CN116914371B

CN116914371B - Separator, preparation method thereof, battery and power utilization device

Info

Publication number: CN116914371B
Application number: CN202311183984.7A
Authority: CN
Inventors: 吴凯; 张楠楠; 王东浩; 景二东; 谢浩添; 孙信; 陈晓
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-09-14
Filing date: 2023-09-14
Publication date: 2024-02-06
Anticipated expiration: 2043-09-14
Also published as: CN116914371A

Abstract

The application discloses barrier film and preparation method, battery and power consumption device thereof, the barrier film includes polymer layer and pre-lithiation layer, pre-lithiation layer forms in one side of polymer layer, pre-lithiation layer includes the benefit lithium agent, the decomposition potential of benefit lithium agent is less than or equal to 4.2V, based on the total mass of pre-lithiation layer, the content of benefit lithium agent is 1wt% -10wt%. The isolating film can provide active lithium for the battery in the circulating process, and reduces the damage to the structure of the battery anode active material and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulating performance of the battery.

Description

Separator, preparation method thereof, battery and power utilization device

Technical Field

The application belongs to the field of batteries, and particularly relates to a separation film, a preparation method thereof, a battery and an electric device.

Background

The lithium ion battery becomes the most popular energy storage system due to the characteristics of high working potential, long service life, environmental friendliness and the like, and is widely applied to the fields of pure electric vehicles, hybrid electric vehicles, smart grids and the like. In recent years, with the continuous development of electric vehicles and energy storage systems, the requirements of battery energy density are also continuously increasing. In the formation process of the lithium ion battery, a large amount of active lithium is consumed by the formation of an SEI film (solid electrolyte interface) on the surface of the negative electrode, so that the first-cycle charge and discharge efficiency of the battery is reduced and the irreversible capacity loss is serious.

In order to solve the problems of low initial charge and discharge efficiency and serious irreversible capacity loss of the battery, the lithium supplementing of the positive pole piece and the negative pole piece is an effective solution idea. However, the stability of the positive electrode plate and the negative electrode plate after lithium supplementation is lower, so that the cycle performance of the battery is affected.

Disclosure of Invention

In view of the technical problems in the background art, the present application provides a separator for improving the cycle performance of a battery including the separator.

In order to achieve the above object, one aspect of the present application proposes a separator comprising a polymer layer and a pre-lithiated layer formed on one side of the polymer layer, the pre-lithiated layer comprising a lithium supplementing agent having a decomposition potential of 4.2V or less, the content of the lithium supplementing agent being 1wt% to 10wt% based on the total mass of the pre-lithiated layer.

The application at least comprises the following beneficial effects: the isolating film can provide active lithium for the battery in the circulating process, and reduces the damage to the structure of the battery anode active material and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulating performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent has a decomposition potential of 4.1V to 4.2V. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the volume average particle diameter Dv50 of the lithium supplement is 0.2 μm to 4 μm. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the volume average particle diameter Dv50 of the lithium supplement is 0.5 μm to 2 μm. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the lithium-compensating agent is present in an amount of 2wt% to 7wt% based on the total mass of the prelithiated layer. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the lithium supplementing agent comprisesLi _x AO _0.5(2+x) 、Li ₂ DO ₃ 、Li ₂ EO ₄ 、Li ₃ GO ₄ 、Li ₅ LO ₄ Or Li (lithium) ₅ MO ₆ Wherein x is greater than or equal to 1, A comprises at least one of Ni, co, fe, mn, zn, mg, ca, cu or Sn; d comprises at least one of Ni, co, fe, mn, sn or Cr; e comprises at least one of Ni, co, fe, mn, sn, cr, V or Nb; g comprises at least one of Ni, co, fe, mn, sn, cr, V, mo or Nb; l comprises at least one of Ni, co, fe, mn, sn, cr or Mo; m comprises at least one of Ni, co or Mn, and the valence state of each element in A, D, E, G, L, M is respectively lower than the highest oxidation valence state of the element. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the lithium supplement satisfies at least one of the following conditions: x is more than or equal to 2 and less than or equal to 4; a comprises at least one of Ni, co, fe or Mn; d comprises at least one of Ni, co or Fe; e comprises at least one of Ni, co, fe or Sn; g comprises at least one of Ni, co, fe, sn or Mo; l comprises at least one of Ni, co or Fe; m comprises Ni. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the lithium-supplementing agent comprises Li ₂ CO ₃ 、Li ₂ MnO ₂ 、Li ₅ FeO ₄ 、Li ₆ CoO ₄ 、Li ₂ NiO ₂ 、Li ₂ Cu _x1 Ni _1-x1-y1 M _y1 O ₂ 、Li ₃ VO ₄ Or Li (lithium) ₃ NbO ₄ At least one of 0<x ₁ ≤1，0≤y ₁ Less than or equal to 0.1, M comprises at least one of Zn, sn, mg, fe or Mn.

In some embodiments of the present application, at least one of the following conditions is satisfied: x is more than or equal to 0.2 ₁ ≤0.8；0.01≤y ₁ Less than or equal to 0.07. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, at least one of the following conditions is satisfied: x is more than or equal to 0.4 ₁ ≤0.6；0.03≤y ₁ Less than or equal to 0.06. Thereby making it possible toThe capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the lithium supplement includes at least one of 2-cyclopropene-1-one-2, 3-dihydroxylithium, 3-cyclobutene-1, 2-dione-3, 4-dihydroxylithium, 4-cyclopentene-1, 2, 3-trione-4, 5-dihydroxylithium, 5-cyclohexene-1, 2,3, 4-tetraone-5, 6-dihydroxylithium, lithium oxalate, lithium ketomalonate, lithium diketonosuccinate, or lithium trione glutarate. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the pre-lithiated layer has a thickness of 5 μm to 15 μm. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the pre-lithiated layer has a thickness of 7 μm to 10 μm. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the pre-lithiated layer and the polymer layer comprise a polymer. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the polymer forms a network and the lithium supplement is located on the network of the polymer.

In some embodiments of the present application, the weight average molecular weight of the polymer is 30000-100000. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the weight average molecular weight of the polymer is 50000-70000. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the polymer comprises at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the polymer comprises at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl carbonate, polycyanoacrylate, polymethacrylate, polyacrylonitrile, or polymaleic anhydride. Thereby, the capacity and cycle performance of the battery can be improved.

In some embodiments of the present application, the polymer layer has a thickness of 5 μm to 7 μm. Thereby, the capacity and cycle performance of the battery can be improved.

A second aspect of the present application proposes a method for preparing the above-described separator, comprising:

carrying out electrostatic spinning on a first spinning solution comprising a lithium supplementing agent and a polymer to obtain a pre-lithiated layer;

and forming a polymer layer on the pre-lithiation layer to obtain a separation film.

Therefore, the isolation film can be obtained by adopting the method, and the decomposition potential of the lithium supplementing agent in the isolation film is lower than or equal to 4.2V, so that active lithium can be provided for the battery in the cycle process, the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage are reduced, and the capacity and the cycle performance of the battery are improved.

In some embodiments of the present application, the electrospinning of the first dope comprises at least one of the following conditions: the pushing speed of the spinning nozzle is 0.01mm/min-0.05mm/min; the voltage between the spinning nozzle and the receiver is 10kV-20kV; the distance between the spinning nozzle and the receiver is 10cm-30cm; the temperature of the electrostatic spinning is 20-25 ℃; the humidity of the electrostatic spinning is 10% -20%.

In some embodiments of the present application, the electrospinning of the first dope comprises at least one of the following conditions: the pushing speed of the spinning nozzle is 0.02mm/min-0.04mm/min; the voltage between the spinning nozzle and the receiver is 15kV-20kV; the distance between the spinning nozzle and the receiver is 15cm-20cm; the temperature of the electrostatic spinning is 22-25 ℃; the humidity of the electrostatic spinning is 15% -20%.

In some embodiments of the present application, forming a polymer layer on the prelithiated layer is performed using the steps of: the prelithiated layer is placed on a receiver of an electrospinning apparatus and then a second spinning solution comprising a polymer is electrospun.

In some embodiments of the present application, the pre-lithiated layer is pre-carbonized prior to forming the polymer layer thereon. Therefore, the lithium supplementing agent in the pre-lithiation layer is uniformly and tightly adhered to the surface of the fiber membrane, and can form an excellent 3D conductive network after carbonization, so that the lithium supplementing efficiency of the isolation membrane is effectively improved.

In some embodiments of the present application, the carbonization conditions include: heating to 300-500 ℃ at a speed of 2-10 ℃/min under inert atmosphere, and preserving heat for 1-4 h.

In some embodiments of the present application, the carbonization conditions include: heating to 450-500 ℃ at a speed of 5-8 ℃/min under inert atmosphere, and preserving heat for 2-3 h.

A third aspect of the present application proposes a battery comprising the separator of the first aspect described above or a separator obtained by the method of the second aspect described above. Thus, the battery has excellent capacity and cycle performance.

In some embodiments of the present application, the battery further comprises a positive electrode tab and a negative electrode tab, the separator is disposed between the positive electrode tab and the negative electrode tab, and the pre-lithiation layer of the separator faces the positive electrode tab.

A fourth aspect of the present application proposes an electrical device, characterized in that it comprises the battery of the third aspect described above.

Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the accompanying drawings. In the drawings:

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

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

Fig. 3 is an exploded view of the battery of the embodiment of the present application shown in fig. 2.

Fig. 4 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 5 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 6 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 5.

Fig. 7 is a schematic view of an electric device in which a battery according to an embodiment of the present application is used as a power source.

Reference numerals illustrate:

1, a battery; 11 a housing; 12 electrode assembly; 13 cover plate; 2 a battery module; 3, a battery pack; 31 upper case; 32 lower box bodies; 20 a separation film; a polymer layer 21; 22 prelithiation layer.

Detailed Description

Embodiments of the technical solutions of the present application are described in detail below. The following examples are only for more clearly illustrating the technical solutions of the present application, and thus are only examples, and are not intended to limit the scope of protection of the present application.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 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: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise indicated, 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, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed 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, unless specifically stated otherwise.

All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.

All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

Currently, the wider the application of lithium ion batteries is in view of the development of market situation. Lithium ion batteries are not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles, and the like, as well as a plurality of fields such as military equipment, aerospace, and the like. With the continuous expansion of the application field of lithium ion batteries, the market demand of the lithium ion batteries is also continuously expanding.

In the formation process of the lithium ion battery, a large amount of active lithium is consumed by the formation of the SEI film on the surface of the negative electrode, so that the first-cycle charge and discharge efficiency of the battery is reduced and the irreversible capacity loss is serious.

In order to solve the problems of low initial charge and discharge efficiency and serious irreversible capacity loss of the battery, the lithium supplementing of the positive pole piece and the negative pole piece is an effective solution idea. Lithium is supplemented to the negative electrode sheet usually by adopting a lithium sheet, the lithium sheet has high activity in electrolyte, is easy to react with the electrolyte, so that the lithium supplementing efficiency is low, and when lithium dendrites are generated on the surface of the negative electrode, the SEI film is continuously broken and reconstructed, and lithium is continuously consumed, so that the cycle life of the battery is reduced. The positive electrode sheet is usually added with a lithium-rich additive or a lithiated active material as a lithium supplementing agent, and the lithium supplementing agent has higher decomposition potential and can be decomposed only under high voltage, however, the structure of the positive electrode active material can be damaged under high voltage, and meanwhile, the electrolyte is oxidized and decomposed due to high voltage, so that side reactions are increased, and the cycle performance of the battery is reduced. And the lithium-rich additive generally has strong alkalinity and air instability, and is easy to cause gelation of the positive electrode slurry, so that the structure of the positive electrode plate is easy to break, and the cycle performance of the battery is reduced.

According to the lithium supplementing agent and the preparation method thereof, the isolation film comprising the polymer layer and the pre-lithiation layer is adopted, the pre-lithiation layer comprises the lithium supplementing agent with the decomposition potential lower than or equal to 4.2V, and the content of the lithium supplementing agent is 1-10wt% based on the total mass of the pre-lithiation layer, so that active lithium can be provided in the battery circulation process, the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage are reduced, and the capacity and the circulation performance of the battery are improved.

The isolation film disclosed by the embodiment of the application is suitable for a lithium ion battery, and the battery disclosed by the embodiment of the application can be used for electric equipment using the battery as a power supply or various energy storage systems using the battery as an energy storage element. The powered device may include, but is not limited to, a cell phone, tablet, notebook computer, electric toy, electric tool, battery car, electric car, ship, spacecraft, and the like. Among them, the electric toy may include fixed or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric plane toys, and the like, and the spacecraft may include planes, rockets, space planes, and spacecraft, and the like.

The first aspect of the present application proposes a separator, referring to fig. 1, the separator 20 includes a polymer layer 21 and a pre-lithiated layer 22, wherein the pre-lithiated layer 22 is formed on one side of the polymer layer 21, the pre-lithiated layer 22 includes a lithium supplementing agent having a decomposition potential of 4.2V or less, and the content of the lithium supplementing agent is 1wt% to 10wt% based on the total mass of the pre-lithiated layer.

The pre-lithiation layer 22 of the present application includes a lithium-supplementing agent having a decomposition potential lower than or equal to 4.2V, and the content of the lithium-supplementing agent is 1wt% -10wt%, based on the total mass of the pre-lithiation layer, not only can provide active lithium for the battery cycle process, but also the lithium-supplementing agent can decompose at a low voltage, and damage to the structure of the battery positive electrode active material and oxidative decomposition of the electrolyte at a high voltage are reduced, thereby improving the capacity and cycle performance of the battery. Meanwhile, gas is released in the lithium supplementing agent delithiation process, and holes are formed in the isolating membrane 20, so that the liquid absorption rate of the isolating membrane 20 is improved, and the electrolyte wettability of the isolating membrane is improved. In addition, by adding the lithium supplementing agent into the isolating film 20, the slurry gel risk caused by adding the strong alkaline lithium supplementing agent into the positive electrode slurry is avoided, so that the structure of the positive electrode plate is protected from being damaged, and the cycle performance of the battery is improved.

In the present application, the decomposition potential of the lithium supplementing agent means an initial potential at which decomposition occurs during a voltammetry test or a charge-discharge cycle. And the voltammetric test method of the "decomposition potential of the lithium-compensating agent" of the present application includes cyclic voltammetry or linear sweep voltammetry.

In some embodiments of the present application, the lithium-compensating agent has a decomposition potential less than or equal to 4.2V, such as 3.5V-4.2V,3.6V-4.1V,3.7V-4V,3.8V-3.9V, and the like. Thus, the lithium supplementing agent in the decomposition voltage range is adopted in the isolating film 20, and can be decomposed at low voltage, so that the damage to the structure of the battery positive electrode active material and the oxidative decomposition of the electrolyte at high voltage are reduced, and the capacity and the cycle performance of the battery are improved. In other embodiments of the present application, the decomposition potential of the lithium-supplementing agent may be 4.1V to 4.2V.

In some embodiments of the present application, the volume average particle size Dv50 of the lithium supplement is 0.2 μm to 4 μm, e.g., 0.3 μm to 3.7 μm,0.4 μm to 3.5 μm,0.5 μm to 3.2 μm,0.8 μm to 3 μm,1 μm to 2.8 μm,1.2 μm to 2.5 μm,1.5 μm to 2.3 μm,1.7 μm to 2 μm, etc. Therefore, the lithium supplementing agent with the particle size has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the battery anode active material and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the cycle performance of the battery. In other embodiments of the present application, the volume average particle diameter Dv50 of the lithium supplement is 0.5 μm to 2 μm.

In the present application, the volume average particle diameter Dv50 means a particle diameter corresponding to a cumulative volume distribution percentage of 50%, and for example, the volume average particle diameter Dv50 test method can be measured by a laser particle size analyzer (for example, malvern Master Size 3000) with reference to standard GB/T19077-2016.

In some embodiments of the present application, the lithium supplementing agent is contained in an amount of 1wt% to 10wt%, for example, 1.5wt% to 10wt%,1.5wt% to 9.5wt%,1.5wt% to 9wt%,2wt% to 8.5wt%,2.5wt% to 8wt%,3wt% to 7.5wt%,3.5wt% to 7wt%,4wt% to 6.5wt%,4.5wt% to 6wt%,5wt% to 5.5wt%, etc., based on the total mass of the separator 20. Therefore, the lithium supplementing agent with the content can provide sufficient active lithium for the battery in the circulation process, meet the consumption of active lithium ions in the long-term circulation process of the battery, and improve the circulation performance of the battery. In other embodiments of the present application, the lithium-compensating agent is present in an amount of 2wt% to 7wt% based on the total mass of the prelithiated layer.

In some embodiments of the present application, the lithium-supplementing agent comprises Li _x AO _0.5(2+x) 、Li ₂ DO ₃ 、Li ₂ EO ₄ 、Li ₃ GO ₄ 、Li ₅ LO ₄ Or Li (lithium) ₅ MO ₆ Wherein x is greater than or equal to 1, A comprises at least one of Ni, co, fe, mn, zn, mg, ca, cu or Sn; d comprises at least one of Ni, co, fe, mn, sn or Cr; e comprises at least one of Ni, co, fe, mn, sn, cr, V or Nb; g includes at least one of Ni, co, fe, mn, sn, cr, V, mo or Nb Seed; l comprises at least one of Ni, co, fe, mn, sn, cr or Mo; m comprises at least one of Ni, co or Mn, and the valence state of each element in A, D, E, G, L, M is respectively lower than the highest oxidation valence state of the element. Therefore, the isolating film adopts the lithium supplementing agent with the composition, has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the battery anode active material and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the cycle performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent Li _x AO _0.5(2+x) The value of x is satisfied, x is more than or equal to 2 and less than or equal to 4, for example, x is more than or equal to 2.2 and less than or equal to 3.8,2.5 and x is more than or equal to 3.5,2.7 and x is more than or equal to 3.2,2.8 and x is more than or equal to 3, and a may include at least one of Ni, co, fe, or Mn. Therefore, the lithium supplementing agent with the composition is adopted by the isolating film, so that not only can sufficient active lithium be provided in the battery circulation process, but also the lithium supplementing agent with the composition has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulation performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent Li ₂ DO ₃ The D may include at least one of Ni, co, or Fe. Therefore, the lithium supplementing agent with the composition is adopted by the isolating film, so that not only can sufficient active lithium be provided in the battery circulation process, but also the lithium supplementing agent with the composition has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulation performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent Li ₂ EO ₄ E of (2) may comprise at least one of Ni, co, fe or Sn. Therefore, the lithium supplementing agent with the composition can provide sufficient active lithium for the battery in the circulating process, has lower decomposition voltage, can decompose at low voltage, and reduces the structure of the positive electrode active material of the battery at high voltageDamage and oxidative decomposition of the electrolyte, thereby improving capacity and cycle performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent comprises Li ₃ GO ₄ Wherein G comprises at least one of Ni, co, fe, sn or Mo. Therefore, the lithium supplementing agent with the composition is adopted by the isolating film, so that not only can sufficient active lithium be provided in the battery circulation process, but also the lithium supplementing agent with the composition has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulation performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent comprises Li ₅ LO ₄ Wherein L may comprise at least one of Ni, co or Fe. Therefore, the lithium supplementing agent with the composition is adopted by the isolating film, so that not only can sufficient active lithium be provided in the battery circulation process, but also the lithium supplementing agent with the composition has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulation performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent Li ₅ MO ₆ M may include Ni. Therefore, the lithium supplementing agent with the composition is adopted by the isolating film, so that not only can sufficient active lithium be provided in the battery circulation process, but also the lithium supplementing agent with the composition has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulation performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent comprises Li ₂ CO ₃ 、Li ₂ MnO ₂ 、Li ₅ FeO ₄ 、Li ₆ CoO ₄ 、Li ₂ NiO ₂ 、Li ₂ Cu _x1 Ni _1-x1-y1 M _y1 O ₂ 、Li ₃ VO ₄ Or Li (lithium) ₃ NbO ₄ At least one of 0<x ₁ ≤1，0≤y ₁ Less than or equal to 0.1, M comprises at least one of Zn, sn, mg, fe or Mn. Therefore, the lithium supplementing agent with the composition is adopted by the isolating film, so that not only can sufficient active lithium be provided in the battery circulation process, but also the lithium supplementing agent with the composition has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulation performance of the battery.

In some embodiments of the present application, the lithium-supplementing agent Li ₂ Cu _x1 Ni _1-x1-y1 M _y1 O ₂ 0 in (0)<x ₁ 1.ltoreq.1, e.g.0.001.ltoreq.x ₁ ≤1，0.005≤x ₁ ≤1，0.008≤x ₁ ≤1，0.01≤x ₁ ≤1，0.05≤x ₁ ≤1，0.08≤x ₁ ≤1，0.1≤x ₁ ≤1，0.3≤x ₁ ≤1，0.5≤x ₁ ≤1，0.8≤x ₁ Less than or equal to 1, etc. Thus, the electrochemical performance of the lithium-supplementing agent can be improved by adding Cu in the content to the lithium-supplementing agent. In some embodiments of the present application, the lithium-supplementing agent Li ₂ Cu _x1 Ni _1-x1-y1 M _y1 O ₂ X is more than or equal to 0.2 ₁ Less than or equal to 0.8, further x ₁ The method meets the following conditions: x is more than or equal to 0.4 ₁ ≤0.6。

In some embodiments of the present application, the lithium-supplementing agent Li ₂ Cu _x1 Ni _1-x1-y1 M _y1 O ₂ Wherein y is more than or equal to 0 ₁ 0.1.ltoreq.e.0.001.ltoreq.y ₁ ≤0.1，0.005≤y ₁ ≤0.1，0.008≤y ₁ ≤0.1，0.01≤y ₁ ≤0.1，0.05≤y ₁ ≤0.1，0.08≤y ₁ Less than or equal to 0.1, and M comprises Zn, sn, mg, fe or Mn. Thus, the electrochemical performance of the lithium supplementing agent can be improved by adding the M element with the content into the lithium supplementing agent. In some embodiments of the present application, the lithium-supplementing agent Li ₂ Cu _x1 Ni _1-x1-y1 M _y1 O ₂ Y is more than or equal to 0.01 ₁ Less than or equal to 0.07, further y ₁ The method meets the following conditions: y is more than or equal to 0.03 ₁ ≤0.06。

In some embodiments of the present application, the lithium supplementing agent may include at least one of 2-cyclopropene-1-one-2, 3-dihydroxylithium, 3-cyclobutene-1, 2-dione-3, 4-dihydroxylithium, 4-cyclopentene-1, 2, 3-trione-4, 5-dihydroxylithium, 5-cyclohexene-1, 2,3, 4-tetraone-5, 6-dihydroxylithium, lithium carbonate, lithium oxalate, lithium ketomalonate, lithium diketonosuccinate, or lithium trione glutarate. Therefore, the lithium supplementing agent with the composition is adopted by the isolating film, so that not only can sufficient active lithium be provided in the battery circulation process, but also the lithium supplementing agent with the composition has lower decomposition voltage, can be decomposed at low voltage, and reduces the damage to the structure of the positive electrode active material of the battery and the oxidative decomposition of electrolyte under high voltage, thereby improving the capacity and the circulation performance of the battery.

In some embodiments of the present application, the pre-lithiated layer 22 may have a thickness of 5 μm to 15 μm, for example 6 μm to 14 μm,7 μm to 13 μm,8 μm to 12 μm,9 μm to 11 μm,9 μm to 10 μm, etc. Therefore, the lithium supplementing layer with the thickness is adopted for the isolating film, so that sufficient active lithium can be provided for the battery in the circulating process, and the capacity of the battery is improved. In other embodiments of the present application, the pre-lithiated layer 22 may have a thickness of 7 μm to 10 μm.

In some embodiments of the present application, the prelithiation layer 22 and the polymer layer 21 comprise a polymer, wherein the polymer has a weight average molecular weight of 30000-100000, such as 35000-95000, 40000-90000, 45000-85000, 50000-80000, 55000-75000, 60000-70000, 65000-70000, and the like. Thus, the pre-lithiated layer 22 and the polymer layer 21 in the separator 20 of the present application are both polymers having the above molecular weights, and thus not only the strength of the separator 20 but also the liquid absorption rate of the separator 20 and the electrolyte wettability thereof can be improved. In other embodiments of the present application, the weight average molecular weight of the polymer may be 50000-70000.

In the present application, the weight average molecular weight (Mw) of the polymer can be measured by HLC-8320GPC gel permeation chromatography (SuperMultipore HZ series semi-micro SEC column, standard polystyrene) from Tosoh Corp.

In some embodiments of the present application, the pre-lithiated layer 22 may be formed by directly coating a slurry including a polymer and a lithium supplementing agent on a substrate and drying the same, or the pre-lithiated layer 22 may be obtained by electrospinning a slurry including a polymer and a lithium supplementing agent as a spinning solution, wherein the polymer in the pre-lithiated layer 22 forms a network structure, and the lithium supplementing agent is located on the network structure of the polymer. Thus, the lithium-supplementing agent is uniformly distributed in the prelithiation layer 22, thereby improving the lithium-supplementing efficiency of the lithium-supplementing agent.

In some embodiments of the present application, the polymer may include at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer. Therefore, the pre-lithiation layer 22 and the polymer layer 21 in the isolating film 20 of the present application are made of such polymers, so that not only the strength of the isolating film 20 can be improved, but also the liquid absorption rate of the isolating film 20 can be improved, and the electrolyte wettability of the isolating film can be improved.

As an example, the polymer includes at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl carbonate, polycyanoacrylate, polymethacrylate, polyacrylonitrile, or polymaleic anhydride.

In some embodiments of the present application, the thickness of the polymer layer 21 may be 5 μm to 7 μm, for example 5.5 μm to 6.5 μm,6 μm to 6.5 μm, etc. Thus, the barrier film 20 of the present application can improve puncture resistance of the barrier film 20 by using the polymer layer 21 having such a thickness.

s100: electrospinning a first spinning solution comprising a lithium supplementing agent and a polymer

In some embodiments of the present application, a lithium supplementing agent and a polymer are added to an organic solvent and stirred to prepare a first spinning solution, then the first spinning solution is subjected to electrostatic spinning, and ultrahigh voltage static electricity applied in the electrostatic spinning process causes an acceleration phenomenon of the first spinning solution including the polymer and the lithium supplementing agent under the action of an electric field force, so that a jet flow stretches in the electric field, thereby reducing the size of the lithium supplementing agent and effectively reducing the decomposition potential of the lithium supplementing agent.

In some embodiments of the present application, the volume average particle size Dv50 of the lithium-compensating agent during compounding is 1 μm to 8 μm,2 μm to 7 μm,3 μm to 6 μm,4 μm to 5 μm, etc.

In some embodiments of the present application, the pushing speed of the spinneret in the electrospinning of the first spinning solution is 0.01mm/min to 0.05mm/min, for example, 0.02mm/min to 0.04mm/min,0.03mm/min to 0.04mm/min, and the like. In other embodiments of the present application, the push speed of the spinneret in the electrospinning of the first spinning solution is 0.02mm/min to 0.04mm/min.

In some embodiments of the present application, the voltage between the spinneret and the receiver in the electrospinning of the first spinning solution is 10kV-20kV, such as 11kV-19kV,12kV-18kV,13kV-17kV,14kV-16kV,14kV-15kV, and the like. In other embodiments of the present application, the voltage between the spinneret and the receiver in the electrospinning of the first spinning solution is 15kV-20kV.

In some embodiments of the present application, the distance between the spinneret and the receiver in the electrospinning of the first spinning solution is 10cm to 30cm, for example 15cm to 25cm,17cm to 20cm, etc. In other embodiments of the present application, the distance between the spinneret and the receiver in the electrospinning of the first spinning solution is 15cm to 20cm.

In some embodiments of the present application, the temperature of electrospinning in electrospinning of the first dope is 20 ℃ to 25 ℃, e.g., 21 ℃ to 24 ℃,22 ℃ to 23 ℃, and the like. In some embodiments of the present application, the temperature of the electrospinning in the electrospinning of the first spinning solution is from 22 ℃ to 25 ℃.

In some embodiments of the present application, the first dope has a humidity of 10% to 20%, for example 12% to 18%,14% to 17%,15% to 16%, etc. in electrospinning. In other embodiments of the present application, the first dope has a humidity of 15% to 20% in electrospinning.

S200: forming a polymer layer on the pre-lithiated layer

In some embodiments of the present application, a slurry including a polymer and an organic solvent may be coated on the pre-lithiated layer, and then dried to form a polymer layer on the pre-lithiated layer.

In some embodiments of the present application, forming a polymer layer on the prelithiated layer is performed using the steps of: and placing the pre-lithiated layer on a receiver of an electrostatic spinning device, and then carrying out electrostatic spinning on a second spinning solution comprising a polymer and an organic solvent to form a polymer layer on the pre-lithiated layer.

As an example, the organic solvent in the first spinning solution and the second spinning solution each independently includes at least one of N, N-dimethylformamide, N-dimethylacetamide, acetone, N-methylpyrrolidone, hexafluoroisopropanol, or tetrahydrofuran.

It should be noted that the electrostatic spinning condition of the second spinning solution including the polymer and the organic solvent is the same as that of the first spinning solution, and will not be repeated here.

In some embodiments of the present application, the pre-lithiated layer is pre-carbonized prior to forming the polymer layer thereon. Therefore, the lithium supplementing agent in the pre-lithiation layer is uniformly and tightly adhered to the surface of the fiber membrane after electrostatic spinning, and non-carbon components in the polymer can be effectively removed after carbonization, so that an excellent 3D conductive network can be formed, and the lithium supplementing efficiency of the isolation membrane can be effectively improved.

In some embodiments of the present application, the carbonization conditions include: heating to 300-500 ℃ at a rate of 2-10 ℃ per minute under an inert atmosphere, and preserving heat for 1-4 hours, wherein the heating rate can be 3-9 ℃ per minute, 4-8 ℃ per minute, 5-7 ℃ per minute, and 5-6 ℃ per minute, for example; the carbonization temperature is 320-480 ℃, 350-450 ℃, 370-420 ℃, 380-400 ℃ and the like; the heat preservation time is 1.5h-3.5h,2h-3h,2.5h-3h, etc. As an example, the carbonization conditions include: heating to 450-500 ℃ at a speed of 5-8 ℃/min under inert atmosphere, and preserving heat for 2-3 h.

Since the organic lithium-supplementing agent fails with decomposition during carbonization, if the pre-lithiated layer is carbonized, a non-organic lithium-supplementing agent is used for preparing the pre-lithiated layer, for example, the following lithium-supplementing agent is not used: at least one of 2-cyclopropene-1-one-2, 3-dihydroxylithium, 3-cyclobutene-1, 2-dione-3, 4-dihydroxylithium, 4-cyclopentene-1, 2, 3-trione-4, 5-dihydroxylithium, 5-cyclohexene-1, 2,3, 4-tetraone-5, 6-dihydroxylithium, lithium oxalate, lithium ketomalonate, lithium diketonosuccinate or lithium trione glutarate.

Typically, the battery includes a positive electrode tab and a negative electrode tab, the separator is disposed between the positive electrode tab and the negative electrode tab, and the pre-lithiated layer of the separator faces the positive electrode tab. In the charging process of the battery, the lithium supplementing agent in the pre-lithiation layer is in power-off conversion into lithium ions, is reduced after reaching the negative electrode plate and is stored in the negative electrode active material, and then the lithium storage in the negative electrode active material is gradually released in a circulating way, so that the long cycle life of the battery is realized.

The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode active material layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

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

In some embodiments of the present application, positive electrode active materials may be used as positive electrode active materials for lithium ion batteries, which are 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 battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (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 (also referred to as NCM) ₃₃₃ ）、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ ）、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ ）、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ ）、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.80 Co _0.15 Al _0.05 O ₂ ) Or a modified compound thereof, etc. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO ₄ (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, a composite material of lithium manganese iron phosphate or lithium manganese iron phosphate and carbon.

The battery is charged and discharged with the release and consumption of Li, and the molar contents of Li are different when the battery is discharged to different states. In the list of the positive electrode materials, the molar content of Li is the initial state of the materials, namely the state before charging, and the molar content of Li can be changed after charge and discharge cycles when the positive electrode materials are applied to a battery system.

In the list of the positive electrode materials in the application, the molar content of oxygen is only a theoretical state value, the molar content of oxygen can be changed due to lattice oxygen release, and the actual molar content of oxygen can float.

In some embodiments of the present application, the positive electrode active material layer may further optionally include 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, or carbon nanofibers.

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

In some embodiments of the present application, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode 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 (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode active material layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments of the present application, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material 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 polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments of the present application, the anode active material may employ an anode 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 may include at least one of elemental silicon, a silicon oxygen compound, a silicon carbon compound, a silicon nitrogen compound, or a silicon alloy. The tin-based material may include at least one of elemental tin, a tin oxide, or a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments of the present application, the anode active material layer further optionally includes a binder. The binder may include at least one of Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), or carboxymethyl chitosan (CMCS).

In some embodiments of the present application, the anode active material layer may further optionally include a conductive agent. The conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

In some embodiments of the present application, the anode active material layer may optionally further include other adjuvants, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments of the present application, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

Typically, a battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. During the charge and discharge of the battery, active ions are inserted and extracted back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The isolating film is arranged between the positive pole piece and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and meanwhile ions can pass through the isolating film.

The type of electrolyte is not particularly limited in this application, and may be selected according to the need. For example, the electrolyte may be liquid, gel, or all solid.

In some embodiments of the present application, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments of the present application, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonimide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, or lithium tetrafluorooxalato phosphate.

In some embodiments of the present application, the solvent may include at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl 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, ethylene glycol dimethyl ether, methyl sulfone, or diethyl sulfone.

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

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 outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte described above.

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 exterior package of the secondary battery may also be a pouch type pouch, for example. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The shape of the battery is not particularly limited in this application, and may be cylindrical, square, or any other shape. For example, fig. 2 is a square-structured battery cell 1 as one example.

In some embodiments, referring to fig. 3, the outer package may include a housing 11 and a cover 13. The housing 11 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 11 has an opening communicating with the accommodation chamber, and the cover plate 13 can be provided to cover the opening to close the accommodation chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 12. The number of the electrode assemblies 12 included in the battery cell 1 may be one or more, and one skilled in the art may select according to specific practical requirements.

In some embodiments, the cells may be assembled into a battery module, and the number of cells contained in the battery module may be one or more, with the specific number being selectable by one of ordinary skill in the art based on the application and capacity of the battery module.

Fig. 4 is a battery module 2 as an example. Referring to fig. 4, in the battery module 2, a plurality of battery cells 1 may be sequentially arranged in the longitudinal direction of the battery module 2. Of course, the arrangement may be performed in any other way. The plurality of battery cells 1 may be further fixed by fasteners.

Alternatively, the battery module 2 may further include a housing having an accommodating space in which the plurality of battery cells 1 are accommodated.

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

Fig. 5 and 6 are battery packs 3 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 2 disposed in the battery case may be included in the battery pack 3. The battery case includes an upper case 31 and a lower case 32, and the upper case 31 can be covered on the lower case 32 and forms a closed space for accommodating the battery module 2. The plurality of battery modules 2 may be arranged in the battery case in any manner.

In addition, the application also provides an electric device, which comprises at least one of the secondary battery, the battery module or the battery pack. The secondary battery, the battery module, or the battery pack may be used as a power source of the power consumption device, and may also be used as an energy storage unit of the power consumption device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity consumption device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 7 is an electrical 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 high power and high energy density requirements of the secondary battery by the power consumption device, a battery pack or a battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a battery can be used as a power source.

Hereinafter, embodiments of the present application are described. The embodiments described below are exemplary only for the purpose of illustrating the present application and are not to be construed as limiting the present application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

1. Preparation of positive electrode plate

LiFePO is prepared ₄ (volume average particle diameter Dv50 is 1.2 mu m), acetylene black serving as a conductive agent and polyvinylidene fluoride serving as a binder are added into the aluminum foil according to the weight ratio of 97:1:2, the mixture is fully stirred and uniformly mixed, the slurry is uniformly coated on the surfaces of two sides of the aluminum foil, the aluminum foil is then transferred into a vacuum drying oven for complete drying, the obtained pole piece is rolled and then punched, and the positive pole piece is obtained.

2. Preparation of negative electrode plate

Artificial graphite as a cathode active material, carbon black (Super P) as a conductive agent, styrene-butadiene rubber (SBR) as a binder and sodium carboxymethylcellulose (CMC-Na) as a thickener according to the mass ratio of 96.5:0.7:1.8: and 1, uniformly mixing in a proper amount of solvent deionized water to obtain negative electrode slurry, coating the negative electrode slurry on the surfaces of the two sides of a copper foil of a negative electrode current collector, drying and cold pressing to form a negative electrode active material layer on the surfaces of the two sides of the negative electrode current collector, and finally, carrying out the processes of slitting and cutting to obtain a negative electrode plate.

3. Preparation of electrolyte

In an argon atmosphere glove box (H ₂ O<0.1ppm，O ₂ <0.1 ppm), will be sufficiently dry of the electrolyte salt LiPF ₆ Dissolved in a mixed solvent (the mixed solvent comprises Ethylene Carbonate (EC) and diethyl carbonate)(DEC), and Ethylene Carbonate (EC) and diethyl carbonate (DEC) are mixed according to the mass ratio of 50:50), and the electrolyte with the concentration of 1.1mol/L is obtained after uniform mixing.

4. Preparation of a separator film

Polymer powder polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and lithium ferrite Li ₅ FeO ₄ Drying in a 60 ℃ oven for 12 hours, weighing 19g of dried polyvinylidene fluoride-hexafluoropropylene copolymer and lithium ferrite Li ₅ FeO ₄ 1g of the solution is added into a certain amount of N, N-Dimethylformamide (DMF), the solution is placed in an oil bath at 50 ℃ and mechanically stirred for 3 hours to obtain uniformly mixed first spinning solution, the uniformly mixed first spinning solution is injected into an electrostatic spinning machine, the distance between a spinning nozzle and a receiver is adjusted to be 15cm, the flow rate of the spinning solution injection is 0.03mm/min, the applied voltage is 20kV, the spinning is carried out at room temperature to form a fiber membrane layer, then the fiber membrane layer is taken to be heated to 450 ℃ at a heating rate of 5 ℃/min in argon atmosphere and then is kept warm for 3 hours, and a pre-lithiation layer (lithium ferrite surface density of 0.019g/1540.25mm is obtained ² ) Placing the polymer powder into a receiver of an electrostatic spinning machine, injecting a second spinning solution comprising polymer powder polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and N, N-Dimethylformamide (DMF) into the electrostatic spinning machine, adjusting the distance between a spinning nozzle and the receiver to be 15cm, controlling the flow rate of the spinning solution to be 0.03mm/min, applying a voltage of 20kV, and receiving a polymer layer on the pre-lithiation layer at room temperature to obtain the isolating membrane.

5. Preparation of lithium ions

Sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate (wherein the pre-lithiation layer on the isolating film faces the positive electrode plate) to ensure that the isolating film is positioned between the positive electrode plate and the negative electrode plate to play a role of isolation, and then winding to obtain an electrode assembly; and placing the electrode assembly in an outer package, injecting the prepared electrolyte into a dried lithium ion battery, and performing vacuum packaging, standing, formation (constant current charging at 45 ℃ and 0.33C till 60% of SOC, and 0.1C multiplying power till 4.2V) and shaping to obtain the lithium ion battery.

The lithium ion batteries of examples 2 to 38 and comparative example 1 were prepared in the same manner as in example 1, except that the separator was prepared in a different manner and composition, as shown in Table 1.

Comparative example 2

The lithium ion battery of comparative example 2 was prepared as in example 1, except that the separator was prepared by a different method, specifically as follows:

the isolating film adopts a polyethylene film with the thickness of 6 mu m as a substrate, and lithium ferrite Li ₅ FeO ₄ Slurry coating (lithium ferrite Li) after mixing polyvinylidene fluoride and N, N-Dimethylformamide (DMF) ₅ FeO ₄ The Dv50 of (2) was 5. Mu.m, the decomposition potential was 4.5V) on one side of the polyethylene film, and a pre-lithiated layer (thickness: 9 μm) was formed on the polyethylene film by drying, thereby obtaining a separator (the mass ratio of lithium ferrite was 5% based on the total mass of the separator).

TABLE 1

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The decomposition potential of the lithium-supplementing agent in the separator obtained in examples 1 to 38 and comparative examples 1 to 2 was measured, the characterization results are shown in table 1, and the specific discharge capacity and cycle performance of the lithium ion battery are characterized, and the characterization results are shown in table 2.

(1) And (3) testing the decomposition potential of the lithium supplementing agent in the isolating film:

preparing a button type full battery:

a. preparing a negative electrode plate:

the negative electrode active material graphite, a conductive agent acetylene black, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC) are mixed according to the weight ratio of 96.5:0.7:1.8:1 fully stirring and uniformly mixing in a proper amount of deionized water solvent system to obtain negative electrode slurry, coating the negative electrode slurry on one side surface of copper foil (thickness of 6 mu m) (coating surface density of 0.174g/1540.25 mm) ² ) Then drying and cold pressing to form a negative electrode active material layer (the thickness of the negative electrode active material layer is 0.143 mm) on one side surface of a negative electrode current collector, and finally punching to obtain a negative electrode plate;

b. preparing a positive electrode plate:

the positive electrode active material (LiFePO ₄ ) Conductive carbon (SP), binder (polyvinylidene fluoride PVDF) in mass ratio of 97:1:2 is dissolved in N-methyl pyrrolidone (NMP), and is fully stirred and uniformly mixed to prepare anode slurry, and the anode slurry is coated on one side surface of an aluminum foil (the coating surface density is 0.377g/1540.25 mm) ² ) Then drying and cold pressing to form a positive electrode active material layer (the thickness of which is 0.219 mm) on one side surface of an aluminum foil (13 mu m), and finally punching to obtain a positive electrode plate;

c. preparation of a separation film:

a slurry (solid content: 60%) comprising a polymer powder polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and N, N-Dimethylformamide (DMF) was coated on a glass substrate (coating surface density: 0.05g/1540.25mm ² ) Then drying and cold pressing, and stripping the glass substrate to obtain a polymer layer (the thickness is 15 μm); drying polymer powder polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and lithium supplementing agent in a 60 ℃ oven for 12 hours, weighing 19g of the dried polyvinylidene fluoride-hexafluoropropylene copolymer and 1g of the lithium supplementing agent, adding into N, N-Dimethylformamide (DMF), mechanically stirring for 3 hours to obtain uniformly mixed pre-lithiated slurry (solid content is 63 percent), and then adding The uniformly mixed pre-lithiated slurry was coated on one side of the polymer layer (coating surface density 0.02g/1540.25mm ² ) Then, a pre-lithiated layer (thickness 5 μm) was formed on one side of the polymer layer by baking and cold pressing to obtain a separator.

d. Preparation of electrolyte

Ethylene Carbonate (EC), methyl ethyl carbonate (EMC) and dimethyl carbonate (DMC) are mixed according to the mass ratio of 1:1:1 to obtain a solvent, and drying the electrolyte salt LiPF ₆ Dissolving in the solvent, and uniformly mixing to obtain the electrolyte with the concentration of 1 mol/L.

And (3) assembling: and sequentially stacking a single positive electrode plate, a single isolating film and a single negative electrode plate (wherein one side of the positive electrode plate, which forms a positive electrode active material layer, contacts a pre-lithiation layer on the isolating film, and one side of the negative electrode plate, which forms a negative electrode active material layer, contacts a polymer layer of the isolating film), so that the isolating film is positioned in the middle of the positive electrode and the negative electrode to play a role of isolation, adding electrolyte, and performing pressure packaging (50 MPa) to obtain the CR2032 button type full battery (the capacity is less than or equal to 4.5 mAh).

Taking the button type full battery as an experimental example, carrying out charge-discharge circulation at 25 ℃ by using 0.04C multiplying power, recording a capacity (Q) -voltage (V) curve of a first circle, and differentiating the capacity (Q) -voltage (V) curve to obtain a dQ/dV-V curve; meanwhile, the button type full battery (the lithium supplementing agent is not added into the slurry of the pre-lithiation layer of the isolating film, and the rest is the same as the button type full battery) of the control group is subjected to dQ/dV curve under the same condition, and two curves are compared, so that an additional peak position can be seen from the dQ/dV-V curve of the button type full battery of the experimental example, the peak position is the characteristic peak position of the lithium supplementing agent, and the ordinate corresponding to the peak position is the decomposition potential of the lithium supplementing agent.

(2) Specific discharge capacity test:

at normal temperature (25 ℃), the discharge capacity of E was measured by constant-current discharging the battery at 0.33C to a discharge termination voltage of 2.5V _d0 Using E _d0 The specific discharge capacity, that is, the specific discharge capacity of the battery (mAh/g) =1 st turn discharge capacity/mass of the positive electrode active material, is obtained by dividing the mass of the positive electrode active material of the battery.

(3) And (3) testing the cycle performance:

controlling the ambient temperature to 25 ℃, charging the battery to 3.65V at 1C, then charging to 0.05C at constant voltage, standing for 10min, then discharging to 2.5V at 1C, and recording the discharge capacity as C ₀ 300 cycles were performed according to the charge-discharge flow, and the discharge capacity at 300 th cycle was C ₁ Cell cycle capacity retention = C ₁ /C ₀ *100%。

TABLE 2

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Conclusion: the lithium ion battery separators of examples 1 to 38 each include a polymer layer and a prelithiation layer, and the prelithiation layer adopts a lithium supplementing agent with a decomposition potential lower than or equal to 4.2V, whereas the prelithiation layer of the separator of comparative example 1 does not adopt a lithium supplementing agent, and the separator of comparative example 2 adopts a lithium supplementing agent with a decomposition potential of 4.5V, as can be seen from the data in table 2, the discharge specific capacity and the cycle performance of the lithium ion batteries of examples 1 to 38 are both superior to those of comparative examples 1 to 2, thereby indicating that the prelithiation layer of the separator of the present application adopts a lithium supplementing agent with a decomposition potential lower than or equal to 4.2V, and the content of the lithium supplementing agent in the prelithiation layer is controlled to be 1wt% to 10wt%, which can improve the capacity and cycle performance of the battery.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims

1. A separator comprising a polymer layer and a pre-lithiated layer formed on one side of the polymer layer, the pre-lithiated layer comprising a lithium-supplementing agent having a decomposition potential of 4.2V or less and a carbonized polymer, the content of the lithium-supplementing agent being 1 to 10wt% based on the total mass of the pre-lithiated layer,

the preparation steps of the isolating film comprise:

carrying out electrostatic spinning on a first spinning solution comprising a lithium supplementing agent and a polymer to obtain a pre-lithiated layer, wherein the polymer forms a network structure, and the lithium supplementing agent is positioned on the network structure of the polymer;

Forming a polymer layer on the pre-lithiation layer to obtain a separator,

the formation of the polymer layer on the prelithiation layer is performed using the following steps:

placing the prelithiation layer on a receiver of an electrospinning apparatus, then electrospinning a second spinning solution comprising a polymer,

the pre-lithiated layer is subjected to a carbonization treatment in advance before forming a polymer layer on the pre-lithiated layer.

2. The separator of claim 1, wherein the lithium-compensating agent has a decomposition potential of 4.1V to 4.2V.

3. The separator according to claim 1 or 2, wherein the volume average particle diameter Dv50 of the lithium supplementing agent is 0.2 μm to 4 μm.

4. The separator according to claim 1 or 2, wherein the volume average particle diameter Dv50 of the lithium supplementing agent is 0.5 μm to 2 μm.

5. The separator according to claim 1, wherein the content of the lithium supplementing agent is 2wt% to 7wt%, based on the total mass of the prelithiation layer.

6. According to claimThe separator of claim 1, wherein the lithium supplementing agent comprises Li _x AO _0.5(2+x) 、Li ₂ DO ₃ 、Li ₂ EO ₄ 、Li ₃ GO ₄ 、Li ₅ LO ₄ Or Li (lithium) ₅ MO ₆ At least one of the group consisting of,

wherein x is more than or equal to 1,

a comprises at least one of Ni, co, fe, mn, zn, mg, ca, cu or Sn;

D comprises at least one of Ni, co, fe, mn, sn or Cr;

e comprises at least one of Ni, co, fe, mn, sn, cr, V or Nb;

g comprises at least one of Ni, co, fe, mn, sn, cr, V, mo or Nb;

l comprises at least one of Ni, co, fe, mn, sn, cr or Mo;

m comprises at least one of Ni, co or Mn,

A. d, E, G, L, M each element has a valence state that is lower than its own highest oxidation valence state.

7. The separator of claim 6, wherein the lithium supplement satisfies at least one of the following conditions:

2≤x≤4；

a comprises at least one of Ni, co, fe or Mn;

d comprises at least one of Ni, co or Fe;

e comprises at least one of Ni, co, fe or Sn;

g comprises at least one of Ni, co, fe, sn or Mo;

l comprises at least one of Ni, co or Fe;

m comprises Ni.

8. The separator of claim 1, wherein the lithium supplement comprises Li ₂ CO ₃ 、Li ₂ MnO ₂ 、Li ₅ FeO ₄ 、Li ₆ CoO ₄ 、Li ₂ NiO ₂ 、Li ₂ Cu _x1 Ni _1-x1-y1 M _y1 O ₂ 、Li ₃ VO ₄ Or Li (lithium) ₃ NbO ₄ At least one of 0<x ₁ ≤1，0≤y ₁ Less than or equal to 0.1, M comprises at least one of Zn, sn, mg, fe or Mn.

9. The separator of claim 8, wherein at least one of the following conditions is satisfied:

0.2≤x ₁ ≤0.8；

0.01≤y ₁ ≤0.07。

10. the separator according to claim 8 or 9, wherein at least one of the following conditions is satisfied:

0.4≤x ₁ ≤0.6；

0.03≤y ₁ ≤0.06。

11. The separator of claim 1, wherein the pre-lithiated layer has a thickness of 5 μιη to 15 μιη.

12. The separator according to claim 1 or 11, wherein the pre-lithiated layer has a thickness of 7 μm to 10 μm.

13. The separator of claim 1, wherein the polymer has a weight average molecular weight of 30000-100000.

14. The separator according to claim 1 or 13, wherein the polymer has a weight average molecular weight of 50000-70000.

15. The separator of claim 1, wherein the polymer comprises at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer.

16. The separator of claim 15, wherein the polymer comprises at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinyl carbonate, polycyanoacrylate, polymethacrylate, polyacrylonitrile, or polymaleic anhydride.

17. The separator of claim 1, wherein the polymer layer has a thickness of 5-7 μm.

18. A method of making the separator of any of claims 1-17, comprising:

19. The method of claim 18, wherein the electrospinning of the first dope comprises at least one of the following conditions:

the pushing speed of the spinning nozzle is 0.01mm/min-0.05mm/min;

the voltage between the spinning nozzle and the receiver is 10kV-20kV;

the distance between the spinning nozzle and the receiver is 10cm-30cm;

the temperature of the electrostatic spinning is 20-25 ℃;

the humidity of the electrostatic spinning is 10% -20%.

20. The method of claim 18 or 19, wherein electrospinning of the first dope comprises at least one of the following conditions:

the pushing speed of the spinning nozzle is 0.02mm/min-0.04mm/min;

the voltage between the spinning nozzle and the receiver is 15kV-20kV;

the distance between the spinning nozzle and the receiver is 15cm-20cm;

the temperature of the electrostatic spinning is 22-25 ℃;

the humidity of the electrostatic spinning is 15% -20%.

21. The method of claim 18, wherein the carbonization conditions comprise: heating to 300-500 ℃ at a speed of 2-10 ℃/min under inert atmosphere, and preserving heat for 1-4 h.

22. The method according to claim 18 or 21, wherein the carbonization conditions comprise: heating to 450-500 ℃ at a speed of 5-8 ℃/min under inert atmosphere, and preserving heat for 2-3 h.

23. A battery comprising the separator of any one of claims 1-17 or obtained by the method of any one of claims 18-22.

24. The battery of claim 23, further comprising a positive electrode tab and a negative electrode tab, wherein the separator is disposed between the positive electrode tab and the negative electrode tab, wherein the pre-lithiated layer of the separator faces the positive electrode tab.

25. An electrical device comprising the battery of claim 23 or 24.