A battery material and its preparation method and application

Abstract

The present application provides a battery material and a preparation method and application thereof. The molecular formula of the battery material includes A 3 V 2‑x E x (P 1‑y L y O 4 ) 3 , wherein the E element represents a doping element replacing the V element, the L element represents a doping element replacing the P element, the L element includes one or more of B, Al, Ga, Si, Ge and Sn, the E element includes one or more of transition metal elements, rare earth elements, Mg and Sr, and the A element represents an alkali metal element, wherein 0≤x≤1, 0<y≤1 / 3; and when the L element is the B element, x is not 0. The material can effectively improve the charge and discharge voltage and electronic conductivity of the material by doping the anion phosphorus site of the alkali metal vanadium phosphate.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery material and a preparation method and application thereof. Background Art

[0002] Battery materials, such as electrode materials and solid electrolyte materials, are key components of batteries and have a significant impact on battery performance. Taking sodium-ion batteries as an example, Na3V2(PO4)3 materials, as fast ion conductor materials for three-dimensional ion channels, are often used as positive electrode materials or solid electrolytes because of their potential advantages such as stable crystal structure, adjustable operating voltage, and high theoretical specific capacity. However, this type of material still has pain points such as low electronic conductivity and low charge and discharge voltage platform.

[0003] There are literature reports on doping and modification of the above materials to solve their existing problems, but the doping schemes commonly used in the industry currently have limited effects on improving the electrochemical properties of the materials. Summary of the invention

[0004] In view of this, the present application provides a battery material. The material can effectively improve the charge and discharge voltage and electronic conductivity of the material by doping the anion phosphorus site of alkali metal vanadium phosphate.

[0005] The first aspect of the present application provides a battery material, the molecular formula of which includes A3V 2-x E x (P 1-y L y O4)3, wherein the E element represents a doping element replacing the V element, the L element represents a doping element replacing the P element, the L element includes one or more of B, Al, Ga, Si, Ge and Sn, the E element includes one or more of transition metal elements, Mg and Sr, the A element represents an alkali metal element, x and y represent the molar percentage of the V element and the P element replaced by the doping element, respectively, wherein 0≤x≤1, 0<y≤1 / 3; and when the L element is the B element, x is not 0.

[0006] The electronegativity of the above L elements is smaller than that of the P element. Therefore, the substitution of the doped element L for some of the P elements can cause the valence state of the O atoms originally connected to the P element to change, so that the polyanion group LO4 formed by L and O oxygen atoms m- (-m is the overall charge of the polyanion group, m>0) structure shrinkage, so A3V2 (P 1-y L yThe unit cell structure of the O4)3 compound shrinks, causing the total energy of the unit cell structure to decrease, thereby increasing the working voltage of the material, and the unit cell structure shrinkage is beneficial to improving the structural stability of the material, and further to improving the cycle performance of the material. In addition, the phosphorus doping of the above-mentioned L element can stimulate and induce the V element to undergo redox reaction at a high potential, further increasing the working voltage of the material and the energy density of the material. Furthermore, the phosphorus doping of the L element can reduce the A3V2(P 1-y L y O4)3 compounds, and improve the electronic conductivity of the material. In addition, by controlling the doping amount of the L element within a suitable range, the material can have a higher charge and discharge voltage platform and good electronic conductivity while ensuring good structural stability.

[0007] The second aspect of the present application provides a method for preparing a battery material, comprising the following steps:

[0008] (1) According to the molecular formula of the battery material to be prepared, A3V 2-x E x (P 1-y L y O4)3 weigh A source, vanadium source, E source, phosphorus source, and L source, and mix them to obtain a precursor material; wherein the molecular formula of the battery material includes A3V 2-x E x (P 1- y L y O4)3, wherein the E element represents a doping element replacing the V element, the L element represents a doping element replacing the P element, the L element includes one or more of B, Al, Ga, Si, Ge and Sn, the E element includes one or more of transition metal elements, rare earth elements, Mg and Sr, and the A element represents an alkali metal element; 0≤x≤1, 0<y≤1 / 3; and when the L element is the B element, x is not 0;

[0009] (2) calcining the precursor material to obtain the battery material.

[0010] The preparation method has simple process, strong controllability and can realize large-scale industrial production.

[0011] The third aspect of the present application provides an electrode plate, comprising the battery material provided in the first aspect of the present application.

[0012] The electrode plate can be used to provide a secondary battery with higher energy density and good rate performance.

[0013] The fourth aspect of the present application provides a secondary battery, comprising the electrode plate provided in the third aspect of the present application or the battery material provided in the first aspect of the present application.

[0014] The secondary battery has high energy density and relatively good rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 X-ray diffraction (XRD) spectra of the battery materials of Examples 1-3 and Comparative Example 1 of the present application;

[0016] Figure 2 The specific capacity-cycle number curves of the batteries prepared in Examples 1-3 and Comparative Example 1 of the present application;

[0017] Figure 3 The charge and discharge voltage platform curves of the batteries prepared in Examples 1-3 and Comparative Example 1 of the present application;

[0018] Figure 4 The specific capacity-cycle number curves of the batteries prepared in Examples 1-3 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0019] NASICON compounds are a type of fast ion conductor material with three-dimensional ion channels proposed by Professor Goodenough. The above materials can be used as electrode materials as well as solid electrolyte materials. In order to explain the beneficial effects of the present application more clearly, the crystal structure of NASICON compounds is briefly described below using Na3V2(PO4)3 (abbreviated as NVP) as an example.

[0020] Each structural unit of the NVP material contains three PO4 tetrahedrons and two VO6 octahedra, which are connected by common vertex oxygen atoms to form an alkali metal ion (specifically sodium ions) that can accommodate two types of different oxygen environments. Sodium ions occupy the Na(1) position and the Na(2) position respectively. It is generally believed that only the sodium ions at the Na(2) position can be extracted / embedded during the charge and discharge process, thereby completing the lattice configuration transformation between the empty state Na3V2(PO4)3 and the fully charged state NaV2(PO4)3. However, the above-mentioned crystal transformation that occurs during the charge and discharge cycle will cause the structural stability of the material during the charge and discharge process to gradually decrease, affecting the normal performance of the battery. In addition, the above-mentioned materials still have pain points such as low electronic conductivity and low charge and discharge voltage platform.

[0021] In order to solve the above problems, the present application provides a battery material, the molecular formula of which includes A3V 2-x E x (P 1-y L yO4)3, wherein the E element represents a doping element replacing the V element, the L element represents a doping element replacing the P element, the L element includes one or more of B, Al, Ga, Si, Ge and Sn, the E element includes one or more of transition metal elements, rare earth elements, Mg and Sr, and the A element represents an alkali metal element, wherein x and y respectively represent the molar percentage of the doping element, 0≤x≤1, 0<y≤1 / 3; and when the L element is the B element, x is not 0.

[0022] The electronegativity of the L element is less than that of the P element, and 0<y≤1 / 3, that is, the L atom replaces the P atom in some PO4 tetrahedrons in some structural units, thereby changing the number of charges around the oxygen atoms in the original PO4 tetrahedron, causing the ion radius of some oxygen atoms to shrink, and A3V2(P 1-y L y O4)3 compound is the skeleton structure material, so A3V2(P 1-y L y O4)3 unit cell volume will shrink, making A3V2(P 1-y L y O4)3 unit cell structure total energy is reduced, thereby improving the working voltage of the material and the structural stability of the material. 1-y L y The volume change rate of A3V2(PO4)3 during the charge and discharge process is small, and it can maintain a high structural stability while maintaining a high electronic conductivity. In addition, the PO4 tetrahedron and the VO6 octahedron share the vertex oxygen atoms, so the L element doping causes the charge of the surrounding O atoms to change, forcing the charge environment around the V atoms to change, inducing the V element to undergo oxidation and reduction at a high potential, so the working voltage of the material can be increased, thereby increasing the energy density of the material; at the same time, the doping element L can also significantly reduce the band gap value of the original A3V2(PO4)3 material, so that more electrons gather near the Fermi surface, thereby improving the electronic conductivity of the material and the electrochemical power of the material during the charge and discharge process, which is helpful to improve the rate performance of the secondary battery. In addition, controlling the doping amount of the L element within the above range can ensure that the material has a good structural stability while allowing the material to take into account a higher charge and discharge voltage platform and good electronic conductivity.

[0023] Furthermore, when the above-mentioned appropriate amount of E element is used to treat A3V2 (P 1-y L y When V-doping is performed on A3V2(P)O4)3, the charge-discharge voltage platform of the obtained dual-doped material can be higher than that of the single-doped L A3V2(P)O4)3 by virtue of the synergistic effect of V-doping of the E element and P-doping of the L element. 1-y L y O4)3 is further improved.

[0024] In some embodiments of the present application, the A element includes but is not limited to one or more of Li, Na, and K. The A element can be selected according to the specific type of secondary battery. 2-x E x (P 1-y L y O4)3 is used in sodium secondary batteries, and the A element can be Na.

[0025] In some embodiments of the present application, the L element includes but is not limited to one or more of Si, Ge and Sn. By doping the phosphorus position with the above elements, the preparation process is more controllable, the product yield is higher, and the performance of the obtained battery material is more stable.

[0026] In some embodiments of the present application, the L element is Si and / or B element. Generally, the calculation method of the theoretical specific capacity C of the material is as follows: Among them, F is the Faraday constant, n is A3V during the charging process 2-x E x (P 1-y L y O4)3 (x can be 0) active material is transformed into AV 2-x E x (P 1-y L y O4)3 (x can be 0) when losing electrons, m is the number of fully charged active materials A3V 2-x E x (P 1-y L y O4)3 mass, t is time, M is A3V 2-x E x (P 1-y L y O4)3 molar mass. It can be seen that when the active material A3V 2-x E x (P 1-y L y When the molar mass M of O4)3 becomes lower, it is beneficial to increase the theoretical specific capacity C. Since the atomic mass of Si and B is smaller than that of P, replacing part of P with Si and B can increase the theoretical specific capacity of the material, which is beneficial to further improve the energy density of the material.

[0027] In some embodiments of the present application, the value range of y is: 1 / 18≤y≤1 / 6. Controlling the doping amount of L element within the above range can fully reduce the risk of excessive changes in the unit cell structure of the original A3V2(PO4)3 compound caused by L element doping and is easier to prepare. 2-x E x (P 1-yL y When the O4)3 (x can be 0) material undergoes a crystal configuration transformation between the de-insertion / embedding of A ions and its corresponding fully charged compound during the charge and discharge process, the change rate of each lattice constant (including the unit cell volume) is small. The material doped with the L element has a lower risk of structural collapse during the cyclic charge and discharge process, which can ensure good cycle performance of the material while taking into account the electrical conductivity of the material.

[0028] In some other embodiments of the present application, the value range of y is: 1 / 6≤y≤1 / 3. If the doping amount of L element is controlled within the above range, the improvement of the working voltage is more obvious. In addition, the conductivity of the material can also be controlled to be better.

[0029] In some embodiments of the present application, y is 1 / 18. 2-x E x (P 1-y L y O4)3 (x can be 0) material has high crystallinity. In other embodiments, y is 1 / 6. 2-x E x (P 1-y L y O4)3 material has a higher working voltage, better structural stability, and better electronic conductivity. In some other embodiments, y is 1 / 3. At this time, A3V 2-x E x (P 1-y L y O4)3 (x can be 0) material has the highest working voltage and better electronic conductivity.

[0030] In some embodiments of the present application, 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.

[0031] In some embodiments of the present application, the rare earth element includes but is not limited to La and / or Ce.

[0032] In some embodiments of the present application, the above-mentioned E element includes one or more of Mg, Sr, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ti, Mo, Nb and Zr. These elements are lower in cost than lanthanide elements La and Ce. Among them, the ionic radius of Cr, Mn, Fe, Co, Ni, Cu and Zn is slightly smaller than that of V ions, and doping these elements A3V2(PO4)3 will reduce the unit cell volume, which is conducive to further improving the structural stability of the material. In some other embodiments of the present application, in order to better balance the cost of E elements and the impact on the working voltage of the material, E elements can be selected from one or more of Ti, Cr, Mn and Fe. These elements are also helpful in improving the working voltage of doped materials. Among them, Fe has the lowest cost, and Mn is more conducive to improving the charge and discharge voltage of the material.

[0033] In some specific embodiments, the E element is Mn, and the L element is Si. 2-x Mn x (P 1-y Si y O4)3 has a higher yield, and the produced material has a higher working voltage, and thus the energy density of the material is higher.

[0034] In some embodiments of the present application, the above x is preferably in the range of 0.1≤x≤1. By controlling the doping amount of the E element within the above range, it is possible to avoid excessive doping of the E element and thus causing the above A3V 2-x E x (P 1-y L y O4)3 loses its electrochemical activity, and the doping of E elements can also improve the electrochemical properties of the material.

[0035] Accordingly, the present invention provides a method for preparing a battery material, comprising the following steps:

[0036] (1) According to the molecular formula of the battery material to be prepared, A3V 2-x E x (P 1-y L y O4)3 weigh A source, vanadium source, E source, phosphorus source, and L source, and mix them to obtain a precursor material; wherein the E element represents a doping element replacing the V element, the L element represents a doping element replacing the P element, the L element includes one or more of B, Al, Ga, Si, Ge, and Sn, the E element includes one or more of transition metal elements, Mg, and Sr, the A element represents an alkali metal element, x and y represent the molar percentage of the V element and the P element replaced by the doping element, respectively, wherein 0≤x≤1, 0<y≤1 / 3; and when the L element is the B element, x is not 0;

[0037] (2) calcining the precursor material under the protection of an inert gas to obtain the battery material.

[0038] The above preparation method only needs to mix the raw materials in a preset ratio to obtain a precursor material, and then calcine to obtain the battery material provided in the embodiment of the present application. This preparation method has simple steps, strong process controllability, and can be prepared on a large scale in an industrial manner.

[0039] In some embodiments of the present application, in step (1), the A source, the vanadium source, the E source, the phosphorus source, and the L source are weighed and mixed according to the molar ratio of A element: V element: E element: P element: L element = 3: (2-x): x: (3-3y): 3y. In some embodiments, in order to make up for the loss of the alkali metal element A during the preparation process, the A element can be in excess of 10%.

[0040] In some embodiments of the present application, the mixing treatment method in step (1) includes but is not limited to a solid phase mixing method or a sol-gel method.

[0041] The specific steps of the solid phase mixing method may be: adding the above-mentioned A source, vanadium source, E source, phosphorus source, and L source into a ball mill in proportion, and mixing to obtain a precursor material.

[0042] The specific steps of the sol-gel method may be: adding the above-mentioned A source, vanadium source, E source, phosphorus source, and L source to a solvent in proportion, heating and stirring to react and generate a gel, and continuing to heat and stir to evaporate the solvent in the obtained gel to obtain the above-mentioned precursor material. The heating and stirring temperature is 30°C-200°C, the stirring rate is 300rpm-900rpm, and the time is 1h-6h.

[0043] In the present application, the above-mentioned solvent is a volatile solvent, and specifically can be one or more of water, ethanol and acetone.

[0044] In some embodiments of the present application, in step (2), the calcination treatment conditions are: calcination at a temperature of 400° C.-900° C. for 10 h-30 h under the protection of an inert gas.

[0045] In the present application, the inert gas described in step (2) can specifically be at least one of argon, nitrogen, and helium.

[0046] In the present application, the above-mentioned A source (A element is at least one of Li, Na, K) can be at least one of nitrate, oxalate, acetate and acetylacetonate of element A. For example, when the A element is only Na, the Na source can be at least one of sodium nitrate, sodium oxalate, sodium acetate and sodium acetylacetonate.

[0047] In the present application, 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 tetroxide, vanadium trioxide, ammonium metavanadate, sodium metavanadate, vanadium acetylacetonate and vanadyl acetylacetonate.

[0048] In the present application, the E source is a compound familiar to those skilled in the art. For example, at least one of an organic metal salt, a metal acid salt, and a metal oxide of a specific element corresponding to the E element. Exemplarily, when the E element is Ti, the E source can be at least one of titanium oxide, tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, etc.

[0049] In the present application, the above-mentioned 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, etc.

[0050] In the present application, the L source may be at least one of an acid, an ester or a salt of a specific doping element corresponding to the L element. For example, when the L element is Si, the L source may be tetraethyl silicate, sodium silicate or the like.

[0051] Accordingly, an embodiment of the present application provides an electrode plate comprising the above-mentioned battery material.

[0052] The electrode plate can be used to provide a secondary battery with excellent electrochemical properties such as high energy density and good rate performance.

[0053] In some embodiments of the present application, the electrode plate is a positive electrode plate. The positive electrode plate 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, wherein the positive electrode active material layer contains the positive electrode active material. In addition, the positive electrode active material layer may also contain a binder and an optional conductive agent. Among them, the binder and the conductive agent may be conventional choices in the battery field.

[0054] The positive electrode current collector may be any material suitable for use as a current collector for a positive electrode sheet, including but not limited to metal single substance foil, alloy foil, metal-plated polymer film material, or the aforementioned material with carbon coated on the surface, etc. Among them, the metal single substance foil material may specifically be aluminum foil, the alloy foil material may be aluminum alloy foil, and the metal plated on the surface of the polymer film material may be an aluminum single substance layer or an aluminum alloy layer.

[0055] The present application also provides a secondary battery, comprising the electrode sheet or the battery material. 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 L yO4)3, it 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.), transportation tools (such as cars, ships, etc.) or other electrical equipment to improve the performance and market competitiveness of electrical equipment.

[0056] Among them, the secondary battery can be a liquid battery using a liquid electrolyte, or a semi-solid or solid battery using a semi-solid electrolyte or a solid electrolyte. In some embodiments, the secondary battery may include the above-mentioned positive electrode sheet, the negative electrode sheet, and a diaphragm and an electrolyte disposed between the positive electrode sheet and the negative electrode sheet. In other embodiments, the secondary battery may include a positive electrode sheet, a negative electrode sheet, and a semi-solid electrolyte or a solid electrolyte disposed between the positive electrode sheet and the negative electrode sheet. In particular, the battery material provided in the embodiment of the present application can be used as the above-mentioned semi-solid electrolyte or solid electrolyte material. In addition, when a semi-solid electrolyte or a solid electrolyte is used, the positive electrode sheet and the negative electrode sheet may also contain a semi-solid electrolyte material or a solid electrolyte material.

[0057] The technical solution of the present application is further described in detail below with multiple embodiments.

[0058] Example 1

[0059] The battery materials were prepared as follows:

[0060] (1) Sodium nitrate, a sodium source, vanadium pentoxide, phosphoric acid, and tetraethyl silicate, a Si source, are weighed according to a molar ratio of Na:V:P:Si=3:2:2.84:0.17, added to a solvent, ethanol, and heated and stirred at 80°C until the solvent evaporates to dryness, thereby obtaining a precursor material.

[0061] (2) The above precursor material was calcined at 800°C for 12 h under nitrogen atmosphere to obtain the battery material Na3V2(P 17 / 18 Si 1 / 18 O4)3.

[0062] Example 2

[0063] The only difference from Example 1 is that the content of the silicon source in step (1) is fine-tuned. The molecular formula of the obtained battery material is Na3V2(P 5 / 6 Si 1 / 6 O4)3.

[0064] Example 3

[0065] The only difference from Example 1 is that the content of the silicon source in step (1) is fine-tuned. The molecular formula of the obtained battery material is Na3V2(P 2 / 3 Si 1 / 3 O4)3.

[0066] Example 4

[0067] The only difference from Example 1 is that the content of the silicon source in step (1) is fine-tuned. The molecular formula of the obtained battery material is Na3V2(P 0.97 Si 0.03 O4)3.

[0068] Example 5

[0069] The only difference from Example 1 is that the silicon source in step (1) is replaced with a Ge source - germanium dioxide, and the preparation process is slightly adjusted. The molecular formula of the obtained battery material is Na3V2(P 17 / 18 Ge 1 / 18 O4)3.

[0070] Example 6

[0071] The only difference from Example 1 is that the silicon source in step (1) is replaced with a Sn source - tin oxide, and the preparation process is slightly adjusted. The molecular formula of the obtained battery material is Na3V2(P 17 / 18 Sn 1 / 18 O4)3.

[0072] Example 7

[0073] (1) Sodium source (sodium nitrate), vanadium source (vanadium pentoxide), Mn source (manganese dioxide), phosphorus source (phosphoric acid), and Si source (tetraethyl silicate) were weighed according to the molar ratio of Na element: V element: Mn element: P element: Si element = 3: 1.5: 0.5: 2.84: 0.17, added into a ball mill, and mixed to obtain a precursor material.

[0074] (2) The above precursor material was calcined at 800°C for 12 h under nitrogen atmosphere to obtain the battery material Na3V 1.5 Mn 0.5 (P 17 / 18 Si 1 / 18 O4)3.

[0075] Example 8

[0076] The only difference from Example 6 is that the content of the Mn source is slightly adjusted, and the molecular formula of the obtained battery material is Na3V 1.8 Mn 0.2 (P 17 / 18 Si 1 / 18 O4)3.

[0077] Example 9

[0078] The only difference from Example 6 is that the Mn source is replaced by the Fe source - ferrous oxide, and the preparation process is slightly adjusted. The molecular formula of the prepared battery material is Na3V1.5 Fe 0.5 (P 17 / 18 Si 1 / 18 O4)3.

[0079] Example 10

[0080] The only difference from Example 6 is that the Mn source is replaced by the Ti source - titanium oxide, and the preparation process is slightly adjusted. The molecular formula of the prepared battery material is Na3V 1.5 Ti 0.5 (P 17 / 18 Si 1 / 18 O4)3.

[0081] Embodiment 11

[0082] The only difference from Example 6 is that the Mn source is replaced by the Cr source - chromium oxide, and the preparation process is slightly adjusted. The molecular formula of the prepared battery material is Na3V 1.5 Cr 0.5 (P 17 / 18 Si 1 / 18 O4)3.

[0083] Example 12

[0084] The only difference from Example 6 is that the Si source is replaced by the B source - sodium tetraborate, and the Na source content and subsequent preparation process are slightly adjusted. The molecular formula of the prepared battery material is Na3V 1.5 Mn 0.5 (P 17 / 18 B 1 / 18 O4)3.

[0085] Embodiment 13

[0086] The only difference from Example 6 is that potassium source - potassium nitrate is added, and the content of Na source and subsequent preparation process are slightly adjusted. The molecular formula of the prepared battery material is Na2K1V 1.5 Mn 0.5 (P 17 / 18 Si 1 / 18 O4)3.

[0087] Embodiment 14

[0088] The only difference from Example 1 is that the Na source in step (1) is replaced by a Li source - lithium nitrate. The molecular formula of the obtained battery material is Li3V2(P 17 / 18 Si 1 / 18 O4)3.

[0089] Comparative Example 1

[0090] Battery material, its molecular formula is Na3V2(PO4)3.

[0091] Comparative Example 2

[0092] Battery material, its molecular formula is Na3V 1.5 Fe 0.5 (PO4)3.

[0093] Comparative Example 3

[0094] Battery material, its molecular formula is Na3V2(P 17 / 18 B 1 / 18 O4)3.

[0095] Performance Testing

[0096] (1) Material crystal structure characterization: XRD characterization was performed on the battery materials of Examples 1-3 and Comparative Example 1. The results are as follows: Figure 1 shown.

[0097] (2) Determination of the electronic conductivity of the battery materials of each embodiment and comparative example: The powder to be tested was placed in a powder resistivity tester and a pressure of 50 MPa was applied for 10 seconds. The powder resistivity was measured by a 4-probe method and converted into electronic conductivity (electronic conductivity is the reciprocal of resistivity).

[0098] (3) To further support the beneficial effects of the embodiments of the present application, the materials of the above embodiments and comparative examples were made into batteries and electrochemical performance tests were performed. The relevant results are shown in Table 2.

[0099] Among them, the manufacturing process of the battery is as follows: ① Preparation of positive electrode sheet: Add the conductive agent-acetylene black and the binder-polyvinylidene fluoride (PVDF) of each embodiment or comparative example to the solvent-NMP (N-methylpyrrolidone) at a mass ratio of 88:6:6, and stir evenly to obtain positive electrode slurry; apply the positive electrode slurry on the positive electrode collector-aluminum foil, dry, roll and cut to obtain positive electrode sheet. ② Preparation of negative electrode sheet: Mix the negative electrode active material (specifically graphite) and the binder (specifically styrene-butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC-Na, mass ratio is 2:3) in deionized water at a mass ratio of 95:5, stir evenly to obtain negative electrode slurry; apply the negative electrode slurry on the negative electrode collector-copper foil, dry, roll and cut to obtain negative electrode sheet. ③ Battery assembly: Alternately stack the above-mentioned positive electrode sheets with the separator and the negative electrode sheets to obtain a dry battery cell, and then wind the dry battery cell and place it in an aluminum-plastic film outer packaging foil, inject electrolyte, and complete the preparation of the sodium battery after vacuum packaging, standing, forming, shaping and other processes. The secondary sodium batteries prepared in each embodiment and comparative example are respectively recorded as S1-S14 and DS1-DS3.

[0100] The electrochemical performance tests of the above batteries S1-S14, DS1-DS3 were carried out:

[0101] 1) Cycle performance: Each battery was tested for charge and discharge cycles at 25°C with a current rate of 0.5C, and the voltage range was 2.5-4.3V. When charging, it was first charged at a constant current of 0.5C to a cut-off voltage of 4.3V, and then charged at a constant voltage to a cut-off current of 0.05C. When discharging, it was discharged at a constant current of 0.5C to 2.5V. The first-cycle discharge specific capacity of each battery and the capacity retention rate after 50 cycles were recorded. Among them, the first-cycle discharge specific capacity is equal to the ratio of the first-cycle discharge capacity 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 first-cycle discharge capacity.

[0102] In addition, the discharge curve of each battery obtained by charging and discharging at the above 0.5C constant current is integrated and divided by the first cycle discharge capacity to obtain the average voltage of each battery, that is, the charging and discharging voltage platform.

[0103] The relevant results are summarized in Table 2, and the cycle curves of some embodiments and comparative examples are summarized in Figure 2 .

[0104] 2) Rate performance: The discharge capacity of each battery at different rates of 0.1C, 2C, 5C, 15C, etc. was tested at 25°C to determine the change in discharge capacity with the number of cycles, with a voltage range of 2.5-4.3V. The rate performance curves of some embodiments and comparative examples are shown in Figure 2. Figure 4 As shown. When calculating the gram capacity, the mass ratio of the discharge capacity at a certain current density to the positive electrode active material is taken as the discharge gram capacity at the current density. Table 2 summarizes the first-cycle discharge specific capacity of each battery at a rate of 15C, as well as the ratio of the first-cycle discharge capacity at a rate of 15C to the first-cycle discharge capacity at 0.1C.

[0105] Table 1 Summary of electronic conductivity data of various examples and comparative examples

[0106] Experiment number Molecular formula of battery materials Electronic conductivity (μS / cm) Example 1 <![CDATA[Na3V2(P 17 / 18 And 1 / 18 O4)3]]> 9.9 Example 2 <![CDATA[Na3V2(P 5 / 6 And 1 / 6 O4)3]]> 10.2 Example 3 <![CDATA[Na3V2(P 2 / 3 And 1 / 3 O4)3]]> 11.1 Example 4 <![CDATA[Na3V2(P 0.97 And 0.03 O4)3]]> 8.8 Example 5 <![CDATA[Na3V2(P 17 / 18 Give 1 / 18 O4)3]]> 8.9 Example 6 <![CDATA[Na3V2(P 17 / 18 Sn 1 / 18 O4)3]]> 9.0 Example 7 <![CDATA[Na3V 1.5 Mn 0.5 (P 17 / 18 Yes 1 / 18 O4)3]]> 9.8 Example 8 <![CDATA[Na3V 1.8 Mn 0.2 (P 17 / 18 Yes 1 / 18 O4)3]]> 9.5 Example 9 <![CDATA[Na3V 1.5 Want 0.5 (P 17 / 18 To 1 / 18 O4)3]]> 12.6 Example 10 <![CDATA[Na3V 1.5 You 0.5 (P 17 / 18 Yes 1 / 18 O4)3]]> 12.7 Embodiment 11 <![CDATA[Na3V 1.5 Cr 0.5 (P 17 / 18 Yes 1 / 18 O4)3]]> 12.3 Example 12 <![CDATA[Na3V 1.5 Mn 0.5 (P 17 / 18 B 1 / 18 O4)3]]> 9.4 Embodiment 13 <![CDATA[Na2K1V 1.5 Mn 0.5 (P 17 / 18 Yes 1 / 18 O4)3]]> 9.6 Embodiment 14 <![CDATA[Li3V2(P 17 / 18 And 1 / 18 O4)3]]> 9.6 Comparative Example 1 <![CDATA[Na3V2(PO4)3]]> 8.7 Comparative Example 2 <![CDATA[Na3V 1.5 Fe 0.5 (PO4)3]]> 12.0 Comparative Example 3 <![CDATA[Na3V2(P 17 / 18 B 1 / 18 O4)3]]> 9.0

[0107] Table 2 Summary of electrochemical performance of batteries in various embodiments and comparative examples

[0108]

[0109]

[0110] First combine Figure 2-Figure 4, it can be clearly seen that after Na3V2(PO4)3 is doped at the P position, the highest specific capacity released by the battery material is significantly higher than that of the undoped material, and the capacity retention rate is also improved, showing better cycle performance. In addition, the charge and discharge voltage platform of Examples 1-3 is also significantly improved compared with that of Comparative Example 1. It can be seen that when the phosphorus position is single-doped, the greater the doping amount (y is less than or equal to 1 / 3), the higher the charge and discharge platform voltage of the battery. In addition, the battery capacity of Implementation 1-3 at high current density (5C, 15C) is significantly higher than that of Comparative Example 1, and the undoped material shows severe capacity decay as the current density gradually increases. In contrast, P-position doping shows better rate performance.

[0111] It can be seen from the data in Table 2 that when the same L element is doped, the greater the phosphorus doping amount, the higher the charge and discharge voltage platform of the material. Compared with the battery in Comparative Example 1, it can be found that the rate performance, battery specific capacity and cycle retention rate of the phosphorus doped material are significantly better than Na3V2(PO4)3. Introducing vanadium doping on the basis of phosphorus doping can further improve the charge and discharge voltage platform of the material, but the effects of doping with different E elements are slightly different.

[0112] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. A battery material, characterized in that: The molecular formula of the battery material includes A3V 2-x E x (P 1-y L y O4)3, wherein the E element represents a doping element replacing the V element, the L element represents a doping element replacing the P element, the L element includes one or more of B, Al, Ga, Ge and Sn, the E element includes one or more of transition metal elements, rare earth elements, Mg and Sr, and the A element represents one or more of Li, Na and K, wherein 0≤x≤1, 0<y≤1 / 3; and when the L element is the B element, x is not 0; The transition metal elements include one or more of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb and Zr; the rare earth elements include one or more of La and Ce.

2. The battery material according to claim 1, characterized in that The L element includes one or more of Ge and Sn.

3. The battery material according to claim 1, characterized in that The value range of x is: 0.1≤x≤1.

4. The battery material according to claim 1, characterized in that The value range of y is: 1 / 18≤y≤1 / 3.

5. A method for preparing a battery material, characterized in that: The following steps are involved: (1) According to the molecular formula of the battery material to be prepared, A3V 2-x E x (P 1-y L y O4)3 weigh A source, vanadium source, E source, phosphorus source, and L source, and mix them to obtain a precursor material; wherein the E element represents a doping element replacing the V element, the L element represents a doping element replacing the P element, the L element includes one or more of B, Al, Ga, Ge, and Sn, the E element includes one or more of transition metal elements, rare earth elements, Mg, and Sr, and the A element represents one or more of Li, Na, and K; 0≤x≤1, 0<y≤1 / 3; and when the L element is the B element, x is not 0; the transition metal element includes one or more of Fe, Cr, Mn, Co, Ti, Ni, Cu, Zn, Mo, Nb, and Zr; the rare earth element includes one or more of La and Ce; (2) calcining the precursor material to obtain the battery material.

6. The preparation method according to claim 5, characterized in that: The calcination treatment conditions are: calcination at a temperature of 400° C.-900° C. for 10 h-30 h under inert gas protection.

7. The preparation method according to claim 5, characterized in that: In step (1), the mixing treatment method includes a solid phase mixing method or a sol-gel method.

8. An electrode plate, characterized in that: The electrode plate comprises the battery material according to any one of claims 1 to 4.

9. A secondary battery, characterized in that: The secondary battery comprises the electrode sheet as claimed in claim 8 or has the battery material as claimed in any one of claims 1 to 4.

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