CN115832301A

CN115832301A - Negative pole piece, preparation method thereof and secondary battery with negative pole piece

Info

Publication number: CN115832301A
Application number: CN202111406351.9A
Authority: CN
Inventors: 李月微; 任苗苗; 靳超; 吴子睿; 尤龙震; 赵丰刚
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2021-11-24
Filing date: 2021-11-24
Publication date: 2023-03-21

Abstract

The application provides a negative electrode plate, a preparation method thereof, a secondary battery with the negative electrode plate, a battery module, a battery pack and an electric device. The negative pole piece comprises a reduced graphene oxide layer and a modified nano negative pole material, wherein the modified nano negative pole material comprisesThe rice negative electrode material comprises: a kernel; and a coating layer coated on the surface of the inner core, wherein the molecular formula of the inner core is A _x B _y Wherein A is at least one selected from antimony, molybdenum and silicon, B is at least one selected from sulfur, selenium and oxygen, x is more than or equal to 1 and less than or equal to 3, y is more than or equal to 1 and less than or equal to 4, and the coating layer comprises polydopamine. The negative pole piece has higher tensile modulus and tensile strength, can improve the energy density of the secondary battery, and prolongs the cycle life.

Description

Negative pole piece, preparation method thereof and secondary battery with negative pole piece

Technical Field

The application relates to the field of batteries, in particular to a negative electrode plate, a preparation method of the negative electrode plate, a secondary battery with the negative electrode plate, a battery module, a battery pack and an electric device.

Background

The secondary battery has the advantages of reliable working performance, no pollution, no memory effect and the like, thereby being widely applied. For example, as environmental protection issues become more important and new energy vehicles become more popular, the demand for power type secondary batteries will show explosive growth. However, as the application range of the secondary battery becomes wider, a severe challenge is also posed to the performance of the secondary battery.

The research and development of the cathode material with excellent performance is the key for improving the performance of the secondary battery, most cathode materials face the problems of large volume expansion, poor conductivity and the like, and how to improve the conductivity of the cathode material and reduce or avoid the reduction of the electrochemical performance caused by the volume expansion is the current technical difficulty.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object thereof is to provide a negative electrode sheet having high tensile modulus and tensile strength and capable of improving the capacity and cycle characteristics of a secondary battery, a method for producing the same, a secondary battery including the same, and a battery module, a battery pack, and an electric device.

In order to achieve the above object, a first aspect of the present application provides a negative electrode plate, wherein the negative electrode plate is formed by stacking a reduced graphene oxide sheet layer and a modified nano negative electrode material, and the modified nano negative electrode material includes: a kernel; and a coating layer coated on the surface of the core, wherein the molecular formula of the core is A _x B _y Wherein A is at least one selected from antimony, molybdenum and silicon, B is at least one selected from sulfur, selenium and oxygen, x is more than or equal to 1 and less than or equal to 3, y is more than or equal to 1 and less than or equal to 4, and the coating layer comprises polydopamine.

The polydopamine is coated on the nano negative electrode material core, and the interaction force between the negative electrode material and the reduced graphene oxide can be enhanced through the polydopamine modified nano negative electrode material, so that the obtained negative electrode piece has high tensile modulus and tensile strength, the energy density of the secondary battery can be improved, and the cycle life of the secondary battery can be prolonged.

In some embodiments, the mass ratio of the core to the cladding is from 2 to 1. By setting the mass ratio of the core to the clad within this range, the tensile modulus and tensile strength of the electrode sheet can be further improved, and the energy density of the secondary battery can be improved, and the cycle life can be prolonged.

In some embodiments, the coating layer has a coating rate of 80% or more. By setting the coating rate of the coating layer within the above range, the tensile modulus and tensile strength of the electrode sheet are further improved, the energy density of the secondary battery can be improved, and the cycle life can be prolonged.

In some embodiments, the cladding layer has a thickness of 15nm to 42nm. The thickness of the coating layer is within the range, so that the tensile modulus and tensile strength of the pole piece are further improved, the energy density of the secondary battery can be improved, and the cycle life is prolonged.

In some embodiments, the mass ratio of the modified nano anode material to the reduced graphene oxide is 1. The cycle performance improvement effect of the battery can be effectively exerted only by further setting the mass ratio of the modified nano anode material to the reduced graphene oxide within the range.

In some embodiments, the negative electrode sheet has a tensile modulus of 175 to 700Gpa. By setting the tensile modulus of the negative electrode sheet within this range, the energy density and cycle characteristics of the secondary battery can be simultaneously achieved.

In some embodiments, the tensile strength of the negative electrode sheet is from 3.4MPa to 9.3MPa. By setting the tensile strength of the negative electrode sheet within this range, the energy density and the cycle characteristics of the secondary battery can be both considered.

A second aspect of the present application is to provide a method for producing a negative electrode sheet according to the first aspect of the present application, including the following steps (1) to (3):

step (1): homogenizing the core material and dopamine in a tris buffer solution;

step (2): dispersing the product obtained in the step (1) in a graphene oxide solution, reducing at a first temperature, performing vacuum filtration, pre-freezing the obtained filter membrane at a second temperature, and freeze-drying the pre-frozen material at a third temperature to obtain a porous film;

step (3): and (3) calcining the film prepared in the step (2) in an inert and/or reducing atmosphere to obtain the negative pole piece. The obtained negative pole piece has high tensile modulus and tensile strength, and can improve the energy density of the secondary battery and prolong the cycle life.

In some embodiments, in the process (1), the homogenization treatment is a treatment by sonication and stirring for 6 to 24 hours. Therefore, good poly-dopamine coating can be realized, and the tensile modulus and tensile strength of the pole piece are improved.

In some embodiments, in the process (2), the first temperature is 80 ℃ to 100 ℃ and the time of the reduction is 2min to 30min. Therefore, graphene oxide can be well reduced, the film forming property is improved, and the tensile modulus and the tensile strength of the pole piece are improved.

In some embodiments, in the process (2), the second temperature is-200 ℃ to-80 ℃, the third temperature is-30 ℃ to-50 ℃, and the freeze-drying time is 16h to 48h. Therefore, the film forming property can be improved, and the tensile modulus and the tensile strength of the pole piece can be improved.

In some embodiments, in the procedure (3), the calcination is performed at 100 to 550 ℃ for 0.5 to 5 hours. This makes it possible to obtain a pole piece having excellent electrochemical properties.

In a third aspect, the present application provides a secondary battery, which includes the negative electrode plate according to the first aspect of the present application or the negative electrode plate prepared by the preparation method according to the second aspect of the present application.

A fourth aspect of the present application is to provide a battery module including the secondary battery according to the third aspect of the present application.

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

A sixth aspect of the present application is to provide 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.

According to the application, the tensile modulus and tensile strength of the pole piece can be improved, the energy density of the secondary battery is improved, and the cycle life is prolonged.

Drawings

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

Fig. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in fig. 1.

Fig. 3 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.

Fig. 5 is an exploded view of the battery pack according to the embodiment of the present application shown in fig. 4.

Fig. 6 is a schematic diagram of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.

Description of reference numerals:

1, a battery pack; 2, putting the box body on the box body; 3, discharging the box body; 4 a battery module; 5a secondary battery; 51 a housing; 52 an electrode assembly; 53 Top cover Assembly

Detailed Description

Hereinafter, embodiments of the positive electrode active material and the method for producing the same, the positive electrode sheet, the secondary battery, the battery module, the battery pack, and the electrical device according to the present application are specifically disclosed in detail with reference to the drawings as appropriate. But a detailed description thereof will be omitted. 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.

As disclosed herein, a "range" is defined in terms of lower and upper limits, with a given range being defined by the selection of one lower limit and one upper limit, which 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 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if the

minimum range values

1 and 2 are listed, and if the

maximum range values

3,4, and 5 are listed, the following ranges are all contemplated: 1 to 3,1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless stated otherwise, 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.

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).

[ negative electrode sheet ]

In one embodiment of the present application, the present application provides a negative electrode sheet, which is formed by stacking a reduced graphene oxide sheet layer and a modified nano negative electrode material, wherein the modified nano negative electrode material includes: a kernel; and a coating layer coated on the surface of the inner core, wherein the molecular formula of the inner core is A _x B _y Wherein A is at least one selected from antimony, molybdenum and silicon, B is at least one selected from sulfur, selenium and oxygen, x is more than or equal to 1 and less than or equal to 3, y is more than or equal to 1 and less than or equal to 4, and the coating layer comprises polydopamine.

Specifically, the inner core may be at least one selected from nano-sulfide, nano-selenide, nano-oxide, and nano-selenosulfide.

Although the mechanism is not clear, the applicant has surprisingly found that: the polydopamine is introduced to improve the dispersibility of the nano negative electrode material in water, so that the nano negative electrode material can be uniformly dispersed in a reduced graphene oxide film, meanwhile, the reduction and self-assembly of graphene oxide sheet layers are promoted, and the polydopamine can be used as a tie to enhance the interaction force between the nano negative electrode material and the reduced graphene oxide sheet layers. The reduced graphene oxide sheets are internally and mutually crosslinked through polydopamine, so that the nano negative electrode materials are improved to be mutually crosslinked. After being carbonized, the polydopamine can be converted into a nitrogen-doped carbon layer to improve the electrochemical performance of the nano negative electrode material.

The polydopamine is coated on the nano negative electrode material core, and the interaction force between the negative electrode material and the reduced graphene oxide can be enhanced through the polydopamine modified nano negative electrode material, so that the obtained negative electrode piece has high tensile modulus and tensile strength, the energy density can be improved, and the cycle life can be prolonged.

The inventors of the present application speculate that: the polydopamine can form a uniform coating layer on the surface of the nano cathode, so that on one hand, the nano cathode material is ensured to be uniformly dispersed in a graphene oxide aqueous solution, and meanwhile, the nano cathode material is tightly combined with graphene oxide lamella, the nano cathode material is well packaged between the graphene oxide lamella layers, the volume expansion of the nano cathode material is effectively relieved, the conductivity is improved, on the other hand, the polydopamine can be evolved into a nitrogen-doped carbon layer after calcination, and the electrochemical performance of the nano cathode material is effectively improved. In addition, polydopamine can also be used as a reducing agent of graphene oxide, so that toxic/dangerous reducing agents such as hydrazine hydrate, hydroiodic acid and the like are avoided, and the preparation process is relatively green and environment-friendly.

In addition, the negative pole piece is a porous self-supporting pole piece, so that electron and ion transmission is facilitated, the electrochemical performance of the negative pole material is enhanced, the use of a binder and a conductive agent is avoided, and the process flow can be simplified.

In addition, the negative pole piece can be widely applied to the fields of lithium batteries, sodium batteries, solar batteries, photocatalysis and the like.

In some embodiments, optionally, the mass ratio of the core to the cladding is from 2 to 1. By setting the mass ratio of the core to the clad within this range, the tensile modulus and tensile strength of the electrode sheet can be further improved, and the energy density of the secondary battery can be improved, and the cycle life can be prolonged. By the mass ratio of the core to the coating layer being in a proper range, on one hand, a good coating effect can be achieved, the tensile modulus and tensile strength of the pole piece are improved, the negative electrode material is not easy to fall off from the surface of the reduced graphene oxide after being expanded, and the cycle performance of the secondary battery is improved; on the other hand, the capacity of the secondary battery can be improved while avoiding the decrease in energy density.

In some embodiments, optionally, the coating rate of the coating layer is 80% or more. Here, the coating rate may be calculated from the cross section of the modified nano-anode particle in percentage ratio to how much the surface of the inner core is coated with the poly-dopamine, for example, an average value of 50 modified nano-anode particles may be taken. By setting the coating rate of the coating layer within the above range, the tensile modulus and tensile strength of the electrode sheet are further improved, the energy density of the secondary battery can be improved, and the cycle life can be prolonged. By the coating rate of the coating layer being within the range, the negative electrode material is not easy to fall off from the surface of the reduced graphene oxide after being expanded, so that the cycle performance of the secondary battery is improved.

In some embodiments, optionally, the cladding layer has a thickness of 15nm to 42nm. The thickness of the coating layer is within the range, so that the tensile modulus and tensile strength of the pole piece are further improved, the energy density of the secondary battery can be improved, and the cycle life is prolonged. By the thickness of the coating layer being within the range, on one hand, a good coating effect can be achieved, the tensile modulus and tensile strength of the pole piece are improved, the negative electrode material is not easy to fall off from the surface of the reduced graphene oxide after being expanded, and the cycle performance of the secondary battery is improved; on the other hand, the energy density can be prevented from being too low, and the capacity of the secondary battery can be improved.

In some embodiments, optionally, the mass ratio of the modified nano anode material to the reduced graphene oxide is 1. By further setting the mass ratio of the modified nano anode material to the reduced graphene oxide within the range, the cycle performance improvement effect of the battery can be effectively exerted. By the mass ratio of the modified nanometer negative electrode material to the reduced graphene oxide being in the range, on one hand, the film-forming property can be improved, so that a thin film pole piece can be well formed; on the other hand, the capacity of the secondary battery can be improved by avoiding the energy density from being too low.

Further, in another embodiment of the present application, the present application provides a method for producing a negative electrode sheet, including the following steps (1) to (3):

In some embodiments, in the process (2), the first temperature is 80 ℃ to 100 ℃ and the time of the reduction is 2min to 30min. Therefore, the graphene oxide can be well reduced, the film forming property is improved, and the tensile modulus and the tensile strength of the pole piece are improved.

By adjusting the specific conditions in the above steps, the negative electrode sheet of the present application can be obtained.

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

[ Secondary Battery ]

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

In general, a secondary battery includes a negative electrode tab, a positive 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 includes the anodal mass flow body and sets up the anodal rete on anodal mass flow body at least one surface, anodal rete includes the anodal active material of the first aspect of this application.

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: olivine structured lithium-containing phosphates, 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. Examples of the lithium transition metal oxide include, but are not limited to, at least one of lithium cobalt oxide (e.g., liCoO 2), lithium nickel oxide (e.g., liNiO 2), lithium manganese oxide (e.g., liMnO2, liMn2O 4), lithium nickel cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi1/3Co1/3Mn1/3O2 (also referred to as NCM333 for short), lini0.5co0.2mn0.3o2 (also referred to as NCM523 for short), lini0.5co0.25mn0.25o2 (also referred to as NCM211 for short), lini0.6co0.2mn0.2o2 (also referred to as NCM622 for short), lini0.8co0.1mn0.1o2 (also referred to as NCM811 for short), lithium nickel cobalt oxide (e.g., coi0.850.1al0.052) and modified compounds thereof, and the like, and lithium iron phosphate-carbon phosphate (lithium iron-lithium-carbon phosphate) and lithium iron-carbon phosphate (also referred to as lithium iron-lithium-iron-lithium phosphate).

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.

In addition, as the positive pole piece, the positive active material can also be one or more of sodium transition metal oxide, polyanion compound and prussian blue compound.

Examples of the sodium transition metal oxide include:

Na _1-x Cu _h Fe _k Mn _l M ¹ _m O _2-y wherein M is ¹ Is one or more of Li, be, B, mg, al, K, ca, ti, co, ni, zn, ga, sr, Y, nb, mo, in, sn and Ba, 0<x≤0.33，0<h≤0.24，0≤k≤0.32，0<l≤0.68，0≤m<0.1，h+k+l+m＝1，0≤y<0.2；

Na _0.67 Mn _0.7 Ni _z M ² _0.3-z O ₂ Wherein M is ² Is one or more of Li, mg, al, ca, ti, fe, cu, zn and Ba, 0<z≤0.1；

Na _a Li _b Ni _c Mn _d Fe _e O ₂ Wherein 0.67<a≤1，0<b<0.2，0<c<0.3，0.67<d+e<0.8，b+c+d+e＝1。

Examples of the polyanionic compound include:

A ¹ _f M ³ _g (PO ₄ ) _i O _j X ¹ _3-j wherein A is H, li, na, K and NH ₄ One or more of, M ³ Is one or more of Ti, cr, mn, fe, co, ni, V, cu and Zn, and X ¹ Is one or more of F, cl and Br, 0<f≤4，0<g≤2，1≤i≤3，0≤j≤2；

Na _n M ⁴ PO ₄ X ² Wherein M is ⁴ Is one or more of Mn, fe, co, ni, cu and Zn, and X ² Is one or more of F, cl and Br, 0<n≤2；

Na _p M ⁵ _q (SO ₄ ) ₃ Wherein M is ⁵ Is one or more of Mn, fe, co, ni, cu and Zn, 0<p≤2，0<q≤2；

Na _s Mn _t Fe _3-t (PO ₄ ) ₂ (P ₂ O ₇ ) Wherein 0 is<s.ltoreq.4, 0. Ltoreq. T.ltoreq.3, for example t is 0, 1, 1.5, 2 or 3.

Examples of the prussian blue-based compound include:

A _u M ⁶ _v [M ⁷ (CN) ₆ ] _w ·xH ₂ o, wherein A is H ⁺ 、NH ₄ ⁺ One or more of alkali metal cation and alkaline earth metal cation, M ⁶ And M ⁷ Each independently is one or more of transition metal cations, 0<u≤2，0<

v≤

1，0<w≤1，0<x<6. For example A is H ⁺ 、Li ⁺ 、Na ⁺ 、K ⁺ 、NH ₄ ⁺ 、Rb ⁺ 、Cs ⁺ 、Fr ⁺ 、Be ²⁺ 、Mg ²⁺ 、Ca ²⁺ 、Sr ²⁺ 、Ba ²⁺ And Ra ²⁺ One or more of, M ⁶ And M ⁷ Each independently is a cation of one or more transition metal elements of Ti, V, cr, mn, fe, co, ni, cu, zn, sn and W. Preferably, A is Li ⁺ 、Na ⁺ And K ⁺ One or more of, M ⁶ Is cation of one or more transition metal elements of Mn, fe, co, ni and Cu, M ⁷ Is a cation of one or more transition metal elements of Mn, fe, co, ni and Cu.

The positive electrode active material layer may further optionally include a conductive agent for improving conductivity of the positive electrode active material layer and a binder for firmly binding the positive electrode active material and the binder to the positive electrode current collector. The types of the conductive agent and the binder are not particularly limited, and can be selected according to actual requirements.

As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the binder may be one or more of Styrene Butadiene Rubber (SBR), water-based acrylic resin (water-based resin), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA).

The positive electrode current collector can be made of metal foil, carbon-coated metal foil or porous metal plate, and preferably is made of aluminum foil.

[ isolation film ]

The separator is not particularly limited in the present application, and any known separator having a porous structure and electrochemical stability and mechanical stability may be selected according to actual needs, and may be, for example, a single-layer or multilayer film including one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.

[ 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. For example, the electrolyte may be liquid, gel, or all solid.

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

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, dimethylsulfone, methylethylsulfone, and diethylsulfone.

In some embodiments, the electrolyte includes additives including fluoroethylene carbonate and/or vinylene carbonate, and may further include other additives, such as: the negative electrode film-forming additive and the positive electrode film-forming additive can also comprise additives capable of improving certain performances of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, and the like.

The electrolyte may also include an organic solvent and a sodium salt, and any organic solvent and sodium salt that can be used in a sodium ion battery may be selected according to actual needs. As an example, the organic solvent may be one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), ethyl Methyl Carbonate (EMC), and diethyl carbonate (DEC); the sodium salt may be NaPF ₆ 、NaClO ₄ 、NaBCl ₄ 、NaSO ₃ CF ₃ And Na (CH) ₃ )C ₆ H ₄ SO ₃ One or more of them.

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, referring to fig. 2, the overwrap may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity. The housing 51 has an opening communicating with the accommodating chamber, and a cover plate 53 can be provided to cover the opening to close the accommodating chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. An electrode assembly 52 is enclosed within the receiving cavity. The electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 may be one or more, and those skilled in the art can select them according to the actual needs.

Battery module

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. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in series along the longitudinal 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.

Battery pack

In some embodiments, the battery modules may be assembled into a battery pack, and the number of the battery modules contained in the battery pack 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.

Fig. 4 and 5 are a battery pack 1 as an example. Referring to fig. 4 and 5, a battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case. 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.

Electric device

In addition, this application still provides a power consumption device, power consumption device includes at least one in secondary battery, battery module or the battery package that this application provided. The secondary battery, the battery module, or the battery pack 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 utilization device, a secondary battery, a battery module, or a battery pack may be selected according to its use requirements.

Fig. 6 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or 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 embodiments are described as illustrative only and are not to be construed as limiting the present application. 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>

①Preparation of negative pole piece

In example 1, the method for producing a negative electrode sheet includes the following steps (1) to (3), wherein specific conditions of the steps (1) to (3) are shown in table 1:

(1) And (2) mixing the following components in percentage by mass: carrying out ultrasonic and stirring treatment on 1 nanometer antimony sulfide and dopamine in tris buffer solution at room temperature for 12 hours, mixing uniformly, centrifuging and cleaning;

(2) Dispersing 20mg of the product obtained in the step (1) in 20mL of graphene oxide solution (1 mg/mL), uniformly dispersing by ultrasonic/stirring, reducing at-90 ℃ for 30min, carrying out vacuum filtration, freezing the obtained filter membrane at-200 ℃, and carrying out freeze drying on the pre-frozen material at-40 ℃ for 24h to obtain a porous membrane;

(3) And (3) calcining and reducing the film prepared in the step (2) for 4 hours at 450 ℃ in an inert/reducing atmosphere to obtain the pole piece.

Various parameters of the negative electrode sheet are shown in table 2.

②Evaluation of Performance

For the negative electrode sheet obtained in the above (1), a performance test was performed by the following method. The results are shown in Table 3.

(i) Tensile modulus test

Static mechanical uniaxial in-plane tensile tests were performed on the graphite films in the tensile mode with a dynamic mechanical analyzer (2980dma, ta instrument) to collect the tensile strength and tensile modulus of the films. The test dimensions of the film samples were 25-30 mm in length and 3-7mm in width, respectively. The graphene film was clamped by a test fixture and all tensile tests were performed in a controlled force mode.

(ii) Tensile Strength test

Static mechanical uniaxial in-plane tensile tests were performed on the graphite films using the tensile mode of a dynamic mechanical analyzer (2980dma, ta instrument) to collect the tensile strength and tensile modulus of the films. The test dimensions of the film samples were 25-30 mm in length and 3-7mm in width, respectively. The graphene film was clamped by a test fixture and all tensile tests were performed in a controlled force mode.

(iii) Button cell preparation method

For the negative electrode active material prepared in the above (1), a metallic sodium sheet was used as a counter electrode, a Whatham glass fiber separator was used, and 1M NaClO was injected ₄ (iv)/EC-DEC (1, v/v) + 5%.

(iv) Button cell cycle performance test

Under the environment of 25 ℃ and normal pressure, discharging the button cell with constant current at 0.1C multiplying power until the voltage is 0.005V, then discharging with constant current at 0.05C multiplying power until the voltage is 0.005V, and recording the discharge specific capacity at the moment, namely the first lithium intercalation capacity; and then, carrying out constant current charging at a multiplying power of 0.1C until the voltage is 1.5V, and recording the charging specific capacity at the moment, namely the first lithium removal capacity. The button cell was subjected to 100 cycles of charge and discharge tests according to the above method, and the lithium removal capacity was recorded for each time.

Cycle capacity retention (%) of the negative electrode active material = 100 th delithiation capacity/first delithiation capacity × 100%

< example 2> < example 9>, < comparative example 1> < comparative example 4>

Negative electrode sheets were obtained in examples 2 to 9 and comparative examples 1 to 4 by the same production method as in example 1, except that the specific conditions in steps (1) to (3) were changed as shown in table 1, and the kinds and contents of the respective raw materials were changed as shown in table 2.

< comparative example 5>

A negative electrode sheet was obtained by the same production method as in example 1, except that the step (1) shown in table 1 was not performed and the raw material 2 shown in table 2 was not used.

[ Table 2]

[ Table 3]

From tables 1 to 3 above, the following can be seen:

as can be seen from examples 1 to 9 and comparative example 5, in the negative electrode sheet of the present application, the poly-dopamine-coated nano negative electrode material is introduced, so that the tensile modulus and tensile strength of the sheet can be improved, the energy density of the secondary battery can be improved, and the cycle life can be prolonged.

As is clear from examples 1 to 4 and comparative examples 1 and 2, in the negative electrode sheet of the present invention, the mass ratio of the core to the clad was in a specific range, and the tensile modulus and tensile strength of the sheet could be further improved, and the energy density of the secondary battery could be improved, and the cycle life could be extended.

As is clear from examples 1 to 4 and comparative example 1, in the negative electrode sheet of the present application, the coating rate of the coating layer was within a specific range, and the tensile modulus and tensile strength of the sheet were further improved, and the cycle life of the secondary battery was improved.

As is clear from examples 1 to 4 and comparative examples 1 and 2, in the negative electrode sheet of the present application, the tensile modulus and tensile strength of the sheet can be further improved and the cycle life of the secondary battery can be improved when the thickness of the coating layer is within a specific range.

As can be seen from examples 1 to 4 and comparative examples 3 and 4, in the negative electrode sheet of the present application, the mass ratio of the modified nano negative electrode material to the reduced graphene oxide is within a specific range, and thus a thin film electrode sheet can be formed well, and the capacity and cycle life of the secondary battery can be improved.

< example 10>, < example 11>, < comparative example 6>, < comparative example 7>

Negative electrode sheets were obtained in examples 10 and 11 and comparative examples 6 and 7 by the same production method as in example 3, except that the specific conditions in step (1) were changed as shown in table 4.

[ Table 4]

As can be seen from table 3, examples 3, 10, and 11 and comparative examples 6 and 7 show that the coating rate of the coating layer can be increased and the tensile modulus and tensile strength of the pole piece can be increased by controlling the ultrasonic and stirring treatment time in step (1) within a specific range. When the ultrasonic treatment and the stirring treatment are in a proper range, on one hand, the inner core can be well coated, and higher tensile modulus and tensile strength can be obtained; on the other hand, the coating layer can be prevented from being too thick, so that the overall energy density of the secondary battery is not affected.

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 all 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 plate, wherein,

comprises a reduced graphene oxide lamellar layer and a modified nano cathode material,

the modified nanometer negative electrode material comprises:

a kernel; and

a coating layer coated on the surface of the inner core,

the molecular formula of the inner core is A _x B _y Wherein A is at least one selected from antimony, molybdenum and silicon, B is at least one selected from sulfur, selenium and oxygen, x is more than or equal to 1 and less than or equal to 3, y is more than or equal to 1 and less than or equal to 4,

the coating comprises polydopamine.

2. The negative electrode tab of claim 1,

the mass ratio of the inner core to the coating layer is (2).

3. The negative electrode tab according to claim 1 or 2,

the coating rate of the coating layer is more than 80%.

4. The negative electrode tab according to any one of claims 1 to 3,

the thickness of the coating layer is 15nm to 42nm.

5. The negative electrode tab according to any one of claims 1 to 4,

the mass ratio of the modified nano anode material to the reduced graphene oxide is (1).

6. The negative electrode tab according to any one of claims 1 to 5,

the tensile modulus of the negative pole piece is 175Gpa to 700Gpa.

7. The negative electrode tab according to any one of claims 1 to 6,

the tensile strength of the negative pole piece is 3.4MPa to 9.3MPa.

8. A preparation method of a negative pole piece is provided, wherein,

comprising the following steps (1) to (3):

step (3): and (3) calcining the film prepared in the step (2) in an inert and/or reducing atmosphere to obtain the negative pole piece.

9. The method for producing a negative electrode sheet according to claim 8,

in the step (1), the homogenization treatment is carried out by ultrasonic treatment and stirring treatment for 6 to 24 hours.

10. The method for producing a negative electrode tab according to claim 8 or 9, wherein,

in the step (2), the first temperature is 80 to 100 ℃, and the reduction time is 2 to 30min.

11. The method for producing a negative electrode sheet according to any one of claims 8 to 10,

in the step (2), the second temperature is-200 ℃ to-80 ℃, the third temperature is-30 ℃ to-50 ℃, and the freeze-drying time is 16h to 48h.

12. The method for producing a negative electrode sheet according to any one of claims 8 to 11,

in the step (3), the calcination is carried out at 100 to 550 ℃ for 0.5 to 5 hours.

13. A secondary battery, wherein,

the secondary battery comprises the negative pole piece of any one of claims 1 to 7 or the negative pole piece prepared by the preparation method of any one of claims 8 to 12.

14. A battery module, wherein,

the battery module includes the secondary battery according to claim 13.

15. A battery pack, wherein,

the battery pack includes the battery module of claim 14.

16. An electric device, wherein,

the electricity-using device includes at least one selected from the group consisting of the secondary battery according to claim 13, the battery module according to claim 14, and the battery pack according to claim 15.