CN110649230B - Nanometer rivet core-shell structure anode material and preparation method thereof - Google Patents
Nanometer rivet core-shell structure anode material and preparation method thereof Download PDFInfo
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- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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Abstract
The invention discloses a nano rivet core-shell structure anode material, which comprises a particle unit formed by wrapping an inner core by an outer shell, wherein the inner core of the particle unit is a secondary spherical particle composed of lithium-containing multi-element transition metal oxide primary particles; the lithium-containing multi-element transition metal oxide primary particles are combined with each other through a nano lithium-containing oxide interstitial in gaps between the lithium-containing multi-element transition metal oxide primary particles; the invention can effectively inhibit the secondary particles of the anode material of the lithium ion battery from being pulverized along the interfaces among the primary particles, so that the lithium ion battery has high specific capacity, excellent cycle performance and safety performance, and can form the uniform anode material with the nano rivet core-shell structure and the electrochemical active coating layer.
Description
Technical Field
The invention relates to the technical field of lithium battery materials, in particular to a nano rivet core-shell structure anode material and a preparation method thereof.
Background
The increasing exhaustion of traditional energy sources makes the development and utilization of novel energy sources more and more interesting. The lithium ion battery has the outstanding advantages of high energy density, long cycle life, small self-discharge efficiency, no memory effect, good safety and the like as a green novel energy source, and is widely applied to the fields of electronic products, power automobile batteries and the like. Currently, lithium-containing multi-transition metal oxide materials are mainly spherical secondary particles grown by aggregation of primary particles due to the limitation of synthesis technology. The secondary spherical material is pulverized along the interfaces among the primary particles after long-term electrochemical circulation, so that the electric contact among the electrode materials is poor, the internal resistance is increased, and the capacity of the battery is attenuated prematurely. In addition, the high-nickel ternary material has the problems of high surface activity, instability in wet air and the like.
In order to solve the problems of material electrochemical performance attenuation and the like caused by cracking of ternary material particles, the surfaces of primary particles of the positive electrode material are respectively coated with acetylene black and carbon fibers in patent JP11329504A and EP2571083, so that cracks can be filled when secondary particles are cracked, the conductivity of the positive electrode material is continuously maintained, and the cycle performance of the positive electrode material is maintained. However, acetylene black or carbon fiber coated on the surface of the primary particles is only filled between the primary particles, and the acting force between the acetylene black or carbon fiber and the primary particles is small, so that the contact internal resistance can be reduced only after pulverization of the secondary particles, and pulverization of the secondary particles cannot be well inhibited.
In order to solve the problem of unstable surface of ternary materials, the current common improvement method is to coat the surface of the materials with a layer of inert substances such as MgO and TiO 2 、Al 2 O 3 (Ultrathin Al 2 O 3 Coatings for Improved Cycling Performance and Thermal Stability of LiNi 0.5 Co 0.2 Mn 0.3 O 2 Cathiode, material Electrochimica Acta (2016) 154-161 and patent "a lithium ion battery and its cathode material", publication No.: CN102332577 a), siO 2 (High-performance lithium ion batteries using SiO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 Microspheres as catheters Journal of Alloys and Compounds 709 (2017) 708-716), and the like. Most coating methods are directed at treating sintered materials, and because the coating process generally requires placing the sintered ternary materials in water or an organic solvent for treatment, secondary calcination is required, and a local spinel phase is inevitably generated in the calcination process, so that the material capacity is reduced, the circulation is poor, gas production is achieved, and the potential safety hazard of the battery is increased. In addition, the current coating method has a small coating amount and cannot performA uniform coating layer is formed, and the coating layer substance has no electrochemical activity and cannot have lithium ion deintercalation capability, so that the electrochemical performance of the positive electrode material is affected.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects in the prior art: the cathode material can effectively inhibit secondary particles of the cathode material of the lithium ion battery from being pulverized along the interfaces among primary particles, so that the lithium ion battery has high specific capacity, excellent cycle performance and safety performance, and can form a uniform nano rivet core-shell structure cathode material with an electrochemical active coating layer.
The technical scheme of the invention is as follows: the nanometer rivet core-shell structure anode material comprises a particle unit formed by wrapping an inner core by an outer shell, wherein the inner core of the particle unit is a secondary spherical particle composed of lithium-containing multi-element transition metal oxide primary particles; the lithium-containing multi-element transition metal oxide primary particles are combined with each other through a nano lithium-containing oxide interstitial in gaps between the lithium-containing multi-element transition metal oxide primary particles;
the chemical composition of the lithium-containing multi-element transition metal oxide primary particles is Li 1+a Ni b Co c A d M 1-b-c-d O 2 Wherein, -0.1 is less than or equal to 0.2,0 is less than or equal to b is less than or equal to 1,0 is less than or equal to c is less than or equal to 0.5, and 0 is less than or equal to d is less than or equal to 0.5; the A is Mn or Al; the M is one or more of Cr, mg, ga, ti, fe, cu, sb, sr, ca, K, na, sn, zn, V, sc;
the chemical composition of the nano lithium-containing oxide is Li e R f O g One or more of the following; wherein e+f× (valence of R) =2g; the R is selected from one or more of Nb, la, ag, in, te, hf, pb, ce, pr, nd, sm, eu, gd, ho, er, tm, yb;
the shell of the particle unit comprises at least one shell layer consisting of a crystalline phase material and/or an amorphous phase material;
the crystal phase material is selected from at least one of compounds shown in chemical formulas (I), (II), (III) and (IV):
Li 1+h Ni i Co j Mn 1-h-i O 2 （I）
wherein, -0.1 is less than or equal to h is less than or equal to 0.2, i is less than or equal to 0 and less than or equal to 1, and j is less than or equal to 0 and less than or equal to 0.5;
Li 1+m Mn 2 O 4+n （II）
wherein, -0.1 is more than or equal to m is less than or equal to 0.2, -0.14 is more than or equal to n is less than or equal to 0.5;
Li 1+p Ni 0.5 Mn 1.5 O 4+q （III）
wherein, -p is more than or equal to 0.1 and less than or equal to 0.2, -q is more than or equal to 0.14 and less than or equal to 0.5;
Li 1+t Fe 1-s Mn s PO 4 （IV）
wherein, -0.1 is less than or equal to t is less than or equal to 0.2, and s is less than or equal to 0 and less than or equal to 1;
the amorphous phase material is selected from at least one of compounds of chemical formulas shown in formulas (V) and (VI):
Li u Q v O w （V）
where u+v× (valence of Q) =2w;
Q x O y （VI）
wherein x× (valence of Q) =2y;
and Q is selected from one or more of Zr, ta, Y, sb, mo, pb, bi, W, sn, ga, cd, sc, ba, V, cr, ti, zn.
Concentration C of Ni in the shell layer Ni Shell and shell Concentration C less than Ni in the inner core Ni Nuclear The method comprises the steps of carrying out a first treatment on the surface of the Wherein C is Ni Shell and shell = (number of moles of Ni in shell/sum of number of moles of Ni and other metal elements in shell) ×100%, C Ni Nuclear = (sum of mole number of Ni in core/mole number of Ni and other metal elements in core) ×100%.
The particle size of the primary particles of the lithium-containing multi-element transition metal oxide is 50-1000nm, and the particle size of the secondary spherical particles is 0.5-50 mu m.
The shell thickness of the particle unit is 1-500nm, and the particle unit consists of 1-50 layers of shell layers.
The outer surface of the shell of the particle unit also comprises at least one surface protection layer, and the material of the surface protection layer comprises Al 2 O 3 、MgO、ZrO 2 、ZnO、Y 2 O 3 、Ta 2 O 5 、Cr 2 O 3 、Nb 2 O 5 、Mo 2 O 3 、V 2 O 5 、TiO 2 、Ga 2 O 3 、SrO、BaO、WO 2 、Sb 2 O 5 、SnO、CdO、Bi 2 O 3 At least one of PbO.
The preparation method of the nano rivet core-shell structure anode material comprises the following steps:
1) Stirring and mixing the multi-element transition metal precursor and an R element source or settling or adsorbing the R element source on the surface of the multi-element transition metal precursor to obtain a precursor P1;
2) Stirring and mixing the precursor P1 and the Q element source or settling or adsorbing the Q element source on the surface of the precursor P1 to obtain a precursor P2 coated with 1 layer of Q element source; or mixing the precursor P1 with a lithium source, sintering, and then stirring and mixing with a Q element source, or depositing or adsorbing the Q element source on the surface of the sintered material to obtain a precursor P2 coated with 1 layer of Q element source;
if multiple layers are required to be coated, stirring and mixing the precursor P2 and the Q element source or settling or adsorbing the Q element source on the surface of the precursor P2 to obtain a precursor P3 coated with 2 layers of Q element sources; the coating is repeated in this way, and a precursor P (n+1) of a coating n layers of Q element sources can be prepared, wherein n is more than or equal to 2;
3) Mixing the precursor P (n+1) with a T element source to obtain a precursor P (n+2);
4) And uniformly mixing the precursor P (n+2) with a lithium source, and sintering to obtain the nano rivet core-shell structure anode material.
The multi-element transition metal precursor consists of a plurality of transition metal compounds; the transition metal compound is one or more of oxide, hydroxide, oxyhydroxide and carbonate of transition metal;
the R element source is oxide, carbonate or hydroxide of element R, and R is one or more selected from Nb, la, ag, in, te, hf, pb, ce, pr, nd, sm, eu, gd, ho, er, tm, yb; the Q element source is oxide, carbonate or hydroxide of element Q, and the Q is one or more selected from Zr, ta, Y, sb, mo, pb, bi, W, sn, ga, cd, sc, ba, V, cr, ti, zn; the source of the element T is oxide, carbonate or hydroxide of the element T, and the T is one or more selected from Ni, co, mn, fe.
As optimization, the preparation method of the nano rivet core-shell structure anode material further comprises a step 5), specifically: and 4) sintering and coating at least one of the following surface protection layer materials on the surface of the nano rivet core-shell structure positive electrode material to prepare the nano rivet core-shell structure positive electrode material containing the protection layer: al (Al) 2 O 3 、MgO、ZrO 2 、ZnO、Y 2 O 3 、Ta 2 O 5 、Cr 2 O 3 、Nb 2 O 5 、Mo 2 O 3 、V 2 O 5 、TiO 2 、Ga 2 O 3 、SrO、BaO、WO 2 、Sb 2 O 5 、SnO、CdO、Bi 2 O 3 、PbO。
The lithium source is one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium nitrate and lithium acetate.
The sintering in the steps 2) and 4) is to sinter at 450-700 ℃ for 2-24 hours and then sinter at 700-1000 ℃ for 10-36 hours.
The beneficial effects of the invention are as follows: the lithium ion battery anode material with the nano rivet structure is obtained by a simple and easy-to-implement synthesis method, and the nano lithium-containing oxide which fills gaps among primary particles can effectively generate lattice deformation or dislocation, so that the deformation stress of the lithium ion battery anode material is eliminated, the pulverization of secondary particles of the lithium ion battery anode material along the interfaces among the primary particles can be effectively inhibited, and the lithium ion battery can have high specific capacity, excellent cycle performance and safety performance. By adopting the method provided by the invention, the lithium ion battery anode material with the nano rivet structure can be obtained, the secondary particles of the lithium ion battery anode material can be effectively restrained from being pulverized along the interfaces among primary particles, the transmission distance of lithium ions among the primary particles is reduced, the lithium ion battery can have high specific capacity, excellent cycle performance and safety performance, and meanwhile, a uniform core-shell structure with an electrochemical active coating layer is formed, so that the performance of the anode material is greatly improved, and the surface composite coating layer shell layer has good lithium ion transmission capability and effectively restrains surface side reactions, so that the discharge capacity, rate performance and cycle performance of the anode material are obviously improved.
Drawings
FIG. 1 is a topography of precursor P1 prepared in comparative example 1.
Fig. 2 is a topography of precursor P4 prepared in example 2.
Fig. 3 is a topography of precursor P5 prepared in example 3.
FIG. 4 is preparation 3 of example 1 # Topography of the sample.
FIG. 5 is preparation 5 of example 3 # Topography of the sample.
FIG. 6 is preparation 1 of comparative example 1 # Topography after sample charge-discharge cycle.
FIG. 7 is preparation 5 of example 3 # Topography after sample charge-discharge cycle.
FIG. 8 preparation 5 in example 3 # Transmission electron microscopy of the sample.
FIG. 9 preparation 5 of example 3 # Transmission electron microscopy of the sample.
FIG. 10 is a diagram of example 3, 5 # X-ray diffraction contrast plot of the sample.
FIG. 11 is a diagram of example 7, 9 # X-ray diffraction contrast plot of the sample.
Fig. 12 is an elemental distribution diagram of a cross section of precursor P5 particles prepared in example 3.
FIG. 13 is 5 prepared in example 3 # Elemental distribution map of sample particle cross-section.
Fig. 14 is a discharge graph of the positive electrode materials prepared in comparative example 1, example 1 and example 3.
Fig. 15 is a graph showing the rate performance of the positive electrode materials prepared in comparative example 1, example 1 and example 3.
Fig. 16 is a graph showing cycle performance of the positive electrode materials prepared in comparative example 1, example 1 and example 3.
Detailed Description
The present invention will be described in further detail with reference to the following specific examples, but the present invention is not limited to the following specific examples.
Unless otherwise indicated, all starting materials in the examples of the present application were purchased commercially.
The analytical method in the examples of the present application is as follows:
topography test analysis was performed using a scanning electron microscope S4800H produced by Hitachi, japan and a transmission electron microscope Tecnai F20 produced by FEI, netherlands.
Electrochemical performance test analysis was performed using the LAND electrochemical test system CT2001A manufactured by Wuhan Xinnuo electronics Inc.
The performance test method of the positive electrode material comprises the following steps:
uniformly mixing a positive electrode material, a conductive agent acetylene black and a binder polyvinylidene fluoride (PVdF) in a Nitrogen Methyl Pyrrolidone (NMP) solvent, wherein the mass ratio of the positive electrode material to the conductive agent to the binder is 85:10: and 5, coating the uniformly mixed slurry on an aluminum foil, and vacuum drying at 120 ℃ for 12 hours to obtain the anode of the lithium ion battery.
The pole piece is used as an anode, lithium metal is used as a cathode, 1mol/L solution of ethylene carbonate and dimethyl carbonate of lithium hexafluorophosphate is adopted as electrolyte, and a 20-micrometer-thick polyethylene and polypropylene composite material is adopted as a diaphragm to assemble the CR2032 button lithium ion battery. The assembled button cell is subjected to charge and discharge test, and the voltage range is 2.8-4.3 volts.
Comparative example 1
According to the mole ratio of Ni, co and Mn of 8:1:1, respectively weighing 232.63g,29.10g and 25.10g of nickel nitrate hexahydrate, cobalt nitrate hexahydrate and manganese nitrate tetrahydrate, and adding 500mL of water for dissolution. 1000mL of 5mol/L NaOH solution, and 1000mL of 2mol/L ammonia solution were prepared.
200mL of water is added into a reaction kettle protected by argon, the mixed solution, 5mol/L of NaOH solution and 2mol/L of ammonia water solution are added into the reaction kettle at the same time, and the final pH of the solution is controlled at 7-14. And after the sedimentation is finished, filtering and washing the sediment, and drying at 80 ℃ to obtain the precursor P1.
100g of the precursor P1 was weighed, and Li OH.H was weighed according to a molar ratio of the lithium source to the precursor P1 of 1.05 2 Mixing O47.71 g and the precursor P1 uniformly, sintering at 550 ℃ for 4 hours, and sintering at 850 ℃ for 12 hours to obtain the anode material LiNi 0.8 Co 0.1 Mn 0.1 O 2 Labeled 1 # 。
Comparative example 2
According to the mole ratio of Ni, co and Mn of 5:2:3 preparing a mixed solution, weighing 131.42g of nickel sulfate hexahydrate, cobalt sulfate heptahydrate and manganese sulfate monohydrate, 56.22g and 50.70g respectively, and adding 500mL of water for dissolution. 1000mL of a 4mol/L NaOH solution, and 1000mL of a 2mol/L ammonia solution were prepared.
200mL of water was added to the nitrogen-protected reactor, and the mixed solution was added to the reactor simultaneously with 4mol/L NaOH solution and 2mol/L ammonia solution, with the final pH of the solution being controlled at 11.5. And after the sedimentation is finished, filtering and washing the sediment, and drying at 80 ℃ to obtain a precursor P2.
The precursor P2 is weighed 50g according to the molar ratio of the lithium source to the precursor of 1.05:1 LiOH.H was weighed 2 Mixing 23.94g O with P2 precursor, sintering at 400 deg.c for 6 hr and 850 deg.c for 12 hr to obtain LiNi 0.5 Co 0.2 Mn 0.3 O 2 Material, designated 2 # 。
Example 1
Weighing precursor P1 g and Nb 10g 2 O 5 1.6g of the mixture is uniformly mixed to obtain a precursor P3; weighing 10g of the precursor P3, and weighing LiOH.H according to the molar ratio of the lithium source to the precursor P3 of 1.05 2 Mixing O4.56 g and precursor P3 uniformly, sintering at 650 ℃ for 6 hours, sintering at 900 ℃ for 12 hours to obtain the anode material,marked 3 # 。
Example 2
The precursor P3 was weighed 50g, 200mL of water was added thereto, and the mixture was stirred to form a dispersion. 1mol/L ammonia water solution is prepared. 11.32g of Zr (SO) 4 ) 2 .H 2 O, 60mL of water was added for dissolution.
Zr (SO) 4 ) 2 Adding the solution into the dispersion of the precursor P3, adjusting pH to 8.0 with ammonia water after the addition, filtering, washing with water for three times, and drying at 100deg.C to obtain surface-coated ZrO (OH) 2 Precursor P4 of (a).
10g of the P4 precursor is weighed, and the molar ratio of the lithium salt to the precursor is 1.2:1, weighing LiOH.H 2 Mixing O5.30 g and precursor P4, sintering at 600 deg.c for 6 hr and at 900 deg.c for 12 hr to obtain nanometer rivet structure nuclear LiNi 0.8 Co 0.1 Mn 0.1 O 2 The shell layer is Li 6 Zr 2 O 7 Is marked as 4 # 。
Example 3
Weighing 50g of the precursor P4 in the example 2, adding 200mL of water, and stirring to form a dispersion; 11.93g of Co (CH) 3 COO) 2 •4H 2 O, dissolved in 50mL of water. 4mol/L LiOH solution and 1mol/L ammonia solution were prepared.
Co (CH) 3 COO) 2 The solution was added to the dispersion of precursor P4 simultaneously with 4mol/L LiOH and aqueous ammonia to add Co (OH) 2 Settling on the surface of the precursor P4, controlling the settling pH value to be 12, filtering, washing with water, and drying at 100 ℃ to obtain the composite precursor P5.
50g of the P5 precursor is weighed, and the molar ratio of the lithium salt to the precursor is 1.2:1, weighing LiOH.H 2 Mixing 26.65g of O with the precursor P5 uniformly, sintering at 480 ℃ for 6 hours, and sintering at 950 ℃ for 12 hours to obtain the LiNi with the nano rivet structure as the core 0.8 Co 0.1 Mn 0.1 O 2 The shell layer is crystalline phase LiCoO 2 And amorphous phase Li 6 Zr 2 O 7 Is marked 5 # 。
Example 4
Weigh the sintered core-shell material 5 of example 3 # 50g, 100mL of water was added to form a suspension. Weighing Mg (CH) 3 COO) 2 •4H 2 O5.59 g was dissolved in 50mL of water to prepare a 1mol/L NaOH solution.
Mg (CH) 3 COO) 2 Slowly adding Mg (OH) into the suspension of the positive electrode material together with the NaOH solution 2 Settling on the surface of the positive electrode material, wherein the end point pH value is 11.5; after filtering and washing, calcining the material at 500 ℃ for 6 hours to obtain the LiNi with MgO coated on the surface and nano rivet structure as the core 0.8 Co 0.1 Mn 0.1 O 2 The shell layer is crystalline phase LiMn 2 O 4 And amorphous phase Li 6 Zr 2 O 7 Is marked as 6 # 。
Example 5
10g of precursor P2 was weighed, 100ml of deionized water was added thereto, and the mixture was stirred to form a dispersion. 1mol/L ammonia solution was prepared and 7.04g of TaCl was weighed 5 14mL deionized water was added for dissolution.
TaCl is added to 5 Adding the solution into the dispersion of the precursor P2, adjusting pH to 8.0-9.0 with ammonia water after the addition, filtering, washing with water for three times, and drying at 100deg.C to obtain surface-coated Ta (OH) 5 Is a precursor P6 of (a).
Weighing 10g of the precursor P6, and weighing LiOH.H according to the molar ratio of the lithium source to the precursor P6 of 1.2:1 2 Uniformly mixing O5.34 g with a precursor P6, sintering at 600 ℃ for 6 hours, and sintering at 850 ℃ for 12 hours to obtain the LiNi with the nano rivet structure 0.5 Co 0.2 Mn 0.3 O 2 Positive electrode material, designated 7 # 。
Example 6
The precursor P6 g was weighed, 200mL of water was added thereto, and the mixture was stirred to form a dispersion. 1mol/L ammonia water solution is prepared. 11.36g of Zr (SO) 4 ) 2 .H 2 O, 30mL of water was added for dissolution.
Zr (SO) 4 ) 2 Adding the solution into the dispersion of the precursor P6, and adjusting pH to 8 with ammonia water0, filtering, washing with water for three times, and drying at 100deg.C to obtain surface-coated ZrO (OH) 2 Is a precursor P7 of (a).
10g of the P7 precursor is weighed, and the molar ratio of the lithium salt to the precursor is 1.2:1, weighing LiOH.H 2 Mixing O5.31 g and precursor P7 uniformly, sintering at 600 deg.C for 6 hours, and sintering at 900 deg.C for 12 hours to obtain LiNi with nano rivet structure 0.5 Co 0.2 Mn 0.3 O 2 The shell layer is Li 6 Zr 2 O 7 Is marked 8 # 。
Example 7
Weighing 50g of the precursor P7 in example 6, adding 200mL of water, and stirring to form a dispersion; 14.32g Mn (CH) 3 COO) 2 •4H 2 O, dissolved in 60mL of water. 4mol/L LiOH solution and 1mol/L ammonia solution were prepared.
Mn (CH) 3 COO) 2 The solution was added to the dispersion of precursor P7 simultaneously with 4mol/L LiOH and aqueous ammonia to add Mn (OH) 2 Settling on the surface of the precursor P7, and controlling the settling pH value at 12. Filtering, washing with water, and drying at 100 ℃ to obtain the composite precursor P8.
50g of the P8 precursor is weighed, and the molar ratio of the lithium salt to the precursor is 1.1:1, weighing LiOH.H 2 24.40g of O and the precursor P8 are uniformly mixed, sintered for 6 hours at 500 ℃, and sintered for 12 hours at 950 ℃ to obtain the LiNi with the nano rivet structure as the core 0.5 Co 0.2 Mn 0.3 O 2 The shell layer is crystalline phase LiMn 2 O 4 And amorphous phase Li 6 Zr 2 O 7 Is marked 9 # 。
Example 8
Weigh the sintered core-shell material 9 of example 7 # 50g, 100mL of water was added to form a suspension. Weigh MgSO 4 •7H 2 O6.45 g was dissolved in 50mL of water to prepare a 1mol/L NaOH solution.
MgSO 4 Slowly add to 9 together with NaOH solution # In the suspension of (2), mg (OH) 2 Settling on the positive electrode materialThe material surface, the end point pH value is 11.5; after filtering and washing, calcining the material at 500 ℃ for 6 hours to obtain the LiNi with MgO coated on the surface and nano rivet structure as the core 0.5 Co 0.2 Mn 0.3 O 2 The shell layer is crystalline phase LiCoO 2 And amorphous phase Li 6 Zr 2 O 7 Is marked as 10 # 。
Performance testing
FIGS. 1 to 3 are morphology diagrams of the precursors prepared in comparative example 1, example 2 and example 3, from which it can be seen that the precursor materials are spherical with a diameter of 10 to 40. Mu.m; fig. 4 and 5 are graphs showing the morphology of the positive electrode materials prepared in comparative example 1 and example 3, from which it can be seen that the materials take on a spherical shape, and the morphology of the other materials is similar. It is clear from fig. 1 to 5 that the precursor and the positive electrode material prepared are spherical secondary particles having a particle diameter of about 10 μm, which particles consist of primary particles of 200 to 500 nm.
Fig. 6 and 7 are morphology diagrams of the positive electrode materials prepared in comparative example 1 and example 3 after charge and discharge cycles, and it can be seen from the diagrams that the secondary particles crack after the charge and discharge cycles of the positive electrode material # 1, while the secondary particles of the positive electrode material with the novel structure # 5 have better integrity and no cracking phenomenon after the charge and discharge cycles.
FIGS. 8 and 9 are projection electron microscope images of the core-shell material prepared in FIG. 5, from which LiNbO can be seen 3 The nanocrystalline gap filling forms a nano rivet structure between the primary particles, and more tiny crystallization areas and amorphous areas exist on the surface.
FIGS. 10 and 11 are respectively 5 in example 3 # Sample, example 7, 9 # X-ray diffraction contrast pattern of sample, XRD test result shows that 5 # The sample is alpha-NaFeO with space group of R-3m 2 A shaped lattice structure. 10 # The sample has a layered structure with a space group of R-3m and a spinel structure symbiotic structure of Fd-3 m.
FIG. 12 is a graph showing the elemental distribution of the cross-section of the precursor P5 particles prepared in example 3, showing that the concentration of Ni elements in the precursor prepared gradually decreases from the core to the shell, the content of Co elements in the shell is higher than that in the core, and the content of Co elements in the precursor is higher than that in the coreOn the right side of the highest concentration peak, the highest concentration peak of Zr element appears. The results indicate that the synthesized precursor is Ni as the core 0.8 Co 0.1 Mn 0.1 (OH) 2 The intermediate layer is ZrO (OH) 2 The outermost layer is Co (OH) 2 Is a shell-core-shell structure. FIG. 13 is 5 prepared in example 3 # The elemental distribution of the cross section of the sample particles is shown in the figure, and it can be seen from the figure that the Co element and Zr element are distributed without the occurrence of peaks with higher concentrations. Since the oxide precursor is decomposed during the high temperature sintering process and reacts to form crystalline phase LiCoO 2 And amorphous phase Li 6 Zr 2 O 7 Is a uniform mixing zone of the above-mentioned materials.
Fig. 14 to 16 are discharge curves, rate performance curves, and cycle performance curves of the positive electrode materials prepared in comparative example 1, example 2, and example 3, and discharge voltages were 4.3V to 2.8V. Compared with the prior art, the positive electrode material provided by the invention has the advantages that the pulverization of secondary particles is effectively inhibited to reduce the internal resistance, the surface composite coating layer has good lithium ion transmission capacity and effectively inhibits surface side reactions, and the discharge capacity, the multiplying power performance and the cycle performance of the positive electrode material are obviously improved.
The above is merely exemplary embodiments of the present invention, and the scope of the present invention is not limited in any way. All technical schemes formed by adopting equivalent exchange or equivalent substitution fall within the protection scope of the invention.
Claims (8)
1. The utility model provides a nanometer rivet core-shell structure positive electrode material, includes the granule unit that comprises the shell parcel kernel, its characterized in that:
the inner core of the particle unit is a secondary spherical particle composed of lithium-containing multi-element transition metal oxide primary particles; the lithium-containing multi-element transition metal oxide primary particles are combined with each other through a nano lithium-containing oxide interstitial in gaps between the lithium-containing multi-element transition metal oxide primary particles;
the chemical composition of the lithium-containing multi-element transition metal oxide primary particles is Li 1+a Ni b Co c A d M 1-b-c-d O 2 Wherein, -0.1 is less than or equal to 0.2, b is more than or equal to 0 and less than or equal to 1,c is more than 0 and less than or equal to 0.5, d is more than 0 and less than or equal to 0.5; the A is Mn or Al; the M is one or more of Cr, mg, ga, ti, fe, cu, sb, sr, ca, K, na, sn, zn, V, sc;
the chemical composition of the nano lithium-containing oxide is Li e R f O g One or more of the following; wherein e+f× (valence of R) =2g; the R is selected from one or more of Nb, la, ag, in, te, hf, pb, ce, pr, nd, sm, eu, gd, ho, er, tm, yb;
the shell of the particle unit comprises at least one shell layer consisting of a crystalline phase material and/or an amorphous phase material;
the crystal phase material is selected from at least one of compounds shown in chemical formulas (I), (II), (III) and (IV):
Li 1+h Ni i Co j Mn 1-h-i O 2 (I)
wherein, -0.1 is less than or equal to h is less than or equal to 0.2, i is less than or equal to 0 and less than or equal to 1, j is less than or equal to 0 and less than or equal to 0.5;
Li 1+m Mn 2 O 4+n (II)
wherein, -0.1 is more than or equal to m is less than or equal to 0.2, -0.14 is more than or equal to n is less than or equal to 0.5;
Li 1+p Ni 0.5 Mn 1.5 O 4+q (III)
wherein, -p is more than or equal to 0.1 and less than or equal to 0.2, -q is more than or equal to 0.14 and less than or equal to 0.5;
Li 1+t Fe 1-s Mn s PO 4 (IV)
wherein, -0.1 is less than or equal to t is less than or equal to 0.2, and s is less than or equal to 0 and less than or equal to 1;
the amorphous phase material is selected from at least one of compounds of chemical formulas shown in formulas (V) and (VI):
Li u Q v O w (V)
where u+v× (valence of Q) =2w;
Q x O y (VI)
wherein x× (valence of Q) =2y;
the Q is selected from one or more of Zr, ta, Y, sb, mo, pb, bi, W, sn, ga, cd, sc, ba, V, cr, ti, zn;
the outer surface of the shell of the particle unit is also covered byComprises at least one surface protection layer, wherein the material composition of the surface protection layer is Al 2 O 3 、MgO、ZrO 2 、ZnO、Y 2 O 3 、Ta 2 O 5 、Cr 2 O 3 、Nb 2 O 5 、Mo 2 O 3 、V 2 O 5 、TiO 2 、Ga 2 O 3 、SrO、BaO、WO 2 、Sb 2 O 5 、SnO、CdO、Bi 2 O 3 At least one of PbO;
the preparation method specifically comprises the following steps: 1) Stirring and mixing the multi-element transition metal precursor and an R element source or settling or adsorbing the R element source on the surface of the multi-element transition metal precursor to obtain a precursor P1;
2) Stirring and mixing the precursor P1 and the Q element source or settling or adsorbing the Q element source on the surface of the precursor P1 to obtain a precursor P2 coated with 1 layer of Q element source;
if multiple layers are required to be coated, stirring and mixing the precursor P2 and the Q element source or settling or adsorbing the Q element source on the surface of the precursor P2 to obtain a precursor P3 coated with 2 layers of Q element sources; the coating is repeated in this way, and a precursor P (n+1) of a coating n layers of Q element sources can be prepared, wherein n is more than or equal to 2;
3) Mixing the precursor P (n+1) with a T element source to obtain a precursor P (n+2);
4) And uniformly mixing the precursor P (n+2) with a lithium source, and sintering to obtain the nano rivet core-shell structure anode material.
2. The nano-rivet core-shell structured positive electrode material according to claim 1, wherein: concentration C of Ni in the shell layer Ni Shell and shell Concentration C less than Ni in the inner core Ni Nuclear The method comprises the steps of carrying out a first treatment on the surface of the Wherein C is Ni Shell and shell = (number of moles of Ni in shell/sum of number of moles of Ni and other metal elements in shell) ×100%, C Ni Nuclear = (sum of mole number of Ni in core/mole number of Ni and other metal elements in core) ×100%.
3. The nano-rivet core-shell structured positive electrode material according to claim 1, wherein: the particle size of the primary particles of the lithium-containing multi-element transition metal oxide is 50-1000nm, and the particle size of the secondary spherical particles is 0.5-50 mu m.
4. The nano-rivet core-shell structured positive electrode material according to claim 1, wherein: the shell thickness of the particle unit is 1-500nm, and the particle unit consists of 1-50 layers of shell layers.
5. The method for preparing the nano-rivet core-shell structure positive electrode material according to claim 1, which is characterized in that: the multi-element transition metal precursor consists of a plurality of transition metal compounds; the transition metal compound is one or more of oxide, hydroxide, oxyhydroxide and carbonate of transition metal.
6. The method for preparing the nano-rivet core-shell structure positive electrode material according to claim 1, which is characterized in that: the R element source is oxide, carbonate or hydroxide of element R, and R is one or more selected from Nb, la, ag, in, te, hf, pb, ce, pr, nd, sm, eu, gd, ho, er, tm, yb; the Q element source is oxide, carbonate or hydroxide of element Q, and the Q is one or more selected from Zr, ta, Y, sb, mo, pb, bi, W, sn, ga, cd, sc, ba, V, cr, ti, zn; the source of the element T is oxide, carbonate or hydroxide of the element T, and the T is one or more selected from Ni, co, mn, fe.
7. The method for preparing the nano-rivet core-shell structure positive electrode material according to claim 1, which is characterized in that: also comprises a step 5), which is specifically as follows: and 4) sintering and coating at least one of the following surface protection layer materials on the surface of the nano rivet core-shell structure positive electrode material to prepare the nano rivet core-shell structure positive electrode material containing the protection layer: al (Al) 2 O 3 、MgO、ZrO 2 、ZnO、Y 2 O 3 、Ta 2 O 5 、Cr 2 O 3 、Nb 2 O 5 、Mo 2 O 3 、V 2 O 5 、TiO 2 、Ga 2 O 3 、SrO、BaO、WO 2 、Sb 2 O 5 、SnO、CdO、Bi 2 O 3 、PbO。
8. The method for preparing the nano-rivet core-shell structure positive electrode material according to claim 1, which is characterized in that: the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium chloride, lithium nitrate and lithium acetate.
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| CN113054169A (en) * | 2021-02-02 | 2021-06-29 | 江汉大学 | Ternary cathode material and lithium ion battery |
| CN113233519B (en) * | 2021-07-13 | 2021-09-21 | 浙江帕瓦新能源股份有限公司 | Precursor of magnesium, antimony phosphate, aluminum and lithium phosphate co-modified high-nickel cobalt-free positive electrode material, preparation method of precursor and positive electrode material |
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