LFP / LI-METAL-FLACKED BATTERY CELL

Abstract

A battery cell comprises A anode electrodes with an anode active material layer comprising lithium metal active material and an anode current collector, C cathode electrodes with a cathode active material layer comprising LiFePO4(LFP) active material and a cathode current collector, and S separators arranged between the A anode electrodes and the C cathode electrodes, where A, C, and S are integers greater than 1. The S separators comprise a support with a coating layer.

Description

INITIATIONThe information provided in this section is intended to generally illustrate the context of the disclosure. Work of the present inventors, insofar as described in this section, as well as aspects of the description that may not otherwise be considered prior art at the time of filing, is neither expressly nor silently admitted as prior art against this disclosure.The present disclosure relates to battery cells, and more particularly to battery cells having lithium metal anodes and LFP cathodes.Electric vehicles (EVs), such as battery-powered electric vehicles (BEVs), hybrid vehicles, and / or fuel cell vehicles, include one or more electric machines and a battery system having one / more battery cells, modules, and / or packs. A power control system is used to control the charging and / or discharging process of the battery system during the charging process and / or the trip.SUMMARYA battery cell includes A anode electrodes having an anode active material layer including lithium metal active material and an anode current collector, C cathode electrodes having a cathode active material layer including LiFePO 4( LFP) active material and a cathode current collector, and S separators disposed between the A anode electrodes and the C cathode electrodes, where A, C, and S are integers greater than 1. The S separators comprise a support having a coating layer.In other features, the anode current collector comprises a wire mesh of a material selected from the group consisting of copper and stainless steel. The anode current collector comprises a foil of a material selected from the group consisting of copper and stainless steel. The support of the S separators is selected from a polyolefin-based separator, a cellulose separator, a polyvinylidene fluoride (PVDF) membrane, and a polyimide porous membrane.In other features, the coating layer is selected from a group consisting of ceramic, polymer, aluminum oxide (Al 2 O 3), Li 1,3 Al 0,3 Ti 1,7( PO 4)3( LATP), polyvinylidene difluoride (PVDF), polymethyl methacrylate (PMMA), and combinations thereof, and the coating layer has a thickness in a range from 1 μm to 5 μm.In other features, the wire braid is in a range of 50 to 400 mesh. The thickness of the A anode electrodes is in a range of 70 to 120 μm, and the width of the A anode electrodes is in a range of 50 mm to 500 mm. The S separators have a thickness in the range of 9 μm to 19 μm and a porosity in the range of 35 to 55%.In other features, the cathode active material layer includes the LFP active material, a carbon additive, and a binder. The LFP active material is 90 to 98 wt %, the carbon additive is 1 to 5 wt %, and the binder is 1 to 5 wt %.In other features, the LFP active material further comprises a carbon coating. The carbon coating is in a range of 0.5 wt % to 3 wt %, and the LFP is in a range of 97 wt % to 99.5 wt % of the LFP active material. The binder comprises PTFE.In other features, the carbon additive is selected from a group consisting of Super P, KS-6, graphite, graphene nanoplates, single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and combinations thereof. The electrolyte includes a lithium salt, a solvent, and an additive. The lithium salt is selected from a group consisting of LiPF 6 and LiFSI. The solvent is selected from a group consisting of carbonate ester or ether. The battery cell has an N / P ratio in a range of 1.5 to 1.7.A battery cell includes A anode electrodes having an anode active material layer comprising a lithium metal coating on an anode current collector. The anode current collector comprises a wire mesh of a material selected from the group consisting of copper and stainless steel. The C cathode electrodes include a cathode active material layer including a LiFePO 4( LFP) active material with a carbon coating and a cathode current collector. Between the A anode electrodes and the C cathode electrodes, S separators are disposed, where A, C, and S are integers greater than one. The S separators comprise a support having a coating layer. The support is selected from a group consisting of a polyolefin-based separator, a cellulose separator, a polyvinylidene fluoride (PVDF) membrane, and a polyimide porous membrane, and combinations thereof. The coating layer is selected from a group consisting of ceramic, polymer, alumina (Al 2 O 3), Li 1,3 Al 0,3 Ti 1,7( PO 4)3( LATP), polyvinylidene difluoride (PVDF), and polymethyl methacrylate (PMMA). An electrolyte includes a lithium salt, a solvent, and an additive.In other features, the cathode active material layer includes the LFP active material, a carbon additive, and a binder. The LFP active material is 90 to 98 wt %, the carbon additive is 1 to 5 wt %, and the binder is 1 to 5 wt %. The S separators have a thickness in a range of 9 μm to 19 μm and a porosity in a range of 35 to 55%.In other features, the carbon coating of the LFP active material is in a range of 0.5 to 3 wt %, and the LFP is in a range of 97 to 99.5 wt %. The binder comprises PTFE. The carbon additive is selected from a group consisting of Super P, KS-6, graphite, graphene nanoplatelets, single-wall carbon nanotubes (SWCNT), multi-wall carbon nanotubes (MWCNT), and combinations thereof.Further areas of applicability of the present disclosure will become apparent from the detailed description, claims and drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGSThe present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: FIG. 1 is a side cross-sectional view of an example of a battery cell having cathode electrodes, lithium metal anode electrodes, and separators disposed in a battery cell case according to the present disclosure; FIGS. 2A and 2B are more detailed cross-sectional side views of examples of a battery cell having LFP cathode electrodes, lithium metal anode electrodes, and separators according to the present disclosure; FIG. 3 is a graph depicting heat flux versus temperature for a graphite anode with electrolyte, a LiNi 0,98 Co 0,05 Mn 0,03 Al 0,02 O 2( NCMA) cathode with electrolyte, a lithium iron phosphate or LiFePO 4( LFP) cathode with electrolyte, and a lithium metal anode with electrolyte in accordance with the present disclosure; FIG. 4 is a graph depicting voltage versus capacitance for the battery cell with the LFP cathode and lithium metal anode according to the present disclosure; FIG. 5 is a graph depicting capacity retention versus cycles for the battery cell with the LFP cathode and lithium metal anode according to the present disclosure; FIG. 6 is a graph depicting colombic efficiency versus cycles for the battery cell with the LFP cathode and lithium metal anode according to the present disclosure; and FIGS. 7 and 8 are graphs illustrating heat flux versus temperature for examples of battery cells according to the present disclosure.In the drawings, reference numerals may be reused to identify similar and / or identical elements.DETAILED DESCRIPTIONAlthough battery cells according to the present disclosure are shown in the context of electric vehicles, the battery cells may be used in stationary applications and / or other applications.Lithium ion battery cells with NMC or NMCA cathodes and graphite anodes have a high energy density and good cycling performance. However, these battery cells do not have high thermal stability, so that thermal runaway is problematic.The battery cells according to the present disclosure include a lithium metal anode and an LFP cathode. As described below, the battery cells according to the present disclosure enable high thermal stability and excellent cyclability without suffering the energy density.Referring now to FIG. 1, a battery cell 10 includes C cathode electrodes 20, A anode electrodes 40, and S separators 32 arranged in a predetermined order in a battery stack 12 in a case 50, where C, S, and A are integers greater than zero. The C cathode electrodes 20- 1, 20- 2,..., and 20- C include cathode active material layers 24 including LFP active material disposed on one or both sides of cathode current collectors 26. The A anode electrodes 40- 1, 40- 2,..., and 40- A include anode active material layers 42 including lithium metal disposed on one or both sides of the anode current collectors 46.In some examples, the cathode current collectors 26 and the anode current collectors 46 comprise a metal mesh, a metal foil, or expanded metal. In some examples, the anode current collectors 46 are made of a material selected from a group consisting of copper and stainless steel. In some examples, the cathode current collectors are made of aluminum or other suitable current collector materials.In some examples, the cathode active material layers 24 comprise coatings of one or more active materials, one or more conductive fillers / additives, and / or one or more binders applied to the current collectors 26 in a roll-to-roll production line or other manufacturing process. External tabs 28 and 48 may be connected to the current collectors of the anode and cathode electrodes on the same or opposite sides of the battery stack 12.Referring now to FIGS. 2A and 2B, the cathode active material layer 24 includes an LFP active material 210, a conductive additive 212, and a binder 214. The S separators 32 include a support 220 and a coating layer 222 disposed on opposite sides. In FIG. 2A, the anode active material layer 42 includes a lithium metal coating 218 disposed on the anode current collector 46 (e.g., wire mesh).In FIG. 2B, the anode active material layer 42 includes a lithium metal layer 219, such as a lithium foil, disposed on the anode current collector 46 (e.g., metal foil). In some examples, the metal foil has a thickness in a range from 5 μm to 30 μm.In some examples, the metal mesh of the anode current collector 46 is in a range of 50 to 400 mesh (e.g., openings per inch). In some examples, the anode electrodes 40 have a capacitance charge in a range of 6 to 8 mAh / cm 2( e.g., 6.5 mAh / cm 2) for a single-sided lithium coating having a thickness in a range of 30-40 μm. In some examples, the total thickness of the anode electrodes 40 is in a range from 70 μm to 120 μm. In some examples, the anode electrodes have a width in a range from 50 mm to 500 mm. In some examples, the anode electrodes have a width in a range from 50 mm to 200 mm.In some examples, the support 220 is selected from a group consisting of a polyolefin-based separator (e.g., polyacetylene: polypropylene (PP), polyethylene (PE), two-layer type: PP-PE, three-layer type: PP-PE-PP), a cellulose separator, a polyvinylidene fluoride (PVDF) membrane, and a polyimide porous membrane. In some examples, the coating layer 222 comprises ceramic or polymer. An example of ceramics is alumina (Al 2 O 3) or Li 1,3 Al 0,3 Ti 1,7( PO 4)3( LATP), although other ceramics may also be used. Examples of polymers include polyvinylidene difluoride (PVDF), polymethyl methacrylate (PMMA), or other suitable polymers. The overcoat layer is disposed on one or both sides of the carrier 220.In some examples, the separator 32 has a thickness in a range from 9 μm to 19 μm. In some examples, the separator 32 has a porosity in a range of 35 to 55% (e.g., 40%). In some examples, the coating layer 222 has a thickness in a range from 1 μm to 5 μm. In some examples, the separator 32 has a thickness of 16 μm, a porosity of 40%, and the coating layer 222 includes alumina (Al 2 O 3) having a thickness of 2 μm.In some examples, the cathode active material layer comprises LFP active material, a carbon additive, and a binder. In some examples, the LFP active material is 90 to 98 wt %, the carbon additive is 1 to 5 wt %, and the binder is 1 to 5 wt %.In some examples, the LFP active material has a surface area of 3 m 2 / g to 20 m 2 / g. In some examples, the LFP active material further comprises a carbon coating. In some examples, the carbon coating of the LFP active material is in a range of 0.5 to 3 wt %, and the LFP is in a range of 97 to 99.5 wt %. In some examples, the LFP active material has a D 50- value in a range from 0.5 μm to 15 μm. In some examples, the surface area of the LFP active material is 10.6 m 2 / g and the carbon coating is 1.2 wt % with a D 50- value of 1.2 μm.In some examples, the binder comprises PTFE. In some examples, the carbon additive is selected from a group consisting of Super P, KS-6, graphite, graphene nanoplatelets, single-wall carbon nanotubes (SWCNT), multi-wall carbon nanotubes (MWCNT), and combinations thereof. In some examples, the cathode active material layer comprises LFP, Super P, and PTFE in a mass ratio of 96.5:1.5:2.In some examples, the capacitance charge of the cathode electrode is in a range of 2 to 6 mAh / cm 2( for one-sided coating 0.1 C at room temperature). In some examples, the press density of the cathode electrode is in a range of 1.9 to 3.1 g / cm 3( e.g., 2.4 g / cm 3). In some examples, the porosity is in a range of 25% to 45%. In some examples, the moisture content is less than 600 ppm. In some examples, the cathode electrodes have a width in a range from 50 mm to 500 mm. In some examples, the anode electrodes have a width in a range from 50 mm to 200 mm.In some examples, the electrolyte comprises a lithium salt, a solvent, and an additive. In some examples, the lithium salt is selected from a group consisting of LiPF 6 or LiFSI (e.g., 0.82 mol / L). In some examples, the solvent is selected from a group consisting of carbonate ester or ether. In some examples, the additive is selected from a group consisting of fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), 1,1,2,2-tetrafluoroethylene-2,2,3,3-tetrafluoropropylene ether (TTE), and / or other additives. The electrolyte may comprise, for example, 1 M LiPF 6 in FEC and DMC (1:4 volume) for a 1-Ah-LFP / Li-300 Cu braid stack-pouch battery cell. The electrolyte may comprise, for example, 1 M LiPF 6 in FEC and DMC (1:4 volume) for a 1-Ah-LFP / Li-100 Cu braid stack-pouch battery cell.In some examples, an N / P ratio is in a range from 1.5 to 1.7 (e.g., 1.66). In some examples, the battery cell has a pouch, prismatic, cylindrical, or other suitable format in which it is stacked or wound.Referring now to FIG. 3, the heat flux for an NCMA cathode with electrolyte and a graphite anode with electrolyte is illustrated as compared to an LFP cathode with electrolyte and a lithium metal anode with electrolyte. The peak exothermic reaction intensity for the NCMA cathode at A and the graphite anode at B is significantly higher than for the LFP cathode at C and the lithium metal anode at D, indicating that the LFP cathode and lithium metal anode system has a much lower risk of thermal runaway than the NCMA cathode and graphite anode system.Referring now to FIG. 4, the voltage is shown as a function of capacity for a pouch battery cell of ~ 1 Ah and an LFP load of 4 mAh / cm 2, a press density of 2.4 g / cc, an anode with a 300 mesh Cu anode current collector with a lithium metal coating, an electrolyte with 1 M LiPF 6 in FEC and DMC (1:4 volume), and an energy density of 290 Wh / kg (calculated using a 100 Ah cell format). The initial column efficiency was 95.8% and the initial discharge capacity was 1.07 Ah. The voltage range is between 2.2 and 3.65 volts, the compression pressure is 20 psi, and the CCCV charge occurs at C / 10 and the discharge occurs at C / 10.Referring now to FIGS. 5 and 6, the capacity retention and coulombic efficiency of an example battery cell having a 1-Ah-LFP / Li-300-Cu mesh in a stack pouch format and an electrolyte having 1 M LiPF 6 in FEC and DMC (1:4 volume) are shown. The battery cell has a capacity retention of 98% and an average colombic efficiency of 99.2% after 230 cycles.Referring now to FIGS. 7 and 8, the heat flux performance of an exemplary battery cell is shown that includes a 1-Ah-LFP / Li-300 Cu braid stacked pouch battery cell with 1 M LiPF 6 in FEC and DMC (1:4 volume). After 100 cycles, the exothermic reaction of the Li anode (FIG. 7 ) and the LFP cathode (FIG. 8 ) is relatively unchanged compared to the original performance of the Li anode and the LFP cathode after 1 cycle. As can be seen, the heat emission during the thermal runaway is minimal.The foregoing description is for illustrative purposes only and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure may be practiced in a variety of forms. Although this disclosure includes particular examples, the true scope of the disclosure is not to be considered as limited in this manner, as other modifications will become apparent upon studying the drawings, specification, and the following claims. It should be appreciated that one or more steps within a method may be performed in different order (or simultaneously) without departing from the spirit of the present disclosure. Although each of the embodiments described above has particular features, one or more of these features described with respect to any embodiment of the disclosure may be implemented in any other embodiment and / or combined with features of any other embodiment, even if this combination is not expressly described. In other words, the described embodiments are not mutually exclusive, and combinations of one or more embodiments with each other remain within the scope of this disclosure.Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described with various terms including "connected," "engaged," "coupled," "adjacent," "next to," "on," "over," "under," and "arranged.". When a relationship between first and second elements is not expressly described as "direct" in the above disclosure, this relationship may be a direct relationship in which no other intervening elements are present between the first and second elements, but may also be an indirect relationship in which one or more intervening elements (either spatially or functionally) are present between the first and second elements. As used herein, the phrase "A, B, and / or C" should be construed using a non-exclusive logical OR operation as a logical (A ORed with B ORed with C) rather than as "at least one of A, at least one of B, and at least one of C.".In the figures, the direction of an arrow as indicated by the arrow head generally indicates the flow of information (such as data or instructions) of interest for the display. For example, if element A and element B exchange a variety of information, but the information conveyed from element A to element B is relevant for presentation, the arrow may point from element A to element B. This unidirectional arrow does not mean that no other information is transmitted from element B to element A. Further, when transmitting information from element A to element B, element B may send requests or acknowledgements for the information to element A.

Claims

A battery cell comprising: A anode electrodes having an anode active material layer comprising lithium metal active material and an anode current collector; C cathode electrodes having a cathode active material layer comprising LiFePO 4( LFP) active material and a cathode current collector; and S separators disposed between the A anode electrodes and the C cathode electrodes, wherein A, C and S are integers greater than one, wherein the S separators comprise a support having a coating layer.The battery cell of claim 1, wherein the anode current collector comprises a wire mesh of a material selected from a group consisting of copper and stainless steel.The battery cell of claim 1, wherein the anode current collector comprises a foil of a material selected from a group consisting of copper and stainless steel.The battery cell of claim 1, wherein the support of the S separators is selected from a polyolefin-based separator, a cellulose separator, a polyvinylidene fluoride (PVDF) membrane, and a polyimide porous membrane.The battery cell of claim 1, wherein: the overcoat layer is selected from a group consisting of ceramic, polymer, aluminum oxide (Al 2 O 3), Li 1,3 Al 0,3 Ti 1,7( PO 4)3( LATP), polyvinylidene difluoride (PVDF), polymethyl methacrylate (PMMA), and combinations thereof, and the overcoat layer has a thickness in a range of 1 μm to 5 μm.The battery cell of claim 2, wherein the wire mesh is in a range of 50 to 400 mesh.The battery cell according to claim 1, wherein a thickness of the A anode electrodes is in a range of 70 to 120 μm and a width of the A anode electrodes is in a range of 50 mm to 500 mm.The battery cell of claim 1, wherein: the S separators have a thickness in a range of 9 μm to 19 μm and a porosity in a range of 35 to 55%.The battery cell according to claim 1, wherein: the cathode active material layer comprises the LFP active material, a carbon additive, and a binder, and the LFP active material accounts for 90 to 98 wt%, the carbon additive accounts for 1 to 5 wt%, and the binder accounts for 1 to 5 wt%.The battery cell of claim 9, wherein: the LFP active material further comprises a carbon coating, and the carbon coating is in a range of 0.5 wt% to 3 wt% and the LFP is in a range of 97 wt% to 99.5 wt% of the LFP active material.

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