Modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature, preparation method and application thereof

Abstract

The present invention discloses modified barium titanate ceramic particles with a low Curie temperature and low room temperature resistivity, as well as a preparation method and application thereof. The modified barium titanate ceramic particles with a low Curie temperature and low room temperature resistivity disclosed in the present invention have a room temperature resistivity between 0.6 and 4 Ω·cm and a Curie temperature between 45 and 55°C. They are prepared from the following raw materials: 2 to 3 mol of barium titanate hydrothermal powder, 0.2 to 0.8 mol of a Curie temperature peak shifter, 0.001 to 0.01 mol of a rare earth oxide, 0.1 to 0.4 mol of silicon dioxide powder, 0.2 to 0.5 mol of titanium dioxide powder, and 0.2 to 0.5 mol of nickel metal powder. The modified barium titanate ceramic particles with a low Curie temperature and low room temperature resistivity of the present invention can be used in the recycling of waste lithium batteries, can achieve rapid discharge and prevent thermal runaway, and have sufficient mechanical strength and are reusable.

Description

Technical Field

[0001] The invention belongs to the technical field of waste lithium battery recycling and relates to modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature, as well as a preparation method and application thereof. Background Art

[0002] As the number of electric vehicles increases, the amount of scrapped power lithium batteries will also increase year by year. Power lithium batteries are divided into: lithium iron phosphate batteries (LiFePO4) and ternary lithium batteries (LiNi x Co y Mn 1-x-y Lithium batteries contain large amounts of precious metals such as lithium, nickel, and cobalt (O2), which have high recycling value. However, they also contain toxic and hazardous substances such as electrolytes and binders. The potential environmental impact of discarded lithium batteries and the need for resource recovery technologies have long attracted widespread attention.

[0003] Currently, research on technologies for the harmlessness and resource recovery of scrapped lithium batteries focuses primarily on extracting precious metals from them through methods such as reduction leaching, bioleaching, thermal treatment, and ion exchange. The raw material used is battery "black powder" obtained after crushing and sorting. Because scrapped lithium batteries contain high levels of chemical energy, they are typically discharged before crushing and sorting to eliminate the chemical potential between the positive and negative electrodes. Otherwise, fires and explosions are highly likely to occur.

[0004] Prior art generally employs an unstructured discharge mode involving immersion in a NaCl solution. This salt solution was chosen for its excellent conductivity, superior discharge performance, and low price. However, after research and experimental studies, the company discovered that the solution after discharge contained a high concentration of suspended matter and sediment, exhibiting a black color; the battery's positive electrode casing was severely damaged; and a large amount of harmful substances from the battery casing and interior entered the solution. Testing of the discharge wastewater revealed the presence of significant amounts of metal ions such as Fe, Al, Li, Mn, and Ni, as well as organic compounds and fluorides. Testing of the gases released during discharge revealed, in addition to hydrogen and oxygen, significant amounts of hydrogen fluoride, Cl₂, and organic pollutants. These substances pose a significant threat to the environment and human health.

[0005] Therefore, the development of green, efficient and safe unorganized discharge technology is a major need for the green recycling and utilization of scrapped lithium batteries throughout the entire process. Summary of the Invention

[0006] In response to the deficiencies in the above-mentioned prior art, the present invention provides modified barium titanate ceramic particles with a low Curie temperature and low resistivity at room temperature, as well as a preparation method and application thereof; the modified barium titanate ceramic particles of the present invention have a room temperature resistivity between 0.6 and 4 Ω·cm and a Curie temperature between 45 and 55°C, can achieve rapid and safe discharge of lithium batteries and prevent thermal runaway, and have sufficient mechanical strength and are reusable.

[0007] The present invention ball-mills barium titanate hydrothermal powder, a Curie temperature shifter, rare earth oxides, silicon dioxide, titanium dioxide powder, and deionized water to form a slurry. The mixture is then dried and sieved to form a mixed powder. Nickel metal powder and the mixed powder are then placed in a ball mill and dry-milled to form a uniform mixture of metal and non-metal powders. The uniform mixture of metal and non-metal powders is then extruded and granulated to form particles of a certain size. These particles are then sintered at high temperature in a reducing atmosphere to form ceramic particles with a certain mechanical strength. Finally, the ceramic particles are heat-treated in air to enhance their PTC effect. In the present invention, a Curie temperature shifter refers to an additive that, through doping, can shift the Curie temperature of modified barium titanate ceramic particles; room temperature resistivity refers to the resistivity of the material at 20°C. The technical solution of the present invention is described in detail below.

[0008] The present invention provides a method for preparing modified barium titanate ceramic particles with a low Curie temperature and low room temperature resistivity. The modified barium titanate ceramic particles have a Curie temperature of 45 to 55° C. and a room temperature resistivity of 0.6 to 4 Ω·cm. The method comprises the following steps:

[0009] S1. barium titanate hydrothermal powder, Curie temperature point shift agent, rare earth oxide, silicon dioxide, titanium dioxide and deionized water are ball-milled and mixed to prepare a slurry;

[0010] S2, drying the ball-milled slurry, crushing it, and sieving it to obtain a non-metallic mixed powder;

[0011] S3, adding nickel metal powder to the non-metallic mixed powder and then ball milling to obtain a metal and non-metallic mixed powder;

[0012] S4. After the metal and non-metal mixed powder is extruded and granulated, high-temperature sintering and heat treatment are performed to obtain modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature.

[0013] In the present invention, in step S1, the solid raw materials are calculated by mole: 2-3 mol of barium titanate hydrothermal powder, 0.2-0.8 mol of Curie temperature point shifter, 0.001-0.01 mol of rare earth oxide, 0.1-0.4 mol of silicon dioxide powder, 0.2-0.5 mol of titanium dioxide powder, and 0.2-0.5 mol of nickel metal powder; when ball milling to prepare the slurry, the solid-liquid mass-to-volume ratio is 1:1-1:5 g / mL.

[0014] In the present invention, in step S1, the Curie temperature point shifter is any one of SrO, ZrO2, HfO2, and SnO2 oxides; and the rare earth oxide is one or more of Y2O3, La2O3, Nb2O5, and Ce2O3.

[0015] In the present invention, in step S1, the barium titanate hydrothermal powder, silicon dioxide particle size, titanium dioxide powder particle size, and nickel metal powder particle size are all less than 80 μm.

[0016] In the present invention, in step S1 and step S3, the ball milling speed is independently between 200 and 400 rpm, and the running time is independently between 200 and 500 min.

[0017] In the present invention, in step S2, the drying temperature is 100-110° C., and the mesh size of the sieve is 80 meshes.

[0018] In the present invention, in step S4, the particle size of the extrusion granulation is about 1 cm; after granulation, debinding and sintering are carried out in a reducing atmosphere, the debinding temperature is 400°C, the holding time during debinding is 30 minutes, and the heating rate from room temperature to the debinding temperature is 1.5-3°C / min. After the debinding is completed, the temperature is raised to 1150°C at 2-4°C / min and kept for 30 minutes, and then raised to the sintering temperature at 10°C / min. The sintering temperature is 1250-1350°C, and the sintering holding time is 30-360 minutes.

[0019] In the present invention, in step S4, the sintered sample is placed in a muffle furnace and heat treated under air conditions. The heat treatment temperature is 600-800°C, the heat treatment holding time is 30-120 minutes, and the heating rate is 4-6°C / min.

[0020] The present invention also provides modified barium titanate ceramic particles with low Curie temperature and low room temperature resistivity, obtained by the above-mentioned preparation method. Preferably, the Curie temperature is between 45 and 55°C, and the room temperature resistivity is between 0.6 and 4 Ω·cm.

[0021] Furthermore, the present invention provides an application of the above-mentioned modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature in the discharge process of recycled waste lithium batteries, which realizes discharge by forming a conductive path by placing the waste lithium batteries in a tank filled with modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The present invention utilizes barium titanate material to complete the transition from a ferroelectric phase to a paraelectric phase at the Curie temperature, thereby increasing the resistivity of the barium titanate by 1 to 3 orders of magnitude after the Curie temperature. Under high-temperature sintering conditions, a Curie temperature peak shifter replaces the barium position, thereby lowering the Curie temperature of the barium titanate. Simultaneously, rare earth oxides replace the barium position or the titanium position, thereby allowing the barium titanate to complete the transition from an insulator to a semiconductor. By adding nickel metal powder, the conductivity of the barium titanate ceramic particles is further improved, so that the resistivity of the prepared barium titanate ceramic particles increases by 1 to 3 orders of magnitude after the Curie temperature, and the barium titanate ceramic particles have high conductivity at room temperature, with a room temperature resistivity of 0.6 to 4 Ω·cm and a Curie temperature of 45 to 55°C.

[0024] The modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature can be applied to the discharge process in the recycling of waste lithium batteries, can achieve rapid discharge and prevent thermal runaway, and have sufficient mechanical strength and can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a block diagram of an embodiment of the method for preparing modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature according to the present invention.

[0026] Figure 2 This is the structural diagram of the connection between lithium battery and multimeter.

[0027] Figure 3 Schematic diagram of a lithium battery discharge monitoring device.

[0028] Figure 4 The figure is a resistance-temperature characteristic curve of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared by the present invention.

[0029] Figure 5 A graph showing the changes in battery voltage and temperature over time when a fully charged new lithium battery is placed in a pile of modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in Examples 1, 4, 5 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] The invention provides modified barium titanate ceramic particles with a low Curie temperature and low room temperature resistivity. The room temperature resistivity is between 0.6 and 4 Ω·cm, and the Curie temperature is between 45 and 55°C. The modified barium titanate ceramic particles are prepared from the following raw materials in moles: 2 to 3 mol of barium titanate hydrothermal powder, 0.2 to 0.8 mol of a Curie temperature peak shifter, 0.001 to 0.01 mol of a rare earth oxide, 0.1 to 0.4 mol of silicon dioxide powder, 0.2 to 0.5 mol of titanium dioxide powder, and 0.2 to 0.5 mol of nickel metal powder.

[0032] The present invention uses barium titanate hydrothermal powder as the main raw material. After being sintered into porcelain at high temperature, the raw material has the advantages of being not easy to oxidize, corrosion-resistant and having stable performance. It can also complete the transformation from ferroelectric phase to paraelectric phase after the Curie temperature, so that the resistivity increases rapidly by 1 to 3 orders of magnitude after the Curie temperature. The Curie temperature point peak shifter is any one of SrO, ZrO2, HfO2 and SnO2. The rare earth oxide is any one of Y2O3, La2O3, Nb2O5 and Ce2O3. The silicon dioxide particle size, titanium dioxide powder particle size and nickel metal powder particle size are all less than 80 μm.

[0033] The present invention uniformly mixes barium titanate hydrothermal powder, Curie temperature point shifter, rare earth oxide, silicon dioxide and titanium dioxide powder, so that during the sintering process, while lowering the Curie temperature point, rare earth elements complete the substitution of barium or titanium positions in barium titanate, releasing more electrons and increasing the electron concentration, thereby completing the transformation of barium titanate from an insulator to a semiconductor; the addition of silicon dioxide and titanium dioxide can reduce the sintering temperature of barium titanate ceramics, improve the density and mechanical strength, and at the same time can facilitate the formation of a liquid phase at high temperature, adsorb impurities in the grain boundaries, thereby reducing defects in the barium titanate grain boundaries and reducing the barium titanate grain boundary potential. The thickness of the barrier layer is determined by mixing nickel metal powder, forming ohmic contact during the sintering process, adding two conductive modes (grain-metal-grain and grain-grain boundary-metal-grain boundary-grain), further improving the conductivity of the barium titanate ceramic particles. Finally, by controlling the temperature and holding time in air, the PTC performance of the barium titanate ceramic is improved while reducing the oxidation of the nickel metal powder. This results in the prepared barium titanate ceramic particles having a resistivity increase of 1 to 3 orders of magnitude after the Curie temperature and high conductivity at room temperature, with a resistivity between 0.6 and 4 Ω·cm at room temperature and a Curie temperature between 45 and 55°C. The modified barium titanate ceramic particles of the present invention with a low Curie temperature and low room temperature resistivity can achieve rapid discharge and prevent thermal runaway during the discharge process when used in the recycling of waste lithium batteries.

[0034] See also Figure 1 The method for preparing the modified barium titanate ceramic particles having a low Curie temperature and low resistivity at room temperature specifically comprises the following steps:

[0035] S1. First, barium titanate hydrothermal powder, Curie temperature point shift agent, rare earth oxide, silicon dioxide, titanium dioxide powder and deionized water are ball-milled and mixed to prepare slurry.

[0036] In this step, the particle sizes of the barium titanate hydrothermal powder, the silica powder, and the titanium dioxide powder are all less than 80 μm, the Curie temperature point shifter is any one of SrO, ZrO2, HfO2, and SnO2, and the rare earth oxide is one or more of Y2O3, La2O3, Nb2O5, and Ce2O3. The molar ratio is: 2-3 mol of barium titanate hydrothermal powder, 0.2-0.8 mol of the Curie temperature point shifter, 0.001-0.01 mol of the rare earth oxide, 0.1-0.4 mol of the silica powder, and 0.2-0.5 mol of the titanium dioxide powder.

[0037] In this step, barium titanate hydrothermal powder, Curie temperature point shift agent, rare earth oxide, silicon dioxide, titanium dioxide powder and deionized water are mixed to prepare a slurry. A zirconia ball mill is selected as the equipment. The barium titanate hydrothermal powder, Curie temperature point shift agent, rare earth oxide, silicon dioxide and titanium dioxide powder are poured into a zirconia ball mill jar, and deionized water is added at a solid-liquid mass volume ratio of 1:1~1:5g / mL. Then, zirconia balls are added at a material-ball mass ratio of 1:2. After covering the zirconia ball mill cover, the speed is set to 200~400rpm and the running time is 200~500min to ensure that the raw materials are fully mixed.

[0038] S2. Dry the slurry after ball milling, crush it and sieve it to obtain a mixed powder.

[0039] In this step, the mixed slurry in S1 is poured into a ceramic basin, placed in a vacuum drying oven, and dried at a temperature of 100-110°C. After the water is evaporated, it is crushed in a mortar and passed through an 80-mesh sieve.

[0040] S3. Add nickel metal powder to the mixed powder and perform ball milling to obtain metal and non-metal mixed powder.

[0041] In this step, the mixed powder in S2 is poured into a zirconia ball mill jar, and then 0.2-0.5 mol of nickel metal powder is poured into the zirconia ball mill jar. After the nickel metal powder is covered with a zirconia ball mill cover, the rotation speed is set to 200-400 rpm and the running time is 200-500 min.

[0042] S4 extrudes the metal and non-metal mixed powder into granules and then performs high-temperature sintering and heat treatment to obtain modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature.

[0043] In this step, the metal and non-metal mixed powder in S3 is first extruded into granules and then placed in a high-temperature sintering furnace for high-temperature sintering under reducing atmosphere conditions. The debinding temperature is 400°C, the holding time during debinding is 30 minutes, and the heating rate from room temperature to the debinding temperature is 1.5-3°C / min. After the debinding is completed, the temperature is raised to 1150°C at 2-4°C / min and kept warm for 30 minutes. Then the temperature is raised to the sintering temperature at 10°C / min, the sintering temperature is 1250-1350°C, and the sintering holding time is 30-360 minutes. After the temperature drops to room temperature, it is taken out and placed in a muffle furnace for heat treatment under air conditions. The heat treatment temperature is 600-800°C, the heat treatment holding time is 30-120 minutes, and the heating rate from room temperature to the heat treatment temperature is 4-6°C / min to improve its PTC performance.

[0044] This step is carried out by high-temperature sintering under reducing atmosphere conditions to prevent oxidation of the nickel metal powder while forming a good ohmic contact, completing the substitution of the Curie temperature point shifter and the rare earth oxide for the barium and titanium sites in the barium titanate, lowering the Curie temperature point of the barium titanate ceramic particles, and completing the transformation from an insulator to a semiconductor. Under a reducing atmosphere, the PTC strength of the barium titanate ceramic particles is relatively weak. Therefore, by heat treatment under air conditions and controlling the heat treatment temperature and heat treatment holding time, the PTC performance of the barium titanate ceramic particles is improved and the oxidation of the nickel metal powder is minimized. The prepared modified barium titanate ceramic particles with a low Curie temperature point and low room temperature resistivity have a room temperature resistivity between 0.6 and 4Ω·cm and a Curie temperature between 45 and 55°C.

[0045] Figure 2 This is the structural diagram of the connection between lithium battery and multimeter. Figure 3 Schematic diagram of a lithium battery discharge monitoring device. In the examples, the resistance-temperature curve of the material was tested using a physical comprehensive testing system (PPMS). The method for conducting a discharge test on modified barium titanate ceramic particles is as follows:

[0046] In an indoor environment, place 7 fully charged new lithium batteries into a cubic discharge tank, one at the geometric center of each face of the discharge tank and one at the geometric center of the discharge tank to form a conductive path. During the discharge process, use a multimeter and a thermometer to monitor the voltage and temperature of the lithium battery at the geometric center of the tank. The connection method between the multimeter and the battery is as follows: Figure 2 As shown, the thermometer probe is placed at the geometric center of the particle conductive groove and contacts the surface of the lithium battery. The modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature in the circuit serve as external load resistors.

[0047] The principle of using the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature for lithium battery discharge is as follows:

[0048] In the circuit, the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature are used as external resistors. When electric energy passes through the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature, part of the electric energy will be converted into heat energy and released in the form of heat energy. The temperature gradually rises, and the temperature of the waste lithium battery also rises accordingly. As the temperature of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature rises, the thickness of its barrier layer slowly increases. When the temperature reaches the Curie temperature, due to the transformation of barium titanate from tetragonal phase to cubic phase and the rapid increase in the thickness of the barrier layer, the resistivity will rapidly rise by 1 to 3 orders of magnitude, and the current will rapidly decrease, so that the heating rate is less than the heat dissipation rate, effectively preventing the temperature of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature from further rising, forming a low-temperature discharge environment, and at the same time taking away the heat of the waste lithium battery, which can effectively prevent the waste lithium battery from thermal runaway.

[0049] The following are specific examples.

[0050] Example 1 Preparation of modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature

[0051] S1. Place 2.4 mol of barium titanate hydrothermal powder, 0.6 mol of strontium oxide, 0.007 mol of yttrium oxide, 0.15 mol of silicon dioxide, and 0.3 mol of titanium dioxide powder into a zirconia ball mill, then add 1300 mL of deionized water. Cover the mill with a lid and run for 230 min at a speed of 250 rpm to obtain a mixed slurry.

[0052] S2. Pour the mixed slurry in S1 into a ceramic basin, and place the ceramic basin containing the mixed slurry into a vacuum drying oven for drying at a drying temperature of 105°C. After the water is evaporated, take it out and grind it, and pass it through an 80-mesh sieve to obtain a mixed powder.

[0053] S3. Pour the mixed powder in S2 into a zirconia ball mill, then add 0.25 mol of nickel metal powder. Cover the ball mill with a lid and run it for 230 minutes at a speed of 350 rpm to obtain a mixed powder of metal and non-metal.

[0054] S4. After the metal and non-metal mixed powder obtained in S3 is made into particles with a particle size of 1 cm through an extrusion granulator, all the prepared particles are placed in a high-temperature sintering furnace and sintered at high temperature under reducing atmosphere conditions. The debinding temperature is 400°C, the holding time during debinding is 30 minutes, and the heating rate from room temperature to the debinding temperature is 1.5°C / min. After the debinding is completed, the temperature is raised to 1150°C at a rate of 2°C / min and held for 30 minutes, and then raised to the sintering temperature at a rate of 10°C / min. The sintering temperature is 1300°C and the sintering holding time is 120 minutes. After the temperature drops to room temperature, it is taken out and placed in a muffle furnace for heat treatment under air conditions. The heat treatment temperature is 600°C, the heat treatment holding time is 30 minutes, and the heating rate from room temperature to the heat treatment temperature is 5°C / min to improve its PTC performance.

[0055] The resistance-temperature characteristic curve of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment is shown in FIG. Figure 4 As shown; the lithium battery discharge test results are as follows Figure 5 shown.

[0056] The results show that the room temperature resistivity of the modified barium titanate ceramic particles with low Curie temperature and low room temperature resistivity prepared in this embodiment is 3.05Ω·cm, the Curie temperature is 50°C; the discharge time is 90 minutes, and the maximum temperature reached during the discharge process is 53°C.

[0057] Example 2 Preparation of modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature

[0058] S1. Place 2.4 mol of barium titanate hydrothermal powder, 0.4 mol of hafnium dioxide, 0.002 mol of yttrium oxide, 0.002 mol of niobium oxide, 0.15 mol of silicon dioxide, and 0.3 mol of titanium dioxide powder into a zirconia ball mill, then add 1300 mL of deionized water. Cover the mill with a lid and run for 300 min at a speed of 350 rpm to obtain a mixed slurry.

[0059] S2. Pour the mixed slurry in S1 into a ceramic basin, and place the ceramic basin containing the mixed slurry into a vacuum drying oven for drying at a drying temperature of 105°C. After the water is evaporated, take it out and grind it, and pass it through an 80-mesh sieve to obtain a mixed powder.

[0060] S3. Pour the mixed powder in S2 into a zirconia ball mill, then add 0.25 mol of nickel metal powder. Cover the ball mill with a lid and run it for 400 min at a speed of 350 rpm to obtain a mixed powder of metal and non-metal.

[0061] S4. After the metal and non-metal mixed powder obtained in S3 is made into particles with a particle size of 1 cm through an extrusion granulator, all the prepared particles are placed in a high-temperature sintering furnace and sintered at high temperature under reducing atmosphere conditions. The debinding temperature is 400°C, the holding time during debinding is 30 minutes, and the heating rate from room temperature to the debinding temperature is 1.5°C / min. After the debinding is completed, the temperature is raised to 1150°C at a rate of 2°C / min and held for 30 minutes, and then raised to the sintering temperature at a rate of 10°C / min. The sintering temperature is 1300°C and the sintering holding time is 120 minutes. After the temperature drops to room temperature, it is taken out and placed in a muffle furnace for heat treatment under air conditions. The heat treatment temperature is 600°C, the heat treatment holding time is 30 minutes, and the heating rate from room temperature to the heat treatment temperature is 5°C / min to improve its PTC performance.

[0062] The resistance-temperature characteristic curve of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment is shown in FIG. Figure 4 After testing, the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment have a resistivity of 0.89Ω·cm, a Curie temperature of 50°C, a discharge time of 60 minutes, and a maximum temperature of 55°C during the discharge process.

[0063] Example 3 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature and Low Resistivity at Room Temperature

[0064] The preparation method of modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature is basically the same as that of Example 1, except that: in step S1, the amount of strontium oxide added is 0.5 mol.

[0065] The resistance-temperature characteristic curve of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment is shown in FIG. Figure 4 The results show that the modified barium titanate ceramic particles with low Curie temperature and low room temperature resistivity prepared in this embodiment have a room temperature resistivity of 3.35Ω·cm and a Curie temperature of 55°C.

[0066] Example 4 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature and Low Resistivity at Room Temperature

[0067] The preparation method of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature is basically the same as that in Example 1, except that: in step S4, the amount of nickel metal powder added is 0.5 mol.

[0068] According to tests, the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment have a resistivity of 0.63 Ω·cm at room temperature and a Curie temperature of 50°C.

[0069] Example 5 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature and Low Resistivity at Room Temperature

[0070] The preparation method of modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature is basically the same as that in Example 1, except that: in S1, zirconium oxide is used instead of strontium oxide, and lanthanum oxide is used instead of yttrium oxide. The added zirconium oxide is 0.4 mol and lanthanum oxide is 0.006 mol.

[0071] According to tests, the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment have a resistivity of 1.12 Ω·cm at room temperature and a Curie temperature of 45°C.

[0072] Example 6 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature and Low Resistivity at Room Temperature

[0073] The preparation method of modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature is basically the same as that in Example 1, except that: in S1, tin oxide is used instead of strontium oxide, and niobium oxide is used instead of yttrium oxide. The added tin oxide is 0.25 mol and niobium oxide is 0.006 mol.

[0074] According to tests, the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment have a resistivity of 3.02 Ω·cm at room temperature and a Curie temperature of 50°C.

[0075] Example 7 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature and Low Resistivity at Room Temperature

[0076] The preparation method of modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature is basically the same as that in Example 1, except that: in S1, a mixture of niobium oxide and yttrium oxide is used instead of single yttrium oxide, and the added yttrium oxide is 0.003 mol and niobium oxide is 0.0015 mol.

[0077] According to tests, the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature prepared in this embodiment have a resistivity of 1.62 Ω·cm at room temperature and a Curie temperature of 50°C.

[0078] Comparative Example 1

[0079] The preparation method of the modified barium titanate ceramic particles is substantially the same as that of Example 1, except that in S4, the amount of nickel metal powder added is 0 mol.

[0080] The thermal resistance properties of the modified barium titanate ceramic particles prepared in this comparative example are as follows: Figure 4 The results show that the room temperature resistivity of the modified barium titanate ceramic particles prepared in this comparative example is 31.62Ω·cm, and the Curie temperature is 50°C.

[0081] In order to reflect the effect of modified barium titanate ceramic particles with different Curie temperatures or different room temperature resistivities on the discharge process of waste lithium batteries, lithium battery discharge tests were carried out using Example 1, Example 4, Example 5 and Comparative Example 1. The test results are as follows: Figure 5 shown.

[0082] As described above, the modified barium titanate ceramic particles prepared by the present invention, when the room temperature resistivity of the modified barium titanate ceramic particles is low, the Curie temperature controls the maximum temperature during the discharge process. If the Curie temperature is too high, the lithium battery temperature will be too high, resulting in thermal runaway. If the Curie temperature is too low, the temperature of the lithium battery will remain near the Curie temperature when it is in a low voltage state, resulting in excessive resistance in the conductive path, prolonged discharge time, and reduced discharge efficiency. When the Curie temperature of the modified barium titanate ceramic particles is the same, the higher the room temperature resistivity, the greater the resistance in the conductive path, the longer the discharge time, and the lower the discharge efficiency.

Claims

1. A method for preparing modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature, characterized in that: The modified barium titanate ceramic particles have a Curie temperature of 45 to 55° C. and a room temperature resistivity of 0.6 to 4Ω·cm. The method comprises the following steps: S1. barium titanate hydrothermal powder, Curie temperature point shift agent, rare earth oxide, silicon dioxide, titanium dioxide and deionized water are ball-milled and mixed to prepare a slurry; S2, drying the ball-milled slurry, crushing it, and sieving it to obtain a non-metallic mixed powder; S3, adding nickel metal powder to the non-metallic mixed powder and then ball milling to obtain a metal and non-metallic mixed powder; S4. After the metal and non-metal mixed powder is extruded and granulated, high-temperature sintering and heat treatment are performed to obtain modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature; wherein: In step S1, the solid raw materials are calculated by mole: 2-3 mol of barium titanate hydrothermal powder, 0.2-0.8 mol of Curie temperature point shifter, 0.001-0.01 mol of rare earth oxide, 0.1-0.4 mol of silicon dioxide powder, 0.2-0.5 mol of titanium dioxide powder, and 0.2-0.5 mol of nickel metal powder; the Curie temperature point shifter is any one of SrO, ZrO2, HfO2, and SnO2 oxides; the rare earth oxide is one or more of Y2O3, La2O3, Nb2O5, and Ce2O3; In step S4, after granulation and molding, debinding and sintering are carried out in a reducing atmosphere, the sintering temperature is 1250-1350°C, and the sintering holding time is 30-360 min; the sintered sample is placed in a muffle furnace and heat treated under air conditions, the heat treatment temperature is 600-800°C, the heat treatment holding time is 30-120 min, and the heating rate is 4-6°C / min.

2. The preparation method according to claim 1, characterized in that In step S1, during ball milling to prepare the slurry, the solid-liquid mass-to-volume ratio is 1:1-1:5 g / mL.

3. The preparation method according to claim 1, characterized in that In step S1 and step S3, the ball milling speed is independently between 200 and 400 rpm, and the running time is independently between 200 and 500 min.

4. The preparation method according to claim 1, characterized in that In step S2, the drying temperature is 100-110°C, and the mesh size of the sieve is 80 meshes.

5. The preparation method according to claim 1, characterized in that In step S4, the debinding temperature is 400°C, the holding time during debinding is 30 minutes, and the heating rate from room temperature to the debinding temperature is 1.5-3°C / min. After the debinding is completed, the temperature is raised to 1150°C at 2-4°C / min and held for 30 minutes, and then raised to the sintering temperature at 10°C / min.

6. Modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature, obtained by the preparation method according to any one of claims 1 to 5.

7. A use of the modified barium titanate ceramic particles with low Curie temperature and low resistivity at room temperature according to claim 6 in the discharge process of recycled waste lithium batteries, characterized in that: It achieves discharge by placing waste lithium batteries in a tank filled with modified barium titanate ceramic particles with a low Curie temperature and low resistivity at room temperature to form a conductive path.

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