Temperature response type metal precipitation digestion material, preparation method and secondary battery

Abstract

The invention relates to a temperature response type metal precipitation digestion material, a preparation method and a secondary battery, and the temperature response type metal precipitation digestion material comprises a temperature response type storage bin and a metal precipitation digestion agent located in the temperature response type storage bin. The temperature response type storage bin provided by the invention is made of a temperature response type shape memory material, and can deform at a certain temperature to recover an initial state, so that the release of the metal digestion agent is realized. The temperature response type metal precipitation digestion material provided by the invention can reduce and solve the problems of capacity fading and degradation and safety caused by inactive metal precipitation, and effectively promotes the recovery of the battery capacity and the prolonging of the cycle life.

Description

Technical Field

[0001] The present disclosure relates to the technical field of new energy batteries, and in particular to a temperature-responsive metal precipitation digestion material and a preparation method thereof, a secondary battery, and in particular to a temperature-responsive sodium precipitation digestion material and the application of the sodium precipitated by the digestion, and a sodium ion 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] While sodium-ion batteries are developing rapidly, they also need to face some urgent problems: Studies have shown that sodium-ion batteries are much safer than lithium-ion batteries, but from the perspective of sodium (lithium) precipitation potential, sodium batteries are more prone to sodium precipitation than lithium batteries. This is because the lithium insertion potential of lithium battery graphite is about 0.2V higher than the lithium precipitation potential. As long as the potential does not reach the lithium precipitation potential, lithium will not be deposited. The difference between the sodium insertion potential and the sodium precipitation potential of sodium batteries does not exceed 0.1V. During the sodium insertion process, especially at high rates, sodium precipitation is more likely to occur.

[0004] The sodium precipitation reaction has a certain impact on the safety and electrical performance of sodium batteries, which can be specifically divided into the following points: 1) Sodium dendrites on the surface of the negative electrode continue to grow, puncture the diaphragm, and cause internal short circuits; 2) The metallic sodium deposited on the surface of the negative electrode and the "dead sodium" inside the battery react with the electrolyte, accelerating internal degradation; 3) During fast charging, the large current density further aggravates the sodium precipitation side reaction and increases the temperature of the battery; 4) When the temperature continues to rise, the gas produced by the decomposition of the electrolyte causes the internal pressure of the battery to continue to rise, eventually causing the battery to degas and the metallic sodium to melt, which may further lead to combustion or even explosion. Therefore, solving the safety of sodium-ion batteries and inhibiting or reducing the generation of sodium dendrites are the keys to the widespread application of sodium-ion batteries.

[0005] The current methods to solve or inhibit the sodium dendrite problem are generally to optimize the current density, improve the surface structure of the negative electrode material, or introduce functional additives into the electrolyte. Most strategies focus on inhibiting the initial source and concentrate on stabilizing the SEI film or inhibiting the growth of sodium dendrites. There is little information on how to eliminate or reduce the sodium dendrites that have already been generated during the subsequent operation of the battery in a timely and quantitative manner as needed. Summary of the invention

[0006] In order to solve the above technical problems, the present disclosure provides a temperature-responsive metal precipitation and digestion material, a preparation method, and a secondary battery.

[0007] The present disclosure provides a temperature-responsive metal-separating digestion material, which includes a temperature-responsive storage bin and a metal-separating digestion agent located inside the temperature-responsive storage bin.

[0008] As a preferred technical solution of the present disclosure, the temperature-responsive storage bin is spherical or quasi-spherical below 60°C, and deforms at 60-70°C to release the internal digester.

[0009] As a preferred technical solution of the present disclosure, the deformation time is 1-10 minutes.

[0010] As a preferred technical solution of the present disclosure, below 60°C, the size of the temperature-responsive storage bin is 5-300 μm, preferably 10-100 μm.

[0011] As a preferred technical solution of the present disclosure, below 60°C, the thickness of the temperature-responsive storage bin is 0.5-10 μm.

[0012] As a preferred technical solution of the present invention, the material of the temperature-responsive storage bin includes an elastomeric material and / or a shape memory material, preferably any one of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer, polycaprolactone, ethylene-methyl acrylate copolymer, polylactic acid, polynorbornene, polymethacrylate copolymer, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane or polylactic acid-caprolactone copolymer or a combination of at least two thereof, and further preferably a combination of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone.

[0013] As a preferred technical solution of the present disclosure, the material of the temperature-responsive storage bin is a combination of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone. Based on the total mass of the temperature-responsive storage bin as 100%, the content of the polycaprolactone is 30-70%.

[0014] As a preferred technical solution of the present disclosure, the molecular weight of the polycaprolactone is 30,000-70,000.

[0015] As a preferred technical solution of the present disclosure, the maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer is a Kraton FG 1901 model, containing 30% polystyrene and 1.4-2% maleic anhydride.

[0016] As a preferred technical solution of the present disclosure, the metal precipitation digestion agent is selected from a redox agent, preferably any one of iodine, iodide, sodium iodate, biphenyl or sodium biphenyl, or a combination of at least two thereof, more preferably iodide, and even more preferably tin tetraiodide.

[0017] As a preferred technical solution of the present disclosure, the average particle size of the metal precipitation digestion agent is 0.2-5 μm, preferably 0.5-1 μm.

[0018] In a second aspect, the present disclosure provides a method for preparing the temperature-responsive metal-precipitating digestion material according to the first aspect, the preparation method comprising:

[0019] The slurry of the temperature-responsive storage bin is prepared, and the slurry is processed with a metal-precipitating digestion agent to obtain the temperature-responsive metal-precipitating digestion material.

[0020] 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 or nano-microfluidization, preferably a combination of solution mixing and 3D printing.

[0021] In a third aspect, the present disclosure provides a use of the temperature-responsive metal precipitation and digestion material described in the first aspect in eliminating metals precipitated in a battery.

[0022] In a fourth aspect, the present disclosure provides a secondary battery, comprising the temperature-responsive metal-degrading material described in the first aspect.

[0023] 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.

[0024] In a fifth aspect, the present disclosure provides a method for eliminating metals precipitated during operation of the secondary battery described in the fourth aspect, the method comprising: heating the secondary battery to 60-70°C, maintaining for 1-10 minutes, partially or completely releasing a metal precipitating degrading agent, and achieving partial or complete decomposition of the precipitated metals.

[0025] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0026] (1) The temperature-responsive storage bin provided by the present disclosure is a temperature-responsive shape memory material, which can be deformed at a certain temperature. By controlling the proportion of the switch polymer in the main continuous phase, the storage bin can be quickly opened under a thermal response stimulation signal, and the metal-dissolving agent can be released in a timely and quantitative manner as needed;

[0027] (2) The temperature-responsive storage bin provided by the present disclosure has a relatively low thermal response temperature, and can achieve minute-level response changes at around 60°C. The high temperature environment has little effect on the performance of the battery itself. At the same time, the storage bin will not be stimulated to open at temperatures below 60°C, and the operation of the battery cell at all-weather temperatures will not be affected, which has obvious practicality.

[0028] (3) The temperature-responsive metal precipitation and digestion material provided by the present disclosure can trigger the formation of a redox pair, and can convert the inactive metal precipitated from the negative electrode into soluble metal ions; the metal ions can be reused in subsequent electrochemical processes, thus achieving continuous recovery of inactive metals;

[0029] (4) The present disclosure can reduce and solve the capacity decay and safety issues caused by the precipitation of inactive metals, and effectively promote the recovery of battery capacity and the extension of cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] 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.

[0031] 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.

[0032] Figure 1 This is a schematic diagram of the application principle of the temperature-responsive metal-degrading material disclosed in the present invention;

[0033] Figure 2 The SEM image of the negative electrode surface before and after the release of the metal precipitating digester in the sodium ion battery provided in Application Example 2 of the present disclosure;

[0034] Figure 3 A graph showing the change in negative electrode potential before and after the release of a metal-dissolving agent in a sodium ion battery provided in Application Example 2 of the present disclosure;

[0035] Figure 4 A cycle comparison diagram of the sodium ion battery provided in Application Example 2 of the present disclosure before and after the release of the metal precipitating digester and the sodium ion battery provided in Comparative Application Example 1;

[0036] Figure 5 This is a capacity comparison chart of the sodium ion battery before and after the release of the metal-dissolving agent provided in Application Example 2 of the present disclosure. 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] During the use of secondary batteries, metal (lithium / sodium) deposition side reactions will occur. The deposited metal will cause the capacity of the secondary battery to decay and deteriorate, and safety problems are likely to occur. In order to avoid the above problems as much as possible, currently, starting from the perspective of how to avoid metal deposition side reactions, emphasis is placed on inhibiting the initial source, and focusing on stabilizing SEI and inhibiting the growth of sodium dendrites. However, there is little information on how to digest or reduce the sodium dendrites that have already been generated during the subsequent operation of the battery in a timely, quantitative and required manner. Therefore, the present disclosure provides a temperature-responsive metal-precipitating digestion material capable of eliminating deposited metals, a preparation method thereof, and a secondary battery, in particular, a temperature-responsive sodium-precipitating digestion material for sodium ion batteries.

[0040] In a first aspect, the present disclosure provides a temperature-responsive metal-precipitating digestion material, which includes a temperature-responsive storage bin and a metal-precipitating digestion agent located inside the temperature-responsive storage bin.

[0041] As a preferred technical solution of the present disclosure, the temperature-responsive storage bin includes a temperature-responsive shape memory material. By controlling the proportion of the switch polymer (shape memory material) in the main continuous phase, the storage bin can be quickly opened under a thermal response stimulation signal, and the metal-degrading agent can be released in a timely and quantitative manner as needed.

[0042] See the schematic diagram of the use principle of the temperature-responsive metal-precipitating digestion material disclosed in the present invention. Figure 1 It is processed by programming and solidified by cooling to obtain a temporary fixed shape of sphere or ellipsoid. After being subjected to thermal stimulation of heating, it deforms and returns to its initial state, during which the release of the metal dissolving agent is completed.

[0043] In the present disclosure, after the metal precipitation digester is released, the precipitated inactive metal can be converted into soluble active metal ions, thereby realizing the reuse of metal ions; that is, the temperature-responsive metal precipitation digestion material provided by the present disclosure can reduce and solve the capacity attenuation degradation and safety problems caused by the precipitation of inactive metals, and effectively promote the recovery of battery capacity and the extension of cycle life.

[0044] The temperature-responsive metal-precipitating digestion material provided by the present disclosure uses thermal response stimulation to release the metal-precipitating digestion agent. The method for digesting metal is simple and easy to operate, which is conducive to large-scale production and provides a new idea for subsequent battery recycling.

[0045] As a preferred technical solution of the present disclosure, the temperature-responsive storage bin is spherical or quasi-spherical below 60°C, and deforms at 60-70°C to release the internal digester.

[0046] The deformation at 60-70°C mentioned in the present disclosure means that the material of the temperature-responsive storage bin can be deformed at a temperature of 60-70°C and restore to an initial state, rather than that the material can only be deformed between 60-70°C. For example, it can be 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, etc.

[0047] The present invention specifically selects a temperature-responsive storage bin material that can deform at 60-70°C. When it is applied to a secondary battery, the battery can achieve a minute-level response change at 60-70°C, that is, it deforms at 60-70°C, releases a metal-precipitating digester, and achieves the digestion of the precipitated metal dendrites; and the temperature of 60-70°C has little effect on the performance of the secondary battery, and the secondary battery will not reach this temperature when operating at all-weather temperatures, so it is not affected in any way and has significant practicality. If the temperature at which deformation can occur is too high, the secondary battery needs to be placed at a higher temperature, and the minute-level response is likely to cause damage to the secondary battery, which further leads to the deterioration of the safety performance of the secondary battery; and if the temperature at which deformation can occur is too low, it may lead to the release of the metal-precipitating digester when the secondary battery is used in normal times.

[0048] As a preferred technical solution of the present invention, the time for deformation is 1-10 minutes, for example, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, etc.

[0049] The temperature-responsive storage bin defined in the present disclosure achieves minute-level response changes at 60-70°C, with 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.

[0050] As a preferred technical solution of the present disclosure, below 60°C, the size of the temperature-responsive storage bin is 5-300μm, preferably 10-100μm, for example, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, etc.

[0051] As a preferred technical solution of the present disclosure, below 60°C, the thickness of the temperature-responsive storage bin is 0.5-10 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc.

[0052] As a preferred technical solution of the present invention, the material of the temperature-responsive storage bin includes an elastomeric material and / or a shape memory material, preferably any one of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer, polycaprolactone, ethylene-methyl acrylate copolymer, polylactic acid, polynorbornene, polymethacrylate copolymer, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane or polylactic acid-caprolactone copolymer or a combination of at least two thereof, and further preferably a combination of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone.

[0053] The temperature-responsive storage bin defined in the present disclosure is composed of an elastomer that can be used to maintain structural integrity and a shape memory material that can fix and deform a temporary shape (spherical or quasi-spherical) under temperature stimulation, wherein the elastomer can be used as a continuous phase to maintain structural integrity, while the secondary continuous phase shape memory material can be used as a "switch polymer" to control the "switch" of the storage bin to achieve storage and release of metal-degrading agents.

[0054] As a preferred technical solution of the present invention, the material of the temperature-responsive storage bin is a combination of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone. Taking the total mass of the temperature-responsive storage bin as 100%, the content of the polycaprolactone is 30-70%, for example, 35%, 40%, 45%, 50%, 55%, 60%, 65%, etc., preferably 40%.

[0055] In the present disclosure, by controlling the proportion of "switch polymer" in the material of the temperature-responsive storage bin, the temperature-responsive storage bin can respond quickly under the stimulation of temperature, and the release of the metal-precipitating digester can be realized in a timely, quantitative and on-demand manner. If the content of polycaprolactone is too low, it is difficult for the blending system to form a continuous phase, the temporary fixing ability of the material is poor, and the storage of the metal-precipitating digester cannot be effectively realized. If the content of polycaprolactone is too high, it will lead to phase transition, the material has strong fixing ability but poor recovery ability, and the "switch" of the temperature-responsive storage bin cannot be smoothly controlled.

[0056] As a preferred technical solution of the present disclosure, the molecular weight of the polycaprolactone is 30,000-70,000, for example, 35,000, 40,000, 45,000, 50,000, 55,000, 60,000, 65,000, etc.

[0057] As a preferred technical solution of the present disclosure, the maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer is a specific model Kraton FG 1901, containing 30% polystyrene and 1.4-2% maleic anhydride.

[0058] The function of the metal precipitating agent disclosed in the present invention is to convert the inactive metal that has been precipitated into active metal ions that can be dissolved, and the metal ions can be reused in the subsequent electrochemical process. As a preferred technical solution of the present invention, the metal precipitating agent is selected from a redox agent, preferably any one or a combination of at least two of iodine, iodide, sodium iodate, biphenyl or sodium biphenyl, more preferably iodide, and more preferably tin tetraiodide.

[0059] In the present disclosure, tin tetraiodide can induce I 3 - / I - Formation of a redox couple for continuous recovery of an inactive metal (sodium) where I 3 - As a "scavenger", it can convert inactive metals (sodium) into soluble metal ions (Na + ), in the initiation reaction, Sn 4+ will be reduced to its metallic state and can be used as a sacrificial regulator to transfer I 3 - Therefore, the temperature-responsive metal precipitation digestion material provided by the present disclosure can reduce and solve the capacity decay degradation and safety problems caused by the precipitation of inactive sodium, effectively promote the recovery of secondary battery capacity and the extension of cycle life, and also provide new ideas for the subsequent recycling of secondary batteries.

[0060] For sodium ion batteries, when tin tetraiodide is used as a sodium precipitation digester, its working principle is as follows:

[0061] 4Na+SnI 4 =4NaI+Sn (1)

[0062] 2Na+I 3 - =2Na + +3I - (2)

[0063] 3Na 2 O+3I 3 - =6Na + +8I - +IO 3 - (3)

[0064] 3xI- +2Na 4-x Fe 3 (PO 4 ) 2 P 2 O 7 +2xNa + =xI 3 - +2Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (4)

[0065] 2Na 1-x Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 +2xNa + +3xI - =NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2+xI 3 - (5)

[0066] Sn+2I 3 - =Sn 4+ +6I - (6)

[0067] In the present disclosure, when tin tetraiodide is used as a metal-precipitating digester in a sodium ion battery, the process of metal digestion is as follows: at 60-70° C., tin tetraiodide is released, and tin tetraiodide oxidizes part or all of the inactive sodium on the negative electrode side into soluble sodium iodide (Formula 1). Sodium iodide, as a carrier of the sodium source, diffuses to the positive electrode side under the influence of the concentration gradient, and when it contacts the de-sodiumified layered oxide positive electrode material (NFM111) on the positive electrode side, the sodium ions can be recovered through the sodiumation reaction on the positive electrode, and at the same time, I - Oxidized to I 3 - (Equation 5); During the charging process, the sodium source recovered from the inactive sodium can be reused, I 3 - As a digester, it migrates to the surface of the negative electrode to continue to remove the precipitated inactive sodium (Formulas 2 and 3). That is, tin tetraiodide can be used to construct a reversible I 3 - / I - The redox pair is used to recycle the inactive sodium precipitated; moreover, in the initiation reaction, Sn 4+It will also be reduced to a metallic state and can be used as a sacrificial regulator to transfer I on the negative electrode side. 3 - Losses on active sodium reservoirs.

[0068] In the present disclosure, the metal precipitating agent (especially the sodium precipitating agent) can convert the inactive metal (Na) precipitated from the negative electrode into soluble metal ions (Na + ), metal ions (Na + ) is dissolved in the electrolyte, and the metal ions (Na + ) can gradually diffuse to the positive electrode sheet and can be oxidized by the demetallized (Na) positive electrode sheet to achieve metallization (Naization) of the positive electrode sheet. + ) can be reused in subsequent electrochemical processes, thereby achieving the activation of metal dendrites or dead metals.

[0069] As a preferred technical solution of the present disclosure, the average particle size of the metal precipitation digester is 0.2-5 μm, preferably 0.5-1 μm, such as 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, etc.

[0070] In a second aspect, the present disclosure provides a method for preparing the temperature-responsive metal-precipitating digestion material according to the first aspect, the preparation method comprising:

[0071] The slurry of the temperature-responsive storage bin is prepared, and the slurry is processed with a metal-precipitating digestion agent to obtain the temperature-responsive metal-precipitating digestion material.

[0072] In the present disclosure, there is no limitation on the processing method for obtaining the temperature-responsive metal-precipitating digestion 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 metal-precipitating digestion 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 metal-precipitating digestion agent.

[0073] As a preferred technical solution of the present disclosure, the method for preparing the slurry of the temperature-responsive storage bin is solution dissolution, exemplified by: dissolving an elastomer for maintaining structural integrity and a shape memory material capable of achieving temporary shape fixation and deformation under temperature stimulation in a solvent and stirring until dissolved to obtain a slurry; if the solvent is evaporated, a blend of the two can be obtained.

[0074] As a preferred technical solution of the present disclosure, the processing method includes any one of solution mixing, thermoplastic processing, melt blending, in-situ polymerization, 3D printing or nano-micro jet or a combination of at least two of them, preferably a combination of solution mixing and 3D printing. The solution is mixed to obtain a slurry, and the slurry is formed into a temporary structure with a certain thickness and a curled shape using 3D printing technology and then cooled and fixed. The two methods are used in combination to achieve shape control from micron scale to millimeter scale.

[0075] As a preferred technical solution of the present disclosure, the material of the temperature-responsive storage bin is a combination of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone, and the preparation method of the slurry includes:

[0076] Maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone are dissolved in tetrahydrofuran (THF), wherein the mass ratio of polymer particles to tetrahydrofuran is 1:6, and stirred for 2 hours by a magnetic stirrer until the polymer particles are completely dissolved to obtain a slurry, and the solvent of the slurry is evaporated to obtain a mixture of the two.

[0077] The preparation method of the temperature-responsive metal-precipitating digestion material provided by the present invention is simple and easy.

[0078] In a third aspect, the present disclosure provides a use of the temperature-responsive metal precipitation and digestion material described in the first aspect in eliminating metals precipitated in a battery.

[0079] In a fourth aspect, the present disclosure provides a secondary battery, comprising the temperature-responsive metal-degrading material described in the first aspect.

[0080] 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.

[0081] The present disclosure does not limit the specific type of metal-precipitating digester, as long as it can activate inactive metals into active metal ions, it can be a sodium-precipitating digester, a lithium-precipitating digester, etc.

[0082] The temperature-responsive metal-precipitating and decomposing material provided by the present invention 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 spraying and assembled with the diaphragm. The material can also be placed in the electrolyte and enter the battery together with the injection, or fixed at any position that can be fixed.

[0083] 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.

[0084] In the present disclosure, the preparation method of the secondary battery is exemplified as follows:

[0085] Preparation of positive electrode:

[0086] 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;

[0087] 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 ;

[0088] The positive electrode sheet is rolled and compacted to a density of 1.3-3.1 g / cm 3 ;

[0089] Preparation of negative electrode sheet:

[0090] 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;

[0091] 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 ;

[0092] The negative electrode sheet is rolled to a compaction density of 0.8-1.3g / cm 3 ;

[0093] Assemble the battery:

[0094] 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.

[0095] Among them, the temperature-responsive metal precipitation and digestion material described in the present disclosure can be placed in an electrolyte and injected into a battery cell together with the electrolyte, or it can be used as a part of a diaphragm coating or placed in any part of a battery structure where it can be placed.

[0096] When the temperature-responsive metal-precipitating and digesting material disclosed in the present disclosure is added to an electrolyte, the amount of the metal-precipitating and digesting agent used therein is 1-5 mmol / L of the electrolyte dosage.

[0097] In a fifth aspect, the present disclosure provides a method for eliminating metals precipitated during operation of the secondary battery described in the fourth aspect, the method comprising: heating the secondary battery to 60-70°C, maintaining for 1-10 minutes, partially or completely releasing a metal precipitating degrading agent, and achieving partial or complete decomposition of the precipitated metals.

[0098] In the present disclosure, when the capacity of a secondary battery decays during a cycle, the secondary battery is placed in a temperature environment of 60°C. At this time, the mobility of the molecular chain in the temperature-responsive storage compartment is activated in an environment above the transition temperature, and due to the favorable trend of thermodynamic increase in entropy, the deformed molecular chain conformation will return to a flat state, that is, the temperature-responsive storage compartment is stimulated by the temperature response signal, and the polymer structure changes from curled to flat, thereby releasing the metal-precipitating digester; the metal-precipitating digester acts on the precipitated inactive metal, oxidizing and reducing it to active, thereby replenishing the decayed capacity.

[0099] 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.

[0100] In the following examples and comparative examples, the polycaprolactone (PCL) used was purchased from Daicel Chemical Industries, Ltd., with a molecular weight of 50,000; the maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer (SEBS-G-MAH) was purchased from Kraton, model Kraton FG 1901, containing 30% polystyrene and 1.4-2% maleic anhydride.

[0101] Examples 1-5

[0102] This embodiment provides a temperature-responsive metal precipitation and digestion material and a preparation method thereof.

[0103] The temperature-responsive metal precipitation digestion material comprises a temperature-responsive storage bin and a metal precipitation digestion agent, wherein:

[0104] The average size of the temperature-responsive storage bin is 50 μm, and the average bin thickness is 3 μm; the material is a combination of polycaprolactone and maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer, and the mass ratios of the two are 30:70 (Example 1), 40:60 (Example 2), 50:50 (Example 3), 60:40 (Example 4), and 70:30 (Example 5).

[0105] The metal precipitating agent is tin tetraiodide particles, the average particle size of which is 0.6 μm, and the amount added is 3 mmol / L of the electrolyte.

[0106] The preparation method is as follows:

[0107] The maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone are dissolved in tetrahydrofuran, wherein the mass ratio of polymer particles to tetrahydrofuran is 1:6, and stirred with a magnetic stirrer at a speed of 50 rpm for 2 hours until the polymer particles are completely dissolved, and then the solvent is evaporated to obtain a blend of the two;

[0108] The blend and the metal precipitation digestion agent are 3D printed to obtain a curled spherical warehouse body of specific size and thickness, and then the temperature is cooled to 10° C. and fixed to obtain the temperature-responsive metal precipitation digestion material.

[0109] Embodiment 6-7

[0110] This embodiment provides a temperature-responsive metal precipitation and digestion material and a preparation method thereof.

[0111] The difference from Example 1 is that in this example, the mass ratios of the polycaprolactone and the maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer are 20:80 (Example 6) and 80:20 (Example 7), respectively.

[0112] Application Examples 1-7

[0113] This application example provides a sodium ion battery, and the preparation method is as follows:

[0114] (1) Preparation of positive electrode sheet:

[0115] The polyanion positive electrode material NFPP, the conductive agent SP, CNTs and the adhesive PVDF are mixed in a ratio of 92:2:1:5, 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 positive electrode slurry;

[0116] 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 ; Roll the positive electrode sheet, and the compaction density of the positive electrode sheet is 2.0g / cm 3 .

[0117] (2) Preparation of negative electrode sheet:

[0118] Hard carbon, conductive agent SP and binder PVDF were mixed in a ratio of 90:3:7 and stirred to prepare negative electrode slurry;

[0119] 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 70g / m 2The negative electrode sheet is rolled and the compaction density of the negative electrode sheet is 0.92g / cm 3 ;

[0120] (3) Assembly

[0121] 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, forming, shaping and other processes, the battery is prepared, wherein:

[0122] The electrolyte composition is 1.5 mol / LNaPF 6 and DME (ethylene glycol dimethyl ether): DOL (dioxolane) = 1:1 (vol%), and the temperature-responsive metal-degrading material provided in the embodiment is added in an amount of 3 mmol / L.

[0123] Comparative application example 1

[0124] This comparative application example provides a sodium ion battery.

[0125] The difference from Application Example 1 is that, in the electrolyte of this comparative application example, no temperature-responsive metal precipitation and digestion material is added.

[0126] Performance Testing

[0127] The temperature-responsive metal precipitation and digestion materials provided in Examples 1-7 and the sodium ion batteries provided in the application examples and comparative application examples were tested for performance as follows:

[0128] (1) Shape recovery rate and recovery time:

[0129] The materials of the temperature-responsive storage bins corresponding to Examples 1-5 were prepared into plates (flat plate 200×4×4 μm 3 flat sample), denoted as the initial state θ 0 =180°, and placed in 60°C water for 2 min. Then, the sample was folded into a U-shaped structure (θ 1 =0°), fix the temporary shape in 10°C water for 2 min, and finally, put the sample with temporary shape back into 60°C water to restore its initial shape. The final recovery angle is recorded as θ r , the recovery time is t r Then the shape recovery rate R r =θ r / (θ 0 -θ 1 )×100%.

[0130] The test results are shown in Table 1:

[0131] Table 1

[0132] sample Shape recovery rate / % Shape recovery time / s Example 1 60 170 Example 2 90 200 Example 3 92 280 Example 4 80 400 Example 5 50 600 Example 6 20 130 Example 7 10 900

[0133] It can be seen from the performance test that the temperature-responsive metal precipitation and digestion material provided by the present disclosure can recover to the initial state above 60° C., and the recovery time is in minutes.

[0134] From the comparison between Examples 1-5 and Examples 6-7, it can be seen that when the content of PCL is in the range of 30-70%, the shape recovery rate is higher and the shape recovery time is faster, which is conducive to the full release of the metal precipitating digester.

[0135] (2) Discharge capacity: (Using the sodium ion battery test provided in Application Example 2, the release of the metal precipitating digester is determined by the discharge capacity)

[0136] a) Activation of temperature-responsive storage bins: The batteries were placed in corresponding temperature environments (10°C, 25°C, 45°C, 60°C) for 10 min to activate the micro-nano material bins;

[0137] b) Discharge performance: In an environment of 25°C, the battery was charged at 1C (1.2A) constant current and constant voltage to 3.65V, the cut-off current was 0.1C, and the battery was discharged at 1C constant current to 2.0V, and the constant capacity was repeated for 3 cycles with a voltage range of 2.0-3.65V. The discharge capacity at the third cycle was recorded as discharge capacity C1.

[0138] The results are shown in Table 2:

[0139] Table 2

[0140] Temperature / ℃ Discharge capacity / Ah 10 1.025 25 1.025 45 1.025 60 1.099

[0141] It can be seen from the performance test that the temperature-responsive metal precipitation digestion material provided by the present disclosure can release the metal precipitation digestion agent at above 60° C. to achieve capacity recovery.

[0142] (3) Appearance: SEM was used to observe the microscopic appearance of the sodium ion battery provided in Application Example 2 in the initial state, after a period of operation to produce sodium precipitation reaction, and after the release of metal digester. The results are shown in the figure. Figure 2 :

[0143] Depend on Figure 2 It can be seen that in the initial state of the sodium ion battery, no sodium precipitation reaction occurs, and no metallic sodium is precipitated. After running for a period of time, metallic sodium precipitates to form inactive sodium. When the temperature-responsive metal precipitation digestion material provided by the present invention releases the metal precipitation digestion agent, the precipitated inactive sodium disappears.

[0144] (4) Change in negative electrode potential (using the sodium ion battery provided in Application Example 2): The battery is introduced into a reference electrode to form a three-electrode system, with a constant capacity of 1C and a voltage range of 2.0-3.65V. The change in negative electrode potential during charging is monitored.

[0145] (5) Electrochemical performance: (The sodium ion battery provided in Application Example 2 and Comparative Application Example 1 was used for testing, and the effect of the metal precipitation digester was characterized by the following electrochemical performance)

[0146] a) Cycle stability: In a 25°C environment, perform constant current charge and discharge cycles at 2C (2.4A) with a voltage range of 2.0-3.65V 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.

[0147] b) 1C charge and discharge test: In a 25°C environment, charge the battery at 1C (1.2A) constant current and constant voltage to 3.65V, with a cut-off current of 0.1C, and discharge at 1C constant current to 2.0V. The test was repeated for 3 cycles with a voltage range of 2.0-3.65V. The charge and discharge data of the third cycle were recorded.

[0148] Figure 3 The negative electrode potential change diagram of the sodium ion battery before and after the release of the metal digester provided in Application Example 2 is shown in FIG. Figure 3 It can be seen that after the metal-precipitated digester is released, the potential on the negative electrode side is higher than 0 V, indicating that the precipitated sodium is effectively digested. At the same time, the specific capacity also increases to a certain extent, indicating that the attenuated capacity is supplemented to a certain extent.

[0149] Figure 4 The cycle comparison diagram of the sodium ion battery provided in Application Example 2 before and after the release of the metal digester and the sodium ion battery provided in Comparative Application Example 1 is shown. Figure 5 The capacity comparison diagram of the sodium ion battery before and after the release of the metal-precipitating digester provided for Application Example 2 shows that after the metal-precipitating digester is released, the attenuated capacity can be supplemented to a certain extent.

[0150] It should be noted that, in this article, relational terms such as "first" and "second" are only used 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, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[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 temperature-responsive metal precipitation digestion material, characterized in that: The temperature-responsive metal-separating and digesting material comprises a temperature-responsive storage bin and a metal-separating and digesting agent located inside the temperature-responsive storage bin.

2. The temperature-responsive metal-decomposing material according to claim 1, characterized in that: The temperature-responsive storage bin is spherical or quasi-spherical at temperatures below 60°C, and deforms at 60-70°C to release the internal digester; Preferably, the deformation occurs for 1-10 minutes.

3. The temperature-responsive metal-decomposing material according to claim 1 or 2, characterized in that: Below 60°C, the size of the temperature-responsive storage bin is 5-300 μm, preferably 10-100 μm; And / or, below 60° C., the thickness of the temperature-responsive storage chamber is 0.5-10 μm.

4. The temperature-responsive metal-decomposing material according to any one of claims 1 to 3, characterized in that: The material of the temperature-responsive storage bin includes an elastomeric material and / or a shape memory material, preferably any one or a combination of at least two of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer, polycaprolactone, ethylene-methyl acrylate copolymer, polylactic acid, polynorbornene, polymethacrylate copolymer, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane or polylactic acid-caprolactone copolymer, and more preferably a combination of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone; Preferably, the material of the temperature-responsive storage bin is a combination of maleic anhydride grafted hydrogenated styrene-butadiene triblock copolymer and polycaprolactone, and the content of the polycaprolactone is 30-70% based on the total mass of the temperature-responsive storage bin as 100%; Preferably, the molecular weight of the polycaprolactone is 30,000-70,000.

5. The temperature-responsive metal-precipitating digestion material according to any one of claims 1 to 4, characterized in that: The metal precipitating agent is selected from a redox agent, preferably any one of iodine, iodide, sodium iodate, biphenyl or sodium biphenyl, or a combination of at least two thereof, more preferably iodide, and even more preferably tin tetraiodide; And / or, the average particle size of the metal precipitation digestion agent is 0.2-5 μm, preferably 0.5-1 μm.

6. A method for preparing a temperature-responsive metal precipitation digestion material according to any one of claims 1 to 5, characterized in that: The preparation method comprises: Preparing slurry for a temperature-responsive storage bin, and processing the slurry with a metal-precipitating digestion agent to obtain the temperature-responsive metal-precipitating digestion material; Preferably, the processing method comprises any one of solution mixing, thermoplastic processing, melt blending, in-situ polymerization, 3D printing or nano-microfluidization or a combination of at least two thereof, preferably a combination of solution mixing and 3D printing.

7. Use of the temperature-responsive metal precipitation and digestion material according to any one of claims 1 to 5 in eliminating precipitated inactive metals.

8. A secondary battery, characterized in that: The invention comprises the temperature-responsive metal precipitation and digestion 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.

10. A method for eliminating metals precipitated during operation of the secondary battery according to claim 8 or 9, characterized in that: The method comprises: heating the secondary battery to 60-70° C. and maintaining the temperature for 1-10 minutes, releasing part or all of the metal precipitating degrading agent, and achieving partial or complete decomposition of the precipitated metal.

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