Positive and negative electrode slurries and their preparation methods, positive and negative electrode materials, batteries and their preparation methods

Abstract

This application discloses a positive and negative electrode slurry and its preparation method, positive and negative electrode materials, a battery and its preparation method. The preparation method of the positive or negative electrode slurry includes: preparing a first mixture: mixing a binder and liquid raw materials to obtain a first mixture; preparing a second mixture: mixing solid raw materials to obtain a second mixture; preparing a third mixture: adding the first mixture to the second mixture and mixing evenly to obtain a third mixture, i.e., a positive or negative electrode slurry; wherein at least one step of preparing the first mixture, the second mixture, and the third mixture is carried out in a vacuum environment and mixed by ultrasonic treatment. The positive and negative electrode slurries of this application do not exhibit agglomeration, can be uniformly coated on the electrode sheet, have good adhesion, and can improve the stability and safety of the battery.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a positive and negative electrode slurry and its preparation method, positive and negative electrode materials, a battery and its preparation method. Background Technology

[0002] With the development of the new energy industry, the requirements for battery safety performance are becoming increasingly stringent. Batteries need to remain stable and reliable under various environmental conditions. Thermal chamber testing is a key testing method for evaluating battery performance and safety under different temperature environments. By simulating various temperature conditions that batteries may encounter in actual use, thermal chamber testing can comprehensively evaluate the battery's thermal stability, charge-discharge performance, cycle life, and safety. This test is crucial for ensuring the reliability and safety of batteries under extreme temperature conditions.

[0003] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and energy storage systems. The positive electrode active materials for lithium-ion batteries can include lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide (NMC), and lithium nickel cobalt aluminum oxide (NCA), among others. Ternary materials possess high energy density and rate performance, showing promising application prospects. However, ternary materials have poor thermal stability, especially high-nickel materials, which have low decomposition temperatures and are prone to decomposition at excessively high temperatures. Furthermore, the chemical reactions of ternary materials are very vigorous, easily generating many flammable and explosive gases. Due to the properties of ternary materials, ternary lithium batteries face challenges in hot-box testing and are difficult to pass safety performance tests such as hot-box testing.

[0004] In summary, a method to improve battery stability is needed. Summary of the Invention

[0005] The purpose of this application is to provide a positive and negative electrode slurry and its preparation method, positive and negative electrode materials, battery and its preparation method that are beneficial to improving battery stability.

[0006] To solve the above problems, this application adopts the following technical solution:

[0007] The first aspect of this application discloses a method for preparing a positive electrode slurry or a negative electrode slurry. The raw materials of the positive electrode slurry include a positive electrode active material, a conductive agent, a binder, and a solvent. The raw materials of the negative electrode slurry include a negative electrode active material, a conductive agent, a binder, and a solvent. The raw materials of both the positive and negative electrode slurries include liquid raw materials and solid raw materials. The preparation method includes: preparing a first mixture: mixing the binder and the liquid raw materials to obtain the first mixture; preparing a second mixture: mixing the solid raw materials to obtain the second mixture; preparing a third mixture: adding the first mixture to the second mixture and mixing evenly to obtain the third mixture, i.e., the positive electrode slurry or the negative electrode slurry; wherein: at least one step of preparing the first mixture, the second mixture, and the third mixture is carried out in a vacuum environment; at least one step of preparing the first mixture, the second mixture, and the third mixture includes mixing by ultrasonic treatment.

[0008] In one implementation of this application, the vacuum level of the vacuum environment is -5MPa to -1MPa.

[0009] In one implementation of this application, at least one step of preparing the first mixture, the second mixture, and the third mixture includes mixing by stirring and ultrasonic treatment.

[0010] In one implementation of this application, the vacuum level of the vacuum environment is -5MPa to -1MPa.

[0011] In one implementation of this application, the frequency of the ultrasound is 10kHz to 20kHz.

[0012] In one implementation of this application, at least one step of preparing the first mixture, the second mixture, and the third mixture further includes mixing by stirring, wherein the stirring rate is 2000 rpm to 4000 rpm and the processing time is 0.5 h to 3 h.

[0013] In one implementation of this application, in the step of preparing the third mixture, the first mixture is added to the second mixture in multiple batches.

[0014] The second aspect of this application discloses a positive electrode slurry or a negative electrode slurry, which is prepared by the preparation method disclosed in the first aspect of this application.

[0015] The third aspect of this application discloses a positive electrode material or a negative electrode material, wherein the positive electrode material or a negative electrode material includes the positive electrode slurry or a negative electrode slurry disclosed in the second aspect of this application.

[0016] The fourth aspect of this application discloses a battery comprising an electrolyte and the positive electrode material and negative electrode material disclosed in the third aspect of this application.

[0017] In one implementation of this application, the electrolyte comprises 0.1% to 20% LiFSi.

[0018] The fifth aspect of this application discloses a method for preparing the battery described in the fourth aspect of this application, comprising: preparing a positive electrode material and a negative electrode material, including preparing a positive electrode slurry and a negative electrode slurry, and coating the positive electrode material and the negative electrode material; preparing an electrolyte, the electrolyte comprising a lithium salt, a solvent and an additive; assembling the positive electrode material and the negative electrode material, and injecting the electrolyte to obtain the battery.

[0019] The beneficial effects of this application are as follows:

[0020] The positive and negative electrode slurries of this application do not exhibit agglomeration, can be coated relatively uniformly on the electrode surface, and have good adhesion, which can improve the stability and safety of the battery. Attached Figure Description

[0021] Figure 1 This is a surface morphology diagram of the positive electrode sheet of Embodiment 1 of this application.

[0022] Figure 2 This is a surface morphology diagram of the negative electrode sheet of Embodiment 1 of this application.

[0023] Figure 3 This is a surface morphology diagram of the positive electrode sheet of Comparative Example 1 of this application.

[0024] Figure 4 This is a surface morphology diagram of the negative electrode sheet of Comparative Example 1 of this application.

[0025] Figure 5 This is a surface morphology diagram of the positive electrode of Comparative Example 2 of this application.

[0026] Figure 6 This is a surface morphology diagram of the negative electrode sheet of Comparative Example 2 of this application.

[0027] Figure 7 This is a surface morphology diagram of the positive electrode sheet of Comparative Example 3 of this application.

[0028] Figure 8 This is a surface morphology diagram of the negative electrode sheet of Comparative Example 3 of this application.

[0029] Figure 9This is a surface morphology diagram of the positive electrode sheet of Comparative Example 4 of this application.

[0030] Figure 10 This is a surface morphology diagram of the negative electrode sheet of Comparative Example 4 of this application. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other materials or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0032] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0033] The serial numbers assigned to components in this article, such as "first" and "second", are used only to distinguish the objects being described and have no sequential or technical meaning.

[0034] The cathode materials in lithium-ion batteries are classified into lithium iron phosphate, lithium manganese iron phosphate, and lithium nickel cobalt manganese oxide (Li(Ni) phosphate). x Co y Mn 1-x-y Lithium nickel cobalt manganese oxide (LiCO) is a multifunctional positive electrode active material for lithium-ion batteries. By adjusting the ratio of nickel, cobalt, and manganese, battery performance can be optimized to meet different application requirements. High-nickel materials are suitable for applications requiring high energy density. Ternary materials, in particular, offer high energy density and rate performance, but suffer from poor safety. This is primarily due to their poor thermal stability, especially high-nickel materials, which have a low decomposition temperature; decomposition occurs above 150°C. Secondly, ternary materials undergo vigorous chemical reactions, generating many flammable and explosive gases. The materials themselves are also sensitive to moisture and prone to side reactions. Finally, ternary materials are primarily designed for high-energy-density, high-power batteries, resulting in high nickel content. Therefore, current ternary lithium batteries often fail hot-chamber testing.

[0035] In this application, by improving the coating of the positive and negative electrodes and adding LiFSI to the electrolyte, the stability of the battery can be improved, especially for ternary lithium batteries with poor safety and difficulty in passing the hot box test. By using our method, the battery can meet the standards and pass the hot box test. This application provides a high-capacity, high-energy-density, and highly safe nickel-cobalt-manganese lithium oxide battery.

[0036] In view of this, this application creatively proposes a positive and negative electrode slurry and its preparation method, positive and negative electrode materials, a battery and its preparation method, and has the following advantages:

[0037] (1) By adding the first mixture (liquid) to the second mixture (solid), the amount of the first mixture added can be adjusted and the appropriate amount can play a better kneading role.

[0038] (2) Adding the first mixture to the second mixture in several steps can stabilize the separated particles, prevent the particles from agglomerating again, and make the dispersion more uniform.

[0039] (3) The addition of ultrasonic technology during the preparation process allows the growth and rupture of bubbles generated by ultrasound to impact and disperse agglomerates in the mixture, and also induces material flow on a macroscopic level, resulting in more uniform mixing. Specifically, on a microscopic level, continuous ultrasonic vibration is used during the preparation process, causing a large number of bubbles to be generated inside the material during mixing. The bubbles float upward and grow. When the bubble size reaches a certain critical value, the bubble growth rate increases rapidly and then bursts instantly, forming a shock wave to disperse the agglomerates in the material. On a macroscopic level, the salt environment during the material mixing process is conducive to the discharge of gas from the material, preventing the gas in the material from affecting the subsequent coating quality.

[0040] (5) Lithium salts include LiFSI. Compared with LiPF6, LiFSI has better ionic conductivity, thermal stability and electrochemical stability. It is also easily soluble in water and various organic solvents and has almost no side reactions. Its excellent thermal stability can help the battery pass the 135℃ hot box test.

[0041] (6) The positive and negative electrode slurries do not agglomerate and adhere to the electrode sheets relatively uniformly, with good adhesion. The electrolyte has good thermal stability and the battery has good safety performance.

[0042] The present application will now be described in conjunction with the accompanying drawings and specific embodiments.

[0043] This application first relates to a method for preparing a positive electrode slurry or a negative electrode slurry.

[0044] In one specific embodiment, the raw materials for the positive electrode slurry include positive electrode active material, conductive agent, binder and solvent, and the raw materials for the negative electrode slurry include negative electrode active material, conductive agent, binder and solvent, wherein the raw materials include liquid raw materials and solid raw materials.

[0045] Positive electrode active materials refer to substances such as lithium iron phosphate, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium cobalt oxide, while negative electrode active materials refer to substances such as graphite and silicon. Both positive and negative electrode active materials are usually solid materials.

[0046] In one specific embodiment, the positive electrode active material is lithium nickel cobalt manganese oxide.

[0047] In one specific embodiment, the particle size D50 of the lithium nickel cobalt manganese oxide material is 1 μm to 30 μm.

[0048] In one specific embodiment, the nickel content in the lithium nickel cobalt manganese oxide material is relatively high. In other words, in one specific embodiment of this application, the lithium nickel cobalt manganese oxide material is a high-nickel material.

[0049] In one specific embodiment, in the lithium nickel cobalt manganese oxide material, the proportion of nickel to cobalt and lithium is 60% to 95%. For example, in lithium nickel cobalt manganese oxide, the proportion of nickel to cobalt and lithium is 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0050] In one specific embodiment, in the lithium nickel cobalt manganese oxide material, nickel accounts for 80% to 95% of the total nickel, cobalt, and lithium elements.

[0051] In one specific embodiment, the ratio of nickel, cobalt, and lithium in the lithium nickel cobalt manganese oxide material is 9:0.5:0.5.

[0052] In the positive electrode slurry, the binder can be PVDF (polyvinylidene fluoride), the conductive agent can be CNT (carbon nanotubes) or SP (SuperP), and the solvent can be NMP (N-methylpyrrolidone). In the negative electrode slurry, the binder can be CMC (carboxymethyl cellulose) or SBR (styrene-butadiene rubber), the conductive agent can be carbon nanotubes (CNTs), SP (SuperP), or conductive adhesive, and the solvent can be NMP or water. The positive and negative electrode active materials and SP are typically solid raw materials, while NMP, water, CNTs, and conductive adhesive are typically liquid raw materials.

[0053] In one specific embodiment, the method for preparing the positive electrode slurry or the negative electrode slurry includes:

[0054] (1) Preparation of the first mixture: The binder and the liquid raw material are mixed to obtain the first mixture.

[0055] (2) Preparation of the second mixture: Mix the solid raw materials to obtain the second mixture.

[0056] (3) Preparation of the third mixture: Add the first mixture to the second mixture and mix evenly to obtain the third mixture, namely the positive electrode slurry or the negative electrode slurry.

[0057] The steps of preparing the first mixture and preparing the second mixture can be performed in any order.

[0058] In one specific embodiment, at least one step of preparing the first mixture, the second mixture, and the third mixture is performed in a vacuum environment.

[0059] In one specific embodiment, the entire preparation process of the positive or negative electrode slurry is carried out in a vacuum environment. That is, each step is performed in a vacuum environment.

[0060] In one specific embodiment, the vacuum level of the vacuum environment is -5 MPa to 0 MPa. For example, the vacuum level of the vacuum environment can be -5 MPa, -4 MPa, -3 MPa, -2 MPa, -1 MPa, -0.5 MPa, or 0 MPa. Preferably, the vacuum level of the vacuum environment is -5 MPa to -1 MPa. It should be noted that MPa is megapascal; a vacuum level of -1 MPa is approximately equal to -10 standard atmospheres.

[0061] In one specific embodiment, at least one step in preparing the first mixture, the second mixture, and the third mixture includes mixing by ultrasonic treatment.

[0062] In one specific embodiment, ultrasonic mixing can be used throughout the entire preparation process of the positive or negative electrode slurry. That is, ultrasonic mixing is included in every step.

[0063] In one specific embodiment, the frequency of the ultrasound is 10 kHz to 20 kHz. For example, the frequency of the ultrasound can be 10 kHz, 11 kHz, 12 kHz, 13 kHz, 14 kHz, 15 kHz, 16 kHz, 17 kHz, 18 kHz, 19 kHz or 20 kHz.

[0064] In one specific embodiment, at least one step of preparing the first mixture, the second mixture, and the third mixture includes mixing by stirring.

[0065] In one specific embodiment, the stirring rate is 2000 rpm to 4000 rpm, and the processing time is 0.5 h to 3 h.

[0066] In one specific embodiment, an ultrasonic dual planetary mixer can be used to mix the materials. The ultrasonic dual planetary mixer has a revolution speed of 20 rpm to 60 rpm and a rotation speed of 2800 rpm to 3200 rpm.

[0067] In one specific embodiment, during the preparation of the third mixture, the first mixture is added to the second mixture in multiple batches. For example, the first mixture can be added in two, three, or four batches. It should be noted that adding the first mixture to the second mixture in batches can knead the second mixture. The high-speed rotating impeller, through the friction between its angled surface and the material, causes the material to move tangentially along the impeller surface. Simultaneously, due to centrifugal force, the material is thrown against the wall of the mixing chamber and rises along the wall. After rising to a certain height, it falls back to the center of the impeller due to gravity, and is then thrown up again. This combination of upward and tangential motion puts the material in a continuous spiral motion. Because the impeller speed is very high, the material moves very fast. The collisions and friction between the rapidly moving particles break up any clumps or agglomerates, and the temperature of the material also rises accordingly, which is beneficial for the adsorption of various additives by the powder.

[0068] In one specific embodiment, the method for preparing the positive electrode slurry or the negative electrode slurry further includes: adding a binder to the third mixture and adjusting the viscosity to obtain the positive electrode slurry or the negative electrode slurry.

[0069] In one specific embodiment, the viscosity of the positive electrode slurry or the negative electrode slurry is 2000 MPa·s to 4000 MPa·s.

[0070] In one specific embodiment, the method for preparing the positive electrode slurry or the negative electrode slurry further includes: sieving and / or removing iron from the third mixture after adjusting the viscosity.

[0071] In one specific embodiment, the sieving process includes filtration using a 200-mesh sieve.

[0072] In one specific embodiment, the iron removal process includes stirring the slurry using an iron removal device to remove magnetic materials from the slurry.

[0073] In one specific embodiment, the solid content of the first mixture is 3% to 5%.

[0074] In one specific embodiment, the solid content in the positive electrode slurry or negative electrode slurry is 55% to 80%, the viscosity is 2000 to 4000 MPa.s, and the fineness is ≤15 μm.

[0075] This application also relates to a positive electrode slurry or negative electrode slurry prepared by the above-described method for preparing positive electrode slurry or negative electrode slurry.

[0076] This application also relates to a positive electrode material or a negative electrode material, wherein the positive electrode material has the above-mentioned positive electrode slurry, and the negative electrode material has the above-mentioned negative electrode slurry.

[0077] In one specific embodiment, the cathode material has a particle size D50 of 1 μm to 5 μm and a specific surface area of ​​5 to 20 μm. 2 / g, density is 0.5~1g / cm³ 3 .

[0078] In one specific embodiment, the particle size D50 of the negative electrode material is 1 μm to 5 μm, and the specific surface area is 5 to 20 μm. 2 / g, density is 0.5~1g / cm³ 3 .

[0079] This application also relates to a battery, which includes: the above-described positive electrode material, the above-described negative electrode material, and an electrolyte.

[0080] In one specific embodiment, the electrolyte includes: lithium salt, solvent, and additives.

[0081] In one specific embodiment, the lithium salt includes LiFSI (lithium bis(fluorosulfonyl)imide).

[0082] In one specific embodiment, the lithium salt includes LiPF6 (lithium hexafluorophosphate) and LiFSI (lithium bis(fluorosulfonyl)imide).

[0083] In one specific embodiment, the electrolyte comprises 0.1% to 20% LiPF6 and / or 0.1% to 20% LiFSI. For example, the electrolyte may include 0.1%, 0.5%, 1%, 5%, 10%, 15%, or 20% LiPF6 and / or 0.1%, 0.5%, 1%, 5%, 10%, 15%, or 20% LiFSI. All contents are expressed as mass fractions.

[0084] In one specific embodiment, the solvent of the electrolyte includes at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC).

[0085] In one specific embodiment, the electrolyte additives include at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl acetate (DTD), propylene sulfate (PS), and trivinylsilane (TVSi).

[0086] In one specific embodiment, the electrolyte contains 45%–55% DMC, 8%–12% EMC, 8%–12% PE, 0.1%–0.3% VC, 0.2%–0.6% TVSi, 8%–16% FEC, 2.5%–3.1% EC, 12%–16% PC, 0.2%–0.7% DTD, and 1%–1.4% PS. All contents are expressed as mass fractions.

[0087] In one specific embodiment, the battery is a ternary lithium battery.

[0088] This application also relates to a method for preparing a battery, comprising: preparing a positive electrode material and a negative electrode material, preparing an electrolyte, assembling the positive electrode material and the negative electrode material, and injecting the electrolyte to obtain a battery. The positive electrode material, negative electrode material, and electrolyte are as described above and will not be repeated here.

[0089] The present application will be further described in detail below through specific embodiments. These embodiments are only for further illustration and should not be construed as limiting the present application. It should be noted that the reagents, kits, instruments, etc., used in the embodiments are all commercially available, and the operating steps are performed according to the instruction manual or general operating steps in the art.

[0090] Example 1:

[0091] (1) Preparation of positive electrode slurry:

[0092] 1) Preparation of wet materials:

[0093] PVDF and NMP were mixed and dispersed using an ultrasonic dual planetary stirrer at a revolution speed of 30 rpm and a rotation speed of 2800 rpm, an ultrasonic frequency of 20 kHz, a time of 3 h, a temperature of 20-30 °C, and a vacuum of -1 MPa to obtain material A.

[0094] CNTs were added to material A and dispersed using an ultrasonic-double planetary stirrer at a revolution speed of 20 rpm, a rotation speed of 2800 rpm, an ultrasonic frequency of 10 kHz, a time of 0.5 h, a temperature of 20-30 °C, and a vacuum of -1 MPa to obtain material B.

[0095] 2) Preparation of dry materials:

[0096] Lithium nickel cobalt manganese oxide was mixed and dispersed using an ultrasonic-double planetary stirrer at a speed of 5 rpm, an ultrasonic frequency of 10 kHz, a time of 30 min, a temperature of 20-30℃, and a vacuum of -1 MPa to obtain material C.

[0097] SP was added to material C and dispersed using an ultrasonic-double planetary stirrer at a speed of 40 rpm, an ultrasonic frequency of 20 kHz, a time of 0.5 h, a temperature of 20-30 °C, and a vacuum of -1 MPa to obtain material D.

[0098] 3) Total Mixing:

[0099] Add 70% and 30% of material B to material D in two batches, and disperse using an ultrasonic-double planetary stirrer at a revolution speed of 20 rpm, a rotation speed of 1300 rpm, an ultrasonic frequency of 20 kHz, a time of 3.5 h, a temperature of 20-30 °C, and a vacuum of -1 MPa to obtain material E.

[0100] Add appropriate amounts of NMP to material E to adjust its viscosity to 2000-4000 MPa.s, thus obtaining material F.

[0101] 4) Use a 200-mesh sieve to sieve material F under a vacuum of -0.01MPa to remove larger particles from the slurry. Use an iron removal device to stir the slurry to remove magnetic substances from the slurry.

[0102] In this embodiment, by weight, it includes 0.55 parts of PVDF, 15.5 parts of NMP, 15 parts of CNT, 100 parts of lithium nickel cobalt manganese oxide (wherein the ratio of nickel, cobalt and lithium is 9:0.5:0.5), and 1 part of SP.

[0103] (2) Preparation of negative electrode slurry:

[0104] 1) Preparation of wet materials:

[0105] CMC and deionized water were mixed and dispersed using an ultrasonic dual planetary stirrer at a revolution speed of 20 rpm and a rotation speed of 2800 rpm, an ultrasonic frequency of 10 kHz, a time of 1.5 h, a temperature of 20-30 °C, and a vacuum of -1 MPa to obtain material G.

[0106] Material G was mixed with CNT and dispersed using an ultrasonic-double planetary stirrer at a revolution speed of 60 rpm, a rotation speed of 2800 rpm, an ultrasonic frequency of 20 kHz, a time of 0.5 h, a temperature of 20-30 ℃, and a vacuum of -1 MPa to obtain material H.

[0107] Material H was mixed with conductive adhesive and dispersed using an ultrasonic dual planetary stirrer at a revolution speed of 20 rpm and a rotation speed of 3200 rpm, an ultrasonic frequency of 20 kHz, a time of 1 hour, a temperature of 20-30℃, and a vacuum degree of -1 MPa to obtain material I.

[0108] 2) Preparation of dry materials:

[0109] Graphite and SP were mixed and dispersed using an ultrasonic-double planetary stirrer at a revolution speed of 10 rpm and a rotation speed of 3200 rpm, an ultrasonic frequency of 20 kHz, a time of 3 h, a temperature of 20-30 ℃, and a vacuum of -1 MPa to obtain material J.

[0110] 3) Total Mixing:

[0111] Material J was mixed with 20% of material I and dispersed using an ultrasonic-double planetary stirrer at a revolution speed of 20 rpm and a rotation speed of 300 rpm, an ultrasonic frequency of 20 kHz, a time of 1.5 h, a temperature of 20-30 °C, and a vacuum of -1 MPa to obtain material K.

[0112] Material K was mixed with 55% of material I and dispersed using an ultrasonic-double planetary stirrer at a revolution speed of 20 rpm and a rotation speed of 3000 rpm, an ultrasonic frequency of 10 kHz, a time of 1.5 h, a temperature of 20-30 °C, and a vacuum of -1 MPa to obtain material L.

[0113] Material L was mixed with 25% of material I and dispersed using an ultrasonic-double planetary stirrer at a revolution speed of 2 rpm and a rotation speed of 500 rpm, an ultrasonic frequency of 10 kHz, a time of 1.5 h, a temperature of 20-30 ℃, and a vacuum degree of -1 MPa to obtain material M.

[0114] Add appropriate amounts of NMP and SBR to material M to adjust its viscosity. The viscosity range is 2000-4000 MPa·s.

[0115] 4) Use a 200-mesh sieve to sieve material M under a vacuum of -0.01MPa to remove larger particles from the slurry. Use an iron removal device to stir the slurry to remove magnetic substances from the slurry.

[0116] In this embodiment, by weight, it includes 0.45 parts of CMC, 82 parts of deionized water, 15 parts of CNT, 2 parts of conductive adhesive, 100 parts of graphite, 1 part of SP, and 1.2 parts of SBR.

[0117] (3) Electrolyte preparation:

[0118] The electrolyte includes lithium salts, solvents, and additives, wherein the lithium salts include LiPF6 and LiFSI, the solvents include DMC, EMC, EC, and PC, and the additives include VC, PE, FEC, DTD, PS, and TVSi.

[0119] In the electrolyte, by mass percentage, LiPF6 accounts for 3%, LiFSI for 3.5%, DMC for 50%, EMC for 9%, EC for 2.8%, PC for 13.8%, VC for 0.2%, PE for 9%, FEC for 12%, DTD for 0.5%, PS for 1.2%, and TVSi for 0.4%.

[0120] (4) Battery fabrication:

[0121] The positive electrode slurry is coated onto the positive electrode sheet (aluminum foil), and the negative electrode slurry is coated onto the negative electrode sheet (copper foil). Coating parameters: areal density 17.3 mg / cm³. 2 Compacted density 1.6 g / cm³ 3 The thickness is 0.047 mm. Subsequently, the positive and negative electrode sheets and electrolyte are wound into a cylindrical battery.

[0122] Comparative Example 1:

[0123] LiSFI was removed from the electrolyte, and other conditions were the same as in Example 1.

[0124] Comparative Example 2:

[0125] The ultrasonic treatment during the preparation of the positive and negative electrode slurries was removed, and other conditions were the same as in Example 1.

[0126] Comparative Example 3:

[0127] The vacuum conditions in the preparation process of the positive and negative electrode slurries were removed, and the preparation was carried out under normal indoor air pressure, with other conditions the same as in Example 1.

[0128] Comparative Example 4:

[0129] The stepwise feeding in the overall mixing step of the positive and negative electrode slurry preparation process was changed to a one-time feeding, with other conditions the same as in Example 1.

[0130] Electrode surface morphology observation:

[0131] The positive and negative electrode sheets prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were photographed using a scanning electron microscope (SEM) to observe the surface micromorphology of the samples. Figure 1 This is a surface morphology diagram of the positive electrode sheet of Embodiment 1 of this application. Figure 2 This is a surface morphology diagram of the negative electrode sheet in Embodiment 1 of this application. Figure 3 This is a surface morphology diagram of the positive electrode sheet of Comparative Example 1 of this application. Figure 4 This is a surface morphology diagram of the negative electrode sheet of Comparative Example 1 of this application. Figure 5 This is a surface morphology diagram of the positive electrode sheet of Comparative Example 2 of this application. Figure 6This is a surface morphology diagram of the negative electrode sheet of Comparative Example 2 of this application. Figure 7 This is a surface morphology diagram of the positive electrode sheet of Comparative Example 3 of this application. Figure 8 This is a surface morphology diagram of the negative electrode sheet of Comparative Example 3 of this application. Figure 9 This is a surface morphology diagram of the positive electrode sheet of Comparative Example 4 of this application. Figure 10 This is a surface morphology image of the negative electrode sheet of Comparative Example 4 of this application. The surface morphology of the electrodes in the examples and comparative examples was observed using a scanning electron microscope, with reference to... Figures 1 to 10 In Example 1, the coatings on the positive and negative electrodes were uniformly dispersed and showed no agglomeration; in Comparative Example 1, the coatings on the positive and negative electrodes were uniformly dispersed and showed no agglomeration. Figures 1 to 10 The electron micrographs are images of the dry electrode sheets before the addition of electrolyte, therefore the influence of the electrolyte on the electrode sheets is not visible. (During subsequent performance testing of the batteries, the electrolyte composition in Comparative Example 1 was different, and Comparative Example 1 batteries failed the test). In Comparative Example 2, after the ultrasonic process was removed from the positive electrode sheet, the positive electrode material showed significant agglomeration and uneven dispersion. In Comparative Example 3, after the vacuum was removed from the positive electrode sheet, there were many pits on the electrode surface (the reason being that the gas inside the slurry could not be expelled in time and remained on the electrode surface after coating), and pitting was visible on the negative electrode sheet. In Comparative Example 4, no stepwise feeding was used, resulting in poor uniformity of primary particles coating secondary particles in the positive electrode material, and pitting on the surfaces of both the positive and negative electrode sheets.

[0132] It should be noted that pitting refers to many small, uneven, point-like defects formed on the surface of the electrode sheet. Pitting causes the electrode surface to be uneven, affecting the uniformity and conductivity of the electrode, thereby reducing the battery performance, such as capacity, rate performance and cycle life.

[0133] Performance testing:

[0134] 1) Peel force test: The peeling of the electrode surface material was tested using an electronic tensile testing machine at a speed of 250 mm / min, a test time of 36.2 s, and a maximum deformation of 150 mm.

[0135] 2) Internal resistance test: Use a lithium-ion battery internal resistance tester to test the battery's internal resistance.

[0136] 3) Battery AC internal resistance (DCR) test: The battery is charged to 100% SOC using the Nebula lithium-ion battery test cabinet, then discharged to 50% SOC and left to stand for 1 hour. Then it is discharged at 1C for 30 seconds, and the battery AC internal resistance is calculated.

[0137] 4) Overcharge and over-discharge test: According to the national standard GB31241-2022, the battery passes the overcharge test if it does not catch fire or explode when charged to 6.3V at 1C, and passes the over-discharge test if it does not catch fire or explode when discharged to 2V at 1C; the battery fails the overcharge and over-discharge test if it catches fire or explodes.

[0138] 5) Hot Box Test: With the battery fully charged, heat it to 135℃ and keep it at that temperature for 1 hour. If the battery does not catch fire or explode, it passes the hot box test; if the battery catches fire or explodes, it fails the hot box test.

[0139] 6) Thermal runaway test: The fully charged battery is heated until it catches fire and explodes. If the battery can open the valve in a directional manner, it passes the thermal runaway test. If the battery explodes and does not open the valve in a directional manner to release pressure, it fails the test.

[0140] The test results are shown in the table below:

[0141]

[0142] In this application, Comparative Example 1 removed LiSFI from the electrolyte, causing the battery to overheat and eventually explode during the hot box test, failing the hot box test. Comparative Example 2 removed the positive and negative electrode materials using ultrasound during preparation, resulting in high internal resistance and poor electrode adhesion, failing the overcharge and over-discharge test. Comparative Example 3 removed the positive and negative electrode materials using vacuum during preparation, resulting in high internal resistance and poor electrode adhesion, failing the thermal runaway test. Comparative Example 4 did not perform stepwise mixing, resulting in high internal resistance and poor electrode adhesion, failing both the overcharge and over-discharge test and the thermal runaway test.

[0143] The above description, in conjunction with specific embodiments, provides a further detailed explanation of this application and should not be construed as limiting the specific implementation of this application to these descriptions. Those skilled in the art to which this application pertains can make several simple deductions or substitutions without departing from the concept of this application.

Claims

1. A battery, characterized in that, The battery includes: a positive electrode material, a negative electrode material, and an electrolyte. The electrolyte includes LiFSI with a content of 0.1% to 20%. The positive electrode material is prepared by coating a positive electrode slurry onto a positive electrode sheet, and the negative electrode material is prepared by coating a negative electrode slurry onto a negative electrode sheet. The raw materials for the positive electrode slurry include a positive electrode active material, a conductive agent, a binder, and a solvent; the raw materials for the negative electrode slurry include a negative electrode active material, a conductive agent, a binder, and a solvent; and the raw materials for both the positive and negative electrode slurries include liquid and solid raw materials. The preparation methods for the positive and negative electrode slurries include: Preparation of the first mixture: The binder and the liquid raw material are mixed to obtain the first mixture; Preparation of the second mixture: The solid raw materials, excluding the binder, are mixed to obtain the second mixture; Preparation of the third mixture: The first mixture is added to the second mixture and mixed evenly to obtain the third mixture, namely the positive electrode slurry or the negative electrode slurry; in: The steps of preparing the first mixture, the second mixture, and the third mixture are all performed in a vacuum environment; The steps of preparing the first mixture, the second mixture, and the third mixture all include mixing by ultrasonic treatment. In the step of preparing the third mixture, the first mixture is added to the second mixture in multiple batches.

2. The battery according to claim 1, characterized in that, The vacuum level of the vacuum environment is -5MPa to -1MPa.

3. The battery according to claim 1, characterized in that, The frequency of the ultrasound is 10kHz~20kHz.

4. The battery according to claim 1, characterized in that, In at least one step of preparing the first mixture, the second mixture, and the third mixture, mixing is further performed by stirring, wherein the stirring rate is 2000 rpm to 4000 rpm and the processing time is 0.5 h to 3 h.

5. A method for preparing a battery, characterized in that, include: Preparation of positive electrode material and negative electrode material: including the preparation of positive electrode slurry and negative electrode slurry, and coating to obtain the positive electrode material and the negative electrode material; Preparation of electrolyte: The electrolyte includes lithium salt, solvent and additives; the electrolyte includes LiFSI in a content of 0.1%~20%; The positive electrode material and the negative electrode material are assembled and injected with the electrolyte to obtain the battery; The raw materials for the positive electrode slurry include a positive electrode active material, a conductive agent, a binder, and a solvent; the raw materials for the negative electrode slurry include a negative electrode active material, a conductive agent, a binder, and a solvent; and the raw materials for both the positive and negative electrode slurries include liquid and solid raw materials. The preparation methods for the positive and negative electrode slurries include: Preparation of the first mixture: The binder and the liquid raw material are mixed to obtain the first mixture; Preparation of the second mixture: The solid raw materials, excluding the binder, are mixed to obtain the second mixture; Preparation of the third mixture: The first mixture is added to the second mixture and mixed evenly to obtain the third mixture, namely the positive electrode slurry or the negative electrode slurry; in: The steps of preparing the first mixture, the second mixture, and the third mixture are all performed in a vacuum environment; The steps of preparing the first mixture, the second mixture, and the third mixture all include mixing by ultrasonic treatment. In the step of preparing the third mixture, the first mixture is added to the second mixture in multiple batches.

6. The preparation method according to claim 5, characterized in that, The vacuum level of the vacuum environment is -5MPa to -1MPa.

7. The preparation method according to claim 5 or 6, characterized in that, The frequency of the ultrasound is 10kHz~20kHz.

8. The preparation method according to claim 5, characterized in that, In at least one step of preparing the first mixture, the second mixture, and the third mixture, mixing is further performed by stirring, wherein the stirring rate is 2000 rpm to 4000 rpm and the processing time is 0.5 h to 3 h.

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