the lithium source 506 using one of resistive heating or electron beam evaporation and discharged toward the substrate 502. A power supply 512 is used to power the heating device. Lithium is deposited to a thickness of less than 10 nanometers, including all values ​​and ranges from 1 nanometer to 10 nanometers, to form a lithium layer 166. Light shield 520 may be used to control the flow of evaporated lithium, and deposition monitor 518 may be used to determine the deposition rate and thickness of the lithium. In alternative embodiments, lithium layer 166 may be received, preformed, and packaged with or without negative current collector 154 .

[0044] At block 304, a layer of lithium carbonate (Li2CO3) 184 is formed on the lithium layer 166. To form the lithium carbonate layer 184, a chemical vapor deposition process, such as atomic layer deposition or low pressure chemical vapor deposition, may be used. The exposed surface of the lithium layer 166 is exposed to carbon dioxide gas 602 supplied to a processing chamber 606 of the chemical vapor deposition system 600, such as Figure 6 as shown, or exposed to the supply to which this document is incorporated by reference Figure 6 The carbon dioxide gas 602 of the first process chamber 504 of the described functions and features. Before the lithium layer 166 is introduced, the process chamber 606 is evacuated by a vacuum system 610 including one or more vacuum pumps, and then the lithium layer 166 is exposed to the process chamber environment. Carbon dioxide is supplied by the carbon dioxide source 604 at a feed rate and amount sufficient to grow a lithium carbonate layer 184 with a thickness of less than 50 nanometers (including all values ​​and ranges therein, such as 1 nanometer to at most 50 nanometers) on the lithium layer 166.

[0045] At block 306, a fluoropolymer layer 190 is then deposited on the surface 192 of the lithium carbonate layer 184. The fluoropolymer layer 194 exhibits a thickness in the range of 5 nanometers to 100 nanometers, including all values ​​and ranges therein. The fluoropolymer layer 190 is deposited by a physical deposition process such as thermal evaporation or sputtering. Figure 6 The processing chamber 606 shown or Figure 5The process chamber 504 is shown, any excess carbon dioxide (if present) can be removed from the process chamber 606, 504, and an inert gas such as argon (Ar) can be provided to the process chamber from the inert gas source 614, 514. Fluoropolymer targets 618, 506 are contained in the process chambers 606, 504. Fluoropolymer targets 618, 506 in embodiments include one or more of the following fluoropolymers: polyvinyl fluoride (PVD), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), and polytrifluorochloroethylene (PCTFE), tetrafluoroethylene (TFE), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene perfluoromethylvinyl ether (i.e., methylfluoroalkoxy (MFA)), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and ethylene trifluorochloroethylene (ECTFE). In the case of thermal evaporation, the fluoropolymer targets 618, 506 are heated to their decomposition temperature by a heating device such as a laser or a filament. Fluoropolymer vapor 622 is ejected from the fluoropolymer target 618, 506 and coated on the exposed surface 192 of the lithium carbonate layer 184 formed on the lithium layer 166. In the case of sputtering, the fluoropolymer target 618, 506 is struck by ions 624 (e.g., hydrogen ions) generated within the processing chamber 606 or provided to the processing chamber 606 from an ion generator 626 including a magnetron or an ion gun, and fluoropolymer fragments are ejected from the target and strike the lithium carbonate layer 184.

[0046] Alternatively, the fluoropolymer layer 194 may be formed using Figure 6 The chemical vapor deposition system 600 shown is deposited by plasma assisted or thermal assisted chemical vapor deposition. The process includes introducing one or more precursor gases such as hexafluoropropylene oxide (C3F6O), carbon tetrafluoride (CF4), octafluorobutane (C4F8), trifluoromethane (CHF3), difluoromethane (CH2F2) and fluoromethane (CH3F) into the chemical vapor deposition chamber 606 through the gas supply 604 after evacuating the processing chamber 606. The gas precursor is then polymerized by plasma or thermal assistance. If plasma assistance is used, plasma ions (e.g., hydrogen ions) are ejected to interact with the precursor gas to provide a polymer film. If thermal assistance is used, a nickel-chromium alloy mesh catalyst activator is used to catalyze the reaction.

[0047] At this stage, the lithium negative electrode 158 or the universal substrate 502 on the negative current collector 154 can be packaged and shipped or stored before being assembled into the battery 126. Once formed, the hybrid coating 164 including the lithium carbonate layer 184 and the fluoropolymer layer 194 can protect the lithium negative electrode 158, such as Figure 4BAs shown. For example, the fluoropolymer layer 194 and the lithium carbonate layer 184 can protect the lithium layer 166 from exposure to moisture, thereby allowing the lithium negative electrode 158 to have greater flexibility in storage, transportation, and integration into the battery 126. In addition, the fluoropolymer layer 194 can prevent the lithium carbonate layer from peeling off. In addition, Li2CO3 prevents defluorination reactions between lithium and the fluoropolymer.

[0048] At block 308, the lithium negative electrode 158 is assembled into the battery cell 150. In the assembly process 700, embodiments of the present invention are described in Figure 7 , at box 702, a positive electrode including a positive current collector 152 and a positive electrode 156, a separator 160, and a negative electrode including a negative electrode 158 and a negative current collector 154 are assembled into a battery cell 150, and the separator 160 is placed between them. It should be understood that the positive electrode 156 and the negative electrode 158 are located on opposite sides of the separator 160, the positive electrode 156 is located between the separator 160 and the positive current collector 152, and the negative electrode 158 is located between the separator 160 and the negative current collector 154. The separator 160 can also be placed between two battery cells 150. In an embodiment, the separator 160 can be in the form of a strip and can be folded. The positive electrode and the negative electrode can be interlaced between the folds of the separator 160. The separator can present a general "z" shape around the positive electrode and the negative electrode, sometimes referred to as a "z fold". In other embodiments, the positive electrode, the first separator 160 , the negative electrode, and the second separator 160 may be wound around a mandrel to form the battery cell 150 .

[0049] Once the battery cell 150 is assembled, at block 704, the battery cell 150 is baked in a vacuum oven to minimize reactivity with environmental factors such as moisture and reactive gases. During the baking process, defluorination reactions occur, such as Figure 4C As shown, the lithium carbonate layer 184 and the fluoropolymer layer 194 are transformed into a composite of lithium fluoride (LiF) and lithium carbonate (Li2CO3) embedded in the hybrid coating 164. That is, the lithium fluoride and lithium carbonate form separate domains 196 within the carbonaceous matrix 198 in the hybrid coating 164. The carbonaceous matrix 198 includes one or more of carbon and short-chain hydrocarbons, whose chain length is no greater than the chain length of the deposited polymer, which is generated by the extraction of fluorine atoms and exposure to elevated temperatures. Since lithium carbonate blocks the lithium ions (Li + ) is transferred to the lithium negative electrode 158, so the formation of domain 196 provides a path for lithium ions to be transferred to the lithium negative electrode 158. In an embodiment, the baking temperature is lower than the heat deformation temperature of the separator 160 material (if formed from a thermoplastic polymer) and greater than the vaporization temperature of water, including all values ​​and ranges between the vaporization temperature of water and less than the heat deformation temperature of the separator 160.

[0050] At box 706, the tabs are welded to the positive current collector 152 and the negative current collector 154. At box 708, the baked battery cell 150 is arranged in an inner package or pouch cell case 168, and at box 710, the electrolyte 162 is introduced into the battery cell 150. The electrolyte 162 permeates through the separator 160 and contacts the positive electrode 156 and the negative electrode 158. Then, at box 712, the pouch cell case 168 is sealed and placed in the outer shell 170.

[0051] In embodiments, the contact between lithium fluoride and lithium carbonate domains 196 in the carbonaceous matrix 198 generates space charge, and the ion diffusion in the solid-solid dispersion of lithium fluoride and lithium carbonate is increased, which facilitates charge transfer. In addition, the carbonaceous matrix 198 accommodates the volume change of the negative electrode 158 during the charge and discharge cycle, thereby enhancing the cycle stability. During the cycle process (charge and discharge), the defluorination reaction may continue.

[0052] The negative electrode, battery cell, battery and method of the present invention provide many advantages. These advantages include, for example, the formation of a flexible coating that allows the negative electrode to undergo mechanical deformation and strain during transportation and battery assembly. These advantages also include the protection of lithium from moisture present in the environment during transportation and battery assembly, and the possibility of more relaxed environmental control in the battery manufacturing unit. These advantages also include the prevention of defluorination reactions between lithium and fluoropolymers during transportation and battery assembly due to the presence of a lithium carbonate layer, which acts as a buffer layer. Another advantage includes the ability to trigger defluorination reactions during battery formation. Another advantage includes the ability of the carbonaceous matrix to accommodate volume changes of the negative electrode and the negative electrode during discharge and charge cycles.

[0053] As used herein, the term "controller" and related terms such as microcontroller, control module, module, controller, control unit, processor and similar terms refer to one or more combinations of application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), electronic circuits, central processing units, such as microprocessors, and associated non-transitory memory components in the form of memory and storage devices (read-only, programmable read-only, random access, hard drives, etc.). The controller 132 may also be composed of multiple controllers that are electrically connected to each other. The controller 132 may be interconnected with additional systems and / or controllers of the vehicle 100, thereby allowing the controller 132 to access data such as the speed, acceleration, braking, and steering angle of the vehicle 100.

[0054] The processor can be a custom or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), a secondary processor among multiple processors associated with the controller 132, a semiconductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, a combination thereof, or generally a device for executing instructions.

[0055] The tangible non-transitory memory 134 may include volatile and non-volatile storage devices such as read-only memory (ROM), random access memory (RAM), and save-action memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables when the processor is powered off. The tangible non-transitory memory 134 can be implemented using a plurality of storage devices, such as PROM (programmable read-only memory), EPROM (electrical PROM), EEPROM (electrically erasable PROM), flash memory, or other electrical, magnetic, optical, or combination storage devices capable of storing data, some of which represent various system executable instructions used by the controller 132 to control the vehicle 100.

[0056] The description of the present disclosure is merely exemplary in nature, and variations that do not depart from the gist of the present disclosure are intended to fall within the scope of the present disclosure. These variations should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A method of forming a lithium ion battery, comprising: exposing the first surface of the lithium layer to carbon dioxide gas; forming a lithium carbonate layer on the first surface of the lithium layer; as well as A fluorine-containing polymer layer is deposited on the second surface of the lithium carbonate layer to provide a lithium negative electrode.

2. The method of claim 1, wherein forming the lithium carbonate layer comprises forming the lithium carbonate layer to a thickness of less than 50 nanometers.

3. The method of claim 2, wherein depositing the fluoropolymer layer comprises depositing a plurality of fluoropolymer fragments of a fluoropolymer using a physical deposition process, wherein the plurality of fluoropolymer fragments impinge on the lithium carbonate layer. 4 . The method of claim 3 , wherein depositing the fluoropolymer layer comprises depositing a fluoropolymer layer having a thickness in a range of 5 nanometers to 100 nanometers.

5. The method of claim 4, wherein depositing the fluoropolymer layer comprises depositing the plurality of fluoropolymer segments of at least one of polyvinyl fluoride (PVD), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), and polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene (TFE), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene perfluoromethylvinyl ether (methylfluoroalkoxy, MFA), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), and ethylene chlorotrifluoroethylene (ECTFE). 6 . The method of claim 3 , wherein depositing the fluoropolymer layer using a physical deposition process comprises depositing the fluoropolymer layer by thermally evaporating the fluoropolymer from a fluoropolymer target. 7 . The method of claim 3 , wherein depositing the fluoropolymer layer using a physical deposition process comprises depositing the fluoropolymer layer by sputtering the fluoropolymer from a fluoropolymer target.

8. The method of claim 3, further comprising forming the lithium layer by thermally evaporating lithium and depositing the lithium on a substrate. 9 . The method according to claim 8 , wherein the substrate is a negative electrode current collector.

10. A lithium ion battery for a vehicle, comprising: One or more battery cells, wherein each battery cell comprises a positive electrode disposed on a positive electrode current collector, a negative electrode disposed on a negative electrode current collector, a porous separator between the positive electrode and the negative electrode, and an electrolyte permeating the porous separator, wherein the negative electrode comprises: including a first surface lithium layer, and a hybrid coating disposed on the first surface, wherein the hybrid coating comprises a plurality of lithium fluoride domains and a plurality of lithium carbonate domains within a carbonaceous matrix; A soft-pack battery cell shell, which defines a volume for accommodating the battery cell; a negative electrode tab welded to a portion of the negative electrode current collector extending from the soft-pack battery core case; and A positive electrode tab is welded to a portion of the positive electrode collector extending from the soft-pack battery core case.

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