Melt process involving direct use of metal sulfate precursors to prepare lithium metal phosphate cathode materials

Abstract

A melting process for preparing lithium metal phosphate (LMP) cathode material is provided, wherein M is at least one transition metal. The metal sulfate precursor is used directly without significant conversion after its extraction from ore materials or recycling from electrode materials of spent lithium batteries. The invention also relates to LMP cathode materials obtained by such processes, batteries having cathodes comprising such materials, and cathode or battery manufacturing plants embodying such processes.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 479,271, filed January 10, 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] The present invention generally relates to a melting process using metal sulfate precursors for preparing lithium metal phosphate (LMP) cathode materials. More specifically, the present invention relates to a melting process in which the metal sulfate precursor is used directly without significant transformation after its extraction from ore materials or recycling from electrode materials of spent lithium batteries. Furthermore, the present invention relates to LMP cathode materials obtained by such processes, batteries having cathodes comprising such materials, and cathode or battery manufacturing plants embodying such processes. [Background technology]

[0003] General LiFe where x varies from 0 to 1 x Mn 1-x Olivine-structured lithium metal phosphate (LMP) cathodes of PO4 composition, particularly lithium iron phosphate (LFP) and lithium iron manganese phosphate (LFMP), are becoming the cathodes of choice for most lithium battery technologies. Selection is based on their performance, long cycle life, stability, non-toxicity, and, more importantly, their potential for cost reduction.

[0004] In contrast to the cobalt and nickel currently used in alternative lithium metal oxide cathodes, the availability and cost of iron (and phosphorous acid) leaves lithium as the primary material cost driver for phosphate-based cathodes. For cathode synthesis, lithium is most often introduced as lithium hydroxide (LiOH) or lithium carbonate (Li2CO3), which constitute standard lithium chemistries obtained from brine or spodumene ore conversion. Reactions for cathode material synthesis are typically reactant-specific and optimized for one of these two chemistries. For example, most currently commercially available LFPs are made by the solid-state thermal reaction between Li2CO3 and FePO4, as disclosed, for example, in WO 02 / 27823 A1 and WO 02 / 27824, while most lithium nickel manganese cobalt oxide (NMC) cathodes use a LiOH precursor.

[0005] With respect to currently used lithium precursors such as Li2CO3, the metal-based precursor currently used to make LFP, FePO4, is obtained from FeSO4, which is oxidized with HO and treated with sodium phosphate salts to form FePO4 together with waste salts, e.g., Na2SO4.

[0006] The discovery of melt processing as an efficient and rapid method of making LFPs and LFMPs (WO2005 / 062404A1, WO2013 / 177671A1, and WO2015 / 179972A1) has resulted in several cost improvements by allowing the use of iron oxide, iron metal, and even concentrated iron minerals instead of more converted iron precursors such as FePO4 or FeCO4.

[0007] Typically, lithium precursors used in the lithium battery industry are derived from ore materials or recycled cathode and anode materials. Lithium sulfate is often an intermediate species that generates the desired Li2CO3 and LiOH precursors. Similarly, iron sulfate from ilmenite mineral processing is a starting intermediate for making FePO4. Some challenges facing the industry relate to the requirement to significantly reduce or eliminate the conversion steps associated with these precursors. This requirement is necessary to minimize environmental impact and reduce costs.

[0008] There is a need for improved melt processes for preparing lithium metal phosphate cathode materials, particularly those in which the precursors used undergo minimal conversion, resulting in a cost-effective and environmentally friendly process. Summary of the Invention

[0009] The present inventors have developed and implemented a melting process for preparing lithium metal phosphate (LMP) cathode materials, which involves the use of metal sulfate precursors, which are used directly without significant transformation after their extraction from ore materials or recycling from electrode materials of used lithium batteries. Such metal sulfate precursors are, for example, LiSO, FeSO, or MnSO. The cost and environmental benefits of the process according to the invention result from improving the mineral supply chain.

[0010] In an embodiment of the present invention, a mixture of two or three metal sulfate precursors is used.

[0011] In an embodiment of the present invention, a mixture of Li2SO4 precursor and one of FeSO4 and MnSO4 is used.

[0012] In embodiments of the present invention, hydrated forms of metal sulfate precursors are used.

[0013] In embodiments of the present invention involving the use of a LiSO precursor, the precursor is in the form of a mixture comprising LiSO and LiPO, which is obtained after subjecting lithium sulfate to a precipitation process.

[0014] Embodiments of the invention involving the use of a Li2SO4 precursor are substantially free of Li2CO3 or LiOH.

[0015] In embodiments of the invention involving the use of a Li2SO4 precursor, the hydrated form is of the general formula Li2SO4·xH2O, where x varies from about 0 to about 30, or from about 1 to about 5, or from about 0 to about 3, or x is 1, or x is 2.

[0016] In an embodiment of the present invention, at least one other source of metal is used. For iron, at least one source is Fe 0 The iron source may be FeO, Fe2O3, Fe3O4, ferrous phosphate, ferric phosphate, or a mixture thereof containing iron oxide-enriched minerals. The iron source is adjusted to fix the iron's oxidation state at +2.

[0017] In an embodiment of the present invention, for the preparation of LFMP, other sources of Mn include Mn 0 , MnO, Mn2O3, MnO2, MnCO3, or mixtures thereof.

[0018] In embodiments of the present invention, the phosphorus or phosphate source (source of P or PO) may be PO, HPO, (NH)HPO (ammonium dihydrogen phosphate; MAP), (NH)HPO (diammonium phosphate; DAP), and mineral apatites such as Ca(PO)(OH). The source of PO is preferably selected to avoid or significantly reduce emissions of SO or SO gases.

[0019] In an embodiment of the present invention, a metal sulfate precursor is added to the melt simultaneously with a source of PO4.

[0020] In an embodiment of the present invention, a metal sulfate precursor is subjected to an incipient melting process, thereby obtaining an incipient molten reactive pool, into which a source of PO4 is added.

[0021] In accordance with an embodiment of the present invention, there is provided an LMP or LiMPO cathode material that is LFP or LiFePO. There is also provided an LMP cathode material that is LiMnPO. The LMP or LFP cathode material is obtained by the melting process according to the present invention and has a sulfur content of 0.1% or less as measured by LECO sulfur analysis.

[0022] In the embodiment of the present invention, LFMP or LiFe x Mn 1-x A PO4 cathode material is provided. The LFMP cathode material is obtained by the melting process according to the present invention and has a sulfur content of 0.1% or less as determined by LECO sulfur analysis.

[0023] In an embodiment of the present invention, a battery is provided having a cathode comprising an LMP, LFP, or LFMP material obtained by a melt process according to the present invention.

[0024] In an embodiment of the present invention, a cathode or battery manufacturing plant is provided that embodies the melting process according to the present invention.

[0025] Thus, according to its aspects, the present invention provides: (1) A melt process for preparing lithium metal phosphate (LMP) cathode material, wherein M is at least one transition metal, the process comprising the use of a metal sulfate precursor that is LiSO, FeSO, MnSO, ​​or a hydrated form thereof, or a mixture thereof; A melt process in which the metal sulfate precursor is used directly without significant transformation. (2) The melting process according to (1) above, wherein the metal sulfate precursor is obtained after its extraction from an ore material or recycling from an electrode material of a used lithium battery, and optionally the metal sulfate precursor is obtained as a product of a chemical process. (3) The melting process according to (1) or (2) above, wherein the LMP cathode material is of olivine structure, and optionally the LMP is lithium iron phosphate (LFP) or lithium manganese iron phosphate (LFMP). (4) The melting process according to any one of (1) to (3) above, wherein the ore material is spodumene. (5) A melting process according to any one of (1) to (4) above, wherein the metal sulfate precursor is a mixture of Li2SO4 and one of FeSO4 and MnSO4. (6) The melting process according to any one of (1) to (4) above, wherein the metal sulfate precursor is a mixture of Li2SO4, FeSO4, and MnSO4. (7) The melting process according to any one of (1) to (6) above, wherein the Li2SO4 precursor is used as a mixture comprising Li2SO4 and Li3PO4, and optionally the mixture is obtained after subjecting Li2SO4 to a precipitation process. (8) The melting process according to any one of (1) to (7) above, wherein the Li2SO4 precursor is substantially free of Li2CO3 or LiOH. (9) The melt process according to any one of (1) to (8) above, wherein the hydrated form is of a Li2SO4 precursor of general formula Li2SO4·xH2O, where x varies from about 0 to about 30, or from about 1 to about 5, or from about 0 to about 3, or x is 1, or x is 2. (10) A melting process according to any one of (1) to (9) above, wherein at least one other source of metal is used. (11) At least one other source of Fe is used, preferably the at least one other source of Fe is Fe 0, FeO, Fe2O3, Fe3O4, ferric phosphate, or a mixture thereof containing iron oxide-enriched minerals, preferably the source of Fe is adjusted to fix the oxidation state of Fe at +2. (12) At least one other source of Mn is used, preferably the at least one other source of Mn is Mn 0 , MnO, Mn2O3, MnO2, MnCO3, or a mixture thereof. (13) The melting process according to any one of the above (1) to (12), wherein at least one source of phosphorus or phosphate (source of P or PO) is used, preferably the source of P or PO is P2O5, HPO3, (NH4)H2PO4 (ammonium dihydrogen phosphate; MAP), (NH4)2HPO4 (diammonium phosphate; DAP), or a mineral apatite such as Ca5(PO4)3(OH), and preferably the source of PO is suitably selected to avoid or significantly reduce any emissions of SO2 and / or SO3 gases. (14) A melting process according to any one of (1) to (13) above, wherein a metal sulfate precursor is added to the melt simultaneously with a source of PO4. (15) The melting process according to any one of (1) to (12) above, wherein at least one source of phosphorus or phosphate (source of P or PO) is used, which is (NH)HPO (ammonium dihydrogen phosphate; MAP) or (NH)HPO (diammonium phosphate; DAP), and (NH)SO is formed as a by-product, preferably MAP and DAP are used simultaneously with the metal sulfate precursor, and preferably SO and / or SO gas emissions are eliminated or significantly reduced. (16) The melting process according to (13) above, wherein the metal sulfate precursor is subjected to an initial melting process, thereby obtaining an initial melt reactive pool, into which a source of PO4 is added. (17) The melting process according to (2) above, wherein the ore material or electrode material of a used lithium battery is subjected to a treatment including heat treatment and / or acid leaching and / or crystallization to obtain a metal sulfate precursor. (18) The process of any one of (1) to (17) above, wherein the melt temperature is about 850°C to about 1300°C, and the reaction melt is maintained at substantially the same temperature, preferably under an inert or reducing atmosphere, preferably the inert or reducing atmosphere comprises CO, CO, H, HO, Ar, N, CH, and natural gas, preferably in proportions suitable to stabilize the cathode composition in the melt and as it is cast and solidified, and preferably under stirring. (19) The melting process according to (16) above, wherein the reactive melt is further consolidated to obtain a solid crystalline form of LMP upon casting and solidification, optionally the solid crystalline LMP is reduced to a powder, and optionally the powdered solid crystalline LMP is coated with carbon to form an electrochemically active cathode material, preferably the carbon coating process uses a carbon precursor. (20) A metal sulfate precursor for direct use in a melt process for the preparation of lithium metal phosphate (LMP) cathode materials, wherein M is at least one transition metal; 1. A metal sulfate precursor comprising LiSO4, FeSO4, MnSO4, or a hydrated form thereof, or a mixture thereof, wherein the metal sulfate precursor is suitable for direct use without significant transformation, optionally wherein the metal sulfate precursor is obtained after its extraction from an ore material or recycling from an electrode material of a used lithium battery, optionally wherein the metal sulfate precursor is obtained as the product of a chemical process. (21) An LMP, LFP, or LFMP cathode material made by a melt process as defined in any one of (1) to (19) above, wherein the LMP, LFP, or LFMP cathode material contains about 0.1% or less sulfur as measured by LECO sulfur analysis. (22) A cathode comprising a material produced by the melting process defined in any one of (1) to (19) above. (23) A battery having a cathode comprising a material made by the melting process defined in any one of (1) to (19) above. (24) A cathode or battery manufacturing plant embodying the melting process defined in any one of (1) to (19) above. (25) Use of a metal sulfate precursor in a melt process for preparing a lithium metal phosphate (LMP) cathode material, wherein M is at least one transition metal, and the metal sulfate precursor is LiSO, FeSO, MnSO, ​​or a hydrated form thereof, or a mixture thereof, wherein the metal sulfate precursor is used directly without significant conversion, optionally the metal sulfate precursor is obtained after its extraction from an ore material or recycling from an electrode material of a used lithium battery, and optionally the metal sulfate precursor is obtained as a product of a chemical process.

[0026] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-limiting description of specific embodiments, given by way of example only with reference to the accompanying drawings.

[0027] This patent or application contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0028] In the accompanying drawings: [Brief explanation of the drawings]

[0029] [Figure 1a] 1 is an XRD pattern on the product of Example 1. [Figure 1b] 1 is a TGA curve of the reaction of Example 1. [Figure 1c] The corresponding MS results coupled with TGA are [Figure 1d]The charge / discharge capacity of the product of Example 1 [Figure 2a] 1 is an XRD pattern of the product of Example 2a. [Figure 2b] 1 is an XRD pattern of the Li precursor of Example 2b. [Figure 3a] 1 is an XRD pattern of the product of Example 4. [Figure 3b] 1 is an XRD pattern of the by-product of Example 4. [Figure 4a] XRD spectrum confirming the apatite Ca10(PO4)6(OH)2 structure. [Figure 4b] 1 is an XRD spectrum showing the formation of Li3PO4 and CaSO4 [Figure 5a] 1 is an XRD pattern of the product of Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0030] Before further describing the present invention, it is to be understood that the present invention is not limited to the specific embodiments described below, and that variations of these embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology used is for the purpose of describing particular embodiments, and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.

[0031] In order to provide a clear and consistent understanding of the terminology used herein, certain definitions are provided below. Furthermore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0032] The words "a" or "an," when used in conjunction with the word "comprising" in the claims and / or specification, may mean "one," but may also be used consistently with the meanings of "one or more," "at least one," and "one or more than one." Similarly, the word "another" may mean at least a second, or more.

[0033] As used in this specification and claim(s), the words "comprising" (and any form of including, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes"), or "containing" (and any form of containing, such as "contain" and "contains") are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0034] As used herein, the term "metal sulfate precursor" refers to compounds such as Li2SO4, FeSO4, or MnSO4 used in the preparation of lithium metal phosphate (LMP) cathode materials. The term also refers to hydrated forms of such compounds. Furthermore, the term refers to mixtures of two or more such compounds and / or hydrated forms thereof. In particular, the term "lithium sulfate precursor" refers to the compound Li2SO4 in its hydrated form, or a mixture of Li2SO4 with one or more other metal sulfate precursors and / or hydrated forms thereof. Additionally, the term "lithium sulfate precursor" refers to a mixture of Li2SO4 and Li3PO4.

[0035] As used herein, the term "direct use" in reference to the introduction of a metal sulfate precursor into a melt refers to the use of the metal sulfate without prior conversion to other reactants. For example, direct introduction of a LiSO precursor refers to use without prior conversion to LiCO or LiOH, as currently known in the art. In other embodiments of the present invention, the metal sulfate precursor can be subjected to an initial melting process before use as a molten reaction pool. For example, LiSO can be partially precipitated as LiPO prior to use, thus using a mixture of LiSO and LiPO. In embodiments of the present invention, the metal sulfate precursor is subjected to known purification techniques, such as crystallization and filtration. It should be noted that such partial precipitation, initial melting process, and purification techniques are not considered significant conversion. The term "direct introduction" or variations thereof are also used and refer to the same thing. Therefore, the terms "direct use" and "direct introduction" are used interchangeably herein.

[0036] The present inventors have designed, developed, and implemented a melting process involving the use of metal sulfate precursors to prepare lithium metal phosphate (LMP) cathode materials. The metal sulfate precursors are used directly without significant transformation after their extraction from ore materials or recycling from electrode materials of used lithium batteries. The metal sulfate precursors may also be the product of chemical processes. The metal sulfate precursors are, for example, Li2SO4, FeSO4, or MnSO4.

[0037] In the present invention, the versatility of the melting process for reactant selection benefits in order to further optimize the lithium cost contribution by using other lithium chemical intermediates, e.g., Li2SO4, that exist or may be formed in the initial steps of lithium salt extraction of minerals, or that come from other chemical sources such as recycled or are by-products of other chemical processes.

[0038] To illustrate the concerns of the present invention, of particular relevance are lithium salts, e.g., Li2SO4, obtained by extraction from the spodumene mineral LiAlSi2O6 or from recycling spent cathodes from used batteries, which can be used as is or at least partially precipitated as Li3PO4.

[0039] In most industrial processes for converting spodumene to Li2CO3 or LiOH, the initial steps include at least mineral grinding, heat treatment to β-spodumene, extraction with H2SO4 to form Li2SO4, addition of Na2CO3 to form Li2CO3 (optionally adding Ca(OH)2 to further form LiOH), followed by crystallization and a final grinding step. The processing of spodumene to form Li2SO4 is described, for example, in China Geology, Volume 6, Issue 1, January 2023, Pages 137-153. The processing of spent battery materials to form Li2SO4 is described, for example, in Ionics (2019) 25:5643-5653 and Materials 2020, 13, 801; doi:10.3390 / ma13030801. The typical reactions involved can be summarized as follows: For oxides: LiMO2(M=Ni, Co, Mn):2LiMO2+3H2SO4=>Li2SO4+2MSO4+3H2O+1 / 2 O2 For LFP: 2LiFePO4+H2SO4+H2O2→2FePO4+Li2SO4+2H2O.

[0040] Some intermediate purification steps may be added to meet the stringent requirements of most cathode battery material synthesis processes. In the present invention, the Li2SO4 intermediate can be used directly in the melt process of the present invention, optionally after simple recrystallization, or after partial precipitation as Li3PO4 with some residual Li2SO4, and both reactants are compatible with the melt process. Such a mixture makes it relatively easy to obtain and avoid further separation steps between Li2SO4 and Li3PO4.

[0041] The direct use of lithium precursors such as Li2SO4 without conversion to Li2CO3 or LiOH has not been used in the reactant-specific solid-state processes currently applied by the industry, despite the cost advantages of the lithium sulfate intermediates currently produced to obtain lithium carbonate or hydroxide. Its direct use in the melt process of the present invention, while possible in principle, was not obvious and was not put into practice considering either the multiple reaction pathways possible at the melt temperature, the selected reducing atmosphere, and the possible formation of mixed phosphate-sulfate compositions such as Li3Fe(SO4)(PO4), all of which are inhibiting factors for sulfate-based precursors, considering the stability of sulfate salts. No feasibility study has been presented, nor have methods for the complete conversion of Li2SO4 or Li2SO4·xH2O to LMPs in melt synthesis been known or described in the art.

[0042] Using various Fe, Mn, and PO4 molten precursors in the present invention, LiFe, where x varies from 0 to 1, can be synthesized using the Li2SO4 or Li2SO4-containing precursors as low-cost reactants. x M 1-xIt has been discovered that it is possible to make PO cathode compositions. For example, it has surprisingly been found that LFP or LFMP ingots made from LiSO contain less than 0.1% sulfur as measured by LECO sulfur analysis. Doing so reduces the number of steps and costs involved in making cathode materials directly from the LiSO intermediate obtained from mineral processing. This intermediate chemical, LiSO, is currently used in the industry to make LiCO and LiOH reactants from lithium minerals, or is obtained as a product from spent cathode material from used battery recycling.

[0043] A non-limiting example of the global reactions involved in the lithium sulfate precursor and melting process of the present invention can be represented as follows: Li2SO4+2FeO+P2O5=2LiFePO4+SO3 formula 1 Or it can be expressed as follows: 2Li2SO4+4FeO+2P2O5=4LiFePO4+2SO2+O2 formula 2

[0044] For simplicity, the FeO formalism is used, but in practice an equivalent mixture of Fe2O3 and Fe is used below 650°C to account for FeO instability.

[0045] Nevertheless, other different reactions are possible depending on the temperature and oxygen partial pressure pO2, as well as the exact nature or combination of Fe, Mn, or P.

[0046] It has also surprisingly been found that when (NH4)H2PO4 (ammonium dihydrogen phosphate; MAP) or (NH4)2HPO4 (diammonium phosphate; DAP) are used as phosphorus sources in the melting process along with Li2SO4, LiFePO4 is obtained with the useful by-product of (NH4)2SO4 formed, thus avoiding or greatly reducing any SO2 or SO3 gas emissions. The following reaction can be suggested as the sole mechanism for this surprising observation, without being limiting: Li2SO4+2(NH4)H2PO4+2FeO=2LiFePO4+(NH4)2SO4+2H2O Equation 3

[0047] Also, the following reaction can be presented in relation to the FeSO4 precursor: Li++(NH4)2HPO4+FeSO4=LiFePO4+(NH4)2SO4+2H2O 2Li++2(NH4)H2PO4+2FeSO4=2LiFePO4+(NH4)2SO4+SO2+2H2O

[0048] Several other reactions may occur, particularly depending on the use of a reducing atmosphere and the order in which the reactants are introduced. However, the primary concern is the possibility of avoiding or reducing sulfur anhydride production by forming a valuable by-product, ammonium sulfate (e.g., a fertilizer).

[0049] The present invention illustrates the conversion of lithium sulfate precursors to lithium metal phosphate olivine via a melt process. The inventors further extended this to the use of transition metal sulfate precursors, such as FeSO4 and MnSO4, which are frequently used as intermediates to form equivalent metal phosphates, e.g., FePO4 or LFMP compositions. In the North American context, iron oxides or metals are preferred as precursors used directly in the melt, but due to their simplicity of use, the possibility of converting transition metal sulfates to the equivalent lithium metal phosphate in the melt to obtain electrochemically active olivine cathode material is also interesting, given the availability of large amounts of oxide cathode production, e.g., MnSO4, from NMC.

[0050] Other patents and published patent applications related to melt processes cited in this application describe typical operating conditions for molten salt synthesis, which are also used in the present invention, particularly WO 2013 / 177671 A1 and WO 2015 / 179972 A1. Co-pending applications US 63 / 479,266 and US 63 / 479,276 also describe additional implementations encompassed by the present invention. A unique feature of melt synthesis is that it allows for slight deviations from pure stoichiometry even after solidification. For example, substitutional elements can be observed under certain conditions after solidification, such as when some Mg, Ca, Zn, Ni, Co, Al, or Si is present in the melt during synthesis. The formula encompasses these compositional deviations as long as the useful structure remains olivine and the electrochemical capacity for lithium ion exchange is not significantly reduced—for example, less than 15 mAh / g relative to a theoretical capacity of 170 mAh / g.

[0051] The direct use of such lithium sulfate intermediate chemicals in the melting process reduces the number of operations typically required to convert lithium minerals to Li2CO3 or LiOH, as well as the costs of purchasing Na2CO3 chemicals and disposing of by-products such as Na2SO4, which can be undesirable contaminants for battery cycle life. Similarly, the direct use of such metal sulfate intermediate chemicals in the melting process generally reduces the number of operations typically required to convert lithium minerals to FePO4 or MnPO4, as well as the costs of purchasing Na2CO3 chemicals and disposing of by-products such as Na2SO4.

[0052] In another variation of the present invention, it has been found possible and useful to at least partially convert the LiSO intermediate to an insoluble LiPO-rich precursor and precipitate it. Such a precipitation step facilitates lithium separation of the lithium precursor, since LiPO is mixed with a small amount of LiSO. This precipitate can be used directly in the melting process of the present invention to obtain pure LFP or LFMP containing no or less than 0.1% sulfur, as confirmed by LECO sulfur analysis. As observed in the examples, total sulfate conversion to phosphate in the melt to form a lithium metal phosphate composition that results in an olivine structure upon solidification is particularly thermodynamically favorable.

[0053] In another variation of the present invention, Li2SO4, which has a low melting point of about 850°C, is mixed with the desired LiFe, where x varies from 0 to 1. x Mn 1-x It can be used as an initial molten reactive pool to which Fe, Mn, or other precursors for PO4 can be added to form the PO4 composition.

[0054] In such cases, the Li2SO4 can be adjusted to the melt stoichiometric composition or over-planed, leaving an additional water-soluble Li2SO4 phase that can be washed out after casting and solidification of the olivine crystal. Although not optimized in this invention, it has nevertheless been found in this invention that the melting process of the present invention can be used with a Li2SO4 lithium precursor together with a concentrated apatite mineral of Ca5(PO4)3(OH) composition to form Li3PO4 and CaSO4 with no or low release of sulfur oxides. Furthermore, the same Li2SO4 lithium precursor can be used in combination with Fe and / or Mn +2 In the presence of precursors, concentrated apatite minerals of Ca5(PO4)3(OH) can be used with additional P2O5 in appropriate proportions to produce LiFePO4 or LiFe, as shown in the examples below. x Mn 1-xPO4 olivine crystals can be formed. In such cases, capturing a large portion of the SO3 or SO2 gas formed as CaSO4 constitutes an additional benefit of the present invention.

[0055] The use of both Li2SO4 and apatite minerals as sources of Li and P, made possible by the present invention, significantly reduces the number of chemical steps and waste products to form lithium metal phosphate cathodes.

[0056] Obviously, other sources of Li2SO4 can be used in the present invention, but a useful mode of realization of the present invention is the use of such lithium sulfate precursors in the melting process of the present invention as a continuation of the initial steps of lithium extraction from spodumene minerals by heat treatment and acid leaching, and also as a by-product of recycling spent cathodes from end-of-life batteries.

[0057] Although the introduction of precursors in a melt used as a reaction pool is preferred in the present invention as described in WO 2013 / 177671 A1 due to the rapidity and uniformity of the reaction, it is nevertheless possible to melt at least one component and react it stepwise and simultaneously, as illustrated in the examples below, for the sake of simplicity in small-scale experimental setups. [Example]

[0058] Example 1 The C-LiFePO4 cathode is made using the following mixture of precursors in their solid powder form: Li2SO4·H2O, Fe 0 , Fe2O3, and P2O5. To replicate the essence of the recycling process for spent oxide cathodes as described in Materials 2020, 13, 801; doi:10.3390 / ma13030801, the lithium sulfate monohydrate used in this example is obtained from the H2SO4 leaching of LiCoO2, the acid solution neutralized with ammonium hydroxide solution, and the hydrate Li2SO4 separated by crystallization.

[0059] The proportions of each reactant are adjusted to adhere to the stoichiometry of 1.03, 1, 1.03 for the ratio of lithium, iron, and phosphorus in the final LFP composition. The two sources of iron are adjusted to fix the oxidation state of iron at +2.

[0060] The synthesis is carried out in a graphite crucible with a graphite lid, held at 1100 °C under air for 1 h to maintain a reducing atmosphere within the crucible. After casting under N2, the product is ground into powder. XRD analysis reveals the absence of Li2SO4 peaks, as attributed to the targeted starting composition, as shown in Figure 1a. x P y O z The LiFePO4 olivine structure is confirmed along with the impurities. Sulfur analysis by LECO confirmed less than 0.1% S present in the olivine product, confirming complete lithium sulfate conversion to lithium metal phosphate.

[0061] To further confirm the reaction pathway of this synthesis, thermogravimetric analysis (TGA) coupled with mass spectrometry (MS) is performed on the same initial powder mixture (see Figures 1b and 1c).

[0062] The released SO2 observed by MS confirms the formation mechanism of LiFePO4 olivine according to the TGA characteristics and Equation 2. The observed delay can be explained by the effect of the rapid temperature increase: 35–1100 °C at 50 °C / min (N2 flow of 10 ml / min).

[0063] The obtained olivine powder was further wet-milled to a D50 of 200 nm in the presence of lactose carbon precursor to obtain C-LiFePO4 with approximately 2% carbon after pyrolysis at 700 °C, resulting in a black powder, which was found to have an electrochemical capacity of over 150 mAh / g at a rate of C / 10 (see Figure 1d).

[0064] Example 2a The anhydrous Li2SO4 precursor is obtained by drying the Li2SO4·xH2O from Example 1 under vacuum at 200 °C. The results obtained are similar to those confirmed by XRD (see Figure 2a and the reversible electrochemical capacity of 150 mAh / g at a rate of C / 10 for the production of C-LiFePO4) and are similar to Figure 1d.

[0065] Example 2b Diammonium hydrogen phosphate was added to the leached and neutralized Li2SO4 solution of Example 1 to precipitate Li3PO4 and the product was treated with SO4 2- Further purification is attempted by filtration along with the remaining trace of (see Figure 2b). Residual sulfur detected by LECO is approximately 0.84% ​​S. When this sulfate-containing lithium precursor is used to form LiFePO4 as in the previous two examples, the resulting product is pure LFP, and sulfur analysis by LECO confirms the presence of less than 0.1% S in the olivine product, confirming complete conversion of any remaining lithium sulfate.

[0066] Example 3 LiFe using the following mixture of precursors in their solid powder form: 0.2 Mn 0.8 Prepare PO4 powder. Li2SO4, Fe 0 , Fe2O3, MnCO3, and P2O5.

[0067] The proportions of each reactant are adjusted to adhere to the stoichiometry of 1.03, 1, 1.03 for the ratios of lithium, iron + manganese, and phosphorus in the final LFMP composition. The two sources of iron are adjusted to fix the oxidation state of the iron and manganese transition metals at +2. The synthesis is carried out in a graphite crucible with a graphite lid, held at 1100 °C under nitrogen to maintain a reducing atmosphere within the crucible, for 1 hour. After casting under N2, the product is crushed to a powder of less than 75 μm. XRD analysis shows that the resulting LiFe 0.2 Mn 0.8 Confirm the PO4 olivine structure and expected cell parameters.

[0068] Example 4 In this example, LiFePO4 powder is made using the following mixture of precursors in their solid powder form: Li2SO4.H2O, (NH4)H2PO4, Fe 0 , Fe2O3.

[0069] The proportions of each reactant used in the melting process were adjusted to adhere to a stoichiometry of 1.03:1:1.03 for the lithium, iron, and phosphorus ratios in the final LFP composition. Synthesis was performed in a graphite crucible held at 1100 °C for 1 hour under a nitrogen atmosphere. The sample was then cooled to room temperature in the crucible. The product was then ground to a powder of less than 75 μm. XRD analysis confirmed the formation of the resulting LiFePO4 olivine structure and the expected cell parameters (see Figure 3a). LECO analysis of sulfur in the formed LFP composition was less than 0.1%.

[0070] During the experiment, gases released in the furnace exhaust were captured in water. The resulting solution consisted primarily of (NH)SO, as confirmed by XRD analysis after water evaporation. (See Figure 3b, which illustrates the possibility of reducing or avoiding anhydrous sulfur gas emissions by using a MAP or DAP source of P in the melting process along with the LiSO precursor of the present invention.) The by-product (NH)SO is formed, which captures sulfur and ammonia and has useful applications, for example, as a fertilizer.

[0071] Example 5 In this example, enriched apatite mineral was used as a phosphorus source for two different reactions. The apatite XRD shown in Figure 4a shows that Ca 10 It corresponds to (PO4)6(OH)2.

[0072] In the first test, apatite powder and Li2SO4.H2O powder are ground together in a ratio of 3 Li to 1 P and introduced into a graphite crucible equipped with a graphite lid. The mixture is heated at 1100 °C for 2 h. The XRD spectrum of the powder obtained from the formed ingot (Figure 4b) confirms the formation of Li3PO4 and CaSO4 with some unreacted apatite and Li2SO4.

[0073] Although not an optimized test, the XRD nevertheless confirms the substitution of SO4 for PO4 to form lithium phosphate, as well as the possibility of capturing in situ the released SO2 as CaSO4.

[0074] In the second test, the same olivine mineral is used as a mixture of Li2SO4·xH2O and P2O5 precursors to form LiFePO4 using apatite as both the phosphorus source (PO4) and sulfur oxide trap. The Li, Fe, and P reactant powders are milled together with excess Li2SO4 in approximate proportions corresponding to the following formula: 10Li2SO4+(Ca) 10 (PO4)6(OH)2+7P2O5+20FeO=20LiFePO4+10CaSO4+H2O The mixture was introduced into a graphite crucible equipped with a graphite lid and held at 1150°C under a N2 atmosphere for 2 hours. While this example is not optimized for battery-grade LiFePO4, it is used to confirm the feasibility of using Li2SO4 directly in the melting process of the present invention with concentrated phosphate minerals, with the added benefit of capturing SO2-SO3 gases that may be produced during synthesis as CaSO4. In this case, filtration of the solid CaSO4 before casting, or alternatively, phase separation before or after solidification, is desirable. The presence of peaks of the LiFePO4 olivine structure is confirmed by XRD after the powder is crushed and washed with water to remove excess Li2SO4.

[0075] Example 6 The lithium precursor used is a mixture of Li3PO4 containing 5% residual Li2SO4 obtained from the Li2SO4 solution after precipitation and filtration of Li3PO4. Such Li and partial PO4 sources are added to the melt in the proportions required to obtain the required Li / Fe / P stoichiometry. 0 , Fe2O3, and P2O5 precursors. These reactants are introduced into a molten pool of LiFePO4 held at 1150°C stirred for 1 / 2 hour under a reducing CO2 / H2 / N2 atmosphere; the molten composition has the stoichiometry of LiFePO4 before casting and solidification. XRD confirms pure LiFePO4 olivine.

[0076] Example 7 LFP synthesis is performed using transition metal sulfate precursors rather than lithium sulfate precursors. This is exemplified using ferrous sulfate, which is introduced into the melt along with the lithium precursor and phosphate source. 21.75 g of FeSO4, 5H2O, 3.34 g of Li2CO3, and 11.9 g of (NH4)2HPO4 (DAP) are used. The reaction is carried out in a graphite crucible placed in a tube furnace. The temperature is ramped to 600 °C at 5 °C / min, followed by 10 °C / min to 1100 °C, plateauing for 1 hour before cooling under N2 in the crucible. The gas effluent is captured in water, and the residue is analyzed after evaporation. The product formed in the crucible is crushed to 75 microns or less. The XRD pattern in Figure 5a confirms pure LFP, and S analysis of the LFP confirms less than 0.1% S. As shown by XRD, the evaporated residue is mostly (NH4)2SO4. Without being limiting, one possible reaction pathway can be described as follows: FeSO4.5H2O+1 / 2Li2CO3+(NH4)2H(PO4)->LiFePO4+5H2O+CO2+(NH4)2SO4.

[0077] It can be concluded from this example and previous examples using lithium sulfate precursors that under the conditions of the melt process of the present invention, it is possible and advantageous to convert metal sulfate precursors directly and completely into the equivalent phosphates, LFPs, or LFMPs.

[0078] As will be appreciated by those skilled in the art, other modifications and combinations may be made to the various embodiments of the invention as described hereinabove.

[0079] In this description, a number of documents are cited, the contents of which are incorporated herein by reference in their entirety.

[0080] The scope of the claims should not be limited by the preferred embodiments described herein above, but should be accorded the broadest interpretation consistent with the description as a whole.

Claims

1. A melt process for preparing lithium metal phosphate (LMP) cathode material, wherein M is at least one transition metal, said process comprising: ２ SO ４ , FeSO ４ , MnSO ４ or a hydrated form thereof, or a mixture thereof, A melt process in which the metal sulfate precursor is used directly without significant transformation.

2. 2. The melting process of claim 1, wherein the metal sulfate precursor is obtained after its extraction from an ore material or recycling from an electrode material of a used lithium battery, optionally the metal sulfate precursor is obtained as a product of a chemical process.

3. 3. The melting process of claim 1 or 2, wherein the LMP cathode material is of olivine structure, and optionally the LMP is lithium iron phosphate (LFP) or lithium manganese iron phosphate (LFMP).

4. A smelting process according to any one of claims 1 to 3, wherein the ore material is spodumene.

5. The metal sulfate precursor is ２ SO ４ and FeSO ４ and MnSO ４ The melt process according to any one of claims 1 to 4, wherein the melt process is a mixture of the above with one of the following:

6. The metal sulfate precursor is Li ２ SO ４ , FeSO ４ , and MnSO ４ The melt process according to any one of claims 1 to 4, wherein the mixture is

7. Li ２ SO ４ The precursor is Li ２ SO ４ and Li ３ P.O. ４ It is used as a mixture containing Optionally, the mixture comprises the Li ２ SO ４ The melting process according to any one of claims 1 to 6, obtained after subjecting the

8. The Li ２ SO ４ The precursor is Li ２ CO ３ or substantially free of LiOH.

9. The hydrated form has the general formula Li ２ SO ４ ・xH ２ The Li of O ２ SO ４ 9. The melt process of any one of claims 1 to 8, wherein the precursor is x, which varies from about 0 to about 30, or from about 1 to about 5, or from about 0 to about 3, or x is 1, or x is 2.

10. Melting process according to any one of claims 1 to 9, wherein at least one other source of metal is used.

11. At least one other source of Fe is used; Preferably, the at least one other source of Fe is Fe ０ , FeO, Fe ２ O ３ , Fe ３ O ４ , ferric phosphate, or mixtures thereof containing iron oxide concentrated minerals, A melting process according to any one of claims 1 to 10, wherein preferably the source of Fe is adjusted to fix the oxidation state of Fe at +2.

12. At least one other source of Mn is used; Preferably, the at least one other source of Mn is Mn ０ , MnO, Mn ２ O ３ , MnO ２ , MnCO ３ or a mixture thereof.

13. At least one source of phosphorus or phosphate (P or PO ４ sources) are used, Preferably, the P or PO ４ The source of P ２ O ５ , H.P.O. ３ , (NH ４ ) H ２ P.O. ４ (ammonium dihydrogen phosphate; MAP), (NH ４ ) ２ HPO ４ (diammonium phosphate; DAP), or Ca ５ (P.O. ４ ) ３ (OH) and the mineral apatite, Preferably, the PO ４ The source of SO ２ and / or SO ３ A melting process according to any one of claims 1 to 12, suitably selected to avoid or significantly reduce any emission of gases.

14. The metal sulfate precursor is ４ The melting process of any one of claims 1 to 13, wherein the source of

15. (NH ４ ) H ２ P.O. ４ (ammonium dihydrogen phosphate; MAP) or (NH ４ ) ２ HPO ４ At least one source of phosphorus or phosphate (P or PO) is diammonium phosphate (DAP). ４ A source of (NH ４ ) ２ SO ４ is formed as a by-product, Preferably, MAP and DAD are used simultaneously with said metal sulfate precursor; Preferably, SO ２ and / or SO ３ A melting process according to any one of claims 1 to 12, wherein gas emissions are eliminated or significantly reduced.

16. The metal sulfate precursor is subjected to an incipient melting process, thereby obtaining an incipient melt reactive pool, and the PO ４ 14. The melt process of claim 13, wherein a source of

17. 3. The melting process of claim 2, wherein the ore material or the electrode material of a used lithium battery is subjected to a treatment comprising heat treatment and / or acid leaching and / or crystallization to provide the metal sulfate precursor.

18. the temperature of the melt is from about 850°C to about 1300°C, and the reaction melt is maintained at substantially the same temperature; Preferably, the atmosphere is in an inert or reducing atmosphere, and preferably, the inert or reducing atmosphere is CO ２ , CO, H ２ , H ２ O, Ar, N ２ , C.H. ４ and natural gas, preferably in proportions suitable to stabilize the cathode composition in the melt and upon casting and solidification; The process according to any one of claims 1 to 17, preferably under stirring.

19. the reaction melt is further confined to obtain the LMP in a solid crystalline form upon casting and solidification; Optionally, the solid crystalline LMP is reduced to a powder; 17. The melting process of claim 16, optionally coating the solid crystalline LMP in powder form with carbon to form an electrochemically active cathode material, preferably the carbon coating process using a carbon precursor.

20. 1. A metal sulfate precursor for direct use in a melt process for the preparation of lithium metal phosphate (LMP) cathode material, wherein M is at least one transition metal; The metal sulfate precursor is Li ２ SO ４ , FeSO ４ , MnSO ４ or a hydrated form thereof, or a mixture thereof; the metal sulfate precursor is suitable for direct use without significant transformation; Optionally, the metal sulfate precursor is obtained after its extraction from an ore material or recycling from an electrode material of a used lithium battery, and optionally, the metal sulfate precursor is obtained as the product of a chemical process.

21. 20. An LMP, LFP, or LFMP cathode material made by the melt process defined in any one of claims 1 to 19, wherein the LMP, LFP, or LFMP cathode material contains about 0.1% or less sulfur as measured by LECO sulfur analysis.

22. A cathode comprising a material made by a melt process as defined in any one of claims 1 to 19.

23. A battery having a cathode comprising a material made by a melt process as defined in any one of claims 1 to 19.

24. A cathode or battery manufacturing plant embodying a melting process as defined in any one of claims 1 to 19.

25. 1. Use of a metal sulfate precursor in a melt process for preparing a lithium metal phosphate (LMP) cathode material, wherein M is at least one transition metal; The metal sulfate precursor is Li ２ SO ４ , FeSO ４ , MnSO ４ or a hydrated form thereof, or a mixture thereof; the metal sulfate precursor is used directly without significant transformation; Optionally, the metal sulfate precursor is obtained after its extraction from an ore material or recycling from an electrode material of a used lithium battery, and optionally, the metal sulfate precursor is obtained as the product of a chemical process.

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