Electrolyte sustained-release microcapsule, preparation method and application thereof

Abstract

The application belongs to the technical field of batteries, and discloses an electrolyte slow-release microcapsule, a preparation method thereof, a battery pole piece, a battery and an electric device. The electrolyte slow-release microcapsule comprises a capsule core and a capsule wall. The capsule core comprises a lithium salt, a functional additive and a lithium supplement. The capsule wall comprises a polylactic acid-aliphatic polyester copolymer. The introduction of the electrolyte slow-release microcapsule into a battery electrode can effectively improve the electrochemical performance of the battery pole piece.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to electrolyte sustained-release microcapsules and their preparation methods and applications, and more specifically relating to electrolyte sustained-release microcapsules and their preparation methods, battery electrodes, batteries, and electrical devices. Background Technology

[0002] With the widespread application of lithium-ion batteries in new energy vehicles, energy storage systems, and other fields, the requirements for battery energy density and cycle performance are constantly increasing. To effectively improve battery energy density, thick electrode battery design has become one of the current research hotspots. However, thick electrodes suffer from problems such as long ion transport paths and insufficient electrolyte wetting, especially the difficulty for the electrolyte to penetrate to the thickest part of the electrode. This results in the active material in that area not being able to effectively participate in the charge-discharge reaction, leading to low utilization of the active material and, to some extent, reducing the battery's electrochemical performance. Therefore, solving these problems is one of the current challenges. Summary of the Invention

[0003] This application aims to at least partially solve one of the technical problems in the related art. To this end, this application proposes an electrolyte slow-release microcapsule and its preparation method, a battery electrode, a battery, and an electrical device. The electrolyte slow-release microcapsule can be controllably dissolved upon contact with a carbonate electrolyte. After dissolution, the battery electrode using the electrolyte slow-release microcapsule can form interconnected pores on the electrode, constructing an electrolyte transport channel that penetrates the surface layer of the electrode to the middle region, thereby improving the electrochemical performance of the battery.

[0004] In a first aspect of this application, an electrolyte sustained-release microcapsule is proposed, comprising a core and a wall. The core includes lithium salt, functional additives, and lithium replenishment agents; The capsule wall comprises polylactic acid-aliphatic polyester copolymer.

[0005] The electrolyte slow-release microcapsules have excellent heat resistance. Even when used in battery electrodes, they can still maintain their performance during the electrode drying process (around 130°C). Furthermore, the capsule walls can gradually dissolve in carbonate solvents, and the components in the capsule core can be continuously released during battery cycling, thereby replenishing the electrolyte and improving the battery's cycle performance.

[0006] In addition, the electrolyte sustained-release microcapsules according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the capsule wall comprises an unsaturated anhydride-modified polylactic acid-aliphatic polyester copolymer. This contributes to further improving the heat resistance of the electrolyte-release microcapsules.

[0007] In some embodiments of this application, the polylactic acid-aliphatic polyester copolymer includes a polylactic acid-polycaprolactone copolymer.

[0008] In some embodiments of this application, the unsaturated anhydride-modified polylactic acid-aliphatic polyester copolymer includes maleic anhydride-modified polylactic acid-aliphatic polyester copolymer.

[0009] In some embodiments of this application, at least one of the following conditions is satisfied: In the core, the mass ratio of the lithium salt, the functional additive, and the lithium replenishing agent is (5~6):(1~2):(1~4); The thickness of the capsule wall is 0.5 μm to 6 μm; The functional additives include unsaturated cyclic carbonate additives; The lithium replenishing agent includes at least one of inorganic lithium replenishing agents, organic lithium replenishing agents, and polymer lithium replenishing agents; The lithium salt includes at least one of LiPF6 and LiFSI; The electrolyte sustained-release microcapsules have a particle size of 5μm~50μm; The electrolyte sustained-release microcapsules maintained ≥95% integrity after being incubated at 130℃~140℃ for 2 hours. The electrolyte-release microcapsules dissolve at a rate of 0.5 mg / (cm³) in carbonate solvents at 25°C to 30°C. 2 ·h)~5mg / (cm 2 ·h).

[0010] A second aspect of this application provides a method for preparing the aforementioned electrolyte sustained-release microcapsules, comprising: Polylactic acid and aliphatic polyester compounds are mixed and melt-reacted to obtain the capsule wall material; Under an inert atmosphere, solvent, lithium salt, functional additives and lithium replenishing agent are mixed to obtain core material; Electrolyte sustained-release microcapsule intermediates were obtained using a coaxial nozzle high-voltage electrostatic spraying method. The electrolyte sustained-release microcapsule intermediate was vacuum dried to obtain electrolyte sustained-release microcapsules.

[0011] In some embodiments of this application, the unsaturated anhydride graft modifier, the polylactic acid, and the aliphatic polyester compound are mixed and subjected to a melt reaction to obtain the capsule wall material.

[0012] In some embodiments of this application, at least one of the following conditions is satisfied: The solvent includes at least one of carbonate solvents and carboxylic acid ester solvents; The temperature of the melting reaction is 160℃~180℃; The melting reaction time is 30 min to 60 min; The mass ratio of the unsaturated anhydride graft modifier, the polylactic acid, and the aliphatic polyester compound is (0.1~0.5):(3~7):(3~7). The inert atmosphere includes at least one of nitrogen, helium, and argon; The drying temperature is 40℃~60℃; The drying time is 4 to 8 hours; The vacuum degree of the drying process is -0.08 MPa to -0.098 MPa, preferably -0.09 MPa to -0.098 MPa; The aliphatic polyester compound includes polycaprolactone; The unsaturated anhydride graft modifier includes a maleic anhydride graft modifier.

[0013] A third aspect of this application provides a battery electrode comprising the aforementioned electrolyte-releasing microcapsules. Therefore, this battery electrode exhibits excellent electrochemical performance.

[0014] In some embodiments of this application, the battery electrode includes a current collector and a dressing layer disposed on at least one side of the current collector, and the mass content of the electrolyte sustained-release microcapsules is 3% to 10% based on the total mass of the dressing layer.

[0015] A fourth aspect of this application provides a battery comprising the aforementioned electrolyte-releasing microcapsules or the aforementioned battery electrodes. Therefore, this battery exhibits excellent electrochemical performance and a long service life.

[0016] In some embodiments of this application, the battery includes the battery electrode, the surface of which has a porous structure with a pore size of 5 μm to 50 μm.

[0017] A fifth aspect of this application provides an electrical device comprising the aforementioned battery. This electrical device possesses all the features and advantages of the aforementioned battery, which will not be elaborated upon here. Detailed Implementation

[0018] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0019] The thick electrode mentioned above refers to an electrode with a high surface density, such as a positive electrode with a single-sided surface density ≥250g / m². 2 The surface density of the negative electrode sheet is ≥130g / m². 2Alternatively, the positive and negative electrode sheets can be cold-pressed to a thickness of 100μm to 600μm. To address the drawbacks of thick electrodes, existing technologies typically employ electrode pore-forming methods to create ion transport channels within the thick electrodes. Specifically, volatile pore-forming agents can be added to the battery slurry, and after drying, pores can be formed on the electrode sheet; alternatively, micropore-forming treatment can be performed on the electrode surface through mechanical processing. However, both of these methods have shortcomings: volatile pore-forming agents are prone to generating uneven or uncontrollable bubble regions during the drying and mechanical processing processes, leading to uneven electrode structures.

[0020] Furthermore, during long-term battery cycling, the electrolyte is gradually consumed as it participates in electrode reactions, which further exacerbates the problem of insufficient wetting of thick electrodes. In view of this, the inventors considered developing an electrolyte slow-release capsule that can dissolve in commonly used electrolyte solvents and, during dissolution, forms interconnected pores on the electrode, thereby further constructing an electrolyte transport channel penetrating from the electrode surface to the middle region. Simultaneously, the composition of the electrolyte slow-release capsule is made consistent with the electrolyte composition, allowing it to replenish the consumed electrolyte during battery cycling.

[0021] Therefore, in a first aspect, this application provides an electrolyte sustained-release microcapsule, comprising a core and a wall. The core comprises a lithium salt, functional additives, and a lithium replenishing agent, and the wall comprises a polylactic acid-aliphatic polyester copolymer.

[0022] The capsule wall of the electrolyte sustained-release microcapsule in this application is composed of polylactic acid-aliphatic polyester copolymer. Specifically, it is formed by polylactic acid (PLA) and aliphatic polyester compounds linked by ester bonds. The main chain of this copolymer is linked by ester bonds, which itself has good thermal stability. Its decomposition temperature can reach above 200°C. Therefore, the electrolyte sustained-release microcapsule has excellent heat resistance. Even when used in battery electrodes, it can still maintain its performance during the electrode drying process (around 130°C).

[0023] Furthermore, the electrolyte-release microcapsules can dissolve in commonly used electrolyte solvents (carbonate solvents) because PLA-aliphatic polyester copolymers are semi-crystalline polymers. The PLA segments are flexible segments with good hydrophobicity, while the aliphatic polyester segments are rigid segments with strong hydrophilicity. Carbonate electrolytes, such as ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (EMC), are typical polar aprotic solvents. Their molecular structures are well-compatible with the aliphatic polyester segments, allowing them to penetrate the amorphous regions of the copolymer and cause the segments to swell. As the degree of swelling increases, the intermolecular forces are weakened, eventually leading to the gradual dissolution of the capsule wall and the release of the components in the capsule core.

[0024] Furthermore, the core components include lithium salts, functional additives, and lithium replenishing agents, which are compatible with the electrolyte composition. These components are continuously released during battery cycling, replenishing the electrolyte and thus improving the battery's cycle performance. Most importantly, when these electrolyte-releasing microcapsules are used in the battery electrodes, pores are formed on the electrodes as the core releases. Specifically, during electrode preparation, the electrolyte-releasing microcapsules are dispersed as solid particles inside the electrode. With subsequent dissolution and release, the solid particles gradually break down, transforming the initial space occupied by the solid particles into pores. This facilitates ion transport pathways, improves the utilization rate of active materials, and ultimately enhances the battery's electrochemical performance.

[0025] In some embodiments, the capsule wall comprises an unsaturated anhydride-modified polylactic acid-aliphatic polyester copolymer, specifically, the grafting of unsaturated anhydride groups onto the main chain of the polylactic acid-aliphatic polyester copolymer. The introduction of unsaturated anhydrides helps to further enhance the crystallinity of the polylactic acid-aliphatic polyester copolymer, enabling it to maintain an intact capsule wall morphology at high temperatures without softening or rupture. Furthermore, the unsaturated anhydride groups on the polylactic acid-aliphatic polyester copolymer main chain can further enhance the hydrophilicity of the copolymer, thereby further enabling controllable dissolution of the electrolyte-release microcapsules (i.e., adjusting the grafting rate of the unsaturated anhydride to regulate the dissolution rate of the microcapsules).

[0026] In some embodiments, unsaturated anhydride-modified polylactic acid-aliphatic polyester copolymers include maleic anhydride-modified polylactic acid-aliphatic polyester copolymers. Maleic anhydride-modified polylactic acid-aliphatic polyester copolymers refer to those in which maleic anhydride groups are grafted onto the main chain of the polylactic acid-aliphatic polyester copolymer. The introduction of maleic anhydride (MAH) helps to further improve the crystallinity of the polylactic acid-aliphatic polyester copolymer, enhance its high-temperature resistance, and further enable the controlled dissolution of electrolyte-release microcapsules.

[0027] In some embodiments, the polylactic acid-aliphatic polyester copolymer includes a polylactic acid-polycaprolactone copolymer. Polycaprolactone (PCL), as an aliphatic polyester compound, has strong hydrophilicity. Therefore, the polylactic acid-polycaprolactone (PLA-PCL) copolymer has good thermal stability and is easily soluble in carbonate solvents.

[0028] In some embodiments of this application, the functional additives include unsaturated cyclic carbonate additives. Specifically, unsaturated cyclic carbonate additives include, but are not limited to, vinylene carbonate (VC), ethylene ethyl carbonate (VEC), methyl vinylene carbonate (MVEC), and dimethyl vinylene carbonate (DMVC). The lithium replenishing agent includes at least one of inorganic lithium replenishing agents, organic lithium replenishing agents, and polymeric lithium replenishing agents, specifically including, but not limited to, lithium carbonate (Li₂CO₃), lithium polyphosphate (LiPP), lithium oxalate (Li₂C₂O₄), and lithium sulfide (Li₂S); lithium salts include, but are not limited to, LiPF₆ and LiFSI. The above components are conventional components of the electrolyte, which helps to ensure compatibility with the electrolyte and replenish it; at the same time, they do not introduce side reactions during battery operation, thereby improving battery safety performance.

[0029] In some embodiments of this application, the mass ratio of the lithium salt, the functional additive, and the lithium replenishing agent in the core is (5~6):(1~2):(1~4), specifically, it can be 5:1:2, 5:1:3, 6:1:2, 5:1:4, etc. The mass of the lithium salt, the functional additive, and the lithium replenishing agent can be adjusted according to the actual electrolyte ratio to ensure compatibility between the core composition and the electrolyte.

[0030] In some embodiments of this application, the thickness of the capsule wall is 0.5 μm to 6 μm, specifically, it can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or any range between two of these. A capsule wall thickness within this range essentially ensures that the electrolyte-releasing microcapsules of this application have stable structural strength, thereby guaranteeing the integrity of the microcapsules during the electrode fabrication process, i.e., preventing softening or rupture. Furthermore, a thickness within this range can match the dissolution rate of the capsule wall after battery electrolyte injection.

[0031] In some embodiments of this application, the particle size of the electrolyte-release microcapsules is 5 μm to 50 μm, specifically, it can be 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or any combination thereof. The fact that the particle size of the electrolyte-release microcapsules is within this range essentially indicates that the diameter of the pores formed on the electrode after the microcapsules dissolve is also within this range (i.e., pores of 5 μm to 50 μm can be formed on the electrode). This range matches the diffusion path of lithium ions, ensuring rapid ion passage without affecting the energy density of the electrode.

[0032] In some embodiments of this application, the electrolyte-release microcapsules retain ≥95% integrity after being incubated at 130°C for 2 hours. This demonstrates that the electrolyte-release microcapsules of this application exhibit excellent stability when not in contact with the electrolyte.

[0033] Specifically, the integrity retention rate can be tested using the following method: Take an appropriate amount of electrolyte-release microcapsules and place them at 130℃ for 2 hours. Then, determine the mass of the electrolyte-release microcapsules and detect their integrity retention rate by measuring the change in mass. The formula for calculating the integrity retention rate is η = m1 / m0 × 100%, where η is the integrity retention rate, m0 is the dry constant weight of the microcapsules before heat preservation, and m1 is the dry constant weight of the microcapsules after heat preservation. Take an appropriate amount of electrolyte-release microcapsules and dry them in a vacuum drying oven at 50℃ until constant weight. Accurately weigh the microcapsules and record the mass as m0 (g). Place the microcapsules after constant weight in a forced-air drying oven and keep them at 130℃ for 2 hours. After naturally cooling to room temperature, accurately weigh them again and record the mass as m1 (g).

[0034] In some embodiments of this application, the dissolution rate of the electrolyte-release microcapsules in carbonate solvents at 20°C to 30°C is 0.5 mg / (cm³). 2 ·h)~5mg / (cm 2 ·h), specifically, it can be 0.5mg / (cm³). 2 ·h), 1mg / (cm) 2 ·h), 2mg / (cm) 2 ·h), 3mg / (cm) 2 ·h), 4mg / (cm) 2 ·h), 5mg / (cm) 2 •h) or any two of the above dissolution rates. The above dissolution rates can ensure the gradual increase of electrode porosity, which can ensure that the electrode maintains stable mechanical properties during the dissolution process (that is, it can basically avoid the loss of active material and electrode cracking that may be caused by the instantaneous formation of pores), while ensuring the formation of sufficient ion channels.

[0035] Specifically, the test method for the dissolution rate of the electrolyte sustained-release microcapsules mentioned above is as follows: Take 1.0000 g (m0) of microcapsules that have been vacuum dried to constant weight, add 100 mL of anhydrous carbonate solvent (mass ratio EC:DMC=3:7), soak at a constant temperature of 25±5℃ for 1 h (t), filter to separate undissolved microcapsules and dry to constant weight, and weigh the remaining mass m. t Meanwhile, the apparent specific surface area of ​​the initial electrolyte-release microcapsules is S. 比 According to the formula The dissolution rate of the electrolyte-release microcapsules was calculated. The initial apparent specific surface area of ​​the electrolyte-release microcapsules was determined using the BET low-temperature nitrogen adsorption method.

[0036] A second aspect of this application provides a method for preparing the aforementioned electrolyte sustained-release microcapsules, comprising: S10: Polylactic acid and aliphatic polyester compounds are mixed and melted to obtain the capsule wall material.

[0037] In this step, polylactic acid and aliphatic polyester compounds are mixed and melt-reacted in a twin-screw extruder. After the reaction is completed, the mixture is extruded and granulated to obtain the capsule wall material.

[0038] In some embodiments, when the capsule wall comprises an unsaturated anhydride-modified polylactic acid-aliphatic polyester copolymer, the preparation process requires mixing the unsaturated anhydride graft modifier, polylactic acid, and aliphatic polyester compound in a twin-screw extruder while simultaneously carrying out a melt reaction. After the reaction is completed, the mixture is extruded and granulated to obtain the capsule wall material.

[0039] Specifically, aliphatic polyester compounds include, but are not limited to, polycaprolactone; unsaturated anhydride graft modifiers include, but are not limited to, maleic anhydride graft modifiers.

[0040] In some embodiments of this application, the melting reaction temperature is 160℃~180℃, specifically, it can be 160℃, 165℃, 170℃, 175℃, 180℃, etc. PLA has a melting point of approximately 150~160℃, and PCL has a melting point of approximately 59℃~64℃. A temperature of 160℃~180℃ essentially ensures that both polymers completely melt, forming a homogeneous melt, providing a favorable reaction environment for the MAH grafting reaction. Simultaneously, this temperature activates the reactivity of maleic anhydride, enabling it to graft onto the hydroxyl groups on the PLA-PCL copolymer backbone, achieving effective modification.

[0041] In some embodiments of this application, the melting reaction time is 30 min to 60 min, specifically 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc. These times generally ensure that the melting reaction proceeds sufficiently and that the grafting rate of maleic anhydride is maintained.

[0042] In some embodiments of this application, the mass ratio of the unsaturated anhydride graft modifier, the polylactic acid, and the aliphatic polyester compound is (0.1~0.5):(3~7):(3~7). Specifically, the mass ratio of the unsaturated anhydride graft modifier, polylactic acid, and aliphatic polyester compound can be 0.1:3:3, 0.3:3:3, 0.5:3:3, 0.1:7:3, 0.1:5:3, 0.5:7:7, etc. This ensures the introduction of an appropriate amount of unsaturated anhydride groups, guaranteeing a controllable dissolution rate of the electrolyte-released microcapsules in the electrolyte; simultaneously, it ensures the heat resistance and flexibility of the electrolyte-released microcapsules.

[0043] S20: Under an inert atmosphere, solvent, lithium salt, functional additives and lithium replenishing agent are mixed to obtain core material.

[0044] In this step, for example, under an inert atmosphere, the functional additive, lithium supplement, and solvent are mixed evenly and stirred for 30 to 50 minutes until completely dissolved. Then, the lithium salt is added to the mixture, and stirring continues until dissolved, resulting in a clear and transparent core material. The mixing method here is not limited and can be carried out according to actual conditions, ensuring uniform mixing.

[0045] Specifically, the solvent includes at least one of carbonate solvents and carboxylic acid ester solvents. More specifically, the solvents mentioned above include, but are not limited to, ethyl acetate, methyl propionate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate.

[0046] In some embodiments of this application, the lithium supplement can be sieved (using a 200-mesh sieve) before mixing, which helps to disperse the lithium supplement evenly.

[0047] In some embodiments of this application, the inert atmosphere includes at least one of nitrogen, helium, and argon.

[0048] S30: Electrolyte sustained-release microcapsule intermediates were obtained by high-pressure electrostatic spraying with a coaxial nozzle.

[0049] In this step, a coaxial nozzle high-pressure electrostatic spraying method is used. This involves using a coaxial double-layer nozzle (the inner tube delivers the core material, and the outer tube delivers the wall material) to simultaneously spray out the core and wall materials under the influence of a high-voltage electrostatic field. The electrostatic force causes the droplets to break into uniform microcapsules. The flow rate ratio between the inner and outer tubes in this step can be set according to the actual wall thickness.

[0050] In some embodiments of this application, the material transported through the inner and outer tubes must be in solution form. Therefore, the capsule wall material solution transported through the outer tube can be obtained by dissolving the capsule wall material prepared in step S10 in dichloromethane. The mass concentration of the capsule wall material in the prepared capsule wall material solution is 10%~15%.

[0051] S40: The electrolyte sustained-release microcapsule intermediate is vacuum dried to obtain electrolyte sustained-release microcapsules.

[0052] In this step, for example, the electrolyte sustained-release microcapsule intermediate is placed in a vacuum drying oven for drying to remove excess solvent and obtain dried electrolyte sustained-release microcapsules.

[0053] In some embodiments of this application, the drying temperature is 40℃~60℃, specifically 40℃, 45℃, 50℃, 55℃, 60℃, etc. The drying time is 4h~8h, specifically 4h, 5h, 6h, 7h, 8h, etc. The above drying temperature and time can basically ensure the complete removal of solvent, resulting in dried electrolyte sustained-release microcapsules.

[0054] In some embodiments of this application, the drying vacuum degree is -0.08 MPa to -0.098 MPa, specifically -0.09 MPa to -0.098 MPa. Exemplarily, the vacuum degree can be -0.08 MPa, -0.085 MPa, -0.09 MPa, -0.098 MPa, etc. This helps to improve drying efficiency and, at the same time, further ensures the structural stability of the electrolyte-release microcapsules.

[0055] In a third aspect of this application, a battery electrode is proposed, comprising the aforementioned electrolyte-releasing microcapsules. Specifically, the battery electrode comprises a positive electrode and a negative electrode. Thus, both the positive and negative electrode possess all the beneficial effects of the aforementioned electrolyte-releasing microcapsules, which will not be elaborated further here.

[0056] Specifically, the positive electrode sheet includes a positive current collector and a positive electrode coating layer disposed on at least one side of the positive current collector. The positive electrode coating layer includes, but is not limited to, positive electrode active material, electrolyte sustained-release microcapsules, positive electrode binder, and positive electrode conductive agent. The mass content of the electrolyte sustained-release microcapsules is 3% to 10% based on the total mass of the positive electrode coating layer; specifically, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. Maintaining the mass content of the electrolyte sustained-release microcapsules within the above range generally ensures that the subsequently obtained positive electrode sheet can form sufficient ion channels.

[0057] Furthermore, the negative electrode sheet includes a negative electrode current collector and a negative electrode coating layer disposed on at least one side of the negative electrode current collector. The negative electrode coating layer includes, but is not limited to, a negative electrode active material, electrolyte sustained-release microcapsules, a negative electrode binder, and a negative electrode conductive agent. The mass content of the electrolyte sustained-release microcapsules is 3% to 10% based on the total mass of the negative electrode coating layer; specifically, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc. Maintaining the mass content of the electrolyte sustained-release microcapsules within the above range generally ensures that the subsequently obtained negative electrode sheet can form sufficient ion channels.

[0058] In some embodiments of this application, the positive electrode current collector includes aluminum foil, which has strong electrochemical stability and will not undergo side reactions with the positive electrode material or electrolyte, thus maintaining the stability of the positive electrode current collector over a long period. The negative electrode current collector includes copper foil. Copper has excellent conductivity, which can efficiently transport electrons from the negative electrode, reduce the internal resistance of the electrode, and improve the rate performance of the battery. At the same time, copper will not undergo side reactions with the negative electrode material.

[0059] In some embodiments of this application, the positive electrode active material includes at least one of the following: layered positive electrode active materials (e.g., nickel-cobalt-manganese ternary positive electrode materials, nickel-cobalt-aluminum ternary positive electrode materials, lithium nickel oxide / sodium, lithium cobalt oxide / sodium, lithium manganese oxide / sodium, lithium-rich / sodium layered and rock salt phase layered materials), olivine-type phosphate active materials (e.g., lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, etc.), and spinel-structured positive electrode active materials (e.g., spinel lithium manganese oxide, spinel lithium nickel manganese oxide, lithium-rich spinel lithium manganese oxide, and lithium nickel manganese oxide, etc.). It is understood that the above-mentioned positive electrode active materials may further include doping elements and coating layers. As a specific example, the positive electrode active material includes lithium iron phosphate. Therefore, the lithium-ion battery has better cycle stability and safety performance.

[0060] In some embodiments of this application, the positive electrode conductive agent includes at least one selected from Super P, superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes (CNTs), graphene, and carbon nanofibers. This effectively improves conductivity, reduces internal resistance, and enhances the electrochemical performance of lithium-ion batteries.

[0061] In some embodiments of this application, the positive electrode adhesive includes at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. This allows the positive electrode dressing layer to adhere well to the positive electrode current collector, resulting in strong adhesion and reducing the likelihood of problems such as positive electrode dressing detachment.

[0062] In some embodiments of this application, the negative electrode active material includes artificial graphite, porous carbon, etc. These negative electrode active materials possess excellent capacity performance and low cost; different active materials can be selected according to actual needs.

[0063] In some embodiments of this application, the negative electrode binder may include, but is not limited to, at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The negative electrode conductive agent may include, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0064] A fourth aspect of this application provides a battery comprising the aforementioned electrolyte-releasing microcapsules, the aforementioned battery slurry, or the aforementioned electrode. This battery exhibits excellent electrochemical performance.

[0065] In some embodiments of this application, after the electrolyte-release microcapsules dissolve, the surface of the battery electrode has a pore structure with a diameter of 5 μm to 50 μm. This range matches the diffusion path of lithium ions, ensuring rapid ion passage without affecting the energy density of the electrode.

[0066] According to the embodiments of this application, it can be understood that there is no particular limitation on the specific type of battery, which can be a primary battery or a secondary battery; the shape of the battery can be a cylindrical battery, a square battery or other arbitrary shape batteries, and according to the outer packaging, the battery can be a hard-shell battery, a soft-pack battery, etc.

[0067] Typically, a battery includes the aforementioned positive electrode, negative electrode, electrolyte, and separator. The positive electrode, negative electrode, and separator can be manufactured into a cell using winding or stacking processes. The cell and electrolyte can be housed in an outer package. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0068] In some embodiments of this application, the separator can be a separator known in the art that can be used in lithium-ion batteries and is stable to the electrolyte used, such as a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene composite separator, etc.

[0069] According to embodiments of this application, the electrolyte includes a lithium salt and a solvent. Furthermore, additives with specific functions, such as film-forming additives, lithium replenishing agents, flame retardants, and thermal stability additives, may be added to the electrolyte as needed. As an example, the electrolyte may include a lithium salt, a solvent, and additives. In some embodiments of this application, the lithium salt may include LIPF6. The lithium salt can provide lithium ions to the battery, support the stability of the electrolyte and electrochemical reactions, help form a protective SEI film, improve conductivity, and enhance the safety of the lithium-ion battery. Functional additives may include vinylene carbonate (VC), etc., and lithium replenishing agents include lithium carbonate (Li2CO3), lithium polyphosphate (LiPP), etc.

[0070] According to embodiments of this application, the solvent may include ethylene carbonate, dimethyl carbonate, diethyl carbonate, etc. This allows for the sufficient dissolution of lithium salts, providing an ion transport medium and also improves the electrochemical and safety performance of lithium-rich manganese-based batteries.

[0071] According to the embodiments of this application, the battery can be a single cell, a battery module, or a battery pack. The specific structure of the battery module or battery pack is not particularly limited and can be carried out with reference to conventional techniques in the art.

[0072] In a fifth aspect of this application, an electrical device is provided, comprising the aforementioned battery. Therefore, this electrical device exhibits excellent electrochemical performance and a long service life.

[0073] In some embodiments of this application, the specific type of electrical device is not particularly limited and can be any device that uses a battery as a power source or energy storage unit. For example, electrical devices include, but are not limited to, electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (e.g., mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, and so on.

[0074] It is understood that, in addition to the battery mentioned above, the electrical device also includes other necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0075] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art or in accordance with the product manual.

[0076] Example 1 Capsule wall material preparation: Weigh 30g of polylactic acid, 70g of polycaprolactone, and 2g of maleic anhydride graft modifier, add them to a twin-screw extruder, melt-blend at 170℃ for 60min, and extrude and granulate to obtain maleic anhydride modified polylactic acid-polycaprolactone copolymer particles. Core material preparation: Under argon protection, EC 30g and DMC 60g were mixed evenly, then VC 2g and Li2CO3 8g were added and stirred for 25min until completely dissolved. Finally, 10.1g LiPF6 was slowly added to the mixture and stirred for 40min until completely dissolved to obtain a core material with a LiPF6 concentration of 1mol / L. Maleic anhydride-modified polylactic acid-polycaprolactone copolymer particles were dissolved in dichloromethane to prepare a capsule wall material solution with a mass concentration of 10% maleic anhydride-modified polylactic acid-polycaprolactone copolymer. A high-voltage electrostatic spraying method with a coaxial nozzle was used, in which the outer tube of the coaxial nozzle transported the capsule wall material solution and the inner tube transported the capsule core material. The flow rate ratio of the inner and outer tubes was 1:4, and the electrostatic voltage was 20kV, thus obtaining an electrolyte sustained-release microcapsule intermediate. The electrolyte sustained-release microcapsule intermediate was placed in a vacuum drying oven and dried at 45°C for 7 hours to obtain electrolyte sustained-release microcapsules with a particle size of 20 μm and a capsule wall thickness of 2 μm. Preparation of positive electrode sheet: The above-mentioned electrolyte sustained-release microcapsules, positive electrode active material LiFePO4, conductive agent carbon black, and binder PVDF are mixed evenly in a mass ratio of 5:90:2:3 and dispersed in N-methylpyrrolidone to obtain a positive electrode slurry (solid content of 68±1%). The positive electrode slurry is stirred and dispersed evenly and then coated onto an aluminum foil current collector. It is dried in an oven at 80℃ and then processed by cold pressing and other processes to obtain a positive electrode sheet with a thickness of 300μm. Negative electrode preparation: The above-mentioned electrolyte slow-release microcapsules, artificial graphite, conductive agent SP, and binder CMC are mixed evenly in a mass ratio of 2:94:2:2 and dispersed in deionized water to obtain a negative electrode slurry (solid content of 48±1%). After the negative electrode slurry is stirred and dispersed evenly, it is coated on a copper foil current collector, dried in an oven at 80℃, and then processed by cold pressing and other processes to obtain a negative electrode sheet with a thickness of 200μm. The positive electrode, negative electrode, and separator are assembled into a soft-pack battery cell, which is then placed in an aluminum-plastic film and vacuum-baked at 85°C for 12 hours. After the battery baking is completed, the battery moisture content is tested and found to be within acceptable limits before electrolyte is injected. The electrolyte consists of solvent, LiPF6, and VC. The solvent includes EC and DMC (mass ratio 3:7). The concentration of LiPF6 in the electrolyte is 1 mol / L, and the mass concentration of VC is 2%.

[0077] Examples 2-10 Same as Example 1, the main differences are shown in Table 1.

[0078] Example 11 Similar to Example 1, the main differences are shown in Table 1, and the more specific differences are as follows: Core material preparation: Under argon protection, 40g of EC and 30g of DMC were mixed evenly, then 5g of VC and 12g of LiPO3 were added and stirred for 30min until completely dissolved. Finally, 15.7g of LiFSI was slowly added to the mixture and stirred for 40min until completely dissolved to obtain a 1.2mol / L core material. Maleic anhydride-modified polylactic acid-polycaprolactone copolymer particles were dissolved in dichloromethane to prepare a capsule wall material solution with a mass concentration of 15% maleic anhydride-modified polylactic acid-polycaprolactone copolymer. The electrolyte consists of solvent, LiPF6, and VC. The solvent includes EC and DMC (mass ratio 2:8). The concentration of LiFSI in the electrolyte is 1.2 mol / L, and the mass concentration of VC is 2%.

[0079] Examples 12-17 Same as Example 1, the main differences are shown in Table 1.

[0080] Comparative Example 1 Same as Example 1, the main difference is that electrolyte slow-release microcapsules were not added to the battery slurry.

[0081] Comparative Example 2 Same as Example 11, the main difference being that electrolyte slow-release microcapsules were not added to the battery slurry.

[0082] Test Results The particle size, capsule wall thickness, high temperature resistance, dissolution rate in carbonate solvents, first charge / discharge efficiency, and capacity retention of the electrolyte sustained-release microcapsules in Examples 1-17 and Comparative Examples 1-2 were tested. The specific results are shown in Tables 1 and 2.

[0083] Test methods Particle size of electrolyte sustained-release microcapsules: tested using a laser diffraction particle size analyzer.

[0084] Thickness of the cyst wall: The thickness of the cyst wall was measured by freezing sections and then scanning electron microscopy (SEM).

[0085] First charge / discharge efficiency (first efficiency): At 25±3℃ and 1C charge / discharge rate, charge at 1C constant current to the cutoff voltage of 3.65V (graphite system), then switch to constant voltage charging until the current drops to 0.05C, and record the first charge capacity (Q charge); after standing for 5 min, discharge at 1C constant current to the cutoff voltage of 0.005V (graphite system), and record the first discharge capacity (Q discharge); First charge / discharge efficiency (coulombic efficiency) = (Q discharge / Q charge) × 100%, 5 batteries are assembled in parallel for each group, and the average value is taken after removing outliers (deviation > 5%).

[0086] Capacity retention: 1000 cycles at 25±3℃ and 1C charge / discharge rate. Specifically, the cycle regime is: constant temperature of 25±3℃, constant current and constant voltage charging at 1C (same as the initial charge cutoff condition), resting for 5 minutes, then constant current discharging at 1C (same as the initial discharge cutoff condition), followed by another 5 minutes of rest. This constitutes one cycle, and 1000 cycles are performed consecutively. Capacity retention is calculated as η. 1000 次循环容量保持率 = (1000th discharge capacity / 1st discharge capacity) × 100%.

[0087] High temperature tolerance of electrolyte sustained-release microcapsules: They were placed in a constant temperature oven at 130±5℃ and stored in a sealed container for 2 hours. After cooling, it was observed whether there was electrolyte evaporation (weighing method). For specific methods, please refer to the test method for integrity retention rate mentioned above.

[0088] Dissolution rate of electrolyte sustained-release microcapsules in carbonate solvents: swelling rate method, see the test method for dissolution rate of electrolyte sustained-release microcapsules in the previous text.

[0089]

[0090]

[0091] Conclusion: As shown in Table 1, the electrolyte sustained-release microcapsules prepared in this application have a wall thickness ranging from 0.5 μm to 6 μm and a particle size ranging from 5 μm to 50 μm. Furthermore, the integrity retention rate of the electrolyte sustained-release microcapsules after incubation at 130℃ for 2 hours is ≥95%, and their solubility rate in carbonate solvents is 0.5 mg / (cm³). 2 h)~5.0mg / (cm 2 Within the range of h), it is evident that the electrolyte sustained-release microcapsules prepared in this application have a stable structure, good heat resistance, and controllable dissolution rate; As can be seen from Table 2, the battery using the electrolyte slow-release microcapsules of this application has an initial charge-discharge efficiency of 90.5% to 92.6% and a capacity retention rate of 90.2% to 93.3% after 1000 cycles at 1C rate; while the batteries without electrolyte slow-release microcapsules (Comparative Examples 1 and 2) have significantly lower initial efficiency and cycle capacity retention rates than the examples. In summary, the electrolyte-release microcapsules described in this application can significantly improve the initial efficiency and long-cycle performance of batteries, demonstrating outstanding effects.

[0092] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0093] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0094] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An electrolyte sustained-release microcapsule, characterized in that, Including the core and the wall; The core includes lithium salt, functional additives, and lithium replenishment agents; The capsule wall comprises polylactic acid-aliphatic polyester copolymer.

2. The electrolyte sustained-release microcapsule according to claim 1, characterized in that, The capsule wall comprises unsaturated anhydride-modified polylactic acid-aliphatic polyester copolymer.

3. The electrolyte sustained-release microcapsule according to claim 2, characterized in that, The unsaturated anhydride-modified polylactic acid-aliphatic polyester copolymer includes maleic anhydride-modified polylactic acid-aliphatic polyester copolymer.

4. The electrolyte sustained-release microcapsule according to claim 1, characterized in that, The polylactic acid-aliphatic polyester copolymer includes polylactic acid-polycaprolactone copolymer.

5. The electrolyte sustained-release microcapsule according to claim 1, characterized in that, At least one of the following conditions must be met: In the core, the mass ratio of the lithium salt, the functional additive, and the lithium replenishing agent is: （5~6）：（1~2）：（1~4）； The thickness of the capsule wall is 0.5 μm to 6 μm; The functional additives include unsaturated cyclic carbonate additives; The lithium replenishing agent includes at least one of inorganic lithium replenishing agents, organic lithium replenishing agents, and polymer lithium replenishing agents; The lithium salt includes at least one of LiPF6 and LiFSI; The electrolyte sustained-release microcapsules have a particle size of 5μm~50μm; The electrolyte sustained-release microcapsules maintained ≥95% integrity after being incubated at 130℃~140℃ for 2 hours. The electrolyte-release microcapsules dissolve at a rate of 0.5 mg / (cm³) in carbonate solvents at 20°C to 30°C. 2 ·h)~5mg / (cm 2 ·h).

6. A method for preparing electrolyte sustained-release microcapsules as described in any one of claims 1 to 5, characterized in that, include: Polylactic acid and aliphatic polyester compounds are mixed and melt-reacted to obtain the capsule wall material; Under an inert atmosphere, solvent, lithium salt, functional additives and lithium replenishing agent are mixed to obtain core material; Electrolyte sustained-release microcapsule intermediates were obtained using a coaxial nozzle high-voltage electrostatic spraying method. The electrolyte sustained-release microcapsule intermediate was vacuum dried to obtain electrolyte sustained-release microcapsules.

7. The preparation method according to claim 6, characterized in that, The unsaturated anhydride graft modifier, the polylactic acid, and the aliphatic polyester compound are mixed and subjected to a melt reaction to obtain the capsule wall material.

8. The preparation method according to claim 7, characterized in that, At least one of the following conditions must be met: The solvent includes at least one of carbonate solvents and carboxylic acid ester solvents; The temperature of the melting reaction is 160℃~180℃; The melting reaction time is 30 min to 60 min; The mass ratio of the unsaturated anhydride graft modifier, the polylactic acid, and the aliphatic polyester compound is (0.1~0.5):(3~7):(3~7). The inert atmosphere includes at least one of nitrogen, helium, and argon; The drying temperature is 40℃~60℃; The drying time is 4 to 8 hours; The vacuum degree of the drying process is -0.08 MPa to -0.098 MPa, preferably -0.09 MPa to -0.098 MPa; The aliphatic polyester compound includes polycaprolactone; The unsaturated anhydride graft modifier includes a maleic anhydride graft modifier.

9. A battery electrode, characterized in that, Includes the electrolyte sustained-release microcapsules as described in any one of claims 1 to 5.

10. The battery electrode according to claim 9, characterized in that, The battery electrode includes a current collector and a dressing layer disposed on at least one side of the current collector. Based on the total mass of the dressing layer, the mass content of the electrolyte sustained-release microcapsules is 3% to 10%.

11. A battery, characterized in that, It includes the electrolyte slow-release microcapsules according to any one of claims 1 to 5 or the battery electrode according to any one of claims 9 to 10.

12. The battery according to claim 11, characterized in that, The battery includes the battery electrode, the surface of which has a porous structure with a pore size of 5μm to 50μm.

13. An electrical appliance, characterized in that, Includes the battery as described in claim 11 or 12.

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