Battery cell, electrode sheet, active material and preparation method therefor, battery device and electric device

Abstract

Disclosed in the present application are a battery cell, an electrode sheet, an active material and a preparation method therefor, a battery device and an electric device. The battery cell comprises an electrode sheet and an electrolyte, wherein the electrode sheet comprises a current collector and a film layer arranged on at least one surface of the current collector and having an active material, and the active material comprises a bulk phase material and a sodium phosphate layer that coats the surface of the bulk phase material. An XRD pattern of the sodium phosphate layer has characteristic peaks at 23.5-24.5° and 33.5-34.5°; or, the XRD pattern of the sodium phosphate layer has characteristic peaks at 20.5-21.5° and 34.0-35.0°; or, the XRD pattern of the sodium phosphate layer has characteristic peaks at 32.0-33.0° and 33.0-34.0°. According to the embodiments of the present application, the reliability and rate performance of the battery cell can be improved.

Description

Battery cells, electrodes, active materials and their preparation methods, battery devices and electrical devices

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese patent application 202411746155.X, filed on November 29, 2024, entitled “Battery cell, electrode, active material and preparation method thereof, battery device and power device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to battery cells, and more particularly to a battery cell, electrode, active material, preparation method thereof, battery device and power-consuming device. Background Technology

[0004] Because battery cells can convert chemical energy into electrical energy, they have become one of the important energy sources for human production and life, and are therefore widely used in many fields such as power tools, electric vehicles, and electronic devices to provide them with power.

[0005] With the widespread application of battery cells in various fields, the requirements for their performance are becoming increasingly stringent. Among these requirements, the reliability and rate performance of battery cells have become key areas of focus. Therefore, improving the reliability and rate performance of battery cells is one of the most pressing technical challenges that needs to be addressed. Summary of the Invention

[0006] This application provides a battery cell, electrode, active material, preparation method thereof, battery device, and power-consuming device, which can improve the reliability and rate performance of the battery cell.

[0007] In a first aspect, embodiments of this application provide a battery cell, including an electrode and an electrolyte. The electrode includes a current collector and a film layer having an active material disposed on at least one surface of the current collector. The active material includes a bulk material and a sodium phosphate layer coated on the surface of the bulk material. The sodium phosphate layer has characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0008] This application embodiment, by depositing a sodium phosphate layer with characteristic peaks at specific locations on the surface of the bulk material, can better isolate the bulk material and the electrolyte, thereby reducing the possibility of side reactions between the bulk material and the electrolyte, and thus improving the reliability of the battery cell. Simultaneously, by introducing a sodium phosphate layer with characteristic peaks at specific locations—that is, a long-range ordered sodium phosphate layer—the ion transport performance of the sodium phosphate layer can be improved, thereby enhancing the rate performance of the battery cell.

[0009] In any embodiment of this application, the thickness of the sodium phosphate salt layer is 15–50 nm.

[0010] In any embodiment of this application, the bulk material includes one or more of lithium-ion active materials and sodium-ion active materials, wherein the sodium-ion active material includes layered oxides, and the layered oxides include P2-type layered oxides and / or O3-type layered oxides.

[0011] In any embodiment of this application, the general chemical formula of sodium phosphate is NaMPO4, wherein M is selected from one or more of Mg, Ca and Zn elements.

[0012] In any embodiment of this application, the sodium phosphate salt includes one or more of NaZnPO4, NaCaPO4, and NaMgPO4.

[0013] In any embodiment of this application, the general chemical formula of the layered oxide is Na. x Ni a Fe b Mn c N d O2; where N is selected from one or more of Cu, Zn and Ti elements, 0.85≤x≤1, 0.2≤a≤0.45, 0.1≤b≤0.35, 0.25≤c≤0.45, 0.0≤d≤0.15, and a+b+c+d=1.

[0014] In any embodiment of this application, a doped layer is further included between the layered oxide and the sodium phosphate layer. The doped layer includes a metal element, which includes one or more of Mg, Ca and Zn.

[0015] In any embodiment of this application, the molar ratio of sodium phosphate layer to layered oxide is 0.25:100 to 2.5:100, wherein the number of moles of sodium phosphate layer is in terms of the number of moles of element M, and the number of moles of layered oxide is in terms of the number of moles of element Na.

[0016] Secondly, embodiments of this application provide an electrode, the electrode comprising a current collector and a film layer having an active material disposed on at least one surface of the current collector, the active material comprising a bulk material and a sodium phosphate layer coated on the surface of the bulk material; the sodium phosphate layer having characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer having characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer having characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0017] This application embodiment, by depositing a sodium phosphate layer with characteristic peaks at specific locations on the surface of the bulk material, can better isolate the bulk material and the electrolyte, thereby reducing the possibility of side reactions between the bulk material and the electrolyte, and thus improving the reliability of the battery cell. Simultaneously, by introducing a sodium phosphate layer with characteristic peaks at specific locations—that is, a long-range ordered sodium phosphate layer—the ion transport performance of the sodium phosphate layer can be improved, thereby enhancing the rate performance of the battery cell.

[0018] Thirdly, embodiments of this application provide an active material, which includes a bulk material and a sodium phosphate layer coated on the surface of the bulk material; the sodium phosphate layer has characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0019] This application embodiment, by depositing a sodium phosphate layer with characteristic peaks at specific locations on the surface of the bulk material, can better isolate the bulk material and the electrolyte, thereby reducing the possibility of side reactions between the bulk material and the electrolyte, and thus improving the reliability of the battery cell. Simultaneously, by introducing a sodium phosphate layer with characteristic peaks at specific locations—that is, a long-range ordered sodium phosphate layer—the ion transport performance of the sodium phosphate layer can be improved, thereby enhancing the rate performance of the battery cell.

[0020] In any embodiment of this application, the thickness of the sodium phosphate salt layer is 15–50 nm.

[0021] In any embodiment of this application, the general chemical formula of sodium phosphate is NaMPO4, wherein M is selected from one or more of Mg, Ca and Zn elements.

[0022] In any embodiment of this application, the general chemical formula of the layered oxide is Na. x Ni a Fe b Mnc N d O2; where N is selected from one or more of Cu, Zn and Ti elements, 0.85≤x≤1, 0.2≤a≤0.45, 0.1≤b≤0.35, 0.25≤c≤0.45, 0.0≤d≤0.15, and a+b+c+d=1.

[0023] In any embodiment of this application, the molar ratio of sodium phosphate layer to layered oxide is 0.25:100 to 2.5:100, wherein the number of moles of sodium phosphate layer is in terms of the number of moles of element M, and the number of moles of layered oxide is in terms of the number of moles of element Na.

[0024] Fourthly, embodiments of this application provide a method for preparing an active material, comprising: obtaining a bulk material; mixing the bulk material, a sodium source, a metal source, and a phosphorus source in a certain ratio, and obtaining the active material after heat treatment; the active material includes the bulk material and a sodium phosphate layer coated on the surface of the bulk material, wherein the sodium phosphate layer has characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0025] This application embodiment involves reacting a sodium source, a metal source, a phosphorus source, and a bulk material, followed by heat treatment within a suitable range, to generate a sodium phosphate layer with a long-range ordered structure on the surface of the bulk material. Compared to related technologies that only utilize the residual alkali on the surface of the bulk material as a source of sodium and only obtain a short-range disordered sodium phosphate layer, this application, by introducing an additional sodium source and controlling appropriate raw material ratios and heat treatment parameters, can obtain a sodium phosphate layer with a long-range ordered structure.

[0026] In any embodiment of this application, the sodium source includes one or more of sodium oxide, sodium carbonate, and sodium bicarbonate; the metal source includes one or more of metal oxide, metal carbonate, and metal bicarbonate; and the phosphorus source includes one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0027] In any embodiment of this application, the molar ratio of sodium source, metal source and phosphorus source is 1.0:1.0~1.5:1.0~1.5, wherein the molar number of sodium source, metal source and phosphorus source is calculated in terms of the molar number of sodium element, metal element and phosphorus element, respectively.

[0028] In any embodiment of this application, the bulk material comprises layered oxides.

[0029] In any embodiment of this application, the ratio of the number of moles of the metal source to the number of moles of the layered oxide is 0.005:1 to 0.020:1, wherein the number of moles of the metal source is calculated in terms of the number of moles of the metal element, and the number of moles of the layered oxide is calculated in terms of the sodium element therein.

[0030] In any embodiment of this application, the heat treatment temperature is 500–900°C, and the heat treatment time is 5–12 hours.

[0031] Fifthly, embodiments of this application provide a battery device including a battery cell as described in the first aspect.

[0032] In a sixth aspect, embodiments of this application provide an electrical device including a battery cell as described in the first aspect. Attached Figure Description

[0033] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 shows a schematic diagram of a battery cell provided in some embodiments of this application.

[0035] Figure 2 shows an exploded view of a battery cell provided in some embodiments of this application.

[0036] Figure 3 shows a schematic diagram of a battery module provided in some embodiments of this application.

[0037] Figure 4 shows a schematic diagram of a battery pack provided in some embodiments of this application.

[0038] Figure 5 is an exploded view of the battery pack shown in Figure 4.

[0039] Figure 6 shows a schematic diagram of an electrical device provided in some embodiments of this application.

[0040] Figure 7 is a scanning electron microscope (SEM) image of the active material prepared in Example 1 of this application.

[0041] Figure 8 is a scanning electron microscope image of the active material prepared in Comparative Example 1 of this application.

[0042] Figure 9 shows the X-ray diffraction (XRD) pattern of the active material prepared in Example 1 of this application.

[0043] Figure 10 shows the cycle performance of a single battery cell in Embodiment 1 and Comparative Example 1 of this application.

[0044] The accompanying drawings are not necessarily drawn to scale.

[0045] The reference numerals in the attached diagram are explained as follows: 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate. Detailed Implementation

[0046] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0047] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0048] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, electrode, active material, preparation method thereof, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters 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 application and are not intended to limit the subject matter of the claims.

[0049] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a 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 understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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 application, unless otherwise stated, the numerical range "a–b" 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.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0051] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0052] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates 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.

[0053] During high-voltage cycling, individual battery cells undergo side reactions with the electrolyte, resulting in significant polarization and affecting the rate performance and capacity of the cells. Furthermore, during ion insertion / extraction, volume changes in the bulk material cause layer slippage of the bulk material particles, exposing new bulk material surfaces and exacerbating the side reactions between the bulk material and the electrolyte.

[0054] In view of this, embodiments of this application provide a battery cell, electrode, active material and its preparation method, battery device and power-consuming device, which can improve the reliability and rate performance of the battery cell.

[0055] battery cell

[0056] This application provides a battery cell, including an electrode and an electrolyte. The electrode includes a current collector and a film layer having an active material disposed on at least one surface of the current collector. The active material includes a bulk material and a sodium phosphate layer coated on the surface of the bulk material. The sodium phosphate layer has characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0057] Compared to related technologies that use oxide-based coatings, which have lower ionic conductivity and slower ion transport, this application's embodiments, by providing a coating layer on the surface of the bulk material, can reduce the possibility of layer slippage during electrode insertion / extraction, thereby reducing the likelihood of cell polarization. It can also isolate the bulk material from the electrolyte, reducing the possibility of side reactions between the bulk material and the electrolyte, thus improving the reliability of the cell. Simultaneously, by introducing a sodium phosphate layer with characteristic peaks at specific locations—that is, a long-range ordered sodium phosphate layer—the sodium phosphate salts in the layer are arranged in an orderly manner, providing more and more efficient ion transport channels to improve the ion transport performance of the coating layer, thereby improving the rate performance of the cell.

[0058] The presence of characteristic peaks at specific positions in the sodium phosphate layer of this application indicates that the atoms in the sodium phosphate are arranged in a long-range ordered manner. For example, when the sodium phosphate layer is NaZnPO4, the presence of characteristic peaks at 20.5–21.5° and 34.0–35.0° indicates that NaZnPO4 is long-range ordered. When the sodium phosphate layer is NaCaPO4, the presence of characteristic peaks at 32.0–33.0° and 33.0–34.0° indicates that NaCaPO4 is long-range ordered. When the sodium phosphate layer is NaMgPO4, the presence of characteristic peaks at 23.5–24.5° and 33.5–34.5° indicates that NaMgPO4 is long-range ordered.

[0059] The characteristic peaks of sodium phosphate in the embodiments of this application have meanings known in the art and can be tested using conventional methods. As an example, the following testing method can be used: The active material on the sample (electrode) to be tested is scraped off in a drying room or glove box, and the sample is prepared. After sample preparation, a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS (Germany) is used with CuKα rays as the radiation source, and the ray wavelength is... The 2θ angle was scanned in the range of 5° to 60° at a scanning rate of 4° / min. After the test, the XRD diffraction peaks of the sample were compared with the standard card of the XRD analysis software.

[0060] In some embodiments, the thickness of the sodium phosphate layer is 15–50 nm.

[0061] The sodium phosphate layer in this embodiment has a suitable thickness range, which can reduce the possibility of the sodium phosphate layer hindering ion transport while isolating the bulk material, thereby improving the reliability and rate performance of the battery cell.

[0062] The thickness of the sodium phosphate salt layer can be determined using methods known in the art. As an example, a cross-section of the active material particles can be prepared using a cross-section polisher (such as the JEOL IB-09010CP argon ion cross-section polisher), passing through the core of the active material particles. Then, elemental analysis using EDX or EDS combined with TEM or SEM (such as the Oxford Instruments X-Max EDS combined with the ZEISS Sigma-02-33 SEM) is performed to obtain an elemental distribution map of the cross-section. The thickness of the coating layer is then determined based on the elemental distribution of the cross-section. More precisely, the thickness of the coating layer can be measured at multiple (more than 3, such as 8, 10, 12, etc.) different locations on the cross-section, and the average value is recorded as the coating layer thickness.

[0063] Optionally, the thickness of the sodium phosphate layer is independently selected from any value or a range between any two of 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm, 45nm, 46nm, 47nm, 48nm, 49nm, and 50nm.

[0064] In some embodiments, the bulk material includes one or more of lithium-ion active materials and sodium-ion active materials, wherein the sodium-ion active material includes layered oxides, and the layered oxides include P2-type layered oxides and / or O3-type layered oxides.

[0065] In some embodiments, the molar ratio of sodium phosphate layer to layered oxide is 0.25:100 to 2.5:100, wherein the number of moles of sodium phosphate layer is in terms of the number of moles of element M, and the number of moles of layered oxide is in terms of the number of moles of element Na.

[0066] The embodiments of this application have a suitable ratio of sodium phosphate salt layer and layered oxide, which can take into account both the energy density brought by the layered oxide and the coating effect of sodium phosphate salt layer.

[0067] The molar ratio of sodium phosphate salt layer to layered oxide in the embodiments of this application has a meaning known in the art and can be tested using conventional methods. As an example, the following test method can be used: the elemental proportions of the sodium-coated layered cathode oxide material are determined by ICP-OES to determine the molar ratio.

[0068] Optionally, the molar ratio of sodium phosphate salt layer to layered oxide is independently selected from 0.25:100, 0.26:100, 0.27:100, 0.28:100, 0.29:100, 0.30:100, 0.35:100, 0.40:100, 0.45:100, 0.50:100, 0.55:100, 0.60:100, 0.65:100, 0.70:100, 0.75:100, 0.80:100, 0.85:100, 0.90:100, 0.95:100, 1.00: Any value from 100, 1.05:100, 1.10:100, 1.15:100, 1.20:100, 1.25:100, 1.30:100, 1.35:100, 1.40:100, 1.45:100, 1.50:100, 1.60:100, 1.70:100, 1.80:100, 1.90:100, 2.00:100, 2.10:100, 2.20:100, 2.30:100, 2.40:100, 2.50:100, or a range of values ​​between any two.

[0069] In some embodiments, the general chemical formula of sodium phosphate is NaMPO4, wherein M is selected from one or more of Mg, Ca and Zn.

[0070] In some embodiments, the sodium phosphate salt includes one or more of NaZnPO4, NaCaPO4, and NaMgPO4.

[0071] The sodium phosphate salts used in this application embodiment, with their appropriate range, can better reduce the possibility of layer slippage during electrode insertion / extraction and can also better reduce the possibility of side reactions between the bulk material and the electrolyte, thereby improving the reliability of the battery cell. Simultaneously, they can also better enhance the ion transport performance of the sodium phosphate layer, thereby improving the rate performance of the battery cell.

[0072] The types of sodium phosphate salts in the embodiments of this application can be tested using conventional methods. As an example, the following testing method can be used: Weigh 0.2g of sample into a 100mL beaker, add 10mL of 10% nitric acid solution, heat and digest at 120°C for 0.5h, and dilute to volume with a 100mL volumetric flask; then pipette 1mL to the 100mL volumetric flask and dilute to volume to obtain the test solution. Use an inductively coupled plasma optical emission spectrometer (ICP-OES, instrument brand: Agilent 5800) to determine the types and contents of elements in the test solution.

[0073] In some embodiments, the layered oxides include P2-type layered oxides and / or O3-type layered oxides.

[0074] In some embodiments, the general chemical formula of the layered oxide is Na. x Ni a Fe b Mn c N d O2; where N is selected from one or more of Cu, Zn and Ti elements, 0.85≤x≤1, 0.2≤a≤0.45, 0.1≤b≤0.35, 0.25≤c≤0.45, 0.0≤d≤0.15, and a+b+c+d=1.

[0075] The layered oxides in this application, with their suitable range, can better reduce the possibility of layer slippage during electrode insertion / extraction and can also better reduce the possibility of side reactions between the layered oxides and the electrolyte, thereby improving the reliability of the battery cell. Simultaneously, they can also better enhance the ion transport performance of the sodium phosphate layer, thereby improving the rate performance of the battery cell.

[0076] The types of layered oxides in this application embodiment can be tested using conventional methods. As an example, the following testing method can be used: Weigh 0.2g of sample into a 100mL beaker, add 10mL of 10% nitric acid solution, heat and digest at 120°C for 0.5h, and dilute to volume with a 100mL volumetric flask; then pipette 1mL to the 100mL volumetric flask and dilute to volume to obtain the test solution. Use an inductively coupled plasma optical emission spectrometer (ICP-OES, Agilent 5800) to determine the types and contents of elements in the test solution.

[0077] In some embodiments, a doped layer is further included between the layered oxide and the sodium phosphate layer. The doped layer includes a metal element, which includes one or more of Mg, Ca and Zn.

[0078] In this embodiment, a metal element is also present between the layered oxide and the sodium phosphate layer. This metal element can be doped into the surface of the layered oxide, stabilizing the octahedral structure near the metal and weakening the Ni content. 3+ The Ginger-Taylor effect reduces the degree of volume change of layered oxides during sodium insertion / extraction, thereby reducing the degree of slippage of layered oxides.

[0079] A battery cell includes an electrode assembly and an electrolyte. The electrode assembly consists of a positive electrode, a negative electrode, and a separator. The battery cell primarily functions by the movement of metal ions between the positive and negative electrodes. The positive electrode includes a positive current collector and a positive active material layer. The positive active material layer is coated on the surface of the positive current collector, and the uncoated positive current collector protrudes beyond the coated positive current collector, serving as the positive electrode tab.

[0080] In addition, the battery cell also includes a housing for housing the electrode assembly and electrolyte, wherein the electrolyte can play a role in transferring electrons between the positive and negative electrode plates.

[0081] [Positive electrode plate]

[0082] In some embodiments, 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 and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0083] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0084] As examples, positive electrode active materials may include, but are not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, lithium titanium oxides, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, lithium iron manganese phosphate and carbon composites, and their respective modified compounds.

[0085] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e D f One or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include, but is not limited to, one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include, but is not limited to, one or more of N, F, S and Cl.

[0086] In some embodiments, the positive electrode active material may simultaneously comprise lithium transition metal oxide and lithium phosphate. This is advantageous for obtaining battery cells that balance high capacity and high reliability.

[0087] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, and LiNi 1 / 2 Mn 1 / 2 O2, LiMn2O4, Li 4 / 3 Ti 5 / 3 O4, LiNi 1 / 2 Mn 1 / 2 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0088] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting sodium. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0089] In some embodiments, as an example, the positive electrode active material may include, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0090] The modified compounds for the above-mentioned positive electrode active materials can be obtained by doping and / or surface coating of the positive electrode active materials.

[0091] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0092] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylate resins, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0093] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0094] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0095] [Negative electrode plate]

[0096] In some embodiments, the negative electrode sheet may include a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0097] The negative electrode active material may be any material known in the art that can be used in battery cells. As an example, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include, but are not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include, but are not limited to, one or more of elemental tin, tin oxide, and tin alloys.

[0098] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0100] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0101] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0102] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0103] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet also includes a conductive undercoat layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.

[0104] In some embodiments, the negative electrode sheet can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0105] [Electrolytes]

[0106] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0107] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0108] Taking a lithium battery cell as an example, the electrolyte salt may include, but is not limited to, one or more of the following: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0109] Taking sodium battery cells as an example, the electrolyte salt may include, but is not limited to, one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium difluorosulfonyl imide (NaFSI), sodium difluoromethanesulfonyl imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0110] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0111] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve the overcharge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature power performance of the battery cell.

[0112] [Isolation membrane]

[0113] Battery cells using electrolytes, as well as some battery cells using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes, while allowing metal ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0114] In some embodiments, the isolation membrane includes a porous base membrane and a coating located on at least one side of the porous base membrane.

[0115] In some embodiments, the material of the separator may include at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0116] In some embodiments, the coating includes a heat-resistant layer and an adhesive layer, the heat-resistant layer being disposed between the base film and the adhesive layer, the heat-resistant layer including heat-resistant particles, and the adhesive layer including organic particles.

[0117] In some embodiments, the heat-resistant particles include one or more of inorganic particles or organic particles.

[0118] In some embodiments, inorganic particles may include one or more of the following: inorganic particles having a dielectric constant of 5 or greater, inorganic particles having ion conductivity but not storing ions, or inorganic particles capable of undergoing electrochemical reactions.

[0119] In some embodiments, inorganic particles having a dielectric constant of 5 or higher may include boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon oxides, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, hafnium dioxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride, aluminum hydroxide, barium oxide, silicon carbide, boron carbide, aluminum nitride, silicon nitride, boron nitride, calcium fluoride, barium fluoride, magnesium aluminum silicate, lithium magnesium silicate, sodium magnesium silicate, bentonite, hydropyrite, Pb(Zr,Ti)O3 (abbreviated as PZT), Pb 1-m La m Zr 1-n Ti n O3 (abbreviated as PLZT, 0 < m < 1, 0 < n < 1), Pb (Mg3Nb) 2 / 3 The inorganic particles can be selected from one or more of PbTiO3 (PMN-PT) and their respective modified inorganic particles. Optionally, the modification of each inorganic particle can be chemical modification and / or physical modification.

[0120] In some embodiments, inorganic particles that are ion-conductive but do not store ions may include Li3PO4, lithium titanium phosphate (Li3PO4), etc. x1 Ti y1 (PO4)3, Lithium aluminum titanium phosphate (Li) x2 Al y2 Ti z1 (PO4)3、(LiAlTiP) x3 O y3 Type glass, lithium lanthanum titanate (Li) x4 La y4 TiO3, lithium germanium thiophosphate (Li) x5 Ge y5 P z2 S w Lithium nitride (Li) x6 N y6 SiS2 type glass Li x7 Si y7 S z3 and P2S5 type glass Li x8 P y8 S z4One or more of the following are given: 0 < x1 < 2, 0 < y1 < 3, 0 < x2 < 2, 0 < y2 < 1, 0 < z1 < 3, 0 < x3 < 4, 0 < y3 < 13, 0 < x4 < 2, 0 < y4 < 3, 0 < x5 < 4, 0 < y5 < 1, 0 < z2 < 1, 0 < w < 5, 0 < x6 < 4, 0 < y6 < 2, 0 < x7 < 3, 0 < y7 < 2, 0 < z3 < 4, 0 < x8 < 3, 0 < y8 < 3, 0 < z4 < 7. This can improve the ion conductivity of the separator.

[0121] In some embodiments, the inorganic particles capable of undergoing electrochemical reactions may include one or more of lithium-containing transition metal oxides, lithium-containing phosphates, carbon-based materials, silicon-based materials, tin-based materials, and lithium-titanium compounds.

[0122] In some embodiments, the organic particles may include at least one of a thermoplastic resin polymer, a thermosetting resin polymer, or a crosslinked polymer.

[0123] In some embodiments, the thermoplastic resin polymer may include one or more of the following: polycarbonate organic particles, polymethyl methacrylate organic particles, polyoxymethylene organic particles, polyamide organic particles, styrene-acrylonitrile copolymer, polyphenylene sulfide organic particles, polyether ether ketone organic particles, polyimide organic particles, polysulfone organic particles, polyether sulfone organic particles, polyphenylene sulfone organic particles, polybenzimidazole organic particles, polyamide-imide organic particles, and polyethyleneimine organic particles.

[0124] In some embodiments, the thermosetting resin polymer may include one or more of the following: phenolic resin organic particles, polymer particles containing triazine ring structural units, epoxy resin organic particles, unsaturated polyester resin organic particles, urea-formaldehyde resin organic particles, and furan resin organic particles.

[0125] In some embodiments, the crosslinking polymer may include one or more of crosslinked styrene organic particles and silicon-containing organic crosslinked resin particles.

[0126] In some embodiments, the coating includes an adhesive, which may include, but is not limited to, one or more of polyacrylate adhesives, nitrile rubber adhesives, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0127] In some embodiments, the coating may further include a dispersant, such as one or more of alkylphenol polyoxyethylene ethers, polyacrylic acid dispersants, and cellulose dispersants, including but not limited to. For example, the dispersant may include one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0128] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0129] In some embodiments, the battery cell may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0130] In some embodiments, the outer packaging of the battery cell can be a hard 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 soft pack, such as a pouch. The material of the soft pack can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0131] This application does not impose any particular restrictions on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 1 shows a square battery cell 5 as an example.

[0132] In some embodiments, as shown in FIG2, the outer packaging may include a housing 51 and a cover plate 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 cover plate 53 is used to cover the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, and can be adjusted according to requirements.

[0133] The method for preparing the battery cell of this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0134] In some embodiments, the battery cells according to this application can be assembled into a battery module, and the number of battery cells contained in the battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0135] Figure 3 is a schematic diagram of a battery module 4 as an example. As shown in 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 way. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0136] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0137] 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 adjusted according to the application and capacity of the battery pack.

[0138] Figures 4 and 5 are schematic diagrams of a battery pack 1 as an example. As shown in 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. The upper box 2 covers the lower box 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0139] Polaroid

[0140] This application provides an electrode, which includes a current collector and a film layer having an active material disposed on at least one surface of the current collector. The active material includes a bulk material and a sodium phosphate layer coated on the surface of the bulk material. The sodium phosphate layer has characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0141] This application embodiment reduces the likelihood of layer slippage during ion insertion / extraction on the surface of the bulk material by forming a coating layer, thereby reducing the possibility of cell polarization. It also isolates the bulk material from the electrolyte, reducing the possibility of side reactions between the bulk material and the electrolyte, thus improving the reliability of the cell. Simultaneously, by introducing a sodium phosphate layer with characteristic peaks at specific locations—that is, a long-range ordered sodium phosphate layer—the sodium phosphate salts in the layer are arranged in an orderly manner, providing more and more efficient ion transport channels to enhance the ion transport performance of the coating layer, thereby improving the rate performance of the cell.

[0142] The characteristic peaks of sodium phosphate in the embodiments of this application have meanings known in the art and can be tested using conventional methods. As an example, the following testing method can be used: The active material on the sample (electrode) to be tested is scraped off in a drying room or glove box, and the sample is prepared. After sample preparation, a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS (Germany) is used with CuKα rays as the radiation source, and the ray wavelength is... The 2θ angle was scanned in the range of 5° to 60° at a scanning rate of 4° / min. After the test, the XRD diffraction peaks of the sample were compared with the standard card of the XRD analysis software.

[0143] Active materials

[0144] This application provides an active material comprising a bulk material and a sodium phosphate layer coated on the surface of the bulk material; the sodium phosphate layer has characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0145] This application embodiment reduces the likelihood of layer slippage during ion insertion / extraction on the surface of the bulk material by forming a coating layer, thereby reducing the possibility of cell polarization. It also isolates the bulk material from the electrolyte, reducing the possibility of side reactions between the bulk material and the electrolyte, thus improving the reliability of the cell. Simultaneously, by introducing a sodium phosphate layer with characteristic peaks at specific locations—that is, a long-range ordered sodium phosphate layer—the sodium phosphate salts in the layer are arranged in an orderly manner, providing more and more efficient ion transport channels to enhance the ion transport performance of the coating layer, thereby improving the rate performance of the cell.

[0146] The characteristic peaks of sodium phosphate in the embodiments of this application have meanings known in the art and can be tested using conventional methods. As an example, the following testing method can be used: Grind the sample to be tested finely in an agate mortar in a drying room or glove box, then pass it through a 350-mesh sieve. Take an appropriate amount of the sieved sample and place it in the center of the sample holder groove, ensuring the loose sample powder is slightly higher than the sample holder plane. Gently press a glass slide onto the sample surface to level it with the frame plane, and scrape off any excess powder. After sample preparation, use a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS (Germany) with CuKα rays as the radiation source, and the ray wavelength... The 2θ angle was scanned in the range of 5° to 60° at a scanning rate of 4° / min. After the test, the XRD diffraction peaks of the sample were compared with the standard card of the XRD analysis software.

[0147] In some embodiments, the thickness of the sodium phosphate layer is 15–50 nm.

[0148] The sodium phosphate layer in this embodiment has a suitable thickness range, which can reduce the possibility of the sodium phosphate layer hindering ion transport while isolating the bulk material, thereby improving the reliability and rate performance of the battery cell.

[0149] The thickness of the sodium phosphate salt layer can be determined using methods known in the art. As an example, a cross-section of the active material particles can be prepared using a cross-section polisher (such as the JEOL IB-09010CP argon ion cross-section polisher), passing through the core of the active material particles. Then, elemental analysis using EDX or EDS combined with TEM or SEM (such as the Oxford Instruments X-Max EDS combined with the ZEISS Sigma-02-33 SEM) is performed to obtain an elemental distribution map of the cross-section. The thickness of the coating layer is then determined based on the elemental distribution of the cross-section. More precisely, the thickness of the coating layer can be measured at multiple (more than 3, such as 8, 10, 12, etc.) different locations on the cross-section, and the average value is recorded as the coating layer thickness.

[0150] Optionally, the thickness of the sodium phosphate layer is independently selected from any value or a range between any two of 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm, 45nm, 46nm, 47nm, 48nm, 49nm, and 50nm.

[0151] In some embodiments, the general chemical formula of sodium phosphate is NaMPO4, wherein M is selected from one or more of Mg, Ca and Zn.

[0152] In some embodiments, the general chemical formula of the layered oxide is Na. x Ni a Fe b Mn c N dO2; where N is selected from one or more of Cu, Zn and Ti elements, 0.85≤x≤1, 0.2≤a≤0.45, 0.1≤b≤0.35, 0.25≤c≤0.45, 0.0≤d≤0.15, and a+b+c+d=1.

[0153] Preparation method

[0154] This application provides a method for preparing an active material, comprising: obtaining a bulk material; mixing the bulk material, a sodium source, a metal source, and a phosphorus source in a certain ratio, and then heat-treating the mixture to obtain the active material; the active material includes the bulk material and a sodium phosphate layer coated on the surface of the bulk material, wherein the sodium phosphate layer has characteristic peaks at 23.5–24.5° and 33.5–34.5° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 20.5–21.5° and 34.0–35.0° in the XRD pattern; or, the sodium phosphate layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

[0155] This application embodiment involves reacting a sodium source, a metal source, a phosphorus source, and a bulk material, followed by heat treatment within a suitable range, to generate a sodium phosphate layer with a long-range ordered structure on the surface of the bulk material. Compared to related technologies that only utilize the residual alkali on the surface of the bulk material as a source of sodium and only obtain a short-range disordered sodium phosphate layer, this application, by introducing an additional sodium source and controlling appropriate raw material ratios and heat treatment parameters, can obtain a sodium phosphate layer with a long-range ordered structure.

[0156] Those skilled in the art can prepare the corresponding bulk materials as needed.

[0157] In some embodiments, in order to better obtain a sodium phosphate salt layer with a long-range ordered structure, the sodium source includes one or more of sodium oxide, sodium carbonate, and sodium bicarbonate; the metal source includes one or more of metal oxide, metal carbonate, and metal bicarbonate; and the phosphorus source includes one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0158] In some embodiments, in order to better obtain a sodium phosphate layer with a long-range ordered structure and a sodium phosphate layer with a suitable thickness range, the molar ratio of sodium source, metal source and phosphorus source is 1.0:1.0~1.5:1.0~1.5, wherein the molar number of sodium source, metal source and phosphorus source is calculated in terms of the molar number of sodium element, metal element and phosphorus element, respectively.

[0159] Optionally, the molar ratio of the sodium source, the metal source, and the phosphorus source is independently selected from any value or a range between 1.0:1.0:1.0, 1.0:1.1:1.1, 1.0:1.2:1.2, 1.0:1.3:1.3, 1.0:1.4:1.4, 1.0:1.5:1.5.

[0160] In some embodiments, in order to better obtain a sodium phosphate layer with a long-range ordered structure and a sodium phosphate layer with a suitable thickness range, the ratio of the number of moles of the metal source to the number of moles of the layered oxide is 0.005:1 to 0.020:1, wherein the number of moles of the metal source is calculated in terms of the number of moles of the metal element, and the number of moles of the layered oxide is calculated in terms of the number of moles of sodium element therein.

[0161] Optionally, the ratio of the number of moles of the metal source to the number of moles of the layered oxide is independently selected from any value among 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.010:1, 0.011:1, 0.012:1, 0.013:1, 0.014:1, 0.015:1, 0.016:1, 0.017:1, 0.018:1, 0.019:1, 0.020:1, or any range between the two.

[0162] In some embodiments, in order to better obtain a sodium phosphate layer with a long-range ordered structure, the heat treatment temperature is 500–900°C and the heat treatment time is 5–12 h.

[0163] Optionally, the heat treatment temperature is independently selected from any value or a range between 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, and 900°C.

[0164] Optionally, the heat treatment time is independently selected from any value of 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or a range between any two.

[0165] Battery device

[0166] The battery apparatus mentioned in this application embodiment may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0167] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0168] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0169] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0170] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0171] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0172] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0173] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0174] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0175] The technical solutions described in this disclosure are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. Battery cells and battery devices are used to store or provide electrical energy.

[0176] Figure 6 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0177] Example

[0178] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0179] Examples 1-7, Comparative Examples 1-2

[0180] 1. Preparation of active materials

[0181] 1.1 Sodium source (Na₂CO₃), manganese source (Mn₂O₃), nickel source (NiO), and copper source (CuO) were mixed evenly in a specific ratio, then placed in a sagger in a box furnace and sintered at 900℃ for 15 hours. After sintering, the mixture was cooled to room temperature (20–30℃) and then crushed to obtain layered oxide NaNi. 0.3 Mn 0.3 Fe 0.3 Cu 0.1 O2.

[0182] 1.2 Weigh out the sodium source, metal source and phosphorus source according to the preset molar ratio, and then mix them evenly through a ball mill to obtain the coating material.

[0183] 1.3 Weigh the coating material and layered oxide NaNi according to the preset molar ratio. 0.3 Mn 0.3 Fe 0.3 Cu 0.1 O2 (wherein, the molar number of the coating material is calculated based on the molar number of the metal element, layered oxide NaNi) 0.3 Mn 0.3 Fe 0.3 Cu 0.1 The number of moles of O2 is calculated by the number of moles of Na in it. The mixture is thoroughly mixed using a mixing device. The mixed material is then placed in a muffle furnace for heat treatment, during which dry air is circulated. After the heat treatment is completed, the material is naturally cooled to room temperature to obtain the active material.

[0184] 2. Preparation of the positive electrode sheet

[0185] The active material, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are thoroughly mixed in an appropriate amount of solvent NMP at a mass ratio of 80:15:5 to form a uniform positive electrode slurry. The positive electrode slurry is uniformly coated on the surface of the positive electrode current collector aluminum foil, dried, cold-pressed, and then punched into a disc with a diameter of 14 mm to obtain the positive electrode sheet.

[0186] 3. Preparation of negative electrode sheet

[0187] Sodium metal sheets are used.

[0188] 4. Preparation of the separating membrane

[0189] Porous polyethylene film is used as the separator.

[0190] 5. Electrolyte

[0191] Equal volumes of ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed to obtain an organic solvent. NaClO4 was then dissolved in the organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0192] 6. Assembly

[0193] Preparation of button cell: Stack the above-mentioned positive electrode, separator, and negative electrode in sequence, so that the separator is placed between the positive electrode and the negative electrode to play a role in isolation. Add the prepared electrolyte to complete the preparation of button cell.

[0194] Table 1. Specific parameters for the preparation of active materials in Examples 1-7 and Comparative Examples 1-2.

[0195] Data Analysis

[0196] XRD Analysis: The sample to be tested was ground finely in an agate mortar and pestle and passed through a 350-mesh sieve in a drying room or glove box. An appropriate amount of the sieved sample was placed in the center of the sample holder groove, ensuring the loose sample powder was slightly higher than the sample holder plane. A glass slide was gently pressed against the sample surface to level it with the frame plane, and excess powder was scraped off. After sample preparation, a Brucker D8A_A25 X-ray powder diffractometer from Brucker AxS (Germany) was used with CuKα rays as the radiation source. The wavelength of the rays was... The 2θ angle range is 5° to 60°, and the scanning rate is 4° / min. After the test is completed, the space group of the sample can be confirmed by comparing the XRD diffraction peaks of the sample with the standard card of the XRD analysis software.

[0197] Rate performance analysis: At 25℃, the battery was charged to 4.2V at a constant current density of 15mA / g, and then discharged to 1.5V at a constant current density of 15mA / g to obtain the discharge specific capacity C0 of the coin cell. Subsequently, it underwent one charge-discharge cycle at a constant current density of 150mA / g, and the discharge specific capacity C1 was obtained. The larger the C1 / C0 value, the better the rate performance.

[0198] Cyclic performance analysis: At 25℃, the battery cell is charged at a constant current of 1C to 4.2V, and then charged at a constant voltage until the current is 0.05C. At this point, the battery cell is fully charged, and the charging capacity at this point is recorded as the first charge capacity. After the battery cell is left to stand for 5 minutes, it is discharged at a constant current of 1C to 1.5V. This completes one charge-discharge cycle, and the discharge capacity at this point is recorded as the first discharge capacity. The battery cells are subjected to cyclic charge-discharge tests using the above method, and the discharge capacity after each cycle is recorded. The battery cell capacity retention rate (%) after 100 cycles at 25℃ = discharge capacity after 100 cycles / discharge capacity of the first cycle × 100%.

[0199] Table 2 Performance of active materials and battery cells in Examples 1-7 and Comparative Examples 1-2

[0200] Note: The number of moles of sodium phosphate salt layers is calculated based on the number of moles of non-sodium metal elements, such as the layered oxide NaNi. 0.3 Mn 0.3 Fe 0.3 Cu 0.1 The number of moles of O2 is determined by the number of moles of sodium in it.

[0201] As shown in Tables 1 and 2, when the long-range ordered material obtained in the examples is used as a coating layer, it can improve the ion transport performance and the effect of isolating the electrolyte, thereby improving the rate performance and cycle stability of the battery cell.

[0202] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A battery cell, comprising an electrode and an electrolyte, wherein the electrode comprises a current collector and a film layer having an active material disposed on at least one surface of the current collector, the active material comprising a bulk material and a sodium phosphate layer coated on the surface of the bulk material; The sodium phosphate layer exhibits characteristic peaks at 23.5–24.5° and 33.5–34.5° in its XRD pattern; or, The sodium phosphate layer exhibits characteristic peaks at 20.5–21.5° and 34.0–35.0° in its XRD pattern; or, The sodium phosphate salt layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

2. The battery cell according to claim 1, wherein, The thickness of the sodium phosphate layer is 15–50 nm.

3. The battery cell according to claim 1 or 2, wherein, The general chemical formula of the sodium phosphate salt is NaMPO4, wherein M is selected from one or more of the elements Mg, Ca and Zn.

4. The battery cell according to any one of claims 1-3, wherein, The sodium phosphate salt includes one or more of NaZnPO4, NaCaPO4, and NaMgPO4.

5. The battery cell according to any one of claims 1-4, wherein, The bulk material includes one or more of lithium-ion active materials and sodium-ion active materials, wherein the sodium-ion active material includes layered oxides, and the layered oxides include P2-type layered oxides and / or O3-type layered oxides.

6. The battery cell according to claim 5, wherein, The chemical formula of the layered oxide is Na. x Ni a Fe b Mn c N d O2; Wherein, N is selected from one or more of Cu, Zn and Ti elements, 0.85≤x≤1, 0.2≤a≤0.45, 0.1≤b≤0.35, 0.25≤c≤0.45, 0.0≤d≤0.15, and a+b+c+d=1.

7. The battery cell according to claim 6, wherein, The layered oxide layer and the sodium phosphate layer are further divided into a doped layer, which includes a metal element, including one or more of Mg, Ca and Zn.

8. The battery cell according to claim 6 or 7, wherein, The molar ratio of the sodium phosphate salt layer to the layered oxide is 0.25:100 to 2.5:100, wherein the number of moles of the sodium phosphate salt layer is in terms of the number of moles of element M, and the number of moles of the layered oxide is in terms of the number of moles of element Na.

9. An electrode, the electrode comprising a current collector and a film layer having an active material disposed on at least one surface of the current collector, the active material comprising a bulk material and a sodium phosphate layer coated on the surface of the bulk material; The sodium phosphate layer exhibits characteristic peaks at 23.5–24.5° and 33.5–34.5° in its XRD pattern; or, The sodium phosphate layer exhibits characteristic peaks at 20.5–21.5° and 34.0–35.0° in its XRD pattern; or, The sodium phosphate salt layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

10. An active material, said active material comprising a bulk material and a sodium phosphate layer coated on the surface of said bulk material; The sodium phosphate layer exhibits characteristic peaks at 23.5–24.5° and 33.5–34.5° in its XRD pattern; or, The sodium phosphate layer exhibits characteristic peaks at 20.5–21.5° and 34.0–35.0° in its XRD pattern; or, The sodium phosphate salt layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

11. The active material according to claim 10, wherein, The thickness of the sodium phosphate layer is 15–50 nm; and / or, The bulk material comprises a layered oxide, wherein the molar ratio of the sodium phosphate layer to the layered oxide is 0.25:100 to 2.5:100, wherein the number of moles of the sodium phosphate layer is in terms of the number of moles of element M, and the number of moles of the layered oxide is in terms of the number of moles of element Na.

12. The active material according to claim 10 or 11, wherein, The general chemical formula of the sodium phosphate salt is NaMPO4, wherein M is selected from one or more of Mg, Ca, and Zn; and / or, The chemical formula of the layered oxide is Na. x Ni a Fe b Mn c N d O2; where N is selected from one or more of Cu, Zn and Ti elements, 0.85≤x≤1, 0.2≤a≤0.45, 0.1≤b≤0.35, 0.25≤c≤0.45, 0.0≤d≤0.15, and a+b+c+d=1.

13. A method for preparing an active material, comprising: Obtaining bulk materials; The bulk material, sodium source, metal source and phosphorus source are mixed in a certain ratio and then heat-treated to obtain the active material. The active material includes a bulk material and a sodium phosphate layer coated on the surface of the bulk material; The sodium phosphate layer exhibits characteristic peaks at 23.5–24.5° and 33.5–34.5° in its XRD pattern; or, The sodium phosphate layer exhibits characteristic peaks at 20.5–21.5° and 34.0–35.0° in its XRD pattern; or, The sodium phosphate salt layer has characteristic peaks at 32.0–33.0° and 33.0–34.0° in the XRD pattern.

14. The preparation method according to claim 13, wherein, The sodium source includes one or more of sodium oxide, sodium carbonate, and sodium bicarbonate; the metal source includes one or more of metal oxides, metal carbonates, and metal bicarbonates; and the phosphorus source includes one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate; and / or, The bulk material comprises layered oxides; and / or, The molar ratio of the sodium source, the metal source, and the phosphorus source is 1.0:1.0-1.5:1.0-1.5, wherein the molar number of the sodium source, the metal source, and the phosphorus source is calculated in terms of the molar number of sodium element, metal element, and phosphorus element, respectively; and / or, The ratio of the number of moles of the metal source to the number of moles of the layered oxide is 0.005:1 to 0.020:1, wherein the number of moles of the metal source is calculated in terms of the number of moles of the metal element, and the number of moles of the layered oxide is calculated in terms of the sodium element therein.

15. The preparation method according to claim 13 or 14, wherein, The heat treatment temperature is 500–900℃, and the heat treatment time is 5–12 hours.

16. A battery device comprising a battery cell according to any one of claims 1-8.

17. An electrical device comprising a battery cell according to any one of claims 1-8.

Images