CN115810741A

CN115810741A - Negative active material, method of preparing the same, and secondary battery and device using the same

Info

Publication number: CN115810741A
Application number: CN202111631872.4A
Authority: CN
Inventors: 吕子建; 王家政
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2021-12-28
Filing date: 2021-12-28
Publication date: 2023-03-17
Also published as: WO2023124913A1

Abstract

Provided are a negative active material, a method of preparing the same, and a secondary battery and device related thereto, wherein the negative active material includes silica particles having a conductive component contained therein in bulk phase. By distributing the conductive component in the silicon monoxide bulk phase, the bulk phase conductivity is improved, the lithium intercalation and lithium deintercalation capacity of the material is improved, and the realization of higher first coulombic efficiency and better quick charge performance is facilitated.

Description

Negative active material, method of preparing the same, and secondary battery and device using the same

Technical Field

The present application relates to the field of lithium battery technology, and more particularly, to a negative active material, a method of preparing the same, and a secondary battery and a device using the same.

Background

With the increasing demand of people on the specific energy of lithium ion batteries, the application of silicon negative electrode materials has become an unblocked trend, and the research hotspots of various large material manufacturers are mainly focused on SiOx materials because the volume expansion of crystalline Si materials is large at present. However, because the SiOx material can generate inactive Li2O and Li4SiO4 products in the process of lithium insertion, and partial Li loses activity, the first efficiency of the SiOx material is only about 70% generally, and the low first efficiency is one of the important factors restricting the practical application of the SiOx.

Therefore, it is highly desirable to develop a novel silicon-based material that can simultaneously achieve better electrochemical and kinetic properties for secondary batteries.

Disclosure of Invention

The application aims to provide a negative electrode active material, a preparation method thereof, a related secondary battery and a device, and aims to enable the battery to simultaneously give consideration to high first coulomb efficiency and good quick charge performance.

A first aspect of the present application provides a negative electrode active material including a silica particle containing a conductive component in its bulk phase.

The silicon monoxide (SiO) is one of the most practical lithium ion battery cathode materials at present due to the advantages of high theoretical specific capacity, proper lithium intercalation and deintercalation potential, long cycle charge and discharge life, rich reserves, environmental friendliness and the like. However, the inherent low intrinsic conductivity of SiO materials and the volume change effects encountered during cycling remain major technical hurdles that limit their practical commercialization. Therefore, the conductive component is distributed in the silicon monoxide bulk phase, so that the conductivity of the silicon monoxide bulk phase is improved, the lithium insertion and removal capacity of the material is improved, and the realization of higher first coulombic efficiency and better quick charge performance is facilitated.

In any embodiment herein, the conductive component is selected from carbon-based materials; optionally, the carbon-based material is selected from one or more of conductive carbon black, carbon nanotubes, graphene and carbon fibers. The porous carbon with high specific surface area is used as a conductive component, so that the conductivity of the negative active material is further improved.

In any embodiment of the present application, the conductive component includes carbon nanotubes, and optionally, the tube diameter of the carbon nanotubes is 1.6 ± 0.4nm, and the tube length is 5 to 20 μm. The carbon nano tube is beneficial to further improving the conductivity and the volume expansion adaptability of the negative electrode active material, and the fibrous structure of the carbon nano tube can form a continuous conductive network in the negative electrode active material, so that the permeability of electrolyte in the electrode material is further improved. The carbon nano tube has better fillability and compressibility when the tube diameter is 1.6 +/-0.4 nm and the tube length is 5-20 mu m, can improve the combination efficiency of the conductive component and the silicon monoxide phase, and further improves the conductivity and the first coulombic efficiency.

In any embodiment herein, the mass percentage of the conductive component to the silica is 1% to 5%, optionally 2% to 4%. The addition amount of the conductive component is not suitable to be too high or too low, the conductivity cannot be obviously improved when the addition amount is too small, the specific surface is increased when the addition amount is too large, and the first coulombic efficiency and gram capacity of the material are influenced. The content ratio of the conductive component is within an appropriate range, and the capacity can be further improved.

In any of the embodiments herein, at least a portion of a surface of the anode active material is provided with a carbon coating layer. The surface of the cathode active material is coated with the carbon coating layer, so that the conductivity of the material can be further improved, and the addition of the carbon coating layer plays a role in buffering the volume expansion and shrinkage of the material in the charging and discharging processes, so that the cycle performance of the battery is further improved.

In any embodiment herein, the volume distribution particle diameter Dv50 of the negative electrode active material is 4 μm to 10 μm; and is selected from 6 μm to 8 μm. The Dv50 of the negative electrode active material is within an appropriate range, and the quick charge performance of the secondary battery can be further improved, and it is also advantageous to increase the energy density of the battery.

In any of the embodiments herein, the specific surface area of the negative electrode active material is from 0.5m2/g to 2m2/g; and can be selected from 0.8m2/g to 1.6m2/g. The specific surface area of the negative electrode active material is within the above range, and lithium consumption can be reduced, thereby further improving the first coulombic efficiency of the secondary battery.

In any of the embodiments of the present application, the negative electrode active material has a powder resistivity of 1 Ω · cm or less at 4 MPa; can be selected to be less than or equal to 0.8 omega cm. The powder resistivity of the negative electrode active material is within the above range, and the first coulombic efficiency and cycle life of the negative electrode active material can be further improved.

The second aspect of the present application also provides a method for preparing an anode active material, comprising the steps of:

s1: providing silicon dioxide powder, silicon powder and a conductive component;

s2: mixing the silicon dioxide powder and the silicon powder, placing the mixture into a heating chamber of a vapor deposition furnace, placing the conductive component into a deposition chamber of the vapor deposition furnace, arranging a valve between the heating chamber and the deposition chamber, and vacuumizing the heating chamber and the deposition chamber;

s3: forming silicon dioxide vapor from the silicon dioxide powder and the silicon powder at a certain temperature, opening a valve between the heating chamber and the deposition chamber, and depositing the silicon dioxide vapor on at least one part of the surface of the conductive component by adopting a vapor deposition method to obtain the negative electrode active material;

wherein the negative electrode active material includes a silica particle containing a conductive component in a bulk phase.

The negative active material obtained by the preparation method comprises the silicon monoxide composition containing the conductive component in the bulk phase, and the vapor deposition process is adopted, so that the process is simple, the consumed material is less, the combination efficiency of the conductive component and the silicon monoxide is high, the strength is high, the conductivity of the silicon monoxide bulk phase is obviously improved, the lithium insertion and removal capacity of the material is improved, and the energy density and the quick charge performance of the secondary battery are improved.

In any embodiment of the present application, in step S2, the silicon powder and the silicon dioxide powder are mixed in a molar ratio of (0.75-1) to 1. The molar ratio of the silicon powder to the silicon dioxide powder is in the range, the effect of generating the silicon monoxide is better, and the phenomenon that the first coulombic efficiency of the material is influenced by excessively high oxygen content or the circulation stability of the material is influenced by excessively low oxygen content is avoided.

In any embodiment of the present application, in step S2, the heating chamber and the deposition chamber of the vapor deposition method are evacuated to 100Pa to 500Pa; and can be selected from 200Pa to 400Pa.

In any embodiment herein, in step S3, the silica powder and the silicon powder are formed into a silica vapor at a temperature of 1200 ℃ to 1500 ℃.

In any embodiment of the present application, in step S3, the mass percentage of the conductive component to the total mass of the silicon dioxide powder and the silicon powder is 1 to 5%; optionally 2-4%.

In any embodiment herein, in step S3, the deposition temperature in the vapor deposition process is from 400 ℃ to 800 ℃, optionally from 600 ℃ to 800 ℃. With the vapor deposition temperature in the above range, the deposition rate of the silicon oxide is moderate, which contributes to better achieving the bulk combination of the silicon oxide and the conductive component.

In any of the embodiments of the present application, in step S3, the step of the vapor deposition method includes moving the deposition chamber while passing the silicon monoxide vapor into the deposition chamber containing the conductive component for the free-cooling deposition. The deposition chamber is in a moving state, so that the conductive components are more uniformly distributed in the deposited silicon oxygen, and the distribution uniformity is improved.

In any embodiment of the application, the deposition chamber is in a rotating state, and the rotating speed of the deposition chamber is 0.5r/min-3r/min; can be selected to be 1r/min-2r/min. The deposition chamber is in the proper rotating speed range, and the uniformity of deposition and the consistency of material structure are further improved.

In any embodiment of the present application, the preparation method further comprises step S4: and (4) performing carbon coating treatment on the surface of the negative active material prepared in the step (S3).

In any embodiment of the present application, in step S4, a carbon coating process is performed by using a vapor deposition method; optionally, in the vapor deposition method, hydrocarbon gas is used as a carbon source for carbon coating treatment; optionally, the hydrocarbon gas includes one or more of methane, acetylene, and ethylene.

In any embodiment of the present application, in step S4, the deposition temperature in the vapor deposition process is 650 to 950 ℃, optionally 750 to 900 ℃. The vapor deposition temperature is in the range, the formed material has good performance, and the low temperature can cause more defects of the carbon layer structure and influence the first effect; the disproportionation of silica is easily caused by the over-high temperature.

A third aspect of the present application provides a secondary battery comprising the anode active material of the first aspect of the present application or the anode active material prepared according to the method of the second aspect of the present application.

A fourth aspect of the present application provides a battery module including the secondary battery as in the third aspect of the present application.

A fifth aspect of the present application provides a battery pack including the battery module according to the fourth aspect of the present application.

A sixth aspect of the present application provides an electric device including at least one of the secondary battery according to the third aspect of the present application, the battery module according to the fourth aspect of the present application, and the battery pack according to the fifth aspect of the present application.

Drawings

Fig. 1 is a schematic view of an embodiment of a secondary battery according to the present application.

Fig. 2 is a schematic view of an embodiment of a battery module according to the present application.

Fig. 3 is a schematic diagram of an embodiment of a battery pack according to the present application.

Fig. 4 is an exploded view of the battery pack according to the embodiment of the present application shown in fig. 3.

Fig. 5 is a schematic view of an embodiment of an apparatus in which a secondary battery according to the present application is used as a power source.

Reference numerals indicate the same.

1, a battery pack; 2, putting the box body on the box body; 3, a lower box body; 4 a battery module; 5 a secondary battery.

Detailed Description

Hereinafter, embodiments of an anode active material, a method of preparing the same, and a secondary battery, a battery module, a battery pack, and a device related thereto according to the present application are specifically disclosed in detail with reference to the accompanying drawings as appropriate. But detailed description thereof will be omitted unnecessarily. For example, detailed descriptions of already known matters and repetitive descriptions of actually the same configurations may be omitted. This is to avoid unnecessarily obscuring the following description, and to facilitate understanding by those skilled in the art. The drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

The "ranges" disclosed herein are defined in terms of lower limits and upper limits, with a given range being defined by a selection of one lower limit and one upper limit that define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Further, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, if not specifically stated.

All technical and optional features of the present application may be combined with each other to form new solutions, if not otherwise specified.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, if not specifically stated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to the process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.

The terms "comprises" and "comprising" as used herein mean either open or closed unless otherwise specified. For example, the terms "comprising" and "comprises" may mean that other components not listed may also be included or included, or that only listed components may be included or included.

In this application, the term "or" is inclusive, if not otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).

In one embodiment, the present application provides a negative active material including a silica particle containing a conductive component in a bulk phase.

The SiOx is one of the most practical lithium ion battery negative electrode materials at present due to the advantages of high theoretical specific capacity, proper lithium intercalation and deintercalation potential, long cycle charge and discharge life, rich reserves, environmental friendliness and the like.

The inventor finds that the conductivity of the material can be effectively improved, the lithium insertion and lithium removal capacity of the material can be improved, and the first coulombic efficiency and the quick charge performance of the material can be effectively improved by distributing the conductive component in the silicon oxide bulk phase. Specifically, in a half-cell test, when 0.05C/50 muA is sequentially used for lithium intercalation to 5mV, the 0.05C lithium intercalation capacity accounts for 90-96% of the total lithium intercalation capacity.

In some embodiments, the conductive component is selected from carbon-based materials; optionally, the carbon-based material is selected from one or more of conductive carbon black, carbon nanotubes, graphene and carbon fibers.

In some embodiments, the conductive component comprises carbon nanotubes, and the carbon nanotubes have a tube diameter of 1.6 ± 0.4nm and a tube length of 5-20 μm.

In some embodiments, the conductive component is present in the silica particles in a mass fraction of 1% to 5%, optionally 2% to 4%. The addition amount of the conductive component is not suitable to be too high or too low, the conductivity cannot be obviously improved when the addition amount is too small, the specific surface is increased when the addition amount is too large, and the first coulombic efficiency and gram capacity of the material are influenced. The content ratio of the conductive component is within an appropriate range, and the capacity can be further improved.

In some embodiments, at least a portion of the surface of the silica particles is provided with a carbon coating.

In the application, the surface carbon coating content test: according to GB/T20123-2006/ISO 15350: 2000. and (4) testing the carbon content (%) of the powder before and after surface coating by adopting an HSC-140 carbon content analyzer, wherein the carbon coating amount (%) on the surface is not less than the carbon content (%) after coating but is not more than the carbon content (%) before coating.

The surface of the negative active material is coated with the carbon coating layer, so that the conductivity of the negative active material is further improved, and the addition of the carbon coating layer plays a buffering role in volume expansion and contraction of the negative active material in the charge-discharge process, so that the cycle performance of the battery is further improved.

In some embodiments, the volume distribution particle diameter Dv50 of the negative electrode active material is 4 μm to 10 μm; and is selected from 6 μm to 8 μm.

In the present application, the average particle diameter Dv50 of the negative electrode active material is a known meaning in the art, and can be measured by an instrument and a method known in the art. This can be conveniently determined, for example, by a laser particle size analyzer such as the Mastersizer2000E laser particle size analyzer from Malvern instruments, inc., U.K., with reference to the GB/T19077-2016 particle size distribution laser diffraction method. Wherein Dv50 represents the particle size at which the cumulative volume distribution percentage of the silicone compound reaches 50%.

The Dv50 of the negative electrode active material is within an appropriate range, and the quick charge performance of the secondary battery can be further improved, and it is also advantageous to increase the energy density of the battery.

In some embodiments, the negative electrode active material has a specific surface area of 0.5m2/g to 2m2/g; and can be selected from 0.8m2/g to 1.6m2/g.

In the present application, the specific surface area of the negative active material is a known meaning in the art, and can be measured by an apparatus and a method known in the art, for example, by referring to the GB/T19587-2004 gas adsorption BET method for measuring the specific surface area of solid materials, by using the nitrogen adsorption specific surface area analysis test method which can be performed by a Tni StarlI 3020 specific surface area and pore analyzer manufactured by Micromeritics, USA, and calculated by the BET (Brunauer Emmett Teller) method.

The specific surface area of the negative active material is too small, the internal resistance of the battery is higher, the discharge platform is low, the capacity exertion is low, the rate performance is poor, and the cycle performance is poor; the specific surface area is too large, the electrochemical performance of the material is good, but the activity is high, the agglomeration is easy, the dispersion is difficult, and the processing of the pole piece is difficult.

The specific surface area of the negative electrode active material is within the above range, and lithium consumption can be reduced, thereby further improving the first coulombic efficiency of the secondary battery.

In some embodiments, the negative active material has a powder resistivity of ≦ 1 Ω -cm at 4 MPa; can be selected to be less than or equal to 0.8 omega cm.

And testing the powder resistivity by using an ST2722 resistivity tester according to a GB/T30835-2014 testing method to obtain the powder resistance data of the material under the pressure of 4 MPa. The powder resistivity of the negative electrode active material is within the above range, and the first coulombic efficiency and cycle life of the negative electrode active material can be further improved.

s1: providing a silicon dioxide powder, a silicon powder and a conductive component;

The negative active material obtained by the preparation method comprises the silicon monoxide composition containing the conductive component in the bulk phase, and the vapor deposition process is adopted, so that the process is simple, the consumed materials are few, the combination efficiency of the conductive component and the silicon monoxide is high, the strength is high, the conductivity of the silicon monoxide bulk phase is obviously improved, the lithium insertion and removal capacity of the material is improved, and the energy density and the quick charge performance of the secondary battery are improved.

In some embodiments, in step S2, the silicon powder and the silicon dioxide powder are mixed in a molar ratio of (0.75-1): 1. The effect of generating the silicon monoxide is better, and the influence of the excessive oxygen content on the first coulombic efficiency of the material or the influence of the excessive oxygen content on the cycle stability of the material is avoided.

In some embodiments, in step S2, the heating chamber and the deposition chamber of the vapor deposition method are evacuated to 100Pa to 500Pa; and can be selected from 200Pa to 400Pa. The degree of vacuum is within the above range, the reaction proceeds more easily, and the preparation efficiency of the negative active material can be further improved.

In some embodiments, in step S3, the silica powder and the silicon powder are formed into a silica vapor at a temperature of from 1200 ℃ to 1500 ℃. When the temperature is within the above range, the efficiency of producing the silicon monoxide is further improved.

In some embodiments, in step S3, the mass percentage of the conductive component to the total mass of the silicon dioxide powder and the silicon powder is 1 to 5%; optionally 2-4%. The proper mass percentage of the conductive component to the total mass of the silicon dioxide powder and the silicon powder can avoid over-agglomeration or over-low yield, and further improve the preparation efficiency of the cathode active material.

In any embodiment herein, in step S3, the deposition temperature in the vapor deposition process is 400 to 800 ℃, optionally 600 to 800 ℃. With the vapor deposition temperature in the above range, the deposition rate of the silicon oxide is moderate, which contributes to better achieving the bulk combination of the silicon oxide and the conductive component.

In some embodiments, in step S3, the step of vapor deposition includes moving the deposition chamber while passing the silicon monoxide vapor into the deposition chamber containing the conductive component for free-cooling deposition. The deposition chamber is in a moving state, so that the conductive components are more uniformly distributed in the deposited silicon oxygen, and the distribution uniformity is improved.

In some embodiments, the method comprises size classifying the obtained anode active material bulk using a pulverization classification apparatus. The average grain size of the intermediate silicon oxygen obtained by grading is not suitable to be too large, the dynamics of the material corresponding to the larger Dv50 is worsened, and the specific surface is too high when the grain size is smaller, thus being unfavorable for the first effect of the material; the proper particle size distribution is also beneficial to improving the dynamic performance of the material, and if the particle size distribution is too small, the yield is low, thus being unfavorable for the cost. The granularity of the product meets the production requirement through the granularity grading treatment, and the granularity distribution range of the product is optimized through grading, so that the quality stability of the product is improved.

In some embodiments, the method of making further comprises S4: and (4) performing carbon coating treatment on the surface of the negative active material prepared in the step (S3).

In some embodiments, the carbon coating process may be performed using a vapor deposition process. Optionally, the carbon coating treatment is performed by using hydrocarbon gas as a carbon source in the vapor deposition method. Optionally, the hydrocarbon gas comprises one or more of methane, acetylene, and ethylene.

The secondary battery, the battery module, the battery pack, and the device according to the present invention will be described below with reference to the drawings as appropriate.

In one embodiment of the present application, a secondary battery is provided.

In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. In the process of charging and discharging the battery, active ions are embedded and separated back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable ions to pass through.

[ Positive electrode sheet ]

The positive pole piece comprises a positive pole current collector and a positive pole film layer arranged on at least one surface of the positive pole current collector.

As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.

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

In some embodiments, the positive active material may employ a positive active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates of olivine structure, lithium transition metal oxides and their respective modified compounds.However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxides (e.g., liNiO) ₂ ) Lithium manganese oxide (e.g., liMnO) ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/3 Mn _1/3 O ₂ (may also be abbreviated as NCM) ₃₃₃ )、 LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (may also be abbreviated as NCM) ₅₂₃ )、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (may also be abbreviated as NCM) ₂₁₁ )、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (may also be abbreviated as NCM) ₆₂₂ )、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (may also be abbreviated as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxides (e.g., liNi) _0.85 Co _0.15 Al _0.05 O ₂ ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) ₄ (also referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.

[ negative electrode sheet ]

The negative pole piece includes the negative pole mass flow body and sets up the negative pole rete on the negative pole mass flow body at least one surface, the negative pole rete includes the negative pole active material, and the negative pole active material includes this application first aspect internal portion contains conducting component's silica oxide.

As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector.

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

In some comparative embodiments, the negative active material may employ a negative active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate and the like. The silicon-based material can be at least one selected from the group consisting of elemental silicon, a silicon oxy compound, a silicon carbon compound, a silicon nitrogen compound and a silicon alloy. The tin-based material may be selected from at least one of elemental tin, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material may also be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the anode film layer further optionally includes a binder. The binder may be at least one selected from 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).

In some embodiments, the negative electrode film layer further optionally includes 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.

In some embodiments, the negative electrode film layer may also optionally include other adjuvants, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet can be prepared by: dispersing the components for preparing the negative electrode plate, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (such as deionized water) to form negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying, cold pressing and the like to obtain the negative electrode pole piece.

[ electrolyte ]

The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The kind of the electrolyte is not particularly limited and may be selected as desired.

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

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery, such as an additive for improving overcharge properties of the battery, an additive for improving high-temperature or low-temperature properties of the battery, and the like.

[ isolation film ]

In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known separator having a porous structure and good chemical and mechanical stability may be used.

In some embodiments, the material of the isolation film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.

In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The outer package of the secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

The shape of the secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other arbitrary shape. For example, fig. 1 is a secondary battery 5 of a square structure as an example.

In some embodiments, the secondary batteries may be assembled into a battery module, and the number of the secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

Fig. 2 is a battery module 4 as an example, in which a plurality of secondary batteries 5 may be arranged in series in the lengthwise direction of the battery module 4. Of course, the arrangement may be in any other manner. The plurality of secondary batteries 5 may be further fixed by a fastener.

Alternatively, the battery module 4 may further include a case having an accommodation space in which the plurality of secondary batteries 5 are accommodated.

In some embodiments, the battery modules 4 may be assembled into the battery pack 1, and the number of the battery modules 4 included in the battery pack 1 may be one or more, and the specific number may be selected by one skilled in the art according to the application and the capacity of the battery pack 1.

Fig. 3 is a battery pack 1 as an example. A battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box comprises an upper box body 2 and a lower box body 3, wherein the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. A plurality of battery modules 4 may be arranged in any manner in the battery box.

In addition, the present application also provides an electric device, including at least one of secondary battery 5, battery module 4, battery package 1 that the present application provided. The secondary battery 5, the battery module 4, or the battery pack 1 may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The powered device may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

As the electricity-using device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirement thereof.

Fig. 4 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle and the like. In order to meet the demand of the electric device for high power and high energy density of the secondary battery, a battery pack or a battery module may be used.

As another example, the device may be a cell phone, a tablet, a laptop, etc. The device is generally required to be thin and light, and a secondary battery may be used as a power source.

Examples

Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

(1) Adopting a carbon nano tube with the tube diameter of 1.6nm and the tube length of 10 mu m as a conductive component;

physically mixing silicon powder and silicon dioxide powder according to the molar ratio of 0.85: 1, placing the mixture into a heating chamber of a vapor deposition furnace, placing conductive components accounting for 5% of the total mass of the silicon dioxide and the silicon powder into a deposition chamber of the vapor deposition furnace, and communicating the heating chamber with the deposition chamber through a valve;

(2) vacuumizing the heating chamber and the deposition chamber to 100Pa by using a vacuum pump;

(3) heating the heating chamber and the deposition chamber to 1400 ℃ and 700 ℃ respectively;

(4) after the heating chamber is kept warm for 4h, opening a communicating valve, and introducing the formed silicon monoxide steam into a deposition chamber which is in a rotating state and has the rotating speed of 1.5r/min for natural cooling deposition to obtain a silicon monoxide block body containing a conductive component in the bulk phase;

(5) crushing and grading by using a crusher for coarse crushing and a jet mill for fine crushing in sequence, and finally sieving to obtain the silicon monoxide negative electrode active material; wherein, the silica negative active material obtained by sieving meets the following requirements: the bulk phase contains conductive component carbon nanotubes, the particle size distribution Dv50=7 μm, the specific surface area is 1.4m2/g, and the powder resistivity at 4MPa is 0.2 Ω · cm.

(6) And (3) performing gas phase carbon coating on the intermediate by using methane and nitrogen in a flow ratio of 1: 5, wherein the coating temperature is 900 ℃, and the coating time is 3 hours, so as to obtain the final product, namely the cathode active material.

Examples 2 to 26

Different from the embodiment 1, relevant parameters in the preparation process are regulated and controlled to obtain corresponding negative active materials, which are detailed in table 1.

Comparative example 1

(1) Uniformly dispersing silicon monoxide (Dv 50=6-7 μm), carbon nanotubes and resin in an ethanol solvent according to the mass ratio of 100: 1: 10 to obtain slurry;

(2) spray drying the slurry to obtain a precursor A;

(3) carrying out heat treatment on the precursor A to solidify the resin to obtain a precursor B;

(4) mixing the precursor B with a carbon coating agent, and coating, wherein the carbon coating agent is asphalt, and the addition amount of the carbon coating agent is 10% of that of the precursor B to obtain a precursor C;

(5) and carbonizing the precursor C at 850 ℃ to obtain the negative active material. The carbon nanotubes in the negative active material are dispersed between the silica core and the carbon layer and do not enter the silica bulk phase.

Comparative example 2:

(1) mixing and uniformly dispersing silica oxide (Dv 50=6-7 μm), carbon nano tubes and a glucose carbon source in an ethanol solvent according to the mass percent of 75: 5: 20 to obtain slurry.

(2) And carrying out spray granulation and 600 ℃ heat treatment on the slurry to obtain a precursor A.

(3) And (3) carrying out gas phase coating treatment on the precursor A, taking acetylene as a carbon source, and coating for 2 hours at 900 ℃ to obtain a finished product. The carbon nanotubes in the finished product are dispersed between the silica core and the carbon layer and do not enter the silica phase.

Comparative example 3:

(1) and performing ball milling on the silicon monoxide (Dv 50=6-7 μm), the carbon nano tube and the asphalt according to the mass percentage of 100: 1: 10, and performing heat treatment for 2 hours at 800 ℃ to obtain a precursor A.

(2) Performing ball milling on the asphalt, the carbon nano tube and the pore-foaming agent calcium carbonate according to the proportion of 10: 1: 20 to obtain a mixture X, kneading the mixture X and the precursor A according to the proportion of 1: 50, and performing heat treatment at 700 ℃ for 2h to obtain a precursor B.

(3) Heating 160g naphthalene oil bath to 130 ℃ to be in a liquid state, adding the asphalt, the precursor B and the carbon nano tube according to the proportion of 10: 100: 1 and the total mass of 120g, and stirring and heating to 180 ℃ to volatilize naphthalene. And carrying out heat treatment on the obtained product at 850 ℃ for 2h to obtain a precursor C.

(4) The precursor C is screened and treated with 0.5mol/L HCL for 4h. Filtering, washing with deionized water and drying to obtain the product. The carbon nanotubes in the obtained product are dispersed among the silicon oxide particles and between the carbon layers, and do not enter the silicon oxide bulk phase.

Preparation of button cell

Mixing the negative active material, the conductive carbon black and the polyacrylic acid binder prepared in the embodiments and the comparative examples according to the mass ratio of 8: 1, adding deionized water as a solvent, and stirring the mixture under the action of a stirrer until the system is uniform to obtain negative slurry; and uniformly coating the negative electrode slurry on a copper foil of a negative current collector, drying, performing cold pressing to obtain an electrode plate, and cutting the electrode plate into small round pieces with the diameter of 14 mm.

And (3) taking metal lithium as a counter electrode (cutting into metal lithium sheets with the diameter of 14 mm), adopting a Celgard 2400 isolating membrane, injecting an electrolyte, and assembling to obtain the button cell. The electrolyte is a mixed solution of Ethylene Carbonate (EC), ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is 20: 60. Then, liPF6 was dissolved in the organic solvent, and an additive, fluoroethylene carbonate (FEC), was added, wherein the concentration of LiPF6 was 1mol/L, and the mass ratio of FEC in the electrolyte was 5%.

Performance test process of button cell:

standing the button cell for 60min at 25 ℃ under normal pressure, discharging the button cell to 5mV at a constant current of 0.05C multiplying power and 5mV at a constant current of 50 muA, standing for 10min, respectively recording the discharge capacities at the moment, and obtaining the discharge capacity of 1 st circle of lithium intercalation when the button cell is discharged to 5mV at a constant current of 0.05C multiplying power; and then charging to 2V at a constant current of 0.1C multiplying power, standing for 10min, wherein the process is a cyclic charge-discharge process, and the charge capacity at the moment is recorded, namely the delithiation capacity of the 1 st circle.

First coulombic efficiency (%) = 1 st cycle delithiation capacity/1 st cycle lithium intercalation capacity x100%

The lithium intercalation capacity of the material under a higher rate is indirectly reacted according to the value of the ratio of the 0.05C lithium intercalation capacity to the (%) 0.05C lithium intercalation capacity/(0.05C lithium intercalation capacity +50 muA lithium intercalation capacity) x100%, and the larger the value, the better the quick charge performance of the material is represented.

The test results of examples 1 to 26 and comparative examples 1 to 3 are shown in Table 2.

Table 1: technological parameter table for preparing negative active material

In table 1, "/" indicates that the parameter is not present.

Table 2: test results

As can be seen from the data in table 2, the negative active material of the present application effectively improves the first coulombic efficiency and the fast charge performance of the negative active material by distributing the conductive component in the silica bulk phase.

In the negative active materials of comparative examples 1 to 3, none of the conductive components was distributed inside the bulk phase of the silica particles, and thus the performance was poor.

The present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exhibiting the same operation and effect within the technical scope of the present application are included in the technical scope of the present application. In addition, various modifications that can be conceived by those skilled in the art are applied to the embodiments and other embodiments are also included in the scope of the present application, in which some of the constituent elements in the embodiments are combined and constructed, without departing from the scope of the present application.

Claims

1. A negative electrode active material includes a silica particle containing a conductive component in its bulk phase.

2. The negative electrode active material according to claim 1, characterized in that: the conductive component is selected from carbon-based materials; optionally, the carbon-based material is selected from one or more of conductive carbon black, carbon nanotubes, graphene and carbon fibers.

3. The negative electrode active material according to claim 1 or 2, characterized in that: the conductive component includes carbon nanotubes; optionally, the tube diameter of the carbon nanotube is 1.6 ± 0.4nm; optionally, the tube length is 5-20 μm.

4. The negative electrode active material according to any one of claims 1 to 3, characterized in that: the mass percentage of the conductive component to the silicon monoxide is 1-5%, and optionally 2-4%.

5. The negative electrode active material according to any one of claims 1 to 4, characterized in that: at least a part of the surface of the negative electrode active material is provided with a carbon coating layer.

6. The negative electrode active material according to any one of claims 1 to 5, characterized in that: the volume distribution particle diameter Dv50 of the negative electrode active material is 4 μm to 10 μm; and is selected from 6 μm to 8 μm.

7. The negative electrode active material according to any one of claims 1 to 6, characterized in that: the specific surface area of the negative electrode active material was 0.5m ² /g-2m ² (iv) g; optionally 0.8m ² /g-1.6m ² /g。

8. The negative electrode active material according to any one of claims 1 to 7, characterized in that: the powder resistivity of the negative active material under 4MPa is less than or equal to 1 omega cm; can be selected to be less than or equal to 0.8 omega cm.

9. A method for preparing an anode active material, comprising the steps of:

10. The method for producing an anode active material according to claim 9, characterized in that: in S2, the silicon powder and the silicon dioxide powder are mixed according to the molar ratio of (0.75-1) to 1.

11. The method for producing the anode active material according to claim 9 or 10, characterized in that: in S2, a heating chamber and a deposition chamber of the vapor deposition method are vacuumized to 100Pa-500Pa; and can be selected from 200Pa to 400Pa.

12. The method for producing the anode active material according to any one of claims 9 to 11, characterized in that: forming the silicon dioxide powder and the silicon powder into a silicon monoxide vapor at a temperature of 1200 ℃ to 1500 ℃ in S3.

13. The method for producing the anode active material according to any one of claims 9 to 12, characterized in that: in S3, the mass percentage of the conductive component to the total mass of the silicon dioxide powder and the silicon powder is 1-5%; can be selected to be 2 to 4 percent.

14. The method for producing the negative active material according to any one of claims 9 to 13, characterized in that: in S3, the deposition temperature in the vapor deposition method is 400-800 ℃; can be selected from 600 ℃ to 800 ℃.

15. The method for producing the anode active material according to any one of claims 9 to 14, characterized in that: in S3, the step of the vapor deposition method includes moving the deposition chamber while passing the silicon monoxide vapor into the deposition chamber containing the conductive component for the free-cooling deposition.

16. The method for producing an anode active material according to claim 15, characterized in that: the deposition chamber is in a rotating state, and the rotating speed of the deposition chamber is 0.5r/min-3r/min; can be selected to be 1r/min-2r/min.

17. The method for producing the negative active material according to any one of claims 9 to 16, characterized in that: the preparation method further comprises S4: performing carbon coating treatment on the surface of the negative active material prepared in the step S3;

optionally, in step S4, performing a carbon coating treatment by using a vapor deposition method;

optionally, in the vapor deposition method, hydrocarbon gas is used as a carbon source for carbon coating treatment;

optionally, the hydrocarbon gas comprises one or more of methane, acetylene and ethylene;

optionally, in step S4, the deposition temperature in the vapor deposition process is 650 ℃ to 950 ℃.

18. A secondary battery, characterized in that: comprising the negative active material of any of claims 1-8 or comprising the negative active material prepared according to the method of any of claims 9-17.

19. An electric device, characterized in that: comprising the secondary battery according to claim 18.