Patent Grant
10593947
The present invention relates to metal (II) phosphate powders, lithium metal phosphate powders prepared therefrom, and methods for manufacturing the same. More specifically, the present invention relates to metal (II) phosphate powders for preparing Li-ion batteries having large length to thickness ratio, lithium metal phosphate powders prepared therefrom, and methods for manufacturing the same.
As the development of various portable electronic devices continues, more and more attention focuses on the techniques of energy storage, and batteries are the main power supplies for these portable electronic devices. Among commercial batteries, small-sized secondary batteries are especially the major power supplies for portable electronic devices such as cell phones and notebooks. In addition, secondary batteries are applied to not only portable electronic devices, but also electric vehicles.
Among the developed secondary batteries, the lithium secondary batteries (also named as the Li-ion batteries) developed in 1990 are the most popular batteries used nowadays. The cathode material of the initial lithium secondary batteries is LiCoO2. LiCoO2 has the properties of high working voltage and stable charging and discharging voltage, so the secondary batteries which use LiCoO2 as a cathode material are widely applied to portable electronic devices. Then, LiFePO4 with an olivine structure and LiMn2O4 with a spinal structure were also developed as a cathode material for lithium secondary batteries. Compared to LiCoO2, the safety of the batteries can be improved, the charge/discharge cycles can be increased, and the cost can be further reduced when LiFePO4 or LiMn2O4 is used as cathode material of secondary batteries.
Although the batteries which use LiMn2O4 as cathode materials have low cost and improved safety, the spinal structure of LiMn2O4 may collapse during the deep discharge process, due to Jahn-Teller effect. In this case, the cycle performance of the batteries may further be decreased. When LiFePO4 is used as cathode material of batteries, the batteries also have the properties of low cost and improved safety. In addition, the capacity of LiFePO4 is higher than that of LiMn2O4, so the batteries made from LiFePO4 can further be applied to devices which need large current and high power. Furthermore, LiFePO4 is a non-toxic and environmentally friendly material, and also has great high temperature characteristics. Hence, LiFePO4 is considered as an excellent cathode material for lithium batteries. Currently, the average discharge voltage of the lithium batteries using LiFePO4 as a cathode material is 3.2˜3.4 V vs. Li+/Li.
A conventional structure of the Li-ion batteries comprises: a cathode, an anode, a separator, and a Li-containing electrolyte. The batteries perform the charge/discharge cycles by the lithium insertion and extraction mechanism, which is represented by the following equations (I) and (II).
Charge: LiFePO4−xLi+−xe−→xFePO4+(1−x)LiFePO4 (I)
Discharge: FePO4+xLi++xe→xLiFePO4+(1−x)FePO4 (II)
When a charge process of the batteries is performed, Li ions extract from the structure of LiFePO4; and the Li ions insert into the structure of FePO4 when a discharge process is performed. Hence, the charge/discharge process of the Li-ion batteries is a two-phase process of LiFePO4/FePO4.
Currently, the LiFePO4 powders are usually prepared by a solid-state process. However, the property of the product is highly related to the thermal-annealing temperature of the solid-state process. When the thermal-annealing temperature is below 700° C., all the raw materials have to be mixed well. If the raw materials are not mixed well, Fe3+ impurity phase will be present in the LiFePO4 powders. When thermal-annealing temperature is below 600° C., the average grain size of the LiFePO4 powders will be smaller than 30 μm. However, if the thermal-annealing temperature is increased, the average grain size of the LiFePO4 powders will be larger than 30 μm. When the average grain size of the LiFePO4 powders is larger than 30 μm, a grinding process and a sieving process have to be performed to obtain powders with specific grain size between μm to 10 μm, in order to be used for preparing Li-ion batteries. Hence, in the case that the LiFePO4 powders are prepared through a solid-state process, the grinding process and the sieving process have to be performed, which may increase the cost of the Li-ion batteries. In addition, the problem of large and non-uniform grain size of the LiFePO4 powders may also occur.
In addition, LiFePO4, LiMnPO4, LiNiPO4 and LiCoPO4 has olivine structure and similar theoretical specific capacities. But the theoretical voltage plateaus are different. For example, the voltage plateau of LiFePO4 is 3.4V, the voltage plateau of LiMnPO4 is 4.1V, the voltage plateau of LiCoPO4 is 4.8V, and the voltage plateau of LiNiPO4 is 5.6V. Although LiMnPO4, LiNiPO4 and LiCoPO4 has higher theoretical mass-energy density than LiFePO4, the conductivity of LiMnPO4, LiNiPO4 and LiCoPO4 is lower, and the ability for transferring lithium ions of LiMnPO4, LiNiPO4 and LiCoPO4 is also poor, resulting in the actual capacitance of the batteries using LiMnPO4, LiNiPO4 and LiCoPO4 is lower.
Therefore, it is desirable to provide a method for manufacturing micro-sized, submicro-sized, even nano-sized cathode materials of Li-ion batteries in a simple way, in order to increase the charge/discharge efficiency, mass-energy density of the batteries and reduce the cost thereof.
The object of the present invention is to provide metal (II) phosphate powders for manufacturing an electrode material (especially, a cathode material) of a Li-ion battery and a method for manufacturing the same, wherein the metal (II) phosphate powders have nano, micro, or sub-micro grain size and large length to thickness ratio, and can be applied to the current process for preparing lithium metal phosphate powders.
Another object of the present invention is to provide lithium metal phosphate powders for Li-ion batteries and a method for manufacturing the same, wherein the metal (II) phosphate powders of the present invention is used to manufacture the lithium metal phosphate powders. Hence, the thermal-annealed powders have uniform and small grain size in nano, micro, or sub-micro scale, so the grinding process and the sieving process can be omitted. Additionally, the obtained lithium metal phosphate powders have large length to thickness ratio, which can improve the charge/discharge efficiency of the Li-ion batteries.
To achieve the object, the method for manufacturing metal (II) phosphate powders of the present invention comprises the following steps: (A) providing a P-containing precursor solution, wherein the P-containing precursor solution comprises: a P-containing precursor, and a weakly alkaline compound; and (B) adding at least one metal (II) compound into the P-containing precursor solution to obtain metal (II) phosphate powders.
In addition, the present invention also provides metal (II) phosphate powders, which are prepared through the aforementioned method, to apply to prepare electrode materials for Li-ion batteries. The metal (II) phosphate powders for manufacturing the electrode materials of Li-ion of the present invention are represented by the following formula (I):
(Fe1-xMx)3(PO4)2.yH2O (1)
wherein M comprises at least one metal selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<x≤1, y is an integer of 0 to 8, the metal phosphate (II) powders are composed of plural flake powders, and the length of each of the flake powders is ranged from 50 nm to 10 μm.
In addition, the present invention also provides a method for manufacturing lithium metal phosphate powders for a Li-ion battery, wherein the aforementioned metal (II) phosphate powders are used as Fe-containing precursors. The method for manufacturing lithium metal phosphate powders of the present invention comprises the following steps: (a) providing the aforementioned metal (II) phosphate powders; (b) mixing the metal (II) phosphate powders with a Li-containing precursor to obtain mixed powders; and (c) heat-treating the mixed powders to obtain lithium metal phosphate powders.
When the aforementioned method for manufacturing lithium metal phosphate powders of the present invention is applied, the obtained lithium metal phosphate powders of the present invention are represented by the following formula (II):
LiFe1-aMaPO4 (II)
wherein M comprises at least one metal selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, 0.5<a≤1, the lithium metal phosphate powders are composed of plural flake powders, and the length of each of the flake powders is ranged from 50 nm to 10 μm.
The metal (II) phosphate powders for manufacturing electrode materials of Li-ion batteries of the present invention have uniform and small grain size in nano, micro, or sub-micro scale, and especially large length to thickness ratio. However, the grain size of the conventional metal (II) phosphate powders or the conventional ferrous phosphate precursors is large and non-uniform, so the thermal-annealing process (i.e. the heat-treating process) has to be performed for at least ten hours, in order to completely transform the metal (II) phosphate powders or the ferrous phosphate precursors into lithium metal phosphate or lithium iron phosphate. In addition, the grain size of the conventional thermal-annealed powders is usually large, so a grinding process and a sieving process have to be performed to obtain powders with specific size between 1 μm to 10 μm. However, the metal (II) phosphate powders of the present invention have uniform and small size, large length to thickness ratio, and specific shapes. Hence, the metal (II) phosphate powders can be completely transformed into lithium metal phosphate within several hours (less than 10 hours), so the time for the thermal-annealing process can be greatly reduced. In addition, the obtained lithium metal phosphate powders still have the similar size and the similar shape as those of the metal (II) phosphate powders after the thermal-annealing process, so the electrode materials of the Li-ion batteries can be obtained without performing the grinding process and the sieving process. Hence, when the metal (II) phosphate powders of the present invention are used to prepare lithium metal phosphate powders, the time for the thermal-annealing process can be reduced, and the grinding process and the sieving process can be omitted. Therefore, the cost for manufacturing the Li-ion batteries can be further reduced. In addition, the metal (II) phosphate powders of the present invention can be directly applied to the current production lines of lithium metal phosphate powders, so it is unnecessary to build new production lines for manufacturing lithium metal phosphate powders by use of the metal (II) phosphate powders of the present invention. Therefore, the cost for manufacturing the Li-ion batteries can be further reduced.
In the metal (II) phosphate powders or the lithium metal phosphate powders of the present invention, the flake powders are powders composed of independent flakes, flake powders that one end of each of the flake powders connects to each other, flake powders connecting to each other at the center of the flakes, or flake powders that one end of each of the flake powders connects to each other to form a connecting center. In one embodiment of the present invention, the flake powders are independent flakes. In another embodiment of the present invention, the flake powders connect to each other to form a connecting center.
Furthermore, in the metal (II) phosphate powders or the lithium metal phosphate powders of the present invention, the length of each of the flake powder may be ranged from 50 nm to 10 μm. For example, the length of each of the flake powder may be 50 nm˜10 μm, 50 nm˜5 μm, 50 nm˜3 μm, 50 nm˜2 μm, 50 nm˜1 μm, 50 nm˜900 nm, 50 nm˜800 nm, 50 nm˜700 nm, 50 nm˜600 nm, 50 nm˜500 nm, 50 nm˜400 nm, 50 nm˜300 nm, 100 nm-10 μm, 100 nm˜5 μm, 100 nm˜3 μm, 100 nm˜2 μm, 100 nm˜1 μm, 100 nm˜900 μm, 100 nm˜800 nm, 100 nm˜700 nm, 100 nm˜600 nm, 100 nm˜500 nm, 100 nm˜400 nm, 100 nm˜300 nm, 200 nm˜10 nm, 200 nm˜5 μm, 200 nm˜3 μm, 200 nm˜2 μm, 200 nm-1 μm, 200 nm˜900 nm, 200 nm˜800 nm, 200 nm˜200 nm, 200 nm˜600 nm, 200 nm˜500 nm, 200 nm˜400 nm, 200 nm˜300 nm, 300 nm˜10 μm, 300 nm˜5 μm, 300 nm˜3 μm, 300 nm˜2 μm, 300 nm-1 μm, 300 nm˜900 nm, 300 nm˜800 nm, 300 nm˜700 nm, 300 nm˜600 nm, 300 nm˜500 nm, 300 nm˜400 nm, 400 nm˜10 μm, 400 nm˜5 μm, 400 nm˜3 μm, 400 nm˜2 μm, 400 nm˜1 μm, 400 nm˜900 nm, 400 nm˜800 nm, 400 nm˜700 nm, 400 nm˜600 nm, or 400 nm˜500 nm.
In addition, in the metal (II) phosphate powders or the lithium metal phosphate powders of the present invention, the thickness of each of the flake powder may be ranged from 5 nm to 1 μm. For example, the thickness of each of the flake powder may be 5 nm˜1 μm, 5 nm˜900 nm, 5 nm˜800 nm, 5 nm˜700 nm, 5 nm˜600 nm, 5 nm˜500 nm, 5 nm˜400 nm, 5 nm˜300 nm, 5 nm˜200 nm, 5 nm˜150 nm, 5 nm˜140 nm, 5 nm˜130 nm, 5 nm˜120 nm, 5 nm˜110 nm, 5 nm˜100 nm, 5 nm˜90 nm, 5 nm˜80 nm, 5 nm˜70 nm, 5 nm˜60 nm, 5 nm˜50 nm, 5 nm˜40 nm, 5 nm˜30 nm, 5 nm˜25 nm, 5 nm˜20 nm, 5 nm˜15 nm, 5 nm-10 nm, 10 nm-1 μm, 10 nm˜900 nm, 10 nm˜800 nm, 10 nm˜700 nm, 10 nm˜600 nm, 10 nm˜-500 nm, 10 nm˜400 nm, 10 nm˜300 nm, 10 nm˜200 nm, 10 nm˜150 nm, 10 nm˜140 nm, 10 nm˜130 nm, 10 nm˜120 nm, 10 nm-110 nm, 10 nm˜100 nm, 10 nm˜90 nm, 10 nm˜80 nm, 10 nm˜70 nm, 10 nm˜60 nm, 10 nm˜50 nm, 10 nm˜40 nm, 10 nm˜30 nm, 10 nm˜25 nm, 10 nm˜20 nm, 10 nm˜15 nm, 15 nm-1 μm, 15 nm˜900 nm, 15 nm˜800 nm, 15 nm˜700 nm, 15 nm˜600 nm, 15 nm˜500 nm, 15 nm˜400 nm, 15 nm˜300 nm, 15 nm˜200 nm, 15 nm˜150 nm, 15 nm˜140 nm, 15 nm˜130 nm, 15 nm˜120 nm, 15 nm-110 nm, 15 nm˜100 nm, 15 nm˜90 nm, 15 nm˜80 nm, 15 nm˜70 nm, 15 nm˜60 nm, 15 nm˜50 nm, 15 nm˜40 nm, 15 nm˜30 nm, 15 nm˜25 nm, 15 nm˜20 nm, 20 nm˜1 μm, 20 nm˜900 nm, 20 nm˜800 nm, 20 nm˜700 nm, 20 nm˜600 nm, 20 nm˜500 nm, 20 nm˜400 nm, 20 nm˜300 nm, 20 nm˜200 nm, 20 nm˜150 nm, 20 nm˜140 nm, 20 nm˜130 nm, 20 nm˜120 nm, 20 nm˜110 nm, 20 nm˜100 nm, 20 nm˜90 nm, 20 nm˜80 nm, 20 nm˜70 nm, 20 nm˜60 nm, 20 nm˜50 nm, 20 nm˜40 nm, 20 nm˜30 nm, 30 nm-1 μm, 30 nm˜900 nm, 30 nm˜800 nm, 30 nm˜700 nm, 30 nm˜600 nm, 30 nm˜500 nm, 30 nm˜400 nm, 30 nm˜300 nm, 30 nm˜200 nm, 30 nm˜150 nm, 30 nm˜140 nm, 30 nm˜130 nm, 30 nm˜120 nm, 30 nm˜110 nm, 30 nm˜100 nm, 30 nm˜90 nm, 30 nm˜80 nm, 30 nm˜70 nm, 30 nm˜60 nm, 30 nm˜50 nm, 30 nm˜40 nm, 40 nm-1 μm, 40 nm˜900 nm, 40 nm˜800 nm, 40 nm˜700 nm, 40 nm˜600 nm, 40 nm˜500 nm, 40 nm˜400 nm, 40 nm˜300 nm, 40 nm˜200 nm, 40 nm˜150 nm, 40 nm˜140 nm, 40 nm˜130 nm, 40 nm˜120 nm, 40 nm˜110 nm, 40 nm˜100 nm, 40 nm˜90 nm, 40 nm˜80 nm, 40 nm˜70 nm, 40 nm˜60 nm, or 40 nm˜50 nm.
Moreover, in the metal (II) phosphate powders or the lithium metal phosphate powders of the present invention, the ratio of the length and the thickness of each of the flake powder may be in a range from 10 to 500. For example, the ratio of the length and the thickness of each of the flake powder may be 10˜500, 10˜400, 10˜300, 10˜200, 10˜150, 10˜130, 10˜100, 10˜90, 10˜80, 10˜70, 10˜60, 10˜50, 10˜40, 10˜30, 10˜20, 10˜15, 20˜500, 20˜400, 20˜300, 20˜200, 20˜150, 20˜130, 20˜100, 20˜90, 20˜80, 20˜70, 20˜60, 20˜50, 20˜40, 20˜30, 30˜500, 30˜400, 30˜300, 30˜200, 30˜150, 30˜130, 30˜100, 30˜90, 30˜80, 30˜70, 30˜60, 30˜50, 30˜40, 40˜500, 40˜400, 40˜300, 40˜200, 40˜150, 40˜130, 40˜100, 40˜90, 40˜80, 40˜70, 40˜60, 40˜50, 50˜500, 50˜400, 50˜300, 50˜200, 50˜150, 50˜130, 50˜100, 50˜90, 50˜80, 50˜70, or 50˜60.
Since the thickness of the metal (II) phosphate powders is in nano-scale, the thermal-annealing time for preparing the lithium metal phosphate powders can be greatly reduced and the grinding process and a sieving process can further be omitted. In addition, since the thickness of the lithium metal phosphate powders is also in nano-scale, the charge/discharge efficiency of the obtained Li-ion batteries can further be improved.
Furthermore, the metal (II) phosphate powders of the present invention are crystallized metal (II) phosphate powders, which may have a crystallization degree of more than 10%.
In the method for manufacturing metal (II) phosphate powders of the present invention, the metal (II) compound can be any metal salt containing Fe, Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and/or Nb. Preferably, the metal (II) compound is a sulfate, a carbonate, a nitrate, an oxalate, an acetate, a chlorite, a bromide, or an iodide of Fe, Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B or Nb. More preferably, the metal (II) compound is a sulfate, a carbonate, a nitrate, an oxalate, an acetate, a chlorite, a bromide, or an iodide of Fe, Mn, Co, Cu, Ni, Zn, or Mg. Hence, in one embodiment of the present invention, the M in the formula (I) can comprise at least one metal selected from the group consisting of Mn, Co, Cu, Ni, Zn, and Mg. In another embodiment of the present invention, the M in the formula (II) can comprise at least one metal selected from the group consisting of Mn, Co, Cu, Ni, Zn, and Mg.
In one embodiment of the present invention, the M in the formula (I) can be Mn, Co, Ni or Cu, and 0.6≤x≤1. In another embodiment of the present invention, the metal (II) phosphate powders may be represented by the following formula (I-1):
(Fe1-x1-x2Mnx1M′x2)3(PO4)2.yH2O (I-1)
wherein M′ comprises at least one metal selected from the group consisting of Co, Cu, Ni, Zn, and Mg, 0.2≤x≤0.8, 0.05≤x2≤0.4, 0.5<x1+x2≤1, and y is an integer of 0 to 8.
In one embodiment of the present invention, the M in the formula (II) can be Mn, Co, Ni or Cu, and 0.6≤a≤1. In another embodiment of the present invention, when M in the formula (II) is Mn, 0.5<a<1. For example, 0.5<a<0.99, 0.6≤a<1, or 0.6≤a<0.99. In another embodiment of the present invention, the lithium metal phosphate powders may be represented by the following formula (II-1):
LiFe1-a1-a2Mna1M′a2PO4 (II-1)
wherein M′ comprises at least one metal selected from the group consisting of Co, Cu, Ni, Zn, and Mg, 0.2≤a1≤0.8, 0.05≤a2≤0.4, and 0.5<a1+a2≤1.
The method for manufacturing metal (II) phosphate powders of the present invention may further comprise a step (c) after the step (b): washing the metal (II) phosphate powders. Herein, the metal (II) phosphate powders can be washed with ethanol, water, or a combination thereof. Preferably, the metal (II) phosphate powders are washed with deionized water. In addition, the method for manufacturing metal (II) phosphate powders of the present invention may further comprise a step (d) after the step (c): drying the obtained metal (II) phosphate powders. As the temperature of the drying process is increased, the time thereof can be reduced. Preferably, the metal (II) phosphate powders are dried at 40-120° C. for 10-120 hours. More preferably, the metal (II) phosphate powders are dried at 50-70° C. for 10-120 hours.
In the lithium metal phosphate powders of the present invention, the lithium metal phosphate powders of the present invention have olivine structures. In one embodiment of the present invention, the X-ray diffraction pattern of the obtained lithium metal phosphate powders can be consistent with the standard lithium metal phosphate. In another embodiment of the present invention, at least one peak in the X-ray diffraction pattern of the obtained lithium metal phosphate powders can be a little bit shifted compared with the standard lithium metal phosphate.
In one embodiment of the present invention, the X-ray diffraction pattern of the obtained metal (II) phosphate powders can be consistent with the standard metal (II) phosphate. In another embodiment of the present invention, at least one peak in the X-ray diffraction pattern of the obtained metal (II) phosphate powders can be a little bit shifted compared with the standard metal (II) phosphate.
Furthermore, in the methods for manufacturing the metal (II) phosphate powders, the P-containing precursor can be at least one selected from the group consisting of H3PO4, NaH2PO4, Na2HPO4, Mg3(PO4)2, and NH4H2PO4. Preferably, the P-containing precursor is H3PO4, NH4H2PO4, or a combination thereof.
In addition, in the methods for manufacturing the metal (II) phosphate powders of the present invention, the weakly alkaline compound may be at least one selected from the group consisting of Na2CO3, and NaHCO3. Preferably, the weakly alkaline compound is NaHCO3.
In the methods for manufacturing the lithium metal phosphate powders of the present invention, the Li-containing precursor may be at least one selected from the group consisting of LiOH, Li2CO3, LiNO3, CH3COOLi, Li2C2O4, Li2SO4, LiCl, LiBr, LiI, LiH2PO4, Li2HPO4, and Li3PO4. Preferably, the Li-containing precursor is LiOH, Li2SO4, LiH2PO4, or Li3PO4. More preferably, the Li-containing precursor is Li3PO4.
In addition, in the methods for manufacturing the lithium metal phosphate powders of the present invention, the metal (II) phosphate powders are mixed with the Li-containing precursor and a carbon-containing material to obtain mixed powders in step (b). In this case, the surfaces of the obtained lithium metal phosphate powders are coated with carbon, so the conductivity of the obtained lithium metal phosphate powders can further be increased. In addition, the carbon-containing material can also inhibit the growth of the lithium metal phosphate powders, so the size of the lithium metal phosphate powders can be kept small. Herein, the carbon-containing material can be any sugar such as sucrose, stearic acid, citric acid, lauric acid, polystyrene, polystyrene ball (PS ball), and also be vitamin C (L-ascorbate). In addition, the additional amount of the carbon-containing material can be 0.1-40 wt % of the weight of the obtained lithium metal phosphate powders. Preferably, the additional amount of the carbon-containing material is 2.5-30 wt % of the weight of the obtained lithium metal phosphate powders.
In the methods for manufacturing the lithium metal phosphate powders of the present invention, one or more types of the metal (II) phosphate powders can be used in the step (b). In one embodiment of the present invention, if lithium metal phosphate powders containing one metal is desired, one type of the metal (II) phosphate powders can be used in the step (b). In another embodiment of the present invention, if lithium metal phosphate powders containing two metals is desired, one type of the metal (II) phosphate powders containing two metals can be used in the step (b), or one type of the metal (II) phosphate powders containing one metal and another type of the metal (II) phosphate powders containing another metal can be used together in the step (b). However, the present disclosure is not limited thereto, and the use of the metal (II) phosphate powders can be adjusted according to the metals contained in the desired lithium metal phosphate powders.
In the methods for manufacturing the lithium metal phosphate powders of the present invention, the mixed powders can be heat-treated under an atmosphere or vacuum or with an introduced gas flow to obtain the lithium metal phosphate powders, in step (c). In one aspect, the mixed powders can be heat-treated under an introduced gas flow to obtain the lithium metal phosphate powders, and the pressure of the introduced gas flow was around 1 atm. In another aspect, a vacuum is created in the heat-treating tube, followed by introducing gas into the heat-treating tube, and then the heat-treating tube is sealed to undergo the heat-treating process to obtain the lithium metal phosphate powders, wherein the pressure in the heat-treating tube has to be keep less than 1 atm during the heat-treating process. In further another aspect, a vacuum is created in the heat-treating tube and sealed without introducing any gas, followed by undergoing the heat-treating procedure to obtain the lithium metal phosphate powders. Herein, the atmosphere or the introduced gas flow can be used as a protection gas or a reduction gas, which may comprise at least one selected from the group consisting of N2, H2, He, Ne, Ar, Kr, Xe, CO, methane, N2—H2 mixed gas, and a mixture thereof. Preferably, the protection gas or the reduction gas is N2, H2, Ar, Ar—H2 or N2—H2 mixed gas. More preferably, the protection gas or the reduction gas is N2—H2 or Ar—H2 mixed gas.
Furthermore, in the methods for manufacturing the lithium metal phosphate powders of the present invention, the mixed powders are heat-treated at 300-900° C., preferably. In addition, the mixed powders are preferably heat-treated for 1-20 hours. More preferably, the mixed powders are heat-treated at 500-860° C. for 2-10 hours.
The obtained lithium metal phosphate powders of the present invention can be used as electrode materials (for example, cathode materials) to prepare Li-ion batteries, through any conventional method in the art. Here, the method for manufacturing the Li-ion batteries is simply described, but the present invention is not limited thereto.
An anode and a cathode are provided. Herein, the anode can be a Li-plate or an anode made by a carbon material, which is prepared by coating an anode current collector with a carbon material, and then drying and pressing the carbon material to form an anode for the Li-ion battery. The cathode current collector is coated with a cathode active material (i.e. the lithium metal phosphate powders of the present invention), and then the cathode active material is dried and pressed to form a cathode for the Li-ion battery. Next, a separator is inserted between the cathode and the anode, a Li-containing electrolyte is injected, and then a Li-ion battery is obtained after an assembling process.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
The present invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
Analysis
The shapes of the metal (II) phosphate powders and the lithium metal phosphate powders obtained in the following examples (Ex) were observed with a scanning electron microscope (SEM) (Hitachi S-4000).
In addition, the metal (II) phosphate powders and the lithium metal phosphate powders obtained in the following examples were also examined with an X-ray diffraction microscope (Shimadzu 6000) to understand the crystal structure thereof. The X-ray diffraction pattern was collected by Cu Kα radiation, the 2θ-scanning angle is 15°-45°, and the scanning rate is 1°/min. The standards for X-ray examination are listed in the following Table 1.
Preparation of Metal (II) Phosphate Powders
Step I
H3PO4 and NaHCO3 were added into 500 ml of de-ionized water in a molar ratio of 1:3 to obtain a P-containing precursor solution, and the P-containing precursor solution was stirred for 30 min.
Step II
To prepare Mn3(PO4)2, MnSO4.5H2O was added into the obtained P-containing precursor solution, wherein a molar ratio of MnSO4.5H2O to H3PO4 was 3:2.
To prepare (Fe1-xMnx)3(PO4)2, MnSO4.5H2O and FeSO4.7H2O were added into the obtained P-containing precursor solution, wherein a molar ratio of a total amount of MnSO4.5H2O and FeSO4.7H2O to H3PO4 was 3:2, and a molar ratio of MnSO4.5H2O to FeSO4.7H2O was adjusted on the basis of the desired (Fe1-xMnx)3(PO4)2 shown in the following Table 2.
To prepare Fe3(PO4)2, FeSO4.7H2O was added into the obtained P-containing precursor solution, wherein a molar ratio of FeSO4.7H2O to H3PO4 was 3:2.
To prepare metal (II) phosphate powders containing two or more metals selected from the group consisting of Mn, Co, Ni, Cu, Cr, V, Mo, Ti, Zn, Zr, Tc, Ru, Rh, Pd, Ag, Cd, Pt, Au, Al, Ga, In, Be, Mg, Ca, Sr, B and Nb, two or more suitable metal (II) sulfates were used, wherein a molar ratio of a total amount of the used metal (II) sulfates to H3PO4 was 3:2, and a molar ratio between the used metal (II) sulfates are adjusted on the basis of the desired metal (II) phosphate powders shown in the following Table 2.
Step III
The obtained products in Step II were washed with de-ionized water and then collected with centrifugation for three times.
Step IV
The collected products in Step III were dried at 55° C. for 12 to 108 hr, and metal (II) phosphate powders shown in the following Table 2 were obtained.
The shapes of the metal (II) phosphate powders were observed by SEM, and the obtained were also examined with an X-ray diffraction microscope. The results are listed in the following Table 2.
In addition, the rate for adding MnSO4.5H2O into the P-containing precursor solution relates to the formation of Mn3(PO4)2.3H2O and Mn3(PO4)2.7H2O. When MnSO4.5H2O is added rapidly, more Mn3(PO4)2.3H2O is obtained. When MnSO4.5H2O is added slowly, more Mn3(PO4)2.7H2O is obtained. Furthermore, even though the collected products in Step III were dried at 55° C. for 12 to 108 hr, the water molecules in Mn3(PO4)2.7H2O cannot be removed completely. Thus, for preparing lithium metal phosphate powders, the thermal gravimetric analysis (TGA) is held to calculate the content of the water molecular in the manganese (II) phosphate.
Similarly, for other metal (II) phosphate with different crystals containing different amount of water molecules, TGA is also held to calculate the content of the water molecular in the metal (II) phosphate.
Furthermore, the rate for adding metal (II) sulfates into the P-containing precursor solution is also related to the thickness of the obtained metal (II) phosphate.
Preparation of Lithium Metal Phosphate Powders
Step A: Ball Milling Process
A-1: Preparation by One Metal (II) Phosphate Powder and Li3PO4
One metal (II) phosphate powder was used as a precursor, and mixed with Li3PO4 in a molar ratio of 1:1. In addition, 15 wt % of sugar or 6.5 wt % of polystyrene was also added in the mixture. The mixture was mixed with a 3D shaker containing 0.8 mm zirconia balls for 2 hr to obtain mixed powders.
A-2: Preparation by Two or More Metal (II) Phosphate Powder and Li3PO4
Two or more metal (II) phosphate powders was used as precursors, and mixed with Li3PO4, wherein a molar ratio of a total amount of the metal (II) phosphate powders to Li3PO4 was 1:1. In addition, 15 wt % of sugar or 6.5 wt % of polystyrene (PS) was also added in the mixture. The mixture was mixed with a 3D shaker containing 0.8 nm zirconia balls for 2 hr to obtain mixed powders.
In one example, 1 wt % of graphene oxide was also added as a carbon source into the mixture.
Step B: Heat Treating Process
The product obtained in Step A was thermal-annealed at 750° C., under a N2 gas flow (1 atm) for 3 hr. Finally, lithium metal phosphate powders coated with carbon and formed in flake shapes were obtained.
Alternatively, a vacuum is created in the heat-treating tube, followed by introducing N2 gas into the heat-treating tube, and then the heat-treating tube is sealed. The product obtained in Step A was thermal-annealed at 750° C. in the sealed heat-treating tube under N2 atmosphere for 3 hr. The pressure was kept under 1 atm during the heat-treating process. Finally, lithium metal phosphate powders coated with carbon and formed in flake shapes were obtained.
The shapes of the obtained lithium metal phosphate powders were observed by SEM, and the obtained were also examined with an X-ray diffraction microscope. The results are listed in the following Table 3.
According to the results of Examples 1 to 17, the meal (II) phosphate powders have small and uniform grain size. When these metal (II) phosphate powders are used as a precursor for preparing lithium ion phosphate powders, the time for the heat-treating process can be shortened. Hence, the cost for manufacturing the Li-ion batteries can be further reduced. In addition, the thermal-annealed lithium metal phosphate powders have similar shape to that of metal (II) phosphate powders, so the thermal-annealed lithium metal phosphate powders also have small and uniform grain size. Hence, the grinding process and the sieving process can be omitted during the process for preparing the cathode materials, so the cost of Li-ion batteries can be reduced. Furthermore, according to the results of Examples 18 to 29, the lithium metal phosphate powders of the present invention have nano, micro, or sub-micro grain size. When the lithium metal phosphate powders of the present invention are used as cathode materials of Li-ion batteries, the Li-ion batteries can exhibit uniform charging and discharging current, and excellent charge/discharge efficiency. Hence, not only the cost of the Li-ion batteries can be reduced, but also the charge/discharge time can be shortened and the capacity of the batteries can be further improved.
Preparation and Testing of Li-Ion Batteries
The Li-ion battery of the present invention was prepared through the conventional manufacturing method thereof. Briefly, PVDF, lithium metal phosphate powders of Examples 19 and 20, ZrO, KS-6 [TIMCAL] and Super-P [TIMCAL] were dried in a vacuum oven for 24 hr, and a weight ratio of lithium metal phosphate powders:PVDF:KS-6:Super-P was 85:10:3:2. Next, the aforementioned materials were mixed with a 3D miller containing NMP to obtain slurry. An Al foil was provided and coated with the slurry through a blade coating process, and then placed in a vacuum oven at 90° C. for 12 hr. The dried foil coated with the slurry was pressed by a roller, and cut into Φ13 mm circular plates.
Next, as shown in
The obtained Li-ion batteries prepared by lithium metal phosphate powders of Examples 19 and 20 were tested with automatic cell charge-discharge test system (AcuTech Systems BAT-750B).
In conclusion, the metal (II) phosphate powders of the present invention have thin thickness, and high length to thickness ratio. Hence, the time for preparing lithium metal phosphate powders can be greatly reduced. In addition, when the obtained lithium metal phosphate powders are further applied to prepare Li-ion batteries, the performance of the batteries can be greatly improved.
Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 100121234 A | Jun 2011 | TW | national |
This application is a continuation-in-part (CIP) of U.S. patent application for “Ferrous Phosphate Powders, Lithium Iron Phosphate Powders for Li-Ion Battery, and Methods for Manufacturing the Same”, U.S. application Ser. No. 15/853,579 filed Dec. 22, 2017, and the subject matter of which is incorporated herein by reference. U.S. application Ser. No. 15/853,579 filed December 22 is a continuation-in-part (CIP) of Ser. No. 14/705,618 filed May 6, 2015; U.S. application Ser. No. 14/705,618 filed May 6, 2015 is a continuation-in-part (CIP) of Ser. No. 14/057,372 filed Oct. 18, 2013; U.S. application Ser. No. 14/057,372 filed Oct. 18, 2013 is a continuation-in-part (CIP) of U.S. application Ser. No. 13/908,393 filed Jun. 3, 2013; and U.S. application Ser. No. 13/908,393 filed Jun. 3, 2013 is a continuation-in-part (CIP) of U.S. application Ser. No. 13/524,287 filed Jun. 15, 2012, which claims the benefits of the Taiwan Patent Application Serial Number 100121234, filed on Jun. 17, 2011.
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| Number | Date | Country | |
|---|---|---|---|
| 20180309129 A1 | Oct 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15853579 | Dec 2017 | US |
| Child | 16016968 | US | |
| Parent | 14705618 | May 2015 | US |
| Child | 15853579 | US | |
| Parent | 14057372 | Oct 2013 | US |
| Child | 14705618 | US | |
| Parent | 13908393 | Jun 2013 | US |
| Child | 14057372 | US | |
| Parent | 13524287 | Jun 2012 | US |
| Child | 13908393 | US |
