Octahedral material, secondary battery, and electronic device

Abstract

The invention discloses an octahedral material, a secondary battery and an electronic device, the octahedral material comprises a plurality of octahedral structures, the octahedral structures have mesopores, the pore volume of the mesopores is 1.3 cm < 3 > / g to 2.0 cm < 3 > / g, and the pore diameter of the mesopores is 8 nm to 12 nm. Through the octahedral and mesoporous structure, the octahedral material can quickly transmit lithium ions, improve dynamics and greatly improve the low-temperature performance of the lithium ion battery; the pore volume in the octahedral material can absorb and store the electrolyte, improve the electrolyte retention capacity, reduce the loss of the electrolyte and ensure the uniform distribution of the electrolyte in the battery, so that the electrochemical performance and the stability of the battery are improved, the performance of the battery is improved, and the service life of the battery is prolonged.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, and particularly to an octahedral material, a secondary battery, and an electronic device. Background Art

[0002] Secondary batteries (such as lithium-ion batteries) are widely used in electronic mobile devices, power tools, electric vehicles and other electronic products. People have higher and higher requirements for the electrical performance of lithium-ion batteries in low-temperature and high-temperature environments.

[0003] However, under low-temperature conditions, the viscosity of the electrolyte increases or even partially solidifies, resulting in a decrease in the conductivity of the lithium-ion battery. At the same time, the compatibility between the electrolyte and the negative active material and the separator becomes poor, resulting in a significant increase in the charge transfer impedance. Therefore, the performance of lithium-ion batteries at low temperatures drops significantly, specifically manifested as low discharge capacity, increased internal resistance, unbalanced lithium deintercalation and intercalation, and obvious lithium deposition. On the other hand, at high temperatures, the electrochemical reaction rate of lithium-ion batteries accelerates, the electrolyte consumption intensifies, and the cycle life drops rapidly. Therefore, how to improve the low-temperature and high-temperature performance of lithium-ion batteries has become an urgent problem to be solved.

[0004] At present, the common method to improve the low-temperature performance of lithium-ion batteries is to regulate the composition of the electrolyte. By changing the components and physical and chemical properties of the electrolyte, using a fluorinated electrolyte to increase its ionic conductivity at low temperatures, accelerate the charge transfer process, and slow down the formation of lithium dendrites; or using electrode materials with higher activity and stability to reduce the impact of low temperature on battery performance.

[0005] However, in practical applications, on the one hand, using fluorinated carbonates with a lower freezing point to improve low temperature is too costly and also causes serious environmental safety problems; higher-activity electrode materials require ingenious design of the unit cell and structural composition of the material itself, with a long R & D cycle and still in the scientific research stage, and there is still a long way to go before mass production and commercialization. Therefore, a material that can improve the low-temperature performance of the battery is needed. Summary of the Invention

[0006] In view of this, this application provides an octahedral material, a secondary battery, and an electronic device.

[0007] In the first aspect of this application, an octahedral material is provided. The octahedral material includes a plurality of octahedral structures, and the octahedral structure has uniform mesopores, and the pore volume of the mesopores is 1.3 cm 3 / g to 2.0 cm 3 / g; The pore diameter of the mesopores is 8 nm to 12 nm. The octahedral structure itself has a high space utilization rate and good electrical conductivity, which helps the rapid diffusion of lithium ions; the octahedral material in this application has an octahedral structure, as well as uniform mesopores and a rich pore structure, which can provide abundant active sites, promote the insertion and extraction of lithium ions, can rapidly transport lithium ions, improve the kinetic performance, and thus improve the charge and discharge efficiency of the battery. When the pore diameter of the mesopores in the octahedral structure is 8 nm to 12 nm, the mesopores help to form an effective ion transport path, reduce the ion diffusion resistance, and greatly improve the low-temperature performance of the lithium-ion battery; when the pore volume of the mesopores in the octahedral structure is in the range of 1.3 cm 3 / g to 2.0 cm 3 / g, the mesopores can absorb and store more electrolytes, which can achieve the effects of increasing the liquid retention amount, reducing the loss of electrolytes, and ensuring the uniform distribution of electrolytes inside the battery, thereby improving the electrochemical performance and stability of the battery and enhancing the performance and lifespan of the battery.

[0008] Based on the first aspect, in some possible implementation manners, the pore diameter of the mesopores of the octahedral material is 10 nm to 11 nm; the diffusion rate of the electrolyte in the pore channels within this range is relatively fast, avoiding the retention of the electrolyte in the pore channels, and the contact area between the electrolyte and the electrode material is appropriate, thereby improving the charge and discharge efficiency of the battery under low-temperature conditions.

[0009] Based on the first aspect, in some possible implementation manners, the tap density of the octahedral material is 2.0 g / m 3 to 2.5 g / m 3 . When the tap density is within the range of this application, the overall capacity of the negative electrode sheet is relatively good, and the mesoporous structure on the surface of the octahedral material will not be collapsed or damaged, and the octahedral and complete mesoporous structure can be retained, enabling the secondary battery to have good low-temperature performance.

[0010] Based on the first aspect, in some possible implementation manners, the octahedral material contains boron element and sulfur element. Doping with boron element and sulfur element enables the octahedral material to have high ionic conductivity; when the ionic conductivity is high, the low-temperature performance of the battery is good.

[0011] Based on the first aspect, in some possible implementation manners, the octahedral material contains boron element. Based on the total mass of the octahedral material, the mass ratio of the boron element is 2% to 10%; when the mass ratio of the boron element is in the range of 2% to 10%, the octahedral material has high ionic conductivity; when the ionic conductivity is high, the low-temperature performance of the secondary battery is good.

[0012] Based on the first aspect, in some possible embodiments, the octahedral material contains sulfur element. Based on the total mass of the octahedral material, the mass percentage of the sulfur element is 10% to 20%. When the mass percentage of the sulfur element is in the range of 10% to 20%, the octahedral material has high ionic conductivity; when the ionic conductivity is high, the low-temperature performance of the secondary battery is good.

[0013] Based on the first aspect, in some possible embodiments, the mass percentage of boron element in the octahedral material is 2% to 10%; the mass percentage of sulfur element is 10% to 20%; when the contents of boron element and sulfur element in the octahedral material are within the above ranges, the octahedral material has high ionic conductivity, and when the ionic conductivity is high, the low-temperature performance of the secondary battery is good.

[0014] Based on the first aspect, in some possible embodiments, the ionic conductivity of the octahedral material is 9 mS / cm to 18 mS / cm. Under low-temperature conditions, the viscosity of the electrolyte increases, and the migration speed of ions slows down, resulting in an increase in the internal resistance of the battery, thereby affecting the discharge performance of the battery. High ionic conductivity helps to increase the diffusion rate of lithium ions in the material, reduce the formation of dendrites on the surface of the negative electrode, thereby reducing the risk of battery failure, effectively reducing the polarization phenomenon at low temperatures, and improving the low-temperature performance of the battery. Therefore, the octahedral material of the present application with an ionic conductivity in the range of 9 mS / cm to 18 mS / cm has good low-temperature performance.

[0015] Based on the first aspect, in some possible embodiments, the specific surface area of the octahedral material is 0.5 m 2 / g to 5 m 2 / g; when the specific surface area S of the octahedral material is in the range of 0.5 m 2 / g to 5 m 2 / g, a sufficient mesoporous structure can be formed on the surface of the octahedral material, while avoiding the influence of excessive defects on the first efficiency of the secondary battery, thereby ensuring that the first efficiency performance of the secondary battery is not affected.

[0016] Based on the first aspect, in some possible embodiments, in the Raman spectrum obtained by Raman testing, the peak intensity ratio of the D peak to the G peak of the octahedral material is 0.8 to 1.5; the peak intensity ratio of the D peak to the G peak in the Raman testing is the Raman value. The D peak is the peak in the Raman spectrum of the composite material with a displacement range of 1330 cm-1 to 1360 cm-1, and the G peak is the peak in the Raman spectrum of the composite material with a displacement range of 1580 cm-1 to 1582 cm-1; when the Raman value of the octahedral material is in the range of 0.8 to 1.5, amorphous carbon and other defects can be fully formed on the surface of the octahedral material, while avoiding the influence of excessive defects on the first efficiency of the secondary battery, thereby ensuring that the first efficiency performance of the secondary battery is not affected.

[0017] Based on the first aspect, in some possible embodiments, all eight faces of the octahedral structure of the octahedral material are triangles.

[0018] Based on the first aspect, in some possible embodiments, the eight faces of the octahedral structure of the octahedral material are equilateral triangles.

[0019] Based on the first aspect, in some possible embodiments, the triangles of the eight faces of the octahedral material are congruent triangles, and the ratio of the side length to the height of each triangle is from 0.5 to 5; when the triangles of the eight faces of the octahedral material are congruent triangles and the ratio of the side length to the height of each triangle ranges from 0.5 to 5, the octahedral material has high ionic conductivity, and when the ionic conductivity is high, the low-temperature performance of the battery is good.

[0020] The second aspect of the present application provides a preparation method of an octahedral material, including:

[0021] Dissolve a thiophene derivative, boric acid and a stabilizer in water to obtain a mixed solution;

[0022] Add an initiator to the mixed solution to carry out a synthesis reaction to obtain an intermediate product;

[0023] Under an inert gas, carry out carbonization treatment on the intermediate product to prepare the octahedral material.

[0024] In the above preparation method: the thiophene derivative is used as a reaction monomer, boric acid is used as a catalytic crosslinking agent, the stabilizer is used to control the reaction rate, improve the product stability and improve the surface morphology and properties of the material, and the initiator is used to initiate the reaction polymerization.

[0025] In the above preparation method, by dissolving a thiophene derivative, boric acid and a stabilizer in water, an intermediate product is synthesized and carbonized to obtain an octahedral material. The doping of two hetero elements, boron element and sulfur element, in the octahedral material makes the prepared octahedral material have high ionic conductivity. Further, the secondary battery has good low-temperature performance and also takes into account good high-temperature performance.

[0026] In the above preparation process, when the heating temperature, heating time, carbonization temperature and carbonization time meet a certain range, the ionic conductivity of the prepared octahedral material is higher.

[0027] Based on the second aspect, in some possible embodiments, the temperature of the synthesis reaction is from 10°C to 50°C, and the time of the synthesis reaction is from 1 h to 6 h.

[0028] Based on the second aspect, in some possible embodiments, the carbonization temperature is from 600°C to 1000°C, and the carbonization time is from 2 h to 6 h.

[0029] Based on the second aspect, in some possible embodiments, nitrogen is used for reaction protection throughout the preparation method.

[0030] Based on the second aspect, in some possible embodiments, the stabilizer is at least one of polyvinylpyrrolidone, polyethylene glycol - polypropylene glycol - polyethylene glycol triblock copolymer, and polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer.

[0031] Based on the second aspect, in some possible embodiments, when the stabilizer is polyethylene glycol - polypropylene glycol - polyethylene glycol triblock copolymer, the thiophene derivative does not include 5 - bromo - 2 - thiophenemethanol.

[0032] Based on the second aspect, in some possible embodiments, the stabilizer is polyvinylpyrrolidone and polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer; the thiophene derivative is at least one of 2 - thiophenemethanol, 3 - thiophenemethanol, 5 - chloro - 2 - thiophenemethanol, and 5 - bromo - 2 - thiophenemethanol.

[0033] Based on the second aspect, in some possible embodiments, the stabilizer is at least one of polyvinylpyrrolidone, polyethylene glycol - polypropylene glycol - polyethylene glycol triblock copolymer, and polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer; the thiophene derivative is at least one of 2 - thiophenemethanol, 3 - thiophenemethanol, and 5 - bromo - 2 - thiophenemethanol.

[0034] Based on the second aspect, in some possible embodiments, the thiophene derivative is at least one of 2 - thiophenemethanol, 3 - thiophenemethanol, 5 - chloro - 2 - thiophenemethanol, and 5 - bromo - 2 - thiophenemethanol.

[0035] Based on the second aspect, in some possible embodiments, the initiator is at least one of ammonium persulfate and potassium persulfate.

[0036] The third aspect of the present application provides a secondary battery, including a negative electrode sheet, and the negative electrode sheet includes a negative electrode active material layer. It is characterized in that the negative electrode active material layer includes the octahedral material as described in any one of the first aspect. Based on the total mass of the negative electrode active material layer, the mass ratio of the octahedral material is 0.5% to 2%; when the mass of the octahedral material accounts for 0.5% to 2% of the total mass of the negative electrode active material layer, the secondary battery has good low - temperature performance.

[0037] Based on a third aspect, in some possible implementation manners, based on the total mass of the negative electrode active material layer, the mass ratio of boron element is 0.01% to 0.2%, and the mass ratio of sulfur element is 0.05% to 0.4%; based on the total mass of the negative electrode active material layer, when the mass ratio of boron element is 0.01% to 0.2% and the mass ratio of sulfur element is 0.05% to 0.4%, the secondary battery has good low-temperature performance.

[0038] A fourth aspect of the present application provides an electronic device, and the electronic device includes the secondary battery described in the third aspect.

[0039] Beneficial effects: The present application synthesizes and prepares an octahedral material with a homogeneous mesoporous octahedral structure. The octahedral material is rich in homogeneous mesopores, has a developed internal pore structure, can rapidly transport lithium ions, improve kinetics, and greatly improve the low-temperature performance of lithium-ion batteries; the pore volume in the octahedral material can absorb and store the electrolyte, increase the liquid retention amount, reduce the loss of the electrolyte, ensure the uniform distribution of the electrolyte inside the battery, thereby improving the electrochemical performance and stability of the battery, and enhancing the performance and lifespan of the battery. Description of the Drawings

[0040] Figure 1 It is a scanning electron microscope (SEM) photograph of the octahedral material in Example 1-1 of the present application.

[0041] Figure 2 It is the pore size distribution diagram of the octahedral material in Example 1-1.

[0042] Figure 3 It is the SEM photograph of the negative electrode sheet in Example 1-1 of the present application.

[0043] Figure 4 It is the impedance spectroscopy (EIS) test curve graph of the coin-type lithium-ion battery at 0 °C in Examples 1-16 and Comparative Example 1 of the present application.

[0044] Figure 5 It is the 3.4V discharge test curve graph of the single-layer full electric laminated battery in Examples 1-16 and Comparative Example 4 of the present application. Detailed Embodiments

[0045] The technical solutions in the embodiments of the present application will be clearly and detailedly described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application.

[0046] Octahedral material

[0047] In the first aspect of the present application, an octahedral material is provided. The octahedral material includes a plurality of octahedral structures, and the octahedral structures have uniform mesopores. The pore volume of the mesopores is 1.3 cm 3 / g to 2.0 cm 3 / g; the pore diameter of the mesopores is 8 nm to 12 nm; for example, the pore volume can be 1.3 cm 3 / g, 1.4 cm 3 / g, 1.5 cm 3 / g, 1.6 cm 3 / g, 1.7 cm 3 / g, 1.8 cm 3 / g, 1.9 cm 3 / g, 2.0 cm 3 / g or any value within the range composed of any of the above values; the pore diameter of the mesopores is 8 nm to 12 nm; for example, the pore diameter can be 8 nm, 8.5 nm, 9 nm, 9.5 nm, 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm or any value within the range composed of any of the above values.

[0048] The octahedral structure itself has a high space utilization rate and good electrical conductivity, which helps the rapid diffusion of lithium ions; the octahedral material in the present application has an octahedral structure and is rich in a uniform mesoporous structure. The internal pore structure is developed, which can provide abundant active sites, promote the insertion and extraction of lithium ions, can rapidly transport lithium ions, improve the kinetic performance, and thus improve the charge and discharge efficiency of the battery. When the pore diameter of the mesopores in the octahedral structure is 8 nm to 12 nm, the mesopores help to form an effective ion transport path, reduce the ion diffusion resistance, and greatly improve the low-temperature performance of the lithium-ion battery; when the pore volume of the mesopores in the octahedral structure is in the range of 1.3 cm 3 / g to 2.0 cm 3 / g, the mesopores can absorb and store more electrolytes, which can achieve the effects of increasing the liquid retention amount, reducing the loss of the electrolyte, and ensuring the uniform distribution of the electrolyte inside the battery, thereby improving the electrochemical performance and stability of the battery and enhancing the performance and lifespan of the battery. In the present application, low temperature means a temperature less than or equal to 0 °C. By testing the pore size distribution curve of the octahedral material, it can be analyzed that the octahedral material has a uniform mesoporous structure.

[0049] Based on the first aspect, in some possible implementation manners, the pore diameter of the mesopores of the octahedral material is 10 nm to 11 nm; the diffusion rate of the electrolyte in the pore channels within this range is relatively fast, avoiding the retention of the electrolyte in the pore channels, and the contact area between the electrolyte and the electrode material is appropriate, thereby improving the charge and discharge efficiency of the battery under low-temperature conditions.

[0050] Based on the first aspect, in some possible embodiments, the tap density of the octahedral material is 2.0 g / m 3 to 2.5 g / m 3 ; when the tap density of the negative electrode sheet is in the range of 2.0 to 2.5 g / m 3 , the tap density does not affect the overall capacity of the negative electrode sheet, and at the same time, the octahedral material can retain the octahedral and complete mesoporous structure, enabling the secondary battery to have good low-temperature performance.

[0051] Based on the first aspect, in some possible embodiments, in some possible embodiments, the octahedral material contains boron element and sulfur element. Doping with boron element and sulfur element makes the octahedral material have high ionic conductivity;

[0052] Based on the first aspect, in some possible embodiments, the octahedral material contains boron element. Based on the total mass of the octahedral material, the mass fraction of the boron element is 2% to 10%; for example, the mass fraction of the boron element can be any value within the range composed of 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value above. When the mass fraction of the sulfur element is in the range of 10% to 20%, the octahedral material has high ionic conductivity; when the ionic conductivity is high, the low-temperature performance of the battery is good.

[0053] In some possible embodiments, the octahedral material contains sulfur element. Based on the total mass of the octahedral material, the mass fraction of the sulfur element is 10% to 20%; for example, the mass fraction of the sulfur element can be any value within the range composed of 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% or any value above.

[0054] In some possible embodiments, the mass fraction of the boron element in the octahedral material is 2% to 10%; the mass fraction of the sulfur element is 10% to 20%; when the contents of the boron element and the sulfur element in the octahedral material are within the above ranges, the octahedral material has high ionic conductivity.

[0055] In some possible embodiments, the ionic conductivity of the octahedral material is from 9 mS / cm to 18 mS / cm. For example, the ionic conductivity can be any value within the range composed of 9 mS / cm, 9.5 mS / cm, 10 mS / cm, 10.5 mS / cm, 11 mS / cm, 11.5 mS / cm, 12 mS / cm, 12.5 mS / cm, 13 mS / cm, 13.5 mS / cm, 14 mS / cm, 14.5 mS / cm, 15 mS / cm, 15.5 mS / cm, 16 mS / cm, 16.5 mS / cm, 17 mS / cm, 17.5 mS / cm, 18 mS / cm or any value above. At low temperatures, the viscosity of the electrolyte increases, the migration speed of ions slows down, resulting in an increase in the internal resistance of the battery, thus affecting the discharge performance of the battery. High ionic conductivity helps to increase the diffusion rate of lithium ions in the material, reduce the formation of dendrites on the surface of the negative electrode, thereby reducing the risk of battery failure, effectively reducing the polarization phenomenon at low temperatures, and improving the low-temperature performance of the battery. Therefore, the octahedral material of the present application with an ionic conductivity in the range of 9 mS / cm to 18 mS / cm has good low-temperature performance.

[0056] In some possible embodiments, the specific surface area of the octahedral material is 0.5 m 2 / g to 5 m 2 / g; for example, the ionic conductivity can be 0.5 m 2 / g, 1 m 2 / g, 1.5 m 2 / g, 2 m 2 / g, 2.5 m 2 / g, 3 m 2 / g, 3.5 m 2 / g, 4 m 2 / g, 4.5 m 2 / g, 5 m 2 / g or any value within the range composed of any value above.

[0057] When the specific surface area S of the octahedral material is in the range of 0.5 m 2 / g to 5 m 2 / g, a sufficient mesoporous structure can be formed on the surface of the octahedral material, while avoiding the influence of excessive defects on the first efficiency of the secondary battery, thereby ensuring that the first efficiency performance of the secondary battery is not affected.

[0058] In some possible embodiments, in the Raman spectrum obtained by Raman testing, the peak intensity ratio of the D peak to the G peak of the octahedral material is 0.8 to 1.5; the peak intensity ratio of the D peak to the G peak in Raman testing is the Raman value; the D peak is the peak in the Raman spectrum of the composite material with a displacement range of 1330 cm-1 to 1360 cm-1, and the G peak is the peak in the Raman spectrum of the composite material with a displacement range of 1580 cm-1 to 1582 cm-1; for example, the Raman value can be any value within the range composed of 0.8, 0.85, 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5 or any value above.

[0059] When the Raman value of the octahedral material is in the range of 0.8 to 1.5, amorphous carbon and other defects can be fully formed on the surface of the octahedral material, while avoiding the influence of excessive defects on the initial efficiency of the secondary battery, thereby ensuring that the initial efficiency performance of the secondary battery is not affected.

[0060] In some possible embodiments, all eight faces of the octahedral material are triangles.

[0061] In some possible embodiments, the eight faces of the octahedral material are equilateral triangles.

[0062] In some possible embodiments, the triangles of the eight faces of the octahedral material are congruent triangles, and the ratio of the side length to the height of each triangle ranges from 0.5 to 5; for example, the ratio of the side length to the height of the triangle can be any value within the range composed of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 or any value above.

[0063] When the triangles of the eight faces of the octahedral material are congruent triangles and the ratio of the side length to the height of each triangle ranges from 0.5 to 5, the octahedral material has high ionic conductivity, and when the ionic conductivity is high, the low-temperature performance of the battery is good.

[0064] The second aspect of the present application provides a method for preparing an octahedral material, including:

[0065] Dissolve a thiophene derivative, boric acid, and a stabilizer in water to obtain a mixed solution;

[0066] Add an initiator to the mixed solution for a synthesis reaction to obtain an intermediate product;

[0067] Under an inert gas, the intermediate product is carbonized to obtain the octahedral material. Among them, in the above preparation method, the thiophene derivative is used as the reaction monomer, boric acid is used as the catalytic crosslinking agent, the stabilizer is used to control the reaction rate, improve the product stability and improve the surface morphology and properties of the material, and the initiator is used to initiate the reaction polymerization.

[0068] Take the thiophene derivative, boric acid, and stabilizer and dissolve them in water. Add the initiator under nitrogen protection, stir for 20 min to 40 min, and react at 10 °C to 50 °C for 1 h to 6 h to obtain an intermediate product. The obtained intermediate product is repeatedly filtered and washed, and vacuum dried in an oven at 40 °C to 80 °C for 16 h to 32 h; transfer the dried octahedral powder to a tube furnace and perform carbonization treatment under nitrogen protection to obtain the octahedral material.

[0069] In the above preparation method, by dissolving the thiophene derivative, boric acid, and stabilizer in water, an intermediate product is synthesized and carbonized to obtain an octahedral material. The doping of two heteroelements, boron and sulfur, in the octahedral material makes the prepared octahedral material have a high ionic conductivity. Further, the secondary battery has good low-temperature performance while also taking into account good high-temperature performance.

[0070] In the above preparation process, when the heating temperature, heating time, carbonization temperature, and carbonization time meet a certain range, the ionic conductivity of the prepared octahedral material is higher.

[0071] Based on the second aspect, in some possible implementation manners, the temperature of the synthesis reaction is 10 °C to 50 °C, and the time of the synthesis reaction is 1 h to 6 h; for example, the temperature of the synthesis reaction can be any value within the range composed of 10 °C, 20 °C, 30 °C, 40 °C, 50 °C, or any other value; the time of the synthesis reaction can be any value within the range composed of 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or any other value.

[0072] In some possible implementation manners, the carbonization temperature is 600 °C to 1000 °C, and the carbonization time is 2 h to 6 h; the carbonization temperature can be any value within the range composed of 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C, or any other value; the carbonization time can be any value within the range composed of 2 h, 3 h, 4 h, 5 h, 6 h, or any other value.

[0073] In some possible implementation manners, nitrogen is used for reaction protection throughout the preparation method.

[0074] In some possible embodiments, the stabilizer is at least one of polyvinylpyrrolidone, polyethylene glycol - polypropylene glycol - polyethylene glycol triblock copolymer, and polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer; the water includes but is not limited to deionized water.

[0075] In some possible embodiments, when the stabilizer is polyethylene glycol - polypropylene glycol - polyethylene glycol triblock copolymer, the thiophene derivative does not include 5 - bromo - 2 - thiophene methanol.

[0076] In some possible embodiments, the thiophene derivative is at least one of 2 - thiophene methanol, 3 - thiophene methanol, 5 - chloro - 2 - thiophene methanol, and 5 - bromo - 2 - thiophene methanol.

[0077] In some possible embodiments, the initiator is at least one of ammonium persulfate and potassium persulfate.

[0078] Negative electrode sheet

[0079] The negative electrode sheet of the present application includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector. The negative electrode current collector can be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon - based current collector, and can also be a composite current collector disclosed in any prior art, such as but not limited to the current collector formed by combining the aforementioned conductive foil and a polymer substrate. The negative electrode active material layer contains a negative electrode active material, the octahedral material of the present application, and optionally a conductive agent, a binder, and a thickening agent.

[0080] In some embodiments, the negative electrode active material layer includes the octahedral material as described above. Based on the total mass of the negative electrode active material layer, the mass proportion of the octahedral material is 0.5% to 2%; for example, the mass proportion of the octahedral material can be any value within the range composed of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2% or any value above. When the mass of the octahedral material accounts for 0.5% to 2% of the total mass of the negative electrode active material layer, the secondary battery has good low - temperature performance and reduces the production cost of the lithium - ion battery.

[0081] In some embodiments, based on the total mass of the negative electrode active material layer, the mass proportion of boron element is 0.01% to 0.2%, and the mass proportion of sulfur element is 0.05% to 0.4%; for example, the mass proportion of boron element can be any value within the range composed of 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08, 0.09, 0.1%, 0.12%, 0.15%, 0.18%, 0.2% or any value above. For example, the mass proportion of sulfur element can be any value within the range composed of 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4% or any value above.

[0082] By regulating sulfur element and boron element within the scope of the present application, good low-temperature performance of lithium ions can be achieved.

[0083] The specific type of the negative electrode active material is not specifically limited and can be selected according to requirements. As an example, the negative electrode active material includes but is not limited to natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Sn, Sn-O, SnO2, Li4Ti5O with spinel structure 12 , at least one of Li-Al alloy.

[0084] The specific type of the conductive agent is not specifically limited and can be selected according to requirements. As an example, the conductive agent includes but is not limited to at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0085] The specific type of the binder is not specifically limited and can be selected according to requirements. As an example, the binder includes but is not limited to at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose.

[0086] The specific type of the thickening agent is not specifically limited and can be selected according to requirements. As an example, the thickening agent includes but is not limited to sodium carboxymethyl cellulose (CMC).

[0087] However, the present application is not limited to the above materials, and other well-known materials that can be used as negative electrode active materials, conductive agents, binders, and thickening agents can also be used for the negative electrode sheet of the present application.

[0088] Separator

[0089] There are no particular limitations on the material and shape of the separator used in the lithium-ion battery of the present application, and it can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer, an inorganic substance, etc. formed of a material stable to the electrolyte of the present application.

[0090] For example, the separator may include a base material layer and a surface treatment layer. The base material layer is a non-woven fabric, a film or a composite film having a porous structure, and the material of the base material layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0091] A surface treatment layer is provided on at least one surface of the base material layer. The surface treatment layer can be a polymer layer, an inorganic substance layer, or a layer formed by mixing a polymer and an inorganic substance. The inorganic substance layer includes inorganic particles and a binder, and the inorganic particles are selected from at least one of alumina, silica, magnesia, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate salt, polyvinyl pyrrolidone, polyethylene alkoxide, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate salt, polyvinyl pyrrolidone, polyethylene alkoxide, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene).

[0092] Electrolyte

[0093] According to some embodiments of the present application, the electrolyte includes an organic solvent, a lithium salt, and an optional additive. The organic solvent in the electrolyte of the present application can be any organic solvent known in the prior art that can be used as a solvent for the electrolyte. There is no limitation on the electrolyte used in the electrolyte according to the present application, and it can be any electrolyte known in the prior art. The additive of the electrolyte according to the present application can be any additive known in the prior art that can be used as an electrolyte additive. In some embodiments, the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate. In some embodiments, the organic solvent includes an ether solvent, such as including at least one of 1,3-dioxolane (DOL) and dimethoxyethane (DME). In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalato)borate LiB(C2O4)2 (LiBOB), or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB). In some embodiments, the additive includes at least one of fluoroethylene carbonate and adiponitrile.

[0094] Positive electrode sheet

[0095] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector. The positive electrode current collector can use aluminum foil, nickel foil, etc., or can also be any composite current collector disclosed in the prior art, such as including but not limited to the current collector formed by combining the aforementioned conductive foil and a polymer substrate. The positive electrode active material layer contains a positive electrode active material, and the positive electrode active material includes a compound that can reversibly intercalate and deintercalate lithium ions (i.e., a lithiated intercalation compound). In some embodiments, the positive electrode active material can include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese, and nickel. In some embodiments, the positive electrode active material can include, but is not limited to, at least one of lithium cobaltate, lithium nickel manganese cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel-type lithium manganate, spinel-type lithium nickel manganate, and lithium titanate.

[0096] The positive electrode active material layer further includes a binder for binding the positive electrode active material particles to facilitate the formation of a film layer, and at the same time can also improve the bonding force between the positive electrode active layer and the positive electrode current collector. In some embodiments, the binder may include but is not limited to at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin or nylon, etc.

[0097] The positive electrode active material layer may further include a conductive material, and the conductive material includes but is not limited to carbon-based materials, metal-based materials, conductive polymers or any combination thereof. In some embodiments, the carbon-based materials may include but are not limited to natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber or any combination thereof. In some embodiments, the metal-based materials may include but are not limited to metal powder or metal fiber, such as copper, nickel, aluminum or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0098] Secondary battery

[0099] The secondary battery of the present application further includes a housing (such as a packaging bag) for accommodating the above-mentioned positive electrode plate, separator, negative electrode plate and electrolyte, as well as other components known in the field of electrochemistry. The present application does not limit the above-mentioned other components. The present application has no particular limitation on the housing, and it can be a housing well-known in the art as long as it can achieve the purpose of the present application. For example, an aluminum-plastic film packaging bag can be used. The present application has no particular limitation on the type of lithium-ion battery, and it can include any device that undergoes an electrochemical reaction. The lithium-ion battery containing the above-mentioned octahedral material has good low-temperature performance and also takes into account good high-temperature performance.

[0100] Electronic device

[0101] The lithium-ion battery is applied to an electronic device to power the load in the electronic device. Moreover, the lithium-ion battery has good low-temperature performance while also taking into account good high-temperature performance, which is beneficial to improving the service life of the electronic device and the universality in high and low temperature environments. Among them, the electronic device may include but is not limited to a laptop computer, a pen-input computer, a mobile computer, an e-book player, a portable phone, a portable fax machine, a portable copier, a portable printer, a head-mounted stereo headset, a video recorder, an LCD TV, a portable cleaner, a portable CD player, a mini CD, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, a car, a motorcycle, a power-assisted bicycle, a bicycle, a lighting fixture, a toy, a game console, a clock, an electric tool, a flashlight, a camera, a large household battery and a lithium-ion capacitor, etc.

[0102] Embodiment The present application is described by taking a lithium-ion battery as an example.

[0103] Example 1-1

[0104] <Preparation of octahedral materials>

[0105] Take 15g of 2-thiophene methanol, 8g of boric acid, 5g of polyvinyl pyrrolidone, and 500g of deionized water in a flask, stir and dissolve, pass nitrogen to exclude the air in the flask, add 2g of ammonium persulfate initiator under nitrogen protection, stir rapidly for 30min, stop stirring, react at 10°C for 1h, and after the reaction, filter and wash repeatedly with deionized water, and vacuum dry in an oven at 60°C for 24h; the dried octahedral powder is transferred to a tubular furnace, heated to 600°C at 2°C / min under nitrogen protection, and kept warm for 2h to prepare the octahedral material of Example 1-1 of the present application.

[0106] <Preparation of negative electrode sheet>

[0107] Artificial graphite, carbon nanotubes, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber (SBR) and the above octahedral materials are uniformly dispersed in an appropriate amount of deionized water at a mass ratio of 97:1.2:1.3:0.5 to obtain a negative electrode slurry, wherein the solid content of the negative electrode slurry is 75wt%. The negative electrode slurry is uniformly coated on one surface of a current collector copper foil with a thickness of 10μm, and dried at 120°C to obtain a negative electrode sheet with a single-sided coating of a negative electrode active material layer with a coating thickness of 80μm. Repeat the above steps on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of a negative electrode active material layer. Dry under vacuum conditions at 120°C for 1 hour, and then obtain a negative electrode sheet with a specification of 78mm×875mm after cold pressing, cutting and slitting.

[0108] <Preparation of positive electrode sheet>

[0109] The cathode active material lithium cobalt oxide (LiCoO₂), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in a mass ratio of 96.3:2.2:1.5 in an appropriate amount of N-methylpyrrolidone (NMP) solvent to form a uniform cathode slurry, where the solid content of the cathode slurry is 70 wt%. The cathode slurry is uniformly coated on one surface of a cathode current collector aluminum foil with a thickness of 10 μm and dried at 120 °C for 1 hour to obtain a cathode plate with a cathode active material layer with a thickness of 60 μm coated on one side. Repeat the above steps on the other surface of the aluminum foil to obtain a cathode plate with a cathode active material layer coated on both sides. Dry it under vacuum conditions at 120 °C for 1 hour, and then after cold pressing, slicing, and slitting, a cathode plate with a specification of 74 mm × 867 mm is obtained.

[0110] <Preparation of the electrolyte>

[0111] In an argon atmosphere glove box with a water content of less than 10 ppm, the non-aqueous organic solvents ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:PC:EMC:DEC = 1:3:3:3. Then, fluoroethylene carbonate and 1,3-propane sultone are added, dissolved and fully stirred, and then the lithium salt lithium hexafluorophosphate (LiPF₆) is added. After mixing evenly, the electrolyte is obtained. Among them, based on the total mass of the electrolyte, the mass percentage content of LiPF₆ is 12.5%, the mass percentage content of fluoroethylene carbonate is 2%, the mass percentage content of 1,3-propane sultone is 2%, and the balance is non-aqueous organic solvents.

[0112] <Preparation of the separator>

[0113] A polyethylene porous polymer film with a thickness of 7 μm is used as the separator.

[0114] <Preparation of the coin cell>

[0115] The anode plate is cut into a circular piece with a Φ (diameter) = 14 mm as the working electrode, and a metal lithium sheet with a Φ (diameter) = 18 mm is used as the reference electrode. The two are separated by a separator with a Φ (diameter) = 20 mm in the middle, and an appropriate amount of electrolyte is dropped to assemble a CR2430 coin-type lithium-ion battery.

[0116] <Preparation of the single-layer full electrical laminated cell>

[0117] The negative electrode plate is cut into an anode electrode with a tab area of 51×43.5 mm, and the positive electrode plate is cut into a cathode electrode with a tab area of 49.5×42 mm. The two are separated by a separator with a size of 53×45.5 mm, and an appropriate amount of electrolyte is dropped. A standard XX5775 single-layer all-electric laminated lithium-ion battery is assembled.

[0118] The other preparation parameters of Example 1-1 are shown in Table 1.

[0119] Examples 1-2 to Example 1-22

[0120] Except in the preparation of the octahedral material, the relevant preparation parameters are adjusted according to Table 1, and the remaining conditions / preparation methods are the same as those of Example 1-1.

[0121] Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 5 and Comparative Example 6

[0122] Except in the preparation of the octahedral material, the relevant preparation parameters are adjusted according to Table 1, and the remaining conditions / preparation methods are the same as those of Example 1-1; the octahedral material prepared by the method of Comparative Example 1 cannot obtain an octahedral structure; the pore volume of the octahedral material prepared by the method of Comparative Example 2 is 1.2 cm 3 / g; the pore volume of the octahedral material prepared by the method of Comparative Example 3 is 2.2 cm 3 / g, the pore diameter of the octahedral material prepared by the method of Comparative Example 5 is 7.9 nm, and the pore diameter of the octahedral material prepared by the method of Comparative Example 6 is 12.3 nm.

[0123] Comparative Example 4

[0124] Except that the octahedral material is not added in the preparation of the negative electrode plate, the remaining conditions / preparation methods are the same as those of Example 1-1.

[0125] Testing methods

[0126] (1) Element content test

[0127] The Shimadzu / Kratos X-ray photoelectron spectrometer AXIS SUPRA+ is used to quantitatively test the sulfur and boron element contents in the negative electrode plate and the octahedral material.

[0128] (2) Electrochemical impedance spectroscopy (EIS) test

[0129] The Solartron1470E / 1455 electrochemical workstation from the UK is used for the 0°C electrochemical impedance spectroscopy test of the coin-type lithium-ion battery; the diffusion impedance (Rcp) is obtained through the refined decomposition of EIS.

[0130] (3) Low-temperature rate discharge test of the single-layer all-electric laminated battery

[0131] 1) Place the battery in a test environment at 0 °C.

[0132] 2) Let it stand for 30 minutes.

[0133] 3) Discharge at a rate of 0.2C until 3V: Here, "0.2C" refers to discharging at a current rate that is 0.2 times the battery capacity until the voltage drops to 3 volts.

[0134] 4) Let it stand for another 20 minutes: Give the battery time to recover and reduce the impact of the previous step on the subsequent steps.

[0135] 5) Charge at a constant current of 0.7C to 4.52V, then charge at a constant voltage until the current drops to 0.025C: First, quickly charge to 4.52 volts, and then keep the voltage constant until the charging current significantly drops to 0.025 times the original rate.

[0136] 6) Let it stand for 10 minutes.

[0137] 7) Repeat step 3: Discharge at 0.2C until 3V again.

[0138] 8) Let it stand for 20 minutes.

[0139] 9) Repeat step 5: Charge at a rate of 0.7C to 4.52V again and charge at a constant voltage until the current drops to 0.025C.

[0140] 10) Let it stand for 240 minutes.

[0141] 11) Discharge to 3.0V according to the set rate, i.e., 2.0C or 5.0C. In this low-temperature rate discharge test, the discharge capacity of the battery is tested at two different high rates of 2.0C and 5.0C respectively.

[0142] 12) Let it stand for 20 minutes.

[0143] 13) Loop through steps 9) to 12): Conduct tests sequentially under different discharge rate conditions, so that the performance of the same battery at different discharge rates can be compared. Finally, the performance parameters at a discharge rate of 2.0C are recorded as: Discharge capacity ratio at 3.4V @ 0 °C @ 2.0C; the performance parameters at a discharge rate of 5.0C are recorded as: Discharge capacity ratio at 3.4V @ 0 °C @ 2.0C.

[0144] (4) Test with a scanning electron microscope

[0145] Use a Nova Nano SEM 450 scanning electron microscope (SEM) to characterize the cross-sectional morphology of the octahedral material and the negative electrode sheet. The sputtering time before sample testing is 20s, and the scanning voltage during testing is 10kV.

[0146] (5) Testing of pore structure

[0147] The pore size structure of the octahedral material was characterized by using a Micromeritics physical adsorption instrument produced by the United States. Before the octahedral material sample was tested, it needed to be vacuum activated at 200 - 250 °C for at least 6 h to remove the adsorbed water vapor and impurities in the pores. The activated sample was tested in a liquid nitrogen environment at -196 °C to obtain the N2 adsorption - desorption isotherm. Using the Brunauer - Emmett - Teller (BET) method, the test points within the relative pressure range of 0.05 < P / P0 < 0.30 were selected to calculate the specific surface area of the sample (SBET, i.e., Specific Surface Area by the BET method), and the single - point adsorption volume at P / P0 = 0.95 was taken to calculate the total pore volume of the sample. When the pore size of the material was smaller than the N2 molecular size, CO2 could be selected as the probe molecule, and the pore structure was characterized at 0 °C, and the density functional theory (DFT) method was used to calculate the pore size distribution of the sample, and the pore volume contributed by ultra - micropores with a pore size < 1 nm and the pore volume contributed by micropores with a pore size < 2 nm were calculated.

[0148] (6) Testing of ionic conductivity

[0149] Calculation of ionic conductivity: 100 mg of octahedral material powder was placed in a die cell, a pressure of 380 MPa was applied, and the pressure was maintained for 1 minute. Subsequently, indium sheets were attached to both sides of the electrolyte sheet as blocking electrodes, and then a certain pressure was applied for AC impedance testing. The frequency range of the impedance test was from 1 Hz to 3 MHz, and the amplitude voltage was 50 mV. The obtained resistance results were used to calculate the ionic conductivity according to the formula σ = L / (R×S). Among them, S was the cross - sectional area, L was the thickness, and R was the measured resistance value. The ionic conductivity of the octahedral material was tested at different temperatures.

[0150] (7) Specific surface area testing

[0151] The nitrogen adsorption isotherm was measured by using a Micromeritics physical adsorption instrument TriStar3000 of the United States at the liquid nitrogen temperature (77 K). The specific surface area of the octahedral material sample was calculated by using the BET method, with the test points within the relative pressure range (0.05 < P / P0 < 0.30) of the adsorption branch of the isotherm, calculated by the t - plot method, and calculated by the non - local density functional theory (NLDFT) theory using the slit - forming parameters with the data of the adsorption branch of the isotherm.

[0152] (8) Raman spectroscopy testing

[0153] The Raman test was carried out on a DXR laser micro-Raman spectrometer in the United States, with a laser wavelength of 532 nm. The sample to be tested was scanned at 100 points within a square area with a side length of 100 microns. The Id / Ig of these 100 points was calculated, and the 100 Id / Ig values were statistically analyzed to calculate the average value to obtain the peak intensity ratio of the D peak to the G peak of the octahedral material.

[0154] (9) Compaction density test

[0155] Weigh a certain mass of octahedral material powder and add it to a special compaction mold. Place the mold on a compaction density instrument, set the required pressure, and read the thickness of the powder under the corresponding pressure on the equipment. Calculate the compaction density through the density formula ρ = m / v.

[0156] Among them, the preparation conditions of the examples and comparative examples are recorded in Table 1.

[0157] Table 1

[0158]

[0159]

[0160] The relevant performance parameters of the examples and comparative examples are recorded in Table 2.

[0161] Table 2 Note: " / " in Table 2 indicates the absence of the corresponding substance or parameter.

[0162]

[0163] Figure 1 is the scanning electron microscope image of the octahedral material in Example 1-1. From Figure 1 it can be seen that the octahedral material contains multiple octahedral structures; Figure 2 is the pore size distribution diagram of the octahedral material in Example 1-1. From Figure 2 it can be seen that the octahedral material has uniform mesopores, and the pore size of the mesopores is mainly distributed in 10-11 nm; Figure 3 is the scanning electron microscope image of the negative electrode plate in Example 1-1. From Figure 2 it can be seen that the octahedral material with an octahedral structure is embedded in the negative electrode plate and is evenly distributed in the negative electrode plate, which can quickly transport lithium ions, improve kinetics. The octahedral material with a uniform mesopore structure can absorb and store the electrolyte, increase the liquid retention amount, reduce the loss of the electrolyte, ensure the uniform distribution of the electrolyte inside the battery, thereby improving the electrochemical performance and stability of the battery and enhancing the low-temperature discharge performance of the battery.

[0164] According to Table 1 and Table 2, compared with Comparative Example 4 in which the octahedral material was not added in the preparation of the battery, the octahedral material of the present application was added in Examples 1-1 to 1-22; Figure 4 It is a test chart of impedance spectroscopy (EIS) at 0 °C for the coin-type lithium-ion batteries in Examples 1-16 and Comparative Example 4. From Figure 4 it can be seen that after adding the octahedral material of the present application in the coin-type lithium-ion battery, the low-temperature diffusion impedance is effectively reduced, and the low-temperature performance of the lithium-ion battery is further improved. Figure 5 It is a discharge test curve graph at 3.4 V for the single-layer full electrical laminated battery in Examples 1-16 and Comparative Example 4. From Figure 5 it can be seen that after adding the octahedral material of the present application in the single-layer full electrical laminated battery, at 0 °C, the low-temperature discharge performance of the battery is significantly improved, and the low-temperature performance of the battery is further improved. Therefore, according to Figure 4 、 Figure 5 and Figure 2 the test data in, it can be seen that the low-temperature performance of the lithium-ion battery added with the octahedral material is significantly improved.

[0165] According to Table 1 and Table 2, compared with Comparative Example 1 in which the octahedral structure could not be formed, the octahedral materials in Examples 1-1 to 1-22 all contained an octahedral structure. It can be seen that using the material with an octahedral structure makes the low-temperature performance of the lithium-ion battery better.

[0166] According to Table 1 and Table 2, compared with Examples 1-1 to 1-22, the pore volumes of the octahedral materials in Comparative Examples 2 to 3 are 1.2 cm 3 / g and 2.2 cm 3 / g respectively. The low-temperature performance of the lithium-ion batteries made of the octahedral materials in Comparative Example 2 and Comparative Example 3 decreases, indicating that when the pore volume of the octahedral material of the present application is in the range of 1.2 - 2.0 cm 3 / g, the prepared lithium-ion battery has better low-temperature performance.

[0167] According to Table 1 and Table 2, the pore diameters of Comparative Example 5 and Comparative Example 6 are 7.9 nm and 12.3 nm respectively; compared with Comparative Example 6 and Comparative Example 5, the pore diameter range of Examples 1-1 to 1-22 is within 8 - 12 nm; the lithium-ion battery prepared with the octahedral material within this range has better low-temperature performance.

[0168] The above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the scope of the technical solutions of the present application.

Claims

1. An octahedral material, characterized in that: The octahedral material comprises a plurality of octahedral structures, wherein the octahedral structures have mesopores, and the pore volume of the mesopores is 1.3 cm 3 / g to 2.0cm 3 / g; the pore size of the mesopores is 8nm to 12nm.

2. The octahedral material according to claim 1, characterized in that The compacted density of the octahedral material is 2.0 g / m 3 Up to 2.5g / m 3 .

3. The octahedral material according to claim 1, characterized in that The octahedral material also satisfies at least one of the following conditions: (1) The octahedral material contains at least one of boron and sulfur; (2) The octahedral material contains a boron element, and the mass proportion of the boron element is 2% to 10% based on the total mass of the octahedral material; (3) The octahedral material contains sulfur, and the mass proportion of the sulfur element is 10% to 20% based on the total mass of the octahedral material.

4. The octahedral material according to claim 1, characterized in that The octahedral material satisfies at least one of the following conditions: (4) The ionic conductivity of the octahedral material is 9 mS / cm to 18 mS / cm; (5) The specific surface area of ​​the octahedral material is 0.5 m 2 / g to 5m 2 / g; (6) In the Raman spectrum obtained by Raman testing, the peak intensity ratio of the D peak to the G peak of the octahedral material is 0.8 to 1.5; (7) The eight faces of the octahedral structure of the octahedral material are all triangles; (8) The eight faces of the octahedral structure of the octahedral material are congruent triangles, and the ratio of the side length to the height of each triangle is 0.5 to 5.

5. A method for preparing an octahedral material according to any one of claims 1 to 4, characterized in that: include: dissolving a thiophene derivative, boric acid and a stabilizer in water to obtain a mixed solution; adding an initiator to the mixed solution to carry out a synthesis reaction to obtain an intermediate product; The intermediate product is carbonized under an inert gas to obtain the octahedral material.

6. The method for preparing an octahedral material according to claim 5, characterized in that: The preparation method also satisfies at least one of the following conditions: (9) The temperature of the synthesis reaction is 10°C to 50°C, and the time of the synthesis reaction is 1h to 6h; (10) The carbonization temperature is 600° C. to 1000° C., and the carbonization time is 2 h to 6 h; (11) Nitrogen is used for reaction protection throughout the preparation method.

7. The method for preparing an octahedral material according to claim 5, characterized in that: The preparation method satisfies at least one of the following conditions: (12) The stabilizer is at least one of polyvinyl pyrrolidone, polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer; when the stabilizer is polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer, the thiophene derivative does not include 5-bromo-2-thiophene methanol; (13) The thiophene derivative is at least one of 2-thiophene methanol, 3-thiophene methanol, 5-chloro-2-thiophene methanol, and 5-bromo-2-thiophene methanol; (14) The initiator is at least one of ammonium persulfate and potassium persulfate.

8. A secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises a negative electrode active material layer, characterized in that: The negative electrode active material layer includes the octahedral material according to any one of claims 1 to 4.

9. The secondary battery according to claim 8, characterized in that The negative electrode active material layer satisfies at least one of the following conditions: (15) Based on the total mass of the negative electrode active material layer, the mass proportion of the octahedral material is 0.5% to 2%; (16) Based on the total mass of the negative electrode active material layer, the mass proportion of the boron element is 0.01% to 0.2%; (17) Based on the total mass of the negative electrode active material layer, the mass percentage of the sulfur element is 0.05% to 0.4%.

10. An electronic device, characterized in that: The electronic device includes the secondary battery according to claim 8 or 9.

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