Oxide shell formation on inorganic substrate via oxidative polyoxoanion salt deposition

0001The present invention relates to methods and compositions useful for forming metal oxide coatings on inorganic substrates. More specifically, the present invention relates to the formation of a metal oxide coating (eg, alumina) on an inorganic substrate (eg, ceramic powder) by the use of quaternary ammonium metallates (eg, aluminate) and peroxides. .. More specifically, the present invention relates to the formation of a metal oxide coating (eg, alumina) on a lithium ion battery cathode material.

0002Lithium-ion battery cathode ceramic materials have been an intriguing research area for many years. Of the various cathode materials, lithium transition metal oxides represent the most successful category of cathode materials. The crystal structure of the lithium transition metal oxide is LiMO.₂A laminated structure having a chemical formula (where M is, for example, Mn, Co, and / or Ni), or LiM.₂O₄It can be a three-dimensional spinel structure with a typical chemical formula (M is, for example, Mn). Both laminated and spinel structures include transition metal and oxygen frameworks in which lithium ions are intercalated.

0003Lithium ion battery cathode ceramic materials (eg, lithium cobalt oxide, lithium nickel oxide or lithium cobalt nickel oxide) have excellent basic properties for energy storage. However, these materials also have drawbacks such as inadequate safety with respect to thermal stability and overcharge properties. To solve these problems, various safety methods have been introduced, which include a separator blocking function, an additive to the electrolyte, a safety protection circuit, and a PTC (Positive Temperature Coefficient) device. Unfortunately, all of these methods were designed for use under conditions where the chargeability of the cathode active material is not very high. As such, if the charge properties of the cathode active material are increased to meet the increasing demand for high capacity in such batteries, the safety of these systems can be compromised.

0004On the other hand, the driving of an electrochemical cell always produces an interface layer between an active cathode material and an electrolyte called a solid electrolyte interface (SEI). High voltage drive can easily break this interface layer, leading to poor cycle characteristics and capacitance loss. Therefore, SEI formation and structural control and stabilization are still of great importance and practical concern.

0005In addition, some active manganese-containing cathode materials, such as lithium manganese oxide, have the problem of manganese separating into the cell electrolyte solution during cell drive when in direct contact with the electrolyte. This can cause capacity loss, i.e. capacity loss through repeated charge and discharge cycles.

0006To eliminate the above drawbacks, core / shell structures have been proposed to improve the cycle life and safety of lithium batteries. The formation of a passivation shell on the surface (core) of the active cathode ceramic particles provides structural and thermal stability in highly delithium (discharged) conditions, thus improving cycle life and safety. .. There are various shells described for cathode ceramic particle surfaces, such as barium titanate (BaTiO).₃), Lithium iron phosphate oxide, and gradient LiCoO₂Includes a shell formed from. Most of these shell formations envision either the use of expensive raw materials, the adoption of complex processes, or both. In addition to the active material shells described above, inert metal oxide shells have been studied for many years. The formation of inert metal oxide shells is a relatively inexpensive process. Various inert metal oxide shells (eg, TiO)₂, Al₂O₃, MgO and ZnO) are so-called heterogeneous nucleation wet. Prepared on the surface of ceramic particles through chemistry). However, the current heterogeneous nuclei for forming the Inactive Oxide Shell are not controllable, especially in the absence of a known process to control the shell thickness with acceptable precision. By definition, inert metal oxide shells are not electrochemically active, meaning that they do not facilitate ion or electron transport. At the same time, such a shell must not interfere with the drive. If an inert shell is formed that is too thick and / or too dense, the resistance of the shell can limit the tolerance of the charge / discharge rate of the electrodes and deteriorate the performance of the cell. Current processes for precipitating aluminum oxide (and other inert oxides) by heterogeneous nucleation with aluminum nitrate (or other aluminum salts) are Li cations in active ceramic materials and Al ions in the process solution. Includes ion exchange with. This can cause Li ion loss from the active ceramic material, waste generation, and the potential for cathode structural defects as the shell precipitates.

<p num="0007"> Therefore, the problem of the method of providing the oxide coating on the inorganic base material such as the active ceramic material in the cathode of the lithium ion battery has existed for many years, and a satisfactory solution has not been made to date.</p>

<p num="0008"> To address the above issues, the present invention provides a method for making an oxide shell containing either a metal oxide or a particular non-metal oxide on a ceramic or other inorganic substrate. The shell has a thickness that can be precisely controlled. This thickness can be precisely controlled by controlling the content of the quaternary ammonium cation and the polyoxoanion in the reaction composition and the precipitation rate. The substrate may include the surface of the active cathode ceramic particles (eg, the ceramic material used for the lithium ion battery cathode). This method uses an organic salt composed of a quaternary ammonium cation and a polyoxoanion as a shell-forming material source. By adding an oxidant (eg, hydrogen peroxide), the organic salt can slowly form one of a conductive shell layer, a semiconductor shell layer or an insulating shell layer on such a ceramic surface. .. Therefore, the precipitation rate can be influenced by the content of hydrogen peroxide in the reaction composition.</p><p num="0009"> Therefore, in one embodiment, the present invention is a method for depositing an oxide coating on an inorganic substrate. A step of providing an aqueous composition containing a tetraalkylammonium polyoxoanion and hydrogen peroxide; A step of contacting the aqueous composition with an inorganic base material for a time sufficient to precipitate a hydroxide derived from the polyoxoanion on the surface of the inorganic base material to form an initially coated inorganic base material. ; And The step of heating the initially coated inorganic substrate for a time sufficient to convert the hydroxide into an oxide to form an oxide coating derived from the polyoxoanion on the inorganic substrate; With respect to methods, including.</p><p num="0010"> In one embodiment, the tetraalkylammonium polyoxoanion comprises tetramethylammonium hydroxide.</p><p num="0011"> In one embodiment, the tetraalkylammonium polyoxoanion is represented by the general formula A._xO_y^Z-Includes polyoxoanions with, where A represents one or more transition metals, or other metals or metalloids capable of forming polyoxoanions. In one embodiment, the atom A in this general formula is selected from Al, Si, B, Ga, Ge, As, In, Sn, Sb, Tl, Pb and Bi, or any two or more of them. O is an oxygen atom, and the values of x, y and z depend on the valence of A in the polyoxoanion and y&gt; x.</p><p num="0012"> In one embodiment, the transition metal comprises one or more of Ti, V, Zn, Ni, Co, Mn, Fe and Cu.</p><p num="0013"> In one embodiment, the inorganic substrate comprises a ceramic oxide. In one embodiment, the ceramic oxide is Li⁺Contains ions and is suitable for use in lithium-ion battery ceramic cathode materials.</p><p num="0014"> In one embodiment, the inorganic substrate comprises a semiconductor material. In one embodiment, the semiconductor material comprises a semiconductor wafer, where optionally the semiconductor wafer comprises an electronic circuit component.</p><p num="0015"> In one embodiment, the tetraalkylammonium polyoxoanion is tetramethylammonium aluminate, and the inorganic substrate is a ceramic material. In one embodiment, the ceramic material is a lithium-ion battery cathode material.</p><p num="0016"> In another more detailed embodiment, the present invention is a method for depositing an alumina coating on an inorganic substrate. And A step of providing an aqueous composition containing tetraalkylammonium aluminate and hydrogen peroxide; The step of contacting the aqueous composition with an inorganic substrate for a time sufficient to precipitate aluminum hydroxide on the surface of the inorganic substrate to form an initially coated inorganic substrate; The step of heating the initially coated inorganic substrate for a time sufficient to convert the aluminum hydroxide to alumina; With respect to methods, including.</p><p num="0017"> In one embodiment, the inorganic substrate is a ceramic material. In one embodiment, the ceramic material is a lithium-ion battery cathode material.</p><p num="0018"> In one embodiment, the tetraalkylammonium aluminate is a tetramethylammonium aluminate.</p><p num="0019"> In one embodiment, the heating step is carried out at a temperature in the range of about 450 ° C to about 1000 ° C, or at a temperature of about 500 ° C.</p><p num="0020"> In one embodiment, the aqueous composition is further Li⁺Contains ions. Li in an aqueous composition⁺The presence of ions is the presence of Li in the oxide shell⁺Produces an inclusion of ions.</p><p num="0021"> The inventions described herein are not only applicable to the formation of core-shell structures for ceramic particles, but also the passivation of the surface of the inorganic material in flat plates or almost any other irregularly shaped body. It can also be applied to the formation of ceramic shells. Thus, for example, the present invention relates to semiconductors (eg, silicon or silicon / magnesium), wafer surfaces, or other inorganic surfaces (eg, glass surfaces), as well as oxide layers on semiconductor devices with electronic components that are already present. Can be applied to formation.</p><p num="0022"> The advantages of the present invention are (1) the method of the present invention is a room temperature method; (2) the method of the present invention is a simple one-step method; (3) the method of the present invention is predictable and controllable. (4) The method of the present invention is a homogeneous shell; (5) The method of the present invention is applicable to the formation of a thin film shell on a substrate; (6) The method of the present invention is not an ion exchange method for removing ions from the substrate; (7) The method of the present invention prepares for the formation of each shell of the single crystal particles of the substrate; (8) The method of the present invention is Li ion. In addition to the battery cathode ceramic material, it is prepared for a wide range of applications with many substrates; including one or more.</p>

0023<figref num="1">FIG. 1 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="2">FIG. 2 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="3">FIG. 3 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="4">FIG. 4 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="5">FIG. 5 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="6">FIG. 6 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="7">FIG. 7 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="8">FIG. 8 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="9">FIG. 9 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="10">FIG. 10 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="11">FIG. 11 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="12">FIG. 12 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="13">FIG. 13 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="14">FIG. 14 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="15">FIG. 15 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="16">FIG. 16 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="17">FIG. 17 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="18">FIG. 18 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="19">FIG. 19 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="20">FIG. 20 is an X-ray diffraction (XRD) pattern for an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="21">FIG. 21 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="22">FIG. 22 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref><figref num="23">FIG. 23 is a scanning electron microscope (SEM) micrograph of an exemplary inorganic substrate with and without an oxide coating according to a particular embodiment of the invention.</figref>

0024The drawings are provided as an unlimited example of embodiments and comparative examples of the invention and are intended to facilitate understanding of the invention.

0025As used herein, the term polyoxoanion is the general formula A._xO_y^z-(Here, A is a transition metal ion known from the periodic table (for example, Ti, V, Zn, Ni, Co, Mn, Fe, Cu), or Al, Si, B, Ga, Ge, As, In, Sn. , Sb, Tl, Pb and Bi, or any combination of any two or more of them, and O is an oxygen atom). The values of x, y and z depend on the valence of atom A in the polyoxoanion and y&gt; x. In most embodiments, atom A is in the highest oxidation (+) state. Atom A should contain those capable of forming polyoxoanions.

0026As mentioned above, the present invention relates to the formation of oxide shells (eg, passivation shells) on the surface of an inorganic material substrate. The present invention is particularly applicable to Li-ion battery cathode ceramic particles. This method is disassembled and H⁺An organic salt composed of a quaternary ammonium cation and a polyoxoanion is used in combination with an oxidizing agent such as hydrogen peroxide that produces ions. The decomposition of hydrogen peroxide is shown as follows.

0027<chemistry num="1"><img id="000002" he="23" wi="134" file="JP2016516654A_D0001.tif" img-format="tif" img-content="drawing" /></chemistry>

0028When the inorganic oxide material is exposed to a hydrogen peroxide solution, the following reactions occur on the surface of the inorganic oxide material and OH^-Is believed to generate. M in the formula is an element (eg, LiCo) that forms the inorganic material framework in the substrate._0.2Ni_0.8O₂Ni or Co inside, or Si) in a silicon wafer.

0029Oxide framework Inorganic materials are as follows:

0030<chemistry num="2"><img id="000003" he="22" wi="134" file="JP2016516654A_D0001.tif" img-format="tif" img-content="drawing" /></chemistry>

0031For semiconductor elemental inorganic materials (eg silicon):

0032<chemistry num="3"><img id="000004" he="22" wi="134" file="JP2016516654A_D0001.tif" img-format="tif" img-content="drawing" /></chemistry>

0033In the following, TMA (tetramethylammonium) aluminate salt will be used as an example to show a possible mechanism for shell formation on the surface of inorganic materials.

0034Without being bound by theory, it is believed that the method of the present invention proceeds as follows. When TMA aluminate is present in a solution containing an oxidizing agent such as hydrogen peroxide, the hydrogen peroxide decomposes and slowly H.⁺Since it emits ions, H⁺It is believed that the ions trap the aluminate anion and gradually form a layer (or crystal) of aluminum hydroxide on the surface of the inorganic substrate through homogeneous nucleation. More H until the aluminate ions in the solution disappear completely⁺Ions are generated from the continuous decomposition of hydrogen peroxide and the layer of aluminum hydroxide can grow. In this way, the aluminum hydroxide precursor of the initial alumina shell is formed on the surface of the inorganic material. The inorganic material (which has a precursor aluminum hydroxide shell formed on its surface) is then removed from the wet chemical solution and over several hours (eg 5 hours) at about 450 ° C to about 1000 ° C. It is heated in the oven in the range, or at a high temperature of, for example, about 500 ° C. The hydroxyl group of aluminum hydroxide bonded to the surface of the inorganic material is formed by the reaction with hydrogen peroxide and undergoes the condensation reaction with aluminum hydroxide to form a -MO-Al- bond between the shell and the inorganic base material. To form. Thus, hot heating transforms the aluminum hydroxide shell into an aluminum oxide (alumina) shell, removing water in this process. Thus, a very thin layer of aluminum oxide (or other atom as described herein) shell chemically bonded to the surface of the substrate can be prepared.

0035The inventions described herein are for the formation of core-shell structures on inorganic material particles, or for the formation of passivation shells on the surface of inorganic materials in planar or any regular or irregularly shaped form. Applicable to. That is, the present invention relates to surfaces ranging from fine ceramic particles (such as those used in the formation of Li-ion battery cathodes) to large flat surfaces (such as those on semiconductor wafers and devices) and irregular surfaces of any kind. The oxide shell disclosed above can be formed.

0036Inorganic material particles or substrates can be any other inorganic material that can form bonds to metal oxides through atoms such as oxides, ceramics, glass, silicon, and oxygen atoms.

0037Shell materials or passivation materials include transition metals (eg Ti, V, Zn, Ag, Ni, Co, Mn, Fe, Cu, Au), as well as Al, Si, B, Ga, Ge, As, In, It can be any polyoxoanion of metals and metalloids, including Sn, Sb, Tl, Pb and Bi. As such, the polyoxoanions useful in the present invention include all possible metallic and non-metallic elements that have or can form polyoxoanions, but N, O, P, S, F, Cl, Does not contain Br, I, etc., or alkali metals or alkaline earth metals.

0038Therefore, the present invention provides a method for controllingly depositing an oxide coating on an inorganic substrate, and the thickness of the oxide coating can be controlled easily and predictably.

0039The aqueous composition contains a tetraalkylammonium polyoxoanion and hydrogen peroxide. Aqueous compositions include tetraalkylammonium polyoxoanions in the range of about 0.0001% to about 30% by weight, and in one embodiment from about 0.011% to about 1.1% by weight, based on the total weight of the aqueous composition. It is contained at a concentration in the range of. The content of the tetraalkylammonium polyoxoanion should be selected based on the amount of inorganic substrate to be treated and the thickness of the oxide shell precipitate to be obtained. By adjusting the stoichiometric composition of the aqueous composition, as shown in the Examples, different but controllable thicknesses of the oxide shell can be obtained.

0040In one embodiment, the aqueous composition contains hydrogen peroxide as an oxidant. Hydrogen peroxide is in an aqueous composition at a concentration in the range of about 0.0001% to about 30% by weight, or in a concentration in the range of 0.004% to about 5% by weight, or 0.02% to about 1% by weight. Provided at concentrations in the range of, or at concentrations of about 0.035% by weight, all based on the total content of the aqueous composition.

0041In one embodiment, the weight ratio of tetraalkylammonium polyoxoanion to the inorganic substrate ranges from about 0.0001 to about 2, and in one embodiment it is from about 0.002 to about 0.5. As will be appreciated, this ratio depends on the surface area of the inorganic substrate and the desired thickness of the deposited oxide shell. As shown in the examples below, oxide shells with ratios in the range 0.01 to about 0.15 from about 1 nm to about 10 nm are deposited on finely ground ceramic particles intended for use with lithium-ion battery cathode materials. Is calculated for. The above range is merely exemplary, and the desired ratio is based on the desired thickness of the oxide shell and the properties of the inorganic substrate, along with relatively simple and simple calculations and some small but reasonable amount of experimentation. Can be calculated by one of ordinary skill in the art. The examples described below provide a good starting point for such calculations.

0042In one embodiment, the aqueous composition is further lithium ion (Li).⁺), As a result, the oxide coating can be provided with a controllable lithium ion content, facilitating the use of the product of the lithium ion battery cathode material. Lithium ions, if present, are provided in concentrations ranging from about 1 ppm (one millionth) to about 1000 ppm, and in one embodiment, from about 90 ppm to about 230 ppm. The lithium ion content in the oxide shell should be from 0 to about 50% by weight, preferably about 22% by weight for the aluminum oxide shell. The content of lithium ions added in the aqueous composition can be adjusted as needed to obtain the desired content of lithium ions in the oxide shell.

0043When lithium is included in the aqueous composition, it is included in the precursor shell. Upon heating, the lithium cations in the precursor shell can migrate to the substrate by an intercalation reaction with the inorganic substrate, leaving the aluminate to form an aluminum oxide shell. The degree to which lithium ions move to the core depends on the lithium content of the core. If the core is already saturated with lithium ions, migration can occur little or no. If no lithium ions can move to the core, some lithium ions remain in the shell. This has the advantage of obtaining the desired alumina shell on the inorganic substrate core while simultaneously adding lithium ions to the core. This may be particularly desired for the production of lithium ion battery cathode ceramic particles.

0044The contact step between the aqueous composition and the inorganic substrate took sufficient time to precipitate the hydroxide derived from the polyoxoanion on the surface of the inorganic substrate to form the first coated inorganic substrate. Is done. This precipitation time generally ranges from about 4 hours to about 24 hours, and in one embodiment it is from about 6 hours to about 12 hours, and in one embodiment it is from about 8 hours to about. 10 hours.

0045The contacting step is carried out by constantly mixing the components in a mixture of the aqueous composition and the particles of the inorganic substrate. The actual method of mixing, of course, depends on the volume of material being processed. On small scales, simple experimental shakers can be used, on large scales (eg, preparation or industrial scales) suitable larger mechanical mixing devices can be used, and these can be used by those skilled in the art. Can be selected appropriately.

0046The heating step of the first coated inorganic substrate takes a sufficient amount of time to convert the hydroxide to form the oxide. The oxide coating is derived from the polyoxoanion, and the time required to convert the hydroxide to the oxide is the polyoxoanion and the central atom (ie, general formula A as follows)._xO_y^z-It depends to some extent on the identity of the element A) in.

0047The tetraalkylammonium polyoxoanion may contain an alkyl group having any desired size, but in most embodiments, each of these alkyl groups is C.₁~ C₁₈Alkyl group, or C₁~ C₈Alkyl group, or C₁~ C₄It is an alkyl group and may be branched or unbranched. In general, the size of the alkyl group is not considered critical, but the alkyl group must not be long enough to prevent the solubility of the resulting tetraalkylammonium polyoxoanion in the aqueous composition. In one embodiment, the tetraalkylammonium polyoxoanion comprises tetramethylammonium hydroxide (TMAH). TMAH is usually a suitable quaternary ammonium compound because it is readily available and highly soluble in aqueous compositions.

0048As mentioned above, the polyoxoanion of the tetraalkylammonium polyoxoanion is the general formula A._xO_y^z-Where A represents a transition metal ion or a metal or metalloid capable of forming a polyoxoanion. In one embodiment, the atom A in this general formula is selected from Al, Si, B, Ga, Ge, As, In, Sn, Sb, Tl, Pb and Bi, or any two of them or it. In the above combination, O is the oxygen atom, and the values of x, y and z depend on the valence of A in the polyoxoanion and y&gt; x. Therefore, as will be readily recognized by those skilled in the art, if A is Al, x = 1, y = 3 and z = 1; if A is B, then x = 1, y = 3 and z = 3 If A is Mn, then x = 1, y = 4 and z = 1 ;, and so on.

0049In one embodiment, the transition metal comprises one or more of Ti, V, Zn, Ni, Co, Mn, Fe and Cu.

0050In one embodiment, the inorganic substrate comprises a ceramic oxide. In one embodiment, the ceramic oxide is Li⁺Containing, and suitable for the use of lithium-ion battery ceramic cathode materials. The ceramic oxide can be, for example, one of the following: Lithium Nickel Manganese Cobalt Oxide, LiNi_0.33Mn_0.33Co_0.33O₂ Lithium Nickel Cobalt Aluminum Oxide, LiNi_0.8Co_0.15Al_0.05O₂ Lithium Nickel Cobalt Aluminum Oxide, LiNi_0.79Co_0.20Al_0.01O₂ Lithium Nickel Cobalt Oxide, LiNi_0.8Co_0.2O₂ Lithium iron phosphate, LiFePO₄ Lithium nickel oxide, LiNiO₂ Lithium trivanadium salt, LiV₃O₈ Manganese Nickel Carbonate; Mn_0.75Ni_0.25CO₃ Copper vanadium oxide, CuV₂O₆ Lithium cobalt phosphate, LiCoPO₄ Lithium manganese dioxide, LiMnO₂ Lithium manganese oxide, LiMn₂O₄ Lithium manganese nickel oxide, Li₂Mn₃NiO₈ Lithium iron oxide, LiFeO₂ Lithium cobalt oxide, LiCoO₂ Lithium molybdate, LiMoO₄ Lithium titanate, Li₂TiO₃ Lithium cobalt manganese oxide, LiCo_0.8Mn_0.2O₂ Lithium Nickel Manganese Oxide, LiNi_0.85Mn_0.15O₂ Lithium cobalt nickel manganese oxide, LiCo_0.45Ni_0.45Mn_0.10O₂ Lithium Nickel Manganese Oxide, LiNi_0.8Mn_0.2O₂ Lithium Nickel Cobalt Boron Oxide, LiNi_0.79Co_0.2B_0.01O₂ Lithium Nickel Cobalt Tin Oxide, LiNi_0.79Co_0.2Sn_0.01O₂ Lithium Nickel Cobalt Aluminum Oxide, LiNi_0.72Co_0.2B_0.08O₂。

0051In addition to ceramics containing the above-exemplified materials suitable for use as lithium-ion battery cathodes (this list does not include all such materials), the inorganic substrate is almost any inorganic material. Possible, including ceramic materials and other inorganic materials such as silicon, glass, metals, dielectrics and conductive materials. In one embodiment, the inorganic substrate comprises a semiconductor material. In one embodiment, the semiconductor material comprises a semiconductor wafer, and optionally the semiconductor wafer comprises an electronic circuit.

0052In one embodiment, the tetraalkylammonium polyoxoanion is tetramethylammonium aluminate, and the inorganic substrate is a ceramic material. In one embodiment, the ceramic material is a lithium-ion battery cathode material. In the current preferred embodiment, the present invention relates to a method for precipitating an alumina coating on a lithium ion battery cathode material as an inorganic substrate, comprising the above steps, wherein the aqueous composition is tetramethylammonium aluminate and hydrogen peroxide. Contains hydrogen peroxide.

0053The present invention provides a thin layer of oxide derived from a polyoxoanion on the surface of the target substrate, but the precipitated layer is so thin that the resulting material has a substantially X-ray diffraction (XRD) pattern. It is noted that it does not change. If it is too heavy, a layer of oxide derived from the polyoxoanion will precipitate on the surface of the target substrate and the XRD pattern may change, which requires or desires a layer to precipitate. Reveal that it is thicker than what is done. Thickness, especially excess thickness, can be observed and evaluated via SEM by comparing SEM micrographs of the inorganic substrate taken before and after precipitation of the oxide shell. See, for example, FIGS. 6-10 and its description in the examples below. For materials used as Li-ion battery cathode materials, a layer of oxide derived from polyoxoanions on the surface of the ceramic material is Li during battery operation.⁺It should be thin enough to allow the passage of ions. The layer is Li⁺If it is thick enough to block the free flow of ions, it is too thick. In one embodiment, the thickness of the oxide derived from the polyoxoanion on the surface of the target substrate ranges from about 1 nm to about 20 nm, and in another embodiment it ranges from about 2 nm to about 10 nm. is there. Here, and elsewhere within the specification and claims of the present application, scope limitations may be combined, and the scope is all considered to include interposing integer values and fractional values. Therefore, for example, the thickness of 4 nm is not specifically mentioned, but this value is within the scope of the above disclosure and is included in the disclosure. Similarly, the 3.5 nm thickness is not specifically mentioned, but it is also included in the disclosure.

<p num="0054"> The quaternary ammonium polyoxoanion material used herein can be prepared using a two-step process involving precipitation and dissolution. The following examples use aluminum oxide as the polyoxoanion, but as mentioned above, this process is widely applicable to many metal and metalloid atoms. Preferably, the quaternary ammonium polyoxoanion used is tetramethylammonium aluminate.</p><p num="0055">(Preparation of quaternary ammonium aluminate) To a 200 ml flask equipped with a magnetic stirrer bar, add 37.51 g (0.1 mol) of aluminum nitrate nine hydrate and 200 g of deionized water. Stir the solution until a clear solution is formed. To this solution is slowly added 114.04 g (0.3 mol) of 23.98 wt% tetramethylammonium hydroxide (TMAH) solution. A white precipitate occurs immediately. The resulting white precipitate is filtered and rinsed 3 times with 200 ml of deionized water. The obtained white solid is freeze-dried to obtain dry aluminum hydroxide.</p><p num="0056"> Then, 5.69 g (0.073 mol) of the aluminum hydroxide powder and 145.83 g of deionized water are added to a 200 ml flask equipped with a magnetic stirrer bar. To this suspension is slowly added 83.15 g (0.22 mol) of 23.98 wt% TMAH solution. The white aluminum hydroxide powder disappears upon addition of all TMAH, thereby forming tetramethylammonium aluminate at a concentration of 0.311 mmol / g (ie 9.24 wt%). Excess TMAH suppresses the precipitation of oxide shells on the ceramic powder core, as described in more detail below, so stoichiometric amounts of TMAH should be used in both steps of preparation. Is noted.</p><p num="0057"> A similar two-step procedure can be performed with appropriate adjustment of the molecular weight calculation to produce the corresponding quaternary ammonium polyoxoanions disclosed herein.</p><p num="0058"> The ceramic powder to which the present invention can be applied is not limited, but the formula LiCo._0.2Ni_0.8O₂Includes the following illustrated Li-ion battery cathode ceramic materials with lithium nickel cobalt oxide having. Ceramic powders useful in the present invention are either commercially available or can be found in the literature and / or prepared according to procedures known to those of skill in the art. Ceramic powder LiCo_0.2Ni_0.8O₂The XRD pattern of is shown in Figure 1 and its SEM micrograph is shown in Figure 6.</p><p num="0059">(Example 1 (CS1P012) Lithium nickel cobalt oxide LiCo with an estimated 1 nm shell_0.2Ni_0.8O₂Core-shell structure preparation) To a 100 ml plastic beaker, add 0.0594 g of 0.311 mmol / g TMA aluminate, 40 g of deionized water and 0.0594 g of 30 wt% hydrogen peroxide. Increase the total weight of the solution to 50 g by adding additional deionized water. In the solution thus prepared, 0.5 g of LiCo having an average crystal particle size of about 3 μm_0.2Ni_0.8O₂Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours to obtain a ceramic powder with a core-shell structure according to an embodiment of the present invention. The XRD pattern of the obtained product is shown in FIG. 2, and the SEM micrograph is shown in FIG.</p><p num="0060">(Example 2 (CS2P012) Lithium nickel cobalt oxide LiCo with an estimated 10 nm shell_0.2Ni_0.8O₂Core-shell structure preparation) To a 100 ml plastic beaker, add 0.594 g of 0.311 mmol / g TMA aluminate, 40 g of deionized water and 0.594 g of 30 wt% hydrogen peroxide. Increase the total weight of the solution to 50 g by adding additional deionized water. In the solution thus prepared, 0.5 g of LiCo having an average crystal particle size of about 3 μm_0.2Ni_0.8O₂Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours. According to the embodiment of the present invention, the XRD pattern of the obtained product is shown in FIG. 3, and the SEM micrograph is shown in FIG.</p><p num="0061">(Example 3 (CS3P012) Lithium nickel cobalt oxide LiCo with an estimated 20 nm shell_0.2Ni_0.8O₂Core-shell structure preparation) To a 100 ml plastic beaker, add 1.188 g 0.311 mmol / g TMA aluminate, 40 g deionized water and 1.188 g 30 wt% hydrogen peroxide. Increase the total weight of the solution to 50 g by adding additional deionized water. In the solution thus prepared, 0.5 g of LiCo having an average crystal particle size of about 3 μm_0.2Ni_0.8O₂Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours. According to an embodiment of the present invention, the XRD pattern of the obtained product is shown in FIG. 4, and the SEM micrograph is shown in FIG.</p><p num="0062">(Example 4 (CS4P012) Lithium nickel cobalt oxide LiCo with an estimated 30 nm shell_0.2Ni_0.8O₂Core-shell structure preparation) To a 100 ml plastic beaker, add 1.782 g 0.311 mmol / g TMA aluminate, 40 g deionized water and 1.50 g 30 wt% hydrogen peroxide. Increase the total weight of the solution to 50 g by adding additional deionized water. In the solution thus prepared, 0.5 g of LiCo having an average crystal particle size of about 3 μm_0.2Ni_0.8O₂Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours. According to the embodiment of the present invention, the XRD pattern of the obtained product is shown in FIG. 5, and the SEM micrograph is shown in FIG.</p><p num="0063">(Example 5 Lithium nickel cobalt oxide LiCo with TMAH added to the formulation_0.2Ni_0.8O₂Core-shell structure preparation) This experiment is used to measure the effect of the presence of TMAH in the reaction mixture on shell formation.</p><p num="0064"> Each of the five 100 ml plastic beakers consists of 0.0594 g, 0.594 g, 1.782 g, 4.158 g and 5.94 g solutions (0.254 mmol / g TMA aluminate and 0.153 mmol / g TMAH, respectively. ) Is added. The Al content of each solution is well estimated to form shells with thicknesses of 1 nm, 10 nm, 30 nm, 70 nm and 100 nm on the ceramic particles under normal conditions. To each of the above solutions, add 40 g of deionized water and 1.5 g of 30 wt% hydrogen peroxide. Increase the total weight of each solution to 50 g by adding additional deionized water. Each of the solutions thus prepared has an average crystal particle size of about 3 μm and 0.5 g of LiCo._0.2Ni_0.8O₂Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours. The filtrate obtained as described above was filtered twice with a 0.2 μm filter. The resulting filtrate is subjected to elemental analysis to measure Al content. The XRD spectra are shown in Figures 11-15. SEM micrographs of the obtained ceramic powder are shown in FIGS. 16 and 17. Some ceramic particles are coated according to the present invention, but the presence of excess TMAH, or other quaternary ammonium hydroxide, is not preferred.</p><p num="0065">(Example 6 (CS7P144) Lithium nickel cobalt oxide LiCo having an estimated 10 nm shell in the absence of hydrogen peroxide component_0.2Ni_0.8O₂Core-shell structure preparation) This experiment was performed with an oxidizer for the formation of core-shell structures (H in this example).₂O₂) Is used to show the importance.</p><p num="0066"> To a 100 ml plastic beaker, add 0.594 g of 0.311 mmol / g TMA aluminate, zero hydrogen peroxide and deionized water to increase the total weight of the solution to 50 g. In the solution thus prepared, 0.5 g of LiCo having an average crystal particle size of about 3 μm_0.2Ni_0.8O₂Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours. The product thus obtained is filtered twice with a 0.2 μm filter. The resulting filtrate is subjected to elemental analysis to measure Al content. The SEM micrograph of the obtained ceramic particles is shown in FIG. This example is not according to the present invention and is therefore a comparative example.</p><p num="0067">(Examination of the results of the above examples) LiCo_0.2Ni_0.8O₂XRD patterns and SEM micrographs of ceramic particles are shown in Figures 1 and 6, respectively. Examples 1 to 4 are LiCo as a core._0.2Ni_0.8O₂Uses ceramic particles and Al as a shell₂O₃A detailed method for preparing a core-shell structure according to the present invention using the above is described. The core-shell structure is LiCo in an aqueous solution containing tetramethylammonium aluminate and hydrogen peroxide._0.2Ni_0.8O₂Prepared by suspending ceramic particles. The formulation solution generated some small bubbles when prepared, but many bubbles were generated as the ceramic particles were added to the solution. This is H in the reaction sequence of the present invention.₂O₂Surface-catalyzed H₂O₂Corresponds to the decomposition of. LiCo_0.2Ni_0.8O₂The ceramic powder is carefully ground in a mortar and pestle before filling the formulation solution for shell preparation so that there is no mechanical adhesion between the ceramic particles and the surface of all particles is covered by the shell. be able to. After the shell forming process, the ceramic powder isolated by the centrifuge tends to reaggregate the particles. However, the agglomerated ceramic particles are already coated with a shell.</p><p num="0068"> Shell thickness can be controlled by manipulating the TMA aluminate concentration, and estimated Al₂O₃Formulations with shell thicknesses of 1 nm, 10 nm, 20 nm and 30 nm can be designed as in the Examples. LiCo with core-shell structure as prepared_0.2Ni_0.8O₂The XRD patterns of the ceramic particles are shown in FIGS. 2 to 5. Obviously, the shell forming process has no impact on the ceramic crystal structure and the shell thickness is small enough not to significantly affect the XRD pattern.</p><p num="0069"> LiCo with core-shell structure as prepared_0.2Ni_0.8O₂SEM micrographs of ceramic particles are shown in FIGS. 7-10. Pure LiCo with very sharp crystal face edges_0.2Ni_0.8O₂LiCo produced according to the present invention as compared to ceramic particles_0.2Ni_0.8O₂The core-shell structure of the ceramic particles exhibits rounded crystalline edges. As the thickness of the coating increases, thicker shells can be observed based on a clear difference in appearance compared to uncoated ceramic particles, eg, as shown in FIG.</p><p num="0070"> The process solution after core-shell formation is analyzed to check for changes in the aluminum content of the residue. The results are shown in Table 1. In Table 1, the aluminum conversion rate refers to the amount of aluminum deposited on the surface of ceramic particles. Apparently, substantially all of the aluminum in the solutions of Examples 1-4 was deposited on the surface of the ceramic particles. Therefore, the present invention provides an effective method for controlling the thickness of the shell by controlling the concentration of aluminate in the reaction solution.</p><p num="0071"><tables num="1"><img id="000005" he="48" wi="134" file="JP2016516654A_D0001.tif" img-format="tif" img-content="drawing" /></tables></p><p num="0072"> Example 5 deals with the effects of TMAH on formulations. When TMAH is present in the process solution, shell formation is severely suppressed. 11 to 15 show the XRD spectrum of the treated ceramic, which shows that the ceramic crystals were unaffected. Table 2 shows the conversion rate of the aluminum content for aluminum transferred from the solution in the presence of TMAH in the reaction solution to the surface of the ceramic particles. Apparently, shell formation at 1 nm and 10 nm did not work very well, and shell formation at 20 nm, 30 nm, 70 nm and 100 nm still seems to work, but does not show 100% conversion. FIG. 16 shows a SEM micrograph of the ceramic particles, which appears to have a 10 nm shell formed on the surface according to the aluminum content of the reaction solution. Obviously, there is no prominent shell formed on these ceramic particles. FIG. 17 is an SEM micrograph of ceramic particles with an assumed shell thickness of 100 nm. The aluminum source is in large excess in this case, and produces a thick film on the ceramic particles. Aluminate content is higher than TMAH content, and the underlying behavior of TMAH is clearly overwhelming in this example. Therefore, excess TMAH appears to reduce the effectiveness of aluminate and suppress the precipitation of aluminum on the surface of the ceramic particles. As mentioned above, the ceramic particles in this test with a higher content of TMA aluminate are coated according to the invention, but the presence of excess TMAH or excess other quaternary ammonium hydroxide is not suitable.</p><p num="0073"><tables num="2"><img id="000006" he="39" wi="144" file="JP2016516654A_D0001.tif" img-format="tif" img-content="drawing" /></tables></p><p num="0074"> Example 6 was used to test the need for hydrogen peroxide to obtain the desired shell precipitation function. It seems that a 10 nm shell will be constructed on the surface of the ceramic particles. In the absence of hydrogen peroxide, no noticeable shell is observed in the SEM micrograph shown in FIG. Therefore, Example 6 is a comparative example.</p><p num="0075">(Additional examples) Example 7 (CS3P151) Lithium Nickel Cobalt Oxide LiCo with Estimated 20 nm Silicon Dioxide Shell_0.2Ni_0.8O₂Core-shell structure preparation) To a 100 ml plastic beaker, add 0.0496 g of 12.6 wt% TMA silicate, 40 g of deionized water and 1.5 g of 30 wt% hydrogen peroxide. Increase the total weight of the solution to 50 g by adding additional deionized water. In the solution thus prepared, 0.5 g of LiCo having an average crystal particle size of about 3 μm_0.2Ni_0.8O₂Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours to produce the core-shell structural ceramic powder of the present invention. A SEM micrograph is shown in FIG.</p><p num="0076">(Example 8 (CSXP151) Lithium manganese oxide LiMn having a silicon dioxide shell₂O₄Core-shell structure preparation) To a 100 ml plastic beaker, add 0.0496 g of 12.6 wt% TMA silicate, 40 g of deionized water and 1.5 g of 30 wt% hydrogen peroxide. Increase the total weight of the solution to 50 g by adding additional deionized water. In the solution prepared in this way, 0.5 g of LiMn having an average crystal particle size of about 1 to 2 μm₂O₄Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours to obtain the core-shell structural ceramic powder of the present invention. Pure LiMn₂O₄XRD is shown in Figure 20, and LiMn₂O₄The SEM micrograph of the above is shown in FIG. Core as prepared-shell LiMn₂O₄The SEM micrograph of the above is shown in FIG.</p><p num="0077">(Example 9 (CSYP151) Lithium manganese oxide LiMn having an aluminum oxide shell₂O₄Core-shell structure preparation) To a 100 ml plastic beaker, add 3.0 g 0.311 mmol / g TMA aluminate, 40 g deionized water and 1.5 g 30 wt% hydrogen peroxide. Increase the total weight of the solution to 50 g by adding additional deionized water. In the solution prepared in this way, 0.5 g of LiMn having an average crystal particle size of about 1 to 2 μm₂O₄Is added. The mixture is vibrated overnight and then the ceramic powder is isolated by a centrifuge. The recovered ceramic powder is placed in an oven and heated at 500 ° C. for 5 hours to obtain a core-shell structure ceramic powder. A SEM micrograph is shown in FIG.</p><p num="0078"> It is noted that throughout the specification and claims, numerical limitations of the scope and ratio of disclosure may be combined and are considered to include all intervening values. In addition, all numbers are considered prefaced by the modifier "about", whether or not the term is specifically mentioned.</p><p num="0079"> Although the principles of the present invention are provided for purposes described and illustrated in the context of certain embodiments, it should be understood that their various modifications will be apparent to those skilled in the art reading the specification. is there. Therefore, it should be understood that the inventions disclosed herein are intended to cover such modifications within the scope of the appended claims. The scope of the present invention is limited only by the scope of claims.</p>