Multi-cell battery pack

Abstract

The present disclosure relates to a multi-cell battery pack. A battery pack according to an embodiment of the present technology may include a first battery cell comprising a lithium-containing material. The first battery cell may be configured to operate in a voltage window extending to or above approximately 4V. The battery pack may include a second battery cell electrically coupled in parallel with the first battery cell. The second battery cell may be configured to operate in a voltage window maintained at or below approximately 4.0V. The battery pack may also include a controller configured to receive a measured terminal voltage from the first battery cell. The controller may be configured to determine whether to disconnect the second battery cell from the first battery cell based on the measured terminal voltage of the first battery cell.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. non-provisional patent application No. 16 / 577,476, filed on September 20, 2019, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present technology relates to batteries and, more particularly, to battery cell configurations. Background Art

[0004] Batteries are used in many devices. As electronic devices and applications continue to expand with power demands, battery cell materials can affect capacity and operating time between charges. Summary of the Invention

[0005] A battery pack according to an embodiment of the present technology may include a first battery cell comprising a lithium-containing material. The first battery cell may be configured to operate in a voltage window extending to or above about 4V. The battery pack may include a second battery cell electrically coupled in parallel with the first battery cell. The second battery cell may be configured to operate in a voltage window maintained at or below about 4.0V. The battery pack may also include a controller configured to receive a measured terminal voltage from the first battery cell. The controller may be configured to determine whether to disconnect the second battery cell from the first battery cell based on the measured terminal voltage of the first battery cell.

[0006] In some embodiments, the first battery cell may be characterized by a cathode electrode density greater than or approximately 3.85 g / cc. The first battery cell may include a cathode electrode material comprising cobalt. The second battery cell may be characterized by a capacity less than or approximately 25% of the capacity of the first battery cell. The second battery cell may be configured to operate within a voltage window maintained between approximately 2.6 V and approximately 4.0 V. The second battery cell may include a lithium-containing cathode material comprising one or more of iron, nickel, or manganese. The second battery cell may include a lithium iron phosphate cathode electrode material. The second battery cell may include an anode material comprising graphite, titanium, or silicon. The controller may be configured to monitor a measured terminal voltage from the first battery cell during charging. The controller may be configured to disconnect the second battery cell from the first battery cell when the measured terminal voltage from the first battery cell exceeds a voltage threshold of the second battery cell. The controller may be configured to electrically connect the second battery cell to the first battery cell during discharging operations. The controller may be configured to connect the second battery cell with the first battery cell during a discharge operation when a measured terminal voltage of the first battery cell is lower than or approximately a voltage threshold of the first battery cell.

[0007] Some embodiments of the present technology may include a battery pack. The battery pack may include a first battery cell that includes a lithium cobalt cathode material. The first battery cell may be electrically coupled to an output terminal of the battery pack. The battery pack may also include a second battery cell electrically coupled in parallel with the first battery cell. The second battery cell may include a cathode material that is different from the first battery cell. The second battery cell may be characterized by a capacity that is less than or approximately 50% of the capacity of the first battery cell. The battery pack may also include a controller configured to receive a measured terminal voltage from the first battery cell during a charging operation. The controller may also be configured to electrically disconnect the second battery cell from the first battery cell when the measured terminal voltage from the first battery cell exceeds a voltage threshold of the second battery cell.

[0008] In some embodiments, the first battery cell may be configured to operate in a voltage window extending between about 2.8 V and about 4.5 V. The second battery cell may be configured to operate in a voltage window extending between about 2.6 V and about 4.0 V. The second battery cell may include a lithium-containing cathode material comprising one or more of iron, nickel, or manganese. The controller may be configured to electrically connect the second battery cell to the first battery cell during a discharge operation. The controller may be configured to connect the second battery cell to the first battery cell during a discharge operation when a measured terminal voltage of the first battery cell may be less than or about a voltage threshold of the first battery cell.

[0009] Some embodiments of the present technology may include a battery pack. The battery pack may include one or more output terminals. The battery pack may include a first battery cell, the first battery cell including a lithium cobalt oxide cathode material. The first battery cell may be electrically coupled to the one or more output terminals. The battery pack may include a second battery cell electrically coupled in parallel with the first battery cell. The second battery cell may be configured to operate in a voltage window that remains equal to or below approximately 4.0V. The battery pack may also include a controller configured to receive a measured terminal voltage from the first battery cell during a charging operation. The controller may also be configured to electrically disconnect the second battery cell from the first battery cell when the measured terminal voltage from the first battery cell exceeds a voltage threshold of the second battery cell. In some embodiments, the controller may be configured to electrically connect the second battery cell to the first battery cell during a discharging operation. The second battery cell may include lithium iron phosphate, lithium nickel manganese oxide, or lithium manganese oxide as a cathode material.

[0010] Such technology can offer numerous advantages over conventional techniques. For example, the battery packs of the present invention can provide extended operation before needing to be regulated or shut down. Furthermore, the battery packs can provide improved charge and discharge characteristics relative to conventional configurations. These and other embodiments, as well as their many advantages and features, are described in greater detail in conjunction with the following description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A further understanding of the nature and advantages of the disclosed embodiments may be realized by reference to the remainder of the specification and drawings.

[0012] Figure 1A A graph illustrating voltage distribution of materials used for a cathode electrode of a battery cell is shown, according to some embodiments of the present technology.

[0013] Figure 1B A graph illustrating the dependence of impedance on the depth of discharge of a battery cell is shown, according to some embodiments of the present technology.

[0014] Figure 2 Schematic cross-sectional views of battery cells according to some embodiments of the present technology are shown.

[0015] Figure 3 A schematic diagram of a battery pack including two parallel cells is shown, according to some embodiments of the present technology.

[0016] Figure 4 Graphs showing voltage distribution of battery cells and battery packs are shown, according to some embodiments of the present technology.

[0017] Figure 5 Graphs showing start and end pulse profiles for battery cells and battery packs are shown, according to some embodiments of the present technology.

[0018] Several of the figures are included as schematic diagrams. It should be understood that the figures are for illustrative purposes only and should not be considered to scale unless specifically indicated to scale. Additionally, the figures are provided as schematic diagrams to aid understanding and may not include all aspects or information as compared to actual representations and may include exaggerated material for illustrative purposes.

[0019] In the accompanying drawings, similar components or features may have the same numerical reference numerals. In addition, various components of the same type may be distinguished by following the reference numeral with a letter that distinguishes between similar components and / or features. If only the first numerical reference numeral is used in the specification, the description applies to any similar component and / or feature having the same first numerical reference numeral, regardless of the letter suffix. DETAILED DESCRIPTION

[0020] Batteries, battery cells, and more generally, energy storage devices are used in a host of different systems. In many devices, battery cells can be designed with a balance of characteristics in mind. For example, including larger batteries can increase the amount of time a device can last between charges. Similarly, including multiple battery cells within a housing can increase the device's operating life.

[0021] The operation of each individual battery cell can be affected by the chemical or material properties of the materials within the cell. For example, different electrode materials can affect the voltage profile of the battery cell in operation and can affect the operation of the battery pack in which the cells are incorporated. Figure 1 shows a variety of materials that can be incorporated into the electrodes of a battery cell. For example, the material can be included in the cathode electrode and can produce a battery cell characterized by a specific voltage profile as shown. As can be seen from the figure, different materials produce cells with different characteristics. For example, a cathode material comprising a lithium cobalt oxide material (shown as LCO in the graph) can be characterized by a relatively high voltage potential, but the voltage curve can be characterized by a slope within the operating range followed by a relatively sharp drop in capacity. The benefit of this type of material is that it can be effectively used in higher volumetric energy density applications, but as will be explained below, the impedance steadily increases during discharge.

[0022] Another exemplary material shown is lithium iron phosphate (shown as LFP in the chart), which can be characterized by a relatively flat voltage profile during discharge, but is characterized by a lower potential relative to other materials such as LCO. This material can be used in high-power applications where a lower voltage may be more acceptable, but as a primary cell, it may be less efficient for higher energy density relative to the space consumed by the cell. The other materials shown also have advantages and disadvantages, and in some applications, the materials can be combined or modified to adjust the characteristics of the battery cell.

[0023] As noted, cobalt-containing cathode materials such as LCO may function well in many electronic devices due to the high volumetric energy density of the battery provided by the characteristics of LCO. However, as a battery cell or a battery pack including one or more cells further discharges, the impedance of the cell may increase, which may affect the voltage and operation of the cell. Figure 1B A graph illustrating the dependence of impedance on the depth of discharge of a battery cell, according to some embodiments of the present technology, is shown. Line 105 is for a battery cell including a cobalt-containing material for the cathode electrode. This line illustrates how the internal resistance of the battery cell increases as the battery cell depletes. Line 110 illustrates the same cell after multiple charge and discharge cycles, showing how the resistance increases further over time. This resistance can cause the cell's voltage to drop, which can trigger protection mechanisms in the cell.

[0024] For example, a cell comprising LCO or some other cobalt-containing material can provide the required output voltage for operating an electronic device. As the cell depletes due to use, the cell's resistance can increase, and the voltage can decrease further for similar process current draw. If additional applications are enabled at this depth of discharge that could draw further current from the cell, the voltage can drop even more rapidly due, at least in part, to polarization associated with the high impedance. Protection circuits or mechanisms within the electronic device can be triggered based on the voltage drop caused by these conditions at greater depths of discharge, even though the cell itself may still be characterized by a remaining 10%-20% or more capacity. Additional cells comprising the same material can reduce the overall space within a given form factor, or multiple cells with the same challenges can be created.

[0025] The present technology overcomes these problems by combining a secondary cell that includes a separate electrode chemistry from the primary cell. By utilizing a chemistry that can be characterized by a lower potential but a flatter voltage profile, a battery pack that includes both cell types can be characterized by extended discharge before shutdown and additional advantages associated with charging and discharging. A flatter voltage profile can be defined as less voltage variation during discharge. For example, Figure 1A As shown, some materials, such as LCO, can be characterized by a sloping voltage profile that can extend over 5% of voltage or over 10% of voltage between approximately 20% and approximately 80% of discharge. Additional materials, such as LFP, can be characterized by a relatively flat voltage profile that can extend between approximately 20% and approximately 80% of discharge or between approximately 10% and approximately 90% of discharge by less than or about 5%, less than or about 3%, less than or about 2%, less than or about 1%, or can remain at a stable voltage. This can allow the cell voltage to be pinned to a second cell when the impedance of the first cell increases, which can cause the voltage to drop. Because the second cell can remain at a stable voltage for a longer period of time, the usable voltage range provided by the battery pack can be increased without risking the cell's operation or performance.

[0026] While the remainder of the specification will refer to lithium-ion batteries, those skilled in the art will readily appreciate that the technology is not limited thereto. The technology can be used with any number of batteries or energy storage devices, including other rechargeable battery types and primary battery types, as well as secondary batteries or electrochemical capacitors. Furthermore, the technology can be applied to batteries and energy storage devices used in any number of technologies, including but not limited to phones and mobile devices, watches, eyewear, bracelets, anklets, and other wearable technologies, including fitness equipment, handheld electronic devices, laptops and other computers, and other devices that may benefit from using the various battery technologies described.

[0027] Figure 2A schematic cross-sectional view of an energy storage device or battery cell 200 according to an embodiment of the present technology is shown. The battery cell 200 may be or may include a battery cell, and may be one of a plurality of cells coupled together to form a battery structure. As will be readily understood, these layers are not shown to any particular scale and are intended only to illustrate possible cell material layers that may be incorporated into one or more cells in an energy storage device. In some embodiments, as Figure 2 As shown, the battery cell 200 includes a first current collector 205 and a second current collector 210. In an embodiment, one or both current collectors may include a metal or non-metallic material, such as a polymer or composite that may include a conductive material. The first current collector 205 and the second current collector 210 may be different materials in the embodiment. For example, in some embodiments, the first current collector 205 may be a material selected based on the potential of the anode active material 215, and may be or may include copper, stainless steel, or any other suitable metal, as well as non-metallic materials including polymers. The second current collector 210 may be a material selected based on the potential of the cathode active material 220, and may be or may include aluminum, stainless steel, or other suitable metal, as well as non-metallic materials including polymers. In other words, the materials for the first current collector and the second current collector may be selected based on the electrochemical compatibility with the anode active material and cathode active material used, and may be any material known to be compatible.

[0028] In some cases, the metal or non-metal used for the first current collector and the second current collector may be the same or different. The materials selected for the anode active material and the cathode active material may be any suitable battery material that can be operated in a rechargeable battery design as well as a primary battery design. For example, the anode active material 215 may be silicon, silicon oxide, silicon alloy, graphite, carbon, tin alloy, lithium metal, lithium-containing materials such as lithium titanium oxide (LTO), a combination of any of these materials, or other suitable materials that can form an anode in a battery cell. In addition, for example, the cathode active material 220 may be a lithium-containing material. In some embodiments, the lithium-containing material may be a lithium metal oxide such as lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate, or a combination of any of these materials, while in other embodiments, the lithium-containing material may be lithium iron phosphate or other suitable materials that can form a cathode in a battery cell.

[0029] The first and second current collectors and the active material may have any suitable thickness. The separator 225 may be disposed between the electrodes and may be a polymer film, a ceramic film, or a material that allows lithium ions to pass through the structure rather than conducting electricity in other ways. In a complete unit configuration, the active materials 215 and 220 may also include a certain amount of electrolyte, which may also be absorbed within the separator 225. The electrolyte may be a liquid comprising one or more salt compounds dissolved in one or more solvents. In an embodiment, the salt compound may include a lithium-containing salt compound, and may include one or more lithium salts, including, for example, lithium compounds doped with one or more halogen elements such as fluorine or chlorine, and other non-metallic elements such as phosphorus and semi-metallic elements including, for example, boron.

[0030] In some embodiments, the salt may include any lithium-containing material that is soluble in an organic solvent. The solvent included with the lithium-containing salt may be an organic solvent and may include one or more carbonates. For example, the solvent may include one or more carbonates, including propylene carbonate, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and fluoroethylene carbonate. Combinations of solvents may be included, and may include, for example, propylene carbonate and ethyl methyl carbonate as an exemplary combination. Any other solvent may be included that enables dissolution of one or more lithium-containing salts and other electrolyte components, or that may provide useful ionic conductivity, such as greater than or about 5 -10 mS / cm.

[0031] Although shown as a single layer of electrode material, the battery cell 200 can be any number of layers. Although the cell can be constructed of a single layer of anode and cathode material as a sheet, the layers can also be formed into a jelly roll design or a folded design, a prismatic design, or any form such that any number of layers can be included in the battery cell 200. For embodiments including multiple layers, the tab portions of each anode current collector can be coupled together, just like the tab portions of each cathode current collector. Once the cell has been formed, a pouch, shell, or casing can be formed around the cell to contain the electrolyte and other materials within the cell structure, as described below. Terminals can extend from or be coupled to the casing to allow the cell to be electrically coupled for use in a device, the terminals including an anode terminal and a cathode terminal. The connector can be directly connected to a load that can utilize the power, and in some embodiments, the battery cell can be coupled to a control module that can monitor and control the charging and discharging of the battery cell. Figure 2 Included as exemplary batteries that may be incorporated into batteries according to the present technology. However, it should be understood that any number of battery and cell designs and materials that may include similar configurations as described below may be encompassed by or incorporated with the present technology.

[0032] Figure 3A schematic diagram of a battery pack 300 including two parallel cells is shown in accordance with some embodiments of the present technology. This configuration can couple the two cells in parallel to provide utilization of the first cell during a first time period during battery pack discharge, and to provide utilization of the second cell during a second time period during battery pack discharge, which can be based on a load coupled to the cell or battery pack.

[0033] The battery pack 300 may have one or more output terminals 302 that can provide coupling to a load or electronic device. The battery pack 300 may include a first cell 305 and a second cell 310, one or both of which may be electrically coupled to the one or more output terminals 302. In some embodiments of the present technology, each cell may represent one or more cells, including multiple cells of different sizes or capacities. Any cell may include the materials previously described and may include any of the structures, components, or characteristics of the battery cell 200 described above. In some embodiments, the first cell 305 may differ from the second cell 310 in one or more ways. For example, in some embodiments, the first cell 305 and the second cell 310 may include one or more different materials, such as different electrode materials. The electrode material may be selected based in part on the operation of the cells in the battery pack. For example, in some embodiments, one or more first cells may be larger than one or more second cells and may include materials selected for different purposes. The first cell 305 may operate as the primary power source for an electronic device associated with the battery pack. The second unit 310 may operate as a secondary power source that may operate in conjunction with the first unit 305 during battery pack operation.

[0034] In some embodiments, the first cell 305 may include a lithium-containing material as the cathode electrode active material and may include a cobalt-containing material. For example, the first cell 305 may include lithium cobalt oxide in the cathode as previously described, although other battery materials described above may be used similarly. The first cell material may be selected to generally operate in a voltage window extending to greater than or about 3.5V, and the material may be selected to operate in a voltage window extending to greater than or about 3.8V, greater than or about 4.0V, greater than or about 4.2V, greater than or about 4.5V, or higher. In some embodiments, the electrolyte chemistry may limit the operable voltage window to limit decomposition of the electrolyte components. Therefore, in some embodiments, the operating voltage window of the first cell 305 may be less than or about 4.8V, less than 4.5V, or less. By utilizing materials such as those including lithium cobalt oxide, the first cell 305 can be developed for high volumetric energy density applications in electronic devices that can be combined with battery packs. The first unit 305 may also include one or more materials in the cathode that can be characterized by a cathode electrode density greater than or about 3 g / cc, and can be characterized by a cathode electrode density greater than or about 3.2 g / cc, greater than or about 3.5 g / cc, greater than or about 3.75 g / cc, greater than or about 3.85 g / cc, greater than or about 3.95 g / cc, or greater.

[0035] Second cell 310 can be made of the same or different materials as first cell 305, and in some embodiments, can include a different cathode material than first cell 305. Second cell 310 can also include a lithium-containing material as the cathode electrode active material, but in some embodiments, second cell 310 may not include lithium cobalt oxide. In some embodiments, second cell 310 can include one or more additional elements, such as iron, nickel, or manganese. As non-limiting examples, second cell 310 can include cathode materials including lithium iron phosphate, lithium nickel manganese cobalt oxide, lithium manganese oxide, and other materials that can produce a cell with a flatter voltage profile. Second cell 310 can be configured to operate as a high-power cell that can operate after an extended discharge of first cell 305. Therefore, second cell 310 can be characterized by a flatter voltage profile, as previously described, which can also be characterized by a lower impedance dependence on state of charge. Because, in some embodiments, second cell 310 can operate after a certain amount of discharge of first cell 305, corresponding to the lower voltage from the cell, second cell 310 can be characterized by a lower operating voltage window than first cell 305. For example, the second cell 310 may be characterized by a voltage window that may be less than or approximately 4.0 V, and may be less than or approximately 3.8 V, less than or approximately 3.6 V, less than or approximately 3.4 V, less than or approximately 3.2 V, or less. Thus, in some embodiments, the first cell 305 may be configured to operate in a voltage window extending between approximately 2.8 V and approximately 4.5 V, and the second cell 310 may be configured to operate in a voltage window extending between approximately 2.6 V and approximately 3.6 V, as well as smaller ranges within these stated ranges.

[0036] The second cell 310 can be of any size relative to the capacity of the first cell 305, but in some embodiments, the second cell 310 can be characterized by a lower capacity than the first cell 305. The first cell 305 can include materials that operate efficiently with a high volumetric energy density, which can provide a reduced form factor for the first cell. Because the second cell 310 can include materials characterized by a lower volumetric energy density than the materials of the first cell 305, and because the second cell 310 can be configured to operate after a certain amount of discharge of the first cell 305, the second cell 310 can be sized to be less than or about 50% of the capacity of the first cell 305. In some embodiments, the second cell 310 can be sized to be less than or about 45% of the capacity of the first cell 305, less than or about 40% of the capacity, less than or about 35% of the capacity, less than or about 30% of the capacity, less than or about 25% of the capacity, less than or about 20% of the capacity, less than or about 15% of the capacity, less than or about 10% of the capacity, or less.

[0037] like Figure 3As shown, a first cell 305 and a second cell 310 can be coupled in parallel within a battery pack 300. Because the second cell 310 can operate in a lower voltage window than the first cell 305, a controller 315 can be coupled within the battery pack to control the connection and disconnection of the second cell 310 from the parallel coupling of the first cell 305. The controller 315 can be electrically coupled to the first cell 305 and can receive or measure a terminal voltage from the first cell 305. Based on the measured terminal voltage, the controller 315 can operate one or more switches, which can be one or more MOSFETs 320 as shown, or some other switches operable by the controller 315, and the one or more switches can disconnect or reconnect the second battery cell from the first battery cell.

[0038] During a charging operation, the two parallel battery cells can be charged in series until the threshold voltage of the second battery cell indicates that the second battery cell is fully charged. Because the first battery cell 305 may not be fully charged, continued charging of the system may cause damage to the second battery cell 310. By measuring the terminal voltage of the first battery cell, the controller 315 can monitor the voltage to identify when the cell voltage may increase to exceed the maximum voltage or threshold voltage of the second battery cell. Therefore, when the measured terminal voltage from the first battery cell exceeds the voltage threshold of the second battery cell, the controller 315 can disconnect the second battery cell from the first battery cell and from the power source.

[0039] The controller 315 can reconnect the second cell 310 at any time after charging of the first cell 305 has occurred. For example, after charging, the controller 315 can reconnect the second cell 310 within the battery pack. Additionally, the controller 315 can electrically connect the second cell to the first cell during a discharge operation. For example, once the first cell begins discharging to the load, the controller 315 can reconnect the second cell 310 within the battery pack. This reconnection can occur at any time during discharge and can also be related to the depth of discharge of the first cell. For example, in some embodiments, the first cell cathode material can be or include lithium cobalt oxide, which, as previously described, can be characterized by a voltage decay during discharge, which can be based at least in part on increased impedance. In some embodiments, the second cell 310 can be reconnected to the system when the measured terminal voltage of the first cell during discharge drops to a threshold. This operation can occur at any measured voltage of the first cell. For example, the second cell 310 can be recoupled when the measured voltage of the first cell drops to less than or approximately 4.0V. The second cell may also be recoupled when the measured voltage of the first cell decreases to less than or approximately 3.9V, less than or approximately 3.8V, less than or approximately 3.7V, less than or approximately 3.6V, less than or approximately 3.5V, less than or approximately 3.4V, less than or approximately 3.3V, less than or approximately 3.2V, less than or approximately 3.1V, less than or approximately 3.0V, or less.

[0040] By utilizing a second cell as described in a battery pack according to some embodiments of the present technology, extended operation and a lower likelihood of premature device shutdown may occur. Figure 4 A graph showing voltage profiles for battery cells and battery packs according to some embodiments of the present technology is shown. The graph may illustrate one possible configuration encompassed by the present technology. The configuration is not intended to limit the scope of the claimed technology and is intended only to provide additional illustration of the multi-cell configurations encompassed. Line 405 shows the voltage profile relative to the capacity of an exemplary first cell according to some embodiments of the present technology. For example, line 405 is based on a 4.8Ah energy cell including a lithium cobalt oxide cathode material. Line 410 shows the voltage profile relative to the capacity of an exemplary second cell according to some embodiments of the present technology. For example, line 410 is based on a 1.1Ah energy cell including a lithium iron phosphate cathode material. As shown, while line 405 is characterized by a sloped and reduced voltage profile as the cell discharges, line 410 is characterized by a relatively flat voltage profile as the cell discharges due to material properties and increased impedance, as previously described.

[0041] Line 415 illustrates the operation of a battery pack comprising both a first cell on line 405 and a second cell on line 410 coupled in parallel within the pack. As shown, during the initial discharge of the battery pack, the voltage profile of the battery pack tracks and corresponds to the profile of line 405 for the first cell. As the cell continues to discharge and the voltage continues to decrease, the resistance may increase to the point where the voltage drops to a threshold at which the first cell, the battery pack, or an electronic device incorporating the battery pack may be shut down. However, rather than the battery pack also shutting down, the pack voltage will follow the profile of the second cell on line 410, which may allow power delivery from the battery pack to continue for a longer period of time than if the first cell were simply sized for a larger capacity.

[0042] Figure 5 A graph showing the start and end pulse profiles of a battery cell and a battery pack according to some embodiments of the present technology is shown. The graph shows each of the battery cells and parallel coupled battery packs discharged at 4.35V, 4.2V, 4.0V, 3.8V, 3.6V, 3.5V, 3.4V, 3.3V and 3.2V at a 2C rate for 30 seconds. Line 505 shows the discharge of the first cell as described above and based on a 4.8Ah energy cell including a lithium cobalt oxide cathode material. Line 510 shows the discharge of the second cell as described above and based on a 1.1Ah energy cell including a lithium iron phosphate cathode material. Line 515 shows the discharge of the battery pack having the first cell and the second cell coupled in parallel. The voltages at the start and end pulses are plotted as shown, and a cutoff voltage of 2.5V is implemented, as may be associated with the operation of a battery pack in an electronic device.

[0043] For a high energy density first cell where the resistance increases with increasing depth of discharge, when the pulse voltage reaches 3.5V or less, the end of pulse voltage reaches a cutoff voltage of 2.5V, indicating cell shutdown. However, as shown, this same shutdown may not occur for a second cell characterized by stable power delivery. When the battery pack also includes a second cell coupled in parallel, the battery pack operating voltage continues to extend beyond the cutoff voltage of the first cell and extends to about 3.3V, as shown. Again, this shows an improvement in discharge over a larger cell, such as a 6Ah first cell, which may still reach the cutoff voltage when the voltage reaches 3.5. By incorporating a second cell characterized by a flatter profile, the operation of the battery pack can extend beyond the capabilities of the first cell material while substantially retaining the form factor and energy density benefits of utilizing the first cell material.

[0044] As previously mentioned, one or more computing devices or components may be adapted to provide some of the desired functions described herein by accessing software instructions presented in a computer-readable form. A computing or processing device may process or interpret signals from one or more components of the present technology, such as a controller. When using software, any suitable programming, scripting, or other type of language or combination of languages may be used to execute the process. However, software does not need to be used specifically, or may not be used at all. For example, some embodiments of the present technology described above may also be implemented by hard-wired logic components or other circuits, including but not limited to dedicated circuits. A combination of computer-executed software and hard-wired logic components or other circuits may also be suitable.

[0045] Some embodiments of the present technology may be performed by one or more suitable computing devices adapted to perform one or more of the operations previously discussed. As described above, such devices may have access to one or more computer-readable media embodying computer-readable instructions that, when executed by at least one processor that may be incorporated into the device, cause the at least one processor to implement one or more aspects of the present technology. Additionally or alternatively, the computing device may include circuitry that enables the device to operate to implement one or more of the methods or operations described.

[0046] One or more aspects of the present technology may be implemented or practiced using any suitable computer-readable medium or media, including but not limited to floppy disks, drives and other magnetic-based storage media, optical storage media including disks such as CD-ROMs, DVD-ROMs or variations thereof, flash memory, RAM, ROM, and other memory devices, etc.

[0047] In the foregoing description, for the purpose of explanation, numerous specific details are discussed in order to provide an understanding of the embodiments of the present technology. However, it will be apparent to one skilled in the art that certain embodiments may be practiced without some of these specific details, or with additional details.

[0048] Several embodiments are disclosed, and those skilled in the art will recognize that various modifications, alternative structures, and equivalents may be used without departing from the spirit of the embodiments. In addition, many well-known processes and elements are not described to avoid unnecessarily obscuring the present technology. Therefore, the above description should not be considered to limit the scope of the present technology.

[0049] If a series of values is provided, it should be understood that, unless the context clearly dictates otherwise, each intervening value of the smallest fraction of the unit of the lower limit between the upper and lower limits of the range is also specifically disclosed. Any narrower range between any stated value or unstated intervening value in the stated range and any other stated or intervening value in the stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included in or excluded from the stated range, and any limits, none of which or both are included in each of the smaller ranges, are also encompassed within the technical scope, subject to any specifically excluded limits within the stated range. Where the range includes one or two limiting ranges, ranges excluding one or both of those included limits are also encompassed. If multiple values are provided in a list, any range encompassing or based on any of these values is similarly specifically disclosed.

[0050] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a material" includes a plurality of such materials and reference to "an element" includes reference to one or more elements and equivalents thereof known to those skilled in the art, and so forth.

[0051] In addition, the words “comprises,” “includes,” and “contains,” when used in this specification and the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groupings.

Claims

1. A battery pack comprising: one or more output terminals; a first battery cell comprising a lithium-containing material, wherein the first battery cell is configured to operate in a voltage window extending from 2.5V to or above 4V, and wherein the first battery cell is electrically coupled to the one or more output terminals; a second battery cell electrically coupled in parallel with the first battery cell, wherein the second battery cell is configured to operate in a voltage window that remains equal to or below 4.0V; and A controller configured to: receiving a measured terminal voltage from the first battery cell, and Whether to disconnect the second battery cell from the first battery cell is determined based on the measured terminal voltage of the first battery cell. 2 . The battery pack of claim 1 , wherein the first battery cell is characterized by a cathode electrode density greater than or equal to 3.85 g / cc.

3. The battery pack of claim 2, wherein the first battery cell comprises a cobalt-containing cathode electrode material. 4 . The battery pack of claim 1 , wherein the second battery cell is characterized by a capacity that is less than or equal to 25% of the capacity of the first battery cell. 5 . The battery pack according to claim 1 , wherein the second battery cell is configured to operate in a voltage window maintained between 2.6 V and 4.0 V.

6. The battery pack of claim 5, wherein the second battery cell comprises a lithium-containing cathode material comprising one or more of iron, nickel, or manganese.

7. The battery pack according to claim 6, wherein the second battery cell comprises at least one of the following: Lithium iron phosphate cathode electrode material; or Anode material, wherein the anode material includes graphite, titanium or silicon. 8 . The battery pack according to claim 1 , wherein the voltage window of the first battery cell extends from 2.8 V to or above 4 V.

9. The battery pack according to any one of claims 1 to 3, wherein the controller is further configured to: monitoring the measured terminal voltage from the first battery cell during charging; and When the measured terminal voltage from the first battery cell exceeds a voltage threshold of the second battery cell, the second battery cell is disconnected from the first battery cell. 10 . The battery pack according to claim 1 , wherein the controller is further configured to electrically connect the second battery cell with the first battery cell during a discharge operation. 11 . The battery pack of claim 10 , wherein the controller is configured to connect the second battery cell with the first battery cell during a discharge operation when the measured terminal voltage of the first battery cell is lower than or equal to a voltage threshold of the first battery cell.

12. A battery pack comprising: a first battery cell comprising a lithium cobalt cathode material, wherein the first battery cell is electrically coupled to an output terminal of the battery pack; a second battery cell electrically coupled in parallel with the first battery cell, wherein the second battery cell comprises a different cathode material than the first battery cell, and wherein the second battery cell is characterized by a capacity less than or equal to 50% of the first battery cell; and A controller configured to: receiving a measured terminal voltage from the first battery cell during a charging operation, and When the measured terminal voltage from the first battery cell exceeds a voltage threshold of the second battery cell, the second battery cell is electrically disconnected from the first battery cell.

13. The battery pack of claim 12, wherein the first battery cell is configured to operate in a voltage window extending between 2.8V and 4.5V.

14. The battery pack of claim 12 or 13, wherein the second battery cell is configured to operate in a voltage window extending between 2.6V and 4.0V.

15. The battery pack of claim 12 or 13, wherein the second battery cell comprises a lithium-containing cathode material comprising one or more of iron, nickel, or manganese. 16 . The battery pack according to claim 12 , wherein the controller is further configured to electrically connect the second battery cell with the first battery cell during a discharge operation.

17. The battery pack of claim 12 or 13, wherein the controller is configured to connect the second battery cell with the first battery cell during a discharge operation when the measured terminal voltage of the first battery cell is lower than or equal to a voltage threshold of the first battery cell.

18. A battery pack comprising: one or more output terminals; a first battery cell comprising a lithium cobalt oxide cathode material, wherein the first battery cell is electrically coupled to the one or more output terminals; a second battery cell electrically coupled in parallel with the first battery cell, wherein the second battery cell is configured to operate in a voltage window that remains equal to or below 4.0V; and A controller configured to: receiving a measured terminal voltage from the first battery cell during a charging operation, and When the measured terminal voltage from the first battery cell exceeds a voltage threshold of the second battery cell, the second battery cell is electrically disconnected from the first battery cell. 19 . The battery pack of claim 18 , wherein the controller is further configured to electrically connect the second battery cell with the first battery cell during a discharge operation.

20. The battery pack according to claim 18 or 19, wherein the second battery cell comprises lithium iron phosphate, lithium nickel manganese oxide or lithium manganese oxide as a cathode material.

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