Metal digestion with anion regeneration for one-pot synthesis of CAM precursor

Abstract

An improved method of forming a lithium-ion cathode material is provided. The method comprises: dispersing elemental metal in a liquid comprising an acid wherein the acid is sub-stoichiometric relative to the elemental metal to form a dispersion; adding peroxide and a multi-carboxylic acid to the dispersion at a rate sufficient to maintain a temperature of at least 20oC to no more than 70oC to form precipitated metal salts of the multi-carboxylic acid; adding a lithium salt to the liquid; removing the liquid to form a lithium-ion cathode material precursor; and firing the lithium-ion cathode material precursor to form the lithium-ion cathode material.

Description

METAL DIGESTION WITH ANION REGENERATION FOR ONE-POT SYNTHESISOF CAM PRECURSORBACKGROUND

[0001] The present invention is related to an improved method of forming fine and ultrafine powders and nanopowders of cathode active materials (CAM) for batteries. More specifically, the present invention is related to, but not limited to, lithium-ion battery cathodes and an efficient method of preparing the CAMs with a minimal waste of material and a reduction in the number of process steps some of which are detrimental to sintering and calcining.

[0002] There is an ever-present demand for improvements in batteries. There are two primary applications for batteries with one being stationary applications and the other being mobile applications. With both stationary and mobile applications there is a desire for increased storage capacity, longer battery life, the ability to reach full charge quicker and lower cost. Lithium-ion batteries, comprising a lithium metal oxide cathode as the CAM, are highly advantageous as a suitable battery for most applications and they have found favor across the spectrum of applications. Still, there is a desire for an improvement in, particularly, the storage capability, recharge time, cost and storage stability of lithium-ion batteries.

[0003] The preparation of lithium-ion batteries comprising lithium and transition metal based cathodes in a rock-salt crystalline form are described in U.S. Pat. Nos. 9,136,534; 9,159,999 and 9,478,807 and U.S. Published Pat. Appl. Nos.2014 / 0271413; 2014 / 0272568 and 2014 / 0272580 each of which are incorporated herein by reference. Cathode materials having a rock-salt crystalline form have general formula :LiNiaMnbXcO2 wherein X is preferably Co or Al and a+b+c = 1 . When X is cobalt the cathode materials are referred to as NMC’s, for convenience, and when X is aluminum the cathode materials are referred to as NCA’s, for convenience.

[0004] Cathode materials having the spinel crystalline structure have general formula:LiNixMnyCozO4 wherein x+y+z = 2.

[0005] In a recently reported advance the CAM, either rock-salt or spinel, is formed by the digestion of metals in oxalic acid with U2CO3 in a molar excess of nitric acid to make a mixed oxalate precursor. The mixed oxalate precursor is then calcined to make the CAM. The supply chain for transition metal carbonates is not well established since the supply chain is primarily based on metal sulfates. Metal carbonates are typically made from metal sulfates.

[0006] Metal sulfates are very low in metal content, 21 wt% for nickel in nickel sulfate for example, and therefore the cost associated with the formation of metal carbonates from metal sulfates significantly mitigates the cost efficiencies associated with the oxalate process discussed above. In the formation of the metal sulfate the transition metals are extracted from the original source, often purified as metals, and then redissolved in acids. Therefore, the formation of metal carbonates, from metal sulfates, creates a Na2SO4 waste stream and the purity of the waste stream would typically be insufficient for reuse in the formation of CAMs for battery production unless additional, expensive, purification steps are utilized.

[0007] Though the waste streams related to sulfate formation have been improved, the necessity for the use of an excess of nitric acid has generated supplychain issues related to nitric acid which will be exasperated at scale. There has been a desire for an improved method of manufacturing lithium-ion cathodes, and particularly lithium / manganese / nickel based cathodes in spinel and rock salt crystalline structures, which is not encumbered by the precursor and reactant supply issues and waste stream issues common in the art. The present invention provides such a method.SUMMARY OF THE INVENTION

[0008] It is an object of this invention to provide an improved method of preparing a CAM for lithium-ion batteries.

[0009] More specifically, the present invention is related to improvements in the formation of precursors for CAM which eliminates the necessity of forming the metal sulfate, eliminating the need of converting the metal sulfate to metal carbonate thereby streamlining metal precursor production.

[0010] Even more specifically, the present invention is related to improvements in the formation of precursors for CAM which utilize sub-stoichiometric amounts of acid, specifically nitric acid, and a peroxide, preferably hydrogen peroxide, thereby simplifying the manufacturing process and reducing the amount of materials which are difficult to handle at scale.

[0011] It is an object of the invention to provide an improved method for forming metal salt precursors of a lithium metal oxide wherein the metal salt precursors are calcined to form the lithium metal oxide cathode.

[0012] It is a particular object of the invention to provide an improved method for forming lithium-ion batteries comprising a transition metal-based cathode in a spinel crystalline structure or a rock-salt structure preferably chosen from NMC and NCA.

[0013] A particular advantage of the instant invention is the ability to form high nickel CAMs wherein the precursor materials suitable for the formation of high nickel CAMs are readily available at reasonable cost and purity level.

[0014] An embodiment of the invention is provided in a method of forming a lithium-ion cathode material comprising: dispersing elemental metal in a liquid comprising an acid wherein the acid is sub- stoichiometric relative to the elemental metal to form a dispersion; adding peroxide and a multi-carboxylic acid to the dispersion at a rate sufficient to maintain a temperature of at least 20°C to no more than 70°C to form precipitated metal salts of the multi-carboxylic acid; adding a lithium salt to the liquid; removing the liquid to form a lithium-ion cathode material precursor; and firing the lithium-ion cathode material precursor to form the lithium-ion cathode material.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Fig. 1 is an XRD pattern.

[0016] Fig. 2 is a graphical representation of particle size.

[0017] Fig. 3 graphically illustrated charge and discharge and cycling performance.

[0018] Fig. 4 is an XRD pattern.

[0019] Fig. 5 is a graphical representation of particle size.

[0020] Fig. 6 graphically illustrated charge and discharge and cycling performance.

[0021] Fig. 7 is an XRD pattern.

[0022] Fig. 8 is a graphical representation of particle size.

[0023] Fig. 9 graphically illustrated charge and discharge and cycling performance.DESCRIPTION

[0024] The instant invention is specific to an improved method for preparing a lithium-ion battery, and particularly the CAM of a lithium-ion battery. More particularly, the present invention is specific to an improved process for forming cathodes for use in a lithium-ion battery wherein the cathode is in a spinel crystalline form or a rock-salt form with preferred rock salt forms being NMC and NCA materials. Even more specifically, the present invention is directed to the formation of metal salt precursors, from elemental metal, directly without the requirement for the formation of sulfates and carbonates and with a reduction in the amount of acid, particularly nitric acid, required to from the CAM.

[0025] In a preferred embodiment the CAM of the instant invention comprises a lithium metal compound in a spinel crystal structure defined by the Formula I:Li N ix M nyCoz Ew04Formula I wherein E is an optional dopant; and x+y+z+w = 2 and w < 0.2; or a rock-salt crystal structure defined by Formula II; LiNiaMnbXcGdO2 Formula II wherein G is an optional dopant;X is Co or Al; and wherein a+b+c+d = 1 and d < 0.1.

[0026] In a preferred embodiment the spinel crystal structure of Formula I has 0.4< x < 0.6; 1 .4 < y < 1 .6 and z < 0.2 . More preferably 0.5 < x < 0.55, 1 .45 < y < 1 .5 and z < 0.05. In a preferred embodiment neither x nor y is zero. In Formula I it is preferable that the Mn / Ni ratio is no more than 4, preferably at least 2.33 to no more than 3 and most preferably at least 2.6 to less than 3.

[0027] In a preferred embodiment the rock-salt crystal structure of Formula II is a high nickel NMC wherein 0.5 < a < 0.95 and more preferably 0.58 < a < 0.62 as represented by NMC622 or 0.78 < a < 0.82 as represented by NMC811 . In a preferred embodiment a=b=c as represented by NMC111 . The term NMCxxx is a shorthand notation used in the art to represent the nominal relative molar ratio of nickel, manganese and cobalt. NMC811 , for example, represents LiNio.8Mno.1Xo.1O2.

[0028] In the formulas throughout the specification, the lithium is defined stoichiometrically to balance charge with the understanding that the lithium is mobile between the anode and cathode. Therefore, at any given time the cathode may be relatively lithium rich or relatively lithium depleted. In a lithium depleted cathode the lithium will be below stoichiometric balance and when charged the lithium may be above stoichiometric balance. Likewise, in formulations listed throughout the specification the metals are represented in charge balance with the understanding that the metal may be slightly rich or slightly depleted, as determined by elemental analysis, due to the inability to formulate a perfectly balanced stoichiometry in practice. In the present application for a stoichiometric representation, such as in NMC81 1 , the stoichiometric ratio is ± 1 molar % due to manufacturing and elemental analysis variations. By way of non-limiting example, NMC81 1 or the equivalent representation LiNi0.8Mn0.1Co0.1O2, is intended to represent LiNi0.792-0.808Mn0.099-0.101C00.099-0.101O2 with the sum of the molar amounts, including any dopants, equal to 1.

[0029] Dopants can be added to enhance the properties of the oxide such as electronic conductivity and stability. The dopant is preferably a lattice site substitutional dopant added in concert with the primary nickel, manganese and optional cobalt or aluminum. The dopant preferably represents no more than 10 mole% and preferably no more than 5 mole % of the oxide. Preferred dopants include Al, Gd, Ti, Zr, Ca, Sr, Ba, Mg, Cr, Cu, Fe, Zn, V, Bi, Nb and B with Al and Gd being particularly preferred. Al would be a dopant when X is Co. Dopants and coating materials may be added to the reactor either as carbonates, oxides or metals as appropriate to make the desired composition.

[0030] The oxide precursors are formed by dispersing metal powder (M), wherein the metal is selected from nickel, manganese, cobalt or aluminum and any optional dopant, in diluted acid, preferably nitric acid, wherein the acid is substoichiometric relative to the dispersed metal powder. Substoichiometric, for the purposes of this disclosure, is defined as less than one mole of acid per mole of dispersed metal powder, preferably no more than 0.5 moles of acid per mole of dispersed metal powder and most preferably 0.1 to 0.3 moles of acid per mole of dispersed metal powder. A peroxide, preferably hydrogen peroxide, and multi-carboxylic acid, preferably oxalic acid, is then added to regenerate acid thereby forming metal oxalate, when oxalic acid is used, and nitric acid, when nitric acid is use in a reaction represented by Reaction (I):Mxs + 2x HNO3 + H2C2O4 + H2O2 — >x MC2O4 + 2x HNO3 + 2 H2O + Mxs-x (I).As would be realized, in Reaction (I) the nitric acid is not consumed and therefore the reaction rate can be controlled by the rate of addition of the oxalic acid and hydrogen peroxide as representative additives with peroxide being the rate limiting additive. The metal oxalate precipitates and the hydrogen peroxide is consumed thereby driving the reaction to stoichiometric completion relative to the metal.

[0031] The peroxide and multi-carboxylic acid can be added in alternating fashion or the peroxide and multi-carboxylic acid can be combined. Aliquots of the peroxide and multi-carboxylic acid can be added over time or the peroxide and multicarboxylic acid can be added in a continuous stream. The rate of addition is determined by temperature and the ability to dissipate heat generated from the reaction. It is preferable that the rate of addition, particularly of the peroxide, be sufficient to maintain a temperature of at least 20°C. Below about 20°C the rate of metal digestion decreases which is detrimental to efficiency and risk incomplete reaction of the metal. At temperatures above about 70°C the multicarboxylic acid, particularly oxalic acid, can have a redox reaction with peroxide resulting in reactant loss. Nitric acid can also react potentially liberating nitrous oxides. When nickel is digested the preferred temperature is 30-50°C and more preferably 30-40°C. In an embodiment, the nickel is digested first, to completion, at a temperature of 30-40°C followed by digestion of manganese and / or cobalt at 50-70°C preferably with termination of the peroxide addition and additional oxalate addition. Dopants can be added as an elemental metal during digestion or as a metal compound, such as a carbonate, after digestion.

[0032] Controlling pH is not necessary. During nickel digestion pH can be as low as about 1 .0 with a rise to at least 4.0 up to about 8.0 near the end of the synthesis.

[0033] A lithium salt is added wherein the lithium salt is preferably selected fromU2CO3 and LiOH. In a particularly preferred embodiment U2CO3 is added with the last portion of multi carboxylic acid to increase pH thereby insuring completion of the metal digestion resulting in a net reaction; assuming hydrogen peroxide, oxalic acid and lithium carbonate for simplicity, represented by Reaction (II):M + 14 U2CO3 + 1.5 H2C2O4 + H2O2 — ► MC2O4 + 14 U2C2O4 + 2.5 H2O + 14 CO2 (II).

[0034] The acid is preferably selected from nitric acid or hydrochloric acid with nitric acid being preferred. The acid is preferably added to the metal as a dilute aqueous solution of up to 5 molar and preferably no more than 1 molar acid with no more than 1 molar nitric acid being particularly preferred. Increasing the acid concentration provides some benefits, however, handling of concentrated acid solutions at manufacturing scale is undesirable and therefore dilute acid solutions are particularly preferred, especially since the acid is regenerated.

[0035] The peroxide is selected from hydrogen peroxide, organic hydroperoxide and peracid with hydrogen peroxide being preferred.

[0036] The cathode is formed from an oxide precursor comprising the aforementioned salts of Li, Ni, Mn, Co, Al and optional dopants as will be more fully described herein. The oxide precursor is calcined to form the cathode material as a lithium metal oxide.

[0037] The cathode material is optionally, and preferably, treated with a phosphate salt, DPO4, wherein D is the atoms necessary to balance the charge. D may be a monovalent atom, a divalent atom or a trivalent with the understanding that combinations may be used as desired. It is particularly preferred that D be easily removed either by washing or vaporization after application. The phosphate salt isapplied to the surface of the metal oxide wherein the phosphate moiety formsMnPO4 on the surface of the metal oxide, or is bonded to the surface of the metal oxide. The manganese is preferably predominantly in the +3 oxidation state with preferably less than 10 % of the surface manganese being in the +2 oxidation state and the manganese is thereby stabilized against reduction to Mn2+at the surface by the phosphate. The reaction liberates D which is removed by washing or vaporization. In preferred phosphates, D is selected from NH4+, H+, Li+, Na+, and combinations thereof. Particularly preferred phosphates include (NH4)sPO4, (NH4)2HPO4, (NH4)H2PO4, and H3PO4 due to the ease of removal of D after formation of the surface manganese phosphate. It is preferred that the native manganese oxide of the calcined oxide precursor be reacted with phosphate as opposed to an added manganese or other metal. Therefore, it is preferred that the added phosphate be relatively free of Mn and more preferably less than 1 wt% manganese impurity. It is preferable that no Mn+2be added with the phosphate or after formation of the oxide. It is preferable that there be no separate manganese phosphate phase such as manganese phosphate as a distinct phase on the surface. It is preferable that the phosphate ligate to the surface of the metal oxide.

[0038] The reaction is preferably stirred or agitated to ensure continued reaction. Alternatively, the reaction may be accomplished in a horizontal bead-mill to increase the reaction rate.

[0039] The time of addition of lithium, preferably in the form of Li2COs, is not particularly critical. If Li2COs is added early in the process lithium salts, such as lithium oxalate, are formed by digestion of the carbonate and the lithium salt remains. Alternatively, the Li2COs can be added after the transition metal reaction is complete, or near complete, which is preferable.

[0040] The reaction time is dependent on temperature and agitation, however, the reaction is allowed to continue until completion which is indicated by a colour change in the slurry or in the stabilization of the slurry pH. Following this step, the slurry must be dried, such as by spray drying or drum drying, followed by calcining as usual in air and / or O2 depending upon the final formulation of the CAM.

[0041] In a preferred embodiment, the metal powder is mixed in the intended ratios of the ultimate CAM. By way of non-limiting example, if LiNi0.8Mn0.1Co0.1O2 is to be prepared the metal powder would have 8 molar parts Ni, 1 molar part Mn and 1 molar part Co with one molar part Li added prior to calcining. The elemental metal feedstock particle size may be adjusted so that the elemental metals react at similar rate. By way of non-limiting example, the particle size may be inversely related to the reaction rate such that the surface area increase mitigates the difference in reaction rate. Since the reaction rate follows the general relationship Co>Mn>Ni, in commonly measured chemistry, it may be advantageous to utilize particle size differences to adjust reaction rates.

[0042] Sulfur concentration, as an impurity, is particularly important for nickel wherein higher sulfur concentrations increase the reaction rate. It would be understood to those in the art that sulfur is undesirable for electrical performance and therefore sulfur is typically to be avoided, or below detectable limits. However, a small level of impurity may be acceptable to balance the reaction rate with electrical performance. A sulfur impurity of no more than 0.05 wt%, relative to nickel metal, can be effective at sufficiently increasing the reaction rate with the carbonate without significant decrease in electrical performance.

[0043] Divalent metal oxalates such as NiC2O4, MnC2O4, COC2O4, ZnC2O4, etc. are highly insoluble, however monovalent metal oxalates such as U2C2O4 aresomewhat soluble with a solubility of about 8g / 100mL at 25°C in water. If it is necessary to have the lithium oxalate in solution and homogeneously dispersed throughout a mixed metal oxalate precipitate, then keeping the water volume above the solubility limit of lithium oxalate may be desirable.

[0044] Multi-carboxylic acids comprise at least two carboxyl groups. A particularly preferred multi-carboxylic acid is oxalic acid due, in part, to the minimization of carbon which must be removed during calcining. Other low molecular weight di-carboxylic acids can be used such as malonic acid, succinic acid, glutaric acid and adipic acid. Higher molecular weight di-carboxylic acids can be use, particularly with an even number of carbons which have a higher solubility, however the necessity of removing additional carbons and decreased solubility renders them less desirable. Other acids such as citric, oxaloacetic, fumaric, maleic and other polycarboxylic acids can be utilized with the proviso they have sufficient solubility to achieve at least a small stoichiometric excess and have sufficient chelating properties. It is preferable that acids with hydroxyl groups not be used due to their increased hygroscopic characteristics.

[0045] The dried powders may be transferred into the calcining system batch- wise or by continuous flow such as by a conveyor belt or similar transfer mechanisms. In large scale production, this transfer may be continuous or batch. The calcining 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 countercurrent, a rotary tube furnace and other similar equipment without limit thereto.

[0046] The heating rate and cooling rate during calcinations depend on the type of final product desired. Generally, a heating rate of about 5°C per minute is preferred but the usual industrial heating rates are also applicable.

[0047] The final powder obtained is consistent with teachings in the art. A particular advantage is that the powder may not require additional crushing, grinding or milling as is currently done in conventional processing. Particles are relatively soft and not sintered as in conventional processing.

[0048] The final calcined oxide powder is an agglomerate of crystallites which are 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.

[0049]

[0050] 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. A rotary calciner or fluidized bed calciner can be used to demonstrate the invention. 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 sieved as these are soft and not sintered. The calcined oxide does not require long milling times nor classifying to obtain narrow particle size distribution.

[0051] The calcined powder comprises primary particles which agglomerate to form secondary particles. Primary particles typically have an average particle size of 100 nm to 5 pm with materials of Formula I typically having an average primary particle size of 1-5 pm and materials of Formula II typically having an average primary particle size of 100nm - 1 pm. The secondary particles typically have an average particle size of 10-30 pm.

[0052] A particular advantage of the present invention is the formation of metal chelates of multi-carboxylic acids as opposed to acetates. Acetates function as a combustion fuel during subsequent calcining of the oxide precursor and additional oxygen is required for adequate combustion. Lower molecular weight multicarboxylic acids, particularly lower molecular weight dicarboxylic acids, and more particularly oxalic acid, decompose at lower temperatures without the introduction of additional oxygen. The oxalates, for example, decompose at about 300°C, without additional oxygen, thereby allowing for more accurate control of the calcining temperature. This may allow for reduced firing temperatures thereby facilitating the formation of disordered Fd3m spinel crystalline structures with minimal impurity phase occurring as seen at high temperature

[0053] The current invention provides significant manufacturing flexibility. The metal digestion steps can be done separately, in smaller portions, followed by mixing. For example, one can digest 10% of all metals with the corresponding reagents and then precipitate them to form the precursors, followed by repetition until the digestion is completed. Transmission electron microscopy (TEM) images and corresponding energy dispersive X-ray (EDX) mappings of precursors prepared by the prior art techniques utilizing nitric acid at above stoichiometric amounts and the inventive process demonstrates a significant improvement in transition metal homogeneity in the sample prepared by the inventive process.

[0054]

[0055] The process is easily scalable for large scale manufacturing using presently available equipment and / or innovations of the present industrial equipment. EXAMPLESRepresentative Electrode preparations:

[0056] Composite electrodes would be prepared by mixing the active material with 10 wt% conductive carbon black, as a conductive additive, 5 wt% polyvinylidene fluoride (PVDF), as a binder, dissolved in N-methyl-2-pyrrolidinone (NMP) solvent. The slurry would be cast on graphite-coated aluminum foil and dried overnight at 60 °C under vacuum. Electrode disks with an area of 1 .54 cm2would be cut form the electrode sheets with a typical loading of 4 mg. cm-2.Representative Coin cell assembly:

[0057] Coin cells would be assembled in an argon-fi lied glovebox. Lithium foil (340 pm) would be used as counter and reference electrodes in half-cells, and commercial Li4TisOi2 (LTO) composite electrodes would be used as counter and reference electrodes in full-cells. 1 M LiPFe in 7:3 (vol%) ethylene carbonate (EC):diethylene carbonate (DEC) would be used as the electrolyte. The electrodes would be separated by one or two 25pm thick sheets of Celgard® membranes in half-cells, and one sheet of Celgard membrane full-cells.Representative Cycling protocol:

[0058] The spinel cathode cells would be galvanostatically cycled in the voltage range of 3.5 V - 4.9 V at various C-rates (1C rate equivalent to 146 mAg'1) at 25 °C, using an Arbin Instrument battery tester (model number BT 2000). A constant voltage charging step at 4.9 V for 10 minutes would be applied to the cells at the end of 1 C or higher rate galvanostatic charging steps. The rock-salt NMC cells would be galvanostatically cycled in the voltage range of 2.7 V - 4.35 V at various C-rates (1C rate equivalent to 200 mAg'1) at 25 °C. A constant voltage charging step at 4.35 V for 10 minutes would be applied to the cells at the end of 1C or higher rate galvanostatic charging step.EXAMPLE 1 : Synthesis of Spinel LiNio sMni

[0059] LNMO was made on a 200 g scale. Figs. 1 a and 1 b are X-Ray diffraction(XRD) patterns of the precursor and fire samples, respectively, prepared using the inventive method. There is no significant difference when compared to the control LNMO samples. The XRD confirms formation of the desirable crystal phase and elimination of most impurities. SEM images of the fired LNMO samples show that the primary particles adapt octahedral morphology with sizes ranging from 1 to 4 pm. Particle size distribution of the precursor and samples are provided in Fig. 2a and 2b, respectively. The D50 was 14.08pm for the precursor and 18.40 pm for the fired samples. Inductively Coupled Plasma Mass Spectroscopy (ICP) results confirmed that the samples reached the targeted Li / Ni / Mn ratio, ensuring that elemental ratio of the products are not affected by the inventive process and the ratio can be solely controlled through adjusting the stoichiometry of the reactants.

[0060] Fig. 3A is the charge discharge curve of the sample of EXAMPLE 1 at the 20thcycle of operation, delivering a discharge capacity of 136 mAhg-1with three characteristics plateaus of LNMO, which includes the Ni2+ / Ni3+redox at 4.75V, Ni3+ / Ni4+redox at 4.65V and the Mn3+ / Mn4+redox at around 4V. This electrochemical behavior matches well with the reference LNMO sample, confirming the proper synthesis of the product. Fig. 3B is the cycling performance of the LNMO samples at a current of 1 C demonstrating that the samples maintain the capacity of around 135 mAhg'1for 100 cycles of charge / discharge, which is ~8% shy from the theoretical maximum of 147mAhg'1. The capacity retention for this LNMO sample is 99.5% after 100 cycles of charge and discharge.EXAMPLE 2: Synthesis of LNMO using HCI

[0061] In the same scale as EXAMPLE 1 , the LNMO synthesis was also conducted using HCI as the digestion acid. No changes were made with the Nidigestion, but addition time for the Mn portion of oxalic acid was lowered to 15 mins and the Mn digestion was completed in 4 hours with heating at 80°C. No additional HCI was added for Mn digestion, resulting in a final transition metal to HCI ratio of 1 to 0.05. The SEM images of the fired product, show that the particles adapt the same octahedral morphology as EXAMPLE 1 . The XRD pattern of HCI precursor resembles ones synthesized using HNOs with small variations in peak intensity, while the XRD pattern for the fired products provided in Fig. 4 are almost identical to EXAMPLE 1 . The particle size distribution has a D50 of 14.16 pm and the fired sample has a D50 of 26.49 pm.

[0062] The discharge capacity was 135 mAhg-1with the three intrinsic discharge plateaus Of the N i2+ / N i3+, N i3+ / N i4+and the Mn3+ / Mn4+redox as illustrated in Fig. 5. There are no apparent differences compared to EXAMPLE 1 . Upon operating to the 100thcycle, the samples achieved an average capacity retention of 99.1 % as illustrated in Fig. 6.EXAMPLE 3: Synthesis of NMC811

[0063] NMC81 1 was prepared at a 1 kg scale. Compared to example 1 LNMO synthetic process, there is no major difference except for the different transition metal ratio. The Co was reacted in a similar manner as Mn and the final transition metal to HNOs ratio was around 1 to 0.184. The SEM images of the fired NMC sample demonstrate that the primary particles have a size range of 0.5 to 2 pm with sphere-like morphology. XRD patterns of the sample reveal peaks commonly associated with typical NMC cathode, as illustrated in Fig. 7, confirming proper formation of the crystal phases. PSD of the NMC precursor and samples are shown in Fig. 8, the precursor has a D50 of 30.64 pm and the fired sample has a D50 of12.05 pm.

[0064] As for the electrochemical performance, the NMC samples reached an average capacity of -211 mAhg-1at 1 / 10C and -194 mAhg-1at 1C as shown in Fig.9. The material exhibits a sloping discharge curve between 4.3 to 3.5 V associated to the redox of Ni2+ / Ni4+, Co3+ / Co4+and Mn3+ / Mn4+. Their capacity retention at 1C is 92.8% at the 50thcycle and 88.0% at the 100thcycle.

[0065] 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.

Claims

Claimed is:1 . A method of forming a lithium-ion cathode material comprising: dispersing elemental metal in a liquid comprising an acid wherein said acid is sub-stoichiometric relative to said elemental metal to form a dispersion; adding peroxide and a multi-carboxylic acid to said dispersion at a rate sufficient to maintain a temperature of at least 20°C to no more than 70°C to form precipitated metal salts of said multi-carboxylic acid; adding a lithium salt to said liquid; removing said liquid to form a lithium-ion cathode material precursor; and firing said lithium-ion cathode material precursor to form said lithium-ion cathode material.

2. The method of forming a lithium-ion cathode material of claim 1 wherein said liquid comprises less than 1 mole of said acid per mole of said metal.

3. The method of forming a lithium-ion cathode material of claim 2 wherein said liquid comprises less than 0.5 mole of said acid per mole of said metal.

4. The method of forming a lithium-ion cathode material of claim 3 wherein said liquid comprises at least 0.1 mole of said acid per mole of said metal to 0.3 moles of said acid per mole of said metal.

5. The method of forming a lithium-ion cathode material of claim 1 wherein said acid is selected from nitric acid and hydrochloric acid.

6. The method of forming a lithium-ion cathode material of claim 5 wherein said acid is nitric acid.

7. The method of forming a lithium-ion cathode material of claim 1 wherein said acid is in said liquid at a concentration of no more than 1 molar.

8. The method of forming a lithium-ion cathode material of claim 1 wherein said peroxide is selected from the group consisting of hydrogen peroxide, organic hydroperoxide and peracid.

9. The method of forming a lithium-ion cathode material of claim 8 wherein said peroxide is hydrogen peroxide.

10. The method of forming a lithium-ion cathode material of claim 1 wherein said peroxide and said multi-carboxylic acid are added separately or in combination.11 . The method of forming a lithium-ion cathode material of claim 1 further comprising the addition of U2CO3 to said liquid.

12. The method of forming a lithium-ion cathode material of claim 11 wherein said U2CO3 is added after said adding of peroxide and said multi-carboxylic acid have begun.

13. The method of forming a lithium-ion cathode material of claim 11 wherein said U2CO3 is added after said adding of peroxide and said multi-carboxylic acid is complete.

14. The method of forming a lithium-ion cathode material of claim 1 comprising dispersing nickel metal and maintaining a temperature of 30-50°C.

15. The method of forming a lithium-ion cathode material of claim 14 comprising dispersing at least one of manganese metal or cobalt metal after said dispersing of said nickel metal and maintaining a temperature of 50-70°C.

16. The method of forming a lithium-ion cathode material of claim 1 comprising adding a phosphate after said firing.

17. The method of forming a lithium-ion cathode material of claim 16 wherein said phosphate is selected from the group consisting of (NH4)3PO4, (NH4)2HPO4, (NH4)H2PO4, and H3PO4.

18. The method of forming a lithium-ion cathode material of claim 16 wherein said phosphate wherein said phosphate comprises less than 1 wt% manganese impurity.

19. The method of forming a lithium-ion cathode material of claim 1 wherein said elemental metal comprises at least two metals selected from the group consisting of Mn, Ni, Co and Al.

20. The method of forming a lithium-ion cathode material of claim 19 wherein said elemental metal comprises at least two metals selected from the group consisting of Mn, NI and Co.21 . The method of forming a lithium-ion cathode material of claim 1 wherein said multi-carboxylic acid is selected from the group consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, citric acid, oxaloacetic acid, fumaric acid and maleic acid.

22. The method of forming a lithium-ion cathode material of claim 21 wherein said multi-carboxylic acid is oxalic acid.

23. The method of forming a lithium-ion cathode material of claim 1 wherein said lithium-ion cathode material is defined by the Formula I:LiNixMnyCozEeO4Formula I wherein E is a dopant; x+y+z+e = 2; and0 < e < 0.

224. The method of forming a lithium-ion cathode material of claim 23 wherein said Formula I is in a spinel crystalline form.

25. The method of forming a lithium-ion cathode material of claim 24 wherein said spinel crystalline form has a crystallite size of 1-5pm.

26. The method of forming a lithium-ion cathode material of claim 23 wherein neither x nor y are zero.

27. The method of forming a lithium-ion cathode material of claim 26 wherein said lithium-ion cathode material is LiNio.5Mn1.5O4.

28. The method of forming a lithium-ion cathode material of claim 23 wherein said lithium-ion cathode material is defined by the formula LiNixMnyO4 wherein 0.4 < x < 0.6 and 1.4 < y < 1.6.

29. The method of forming a lithium-ion cathode material of claim 28 wherein said 0.5 < x < 0.55 and 1 .45 < y < 1 .5.

30. The method of forming a lithium-ion cathode material of claim 23 wherein said lithium-ion cathode material has a molar ratio of Mn to Ni of no more than 4.31 . The method of forming a lithium-ion cathode material of claim 30 wherein said lithium-ion cathode material has a molar ratio of Mn to Ni of at least 2.33 to no more than 3.

32. The method of forming a lithium-ion cathode material of claim 31 wherein said lithium-ion cathode material has a molar ratio of Mn to Ni of at least 2.64 to less than 3.

33. The method of forming a lithium-ion cathode material of claim 23 wherein said dopant is selected from the group consisting of Al, Gd, Ti, Zr, Mg, Ca, Sr, Ba,Cr Fe, Cu, Zn, V, Bi, Nb and B.

34. The method of forming a lithium-ion cathode material of claim 33 wherein said dopant is selected from the group consisting of Al and Gd.

35. The method of forming a lithium-ion cathode material of claim 1 wherein said lithium-ion cathode material is defined by the Formula II:LiNiaMnbXcGdO2Formula II wherein G is a dopant;X is Co or Al; wherein a+b+c+d = 1 ; and0 < d < 0.1.

36. The method of forming a lithium-ion cathode material of claim 35 wherein 0.5< a < 0.95.

37. The method of forming a lithium-ion cathode material of claim 36 wherein 0.58< a < 0.62 or 0.78 < a < 0.82.

38. The method of forming a lithium-ion cathode material of claim 35 wherein a=b=c.

39. The method of forming a lithium-ion cathode material of claim 35 wherein said lithium-ion cathode material has a crystallite size of 50-250 nm.

40. The method of forming a lithium-ion cathode material of claim 39 wherein said lithium-ion cathode material has a crystallite size of 150-200 nm.41 . The method of forming a lithium-ion cathode material of claim 1 wherein said lithium salt is lithium carbonate.

42. The method of forming a lithium-ion cathode material of claim 1 wherein said heating is in air.

43. A battery comprising the lithium metal oxide made of the method of claim 1.

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