A lithium cathode hybrid material and its preparation method

Abstract

The present invention discloses a lithium cathode hybrid material and a preparation method thereof, belonging to the field of cathode active materials for lithium-ion batteries. The lithium cathode hybrid material is composed of large cobaltate lithium particles doped with micron-scale spinel phases and coated with submicron-scale spinel phases, and small ternary particles coated with submicron-scale spinel phases. It is prepared by two methods. One is prepared by precursor doping and secondary coating, and the other is prepared by primary doping and secondary coating. The lithium cathode hybrid material has a high energy density and can be used in power lithium batteries, having a higher energy density than lithium iron phosphate, and at the same time having a long cycle life and good safety performance.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion battery positive electrode active materials, and relates to a layered structure power lithium positive electrode mixed material doped with a micron-sized spinel phase and coated with a submicron-sized spinel phase, and a preparation method thereof. Background Art

[0002] At present, the most commonly used cathode materials for consumer lithium batteries are lithium cobalt oxide and three-element (lithium nickel cobalt manganese oxide) materials. Both materials have layered structures. In comparison, lithium cobalt oxide has higher rate performance and three-element has better safety performance. Combining the characteristics of these two materials, mixed cathode materials of lithium cobalt oxide and three-element have appeared on the market. In recent years, with the continuous improvement of the energy density requirements for power lithium batteries, mixed materials of lithium cobalt oxide and three-element are expected to become high-end power lithium battery cathode materials, because the energy density of these two materials is higher than that of lithium iron phosphate, which is currently the most widely used. However, the cycle life and safety performance of these two materials are lower than that of lithium iron phosphate, and need to be improved through doping, coating and other methods.

[0003] Several patents (CN108091832A, CN108550791A, CN108550830A, CN114284499A) have proposed the technology of coating lithium battery positive electrode materials with spinel phase materials. This does not reduce the overall energy density of the material, because many types of spinel phase materials have electrochemical activity and can be directly used as lithium battery positive electrode materials, such as LiCo2O4, Li2MnO3, LiNi 0.5 Mn 1.5 O4、LiCo 0.5 Mn 1.5 O4, etc. Moreover, during high temperature and long cycle processes, the crystal structure of the spinel phase is more stable than the layered structure. As a coating layer, it can improve the overall cycle life and safety performance of the material. In addition, the crystal structure of the spinel phase is similar to the layered structure. As a coating layer, it can be tightly combined with the main body of the layered structure to generate a transition layer in which the crystal structure and element content are close to linear changes. However, the application of the spinel phase in these patents is limited to coating, and the thickness of the coating layer is nanometer level (≤100nm). Apple's patent (CN109715561B) proposes the chemical formula (v) [Li2MnO3] · (1-v) [Li α Co 1-σ Al σ O2], which contains Li2MnO3, but it does not indicate that Li2MnO3 is a spinel phase, nor does it indicate whether Li2MnO3 is introduced in the form of doping or coating. Summary of the invention

[0004] The object of the present invention is to provide a layered lithium cathode hybrid material doped with micron-sized spinel phase and coated with submicron-sized spinel phase, which can be used in power lithium batteries, has a higher energy density than lithium iron phosphate, and at the same time has a long cycle life and good safety performance.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A lithium cathode hybrid material, whose chemical formula is:

[0007] (1 - a)[Li b Mg c [Co 1-d-f Mn d Me f O 2-g F g ·a[Li u Sr v [Ni 1-w-x-y Co w Mn x Me y O 2-z F z ;

[0008] Wherein, [Li b Mg c [Co 1-d-f Mn d Me f O 2-g F g is the chemical formula of large cobalt lithium oxide particles doped with micron-sized spinel phase and coated with submicron-sized spinel phase. The Mg element occupies the Li position in the large cobalt lithium oxide particles, the Mn element occupies the Co position in the large cobalt lithium oxide particles, the Me element occupies the Co position in the large cobalt lithium oxide particles, the F element occupies the O position in the large cobalt lithium oxide particles, Me is at least one of Ni, Al, Ga, Y, La, Sm, Ti, Zr, V, P, 0.960 ≤ b ≤ 1.000, 0 < c ≤ 0.010, 0.002 ≤ d ≤ 0.007, 0 < f ≤ 0.025, 0 < g ≤ 0.030; [Li u Sr v [Ni 1-w-x-y Co w Mn x Me y O 2-z F zis the chemical formula of the ternary small particles coated with submicron spinel phase, where a is the mass percentage of the ternary small particles in the lithium cathode composite material, 0 < a ≤ 0.40, the Sr element occupies the Li site in the ternary small particles, Ni, Co, and Mn all occupy the transition metal sites in the ternary small particles, the Me element occupies the transition metal site in the ternary small particles, the F element occupies the O site in the ternary small particles, Me is at least one of Ni, Al, Ga, Y, La, Sm, Ti, Zr, V, P, 1.000 < u ≤ 1.010, 0 < v < 0.003, 0.050 ≤ w ≤ 0.200, 0.050 ≤ x ≤ 0.300, 0 ≤ y ≤ 0.020, 0 < z ≤ 0.030.

[0009] Furthermore, the particle size range of the large lithium cobaltate particles in the chemical formula is D0 > 6 μm, 15 ≤ D50 ≤ 20 μm, D100 < 60 μm. The large lithium cobaltate particles can be single crystals or aggregates. The diameter range of the micron-sized spinel phase doped in the lithium cobaltate large particles is 0.5 ≤ d1 ≤ 2.0 μm. This spinel phase is introduced in the form of micron-sized particles during the preparation process and also exists in the form of micron-sized particles in the finished product. The particle size range of the ternary small particles is D0 > 1 μm, 3 ≤ D50 ≤ 8 μm, D100 < 30 μm. The ternary small particles can be single crystals or aggregates. The diameter range of the submicron-sized spinel phase coating the large lithium cobaltate particles and the ternary small particles is 0.1 < d2 < 0.5 μm. This spinel phase is introduced in the form of submicron-sized particles during the preparation process and also exists in the form of submicron-sized particles in the finished product.

[0010] In order to prepare the above-mentioned lithium cathode composite material, the present invention adopts the following two process routes:

[0011] The first method for preparing the lithium cathode composite material is to prepare the composite lithium cathode material through precursor doping and secondary coating, including the following steps:

[0012] 1) Prepare a micron-sized spinel phase precursor containing Mn by the co-precipitation method, grind it to the submicron level, measure the particle size of the slurry with a nano particle size analyzer, dry the slurry and crush it, and then screen it to obtain a submicron-sized spinel phase precursor;

[0013] 2) Prepare a micron-sized lithium cobaltate precursor doped with Mn spinel phase and uniformly doped with Me by the co-precipitation method in a carbonate system, and obtain large cobalt tetroxide particles after calcining the lithium cobaltate precursor;

[0014] 3) Mix the large cobalt tetroxide particles, lithium source, and Me raw materials evenly, then carry out calcination, crushing, and screening to obtain micron-sized lithium cobaltate large particles doped with spinel phase;

[0015] 4) Prepare a ternary precursor with uniform doping of Me by the coprecipitation hydroxide system;

[0016] 5) Mix the ternary precursor, lithium source, and Me raw material evenly, calcine, crush, and screen to obtain ternary small particles;

[0017] 6) Mix the large particles of lithium cobaltate, ternary small particles, submicron spinel-phase precursor, lithium source, and Me raw material evenly, calcine, crush, and screen to obtain the lithium cathode composite material.

[0018] Further, the micron-scale spinel-phase precursor containing Mn in step 1) includes oxides, oxyhydroxides, hydroxides, carbonates, mixtures of hydroxides and carbonates, mixtures of hydroxides and oxyhydroxides, etc., and the Mn raw material is at least one of Mn chlorides, sulfates, acetates, oxalates, nitrates.

[0019] Further, the grinding solvent in step 1) is one of water, methanol, and ethanol.

[0020] Further, the Mn raw material used in step 2) is at least one of Mn chlorides, sulfates, acetates, oxalates, nitrates; the Me raw material is at least one of Me chlorides, sulfates, acetates, oxalates, nitrates, phosphates, fluorides.

[0021] Further, the feeding method adopted in the coprecipitation method of step 2) is the co-current method. By adjusting the feeding rate, pH, and ammonia content, the precipitate product contains a Mn-rich micro-region; the particle size range of the lithium cobaltate precursor is D0 > 5 μm, 15 ≤ D50 ≤ 18 μm, D100 < 40 μm.

[0022] Further, the lithium source in step 3) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, lithium fluoride; the Me raw material is at least one of Me oxides, carbonates, basic carbonates, acetates, oxalates, nitrates, phosphates, fluorides.

[0023] Further, in step 3), calcine in an air atmosphere, the calcination temperature range is 850 - 1100 °C, and the holding time is 5 - 20 hours; screen through a 300-mesh sieve.

[0024] Further, the Me raw material used in step 4) is at least one of Me chlorides, sulfates, acetates, oxalates, nitrates, phosphates, fluorides.

[0025] Further, in step 5), the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, and lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, and fluoride.

[0026] Further, in step 5), it is calcined in air or an oxygen-rich atmosphere, the calcination temperature range is 700 - 1000 °C, and the heat preservation duration is 1 - 10 hours; it is sieved through a 300-mesh sieve.

[0027] Further, in step 6), the lithium source is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, and lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, and fluoride.

[0028] Further, in step 6), it is calcined in an air atmosphere, the calcination temperature range is 500 - 1000 °C, and the heat preservation duration is 1 - 10 hours; it is sieved through a 300-mesh sieve.

[0029] The preparation method of the second lithium cathode composite material is to prepare the composite lithium cathode material through primary doping and secondary coating, including the following steps:

[0030] 1) Prepare a micron-sized spinel-phase precursor containing Mn by the coprecipitation method, grind it to the submicron level, measure the particle size of the slurry with a nano particle size analyzer, dry and crush the slurry, and sieve it to obtain a submicron-sized spinel-phase precursor.

[0031] 2) Prepare a cobalt lithium oxide precursor with uniformly doped Me by the coprecipitation method in a carbonate system, and obtain cobalt tetroxide particles after calcining the cobalt lithium oxide precursor.

[0032] 3) Mix the cobalt tetroxide particles, the micron-sized spinel-phase precursor, the lithium source, and the Me raw material evenly, calcine, crush, and sieve to obtain micron-sized spinel-phase doped cobalt lithium oxide large particles.

[0033] 4) Prepare a ternary precursor with uniformly doped Me by the coprecipitation method in a hydroxide system.

[0034] 5) Mix the ternary precursor, the lithium source, and the Me raw material evenly, calcine, crush, and sieve to obtain ternary small particles.

[0035] 6) Mix the cobalt lithium oxide large particles, the ternary small particles, the submicron-sized spinel-phase precursor, the lithium source, and the Me raw material evenly, calcine, crush, and sieve to obtain the lithium cathode composite material.

[0036] Further, the micron-sized spinel-phase precursor in step 1) includes oxides, oxyhydroxides, hydroxides, carbonates, hydroxide / carbonate mixtures, hydroxide / oxyhydroxide mixtures, etc.; the Mn raw material is at least one of Mn chloride, sulfate, acetate, oxalate, and nitrate.

[0037] Further, the grinding solvent in step 1) is one of water, methanol, and ethanol.

[0038] Further, the Me raw material used in step 2) is at least one of Me chloride, sulfate, acetate, oxalate, nitrate, phosphate, and fluoride.

[0039] Further, the particle size range of the lithium cobaltate precursor is D0 > 1 μm, 5 ≤ D50 ≤ 10 μm, and D100 < 40 μm.

[0040] Further, the lithium source in step 3) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, and lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, and fluoride.

[0041] Further, step 3) is calcined in an air atmosphere, the calcination temperature range is 850 - 1100 °C, the heat preservation duration is 5 - 20 hours; sieved through a 300-mesh sieve.

[0042] Further, the Me raw material used in step 4) is at least one of Me chloride, sulfate, acetate, oxalate, nitrate, phosphate, and fluoride.

[0043] Further, the lithium source in step 5) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, and lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, and fluoride.

[0044] Further, step 5) is calcined in an air or oxygen-rich atmosphere, the calcination temperature range is 700 - 1000 °C, the heat preservation duration is 1 - 10 hours; sieved through a 300-mesh sieve.

[0045] Further, the lithium source in step 6) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, and lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, and fluoride.

[0046] Further, step 6) is calcined in an air atmosphere, the calcination temperature range is 500 - 1000 °C, the heat preservation duration is 1 - 10 hours; sieved through a 300-mesh sieve.

[0047] The present invention proposes an improved method for simultaneous doping and coating with spinel. The spinel phases used for doping and coating can be the same or different. The innovation of the present invention lies in the design of the size of the spinel phase. The spinel phase for doping is micron-sized and embedded inside the large lithium cobaltate particles, while the spinel phase for coating is sub-micron-sized and embedded on the surfaces of the large lithium cobaltate particles and the ternary small particles. Figure 1 The cross-sectional schematic diagrams of the large lithium cobaltate particles doped with micron-sized spinel phase, the large lithium cobaltate particles coated with sub-micron-sized spinel phase, and the ternary small particles are shown. Among them, the large circle is the large lithium cobaltate particle, the small circle is the ternary small particle, the large rhombus is the spinel phase doped inside the large lithium cobaltate particle, and the small rhombus is the spinel phase coated on the surfaces of the large lithium cobaltate particle and the ternary small particle. During the charge and discharge process, the lattice expansion / contraction amount of the spinel phase is less than that of the layered structure, the structural stability is higher than that of the layered structure, and the cycle life and safety performance are also better. The cracks in the large lithium cobaltate particles have directions of spreading from the surface to the inside and from the internal defects to the outside. Coating only on the surface cannot fully exert the advantages of the spinel phase, and if the size of the spinel phase is too small, its ability to stabilize the structure, deflect or prevent cracks will also be weakened. Therefore, the doping of micron-sized spinel phase with sufficient size can inhibit the lattice distortion of the large lithium cobaltate particles, hinder the crack propagation inside the large particles, inhibit the cracking and fragmentation of the large particles, avoid exposing more fresh surfaces to be corroded by the electrolyte, and improve the cycle life and safety performance. During the high-voltage and high-temperature cycling process, the phase transformation failure of the layered structure mostly starts from the surface and usually transforms into an inactive spinel phase. The thickness of this failure layer can reach more than 100 nm. Therefore, it is considered that the spinel coating layer with a nanoscale thickness (<100 nm) is not sufficient to resist the surface layered structure failure, and sub-micron-sized spinel phase particles with a larger size are selected. At the same time, considering that if a spinel phase shell that completely covers the surface of the main body particles is prepared as in the existing patents (CN108091832A, CN108550791A), during the charge and discharge process, the lattice expansion / contraction amount of the spinel phase is less than that of the layered structure, and cracks may appear between the core and the shell, resulting in the separation of the core and the shell, the reduction of the lithium ion migration path, or the shell being cracked by the core, resulting in the cracking and peeling of the shell, and it cannot play the role of isolating the electrolyte and reducing electrochemical corrosion. Therefore, island coating with sub-micron-sized spinel phase is adopted to reduce the corrosion of the surface by the electrolyte and can also improve the cycle life and safety performance. The particle size of the sub-micron-sized spinel phase is smaller than that of the micron-sized spinel phase, and it is more evenly dispersed on the surfaces of the large and small particles, and the protection effect is better.

[0048] The mixed material of micron-sized spinel phase-doped and sub-micron-sized spinel phase-coated lithium cobaltate large particles and ternary small particles prepared by the above two process routes of the present invention has a high energy density, and its cycle life and safety performance are also improved. The cross-sectional SEM can observe the micron-sized spinel phase doped inside the lithium cobaltate large particles, such as Figure 2A and Figure 2B as shown BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a cross-sectional schematic diagram of micron-sized spinel phase-doped lithium cobaltate large particles, sub-micron-sized spinel phase-coated lithium cobaltate large particles and ternary small particles

[0050] Figures 2A-2B is the cross-sectional SEM image of the micron-sized Ni / Mn spinel phase-doped lithium cobaltate large particles in Example 5 DETAILED DESCRIPTION OF THE INVENTION

[0051] In order to make the above features and advantages of the present invention more obvious and understandable, the following specific examples are given and described in detail in conjunction with the accompanying drawings

[0052] The following gives three groups of examples and comparative examples, each group consists of two examples and one comparative example. The two examples respectively adopt a preparation method provided by the present invention, and the comparative example adopts a conventional preparation method

[0053] Example 1

[0054] The chemical formula of the mixed material of micron-sized spinel phase-doped and sub-micron-sized spinel phase-coated is 0.6[Li 0.960 Mg 0.010 [Co 0.973 Mn 0.002 Al 0.025 O 2.99 F 0.01 ·0.4[Li 1.000 Sr 0.002 [Ni 0.500 Co 0.200 Mn 0.300 O 2.99 F 0.01 , and is prepared by the first process route

[0055] The micron-sized Co / Mn spinel phase precursor is prepared by the coprecipitation carbonate system and ground by a nano mill to obtain a sub-micron-sized Co / Mn spinel phase precursor

[0056] Using the coprecipitation method in a carbonate system, a micron-sized lithium cobaltate large-particle precursor doped with Co / Mn spinel phase and uniformly doped with Al was prepared. After calcination, large particles of cobalt tetroxide were obtained. Weigh the masses of the above-mentioned cobalt tetroxide large particles, lithium carbonate, and basic magnesium carbonate according to the chemical formula. After mixing the materials evenly, calcine them in an air atmosphere and hold at 850 °C for 20 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain large particles of lithium cobaltate.

[0057] Using the coprecipitation method in a hydroxide system, a ternary precursor was prepared. Weigh the masses of the above-mentioned ternary precursor, lithium carbonate, and strontium carbonate according to the chemical formula. After mixing the materials evenly, calcine them in an air atmosphere and hold at 1000 °C for 1 hour. Crush the calcined material block and pass it through a 300-mesh sieve to obtain small ternary particles.

[0058] Mix the above-mentioned large particles of lithium cobaltate, small ternary particles, submicron Co / Mn spinel phase precursor, and lithium fluoride evenly according to the ratio in the chemical formula, and calcine them in an air atmosphere and hold at 1000 °C for 1 hour. Crush the calcined material block and pass it through a 300-mesh sieve to obtain a mixed material.

[0059] Example 2

[0060] The chemical formula of the mixed material with micron-sized spinel phase doping and submicron-sized spinel phase coating is 0.6[Li 0.960 Mg 0.010 [Co 0.973 Mn 0.002 Al 0.025 O 2.99 F 0.01 ·0.4[Li 1.000 Sr 0.002 [Ni 0.500 Co 0.200 Mn 0.300 O 299 F 0.01 , and it is prepared by the second process route.

[0061] Using the coprecipitation method in a carbonate system, a submicron Co / Mn spinel phase precursor was prepared from a part of the micron-sized Co / Mn spinel phase precursor ground by a nano mill.

[0062] Using the coprecipitation method in a carbonate system, a lithium cobaltate precursor uniformly doped with Al was prepared. After calcination, cobalt tetroxide particles were obtained. Weigh the masses of the above-mentioned cobalt tetroxide particles, micron-sized Co / Mn spinel phase precursor, lithium carbonate, and basic magnesium carbonate according to the chemical formula. After mixing the materials evenly, calcine them in an air atmosphere and hold at 850 °C for 20 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain large particles of lithium cobaltate.

[0063] The ternary precursor was prepared by a co-precipitation hydroxide system. The above ternary precursor, lithium carbonate, and strontium carbonate were mixed evenly and calcined in an air atmosphere at 1000 °C for 1 hour. The calcined material block was crushed and sieved through a 300-mesh sieve to obtain ternary small particles.

[0064] The above large lithium cobaltate particles, ternary small particles, sub-micron Co / Mn spinel phase precursor, and lithium fluoride were mixed evenly according to the ratio in the chemical formula and calcined in an air atmosphere at 1000 °C for 1 hour. The calcined material block was crushed and sieved through a 300-mesh sieve to obtain a mixed material.

[0065] Comparative Example 1

[0066] The chemical formula of the layered structure mixed material is 0.6[Li 0.960 Mg 0.010 [Co 0.973 Mn 0.002 Al 0.025 O 2.99 F 0.01 ·0.4[Li 1.000 Sr 0.002 [Ni 0.500 Co 0.200 Mn 0.300 O 2.99 F 0.01 , and it was prepared by a conventional process route.

[0067] A large lithium cobaltate precursor with uniformly doped Mn / Al was prepared by a co-precipitation carbonate system. After calcining the lithium cobaltate precursor, large cobalt tetroxide particles were obtained. The masses of the above cobalt tetroxide large particles, lithium carbonate, and basic magnesium carbonate were weighed according to the chemical formula. After mixing the materials evenly, they were calcined in an air atmosphere at 850 °C for 20 hours. The calcined material block was crushed and sieved through a 300-mesh sieve to obtain large lithium cobaltate particles.

[0068] The ternary precursor was prepared by a co-precipitation hydroxide system. The masses of the above ternary precursor, lithium carbonate, and strontium carbonate were weighed according to the chemical formula. After mixing the materials evenly, they were calcined in an air atmosphere at 1000 °C for 1 hour. The calcined material block was crushed and sieved through a 300-mesh sieve to obtain ternary small particles.

[0069] The large lithium cobaltate particles, ternary small particles, and lithium fluoride were mixed evenly according to the ratio in the chemical formula and calcined in an air atmosphere at 1000 °C for 1 hour. The calcined material block was crushed and sieved through a 300-mesh sieve to obtain a mixed material.

[0070] Example 3

[0071] The chemical formula of the mixed material doped with micron-sized spinel phase and coated with sub-micron-sized spinel phase is 0.7[Li1.000 Mg 0.005 [Co 0.981 Mn 0.007 Al 0.010 Ti 0.002 O 2.97 F 0.03 ·0.3[Li 1.010 Sr 0.001 [Ni 0.600 Co 0.100 Mn 0.298 Ti 0.010 O 2.97 F 0.03 , prepared by the first process route.

[0072] A micron-sized Mn spinel phase precursor was prepared by the coprecipitation carbonate system, and a submicron-sized Mn spinel phase precursor was obtained by grinding with a nano mill.

[0073] A large particle precursor of lithium cobaltate doped with a micron-sized Co / Mn spinel phase was prepared by the coprecipitation carbonate system, and large particles of cobalt tetroxide were obtained after calcination. Weigh the masses of the above-mentioned large particles of cobalt tetroxide, lithium hydroxide monohydrate, magnesium fluoride, and nano-aluminum oxide according to the chemical formula. After mixing the materials evenly, they were calcined in an air atmosphere and held at 1100 °C for 5 hours. The calcined material block was crushed and passed through a 300-mesh sieve to obtain large particles of lithium cobaltate.

[0074] A three-element precursor was prepared by the coprecipitation hydroxide system. Weigh the masses of the above-mentioned three-element precursor, lithium hydroxide monohydrate, strontium fluoride, and nano-titanium dioxide according to the chemical formula. After mixing the materials evenly, they were calcined in an oxygen-rich atmosphere (oxygen content 40%) and held at 800 °C for 6 hours. The calcined material block was crushed and passed through a 300-mesh sieve to obtain three-element small particles.

[0075] Mix the above-mentioned large particles of lithium cobaltate, three-element small particles, submicron-sized Mn spinel phase precursor, lithium fluoride, and nano-titanium dioxide evenly according to the ratio in the chemical formula, and calcine them in an air atmosphere and hold at 500 °C for 10 hours. The calcined material block was crushed and passed through a 300-mesh sieve to obtain a mixed material.

[0076] Example 4

[0077] The chemical formula of the mixed material doped with micron-sized spinel phase and coated with submicron-sized spinel phase is 0.7[Li 1.000 Mg 0.005 [Co 0.981 Mn 0.007 Al 0.010 Ti 0.002 O 2.97 F 0.03 ·0.3[Li1.010 Sr 0.001 [[Ni 0.600 Co 0.100 Mn 0.298 Ti 0.010 O 2.97 F 0.03 , prepared by adopting the second process route.

[0078] A micron-sized Mn, Co / Mn spinel phase precursor is prepared by the coprecipitation carbonate system, and a submicron-sized Mn spinel phase precursor is obtained by grinding with a nano mill.

[0079] A lithium cobaltate precursor is prepared by the coprecipitation carbonate system, and cobalt tetroxide particles are obtained after calcination. Weigh the masses of the above cobalt tetroxide particles, micron-sized Co / Mn spinel phase precursor, lithium hydroxide monohydrate, magnesium fluoride, and nano-aluminum oxide according to the chemical formula. After mixing the materials evenly, calcine them in an air atmosphere and hold at 1100 °C for 5 hours. The calcined material block is crushed and sieved through a 300-mesh sieve to obtain large lithium cobaltate particles.

[0080] A ternary precursor is prepared by the coprecipitation hydroxide system. Mix the above ternary precursor, lithium hydroxide monohydrate, strontium fluoride, and nano-titanium dioxide evenly, and calcine them in an oxygen-rich atmosphere (oxygen content 40%) and hold at 800 °C for 6 hours. The calcined material block is crushed and sieved through a 300-mesh sieve to obtain small ternary particles.

[0081] Mix the above large lithium cobaltate particles, small ternary particles, submicron-sized Mn spinel phase precursor, lithium fluoride, and nano-titanium dioxide evenly according to the ratio in the chemical formula, calcine them in an air atmosphere, and hold at 500 °C for 10 hours. The calcined material block is crushed and sieved through a 300-mesh sieve to obtain a mixed material.

[0082] Comparative Example 2

[0083] The chemical formula of the layered structure mixed material is 0.7[Li 1.000 Mg 0.005 [[Co 0.981 Mn 0.007 Al 0.010 Ti 0.002 O 2.97 F 0.03 ·0.3[Li 1.010 Sr 0.001 [[Ni 0.600 Co 0.100 Mn 0.298 Ti 0.010 O 2.97 F 0.03 , prepared by adopting the conventional process route.

[0084] A large-particle precursor of lithium cobaltate with uniform Mn doping was prepared by a coprecipitation method in a carbonate system. After calcining the lithium cobaltate precursor, large particles of cobalt tetroxide were obtained. Weigh the masses of the above-mentioned large particles of cobalt tetroxide, lithium hydroxide monohydrate, magnesium fluoride, and nano-aluminum oxide according to the chemical formula. After mixing the materials evenly, calcine them in an air atmosphere and keep them at 1100 °C for 5 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain large particles of lithium cobaltate.

[0085] A ternary precursor was prepared by a coprecipitation method in a hydroxide system. Weigh the masses of the ternary precursor, lithium hydroxide monohydrate, strontium fluoride, and nano-titanium dioxide according to the chemical formula. After mixing the materials evenly, calcine them in an oxygen-rich atmosphere (oxygen content 40%) and keep them at 800 °C for 6 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain small ternary particles.

[0086] Mix the large particles of lithium cobaltate, small ternary particles, lithium fluoride, and nano-titanium dioxide evenly according to the ratio in the chemical formula, calcine them in an air atmosphere, and keep them at 500 °C for 10 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain the mixed material.

[0087] Example 5

[0088] The chemical formula of the mixed material doped with micron-sized spinel phase and coated with submicron-sized spinel phase is 0.8[Li 0.980 Mg 0.003 [Co 0.978 Mn 0.005 Al 0.015 Ni 0.002 O 2.98 F 0.02 ·0.2[Li 1.005 Sr 0.002 [Ni 0.780 Co 0.100 Mn 0.100 Al 0.015 Zr 0.005 O 2.98 F 0.02 , and it is prepared by the first process route.

[0089] A micron-sized Ni / Mn spinel phase precursor was prepared by a coprecipitation method in a hydroxide system, and a submicron-sized Ni / Mn spinel phase precursor was obtained by grinding with a nano mill.

[0090] Using the coprecipitation method in a carbonate system, a large-sized precursor of lithium cobaltate doped with micron-sized Ni / Mn spinel phase and uniformly doped with Mg / Al was prepared. After calcination, large-sized cobalt tetroxide particles were obtained. Weigh the masses of the above-mentioned large-sized cobalt tetroxide particles and lithium carbonate according to the chemical formula. After mixing the materials evenly, calcine them in an air atmosphere and keep them at 1000 °C for 10 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain large-sized lithium cobaltate particles.

[0091] Using the coprecipitation method in a hydroxide system, a ternary precursor uniformly doped with Al was prepared. Weigh the masses of the above-mentioned ternary precursor, lithium hydroxide, strontium carbonate, and nano-zirconia according to the chemical formula. After mixing the materials evenly, calcine them in an oxygen atmosphere and keep them at 700 °C for 10 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain ternary small particles.

[0092] Mix the above-mentioned large-sized lithium cobaltate particles, ternary small particles, submicron-sized Ni / Mn spinel phase precursor, and lithium fluoride evenly according to the ratio in the chemical formula, and calcine them in an air atmosphere and keep them at 700 °C for 4 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain a mixed material. The cross-sectional SEM image of the large-sized lithium cobaltate particles doped with micron-sized Ni / Mn spinel phase is as Figures 2A-2B shown, Figure 2A which is a figure with a magnification of 5k, Figure 2B and this is a figure with a magnification of 50k, Figure 2B This is an amplification of Figure 2A the small particles within the white circle in

[0093] Example 6

[0094] The chemical formula of the mixed material doped with micron-sized spinel phase and coated with submicron-sized spinel phase is 0.8[Li 0.980 Mg 0.003 [Co 0.978 Mn 0.005 Al 0.015 Ni 0.002 O 2.98 F 0.02 ·0.2[Li 1.005 Sr 0.002 [Ni 0.780 Co 0.100 Mn 0.100 Al 0.015 Zr 0.005 O 2.98 F 0.02 , and it is prepared by the second process route.

[0095] A micron-sized Ni / Mn spinel-phase precursor was prepared by a co-precipitation hydroxide system, and a part of it was ground with a nano-grinder to obtain a submicron-sized Ni / Mn spinel-phase precursor.

[0096] A lithium cobaltate precursor uniformly doped with Mg / Al was prepared by a co-precipitation carbonate system, and cobalt tetroxide particles were obtained after calcination. According to the chemical formula, the masses of the above cobalt tetroxide particles, micron-sized Ni / Mn spinel-phase precursor, and lithium carbonate were weighed. After mixing the materials evenly, they were calcined in an air atmosphere and kept at 1000 °C for 10 hours. The calcined material block was crushed and passed through a 300-mesh sieve to obtain large lithium cobaltate particles.

[0097] A ternary precursor uniformly doped with Al was prepared by a co-precipitation hydroxide system. The above ternary precursor, lithium hydroxide, strontium carbonate, and nano-zirconia were mixed evenly and calcined in an oxygen atmosphere at 700 °C for 10 hours. The calcined material block was crushed and passed through a 300-mesh sieve to obtain small ternary particles.

[0098] The above large lithium cobaltate particles, small ternary particles, submicron-sized Ni / Mn spinel-phase precursor, and lithium fluoride were mixed evenly according to the ratio in the chemical formula and calcined in an air atmosphere at 700 °C for 4 hours. The calcined material block was crushed and passed through a 300-mesh sieve to obtain a mixed material.

[0099] Comparative Example 3

[0100] The chemical formula of the layered structure mixed material is 0.8[Li 0.980 Mg 0.003 [Co 0.978 Mn 0.005 Al 0.015 Ni 0.002 O 2.98 F 0.02 ·0.2[Li 1.005 Sr 0.002 [Ni 0.780 Co 0.100 Mn 0.100 Al 0.015 Zr 0.005 O 2.98 F 0.02 and was prepared by a conventional process route.

[0101] A large lithium cobaltate particle precursor uniformly doped with Ni / Mn / Mg / Al was prepared by a co-precipitation carbonate system, and large cobalt tetroxide particles were obtained after calcining the lithium cobaltate precursor. According to the chemical formula, the masses of the above large cobalt tetroxide particles and lithium carbonate were weighed. After mixing the materials evenly, they were calcined in an air atmosphere and kept at 1000 °C for 10 hours. The calcined material block was crushed and passed through a 300-mesh sieve to obtain large lithium cobaltate particles.

[0102] A ternary precursor with uniform Al doping was prepared by a co-precipitation hydroxide system. Weigh the masses of the above ternary precursor, lithium hydroxide, strontium carbonate, and nano-zirconia according to the chemical formula. After mixing the materials evenly, calcine them in an oxygen atmosphere and keep them at 700 °C for 10 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain ternary small particles.

[0103] Mix the above large lithium cobaltate particles, ternary small particles, and lithium fluoride evenly according to the ratio in the chemical formula, calcine them in an air atmosphere, and keep them at 700 °C for 4 hours. Crush the calcined material block and pass it through a 300-mesh sieve to obtain a mixed material.

[0104] In this invention, a soft-pack battery was used to evaluate the above novel mixed cathode material, and the results of the examples are shown in Table 1:

[0105] Table 1. Test results in 4.48V soft-pack batteries

[0106]

[0107] As can be seen from Table 1, compared with the mixed materials prepared by conventional methods, the mixed materials with micron-scale spinel phase doping and sub-micron-scale spinel phase coating have higher capacity, better high-temperature cycling, and high-temperature storage performance. The first preparation process has disadvantages in capacity but advantages in high-temperature cycling and storage; while the second preparation process has advantages in capacity but disadvantages in high-temperature cycling and storage. This is because the first preparation process uses large particle precursors to prepare large lithium cobaltate particles, and the second preparation process uses medium particle precursors to prepare large lithium cobaltate particles. Under the same sintering system, the particle size distribution of the large particles in the first preparation process is narrower than that in the second preparation process, and the specific surface area is smaller, which is not conducive to the exertion of capacity, but reduces the corrosion of the electrolyte. Therefore, the second preparation process can be used when capacity needs to be improved, and the first preparation process can be used when high-temperature cycling and storage performance need to be improved. Note: The chemical formula is the key factor determining the electrical performance of the soft-pack battery. The grading ratio of large and small particles will affect the compaction density of the positive electrode sheet, and then indirectly affect the electrical performance of the soft-pack battery. Therefore, the comparison of these two preparation processes can only be carried out within a group of samples with the same chemical formula and the same grading ratio.

[0108] Although the present invention has been disclosed as above by way of examples, it is not intended to limit the present invention. Any appropriate modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention shall be covered within the protection scope of the present invention. The protection scope of the present invention shall be defined by the claims.

Claims

1. A lithium cathode hybrid material, characterized in that, The chemical formula is: (1-a)[Li b Mg c [Co 1-d-f Mn d Me f O 2-g F g ·a[Li u Sr v [Ni 1-w-x-y Co w Mn x Me y O 2-z F z ; Among them, [Li b Mg c [Co 1-d-f Mn d Me f O 2-g F g is the chemical formula of large lithium cobaltate particles doped with micron-scale spinel phase and coated with sub-micron-scale spinel phase. The Mg element occupies the Li site in the large lithium cobaltate particles, the Mn element occupies the Co site in the large lithium cobaltate particles, the Me element occupies the Co site in the large lithium cobaltate particles, the F element occupies the O site in the large lithium cobaltate particles. Me is at least one of Ni, Al, Ga, Y, La, Sm, Ti, Zr, V, P. 0.960 ≤ b ≤ 1.000, 0 < c ≤ 0.010, 0.002 ≤ d ≤ 0.007, 0 < f ≤ 0.025, 0 < g ≤ 0.030; [Li u Sr v [Ni 1-w-x-y Co w Mn x Me y O 2-z F z is the chemical formula of small three-element particles coated with sub-micron-scale spinel phase. a is the mass percentage of the small three-element particles in the lithium cathode composite material. 0 < a ≤ 0.

40. The Sr element occupies the Li site in the small three-element particles, Ni, Co, and Mn all occupy the transition metal sites in the small three-element particles, the Me element occupies the transition metal site in the small three-element particles, the F element occupies the O site in the small three-element particles. Me is at least one of Ni, Al, Ga, Y, La, Sm, Ti, Zr, V, P. 1.000 < u ≤ 1.010, 0 < v < 0.003, 0.050 ≤ w ≤ 0.200, 0.050 ≤ x ≤ 0.300, 0 ≤ y ≤ 0.020, 0 < z ≤ 0.

030.

2. The lithium cathode hybrid material according to claim 1, wherein The particle size range of the large lithium cobalt oxide particles is D0 > 6μm, 15 ≤ D50 ≤ 20μm, D100 < 60μm. The large lithium cobalt oxide particles are single crystals or aggregates. The diameter range of the micron-sized spinel phase is 0.5 ≤ d1 ≤ 2.0μm; the particle size range of the ternary small particles is D0 > 1μm, 3 ≤ D50 ≤ 8μm, D100 < 30μm. The ternary small particles are single crystals or aggregates. The diameter range of the submicron-sized spinel phase is 0.1 < d2 < 0.5μm.

3. A method for preparing a lithium cathode hybrid material, characterized in that, It includes the following steps: 1) Prepare a micron-sized spinel phase precursor containing Mn by coprecipitation method, grind it to submicron size, measure the particle size of the slurry with a nano particle size analyzer, dry the slurry and crush it, and then screen it to obtain the submicron-sized spinel phase precursor; 2) Prepare a lithium cobalt oxide precursor doped with a micron-sized Mn-containing spinel phase and uniformly doped with Me in a carbonate system by coprecipitation method, and obtain large cobalt tetroxide particles after calcining the lithium cobalt oxide precursor; 3) Mix the large cobalt tetroxide particles, lithium source, and Me raw material evenly, then carry out calcination, crushing, and screening to obtain large lithium cobalt oxide particles doped with a micron-sized spinel phase; 4) Prepare a ternary precursor uniformly doped with Me in a hydroxide system by coprecipitation method; 5) Mix the ternary precursor, lithium source, and Me raw material evenly, calcine, crush, and screen to obtain ternary small particles; 6) Mix the large lithium cobalt oxide particles, ternary small particles, submicron-sized spinel phase precursor, lithium source, and Me raw material evenly, calcine, crush, and screen to obtain the lithium positive electrode composite material.

4. The method according to claim 3, wherein In step 1), the micron-sized spinel phase precursor containing Mn includes oxides, hydroxyoxides, hydroxides, carbonates, mixtures of hydroxides and carbonates, mixtures of hydroxides and hydroxyoxides, where the Mn raw material is at least one of Mn chlorides, sulfates, acetates, oxalates, nitrates; the grinding solvent is one of water, methanol, and ethanol.

5. The method according to claim 3, wherein The Mn raw material used in step 2) is at least one of Mn chloride, sulfate, acetate, oxalate, nitrate; the Me raw material is at least one of Me chloride, sulfate, acetate, oxalate, nitrate, phosphate, fluoride; the lithium source in step 3) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, fluoride; the Me raw material used in step 4) is at least one of Me chloride, sulfate, acetate, oxalate, nitrate, phosphate, fluoride; the lithium source in step 5) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, fluoride; the lithium source in step 6) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, fluoride.

6. The method according to claim 3, characterized in that In step 3), calcine in air atmosphere, the calcination temperature range is 850 - 1100 °C, and the heat preservation duration is 5 - 20 hours; sieve through a 300-mesh sieve; in step 5), calcine in air or oxygen-rich atmosphere, the calcination temperature range is 700 - 1000 °C, and the heat preservation duration is 1 - 10 hours; sieve through a 300-mesh sieve; in step 6), calcine in air atmosphere, the calcination temperature range is 500 - 1000 °C, and the heat preservation duration is 1 - 10 hours; sieve through a 300-mesh sieve.

7. A method for preparing a lithium cathode composite material, characterized in that, It includes the following steps: 1) Prepare a micron-sized spinel-phase precursor containing Mn by coprecipitation method, grind it to submicron size, measure the particle size of the slurry with a nano particle size analyzer, dry the slurry and crush it, and sieve it to obtain a submicron-sized spinel-phase precursor; 2) Prepare a lithium cobaltate precursor with uniform Me doping by coprecipitation method in carbonate system, and obtain cobalt tetroxide particles after calcining the lithium cobaltate precursor; 3) Mix the cobalt tetroxide particles, micron-sized spinel-phase precursor, lithium source and Me raw material evenly, calcine, crush, and sieve to obtain micron-sized spinel-phase doped lithium cobaltate large particles; 4) Prepare a ternary precursor with uniform Me doping by coprecipitation method in hydroxide system; 5) Mix the ternary precursor, lithium source and Me raw material evenly, calcine, crush, and sieve to obtain ternary small particles; 6) Mix the lithium cobaltate large particles, ternary small particles, submicron-sized spinel-phase precursor, lithium source and Me raw material evenly, calcine, crush, and sieve to obtain a lithium cathode composite material.

8. The method according to claim 7, characterized in that In step 1), the micron-sized spinel-phase precursor includes oxide, hydroxyoxide, hydroxide, carbonate, hydroxide / carbonate mixture, hydroxide / hydroxyoxide mixture; the Mn raw material is at least one of Mn chloride, sulfate, acetate, oxalate, nitrate; the grinding solvent is one of water, methanol, ethanol.

9. The method according to claim 7, wherein The Me raw material used in step 2) is at least one of Me chloride, sulfate, acetate, oxalate, nitrate, phosphate, fluoride; the lithium source in step 3) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, fluoride; the Me raw material used in step 4) is at least one of Me chloride, sulfate, acetate, oxalate, nitrate, phosphate, fluoride; the lithium source in step 5) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, fluoride; the lithium source in step 6) is at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium acetate, lithium oxalate, lithium fluoride; the Me raw material is at least one of Me oxide, carbonate, basic carbonate, acetate, oxalate, nitrate, phosphate, fluoride.

10. The method according to claim 7, wherein In step 3), calcine in an air atmosphere, the calcination temperature range is 850 - 1100 °C, and the heat preservation duration is 5 - 20 hours; sieve through a 300 - mesh sieve; in step 5), calcine in an air or oxygen - rich atmosphere, the calcination temperature range is 700 - 1000 °C, and the heat preservation duration is 1 - 10 hours; sieve through a 300 - mesh sieve; in step 6), calcine in an air atmosphere, the calcination temperature range is 500 - 1000 °C, and the heat preservation duration is 1 - 10 hours; sieve through a 300 - mesh sieve.

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