CN115763747A - Single-crystal ternary cathode material, manufacturing method thereof and lithium ion battery - Google Patents
Single-crystal ternary cathode material, manufacturing method thereof and lithium ion battery Download PDFInfo
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Abstract
The embodiment of the application provides a single crystal ternary cathode material and a manufacturing method thereof, and a lithium ion battery, which comprises the following steps: uniformly mixing a ternary precursor, a lithium salt and an additive, and performing primary roasting to obtain a primary material, wherein the additive at least comprises halogen anions X, namely the halogen anions X are introduced by using the primary roasting, and the primary material and the additive are uniformly mixed and subjected to secondary roasting to obtain a single crystal ternary cathode material, the additive at least comprises target cations Q with the ionic radius larger than or equal to a threshold value, namely the target cations Q with the larger ionic radius are introduced by using the secondary roasting, and enter crystal lattices to form surface coating, so that the formed single crystal ternary cathode material comprises the halogen anions X and the target cations Q, the crystal structure stability of the formed single crystal ternary cathode material is improved by using the halogen anions X and the target cations Q, and the transmission performance and the electrochemical performance of the single crystal ternary cathode material are finally improved.
Description
Technical Field
The invention relates to the field of batteries, in particular to a single crystal ternary cathode material, a manufacturing method thereof and a lithium ion battery.
Background
With the development of society, the increasing demand for energy and the continuous consumption of energy have prompted research on renewable energy sources. Among renewable energy sources, lithium ion batteries have the advantages of high volume/mass energy density, no memory effect, safety, environmental protection and the like, and are widely applied to the fields of electric automobiles, electronic equipment, energy storage and the like. The positive electrode material plays a crucial role in the composition of the individual components of a lithium ion battery.
In recent years, ternary positive electrode materials have received much attention from the industry because of their high specific discharge capacity, high energy density, and low cost. At present, most widely researched ternary cathode materials are secondary sphere polycrystalline materials formed by stacking and agglomerating primary particles, but the polycrystalline materials can generate phase change in the actual battery charging and discharging process, so that the performance of the battery is reduced rapidly. The single crystal ternary anode material has no crystal boundary and uniform stress distribution, so that the problems of a polycrystalline material can be avoided.
But the single crystal ternary cathode material manufactured currently has the defect of poor electrochemical performance.
Disclosure of Invention
In view of this, an object of the present invention is to provide a single crystal ternary cathode material, a method for manufacturing the same, and a lithium ion battery, which can manufacture a single crystal ternary cathode material having good transmission performance and electrochemical performance.
In order to achieve the purpose, the technical scheme is as follows:
the embodiment of the application provides a method for manufacturing a single crystal ternary cathode material, which comprises the following steps:
uniformly mixing a ternary precursor, a lithium salt and an additive, and roasting for the first time to obtain a first material, wherein the additive at least comprises halogen anions X;
and uniformly mixing the primary material and an additive, and roasting for the second time to obtain the single crystal ternary cathode material, wherein the additive at least comprises a target cation Q with the ionic radius larger than or equal to a threshold value, and the single crystal ternary cathode material at least comprises the halogen anion X and the target cation Q.
Optionally, the method further comprises:
forming a coating layer, wherein the coating layer coats the single crystal ternary cathode material and at least comprises a target cation Q.
Optionally, the additive is a lithium compound corresponding to the halide anion X.
Optionally, the additive is one or more of LiF, liCl, liBr, and LiI.
Optionally, the molar ratio of the halide anion X to the metal element in the ternary precursor is in the range of (0, 0.1).
Optionally, the element of the target cation Q is one or more of Sr, Y, ba, la, ce.
Optionally, the additive is one or more of an oxide, nitrate, sulfate, hydroxide, bicarbonate, and carbonate of the target cation Q.
Alternatively, the molar ratio of the target cation Q to the transition metal element in the primary charge is in the range of (0,0.05).
The embodiment of the application provides a single-crystal ternary cathode material which is characterized by comprising a matrix, wherein the matrix at least comprises a halogen anion X and a target cation Q;
the target cation Q is an ionic radius greater than or equal to a threshold value.
Optionally, the single crystal ternary positive electrode material further comprises a coating layer, wherein the coating layer at least comprises a target cation Q.
The embodiment of the application provides a lithium ion battery, which is characterized by at least comprising the single crystal ternary cathode material in the embodiment.
The embodiment of the application provides a method for manufacturing a single crystal ternary cathode material, which comprises the following steps: uniformly mixing a ternary precursor, a lithium salt and an additive, and performing primary roasting to obtain a primary material, wherein the additive at least comprises halogen anions X, namely the halogen anions X are introduced by using the primary roasting, and the primary material and the additive are uniformly mixed and subjected to secondary roasting to obtain a single crystal ternary cathode material, wherein the additive at least comprises target cations Q with the ionic radius larger than or equal to a threshold value, namely the target cations Q with the larger ionic radius are introduced by using the secondary roasting, so that the formed single crystal ternary cathode material comprises the halogen anions X and the target cations Q, the crystal structure stability of the formed single crystal ternary cathode material is improved by using the halogen anions X and the target cations Q, and the transmission performance and the electrochemical performance of the single crystal ternary cathode material are finally improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic flow chart illustrating a method for manufacturing a single crystal ternary cathode material according to an embodiment of the present disclosure;
FIG. 2 shows a schematic crystal structure diagram of a single-crystal ternary cathode material provided by an embodiment of the present application;
FIG. 3 shows a schematic scanning electron microscope of a single-crystal ternary cathode material provided by an embodiment of the present application;
fig. 4 shows an X-ray diffraction diagram of a single-crystal ternary cathode material provided in an embodiment of the present application.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways than those described herein, and it will be appreciated by those skilled in the art that the present application may be practiced without departing from the spirit and scope of the present application, and that the present application is not limited to the specific embodiments disclosed below.
With the development of society, the increasing demand for energy and the continuous consumption of energy are driving the research on renewable energy sources. Among renewable energy sources, lithium ion batteries are widely used in the fields of electric vehicles, electronic devices, energy storage and the like due to the advantages of high volume/mass energy density, no memory effect, safety, environmental protection and the like. The positive electrode material plays a crucial role in the composition of the individual components of a lithium ion battery.
In recent years, ternary positive electrode materials have received much attention from the industry because of their high specific discharge capacity, high energy density, and low cost. The most widely used ternary positive electrode material currently studied is a secondary spherical polycrystalline material formed by stacking and agglomerating primary particles, but the polycrystalline material has grain boundaries among the primary particles, which causes lithium ions (Li) + ) Transport is limited and during actual battery charging and discharging, the polycrystalline material undergoes phase changes, particularly those of the high nickel materials H2-H3, resulting in the formation of microcracks and severe lattice distortion. The formation of microcracks can disrupt the CEI solid electrolyte interface film, leading to more active site exposure, accelerating material deterioration, leading to faster degradation of the battery performance. The single crystal ternary anode material has no crystal boundary and uniform stress distribution, so that the formation of microcracks can be effectively relieved, and the problems of polycrystalline materials can be avoided.
One of the current methods for manufacturing the single crystal ternary cathode material is to grind and mix the novel efficient composite additive and the high nickel ternary precursor uniformly according to a certain proportion, place the mixture in a tube furnace, and obtain a single crystal type high nickel ternary intermediate with doped anions and cations by adopting a gradient calcination technology. And grinding and uniformly mixing the intermediate and a lithium source, and calcining the mixture in a tubular furnace for a period of time to finally prepare the highly monodisperse single crystal type high-nickel ternary cathode material.
However, in the manufacturing method, due to the simultaneous addition of the anion and cation dopants, mutual influence is easy to occur and the doping amount is difficult to control, so that the single crystal ternary cathode material manufactured at present has the defect of poor electrochemical performance.
Based on this, the embodiment of the application provides a method for manufacturing a single crystal ternary cathode material, which comprises the following steps: uniformly mixing a ternary precursor, a lithium salt and an additive, and performing primary roasting to obtain a primary material, wherein the additive at least comprises halogen anions X, namely the halogen anions X are introduced by the primary roasting, and the primary material and the additive are uniformly mixed and subjected to secondary roasting to obtain a single crystal ternary cathode material, the additive at least comprises target cations Q with the ionic radius larger than or equal to a threshold value, namely the target cations Q with the larger ionic radius are introduced by the secondary roasting, so that the formed single crystal ternary cathode material comprises the halogen anions X and the target cations Q, the crystal structure stability of the formed single crystal ternary cathode material is improved by the halogen anions X and the target cations Q, and the transmission performance and the electrochemical performance of the single crystal ternary cathode material are finally improved.
For better understanding of the technical solutions and effects of the present application, specific embodiments will be described in detail below with reference to the accompanying drawings.
Referring to fig. 1, a schematic flow chart of a method for manufacturing a single crystal ternary cathode material provided in an embodiment of the present application is shown, and the method includes the following steps:
s101, uniformly mixing the ternary precursor, the lithium salt and the additive, and roasting for the first time to obtain a primary material.
In the embodiment of the application, a ternary precursor, a lithium salt and an additive can be obtained, wherein the additive at least comprises halogen anions X, and the obtained ternary precursor, lithium salt and additive are uniformly mixed and subjected to primary roasting to obtain a roasted primary material.
Specifically, the ternary precursor can be obtained by adopting a hydroxide coprecipitation method, and the chemical molecular formula of the ternary precursor can be Ni a Co b Mn c (OH) 2 Wherein a is more than or equal to 0.50 and less than or equal to 0.95<b≤0.20，0<c is less than or equal to 0.30, a + b c =1, and the lithium salt can be Li 2 CO 3 Or LiOH. H 2 O, the molar ratio of Li element in lithium salt to total metal elements in the ternary precursor is 1.00-1.10.
In practical application, after primary roasting, the primary roasted crystals can be treated by cooling, crushing and sieving to obtain a primary material.
In the examples of the present application, a halogen anion X, which may be F, is introduced using an additive at the time of primary firing - 、Cl - 、Br - And I - And the halogen can enter the oxygen site of the single crystal ternary cathode material, as shown in fig. 2, namely, the halogen anion X can partially replace the oxygen ion, and compared with the oxygen ion, the halogen anion X has stronger electronegativity, and in the single crystal ternary cathode material, the bond energy of the formed transition metal-halogen (TM-X) bond is stronger than that of the transition metal-oxygen (TM-O) bond, so that the crystal structure stability of the single crystal ternary cathode material can be improved by using the formed TM-X bond.
Specifically, the molar ratio of the halogen anion X to the metal element in the ternary precursor is in the range of (0, 0.1), that is, the formation control of the single crystal ternary cathode material can be realized by controlling the proportion of the introduced halogen anion X.
In the embodiment of the application, the additive can be a lithium compound corresponding to the halogen anion X, and the lithium compound corresponding to the halogen anion X has a fluxing action, so that the growth of single crystal particles can be assisted, and the single crystallization degree of the single crystal ternary cathode material can be improved.
As an example, the additive may be one or more of LiF, liCl, liBr, and LiI.
In the embodiment of the application, the conditions for carrying out the primary roasting are that the primary roasting temperature is 700-1000 ℃, the primary roasting time is 8-20 h, the temperature rising rate is 2-10 ℃/min, and the roasting atmosphere is oxygen.
Specifically, after primary roasting, the chemical molecular formula of the primary material can be LiNi a Co b Mn c O 2-y/2 X y Wherein a is more than or equal to 0.50 and less than or equal to 0.95<b≤0.20，0<c≤0.30，a+b+c＝1，0<y<0.1。
And S102, uniformly mixing the primary material and the additive, and roasting for the second time to obtain the single crystal ternary cathode material.
In the embodiment of the application, a primary material introduced with halogen anions X is obtained after primary roasting, and the primary material and an additive are uniformly mixed and subjected to secondary roasting to obtain the single crystal ternary cathode material, wherein the additive at least comprises a target cation Q with the ionic radius larger than or equal to a threshold value.
In the embodiment of the application, when the secondary baking is performed, because the ionic radius of the target cations Q is large, part of the target cations Q can be doped into the crystal structure of the single crystal ternary cathode material, as shown in fig. 2, that is, part of the target cations Q enter the transition metal site of the single crystal ternary cathode material, the stability of the crystal structure of the single crystal ternary cathode material can be further improved, and part of the target cations Q are coated on the surface of the material in an oxide form, so that the stability of the single crystal ternary cathode under high voltage can be further improved.
Specifically, the threshold may be 0.08 nanometers (nm), i.e., the ionic radius of the target cation Q is greater than or equal to 0.8 angstroms.
In the embodiment of the present application, the element of the target cation Q may be one or more of Sr, Y, ba, la, ce, and the additive may be one or more of oxide, nitrate, sulfate, hydroxide, bicarbonate, and carbonate of the target cation Q.
As an example, the additive may be one or more of oxides, nitrates, sulfates, hydroxides, bicarbonates and carbonates of Sr, Y, ba, la, ce.
In the examples of the present application, the molar ratio of the target cation Q to the transition metal element in the primary charge is in the range of (0,0.05), that is, the formation control of the single-crystal ternary cathode material can be achieved by controlling the ratio of introduction of the target cation Q.
In practical application, after secondary roasting, the crystal after secondary roasting can be treated by cooling, roll-to-roll and sieving to obtain the single crystal ternary cathode material.
In the embodiment of the application, the conditions for carrying out the secondary roasting are that the secondary roasting temperature is 600-850 ℃, the secondary roasting time is 2-10 h, the temperature rising rate is 2-10 ℃/min, and the roasting atmosphere is oxygen.
Specifically, after the secondary roasting, the chemical molecular formula of the single crystal ternary cathode material can be Li (Ni) a Co b Mn c ) 1-d Q d O 2-y/2 X y Wherein a is more than or equal to 0.50 and less than or equal to 0.95<b≤0.20，0<c≤0.30，0<d<0.05，a+b+c+d＝1，0<y<0.1。
In the embodiment of the application, halogen anions X are introduced through primary roasting, and target cations Q are introduced through secondary roasting, so that the finally formed single crystal ternary cathode material at least comprises the halogen anions X and the target cations Q, namely, through twice roasting, the anion and cation co-doping of an oxygen site and a transition metal site is realized, and the stability of the lattice structure of the single crystal ternary cathode material is improved.
In the embodiment of the application, in the process of secondary roasting, because the ionic radius of the target cations Q is relatively large, besides entering the lattice structure of the single crystal ternary cathode material to improve the stability of the lattice structure, part of the target cations Q can form a coating layer on the surface of the single crystal ternary cathode material, that is, the target cations Q are doped and simultaneously realize surface coating on the single crystal ternary cathode material. Specifically, the coating layer may be an oxide of the target cation Q.
That is to say, the coating layer formed by the target cations Q can modify the surface state of the single crystal ternary cathode material, relieve the side reaction between the single crystal ternary cathode material and the electrolyte, improve the electrochemical performance of the single crystal ternary cathode material and improve the cycle performance of the single crystal ternary cathode material under high voltage.
Referring to fig. 3 and 4, fig. 3 is a Scanning Electron Microscope (SEM) schematic diagram of a single-crystal ternary cathode material provided in an embodiment of the present application, and fig. 4 is an X-ray diffraction (XRD) schematic diagram of a single-crystal ternary cathode material provided in an embodiment of the present application. From fig. 3, it can be seen that the single crystal ternary cathode material has good single crystallization degree, uniformly dispersed particles, and a coating substance on the surface. Fig. 4 shows that the crystallinity of the single-crystal ternary cathode material is good, the index of the single-crystal ternary cathode material is a hexagonal layered structure, and no obvious impurity phase is found.
The method for manufacturing the single crystal ternary positive electrode material provided in the embodiment of the present application is specifically described below by adjusting the introduced halogen anion X and target cation Q of the primary firing and the secondary firing and the firing conditions:
the first embodiment is to use a ternary precursor Ni 0.63 Co 0.07 Mn 0.30 (OH) 2 Lithium salt LiOH. H 2 Grinding O and additive LiF, and mixing completely, wherein LiOH & H 2 The molar ratio of Li in O to the total metal elements in the ternary precursor is 1.04, and the molar ratio of F in LiF to the total metal elements in the ternary precursor is 0.02. Roasting at 930 deg.c for 15 hr in oxygen atmosphere at a temperature of 3.0 deg.c/min, cooling, crushing and sieving to obtain the first material with chemical molecular formula LiNi 0.63 Co 0.07 Mn 0.30 O 1.99 F 0.02 . Mixing the first material with additive Y (OH) 3 Grinding and mixing evenly, wherein the molar ratio of Y in the additive to the total transition metal elements in the primary material is 0.01. Performing secondary roasting in an oxygen atmosphere, wherein the roasting temperature is 750 ℃, the roasting time is 5h, the heating rate is 5 ℃/min, after the roasting is finished, cooling, roll-to-roll and sieving are performed to obtain the ternary single crystal anode material, the surface coating substance of the material is yttrium oxide, and the chemical molecular formula of the material is Li (Ni) 0.63 Co 0.07 Mn 0.30 ) 0.99 Y 0.01 O 1.99 F 0.02 。
The second example is to use a ternary precursor Ni 0.68 Co 0.05 Mn 0.27 (OH) 2 、LiOH·H 2 Grinding and fully mixing O and LiCl, wherein LiOH & H 2 The molar ratio of Li in O to the total metal elements in the ternary precursor was 1.02, and the molar ratio of Cl in LiCl to the total metal elements in the ternary precursor was 0.04. Roasting at 920 deg.C for 13 hr under oxygen atmosphere at a temperature of 2.5 deg.C/min, cooling, pulverizing, and sieving to obtain primary material with chemical formula LiNi 0.68 Co 0.05 Mn 0.27 O 1.98 Cl 0.04 . Mixing the primary material with additive La (NO) 3 ) 3 Grinding and fully mixing uniformly, wherein the molar ratio of La in the additive to the total transition metal elements in the primary material is 0.03. Carrying out secondary roasting in an oxygen atmosphere, wherein the roasting temperature is 820 ℃, the roasting time is 4h, the heating rate is 5 ℃/min, cooling, roll-to-roll and sieving are carried out after the roasting is finished, and the ternary single crystal anode material is obtained, wherein a coating substance on the surface of the material is a lanthanum oxide compound, and the chemical molecular formula of the material is Li (Ni) 0.68 Co 0.05 Mn 0.27 ) 0.97 La 0.03 O 1.98 Cl 0.04 。
The third embodiment is to use ternary precursor Ni 0.75 Co 0.05 Mn 0.20 (OH) 2 、LiOH·H 2 Grinding O and LiBr, mixing well, wherein LiOH & H 2 The molar ratio of Li in O to the total metal elements in the ternary precursor is 1.01, and the molar ratio of Br in LiBr to the total metal elements in the ternary precursor is 0.03. Roasting at 900 deg.c for 10 hr in oxygen atmosphere at a temperature of 3.0 deg.c/min, cooling, crushing and sieving to obtain the first material with chemical molecular expression LiNi 0.75 Co 0.05 Mn 0.20 O 1.985 Br 0.03 . Mixing the primary material with an additive BaSO 4 Grinding, and mixing completely, wherein the molar ratio of Ba in the additive to the total transition metal elements in the primary material is 0.02. In an oxygen atmosphereSecondary roasting is carried out, the roasting temperature is 680 ℃, the roasting time is 8h, the heating rate is 5 ℃/min, after the roasting is finished, a ternary monocrystal anode material is obtained through cooling, roll aligning and sieving, a surface coating substance of the material is a barium-oxygen compound, and the chemical formula of the material is Li (Ni) 0.75 Co 0.05 Mn 0.20 ) 0.98 Ba 0.02 O 1.985 Br 0.03 。
The fourth embodiment is to use a ternary precursor Ni 0.80 Co 0.01 Mn 0.10 (OH) 2 、LiOH·H 2 Grinding O, liF and LiI, and mixing well, wherein LiOH & H 2 The molar ratio of Li in O to the total metal elements in the ternary precursor is 1.01, the molar ratio of F in LiF to the total metal elements in the ternary precursor is 0.001, and the molar ratio of I in LiI to the total metal elements in the ternary precursor is 0.001. Roasting at 860 deg.c for 12 hr in oxygen atmosphere at a heating rate of 3.0 deg.c/min, cooling, crushing and sieving to obtain the first material with chemical molecular expression LiNi 0.80 Co 0.10 Mn 0.10 O 1.99 F 0.005 I 0.005 . Mixing the primary material with SrCO as additive 3 Grinding and mixing evenly, wherein the mol ratio of Sr in the additive to the total transition metal elements in the primary material is 0.01. Carrying out secondary roasting in an oxygen atmosphere, wherein the roasting temperature is 650 ℃, the roasting time is 10h, the heating rate is 5 ℃/min, cooling, roll-to-roll and sieving are carried out after the roasting is finished, and the ternary single crystal anode material is obtained, wherein a substance coated on the surface of the material is a strontium oxide compound, and the chemical molecular formula of the material is Li (i) 0.80 Co 0.10 Mn 0.10 ) 0.99 Sr 0.01 O 1.99 F 0.01 I 0.01 。
The fifth embodiment is to use ternary precursor Ni 0.85 Co 0.05 Mn 0.10 (OH) 2 、LiOH·H 2 Grinding O and LiF, and mixing well, wherein LiOH & H 2 The molar ratio of Li in O to the total metal elements in the ternary precursor is 1.01, and the molar ratio of F in LiF to the total metal elements in the ternary precursor is 0.02. Primary roasting is carried out in an oxygen atmosphere, the primary roasting temperature is 830 DEG CThe secondary roasting time is 12h, the heating rate is 3.0 ℃/min, and a primary material is obtained by cooling, crushing and sieving after the roasting is finished, and the chemical molecular formula of the primary material is LiNi 0.85 Co 0.05 Mn 0.10 O 1.99 F 0.02 . Mixing the primary material with an additive Ce (NO) 3 ) 4 、Y(OH) 3 Grinding, and mixing thoroughly, wherein the molar ratio of Ce in the additive to the total transition metal elements in the primary material is 0.005, and the molar ratio of Y in the additive to the total transition metal elements in the primary material is 0.005. Carrying out secondary roasting in an oxygen atmosphere, wherein the roasting temperature is 800 ℃, the roasting time is 5h, the heating rate is 5 ℃/min, cooling, roll-to-roll and sieving are carried out after the roasting is finished to obtain the ternary single crystal anode material, surface coating substances of the ternary single crystal anode material are barium oxide and yttrium oxide, and the chemical molecular formula is Li (Ni) 0.85 Co 0.05 Mn 0.10 ) 0.99 Ce 0.005 Y 0.005 O 1.99 F 0.02 。
The first comparative example is a comparative example of the first example, and is different from the first example in that the lithium oxyhalide LiF is not added in one firing, and the remaining steps are the same, and the chemical formula of the prepared ternary single crystal positive electrode material is Li (Ni) 0.63 Co 0.07 Mn 0.30 ) 0.99 Y 0.01 O 2 The surface coating substance of the material is also yttrium oxide.
The second comparative example is also a comparative example of the first example, and is different from the first example in that no additive is added in the secondary firing, and the remaining steps are the same, and the chemical formula of the prepared ternary single crystal positive electrode material is LiNi 0.63 Co 0.07 Mn 0.30 O 1.99 F 0.02 。
The embodiment of the application provides a method for manufacturing a single crystal ternary cathode material, which comprises the following steps: uniformly mixing a ternary precursor, a lithium salt and an additive, and performing primary roasting to obtain a primary material, wherein the additive at least comprises halogen anions X, namely the halogen anions X are introduced by the primary roasting, and the primary material and the additive are uniformly mixed and subjected to secondary roasting to obtain a single crystal ternary cathode material, the additive at least comprises target cations Q with the ionic radius larger than or equal to a threshold value, namely the target cations Q with the larger ionic radius are introduced by the secondary roasting, so that the formed single crystal ternary cathode material comprises the halogen anions X and the target cations Q, the crystal structure stability of the formed single crystal ternary cathode material is improved by the halogen anions X and the target cations Q, and the transmission performance and the electrochemical performance of the single crystal ternary cathode material are finally improved.
Based on the manufacturing method of the single crystal ternary cathode material provided by the above embodiments, the embodiments of the present application further provide a single crystal ternary cathode material, the single crystal ternary cathode material provided by the embodiments of the present application includes a matrix, the matrix at least includes a halogen anion X and a target cation Q, wherein an ionic radius of the target cation Q is greater than or equal to a threshold value
Specifically, the chemical formula of the single crystal ternary cathode material is Li (Ni) a Co b Mn c ) 1-d Q d O 2-y/2 X y Wherein a is more than or equal to 0.50 and less than or equal to 0.95<b≤0.20，0<c≤0.30，0<d<0.05，a+b+c+d＝1，0<y<0.1, X is a halogen anion and Q is a target cation Q having an ionic radius greater than or equal to a threshold value.
Optionally, the single crystal ternary cathode material further comprises a coating layer, the coating layer comprising at least the target cation Q.
Based on the single-crystal ternary cathode material provided by the embodiment, the embodiment of the application further provides a lithium ion battery, and the lithium ion battery provided by the embodiment of the application comprises the single-crystal ternary cathode material provided by the embodiment.
In the examples of the present application, the fabricated single crystal ternary positive electrode material can be assembled into CR2032 button cells and subjected to electrochemical performance testing.
Specifically, the single crystal ternary cathode material obtained by manufacturing can be mixed with acetylene black and a binder (PVDF) according to a mass ratio of 90:5:5, weighing and mixing the raw materials in proportion, and adding a proper amount of N-methylpyrrolidone solvent (NMP) for size mixing. And then uniformly coating the slurry on an aluminum foil current collector, and drying for 12 hours in a vacuum drying oven at 120 ℃. After drying, taking out the mixture after cooling to ensure thatThe anode material was cut into a 14mm diameter anode disc by a microtome, accurately weighed, and transferred to a glove box filled with high purity argon gas for use. Assembling the positive electrode material into a button cell in a glove box, taking metal lithium as a negative electrode, and adopting 1M LiPF as electrolyte 6 Solution (solvent V) Ethylene carbonate :V Carbonic acid methyl ethyl ester :V Carbonic acid dimethyl ester 1). The assembled battery needs to be kept stand at normal temperature for 12 hours, so that the pole piece is fully soaked by the electrolyte, and then the electrochemical performance test is carried out.
The seven single crystal ternary positive electrode materials obtained by manufacturing can be assembled into a CR2032 button cell, and electrochemical performance tests are carried out to respectively test the first charge-discharge specific capacity, the first coulombic efficiency and the capacity retention rate after 30 cycles. Wherein, the first capacity test condition is 3.0-4.5V at 25 ℃, and 0.1C charging and discharging. The cyclic test conditions are 3.0-4.5V at 45 ℃, and 1C charging and discharging. The test results are given in the following table:
as can be seen from the above table, compared with the 1 st comparative example and the 2 nd comparative example, the 1 st to 5 th examples all have higher specific discharge capacity, first coulombic efficiency and cycle retention rate, which are attributed to that the halogen anion X is doped to the oxygen site during the first firing and part of the target cation Q is doped to the transition metal site during the second firing, the halogen anion X has stronger electronegativity and stronger bond energy with the transition metal compared with the oxygen ion, and in addition, the target cation Q can enter the transition metal layer of the material, thereby stabilizing the crystal structure of the single crystal ternary cathode material and improving the electrochemical performance of the single crystal ternary cathode material. Meanwhile, part of target cations Q of secondary roasting are coated on the surface of the single crystal ternary cathode material, so that the surface state of the single crystal ternary cathode material is improved, the side reaction between the single crystal ternary cathode material and electrolyte is reduced, and the cycle performance of the single crystal ternary cathode material under high voltage is improved.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the structural embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and reference may be made to the partial description of the method embodiment for relevant points.
The foregoing is merely a preferred embodiment of the present application and, although the present application discloses the foregoing preferred embodiments, the present application is not limited thereto. Those skilled in the art can now make numerous possible variations and modifications to the disclosed embodiments, or modify equivalent embodiments, using the methods and techniques disclosed above, without departing from the scope of the claimed embodiments. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application are still within the protection scope of the technical solution of the present application without departing from the content of the technical solution of the present application.
Claims (11)
1. A method for manufacturing a single-crystal ternary cathode material is characterized by comprising the following steps:
uniformly mixing a ternary precursor, a lithium salt and an additive, and roasting for the first time to obtain a first material, wherein the additive at least comprises halogen anions X;
and uniformly mixing the primary material and an additive, and roasting for the second time to obtain the single crystal ternary cathode material, wherein the additive at least comprises a target cation Q with the ionic radius larger than or equal to a threshold value, and the single crystal ternary cathode material at least comprises the halogen anion X and the target cation Q.
2. The method of claim 1, further comprising:
forming a coating layer, wherein the coating layer coats the single crystal ternary cathode material, and the coating layer at least comprises a target cation Q.
3. The method according to claim 1, characterized in that the additive is a lithium compound corresponding to the halide anion X.
4. The method of claim 3, wherein the additive is one or more of LiF, liCl, liBr, and LiI.
5. The method according to claim 1, wherein the molar ratio of the halide anion X to the metal element in the ternary precursor is in the range of (0, 0.1).
6. The method according to any one of claims 1 to 5, wherein the element of the target cation Q is one or more of Sr, Y, ba, la, ce.
7. The method of any one of claims 1 to 5, wherein the additive is one or more of an oxide, nitrate, sulfate, hydroxide, bicarbonate and carbonate of the target cation Q.
8. The method according to any one of claims 1 to 5, wherein the molar ratio of the target cation Q to the transition metal element in the primary charge is in the range of (0,0.05).
9. A single-crystal ternary cathode material, characterized in that it comprises a matrix comprising at least said halogen anion X and said target cation Q;
the ionic radius of the target cation Q is greater than or equal to a threshold value.
10. A single crystal ternary positive electrode material according to claim 9, further comprising a cladding layer comprising at least a target cation Q.
11. A lithium ion battery, characterized in that it comprises at least a single-crystal ternary positive electrode material according to any of claims 9 or 10.
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