CN114400326A - Electrochemical device and electronic device comprising same - Google Patents
Electrochemical device and electronic device comprising same Download PDFInfo
- Publication number
- CN114400326A CN114400326A CN202111680088.2A CN202111680088A CN114400326A CN 114400326 A CN114400326 A CN 114400326A CN 202111680088 A CN202111680088 A CN 202111680088A CN 114400326 A CN114400326 A CN 114400326A
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- material layer
- negative electrode
- electrochemical device
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- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
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- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 1
- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
Abstract
An electrochemical device and an electronic device including the same are provided, wherein the electrochemical device includes a negative electrode including 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 wave number of the negative active material layer is 2500cm by infrared spectrum test‑1To 3200cm‑1Has at least a first peak and a second peak. The negative active material layer contains the auxiliary agent, and the addition of the auxiliary agent improves the production efficiency of the negative electrode, so that the production efficiency of the electrochemical device is improved. Meanwhile, the electrochemical device has good discharge capacity.
Description
Technical Field
The present disclosure relates to the field of electrochemistry, and more particularly, to an electrochemical device and an electronic device including the same.
Background
Electrochemical devices, such as lithium ion batteries, as a novel movable energy storage device, have the advantages of high energy density, high operating voltage, long cycle life, no memory effect, environmental friendliness and the like, and therefore, the demands in the fields of portable small-sized electronic devices such as mobile phones, notebook computers and cameras, large-sized electric transportation and renewable energy storage are increasing, and manufacturers need to improve the production efficiency of the lithium ion batteries as much as possible in order to meet market demands.
It is an effective method to improve the production efficiency of lithium ion batteries by increasing the coating speed of the pole pieces (positive pole pieces and/or negative pole pieces). The method is often accompanied with the increase of the temperature of an oven for drying the pole piece, the shaking of the pole piece is aggravated in the coating process of the active material, and then the active material layer of the pole piece is cracked, so that the quality of the pole piece does not reach the standard, and the production cost is increased. The above problems are solved by a method of reducing the coating weight of the active material layer, which results in a reduction in the discharge capacity of the lithium ion battery. Therefore, how to improve the production efficiency of the lithium ion battery without affecting the discharge capacity of the lithium ion battery becomes a problem that needs to be solved by those skilled in the art.
Disclosure of Invention
The present application provides an electrochemical device and an electronic device including the same, which aims to improve the production efficiency of the electrochemical device while the electrochemical device has high discharge capacity.
In the summary of the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery. The specific technical scheme is as follows:
in a first aspect, the present application provides an electrochemical device comprising a negative electrode including 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 wave number of the negative active material layer is 2500cm by infrared spectrum test-1To 3200cm-1Has at least a first peak and a second peak. Capable of making electrochemical deviceThe device has high discharge capacity and improves the production efficiency.
In one embodiment of the present application, the first peak is at the wavenumber k1In the range of 2800cm-1≤k1≤2900cm-1Second peak at wavenumber k2In the range of 2900cm-1<k2≤3000cm-1Intensity of the first peak ε1And the intensity of the second peak ε2Satisfies the following conditions: 0.9 ≤ epsilon1/ε2Less than or equal to 1.0. The electrochemical device can have high discharge capacity and improve the production efficiency.
In one embodiment of the present application, the negative electrode active material layer includes an auxiliary agent including at least one of stearic acid, stearic acid amide, magnesium stearate, calcium stearate, sodium stearate, lithium stearate, zinc stearate, aluminum stearate, chromium stearate, or barium stearate. The negative electrode active material layer including the above-described additive enables an electrochemical device to have a high discharge capacity and a high production efficiency.
In one embodiment of the present application, the mass percentage content W of the auxiliary agent is based on the mass of the anode active material layer1% is 0.05% to 5%. By mixing the mass percentage of the auxiliary agent W1% control within the above range enables the electrochemical device to have a high discharge capacity while effectively improving the production efficiency of the electrochemical device.
In one embodiment of the present application, the anode active material layer includes a metal element including at least one of Mg, Al, Co, Ti, Cr, Y, W, or Ca. The negative active material layer includes the above-mentioned kind of metal elements, the production efficiency of the electrochemical device is improved, and the discharge capacity of the electrochemical device is further improved.
In one embodiment of the present application, the content of the metal element is M ppm, M.ltoreq.300, based on the mass of the anode active material layer. By regulating the content of the metal element within the above range, the electrochemical device has higher production efficiency and further improves the discharge capacity of the electrochemical device. In one embodiment of the present application, the metalThe element includes Al, and the content of Al is M based on the mass of the anode active material layer1 ppm，10≤M1Is less than or equal to 90. By regulating the content of Al within the above range, the electrochemical device has higher production efficiency and the discharge capacity of the electrochemical device is further improved.
In one embodiment of the present application, the metal element includes Co in an amount of M based on the weight of the anode active material layer2 ppm，0.5≤M2Less than or equal to 20. By controlling the content of Co within the above range, the electrochemical device has higher production efficiency and the discharge capacity of the electrochemical device is further improved.
In one embodiment of the present application, the metal element includes Cr in an amount of M based on the weight of the anode active material layer3 ppm，0＜M3Less than or equal to 5. By regulating the content of Cr within the above range, the electrochemical device has higher production efficiency and further improves the discharge capacity of the electrochemical device.
In one embodiment of the present application, the metal elements include Al and Co, and the content of Al is M based on the weight of the anode active material layer1ppm, Co content is M2 ppm，5≤M1/M2≤60，1≤M2Less than or equal to 20. The ratio of the Al content to the Co content and the Co content are simultaneously regulated and controlled within the range, so that the Al and the Co play a synergistic effect, the electrochemical device has higher production efficiency, and the discharge capacity of the electrochemical device is further improved.
In one embodiment of the present application, the metal elements include Al and Cr, and the content of Al is M based on the weight of the anode active material layer1ppm, Cr content is M3 ppm，30≤M1/M3Is less than or equal to 100. The ratio of the content of Al to the content of Cr is regulated and controlled within the claimed range, so that Al and Cr play a synergistic effect, the electrochemical device has higher production efficiency, and the discharge capacity of the electrochemical device is further improved.
In one embodiment of the present application, the negative active material layer further includes a dispersant includingAt least one of lithium hydroxymethyl cellulose, sodium hydroxymethyl cellulose, polyacrylic acid or sodium polyacrylate; a mass percentage content W of a dispersant based on the mass of the negative electrode active material layer2% of auxiliary agent and W1% satisfies: w is not less than 02－W1Less than or equal to 3. The selection of the dispersant makes the functions of the components in the negative active material layer fully exerted, and can improve the electrochemical performance of the electrochemical device. By regulating and controlling the mass percentage content W of the dispersant2% of auxiliary agent and W1% of the above range, thereby improving the productivity of the electrochemical device while achieving high energy density and other excellent electrochemical properties.
In one embodiment of the present application, the porosity α of the negative electrode active material layer is 15% to 60%; the porosity alpha is regulated and controlled within the range, so that the dynamic performance of the electrochemical device can be improved.
In one embodiment of the present application, the anode active material layer has a single-layer area mass of 0.02mg/mm2To 0.4mg/mm2. The single-layer area quality of the negative active material layer is regulated within the range, so that the discharge capacity and the production efficiency of the electrochemical device are improved.
In one embodiment of the present application, the negative active material layer has a weight loss percentage of W in a temperature range of 400 ℃ to 800 ℃ using thermogravimetric analysisT％，WTLess than or equal to 1. The negative active material layer has good thermal stability in the temperature range of 400 ℃ to 800 ℃, and is more beneficial to improving the discharge capacity of the electrochemical device.
In one embodiment of the present application, the negative active material layer further includes a negative active material including at least one of graphite, hard carbon, silicon, or silicon oxygen material. The above negative active materials are selected to be more beneficial to improving the discharge capacity of the electrochemical device.
In one embodiment of the present application, any one of the regions having a size of 20cm × 40cm is selected on the negative electrode active material layer, and the number of cracks in the region is 2 or less. The electrochemical device has high discharge capacity and high production efficiency.
In one embodiment of the present application, the tensile strength of the negative electrode is 300MPa to 600 MPa. The cathode has good tensile property, so that the number of cracks of the cathode can be further reduced, the cathode productivity is improved, and the production efficiency of the electrochemical device is improved.
In a second aspect, the present application provides an electronic device comprising the electrochemical device of the first aspect of the present application.
An electrochemical device and an electronic device including the same are provided, wherein the electrochemical device includes a negative electrode including 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 wave number of the negative active material layer is 2500cm by infrared spectrum test-1To 3200cm-1Has at least a first peak and a second peak. The negative electrode active material layer contains a substance capable of improving the performance of the negative electrode active material layer, such as an auxiliary agent, and the addition of the substance improves the production efficiency of the negative electrode, thereby improving the production efficiency of the electrochemical device. Meanwhile, the electrochemical device has good discharge capacity.
Of course, not all advantages described above need to be achieved at the same time in the practice of any one product or method of the present application.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained by referring to these drawings.
FIG. 1 is an infrared spectrum of example 2-1 of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other technical solutions obtained by a person of ordinary skill in the art based on the embodiments in the present application belong to the scope of protection of the present application.
In the embodiments of the present application, the present application is explained by taking a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present application is not limited to a lithium ion battery.
In a first aspect, the present application provides an electrochemical device comprising a negative electrode including 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 wave number of the negative active material layer is 2500cm by infrared spectrum test-1To 3200cm-1Has at least a first peak and a second peak. When the negative active material layer has a wave number of 2500cm-1To 3200cm-1When having at least the first peak and the second peak, indicates that the negative electrode active material layer contains a substance capable of improving the performance of the negative electrode active material layer, such as an auxiliary. Specifically, on the one hand, the substance capable of improving the performance of the negative electrode active material layer, such as the auxiliary agent, is present in the negative electrode active material layer, so that the plasticizing effect of the negative electrode active material layer can be improved, that is, the negative electrode active material layer has good flexibility, the risk of cracking of the negative electrode active material layer in the negative electrode baking process can be reduced, and the negative electrode production efficiency can be improved. On the other hand, the auxiliary agent is present in the negative electrode active material layer, which is beneficial to reducing the contact angle between the negative electrode slurry and the negative electrode current collector to improve the wettability of the negative electrode slurry. Like this, the distribution of negative pole thick liquids on the negative pole mass flow body is more even, and when the negative pole was toasting, the moisture in the negative pole active material layer can evaporate more fast more evenly to can reduce because the negative pole internal stress inequality and cause the risk of negative pole active material layer fracture in the quick drying negative pole, make the coating speed of negative pole active material layer effectively promote. Thereby, the loss of discharge capacity of the electrochemical device due to the increase of the coating weight of the negative active material layer is reduced, and the loss of discharge capacity due to the decrease of the coating speed of the negative active material layer is also reducedAnd the risk of the production efficiency of the electrochemical device. In the present application, the contact angle between the negative electrode slurry and the negative electrode current collector is less than or equal to 60 °, indicating that the negative electrode has good wettability.
Overall, the negative electrode active material layer contained 2500cm in wave number using infrared spectroscopy-1To 3200cm-1When the substance having at least the first peak and the second peak is contained in the above range, the electrochemical device can have a high discharge capacity and the production efficiency thereof can be improved.
In one embodiment of the present application, the first peak is at the wavenumber k1In the range of 2800cm-1≤k1≤2900cm-1Second peak wave number k2In the range of 2900cm-1<k2≤3000cm-1. Intensity of the first peak ε1And the intensity of the second peak ε2Satisfies the following conditions: 0.9 ≤ epsilon1/ε2Less than or equal to 1.0. E.g. epsilon1/ε2Is 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, or any value between any two of the above numerical ranges. Intensity of the first peak ε1And the intensity of the second peak ε2When the above relationship is satisfied, the intensity ε of the first peak1And the intensity of the second peak ε2The difference is small, which shows that the surface substitution degree of the substance capable of improving the performance of the negative active material layer is in a better range, and the substance has a more stable structure and is not easy to decompose, and the substance can still maintain the characteristics at high temperature, so that the electrochemical device has high discharge capacity and the production efficiency is improved.
Intensity of the first peak ε1And the intensity of the second peak ε2There is no particular limitation as long as the object of the present application can be achieved.
In one embodiment of the present application, the negative electrode active material layer includes an auxiliary agent including at least one of stearic acid, stearic acid amide, magnesium stearate, calcium stearate, sodium stearate, lithium stearate, zinc stearate, aluminum stearate, chromium stearate, or barium stearate. The negative active material layer comprises the auxiliary agents of the types, so that the plasticizing effect of the negative active material layer is improved, the risk of cracking of the negative active material layer is reduced, and the production efficiency of the negative electrode is improved. And make the negative pole when toasting, the moisture in the negative pole active material layer can evaporate more fast more evenly to when can be in the fast drying negative pole, reduce because the negative pole internal stress inequality and cause the risk of negative pole active material layer fracture, make the coating speed of negative pole active material layer effectively promote, and then improve the production efficiency of negative pole. Therefore, the electrochemical device has high discharge capacity and effectively improves the production efficiency.
In one embodiment of the present application, the mass percentage content W of the auxiliary agent is based on the mass of the anode active material layer1% is 0.05% to 5%. For example, the mass percentage of the auxiliary W1% is 0.05%, 0.1%, 0.2%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, or any value between any two of the above numerical ranges. Mass percentage content W of auxiliary agent1% too small (e.g., less than 0.05%), the improvement effect on the production efficiency of the electrochemical device is insignificant; according to the mass percentage content W of the auxiliary agent1% increase, has good effect of improving the production efficiency of the electrochemical device, and when the mass percentage of the auxiliary agent W1When the percentage is too large (for example, more than 5%), the improvement effect of the auxiliary on the production efficiency of the electrochemical device is not significantly increased, and the discharge capacity of the electrochemical device is affected by occupying too much of the original content of the negative active material. Thus, the mass percentage content W of the auxiliary agent1% control within the above range enables the electrochemical device to have a high discharge capacity while effectively improving the production efficiency of the electrochemical device.
In one embodiment of the present application, the mass percentage content W of the auxiliary agent is based on the mass of the anode active material layer1% is 0.1% to 1%. The electrochemical device with the mass percentage of the auxiliary agent within the range has better comprehensive performance.
In one embodiment of the present application, the anode active material layer includes a metal element including at least one of Mg, Al, Co, Ti, Cr, Y, W, or Ca. The negative electrode active material layer comprises the metal elements, and can improve the lithium intercalation performance of the negative electrode, so that the discharge capacity loss of the electrochemical device caused by the content of the negative electrode active material occupied by the auxiliary agent is compensated. This improves the productivity of the electrochemical device, and further improves the discharge capacity of the electrochemical device.
In one embodiment of the present application, the content of the metal element is M ppm, M.ltoreq.300, based on the mass of the anode active material layer. Preferably, 0.01. ltoreq. M.ltoreq.200. For example, the metallic element can be present in an amount of 0.01ppm, 1ppm, 2ppm, 5ppm, 10ppm, 20ppm, 30ppm, 50ppm, 90ppm, 150ppm, 200ppm, 250ppm, 300ppm, or any value between any two of the foregoing ranges. When the content of the metal element is higher, metal ion complexation is easy to occur in the process of preparing the cathode slurry, and the gel of the cathode slurry is influenced, so that the production is influenced. By regulating the content of the metal element within the above range, the electrochemical device has higher production efficiency and further improves the discharge capacity of the electrochemical device.
In one embodiment of the present application, the content of the metal element is M ppm, 0.01. ltoreq. M.ltoreq.200, based on the mass of the anode active material layer. The electrochemical device with the mass percentage of the metal elements within the range has better comprehensive performance.
In one embodiment of the present application, the metal element includes Al, and the content of Al is M based on the mass of the anode active material layer1 ppm，10≤M1Is less than or equal to 90. For example, the Al content is 10ppm, 20ppm, 30ppm, 40ppm, 50ppm, 60ppm, 70ppm, 80ppm, 90ppm, or any value between any two of the foregoing ranges. The metal element comprises Al, which is more beneficial to improving the lithium intercalation performance of the negative electrode, thereby improving the discharge capacity of the electrochemical device. Since Al has a conductive property, the inventors have found through extensive studies that the effect of improving the lithium intercalation property of the negative electrode is insignificant when the content of Al is too small (for example, less than 10 ppm); an excessively high Al content (e.g., greater than 90ppm) may cause a large number of side reactions in the negative electrode, which may affect the first efficiency of the electrochemical device. By controlling the content of Al within the above range, the electrochemical device hasThe discharge capacity of the electrochemical device is further improved while the production efficiency is high.
In one embodiment of the present application, the metal element includes Co in an amount of M based on the weight of the anode active material layer2 ppm，0.5≤M2Less than or equal to 20. For example, the Co content is 0.5ppm, 1ppm, 2ppm, 4ppm, 6ppm, 8ppm, 10ppm, 15ppm, 20ppm, or any value between any two of the foregoing ranges. The metal element comprises Co, which is more beneficial to improving the lithium intercalation performance of the negative electrode, thereby improving the discharge capacity of the electrochemical device. Due to the conductive property of Co, the inventor finds that the improvement effect of the lithium insertion performance of the negative electrode is not obvious when the content of Co is too small (for example, less than 0.5 ppm); too high a Co content (e.g., greater than 20ppm) can form complexation with the dispersant in the slurry, affect dispersant dispersion, and affect slurry production. By controlling the content of Co within the above range, the electrochemical device has higher production efficiency and the discharge capacity of the electrochemical device is further improved.
In one embodiment of the present application, the metal element includes Cr in an amount of M based on the weight of the anode active material layer3 ppm，0＜M3Less than or equal to 5. For example, the Cr content is 0.01ppm, 1ppm, 2ppm, 3ppm, 4ppm, 5ppm, or any value between any two of the foregoing ranges. The metal element comprises Cr, which is more beneficial to improving the lithium intercalation performance of the negative electrode, thereby improving the discharge capacity of the electrochemical device. Due to the conductive property of Cr, even a small amount of Cr is contained in the negative electrode active material layer, the lithium intercalation performance of the negative electrode can be improved, and as the Cr content increases, when the Cr content is excessively large (for example, more than 10ppm), the overall performance of the negative electrode slurry is affected, which is not favorable for improving the production efficiency. By regulating the content of Cr within the above range, the electrochemical device has higher production efficiency and further improves the discharge capacity of the electrochemical device.
In one embodiment of the present application, the metal elements include Al and Co, and the content of Al is M based on the weight of the anode active material layer1ppm, Co content is M2 ppm，5≤M1/M2≤60，1≤M2Less than or equal to 20. For example, M1/M2Is 5, 10, 20, 30, 40, 50, 60, or any value between any two of the above numerical ranges. The Co content is 1ppm, 2ppm, 3ppm, 4ppm, 5ppm, 6ppm, 7ppm, 8ppm, 9ppm, 10ppm or any value between any two of the foregoing numerical ranges. The ratio of the Al content to the Co content and the Co content are simultaneously regulated and controlled within the range, so that the Al and the Co play a synergistic effect, the electrochemical device has higher production efficiency, and the discharge capacity of the electrochemical device is further improved. It should be noted that, in this embodiment, the content of Al is not particularly limited as long as the above M is satisfied1/M2The numerical range of (2) is only required.
In one embodiment of the present application, the metal elements include Al and Cr, and the content of Al is M based on the weight of the anode active material layer1ppm, Cr content is M3 ppm，30≤M1/M3≤100。M1/M3Is 30, 40, 50, 60, 70, 80, 90, 100, or any value between any two of the above numerical ranges. The ratio of the content of Al to the content of Cr is regulated and controlled within the range, so that Al and Cr exert a synergistic effect, the electrochemical device has higher production efficiency, and the discharge capacity of the electrochemical device is further improved.
It should be noted that, in this embodiment, the content of Al and the content of Cr are not particularly limited as long as the above M is satisfied1/M3The numerical range of (2) is only required.
In one embodiment of the present application, the metal element of the negative electrode active material layer may be introduced during the production of the auxiliary or part of the metal ion in the positive electrode active material may be dissociated to the negative electrode active material layer during the charge and discharge processes.
In one embodiment of the present application, the negative active material layer further includes a dispersant including at least one of lithium hydroxymethylcellulose, sodium hydroxymethylcellulose, polyacrylic acid, or sodium polyacrylate; a mass percentage content W of a dispersant based on the mass of the negative electrode active material layer2% of auxiliary agent and W1% satisfies: w is not less than 02－W1Less than or equal to 3. The selection of the dispersant type can prevent the sedimentation and the agglomeration of each component particle in the negative active material slurry, so that each component particle is uniformly dispersed in the negative active material layer, thus the function of each component in the negative active material layer can be fully exerted, and the electrochemical performance of the electrochemical device can be improved. By regulating and controlling the mass percentage content W of the dispersant2% of auxiliary agent and W1% difference, the assistant and the dispersant generate synergistic effect, so that the risk of cracking of the negative active material layer is reduced while the functions of all components in the negative active material layer are fully exerted, and the electrochemical device has high energy density and other good electrochemical performances and improves the production efficiency. In the present application, W represents the weight percentage of the dispersant2There is no particular limitation as long as the object of the present application can be achieved. For example, the mass percentage of the dispersant W2% is 0.3% to 5%.
In one embodiment of the present application, the porosity α of the anode active material layer is 15% to 60%. For example, the porosity α is 15%, 20%, 30%, 40%, 50%, 60%, or a range consisting of any two of the foregoing values. The porosity alpha is regulated and controlled within the range, so that the contact failure between negative active material particles in the charge-discharge cycle process of the electrochemical device can be inhibited, and the cycle performance and the energy density of the electrochemical device are reduced; meanwhile, the cathode active material can be ensured to be fully soaked by the electrolyte, the transmission distance of lithium ions is reduced, and the dynamic performance of the electrochemical device, such as low-temperature discharge performance, is improved. In the present application, the porosity α of the anode active material layer means a percentage of a volume of pores between the components in the anode active material layer to an apparent volume of the anode active material layer. The porosity of the negative electrode active material layer can be controlled by controlling the drying temperature, the cold pressing time, the coating quality, the magnitude of the cold pressing force, or the like when the negative electrode is prepared.
In one embodiment of the present application, the porosity α of the anode active material layer is 20% to 40%. The electrochemical device having the porosity α of the negative active material layer within this range has a superior overall performance.
In one embodiment of the present application, the anode active material layer has a single-layer area mass of 0.02mg/mm2To 0.4mg/mm2. For example, the single-layer area mass of the anode active material layer is 0.02mg/mm2、0.13mg/mm2、0.3mg/mm2、0.4mg/mm2Or any value between any two of the above numerical ranges. The single-layer area mass of the negative electrode active material layer is too small (e.g., less than 0.02 mg/mm)2) Too little negative active material will affect the discharge capacity of the electrochemical device; the addition of the auxiliary agent in the negative active material layer enables the area mass of the negative active material layer to be larger than that of the prior art, the discharge capacity of the electrochemical device can be further improved, but the single-layer area mass of the negative active material layer is too large (for example, more than 0.4 mg/mm)2) The thickness of the negative electrode active material layer is too large, so that the volume of the electrochemical device is increased, the energy density of the electrochemical device is influenced, the negative electrode active material layer is too thick, the baking time of the negative electrode is prolonged, the production efficiency of the electrochemical device is reduced or the cracking of the negative electrode is increased, the infiltration performance of electrolyte in the negative electrode active material layer is reduced, and the improvement of the comprehensive performance of the electrochemical device is not facilitated. The single-layer area quality of the negative active material layer is regulated within the range, so that the discharge capacity and the production efficiency of the electrochemical device are improved.
In one embodiment of the present application, the negative active material layer has a weight loss percentage of W in a temperature range of 400 ℃ to 800 ℃ using thermogravimetric analysisT％，WTLess than or equal to 1. The negative active material layer has good thermal stability in the temperature range of 400 ℃ to 800 ℃, and is more beneficial to improving the discharge capacity of the electrochemical device.
In one embodiment of the present application, the negative active material layer further includes a negative active material including at least one of graphite, hard carbon, silicon, or silicon oxygen material. The above negative active materials are selected to be more beneficial to improving the discharge capacity of the electrochemical device.
In one embodiment of the present application, any region having a size of 20cm × 40cm is selected on the negative electrode active material layer, and the number of cracks in the region is 2 or less. The electrochemical device has high discharge capacity, and the negative active material layer produced by high production efficiency has less cracks, the negative electrode has good quality, the rejection rate of the negative electrode is reduced, and the productivity is improved, so that the production efficiency of the electrochemical device is further improved. The "crack" in the present application means a gap having a length of more than 2cm appearing on the negative electrode active material layer.
In one embodiment of the present application, the tensile strength of the negative electrode is 300MPa to 600 MPa. The cathode has good tensile property, so that the number of cracks of the cathode can be further reduced, the cathode productivity is improved, and the production efficiency of the electrochemical device is improved.
The present application is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode current collector may include a copper foil, a copper alloy foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, a composite current collector, or the like. In the present application, the thickness of the anode current collector and the anode active material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the negative electrode current collector is 6 to 10 μm, and the thickness of the single-sided negative electrode active material layer is 30 to 130 μm. In the present application, the negative electrode active material layer may be provided on one surface in the thickness direction of the negative electrode current collector, and may also be provided on both surfaces in the thickness direction of the negative electrode current collector. The "surface" herein may be the entire region of the negative electrode current collector or a partial region of the negative electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved. Optionally, the negative electrode may further include a conductive layer between the negative electrode current collector and the negative electrode active material layer. The composition of the conductive layer is not particularly limited in the present application, and may be a conductive layer commonly used in the art. For example, the conductive layer includes a conductive agent and a binder.
The electrochemical device of the present application further comprises a positive electrode. The positive electrode is not particularly limited as long as the object of the present invention can be achieved. For example, the positive electrode includes a positive electrode current collector and a positive electrode active materialAnd (7) a material layer. The positive electrode current collector is not particularly limited as long as the object of the present invention can be achieved. For example, the positive electrode current collector may include an aluminum foil, an aluminum alloy foil, a composite current collector, or the like. The positive electrode active material layer of the present application contains a positive electrode active material. The kind of the positive electrode active material is not particularly limited as long as the object of the present application can be achieved. For example, the positive electrode active material may include lithium nickel cobalt manganese oxide (811, 622, 523, 111), lithium nickel cobalt aluminate, lithium iron phosphate, lithium rich manganese-based material, lithium cobalt oxide (LiCoO)2) And at least one of lithium manganate, lithium iron manganese phosphate, lithium titanate, and the like. In the present application, the positive electrode active material may further include a non-metal element, for example, the non-metal element includes at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur, which can further improve the stability of the positive electrode active material. In the present application, the thickness of the positive electrode current collector and the positive electrode active material layer is not particularly limited as long as the object of the present application can be achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. The thickness of the single-sided positive electrode active material layer is 30 μm to 120 μm. In the present application, the positive electrode active material layer may be provided on one surface in the thickness direction of the positive electrode current collector, and may also be provided on both surfaces in the thickness direction of the positive electrode current collector. The "surface" herein may be the entire region of the positive electrode current collector or a partial region of the positive electrode current collector, and the present application is not particularly limited as long as the object of the present application can be achieved. Optionally, the positive electrode may further include a conductive layer between the positive electrode current collector and the positive electrode active material layer. The composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.
The conductive agent and the binder are not particularly limited as long as the object of the present invention can be achieved. For example, the conductive agent may include at least one of conductive carbon black (Super P), Carbon Nanotubes (CNTs), carbon nanofibers, flake graphite, acetylene black, carbon dots, or graphene. For example, the binder may include at least one of polyvinyl alcohol, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, Styrene Butadiene Rubber (SBR), polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), aqueous acrylic resin, carboxymethyl cellulose (CMC), or sodium carboxymethyl cellulose (CMC-Na).
In the present application, unless otherwise specified, the negative electrode active material layer refers to a single negative electrode active material layer, and the positive electrode active material layer refers to a single positive electrode active material layer.
The electrochemical device of the present application further includes an electrolyte, and the present application does not particularly limit the kind of the electrolyte as long as the object of the present application can be achieved. For example, at least one of Ethylene Carbonate (EC), Propylene Carbonate (PC), diethyl carbonate (DEC), Ethyl Propionate (EP), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC) and the like is mixed in a predetermined mass ratio to obtain an organic solution, and then a lithium salt is added to dissolve and uniformly mix the organic solution. The present application does not limit the kind of the lithium salt as long as the object of the present application can be achieved. For example, the lithium salt may include LiPF6、LiBF4、LiAsF6、LiClO4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、LiSiF6At least one of LiBOB or lithium difluoroborate. Preferably, the lithium salt may be LiPF6Since it can give high ionic conductivity and improve cycle characteristics.
The electrochemical device further comprises a diaphragm which is used for separating a positive electrode (also called a positive pole piece) and a negative electrode (also called a negative pole piece), preventing short circuit inside the lithium ion battery, allowing electrolyte ions to freely pass through and finishing the function of an electrochemical charging and discharging process. The separator in the present application is not particularly limited as long as the object of the present application can be achieved.
The electrochemical device of the present application is not particularly limited, and may include any device in which electrochemical reactions occur. In some embodiments, the electrochemical device may include, but is not limited to: a lithium metal secondary battery, a lithium ion battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, or the like.
The preparation process of the electrochemical device is well known to those skilled in the art, and the present application is not particularly limited, and for example, may include, but is not limited to, the following steps: stacking the anode, the diaphragm and the cathode in sequence, winding and folding the anode, the diaphragm and the cathode according to needs to obtain an electrode assembly with a winding structure, putting the electrode assembly into a packaging shell, injecting electrolyte into the packaging shell and sealing the packaging shell to obtain the electrochemical device; or, stacking the positive electrode, the separator and the negative electrode in sequence, fixing four corners of the entire lamination structure with an adhesive tape to obtain an electrode assembly of the lamination structure, placing the electrode assembly in a packaging case, injecting an electrolyte into the packaging case, and sealing the packaging case to obtain the electrochemical device. In addition, an overcurrent prevention element, a guide plate, or the like may be placed in the package case as necessary to prevent a pressure rise and overcharge/discharge inside the electrochemical device.
A second aspect of the present application provides an electronic device comprising an electrochemical device according to any one of the previous aspects of the present application. The electronic device has good discharge capacity and high production efficiency.
The electronic device of the present application is not particularly limited, and may include, but is not limited to, the following categories: notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, clocks, electric tools, flashlights, cameras, large household batteries, and the like.
Examples
Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out according to the following methods.
The test method and the test equipment are as follows:
infrared spectrum test:
discharging the lithium ion battery until the voltage is 2.8V, disassembling to obtain a negative electrode, drying the negative electrode, scraping a negative electrode active material layer, soaking the negative electrode active material layer in tetrahydrofuran for 24h, then centrifuging, pouring out the solution after the centrifugation is finished, placing the solution at 70 ℃ for evaporation until the tetrahydrofuran is evaporated, retaining the residual liquid, and then testing the residual liquid by adopting an FTIR-1500 Fourier transform infrared spectrometer.
Testing of the content of each metal element in the negative electrode active material layer:
discharging the lithium ion battery until the voltage is 2.8V, disassembling to obtain a negative electrode, soaking the negative electrode in a DMC solution for 24h, drying, scraping a negative electrode active material layer from the negative electrode after drying, and rolling into powder after drying. Taking 6 parallel samples of the negative active material layer powder, respectively weighing, digesting and diluting, then testing the mass percentage of different metal elements by using a Thermo ICAP6300 model inductively coupled plasma emission spectrometer, and averaging, wherein the mass percentage of each metal element is the mass percentage of the negative active material layer.
Testing of porosity α of the negative active material layer:
the negative electrode with radius d was punched, the thickness h1 of the negative electrode was measured using a ten-thousandth ruler, and loaded into the sample chamber of the AccuPyc 1340 apparatus, and the negative electrode was filled with helium (He) in the closed sample chamber, whereby the true volume V of the negative electrode was measured using the bol law PV-nRT. After the test is finished, the negative active material layer on the surface of the negative electrode is cleaned, the thickness of the current collector is measured to be h2 by using a ten-thousandth micrometer, and the apparent volume pi d of the negative active material layer is calculated2X (h1-h 2). Finally, the porosity α ═ 1- (V-pi d) of the anode active material layer was obtained by the following formula2×h2)/[πd2×(h1-h2)]。
Testing of the single-layer area quality of the negative electrode active material layer:
1) taking the negative electrode coated with the single-layer negative electrode active material layer, cutting the negative electrode into a square of 10cm multiplied by 10cm, weighing, and recording the weight as M1;
2) washing the negative electrode with deionized water to remove the negative electrode active material layer, drying, then weighing the weight of the current collector, and recording the weight as M2;
3) the area mass of the monolayer was (M1-M2)/(10 cm. times.10 cm).
Test of thermogravimetric analysis:
taking 10mg of the negative active material layer material, placing the material in a thermogravimetric analyzer, setting the test atmosphere in the air atmosphere, wherein the test temperature is 20-800 ℃, and the heating rate is 5 ℃/min.
After the test was completed, the mass loss in weight between 400 ℃ and 800 ℃ was recorded, percentage loss in weight WTPercent is 100% - (weight loss percentage from 20 ℃ to 400 ℃ plus residual mass percentage).
Testing of contact Angle:
taking 10ml of uniformly dispersed negative electrode slurry, placing the negative electrode slurry into a sample injector of a contact angle tester according to the equipment operation flow of the contact angle tester, cutting a copper foil with the thickness of 6 microns into strips with the thickness of 2cm multiplied by 4cm, placing the strips on a glass slide, placing the strips below the contact angle tester, dripping the negative electrode slurry in the sample injector onto the glass slide, dripping 3-5 mu l of the negative electrode slurry each time, photographing the negative electrode slurry after dripping, and fitting according to the requirements of the tester to obtain a result.
Characterization of the anode cracking:
and (3) placing the negative electrode coated with the negative electrode active material layer in each example and each comparative example in a 120 ℃ oven (vacuum drying oven DZF-6030A) for baking for 10min, taking out the negative electrode, placing the negative electrode for 25min at room temperature, observing the cracking condition, and determining that no crack with the length of more than 2cm appears in the appearance of the negative electrode active material layer, namely no crack.
Testing of tensile Strength:
and cutting the negative electrodes in each embodiment and each proportion into 2mm multiplied by 10mm strip samples, respectively fixing the strip samples at two ends of a high-speed rail tensile machine, starting the high-speed rail tensile machine, stretching the strip samples, and recording data after the strip samples are broken.
Testing of discharge capacity:
the lithium ion batteries of the embodiments and the comparative examples are set according to the calibration capacity and the voltage use range of the lithium ion battery (assuming that the calibration capacity is C0, and the use range is 3V to 4.4V).
Placing the lithium ion battery at a constant temperature of 25 ℃, standing for 30min, and discharging to 3.0V according to a capacity of 0.2C (current is 0.2 XC 0); then, the mixture was left to stand for 10min, and the lithium ion battery was charged (current 0.2 × C0) to 4.4V, and then was charged at a constant voltage of 4.4V until the current was reduced to 0.05C (current 0.05 × C0). Standing for 10min, and discharging the lithium ion battery to 3.0V according to 0.2C (current ═ 0.2 × C0), namely the discharge capacity of the application.
Examples 1 to 1
< preparation of Positive electrode >
LiCoO as positive electrode active material2Mixing acetylene black and PVDF according to the mass ratio of 96.5:2:1.5, adding N-methyl pyrrolidone (NMP) as a solvent, blending into slurry with the solid content of 75 wt%, and stirring under the action of a vacuum stirrer until the system becomes uniform anode slurry. And uniformly coating the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 10 mu m, and drying at 90 ℃ to obtain the positive electrode with the coating thickness of 110 mu m and the single-side coated positive electrode active material layer. And then, repeating the steps on the other surface of the positive electrode to obtain the positive electrode with the positive active material layer coated on the two surfaces. Drying at 90 ℃, cold pressing, cutting into pieces, and welding tabs to obtain the anode.
< preparation of negative electrode >
Mixing graphite, sodium carboxymethylcellulose and SBR according to the mass ratio of 97:1:2, adding deionized water and an auxiliary agent of stearic acid amide after uniformly mixing, then dispersing at high speed again, wherein the dispersion temperature is 35 ℃, and preparing into uniformly dispersed negative electrode slurry with the solid content of 70 wt%. And uniformly coating the negative electrode slurry on one surface of a negative electrode current collector copper foil with the thickness of 6 mu m, and drying at 90 ℃ to obtain the negative electrode with the coating thickness of 130 mu m and the single-side coated negative electrode active material layer. And then, repeating the steps on the other surface of the cathode to obtain the cathode with the cathode active material layer coated on the two surfaces. Drying at 90 deg.C, cold pressing, cutting into pieces,And welding a tab to obtain the negative electrode. Based on the mass of the negative electrode active material layer, the mass percentage of the auxiliary agent stearic acid amide is 0.5%, and the sum of the mass percentages of the graphite, the sodium carboxymethyl cellulose and the SBR is 99.5%; the porosity α of the negative electrode active material layer was 40%, and the single-layer area mass of the negative electrode active material layer was 0.13mg/mm2。
< preparation of separator >
A polyethylene porous polymer film having a thickness of 14 μm was used.
< preparation of electrolyte solution >
Mixing EC, PC, EMC and DEC in a mass ratio of 20:20:40:20 in a dry argon atmosphere to obtain an organic solvent, and adding fluoroethylene carbonate and lithium hexafluorophosphate into the organic solvent to dissolve and uniformly mix. Based on the total mass of the electrolyte, the content of lithium hexafluorophosphate is 12%, the content of fluoroethylene carbonate is 2%, and the balance is an organic solvent.
< preparation of lithium ion Battery >
And (3) stacking the prepared positive electrode, the diaphragm and the negative electrode in sequence to enable the diaphragm to be positioned between the positive electrode and the negative electrode to play a role in isolation, and then winding to obtain the electrode assembly. And (3) putting the electrode assembly into an aluminum plastic film packaging shell, placing the aluminum plastic film packaging shell in a vacuum oven at 85 ℃ for drying for 12h to remove water, injecting the prepared electrolyte, and performing vacuum packaging, standing, formation, degassing, shaping and other processes to obtain the lithium ion battery.
Examples 1-2 to examples 1-13
The procedure was as in example 1-1, except that the relevant production parameters were adjusted as shown in Table 1.
Example 2-1 to example 2-23
The same as in example 1-1 was performed except that the preparation parameters shown in table 2 were adjusted, and the metal elements shown in table 2 were introduced into the auxiliary, and, for example, magnesium chloride, aluminum chloride, and cobalt oxide were added in appropriate amounts during the production of the auxiliary so that the metal element content in the negative active material layer was as shown in table 2.
Example 3-1 to example 3-5
The procedure of example 1-1 was repeated, except that the materials and contents were adjusted in accordance with Table 3, and the graphite and SBR were changed in mass percentage based on the mass ratio of 97: 2.
Example 4-1 to example 4-8
The procedure was as in example 1-1, except that the relevant production parameters were adjusted as shown in Table 4.
Comparative examples 1 to 2
The procedure was as in example 1-1, except that the relevant production parameters were adjusted as shown in Table 1.
Wherein FIG. 1 shows the infrared spectrum of example 2-1, and as can be seen from FIG. 1, the wave number is 2500cm-1To 3200cm-1Has three peaks, indicating that the negative electrode active material layer of example 2-1 has a wave number of 2500cm-1To 3200cm-1Has at least a first peak and a second peak within the range of (a).
The preparation and performance parameters for each example and each comparative example are shown in tables 1 to 4:
the kind and content of the metal element in the negative active material layer also generally affect the discharge capacity and production efficiency of the lithium ion battery. It can be seen from examples 1-1, 2-1 to 2-23 that the lithium ion batteries having the types and contents of the metal elements in the negative electrode active material layer within the ranges of the present application have good discharge capacities and high production efficiencies.
When Al is included in the negative active material layer, the content of Al also generally affects the discharge capacity and production efficiency of the lithium ion battery. From examples 2-2 to 2-4, it can be seen that the lithium ion battery having an Al content within the range of the present application has a good discharge capacity and a high production efficiency.
When Co is included in the negative active material layer, the content of Co also generally affects the discharge capacity and production efficiency of the lithium ion battery. From examples 2-5 to examples 2-8, it can be seen that the lithium ion batteries having a Co content within the range of the present application have good discharge capacity and high production efficiency.
When Cr is included in the negative active material layer, the content of Cr also generally affects the discharge capacity and production efficiency of the lithium ion battery. As can be seen from examples 2-9 to examples 2-11, the lithium ion batteries containing Cr in the range of the present application have good discharge capacity and high production efficiency.
When the anode active material layer includes Al and Co, the ratio M of the content of Al to the content of Co1/M2The discharge capacity and production efficiency of lithium ion batteries are also typically affected. As can be seen from examples 2 to 12 to examples 2 to 14, the ratio M of the Al content to the Co content1/M2The lithium ion battery in the range has good discharge capacity and higher production efficiency.
When Al and Cr are included in the anode active material layer, the ratio M of the Al content to the Cr content1/M3The discharge capacity and production efficiency of lithium ion batteries are also typically affected. As can be seen from examples 2 to 15 to examples 2 to 18, the ratio M of the Al content to the Cr content1/M3The lithium ion battery in the range has good discharge capacity and higher production efficiency.
When the anode active material layer includes Al, Co and Cr, the ratio M of the Al content to the Co content1/M2The ratio M of the content of Al to the content of Cr1/M3The discharge capacity and production efficiency of lithium ion batteries are also typically affected. As can be seen from examples 2 to 19 to examples 2 to 23, the ratio M of the Al content to the Cr content1/M3The lithium ion battery in the range has good discharge capacity and higher production efficiency.
TABLE 3
Note: the "\\" in Table 3 indicates no relevant parameters.
The type of dispersant also generally affects the discharge capacity and production efficiency of lithium ion batteries. As can be seen from examples 1-1, 3-1 to 3-5, the lithium ion batteries having the dispersant within the range of the present application have good discharge capacity and high production efficiency.
Content W of dispersant2Content W of the auxiliary1Difference value W between2－W1The discharge capacity and production efficiency of lithium ion batteries are also typically affected. As can be seen from examples 1-1, 3-3 to 3-4, the content W of the dispersant2Content W of the auxiliary1Difference value W between2－W1The lithium ion battery in the range has good discharge capacity and higher production efficiency.
TABLE 4
Note: the "\\" in Table 4 indicates no relevant parameters.
The porosity α of the negative active material layer also generally affects the discharge capacity and production efficiency of the lithium ion battery. It can be seen from examples 1-1, 4-1 to 4-4 that the lithium ion batteries in which the porosity α of the negative electrode active material layer is within the range of the present application have good discharge capacity and high production efficiency.
The monolayer area quality of the negative active material layer also generally affects the discharge capacity and production efficiency of the lithium ion battery. It can be seen from examples 1-1, 4-5 to 4-8 that the lithium ion batteries having the negative electrode active material layer with the single layer area quality within the range of the present application have good discharge capacity and high production efficiency.
The type of negative active material also generally affects the discharge capacity of the lithium ion battery. It can be seen from examples 1 to 1 and 4 to 8 that the lithium ion batteries having the negative electrode active material within the range of the present application have good discharge capacities.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (12)
1. An electrochemical device comprising a negative electrode including 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 wave number of the negative active material layer is 2500cm by infrared spectrum test-1To 3200cm-1Has at least a first peak and a second peak.
2. The electrochemical device of claim 1, wherein the first peak is at a wavenumber k1In the range of 2800cm-1≤k1≤2900cm-1Said second peak being at wavenumber k2In the range of 2900cm-1<k2≤3000cm-1Intensity of said first peak ε1And the intensity ε of the second peak2Satisfies the following conditions: 0.9 ≤ epsilon1/ε2≤1.0。
3. The electrochemical device according to claim 1, wherein the negative electrode active material layer includes an auxiliary agent including at least one of stearic acid, stearic acid amide, magnesium stearate, calcium stearate, sodium stearate, lithium stearate, zinc stearate, aluminum stearate, chromium stearate, or barium stearate.
4. The electrochemical device according to claim 3, wherein the auxiliary is contained in an amount of W by mass based on the mass of the negative electrode active material layer1% is 0.05% to 5%.
5. The electrochemical device according to claim 1, wherein the anode active material layer includes a metal element including at least one of Mg, Al, Co, Ti, Cr, Y, W, or Ca.
6. The electrochemical device according to claim 5, wherein the content of the metal element is M ppm, M.ltoreq.300, based on the mass of the anode active material layer.
7. The electrochemical device according to claim 5, wherein the metal element satisfies at least one of the following features (a) to (e):
(a) the metal element includes Al, and the content of Al is M based on the mass of the anode active material layer1 ppm，10≤M1≤90；
(b) The metal element includes Co in an amount of M based on the weight of the anode active material layer2ppm，0.5≤M2≤20；
(c) The metal element includes Cr in an amount of M based on the weight of the anode active material layer3 ppm，0＜M3≤5；
(d) The metal elements include Al and Co, and the content of Al is M based on the weight of the anode active material layer1ppm, the content of the Co element is M2 ppm，5≤M1/M2≤60，1≤M2≤20；
(e) The metal elements include Al and Cr, and the content of Al is M based on the weight of the anode active material layer1ppm, the content of Cr is M3 ppm，30≤M1/M3≤100。
8. The electrochemical device of claim 3, wherein the negative active material layer further comprises a dispersant comprising at least one of lithium hydroxymethylcellulose, sodium hydroxymethylcellulose, polyacrylic acid, or sodium polyacrylate;
the mass percentage content W of the dispersant based on the mass of the negative electrode active material layer2% of the auxiliary agent and the mass percentage content W of the auxiliary agent1% satisfies: w is not less than 02－W1≤3。
9. The electrochemical device according to claim 1, wherein the anode active material layer satisfies at least one of the following conditions:
(I) the porosity α of the negative electrode active material layer is 15% to 60%;
(II) the single-layer area mass of the negative electrode active material layer was 0.02mg/mm2To 0.4mg/mm2；
(III) the weight loss percentage of the negative active material layer is W in the temperature range of 400-800 ℃ by adopting thermogravimetric analysisT％，WT≤1；
(IV) the negative active material layer further comprises a negative active material comprising at least one of graphite, hard carbon, silicon, or silicon oxygen material.
10. The electrochemical device according to claim 1, wherein any region having a size of 20cm x 40cm is selected on the negative electrode active material layer, and the number of cracks in the region is 2 or less.
11. The electrochemical device according to claim 1, wherein the tensile strength of the negative electrode is 300 to 600 MPa.
12. An electronic device comprising the electrochemical device of any one of claims 1 to 11.
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