Electrochemical devices and electronic devices

Abstract

In an electrochemical device and an electronic device, the electrochemical device comprises a positive electrode, a negative electrode, and an electrolyte, the positive electrode comprises a positive active material layer, the positive active material layer comprises a positive active material, and the positive active material comprises a first positive active material and a second positive active material, wherein, after the electrochemical device undergoes full discharge, the Raman spectrum of the positive active material layer has a first characteristic peak at a wavenumber of 398 cm⁻¹ to 408 cm⁻¹ and a second characteristic peak at a wavenumber of 940 cm⁻¹ to 960 cm⁻¹, and the second positive active material comprises an aluminum element. The electrochemical device simultaneously possesses a relatively high energy density and excellent high-temperature cycle performance.

Description

Technology Field

[0001] This application belongs to the field of electrochemical technology, and more specifically relates to electrochemical devices and electronic devices. Background Technology

[0002] In recent years, electrochemical devices, represented by lithium-ion batteries, have been rapidly advancing in the fields of portable consumer electronics, new energy vehicles, and large-scale energy storage, thanks to their advantages such as high operating voltage, eco-friendliness, small volume, light weight, and long cycle life. Lithium iron phosphate is widely applied as a cathode material in electrochemical devices, including lithium-ion batteries, due to its excellent cycle and safety performance. Furthermore, as the adoption of new energy vehicles continues to accelerate, the demand for longer driving ranges is increasing requirements for battery energy density and cycle performance. The problem to be solved

[0003] The objective of the present application is to provide an electrochemical device and an electronic device to improve the energy density of the electrochemical device and to improve the high-temperature cycle performance of the electrochemical device. means of solving the problem

[0004] In the first aspect of the present application, an electrochemical device is provided, wherein the electrochemical device comprises a positive electrode, a negative electrode, and an electrolyte, the positive electrode comprises a positive active material layer, the positive active material layer comprises a positive active material, and the positive active material comprises a first positive active material and a second positive active material, wherein, after the electrochemical device undergoes full discharge, the Raman spectrum of the positive active material layer has a wavenumber of 398 cm⁻¹ -1 to 408cm -1 It has a first characteristic peak at the in position, and a wavenumber of 940 cm -1 to 960cm -1The second positive active material has a second characteristic peak at the in position, and the second positive active material contains an aluminum element. The first characteristic peak is a characteristic peak of the second positive active material, and the second characteristic peak is a characteristic peak of the first positive active material. The second positive active material has a relatively high capacity per gram, and the aluminum element can increase the stability of the manganese-oxygen bond of the second positive active material during the cycling process, thereby enabling the positive active material layer to have relatively excellent structural stability, and thus improves the high energy density of the electrochemical device and improves the high-temperature cycling performance of the electrochemical device.

[0005] In some embodiments of the present application, after the electrochemical device undergoes full discharge, the Raman spectrum of the positive active material layer has a wavenumber of 591 cm⁻¹ -1 to 611cm -1 It is equipped with a third characteristic peak at the in position, and the half-width of the third characteristic peak is 15 cm -1 up to 60cm -1 And, the third characteristic peak is the characteristic peak of the second positive active material. When the full width at half maximum of the third characteristic peak is within the above range, the second positive active material has a stable crystalline structure internally, which suppresses the phase change of the material structure during the cycling process, thereby improving the structural stability of the material and improving the cycling performance of the electrochemical device.

[0006] In some embodiments of the present application, the full width at half maximum of the first characteristic peak is 15 cm -1 up to 60cm -1 And, the full width at half maximum of the second characteristic peak is 5cm -1 inner 25cm -1And, the full width at half maximum of the first characteristic peak is greater than the full width at half maximum of the second characteristic peak. Since the second positive active material has lower crystallinity than the first positive active material, the full width at half maximum is relatively large, the full width at half maximum of the first positive active material is relatively small, and the crystallinity is excellent, and the structural change during the charge / discharge process is small, and the active ions inside the second positive active material compensate for the loss of active ions on the surface of the negative active material, thereby ensuring the transmission of active ions, which is advantageous for improving the cycle performance of the electrochemical device.

[0007] In some embodiments of the present application, the first positive active material comprises an iron element, and the second positive active material comprises a manganese element. The second positive active material has a relatively high capacity per gram, so that the electrochemical device can have a relatively high discharge capacity, and a synergistic effect occurs between the first positive active material and the second positive active material. During the charge / discharge process of the electrochemical device, active ions in the second positive active material are deintercalated from the second positive active material, which can effectively compensate for the irreversible loss of active ions on the surface of the negative active material, and the remaining active ions can be intercalated into the first positive active material, thereby effectively improving the capacity of the positive active material and improving the cycle performance of the electrochemical device.

[0008] In some embodiments of the present application, the positive active material layer comprises a manganese element, and based on the mass of the manganese element in the positive active material layer, the mass fraction ω of the aluminum element Al is 0.1%≤ω Al It satisfies the condition that ≤5%. When the mass fraction of the aluminum element satisfies the above relationship, the stability of the manganese-oxygen bond in the second positive active material can be increased, thereby improving the cycle performance of the electrochemical device.

[0009] In some embodiments of the present application, based on the mass of the positive electrode active material layer, the mass percentage content ω of the manganese element Mnand mass percentage content of iron element ω Fe 0.01%≤ω Mn / ω Fe Satisfying that ≤30%, and preferably, 1%≤ω Mn / ω Fe It satisfies the condition that ≤25%. When the mass percentage content of manganese and iron elements is within the above range, the energy density of the electrochemical device can be further improved and the cycle performance of the electrochemical device can be improved.

[0010] In some embodiments of the present application, the positive electrode active material layer comprises an element M, said element M is selected from one or more of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Cr, Sn, La, and Ce. After adding the element M to the second positive electrode active material, the stability of the manganese-oxygen bond within the material can be improved, the leaching of the manganese element can be suppressed, cycle performance can be further improved, and the energy density of the electrochemical device can be improved.

[0011] In some embodiments of the present application, based on the mass of the positive electrode active material layer, the mass percentage content ω of element M M is 0.03%<ω M It satisfies the condition that ≤2.5%. When the mass percentage content of element M is within the corresponding range, the cycle performance of the electrochemical device can be improved more effectively and the energy density of the electrochemical device can be improved.

[0012] In some embodiments of the present application, the electrolyte comprises an additive, and the additive comprises a fluorinated carbonate and / or an inorganic lithium salt. The fluorinated carbonate and / or the inorganic lithium salt contribute to forming a dense and stable interfacial film on the surface of the positive electrode active material, thereby further enhancing protection of the positive electrode active material and improving the cycle performance of the electrochemical device.

[0013] In some embodiments of the present application, the mass percentage content of the additive is 0.01% to 10% based on the mass of the electrolyte. Having the mass percentage content of the additive in the electrolyte within an appropriate range contributes to the surface of the positive electrode active material forming an interfacial film of appropriate thickness while having a relatively low impedance, thereby further improving the cycle performance of the electrochemical device.

[0014] In some embodiments of the present application, the fluorinated carbonate comprises at least one of fluoroethylene carbonate and fluoropropylene carbonate.

[0015] In some embodiments of the present application, the inorganic lithium salt comprises at least one of lithium difluorophosphate and lithium tetrafluoroborate.

[0016] In some embodiments of the present application, based on the mass of the electrolyte, the mass percentage content of the fluorinated carbonate is 0.01% to 8%.

[0017] In some embodiments of the present application, based on the mass of the electrolyte, the mass percentage content of the fluorinated carbonate is 0.01% to 5%.

[0018] In some embodiments of the present application, based on the mass of the electrolyte, the mass percentage content of the inorganic lithium salt is 0.01% to 3%.

[0019] In some embodiments of the present application, the mass percentage content of the inorganic lithium salt is 0.01% to 1.5% based on the mass of the electrolyte.

[0020] In the second aspect of the present application, an electronic device is provided, said electronic device comprises the electrochemical device of the first aspect of the present application. Brief explanation of the drawing

[0021] Figure 1 is the Raman spectrum of the positive active material layer of Example 1. Specific details for implementing the invention

[0022] To make the purpose, technical solution, and advantages of the present application clearer, the following examples combine to provide a clear and complete description of the technical solution of the present application; however, it is clear that the described examples are only some of the examples of the present application, not all of them. The related examples described herein are for illustrative purposes only and are intended to provide a basic understanding of the present application. The present application should not be interpreted as being limited by the examples of the present application. Based on the technical solution and given examples provided in the present application, all other examples obtained without creative effort by those skilled in the art to which the present application pertains are also within the scope of protection of the present application.

[0023] For the sake of simplicity and clarity, this specification has disclosed only certain numerical ranges. However, any lower limit may be combined with any upper limit to form a range not explicitly described; any lower limit may be combined with other lower limits to form a range not explicitly described, and likewise any upper limit may be combined with any other upper limit to form a range not explicitly described. Additionally, each individually disclosed point or single numerical value itself may be combined with any other point or single numerical value as a lower or upper limit, or combined with other lower or upper limits to form a range not explicitly described.

[0024] In the description of this specification, unless otherwise specified, “greater than” and “less than” include this value.

[0025] Unless otherwise specified, the terms used in this application have the known meanings commonly understood by those skilled in the art to which this application pertains. Unless otherwise specified, the numerical values ​​of each parameter mentioned in this application may be measured by various measurement methods commonly used in the art (e.g., tests may be performed according to the methods presented in the embodiments of this application).

[0026] A list of items linked to the terms “at least one of,” “at least one of,” “at least one of,” or other similar terms means that it may be any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if items A, B and C are listed, 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 include a single component or multiple components. Item B may include a single component or multiple components. Item C may include a single component or multiple components.

[0027] Electrochemical devices

[0028] In a first aspect of an embodiment of the present application, an electrochemical device is provided, comprising any device that converts chemical energy and electrical energy into one another by causing an electrochemical reaction internally, and specific examples of the electrochemical device include, but are not limited to, lithium-ion batteries.

[0029] The electrochemical device of the present application comprises an anode, a cathode, and an electrolyte, wherein the anode comprises an anode active material layer, the anode active material layer comprises an anode active material, the anode active material comprises a first anode active material and a second anode active material, and after the electrochemical device undergoes full discharge, the Raman spectrum of the anode active material layer has a wavenumber of 398 cm⁻¹ -1 to 408cm -1 It has a first characteristic peak at the in position, and a wavenumber of 940 cm -1 to 960cm -1It has a second characteristic peak at the n position, and the second positive active material contains an aluminum element. The Raman spectrum of the positive active material layer has a wavenumber of 398 cm⁻¹. -1 to 408cm -1 It has a first characteristic peak at the in position, and a wavenumber of 940 cm -1 to 960cm -1 A second characteristic peak is provided at the in position, wherein the first characteristic peak is a characteristic peak corresponding to the second positive active material, and the second characteristic peak is a characteristic peak corresponding to the first positive active material. Since the second positive active material has a relatively high capacity per gram, the positive active material including the second positive active material and the first positive active material also has a relatively high capacity per gram, thereby contributing to improving the energy density of the electrochemical device. The second positive active material includes an aluminum element, and the aluminum element improves the variation in the bond length of the manganese-oxygen bond of the second positive active material during the cycling process, thereby increasing the stability of the manganese-oxygen bond and improving the cycling performance of the electrochemical device. In addition, due to the synergistic action of the first positive active material and the second positive active material, the positive active material layer can have relatively excellent structural stability, and the electrochemical device can be enabled to have high energy density and high-temperature cycling performance.

[0030] In some embodiments of the present application, the wavenumber is 398 cm -1 to 408cm -1 The first characteristic peak is a characteristic peak generated by the stretching vibration of the Mn-O bond in the second positive active material, and its wavenumber is 940 cm⁻¹. -1 to 960cm -1 The second characteristic peak is (PO4) in the first positive active material 3- It is the characteristic peak of the internal mode.

[0031] In the present application, the electrochemical device in a full discharge state indicates that the electrochemical device is in a full discharge state after being charged to 3.65V with a constant current of 0.2C, then charged to a constant voltage until the current becomes 0.05C, left to stand for 5 minutes, then discharged to 2.5V with a constant current of 0.2C, and then cycled twice according to the charge-discharge process.

[0032] In some embodiments of the present application, the full width at half maximum of the first characteristic peak is 15 cm -1 up to 60cm -1 It may be, and the full width at half maximum of the second characteristic peak is 5cm -1 inner 25cm -1 It may be, and the full width at half maximum of the first feature peak may be larger than the full width at half maximum of the second feature peak. For example, the full width at half maximum of the first feature peak is 15 cm -1 , 25cm -1 , 38cm -1 , 45cm -1 , 52cm -1 , 60cm -1 Alternatively, it may be a range of any combination of the above arbitrary values. The full width at half maximum of the second characteristic peak is 5 cm. -1 , 8cm -1 , 12cm -1 , 16cm -1 , 22cm -1 , 25cm -1 Alternatively, it may be a range of any combination of the above arbitrary values. Since the second positive active material has lower crystallinity than the first positive active material, the full width at half maximum of the second positive active material is relatively large, and since the first positive active material has a relatively small full width at half maximum of the first positive active material, the crystallinity is excellent, structural changes are small during the charge-discharge process, and active ions inside the second positive active material compensate for the loss of active ions on the surface of the negative active material, allowing sufficient active ions to back-intercalate into the second positive active material, thereby ensuring the transfer of active ions and being advantageous for improving the cycle performance of the electrochemical device.

[0033] In some embodiments of the present application, after the electrochemical device undergoes full discharge, the Raman spectrum of the positive active material layer has a wavenumber of 591 cm⁻¹ -1 to 611cm -1 It is equipped with a third characteristic peak at the in position, and the half-width of the third characteristic peak is 15 cm -1 up to 60cm -1 It can be. For example, the full width at half maximum of the third characteristic peak is 15 cm -1 , 25cm -1 , 40cm -1 , 45cm -1 , 54cm -1 , 60cm -1 Alternatively, it may be a range of any combination of the above arbitrary values. When the full width at half maximum of the third characteristic peak is within the above range, the second positive active material has a stable crystalline structure internally, which can suppress phase changes in the material structure during the cycling process, thereby improving the structural stability of the material and improving the cycling performance of the electrochemical device.

[0034] In the electrochemical device of the present application, the third characteristic peak is a characteristic peak corresponding to the second positive active material. As can be seen from FIG. 1, the Raman spectrum of the positive active material layer of Example 1 provided in the present application includes 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 of the first, second, and third characteristic peaks have the meaning known in the art and can be tested using methods known in the art. For example, a lithium-ion battery is charged to 3.65V with a constant current of 0.2C, then charged to a constant voltage until the current reaches 0.05C, left to stand for 5 minutes, then discharged to 2.5V with a constant current of 0.2C, and this cycle is repeated twice. After completion, the lithium-ion battery is disassembled to extract the positive electrode, and the positive electrode is immersed in DMC (dimethyl carbonate) for 30 minutes to remove the electrolyte and byproducts from the surface of the positive electrode, and then dried in a fume hood for 4 hours. The anode specimens after drying were sliced ​​using an ion polisher (JN E-IB-09010CP), tested using a Raman spectrometer (Model: HR Evolution), and the wavenumber range was 150 to 1200 cm⁻¹. -1 And, by selecting a 2cm x 2cm range and taking the average value of the spectrum lines, a Raman spectrum is obtained. The full width at half maximum refers to the full width of the band when the characteristic peak band height is half the maximum height, that is, the peak width when the peak value height is half.

[0036] In some embodiments, the first positive active material comprises an iron element, and the second positive active material comprises a manganese element. The first positive active material among the positive active materials comprises an olivine structure, and the structure is relatively stable and the volume change is relatively small during the charging and discharging process of the electrochemical device, that is, the structural influence of the intercalation and deintercalation of active ions on the first positive active material is relatively small, and the first positive active material has excellent charge-discharge reversibility; and the second positive active material has a relatively high capacity per gram, so that the electrochemical device can have a relatively high discharge capacity. The electrochemical device of the present application can fully exhibit a synergistic effect between the first positive active material and the second positive active material, and during the charge / discharge process of the electrochemical device, active ions in the second positive active material are deintercalated from the second positive active material, and some active ions can be deposited on the cathode, thereby effectively compensating for the irreversible loss of active ions on the surface of the cathode active material caused by the repair of the SEI film, and the remaining active ions can be intercalated into the first positive active material, thereby effectively improving the cycle performance of the electrochemical device.

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

[0038] In some embodiments, the positive active material layer comprises a manganese element, and based on the mass of the manganese element in the positive active material layer, the mass fraction ω of the aluminum element Al is 0.1%≤ω Al It satisfies that ≤5%. For example, based on the mass of manganese element in the positive active material layer, the mass fraction ω of the aluminum element Al is 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 It satisfies that ≤1%. Preferably, based on the mass of manganese element in the positive active material layer, the mass fraction ω of the aluminum element Al is 0.3%≤ω Al It satisfies the condition that ≤3%. The aluminum element is closely related to the peak position of the first characteristic peak of the second positive electrode active material, and when the mass fraction of the aluminum element satisfies the above relationship, the peak position of the first characteristic peak shifts to the right, which can increase the stability of the manganese-oxygen bond in the second positive electrode active material and improve the high-temperature cycle performance of the electrochemical device. If the doping amount of the aluminum element in the second positive electrode active material is too large, the aluminum element occupies the active position of the active ion, which causes a decrease in the capacity per gram of the second positive electrode active material, which is disadvantageous for improving the energy density of the electrochemical device.

[0039] In some embodiments, based on the mass of the positive electrode active material layer, the mass percentage content ω of the manganese element Mn and mass percentage content of iron element ω Fe 0.01%≤ω Mn / ω Fe It satisfies the condition that ≤30%. Mass percentage content ω of the manganese element Mn and mass percentage content of iron element ω Fecan reflect the mass percentage content of the second cathode active material and the first cathode active material in the cathode active material. Mass percentage content ω of the manganese element Mn The higher the value, the higher the mass percentage content of the second positive active material in the positive active material is explained as being relatively high, and based on the fact that the second positive active material has a relatively high capacity per gram, the electrochemical device has a relatively high discharge capacity; and since the active ions of the second positive active material can be deintercalated and deposited on the negative electrode during the cycling process of the electrochemical device, the loss of active ions on the surface of the negative active material can be compensated, and when the mass percentage content of the second positive active material in the positive active material is relatively high, there are relatively many active ions capable of deintercalation that the second positive active material can provide, so not only can the loss of active ions on the surface of the negative active material be effectively compensated, but sufficient active ions can be back-intercalated to the second positive active material, thereby securing the transmission of active ions, effectively improving the cycle capacity retention rate of the electrochemical device, improving the energy density of the electrochemical device, and improving the cycle performance of the electrochemical device. Compared to the first positive electrode active material, the mass percentage content of the second positive electrode active material must not be too high. When the mass percentage content of the second positive electrode active material is too high, there are too many active ions capable of deintercalation and compensation that the second positive electrode active material can provide. When the amount of such active ions exceeds the amount of active ions capable of back-intercalation in the positive electrode active material layer, this results in an increase in internal resistance, thereby reducing the discharge capacity of the electrochemical device. Therefore, the mass percentage content of the second positive electrode active material and the first positive electrode active material in the positive electrode active material, i.e., the mass percentage content ω of the manganese element Mn and mass percentage content of iron element ω FeBy controlling it within the above range, the cycle performance of the electrochemical device can be effectively improved and the energy density of the electrochemical device can be improved.

[0040] In some embodiments, the mass percentage content ω of the manganese element Mn and mass percentage content of iron element ω Fe is 0.05%≤ω Mn / ω Fe ≤30%, 0.1%≤ω Mn / ω Fe ≤30%, 0.5%≤ω Mn / ω Fe ≤30%, 1%≤ω Mn / ω Fe ≤30%, 5%≤ω Mn / ω Fe ≤30%, 10%≤ω Mn / ω Fe ≤30%, 15%≤ω Mn / ω Fe ≤30%, 20%≤ω Mn / ω Fe ≤30%, 25%≤ω Mn / ω Fe ≤30%, 0.05%≤ω Mn / ω Fe ≤25%, 0.1%≤ω Mn / ω Fe ≤25%, 0.5%≤ω Mn / ω Fe ≤25%, 1%≤ω Mn / ω Fe ≤25%, 5%≤ω Mn / ω Fe ≤25%, 10%≤ω Mn / ω Fe ≤25%, 15%≤ω Mn / ω Fe ≤25%, 20%≤ω Mn / ω Fe ≤25%, 0.05%≤ω Mn / ω Fe ≤20%, 0.1%≤ω Mn / ω Fe ≤20%, 0.5%≤ω Mn / ω Fe ≤20%, 1%≤ω Mn / ωFe ≤20%, 5%≤ω Mn / ω Fe ≤20%, 10%≤ω Mn / ω Fe ≤20%, 15%≤ω Mn / ω Fe ≤20%, 0.05%≤ω Mn / ω Fe ≤15%, 0.1%≤ω Mn / ω Fe ≤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 It satisfies that ≤0.1%. Preferably, the mass percentage content ω of the manganese element. Mn and mass percentage content of iron element ω Fe 1%≤ω Mn / ω FeIt satisfies the condition that ≤25%, and in this case, the electrochemical device has superior cycle performance and high energy density.

[0041] In some embodiments, the positive active material layer comprises an element M, and the element M is selected from one or more of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Cr, Sn, La, and Ce. For example, the element M may be Nb, Ga, Mo, V, W, Y, La, and Ce. The element M may be any one or more of the above elements. After adding the element M to the second positive active material, the stability of the manganese-oxygen bond within the material can be improved, the leaching of the manganese element can be suppressed, and the high-temperature cycle performance of the electrochemical device can be further improved; In addition, element M improves the content of deintercalable active ions in the second positive active material, thereby ensuring that sufficient active ions capable of deintercalation exist in the second positive active material to compensate for the loss of active ions on the surface of the negative active material, while still allowing sufficient active ions to back-intercalate in the positive active material layer, thereby further improving the capacity and energy density of the electrochemical device.

[0042] In some embodiments, based on the mass of the positive active material layer, the mass percentage content ω of element M M is 0.03%<ω M It satisfies that ≤2.5%. For example, the mass percentage content ω of element M M is 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 MIt satisfies that ≤1%. Mass percentage content ω of element M M This 0.03%<ω M When satisfying the condition ≤2.5%, it is advantageous to further improve the stability of the manganese-oxygen bond and suppress the leaching of manganese; it is also advantageous to ensure that the content of deintercalable lithium in the second positive electrode active material is within an appropriate range, thereby allowing sufficient active ions to exist 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 also allowing sufficient active ions to exist to perform back-intercalation on the positive electrode active material layer, thereby further improving the energy density of the electrochemical device and improving the high-temperature cycle performance of the electrochemical device. In some embodiments, based on the mass of the positive electrode active material layer, the mass percentage content ω of element M M is 0.03%<ω M Satisfying the condition that it is ≤1.5% is more advantageous for improving the energy density of the electrochemical device and improving the high-temperature cycle performance of the electrochemical device.

[0043] In the present application, the type of element in the positive electrode active material layer can be tested using methods known in the art. For example, a positive electrode obtained by disassembling a lithium-ion battery is dried, and the dried positive electrode is sliced ​​using an ion polishing machine (JEK Electronics -IB-09010CP). Then, the cross-section of the slice is observed using a scanning electron microscope (SEM) to locate particles in the cross-section, and the type of element in the positive electrode active material layer is determined after testing using an energy spectrometer (EDS).

[0044] In the present application, the content of each element in the positive electrode active material layer can be tested using methods known in the art. For example, a positive electrode obtained by disassembling a lithium-ion battery is washed with DMC, and the active material layer of the positive electrode after washing with DMC is scraped off using a scraper, dissolved using a mixed solvent (for example, a 0.4 g positive electrode active material layer is dissolved using a mixed solvent of 10 mL of aqua regia (mixed nitric acid and hydrochloric acid in a 1:1 ratio) and 2 mL of HF), and then diluted to 100 mL, and 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 active material may be prepared using the method described below. That is, MnOOH is placed in a corundum crucible and heated to 500°C at a heating rate of 5°C / min in an air atmosphere and maintained at a constant temperature for 1 hour to obtain anhydrous Mn3O4. Anhydrous Mn3O4 and LiOH are weighed according to a molar ratio of Li:Mn of 1.05:1, while nano Al2O3 is added according to an elemental mass ratio of Al:Mn of 0.0163:1, nano magnesium oxide is added according to an elemental mass ratio of Mg:Mn of 0.008:1, and one or more of the elements M such as Nb, Ti, W, Ga, Zr, Y, V, Sr, Mo, Cr, Sn, La, and Ce may be added according to a certain ratio, and each of the above materials is uniformly mixed using a sand mill to obtain a mixture precursor. Place the precursor in a corundum crucible, and 2m 3Nitrogen is injected at a rate of / h, and the temperature is raised to 940℃ at a heating rate of 5℃ / min and maintained at a constant temperature for 10h, and then naturally cooled to room temperature to obtain the second cathode active material. Here, Mn3O4 may be replaced with MnO2, and at the same time, the mixing ratio with LiOH is adjusted according to the Mn content.

[0046] In some embodiments, the positive active material layer optionally further comprises a conductive agent and a binder. The specific types of the conductive agent and the binder are not specifically limited and can be selected according to demand. As an example, the conductive agent comprises, but is not limited to, at least one of conductive graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene, and carbon nanofibers. As an example, the binder comprises, but is 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 the present application, the positive electrode is a positive electrode piece, the positive electrode piece further comprises a positive current collector, and the positive active material layer is installed on at least one surface of the positive current collector.

[0048] In some embodiments, the anode current collector may use a metal foil or a porous metal plate, for example, a foil or porous plate of a metal or an alloy thereof such as aluminum, copper, nickel, titanium, silver, etc. As an example, the anode current collector is an aluminum foil.

[0049] In some embodiments, the positive current collector has two surfaces facing each other in its thickness direction, and a positive active material layer is installed on one or both of the two surfaces facing each other of the positive current collector. When the positive active material layer is installed on two surfaces of the positive current collector, if the parameter of the positive active material layer on any one of the surfaces satisfies the parameter range of the present application, it is deemed to fall within the scope of protection of the present application.

[0050] The positive electrode can be manufactured according to conventional methods in the field. Generally, a first positive active material, a second positive active material, an optional conductive agent, and a binder are dispersed in a solvent to form a uniform positive slurry, and the positive slurry is coated onto a positive current collector to obtain a positive electrode through processes such as drying and cold pressing, wherein the solvent may be N-methylpyrrolidone (NMP).

[0051] The positive electrode of the present application does not exclude other additional functional layers other than the positive active material layer. For example, in some embodiments, the positive electrode of the present application further comprises a conductive undercoating layer (e.g., composed of a conductive agent and a binder) interposed between the positive current collector and the positive active material layer and installed on the surface of the positive current collector. In other embodiments, the positive electrode of the present application further comprises a protective layer covered on the surface of the positive active material layer.

[0052] In the present application, the electrolyte serves to transfer active ions between the anode and the cathode.

[0053] In some embodiments, the electrolyte comprises an additive, and the additive may comprise a fluorinated carbonate and / or an inorganic lithium salt. For example, the additive may comprise a fluorinated carbonate and an inorganic lithium salt simultaneously, or may comprise one of a fluorinated carbonate and an inorganic lithium salt.

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

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

[0056] The additive included in the electrolyte in this application contributes to forming a dense and stable interfacial film on the surface of the positive electrode active material, thereby further enhancing protection of the positive electrode active material, suppressing side reactions between the electrolyte and the positive electrode active material, reducing interfacial impedance, and improving the high-temperature cycle performance of the electrochemical device.

[0057] In some embodiments, based on the mass of the electrolyte, the mass percentage content of the additive is 0.01% to 10%. The mass percentage content of the additive is within a range consisting of 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 10% or any of the above values.

[0058] In this application, having the mass percentage content of the additive in the electrolyte within an appropriate range contributes to forming an interfacial film of appropriate thickness on the surface of the positive electrode active material while simultaneously providing a relatively low impedance, which is advantageous for improving the cycle performance of the electrochemical device. If the mass percentage content of the additive is too low, the formation of the interfacial film on the surface of the positive electrode active material is insufficient, which affects the performance of the electrochemical device; if the mass percentage content of the film-forming additive is too high, the impedance of the electrolyte increases and the mobility of active ions decreases, which affects the high-temperature cycle performance of the electrochemical device.

[0059] In some embodiments, the mass percentage content of the fluorinated carbonate may be 0.01% to 8%, and the high-temperature cycle performance of the electrochemical device may be further improved.

[0060] In some embodiments, the mass percentage content of the fluorinated carbonate may be 0.01% to 5%, and the high-temperature cycle performance of the electrochemical device may be further improved.

[0061] In some embodiments, the mass percentage content of the inorganic lithium salt may be 0.01% to 3%, and the high-temperature cycle performance of the electrochemical device may be further improved.

[0062] In some embodiments, the mass percentage content of the inorganic lithium salt may be 0.01% to 1.5%, and the high-temperature cycle performance of the electrochemical device may be further improved.

[0063] In some embodiments, the electrolyte further comprises an organic solvent and other optional electrolyte additives, and the types of the organic solvent and other optional electrolyte additives are not subject to specific limitations and can be selected according to demand.

[0064] In some embodiments, as an example, the organic solvent comprises, 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), butylene 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). The above organic solvent may be used individually, or two or more may be used simultaneously. Optionally, two or more organic solvents may be used simultaneously.

[0065] In some embodiments, the other additives may include additives capable of improving specific performance of the battery, such as additives that improve the overcharge performance of the battery and additives that improve the high or low temperature performance of the battery.

[0066] The electrolyte can be prepared according to conventional methods in the field. For example, the electrolyte can be obtained by uniformly mixing an additive, an organic solvent, and other optional additives. The order of addition of each material is not particularly limited, and for example, the electrolyte can be obtained by adding the additive and other optional additives to the organic solvent and mixing them uniformly.

[0067] In the present application, the cathode is a cathode electrode, and the cathode electrode may be a metallic lithium sheet, or may be an electrode sheet comprising a cathode current collector and a cathode active material layer installed on at least one surface of the cathode current collector. The cathode active material layer generally comprises a cathode active material and an optional conductive agent, a binder, and a thickener.

[0068] The material, composition, and manufacturing method of the cathode electrode used in the present application may include any technology known in the prior art.

[0069] The specific type of cathode active material is not specifically limited and can be selected according to demand. As an example, cathode active materials include natural graphite, synthetic graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, SiO₂, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO₂, and spinel-structured Li₄Ti₅O₂. 12 , includes at least one of the Li-Al alloys, but is not limited thereto.

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

[0071] The specific type of binder is not specifically limited and can be selected according to demand. As an example, the binder includes, but is not limited to, at least one of styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethylcellulose.

[0072] The specific type of thickener is not specifically limited and can be selected according to demand. As an example, the thickener includes, but is not limited to, sodium carboxymethylcellulose (CMC-Na).

[0073] However, the present application is not limited to the above materials, and the cathode electrode of the present application may use other known materials that can be used as cathode active materials, conductive agents, binders, and thickeners.

[0074] In some embodiments, the negative current collector has two surfaces facing each other in its thickness direction, and a negative active material layer is installed on one or both of the two surfaces facing each other of the negative current collector.

[0075] The negative current collector may use a metal foil or a porous metal plate, for example, a foil or porous plate of a metal or an alloy thereof such as copper, nickel, titanium, or iron is used. As an example, the negative current collector is a copper foil.

[0076] The cathode electrode can be manufactured according to conventional methods in the field. Generally, a cathode active material, a selectable conductive agent, a binder, and a thickener are dispersed in a solvent to form a uniform cathode slurry, and the cathode slurry is coated onto a cathode current collector to obtain a cathode electrode through processes such as drying and cold pressing, wherein the solvent may be N-methylpyrrolidone (NMP) or deionized water.

[0077] The cathode electrode of the present application does not exclude additional functional layers other than the cathode active material layer. For example, in some embodiments, the cathode electrode of the present application further comprises a conductive undercoating layer (e.g., composed of a conductive agent and a binder) interposed between the cathode current collector and the cathode active material layer and installed on the surface of the cathode current collector. In other embodiments, the cathode electrode of the present application further comprises a protective layer covered on the surface of the cathode active material layer.

[0078] In the present application, the electrochemical device further comprises a separator. The separator is installed between the positive electrode and the negative electrode and primarily serves to prevent short circuits between the positive and negative electrodes, while simultaneously allowing active ions to pass through. In the present application, there are no specific restrictions on the type of separator, and any known porous separator having excellent chemical and mechanical stability may 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 thereto. The separator may be a single-layer thin film or a multi-layer composite thin film. When the separator is a multi-layer composite thin film, the material of each layer may be the same or different. In some embodiments, a ceramic coating layer or a metal oxide coating layer may be installed on the separator.

[0080] electronic devices

[0081] An electronic device is provided in a second aspect of an embodiment of the present application, said electronic device comprises an electrochemical device of a first aspect of an embodiment of the present application, wherein the electrochemical device can be used as a power source in said electronic device.

[0082] The electronic devices of the present application are not particularly limited and may be any known electronic devices used in the prior art. In some embodiments, the electrical devices of the present application may include, but are not limited to, notebooks, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable photocopiers, portable printers, headsets, video devices, liquid crystal TVs, portable vacuum cleaners, portable CD players, minidiscs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, watches, power tools, flashlights, cameras, household high-capacity storage batteries and lithium-ion capacitors.

[0083] Examples

[0084] The following examples further explain the contents disclosed in this application, and these examples are for descriptive purposes only. This is because it is obvious to those skilled in the art that various modifications and changes can be made within the scope of the contents disclosed in this application. Unless otherwise specified, all values ​​of parts, percentages, and ratios reported in the following examples are based on mass, all reagents used in the examples can be obtained by commercial purchase or by synthesis according to conventional methods and can be used directly without additional processing, and all instruments used in the examples can be obtained by commercial purchase.

[0085] Example 1

[0086] Manufacturing of positive electrodes

[0087] A first positive active material, LiFePO4, and a second positive active material are uniformly mixed in a mass ratio of 92:8 and sintered for 2 hours in a nitrogen atmosphere at 300°C to obtain a positive active material; wherein the manufacturing process of the second positive active material is as follows: MnOOH is placed in a corundum crucible and heated to 500°C at a heating rate of 5°C / min in an air atmosphere and maintained at a constant temperature for 1 hour to obtain anhydrous Mn3O4; anhydrous Mn3O4 and LiOH are weighed according to a molar ratio of Li:Mn of 1.05:1, while nano Al2O3 is added according to an elemental mass ratio of Al:Mn of 0.0163:1, and nano magnesium oxide is added according to an elemental mass ratio of Mg:Mn of 0.008:1, and each of the above materials is uniformly mixed using a sand mill to obtain a mixture precursor. Place the precursor in a corundum crucible, and 2m 3 Nitrogen is injected at a rate of / h, and the temperature is raised to 940℃ at a heating rate of 5℃ / min and maintained at a constant temperature for 10h, and then naturally cooled to room temperature to obtain the second positive active material.

[0088] A positive electrode active material, a conductive agent Super P, and a binder polyvinylidene fluoride are mixed in a mass ratio of 96:2.4:1.6, N-methylpyrrolidone (NMP) is added, and the mixture is stirred by the action of a vacuum stirrer until the system becomes uniform to obtain a positive electrode slurry, wherein the solid content of the positive electrode slurry is 70 wt%. The positive electrode slurry is uniformly coated on one surface of an aluminum foil positive current collector with a thickness of 10 μm, and the aluminum foil is dried at 85°C to obtain a positive electrode board with a coating layer thickness of 65 μm and a positive electrode active material layer coated on a single surface. The above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode board with a positive electrode active material layer coated on both sides. Next, after undergoing cold pressing, sheet cutting, and slitting, the board is dried for 4 hours under vacuum conditions at 85°C to obtain a positive electrode board with dimensions of 74 mm × 867 mm.

[0089] Manufacturing of cathode electrodes

[0090] Artificial graphite as a cathode active material, Super P as a conductive agent, sodium carboxymethylcellulose (CMC-Na) as a thickener, and styrene butadiene rubber (SBR) as an adhesive are mixed in a mass ratio of 96.4:1.5:0.5:1.6, deionized water is added, and a cathode slurry is obtained by the action of a vacuum stirrer, wherein the solid content of the cathode slurry is 70 wt%. The cathode slurry is uniformly coated on one surface of a copper foil cathode current collector with a thickness of 10 μm, and the copper foil is dried at 85°C to obtain a cathode electrode piece with a coating layer thickness of 63 μm and a cathode active material layer coated on a single surface. The above steps are repeated on the other surface of the copper foil to obtain a cathode electrode piece with a cathode active material layer coated on both sides. Next, after cold pressing, sheet cutting, and slitting, the product is dried for 12 hours under vacuum conditions at 120°C to obtain a cathode electrode with dimensions of 79 mm × 972 mm.

[0091] Preparation of electrolyte

[0092] In a glove box under an argon gas atmosphere with a moisture content <10 ppm, a basic solvent is obtained by mixing chain carbonate DEC and cyclic carbonates EC and PC in a mass ratio of 1:2:1, and then lithium salt LiPF6 is added to the basic solvent to dissolve and uniformly mix. Here, based on the mass of the electrolyte, the mass percentage content of LiPF6 is 12.5%, or FEC or lithium difluorophosphate is further added to the electrolyte.

[0093] Manufacturing of separation membranes

[0094] Aqueous polyvinylidene fluoride, aluminum trioxide, and polypropylene are mixed in a mass ratio of 1:8:1, added to deionized water, and stirred to obtain a coating layer slurry with a solid content of 50 wt%. The coating layer slurry is uniformly coated on one surface of a PE film (manufactured by Celgard Company) with a thickness of 5 μm and dried at 85°C to obtain a separator with a coating layer thickness of 5 μm and a coating layer coated on a single surface. The above steps are repeated on the other surface of the separator to obtain a separator with a coating layer coated on both sides. The separator is then obtained by drying and cold pressing.

[0095] Manufacturing of lithium-ion batteries

[0096] An electrode assembly is obtained by sequentially stacking the positive electrode, separator, and negative electrode obtained by the above manufacturing process so that the separator is positioned between the positive electrode and the negative electrode to perform a separating function, and then winding them. The electrode assembly is placed in an aluminum plastic film packaging bag, and after drying, an electrolyte is injected. A lithium-ion battery is obtained through processes such as vacuum sealing, settling, formation, degassing, and edge trimming. Here, the formation conditions are as follows: charging to 3.3V with a constant current of 0.02C, then charging to 3.6V with a constant current of 0.1C. Charging to 4.2V with a constant current of 0.2C, settling for 10 minutes, discharging to 2.5V, settling for 10 minutes, and then charging to 3.0V with a constant current of 0.2C.

[0097] Examples 2 to 25 and Comparative Examples 1 to 2

[0098] The method of manufacturing the lithium-ion battery is similar to Example 1, and the difference is that the relevant parameters in the manufacturing process of the positive electrode and the electrolyte have been adjusted. The specific parameters are described in detail in Table 1, and “ / ” indicates that the corresponding compositional component was not added.

[0099] Test section

[0100] (1) Test of the discharge capacity of a lithium-ion battery

[0101] After charging the lithium-ion battery to 3.65V with a constant current of 0.2C, it is charged to a constant voltage until the current reaches 0.05C, left to stand for 5 minutes, and then discharged to 2.5V with a constant current of 0.2C. Two cycles are performed according to the above charging and discharging process, and the capacity of the second cycle is recorded as D0. The battery is disassembled to extract the positive electrode, and the positive electrode is immersed in DMC (dimethyl carbonate) for 30 minutes to remove the electrolyte and by-products from the surface of the positive electrode, then dried in a fume hood for 4 hours, and the electrode is calcined into a powder at 400°C under vacuum, and the weighed mass is m1.

[0102] Discharge capacity of lithium-ion battery = D0 / m1.

[0103] (2) Cycle performance test of lithium-ion batteries

[0104] After charging the lithium-ion battery to 3.65V with a constant current of 1C at 45℃, then charging it with a constant voltage until the current becomes 0.05C, leaving it for 5 minutes, then discharging it to 2.5V with a constant current of 1C, and this constitutes one full charge-discharge cycle. The discharge capacity at this time is tested and recorded as D01; the lithium-ion battery is made to perform 1000 full cycles according to the above charge-discharge process, and the discharge capacity of the 1000th full cycle is tested and recorded as D1.

[0105] Lithium-ion battery cycle capacity retention rate (%) = D1 / D01 × 100%.

[0106] Tables 1 to 3 show the performance test results of Examples 1 to 25 and Comparative Examples 1 to 2.

[0107]

[0108] FIG. 1 is the Raman spectrum of the positive active material layer of Example 1, and as can be seen from FIG. 1, the positive active material layer is 398 cm -1 to 408cm-1 It has a first characteristic peak at the in position, and a wavenumber of 940 cm -1 to 960cm -1 It has a second characteristic peak at the in position, and a wavenumber of 591 cm -1 to 611cm -1 It has a third characteristic peak at the in position. As can be seen from the test results in Table 1, the full width at half maximum of the first characteristic peak of the anode active material layer of Examples 1 to 7 is 20.8 cm -1 to 29.6cm -1 and the full width at half maximum of the second characteristic peak is 10.3 cm -1 Comparative Example 1 does not contain a second positive electrode active material, so there is no first characteristic peak in the Raman spectrum, and both the discharge capacity and high-temperature cycle performance are relatively low. The above test results explain that after adding a second positive electrode active material containing aluminum elements to the positive electrode active material layer, the discharge capacity of the lithium-ion battery can be significantly improved; and through the synergistic effect between the first positive electrode active material and the second positive electrode active material, the loss of active lithium on the surface of the negative electrode active material can be effectively compensated, thereby effectively improving the energy density and cycle capacity retention rate of the lithium-ion battery and improving the high-temperature cycle performance of the lithium-ion battery.

[0109]

[0110] As can be seen from the test results in Table 2 above, ω Mn / ω Fe As the value increases, the full width at half maximum of the third characteristic peak of the cathode active material gradually increases, and within a certain range, ω Mn / ω Fe The larger the value of , the stronger the discharge capacity and high-temperature cycle stability of the electrochemical device. However, if the Mn content is too high, it causes Mn to leach out when the electrochemical device performs cycle charge / discharge at 45°C, which affects the high-temperature cycle performance of the electrochemical device.

[0111]

[0112] As can be seen from the test results of Example 1 and Examples 16 to 25 in Table 3 above, when the electrolyte simultaneously contains the additive fluorinated carbonate and / or inorganic lithium salt, the retention rate of the electrochemical device after 1,000 cycles at 45°C is higher than that of Example 1, which does not contain the additive. These results explain that the additive in the electrolyte can form an interfacial film on the surface of the cathode material, enhance protection for the cathode active material, suppress side reactions between the electrolyte and the cathode active material, reduce interfacial impedance, and further improve the high-temperature cycle performance of the electrochemical device.

[0113] As described above, under the synergistic action of the first positive active material and the second positive active material containing aluminum, the capacity per gram of the positive active material can be increased to a relatively large degree, thereby improving the energy density of the electrochemical device and improving the high-temperature cycle performance of the electrochemical device.

[0114] The foregoing description is merely a specific description for practicing the invention of the present application, and the scope of protection of the present application is not limited thereto. Any person of ordinary knowledge familiar with the technical field to which the present application pertains can readily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present application, and all such modifications or substitutions should be included within the scope of protection of the present application. Accordingly, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

Claim 1 An electrochemical device comprising an anode, a cathode, and an electrolyte, wherein the anode comprises a positive active material layer, the positive active material layer comprises a positive active material, and the positive active material comprises a first positive active material and a second positive active material, wherein, after the electrochemical device undergoes full discharge, the Raman spectrum of the positive active material layer has a wavenumber of 398 cm⁻¹ -1 to 408cm -1 It has a first characteristic peak at the in position, and a wavenumber of 940 cm -1 to 960cm -1 It has a second characteristic peak at the in position, and the second positive active material comprises aluminum and manganese elements, and Based on the mass of the manganese element in the above positive active material layer, the mass fraction ω of the aluminum element Al is 0.9%≤ω Al Satisfying that ≤4%, The above electrolyte includes an additive, and the additive includes an inorganic lithium salt, and The above-mentioned inorganic lithium salt includes lithium difluorophosphate, and Based on the mass of the electrolyte, the mass percentage content of the inorganic lithium salt is 0.01% to 3%, Electrochemical device. Claim 2 In claim 1, after the electrochemical device undergoes full discharge, the Raman spectrum of the positive active material layer has a wavenumber of 591 cm⁻¹ -1 to 611cm -1 It is provided with a third characteristic peak at the in position, and the full width at half maximum of the third characteristic peak is 15 cm -1 up to 60cm -1 Phosphorus, electrochemical device. Claim 3 In claim 1, the full width at half maximum of the first characteristic peak is 15 cm -1 up to 60cm -1 and the full width at half maximum of the second characteristic peak is 5cm -1 inner 25cm -1 An electrochemical device in which the full width at half maximum of the first characteristic peak is greater than the full width at half maximum of the second characteristic peak. Claim 4 An electrochemical device according to claim 1, wherein the first positive active material comprises an iron element. Claim 5 delete Claim 6 In claim 4, based on the mass of the positive electrode active material layer, the mass percentage content ω of the manganese element Mn and the mass percentage content ω of the above iron element Fe 0.01%≤ω Mn / ω Fe Electrochemical device satisfying ≤30%. Claim 7 In claim 1, the positive active material layer comprises element M, wherein the element M is selected from one or more of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Cr, Sn, La, and Ce; and, based on the mass of the positive active material layer, the mass percentage content ω of the element M M is 0.03%<ω M Electrochemical device satisfying ≤2.5%. Claim 8 An electrochemical device according to claim 1, wherein the additive further comprises a fluorinated carbonate; and, based on the mass of the electrolyte, the mass percentage content of the additive is 0.01% to 10%. Claim 9 An electrochemical device according to claim 8, wherein the additive satisfies at least one of the following conditions (1) to (3): (1) the fluorinated carbonate comprises at least one of fluoroethylene carbonate and fluoropropylene carbonate; (2) the inorganic lithium salt further comprises lithium tetrafluoroborate; and (3) the mass percentage content of the fluorinated carbonate is 0.01% to 8% based on the mass of the electrolyte. Claim 10 An electrochemical device according to claim 8, wherein the additive satisfies at least one of the following conditions (5) to (6): (5) the mass percentage content of the fluorinated carbonate is 0.01% to 5% based on the mass of the electrolyte; and (6) the mass percentage content of the inorganic lithium salt is 0.01% to 1.5% based on the mass of the electrolyte. Claim 11 In claim 1, the electrochemical device is based on the following conditions (7) to (9), (7) the mass fraction ω of the aluminum element based on the mass of the manganese element in the positive active material layer. Al This 0.9%≤ω Al Satisfying that ≤3%; (8) the first positive active material comprises an iron element, and based on the mass of the positive active material layer, the mass percentage content ω of the manganese element Mn and mass percentage content of iron element ω Fe This 1%≤ω Mn / ω Fe Satisfying that ≤25%; and (9) the positive active material layer comprises an element M, wherein the element M is selected from one or more of Nb, Mg, Ti, W, Ga, Zr, Y, V, Sr, Mo, Cr, Sn, La and Ce, and, based on the mass of the positive active material layer, a mass percentage content ω of the element M M This 0.03%<ω M An electrochemical device satisfying at least one of the following: ≤1.5%. Claim 12 An electronic device comprising an electrochemical device according to any one of claims 1 to 4 and claims 6 to 11.

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