A dual-phase structured electrolyte material, and a preparation method and application thereof

Abstract

The present application relates to a kind of dual-phase structure electrolyte material and its preparation method and application, it simultaneously exists rhombic phase and monoclinic phase at 25 ℃~35 ℃, and it is atom level between two phases It is combined;Its nominal composition is Li 3+a Zr 2‑x‑y Sc x M y Si2PO 12 Wherein, M is other metal element except Li, Zr and Sc, 0≤a≤0.5, 0.1≤x≤0.5, 0.3≤x+y≤1.2.The present application can promote the configuration entropy of electrolyte material by introducing Sc and other metal elements to replace part of Zr elements in crystal lattice, make the rhombic phase of high ionic conductivity stable exist at room temperature and combine with monoclinic phase through superlattice structure, improve bulk conductivity at room temperature.In practical application, it can be used as positive electrode filler, reduce concentration polarization, improve the kinetic performance of positive electrode;It can also be used as solid electrolyte membrane or diaphragm coating, applied to lithium ion battery and / or lithium metal battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to an electrolyte material, particularly a two-phase structure electrolyte material, its preparation method, and its application. Background Technology

[0002] While the energy density of lithium-ion batteries is now close to its theoretical value, it still falls short of meeting the demand for long-lasting battery life. Currently, reducing the proportion of inactive materials by fabricating thick electrodes with high charge loading is an effective way to further improve battery energy density. However, thicker electrodes increase the ion / electron transport distance, leading to a significant increase in concentration polarization at higher current densities. This reduces the utilization rate of active materials and causes excessively high state of charge (overcharging) in the active materials on the electrode surface, thus reducing the rate performance of lithium-ion batteries and affecting their cycle life.

[0003] Oxide-based solid electrolytes, which exhibit high electrochemical stability, offer an effective solution to the aforementioned problems. By filling the electrode with appropriate solid electrolyte particles, these particles can spontaneously polarize under an electric field, reducing the Li content in the electrode. + The concentration gradient is reduced, thereby suppressing concentration polarization, improving kinetic performance, increasing the utilization rate of active materials, and extending the cycle life of the battery.

[0004] CN116646527A discloses a cathode electrode, a lithium-ion battery, and an electrical device, which combines a three-dimensional ion transport channel with high ion conductivity (≥3×10⁻⁶). -3 Inorganic fast ion conductors (such as lithium titanium aluminum phosphate Li) with a speed of S / cm 1.3 Al 0.3 Ti 1.7 Introducing (PO4)3 and other substances into the cathode active material promotes the ion transport rate on the surface of the cathode active material particles, forms continuous ion transport channels between particles, and constructs multiple ion transport paths, thereby overcoming the problem of limited ion transport capacity in thick film electrodes and improving kinetic performance.

[0005] However, oxide-based solid electrolytes still suffer from problems such as low ionic conductivity (mS / cm level) and poor processing performance due to excessively high modulus (Young's modulus > 100 GPa), which severely restricts their application in lithium-ion batteries.

[0006] Therefore, how to balance the high electrochemical stability, high ionic conductivity, and low modulus of oxide solid electrolytes, and thus enable lithium-ion batteries to have excellent energy density and rate performance at high current densities while taking into account processing costs, is an urgent problem to be solved in the field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a dual-phase electrolyte material, its preparation method, and its applications. By introducing Sc and other metal elements to replace some Zr elements in the crystal lattice, the present invention effectively increases the configurational entropy of the electrolyte material and causes Li-OM lattice distortion. This allows the high-ionic-conductivity rhombic phase to exist stably at room temperature and combine with the highly structurally stable monoclinic phase through a superlattice structure. Thus, the dual-phase electrolyte material simultaneously contains both the rhombic and monoclinic phases at 25℃~35℃, with atomic-level bonding between the two phases. This combination achieves high room-temperature ionic conductivity, high oxidation potential, and low DMT modulus, enabling lithium-ion batteries to exhibit excellent energy density and rate performance at high current densities while maintaining good processing performance.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, the present invention provides a dual-phase electrolyte material, wherein the dual-phase electrolyte material simultaneously contains a rhombic phase and a monoclinic phase at 25℃~35℃, and the two phases are atomically bonded; the nominal composition of the dual-phase electrolyte material is Li 3+a Zr 2-x-y Sc x M y Si2PO 12 Where M is a metallic element other than Li, Zr and Sc, 0≤a≤0.5, 0.1≤x≤0.5, 0.3≤x+y≤1.2.

[0010] For example, a can be 0, 0.1, 0.2, 0.3, 0.4 or 0.5, etc.; x can be 0.1, 0.2, 0.3, 0.4 or 0.5, etc.; x+y can be 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1 or 1.2, etc.

[0011] The nominal composition of this type of electrolyte is Li 1+x M2Si x P 3-x O 12 M represents a transition metal element, primarily Zr. However, due to the short Li-O bond, it cannot effectively stabilize the tetrahedral and octahedral structures of SiO4 / PO4, making this electrolyte difficult to synthesize directly. Consequently, information regarding its crystal structure is lacking. (The text then abruptly shifts to a seemingly unrelated topic: Na3Zr2Si2PO4...) 12 Li3Zr2Si2PO4 prepared by ion exchange of (NZSP) 12LZSP (Leaf-Zinc Spindle Polymer) is believed to retain the framework structure formed by SiO4 / PO4 tetrahedra and MO6 octahedrons. However, due to the energy differences at the Na2, Na3, and Na1 positions in LZSP, Na at the Na1 position is easily replaced by Li, while a small amount of Na ions usually remain at the Na2 and Na3 positions. This results in a higher room-temperature ionic conductivity of the LZSP product due to the larger radius of the Na ions, but it also makes it difficult to determine the crystal structure of the product. Currently, the mainstream view is that LZSP is a monoclinic phase with high symmetry at room temperature.

[0012] Li, which belongs to the NASICON type electrolyte like NZSP, 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP) is a rhombic phase at room temperature. Even when the carrier concentration is much lower than that of LZSP, its room temperature ionic conductivity can still reach the order of mS / cm. This indicates that, similar to the case where NZSP transforms into a rhombic phase at high temperature and its ionic conductivity increases significantly, the rhombic phase NASICON-type lithium-ion conductor can also accelerate lithium-ion conduction by improving the symmetry of the crystal structure.

[0013] To this end, the present invention introduces Sc and other metal elements at the M site to replace part of the Zr element in the lattice, thereby increasing the configuration entropy of the electrolyte material and causing Li-OM lattice distortion. This allows the rhombic phase with high ionic conductivity to exist stably at room temperature and to combine with the monoclinic phase with high structural stability through a superlattice structure. As a result, the biphase electrolyte material has both rhombic and monoclinic phases at 25℃~35℃, and the two phases are atomically bonded.

[0014] The dual-phase electrolyte material provided by this invention, on the one hand, has two crystalline phases forming a framework structure in a shared-corner configuration, which can improve the intraphase Li content. + Transmission rate; on the other hand, since the cell parameters α of the two crystal phases are close, atomic-level bonding is achieved between the two phases, which can reduce interphase Li + The conduction energy barrier is reduced, thus significantly improving ionic conductivity. High ionic conductivity is beneficial for improving the kinetic performance of the cathode, suppressing concentration polarization, and thereby improving the rate performance of lithium-ion batteries at higher current densities.

[0015] The dual-phase electrolyte material provided by this invention also maintains the high chemical stability of oxide-based solid electrolytes, making it compatible with high-energy-density cathode materials. This is beneficial for improving the kinetic performance of the cathode, thereby increasing the energy density of lithium-ion batteries.

[0016] The dual-phase electrolyte material provided by this invention can reduce its DMT modulus due to the lattice softening caused by the Li-OM lattice distortion and the nano-heterogeneous structure, thus exhibiting good processing performance.

[0017] In some embodiments, the Li 3+a Zr 2-x-y Sc x M y Si2PO 12 M in the M includes at least three of Mg, Ca, Al, In, Sn, Hf, La, Nd, Ce, Y, Zn, or Nb. Typical but non-limiting combinations include combinations of Mg, Ca, and Al; combinations of In, Sn, and Hf; combinations of La, Nd, and Ce; combinations of Y, Zn, and Nb; combinations of Mg, Ca, Al, and In; combinations of Sn, Hf, La, and Nd; combinations of Ce, Y, Zn, and Nb; combinations of In, Hf, Zn, and Nb; combinations of Mg, Ca, Al, In, Sn, and Hf; and combinations of La, Nd, Ce, Y, Zn, and Nb. Preferably, there are 4 to 6 types.

[0018] This invention introduces 4 to 6 additional M elements besides Sc to replace some of the Zr elements in the crystal lattice. Due to the different atomic radii and interactions with O, the configuration entropy of the electrolyte material can be further increased and the Li-OM lattice can be distorted, resulting in an increase in the proportion of rhombic phase, which is beneficial to further improve the bulk conductivity of the two-phase electrolyte material.

[0019] In some embodiments, the proportion of the rhomboid phase is 20% to 60%, for example, it can be 20%, 30%, 40%, 45%, 50%, 55% or 60%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 30% to 60%.

[0020] The biphase electrolyte material provided by this invention, when the proportions of the rhombic phase and the monoclinic phase are similar, is beneficial to improving the bulk conductivity and reducing the DMT modulus.

[0021] In some embodiments, the bulk conductivity of the biphase electrolyte material at 25°C to 35°C is 8mS / cm to 16mS / cm, for example, it can be 8mS / cm, 10mS / cm, 12mS / cm, 14mS / cm or 16mS / cm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] The biphase electrolyte material provided by this invention simultaneously exhibits two phase structures at room temperature: a rhombic phase with high ionic conductivity and a monoclinic phase with high structural stability. On one hand, both crystalline phases form a framework structure with shared angles, which can improve the intraphase Li... + Transmission rate; on the other hand, since the cell parameters α of the two crystal phases are close, atomic-level bonding is achieved between the two phases, which can reduce interphase Li +The conduction energy barrier is reduced, and the ionic conductivity is significantly improved.

[0023] In some embodiments, the DMT modulus of the dual-phase electrolyte material is 40 GPa to 80 GPa, for example, it can be 40 GPa, 50 GPa, 60 GPa, 70 GPa or 80 GPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] The dual-phase electrolyte material provided by this invention has a DMT modulus that drops below 80 GPa due to the lattice softening caused by the Li-OM lattice distortion and the nano-heterogeneous structure, and thus has good processing performance.

[0025] In some embodiments, the biphase electrolyte material is subjected to temperature variations between 25°C and 35°C compared to Li / Li. + The oxidation potential is 4.2V~4.9V, for example, it can be 4.2V, 4.3V, 4.4V, 4.5V, 4.6V, 4.7V, 4.8V or 4.9V, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] The biphase electrolyte material provided by this invention has a high oxidation potential (vs. Li / Li). + It can be matched with high specific energy cathode materials, which is beneficial to improve the dynamic performance of the cathode, thereby increasing the energy density of lithium-ion batteries.

[0027] In a second aspect, the present invention provides a method for preparing a biphase electrolyte material as described in the first aspect, comprising the following steps: mixing Na2CO3, SiO2, NH4H2PO4 and oxides or carbonates of Zr, Sc, and M in stoichiometric ratios, then adding 3% to 10% excess Na2CO3 in stoichiometric ratio, and sequentially performing a first ball milling and a first calcination to obtain a first precursor; sequentially performing a second ball milling and a second calcination on the first precursor to obtain a second precursor; and mixing the second precursor with excess LiNO3 and performing at least one ion exchange to obtain the biphase electrolyte material.

[0028] It should be noted that excess LiNO3 means that the stoichiometric ratio of Li in LiNO3 to Na in the second precursor is greater than 6, and as the stoichiometric ratio of LiNO3 to Na in the second precursor and the number of ion exchanges increase, the residual Na in the product decreases. Under the condition of the lowest stoichiometric ratio (6) and only one ion exchange, the residual Na is less than 15% (stoichiometric ratio).

[0029] In this invention, Sc and M ions work together. Sc, due to its larger ionic radius, can improve the symmetry of the crystal structure, which is conducive to the formation of the rhombic phase. The introduction of multiple M ions can increase the configurational entropy of the electrolyte material and cause Li-OM lattice distortion, reducing the ion transport activation energy. The combined effect of these two ions allows the high-conductivity rhombic phase to exist stably at room temperature and combine with the highly structurally stable monoclinic phase through a superlattice structure. This results in a two-phase electrolyte material that simultaneously contains both the rhombic and monoclinic phases at 25℃~35℃, with atomic-level bonding between the two phases. This allows for a combination of high room-temperature ionic conductivity, high oxidation potential, and low DMT modulus, thereby enabling lithium-ion batteries to achieve excellent energy density and rate performance at high current densities while maintaining good processing performance.

[0030] In some embodiments, the rotational speeds of the first ball mill and the second ball mill are independently 600 rpm to 1000 rpm, for example, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, but not limited to the listed values, and other unlisted values ​​within the range are also applicable; the grinding times of the first ball mill and the second ball mill are independently 6h to 12h, for example, 6h, 7h, 8h, 9h, 10h, 11h or 12h, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] In some embodiments, the temperature of the first calcination is 1000℃~1300℃, for example, it can be 1000℃, 1050℃, 1200℃, 1250℃ or 1300℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable; the time of the first calcination is 3h~8h, for example, it can be 3h, 4h, 5h, 6h, 7h or 8h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0032] In some embodiments, the second calcination temperature is 1000℃~1250℃, for example, it can be 1000℃, 1050℃, 1100℃, 1150℃, 1200℃ or 1250℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable; the second calcination time is 6h~18h, for example, it can be 6h, 8h, 10h, 12h, 14h, 16h or 18h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0033] In some embodiments, the ion exchange temperature is 200°C to 400°C, for example, 200°C, 250°C, 300°C, 350°C or 400°C, but not limited to the listed values, and other unlisted values ​​within the range are also applicable; the ion exchange time is 2h to 10h, for example, 2h, 4h, 6h, 8h or 10h, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0034] In some embodiments, the number of ion exchanges is 1 to 3 times, for example, 1, 2 or 3 times.

[0035] Thirdly, the present invention provides a positive electrode comprising a biphase electrolyte material as described in the first aspect.

[0036] This invention adds a biphase electrolyte material to the positive electrode. The high bulk conductivity of the biphase electrolyte material helps improve the kinetic performance of the positive electrode and avoids concentration polarization, thereby significantly improving the rate performance of the lithium-ion battery while maintaining its high energy density.

[0037] In some embodiments, the positive electrode further includes a positive electrode active material, a conductive agent, and a binder.

[0038] In some embodiments, the positive electrode active material includes lithium cobalt oxide (LCO) and / or LiNi. m Co n Mn (1-m-n) O2 ternary (NCM) cathode material, wherein 0 < m < 1, 0 < n < 1, 0 < m + n < 1.

[0039] In some embodiments, the conductive agent comprises multi-walled carbon nanotubes and / or vapor-grown carbon fibers.

[0040] In some embodiments, the adhesive comprises any one or a combination of at least two of polyvinylidene fluoride, polyacrylic acid, or polytetrafluoroethylene. Typical but non-limiting combinations include combinations of polyvinylidene fluoride and polyacrylic acid, combinations of polyacrylic acid and polytetrafluoroethylene, combinations of polyvinylidene fluoride and polytetrafluoroethylene, and combinations of polyvinylidene fluoride, polyacrylic acid, and polytetrafluoroethylene.

[0041] In some embodiments, the mass ratio of the positive electrode active material, conductive agent, binder, and biphase electrolyte material is (80~95):(1~5):(1~5):(1~10), for example, it can be 90:2:3:5, 95:2:2:1, 80:5:5:10, 85:5:5:5, 90:1:1:8, 90:3:3:4, or 95:1:1:3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] In some embodiments, the positive electrode is prepared by a wet process or a dry process.

[0043] For example, the wet preparation includes the following steps:

[0044] (1) Dissolve the binder in N-methylpyrrolidone, and at the same time, dry mix the positive electrode active material, the biphase electrolyte material and the conductive agent according to the mass ratio to obtain a mixture. After the binder is fully dissolved, add it to the above mixture and stir for 1h~8h to obtain the positive electrode slurry.

[0045] (2) The positive electrode slurry is coated on both sides of the current collector foil, dried and rolled to obtain the positive electrode.

[0046] For example, the dry preparation includes the following steps:

[0047] (1) Mix the positive electrode active material, biphase electrolyte material, conductive agent and binder in proportion, and use a planetary ball mill. Add a small amount of ethanol and then ball mill the mixture. The ball milling speed is 200 rpm to 500 rpm and the ball milling time is 2 h to 8 h.

[0048] (2) The dough-like material after ball milling is hot rolled and pressed at a temperature of 45℃~75℃. The material is rolled and pressed to a certain thickness, such as 75μm~500μm.

[0049] (3) The positive electrode after hot rolling is hot-pressed onto the surface of the current collector foil to obtain the positive electrode.

[0050] In some embodiments, the areal loading of the positive electrode active material in the positive electrode is 20 mg / cm³. 2 ~50mg / cm 2 For example, it could be 20 mg / cm³ 2 25mg / cm 2 30mg / cm 2 35mg / cm 2 40mg / cm 2 45mg / cm or 50mg / cm 2 However, this does not limit the listed values; any other unlisted values ​​within the range are also applicable.

[0051] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode as described in the third aspect.

[0052] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] This invention improves the configurational entropy of the electrolyte material and causes Li-OM lattice distortion by introducing Sc and other metal elements at the M site to replace some Zr elements in the lattice. This allows the high ionic conductivity rhombic phase to exist stably at room temperature and combine with the high structural stability monoclinic phase through a superlattice structure. As a result, the two-phase electrolyte material simultaneously contains both the rhombic and monoclinic phases at 25℃~35℃, and the two phases are atomically bonded.

[0055] The dual-phase electrolyte material provided by this invention, on the one hand, has two crystalline phases forming a framework structure in a shared-corner configuration, which can improve the intraphase Li content. + Transmission rate; on the other hand, since the cell parameters α of the two crystal phases are close, atomic-level bonding is achieved between the two phases, which can reduce interphase Li + The conduction energy barrier is reduced, thus significantly improving ionic conductivity. High ionic conductivity is beneficial for improving the kinetic performance of the cathode, suppressing concentration polarization, and thereby improving the rate performance of lithium-ion batteries at higher current densities.

[0056] The dual-phase electrolyte material provided by this invention also maintains the high chemical stability of oxide-based solid electrolytes, making it compatible with high-energy-density cathode materials. This is beneficial for improving the kinetic performance of the cathode, thereby increasing the energy density of lithium-ion batteries.

[0057] The dual-phase electrolyte material provided by this invention can reduce its DMT modulus due to the lattice softening caused by the Li-OM lattice distortion and the nano-heterogeneous structure, thus exhibiting good processing performance. Attached Figure Description

[0058] Figure 1 The results are linear voltammetry test results for the biphase electrolyte material in Example 1.

[0059] Figure 2 This is a cryo-transmission electron microscope image of the biphase electrolyte material in Example 1;

[0060] ① and ③ - Rhomboid phase, ② - Monoclinic phase.

[0061] Figure 3 The image shows the AFM diagram of a single particle of the biphase electrolyte material in Example 1.

[0062] Figure 4 The XRD refinement images are of the biphase (single-phase) structure electrolyte materials in Example 1 and Comparative Examples 1 to 2. Detailed Implementation

[0063] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0064] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0065] Unless otherwise specified, the term "at least two combinations" in this invention refers to a quantity greater than or equal to 2. For example, "any one or at least two combinations" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention.

[0066] In this invention, unless otherwise specified, the feature or solution corresponding to "and / or" covers any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a set consisting of A, B, and combinations of A and B. "Including A and / or B" can be understood, depending on the context of the statement, as including A, including B, or simultaneously including both A and B. In this invention, "optional" means that the corresponding feature, component, step, or solution is not essential, i.e., selected from either "present" or "absent" parallel solutions. If multiple "optional" limitations appear in a technical solution, unless otherwise specified and without technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0067] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A may consist only of a1, a2, and a3, or it may include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements."

[0068] All embodiments and optional embodiments of the present invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of the present invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment or implementation of the present invention. The appearance of this phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art can explicitly and implicitly understand that the embodiments described in this invention can be combined with other embodiments without technical conflict.

[0069] In this invention, the ordinal numbers “first,” “second,” “third,” and “fourth” used in expressions such as “first aspect,” “second aspect,” “third aspect,” and “fourth aspect” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0070] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0071] Example 1

[0072] This embodiment provides a two-phase electrolyte material with a nominal composition of Li. 3.3 ZrSc 0.2 Zn 0.1 In 0.1 Hf 0.3 Nb 0.3 Si2PO 12 It exhibits both rhombic and monoclinic phases at temperatures ranging from 25℃ to 35℃, with the two phases bonded at the atomic level, and the rhombic phase accounting for 59%.

[0073] The biphase electrolyte material was pressed into an electrolyte sheet, and its ionic conductivity was tested at 25°C using a symmetrical blocking electrode (stainless steel sheet). The bulk conductivity at room temperature was 12.3 mS / cm.

[0074] The biphase electrolyte material was pressed into an electrolyte sheet and polished. The polished electrolyte sheet was tested using an atomic force microscope. Its DMT modulus was less than 70 GPa, and the average DMT modulus was 55.6 GPa.

[0075] The biphase electrolyte material was pressed into an electrolyte sheet, and a Li anode / electrolyte sheet / stainless steel sheet battery was assembled. Electrochemical window testing was performed to measure its oxidation potential (vs. Li / Li). + The voltage is 4.71V.

[0076] The method for preparing the two-phase electrolyte material provided in this embodiment includes the following steps:

[0077] (1) Na2CO3, SiO2, NH4H2PO4, ZrO2, Sc2O3, ZnO, In2O3, HfO2 and Nb2O5 are mixed in stoichiometric ratio, and an additional 5% excess (stoichiometric ratio) of Na2CO3 is added. The mixture is then subjected to a first ball mill and a first calcination to obtain a first precursor. The first ball milling speed is 800 rpm and the first ball milling time is 8 h. The first calcination temperature is 1050℃ and the first calcination time is 6 h.

[0078] (2) The first precursor is subjected to a second ball mill and a second calcination in sequence to obtain a second precursor; wherein the rotation speed of the second ball mill is 800 rpm and the time of the second ball mill is 8 h; the temperature of the second calcination is 1150℃ and the time of the second calcination is 12 h.

[0079] (3) The second precursor is mixed with excess LiNO3 and subjected to one ion exchange to obtain a biphase electrolyte material; wherein the ion exchange temperature is 350℃ and the ion exchange time is 6h.

[0080] Figure 1 The linear voltammetry results of the two-phase electrolyte material in this embodiment show that the electrolyte material exhibits good performance at 4.71V (vs. Li / Li). + Oxidative decomposition begins at ().

[0081] Figure 2 The transmission electron microscope (TEM) images of the dual-phase electrolyte material in this embodiment show that both monoclinic and rhombic phases coexist and have the same α value, thus allowing them to bond well. Li + There is no significant phase-to-phase energy barrier during transmission.

[0082] Figure 3 The image shows the AFM diagram of a single particle of the biphase electrolyte material in this embodiment. It can be seen that its DMT modulus is less than 70 GPa, and the calculated average DMT modulus is 55.6 GPa.

[0083] Example 2

[0084] This embodiment provides a two-phase electrolyte material with a nominal composition of Li. 3.3 ZrSc 0.2 Mg 0.1 In 0.1 Hf 0.3 Nb 0.3 Si2PO 12 It exhibits both rhombic and monoclinic phases at temperatures ranging from 25℃ to 35℃, with the two phases bonded at the atomic level, and the rhombic phase accounting for 52%.

[0085] The biphase electrolyte material was pressed into an electrolyte sheet, and its ionic conductivity was tested at 25°C using a symmetrical blocking electrode (stainless steel sheet). The bulk conductivity at room temperature was 11.2 mS / cm.

[0086] The biphase electrolyte material was pressed into an electrolyte sheet and polished. The polished electrolyte sheet was tested using an atomic force microscope. Its DMT modulus was less than 70 GPa, and the average DMT modulus was 54.5 GPa.

[0087] The biphase electrolyte material was pressed into an electrolyte sheet, and a Li anode / electrolyte sheet / stainless steel sheet battery was assembled. Electrochemical window testing was performed to measure its oxidation potential (vs. Li / Li). + The voltage is 4.8V.

[0088] The preparation method of the biphase electrolyte material provided in this embodiment is the same as that in Example 1, except that ZnO is replaced with MgO with the same stoichiometric ratio and the number of ion exchanges is increased to 2.

[0089] Example 3

[0090] This embodiment provides a two-phase electrolyte material with a nominal composition of Li. 3.4 ZrSc 0.3 Mg 0.1 In 0.1 Hf 0.3 Nb 0.2 Si2PO 12 It exhibits both rhombic and monoclinic phases at temperatures ranging from 25℃ to 35℃, with the two phases bonded at the atomic level, and the rhombic phase accounting for 54%.

[0091] The biphase electrolyte material was pressed into an electrolyte sheet, and its ionic conductivity was tested at 25°C using a symmetrical blocking electrode (stainless steel sheet). The bulk conductivity at room temperature was 13.2 mS / cm.

[0092] The biphase electrolyte material was pressed into an electrolyte sheet and polished. The polished electrolyte sheet was tested using an atomic force microscope. Its DMT modulus was less than 70 GPa, and the average DMT modulus was 51.5 GPa.

[0093] The biphase electrolyte material was pressed into an electrolyte sheet, and a Li anode / electrolyte sheet / stainless steel sheet battery was assembled. Electrochemical window testing was performed to measure its oxidation potential (vs. Li / Li). + The voltage is 4.9V.

[0094] The preparation method of the biphase electrolyte material provided in this embodiment is the same as that in Example 2, except that the amount of Nb2O5 and Sc2O3 added is adjusted according to the stoichiometric ratio and the ion exchange time is increased to 8h.

[0095] Comparative Example 1

[0096] This comparative example provides a two-phase electrolyte material with a nominal composition of Li. 3.4 Zr 1.6 Sc 0.4 Si2PO 12 It exists simultaneously as a monoclinic phase and a rhombic phase at 25℃~35℃, and the two phases are bonded at the atomic level, with the rhombic phase accounting for about 17%.

[0097] The biphase electrolyte material was pressed into an electrolyte sheet, and its ionic conductivity was tested at 25°C using a symmetrical blocking electrode (stainless steel sheet). The bulk conductivity at room temperature was 7.02 mS / cm.

[0098] The biphase electrolyte material was pressed into an electrolyte sheet and polished. The polished electrolyte sheet was tested using an atomic force microscope, and its average DMT modulus was 90.5 GPa.

[0099] The biphase electrolyte material was pressed into an electrolyte sheet, and a Li anode / electrolyte sheet / stainless steel sheet battery was assembled. Electrochemical window testing was performed to measure its oxidation potential (vs. Li / Li). + The voltage is 4.7V.

[0100] The preparation method of the biphase electrolyte material provided in this comparative example is the same as that in Example 1, except that ZnO, In2O3, HfO2 and Nb2O5 are not added and the amounts of Na2CO3, SiO2, NH4H2PO4, ZrO2 and Sc2O3 are adjusted according to the stoichiometric ratio.

[0101] Comparative Example 2

[0102] This comparative example provides a single-phase electrolyte material with a nominal composition of Li3Zr2Si2PO4. 12 Only monoclinic phases exist; rhomboid phases do not exist.

[0103] The single-phase electrolyte material was pressed into an electrolyte sheet, and its ionic conductivity was tested at 25°C using a symmetrical blocking electrode (stainless steel sheet). The bulk conductivity at room temperature was 5.01 mS / cm.

[0104] The single-phase electrolyte material was pressed into an electrolyte sheet and polished. The polished electrolyte sheet was tested using an atomic force microscope, and its average DMT modulus was 100.8 GPa.

[0105] The single-phase electrolyte material was pressed into an electrolyte sheet, and a Li anode / electrolyte sheet / stainless steel sheet battery was assembled. Electrochemical window testing was performed to measure its oxidation potential (vs. Li / Li). + The voltage is 4.7V.

[0106] The preparation method of the single-phase electrolyte material provided in this comparative example is the same as that in Example 1, except that Sc2O3, ZnO, In2O3, HfO2 and Nb2O5 are not added and the amounts of Na2CO3, SiO2, NH4H2PO4 and ZrO2 are adjusted according to the stoichiometric ratio.

[0107] The biphase (single-phase) electrolyte materials in Examples 1 to 3 and Comparative Examples 1 to 2 were subjected to X-ray diffraction (XRD) analysis at 25°C and then refined to analyze their phase structure and the proportion of each phase.

[0108] Figure 4 These are refined XRD patterns of the biphase (single-phase) electrolyte materials from Example 1 and Comparative Examples 1-2. Figure 4 It can be seen that Sc 3+ The introduction of [a specific element] can generate a rhombic phase in electrolyte materials, and the high configuration entropy caused by the additional introduction of other metal elements can further increase the proportion of the rhombic phase.

[0109] The dual-phase electrolyte materials provided in Examples 1-3 exhibit high bulk conductivity, high oxidation potential, and low DMT modulus. On one hand, the high bulk conductivity improves the kinetic performance of the cathode, preventing concentration polarization and thus significantly enhancing the rate performance while maintaining the high energy density of the lithium-ion battery. On the other hand, the high oxidation potential facilitates matching with high-specific-energy cathode materials, improving the kinetic performance of the cathode and thereby increasing the energy density of the lithium-ion battery. Furthermore, the low DMT modulus improves its processing performance.

[0110] Compared to Example 1, Comparative Example 1, which only contains Sc as a substituted element, also yielded a two-phase structure, but this only increased the symmetry of the crystal. The Li-OM lattice was not sufficiently twisted, resulting in a minimal increase in bulk conductivity, and its modulus was significantly higher than that of Example 1. Comparative Example 2, lacking Sc and other metal elements, is a single monoclinic phase. Although its ionic conductivity is also high, its modulus is much higher than that of Example 1 and Comparative Example 1.

[0111] Application Examples 1 to 3 and Comparative Application Examples 1 to 2

[0112] Application Examples 1 to 3 and Comparative Application Examples 1 to 2 provide a positive electrode and a lithium-ion battery, the preparation method of which includes the following steps:

[0113] (1) The biphase (single-phase) electrolyte materials from Examples 1 to 3 and Comparative Examples 1 to 2 were respectively mixed with LiNi 0.8 Co 0.1 Mn 0.1 O2 ternary (NCM811) cathode material and vapor-grown carbon fiber were dry-mixed to obtain a mixture; polyvinylidene fluoride was dissolved in N-methylpyrrolidone, and after complete dissolution, it was added to the above mixture. After stirring for 4 hours, a cathode slurry was obtained. The mass ratio of NCM811 material, vapor-grown carbon fiber, polyvinylidene fluoride, and biphase (single-phase) electrolyte material was 90:2:3:5.

[0114] (2) The positive electrode slurry is coated on both sides of the current collector foil, dried, and rolled to obtain the positive electrode, wherein the areal loading of the positive electrode active material is approximately 25.2 mg / cm². 2 .

[0115] (3) In a glove box where the moisture and oxygen content are both less than 1 ppm, the positive electrode is used as the positive electrode and the lithium metal is used as the negative electrode. The battery is assembled using commercially available separators and electrolytes to obtain a lithium-ion battery.

[0116] Comparative Application Example 3

[0117] Comparative Application Example 3 provides a positive electrode and a lithium-ion battery, which are identical to Application Example 1 except that no biphase electrolyte material is added.

[0118] The lithium-ion batteries from Application Examples 1-3 and Comparative Application Examples 1-3 were activated at room temperature by charging and discharging at a rate of 0.05C for one week. Their capacity was then calibrated by charging and discharging at 3.0V-4.3V for one week at room temperature with a charge and discharge rate of 0.1C. After 5 cycles, the charge rate was fixed at 0.1C, and the discharge rate was increased to 0.2C, 0.5C, and 1C, respectively, and 5-week charge-discharge tests were performed for each. Finally, the discharge rate was reduced to 0.1C, and another 5-week charge-discharge test was performed. To eliminate the specific capacity anomaly caused by fluctuations in the coulombic efficiency of the counter electrode (lithium metal) under high areal loading, the specific capacity (in mAh / g) at the second week of each discharge rate was recorded as the reversible capacity, and its rate performance was evaluated.

[0119] The test results are shown in Table 1.

[0120]

[0121] Application Examples 4-6 and Comparative Application Examples 4-5

[0122] Application Examples 4-6 and Comparative Application Examples 4-5 provide a positive electrode and a lithium-ion battery, the preparation method of which includes the following steps:

[0123] (1) The biphase (single-phase) electrolyte materials from Examples 1 to 3 and Comparative Examples 1 to 2 were mixed with NCM811 cathode material, vapor-grown carbon fiber, and polyvinylidene fluoride in proportion. The mixture was then ball-milled using a planetary ball mill with a small amount of ethanol added at a speed of 300 rpm for 4 hours. The mass ratio of NCM811 cathode material, vapor-grown carbon fiber, polyvinylidene fluoride, and biphase (single-phase) electrolyte material was 95:2:2:1.

[0124] (2) The dough-like material after ball milling is hot rolled at a temperature of 65°C and rolled to 100μm.

[0125] (3) The above-mentioned hot-rolled positive electrode is hot-pressed onto the surface of the current collector foil to obtain the positive electrode, wherein the areal loading of the positive electrode active material is approximately 39.8 mg / cm². 2 .

[0126] (4) In a glove box where the moisture and oxygen content are both below 1 ppm, the positive electrode is used as the positive electrode and metallic lithium is used as the negative electrode. The battery is assembled using commercially available separators and electrolytes to obtain a lithium-ion battery.

[0127] Comparative Application Example 6

[0128] Comparative Application Example 6 provides a positive electrode and a lithium-ion battery, which are identical to Application Example 4 except that no biphase electrolyte material is added.

[0129] The lithium-ion batteries from Application Examples 4-6 and Comparative Application Examples 4-6 were activated at room temperature by charging and discharging at a rate of 0.05C for one week. Their capacity was then calibrated by charging and discharging at 3.0V-4.4V for one week at room temperature with a charge and discharge rate of 0.1C. After 5 cycles, the charge rate was fixed at 0.1C, and the discharge rate was increased to 0.2C, 0.5C, and 1C, respectively, and 5-week charge-discharge tests were performed for each. Finally, the discharge rate was reduced to 0.1C, and another 5-week charge-discharge test was performed. To eliminate the specific capacity anomaly caused by fluctuations in the coulombic efficiency of the counter electrode (lithium metal) under high areal loading, the specific capacity (in mAh / g) at the second week of each discharge rate was recorded as the reversible capacity, and its rate performance was evaluated.

[0130] The test results are shown in Table 2.

[0131]

[0132] As can be seen from Tables 1 and 2, the lithium-ion batteries provided in Application Examples 1 to 6 exhibit high energy density and excellent rate performance. This indicates that the biphase electrolyte materials provided in Examples 1 to 3, regardless of whether the electrodes are prepared by wet or dry methods, can effectively suppress concentration polarization, thereby improving the utilization rate of active materials, and the residual Na ions do not have any side effects on the battery. In contrast, in Comparative Application Examples 1 and 4, the biphase electrolyte material provided in Comparative Example 1 is used, which contains only Sc, resulting in a significant decrease in ionic conductivity. At high current densities, it cannot effectively suppress concentration polarization, thus significantly reducing the reversible capacity at 1C discharge. In Comparative Application Examples 2 and 5, the single-phase electrolyte material provided in Comparative Example 2 is used, whose room temperature ionic conductivity and modulus are similar to LATP. Therefore, it cannot effectively conduct lithium ions at thick electrodes or high current densities, leading to a decrease in the utilization rate of active materials. Comparative Application Examples 3 and 6, which do not incorporate biphase (single-phase) electrolyte materials, can only exhibit high specific capacity at low current densities such as 0.1C.

[0133] In summary, this invention improves the configurational entropy of the electrolyte material and causes Li-OM lattice distortion by introducing Sc and other metal elements at the M site to replace some Zr elements in the lattice. This allows the high ionic conductivity rhombic phase to exist stably at room temperature and combine with the high structural stability monoclinic phase through a superlattice structure. As a result, the biphase electrolyte material simultaneously contains both the rhombic and monoclinic phases at 25℃~35℃, and the two phases are atomically bonded.

[0134] The dual-phase electrolyte material provided by this invention, on the one hand, has two crystalline phases forming a framework structure in a shared-corner configuration, which can improve the intraphase Li content. + Transmission rate; on the other hand, since the cell parameters α of the two crystal phases are close, atomic-level bonding is achieved between the two phases, which can reduce interphase Li + The conduction energy barrier is reduced, thus significantly improving ionic conductivity. High ionic conductivity is beneficial for improving the kinetic performance of the cathode, suppressing concentration polarization, and thereby improving the rate performance of lithium-ion batteries at higher current densities.

[0135] The dual-phase electrolyte material provided by this invention also maintains the high chemical stability of oxide-based solid electrolytes, making it compatible with high-energy-density cathode materials. This is beneficial for improving the kinetic performance of the cathode, thereby increasing the energy density of lithium-ion batteries.

[0136] The dual-phase electrolyte material provided by this invention can reduce its DMT modulus due to the lattice softening caused by the Li-OM lattice distortion and the nano-heterogeneous structure, thus exhibiting good processing performance.

[0137] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A two-phase electrolyte material, characterized in that, The dual-phase electrolyte material exhibits both a rhombic phase and a monoclinic phase at 25℃~35℃, with the two phases bonded at the atomic level. The nominal composition of the dual-phase electrolyte material is Li 3+a Zr 2-x-y Sc x M y Si2PO 12 Where M is a metallic element other than Li, Zr and Sc, 0≤a≤0.5, 0.1≤x≤0.5, 0.3≤x+y≤1.

2.

2. The dual-phase electrolyte material according to claim 1, characterized in that, The Li 3+a Zr 2-x- y Sc x M y Si2PO 12 M in the formula includes at least three of Mg, Ca, Al, In, Sn, Hf, La, Nd, Ce, Y, Zn or Nb, preferably four to six.

3. The dual-phase electrolyte material according to claim 1 or 2, characterized in that, The rhomboid phase accounts for 20% to 60%, preferably 30% to 60%.

4. The dual-phase electrolyte material according to any one of claims 1 to 3, characterized in that, The bulk conductivity of the biphase electrolyte material at 25℃~35℃ is 8mS / cm~16mS / cm; And / or, the DMT modulus of the dual-phase electrolyte material is 40 GPa to 80 GPa; And / or, the dual-phase electrolyte material at 25°C~35°C vs. Li / Li + Its oxidation potential is 4.2V~4.9V.

5. A method for preparing a biphase electrolyte material as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The oxides or carbonates of Na2CO3, SiO2, NH4H2PO4 and Zr, Sc and M are mixed in stoichiometric ratio, and then 3% to 10% excess of Na2CO3 is added. The mixture is then subjected to a first ball milling and a first calcination to obtain the first precursor. The first precursor is subjected to a second ball milling and a second calcination in sequence to obtain a second precursor; The second precursor is mixed with excess LiNO3 and subjected to at least one ion exchange to obtain the biphase electrolyte material.

6. The preparation method according to claim 5, characterized in that, The rotational speeds of the first ball mill and the second ball mill are independently 600 rpm to 1000 rpm, and the milling times of the first ball mill and the second ball mill are independently 6 h to 12 h. And / or, the temperature of the first calcination is 1000℃~1300℃, and the time of the first calcination is 3h~8h; And / or, the temperature of the second calcination is 1000℃~1250℃, and the time of the second calcination is 6h~18h; And / or, the temperature of the ion exchange is 200℃~400℃, and the time of the ion exchange is 2h~10h; And / or, the number of ion exchanges is 1 to 3 times.

7. A positive electrode, characterized in that, The positive electrode comprises a biphase electrolyte material as described in any one of claims 1 to 4.

8. The positive electrode according to claim 7, characterized in that, The positive electrode also includes a positive electrode active material, a conductive agent, and a binder; And / or, the positive electrode active material includes lithium cobalt oxide and / or LiNi m Co n Mn (1-m-n) O2 ternary cathode material, wherein 0 < m < 1, 0 < n < 1, 0 < m + n < 1; And / or, the mass ratio of the positive electrode active material, conductive agent, binder and biphase electrolyte material is (80~95):(1~5):(1~5):(1~10).

9. The positive electrode according to claim 7 or 8, characterized in that, The positive electrode is prepared by a wet method or a dry method; And / or, the areal loading of the positive electrode active material in the positive electrode is 20 mg / cm³. 2 ~50mg / cm 2 .

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a positive electrode as described in any one of claims 7 to 9.

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