Lead-free energy storage ceramic material with excellent fatigue resistance as well as preparation method and application of lead-free energy storage ceramic material

Abstract

The invention discloses a lead-free energy storage ceramic material with excellent fatigue resistance and a preparation method and application thereof, the chemical composition of the lead-free energy storage ceramic material with excellent fatigue resistance is (1-x) NaNbO3-x (Bi0. 5Mg0. 5) TiO3, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 lt, 0 X is smaller than or equal to 0.5; after the lead-free energy storage ceramic material with excellent fatigue resistance is subjected to 100,000 times of cycle tests, the change of the energy storage density and the energy storage efficiency is less than 0.11%. The lead-free energy-storage ceramic material with the excellent fatigue resistance has remarkable economic benefits, is prepared by adopting matrix elements and a traditional solid-phase sintering method, is cheap and easily available in raw materials, simple in process flow and remarkably reduced in total manufacturing cost, does not contain elements harmful to the environment such as Pb, is beneficial to environmental protection, and is suitable for industrial production. Good popularization and application prospects are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage materials, and particularly relates to a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of modern electronic technology, the performance requirements for energy storage components are increasing day by day. Dielectric energy storage ceramics have shown broad application prospects in many fields such as pulsed power systems, electric vehicles, and smart grids due to their advantages of high power density, fast charge and discharge characteristics, long cycle life, and good temperature stability. For example, in pulsed power systems, energy storage components that can instantaneously release high energy are required to drive devices such as radars and laser weapons; in electric vehicles, an efficient energy storage system can improve their endurance and power performance; and smart grids rely on stable energy storage components to balance power supply and demand and improve power quality.

[0003] However, dielectric energy storage ceramics face challenges in terms of stability in practical applications. On the one hand, under the action of a high electric field, the ceramic material may undergo electrostriction, resulting in changes in its internal structure, and thus affecting the stability of its energy storage performance. On the other hand, environmental factors such as temperature and humidity changes will also have a significant impact on the performance of dielectric energy storage ceramics. For example, an increase in temperature may change the dielectric constant of the ceramic, thereby altering its energy storage density and efficiency.

[0004] According to the review by Qi Li et al. in "Progress and perspectives in dielectric energy storage ceramics" (Journal of Advanced Ceramics 2021), the performance stability of dielectric energy storage ceramics is one of the key bottlenecks for their large-scale practical applications. The interaction of various internal and external factors makes it extremely challenging to maintain their stable energy storage performance. In addition, Shiyu Zhou et al. in "Dielectric temperature stability and energy storage performance of NBT-based ceramics by introducing high-entropy oxide" (Journal of American ceramics society 2022) also mentioned that in-depth understanding and improvement of the stability of dielectric energy storage ceramics are of great significance for the development of next-generation high-performance energy storage devices. The article improves the stability of lead-free energy storage ceramics by introducing oxides, enabling energy storage ceramics to be more widely used.

[0005] In the prior art, Chinese Patent Application CN119118668A proposed a high-entropy lead-free energy storage ceramic material, its preparation method and application. The preparation method includes the following steps: S1. Weighing: Weigh each precursor raw material according to the metering ratio and set aside; S2. Primary ball milling: Mix the weighed precursor raw materials and perform ball milling; S3. Pre-sintering: Pre-sinter the ball-milled slurry; S4. Secondary ball milling: Re-ball mill the pre-sintered raw materials, and obtain pre-sintered ceramic powder after drying; S5: Molding: Add a binder to the pre-sintered ceramic powder, and then perform pressing molding to obtain a ceramic green body; S6. Debinding and sintering: Heat the obtained ceramic green body and perform heat preservation treatment to obtain a debound green body; Subsequently, sinter the debound green body. In this invention, the magnesium-lanthanum co-doped high-entropy ceramic strategy significantly increases the relaxation behavior and anti-voltage breakdown ability of the ceramic material, improves the polarization intensity, and at the same time realizes high energy storage density and high energy storage efficiency. The prepared high-entropy ceramic has good comprehensive performance. However, it has the defect of low stability. In the range of 20°C–150°C, the energy storage density and energy storage efficiency show an obvious downward trend.

[0006] Therefore, there are still challenges in developing lead-free energy storage ceramic materials with excellent fatigue resistance characteristics. In view of this, the present invention is proposed. Summary of the Invention

[0007] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, its preparation method and application.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A lead-free energy storage ceramic material with excellent fatigue resistance characteristics, the chemical composition of the lead-free energy storage ceramic with excellent fatigue resistance characteristics is (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3, where 0 < x ≤ 0.5; after 100,000 cycles of cyclic testing, the changes in its energy storage density and energy storage efficiency are less than 3.06%.

[0010] Preferably, a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, the chemical composition of the lead-free energy storage ceramic with excellent fatigue resistance characteristics is (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3, where 0.3 ≤ x ≤ 0.5; after 100,000 cycles of cyclic testing, the changes in its energy storage density and energy storage efficiency are less than 1.35%, and in the wide temperature range from 25°C to 170°C under the conditions of 10 Hz frequency and 200 kV / cm, the changes in its energy storage density and energy storage efficiency are less than 8.12%.

[0011] Preferably, a lead-free energy storage ceramic material with excellent fatigue resistance, the chemical composition of the lead-free energy storage ceramic with excellent fatigue resistance is (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3, where x = 0.4; after 100,000 cycles of cyclic testing, the changes in the energy storage density and energy storage efficiency of the lead-free energy storage ceramic with excellent fatigue resistance are less than 0.11%; in the wide temperature range from 25°C to 170°C under the conditions of 10 Hz frequency and 200 kV / cm, the changes in the energy storage density and energy storage efficiency are less than 3.05%; at room temperature and under the condition of an electric field strength of 300 kV / cm, when the frequency is gradually increased from 10 HZ to 500 HZ, the changes in the energy storage density and energy storage efficiency are less than 1.1%.

[0012] The present invention also protects a preparation method of the lead-free energy storage ceramic material with excellent fatigue resistance as described above, including the following steps:

[0013] S1. Weigh the precursor raw materials of sodium salt, niobium salt, bismuth salt, magnesium salt, and titanium salt according to the chemical composition formula (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3 respectively, carry out ball milling to obtain a mixed material, and set it aside for later use;

[0014] S2. Pre-sinter the mixed material in step S1, and after the pre-sintering is completed, carry out secondary ball milling to obtain pre-sintered ceramic powder;

[0015] S3. Mix the pre-sintered ceramic powder in step S2 evenly with a binder, carry out pressing molding to obtain a ceramic green body;

[0016] S4. Carry out heat preservation treatment on the ceramic green body in step S3 to obtain a degreased green body, and then carry out sintering to obtain the product.

[0017] Preferably, the precursor raw materials of sodium salt, niobium salt, bismuth salt, magnesium salt, and titanium salt in step S1 are Na2CO3, Nb2O5, Bi2O3, MgO, and TiO2 respectively.

[0018] Preferably, in step S1, the ball milling is carried out using zirconia ball milling, and anhydrous ethanol accounting for 70-90% of the total mass of each precursor raw material is added before ball milling; the ball milling time is 0.5-5 h.

[0019] Preferably, the temperature of the pre-sintering in step S2 is 650-950°C, and the pre-sintering time is 0.5-5 h; the secondary ball milling time is 3-8 h.

[0020] Preferably, the binder in step S3 is a 5-10 wt% polyvinyl alcohol ethanol solution, and the addition amount is 5%-8% of the mass of the pre-fired ceramic powder; the pressure for pressing and forming is 2-4 MPa, and the pressing and forming time is 10-20 s.

[0021] Preferably, the temperature for the heat preservation treatment in step S4 is 600-700 °C, and the heat preservation treatment time is 0.5-5 h; the sintering temperature is 1090-1360 °C, and the sintering time is 2-8 h.

[0022] The present invention also protects the application of the lead-free energy storage ceramic material with excellent fatigue resistance characteristics as described above in the storage of unstable energy such as solar energy and wind energy, high-frequency electronic devices, aerospace, and medical fields.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The lead-free energy storage ceramic material with excellent fatigue resistance characteristics provided by the present invention preferably selects matrix elements, determines NaNbO3 (i.e., NN) as the matrix material through screening, and then dopes (Bi 0.5 Mg 0.5 )TiO3 (i.e., BMT) to prepare the (1-x)NN-xBMT lead-free energy storage ceramic, and optimizes the content of BMT, so that the prepared ceramic has a high energy storage density (8.07 J / cm 3 ) and energy storage efficiency (92%). Moreover, when the frequency is gradually increased from 10 HZ to 500 HZ, the fluctuations of the energy storage density and the energy storage efficiency are extremely small, and the change ranges of both are strictly controlled within 1.1%; further cyclic testing is carried out on it. After up to 100,000 cyclic tests, the changes in its energy storage density and energy storage efficiency still remain within 0.11%; not only that, in the range of 25 °C to 170 °C, the change ranges of its energy storage density and energy storage efficiency are only about 3.05%. Therefore, the strategy of doping BMT with NN provided by the present invention is beneficial to achieving excellent frequency stability, cyclic stability, and temperature stability of the lead-free energy storage ceramic while also having a high energy storage performance.

[0025] (2) The lead-free energy storage ceramic material with excellent fatigue resistance characteristics provided by the present invention has significant economic benefits. The present invention uses all matrix elements and is prepared by the traditional solid-phase sintering method. The raw materials are cheap and easy to obtain, the process flow is simple, the overall manufacturing cost is significantly reduced, and the material elements do not contain elements harmful to the environment such as Pb, which is beneficial to environmental protection and has a good prospect of popularization and application. Description of the Drawings

[0026] Figure 1The natural surface grain morphology of the (1-x)NN-xBMT ceramics prepared in Comparative Example 1 and Examples 1-4 is shown in the figure, and the inset is the grain size statistical chart;

[0027] Figure 2 XRD patterns of the (1-x)NN-xBMT ceramics prepared in Comparative Example 1 and Examples 1-4;

[0028] Figure 3 Energy storage density and energy storage efficiency diagrams of the (1-x)NN-xBMT ceramics prepared in Comparative Example 1 and Examples 1-4;

[0029] Figure 4 Frequency stability, cycle stability, and temperature stability diagrams of the 0.6NN-0.4BMT ceramics prepared in Example 4. Detailed implementation mode

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] In the present invention, a lead-free energy storage ceramic material with excellent fatigue resistance is provided, and its chemical formula is (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3, where 0 < x ≤ 0.5; after 100,000 cycles of cyclic testing, the changes in the energy storage density and energy storage efficiency of the lead-free energy storage ceramic with excellent fatigue resistance are less than 3.06%; in the wide temperature range from 25°C to 170°C under the conditions of 10 Hz frequency and 200 kV / cm, the changes in the energy storage density and energy storage efficiency are less than 8.12%; at room temperature and under the condition of an electric field strength of 300 kV / cm, when the frequency is gradually increased from 10 HZ to 500 HZ, the changes in the energy storage density and energy storage efficiency are less than 2.65%.

[0032] Its preparation method includes the following steps:

[0033] S1. Primary ball milling: Weigh the precursor raw materials of sodium salt, niobium salt, bismuth salt, magnesium salt, and titanium salt according to the chemical composition formula (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3 respectively, and perform ball milling to obtain a mixed material for standby;

[0034] S2. Pre-sintering and secondary ball milling: Pre-sinter the mixed material in step S1, and then perform secondary ball milling after the pre-sintering is completed to obtain pre-sintered ceramic powder;

[0035] S3. Shaping: Mix the pre-fired ceramic powder in step S2 with a binder evenly, and carry out pressing to form a ceramic green body.

[0036] S4. Binder burnout and sintering: Carry out heat preservation treatment on the ceramic green body in step S3 to obtain a green body after binder burnout, and then carry out sintering to obtain the product.

[0037] In the above technical solution, by doping (Bi 0.5 Mg 0.5 )TiO3 into NaNbO3 ceramics, a lead-free energy storage ceramic material with high energy storage density, high energy storage efficiency and excellent fatigue resistance characteristics is successfully prepared; and the above synthesis strategy also has the advantages of few element types and low manufacturing cost.

[0038] In some embodiments, in step S1, the precursor raw materials of sodium salt, niobium salt, bismuth salt, magnesium salt and titanium salt are Na2CO3, Nb2O5, Bi2O3, MgO and TiO2 respectively. More preferably, the purity of the above raw materials is: for Na2CO3, the purity ≥ 99.90%; for Nb2O5, the purity ≥ 99.99%; for Bi2O3, the purity ≥ 99.90%; for MgO, the purity ≥ 99.99%; for TiO2, the purity ≥ 99.80%.

[0039] In some embodiments, in step S1, zirconia ball milling is adopted, and anhydrous ethanol accounting for 70 - 90% of the total mass of the precursor raw materials is added before ball milling; the ball milling time is 0.5 - 5 h. Preferably, the addition amount of anhydrous ethanol is 80% of the total mass of the precursor raw materials, and the ball milling time is 4 h.

[0040] In some embodiments, in step S2, the pre-firing temperature is 650 - 950 °C, and the pre-firing time is 0.5 - 5 h. It can be understood that the pre-firing temperature can be a certain value among 650 °C, 660 °C, 670 °C, 680 °C, 690 °C, 700 °C, 710 °C, 720 °C, 730 °C, 740 °C, 750 °C, 760 °C, 770 °C, 780 °C, 790 °C, 800 °C, 810 °C, 820 °C, 830 °C, 840 °C, 850 °C, 860 °C, 870 °C, 880 °C, 890 °C, 900 °C, 910 °C, 920 °C, 930 °C, 940 °C, 950 °C or any value within the above range; similarly, the pre-firing time can be a certain value among 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or any value within the above range; preferably, the pre-firing time is 3 h.

[0041] In some embodiments, in step S2, the secondary ball milling time is 3 to 8 h. The ball milling is also carried out using zirconia balls, and the ball milling time can be a certain value among 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h or any value within the above range. Preferably, the ball milling time is 4 h. The drying temperature is preferably 100 °C.

[0042] In some embodiments, in step S3, the binder is a 5 to 10 wt% polyvinyl alcohol ethanol solution; more preferably, the concentration of the binder is 8 wt%. The addition amount of the binder is 5% to 8% of the mass of the pre-fired ceramic powder.

[0043] In some embodiments, in step S3, the compaction pressure is 2 to 4 MPa; the compaction time is 10 to 20 s. It can be understood that the compaction pressure can be a certain value among 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 2.9 MPa, 3 MPa, 3.1 MPa, 3.2 MPa, 3.3 MPa, 3.4 MPa, 3.5 MPa, 3.6 MPa, 3.7 MPa, 3.8 MPa, 3.9 MPa, 4 MPa or any value within the above range; the compaction time can be a certain value among 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s, 20 s or any value within the above range. Preferably, the compaction pressure is 3 MPa; the compaction time is 15 s.

[0044] In some embodiments, in step S4, the heat preservation treatment temperature is 600 to 700 °C, and the heat preservation treatment time is 0.5 to 5 h. It can be understood that the heat preservation treatment temperature can be a certain value among 600 °C, 610 °C, 620 °C, 630 °C, 640 °C, 650 °C, 660 °C, 670 °C, 680 °C, 690 °C, 700 °C or any value within the above range; the heat preservation treatment time is a certain value among 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h or any value within the above range. Preferably, the heat preservation treatment temperature is 650 °C, and the heat preservation treatment time is 1 h.

[0045] In some embodiments, in step S4, the sintering temperature is 1090 - 1360 °C, and the sintering time is 2 - 8 h. It can be understood that the sintering temperature can be a certain value among 1090 °C, 1100 °C, 1110 °C, 1120 °C, 1130 °C, 1140 °C, 1150 °C, 1160 °C, 1170 °C, 1180 °C, 1190 °C, 1200 °C, 1210 °C, 1220 °C, 1230 °C, 1240 °C, 1250 °C, 1260 °C, 1270 °C, 1280 °C, 1290 °C, 1300 °C, 1310 °C, 1320 °C, 1330 °C, 1340 °C, 1350 °C, 1360 °C or any value within the above range; the sintering time can be a certain value among 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h or any value within the above range. More preferably, the sintering time is 2 h.

[0046] Next, the technical solution of the present invention will be further described with specific examples.

[0047] Example 1

[0048] A preparation method of a lead-free energy storage ceramic material with excellent fatigue resistance characteristics includes the following steps:

[0049] S1. Primary ball milling: According to the stoichiometric ratios of the components in the chemical composition formula 0.9NaNbO3 - 0.1(Bi 0.5 Mg 0.5 )TiO3, Na2CO3, Nb2O5, Bi2O3, MgO, and TiO2 are respectively weighed and placed in a ball mill tank together with zirconia ball milling beads, and 80% of the total mass of the drugs of anhydrous ethanol is added for ball milling. The speed is increased to 50, 100, 150, 200 until 250 r / min every 5 min in turn, and finally ball milled at a speed of 250 r / min for 2 h to obtain a mixed material for standby;

[0050] S2. Pre-sintering and secondary ball milling: The mixed material in step S1 is placed in a constant temperature drying oven at 80 °C to completely volatilize the alcohol, then placed in a crucible and transferred to a muffle furnace for pre-sintering. The pre-sintering temperature is 900 °C, and the pre-sintering time is 3 h. The pre-sintered powder is mixed with anhydrous ethanol again for ball milling for 4 h, and the ball milled slurry is dried at 80 °C to obtain the final pre-sintered ceramic powder;

[0051] S3. Shaping: Add 8 wt% polyvinyl alcohol ethanol solution as a binder to the pre-fired ceramic powder in step S2 and mix evenly. The addition amount of the binder is 7% of the mass of the pre-fired ceramic powder. Fill the evenly mixed powder into a mold and use a tablet press to press and form it. Apply a pressure of 3 MPa for a constant pressure of 15 s to obtain a ceramic green body wafer with a flat and delicate surface and no delamination inside. Its diameter is about 8 mm and its thickness is about 1.0 mm.

[0052] S4. Debinding and sintering: Put the ceramic green body in step S3 into a muffle furnace and heat it to 650 °C, keep it warm for 1 h for debinding treatment to obtain a debound green body. Put the debound green body into a muffle furnace for sintering. The sintering temperature is 1250 °C and the sintering holding time is 4 h to obtain a ceramic with 10% BMT doping, denoted as 0.9NN-0.1BMT.

[0053] Example 2

[0054] A preparation method of a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, comprising the following steps:

[0055] S1. Primary ball milling: According to the stoichiometric ratios of the components in the chemical composition formula 0.8NaNbO3-0.2(Bi 0.5 Mg 0.5 )TiO3, respectively weigh Na2CO3, Nb2O5, Bi2O3, MgO, TiO2, put them together with zirconia ball milling beads in a ball milling tank, and add anhydrous ethanol accounting for 80% of the total mass of the drugs for ball milling. Every 5 min

[0056] Increase the speed to 50, 100, 150, 200 and finally 250 r / min in sequence, and finally ball mill at a speed of 250 r / min for 2 h to obtain a mixture for standby;

[0057] S2. Pre-firing and secondary ball milling: Place the mixture in step S1 in a constant temperature drying oven at 80 °C to completely volatilize the alcohol, then place it in a crucible and transfer it to a muffle furnace for pre-firing. The pre-firing temperature is 850 °C and the pre-firing time is 3 h. The pre-fired powder is mixed with anhydrous ethanol again for ball milling for 4 h. After drying the ball-milled slurry at 80 °C, the final pre-fired ceramic powder is obtained;

[0058] S3. Shaping: Add 8 wt% polyvinyl alcohol ethanol solution as a binder to the pre-fired ceramic powder in step S2 and mix evenly. The addition amount of the binder is 7% of the mass of the pre-fired ceramic powder. Fill the evenly mixed powder into a mold and use a tablet press to press and form it. Apply a pressure of 3 MPa for a constant pressure of 15 s to obtain a ceramic green body wafer with a flat and delicate surface and no delamination inside. Its diameter is about 8 mm and its thickness is about 1.0 mm;

[0059] S4. Debinding and sintering: Put the ceramic green body in step S3 into a muffle furnace and heat it to 650 °C, hold for 1 h for debinding treatment to obtain a debound green body. Then put the debound green body into the muffle furnace for sintering. The sintering temperature is 1130 °C and the sintering holding time is 4 h, thus obtaining a ceramic with 20% BMT doping amount, denoted as 0.8NN - 0.2BMT.

[0060] Example 3

[0061] A preparation method of a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, comprising the following steps:

[0062] S1. Primary ball milling: According to the stoichiometric ratios of the components in the chemical composition formula 0.7NaNbO3 - 0.3(Bi 0.5 Mg 0.5 )TiO3, weigh Na2CO3, Nb2O5, Bi2O3, MgO, TiO2 respectively, place them together with zirconia ball milling beads in a ball milling tank, and add absolute ethanol accounting for 80% of the total mass of the drugs for ball milling. Increase the speed to 50, 100, 150, 200 and finally 250 r / min every 5 min in turn, and finally ball mill at a speed of 250 r / min for 2 h to obtain a mixed material for standby;

[0063] S2. Pre-sintering and secondary ball milling: Place the mixed material in step S1 in a constant temperature drying oven at 80 °C to completely volatilize the alcohol, then place it in a crucible and transfer it to a muffle furnace for pre-sintering. The pre-sintering temperature is 800 °C and the pre-sintering time is 3 h. The pre-sintered powder is mixed with absolute ethanol again for ball milling for 4 h, and the ball milled slurry is dried at 80 °C to obtain the final pre-sintered ceramic powder;

[0064] S3. Forming: Add 8 wt% polyvinyl alcohol ethanol solution as a binder to the pre-sintered ceramic powder in step S2 and mix evenly. The addition amount of the binder is 7% of the mass of the pre-sintered ceramic powder. Fill the mixed powder into a mold and press it into shape with a tablet press. The applied pressure is 3 MPa and the constant pressure is 15 s to obtain a ceramic green body wafer with a flat and delicate surface and no delamination inside, with a diameter of about 8 mm and a thickness of about 1.0 mm;

[0065] S4. Debinding and sintering: Put the ceramic green body in step S3 into a muffle furnace and heat it to 650 °C, hold for 1 h for debinding treatment to obtain a debound green body. Then put the debound green body into the muffle furnace for sintering. The sintering temperature is 1120 °C and the sintering holding time is 4 h, thus obtaining a ceramic with 30% BMT doping amount, denoted as 0.7NN - 0.3BMT.

[0066] Example 4

[0067] A preparation method of a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, comprising the following steps:

[0068] S1. Primary ball milling: According to the stoichiometric ratios of the components in the chemical composition formula 0.6NaNbO3 - 0.4(Bi 0.5 Mg 0.5 )TiO3, weigh Na2CO3, Nb2O5, Bi2O3, MgO, TiO2 respectively, place them together with zirconia ball milling beads in a ball milling tank, and add anhydrous ethanol accounting for 80% of the total mass of the drugs for ball milling. Raise the speed to 50, 100, 150, 200 until 250 r / min in turn every 5 min, and finally ball mill at a rotation speed of 250 r / min for 2 h to obtain a mixed material for standby;

[0069] S2. Pre-sintering and secondary ball milling: Place the mixed material in step S1 in a constant temperature drying oven at 80 °C to completely volatilize the alcohol, then place it in a crucible and transfer it to a muffle furnace for pre-sintering. The pre-sintering temperature is 750 °C and the pre-sintering time is 3 h. The pre-sintered powder is mixed with anhydrous ethanol again for ball milling for 4 h, and the ball-milled slurry is dried at 80 °C to obtain the final pre-sintered ceramic powder;

[0070] S3. Forming: Add 8 wt% polyvinyl alcohol ethanol solution as a binder to the pre-sintered ceramic powder in step S2 and mix evenly. The addition amount of the binder is 7% of the mass of the pre-sintered ceramic powder. Fill the mixed powder into a mold and press it into shape with a tablet press. The applied pressure is 3 MPa and the constant pressure is 15 s to obtain a ceramic blank disc with a flat and delicate surface and no delamination inside, with a diameter of about 8 mm and a thickness of about 1.0 mm;

[0071] S4. Debinding and sintering: Place the ceramic blank in step S3 in a muffle furnace and heat it to 650 °C, keep it warm for 1 h for debinding treatment to obtain a debound green body. Place the debound green body in a muffle furnace for sintering. The sintering temperature is 1110 °C and the sintering holding time is 4 h to obtain a ceramic with a BMT doping amount of 40%, denoted as 0.6NN - 0.4BMT.

[0072] Example 5

[0073] A preparation method of a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, comprising the following steps:

[0074] S1. Primary ball milling: According to the stoichiometric ratios of the components in the chemical composition formula 0.5NaNbO3 - 0.5(Bi 0.5 Mg 0.5 )TiO3, weigh Na2CO3, Nb2O5, Bi2O3, MgO, TiO2 respectively, place them together with zirconia ball milling beads in a ball milling tank, and add anhydrous ethanol accounting for 80% of the total mass of the drugs for ball milling. Every 5 min

[0075] Raise the speed to 50, 100, 150, 200, and finally 250 r / min in sequence, and finally ball-mill for 2 h at a rotation speed of 250 r / min to obtain a mixed material for standby;

[0076] S2. Pre-sintering and secondary ball-milling: Place the mixed material in step S1 in a constant-temperature drying oven at 80 °C to completely volatilize the alcohol, then place it in a crucible and transfer it to a muffle furnace for pre-sintering. The pre-sintering temperature is 900 °C and the pre-sintering time is 3 h. The powder after pre-sintering is mixed with absolute ethanol again and ball-milled for 4 h. The ball-milled slurry is dried at 80 °C to obtain the final pre-sintered ceramic powder;

[0077] S3. Forming: Add 8 wt% polyvinyl alcohol ethanol solution as a binder to the pre-sintered ceramic powder in step S2 and mix evenly. The addition amount of the binder is 7% of the mass of the pre-sintered ceramic powder. Fill the mixed powder into a mold and press it into shape with a tablet press. The applied pressure is 3 MPa and the constant pressure is 15 s to obtain a ceramic green body disc with a flat and delicate surface and no delamination inside, with a diameter of about 8 mm and a thickness of about 1.0 mm;

[0078] S4. Debinding and sintering: Place the ceramic green body in step S3 in a muffle furnace and heat it to 650 °C, keep it warm for 1 h for debinding treatment to obtain a debound green body. Place the debound green body in a muffle furnace for sintering. The sintering temperature is 1250 °C and the sintering holding time is 4 h to obtain a ceramic with 10% BMT doping, denoted as 0.5NN-0.5BMT.

[0079] Comparative Example 1

[0080] A preparation method of a lead-free energy storage ceramic material with excellent fatigue resistance characteristics, comprising the following steps:

[0081] S1. Primary ball-milling: According to the stoichiometric ratios of the components in the chemical composition formula NaNbO3-0(Bi 0.5 Mg 0.5 )TiO3, respectively weigh Na2CO3, Nb2O5, place them together with zirconia ball-milling beads in a ball-milling tank, and add 80% of the total mass of the drugs of absolute ethanol for ball-milling. Raise the speed to 50, 100,

[0082] 150, 200, and finally 250 r / min every 5 min, and finally ball-mill for 2 h at a rotation speed of 250 r / min to obtain a mixed material for standby;

[0083] S2. Pre-sintering and secondary ball milling: The mixture obtained in step S1 is placed in a constant-temperature drying oven at 80 °C to completely volatilize the alcohol, then placed in a crucible and transferred to a muffle furnace for pre-sintering. The pre-sintering temperature is 750 °C, and the pre-sintering time is 3 h. After pre-sintering, the powder is mixed with absolute ethanol again and ball milled for 4 h. The ball-milled slurry is dried at 80 °C to obtain the final pre-sintered ceramic powder.

[0084] S3. Forming: 8 wt% polyvinyl alcohol ethanol solution is added to the pre-sintered ceramic powder obtained in step S2 as a binder and mixed evenly. The addition amount of the binder is 7% of the mass of the pre-sintered ceramic powder. The uniformly mixed powder is filled into a mold and pressed into shape by a tablet press. The applied pressure is 3 MPa, and the constant pressure is 15 s to obtain a ceramic green body disc with a flat and delicate surface and no delamination inside. Its diameter is about 8 mm and its thickness is about 1.0 mm.

[0085] S4. Debinding and sintering: The ceramic green body obtained in step S3 is placed in a muffle furnace and heated to 650 °C, and held for 1 h for debinding treatment to obtain a debound green body. The debound green body is placed in a muffle furnace for sintering. The sintering temperature is 1110 °C, and the sintering holding time is 4 h to obtain the ceramic without BMT doping, denoted as NN-0BMT.

[0086] Perform performance testing on the ceramic materials prepared in each example and comparative example, see Figures 1 to 4 .

[0087] From Figure 1 it can be seen that SEM pictures of the natural surfaces of NN-xBMT ceramics are shown. All ceramics have a dense microstructure, with grains tightly bonded to each other and no obvious large pores, indicating that the samples have good sintering quality, and with the increase of x, the grain size first decreases and then increases.

[0088] From Figure 2 it can be seen that all samples exhibit a perovskite structure and no secondary phase is generated, indicating that BMT has been fully dissolved into the NN ceramics.

[0089] From Figure 3 it can be seen that at room temperature and a frequency of 10 Hz, with the increase of x, the energy storage density of the samples first increases and then decreases. When x = 0.4, the energy density is the largest, which is 8.07 J / cm 3 , and the energy storage efficiency is as high as 92.09%.

[0090] Table 1 Energy storage density and energy storage efficiency of different groups of ceramic materials

[0091] Energy storage density Energy storage efficiency Example 1 2.48180 76.18％ Example 2 4.09277 86.77％ Example 3 4.47692 85.97％ Example 4 8.07192 92.09％ Example 5 5.55184 93.04％ Comparative Example 1 0.63799 49.02％

[0092] From Figure 4In (a-c), for the 0.6NN-0.4BMT ceramic at room temperature and under the condition of an electric field strength of 300 kV / cm, when the frequency is gradually increased from 10 Hz to 500 Hz, the fluctuations of the energy storage density and the energy storage efficiency are extremely small, and the change ranges of both are strictly controlled within 1.1%; in (d-f), it can be seen that for the 0.6NN-0.4BMT ceramic at room temperature, under the conditions of 10 Hz frequency and 300 kV / cm, after undergoing up to 100,000 cycle tests, the changes in its energy storage density and energy storage efficiency still remain within 0.11%; in (g-i), it can be seen that for the 0.6NN-0.4BMT ceramic under the conditions of 10 Hz frequency and 200 kV / cm in a wide temperature range from 25 °C to 170 °C, the changes in its energy storage density and energy storage efficiency still remain within 3.05%.

[0093] Table 2 Stability of the ceramic material prepared in Example 4 at 10 Hz frequency and 200 kV / cm from 25 °C to 170 °C

[0094] Temperature (°C) <![CDATA[W rec (J / cm 3 )]]> η (%) <![CDATA[P max (μC / cm 2 )]]> <![CDATA[P r (μC / cm 2 )]]> <![CDATA[△P(μC / cm 2 )]]> 25 0.88284 90.02 9.6265 0.475 9.1515 50 0.87962 93.68 9.32806 0.24885 9.07921 70 0.88371 94.26 9.3189 0.20859 9.11031 90 0.882 94.24 9.33538 0.27263 9.06275 110 0.87646 93.65 9.30428 0.29093 9.01335 130 0.88295 93.20 9.33355 0.29642 9.03713 150 0.86169 91.12 9.32075 0.42084 8.89991 170 0.85502 88.16 9.48725 0.68799 8.79926

[0095] Table 3 Stability of the ceramic material prepared in Example 4 at room temperature, 10 Hz frequency and 300 kV / cm for different numbers of cycles

[0096] Number of cycles <![CDATA[W rec (J / cm 3 )]]> η (%) <![CDATA[P max (μC / cm 2 )]]> <![CDATA[P r (μC / cm 2 )]]> <![CDATA[△P(μC / cm 2 )]]> 1 2.0297 92.74 14.6867 0.46465 14.22206 10 2.0188 92.80 14.6119 0.52638 14.08552 100 2.03401 92.79 14.7159 0.53938 14.17652 1000 2.02296 92.98 14.6282 0.58812 14.04008 10000 2.01956 92.96 14.6217 0.48739 14.13431 100000 2.01718 92.90 14.6347 0.50364 14.13106

[0097] Table 4 Stability of the ceramic material prepared in Example 4 at room temperature and an electric field strength of 300 kV / cm at different frequencies

[0098] Frequency (Hz) <![CDATA[W rec (J / cm 3 )]]> η (%) <![CDATA[P max (μC / cm 2 )]]> <![CDATA[P r (μC / cm 2 )]]> <![CDATA[△P (μC / cm 2 )]]> 10 2.05663 91.12 15.0863 0.80582 14.28048 100 2.03534 92.51 14.7257 0.55238 14.17333 200 2.05569 92.95 14.7452 0.62711 14.11809 300 2.04734 93.06 14.6964 0.6466 14.0498 400 2.06798 93.27 14.7939 0.51988 14.27402 500 2.06874 93.44 14.7192 0.39641 14.32279

[0099] As can be seen from Tables 2-4, the ceramic material prepared in Example 4 of the present invention has good stability under different frequencies, different temperatures and 100,000 cycle tests, indicating that the ceramic material of the present invention has excellent fatigue resistance characteristics and can be applied to scenarios with higher requirements.

[0100] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirits of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A lead-free energy storage ceramic material with excellent fatigue resistance, characterized in that: The chemical composition of the lead-free energy storage ceramic with excellent fatigue resistance is (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3, where 0 < x ≤ 0.5; after 100,000 cycles of cyclic testing, the changes in the energy storage density and energy storage efficiency of the lead-free energy storage ceramic with excellent fatigue resistance are less than 3.06%.

2. The lead-free energy storage ceramic material with excellent fatigue resistance according to claim 1, characterized in that: The chemical composition of the lead-free energy storage ceramic with excellent fatigue resistance is (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3, wherein 0.3≤x≤0.5; after 100,000 cycles of testing, the energy storage density and energy storage efficiency of the lead-free energy storage ceramic with excellent fatigue resistance change by less than 1.35%, and under the conditions of 10 Hz frequency and 200 kV / cm in a wide temperature range of 25°C to 170°C, the energy storage density and energy storage efficiency change by less than 8.12%.

3. The lead-free energy storage ceramic material with excellent fatigue resistance according to claim 1, characterized in that: The chemical composition of the lead-free energy storage ceramic with excellent fatigue resistance is (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3, wherein x=0.4; after 100,000 cycles of testing, the energy storage density and energy storage efficiency of the lead-free energy storage ceramic with excellent fatigue resistance change by less than 0.11%; under the conditions of 10 Hz frequency and 200 kV / cm in a wide temperature range of 25°C to 170°C, the energy storage density and energy storage efficiency change by less than 3.05%; at room temperature and an electric field strength of 300 kV / cm, when the frequency is gradually increased from 10 Hz to 500 Hz, the energy storage density and energy storage efficiency change by less than 1.1%.

4. A method for preparing a lead-free energy storage ceramic material with excellent fatigue resistance as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: S1, according to the chemical composition formula (1-x)NaNbO3-x(Bi 0.5 Mg 0.5 )TiO3 respectively weigh the precursor raw materials of sodium salt, niobium salt, bismuth salt, magnesium salt and titanium salt, and perform ball milling to obtain a mixed material for standby use; S2, pre-sintering the mixture, and then performing secondary ball milling after the pre-sintering to obtain pre-sintered ceramic powder; S3, mixing the pre-fired ceramic powder and the binder evenly, and pressing and molding to obtain a ceramic body; S4, performing heat preservation treatment on the ceramic body to obtain a binder-removing green body, and then sintering the green body to obtain the ceramic body.

5. The preparation method according to claim 1, characterized in that: In step S1, the precursor raw materials of sodium salt, niobium salt, bismuth salt, magnesium salt and titanium salt are Na2CO3, Nb2O5, Bi2O3, MgO and TiO2 respectively.

6. The preparation method according to claim 1, characterized in that: The ball milling in step S1 adopts zirconium dioxide ball milling, and 70-90% of the total mass of each precursor raw material is added with anhydrous ethanol before ball milling; the ball milling time is 0.5-5h.

7. The preparation method according to claim 1, characterized in that: The pre-burning temperature in step S2 is 650-950° C., and the pre-burning time is 0.5-5 h; the secondary ball milling time is 3-8 h.

8. The preparation method according to claim 1, characterized in that: In step S3, the binder is a 5-10wt% polyvinyl alcohol ethanol solution; the pressing pressure is 2-4MPa, and the pressing time is 10-20s.

9. The preparation method according to claim 1, characterized in that: The temperature of the insulation treatment in step S4 is 600-700° C., and the insulation treatment time is 0.5-5 hours; the temperature of the sintering is 1090-1360° C., and the sintering time is 2-8 hours.

10. Application of the lead-free energy storage ceramic material with excellent fatigue resistance as claimed in any one of claims 1 to 3 in unstable energy storage such as solar energy and wind energy, high-frequency electronic equipment, aerospace and medical fields.

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