Sodium-ion battery pack

Abstract

The present invention relates to a sodium-ion battery pack comprising one or more sodium-ion cells and one or more voltage converters. Methods and uses of such a sodium-ion battery pack are also disclosed.

Description

Technology Field

[0001] The present invention relates to a sodium-ion battery pack designed to enable the efficient transfer of available energy within a sodium-ion cell present in the battery pack to an electric device. Furthermore, the present invention relates to a method for efficiently transferring available energy within a sodium-ion cell, and an electric device employing the sodium-ion battery pack according to the present invention. To avoid any questions, supercapacitors are not included within the scope of the present invention. Background Technology

[0002] Sodium-ion batteries are similar in many ways to the lithium-ion batteries commonly used today; both are reusable secondary batteries comprising an anode (negative electrode), a cathode (positive electrode), and electrolyte materials, both can store energy, and both are charged and discharged through similar reaction mechanisms. When a sodium-ion (or lithium-ion) battery is charged, Na + (or Li + Ions are deintercalated from the cathode and inserted into the anode. Meanwhile, charge-equilibrium electrons enter the battery's anode from the cathode through the external circuit, including the charger. The same process occurs during discharge, but in the opposite direction.

[0003] Lithium-ion battery technology has recently garnered significant attention and provides desirable portable batteries for almost all electronic application devices currently in use; however, lithium is not an inexpensive metal to source and is considered too expensive for use in high-volume applications. In contrast, sodium is much more abundant than lithium, and sodium-ion batteries are highly anticipated to offer a cheaper and more sustainable method for energy storage into the future, particularly for high-volume applications such as storing energy in the electric grid. Nevertheless, further research is required for sodium-ion batteries to be commercially implemented.

[0004] For any rechargeable battery, the energy available for practical use is a function of the depth of discharge (DoD) and the voltage of each cell. For conventional lithium-ion batteries, such as those using lithium cobalt oxide (LCO), lithium nickel manganese cobalt oxide (NMC), or lithium nickel cobalt aluminum oxide (NCA) cathode materials, carbon or silicon anodes, copper anode current collectors, and aluminum-containing cathode current collectors, problems can arise when these cells are stored in a fully discharged state or downcycled to 0 volts or near 0 volts. For example, copper leaching from the negative (anode) electrode current collector can reduce the cathode's discharge capacity, and the lithium-ion battery will experience increasingly shorter cycle times. However, the real problem with cycling lithium-ion cells to near 0 volts is that they become unstable, overheat, and pose a risk of unpredictable fire. To date, attempts to eliminate copper leaching by using aluminum instead of copper in the negative current collector have resulted in an alloying reaction between lithium and aluminum within a fully discharged cell; even if alternative negative (anode) electrode materials exist that operate at a sufficiently high potential-to-lithium relationship to prevent the formation of a lithium / aluminum alloy, only a small number of such negative electrode materials, e.g., Li4Ti5O, exist. 12 It was not successful because it is known that only [the other person] can perform this.

[0005] To mitigate these difficulties, established practices for handling standard lithium-ion batteries require a charge state between approximately 90% and approximately 30% (20% for LFP and LiFePO4 batteries), meaning their depth of discharge (DoD) should be approximately 70%–80% or less. Immediately after manufacturing, lithium-ion batteries are conditioned using a final charge to at least approximately 40% charge state after at least two or three charge / discharge cycles, and all charge states at or near 0 volts are avoided. However, due to these precautions, the energy remaining within the charge state of approximately 30% (or approximately 20% for LFP) cannot be accessed, and thus this energy is wasted.

[0006] On the other hand, sodium-ion batteries are extremely stable when fully discharged and when cycled down to 0 volts, and the applicant of the present invention has found that even when a sodium-ion cell is in a very low state of charge (e.g., SOC 0% to less than 30%), substantially all of the energy within the sodium-ion cell (e.g., energy exceeding 95%) can be accessed and accessed repeatedly without affecting the lifespan of the sodium-ion cell. However, the design of commercially available sodium-ion batteries is currently facing difficulties due to the fact that many electrical systems used in common applications employ traditional narrow voltage limits designed to keep lead-acid and lithium-ion cells within a voltage window that maximizes repeatability and ensures battery safety. For example, a commercial nominal 12V lead-acid battery (Yuas NPC24-12I Industrial VRLA employing six cells connected in series) will only operate within a voltage window between 14.5V and 10.5V. Table 1 lists known voltage limits for common cell chemistry.

[0007]

[0008] As a result of this voltage window, electronic components, such as inverters and motors, have also been designed to operate within these limits. Apart from sodium-ion cells, all other chemicals at minimum voltage ( V min ) this cell V max It can be seen that it can operate only in a voltage range greater than 60% of. Sodium-ion cells only V min This cell V max It can operate in a voltage range of less than 60%. In other words, sodium-ion cells are distinguished from other types of rechargeable cells by having a much wider voltage range, and therefore have less compatibility with existing electronic components. The problem to be solved

[0009] Therefore, the object of the present invention is to provide a sodium-ion battery pack designed to enable efficient and comprehensive access to available energy from one or more sodium-ion cells adopted by the battery pack.

[0010] In particular, the object of the present invention is to provide a sodium-ion battery pack that enables practical access to all or at least substantially all of the energy from a sodium-ion cell, thereby increasing the total energy available from the sodium-ion cell. Another object is to enable such practical access to the energy from the sodium-ion cell when the sodium-ion cell is in a low cell voltage state, that is, when the voltage is below the usual lower limit of the electronic component. Yet another object is to provide a sodium-ion battery pack capable of controlling the voltage so that the output voltage of the battery matches the requirements of any external electronic component connected to the battery pack. Additionally, the object of the present invention is to increase the available specific energy of the sodium-ion cell within the sodium-ion battery pack (i.e., increase the available energy per unit mass (J / Kg)), and / or increase the volumetric energy density of the sodium-ion battery pack or the sodium-ion cell to the maximum value obtainable within a cost window. Furthermore, the objective of the present invention is to design a sodium-ion battery pack that does not affect the performance of any aspect of the sodium-ion cell, such as safety, cycle life, and rate performance.

[0011] The object of the present invention is also a sodium-ion battery and / or one or more sodium-ion cells contained therein that fall within a range greater than 0 V and less than 2.0 V. V min The present invention provides a method for delivering all or at least substantially all of the energy from a sodium-ion battery capable of operating in a sodium-ion battery, i.e., preferably at least 90%, more preferably at least 93%, and more preferably at least 95%. An additional objective is to provide an electronic application device connected to a sodium-ion battery pack according to the present invention. means of solving the problem

[0012] In the context of this specification, the term "operable" refers to a sodium-ion cell according to the present invention. V max and cell V min This means that it can be operated between. Such cells are used within a battery pack according to the present invention. This is the cell according to the present invention as discussed above. V max and cell V min It is contrasted with non-sodium-ion cell chemicals that are not operable (i.e., cannot be operated) between them.

[0013] As described below, the sodium-ion battery pack according to the present invention is designed to enable access to a much wider input voltage range than is available in traditional battery chemistry, thereby increasing the amount of usable energy. In particular, the present invention provides an efficient and cost-effective means for converting energy present at low voltage within a sodium-ion cell into energy that is available for use and would otherwise be wasted. Ideally, the sodium-ion battery pack of the present invention is designed using components that do not add any unnecessary mass to the battery pack.

[0014] In its broadest aspect, the present invention provides a sodium-ion battery pack comprising one or more sodium-ion cells and one or more voltage converters. Preferably, the sodium-ion battery pack comprises more than one sodium-ion cell.

[0015] One or more sodium-ion cells are cells in the range greater than 0.0 V and less than 2.0 V V min and cells falling within the range of greater than 3.60 V and less than 4.30 V V max It can operate between. As discussed above, cell V min and cell V max The ability of a sodium-ion cell to operate within a voltage range (i.e., to be operated) is an intrinsic characteristic of the sodium-ion cell that is not shared with other cell chemistry.

[0016] Preferably, one or more sodium-ion cells are cells falling within the range of greater than 0.0 V and less than or equal to 1.50 V. V min , and ideally cells falling within the range of greater than 0.0 V and less than or equal to 1.0 V V min It can operate at. Preferably, one or more sodium-ion cells are cells in the range of greater than 3.70 V and less than or equal to 4.25 V. V max With, ideally a cell falling within the range of greater than 3.70 V and less than or equal to 4.20 V V max It can be operated in.

[0017] In some embodiments, one or more sodium-ion cells, preferably all of one or more sodium-ion cells, are cells V min This cell V max greater than 0% and less than or equal to 55%, preferably cell V max greater than 0% and less than or equal to 50%, and more preferably cell V max It can operate in a voltage range exceeding 0% and up to 45% of . In other words, as discussed above, the sodium-ion cell such V min / V max The ability to operate within a percentage is an intrinsic characteristic of sodium-ion cells that is not shared with other cell chemicals.

[0018] Two or more cells have the same cell voltage, preferably the nominal cell voltage, and all of them have the same electrochemical design. As used herein, the terms "same cell voltage profile" or "same cell nominal voltage profile" mean the same voltage-to-capacity relationship.

[0019] Furthermore, when "nominal" (or "named") cell voltages as shown in Table 1 are used in this specification, they are intended to mean cell voltage values ​​assigned (nominated) to the cell or battery, for example, by the manufacturer, and are based on the electrochemical configuration of the cell.

[0020] The actual measured voltage of a cell or battery will decrease as the cell or battery discharges. Furthermore, fluctuations from these nominal cell voltage values ​​may occur, for example, during manufacturing or over the lifespan of the cell or battery. These fluctuations may be most severe during the aging of the cell or battery in use. However, as will be understood by those skilled in the art, the nominal cell voltage specified for the cell or battery will remain constant; that is, the specified nominal voltage will not change even if the actual measured voltage decreases as discussed above.

[0021] More than one sodium-ion cell also typically has the same electrochemical design. The expression "same electrochemical design" implies that they share the same combination of cell structure and cell chemistry. In particular, the electrode / electrolyte chemistry, power density (per unit mass or per unit volume), and energy density (per unit mass or per unit volume) of more than one sodium-ion cell are therefore qualitatively identical when initially installed in the battery.

[0022] As a result of having more than one sodium-ion cell all having the same electrochemical design and the same nominal voltage, they will operate in tandem within the sodium-ion battery pack; that is, more than one sodium-ion cell will initially all behave in an essentially similar manner. The advantage of this configuration is that the lifespan of the sodium-ion battery pack will be much longer.

[0023] As used herein, one or more voltage converters within the sodium-ion battery pack of the present invention provide means for aligning (preferably boosting) the output voltage (also known as terminal voltage) of the sodium-ion battery pack containing a sodium-ion cell to an acceptable level at any electronic component outside the sodium-ion battery pack. This is particularly useful for sodium-ion cells containing a hard carbon anode in which the complete discharge of the cell occurs only over a wide voltage window.

[0024] In some embodiments, the present invention uses two or more voltage converters. These may be identical, similar, or completely different from each other, for example, in their physical and / or performance characteristics and / or their type and / or their mode of operation.

[0025] In some embodiments, each of one or more voltage converters is connected separately to individual cells. Additionally or alternatively, each of one or more voltage converters may be connected to two or more cells. One or more voltage converters may be connected to the inside and / or outside of a sodium-ion battery comprising one or more sodium-ion cells.

[0026] If the energy within the cell at a low voltage is not converted to a higher voltage, it cannot be used for its intended purpose, and therefore this will adversely affect the cell's specific energy. Low voltage (60-70% cell V max The energy remaining in the sodium-ion cell (and thus, wasted energy) in the cell (exceeding) can amount to 14% of the total energy in the cell.

[0027] Therefore, most preferably, one or more voltage converters the terminal voltage of a sodium-ion battery pack, and the voltage measured between the terminals of one or more sodium-ion cells connected in series of the sodium-ion battery pack is battery V max If it is 60% or less (preferably 70% or less), 60% battery V max It is provided to increase to exceed (preferably to exceed 70%).

[0028] "battery V max " is cell V max It is the product of the number of cells connected in series within the pack and relates to the combined voltage of these cells when there is no one or more voltage converters. Therefore, this is the maximum operating voltage of the battery when there is no one or more voltage converters.

[0029] "cell" as described with reference to Table 1 V max " is the maximum operating voltage of the cell itself when there is no voltage converter.

[0030] The terminal voltage of a sodium-ion battery pack corresponds to the voltage measured between the terminals of one or more sodium-ion cells connected in series within the sodium-ion battery pack.

[0031] Preferably, the efficiency of one or more voltage converters will be such that the energy obtained from the conversion is greater than the energy lost within one or more voltage converters through resistive heating and switching; that is, the voltage conversion must be highly efficient. Furthermore, it is desirable that the mass of one or more voltage converters ensures that the additional contribution to the specific energy from the "up-conversion" is not out-weighed by the influence of the mass of one or more voltage converters. A similar discussion applies to the combined volume of the pack and one or more voltage converters.

[0032] A preferred voltage converter is a DC / DC converter, which is a type of power converter comprising an electronic circuit or electrochemical device that converts a DC source at one voltage level to another voltage level. Particularly preferably, the DC / DC converter is a bidirectional DC / DC converter that allows power to flow in both forward and reverse directions. Conventional DC / DC converters include boost converters and buck / boost converters, but the present invention is not limited to these two types. Generally speaking, a boost converter increases the voltage from a DC source, whereas a buck / boost converter will increase and decrease the output voltage.

[0033] Relying on the voltage converter circuitry, one or more voltage converters (e.g., DC / DC converters) will either produce a fixed output voltage or replicate an existing or known voltage profile. One or more voltage converters, particularly where at least one is a DC / DC converter, may be part of a standalone circuitry (such as that used in the examples described below) or may be included in or linked to other components, such as a battery management system (BMS). Therefore, in some embodiments, the present invention further includes a battery management system (BMS).

[0034] In this context and as used herein, the term "battery management system (BMS)" generally further includes a management system for an energy storage device. A battery management system is an electronic system that manages a rechargeable battery (cell or battery or energy storage device) by monitoring the state of the battery (energy storage device), for example by protecting it from operating outside its safe operating region, by calculating and reporting secondary data, and by using this to control the performance of the battery (energy storage device), for example by rebalancing the charge within each of the cells. Since the sodium-ion cells used in the sodium-ion battery pack of the present invention can be safely discharged to at least 0 volts without any loss of charge / discharge performance of the cells, the associated battery management system is not required to monitor the lower limit of the safe operating region or to perform measures to equalize the charge at this low level; nevertheless, it is important to manage the sodium-ion cells at the top of the charge. Therefore, the BMS will typically monitor individual cell voltage, current, and temperature and control the battery safety system, and preferably employ cell balancing.

[0035] Preferably, one or more voltage converters will not add unnecessary mass to at least one sodium-ion cell or battery pack, thus ensuring that the usable specific energy of the sodium-ion battery pack is greater than the usable specific energy of at least one sodium-ion cell. The present invention preferably employs one or more highly efficient voltage converters, which are lightweight and lose only a small amount of energy through resistive heating and switching.

[0036] Although it is known that a DC / DC converter is used in combination with a lithium-ion cell and also used within an electronic application device to ensure that the lithium-ion cell output voltage matches the voltage requirements of a specific application / device, as of the filing date, there is no prior art disclosure for a battery pack comprising one or more sodium-ion cells and one or more voltage converters (preferably, at least one of which is a DC / DC converter) for providing means to align the sodium-ion battery pack output voltage to a level accessible to an electronic component (e.g., an electronic application device) located outside the sodium-ion battery pack. Furthermore, as of the filing date, there is no prior art disclosure describing a specific design of a sodium-ion battery pack in which such a specific design of the sodium-ion battery pack can provide an increase in the total available energy from at least one sodium-ion cell employed by the battery pack; There is no disclosure describing a specific design of a sodium-ion battery pack that can provide an increase in the specific energy available from the sodium-ion battery pack, nor is there any disclosure of a specific design of a sodium-ion battery pack that can obtain an increased volumetric energy density.

[0037] Therefore, the present invention provides a sodium-ion battery pack comprising one or more sodium-ion cells and one or more voltage converters (preferably at least one of which is a DC / DC converter as described above), and the transferable specific energy of the sodium-ion battery pack satisfies the following conditions:

[0038] (battery V max Difference in energy between 0V and 0V) * (Efficiency of one or more voltage converters) / (Mass of one or more sodium-ion cells + Mass of one or more voltage converters) > (batteryV max and battery V max Difference in energy between 60% and 70% of) / (Mass of one or more sodium-ion cells);

[0039] battery here V max is determined as the maximum output voltage of a sodium-ion battery pack containing one or more sodium-ion cells without one or more voltage converters.

[0040] Preferably, the transferable specific energy of the sodium-ion battery pack satisfies the following conditions:

[0041] (battery V max Difference in energy between 0V and 0V) * (Efficiency of one or more voltage converters) / (Mass of one or more sodium-ion cells + Mass of one or more voltage converters) > (battery V max and battery V max Difference in energy between 60% and 65% of) / (Mass of one or more sodium-ion cells);

[0042] battery here V max is determined as the maximum output voltage of a sodium-ion battery pack containing one or more sodium-ion cells without one or more voltage converters.

[0043] Undoubtedly, the maximum output voltage of a sodium-ion battery pack containing one or more sodium-ion cells in the absence of one or more voltage converters, which is the battery V max will be defined as the initial design maximum voltage of a sodium-ion battery pack as used herein. The fact that this initial design maximum voltage typically decreases over the cycle life of the pack is battery V max It is specifically ignored in the definition of the applicant.

[0044] In another embodiment, the present invention provides a sodium-ion battery pack comprising one or more sodium-ion cells and one or more voltage converters (preferably at least one of which is a DC / DC converter as described above), wherein the volumetric energy density satisfies the following conditions:

[0045] (battery V max Difference in energy between 0V and 0V) * (Efficiency of one or more voltage converters) / (Volume of one or more sodium-ion cells + Volume of one or more voltage converters) > (battery V max and battery V max Difference in energy between 60% and 70% of) / (Volume of one or more sodium-ion cells);

[0046] battery here V max is determined as the maximum output voltage of a sodium-ion battery pack containing one or more sodium-ion cells without one or more voltage converters.

[0047] Preferably, the volumetric energy density satisfies the following conditions:

[0048] (battery V max Difference in energy between 0V and 0V) * (Efficiency of one or more voltage converters) / (Volume of one or more sodium-ion cells + Volume of one or more voltage converters) > (battery V max and battery V max Difference in energy between 60% and 65%) / (Volume of one or more sodium-ion cells);

[0049] battery here V max is determined as the maximum output voltage of a sodium-ion battery pack containing one or more sodium-ion cells without one or more voltage converters.

[0050] In a further embodiment, the present invention provides the use of one or more voltage converters (preferably DC / DC converters as described above) combined with one or more sodium-ion cells to produce a sodium-ion battery pack having a transmittable specific energy or transmittable volumetric energy density that is at least 3% (preferably at least 5%) higher than the transmittable specific energy or transmittable volumetric energy density in the case of a sodium-ion battery pack comprising one or more sodium-ion cells without one or more voltage converters.

[0051] In an additional embodiment, the present invention relates to a terminal voltage of a sodium-ion battery pack, wherein the voltage measured between the terminals of one or more sodium-ion cells connected in series of the sodium-ion battery pack is a battery V max If it is 60% or less (preferably 70% or less), battery V max The present invention provides a use of a sodium-ion battery pack according to the invention for increasing to more than 60% (preferably more than 70%).

[0052] As previously mentioned, "battery V max " is cell V max It is the product of the number of cells connected in series within the pack, and is related to the integrated voltage of these cells.

[0053] Additionally or alternatively, one or more voltage converters convert the terminal voltage of the sodium-ion battery pack, and the sodium-ion battery pack cell voltage to cell V max If it is 60% or less (preferably 70% or less), battery V max It is provided to increase it to exceed 60% (preferably to exceed 70%). As also explained above, "cell V max " is the maximum operating voltage of the cell itself.

[0054] To summarize the foregoing, in an additional embodiment, the present invention relates to a terminal voltage of a sodium-ion battery pack, wherein the voltage measured between the terminals of one or more sodium-ion cells connected in series of the sodium-ion battery pack is a battery V max If it is 60% or less V max It provides an application for the sodium-ion battery pack as described above to increase (to exceed 60% of). In this latter example V max is battery V max and / or cell V max It should be interpreted as.

[0055] In another preferred embodiment, the present invention provides a method for accessing available energy, preferably non-energy, from a battery comprising one or more sodium-ion cells, wherein

[0056] a) providing a sodium-ion battery pack comprising one or more voltage converters and one or more sodium-ion cells, wherein the one or more sodium-ion cells are cells in the range greater than 0.0 V and less than 2.0 V. V min and cells falling within the range of greater than 3.60 V and less than 4.30 V V max It can operate between, and furthermore, if the sodium-ion battery pack includes more than one sodium-ion cell, all of the more than one sodium-ion cell have the same cell nominal voltage profile and the same electrochemical design -;

[0057] b) associating or integrating the battery pack with an electronic application device; and

[0058] c) The output voltage of the above sodium-ion battery pack is battery V max More than 60% of, preferably battery V max The step of directly or indirectly operating at least one of the above one or more voltage converters to increase by more than 70%, and

[0059] battery V max The method provides an energy access method determined as the maximum output voltage of a sodium-ion battery pack comprising one or more sodium-ion cells without one or more voltage converters.

[0060] In this method, one or more voltage converters can be operated directly or indirectly.

[0061] Indirect operation may use a signal generated in response to the power requirements of an application device (e.g., generated by a BMS or other computer software). Additionally, one or more voltage converters may operate continuously or discontinuously over part or all of the operating voltage range of the electronic application device, or outside of it (e.g., below the minimum operating voltage), and depending on the required output voltage profile.

[0062] Preferably, one or more voltage converters have an output voltage of one or more sodium-ion cells. V max It operates when it is 70% or less. Preferably, one or more voltage converters have an output voltage of one or more sodium-ion cells V max It operates when it is 60% or less.

[0063] Since one or more voltage converters (preferably, at least one of them is a DC / DC converter) have a response time and some of the voltage will be lost within one or more converters as converter energy consumed, one or more converters voltage, for example, in a discharge cycle V max In order to reliably raise it to less than 60% of, at least one of the one or more converters, just before the desired voltage is obtained, for example, the voltage V max Those skilled in the art will become familiar with the fact that it is advantageous to switch on just before reaching 60%.

[0064] In another preferred embodiment, the present invention provides a use of a sodium-ion battery pack according to the present invention for increasing the available and / or transmittable specific energy and / or transmittable volumetric energy density of a sodium-ion battery pack comprising one or more sodium-ion cells without one or more voltage converters by at least 3% (preferably by at least 5%).

[0065] Preferably, one or more voltage converters (preferably comprising at least one DC-DC converter) can convert all or substantially all (preferably at least 90%, more preferably at least 95%) of the energy available at a low voltage (e.g., less than 3.5 to less than 2.5 volts) into energy available within a predetermined narrow and higher voltage window (e.g., from 4.2 V to 3.5 V or from 4.2 V to 2.5 V), efficiently, cost-effectively, and without unnecessary mass. Preferably, the present invention can convert 94-95% of the cell energy available at a minimum cell voltage of 1.5 V into energy available within a voltage window of 2.4 V to 4.2 V. Theoretically, the present invention is suitable for use in static storage and mobile systems.

[0066] In another preferred embodiment, the present invention relates to a backup power supply for static or stationary applications and for portable (mobile) applications (e.g., mobile phones, computers, tablets, etc., and motor drives for starting, lighting, and ignition (SLI) batteries and electric vehicles), where the battery pack output voltage for such electronic application devices is in a low voltage range (e.g., battery V max The present invention provides a sodium-ion battery pack that is highly suitable for use in conjunction with an applicable electronic application device (e.g., used in a large-capacity energy storage) when the amount is 70% or less, preferably 60% or less. Therefore, the present invention provides an electronic application device integrated with or associated with the sodium-ion battery pack according to the present invention.

[0067] As used herein, the term “sodium-ion cell” is defined to refer to any secondary sodium-ion electrochemical cell, and suitable examples include non-aqueous sodium-ion cells, aqueous sodium-ion cells, sodium-air cells, and sodium-oxygen cells (but the invention is not limited to these examples). A plurality of such electrochemical cells may be utilized in any small or large capacity energy storage device, including but not limited to batteries, battery modules, electrochemical devices, and electrochromic devices. The term “sodium-ion battery pack” according to the invention includes any such small or large capacity energy storage device used in association with, integrated with, or in combination with one or more voltage converters as described above. Typically, the pack will include a container and, preferably, a safety system and a battery management system.

[0068] Typically, the sodium-ion cell used in the battery pack of the present invention has i) a negative electrode comprising a negative electrode material and a negative electrode current collector, and ii) a positive electrode comprising a positive electrode material and a positive electrode current collector. Suitable negative electrode materials include amorphous carbon, hard carbon, silicon, and any other materials, such as alloy metals like tin, germanium, or antimony, the structure of which is adapted to allow insertion / removal of sodium ions during charging / discharging. Preferably, the negative and positive current collectors comprise one or more conductive materials that are stable under conditions of low voltage (i.e., within the aforementioned preferred cell voltage range) and / or low charge state (e.g., less than 20% charge state) and do not dissolve or alloy with sodium. Preferably, one or more conductive materials may be in a pure form, an impure form, an alloy, or a mixture, and may be combined alone or with varying amounts of one or more other elements, without alloying with sodium and / or otherwise reacting. More preferably, at least one of the one or more conductive materials comprises one or more metals selected from copper, aluminum, and titanium. Ideally, one or both of the current collectors comprise aluminum, either in a pure form, an impure form, or as an alloy or mixture, either alone or in combination with varying amounts of one or more other elements. For example, low-grade aluminum obtained from impure or household-grade sources is particularly preferred, and thus clearly significant commercial advantages are obtained. Carbon-coated negative electrode current collectors are also advantageous because they provide benefits such as better junction between the active negative electrode material and the negative electrode current collector, which now results in lower contact resistance.Current collectors containing carbon coatings are also found to improve rate performance, which allows current to be charged / discharged quickly. Similar advantages are obtained when a sodium-ion cell includes a positive electrode current collector containing a carbon coating. A sodium-ion cell containing carbon-coated positive and negative current collectors is particularly electrically efficient.

[0069] The positive electrode (cathode) material used in the sodium-ion cell of the present invention comprises any material that enables sodium ions to be intercalated and deintercalated (moved in and out of their lattice or side-phase structure) during charging and discharging. Suitable examples include metal sulfide compounds such as TiS2, metal oxide compounds, phosphate-containing compounds, polyanion-containing compounds, Prussian blue analogs, and nickelated or non-nickelized compounds of the following general formula:

[0070] A 1±δ M 1 V M 2 W M 3 X M 4 Y M 5 Z O 2-c

[0071] Here,

[0072] A is one or more alkali metals selected from sodium, potassium, and lithium;

[0073] M 1 It comprises one or more redox active metals having an oxidation state of +2, preferably one or more redox active metals having an oxidation state of +2 selected from nickel, copper, cobalt, and manganese;

[0074] M 2 It includes metals with an oxidation state greater than 0 and less than or equal to +4;

[0075] M 3 It includes a metal with an oxidation state of +2;

[0076] M 4 It includes metals with an oxidation state greater than 0 and less than or equal to +4;

[0077] M 5 It includes a metal with an oxidation state of +3;

[0078] Here,

[0079] 0 ≤ δ ≤ 1;

[0080] V > 0;

[0081] W ≥ 0;

[0082] X ≥ 0;

[0083] Y ≥ 0;

[0084] At least one of W and Y > 0

[0085] Z ≥ 0 and;

[0086] C falls within the following range: 0 ≤ c < 2

[0087] Here, V, W, X, Y, Z, and C are selected to maintain electrochemical neutrality.

[0088] Ideally, metal M 2 comprises one or more transition metals, preferably selected from manganese, titanium, and zirconium; M 3 is preferably one or more selected from magnesium, calcium, copper, tin, zinc, and cobalt; M 4 comprises one or more transition metals, preferably one or more selected from manganese, titanium, and zirconium; and M 5The material is preferably one or more selected from aluminum, iron, cobalt, tin, molybdenum, chromium, vanadium, scandium, and yttrium. Any cathode active material having a crystalline structure may be used, and such structure is preferably O3 or P2 or a derivative thereof; specifically, it is also possible for the cathode material to comprise a mixture of phases, that is, to have a heterogeneous structure composed of various different crystalline forms. Layered metal oxide cathode materials are particularly preferred. Brief explanation of the drawing

[0089] The present invention will now be described with reference to the accompanying drawings: Figure 1 is a schematic diagram of a sodium-ion battery (without a voltage converter) used in reference experiment 1, in which the battery is used to supply power directly to the load. Figure 2 shows a schematic discharge voltage profile for a sodium-ion battery (with voltage converter) connected to a 295 W load and discharged within a 35 V - 56 V operating window according to reference experiment 1. FIG. 3 is a schematic diagram of a sodium-ion battery pack according to the present invention used in Experiment 2. This battery pack employs a DC / DC converter when the battery pack is operated at 35V to 56V, and the result highlights losses in the system caused by DC / DC converter switching and heating. FIG. 4 shows the discharge profile for a Na-ion battery (with voltage converter) according to the present invention, connected to a 295 W load and discharged within 35 V - 56 V according to Experiment 2. In this case, the output voltage of the battery pack is constant at 48 V. For comparison, the voltage profile obtained from reference Experiment 1 (without voltage converter) is also shown. FIG. 5 is a schematic diagram of a sodium-ion battery pack according to the present invention used in Experiment 3. FIG. 6 shows the discharge profile for a Na-ion battery (with voltage converter) according to the present invention, connected to a 295 W load and discharged within 18 V - 56 V according to Experiment 3. In this case, the output voltage of the battery pack is constant at 48 V. For comparison, voltage profiles obtained from reference Experiment 1 and Experiment 2 are also shown. FIG. 7 is a schematic diagram of a simulated model of a sodium-ion battery pack according to the present invention used in Calculation B, which assumes that the battery pack is discharged between 18V and 56V but the DC / DC converter is used only below 38V. The result indicates that the energy loss resulting from the addition of the DC / DC converter will be minimized. FIG. 8 shows a simulated model of the discharge profile for a hypothetical Na-ion battery pack (simulated model 2) according to the present invention used in calculation B (with voltage converter), which is connected to a 295 W load and discharges within an operating window of 18 V - 56 V, and the voltage converter operates only when the discharge voltage drops to 38 V. Specific details for implementing the invention

[0090] In subsequent experiments, the battery pack according to the present invention employs one of two types of buck / boost DC / DC converters: the MeanWell SD-1000L-48 converter available from Mean Well Enterprises Co. Ltd., or the converter available from Vicor Corporation. These converters were selected because they are readily available, not because of their specific performance and / or physical characteristics. It will be understood that any suitable voltage converter having appropriate mass, efficiency, volume, and voltage characteristics can be used in the sodium-ion battery pack according to the present invention. To be more specific, the MeanWell SD-1000L-48 converter is a wide-input voltage buck / boost converter with an input voltage range of 19V-72V and has a mass of 1.675kg. The dimensions of this converter are 295mm x 125mm x 41mm.

[0091] The converter available from Vicor Corporation has an input window of 16V-50V and weighs 255g. The dimensions of this converter are 85.93mm x 35.50mm x 9.4mm.

[0092] General experimental methods

[0093] A 300 Wh sodium-ion battery pack containing 14 series-connected sodium-ion cells, equipped with a safety system such as a BMS, was selected as the test vehicle. All cells within this pack possess the same cell nominal voltage profile and the same electrochemical design, implying that they would all behave in essentially similar ways initially. The pack was charged to 56 V and then discharged through an electronic load of 295 W. The pack's fuses and wiring were designed to withstand a maximum current of 25 amperes. The pack's voltage was measured and recorded during discharge using a data stream from the BMS, and the results are provided in Figures 2, 4, and 6. The total energy output was also measured. All data collected for each experiment are provided in the following Table 2.

[0094] Reference Experiment 1 - Discharging the pack to the lower limit of the pack voltage at 35V without a DC / DC converter.

[0095] As illustrated in Fig. 1, a 14S 1P 300Wh sodium-ion battery pack designed to discharge from 56V to 35V was directly connected to an electronic load of 295W. The discharge voltage over time was measured, and the results are provided in Fig. 2. This experiment (without a DC / DC converter) provides a reference or benchmark for comparison with the results of Experiments 2 and 3 described later. It should be noted that in this experiment, the electronic load experiences a voltage drop as the battery pack discharges, and the load maintains a constant power output by drawing an increasing current.

[0096] As shown in Table 2 below, the total output energy of reference experiment 1, that is, the energy available to the electronic load, is 322Wh.

[0097] Experiment 2 - Discharging the pack to the lower limit of 35V through a DC / DC converter.

[0098] This test was identical to Experiment 1, except that a MeanWell SD-1000L-48 DC / DC converter providing a constant 48V output was introduced between the pack and the load. Refer to Fig. 3 for a schematic representation of the sodium-ion battery pack designed for the test in Experiment 2. The battery pack was charged to 56V and then discharged to 35V. The battery voltage profile was measured over time, and the results are provided in Fig. 4 along with the voltage discharge curve for reference Experiment 1. From Fig. 4, it can be seen that there is energy loss caused by the DC / DC converter over the same voltage window. In this case, the battery pack energy input to the DC / DC converter was 322Wh, and the total output energy was 297.5Wh. From these results, it can be seen that the energy efficiency of the DC / DC converter over this voltage window is 92.38%.

[0099] Note: In this test, the electronic load will experience a constant 48 volts over the discharge and will draw a constant current from the DC / DC converter.

[0100] Experiment 3 - Discharging using a DC / DC converter with the pack voltage lower limit set to 18V.

[0101] The test setup was identical to that of Experiment 2, except that the pack voltage lower limit was set to 18V this time, refer to the schematic representation shown in Fig. 5. The battery pack was charged to 56V and then discharged to 18V. The battery voltage profile was measured over time, and the results are provided in Fig. 6. The benchmark discharge voltage curve from reference Experiment 1 (without converter) and the discharge voltage curve from Experiment 2 with a voltage cut-off of 35V are also shown. Fig. 6 shows that the electronic load runtime increased compared to Experiments 1 and 2, and since the load was at constant power, the additional energy is a function of this added runtime.

[0102] In this experiment 3, the battery pack energy input to the DC / DC converter was 390.55Wh, and the total output energy available to the electronic load was 353.4Wh. Compared to reference experiment 1, the available energy increased by 9.75% as a result of using this DC / DC converter.

[0103] The energy efficiency of the DC / DC converter over this voltage window was 90.49%.

[0104] Note: In this test, the electronic load will experience a constant 48 volts over the discharge and will draw a constant current from the DC / DC converter.

[0105] Summary and Results Analysis

[0106] Increase in available energy

[0107] As can be seen from the results provided in Table 2 below, using a commercial DC / DC converter allowed access to a wider cell voltage window compared to when the minimum cell voltage was set to be equal to the minimum voltage that is acceptable to the system or application.

[0108] In the case of Experiment 2, the decrease in available energy (-7.61%) is attributed to the converter consuming energy during operation.

[0109] In the case of Experiment 3, the benefit in total energy is an increase in available energy of about 10% (353.4-322) / 322). Such a large increase in available energy enables important commercial advantages for the use of sodium-ion cells that have not been realized to date.

[0110]

[0111] Simulated Model 1 - Calculation A

[0112] It can be calculated that the percentage improvement in available energy will be increased by using a more efficient DC / DC converter, and, for example, under the conditions of Experiment 3, using a commercially available converter with an average converter efficiency of 97% will provide a total energy increase of 17.5%.

[0113] Simulated Model 2 - Calculation B (Activates the DC / DC converter only when the battery pack voltage approaches the minimum operating voltage of the application device powered by the battery pack)

[0114] This simulated experiment models the amount of energy expected to be accessed when a DC / DC converter within a battery pack, such as the one used in Experiment 3, operates only when the battery pack voltage approaches the cut-off voltage to reduce parasitic loads in the battery pack. A schematic diagram of this simulated model battery pack is provided in Fig. 7.

[0115] Assume that the application device to be powered by the battery pack has a minimum operating voltage of 35V, and that the battery pack is designed to have an apparent voltage lower limit of 38V (slightly higher than 35V to prevent switching out). Then, if the battery is operated as in Experiment 1 (without a converter) until it initially reaches the 38V limit, it can be achieved for the DC / DC converter to take over and supply a constant voltage of 38V to the load terminals until it reaches the 18V battery limit.

[0116] As mentioned above, the battery pack used in these simulated experiments is the same as that used in Experiment 3, and as a result, the battery pack output energy will be 390.55Wh, because the battery pack will operate in the same voltage window from 56V to 18V.

[0117] In addition, from the data collected in Experiment 3, the battery output energy between 56V and 38V is 299.9Wh. Since the DC / DC converter is not operating within this voltage window, there is no energy loss.

[0118] Assuming the efficiency of the DC / DC converter is approximately 90%, it is expected that the battery output voltage will be boosted to 38V from below 38V. For this example, a suitable converter would include the Vicor Corporation DCM3414x50M53C2yzz, which has an efficiency of approximately 90%. Figure 8 shows the simulated model discharge profile for the Na-ion battery pack that forms the basis of this calculation B.

[0119] From the results previously provided in Table 2 for Experiment 3, the energy available from the battery (with DC / DC converter) between 38V and 18V is (390.55Wh - 299.9Wh) = 90.65Wh, and therefore the additional energy available at the load will be 90.65Wh * 90% = 81.6Wh.

[0120] Then, the battery pack and part-time DC / DC converter system will be provided with a total energy output of (299.9Wh + 81.6Wh) = 381.5Wh, and the overall efficiency (averaged over 56V to 18V) is 97.7%.

[0121] Therefore, the total output energy of this simulation model shows an increase of 18.47% compared to the reference experiment 1. This is also an increase compared to the simulated model A.

[0122] Simulated Model 3 - Calculation B using a mass-reduced DC / DC converter to increase the available specific energy density of the battery pack

[0123] An increase in available specific energy density (Wh / Kg) can be achieved as a result of reducing the weight of the DC / DC converter. Mean Well converters are not the best converters for this purpose due to their heavy mass (see Calculation C); however, the converter from Vicor Corporation (DCM3414x50M53C2yzz) is lightweight and possesses efficiency matching that of Mean Well converters within the low voltage range. Therefore, it can be calculated that operating the Vicor power converter only below 38 and 18 V results in an increase of approximately 15% in available pack specific energy density between 56 and 38 V. From the aforementioned Table 2: ((41.9-36.5) / 36.5)*100)

[0124] Simulated Model 4 - Calculation D (Test using reduced-mass DC / DC converter to increase available cell specific energy density)

[0125] It is desirable to secure an increase in available cell specific energy and available pack specific energy, as this results in increased flexibility in pack design. When comparing the cell from Experiment 1, weighing 4.90 kg without a converter, with the same cell and Vicor power converter weighing 5.16 kg combined (used only in the range of 38 and less than 18 V), an increase in available cell specific energy density between 56 V and 38 V was obtained from 65.7 Wh / kg (322 / 4.9) to 74 Wh / kg (381.5 / 5.16), which is a 13% increase.

[0126] Simulated Model 5 - Calculation E (Test using a reduced-volume DC / DC converter to increase battery pack available volumetric energy density)

[0127] In order to secure an increase in volumetric energy density as a result of using a DC / DC converter, a converter with a small volume needs to be used. The converter from Vicor Corporation (DCM3414x50M53C2yzz) has a small volume and good efficiency. When comparing the same pack from Experiment 1, which has a volume of 6.725 L without a converter, with the same pack (used only in the range of 38 and less than 18 V), the available volumetric energy density between 56 and 38 V increases from 48.1 Wh / L (322 / 6.696) in Experiment 1 to 56.7 Wh / L (381.5 / 6.725), which is an 18% increase in available pack volumetric energy.

[0128] Simulated Model 6 - Calculation F (Test using a reduced-volume DC / DC converter to increase available cell volumetric energy density)

[0129] It is desirable to ensure an increase in available cell volumetric energy density and available pack volumetric energy density, as this results in increased flexibility in pack design. When combining only the cells from Experiment 1 with a volume of 4.416 liters without a converter and comparing them with the same cells with a volume of 4.445 liters and a Vicor Power converter (used only in the range between 38 and 18V), the available volumetric energy density between 56 and 38V increases from 72.9 Wh / l (322 / 4.416) in Experiment 1 to 85.8 Wh / l (381.5 / 4.445), which is an 18% increase in available cell specific energy density.

[0130] As shown by experiments with the actual battery pack and simulated model described above, the inclusion of a DC / DC converter results in an unexpected increase in available energy, specific energy density, and volumetric energy density for the sodium-ion battery pack as well as for the individual sodium-ion cells contained within the battery pack. Particularly surprising is that these improved results can be obtained even when the weight (and volume) of the sodium-ion cells increases due to the inclusion of the DC / DC converter; nevertheless, as shown by the simulated model calculations described above, an additional increase in specific energy density is expected when a DC / DC converter with optimized mass and efficiency is used. These results are commercially very promising because the sodium-ion battery pack according to the present invention has the potential to be lighter and more compact, reduce waste by being contained within the cells, extend the time between charge cycles, and require fewer cells for any specific application.

Claims

Claim 1 A sodium-ion battery pack comprising one or more sodium-ion cells and one or more voltage converters, wherein the one or more sodium-ion cells have a minimum operating voltage (cell) falling within the range of greater than 0.0 V and less than 2.0 V. V min ) and maximum operating voltage (cell) in the range of greater than 3.60 V and less than 4.30 V V max A sodium-ion battery pack that can operate between, and furthermore, where the sodium-ion battery pack comprises two or more sodium-ion cells, the sodium-ion battery pack in which both or more sodium-ion cells have the same cell nominal voltage profile and the same electrochemical design. Claim 2 In claim 1, the sodium-ion battery pack further comprises a battery management system (BMS). Claim 3 In claim 1 or 2, all of the one or more sodium-ion cells are, cell V min This cell V max greater than 0% and less than or equal to 55%, or cell V max greater than 0% and less than or equal to 50%, or cell V max A sodium-ion battery pack capable of operating in a voltage range of greater than 0% and less than or equal to 45%. Claim 4 In claim 1 or 2, the one or more sodium-ion cells are cells falling within the range of greater than 3.70 V and less than or equal to 4.25 V. V max Between, or cells falling within the range of greater than 3.8 V and less than or equal to 4.20 V V max A sodium-ion battery pack capable of operating between. Claim 5 In claim 1 or 2, each of the one or more voltage converters is connected to more than one sodium-ion cell, forming a sodium-ion battery pack. Claim 6 A sodium-ion battery pack according to claim 1, wherein at least one of the one or more voltage converters is a DC / DC converter. Claim 7 In claim 6, the sodium-ion battery pack, wherein at least one DC / DC converter is a bidirectional DC / DC converter. Claim 8 In claim 7, the bidirectional DC / DC converter is selected from a boost converter and / or a buck / boost converter, for a sodium-ion battery pack. Claim 9 A sodium-ion battery pack according to claim 1 or 2, wherein at least one of the one or more voltage converters is part of a standalone circuit, or is embedded in or linked to a battery management system (BMS). Claim 10 In claim 1 or 2, the sodium-ion battery pack is intended to deliver an amount of specific energy, and the amount of specific energy is, (battery V max Difference in energy between 0V and 0V) * (Efficiency of one or more voltage converters) / (Mass of one or more sodium-ion cells + Mass of one or more voltage converters) > (battery V max and battery V max Satisfying the condition of (difference in energy between 60 and 70% of) / (mass of one or more sodium-ion cells), and battery V max A sodium-ion battery pack, which is determined as the maximum output voltage of a sodium-ion battery pack comprising one or more sodium-ion cells without one or more voltage converters. Claim 11 In claim 1 or 2, the sodium-ion battery pack has a voltage measured between the terminals of one or more sodium-ion cells connected in series of the sodium-ion battery pack of 60% V max In the case below, the terminal voltage of the sodium-ion battery pack is battery V max Sodium-ion battery pack for increasing to more than 60%. Claim 12 A method for accessing available energy from a battery comprising one or more sodium-ion cells, comprising: a) providing a sodium-ion battery pack comprising one or more voltage converters and one or more sodium-ion cells, wherein the one or more sodium-ion cells have a minimum operating voltage (cell) in the range greater than 0 V and less than 2.0 V. V min ) and maximum operating voltage (cell) in the range of greater than 3.6 V and less than 4.30 V V max ...can operate between; and furthermore, if the sodium-ion battery pack includes two or more sodium-ion cells, all two or more sodium-ion cells have the same cell nominal voltage profile and the same electrochemical design -; b) associating or integrating the sodium-ion battery pack with an electronic application device; and c) the output voltage of the sodium-ion battery pack is battery V max The step of directly or indirectly operating at least one of the above one or more voltage converters to increase the battery by more than 60%, and V max An energy access method determined as the maximum design output voltage of a sodium-ion battery pack comprising one or more sodium-ion cells without one or more voltage converters. Claim 13 An energy access method according to claim 12, wherein at least one of the one or more voltage converters is operated discontinuously over some or all of the operating voltage range of the electronic application device. Claim 14 In claim 12 or 13, the output voltage of at least one sodium-ion cell of the sodium-ion pack is V max An energy access method operated when 60% or less of Claim 15 A sodium-ion battery pack according to claim 1 or 2, wherein the sodium-ion battery pack is intended to increase the available and / or transmittable specific energy of a sodium-ion battery pack comprising one or more sodium-ion cells without one or more voltage converters by at least 3%. Claim 16 A sodium-ion battery pack according to claim 1 or 2, wherein the sodium-ion battery pack is intended to increase the available and / or transferable volumetric energy density of a sodium-ion battery pack comprising one or more sodium-ion cells without one or more voltage converters by at least 3%. Claim 17 An electronic application device integrated with or associated with a sodium-ion battery pack according to claim 1 or 2.

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