Modified barium titanate ceramic particle with low Curie temperature point and low resistivity at room temperature as well as preparation method and application of modified barium titanate ceramic particle

Abstract

The invention discloses modified barium titanate ceramic particles with low Curie temperature point and low resistivity at room temperature as well as a preparation method and application of the modified barium titanate ceramic particles. The room-temperature resistivity of the modified barium titanate ceramic particles with the low Curie temperature point and the room-temperature low resistivity ranges from 0.6 ohm.cm to 4 ohm.cm, the Curie temperature point ranges from 45 DEG C to 55 DEG C, and the modified barium titanate ceramic particles are prepared from 2 mol to 3 mol of barium titanate hydrothermal powder, 0.2 mol to 0.8 mol of a Curie temperature point peak shifting agent, 0.001 mol to 0.01 mol of rare earth oxide, 0.1 mol to 0.4 mol of silicon dioxide powder, 0.2 mol to 0.5 mol of titanium dioxide powder and 0.2 mol to 0.5 mol of nickel metal powder. The modified barium titanate ceramic particles with low Curie temperature point and low resistivity at room temperature can be applied to waste lithium battery recovery, can realize rapid discharge and prevent thermal runaway, have enough mechanical strength, and can be reused.

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, and 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 O2), etc., which contain a large amount of precious metals such as Li, Ni, and Co, and have high recycling value. At the same time, lithium batteries also contain toxic and harmful substances such as electrolytes and binders. The environmental problems that may be caused by scrapped lithium batteries and the demand for resource recovery technology have long attracted widespread attention.

[0003] At present, the research on the harmlessness and resource utilization technology of scrapped lithium batteries mainly focuses on the extraction of precious metals in batteries by reduction leaching, bioleaching, heat treatment methods, ion exchange methods, etc. The raw materials used are all battery "black powder" obtained after crushing and sorting. Since scrapped lithium batteries contain high chemical energy, they are generally discharged before crushing and sorting, that is, the chemical potential between the positive and negative electrodes of the battery is eliminated, otherwise it is very easy to catch fire and explode.

[0004] In the prior art, the unorganized discharge mode of immersion in NaCl solution is generally adopted. This salt solution is selected because of its good conductivity, good discharge effect and low price. However, after investigation and experimental research, the company found that: the solution after discharge has more suspended matter and sediment, and the color is black; the positive electrode shell of the battery is seriously damaged; and a large amount of harmful substances in the battery shell and inside enter the solution. After measuring the discharge wastewater, it was found that the solution contained a large amount of metal ions such as Fe, Al, Li, Mn, Ni, organic compounds and fluorides. After measuring the gases released during the discharge process, it was found that in addition to hydrogen and oxygen, there were also a large amount of hydrogen fluoride, Cl2 and organic pollutants. These substances pose a great 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 full-process green recycling of scrapped lithium batteries. Summary of the invention

[0006] Aiming at the deficiencies of the above-mentioned existing technologies, the present invention provides modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity, a preparation method thereof, and an 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 point between 45 and 55 °C, can achieve rapid and safe discharge of lithium batteries and prevent thermal runaway, and have sufficient mechanical strength and can be reused.

[0007] In the present invention, barium titanate hydrothermal powder, a Curie temperature point peak-shifting agent, rare earth oxides, silicon dioxide, titanium dioxide powder, and deionized water are ball-milled and mixed to form a slurry, dried and sieved to form a mixed powder. Then, nickel metal powder and the mixed powder are put into a ball-milling tank for dry-milling and mixing to obtain a powder with uniformly mixed metal and non-metal. Subsequently, the powder with uniformly mixed metal and non-metal is extruded and granulated to form particles with a certain particle size, and is sintered at a 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 the PTC effect of the ceramic particles. In the present invention, the Curie temperature point peak-shifting agent refers to a type of additive that can shift the Curie temperature point of the modified barium titanate ceramic particles through doping; the room-temperature resistivity refers to the resistivity of the material at a temperature of 20 °C. The technical solution of the present invention is specifically introduced as follows.

[0008] The present invention provides a preparation method for modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity. The Curie temperature point of the modified barium titanate ceramic particles is between 45 and 55 °C, and the room-temperature resistivity is between 0.6 and 4 Ω·cm. The method includes the following steps: S1. Ball-mill and mix barium titanate hydrothermal powder, a Curie temperature point peak-shifting agent, rare earth oxides, silicon dioxide, titanium dioxide, and deionized water to form a slurry; S2. Dry the slurry after ball-milling and mixing, crush it, and sieve it to obtain a non-metal mixed powder; S3. Add nickel metal powder to the non-metal mixed powder and then ball-mill and mix to obtain a metal and non-metal mixed powder; S4. After extruding and granulating the metal and non-metal mixed powder, perform high-temperature sintering and heat treatment to obtain modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity.

[0009] In the present invention, in step S1, calculated by mole number of the solid raw materials, the barium titanate hydrothermal powder is 2 - 3 mol, the Curie temperature point peak-shifting agent is 0.2 - 0.8 mol, the rare earth oxides are 0.001 - 0.01 mol, the silicon dioxide powder is 0.1 - 0.4 mol, the titanium dioxide powder is 0.2 - 0.5 mol, and the nickel metal powder is 0.2 - 0.5 mol; when ball-milling to form a slurry, the solid-liquid mass-volume ratio is 1:1~1:5 g / mL.

[0010] In the present invention, in step S1, the Curie temperature point shifting agent is any one of SrO, ZrO2, HfO2, and SnO2 oxides; the rare earth oxide is one or more of Y2O3, La2O3, Nb2O5, and Ce2O3.

[0011] In the present invention, in step S1, the particle sizes of the barium titanate hydrothermal powder, silicon dioxide, titanium dioxide powder, and nickel metal powder are all less than 80 μm.

[0012] In the present invention, in steps S1 and S3, the ball milling speed independently ranges from 200 to 400 rpm, and the running time independently ranges from 200 to 500 min.

[0013] In the present invention, in step S2, the drying temperature is 100 - 110 °C, and the mesh number of the sieve is 80 mesh.

[0014] In the present invention, in step S4, the particle size of the extruded and granulated product is about 1 cm; after granulation and forming, debinding and sintering are carried out in a reducing atmosphere. The debinding temperature is 400 °C, the holding time during debinding is 30 min, the heating rate from room temperature to the debinding temperature is 1.5 - 3 °C / min. After debinding is completed, the temperature is raised to 1150 °C at a rate of 2 - 4 °C / min and held for 30 min, and then the temperature is raised to the sintering temperature at a rate of 10 °C / min. The sintering temperature is 1250 - 1350 °C, and the sintering holding time is 30 - 360 min.

[0015] 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 min, and the heating rate is 4 - 6 °C / min.

[0016] The present invention also provides modified barium titanate ceramic particles with a low Curie temperature point and low room temperature resistivity prepared by the above preparation method. Preferably, the Curie temperature point is between 45 and 55 °C, and the room temperature resistivity is between 0.6 and 4 Ω·cm.

[0017] Furthermore, the present invention provides an application of the above modified barium titanate ceramic particles with a low Curie temperature point and low room temperature resistivity in the discharging process of waste lithium battery recycling, which realizes discharging by placing the waste lithium battery in a tank filled with modified barium titanate ceramic particles with a low Curie temperature point and low room temperature resistivity to form a conductive path.

[0018] Above, compared with the prior art, the beneficial effects of the present invention are as follows: The present invention utilizes the phase transition of barium titanate material from ferroelectric phase to paraelectric phase at the Curie temperature point, thereby causing the resistivity of barium titanate to increase by 1 to 3 orders of magnitude after the Curie temperature point. Under the condition of high-temperature sintering, the peak-shifting agent for the Curie temperature point completes the substitution of the barium site, thereby reducing the Curie temperature point of barium titanate. At the same time, rare-earth oxides complete the substitution of the barium site or titanium site, enabling barium titanate to complete the transformation from insulator to semiconductor. By adding nickel metal powder, the conductivity of barium titanate ceramic particles is further improved, making the resistivity of the prepared barium titanate ceramic particles increase by 1 to 3 orders of magnitude after the Curie temperature point, and also having high conductivity at room temperature, with the room-temperature resistivity between 0.6 and 4 Ω·cm and the Curie temperature point between 45 and 55 °C.

[0019] The modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity of the present invention can be applied to the discharging process in the recycling of waste lithium batteries, enabling rapid discharging and preventing thermal runaway, and having sufficient mechanical strength for repeated use. Brief Description of the Drawings

[0020] Figure 1 It is a block diagram of an embodiment of the preparation method of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity of the present invention.

[0021] Figure 2 It is a structural diagram of the connection mode between a lithium battery and a multimeter.

[0022] Figure 3 It is a schematic diagram of a lithium battery discharging monitoring device.

[0023] Figure 4 It is a resistance-temperature characteristic curve diagram of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared by the present invention.

[0024] Figure 5 It is a diagram showing the change of battery voltage and temperature with time when a fully charged new lithium battery is placed in the pile of modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in Example 1, Example 4, Example 5 and Comparative Example 1 of the present invention. Detailed Embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following examples are used to further describe the present invention in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The present invention provides a modified barium titanate ceramic particle with a low Curie temperature point and a low room-temperature resistivity. The room-temperature resistivity is between 0.6 and 4 Ω·cm, and the Curie temperature point is between 45 and 55 °C. It is prepared from the following raw materials in terms of molar amounts: 2-3 mol of hydrothermal barium titanate powder, 0.2-0.8 mol of Curie temperature point peak-shifting agent, 0.001-0.01 mol of rare earth oxide, 0.1-0.4 mol of silica powder, 0.2-0.5 mol of titanium dioxide powder, and 0.2-0.5 mol of nickel metal powder.

[0027] The present invention selects hydrothermal barium titanate powder as the main raw material. After being sintered into ceramics at high temperature, this raw material has the advantages of being not easily oxidized, corrosion-resistant, and having stable properties. Moreover, it can complete the transformation from ferroelectric phase to paraelectric phase after the Curie temperature point, causing the resistivity to increase rapidly by 1-3 orders of magnitude after the Curie temperature point. The Curie temperature point peak-shifting agent is any one of SrO, ZrO2, HfO2, and SnO2. The rare earth oxide is any one of Y2O3, La2O3, Nb2O5, and Ce2O3. The particle sizes of the silica powder, titanium dioxide powder, and nickel metal powder are all less than 80 μm.

[0028] The present invention mixes the hydrothermal barium titanate powder, Curie temperature point peak-shifting agent, rare earth oxide, silica, and titanium dioxide powder evenly. During the sintering process, while reducing the Curie temperature point, the rare earth elements complete the substitution of barium sites or titanium sites 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 silica and titanium dioxide can reduce the sintering temperature of barium titanate ceramics, improve the density and mechanical strength, and at the same time is beneficial to the formation of a liquid phase at high temperature, adsorbing impurities in the grain boundaries, thereby reducing the defects in the barium titanate grain boundaries and reducing the thickness of the barium titanate grain boundary barrier layer. After mixing the nickel metal powder, ohmic contact is formed during the sintering process, increasing two conduction 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 the air, while improving the PTC performance of the barium titanate ceramics, the oxidation of the nickel metal powder is reduced, enabling the resistivity of the prepared barium titanate ceramic particles to increase by 1-3 orders of magnitude after the Curie temperature point and having high conductivity at room temperature. The room-temperature resistivity is between 0.6 and 4 Ω·cm, and the Curie temperature point is between 45 and 55 °C. The modified barium titanate ceramic particles with a low Curie temperature point and a low room-temperature resistivity of the present invention can achieve rapid discharge and prevent thermal runaway during the discharge process when used for the recycling of waste lithium batteries.

[0029] See Figure 1 For the preparation method of the above-mentioned modified barium titanate ceramic particles with a low Curie temperature point and a low room-temperature resistivity, it specifically includes the following steps: S1. First, hydrothermal barium titanate powder, a Curie temperature peak-shifting agent, rare earth oxides, silicon dioxide, titanium dioxide powder, and deionized water are ball-milled and mixed to make a slurry.

[0030] In this step, the particle sizes of the hydrothermal barium titanate powder, silicon dioxide powder, and titanium dioxide powder are all less than 80 μm. The Curie temperature peak-shifting agent is any one of SrO, ZrO2, HfO2, and SnO2, and the rare earth oxides are one or more of Y2O3, La2O3, Nb2O5, and Ce2O3. Among them, in terms of molar quantity: 2 - 3 mol of hydrothermal barium titanate powder, 0.2 - 0.8 mol of Curie temperature peak-shifting agent, 0.001 - 0.01 mol of rare earth oxides, 0.1 - 0.4 mol of silicon dioxide powder, and 0.2 - 0.5 mol of titanium dioxide powder.

[0031] In this step, the hydrothermal barium titanate powder, Curie temperature peak-shifting agent, rare earth oxides, silicon dioxide, titanium dioxide powder, and deionized water are mixed to make a slurry. The equipment selected is a zirconia ball mill. The hydrothermal barium titanate powder, Curie temperature peak-shifting agent, rare earth oxides, silicon dioxide, and titanium dioxide powder are poured into a zirconia ball mill tank, and deionized water is added according to the solid-liquid mass-volume ratio of 1:1 - 1:5 g / mL. Then, zirconia balls are added according to the material-ball mass ratio of 1:2. After covering the zirconia ball mill cover, the rotation speed is set to 200 - 400 rpm, and the running time is 200 - 500 min to make the raw materials fully and evenly mixed.

[0032] S2. The ball-milled and mixed slurry is dried, crushed, and then sieved to obtain a mixed powder.

[0033] In this step, the mixed slurry in S1 is poured into a ceramic basin and then placed in a vacuum drying oven to be dried at a temperature of 100 - 110 °C. After the water is evaporated, it is crushed using a mortar and sieved through an 80-mesh sieve.

[0034] S3. Nickel metal powder is added to the mixed powder and then ball-milled and mixed to obtain a metal and non-metal mixed powder.

[0035] In this step, the mixed powder in S2 is poured into a zirconia ball mill tank, and then 0.2 - 0.5 mol of nickel metal powder is poured in. After covering the zirconia ball mill cover, the rotation speed is set to 200 - 400 rpm, and the running time is 200 - 500 min.

[0036] S4. After the metal and non-metal mixed powder is extruded and granulated, it is subjected to high-temperature sintering and heat treatment to obtain modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity.

[0037] In this step, the metal and non-metal mixed powder in S3 is first extruded and granulated, and then placed in a high-temperature sintering furnace. High-temperature sintering is carried out under a reducing atmosphere. The degreasing temperature is 400°C, the holding time during degreasing is 30 min, the heating rate from room temperature to the degreasing temperature is 1.5 - 3°C / min. After degreasing is completed, the temperature is raised to 1150°C at a rate of 2 - 4°C / min and held for 30 min, and then the temperature is raised to the sintering temperature at a rate of 10°C / min. The sintering temperature is 1250 - 1350°C, and the sintering holding time is 30 - 360 min. After the temperature drops to room temperature, it is taken out and then 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 min, and the heating rate from room temperature to the heat treatment temperature is 4 - 6°C / min to improve its PTC performance.

[0038] In this step, high-temperature sintering is carried out under a reducing atmosphere to prevent the oxidation of nickel metal powder while forming good ohmic contact, completing the substitution of the Curie temperature peak-shifting agent and rare earth oxides for barium sites and titanium sites in barium titanate, and reducing the Curie temperature point of barium titanate ceramic particles, and completing the transformation from insulator to semiconductor; under a reducing atmosphere, the PTC strength of barium titanate ceramic particles is weak. Therefore, by carrying out heat treatment under air conditions and controlling the heat treatment temperature and heat treatment holding time, the PTC performance of barium titanate ceramic particles is improved and the oxidation of nickel metal powder is minimized as much as possible. 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 4 Ω·cm and a Curie temperature between 45 and 55°C.

[0039] Figure 2 It is a structural diagram of the connection method between a lithium battery and a multimeter. Figure 3 It is a schematic diagram of a lithium battery discharge monitoring device. In the embodiment, the resistance-temperature curve of the material is tested using a physical comprehensive test system (PPMS). The method for discharging the modified barium titanate ceramic particles is as follows: Under indoor environment, 7 fully charged new lithium batteries are placed in a cube discharge tank. One is placed at the geometric center of each face of the discharge tank and one is placed at the geometric center of the body of the discharge tank to form an electrical conduction path. During the discharge process, a multimeter and a thermometer are used to monitor the voltage and temperature of the lithium battery at the geometric center of the body. The connection method between the multimeter and the battery is as Figure 2 shown. The probe of the thermometer is placed at the geometric center of the inner part of the particle conduction tank in contact with the surface of the lithium battery. In the circuit, the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity are used as an external load resistor.

[0040] The principle of using the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity of the present invention for lithium battery discharge is as follows: In the circuit, modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity are used as an external load resistor. When electric energy passes through the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity, part of the electric energy will be converted into heat energy and released in the form of heat energy, and the temperature gradually rises. The temperature of the waste lithium battery also rises accordingly. As the temperature of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity increases, the thickness of its barrier layer slowly increases. When the temperature reaches the Curie temperature point, due to the transformation of barium titanate from the tetragonal phase to the cubic phase and the rapid increase in the thickness of the barrier layer, the resistivity will rapidly increase by 1 to 3 orders of magnitude, and the current will rapidly decrease, making the heating rate less than the heat dissipation rate, effectively preventing the temperature of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity from further increasing, 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 thermal runaway of the waste lithium battery.

[0041] The following are specific embodiments.

[0042] Example 1 Preparation of Modified Barium Titanate Ceramic Particles with a Low Curie Temperature Point and Low Room-Temperature Resistivity S1. Put 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 milling tank, then add 1300 mL of deionized water, cover the ball milling cover, and run for 230 min at a rotation speed of 250 rpm to obtain a mixed slurry.

[0043] S2. Pour the mixed slurry in S1 into a ceramic basin, put the ceramic basin containing the mixed slurry into a vacuum drying oven for drying, the drying temperature is 105 °C, take it out and crush it after the water is evaporated, and pass through an 80-mesh sieve to obtain a mixed powder.

[0044] S3. After pouring the mixed powder in S2 into a zirconia ball milling tank, pour in 0.25 mol of nickel metal powder, cover the ball milling cover, and run for 230 min at a rotation speed of 350 rpm to obtain a metal-nonmetal mixed powder.

[0045] S4. After making the metal and non-metal mixed powder prepared in S3 into particles with a particle size of 1 cm through an extrusion granulator, all the prepared particles are put into a high-temperature sintering furnace, and high-temperature sintering is carried out under a reducing atmosphere condition. The debinding temperature is 400 °C, the holding time during debinding is 30 min, the heating rate from room temperature to the debinding temperature is 1.5 °C / min. After debinding is completed, the temperature is raised to 1150 °C at a rate of 2 °C / min and held for 30 min, then the temperature is 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 min. After the temperature drops to room temperature, it is taken out and then put into a muffle furnace, and heat treatment is carried out under air conditions. The heat treatment temperature is 600 °C, the heat treatment holding time is 30 min, and the heating rate from room temperature to the heat treatment temperature is 5 °C / min to improve its PTC performance.

[0046] The resistance-temperature characteristic curve of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in this example is as Figure 4 shown; the lithium battery discharge test results are as Figure 5 shown.

[0047] The results show that the room-temperature resistivity of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in this example is 3.05 Ω·cm, and the Curie temperature point is 50 °C; the discharge time is 90 min, and the highest temperature reached during the discharge process is 53 °C.

[0048] Example 2 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature Point and Low Room-Temperature Resistivity S1. Put 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 milling tank, then add 1300 mL of deionized water. After covering the ball milling cover, run for 300 min at a rotation speed of 350 rpm to obtain a mixed slurry.

[0049] S2. Pour the mixed slurry in S1 into a ceramic basin, put the ceramic basin containing the mixed slurry into a vacuum drying oven for drying. The drying temperature is 105 °C. After the water is evaporated, take it out, crush it, and pass through an 80-mesh sieve to obtain a mixed powder.

[0050] S3. After pouring the mixed powder in S2 into a zirconia ball milling tank, then pour 0.25 mol of nickel metal powder into it. After covering the ball milling cover, run for 400 min at a rotation speed of 350 rpm to obtain a metal and non-metal mixed powder.

[0051] S4. After making the metal and non-metal mixed powder obtained in S3 into particles with a particle size of 1 cm through an extrusion granulator, all the prepared particles are put into a high-temperature sintering furnace and sintered at a high temperature under a reducing atmosphere. The debinding temperature is 400 °C, the holding time during debinding is 30 min, the heating rate from room temperature to the debinding temperature is 1.5 °C / min. After debinding is completed, the temperature is raised to 1150 °C at a rate of 2 °C / min and held for 30 min, then the temperature is 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 min. After the temperature drops to room temperature, it is taken out and then put into a muffle furnace for heat treatment under air conditions. The heat treatment temperature is 600 °C, the heat treatment holding time is 30 min, and the heating rate from room temperature to the heat treatment temperature is 5 °C / min to improve its PTC performance.

[0052] The resistance-temperature characteristic curve of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in this example is as Figure 4 shown. After testing, the resistivity of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in this example is 0.89 Ω·cm, the Curie temperature point is 50 °C, the discharge time is 60 min, and the highest temperature reached during the discharge process is 55 °C.

[0053] Example 3 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature Point and Low Room-Temperature Resistivity The preparation method of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity is basically the same as that of Example 1, except that: in step S1, 0.5 mol of strontium oxide is added.

[0054] The resistance-temperature characteristic curve of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in this example is as Figure 4 shown. The results show that the room-temperature resistivity of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in this example is 3.35 Ω·cm, and the Curie temperature point is 55 °C.

[0055] Example 4 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature Point and Low Room-Temperature Resistivity

[0056] The preparation method of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity is basically the same as that of Example 1, except that: in step S4, 0.5 mol of nickel metal powder is added.

[0057] After testing, the room-temperature resistivity of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity prepared in this example is 0.63 Ω·cm, and the Curie temperature point is 50 °C.

[0058] Example 5 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature Point and Low Room Temperature Resistivity

[0059] The preparation method of the modified barium titanate ceramic particles with low Curie temperature point and low room temperature resistivity 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 the added lanthanum oxide is 0.006 mol.

[0060] After testing, the room temperature resistivity of the modified barium titanate ceramic particles prepared in this example with low Curie temperature point and low room temperature resistivity is 1.12 Ω·cm, and the Curie temperature point is 45 °C.

[0061] Example 6 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature Point and Low Room Temperature Resistivity

[0062] The preparation method of the modified barium titanate ceramic particles with low Curie temperature point and low room temperature resistivity 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 the added niobium oxide is 0.006 mol.

[0063] After testing, the room temperature resistivity of the modified barium titanate ceramic particles prepared in this example with low Curie temperature point and low room temperature resistivity is 3.02 Ω·cm, and the Curie temperature point is 50 °C.

[0064] Example 7 Preparation of Modified Barium Titanate Ceramic Particles with Low Curie Temperature Point and Low Room Temperature Resistivity

[0065] The preparation method of the modified barium titanate ceramic particles with low Curie temperature point and low room temperature resistivity 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 a single yttrium oxide. The added yttrium oxide is 0.003 mol and the added niobium oxide is 0.0015 mol.

[0066] After testing, the room temperature resistivity of the modified barium titanate ceramic particles prepared in this example with low Curie temperature point and low room temperature resistivity is 1.62 Ω·cm, and the Curie temperature point is 50 °C.

[0067] Comparative Example 1 The preparation method of the modified barium titanate ceramic particles is basically the same as that in Example 1, except that: in S4, the added nickel metal powder is 0 mol.

[0068] The resistance-temperature characteristics of the modified barium titanate ceramic particles prepared in this comparative example are as Figure 4 shown. The results show that the room temperature resistivity of the modified barium titanate ceramic particles prepared in this comparative example is 31.62 Ω·cm, and the Curie temperature point is 50 °C.

[0069] To reflect the influence of modified barium titanate ceramic particles with different Curie temperature points or different room temperature resistivity on the discharge process of waste lithium batteries, Example 1, Example 4, Example 5 and Comparative Example 1 were used to conduct lithium battery discharge tests, and the test results are as Figure 5 shown.

[0070] Above, for the modified barium titanate ceramic particles prepared by the present invention, when the room temperature resistivity of the modified barium titanate ceramic particles is relatively low, the Curie temperature point controls the highest temperature during the discharge process. If the Curie temperature point is too high, it will cause the temperature of the lithium battery to be too high and thermal runaway will occur. If the Curie temperature point is too low, when the lithium battery is in a low voltage state, the temperature will still be near the Curie temperature point, the resistance in the conductive path will be too large, the discharge time will be prolonged, and the discharge efficiency will be reduced. When the Curie temperature points of the modified barium titanate ceramic particles are the same, the greater 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 preparation method of modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity, characterized in that, The Curie temperature point of the modified barium titanate ceramic particles is between 45 and 55 °C, and the room temperature resistivity is between 0.6 and 4 Ω·cm; it includes the following steps: S1. Ball-mill and mix the hydrothermal barium titanate powder, Curie temperature point peak-shifting agent, rare earth oxide, silicon dioxide, titanium dioxide and deionized water to make a slurry; S2. Dry the slurry after ball-milling and mixing, crush it, and then screen it to obtain a non-metal mixed powder; S3. Add nickel metal powder to the non-metal mixed powder and then ball-mill and mix to obtain a metal and non-metal mixed powder; S4. After extruding and granulating the metal and non-metal mixed powder, perform high-temperature sintering and heat treatment to obtain modified barium titanate ceramic particles with a low Curie temperature point and low room temperature resistivity.

2. The preparation method according to claim 1, characterized in that, In step S1, based on the molar amount of the solid raw materials, 2-3 mol of hydrothermal barium titanate powder, 0.2-0.8 mol of Curie temperature point peak-shifting agent, 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 make a slurry, the solid-liquid mass-volume ratio is 1:1~1:5 g / mL.

3. The preparation method according to claim 1, characterized in that, In step S1, the Curie temperature point peak-shifting agent is any one of SrO, ZrO2, HfO2, SnO2 oxides; the rare earth oxide is one or more of Y2O3, La2O3, Nb2O5, Ce2O3.

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

5. The preparation method according to claim 1, wherein In step S2, the drying temperature is 100-110 °C, and the mesh number of the sieve is 80 mesh.

6. The preparation method according to claim 1, wherein In step S4, after granulating and forming, degumming and sintering are carried out in a reducing atmosphere. The degumming temperature is 400 °C, the holding time during degumming is 30 min, the heating rate from room temperature to the degumming temperature is 1.5-3 °C / min. After degumming is completed, heat up to 1150 °C at a rate of 2-4 °C / min and hold for 30 min, then heat up to the sintering temperature at a rate of 10 °C / min. The sintering temperature is 1250-1350 °C, and the sintering holding time is 30-360 min.

7. The preparation method according to claim 1, characterized in that, 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 min, and the heating rate is 4-6 °C / min.

8. Modified barium titanate ceramic particles with a low Curie temperature point and low room temperature resistivity prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the modified barium titanate ceramic particles with a low Curie temperature point and low room-temperature resistivity according to claim 8 in the discharging process of waste lithium battery recycling, characterized in that, It discharges by putting the waste lithium battery into a tank filled with modified barium titanate ceramic particles with a low Curie temperature point and low room temperature resistivity to form a conductive path.

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