Composite negative electrode active material pellet

Abstract

The present application provides a composite negative electrode active material sphere, which comprises a substantially non-porous conductive metal core and a plurality of silicon or silicon compound particles distributed on the surface of the conductive metal core and partially embedded in the conductive metal core. The silicon or silicon compound particles maintain good contact with the conductive metal core when alloying or de-alloying with lithium, so that the composite negative electrode active material sphere has excellent conductivity.

Description

TECHNICAL FIELD

[0001] The present invention provides a negative electrode material for lithium batteries, in particular, a composite negative active material ball having a shared conductive metal core. BACKGROUND

[0002] Due to the higher energy density and / or longer life span of lithium ion batteries compared to other energy storage devices, lithium ion batteries are widely used in various products, such as transportation vehicles, consumer and industrial application wearable products, portable devices, and energy storage devices, almost covering all fields of human daily life.

[0003] The commonly used negative active material for lithium ion batteries is graphite. However, the use of graphite in high-capacity lithium batteries is limited due to the theoretical discharge capacity limit of about 360 mAh / g. Therefore, other materials that can alloy with lithium, such as silicon materials, are gradually gaining attention as a replacement for graphite as the negative active material for lithium ion batteries. However, although silicon materials have a significantly superior theoretical capacity of 4200 mAh / g compared to graphite, silicon materials undergo a volume expansion of 300% or more during charging and discharging, and the expansion stress will cause the silicon material to crack along the silicon crystalline or boundary.

[0004] Therefore, various new architectures for applying silicon materials to the negative electrode of lithium batteries have been proposed. For example, nanoscale particles or nanowires of silicon are used to increase the surface area by miniaturizing the particles, release the volume expansion stress, and avoid cracking. However, the use of more conductive materials and adhesives after nanosizing the silicon material will significantly reduce the proportion of active materials in the electrode layer that can undergo electrochemical reactions. In addition, nanosizing will cause the surface area to be too large, making dispersion difficult, and making it difficult to prepare the slurry. Furthermore, the larger surface area also leads to an increase in the area of the SEI layer with higher resistance, and the formation of a larger amount of SEI layer, resulting in waste of lithium resources. Therefore, a secondary particle architecture formed by stacking and agglomerating multiple nanosilicon materials has been proposed. In this architecture, the silicon in the interior can avoid forming an SEI layer, but still cannot avoid the volume variation caused by the reaction with lithium, resulting in gaps between the originally abutting silicon particles, so that lithium diffusing through the abutting points loses its diffusion path.

[0005] Another proposed architecture is a micrometer-sized silicon ball with nanoholes, which disperses the stress caused by volume expansion through the presence of nanoholes. However, under the same weight, the surface area of a micrometer-sized silicon ball with nanoholes is almost the same as that of a nanometer-sized silicon ball without holes. Therefore, in the case where the electrolyte can invade the nanoholes to form an SEI layer, there is still a problem of a large amount of SEI layer regeneration and lithium resource consumption.

[0006] In view of this, in order to solve the above-mentioned shortcomings, a filling material such as SiOx or Si / C is arranged in the nanopores. After formation, SiOx will form Si and lithium silicate (LiSixOy), and the lithium silicate is sandwiched in the Si, and the Si / C will have carbide existing in the initial stage to reduce the formation area of the SEI layer. However, the formation of lithium silicate will also cause the loss of lithium, and the presence of the filling material will reduce the overall coulombic efficiency and utilization. In addition, a composite type of using liquid metal to coat multiple silicon powder bodies is also proposed, such as U.S. Patent Application No. 16 / 514,953. The advantage of this type is that the overall surface area is relatively small, the conductivity is good, and the liquid metal can act as a stress absorber. However, the SEI layer formed by the liquid metal in contact with the electrolyte is less stable in structure than the SEI layer formed by silicon and electrolyte. Furthermore, the coulombic efficiency and utilization of the liquid metal in electrochemical reaction are poor.

[0007] In view of the shortcomings of existing silicon materials, the present application proposes a new composite negative electrode active material ball to solve the above-mentioned problems. SUMMARY

[0008] The main purpose of the present application is to provide a new composite negative electrode active material ball, in which the silicon or silicon compound particles can maintain good contact with the conductive metal core during the volume variation process of alloying and de-alloying with lithium by being partially embedded in the conductive metal core, so that the composite negative electrode active material ball maintains excellent electron transfer capability.

[0009] Another purpose of the present application is to provide a new composite negative electrode active material ball, in which the conductive metal core is selected from materials that can alloy with lithium, so that pre-lithiation can be performed before the conductive metal core material is provided with silicon or silicon compound particles. After the composite negative electrode active material ball is formed, the metal core can act as a source of lithium supplementation to reduce the irreversible loss of lithium ions during charging and discharging.

[0010] Another purpose of the present application is to provide a new composite negative electrode active material ball, in which the partial solid electrolyte interface films (SEI) between the silicon or silicon compound particles are shared and the surface of the conductive metal core is almost covered and shielded by the silicon or silicon compound particles, so that the loss of electrolyte and lithium ions when the composite negative electrode active material ball is assembled into a lithium battery component can be effectively reduced.

[0011] Another objective of this invention is to provide a novel composite negative electrode active material ball, which utilizes a micron-sized conductive metal core as a carrier for the attachment of nano-sized silicon or silicon compound particles, so that when mixed as a negative electrode slurry for lithium batteries, it has an easily dispersible size, thereby solving the disadvantage that nano-sized silicon or silicon compound particles are easy to agglomerate and thus difficult to disperse.

[0012] Another objective of this invention is to provide a novel composite negative electrode active material ball, in which the conductive metal core is a material with lower hardness than silicon or silicon compound particles. Therefore, when silicon or silicon compound particles undergo volume changes due to charging and discharging, the stress generated by the volume changes can be absorbed by the conductive metal core.

[0013] To achieve the above objectives, the present invention provides a composite negative electrode active material sphere comprising a conductive metal core having a first average radius at room temperature, and a plurality of silicon or silicon compound particles distributed on the surface of the conductive metal core having a second average radius. The portion of the silicon or silicon compound particles in direct contact with the surface of the conductive metal core is embedded within the conductive metal core, ensuring that the silicon or silicon compound particles remain in direct contact with the conductive metal core even when experiencing volume changes. This maintains the composite negative electrode active material sphere's good electronic conductivity. Therefore, the conductive metal core can serve as a shared internal conductive component for the silicon or silicon compound particles. The first average radius is more than 10 times the second average radius.

[0014] The following detailed description through specific embodiments will make it easier to understand the purpose, technical content, features and effects achieved by the present invention. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the composite negative electrode active material sphere structure of the present invention.

[0016] Figure 2 This is a schematic diagram of a battery cell structure composed of composite negative electrode active material spheres using the present invention.

[0017] Figure 3 This is a schematic diagram showing that the SEI film between adjacent silicon or silicon compound particles embedded on the surface of a conductive metal core is in a shared state.

[0018] Figure 4 This is a schematic diagram showing a portion of the volume of silicon or silicon compound particles embedded in a conductive metal core.

[0019] Figure 5 and Figure 6 These are schematic diagrams showing silicon or silicon compound particles of different sizes stacked on the surface of a conductive metal core, with a portion of the volume of the silicon or silicon compound particles in direct contact with the surface of the conductive metal core embedded in the conductive metal core.

[0020] Figure 7 This is a schematic diagram showing that when silicon or silicon compound particles of different sizes are stacked on the surface of a conductive metal core, the solid electrolyte insulating (SEI) layer of these silicon or silicon compound particles partially exhibits a shared state.

[0021] Figure 8 This is another structural schematic diagram of the composite negative electrode active material ball of the present invention.

[0022] Figure Labels

[0023] 10 Composite Anode Active Material Balls

[0024] 12 Conductive metal core

[0025] 14. Silicon or silicon compound particles

[0026] 14a Exposed portion

[0027] 14b Embedded portion

[0028] 16 Conductive Materials

[0029] 18 SEI membrane

[0030] 18a Shared SEI membrane

[0031] 19. Depression

[0032] 20 battery cells

[0033] 22 Negative electrode layer

[0034] 222 Negative electrode current collector layer

[0035] 24 Positive electrode layer

[0036] 242 Positive Electrode Active Material

[0037] 244 Positive current collector layer

[0038] 26 Isolation Layer

[0039] 28 Frame

[0040] 32 Carbide shell

[0041] a Enclosed Area Detailed Implementation

[0042] To make the advantages, spirit, and features of the present invention more readily apparent, detailed descriptions and discussions will follow with examples. It should be noted that these examples are merely representative embodiments of the present invention and are not intended to limit the scope of the invention or the claims to these specific examples. The purpose of providing these examples is solely to make the disclosure of the present invention more thorough and easily understood.

[0043] The terms used in the various embodiments disclosed herein are for the purpose of describing particular embodiments only and are not intended to limit the various embodiments disclosed herein. As used herein, including in the claims, singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used herein, including in the claims, "or" as used in a list of items prefaced by "comprising," "including," "carrying," "having," "containing," "characterized by," "comprised of," "defined herein as," "including the term," etc. means one or more

[0044] In the description of the specification, reference to terms such as "an embodiment", "one embodiment", etc. means that a particular feature, structure, material or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The illustrative representations of the above terms in the specification do not necessarily refer to the same embodiment. Furthermore, the described particular features, structures, materials or characteristics can be combined in any suitable manner in one or more embodiments.

[0045] First, as shown in Figure 1 The present application relates to a composite negative active material ball 10, which includes a substantially non-porous conductive metal core 12 and a plurality of silicon or silicon compound particles 14 and conductive material 16 distributed on the surface of the conductive metal core 12. As shown in the figure, the silicon or silicon compound particles 14 directly contact the surface of the conductive metal core 12, but some of the silicon or silicon compound particles 14 can be distributed on the surface of the conductive metal core 12 without contacting the conductive metal core 12 (see Figures 5 to 7 ). The volume of the silicon or silicon compound particles 14 directly contacting the surface of the conductive metal core 12 is embedded in the conductive metal core 12, not just a single point of adhesion or contact on the surface. The volume of the silicon or silicon compound particles 14 embedded in the conductive metal core 12 after formation can be at least 10% of the volume of the silicon or silicon compound particles 14. The conductive metal core 12 has a first average particle size and a first average hardness at room temperature, and the silicon or silicon compound particles 14 have a second average particle size and a second average hardness. The first average particle size is more than 10 times the second average particle size. The first average particle size is 0.1 microns to 50 microns, and the second average particle size is 10 nanometers to 500 nanometers. The second average hardness is greater than the first average hardness, which facilitates the embedding of the volume of the silicon or silicon compound particles 14 in the conductive metal core 12. As Figure 4As shown, the silicon or silicon compound particles 14 in direct contact with the surface of the conductive metal core 12 comprise an exposed portion 14a exposed outside the conductive metal core 12 and an embedded portion 14b embedded in the conductive metal core 12. Therefore, when the composite negative electrode active material ball 10 of the present application undergoes volume variation of the silicon or silicon compound particles 14 due to alloying and de-alloying caused by lithium ion insertion and extraction, the silicon or silicon compound particles 14 in direct contact with the surface of the conductive metal core 12 can maintain direct contact with the conductive metal core 12 through the embedded portion 14b embedded in the conductive metal core 12, so that the composite negative electrode active material ball 10 can maintain good electron transfer characteristics. In this way, the problem of electrical transfer depletion zone caused by volume variation of the silicon or silicon compound particles in the prior art can be effectively solved. For example, the depletion zone is formed due to the repeated volume expansion and contraction of the silicon or silicon compound particles during alloying and de-alloying. When the silicon or silicon compound particles expand in volume, the conductive additives such as carbon black / carbon tubes will be pushed outwards, and then when the silicon or silicon compound particles shrink in volume or break, a gap region in which electrons cannot be transferred will be formed with the displaced conductive additives, which is called a depletion zone.

[0046] In the present application, the conductive material 16 can be in direct contact with the conductive metal core 12 or in contact with the silicon or silicon compound particles 14, or both. In the present application, as long as any conductive material 16 is in contact with the conductive metal core 12, electrons can be transferred to all the silicon or silicon compound particles 14 in contact through the conductive metal core 12, or electrons can be transferred outward from the silicon or silicon compound particles 14; therefore, the conductive metal core 12 can serve as a shared internal conductive component for the silicon or silicon compound particles 14.

[0047] Furthermore, the conductive metal core 12 is selected from materials capable of alloying with lithium at a first potential, while the aforementioned silicon or silicon compound particles 14 can alloy with lithium at a first and second potential, where the first and second potentials are different, preferably the first potential is greater than the second potential. Therefore, when the silicon or silicon compound particles 14 undergo alloying or dealloying reactions with lithium, the conductive metal core 12 exhibits an inert state without alloying with lithium. However, this inert conductive metal core 12 can serve as a lithium diffusion host and exist in the conductive metal core 12 through alloying, thereby increasing the total amount of lithium that the composite negative electrode active material sphere 10 can accept. Moreover, the lithium diffused into the conductive metal core 12 can diffuse again into the silicon or silicon compound particles 14, so the lithium diffused into the conductive metal core 12 can also serve as a source of replenished lithium for the silicon or silicon compound particles 14. Furthermore, since the aforementioned conductive metal core 12 can be selected from materials capable of alloying with lithium, lithium diffusion / doping can be performed on the conductive metal core 12 before silicon or silicon compound particles 14 are deposited on its surface, i.e., pre-lithiation can be carried out. Subsequently, the conductive metal core 12 and silicon or silicon compound particles 14 are mixed to prepare the composite negative electrode active material sphere 10 of the present invention. The above-mentioned mixing method can be a method that applies appropriate pressure, such as ball milling, to embed a portion of the silicon or silicon compound particles 14 into the conductive metal core 12. When the composite negative electrode active material sphere 10 of the present invention is used to assemble a battery cell, the pre-lithiated conductive metal core 12 can also serve as a lithium replenishment source for the battery cell, thereby reducing the irreversible loss of lithium ions during charging and discharging.

[0048] Furthermore, such as Figure 5 and Figure 6 As shown, when silicon or silicon compound particles 14 are stacked with different particle sizes, the silicon or silicon compound particles 14 directly disposed on or in contact with the surface of the conductive metal core 12 will be partially embedded in the conductive metal core 12. Furthermore, as shown, the same depression 19 in the conductive metal core 12 caused by the compression of the silicon or silicon compound particles 14 may be filled with stacked silicon or silicon compound particles 14 of different sizes. Figure 5 In the middle, small silicon or silicon compound particles are in contact with the recess 19, and large silicon or silicon compound particles 14 are stacked on the small silicon or silicon compound particles 14. Figure 6 It presents another size of silicon or silicon compound particles 14 that are in contact with the recess 19.

[0049] The conductive metal core 12 is made of a low-melting-point metal, which can be an alloy formed by mixing at least two of the elements selected from indium (melting point 156.6°C), tin (melting point 231.9°C), aluminum (660.4°C), bismuth (271.4°C), or germanium (melting point 937.7°C). In this invention, a low-melting-point metal refers to an alloy with a melting point below 232°C. For example, a low-melting-point metal formed by mixing 45% tin and 55% bismuth has a melting point of approximately 150°C. The low-melting-point metal is less hard than silicon or silicon compound particles, meaning it is softer than the silicon or silicon compound particles 14, thus allowing the conductive metal core 12 to deform under pressure from the silicon or silicon compound particles 14. Furthermore, in… Figure 1 Although the conductive metal core 12 is represented as a circle of uniform diameter, it can actually be other geometric shapes or irregular shapes. Furthermore, by selecting the appropriate material composition, the conductive metal core 12 can be at least partially softened at the battery operating temperature, thus allowing it to be compressed by the stress generated by the volume expansion of the silicon or silicon compound particles 14 due to alloying, or to fill the cracks created by the volume expansion of the silicon or silicon compound particles 14. When the silicon or silicon compound particles 14 are de-alloyed, the volume of the silicon or silicon compound particles 14 will shrink, expelling the low-melting-point metal embedded in the cracks of the silicon or silicon compound particles 14. This expelled low-melting-point metal can then serve as a new conductive bonding point for the silicon or silicon compound particles 14.

[0050] The silicon or silicon compound particles 14 used in this invention can be selected from silicon-based active materials such as pure silicon, silicon oxide, or silicon nitride, which can be used as negative electrodes, or a mixture of the above types. Therefore, based on the differences in particle size of materials such as pure silicon, silicon oxide, or silicon nitride, optimization can be performed to achieve better surface coverage by embedding silicon or silicon compound particles 14 of different particle sizes on the surface of a conductive metal core 12 with high cohesion. For example, at least 50% of the outer surface area of ​​the conductive metal core 12 is covered or shielded by silicon or silicon compound particles, preferably more than 85%. The particle size distribution of the silicon or silicon compound particles 14 can be between 10 nanometers and 500 nanometers. Nanoscale silicon or silicon compound particles 14 have a high surface area / volume ratio, which is beneficial to increasing the reactive area area for lithium-ion contact embedding. However, due to the agglomeration force, nanoscale silicon or silicon compound particles 14 are very difficult to disperse in the electrode coating slurry, thus creating a bottleneck in use. The present invention uses a highly cohesive conductive metal core 12 as a carrier for the attachment of nanoscale silicon or silicon compound particles 14. Therefore, when using nanoscale silicon or silicon compound particles 14 as the electrode slurry of active material, the main body dispersed in the slurry will be transferred from nanoscale silicon or silicon compound particles 14 to larger-scale micron-sized composite negative electrode material spheres 10, so as to solve the disadvantage that nanoscale particles are easy to agglomerate and thus difficult to disperse.

[0051] The conductive material 16 used in this invention can be selected from carbon nanotubes, graphene, carbon fibers, carbon black, graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, etc.; metal powders; or conductive polymers, etc. The conductive material 16 is not limited to these materials; any conductive material suitable for lithium batteries can be used. When the conductive material 16 contacts the conductive metal core 12, it can transfer electrons to all contacted silicon or silicon compound particles 14 through the conductive metal core 12, or remove electrons from the silicon or silicon compound particles 14. The conductive material 16 can be mixed together with the aforementioned silicon or silicon compound particles 14 and then formed on the conductive metal core 12.

[0052] Please see Figure 2 This is a schematic diagram of a battery cell structure using the composite negative electrode active material spheres of the present invention. As shown, the composite negative electrode active material spheres 10 are mixed with an adhesive (not shown) and then coated on the surface of a negative electrode current collector layer 222 to serve as the negative electrode layer 22 of the battery cell 20. This battery cell 20 includes a positive electrode layer 24 and an insulating layer 26 located between the negative electrode layer 22 and the positive electrode layer 24. The positive electrode active material 242 of the aforementioned positive electrode layer 24 can be selected from any material used in the art without any limitation. For example, a compound that enables the insertion and extraction of lithium ions can be used as the positive electrode active material, such as lithium and a compound selected from cobalt, nickel, manganese, and combinations thereof.

[0053] The conductive material and / or adhesive used in the positive electrode layer 24 may be the same as or different from that used in the negative electrode layer 22. The insulating layer 26 disposed between the positive electrode layer 24 and the negative electrode layer 22 may be selected from any material in the same field, for example, materials with low electrolyte ion migration resistance, such as glass fiber, polyester, polyethylene, polypropylene, PTFE, and combinations thereof, woven or nonwoven into porous sheets that block contact between the positive electrode layer 24 and the negative electrode layer 22. Alternatively, the insulating layer 26 may also be selected from solid electrolytes. Figure 2 The battery cell 20 structure shown in the figure uses a positive electrode current collector layer 244, a negative electrode current collector layer 222, and a plastic frame 28 sandwiched between the positive electrode current collector layer 244 and the negative electrode current collector layer 222 as a packaging component to isolate the battery cell 20 from the external environment. However, this does not limit the composite negative electrode active material ball 10 of the present invention to only be used in such a battery cell structure. Instead, it can be widely applied to various battery cell / battery architectures that can use silicon-based materials as negative electrode active materials.

[0054] Please refer to the following: Figure 3 and Figure 1 As shown in the figure, when a battery composed of the composite negative electrode active material spheres 10 of the present invention undergoes a charge-discharge reaction, a solid electrolyte insulating (SEI) film 18 is formed on the surface of the composite negative electrode active material spheres 10. Because the SEI film 18 forms on a surface that can contact the lithium alloy material and the electrolyte, in this invention, most of the outer surface of the conductive metal core 12 is shielded by silicon or silicon compound particles 14, effectively reducing the contact between the electrolyte and the conductive metal core 12 to form an SEI film and reducing electrolyte loss. Furthermore, the SEI film 18 between two adjacent silicon or silicon compound particles 14 is a shared SEI film 18a, as indicated by the dotted circle around area a in the figure. Compared to existing negative electrode layers composed of multiple independently formed silicon or silicon compound particles, the partially shared SEI film 18a of the present invention significantly reduces the amount of SEI film 18 formed, reducing electrolyte loss. Figure 7 When silicon or silicon compound particles 14 are stacked on the surface of the conductive metal core 12 with different particle sizes, the solid electrolyte membrane 18 of these silicon or silicon compound particles 14 also has a partially shared state, becoming a shared SEI membrane 18a.

[0055] Compared to the SEI film formed by the conductive metal core 12, the SEI film formed by silicon or silicon compound particles 14 is thinner, more stable, and facilitates lithium ion passage, resulting in better coulombic efficiency for the silicon or silicon compound particles 14. Therefore, compared to the US Patent Application No. 16 / 514,953, which uses a low-melting-point metal to completely coat the silicon or silicon compound particles, the structure of the composite active material spheres 10 of this invention has most of the surface of the conductive metal core 12 covered by silicon or silicon compound particles 14, thus significantly reducing the contact area between the conductive metal core 12 and the electrolyte, thereby reducing the proportion of the SEI film that is less conducive to lithium ion passage.

[0056] In addition, such as Figure 8 As shown, at least a portion (e.g., 75%) of the surface of the silicon or silicon compound particles 14 of the present invention may also be formed with a carbide shell 32 to minimize direct contact between the electrolyte and the silicon or silicon compound particles 14, thereby improving electrolyte decomposition caused by dangling bonds on the silicon surface. In a preferred embodiment, a carbide shell 32 may be formed on more than 90% of the surface of the silicon or silicon compound particles 14.

[0057] In summary, this invention provides a composite negative electrode active material sphere comprising a essentially non-porous conductive metal core and a plurality of silicon or silicon compound particles distributed on the surface of the conductive metal core. A portion of the volume of the silicon or silicon compound particles in direct contact with the surface of the conductive metal core is embedded within the conductive metal core. Through these embedded silicon or silicon compound particles, direct contact with the conductive metal core is maintained even when the silicon or silicon compound particles undergo volume changes due to electrochemical ion insertion / extraction, thus ensuring good electron transport properties in the negative electrode layer. Furthermore, the composite negative electrode active material sphere of this invention effectively reduces electrolyte loss due to the shared SEI film among the silicon or silicon compound particles and the shielding effect of the silicon or silicon compound particles disposed outside the conductive metal core on its external surface. Furthermore, the conductive metal core of the present invention is a material that can be alloyed with lithium. Therefore, the conductive metal core can be pre-lithiated so that it can be used as a source of lithium replenishment when assembling a battery cell, reducing the irreversible loss of lithium ions during charging and discharging. Alternatively, the conductive metal core can serve as a new host for receiving lithium diffusion, thereby increasing the total amount of lithium that the composite active material sphere can receive or release, resulting in higher electrochemical operating efficiency. Therefore, the battery cell composed of the composite negative electrode active material sphere of the present invention can maintain excellent charge and discharge performance reproducibility based on the above advantages.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Therefore, those skilled in the art can make various modifications or equivalent substitutions to the present invention within its scope and spirit, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A composite negative electrode active material ball, comprising: A conductive metal core having a first average particle size at room temperature, the conductive metal core being a 45% tin, 55% bismuth alloy, and the conductive metal core being non-porous; and Several particles are distributed on the surface of a conductive metal core. The particle material is silicon or multiple silicon compounds and has a second average particle size. These particles are in direct contact with the surface of the conductive metal core and are partially embedded in the conductive metal core. The conductive metal core is a shared internal conductive component of these particles. The first average particle size is 10 times larger than the second average particle size; At least 85% of the outer surface area of ​​the conductive metal core is covered by these particles.

2. The composite negative electrode active material sphere according to claim 1, wherein the particle size distribution of the silicon compound particles is in the range of 10 nanometers to 500 nanometers.

3. The composite negative electrode active material ball according to claim 1, wherein the conductive metal core can be alloyed with lithium at a first potential, and the silicon compound particles can be alloyed with lithium at a second potential, wherein the first potential is greater than the second potential.

4. The composite negative electrode active material ball according to claim 1 further comprises at least one conductive material, a portion of which is in direct contact with the surface of the conductive metal core.

5. The composite negative electrode active material sphere according to claim 1, wherein the first average particle size is 0.1 micrometer to 50 micrometers, and the second average particle size is 10 nanometers to 500 nanometers.

6. The composite negative electrode active material ball according to claim 1, wherein the conductive metal core is a pre-lithiated lithium-rich conductive core.

7. A lithium secondary battery, wherein the negative electrode is composed of a plurality of composite negative electrode active material spheres as described in claim 1, characterized in that: After the lithium secondary battery is charged and discharged, a solid electrolyte insulating film is formed on the surface of the composite negative electrode active material ball, and the solid electrolyte insulating film is shared between any two adjacent particles.

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