Complexometric precursor formulation methodology for industrial production of fine and ultrafine powders and nanopowders of lithium metal oxides for battery applications
10446835 ยท 2019-10-15
Assignee
Inventors
Cpc classification
H01M4/5825
ELECTRICITY
C01F7/02
CHEMISTRY; METALLURGY
C01P2004/61
CHEMISTRY; METALLURGY
H01M4/136
ELECTRICITY
Y02P70/50
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
H01M4/525
ELECTRICITY
C01G45/12
CHEMISTRY; METALLURGY
C01B35/126
CHEMISTRY; METALLURGY
H01M4/505
ELECTRICITY
Y02E60/10
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C01B25/45
CHEMISTRY; METALLURGY
C01B35/128
CHEMISTRY; METALLURGY
C01G53/50
CHEMISTRY; METALLURGY
C01G45/1235
CHEMISTRY; METALLURGY
C01B33/26
CHEMISTRY; METALLURGY
H01M4/131
ELECTRICITY
International classification
H01M4/131
ELECTRICITY
H01M4/525
ELECTRICITY
H01M4/36
ELECTRICITY
H01M4/505
ELECTRICITY
H01M4/58
ELECTRICITY
C01B25/45
CHEMISTRY; METALLURGY
H01M4/136
ELECTRICITY
C01B33/26
CHEMISTRY; METALLURGY
C01F7/02
CHEMISTRY; METALLURGY
C01G45/12
CHEMISTRY; METALLURGY
Abstract
A compound M.sub.jX.sub.p which is particularly suitable for use in a battery prepared by the complexometric precursor formulation methodology wherein: M.sub.j is at least one positive ion selected from the group consisting of alkali metals, alkaline earth metals and transition metals and j is an integer representing the moles of said positive ion per moles of said M.sub.jX.sub.p; and X.sub.p, a negative anion or polyanion from Groups IIIA, IVA, VA, VIA and VIIA and may be one or more anion or polyanion and p is an integer representing the moles of said negative ion per moles of said M.sub.jX.sub.p.
Claims
1. A compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology wherein: M.sub.j is at least one positive ion selected from the group consisting of alkali metals, alkaline earth metals and transition metals and j represents the moles of said positive ion per mole of said M.sub.jX.sub.p wherein at least one said positive ion is lithium; and X.sub.p is a negative anion or polyanion selected from the group consisting of Groups IIIA, IV A, VA, VIA and VIIA and may be one or more anion or polyanion and p represents the moles of said negative anion per mole of said M.sub.jX.sub.p and said compound is a powder wherein said powder has a nanostructure and said nanostructure is a layered nanostructure.
2. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 1 wherein said M.sub.j comprises M.sub.1 and M.sub.2 and wherein M.sub.1 is lithium and M.sub.2 is a transition metal selected from the group consisting of Fe, Mn, Co, Ni and V.
3. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 2 wherein said transition metal is selected from the group consisting of Ni, Mn and Co.
4. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 1 further comprising a dopant.
5. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 4 wherein said dopant is selected from the group consisting of alkali or alkaline earth metals, Group III A, Group IV A and transition metals.
6. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 4 comprising up to 10 weight % of said dopant.
7. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 1 further comprising a coating.
8. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 7 wherein said coating comprises alkali or alkaline earth metals, Group III A, Group IV A or transition metals.
9. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 7 wherein said coating further comprises an organic or inorganic compound.
10. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 9 wherein said coating comprises said MjXp.
11. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 9 wherein said coating is a nanolayer.
12. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 9 wherein said coating comprises carbon or a carbon-containing compound.
13. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 1 wherein said compound has a particle size of less than 1 micron.
14. The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology of claim 1 wherein said compound has a surface area of at least 1 m.sup.2/gm.
15. A battery comprising the compound of claim 1.
16. The battery of claim 15 comprising a cathode comprising a lithium salt of at least one of Ni, Mn, Co, Ti, Mg, or Zn.
17. The battery of claim 15 wherein said lithium salt is a lithium nickel manganese cobalt salt.
18. The battery of claim 15 wherein said compound is defined by the formula Li.sub.2-x-y-zNi.sub.xMn.sub.yCo.sub.zO.sub.2 wherein x+y+z1 and at least one of x, y or z is not zero.
19. The battery of claim 15 wherein said compound is Li.sub.1-x-y-zNi.sub.xMn.sub.yCo.sub.zO.sub.2 wherein x+y+z1 and none of x, y or z are zero.
20. The battery of claim 15 having a capacity of at least 80 mAh/g after 500 cycles at discharge rate of 1 C at room temperature from 4.2 volts to 3 volts .
21. The battery of claim 15 having a capacity of 150 mAh/g after 500 cycles at discharge rate of 1 C at room temperature from 4.6 volts to 2.5 volts.
22. The battery of claim 15 wherein at 1 C said battery is capable of at least 500 cycles.
Description
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DESCRIPTION
(54) The instant invention is specific to an improved method of forming nanoparticles. More specifically, the instant invention is specific to a method of forming particles through formation of a complexometric precursor formed on a bubble surface thereby allowing for careful control of nucleation and crystal growth.
(55) The invention will be described with reference to the various figures which form an integral non-limiting component of the disclosure. Throughout the disclosure similar elements will be numbered accordingly.
(56) This invention described herein is a complexometric precursor formulation methodology, hereinafter referred to as CPF, suitable for large scale industrial production of high performance fine, ultrafine and nanosize powders requiring defined unique chemical and physical properties that are essential to meet performance specifications for specialized applications.
(57) A particularly suitable material formed by the CPF process is a lithium nickel manganese cobalt compound defined by formula is Li.sub.2-x-y-zNi.sub.xMn.sub.yCo.sub.zO.sub.2 wherein x+y+z1 and at least one of x, y or z is not zero and more preferably none of x, y or z is zero.
(58) The CPF method proceeds in the formation of a complex precursor, herein called complexcelle, on a bubble surface thereby providing for the controlled formation of specialized microstructures or nanostructures and a final product with particle size, surface area, porosity, phase purity, chemical purity and other essential characteristics tailored to satisfy performance specifications. Powders produced by CPF are obtained with a reduced number of processing steps relative to currently used technology and can utilize presently available industrial equipment. CPF is simple to implement and preferred design configurations are further described and illustrated in
(59) The CPF method produces fine, ultrafine and nanosize powders in a simple efficient way by integrating chemical principles of crystallization, solubility, transition complex formation, phase chemistry, acidity and basicity, aqueous chemistry, thermodynamics and surface chemistry.
(60) It is preferred to produce these powders with the selected properties at the onset of the contact among the elements as these are combined to make the desired compound. The time when crystallization begins and, in particular, when the nucleation step begins, is the most crucial stage of formation of nanosize powders. A particular advantage provided by CPF is the ability to prepare the nanosize particles at the onset of this nucleation step. The solute molecules from the starting reactants are dispersed in a given solvent and are in solution. At this instance, clusters begin to form on the nanometer scale on the bubble surface under the right conditions of temperature, supersaturation, and other conditions. These clusters constitute the nuclei wherein the atoms begin to arrange themselves in a defined and periodic manner which later defines the crystal microstructure. Crystal size and shape are macroscopic properties of the crystal resulting from the internal crystal structure.
(61) After the nucleation begins, crystal growth also starts and both nucleation and crystal growth may occur simultaneously as long as supersaturation exists. The rate of nucleation and growth is determined by the existing supersaturation in the solution and either nucleation or growth occurs over the other depending on the supersaturation state. It is critical to define the concentrations of the reactants required accordingly in order to tailor the crystal size and shape. If nucleation dominates over growth, finer crystal size will be obtained. The nucleation step is a very critical step and the conditions of the reactions at this initial step define the crystal obtained. By definition, nucleation is an initial phase change in a small area such as crystal forming from a liquid solution. It is a consequence of rapid local fluctuations on a molecular scale in a homogeneous phase that is in a state of metastable equilibrium. Total nucleation is the sum effect of two categories of nucleationprimary and secondary. In primary nucleation, crystals are formed where no crystals are present as initiators. Secondary nucleation occurs when crystals are present to start the nucleation process. It is this consideration of the significance of the initial nucleation step that forms the basis for this CPF methodology.
(62) In the CPF methodology, the reactants are dissolved in a solution preferably at ambient temperature or if needed, at a slightly elevated temperature but preferably not more than 100 C. Selection of inexpensive raw materials and the proper solvent are important aspects of this invention. The purity of the starting materials are also important since this will affect the purity of the final product which may need specified purity levels required for its performance specifications. As such, low cost starting materials which can be purified during the preparation process without significantly increasing the cost of processing must be taken into consideration. For instance, if a preferred starting raw material is a carbonate salt, one can start with a chloride salt as most reactants from rock processing are chloride salts. There may be some impurities in this chloride salt that may need to be removed and depending on the ease of impurity reduction, this chloride salt can be converted to the carbonate salt and at the same time remove any impurity or reduce the impurity levels.
(63) CPF uses conventional equipment in an innovative way to produce the nanosize nuclei required for the final product. CPF utilizes a reactor fitted with a gas diffuser to introduce gas into the solution thereby creating bubbles. An agitator vigorously disperses the solution simultaneously with the bubble formation, as the second reactant is introduced into the first solution. The combination of gas flow and agitation provides a bubble surface. The bubble surface serves as the interface of contact between the molecules of the first solution and the molecules of the second solution thereby providing a surface reaction.
(64) A surface reaction is the adsorption of one or more reactants from a gas, liquid or dissolved solid on a surface. Adsorption may be a physical or chemical adsorption.
(65) The CPF process creates a film of the adsorbate on the bubble surface of the adsorbent. The bubble surface is the adsorbent and the adsorbates are the reactants in the solution. As illustrated in
(66) In
(67) It is preferred that the gas be introduced directly into the solution without limit to the method of introduction. The gas can be introduced into the solution within the reactor by having several gas diffusers, such as tubes, located on the side of the reactor, wherein the tubes have holes for the exit of the gas as illustrated in
(68) In one embodiment an aerator can be used as a gas diffuser. Gas diffusing aerators can be incorporated into the reactor. Ceramic diffusing aerators which are either tube or dome-shaped are particularly suitable for demonstration of the invention. The pore structures of ceramic bubble diffusers produce relatively fine small bubbles resulting in an extremely high gas to liquid interface per cubic feet per minute (cfm) of gas supplied. This ratio of high gas to liquid interface coupled with an increase in contact time due to the slower rate of the fine bubbles accounts for the higher transfer rates. The porosity of the ceramic is a key factor in the formation of the bubble and significantly contributes to the nucleation process. While not limited thereto for most configurations a gas flow rate of at least one liter of gas per liter of solution per minute is suitable for demonstration of the invention.
(69) A ceramic tube gas diffuser on the sides of the reactor wall is particularly suitable for demonstration of the invention. Several of these tubes may be placed in positions, preferably equidistant from each other, to create bubbling more uniformly throughout the reactor. The gas is preferably introduced into the diffuser within the reactor through a fitting connected to the header assembly which slightly pressurizes the chamber of the tube. As the gas permeates through the ceramic diffuser body, fine bubbles start being formed by the porous structure of the material and the surface tension of the liquid on the exterior of the ceramic tube. Once the surface tension is overcome, a minute bubble is formed. This small bubble then rises through the liquid forming an interface for transfer between gas and liquid before reaching the surface of the liquid level.
(70) A dome-shaped diffuser can be placed at the bottom of the reactor or on the sides of the reactor. With dome shape diffusers a plume of gas bubbles is created which is constantly rising to the surface from the bottom providing a large reactive surface.
(71) A membrane diffuser which closes when gas flow is not enough to overcome the surface tension is suitable for demonstration of the invention. This is useful to prevent any product powder from being lost into the diffuser.
(72) In order to have higher gas efficiencies and utilization, it is preferred to reduce the gas flow and pressure and expend less pumping energy. A diffuser can be configured such that for the same volume of gas, smaller bubbles are formed with higher surface area than if fewer larger bubbles are formed. The larger surface area means that the gas dissolves faster in the liquid. This is advantageous in solutions wherein the gas is also used to solubilize the reactant by increasing its solubility in the solution.
(73) Smaller bubbles also rise more slowly than the larger bubbles. This is due to the friction, or surface tension, between the gas and the liquid. If these bubbles start from the same position or depth in the reactor, the larger bubbles reach the surface more quickly than several smaller bubbles. The smaller bubbles will have more liquid as it rises. The bubble surface interface between the two reactants determines the nucleation rate and size can therefore be tailored by controlling the bubble size formation.
(74) Nozzles, preferably one way nozzles, can be used to introduce gas into the solution reactor. The gas can be delivered using a pump and the flow rate should be controlled such that the desired bubbles and bubble rates are achieved. A jet nozzle diffuser, preferably on at least one of the sides or bottom of the reactor, is suitable for demonstration of the invention.
(75) The rate of gas introduction is preferably sufficient to increase the volume of the solution by at least 5% excluding the action of the agitator. In most circumstances at least about one liter of gas per liter of solution per minute is sufficient to achieve adequate bubble formation. It is preferable to recycle the gas back into the reactor.
(76) Transfer of the second reactant solution into the first reactor solution is preferably done using a tube attached to a pump connecting the solution to be transferred to the reactor. The tube into the reactor is preferably a tube with a single orifice or several orifices of a chosen predetermined internal diameter such that the diameter size can deliver a stream of the second solution at a given rate. Atomizers with fine nozzles are suitable for delivering the second solution into the reactor. The tip of this transfer tube can comprise a showerhead thereby providing several streams of the second solution reacting on several surface bubbles simultaneously. Nucleation is influenced not only by the concentration of the second solution but also by the instantaneous concentration of this solution as it reaches the surface bubble interface to form the complexcelle. In large scale production, the rate of transfer is a time factor so the transfer rate should be sufficiently rapid enough to produce the right size desired.
(77) The agitator can be equipped with several propellers of different configurations, each set comprising one or more propellers placed at an angle to each other or on the same plane. Furthermore, the mixer may have one or more sets of these propellers. The objective is to create enough turbulence for rapid bubble formation and turnover. Examples of the agitator arrangements are shown in
(78) Straight paddles or angled paddles are suitable. The dimensions and designs of these paddles determine the type of flow of the solution and the direction of the flow. One preferred blade design for CPF methodology is shown in
(79) The CPF process steps are demonstrated in the following examples below for a desired final product M.sub.jX.sub.p such that M=M.sub.1 M.sub.2 M.sub.3 (dual metal cation) or more and X.sub.pO. The flow chart in
(80) The starting raw materials for this process are chosen from Groups IA, IIA, IIIA, IVA and transition metals with the anion being monatomic or a polyanion selected from Groups IIIA, IVA, VA, VIA and VIIA. The final powders are cation compounds of anions or polyanions such that the formula is M.sub.jX.sub.p where M.sub.j may be a single cation or a mixture of metal cations and X.sub.p may be a single anion, a single polyanion or a mixture of mixed anions and polyanions. M.sub.j may be M.sub.1 M.sub.2 M.sub.3 or more which are in stoichiometric or non-stoichiometric ratios and one or two may be small dopant amounts not more than 10 weight % of the final powder. The anion and polyanions may be oxides, carbonates, silicates, phosphates, borates, aluminates, silicophosphates, stannates, hydroxides, nitrates, oxycarbonates, hydroxycarbonates, fluorides, and oxyfluorides without limited thereto. Examples of these desired high performance powders are utilized in lithium ion battery applications, rechargeable batteries, bone implants, dental implants, structural ceramics, optical communication fibers, medical patches for drug delivery and specialized composites of metal-metal, metal-ceramic, glass-ceramic, glass-metal and others but not limited to these. The following discussion will illustrate the complexometric precursor formulation technology as applied to the synthesis of a lithium cathode material for lithium ion batteries. It is known that this art is not limited to this illustrative example but is applicable to numerous specialized high performance powders which are very expensive to manufacture today. The reactants in each solution are preferably no more than 30 wt. % of the solution.
(81) A first reactant solution A is prepared by dissolving the solid in a selected solvent, preferably a polar solvent such as water but not limited thereto. It is understood that the choice of solvent depends on the type of final powder product desired, the formulated composition of the final powder and the physical characteristics required for achieving the performance of the final powder. The choice of the solvent is determined by the solubility of the solid reactant A in the solvent and the temperature of dissolution. It is preferred to dissolve at ambient temperature and to dissolve at a fast rate so that solubilization is not energy intensive. The dissolution may be carried out at a slightly higher temperature but preferably below 100 C. Only if other dissolution methods fail should a higher temperature be used. Other dissolution aids may be addition of an acid or a base. The solution concentration is preferably low as this influences concentration at the surface bubble interphase during the nucleation which determines the final powder size. It is important to select the proper chemical environment in order to produce the right nucleation to yield the desired final powder characteristics.
(82) The cost of the starting materials should also be considered in the sum total of the process cost. Generally, lower cost raw materials are the salts of chlorides, nitrates, hydroxides and carbonates. Acetate salts and other compounds are usually prepared from these so these downstream compounds will be at higher cost. Nitrates and sulfates are readily soluble in water but they also release noxius gases during high temperature calcination. The purity of the starting materials is also a cost consideration and technical grade materials should be the first choice and additional inexpensive purification should be factored in the selection of the starting materials.
(83) A second reactant solution B is also prepared in the same way as reactant solution A. The solid starting material and the solvent selected for dissolution should yield the fastest dissolution under mild conditions as possible.
(84) The reactor, 1, set-up for both solutions A and B is diagrammed in
(85) The agitator blade illustrated in
(86) The rate of transfer has a kinetic effect on the rate of nucleation. A preferred method is to have a fine transfer stream to control the concentration of the reactants at the bubble surface interface which influences the complexcelle formation and the rate of nucleation over the rate of crystal growth. For smaller size powder, a slower transfer rate will yield finer powders. The right conditions of the competing nucleation and growth must be determined by the final powder characteristics desired. The temperature of reaction is preferably ambient or under mild temperatures if needed.
(87) Upon completion of the reaction of reactant A and reactant B, the resulting slurry mixture containing the intermediate complexcelle is dried to remove the solvent and to obtain the dried powder. Any type of drying method and equipment can be used and such drying is preferably at less than 350 C. Drying can be done using an evaporator such that the slurry mixture is placed in a tray and the solvent is released as the temperature is increased. Any evaporator in industrial use can be employed. The preferred method of drying is by using a spray dryer with a fluidized nozzle or a rotary atomizer. These nozzles should be the smallest size diameter although the size of the powder in the slurry mixture has already been predetermined by the reaction conditions. The drying medium is preferably air unless the product is air-sensitive. The spray dryer column should also be designed such that the desired moisture content is obtained in the sprayed particulates and are easily separated and collected.
(88) The spray dried particles obtained by the CPF methodology are very fine and nanosize. Definitive microstructures or nanostructures by the CPF process are already formed during the mixing step. Novel microstructures or nanostructures looking like flowers or special layering such that these structures are called nanorose, nanohydrangea, or nanocroissant or other description depending on the formulation of the powder. Such structures also translate to the final powder after the calcination step.
(89) After spray drying, the powder is transferred to a calciner. No crushing or milling is required since the spray dried powders are very fine. In large scale production, this transfer may be continuous or batch. A modification of the spray dryer collector such that an outlet valve opens and closes as the spray powder is transferred to the calciner can be implemented. Batchwise, the spray dried powder in the collector can be transferred into trays or saggers and moved into a calciner like a box furnace although protection from powder dust should also be implemented. A rotary calciner is also another way of firing the powder. A fluidized bed calciner is also another way of higher temperature heat treatment of the spray dried powder. The calcination temperature is determined by the composition of the powder and the final phase purity desired. For most oxide type powders, the calcination temperatures range from as low as 400 C. to slightly higher than 1000 C. After calcination, the powders are crushed as these are soft and not sintered. The CPF process delivers non-sintered material that does not require long milling times nor does the final CPF process require classifiers to obtain narrow particle size distribution. The particle sizes achievable by the CPF methodology are of nanosize primary and secondary particles and up to small micron size secondary particles ranging to less than 50 micron aggregates which are very easily crushed to smaller size. It should be known that the composition of the final powder influences the morphology as well.
(90) A brief stepwise summary of the CPF methodology is given below.
(91) A first solution or slurry solution of M=M.sub.1 chosen from the metal chlorides, metal nitrates, metal hydroxides, metal acetates, metal carbonates, metal hydroxvcarbonates, metal hydroxyl phosphates and metal hydroxysilicates but not limited to these would be prepared. The purity of the starting reactant for M.sub.1 should be defined by the final purity desired and the degree of purification that may be done in a preliminary step.
(92) A second solution or slurry solution of M=M.sub.2 also chosen from the same metal salts as for the first solution. The purity of the starting reactant for M.sub.2 should also be chosen on the basis of the final purity of the final product and the degree of purification needed in a preliminary step.
(93) The solvent in both the first and second solution is preferably deionized water at acidic or basic pH and ambient temperature. An acid or a base may be added to the first or second solution to aid in solubilizing the reactants and/or the temperature may be increased but preferably not more than 100 C., and/or the solubilizing mixing rate be more vigorous and solubilizing time increased. If conditions require more adverse temperature and time, then the process may proceed as slurry solutions. Other solvents to dissolve the starting materials may also be used if water is insufficient for dissolution. Such solvents may be polar solvents as alcohols or non-polar solvents typically used in general organic preparations. It is important to consider raw material costs during the evaluation of the process so that production cost does not decrease the value-added performance advantages of the CPF powder.
(94) A CPF reactor designed or configured so that gas may be introduced into the vessel is charged with the first solution. The gas may be air, argon, carbon dioxide, nitrogen, or mixtures of these preferably of normal purity. The gas may be inert for reactions that are adverse in air. Likewise, the gas may also be a possible reactant such as, for example, those reactions wherein carbon dioxide is utilized to produce carbonates or bicarbonates, or hydroxycarbonates and oxycarbonates but not limited to these.
(95) The gas may be introduced by a gas diffuser such as gas tubes having holes in the tube from which the gas introduced from the inlet exits into the reactor vessel creating a vigorous flow and a bubbling solution with numerous fine micro-bubbles. The holes may be sized to insure bubbles are generated over the entire length of the tube.
(96) The gas may also be introduced by mechanical gas diffusers with pumps that may circulate both gas and solution which also improves mixing of the solutions.
(97) The gas flow rate, in conjunction with the mixing speed of the agitator, should be enough to create suspended micro bubbles such as a foamy solution.
(98) An agitator blade is configured to produce vigorous mixing to produce a frothy slurry solution or frothy solution. The agitator blade may be a concentric loop to promote incorporation of the gas and the formation of fine bubbles. The concentric loop may rotate horizontally and vertically. In addition, the agitator blade may be dual, triple, quadruple, quintuple or other configuration and not limited to these. Depending on the height of the reactor vessel, several agitator blades may be used.
(99) The mixing speed should be fast enough to maintain bubbles of first solution such that the second solution being added drops into the bubbles of the first solution creating a micro or nano contact onto the surface of the bubbles of the second solution.
(100) The first solution may be added to the second solution. The resulting product performance may be different depending on the method of addition.
(101) The mixing temperature is preferably ambient or slightly elevated but not more than 100 C.
(102) The resulting mixture of first and second solutions may be a solution or a slurry mixture.
(103) The resulting reaction product is dried by any drying method using known industrial equipment including spray dryers, tray dryers, freeze dryers and the like, chosen depending on the final product preferred. The drying temperatures would be defined and limited by the equipment utilized. The desired drying temperatures are usually from 200-325 C.
(104) The resulting mixture is continuously agitated as it is pumped into the spray dryer head if spray dryers, freeze dryers or the like are used. For tray dryers, the liquid evaporates from the surface of the solution.
(105) The dried powders are transferred into the next heating system batch-wise or by means of a conveyor belt. The second heating system may be a box furnace utilizing ceramic trays or saggers as containers, a rotary calciner, a fluidized bed, which may be co-current or counter-current, a rotary tube furnace and other similar equipment but not limited to these. The calcination temperature depends on the final product requirements and could be as high as 1000 C. and up to as much as 3000 C. or more as in the case of glassy silicates.
(106) The heating rate and cooling rate during calcinations depend on the type of final product desired. Generally, a heating rate of about 10 C. per minute is preferred but the usual industrial heating rates are also applicable.
(107) Calcining may also require inert gases as in the case of those materials that are sensitive to oxidation. As such, a positive flow of the inert gas may be introduced into the calcining equipment.
(108) The final powder obtained after the calcining step is a fine, ultrafine or nanosize powder that does not require additional grinding or milling as is currently done in conventional processing. Particles are relatively soft and not sintered as in conventional processing.
(109) The final powder is preferably characterized for surface area, particle size by electron microscopy, porosity, chemical analyses of the elements and also the performance tests required by the preferred specialized application.
(110) The CPF methodology for the production of fine, ultrafine and nanosize powders offers several advantages. One of the improvements is reduction in the number of processing steps. There is no significant milling and firing sequence in the CPF method. The total production time for this CPF methodology route to fine, ultrafine and nanosize powders is less than or equal to 25% of current conventional processing technologies for such similar powders. Final powder production cost using CPF methodology can be significantly reduced by as much as 75-80% of current conventional processing. Performance improvements of these powders produced by CPF are at least 15% or more than those traditional ceramic powders currently produced by presently known technologies. The CPF process can be utilized for the preparation of different types of powders and is not limited to a group of powder formulations.
(111) This CPF process can be applied to make the desired powder for the lithium ion batteries, such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide and the doped lithium metal oxides of this type, the mixed lithium metal oxides of said metals and the doped derivatives, lithium iron phosphate and the doped lithium iron phosphates as well as other lithium metal phosphates, lithium titanates and other materials for the storage batteries. The CPF process can be applied to produce medical powders such as the specialized calcium phosphates for medical applications like bone implants. The CPF process can also be used for the preparation of other advanced ceramic powders such as lithium niobates and lithium tantalates, lithium silicates, lithium aluminosilicates, lithium silicophosphates and the like. Semiconductor materials can also be prepared by the CPF process as well as specialized pharmaceutical drugs. High surface area catalysts can be made by the CPF process and such catalysts would have higher catalytic activity as a result of a finer particle size, higher surface area and higher porosity made possible by the CPF methodology. Specialized coatings requiring nanosize powders can be economically prepared by the CPF method. This CPF process can also be used for the preparation of non-lithium based materials. The versatility of this methodology allows itself to be easily modified in order to achieve the customized, tailored powder needed. Furthermore, this methodology is easily adapted for large scale industrial production of specialized powders requiring a narrow particle size distribution and definitive microstructures or nanostructures within the fine, ultrafine or nanosize powders. Having a cost effective industrial scale powder for these specialized applications will allow commercial development of other devices otherwise too costly to manufacture.
(112) The complexometric precursor formulation methodology or CPF, creates a fine, ultrafine or nanosize powders via the formation of a complexcelle of all the ions of the desired powder composition on a bubble surface interface. CPF has many advantages over known prior art.
(113) Only the main reactants for the chemical formula of the compound to be synthesized are used. This will reduce the cost of the raw materials. The starting raw materials can be low cost. Technical grade materials can be used and if needed, purification can be done in-situ.
(114) Total processing time is significantly less, about to of the processing times for the present industrial processes.
(115) Special nanostructures are preformed from the complexcelle which are carried over to the final product thus enhancing the performance of the material in the desired application. For the purposes of the present invention nanostructures are defined as structures having an average size of 100 to 300 nm primary particles.
(116) Neither surfactants nor emulsifiers are used. The initiation reaction occurs at the surface of the bubble interface. In fact, it is preferable that surfactants and emulsifiers are not used since they may inhibit drying.
(117) Size control can be done by the size of the bubbles, concentration of the solutions, flow rate of the gas, transfer rate of second reactant into the first reactant.
(118) No repetitive and cumbersome milling and classification steps are used.
(119) Reduced calcination time can be achieved and repetitive calcinations are typically not required.
(120) Reaction temperature is ambient. If need for solubilization, temperature is increased but preferably not more than 100 C.
(121) Tailored physical properties of the powder such as surface area, porosity, tap density, and particle size can be carefully controlled by selecting the reaction conditions and the starting materials.
(122) The process is easily scalable for large scale manufacturing using presently available equipment and/or innovations of the present industrial equipment.
(123) Examples
(124) Preparation of Coin Cells
(125) The standard practice for coin cell testing has been used in all example and is described herein for reference. The material was made into electrodes in the same way and tested in an Arbin battery cycler (BT-2000) under the same cycling conditions of voltage and current. As such, side-by-side comparison of the battery cycling performances definitively exemplifies the advantages of the CPF methodology over current industrial production processes.
(126) Electrodes were prepared by mixing 80 wt. % of active material, 10 wt. % of carbon black, and 10 wt. % PVDF (polyvinylideneflouride) in NMP (1-methyl-2-pyrrolidone). The resulting slurry was cast on aluminum foil and dried in a vacuum oven at 115 C. for 24 h. CR2032-type coin cells were fabricated in an argon-filled glove box using lithium metal as the counter electrode. The cathode weight was around 4 mg per electrode. The electrolyte was a 1 M solution of LiPF.sub.6 (lithium hexafluorophosphate) in a 1:1:1 volume mixture of EC:DMC:DEC (ethylene carbonate, dimethyl carbonate, and diethyl carbonate). The separator (Celgard 2400) was soaked in the electrolyte for 24 h prior to battery testing. Coin-cells were galvanostatically charged/discharged on the Arbin battery cycler at the stipulated current densities. Tests were done at ambient temperature. Both comparative example and the example coin cells were done at the same time under the same conditions.
EXAMPLES
Comparative Example 1
(127) Commercially available lithium cobalt oxide powder was obtained from Sigma Aldrich and characterized by field emission SEM (
(128) The scanning electron micrograph of this commercial LiCoO.sub.2 in
(129) The X-ray powder diffraction in
(130) The capacity of this lithium cobalt oxide prepared commercially is shown in
Example 2
(131) Lithium cobalt oxide was prepared using a reactor vessel as shown in
(132) The slurry after mixing the reactants was placed on a glass surface to dry in air. The air-dried powder was analyzed by field emission SEM and the micrograph is shown in
(133) In
(134) After the calcination step for 5 h at 900 C., the layered nanostructure observed in
(135) Coin cells were prepared as described in the preparation of coin cells. The capacity of this lithium cobalt oxide prepared by the CPF methodology is shown in
Example 3
(136) The powders in Examples 1 and 2 were refired at 900 C. for another 5 h. Coin cells were prepared as described. A comparison of the battery cycling tests is given in
(137) In the battery cycling tests at a higher C rate of 1 C, the lithium cobalt oxide powder from Example 2 that was refired again performed significantly better than the commercial powder that was also refired at the same temperature and for the same time period. The capacity of the commercial sample dropped from 120 mAh/g to 20 mAh/g after 200 cycles. The CPF sample had a capacity of 100 mAh/g after 300 cycles and 80 mAh/g at 400 cycles.
(138) The present invention provides a cathode for a battery wherein the battery has a capacity of at least 80 mAh/g after 200 cycles
(139) The scanning electron micrographs of the refired samples are shown in
Example 4
(140) The same procedure described in Example 2 was used in this example but with the added nickel and manganese compounds to illustrate the synthesis of multicomponent lithium oxides by the CPF methodology. The formulation made is Li.sub.1.20Ni.sub.0.18Mn.sub.0.50Co.sub.0.12O.sub.2 which is a high energy lithium nickel manganese cobalt oxide material for lithium ion batteries that would meet the electric vehicle performance standards.
(141) Nickel hydroxide (16.8 grams, 99%) and cobalt carbonate (14.4 grams, 99.5%) were weighed out and placed in a reactor vessel described in
(142) Scanning electron micrographs (
(143) A crystalline lithium nickel manganese cobalt oxide was obtained in the X-ray powder diffraction pattern in
(144) Coin cells were prepared as described in Example 1. The capacity of this lithium nickel cobalt manganese oxide prepared by the CPF methodology is shown in
(145) In
(146) In
(147) In
(148) In
Example 5
(149) A cathode material, LMPO.sub.4, such as LiFePO.sub.4, which is also preferably coated with carbon to promote conductivity and may be doped or not, can be made by this CPF methodology. The iron source can be selected from divalent salts of iron. The phosphate source can be H.sub.3PO.sub.4, ammonium phosphates, ammonium dihydrogen phosphates and the like. Iron is either a +2 or a +3 ion. The Fe.sup.+2 salt is preferred over the Fe.sup.+3 salt. The reactions must be done under inert atmosphere to prevent the oxidation of Fe.sup.+2to Fe.sup.+3. A reducing atmosphere can also be used to reduce the Fe.sup.+3 to Fe.sup.+2.
(150) To illustrate the preparation of LiFePO.sub.4, an iron salt soluble in aqueous solvents like water is prepared in one reactor. Such salts can be iron oxalate, iron nitrate and others. Carbon dioxide gas can be introduced in the solution. Phosphoric acid is also added to the solution. In a second reactor, a lithium salt such as lithium carbonate, lithium hydroxide and the like is dissolved in water under carbon dioxide gas. The iron phosphate solution in reactor 1 is then slowly transferred into the lithium solution in the second reactor. Ammonia solution may be introduced simultaneously as the iron solution or at the end of the transfer of the iron solution. The slurry solution is then dried using a spray dryer and the spray dried powder is calcined under inert atmosphere to obtain LiFePO.sub.4. If a dopant is added from selected metals, this dopant solution must be dissolved in any reactor. The carbon coating can be attained by adding a carbon material to obtain not more than a 10 wt. % carbon in the product. The coating may comprise alkali or alkaline earth metals, Group IIIA and IVA and transition metals or an organic or another inorganic compound.
(151) The compound M.sub.jX.sub.p prepared by the complexometric precursor formulation methodology wherein said coating comprises carbon or a carbon-containing compound
(152) Other types of phosphate compounds such as calcium phosphate may be made in a similar way to obtain a calcium phosphate nanopowder that can be used for bone implants and other medical applications as well as dental applications.
Example 6
(153) Lithium cobalt oxide was prepared using a reactor vessel as in
(154) The SEM micrographs in
(155) The X-ray powder diffraction pattern in
(156) The coin cell tests in
Example 7
(157) Example 2 was repeated. Lithium carbonate (46.6 grams) was weighed and dissolved in 1 L of deionized water under CO.sub.2 gas at ambient temperature. In another vessel with a liter of deionized water and CO.sub.2, 120.6 grams of cobalt carbonate was weighed and 250 mL of ammonium hydroxide was also added. The second mixture was transferred into the lithium solution in about one hour, spray dried (inlet temperature of 220 C.) then calcined for 5 h at 900 C.
(158) The X-ray powder diffraction pattern in
(159) Particle size of the calcined powder was done by FESEM (field emission scanning electron microscopy) in
(160) Coin cell test data is given in
Example 8
(161) The calcined product in Example 7 was fired again for another 5 h at 900 C. The X-ray powder diffraction pattern is given in
(162) The refired LiCoO2 had particle sizes similar to Example 7 which is a single fire at 5 h at 900 C. The SEM photos in
(163) A comparison of Example 8 against the refired commercial sample in Example 3 is shown in
Example 9
(164) The reactants in Example 7 can be prepared in the same manner. Another compound such as aluminum oxide or aluminum fluoride can be added to the second solution already containing cobalt as a dopant. The amount of this dopant compound depends on the preferred dopant concentration for enhanced performance but is usually less than 10% by weight of the total composition. In some cases, more than one dopant is added depending on the desired improvement in performance in the presence of the dopant. One of these is improvement in battery cycling results such as longer cycle life and higher stable capacity.
(165) Dopant starting materials are usually salts of oxides, hydroxides, carbonates favorably over the nitrates, sulfates, acetates and the like. Among those already used by other researchers are alkaline metals and transition metals such as Al, Ti, Zr, Mg, Ca, Sr, Ba, Mg, Cr, Ga, B and others but not limited to these. A general formula for doped lithium cobalt oxide would be LiCo.sub.1-pD.sub.pO.sub.2.
Example 10
(166) The CPF process can also be used to make other lithium metal oxides of formula LiMO.sub.2 such as LiMn.sub.2O.sub.4, LiNiO.sub.2, and other formulations of Example 2, as well as the doped derivatives and coated derivatives of the formula LiM.sub.1-pD.sub.pO.sub.2.
(167) The anion may also be a polyanion such as oxyfluorides and others. These formulations will be then be variants of LiM.sub.1-pD.sub.pO.sub.2-xF.sub.x and the like.
(168) Starting materials for these would be chosen from their corresponding salts, preferably oxides, carbonates, hydroxides, nitrates, acetates and others that can be dissolved preferably under mild conditions of time, temperature and pressure, rendering easily scale-up to industrial production. Another specialized cathode is a core shell lithium transition metal oxide wherein a CPF prepared coating compound forms the shell of the lithium metal oxide core in order to improve surface characteristics for better temperature stability, better structural integrity over longer cycles, and improved capacity.
(169) The invention has been described with reference to the preferred embodiments without limit thereto. One of skill in the art would realize additional embodiments and improvements which are not specifically set forth herein but which are within the scope of the invention as more specifically set forth in the claims appended hereto.