Thermal response type capacity recovery material, preparation method thereof and secondary battery

Abstract

The invention relates to a thermal response type capacity recovery material, a preparation method thereof and a secondary battery. The thermal response type capacity recovery material comprises a thermal response type micro-nano storage bin and a capacity recovery agent located in the thermal response type micro-nano storage bin. The thermal response type capacity recovery material provided by the invention can reduce and solve the problems of capacity fading and degradation and safety caused by loss of active sodium ions, effectively promotes recovery of battery capacity and prolonging of cycle life, and also can provide a new thought for subsequent battery recovery and waste battery treatment.

Description

Technical Field

[0001] The present disclosure relates to the technical field of sodium ion batteries, and in particular to a thermally responsive capacity recovery material and a preparation method thereof, and a secondary battery. Background Art

[0002] Lithium-ion batteries dominate the field of large-scale energy storage due to their high energy efficiency, long cycle life, and relatively mature technology. However, lithium resources are limited and unevenly distributed, which limits their application. Na and Li belong to the same Group IA elements, and have similar physical and chemical properties. The production processes and equipment of the two batteries are also mostly compatible. In addition, sodium-ion batteries have great advantages and development prospects in large-scale applications due to their abundant raw material resources, low price, and high safety.

[0003] However, both lithium-ion batteries and sodium-ion batteries will experience capacity degradation and attenuation during long-term use. Especially at the current level of technology, compared with the SEI membrane (Solid Electrolyte Interface) of lithium-ion batteries, the stability of the SEI membrane of sodium-ion batteries is generally poor, and to a certain extent, its attenuation is faster than that of lithium-ion batteries. This will not only reduce the service life of sodium-ion batteries and increase replacement costs, but also with the further transformation of social electrification, the number of waste sodium-ion batteries will also increase sharply. Therefore, slowing down the attenuation of batteries or restoring the capacity of batteries can effectively increase the service life of batteries and save energy, time and cost to a certain extent.

[0004] Generally, the capacity degradation of sodium-ion batteries during long-term use mainly includes damage to active materials (such as irreversible phase change, particle cracking and electrical contact loss) and loss of active ions (consumption of SEI film, decomposition of electrolyte, etc.). In practical applications, sodium-ion batteries usually operate in systems with certain temperature and humidity control, and the loss of active ions is often their main attenuation mode. Therefore, how to slow down the loss of active ions in sodium-ion batteries or increase the amount of active ions is of great significance to improving the service life of sodium-ion batteries and promoting their widespread application.

[0005] Current methods for solving or inhibiting the problem of active ion loss generally include: optimizing the electrode material structure, improving the electrolyte formula and additives, building a stable SEI membrane, etc. Most strategies focus on inhibiting or solving the initial source, and mainly focus on how to stabilize the SEI. There is little discussion on how to restore the capacity attenuation that has occurred during the subsequent operation of the battery in a timely, quantitative and on-demand manner. Summary of the invention

[0006] In order to solve the above technical problems, the present disclosure provides a thermal responsive capacity recovery material and a preparation method thereof, and a secondary battery.

[0007] The present disclosure provides a thermally responsive capacity recovery material, which includes a thermally responsive micro-nano storage chamber and a capacity recovery agent located inside the thermally responsive micro-nano storage chamber.

[0008] As a preferred technical solution of the present disclosure, the thermally responsive micro-nano storage compartment is a spherical or quasi-spherical structure below 80°C, and deforms at 80-85°C to release the capacity recovery agent inside.

[0009] As a preferred technical solution of the present disclosure, the time for deformation to occur is 1-30s.

[0010] As a preferred technical solution of the present disclosure, below 80°C, the size of the thermally responsive micro-nano storage chamber is 10-5000 μm.

[0011] As a preferred technical solution of the present disclosure, below 80°C, the thickness of the thermally responsive micro-nano storage chamber is 0.5-100 μm.

[0012] As a preferred technical solution of the present disclosure, the material of the thermally responsive micro-nano storage warehouse includes any one or a combination of at least two of DA-bonded polymer materials, triblock copolymers, polycaprolactone, ethylene-methyl acrylate copolymers, ionomers, polylactic acid, polynorbornene, polymethacrylate copolymers, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane or polylactic acid-caprolactone copolymers, more preferably DA-bonded polymer materials, and even more preferably DA-bonded polyurethane materials.

[0013] As a preferred technical solution of the present disclosure, the DA-bonded polyurethane material is a bonding material of polyurethane acrylate and hydroxyethyl acrylate containing DA bonds.

[0014] As a preferred technical solution of the present disclosure, in the bonding material of polyurethane acrylate and hydroxyethyl acrylate containing DA bonds, the mass percentage of hydroxyethyl acrylate is 40-80%, preferably 60%.

[0015] As a preferred technical solution of the present disclosure, the capacity recovery agent includes an ionic compound and an electrolyte.

[0016] As a preferred technical solution of the present disclosure, the ionic compound is selected from any one of sodium naphthalene, sodium biphenyl, sodium pyrene, sodium anthracene, sodium phenanthrene or sodium methylnaphthalene, or a combination of at least two thereof, preferably sodium naphthalene.

[0017] As a preferred technical solution of the present disclosure, the capacity recovery agent is a mixture of sodium naphthalene solution and an electrolyte, preferably the sodium naphthalene solution is a DME solution containing sodium naphthalene, preferably the mass ratio of the sodium naphthalene solution to the electrolyte is 2:1-1:5, preferably the concentration of the sodium naphthalene solution is 0.1-1.5 mol / L, and preferably the concentration of the electrolyte is 0.5-5 mol / L.

[0018] As a preferred technical solution of the present disclosure, the mass ratio of the sodium naphthalene solution to the electrolyte is 1:1, preferably the concentration of the sodium naphthalene solution is 1.0 mol / L, and preferably the concentration of the electrolyte is 1.5 mol / L.

[0019] In a second aspect, the present disclosure provides a method for preparing the thermally responsive capacity recovery material according to the first aspect, the preparation method comprising:

[0020] The material of the thermally responsive micro-nano storage bin is processed with a capacity recovery agent to obtain the thermally responsive capacity recovery material.

[0021] As a preferred technical solution of the present disclosure, the processing method includes any one or a combination of at least two of solution mixing, thermoplastic processing, melt blending, in-situ polymerization, 3D printing, 4D digital light processing or nano-microfluidics, preferably a combination of solution mixing and 3D printing.

[0022] In a third aspect, the present disclosure provides a use of the thermally responsive capacity recovery material described in the first aspect in replenishing the lost capacity of a secondary battery.

[0023] In a fourth aspect, the present disclosure provides a secondary battery comprising the thermal-responsive capacity recovery material described in the first aspect.

[0024] As a preferred technical solution of the present disclosure, the secondary battery is a sodium ion battery, a lithium ion battery, a potassium ion battery, a zinc ion battery or a magnesium ion battery.

[0025] As a preferred technical solution of the present disclosure, the thermal responsive capacity recovery material is dot-coated on the surface of the diaphragm of the secondary battery, or added to the electrolyte, or fixed at any position inside the secondary battery.

[0026] In a fifth aspect, the present disclosure provides a method for replenishing the capacity lost during operation of the secondary battery described in the fifth aspect, the replenishment method comprising: heating the secondary battery to 80-85°C, maintaining for 1-30s, releasing part or all of the capacity recovery agent, and then using a CV process based on the Gibbs energy of the reaction, thereby effectively replenishing the lost capacity of the secondary battery.

[0027] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0028] (1) The thermally responsive capacity recovery material defined in the present disclosure can deform at a certain temperature, restore to an initial state, and release the capacity recovery agent in a timely and quantitative manner as required;

[0029] (2) The thermally responsive capacity recovery material defined in the present disclosure has a high potential control, and can selectively provide electrons and active sodium ions to the cathode of the battery system to induce a recovery effect, while inhibiting the reaction at the anode, and controlling the reaction potential of the capacity recovery agent through the coordination effect of the solvent. After the CV process, the capacity lost by the secondary battery can be replenished;

[0030] (3) The thermally responsive capacity recovery material provided by the present invention can reduce and solve the capacity attenuation and safety problems caused by the loss of active sodium ions, effectively promote the recovery of battery capacity and the extension of cycle life, and use thermal response stimulation for release. At the same time, it can also provide new ideas for subsequent battery recycling and waste battery treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 A schematic diagram of the application principle of the thermal responsive capacity recovery material disclosed in the present invention;

[0034] Figure 2 A simplified schematic diagram of the thermal responsive capacity recovery material disclosed in the present invention at any position in the secondary battery;

[0035] Figure 3 A cycle comparison diagram of the sodium ion battery provided for Application Example 4 and Comparative Example 1;

[0036] Figure 4 A comparison chart of the discharge capacity of the sodium ion battery provided for Application Example 4 before and after releasing the capacity recovery agent. DETAILED DESCRIPTION

[0037] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0038] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0039] For the capacity degradation or attenuation of sodium ions, the general approach is to solve or suppress the loss of active ions, which can be achieved by optimizing the electrode material structure, improving the composition of the electrolyte or adding additives, and constructing a stable SEI film. However, there is little information on how to effectively restore a secondary battery that has experienced capacity attenuation. Therefore, the present disclosure provides a thermally responsive capacity recovery material and a preparation method and application thereof, which can supplement the capacity of a secondary battery after capacity attenuation has occurred, so as to increase the cycle life of the secondary battery.

[0040] The present disclosure provides a thermally responsive capacity recovery material, which includes a thermally responsive micro-nano storage chamber and a capacity recovery agent located inside the thermally responsive micro-nano storage chamber.

[0041] As a preferred technical solution of the present invention, the thermally responsive micro-nano storage chamber is a thermally responsive shape memory material. By controlling the ratio of the fixed phase and the reversible phase in the shape memory polymer, the storage chamber can be quickly opened under a thermal response stimulation signal, and the capacity recovery agent can be released in a timely and quantitative manner as needed.

[0042] The schematic diagram of the use principle of the thermal responsive capacity recovery material disclosed in the present invention is shown in Figure 1 It is programmed through processing and solidified by cooling to obtain a temporary fixed shape of a sphere or ellipsoid. After receiving thermal stimulation of heating, it deforms and returns to its initial state, during which the capacity recovery agent is released.

[0043] As a preferred technical solution of the present disclosure, the thermally responsive micro-nano storage compartment is a spherical or quasi-spherical structure below 80°C, and deforms at 80-85°C to release the capacity recovery agent inside.

[0044] The deformation at 80-85°C mentioned in the present disclosure means that the material of the thermally responsive micro-nano storage bin can deform at a temperature of 80-85°C and restore to an initial state, rather than that the material can only deform between 80-85°C. For example, it can be 80.5°C, 81°C, 81.5°C, 82°C, 82.5°C, 83°C, 83.5°C, 84°C, 84.5°C, etc.

[0045] As a preferred technical solution of the present invention, the deformation time is 1-30s, for example, 2s, 5s, 8s, 10s, 12s, 15s, 18s, 20s, 22s, 25s, 28s, etc., preferably 6-8s.

[0046] The thermally responsive micro-nano storage chamber defined in the present disclosure achieves response changes in seconds at 80-85°C, and has a short response time. When applied to secondary batteries, it can reduce the placement time of the secondary batteries in high temperatures, further ensuring the safety of the secondary batteries.

[0047] The present invention specifically selects a heat-responsive micro-nano storage bin material that can deform at 80-85°C. When applied to a secondary battery, the secondary battery can be placed in an environment of 80-85°C to deform and release a capacity recovery agent to replenish the degraded capacity. Furthermore, the secondary battery will not reach a temperature of 80-85°C when operating at all-weather temperatures, so it will not be affected in any way and has significant practicality.

[0048] In addition, the response time of the material is in the order of seconds, which is extremely short. That is, the secondary battery can replenish its capacity by being placed in an environment of 80-85°C for only seconds, thus avoiding temperature damage to the secondary battery as much as possible. If the temperature at which deformation can occur is too high or the time required for response is too long, the secondary battery needs to be placed in a higher temperature or for a longer time, which can easily cause damage to the secondary battery and deteriorate the safety performance of the secondary battery; and if the temperature at which deformation can occur is too low, the capacity recovery agent may be released during normal use of the secondary battery.

[0049] As a preferred technical solution of the present invention, below 80°C, the size of the thermally responsive micro-nano storage chamber is 10-5000μm, for example, 50μm, 100μm, 200μm, 500μm, 1000μm, 1500μm, 2000μm, 2500μm, 3000μm, 3500μm, 4000μm, 4500μm, etc., preferably 100-1000μm.

[0050] As a preferred technical solution of the present invention, below 80°C, the thickness of the thermally responsive micro-nano storage warehouse is 0.5-100μm, for example, 1μm, 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, etc. The thickness of the thermally responsive micro-nano storage warehouse can be adjusted accordingly with the size of the thermally responsive micro-nano storage warehouse.

[0051] As a preferred technical solution of the present disclosure, the material of the thermally responsive micro-nano storage warehouse includes any one or a combination of at least two of DA-bonded polymer materials, triblock copolymers, polycaprolactone, ethylene-methyl acrylate copolymers, ionomers, polylactic acid, polynorbornene, polymethacrylate copolymers, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane or polylactic acid-caprolactone copolymers, more preferably DA-bonded polymer materials, and even more preferably DA-bonded polyurethane materials.

[0052] As a preferred technical solution of the present disclosure, the DA-bonded polyurethane material is a bonding material of polyurethane acrylate (PUDA) and hydroxyethyl acrylate (HEA) containing DA bonds.

[0053] As a specific embodiment of the present disclosure, the preparation method of the DA-bonded polyurethane material includes:

[0054] N,N'-4,4'-diphenylmethane-bismaleimide (BMI) and furfuryl alcohol (FA) are reacted to obtain an intermediate;

[0055] The intermediate, isophorone diisocyanate (IPDI) and HEA undergo polymerization reaction under the action of a catalyst to obtain polyurethane acrylate (PUDA) containing a DA bond;

[0056] Polyurethane acrylate (PUDA) containing DA bonds and hydroxyethyl acrylate (HEA) are mixed in a certain ratio to obtain a DA-bonded polyurethane material.

[0057] As a specific embodiment of the present disclosure, the preparation method of the DA-bonded polyurethane material includes:

[0058] BMI and FA were dissolved in a solvent and reacted at 60°C for 24 h, and then the solvent was removed to obtain an intermediate;

[0059] The intermediate product, IPDI and catalyst DBTDL are dissolved in a solvent, refluxed at 60°C, and then HEA is added to react to obtain polyurethane acrylate (PUDA) containing DA bonds;

[0060] PUDA and HEA are mixed in a certain ratio to obtain the DA-bonded polyurethane material (ie, a bonding material of polyurethane acrylate and hydroxyethyl acrylate containing a DA bond).

[0061] As a preferred technical solution of the present invention, in the bonding material of polyurethane acrylate and hydroxyethyl acrylate containing DA bonds, the mass percentage of hydroxyethyl acrylate is 40-80%, for example, 45%, 50%, 55%, 60%, 65%, 70%, 75%, etc., preferably 60%.

[0062] The thermally responsive micro-nano storage bin defined in the present disclosure is composed of a material with shape memory function, and the shape memory material may include a two-phase grid structure, wherein the rigid chain segments form a cross-linked structure as a fixed phase to maintain the integrity of the structure; the monomer soft segments serve as a "shape memory phase" to achieve temporary shape fixation and recovery of the initial state under the stimulation of thermal response.

[0063] In the present disclosure, the capacity recovery agent is placed in a thermally responsive micro-nano storage compartment. By controlling the ratio of the rigid segments and the monomer soft segments in the cross-linked network of the shape memory material, the thermally responsive micro-nano storage compartment can be quickly opened (restored to the initial shape) under the stimulation of a thermally responsive stimulation signal, and the capacity recovery agent can be released in a timely, quantitative and on-demand manner.

[0064] In the present disclosure, if the content of hydroxyethyl acrylate is too low, the material viscosity of the thermally responsive micro-nano storage warehouse is relatively large and processing is relatively difficult; if the content of hydroxyethyl acrylate is too high, the proportion of the rigid structure is low, which can easily lead to incomplete cross-linking network of the material and poor rigidity.

[0065] As a preferred technical solution of the present disclosure, the capacity recovery agent includes an ionic compound and an electrolyte.

[0066] As a preferred technical solution of the present disclosure, the ionic compound is selected from any one of sodium naphthalene, sodium biphenyl, sodium pyrene, sodium anthracene, sodium phenanthrene or sodium methylnaphthalene, or a combination of at least two thereof, preferably sodium naphthalene.

[0067] The capacity recovery agent provided in the present disclosure can selectively provide electrons and active sodium ions to the cathode of the battery system through a redox reaction to induce recovery of lost capacity. In the present disclosure, the capacity recovery agent can control its reaction potential through the coordination effect of the solvent, and then the CV process is used based on the Gibbs energy of the reaction to effectively realize the capacity recovery of the secondary battery.

[0068] In the present disclosure, the selected capacity recovery agent is a radical anion compound based on alkali metal olefin reduction, a radical anion with a controlled potential, which can selectively provide electrons and active sodium ions to the cathode, thereby restoring the capacity without degradation with cycles. The capacity recovery agent described in the present disclosure is composed of an ionic compound and a corresponding electrolyte system. In order to maintain the stability of the ionic compound, it can be placed in a solvent, and the ionic compound solution is mixed with the electrolyte for use as a capacity recovery agent. It has a higher potential control and can selectively provide electrons and active sodium ions to the cathode to induce a recovery effect, while inhibiting the anode reaction.

[0069] As a specific embodiment of the present disclosure, the ionic compound is sodium naphthalene, and the sodium naphthalene is dissolved in ethylene glycol dimethyl ether (DME) to obtain a solution of the ionic compound, the concentration of which is 0.1-1.5 mol / L, for example, 0.2 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, etc., preferably 1.0 mo l / L, and then mixed with an electrolyte, the mass ratio of the mixture can be 2:1-1:5, such as 1:1, 1:2, 1:3, 1:4, etc., preferably 1:1, and the concentration of the electrolyte is 0.5-5mol / L, such as 1mol / L, 2mol / L, 3mol / L, 4mol / L, etc., preferably 1.5mol / L.

[0070] For sodium ion batteries, when sodium naphthalene is used as the ionic compound, the working principle is as follows:

[0071] xNa·Naph=xNaph+xe - +xNa + (1)

[0072] Na 1-x MeO2+xe - +xNa + =NaMeO2 (2)

[0073] Na 4-x Fe3(PO4)2P2O7+xe - +xNa + =Na4Fe3(PO4)2P2O7 (3)

[0074] Sodium naphthalene contains a radical anion compound based on alkali metal olefin reduction, and the radical anion has a controlled potential, which can selectively provide electrons and active sodium ions to the cathode (schematic formula 1), thereby restoring the capacity without degradation with cycles. In the present disclosure, the sodium naphthalene / DME system exhibits strong reduction performance and is similar to Na / Na +In comparison, the potential is about 0.2-0.3V, while the reaction potential of the hard carbon negative electrode is about 1.1V. In the sodium naphthalene / DME system, the charge is transferred from the high-energy sodium naphthalene to the low-energy hard carbon, and the highly reducible sodium naphthalene will react on the hard carbon anode. Sodium naphthalene is mixed with the electrolyte system in a certain proportion as a capacity recovery agent, which has a higher potential control (~1.5V) and can selectively provide electrons and active sodium ions to the cathode to induce the recovery effect, while inhibiting the reaction at the anode.

[0075] After the capacity recovery agent system is released in the battery, the CV process is used to effectively achieve capacity recovery based on the Gibbs energy of the reaction. ΔE=-(ΔrG / nF), ΔrG<0 is a highly spontaneous reaction, and ΔrG→0 indicates an equilibrium state; when the capacity recovery agent is released, the electrons and Na + All flow to the cathode, ΔE decreases as the reaction proceeds, and the driving force decreases (ΔrG→0); when the capacity recovery agent is released, the battery is treated with CV, and the electrons provided to the cathode by sodium naphthalene are provided to the anode through an external circuit to maintain the voltage, thereby generating a large reaction driving force (ΔrG<0) and effectively realizing capacity recovery.

[0076] In a second aspect, the present disclosure provides a method for preparing the thermally responsive capacity recovery material according to the first aspect, the preparation method comprising:

[0077] The material of the thermally responsive micro-nano storage bin is processed with a capacity recovery agent to obtain the thermally responsive capacity recovery material.

[0078] In the present disclosure, there is no limitation on the processing method for obtaining the thermally responsive capacity recovery material. Any method that can achieve the purpose of the present invention can be applied to the present disclosure. An exemplary example is as follows: the polymer slurry can be "plasticized" using technologies such as 3D printing and then cooled and solidified to obtain a temporary fixed shape. In the present disclosure, the temporary fixed shape is a sphere or an ellipsoid, which is used to encapsulate the capacity recovery agent; the above-mentioned temporary shape is deformed under the stimulation of a thermal signal and returns to its initial shape to achieve the release of the capacity recovery agent.

[0079] As a preferred technical solution of the present disclosure, the processing method includes any one or a combination of at least two of solution mixing, thermoplastic processing, melt blending, in-situ polymerization, 3D printing, 4D digital light processing or nano-microfluidics, preferably a combination of solution mixing and 3D printing. The thermally responsive micro-nano storage warehouse uses 3D printing technology to form a temporary structure with a certain thickness and a curled shape, and then cools down (to below 10°C) to fix the micro-nano storage warehouse for storing the capacity recovery agent, and then injects the capacity recovery agent to achieve shape control from micrometer scale to millimeter scale. The temporary structure will return to its original shape under the stimulation of the thermal signal to achieve the release of the capacity recovery agent.

[0080] In a third aspect, the present disclosure provides a use of the thermally responsive capacity recovery material described in the first aspect in replenishing the lost capacity of a secondary battery.

[0081] In a fourth aspect, the present disclosure provides a secondary battery comprising the thermal-responsive capacity recovery material described in the first aspect.

[0082] The thermal responsive capacity recovery material provided by the present disclosure can reduce and solve the capacity attenuation degradation and safety problems caused by the loss of active ions, and effectively promote the recovery of battery capacity and the extension of cycle life. The present disclosure uses thermal responsive stimulation to achieve the release of the capacity recovery agent. The process method is simple, easy to operate, and is conducive to large-scale production. At the same time, it can also provide new ideas for the recycling of secondary batteries and the treatment of waste batteries.

[0083] As a preferred technical solution of the present disclosure, the secondary battery is a sodium ion battery, a lithium ion battery, a potassium ion battery, a zinc ion battery or a magnesium ion battery.

[0084] like Figure 2 As shown, the thermal responsive capacity recovery material provided by the present disclosure can be placed at any position of the secondary battery that can be placed, and can be fixed on the surface of the diaphragm by point spraying, and assembled with the diaphragm. The battery can also be placed in the electrolyte and enter the battery with the injection, or fixed at any position that can be fixed. The position of the thermal responsive capacity recovery material provided by the present disclosure can be adjusted according to actual conditions, the process is simple, easy to operate, and is conducive to large-scale production.

[0085] The present disclosure does not limit the specific preparation method of the secondary battery, which includes the preparation of the positive electrode sheet, the preparation of the negative electrode sheet, the preparation of the separator, etc., and finally assembling the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte, etc., and general assembly methods are acceptable, including but not limited to lamination, winding, etc.

[0086] In the present disclosure, the preparation method of the secondary battery is exemplified as follows:

[0087] Preparation of positive electrode:

[0088] The positive electrode active material, the conductive agent and the binder are mixed in a ratio of (90-97%): (1.5-5%): (1.5-5%) and stirred to prepare a positive electrode active slurry;

[0089] The positive electrode active slurry is evenly coated on the positive electrode current collector, and the coating double-sided surface density of the positive electrode active slurry is 70-500g / m 2 ;

[0090] The positive electrode sheet is rolled and compacted to a density of 1.3-3.1 g / cm 3 ;

[0091] Preparation of negative electrode sheet:

[0092] The negative electrode active material, the conductive agent and the binder are mixed in a ratio of (87-96%): (1-5%): (3-8%) and stirred to prepare a negative electrode active slurry;

[0093] The negative electrode active slurry is evenly coated on the negative electrode current collector, and the coating double-sided surface density of the negative electrode active slurry is 30-190g / m 2 ;

[0094] The negative electrode sheet is rolled to a compaction density of 0.8-1.3g / cm 3 ;

[0095] Assemble the battery:

[0096] The positive electrode sheet and the negative electrode sheet are separated by a separator, arranged regularly and stacked or wound multiple times, a positive electrode ear is connected to the positive electrode collector, a negative electrode ear is connected to the negative electrode collector, and an electrolyte is injected to obtain a battery cell.

[0097] Among them, the thermally responsive capacity recovery material defined in the present disclosure can be fixed on the surface of the diaphragm by spot spraying and assembled into a battery together with the diaphragm; it can also be placed in the electrolyte and enter the battery along with the injection; or it can also be fixed at any position that can be fixed in the battery structure.

[0098] In a fifth aspect, the present disclosure provides a method for replenishing the capacity lost during operation of the secondary battery described in the fifth aspect, the replenishment method comprising: heating the secondary battery to 80-85°C, maintaining for 1-30s, releasing part or all of the capacity recovery agent, and then using a CV process based on the Gibbs energy of the reaction, thereby effectively replenishing the lost capacity of the secondary battery.

[0099] In the present disclosure, when a secondary battery suffers from capacity attenuation and degradation during a long cycle, the secondary battery is placed in a temperature environment of 80-85°C. At this time, the thermally responsive micro-nano storage compartment is in an environment above the transition temperature, and in the absence of any external load, the mobility of the molecular chain is reactivated, and the internal stress in the material network is released and restored to its initial shape. That is, the thermally responsive micro-nano storage compartment is stimulated by the thermal response signal, and the polymer structure changes from curling to flatness, thereby achieving the release of the capacity recovery agent; the released capacity recovery agent is first left to stand for 24 hours, and then the CV process is used to provide a continuous driving force for the reaction to achieve capacity recovery.

[0100] In a sixth aspect, the present disclosure provides an electrical device, which includes the secondary battery described in the fourth aspect, and the assembly method may be stacking and / or winding, etc.

[0101] The effects of the present disclosure are not limited to the above effects. It should be understood that the effects of the present disclosure include all effects that can be inferred from the following description. The following embodiments are merely illustrative to help understand the present disclosure, and the scope of the present disclosure is not limited thereto.

[0102] In the following examples and comparative examples, all materials used are commercially available products, BMI used was purchased from Beijing Bailingwei Technology Co., Ltd., IPDI and HEA were purchased from Macklin, FA was purchased from Sigma aldrich, and the catalyst dibutyltin dilaurate (DBTDL) was purchased from Sinopharm Chemical Reagent.

[0103] Examples 1-7

[0104] This embodiment provides a thermally responsive capacity recovery material and a preparation method thereof.

[0105] (1) Preparation of capacity recovery agent

[0106] Naphthalene is dissolved in DME to obtain a 1.0 mol / L solution, and an equal molar amount of sodium metal is added and stirred to dissolve to obtain a sodium naphthalene / DME solution;

[0107] Then the sodium naphthalene / DME solution was mixed with 1.5 mol / L NaPF6 electrolyte [EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 1:1:1 vol %] in a mass ratio of 1:1.

[0108] (2) Materials for preparing thermally responsive micro-nano storage chambers

[0109] BMI and FA were dissolved in acetone and mixed at a ratio of BMI:FA:acetone = 1:3:38 (mol%), and refluxed at 60 °C for 24 h to trigger the DA reaction, and then the solvent was evaporated and washed with ether to obtain the intermediate product DA-diol;

[0110] DA-diol, IPDI and DBTDL were dissolved in acetone, refluxed at 60° C. for 24 h, and then HEA was added and mixed according to DA-diol: IPDI: acetone: HEA = 1:2:62:2 (mol%) to obtain polyurethane acrylate PUDA containing DA bonds. PUDA and HEA were mixed in proportion as a preparation material for a thermally responsive micro-nano storage bin, wherein:

[0111] The mass ratio of PUDA:HEA is 70:30 (Example 1), 60:40 (Example 2), 50:50 (Example 3), 40:60 (Example 4), 30:70 (Example 5), 20:80 (Example 6), and 10:90 (Example 7).

[0112] (3) Preparation of thermally responsive capacity recovery materials

[0113] The preparation material of the thermal responsive micro-nano storage bin and the capacity recovery agent are 3D printed to obtain a curled spherical bin of specific size and thickness, and the capacity recovery agent is injected, and then the temperature is cooled to 10° C. to be fixed, thereby obtaining the thermal responsive capacity recovery material, wherein:

[0114] The average size of the thermally responsive micro-nano storage compartments is 200 μm and the average thickness is 4 μm.

[0115] Application Examples 1-7

[0116] This application example provides a sodium ion battery, and the preparation method is as follows:

[0117] (1) Preparation of positive electrode sheet:

[0118] The layered oxide cathode material NFM111, the conductive agent SP, CNTs and the adhesive PVDF are mixed in a ratio of 93:2:1:4, the CNTs are mixed with the glue solution first, the CNTs are fully stretched by high-speed stirring and ultrasound, and then SP is added, and high-speed stirring and centrifugation are performed to obtain a uniform conductive slurry, and the active material is added, and the above materials are mixed by ultrasonic oscillation and vacuum stirring to obtain a cathode slurry;

[0119] The positive electrode slurry is evenly coated on the positive electrode current collector, and the coating double-sided surface density of the positive electrode slurry is 200g / m 2 ; The positive electrode sheet is rolled, and the compaction density of the positive electrode sheet is 3.0g / cm 3 .

[0120] (2) Preparation of negative electrode sheet:

[0121] Hard carbon, conductive agent SP and binder PVDF were mixed in a ratio of 90:3:7 and stirred to prepare negative electrode slurry;

[0122] The negative electrode slurry is evenly coated on the negative electrode current collector, and the double-sided surface density of the negative electrode slurry coating is 88g / m 2 The negative electrode sheet is rolled and the compaction density of the negative electrode sheet is 0.92g / cm 3 ;

[0123] (3) Assembly

[0124] The positive electrode sheet, the PE separator and the negative electrode sheet are stacked in order, and then stacked and placed in an aluminum-plastic film, and then dried at 55°C and injected with electrolyte. After vacuum packaging, standing, formation, aging and capacity separation, the preparation of the sodium ion battery is completed, wherein:

[0125] The electrolyte composition used in the battery is consistent with the electrolyte components in the capacity recovery agent, and the thermal responsive capacity recovery material provided in the embodiment is added, and the added amount is 10wt% of the battery electrolyte amount.

[0126] Comparative application example 1

[0127] This comparative application example provides a sodium ion battery.

[0128] The difference from Application Example 1 is that no thermal responsive capacity recovery material is added to the electrolyte in this comparative application example.

[0129] Performance Testing

[0130] The performance test of the thermal responsive capacity recovery material provided in Examples 1-7, and the sodium ion battery provided in the application examples and comparative application examples is performed as follows:

[0131] (1) Shape recovery rate and recovery time:

[0132] The materials of the thermally responsive micro-nano storage bins corresponding to Examples 1-7 were prepared into plates (flat plate 200×4×4 μm 3 The flat sample was placed in water at 80°C for 1 min. Then, the sample was folded into a U-shaped structure (θ1=0°) under external force and fixed in water at 10°C for 1 min. Finally, the sample with the temporary shape was placed in water at 80°C to restore its initial shape. The final recovery angle was recorded as θ. r , the recovery time is t r Then the shape recovery rate R r =θ r / (θ0-θ1)×100%.

[0133] The test results are shown in Table 1:

[0134] Table 1

[0135] sample Shape recovery rate / % Shape recovery time / s Example 1 (HEA-30) 40 80 Example 2 (HEA-40) 88 30 Example 3 (HEA-50) 90 14 Example 4 (HEA-60) 99 6 Example 5 (HEA-70) 92 6 Example 6 (HEA-80) 60 5 Example 7 (HEA-90) 20 4

[0136] From the performance test, it can be seen that the thermally responsive capacity recovery material provided by the present disclosure can recover to the initial state at above 80°C, and the recovery time is in seconds. When the HEA content is about 60% (Example 4), the response time is about 6s. The short response time can avoid the secondary battery from being damaged at high temperature to the greatest extent possible.

[0137] From the comparison between Examples 2-6 and Examples 1 and 7, it can be seen that when the content of HEA is in the range of 40-80%, the shape recovery rate is higher and the shape recovery time is faster, which is conducive to the full release of the capacity recovery agent.

[0138] (2) Discharge capacity: (Using the sodium ion battery test provided in Application Example 4, the release of the capacity recovery agent is determined by the discharge capacity)

[0139] a) Activation of the micro-nano storage compartment: The battery was placed in the corresponding temperature environment (10°C, 45°C, 60°C, 80°C) for 15 seconds to activate the micro-nano material compartment;

[0140] b) CV process treatment of capacity recovery agent: the battery was left to stand for 24 hours, then charged to 3.4V at 0.2C constant current, left to stand for 12 hours, charged at constant voltage for 6 hours, charged to 4.0V at 0.2C constant current, charged to a cut-off current of 0.02C at constant voltage, and discharged to 2.0V at 1C constant current.

[0141] c) Discharge performance: In an environment of 25°C, the battery was charged at a constant current of 1C (1.2A) to 4.0V, and discharged at a constant current of 1C to 2.0V, for 3 cycles with a voltage range of 2.0-4.0V. The discharge capacity at the third cycle was recorded as discharge capacity C1.

[0142] The results are shown in Table 2:

[0143] Table 2

[0144] Temperature / ℃ Discharge capacity / Ah 10 1.167 45 1.167 60 1.167 80 1.253

[0145] It can be seen from the performance test that the thermally responsive capacity recovery material provided by the present disclosure can release the capacity recovery agent at above 80°C to achieve capacity recovery.

[0146] (3) Electrochemical performance (capacity retention rate): In an environment of 25°C, constant current charge and discharge cycles were performed at a current of 2C (2.4A) and a voltage range of 2.0-4.0V for n cycles. The capacity retention rate of the nth cycle = the discharge capacity of the nth cycle / the discharge capacity of the first cycle (tested using the sodium ion batteries provided in Application Example 4 and Comparative Application Example 1).

[0147] (4) Electrochemical performance (discharge capacity comparison): In an environment of 25°C, the battery provided in Application Example 4 was charged to 4.0 V at a constant current of 1 C (CV treatment details: 0.2 C constant current charging to 3.4 V, standing for 12 h, constant voltage charging for 6 h, 0.2 C constant current charging to 4.0 V, constant voltage charging to a cutoff current of 0.02 C), and discharged to 2.0 V at a constant current of 1 C.

[0148] Figure 3This is a cycle comparison diagram of the sodium ion battery provided in Application Example 4 and Comparative Example 1, wherein the normal cycle battery is the sodium ion battery provided in Comparative Example 1, and the cycle battery containing the recovery agent is the sodium ion battery provided in Application Example 4. It can be seen from the figure that when the capacity recovery agent in Application Example 4 is released and takes effect, it will supplement the lost capacity to a certain extent.

[0149] Figure 4 The discharge capacity comparison diagram of the sodium ion battery provided for Application Example 4 before and after the release of the capacity recovery agent is shown in the figure. It can be seen from the figure that when the capacity recovery agent is released and subjected to the CV process, the discharge capacity can be supplemented to a certain extent.

[0150] It should be noted that, herein, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0151] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thermally responsive capacity recovery material, characterized in that: The thermally responsive capacity recovery material includes a thermally responsive micro-nano storage chamber and a capacity recovery agent located inside the thermally responsive micro-nano storage chamber.

2. The thermally responsive capacity recovery material according to claim 1, characterized in that: The thermally responsive micro-nano storage compartment is spherical or quasi-spherical at temperatures below 80°C, and deforms at 80-85°C to release the internal capacity recovery agent; Preferably, the deformation occurs over a period of 1-30 seconds.

3. The thermally responsive capacity recovery material according to claim 1 or 2, characterized in that: Below 80°C, the size of the thermally responsive micro-nano storage chamber is 10-5000 μm; And / or, below 80° C., the thickness of the thermally responsive micro-nano storage chamber is 0.5-100 μm.

4. The thermally responsive capacity recovery material according to any one of claims 1 to 3, characterized in that: The material of the thermally responsive micro-nano storage bin includes any one or a combination of at least two of DA-bonded polymer materials, triblock copolymers, polycaprolactone, ethylene-methyl acrylate copolymers, ionomers, polylactic acid, polynorbornene, polymethacrylate copolymers, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane or polylactic acid-caprolactone copolymers, more preferably DA-bonded polymer materials, and even more preferably DA-bonded polyurethane materials; Preferably, the DA-bonded polyurethane material is a bonding material of polyurethane acrylate and hydroxyethyl acrylate containing DA bonds; Preferably, in the bonding material of polyurethane acrylate and hydroxyethyl acrylate containing DA bonds, the mass percentage of hydroxyethyl acrylate is 40-80%, preferably 60%.

5. The thermally responsive capacity recovery material according to any one of claims 1 to 4, characterized in that: The capacity recovery agent includes a combination of an ionic compound and an electrolyte; Preferably, the ionic compound is selected from any one or a combination of at least two of sodium naphthalene, sodium biphenyl, sodium pyrene, sodium anthracene, sodium phenanthrene or sodium methylnaphthalene, preferably sodium naphthalene; Preferably, the capacity recovery agent is a mixture of a sodium naphthalene solution and an electrolyte, preferably the sodium naphthalene solution is a DME solution containing sodium naphthalene, preferably the mass ratio of the sodium naphthalene solution to the electrolyte is 2:1-1:5, preferably the concentration of the sodium naphthalene solution is 0.1-1.5 mol / L, and preferably the concentration of the electrolyte is 0.5-5 mol / L; Preferably, the mass ratio of the sodium naphthalene solution to the electrolyte is 1:1, preferably the concentration of the sodium naphthalene solution is 1.0 mol / L, and preferably the concentration of the electrolyte is 1.5 mol / L.

6. A method for preparing a thermally responsive capacity recovery material according to any one of claims 1 to 5, characterized in that: The preparation method comprises: Processing the material of the thermally responsive micro-nano storage bin and the capacity recovery agent to obtain the thermally responsive capacity recovery material; Preferably, the processing method comprises any one or a combination of at least two of solution mixing, thermoplastic processing, melt blending, in-situ polymerization, 3D printing, 4D digital light processing or nano-microfluidics, preferably a combination of solution mixing and 3D printing.

7. Use of the thermally responsive capacity recovery material according to any one of claims 1 to 5 in replenishing the lost capacity of a secondary battery.

8. A secondary battery, characterized in that: The thermally responsive capacity recovery material comprises the thermally responsive capacity recovery material according to any one of claims 1 to 5.

9. The secondary battery according to claim 8, characterized in that: The secondary battery is a sodium ion battery, a lithium ion battery, a potassium ion battery, a zinc ion battery or a magnesium ion battery; Preferably, the thermal responsive capacity recovery material is dot-coated on the surface of the separator of the secondary battery, or added into the electrolyte, or fixed at any position inside the secondary battery.

10. A method for replenishing the capacity lost during operation of a secondary battery according to claim 8 or 9, characterized in that: The replenishment method comprises: heating the secondary battery to 80-85° C., maintaining the temperature for 1-30 seconds, releasing part or all of the capacity recovery agent, and performing a CV process to replenish the lost capacity of the secondary battery.

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