POSITIVE LMFP ELECTRODE COMPOSITE PARTICLES

Abstract

A positive LMFP electrode composite particle used in the positive electrode of a solid-state or semi-solid-state battery. The positive electrode composite particle comprises an LMFP particle and a conductive layer deposited on an outer surface of the LMFP particle. The conductive layer consists of a variety of carbon agglomerates or lithium-ion conductor particles. The carbon agglomerates are formed by a dehydration reaction of carbohydrates, water-soluble fibers, or amino acid polymers. The lithium-ion conductor particles are formed by a first oxide or phosphate capable of conducting lithium ions, or by a second oxide with a garnet or perovskite structure.

Description

AREA OF INVENTION

[0001] The invention relates to a positive electrode material for a battery and in particular to an LMFP composite particle for a positive electrode. BACKGROUND OF THE INVENTION

[0002] A typical battery comprises a positive and a negative electrode. The positive electrode, located inside the battery, is called the cathode. The positive electrode of a solid-state or semi-solid-state battery consists of a positive electrode substrate and a positive electrode mass layer. This positive electrode mass layer comprises a positive electrode mass and a multitude of positive electrode particles. The positive electrode particles must be either conductive or electrically conductive to allow free electrons to migrate through the positive electrode mass without dissipating too much energy due to internal resistance. The material of the positive electrode particles can be LMFP (lithium manganese iron phosphate), which produces a better operating voltage than LFP (lithium iron phosphate), releases a higher energy density, and is also cost-effective and hydrophobic.

[0003] However, LMFP exhibits poor charge and discharge rates, lower lithium-ion conductivity and electrical conductivity, and is prone to wear with prolonged battery use. Although many methods exist to increase the lithium-ion conductivity of positive electrode particles, the electrical conductivity remains insufficient for practical applications. SUMMARY OF THE INVENTION

[0004] To overcome the aforementioned shortcomings of the current state of the art, the object of the invention is to provide a positive LMFP composite electrode particle, wherein the LMFP particle is coated with a conductive layer to increase its overall performance. The cost of LMFP is lower than that of ternary oxide, and the charging and discharging performance of LMFP can be utilized in a specific range of applications. The conductive layer on the outer surface of the LMFP particle compensates for the lower conductivity of LMFP, and the LMFP particle is further coated with lithium-ion conductor particles to improve the overall lithium-ion conductivity and electrical conductivity, resulting in better battery performance. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 shows a cross-sectional view illustrating the structure of the composite particle of the positive electrode according to the invention. Fig. Figure 2 shows a schematic view illustrating an application of the invention. Fig. Figure 3 shows a schematic view illustrating the overall structure and a partial structure of the composite particle of the positive electrode of the invention. Fig. Figure 4 shows a schematic view illustrating the carbon-coated composite particle of the positive electrode of the invention. Fig. Figure 5 shows a schematic view illustrating the composite particle for the lithium ions of the invention. Fig. Figure 6 shows a schematic view illustrating the structure of a further embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0005] Referring to the Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5 to Fig. 6. The invention provides an LMFP composite particle for positive electrodes 200, which is used in a positive (+) electrode 100 of a solid-state or semi-solid-state battery. The positive electrode 100 comprises a positive electrode substrate 105 and a positive electrode mass layer 108, which is applied to the positive electrode substrate 105 (as shown in Figure 6). Fig. (2 shown). The positive electrode mass layer 108 comprises a variety of composite particles for positive electrodes 200 and a positive electrode mass 103 together with a binder. The weight fraction of the composite particles for positive electrodes 200 in the positive electrode mass layer 108 is 88 wt.% to 98 wt.%.

[0006] Referring to Fig. 1 Each of the composite particles for positive electrodes 200 comprises the following elements: An LMFP particle 121, wherein a D50 value (mean mass diameter, MMD) of the LMFP particle 121 is less than 1 µm. The LMFP particle 121 is a polymer made of monocrystalline materials or microcrystalline particles. The LMFP particle 121 is produced by LMFP (lithium manganese iron phosphate, LiMn₂). x Fe 1-x PO4, 0.1 ≤ x ≤ 0.8) or by LMFP doped with at least one metal.

[0007] A conductive layer 122 is applied to an outer surface of the LMFP particle 121. The conductive layer 122 comprises a variety of carbon agglomerates 123 and a variety of conductor particles for lithium ions 10 to increase the conductivity of the positive electrode composite particle 200. The carbon agglomerates 123 are formed from a carbon source that is added during the fabrication of the positive electrode composite particle 200.

[0008] Carbon agglomerates 123 are formed by an organic compound that can form carbons in a reducing atmosphere. The organic compound is selected from carbohydrates (such as monosaccharides, disaccharides, oligosaccharides, or polysaccharides), water-soluble fibers, and amino acid polymers.

[0009] Preferably, the organic compound is a compound comprising carbon, nitrogen, fluorine, phosphorus and sulfur, wherein nitrogen, fluorine, phosphorus and sulfur are added to the carbon by a reduction reaction, which increases the electrical conductivity of the composite positive electrode particle 200.

[0010] Preferably, the carbon agglomerates 123 are formed by a dehydration reaction of carbohydrates or by carbon skeletons and functional groups which are formed from a dehydration reaction of water-soluble fibers or from carbon skeletons with straight chains and side chains which contain dopants and are formed in a dehydration reaction of amino acid polymers (such as peptides).

[0011] Fig. Figure 6 shows a further embodiment of the invention, wherein the conductive layer 122 also comprises a plurality of conductive carbons 124 which are bonded to the carbon agglomerates 123 to enable electrons to flow across different carbon agglomerates 123, thereby increasing the electrical conductivity. The conductive carbons 124 are formed by at least one of the following materials: graphite, graphene, nanoscale amorphous carbons, and carbon nanotubes with a length of less than or equal to 1 µm.

[0012] The lithium-ion conductor particles 10 are distributed within the conductive layer 122, near an outer surface of the conductive layer 122, or near the outer surface of the LMFP particle 121. The thickness of the conductive layer 122 is less than or equal to 200 nm. The size of each lithium-ion conductor particle 10 is less than or equal to 200 nm.

[0013] Each of the lithium-ion conductor particles 10 is formed by a first oxide or phosphate, which can conduct lithium ions, or by a second oxide with a garnet or perovskite structure. The lithium-ion conductivity of the first oxide or phosphate is higher than 10. -5 S / cm (Siemens per centimeter). The first oxide or phosphate with lithium ion conductivity can be LATP (lithium aluminum titanium phosphate) with a NASICON structure (sodium (Na) superion conductor), LAGP (lithium aluminum germanium phosphate), or lithiophosphate (Li3PO4). The second oxide with the garnet or perovskite structure can be LLZO (Li7La3Zr2O). 12 The lithium ion conductor particle 10 can be made from lithium lanthanum zirconium oxide or LLTO (lithium lanthanum titanium oxide). It can also be formed by combining the above-mentioned materials in any desired ratio.

[0014] An outer surface of each of the lithium-ion conductor particles 10 is additionally coated with a borate layer 5 to cause the lithium-ion conductor particles 10 to form a multitude of composite lithium-ion conductor particles 101. The composite lithium-ion conductor particles 101 on the LMFP particle 121 form a continuous layered structure, a discontinuously distributed structure, or an island-like structure, which arises naturally during the manufacturing process.

[0015] During oxygen-free sintering for the production of the positive composite electrode particle 200, the conductivity of the lithium-ion conductor particles 10 is reduced due to the lithium deficiency caused by oxygen deprivation. Therefore, the borate layer 5 is applied to the outer surface of the lithium-ion conductor particles 10 and serves as a protective layer, preventing damage to the structure of the lithium-ion conductor particles 10.

[0016] Preferably, each of the conductor particles for lithium ions 10 consists of at least one of the following materials: LLZO (Li7La3Zr2O 12 ), Ga-LLZO (Gallium-doped LLZO), Cu-LLZO (Copper-doped LLZO), Ta-LLZO (Tantalum-doped LLZO), Sr-LLZO (Strontium-doped LLZO) and Al-LLZO (Aluminium-doped LLZO).

[0017] Preferably, each of the conductor particles for lithium ions 10 is encased by Cu a ,X b -LLZO is formed, which is LLZO doped with copper (Cu) and a metal X, where X is selected from gallium (Ga), tantalum (Ta), strontium (Sr), barium (Ba), and aluminum (Al), and a > 0 and b > 0. Preferably, a + b = 0.25 ~ 0.8 and a > 0.1. Doping the copper in the LLZO is technically difficult, but Cu a ,X b-LLZO can stabilize the overall structure, smooth the channels for lithium ions, and increase the sintering rate, thereby also reducing costs. It also reduces the production of lithium carbonate (Li2CO3) upon contact with air, which increases surface stability during sintering.

[0018] If each of the conductor particles for lithium ions 10 is formed by LAGP or LATP, the LAGP or LATP is produced from Li 1+x Al x A 2-x (PO4)3 or Li 1+x+y Al x A 2-x-y-z M y N z (PO4)3 selected where 0.1 ≤ x ≤ 0.8, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.2, A germanium (Ge) or titanium (Ti), M a trivalent cation (such as scandium cation (Sc) 3+ ), Yttrium cation (Y 3+ ), Gallium cation (Ga 3+ ), Indium cation (In 3+ ) or lanthanum cation (La 3+ )) and N a tetravalent cation (such as zirconium cation (Zr) 4+ ), silicon cation (Si 4+ ) or tin cation (Sn4+ )) is.

[0019] Referring to Fig. 4 is an outer surface of the positive electrode composite particle 200 coated with a carbon material to increase conductivity. The carbon material comprises a variety of first carbon nanotubes 40 and a variety of nanoscale amorphous carbons 45. The positive electrode composite particle 200 and the carbon material form a carbon-coated positive electrode composite particle 280.

[0020] The first carbon nanotubes 40 comprise a variety of short-chain carbon nanotubes 42 and a variety of long-chain carbon nanotubes 44. The length of each of the short-chain carbon nanotubes 42 is 0.2 µm to 1 µm. The length of each of the long-chain carbon nanotubes 44 is 1 µm to 3 µm. The weight ratio of the short-chain carbon nanotubes 42 to the weight of the long-chain carbon nanotubes 44 is 10:1 to 2:1. The weight ratio of the first carbon nanotubes 40 to the weight of the nanoscale amorphous carbons 45 is 1:1 to 1:10. Each of the nanoscale amorphous carbons 45 has a size of 10 nm to 40 nm. The ratio of the total weight of the first carbon nanotubes 30 and the nanoscale amorphous carbons 45 to the weight of the positive electrode composite particle 200 is less than or equal to 0.01; that is, the ratio is not higher than 1:100.

[0021] Different lengths of the first carbon nanotubes 40 form different strain planes on the positive electrode composite particle 200. The short-chain carbon nanotubes 42 are transversely connected between the lithium-ion conductor particles 10 and the LMFP particle 121. The long-chain carbon nanotubes 44 cover the positive electrode composite particle 200 to increase its structural strength. The positive electrode composite particle 200 covered by the first carbon nanotubes 40 forms a hairball-like structure.

[0022] The advantages of the first carbon nanotubes 40 are that lithium ions can be easily stabilized between them, thereby increasing lithium-ion conductivity. Electrons can also be easily stabilized between the carbon nanotubes 40, further increasing lithium-ion conductivity. This very high lithium-ion conductivity helps the entire battery charge and discharge quickly.

[0023] Preferably, the nanoscale amorphous carbons 45 are amorphous carbons of a Super P auxiliary. The first carbon nanotubes 40 and the nanoscale amorphous carbons 45 are also used as auxiliary materials. The nanoscale amorphous carbons 45 are present in the form of particles, which are present in the first carbon nanotubes 40 in the form of long strips. The nanoscale amorphous carbons 45 are filled into the gaps that arise in the intervening first carbon nanotubes 40 in order to transfer the electrical charge between the first carbon nanotubes 40 by bridging the gaps with the nanoscale amorphous carbons 45, which further increases the transmission efficiency of the electrical current.

[0024] In describing the invention, it is obvious that it can be varied in many ways. Such variations are not to be considered a departure from the spirit and scope of the invention, and all modifications that are obvious to a person skilled in the art are to fall within the scope of the following claims.

Claims

[1] A positive LMFP electrode composite particle; the positive electrode composite particle is used in a positive electrode of a solid-state or semi-solid-state battery; the positive electrode composite particle comprises: an LMFP particle; a conductive layer applied to an outer surface of the LMFP particle; and the conductive layer comprises a variety of carbon agglomerates as well as a variety of lithium ion conductor particles; wherein the carbon agglomerates are formed by a dehydration reaction of carbohydrates or by carbon skeletons and functional groups which are formed by a dehydration reaction of water-soluble fibers or by carbon skeletons with straight chains and side chains which contain dopants which are formed by a dehydration reaction of amino acid polymers; wherein the conductor particles for lithium ions are dispersed within the conductive layer or near an outer surface of the conductive layer or near the outer surface of the LMFP particle; and wherein each of the conductor particles for lithium ions consists of a first oxide or phosphate which can conduct lithium ions or of a second oxide with a garnet or perovskite structure. [2] The positive LMFP electrode composite particle according to claim 1, wherein the organic compound is selected from monosaccharide, disaccharide, oligosaccharide and polysaccharide. [3] The positive LMFP electrode composite particle according to claim 1, wherein a lithium ion conductivity of the first oxide or phosphate is higher than 10 -5S / cm (Siemens per centimeter) is; and the first oxide or phosphate is selected from LATP (lithium aluminum titanium phosphate) with a NASICON structure (sodium (Na) superion conductor), LAGP (lithium aluminum germanium phosphate) and lithiophosphate (Li3PO4). [4] The positive LMFP electrode composite particle according to claim 1, wherein the second oxide has the garnet or perovskite structure of LLZO (Li7La3Zr2O 12 , lithium lanthanum zirconium oxide) and LLTO (lithium lanthanum titanium oxide). [5] The positive LMFP electrode composite particle according to claim 1, wherein a D50 value (mean mass diameter, MMD) of the LMFP particle is less than 1 µm; and the LMFP particle is a polymer of monocrystalline materials or microcrystalline particles. [6] The positive LMFP electrode composite particle according to claim 1, wherein the LMFP particle is made of LMFP (lithium manganese iron phosphate, LiMn x Fe 1-xPO4, 0.1 ≤ x ≤ 0.8) or is formed with at least one metal-doped LMFP. [7] The positive LMFP electrode composite particle according to claim 1, wherein the carbon agglomerates are formed by a compound containing carbon, nitrogen, fluorine, phosphorus and sulfur; and the carbon is doped with nitrogen, fluorine, phosphorus and sulfur. [8] The positive LMFP electrode composite particle according to claim 1, wherein an outer surface of each of the lithium ion conductor particles is additionally coated with a borate layer to cause the lithium ion conductor particles to form a plurality of lithium ion composite particles; and the lithium ion composite particles on the LMFP particle form a continuous layered structure or a discontinuously distributed structure or an island-like structure. [9] The positive LMFP electrode composite particle according to claim 1, wherein the thickness of the conductive layer is less than or equal to 200 nm; and the size of each of the lithium ion conductor particles is less than or equal to 200 nm. [10] The positive LMFP electrode composite particle according to claim 1, wherein each of the conductor particles for lithium ions is formed from at least one of the following materials: LLZO (Li7La3Zr2O 12 ), Ga-LLZO (gallium-doped LLZO), Cu-LLZO (copper-doped LLZO), Ta-LLZO (tantalum-doped LLZO), Sr-LLZO (strontium-doped LLZO) and Al-LLZO (aluminium-doped LLZO). [11] The positive LMFP electrode composite particle according to claim 1, wherein each of the conductor particles for lithium ions is made of Cu a ,X b -LLZO is formed, which represents LLZO doped with copper (Cu) and a metal X, where X is selected from gallium (Ga), tantalum (Ta), strontium (Sr), barium (Ba) and aluminium (Al) and a>0 and b>0. [12] The positive LMFP electrode composite particle according to claim 11, wherein a+b=0.25~0.8 and a>0.

1. [13] The positive LMFP electrode composite particle according to claim 1, wherein each of the lithium ion conductor particles is formed from LAGP (lithium aluminum germanium phosphate) or LATP (lithium aluminum titanium phosphate); the LAGP or LATP is made of Li 1+x Al x A 2-x (PO4)3 or Li 1+x+y Al x A 2-x-y-z M y N z (PO4)3 selected where 0.1 ≤ x ≤ 0.8, 0 ≤ y ≤ 0.2, 0 ≤ z ≤ 0.2, A germanium (Ge) or titanium (Ti), M a trivalent cation and N a tetravalent cation. [14] The positive LMFP electrode composite particle according to claim 1, wherein an outer surface of the positive electrode composite particle is coated with a carbon material; and the carbon material comprises a plurality of first carbon nanotubes and a plurality of amorphous carbons on the nanoscale; and the size of each of the amorphous carbons is 10 nm to 40 nm on the nanoscale. [15] The positive LMFP electrode composite particle according to claim 14, wherein the first carbon nanotubes comprise a plurality of short-chain carbon nanotubes and a plurality of long-chain carbon nanotubes; a length of each of the short-chain carbon nanotubes is 0.2 µm to 1 µm; and a length of each of the long-chain carbon nanotubes is 1 µm to 3 µm.

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