Negative electrode active material and method for producing the same, and secondary battery and power consumption device containing the same

Abstract

The present application provides a negative electrode active material, a method for manufacturing the same, a secondary battery including the same, and an electric consumption device. The negative electrode active material includes a carbon substrate and a filler. The graphitization degree of the carbon substrate is 87% or less. The carbon substrate includes a plurality of pore structures. At least a part of the filler is located in the pore structures of the carbon substrate, and the filler includes one or more of elements capable of alloying reaction with Li. The negative electrode active material according to the present application can have high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability. Figure 1

Description

Technical Field

[0001] This application belongs to the technical field of batteries, and specifically relates to a negative electrode active material, a method for manufacturing the same, and a secondary battery and an electric consumption device including the same.

Background Art

[0002] In recent years, secondary batteries have been widely used in many fields such as energy storage power systems such as hydraulic, thermal, wind, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. In the process of the rapid development of secondary batteries, the requirements for their energy density have become higher. Carbon-based materials represented by graphite are the most commonly used negative electrode active materials in secondary batteries, but the capacity of them is approaching the theoretical specific capacity. Non-carbon-based materials such as silicon-based materials, tin-based materials, and germanium-based materials have attracted wide attention because they have high theoretical specific capacities. However, such negative electrode active materials generally have the disadvantages of large volume expansion, low initial Coulomb efficiency, and / or poor conductivity.

Summary of the Invention

[0003] An object of this application is to provide a negative electrode active material having high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability, a method for manufacturing the same, and a secondary battery and an electric consumption device including the same.

[0004] A first aspect of this application provides a negative electrode active material including a carbon matrix and a filler, wherein the graphitization degree of the carbon matrix is 87% or less, the carbon matrix includes a plurality of pore structures, at least a part of the filler is located in the pore structures of the carbon matrix, and the filler includes one or more kinds of elements capable of alloying reaction with Li.

[0005] The inventors have found through research that by providing a filler with high specific capacity in the pore structure of a carbon substrate with a low degree of graphitization (greater than 0 and 87% or less), the resulting negative electrode active material can possess high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability, and that the secondary battery can also possess high energy density, high initial Coulomb efficiency, and long cycle life. The carbon substrate of this application has a degree of graphitization of 87% or less, and has the advantages of higher conductivity and higher initial Coulomb efficiency compared to carbon substrates obtained by pore formation with pore-forming agents, and has the advantages of lower volume expansion and higher cycle stability compared to natural graphite. Therefore, the negative electrode active material according to this application can fully utilize the advantage of the high specific capacity of the filler and can compensate for the disadvantages of poor conductivity and low initial Coulomb efficiency of the filler. In addition, since at least a portion of the filler is located in the pore structure of the carbon substrate, the volume expansion of the filler can be reduced by the carbon substrate.

[0006] In any embodiment of the present application, the degree of graphitization of the carbon substrate is 65% to 87%. This is advantageous for the negative electrode active material to better combine high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability.

[0007] In any embodiment of the present application, the elements capable of alloying with Li include one or more of silicon, tin, and germanium. This is advantageous for the negative electrode active material to have a high specific capacity.

[0008] In any embodiment of the present application, the filler includes one or more types of silicon-based materials, tin-based materials, and germanium-based materials.

[0009] In any embodiment of the present application, the silicon-based material includes one or more of elemental silicon, silicon oxides, silicon-carbon materials, silicon-nitrogen composites, and silicon alloys.

[0010] In any embodiment of the present application, the tin-based material includes one or more of the following: elemental tin, tin oxide, tin sulfide, tin phosphate, tin composite oxide, tin carbon material, and tin alloy material.

[0011] In any embodiment of the present application, the germanium-based material includes one or more types from among elemental germanium, germanium oxide, germanium carbon material, germanium alloy material, and germanium salt.

[0012] In any embodiment of the present application, the filler includes a crystalline filler and / or an amorphous filler, and optionally includes a crystalline silicon-based material and / or an amorphous silicon-based material. The silicon-based material has a high specific capacity and is advantageous for improving the energy density of the secondary battery.

[0013] In any embodiment of the present application, the grain size of the crystalline filler is 100 nm or less, and selectively between 2 nm and 50 nm. When the crystalline filler has an appropriate grain size, it is possible to improve the initial Coulomb efficiency of the secondary battery while avoiding significant adverse effects on the cycle performance and storage performance of the secondary battery.

[0014] In any embodiment of the present application, the filler includes one or more of vapor-deposited (also called vapor-grown) silicon-based materials, tin-based materials, and germanium-based materials, and optionally includes vapor-deposited silicon-based materials.

[0015] In this application, the negative electrode active material includes a (002) crystal plane peak at 26.4° and a (111) crystal plane peak at 28.6° in the X-ray diffraction spectrum measured by an X-ray diffractometer, and the ratio of the full width at half maximum of the (002) crystal plane peak to the full width at half maximum of the (111) crystal plane peak is 0.2 to 50, and selectively between 0.2 and 20. By controlling the full width at half maximum of the (002) crystal plane peak and the full width at half maximum of the (111) crystal plane peak to be within an appropriate range, the carbon substrate has an appropriate degree of graphitization and the filler has an appropriate crystal grain size, which is advantageous for the negative electrode active material to possess a high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability.

[0016] In any embodiment of the present application, at least a portion of the filler is located in the pore structure of the carbon substrate, and there is a gap between the filler and the carbon substrate. When there is a gap between the filler and the carbon substrate, this portion of the gap can accommodate the volume expansion of the filler, thereby easing the stress generated during the expansion process of the filler, and thereby further reducing the probability of particle crushing and pulverization.

[0017] In any embodiment of the present application, the negative electrode active material further includes a coating layer located on at least a portion of the surface of the carbon substrate. The coating layer can prevent direct contact between the filler and the electrolyte, thereby reducing side reactions of the electrolyte, decreasing the consumption of active ions, improving the cycle performance of the secondary battery, improving the stability of the negative electrode slurry, and avoiding increased processing difficulty of the negative electrode slurry due to the filler reacting with solvent water or the like. The coating layer also plays a role in mitigating the volume expansion of the filler, which is advantageous in improving the structural stability of the negative electrode active material and improving the electrochemical performance of the secondary battery.

[0018] In any embodiment of the present application, the coating layer comprises one or more of the following: carbon material, conductive polymer, metal oxide, and metal sulfide, and optionally comprises a carbon material.

[0019] In any embodiment of the present application, the thickness of the coating layer is 100 nm or less, and selectively between 10 nm and 100 nm. When the thickness of the coating layer is within the above range, the integrity of the coating layer is higher, and contact between the filler and the electrolyte can be more effectively avoided, which is advantageous in reducing side reactions of the electrolyte and providing the negative electrode active material with a high specific capacity, high initial Coulomb efficiency, and low volume expansion.

[0020] In any embodiment of the present application, the negative electrode active material comprises a carbon element and an element capable of alloying with Li.

[0021] In any embodiment of the present application, the mass percentage of the carbon element in the negative electrode active material is 20 wt% to 80 wt%, and selectively 30 wt% to 70 wt%.

[0022] In any embodiment of the present application, the mass percentage of elements in the negative electrode active material that can react with Li for alloying is 20 wt% to 80 wt%, and selectively 30 wt% to 70 wt%.

[0023] When the content of carbon and / or elements capable of alloying with Li in the negative electrode active material is within the above range, it is advantageous for the negative electrode active material to achieve both high specific capacity and high conductivity.

[0024] In any embodiment of the present application, the negative electrode active material further comprises other elements, the other elements comprising one or more of the elements oxygen, metals, and nitrogen.

[0025] In any embodiment of the present application, the total mass percentage of the other elements in the negative electrode active material is 20 wt% or less, and selectively 10 wt% or less.

[0026] In any embodiment of the present application, the initial Coulomb efficiency of the carbon substrate is 75% or more, and selectively between 75% and 87%. This is advantageous for improving the initial Coulomb efficiency of the negative electrode active material.

[0027] In any embodiment of the present application, the powder resistivity of the carbon substrate at a pressure of 16 MPa is 5 × 10⁻⁶. -2 It is less than or equal to Ω·cm, and is selectively 3.5 × 10 -2 It is less than Ω·cm. This is advantageous for improving the conductivity of the negative electrode active material.

[0028] In any embodiment of the present application, the BET specific surface area of ​​the carbon substrate is 50 m². 2 / g~1000m 2 It is / g, and can be selected as 100m 2 / g~700m 2 This is advantageous for the negative electrode active material to have an appropriate BET specific surface area, thereby reducing the surface activity of the negative electrode active material, decreasing interfacial side reactions, reducing the film deposition consumption of the SEI film, and further improving the initial Coulomb efficiency and cycle performance of the secondary battery.

[0029] In any embodiment of the present application, the degree of graphitization of the negative electrode active material is 65% or more, and selectively between 65% and 87%. This is advantageous for the negative electrode active material to better combine high initial Coulomb efficiency, high conductivity, and good cycle stability.

[0030] In any embodiment of the present application, the initial Coulomb efficiency of the negative electrode active material is 92% or higher, and is selectably between 92% and 95%. This reduces the irreversible consumption of active ions and improves the capacity performance and cycle performance of the secondary battery.

[0031] In any embodiment of the present application, the volume particle size Dv50 of the negative electrode active material is 3 μm to 50 μm, and selectively 5 μm to 20 μm.

[0032] In any embodiment of the present application, the volume particle size Dv90 of the negative electrode active material is 60 μm or less, and selectively between 20 μm and 50 μm.

[0033] In any embodiment of the present application, the particle size distribution width (Dv90 - Dv10) / Dv50 of the negative electrode active material is 1.0 to 3.0, and optionally 1.0 to 2.0.

[0034] When at least one of the volume particle size Dv50, volume particle size Dv90, and particle size distribution width (Dv90 - Dv10) / Dv50 of the negative electrode active material is within the above range, it contributes to the reduction of the surface activity of the negative electrode active material, the reduction of interface side reactions, and the reduction of the film formation consumption of the SEI film, and is also advantageous for improving the active ion and electron transmission performance. Therefore, the cycle performance of the secondary battery can be further improved.

[0035] In any embodiment of the present application, the BET specific surface area of the negative electrode active material is 2 m 2 / g to 100 m 2 / g, and optionally 2 m 2 / g to 30 m 2 / g. When the BET specific surface area of the negative electrode active material is within the above range, it contributes to the reduction of interface activity, the reduction of interface side reactions, and the reduction of the film formation consumption of the SEI film. Therefore, the initial Coulomb efficiency and cycle performance of the secondary battery can be improved.

[0036] In any embodiment of the present application, the powder resistivity of the negative electrode active material at a pressure of 16 MPa is 5×10 -1 Ω·cm or less, and optionally 2×10 -1 Ω·cm. Thereby, the negative electrode active material has good conductivity, which is advantageous for improving the cycle performance and rate performance of the secondary battery.

[0037] A second aspect of the present invention provides a method for producing a negative electrode active material, comprising: step 1 providing a carbon substrate having a degree of graphitization of 87% or less, selectively between 65% and 87%, and including a plurality of pore structures; and step 2 dispersing a filler in the pore structure of the carbon substrate to obtain a negative electrode active material, wherein the negative electrode active material comprises a carbon substrate and a filler, the carbon substrate includes a plurality of pore structures, at least a portion of the filler is located in the pore structure of the carbon substrate, the filler includes one or more elements that can alloy with Li, and selectively the elements that can alloy with Li include one or more elements from silicon, tin, and germanium.

[0038] In any embodiment of the present invention, in step 1, the carbon substrate is produced by placing a carbon source containing a plurality of pore structures into a high-temperature furnace, performing a graphitization treatment in a protective gas atmosphere at 1600°C to 2400°C, and obtaining the carbon substrate after completion. This makes it possible to obtain a carbon substrate having a degree of graphitization of 87% or less, selectively between 65% and 87%, and having a plurality of pore structures.

[0039] In any embodiment of the present invention, the heat retention time for the graphitization treatment is 1 to 12 hours.

[0040] In any embodiment of the present application, the carbon source includes one or more types selected from hard carbon, petroleum coke, pitch coke, biomass carbon, and resin carbon.

[0041] By graphitizing a carbon source containing multiple pore structures at a constant temperature, the number of micropores in the carbon source is reduced, improving the uniformity of the dispersion of the subsequent filler. At the same time, excess chemical bonds on the surface of the carbon source are removed, reducing the content of oxygen-containing functional groups in the carbon source and decreasing side reactions in the electrolyte. As a result, the initial Coulomb efficiency, conductivity, and high-temperature performance of the obtained carbon substrate are improved, and the secondary battery can be given good cycle performance.

[0042] In any embodiment of the present application, in step 1, the initial Coulomb efficiency of the carbon substrate is 75% or more, and selectively between 75% and 87%.

[0043] In any embodiment of the present application, in step 1, the powder resistivity of the carbon substrate at a pressure of 16 MPa is 5 × 10⁻⁶. -2 It is less than or equal to Ω·cm, and is selectively 3.5 × 10 -2 It is less than or equal to Ω·cm.

[0044] In any embodiment of the present application, in step 1, the BET specific surface area of ​​the carbon substrate is 50 m². 2 / g~1000m 2 It is / g, and can be selected as 100m 2 / g~700m 2 It is / g.

[0045] In any embodiment of the present application, in step 1, the volume particle size Dv50 of the carbon substrate is 3 μm to 50 μm, and selectively 5 μm to 20 μm.

[0046] In any embodiment of the present application, step 2 includes a process for dispersing the filler in the pore structure of the carbon substrate, and optionally a gas-phase deposition process. Compared to the liquid-phase deposition process, the gas-phase deposition process is advantageous for good deposition and uniform dispersion of the filler in the pore structure of the carbon substrate, and can avoid problems of filler aggregation and / or large-scale deposition on the surface of the carbon substrate. Furthermore, the gas-phase deposition process is mature and easily applicable to industrial mass production.

[0047] In any embodiment of the present application, the gas phase deposition process includes a chemical gas phase deposition process and a physical gas phase deposition process, and is selectively a chemical gas phase deposition process.

[0048] In any embodiment of the present application, step 2, the step of dispersing a filler in the pore structure of the carbon substrate, includes the steps of placing the carbon substrate in a reaction furnace, introducing a first mixture containing a source of elements capable of alloying with Li, depositing at a first temperature T1 for a first time t1, and obtaining a negative electrode active material after completion.

[0049] In any embodiment of the present application, the first mixture comprises a source of elements alloyable with Li and a protective gas, and optionally, the volume occupancy of the source of elements alloyable with Li in the first mixture is 10% to 50%.

[0050] In any embodiment of the present application, the first mixture further comprises a carbon source gas.

[0051] In any embodiment of the present application, the volume ratio of the source of elements capable of alloying with Li to the carbon source gas is 0.5:1 or greater, and selectively (2-10):1.

[0052] In any embodiment of the present application, the volume occupancy of the carbon source gas in the first mixture is 20% or less, and selectively between 5% and 20%.

[0053] In any embodiment of the present invention, the pressure inside the reactor is 200 Pa to 600 Pa higher than atmospheric pressure.

[0054] In any embodiment of the present application, the total gas flow rate of the first mixture is 0.5 L / min to 20 L / min.

[0055] In any embodiment of the present application, the first temperature T1 is 400°C to 1000°C.

[0056] In any embodiment of the present application, the first time t1 is between 1h and 12h.

[0057] By adjusting at least one of the following—the composition ratio of the first mixture, the total gas flow rate of the first mixture, the first temperature, and the first time—to fall within the above range, it is advantageous to deposit the filler material into the pore structure of the carbon substrate, and also advantageous to adjust the degree of crystallinity and / or grain size of the filler material to fall within an appropriate range.

[0058] In any embodiment of the present application, the method further comprises step 3, which involves forming a coating layer on at least a portion of the negative electrode active material obtained in step 2, comprising one or more of the following: carbon material, conductive polymer, metal oxide, and metal sulfide.

[0059] In any embodiment of the present application, the step of forming the coating layer includes placing the negative electrode active material obtained in step 2 into a reaction furnace, introducing a second mixture containing a carbon source gas, depositing at a second temperature T2 for a second time t2, and obtaining a carbon-coated negative electrode active material after completion.

[0060] In any embodiment of the present application, the second mixture comprises a carbon source gas and a protective gas, and optionally, the volume occupancy V2 of the carbon source gas in the second mixture is 5% to 50%.

[0061] In any embodiment of the present application, the total gas flow rate of the second mixture is 0.5 L / min to 20 L / min.

[0062] In any embodiment of the present application, the second temperature T2 is 700°C to 850°C.

[0063] In any embodiment of the present application, the second time t2 is 1h to 6h.

[0064] In step 3, adjusting at least one of the composition ratio of the second mixture, the total gas flow rate of the second mixture, the second temperature, and the second time to be within the above range is advantageous for forming a coating layer of appropriate thickness and avoids reducing the specific capacity of the negative electrode active material due to the coating layer being too thick.

[0065] A third aspect of the present application provides a secondary battery comprising a negative electrode sheet containing the negative electrode active material of the first aspect of the present disclosure or a negative electrode active material manufactured by the method of the second aspect of the present application.

[0066] A fourth aspect of the present application provides an electrical consumption device including a secondary battery according to the third aspect of the present application.

[0067] Through research, the inventors have found that by filling the pore structure of a carbon substrate having a low degree of graphitization with a filler that has the advantage of high capacity, the resulting negative electrode active material can be made to possess high capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability, and the secondary battery can be made to possess high energy density, high initial Coulomb efficiency, and long cycle life. The electricity consumption device of the present invention is equipped with the secondary battery according to the present invention and therefore has at least the same advantages as the secondary battery described above. [Brief explanation of the drawing]

[0068] To more clearly explain the technical concept of the embodiments of this application, the following is a brief introduction of the drawings necessary for the embodiments of this application. It is clear that the drawings described below are only a few embodiments of this application. Those skilled in the art can obtain further drawings based on these drawings, even without creative work. [Figure 1] This is a schematic diagram of one embodiment of the battery cell of the present invention. [Figure 2] This is an exploded schematic diagram of one embodiment of the battery cell of the present invention. [Figure 3] This is a schematic diagram of one embodiment of the battery module of the present invention. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of the present invention. [Figure 5] Figure 4 is an exploded schematic diagram of an embodiment of the battery pack shown. [Figure 6]This is a schematic diagram of one embodiment of an electrical consumption device powered by a secondary battery of the present invention. In the drawing, the figures are not necessarily drawn to actual proportions. Reference numerals: 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 battery cell, 51 housing, 52 electrode assembly, 53 cover plate. [Modes for carrying out the invention]

[0069] The following describes in detail embodiments specifically disclosing the negative electrode active material and its manufacturing method, as well as secondary batteries and power consumption devices containing the same, with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. The accompanying drawings and the following explanation are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0070] The “range” disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting one lower limit and one upper limit, the selected lower limit and upper limit limit the boundary of a special range. The range thus limited may include or exclude endpoints, and may be any combination, that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are given for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Also, if minimum range values ​​1 and 2 and maximum range values ​​3, 4 and 5 are given, the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 may all be expected. In this application, unless otherwise stated, the numerical range “a-b” is an abbreviation indicating any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" in this specification refers to all real numbers between "0 to 5," and "0 to 5" is an abbreviation for combinations of these numbers. Also, when a parameter is described as an integer greater than or equal to 2 (≧2), it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0071] Unless otherwise specified, all embodiments and optional embodiments of this Application may be combined to form new technical solutions. Such technical solutions are considered to be included in the disclosures of this Application.

[0072] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical concepts. Such technical concepts are considered to be included in the disclosures of this application.

[0073] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly, but it is preferable that they be performed sequentially. For example, when it is mentioned that the above method includes steps (a) and (b), it means that the above method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, when it is mentioned that the above method may further include step (c), it means that step (c) may be added to the above method in any order. For example, the above method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0074] Unless otherwise specified, the terms "equip" and "include" in this application mean open-ended or closed-ended. For example, the terms "equip" and "include" above may mean further "equip" or "include" other components not listed, or "equip" or "include" only the listed components.

[0075] Unless otherwise specified, the term "or" in this application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions are met: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0076] Unless otherwise specified, relational terms such as "first" and "second" in this application are used to distinguish between different objects and do not necessarily indicate the existence of a specific order or hierarchical relationship.

[0077] In this application, the terms "multiple," "multiple types," and "several" mean two or more of two or more types.

[0078] Unless otherwise specified, terms used in this application have the meanings commonly understood by those skilled in the art.

[0079] Unless otherwise specified, the numerical values ​​of each parameter referred to herein can be measured according to various commonly used test methods in the art, such as the test methods described herein.

[0080] To meet the high energy density requirements of secondary batteries, non-carbon materials such as silicon-based, tin-based, and germanium-based materials are attracting widespread attention due to their high theoretical specific capacity. Silicon has a high theoretical specific capacity of 4200 mAh / g, tin has a high theoretical specific capacity of 994 mAh / g, and germanium has a high theoretical specific capacity of 1600 mAh / g, which can significantly improve the energy density of secondary batteries.

[0081] However, unlike the energy storage mechanism of graphite, non-carbon materials such as silicon-based, tin-based, and germanium-based materials store energy by forming alloys through alloying reactions with metals (e.g., lithium, sodium, etc.). This results in a huge volume effect during the charge-discharge process, easily causing particle fragmentation and pulverization. Furthermore, pulverization problems occur in the negative electrode film layer, easily releasing electrical contact with the current collector, hindering the desorption process of active ions, and significantly increasing irreversible capacity. In addition, the huge volume effect causes repeated destruction and reconstruction of the solid electrolyte interface (SEI) film on the surface of the negative electrode active material particles, further increasing the irreversible depletion of active ions and ultimately affecting the capacity of the secondary battery. Simultaneously, as the charge-discharge process progresses, the SEI film on the surface of the negative electrode active material particles becomes increasingly thicker, thereby increasing the impedance of the secondary battery. Furthermore, the unstable SEI film on the surface of the negative electrode active material particles further increases interfacial side reactions and irreversible capacity by bringing the negative electrode active material into direct contact with the electrolyte.

[0082] Therefore, when the aforementioned non-carbon materials are used as negative electrode active materials, they generally have the disadvantages of high irreversible capacity, low initial Coulomb efficiency, and large volume expansion, resulting in a large loss of actual capacity in the secondary battery and a reduced cycle life. Furthermore, silicon is a semiconductor material with low intrinsic conductivity and poor conductivity, which further worsens the electrochemical performance of the secondary battery.

[0083] In view of this, the inventors of the present invention have proposed a novel negative electrode active material through extensive research. This negative electrode active material can combine high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability, and can also provide secondary batteries with high energy density, high initial Coulomb efficiency, and long cycle life. negative electrode active material A first embodiment of the present invention provides a negative electrode active material. The negative electrode active material comprises a carbon substrate having a degree of graphitization of 87% or less and having a plurality of pore structures, and a filler containing one or more elements that are located in the pore structure of the carbon substrate and are capable of alloying with Li.

[0084] The filler material, by containing one or more elements that can alloy with Li, contributes to high capacity and can compensate for the low capacity of the carbon substrate. However, it has a significant volume effect, which affects the electrochemical performance.

[0085] In conventional technology research, to overcome the drawback of large volume expansion of the filler material, currently employed methods involve depositing the filler material onto a carbon substrate or natural graphite containing multiple pore structures through processes such as deposition. However, the carbon substrates containing multiple pore structures currently employed are obtained, for example, by etching using an alkaline solution pore-forming agent. The carbon substrate itself is non-graphitizable carbon (or amorphous carbon), and therefore has the disadvantages of high irreversible capacity, low initial Coulomb efficiency, and poor conductivity. Natural graphite itself has the advantage of being suitable as a deposited substrate due to its pore structure and excellent conductivity, but the irregular structure of natural graphite pores results in poor dispersion uniformity of the filler material. Furthermore, natural graphite also has the disadvantages of poor structural stability, large volume expansion, and poor cycle performance.

[0086] Therefore, conventional methods cannot produce a negative electrode active material that possesses high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability.

[0087] The present inventors have found through research that by providing a filler with high specific capacity in the pore structure of a carbon substrate with a low degree of graphitization (greater than 0 and 87% or less), the resulting negative electrode active material can possess high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability, and the secondary battery can possess high energy density, high initial Coulomb efficiency, and long cycle life. The degree of graphitization of the carbon substrate of the present invention is 87% or less, and compared to the carbon substrate obtained by pore formation with the above-mentioned pore-forming agent, it has the advantages of higher conductivity and higher initial Coulomb efficiency, and compared to natural graphite, it has the advantages of lower volume expansion and higher cycle stability. Therefore, the negative electrode active material according to the present invention can fully utilize the advantage of the high specific capacity of the filler and can compensate for the disadvantages of the filler having poor conductivity and low initial Coulomb efficiency. In addition, since at least a portion of the filler is located in the pore structure of the carbon substrate, the volume expansion of the filler can be reduced by the carbon substrate.

[0088] In this application, the degree of graphitization of the carbon substrate is 87% or less, and may be, for example, 85% or less, 80% or less, 75% or less, or 70% or less. If the degree of graphitization of the carbon substrate exceeds 87%, the volume expansion of the carbon substrate during the charge-discharge process is large, resulting in poor structural stability, which affects the cycle stability and cycle life of the negative electrode active material. When the degree of graphitization of the carbon substrate decreases, its structural stability improves, which is advantageous in improving the cycle stability of the negative electrode active material and extending the cycle life of the secondary battery.

[0089] The inventors of this application have found through further research that a low degree of graphitization of the carbon substrate is also undesirable. In this case, the initial Coulomb efficiency and conductivity are poor, and the improvement effect of the negative electrode active material on the initial Coulomb efficiency and conductivity becomes less significant. For example, the degree of graphitization of the carbon substrate may be 10% or more, 20% or more, 30% or more, 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, or 65% or more.

[0090] In some embodiments, the degree of graphitization of the carbon substrate may be 40% to 87%, 50% to 87%, 60% to 87%, 65% to 87%, 65% to 85%, 65% to 82%, or 65% to 80%. This is advantageous for the negative electrode active material to better combine high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity, and good cycle stability.

[0091] In some embodiments, at least a portion of the filler is located within the pore structure of the carbon substrate, and there is a gap between the filler and the carbon substrate. When there is a gap between the filler and the carbon substrate, this gap can accommodate the volume expansion of the filler, thereby easing the stress generated during the expansion process of the filler, and thereby further reducing the probability of particle crushing and pulverization.

[0092] In some embodiments, the elements that can react with Li in an alloy are selectively selected to include one or more elements from silicon, tin, and germanium. This is advantageous because the negative electrode active material has the benefit of high specific capacity.

[0093] In some embodiments, the filler includes one or more types of silicon-based materials, tin-based materials, and germanium-based materials, and optionally includes silicon-based materials.

[0094] In this application, the term "silicon-based material" means a compound containing the element silicon. In some embodiments, the silicon-based material may include one or more of the following: elemental silicon, silicon oxides, silicon-carbon materials, silicon-nitrogen composites, and silicon alloys.

[0095] In this application, the term "tin-based material" means a compound containing the element tin. In some embodiments, the tin-based material may include one or more of the following: elemental tin, tin oxide, tin sulfide, tin phosphate, tin composite oxide, tin carbon material, and tin alloy material. A tin composite oxide refers to a tin oxide into which several glassy phase metal and / or nonmetallic oxides have been introduced.

[0096] In this application, the term "germanium-based material" means a compound containing the element germanium. In some embodiments, the germanium-based material may include one or more of the following: elemental germanium, germanium oxide, germanium carbon material, germanium alloy material, and germanate.

[0097] In some embodiments, the filler may include crystalline fillers and / or amorphous fillers.

[0098] In some embodiments, the filler includes crystalline silicon-based materials and / or amorphous silicon-based materials. Silicon-based materials have the advantage of high specific capacity, which is beneficial for improving the energy density of secondary batteries. Optionally, the filler includes elemental crystalline silicon and / or elemental amorphous silicon.

[0099] In some embodiments, the grain size of the crystalline filler is 100 nm or less, and may be, for example, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, or 20 nm or less. Selectively, the grain size of the crystalline filler is 2 nm to 50 nm, 2 nm to 40 nm, 2 nm to 30 nm, or 2 nm to 20 nm.

[0100] While a larger grain size in crystalline fillers is advantageous for improving the initial Coulombic efficiency of a secondary battery, it is disadvantageous for the battery's cycle performance and storage performance. Therefore, when the crystalline filler has an appropriate grain size, it is possible to improve the initial Coulombic efficiency of the secondary battery while avoiding significant adverse effects on its cycle performance and storage performance.

[0101] The grain size of crystalline fillers is a known concept in this art and can be measured using known instruments and methods. For example, it can be tested and measured using a high-resolution transmission electron microscope (HRTEM).

[0102] In some embodiments, the filler can be obtained by a vapor deposition process. For example, the filler may include one or more vapor-deposited silicon-based materials, tin-based materials, and germanium-based materials, selectively comprising vapor-deposited silicon-based materials, and more selectively comprising vapor-deposited silicon. The vapor deposition process includes physical vapor deposition processes and chemical vapor deposition processes, selectively being a chemical vapor deposition process, which may be, for example, a thermochemical vapor deposition process, a plasma-enhanced chemical vapor deposition process, or a microwave plasma-enhanced chemical vapor deposition process. Compared to liquid-phase deposition processes, vapor deposition processes are advantageous for good deposition and uniform dispersion of the filler in the pore structure of a carbon substrate, and can avoid problems of filler aggregation and / or large-scale deposition on the surface of the carbon substrate. Furthermore, vapor deposition processes are mature and readily available for industrial mass production.

[0103] In some embodiments, the X-ray diffraction spectrum of the negative electrode active material measured by an X-ray diffractometer includes a (002) crystal plane peak at 26.4° and a (111) crystal plane peak at 28.6°, and the ratio of the full width at half maximum (FMAX) of the (002) crystal plane peak to the full width at half maximum (FMAX) of the (111) crystal plane peak is 0.2 to 50, and may be in the range of any number, for example, 0.2, 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 or higher. Selectively, the ratio of the full width at half maximum (FMAX) of the (002) crystal plane peak to the full width at half maximum (FMAX) of the (111) crystal plane peak is 0.2 to 20.

[0104] The full width at half maximum (FWHM) of the (002) crystal plane peak and the (111) crystal plane peak can be determined by calculating the crystal lattice constant using an X-ray diffractometer (e.g., Bruker D8 Discover) in reference to JIS K0131-1996, searching for peaks using the centroid method to obtain the C 002 peak position and Si 111 peak position of two parallel samples, and the test angle range may be 20° to 80°.

[0105] The full width at half maximum (FWHM) of the (002) crystal plane peak can characterize the alignment integrity of the (002) crystal plane in the carbon substrate, and the full width at half maximum (FWHM) of the (111) crystal plane peak can characterize the content of elemental silicon in the packing material and the crystal grain size of elemental silicon. By controlling the FWHM of the (002) crystal plane peak and the FWHM of the (111) crystal plane peak to be within an appropriate range, the carbon substrate can be made to have an appropriate degree of graphitization and the packing material can have an appropriate crystal grain size, which is advantageous for the negative electrode active material to have a high specific capacity, high initial Coulomb efficiency, low volume expansion, high conductivity and good cycle stability.

[0106] In some embodiments, the negative electrode active material further includes a coating layer located on at least a portion of the surface of the carbon substrate. The coating layer prevents direct contact between the filler and the electrolyte, thereby reducing side reactions of the electrolyte, decreasing the consumption of active ions, improving the cycle performance of the secondary battery, and improving the stability of the negative electrode slurry, thus avoiding increased processing difficulty of the negative electrode slurry due to the filler reacting with solvent water, etc. Furthermore, the coating layer also plays a role in mitigating the volume expansion of the filler, which is advantageous in improving the structural stability of the negative electrode active material and improving the electrochemical performance of the secondary battery.

[0107] In some embodiments, the coating layer optionally comprises one or more of the following: carbon materials, conductive polymers, metal oxides, and metal sulfides.

[0108] In some embodiments, the carbon material includes one or more types of hard carbon, soft carbon, graphene, carbon fibers, and carbon nanotubes.

[0109] In some embodiments, the conductive polymer comprises one or more of polyaniline, polypyrrole, and polythiophene.

[0110] In some embodiments, the metal oxide includes one or more of iron oxide, zinc oxide, tin oxide, copper oxide, and titanium oxide.

[0111] In some embodiments, the metal sulfide includes one or more of the following: tin sulfide, molybdenum sulfide, titanium sulfide, iron sulfide, and copper sulfide.

[0112] In some embodiments, the coating layer includes a carbon material. This allows the coating layer to increase the specific capacity of the negative electrode active material by preventing direct contact between the filler and the electrolyte, buffering the volume expansion of the filler, and also providing some capacity. Furthermore, when the coating layer includes a carbon material, it also contributes to improving the conductivity of the filler, especially silicon-based materials, which is advantageous for further increasing the capacity of the negative electrode active material.

[0113] In some embodiments, the thickness of the coating layer is 100 nm or less, and selectively between 10 nm and 100 nm. When the thickness of the coating layer is within the above range, the integrity of the coating layer is higher, and contact between the filler and the electrolyte can be more effectively avoided, which is advantageous in reducing side reactions of the electrolyte and providing the negative electrode active material with high specific capacity, high initial Coulomb efficiency, and low volume expansion. When the thickness of the coating layer is greater than 100 nm, the integrity is better, but brittleness increases, making it more prone to crushing and pulverization during repeated charge and discharge cycles, and also reducing the specific capacity of the negative electrode active material.

[0114] In some embodiments, the negative electrode active material includes carbon and elements capable of alloying with Li.

[0115] In some embodiments, the mass percentage of the carbon element in the negative electrode active material is 20 wt% to 80 wt%, and may be, for example, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, or any of these values. Optionally, the mass percentage of the carbon element in the negative electrode active material is 30 wt% to 70 wt%. The distribution region of the carbon element is not specifically limited and may be located, for example, in at least one of the carbon substrate, the filler, and the coating layer.

[0116] In some embodiments, the mass percentage of elements capable of alloying with Li in the negative electrode active material is 20 wt% to 80 wt%, and may be, for example, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, or any of these values. Optionally, the mass percentage of elements capable of alloying with Li in the negative electrode active material is 30 wt% to 70 wt%. Optionally, the elements capable of alloying with Li include silicon.

[0117] If the content of carbon and / or elements capable of alloying with Li in the negative electrode active material is within the above range, it is advantageous for the negative electrode active material to possess both high specific capacity and high conductivity.

[0118] In some embodiments, the negative electrode active material further comprises elements other than carbon and elements capable of alloying with Li. These other elements include one or more of oxygen, metallic, and nitrogen elements. The distribution region of these other elements is not specifically limited and may be located, for example, in at least one of the coating layer, the filler, and the carbon substrate.

[0119] In some embodiments, selectively, the total mass percentage of the other elements in the negative electrode active material is 20 wt% or less, more selectively, 10 wt% or less, and 5 wt% or less.

[0120] In some embodiments, the initial Coulomb efficiency of the carbon substrate is 75% or higher, and selectively between 75% and 87%. This is advantageous for improving the initial Coulomb efficiency of the negative electrode active material.

[0121] In some examples, the powder resistivity of the carbon substrate at a pressure of 16 MPa was 5 × 10⁻⁶. -2 It is less than or equal to Ω·cm, and is selectively 3.5 × 10 -2 It is less than Ω·cm. This is advantageous for improving the conductivity of the negative electrode active material.

[0122] In some examples, the BET specific surface area of ​​the carbon substrate is 50 m². 2 / g~1000m 2 It is / g, and can be selected as 100m 2 / g~700m 2 This is advantageous because the negative electrode active material has an appropriate BET specific surface area, thereby reducing the surface activity of the negative electrode active material, decreasing interfacial side reactions, reducing the film deposition consumption of the SEI film, and further improving the initial Coulomb efficiency and cycle performance of the secondary battery.

[0123] In some embodiments, the degree of graphitization of the negative electrode active material is 65% or higher, and selectively between 65% and 87%. This is advantageous for the negative electrode active material to better combine high initial Coulomb efficiency, high conductivity, and good cycle stability.

[0124] In some embodiments, the initial Coulomb efficiency of the negative electrode active material is 92% or higher, and selectively between 92% and 95%. This reduces the irreversible consumption of active ions and improves the capacity and cycle performance of the secondary battery.

[0125] In some embodiments, the volume particle size Dv50 of the negative electrode active material is 3 μm to 50 μm, and selectively 5 μm to 20 μm.

[0126] In some embodiments, the volume particle size Dv90 of the negative electrode active material is 60 μm or less, and selectively between 20 μm and 50 μm.

[0127] In some embodiments, the particle size distribution width (Dv90-Dv10) / Dv50 of the negative electrode active material is 1.0 to 3.0, and selectively between 1.0 and 2.0.

[0128] If at least one of the volume particle size Dv50, volume particle size Dv90, and particle size distribution width (Dv90-Dv10) / Dv50 of the negative electrode active material is within the above range, it contributes to reducing the surface activity of the negative electrode active material, reducing interfacial side reactions, and reducing the film deposition consumption of the SEI film. Furthermore, it is advantageous for improving the active ion and electron transmission performance, and can further improve the cycle performance of the secondary battery.

[0129] In some embodiments, the BET specific surface area of ​​the negative electrode active material is 2m². 2 / g~100m 2 / g, and selectively, 2m 2 / g~30m 2 / g is 2m 2 / g~20m 2 The value is / g. When the BET specific surface area of ​​the negative electrode active material is within the above range, it contributes to reducing surface activity, reducing interfacial side reactions, and reducing the film formation consumption of the SEI film, thereby improving the initial Coulomb efficiency and cycle performance of the secondary battery.

[0130] In some embodiments, the powder resistivity of the negative electrode active material at a pressure of 16 MPa is 5 × 10⁻⁶. -1 It is less than or equal to Ω·cm, and selectively, 2 × 10 -1 The conductivity is Ω·cm. As a result, the negative electrode active material has good conductivity, which is advantageous for improving the cycle performance and rate performance of secondary batteries.

[0131] In this application, the volume particle sizes Dv10, Dv50, and Dv90 of the material (e.g., negative electrode active material, carbon substrate, etc.) have meanings known in the art, and represent the particle sizes corresponding to when the cumulative percentage of the material's volume reaches 10%, 50%, and 90%, respectively, and can be measured with instruments and methods known in the art. For example, they can be easily measured using a laser particle size analyzer, referring to GB / T 19077-2016. The test instrument may be a Mastersizer 3000 laser particle size analyzer from Malvern, UK.

[0132] In this application, the BET specific surface area of ​​a material (e.g., negative electrode active material, carbon substrate, etc.) has a meaning known in the art and can be measured with instruments and methods known in the art. For example, it can be tested by employing the nitrogen gas adsorption specific surface area analysis test method, referring to GB / T 19587-2017, and calculated by the BET (Brunauer Emmett Teller) method. The nitrogen gas adsorption specific surface area analysis test can be performed using a specific surface area and void ratio analyzer, such as the TRISTAR II 3020, manufactured by Micromeritics, Inc., USA.

[0133] In this application, the powder resistivity of a material (e.g., negative electrode active material, carbon substrate, etc.) has a meaning known in the art and can be measured with instruments and methods known in the art. For example, a powder sample of a certain mass may be placed in the sample cup of a resistivity tester, a certain pressure may be applied, and then data may be artificially collected to record the test results of the powder resistivity of the sample at different pressures. In this application, the test pressure may be 16 MPa.

[0134] In this application, the degree of graphitization of a material (e.g., negative electrode active material, carbon substrate, etc.) has a meaning known in the art and can be measured with instruments and methods known in the art. For example, referring to JIS K 0131-1996, the interplanar spacing d of the crystal planes can be measured using an X-ray diffractometer (Bruker D8 Discover). 002 After obtaining the equation g=(0.3440-d 002The degree of graphitization of the material is calculated based on ) / (0.3440-0.3354)×100%.

[0135] In this application, the content of each element in the negative electrode active material can be measured using instruments and methods known in the art. For example, the carbon content can be measured by referring to GB / T 20123-2006 / ISO 15350:2000, and the test instrument may be an HCS-140 infrared carbon-sulfur analyzer. The silicon content may be measured by referring to GB / T 20975.5-2020. The tin content in the negative electrode active material may be measured by referring to GB / T 20975.10-2020. The germanium content may be measured by referring to GB / T 20127.6-2006. Manufacturing method

[0136] A second embodiment of the present invention provides a method for producing a negative electrode active material that can produce the negative electrode active material according to the first embodiment of the present invention.

[0137] The above method comprises the steps of: 1) providing a carbon substrate having a degree of graphitization of 87% or less, selectively between 65% and 87%, and including a plurality of pore structures; and 2) dispersing a filler in the pore structure of the carbon substrate to obtain a negative electrode active material, wherein the negative electrode active material includes a carbon substrate and a filler, the carbon substrate includes a plurality of pore structures, at least a portion of the filler is located in the pore structure of the carbon substrate, and the filler includes one or more elements that can alloy with Li, and selectively, the elements that can alloy with Li include one or more elements from silicon, tin, and germanium.

[0138] In some embodiments, in step 1, the carbon substrate is produced by placing a carbon source containing multiple pore structures into a high-temperature furnace, performing a graphitization treatment in a protective gas atmosphere at 1600°C to 2400°C, and then obtaining the carbon substrate after completion. For example, the graphitization treatment may be performed in a range consisting of 1600°C, 1700°C, 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, 2400°C, or any value above. This makes it possible to obtain a carbon substrate with a graphitization degree of 87% or less, selectively between 65% and 87%, and having multiple pore structures.

[0139] If the graphitization temperature is too low, the resulting carbon substrate remains non-graphitizable carbon (or amorphous carbon), resulting in high irreversible capacity, low initial Coulomb efficiency, and poor conductivity, which affects the initial Coulomb efficiency and cycle performance of the secondary battery. If the graphitization temperature is too high, the resulting carbon substrate undergoes large volume expansion during the charge-discharge process, resulting in poor structural stability, which affects the cycle stability of the negative electrode active material and the cycle performance of the secondary battery.

[0140] In some embodiments, the heating rate of the high-temperature furnace is selectively 10°C / min or less, for example, 8°C / min or less, and 5°C / min or less.

[0141] In some embodiments, the holding time for the graphitization treatment is selectively 1h to 12h, and may be in the range of, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any other number above.

[0142] In some embodiments, the carbon source may optionally include one or more of the following: hard carbon, petroleum coke, pitch coke, biomass carbon, and resin carbon.

[0143] In some embodiments, the high-temperature furnace is selectively one of the following graphitization furnaces: a box-type graphitization furnace, an Acheson-type graphitization furnace, a continuous graphitization furnace, and a lengthwise graphitization furnace.

[0144] In step 1, the carbon source for producing the carbon substrate is of a variety of types, is abundant in nature, is inexpensive, and the production process for the carbon substrate is simple. The carbon source containing the plurality of pore structures may be directly commercially available or may be produced according to methods known in the art, for example, by etching holes using an alkaline pore-forming agent.

[0145] By graphitizing a carbon source containing multiple pore structures at a constant temperature, the number of micropores in the carbon source is reduced, improving the uniformity of the dispersion of the subsequent filler. At the same time, excess chemical bonds on the surface of the carbon source are removed, reducing the content of oxygen-containing functional groups in the carbon source and decreasing side reactions in the electrolyte. As a result, the initial Coulomb efficiency, conductivity, and high-temperature performance of the obtained carbon substrate are improved, and the secondary battery can be given good cycle performance.

[0146] In some embodiments, in step 1, the initial Coulomb efficiency of the carbon substrate is 75% or higher, and selectively between 75% and 87%.

[0147] In some embodiments, in step 1, the powder resistivity of the carbon substrate at a pressure of 16 MPa is 5 × 10⁻⁶. -2 It is less than or equal to Ω·cm, and selectively, 3.5 × 10 -2 It is less than or equal to Ω·cm.

[0148] In some embodiments, in step 1, the BET specific surface area of ​​the carbon substrate is 50 m². 2 / g~1000m 2 It is / g, and can be selected as 100m 2 / g~700m 2 It is / g.

[0149] In some examples, in step 1, the volume particle size Dv50 of the carbon substrate is 3 μm to 50 μm, and selectively 5 μm to 20 μm.

[0150] In some embodiments, step 2 includes a liquid-phase deposition process and a gas-phase deposition process, and is selectively a gas-phase deposition process. Compared to the liquid-phase deposition process, the gas-phase deposition process is advantageous for well depositing and uniformly dispersing the filler in the pore structure of the carbon substrate, and can avoid problems of filler aggregation and / or large-scale deposition on the surface of the carbon substrate. Furthermore, the gas-phase deposition process is mature and easily applicable to industrial mass production.

[0151] In some embodiments, the vapor deposition process may optionally include a chemical vapor deposition process and a physical vapor deposition process, and more optionally, it may be a chemical vapor deposition process, such as a thermochemical vapor deposition process, a plasma-enhanced chemical vapor deposition process, or a microwave plasma-enhanced chemical vapor deposition process.

[0152] In some embodiments, step 2, the step of dispersing the filler in the pore structure of the carbon substrate, includes placing the carbon substrate in a reaction furnace, introducing a first mixed gas containing a source of elements capable of alloying with Li, depositing at a first temperature T1 for a first time t1, and obtaining a negative electrode active material after completion.

[0153] In some embodiments, the first mixture optionally includes a source of elements that can alloy with the Li and a protective gas.

[0154] In some embodiments, the volume occupancy of the source of elements capable of alloying with Li in the first mixture is selectively 10% to 50%, and may be in the range of any number, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or higher.

[0155] In some embodiments, the first mixture may further contain a carbon source gas.

[0156] In some embodiments, the volume ratio of the source of elements capable of alloying with Li to the carbon source gas is selectively 0.5:1 or greater, and selectively (2-10):1. When the volume ratio of the source of elements capable of alloying with Li to the carbon source gas is within the above range, it is advantageous for the negative electrode active material to have a high specific capacity. If the volume ratio of the two is too small, the carbon content in the resulting filler becomes high, the content of elements capable of alloying with Li becomes low, and consequently, the effect of improving the negative electrode active material capacity becomes less significant.

[0157] In some embodiments, the volume occupancy of the carbon source gas in the first mixture is selectively 20% or less, and more selectively 5% to 20%. In this case, it is advantageous for the negative electrode active material to possess both high specific capacity and high conductivity.

[0158] In some embodiments, the volume occupancy of the protective gas in the first mixture is selectively 30% to 90%, and may be in the range of any number, for example, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or higher.

[0159] In some embodiments, the total gas flow rate of the first mixture may be 0.5 L / min to 20 L / min. For example, it may be in the range of any value, such as 1 L / min, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 12 L / min, 14 L / min, 16 L / min, 18 L / min, 20 L / min, or higher.

[0160] In some embodiments, the pressure inside the reactor may be a micro positive pressure, for example, 200 Pa to 600 Pa higher than atmospheric pressure, which is advantageous for the deposition process to proceed smoothly.

[0161] In some embodiments, the reactor includes, but is not limited to, a growth furnace, a rotary kiln, a tubular furnace, and a fluidized bed.

[0162] In some embodiments, the first temperature T1 may be between 400°C and 1000°C, and may be in the range of, for example, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, or any of the above values.

[0163] In some embodiments, the first time t1 may be between 1h and 12h, for example, within a range of 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, or any of the above values.

[0164] In the gas phase deposition process, adjusting at least one of the following—the composition ratio of the first gas mixture, the total gas flow rate of the first gas mixture, the first temperature, and the first time—to fall within the above range is advantageous for depositing the packing material into the pore structure of the carbon substrate, as well as for adjusting the crystallinity and / or grain size of the packing material to fall within an appropriate range.

[0165] In some embodiments, the method further includes step 3, which involves forming a coating layer on at least a portion of the negative electrode active material obtained in step 2, comprising one or more of the following: carbon material, conductive polymer, metal oxide, and metal sulfide.

[0166] The method for forming a coating layer on at least a portion of the surface of the negative electrode active material obtained in step 2 is not particularly limited and can be selected according to the composition of the coating layer, for example, solid-phase coating, liquid-phase coating or gas-phase coating may be employed.

[0167] In some embodiments, the step of forming the coating layer includes a step of mixing the negative electrode active material obtained in step 2 with the coating material, followed by a carbonization treatment. Optionally, the coating material includes one or more types of pitch (e.g., coal pitch, petroleum pitch, etc.) and polymer materials. Optionally, the temperature of the carbonization treatment is 500°C to 1000°C.

[0168] In some embodiments, the step of forming the coating layer includes placing the negative electrode active material obtained in step 2 into a reaction furnace, introducing a second mixture containing a carbon source gas, depositing at a second temperature T2 for a second time t2, and obtaining a carbon-coated negative electrode active material after completion.

[0169] In some embodiments, the second mixture comprises a carbon source gas and a protective gas, and optionally, the volume occupancy V2 of the carbon source gas in the second mixture is 5% to 50%, and may be in the range of, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any of the above values.

[0170] In some embodiments, the total gas flow rate of the second mixture is 0.5 L / min to 20 L / min. For example, it may be in the range of 0.8 L / min, 1 L / min, 2 L / min, 3 L / min, 4 L / min, 5 L / min, 6 L / min, 7 L / min, 8 L / min, 9 L / min, 10 L / min, 12 L / min, 14 L / min, 16 L / min, 18 L / min, 20 L / min, or any of the above values.

[0171] In some embodiments, the second temperature T2 is 700°C to 850°C, and may be, for example, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, or any of the above values.

[0172] In some embodiments, the second time t2 is 1h to 6h, and may be in the range of, for example, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or any of the above values.

[0173] In step 3, adjusting at least one of the composition ratio of the second mixture, the total gas flow rate of the second mixture, the second temperature, and the second time to be within the above range is advantageous for forming a coating layer of appropriate thickness and avoids reducing the specific capacity of the negative electrode active material due to the coating layer being too thick.

[0174] In this application, the term "protective gas" includes one or more types of nitrogen gas and noble gases, and optionally, the noble gas may include one or more types of argon gas, helium gas, etc.

[0175] In this application, the term "source of elements capable of alloying with Li" means a gas capable of forming the filler of this application, and may include, for example, one or more of silicon source gas, tin source gas, and germanium source gas.

[0176] The silicon source gas is a gas capable of forming the silicon-based material of the present invention. Selectively, the silicon source gas may be monosilane (H4Si), disilane (H6Si2), trisilane (H8Si3), tetrachlorosilane (Cl4Si), trichlorosilane (Cl3HSi), dichlorosilane (Cl2H2Si), monochlorosilane (ClH3Si), silicon tetrafluoride (F4Si), trifluorosilane (F3HSi), difluorosilane (F2H2Si), or monofluorosilane (FH3Si). , hexachlorodisilane (Cl6Si2), pentachlorodisilane (Cl5HSi2), tetrachlorodisilane (Cl4H2Si2 and also containing 1,1,2,2-tetrachlorodisilane and 1,1,1,2-tetrachlorodisilane), trichlorodisilane (Cl3H3Si2 and also containing 1,1,2-trichlorodisilane and 1,1,1-trichlorodisilane), dichlorodisilane (Cl2H4Si2 and It may contain one or more of the following: 1,1-dichlorodisilane (including 1,1-dichlorodisilane and 1,2-dichlorodisilane), monochlorodisilane (ClH5Si2), hexafluorodisilane (F6Si2), pentafluorodisilane (F5HSi2), 1,1,2,2-tetrafluorodisilane (F4H2Si2), 1,1,1-trifluorodisilane (F3H3Si2), difluorodisilane (F2H4Si2, and including 1,1-difluorodisilane and 1,2-difluorodisilane), monofluorodisilane (FH5Si2), methylsilane, ethylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, methyldisilane, dimethyldisilane, trimethyldisilane, tetramethyldisilane, hexamethylsilane, methyltrichlorosilane, methylchlorosilane, chloroethylsilane, dichlorodimethylsilane, and dichlorodiethylsilane.

[0177] The tin source gas is a gas capable of forming the tin-based material of this application. Selectively, the tin source gas includes, but is not limited to, one or more of the following: stannan (H4Sn), Cl4Sn, Cl3HSn, Cl2H2Sn, ClH3Sn, F4Sn, F3HSn, F2H2Sn, and FH3Sn.

[0178] The germanium source gas is a gas capable of forming the germanium-based material of the present invention. Selectively, the germanium source gas includes, but is not limited to, one or more of monogermane (H4Ge), Cl4Ge, and F4Ge.

[0179] In this application, “carbon source gas” means a gas capable of forming a carbon material. Optionally, the carbon source gas includes, but is not limited to, one or more of the following: methane, ethane, propane, isopropane, butane, isobutane, ethylene, propylene, butene, acetylene, chloroethane, fluoroethane, difluoroethane, chloromethane, fluoromethane, difluoromethane, trifluoromethane, vinyl chloride, fluoroethylene, difluoroethylene, methylamine, formaldehyde, benzene, toluene, xylene, styrene, and phenol.

[0180] Unless otherwise specified, all raw materials and equipment used in the manufacturing method of this invention are commercially available. secondary battery

[0181] A third aspect of the embodiments of the present invention provides a secondary battery.

[0182] A secondary battery as referred to in the embodiments or examples of this application is a single physical module comprising one or more battery cells that provides higher voltage and capacity. For example, a secondary battery as referred to in this application may include battery cells, battery modules, or battery packs. A battery cell is the smallest unit constituting a secondary battery and can independently perform charging and discharging functions. The shape of the battery cell in this application is not particularly limited and may be cylindrical, prismatic, or any other shape. Figure 1 shows a prismatic battery cell 5 as an example.

[0183] In some embodiments, the battery cell includes an electrode assembly, and the cell battery may further include an outer casing. The electrode assembly is manufactured from a positive electrode sheet, a negative electrode sheet, and a separator, etc., by a winding process and / or a lamination process, and the outer casing can be used to package the electrode assembly. The outer casing may be a hard case, such as a rigid plastic case, an aluminum case, or a steel case. The outer casing may also be a soft package, such as a bag package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0184] In some embodiments, as shown in Figure 2, the exterior may comprise a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing each other to form a housing chamber. The housing 51 has an opening that communicates with the housing chamber, and the cover plate 53 covers the opening to seal the housing chamber. The electrode assembly 52 is packaged in the housing chamber. The number of electrode assemblies 52 included in the battery cell 5 may be one or more and may be adjusted as required.

[0185] In some embodiments of the present invention, the battery cells may be assembled as a battery module, and the number of battery cells included in the battery module may be multiple, with the specific number being adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, multiple battery cells 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the multiple battery cells 5 may be fixed by fasteners.

[0186] Optionally, the battery module 4 further includes a housing having a housing space, and a plurality of battery cells 5 are housed in the housing space.

[0187] In some embodiments, the battery modules may be assembled as a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack. Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery case and a plurality of battery modules 4 provided in the battery case. The battery case includes an upper case 2 and a lower case 3, the upper case 2 covering the lower case 3 and forming a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery case in any manner.

[0188] This application does not impose any particular restrictions on the type of secondary battery, and for example, secondary batteries include, but are not limited to, lithium-ion batteries and sodium-ion batteries. [Negative electrode sheet]

[0189] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0190] In some embodiments, the negative electrode film layer includes a negative electrode active material according to the first embodiment of the present invention or a negative electrode active material manufactured by the method described in the second embodiment of the present invention. This enables the secondary battery to have high energy density, high initial Coulomb efficiency, and long cycle life. In some embodiments, the negative electrode film layer may further include other negative electrode active materials other than the negative electrode active material. In some embodiments, the other negative electrode active material includes, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, elemental silicon, silicon oxide, silicon nitrogen composite, silicon alloy material, elemental tin, tin oxide, tin alloy material, and lithium titanate. The present invention is not limited to these materials, and other conventionally known materials used as negative electrode active materials for secondary batteries may be used.

[0191] In some embodiments, the negative electrode film layer may optionally further contain a negative electrode conductive agent. The type of the negative electrode conductive agent is not particularly limited in this application. For example, the negative electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, kecheng black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0192] In some embodiments, the negative electrode film layer may further include a negative electrode adhesive. In this application, the type of negative electrode adhesive is not particularly limited. For example, the negative electrode adhesive may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0193] In some embodiments, the negative electrode film layer may further contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC-Na) or PTC thermistor material.

[0194] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. Copper foil can be used as an example of the metal foil sheet. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more types from copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more types from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0195] The negative electrode film layer is generally formed by applying a negative electrode slurry to a negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a selectable conductive agent, a selectable adhesive, and other selectable auxiliary agents in a solvent and stirring them uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0196] The negative electrode sheet does not exclude any additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet according to the present invention may further include a conductive primer layer (e.g., including a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and provided on the surface of the negative electrode current collector. In some embodiments, the negative electrode sheet according to the present invention may further include a protective layer covering the surface of the negative electrode film layer. [Positive electrode sheet]

[0197] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector and containing a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in the thickness direction of itself, and the positive electrode film layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0198] The positive electrode film layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material used in secondary batteries known in this field.

[0199] When the secondary battery of this application is a lithium-ion battery, the positive electrode active material may include one or more of the following: lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and modified compounds thereof. Examples of lithium transition metal oxides may include one or more of the following: lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include one or more of the following: lithium iron phosphate, composite materials of lithium iron phosphate and carbon, lithium manganese phosphate, composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon, and modified compounds thereof. This application is not limited to these materials, and other conventionally known materials used as positive electrode active materials for secondary batteries may be used.

[0200] In some embodiments, in order to further increase the energy density of the secondary battery, the positive electrode active material used in the lithium-ion battery has the general formula Li a Ni b Co c M d O e A fIt may contain one or more of the lithium transition metal oxides and their modified compounds thereof. 0.8 ≦ a ≦ 1.2, 0.5 ≦ b < 1, 0 < c < 1, 0 < d < 1, 1 ≦ e ≦ 2, 0 ≦ f ≦ 1, M contains one or more selected from Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A contains one or more selected from N, F, S and Cl.

[0201] As an example, the cathode active material used in a lithium ion battery is LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4 and LiMnPO4 may contain one or more of them.

[0202] When the secondary battery of the present application is a sodium ion battery, the cathode active material may contain one or more of sodium-containing transition metal oxides, polyanion materials (for example, phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), Prussian blue-based materials, but is not limited thereto.

[0203] As an example, the cathode active material used in a sodium ion battery is NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue-based materials, and general formula X p M' q (PO4) r O x Y 3-x It may contain one or more of the materials that are General Formula X. p M' q (PO4) r O x Y 3-x In 0 <p≦4、0<q≦2、1≦r≦3、0≦x≦2であり、Xは、H + Li + kaNa + , K + and NH4 + It includes one or more of the following, where M' is a transition metal cation, selectively one or more of V, Ti, Mn, Fe, Co, Ni, Cu, and Zn, and Y is a halogen anion, selectively one or more of F, Cl, and Br.

[0204] In this application, the modified compound for each of the positive electrode active materials may be obtained by doping and / or surface coating modification of the positive electrode active material.

[0205] In some embodiments, the positive electrode film layer may optionally further contain a positive electrode conductive agent. In this application, the type of positive electrode conductive agent is not particularly limited, and as an example, the positive electrode conductive agent may include one or more of the following: superconducting carbon, conductive graphite, acetylene black, carbon black, kecheng black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0206] In some embodiments, the positive electrode film layer may optionally further contain a positive electrode adhesive. In this application, the type of positive electrode adhesive is not particularly limited, and for example, the positive electrode adhesive may contain one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a ternary copolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a ternary copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropylene, and a fluorine-containing acrylate resin.

[0207] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. An example of the metal foil sheet is aluminum foil. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more types from aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more types from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0208] The positive electrode film layer is generally formed by applying a positive electrode slurry to a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a selectable conductive agent, a selectable adhesive, and any other components in a solvent and stirring them uniformly. The solvent may, but is not limited to, N-methylpyrrolidone (NMP). [Electrolyte]

[0209] The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. In this application, the type of electrolyte is not particularly limited and can be selected as required. For example, the electrolyte may include one or more types selected from solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0210] In some embodiments, the electrolyte is an electrolyte solution, which comprises an electrolyte salt and a solvent.

[0211] If the secondary battery of the present application is a lithium-ion battery, the electrolyte salt may, for example, include one or more of the following: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium disoxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodisoxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0212] When the secondary battery of the present application is a sodium-ion battery, particularly a sodium-ion secondary battery, the electrolyte salt may include one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bisfluorosulfonylimide (NaFSI), sodium bistrifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium disoxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodisoxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0213] The type of solvent is not particularly limited and can be selected according to actual requirements. In some examples, the solvent may include, for instance, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0214] In some embodiments, the electrolyte may further contain additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve some aspects of the battery's performance, such as additives that improve the battery's overcharge performance, additives that improve the battery's high-temperature performance, and additives that improve the battery's low-temperature power performance. [Separator]

[0215] In secondary batteries using an electrolyte or a solid electrolyte, a separator is also included. The separator is provided between the positive electrode sheet and the negative electrode sheet and mainly serves to prevent short circuits between the positive and negative electrodes, while also allowing active ions to pass through. In this application, the type of separator is not particularly limited, and any known porous membrane having good chemical and mechanical stability can be selected.

[0216] In some embodiments, the material of the separator may include one or more of the following: glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. If the separator is a multilayer composite film, the materials of each layer may be the same or different. [Manufacturing method]

[0217] The method for manufacturing the secondary battery of the present invention is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, an electrode assembly can be formed by winding or laminating a positive electrode sheet, a separator, and a negative electrode sheet, the electrode assembly can be placed in an outer casing, dried, and then the electrolyte can be injected. A battery cell can then be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping. Multiple battery cells may further constitute a battery module in series, parallel, or series-parallel. Multiple battery modules may form a battery pack in series, parallel, or series-parallel. In some embodiments, multiple battery cells may directly constitute a battery pack. Electrical consumption device

[0218] Embodiments of the present invention further provide an electrical consumption device including a secondary battery of the present invention. The secondary battery may be used as a power source for the electrical consumption device or as an energy storage means for the electrical consumption device. The electrical consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, tablet computers, laptop computers, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0219] The aforementioned power consumption device may, as required, select a specific type of secondary battery, such as a battery cell, battery module, or battery pack.

[0220] Figure 6 is a schematic diagram of an example of an electrical power consumption device. This device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this electrical power consumption device, a battery pack or battery module may be used as the power source.

[0221] As another example, the power-consuming device may be a mobile phone, tablet computer, or laptop computer. Such power-consuming devices are generally required to be thin, and may use battery cells as a power source. Examples

[0222] The following examples illustrate the disclosure of this application in more detail; however, these examples are merely illustrative, and it will be apparent to those skilled in the art that various modifications and changes can be made within the scope of the disclosure. All parts, percentages, and ratios described in the following examples are based on mass unless otherwise specified. All reagents used in the examples may be commercially available or synthesized according to conventional methods, and may be used as is without requiring further processing. The apparatus used in the examples is also commercially available. Example 1 (1) Manufacturing of negative electrode active material

[0223] Step 1: 1 kg of commercially available porous biomass carbon (BET surface area is 1545 m²) 2 The powder (which is 6 μm in volume particle size Dv50, and may also be obtained by pore formation with a pore-forming agent) was placed in a graphitization furnace, and the temperature was raised to 2400°C at a rate of 5°C / min under nitrogen gas protection to perform the graphitization treatment. The temperature was maintained at 2400°C for 2 hours, and after completion, it was cooled to room temperature to obtain a degree of graphitization of 87%, an initial Coulomb efficiency of 85%, and a powder resistivity of 5.5 × 10⁻⁶. -3 Ω cm, BET specific surface area 100m 2 Obtain a carbon substrate of / g

[0224] Step 2: The above carbon substrate is placed in a gas-phase deposition furnace, the temperature is raised to 500°C at a rate of 5°C / min, and the first mixture of 20% monosilane + 80% nitrogen gas (by volume) is introduced. The total gas flow rate is 5 L / min, the pressure inside the reactor is 200 Pa higher than atmospheric pressure, and the deposition reaction is 8 hours.

[0225] Step 3: The introduction of the first mixture is stopped, the temperature is further increased to 800°C at a rate of 5°C / min, a second mixture of 40% acetylene + 60% nitrogen gas (by volume) is introduced, the total gas flow rate is set to 0.8 L / min, the deposition reaction is carried out for 2 hours, after which it is cooled, discharged, and passed through a 325 mesh sieve to obtain the negative electrode active material. (2) Manufacturing of secondary batteries (full cells)

[0226] Manufacture of the negative electrode sheet: The negative electrode active material manufactured above, the conductive carbon black and carbon nanotubes as conductive agents, and polyacrylic acid as an adhesive were uniformly mixed at a mass ratio of 95:1.9:0.1:3, and then added to deionized water as a solvent. After stirring with a high-speed stirrer until the system becomes uniform, a negative electrode slurry with a solid content of 45% is obtained. The negative electrode slurry is uniformly coated on a copper foil as a negative electrode current collector, dried at 85°C, and cold-pressed to obtain a negative electrode sheet.

[0227] Manufacture of the positive electrode sheet: LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), carbon black (Super P) as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive were sufficiently stirred and mixed in an appropriate amount of solvent NMP at a mass ratio of 97:1:2 to form a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on the surface of an aluminum foil as a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode sheet.

[0228] Manufacture of the electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were uniformly mixed at a volume ratio of 20:20:60 to obtain an organic solvent. Then, LiPF6 was dissolved in the above organic solvent, and fluoroethylene carbonate (FEC) was added. The concentration of LiPF6 in the electrolyte is 1 mol / L, and the mass percentage of FEC is 5 wt%.

[0229] Manufacture of the separator: Celgard 2400 separator is used.

[0230] Manufacture of the secondary battery: The positive electrode sheet, separator, and negative electrode sheet were stacked and wound in sequence to obtain an electrode assembly. The electrode assembly was placed in an outer package, dried, and then the electrolyte was injected. After passing through processes such as vacuum encapsulation, standing, formation, and shaping, a secondary battery was obtained. (3) Manufacture of coin cells (half cells)

[0231] The negative electrode active material produced above, conductive carbon black as a conductive agent, and polyacrylic acid as an adhesive are uniformly mixed in a mass ratio of 8:1:1. This mixture is then added to ionized water for solvent removal, and stirred with a high-speed stirrer until the system is uniform to obtain a negative electrode slurry with a solid content of 45%. The negative electrode slurry is uniformly applied to copper foil, which is the negative electrode current collector, dried at 85°C, and cold-pressed to obtain an electrode sheet. A metallic lithium sheet is used as the counter electrode, and using a Celgard 2400 separator, the same electrolyte as used in the production of the secondary battery described above is injected and assembled to obtain a coin cell. Example 2-24

[0232] The method for manufacturing the secondary battery and coin cell is similar to that of Example 1, the only difference being that the parameters of the manufacturing process for the negative electrode active material have been adjusted. See Tables 1A and 1B for details. Comparative Example 1

[0233] The method for manufacturing the secondary battery and coin cell is similar to that of Example 1, the difference being that crystalline silicon coated with amorphous carbon is used as the negative electrode active material, and the thickness of the coating layer is 80 nm.

[0234] Step 1: Provide crystalline silicon particles with a volume particle size Dv50 of 500 nm.

[0235] Step 2: The crystalline silicon particles are placed in a rotary kiln, a mixture of 40% acetylene and 60% nitrogen gas (by volume) is introduced, the total gas flow rate is set to 0.8 L / min, and the deposition reaction is carried out at 800°C for 2 hours. After completion, the mixture is cooled and discharged to obtain a crystalline silicon material coated with amorphous carbon. Comparative Example 2

[0236] The method for manufacturing the secondary battery and coin cell is similar to that of Example 1, the only difference being that the parameters of the manufacturing process for the negative electrode active material have been adjusted.

[0237] Step 1: Flake graphite is mechanically crushed, classified, spheroidized, and purified to obtain natural spheroidal graphite.

[0238] Step 2: 1 kg of natural spheroidal graphite is placed in a gas-phase deposition furnace as the base, and the temperature is raised to 500°C at a rate of 5°C / min. A first gas mixture of 20% monosilane + 80% nitrogen gas (by volume) is introduced, with a total gas flow rate of 5 L / min. The pressure inside the reactor is 200 Pa higher than atmospheric pressure, and the deposition reaction is carried out for 8 hours.

[0239] Step 3: The introduction of the first mixture is stopped, the temperature is further increased to 800°C at a rate of 5°C / min, a second mixture of 40% acetylene + 60% nitrogen gas (by volume) is introduced, the total gas flow rate is set to 0.8 L / min, the deposition reaction is carried out for 2 hours, after which it is cooled, discharged, and passed through a 325 mesh sieve to obtain the negative electrode active material. Comparative Example 3

[0240] The method for manufacturing the secondary battery and coin cell is similar to that of Example 1, the only difference being that the parameters of the manufacturing process for the negative electrode active material have been adjusted. See Tables 1A and 1B for details. Comparative Example 4

[0241] The method for manufacturing the secondary battery and coin cell is similar to that of Example 1, the only difference being that the parameters of the manufacturing process for the negative electrode active material have been adjusted.

[0242] Step 1: Select 1 kg of porous biomass carbon and use it as the carbon substrate without graphitization treatment.

[0243] Step 2: The above carbon substrate is placed in a gas-phase deposition furnace, and the temperature is raised to 500°C at a rate of 5°C / min. A first mixture of 20% monosilane + 80% nitrogen gas (by volume) is introduced, the total gas flow rate is 5 L / min, and the pressure inside the reactor is 200 Pa higher than atmospheric pressure. The deposition reaction is carried out.

[0244] Step 3: The introduction of the first mixture is stopped, the temperature is further increased to 800°C at a rate of 5°C / min, a second mixture of 40% acetylene + 60% nitrogen gas (by volume) is introduced, the total gas flow rate is set to 0.8 L / min, the deposition reaction is carried out for 2 hours, after which it is cooled, discharged, and passed through a 325 mesh sieve to obtain the negative electrode active material. Test section (1) Testing of the degree of graphitization of carbon substrate and negative electrode active material

[0245] Referring to JIS K 0131-1996, the interplanar spacing d of the crystal planes (002) was determined using an X-ray diffractometer. 002 After obtaining the equation g=(0.3440-d 002 The degree of graphitization of the carbon substrate and negative electrode active material is calculated based on ) / (0.3440-0.3354)×100%. A Bruker D8 Discover X-ray diffractometer can be used as the test equipment. (2) Initial Coulomb efficiency test of carbon substrate

[0246] The carbon substrate prepared above, conductive carbon black as a conductive agent, and polyacrylic acid as an adhesive are uniformly mixed in a mass ratio of 8:1:1. This mixture is then added to deionized water as a solvent, and stirred with a high-speed stirrer until the system is uniform to obtain a negative electrode slurry with a solid content of 45%. The negative electrode slurry is uniformly applied to copper foil, which is the negative electrode current collector, dried at 85°C, and cold-pressed to obtain an electrode sheet. A metallic lithium piece is used as the counter electrode, and using a Celgard 2400 separator, the same electrolyte as in Example 1 is injected and assembled to obtain a coin cell.

[0247] After letting the coin cell stand for 4 hours, place it in a Land Battery Test System, discharge it to 5mV with a constant current of 0.05C, let it stand for 10 minutes, then discharge it to 5mV with a constant current of 50μA, and record the total discharge capacity of the coin cell. After letting the coin cell stand for 10 minutes, charge it to 2.0V with a constant current of 0.1C, and record the charge capacity of the coin cell. The initial Coulomb efficiency of the carbon substrate is equal to the charge capacity / total discharge capacity. (3) Test of powder resistivity of carbon substrate and negative electrode active material

[0248] Put a carbon matrix of fixed mass and a sample of negative electrode active material powder into the sample cup of a resistivity tester. After applying a certain pressure, collect data artificially and record the test results of the powder resistivity of the sample at different pressures. In this application, the test pressure may be 16 MPa. (4) Test of the specific surface area of the carbon matrix

[0249] Referring to GB / T 19587-2017, adopt the nitrogen gas adsorption specific surface area analysis test method for testing, and calculate the specific surface area of the carbon matrix by the BET (Brunauer Emmett Teller) method. The test equipment can adopt the TRISTAR II 3020 type specific surface area and porosity analyzer of Micromeritics, USA. (5) Test of the crystal grain size of the filler

[0250] After cutting out a sample from the middle region of the negative electrode active material particles using a Dual Beam Focused Ion Beam-Transmission Electron Microscope (Dual Beam FIB-SEM), test the crystal grain size of the filler by a High Resolution Transmission Electron Microscope (HRTEM). (6) Test of the content of each element in the negative electrode active material

[0251] Referring to GB / T 20123-2006 / ISO 15350:2000, measure the content of carbon element in the negative electrode active material, and the measuring instrument may be an HCS-140 type infrared carbon and sulfur analyzer. Referring to GB / T 20975.5-2020, measure the content of silicon element in the negative electrode active material. Referring to GB / T 20975.10-2020, measure the content of tin element in the negative electrode active material. Referring to GB / T 20127.6-2006, measure the content of germanium element in the negative electrode active material. (7) Test of the X-ray diffraction spectrum of the negative electrode active material

[0252] Referring to JIS K 0131-1996, the lattice constant of the crystal is calculated using an X-ray diffractometer, and the C 002 peak position and Si 111 peak position of two parallel samples are obtained using the centroid method. The test angle range may be 20° to 80°. From the X-ray diffraction spectrum of the negative electrode active material, the half-value widths of the (002) crystal plane peak at 26.4° and the (111) crystal plane peak at 28.6° can be obtained. The test equipment can use a Bruker D8 Discover X-ray diffractometer. (8) Test of the initial Coulomb efficiency of the negative electrode active material

[0253] After standing the coin cells manufactured in each of the above examples and comparative examples for 4 h, they were placed in a land battery tester and discharged to 5 mV at a constant current of 0.05C. After standing for 10 min, they were discharged to 5 mV at a constant current of 50 μA, and the total discharge capacity of the coin cells was recorded and used as the lithium insertion capacity. Then, after standing the coin cells for 10 min, they were charged to 2V at a constant current of 0.1C, and the charging capacity of the coin cells was recorded and used as the lithium desorption capacity. The initial Coulomb efficiency of the negative electrode active material = lithium desorption capacity / lithium insertion capacity. (9) Test of the cycle performance of the secondary battery

[0254] At 25°C, after fully charging the secondary battery manufactured above at 0.5C (100% SOC), it was fully discharged at 1C, and this was regarded as one cycle charge-discharge process. The discharge capacity at this time was recorded and used as the initial discharge capacity. The secondary battery was subjected to cycle charge-discharge tests according to the above method, and the discharge capacity after each cycle was recorded until the discharge capacity of the secondary battery decayed to 80% of the initial discharge capacity. The cycle performance of the secondary battery was characterized by the number of cycles at this time. The cycle performance is better as the number of cycles of the secondary battery is higher.

[0255]

Table 1A

Table 1B

[0256] Summarizing the test results in Table 2, it was found that by filling the pore structure of a carbon substrate with a graphitization degree of 87% or less with a filler material having the advantage of high specific capacity, such as silicon-based materials, tin-based materials, or germanium-based materials, the resulting negative electrode active material can achieve a combination of high specific capacity, high initial Coulomb efficiency, high conductivity, and good cycle stability. Furthermore, it was found that the secondary battery can be endowed with high energy density, high initial Coulomb efficiency, and a long cycle life. Summarizing the test results of Examples 1 to 7, it was found that when the graphitization degree of the carbon substrate was 65% to 87%, the conductivity of the manufactured negative electrode active material was better, the initial Coulomb efficiency was higher, reaching 92% or more, and the secondary battery also had a longer cycle life.

[0257] In the negative electrode active material according to the present invention, at least a portion of the filler material is located within the pore structure of the carbon substrate, thereby reducing the volume expansion of the filler material. Comparative Example 1 employs carbon-coated crystalline silicon as the negative electrode active material. Because crystalline silicon has a huge volume effect, the carbon layer on the surface has a finite protective effect on the crystalline silicon, and after multiple charge-discharge cycles, the carbon layer ruptures, leading to repeated destruction and reconstruction of the SEI film and increasing the irreversible depletion of active ions. Furthermore, as the number of charge-discharge cycles increases, the thickness of the SEI film also continues to increase, and the impedance of the secondary battery also increases. Therefore, the secondary battery manufactured in Comparative Example 1 has poor cycle performance.

[0258] Comparative Example 2 uses natural spheroidal graphite as the carbon substrate. While natural spheroidal graphite itself has a porous structure and can be used as a deposited base, and also has the advantage of excellent conductivity, the pore structure of natural spheroidal graphite is irregular, resulting in poor dispersion uniformity of the filler material. Furthermore, natural spheroidal graphite has defects such as poor structural stability and large volume expansion, which leads to poor cycle performance of the secondary battery, making it impossible to achieve a secondary battery with high energy density, high initial Coulomb efficiency, and long cycle life.

[0259] Comparative Example 3 shows that when the temperature used to graphitize porous biomass carbon in step 1 is higher than 2400°C, the degree of graphitization of the resulting carbon substrate is too high. As a result, the negative electrode active material produced at this time undergoes significant volume expansion during the charge-discharge process and has poor structural stability. Consequently, the cycle performance of the secondary battery deteriorates, making it impossible to achieve a secondary battery with high energy density, high initial Coulomb efficiency, and long cycle life.

[0260] Comparative Example 4 uses porous biomass carbon that has not been graphitized as the carbon substrate. In this case, the carbon substrate is non-graphitizable carbon, which has the disadvantages of high irreversible capacity, low initial Coulomb efficiency, and poor conductivity. As a result, the negative electrode active material produced from it has low initial Coulomb efficiency and poor conductivity, making it impossible to achieve a secondary battery with high energy density, high initial Coulomb efficiency, and long cycle life.

[0261] Furthermore, this application is not limited to the embodiments described above. The embodiments described above are for illustrative purposes only, and any configuration that is substantially identical to the technical idea and produces similar effects within the technical scope of this application is included. In addition, other forms constructed by combining some of the components of the embodiments, by applying various modifications to the embodiments that a person skilled in the art could conceive of, without departing from the spirit of this application, are also included in the scope of this application.

[0262] [Table 2A] [Table 2B]

Claims

1. A negative electrode active material comprising a carbon substrate and a filler, The degree of graphitization of the carbon substrate is 40% to 87%. The carbon substrate includes a plurality of pore structures, At least a portion of the filler is located in the pore structure of the carbon substrate, and The filler contains one or more elements that can react with Li in an alloying manner. The negative electrode active material, in an X-ray diffraction spectrum measured by an X-ray diffractometer, includes a (002) crystal plane peak at 26.4° and a (111) crystal plane peak at 28.6°, and the ratio of the full width at half maximum of the (002) crystal plane peak to the full width at half maximum of the (111) crystal plane peak is 0.2 to 50. Negative electrode active material.

2. The filler includes one or more types of silicon-based materials, tin-based materials, and germanium-based materials. The negative electrode active material according to claim 1.

3. The silicon-based material includes one or more types from among elemental silicon, silicon oxide, silicon carbon material, silicon nitrogen composite, and silicon alloy. The tin-based material includes one or more of the following: elemental tin, tin oxide, tin sulfide, tin phosphate, tin composite oxide, tin carbon material, and tin alloy material. The aforementioned germanium-based material includes one or more types from among elemental germanium, germanium oxide, germanium carbon material, germanium alloy material, and germanium salt. The negative electrode active material according to claim 2.

4. The filler includes a crystalline filler and / or an amorphous filler. The grain size of the crystalline filler is 100 nm or less. The negative electrode active material according to claim 1.

5. The negative electrode active material, in an X-ray diffraction spectrum measured by an X-ray diffractometer, includes a (002) crystal plane peak at 26.4° and a (111) crystal plane peak at 28.6°, and the ratio of the full width at half maximum of the (002) crystal plane peak to the full width at half maximum of the (111) crystal plane peak is 0.2 to 20. The negative electrode active material according to claim 1.

6. At least a portion of the filler is located in the pore structure of the carbon substrate, and A gap is provided between the filler and the carbon substrate. The negative electrode active material according to claim 1.

7. The negative electrode active material further includes a coating layer located on at least a portion of the surface of the carbon substrate, The coating layer comprises one or more of the following: carbon material, conductive polymer, metal oxide, and metal sulfide. The thickness of the coating layer is 100 nm or less. The negative electrode active material according to claim 1.

8. The negative electrode active material comprises a carbon element and an element capable of alloying with Li. The mass percentage of the carbon element in the negative electrode active material is 20 wt% to 80 wt%, The mass percentage of elements capable of alloying with Li in the negative electrode active material is 20 wt% to 80 wt%. The negative electrode active material according to claim 1.

9. The negative electrode active material further comprises other elements, the other elements comprising one or more of the elements oxygen, metals, and nitrogen. The total mass percentage of the other elements in the negative electrode active material is 20 wt% or less. The negative electrode active material according to claim 8.

10. The carbon substrate satisfies the following conditions: (1) The initial Coulomb efficiency of the carbon substrate is 75% or more; (2) The powder resistivity of the carbon substrate at a pressure of 16 MPa is 5 × 10 －２ It is less than or equal to Ω·cm; (3) The BET specific surface area of ​​the carbon substrate is 50 m². ２ / g to 1000m ２ / g is; The negative electrode active material according to claim 1.

11. The aforementioned negative electrode active material satisfies the following conditions: (1) The degree of graphitization of the negative electrode active material is 65% or more; (2) The initial Coulomb efficiency of the negative electrode active material is 92% or higher; (3) The volume particle size Dv50 of the negative electrode active material is 3 μm to 50 μm; (4) The volume particle size Dv90 of the negative electrode active material is 60 μm or less; (5) The particle size distribution width (Dv90-Dv10) / Dv50 of the negative electrode active material is 1.0 to 3.0; (6) The BET specific surface area of ​​the negative electrode active material is 2 m² ２ / g to 100m ２ / g is; (7) The powder resistivity of the negative electrode active material at a pressure of 16 MPa is 5 × 10 －１ It is less than or equal to Ω·cm; The negative electrode active material according to claim 1.

12. A method for producing a negative electrode active material according to Claim 1, Step 1 provides a carbon substrate having a degree of graphitization of 87% or less and containing multiple pore structures, The process includes step 2, in which a filler is dispersed in the pore structure of the carbon substrate to obtain a negative electrode active material, The negative electrode active material comprises a carbon substrate and a filler, the carbon substrate comprising a plurality of pore structures, at least a portion of the filler located in the pore structures of the carbon substrate, and the filler comprising one or more elements capable of alloying with Li. A method for producing a negative electrode active material.

13. In step 1, the carbon substrate is manufactured by placing a carbon source containing multiple pore structures into a high-temperature furnace, performing a graphitization treatment in a protective gas atmosphere at 1600°C to 2400°C, and then obtaining the carbon substrate after the treatment is completed. The heat retention time for the graphitization treatment is 1 to 12 hours. The carbon source includes one or more types selected from hard carbon, petroleum coke, pitch coke, biomass carbon, and resin carbon. The method according to claim 12.

14. In step 1, the carbon substrate satisfies the following conditions: (1) The initial Coulomb efficiency of the carbon substrate is 75% or more; (2) The powder resistivity of the carbon substrate at a pressure of 16 MPa is 5 × 10 －２ It is less than or equal to Ω·cm; (3) The BET specific surface area of the carbon matrix is 50 m ２ / g to 1000 m ２ / g; (4) The volume particle size Dv50 of the carbon substrate is 3 μm to 50 μm; The method according to claim 12.

15. In step 2, the step of dispersing the filler in the pore structure of the carbon substrate includes a liquid phase deposition process and a gas phase deposition process. The method according to claim 12.

16. In step 2, the step of dispersing the filler in the pore structure of the carbon substrate involves placing the carbon substrate into a reaction furnace, introducing a first mixture containing a source of elements capable of alloying with Li, and setting the temperature to a first temperature T １ First hour １ The process includes depositing and obtaining a negative electrode active material after completion. The first mixture includes a source of elements that can alloy with Li and a protective gas. The pressure inside the reactor is 200 Pa to 600 Pa higher than atmospheric pressure. The total gas flow rate of the first mixture is 0.5 L / min to 20 L / min. The first temperature T １ The temperature range is 400°C to 1000°C. The first time t １ It is 1 hour to 12 hours. The method according to claim 15.

17. The first mixture further contains a carbon source gas, The volume ratio of the source of elements capable of alloying with Li to the carbon source gas is 0.5:1 or greater. The volume occupancy rate of the carbon source gas in the first mixture is 20% or less. The method according to claim 16.

18. Step 3 further includes forming a coating layer on at least a portion of the surface of the negative electrode active material obtained in step 2, the coating layer comprising one or more types selected from carbon material, conductive polymer, metal oxide, and metal sulfide. The method according to claim 12.

19. The negative electrode active material obtained in step 2 is placed in the reactor, a second mixture containing a carbon source gas is introduced, and the second temperature T is set. ２ Then the second time t ２ The process includes a step of depositing and, after completion, obtaining a carbon-coated negative electrode active material. The second mixture includes a carbon source gas and a protective gas. The total gas flow rate of the second mixture is 0.5 L / min to 20 L / min. The second temperature T ２ The temperature range is 700°C to 850°C. The second time t ２ It is 1 to 6 hours. The method according to claim 18.

20. A secondary battery including a negative electrode sheet, The negative electrode sheet comprises the negative electrode active material described in any one of claims 1 to 11. Secondary battery.

21. An electrical consumption device including the secondary battery described in claim 20.

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