Manganese oxide nanoparticles, methods and applications

Manganese oxide nanoparticles, methods and applications

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] Please refer to and request the priority of U.S. Provisional Patent Application Serial No. 61/492,661 filed on June 2, 2011 under the title "Materials, Methods and Applications of Oxidation", the entire contents of which are incorporated by reference. This article.

[0003] Government interest statement

[0004] The research to obtain the embodiments described in this application and the invention claimed in this application was carried out under the funding of the US Department of Energy with the project number DESC0001086. The U.S. government has the rights and interests claimed in this invention.

BACKGROUND OF THE INVENTION Field of Invention

[0005] Embodiments generally relate to metal oxide nanoparticles, methods, and applications. More specifically, embodiments relate to metal oxide nanoparticles with enhanced performance, methods, and applications.

[0006] Description of Related Technology

[0007] Rechargeable lithium batteries have revolutionized portable electronic devices. They are also increasingly used as power sources for electric and hybrid electric vehicles. However, a major concern for rechargeable lithium batteries is safety, especially when metallic lithium is used as the anode material for rechargeable lithium batteries. This safety problem is caused by the gradual formation of lithium dendrites, which can penetrate the separator that separates the anode and cathode in the rechargeable lithium battery and cause the battery to short circuit.

[0008] Considering that lithium batteries have clear commercial value, it is necessary to find other materials and methods that can provide safer and more effective lithium batteries and lithium battery components.

[0009] Summary of the invention

[0010] Embodiments include manganese oxide nanoparticles, methods for preparing manganese oxide nanoparticles, and applications of manganese oxide nanoparticles in lithium batteries. The manganese oxide nanoparticles, the method for preparing manganese oxide nanoparticles, and the application of manganese oxide nanoparticles in lithium batteries may involve stoichiometric manganese oxide Mn3θ4 and Mn2θ3 · Mn 0, as well as non-stoichiometric manganese oxide. Lithium oxide manganese LixMn3 () 4 (χ 20).

[0011] In particular, the embodiment provides a specific manganese oxide nanoparticle with specific physical properties, and the specific physical property is obtained by a specific manganese oxide nanoparticle preparation method. The specific physical properties include a sponge-like morphology (ie, when imaged under 2000 times magnification using a scanning electron microscope) and a particle size of about 65 to about 95 nanometers. The manganese oxide nanoparticles may include anode materials for rechargeable lithium batteries.

[0012] The method for preparing the manganese oxide nanoparticles according to the embodiment is relatively simple, requiring only the use of cheap and easily available raw materials, and no special equipment is required. More importantly, the anode used in the lithium battery according to the embodiment (ie, lithium ion battery) including the manganese oxide nanoparticles according to the embodiment not only provides a higher first-time reversible capacity (869mAh/g). ), high stable reversible capacity (800mAh/g) and high coulombic efficiency (65%), and show very good cycle performance. Within the scope of the embodiment, "very good" cycle performance refers to the cycle performance: when an anode electrode including the manganese oxide nanoparticles according to the embodiment is used, after 40 battery charge and discharge cycles After that, it still maintains at least about 90% of the initial charge value.

[0013] The embodiment also provides an anode material for a rechargeable lithium battery, which has improved safety

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Can and more attractive working voltage. The lithiation voltage (~0.6V) of manganese oxide in the form of Mn3θ4 is higher than that of typical graphitic carbon (less than 0.2V). This property of the manganese oxide nanoparticles according to the described embodiment fundamentally eliminates the deposition of lithium. The oxidative manganese in the form of Mn3θ4 also has a₃0₄(Delithiation is 2.IV, lithiation is 1.2V) Lower working voltage (the average potential of delithiation and lithiation is ~1.3V and 0.6V, respectively). In this way, when combined with a specific cathode, a lithium battery including a manganese oxide anode in the form of Mn3θ4 will have a higher fuel cell (fullcell) operating voltage and the resulting energy density compared to, for example, a cobalt oxide anode in the form of CO03O4. .

[0014] Considering the following detailed description and drawings of the embodiments, those skilled in the art will more easily understand these and other properties of the embodiments.

[0015] The specific manganese oxide nanoparticle according to the embodiment includes a nanoparticle including a manganese oxide material having a particle size of about 65 to about 95 nanometers.

[0016] The specific battery assembly according to the embodiment includes a nanoparticle including a manganese oxide material having a particle size of about 65 to about 95 nanometers.

[0017] The specific battery according to the embodiment includes a battery assembly including a nanoparticle including a manganese oxide material having a particle size of about 65 to about 95 nanometers.

[0018] A particular method for preparing nanoparticles according to the described embodiments includes fumigating a manganese hydroxide material to form a manganese oxide nanoparticle material having a particle size of about 65 to about 95 nanometers.

[0019] Brief Description of the Drawings

[0020] The following drawings are used as part of this application to further prove certain aspects of the implementation of this application. The embodiments can be better understood by referring to one or more of these drawings in combination with the more detailed description of specific embodiments below.

[0021] FIG. 1 shows an illustration for explaining the preparation of an oxide (Mη) according to the embodiment₃0₄) Flow chart of the process sequence of nano-particle powder.

[0022] FIG. 2 shows the x-ray diffraction spectrum of the manganese oxide (Mn3θ4) powder according to the embodiment.

[0023] FIG. 3 shows the oxide (Mn) according to the embodiment₃0₄) Scanning electron microscope (SEM) photograph of powder sample.

[0024] FIG. 4 shows that when the current rate is 0.25C (1C is defined as 1 lithium atom per standard unit within 1 hour, that is, 117mA/g for blood 3.4), MnsOVLiPFe+EC+DEC /Li button battery's first and second discharge/charge curves. [0025] FIG. 5 shows a trend diagram of the discharge/charge capacity of the MnsOVLiPFe+EC+DEC/Li button battery with the number of cycles when the current rate is 0.25C.

[0026] FIG. 6 shows a trend graph of the coulombic efficiency of the MnsOVLiPFe+EC+DEC/Li button cell with the number of cycles when the current rate is 0.25C.

[0027] FIG. 7 shows the trend graph of the discharge/charge capacity of the Mn30"LiPF6+EC+DEC/Li button battery with the number of cycles when the current rate is 2.5C.

[0028] FIG. 8 shows that when the current rate is 10C, Mn₃0₄/LiPF6+EC+DEC/Li button battery discharge/charge capacity trend graph with the number of cycles.

[0029] FIG. 9 shows a schematic diagram for explaining a lithium battery according to the embodiment.

Detailed ways

[0030] This embodiment provides manganese oxide nanoparticles, a method for preparing manganese oxide nanoparticles, and oxidation

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Battery applications related to manganese nanoparticles. The specific battery application of the manganese oxide nanoparticles according to the embodiment is as a rechargeable lithium battery such as but not limited to the negative electrode of a rechargeable lithium ion battery. The specific method for preparing manganese oxide nanoparticles provides specific manganese oxide nanoparticles with specific structural characteristics, which are required in specific battery applications involving manganese oxide nanoparticles.

[0031] It will be understood that various changes and modifications to the materials and methods according to the following description are anticipated and can be carried out without departing from the spirit of the embodiments. Therefore, the following detailed description of the embodiments will not have a restrictive meaning. Rather, the embodiments described below are intended to be illustrative rather than restrictive.

[0032] As shown above, the described embodiments relate to new materials, particularly manganese oxide nanoparticle materials used as anode materials in rechargeable lithium batteries. It will be understood that the cathode in the rechargeable lithium battery according to the embodiment used with the anode according to the embodiment may be any lithium-based cathode material, provided that the lithium-based cathode material can provide lithium during charging. ion. Preferably, the cathode material will have a higher voltage than Li+/Li, such as LiCo02, LiMn₂0₄LiFePO, binders and other materials generally related to electrolytes and anodes and cathodes are well known and will not be described here, but they are included in this application according to the understanding of those skilled in the art.

[0033] The lithium battery anode according to the embodiment preferably includes a manganese oxide nanoparticle material composition, specifically, a stoichiometric manganese oxide nanoparticle material composition, and Mn3θ4 and Mn2θ3·Mn0 are its representatives. The embodiment may also include lithiated manganese oxide nanoparticles LixMn304 (x20) and non-stoichiometric manganese oxide nanoparticles.

[0034] Nano-scale transition metal oxides have been extensively studied as promising anode materials for lithium batteries, most of which exhibit much higher capacity than graphite anodes. It has been suggested that transition metal oxides react with lithium through a conversion reaction: M0+2Li⁺+2e=Li₂0+M°. Compared with graphite, it generally has a higher lithiation potential, which tends to prevent the precipitation of metallic lithium. Several transition metal oxides as anodes of lithium batteries have been discovered, such as but not limited to NiO.CoO and CO304. Many reports focus on (Wk. However, drills are generally economically unattractive and toxic.

[0035] In view of the shortcomings of CO3O4 as a lithium battery anode material, the described embodiments alternatively provide a manganese oxide nanoparticle material and prepare a manganese oxide nanoparticle material with a unique structure (ie, the most common one is blood 3. The method of 4) The manganese oxide nanoparticle material described herein, especially the manganese oxide nanoparticle material in the form of Mί13θ4, provides higher capacity and higher coulombic efficiency, and more importantly, it provides Very good cycle performance. The described embodiment uses manganese oxide nanoparticle materials without using graphene oxide composite bases (or other conductive composite base materials that are less economical than graphite materials) to obtain the foregoing results. Therefore, the embodiment realizes the performance-enhanced lithium battery according to the embodiment without using relatively expensive materials such as but not limited to graphene oxide materials.

[0036] In the schematic process flow diagram shown in FIG. 1, the preparation process sequence of the manganese oxide nanoparticle material in the form of Mn3θ4 is described. As shown on the left hand side, in the top process step, manganese salt is used as a source of manganese salt to form a manganese salt solution. Manganese salts may include, but are not limited to, manganese nitrate (Mn(NO3)2), manganese sulfate (MnSOQ, manganese acetate (Mn(COOCH)₃) At least one of 2) and manganese chloride (MnC12). The water-soluble manganese (II) salt is preferred. There is no limitation on the concentration of manganese salt, but the preferred range is about 0.05 mol/L to its saturation limit.

[0037] In the schematic process flow chart shown in FIG. 1, as shown in the first process step on the right hand side and the second process step on the left hand side, equipment, such as but not limited to an oil bath, will be used in the following The manganese salt solution that reacts with the hydroxide in the process step is heated to a certain temperature. This heating process step is not necessary, but generally increasing the temperature will shorten the reaction time. The range of the elevated temperature can be from about 20°C to about 120°C

[0038] In the schematic process flow diagram shown in FIG. 1, as shown in the second process step from the top on the right hand side, in order to form a hydrogen hydroxide precipitate, a hydroxide solution is added to the magnesium salt solution. The hydroxide solution can include, but is not limited to,

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Lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(0H)2) and hydroxide plating (NftiOH) solutions. The money hydroxide solution is preferred because the use of saddle hydroxide does not introduce any cationic impurities in the final product of manganese oxide nanoparticle materials. The concentration of the hydroxide solution can vary. The total amount of the hydroxide solution used may also vary, but it is preferable to use the manganese in the manganese salt solution as the stoichiometric amount. After the hydroxide solution is added, it is preferable to perform the hydroxide precipitation reaction for a period of time, for example, about 10 minutes to about 10 minutes, as shown in the third process step from the top on the left-hand side of the schematic process flow chart shown in FIG. 10 hours.

[0039] In the schematic process flow diagram shown in FIG. 1, as shown in the third process step from the top on the right hand side, the hydrogen hydroxide precipitate can be collected from the reaction vessel by filtration or centrifugation. It is preferable to wash the collected precipitate with distilled water or deionized water to remove all impurities. After washing, as shown in the fourth step from the top on the left hand side of the schematic flow chart shown in Figure 1, the magnesium hydroxide should be precipitated in an oven and dried for about 5 hours to about 30 hours to remove water. Preferably, a vacuum oven is used in order to dry the hydroxide precipitates more effectively. The temperature for drying the hydrogen hydroxide is preferably about 50°C to about 150°C.

[0040] In the schematic process flow diagram shown in FIG. 1, as shown in the fourth process step from the top on the right hand side, in order to form Mn3θ, it needs to be dried in the presence of oxygen, preferably in air. The precipitate is smoked in a furnace. The burning temperature is preferably about 200°C to about 400°C. The burning time can be about 1 hour to about 20 hours, depending on the burning temperature. The preferred smoking conditions are about 200°C to about 400°C. 300 °C Μ firing for about 5 hours. After flaming, as shown in the schematic flow chart shown in Figure 1, the last step from the top on the left hand side, the powder, more specifically ΜΠ304, can be directly used for the preparation as follows The electrode according to the embodiment described in the example above.

[0041] As shown in FIG. 2, the result of further characterization by x-ray diffraction is that the manganese oxide obtained from the foregoing fumigation step is a pure phase material with a tetragonal spinel structure, which can be determined by indexing. Group 141/ and (JCPDS card: 24-0734) Mn3θ4. Under normal circumstances, no impurities can be detected. Estimated from the Scherrer formula, the width of the diffraction peak is a domain size of about 30 nanometers. As understood by those skilled in the art, the aforementioned crystal grain size of about 30 nanometers of the Mn3θ4 nanoparticles according to the embodiment is different from the particle size of the manganese oxide nanoparticles according to the embodiment, which will be described below according to FIG. 3 For further discussion, this is due to the peak broadening of the instrument and the accumulation of smaller primary domains into larger secondary particles.

[0042] The oxidation obtained from the aforementioned fumigation, more particularly Mn₃θ4, has a special sponge-like structure (that is, within the range of scanning electron microscope imaging), which includes and consists of nano-scale particles. For this purpose, Figure 3 shows a scanning electron microscope (SEM) image of a typical Mn3θ4 sample with a sponge-like morphology and structure. At a low magnification of 2000 times, such an oxidized sample looks like a sponge (see, for example, Figure 3a). At a high magnification of 20000 times (see, for example, Figure 3b), it can be easily seen that the "sponge" is composed of nanometer-sized Mn3θ4 particles with an average size of about 80 nanometers, and more generally, its range is about 65 To about 95 nanometers, and more specifically, the range is from about 75 to about 85 nanometers.

[0043] When included in the anode of a lithium battery, this Mn3θ4 manganese oxide nanoparticle material provides a very high reversible capacity. Figure 4 shows the current rate of 0.25C (1C is defined as 1 lithium atom per standard unit within 1 hour, that is, the blood 3.4 in 1 · OM LiPFeEC/DEC (1:1 volume ratio). Under the condition that the manganese oxide nanoparticle material is 117 mA/g), the first and second discharge-charge spectra of the battery electrode including MΠ304 manganese oxide are included. For Figure 4, during the first discharge, a slope of 1.5V to 0.38V is formed. This slope can be attributed to the formation of a solid-electrolyte interface (SEI) film. Subsequently, a well-defined voltage plateau around 0.38V was observed, which corresponds to the main reaction of lithium and blood 3.4. The total discharge capacity reaches 1327mAh/g_oThe curve of the first charge also shows a well-defined voltage plateau around 1.3V. The first charge capacity reaches 869mAh/g, which is very close to the theoretical capacity of 937mAh/g if it is assumed to be the conversion reaction._oThe second discharge spectrum is different from the first. A single voltage plateau was observed around 0.6V, which was slightly higher than the first time. This

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It may indicate that the reaction mechanism is different. It is worth noting that the second charge spectrum is very close to the first charge spectrum, which may indicate that the electrochemical reaction after the first discharge cycle is highly reversible.

[0044] The described embodiments provide an anode material that exhibits much better safety performance than other anode materials. The lithiation voltage (~0.6V) of Mn3θ4 is higher than that of typical graphite carbon (less than 0.2V). This property largely eliminates the deposition of lithium. In this way, the described embodiment can completely overcome the safety problem because it is almost impossible to deposit metallic lithium under such a high voltage. Compared with C03O4 (oxidized to 2. IV, reduced to 1.2V), Mn₃0₄Manganese oxide also has a lower operating voltage (peak potentials for oxidation and reduction are ~1.3V and 0.6V, respectively). When combined with a specific cathode, the resulting battery will have a higher full battery operating voltage and resulting energy density.

[0045] The described embodiments also provide Mn3θ4 oxidation with very good cycle performance. Figure 5 shows the capacity of the first 40 cycles of the Mn3θ4 manganese oxide anode in the cycle range of 3.0 to 0.01V versus the number of cycles. It can be seen that the cycle is very stable. After 40 cycles, the reversible capacity did not show a significant decrease.

[0046] FIG. 6 shows a graph of the coulombic efficiency versus the number of cycles for the first 40 cycles of the Mn3θ4 manganese oxide anode in the cycle range of 3.0 to 0.01V. For the first cycle, the coulombic efficiency reached more than 65%, which is much higher than the previous reports on Mn3 (k manganese oxide anode materials. More importantly, it remained above 95% in the subsequent cycles. .

[0047] The described embodiment also provides a Mn3θ4 oxide with higher power capacity. As shown in Figure 7, when the current rate is 2.5C, the first reversible capacity of Mn3θ4 oxidation reaches about 700mAh/g_oIt can be seen from Figure 8 that at 10C, this blood 3.4 manganese oxide anode can be cycled with a qualified initial capacity of about 550 mAh/g.

[0048] For reference, a schematic diagram of a lithium battery according to the embodiment is shown in FIG. 9, wherein the common cathode is a lithium cathode.

[0049] The superior electrochemical performance of this Mn3θ4 manganese oxide anode can be attributed to its unique structural characteristics and structure. Nano-sized manganese oxide nanoparticles provide a larger surface area, which improves the utilization of active materials. The open sponge structure allows lithium ions to be easily transferred in and out. It can also adjust the strain caused by the volume change that may occur in the discharge-charge cycle, and maintain the integrity of the anode electrode. This may enable the MΠ304 manganese oxide anode according to the embodiment to have excellent cycle stability.

[0050] The synthesis process of the Mn3θ4 manganese oxide nanoparticle material is also very simple, and does not require expensive chemical reagents and special equipment. Compared with diamonds, Meng is more environmentally friendly, has higher abundance and greater economic attractiveness. The synthesis process and battery configuration can be easily optimized without departing from the gist of this embodiment. It is expected that better electrochemical performance can be obtained through optimization. All the above-mentioned advantages and its high capacity, excellent cycling ability, and high charge/discharge rate capability show that the Μί!3θ4 manganese oxide nanoparticle material is a kind of anode material for the next generation of rechargeable lithium batteries. Attractive candidate.

[0051] Examples

Example 1

[0053] This example illustrates the preparation method of nano-scale Mn3θ4 oxidation manganese.

[0054] Nano-scale blood 3.4 manganese oxide is synthesized by a simple precipitation method. First, Mn (00CCH₃）₂-4H₂0 is soluble in deionized water. The solution was heated to 100°C in an oil bath. The stoichiometric required amount of saddle hydroxide is added to the solution to form a precipitate. After stirring for ~4h, the pellet was centrifuged, washed with deionized water, and dried at 80°C overnight. After the dried precipitate was heated at 300°C for 5 hours, nano-scale Mn3θ4α was formed. As shown in Figure 2, the X-ray diffraction data collected by the Rigaku Ultima IV X-ray diffractometer using Cuka radiation showed that Mn3θ4 had tetragonal crystals. It is a single-phase material with spinel structure. As shown in Figure 3, the prepared Mn3θ4 scanning electron microscope image shows that its average size is about 80 nm.

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Example 2

[0056] This example illustrates the preparation of the Mn3θ4 electrode.

[0057] Using 70wt.% Mn3θ4 as the active material>20wt.% Super P-Li (Timcal Company) as a conductive carbon-based additive and 10wt.% poly(vinylidene fluoride) (PVDF) as a binder to prepare a Mn3θ4 electrode film . The slurry was prepared using N-methyl-2T pyrrolidone (NMP) as the solvent. Use a doctor blade to evenly coat the slurry on the copper foil. Cut it into an area of 0.71cm²The round electrode was dried overnight under vacuum at 100 °C.

Example 3

[0059] This example illustrates the configuration of a button cell used to measure the electrochemical performance of the Mn3θ4 electrode.

[0060] The CR2032 button cell was used for electrochemical detection. Assemble the button cell in a glove box filled with nitrogen, using lithium foil as the anode, and using the Mn3θ4 from Example 2 as the cathode, Celgard2320 as the separator and 1.0M LiPFe in EC/DEC (1:1 volume ratio). The solution serves as the electrolyte. Perform constant current discharge-charge detection in Maccor4000 battery detection system. The battery is cycled at 3 · OV-0.01V, and the current density of discharge and charge are both 0.25C (1C is defined as 1 lithium atom per standard cell in 1 hour, that is, 117mA/g for Μιΐ3θ4)_oThe first and second discharge-charge curves are shown in Figure 4, and the cycle performance is shown in Figure 5. The variation of Coulomb efficiency with the number of cycles is shown in Figure 6.

[0061] Example 4

[0062] This example shows the performance of Mιΐ3θ4 under high current intensity.

[0063] Except that the current density of discharging and charging is 2.5C, the rest of the details are the same as in Example 3. The cycle performance is shown in Figure 7.

Embodiment 5

[0065] This example shows the performance of Mιΐ3θ4 under high current intensity.

[0066] Except that the current density of discharging and charging is 10C, the rest of the details are the same as in Example 3. The cycle performance is shown in Figure 8.

[0067] All references cited herein, including publications, patent applications, and patents, are incorporated herein by reference in their entirety to the extent permitted, and as if each reference were individually and specifically pointed out, are hereby incorporated by reference, and Listed in full in this article.

[0068] The terms "a" and "an" and "the" used in the context of describing the present invention (especially in the claims) should be construed as including Singular and plural, unless otherwise specified in this article or clearly contradictory to the context. The terms "comprising", "having", "including" and "containing" shall be interpreted as open-ended terms (ie, meaning "including, but not limited to") unless otherwise stated. The term "connected" should be understood as partly or fully contained in, attached to or joined together, even if there is an intervening substance.

[0069] Unless otherwise stated, the quotation of a range of values herein is merely a shorthand method for individually quoting each individual value falling within the range, and each individual value is incorporated herein as if It is individually cited in this article.

[0070] Unless otherwise stated herein, or clearly contradictory to the context, all methods described herein can be performed in any appropriate order. The use of any and all of the examples, or the exemplary language provided herein (for example, "such as"), is only to better clarify the implementation of the present invention, and is not intended to limit the scope of the present invention, and additionally requires protection Except for.

[0071] No language in this text should be understood to mean that any unclaimed element is necessary to implement the present invention.

[0072] Without departing from the spirit and scope of the present invention, various modifications and changes to the present invention are important to the art.

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It is obvious to the technician. It is not intended to limit the present invention to the specific one or more forms disclosed, but on the contrary, it is intended to cover all modifications, alternative constructions, and equivalents that fall within the spirit and scope of the present invention. The spirit and scope are as defined in the claims of the present invention. Therefore, the present invention is intended to cover modifications and changes falling within the scope of the claims of the present invention and their equivalents.

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