WO2020261214A1

WO2020261214A1 - Modular battery formation system and battery conditioning apparatus

Info

Publication number: WO2020261214A1
Application number: PCT/IB2020/056080
Authority: WO
Inventors: Kent Thoresen
Original assignee: Exro Technologies Inc.
Priority date: 2019-06-27
Filing date: 2020-06-26
Publication date: 2020-12-30

Abstract

A modular battery formation system includes terminals to provide electrical connections to batteries and a controller having a processor. A number of chargers are communicatively coupled to the controller, each of the chargers operatively coupled to output charging voltages and to receive discharging voltages, based on a defined formation protocol, via a pair of terminals. Each charger includes a microcontroller, and one or more solid state switches, in communication with the microcontroller, operatively coupled to receive input power and to selectively output charging voltages and receive discharging voltages.

Description

MODULAR BATTERY FORMATION SYSTEM AND

BATTERY CONDITIONING APPARATUS

TECHNICAL FIELD

The present disclosure generally relates to a modular battery formation system, and more particularly, to a system having a number of chargers which are each operatively coupled to output a voltage to terminals of a corresponding battery. The disclosure also relates to a battery conditioning apparatus.

DESCRIPTION OF THE RELATED ART

Prior to use, batteries undergo a stage in the manufacturing process called battery formation. The purpose of battery formation is to activate battery chemistries and to determine the characteristics of the battery. In this process, newly assembled batteries are initially charged and discharged with high accuracy using a pattern of applied voltage and current. The battery formation process has a significant impact on battery life, quality, and cost.

Battery formation is often the bottleneck of battery production because it can take up to several days, or even weeks, depending on the cell manufacturer and cell chemistry. The battery formation process relies on specialized battery formation equipment to charge and discharge large quantities of batteries with a high degree of voltage and current accuracy. Battery formation equipment is typically expensive to purchase, operate, and maintain. Furthermore, in conventional approaches, an entire set of batteries being processed is subjected to the same voltage and current patterns, such that a change in those patterns affects all of the batteries undergoing the formation process.

BRIEF SUMMARY

A battery formation system may be summarized as including a plurality of terminals to provide electrical connections to batteries, a controller having a processor, and a plurality of chargers communicatively coupled to the controller, each of the chargers operatively coupled to output charging voltages and to receive discharging voltages, based on a defined formation protocol, via a pair of terminals of the plurality of terminals. Each charger includes a microcontroller, and one or more solid state switches, in communication with the microcontroller, operatively coupled to receive input power and to selectively output charging voltages and receive discharging voltages.

A battery conditioning apparatus may be summarized as including a system chassis, one or more fixtures sized and shaped to be received in the chassis, each fixture having a plurality of terminals to provide electrical connections to batteries, a controller positioned in the chassis, the controller having a processor, and a plurality of chargers positioned in the chassis, the plurality of chargers communicatively coupled to the controller, each of the chargers operatively coupled to output charging voltages and to receive discharging voltages, based on a defined formation protocol, via a pair of terminals of the plurality of terminals of each fixture. Each charger includes a microcontroller, and one or more solid state switches, in communication with the microcontroller, operatively coupled to receive input power and to selectively output charging voltages and receive discharging voltages.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1A depicts a battery tray which has an array of receptacles to hold

batteries for formation and testing, according to at least one disclosed implementation.

Fig. 1 B depicts a battery formation/testing system chassis with a number of battery trays, such as the battery tray depicted in Fig. 1A, installed therein, according to at least one disclosed implementation.

Fig. 2 depicts chargers electrically coupled together in a matrix

arrangement to perform battery formation charging and discharging, according to at least one disclosed implementation. Fig. 3 depicts synthesis of an output waveform by combining wavelets in various combinations, according to at least one disclosed implementation.

Fig. 4 depicts output waveform synthesis using wavelets which are in phase and in quadrature phase, according to at least one disclosed implementation.

Fig. 5 is a schematic of a charger in the form of a module providing

wavelet generation, according to at least one disclosed

implementation.

Fig. 6 depicts electronic switching components arranged to form a

rectifier/switch circuit for use in a charger such as the type depicted in Fig. 5.

Fig. 7 depicts two examples of battery formation protocols for a Lithium ion battery, according to at least one disclosed implementation.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed implementations. However, one skilled in the relevant art will recognize that implementations may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with computer systems, server computers, and/or communications networks have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the implementations.

Unless the context requires otherwise, throughout the specification and claims that follow, the word "comprising" is synonymous with "including," and is inclusive or open- ended (i.e., does not exclude additional, unrecited elements or method acts). Reference throughout this specification to "one implementation" or "an implementation" means that a particular feature, structure or characteristic described in connection with the implementation is included in at least one implementation. Thus, the appearances of the phrases "in one implementation" or "in an implementation" in various places throughout this specification are not necessarily all referring to the same

implementation. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more implementations.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the context clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are for convenience only and do not interpret the scope or meaning of the implementations.

Fig. 1A shows a battery tray 100 which has an array of receptacles 110 to hold batteries 120 for formation and testing. The batteries 120 are inserted into the receptacles, e.g., by a robot. One of the terminals of each of the batteries 120 is brought into electrically conductive contact with a terminal 610 (see Fig. 6) of the battery tray, for example a respective terminal located at the bottom of each receptacle 110. Various other types of fixtures may also be used to hold the batteries 120. For example, the batteries 120 may be inserted between a pair of clamping terminals which extend from a plate or panel. The batteries 120 are typically electrochemical battery cells, and typically include a first terminal (e.g., a positive terminal or cathode) and a second terminal (e.g., negative terminal or anode), across which a voltage is developed. The batteries 120 may employ any of a variety of known or later developed battery chemistries, for instance Lithium ion chemistry.

The tray 100 is inserted into a battery formation/testing system chassis 150, as shown in Fig. 1 B, e.g., by a robot. Insertion brings the other terminal of each of the batteries 120 into electrically conductive contact with another terminal 630 (see Fig. 6) of the battery formation/testing system chassis 150. In operation, the battery conditioning apparatus may apply battery formation voltages/currents and/or detect or measure characteristics (i.e. , battery characteristics) of individual ones of the batteries 120. For example, the tray 100 may provide a common ground connection for all of the batteries 120, while terminals applied to the tops of the batteries 120 separately apply individual formation voltages to each battery 120, as explained in further detail below.

Operation of the battery formation stage may advantageously create a solid electrolyte interphase (SEI) on the anode and to create the cathode electrolyte interphase (CEI). The battery conditioning apparatus may additionally or alternatively collect battery cell performance measurements, such as impedance and current capacity, during the formation process for process and/or quality analysis. SEI and CEI layers are created by deposition in the formation process when the cells take their first charge. Since the electrolyte lithium salt is dissolved in organic solvent, it reacts vigorously with carbon anode during the initial formation charge and builds a thin SEI layer by the moderated charge rate with 0.1 C-rate current (“C-rate” or“C” refers to a discharge current which will discharge the entire battery in one hour). To complete the formation process, 3-5 cycles at 0.1 C at room temperature and 3-5 cycles at higher C-rate at higher temperature may be required to control the thickness of the SEI layer - this may take several days. The thick SEI layer increases the internal impedance of the battery, which reduces current capability and decreases charging and discharging cycle times. Unlike the battery standard charging procedures, battery formation process begins with a low current, 0.1 C, and variable output voltage which requires the reliable battery formation power supply to provide stable charging and discharging current.

As illustrated in Fig. 2, a plurality of chargers 80 (also referred to as“modules” herein), which may be electrically coupled together in a matrix 200 arrangement including m x n chargers 80. The batteries 120 to which formation is to be performed may be stored in a fixture, e.g., the tray 100 depicted in Fig. 1 , and may be individually supplied with a formation voltage (or the formation voltage may be defined in terms of a formation current) by a corresponding charger 80 of the plurality of chargers 80. The modules 80 may be connected together by a first terminal (T1) of each module 80 to a common ground 210. A second terminal (T2) of each module 80 may be connected to one or more receptacles 110 of the battery tray 100 (e.g., by wired connections, not shown, to terminals in each receptacle). In the depicted example, each module 80 has a coil 320 to receive power via an inductive connection. In alternative embodiments, the coil 320 of each module may be replaced with a wired connection to an AC power supply (not shown). As shown in Fig. 3, to provide stable and precise charging currents and voltages, a charging voltage output 10 provided by the battery formation power source 20 may be synthesized by combining the outputs of a number of modules 80 to selectively switch a number of smaller wavelets 30 which have a magnitude p and a duration d which are considerably smaller and shorter respectively than a magnitude M and a duration D of the charging voltage output of an individual module 80. If required, a filter, for example implemented by a combination of inductors and capacitors, may be employed to filter high-order harmonic signal components present in the output 10 from the battery formation power source 20. A benefit of this approach is that the individual wavelets 30 are capable of being switched rapidly to dynamically change characteristics of the battery formation power source 20. Although the wavelets 30 are depicted as being in phase and of similar size, it will be appreciated that the battery formation power source 20 may be constructed so that the wavelets 30 have mutually different polarities, mutually different relative phases and mutually different magnitudes, e.g., by including phase shifters or other phase or amplitude components.

Referring to Fig. 4, in implementations, a plurality of modules 80 (see Fig. 2) may be used to generate wavelets 30 which are then selectively combined by binary switching to synthesize an output power waveform. This approach provides the following benefits: (a) wavelet 30 switching can occur at a much lower frequency which reduces switching losses and thereby improves efficiency, and also enables lower-performance silicon switching devices to be utilized, and (b) loss of supply of one wavelet 30 does not cause catastrophic failure of the battery formation power source 20 because if one or more of the modules 80 become defective, such that their wavelets 30 are not available for output waveform synthesis, the control unit 70 is operable to select from among other available wavelets 30 to provide a next-best possible synthesis of the output 10.

Fig. 4 depicts producing a combination of wavelets 30 to synthesize output waveforms, e.g., sinusoidal waveforms, for the combined output 10 of a group of modules 80 by employing wavelets 30 which are mutually in quadrature phase. An approximate half sinusoidal signal 410 is thus generated as illustrated at the top region of Fig. 4 by combining one in-phase wavelet 30A with two quadrature wavelets 30B and three in- phase wavelets 30C, wherein the wavelets are of similar polarity. It is feasible to synthesize a half sinusoidal signal of longer relative duration 430 by combining more wavelets 30D, 30E, 30F, 30G, as further illustrated in Fig. 4. By combining these individual wavelets, the battery formation power source 20 is capable of generating output at any desired frequency, overall waveform shape, voltage magnitude and phase relative to a reference signal. The battery formation power source 20 can generate direct current (DC), thereby avoiding a need for rectification components external to the battery formation power source 20. With conventional battery formation power sources, on the other hand, separate operations of rectification of alternating coil signals to direct current state (DC) may be required and then subsequent waveform generation using electronic devices may be required to generate a synthesized output signal. By such an arrangement, current load can be shared between modules 80 coupled in parallel, and large potentials can be provided at the output 10 by the modules 80 being coupled in series. In implementations, the matrix may include several hundred modules 80 for synthesizing the output 10 of the entire matrix as a sinusoidal signal with relatively little harmonic content, for example less than 1% harmonic content. In implementations, the modules 80 of the matrix may provide mutually different wavelet 30 amplitudes for producing even more accurately synthesized waveforms for the output 10 of a plurality of, or all of, the modules 80.

As shown in Fig. 5, each module 80 is a wavelet 30 generator which includes a coil 320 for interacting with magnetic flux generated by a transformer or other induction source. Alternatively, a pair of terminals may be provided instead of a coil 320, the pair of terminals being operatively connected to an AC source to receive input power. An output of the coil 320 is coupled to a rectifier 330 and then via a switching network 340 to the module output 30. In implementations, the switching network 340 is designed to operate at relatively low switching frequencies, e.g., corresponding to the duration d of the wavelets 30. The switching network 340 is also operable to switch power received during a discharge cycle of a battery formation protocol to a storage/dissipation circuit 345, which is operable to discharge the received power in a resistive load and/or store the received power using a capacitor or super capacitor circuit.

The module 80 includes a bi-directional optical interface 360 to receive control instruction from the control unit 70 and to output diagnostic data and/or confirmatory data to the control unit 70. The interface 360 is able to provide for rapid data rates as well as providing electrical isolation between modules 80 in a robust and cost-effective manner. A microcontroller 350 controls operation of the module 80 at a local level. In implementations, control of the battery formation power source 20 is beneficially executed in a distributed manner between the control unit 70 and the microcontrollers 350 of the modules 80. Moreover, the interface 360 is conveniently implemented using high-speed photodetectors and data-modulated solid-state laser devices. The interface 360 is designed to receive and transmit at various different optical carrier radiation wavelengths, for example in a manner of wavelength division multiplexing (WDM), to enable a single general optical data path to be used within the battery formation power source 20 to control operation of all the modules 80 of the battery formation power source 20. In implementations, each module 80 and its associated electronic components are constructed as a stand-alone mass-produced unit that can easily be replaced, for example even while in operation.

An adaptive control system of the control unit 70 steers power flow within the battery formation power source 20 so that outputs of the individual modules 80 are re arranged in cooperation with all the other modules 80 in real time to produce the desired output 10. Since control electronic components of each module 80 only deal with their own associated pickup coil 320, for example each pickup coil 320 having a maximum power in a range of 5 kW to 10 kW, considerable amounts of power within the battery formation power source 20 can be controlled and modulated with simple mass-produced off-the-shelf electronic switching components. Thus, the battery formation power source 20 eliminates conventional rectification and phase forming stages of conventional systems, thereby providing cost savings, more efficient operation and more reliable operation.

The module 80 is provided with a cooling arrangement 300, for example based upon circulated electrically-insulating silicone cooling oil and/or forced air cooling. The module 80 also includes a releasable mounting arrangement 310 for enabling the module 80 to be adequately mechanically supported, including, e.g., screws, registration pins, rubber bushes and so forth. For example, the modules 80 can be mounted in a stacked configuration with other similar modules 80 or mounted in a chassis 150 (Fig. 1 B) of a battery formation/testing system.

Fig. 6 depicts a circuit 600 in which electronic switching components are arranged to provide a particular implementation of the rectifier 330 and switching network 340 of a module 80 (including the pickup coil 320). In the implementation depicted, a rectification/switching circuit 600 performs the combined functions of the rectifier 330 and the switching network 340. In operation, the circuit 600 is operably connected via its terminals (T 1 , T2) to a battery 120 which is to undergo formation

charging/discharging. In the example depicted, one terminal T1 is connected to a terminal 610 of a receptacle 110 of a battery tray 100 holding the subject battery 120. The terminal 610 of the receptacle 110 is positioned to make electrical contact with a first terminal 620 of the battery 120. The other terminal T2 is connected to a terminal 630 of an upper plate 640 of the battery formation system. The terminal 630 of the upper plate 640 is positioned to make electrical contact with a second terminal 650 of the battery 120.

The circuit can be implemented using a variety of electronic switching components, for example, field effect transistors (FET), bipolar transistors (BJT), triacs, silicon- controlled rectifiers (SCR), Darlington transistors, silicon carbide transistors, silicon germanium transistors, and so forth. In implementations, due to low cost and robustness, the circuit is implemented using silicon controlled rectifiers SCR1 to SCR8, as illustrated. Silicon controlled rectifiers are available packaged, e.g., in flat ceramic capsules which are easily mechanically incorporated into the module 80. The module 80 may include a first safety fuse FS1 for isolating the entire module 80 in the event of gross failure and a second safety fuse FS2 for protecting the coil 320 in the event of gross failure.

The silicon controlled rectifiers SCR include gate terminals which are triggered from the microcontroller 350 of the module 80 (for clarity, these connections are not shown). In implementations, triggering of the silicon controlled rectifiers may be achieved via optical triggering and/or via isolation ferrite pulse transformers. In operation, a silicon controlled rectifier only conducts when triggered at its gate terminal. Conduction through a silicon controlled rectifier ceases when a potential across the device is smaller than a threshold magnitude or the device becomes reversed-biased across its two main terminals. The silicon controlled rectifiers SCR1 to SCR8 are arranged in a bridge-type configuration as illustrated in Fig. 6.

The circuit depicted in Fig. 6 has four conducting modes: (a) a first mode, in which the module 80 provides effectively a short-circuit path between its terminals T1 , T2, (b) a second mode, in which there is an open circuit between the terminals T1 , T2, (c) a third mode, in which a negative wavelet 30 half-cycle is directed from the coil 320 to the terminals T1 , T2, and (d) a fourth mode, in which a positive wavelet 30 half-cycle is directed from the coil 320 to the terminals T1 , T2. In the first mode, the silicon controlled rectifiers SCR3, SCR4, SCR7 and SCR8 are triggered into a conducting state, whereas the silicon controlled rectifiers SCR1 , SCR2, SCR5 and SCR6 are in a non-conducting state. In the second mode, none of the silicon controlled rectifiers SCR1 to SCR8 are in a conducting state - they are all in an open-circuit state. In the third mode, the silicon controlled rectifiers SCR2 and SCR7 are in a conducting state, and the silicon controlled rectifiers SCR1 , SCR3 to SCR6, and SCR8 are in a non conducting state. In the fourth mode, the silicon controlled rectifiers SCR1 and SCR8 are in a conducting state, and the silicon controlled rectifiers SCR2 to SCR7 are in a non-conducting state.

As discussed above with respect to Figs. 3 and 4, the modules 80 can be used to produce wavelets 30 which can be combined to form desired waveforms. The modules 80 are individually controllable, for example, via a general optical data bus from the control unit 70 operable to direct operation of the battery formation power source 20. Such a manner of operation is beneficial because failure of one or a few of the modules 80 merely results in potentially a more coarsely-synthesized output 10. The modules 80 may be powered via a transformer 90 inductively coupled to a coil 320. Alternatively, an alternating current (AC) may be applied to terminals power input terminals provided in lieu of the coil 320. In implementations, the modules 80 may receive an external synchronization signal operable to couple the wavelets 30 generated by the modules 80 to generate an output 10 synchronized to the signal S. However, it will be appreciated that the wavelets can be switched in such a manner that the modules 80, e.g., in combinations of two or more, are also capable of generating a direct current (DC) output 10 as well as an alternating current (AC) output 10.

The variable battery formation power source 20 provides many benefits in comparison to conventional approaches to battery formation power sources. Conceptually, the variable battery formation power source 20 can be considered to be a spatial collocation of small chargers that can be used individually or dynamically rearranged to combine their power outputs in various combinations to charge and discharge connected batteries in accordance with a battery formation protocol. Various measured parameters can be used by the microcontrollers 350 and/or the control unit 70 to control the battery formation power source 20, or even a configuration of several battery formation power sources 20 operating together in a coordinated manner. An example of a measured parameter is temperature within a given module 80, or number of hours a given battery formation power source 20 has been operating.

Fig. 7 depicts two battery formation protocols (i.e., electrolyte interphase formation protocols) for a Lithium ion battery, a first protocol which is referred to as a“baseline protocol” and a second protocol, referred to as an“alternative protocol,” which is meant to shorten the time require for formation - the graph showing a normalized time scale versus the voltage between the anode and cathode. The baseline protocol

incorporates a series of charge and discharge cycles at a constant C-rate without any interruption between the lower and upper cut-off voltages (“C-rate” or“C” refers to a discharge current which will discharge the entire battery in one hour). The cut-off voltages are defined based on voltage ranges in which the cathode or anode experience instability in forming the electrolyte interphase layers. The baseline formation protocol and the alternative protocol may be performed at different charge/discharge C-rates, e.g., C/20, C/10, and C/5 (the time scales for these different rates have been normalized for purposes of illustration). Rates of C/20 or C/10 are typically used for at least the first formation cycle in conventional cell manufacturing. The alternative protocol, in contrast to the baseline protocol, involves repeated cycling within a high state-of-charge (SOC) region (i.e., after the first charge) until the last cycle, where a full discharge takes place. (See, e.g., An, S. J., Li, J., Du, Z., Daniel, C., Wood, D. L., Fast formation cycling for lithium ion batteries. Journal of Power Sources 2017, 342, 846-852).

The foregoing detailed description has set forth various implementations of the devices and/or processes via the use of block diagrams, schematics, and examples. Insofar as such block diagrams, schematics, and examples contain one or more functions and/or operations, it will be understood by those skilled in the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. Those of skill in the art will recognize that many of the methods or algorithms set out herein may employ additional acts, may omit some acts, and/or may execute acts in a different order than specified. The various implementations described above can be combined to provide further implementations.

These and other changes can be made to the implementations in light of the above- detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific implementations disclosed in the

specification and the claims, but should be construed to include all possible

implementations along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

1. A battery formation system , comprising:

a plurality of terminals to provide electrical connections to batteries,

a controller having a processor, and

a plurality of chargers communicatively coupled to the controller, each of the chargers operatively coupled to output charging voltages and to receive discharging voltages, based on a defined formation protocol, via a pair of terminals of the plurality of terminals, wherein each charger comprises:

a microcontroller, and

one or more solid state switches, in communication with the microcontroller, operatively coupled to receive input power and to selectively output charging voltages and receive discharging voltages.

2. The system of claim 1 wherein each charger further comprises a coil communicatively connected to receive the input power by induction.

3. The system of claim 1 wherein each charger further comprises power input terminals to receive the input power.

4. The system of claim 3, further comprising a rectifier operably coupled to receive the input power and output a rectified signal to the one or more solid state switches.

5. The system of claim 1 wherein the solid state switches of each charger of the plurality of chargers are operably coupled to provide:

a first mode in which the pair of terminals presents a short circuit,

a second mode in which the pair of terminals presents an open circuit, a third mode in which each charger of the plurality of chargers produces a negative wavelet half-cycle, and

a fourth mode in which each charger of the plurality of chargers produces a positive wavelet half-cycle.

6. The system of claim 1 wherein the defined formation protocol is stored in at least one of the following: memory of the controller and memory of the microcontroller of each charger.

7. The system of claim 1 wherein the defined formation protocol comprises a first charge, repeated cycling within a high state-of-charge region, and a full discharge.

8. The system of claim 1 wherein the defined formation protocol comprises cycles of a full charge followed by a full discharge.

9. The system of claim 1 , further comprising a battery tray having a plurality of receptacles, each receptacle having a first terminal of the pair of terminals, each receptacle being shaped and sized to hold a battery in communication with the first terminal.

10. The system of claim 8, further comprising a terminal plate to be positioned opposing the battery tray and having a plurality of terminal sites in correspondence with the receptacles of the battery tray, each terminal site having a second terminal of the pair of terminals.

1 1. A battery conditioning apparatus, comprising:

a system chassis,

one or more fixtures sized and shaped to be received in the chassis, each fixture having a plurality of terminals to provide electrical connections to batteries, a controller positioned in the chassis, the controller having a processor, and a plurality of chargers positioned in the chassis, the plurality of chargers communicatively coupled to the controller, each of the chargers operatively coupled to output charging voltages and to receive discharging voltages, based on a defined formation protocol, via a pair of terminals of the plurality of terminals of each fixture, wherein each charger comprises:

a microcontroller, and

one or more solid state switches, in communication with the

microcontroller, operatively coupled to receive input power and to selectively output charging voltages and receive discharging voltages.

12. A battery conditioning apparatus of claim 10 wherein each fixture comprises receptacles, each receptacle having a first terminal of the pair of terminals, each receptacle being shaped and sized to hold a battery in communication with the at least one terminal.

13. A battery conditioning apparatus of claim 10 wherein the plurality of term inals of each fixture comprises pairs of clamping terminals, each pair of clamping terminals having a first terminal and a second terminal of the pair of terminals, each pair of clamping terminals being shaped and sized to hold a battery in communication with the first terminal and the second terminal.