Surface doping of lithium- and manganese-rich powder for improved cycling stability

Abstract

A method for doping a battery cathode comprises producing a coating with a complex containing a metal-based molecular precursor, applying the coating to a battery cathode, and calcining the coating applied to the battery cathode at a calcination temperature of at least 300 °C.

Description

INTRODUCTION The information contained in this section serves to present the general context of the disclosure. Works of the inventors mentioned herein, insofar as they are described in this section, as well as aspects of the description that might not otherwise be considered prior art at the time of filing, are neither expressly nor implicitly admitted as prior art against the present disclosure. The present disclosure relates generally to battery cathodes. More specifically, the present disclosure relates to the application of a metal oxide to a cathode of a lithium-ion battery. Vehicles are often equipped with batteries for various purposes. Batteries have different cycle lives and discharge capacities, which can be increased or decreased depending on the different films that can be applied to the battery's cathode. For example, applying a metal oxide-based film can extend the cycle life of the cathode material and thus the battery. One technique for coating the cathode is vapor deposition, such as atomic layer deposition (ALD) and chemical vapor deposition (CVD). However, applying a film layer to the cathode can lead to a reduction in the battery's overall discharge capacity. Therefore, there is a need for an improved battery cathode coating process that maintains or improves both the battery's cycle life and discharge capacity. SUMMARY In some aspects, a process for doping a battery cathode includes the production of a coating with a complex containing a metal-based molecular precursor, the application of the coating to a battery cathode, and the calcination of the coating applied to the battery cathode at a calcination temperature of at least 300 °C. In some examples, the metal-based molecular precursor may contain organic ligands. In some configurations, the metal-based molecular precursor may be a metal alkoxide. In some cases, the metal alkoxide may contain a metal isopropoxide. Optionally, the metal isopropoxide may comprise one or more of aluminum isopropoxide, titanium isopropoxide, manganese isopropoxide, boric acid isopropoxide, sodium isopropoxide, lithium isopropoxide, and potassium isopropoxide. Additionally or alternatively, the complex may contain at least two metal-based molecular precursors, each containing a different metal alkoxide. In other examples, the metal alkoxide coating may contain 0.01 wt% to 2 wt% of a transition metal. In other examples, the battery cathode may contain at least one of the following: a lithium and manganese rich (LMR) cathode, a nickel manganese cobalt oxide (NMC) cathode, a nickel cobalt manganese aluminum (NCMA) cathode, a lithium iron phosphate (LFP) cathode, a lithium nickel dioxide (LNO) cathode, a lithium manganese iron phosphate (LMFP) cathode, a lithium manganese oxide (LMO) cathode, and a lithium nickel manganese oxide (LNMO) cathode. In other aspects, a battery doping process includes the preparation of a coating with a complex containing a metal alkoxide with organic ligands, the application of the coating to a battery cathode, and the calcination of the coating applied to the battery cathode at a calcination temperature of at least 300 °C. In some examples, the metal alkoxide may contain a metal isopropoxide. Optionally, the metal isopropoxide may comprise one or more of aluminum isopropoxide, titanium isopropoxide, manganese isopropoxide, boric acid isopropoxide, sodium isopropoxide, lithium isopropoxide, and potassium isopropoxide. Additionally or alternatively, the complex may contain at least two metal alkoxides. In other examples, the metal alkoxide coating may contain 0.01 wt.% to 2 wt.% of a transition metal. In further examples, the calcination temperature may be between 400 °C and 900 °C. In some examples, the battery cathode may contain at least one of the following: a lithium and manganese rich (LMR) cathode, a nickel manganese cobalt oxide (NMC) cathode, a nickel cobalt manganese aluminum (NCMA) cathode, a lithium iron phosphate (LFP) cathode, a lithium nickel dioxide (LNO) cathode, a lithium manganese iron phosphate (LMFP) cathode, a lithium manganese oxide (LMO) cathode, and a lithium nickel manganese oxide (LNMO) cathode. In other aspects, a process for doping an LMR battery cathode for use in a vehicle includes the preparation of a coating containing an alcohol-based solution comprising a metal-based molecular precursor. The metal-based molecular precursor contains aluminum isopropoxide, and the aluminum isopropoxide has organic ligands. The process also includes spraying the coating onto an LMR battery cathode and drying the coating. The process further includes evaporating alcohol from the coating to define a coating layer of aluminum isopropoxide on the LMR cathode. The aluminum isopropoxide coating layer contains 0.58 wt% aluminum ions.The process also includes calcining the coating layer on the LMR cathode at a calcination temperature of at least 450 °C to define a doped LMR cathode, wherein the doped LMR cathode is doped with aluminum ions. The process further includes installing the battery in a vehicle and connecting at least one electrical component of the vehicle to the battery. In some examples, the calcination temperature may range from 450 °C to 900 °C. In other examples, coating application may involve spraying the alcohol-based solution from a nozzle at a frequency of 0.2 hertz (Hz) and a flow rate of five (5) cubic centimeters per minute (cm³ / min). In still other examples, coating drying may involve circulating air over the LMR cathode at a rate of thirty (30) liters of air per minute (L / min), with the air temperature being eighty (80) degrees Celsius (°C). Optionally, the alcohol in the alcohol-based solution may contain one or more of the following: ethanol, methanol, and isopropanol. The alcohol-based solution may have a concentration of one (1) gram (g) of aluminum isopropoxide per thirty (30) milliliters (mL) of alcohol.In other examples, the metal-based molecular precursor may contain one or more of titanium isopropoxide, manganese isopropoxide, boric acid isopropoxide, sodium isopropoxide, lithium isopropoxide, and potassium isopropoxide. BRIEF DESCRIPTION OF THE DRAWINGS The drawings described herein serve only to illustrate selected configurations and are not intended to limit the scope of this disclosure. Fig. 1 is a perspective view of a vehicle containing a battery according to the present disclosure; Fig. 2 is a perspective view of a battery according to the present disclosure; Fig. 3 is an exemplary block diagram for a battery according to the present disclosure and reference batteries; Fig. 4 is an exemplary flowchart for a method for doping a battery cathode according to the present disclosure; and Fig. 5 is an example diagram of performance characteristics of a battery according to the present disclosure compared to reference batteries. The corresponding reference symbols consistently indicate the relevant parts in the drawings. DETAILED DESCRIPTION Example configurations are now described in more detail with reference to the accompanying drawings. Example configurations are provided to ensure that this disclosure is comprehensive and fully conveys its scope to the person skilled in the art. Specific details are included, such as examples of specific components, devices, and processes, to provide a thorough understanding of the configurations of this disclosure. The person skilled in the art will recognize that specific details need not be used, that example configurations can be implemented in many different forms, and that the specific details and example configurations should not be interpreted as limiting the scope of this disclosure. The terminology used herein serves only to describe certain exemplary configurations and is not to be understood as restrictive. As used herein, the singular forms "a," "an," and "the" can also include the plural forms unless the context clearly indicates otherwise. The terms "comprise," "comprehensive," "contain," and "exhibit" are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. The procedural steps, processes, and operations described herein are not to be interpreted as necessarily being carried out in the particular order discussed or illustrated, unless they are expressly identified as a sequence of execution.Additional or alternative steps can be applied. When an element or layer is described as being "on" or "interacting with" another element or layer, or as being "connected" or "coupled" or "attached" to the same, it may be directly on or interacting with, connected with, coupled to, or attached to the other element or layer, or there may be intervening elements or layers. However, when an element is described as being "directly on" or "directly interacting with" another element or layer, or as being "directly connected" or "directly coupled" or "directly attached" to the same, there must be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted similarly (e.g.,B. “between” versus “directly between”, “neighboring” or “adjacent” versus “directly adjacent” or “directly bordering”, etc.). As used herein, the term “and / or” includes all combinations of one or more of the related listed items. The terms "first," "second," "third," etc., may be used herein to describe different elements, components, areas, layers, and / or sections. These elements, components, areas, layers, and / or sections should not be restricted by these terms. These terms may only be used to distinguish one element, component, area, layer, or section from another. Terms such as "first," "second," and other numerical terms do not imply any sequence or order unless the context clearly indicates otherwise.Thus, one could refer to a first element, a first component, a first area, a first layer or a first section discussed below as a second element, second component, second area, second layer or second section, without deviating from the lessons of the example configurations. In this application, including the definitions below, the term "module" may be replaced by the term "circuit".The term "module" may refer to, be part of, or include: an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a (shared, dedicated, or grouped) processor that executes code; a (shared, dedicated, or grouped) memory that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-a-chip. The term "code," as used above, may include software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, and / or objects. The term "shared processor" includes a single processor that executes all or part of the code from multiple modules. The term "group processor" includes a processor that, in combination with additional processors, executes all or part of the code from one or more modules. The term "shared memory" includes a single memory that stores all or part of the code from multiple modules. The term "group memory" includes memory that, in combination with additional memory, stores all or part of the code from one or more modules. The term "memory" may be a subset of the term "computer-readable medium."The term "computer-readable medium" encompasses non-transient electrical and electromagnetic signals that propagate through a medium and can therefore be considered tangible and non-transient storage. Non-restrictive examples of non-transient storage include tangible computer-readable media, such as non-volatile memory, magnetic storage, and optical storage. The devices and procedures described in this application can be implemented in whole or in part by one or more computer programs executed by one or more processors. The computer programs contain processor-executable instructions stored on at least one non-transitory, tangible, computer-readable medium. The computer programs may also contain and / or rely on stored data. A software application (i.e., a software resource) can refer to computer software that causes a computing device to perform a task. In some examples, a software application may be called an "application," "app," or "program." Examples of software applications include, but are not limited to, system diagnostic applications, system management applications, system maintenance applications, word processing applications, spreadsheet applications, messaging applications, media streaming applications, social networking applications, and gaming applications. Non-transitory memory can be physical devices used for the temporary or permanent storage of programs (e.g., instruction sequences) or data (e.g., program status information) for use by a computing device. Non-transitory memory can be volatile and / or non-volatile addressable semiconductor memory. Examples of non-volatile memory include flash memory and read-only memory (ROM) / programmable read-only memory (PROM) / erasable programmable read-only memory (EPROM) / electrically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware, such as boot programs). Examples of volatile memory include random-access memory (RAM), dynamic random-access memory (DRAM), static random-access memory (SRAM), phase-change memory (PCM), and disks or tapes. These computer programs (also referred to as programs, software, software applications, or code) contain machine instructions for a programmable processor and may be implemented in a procedural and / or object-oriented high-level programming language and / or in assembly / machine language. The terms "machine-readable medium" and "computer-readable medium" as used herein refer to any computer program product, non-transitory computer-readable medium, device, and / or apparatus (e.g., magnetic disks, optical disks, memory, programmable logic devices (PLDs)) that serves to provide machine instructions and / or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal.The term "machine-readable signal" refers to any signal that serves to provide machine instructions and / or data to a programmable processor. Various implementations of the systems and techniques described herein may be realized in digital electronic and / or optical circuits, integrated circuits, specially designed ASICs (application-specific integrated circuits), computer hardware, firmware, software, and / or combinations thereof. These various implementations may include the implementation in one or more computer programs that are executable and / or interpretable on a programmable system that includes at least one programmable processor, which can be used as a special-purpose or general-purpose processor and is coupled such that it receives data and instructions from and transmits data and instructions to a storage system, as well as at least one input device and at least one output device. The processes and logic sequences described in this description can be performed by one or more programmable processors, also known as data processing hardware, which execute one or more computer programs to perform functions by working on input data and generating outputs. The processes and logic sequences can also be performed by specialized logic circuits, such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Processors suitable for executing a computer program include, for example, both general-purpose and specialized microprocessors, as well as one or more processors from digital computers of any type. Generally, a processor receives instructions and data from read-only memory, random-access memory, or both.The essential elements of a computer are a processor for executing instructions and one or more storage devices for storing instructions and data. Generally, a computer also includes one or more mass storage devices for storing data, such as magnetic, magneto-optical, or optical disks, or is functionally coupled to them to receive data from or transmit data to them, or both. However, a computer does not necessarily have to have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and storage devices, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.The processor and memory can be supplemented or integrated with special logic circuits. To enable interaction with a user, one or more aspects of the revelation can be implemented on a computer that has a display device, such as a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or touchscreen, to show information to the user, and optionally a keyboard and pointing device, such as a mouse or trackball, with which the user can input information into the computer. Other types of devices can also be used to enable interaction with the user; for example, the user can receive any form of sensory feedback, such as visual, auditory, or tactile feedback, and user input can be received in any form, including auditory, verbal, or tactile input.Furthermore, a computer can interact with a user by sending and receiving documents to and from a device used by the user, for example, by sending web pages to a web browser on a user's client device in response to requests received from the web browser. Referring to Fig. 1-3, a vehicle 10 includes a battery 12, e.g., a lithium-ion battery, configured to supply at least part of the vehicle 10 with energy. The vehicle 10 can be, for example, an electric vehicle (EV) or a hybrid vehicle equipped with a battery 12 and an internal combustion engine (ICE). The battery 12 comprises at least two electrodes, including a cathode 14 and an anode 16, to which EV components powered by the battery 12 can be coupled. The cathode 14 consists of cathode active materials 18 configured to optimize various aspects of the battery performance 20 (e.g., the electrochemical performance) of the battery 12. The battery performance 20 can, for example, include the energy density, power density, and / or thermal stability of the battery 12.In some non-restrictive examples, the cathode active materials may include lithium and manganese rich (LMR) material, nickel manganese cobalt oxide (NMC), nickel cobalt manganese aluminum (NCMA), lithium iron phosphate (LFP), lithium nickel dioxide (LNO), lithium manganese iron phosphate (LMFP), lithium manganese oxide (LMO), and lithium nickel manganese oxide (LNMO). Another measure of battery performance 20 is the discharge capacity 24 of battery 12. The discharge capacity 24 refers to the amount of charge that battery 12 can store per unit mass. A higher discharge capacity 24 means that battery 12 can store a greater amount of charge. The cycle stability 26 and the cycle life 30 of the battery 12 can be summarized as discharge capacity maintenance 32. The discharge capacity maintenance 32 refers to the discharge capacity 24 of the battery 12, which is tracked over several battery cycles 34. For example, if the battery 12 has a discharge capacity 24 of 100 milliampere-hours per gram (mAh g-1) in a first battery cycle 34a, and the battery 12 has a discharge capacity 24 of ninety (90) mAh g-1 in a second battery cycle 34b, then the battery 12 has a discharge capacity maintenance 32 of ninety percent (90%) in the second battery cycle 34b. The battery cycle 34 refers to a complete charge and a complete discharge of the battery 12. A complete charge and a complete discharge of the battery 12 corresponds, for example, to one battery cycle 34. The battery 12 also includes a battery lifetime 36, which refers to the number of battery cycles 34 that the battery 12 can undergo before its discharge capacity 24 drops to a threshold capacity 38. An example of a threshold capacity 38 could be approximately eighty percent (80%) of the battery 12's initial discharge capacity 24a (i.e., approximately eighty percent (80%) discharge capacity maintenance), where the initial discharge capacity 24a is the battery 12's discharge capacity 24a at the first battery cycle 34a (i.e., zero (0)). Alternatively, the exemplary threshold capacities 38 could be approximately seventy percent (70%), approximately sixty percent (60%), or approximately fifty percent (50%) of the battery 12's specific initial discharge capacity 24a. With further reference to Figs. 1-3, the initial discharge capacity 24a and the battery lifetime 36 of the battery 12 are determined, at least in part, based on the cathode active materials 18 of the battery 12. The introduction of transition metals 40 into the cathode 14 increases the lifetime of the battery 36. When the transition metals 40 penetrate or are absorbed by the cathode 14 (i.e., the cathode 14 is doped with the transition metals 40), the battery 12 has a longer lifetime 36 while maintaining a high initial discharge capacity 24a. For comparison with the battery 12 described herein, a series of reference batteries 100a-100c are shown in Fig. 3. Due to the considerable similarity, a similar numbering system can be used for each of the reference batteries 100a-100c, with each reference battery 100a-100c being distinguished by letter extensions.Reference battery 100a may have a film layer 102a of transition metal oxide nanoparticles 104a deposited onto a cathode 106a. Reference battery 100b may have a film layer 102b of transition metals 104b deposited onto a cathode 106b by a vapor deposition process. The cathode 106c of reference battery 100c may remain free of a film layer (i.e., the cathode 106c is an "uncoated cathode"). Each of the reference batteries 100a-100c has a discharge capacity 110a-110c, including an initial discharge capacity 112a-112c, and a battery lifetime 114a-114c, including a discharge capacity maintenance 116a-116c. The film layer 102a, 102b on the surface of the cathode 106a, 106b can extend the lifespan of the battery 114a, 114b, but reduces the initial discharge capacity 112a, 112b. The film layer 102a applied to the cathode 106a may contain transition metal oxide nanoparticles 104a. These transition metal oxide nanoparticles 104a can lead to an unevenness in the film layer 102a. This uneven film layer 102a does not significantly increase the electrical resistance between the cathode 106a and the electrical components coupled to the cathode 106a, as was observed for the cathode 106b. Accordingly, the reference battery 100a exhibits a higher initial discharge capacity 112a than the initial discharge capacity 112b of the reference battery 100b. However, the uneven film layer 102a does not form a barrier between the cathode 106a and the electrolyte of the reference battery 100a.Accordingly, the film layer 102a only slightly improves the discharge capacity retention 116a and the battery life 114a of the reference battery 100a compared to the discharge capacity retention 116c and the battery life 114c of the reference battery 100c with the uncoated cathode 106c. The film layer 102b can be applied to the cathode 106b by a vapor deposition process, e.g., by atomic layer deposition (ALD) or chemical vapor deposition (CVD). The vapor deposition process creates a uniform layer (i.e., a film) of the film layer 102b along the cathode 106b. The film layer 102b leads to an increase in the electrical resistance between the cathode 106b and electrical components that may be coupled to the reference battery 100b. Accordingly, the reference battery 100b has a lower initial discharge capacity 110b than the discharge capacity 110c of the reference battery 100c with an uncoated cathode 106c (i.e., a cathode 106c without film layers 102a, 102b).However, the film layer 102b made of transition metals 104b forms a barrier between the cathode 106b and the electrolyte of the reference battery 100b, giving the reference battery 100b a higher discharge capacity retention 116b and a longer battery life 114b compared to the discharge capacity retention 116c and battery life 114c of the reference battery 100c with the uncoated cathode 106c. In contrast, the cathode 14 of the battery 12 is doped with the transition metals 40, which increase the discharge capacity retention 32 of the battery 12 while maintaining the initial discharge capacity 24a. For example, the maintained initial discharge capacity 24a of the doped cathode 14 is approximately equal to the initial discharge capacity 112c of the reference battery 100c with the uncoated cathode 106c. The method for doping the cathode 14 with the transition metals 40 involves applying a coating 42 to the cathode 14, which encloses a complex 44 with a metal-based molecular precursor 46. In one example, the metal-based molecular precursor 46 is a metal alkoxide 50 containing the transition metals 40 and organic ligands 48. The method for doping the cathode 14 further includes calcining the coating 42 to define a doped cathode 14.When complex 44 decomposes during calcination, the organic ligands 48 detach from the transition metals 40 of the metal-based molecular precursor 46, and the transition metals 40 are uniformly absorbed and distributed in the cathode 14. For example, ions of the transition metals 40 migrate into the cathode 14. This minimizes the resistance between the cathode 14 and the electrical components coupled to the battery 12. The doping of the cathode 14 causes the transition metal ions 40 to be absorbed into the cathode 14 instead of forming a film on its surface. The cathode 14 doped with the transition metals 40 forms a barrier between the cathode 14 and the electrolyte of the battery 12. Accordingly, the battery 12, whose cathode 14 is doped with the transition metals 40, extends the battery life 36 and maintains the discharge capacity 32 without reducing the initial discharge capacity 24a of the battery 12. Thus, the battery 12 has approximately the same extended battery life 36 and discharge capacity maintenance 32 as the reference battery 100b, while maintaining approximately the same initial discharge capacity 24a as the reference battery 100c. As illustrated in Fig. 4, a method 400 for doping a cathode 14 comprises, at 402, the preparation of a coating 42 with a complex 44 containing a metal-based molecular precursor 46, at 404, the application of the coating 42 to the cathode 14, and at 406, the calcination of the coating 42 applied to the cathode 14. The coating 42 prepared for doping the cathode 14 is produced with a selected complex 44. The complex 44 may contain one or more metal-based molecular precursors 46. In one aspect, each metal-based molecular precursor 46 may contain a metal alkoxide 50. The complex 44 may, for example, but not limited to, contain at least two metal-based molecular precursors 46, each containing a metal alkoxide 50 with a different transition metal 40.The exemplary metal alkoxides 50 may include a metal isopropoxide, including but not limited to aluminium isopropoxide, titanium isopropoxide, manganese isopropoxide, boric isopropoxide, sodium isopropoxide, lithium isopropoxide or potassium isopropoxide. The application of the coating 42 from complex 44 to the battery cathode 12 involves spray-drying the cathode 14 with complex 44. The coating 42 is a thin, uniform layer of complex 44 applied to the surface of the cathode 14. Spray-drying the cathode 14 involves preparing a concentration of complex 44 in an alcohol-based solution 60. In some examples, complex 44 may be in powder form when added to the alcohol-based solution 60. Examples of alcohols used in the alcohol-based solution 60 include ethanol, methanol, and isopropanol. The alcohol-based solution 60 may have a concentration ranging from 0.5 grams (g) of metal alkoxide per thirty milliliters (ml) of alcohol to two grams (g) of metal alkoxide per thirty milliliters (ml) of alcohol. An example concentration of the alcohol-based solution 60 is approximately one gram (1 g) of metal alkoxide per thirty (30) milliliters (ml) of alcohol.In an exemplary spray drying process, complex 44 is applied to the cathode 14 using a nozzle. In one aspect, the nozzle can have a flow rate of two (2) cubic centimeters per minute (cm³ / min) to twenty (20) cubic centimeters per minute (cm³ / min). An exemplary nozzle flow rate is approximately five (5) cubic centimeters per minute (cm³ / min). In another aspect, the nozzle can have a cleaning frequency of 0.1 hertz (Hz) to one (1) hertz (Hz). An example of a nozzle cleaning frequency is 0.2 hertz (Hz). The example of spray drying further includes drying the cathode coated with the alcohol-based solution, wherein the drying process involves circulating a drying gas over the cathode. In one aspect, the drying gas is circulated at a gas flow rate of fifteen (15) liters per minute (l / min) to fifty (50) liters per minute (l / min). In another aspect, the drying gas is circulated at a gas temperature of seventy (70) degrees Celsius (°C) to ninety (90) degrees Celsius (°C). In yet another aspect, the drying gas can be air, nitrogen, or argon. One example of drying is the circulation of air over the cathode at a gas flow rate of thirty (30) liters of air per minute (l / min) and a gas temperature of approximately eighty (80) degrees Celsius. The spray drying results in a thin, uniform coating 42 of complex 44 on the surface of the cathode 14.The coating 42 can have a concentration of 0.01 wt.% to 2 wt.% of transition metals 40. In one example, the coating 42 has a concentration of 0.58 wt.% of transition metals 40. With further reference to Fig. 2-5, the film layers 102a of the reference batteries 100a can utilize transition metal oxide nanoparticles 104a, which do not decompose readily, resulting in a non-uniform film layer 102a of transition metal oxide nanoparticles 104a along the cathode 106a. By comparison, the complex 44 of the coating 42 contains organic ligands 48. In contrast to the transition metal oxide nanoparticles 104a, the organic ligands 48 readily decompose from the transition metals 40 upon calcination. The remaining transition metals 40 are absorbed into the cathode 14 once the organic ligands 48 have decomposed. Thus, the organic ligands 48 cause the metal-based molecular precursor 46 to dope the cathode during calcination. Calcination involves applying heat or otherwise increasing the temperature of the cathode 14 to cause the organic ligands 48 to decompose relative to the metal-based molecular precursors 46 (i.e., the metal alkoxide 50). For example, during calcination, the organic ligands 48 detach from the metal-based molecular precursors 46. This causes the metal alkoxides 50 of the coating 42 to be absorbed (i.e., doped) into the cathode 14. As a result of the doping process, the cathode 14 can thus be free of a separate film, since the metal-based molecular precursors 46 are incorporated into the cathode 14. The decomposition of the organic ligands during the calcination of complex 44 releases the metal alkoxides 50 for absorption by the cathode 14. Calcining the complex-coated cathode 14 involves heating it to a temperature of at least approximately 300 °C. For example, the coated cathode 14 can be heated to a temperature of approximately 450 °C. Heating the coated cathode 14 decomposes the organic ligands 48 of complex 44, leaving the transition metals 40 (e.g., the metal alkoxide 50) firmly bonded to the cathode 14. Decomposition of the organic ligands 48 can begin at approximately 200 °C, and doping of the cathode 14 with transition metals 40 can begin at approximately 300 °C. Doping can continue from approximately 300 °C to approximately 900 °C. During doping, the transition metals 40 penetrate the cathode active materials 18. Accordingly, as a result of the doping process, the cathode 14 is free of a film or an external coating of the transition metals 40 on a surface of the cathode 14.Instead, the transition metals 40 are absorbed uniformly and distributed within the cathode 14 as the metal alkoxide 50 migrates into the cathode 14. The metal alkoxide 50 used with the coating 42 can, for example, be an aluminum isopropoxide, and the cathode 14 can have an LMR lattice. As a result of the calcination process, aluminum ions can migrate into the LMR lattice of the cathode 14, leading to an aluminum-LMR composite cathode 14. Before doping, the cathode 14 coated with transition metals 40 may exhibit a microscopically visible layer of these metals on its surface, as they are arranged on the surface but not yet absorbed into the cathode's chemical structure. In contrast, after doping, the transition metals are absorbed into the cathode's chemical structure and may not be visible on its surface. For example, microscopic analysis of the cathode 14 may reveal that it is generally free of any film or other traces of the transition metals 40 on or along its surface. Instead, the presence of the transition metals in the LMR lattice can be determined by a decrease in the binding energy of the transition metal-doped cathode 14. Doping a battery cathode with transition metals 40 can improve the battery performance 20 for cathodes 14 made of different cathode active materials 18, including LMR cathodes, NMC cathodes, NCMA cathodes, LFP cathodes, LNO cathodes, LMFP cathodes, LMO cathodes, and LNMO cathodes. Doping can also improve the battery performance 20 for batteries 12 operating under different operating conditions. A voltage window 70 of the battery 12 can range from 2.0 volts (V) to 5.0 V. The improved battery performance 20 can also be achieved through different discharge rates 72 (i.e., c-rates). The exemplary discharge rates 72 can range from a 100-hour discharge to a 10-minute discharge. Fig. 5 illustrates an exemplary diagram in which the discharge capacity 24 of battery 12 and the discharge capacities 110a-110c of reference batteries 100a-100c are plotted over a number of battery cycles 34, 120a-120c, as well as the discharge capacity maintenance 32, 116a-116c of battery 12 and the reference batteries 100a-100c. Curve 122c illustrates the battery performance of reference battery 100c with an uncoated LMR cathode 106c. Curve 122b illustrates the battery performance of reference battery 100b with the same construction and the same LMR cathode, wherein the LMR cathode 106b has been coated with an aluminum oxide film layer 102b applied by an ALD coating process. As a result of the aluminium oxide film layer 102b, the reference battery 100b has a lower initial discharge capacity 112b than the initial discharge capacity 112c of the reference battery 100c.Compared to reference battery 100c, reference battery 100b exhibits a more gradual decrease in discharge capacity 110b over a number of battery cycles 120b, which corresponds to the higher discharge capacity retention 116b of reference battery 100b compared to the discharge capacity retention 116c of reference battery 100c. The increased discharge capacity retention 116b of battery 100b results from the film layer 102b of transition metals 104b on the surface of the cathode 106b, which forms a barrier between the cathode 106b and the electrolyte of reference battery 100b. With further reference to Fig. 5, curve 80 illustrates the discharge performance of battery 12. Battery 12 has an LMR cathode 14 doped with a complex 44 containing an aluminum isopropoxide precursor (i.e., a metal-based molecular precursor 46) with organic ligands 48. Doping the LMR cathode 14 integrates the aluminum ions into or otherwise bonds them to the LMR cathode 14, while the organic ligands 48 detach or otherwise remain attached to the LMR cathode 14 without bonding. The integrated aluminum ions form a barrier between the LMR cathode 14 and the electrolyte of battery 12 without forming a film on the surface of the LMR cathode 14. Thus, doping the LMR cathode 14 does not measurably increase the electrical resistance of the LMR cathode 14's surface. Accordingly, battery 12 has an initial discharge capacity 24a, which is approximately equal to the initial discharge capacity 112c of reference battery 100c, and battery 12 has a higher discharge capacity retention 32 than the discharge capacity retention 116c of battery 100c. With the improved discharge capacity retention 32 of battery 12, battery 12 can undergo at least about 100 more cycles than an uncoated cathode (i.e., the cathode 106c of reference battery 100c) before reaching the end of its battery life 36 when cycled at high voltage. Battery 12 also has a higher initial discharge capacity 24a than the initial discharge capacity 112b of reference battery 100b as a result of the doping process, while battery 12 has a discharge capacity retention 32 which is approximately the same as the discharge capacity retention 116b of reference battery 100b.Overall, the doping process results in battery 12 having a higher discharge capacity retention 32 compared to the discharge capacity retention 116c of reference battery 100c and a higher initial discharge capacity 24a than the initial discharge capacity 112b of reference battery 100b. Curve 80 and curve 122a illustrate the difference in battery performance between battery 12 and reference battery 100a. Curve 122a illustrates the discharge performance of battery 100a, which has an LMR cathode 106a containing a film layer 102a of transition metal oxide nanoparticles 104a. The transition metal oxide nanoparticles 104a do not readily decompose, resulting in an uneven film layer 102a of transition metal oxide nanoparticles 104a on the surface of the cathode 106a. This uneven film layer 102a causes reference battery 100a to have a lower discharge capacity retention 116a compared to battery 12. Curve 90 illustrates the battery performance of battery 12 with cathode 14, which was prepared with complex 44 including the metal-based molecular precursor 46 and the organic ligands 48. However, curve 90 illustrates that the cathode 14 of battery 12 was calcined at a temperature of approximately 200 °C, compared to curve 80, where the cathode 14 of battery 12 was calcined at a temperature of approximately 450 °C. Since 200 °C is approximately the temperature at which the decomposition of the organic ligands 48 begins, fewer transition metals 40 were absorbed into the cathode 14 of battery 12 than if the cathode 14 of battery 12 had been calcined at 450 °C. As a result of the lower calcination temperature (i.e.,At temperatures of approximately 200 °C, some of the transition metals 40 may remain on the surface of the cathode 12 of the battery 14, which may result in the battery 12 having a lower initial discharge capacity 94 than a cathode 14 calcined at a higher temperature of approximately 300 °C to 900 °C, such as the cathode 14 of the battery 12 calcined at approximately 450 °C. The resulting effect of the battery 12 represented by curve 90 is that the battery 12 may exhibit a lower discharge capacity retention 96 than the doped cathode 14 of the battery 12 represented by curve 80. Several implementations have been described. However, it is understood that various modifications can be made without deviating from the spirit and scope of the revelation. Accordingly, other implementations also fall within the scope of the following claims. The foregoing description is provided for illustrative and descriptive purposes only. It makes no claim to be exhaustive or to limit the disclosure. Individual elements or features of a particular configuration are generally not restricted to that specific configuration but are interchangeable and may be used in a selected configuration even if they are not specifically shown or described. These may also be varied in many ways. Such variations are not to be considered a deviation from the disclosure, and all such modifications are to be included within the scope of the disclosure.

Claims

Method for doping a battery cathode, comprising: producing a coating with a complex containing a metal-based molecular precursor; applying the coating to a battery cathode; and calcining the coating applied to the battery cathode at a calcination temperature of at least 300 °C. The method of claim 1, wherein the metal-based molecular precursor contains organic ligands. The method of claim 1, wherein the metal-based molecular precursor is a metal alkoxide. The method of claim 3, wherein the metal alkoxide contains a metal isopropoxide, wherein the metal isopropoxide contains one or more of aluminium isopropoxide, titanium isopropoxide, manganese isopropoxide, boric isopropoxide, sodium isopropoxide, lithium isopropoxide and potassium isopropoxide. The method of claim 1, wherein the complex contains at least two metal-based molecular precursors, each metal-based molecular precursor containing a different metal alkoxide. Method according to claim 1, wherein the metal alkoxide coating contains 0.01 wt% to 2 wt% of a transition metal. The method of claim 1, wherein the battery cathode includes at least one of the following cathodes: a lithium-manganese-rich (LMR) cathode, a nickel-manganese-cobalt oxide (NMC) cathode, a nickel-cobalt-manganese-aluminum (NCMA) cathode, a lithium iron phosphate (LFP) cathode, a lithium nickel dioxide (LNO) cathode, a lithium manganese iron phosphate (LMFP) cathode, a lithium manganese oxide (LMO) cathode and a lithium nickel manganese oxide (LNMO) cathode. Method according to claim 1, wherein the calcination temperature is a temperature of 400 °C to 900 °C. The method of claim 1, wherein the application of the coating to the battery cathode further includes spraying the coating onto the battery cathode, drying the coating and evaporating alcohol from the coating to form a coating layer on the battery cathode. Battery cathode doped according to the method of claim 1.

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