Secondary battery, negative electrode active material, preparation method of negative electrode active material and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a secondary battery, a negative electrode active material, a preparation method of the negative electrode active material and an electric device. The secondary battery comprises a positive pole piece, a negative pole piece and a diaphragm, the negative pole piece comprises a negative current collector and a negative coating arranged on at least one surface of the negative current collector, the negative coating comprises a negative active material, and the negative active material comprises a silicon-oxygen-carbon composite material. The silicon-oxygen-carbon composite material comprises SiOC and a conductive agent located in pores of the SiOC and / or located on the surface of the SiOC. According to the scheme, the cycle performance of the battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a secondary battery, a negative electrode active material, a method for preparing the same, and an electrical device thereof. Background Technology

[0002] With the rapid growth of portable electronic devices, electric vehicles, and other technologies, the demand for power batteries is also constantly increasing. Among these, the electrochemical performance of batteries is receiving increasing attention.

[0003] To improve energy density, a new generation of silicon materials has come into view. Existing anode materials use a network structure formed by silicon, oxygen, and carbon, but the conductivity of these materials is relatively low, which affects the overall performance of the battery. Summary of the Invention

[0004] The main objective of this invention is to provide a secondary battery that improves the cycle performance of secondary batteries.

[0005] To achieve the above objectives, the present invention proposes a secondary battery, the secondary battery comprising a positive electrode, a negative electrode, and a separator, wherein the negative electrode comprises a negative current collector and a negative electrode coating disposed on at least one surface of the negative current collector, the negative electrode coating comprises a negative electrode active material, the negative electrode active material comprises a silicon-oxygen-carbon composite material, the silicon-oxygen-carbon composite material comprises SiOC and conductive agents located in the pores of the SiOC and / or located on the surface of the SiOC.

[0006] The negative electrode active material of this application includes a silicon-oxygen-carbon composite material, which includes SiOC and conductive agents located in the pores of SiOC and / or on the surface of SiOC. That is, SiOC with conductive agents disposed in the pores and / or on the surface is used as the negative electrode material. The conductive agents in the pores and / or on the surface of SiOC improve the conductivity of the silicon-oxygen-carbon composite material. In other words, the conductive agents can provide high-speed channels for the transport of active ions and electrons, reduce polarization, optimize the surface potential energy distribution state of SiOC, improve the transport rate of active ions in SiOC, and improve the sites for binding active ions in SiOC, thereby improving the energy storage of the negative electrode sheet and thus improving the cycle performance of the battery.

[0007] It is understandable that SiOC has a porous structure, and conductive agents can be located in its pore core and / or surface. Pure SiOC has a low surface energy, which is not conducive to the migration and diffusion of active ions and electrons in it. The distribution of conductive agents in the pores and / or surface of SiOC can increase its surface energy, thereby improving the diffusion and migration of active ions and electrons in SiOC, improving the insertion and extraction of active ions in SiOC, and improving the cycle performance of the battery.

[0008] Optionally, the conductive agent includes carbon nanotubes and / or graphene.

[0009] The conductive agents located in the pores of SiOC and / or on the surface of SiOC in this application include carbon nanotubes and / or graphene. Carbon nanotubes and graphene have ordered crystal structures and good conductivity, which helps to improve the conductivity of silicon-oxygen-carbon composite materials.

[0010] Optionally, the carbon nanotubes comprise 0% to 27% of the weight of the silicon-oxygen-carbon composite material.

[0011] The mass percentage of carbon nanotubes in the silicon-oxygen-carbon composite material of this application meets the above range, that is, carbon nanotubes can be set in the pores and / or surface of SiOC as needed. More carbon nanotubes can provide more channels for the transport of active ions and electrons, which helps to improve the cycle performance of the battery.

[0012] It is understandable that carbon nanotubes are located in the pores and / or surface of SiOC. That is, abundant carbon nanotubes are located in various parts of SiOC. Carbon nanotubes act as bridges, enabling active ions and electrons to migrate rapidly to various sites inside and on the surface of SiOC. This allows for full utilization of the sites in SiOC to bind active ions and store electrons, thereby improving the specific capacity of the negative electrode active material and thus improving the cycle performance of the battery.

[0013] Optionally, the volume average particle size Dv50 of the silicon-oxygen-carbon composite material is 5 μm to 15 μm;

[0014] And / or, the specific surface area of ​​the silicon-oxygen-carbon composite material is 30 m². 2 / g to 150m 2 / g;

[0015] And / or, the powder resistivity of the silicon-oxygen-carbon composite material is 5.7*10⁻⁶. -5 Ω·m to 1.1*10 -1 Ω·m.

[0016] When the volume average particle size of the silicon-oxygen-carbon composite material of this application meets the above-mentioned range, the battery has better kinetics. For example, it helps the transport of active ions in the electrolyte and the ion diffusion process inside the silicon-oxygen-carbon composite material, thereby helping to improve the rate performance and cycle stability of the battery.

[0017] The specific surface area of ​​the silicon-oxygen-carbon composite material in this application is 30 m². 2 / g to 150m 2 / g, that is, introducing a conductive agent into SiOC can increase the specific surface area of ​​the material. The increase in specific surface area gives the negative electrode active material more surface area for the insertion and extraction of active ions, thereby increasing the electrochemical active area. It can also provide more channels to make it easier for the electrolyte to penetrate into the interior of the negative electrode active material particles, increasing the contact area between the negative electrode coating and the electrolyte. At the same time, the large specific surface area can provide more space to mitigate the huge volume change of SiOC during charging and discharging, thereby achieving the goal of improving the electrochemical performance of the battery.

[0018] It is understandable that the carbon nanotubes in SiOC are not only located within the pores of SiOC, but also extend along the pores to the surface of SiOC, forming a villous structure on the surface of SiOC. This villous structure is essentially a situation where numerous carbon nanotubes extend on the surface of SiOC. Based on the unique nanoscale hollow structure of carbon nanotubes, they can theoretically exhibit capillary action. Thus, the carbon nanotubes distributed on the surface of SiOC can effectively draw the electrolyte into the interior of SiOC, improve the wettability of SiOC to the electrolyte, and thereby enhance the transport of active ions.

[0019] The powder resistivity of the silicon-oxygen-carbon composite material in this application meets the above-mentioned range, indicating that the introduction of conductive agent in SiOC can improve the electrical conductivity of the material, reduce the powder resistivity of the material, and is beneficial to improving the migration rate of active ions and electrons.

[0020] Optionally, the mass percentage of the silicon-oxygen-carbon composite material is 50% to 97% based on the total mass of the negative electrode coating;

[0021] And / or, the resistance of the negative electrode coating is 1.9 mΩ·cm. 2 Up to 13.8 mΩ·cm 2 ;

[0022] And / or, the compaction density of the negative electrode coating is 0.75 g / cm³. 3 Up to 1.96 g / cm 3 ;

[0023] And / or, the specific surface area of ​​the negative electrode coating is 2.1 m². 2 / g to 34.6m 2 / g;

[0024] And / or, the porosity of the negative electrode coating is 21% to 57%;

[0025] And / or, the thickness of the negative electrode coating is from 43 μm to 161 μm.

[0026] The mass percentage of silicon-oxygen-carbon composite material in the negative electrode coating of this application meets the above range, which helps to improve the cycle performance of the battery.

[0027] When the aforementioned silicon-oxygen-carbon composite material is added to the negative electrode coating, the resistivity of the negative electrode coating is 1.9 mΩ·cm. 2 Up to 13.8 mΩ·cm 2 In other words, based on the low powder resistivity of silicon-oxygen-carbon composite materials, the resistance of the negative electrode coating can be reduced, thereby improving the cycle performance of the battery.

[0028] Adding the aforementioned silicon-oxygen-carbon composite material to the negative electrode coating, with the compaction density of the negative electrode coating meeting the above-mentioned range, can improve the battery capacity.

[0029] Adding the aforementioned silicon-oxygen-carbon composite material to the negative electrode coating improves the porosity of the coating, as it meets the above-mentioned range and enhances the wettability of the electrolyte to the coating.

[0030] Adding the aforementioned silicon-oxygen-carbon composite material to the negative electrode coating, with the thickness of the negative electrode coating meeting the above-mentioned range, can further improve the cycle performance of the battery.

[0031] Optionally, this application also provides a negative electrode active material, the negative electrode active material comprising a silicon-oxygen-carbon composite material, the silicon-oxygen-carbon composite material comprising SiOC and conductive agents located in the pores of the SiOC and / or located on the surface of the SiOC.

[0032] Optionally, the conductive agent includes carbon nanotubes and / or graphene.

[0033] Optionally, the carbon nanotubes comprise 0% to 27% of the weight of the silicon-oxygen-carbon composite material.

[0034] Optionally, the volume average particle size (DV50) of the silicon-oxygen-carbon composite material is 5 μm to 15 μm;

[0035] And / or, the specific surface area of ​​the silicon-oxygen-carbon composite material is 30 m². 2 / g to 150m 2 / g;

[0036] And / or, the powder resistivity of the silicon-oxygen-carbon composite material is 5.7*10⁻⁶. -5 Ω·m to 1.1*10 -1 Ω·m.

[0037] Optionally, this application also provides a method for preparing a negative electrode active material, comprising: introducing a catalyst into the pores of SiOC and / or the surface of SiOC, pyrolyzing a carbon source on the SiOC to form a conductive agent, and obtaining a silicon-oxygen-carbon composite material in which the conductive agent is disposed in the pores of the SiOC and / or on the surface of the SiOC.

[0038] It is understandable that carbon sources can pyrolyze to form conductive agents under catalytic conditions. Based on this principle, a catalyst is introduced into the pores and / or surface of SiOC, and the carbon source on SiOC is pyrolyzed to form a conductive agent, thereby forming a conductive agent in situ in the pores and / or surface of SiOC. Compared to doping conductive agents on SiOC, this method of in-situ preparation of conductive agents on SiOC results in a more uniform distribution of the conductive agent. Doping conductive agents on SiOC often leads to agglomeration, which blocks the transport channels of active ions, affecting their transport efficiency in the negative electrode active material. This prevents the formation of an effective conductive network within the negative electrode active material, thus impacting the battery's electrochemical performance. The in-situ preparation method of this application provides better dispersion of the conductive agent, offering more transport channels for the negative electrode active material. In other words, the conductive agent provides high-speed channels for the transport of active ions and electrons, reducing polarization, optimizing the surface potential energy distribution of SiOC, increasing the transport rate of active ions in SiOC, and increasing the sites for binding active ions in SiOC, thereby improving the energy storage of the negative electrode and ultimately enhancing the battery's cycle performance.

[0039] Furthermore, while catalyzing the formation of carbon nanotube structures, SiOC derives microstructures with high specific surface area. Due to the growth of carbon nanotubes, SiOC is separated from its original micron-scale bulk into several small nano-scale bulks, resulting in changes in the microstructure of free carbon and glass phase within SiOC, forming structures with even higher specific surface area.

[0040] This high specific surface area provides the negative electrode active material with more surface area for the insertion and extraction of active ions, which can increase the electrochemical reaction surface area. The microstructure can provide more channels to make it easier for the electrolyte to penetrate into the interior of the negative electrode active material particles, increasing the contact area between the negative electrode coating and the electrolyte. At the same time, the microstructure with a high specific surface area can provide more space to mitigate the huge volume changes that occur in SiOC during charging and discharging, thereby improving the electrochemical performance of the battery.

[0041] The SiOC anode active material itself contains a lot of free carbon, which is in an amorphous state. By introducing a catalyst, the free carbon inside the SiOC material can be transformed from amorphous carbon to ordered carbon. This method transforms amorphous carbon into ordered carbon, which reduces the low conductivity carbon inside the SiOC, reduces the adverse factors of the original low conductivity carbon, improves the conductivity of SiOC, and improves the electrochemical performance of the battery.

[0042] Understandably, the step of introducing the catalyst into the pores and / or surface of SiOC can involve preparing SiOC and introducing the catalyst into it. For example, the catalyst may be particulate, and since SiOC has a porous structure, the particulate catalyst can be introduced into the channels and surface of the SiOC. Alternatively, a SiOC precursor may be prepared, which also has a porous structure, and the catalyst can be introduced into the channels and surface of the SiOC precursor. Another approach is to prepare a solution for preparing the SiOC precursor, typically an organosilicon compound containing silicon, oxygen, and carbon. The catalyst is then introduced into the SiOC precursor solution, and the solution is converted into SiOC using processes such as the sol-gel method, thus positioning the catalyst within the channels and on the surface of the SiOC.

[0043] It is understandable that the carbon source on SiOC includes the carbon source inherent in SiOC itself, such as the carbon source formed by the cleavage of the branched alkyl groups of the SiOC precursor polymer during the SiOC preparation process, or the carbon source introduced from the outside.

[0044] Optionally, the step of introducing the catalyst into the pores and / or surface of the SiOC, and pyrolyzing the carbon source on the SiOC to form a conductive agent, includes:

[0045] The catalyst source was mixed with a polysiloxane monomer solution to obtain a mixed solution;

[0046] The mixed solution was heated to obtain the precursor;

[0047] The precursor is calcined in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC.

[0048] Understandably, the catalytic source is used to form the catalyst, and the polysiloxane monomer solution is used to form SiOC.

[0049] The catalyst source is introduced into the polysiloxane monomer solution by sol-gel method, and the catalyst is formed in situ in SiOC after pyrolysis. In addition, a conductive agent can also be formed in situ during the pyrolysis process. It can be understood that the polysiloxane monomer and / or the alkanes generated during the pyrolysis process can be used as carbon sources. During the calcination process, the carbon source can be converted into carbon materials with conductive properties, so that a conductive agent is provided on SiOC.

[0050] Alternatively, an external carbon source can be added to the mixed solution. During the calcination process, the carbon source can be converted into a carbon material with conductive properties, thus providing a conductive agent on the SiOC.

[0051] Specifically, in the preparation process of the negative electrode active material, the catalyst source used to form the catalyst is mixed with the polysiloxane monomer solution used to form SiOC, so that the catalyst source can be effectively dispersed in the polysiloxane monomer solution. The components in the polysiloxane monomer solution are reacted and converted into a precursor by heating. The catalyst source is dispersed in the precursor. Then, the precursor is converted into SiOC by calcination under an inert atmosphere, the catalyst source is converted into a catalyst, and the carbon source is converted into a carbon material with conductive properties, thus obtaining SiOC and catalyst and conductive agent located in the pores of SiOC and / or located on the surface of SiOC.

[0052] It is also understandable that the organic components in the polysiloxane monomer solution can serve as a carbon source, and alkane gases, which are also produced during the pyrolysis of polysiloxanes, can also serve as a carbon source. Specifically, since the side and end groups of polysiloxanes contain CH3, these will detach and form CH4 gas during molecular rearrangement. The ceramic yield of the polysiloxane pyrolysis process is below 70%, so there must be some pre-existing reactants that are pyrolyzed into gas during the pyrolysis process. That is, during the pyrolysis process, an in-situ carbon source can be used to obtain a conductive agent on SiOC, or an external carbon source or conductive agent can be added to the mixed solution to obtain a conductive agent on SiOC.

[0053] It is also understandable that, compared to adding carbon sources or conductive agents externally, using organic raw materials added during the overall preparation process, or organic products generated during the preparation process as carbon sources, results in a more uniform distribution of carbon nanotubes generated in SiOC.

[0054] Optionally, the step of mixing the catalyst source with the polysiloxane monomer solution to obtain a mixed solution includes:

[0055] Prepare the catalyst source solution;

[0056] Prepare a polysiloxane monomer solution;

[0057] The catalyst source solution is mixed with the polysiloxane monomer solution to obtain a mixed solution.

[0058] Considering that the uneven dispersion of the catalyst source on the precursor will affect the uniform dispersion of the catalyst on SiOC, and thus affect the uniform dispersion of the conductive agent formed by catalysis, and will also cause the catalyst particle size to be too large, resulting in the large catalyst particles squeezing the pores of SiOC and destroying the structure of SiOC. Therefore, this application adopts the following method: preparing a catalyst source solution; preparing a polysiloxane monomer solution; and mixing the catalyst source solution and the polysiloxane monomer solution to obtain a mixed solution.

[0059] Understandably, the high viscosity of polysiloxane monomer solutions hinders the dispersion of the catalyst source. Therefore, preparing the catalyst source as a low-viscosity solution separately, and then mixing the two solutions, can yield a catalyst source with molecular-level homogeneity in a short time. In other words, a catalyst source solution can be prepared in advance to achieve low viscosity, allowing for the rapid acquisition of a catalyst source with molecular-level homogeneity.

[0060] Optionally, the step of preparing the polysiloxane monomer solution and mixing the catalyst source solution with the polysiloxane monomer solution to obtain a mixed solution includes:

[0061] Prepare a polysiloxane monomer solution;

[0062] The polysiloxane monomer solution was heated to obtain a pre-crosslinked solution;

[0063] The catalyst source solution is mixed with the pre-crosslinked solution to obtain a mixed solution.

[0064] To ensure effective adsorption and localization of the catalyst source and improve the yield of precursor pyrolysis to SiOC, after preparing the polysiloxane monomer solution, the polysiloxane monomer solution is heated to obtain a pre-crosslinked solution. That is, during the pre-crosslinking process, silane hydrogen undergoes hydrosilylation with some alkenyl groups to form small molecule silane polymers. This can increase the viscosity and improve the reaction yield of the reactants in the polysiloxane monomer solution, reducing the risk of unreacted reactants volatilizing during pyrolysis, thereby increasing the yield of precursor pyrolysis to SiOC.

[0065] Optionally, in the step of heating the polysiloxane monomer solution to obtain a pre-crosslinked solution, the heating temperature is 50°C to 80°C, and the heating time is 10 min to 60 min.

[0066] In order to effectively adsorb and locate the catalyst source and improve the yield of precursor pyrolysis to SiOC, in the step of heating the polysiloxane monomer solution to obtain a pre-crosslinked solution, the heating temperature is 50°C to 80°C and the heating time is 10 min to 60 min.

[0067] Optionally, the step of heating the mixed solution to obtain the precursor includes: heating the mixed solution to obtain a block, crushing the block to obtain the precursor, wherein the volume average particle size D50 of the precursor ranges from 9 μm to 30 μm.

[0068] In the step of heating the mixed solution to obtain the precursor, the bulk material is ground into powder before the subsequent calcination step. If the bulk precursor is directly calcined, the resulting large blocks would be difficult to grind further. This is understandable because after calcination, carbon nanotubes are already formed within or on the surface of the SiOC pores. During the grinding of these larger blocks into powder, i.e., during the SiOC crushing process, ruptures can occur at the pores, causing carbon nanotubes to detach from the SiOC and reducing its content. Therefore, grinding the precursor into powder before calcination mitigates the risk of carbon nanotube detachment during subsequent processing, increases the carbon nanotube content, and improves the conductivity of the negative electrode active material. Furthermore, the powdered precursor undergoes a shorter and more thorough conversion during calcination, further reducing the overall calcination time.

[0069] Optionally, in the step of heating the mixed solution to obtain the precursor, the heating temperature range is 80°C to 200°C, and the heating time is 1 hour to 12 hours.

[0070] And / or, in the step of calcining the precursor in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC, the precursor is heated to 300°C to 1000°C in an inert gas atmosphere at a heating rate of 1°C / min to 20°C / min, calcined at a constant temperature for 5 min to 240 min, and cooled at a cooling rate of 1°C / min to 20°C / min.

[0071] And / or, after the step of calcining the precursor in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC, an acid washing step is further included.

[0072] The mixed solution is heated to cause the polysiloxane monomers in the mixed solution to react and generate polysiloxane. The catalyst source is uniformly dispersed in the polysiloxane skeleton to form a precursor. The heating temperature range is 80℃ to 200℃ and the heating time is 1h to 12h.

[0073] During the calcination of the precursor in an inert atmosphere, the polysiloxane is pyrolyzed into SiOC, the catalytic source is converted into a catalyst, and the catalyst is located on SiOC. The calcination program is as follows: heating to 300℃ to 1000℃ at a heating rate of 1℃ / min to 20℃ / min, constant temperature calcination for 5min to 240min, and cooling at a cooling rate of 0.5℃ / min to 20℃ / min.

[0074] Metal-type catalysts on SiOCs can cause battery self-discharge to some extent. Acid washing is used to reduce and remove metal-type catalysts.

[0075] Optionally, the catalyst source includes a transition metal source;

[0076] And / or, the polysiloxane monomer solution includes hydrogen-containing silicone oil, crosslinking agent, and hydrosilylation catalyst;

[0077] And / or, the conductive agent includes carbon nanotubes and / or graphene.

[0078] Transition metals can act as catalysts to convert carbon sources into carbon nanotubes during calcination.

[0079] The polysiloxane monomer solution includes hydrogen-containing silicone oil, crosslinking agent, and hydrosilylation catalyst.

[0080] Conductive agents include carbon nanotubes and / or graphene.

[0081] Optionally, the transition metal source includes at least one of an iron source, a nickel source, and a cobalt source;

[0082] And / or, the mass ratio of the hydrogen-containing silicone oil to the crosslinking agent ranges from 100:(1 to 300);

[0083] And / or, the mass ratio of the hydrogen-containing silicone oil to the catalyst source ranges from 10:(0.001 to 4);

[0084] And / or, the hydrogen-containing silicone oil includes at least one of polymethylhydrosiloxane, tetramethyltetrahydrocyclotetrasiloxane, carboxylated siloxane polymer, aminosiloxane polymer, and cyclosiloxane siloxane polymer;

[0085] And / or, the crosslinking agent includes at least one of divinylbenzene, 1,5-hexadiene, bis(trivinyl)disiloxane, and trivinylethylene oxide;

[0086] And / or, the hydrosilylation catalyst includes at least one of chloroplatinic acid and castalplatin.

[0087] In the preparation of negative electrode active materials, the transition metal source includes at least one of iron, nickel, and cobalt. It is understood that to obtain in-situ generated carbon nanotubes, the transition metal source includes at least one of iron, nickel, and cobalt. The generation of carbon nanotubes requires at least one of iron, nickel, and cobalt as a catalyst. Specifically, the surface of transition metal particles (iron, nickel, cobalt, and their alloys) has active sites for adsorbing carbon source gas. The carbon source adsorbs and decomposes on the metal surface to form carbon atoms, resulting in a nucleation reaction of carbon nanotubes. The carbon atoms self-assemble to form a hexagonal structure, and as the reaction proceeds, the carbon nanotubes gradually grow.

[0088] In this application, the mass ratio of hydrogen-containing silicone oil to the catalyst source ranges from 10:(0.001 to 4). Theoretically, as the mass of the transition metal source increases within a certain range, the catalyst content will also increase. However, metal catalysts are prone to causing the risk of battery self-discharge. Therefore, the catalyst content is reduced.

[0089] In this application, the hydrogen-containing silicone oil includes at least one of polymethylhydrosiloxane, tetramethyltetrahydrocyclotetrasiloxane, carboxylated siloxane polymer, aminosiloxane polymer, and cyclosiloxane siloxane polymer.

[0090] In this application, the crosslinking agent includes at least one of divinylbenzene, 1,5-hexadiene, bis(trivinyl)disiloxane, and trivinyl ethylene oxide.

[0091] In this application, the hydrosilylation catalyst includes at least one of chloroplatinic acid and castalplatin.

[0092] Optionally, the iron source includes at least one of ferric nitrate, ferric acetylacetone, and ferrous carbonate;

[0093] And / or, the nickel source includes at least one of nickel nitrate, nickel acetylacetonate, and nickel carbonate;

[0094] And / or, the cobalt source includes at least one of cobalt nitrate, cobalt acetylacetonate, and cobalt carbonate;

[0095] And / or, the mass ratio of iron in the iron source to nickel in the nickel source and / or cobalt in the cobalt source is in the range of (1:0.01):(1:2).

[0096] In this application, the iron source includes at least one of ferric nitrate, ferric acetylacetone, and ferrous carbonate.

[0097] In this application, the nickel source includes at least one of nickel nitrate, nickel acetylacetonate, and nickel carbonate.

[0098] In this application, the cobalt source includes at least one of cobalt nitrate, cobalt acetylacetonate, and cobalt carbonate.

[0099] In this application, the mass ratio of iron in the iron source to nickel in the nickel source and / or cobalt in the cobalt source is in the range of (1:0.01):(1:2). The alloy catalysis effect of carbon nanotube formation is better. Compared with introducing a single metal Fe in SiOC, introducing multiple alloys (Fe, Ni, Co, etc.) can catalyze the formation of more carbon nanotubes to provide more transport channels for active ions.

[0100] Optionally, the solvent in the catalyst source solution includes at least one of toluene, xylene, acetone, dimethylformamide, dimethylacetamide, tetrahydrofuran, and N-methylpyrrolidone;

[0101] And / or, the mass ratio of the catalyst source to the solvent in the catalyst source solution ranges from 1:(0.5 to 50).

[0102] In this application, the solvent of the catalyst source solution includes at least one of toluene, xylene, acetone, dimethylformamide, dimethylacetamide, tetrahydrofuran, and N-methylpyrrolidone.

[0103] In this application, the mass ratio of the catalyst source to the solvent is in the range of 1:(0.5 to 50). Within the above range, the transition metal source can be well dissolved and dispersed in the solvent.

[0104] Optionally, this application also provides an electrical device, which includes a catalytic rechargeable battery as described above.

[0105] The negative electrode active material of this application includes a silicon-oxygen-carbon composite material, which includes SiOC and conductive agents located in the pores of SiOC and / or on the surface of SiOC. That is, SiOC with conductive agents disposed in the pores and / or on the surface is used as the negative electrode material. The conductive agents in the pores and / or on the surface of SiOC improve the conductivity of the silicon-oxygen-carbon composite material. In other words, the conductive agents can provide high-speed channels for the transport of active ions and electrons, reduce polarization, optimize the surface potential energy distribution state of SiOC, improve the transport rate of active ions in SiOC, and improve the sites for binding active ions in SiOC, thereby improving the energy storage of the negative electrode sheet and thus improving the cycle performance of the battery. Attached Figure Description

[0106] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0107] Figure 1 A schematic diagram of the structure of SiOC and the catalyst and conductive agent located in the pores of SiOC and / or on the surface of SiOC;

[0108] Figure 2 This is a scanning electron microscope (SEM) image of Embodiment 1 of this application;

[0109] Figure 3 This is a transmission electron microscope (TED) image of Embodiment 1 of this application;

[0110] Figure 4 This is a schematic diagram of the process for preparing the negative electrode active material in this application;

[0111] Figure 5 This is a schematic diagram of the structure of a battery cell according to one embodiment of this application;

[0112] Figure 6 yes Figure 5 An exploded view of a battery cell according to one embodiment of this application is shown.

[0113] Figure 7 This is a schematic diagram of a battery module according to one embodiment of this application;

[0114] Figure 8 This is a schematic diagram of a battery pack according to one embodiment of this application;

[0115] Figure 9 yes Figure 8 An exploded view of a battery pack according to one embodiment of this application is shown;

[0116] Figure 10 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0117] Explanation of icon numbers:

[0118] label name label name 1 Battery pack 5 battery cell 2 Upper box 51 case 3 Lower box 52 Electrode assembly 4 Battery Module 53 cover plate 100 Silicon-oxygen-carbon composite materials 20 carbon nanotubes 10 SiOC

[0119] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0120] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0121] The secondary battery, negative electrode active material, preparation method thereof, and electrical device of this application are disclosed in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0122] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥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.

[0123] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0124] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0125] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0126] A new generation of silicon materials has emerged, boasting an extremely high theoretical specific capacity (approximately 4200 mAh / g). However, silicon undergoes volume changes exceeding 300% during lithiation and delithiation. This massive expansion and contraction leads to material fragmentation and electrode structure damage, resulting in rapid capacity decay of the battery. To address this, a novel anode active material, SiOC, has been proposed, featuring a network structure of silicon, oxygen, and carbon. This material combines high specific capacity (890 mAh / g) with good cycle stability (>3000 cycles). However, SiOC materials exhibit relatively low conductivity, which affects their electron transport efficiency and consequently impacts the overall battery performance.

[0127] This application proposes a secondary battery, which includes a positive electrode, a negative electrode, and a separator. The negative electrode includes a negative current collector and a negative electrode coating disposed on at least one surface of the negative current collector. The negative electrode coating includes a negative electrode active material, which includes a silicon-oxygen-carbon composite material. The silicon-oxygen-carbon composite material includes SiOC and conductive agents located in the pores of SiOC and / or on the surface of SiOC.

[0128] SiOC's structure mainly consists of amorphous SiOC tetrahedral structures and free carbon phases. SiOC can be detected by XRD, exhibiting a broad amorphous peak around 23°. (See attached image) Figure 1 The diagram shown is a schematic diagram of the structure of the silicon-oxygen-carbon composite material of this application. The silicon-oxygen-carbon composite material 100 includes SiOC10 and a conductive agent (e.g., carbon nanotubes 20) located on SiOC10.

[0129] The negative electrode active material of this application includes a silicon-oxygen-carbon composite material, which includes SiOC and conductive agents located in the pores of SiOC and / or on the surface of SiOC. That is, SiOC with conductive agents disposed in the pores and / or on the surface is used as the negative electrode material. The conductive agents in the pores and / or on the surface of SiOC improve the conductivity of the silicon-oxygen-carbon composite material. In other words, the conductive agents can provide high-speed channels for the transport of active ions and electrons, reduce polarization, optimize the surface potential energy distribution state of SiOC, improve the transport rate of active ions in SiOC, and improve the sites for binding active ions in SiOC, thereby improving the energy storage of the negative electrode sheet and thus improving the cycle performance of the battery.

[0130] It is understandable that SiOC has a porous structure, and conductive agents can be located in its pore core and / or surface. Pure SiOC has a low surface energy, which is not conducive to the migration and diffusion of active ions and electrons in it. The distribution of conductive agents in the pores and / or surface of SiOC can increase its surface energy, thereby improving the diffusion and migration of active ions and electrons in SiOC, improving the insertion and extraction of active ions in SiOC, and improving the cycle performance of the battery.

[0131] In one embodiment, the conductive agent includes carbon nanotubes and / or graphene.

[0132] The conductive agents located in the pores of SiOC and / or on the surface of SiOC in this application include carbon nanotubes and / or graphene. Carbon nanotubes and graphene have ordered crystal structures and good conductivity, which helps to improve the conductivity of silicon-oxygen-carbon composite materials.

[0133] In one embodiment, the carbon nanotubes comprise 0% to 27% of the weight of the silicon-oxygen-carbon composite material.

[0134] The mass percentage of carbon nanotubes in the silicon-oxygen-carbon composite material of this application is greater than 0% and less than or equal to 27%. That is, carbon nanotubes can be set in the pores and / or surface of SiOC as needed. More carbon nanotubes can provide more channels for the transport of active ions and electrons, which helps to improve the cycle performance of the battery.

[0135] It is understandable that carbon nanotubes are located in the pores and / or surface of SiOC. That is, abundant carbon nanotubes are located in various parts of SiOC. Carbon nanotubes act as bridges, enabling active ions and electrons to migrate rapidly to various sites inside and on the surface of SiOC. This allows for full utilization of the sites in SiOC to bind active ions and store electrons, thereby improving the specific capacity of the negative electrode active material and thus improving the cycle performance of the battery.

[0136] The values ​​from 0% to 27% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0%, 0.1%, 1%, 5%, 8%, 10%, 15%, 18%, 20%, 25%, 26%, 27%, as well as the range values ​​between any two of the above point values.

[0137] Thermogravimetric / differential thermal analysis (TG / DTA) can be used to analyze the mass percentage of carbon nanotubes. For example, the DTG-60 thermal analyzer can simultaneously measure the mass change, exothermic peak temperature, and calorific value, which means it can test the thermogravimetric curve and differential thermal analysis curve of carbon nanotubes to determine their mass.

[0138] In one embodiment, the volume average particle size Dv50 of the silicon-oxygen-carbon composite material is 5 μm to 15 μm; and / or, the specific surface area of ​​the silicon-oxygen-carbon composite material is 30 m². 2 / g to 150m 2 / g; and / or, the powder resistivity of the silicon-oxygen-carbon composite material is 5.7*10 -5 Ω·m to 1.1*10 -1 Ω·m.

[0139] Dv50 is the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%. Physically, it means that 50% of the particles are larger than Dv50, and 50% are smaller. Dv50 is also called the median diameter or median particle size. Dv50 is often used to represent the average particle size of powders.

[0140] In a sample, 50% of the particles by total volume have a particle size greater than this value, and another 50% of the particles by total volume have a particle size smaller than this value; Dv50 can represent the median particle size of the sample.

[0141] Dv50 can be tested using methods known in the art. As an example, GB / T19077-2016 can be referenced for characterization testing using a Malvern laser particle size analyzer, such as the Malvern Mastersizer-3000.

[0142] The specific surface area was determined using a BELSORP MAX II BET analyzer to characterize the catalyst sample. The method involves measuring the amount of gas adsorbed on the solid surface to determine the specific surface area. The specific experimental steps are roughly as follows: Sample pretreatment: The sample was degassed under high vacuum and high temperature conditions to remove adsorbed impurities. Sample weighing: The degassed sample was accurately weighed in the analysis tube. Sample cooling: The analysis tube was immersed in a liquid nitrogen bath to cool the sample to 77K (-196℃). Adsorption measurement: A known amount of adsorbate (usually N2 gas) was slowly injected at different relative pressures using a precision pressure gauge and volume meter. The adsorption amount at each relative pressure point was recorded. Desorption measurement: The adsorbed gas was gradually removed from the sample surface by decreasing the pressure or increasing the temperature. The desorption amount at each relative pressure point was recorded. Data processing: Linear fitting was performed on the adsorption isotherm data according to the BET theoretical equation. The monolayer adsorption amount and specific surface area of ​​the sample were calculated from the slope and intercept of the fitted line.

[0143] The powder resistivity test method uses the four-probe method. Four probes are placed on the powder sample that has been flattened into a plate, and current is passed through it. The voltage drop is measured, and the resistivity is calculated according to Ohm's law.

[0144] In one embodiment, when the volume average particle size of the silicon-oxygen-carbon composite material of this application meets the above-mentioned range, the battery has better kinetics. For example, it helps the transport of active ions in the electrolyte, helps the ion diffusion process inside the silicon-oxygen-carbon composite material, and thus helps improve the rate performance and cycle stability of the battery.

[0145] The values ​​in the range of 5μm to 15μm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, etc., as well as the range values ​​between any two of the above point values.

[0146] In one embodiment, the specific surface area of ​​the silicon-oxygen-carbon composite material of this application is 30 m². 2 / g to 150m 2 / g, that is, introducing a conductive agent into SiOC can increase the specific surface area of ​​the material. The increase in specific surface area gives the negative electrode active material more surface area for the insertion and extraction of active ions, thereby increasing the electrochemical active area. It can also provide more channels to make it easier for the electrolyte to penetrate into the interior of the negative electrode active material particles, increasing the contact area between the negative electrode coating and the electrolyte. At the same time, the large specific surface area can provide more space to mitigate the huge volume change of SiOC during charging and discharging, thereby achieving the goal of improving the electrochemical performance of the battery.

[0147] It is understandable that the carbon nanotubes in SiOC are not only located within the pores of SiOC, but also extend along the pores to the surface of SiOC, forming a villous structure on the surface of SiOC. This villous structure is essentially a situation where numerous carbon nanotubes extend on the surface of SiOC. Based on the unique nanoscale hollow structure of carbon nanotubes, they can theoretically exhibit capillary action. Thus, the carbon nanotubes distributed on the surface of SiOC can effectively draw the electrolyte into the interior of SiOC, improve the wettability of SiOC to the electrolyte, and thereby enhance the transport of active ions.

[0148] The above 30m 2 / g to 150m 2 In / g, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 30m. 2 / g、40m 2 / g、60m 2 / g、80m 2 / g, 100m 2 / g、120m 2 / g、130m 2 / g, 150m 2 / g, etc., and the range of values ​​between any two of the above point values.

[0149] In one embodiment, the powder resistivity of the silicon-oxygen-carbon composite material of this application meets the above-mentioned range, indicating that the introduction of conductive agent in SiOC can improve the conductivity of the material, reduce the powder resistivity of the material, and is beneficial to improving the migration rate of active ions and electrons.

[0150] The above 5.7*10 -5 Ω·m to 1.1*10 -1 In Ω·m, the values ​​include the minimum and maximum values ​​within the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 5.7*10. -5 Ω·m, 9*10 -5 Ω·m, 1*10 -4 Ω·m, 1*10 -3 Ω·m, 1*10 -2 Ω·m, 1.1*10 -1 Ω·m, etc., and the range between any two of the above point values.

[0151] In one embodiment, the mass percentage of the silicon-oxygen-carbon composite material is 50% to 97% based on the total mass of the negative electrode coating; and / or, the resistivity of the negative electrode coating is 1.9 mΩ·cm. 2 Up to 13.8 mΩ·cm 2 ; and / or, the compaction density of the negative electrode coating is 0.75 g / cm³. 3 Up to 1.96 g / cm 3 ; and / or, the specific surface area of ​​the negative electrode coating is 2.1 m². 2 / g to 34.6m 2 / g; and / or, the porosity of the negative electrode coating is 21% to 57%; and / or, the thickness of the negative electrode coating is 43μm to 161μm.

[0152] Coating resistance test method: Under 5% humidity and room temperature, take one 100mm×100mm electrode sheet that has been soaked in lithium-ion battery electrolyte, fold it in half from the middle (here we take an electrode sheet with double-sided negative active material coating as an example; for an electrode sheet with single-sided negative active material coating, the negative active material coating should be folded outwards), place it in the middle of the probe of the film resistance meter, and then perform the test to obtain the film resistance of the active material layer of the electrode sheet being tested. After testing 5 electrode samples, calculate the average value, which is the film resistance of the active material layer.

[0153] For example, the electrode resistance meter can be model BER2500, and the specific test procedures can be followed according to the instrument manual.

[0154] Compacted density = Areal density / (Thickness of electrode sheet after compaction - Thickness of current collector), Unit: g / cm 3Areal density = (electrode mass - current collector mass) / electrode area.

[0155] Porosity is the ratio of pore volume to the total volume of a sample. The sample is cut to a suitable size and shape. Before testing, the sample needs to be heated in a vacuum to remove gas and moisture from the pores. The sample is then placed in a mercury porosimeter, and the pressure is gradually increased to allow mercury to penetrate into the pores of the sample.

[0156] The mass percentage of silicon-oxygen-carbon composite material in the negative electrode coating of this application meets the above range, which helps to improve the cycle performance of the battery.

[0157] The values ​​in the range of 50% to 97% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 50%, 55%, 60%, 70%, 80%, 90%, 95%, 97%, etc., as well as the range values ​​between any two of the above point values.

[0158] When the aforementioned silicon-oxygen-carbon composite material is added to the negative electrode coating, the resistivity of the negative electrode coating is 1.9 mΩ·cm. 2 Up to 13.8 mΩ·cm 2 In other words, based on the low powder resistivity of silicon-oxygen-carbon composite materials, the resistance of the negative electrode coating can be reduced, thereby improving the cycle performance of the battery.

[0159] Adding the aforementioned silicon-oxygen-carbon composite material to the negative electrode coating, with the compaction density of the negative electrode coating meeting the above-mentioned range, can improve the battery capacity.

[0160] Adding the aforementioned silicon-oxygen-carbon composite material to the negative electrode coating improves the porosity of the coating, as it meets the above-mentioned range and enhances the wettability of the electrolyte to the coating.

[0161] Adding the aforementioned silicon-oxygen-carbon composite material to the negative electrode coating, with the thickness of the negative electrode coating meeting the above-mentioned range, can further improve the cycle performance of the battery.

[0162] The above 1.9mΩ·cm 2 Up to 13.8 mΩ·cm 2 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 1.9 mΩ·cm. 2 3mΩ·cm 2 5mΩ·cm 2 8mΩ·cm 2 10mΩ·cm 2 12mΩ·cm 2 13.8mΩ·cm 2And so on, as well as the range of values ​​between any two of the above point values.

[0163] The above 0.75g / cm 3 Up to 1.96 g / cm 3 In this context, the values ​​include the minimum and maximum values ​​within the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 0.75 g / cm³. 3 1g / cm 3 1.5g / cm 3 1.75g / cm 3 1.96g / cm 3 And so on, as well as the range of values ​​between any two of the above point values.

[0164] The above 2.1m 2 / g to 34.6m 2 In / g, the values ​​include the minimum and maximum values ​​within that range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 2.1m. 2 / g、5m 2 / g, 10m 2 / g, 15m 2 / g、20m 2 / g、25m 2 / g、30m 2 / g, 34.6m 2 / g, etc., and the range of values ​​between any two of the above point values.

[0165] The values ​​in the range of 21% to 57% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments and 21%, 25%, 30%, 35%, 40%, 45%, 50%, 57%, etc., as well as the range values ​​between any two of the above point values.

[0166] The values ​​in the range of 43μm to 161μm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 43μm, 50μm, 80μm, 100μm, 120μm, 140μm, 161μm, etc., and the range values ​​between any two of the above point values.

[0167] In one embodiment, this application also provides a negative electrode active material, which includes a silicon-oxygen-carbon composite material, comprising SiOC and conductive agents located in the pores of SiOC and / or on the surface of SiOC.

[0168] In one embodiment, the conductive agent includes carbon nanotubes and / or graphene.

[0169] In one embodiment, the carbon nanotubes comprise 0% to 27% of the weight of the silicon-oxygen-carbon composite material.

[0170] In one embodiment, the volume average particle size (DV50) of the silicon-oxygen-carbon composite material is 5 μm to 15 μm; and / or, the specific surface area of ​​the silicon-oxygen-carbon composite material is 30 m². 2 / g to 150m 2 / g; and / or, the powder resistivity of the silicon-oxygen-carbon composite material is 5.7*10 -5 Ω·m to 1.1*10 -1 Ω·m.

[0171] In one embodiment, such as Figure 4 As shown, this application also provides a method for preparing a negative electrode active material, comprising: introducing a catalyst into the pores of SiOC and / or the surface of SiOC, pyrolyzing a carbon source on SiOC to form a conductive agent, and obtaining a silicon-oxygen-carbon composite material in which the pores of SiOC and / or the surface of SiOC are provided with a conductive agent.

[0172] It is understandable that carbon sources can pyrolyze to form conductive agents under catalytic conditions. Based on this principle, a catalyst is introduced into the pores and / or surface of SiOC, and the carbon source on SiOC is pyrolyzed to form a conductive agent, thereby forming a conductive agent in situ in the pores and / or surface of SiOC. Compared to doping conductive agents on SiOC, this method of in-situ preparation of conductive agents on SiOC results in a more uniform distribution of the conductive agent. Doping conductive agents on SiOC often leads to agglomeration, which blocks the transport channels of active ions, affecting their transport efficiency in the negative electrode active material. This prevents the formation of an effective conductive network within the negative electrode active material, thus impacting the battery's electrochemical performance. The in-situ preparation method of this application provides better dispersion of the conductive agent, offering more transport channels for the negative electrode active material. In other words, the conductive agent provides high-speed channels for the transport of active ions and electrons, reducing polarization, optimizing the surface potential energy distribution of SiOC, increasing the transport rate of active ions in SiOC, and increasing the sites for binding active ions in SiOC, thereby improving the energy storage of the negative electrode and ultimately enhancing the battery's cycle performance.

[0173] Furthermore, while catalyzing the formation of carbon nanotube structures, SiOC derives microstructures with high specific surface area. Due to the growth of carbon nanotubes, SiOC is separated from its original micron-scale bulk into several small nano-scale bulks, resulting in changes in the microstructure of free carbon and glass phase within SiOC, forming structures with even higher specific surface area.

[0174] This high specific surface area provides the negative electrode active material with more surface area for the insertion and extraction of active ions, which can increase the electrochemical reaction surface area. The microstructure can provide more channels to make it easier for the electrolyte to penetrate into the interior of the negative electrode active material particles, increasing the contact area between the negative electrode coating and the electrolyte. At the same time, the microstructure with a high specific surface area can provide more space to mitigate the huge volume changes that occur in SiOC during charging and discharging, thereby improving the electrochemical performance of the battery.

[0175] The SiOC anode active material itself contains a lot of free carbon, which is in an amorphous state. By introducing a catalyst, the free carbon inside the SiOC material can be transformed from amorphous carbon to ordered carbon. This method transforms amorphous carbon into ordered carbon, which reduces the low conductivity carbon inside the SiOC, reduces the adverse factors of the original low conductivity carbon, improves the conductivity of SiOC, and improves the electrochemical performance of the battery.

[0176] Understandably, the step of introducing the catalyst into the pores and / or surface of SiOC can involve preparing SiOC and introducing the catalyst into it. For example, the catalyst may be particulate, and since SiOC has a porous structure, the particulate catalyst can be introduced into the channels and surface of the SiOC. Alternatively, a SiOC precursor may be prepared, which also has a porous structure, and the catalyst can be introduced into the channels and surface of the SiOC precursor. Another approach is to prepare a solution for preparing the SiOC precursor, typically an organosilicon compound containing silicon, oxygen, and carbon. The catalyst is then introduced into the SiOC precursor solution, and the solution is converted into SiOC using processes such as the sol-gel method, thus positioning the catalyst within the channels and on the surface of the SiOC.

[0177] It is understandable that the carbon source on SiOC includes the carbon source inherent in SiOC itself, such as the carbon source formed by the cleavage of the branched alkyl groups of the SiOC precursor polymer during the SiOC preparation process, or the carbon source introduced from the outside.

[0178] In one embodiment, the step of introducing a catalyst into the pores and / or surface of SiOC and pyrolyzing a carbon source on SiOC to form a conductive agent includes: mixing a catalyst source with a polysiloxane monomer solution to obtain a mixed solution; heating the mixed solution to obtain a precursor; and calcining the precursor in an inert atmosphere to obtain SiOC and a catalyst and conductive agent located in the pores and / or on the surface of SiOC.

[0179] Understandably, the catalytic source is used to form the catalyst, and the polysiloxane monomer solution is used to form SiOC.

[0180] The catalyst source is introduced into the polysiloxane monomer solution by sol-gel method, and the catalyst is formed in situ in SiOC after pyrolysis. In addition, a conductive agent can also be formed in situ during the pyrolysis process. It can be understood that the polysiloxane monomer and / or the alkanes generated during the pyrolysis process can be used as carbon sources. During the calcination process, the carbon source can be converted into carbon materials with conductive properties, so that a conductive agent is provided on SiOC.

[0181] Alternatively, an external carbon source can be added to the mixed solution. During the calcination process, the carbon source can be converted into a carbon material with conductive properties, thus providing a conductive agent on the SiOC.

[0182] Specifically, in the preparation process of the negative electrode active material, the catalyst source used to form the catalyst is mixed with the polysiloxane monomer solution used to form SiOC, so that the catalyst source can be effectively dispersed in the polysiloxane monomer solution. The components in the polysiloxane monomer solution are reacted and converted into a precursor by heating. The catalyst source is dispersed in the precursor. Then, the precursor is converted into SiOC by calcination under an inert atmosphere, the catalyst source is converted into a catalyst, and the carbon source is converted into a carbon material with conductive properties, thus obtaining SiOC and catalyst and conductive agent located in the pores of SiOC and / or located on the surface of SiOC.

[0183] It is also understandable that the organic components in the polysiloxane monomer solution can serve as a carbon source, and alkane gases, which are also produced during the pyrolysis of polysiloxanes, can also serve as a carbon source. Specifically, since the side and end groups of polysiloxanes contain CH3, these will detach and form CH4 gas during molecular rearrangement. The ceramic yield of the polysiloxane pyrolysis process is below 70%, so there must be some pre-existing reactants that are pyrolyzed into gas during the pyrolysis process. That is, during the pyrolysis process, an in-situ carbon source can be used to obtain a conductive agent on SiOC, or an external carbon source or conductive agent can be added to the mixed solution to obtain a conductive agent on SiOC.

[0184] It is also understandable that, compared to adding carbon sources or conductive agents externally, using organic raw materials added during the overall preparation process, or organic products generated during the preparation process as carbon sources, results in a more uniform distribution of carbon nanotubes generated in SiOC.

[0185] In one embodiment, the step of mixing the catalyst source with the polysiloxane monomer solution to obtain a mixed solution includes: preparing a catalyst source solution; preparing a polysiloxane monomer solution; and mixing the catalyst source solution with the polysiloxane monomer solution to obtain a mixed solution.

[0186] Understandably, in theory, during the preparation of the mixed solution, the catalyst source can be directly mixed with the polysiloxane monomer solution, or the catalyst source can be dispersed in the solution and then the catalyst source solution can be mixed with the polysiloxane monomer solution.

[0187] Considering that the uneven dispersion of the catalyst source on the precursor will affect the uniform dispersion of the catalyst on SiOC, and thus affect the uniform dispersion of the conductive agent formed by catalysis, and will also cause the catalyst particle size to be too large, resulting in the large catalyst particles squeezing the pores of SiOC and destroying the structure of SiOC. Therefore, this application adopts the following method: preparing a catalyst source solution; preparing a polysiloxane monomer solution; and mixing the catalyst source solution and the polysiloxane monomer solution to obtain a mixed solution.

[0188] Understandably, the high viscosity of polysiloxane monomer solutions hinders the dispersion of the catalyst source. Therefore, preparing the catalyst source as a low-viscosity solution separately, and then mixing the two solutions, can yield a catalyst source with molecular-level homogeneity in a short time. In other words, a catalyst source solution can be prepared in advance to achieve low viscosity, allowing for the rapid acquisition of a catalyst source with molecular-level homogeneity.

[0189] Specifically, taking the FeNi alloy catalyst as an example, the iron and nickel sources are first dispersed in a solvent to form a low-viscosity solution, which can achieve molecular-level uniformity in a short time. This facilitates the nanoscale dispersion of iron and nickel elements in the polysiloxane monomer solution, achieving uniform doping at the molecular level. During the pyrolysis of the polysiloxane, iron and nickel elements derive uniformly dispersed FeNi alloy catalysts within SiOC. The surface of the FeNi alloy catalyst has active sites for adsorbing carbon source gas. The carbon source adsorbs and decomposes on the FeNi alloy surface to form carbon atoms, resulting in the nucleation reaction of carbon nanotubes. The carbon atoms self-assemble to form hexagonal structures, and as the reaction proceeds, the carbon nanotubes gradually grow. Furthermore, the FeNi alloy particles are generally located at the top of the carbon nanotubes, serving as growth templates. The uniform dispersion of the catalyst in SiOC helps to uniformly disperse the in-situ formed carbon nanotubes within SiOC, thereby providing more transport channels for the negative electrode active material.

[0190] In one embodiment, the steps of preparing a polysiloxane monomer solution and mixing a catalyst source solution with the polysiloxane monomer solution to obtain a mixed solution include: preparing a polysiloxane monomer solution; heating the polysiloxane monomer solution to obtain a pre-crosslinked solution; and mixing the catalyst source solution with the pre-crosslinked solution to obtain a mixed solution.

[0191] To ensure effective adsorption and localization of the catalyst source and improve the yield of precursor pyrolysis to SiOC, after preparing the polysiloxane monomer solution, the polysiloxane monomer solution is heated to obtain a pre-crosslinked solution. That is, during the pre-crosslinking process, silane hydrogen undergoes hydrosilylation with some alkenyl groups to form small molecule silane polymers. This can increase the viscosity and improve the reaction yield of the reactants in the polysiloxane monomer solution, reducing the risk of unreacted reactants volatilizing during pyrolysis, thereby increasing the yield of precursor pyrolysis to SiOC.

[0192] In one embodiment, in the step of heating the polysiloxane monomer solution to obtain a pre-crosslinked solution, the heating temperature is 50°C to 80°C and the heating time is 10 min to 60 min.

[0193] In order to effectively adsorb and locate the catalyst source and improve the yield of precursor pyrolysis to SiOC, in the step of heating the polysiloxane monomer solution to obtain a pre-crosslinked solution, the heating temperature is 50°C to 80°C and the heating time is 10 min to 60 min.

[0194] The values ​​in the range of 50°C to 80°C include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc., as well as the range values ​​between any two of the above point values.

[0195] The values ​​within the range of 10 min to 60 min include the minimum and maximum values ​​of that range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc., as well as the range values ​​between any two of the above point values.

[0196] In one embodiment, the step of heating the mixed solution to obtain the precursor includes: heating the mixed solution to obtain a block, crushing the block to obtain the precursor, wherein the volume average particle size D50 of the precursor ranges from 9 μm to 30 μm.

[0197] In the step of heating the mixed solution to obtain the precursor, the bulk material is ground into powder before the subsequent calcination step. If the bulk precursor is directly calcined, the resulting large blocks would be difficult to grind further. This is understandable because after calcination, carbon nanotubes are already formed within or on the surface of the SiOC pores. During the grinding of these larger blocks into powder, i.e., during the SiOC crushing process, ruptures can occur at the pores, causing carbon nanotubes to detach from the SiOC and reducing its content. Therefore, grinding the precursor into powder before calcination mitigates the risk of carbon nanotube detachment during subsequent processing, increases the carbon nanotube content, and improves the conductivity of the negative electrode active material. Furthermore, the powdered precursor undergoes a shorter and more thorough conversion during calcination, further reducing the overall calcination time.

[0198] The values ​​in the range of 9μm to 30μm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 9μm, 11μm, 12μm, 13μm, 14μm, 15μm, 17μm, 20μm, 25μm, 30μm, etc., as well as the range values ​​between any two of the above point values.

[0199] In one embodiment, in the step of heating the mixed solution to obtain the precursor, the heating temperature range is 80°C to 200°C, and the heating time is 1h to 12h; and / or, in the step of calcining the precursor in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of SiOC and / or on the surface of SiOC, the step includes heating the precursor in an inert gas atmosphere to 300°C to 1000°C at a heating rate of 1°C / min to 20°C / min, calcining at a constant temperature for 5min to 240min, and cooling at a cooling rate of 0.5°C / min to 20°C / min; and / or, after the step of calcining the precursor in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of SiOC and / or on the surface of SiOC, an acid washing step is further included.

[0200] In one embodiment, the mixed solution is heated to cause the polysiloxane monomers in the mixed solution to react and generate polysiloxane. The catalyst source is uniformly dispersed in the polysiloxane skeleton to form a precursor. The heating temperature range is 80°C to 200°C, and the heating time is 1h to 12h.

[0201] The values ​​in the range of 80℃ to 200℃ include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, etc., as well as the range values ​​between any two of the above point values.

[0202] The values ​​in the range 1h to 12h include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, as well as 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc., and the range values ​​between any two of the above point values.

[0203] In one embodiment, during the calcination of the precursor in an inert atmosphere, the polysiloxane is pyrolyzed into SiOC, the catalytic source is converted into a catalyst, and the catalyst is located on the SiOC. The calcination procedure is as follows: heating to 300°C to 1000°C at a heating rate of 1°C / min to 20°C / min, constant-temperature calcination for 5 min to 240 min, and cooling at a cooling rate of 1°C / min to 20°C / min.

[0204] The values ​​in the range of 1℃ / min to 20℃ / min include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1℃ / min, 2℃ / min, 5℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 15℃ / min, 18℃ / min, 20℃ / min, etc., as well as the range values ​​between any two of the above point values.

[0205] The values ​​in the range of 300℃ to 1000℃ include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, etc., as well as the range values ​​between any two of the above point values.

[0206] In one embodiment, the metal-type catalyst on the SiOC can cause battery self-discharge to some extent, and acid washing is used to reduce and remove the metal-type catalyst.

[0207] In one embodiment, the catalyst source includes a transition metal source; and / or, the polysiloxane monomer solution includes hydrogen-containing silicone oil, a crosslinking agent, and a hydrosilylation catalyst; and / or, the conductive agent includes carbon nanotubes and / or graphene.

[0208] In one embodiment, a transition metal can act as a catalyst to convert a carbon source into carbon nanotubes during calcination.

[0209] In one embodiment, the polysiloxane monomer solution includes hydrogen-containing silicone oil, a crosslinking agent, and a hydrosilylation catalyst.

[0210] In one embodiment, the conductive agent includes carbon nanotubes and / or graphene.

[0211] In one embodiment, the transition metal source includes at least one of an iron source, a nickel source, and a cobalt source; and / or, the mass ratio of the hydrogen-containing silicone oil to the crosslinking agent ranges from 100:(1 to 300); and / or, the mass ratio of the hydrogen-containing silicone oil to the catalyst source ranges from 10:(0.001 to 4); and / or, the hydrogen-containing silicone oil includes at least one of polymethylhydrosiloxane, tetramethyltetrahydrocyclotetrasiloxane, carboxylated siloxane polymer, aminosiloxane polymer, and cyclosiloxane siloxane polymer; and / or, the crosslinking agent includes at least one of divinylbenzene, 1,5-hexadiene, bis(trivinyl)disiloxane, and trivinylethylene oxide; and / or, the hydrosilylation catalyst includes at least one of chloroplatinic acid and castalplatin.

[0212] In the preparation of negative electrode active materials, the transition metal source includes at least one of iron, nickel, and cobalt. It is understood that to obtain in-situ generated carbon nanotubes, the transition metal source includes at least one of iron, nickel, and cobalt. The generation of carbon nanotubes requires at least one of iron, nickel, and cobalt as a catalyst. Specifically, the surface of transition metal particles (iron, nickel, cobalt, and their alloys) has active sites for adsorbing carbon source gas. The carbon source adsorbs and decomposes on the metal surface to form carbon atoms, resulting in a nucleation reaction of carbon nanotubes. The carbon atoms self-assemble to form a hexagonal structure, and as the reaction proceeds, the carbon nanotubes gradually grow.

[0213] In one embodiment, the mass ratio of hydrogen-containing silicone oil to the catalyst source ranges from 10:(0.001 to 4). Theoretically, as the mass of the transition metal source increases within a certain range, the catalyst content will also increase. However, metal catalysts are prone to causing the risk of battery self-discharge. Therefore, the catalyst content is reduced.

[0214] In the above 10: (0.001 to 4), the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 10:0.001, 10:0.01, 10:0.1, 10:0.4, 10:0.5, 10:0.6, 10:0.7, 10:0.8, 10:0.9, 10:1, 10:2, 10:3, 10:4, etc., as well as the range values ​​between any two of the above point values.

[0215] In one embodiment, the hydrogen-containing silicone oil includes at least one of polymethylhydrosiloxane, tetramethyltetrahydrocyclotetrasiloxane, carboxylated siloxane polymer, aminosiloxane polymer, and cyclosiloxane siloxane polymer.

[0216] In one embodiment, the crosslinking agent includes at least one of divinylbenzene, 1,5-hexadiene, bis(trivinyl)disiloxane, and trivinylethylene oxide.

[0217] In one embodiment, the hydrosilylation catalyst includes at least one of chloroplatinic acid and castalplatin.

[0218] In one embodiment, the iron source includes at least one of ferric nitrate, ferric acetylacetonate, and ferrous carbonate; and / or, the nickel source includes at least one of nickel nitrate, nickel acetylacetonate, and nickel carbonate; and / or, the cobalt source includes at least one of cobalt nitrate, cobalt acetylacetonate, and cobalt carbonate; and / or, the mass ratio of iron in the iron source to nickel in the nickel source and / or cobalt in the cobalt source is in the range of (1:0.01):(1:2).

[0219] In one embodiment, the iron source includes at least one of ferric nitrate, ferric acetylacetone, and ferrous carbonate.

[0220] In one embodiment, the nickel source includes at least one of nickel nitrate, nickel acetylacetonate, and nickel carbonate.

[0221] In one embodiment, the cobalt source includes at least one of cobalt nitrate, cobalt acetylacetonate, and cobalt carbonate.

[0222] In one embodiment, the mass ratio of iron in the iron source to nickel in the nickel source and / or cobalt in the cobalt source is in the range of (1:0.01):(1:2). The alloy catalysis effect on the formation of carbon nanotubes is better. Compared with introducing a single metal Fe in SiOC, introducing multiple alloys (Fe, Ni, Co, etc.) can catalyze the formation of more carbon nanotubes to provide more transport channels for active ions.

[0223] In the above (1:0.01):(1:2), the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1:0.01, 1:0.1, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:2, etc., as well as the range values ​​between any two of the above point values.

[0224] In one embodiment, the solvent in the catalyst source solution includes at least one of toluene, xylene, acetone, dimethylformamide, dimethylacetamide, tetrahydrofuran, and N-methylpyrrolidone; and / or, the mass ratio of the catalyst source to the solvent in the catalyst source solution ranges from 1:(0.5 to 50).

[0225] In one embodiment, the solvent of the catalyst source solution includes at least one of toluene, xylene, acetone, dimethylformamide, dimethylacetamide, tetrahydrofuran, and N-methylpyrrolidone.

[0226] In one embodiment, the mass ratio of the catalyst source to the solvent is in the range of 1:(0.5 to 50). Within this range, the transition metal source can be well dissolved and dispersed in the solvent.

[0227] In the above 1: (0.5 to 50), the value includes the minimum and maximum value of the range, as well as every value between the minimum and maximum value. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1:0.5, 1:1, 1:5, 1:10, 1:20, 1:30, 1:40, 1:45, 1:50, etc., as well as the range values ​​between any two of the above point values.

[0228] In one embodiment, this application also provides an electrical device, which includes a secondary battery as described above.

[0229] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0230] In one embodiment of this application, a secondary battery is provided.

[0231] Typically, a secondary battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the electrodes while allowing ions to pass through. The separator described above is the type used in this application.

[0232] The positive electrode includes a positive current collector and a positive coating disposed on at least one surface of the positive current collector.

[0233] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive coating is disposed on either or both of the two opposite surfaces of the positive current collector.

[0234] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0235] In some embodiments, when the secondary battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0236] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0237] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0238] In some embodiments, the positive electrode coating may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0239] In some embodiments, the positive electrode coating may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0240] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0241] The negative electrode sheet includes a negative current collector and a negative electrode coating disposed on at least one surface of the negative current collector, the negative electrode coating including a negative electrode active material.

[0242] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode coating is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0243] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0244] In some embodiments, in addition to the silicon-oxygen-carbon composite material of this application, other negative electrode active materials known in the art for use in batteries may also be used as the negative electrode active material. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0245] In some embodiments, the negative electrode coating may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0246] In some embodiments, the negative electrode coating may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0247] In some embodiments, the negative electrode coating may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0248] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0249] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0250] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0251] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0252] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0253] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0254] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0255] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 5 The example shown is a square-structured battery cell 5.

[0256] In some implementations, refer to Figure 6 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0257] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0258] Figure 7 This is battery module 4, used as an example. (See reference...) Figure 7 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0259] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0260] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0261] Figure 8 and Figure 9 This is battery pack 1 as an example. (See reference...) Figure 8 and Figure 9 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0262] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, 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.), electric trains, ships and satellites, energy storage systems, etc.

[0263] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0264] Figure 10 This is an example of an electrical device. The 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 individual battery cells, a battery pack or battery module can be used.

[0265] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0266] Example

[0267] Example 1

[0268] Preparation of silicon-oxygen-carbon composite materials

[0269] Preparation of the catalyst source solution: 1g of iron acetylacetone (iron source) and 2.9g of cobalt acetylacetone (cobalt source) were added to 10ml of dimethylacetamide and stirred magnetically at 80℃ for 30min to obtain the catalyst source solution.

[0270] Preparation of polysiloxane monomer solution: 100g of polymethylhydrosiloxane (containing hydrosilicone oil) was mixed with divinylbenzene (crosslinking agent) and casterplatin catalyst, and the ratio of m(polymethylhydrosiloxane) / m(divinylbenzene) / m(casterplatin catalyst) was controlled to be 100:50:0.00005. The mixture was heated at 60℃ for 30min to obtain a pre-crosslinked solution.

[0271] Preparation of the mixed solution: The catalyst source solution obtained above is mixed with the pre-crosslinked solution to obtain the mixed solution.

[0272] Preparation of precursor: The above mixed solution was dried in an oven at 100°C to obtain a block, which was then crushed to obtain precursor powder.

[0273] The steps for converting polysiloxane into SiOC are as follows: The above precursor powder is heated from room temperature to 750°C at a heating rate of 2°C / min under an argon atmosphere, calcined at a constant temperature for 120 min, and then cooled to room temperature at a rate of 2°C / min to obtain a silicon-oxygen-carbon composite material. The silicon-oxygen-carbon composite material consists of SiOC and carbon nanotubes located in the pores of SiOC and / or located on the surface of SiOC.

[0274] Material purification steps: The obtained silicon-oxygen-carbon composite material was acid-washed, then washed with deionized water and ethanol, and finally centrifuged. The silicon-oxygen-carbon composite material was dried in an oven at 80℃ for 12 hours to obtain the desired silicon-oxygen-carbon composite material.

[0275] Understandably, after obtaining the silicon-oxygen-carbon composite material sample, it was first subjected to a fire treatment, which did not decompose it. Then, X-ray diffraction (XRD) was used to test its characteristic peaks, revealing a broad peak near 23°. X-ray photoelectron spectroscopy (XPS) analysis confirmed the elemental composition as Si, O, and C, and the presence of SiO bonds on the surface indicated the preparation of SiOC. The silicon-oxygen-carbon composite material sample was characterized using a Rigaku D / max 2550PC X-ray diffractometer, which used CuKα as the radiation source, to obtain information on its phase structure, composition, particle size, and crystallinity. The operating voltage is 40kV, the tube current is 40mA, the measurement range is 2θ=10° to 80°, and X-ray diffraction data are recorded with a step width of 0.02° and a step rate of 12° / min.

[0276] SEM testing was performed on the catalyst material from Example 1 using a ZEISS Sigma 300 scanning electron microscope, and then the morphology of the samples was observed according to standard JY / T010-1996. Figure 2 As shown, the silicon-oxygen-carbon composite material has a porous framework and a fluffy surface. The fluffy structure is essentially a case of numerous carbon nanotubes extending on the SiOC surface.

[0277] TEM testing was performed using a transmission electron microscope (FEI Tecnai G2F20 S-TWIN type) manufactured by FEI Corporation, USA, to analyze the surface morphology and microstructure of the silicon-oxygen-carbon composite material. The maximum accelerating voltage was 200 kV, and the maximum magnification was 1,000,000 times. The TEM sample preparation method was as follows: a small amount of the ground silicon-oxygen-carbon composite material sample powder was placed in anhydrous ethanol and sonicated for 30 minutes to form a uniform light gray dispersion. A small amount of the liquid was then pipetted onto the front side of a porous carbon support copper mesh, allowed to dry naturally, and then placed in the instrument for testing. Figure 3 As shown in the TEM image, carbon nanotubes with diameters ranging from 20 nm to 50 nm are uniformly distributed in the structure of SiOC. This dispersed structure can effectively increase the specific surface area of ​​SiOC, providing a high-speed channel for lithium-ion transport. The silicon-oxygen-carbon composite material has high electrical conductivity, which improves the transport rate of lithium ions in the material.

[0278] Preparation of negative electrode sheet

[0279] The silicon-oxygen-carbon composite material (Dv50 11.2μm), conductive carbon black, binder vinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) of Example 1 were mixed in a weight ratio of 96.2:5:5:10 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry was uniformly coated on the negative electrode current collector copper foil, and then dried, cold-pressed, and slit to obtain the negative electrode sheet.

[0280] Preparation of positive electrode sheet

[0281] Nickel-cobalt-manganese (NCM) ternary material, conductive agent carbon black, binder polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) were mixed evenly in a weight ratio of 67.34:30:28.86:2.7 to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the positive electrode current collector, followed by drying, cold pressing, and slitting to obtain the positive electrode sheet.

[0282] Preparation of electrolyte

[0283] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly at a volume ratio of 3 / 7. 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent and stirred evenly to obtain the electrolyte of Example 1.

[0284] diaphragm

[0285] Polypropylene membrane is used as the diaphragm.

[0286] Preparation of lithium-ion batteries

[0287] The negative electrode sheet, separator, and negative electrode sheet of Example 1 are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. They are then wound to obtain a bare cell. Tabs are welded to the bare cell, which is then placed in an aluminum casing and baked at 80°C to remove moisture. Electrolyte is then injected and the casing is sealed to obtain a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product of Example 1.

[0288] Examples 2 to 8

[0289] Based on Example 1, the type and proportion of the catalyst source were adjusted.

[0290] Comparative Example 1

[0291] Based on Example 1, with other conditions remaining unchanged, the negative electrode active material was replaced with commercially available SiOC, which has a Dv50 of 13 μm.

[0292] Comparative Example 2

[0293] Based on Example 1, commercially available SiOC was physically mixed with commercially available carbon nanotubes to obtain a mixed negative electrode active material.

[0294] The steps for blending SiOC with carbon nanotubes are as follows: SiOC, carbon nanotubes, and carboxymethyl cellulose are prepared in a mass ratio of 9.5:0.5:1.5, stirred in ethanol solvent for 6 hours, and dried to obtain the blended negative electrode active material.

[0295] Battery capacity retention test

[0296] Taking Example 1 as an example, the battery capacity retention rate test process is as follows: At 25°C, the battery corresponding to Example 1 is charged to 4.3V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 4.3V, left to rest for 5 minutes, and then discharged to 2.8V at 1 / 3C. The resulting capacity is recorded as the initial capacity C0. The above steps are repeated for the same battery, and the discharge capacity Cn of the battery after the nth cycle is recorded. Then, the battery capacity retention rate Pn after each cycle is Pn = Cn / C0*100%. The relationship between the battery capacity retention rate and the number of cycles is obtained by using the 500 points P1, P2...P500 as the vertical axis and the corresponding number of cycles as the horizontal axis.

[0297] During this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 500th cycle to n=500. The battery capacity retention rate and specific capacity data corresponding to Example 1 in Table 1 are data measured after 500 cycles under the above test conditions, i.e., the value of P500. The test process for the comparative example and other examples is the same as above.

[0298] Table 1 List of Examples

[0299]

[0300] As shown in Table 1 above, the powder resistivity of the silicon-oxygen-carbon composite material in the examples is lower than that in Comparative Example 1, and the battery capacity retention is improved. This indicates that the pores and / or conductive agents on the surface of SiOC can provide high-speed channels for the transport of active ions and electrons, improving the energy storage capacity of the negative electrode and thus enhancing the cycle performance of the battery. Furthermore, compared to a single metal catalyst, the introduction of multiple metal alloys as catalysts results in lower powder resistivity and increased specific surface area of ​​the silicon-oxygen-carbon composite material, indicating that the alloy catalyst can catalyze the formation of more carbon nanotubes.

[0301] Comparative Example 2, which uses a physical mixing method to prepare the negative electrode active material by mixing SiOC and carbon nanotubes, exhibits inferior cycle performance compared to the negative electrode active material obtained by in-situ growth of carbon nanotubes in SiOC in the examples. In other words, the in-situ growth of carbon nanotubes in SiOC using the method described in this application introduces carbon nanotubes into the pores of SiOC, providing high-speed channels for the transport of active ions and electrons, improving the energy storage capacity of the negative electrode, and thus enhancing the cycle performance of the battery.

[0302] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A secondary battery, characterized in that, The secondary battery includes a positive electrode, a negative electrode, and a separator; The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one surface of the negative electrode current collector; The negative electrode coating includes a negative electrode active material, which includes a silicon-oxygen-carbon composite material, comprising SiOC and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC.

2. The secondary battery as described in claim 1, characterized in that, The conductive agent includes carbon nanotubes and / or graphene.

3. The secondary battery as described in claim 2, characterized in that, The carbon nanotubes comprise 0% to 27% of the total weight of the silicon-oxygen-carbon composite material.

4. The secondary battery as described in any one of claims 1 to 3, characterized in that, The volume average particle size Dv50 of the silicon-oxygen-carbon composite material is 5 μm to 15 μm; And / or, the specific surface area of ​​the silicon-oxygen-carbon composite material is 30 m². 2 / g to 150m 2 / g; And / or, the powder resistivity of the silicon-oxygen-carbon composite material is 5.7*10⁻⁶. -5 Ω·m to 1.1*10 -1 Ω·m.

5. The secondary battery as described in any one of claims 1 to 4, characterized in that, The mass percentage of the silicon-oxygen-carbon composite material is 50% to 97% based on the total mass of the negative electrode coating; And / or, the resistance of the negative electrode coating is 1.9 mΩ·cm. 2 Up to 13.8 mΩ·cm 2 ; And / or, the compaction density of the negative electrode coating is 0.75 g / cm³. 3 Up to 1.96 g / cm 3 ; And / or, the specific surface area of ​​the negative electrode coating is 2.1 m². 2 / g to 34.6m 2 / g; And / or, the porosity of the negative electrode coating is 21% to 57%; And / or, the thickness of the negative electrode coating is from 43 μm to 161 μm.

6. A negative electrode active material, characterized in that, The negative electrode active material includes a silicon-oxygen-carbon composite material, which includes SiOC and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC.

7. The negative electrode active material as described in claim 6, characterized in that, The conductive agent includes carbon nanotubes and / or graphene.

8. The negative electrode active material as described in claim 7, characterized in that, The carbon nanotubes comprise 0% to 27% of the total weight of the silicon-oxygen-carbon composite material.

9. The negative electrode active material according to any one of claims 6 to 8, characterized in that, The volume average particle size (DV50) of the silicon-oxygen-carbon composite material is 5 μm to 15 μm. And / or, the specific surface area of ​​the silicon-oxygen-carbon composite material is 30 m². 2 / g to 150m 2 / g; And / or, the powder resistivity of the silicon-oxygen-carbon composite material is 5.7*10⁻⁶. -5 Ω·m to 1.1*10 -1 Ω·m.

10. A method for preparing a negative electrode active material, characterized in that, include: A catalyst is introduced into the pores and / or surface of SiOC, and a carbon source on the SiOC is pyrolyzed to form a conductive agent, resulting in a silicon-oxygen-carbon composite material in which the conductive agent is disposed in the pores and / or surface of the SiOC.

11. The method for preparing the negative electrode active material according to claim 10, characterized in that, The step of introducing the catalyst into the pores and / or surface of SiOC, and pyrolyzing the carbon source on the SiOC to form a conductive agent includes: The catalyst source was mixed with a polysiloxane monomer solution to obtain a mixed solution; The mixed solution was heated to obtain the precursor; The precursor is calcined in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC.

12. The method for preparing the negative electrode active material as described in claim 11, characterized in that, The step of mixing the catalyst source with the polysiloxane monomer solution to obtain a mixed solution includes: Prepare the catalyst source solution; Prepare a polysiloxane monomer solution; The catalyst source solution is mixed with the polysiloxane monomer solution to obtain a mixed solution.

13. The method for preparing the negative electrode active material as described in claim 12, characterized in that, The steps of preparing the polysiloxane monomer solution and mixing the catalyst source solution with the polysiloxane monomer solution to obtain a mixed solution include: Prepare a polysiloxane monomer solution; The polysiloxane monomer solution was heated to obtain a pre-crosslinked solution; The catalyst source solution is mixed with the pre-crosslinked solution to obtain a mixed solution.

14. The method for preparing the negative electrode active material as described in claim 13, characterized in that, In the step of heating the polysiloxane monomer solution to obtain a pre-crosslinked solution, the heating temperature is 50°C to 80°C, and the heating time is 10 min to 60 min.

15. The method for preparing the negative electrode active material according to any one of claims 11 to 14, characterized in that, The step of heating the mixed solution to obtain the precursor includes: heating the mixed solution to obtain a block, crushing the block to obtain the precursor, wherein the volume average particle size D50 of the precursor ranges from 9 μm to 30 μm.

16. The method for preparing the negative electrode active material according to any one of claims 11 to 15, characterized in that, In the step of heating the mixed solution to obtain the precursor, the heating temperature range is 80°C to 200°C, and the heating time is 1 hour to 12 hours. And / or, in the step of calcining the precursor in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC, the precursor is heated to 300°C to 1000°C in an inert gas atmosphere at a heating rate of 1°C / min to 20°C / min, isothermal calcined for 5 min to 240 min, and cooled at a cooling rate of 0.5°C / min to 20°C / min. And / or, after the step of calcining the precursor in an inert atmosphere to obtain SiOC and catalysts and conductive agents located in the pores of the SiOC and / or on the surface of the SiOC, an acid washing step is further included.

17. The method for preparing the negative electrode active material according to any one of claims 11 to 16, characterized in that, The catalyst source includes a transition metal source; And / or, the polysiloxane monomer solution includes hydrogen-containing silicone oil, crosslinking agent, and hydrosilylation catalyst; And / or, the conductive agent includes carbon nanotubes and / or graphene.

18. The method for preparing the negative electrode active material as described in claim 17, characterized in that, The transition metal source includes at least one of iron source, nickel source, and cobalt source; And / or, the mass ratio of the hydrogen-containing silicone oil to the crosslinking agent ranges from 100:(1 to 300); And / or, the mass ratio of the hydrogen-containing silicone oil to the catalyst source ranges from 10:(0.001 to 4); And / or, the hydrogen-containing silicone oil includes at least one of polymethylhydrosiloxane, tetramethyltetrahydrocyclotetrasiloxane, carboxylated siloxane polymer, aminosiloxane polymer, and cyclosiloxane siloxane polymer; And / or, the crosslinking agent includes at least one of divinylbenzene, 1,5-hexadiene, bis(trivinyl)disiloxane, and trivinylethylene oxide; And / or, the hydrosilylation catalyst includes at least one of chloroplatinic acid and castalplatin.

19. The method for preparing the negative electrode active material as described in claim 18, characterized in that, The iron source includes at least one of ferric nitrate, ferric acetylacetone, and ferrous carbonate. And / or, the nickel source includes at least one of nickel nitrate, nickel acetylacetonate, and nickel carbonate; And / or, the cobalt source includes at least one of cobalt nitrate, cobalt acetylacetonate, and cobalt carbonate; And / or, the mass ratio of iron in the iron source to nickel in the nickel source and / or cobalt in the cobalt source is in the range of (1:0.01):(1:2).

20. The method for preparing the negative electrode active material according to any one of claims 12 to 19, characterized in that, The solvent in the catalyst source solution includes at least one of toluene, xylene, acetone, dimethylformamide, dimethylacetamide, tetrahydrofuran, and N-methylpyrrolidone. And / or, the mass ratio of the catalyst source to the solvent in the catalyst source solution ranges from 1:(0.5 to 50).

21. An electrical appliance, characterized in that, The electrical device includes a secondary battery as described in any one of claims 1 to 5.

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