Battery material, method for preparing same, and secondary battery

Abstract

Battery material, its preparation method, and secondary battery. The general molecular formula of the battery material is A3V 2-x E x (P 1-y M y O4)3, wherein element A is an alkali metal element; element E is a doping element that substitutes for V and includes at least one of a transition metal element, a rare earth element, Mg, and Sr; element M is a doping element that substitutes for P and includes at least one of S and Se; and 0≦x≦1 and 0

Description

[Technical Field]

[0001] This application claims priority to and the benefit of Chinese Patent Application No. 202210957767.8, filed on August 10, 2022. The entire contents of the above application are incorporated herein by reference.

[0002] The present disclosure relates to the field of battery technology, and in particular to battery materials and methods for preparing same, and secondary batteries.

[0003] Background technology Sodium superionic conductor (NASICON) compounds are polyanionic materials with three-dimensional ion channels. NASICON compounds are often used as electrode materials or solid electrolytes due to their good cycling performance, safety, and flexible charge / discharge voltage plateaus. However, this polyanionic structure contributes to the poor electronic conductivity and electrochemical activity of NASICON-based compounds. Furthermore, alkali metal ions cannot rapidly intercalate into or deintercalate from the three-dimensional crystalline framework, affecting the material's rate performance.

[0004] In the prior art, material problems are commonly solved by doping and modification, however, the doping schemes currently prevalent in the industry have limited effectiveness in improving the electrochemical performance of materials.

[0005] Summary of the Invention Thus, the present disclosure provides a battery material in which phosphorus site is doped with a non-metallic element that is more electronegative than phosphorus, thereby significantly improving the electronic conductivity and rate performance of the material.

[0006] A first aspect of the present disclosure is a battery material, the battery material having a general molecular formula of A3V 2-x E x (P 1-y M yIt provides a battery material containing A₂(VO₄)₃, where element A is an alkali metal element; element E is a doping element that replaces V and contains at least one of transition metal elements, rare earth elements, Mg, and Sr; element M is a doping element that replaces P and contains at least one of S and Se; and 0 ≦ x ≦ 1 and 0 < y ≦ 1 / 3.

[0007] Element M is a non-metal element with a stronger electronegativity than element P. After the doping element M replaces part of the P atoms, it can reduce the charge number of the O atoms originally connected to the P atoms, thereby reducing the Coulomb effect between the O atoms and the A atoms. Therefore, it can reduce the binding effect of the O atoms on the A atoms during the charge and discharge process, which is beneficial to the deintercalation / intercalation of the A atoms, thereby improving the rate performance of the material. Furthermore, by doping element M into the olivine, the band gap value of the compound A₃V₂(P 1-y M y O₄)₃ can be reduced to improve the electronic conductivity of the material.

[0008] In some embodiments, the transition metal element contains at least one of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, and Zr, and the rare earth element contains at least one of La and Ce.

[0009] In some embodiments, the value range of x is 0.1 ≦ x ≦ 1.

[0010] In some embodiments, the value range of y is 1 / 18 ≦ y ≦ 1 / 3.

[0011] In some embodiments, element A contains at least one of Na, K, and Li.

[0012] The second aspect of the present disclosure is a method for preparing a battery material, The general molecular formula of the battery material to be prepared is A₃V 2-x E x (P1-y M y O4)3, and mixing these sources to obtain a precursor material, wherein the element A is an alkali metal element; the element E is a doping element that substitutes for V and includes at least one of a transition metal element, a rare earth element, Mg, and Sr; the element M is a doping element that substitutes for P and includes at least one of S and Se; and 0≦x≦1 and 0 <y≦1 / 3であり、かつ、 A method for producing a battery material is provided, which includes the step of calcining a precursor material to obtain the battery material.

[0013] The present preparation method has the advantages of simple operation and high process controllability, and can be realized in large-scale industrial preparation.

[0014] In some embodiments, the calcination conditions include calcining the precursor material under an inert gas atmosphere at 400° C. to 900° C. for 10 hours to 30 hours.

[0015] In some embodiments, the inert gas is at least one of argon, nitrogen, or helium.

[0016] In some embodiments, the mixing comprises a solid state mixing method or a sol-gel method.

[0017] In some embodiments, the transition metal element comprises at least one of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, and Zr, and the rare earth element comprises at least one of La and Ce.

[0018] In some embodiments, the element A comprises at least one of Na, K, and Li.

[0019] In some embodiments, the value of x is in the range of 0.1≦x≦1.

[0020] In some embodiments, the value of y is in the range 1 / 18≦y≦1 / 3.

[0021] A third aspect of the present disclosure provides a secondary battery comprising the battery material according to the first aspect of the present disclosure.

[0022] Secondary batteries have good rate performance. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing X-ray diffraction (XRD) patterns of the battery materials of Examples 1 to 3 and Comparative Example 1. [Figure 2] 1 is a curve showing the specific capacity of batteries prepared from the battery materials of Examples 1 to 4 and Comparative Example 1 as a function of cycle number.

[0024] MODE FOR CARRYING OUT THE INVENTION NASICON compound is a polyanionic material with a three-dimensional ion channel proposed by Professor Goodenough, and can be used as both an electrode material and a solid electrolyte material. To more clearly explain the beneficial effects of the present disclosure, the crystal structure of NASICON compound is briefly described below using Na3V2(PO4)3 (abbreviated as NVP) as an example.

[0025] Each structural element of Na3V2(PO4)3 contains three PO4 tetrahedra and two VO6 octahedra, which are connected by a common apex oxygen atom to form an alkali metal ion (specifically, a sodium ion) that can adapt to two different oxygen environments. The sodium ions occupy the Na(1) and Na(2) positions, respectively. It is generally believed that only the sodium ions at the Na(2) positions can deintercalate or intercalate during charging and discharging, thus completing the lattice configuration transformation between depleted Na3V2(PO4)3 and fully charged NaV2(PO4)3. However, the high energy barrier for the sodium ions during migration severely affects the sodium ion migration rate, resulting in a decrease in the ionic conductivity and rate performance of the material. Furthermore, the electronic conductivity of such materials is also low.

[0026] To solve the above problems, one embodiment of the present disclosure provides a battery material with doping in phosphorussite, the general molecular formula of which is A3V 2-x E x (P 1-y M y O4)3, wherein element A is an alkali metal element; element E is a doping element that substitutes for V and includes one or more of a transition metal element, a rare earth element, Mg, and Sr; element M is a doping element that substitutes for P and includes at least one of S and Se; x is a molar ratio of element E that substitutes for element V, and y is a molar ratio of element M that substitutes for element P, and 0≦x≦1 and 0 <y≦1 / 3である。

[0027] The element M is more electronegative than the element P. The M atom is present in the compound A3V2(P 1-y M y O4)3, the M atom replaces the P atom and connects with the O atom. The M atom has a strong ability to attract electrons, so it can reduce the charge of the O atom that is originally connected with the P element, thereby weakening the Coulomb effect between the O atom and the A atom. Therefore, the PO4 3-The binding effect of the anionic group is reduced, and the ion migration barrier is reduced, which can accelerate the deintercalation and intercalation of A atoms, thereby improving the ionic conductivity and the rate performance of the material. Furthermore, the doping element M can also accumulate more electrons near the Fermi surface, thereby improving the electronic conductivity of the material and the electrochemical reaction rate during charging and discharging of the material, further improving the rate performance of secondary batteries using this material. By controlling the doping amount of element M within the above range, the rate performance and electronic conductivity of the material can be improved while ensuring good structural stability of the material.

[0028] Furthermore, an appropriate amount of element E is used to create A3V2(P 1-y M y Doping the V-site of O4)3 can maintain high electronic conductivity in the resulting double-doped material.

[0029] In some embodiments of the present disclosure, the element A includes, but is not limited to, one or more of Li, Na, or K. The element A may be selected depending on the specific type of secondary battery. For example, the battery material A3V 2-x E x (P 1-y M y When O4)3 is used in a sodium secondary battery, element A is Na.

[0030] In some embodiments of the present disclosure, the element M is the element S. Using the element S to dope phosphorus site (where S atoms substitute for some of the P atoms in the crystal lattice) makes the preparation process more controllable, improves product yield, and makes the performance of the prepared battery material more stable. Furthermore, using the element S to dope phosphorus site significantly improves the electronic conductivity of the material, reduces the powder resistivity of the resulting material, and increases the structural stability of the material during charging and discharging.

[0031] In some embodiments of the present disclosure, the element M is element Se. The ionic radius (tetravalent) of element Se is larger than that of element P, which can moderately expand the unit cell volume of the original compound A3V2(PO4)3, further weaken the binding effect of the anionic group on the A ions, and further reduce the migration barrier of the A ions, thereby improving the rate performance of the material.

[0032] In some embodiments of the present disclosure, A3V 2-x E x (P 1-y M y In the formula, x can be 0, the value of y is in the range of 1 / 18≦y≦1 / 6. By controlling the doping amount of element M within the above range, the risk of damage to the unit cell structure of the original compound A3V2(PO4)3 due to doping with element M can be sufficiently reduced, thereby 2-x D x (P 1-y M y O4)3 has good structural stability and can continuously maintain a stable structure even during repeated charging and discharging.

[0033] In some embodiments of the present disclosure, A3V 2-x E x (P 1-y M y O4)3 (wherein x can be 0), the value of y is in the range of 1 / 6≦y≦1 / 3. By controlling the doping amount of element M within the above range, the electronic conductivity of the active material can be improved, the migration barrier of Na ions can be reduced (i.e., the ionic conductivity can be improved), and the rate performance of the secondary battery can be further improved.

[0034] In some embodiments of the present disclosure, y is 1 / 18. In this case, material A3V 2-x E x (P 1-y M y O4)3 (x can be 0) has very high crystallinity and optimal structural stability. In some other embodiments, y is 1 / 6. In this case, material A3V 2-x Ex (P 1-y M y O4)3 (x can be 0) has good electronic conductivity and a low migration barrier for A ions. In some other embodiments, y is 1 / 3. In this case, material A3V 2-x E x (P 1-y M y O4)3 (where x can be 0) has a low transition barrier and high electronic conductivity.

[0035] In some embodiments of the present disclosure, the transition metal elements include one or more of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, and Zr.

[0036] In some embodiments of the present disclosure, the rare earth element includes at least one of La and Ce.

[0037] In some embodiments of the present disclosure, element E includes one or more of Mg, Sr, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ti, Mo, Nb, and Zr. The cost of these elements is lower than that of the lanthanide elements La and Ce. The ionic radii of Cr, Mn, Fe, Co, Ni, Cu, and Zn are slightly smaller than that of the V ion. Doping with such elements reduces the unit cell volume of A3V2(PO4)3, thereby further improving the structural stability of the material. In other embodiments of the present disclosure, element E may be one or more of Ti, Cr, Mn, and Fe to better balance the cost of element E and its impact on the material's operating voltage. These elements also help increase the operating voltage of the doped material. Fe has the lowest cost and provides a greater improvement in electronic conductivity, while Mn has a better effect on increasing the operating voltage of the doped material.

[0038] In some particular embodiments, the element E is Mn and the element M is S. A3V 2-x Mn x (P 1-y S yThe yield of O4)3 is high and the prepared material has good electronic conductivity.

[0039] In some embodiments of the present disclosure, x is preferably within the range of 0.1≦x≦1. By controlling the doping amount of element E within the above range, A3V due to excessive doping amount of E can be reduced. 2-x E x (P 1-y M y It can be ensured that the loss of electrochemical activity of O4)3 can be avoided and that doping with element E can sufficiently improve the electrochemical performance of the material.

[0040] Correspondingly, one embodiment of the present disclosure provides a method for preparing a battery material, comprising: The general molecular formula of the prepared battery material is A3V 2-x E x (P 1-y M y O4)3, and mixing these sources to obtain a precursor material, wherein the element A is an alkali metal element; the element E is a doping element that substitutes for V and includes one or more of a transition metal element, a rare earth element, Mg, and Sr; the element M is a doping element that substitutes for P and includes at least one of S and Se; and 0≦x≦1 and 0 <y≦1 / 3であり、かつ、 A method for producing a battery material is provided, which includes the step of calcining a precursor material to obtain the battery material.

[0041] According to the above-mentioned preparation method, raw materials are mixed in a predetermined ratio to obtain a precursor material, and then the mixed raw materials are calcined to obtain the battery material provided in the embodiment of the present disclosure. This preparation method has the advantages of simple operation and high process controllability, and can be realized in large-scale industrial preparation.

[0042] In some embodiments of the present disclosure, the A source, vanadium source, E source, phosphorus source, and M source are weighed and mixed according to a molar ratio of A:V:E:P:M=3:(2-x):x:(3-3y):3y. In some embodiments, the element A may be more than 10% to compensate for the loss of the alkali metal element A during the preparation process.

[0043] In some embodiments of the present disclosure, mixing includes, but is not limited to, solid state mixing or sol-gel methods.

[0044] Specifically, the solid-phase mixing method may be a method in which an A source, a vanadium source, an E source, a phosphorus source, and an M source are mixed in proportions in a ball mill to obtain a precursor material.

[0045] Specifically, the sol-gel method involves adding the A source, vanadium source, E source, phosphorus source, and M source in proportion to the solvent, heating and stirring the mixture to form a gel, and then continuing to heat and stir to evaporate the solvent to obtain the precursor material. Heating and stirring are performed at 30°C to 200°C, with a stirring speed of 300 rpm to 900 rpm, for 1 hour to 6 hours.

[0046] In the present disclosure, the solvent is a volatile solvent, and may specifically be one or more of water, ethanol, and acetone.

[0047] In some embodiments of the present disclosure, the calcination conditions include calcining the precursor material under an inert gas atmosphere at 400° C. to 900° C. for 10 hours to 30 hours.

[0048] In the present disclosure, the inert gas is specifically at least one of argon, nitrogen, and helium.

[0049] In the present disclosure, the A source (wherein element A is at least one of Li, Na, and K) can be at least one of nitrate, oxalate, acetate, and acetylacetonate of element A. For example, when element A is Na, the Na source can be at least one of sodium nitrate, sodium oxalate, sodium acetate, and sodium acetylacetonate.

[0050] In the present disclosure, the vanadium source includes, but is not limited to, at least one of vanadium sources in which the vanadium element in the compound is trivalent, tetravalent, or pentavalent. For example, the vanadium source may be at least one of vanadium pentoxide, vanadium tetroxide, vanadium trioxide, ammonium metavanadate, sodium metavanadate, vanadium acetylacetonate, vanadyl acetylacetonate, etc.

[0051] In the present disclosure, the E source is a compound well known to those skilled in the art. For example, the E source is at least one of an organometallic salt, a metal acid salt, and a metal oxide of a specific element corresponding to the element E. For example, when the element E is the element Ti, the E source can be at least one of titanium oxide, tetrabutyl titanate, titanium tetraisopropoxide, titanium ethoxide, etc.

[0052] In the present disclosure, the phosphorus source can be at least one of phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, and the like.

[0053] In the present disclosure, the M source can be at least one of an acid or a salt of a specific doping element corresponding to the element M. For example, when the element M is the element S, the M source can be sodium sulfate, ammonium sulfate, sulfuric acid, etc.

[0054] Accordingly, one embodiment of the present disclosure provides an electrode, the electrode comprising the battery material described above.

[0055] The electrodes can be used to provide batteries with high rate capability, good cycling capability, and good energy density.

[0056] In some embodiments of the present disclosure, the electrode is a positive electrode. The positive electrode generally includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector. The positive electrode active material layer includes the battery materials described above. Furthermore, the positive electrode active material layer may further include a binder and, optionally, a conductive agent. The binder and conductive agent may be conventional choices in the battery field.

[0057] The positive electrode current collector can be a variety of materials suitable for use as a positive electrode current collector, including, but not limited to, elemental metal foil, alloy foil, metal-plated polymer film, or any of the above materials with a carbon coating on its surface. The elemental metal foil can be aluminum foil. The alloy foil can be aluminum alloy foil. The metal plated on the surface of the polymer film can be an elemental aluminum layer or an aluminum alloy layer.

[0058] One embodiment of the present disclosure provides a secondary battery, which includes the electrode described above.

[0059] One embodiment of the present disclosure provides a secondary battery, which includes the battery material described above.

[0060] Specifically, the secondary battery may be a lithium secondary battery, a sodium secondary battery, or a potassium secondary battery. 2-x E x (P 1-y M yBecause they contain 04)3, secondary batteries have high energy density, good rate performance, good cycle performance, etc. Secondary batteries can be used in 3C electronic products (e.g., mobile phones, tablet computers, etc.), vehicles (e.g., automobiles, boats, etc.), and other electrical equipment to improve the performance and market competitiveness of electrical equipment.

[0061] The secondary battery may be a liquid battery using a liquid electrolyte, or a semi-solid or solid battery using a semi-solid or solid electrolyte. In some embodiments, the secondary battery may include the above-described positive electrode, negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte solution. In some other embodiments, the secondary battery may include a positive electrode, a negative electrode, and a semi-solid or solid electrolyte between the positive electrode and the negative electrode. In particular, the battery materials provided by embodiments of the present disclosure may be used as the semi-solid or solid electrolyte. Furthermore, when a semi-solid or solid electrolyte is used, the positive electrode and the negative electrode may further include a semi-solid or solid electrolyte material.

[0062] The technical solutions of the present disclosure are described in further detail below through several examples.

[0063] Example 1 The battery material was prepared according to the following procedure.

[0064] Sodium nitrate as a sodium source, vanadium pentoxide as a vanadium source, phosphoric acid as a phosphorus source, and sodium sulfate as a sulfur source were weighed out in a molar ratio of Na:V:P:S = 3:2:2:84:0.17 and added to ethanol as a solvent. The mixture was heated and stirred at 80 °C to evaporate the solvent, yielding a precursor material.

[0065] The precursor material was calcined at 800°C for 12 hours under a protective nitrogen atmosphere to produce the battery material Na3V2(P 17 / 18 S 1 / 18 O4)3 (hereafter abbreviated as S1-NVP) was obtained.

[0066] Example 2 This example was the same as Example 1, except that the content of the S source was adjusted so that the molar ratio of Na:V:P:S was 3:2:2:5:0.5. The general molecular formula of the prepared battery material was Na3V2(P 5 / 6 S 1 / 6 O4)3 (hereafter abbreviated as S3-NVP).

[0067] Example 3 This example was the same as Example 1, except that the content of the S source was adjusted so that the molar ratio of Na:V:P:S was 3:2:2:1. The general molecular formula of the prepared battery material was Na3V2(P 2 / 3 S 1 / 3 O4)3 (hereafter abbreviated as S6-NVP).

[0068] Example 4 This example was the same as Example 1, except that the content of the S source was adjusted to give a molar ratio of Na:V:P:S of 3:2:2.94:0.06. The general molecular formula of the prepared battery material was Na3V2(P 0.98 S 0.02 O4)3.

[0069] Example 5 This example was the same as Example 1, except that the S source was replaced with a Se source, which was sodium selenate, and the process parameters were adjusted. The general molecular formula of the prepared battery material was Na3V2(P 17 / 18 Se 1 / 18 O4)3.

[0070] Example 6 (1) Sodium nitrate as a sodium source, vanadium pentoxide as a vanadium source, manganese dioxide as a Mn source, phosphoric acid as a phosphorus source, and sodium sulfate as a S source were weighed out in a molar ratio of Na:V:Mn:P:S=3:1.5:0.5:2.84:0.17, and the mixture was fed into a ball mill and thoroughly mixed to obtain a precursor material.

[0071] (2) The precursor material was calcined at 800°C for 12 hours under a protective nitrogen atmosphere to produce the battery material Na3V 1.5 Mn 0.5 (P17 / 18 S 1 / 18 O4)3 was obtained.

[0072] Example 7 (1) The content of the Mn source was finely adjusted, and the general molecular formula of the prepared battery material was Na3V 1.8 Mn 0.2 (P 17 / 18 S 1 / 18 O4)3.

[0073] Example 8 This example was the same as Example 5, except that the Mn source was replaced with a ferrous iron source, the process parameters were adjusted, and the raw materials were mixed uniformly in a ball mill to obtain a precursor material, which was then calcined. The general molecular formula of the prepared battery material was Na3V 1.5 Fe 0.5 (P 17 / 18 S 1 / 18 O4)3.

[0074] Example 9 This example was the same as Example 5, except that the Mn source was replaced with a Ti source, which was titanium oxide, and the preparation process was slightly adjusted. The general molecular formula of the prepared battery material was NaV 1.5 Ti 0.5 (P 17 / 18 S 1 / 18 O4)3.

[0075] Example 10 This example was the same as Example 5, except that the Mn source was replaced with a chromium oxide Cr source, and the content of the Na source and the subsequent preparation process were slightly adjusted. The general molecular formula of the prepared battery material was NaV 1.5 Cr 0.5 (P 17 / 18 S 1 / 18 O4)3.

[0076] Example 11 This example was the same as Example 5, except that the S source was replaced with selenium dioxide, which was the Se source, and the subsequent process parameters were adjusted. The general molecular formula of the prepared battery material was NaV. 1.5 Mn0.5 (P 17 / 18 Se 1 / 18 O4)3.

[0077] Example 12 This example was the same as Example 5, except that potassium nitrate was further added as a potassium source, and the content of the Na source and subsequent process parameters were fine-tuned. The general molecular formula of the prepared battery material was Na2K1V 1.5 Mn 0.5 (P 17 / 18 S 1 / 18 O4)3.

[0078] Example 13 This example was the same as Example 1, except that the Na source was replaced with a lithium source, which was lithium nitrate, and the preparation process was slightly adjusted. The general molecular formula of the prepared battery material was Li3V2(P 17 / 18 S 1 / 18 O4)3.

[0079] Comparative Example 1 Battery materials were prepared. The general molecular formula of the battery materials was Na3V2(PO4)3.

[0080] Comparative Example 2 Battery materials were prepared. The general molecular formula of the battery materials is Na3V 1.5 Fe 0.5 (PO4)3.

[0081] Performance Test (1) Characterization of the crystalline structure of the materials: The battery materials of Examples 1 to 3 and Comparative Example 1 are characterized by XRD. The results are shown in FIG.

[0082] (2) Electronic Conductivity Test: The powder to be tested was placed in a powder resistivity tester. A pressure of 50 MPa was applied and held for 10 seconds. The powder resistivity was measured using a four-point probe method and can be converted to electronic conductivity (in this case, electronic conductivity is the reciprocal of resistivity). The results are shown in Table 1 below.

[0083] (3) Battery preparation 1. Preparation of positive electrode: The battery materials of each example or comparative example, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were added to the solvent NMP (N-methylpyrrolidone) in a mass ratio of 88:6:6, and the mixture was stirred uniformly to obtain a positive electrode slurry. This positive electrode slurry was applied to an aluminum foil serving as a positive electrode current collector, dried, rolled, and cut to obtain a positive electrode. 2. Preparation of negative electrode: The negative electrode active material (specifically, graphite) and binder (specifically, a mixture of styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) in a mass ratio of 2:3) were mixed with ionized water in a mass ratio of 95:5 and stirred uniformly to obtain negative electrode slurry. This negative electrode slurry was applied to copper foil, which served as the negative electrode current collector, and then dried, rolled, and cut to obtain the negative electrode. 3. Battery assembly: The positive electrode, separator, and negative electrode are alternately stacked to obtain a battery core. The battery core is wound up, placed in an outer foil made of aluminum plastic film, and the electrolyte is injected. The sodium battery is then prepared through processes such as vacuum packaging, standing, molding, and cutting. The secondary sodium batteries prepared from the battery materials of the examples and comparative examples are designated S1-S13 and DS1-DS2, respectively.

[0084] Batteries S1-S13 and DS1-DS2 were tested for electrochemical performance.

[0085] a) Cycle Performance Test: Each battery underwent a charge-discharge cycle test at 25°C, a current of 0.5C, and a voltage range of 2.5V to 4.3V. During charging, the battery was first charged at a constant current of 0.5C up to a cutoff voltage of 4.3V, and then charged at a constant voltage down to a cutoff current of 0.05C. During discharging, the battery was discharged at a constant current of 0.5C down to 2.5V. The first-cycle specific discharge capacity and the capacity retention rate after 50 cycles for each cell were recorded. The first-cycle specific discharge capacity is equal to the ratio of the first-cycle discharge capacity of each button cell to the mass of the positive electrode active material in the cell. The capacity retention rate after 50 cycles is equal to the ratio of the discharge capacity after 50 cycles to the initial discharge capacity.

[0086] b) Rate Performance Test: The change in discharge gram capacity of each battery with the number of cycles at different rates, such as 5C, 10C, 20C, and 50C, was tested at 25°C, with the voltage range being 2.5V to 4.3V. The rate performance curves of several examples and comparative examples are shown in Figure 2. To calculate the gram capacity, the ratio of the discharge capacity at a current density to the mass of the positive electrode active material is used as the discharge gram capacity at a current density. Table 1 shows the first cycle specific discharge capacity at 50C for each battery, and the ratio of the first cycle discharge capacity at 50C to the first cycle discharge capacity at 5C. The test results of the batteries were as shown in Table 1 below. [Table 1]

[0087] When the batteries were subjected to charge-discharge cycling tests using different current densities, especially at high current densities, the curves of the specific capacity of the batteries as a function of cycle number in Figure 2 show that the specific capacity of the battery of Comparative Example 1 was significantly inferior to that of the batteries of Examples 1 to 4. Furthermore, as the current density gradually increased, the battery prepared from the undoped NVP material experienced severe capacity fade.

[0088] From the data in Table 1, it can be seen that doping with element M at the phosphosite can significantly improve the electronic conductivity, cycle performance, and rate performance of NVP materials, but doping with different M elements has slightly different effects on the electrochemical performance of the materials. The electrochemical performance of the dual-doped materials with doping at both the phosphosite and vanadium sites was improved to different degrees compared to the undoped NVP material. Further comparison of the data in Example 8 with that in Comparative Example 2 reveals that the dual-doped material Na3V 1.5 Fe 0.5 (P 17 / 18 S 1 / 18 All the electrochemical properties of O4)3 were compared with those of Na3V, which was doped only with Fe element. 1.5 Fe 0.5 It can be seen that the electrochemical properties were significantly better than those of (PO4)3.

[0089] Although the exemplary embodiments of the present disclosure have been described above, the present disclosure is not limited thereto. It should be understood that those skilled in the art can make some improvements and modifications without departing from the technical principles of the present disclosure, and they are also considered to be within the scope of the present disclosure.

Claims

1. A battery material, the general molecular formula of which is: A ３ V ２－ｘ E ｘ (P １－ｙ M ｙ O ４ ) ３ wherein the element A is an alkali metal element; the element E is a doping element that substitutes for V and includes at least one of a transition metal element, a rare earth element, Mg, and Sr; the element M is a doping element that substitutes for P and includes at least one of S and Se; and 0≦x≦1 and 0<y≦1 / 3.

2. 2. The battery material of claim 1, wherein the transition metal element comprises at least one of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, and Zr, and the rare earth element comprises at least one of La and Ce.

3. The battery material according to claim 1 or 2, wherein the value of x is in the range of 0.1≦x≦1.

4. The battery material according to claim 1 , wherein the value of y is in the range of 1 / 18≦y≦1 / 3.

5. The battery material according to claim 1 , wherein the element A includes at least one of Na, K, and Li.

6. A method for preparing a battery material, comprising: The general molecular formula A of the prepared battery material ３ V ２－ｘ E ｘ (P １－ｙ M ｙ O ４ ) ３ and mixing these sources to obtain a precursor material according to the formula (I): wherein the element A is an alkali metal element; the element E is a doping element that substitutes for V and includes at least one of a transition metal element, a rare earth element, Mg, and Sr; the element M is a doping element that substitutes for P and includes at least one of S and Se; 0≦x≦1 and 0<y≦1 / 3; and and calcining the precursor material to obtain the battery material.

7. 7. The method of claim 6, wherein the calcination conditions include calcining the precursor material under an inert gas atmosphere at 400 to 900° C. for 10 to 30 hours.

8. 8. The method of claim 7, wherein the inert gas is at least one of argon, nitrogen, and helium.

9. The method according to any one of claims 6 to 8, wherein the mixing comprises a solid-state mixing method or a sol-gel method.

10. 10. The method of any one of claims 6 to 9, wherein the transition metal element comprises at least one of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, and Zr, and the rare earth element comprises at least one of La and Ce.

11. 11. The method according to claim 6, wherein the element A comprises at least one of Na, K, and Li.

12. 12. The method according to any one of claims 6 to 11, wherein the value of x is in the range of 0.1≦x≦1.

13. 13. The method according to any one of claims 6 to 12, wherein the value of y is in the range of 1 / 18≦y≦1 / 3.

14. A secondary battery comprising the battery material according to claim 1 .

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