Secondary battery and preparation method therefor, and electric device

Abstract

A secondary battery and a preparation method therefor, and an electric device. The secondary battery comprises a positive electrode sheet, which positive electrode sheet comprises a positive-electrode current collector and a positive-electrode film layer which is located on at least one side of the positive-electrode current collector and comprises a positive-electrode material, wherein the positive-electrode material comprises a substrate and a coating material located on at least part of the surface of the substrate, the coating material comprising a first electrolyte material and a conductive material, and at least part of the coating material being amorphous on the surface of the substrate.

Description

Secondary batteries, their preparation methods, and electrical devices

[0001] Cross-references to related applications

[0002] This disclosure is based on and claims priority to Chinese Patent Application No. 202510124900.5, filed on January 26, 2025, entitled "Secondary Battery and Method for Preparation Thereof, Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of battery technology, and in particular to a secondary battery, its preparation method, and an electrical device thereof. Background Technology

[0004] In recent years, with the increasingly wide application of rechargeable batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, aerospace, and many other fields. With the application and promotion of rechargeable batteries, people have increasingly higher requirements for their initial coulombic efficiency, rate performance, and cycle performance.

[0005] Therefore, how to achieve excellent initial coulombic efficiency, rate performance, and cycle performance in rechargeable batteries has become an urgent technical problem to be solved. Summary of the Invention

[0006] This disclosure is made in view of the above-mentioned problems, and its purpose is to provide a secondary battery and a method for preparing the same, as well as an electrical device thereof. The secondary battery prepared by this disclosure can achieve excellent initial coulombic efficiency, rate performance and cycle performance.

[0007] To achieve the above objectives, the first aspect of this disclosure provides a secondary battery, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer located on at least one side of the positive current collector and including a positive electrode material; the positive electrode material includes a substrate and a coating material located on at least a portion of the surface of the substrate, the coating material including a first electrolyte material and a conductive material, and at least a portion of the coating material is amorphous on the surface of the substrate.

[0008] The first electrolyte material exhibits good ionic conductivity, and the conductive material exhibits good electronic conductivity. In this disclosure, by providing a mixed coating material comprising the first electrolyte material and the conductive material on at least a portion of the surface of the substrate, ion transport channels and electron transport channels can be constructed on the surface of the cathode material. This improves the ionic and electronic conductivity of the cathode material, which is beneficial for balancing the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery. Furthermore, the amorphous coating material has lower mechanical strength, allowing for better interfacial contact with the substrate. This reduces interfacial impedance and improves electron transport efficiency between the coating material and the substrate. Simultaneously, the grain boundary effect of the amorphous coating material is insignificant, which helps improve the bulk electronic conductivity of the cathode material, thereby further enhancing the initial coulombic efficiency of the secondary battery.

[0009] In some embodiments, the coating material is distributed on the substrate surface in an island-like manner. The island-like distribution of the coating material can, on the one hand, build a better ion transport network and electron transport network on the surface of the cathode material, and on the other hand, it can build an electron transport channel between the cathode material substrate and the second electrolyte material, which is more conducive to balancing the initial coulombic efficiency, rate performance and cycle performance of the secondary battery.

[0010] In some embodiments, the conductive material includes conductive carbon materials and / or conductive polymers. This improves the electron transport efficiency between the matrix and the conductive material, thereby increasing the electronic conductivity of the cathode material and improving the initial coulombic efficiency of the secondary battery.

[0011] In some embodiments, the conductive carbon material includes one or more of conductive carbon black, Ketjen black, acetylene black, vapor-grown carbon fibers, and carbon nanotubes. This improves the electronic conductivity of the cathode material, thereby enhancing the initial coulombic efficiency of the secondary battery.

[0012] In some embodiments, the conductive carbon material includes vapor-grown carbon fibers and / or carbon nanotubes. This further improves the electronic conductivity of the cathode material, thereby enhancing the initial coulombic efficiency of the secondary battery.

[0013] In some embodiments, the conductive polymer includes one or more of polyaniline, polycarbazole, polythiophene, polyetheretherketone, and their respective modified compounds. Thus, the aforementioned conductive polymer can construct a good conductive network on the surface of the cathode material and can exist stably within the cathode material, thereby improving the electronic conductivity of the cathode material and consequently improving the initial coulombic efficiency of the secondary battery.

[0014] In some embodiments, the first electrolyte material includes a halide solid electrolyte material. Halide solid electrolyte materials have high ionic conductivity, which can increase the diffusion rate of active ions at the interface between the matrix and the first electrolyte material, thereby reducing interfacial impedance and improving the rate performance and cycle performance of the secondary battery.

[0015] In some embodiments, the halide solid electrolyte material includes materials with the chemical formula Li. x M1 a M2 b M3 c Q d X e The materials are defined as follows: 1≤x≤4, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 3≤e≤6, a+b+c=1; M1 includes one or more of B, Al, Ga, In, Sc, Y, La, Ce, Lu, Yb, Ho, Er, Tb, and Dy; M2 includes one or more of Si, Ge, Sn, Ti, Zr, and Hf; M3 includes one or more of V, Nb, and Ta; Q includes O and / or S; and X includes one or more of F, Cl, Br, and I. These halide solid electrolyte materials exhibit good stability under high voltage and good compatibility with the substrate. They can improve the diffusion rate of active ions at the substrate-electrolyte interface, which is beneficial for reducing interfacial impedance and improving the rate performance and cycle performance of secondary batteries.

[0016] In some embodiments, the first electrolyte material includes Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.6 In 0.6 Zr 0.4 Cl6, Li 1.5 ZrOCl 3.5 Li3InO 0.2 Cl 5.6 LiNbOCl4, LiNbOCl 3.6 F 0.4 Li 1.5 AlOCl 2.5 、Li3In 0.5 Y 0.5 One or more of Cl6.

[0017] In some embodiments, the thickness of the coating material is 50 nm to 100 nm. This helps to suppress the interfacial reaction between the cathode material matrix and the second electrolyte material, while also ensuring that the cathode material has a good lithium-ion transport rate.

[0018] In some embodiments, the mass ratio of the conductive material, the first electrolyte material, and the matrix in the positive electrode material is (0.1–0.3):1:(20–50). This is beneficial for improving the ionic and electronic conductivity of the positive electrode material, and thus helps to balance the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery.

[0019] In some embodiments, the ionic conductivity of the positive electrode is 0.8 × 10⁻⁶. -5 S / cm~8×10 -5 S / cm. This is beneficial for improving the rate performance and cycle performance of secondary batteries.

[0020] In some embodiments, the electronic conductivity of the cathode material is 1×10⁻⁶. -5 S / cm ~ 5×10 -5 S / cm. This is beneficial for improving the initial coulombic efficiency of secondary batteries.

[0021] In some embodiments, the positive electrode film layer further includes a second electrolyte material, which may be one or more of a sulfide solid electrolyte material, an oxide solid electrolyte material, and a polymer solid electrolyte material. This can increase the diffusion rate of active ions at the interface between the positive electrode material and the second electrolyte material, which is beneficial for reducing polarization and improving the rate performance and cycle performance of the secondary battery.

[0022] In some embodiments, the mass ratio of the positive electrode material to the second electrolyte material in the positive electrode film is (7–9.5):1. This is beneficial for increasing the diffusion rate of active ions at the interface between the positive electrode material and the second electrolyte material, thereby reducing polarization and improving the rate performance and cycle performance of the secondary battery.

[0023] In some embodiments, the matrix includes one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds.

[0024] In some embodiments, the secondary battery further includes a negative electrode and a solid electrolyte membrane, with the solid electrolyte membrane located between the positive and negative electrode.

[0025] The second aspect of this disclosure provides a method for preparing a secondary battery, comprising a first mixing step, including adding a matrix, a first electrolyte material, and a conductive material into a ball mill jar, and performing a first ball milling treatment under the conditions of a ball-to-material ratio of (5-15):1, a ball milling speed of 150 rpm to 300 rpm, and a ball milling time of 10 min to 30 min to obtain a first mixed powder, wherein the volume distribution particle size Dv50 of the first electrolyte material is less than or equal to 1 μm; a second mixing step, including continuing to add a mixed powder of the first electrolyte material and the conductive material to the first mixed powder, performing a second ball milling treatment under the same ball milling conditions as the first ball milling treatment, repeating the second mixing step multiple times to obtain a second mixed powder; and a heat treatment step, including heat treating the second mixed powder to obtain a positive electrode material.

[0026] In this disclosure, by repeatedly adding a first electrolyte material and a conductive material, the first electrolyte material and the conductive material can be uniformly mixed on the substrate surface. Then, heat treatment can further promote the interaction between the first electrolyte material and the conductive material and the substrate, thereby obtaining a uniform and stable coating material. The first electrolyte material and the conductive material in the coating material can construct ion transport channels and electron transport channels on the surface of the cathode material, which is beneficial to improving the ionic conductivity and electronic conductivity of the cathode material, and thus helps to balance the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery.

[0027] By controlling the ball milling conditions of the first and second ball milling processes and the volume distribution particle size Dv50 of the first electrolyte material within the aforementioned range, it is beneficial to form an amorphous coating material on the substrate surface. The amorphous coating material has lower mechanical strength, which allows for better interfacial contact with the substrate, thus reducing the impedance at the interface and improving the electron transport efficiency between the coating material and the substrate. At the same time, the grain boundary effect of the amorphous coating material is not significant, which is beneficial to improving the bulk electronic conductivity of the cathode material, thereby further improving the initial coulombic efficiency of the secondary battery.

[0028] In some embodiments, the preparation method includes one or more of the following features:

[0029] (1) The first ball milling process includes dry ball milling and / or wet ball milling; (2) The second ball milling process includes dry ball milling and / or wet ball milling; (3) The solvent used in the wet ball milling process includes one or more of cyclohexane, n-heptane, pseudotrimethylbenzene, m-xylene, toluene, and benzene; (4) The first ball milling process and / or the second ball milling process uses a planetary ball mill; (5) The planetary ball mill has a rotation ratio of 1:(2-4). This facilitates more uniform dispersion of materials, improves the uniformity of the mixing of the matrix, the first electrolyte material, and the conductive material, and thus enables the formation of a stable and uniform coating material on the matrix surface.

[0030] In some embodiments, the mass ratio of the conductive material, the first electrolyte material, and the matrix in the second mixed powder is (0.1–0.3):1:(20–50). This is beneficial for improving the ionic and electronic conductivity of the cathode material, thereby balancing the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery.

[0031] In some implementations, the heat treatment includes one or more of the following features:

[0032] (1) The heat treatment temperature is 150℃~400℃; (2) The heat treatment time is 2h~5h; (3) It is carried out in an oxygen and / or inert atmosphere. Thus, on the one hand, it can suppress the side reactions such as oxygen release in the matrix and ensure the stability of the matrix, and on the other hand, it can improve the stability of the coating material on the surface of the matrix.

[0033] A third aspect of this disclosure provides an electrical device comprising a secondary battery according to the first aspect, or a secondary battery prepared according to the preparation method of the second aspect. Attached Figure Description

[0034] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present disclosure.

[0035] Figure 2 is an exploded view of a secondary battery according to an embodiment of the present disclosure shown in Figure 1.

[0036] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present disclosure.

[0037] Figure 4 is a schematic diagram of a battery pack according to one embodiment of the present disclosure.

[0038] Figure 5 is an exploded view of a battery pack according to an embodiment of the present disclosure, as shown in Figure 4.

[0039] Figure 6 is a schematic diagram of a power supply device using a battery device according to an embodiment of the present disclosure.

[0040] Figure 7 is a transmission electron microscope image and elemental overlay spectrum of the cathode material in Embodiment 1 of this disclosure.

[0041] Figure 8 is the X-ray diffraction pattern of the cathode material in Embodiment 1 of this disclosure.

[0042] Explanation of reference numerals in the attached figures:

[0043] 1 Battery pack; 2 First housing; 3 Second housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0044] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the secondary battery, its preparation method, and the power-consuming device thereof. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0045] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this disclosure, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of this disclosure can be combined to form new technical solutions.

[0047] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions.

[0048] Unless otherwise specified, all steps of this disclosure may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if it is mentioned that the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] Unless otherwise specified, the terminology used in this disclosure has the common meaning as commonly understood by those skilled in the art.

[0050] Unless otherwise specified, the values ​​of the parameters mentioned in this disclosure can be determined using various test methods commonly used in the art, for example, according to the test methods given in this disclosure.

[0051] Currently, the common method is to coat the surface of the cathode material to suppress volume expansion during charge and discharge and improve the interfacial reaction between the cathode material and the electrolyte. However, conventional lithium salts used as coating materials have low ionic conductivity, leading to increased interfacial impedance and significant electrode polarization during battery cycling, which is detrimental to lithium-ion transport and affects the rate and cycle performance of the rechargeable battery. Using halide electrolyte materials as coating materials can reduce interfacial impedance and improve the rate and cycle performance of the rechargeable battery. However, halide electrolyte coating materials have high ionic conductivity and low electronic conductivity, hindering electron transport in the electrochemical reaction and causing concentration polarization at the cathode, thus affecting the initial coulombic efficiency of the rechargeable battery. Therefore, current methods using halide electrolyte materials as cathode coating materials cannot simultaneously improve cycle and rate performance while maintaining initial coulombic efficiency.

[0052] In related technologies, after coating the positive electrode material with a halide electrolyte material, the electronic conductivity of the positive electrode is improved by forming a positive electrode film layer through doping with conductive materials. However, in the positive electrode film layer formed by doping with conductive materials, the uniformity of the conductive material distribution is poor, and a uniform conductive network cannot be constructed, resulting in a poor effect on improving electronic conductivity, that is, it cannot effectively improve the initial coulombic efficiency of the secondary battery.

[0053] Based on this, this disclosure proposes a secondary battery, its preparation method, and an electrical device thereof. The secondary battery prepared by this disclosure can achieve excellent initial coulombic efficiency, rate performance, and cycle performance. The following provides a more detailed description of this disclosure and optional embodiments.

[0054] Secondary batteries

[0055] The first aspect of this disclosure provides a secondary battery, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer located on at least one side of the positive current collector and including a positive electrode material; the positive electrode material includes a substrate and a coating material located on at least a portion of the substrate surface, the coating material including a first electrolyte material and a conductive material, and at least a portion of the coating material is amorphous on the surface of the substrate.

[0056] The first electrolyte material exhibits good ionic conductivity, and the conductive material exhibits good electronic conductivity. In this disclosure, by providing a mixed coating material comprising the first electrolyte material and the conductive material on at least a portion of the surface of the substrate, ion transport channels and electron transport channels can be constructed on the surface of the cathode material. This improves the ionic and electronic conductivity of the cathode material, which is beneficial for balancing the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery. Furthermore, the amorphous coating material has lower mechanical strength, allowing for better interfacial contact with the substrate. This reduces interfacial impedance and improves electron transport efficiency between the coating material and the substrate. Simultaneously, the grain boundary effect of the amorphous coating material is insignificant, which helps improve the bulk electronic conductivity of the cathode material, thereby further enhancing the initial coulombic efficiency of the secondary battery.

[0057] In this disclosure, the first electrolyte material and the conductive material can be tested using transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). Specifically, 5 mg to 10 mg of cathode material powder is dispersed in 1 mL of cyclohexane solution, and after ultrasonic treatment, a dispersion is obtained. The dispersion is dropped onto a microgrid copper grid, dried at 40°C for 1 to 2 hours, and then transferred to a transmission electron microscope under vacuum for TEM testing. TEM can reveal that the crystalline state of the coating material on the surface of the cathode material particles is amorphous through high-resolution bright-field phase observation, and the elemental distribution in the coating material can be characterized by dark-field EDS testing. From the obtained TEM image and elemental overlay spectrum of the cathode material, it can be seen that the cathode material includes an island-like distribution of coating material, and the first electrolyte material and the conductive material are uniformly distributed in the coating material.

[0058] In some implementations, if the conductive material includes carbon, the reverse can also be achieved using a Raman spectrometer. Specifically, 10 mg of positive electrode material powder is pressed into a sheet, placed on a Raman observation stage, and the wavelength is set to 532 nm with a test wavenumber range of 300 cm⁻¹. -1 ~200cm -1 The test area was selected as the surface of an independent cathode material particle and observed using a microscope. The Raman spectrum was recorded. The characteristic peaks D and G of carbon elements, as well as weaker Alg and Eg peaks, were observed on the surface of the cathode material. Therefore, it can be proved that carbon material is distributed in the coating material on the surface of the cathode material.

[0059] The aforementioned transmission electron microscopy, energy dispersive spectroscopy, and / or Raman spectroscopy results demonstrate that the first electrolyte material and the conductive material are distributed within the coating material on the surface of the cathode material. Further analysis of the cathode material was then performed using X-ray diffraction (XRD). Specifically, an X-ray powder diffractometer (Bruker D8 ADVANCE, target material Cu Kα, voltage / current 40 kV / 40 mA, scanning angle range 10° to 70°) was used to analyze the cathode material, obtaining its X-ray diffraction pattern. No diffraction peaks for the first electrolyte material and the conductive material were observed in the X-ray diffraction pattern of the cathode material; therefore, this further confirms that the coating material on the surface of the cathode material is amorphous.

[0060] In some embodiments, the coating material is distributed on the substrate surface in an island-like manner. The island-like distribution of the coating material can, on the one hand, build a better ion transport network and electron transport network on the surface of the cathode material, and on the other hand, it can build an electron transport channel between the cathode material substrate and the second electrolyte material, which is more conducive to balancing the initial coulombic efficiency, rate performance and cycle performance of the secondary battery.

[0061] In this disclosure, the term "island-like" refers to the coating material presenting itself as a series of dispersed, spaced-apart island-like structures on the matrix.

[0062] In this disclosure, the morphology of the coating material can be determined using methods and instruments known in the art. For example, when observing the cathode material under a transmission electron microscope (JEM-F200), it can be observed that the coating material is not continuously covering the surface of the substrate, but rather covers the surface of the substrate in a discrete, "island-like" morphology.

[0063] In some embodiments, the conductive material includes conductive carbon materials and / or conductive polymers; optionally, the conductive material includes conductive carbon materials. Conductive carbon materials and / or conductive polymers have high electronic conductivity, enabling the formation of a good conductive network on the surface of the cathode material, improving the electron transport efficiency between the substrate and the conductive material, thereby improving the electronic conductivity of the cathode material and increasing the initial coulombic efficiency of the secondary battery.

[0064] In some embodiments, the conductive carbon material includes one or more of conductive carbon black, Ketjen black, acetylene black, vapor-grown carbon fiber (VGCF), and carbon nanotubes. Optionally, the conductive carbon material includes vapor-grown carbon fiber and / or carbon nanotubes. The aforementioned conductive carbon materials can construct a good conductive network on the surface of the cathode material, thereby improving the electronic conductivity of the cathode material and consequently improving the initial coulombic efficiency of the secondary battery.

[0065] In some embodiments, the conductive polymer includes one or more of polyaniline, polycarbazole, polythiophene, polyetheretherketone, and their respective modified compounds. Thus, the aforementioned conductive polymer can construct a good conductive network on the surface of the cathode material and can exist stably within the cathode material, thereby improving the electronic conductivity of the cathode material and consequently improving the initial coulombic efficiency of the secondary battery.

[0066] In some embodiments, the first electrolyte material includes a halide solid electrolyte material. Halide solid electrolyte materials have high ionic conductivity, which can increase the diffusion rate of active ions at the interface between the matrix and the first electrolyte material, thereby reducing interfacial impedance and improving the rate performance and cycle performance of the secondary battery.

[0067] In some embodiments, the halide solid electrolyte material includes materials with the chemical formula Li. x M1 a M2 b M3 c Q d X e The materials are defined as follows: 1≤x≤4, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 3≤e≤6, a+b+c=1; M1 includes one or more of B, Al, Ga, In, Sc, Y, La, Ce, Lu, Yb, Ho, Er, Tb, and Dy; M2 includes one or more of Si, Ge, Sn, Ti, Zr, and Hf; M3 includes one or more of V, Nb, and Ta; Q includes O and / or S; and X includes one or more of F, Cl, Br, and I. These halide solid electrolyte materials exhibit good stability under high voltage and good compatibility with the substrate. They can improve the diffusion rate of active ions at the substrate-electrolyte interface, which is beneficial for reducing interfacial impedance and improving the rate performance and cycle performance of secondary batteries.

[0068] In some embodiments, the first electrolyte material includes Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.6 In 0.6 Zr 0.4 Cl6, Li 1.5 ZrOCl 3.5 Li3InO 0.2 Cl 5.6 LiNbOCl4, LiNbOCl 3.6 F 0.4 Li 1.5 AlOCl 2.5 、Li3In 0.5 Y 0.5 One or more of Cl6.

[0069] In some embodiments, the thickness of the coating material is 50 nm to 100 nm. A coating material thickness within this range is beneficial for suppressing interfacial reactions between the cathode material matrix and the second electrolyte material, while also enabling the cathode material to possess a good lithium-ion transport rate. For example, the thickness of the coating material is a value within the range of 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any combination thereof.

[0070] In this disclosure, the thickness of the coating material has a meaning known in the art and can be measured using methods and instruments known in the art. For example, the cathode material of this disclosure can be dispersed in an ethanol solvent, dropped onto a microgrid support film, and the thickness of the coating material can be measured multiple times using a high-resolution transmission electron microscope. The average value of the multiple measurements is taken as the thickness of the coating material.

[0071] In some embodiments, the mass ratio of the conductive material, the first electrolyte material, and the matrix in the cathode material is (0.1–0.3):1:(20–50). A mass ratio of the conductive material, the first electrolyte material, and the matrix within this range is beneficial for constructing good ion and electron transport channels on the surface of the cathode material, thereby improving the ionic and electronic conductivity of the cathode material. This, in turn, helps to balance the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery.

[0072] In some embodiments, the ionic conductivity of the cathode material is 0.8 × 10⁻⁶. -5 S / cm~8×10 -5 S / cm, optionally, is 4 × 10 -5 S / cm~8×10 -5 S / cm. Ionic conductivity of the cathode material within the above range is beneficial for improving the rate performance and cycle performance of the secondary battery. For example, the ionic conductivity of the cathode material is 0.8 × 10⁻⁶ S / cm. -5 S / cm, 1×10 -5 S / cm, 2×10 -5 S / cm, 4×10 -5 S / cm, 6×10 -5 S / cm, 8×10 -5 The value between S / cm or any two of them.

[0073] In this disclosure, the term "ionic conductivity" refers to the rate of movement and migration of ions in an electrolyte, reflecting the electrolyte's ability to conduct current.

[0074] In this disclosure, the ionic conductivity of the cathode material can be measured using instruments or methods known in the art. Specifically, a second electrolyte material (sulfide solid electrolyte Li6PS5Cl) and the cathode material are mixed at a mass ratio of 1:9 to obtain a composite cathode powder. 100 mg of the composite cathode powder is placed in a mold and pressed into a sheet under a pressure of 20 MPa to obtain a test film. Subsequently, sulfide solid electrolyte Li6PS5Cl is added to both sides of the test film, and the film is cold-pressed twice under a pressure of 20 MPa to obtain a solid electrolyte film. Then, an indium sheet and a composite copper-lithium sheet are added to both sides of the solid electrolyte film. The resulting test system includes an indium sheet, a solid electrolyte film, a cathode sheet, a solid electrolyte film, and a composite copper-lithium sheet (with the lithium sheet facing the solid electrolyte film side) arranged sequentially. At 30°C, the system under test is connected to an electrochemical workstation, and electrochemical impedance spectroscopy (EIS) is performed with a bias voltage of 10mV and a frequency range of 106Hz to 10Hz to obtain an electrochemical impedance spectrum. The intersection of the curve in the electrochemical impedance spectrum from the high frequency band to the low frequency band with the Z' axis is recorded as the impedance value R.

[0075] In addition, the impedance value R' of the above system without the membrane under test is tested. That is, the system under test includes an indium sheet, a solid electrolyte membrane, and a composite copper-lithium sheet arranged in sequence (the lithium sheet faces the solid electrolyte membrane). The actual impedance value of the composite positive electrode powder is calculated to be R0 = R - R'. Based on the actual impedance value R0, the ionic conductivity of the positive electrode is calculated according to the formula κ = d / (R0 × A), where κ is the ionic conductivity, d is the thickness of the membrane under test, and A is the contact area between the membrane under test and the solid electrolyte membrane.

[0076] In some embodiments, the electronic conductivity of the cathode material is 1×10⁻⁶. -5 S / cm ~ 5×10 -5 S / cm, optionally, is 3 × 10 -5 S / cm ~ 5×10 -5 S / cm. Electronic conductivity of the cathode material within the above range is beneficial for improving the initial coulombic efficiency of the secondary battery. For example, the electronic conductivity of the cathode material is 1×10⁻⁶ S / cm. -5 S / cm, 1.2×10 -5 S / cm, 1.5×10 -5 S / cm, 2×10 -5 S / cm, 3×10 -5 S / cm, 4×10 -5 S / cm, 5×10 -5 The value between S / cm or any two of them.

[0077] In this disclosure, the electronic conductivity of the cathode material can be tested using instruments or methods known in the art. Specifically, 120 mg to 150 mg of cathode material powder is added to an alumina sleeve, and stainless steel molds are used on both sides of the sleeve. The sleeve is pressed into a sheet under a pressure of 20 MPa to obtain a test sheet. A DC polarization test is performed on the test sheet, with the test voltage set to 300 mV. After reaching a steady state, the steady-state current is obtained. The resistance of the cathode material is the test voltage / steady-state current. The electronic conductivity of the cathode material is calculated using the formula σ = L / (R × A), where σ is the electronic conductivity, L is the thickness of the test sheet, A is the steady-state current, and R is the resistance.

[0078] In this disclosure, the term "electronic conductivity" is a physical quantity that describes the electrical conductivity of a material, specifically referring to the ability of electrons to conduct electricity in a solid conductor.

[0079] In some embodiments, the positive electrode film layer further includes a second electrolyte material, which includes one or more of sulfide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials. Sulfide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials have high ionic conductivity, which can improve the diffusion rate of active ions at the interface between the positive electrode material and the second electrolyte material, thus helping to reduce polarization and improve the rate performance and cycle performance of the secondary battery.

[0080] For example, the sulfide solid electrolyte includes one or more of binary compounds such as Li6PS5Cl, Li3PS4, Li2S-P2S5, Li2S-GeS2, and Li2S-SiS2, and ternary compounds such as Li2S-MeS2-P2S5 (Me = Si, Ge, Sn, Al, etc.). The oxide solid electrolyte includes lithium lanthanum zirconium oxide series oxides or tin oxide solid electrolytes. The polymer solid electrolyte includes one or more of polyethylene oxide, poly(vinylidene fluoride-co-hexafluoropropylene), and poly(ethylene glycol) methacrylate.

[0081] In some embodiments, the mass ratio of the positive electrode material to the second electrolyte material in the positive electrode film layer is (7–9.5):1. A mass ratio within this range is beneficial for increasing the diffusion rate of active ions at the interface between the positive electrode material and the second electrolyte material, thereby reducing polarization and improving the rate performance and cycle performance of the secondary battery. For example, the mass ratio of the positive electrode material to the second electrolyte material in the positive electrode film layer is a value within a range of 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, or any combination thereof.

[0082] In some embodiments, the matrix includes one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds.

[0083] For example, lithium-containing transition metal oxides include lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 One or more of O2 and its modified compounds.

[0084] For example, lithium-containing phosphates include one or more of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0085] In some embodiments, the secondary battery further includes a negative electrode and a solid electrolyte membrane, the solid electrolyte membrane being located between the positive and negative electrode. Exemplarily, the solid electrolyte membrane includes one or more of sulfide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials.

[0086] Methods for preparing secondary batteries

[0087] The second aspect of this disclosure provides a method for preparing a secondary battery, used to prepare the secondary battery described in the first aspect. The method for preparing the secondary battery includes the following steps: a first mixing step, comprising adding a matrix, a first electrolyte material, and a conductive material into a ball mill jar, and performing a first ball milling treatment under conditions of a ball-to-material ratio of (5-15):1, a ball milling speed of 150 rpm to 300 rpm, and a ball milling time of 10 min to 30 min, to obtain a first mixed powder, wherein the volume distribution particle size Dv50 of the first electrolyte material is less than or equal to 1 μm; a second mixing step, comprising continuing to add a mixed powder of the first electrolyte material and the conductive material to the first mixed powder, performing a second ball milling treatment under the same ball milling conditions as the first ball milling treatment, repeating the second mixing step multiple times to obtain a second mixed powder; and a heat treatment step, comprising heat treating the second mixed powder to obtain a positive electrode material.

[0088] In this disclosure, by repeatedly adding a first electrolyte material and a conductive material, the first electrolyte material and the conductive material can be uniformly mixed on the substrate surface. Then, heat treatment can further promote the interaction between the first electrolyte material and the conductive material and the substrate, thereby obtaining a uniform and stable coating material. The first electrolyte material and the conductive material in the coating material can construct ion transport channels and electron transport channels on the surface of the cathode material, which is beneficial to improving the ionic conductivity and electronic conductivity of the cathode material, and thus helps to balance the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery.

[0089] By controlling the ball milling conditions of the first and second ball milling processes within the aforementioned range, the generated energy can break down the first electrolyte material and the conductive material with a volume distribution particle size Dv50 less than or equal to 1 μm, thereby forming an amorphous coating material on the substrate surface while keeping the substrate in a crystalline state. The amorphous coating material has lower mechanical strength, which allows for better interfacial contact with the substrate, reducing the impedance at the interface and improving the electron transport efficiency between the coating material and the substrate. At the same time, the grain boundary effect of the amorphous coating material is not significant, which helps to improve the bulk electronic conductivity of the cathode material, thereby further improving the initial coulombic efficiency of the secondary battery. When the ball milling conditions meet one or more of the following: ball-to-material ratio less than 5:1, ball milling speed less than 150 rpm, and ball milling time less than 10 min, the resulting milling energy is too low to break down the first electrolyte material into an amorphous coating material. When the ball milling conditions meet one or more of the following: ball-to-material ratio greater than 15:1, ball milling speed greater than 300 rpm, and ball milling time greater than 30 min, although an amorphous coating material can be formed on the substrate surface, the excessive milling energy significantly reduces the crystallinity of the substrate, resulting in an amorphous substrate and thus reducing the capacity of the cathode material. When the volumetric particle size Dv50 of the first electrolyte material is greater than 1 μm, ball milling cannot completely break it down, causing the first electrolyte material to coat the substrate surface in the form of crystalline particles.

[0090] In some embodiments, the ball-to-material ratio of the first ball milling process is (5 to 15):1, optionally (5 to 10):1, and exemplaryly, the ball-to-material ratio is a value between 5:1, 7:1, 10:1, 13:1, 15:1, or any combination thereof.

[0091] In some embodiments, the ball milling speed of the first ball milling process is 150 rpm to 300 rpm, optionally 200 rpm to 240 rpm. For example, the ball milling speed is a value between 150 rpm, 180 rpm, 200 rpm, 220 rpm, 240 rpm, 250 rpm, 280 rpm, 300 rpm, or any combination thereof.

[0092] In some embodiments, the ball milling time for the first ball milling process is 10 min to 30 min, optionally 10 min to 20 min, and exemplaryly, the ball milling time is a value between 10 min, 15 min, 20 min, 25 min, 30 min, or any combination thereof.

[0093] In some embodiments, the volume distribution particle size Dv50 of the first electrolyte material is less than or equal to 1 μm. For example, the volume distribution particle size Dv50 of the first electrolyte material is a value between 1 μm, 0.8 μm, 0.6 μm, 0.4 μm, 0.2 μm, 0.1 μm, or any combination thereof.

[0094] In this disclosure, the volume distribution particle size Dv50 of the first electrolyte material is the particle size corresponding to a cumulative volume distribution percentage of 50%, which can be determined using instruments and methods known in the art. For example, it can be tested using a laser particle size analyzer with reference to standard GB / T 19077-2016. Specifically, under an inert gas pressure of 4 bar, a Mastersizer 3000 laser particle size analyzer (UK Malvern Instruments Ltd.) is used to perform a dry test on 0.5 g of the first electrolyte material. Based on the test data, a particle size volume distribution map and a particle size number distribution map are plotted to obtain the volume distribution particle size Dv50 of the first electrolyte material.

[0095] In some implementations, one or more of the following features are included:

[0096] (1) The first ball milling process includes dry ball milling and / or wet ball milling; (2) The second ball milling process includes dry ball milling and / or wet ball milling; (3) The solvent used in the wet ball milling process includes one or more of cyclohexane, n-heptane, pseudotrimethylbenzene, m-xylene, toluene, and benzene; (4) The first ball milling process and / or the second ball milling process uses a planetary ball mill; (5) The rotation ratio of the planetary ball mill is 1:(2-4), for example, the rotation ratio of the planetary ball mill is a value between 1:2, 1:2.5, 1:3, 1:3.5, 1:4, or any combination thereof. Under the above conditions, the first ball milling process and / or the second ball milling process are beneficial to achieve more uniform dispersion of materials, improve the uniformity of mixing of the matrix, the first electrolyte material, and the conductive material, thereby forming a stable and uniform coating material on the matrix surface.

[0097] In some implementations, repeating the second mixing step multiple times includes repeating the second mixing step 3 to 5 times.

[0098] In some embodiments, in the second mixing step, the amount of the first electrolyte material added to the first mixed powder is the same as the amount of the first electrolyte material added in the first mixing step, and the amount of the conductive material added is the same as the amount of the conductive material added in the first mixing step.

[0099] In some embodiments, during the second mixing step, the amount of the first electrolyte material and the amount of the conductive material added to the first mixed powder are gradually increased.

[0100] In some embodiments, the mass ratio of the conductive material, the first electrolyte material, and the matrix in the second mixed powder is (0.1–0.3):1:(20–50). A mass ratio of the conductive material, the first electrolyte material, and the matrix in the second mixed powder within the above range is beneficial for improving the ionic and electronic conductivity of the cathode material, thereby balancing the initial coulombic efficiency, rate performance, and cycle performance of the secondary battery.

[0101] In some implementations, the heat treatment includes one or more of the following features:

[0102] (1) The heat treatment temperature is 150℃~400℃, for example, the heat treatment temperature is a value between 150℃, 200℃, 250℃, 300℃, 350℃, 400℃ or any combination thereof; (2) The heat treatment time is 2h~5h, for example, the heat treatment time is a value between 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or any combination thereof; (3) The heat treatment is carried out in an oxygen and / or inert atmosphere, the inert atmosphere including argon and / or nitrogen, and optionally, in an oxygen atmosphere. Under the above conditions, heat treatment can, on the one hand, suppress side reactions such as oxygen release from the matrix and ensure the stability of the matrix, and on the other hand, improve the stability of the coating material on the surface of the matrix.

[0103] In some embodiments, the conductive material includes conductive carbon material and / or conductive polymer; optionally, the conductive material includes conductive carbon material.

[0104] In some embodiments, the conductive carbon material includes one or more of conductive carbon black, Ketjen black, acetylene black, vapor-grown carbon fibers, and carbon nanotubes. Optionally, the conductive carbon material includes vapor-grown carbon fibers and / or carbon nanotubes.

[0105] In some embodiments, the conductive polymer includes one or more of polyaniline, polycarbazole, polythiophene, polyetheretherketone, and their respective modified compounds.

[0106] In some embodiments, the first electrolyte material includes a halide solid electrolyte material.

[0107] In some embodiments, the matrix includes one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds.

[0108] The term "secondary battery" used in this article refers to a single battery cell, a battery module, or a battery pack. These will be explained separately below.

[0109] Typically, a single rechargeable battery cell includes a positive electrode, a negative electrode, and an electrolyte membrane. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The solid electrolyte membrane is positioned between the positive and negative electrodes, serving to conduct ions and prevent short circuits between the positive and negative electrodes.

[0110] Negative electrode sheet

[0111] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0112] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0113] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0114] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this disclosure is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0115] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from 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).

[0116] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0117] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0118] In some embodiments, the negative electrode film layer also includes a solid electrolyte material.

[0119] In some embodiments, the solid electrolyte material includes one or more of sulfide solid electrolyte materials, oxide electrolyte materials, and polymer electrolyte materials. For example, the sulfide solid electrolyte includes at least one of binary compounds such as Li6PS5Cl, Li2S-GeS2, Li2S-P2S5, and Li2S-SiS2, and a ternary compound such as Li2S-MeS2-P2S5 (Me = Si, Ge, Sn, Al, etc.); the oxide solid electrolyte includes lithium lanthanum zirconium oxide series oxides or tin oxide solid electrolytes; and the polymer solid electrolyte includes one or more of PEO (polyethylene oxide), PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)), and PEGMA (poly(ethylene glycol) methacrylate).

[0120] In some embodiments, the solid electrolyte material includes Li d MX d+3 The material includes 1≤d≤6, M including one or more of Al, Ga, In, Y, Zr, Nb, Sc, Ti, Mn, and La, and X including one or more of halogens, S, O, and P.

[0121] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, solid electrolyte material, conductive agent, binder nitrile rubber and any other components, in a non-aqueous solvent (e.g. xylene) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0122] Positive electrode sheet

[0123] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer includes the positive electrode material disclosed herein, or the positive electrode material prepared according to the preparation method of the present disclosure.

[0124] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0125] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0126] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the positive electrode active material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0127] In the examples of positive electrode active materials disclosed herein, the molar content of oxygen is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of oxygen will fluctuate.

[0128] In some embodiments, the positive electrode sheet can be prepared by uniformly mixing the components used to prepare the positive electrode sheet, such as the positive electrode active material, solid electrolyte material, and conductive agent, to obtain a composite positive electrode powder. A binder, nitrile rubber, is added to the composite positive electrode powder, and the mixture is rolled to obtain a positive electrode sheet with a certain thickness.

[0129] Electrolyte membrane

[0130] In some embodiments, the secondary battery includes an electrolyte membrane, which may be a gel electrolyte membrane, a semi-solid electrolyte membrane, or a solid electrolyte membrane. The solid electrolyte membrane can be obtained by mixing one or more of the following: a binary compound such as Li6PS5Cl, Li2S-GeS2, Li2S-P2S5, or Li2S-SiS2; a ternary compound such as Li2S-MeS2-P2S5 (Me = Si, Ge, Sn, Al, etc.); and a binder such as PTFE, polyvinylidene fluoride, ethylene-tetrafluoroethylene-propylene terpolymer, ethylene-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin, and then rolling them out.

[0131] In some implementations, the positive electrode, negative electrode, and solid electrolyte membrane can be fabricated into an electrode assembly using a winding or stacking process.

[0132] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0133] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0134] This disclosure does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square battery cell 5 as an example.

[0135] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0136] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0137] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0138] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0139] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0140] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0141] Electrical appliances

[0142] The third aspect of this disclosure provides an electrical device that includes a secondary battery provided in the first aspect of this disclosure, or a secondary battery prepared by the preparation method provided in the second aspect of this disclosure.

[0143] Secondary batteries can be used as a power source for electrical devices or as an energy storage unit for electrical devices. Electrical devices can include, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0144] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0145] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0146] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0147] Example

[0148] The following describes embodiments of this disclosure. The embodiments described below are exemplary and are only used to explain this disclosure, and should not be construed as limiting this disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0149] Example 1

[0150] Preparation of secondary batteries:

[0151] (1) Preparation of cathode materials

[0152] a. First mixing step: Mix 10g of matrix LiNi0.8 Co 0.1 Mn 0.1 50mg of the first electrolyte material Li 2.6 In 0.6 Zr 0.4 Cl6 and 5 mg of conductive material VGCF were added to a 100 mL ball mill jar and ball-milled for 20 min at a ball-to-powder ratio of 10:1, a planetary ball mill rotation ratio of 1:2, and a ball milling speed of 240 rpm to obtain the first mixed powder and the first electrolyte material Li. 2.6 In 0.6 Zr 0.4 The volumetric particle size distribution (Dv50) of Cl6 is 0.94 μm;

[0153] b. Second mixing step: Add 50 mg of the first electrolyte material Li to the first mixed powder. 2.6 In 0.6 Zr 0.4 Cl6 and 5 mg of conductive material VGCF were ball-milled for 20 min under the conditions of ball-to-material ratio of 10:1, planetary ball mill rotation ratio of 1:2, and ball milling speed of 240 rpm. The second mixing step was repeated 3 times to obtain the second mixed powder.

[0154] c. Heat treatment step: After sieving the second mixed powder, transfer it to a tube furnace, perform oxygen atmosphere replacement twice, and calcine at 260℃ for 4 hours. After cooling, obtain the positive electrode material. In the positive electrode material, the conductive material is VGCF, and the first electrolyte material is Li. 2.6 In 0.6 Zr 0.4 Cl6 and matrix LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio is 0.1:1:50.

[0155] Characterization of cathode materials:

[0156] (a) Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) tests

[0157] 10 mg of cathode material powder was dispersed in 1 mL of cyclohexane solution and ultrasonically treated to obtain a dispersion. The dispersion was then dropped onto a microgrid copper grid, dried at 40 °C for 2 h, and then transferred under vacuum for transmission electron microscopy (TEM). TEM allows for high-resolution bright-field phase observation of the crystalline state of the coating material on the surface of the cathode material particles, while dark-field phase EDS analysis characterizes the elemental distribution within the coating material.

[0158] Figure 7 shows the transmission electron microscope (TEM) image and elemental superposition spectrum of the cathode material in Example 1. As shown in Figure 7, the cathode material includes an island-shaped coating material, and the coating material includes uniformly distributed Cl and In elements. Therefore, it can be proven that the first electrolyte material Li 2.6 In 0.6 Zr 0.4 Cl6 is uniformly distributed on the surface of the cathode material.

[0159] (b) Raman test

[0160] 10 mg of positive electrode material powder was compressed into a sheet and placed on a Raman observation stage. The wavelength was set to 532 nm and the test wavenumber range was 300 cm⁻¹. -1 ~200cm -1 The test area was selected as the surface of an independent cathode material particle, and observation was performed using a microscope to record the obtained Raman spectra. The Raman spectra show that the cathode material in Example 1 exhibits high Raman performance at 610 cm⁻¹. -1 A relatively weak A1g peak exists at 482 cm⁻¹. -1 An Eg peak exists at 1376 cm⁻¹. -1 A D peak exists at 1580 cm⁻¹. -1 A G peak is present, where Eg and A1g are weak characteristic signals of ternary cathode materials, and D and G peaks are characteristic signals of surface carbon materials. The peak height ratio of Eg, A1g, D, and G peaks is 1:3:11:12. The test results indicate that the coating material on the surface of the cathode material contains C elements. Therefore, it can be proved that the conductive material VGCF is distributed in the coating material on the surface of the cathode material.

[0161] (c) X-ray diffraction (XRD) test

[0162] The cathode material was tested using an X-ray powder diffractometer (instrument model: Bruker D8ADVANCE, target material: Cu Kα, voltage and current: 40KV / 40mA, scanning angle range: 10° to 70°) to obtain the X-ray diffraction pattern of the cathode material.

[0163] Figure 8 shows the X-ray diffraction pattern of the cathode material in Example 1. As shown in Figure 8, the X-ray diffraction pattern of the cathode material only shows the matrix LiNi. 0.8 Co 0.1 Mn 0.1 The diffraction peaks were observed, but the first electrolyte material Li did not appear. 2.6 In 0.6 Zr 0.4 The diffraction peaks of Cl6 and the conductive material VGCF prove that the coating material on the surface of the positive electrode material in Example 1 is amorphous.

[0164] (d) Electron conductivity test

[0165] 120 mg of positive electrode material powder was added to an alumina sleeve. Stainless steel molds were used on both sides of the sleeve, and the film was pressed under a pressure of 20 MPa to obtain the test film. DC polarization testing was performed on the test film: the test voltage was set to 300 mV, and the steady-state current was obtained after reaching steady state. The resistance of the positive electrode material was calculated as the test voltage / steady-state current. The electronic conductivity of the positive electrode material was calculated using the formula σ = L / (R × A), where σ is the electronic conductivity, L is the thickness of the test film, A is the steady-state current, and R is the resistance. In Example 1, the electronic conductivity of the positive electrode material was 1.32 × 10⁻⁶. -5 S / cm.

[0166] (e) Ion conductivity test

[0167] The second electrolyte material (Li6PS5Cl) and the cathode material were mixed at a mass ratio of 1:9 to obtain a composite cathode powder. 100 mg of the composite cathode powder was placed in a mold and pressed into a sheet under a pressure of 20 MPa to obtain the electrode to be tested. Subsequently, sulfide solid electrolyte Li6PS5Cl was added to both sides of the electrode to be tested, and the sheets were cold-pressed twice under a pressure of 20 MPa to obtain a solid electrolyte membrane. Then, an indium sheet and a composite copper-lithium sheet were added to both sides of the solid electrolyte membrane, resulting in a test system consisting of, in sequence, an indium sheet, a solid electrolyte membrane, the electrode to be tested, a solid electrolyte membrane, and a composite copper-lithium sheet (with the lithium sheet facing the solid electrolyte membrane). At 30°C, the test system was connected to an electrochemical workstation, and electrochemical impedance spectroscopy (EIS) was performed within a bias voltage of 10 mV and a frequency range from 106 Hz to 10 Hz to obtain an electrochemical impedance spectrum. The intersection point of the curve from high frequency to low frequency with the Z' axis in the electrochemical impedance spectrum was recorded as the impedance value R. Then, the impedance value R' of the above system without the electrode under test was tested. The obtained test system includes an indium sheet, a solid electrolyte membrane, and a composite copper-lithium sheet arranged sequentially (lithium sheet facing the solid electrolyte membrane). The actual impedance value of the electrode under test was calculated as R0 = R - R'. Based on the actual impedance value R0, the ionic conductivity of the electrode under test was calculated using the formula κ = d / (R0 × A), where κ is the ionic conductivity, d is the thickness of the electrode under test, and A is the contact area between the electrode under test and the solid electrolyte membrane. In Example 1, the ionic conductivity of the positive electrode material was 5 × 10⁻¹⁰. -5 S / cm.

[0168] (2) Assembly of half-cell

[0169] The second electrolyte material (Li6PS5Cl) and the above-prepared cathode material were mixed at a mass ratio of 1:9 and ground for 30 minutes to obtain a composite cathode powder. In an argon-filled glove box, 100 mg of sulfide electrolyte Li6PS5Cl was first placed in a solid mold with a diameter of 10 mm and cold-pressed for 1 minute under a pressure of 10 MPa to obtain a solid electrolyte membrane. Then, an indium sheet and a composite copper-lithium sheet were added to one side of the solid electrolyte membrane, with the indium sheet placed close to the solid electrolyte membrane, the lithium sheet facing the indium sheet, and the copper sheet serving as the outer current collector. 15 mg of the above-mentioned composite cathode powder was added to the other side of the solid electrolyte membrane, and then cold-pressed for 3 minutes under a pressure of 200 MPa to prepare a half-cell.

[0170] Half-cell performance test:

[0171] (1) First Coulomb efficiency test

[0172] At 25°C, the prepared half-cell was allowed to stand for 60 minutes, then charged at a constant current of 0.1C to 4.3V, and the charging capacity D1 was recorded. After standing for 5 minutes, the half-cell was discharged at a constant current of 0.1C to 2.6V, and the discharge capacity D0 was recorded. The initial coulombic efficiency (%) of the half-cell was calculated as D0 / D1 × 100%, and the test results are recorded in Table 2 below.

[0173] (2) Ratio Performance Test

[0174] At 25°C, the prepared half-cell was left to stand for 60 minutes, then charged to 4.3V at a constant current of 0.1C. After standing for 5 minutes, the half-cell was discharged to 2.6V at a constant current of 0.1C. This process was repeated three times. Subsequently, the charge / discharge rates of the half-cell were adjusted to 0.33C, 0.5C, and 1C, and the process was repeated sequentially. The 1C discharge capacity is the discharge performance of the half-cell at a 1C rate. The test results are recorded in Table 2 below.

[0175] (3) Cyclic performance test

[0176] At 25°C, the half-cell prepared above was charged to 4.3V with a constant current of 0.33C, then charged to 0.05C with a constant voltage, left to stand for 5 minutes, and then discharged to 2.6V with a constant current of 0.33C to obtain the first discharge capacity C1. The above process was repeated 100 times to obtain the discharge capacity C2 of the 100th cycle.

[0177] The capacity retention rate (%) of a half-cell after 100 cycles is calculated as C2 / C1 × 100%, and the test results are recorded in Table 2 below.

[0178] Examples 2 to 8

[0179] The secondary battery was prepared using the same method as in Example 1, except that the preparation process of the positive electrode material was adjusted according to Table 1 below.

[0180] Example 9

[0181] The secondary battery was prepared using the same method as in Example 1, except that steps a and b included:

[0182] a. First mixing step: Mix 10g of matrix LiNi 0.8 Co 0.1 Mn 0.1 20mg of the first electrolyte material Li 2.6 In 0.6 Zr 0.4 Cl6 and 2 mg of conductive material VGCF were added to a 100 mL ball mill jar and ball-milled for 20 min at a ball-to-powder ratio of 10:1, a planetary ball mill rotation ratio of 1:2, and a ball milling speed of 240 rpm to obtain the first mixed powder and the first electrolyte material Li. 2.6 In 0.6 Zr 0.4 The volume distribution particle size Dv50 of Cl6 is 0.94 μm (same as in Example 1);

[0183] b. Second mixing step: Continue adding 40 mg of the first electrolyte material Li to the first mixed powder. 2.6 In 0.6 Zr 0.4 Cl6 and 4 mg of conductive material VGCF were ball-milled for another 20 min under the above conditions, and then 60 mg of the first electrolyte material Li was added. 2.6 In 0.6 Zr 0.4 Cl6 and 6 mg of conductive material VGCF were ball-milled for another 20 min under the above conditions, and then 80 mg of the first electrolyte material Li was added. 2.6 In 0.6 Zr 0.4 Cl6 and 8 mg of conductive material VGCF were ball-milled for 20 min under the above-mentioned ball-milling conditions to obtain a second mixed powder. The second mixed powder contains conductive material VGCF and the first electrolyte material Li. 2.6 In 0.6 Zr 0.4 Cl6 and matrix LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio is 0.1:1:50.

[0184] Comparative Examples 1 to 4

[0185] The secondary battery was prepared using the same method as in Example 1, except that the preparation process of the positive electrode material was adjusted according to Table 1 below.

[0186] Comparative Example 5

[0187] The secondary battery was prepared using the same method as in Example 1, except that in Comparative Example 5, only the LiNi matrix was added in steps a and b. 0.8 Co 0.1 Mn 0.1 and the first electrolyte material Li 2.6 In 0.6 Zr 0.4 Cl6 undergoes a first ball milling process and a second ball milling process, so that the prepared coating material contains only the first electrolyte material Li. 2.6 In 0.6 Zr 0.4 Cl6.

[0188] Comparative Example 6

[0189] The secondary battery was prepared using the same method as Comparative Example 5. The difference was that in the assembly step of the half-cell, Comparative Example 6 mixed the second electrolyte material (Li6PS5Cl), the positive electrode material, and the conductive material VGCF in a mass ratio of 10:88:2 and then ground them for 30 minutes to obtain composite positive electrode powder.

[0190] The cathode materials prepared in Examples 2 to 9 and Comparative Examples 1 to 6 were characterized using the same test methods as in Example 1, and the half-cells prepared in Examples 2 to 9 and Comparative Examples 1 to 6 were tested for performance using the same test methods as in Example 1.

[0191] Table 1 below shows the relevant parameters of the cathode materials in Examples 1 to 9 and Comparative Examples 1 to 6, and Table 2 below shows the performance test results of the half-cells prepared in Examples 1 to 9 and Comparative Examples 1 to 6.

[0192] Table 1

[0193] In Table 1, " / " indicates that the symbol does not exist.

[0194] Table 2

[0195] As can be seen from Tables 1 and 2, compared with Comparative Example 1 (ball-to-material ratio less than 5:1), Comparative Example 1 (ball milling speed less than 150 rpm), Comparative Example 3 (ball milling time less than 10 min), Comparative Example 4 (volume distribution particle size Dv50 of the first electrolyte material greater than 1 μm), Comparative Example 5 (coating material does not contain conductive material) and Comparative Example 6 (conductive material is doped in the positive electrode film layer), Examples 1 to 9, by controlling the ball-to-material ratio to (5-15):1, the ball milling speed to 150-300 rpm, the ball milling time to 10-30 min, and the volume distribution particle size Dv50 of the first electrolyte material to be less than or equal to 1 μm, and by coating the conductive material on the substrate surface, can form an amorphous coating material on the substrate surface, thus achieving excellent first coulombic efficiency, rate performance, and cycle performance.

[0196] Examples 10 to 21

[0197] The secondary battery was prepared using the same method as in Example 1, except that the types of the first electrolyte material and the conductive material were adjusted according to Table 3 below.

[0198] The cathode materials prepared in Examples 10 to 21 were characterized using the same test methods as in Example 1, and the half-cells prepared in Examples 10 to 21 were subjected to performance tests using the same test methods as in Example 1.

[0199] Table 3 below shows the relevant parameters of the cathode materials in Examples 10 to 21, and Table 4 below shows the performance test results of the half-cells prepared in Examples 10 to 21. In addition, for ease of comparison, the relevant parameters in Example 1 are also shown here.

[0200] Table 3

[0201] Table 4

[0202] As can be seen from Tables 3 and 4, by providing the first electrolyte material and conductive material of the above types on the substrate surface in Examples 1 and 10 to 21, an amorphous coating material can be formed on the substrate surface, which can achieve excellent first coulombic efficiency, rate performance and cycle performance.

[0203] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this disclosure are included within the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included within the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A secondary battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer located on at least one side of the positive current collector and comprising a positive electrode material; The positive electrode material includes a substrate and a coating material located on at least a portion of the surface of the substrate. The coating material includes a first electrolyte material and a conductive material; and at least a portion of the coating material is amorphous on the surface of the substrate.

2. The secondary battery according to claim 1, wherein, The coating material is distributed in an island-like pattern on the surface of the substrate.

3. The secondary battery according to claim 1 or 2, wherein, The conductive material includes conductive carbon materials and / or conductive polymers.

4. The secondary battery according to claim 3, wherein, The conductive carbon material includes one or more of conductive carbon black, Ketjen black, acetylene black, vapor-grown carbon fiber, and carbon nanotubes.

5. The secondary battery according to claim 3 or 4, wherein, The conductive carbon material includes vapor-grown carbon fibers and / or carbon nanotubes.

6. The secondary battery according to any one of claims 3 to 5, wherein, The conductive polymer includes one or more of polyaniline, polycarbazole, polythiophene, polyetheretherketone, and their respective modified compounds.

7. The secondary battery according to any one of claims 1 to 6, wherein, The first electrolyte material includes a halide solid electrolyte material.

8. The secondary battery according to claim 7, wherein, The halide solid electrolyte material includes materials with the chemical formula Li x M1 a M2 b M3 c Q d X e The material has the following properties: 1≤x≤4, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤d≤1, 3≤e≤6, and a+b+c=1; M1 includes one or more of B, Al, Ga, In, Sc, Y, La, Ce, Lu, Yb, Ho, Er, Tb, and Dy; M2 includes one or more of Si, Ge, Sn, Ti, Zr, and Hf; M3 includes one or more of V, Nb, and Ta; Q includes O and / or S; X includes one or more of F, Cl, Br, and I.

9. The secondary battery according to any one of claims 1 to 8, wherein, The first electrolyte material includes Li 2.5 Y 0.5 Zr 0.5 Cl6, Li 2.6 In 0.6 Zr 0.4 Cl6, Li 1.5 ZrOCl 3.5 Li3InO 0.2 Cl 5.6 LiNbOCl4, LiNbOCl 3.6 F 0.4 Li 1.5 AlOCl 2.5 、Li3In 0.5 Y 0.5 One or more of Cl6.

10. The secondary battery according to any one of claims 1 to 9, wherein, The thickness of the coating material is 50 nm to 100 nm.

11. The secondary battery according to any one of claims 1 to 10, wherein, In the positive electrode material, the mass ratio of the conductive material, the first electrolyte material, and the matrix is ​​(0.1-0.3):1:(20-50).

12. The secondary battery according to any one of claims 1 to 11, wherein, The ionic conductivity of the positive electrode material is 0.8 × 10⁻⁶. -5 S / cm~8×10 -5 S / cm.

13. The secondary battery according to any one of claims 1 to 12, wherein, The electronic conductivity of the positive electrode material is 1×10⁻⁶. -5 S / cm ~ 5×10 -5 S / cm.

14. The secondary battery according to any one of claims 1 to 13, wherein, The positive electrode film layer further includes a second electrolyte material, which includes one or more of sulfide solid electrolyte materials, oxide solid electrolyte materials, and polymer solid electrolyte materials.

15. The secondary battery according to claim 14, wherein, In the positive electrode film layer, the mass ratio between the positive electrode material and the second electrolyte material is (7-9.5):

1.

16. The secondary battery according to any one of claims 1 to 15, wherein, The matrix includes one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds.

17. The secondary battery according to any one of claims 1 to 16, wherein, It also includes the negative electrode plate and the solid electrolyte membrane. The solid electrolyte membrane is located between the positive electrode and the negative electrode.

18. A method for preparing a secondary battery, comprising preparing a positive electrode material, wherein the preparation steps of the positive electrode material include: The first mixing step includes adding the matrix, the first electrolyte material and the conductive material into a ball mill jar, and performing a first ball milling process under the conditions of a ball-to-material ratio of (5-15):1, a ball milling speed of 150 rpm to 300 rpm and a ball milling time of 10 min to 30 min to obtain a first mixed powder, wherein the volume distribution particle size Dv50 of the first electrolyte material is less than or equal to 1 μm. The second mixing step includes adding the first electrolyte material and the conductive material mixed powder to the first mixed powder, performing a second ball milling treatment under the same ball milling conditions as the first ball milling treatment, and repeating the second mixing step multiple times to obtain the second mixed powder; The heat treatment step includes heat treating the second mixed powder to obtain the positive electrode material.

19. The preparation method according to claim 18, wherein, Includes one or more of the following features: (1) The first ball milling process includes dry ball milling and / or wet ball milling; (2) The second ball milling process includes dry ball milling and / or wet ball milling; (3) The solvent used in the wet ball milling includes one or more of cyclohexane, n-heptane, pseudotrimethylbenzene, m-xylene, toluene, and benzene; (4) The first ball milling process and / or the second ball milling process are performed using a planetary ball mill; (5) The rotation ratio of the planetary ball mill is 1:(2-4).

20. The preparation method according to claim 18 or 19, wherein, In the second mixed powder, the mass ratio of the conductive material, the first electrolyte material and the matrix is ​​(0.1-0.3):1:(20-50).

21. The preparation method according to any one of claims 18 to 20, wherein, The heat treatment includes one or more of the following features: (1) The heat treatment temperature is 150℃~400℃; (2) The heat treatment time is 2h to 5h; (3) The process shall be carried out in an oxygen and / or inert atmosphere.

22. An electrical device comprising a secondary battery according to any one of claims 1 to 17, or comprising a secondary battery prepared by the preparation method according to any one of claims 18 to 21.

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