Electrochemical device with multifunctional electrode separator arrangement with built-in reference electrodes

Abstract

Presented are electrochemical devices with stacked reference electrodes, methods for making / using such devices, and battery cells with stacked electrodes separated by electrode separator assemblies with built-in reference electrodes. An electrochemical device comprises a protective outer casing containing an ion-conducting electrolyte. A stack of working electrodes is housed within the device casing in electrochemical contact with the electrolyte. At least one electrode separator assembly is located within the casing between an adjacent pair of these working electrodes. The electrode separator assembly comprises an electrically insulating separator plate with a reference electrode. A tab pocket extending from one end of the separator plate contains a tab chamber with a chamber opening.An electrode tab is made of an electrically conductive material and attached to the tab pocket. One end of the electrode tab is positioned within the tab chamber, and the other end protrudes from the chamber opening.

Description

IntroductionThe present description relates generally to electrochemical devices. More specifically, the aspects of this description relate to stacked electrode assemblies having reference electrodes for lithium-class battery cells integrated into the stack.Present-day series vehicles, such as the modern automobile, are originally equipped with a drive train that drives the vehicle and powers the onboard electronics of the vehicle. For example, in motor vehicles, the powertrain typically consists of an engine that transmits drive torque to the driveline of the vehicle (e.g., differential, axle shafts, cam modules, wheels, and so forth) via an automatic or manually shifted transmission. In the past, motor vehicles have been propelled with reciprocating piston internal combustion engines (ICEs) because they were readily available and relatively inexpensive, light weight, and high efficiency. These engines include Diesel Self Ignition (CI) engines, Spark Ignition (SI) engines, two, four and six stroke engines, as well as rotary engines, to name a few examples. Hybrid electric and all-electric vehicles (collectively referred to as "electric-powered vehicles"), on the other hand, use alternative energy sources to power the vehicle and thus minimize or eliminate the dependence on a fossil fuel-based engine on tractive effort.A fully electric vehicle (FEV)-also referred to colloquially as an "electric car"-is an electric-drive vehicle configuration in which the internal combustion engine and associated peripheral components of the powertrain are completely omitted and a rechargeable energy storage system (RESS) and a traction motor are used instead for vehicle propulsion. The engine assembly, fuel supply, and exhaust system of a vehicle with an internal combustion engine are replaced in a battery-backed FEV with one or more traction motors, a traction battery pack, and a battery cooling and charging technique. Hybrid electric vehicle powertrains (HEV), on the other hand, use multiple types of motive power to propel the vehicle, typically operating an internal combustion engine in conjunction with a battery- or fuel-cell-powered traction motor. Because electric-powered vehicles are capable of drawing their energy from sources other than the engine, HEV motors may be fully or partially deactivated while the vehicle is being powered by the electric motor(s).High voltage electrical systems regulate the transfer of power between the traction motors and the rechargeable battery packs that provide the necessary power for operation of many hybrid electric and full electric powertrains. To provide the power capacity and energy density required to propel a vehicle at the desired speed over the desired range, modern traction battery packs group multiple battery cells (e.g., 8-16+ cells / group) into individual battery modules (e.g., 10-40+ modules / pack) that are electrically connected in series or in parallel to one another and are mounted to the vehicle chassis via a battery pack housing or carrier. On the battery side of the high voltage grid is a DC-DC converter electrically connected to the traction batteries to boost the voltage supply to a main DC-DC bus and an inverter module (PIM). A high frequency large capacitor may be placed between the positive and negative rails of the main DC bus to ensure electrical stability and store additional electrical energy. A special battery electronic control module (EBCM), in cooperation with a powertrain control module (PCM) and the power electronics of each engine, controls the operation of the battery pack(s) and traction motor / s.There are four main types of batteries used in electric drive vehicles: lithium-class batteries, nickel-metal hydride batteries, ultracapacitor batteries, and lead-acid batteries. As with the lithium batteries, lithium metal and lithium ion batteries (secondary batteries) make up the majority of commercially available lithium battery configurations (LiB), with lithium ion variants (Li ion) being used in automotive applications due to their improved stability, high energy density and rapid charge capability. A standard Li-ion cell generally consists of at least two conductive electrodes, an electrolyte material and a permeable separator, all enclosed in an electrically insulated package. One electrode serves as a positive ("cathode") electrode and the other electrode serves as a negative ("anode") electrode during discharge of the cell. The separator-often a microporous polymer membrane-is arranged between the two electrodes in order to prevent electrical short circuits and at the same time to enable the transport of ionic charge carriers. The electrolyte is suitable for conducting lithium ions and can be in solid form (for example solid state diffusion), in liquid form (for example liquid phase diffusion) or in quasi-solid form (for example solid electrolyte in a liquid carrier). Rechargeable lithium-ion batteries function by reversibly diverting lithium ions between these working electrodes.CN 2 19 144 259 U describes a three-electrode battery and a reference electrode assembly thereof, wherein the reference electrode assembly comprises a reference electrode, a metal piece and a diaphragm bag, and the reference electrode extends along a first direction; the metal piece is sheet-shaped, the proximal end of the metal piece is connected to the end part of the reference electrode, and the distal end of the metal piece extends away from the reference electrode along the first direction; the membrane bag extends along the first direction and is sheathed outside the reference electrode, one end of the membrane bag that is far away from the metal piece is sealed, and the other end of the membrane bag extends to the proximal end of the metal piece. The reference electrode is connected to the sheet-shaped metal piece, the diaphragm pouch is sheathed outside the reference electrode, and the reference electrode, the diaphragm pouch, and the metal piece are combined in the reference electrode assembly, so that the reference electrode is conveniently positioned and mounted between the positive plate and the negative plate, the reference electrode is fully mounted in the shell, and electrochemical reaction information is output through the metal piece.WO 2003 / 041 209 A2 describes a device and a method for the space- and time-resolved measurement of at least one operating parameter of an electrochemical cell. A plurality of electrodes are provided in the electrochemical cell. An electrolyte solution is disposed in a space between the plurality of electrodes. To measure the state of the electrochemical cell, one or more measuring probes are arranged in different spatial points of the space between the electrodes and are connected to a measuring device for carrying out the spatial and time-resolved measurement.US 2023 / 0 091 154 A1 describes electrochemical devices with stacked sensor arrangements, methods for producing / using such electrochemical devices and lithium-class battery cells with stacked electrode arrangements with stacked sensor arrangements. An electrochemical device includes a device housing that stores an electrolyte composition for conducting ions. An electrode stack located within the device housing in electrochemical contact with the electrolyte includes at least two working electrodes. Between each adjacent pair of working electrodes is disposed an electrically insulating and ion permeable separator. A reference electrode is attached to one side of the separator, which is connected to a plurality of electric sensors. A plurality of electrical sensing lines are mounted on another side of the separator opposite the reference electrode, each of which abuts a discrete region of a working electrode and is connected to one of the sensing devices for transmitting thereto electrical signals indicative of an electrical characteristic, e.g., voltage, of the discrete region it contacts.Summary of the InventionThe invention is defined by the subject matter of the independent claim. Electrochemical devices with reference electrodes arranged in a stack, methods for manufacturing and operating such devices, and lithium battery cells with stacked working electrodes separated by electrode separator arrangements with built-in reference electrodes are presented. A pouch type lithium ion battery cell includes, for example, an electrode stack having a sequence of first (anode) working electrodes interleaved with an equal number of second (cathode) working electrodes. Between each pair of adjacent electrodes is disposed an electrically insulating and ion conductive separator which may be in the form of a polymeric separator plate immersed in or bonded to a liquid electrolyte. The nested electrodes and separator plates may be stacked and housed in a protective bag, rolled into jelly and housed in a cylindrical can, or flat rolled and housed in a prismatic container. A reference electrode may be baked into or otherwise integrally connected to the separator plate.One or more of these electrode separator plates may be manufactured as a multifunctional separator assembly having a reference electrically conductive electrode tab that protrudes from a tab pocket that protrudes longitudinally from one end of the separator plate. The tab pocket may include a reduced width tab panel coplanar and integrally formed with the main body of the separator plate. An integral tab flap extends transversely from one side of the tab panel and folds against the tab panel to form a compartment in which the reference electrode tab is fixedly secured. Functionally attaching the reference electrode tab to the separator plate may include cleaning and roughening a first (proximal) end of the tab; an electrically conductive adhesive is applied to both sides of the proximal end of the tab. One side of the flap is aligned and pressed against the flap panel; the flap is then folded against and adhered to the opposite side of the flap. After attachment, at least about 50% of the tab protrudes from the tab pocket with the proximal end of the tab spaced from the longitudinal end of the separator plate.The attendant advantages of at least some of the disclosed concepts include functional separator assemblies that enable intra-stack measurement of the electrical properties of electrodes while providing electrical and thermal separation of adjacent working electrodes. By measuring the electrical properties of the electrodes using in-stack reference electrodes, the disclosed concepts assist in detecting potential battery failures and optimized control of battery operation. The separators presented also help reduce packaging space and complexity of manufacturing reference electrodes and their conductive tabs. In addition to the improved monitoring and operation of the battery cells, the concepts presented may help to increase the range, fuel consumption, and performance of the battery for electric-powered vehicles.Aspects of this specification relate to electrochemical devices such as cylindrical, pouch-type, and prismatic LiB cells used in, for example, battery modules of vehicle drive batteries.According to the invention, an electrochemical device is constructed with an insulated and sealed housing for storing therein an electrolyte composition chemically configured to conduct ions. An electrode stack located within the device housing in electrochemical contact with the electrolyte includes one or more first working electrodes (e.g., anodes) interleaved with one or more second working electrodes (e.g., cathodes). At least one electrode separator assembly is located within the device housing and is disposed between and physically separated from an adjacent working electrode pair. Each electrode separator assembly includes a separator plate formed in whole or in part from an electrically insulating material. The separator plate includes a reference electrode. A tab pocket protruding from an end of the separator plate defines a tab chamber having a chamber opening. An electrically conductive reference electrode tab is secured to the tab pocket and electrically connected to the reference electrode. One end of the reference electrode tab is disposed within the tab chamber and the other end of the reference electrode tab protrudes from the chamber opening. The tab pocket, in accordance with the invention, includes a tab panel projecting from and coplanar with the separator plate, the separator plate having a first width and a first height, and the tab panel having a second width and a second height less than the first width and the first height, respectively.Application examples of this specification relate to lithium battery cells having stacked electrode assemblies with in-stack sensing capabilities, rechargeable battery packs using such lithium battery cells, and motor vehicles equipped with such battery packs. As used herein, the terms "vehicle" and "motor vehicle" may be used interchangeably and interchangeably to include any relevant vehicle platform, such as passenger vehicles (ICE, HEV, FEV, fuel cell, fully and semi-autonomous vehicles, and so forth), commercial vehicles, industrial vehicles, tracked vehicles, sport utility vehicles, and all-terrain vehicles (ATV), motorcycle, agricultural equipment, E-bikes, E-scooters, watercraft, aircraft, and so forth. For non-automotive applications, the disclosed concepts may be implemented for any logically relevant use, including stand-alone power plants and portable power units, photovoltaic systems, portable electronic devices, pump equipments, machine tools, devices, and so forth Although not limited per se, the disclosed concepts may be particularly advantageous for use in cylindrical, pouch-type, and prismatic lithium metal cells (secondary cells).In one example, a motor vehicle includes a vehicle body having a passenger compartment, a plurality of drive wheels rotatably mounted to the vehicle body (e.g., via corner modules coupled to a unibody or body-on-frame chassis), and other standard equipment. In electric-drive vehicles, one or more electric traction motors operate alone (e.g., in FEV powertrains) or in conjunction with an internal combustion engine (e.g., in HEV powertrains) to selectively propel one or more wheels and propel the vehicle. A rechargeable traction battery pack is mounted to the vehicle body and may provide power to the traction motor(s).As described in the preceding example, the traction battery includes a plurality of lithium-grade battery cells, for example, stacked in one or more battery modules and / or disposed in a battery pack housing. Each battery cell is equipped with a protective battery housing in which a liquid, solid or quasi-solid electrolyte composition for ionic conduction is accommodated. Inside the battery housing is an electrode stack which is in electrochemical contact with the electrolyte. The electrode stack comprises a series of first (anode) working electrodes interleaved with a corresponding number of second (cathode) working electrodes. Also located within the battery housing is an electrode separator assembly disposed between a respective pair of working electrodes. The electrode separator assembly includes a separator plate formed in whole or in part from an electrically insulating material and a tab pocket connected to and protruding from a longitudinal end of the separator plate. A reference electrode is supported by the separator plate. The tab pocket includes an inner tab chamber having a chamber opening at one end. A reference electrode tab is fixedly attached to the tab pocket, for example, via an electrically conductive adhesive, and is formed in whole or in part from an electrically conductive material. The reference electrode tab has a first (proximal) end disposed within the tab chamber and a second (distal) end opposite the first end and protruding from the chamber opening.Non-claimed examples of this specification, which are provided to understand the invention, also relate to manufacturing methods, control logic, and computer readable media (CRM) for making and / or using the disclosed electrochemical devices, battery packs, and / or vehicles. In one example, a method of assembling an electrochemical device is presented. This representative method includes, in any order and in any combination with any of the options and features disclosed above and below: receiving a device housing of the electrochemical device; disposing an electrolyte within the device housing, the electrolyte configured to conduct ions; disposing an electrode stack within the device housing in electrochemical contact with the electrolyte, the electrode stack including first and second working electrodes; and disposing an electrode separator assembly between the first and second working electrodes, the electrode separator assembly including: a separator plate formed of an electrically insulating material and including a reference electrode; a tab pocket protruding from an end of the separator plate and defining a tab chamber having a chamber opening; and a reference electrode tab secured to the tab pocket and formed of an electrically conductive material, the reference electrode tab having a first end disposed in the tab chamber and a second end protruding from the chamber opening.In all disclosed vehicles, methods, and devices, the tab pocket includes a tab panel that protrudes from and is coplanar with the separator plate. The separator plate has a (first) sheet width and height, while the tab panel has a (second) panel width and height that are less than the (first) sheet width and height, respectively.The tab pocket may also include a tab flap projecting from one side of the tab panel; the tab flap may be pressed against and fixedly attached to the tab panel to collectively form the tab chamber therebetween. In this case, the tab flap may have a (third) height that is less than the height of the separator plate and the height of the tab panel. To simplify design and manufacture, it may be desirable that the separator plate and tab pocket, including the tab flap and tab panel, be integrally formed from the electrically insulating material as a unitary, one-piece structure. Another possibility is that the separator plate, the tab flap, and the tab panel each have a particular polyhedral shape (e.g., a square or rectangular polyhedron) with a particular size (e.g., the total surface area).In all disclosed vehicles, methods, and devices, the reference electrode tab may be fixedly attached to the tab pocket via an electrically conductive adhesive. As a further option, the reference electrode tab may comprise a substantially flat, rectangular tab body, one (first) side of which has a panel-facing (first) surface provided with a non-smooth surface texture. On the opposite side of the flap body there is a further (second) side with a (second) surface facing the flap, which may likewise be provided with a non-smooth surface texture. In this case, the electrically conductive adhesive may be on one or both of the surfaces of the tab body having the non-smooth surface texture. In this case, the non-smooth surface texture may include depressions, grooves, cross-hatched grooves, sinusoidal grooves, horizontal grooves, and / or oblique grooves.In all disclosed vehicles, methods, and devices, the reference electrode tab may be made in whole or in part of gold, gold plated plastic, aluminum, nickel, copper, copper plated aluminum, stainless steel, and so forth. As another option, the electrically conductive adhesive may be an air, heat and / or UV cured adhesive, may include a filler material, a conductive additive material and / or a binder material, and may have an epoxy base, an acrylate base and / or a silicone base. Optionally, the reference electrode tab may comprise an elongate tab body, wherein at least 50% of the tab body protrudes from the chamber opening. It may be desirable that the proximal (first) end of the reference electrode tab disposed within the tab chamber is spaced from the end of the separator plate from which the tab pocket protrudes.Brief Description of the DrawingsFIG. 1 is a partial schematic side view of a representative motor vehicle powered by an electrified powertrain with a motor-generator unit powered by a traction battery pack including battery cells with in-stack reference electrodes in accordance with aspects of the present description. FIG. 2 is a schematic illustration of a representative electrochemical device with which aspects of the present description may be practiced. FIG. 3 is a top view of a representative multifunctional electrode separator assembly with a built-in reference electrode for an electrode stack of an electrochemical device in accordance with aspects of the present description. FIG. 4 is a process flow diagram illustrating a representative method of manufacturing an electrode separator assembly with a built-in reference electrode in accordance with aspects of the present description.DETAILED DESCRIPTIONReferring now to the drawings, wherein like reference numerals refer to like features throughout the several views, there is shown in FIG. 1 a representative motor vehicle, generally designated 10, which is shown herein as an electric-powered sedan for discussion purposes. The illustrated motor vehicle 10-also referred to herein briefly as a "motor vehicle" or "vehicle"-is merely an example application with which novel aspects of this description may be practiced. Likewise, the inclusion of the present concepts in an FEV powertrain should be understood as a non-limiting implementation of the disclosed features. It will be appreciated that aspects and features of this description may be applied to other electrochemical device form factors, may be incorporated into any logically relevant type of motor vehicle, and may be utilized for both automotive and non-automotive applications. Moreover, only selected components of the motor vehicles and battery assemblies are shown and described in detail herein. Nevertheless, the vehicles and assemblies discussed below may include numerous additional and alternative features and other available peripheral components to perform the various methods and functions of this description.The representative vehicle 10 of FIG. 1 is originally equipped with a central telecommunications and information unit 14 ("telematics") that wirelessly communicates, for example, via cell towers, satellite services, and so forth, with a remote cloud computing host service 24 (e.g., ONSTAR®). Other in-vehicle hardware components 16 shown in FIG. 1 include, by way of non-limiting examples, a video electronic display device 18, a microphone 28, audio speakers 30, and various user input controls 32 (e.g., buttons, buttons, switches, touch screens, and so forth). These hardware components 16 function as a human-machine interface (HMI) that allows the user to communicate with the telematics unit 14 and other components that are both located in and remote from the vehicle 10. The microphone 28 allows the occupant to input verbal commands, for example. Conversely, the speakers 30 provide acoustic output to the vehicle occupant and may be either a stand-alone speaker intended for use with the telematics unit 14, or they may be part of an audio system 22. Audio system 22 is operatively connected to a network connection interface 34 and audio bus 20 for receiving analog information and reproducing it as sound via one or more speaker components.The network connection interface 34 is communicatively coupled to the telematics unit 14. Suitable examples thereof are twisted pair / fiber Ethernet switches, parallel / serial communication buses, local area network (LAN) interfaces, controller area network (CAN) interfaces, and the like. The network connection interface 34 allows the vehicle hardware 16 to send and receive signals among each other and with systems and subsystems both onboard and offboard the vehicle body 12. This allows the vehicle 10 to perform various vehicle functions, such as modulation of powertrain power, activation of a vehicle braking system, control of vehicle steering, regulation of charging and discharging of vehicle batteries, and other automated functions. For example, telematics unit 14 may receive and transmit signals from / to a powertrain control module (PCM) 52, an onboard charging module (OBCM) 54, an electronic battery control module (EBCM) 56, a steering control module (SCM) 58, a brake system control module (BSCM) 60, and various other vehicle ECUs.With continued reference to FIG. 1, telematics unit 14 is an in-vehicle computing device that provides a mix of services both singly and through its communication with other networked devices. This telematics unit 14 generally consists of one or more processors 40, each of which may be implemented as a discrete microprocessor, an application specific integrated circuit (ASIC), or a special purpose control module. The vehicle 10 may provide centralized vehicle control via a central processing unit (CPU) 36 operatively coupled to an IC real-time clock (RTC) 42 and one or more electronic storage devices 38, each of which may take the form of a CD-ROM, a solid state drive (SSD), a hard disk drive (HDD), a semiconductor memory, and so forth.Long-range communication (LRC) with off-vehicle devices may be via a cellular communication component, a navigation and location component (e.g., GPS transceiver), or a wireless modem, all of which are collectively shown at 44. Short-range communication (SRC) may be provided via a short-range wireless communication device 46 (e.g., a Bluetooth® unit), a dedicated short-range communication component (DSRC) 48, and / or a dual antenna 50. It will be appreciated that the vehicle 10 may be implemented without one or more of the components listed above, or optionally may include additional components and functions desired for a particular end application. The communication devices described above may provide the data exchange as part of periodic broadcast in a vehicle-to-vehicle communication system (V 2V) or a vehicle-to-general communication system (V 2X).The CPU 36 receives sensor data from one or more sensing devices using, for example, photodetection, radar, laser, ultrasound, optics, infrared, or other suitable technologies, including short-range communication (e.g., DSRC) or ultra-wide-band (UWB) radio technologies, for example, to perform automated vehicle operation or vehicle navigation service. According to the illustrated example, the motor vehicle 10 may be equipped with one or more digital cameras 62, one or more range sensors 64, one or more vehicle speed sensors 66, one or more vehicle dynamics sensors 68, and the required filtering, classifying, merging, and analysis hardware and software for processing raw sensor data. The type, placement, number, and interoperability of the distributed array of vehicle sensors may be adjusted individually or jointly to a particular vehicle platform to achieve a desired level of autonomous vehicle operation.To propel the motor vehicle 10, an electrified powertrain is capable of generating and transmitting a traction torque to one or more of the vehicle's drive wheels 26. The powertrain is illustrated in FIG. 1 by a traction electric motor 78 connected to a rechargeable energy storage system (RESS), which may be in the form of a chassis-mounted traction battery pack 70. The battery pack 70 may include one or more battery modules 72 each housing a group of electrochemical battery cells 74, for example, pouch, can, or prismatic type lithium-ion or lithium-polymer battery cells. One or more electric machines, such as a multi-phase permanent magnet motor / generator (M) unit 78, receive electrical energy from and optionally provide electrical energy to the battery pack 70. A high voltage electrical system including an inverter module (PIM) 80 electrically connects the battery pack 70 to the motor / generator unit(s) 78 and modulates the transfer of electrical current between those units. The battery pack 70 may be configured such that the module management, cell sensing, and module-host communication functions are integrated directly into each module 72 and are wirelessly provided via a wireless cell monitoring unit (CMU) 76.Referring now to FIG. 2, an exemplary electrochemical device is shown in the form of a rechargeable lithium battery 110 that powers a desired electrical load, such as the motor 78 of FIG. 1. The battery 110 includes a series of electrically conductive electrodes, namely a first (negative or anode) working electrode 122 and a second (positive or cathode) working electrode 124, stacked and packaged in an outer protective housing 120. The designation of one of the two working electrodes 122, 124 as an "anode" or "cathode" or "positive" or "negative" does not mean that the electrodes 122, 124 are limited to a particular polarity, as the system polarity may change depending on whether the battery 110 is operating in a charge or discharge mode. At least in some configurations, the cell housing 120 (or "cell housing") may take a can-like cylindrical construction, a shell-like pouch construction, or a box-like prismatic construction made of aluminum, nickel-plated steel, ABS, PVC, or other suitable material or composite material. The surfaces of a metallic cell case may be provided with a polymer coating to isolate the metal from the inner cell elements and from adjacent cells. Although FIG. 2 shows a single galvanic mono-cell unit enclosed within the cell housing 120, the housing 120 may also accommodate a stack or roll of mono-cell units (e.g., five to 500 cells or more).The anode electrode 122 may be fabricated with an anode electrode active material capable of accepting lithium ions during a battery charging operation and releasing lithium ions during a battery discharging operation. In at least some embodiments, anode electrode 122 is made in whole or in part of a lithium metal, such as lithium aluminum (LiAl) alloy materials having a Li / Al atomic ratio (as indicated by an atomic percentage (at %) of an atomic ratio relative to a total number of atoms) in a range of 0 at %≤Li / Al<70 at %, and / or aluminum alloys having an Al atomic ratio >50 at % (e.g., lithium metal is melted). Further examples of suitable anode electrode active materials include carbonaceous materials (e.g., graphite, hard carbon, soft carbon, and so forth), silicon, silicon-carbon composites (silicon-graphite composite), Li 4 Ti 5 O 12, transition metals (alloy types, e.g., Sn), metal oxides / sulfides (e.g., SnO 2, FeS, and the like), and so forthWith continued reference to FIG. 2, the cathode electrode 124 may be fabricated with a cathode electrode active material capable of delivering lithium ions during a battery charging operation and receiving lithium ions during a battery discharging operation. The cathode material 124 may include, for example, lithium transition metal oxide, phosphate (including olivines), or silicate, such as LiMO 2( M=Co, Ni, Mn, or combinations thereof), LiM 2 O 4( M=Mn, Ti, or combinations thereof), LiMPO 4( M=Fe, Mn, Co, or combinations thereof), and LiXM'2-xO4(M, M'=Mn, or Ni). Further non-limiting examples of suitable cathode electrode active materials are lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese aluminum oxide (NCMA), and other lithium transition metal oxides.Inside the battery cell case 120 of FIG. 2 and between each paired pair of working electrodes 122, 124, an electrically insulating porous separator 126 is disposed. The porous separator 126 may be in the form of an electrically non-conductive, ion-transporting microporous or nanoporous polymeric separator plate. The separator 126 may be a sheet-like structure consisting of a polyolefin porous membrane, for example, having a porosity of about 35% to about 65% and a thickness of about 10-30 micrometers. Electrically non-conductive ceramic particles (e.g., silica) may be deposited on the porous membrane surfaces of separators 126. The porous separator 126 may include a non-aqueous liquid electrolyte composition, a solid electrolyte composition, and / or a quasi-solid electrolyte composition, collectively referred to as 130, which may also be present in the negative electrode 122 and the positive electrode 124.A negative electrode current collector 132 of the electrochemical battery cell 110 may be disposed on or near the negative electrode 122, and a positive electrode current collector 134 may be disposed on or near the positive electrode 124. The negative electrode current collector 132 and the positive electrode current collector 134 collect and transport free electrons to and from an external circuit 140, respectively. An interruptible external circuit 140 having a load 142 is connected to the negative electrode 122 via its respective current collector 132 and electrode tab 136 and to the positive electrode 124 via its respective current collector 134 and electrode tab 138.The porous separator 126 may function as both an electrical insulator and a mechanical support structure by being interposed between the two electrodes 122, 124 to prevent the electrodes from physically contacting each other and thus causing a short circuit. In addition to providing a physical barrier between the electrodes 122, 124, the separator 126 may provide a path with minimal resistance for internal passage of lithium ions (and related anions) during the cycle of lithium ions to facilitate the function of the battery 110. In some configurations, the porous separator 126 may be a microporous polymeric separator containing a polyolefin. The polyolefin may be a homopolymer consisting of a single monomer component or a heteropolymer consisting of more than one monomer component and may be either linear or branched. In an all-solid-state battery, the role of the separator may be partially / completely taken over by a solid electrolyte layer.In operation as a rechargeable energy storage system, the battery 110 generates electrical power that is transferred to one or more loads 142 connected to the external circuit 140. The load 142 may be any number of electrical devices. Some non-limiting examples of power-consuming and power-generating devices are electric motors for hybrid electric vehicles and fully electric vehicles, photovoltaic cell arrays, stand-alone power plants and portable power units, server systems, wind turbines, and so forth. The battery 110 may include a variety of other components, which are not shown here for simplicity and brevity, but are still readily available. For example, the battery 110 may include one or more gaskets, pole caps, tabs, battery poles, cooling and charging devices, and other commercially available components or materials that may be located on or within the battery 110. Moreover, the size and shape, as well as the operating characteristics of the battery 110 may vary depending on the particular application for which it is designed.Here, multifunctional electrode separator assemblies with robust and compatible reference electrode terminals are presented that allow current flow through the separator plate for measurement and control of the working electrode potential. The separator assembly uses a folded "sandwich" tab pocket with an electrically conductive adhesive to securely attach and operatively connect a reference electrode tab to the separator plate. This space saving approach for connecting tabs uses a tab pocket of a flexible substrate having a plate integrally formed with the upper end of the separator plate and projecting longitudinally therefrom. A foldable tab structure extends transversely from a lateral side of this tab panel; the tab is folded transversely and adhered to the tab panel to create a pocket having a double-sided bond area that substantially increases the fatigue strength and fracture strength of the shell. In addition to preventing peel failure, this tab pocket design may also increase (e.g., double) the contact area between the reference electrode tab and the separator plate to resist shear fractures.Furthermore, simplified and efficient production methods for the production of multifunctional separators with built-in reference electrodes are presented here. In one example, a manufacturing process for assembling a multifunctional electrode separator may begin by stamping, cutting, or forming an electrically conductive workpiece from a metal blank or sheet stock roll and then perform a surface preparation process for roughening the lower 40-65% of the front and back surfaces of the workpiece. After the application of the above-mentioned surface texture, the workpiece can be cleaned and, if desired, passed through further preprocessing steps. At this time, a conductive adhesive is applied to the textured areas of the front and back surfaces of the workpiece, which may be done by gluing, knife-off, and / or air blowing. The textured and coated workpiece is then pressed against the plate or tab portion of the tab pocket that protrudes from the separator plate. The tab flap is simultaneously folded onto the tab panel to firmly secure the reference electrode tab to the separator plate and form the tab pocket enclosing at least the lower half of the reference electrode tab.As mentioned above, the separator plate may be made as a unitary, one-piece microporous or nanoporous structure formed from an electrically non-conductive ion transporting material such as a polyolefin (e.g. polyethylene (PE), polypropylene (PP) or a mixture of PE and PP), or it may be a multilayer structure such as laminated porous films of PE and / or PP. The material of the tab may include, but is not limited to, gold (Au), gold plated plastic, aluminum (Al), nickel (Ni), copper (Cu), copper plated aluminum, stainless steel, and so forth. In contrast, the conductive adhesive material may include, but is by no means limited to, an air-cured conductive adhesive, a heat-cured conductive adhesive, a UV-cured conductive adhesive, which may include an electrode bonding material, a conductive additive, and / or a mixture of conductive particles and epoxy, and so forth. The separators presented may help reduce the footprint for the reference electrode tab, which in turn reduces the overall size and weight of the electrochemical device. Other advantages include reducing manufacturing complexity and processing time for manufacturing / using multifunctional separator assemblies.Referring now to FIG. 3, another non-limiting example of an electrochemical device is shown, shown as a rechargeable battery assembly 210 for storing and supplying high voltage electrical energy, used to propel an electrically powered vehicle, such as the FEV vehicle 10 of FIG. 1, for example. This battery assembly 210 may be part of a high ampere capacity deep cycle vehicle battery system configured for, for example, about 350 to 1200 high voltage direct current (HVDC) or more depending on the desired vehicle range, total vehicle weight, and power levels of the various accessory loads that draw electrical energy from the RESS. Although different in appearance, it is conceivable that all features and options described above with respect to the battery pack 70 of FIG. 1 and the lithium battery cell 110 of FIG. 2 may be incorporated into the battery assembly 210 of FIGS. 3 and 4 individually or in any combination, and vice versa.As a representative point of similarity to the battery pack 70 of FIG. 1 and the battery 110 of FIG. 2, the battery assembly 210 of FIG. 3 may include a liquid-tight, electrically-insulated battery assembly housing 220 (also referred to as "device housing") to store therein an electrolyte material 212 chemically configured to conduct ions (e.g., lithium hexafluorophosphate (LiPF6) in an organic solution). Also within the device housing 220 in electrochemical contact with the electrolyte 212 is an electrode stack 214 consisting of one or more (first) working electrodes 222 interleaved and juxtaposed with one or more (second) working electrodes 224. While a single pair of working electrodes is illustrated in FIG. 3, each electrochemical device may include multiple electrode pairs (e.g., 10-20 or more) stacked and connected in parallel or in series to store and supply electrical energy.Interposed between the two adjacent electrodes 222, 224 is an electrode separator assembly 250 also disposed within the device housing 220 in electrochemical contact with the electrolyte 212. In device configurations having multiple paired pairs of electrodes of opposite polarity, a corresponding electrode separator assembly 250 may be inserted between one, some or all of the paired pairs. According to the illustrated example, the electrode separator assembly 250 may substantially include or consist of a separator plate 230, a tab pocket 252 protruding from an upper end of the separator plate 230, and a reference electrode tab 254 (also referred to herein as a "reference electrode tab") fixedly attached to the tab pocket 252. The separator plate 230 of FIGS. 3 and 4 may be constructed similar or identical to the porous separator 126 of FIG. 2 and thus may include all corresponding features and options thereof, including the fact that it is formed in whole or in part from an electrically insulating but porous material.In contrast to the separator 126 of FIG. 2, the separator plate 230 of FIGS. 3 and 4 may include a reference electrode. As shown, the reference electrode may be supported by or otherwise integrated with the separator plate 230 (and is therefore not labeled with a separate reference number). For example, a dried electrically conductive electrode material may be pressed onto a surface of the sheet 230 and then fired to form a reference electrode. The reference electrode may be formed in whole or in part from an electrically conductive material in a similar manner to the two working electrodes 122, 124 of FIG. 2 ; however, the reference electrode tab 254 may differ in shape, size and function from the working electrodes 122, 124.With continued reference to the representative electrochemical device of FIG. 3, the tab pocket 252 may be fabricated with a "L-shaped" construction prior to assembly, characterized by a tab panel 256 that longitudinally protrudes from and is coplanar with the separator plate 230 and a tab flap 258 that is coplanar with and transversely protrudes from a lateral (right) side of the tab panel 256. After assembly, the tab pocket 252 may have an "I-shaped" construction in which the tab flap 258 is folded across, pressed against, and fixedly attached to the tab panel 256 to collectively form a tab chamber 251 therebetween, as best seen in the inspection view of FIG. 3. It may be desirable for both the upper and lower ends of the tab chamber 251 to have respective chamber openings 253 and 255 (as shown); alternatively, only the upper end of the chamber 251 may have a respective opening 253. To facilitate manufacture and assembly, it may be desirable that the separator plate 230 and tab pocket 252, including the tab panel 256 and tab flap 258, be integrally formed from the same electrically insulating material as a unitary, one-piece structure.According to the example shown, the separator plate 230, the tab panel 256, and the tab flap 258 may each have a polyhedral shape with a corresponding size. By way of non-limiting example, the sheet 230, the plate 256, and the flap 258 may each be a rectangular polyhedron (prism) having a particular width to height ratio and a particular total surface area on the opposing major surfaces. As shown, the separator plate 230 has a (first) sheet width W S1 and a (first) sheet height H S1, while the tab panel 256 has a (second) plate width W P2, which is less than the sheet width W S1, and a (second) plate height H P2, which is less than the sheet height H S1. In comparison, the flap flap flap has a (third) flap width W F3 and a flap height H F3; the flap width W F3 is smaller than the arc width W S1 and may be approximately equal to or smaller than the panel width W P2 and the flap height H F3 is smaller than the arc height H S1 and may be smaller than or approximately equal to the panel height H P2. It should be noted that the panel 230, panel 256 and flap 258 may take other regular and irregular shapes and may have different individual and relative dimensions than those illustrated in the drawings if desired.The reference electrode tab 254 is secured directly to the tab pocket 252 and indirectly to the separator plate 230 via the tab pocket 252 in FIGS. 3 and 4. A lower (first) end portion of the reference electrode tab 254 may be fixedly secured in the tab chamber 251, while an upper (second) end portion of the reference electrode tab 254 may protrude through the opening 253 in the upper end of the tab chamber 251. Optionally, a proximal tip at the lower end of the reference electrode tab 254 may be exposed through the opening 255 in the lower end of the tab chamber 251. According to the illustrated example, the reference electrode tab 254 includes an elongated rectangular tab body that can protrude at least 50% from the chamber opening 253. Alternatively, 55%-75% of the rectangular tab body may be disposed within the tab chamber 251 to ensure secure attachment between the reference electrode tab 254 and the tab pocket 252. As another option, the lower (first) end of the reference electrode tab 254 disposed in the tab chamber 251 may be disposed a predefined distance (e.g., about 2 mm to 10 mm distance) from the upper end of the separator plate 230, for example, to ensure that the reference electrode tab 254 does not interfere with ion flow through the film 230. Moreover, the lower end of the tab body may take other geometries, for example, an enlarged rectangle or circle, to increase the contact area between the reference electrode tab 254 and the tab pocket 252.To ensure a secure connection between the reference electrode tab 254 and the tab pocket 252, the reference electrode tab 254 may be fixedly connected to the tab pocket 252 via an electrically conductive adhesive 260. The conductive adhesive layers 260 may take any of the options described herein, including air cured, thermoset, and UV cured conductive adhesives, conductive additives containing an electrode bonding material, and conductive additives with a mixture of conductive particles encapsulated in epoxy. For example, the inspection view of FIG. 3 shows the reference electrode tab 254 having a pair of opposing (first / front and second / rear) sides; the front side has a bottom (first / front) surface and the back side has a bottom (second / rear) surface, both of which are located within the tab pocket 252. One or both of these surfaces may be machined or shaped to have a non-smooth surface texture 261. The electrically conductive adhesive 260 may be applied to the reference electrode tab 254 so as to be on and substantially cover the surface texture 261 on the front and / or back surfaces. The surface texture 261 may be provided with any suitable surface texture treatment that improves adhesion with the electrically conductive adhesive 260, such as depressions, grooves, cross-hatched grooves, sinusoidal grooves, horizontal grooves, and / or oblique grooves. The surface texture may be created on two planes, a surface profile plane and a roughness plane. On the profile plane, the texturing can consist of linear grooves, cross-hatchings, depressions and so on in the submillimeter range. At the roughness plane, texturing may have an average roughness height (Ra) of at least 0.5 micrometers (μm) and a developed interfacial ratio (Sdr) of at least 50%.After the assembly, the electrode separator assembly 250 may be interposed between the two working electrodes 222, 224; thereby, the separator plate 230 may physically separate the three electrodes 222, 224, 254 (anode, cathode, and reference electrodes). By mounting the reference electrode tab 254 on the tab pocket 252-a flexible surface extension of the non-conductive separator plate 230-the substrate of the separator plate 230 can also serve as electrical insulation for the reference electrode tab 254. The reference electrode tab 254 has a predefined "stable" potential and can therefore be paired with one of the working electrodes 222, 224 to measure the voltage across the paired electrodes (e.g., cathode / reference or anode / reference). In this way, a battery system controller is capable of measuring an absolute potential of the paired electrodes based on the predefined potential of the reference electrode tab 254. It is contemplated that the disclosed multifunctional separators are not limited to reference electrodes and may also be applied to other electrodes.FIG. 4 shows a process flow diagram illustrating a representative method 300 for manufacturing electrode separator assembly with built-in reference electrodes. Some or all of the operations illustrated in FIG. 4 and described in more detail below may represent an algorithm corresponding to non-transitory processor-executable instructions stored, for example, in a main, auxiliary, or remote memory and executable, for example, by an electronic controller, processing unit, special purpose control module, logic circuit, or other module or device or network of modules / devices to perform any or all of the functions described above and below in connection with the disclosed concepts. It should be appreciated that the order of execution of the illustrated operation blocks may be changed, that additional operation blocks may be added, and that some of the operations described herein may be modified, combined, or eliminated. Although aspects of the present description are discussed in the context of rectangular separator plate and reference electrode tab, those skilled in the art will appreciate that the present description is applicable to workpieces of any size, shape, and cross-section.The method 300 may begin with processor-executable instructions executed by a programmable controller or control module or similar suitable processor to invoke a closed-control sequence initialization procedure for performing the various operations depicted. The first stages of the fabrication process may include the provision, access, fabrication, and / or use (collectively "provisioning") of the various materials, tools, and machines needed to fabricate the electrode separator assembly. Additional control commands, tolerances and parameters may be input at this time before a desired assembly process begins. After all required pre-operations are complete, the method 300 proceeds to a first process step (1) in which an electrically conductive workpiece 254A is stamped, cut, or otherwise produced from a metal blank, sheet stock roll, or metal coated plastic substrate.Thereafter, the method 300 proceeds to a second process step (2) to apply a non-smooth surface texture to one or more selected portions of one or more major surfaces of the workpiece 254A to produce a textured workpiece 254B. As mentioned above, a bottom portion (e.g., about 40-65%) of the front and / or back surfaces of the workpiece 254A may be roughened with grooves, channels, recessed grooves, and so forth. At this time, the textured workpiece 254B may be cleaned and undergo other metal pretreatment processes (e.g., overflow rinse-free, polishing, air drying, and so forth). In a third process step (3), the process 300 applies an adhesive to selected portions of the textured and cleaned workpiece 254B to define a coated workpiece 254C. After adhering the un-roughened surface(s) of the textured workpiece 254B, for example with a low bond pressure sensitive adhesive tape (PSA), an electrically conductive adhesive may be applied to the roughened surface(s) of the textured workpiece 254B, for example by knife scraping or air blowing.With continued reference to FIG. 4, the method 300 continues with a fourth method step (4) to attach the adhesive coated workpiece 254C to an electrically insulating, ionically conductive separator plate. As shown, the textured and coated workpiece 254C is pressed against a portion of the tab panel 256 (or a portion of the tab flap 258) of a tab pocket 252 that extends coplanarly from an end of a separator plate 230. The workpiece 254C is placed to electrically connect to a reference electrode supported by the separator plate 230, for example, via the electrically conductive adhesive. The method 300 then performs a fifth process step (5) to form a tab pocket around the workpiece 254C, thereby functionally securing it to the separator. For example, FIG. 4 illustrates how the tab flap 258 is folded onto and pressed against the tab panel 256; the electrically conductive adhesive 260 thereby firmly secures the reference electrode tab 254 to the panel 256 and the tab 258 and simultaneously forms the tab pocket 252 enclosing at least the lower half of the reference electrode tab 254.

Claims

An electrochemical device (110) comprising: a device housing (120); an electrolyte (212) located within the device housing (120) and configured to conduct ions; an electrode stack (214) located within the device housing (120) and comprising first and second working electrodes (122, 124) in electrochemical contact with the electrolyte (212); and an electrode separator assembly (250) disposed between the first and second working electrodes (122, 124), the electrode separator assembly (250) comprising: a separator plate (230) formed of an electrically insulating material and comprising a reference electrode; a tab pocket (252) protruding from an end of the separator plate (230) and defining a tab chamber (251) having a chamber opening (253); and a reference electrode tab (254) attached to the tab pocket (252) and formed of an electrically conductive material, the reference electrode tab (254) having a first end disposed in the tab chamber (251) and a second end protruding from the chamber opening (253); the tab pocket (252) having a tab panel (256) protruding from and coplanar with the separator plate (230), the separator plate (230) having a first width and a first height, and the tab panel (256) having a second width and a second height that are less than the first width and the first height, respectively.The electrochemical device (110) of claim 1, wherein the tab pocket (252) further comprises a tab flap (258) protruding from a side of the tab panel (256), the tab flap (258) pressed against and fixedly attached to the tab panel (256) to collectively define the tab chamber (251) therebetween.The electrochemical device (110) of claim 2, wherein the tab flap (258) has a third height that is less than the first height of the separator plate (230) and the second height of the tab panel (256).The electrochemical device (110) of claim 2, wherein the separator plate (230) and the tab pocket (252), including the tab flap (258) and the tab panel (256), are integrally formed as a one-piece structure with the electrically insulating material.The electrochemical device (110) of claim 2, wherein the separator plate (230), the tab flap (258), and the tab panel (256) each have a polyhedral shape having a particular size.The electrochemical device (110) of claim 1, wherein the reference electrode tab (254) is fixedly secured to the tab pocket (252) via an electrically conductive adhesive (260).The electrochemical device (110) of claim 6, wherein the reference electrode tab (254) has a first side with a first surface that includes a non-smooth surface texture (261), the electrically conductive adhesive (260) being on the first surface with the non-smooth surface texture (261).The electrochemical device (110) of claim 7, wherein the reference electrode tab (254) has a second side opposite the first side with a second surface including the non-smooth surface texture (261), wherein the electrically conductive adhesive (260) is further on the second surface with the non-smooth surface texture (261).The electrochemical device (110) of claim 8, wherein the non-smooth surface texture (261) comprises depressions, grooves, cross-hatched grooves, sinusoidal grooves, horizontal grooves, and / or oblique grooves.

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