Niobium-doped zirconium-based halide solid electrolyte as well as preparation method and application thereof

Abstract

The invention provides niobium-doped zirconium-based halide solid electrolyte as well as a preparation method and application thereof, and relates to the technical field of solid-state batteries. Through collaborative innovation of intermittent ball milling and multi-stage ball bead combination, the performance of the zirconium-based halide solid electrolyte is successfully optimized under the condition that the niobium doping proportion (x is greater than or equal to 0.1 and less than or equal to 0.3) is limited, and the electrolyte is uniform in particle, rich in defect vacancy structure and high in ionic conductivity (gt; 1 mS / cm). The niobium-doped zirconium-based halide solid-state electrolyte shows excellent electrochemical performance when applied to a lithium metal solid-state battery, the first coulombic efficiency is greater than 95%, the capacity retention ratio after 100 times of long circulation is greater than or equal to 90%, and the niobium-doped zirconium-based halide solid-state electrolyte is obviously superior to the prior art. In addition, the preparation method is simple, and the cost is controllable.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and particularly relates to a niobium-doped zirconium-based halide solid electrolyte and a preparation method and application thereof. Background Art

[0002] The increasing price of fossil fuels due to their decreasing availability and the enhanced awareness of environmental protection have accelerated the revolution of electric vehicles. Batteries with long endurance and fast charging and discharging capabilities are the key to the mature manufacturing of electric vehicles. Replacing flammable organic electrolytes with solid electrolytes fundamentally avoids the risk of combustion and explosion. It can be said that all-solid-state lithium batteries equipped with solid electrolytes and ideal lithium metal anodes have undeniable advantages over lithium-ion batteries in terms of both energy density and safety risk coefficient.

[0003] Halide electrolytes have stood out among inorganic solid electrolytes due to their many advantages such as high ionic conductivity, wide electrochemical window, good electrochemical compatibility with high-voltage cathode materials, and stability in dry air, which has led to a new research upsurge. Among them, Li2ZrCl6 not only has advantages such as high deformability and good compatibility with 4V-class cathodes. The price of its raw materials is also several orders of magnitude cheaper than that of the currently most advanced chloride solid electrolytes, with prominent cost advantages. However, its ionic conductivity level is less than 10 -3 S cm -1 , so improving its ionic conductivity is the key problem to be solved urgently at present.

[0004] Currently, mainly by introducing large-radius metal cations through high-speed mechanical ball milling to expand the lithium-ion transport channels, thereby improving the ionic conductivity. For example, Patent Publication No. CN116789177A discloses a method for doping metal cations by two-step ball milling to improve the conductivity of Li2ZrCl6, but its high-speed ball milling is a continuous process, which easily causes local overheating and destroys the defect structure of the material, and the size combination of ball milling beads is not optimized, resulting in uneven element distribution, thus causing the risk of a decrease in ionic conductivity. In addition, although CN118538990A uses a sintering + ball milling method, it does not involve the regulation of lithium vacancies by niobium doping, and there are problems such as insufficient structural stability and low conductivity.

[0005] Therefore, exploring more reasonable preparation conditions to effectively regulate the microstructure of the material is an important means to improve the performance of halide solid electrolytes at present. Based on this, the present invention designs a niobium-doped zirconium-based halide solid electrolyte and a preparation method and application thereof. Summary of the Invention

[0006] The present invention provides a niobium-doped zirconium-based halide solid electrolyte and a preparation method and application thereof, and its purpose is to solve the above problems existing in the background art.

[0007] Embodiments of the present invention provide a niobium-doped zirconium-based halide solid electrolyte, a preparation method thereof, and an application thereof. Through the synergistic innovation of intermittent ball milling and multi-stage bead combination, the performance of the zirconium-based halide electrolyte is successfully optimized under the condition of limited niobium doping ratio (0.1 ≤ x ≤ 0.3). The electrolyte particles are uniform, rich in defective vacancy structures, and have high ionic conductivity (>1 mS / cm). The application of this halide solid electrolyte in lithium metal solid batteries exhibits excellent electrochemical performance, with the initial Coulomb efficiency >95% and the capacity retention rate ≥90% after 100 long cycles, significantly superior to the prior art. The preparation method of the present invention is simple and the cost is controllable.

[0008] Embodiments of the present invention provide a preparation method of a niobium-doped zirconium-based halide solid electrolyte, comprising the following steps:

[0009] S1: Mix lithium chloride and zirconium chloride in a certain proportion, then place them in a ball milling tank, and add a mixture of zirconia beads of three sizes. Ball mill under argon protection to obtain an amorphous zirconium-based precursor;

[0010] S2: Add niobium chloride to the amorphous zirconium-based precursor and perform intermittent ball milling under argon protection to obtain the niobium-doped zirconium-based halide solid electrolyte.

[0011] Preferably, in step S1, the molar ratio of lithium chloride to zirconium chloride is 1.8 - 2.2:1.

[0012] Preferably, in step S1, the mixed beads are composed of zirconia ball milling beads of 10 mm, 8 mm, and 5 mm in three sizes according to a mass ratio of 2:4:5; the ball-to-material mass ratio is 30 - 50:1. The 10 mm beads achieve macroscopic rapid crushing, the 8 mm beads promote mixing, and the 5 mm beads refine the particles. The combination of the three in a ratio of 2:4:5 increases the specific surface area of the amorphous precursor to more than 10 m 2 / g, providing more active sites for subsequent doping while ensuring uniform element distribution.

[0013] Preferably, in step S1, the ball milling speed is 120 - 180 r / min, and the ball milling duration is 40 - 60 min.

[0014] Preferably, when 2θ is 15° - 50° in the XRD pattern of the amorphous zirconium-based precursor, it shows a flat amorphous peak, and the specific surface area is 5 - 15 m 2 / g.

[0015] Preferably, in step S2, the intermittent ball milling speed is 550 - 650 r / min, pause for 3 - 5 min every 25 - 35 min of ball milling, and the total effective ball milling time is 30 - 40 h.

[0016] Preferably, in step S2, the mass ratio of the ball material is 60-80:1, and the mixed beads composed of zirconia with three sizes of 10 mm, 8 mm, and 5 mm in a mass ratio of 2:4:5 are used for ball milling. The 10-mm beads achieve macroscopic rapid fragmentation, the 8-mm beads promote mixing, and the 5-mm beads refine the particles. The three are combined in a ratio of 2:4:5 to increase the specific surface area of the amorphous precursor to more than 10 m 2 / g, which can provide more active sites for subsequent doping while ensuring uniform element distribution.

[0017] Preferably, in step S2, during the pause of the intermittent ball milling process, the ball milling tank is cooled by circulating an inert gas, and the temperature inside the ball milling tank is controlled to be ≤45 °C. By setting a 5-minute pause time for every 30 minutes of ball milling time and supplementing it with cooling means, local heat accumulation is reduced to protect the highly active defective disordered structure of the material.

[0018] Based on the concept of the present invention, an example provides a niobium-doped zirconium-based halide solid electrolyte obtained according to the above preparation method, with the molecular formula Li 2-x Zr 1-x Nb x Cl6 (0.1 ≤ x ≤ 0.3). Controlling the niobium doping ratio to 0.1 ≤ x ≤ 0.3 can appropriately increase the lithium vacancy concentration and maintain structural stability. Experiments show that when x < 0.1, the number of introduced lithium vacancies is insufficient; when x > 0.3, due to the difference in the ionic radii of Zr / Nb, excessive Nb ions will cause the structure to distort, reducing the size of the lithium ion transport channel and resulting in a decrease in conductivity.

[0019] Preferably, the room temperature ionic conductivity of the doped zirconium-based halide solid electrolyte is 0.8-1.2 mS / cm.

[0020] The example of the present invention also provides an application of the niobium-doped zirconium-based halide solid electrolyte or the niobium-doped zirconium-based halide solid electrolyte obtained according to the above preparation method in a solid-state battery.

[0021] Preferably, the Li-In|LiCoO2 battery assembled with the doped zirconium-based halide solid electrolyte at 25 °C has a capacity retention rate of ≥90% after 100 cycles.

[0022] The above solution of the present invention has the following beneficial effects:

[0023] Through the collaborative innovation of intermittent ball milling and multi-stage ball bead combination, the present invention has successfully optimized the performance of zirconium-based halide solid electrolytes under the condition of limited niobium doping ratio (0.1 ≤ x ≤ 0.3). The electrolyte particles are uniform, rich in defective vacancy structures, and have high ionic conductivity (>1 mS / cm). The niobium-doped zirconium-based halide solid electrolyte is applied to lithium metal solid batteries, showing excellent electrochemical performance, with the initial Coulomb efficiency >95%, and the capacity retention rate ≥90% after 100 long cycles, significantly superior to the prior art. In addition, the preparation method of the present invention is simple and the cost is controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a scanning electron microscope image of the halide solid electrolyte prepared in Example 2 and Comparative Example 2 of the present invention.

[0026] Figure 2 It is an X-ray diffraction pattern of the solid electrolytes prepared in Examples 1 to 4 and Comparative Example 1 of the present invention.

[0027] Figure 3 It is an ionic conductivity-temperature curve of the halide solid electrolytes prepared in Examples 1 to 3 and Comparative Example 1 of the present invention.

[0028] Figure 4 It is the initial Coulomb efficiency of the Li-In|LiCoO2 battery assembled with the niobium-doped zirconium-based halide solid electrolyte prepared in Example 2 of the present invention.

[0029] Figure 5 It is the rate performance of the Li-In|LiCoO2 battery assembled with the halide solid electrolytes prepared in Examples 1 and 2 and Comparative Example 1 of the present invention.

[0030] Figure 6 It is the cycle performance of the Li-In|LiCoO2 battery assembled with the halide solid electrolytes prepared in Examples 1 and 2 and Comparative Example 1 of the present invention at 25°C and 0.2C (1C = 145 mAh / g).

[0031] Figure 7 It is the impedance diagram of the Li-In|LiCoO2 battery assembled with the halide solid electrolytes prepared in Example 2 and Comparative Example 1 of the present invention after 100 cycles. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the technical problems, technical solutions, and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0033] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0034] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0035] In view of the existing problems, embodiments of the present invention provide a preparation method of a niobium-doped zirconium-based halide solid electrolyte, including the following steps:

[0036] S1: Mix lithium chloride and zirconium chloride in a proportion, then place them in a ball milling tank, and add a mixture of zirconia beads of three sizes. Ball mill under argon protection to obtain an amorphous zirconium-based precursor.

[0037] S2: Add niobium chloride to the amorphous zirconium-based precursor and perform intermittent ball milling under argon protection to obtain the niobium-doped zirconium-based halide solid electrolyte.

[0038] Preferably, in step S1, the molar ratio of lithium chloride to zirconium chloride is 1.8 - 2.2:1.

[0039] Preferably, in step S1, the mixed beads are composed of zirconia beads of 10mm, 8mm, and 5mm sizes in a mass ratio of 2:4:5; the bead-to-material mass ratio is 30 - 50:1. The 10mm beads achieve macroscopic rapid fragmentation, the 8mm beads promote mixing, and the 5mm beads refine the particles. The three are combined in a ratio of 2:4:5, increasing the specific surface area of the amorphous precursor to more than 10m 2 / g, providing more active sites for subsequent doping while ensuring uniform element distribution.

[0040] Preferably, in step S1, the ball milling speed is 120 - 180 r / min, and the ball milling duration is 40 - 60 min.

[0041] Preferably, when 2θ is 15° - 50° in the XRD pattern of the amorphous zirconium-based precursor, it shows a bread-like amorphous peak, and the specific surface area is 5 - 15m 2 / g.

[0042] Preferably, in step S2, the intermittent ball milling speed is 550 - 650 r / min, pause for 3 - 5 min every 25 - 35 min of ball milling, and the total effective ball milling time is 30 - 40 h.

[0043] Preferably, in step S2, the mass ratio of the balls to the material is 60-80:1, and the mixed ball beads composed of zirconia with three sizes of 10 mm, 8 mm, and 5 mm in a mass ratio of 2:4:5 are used for ball milling. The 10-mm ball beads achieve macroscopic rapid crushing, the 8-mm ball beads promote mixing, and the 5-mm ball beads refine the particles. The three are combined in a ratio of 2:4:5 to increase the specific surface area of the amorphous precursor to more than 10 m 2 / g, which can provide more active sites for subsequent doping while ensuring uniform element distribution.

[0044] Preferably, in step S2, during the pause of the intermittent ball milling process, the ball milling tank is cooled by circulating an inert gas, and the temperature inside the ball milling tank is controlled ≤ 45°C. By setting a 5-minute pause time for every 30 minutes of ball milling time and supplementing with cooling means, local heat accumulation is reduced to protect the highly active defective disordered structure of the material.

[0045] Based on the concept of the present invention, an embodiment provides a niobium-doped zirconium-based halide solid electrolyte obtained according to the above preparation method, and its molecular formula is Li 2-x Zr 1-x Nb x Cl6 (0.1 ≤ x ≤ 0.3). Controlling the niobium doping ratio to 0.1 ≤ x ≤ 0.3 can appropriately increase the lithium vacancy concentration and maintain the structural stability. Experiments show that when x < 0.1, the number of introduced lithium vacancies is insufficient; when x > 0.3, due to the difference in the ionic radii of Zr / Nb, excessive Nb ions will cause the structure to distort, reduce the size of the lithium ion transport channel, and lead to a decrease in conductivity (see Example 4 vs Example 2).

[0046] Preferably, the room temperature ionic conductivity of the doped zirconium-based halide solid electrolyte is 0.8-1.2 mS / cm.

[0047] The embodiment of the present invention also provides an application of a niobium-doped zirconium-based halide solid electrolyte or a niobium-doped zirconium-based halide solid electrolyte obtained according to the above preparation method in a solid-state battery.

[0048] Preferably, the Li-In|LiCoO2 battery assembled with the doped zirconium-based halide solid electrolyte at 25°C has a capacity retention rate ≥ 90% after 100 cycles.

[0049] The following will be described in detail through specific examples

[0050] Example 1

[0051] This example provides a preparation method of a niobium-doped zirconium-based halide solid electrolyte.

[0052] The method of this example specifically includes the following steps:

[0053] (1) Weighing 0.242 g of lithium chloride and 0.629 g of zirconium chloride, under argon protection, put them into a ball mill with zirconium oxide as the inner liner, and calculating the total mass of the ball milling beads according to the ball-to-material ratio of 40:1. At the same time, a multi-grade ball combination consisting of 10, 8, and 5 mm balls is prepared in a mass ratio of 2:4:5, and put into the ball milling jar, and the ball milling jar is installed on a ball mill, and the ball milling is carried out at a low speed of 150 revolutions per minute for 45 minutes to obtain a uniformly mixed amorphous zirconium-based precursor;

[0054] (2) adding 0.08 g of niobium chloride to the amorphous zirconium-based precursor and then ball milling at 600 rpm to increase the ball-to-material ratio to 70:1, with an effective ball milling time of 35 hours and a rest time of 5 minutes every 30 minutes to finally obtain the niobium-doped zirconium-based halide solid electrolyte.

[0055] Example 2

[0056] This embodiment provides a method for preparing a niobium-doped zirconium-based halide solid electrolyte.

[0057] The method of this embodiment specifically includes the following steps:

[0058] (1) Weigh 0.229 g of lithium chloride and 0.559 g of zirconium chloride and put them into a ball mill with zirconium oxide as the inner liner under argon protection. Calculate the total mass of the ball mill beads according to the ball-to-material ratio of 40:1. At the same time, prepare a multi-level ball combination of 10, 8, and 5 mm in a mass ratio of 2:4:5 and put them into the ball mill. The ball mill is installed on a ball mill and low-speed ball milling is performed at a rate of 150 revolutions per minute for 45 minutes to obtain a uniformly mixed amorphous zirconium-based precursor.

[0059] (2) adding 0.162 g of niobium chloride to the amorphous zirconium-based precursor and then ball milling at 600 rpm to increase the ball-to-material ratio to 70:1, with an effective ball milling time of 35 hours and a rest time of 5 minutes every 30 minutes to finally obtain the niobium-doped zirconium-based halide solid electrolyte.

[0060] Example 3

[0061] This embodiment provides a method for preparing a niobium-doped zirconium-based halide solid electrolyte.

[0062] The method of this embodiment specifically includes the following steps:

[0063] (1) Weigh 0.216 g of lithium chloride and 0.489 g of zirconium chloride, and load them into a ball milling jar with a zirconia inner liner under argon protection. Calculate the total mass of the ball milling beads according to a ball-to-material ratio of 40:1. At the same time, prepare a multi-stage ball bead combination composed of 10, 8, and 5 mm with a mass ratio of 2:4:5, load it into the ball milling jar, install the ball milling jar on the ball mill, and carry out low-speed ball milling at a rate of 150 revolutions per minute for 45 minutes to obtain a uniformly mixed amorphous zirconium-based precursor.

[0064] (2) Add 0.243 g of niobium chloride to the amorphous zirconium-based precursor and then carry out ball milling at 600 revolutions per minute. Increase the ball-to-material ratio to 70:1, and the effective ball milling time is 35 hours. Set a 5-minute rest period every 30 minutes, and finally obtain the niobium-doped zirconium-based halide solid electrolyte.

[0065] Example 4

[0066] This example provides a preparation method for a niobium-doped zirconium-based halide solid electrolyte.

[0067] The method of this example specifically includes the following steps:

[0068] (1) Weigh 0.204 g of lithium chloride and 0.420 g of zirconium chloride, and load them into a ball milling jar with a zirconia inner liner under argon protection. Calculate the total mass of the ball milling beads according to a ball-to-material ratio of 40:1. At the same time, prepare a multi-stage ball bead combination composed of 10, 8, and 5 mm with a mass ratio of 2:4:5, load it into the ball milling jar, install the ball milling jar on the ball mill, and carry out low-speed ball milling at a rate of 150 revolutions per minute for 45 minutes to obtain a uniformly mixed amorphous zirconium-based precursor.

[0069] (2) Add 0.324 g of niobium chloride to the amorphous zirconium-based precursor and then carry out ball milling at 600 revolutions per minute. Increase the ball-to-material ratio to 70:1, and the effective ball milling time is 35 hours. Set a 5-minute rest period every 30 minutes, and finally obtain the niobium-doped zirconium-based halide solid electrolyte.

[0070] Comparative Example 1

[0071] This comparative example is an undoped zirconium-based halide solid electrolyte, and the specific preparation method is as follows:

[0072] (1) Weigh 0.254 g of lithium chloride and 0.699 g of zirconium chloride, and load them into a ball milling jar with a zirconia inner liner under argon protection. Calculate the total mass of the ball milling beads according to a ball-to-material ratio of 40:1. At the same time, prepare a multi-stage ball bead combination composed of 10, 8, and 5 mm with a mass ratio of 2:4:5, load it into the ball milling jar, install the ball milling jar on the ball mill, and carry out low-speed ball milling at a rate of 150 revolutions per minute for 45 minutes to obtain a uniformly mixed amorphous zirconium-based precursor.

[0073] (2) Ball milling was carried out at 600 revolutions per minute, with the effective ball milling time set to 35 hours, pausing for 5 minutes every 30 minutes, and finally a halide solid electrolyte was obtained.

[0074] Comparative Example 2

[0075] This comparative example is for the preparation of niobium-doped zirconium-based halide solid electrolyte by one-step ball milling. The specific preparation method is as follows:

[0076] (1) Weigh 0.229 g of lithium chloride, 0.559 g of zirconium chloride and 0.162 g of niobium chloride, and put them into a ball milling jar with a zirconia inner liner under argon protection. Calculate the total mass of the ball milling beads according to the ball-to-material ratio of 70:1. At the same time, prepare a multi-stage ball bead combination composed of 10, 8, and 5 mm with a mass ratio of 2:4:5, and put it into the ball milling jar.

[0077] (2) Ball milling was carried out at 600 revolutions per minute, with the effective ball milling time set to 35 hours, pausing for 5 minutes every 30 minutes, and finally a niobium-doped zirconium-based halide solid electrolyte was obtained.

[0078] Comparative Example 3

[0079] This comparative example is for the preparation of niobium-doped zirconium-based halide solid electrolyte using single-size 10-mm ball milling beads. The specific preparation method is as follows:

[0080] (1) Weigh 0.229 g of lithium chloride and 0.559 g of zirconium chloride, put them into a ball milling jar with a zirconia inner liner under argon protection. Calculate the total mass of the ball milling beads according to the ball-to-material ratio of 40:1. Only use single-size 10-mm ball milling beads and put them into the ball milling jar. Install the ball milling jar on the ball mill and carry out low-speed ball milling at a rate of 150 revolutions per minute for 45 minutes to obtain a precursor.

[0081] (2) Add 0.162 g of niobium chloride to the precursor and then carry out ball milling at 600 revolutions per minute, increase the ball-to-material ratio to 70:1, with the effective ball milling time of 35 hours and a 5-minute pause every 30 minutes. Finally, a niobium-doped zirconium-based halide solid electrolyte was obtained.

[0082] Comparative Example 4

[0083] This comparative example is for the preparation of niobium-doped zirconium-based halide solid electrolyte using a combination of ball beads with similar sizes (5 mm and 8 mm). The specific preparation method is as follows:

[0084] (1) Weigh 0.229 g of lithium chloride and 0.559 g of zirconium chloride, put them into a ball milling jar with a zirconia inner liner under argon protection. Calculate the total mass of the ball milling beads according to the ball-to-material ratio of 40:1. Use a combination of 5- and 8-mm ball beads with similar sizes, put them into the ball milling jar. Install the ball milling jar on the ball mill and carry out low-speed ball milling at a rate of 150 revolutions per minute for 45 minutes to obtain a precursor.

[0085] (2) 0.162 g of niobium chloride was added to the precursor, and then ball milling was carried out at 600 revolutions per minute. The ball-to-material ratio was increased to 70:1, and the effective ball milling time was 35 hours. A 5-minute rest period was set every 30 minutes, and finally, a niobium-doped zirconium-based halide solid electrolyte was obtained.

[0086] Comparative Example 5

[0087] This comparative example was for preparing a yttrium-doped zirconium-based halide solid electrolyte by using common transition metal yttrium doping. The specific preparation method was as follows:

[0088] (1) 0.203 g of lithium chloride and 0.559 g of zirconium chloride were weighed and loaded into a ball milling jar with a zirconia inner liner under argon protection. The total mass of the ball milling beads was calculated according to a ball-to-material ratio of 40:1. At the same time, a multi-stage ball bead combination composed of 10, 8, and 5 mm with a mass ratio of 2:4:5 was prepared and loaded into the ball milling jar. The ball milling jar was installed on a ball mill and ball milled at a low speed of 150 revolutions per minute for 45 minutes to obtain a uniformly mixed amorphous zirconium-based precursor.

[0089] (2) 0.117 g of yttrium chloride was added to the amorphous zirconium-based precursor, and then ball milling was carried out at 600 revolutions per minute. The ball-to-material ratio was increased to 70:1, and the effective ball milling time was 35 hours. A 5-minute rest period was set every 30 minutes, and finally, a yttrium-doped zirconium-based halide solid electrolyte was obtained.

[0090] Commercial molds were used to measure the ionic conductivities of the solid electrolytes obtained in Examples 1 to 4 and Comparative Examples 1 to 5 respectively. The test results are shown in Table 1:

[0091] Table 1 Test results of ionic conductivities of solid electrolytes in Examples 1 to 4 and Comparative Examples 1 to 5

[0092] <![CDATA[Ionic conductivity (mS cm -1 )]]> Example 1 0.772 Example 2 1.03 Example 3 0.886 Example 4 0.751 Comparative Example 1 0.417 Comparative Example 2 0.682 Comparative Example 3 0.563 Comparative Example 4 0.705 Comparative Example 5 0.718

[0093] *All data were measured at 25 °C

[0094] Table 2 is the specific surface area test results of the precursor materials of Example 2 and Comparative Examples 3 and 4

[0095]

[0096] As can be seen from Table 1, after introducing an appropriate amount of niobium ions, compared with Comparative Example 1, the ionic conductivities of the electrolytes in Examples 1-4 have been significantly improved. At the same time, through Comparative Example 2, it is found that maintaining the necessary premixing step can enable the material to obtain the highest ionic conductivity. In addition, the ionic conductivity of the yttrium-doped zirconium-based halide solid electrolyte prepared in Comparative Example 5 is lower than that of the niobium-doped zirconium-based halide solid electrolyte in the examples, indicating that the doping of niobium ions is more conducive to the rapid transport of lithium ions. As can be seen from Table 2, Example 2 using multi-stage beads has a larger specific surface area than Comparative Example 3 using only single-sized beads and Comparative Example 4 using a combination of beads with similar sizes, which can provide more active sites for subsequent doping.

[0097] The solid electrolytes of the above examples and comparative examples were assembled into batteries. The specific process is as follows: Using a commercial battery mold, a composite cathode is prepared by mixing LiCoO2 and the prepared electrolyte in a mass ratio of 7:3 on the cathode side. The prepared solid electrolyte is placed in the middle. The anode side is composed of an indium foil with a diameter of 10 mm and a lithium foil stacked in sequence. Li6PS5Cl is used as a separator between the electrolyte and the anode side. Finally, it is assembled and completed by applying a fixed pressure with a press.

[0098] Figure 1 Figure [SEM image] shows the scanning electron microscope images of the niobium-doped zirconium-based halide solid electrolyte prepared in Example 2 and the solid electrolyte prepared in Comparative Example 2. From Figure 1 it can be seen that the electrolyte particles of Example 2 synthesized by the intermittent ball milling method have smaller nano-scale sizes, indicating the necessity of the intermittent ball milling process.

[0099] Figure 2 Figure [XRD image] shows the X-ray diffraction patterns of the niobium-doped zirconium-based halide solid electrolytes prepared in Examples 1-4 and the solid electrolyte prepared in Comparative Example 1. From Figure 2 it can be seen that there is no obvious displacement of the diffraction peaks in Example 2, indicating that the doping of niobium ions does not change the original structure, maintaining the Li2ZrCl6 main phase, and the full width at half maximum increases, indicating an increase in the defect structure.

[0100] Figure 3 Figure [Ionic conductivity-temperature curve] shows the ionic conductivity-temperature curves of the niobium-doped zirconium-based halide solid electrolytes prepared in Examples 1-4 and the solid electrolyte prepared in Comparative Example 1. From Figure 3 it can be seen that Examples 1-3 all show higher ionic conductivities than Comparative Example 1 at different temperatures, indicating that within the doping amount of niobium in the range of 10%-30% molar ratio, niobium ions are beneficial to the improvement of ionic conductivity. The ionic conductivity of the niobium-doped zirconium-based halide solid electrolyte in Example 2 reaches a peak value (1.03 mS / cm).

[0101] Figure 4The initial Coulombic efficiency of the Li-In|LiCoO2 battery assembled with the niobium-doped zirconium-based halide solid electrolyte prepared in Example 2 is from Figure 4 It can be seen that the initial Coulombic efficiency of the solid-state lithium metal battery assembled in Example 2 > 95%, showing outstanding performance.

[0102] Figure 5 The rate performance at 25 °C of the Li-In|LiCoO2 batteries assembled with the niobium-doped zirconium-based halide solid electrolytes prepared in Example 1 and Example 2 and the halide electrolyte prepared in Comparative Example 1 is from Figure 5 It can be seen that the electrolyte prepared in Example 2 still has a capacity of 110 mAh / g at 1C, and at the same time, the capacity retention rate when returning to 0.2C after cycle tests at different rates is good. In contrast, the capacity of the undoped niobium electrolyte prepared in Comparative Example 1 decreases significantly at different rates, verifying the significant improvement in the performance of the zirconium-based halide electrolyte by the addition of high-valent niobium ions.

[0103] Figure 6 The cycle performance at 25 °C and 0.2C (1C = 145 mAh g -1 ) charge and discharge conditions of the Li-In|LiCoO2 batteries assembled with the niobium-doped zirconium-based halide solid electrolytes prepared in Example 1 and Example 2 and the halide electrolyte prepared in Comparative Example 1 is from Figure 6 It can be seen that the electrolytes prepared in Example 1 and Example 2 still have capacity retention rates of 80.7% and 91.4% after 100 cycles. In contrast, the electrolyte prepared in Comparative Example 1 only has a capacity retention rate of 59%, verifying the significant improvement in the performance of the zirconium-based halide electrolyte by the addition of high-valent niobium ions.

[0104] Figure 7 The impedance diagram of the Li-In|LiCoO2 battery assembled with the niobium-doped zirconium-based halide solid electrolyte prepared in Example 2 and the halide electrolyte prepared in Comparative Example 1 after 100 cycles is from Figure 7 It can be seen that the overall impedance of the battery in Example 2 is significantly smaller than that of the battery in Comparative Example 1 after 100 cycles, verifying the optimization effect of the addition of niobium ions on lithium ion transport.

[0105] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle described in the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a niobium-doped zirconium-based halide solid electrolyte, characterized in that: The steps include: S1: Lithium chloride and zirconium chloride are mixed in proportion, and then placed in a ball mill, and mixed balls of zirconium oxide of three sizes are added, and ball milling is performed under argon protection to obtain an amorphous zirconium-based precursor; S2: adding niobium chloride to the amorphous zirconium-based precursor, and performing intermittent ball milling under argon protection to obtain the niobium-doped zirconium-based halide solid electrolyte.

2. The method for preparing a niobium-doped zirconium-based halide solid electrolyte according to claim 1, characterized in that: In step S1, the molar ratio of lithium chloride to zirconium chloride is 1.8-2.2:

1.

3. The method for preparing a niobium-doped zirconium-based halide solid electrolyte according to claim 1, characterized in that: In step S1, the mixed balls are composed of three sizes of zirconium oxide, 10 mm, 8 mm, and 5 mm, in a mass ratio of 2:4:5; the ball material mass ratio is 30 to 50:

1.

4. The method for preparing a niobium-doped zirconium-based halide solid electrolyte according to claim 1, characterized in that: In step S1, the ball milling speed is 120-180 r / min, and the ball milling time is 40-60 min.

5. The method for preparing a niobium-doped zirconium-based halide solid electrolyte according to claim 1, characterized in that: The XRD spectrum of the amorphous zirconium-based precursor shows a steamed bun-shaped amorphous peak when 2θ is 15° to 50°, and the specific surface area is 5 to 15 m 2 / g.

6. The method for preparing a niobium-doped zirconium-based halide solid electrolyte according to claim 1, characterized in that: In step S2, the intermittent ball milling speed is 550-650 r / min, and the ball milling is paused for 3-5 minutes after every 25-35 minutes of ball milling, and the total effective ball milling time is 30-40 hours.

7. The method for preparing a niobium-doped zirconium-based halide solid electrolyte according to claim 1, characterized in that: In step S2, the ball-to-material mass ratio is 60-80:

1.

8. The method for preparing a niobium-doped zirconium-based halide solid electrolyte according to claim 1, characterized in that: In step S2, during the pause of the intermittent ball milling process, the ball milling jar is cooled by circulating inert gas, and the temperature inside the ball milling jar is controlled to be ≤45°C.

9. A niobium-doped zirconium-based halide solid electrolyte prepared by the preparation method according to any one of claims 1 to 8, characterized in that: Its molecular formula is Li 2-x Zr 1-x Nb x Cl6, where 0.1≤x≤0.

3.

10. Use of the niobium-doped zirconium-based halide solid electrolyte prepared by the preparation method according to any one of claims 1 to 8 or the niobium-doped zirconium-based halide solid electrolyte according to claim 9 in a solid-state battery.

Images