Battery cell for a vehicle and method for forming a battery cell

Abstract

The present disclosure relates to a battery cell for a vehicle, a battery for a vehicle, and a method for forming a battery cell. The battery cell comprises a cathode comprising lithium iron phosphate and lithium aluminum titanium phosphate, an anode comprising a silicon film, and a separator positioned between the cathode and the anode. The battery cell also comprises a first solid electrolyte layer arranged on the separator and a liquid electrolyte in contact with the cathode, the anode, the first solid electrolyte layer, and the separator. The separator comprises a cathode side facing the cathode and an anode side facing the anode. The first solid electrolyte layer comprises a layer of lithium aluminum titanium phosphate, and the liquid electrolyte comprises a primary lithium ion salt, a solvent, and a diluent.

Description

[0001] The technology of electric and hybrid electric vehicles is enabled by the development and use of rechargeable secondary batteries that supply energy to the vehicle's powertrain. Secondary batteries include lithium-ion batteries, which generally comprise a cathode, an anode, a separator, and an electrolyte. The cathode provides the source of lithium ions and determines the battery's capacity and average voltage. The anode stores and releases lithium ions received from the cathode when energy is needed. The separator prevents the cathode and anode from touching and short-circuiting the battery, and the electrolyte provides a medium between the cathode and anode through which the lithium ions move.

[0002] Some lithium iron phosphate batteries contain a non-flammable liquid electrolyte. These non-flammable liquid electrolytes may include fluorinated compounds or phosphate compounds. Additionally, solvent-based ionic liquids, comprising a coordinating solvent and salts with lithium ion salt concentrations exceeding 2.0 moles per liter in the battery solvent, may be present. Non-flammable electrolytes can be viscous. Viscosity can decrease ionic activity and may affect various aspects of battery performance, including capacity retention.

[0003] DE 10 2022 112 495 B3 describes a battery system comprising a battery cell with an anode comprising a first current collector and an anode layer containing an active anode material arranged on the first collector. The cell includes a cathode with a second current collector and a cathode layer containing an active cathode material arranged on the second collector. The cell contains a solid electrolyte, which is either a reduction-tolerant solid electrolyte in contact with the anode or an oxidation-tolerant solid electrolyte in contact with the cathode. The reduction-tolerant solid electrolyte is present in an amount of 0.1 to 5 parts by weight, based on 100 parts by weight of the anode layer. The oxidation-tolerant solid electrolyte is present in an amount of 1 part by weight to 10 parts by weight, based on 100 parts by weight of the cathode layer.

[0004] DE 10 2020 201 402 A1 describes ionically conductive core / shell particles. The core particles contain reduced electrolyte materials based on titanium or zirconium, and the shells are electronically insulating. The core / shell particles can be combined with organic electrolytes to form organic-ceramic composite electrolytes that can be used in lithium battery cells.

[0005] While current electrolyte chemistries and other battery materials achieve their intended purpose, the object of the invention is therefore to provide new and improved electrolyte chemistries that offer a relatively improved capacity retention.

[0006] The problem is solved using a battery cell for a vehicle. The battery cell comprises a cathode consisting of lithium iron phosphate and lithium aluminum titanium phosphate, an anode consisting of a silicon film, and a separator positioned between the cathode and the anode. The battery cell also includes a first solid electrolyte layer arranged on the separator and a liquid electrolyte that comes into contact with the cathode, the anode, the first solid electrolyte layer, and the separator. The separator has a cathode side facing the cathode and an anode side facing the anode. The first solid electrolyte layer consists of a layer of lithium aluminum titanium phosphate, and the liquid electrolyte consists of a primary lithium ion salt, a solvent, and a diluent. The diluent consists of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0007] According to one embodiment, the cathode comprises lithium iron phosphate, present in the range of 80 wt.% to 95 wt.%, lithium aluminum titanium phosphate, present in the range of 1 wt.% to 10 wt.%, a carbon additive, present in the range of 1 wt.% to 5 wt.%, and a polyvinylidene fluoride binder, present in the range of 1 wt.% to 5 wt.%.

[0008] According to a further embodiment, the carbon additive comprises at least one of conductive carbon black powder, conductive synthetic graphite black, graphite, graphite nanoplates, single-walled carbon nanotubes, multi-walled carbon nanotubes and carbon nanofibers.

[0009] According to another embodiment, the cathode is present at a capacitance load in the range of 3.0 milliampere-hours per square centimeter to 4.0 milliampere-hours per square centimeter.

[0010] According to a further embodiment, the cathode comprises a plurality of cavities and has a cavity volume in the range of 25 vol% to 35 vol% of the total volume defined by the cathode. The liquid electrolyte is present in at least some of the plurality of cavities.

[0011] According to another embodiment, the first solid electrolyte layer is arranged on the cathode side of the separator.

[0012] According to a further embodiment, a second solid electrolyte layer is arranged on the anode side of the separator, wherein the second solid electrolyte layer comprises lithium aluminum titanium phosphate.

[0013] According to another embodiment, the primary lithium ion salt comprises at least one of lithium bis(trifluoromethane)sulfonimide, LiTFSI, lithium bis(fluorosulfonyl)imide, LiFSI, lithium bis(pentafluoroethanesulfonyl)imide, LiBETI, and lithium trifluoromethanesulfonate, LiTfo.

[0014] According to another embodiment, the molar ratio of primary lithium ion salt and solvent is 1 to 1.

[0015] According to another embodiment, the diluent is present in the range of 30 vol.% to 80 vol.% of the total volume of the diluent and solvent, and the solvent is present in the range of 20 vol.% to 70 vol.% of the total volume of the diluent and solvent, wherein the total volume percentage of the diluent and solvent is 100 percent.

[0016] According to another embodiment, the anode is present at a capacitance load in the range of 4 milliampere hours per square centimeter to 12 milliampere hours per square centimeter.

[0017] According to another embodiment, the silicon film is pure silicon, has a thickness in the range of 4 micrometers to 30 micrometers and a porosity in the range of 1 percent to 20 percent.

[0018] According to another embodiment, the separator is made of a polyolefin and has a porosity of 35 vol.% to 55 vol.% of the total volume defined by the separator.

[0019] According to a further embodiment, the cathode is arranged on a cathode current collector and the cathode current collector comprises at least one of aluminium-copper clad aluminium and stainless steel and the anode is arranged on an anode current collector and the anode current collector comprises at least one of copper, nickel, stainless steel, iron, titanium and alloys thereof.

[0020] In one application, a battery is provided for a vehicle. The battery comprises a plurality of battery cells according to the invention and its embodiments.

[0021] At least one of the numerous battery cells exhibits a negative to positive ratio in the range of 1:1 to 2.5:1.

[0022] The invention also includes a method for forming an electrolyte. The method comprises applying a cathode, comprising lithium iron phosphate and lithium aluminum titanium phosphate, to a cathode current collector. The method also includes applying an anode, comprising a silicon film, to an anode current collector. Additionally, the method comprises applying a first solid electrolyte layer to a separator, wherein the separator comprises a cathode side facing the cathode and an anode side facing the anode, and the first solid electrolyte layer comprises lithium aluminum titanium phosphate. The method further comprises positioning the separator between the cathode and the anode, wherein the first solid electrolyte layer is positioned between the cathode and the separator.The process further comprises assembling the cathode, anode, and separator into a battery cell cover and adding a liquid electrolyte to the battery cell cover, the liquid electrolyte being in contact with the cathode, anode, first solid electrolyte layer, and separator. The liquid electrolyte comprises a primary lithium ion salt, a solvent, and a diluent. The battery cell comprises the cathode, which includes lithium iron phosphate and lithium aluminum titanium phosphate; the anode, which includes the silicon film; and the separator, which is positioned between the cathode and the anode. The separator comprises the cathode side, which faces the cathode, and the anode side, which faces the anode. The battery cell includes the first solid electrolyte layer, which is arranged on the separator. The first solid electrolyte layer comprises a layer of lithium aluminum titanium phosphate.The battery cell comprises the liquid electrolyte, which contacts the cathode, the anode, the first solid electrolyte layer, and the separator. The liquid electrolyte includes the primary lithium ion salt, the solvent, and the diluent. The diluent comprises 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0023] According to one embodiment, the application of the anode includes the deposition of the silicon film by physical vapor deposition at a load capacity in the range of 4 milliampere hours per square centimeter to 12 milliampere hours per square centimeter.

[0024] The drawings described herein serve illustrative purposes. Fig. Figure 1 illustrates a vehicle and a powertrain that includes a secondary battery. Fig. Figure 2A illustrates an exploded view of the layers of a battery cell. Fig. 2B illustrates a pouch or prismatic battery cell. Fig. Figure 2C illustrates a cylindrical battery cell. Fig. 2D illustrates a button battery cell. Fig. Figure 3 illustrates a close-up of a cross-section of a battery cell with the cover removed. Fig. Figure 4 illustrates a method for forming a battery cell. Fig. Figure 5 illustrates a voltage, measured in volts (y-axis), as a function of a capacity retention percentage (x-axis) for a lithium iron phosphate battery cell comprising lithium aluminum titanium phosphate at 25 degrees Celsius, a lithium iron phosphate battery cell comprising lithium aluminum titanium phosphate at -18 degrees Celsius, and a lithium iron phosphate output cell at -18 degrees Celsius. Fig. Figure 6 illustrates a capacity retention percentage (y-axis) as a function of the number of cycles (x-axis) for a lithium iron phosphate battery cell comprising lithium aluminum titanium phosphate at 25 degrees Celsius and a lithium iron phosphate output cell at 25 degrees Celsius, where the first three cycles (cycles 1 to 3) are performed at a charge and discharge rate of 0.1C, the next three cycles (cycles 4 to 6) are performed at a charge and discharge rate of 0.333C, the next three cycles (cycles 7 to 9) are performed at a charge and discharge rate of 0.5C, the next three cycles (cycles 10 to 12) are performed at a charge and discharge rate of 1C, and the last three cycles (cycles 13 to 15) are performed at a charge and discharge rate of 0.333C will be carried out. Fig. Figure 7 illustrates a capacity retention percentage (y-axis) as a function of the number of cycles (x-axis) for a lithium iron phosphate battery cell comprising lithium aluminum titanium phosphate at 25 degrees Celsius and a lithium iron phosphate output cell at 25 degrees Celsius, at a charge and discharge rate of 0.333C. Fig. Figure 8 illustrates the capacity, measured in milliampere-hours per gram (y-axis) as a function of the number of cycles for a half-button cell comprising a silicon particle anode and a silicon film anode, measured at 25 degrees Celsius and at a charge and discharge rate of C / 3 with a limiting capacity of 1200 mAh / g. Fig. Figure 9 illustrates the voltage, measured in volts (y-axis), as a function of the capacitance, measured in milliampere-hours per gram (x-axis), for the first formation cycle of pouch cells comprising lithium aluminum titanium phosphate deposited on the cathode side of the separator, the anode side of the separator, and both the cathode and anode sides of the separator, measured at a temperature of 25 degrees Celsius. Fig. Figure 10 illustrates the capacity retention percentage (y-axis) as a function of the number of cycles for pouch cells comprising lithium aluminum titanium phosphate deposited on the cathode side of the separator, the anode side of the separator, and both the cathode and anode sides of the separator, measured at a temperature of 25 degrees Celsius and at a charge and discharge rate of C / 3. Fig. Figure 11 illustrates the capacity retention percentage (y-axis) as a function of the number of cycles for a pouch cell comprising a lithium aluminum titanium phosphate deposited on the cathode side of the separator and contained in the cathode, measured at a temperature of 25 degrees Celsius and at a charge and discharge rate of 0.1C.

[0025] The following description is merely exemplary. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding introduction, summary, or subsequent detailed description. It is understood that in the drawings, identical reference symbols denote identical or corresponding parts and features.

[0026] Several examples of the description, illustrated in the accompanying drawings, are now referred to in detail. Wherever possible, the same or similar reference symbols are used in the drawings and the description to refer to identical or similar parts or steps. The drawings are simplified and not to scale.

[0027] This description relates to a vehicle battery cell comprising the electrolyte, a vehicle battery, and a method for forming the battery cell. The battery cell can be provided as one of several battery cell platforms, including prismatic, pouch, cylindrical, or button-shaped battery cells. The battery cell and batteries can be used in batteries for electric or hybrid electric vehicles. The battery cell comprises lithium aluminum titanium phosphate in the cathode and deposited on the separator layer facing the cathode.

[0028] As used herein, the term "vehicle" is not limited to automobiles. Although the technology presented here is mainly described in connection with electric and hybrid electric vehicles, the technology is not limited to electric and hybrid electric vehicles.The concepts can be used in a wide variety of applications, such as in conjunction with components used in motorcycles, mopeds, locomotives, aircraft, watercraft and other vehicles, as well as in other applications that use batteries, such as consumer electronics, power banks for buildings and portable power plants used to supply power to remote construction sites, emergency power supplies and permanent power plants connected to buildings and equipment, all of which can be powered, for example, by solar or wind-powered generator systems, power grids and fuel-based power generators, such as gasoline, propane, kerosene or diesel generators and Sterling engines.

[0029] Fig. Figure 1 illustrates a vehicle 100 comprising a drive system 120. The drive system 120 generally includes an electric motor 124 and a secondary battery 126 for supplying power to the electric motor 124. Furthermore, in many embodiments, the drive system 120 includes an inverter 128 for converting power from direct current (DC), as supplied by the battery 126, to alternating current (AC), as used by the electric motor 124. The inverter 128 may be incorporated into a power electronics module 130, which includes, for example, transistors and diodes for switching the power from DC to AC and vice versa.

[0030] A controller 132 is connected to the inverter 128 and is programmed to control and manage the operation of the electric motor 124 and the associated hardware, including the inverter 128. The electric motor 124 is connected to a gearbox (drive unit) 136 and a drive line 138, which transmits mechanical power and rotation to the wheels 140 of the vehicle 100. The controller 132 includes one or more processors and tangible, non-volatile memory 134. A combustion engine may also be included in the drive system of hybrid electric vehicles.

[0031] Referring again to the electric motor 124, the electric motor 124, which is powered by the battery 126, comprises a stator 142 and a rotor 144 located inside the stator 142. The stator 142 is the stationary part of the electric motor 124. The stator 142 provides a rotating magnetic field with which the stationary magnetic field of the rotor 144 attempts to align, causing the rotor 144 to rotate, which can be referred to as the "motor operation" mode. In other applications, the rotating field (as caused by physical rotation) of the rotor 144 generates an electric current in the stator 142—this operating mode is referred to as "generation," and the electric motor 124 used in this way is called a generator. In traction vehicle applications, the motor operation provides motion to the vehicle 100.The generation mode takes some of the energy recovered from braking when the vehicle is stationary and stores it in the vehicle battery 126.

[0032] It will be directed to the Fig. 2A, Fig. 2B, Fig. 2C and Fig. 2D reference is made, which illustrates an example of a secondary battery 126 for supplying an electric vehicle 100 with power, such as the one in Fig. 1 illustrated electric vehicle 100. As noted above, secondary batteries 126 are understood to be rechargeable batteries that can be discharged when a load is applied and recharged when an external power source is applied. Referring to the Fig. 2A, Fig. 2B, Fig. 2C and Fig. Figure 2D illustrates that a battery 126 is connected to a load 148, such as the electric motor 124. Other loads 148, however, include various systems in the vehicle 100, such as climate control systems and infotainment systems. The battery 126 comprises one or more battery cells 150 that are electrically connected to each other. Each battery 126 can comprise from one (1) battery cell to 20,000 battery cells, including all values ​​and ranges therein. The battery cells 150 can be, for example, pouch-shaped, prismatic, cylindrical, or button-shaped battery cells, which are discussed further below. With reference to the Fig. When a load 148 is applied to the battery 126, Li+ ions move from the anode 158 through the separator 160 via the electrolyte 162 to the cathode 156. Equivalent electrons e- move through the circuit 146 from the cathode 156 to the anode 158, thus providing voltage to the load 148. During charging, when an external voltage is applied, Li+ ions move from the cathode 156 through the electrolyte 162 via the separator 160 to the anode 158 and can be stored in the anode 158.

[0033] Each battery cell contains 150 cells, such as those in the Fig. 2B, Fig. 2C and Fig. The 2D illustrated battery cell generally comprises a cathode current collector 152, a cathode 156 arranged on the cathode current collector 152, an anode current collector 154, an anode 158 arranged on the anode current collector 154, a separator 160 positioned between the cathode 156 and the anode 158, and an electrolyte 162. While the illustrated battery cells 150 comprise an anode 158 (and an anode current collector 154) and a cathode 156 (and a cathode current collector 152), the battery cell 150 can alternatively comprise two or more cathodes 156 (and one or more cathode current collectors 152) and one or more anodes 158 (and one or more anode current collectors 154). In further alternative embodiments, the battery cell 150 can comprise one or more cathodes 156 (and one or more cathode current collectors 152) and two or more anodes 158 (and two or more anode current collectors 154).In each of the above constructions, one or more separators 160 are nested between the cathodes 156 and the anodes 158 to prevent the cathodes 156 and the anodes 158 from touching each other.

[0034] In embodiments, the battery cell 150 is of Fig. 2B is configured as a pouch-like battery cell or in a prismatic battery cell. In each configuration, which includes multiple cathodes 156 and multiple anodes 158, separators 160 are provided between the cathodes 156 and the anodes 158. In embodiments, a ribbon-shaped separator 160 can be z-folded around each cathode 156 (and each cathode current collector 152) and around each anode 158 (and each anode current collector 154). In a pouch-like cell, tabs 164 are welded to the cathode current collectors 152 and the anode current collectors 154. Alternatively, the tabs 164 are integrally formed with the cathode current collectors 152 and the anode current collectors 154 by cutting the tabs 164 together with the cathode current collectors 152 and the anode current collectors 154 from larger sheet material. Additionally, the cover 166 is in the form of a flexible foil bag made of aluminum or another material.Prismatic cells, on the other hand, include terminals to which the cathode current collectors 152 and the anode current collectors 154 are connected, and the cover 166 is formed from a relatively rigid housing, typically in the form of a cuboid. The tabs 164, or terminals, which are connected to the cathode current collectors 152 of several battery cells 150, are interconnected, for example, by a busbar 168 (see ). Fig. 2A) or another electrical connection, and the tabs 164 or terminals connected to the anode current collectors 154 of several battery cells 150 are connected to each other, such as by a busbar 169 (see Fig. 2A) or another electrical connection.

[0035] Alternatively, the battery cell 150 from Fig. 2C is configured as a cylindrical battery cell 150. In this construction, the cathode current collector 152, the anode current collector 154, the cathode 156, the anode 158, and one or more separators 160 are in the form of long strips rolled into a cylinder or a jelly roll. Like the prismatic cell, the cover 166 is formed from a relatively rigid housing made of aluminum or another material. Tabs 164 are welded to the cathode current collector 152 and the anode current collector 154. The tabs 164, which are connected to the cathode current collectors 152 of several battery cells 150, are interconnected, for example, by a busbar 168 (see Fig. 2A) or another electrical connection, and the tabs 164 or terminals connected to the anode current collectors 154 of several battery cells 150 are connected to each other, such as by a busbar 169 (see Fig. 2A) or another electrical connection.

[0036] In alternative embodiments, the battery cell 150 is packaged in a button cell, as in Fig. Illustrated in 2D. In this construction, the cathode current collector 152, the anode current collector 154, the cathode 156, the anode 158, and one or more separators 160 in the form of discs are sandwiched within the button-like packaging that forms the cover 166, which includes a cap 170 and a can 172. A spring washer 174 may be located between the cathode current collector 152 and the cap 170. Before the cap 170 is attached to the can 172, the electrolyte 162 is added to the battery cell 150. The cap includes terminals 164 for the anode 158 and the cathode 156.

[0037] In the various types of battery cells 150 mentioned above, the cathode current collector 152 and the anode current collector 154 are formed from conductive materials. In embodiments, the cathode current collector 152 comprises aluminum. Alternatively or additionally, the cathode current collector 152 may comprise copper-clad aluminum and stainless steel. In embodiments, the anode current collector 154 comprises at least copper and alloys thereof. Alternatively or additionally, the anode current collector 154 may comprise nickel, stainless steel, iron, titanium, and alloys thereof. The current collectors 152 and 154 are illustrated as being in the form of a foil; however, it is understood that other forms, such as a mesh, may be shown. In embodiments, a foil cathode current collector 152 and a foil anode current collector 154 are impermeable to gas.The cathode current collector 152 has a thickness in the range of 5 micrometers to 50 micrometers, including all values ​​and ranges within this range, such as 5 micrometers to 25 micrometers. The anode current collector 154 has a thickness in the range of 4 micrometers to 30 micrometers, including all values ​​and ranges within this range, such as 13 micrometers to 15 micrometers. Additionally, the anode current collector 154 can have either a smooth or a rough surface, that is, including surface features from 25 nanometers to 5 micrometers.

[0038] The cathode 156 includes a source of lithium ions (Li + ) and can be subjected to reversible insertion or deposition of lithium ions, which determines, for example, the capacity and average voltage of a battery. It is applied to Fig. Reference is made to Figure 3, which illustrates a close-up of an embodiment of a battery cell 150 without the cover. The cathode 156 is formed from cathode material comprising a cathode-active material and lithium aluminum titanium phosphate.

[0039] The cathode-active material 302 is lithium iron phosphate, which has the formula LiFePO4. In embodiments, the lithium iron phosphate has a particle size D50 in the range of 0.5 micrometers to 15 micrometers, including all values ​​and ranges therein, such as 1.0 micrometer to 1.5 micrometers. The lithium iron phosphate can also have a surface area, as measured by Brunauer-Emmett-Teller (BET) surface analysis, in the range of 3 square meters per gram to 20 square meters per gram, including all values ​​and ranges therein, such as 11 square meters per gram to 12 square meters per gram. In embodiments, the particles of the cathode-active material are coated with carbon. The carbon can be present in the range of 0.5 wt% to 3 wt% of the total weight of the cathode 156, with the total weight percentage of the cathode being 100 wt%.The cathode-active material has a specific capacity of more than 145 milliampere-hours per gram at a charging rate of 0.1 C (10 hours), measured at 25 degrees Celsius at 2.2 to 3.65 volts in a half-button cell. The cathode-active material is present in the range of 80 wt% to 95 wt% of the total weight of the cathode material, including all values ​​and ranges within this range, such as 87 wt% to 88 wt%.

[0040] Lithium aluminum titanium phosphate 304 has the formula Li 1,3 Al 0,3 Ti 1,7(PO4)3. The lithium aluminum titanium phosphate is present in the range of 1 wt.% to 10 wt.% of the total weight of the cathode material, including all values ​​and ranges therein, such as 1.5 wt.% to 2.5 wt.%. In embodiments, the lithium aluminum titanium phosphate comprises particles with a particle size D50 in the range of 50 nanometers to 500 nanometers, including all values ​​and ranges therein, such as 100 nanometers to 200 nanometers.

[0041] In embodiments, the cathode material also comprises a carbon additive 306. The carbon additive is present in the range of 1 wt.% to 5 wt.% of the total weight of the cathode material, including all values ​​and ranges therein, such as from 3.5 wt.% to 4.0 wt.%. The carbon additive comprises at least one of conductive carbon black powder, conductive synthetic graphite carbon black, graphite, graphite nanoplate, single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanofibers. In embodiments, the carbon additive comprises more than one carbon additive. In further embodiments, the carbon additive comprises conductive carbon black powder and conductive synthetic graphite carbon black.

[0042] In further embodiments, a binder 308 is also present in the cathode material. The binder is present in the range of 1 wt.% to 5 wt.% of the total weight of the cathode material, including all values ​​and ranges therein, such as 3 wt.% to 4 wt.%. The binder is selected from polyvinylidene fluoride and styrene-butadiene rubber. In embodiments, the binder is polyvinylidene fluoride. The total wt. percentage of the various components of the cathode material is 100 wt.%.

[0043] Prior to application, the cathode material, comprising the cathode-active material and the lithium aluminum titanium phosphate, as well as the additives and binder, if present, are combined with a dispersion medium to form a mixture. In embodiments, the dispersion medium is N-methylpyrrolidone. The viscosity of the mixture, measured at room temperature and at a shear rate of 10 s⁻¹, is... -1The pulse width is in the range of 5,000 millipascal-seconds to 8,000 millipascal-seconds, including all values ​​and ranges therein. The mixture is applied to the cathode current collector 152 by coating, such as slip casting. The coating density is in the range of 2.0 grams per cubic centimeter to 2.6 grams per cubic centimeter, including all values ​​and ranges therein, such as 2.4 grams per cubic centimeter. The porosity of the cathode 156 is in the range of 25 vol% to 35 vol%, including all values ​​and ranges therein, such as 30 vol%, where the percentage porosity is understood as the percentage of the open volume or void volume in the cathode. The voids form spaces 310 between the particles that make up the cathode 156, and the liquid electrolyte flows into at least a portion of the voids.The moisture content of the cathode 156 is less than 600 parts per million, for example, in the range of 1 part per million to 600 parts per million, including all values ​​and increments therein. In embodiments, the cathode material is deposited on the cathode current collector 152 at a capacitance load or density on one side in the range of 3.0 milliampere-hours per square centimeter to 4.0 milliampere-hours per square centimeter, including all values ​​and increments therein, such as 3.5 milliampere-hours per square centimeter, measured at 25 degrees Celsius at a charging rate of 0.1 C (10 hours). The electrical conductivity of the cathode is in the range of less than 2 ohms per centimeter in embodiments.

[0044] The cathode electrode 151, which includes both the cathode current collector 152 and the cathode 156, has a thickness in the range of 50 micrometers to 250 micrometers, including all values ​​and ranges therein, when the cathode material is formed on one side of the cathode current collector 152. When the cathode material is formed on both sides of the cathode current collector 152, the cathode electrode has a thickness in the range of 100 micrometers to 500 micrometers, including all values ​​and ranges therein, for a double-sided cathode electrode, such as in the range of 150 micrometers to 400 micrometers.

[0045] The anode 158 comprises materials that can be subjected to reversible insertion or intercalation of lithium ions at a lower electrochemical potential than the cathode material 156, such that an electrochemical potential difference exists between the anode 158 and the cathode 156. The anode material 312 comprises a silicon film. In embodiments, the silicon is pure silicon, that is, 99.9 percent or more, and comprises no binder or carbon. In further embodiments, the anode material is a columnar silicon film, as shown in Fig. Figure 3 illustrates this. In embodiments, the anode material has a porosity, i.e., a void volume, in the range of 0.1 vol.% to 20 vol.%, including all values ​​and ranges therein. The void volume forms spaces 314 between the silicon structures that constitute the silicon film.

[0046] The anode material is applied at a capacitance load ranging from 4 milliampere-hours per square centimeter to 12 milliampere-hours per square centimeter, including all values ​​and ranges within this range. In embodiments, the capacitance load of the anode material is greater than that of the cathode material. The anode material exhibits a specific capacitance of 2500 milliampere-hours per gram to 3500 milliampere-hours per gram, measured at 25 degrees Celsius and a charging rate of 0.1 C (10 hours). The first cycle efficiency of anode 158 is greater than 90 percent at 0 to 1.5 volts and, in embodiments, greater than 93 percent, such as approximately 93.4 percent.

[0047] In embodiments, the anode 158 has a thickness in the range of 4 micrometers to 30 micrometers, including all values ​​and ranges therein. In embodiments, the anode 158 is applied to the anode current collector 154, with a coating being formed on the anode current collector 154 using a vapor deposition process, such as physical vapor deposition. The combined anode 158 and the combined anode current collector 154 provide an anode electrode, which is referred to herein.

[0048] The separator 160 is a porous material formed from an electrically insulating material that prevents the cathode 156 and the anode 158 from touching each other and potentially shortening the circuit. The separator 160 is sandwiched between the cathode 156 and the anode 158 or at least partially enclosed, thereby allowing the passage of lithium ions and the electrolyte 162 through the pores of the separator 160. The separator 160 comprises a polyolefin material, and in embodiments, the polyolefin comprises polyethylene and / or polypropylene. Alternatively or additionally, the separator 160 comprises polyamide, polytetrafluoroethylene, polyvinylidene fluoride, and / or polyvinyl chloride. Additionally, the separator 160 can be filled, that is, it may comprise one or more fillers dispersed therein, the one or more fillers comprising materials such as glass fibers, nonwovens, or woven fabrics.The separator 160 can take the form of a film or a mesh, such as a woven mesh or a slit film. In embodiments, the separator 160 has a thickness in the range of 6 micrometers to 12 micrometers, including all values ​​and ranges therein, such as 9 micrometers. The separator 160 can also have a porosity, that is, a void volume, of 35 vol% to 55 vol% of the total volume defined by the separator 160, including all values ​​and ranges therein, such as 45 percent.

[0049] The electrolyte 162 provides a medium between the cathode 156 and the anode 158 through which lithium ions move. The electrolyte 162 is a semi-solid electrolyte comprising both solid and liquid components. The liquid component of the electrolyte permeates the separator 160, comes into contact with the surfaces of the cathode 156 and the anode 158, and flows into any spaces that may exist between the particles forming the cathode 156 and the anode 158.

[0050] The solid electrolyte is provided as a layer between the cathode 156 and the separator 160. The solid electrolyte layer 318 comprises a lithium aluminum titanium phosphate. The lithium aluminum titanium phosphate has the formula Li 1,3 Al 0,3 Ti 1,7(PO4)3. In embodiments, the separator 160 provides a support layer for the solid electrolyte component, which is formed as a coating on the cathode-facing surface 320 of the separator 160. The layer thickness is in the range of 2 micrometers to 4 micrometers, including all values ​​and ranges therein. The porosity of the coating, that is, the void volume defined by the coating, is in the range of 20 vol% to 40 vol%, including all values ​​and ranges therein, such as 30 vol%. The void volume forms spaces 326 between the lithium aluminum titanium phosphate particles. In additional or alternative embodiments, the solid electrolyte layer 318 is applied as a coating on the anode-facing surface 324 of the support layer 316. This means that the solid electrolyte layer 318 can be present on the anode side or on both the anode and cathode sides of the separator 160.The solid electrolyte layer 318 is applied to the separator 160 by a coating process, such as a slurry coating process or a Mayer-Stab coating process.

[0051] The liquid component of electrolyte 162 comprises a primary lithium ion salt, a solvent, and a diluent. The primary lithium ion salt comprises at least one of lithium bis(trifluoromethane)sulfonimide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), and lithium trifluoromethanesulfonate (LiTfo). In embodiments, the primary lithium ion salt is lithium bis(trifluoromethane)sulfonimide (LiTFSI). In embodiments, the molar ratio of the primary lithium ion salt to the solvent is 1:1. The primary lithium ion salt is present in the solvent to form a solvatic ionic liquid with a concentration (moles of salt per liter of solvent) of 2.5 mol / L to 4.0 M, including all values ​​and ranges therein, such as 3.6 M. The solvent comprises at least one of tetraethylene glycol dimethyl ether (G4) and triethylene glycol dimethyl ether (G3).In embodiments, the solvent is tetraethylene glycol dimethyl ether (G4). The diluent comprises a hydrofluoroether. In embodiments, the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. The diluent is present in a volume ratio of diluent to solvent of 2:1 to 6:1. Thus, the solvent is present in the range of 14 vol% to 33 vol% of the total volume of solvent and diluent, including all values ​​and ranges therein, and the diluent is present in the range of 77 vol% to 86 vol% of solvent and diluent, including all values ​​and ranges therein. The total volume percentage of solvent and diluent is 100 percent.

[0052] After adding the diluent to the solvent-based ionic liquid, the molarity is in the range of 0.6 M to 1.2 M. The liquid component of electrolyte 162 is formed by mixing the primary lithium ion salt, a solvent, and a diluent. The liquid component of electrolyte 162 can then be added to a battery cell comprising one of the battery cells 150, which are in Fig. Figures 2B to 2D illustrate the process once the remaining components of battery cell 150 are available. The negative-to-positive ratio, that is, the ratio of anode capacity to cathode capacity, in the battery cell ranges from 1:1 to 2.5:1, including all values ​​and ranges within this spectrum. Additionally, the battery cells exhibit a capacity retention rate of at least 98 percent after 100 cycles.

[0053] Fig. Figure 4 illustrates an embodiment of a method 400 for forming a battery cell 150 comprising the semi-solid electrolyte 162. In block 402, the cathode current collector 152 with the cathode 156, the anode current collector 154 with the anode 158, and the separator 160 are assembled in a battery cell cover 166, 170, 172. In embodiments, the cathode 156 is deposited on the cathode current collector 152 in front of the battery cell assembly 150, the anode 158 is deposited on the anode current collector 154 in front of the battery cell assembly 150, and the solid electrolyte layer 318 is applied to the separator 160. In block 404, the liquid component of the electrolyte 162 is added to the battery cell 150. In block 406, the battery cell 150 is sealed. In further embodiments, the battery cell 150 is coupled to a circuit in block 408 and undergoes a formation process when current is first applied to the battery cell 150.Subsequent charge and discharge cycles can then be performed for up to 5 cycles. Battery formation takes place at temperatures of 25 degrees Celsius or higher, such as in the range of 25 to 50 degrees Celsius or 45 to 80 degrees Celsius, and with a charge and discharge rate of 3 to 10 hours per charge and 3 to 10 hours per discharge, with the charge and discharge rates often being equal. During battery formation, a solid electrolyte interface forms on the anode. The solid electrolyte interface comprises various phases, such as lithium fluoride (LiF), lithium oxide (Li₂O), and lithium carbonate (Li₂CO₃). Additionally, various structural changes can occur in the cathode and anode materials, and in some embodiments, the cathode and anode current collectors corrode or detach. In block 410, the battery cells 150 are assembled to form a battery 126.It is understood that in alternative embodiments the battery cells 150 are assembled before being formed into a battery. Examples

[0054] The following examples are not intended to limit the scope of the description, but are provided here for illustrative purposes.

[0055] Coin cells were formed, each comprising a lithium iron phosphate cathode. Cell A contained a cathode consisting of 92.8 wt% lithium iron phosphate, 1.85 wt% conductive carbon black (SUPER P), 1.85 wt% conductive synthetic graphite carbon black (KS), and 3.5 wt% polyvinylidene fluoride without lithium aluminum titanium phosphate (LATP) particles. Cells B and C contained lithium iron phosphate at 87.8 wt%, 1.85 wt% conductive carbon black (SUPER P), 1.85 wt% conductive synthetic graphite carbon black (KS), 3.5 wt% polyvinylidene fluoride, and 5 wt% LATP. The coin cells, cells A, B, and C, also included a separator and a silicon film anode deposited at a capacitance load of 8 milliampere-hours per square centimeter.The liquid component of the electrolyte contained lithium bis(trifluoromethane)sulfonimide present at a concentration of 1 M, tetraethylene glycol dimethyl ether (G4) present at 20% by volume of the total volume of the solvent and diluent, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether present at 80% by volume of the total volume of the solvent and diluent.

[0056] Cells A and B were charged to a capacity of over 3 volts at 25 degrees Celsius and then discharged at a rate of 0.1 C (that is, for 10 hours) at a temperature of -18 degrees Celsius. Fig. Figure 5 illustrates the voltage, measured in volts (y-axis), as a function of the capacity retention percentage (x-axis) for the lithium iron phosphate battery cell comprising a lithium iron phosphate initial cell at -18 degrees Celsius (Cell A), where the lithium iron phosphate battery cell includes lithium aluminum titanium phosphate at a temperature of -18 degrees Celsius in the cathode and as a solid component of the electrolyte (Cell B), and the lithium iron phosphate battery cell includes lithium aluminum titanium phosphate in the cathode and as a solid component of the electrolyte at a temperature of 25 degrees Celsius (Cell C). Coin cell A exhibited a relatively low percentage of capacity retention. Coin cell B, which included LATP, exhibited a relatively higher percentage of capacity retention. Cell C was also charged and discharged at a rate of 0.1 C (i.e., for 10 hours) at a temperature of 25 degrees Celsius.The capacity was set to 100% for comparison with cell A and cell B.

[0057] Additional samples from cells A and B were then cycled, i.e., charged and discharged, at various charge and discharge rates at 25 degrees Celsius. The first three cycles (cycles 1 to 3) were performed at a charge and discharge rate of 0.1C (10 hours), the next three cycles (cycles 4 to 6) at a charge and discharge rate of 0.333C (3 hours), the next three cycles (cycles 7 to 9) at a charge and discharge rate of 0.5C (2 hours), the next three cycles (cycles 10 to 12) at a charge and discharge rate of 1C (1 hour), and the last three cycles (cycles 13 to 15) at a charge and discharge rate of 0.333C (3 hours). Fig. Figure 6 illustrates the charge retention percentage (y-axis) over the 15 cycles (x-axis). At the lower charging rate of 0.1C, the battery cells exhibited approximately the same capacity retention percentage at nearly 100%. As the charging rates increased, the difference in capacity retention percentages also increased, with cell B, which includes the LATP, exhibiting higher capacity retention percentages.

[0058] Additional samples from cells A and B were then cycled, i.e., charged and discharged, repeatedly at a charge and discharge rate of 0.333C (3 hours) at 25 degrees Celsius. Fig. Figure 7 illustrates the percentage of capacity retention (y-axis) over 100 charge and discharge cycles (cycle number illustrated on the x-axis). As illustrated, cell B had a higher percentage of capacity retention at 90.1 percent than cell A at 79.6 percent over 100 cycles.

[0059] Half-button cells were cycled, comprising silicon particles deposited at a capacity load of 5 milliampere-hours per square centimeter (cell D) and silicon film deposited at a capacity load of 5 milliampere-hours per square centimeter (cell E). The coin cells contained a silicon anode, a polyolefin separator, and a lithium metal cathode. The electrolyte was lithium hexafluorophosphate present at a concentration of 1 M in a solvent consisting of ethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and fluoroethyl carbonate.The ethyl carbonate was present at 30 percent of the total solvent volume, the dimethyl carbonate was present at 30 percent of the total solvent volume, the ethyl methyl carbonate was present at 30 percent of the total solvent volume, and the fluoroethyl carbonate was present at 10 percent of the total solvent volume, with the total solvent volume percentage being 100 percent. The half-button cells were cycled at least 90 times at a charge / discharge rate of 0.333C (3 hours). As in . Fig. Figure 8, which illustrates the capacity in milliampere-hours per gram (y-axis) at a temperature of 25 degrees Celsius versus the number of charge / discharge cycles (x-axis), shows that cell D, which comprises the silicon particles, exhibited a decreased capacity as the number of charge cycles increased. Cell E, which comprises the silicon film, exhibited a relatively stable capacity up to 90 cycles.

[0060] Tests were conducted using pouch-type battery cells to determine which separator surface—the cathode-facing surface (cell F), the anode-facing surface (cell G), or both surfaces (cell H)—exhibited better capacity retention when lithium aluminum titanium phosphate was deposited as a solid component of the electrolyte. The cathodes contained lithium iron phosphate at 87.8 wt%, 1.85 wt% conductive carbon black (SUPER P), 1.85 wt% conductive synthetic graphite carbon black (KS), 3.5 wt% polyvinylidene fluoride, and 5 wt% LATP. The cathodes were deposited at a capacity loading of 3.5 milliampere-hours per square centimeter. The anodes contained silicon film deposited at a capacity loading of 8 milliampere-hours per square centimeter. The cathode current collector contained aluminum foil and the anode current collector contained copper foil.The liquid component of the electrolyte contained lithium bis(trifluoromethane)sulfonimide present at a concentration of 1 M, tetraethylene glycol dimethyl ether (G4) present at 20% by volume of the total volume of the solvent and diluent, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether present at 80% by volume of the total volume of the solvent and diluent.

[0061] Fig. Figure 9 illustrates the effect of capacity, measured in milliampere-hours (x-axis), as a function of voltage, measured in volts (y-axis), during charging and discharging. The battery was charged and discharged at a rate of 0.05C (or 2 hours). Cell F had the highest capacity, cell G had the lowest capacity, and cell H had a capacity that decreased between that of cell F and cell G with decreasing voltage.

[0062] Fig. Figure 10 illustrates the percentage of capacity retention (y-axis) over 200 cycles (number of cycles illustrated on the x-axis) for three additional cells of cell F, cell G, and cell H, tested at a charge and discharge rate of C / 3 (3 hours) at 25 degrees Celsius. Cell A exhibited the highest percentage of capacity retention after 200 cycles, cell B exhibited the lowest capacity retention after 200 cycles, and the capacity retention of cell C fell between that of cell A and cell B.

[0063] Fig.Figure 11 illustrates the cycling performance of a pouch cell at room temperature, i.e., 25 degrees Celsius, with a charge and discharge rate of 0.1C. The pouch cell contained a cathode comprising lithium iron phosphate (87.8 wt%), lithium aluminum titanium phosphate (5 wt%), conductive carbon black powder (1.85 wt%), conductive synthetic graphite carbon black (1.85 wt%), and polyvinylidene fluoride binder (3.5 wt%), with the total weight percentage of the cathode being 100 wt%. The cathode was deposited at 3.5 milliampere-hours per square centimeter. The anode contained silicon film deposited at a capacity load of 8 milliampere-hours per square centimeter.The separator contained polyethylene with a thickness of 9 micrometers, including a 3-micrometer-thick LATP layer deposited on the cathode side of the separator. The liquid portion of the electrolyte contained lithium bis(trifluoromethane)sulfonimide at a concentration of 1 M in a solvent consisting of tetraethylene glycol dimethyl ether (G4) and a diluent consisting of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, with a volume ratio of 1 part solvent to 4 parts diluent. As shown in the graph, the percentage of capacity retention (y-axis) remained relatively stable up to 120 charge and discharge cycles (number of cycles illustrated on the x-axis). The capacity retention was found to be 98.8 percent after 100 cycles.

[0064] The electrolytes, battery cells, secondary batteries, and manufacturing processes described herein offer a number of advantages. These advantages include, for example, increased capacity retention and ionic activity compared to non-flammable lithium iron phosphate battery cells due to the lithium aluminum titanium phosphate additives. These advantages also include improved cell cycling performance compared to non-flammable lithium iron phosphate battery cells. The use of a liquid electrolyte allows it to penetrate the spaces present in the various layers of the battery cell. These advantages also include improved thermal stability compared to lithium iron phosphate battery cells due to the use of the non-flammable liquid electrolyte. These advantages further include the relatively high energy density provided by the silicon film anode.These advantages also include a reduction in the thickness of the anode compared to graphite anodes.

[0065] 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, for example, microprocessors, and associated non-volatile memory components in the form of storage and memory devices (read-only memory, programmable read-only memory, direct access memory, hard disk, and so on). The controller 132 may also consist of multiple controllers that are in electrical communication with each other. The controller 132 may be connected to additional systems and / or controllers of the vehicle 100, which enables the controller 132 to access data such as, for example, the vehicle 100's speed, acceleration, braking, and steering angle.

[0066] A processor can be a custom-made or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor among several processors belonging to the controller 132, a semi-conductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, a combination thereof, or generally a device for executing instructions.

[0067] The tangible, non-volatile memory 134 can, for example, include volatile and non-volatile storage in read-only memory (ROM), random-access memory (RAM), and keep-alive memory (KAM). KAM is persistent or non-volatile memory that can be used to store various operating variables while the processor is powered off. The tangible, non-volatile memory 134 can be implemented using a variety of storage devices, such as PROMs (programmable read-only memory), EPROMs (electrical PROMs), EEPROMs (electrically erasable PROMs), flash memory, or other electrical, magnetic, optical, or combined storage devices capable of storing data, some of which represents executable instructions used by the controller 132 to control various systems of the vehicle 100.

Claims

[1] Battery cell (150) for a vehicle (100), comprising: a cathode (156) comprising lithium iron phosphate and lithium aluminum titanium phosphate; an anode (158) comprising a silicon film; a separator (160) positioned between the cathode (156) and the anode (158), wherein the separator (160) comprises a cathode side facing the cathode (156) and an anode side facing the anode (158); a first solid electrolyte layer (318) arranged on the separator (160), wherein the first solid electrolyte layer (318) comprises a layer of lithium aluminum titanium phosphate; and a liquid electrolyte (162) contacting the cathode (156), the anode (158), the first solid electrolyte layer (318) and the separator (160), wherein the liquid electrolyte (162) comprises a primary lithium ion salt, a solvent and a diluent; wherein the diluent comprises 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. [2] Battery cell (150) according to claim 1, wherein the cathode (156) comprises the lithium iron phosphate present in the range of 80 wt.% to 95 wt.%, the lithium aluminum titanium phosphate present in the range of 1 wt.% to 10 wt.%, a carbon additive present in the range of 1 wt.% to 5 wt.%, and a polyvinylidene fluoride binder present in the range of 1 wt.% to 5 wt.%. [3] Battery cell (150) according to claim 2, wherein the cathode (156) is present at a capacity load in the range of 3.0 milliampere hours per square centimeter to 4.0 milliampere hours per square centimeter. [4] Battery cell (150) according to claim 1, wherein the cathode (156) comprises a plurality of cavities and has a cavity volume in the range of 25 vol% to 35 vol% of the total volume defined by the cathode (156), wherein the liquid electrolyte (162) is present in at least a part of the plurality of cavities. [5] Battery cell (150) according to claim 1, wherein the first solid electrolyte layer (318) is arranged on the cathode side of the separator (160). [6] Battery cell (150) according to claim 1, wherein the primary lithium ion salt comprises at least one of lithium bis(trifluoromethane)sulfonimide, LiTFSI, lithium bis(fluorosulfonyl)imide, LiFSI, lithium bis(pentafluoroethanesulfonyl)imide, LiBETI, and lithium trifluoromethanesulfonate, LiTfo. [7] Battery cell (150) according to claim 1, wherein the solvent comprises at least one of tetraethylene glycol dimethyl ether and triethylene glycol dimethyl ether. [8] Battery cell (150) according to claim 1, wherein the diluent is present in the range of 30 vol% to 80 vol% of the total volume of the diluent and solvent and the solvent is present in the range of 20 vol% to 70 vol% of the total volume of the diluent and solvent, wherein the total volume percentage of the diluent and solvent is 100 percent. [9] Method (400) for forming a battery cell (150), comprising: Application (402) of a cathode (156) containing lithium iron phosphate and Lithium aluminum titanium phosphate comprises, on a cathode current collector; Applying an anode (158) comprising a silicon film to an anode current collector; Applying a first solid electrolyte layer (318) to a separator (160), wherein the separator (160) has a cathode side facing the cathode (156) and an anode side, which is facing the anode (158) and comprises the first solid electrolyte layer (318) lithium aluminum titanium phosphate; Positioning the separator (160) between the cathode (156) and the anode (158); Assembling the cathode (156), the anode (158) and the separator (160) to form a battery cell cover; and Adding (404) a liquid electrolyte to the battery cell cover, wherein the liquid electrolyte contacts the cathode (156), the anode (158), the first solid electrolyte layer and the separator (160), and wherein the liquid electrolyte comprises a primary lithium ion salt, a solvent and a diluent; where the battery cell (150) comprises: the cathode (156) which comprises lithium iron phosphate and lithium aluminum titanium phosphate; the anode (158) which comprises the silicon film; the separator (160) which is positioned between the cathode (156) and the anode (158), wherein the separator (160) comprises the cathode side which faces the cathode (156) and the anode side which faces the anode (158); the first solid electrolyte layer (318) arranged on the separator (160), wherein the first solid electrolyte layer (318) comprises a layer of lithium aluminum titanium phosphate; and the liquid electrolyte (162) contacting the cathode (156), the anode (158), the first solid electrolyte layer (318) and the separator (160), wherein the liquid electrolyte (162) comprises the primary lithium ion salt, the solvent and the diluent; wherein the diluent comprises 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

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