Novel Process of Synthesizing Cathode Material

Abstract

The present invention provides a novel process of synthesizing a cathode material. A metal selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof is partially oxidized with an agent such as H3PO4. Then, the metal is fully oxidized with an oxidizing agent such as H2O2. Finally, preparation of the cathode material is completed. The process exhibits numerous technical merits such as less water consumption, less electricity usage, improved product purity, and less usage of base raw materials (e.g. NaOH, Na2CO3, NH3·H2O), among others.

Description

FIELD OF THE INVENTION

The present invention generally relates to a process of synthesizing cathode material, and a method thereof. Although the invention will be illustrated, explained, and exemplified by a process of preparing a cathode material based on LiFePO₄ for a lithium secondary battery, it should be appreciated that the present invention can also be applied to other cathode materials.

BACKGROUND OF THE INVENTION

In recent years, electric vehicles and hybrid electric vehicles require advanced battery materials to meet the high demand and performance, in addition to portable electronic devices such as cellular phones, pagers, video cameras, facsimile machines, portable stereophonic equipment, personal organizers and personal computers. As a result, the demand for improved power sources for these devices has been increased. Preferably, the battery materials are environmentally benign and relatively low cost to make these expanded battery applications practical.

Lithium-based batteries have become commercially successful due to their relatively high energy density. Lithium-based batteries generally use electrolytes containing lithium ions. The negative electrodes for these batteries can include lithium metal or alloy (lithium batteries), or compositions that intercalate lithium (lithium-ion batteries). Preferred electroactive materials for incorporation into the positive electrodes are compositions that intercalate lithium. For example, metal phosphates are candidates to produce cathode materials that intercalate lithium.

An example of lithium-ion battery is the lithium iron phosphate (LiFePO₄, LFP) battery, in which LiFePO₄ is used as the cathode material. LFP exhibits some advantages such as low cost, non-toxicity, natural abundance, excellent thermal stability, safety characteristics, electrochemical performance, and specific capacity (170 mA·h/g, or 610 C/g). As such, LFP battery is even finding several roles in vehicle use and backup power, among others.

For example, a process of preparing carbon coated LiFePO₄ cathode materials includes (i) adding a base (e.g. NaOH) to a reaction mixture of Fe salt solution such as FeSO₄ solution, H₃PO₄, and H₂O₂ at pH=1-3, and reacting to produce FePO₄+H2O; and then (ii) reacting a Li source (such as Li₂CO₃ or LiOH) with FePO₄ and a carbon source material such as glucose. The Fe salt aqueous solution such as FeSO₄ solution can be provided by dissolving FeSO₄ and/or FeCl₂ of industrial grade in water. However, such a process is problematic and unsatisfactory because its cost is relatively high, it is not environmentally friendly, its product purity is not super high, and/or it also wastes a lot of water and energy.

Thus, there exists a need for simpler, less water-consuming, more environmentally friendly, and more cost-effective methods for preparing cathode material such as nanosized LiFePO₄ particles. Advantageously, the present invention provides a novel process of synthesizing cathode material that can overcome the problems.

SUMMARY OF THE INVENTION

One aspect of the present invention provides a process of synthesizing a target cathode material. The process includes (i) mixing a P source containing element P with a first metal source containing one or more metal elements selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof, to form a first intermediate material. In step (i), a portion of at least one element (such as Fe) among the one or more metal elements is oxidized. Step (ii) of the process is mixing and reacting the first intermediate material with an oxidizing agent to oxidize a remaining portion of the at least one element among the one or more metal elements, to form a second intermediate material. Further, the process includes step (iii) of mixing the second intermediate material with one or more add-on source materials selected from a P source containing element P, a first metal source containing one or more metal elements selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof, and a second metal source containing one or more elements selected from Li, Na, K or any combination thereof. The one or more add-on source materials are introduced in an amount or amounts that are needed for accomplishing a formula of the target cathode material.

Other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings (if any).

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements. All the figures are schematic and generally only show parts which are necessary in order to elucidate the invention. For simplicity and clarity of illustration, elements shown in the figures and discussed below have not necessarily been drawn to scale. Well-known structures and devices are shown in simplified form, omitted, or merely suggested, in order to avoid unnecessarily obscuring the present invention.

FIG. 1 is a flow chart that illustrates a general process of synthesizing a target cathode material in accordance with an exemplary embodiment of the present invention.

FIG. 2 shows an X-ray diffraction pattern of LiFePO₄ obtained in an exemplary embodiment of the present invention.

FIG. 3 shows the charge/discharge performance (Voltage vs. Capacity) of LiFePO₄ obtained in an exemplary embodiment of the present invention.

FIG. 4 shows an X-ray diffraction pattern of LiFePO₄ obtained in an exemplary embodiment of the present invention.

FIG. 5 shows the charge/discharge performance (Voltage vs. Capacity) of LiFePO₄ obtained in an exemplary embodiment of the present invention.

FIG. 6 shows an X-ray diffraction pattern of LiFeMnPO₄ obtained in an exemplary embodiment of the present invention.

FIG. 7 shows the charge/discharge performance (Capacity vs. Cycle Number) of LiFeMnPO₄ obtained in an exemplary embodiment of the present invention.

FIG. 8 shows the charge/discharge performance (Voltage vs. Capacity) of LiFePO₄ obtained in an exemplary embodiment of the present invention.

FIG. 9 shows an X-ray diffraction pattern of LiFeMnPO₄ obtained in an exemplary embodiment of the present invention.

FIG. 10 shows the charge/discharge performance (Capacity vs. Cycle Number) of LiFeMnPO₄ obtained in an exemplary embodiment of the present invention.

FIG. 11 shows the charge/discharge performance (Voltage vs. Capacity) of LiFeMnPO₄ obtained in an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It is apparent, however, to one skilled in the art that the present invention may be practiced without these specific details or with an equivalent arrangement.

Where a numerical range is disclosed herein (such as 10˜30% H₃PO₄ solution), unless otherwise specified, such range is continuous, inclusive of both the minimum and maximum values of the range as well as every value between such minimum and maximum values (such as 15˜25% H₃PO₄ solution). Still further, where a range refers to integers, only the integers from the minimum value to and including the maximum value of such range are included. In addition, where multiple ranges are provided to describe a feature or characteristic, such ranges can be combined.

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the invention. For example, when an element is referred to as being “on”, “connected to”, or “coupled to” another element, it can be directly on, connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly on”, “directly connected to”, or “directly coupled to” another element, there are no intervening elements present.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. Furthermore, the phrase “in another embodiment” does not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined without departing from the scope or spirit of the invention.

In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.”

In various exemplary embodiments, the present invention provides a process of synthesizing a target cathode material as shown in FIG. 1. Briefly, the process includes (i) oxidization of a portion of metal X; (ii) oxidization of unoxidized portion of the metal X; and (iii) completion of the cathode material having a target formula. For example, the cathode material may have a target formula of Li_1.04Fe_0.98PO₄, which will be used as a specific but only representative example for explaining the process.

Steps (i), (ii) and (iii) may be conducted in one single container. Alternatively, steps (i), (ii) and (iii) may be conducted in two or more containers. For example, steps (i) and (ii) are conducted in one container while step (iii) is conducted in another container. Steps (ii) and (iii) are conducted in one container while step (i) is conducted in another container. Steps (i), (ii) and (iii) are conducted separately in three separate containers. In preferred embodiments, steps (i), (ii) and (iii) are conducted in one single container.

Step (i) comprises mixing a P source containing element P with a first metal source containing one or more metal elements selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof, to form a first intermediate material. In step (i), a portion of at least one element (such as Fe) among the one or more metal elements is oxidized. For the exemplary target formula of Li_1.04Fe_0.98PO₄, Fe Powder of 25-2000 um in 10-30% H₃PO₄ solution [molar ratio Fe:P=0.98:1] may be added into a container and heated for 1-8 hours (T=60-100° C.) to oxidize a portion of the Fe powder and produce the first intermediate material.

Step (ii) of the process may be conducted in a different container, or in the same container as in step (i), i.e. without transferring the first intermediate material to any other reaction container(s) or equipment(s) such as a milling apparatus. This step is mixing and reacting the first intermediate material with an oxidizing agent to oxidize a remaining portion of the at least one element [which was unoxidized in step (i)] among the one or more metal elements, to form a second intermediate material. For the exemplary target formula of Li_1.04Fe_0.98PO₄, one or more oxidants such as O₂, H₂O₂ and HNO₃ may be introduced to push/promote the Fe oxidization to completeness. The remaining Fe powder that is not oxidized in step (i) may be oxidized in this step, to produce the second intermediate material comprising a mixture of Fe in oxidized form(s) and phosphate.

Step (iii) of the process may be conducted in a different container, or in the same container as in step (ii) without transferring the second intermediate material to any other reaction container(s) or equipment(s) such as a milling apparatus. Step (iii) comprises mixing the second intermediate material with one or more add-on source materials selected from a P source containing element P, a first metal source containing one or more metal elements selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof, and a second metal source containing one or more elements selected from Li, Na, K or any combination thereof. The one or more add-on source materials may be introduced in an amount or amounts that are needed for accomplishing a formula of the target cathode material.

It should be appreciated that the P source in step (iii) may be the same as, or different from, the P source in step (i). The first metal source in step (iii) may be the same as, or different from, the first metal source in step (i).

For the exemplary target formula of Li_1.04Fe_0.98PO₄, a Li source (such as Li₂CO₃) and a C source (e.g. glucose) may be introduced in step (iii) and mixed with the second intermediate material therein. As an add-on source material, the Li source may be introduced in an amount that is needed for accomplishing target formula of Li_1.04Fe_0.98PO₄. In this example, the Li source may be introduced in an amount to make the molar ratio Li:P=1.04:1 in the container.

It should be appreciated that, if the target formula is Cx·Li_1.04Fe_0.98PO₄ (which stands for carbon-coated lithium iron phosphate cathode material), then step (iii) may further comprise mixing the second intermediate material with a C source material (e.g. glucose) in a suitable amount. By “suitable amount,” it is indented to mean that the amount of C source material is enough to make the molar ratio of C:P=x:1, or molar ratio of C:Li=x:1.04.

In alternative but still exemplary embodiments, steps (i), (ii) and/or (iii) may be modified to achieve the exemplary target formula of Li_1.04Fe_0.98PO₄ as mentioned above. For example, the molar ratio Fe:P in step (i) may be lowered to 0.8:1. As a result, step (iii) is so adjusted that an add-on Fe source material (in addition to the Li source and the C source) may be introduced into the container and mixed with the second intermediate material therein. The add-on Fe source material in step (iii) may have a molar ratio of Fe:P=0.18:1 relative to the amount (moles) of P present in the container. The same final molar ratio of Fe:P=0.98:1 is also achieved after such step (iii) is completed. The add-on Fe source material in step (iii) may be selected from Fe2+ and Fe3+ compounds such as FeO, Fe₂O₃, Fe₃O₄, FeCO₃, and FeC₂O₄.

In exemplary embodiments, the P source in step (i) and step (iii) may be selected from H₃PO₄, a salt of H₂PO₄⁻, a salt of HPO₄²⁻, a salt of PO₄³⁻, or any combination thereof. The P source in step (i) may include 5-55% H₃PO₄ aqueous solution, preferably 10-30% H₃PO₄ aqueous solution, and more preferably 15-25% H₃PO₄ aqueous solution. The first metal source in step (i) may comprise a metallic powder (i.e. with a valence of 0) of Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof. In preferred embodiments, the first metal source in step (i) comprises iron powder (i.e. with a Fe valence of 0) and/or Mn powder (i.e. with a Mn valence of 0).

Without being bound to any particular theory, it is believed that an element selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, and Mo in the first metal source is partially oxidized.

In an example, a single displacement reaction (AKA exchange reaction) may occur between iron powder and H₃PO₄ solution in step (i). In step (ii), the first intermediate material is mixed and reacted with an oxidizing agent (which typically is not H⁺) to oxidize the unoxidized portion of the partially oxidized metal, to form a second intermediate material.

In exemplary embodiments, the oxidizing agent in step (ii) may be selected from O₂, H₂O₂, HNO₃, KMnO₄, NaMnO₄, or any combination thereof. Step (i) may include heating the reaction mixture to an elevated temperature such as 40-100° C. for 1-10 hours; and step (ii) may include maintaining the reaction mixture at the elevated temperature such as 40-100° C.

In exemplary embodiments, the first metal source in step (iii) may comprise a metal compound selected from oxides, hydrogen carbonates, hydrogen sulfates, hydrogen oxalates, carbonates, sulfates, and oxalates of Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof. In preferred embodiments, the first metal source in step (iii) may comprise a metal compound selected from FeO, Fe₂O₃, Fe₃O₄, FeC₂O₄, MnO, Mn₂O₃, Mn₃O₄, MnCO₃, MnO₂, CoO, Co₂O₃, and Co₃O₄. In exemplary embodiments, the second metal source in step (iii) may comprise a metal compound selected from oxides, hydroxides, carbonates, hydrogen carbonates, phosphates, hydrogen phosphates, dihydrogen phosphates, nitrates, oxalates and hydrogen oxalates of Li, Na, K or any combination thereof. In preferred embodiments, the second metal source in step (iii) comprises a metal compound selected from Li₂O, LiOH, Li₂CO₃, LiHCO₃, Li₃PO₄, Li₂HPO₄, LiH₂PO₄, Li₂C₂O₄, LiHC₂O₄, LiNO₃, Na₂O, NaOH, Na₂CO₃, NaHCO₃, Na₃PO₄, Na₂HPO₄, NaH₂PO₄, Na₂C₂O₄, NaHC₂O₄, K₂O, KOH, K₂CO₃, KHCO₃, K₃PO₄, K₂HPO₄, KH₂PO₄, K₂C₂O₄, KHC₂O₄, NaNO₃, KCH₃CO₂, KHCO₂, and KNO₃.

In some exemplary embodiments, the P source and the first metal source in step (iii) may be combined into a composite source such as a mixture of compounds. The P source and the second metal source in step (iii) may be combined into a composite source such as Li₃PO₄, Na₃PO₄, K₃PO₄, Li₂HPO₄, Na₂HPO₄, K₂HPO₄, LiH₂PO₄, NaH₂PO₄, and KH₂PO₄. The first metal source and the second metal source in step (iii) may be combined into a composite source such as KMnO₄.

In some exemplary embodiments, step (iii) may further comprise mixing the second intermediate material with a C source material (e.g. glucose).

Within step (iii) or after step (iii) of the process of the invention, other known steps or reaction schemes may be conducted. For example, the process may further comprise milling or grinding the product from step (iii) to cream-like particles having an average size of 300˜400 nm after step (iii) is completed; drying (such as spray drying) the cream-like particles to produce dry particles in a powder form; calcining the dry particles into a solid, grinding the solid into ground particles, and sieving the ground particles to collect nanosized carbon-coated cathode materials.

EXAMPLES

The following examples illustrate the synthesis of various cathode materials according to the present invention. Additional cathode materials within the scope of this invention may be prepared using the methods exemplified and illustrated in these Examples, either alone or in combination with techniques generally known in the prior art.

Example 1: Lithium Iron Phosphate with a Target Molar Ratio Fe:P=(0.95-1):1

In step (i), Fe Powder of 25-2000 um in 15-25% H₃PO₄ solution [molar ratio Fe:P=(0.95-1):1] is added into a container and heated for 1-8 hours (T=60-100° C.) to oxidize a portion of the Fe powder and produce the first intermediate material. In step (ii), one or more oxidants such as O₂, H₂O₂ and HNO₃ are introduced in the same container (or a different container), to push/promote the Fe oxidization to completeness. The remaining Fe powder that is not oxidized in step (i) is oxidized in this step, to produce the second intermediate material comprising a mixture of Fe in oxidized form(s) and phosphate. In step (iii), a Li source (such as Li₂CO₃) and a C source (e.g. glucose) are introduced into the same container (or the different container) and mixed with the second intermediate material therein. As an add-on source material, the Li source is introduced in an amount or amounts that are needed for accomplishing a formula of the target cathode material. For example, if Li_1.04Fe_0.98PO₄ is the formula of the target cathode material, then the Li source is introduced in an amount to make the molar ratio Li:P=1.04:1 in the container, which ratio is needed for accomplishing the formula.

The reaction mixture from step (iii) is transferred to a ball mill or a sand mill and subject to milling or grinding to produce particles of 200-400 nm as a creamy product. The creamy product is then dried such as by spray drying and converted to a powder form. The powder is then calcined, grinded in a ball mill or a sand mill, and then sieved to collect nanosized carbon-coated lithium iron phosphate cathode material.

The cost per ton of FePO₄ product prepared from the invention is reduced as compared to the prior art process as described in the background. For example, the water consumption can be reduced from 30-50 tons down to 3-5 tons. The electricity can be reduced from 2000-2500 kilowatt-hours down to 400-500 kilowatt-hours. The product impurity Na can be reduced from ˜150 ppm down to nearly −0 ppm. Unlike the prior art, base as raw materials (e.g. NaOH, Na₂CO₃, NH₃·H₂O) are not used in the process of the invention.

Example 2: Lithium Iron Phosphate with a Target Molar Ratio Fe:P=(0.95-1):1

The process in this example is similar to that in Example 1 except that the molar ratio Fe:P is (0.75-0.95):1 in step (i). As a result, step (iii) is so adjusted that an add-on Fe source material (in addition to the Li source and the C source) is introduced into the container (or a different container) and mixed with the second intermediate material therein. The add-on Fe source material may have a molar ratio Fe:P of >0:1 and up to 0.2:1, relative to the moles of P present in the container. The final molar ratio Fe:P becomes (0.95-1):1 after step (iii) is completed. The add-on Fe source material is this step can be selected from Fe²⁺ and Fe³⁺ compounds such as FeO, Fe₂O₃, Fe₃O₄, FeCO₃, and FeC₂O₄.

Example 3: Lithium Iron Phosphate with a Target Molar Ratio Li:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced in the same container (or a different container), to push/promote the Fe oxidization to completion. In step (iii), LiOH as the second metal source is introduced into the container and mixed with the second intermediate material therein to produce the cathode active material.

Example 4: Lithium Iron Phosphate with a Target Molar Ratio Li:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), O₂ is introduced in the same container (or a different container), to push/promote the Fe oxidization to completion. In step (iii), LiOH as the second metal source is introduced into the container and mixed with the second intermediate material therein to produce the cathode active material.

Example 5: Lithium Iron Phosphate with a Target Molar Ratio Li:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), HNO₃ is introduced in the same container (or a different container), to push/promote the Fe oxidization to completion. In step (iii), LiOH as the second metal source is introduced into the container and mixed with the second intermediate material therein to produce the cathode active material.

Example 6: Lithium Iron Phosphate with a Target Molar Ratio Li:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced in the same container (or a different container), to push/promote the Fe oxidization to completion. In step (iii), Li₂CO₃ as the second metal source (molar ratio Li₂CO₃:P=1:2) is introduced into the container and mixed with the second intermediate material therein to produce the cathode active material.

Example 7: Lithium Iron Phosphate with a Target Molar Ratio Li:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:⅔ in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), Li₃PO₄ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material. The molar ratio between Fe present in the second intermediate material and the add-on Li₃PO₄ and is 1:⅓.

Example 8: Sodium Iron Phosphate with a Target Molar Ratio Na:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), NaOH as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 9: Sodium Iron Phosphate with a Target Molar Ratio Na:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), NaHCO₃ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 10: Sodium Iron Phosphate with a Target Molar Ratio Na:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), NaNO₃ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 11: Sodium Iron Phosphate with a Target Molar Ratio Na:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), Na₂O as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 12: Sodium Iron Phosphate with a Target Molar Ratio Na:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), Na₂CO₃ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 13: Sodium Iron Phosphate with a Target Molar Ratio Na:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:⅔ in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), Na₃PO₄ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material. The molar ratio between Fe present in the second intermediate material and the add-on Na₃PO₄ and is 1:⅓.

Example 14: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), KOH as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 15: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), KHC₂O₄ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 16: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), KCH₃CO₂ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 17: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), KHCO₂ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 18: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), KHCO₃ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 19: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), KNO₃ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 20: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), K₂O as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 21: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), K₂SO₄ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 22: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), K₂CO₃ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 23: Potassium Iron Phosphate with a Target Molar Ratio K:Fe:P=1:1:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 1:⅔ in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), K₃PO₄ as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material. The molar ratio between Fe present in the second intermediate material and the add-on K₃PO₄ and is 1:⅓.

Example 24: Cathode Active Phosphate Material with a Target Molar Ratio Li:Fe:Mn:P=1:0.4:0.6:1

The process in this example is like that in Example 1 except that: a mixture of Li source and Mn source are used in step (i). The molar ratio Fe:P is 0.4:1 and the molar ratio Mn:P is 0.6:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe and Mn oxidization to completion. In step (iii), LiOH as the second metal source is introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 25: Cathode Active Phosphate Material with a Target Molar Ratio Li:Fe:Mn:P=1:0.4:0.6:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 0.4:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), MnO as the first metal source and LiOH as the second metal source are introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 26: Cathode Active Phosphate Material with a Target Molar Ratio Li:Fe:Mn:P=1:0.4:0.6:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 0.4:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), Mn₂O₃ as the first metal source and LiOH as the second metal source are introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 27: Cathode Active Phosphate Material with a Target Molar Ratio Li:Fe:Mn:P=1:0.4:0.6:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 0.4:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), Mn3O4 as the first metal source and LiOH as the second metal source are introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 28: Cathode Active Phosphate Material with a Target Molar Ratio Li:Fe:Mn:P=1:0.4:0.6:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 0.4:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), MnCO₃ as the first metal source and LiOH as the second metal source are introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 29: Cathode Active Phosphate Material with a Target Molar Ratio Li:Fe:Mn:P=1:0.4:0.6:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 0.4:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), MnO2 as the first metal source and LiOH as the second metal source are introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 30: Cathode Active Phosphate Material with a Target Molar Ratio K:Fe:Mn:P=1:0.4:0.6:1

The process in this example is like that in Example 1 except that: the molar ratio Fe:P is 0.4:1 in step (i). In step (ii), H₂O₂ is introduced to push/promote the Fe oxidization to completion. In step (iii), KMnO4 as a composite source (the first & second metal sources) and KOH as the second metal source are introduced and mixed with the second intermediate material therein to produce the cathode active material.

Example 31: Electrochemical Properties of Cathode Active Materials

FIG. 2 shows an X-ray diffraction pattern of LiFePO₄ obtained in Example 6. FIG. 3 shows the charge/discharge performance (Voltage vs. Capacity) of LiFePO₄ obtained in Example 6. FIG. 4 shows an X-ray diffraction pattern of LiFePO₄ obtained in Example 5. FIG. 5 shows the charge/discharge performance (Voltage vs. Capacity) of LiFePO₄ obtained in Example 5. FIG. 6 shows an X-ray diffraction pattern of LiFe_0.4Mn_0.6PO₄ obtained in Example 27. FIG. 7 shows the charge/discharge performance (Capacity vs. Cycle Number) of LiFe_0.4Mn_0.6PO₄ obtained in Example 27. FIG. 8 shows the charge/discharge performance (Voltage vs. Capacity) of LiFePO₄ obtained in Example 27. FIG. 9 shows an X-ray diffraction pattern of LiFe_0.4Mn_0.6PO₄ obtained in Example 24. FIG. 10 shows the charge/discharge performance (Capacity vs. Cycle Number) of LiFe_0.4Mn_0.6PO₄ obtained in Example 24. FIG. 11 shows the charge/discharge performance (Voltage vs. Capacity) of LiFe_0.4Mn_0.6PO₄ obtained in Example 24. The X-ray diffraction pattern, the charge/discharge performance (Voltage vs. Capacity), and the charge/discharge performance (Capacity vs. Cycle Number) were measured or tested using known methods in the field, the details of which are omitted here for conciseness.

In the foregoing specification, embodiments of the present invention have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the applicant to be the scope of the invention, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction.

Claims

1. A process of synthesizing a target cathode material, comprising: (i) mixing a P source containing element P with a first metal source containing one or more metal elements selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof, to form a first intermediate material, wherein a portion of at least one element among said one or more metal elements is oxidized;(ii) mixing and reacting the first intermediate material with an oxidizing agent to oxidize a remaining portion of said at least one element among said one or more metal elements, to form a second intermediate material; and(iii) mixing the second intermediate material with one or more add-on source materials selected from a P source containing element P, a first metal source containing one or more metal elements selected from Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof, and a second metal source containing one or more elements selected from Li, Na, K or any combination thereof;wherein said one or more add-on source materials are introduced in an amount or amounts that are needed for accomplishing a formula of the target cathode material.

2. The process according to claim 1, wherein said step (i), (ii) and (iii) are conducted in one single container; or wherein said step (i), (ii) and (iii) are conducted in two or more containers including: (A) steps (i) and (ii) are conducted in one container while step (iii) is conducted in another container; (B) steps (ii) and (iii) are conducted in one container while step (i) is conducted in another container; and (C) steps (i), (ii) and (iii) are conducted separately in three separate containers.

3. The process according to claim 1, wherein said P source in step (i) and step (iii) is selected from H3PO4, a salt of H2PO4−, a salt of HPO42−, a salt of PO43−, or any combination thereof; and wherein said first metal source in step (i) comprises a metallic powder (i.e. with a valence of 0) of Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof.

4. The process according to claim 1, wherein said P source in step (i) comprises 5-55% H3PO4 aqueous solution, preferably 10-30% H3PO4 aqueous solution, and more preferably 15-25% H3PO4 aqueous solution; and wherein said first metal source in step (i) comprises iron powder (i.e. with a Fe valence of 0) and/or Mn powder (i.e. with a Mn valence of 0).

5. The process according to claim 1, wherein said oxidizing agent in step (ii) is selected from O2, H2O2, HNO3, KMnO4, NaMnO4, or any combination thereof.

6. The process according to claim 1, wherein step (i) further includes heating the reaction mixture in the container to an elevated temperature such as 40-100° C. for 1-10 hours; and step (ii) further includes maintaining the reaction mixture in the container at an elevated temperature such as 40-100° C.

7. The process according to claim 1, wherein said first metal source in step (iii) comprises a metal compound selected from oxides, hydrogen carbonates, hydrogen sulfates, hydrogen oxalates, carbonates, sulfates, and oxalates of Fe, Mn, Co, Ni, Cu, Zn, Al, Ca, Mg, Ti, V, Cr, Mo or any combination thereof.

8. The process according to claim 1, wherein said first metal source in step (iii) comprises a metal compound selected from FeO, Fe2O3, Fe3O4, FeC2O4, MnO, Mn2O3, Mn3O4, MnCO3, MnO2, CoO, Co2O3, and Co3O4.

9. The process according to claim 1, wherein said second metal source in step (iii) comprises a metal compound selected from oxides, hydroxides, carbonates, hydrogen carbonates, phosphates, hydrogen phosphates, dihydrogen phosphates, nitrates, oxalates and hydrogen oxalates of Li, Na, K or any combination thereof.

10. The process according to claim 1, wherein said second metal source in step (iii) comprises a metal compound selected from Li2O, LiOH, Li2CO3, LiHCO3, Li3PO4, Li2HPO4, LiH2PO4, Li2C2O4, LiHC2O4, LiNO3, Na2O, NaOH, Na2CO3, NaHCO3, Na3PO4, Na2HPO4, NaH2PO4, Na2C2O4, NaHC2O4, K2O, KOH, K2CO3, KHCO3, K3PO4, K2HPO4, KH2PO4, K2C2O4, KHC2O4, NaNO3, KCH3CO2, KHCO2, and KNO3.

11. The process according to claim 1, wherein said P source and said first metal source in step (iii) are combined into a composite source.

12. The process according to claim 11, wherein the composite source is a mixture of compounds.

13. The process according to claim 1, wherein said P source and said second metal source in step (iii) are combined into a composite source.

14. The process according to claim 13, wherein the composite source is selected from Li3PO4, Na3PO4, K3PO4, Li2HPO4, Na2HPO4, K2HPO4, LiH2PO4, NaH2PO4, and KH2PO4.

15. The process according to claim 1, wherein said first metal source and said second metal source in step (iii) are combined into a composite source.

16. The process according to claim 15, wherein the composite source is selected from KMnO4 and NaMnO4.

17. The process according to claim 1, wherein step (iii) further comprises mixing the second intermediate material with a C source material (e.g. glucose).

18. The process according to claim 17, further comprising milling or grinding the product from step (iii) to cream-like particles having an average size of 300˜400 nm after step (iii) is completed.

19. The process according to claim 18, further comprising drying (such as spray drying) the cream-like particles to produce dry particles in a powder form.

20. The process according to claim 19, further comprising calcining the dry particles into a solid, grinding the solid into ground particles, and sieving the ground particles to collect nanosized carbon-coated cathode materials.