A carbon fluoride material coated with a mixed conductor, a preparation method thereof, and a lithium battery

Abstract

A carbon fluoride material coated with a mixed conductor, its preparation method and a lithium battery. Innovatively, the ionic conductivity of carbon fluoride is improved. A nano-level ionic conductor slurry is used to coat carbon fluoride, and after drying, it can be evenly distributed on the surface of the carbon fluoride material to form a uniform coating. And by heating the dried carbon fluoride material at a high temperature, the carbon fluoride material decomposes at high temperature, and a part of carbon is generated inside the cracks of the carbon fluoride material and on the surface of the carbon fluoride material to form an in-situ carbon coating. The process is simpler, the coating uniformity is better, and the electronic conductivity and ionic conductivity of the material are improved synchronously. And using the carbon fluoride material coated with a mixed conductor prepared by the method of the present invention as the positive electrode material of a primary lithium battery, compared with the traditional carbon fluoride positive electrode material coated with a single electronic conductor, the reaction kinetic performance of the primary lithium battery material is good, and the voltage platform and energy density are significantly improved.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, in particular to the field of preparation of carbon fluoride materials, and specifically to a carbon fluoride material coated with a mixed conductor, a preparation method thereof, and a lithium battery. Background Art

[0002] Carbon fluoride (CF x ) materials have advantages such as high energy density, low self-discharge rate, long storage life, excellent high and low temperature performance, stable working voltage, environmental protection, and high safety. As a primary lithium battery cathode material, it is widely used in fields such as aerospace, military, medical, and daily life.

[0003] CF x (x = 1) material has a theoretical open-circuit voltage of 4.57V and a theoretical energy density of 2180 Wh / Kg. However, the actual electrochemical performance of Li / CF x batteries is usually lower than the theoretical value. For example, the actual discharge voltage is only about 2.5V, and the discharge energy density is only about 2000 Wh / Kg. The main reason for the huge difference between theory and reality is that CF x materials have poor electronic conductivity and ionic conductivity. As the fluorination degree of the material increases, the polarization of the battery is serious, the utilization rate of the active material is low, and it can only work at a very low current density.

[0004] In the existing public technologies for coating carbon fluoride materials, single compounds such as carbon materials and metal oxide materials such as Al2O3, SiO2, Cr2O3, V2O5, etc. are used, and composite compounds such as V2O5 / C, VO / C, Ag2CrO4 / Ag, etc. are also used. The existing public technologies mainly improve the electrical performance of carbon fluoride materials by improving their electronic conductivity. The existing technologies do not improve the ionic conductivity of carbon fluoride materials. Moreover, the coating methods used in the existing technologies only mix the coating material and the carbon fluoride material, and the coating cannot be evenly distributed on the surface of the carbon fluoride, resulting in poor coating effect. In addition, the unmodified carbon fluoride raw material, as a primary battery cathode material, has low energy density and voltage.

[0005] Therefore, the technical personnel in this field are committed to developing a carbon fluoride material coated with a mixed conductor, a preparation method thereof, and a lithium battery to solve the above deficiencies of the existing technologies. Summary of the Invention

[0006] In view of the above-mentioned defects of the existing technologies, the technical problem to be solved by the present invention is that in the current existing technologies, only the electronic conductivity is used to improve the electrical performance of carbon fluoride materials, and the coating cannot be evenly distributed on the surface of the carbon fluoride, resulting in poor coating effect; the unmodified carbon fluoride, as a battery cathode material, has low energy density and voltage.

[0007] To achieve the above object, a first aspect of the present invention discloses a method for preparing a carbon fluoride material coated with a mixed conductor,

[0008] The method for preparing the carbon fluoride material coated with a mixed conductor specifically includes the following steps:

[0009] Step 1: Add an ionic conductor slurry to a mixed solvent, stir and disperse evenly, and then add a carbon fluoride powder material to obtain a mixed solution;

[0010] Step 2: Dry the mixed solution obtained in Step 1 to obtain a powder material of carbon fluoride coated with an ionic conductor;

[0011] Step 3: Heat-treat the powder material obtained in Step 2 at a high temperature for a period of time to obtain a carbon fluoride material coated with a mixed ionic conductor;

[0012] The carbon fluoride material is a hydrophobic material and water cannot be used as a single solvent. Therefore, a small amount of alcohol solvent needs to be added to reduce the surface tension of the solvent so that the carbon fluoride material can be well dispersed in the solution;

[0013] The mixed solvent in Step 1 is a mixture of at least two of water, ethanol, isopropanol, and n-butanol;

[0014] The ionic conductor slurry in Step 1 is one or two of a phosphate solid electrolyte and an oxide solid electrolyte;

[0015] The particle size of the ionic conductor is less than 200 nanometers, and the addition amount of the ionic conductor is 0.2% - 1% of the mass of the carbon fluoride material;

[0016] The carbon fluoride powder material added in Step 1 is a micron-sized particle;

[0017] The ionic conductor slurry added in Step 1 is a nano-sized powder material. If the particle size of the ionic conductor is too large, fewer particles will be coated on the surface of the micron-sized carbon fluoride material, making it difficult to form a continuous coating and affecting the improvement of ionic conductivity;

[0018] The temperature of the high-temperature treatment in Step 3 is 300 - 580 °C, and the duration of the high-temperature treatment in Step 3 is 0.5 - 6 hours;

[0019] Furthermore, the addition amount of the ionic conductor slurry in Step 1 cannot be too much or too little. If the addition amount of the ionic conductor slurry is too little, a suitable coating layer cannot be formed, affecting the improvement of ionic conductivity; if the addition amount of the ionic conductor slurry is too much, since the lithium intercalation specific capacity of the ionic conductor itself is low, the energy density of the carbon fluoride composite material will be reduced;

[0020] Furthermore, since the nano-sized powder material added in Step 1 is prone to agglomeration due to its own material properties, it is necessary to perform sufficient stirring and dispersion. Only after ensuring the uniform distribution of each substance in the mixed solution can the next step be carried out;

[0021] Furthermore, the ion conductor added in Step 1 is preferably nano-sized lithium titanium aluminum phosphate;

[0022] Furthermore, the high-temperature treatment in Step 3 can form in-situ carbon coating on the surface of the carbon fluoride material by high-temperature heating and decomposition of the carbon fluoride material, with better uniformity. At the same time, the decomposed carbon can be generated in the internal cracks of the carbon fluoride material, which can expand the ion transport channels and enhance the thermal stability and chemical stability;

[0023] The second aspect of the present invention discloses a carbon fluoride material coated with a mixed conductor, which is prepared by the above preparation method. The surface of the carbon fluoride material is coated with an ion conductor and a carbon material at the same time;

[0024] The ion conductor includes one or two of phosphate solid electrolytes and oxide solid electrolytes;

[0025] The particle size of the ion conductor is less than 200 nanometers, and the addition amount of the ion conductor is 0.2% - 1% of the mass of the carbon fluoride material;

[0026] Furthermore, the ion conductor is preferably nano-sized lithium titanium aluminum phosphate;

[0027] The third aspect of the present invention discloses a lithium battery, including the carbon fluoride material coated with a mixed conductor prepared by the above preparation method. The lithium primary battery made by using the carbon fluoride material coated with a mixed conductor of the present invention as the positive electrode material has a significantly improved discharge voltage platform and energy density compared with the traditional carbon fluoride positive electrode material;

[0028] In the specific embodiment of the present invention, in Step 1, the added mixed solvent is a mixed solvent of water and ethanol, and the mass ratio of water to ethanol is 8:2;

[0029] In the specific embodiment of the present invention, in Step 1, the added ion conductor slurry is a nano-sized lithium titanium aluminum phosphate solid electrolyte aqueous slurry;

[0030] In the specific embodiment of the present invention, in Step 1, the addition amount of the added ion conductor is 1% of the mass of the carbon fluoride material;

[0031] In another specific embodiment of the present invention, in Step 1, the addition amount of the added ion conductor is 0.5% of the mass of the carbon fluoride material;

[0032] In another specific embodiment of the present invention, in step 1, the addition amount of the added ionic conductor is 0.2% of the mass of the carbon fluoride material;

[0033] In a specific embodiment of the present invention, in step 1, the particle size D of the added nano-lithium titanium aluminum phosphate 50 is 60 nanometers;

[0034] In another specific embodiment of the present invention, in step 1, the particle size D of the added nano-lithium titanium aluminum phosphate 50 is 100 nanometers;

[0035] In a specific embodiment of the present invention, in step 3, the period of high-temperature treatment is 0.5 h at 450 °C;

[0036] In another specific embodiment of the present invention, in step 3, the period of high-temperature treatment is 3 h at 350 °C;

[0037] In another specific embodiment of the present invention, in step 3, the period of high-temperature treatment is 6 h at 300 °C;

[0038] In another specific embodiment of the present invention, in step 3, the period of high-temperature treatment is 0.5 h at 580 °C;

[0039] In another specific embodiment of the present invention, in step 3, the period of high-temperature treatment is 1 h at 450 °C.

[0040] Adopting the above scheme, a carbon fluoride material wrapped with a mixed conductor, its preparation method and a lithium battery disclosed by the present invention have the following advantages:

[0041] (1) For the carbon fluoride material wrapped with a mixed conductor and its preparation method of the present invention, the ionic conductivity performance of carbon fluoride is innovatively improved. A nano-scale ionic conductor slurry is used to coat the carbon fluoride, and after drying, it can be evenly distributed on the surface of the carbon fluoride material to form a uniform coating; and by heating the carbon fluoride material at a high temperature, the carbon fluoride material decomposes at a high temperature, and a part of carbon is generated inside the cracks of the carbon fluoride material and on the surface of the carbon fluoride material to form in-situ carbon coating; the process is simpler, the coating uniformity is better, and the electronic conductivity and ionic conductivity of the material are improved simultaneously;

[0042] (2) Using the carbon fluoride material wrapped with a mixed conductor prepared by the method of the present invention as the positive electrode material of a primary lithium battery, compared with the traditional carbon fluoride positive electrode material wrapped with a single electronic conductor, the reaction kinetic performance of the primary lithium battery material is good, and the voltage platform and energy density are significantly improved.

[0043] In summary, a carbon fluoride material wrapped with a mixed conductor, its preparation method and a lithium battery disclosed by the present invention use an ion conductor slurry to coat the carbon fluoride, so that the electronic conductivity and ionic conductivity of the material are improved synchronously, the process is simpler, and the coating uniformity is better. When used as the cathode material of a primary lithium battery, the lithium battery has good reaction kinetics performance, and the voltage platform and energy density are significantly improved.

[0044] The following will further illustrate the concept, specific technical solutions and technical effects of the present invention in conjunction with specific embodiments to fully understand the purpose, features and effects of the present invention. Brief Description of the Drawings

[0045] Figure 1 is the scanning electron microscope image of the carbon fluoride raw material;

[0046] Figure 2 is the scanning electron microscope image of the carbon fluoride material coated with a mixed conductor obtained in Example 1;

[0047] Figure 3 is the constant current discharge curve of the carbon fluoride-lithium primary battery made of the carbon fluoride material obtained in Example 1 at a current density of 20 mA / g;

[0048] Figure 4 is the constant current discharge curve of the carbon fluoride-lithium primary battery made of the carbon fluoride raw material in Comparative Example 1 at a current density of 20 mA / g;

[0049] Figure 5 is the constant current discharge curve of the carbon fluoride-lithium primary battery made of the carbon fluoride material obtained in Comparative Example 2 at a current density of 20 mA / g;

[0050] Figure 6 is the constant current discharge curve of the carbon fluoride-lithium primary battery made of the carbon fluoride material obtained in Comparative Example 3 at a current density of 20 mA / g. Specific Embodiments

[0051] The following introduces multiple preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and these embodiments are described exemplarily. The protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0052] Abbreviation Explanation: LATP: Lithium aluminum titanium phosphate;

[0053] Example 1, Carbon Fluoride Material Wrapped with a Mixed Conductor, Its Preparation Method and Lithium Battery

[0054] Step 1: Prepare 50 g of a mixed solvent in a beaker, where the mass fraction ratio of ethanol to water is 2:8. Stir the mixed solvent thoroughly with a glass rod. Subsequently, add 1 g of an aqueous slurry of nano-lithium titanium aluminum phosphate (LATP) with a solid content of 5%, where the particle size D of lithium titanium aluminum phosphate 50 is 60 nm. Stir and disperse with a magnetic stirrer for 30 minutes, and then perform ultrasonic treatment for 10 minutes. Then add 10 g of carbon fluoride powder material, continue to stir and disperse for 3 hours, and perform ultrasonic treatment for 20 minutes to obtain a uniformly dispersed mixed solution;

[0055] Step 2: Pass the mixed solution through a spray dryer to obtain the dried carbon fluoride material powder coated with LATP;

[0056] Step 3: Subsequently, put the carbon fluoride material powder obtained by spray drying into a magnetic boat, and then put the magnetic boat into a muffle furnace. The high-temperature treatment of the muffle furnace is specifically set as follows: the temperature is 450 °C, and the constant-temperature treatment is 1 h. After the constant-temperature treatment time reaches 1 h, take out the magnetic boat in the muffle furnace and let it cool naturally to obtain the carbon fluoride material coated with a mixed ion conductor, denoted as 0.5%-LATP / C@CF x ;

[0057] Subsequently, use the 0.5%-LATP / C@CF x product prepared in Example 1 as the positive electrode material to make a lithium-carbon fluoride primary battery; in its positive electrode, the active material is LATP / C@CF x , and the ratio of the conductive carbon to the binder is specifically 90:5:5. The electrolyte of this lithium-carbon fluoride primary battery uses 1M LiPF6 / EC+EMC (3:7), and the positive electrode surface density is 3.8 mg / cm 2 ; Subsequently, use a battery test system to perform a constant-current discharge test on this lithium-carbon fluoride primary battery;

[0058] Discharge this battery to 1.5 V at a current density of 20 mA / g, and observe its voltage platform and discharge energy density. After testing with a battery test system, using the 0.5%-LATP / C@CF x product prepared in Example 1 as the positive electrode material of the lithium-carbon fluoride primary battery, the discharge energy density of this primary battery is 2129 Wh / Kg, and the average discharge voltage is 2.65 V.

[0059] Example 2: Carbon fluoride material wrapped with a mixed conductor, its preparation method and lithium battery

[0060] Step 1: Prepare 50 g of a mixed solvent in a beaker, where the mass fraction ratio of ethanol to water is 2:8. Stir the mixed solvent thoroughly with a glass rod. Subsequently, add 2 g of an aqueous slurry of nano-lithium titanium aluminum phosphate (LATP) with a solid content of 5%, where the particle size D of lithium titanium aluminum phosphate50 It is 100 nm. After magnetic stirring for dispersion for 30 minutes and ultrasonic treatment for 10 minutes, 10 g of carbon fluoride powder material is added, and stirring for dispersion is continued for 3 hours and ultrasonic treatment is carried out for 20 minutes to obtain a uniformly dispersed mixed solution;

[0061] Step 2: After passing the mixed solution through a spray dryer, a dried carbon fluoride material powder coated with LATP can be obtained;

[0062] Step 3: Subsequently, the carbon fluoride material powder obtained by spray drying is placed in a magnetic boat, and then the magnetic boat is placed in a muffle furnace. The specific high-temperature treatment setting of the muffle furnace is a temperature of 350 °C and an isothermal treatment for 3 h. After the isothermal treatment time reaches 3 h, the magnetic boat in the muffle furnace is taken out and naturally cooled to obtain a carbon fluoride material coated with a mixed ion conductor, denoted as 1%-LATP / C@CF x .

[0063] Subsequently, the 1%-LATP / C@CF x product prepared in Example 2 is used as the positive electrode material of a lithium-carbon fluoride primary battery. Among them, in the positive electrode, the active material is LATP / C@CF x , and the ratio of the conductive carbon to the binder is specifically 90:5:5. The electrolyte of this lithium-carbon fluoride primary battery uses 1 M LiPF6 / EC+EMC (3:7), and the positive electrode surface density is 3.8 mg / cm 2 . Subsequently, a constant current discharge test is carried out on this lithium-carbon fluoride primary battery using a battery test system.

[0064] The battery is discharged to 1.5 V at a current density of 20 mA / g, and its voltage platform and discharge energy density are observed. After being tested by a battery test system, the 1%-LATP / C@CF x product prepared in Example 2 is used as the positive electrode material of a lithium-carbon fluoride primary battery. The discharge energy density of this primary battery is 2085 Wh / Kg, and the average discharge voltage is 2.61 V.

[0065] Example 3, Carbon Fluoride Material Coated with a Mixed Conductor, Its Preparation Method and Lithium Battery

[0066] Step 1: Prepare 50 g of a mixed solvent in a beaker, where the mass fraction ratio of ethanol to water is 2:8. The mixed solvent is fully stirred with a glass rod, and then 1 g of an aqueous slurry of lithium titanium aluminum phosphate (LATP) with a solid content of 5% is added thereto, where the particle size D 50 of lithium titanium aluminum phosphate is 60 nm. After magnetic stirring for dispersion for 30 minutes and ultrasonic treatment for 10 minutes, 10 g of carbon fluoride powder material is added, and stirring for dispersion is continued for 3 hours and ultrasonic treatment is carried out for 20 minutes to obtain a uniformly dispersed mixed solution;

[0067] Step 2: After passing the mixed solution through a spray dryer, the dried carbon fluoride material powder coated with LATP can be obtained;

[0068] Step 3: Subsequently, put the carbon fluoride material powder obtained by spray drying into a magnetic boat, and then put the magnetic boat into a muffle furnace. The high-temperature treatment of the muffle furnace is specifically set as follows: the temperature is 300 °C, and the constant-temperature treatment is 6 h. After the constant-temperature treatment time reaches 6 h, take out the magnetic boat in the muffle furnace and let it cool naturally to obtain the carbon fluoride material coated with a mixed ionic conductor, denoted as 0.5%-LATP / C@CF x ;

[0069] Subsequently, the 0.5%-LATP / C@CF x product prepared in Example 3 is used as the cathode material to make a lithium-carbon fluoride primary battery; in its cathode, the active material is LATP / C@CF x , and the ratio of the conductive carbon to the binder is specifically 90:5:5. The electrolyte of this lithium-carbon fluoride primary battery uses 1M LiPF6 / EC+EMC (3:7), and the cathode surface density is 3.8 mg / cm 2 ; Subsequently, use a battery test system to conduct a constant-current discharge test on this lithium-carbon fluoride primary battery;

[0070] Discharge the battery to 1.5 V at a current density of 20 mA / g, and observe its voltage platform and discharge energy density. After testing with a battery test system, using the 0.5%-LATP / C@CF x product prepared in Example 1 as the cathode material of the lithium-carbon fluoride primary battery, the discharge energy density of this primary battery is 2040 Wh / Kg, and the average discharge voltage is 2.58 V.

[0071] Example 4, Carbon Fluoride Material Coated with a Mixed Conductor, Its Preparation Method and Lithium Battery

[0072] Step 1: Prepare 50 grams of a mixed solvent in a beaker, where the mass fraction ratio of ethanol to water is 2:8. Stir the mixed solvent thoroughly with a glass rod, and then add 1 gram of an aqueous slurry of nano-lithium titanium aluminum phosphate (LATP) with a solid content of 5%. The particle size D 50 of lithium titanium aluminum phosphate is 60 nanometers. Stir and disperse it magnetically for 30 minutes, and after ultrasonic treatment for 10 minutes; add 10 grams of carbon fluoride powder material, continue to stir and disperse for 3 hours, and ultrasonic treatment for 20 minutes to obtain a uniformly dispersed mixed solution;

[0073] Step 2: After passing the mixed solution through a spray dryer, the dried carbon fluoride material powder coated with LATP can be obtained;

[0074] Step 3: Subsequently, the carbon fluoride material powder obtained by spray drying is placed in a magnetic boat, and then the magnetic boat is placed in a muffle furnace. The high-temperature treatment of the muffle furnace is specifically set as follows: the temperature is 580 °C, and the constant-temperature treatment is 0.5 h. After the constant-temperature treatment time reaches 0.5 h, the magnetic boat in the muffle furnace is taken out and naturally cooled to obtain the carbon fluoride material coated with a mixed ionic conductor, denoted as 0.5%-LATP / C@CF x ;

[0075] Subsequently, the 0.5%-LATP / C@CF x product prepared in Example 4 is used as the positive electrode material to fabricate a lithium-carbon fluoride primary battery; in its positive electrode, the active material LATP / C@CF x , the ratio of the conductive carbon to the binder is specifically 90:5:5. The electrolyte of this lithium-carbon fluoride primary battery uses 1M LiPF6 / EC+EMC (3:7), and the positive electrode surface density is 3.8 mg / cm 2 ; Subsequently, a constant-current discharge test is performed on this lithium-carbon fluoride primary battery using a battery test system;

[0076] The battery is discharged to 1.5 V at a current density of 20 mA / g, and its voltage platform and discharge energy density are observed. After testing with a battery test system, using the 0.5%-LATP / C@CF x product prepared in Example 4 as the positive electrode material of the lithium-carbon fluoride primary battery, the discharge energy density of this primary battery is 1930 Wh / Kg, and the average discharge voltage is 2.73 V.

[0077] Example 5, Carbon Fluoride Material Coated with a Mixed Conductor, Its Preparation Method and Lithium Battery

[0078] Step 1: Prepare 50 grams of a mixed solvent in a beaker, where the mass fraction ratio of ethanol to water is 2:8. Stir the mixed solvent thoroughly with a glass rod, and then add 0.4 grams of an aqueous slurry of nano-lithium titanium aluminum phosphate (LATP) with a solid content of 5%. The particle size D 50 of lithium titanium aluminum phosphate is 60 nanometers. Stir and disperse it magnetically for 30 minutes, and after ultrasonic treatment for 10 minutes; add 10 grams of carbon fluoride powder material, continue to stir and disperse for 3 hours, and perform ultrasonic treatment for 20 minutes to obtain a uniformly dispersed mixed solution;

[0079] Step 2: After passing the mixed solution through a spray dryer, the dried carbon fluoride material powder coated with LATP can be obtained;

[0080] Step 3: Subsequently, put the carbon fluoride material powder obtained by spray drying into a magnetic boat, and then put the magnetic boat into a muffle furnace. The high-temperature treatment of the muffle furnace is specifically set as follows: the temperature is 450 °C, and the constant-temperature treatment is 1 h. After the constant-temperature treatment time reaches 1 h, take out the magnetic boat in the muffle furnace and let it cool naturally to obtain the carbon fluoride material coated with a mixed ionic conductor, denoted as 0.5%-LATP / C@CF x ;

[0081] Subsequently, use the 0.2%-LATP / C@CF x product prepared in Example 5 as the positive electrode material to make a lithium-carbon fluoride primary battery; in its positive electrode, the ratio of the active material LATP / C@CF x , conductive carbon to binder is specifically 90:5:5. The electrolyte of this lithium-carbon fluoride primary battery uses 1M LiPF6 / EC+EMC (3:7), and the positive electrode surface density is 3.8 mg / cm 2 ; Subsequently, use a battery test system to conduct a constant current discharge test on this lithium-carbon fluoride primary battery;

[0082] Discharge this battery to 1.5 V at a current density of 20 mA / g, and observe its voltage platform and discharge energy density. After testing with a battery test system, use the 0.2%-LATP / C@CF x product prepared in Example 5 as the positive electrode material of the lithium-carbon fluoride primary battery. The discharge energy density of this primary battery is 2090 Wh / Kg, and the average discharge voltage is 2.63 V.

[0083] Comparative Example 1: Performance test of a lithium-carbon fluoride primary battery made of a carbon fluoride material as the positive electrode material

[0084] Use the carbon fluoride raw material as the positive electrode material to make a lithium-carbon fluoride primary battery; in its positive electrode, the active material is CFx, and the ratio of conductive carbon to binder is specifically 90:5:5. The electrolyte of this lithium-carbon fluoride primary battery uses 1M LiPF6 / EC+EMC (3:7), and the positive electrode surface density is 3.8 mg / cm 2 ; Subsequently, use a battery test system to conduct a constant current discharge test on this lithium-carbon fluoride primary battery;

[0085] Discharge this battery to 1.5 V at a current density of 20 mA / g, and observe its voltage platform and discharge energy density. After testing with a battery test system, use the CF x prepared in this Comparative Example 1 as the positive electrode material of the lithium-carbon fluoride primary battery. The discharge energy density of this primary battery is 2008 Wh / Kg, and the average discharge voltage is 2.53 V.

[0086] Comparative Example 2

[0087] Step 1: prepare 50 g of a mixed solvent in a beaker, wherein the mass fraction ratio of ethanol to water is 2:8, stir the mixed solvent with a glass rod, and then add 1 g of nano lithium aluminum titanium phosphate (LATP) aqueous slurry with a solid content of 5% to the mixed solvent, wherein the particle size of the lithium aluminum titanium phosphate is D 50 The particle size was 60 nanometers, and the mixture was dispersed by magnetic stirring for 30 minutes and ultrasonically treated for 10 minutes; 10 grams of carbon fluoride powder material was added, and the mixture was stirred and dispersed for 3 hours and ultrasonically treated for 20 minutes to obtain a uniformly dispersed mixed solution;

[0088] Step 2: After the mixed solution passes through a spray dryer, the LATP-coated dry carbon fluoride material powder can be obtained, which is recorded as 0.5%-LATP / C@CF x ;

[0089] Then, the 0.5%-LATP / C@CF prepared in Comparative Example 2 was x The product is used as the positive electrode material to make lithium-carbon fluoride primary batteries; in the positive electrode, the active material LATP / C@CF x The ratio of conductive carbon to binder is 90:5:5. The electrolyte of the lithium-carbon fluoride primary battery adopts 1M LiPF6 / EC+EMC (3:7), and the positive electrode surface density is 3.8mg / cm 2 ; Then the lithium-carbon fluoride primary battery is subjected to a constant current discharge test using a battery testing system;

[0090] The battery was discharged at a current density of 20 mA / g to 1.5 V, and its voltage platform and discharge energy density were observed. After testing by a battery testing system, the 0.5%-LATP / C@CF prepared in Comparative Example 2 was x The product is used as the positive electrode material for lithium-carbon fluoride primary batteries. The discharge energy density of the primary battery is 2036Wh / Kg and the average discharge voltage is 2.58V.

[0091] Comparative Example 3

[0092] The carbon fluoride raw material powder is placed in a magnetic boat, and then the magnetic boat is placed in a muffle furnace. The high temperature treatment setting of the muffle furnace is specifically set as follows: the temperature is 450°C, and the constant temperature treatment is 1 hour. After the constant temperature treatment time reaches 1 hour, the magnetic boat in the muffle furnace is taken out and cooled naturally to obtain a mixed ion conductor coated carbon fluoride material, which is recorded as 0.5%-LATP / C@CF x ;

[0093] Then, the 0.5%-LATP / C@CF prepared in Comparative Example 3 was x The product is used as the positive electrode material to make lithium-carbon fluoride primary batteries; in the positive electrode, the active material LATP / C@CF x, the ratio of conductive carbon to binder is specifically 90:5:5. The electrolyte of this primary lithium-carbon monofluoride battery uses 1M LiPF6 / EC+EMC (3:7), and the positive electrode surface density is 3.8mg / cm 2 ; Subsequently, a constant current discharge test was carried out on this primary lithium-carbon monofluoride battery using a battery test system;

[0094] Discharge the battery to 1.5V at a current density of 20mA / g, and observe its voltage platform and discharge energy density. After testing with the battery test system, the 0.5%-LATP / C@CF prepared using this Comparative Example 3 x product is used as the positive electrode material of the primary lithium-carbon monofluoride battery. The discharge energy density of this primary battery is 2084Wh / Kg, and the average discharge voltage is 2.60V.

[0095] Result analysis:

[0096] Taking the performance test of the primary lithium-carbon monofluoride battery made by directly using carbon monofluoride raw materials as the positive electrode material in Comparative Example 1 as a benchmark;

[0097] Through the comprehensive comparative analysis of Example 1 and Comparative Example 1, it can be found that the mixed

[0098] carbon-coated carbon monofluoride material using the method of the present invention, through separate LATP coating and high-temperature heat treatment, synchronously improves the electronic conductivity and ionic conductivity of the material; the final discharge test results also show that compared with the reference value, the carbon-coated carbon monofluoride material prepared by the method of the present invention has an increase in discharge energy density of 6.03%; and an increase in average discharge voltage of 4.74%.

[0099] By comparing the scanning electron microscopes of the carbon monofluoride obtained in Example 1 and Comparative Example 1, among which Figure 1 is the scanning electron microscope image of the carbon monofluoride raw material, Figure 2 is the carbon-coated carbon monofluoride material with mixed conductors prepared in Example 1. Through the comparative analysis of the two pictures, it can be seen that there is no obvious difference before and after the carbon monofluoride material is coated. The coated material still maintains the raw material-like spherical structure, and no agglomeration of the LATP material is seen after coating, indicating that the nanoscale LATP is evenly distributed on the surface of the carbon monofluoride material; it can also be seen from the scanning electron microscope that the electronic conductivity of the carbon monofluoride raw material is poor and there is an obvious color difference, while the sample in Example 1 has a uniform color, indicating that the electronic conductivity of the sample is good, which also shows that Example 1 realizes good carbon coating on the material surface.

[0100] By comprehensively analyzing the discharge energy density and average discharge voltage data of Examples 1-3, compared with Example 1, although the heat preservation duration in Example 2 is 3 h, the high-temperature treatment temperature is 350 °C. At a relatively low temperature, less carbon is generated by the thermal decomposition of carbon fluoride, so the improvement of the electronic conductivity of the material is not significant. As a result, the increase in the discharge energy density of Example 2 compared to the reference value is only 3.83%; the average discharge voltage increases by 3.16%. The heat preservation duration of Example 3 is as long as 6 h, but the high-temperature treatment temperature is only 300 °C. When the high-temperature treatment temperature is low, carbon fluoride cannot undergo thermal decomposition to generate carbon, so the electronic conductivity of the material cannot be improved. The increase in the discharge energy density compared to the reference value is only 1.59%; the average discharge voltage increases by 1.98%.

[0101] By comprehensively analyzing the discharge data of Examples 1 and 4, it can be seen that the high-temperature treatment temperature of Example 4 is relatively high, reaching 580 °C, and the duration is 0.5 h. The excessively high heat treatment temperature causes a large amount of decomposition of carbon fluoride, resulting in a too high content of carbon material in the product and a significant decrease in the content of active carbon fluoride material. Therefore, although the average battery voltage of Example 4 is 7.91% higher than the reference, which is the highest average voltage among all examples, the discharge energy density of Example 4 decreases by 3.89% relative to the reference value; the energy density is even lower than the reference value.

[0102] By comprehensively analyzing the discharge data of Examples 1 and 6, the only difference between Examples 1 and 6 is the addition amount of the ion conductor slurry, and the other conditions are the same. Through comprehensive analysis, it is concluded that the ion conductor slurry in Example 6 is less, resulting in too low a coating amount and unable to form a suitable coating layer, which affects the ionic conductivity of the material. Although the ion conductor slurry is less, its increase in the discharge energy density compared to the reference value also reaches 4.08%; the increase in the average discharge voltage reaches 3.95%.

[0103] By comprehensively analyzing the discharge data of Example 1 and Comparative Example 2, it can be seen that in the preparation process of the carbon fluoride material coated with the mixed conductor in Comparative Example 2, Step 3 was not performed, that is, the dried LATP-coated carbon fluoride material powder was not heat-treated, resulting in no high-temperature decomposition of the carbon fluoride material and the formation of a part of carbon on the surface of the carbon fluoride to form in-situ carbon coating, so the electronic conductivity of the raw material was not improved. Therefore, the discharge energy density of Comparative Example 2 is only 1.39% higher than the reference value, and the average discharge voltage is only 1.92% higher than the reference value. Among many examples, the improvement amplitude of the battery performance of Comparative Example 2 is the smallest. From this, it can be seen that the high-temperature treatment in Step 3 of this invention method has a great impact on improving the conductivity of the carbon fluoride material coated with the mixed conductor.

[0104] Through comprehensive analysis of the discharge data of Comparative Example 1 and Comparative Example 3, it can be seen that only step 3 in the preparation process is performed on the carbon fluoride raw material, that is, only the carbon fluoride raw material is subjected to high-temperature treatment. It can be seen that after the carbon fluoride raw material is subjected to high-temperature treatment, a part of carbon is generated inside the cracks of the carbon fluoride material and on the surface of the carbon fluoride material, forming in-situ carbon coating; the electronic conductivity of the material is improved, so that the discharge test result of Comparative Example 3 has also reached 3.78% compared with the discharge energy density of the reference value; the increase in the average discharge voltage has reached 2.77%.

[0105] Generally speaking, through comprehensive analysis of the results of 5 examples and 3 comparative examples, it can be concluded that the heat treatment temperature has an obvious effect on the energy density of the material. An appropriate treatment temperature can significantly improve the energy density and average voltage of the material. If the temperature is too low, even if the treatment time is extended, good results cannot be achieved.

[0106] To sum up, the technical solution of this patent innovatively improves the ionic conductivity of carbon fluoride. A nano-level ionic conductor slurry is used to coat carbon fluoride, and after drying, it can be evenly distributed on the surface of the carbon fluoride material to form a uniform coating; and by heating the dried carbon fluoride material at high temperature, the carbon fluoride material decomposes at high temperature, and a part of carbon is generated inside the cracks of the carbon fluoride material and on the surface of the carbon fluoride material, forming in-situ carbon coating; the process is simpler, the coating uniformity is better, and the electronic conductivity and ionic conductivity of the material are improved simultaneously; and using the carbon fluoride material coated with a mixed conductor prepared by the method of the present invention as the positive electrode material of a primary lithium battery, compared with the traditional carbon fluoride positive electrode material coated with a single electronic conductor, the reaction kinetics performance of the primary lithium battery material is good, and the voltage platform and energy density are significantly improved.

[0107] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A carbon fluoride material coated with a mixed conductor, characterized in that, The preparation method of the mixed-conductor-coated carbon fluoride material comprises the following steps: Step 1: Add an ionic conductor slurry into a mixed solvent, and after stirring and dispersing evenly, add a carbon fluoride powder material to obtain a mixed solution; Step 2: Dry the mixed solution obtained in Step 1 to obtain a powder material of the ionic-conductor-coated carbon fluoride; Step 3: Heat-treat the powder material obtained in Step 2 at a high temperature for a period of time to obtain a mixed-ion-conductor-coated carbon fluoride material; Among them, the surface of the mixed-conductor-coated carbon fluoride material is coated with an ionic conductor and a carbon material simultaneously.

2. The mixed-conductor-coated carbon fluoride material according to claim 1, wherein the ionic conductor slurry in Step 1 is one or two of a phosphate solid electrolyte and an oxide solid electrolyte.

3. The mixed-conductor-coated carbon fluoride material according to claim 1, wherein the temperature of the high-temperature treatment in Step 3 is 300-580 °C.

4. The mixed-conductor-coated carbon fluoride material according to claim 1, wherein the time of the high-temperature treatment in Step 3 is 0.5-6 hours.

5. The mixed-conductor-coated carbon fluoride material according to claim 1, wherein the ionic conductor slurry is a nano-scale lithium titanium aluminum phosphate solid electrolyte aqueous slurry, and the particle size of the solid electrolyte is less than 200 nanometers.

6. The mixed-conductor-coated carbon fluoride material according to claim 1, wherein the mixed solvent is a mixture of two of water, ethanol, isopropanol, and n-butanol.

7. A lithium battery, wherein it comprises the mixed-conductor-coated carbon fluoride material according to any one of claims 1-4.

Images