Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device, the electrochemical device including a positive electrode including a positive electrode active material layer including a positive electrode active material including a first positive electrode active material and a second positive electrode active material, a Raman spectrum chart of the positive electrode active material layer has a first characteristic peak at a position with a wavelength of 398 cm <-1 > to 408 cm <-1 > and has a second characteristic peak at a position with a wavelength of 940 cm <-1 > to 960 cm <-1 >, and the second positive electrode active material comprises an aluminum element. The electrochemical device has relatively high energy density and good high-temperature cycle performance at the same time.

Description

[0001] This application is based on the parent application No. 202280060050.1, filed on June 30, 2022, the applicant is Ningde New Energy Technology Co., Ltd., and the invention is named "Electrochemical device and electronic device". The divisional application is proposed. TECHNICAL FIELD

[0002] The present application belongs to the technical field of electrochemistry, and specifically relates to an electrochemical device and an electronic device. BACKGROUND

[0003] In recent years, electrochemical devices represented by lithium ion batteries have the advantages of high working voltage, environmental friendliness, small size, light weight, long cycle life, etc., and have developed rapidly in the fields of portable consumer electronics, new energy vehicles and large-scale energy storage. Lithium iron phosphate is widely used as a positive electrode material in lithium ion batteries and other electrochemical devices due to its excellent cycle performance and safety performance. With the increasing popularity of new energy vehicles, the demand for longer driving range requires higher energy density and cycle performance of the battery. SUMMARY

[0004] The purpose of the present application is to provide an electrochemical device and an electronic device, aiming to improve the energy density of the electrochemical device and improve its high-temperature cycle performance.

[0005] The first aspect of the present application provides an electrochemical device, comprising a positive electrode, a negative electrode and an electrolyte, the positive electrode comprising a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode active material, the positive electrode active material comprising a first positive electrode active material and a second positive electrode active material, wherein after the electrochemical device is fully discharged, the Raman spectrum of the positive electrode active material layer has a first characteristic peak at a wavelength of 398 cm -1 to 408 cm -1 , a second characteristic peak at a wavelength of 940 cm -1 to 960 cm -1 , and the second positive electrode active material comprises aluminum element. The first characteristic peak is the characteristic peak of the second positive electrode active material, the second characteristic peak is the characteristic peak of the first positive electrode active material, the second positive electrode active material has a higher specific capacity, and the aluminum element can enhance the stability of the manganese-oxygen bond of the second positive electrode active material during the cycle process, so that the positive electrode active material layer has a better structural stability, improving the high energy density of the electrochemical device and improving its high-temperature cycle performance.

[0006] In any embodiment of the present application, after the electrochemical device is fully discharged, the Raman spectrum of the positive electrode active material layer has a third characteristic peak at a wavelength of 591 cm -1 to 611 cm -1 , and the half-height width of the third characteristic peak is 15 cm -1Up to 60cm -1 The third characteristic peak is a characteristic peak of the second positive electrode active material. When the full width at half maximum (FWHM) of the third characteristic peak is within the specified range, it indicates that the second positive electrode active material has a stable crystal structure, which can suppress the material structure phase transition during cycling, improve the structural stability of the material, and enhance the cycling performance of the electrochemical device.

[0007] In any embodiment of this application, the full width at half maximum (FWHM) of the first characteristic peak is 15 cm. -1 Up to 60cm -1 The full width at half maximum (FWHM) of the second characteristic peak is 5 cm. -1 Up to 25cm -1 The full width at half maximum (FWHM) of the first characteristic peak is greater than that of the second characteristic peak. The crystallinity of the second positive electrode active material is lower than that of the first positive electrode active material, hence its larger FWHM. In contrast, the FWHM of the first positive electrode active material is smaller, indicating better crystallinity and less structural change during charge and discharge. The active ions inside the second positive electrode active material compensate for the loss of active ions on the surface of the negative electrode active material, ensuring the transport of active ions and improving the cycle performance of the electrochemical device.

[0008] In any embodiment of this application, the first positive electrode active material includes iron, and the second positive electrode active material includes manganese. The second positive electrode active material has a higher specific capacity, enabling the electrochemical device to have a higher discharge specific capacity. A synergistic effect occurs between the first and second positive electrode active materials. During the charging and discharging process of the electrochemical device, active ions in the second positive electrode active material are released, effectively compensating for the irreversible loss of active ions on the surface of the negative electrode active material. The remaining active ions can be inserted into the first positive electrode active material, effectively improving the capacity of the positive electrode active material and enhancing the cycle performance of the electrochemical device.

[0009] In any embodiment of this application, the positive electrode active material layer includes manganese, and the mass fraction ω of aluminum is determined based on the mass of manganese in the positive electrode active material layer. Al Satisfy: 0.1%≤ω Al ≤5%. When the mass fraction of aluminum satisfies the above relationship, it can enhance the stability of manganese-oxygen bonds in the second positive electrode active material, thereby improving the cycle performance of the electrochemical device.

[0010] In any embodiment of this application, the mass percentage of manganese element ω is based on the mass of the positive electrode active material layer. Mn With the mass percentage of iron ω Fe Satisfy: 0.01%≤ω Mn / ω Fe ≤30%, preferably, 1%≤ω Mn / ω Fe≤25%. When the mass percentages of manganese and iron are within the above range, the energy density of the electrochemical device can be further improved and its cycle performance enhanced.

[0011] In any embodiment of this application, the positive electrode active material layer contains element M, wherein element M is selected from one or more of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Cr, Sn, La, and Ce. Adding element M to the second positive electrode active material can improve the stability of the manganese-oxygen bonds within the material, inhibit the dissolution of manganese, and further improve the cycle performance and energy density of the electrochemical device.

[0012] In any embodiment of this application, the mass percentage ω of element M is based on the mass of the positive electrode active material layer. M Satisfies: 0.03% < ω M ≤2.5%. When the mass percentage of element M is within this range, the cycle performance of the electrochemical device and its energy density can be improved more effectively.

[0013] In any embodiment of this application, the electrolyte contains additives, including fluorocarbonates and / or inorganic lithium salts. Fluorocarbonates and / or inorganic lithium salts help form a dense and stable interfacial film on the surface of the positive electrode active material, further enhancing the protection of the positive electrode active material and improving the cycle performance of the electrochemical device.

[0014] In any embodiment of this application, the mass percentage of the additive is from 0.01% to 10% based on the mass of the electrolyte. A suitable mass percentage of the additive in the electrolyte helps to form an interface film of appropriate thickness on the surface of the positive electrode active material, while also exhibiting low impedance, further improving the cycle performance of the electrochemical device.

[0015] In any embodiment of this application, fluorocarbonate includes at least one of fluoroethylene carbonate and fluoropropylene carbonate.

[0016] In any embodiment of this application, the inorganic lithium salt includes at least one of lithium difluorophosphate and lithium tetrafluoroborate.

[0017] In any embodiment of this application, the mass percentage of fluorocarbonate is 0.01% to 8% based on the mass of the electrolyte.

[0018] In any embodiment of this application, the mass percentage of fluorocarbonate is 0.01% to 5% based on the mass of the electrolyte.

[0019] In any embodiment of this application, the mass percentage of inorganic lithium salt is 0.01% to 3% based on the mass of the electrolyte.

[0020] In any embodiment of this application, the mass percentage of inorganic lithium salt is 0.01% to 1.5% based on the mass of the electrolyte.

[0021] A second aspect of this application provides an electronic device that includes the electrochemical device of the first aspect of this application. Attached Figure Description

[0022] Figure 1 This is the Raman spectrum of the positive electrode active material layer in Example 1. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of this application. The embodiments of this application should not be construed as limiting this application. Based on the technical solutions and embodiments provided in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] For the sake of brevity, this article only discloses a few specific numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0025] In this description, unless otherwise stated, "above" and "below" include the stated number.

[0026] Unless otherwise stated, the terms used in this application have their common meanings as commonly understood by those skilled in the art. Unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0027] The list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0028] Electrochemical device A first aspect of this application provides an electrochemical device, including any device in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy, specific examples of which include, but are not limited to, lithium-ion batteries.

[0029] The electrochemical device in this application includes: a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive electrode active material layer, which includes a positive electrode active material. The positive electrode active material includes a first positive electrode active material and a second positive electrode active material. After full discharge, the Raman spectrum of the positive electrode active material layer of the electrochemical device is at a wavelength of 398 cm⁻¹. -1 Up to 408cm -1 The position has the first characteristic peak at a wavelength of 940 cm⁻¹. -1 Up to 960cm -1 The position of the second characteristic peak indicates that the second positive electrode active material includes aluminum. The Raman spectrum of the positive electrode active material layer at a wavelength of 398 cm⁻¹... -1 Up to 408cm -1 The position has the first characteristic peak at a wavelength of 940 cm⁻¹. -1 Up to 960cm -1 The position of the second characteristic peak is where the first characteristic peak corresponds to the second positive electrode active material, and the second characteristic peak corresponds to the first positive electrode active material. Since the second positive electrode active material has a high specific capacity, the positive electrode active material containing both the second and first positive electrode active materials also has a high specific capacity, thus contributing to improved energy density of the electrochemical device. The second positive electrode active material includes aluminum, which can improve the bond length fluctuation of the manganese-oxygen bonds during cycling, enhance the stability of the manganese-oxygen bonds, and thus improve the cycling performance of the electrochemical device. Simultaneously, the synergistic effect of the first and second positive electrode active materials enables the positive electrode active material layer to possess superior structural stability, resulting in high energy density and high-temperature cycling performance for the electrochemical device.

[0030] In some embodiments of this application, the wavelength is 398cm. -1 Up to 408cm -1 The first characteristic peak is generated by the stretching vibration of the Mn-O bond in the second positive electrode active material, with a wavelength of 940 cm⁻¹. -1 Up to 960cm -1 The second characteristic peak is in the first positive electrode active material (PO4). 3- Characteristic peaks of the internal pattern.

[0031] In this application, a fully discharged electrochemical device refers to an electrochemical device that is charged at a constant current of 0.2C to 3.65V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.2C to 2.5V. After repeating the above charge and discharge process twice, the resulting electrochemical device is in a fully discharged state.

[0032] In some embodiments of this application, the full width at half maximum (FWHM) of the first characteristic peak can be 15 cm. -1 Up to 60cm -1 The full width at half maximum (FWHM) of the second characteristic peak can be 5 cm. -1 Up to 25cm -1 The full width at half maximum (FWHM) of the first characteristic peak can be greater than that of the second characteristic peak. For example, the FWHM of the first characteristic peak can be 15 cm. -1 25cm -1 38cm -1 45cm -1 52cm -1 60cm -1 Or any combination of the above values. The full width at half maximum (FWHM) of the second characteristic peak can be 5 cm. -1 8cm -1 12cm -1 16cm -1 22cm -1 25cm -1 Or any combination of the above values. The crystallinity of the second positive electrode active material is lower than that of the first positive electrode active material, so its half-width at half-maximum (WHM) is larger, while the WHM of the first positive electrode active material is smaller, has better crystallinity, and undergoes less structural change during charge and discharge. The active ions inside the second positive electrode active material compensate for the loss of active ions on the surface of the negative electrode active material, and also enable sufficient active ions to be reinserted into the second positive electrode active material, ensuring the transport of active ions and improving the cycle performance of the electrochemical device.

[0033] In some embodiments of this application, after the electrochemical device is fully discharged, the Raman spectrum of the positive electrode active material layer is at a wavelength of 591 cm⁻¹. -1 Up to 611cm -1The position has a third characteristic peak, and the full width at half maximum (FWHM) of the third characteristic peak can be 15 cm. -1 Up to 60cm -1 For example, the full width at half maximum (FWHM) of the third characteristic peak can be 15 cm. -1 25cm -1 40cm -1 45cm -1 54cm -1 60cm -1 Or any combination of the above values. When the full width at half maximum (FWHM) of the third characteristic peak is within the range described above, it indicates that the second positive electrode active material has a stable crystal structure, which can suppress material structure phase transitions during cycling, improve the structural stability of the material, and enhance the cycling performance of the electrochemical device.

[0034] In the electrochemical device of this application, the third characteristic peak is the characteristic peak corresponding to the second positive electrode active material. Figure 1 It is known that the Raman spectrum of the positive electrode active material layer of Example 1 provided in this application contains a first characteristic peak, a second characteristic peak, and a third characteristic peak.

[0035] In this application, the Raman spectrum of the positive electrode active material layer and the full width at half maximum (FWHM) of the first, second, and third characteristic peaks have meanings known in the art and can be tested using methods known in the art. For example, a lithium-ion battery is charged at a constant current of 0.2C to 3.65V, then charged at a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.2C to 2.5V. This cycle is repeated twice. After completion, the lithium-ion battery is disassembled, the positive electrode is removed, and the positive electrode is immersed in DMC (dimethyl carbonate) for 30 minutes to remove the electrolyte and byproducts on the surface of the positive electrode. Then, it is dried in a fume hood for 4 hours. The dried positive electrode is sliced ​​using an ion polishing machine (JEOL-IB-09010CP) and tested using a Raman spectrometer (model HR Evolution) with a wavenumber range of 150 to 1200 cm⁻¹. -1 A 2cm x 2cm range was selected, and the average value of the spectral lines was taken to obtain the Raman spectrum. The full width at half maximum (FWHM) refers to the full width of the spectral band when the height of the characteristic peak is half of its maximum height; that is, the peak width at half the peak height.

[0036] In some embodiments, the first positive electrode active material includes iron, and the second positive electrode active material includes manganese. The first positive electrode active material has an olivine structure, which is relatively stable and exhibits minimal volume change during the charge and discharge process of the electrochemical device. This means that the insertion and extraction of active ions have minimal impact on the structure of the first positive electrode active material, resulting in good charge-discharge reversibility. The second positive electrode active material has a high specific capacity, enabling the electrochemical device to have a high discharge specific capacity. The electrochemical device of this application can fully utilize the synergistic effect between the first and second positive electrode active materials. During the charge and discharge process of the electrochemical device, active ions in the second positive electrode active material are extracted. Some of these active ions can be deposited on the negative electrode, effectively compensating for the irreversible loss of active ions on the surface of the negative electrode active material caused by repairing the SEI film. The remaining active ions can be inserted into the first positive electrode active material, effectively improving the cycle performance of the electrochemical device.

[0037] In some embodiments, the first positive electrode active material includes, but is not limited to, lithium iron phosphate and a composite material of lithium iron phosphate and carbon.

[0038] In some embodiments, the positive electrode active material layer includes manganese, and the mass fraction ω of aluminum is based on the mass of manganese in the positive electrode active material layer. Al Satisfy: 0.1%≤ω Al ≤5%. For example, the mass fraction of aluminum ω is based on the mass of manganese in the positive electrode active material layer. Al Satisfy: 0.15%≤ω Al ≤5%, 0.8%≤ω Al ≤5%, 1.2%≤ω Al ≤5%, 2.6%≤ω Al ≤5%, 3.5%≤ω Al ≤5%, 4%≤ω Al ≤5%, 0.2%≤ω Al ≤4%, 0.9%≤ω Al ≤4%, 1.5%≤ω Al ≤4%, 2.5%≤ω Al ≤4%, 3%≤ω Al ≤4%, 0.3%≤ω Al ≤3%, 1%≤ω Al ≤3%, 1.6%≤ω Al ≤3%, 0.8%≤ω Al ≤2% or 0.1%≤ω Al ≤1%. Preferably, the mass fraction of aluminum ω is based on the mass of manganese in the positive electrode active material layer. Al Satisfy: 0.3%≤ω Al≤3%. The elution position of the first characteristic peak of aluminum is closely related to that of the second cathode active material. When the mass fraction of aluminum satisfies the above relationship, the elution position of the first characteristic peak shifts to the right, and it can enhance the stability of the manganese-oxygen bond in the second cathode active material, thereby improving the high-temperature cycling performance of the electrochemical device. If the aluminum doping amount in the second cathode active material is too large, aluminum will occupy the active sites of the active ions, resulting in a decrease in the specific capacity of the second cathode active material, which is not conducive to improving the energy density of the electrochemical device.

[0039] In some implementations, the mass percentage ω of manganese element is based on the mass of the positive electrode active material layer. Mn With the mass percentage of iron ω Fe Satisfy: 0.01%≤ω Mn / ω Fe ≤30%. Manganese content (ω) by mass. Mn With the mass percentage of iron ω Fe This reflects the mass percentage of the second and first positive electrode active materials in the positive electrode active material. The mass percentage of manganese element ω Mn A higher percentage indicates a higher mass content of the second positive electrode active material in the positive electrode active material. Based on the higher specific capacity of the second positive electrode active material, the electrochemical device exhibits a higher discharge specific capacity. During the cycling process of the electrochemical device, active ions from the second positive electrode active material are released and deposited onto the negative electrode, compensating for the loss of active ions on the surface of the negative electrode active material. When the mass percentage of the second positive electrode active material in the positive electrode active material is high, it can provide more releaseable active ions, effectively compensating for the loss of active ions on the surface of the negative electrode active material and ensuring sufficient active ions can be re-intercalated into the second positive electrode active material, guaranteeing the transport of active ions and effectively improving the cycle capacity retention rate of the electrochemical device, increasing its energy density and cycle performance. Compared to the first positive electrode active material, the mass percentage of the second positive electrode active material should not be too high. If the mass percentage of the second positive electrode active material is too high, it can provide too many releaseable and compensating active ions. When this exceeds the amount of active ions that can be re-intercalated into the positive electrode active material layer, it leads to increased internal resistance, reducing the discharge specific capacity of the electrochemical device. Therefore, by measuring the mass percentage of the second positive electrode active material and the first positive electrode active material in the positive electrode active material, that is, the mass percentage of manganese element ω... Mn With the mass percentage of iron ω Fe Controlling the energy density within the above range can effectively improve the cycle performance of electrochemical devices and increase their energy density.

[0040] In some embodiments, the mass percentage of manganese is ω Mn With the mass percentage of iron ωFe Satisfied:0.05%≤ω Mn / h Fe ≤30%, 0.1%≤ω Mn / h Fe ≤30%, 0.5%≤ω Mn / h Fe ≤30%, 1%≤ω Mn / h Fe ≤30%,5%≤ω Mn / h Fe ≤30%, 10%≤ω Mn / h Fe ≤30%, 15%≤ω Mn / h Fe ≤30%, 20%≤ω Mn / h Fe ≤30%, 25%≤ω Mn / h Fe ≤30%, 0.05%≤ω Mn / h Fe ≤25%, 0.1%≤ω Mn / h Fe ≤25%, 0.5%≤ω Mn / h Fe ≤25%, 1%≤ω Mn / h Fe ≤25%, 5%≤ω Mn / h Fe ≤25%, 10%≤ω Mn / h Fe ≤25%, 15%≤ω Mn / h Fe ≤25%, 20%≤ω Mn / h Fe ≤25%, 0.05%≤ω Mn / h Fe ≤20%, 0.1%≤ω Mn / h Fe ≤20%, 0.5%≤ω Mn / h Fe ≤20%, 1%≤ω Mn / h Fe ≤20%,5%≤ω Mn / h Fe ≤20%, 10%≤ω Mn / h Fe ≤20%, 15%≤ω Mn / h Fe ≤20%, 0.05%≤ω Mn / h Fe ≤15%, 0.1%≤ω Mn / hFe ≤15%, 0.5%≤ω Mn / ω Fe ≤15%, 1%≤ω Mn / ω Fe ≤15%, 5%≤ω Mn / ω Fe ≤15%, 10%≤ω Mn / ω Fe ≤15%, 0.05%≤ω Mn / ω Fe ≤10%, 0.1%≤ω Mn / ω Fe ≤10%, 0.5%≤ω Mn / ω Fe ≤10%, 1%≤ω Mn / ω Fe ≤10%, 5%≤ω Mn / ω Fe ≤10%, 0.05%≤ω Mn / ω Fe ≤5%, 0.1%≤ω Mn / ω Fe ≤5%, 0.5%≤ω Mn / ω Fe ≤5%, 1%≤ω Mn / ω Fe ≤5%, 0.05%≤ω Mn / ω Fe ≤1%, 0.1%≤ω Mn / ω Fe ≤1% or 0.05%≤ω Mn / ω Fe ≤0.1%. Preferably, the mass percentage of manganese is ω. Mn With the mass percentage of iron ω Fe Satisfy: 1%≤ω Mn / ω Fe At ≤25%, the electrochemical device exhibits superior cycle performance and high energy density.

[0041] In some embodiments, the positive electrode active material layer includes element M, which is selected from one or more of Nb, Mg, Ti, W, Ga, Zr, W, Y, V, Sr, Mo, Cr, Sn, La, and Ce. For example, element M can be Nb, Ga, Mo, V, W and Y, or La and Ce. Element M can also be any one or more of the above elements. Adding element M to the second positive electrode active material can improve the stability of the manganese-oxygen bonds within the material, inhibit the dissolution of manganese, and further improve the high-temperature cycling performance of the electrochemical device. Simultaneously, element M can also increase the content of extractable active ions in the second positive electrode active material, ensuring sufficient active ions can be extracted to compensate for the loss of active ions on the surface of the negative electrode active material, while still allowing sufficient active ions to be reinserted into the positive electrode active material layer, further improving the capacity and energy density of the electrochemical device.

[0042] In some implementations, the mass percentage ω of element M is based on the mass of the positive electrode active material layer. M Satisfies: 0.03% < ω M ≤2.5%. For example, the mass percentage ω of element M. M Satisfies: 0.05%≤ω M ≤1.5%, 0.1%≤ω M ≤1.5%, 0.5%≤ω M ≤1.5%, 1%≤ω M ≤1.5%, 0.05%≤ω M ≤1%, 0.1%≤ω M ≤1% or 0.5%≤ω M ≤1%. When the mass percentage of element M is ω M Satisfies: 0.03% < ω M At a concentration ≤2.5%, it is beneficial to further improve the stability of manganese-oxygen bonds and inhibit manganese dissolution; it also helps to keep the content of lithium that can be intercalated or deintercalated in the second positive electrode active material within a suitable range. This ensures that there are sufficient active ions in the second positive electrode active material to compensate for the loss of active ions on the surface of the negative electrode active material, and that there are also sufficient active ions to be re-intercalated into the positive electrode active material layer, further improving the energy density and high-temperature cycling performance of the electrochemical device. In some embodiments, the mass percentage ω of element M is based on the mass of the positive electrode active material layer. M Satisfies: 0.03% < ω M A concentration of ≤1.5% can be more beneficial for improving the energy density of electrochemical devices and enhancing their high-temperature cycling performance.

[0043] In this application, the types of elements in the positive electrode active material layer can be tested using methods known in the art. For example, the positive electrode sheet obtained from disassembling a lithium-ion battery is dried, and the dried positive electrode sheet is sliced ​​using an ion polishing machine (JEOL-IB-09010CP). Then, the cross-section of the slice is observed using a scanning electron microscope (SEM) to look for particles in the cross-section, and the types of elements in the positive electrode active material layer are determined after testing with an energy dispersive spectroscopy (EDS) instrument.

[0044] In this application, the content of each element in the positive electrode active material layer can be tested using methods known in the art. For example, the positive electrode sheet obtained from disassembling a lithium-ion battery is cleaned with DMC, the active material layer of the DMC-cleaned positive electrode sheet is scraped off with a scraper, dissolved in a mixed solvent (for example, 0.4g of the positive electrode active material layer is dissolved in a mixed solvent of 10 mL of aqua regia (nitric acid and hydrochloric acid mixed in a 1:1 ratio) and 2 mL of HF), and the volume is adjusted to 100 mL. Then, the mass percentage content of elements such as Mn, Fe, Al, and M in the solution is tested using an ICP (Inductively Coupled Plasma) analyzer.

[0045] In some embodiments, as an example, the second positive electrode active material can be prepared by the following method: MnOOH is placed in an alumina crucible and heated to 500°C at a heating rate of 5°C / min under an air atmosphere and held at a constant temperature for 1 hour to obtain anhydrous Mn3O4. Anhydrous Mn3O4 and LiOH are weighed in a Li:Mn molar ratio of 1.05:1, and nano-Al2O3 is added in an Al:Mn elemental mass ratio of 0.0163:1, and nano-magnesium oxide is added in a Mg:Mn elemental mass ratio of 0.008:1. Alternatively, one or more of the following elements, such as Nb, Ti, W, Ga, Zr, W, Y, V, Sr, Mo, Cr, Sn, La, and Ce, can be added in a certain proportion. The above substances are mixed evenly using a sand mill to obtain a mixed precursor. The precursor is placed in an alumina crucible and heated at a rate of 2 m... 3 Nitrogen gas is introduced at a rate of 1 h, and the temperature is increased to 940℃ at a rate of 5℃ / min and maintained at a constant temperature for 10 h. After natural cooling to room temperature, the second positive electrode active material is obtained. Mn3O4 can also be replaced by MnO2, and the ratio with LiOH is adjusted according to the Mn content.

[0046] In some embodiments, the positive electrode active material layer may optionally include a conductive agent and a binder. The specific types of conductive agents and binders are not specifically limited and can be selected according to requirements. As examples, conductive agents include, but are not limited to, at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. As examples, binders include, but are not limited to, at least one of styrene-butadiene rubber (SBR), water-based acrylic resin, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA).

[0047] In this application, the positive electrode is a positive electrode sheet, the positive electrode sheet further includes a positive electrode current collector, and the positive electrode active material layer is disposed on at least one surface of the positive electrode current collector.

[0048] In some embodiments, the positive current collector can be a metal foil or a porous metal plate, such as a foil or porous plate of metals or alloys thereof, such as aluminum, copper, nickel, titanium, silver, etc. As an example, the positive current collector is aluminum foil.

[0049] In some embodiments, the positive electrode current collector has two surfaces opposite each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector. When the positive electrode active material layer is disposed on both surfaces of the positive electrode current collector, if the parameters of the positive electrode active material layer on either surface meet the parameter range of this application, it is considered to fall within the protection scope of this application.

[0050] The positive electrode sheet can be prepared according to conventional methods in the art. Typically, a first positive electrode active material, a second positive electrode active material, and optional conductive agents and binders are dispersed in a solvent, which can be N-methylpyrrolidone (NMP), to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and the positive electrode sheet is obtained through processes such as drying and cold pressing.

[0051] The positive electrode sheet of this application does not exclude other additional functional layers besides the positive electrode active material layer. For example, in some embodiments, the positive electrode sheet of this application further includes a conductive undercoat (e.g., composed of a conductive agent and a binder) sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. In other embodiments, the positive electrode sheet of this application further includes a protective layer covering the surface of the positive electrode active material layer.

[0052] In this application, the electrolyte plays a role in conducting active ions between the positive and negative electrodes.

[0053] In some embodiments, the electrolyte contains additives, which may include fluorocarbonates and / or inorganic lithium salts. For example, the additives may include both fluorocarbonates and inorganic lithium salts, or they may include only one of fluorocarbonates and inorganic lithium salts.

[0054] In some embodiments, the fluorocarbonate includes at least one of fluoroethylene carbonate and fluoropropylene carbonate.

[0055] In some embodiments, the inorganic lithium salt includes at least one of lithium difluorophosphate and lithium tetrafluoroborate.

[0056] The additives contained in the electrolyte of this application help to form a dense and stable interfacial film on the surface of the positive electrode active material, further enhancing the protection of the positive electrode active material, inhibiting side reactions between the electrolyte and the positive electrode active material, reducing interfacial impedance, and improving the high-temperature cycling performance of the electrochemical device.

[0057] In some embodiments, the mass percentage of the additive is from 0.01% to 10% based on the mass of the electrolyte. The mass percentage of the additive is 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 6%, 8%, 10%, or within any range of the above values.

[0058] In this application, the appropriate mass percentage of additives in the electrolyte helps form an interfacial film of suitable thickness on the surface of the positive electrode active material, while also exhibiting low impedance, which is beneficial for improving the cycle performance of the electrochemical device. If the mass percentage of additives is too low, the interfacial film on the surface of the positive electrode active material will be insufficient, affecting the performance of the electrochemical device; if the mass percentage of film-forming additives is too high, the impedance of the electrolyte will increase, the migration rate of active ions will decrease, and the high-temperature cycle performance of the electrochemical device will be affected.

[0059] In some embodiments, the mass percentage of fluorocarbonate can be from 0.01% to 8%, which can further improve the high-temperature cycling performance of the electrochemical device.

[0060] In some embodiments, the mass percentage of fluorocarbonate can be from 0.01% to 5%, which can further improve the high-temperature cycling performance of the electrochemical device.

[0061] In some embodiments, the inorganic lithium salt content can be from 0.01% to 3% by mass, which can further improve the high-temperature cycling performance of the electrochemical device.

[0062] In some embodiments, the inorganic lithium salt content can be from 0.01% to 1.5% by mass, which can further improve the high-temperature cycling performance of the electrochemical device.

[0063] In some embodiments, the electrolyte may also include organic solvents and other optional additives, the types of which are not specifically limited and can be selected as needed.

[0064] In some embodiments, as examples, the organic solvent includes, but is not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl 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). One of the above organic solvents may be used alone, or two or more may be used simultaneously. Optionally, two or more of the above organic solvents may be used simultaneously.

[0065] In some embodiments, the other additives may include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0066] The electrolyte can be prepared according to conventional methods in the art. For example, additives, organic solvents, and other optional additives can be mixed evenly to obtain the electrolyte. There are no particular restrictions on the order of addition of the materials; for example, additives and other optional additives can be added to an organic solvent and mixed evenly to obtain the electrolyte.

[0067] In this application, the negative electrode is a negative electrode sheet, which can be a lithium metal sheet or an electrode sheet comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer typically comprises a negative electrode active material and optionally a conductive agent, a binder, and a thickener.

[0068] The materials, composition, and manufacturing methods of the negative electrode used in this application may include any techniques known in the prior art.

[0069] The specific type of negative electrode active material is not limited and can be selected according to requirements. For example, negative electrode active materials include, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured Li4Ti5O.12 At least one of Li-Al alloys.

[0070] The specific type of conductive agent is not limited and can be selected according to needs. As an example, conductive agents include, but are not limited to, at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0071] The specific type of adhesive is not limited and can be selected according to requirements. As an example, adhesives include, but are not limited to, at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose.

[0072] The specific type of thickener is not limited and can be selected according to needs. As an example, thickeners include, but are not limited to, sodium carboxymethyl cellulose (CMC).

[0073] However, this application is not limited to the above-mentioned materials. The negative electrode sheet of this application may also use other known materials that can be used as negative electrode active materials, conductive agents, binders and thickeners.

[0074] In some embodiments, the negative electrode 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 electrode current collector.

[0075] The negative electrode current collector can be made of metal foil or porous metal plate, such as foil or porous plate of metals or alloys thereof, such as copper, nickel, titanium, iron, etc. As an example, the negative electrode current collector is copper foil.

[0076] The negative electrode sheet can be prepared according to conventional methods in the art. Typically, the negative electrode active material and optional conductive agent, binder and thickener are dispersed in a solvent, which can be N-methylpyrrolidone (NMP) or deionized water, to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto the negative electrode current collector, and the negative electrode sheet is obtained through processes such as drying and cold pressing.

[0077] The negative electrode sheet of this application does not exclude other additional functional layers besides the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode active material layer.

[0078] In this application, the electrochemical device further includes 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 active 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.

[0079] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these. 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. In some embodiments, a ceramic coating or a metal oxide coating may also be provided on the separator.

[0080] Electronic device A second aspect of the present application provides an electronic device that includes the electrochemical device of the first aspect of the present application, wherein the electrochemical device can be used as a power source in the electronic device.

[0081] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0082] Examples The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized by conventional methods and can be used directly without further processing. The instruments used in the examples are also commercially available.

[0083] Example 1 Preparation of the positive electrode sheet The first positive electrode active material, LiFePO4, and the second positive electrode active material were mixed uniformly at a mass ratio of 92:8 and sintered at 300℃ in a nitrogen atmosphere for 2 hours to obtain the positive electrode active material. The preparation process of the second positive electrode active material was as follows: MnOOH was placed in an alumina crucible and heated to 500℃ at a heating rate of 5℃ / min under an air atmosphere and held at this temperature for 1 hour to obtain anhydrous Mn3O4. Anhydrous Mn3O4 and LiOH were weighed at a Li:Mn molar ratio of 1.05:1. Simultaneously, nano-Al2O3 was added at an Al:Mn elemental mass ratio of 0.0163:1, and nano-magnesium oxide was added at a Mg:Mn elemental mass ratio of 0.008:1. The above substances were mixed uniformly using a sand mill to obtain a mixed precursor. The precursor was placed in an alumina crucible and sintered at a rate of 2 m... 3 Nitrogen gas was introduced at a rate of 1 h, and the temperature was increased to 940°C at a rate of 5°C / min and kept constant for 10 h. The mixture was then allowed to cool naturally to room temperature to obtain the second positive electrode active material.

[0084] The positive electrode active material, conductive agent Super P, and binder polyvinylidene fluoride were mixed at a mass ratio of 96:2.4:1.6. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until homogeneous to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil current collector. The aluminum foil was dried at 85 °C to obtain a positive electrode sheet with a single-sided coating of positive electrode active material layer and a coating thickness of 65 μm. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode active material layer. After cold pressing, cutting, and slitting, the sheet was dried under vacuum at 85 °C for 4 hours to obtain a positive electrode sheet with a size of 74 mm × 867 mm.

[0085] Preparation of the negative electrode sheet Artificial graphite (anode active material), Super P (conductive agent), sodium carboxymethyl cellulose (CMC) (thickener), and styrene-butadiene rubber (SBR) (binder) were mixed in a mass ratio of 96.4:1.5:0.5:1.6. Deionized water was added, and the mixture was stirred under vacuum to obtain a cathode slurry with a solid content of 70 wt%. The cathode slurry was uniformly coated onto one surface of a 10 μm thick copper foil current collector. The copper foil was dried at 85 °C to obtain a cathode sheet with a single-sided coating of 63 μm thick and coated with the cathode active material. The above steps were repeated on the other surface of the aluminum foil to obtain a cathode sheet with a double-sided coating of the cathode active material. After cold pressing, cutting, and slitting, the cathode sheet was dried under vacuum at 120 °C for 12 h to obtain a cathode sheet with dimensions of 79 mm × 972 mm.

[0086] Preparation of the electrolyte In an argon-atmospheric glove box with a water content of <10 ppm, chain carbonate DEC and cyclic carbonates EC and PC are mixed at a mass ratio of 1:1:1 to obtain a base solvent. Lithium salt LiPF6 is then added to the base solvent, dissolved, and mixed thoroughly. The mass percentage of LiPF6 is 12.5% ​​based on the mass of the electrolyte, or FEC or lithium difluorophosphate may be added to the electrolyte.

[0087] Preparation of the separator A water-based polyvinylidene fluoride, aluminum oxide, and polypropylene were mixed in a mass ratio of 1:8:1 and added to deionized water. The mixture was stirred to obtain a coating slurry with a solid content of 50 wt%. The coating slurry was uniformly coated onto one surface of a 5 μm thick PE film (provided by Celgard) and dried at 85°C to obtain a single-sided coated release liner with a coating thickness of 5 μm. The above steps were repeated on the other surface of the release liner to obtain a double-sided coated release liner. The release liner was then dried and cold-pressed to obtain the final release liner.

[0088] Preparation of the lithium ion battery The positive electrode, separator, and negative electrode prepared above are stacked in sequence, with the separator positioned between the positive and negative electrode to provide isolation. The electrode assembly is then wound to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, degassing, and edge trimming, a lithium-ion battery is obtained. The formation conditions are: constant current charging at 0.02C to 3.3V, then constant current charging at 0.1C to 3.6V; constant current charging at 0.2C to 4.2V; settling for 10 minutes; discharging to 2.5V; settling for 10 minutes; and then constant current charging at 0.2C to 3.0V.

[0089] Examples 2 to 25 and Comparative Examples 1 to 2 The preparation method of the lithium-ion battery is similar to that in Example 1, except that the relevant parameters in the preparation process of the positive electrode and electrolyte are adjusted. For details of the parameters, please refer to Table 1. " / " indicates that the corresponding component was not added.

[0090] Test section (1) Discharge specific capacity test of lithium-ion batteries The lithium-ion battery was charged to 3.65V at a constant current of 0.2C, then charged to 0.05C at a constant voltage. After standing for 5 minutes, it was discharged to 2.5V at a constant current of 0.2C. The charging and discharging process was repeated twice, and the capacity of the second cycle was recorded as D0. The battery was disassembled, the positive electrode was removed, and the positive electrode was immersed in DMC (dimethyl carbonate) for 30 minutes to remove the electrolyte and by-products on the surface of the positive electrode. Then it was dried in a fume hood for 4 hours, and the electrode was calcined into powder at 400℃ in a vacuum. The mass of the powder was measured as m1.

[0091] The specific discharge capacity of a lithium-ion battery = D0 / m1.

[0092] (2) Cycle performance test of lithium-ion batteries The lithium-ion battery was charged at 45°C with a constant current of 1C to 3.65V, then charged with a constant voltage to a current of 0.05C, left to stand for 5 minutes, and then discharged with a constant current of 1C to 2.5V. This constitutes one charge-discharge cycle, and the discharge capacity at this point is recorded as D01. The lithium-ion battery was subjected to the above charge-discharge process for 1000 cycles, and the discharge capacity of the 1000th cycle is recorded as D1.

[0093] The cycle capacity retention rate (%) of a lithium-ion battery = D1 / D01 × 100%.

[0094] Tables 1 to 3 present the performance test results of Examples 1 to 25 and Comparative Examples 1 to 2.

[0095] Table 1

[0096] Figure 1 This is the Raman spectrum of the positive electrode active material layer in Example 1. Figure 1 As can be seen from this, the positive electrode active material layer is 398 cm³. -1 Up to 408cm -1 The position has the first characteristic peak at a wavelength of 940 cm⁻¹. -1 Up to 960cm -1 The position has a second characteristic peak at a wavelength of 591 cm⁻¹. -1 Up to 611cm -1 The position of the peak exhibits a third characteristic peak. As shown in Table 1, the full width at half maximum (FWHM) of the first characteristic peak in the positive electrode active material layers of Examples 1 to 7 is 20.8 cm. -1 Up to 29.6cm -1 The full width at half maximum (FWHM) of the second characteristic peak is 10.3 cm. -1Since Comparative Example 1 does not contain a second positive electrode active material, its Raman spectrum lacks the first characteristic peak, and its discharge specific capacity and high-temperature cycling performance are both low. The above test results demonstrate that adding an aluminum-containing second positive electrode active material to the positive electrode active material layer can significantly improve the discharge specific capacity of the lithium-ion battery; moreover, through the synergistic effect between the first and second positive electrode active materials, the loss of active lithium on the surface of the negative electrode active material can be effectively compensated, effectively improving the energy density and cycle capacity retention rate of the lithium-ion battery, and enhancing its high-temperature cycling performance.

[0097] Table 2

[0098] As can be seen from the test results in Table 2 above, with ω Mn / ω Fe As the value increases, the full width at half maximum (FWHM) of the third characteristic peak of the positive electrode active material gradually increases, within a certain range. Mn / ω Fe The higher the Mn content, the stronger the discharge specific capacity and high-temperature cycling stability of the electrochemical device. However, if the Mn content is too high, Mn will dissolve when the electrochemical device is cyclically charged and discharged at 45°C, thus affecting the high-temperature cycling performance of the electrochemical device.

[0099] Table 3

[0100] As can be seen from the test results of Examples 1 and 16-25 in Table 3 above, when the electrolyte contains both fluorocarbonate and / or inorganic lithium salt additives, the retention rate of the electrochemical device after 1000 cycles at 45°C is higher than that of Example 1 without the above additives. The above results indicate that the additives in the electrolyte can form an interfacial film on the surface of the positive electrode material, strengthen the protection of the positive electrode active material, suppress the side reactions between the electrolyte and the positive electrode active material, reduce the interfacial impedance, and further improve the high-temperature cycling performance of the electrochemical device.

[0101] In summary, the synergistic effect of the first positive electrode active material and the aluminum-containing second positive electrode active material can significantly increase the specific capacity of the positive electrode active material, improve the energy density of the electrochemical device, and enhance its high-temperature cycling performance.

[0102] The above description is merely a specific embodiment of this application, but the scope of protection 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 scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electrochemical device, comprising: Positive electrode, negative electrode, and electrolyte. The positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a first positive electrode active material and a second positive electrode active material. The Raman spectrum of the positive electrode active material layer after full discharge of the electrochemical device is at a wavelength of 398 cm⁻¹. -1 Up to 408cm -1 The position has the first characteristic peak at a wavelength of 940 cm⁻¹. -1 Up to 960cm -1 The position has a second characteristic peak. The second positive electrode active material includes aluminum. The electrolyte contains additives, including fluorocarbonates and / or inorganic lithium salts. Based on the mass of the electrolyte, the additive has a mass percentage content of 0.01% to 10%.

2. The electrochemical device according to claim 1, wherein, After the electrochemical device is fully discharged, the Raman spectrum of the positive electrode active material layer is at a wavelength of 591 cm⁻¹. -1 Up to 611cm -1 The position has a third characteristic peak, and the full width at half maximum (FWHM) of the third characteristic peak is 15 cm. -1 Up to 60cm -1 .

3. The electrochemical device according to claim 1, wherein, The full width at half maximum (FWHM) of the first characteristic peak is 15 cm. -1 Up to 60cm -1 The full width at half maximum (FWHM) of the second characteristic peak is 5 cm. -1 Up to 25cm -1 , The full width at half maximum (FWHM) of the first characteristic peak is greater than that of the second characteristic peak.

4. The electrochemical device according to any one of claims 1-3, wherein, The first positive electrode active material includes iron, and the second positive electrode active material includes manganese.

5. The electrochemical device according to any one of claims 1-3, wherein, The positive electrode active material layer includes manganese, and the mass fraction of aluminum is ω based on the mass of manganese in the positive electrode active material layer. Al Satisfy: 0.1%≤ω Al ≤5%.

6. The electrochemical device according to claim 4, wherein, Based on the mass of the positive electrode active material layer, the mass percentage ω of the manganese element Mn The mass percentage of iron element ω Fe Satisfy: 0.01%≤ω Mn / ω Fe ≤30%.

7. The electrochemical device according to any one of claims 1-3, wherein, The positive electrode active material layer contains element M, which is selected from one or more of Nb, Mg, Ti, W, Ga, Zr, W, Y, V, Sr, Mo, Cr, Sn, La and Ce; Based on the mass of the positive electrode active material layer, the mass percentage ω of element M M Satisfies: 0.03% < ω M ≤2.5%.

8. The electrochemical device according to claim 1, wherein, The additive satisfies at least one of conditions (1) to (4): (1) The fluorocarbonate includes at least one of fluoroethylene carbonate and fluoropropylene carbonate; (2) The inorganic lithium salt includes at least one of lithium difluorophosphate and lithium tetrafluoroborate; (3) Based on the mass of the electrolyte, the mass percentage of the fluorocarbonate is 0.01% to 8%; (4) Based on the mass of the electrolyte, the inorganic lithium salt has a mass percentage content of 0.01% to 3%.

9. The electrochemical device according to claim 8, wherein, The additive satisfies at least one of conditions (5) to (6): (5) Based on the mass of the electrolyte, the mass percentage of the fluorocarbonate is 0.01% to 5%; (6) Based on the mass of the electrolyte, the inorganic lithium salt has a mass percentage content of 0.01% to 1.5%.

10. The electrochemical device according to claim 5, wherein, Based on the mass of manganese in the positive electrode active material layer, the mass fraction of aluminum ω Al Satisfy: 0.3%≤ω Al ≤3%.

11. The electrochemical device according to claim 6, wherein, Based on the mass of the positive electrode active material layer, the mass percentage ω of the manganese element Mn The mass percentage of iron element ω Fe Satisfy: 1%≤ω Mn / ω Fe ≤25%.

12. The electrochemical device according to claim 7, wherein, Based on the mass of the positive electrode active material layer, the mass percentage ω of element M M Satisfies: 0.03% < ω M ≤1.5%.

13. An electronic device comprising the electrochemical device according to any one of claims 1-12.

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