Preparation method of conductive ceramic Mg3Ga2GeO8 for all-solid-state battery

Abstract

The invention relates to a preparation method of conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery, and belongs to the technical field of all-solid-state batteries. The preparation method mainly comprises the following steps: roasting MgO, Ga2O3 and GeO2 powder in an air atmosphere, adding a solvent, and drying after ball milling; adding the primary sintered ceramic wafer and a binder into a solvent, grinding, drying, tabletting, and carrying out air burning at 1200-1400 DEG C to obtain a primary sintered ceramic wafer; and crushing and grinding the primarily sintered ceramic chip, taking powder, and repeatedly sintering for 2-3 times to obtain the Mg3Ga2GeO8 ceramic chip with a compact structure and a single phase. The ionic conductivity of the prepared ionic conductive oxide Mg3Ga2GeO8 is high, the ionic conductivity reaches 10 <-5 > S / cm at 25 DEG C, the activation energy is as low as 0.80 eV, the process is simple, and the method is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of all-solid-state batteries, and in particular to a method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries. Background Art

[0002] All-solid-state magnesium battery is an emerging solid-state battery that can meet the urgent needs of different application scenarios for high-safety, high-energy-density energy storage systems. Traditional magnesium-ion batteries use liquid electrolytes. Although they have a certain ionic conductivity, they are prone to side reactions with highly active magnesium negative electrodes, resulting in thickening of the interfacial passivation layer, decreased Coulomb efficiency, and potential safety hazards such as leakage and flammability. Solid-state electrolytes can fundamentally solve these problems through solid-phase ion conduction mechanisms, but their development has long been limited by the Mg 2+ The special physical and chemical properties of divalent ions: The strong polarization effect of divalent ions leads to extremely high migration energy barriers in the solid lattice. The activation energy is usually greater than 1eV, which is much higher than the 0.2-0.6eV of lithium ions, resulting in room temperature ionic conductivity generally lower than 10 -6 S / cm, which is difficult to meet application requirements. In 2017, the MIT team reported MgSc2Se4 spinel electrolyte, whose activation energy was reduced to 0.15-0.2eV, and achieved room temperature conductivity of 10 for the first time. -5 ~10 -4 S / cm, verifying the feasibility of magnesium solid-state fast ion conductors, but its interface rigidity leads to ion conduction failure. Since then, research has focused on expanding material systems, including selenides (such as MgIn2Se4), metal organic frameworks (MOFs, such as Mg@MIL-101), borohydrides (such as Mg(BH4)(NH2)) and modified NASICON structures (such as MgZrPO4), optimizing ion migration paths through flexible regulation of anion frameworks, lattice doping or pore confinement strategies. However, practical application still faces multiple challenges: poor solid-solid interface contact between electrolyte and electrode causes high interface impedance; Mg 2+ Deposition exfoliation can easily cause electrochemical instability at interfaces; grain boundary resistance in polycrystalline electrolytes can account for over 70%; and some high-conductivity materials contain residual electronic conductivity, leading to self-discharge. Currently, cutting-edge research is accelerating the development of new solid-state electrolytes and the analysis of interfacial structure-activity relationships by designing complex ion-conducting crystal structures and overcoming interface engineering challenges. This aims to simultaneously improve interfacial ion transport kinetics and stability, further advancing the evolution of all-solid-state magnesium batteries towards room-temperature high power and long cycle life. Summary of the Invention

[0003] The present invention designs a complex spinel-like conductive oxide Mg3Ga2GeO8 and combines it with a solid-phase sintering method to achieve high ionic conductivity, low interfacial impedance and low-cost preparation, providing a high-performance electrolyte solution for all-solid-state batteries.

[0004] A method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries, comprising the following steps:

[0005] (1) calcining MgO, Ga2O3, and GeO2 powders in an air atmosphere to remove moisture and impurities;

[0006] (2) Weighing MgO, Ga2O3, and GeO2 powders according to the stoichiometric molar ratio, adding a solvent, ball milling, and drying to obtain a raw material powder;

[0007] (3) adding the raw material powder obtained in step (2) together with a binder into a solvent, grinding and drying, and then pressing the resulting pellets into sheets, which are then fired at 1200° C. to 1400° C. to obtain a primary sintered ceramic sheet;

[0008] (4) The once-sintered ceramic sheet is crushed and ground, and the powder is taken to repeat step (3). After sintering for 2 to 3 times, a Mg3Ga2GeO8 ceramic sheet with a dense structure and a single phase is obtained.

[0009] Furthermore, in step (1), the purity of the raw material is ≥99.99%.

[0010] Furthermore, in step (1), the calcination temperature is 800° C.-1100° C., and the calcination time is 6 h-24 h.

[0011] Furthermore, in step (2), the stoichiometric molar ratio is (2.9-3.1):(0.9-1.1):(0.9-1.1), and the solvent is anhydrous ethanol.

[0012] Furthermore, in step (2), the ball milling is wet ball milling, and during the ball milling process, the ball milling speed is 250 rpm to 600 rpm, and the ball milling time is 3 h to 6 h.

[0013] Furthermore, in step (2), the particle size of the powder obtained after ball milling is 500 nm to 5 μm.

[0014] Furthermore, in step (3), the binder is PVB, and the amount used is 0.5wt.% to 2wt.%, and the solvent is anhydrous ethanol.

[0015] Furthermore, in step (3), the tableting pressure is 10 MPa to 20 MPa.

[0016] Furthermore, in step (3), the heat preservation time of the first empty burning is 5h to 10h, and the cooling method is quenching.

[0017] Furthermore, in step (4), the particle size of the powder after crushing and grinding is 2 μm to 15 μm, and the cooling method after sintering is quenching.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The ionic conductivity of the ion-conductive oxide Mg3Ga2GeO8 prepared by the present invention is high: the ionic conductivity is 10 at 25°C. -5 S / cm, and the activation energy is as low as 0.80eV.

[0020] (2) The ion-conductive oxide Mg3Ga2GeO8 prepared by the present invention has excellent compactness: the relative density of the sintered body is ≥95%, and the grain boundary impedance is low.

[0021] (3) The ion-conductive oxide Mg3Ga2GeO8 prepared by the present invention has excellent chemical stability: after 500 cycles of operation, the working performance remains good and no obvious chemical reaction occurs in the system.

[0022] (4) Step-by-step densification sintering process: low-temperature molding avoids stress cracks in the green billet, and high-temperature solid-phase sintering fully completes the formation reaction of the complex spinel-like structure Mg3Ga2GeO8 phase; quenching cooling inhibits the precipitation of impurity phases at the grain boundaries and maintains a highly ion-active metastable structure.

[0023] (5) Cyclic sintering to eliminate grain boundary defects: The "pressing-sintering-quenching" re-firing cycle can destroy the pores and impurity-rich layers at the grain boundaries, purify the grain boundaries and eliminate closed pores, significantly improve the density of the ceramic and reduce the grain boundary resistance.

[0024] (6) Simple process: The solid phase method does not require complex equipment and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 TEM image of the ion-conductive oxide ceramic prepared in Example 1;

[0026] Figure 2 is the XRD pattern of the ion-conductive oxide ceramic prepared in Example 1;

[0027] Figure 3 is a SEM image of the ion-conductive oxide ceramic prepared in Example 1;

[0028] Figure 4 is an impedance diagram of the ion-conductive oxide ceramic prepared in Example 1;

[0029] Figure 5 is the Arrhenius curve of the ion-conductive oxide ceramic prepared in Example 1. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention and the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. The present invention is further described in detail below with reference to specific implementation cases. However, the scope of protection of the present invention is not limited by the specific implementation methods.

[0031] Example 1

[0032] A method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries, comprising the following steps:

[0033] (1) MgO, Ga2O3, and GeO2 were calcined separately at 1100°C for 12 hours.

[0034] (2) Three oxides were weighed in a stoichiometric ratio of 3:1:1, and an appropriate amount of anhydrous ethanol was added. The mixture was ball-milled for 5 h and then dried at a rotation speed of 400 rpm to obtain a precursor powder with a particle size of approximately 2 μm.

[0035] (3) 1 g of the precursor powder was added with 1 wt.% binder and an appropriate amount of anhydrous ethanol. The powder was ground for 0.5 h, dried, and pressed into a 13 mm diameter mold at a pressure of 15 MPa. The resulting green ceramic tablet was solid-phase sintered at 1250°C for 8 h and cooled by quenching.

[0036] (4) The sintered ceramic sheet is crushed and ground into powder with a particle size of about 12 μm. The pressing-sintering-quenching process is repeated three times to obtain Mg3Ga2GeO8 oxide conductive ceramic.

[0037] A method for preparing an Au / Mg3Ga2GeO8 / Au battery for testing ionic conductivity: polish both sides of a prepared ceramic sheet with a diameter of 11-12 mm and a thickness of 0.5-1 mm. Thin layers of gold paste are applied to both sides, with the gold paste covering an area of ​​approximately 0.7-1.2 cm. 2 A silver wire of a certain length is fixed on the surface of the gold paste, and it is dried at 600-800°C, with a heating rate of 2-5°C / min and a holding time of 1-2h to obtain an Au / Mg3Ga2GeO8 / Au battery.

[0038] Figure 1The TEM image of the conductive ceramic produced shows that an obvious (…S, T, S, T…) sequence arrangement is formed in the crystal structure of the conductive ceramic, which is a structural characteristic of phase III spinel. This structure can form channels that are conducive to ion transmission and improve the ionic conductivity of the ceramic.

[0039] Figure 2 From the XRD diagram of the prepared conductive ceramic, it can be seen that the XRD peak of the measured substance is sharp, which is basically consistent with the main peak of the standard comparison card of Mg3Ga2GeO8, and there is no impurity peak, indicating that the Mg3Ga2GeO8 substance was successfully synthesized.

[0040] Figure 3 The SEM image of the conductive ceramic produced shows that the grain size of the ceramic is relatively uniform, about 1 μm in size, and the grains are connected by necks with a small gap of about 0.5 μm.

[0041] Figure 4 The impedance diagram of the prepared conductive ceramic shows that the curve consists of a semicircle in the high-frequency region and a straight line in the low-frequency region. The semicircle corresponds to the bulk resistance, and the straight line corresponds to the diffusion resistance of ions at the interface. The ionic conductivity is 5.36×10 -5 S / cm.

[0042] Figure 5 The Arrhenius curve of the conductive ceramic obtained shows that the ln(σT)~1000 / T curve basically satisfies the linear relationship of the Arrhenius formula. The ionic conduction of the ceramic piece is a thermally excited process with an activation energy of 0.80 eV.

[0043] Example 2

[0044] A method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries, comprising the following steps:

[0045] (1) MgO, Ga2O3, and GeO2 were calcined separately at 1100°C for 12 h;

[0046] (2) Weigh three oxides in a stoichiometric ratio of 3:1:1, add an appropriate amount of anhydrous ethanol, ball mill for 3 hours at a speed of 500 rpm, and obtain a precursor powder after drying. The powder particle size is about 3.5 μm.

[0047] (3) Take 1g of precursor powder, add 1.25wt.% binder and appropriate amount of anhydrous ethanol, grind for 0.5h and then dry;

[0048] (4) Take 1 g of the ceramic powder obtained in step (3), put it into a mold with a diameter of 13 mm, and press it into tablets with a molding pressure of 20 MPa to obtain a ceramic green body.

[0049] (5) The ceramic green body is solid-phase sintered at a sintering temperature of 1300°C, a holding time of 8 hours, and a cooling method of quenching.

[0050] (6) The ceramic sheet obtained in step (5) is crushed and ground into powder with a particle size of about 12 μm, and the pressing-sintering-quenching process is repeated. After two sintering processes, Mg3Ga2GeO8 oxide ceramics are obtained.

[0051] Example 3

[0052] A method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries, comprising the following steps:

[0053] (1) MgO, Ga2O3, and GeO2 were calcined separately at 1100°C for 15 h;

[0054] (2) Weigh three oxides according to the stoichiometric ratio of 3:1:1.1, add appropriate amount of anhydrous ethanol, ball mill for 5 hours at a speed of 500 rpm, and obtain precursor powder after drying. The powder particle size is about 2 μm.

[0055] (3) Take 1g of precursor powder, add 1wt.% binder and appropriate amount of anhydrous ethanol, grind for 0.5h and then dry;

[0056] (4) Take 1 g of the ceramic powder obtained in step (3), put it into a mold with a diameter of 13 mm, and press it into tablets with a molding pressure of 15 MPa to obtain a ceramic green body.

[0057] (5) The ceramic green body is solid-phase sintered at a sintering temperature of 1250°C, a holding time of 10 h, and a cooling method of quenching.

[0058] (6) The ceramic sheet obtained in step (5) is crushed and ground into powder with a particle size of about 12 μm, and the pressing-sintering-quenching process is repeated. After three sintering processes, Mg3Ga2GeO8 oxide ceramics are obtained.

[0059] Example 4

[0060] A method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries, comprising the following steps:

[0061] (1) MgO, Ga2O3, and GeO2 were calcined separately at 1000°C for 15 h;

[0062] (2) Weigh three oxides according to the stoichiometric ratio of 3.1:1.1:1, add appropriate amount of anhydrous ethanol, ball mill for 5 hours at a speed of 400 rpm, and obtain precursor powder after drying. The powder particle size is about 3 μm.

[0063] (3) Take 1g of precursor powder, add 0.5wt.% binder and appropriate amount of anhydrous ethanol, grind for 0.5h and then dry;

[0064] (4) Take 1 g of the ceramic powder obtained in step (3), put it into a mold with a diameter of 13 mm, and press it into tablets with a molding pressure of 15 MPa to obtain a ceramic green body.

[0065] (5) The ceramic green body is solid-phase sintered at a sintering temperature of 1350°C, a holding time of 6 hours, and a cooling method of quenching.

[0066] (6) The ceramic sheet obtained in step (5) is crushed and ground into powder with a particle size of about 15 μm, and the pressing-sintering-quenching process is repeated. After three sintering processes, Mg3Ga2GeO8 oxide ceramics are obtained.

[0067] Example 5

[0068] A method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries, comprising the following steps:

[0069] (1) MgO, Ga2O3, and GeO2 were calcined separately at 900°C for 20 h;

[0070] (2) Weigh three oxides according to the stoichiometric ratio of 3.1:1:1.1, add appropriate amount of anhydrous ethanol, ball mill for 5 hours at a speed of 400 rpm, and obtain precursor powder after drying. The powder particle size is about 3 μm.

[0071] (3) Take 1g of precursor powder, add 1wt.% binder and appropriate amount of anhydrous ethanol, grind for 0.5h and then dry;

[0072] (4) Take 1 g of the ceramic powder obtained in step (3), put it into a mold with a diameter of 13 mm, and press it into a tablet with a molding pressure of 10 MPa to obtain a ceramic green body.

[0073] (5) The ceramic green body is solid-phase sintered at a sintering temperature of 1350°C, a holding time of 8 hours, and a cooling method of quenching.

[0074] (6) The ceramic sheet obtained in step (5) is crushed and ground into powder with a particle size of about 10 μm, and the tableting-sintering-quenching process is repeated. After three sintering processes, Mg3Ga2GeO8 oxide ceramics are obtained.

[0075] Example 6

[0076] A method for preparing a conductive ceramic Mg3Ga2GeO8 for all-solid-state batteries, comprising the following steps:

[0077] (1) MgO, Ga2O3, and GeO2 were calcined separately at 800°C for 24 h;

[0078] (2) Weigh three oxides according to the stoichiometric ratio of 3:1.1:1, add appropriate amount of anhydrous ethanol, ball mill for 6 hours at a speed of 500 rpm, and obtain precursor powder after drying. The powder particle size is about 2 μm.

[0079] (3) Take 1g of precursor powder, add 2wt.% binder and appropriate amount of anhydrous ethanol, grind for 0.5h and then dry;

[0080] (4) Take 1 g of the ceramic powder obtained in step (3), put it into a mold with a diameter of 13 mm, and press it into tablets with a molding pressure of 20 MPa to obtain a ceramic green body.

[0081] (5) The ceramic green body is solid-phase sintered at a sintering temperature of 1400°C, a holding time of 5 hours, and a cooling method of quenching.

[0082] (6) The ceramic sheet obtained in step (5) is crushed and ground into powder with a particle size of about 10 μm, and the tableting-sintering-quenching process is repeated. After three sintering processes, Mg3Ga2GeO8 oxide ceramics are obtained.

[0083] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery, characterized in that: The specific steps are as follows: (1) calcining MgO, Ga2O3, and GeO2 powders in an air atmosphere to remove moisture and impurities; (2) Weighing MgO, Ga2O3, and GeO2 powders according to the stoichiometric molar ratio, adding a solvent, ball milling, and drying to obtain a raw material powder; (3) adding the raw material powder obtained in step (2) together with a binder into a solvent, grinding and drying, and then pressing the resulting pellets into sheets, which are then fired at 1200° C. to 1400° C. to obtain a primary sintered ceramic sheet; (4) The once-sintered ceramic sheet is crushed and ground, and the powder is taken to repeat step (3). After sintering for 2 to 3 times, a Mg3Ga2GeO8 ceramic sheet with a dense structure and a single phase is obtained.

2. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (1), the purity of the raw material is ≥99.99%.

3. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (1), the calcination temperature is 800° C.-1100° C., and the calcination time is 6 h-24 h.

4. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (2), the stoichiometric molar ratio is (2.9-3.1):(0.9-1.1):(0.9-1.1), and the solvent is anhydrous ethanol.

5. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (2), the ball milling is wet ball milling. During the ball milling process, the ball milling speed is 250 rpm to 600 rpm, and the ball milling time is 3 h to 6 h.

6. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (2), the particle size of the powder obtained after ball milling is 500nm~5μm.

7. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (3), the binder is PVB, and the amount used is 0.5wt.% to 2wt.%, and the solvent is anhydrous ethanol.

8. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (3), the tableting pressure is 10 MPa to 20 MPa.

9. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (3), the primary empty burning holding time is 5h to 10h, and the cooling method is quenching.

10. The method for preparing a conductive ceramic Mg3Ga2GeO8 for an all-solid-state battery according to claim 1, characterized in that: In step (4), the particle size of the powder after crushing and grinding is 2μm to 15μm, and the cooling method after sintering is quenching.

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