Electrochemical device
By using a silicon-based anode and a laminated design combining ternary/phosphate cathode active materials in an electrochemical device, the problem of poor performance of ternary silicon-doped systems at low temperatures was solved, achieving high energy density and improved power performance at low temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- BEIJING CHEHEJIA AUTOMOBILE TECH CO LTD
- Filing Date
- 2025-02-27
- Publication Date
- 2026-05-08
AI Technical Summary
Existing ternary silicon-doped electrochemical devices exhibit poor performance at low temperatures, making it difficult to maintain high energy density while simultaneously improving power performance and energy retention.
The negative electrode uses silicon-based materials, while the positive electrode combines ternary materials and phosphate positive electrode active materials. By setting different film layer structures on the positive electrode, including a stack of ternary materials and phosphate positive electrode active materials, the design of the electrode assembly is optimized to improve low-temperature stability and power performance.
While maintaining high energy density at low temperatures, it significantly improves the power performance and energy retention rate of electrochemical devices, and solves the problem of performance degradation at low temperatures.
Smart Images
Figure CN224217501U_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of electrochemical technology, specifically relating to an electrochemical device. Background Technology
[0002] New energy vehicles have seen significant development in recent years as an important means of achieving carbon emission reduction globally. Lithium-ion batteries, as a common electrochemical device, have become the most popular electrochemical device due to their high operating voltage, long lifespan, and environmental friendliness, and are now widely used in pure electric vehicles, hybrid electric vehicles, smart grids, and other fields.
[0003] In recent years, people have placed more demands on electrochemical devices, such as requiring them to have high energy density. Ternary materials and silicon-based anode materials have high specific capacity. Currently, the industry has begun to improve the energy density of electrochemical devices (ternary silicon-doped systems) by adding silicon-based anode materials to the anode plates and ternary materials to the cathode plates.
[0004] However, while ternary silicon-doped systems possess high energy density, their performance at low temperatures is poor. Improving the low-temperature performance of ternary silicon-doped systems while maintaining their high energy density advantage is a pressing technical problem that needs to be solved. Utility Model Content
[0005] In view of this, the main objective of this application is to provide an electrochemical device. This electrochemical device has high energy density, while exhibiting improved power performance and energy retention at low temperatures.
[0006] To achieve the above objectives, the technical solution of this application is implemented as follows:
[0007] This application provides an electrochemical device, including an electrode assembly, the electrode assembly comprising:
[0008] A negative electrode assembly includes at least one negative electrode sheet, the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one side surface of the negative electrode current collector, the negative electrode film layer includes a silicon-based material.
[0009] The positive electrode assembly includes a phosphate positive electrode active material and a ternary material, and includes at least one positive electrode sheet alternately stacked with a negative electrode sheet. Each positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side surface of the positive current collector. The positive electrode film layer includes any one of a first film layer, a second film layer, and a laminate formed by the first film layer and the second film layer. The positive electrode active material contained in the first film layer is the ternary material, and the positive electrode active material contained in the second film layer is the phosphate positive electrode active material.
[0010] In some embodiments, at least one positive electrode includes a first positive electrode, wherein a positive electrode film layer is disposed on one side surface of the positive current collector and the other side surface of the positive current collector is exposed.
[0011] In some embodiments, at least one positive electrode includes a second positive electrode, wherein a positive electrode film layer is disposed on both sides of the positive current collector.
[0012] In some embodiments, in the second positive electrode sheet, the positive electrode film layers disposed on both sides of the positive electrode current collector contain the same positive electrode active material.
[0013] In some embodiments, the positive electrode film layers disposed on both sides of the positive electrode current collector in the second positive electrode sheet contain different positive electrode active materials.
[0014] In some embodiments, in the second positive electrode sheet, the positive electrode film layer disposed on one side of the positive current collector is the first film layer, and the positive electrode film layer disposed on the other side of the positive current collector is the second film layer.
[0015] In some embodiments, the positive electrode film layer disposed on one side of the positive electrode current collector is a first film layer, and the positive electrode film layer disposed on the other side of the positive electrode current collector is the laminate formed by the first film layer and the second film layer.
[0016] In some embodiments, the positive electrode film layer disposed on one side of the positive electrode current collector is a second film layer, and the positive electrode film layer disposed on the other side of the positive electrode current collector is the laminate formed by the first film layer and the second film layer.
[0017] In some embodiments, in the laminate, the first membrane layer is disposed between the second membrane layer and the positive current collector.
[0018] In some embodiments, in the laminate, the second membrane layer is disposed between the first membrane layer and the positive current collector.
[0019] In some embodiments, the electrochemical device further includes a housing having a receiving cavity, an electrode assembly disposed within the receiving cavity, and a positive electrode film layer adjacent to the housing comprising a second film layer.
[0020] In some embodiments, in the positive electrode assembly, the second film layer accounts for 1% to 10% of the total number of the first and second film layers.
[0021] Compared with the prior art, the beneficial effects of this application are as follows: In the electrochemical device of this application, the negative electrode uses a silicon-based material with high energy density, and at least one positive electrode uses a ternary material with high energy density, thereby endowing the electrochemical device with high energy density. Furthermore, at least one positive electrode in the electrochemical device of this application includes a phosphate positive electrode active material. Since the phosphate positive electrode active material has a low discharge potential (lower than the discharge potential of ternary materials), it can discharge at low SOC levels. In addition, due to the stable crystal structure of the phosphate positive electrode active material, it has good stability at low temperatures and is not prone to phase transitions. Therefore, the probability of a sharp decline in discharge capacity at low temperatures is low, thus the electrochemical device of this application can still maintain high power performance and energy retention at low temperatures. The electrochemical device provided by this application can maintain high energy density while having improved low-temperature performance. Attached Figure Description
[0022] Figure 1 A schematic diagram of the electrode assembly of an electrochemical device according to an embodiment of this application is shown;
[0023] Figure 2 A schematic diagram of the first positive electrode sheet according to an embodiment of this application is shown;
[0024] Figure 3 A schematic diagram showing a second positive electrode sheet according to one embodiment of this application;
[0025] Figure 4 A schematic diagram showing a second positive electrode sheet according to yet another embodiment of this application;
[0026] Figure 5 A schematic diagram showing a second positive electrode sheet according to another embodiment of this application;
[0027] Figure 6 A schematic diagram showing a second positive electrode sheet according to another embodiment of this application;
[0028] Figure 7 A schematic diagram showing a second positive electrode sheet according to yet another embodiment of this application;
[0029] Figure 8 A schematic diagram showing a second positive electrode sheet according to yet another embodiment of this application;
[0030] Figure 9 A schematic diagram showing a second positive electrode sheet according to another embodiment of this application;
[0031] Figure 10 A schematic diagram of a second positive electrode sheet according to yet another embodiment of this application is shown.
[0032] Explanation of reference numerals in the attached figures:
[0033] 100 Electrode assembly; 1 Positive electrode group; 2 Negative electrode group; 10 Positive electrode sheet, 20 Negative electrode sheet; 101 Positive current collector; 102 Positive electrode film; 102a First film layer; 102b Second film layer; 102c Laminated assembly; 10a First positive electrode sheet; 10b Second positive electrode sheet. Detailed Implementation
[0034] The technical solution of this application will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.
[0035] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.
[0036] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
[0037] Unless otherwise specified, in this application, "one or more" or "at least one" refers to any one, two, or more of the listed items. "Several" refers to any two or more.
[0038] Typically, an electrochemical device includes a positive electrode, a negative electrode, a separator, and an electrolyte. During the charging and discharging process, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.
[0039] In existing technologies, when the positive electrode comprises a ternary material and the negative electrode comprises a silicon-based material, the discharge capacity during the final discharge stage (low State of Charge, SOC) is primarily provided by the silicon-based material of the negative electrode due to the higher discharge potential of the ternary material. However, silicon-based materials have poor conductivity, and the significant volume changes during charging and discharging can cause internal cracking, increasing electron transport impedance and consequently affecting the discharge power of the electrochemical device. Existing electrochemical devices exhibit a sharp decline in discharge capacity during the low SOC stage, severely impacting their performance at low temperatures.
[0040] Based on this, this application provides an electrochemical device. See also Figures 1 to 8 The electrochemical device includes an electrode assembly 100, which comprises a positive electrode group 1 and a negative electrode group 2. The negative electrode group 2 includes at least one negative electrode sheet 20, which includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer comprises a silicon-based material. The positive electrode group 1 includes a phosphate positive electrode active material and a ternary material, and the positive electrode group 1 includes at least one positive electrode sheet 10 alternately stacked with the negative electrode sheet 20.
[0041] like Figures 2 to 8 As shown, each positive electrode 10 includes a positive current collector 101 and a positive electrode film 102 disposed on at least one side surface of the positive current collector 101. The positive electrode film 102 includes any one of a first film layer 102a, a second film layer 102b, or a laminate 102c formed by the first film layer 102a and the second film layer 102b. The positive active material contained in the first film layer 102a is a ternary material, and the positive active material contained in the second film layer 102b is a phosphate positive active material.
[0042] In the electrochemical device of this application, the negative electrode uses a silicon-based material with high energy density, and at least one positive electrode uses a ternary material with high energy density, thereby endowing the electrochemical device with high energy density. Furthermore, at least one positive electrode in the electrochemical device of this application includes a phosphate positive electrode active material. Since the discharge potential of the phosphate positive electrode active material is low (lower than that of the ternary material), it can discharge at low SOC levels. In addition, due to the stable crystal structure of the phosphate positive electrode active material, it exhibits good stability at low temperatures and is less prone to phase transitions. Therefore, the probability of a sharp decline in discharge capacity at low temperatures is low, thus the electrochemical device of this application can still maintain high power performance and energy retention at low temperatures. In summary, the electrochemical device provided by this application can maintain high energy density while possessing improved low-temperature performance.
[0043] In this application, "ternary material" refers to a composite material containing three different metallic elements. Ternary materials include, but are not limited to, lithium transition metal oxides. Examples of lithium transition metal oxides include, but are not limited to, 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 0.1 Al 0.05 At least one of O2 and its modified compounds.
[0044] In this application, phosphate cathode active material refers to cathode active material having an olivine structure. Examples of phosphate cathode active materials may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4), 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.
[0045] The components of the electrochemical device of this application are further described below:
[0046] Positive electrode group
[0047] See Figure 1 In this application, the positive electrode assembly 1 includes at least one positive electrode 10 alternately stacked with the negative electrode 20. The positive electrode assembly includes a phosphate positive electrode active material and a ternary material.
[0048] In this application, the positive electrode sheet 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 any one of a first film layer, a second film layer, or a laminate formed by the first film layer and the second film layer. In this application, the first film layer includes a ternary material, and the second film layer includes a phosphate positive electrode active material.
[0049] See Figure 2 In some embodiments, at least one positive electrode 10 includes a first positive electrode 10a, in which a positive electrode film 102 is disposed on one side surface of the positive current collector 101, and the other side surface of the positive current collector 101 is exposed. In this implementation, since the positive electrode film is only disposed on one side surface of the positive current collector 101, the direct contact between the positive electrode active material (ternary material or phosphate positive electrode active material) in the positive electrode film and the electrolyte can be reduced, thereby reducing electrolyte decomposition and improving the cycle stability of the electrochemical device.
[0050] See Figures 3 to 8 In some embodiments, at least one positive electrode 10 includes a second positive electrode 10b, in which a positive electrode film layer 102 is disposed on both sides of the positive current collector 101. In this implementation, a positive electrode film layer 102 is disposed on both sides of the positive current collector 101. This design helps to increase the contact area between the positive active material contained in the positive electrode film layer 102 and the electrolyte, thereby helping to increase the rate of lithium ion insertion / extraction in the positive active material in the electrolyte, and thus improving the fast-charging performance of the electrochemical device.
[0051] Please continue reading Figures 3 to 5 In some embodiments, in the second positive electrode 10b, the positive electrode film layers 102 disposed on both sides of the positive electrode current collector 101 contain the same positive electrode active material. Since the positive electrode film layers 102 on both sides of the positive electrode current collector 101 contain the same positive electrode active material, it is not necessary to prepare different materials for each side during the production process, thereby simplifying the production process of the positive electrode.
[0052] For example, please continue to see Figure 3 In some embodiments, a first film layer 102a is disposed on both sides of the positive current collector 101 in the second positive electrode 10b. Since the positive active material of the first film layer includes a ternary material, this is beneficial to improving the energy density of the electrochemical device.
[0053] For example, please continue to see Figure 4In some embodiments, a second film layer 102b is provided on both sides of the positive current collector 101 in the second positive electrode 10b. Since the positive active material of the second film layer includes phosphate positive active material, it is beneficial to improve the power performance and energy retention rate of the electrochemical device at low temperature.
[0054] For example, please continue to see Figures 5 to 7 In some embodiments, in the second positive electrode 10b, laminates 102c are provided on both sides of the positive current collector 101. This helps to maintain the high energy density of the electrochemical device while significantly improving the power performance and energy retention rate at low temperatures.
[0055] See Figures 8 to 10 In some embodiments, the positive electrode film layers 102 disposed on both sides of the positive electrode current collector 101 in the second positive electrode 10b contain different positive electrode active materials. Different positive electrode active materials have different electrochemical properties. By using different positive electrode active materials on both sides of the positive electrode current collector 101, optimization can be performed for different application requirements, increasing the design flexibility of the electrochemical device.
[0056] Please continue reading Figure 8 In some embodiments, in the second positive electrode 10b, the positive electrode film 102 disposed on one side of the positive electrode current collector 101 is a first film layer 102a, and the positive electrode film 102 disposed on the other side of the positive electrode current collector 102b is a second film layer 102b. This is beneficial for maintaining the high energy density of the electrochemical device while significantly improving the power performance and energy retention rate at low temperatures.
[0057] Please continue reading Figure 9 In some embodiments, in the second positive electrode 10b, the positive electrode film 102 disposed on one side of the positive electrode current collector 101 is a first film layer 102a, and the positive electrode film 102 disposed on the other side of the positive electrode current collector 101 is a laminate 102c formed by the first film layer and the second film layer. This is beneficial for maintaining the high energy density of the electrochemical device while significantly improving the power performance and energy retention rate at low temperatures.
[0058] Please continue reading Figure 10 In some embodiments, in the second positive electrode 10b, the positive electrode film 102 disposed on one side of the positive electrode current collector 101 is a second film layer 102b, and the positive electrode film 102 disposed on the other side of the positive electrode current collector 101 is a laminate 102c formed by the first film layer and the second film layer. This is beneficial for further improving the power performance and energy retention rate of the electrochemical device at low temperatures.
[0059] In the implementation of the positive electrode film layer including a stack formed by a first film layer and a second film layer, this application does not specifically limit the stacking method of the first film layer and the second film layer, and the stacking method of the first film layer and the second film layer can be set according to the requirements.
[0060] See also Figure 9 In some embodiments, in the laminate 102c, the first membrane layer 102a is disposed between the second membrane layer 102b and the positive electrode current collector 101. Since the positive electrode active material contained in the second membrane layer is a phosphate positive electrode active material, which itself has good thermal stability and high safety performance, placing the second membrane layer containing the phosphate positive electrode active material on the outside of the first membrane layer (the side away from the positive electrode current collector) is beneficial to improving the safety performance of the electrochemical device.
[0061] See also Figure 5 In some embodiments, in the laminate 102c, a second film layer 102b is disposed between the first film layer 102a and the positive electrode current collector 101. Since the phosphate positive electrode active material has good adhesion to the positive electrode current collector, placing the second film layer containing the phosphate positive electrode active material close to the current collector helps reduce the shedding of the laminate 102c and the wear of the electrode sheet.
[0062] In some implementations, please refer to Figure 5 The second film layer 102b is configured in both layers 102c on both sides of the positive electrode current collector 101 and is disposed between the first film layer 102a and the positive electrode current collector 101.
[0063] In some implementations, please refer to Figure 6 In the stacked bodies 102c on both sides of the positive electrode current collector 101, a first film layer 102a is disposed between the second film layer 102b and the positive electrode current collector 101.
[0064] In some implementations, please refer to Figure 7 The laminate 102c on one side of the positive electrode current collector 101 is configured as a second film layer 102b disposed between the first film layer 102a and the positive electrode current collector 101, and the laminate 102c on the other side is configured as a first film layer 102a disposed between the second film layer 102b and the positive electrode current collector 101.
[0065] In some embodiments, the electrochemical device further includes a housing with a receiving cavity, within which the electrode assembly is disposed, and the positive electrode film layer of the positive electrode adjacent to the housing includes a second film layer. Because the phosphate positive electrode active material has an olivine structure, this structure exhibits high stability during charge and discharge and is not easily deformed; furthermore, the phase transition of the phosphate positive electrode active material is relatively stable during charge and discharge, without drastic volume changes. Placing the positive electrode containing the phosphate positive electrode active material near the housing can further reduce the impact of such expansion on the internal structure of the electrochemical device. This helps maintain spatial stability between the electrode assemblies and avoids internal short circuits or electrode damage caused by volume changes.
[0066] In some embodiments, in the cathode assembly, the second film layer accounts for 1% to 10% of the total number of the first and second film layers. This design is beneficial for further improving the low-temperature performance of the electrochemical device. For example, the percentage of the second film layer relative to the total number of the first and second film layers can be any value within the range of 1%, 2%, 3%, 4%, 5%, 10%, or any combination thereof.
[0067] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.
[0068] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
[0069] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.
[0070] This application does not specifically limit the type of positive electrode current collector; any positive electrode current collector known in the art can be used. In some embodiments, the positive electrode 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum 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.).
[0071] Negative electrode sheet
[0072] 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, the negative electrode film layer including a negative electrode active material. In this application, the negative electrode active material includes a silicon-based material, which may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys, but is not limited thereto.
[0073] In some embodiments, the mass percentage of silicon in the silicon-based material within the negative electrode active material is between 1% and 30%. By setting the mass percentage of silicon in the silicon-based material within this range, it is beneficial to maintain the high energy density of the electrochemical device while simultaneously improving the low discharge power and low-temperature energy retention rate at low temperatures and low state of charge (SOC). For example, the mass percentage of silicon in the silicon-based material within the negative electrode active material can be any value within the range of 1%, 5%, 10%, 15%, 30%, or any combination thereof.
[0074] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can 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 can 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.).
[0075] 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).
[0076] 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.
[0077] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).
[0078] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.
[0079] electrolytes
[0080] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.
[0081] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.
[0082] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorophosphate (LiPO2F2), lithium bis(fluorosulfonyl)imide (LiTFSI), lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethylsulfonyl)methyl, or lithium bis(trifluoromethylsulfonyl)imide.
[0083] In some embodiments, the solvent comprises a carbonate, wherein the carbonate includes one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). The solvent may also comprise a carboxylic acid ester, wherein the carboxylic acid ester includes one or more of propyl propionate (PP), ethyl propionate (EP), propyl acetate (PA), and ethyl acetate (EA).
[0084] Separating membrane
[0085] In this application, the electrochemical device also includes a separator. 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.
[0086] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.
[0087] In some implementations, the positive electrode, negative electrode, and separator are fabricated into an electrode assembly using a stacking process.
[0088] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.
[0089] Preparation Example
[0090] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. 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 this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.
[0091] Preparation of positive electrode sheet
[0092] Ternary material (chemical formula LiNi) 0.8 CO 0.1 Mn 0.1 O2), conductive carbon (SP), carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) were mixed in the solvent N-methylpyrrolidone at a weight ratio of 96.8:1:1:1.2 and stirred evenly to obtain positive electrode slurry 1.
[0093] Phosphate positive electrode active material (lithium iron phosphate), conductive carbon (SP), carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) were mixed in the solvent N-methylpyrrolidone at a weight ratio of 98:0.5:0.5:1 and stirred evenly to obtain positive electrode slurry 2.
[0094] Preparation Example 1: A 12μm aluminum foil was used as the positive electrode current collector. Positive electrode slurry 1 was coated on both sides of the positive electrode current collector and baked at 95°C for 12 hours to form a positive electrode film layer. Subsequently, it was cold-pressed, cut, and slit to prepare the positive electrode sheet 1, wherein the thickness of the positive electrode film layer was 80μm.
[0095] Preparation Example 2: A 12μm aluminum foil was used as the positive electrode current collector. Positive electrode slurry 2 was coated on both sides of the positive electrode current collector and baked at 95°C for 12 hours to form a positive electrode film layer. Subsequently, it was cold-pressed, cut, and slit to prepare the positive electrode sheet 2, wherein the thickness of the positive electrode film layer was 80μm.
[0096] Preparation Example 3: A 12μm aluminum foil was used as the positive electrode current collector. Positive electrode slurry 1 was coated on one side of the positive electrode current collector, and positive electrode slurry 2 was coated on the other side of the positive electrode current collector. The foil was baked at 95°C for 12 hours to form the first film layer and the second film layer, respectively. The foil was then cold-pressed, cut, and slit to prepare the positive electrode sheet 3. The thickness of the first film layer was 80μm, and the thickness of the second film layer was 80μm.
[0097] Preparation Example 4: A 12μm aluminum foil was used as the positive electrode current collector. Positive electrode slurry 1 was coated on both sides of the positive electrode current collector and baked at 95°C for 12 hours to form a first film layer. Positive electrode slurry 2 was coated on the first film layer and baked at 95°C for 12 hours to form a second film layer. Subsequently, cold pressing, cutting and slitting were performed to prepare the positive electrode sheet 4, wherein the thickness of the first film layer is 40μm and the thickness of the second film layer is 40μm.
[0098] Preparation Example 5: A 12μm aluminum foil was used as the positive electrode current collector. Positive electrode slurry 2 was coated on both sides of the positive electrode current collector and baked at 95°C for 12 hours to form a second film layer. Positive electrode slurry 1 was coated on the formed second film layer and baked at 95°C for 12 hours to form a first film layer. Subsequently, cold pressing, cutting and slitting were performed to prepare the positive electrode sheet 5, wherein the thickness of the first film layer is 40μm and the thickness of the second film layer is 40μm.
[0099] Preparation Example 6: A 12μm aluminum foil was used as the positive electrode current collector. Positive electrode slurry 2 was coated on one side of the positive electrode current collector and baked at 95°C for 12 hours to form a second film layer. Subsequently, cold pressing, cutting and slitting were performed to prepare the positive electrode sheet 6. The thickness of the second film layer was 40μm.
[0100] Example 1
[0101] The preparation method of the electrochemical device is as follows:
[0102] (1) Preparation of positive electrode sheet
[0103] Positive electrode plates 1 and 2 are prepared as positive electrode plates according to the preparation example described above.
[0104] (2) Preparation of negative electrode sheet
[0105] A negative electrode active material (silicon-carbon material, wherein silicon accounts for 5% of the mass of the negative electrode active material), conductive carbon (SP), sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed in deionized water at a weight ratio of 97:1:1:1 and stirred evenly to obtain a negative electrode slurry. A 5μm copper foil was used as the negative electrode current collector. The negative electrode slurry was coated on both sides of the current collector and baked at 80℃ for 12 hours to form a negative electrode film. Subsequently, the film was cold-pressed, cut, and slit to prepare the negative electrode sheet.
[0106] (3) Preparation of electrolytes
[0107] Under an argon atmosphere, dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1:1 to form an organic solvent. LiPF6 is then dissolved in the organic solvent to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.
[0108] (4) Preparation of the separating membrane
[0109] A polyethylene film with a thickness of 9μm was used as the separator.
[0110] (5) Assembly of electrochemical devices
[0111] The electrode assembly is obtained by stacking the positive electrode (positive electrode 1 or positive electrode 2), the separator, and the negative electrode in that order. The stacked electrode assembly is then placed in an aluminum-plastic film (shell), dried, and injected with the prepared electrolyte. After vacuum sealing, settling, formation, and shaping, the electrochemical device is obtained. The electrode assembly comprises a 5-layer positive electrode 2 and a 45-layer positive electrode 1, meaning the number of second film layers in the electrode assembly is 10, the number of first film layers is 90, and the proportion of second film layers is 10%.
[0112] The performance of the obtained electrochemical device was tested using the following methods:
[0113] Energy density test
[0114] ① Charge the electrochemical device to 4.4V using a constant current and constant voltage at 1 / 3C.
[0115] ② Let stand for 30 minutes;
[0116] ③ Discharge to 2.5V with a current of 1 / 3C and record the discharge capacity D1 of the electrochemical device;
[0117] ④ Energy density = D1 / mass of electrochemical device.
[0118] Low-temperature (-10℃) discharge power test:
[0119] Adjust the capacity of the electrochemical device to 30% SOC:
[0120] In an environment of 25°C, the electrochemical device is charged and discharged at a fixed rate of 1 / 3C, with a charging and discharging voltage range of 2.5-4.4V. This step is repeated three times, and the discharge capacity of the third discharge is recorded as the nominal capacity C0 of the electrochemical device.
[0121] Start charging at 1 / 3 CO until 1 / 3 of the nominal capacity is reached, and adjust the SOC state of the electrochemical device to 10% SOC.
[0122] In an environment of -10℃, the electrochemical device is discharged for 30s with I = 0.36C0. The voltage values before and after the discharge are recorded as V0 and V1, respectively. (V0-V1) / 0.36C0 is recorded as the internal resistance R of the electrochemical device. The discharge power of the electrochemical device is P = V1*I.
[0123] Low-temperature (-10℃) energy retention test:
[0124] The total full-discharge energy of the electrochemical device at 25°C and at -10°C was measured using the Xinwei Power Battery Tester (model BTS-5V300A-4CH).
[0125] The energy retention rate (%) of the electrochemical device at -10℃ is calculated by dividing the total fully discharged energy of the electrochemical device at -10℃ by the total fully discharged energy of the electrochemical device at 25℃.
[0126] Example 2
[0127] The electrochemical device was prepared using the same method as in Example 1, except that, in step (5) of assembling the electrochemical device:
[0128] The electrode assembly is formed by stacking the positive electrode (positive electrode 1 or positive electrode 3), the separator, and the negative electrode in that order. The electrode assembly contains one layer of positive electrode 3 and 49 layers of positive electrode 1. That is, the number of second film layers in the electrode assembly is 1, the number of first film layers is 99, and the proportion of second film layers is 1%.
[0129] Example 3
[0130] The electrochemical device was prepared using the same method as in Example 1, except that, in step (5) of assembling the electrochemical device:
[0131] The electrode assembly is formed by stacking the positive electrode (positive electrode 1 or positive electrode 4), the separator, and the negative electrode in that order. The electrode assembly consists of a single-layer positive electrode 4 and 48-layer positive electrode 1. That is, the electrode assembly has 2 second film layers, 98 first film layers, and the second film layers account for 2% of the total number of layers.
[0132] Example 4
[0133] The electrochemical device was prepared using the same method as in Example 1, except that, in step (5) of assembling the electrochemical device:
[0134] The electrode assembly is obtained by stacking the positive electrode (positive electrode 1 or positive electrode 5), the separator, and the negative electrode in that order. The electrode assembly contains one layer of positive electrode 5 and 48 layers of positive electrode 1. That is, the number of second film layers is 2, the number of first film layers is 98, and the number of second film layers accounts for 2% of the total.
[0135] Example 5
[0136] The electrochemical device was prepared using the same method as in Example 1, except that, in step (5) of assembling the electrochemical device:
[0137] An electrode assembly is obtained by stacking positive electrode sheets (positive electrode sheet 1 or positive electrode sheet 6), separator, and negative electrode sheet in that order. The electrode assembly includes one layer of positive electrode sheet 6 and 49 layers of positive electrode sheet 1. That is, the number of second film layers is 1, the number of first film layers is 98, and the number of second film layers accounts for 1%. The positive electrode sheet 6 is disposed on one side adjacent to the housing.
[0138] Comparative Example 1
[0139] The electrochemical device was prepared using the same method as in Example 1, except that, in step (5) of assembling the electrochemical device:
[0140] The electrode assembly is obtained by stacking the positive electrode (positive electrode 1), the separator, and the negative electrode in that order. The electrode assembly contains 50 layers of positive electrode 1, and the second film layer accounts for 0% of the total number of layers.
[0141] Comparative Example 2
[0142] The electrochemical device was prepared using the same method as in Example 1, except that in Comparative Example 2, the negative electrode active material in the negative electrode sheet was carbon.
[0143] Comparative Example 3
[0144] The electrochemical device was prepared using the same method as in Example 1, except that, in step (5) of assembling the electrochemical device:
[0145] The electrode assembly is obtained by stacking the positive electrode (positive electrode 2), separator, negative electrode, and separator in that order. The electrode assembly contains 50 layers of positive electrode 2, and the second film layer accounts for 100% of the total number of layers.
[0146] The electrochemical devices obtained in Examples 2 to 5 and Comparative Examples 1 to 3 were tested using the same test methods as in Example 1. The test results are shown in Table 1 below.
[0147] Table 1
[0148]
[0149]
[0150] As shown in Table 1, compared with Comparative Examples 1 to 3, the electrochemical devices of Examples 1 to 5 can maintain a high energy density (close to or greater than 250 Wh / kg) while exhibiting significantly improved power performance and energy retention at low temperatures.
[0151] It should be noted that this application 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 application are included in the technical scope of this application. 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, without departing from the spirit of this application, are also included in the scope of this application.
Claims
1. An electrochemical device, characterized in that, Includes an electrode assembly, which includes: A negative electrode assembly, the negative electrode assembly including at least one negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode film layer disposed on at least one side surface of the negative electrode current collector, the negative electrode film layer including a silicon-based material; A positive electrode assembly, comprising a phosphate positive electrode active material and a ternary material, and the positive electrode assembly comprising at least one positive electrode sheet alternately stacked with the negative electrode sheet, wherein each positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer disposed on at least one side surface of the positive electrode current collector, the positive electrode film layer comprising any one of a first film layer, a second film layer, and a laminate formed by the first film layer and the second film layer, wherein the positive electrode active material contained in the first film layer is the ternary material, and the positive electrode active material contained in the second film layer is the phosphate positive electrode active material.
2. The electrochemical device according to claim 1, characterized in that, At least one of the positive electrode plates includes a first positive electrode plate. In the first positive electrode, the positive electrode film layer is disposed on one side surface of the positive electrode current collector, and the other side surface of the positive electrode current collector is exposed.
3. The electrochemical device according to claim 1, characterized in that, At least one of the positive electrode plates includes a second positive electrode plate. In the second positive electrode, the positive electrode film layer is disposed on both sides of the positive current collector.
4. The electrochemical device according to claim 3, characterized in that, In the second positive electrode, the positive electrode film layers disposed on both sides of the positive electrode current collector contain the same positive electrode active material.
5. The electrochemical device according to claim 3, characterized in that, In the second positive electrode, the positive electrode film layers disposed on both sides of the positive electrode current collector contain different positive electrode active materials.
6. The electrochemical device according to claim 5, characterized in that, In the second positive electrode plate The positive electrode film layer disposed on one side of the positive electrode current collector is the first film layer, and the positive electrode film layer disposed on the other side of the positive electrode current collector is the second film layer, or The positive electrode film layer disposed on one side of the positive electrode current collector is the first film layer, and the positive electrode film layer disposed on the other side of the positive electrode current collector is the laminate formed by the first film layer and the second film layer, or The positive electrode film layer disposed on one side of the positive electrode current collector is the second film layer, and the positive electrode film layer disposed on the other side of the positive electrode current collector is the laminate formed by the first film layer and the second film layer.
7. The electrochemical device according to any one of claims 1 to 6, characterized in that, In the laminate, the first film layer is disposed between the second film layer and the positive electrode current collector.
8. The electrochemical device according to any one of claims 1 to 6, characterized in that, In the laminate, the second film layer is disposed between the first film layer and the positive electrode current collector.
9. The electrochemical device according to any one of claims 1 to 8, characterized in that, It also includes a housing having a receiving cavity, the electrode assembly being disposed within the receiving cavity, and the positive electrode film layer of the positive electrode adjacent to the housing including the second film layer.
10. The electrochemical device according to any one of claims 1 to 9, characterized in that, In the positive electrode assembly, the second film layer accounts for 1% to 10% of the total number of the first film layer and the second film layer.