Battery material, method for producing the same, and secondary battery

Abstract

Battery material, method for producing the same, and secondary battery. The general molecular formula of the battery material is A3V 2-x E x (P 1-y L y O4)3, where the element E represents a doping element that replaces the element V and comprises at least one of transition metal elements, rare earth elements, Mg, and Sr; the element L represents a doping element that replaces the element P and comprises at least one of B, Al, Ga, Si, Ge, and Sn; the element A represents an alkali metal element, 0 ≦ x ≦ 1 and 0

Description

Technical Field

[0001] (Cross - reference to related applications) This application claims the priority and benefit of Chinese Patent Application No. 202210959434.9, filed on August 10, 2022. The entire content of the application referenced above is incorporated herein by reference.

[0002] This disclosure relates to the field of battery technology, and more particularly, to battery materials and their manufacturing methods, as well as secondary batteries.

Background Art

[0003] Battery materials such as electrode materials and solid electrolyte materials are important components of batteries and have a great influence on battery performance. Taking sodium - ion batteries as an example, the Na3V2(PO4)3 material, which is a fast - ion conductor material for three - dimensional ion channels, has potential advantages such as a stable crystal structure, adjustable operating voltage, and high theoretical specific capacity, so it is often used as a cathode material or a solid electrolyte. However, such materials have problems such as low electronic conductivity and low charge - discharge voltage plateau.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the prior art, generally, the problems of materials are solved by doping and modification. However, in the doping methods that are currently common in the industry, the effect of improving the electrochemical performance of materials is limited.

Means for Solving the Problems

[0005] Therefore, this disclosure provides a battery material. By doping the anion - rich phosphate of alkali metal vanadium phosphate, the charge - discharge voltage and electronic conductivity of the material can be effectively improved.

[0006] The first aspect of the present disclosure provides a battery material, and the general molecular formula of the battery material is A3V 2-x E x (P 1-y L y O4)3, where the element E represents a doping element that replaces the element V and includes one or more of transition metal elements, Mg, and Sr; the element L represents a doping element that replaces the element P and includes one or more of B, Al, Ga, Si, Ge, and Sn; the element A represents an alkali metal element; x and y respectively represent the molar percentage of the element V replaced by the doping element and the molar percentage of the element P replaced by the doping element, 0 ≦ x ≦ 1, 0 < y ≦ 1 / 3, and when the element L is the element B, x is not 0.

[0007] The electronegativity of each element L is smaller than that of the element P. After replacing a part of the element P, the doping element L can cause a change in the valence state of the O atom originally bonded to the element P. As a result, the polyanion group LO4 m- (where m- is the total charge of the polyanion group and m > 0) contracts in structure. Therefore, the unit cell structure of the compound A3V2(P 1-y L y O4)3 contracts, the total energy of the unit cell structure decreases, and as a result, the operating voltage of the material may be increased. In addition, the contraction of the unit cell structure is beneficial for improving the structural stability of the material and also beneficial for improving the cycle performance of the material. In addition, doping the element L into the olivine can excite the element V and induce it to undergo a redox reaction at a high potential, thereby further increasing the operating voltage of the material and increasing the energy density of the material. In addition, doping the element L into the olivine can lower the band gap value of the compound A3V2(P 1-y L y O4)3 and improve the electronic conductivity of the material. In addition, by controlling the doping amount of the element L within an appropriate range, it is possible to ensure good structural stability of the material while enabling the material to have a high charge-discharge voltage plateau and good electronic conductivity.

[0008] In some embodiments, element L comprises at least one of Si, Ge, and Sn.

[0009] 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.

[0010] In some embodiments, the value range of x is 0.1 ≦ x ≦ 1.

[0011] In some embodiments, the value range of y is 1 / 18 ≦ y ≦ 1 / 3.

[0012] The second aspect of the present disclosure provides a method for manufacturing a battery material, the method comprising: Weighing an A source, a vanadium source, an E source, a phosphorus source, and an L source according to the general molecular formula A3V 2-x E x (P 1-y L y O4)3 to obtain a precursor material by mixing these sources, wherein element E represents a doping element that replaces element V and comprises one or more of a transition metal element, a rare earth element, Mg, and Sr, element L represents a doping element that replaces element P and comprises one or more of B, Al, Ga, Si, Ge, and Sn, element A represents an alkali metal element, 0 ≦ x ≦ 1, and 0 < y ≦ 1 / 3, and when element L is element B, x is not 0, obtaining the precursor material; Firing the precursor material to obtain a battery material; and

[0013] This manufacturing method has the advantages of simple process and high controllability, and can realize large-scale industrial production.

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

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

[0016] In some embodiments, the mixing process includes a solid-phase mixing method or a sol-gel method.

[0017] In some embodiments, element L includes at least one of Si, Ge, and Sn.

[0018] In some embodiments, the transition metal element includes at least one of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, and Zr, and the rare earth element includes at least one of La and Ce.

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

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

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

[0022] This secondary battery has a high energy density and relatively good rate performance.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0024] The NASICON compound is a fast ion conductor material having a three-dimensional ion channel proposed by Professor Goodenough and may 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 the NASICON compound is briefly described below by using Na3V2(PO4)3 (abbreviated as NVP) as an example.

[0025] Each structural element of the NVP material contains three PO4 tetrahedra and two VO6 octahedra, which are bonded by shared vertex oxygen atoms to form alkali metal ions (specifically sodium ions) that can adapt to two different oxygen environments and form sodium ions. The sodium ions occupy the Na(1) position and the Na(2) position respectively. Generally, only the sodium ions in the Na(2) position can be deintercalated or intercalated during charge and discharge, and thus it is considered possible to complete the conversion of the lattice structure between Na3V2(PO4)3 lacking sodium and fully charged NaV2(PO4)3. However, the conversion of the crystal form during the charge-discharge cycle causes the structural stability of the material to gradually decrease during charge and discharge, affecting the normal performance of the battery. In addition, the above materials also have problems such as low electronic conductivity and low charge-discharge voltage plateau.

[0026] To solve the above problems, the embodiments of the present disclosure provide a battery material. The general molecular formula of the battery material is A3V 2-x E x (P 1-y L yIt contains E2(O4)3, where the element E represents a doping element that replaces the element V and contains one or more of transition metal elements, rare earth elements, Mg, and Sr; the element L represents a doping element that replaces the element P and contains one or more of B, Al, Ga, Si, Ge, and Sn; the element A represents an alkali metal element; x and y respectively represent the molar percentages of the doping elements, 0 ≦ x ≦ 1, 0 < y ≦ 1 / 3, and when the element L is the element B, x is not 0.

[0027] The electronegativity of the element L is smaller than that of the element P, and 0 < y ≦ 1 / 3. That is, the L atom replaces the P atom in some of the PO4 tetrahedrons in some of the structural elements. As a result, the number of charges around the oxygen atoms of the original PO4 tetrahedron is changed, and the ionic radii of some of the oxygen atoms can be contracted. Since the compound A3V2(P 1-y L y L 1-y O4)3 is a material with a framework structure, so the unit cell volume of A3V2(P y L 1-y O4)3 shrinks. As a result, the total energy of the unit cell structure of A3V2(P y L 1-y O4)3 is reduced, thereby increasing the operating voltage of the material and improving the structural stability of the material. In addition, A3V2(P yA3V2(PO4)3 can maintain high structural stability while having small volume fluctuations during charge and discharge and maintaining high electronic conductivity. In addition, since the PO4 tetrahedron and the VO6 octahedron are bonded by shared apical oxygen atoms, the doping of element L causes a change in the charge of the surrounding O atoms, forcibly changes the charge environment around the V atom, and induces a redox reaction of element V at a high potential. Therefore, the operating voltage of the material can be increased, thereby improving the energy density of the material. In addition, the doping element L can also significantly reduce the bandgap value of the original material A3V2(PO4)3 and accumulate more electrons near the Fermi surface, thereby improving the electronic conductivity of the material, improving the electrochemical reaction rate during charge and discharge of the material, and further improving the rate performance of the secondary battery using this material. In addition, by controlling the doping amount of element L within the above range, it is possible to ensure good structural stability of the material while enabling the material to have a high charge and discharge voltage plateau and good electronic conductivity.

[0028] Furthermore, for doping the V site of A3V2(P 1-y L y O4)3, when an appropriate amount of element E is further used, due to the synergistic effect between the doping of element E into the V site and the doping of element L into the P site, the charge and discharge voltage plateau of the obtained double-doped material may be further increased compared to single-doped A3V2(P 1-y L y O4)3.

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

[0030] In some embodiments of the present disclosure, element L includes, but is not limited to, one or more of Si, Ge, and Sn. Using the above elements for doping of phosphates makes the manufacturing process more controllable, improves the product yield, and stabilizes the performance of the manufactured battery materials.

[0031] In some embodiments of the present disclosure, element L is element Si and / or element B. Generally, the theoretical specific capacity C of a material is calculated according to the following formula, i.e., C = (F × n × m) / (t × M), where F is the Faraday constant, n is the number of electrons lost when the active material A3V 2-x E x (P 1-y L y O4)3 (where x may be 0) is converted to AV 2-x E x (P 1-y L y O4)3 (where x may be 0), m is the mass of the fully charged active material A3V 2-x E x (P 1-y L y O4)3, t is time, and M is the molar mass of A3V 2-x E x (P 1-y L y O4)3. It can be seen that when the molar mass M of the active material A3V 2-x E x (P 1-y L y O4)3 decreases, the theoretical specific capacity C increases. Since the atomic mass of element Si and the atomic mass of element B are smaller than the atomic mass of element P, by substituting part of element P with Si and B, the theoretical specific capacity of the material can be increased, thereby further improving the energy density of the material.

[0032] In some embodiments of the present disclosure, the range of the value of y is 1 / 18 ≤ y ≤ 1 / 6. By controlling the doping amount of element L within the above range, the risk that the unit cell structure of the original compound A3V2(PO4)3 caused by the doping of element L changes excessively can be sufficiently reduced, facilitating the manufacturing process. Furthermore, due to the intercalation / deintercalation of A ions during the charge / discharge process, the change in the lattice constant (including the unit cell volume) during the crystal structure conversion between the material A3V 2-x E x (P 1-y L y (O4)3 (where x may be 0) and its corresponding fully charged compound is small, and the risk of structural collapse of the material doped with element L is small during the charge / discharge cycle. As a result, while achieving good conductivity of the material, good cycle performance of the material can be ensured.

[0033] In some other embodiments of the present disclosure, the range of the value of y is 1 / 6 ≤ y ≤ 1 / 3. By controlling the doping amount of element L within the above range, the operating voltage may be increased more significantly. Furthermore, good conductivity of the material may be achieved.

[0034] In some embodiments of the present disclosure, y is 1 / 18. In this case, the material A3V 2-x E x (P 1-y L y (O4)3 (where x may be 0) has very high crystallinity. In some other embodiments, y is 1 / 6. In this case, the material A3V 2-x E x (P 1-y L y (O4)3 has a high operating voltage, good structural stability, and good electronic conductivity. In some other embodiments, y is 1 / 3. In this case, the material A3V 2-x E x (P 1-y L y (O4)3 (where x may be 0) has the highest operating voltage and good electronic conductivity.

[0035] In some embodiments of the present disclosure, the transition metal element includes, but is not limited to, 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, but is not limited to, La and / or 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 the cost of the lanthanide elements La and Ce. The ionic radii of Cr, Mn, Fe, Co, Ni, Cu, and Zn are slightly smaller than the ionic radius of V ions. Doping with such elements can reduce the unit cell volume of A3V2(PO4)3, thereby further improving the structural stability of the material. In some other embodiments of the present disclosure, in order to better balance the cost of element E and its influence on the operating voltage of the material, element E may be one or more of Ti, Cr, Mn, and Fe. These elements also help to increase the operating voltage of the doped material. Fe has the lowest cost, and Mn contributes by increasing the charge and discharge voltage of the material.

[0038] In some specific embodiments, element E is Mn and element L is Si. A3V 2-x Mn x (P 1-y Si y (O4)3 has a high yield, and the manufactured material has a high operating voltage and thus a high energy density.

[0039] In some embodiments of the present disclosure, x is preferably in the range of 0.1 ≦ x ≦ 1. By controlling the doping amount of element E within the above range, the A3V caused by the excessive doping amount of E 2-x E x (P1-y L y It is possible to avoid the loss of the electrochemical activity of O4)3 and ensure that the doping of element E can improve the electrochemical performance of the material.

[0040] Embodiments of the present disclosure provide a method for manufacturing a battery material, the method comprising: The general molecular formula of the battery material to be manufactured is A3V 2-x E x (P 1-y L y O4)3, weighing an A source, a vanadium source, an E source, a phosphorus source, and an L source, and mixing these sources to obtain a precursor material, wherein element E represents a doping element that replaces element V, the element E includes one or more of a transition metal element, Mg, and Sr, element L represents a doping element that replaces element P, element L includes one or more of B, Al, Ga, Si, Ge, and Sn, element A represents an alkali metal element, x and y respectively represent the molar percentage of element V replaced by the doping element and the molar percentage of element P replaced by the doping element, 0 ≦ x ≦ 1, 0 < y ≦ 1 / 3, and when element L is element B, x is not 0, obtaining a precursor material; firing the precursor material in an inert gas atmosphere to obtain a battery material.

[0041] According to the above manufacturing method, the battery material according to the embodiments of the present disclosure may be obtained by mixing raw materials according to a predetermined ratio to obtain a precursor material and then firing the mixed raw materials. This manufacturing method has the advantages of simple operation, high process controllability, and the ability to realize large-scale industrial production.

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

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

[0044] Specifically, the solid-phase mixing method may be to obtain a precursor material by mixing an A source, a vanadium source, an E source, a phosphorus source, and an L source in a ball mill at a predetermined ratio.

[0045] Specifically, the sol-gel method may be to add an A source, a vanadium source, an E source, a phosphorus source, and an L source to a solvent at a predetermined ratio, heat the mixture, stir it sufficiently to form a gel, and continue to heat and stir the gel to evaporate the solvent to obtain a precursor material. The heating and stirring are performed at 30°C to 200°C, at 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 specifically, it may be one or more of water, ethanol, and acetone.

[0047] In some embodiments of the present disclosure, the firing conditions include firing the precursor material in 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, or helium.

[0049] In the present disclosure, the A source (element A is at least one of Li, Na, and K) may be at least one of a nitrate, oxalate, acetate, and acetylacetonate salt of element A. For example, when element A is only Na, the Na source may 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 is trivalent, tetravalent, or pentavalent in the compound. For example, the vanadium source may be at least one of vanadium pentoxide, vanadium tetraoxide, 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 may be at least one of titanium oxide, titanium tetrabutyl, titanium tetraisopropoxide, titanium ethoxide, etc.

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

[0053] In the present disclosure, the L source may be at least one of an acid, an ester, or a salt of a specific doping element corresponding to the element L. For example, when the element L is the element Si, the L source may be tetraethyl silicate, sodium silicate, etc.

[0054] Embodiments of the present disclosure provide an electrode. The electrode includes the battery material described above.

[0055] This electrode may be used to provide a secondary battery having excellent electrochemical performance such as high energy density and good rate characteristics.

[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 surface of the positive electrode current collector. The positive electrode active material layer includes the positive electrode active material described above. In addition, the positive electrode active material layer may further include a binder and optionally a conductive agent. The binder and the conductive agent may be conventional options in the field of batteries.

[0057] The positive electrode current collector may be various materials suitable for use as the current collector of the positive electrode, including but not limited to metal element foils, alloy foils, metal-plated polymer films, or any of the above materials with carbon coated on their surfaces. The metal element foil may be an aluminum foil. The alloy foil may be an aluminum alloy foil. The metal plated on the surface of the polymer film may be an aluminum element layer or an aluminum alloy layer.

[0058] Embodiments of the present disclosure further provide a secondary battery. The secondary battery includes the electrode or battery material described above. Specifically, the secondary battery may be a lithium secondary battery, a sodium secondary battery, or a potassium secondary battery. This secondary battery contains the above-mentioned AV 2-x E x (P 1-y L y O4)3, and thus has high energy density, good rate performance, good cycle performance, etc. The secondary battery can be used in 3C electronic products (such as mobile phones, tablet computers, etc.), vehicles (such as automobiles, ships, etc.), or other electrical equipment to improve the performance and market competitiveness of the electrical equipment.

[0059] The secondary battery may be a liquid battery using a liquid electrolyte, or may be a semi-solid state or solid state battery using a semi-solid or solid electrolyte. In some embodiments, the secondary battery may include the positive electrode, the negative electrode, and a separator and an electrolyte solution between the positive electrode and the negative electrode as described above. In some other embodiments, the secondary battery may include the positive electrode, the negative electrode, and a semi-solid or solid electrolyte between the positive electrode and the negative electrode. In particular, the battery materials provided by the embodiments of the present disclosure may be used as a semi-solid or solid electrolyte. In addition, when a semi-solid or solid electrolyte is used, the positive electrode and the negative electrode may further include a semi-solid electrolyte material or a solid electrolyte material.

[0060] The technical solutions of the present disclosure will be further described in detail below through a plurality of examples.

[0061] (Example 1) The battery material was manufactured according to the following operations.

[0062] Sodium nitrate as a sodium source, vanadium pentoxide as a vanadium source, phosphoric acid as a phosphorus source, and tetraethyl orthosilicate as an Si source were weighed so that the molar ratio of Na:V:P:Si was 3:2:2.84:0.17, and added to ethanol as a solvent. This mixture was heated and stirred at 80 °C to evaporate the solvent to obtain a precursor material.

[0063] The precursor material was calcined at 800 °C for 12 hours in a protective nitrogen atmosphere to obtain the battery material Na3V2(P 17 / 18 Si 1 / 18 O4)3.

[0064] (Example 2) This example was the same as Example 1 except that the content of the silicon source was finely adjusted. The general molecular formula of the manufactured battery material was Na3V2(P 5 / 6 Si 1 / 6 O4)3.

[0065] (Example 3) This example was the same as Example 1 except that the content of the silicon source was finely adjusted. The general molecular formula of the manufactured battery material was Na3V2(P 2 / 3 Si 1 / 3 O4)3.

[0066] (Example 4) This example was the same as Example 1 except that the content of the silicon source was finely adjusted. The general molecular formula of the manufactured battery material was Na3V2(P 0.97 Si 0.03 O4)3.

[0067] (Example 5) This example was the same as Example 1 except that the silicon source was replaced with a Ge source of germanium dioxide and the manufacturing process was finely adjusted. The general molecular formula of the manufactured battery material was Na3V2(P 17 / 18 Ge 1 / 18 O4)3.

[0068] (Example 6) This example was the same as Example 1 except that the silicon source was replaced with an Sn source of tin oxide and the manufacturing process was finely adjusted. The general molecular formula of the manufactured battery material was Na3V2(P 17 / 18 Sn 1 / 18 O4)3.

[0069] (Example 7) (1) Sodium nitrate as the sodium source, vanadium pentoxide as the vanadium source, manganese dioxide as the Mn source, phosphoric acid as the phosphorus source, and tetraethyl silicate as the Si source were weighed so as to have a molar ratio of Na:V:Mn:P:Si = 3:1.5:0.5:2.84:0.17, and supplied to a ball mill for mixing to obtain a precursor material.

[0070] (2) The precursor material was calcined at 800 °C for 12 hours in a protective nitrogen atmosphere to obtain the battery material Na3V 1.5 Mn 0.5 (P 17 / 18 Si 1 / 18 O4)3.

[0071] (Example 8) This example was the same as Example 6, except that the content of the Mn source was finely adjusted, and the general molecular formula of the produced battery material was Na3V 1.8 Mn 0.2 (P 17 / 18 Si 1 / 18 O4)3

[0072] (Example 9) This example was the same as Example 6, except that the Mn source was replaced with an Fe source which was iron oxide, and the manufacturing process was finely adjusted. The general molecular formula of the produced battery material was Na3V 1.5 Fe 0.5 (P 17 / 18 Si 1 / 18 O4)3

[0073] (Example 10) This example was the same as Example 6, except that the Mn source was replaced with a Ti source which was titanium oxide, and the manufacturing process was finely adjusted. The general molecular formula of the produced battery material was Na3V 1.5 Ti 0.5 (P 17 / 18 Si 1 / 18 O4)3

[0074] (Example 11) This example was the same as Example 6, except that the Mn source was replaced with a Cr source which was chromium oxide, and the manufacturing process was finely adjusted. The general molecular formula of the produced battery material was Na3V 1.5 Cr 0.5 (P 17 / 18 Si 1 / 18 O4)3

[0075] (Example 12) This example was the same as Example 6, except that the Si source was replaced with a B source which was sodium tetraborate, and the content of the Na source and the subsequent manufacturing process were finely adjusted. The general molecular formula of the produced battery material was Na3V 1.5 Mn 0.5 (P 17 / 18 B 1 / 18 O4)3

[0076] (Example 13) This example was the same as Example 6, except that potassium nitrate was further added as the potassium source and the content of the Na source and the subsequent manufacturing process were finely adjusted. The general molecular formula of the manufactured battery material was Na2K1V 1.5 Mn 0.5 (P 17 / 18 Si 1 / 18 O4)3.

[0077] (Example 14) This example was the same as Example 1, except that the Na source was replaced with a Li source which was lithium nitrate. The general molecular formula of the manufactured battery material was Li3V2(P 17 / 18 Si 1 / 18 O4)3.

[0078] (Comparative Example 1) A battery material was manufactured. The general molecular formula of the battery material was Na3V2(PO4)3.

[0079] (Comparative Example 2) A battery material was manufactured. The general molecular formula of the battery material was Na3V 1.5 Fe 0.5 (PO4)3.

[0080] (Comparative Example 3) A battery material was manufactured. The general molecular formula of the battery material was Na3V2(P 17 / 18 B 1 / 18 O4)3.

[0081] Performance Test (1) Characteristic evaluation of the crystal structure of the material: The battery materials of Examples 1 to 3 and Comparative Example 1 were evaluated by XRD. The results are as shown in Figure 1.

[0082] (2) Electronic conductivity of the battery materials of the examples and comparative examples: The powder to be tested was put into a powder resistivity tester. A pressure of 50 MPa was applied and maintained for 10 seconds. The powder resistivity was measured by the four-probe method and could be converted into electronic conductivity (electronic conductivity is the reciprocal of resistivity).

[0083] (3) To further strongly support the beneficial effects of the embodiments of the present disclosure, the materials of the examples and comparative examples were fabricated into batteries and subjected to electrochemical performance tests. The related results are shown in Table 2.

[0084] The manufacturing process of the battery is as follows. (1) Manufacturing of the positive electrode: The battery materials of each example or comparative example, acetylene black conductive agent as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were added to NMP (N-methylpyrrolidone) as a solvent at a mass ratio of 88:6:6, and uniformly stirred to obtain a positive electrode slurry. The positive electrode slurry was coated on an aluminum foil which is a positive electrode current collector, dried, rolled, and cut to obtain a positive electrode. (2) Manufacturing of the negative electrode: The negative electrode active material (specifically, graphite), and a binder (specifically, a mixture of styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na) at a mass ratio of 2:3) were mixed with ionized water at a mass ratio of 95:5, and uniformly stirred to obtain a negative electrode slurry. The negative electrode slurry was coated on a copper foil which is a negative electrode current collector, dried, rolled, and cut to obtain a negative electrode. (3) Battery assembly: The positive electrode, separator, and negative electrode were alternately laminated to obtain a battery core. The battery core was wound, placed in an outer packaging foil which is an aluminum-plastic film, injected with an electrolyte solution, and then processes such as vacuum packaging, standing, formation, and shaping were carried out to complete the manufacturing of the sodium battery. The sodium secondary batteries manufactured from the battery materials of the examples and comparative examples were respectively designated as S1 to S14 and DS1 to DS3.

[0085] The batteries S1 to S14 and DS1 to DS3 were tested for their electrochemical performance.

[0086] 1) Cycle performance: For each battery, a charge-discharge cycle test was carried out at a current of 0.5C at 25°C, and the voltage range was 2.5V to 4.3V. During charging, the battery was first charged at a constant current of 0.5C until the cut-off voltage of 4.3V, and then charged at a constant voltage until the cut-off current of 0.05C. During discharging, the battery was discharged at a constant current of 0.5C until 2.5V. The specific discharge capacity of the first cycle and the capacity retention rate after 50 cycles of each battery were recorded. The specific discharge capacity of the first cycle is equal to the ratio of the discharge capacity of the first cycle of each button battery to the mass of the positive electrode active material in the battery. The capacity retention rate after 50 cycles is equal to the ratio of the discharge capacity after 50 cycles to the discharge capacity of the first cycle.

[0087] In addition, for the charge-discharge curve obtained by charging and discharging each battery at a constant current of 0.5C, the discharge curve was integrated and divided by the discharge capacity of the first cycle to obtain the average voltage of each battery, that is, the charge-discharge plateau voltage.

[0088] The related results are summarized in Table 2, and the cycle curves of some examples and comparative examples are summarized in Figure 2.

[0089] 2) Rate performance: The change in the discharge gram capacity of each battery with the number of cycles at different rates such as 0.1C, 2C, 5C, and 15C was tested at 25°C, and the voltage range was 2.5V to 4.3V. The rate performance curves of some examples and comparative examples are as shown in Figure 4. For the calculation of the gram capacity, the ratio of the discharge capacity at a certain current density to the mass of the positive electrode active material is used as the discharge gram capacity at that current density. Table 2 shows the specific discharge capacity of the first cycle of each battery at 15C, and the ratio of the discharge capacity of the first cycle at 15C to the discharge capacity of the first cycle at 0.1C.

Table 1

Table 2

[0090] First, after doping the P-site of Na3V2(PO4)3, it can be clearly seen from FIGS. 2 to 4 that the maximum specific capacity released by the battery material is significantly higher than that of the undoped material, the capacity retention rate is also improved, and it shows good cycle performance. In addition, the charge-discharge voltage plateau of Examples 1 to 3 was also significantly improved compared to Comparative Example 1. When doped only with the linosite, it can be seen that the higher the doping amount (y is 1 / 3 or less), the higher the charge-discharge plateau voltage of the battery. In addition, the battery capacities of Examples 1 to 3 at high current densities (5C and 15C) were significantly higher than those of Comparative Example 1, and the undoped material showed a serious capacity reduction as the current density gradually increased. In contrast, the material doped at the P-site showed good rate performance.

[0091] Regarding the doping of the same element L, it can be seen from the data in Table 2 that the higher the doping amount of the linosite, the higher the charge-discharge voltage plateau of the material. It can be seen that the rate performance, specific capacity of the battery, and cycle capacity retention rate of the material doped with the linosite were significantly higher than those of Na3V2(PO4)3 compared to the battery of Comparative Example 1. By introducing doping into the vanadium site based on the doping of the linosite, the charge-discharge voltage plateau of the material can be further increased, but the doping effect varies slightly depending on the different element E.

[0092] Although the exemplary embodiments of the present disclosure have been described above, the present disclosure is not limited thereto. It should be understood that some improvements and modifications may be made by those skilled in the art without departing from the technical principle of the present disclosure, and these are also considered to be within the scope of the present disclosure.

Claims

1. A battery material, wherein the general molecular formula of the battery material is A ３ V ２－ｘ E ｘ (P １－ｙ L ｙ O ４ ) ３ and, in the formula, element E represents a doping element that substitutes for element V and includes at least one of a transition metal element, a rare earth element, Mg, and Sr; element L represents a doping element that substitutes for element P and includes at least one of B, Al, Ga, Si, Ge, and Sn; element A represents an alkali metal element; 0 ≦ x ≦ 1 and 0 < y ≦ 1 / 3; and when element L is element B, x is not 0. A battery material.

2. The battery material according to claim 1, wherein the element L contains at least one of Si, Ge, and Sn.

3. The battery material according to claim 1 or 2, wherein 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.

4. The battery material according to any one of claims 1 to 3, wherein the value range of x is 0.1 ≦ x ≦ 1.

5. The battery material according to any one of claims 1 to 4, wherein the value range of y is 1 / 18 ≦ y ≦ 1 / 3.

6. The general molecular formula A of the battery material to be manufactured ３ V ２－ｘ E ｘ (P １－ｙ L ｙ O ４ ) ３ According to this, weigh the A source, vanadium source, E source, phosphorus source, and L source, and mix and process the sources to obtain a precursor material. In the formula, the element E represents a doping element that replaces the element V and comprises at least one of transition metal elements, rare earth elements, Mg, and Sr; the element L represents a doping element that replaces the element P and comprises at least one of B, Al, Ga, Si, Ge, and Sn; the element A represents an alkali metal element, 0 ≦ x ≦ 1, and 0 < y ≦ 1 / 3. When the element L is the element B, x is not 0. Obtaining the precursor material, Firing the precursor material to obtain the battery material; A manufacturing method for a battery material, comprising:

7. The manufacturing method according to claim 6, wherein the firing conditions include firing the precursor material at 400°C to 900°C for 10 hours to 30 hours in an inert gas atmosphere.

8. The manufacturing method according to claim 7, wherein the inert gas contains at least one of argon, nitrogen, and helium.

9. The manufacturing method according to any one of claims 6 to 8, wherein the mixing treatment includes a solid-phase mixing method or a sol-gel method.

10. The manufacturing method according to any one of claims 6 to 9, wherein the element L contains at least one of Si, Ge, and Sn.

11. The manufacturing method according to any one of claims 6 to 10, wherein 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.

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

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

14. A secondary battery comprising the battery material according to any one of claims 1 to 5.

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