Oxyfluoride solid electrolyte and preparation method and application thereof

Abstract

The invention relates to oxyfluoride solid electrolyte as well as a preparation method and application thereof. The general chemical formula of the oxyfluoride solid electrolyte material is Li < x > La < y > M < 1z > M < 2w > M < 3uO6F >, wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1 < x + 3y < 5, 0 < x < = 2, and 1 / 3 < y < 5 / 3; 0 < = z < = 2, 0 < = w < = 2, 0 < = u < = 2, z + w + u = 2; the density of the oxyfluoride solid electrolyte material is greater than 90%, and the purity is greater than 99%; the oxyfluoride solid electrolyte material is prepared from a nanoscale lithium source, a lanthanum source, an M1 source, an M2 source, an M3 source and a composite fluorine source through reaction, and the content of fluorine elements introduced through the composite fluorine source is 0.1%-8% more than the stoichiometric ratio of fluorine required in the oxyfluoride solid electrolyte material. The high-density and high-purity oxyfluoride solid electrolyte material provided by the invention has relatively high volume energy density, relatively low internal resistance and excellent ion conduction performance, is beneficial to improving rate capability, effectively slows down capacity fading and prolongs the cycle life of a battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolyte materials, and in particular to a fluoride oxide solid electrolyte and a preparation method and application thereof. Background Art

[0002] As the safety and energy density requirements for lithium-ion batteries continue to increase in applications such as electric vehicles and portable electronic devices, solid-state electrolytes, as an alternative to liquid electrolytes, have attracted widespread attention due to their excellent thermal stability, electrochemical stability, and intrinsic safety. Among the various solid-state electrolyte systems, fluorine-containing oxide-based solid electrolytes show promising application prospects due to their high ionic conductivity and wide electrochemical window.

[0003] In existing technologies, the preparation of fluoride oxide solid electrolytes often uses processes such as high-temperature solid-phase methods, mechanical ball milling, or sol-gel methods. Although these methods can obtain the target materials to a certain extent, they still have many problems in practical application: First, due to the large particle size and low diffusion rate of the raw materials, sintering must be carried out at relatively high temperatures, resulting in incomplete reaction and the formation of impurities, which affects the conductivity and purity of the final material. Second, volatile elements such as lithium and fluorine are easily lost during the high-temperature sintering process, reducing the accuracy of the material composition and structural stability, thereby affecting the performance of the electrolyte. Third, traditional single fluorine sources (such as LiF or LaF3) have problems such as incomplete reaction or limited fluorine fixation capacity under high temperature conditions, making it difficult to balance reactivity and structural stability.

[0004] In addition, if the mixing uniformity of the reactants is not fully controlled in the existing methods, it is easy to cause low material density and poor particle contact, resulting in increased interfacial ion transfer impedance and affecting the overall performance of the battery.

[0005] Therefore, there is an urgent need to develop a fluoride oxide solid electrolyte material and its preparation method that can control the stability of fluorine content while improving density and purity, reducing internal resistance and simplifying the process flow. Summary of the Invention

[0006] The present invention addresses the shortcomings of existing technologies by providing an oxyfluoride solid electrolyte, its preparation method, and its application. The oxyfluoride solid electrolyte material proposed in this invention exhibits high density and purity, high volumetric energy density, low internal resistance, and excellent ionic conductivity, contributing to improved rate performance, effectively mitigating capacity decay, and extending battery cycle life.

[0007] To achieve the above objectives, in the first aspect, the present invention provides a fluoride oxide solid electrolyte material having the general chemical formula Li x La y M1 z M2 wM3 u O6F; wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1<x+3y<5, 0<x≤2, 1 / 3<y<5 / 3; 0≤z≤2, 0≤w≤2, 0≤u≤2, z+w+u=2;

[0008] The density of the fluoride oxide solid electrolyte material is greater than 90%, and the purity is greater than 99%;

[0009] The fluoride oxide solid electrolyte material is prepared by reacting a nano-scale lithium source, a lanthanum source, an M1 source, an M2 source, an M3 source and a composite fluorine source, and the content of the fluorine element introduced by the composite fluorine source is 0.1%-8% excess relative to the stoichiometric ratio of fluorine required in the fluoride oxide solid electrolyte material.

[0010] Preferably, the M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; the M2 is one or more of Nb, Sb, Bi, V, and Ta; and the M3 is one or more of W, Cr, Mo, and Mn.

[0011] Preferably, the composite fluorine source is a combination of lanthanum fluoride and lithium fluoride.

[0012] In a second aspect, an embodiment of the present invention provides a method for preparing an oxyfluoride solid electrolyte material, comprising:

[0013] Mixing the nano-scale lithium source and lanthanum source with the M1 source, M2 source, and M3 source to obtain a first mixture, placing the first mixture in a first sintering device for a first sintering, heating the mixture to 200°C-800°C at a heating rate of 1°C / min-20°C / min, and keeping the temperature for 1h-8h, then continuing to heat the mixture to 800°C-1500°C at a heating rate of 1°C / min-20°C / min, and keeping the temperature for 1h-12h to obtain a precursor powder;

[0014] Mixing the precursor powder with a composite fluorine source to obtain a second mixture; wherein the content of fluorine introduced by the composite fluorine source is 0.1% to 8% excess relative to the stoichiometric ratio of fluorine required in the oxyfluoride solid electrolyte material;

[0015] The second mixture is transferred to a second sintering device for a second sintering. In an inert atmosphere, the temperature is increased to 600°C-1200°C at a heating rate of 1°C / min-20°C / min and kept at this temperature for 1h-12h to obtain the fluoride oxide solid electrolyte.

[0016] Preferably, the M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; the M2 is one or more of Nb, Sb, Bi, V, and Ta; and the M3 is one or more of W, Cr, Mo, and Mn.

[0017] Preferably, the D50 particle size range of the lithium source, lanthanum source, M1 source, M2 source, M3 source and composite fluorine source is 100 nm-1000 nm.

[0018] Preferably, the composite fluorine source is a combination of lanthanum fluoride and lithium fluoride; wherein the stoichiometric ratio of lanthanum fluoride to lithium fluoride is (0-1 / 3): (0-1);

[0019] The lithium source includes: one or more combinations of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate;

[0020] The lanthanum source includes: one or more combinations of lanthanum trioxide, lanthanum carbonate, lanthanum nitrate, and lanthanum hydroxide;

[0021] The M1 source is a compound containing M1;

[0022] The M2 source is a compound containing M2;

[0023] The M3 source is a compound containing M3;

[0024] The addition ratio of lithium fluoride to lanthanum fluoride in the composite fluorine source and the ratio of lithium source to lanthanum source in the first mixture are coordinated to determine the target stoichiometric ratio Li x La y M1 z M2 w M3 u The contents of Li, La and F elements in O6F.

[0025] Preferably, the mixing equipment is selected from one or more of a VC high-efficiency mixer, a planetary mixer, a vertical mixing tank, and a high-energy ball mill;

[0026] The first sintering equipment and the second sintering equipment are respectively selected from any one of a box furnace, a tube furnace, a pusher furnace, a roller kiln, and a rotary kiln.

[0027] Preferably, during the first sintering process, the process parameters are preferably:

[0028] Raise the temperature to 400-600°C at a heating rate of 2°C / min-8°C / min, keep warm for 3h-5h, then continue to raise the temperature to 900-1100°C at a heating rate of 2°C / min-8°C / min, keep warm for 5h-7h;

[0029] During the second sintering process, the process parameters are preferably:

[0030] In an inert atmosphere, heating the sample to 700-900°C at a heating rate of 2-8°C / min and maintaining the temperature for 5-7 hours; the inert atmosphere includes one or more combinations of nitrogen, helium, or argon;

[0031] The stoichiometric ratio of lanthanum fluoride to lithium fluoride is (0-0.3): (0.1-1);

[0032] The content of the fluorine element introduced by the composite fluorine source is 5% excess relative to the stoichiometric ratio of fluorine required in the fluoride oxide solid electrolyte material.

[0033] In a third aspect, an embodiment of the present invention provides a lithium battery comprising the fluoride oxide solid electrolyte material described in the first aspect, or comprising the fluoride oxide solid electrolyte material obtained by the preparation method described in the second aspect.

[0034] The fluorine oxide solid electrolyte material provided by the embodiment of the present invention has the characteristics of high density and high purity, with a density greater than 90% and a purity higher than 99%. It can carry more active ion channels per unit volume, thereby improving the overall ion migration efficiency. The high purity reduces the interference of impurities on the active substances, making lithium ion deintercalation more efficient, reducing capacity attenuation, and improving the cycle life of the battery. The fluorine content introduced into the material through the composite fluorine source is controlled within a range slightly higher than the stoichiometric ratio (0.1%-8%), which can not only ensure that the fluorine element fully participates in the construction of the crystal structure, but also effectively compensates for the loss caused by high-temperature volatilization during the preparation and sintering process, thereby improving the material structure stability, electrochemical stability window and long-term cycle life. At the same time, the dense structure makes the contact between particles closer, reduces the interface resistance, and helps to achieve stable charge and discharge performance at higher rates, meeting the application requirements of high-performance solid-state lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a comparison chart of X-ray diffraction (XRD) of the solid electrolyte materials of Example 1 and Comparative Example 1 provided in the embodiments of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0037] The embodiment of the present invention provides a fluoride oxide solid electrolyte material, the chemical formula of which is Li x La y M1 z M2 w M3 uO6F; wherein, M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1<x+3y<5, 0<x≤2, 1 / 3<y<5 / 3; 0≤z≤2, 0≤w≤2, 0≤u≤2, z+w+u=2.

[0038] The density of the fluoride oxide solid electrolyte material is greater than 90% and the purity is greater than 99%.

[0039] The fluoride oxide solid electrolyte material is prepared by reacting a nano-scale lithium source, a lanthanum source, an M1 source, an M2 source, an M3 source and a composite fluorine source, and the content of the fluorine element introduced by the composite fluorine source is 0.1%-8% in excess of the stoichiometric ratio of fluorine required in the fluoride oxide solid electrolyte material.

[0040] The composite fluorine source is a combination of lanthanum fluoride and lithium fluoride. M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; M2 is one or more of Nb, Sb, Bi, V, and Ta; and M3 is one or more of W, Cr, Mo, and Mn.

[0041] The fluorine oxide solid electrolyte material provided by the embodiment of the present invention has the characteristics of high density and high purity, with a density greater than 90% and a purity higher than 99%. It can carry more active ion channels per unit volume, thereby improving the overall ion migration efficiency. The high purity reduces the interference of impurities on active substances, making lithium ion deintercalation more efficient, reducing capacity attenuation, and improving the cycle life of the battery. The content of fluorine elements introduced into the material through the composite fluorine source is controlled within a range slightly higher than the stoichiometric ratio (0.1%-8%), which can not only ensure that the fluorine elements fully participate in the construction of the crystal structure, but also effectively compensate for the loss caused by high-temperature volatilization during the preparation and sintering process, thereby improving the material structure stability, electrochemical stability window and long-term cycle life. At the same time, the dense structure makes the contact between particles closer, reduces the interface resistance, and helps to achieve stable charge and discharge performance at higher rates, meeting the application requirements of high-performance solid-state lithium batteries.

[0042] The above-mentioned fluoride oxide solid electrolyte material can be prepared by the following method. The main steps include:

[0043] Step 110: Mix the nano-scale lithium source and lanthanum source with the M1 source, M2 source, and M3 source to obtain a first mixture, place the first mixture in a first sintering device for the first sintering, heat it to 200°C-800°C at a heating rate of 1°C / min-20°C / min, keep it warm for 1h-8h, and then continue to heat it to 800°C-1500°C at a heating rate of 1°C / min-20°C / min, keep it warm for 1h-12h, and obtain a precursor powder.

[0044] Among them, the D50 particle size range of the lithium source, lanthanum source, M1 source, M2 source, M3 source and composite fluorine source is 100nm-1000nm.

[0045] The lithium source includes one or more combinations of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate.

[0046] The lanthanum source includes one or more combinations of lanthanum trioxide, lanthanum carbonate, lanthanum nitrate, and lanthanum hydroxide.

[0047] M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; the M1 source is a compound containing M1, specifically including oxides, hydroxides, carbonates, oxalates, organic complexes (such as isopropyl titanate, titanium tetrachloride), etc. of M1.

[0048] M2 is one or more of Nb, Sb, Bi, V, and Ta; the M2 source is a compound containing M2, which may specifically include oxides, hydroxides, carbonates, oxalates, halides, and the like of M2.

[0049] M3 is one or more of W, Cr, Mo, and Mn; the M3 source is a compound containing M3, specifically including an oxide of M3, a salt containing M3 (such as sodium tungstate, ammonium molybdate, sodium chromate), or an acid containing M3 (such as molybdic acid, chromic acid), etc.

[0050] The composite fluorine source is a combination of lanthanum fluoride and lithium fluoride, wherein the stoichiometric ratio of lanthanum fluoride to lithium fluoride is (0-1 / 3): (0-1), preferably (0-0.3): (0.1-1).

[0051] Furthermore, during the first sintering process, the process parameters are preferably: heating to 400-600°C at a heating rate of 2°C / min-8°C / min, keeping warm for 3h-5h, then continuing to heat to 900-1100°C at a heating rate of 2°C / min-8°C / min, keeping warm for 5h-7h.

[0052] In step 110, the D50 particle size range of the lithium source, lanthanum source, M1 source, M2 source, and M3 source is 100nm-1000nm. Due to the use of a smaller particle size, the material has a large specific surface area, a high proportion of surface atoms and strong activity, which greatly increases the surface energy of sintering, accelerates the atomic diffusion rate, and reduces the diffusion path. During the sintering process, solid-phase chemical reactions occur between the raw materials. The larger particle contact area can increase the probability of reaction, accelerate the reaction rate, and promote the reaction, thereby causing the sintering activation energy to decrease, accelerating the reaction rate of the entire sintering, reducing the sintering temperature and time, and improving the sintering efficiency and product density.

[0053] Step 120 : Mix the precursor powder with the composite fluorine source to obtain a second mixture.

[0054] The content of fluorine element introduced by the composite fluorine source is 0.1%-8% excess relative to the stoichiometric ratio of fluorine required in the fluoride oxide solid electrolyte material; preferably, the excess is 5%.

[0055] The composite fluorine source added in step 120 is a mixture of lanthanum fluoride (LaF3) and lithium fluoride (LiF); the high stability framework of LaF3 is used to fix fluoride ions, and LiF is used to provide reaction activity. The synergistic effect of the two can obtain a more stable fluorine chemical environment. Among lanthanum fluoride and lithium fluoride, LiF has a lower melting point (848°C). During the subsequent second sintering process, it preferentially melts to form a liquid phase, wets the grain boundaries of hard particles, reduces friction between particles, increases the contact surface of particles and promotes the reaction. LaF3 stabilizes the grain boundary structure through its high melting point to prevent excessive grain growth. At the same time, LaF3 binds F through strong ionic bonds (La-F bond energy is high). - Fixed on the lattice site, it inhibits the volatilization of fluorine. Thus, the interaction between lithium fluoride and lanthanum fluoride reduces the reaction temperature and inhibits the volatilization of fluorine.

[0056] Step 130: transfer the second mixture to a second sintering device for a second sintering. In an inert atmosphere, heat the mixture to 600-1200°C at a heating rate of 1-20°C / min and keep the temperature for 1-12 hours to obtain a fluoride oxide solid electrolyte.

[0057] Furthermore, during the second sintering process, the process parameters are preferably: in an inert atmosphere, heating to 700°C-900°C at a heating rate of 2°C / min-8°C / min, and keeping warm for 5h-7h; the inert atmosphere includes: one or more combinations of nitrogen, helium or argon atmosphere.

[0058] The mixing in steps 110 and 120 may specifically include stirring mixing or ball milling mixing, and the mixing equipment used is selected from one or more of a VC high-efficiency mixer, a planetary mixer, a vertical mixing tank, and a high-energy ball mill.

[0059] The first sintering equipment and the second sintering equipment in steps 110 and 130 can be selected from any one of a box furnace, a tube furnace, a pusher furnace, a roller hearth kiln, and a rotary kiln. The equipment types used for the two sintering operations can be the same or different.

[0060] It should be noted that the addition ratio of lithium fluoride to lanthanum fluoride in the composite fluorine source and the ratio of lithium source to lanthanum source in the first mixture are used to determine the target stoichiometric ratio Li x La y M1 z M2 wM3 u The content of Li, La and F elements in O6F. That is, in the present invention, the stoichiometric ratio of each element in the final oxyfluoride solid electrolyte material is determined by the addition of raw materials in two stages: the Li element comes from the lithium source added in the first stage and the lithium fluoride (LiF) in the composite fluorine source in the second stage; the La element comes from the lanthanum source in the first stage and the lanthanum fluoride (LaF3) in the composite fluorine source in the second stage; and the F element is provided entirely by the composite fluorine source (LiF and LaF3).

[0061] Therefore, when preparing raw materials, it is necessary to consider the stoichiometric ratio of the target material (Li x La y M1 z M2 w M3 u O6F) Rationally adjust the amount of lithium source and lanthanum source added to the raw materials in the first stage, and supplement the appropriate amount of lithium fluoride and lanthanum fluoride according to the missing parts, so that the total content of Li, La, and F elements meets the final ratio requirements, and ensure that the F element content is slightly excessive (0.1%-8%) relative to the stoichiometric ratio to compensate for the fluorine volatilization loss during the high-temperature sintering process, thereby improving the composition accuracy and reaction adaptability of the final product.

[0062] Those skilled in the art, provided that the target stoichiometric ratio is clearly defined, can use conventional material ratio design methods to rationally adjust the amounts of precursor raw materials and composite fluorine source added to achieve the desired final elemental composition. This adjustment process is conventional in the art and can be accomplished without requiring any inventive effort.

[0063] The preparation method of the fluoride oxide solid electrolyte provided by the present invention, by introducing nano-scale lithium source, lanthanum source and doped M1, M2, M3 element raw materials, makes the mixed system have a larger specific surface area and faster reaction kinetics, significantly improves the uniformity of raw material mixing, and completes dense phase formation at a lower sintering temperature and a shorter sintering time, effectively reducing energy consumption and process complexity. Furthermore, a composite fluorine source composed of LiF and LaF3 is used. On the one hand, LiF provides reaction activity in the early stage of sintering and forms a liquid phase to assist sintering, thereby enhancing the reaction rate and uniformity; on the other hand, LaF3 is used to stabilize the fluoride structure and fix F - ions, inhibiting the volatilization of fluorine at high temperatures. The synergistic optimization of the above processes not only improves the material yield and preparation stability, but also enhances the structural integrity and chemical stability of the electrolyte, making it suitable for the preparation of large-scale solid-state electrolyte materials.

[0064] To make the objectives, technical solutions, and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some, not all, of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0065] First of all, it should be noted that in this application, the particle size D50 of the material refers to the median particle size of the material, which can be the median value sorted by volume, mass or quantity. In each embodiment of the present invention, the median particle size sorted by quantity is specifically adopted to represent the particle size of the porous carbon matrix ranked at 50% according to the quantity distribution. The particle size D50 has a meaning well known in the art. The particle size D50 of the material provided in the embodiment of the present invention can be measured by instruments and conventional methods well known in the art. Specifically, in each embodiment of the present invention, the particle size D50 is measured using a Mastersizer 3000 laser particle size analyzer produced by Malvern Instruments Ltd. of the United Kingdom.

[0066] Example 1

[0067] The embodiment of the present invention provides a Li 1.25 La 0.58 The preparation method of Nb2O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0068] Press Li 0.5 La 0.5 To achieve the desired stoichiometric ratio for Nb2O6, lithium carbonate (D50: 656 nm), lanthanum trioxide (D50: 772 nm), and niobium pentoxide (D50: 729 nm) were mixed in a stoichiometric ratio of 1:1:4, with a total mass of 2 kg, to produce a first mixture. This mixture was placed in a box furnace and heated to 300°C at a rate of 5°C / min, held at this temperature for 2 hours, and then heated to 1000°C at a further rate of 5°C / min, held at this temperature for 6 hours, to produce a precursor powder.

[0069] Lithium fluoride with a particle size D50 of 892 nm, lanthanum fluoride with a particle size D50 of 717 nm and the above precursor powder were taken in a stoichiometric ratio of 78:8:100 and ball-milled to obtain a second mixture. The second mixture was transferred to a tube furnace, nitrogen was introduced to maintain a nitrogen atmosphere, and the temperature was increased to 900°C at a heating rate of 2°C / min and kept at this temperature for 5 hours to obtain Li 1.25 La 0.58 Nb2O6F oxyfluoride solid electrolyte.

[0070] Example 2

[0071] The embodiment of the present invention provides a Li1.25 La 0.58 The preparation method of Ti2O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0072] Press Li 0.5 La 0.5 To obtain the desired stoichiometric ratio for Ti2O6, lithium carbonate (D50: 656 nm), lanthanum trioxide (D50: 754 nm), and titanium dioxide (D50: 382 nm) were mixed in a stoichiometric ratio of 1:1:4, with a total mass of 2 kg, to obtain a first mixture. The first mixture was placed in a rotary kiln and heated to 300°C at a rate of 5°C / min, held at that temperature for 2 hours, and then heated to 1000°C at a rate of 5°C / min, held at that temperature for 6 hours, to obtain a precursor powder.

[0073] Lithium fluoride with a particle size D50 of 892 nm, lanthanum fluoride with a particle size D50 of 717 nm and the above-mentioned precursor powder were taken in a stoichiometric ratio of 80:8:100 and ball-milled to obtain a second mixture. The second mixture was transferred to a tube furnace, nitrogen was introduced to maintain a nitrogen atmosphere, and the temperature was increased to 1000°C at a heating rate of 2°C / min and kept at this temperature for 6 hours to obtain Li 1.25 La 0.58 Ti2O6F oxyfluoride solid electrolyte.

[0074] Example 3

[0075] The embodiment of the present invention provides a Li 1.25 La 0.58 The preparation method of Nb2O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0076] Press Li 0.5 La 0.5 To achieve the desired stoichiometric ratio for Nb2O6, lithium carbonate (D50: 656 nm), lanthanum trioxide (D50: 772 nm), and niobium pentoxide (D50: 729 nm) were mixed in a stoichiometric ratio of 1:1:4, with a total mass of 2 kg, to produce a first mixture. This mixture was placed in a box furnace and heated to 600°C at a rate of 2°C / min, held at that temperature for 2 hours, and then continued to heat to 1000°C at a rate of 2°C / min, held at that temperature for 6 hours, to produce a precursor powder.

[0077] Lithium fluoride with a particle size D50 of 892 nm, lanthanum fluoride with a particle size D50 of 717 nm and the above precursor powder were taken in a stoichiometric ratio of 80:8:100 and ball-milled to obtain a second mixture. The second mixture was transferred to a tube furnace, argon was introduced to maintain an argon atmosphere, and the temperature was increased to 1000°C at a heating rate of 2°C / min and kept at this temperature for 6 hours to obtain Li1.25 La 0.58 Nb2O6F oxyfluoride solid electrolyte.

[0078] Example 4

[0079] The embodiment of the present invention provides a LiLa 0.66 Ti 0.25 Nb 1.8 The preparation method of O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0080] Press Li 0.5 La 0.5 Ti 0.25 Nb 1.8 To obtain the required stoichiometric ratio of O6, lithium carbonate with a particle size D50 of 656 nm, lanthanum trioxide with a particle size D50 of 772 nm, titanium dioxide with a particle size D50 of 382 nm, and niobium pentoxide with a particle size D50 of 729 nm were mixed in a stoichiometric ratio of 1:1:1:3.6, with a total mass of 2 kg to obtain a first mixture. The first mixture was placed in a box furnace and heated to 600°C at a heating rate of 2°C / min, held at this temperature for 2 hours, and then continued to heat to 1000°C at a heating rate of 2°C / min and held at this temperature for 6 hours to obtain a precursor powder.

[0081] Lithium fluoride with a particle size D50 of 892 nm, lanthanum fluoride with a particle size D50 of 717 nm and the above precursor powder were taken in a stoichiometric ratio of 11:10:100 and ball-milled to obtain a second mixture. The second mixture was transferred to a tube furnace, argon was introduced to maintain an argon atmosphere, and the temperature was increased to 1000°C at a heating rate of 2°C / min and kept at this temperature for 6 hours to obtain LiLa 0.66 Ti 0.25 Nb 1.8 O6F oxyfluoride solid electrolyte.

[0082] Example 5

[0083] The embodiment of the present invention provides a Li 1.25 La 0.58 Mo 0.66 Nb 1.2 The preparation method of O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0084] Press Li 0.5 La 0.5 Mo 0.66 Nb 1.2To obtain the required stoichiometric ratio of O6, lithium carbonate with a particle size D50 of 656 nm, lanthanum trioxide with a particle size D50 of 772 nm, molybdenum trioxide with a particle size D50 of 582 nm, and niobium pentoxide with a particle size D50 of 729 nm were mixed in a stoichiometric ratio of 1:1:2.67:2.4, with a total mass of 2 kg to obtain a first mixture. The first mixture was placed in a box furnace and heated to 600°C at a heating rate of 2°C / min, held at this temperature for 2 hours, and then continued to heat to 1000°C at a heating rate of 2°C / min and held at this temperature for 6 hours to obtain a precursor powder.

[0085] Lithium fluoride with a particle size D50 of 892 nm, lanthanum fluoride with a particle size D50 of 717 nm and the above precursor powder were taken in a stoichiometric ratio of 41:12:50 and ball-milled to obtain a second mixture. The second mixture was transferred to a tube furnace, argon was introduced to maintain an argon atmosphere, and the temperature was increased to 1000°C at a heating rate of 2°C / min and kept at this temperature for 6 hours to obtain Li 1.25 La 0.5 Mo 0.66 Nb 1.2 O6F oxyfluoride solid electrolyte.

[0086] Comparative Example 1

[0087] This comparative example provides a conventional Li 1.25 La 0.58 The preparation method of Nb2O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0088] Lithium carbonate with a particle size of 4.71um, lanthanum trioxide with a particle size of 2.64um, niobium pentoxide with a particle size of 5.28um and lithium fluoride with a particle size of 3.18um were mixed by Li 1.25 La 0.58 The stoichiometric ratio of Nb2O6F is 0.625:0.29:1:1.1 (fluorine element excess is 10%), and the materials are mixed with a total mass of 2 kg to obtain a first mixed material.

[0089] The first mixed material was placed in a box furnace and heated to 500°C at a heating rate of 5°C / min and kept at this temperature for 5 hours. Then, the temperature was further heated to 1200°C at a heating rate of 5°C / min and kept at this temperature for 8 hours to obtain Li 1.25 La 0.58 Nb2O6F oxyfluoride solid electrolyte.

[0090] Comparative Example 2

[0091] This comparative example provides a conventional Li 1.25 La 0.58 The preparation method of Nb2O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0092] Lithium carbonate with a particle size D50 of 4.71um, lanthanum trioxide with a particle size D50 of 2.64um, niobium pentoxide with a particle size D50 of 5.28um, lithium fluoride with a particle size D50 of 892nm, and lanthanum fluoride with a particle size D50 of 717nm are mixed in a stoichiometric ratio of 2.5:1:4:3.44:0.32 (fluorine element excess 10%), with a total mass of 2kg to obtain a first mixed material.

[0093] The first mixed material was placed in a box furnace and heated to 500°C at a heating rate of 5°C / min and kept at this temperature for 5 hours. Then, the temperature was further heated to 1200°C at a heating rate of 5°C / min and kept at this temperature for 8 hours to obtain Li 1.25 La 0.58 Nb2O6F oxyfluoride solid electrolyte.

[0094] Comparative Example 3

[0095] This comparative example provides a conventional Li 1.25 La 0.58 The preparation method of Nb2O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0096] Lithium carbonate with a particle size of 656 nm, lanthanum trioxide with a particle size of 772 nm, niobium pentoxide with a particle size of 729 nm, and lithium fluoride with a particle size of 892 nm were mixed by Li 1.25 La 0.58 The stoichiometric ratio of Nb2O6F is 0.625:0.29:1:1.1 (fluorine element excess is 10%), and the materials are mixed with a total mass of 2 kg to obtain a first mixed material.

[0097] The first mixed material was placed in a box furnace and heated to 500°C at a heating rate of 5°C / min and kept at this temperature for 5 hours. Then, the temperature was further heated to 1200°C at a heating rate of 5°C / min and kept at this temperature for 8 hours to obtain Li 1.25 La 0.58 Nb2O6F oxyfluoride solid electrolyte.

[0098] Comparative Example 4

[0099] This comparative example provides a Li 1.25 La 0.58 The preparation method of Ti2O6F oxyfluoride solid electrolyte specifically comprises the following steps:

[0100] Lithium carbonate with a particle size of 4.71um, lanthanum trioxide with a particle size of 2.64um, titanium dioxide with a particle size of 2.18um, and lithium fluoride with a particle size of 3.18um were mixed by Li 1.25 La0.58 The Ti2O6F stoichiometric ratio was 0.625:0.29:1:1.1 (fluorine element excess 10%), and the materials were mixed with a total mass of 2 kg to obtain a first mixed material.

[0101] The first mixed material was placed in a box furnace and heated to 500°C at a heating rate of 5°C / min and kept at this temperature for 5 hours. Then, the temperature was further heated to 1200°C at a heating rate of 5°C / min and kept at this temperature for 6 hours to obtain Li 1.25 La 0.58 Ti2O6F oxyfluoride solid electrolyte.

[0102] The solid electrolytes of the above examples and comparative examples were subjected to X-ray diffraction (XRD) pattern tests. The results are as follows: Figure 1 shown.

[0103] XRD patterns show that the oxyfluoride solid electrolytes prepared in Examples 1 and 3 exhibit only diffraction peaks of the target phase, with no significant impurity detected, indicating high phase purity. Impurity phases were present in Comparative Examples 1-3. The preparation method proposed in the present invention enables the preparation of high-purity oxyfluoride solid electrolytes with reduced fluorine loss and sintering temperature.

[0104] Furthermore, the content ratio of each phase was calculated using the "peak area fitting" method commonly used in the prior art to obtain purity data, which is recorded in Table 1. The purity here refers to the crystalline phase purity.

[0105] The density test is carried out using the following method:

[0106] 1. Sample preparation: Use a tablet press to press the fluoride oxide solid electrolyte into a ceramic sheet, sinter it at 1000℃ for 5 hours to densify it, and obtain a densified ceramic sheet sample. The obtained ceramic sheet sample is placed in a drying oven at 110℃ for 2 hours;

[0107] 2. Use an analytical balance to measure the mass W of the fluoride oxide solid electrolyte in air (空气) ;

[0108] 3. Place the ceramic sample on the sample holder, connect the sample holder to the analytical balance to test the sample mass, place the sample holder in deionized water, and obtain the mass W of the fluoride oxide solid electrolyte in deionized water under the action of buoyancy. (水) ;

[0109] According to the formula:

[0110] ρ=ρ (水) ×W (空气) / (W (空气) -W (水) )

[0111] α=(ρ / ρ0)*100%

[0112] ρ is the volume density of the fluorine-oxygen compound solid electrolyte ceramic sheet, in grams per cubic centimeter (g / cm 3 );

[0113] W (空气) is the mass of the fluorine-oxygen compound solid electrolyte ceramic sheet in air, in grams (g);

[0114] W (水) is the mass of the fluorine-oxygen compound solid electrolyte ceramic sheet in deionized water, in grams (g);

[0115] ρ (水) is the density of water in grams per cubic centimeter (g / cm 3 );

[0116] ρ0 is the theoretical density of the fluorine-oxygen compound solid electrolyte ceramic sheet, in grams per cubic centimeter (g / cm 3 ).

[0117] The ionic conductivity test is carried out using the following method:

[0118] 1. Grind the fluoride oxide solid electrolyte powder evenly, press it into a ceramic sheet, and sinter it at 1000°C for 5 hours to obtain a densified ceramic sheet sample;

[0119] 2. Polish the two circular surfaces of the sintered ceramic sheet using 400-mesh, 1000-mesh, and 3000-mesh sandpaper in sequence to make the surface of the entire circular surface smooth and clean without defects;

[0120] 3. Use a digital thickness gauge to measure the thickness L of the ceramic sheet and a vernier caliper to measure the diameter of the ceramic sheet. Further calculate the cross-sectional area of ​​the circular surface of the ceramic sheet and record it as S;

[0121] 4. Coat the surface of the polished solid electrolyte sheet sample with conductive silver paste, and then grind off the conductive silver paste on the side of the solid electrolyte sheet;

[0122] 5. Test at a temperature of (25±2)°C and a humidity of less than 50%. Turn on the Zahner electrochemical workstation and set the parameter perturbation voltage to 10mV and the frequency to 0.1-106Hz to measure the impedance curve.

[0123] The resistance R was obtained by fitting and calculation using Zahner Analysis software, and the room temperature ionic conductivity of the solid electrolyte was calculated according to the ionic conductivity formula.

[0124] Ionic conductivity test formula:

[0125] σ=L / (R*S)

[0126] Where:

[0127] σ is the ionic conductivity of the oxyfluoride solid electrolyte ceramic sheet, in Siemens per centimeter (S / cm);

[0128] L is the thickness of the fluoride oxide solid electrolyte ceramic sheet, in centimeters (cm)

[0129] R is the impedance of the fluoride oxide solid electrolyte ceramic piece, in ohms (Ω)

[0130] S is the cross-sectional area of ​​the circular surface of the fluoride oxide solid electrolyte ceramic sheet, in square centimeters (cm2).

[0131]

[0132] Table 1

[0133] According to Table 1, from the comparison of the density and purity of Comparative Examples 1-2 and Examples 1-3, it can be seen that by applying the preparation method of the present invention and using nanoscale raw materials and composite fluorine sources in the preparation, the density of the material and the purity of the prepared powder can be greatly improved. At the same time, the higher density can simultaneously improve the ionic conductivity performance of the material.

[0134] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fluoride oxide solid electrolyte material, characterized in that: The chemical formula of the fluoride oxide solid electrolyte material is Li x La y M1 z M2 w M3 u O6F; wherein M1 is a tetravalent cation, M2 is a pentavalent cation, and M3 is a hexavalent cation; 1<x+3y<5, 0<x≤2, 1 / 3<y<5 / 3; 0≤z≤2, 0≤w≤2, 0≤u≤2, z+w+u=2; The density of the fluoride oxide solid electrolyte material is greater than 90%, and the purity is greater than 99%; The fluoride oxide solid electrolyte material is prepared by reacting a nano-scale lithium source, a lanthanum source, an M1 source, an M2 source, an M3 source and a composite fluorine source, and the content of the fluorine element introduced by the composite fluorine source is 0.1%-8% excess relative to the stoichiometric ratio of fluorine required in the fluoride oxide solid electrolyte material.

2. The fluoride oxide solid electrolyte material according to claim 1, characterized in that The M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; the M2 is one or more of Nb, Sb, Bi, V, and Ta; and the M3 is one or more of W, Cr, Mo, and Mn.

3. The fluoride oxide solid electrolyte material according to claim 1, characterized in that The composite fluorine source is a combination of lanthanum fluoride and lithium fluoride.

4. A method for preparing the fluoride oxide solid electrolyte material according to claims 1 to 3, characterized in that: The preparation method comprises: Mixing the nano-scale lithium source and lanthanum source with the M1 source, M2 source, and M3 source to obtain a first mixture, placing the first mixture in a first sintering device for a first sintering, heating the mixture to 200°C-800°C at a heating rate of 1°C / min-20°C / min, and keeping the temperature for 1h-8h, then continuing to heat the mixture to 800°C-1500°C at a heating rate of 1°C / min-20°C / min, and keeping the temperature for 1h-12h to obtain a precursor powder; Mixing the precursor powder with a composite fluorine source to obtain a second mixture; wherein the content of fluorine introduced by the composite fluorine source is 0.1% to 8% excess relative to the stoichiometric ratio of fluorine required in the oxyfluoride solid electrolyte material; The second mixture is transferred to a second sintering device for a second sintering. In an inert atmosphere, the temperature is increased to 600°C-1200°C at a heating rate of 1°C / min-20°C / min and kept at this temperature for 1h-12h to obtain the fluoride oxide solid electrolyte.

5. The method for preparing the fluoride oxide solid electrolyte material according to claim 4, characterized in that: The M1 is one or more of Zr, Ti, Hf, Si, Ge, and Sn; the M2 is one or more of Nb, Sb, Bi, V, and Ta; and the M3 is one or more of W, Cr, Mo, and Mn.

6. The method for preparing a fluoride oxide solid electrolyte material according to claim 4, wherein the D50 particle size of the lithium source, lanthanum source, M1 source, M2 source, M3 source and composite fluorine source is in the range of 100 nm to 1000 nm.

7. The method for preparing the fluoride oxide solid electrolyte material according to claim 4, characterized in that: The composite fluorine source is a combination of lanthanum fluoride and lithium fluoride; wherein the stoichiometric ratio of lanthanum fluoride to lithium fluoride is (0-1 / 3): (0-1); The lithium source includes: one or more combinations of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate; The lanthanum source includes: one or more combinations of lanthanum trioxide, lanthanum carbonate, lanthanum nitrate, and lanthanum hydroxide; The M1 source is a compound containing M1; The M2 source is a compound containing M2; The M3 source is a compound containing M3; The addition ratio of lithium fluoride to lanthanum fluoride in the composite fluorine source and the ratio of lithium source to lanthanum source in the first mixture are coordinated to determine the target stoichiometric ratio Li x La y M1 z M2 w M3 u The contents of Li, La and F elements in O6F.

8. The method for preparing the fluoride oxide solid electrolyte material according to claim 4, characterized in that: The mixing equipment is selected from one or more of a VC high-efficiency mixer, a planetary mixer, a vertical mixing tank, and a high-energy ball mill; The first sintering equipment and the second sintering equipment are respectively selected from any one of a box furnace, a tube furnace, a pusher furnace, a roller kiln, and a rotary kiln.

9. The method for preparing an oxyfluoride solid electrolyte material according to claim 4, wherein: During the first sintering process, the process parameters are preferably: Raise the temperature to 400-600°C at a heating rate of 2°C / min-8°C / min, keep warm for 3h-5h, then continue to raise the temperature to 900-1100°C at a heating rate of 2°C / min-8°C / min, keep warm for 5h-7h; During the second sintering process, the process parameters are preferably: Under an inert atmosphere, heat the sample to 700-900°C at a heating rate of 2-8°C / min and keep the temperature for 5-7 hours. The inert atmosphere includes: one or more combinations of nitrogen, helium or argon atmosphere; The stoichiometric ratio of lanthanum fluoride to lithium fluoride is (0-0.3): (0.1-1); The content of the fluorine element introduced by the composite fluorine source is 5% excess relative to the stoichiometric ratio of fluorine required in the fluoride oxide solid electrolyte material.

10. A lithium battery, characterized in that: The lithium battery comprises the fluoride oxide solid electrolyte material according to any one of claims 1 to 3, or comprises the fluoride oxide solid electrolyte material obtained by the preparation method according to any one of claims 4 to 8.

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