Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device. The electrochemical device comprises a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a first active material, and a delithiation product of the first active material comprises at least one of Li5-xFeO4-y, Li5-xCoO4-y, Li2-zMnO2, Li1.2-rNi0.13Fe0.13Mn0.54O2 or Li1-tFePO4; and the negative electrode sheet comprises a negative electrode material layer, the negative electrode material layer comprises silicon, and based on the mass of the negative electrode material layer, the mass percentage content of silicon is 1%-50%. The mass of the delithiation product of the first active material in the positive electrode sheet is A mg / 1540 mm2, the mass of silicon in the negative electrode sheet is B mg / 1540 mm2, and 29%≤A / B≤230%. The electrochemical device has the above features, and thus can have high energy density and good safety performance and cycle performance.

Description

An electrochemical device and an electronic device

[0001] This application claims priority to Chinese Patent Application No. 202410916811.X, filed on July 9, 2024, entitled "An Electrochemical Device and Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrochemical technology, and in particular to an electrochemical device and an electronic device. Background Technology

[0003] Electrochemical devices, such as lithium-ion batteries, have entered our daily lives along with technological advancements and increasingly stringent environmental requirements. With the widespread adoption of lithium-ion batteries, safety issues such as external force puncturing the batteries have arisen at the user end, leading to growing concerns about their safety performance. This is especially true given the ongoing series of mobile phone explosion incidents, which have prompted users, after-sales service providers, and lithium-ion battery manufacturers to demand new safety standards for lithium-ion batteries.

[0004] Currently, most methods to improve the safety performance of lithium-ion batteries come at the cost of sacrificing their energy density and cycle performance. Therefore, there is an urgent need to provide a technical means to improve the safety and cycle performance of lithium-ion batteries under the condition of higher energy density. Summary of the Invention

[0005] The purpose of this application is to provide an electrochemical device and an electronic device that enable the electrochemical device to achieve both high energy density and good safety and cycle performance. The specific technical solution is as follows:

[0006] A first aspect of this application provides an electrochemical device comprising a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive electrode material layer. The positive electrode material layer includes a first positive electrode material layer and a second positive electrode material layer, with the first positive electrode material layer disposed between the positive current collector and the second positive electrode layer. The first positive electrode material layer includes a first active material, and the delithiation product of the first active material includes Li. 5-x FeO 4-y Li 5-x CoO 4-y Li 2-z MnO2, Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O2 or Li 1-tAt least one of FePO4, wherein 4≤x≤5, 2≤y≤3, 1.6≤z≤2, 1≤r≤1.2, and 0.8≤t≤1. The second positive electrode material layer includes a second active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide; the negative electrode includes a negative electrode material layer, which includes silicon, and the mass percentage of silicon is 1% to 50% based on the mass of the negative electrode material layer. The mass of the delithiation product of the first active material in the positive electrode is A mg / 1540mm. 2 The mass of silicon in the negative electrode is B mg / 1540mm². 2 The electrochemical device comprises a positive electrode and a negative electrode with the above characteristics, and the mass percentage of silicon and the A / B ratio are controlled within the above range. The negative electrode material layer has a high specific capacity. Simultaneously, the use of a first active material for lithium replenishment helps reduce the irreversible capacity loss of the second active material during the first charge and improves the first coulombic efficiency of the second active material, thereby increasing the energy density and cycle performance of the secondary battery. Furthermore, the delithiation products of the first active material, as described above, allow the positive electrode to have suitable resistivity and bonding properties, thus improving the safety performance of the electrochemical device. Therefore, by satisfying the above characteristics, the electrochemical device can achieve a balance of high energy density, good safety performance, and good cycle performance.

[0007] In some embodiments of this application, 39% ≤ A / B ≤ 200%. Adjusting the value of A / B within the above range can enable the electrochemical device to have high energy density, better safety performance, and better cycle performance.

[0008] In some embodiments of this application, the delithiation products of the first active material include LiFeO2, CoO2, MnO2, and Ni. 0.13 Fe 0.13 Mn 0.54 At least one of O2, FePO4, FeO2, Fe2O3, or FeO. The delithiation products of the first active material in the first cathode material layer include the above-mentioned materials, which can give the first cathode material layer suitable resistivity and good adhesion properties, and can enable the electrochemical device to have high energy density while improving its safety and cycle performance.

[0009] In some embodiments of this application, the mass percentage of delithiation products of the first active material is 30% to 96% based on the mass of the first cathode material layer. Adjusting the mass percentage of delithiation products of the first active material within the above range allows the first cathode material layer to have suitable resistivity and bonding properties, enabling the electrochemical device to have high energy density while improving its safety and cycle performance.

[0010] In some embodiments of this application, the mass of the second active material in the positive electrode sheet is C mg / 1540 mm². 2 The A / C ratio is 0.45% ≤ A / C ≤ 6%, preferably 0.9% ≤ A / C ≤ 4.5%. Adjusting the A / C value within the above range can enable the electrochemical device to have high energy density while improving its safety and cycle performance.

[0011] In some embodiments of this application, the silicon element content is 1% to 20% by mass, based on the mass of the negative electrode material layer, which can enable the electrochemical device to have a high energy density while improving its safety performance.

[0012] In some embodiments of this application, the electrochemical device satisfies at least one of the following characteristics: (1) 1 mg / 1540 mm 2 / ≤A≤14mg / 1540mm 2 (2) 3mg / 1540mm 2 ≤B≤12mg / 1540mm 2 (3) 200mg / 1540mm 2 ≤C≤300mg / 1540mm 2 Meeting the above characteristics allows electrochemical devices to have high energy density while improving their safety and cycle performance.

[0013] In some embodiments of this application, the first positive electrode material layer further includes inorganic materials, including at least one of alumina, lithium lanthanum zirconium oxide, lithium lanthanum titanate, lithium titanium aluminum phosphate, antimony-doped tin oxide, or titanium oxide; the mass percentage of the inorganic materials is 5% to 60% based on the mass of the first positive electrode material layer. Including the aforementioned inorganic materials in the first positive electrode material layer and controlling their mass percentage within the above range can improve the stability of the first positive electrode material layer, giving it good adhesion properties and suitable resistivity, reducing the probability of internal short circuits and the heat generated by internal short circuits, thereby further improving the safety performance of the electrochemical device.

[0014] In some embodiments of this application, the specific capacity of the first positive electrode material layer is from 130 mAh / g to 780 mAh / g. Because the first active material has a high specific capacity, ensuring the specific capacity of the first positive electrode material layer is within the aforementioned range, during the first charge of the electrochemical device, it can mitigate the loss of active lithium caused by the formation of the solid electrolyte interphase (SEI) film, reduce irreversible capacity loss and the decrease in initial coulombic efficiency, thereby enabling the electrochemical device to achieve high energy density while further improving its cycle performance.

[0015] In some embodiments of this application, the specific capacity of the first positive electrode material layer is greater than or equal to the specific capacity of the second positive electrode material layer. The specific capacities of the first and second positive electrode material layers satisfying the aforementioned relationship are more conducive to leveraging the lithium replenishment effect of the first active material during the initial charge-discharge cycle, reducing the loss of active lithium in the second positive electrode material layer, reducing irreversible capacity loss of the electrochemical device, and minimizing the decrease in initial coulombic efficiency. This results in the electrochemical device possessing high energy density while further improving its cycle performance.

[0016] In some embodiments of this application, the first active material comprises at least one of the following compounds: Li5QO4 or Li5QO6, where Q comprises at least one of Ni, Co, Fe, Sn, or Mn, and the valence state of the Q element is lower than its highest oxidation state; Li q Fe 0.5(1+q) PO4, 1≤q≤5; Li 2-a-b-c-d Ni a R b Mn c M d O 2-f , 0≤a<0.35, 0<b<0.5, 0.3<c≤0.6, 0≤d<0.05, 0.7<a+b+c+d<0.9, 0≤f<0.2, R includes at least one of Fe or Co, M includes at least one of Mg, Al, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, La or W; Li 1+e Mn 1-p X p O 2-s Y s The range is defined as follows: -0.1 < e < 0.2, 0 ≤ p < 0.2, 0 ≤ s < 0.2, where X includes at least one of Fe, Co, Ni, Ti, Zn, Mg, Al, V, Cr, or Zr, and Y includes at least one of S, N, F, Cl, or Br. The first active material within this range exhibits high specific capacity and low initial coulombic efficiency, which helps reduce initial coulombic efficiency and irreversible capacity loss. The aforementioned first active material also possesses good stability, enabling the electrochemical device to exhibit good cycle performance. Furthermore, the positive electrode has suitable resistivity, and the positive electrode material layer exhibits high adhesion to the positive electrode current collector, further improving the safety performance of the electrochemical device. Therefore, selecting the aforementioned materials allows the electrochemical device to possess high energy density, good safety performance, and good cycle performance.

[0017] In some embodiments of this application, the first active material includes Li5FeO4, Li5CoO4, Li2MnO2, and Li 1.2 Ni 0.13 Fe 0.13 Mn 0.54At least one of O2 or LiFePO4. Using the aforementioned first active material is more conducive to leveraging its lithium replenishment function, enabling the electrochemical device to achieve high energy density while further improving its safety and cycle performance.

[0018] In some embodiments of this application, the negative electrode material layer includes a negative electrode active material, which includes at least one of silicon, silicon-carbon, or silicon-oxygen. These materials have high specific capacity, and including them in the negative electrode active material enables the electrochemical device to have high energy density.

[0019] In some embodiments of this application, the negative electrode active material further includes at least one of graphite, hard carbon, soft carbon, or mesophase microcarbon spheres.

[0020] In some embodiments of this application, the resistivity of the positive electrode material layer is ρΩ·m, where 44≤ρ≤155. The resistivity of the positive electrode material layer being within this range indicates that the positive electrode material layer has suitable impedance, which can reduce the probability of internal short circuits in the electrochemical device and reduce the heat generated during internal short circuits, thereby further improving the safety performance of the electrochemical device.

[0021] The second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. The electrochemical device provided in the first aspect of this application has high energy density, good safety performance, and good cycle performance, thus the electronic device of this application has good performance and a long service life.

[0022] This application provides an electrochemical device and an electronic device. The electrochemical device includes a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive electrode material layer. The positive electrode material layer includes a first positive electrode material layer and a second positive electrode material layer, with the first positive electrode material layer disposed between the positive current collector and the second positive electrode material layer. The first positive electrode material layer includes a first active material, and the delithiation product of the first active material includes Li. 5-x FeO 4-y Li 5-x CoO 4-y Li 2-z MnO2, Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O2 or Li 1-tThe second positive electrode material layer comprises at least one of FePO4, and includes a second active material, which comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide; the negative electrode comprises a negative electrode material layer, which comprises silicon, and the mass percentage of silicon is 1% to 50% based on the mass of the negative electrode material layer; the mass of the delithiation product of the first active material in the positive electrode is A mg / 1540mm. 2 The mass of silicon in the negative electrode is B mg / 1540mm². 2 The electrochemical device comprises positive and negative electrode plates with the above characteristics. By controlling the mass percentage of silicon and the A / B ratio within the above range, the electrochemical device can achieve high energy density, good safety performance, and good cycle performance.

[0023] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0025] Figure 1 is a schematic diagram of the structure of the positive electrode sheet in one embodiment of this application.

[0026] Reference numerals: positive electrode 10, first positive electrode material layer 11, second positive electrode material layer 12, positive electrode current collector 13. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0028] It should be noted that, in the specific embodiments of this application, a lithium-ion battery is used as an example of an electrochemical device to explain this application; however, the electrochemical device of this application is not limited to lithium-ion batteries. The specific technical solution is as follows:

[0029] A first aspect of this application provides an electrochemical device comprising a positive electrode and a negative electrode. The positive electrode includes a positive current collector and a positive electrode material layer. The positive electrode material layer includes a first positive electrode material layer and a second positive electrode material layer, with the first positive electrode material layer disposed between the positive current collector and the second positive electrode material layer. The first positive electrode material layer includes a first active material, and the delithiation product of the first active material includes Li. 5-x FeO 4-y Li 5-x CoO 4-y Li 2-z MnO2, Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O2 or Li 1-t At least one of FePO4, wherein 4≤x≤5, 2≤y≤3, 1.6≤z≤2, 1≤r≤1.2, and 0.8≤t≤1. The second positive electrode material layer includes a second active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide; the negative electrode sheet includes a negative electrode material layer, which includes silicon element. Based on the mass of the negative electrode material layer, the mass percentage content of silicon element is 1% to 50%, preferably 1% to 20%; for example, the mass percentage content of silicon element can be 1%, 2.2%, 5%, 8%, 10%, 12.2%, 14.2%, 17%, 20%, 23%, 26%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, or a range consisting of any two of these values. The mass of the delithiation product of the first active material in the positive electrode is A mg / 1540 mm. 2 The mass of silicon in the negative electrode is B mg / 1540mm². 2 The ratio is 29% ≤ A / B ≤ 230%, preferably 39% ≤ A / B ≤ 200%. For example, the value of A / B can be 29%, 34%, 39%, 45%, 47%, 50%, 55%, 58%, 60%, 62%, 69%, 70%, 75%, 78%, 80%, 85%, 88%, 92%, 95%, 100%, 105%, 110%, 114%, 116%, 130%, 150%, 160%, 175%, 190%, 210%, 215%, 230%, or a range of any two of these values.

[0030] By including silicon in the negative electrode material layer and controlling the mass percentage of silicon within the aforementioned range, the electrochemical device can achieve a higher energy density. Using the aforementioned second active material as the main positive electrode material allows the electrochemical device to exhibit better cycle performance and a higher initial coulombic efficiency. During the first charge of the electrochemical device, the formation of the solid electrolyte interphase (SEI) film on the surface of the silicon-containing negative electrode consumes a large amount of active lithium extracted from the positive electrode, resulting in a decrease in the initial coulombic efficiency and irreversible capacity loss. The inventors discovered that using the first active material for lithium replenishment results in a higher specific capacity and a lower initial coulombic efficiency. After the first charge of the electrochemical device, the first active material undergoes delithiation to obtain a delithiation product of the first active material. During charging, the first active material undergoes delithiation, yielding a delithiation product. The lithium ions released from the first active material can replace those released from the second active material in the negative electrode film formation. Furthermore, the minimal lithium ion re-intercalation after the initial delithiation helps reduce irreversible capacity loss during the first charge of the second active material, improving its initial coulombic efficiency and thus enhancing the initial coulombic efficiency and cycle performance of the secondary battery. Simultaneously, these characteristics allow for a suitable resistivity in the positive electrode and high adhesion between the positive electrode material layer and the positive current collector, thereby improving the safety performance of the electrochemical device. Therefore, combining the first active material (using the delithiation product) with the second active material and a silicon-containing negative electrode allows for high energy density while simultaneously improving cycle performance and safety. If the A / B ratio is too low, for example, less than 29%, the formation of the SEI film will consume lithium ions in the second active material, reducing active lithium and causing a decrease in the initial coulombic efficiency and irreversible capacity loss of the electrochemical device. This also negatively impacts the safety performance of the lithium-ion battery. When the A / B ratio is too high, for example, greater than 230%, the combination of the first active material and silicon is unreasonable. Simultaneously, excessive side reactions occur between the first active material, the negative electrode material layer, and the electrolyte, significantly impacting the electrical performance of the electrochemical device. Capacity decay is rapid during cycling, which is detrimental to improving the device's cycle performance. Therefore, by selecting a second active material and the delithiation product as the first active material, and by including silicon in the negative electrode material layer and controlling its mass percentage and A / B ratio within the aforementioned range, the electrochemical device can simultaneously possess high energy density, good safety performance, and good cycle performance.

[0031] In some implementations, the initial charging process described above can be as follows: at 45°C, first charge at a constant current of 0.1 times (C) for 10 minutes, then charge at a constant current of 0.5C to a voltage Q (Q≥4.45V), and then charge at a constant voltage until the current is less than or equal to 0.05C. For example, Q can be 4.45V, 4.48V, 4.5V, 4.53V, 4.6V, 4.7V, or a range of any two of these values. In electrochemical devices requiring formation, the initial charging process described above can be a formation process.

[0032] As shown in Figure 1, the positive electrode 10 in this application includes a first positive electrode material layer 11, a second positive electrode material layer 12, and a positive electrode current collector 13. The first positive electrode material layer 11 is disposed between the positive electrode current collector 13 and the second positive electrode material layer 12, which can improve the protection of the positive electrode current collector and the interlayer adhesion of the positive electrode material layer, reduce the probability of internal short circuit and internal short circuit Joule heating caused by external mechanical damage, and make it more conducive to the electrochemical device having high energy density and good safety performance.

[0033] In some embodiments of this application, the delithiation products of the first active material include LiFeO2, CoO2, MnO2, and Ni. 0.13 Fe 0.13 Mn 0.54 At least one of O2, FePO4, FeO2, Fe2O3, or FeO. The delithiation products of the first active material in the first positive electrode material layer include the above-mentioned materials. The lithium ions delithiated from the first active material can be consumed in the negative electrode to form a film instead of the lithium ions delithiated from the second active material. Furthermore, the amount of lithium ion re-intercalation after the first delithiation is small, which helps to reduce the irreversible capacity loss of the second active material during the first charge and improve the first coulombic efficiency of the second active material. This can improve the first coulombic efficiency and cycle performance of the secondary battery. At the same time, the first positive electrode material layer has a suitable resistivity and good adhesion properties, which can enable the electrochemical device to have high energy density while improving its safety and cycle performance.

[0034] In some embodiments of this application, based on the mass of the first cathode material layer, the mass percentage of the delithiation product of the first active material is 30% to 96%. For example, the mass percentage of the delithiation product of the first active material can be 30%, 36%, 40%, 45%, 50%, 55%, 58%, 60%, 62%, 69%, 70%, 75%, 78%, 80%, 85%, 88%, 92%, 96%, or a range consisting of any two of these values. A mass percentage of the delithiation product of the first active material within the above range is beneficial for fully utilizing the lithium replenishment function of the first active material. Simultaneously, the first cathode material layer possesses suitable resistivity and good adhesion properties, enabling the electrochemical device to achieve high energy density while improving its safety and cycle performance.

[0035] Typically, the mass percentage of delithiation products of the first active material can be adjusted by changing the mass percentage of the first active material in the first positive electrode material layer during the preparation process. With other conditions remaining constant, increasing the mass percentage of the first active material increases the mass percentage of the delithiation products; conversely, decreasing the mass percentage of the first active material decreases the mass percentage of the delithiation products.

[0036] This application does not impose any particular limitation on the mass percentage of the first active material in the first cathode material layer. The mass percentage of the delithiation product of the first active material can be adjusted according to the actual needs, as long as the purpose of this application can be achieved.

[0037] In some embodiments of this application, the mass of the second active material in the positive electrode sheet is C mg / 1540 mm². 2 The A / C ratio should be 0.45% ≤ A / C ≤ 6%, preferably 0.9% ≤ A / C ≤ 4.5%. For example, the A / C value can be 0.45%, 0.5%, 0.8%, 1%, 1.4%, 1.8%, 2%, 2.5%, 2.8%, 3%, 3.4%, 3.8%, 4%, 4.5%, 4.8%, 5%, 5.2%, 5.6%, 6%, or a range of any two of these values. Adjusting the A / C value within the above range reduces side reactions between the first active material, the negative electrode material layer, and the electrolyte. This helps the positive electrode material layer achieve a high specific capacity while maintaining good cycle stability, thereby enabling the electrochemical device to have high energy density while improving its safety and cycle performance.

[0038] In some embodiments of this application, 1 mg / 1540 mm 2 ≤A≤14mg / 1540mm 2 3mg / 1540mm 2 ≤B≤12mg / 1540mm 2200mg / 1540mm 2 ≤C≤300mg / 1540mm 2 For example, A can be 1 mg / 1540 mmHg. 2 3mg / 1540mm 2 5mg / 1540mm 2 6mg / 1540mm 2 8mg / 1540mm 2 10mg / 1540mm 2 12mg / 1540mm 2 13mg / 1540mm 2 14mg / 1540mm 2 Or it can be a range consisting of any two of these values, where B can be 3mg / 1540mm. 2 4mg / 1540mm 2 6mg / 1540mm 2 8mg / 1540mm 2 9mg / 1540mm 2 10mg / 1540mm 2 12mg / 1540mm 2 Or it can be a range consisting of any two of these values, where C can be 200mg / 1540mm. 2 220mg / 1540mm 2 240mg / 1540mm 2 250mg / 1540mm 2 280mg / 1540mm 2 300mg / 1540mm 2 Or it can be a range consisting of any two of these values. Satisfying the above characteristics allows electrochemical devices to have high energy density while improving their safety and cycle performance.

[0039] In some embodiments of this application, the negative electrode material layer includes a negative electrode active material, which includes at least one of silicon, silicon-carbon, or silicon-oxygen. The aforementioned silicon-containing materials have high specific capacity, and including these silicon-containing materials in the negative electrode active material enables the electrochemical device to have high energy density.

[0040] In some embodiments of this application, the negative electrode active material further includes at least one of graphite, hard carbon, soft carbon, or mesophase microcarbon spheres. The graphite mentioned above includes at least one of artificial graphite or natural graphite. In this application, based on the mass of the negative electrode material layer, the mass percentage content of the aforementioned carbon material can be from 0.7% to 97.2%.

[0041] In some implementations, the silicon element in the negative electrode material layer is derived from silicon, silicon-carbon, or silicon-oxygen-containing materials. Based on the mass of the negative electrode material layer, the mass percentage of the silicon-containing material can range from 2% to 98.5%. Typically, the mass percentage of silicon and the value of B can be adjusted by changing the mass percentage of the silicon-containing material in the negative electrode material layer and the coating weight of the negative electrode material layer. With other conditions remaining constant, increasing the mass percentage of the silicon-containing material in the negative electrode material layer increases the mass percentage of silicon and the value of B; decreasing the mass percentage of the silicon-containing material in the negative electrode material layer decreases the mass percentage of silicon and the value of B. With other conditions remaining constant, increasing the coating weight of the negative electrode material layer increases the value of B; decreasing the coating weight of the negative electrode material layer decreases the value of B.

[0042] Typically, the value of A can be adjusted by changing the coating weight of the first positive electrode material layer and the mass percentage of the first active material in the first positive electrode material layer. With other conditions remaining constant, increasing the coating weight of the first positive electrode material layer increases A, and decreasing the coating weight decreases A. Similarly, with other conditions remaining constant, increasing the mass percentage of the first active material increases A, and decreasing the mass percentage of the first active material decreases A.

[0043] Typically, the value of C can be adjusted by changing the coating weight of the second positive electrode material layer and the mass percentage of the second active material in the second positive electrode material layer. With other conditions remaining constant, increasing the coating weight of the second positive electrode material layer increases C, and decreasing the coating weight decreases C. Similarly, with other conditions remaining constant, increasing the mass percentage of the second active material increases C, and decreasing the mass percentage of the second active material decreases C.

[0044] In this application, there are no particular limitations on the coating weight of the first positive electrode material layer and the coating weight of the second positive electrode material layer, as long as the purpose of this application can be achieved. For example, the coating weight of the first positive electrode material layer can be 3 mg / 1540 mm. 2 Up to 20mg / 1540mm 2 The coating weight of the second cathode material layer can be 200 mg / 1540 mm². 2 Up to 300mg / 1540mm 2 .

[0045] In some embodiments of this application, the first cathode material layer further includes an inorganic material, which includes at least one of alumina, lithium lanthanum zirconium oxide, lithium lanthanum titanate, lithium titanium aluminum phosphate, antimony-doped tin oxide, or titanium oxide; based on the mass of the first cathode material layer, the mass percentage content of the inorganic material is 0.2% to 60%, preferably 5% to 60%. For example, the mass percentage content of the inorganic material can be 0.2%, 2%, 3%, 5%, 8%, 10%, 12.2%, 14.2%, 17%, 20%, 23%, 26%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 60%, or a range consisting of any two of these values. The first positive electrode material layer includes the aforementioned inorganic materials, and by controlling its mass percentage content within the aforementioned range, the stability of the positive electrode material layer can be improved, enabling the first positive electrode material layer to have good adhesion properties and suitable resistivity, reducing the probability of internal short circuits and the heat generated by internal short circuits, thereby further improving the safety performance of the electrochemical device.

[0046] In some embodiments of this application, the specific capacity of the first positive electrode material layer is between 130 mAh / g and 780 mAh / g. For example, the specific capacity of the first positive electrode material layer can be 130 mAh / g, 150 mAh / g, 160 mAh / g, 180 mAh / g, 200 mAh / g, 250 mAh / g, 300 mAh / g, 350 mAh / g, 400 mAh / g, 500 mAh / g, 600 mAh / g, 700 mAh / g, 780 mAh / g, or a range of any two of these values. Because the first active material has a high specific capacity, the specific capacity of the first positive electrode material layer can be within the above range. This improves the loss of active lithium caused by the formation of the SEI film during the first charge of the electrochemical device, reduces irreversible capacity loss and the decrease in initial coulombic efficiency, thereby enabling the electrochemical device to have high energy density while further improving its cycle performance and safety performance. In some embodiments of this application, preferably, the specific capacity of the first positive electrode material layer is greater than or equal to the specific capacity of the second positive electrode material layer. While the specific capacity of the first cathode material layer is within the scope of this application, the specific capacities of the first cathode material layer and the second cathode material layer satisfy the above relationship, which is more conducive to reducing the loss of active lithium in the second cathode material layer during the first charge and discharge, giving full play to the lithium replenishment role of the first active material, reducing the irreversible capacity loss of the electrochemical device and the reduction of the first coulombic efficiency, thereby enabling the electrochemical device to have high energy density while further improving its cycle performance.

[0047] In some embodiments, the specific capacity of the second cathode material layer can be from 130 mAh / g to 280 mAh / g. For example, the specific capacity of the second cathode material layer can be 130 mAh / g, 150 mAh / g, 170 mAh / g, 186 mAh / g, 192 mAh / g, 200 mAh / g, 220 mAh / g, 245 mAh / g, 260 mAh / g, 280 mAh / g, or a range of any two of these values. A specific capacity of the second cathode material layer within the above range allows the electrochemical device to have a high energy density.

[0048] Generally, the specific capacity of the first positive electrode material layer can be adjusted by changing the type and mass percentage of active materials in the first positive electrode material layer. With other conditions remaining constant, using a first positive electrode material with a high specific capacity or increasing the mass percentage of active materials in the first positive electrode material layer increases the specific capacity of the first positive electrode material layer; using a first positive electrode material with a low specific capacity or decreasing the mass percentage of active materials in the first positive electrode material layer decreases the specific capacity of the first positive electrode material layer. Similarly, the specific capacity of the second positive electrode material layer can be adjusted by changing the type and mass percentage of active materials in the second positive electrode material layer. With other conditions remaining constant, using a second positive electrode material with a high specific capacity or increasing the mass percentage of active materials in the second positive electrode material layer increases the specific capacity of the second positive electrode layer; using a second positive electrode material with a low specific capacity or decreasing the mass percentage of active materials in the second positive electrode material layer decreases the specific capacity of the second positive electrode material layer.

[0049] In some embodiments of this application, the first active material comprises at least one of the following compounds: Li5QO4 or Li5QO6, where Q comprises at least one of Ni, Co, Fe, Sn, or Mn, and the valence state of the Q element is lower than its highest oxidation state; Li q Fe 0.5(1+q) PO4, 1≤q≤5; Li 2-a-b-c-d Ni a R b Mn c M d O 2-f , 0≤a<0.35, 0<b<0.5, 0.3<c≤0.6, 0≤d<0.05, 0.7<a+b+c+d<0.9, 0≤f<0.2, R includes at least one of Fe or Co, M includes at least one of Mg, Al, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, La or W; Li 1+e Mn 1-p X p O 2-s Y sThe range is defined as follows: -0.1 < e < 0.2, 0 ≤ p < 0.2, 0 ≤ s < 0.2, where X includes at least one of Fe, Co, Ni, Ti, Zn, Mg, Al, V, Cr, or Zr, and Y includes at least one of S, N, F, Cl, or Br. The first active material within this range exhibits high specific capacity and low initial coulombic efficiency, which helps reduce initial coulombic efficiency and irreversible capacity loss. The aforementioned first active material also possesses good stability, enabling the electrochemical device to exhibit good cycle performance. Furthermore, the positive electrode has suitable resistivity, and the positive electrode material layer exhibits high adhesion to the positive electrode current collector, further improving the safety performance of the electrochemical device. Therefore, selecting the aforementioned materials allows the electrochemical device to possess high energy density, good safety performance, and good cycle performance.

[0050] In some embodiments of this application, the first active material includes Li5FeO4, Li5CoO4, Li2MnO2, and Li 1.2 Ni 0.13 Fe 0.13 Mn 0.54 At least one of O2 or LiFePO4. Using the aforementioned first active material is more conducive to leveraging its lithium replenishment function, enabling the electrochemical device to achieve high energy density while further improving its safety and cycle performance.

[0051] In some embodiments of this application, the resistivity of the positive electrode material layer is ρΩ·m, where 44≤ρ≤155. For example, the value of ρ can be 44, 50, 58, 65, 72, 84, 95, 100, 114, 130, 135, 148, 150, 155, or a range of any two of these values. Adjusting the resistivity of the positive electrode material layer within the above range allows the positive electrode material layer to have suitable impedance, reducing the probability of internal short circuits in the electrochemical device and reducing the heat generated during internal short circuits, thereby further improving the safety performance of the electrochemical device.

[0052] This application does not impose any particular limitation on the resistivity of the first positive electrode material layer and the second positive electrode material layer, as long as their sum is within the aforementioned range. For example, the resistivity of the first positive electrode material layer can be from 40 Ω·m to 130 Ω·m, and the resistivity of the second positive electrode material layer can be from 2 Ω·m to 50 Ω·m.

[0053] In some embodiments, the first positive electrode material layer of this application may further include a conductive agent. This application does not impose any particular limitation on the conductive agent; for example, it may include, but is not limited to, at least one of conductive carbon black or carbon nanotubes. This application does not impose any particular limitation on its mass percentage content; those skilled in the art can select it according to actual needs, as long as the purpose of this application is achieved. For example, based on the mass of the first positive electrode material layer, the mass percentage content of the conductive agent can be from 0% to 5%.

[0054] In this application, the first positive electrode material layer may further include a binder. This application does not particularly limit the type of binder, as long as it achieves the purpose of this application. This application also does not particularly limit the mass percentage content of the binder, as long as it achieves the purpose of this application. For example, based on the mass of the first positive electrode material layer, the mass percentage content of the binder can be from 3% to 15%.

[0055] In some embodiments, the first cathode material layer includes the delithiation product of the first active material and a binder. In other embodiments, the first cathode material layer includes the delithiation product of the first active material, an inorganic material, and a binder. In still other embodiments, the first cathode material layer includes the delithiation product of the first active material, an inorganic material, a binder, and a conductive agent.

[0056] In this application, the second positive electrode material layer may further include a conductive agent and a binder. This application does not particularly limit the types of these agents, as long as they achieve the purpose of this application. This application does not particularly limit the mass percentage content of the second active material, conductive agent, and binder in the second positive electrode material layer, as long as the purpose of this application is achieved. For example, based on the mass of the second positive electrode material layer, the mass percentage content of the second active material can be 90% to 99%, the mass percentage content of the conductive agent can be 0.2% to 5%, and the mass percentage content of the binder can be 0.2% to 5%.

[0057] The aforementioned binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride. The aforementioned conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers. The aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or carbon nanofibers. The aforementioned metallic materials may include, but are not limited to, metal powders and / or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver. The aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole.

[0058] In this application, the positive electrode material layer is disposed on at least one surface of the positive electrode current collector. That is, the positive electrode material layer can be disposed on one surface or two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface" here can be the entire area of ​​the surface of the positive electrode current collector or a part of the surface of the positive electrode current collector. This application has no particular limitation, as long as the purpose of this application can be achieved.

[0059] This application does not impose any particular limitation on the positive electrode current collector, as long as it achieves the purpose of this application. For example, the positive electrode current collector may comprise aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector). This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector may be 5 μm to 20 μm. This application does not impose any particular limitation on the thickness of the first positive electrode material layer and the second positive electrode material layer, as long as it achieves the purpose of this application. For example, the thickness of the first positive electrode material layer may be 2 μm to 5 μm, and the thickness of the second positive electrode material layer may be 30 μm to 120 μm.

[0060] In this application, there are no particular limitations on the preparation method of the positive electrode sheet, as long as it achieves the purpose of this application. In some embodiments, the positive electrode sheet can be prepared by the following method: a first positive electrode material layer slurry is uniformly coated onto one surface of the positive electrode current collector and dried; then, a second positive electrode material layer slurry is uniformly coated onto the surface of the first positive electrode material layer, and after drying, a positive electrode sheet with a single-sided positive electrode material layer is obtained. The above coating steps are repeated on the other surface of the positive electrode current collector, and after drying, a positive electrode sheet with a double-sided positive electrode material layer is obtained. After coating, the positive electrode sheet is obtained by cold pressing and cutting.

[0061] The first positive electrode material layer slurry described above can be prepared by the following steps: mixing a first active material and a binder, optionally adding an inorganic material or mixing an inorganic material and a conductive agent, adding N-methylpyrrolidone (NMP) and stirring until homogeneous, to obtain a first positive electrode material layer slurry with a solid content of 40 wt% to 85 wt%. The second positive electrode material layer slurry described above can be prepared by the following steps: mixing a second active material, a binder, and a conductive agent, adding N-methylpyrrolidone (NMP) and stirring until homogeneous, to obtain a second positive electrode material layer slurry with a solid content of 65 wt% to 85 wt%.

[0062] The negative electrode sheet of this application also includes a negative electrode current collector. A negative electrode material layer is disposed on at least one surface of the negative electrode current collector. In this application, the negative electrode material layer can be disposed on one surface or two surfaces along the thickness direction of the negative electrode current collector. It should be noted that "surface" here can refer to the entire area of ​​the negative electrode current collector or only a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved. In this application, there are no particular limitations on the thickness of the negative electrode current collector and the negative electrode material layer, as long as the purpose of this application is achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the single-sided negative electrode material layer is 30 μm to 160 μm.

[0063] The negative electrode material layer of this application may further include a conductive agent, a binder, and a thickener. This application does not impose any particular limitation on the conductive agent and binder, as long as they achieve the purpose of this application; for example, they may be at least one of the aforementioned conductive agents and binders. The thickener may include at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, or carboxymethyl cellulose. Based on the mass of the negative electrode material layer, the mass percentage content of the conductive agent may be 0.5% to 5%, the mass percentage content of the binder may be 0.2% to 2%, and the mass percentage content of the thickener may be 0.1% to 2%.

[0064] In this application, there are no particular limitations on the preparation method of the negative electrode sheet, as long as it can achieve the purpose of this application. For example, it can be prepared by the following method: mixing negative electrode active material, conductive agent, binder, and thickener, adding deionized water and stirring evenly to obtain a negative electrode slurry with a solid content of 40wt% to 75wt%. The negative electrode slurry is uniformly coated on one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector, and after drying, a negative electrode sheet with a double-sided negative electrode material layer is obtained. After coating, the negative electrode sheet is obtained by cold pressing and cutting.

[0065] The secondary battery of this application further includes an electrolyte, which comprises a lithium salt and a non-aqueous solvent. The lithium salt may include at least one of LiPF6, LiNO3, LiBF4, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or lithium difluoroborate. The non-aqueous solvent may include, but is not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents. The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds or cyclic carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, or methyl ethyl carbonate. The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate, propylene carbonate (PC), butylene carbonate, or vinyl ethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,3-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. This application does not limit the mass percentage of lithium salt and non-aqueous solvents, as long as the purpose of this application is achieved.

[0066] The electrochemical device of this application also includes a separator membrane. This application does not impose any particular limitation on the separator membrane, as long as it achieves the purpose of this application. For example, the material of the separator membrane may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of separator membrane may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane. In some embodiments, the separator membrane may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixture of polymer and inorganic materials. In some embodiments, the inorganic layer includes inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene). In this application, there is no particular limitation on the thickness of the separator, as long as it can achieve the purpose of this application. For example, the thickness of the separator can be from 3 μm to 30 μm.

[0067] The electrochemical device also includes a housing for accommodating the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of electrochemical devices. This application does not limit the scope of these other components. This application does not impose any particular limitation on the housing; it can be a housing known in the art, as long as it achieves the purpose of this application. For example, the housing can be a rigid housing or a flexible housing. The material of the rigid housing can be metal; this application does not limit the type of metal and can use known metal rigid housings, as long as they achieve the purpose of this application. The flexible housing can be a metal-plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0068] This application does not impose any particular limitation on the type of electrochemical device, which may include any device in which an electrochemical reaction occurs. For example, electrochemical devices may include, but are not limited to: lithium-ion batteries, sodium-ion batteries, lithium polymer secondary batteries, and lithium-ion polymer secondary batteries.

[0069] The preparation process of the electrochemical device described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the preparation process of the electrochemical device may include, but is not limited to, the following steps: stacking the positive electrode, the separator, and the negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. Alternatively, stacking the positive electrode, the separator, and the negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0070] The second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application. The electrochemical device provided in the first aspect of this application has high energy density, good safety performance, and good cycle performance, thus the electronic device of this application has good performance and a long service life.

[0071] This application does not specifically limit the type of electronic device, which can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0072] Example

[0073] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0074] Test methods and equipment:

[0075] Sampling methods for positive and negative electrode plates:

[0076] Disassembly process under full charge: The lithium-ion batteries prepared in each embodiment and comparative example were charged at a constant current of 0.2C to the upper voltage limit setting value, reaching the full charge state. After disassembly, the positive and negative electrode plates were removed, cleaned with dimethyl carbonate, and dried at 60°C to obtain positive and negative electrode plate samples. The above-mentioned upper voltage limit setting value is determined by the type of second active material. When the second active material is lithium cobalt oxide, the above-mentioned upper voltage limit setting value is 4.53V; when the second active material is lithium nickel cobalt manganese oxide, the above-mentioned upper voltage limit setting value is 4.25V; when the second active material is lithium iron phosphate, the above-mentioned upper voltage limit setting value is 4.3V; when the second active material is lithium nickel cobalt aluminum oxide, the above-mentioned upper voltage limit setting value is 4.2V; and when the second active material is lithium manganese oxide, the above-mentioned upper voltage limit setting value is 4.3V.

[0077] Disassembly process under full discharge condition: The lithium-ion batteries prepared in each embodiment and comparative example were discharged at a constant current of 0.2C to the lower voltage limit setting value to reach the full discharge state. After disassembly, the positive and negative electrode sheets were removed, cleaned with dimethyl carbonate, and dried at 60°C to obtain positive and negative electrode sheet samples. The aforementioned lower voltage limit setting value is determined by the type of the second active material. When the second active material is lithium cobalt oxide, the aforementioned lower voltage limit setting value is 3V; when the second active material is lithium nickel cobalt manganese oxide, the aforementioned lower voltage limit setting value is 3.2V; when the second active material is lithium iron phosphate, the aforementioned lower voltage limit setting value is 2.4V; when the second active material is lithium nickel cobalt aluminum oxide, the aforementioned lower voltage limit setting value is 2.8V; and when the second active material is lithium manganese oxide, the aforementioned lower voltage limit setting value is 2.4V.

[0078] Determination of delithiation products of the first active material:

[0079] A positive electrode sample was obtained by disassembling a lithium-ion battery in a fully discharged state. The positive electrode material layer was scraped off from the surface of the positive electrode current collector. Powder from the first positive electrode material layer was scraped off from the side that was originally close to the positive electrode current collector. The sample was placed in a muffle furnace and sintered at 500°C for 6 hours. The calcined powder sample was collected and then the following elemental analysis was performed. The composition and structure information of the delithiation product of the first active material were obtained by X-ray diffraction (XRD) and Raman spectroscopy, thereby deducing its chemical formula and calculating its mass percentage content.

[0080] Elemental analysis: 0.4 g of the above powder sample was digested with 10 mL of aqua regia, which was obtained by mixing concentrated nitric acid and concentrated hydrochloric acid in a 1:1 volume ratio. The volume was then adjusted to 100 mL, and the content of each element in the solution was measured using an inductively coupled plasma optical emission spectrometer (ICP).

[0081] XRD Analysis: The powder sample was subjected to XRD testing using an X-ray diffractometer (Bruker D8 ADVANCE). The XRD pattern of the first cathode material layer was obtained. By analyzing the XRD pattern and comparing the position, intensity, and shape of the diffraction peaks with the standard pattern, the phase composition of the delithiation products of the first active material could be obtained. Cu Kα rays were used.

[0082] Raman spectroscopy analysis: The above powder sample was subjected to Raman testing using a Raman spectrometer (LabRAM HR Evolution) to obtain the Raman spectrum of the first cathode material layer. By comparing the characteristic peaks with the standard spectrum, the material metal bond structure information of the delithiation products of the first active material can be obtained.

[0083] Test for the mass percentage (Y) of silicon:

[0084] A negative electrode sample was obtained by disassembling a lithium-ion battery in a fully discharged state. The negative electrode material layer powder on the surface of the negative electrode current collector was scraped off. 1g of the powder sample was taken, and the mass percentage of silicon in the negative electrode material layer was determined by ICP.

[0085] Mass (A) test of the delithiation product of the first active material in the positive electrode:

[0086] A positive electrode sample was obtained by disassembling a lithium-ion battery in a fully charged state. The positive electrode material layer was scraped off from the surface of the positive electrode current collector. Powder of the first positive electrode material layer in the positive electrode sample was scraped from the side that was originally close to the positive electrode current collector (i.e., within a range of 0 to 2 μm from the surface of the positive electrode current collector, parallel to the thickness direction of the current collector). Its mass was weighed as M1 mg, and the area of ​​the positive electrode current collector was measured as S1 mm. 2 Then, the mass percentage w1 of the delithiation product of the first active material was measured using a thermogravimetric analyzer. Therefore, the mass of the delithiation product of the first active material in the positive electrode sheet is calculated as M1 × w1 × 1540 / S1, in mg / 1540 mm². 2 .

[0087] Mass (B) test of silicon in the negative electrode:

[0088] A negative electrode sample was obtained by disassembling a lithium-ion battery in a fully discharged state. The negative electrode material layer powder on the surface of the negative electrode current collector was scraped off and weighed as M² mg. The area of ​​the current collector on the negative electrode sample was measured as S² mm. 2 Then, the mass percentage of silicon in the negative electrode material layer, w2, is measured using ICP. Therefore, the mass of silicon in the negative electrode sheet is calculated as M2 × w2 × 1540 / S2, in mg / 1540 mm². 2 .

[0089] Mass (C) test of the second active material in the positive electrode sheet:

[0090] A positive electrode sample was obtained by disassembling a lithium-ion battery in a fully discharged state. The positive electrode material layer was scraped off from the surface of the positive electrode current collector. Powder of the second positive electrode material layer was scraped from the side of the positive electrode sample that was originally away from the positive electrode current collector (i.e., within a range of 0 to 20 μm from the surface of the positive electrode sheet along the direction parallel to the thickness of the current collector). Its mass was measured to be M3 mg, and the area of ​​the positive electrode current collector was measured to be S3 mm. 2 Then, the mass percentage w3 of the second active material was measured using a thermogravimetric analyzer. Therefore, the mass of the second active material in the positive electrode sheet is calculated as M3 × w3 × 1540 / S3, with units of mg / 1540 mm². 2 .

[0091] Specific capacity (θ1) test of the first cathode material layer:

[0092] The first positive electrode material layer slurry was prepared according to the slurry ratios in the various embodiments and comparative examples. The slurry of the first positive electrode material layer was coated onto the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet with a single-sided thickness of 12.6 μm was obtained. During the preparation process, the mass of the positive electrode current collector and the positive electrode sheet were weighed, and the mass of the positive electrode current collector per unit area and the mass of the positive electrode sheet per unit area were calculated. The mass of the first positive electrode material layer per unit area was calculated to be M4. The above-mentioned positive electrode sheet, separator, and lithium sheet were stacked sequentially, and an electrolyte was injected to obtain a coin cell. The above-mentioned positive electrode current collector, separator, and electrolyte are the same as in Example 1.

[0093] The coin cell was charged to 4.58V at a constant current rate of 0.05C, and the initial charge capacity was recorded. The specific capacity θ1 of the first positive electrode material layer is equal to the initial charge capacity / M4, in mAh / g.

[0094] Specific capacity (θ2) test of the second cathode material layer:

[0095] The second positive electrode material layer slurry was prepared according to the slurry ratios in the various embodiments and comparative examples. The slurry of the second positive electrode material layer was coated onto the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet with a single-sided thickness of 53.6 μm was obtained. During the fabrication of the coin cell, the mass of the positive electrode current collector and the positive electrode sheet were weighed, and the mass of the positive electrode current collector per unit area and the mass of the positive electrode sheet per unit area were calculated. The mass of the second positive electrode material layer per unit area was calculated to be M5. The above-mentioned positive electrode sheet, separator, and lithium sheet were stacked sequentially, and an electrolyte was injected to obtain a coin cell. The above-mentioned positive electrode current collector, separator, and electrolyte were the same as in Example 1.

[0096] The coin cell was charged to 4.58V at a constant current rate of 0.05C, and the initial charge capacity was recorded. The specific capacity θ2 of the second positive electrode material layer is calculated as: initial charge capacity / M5, in mAh / g.

[0097] Adhesion strength (F) test:

[0098] The positive electrode sheet was obtained by disassembling a lithium-ion battery in a fully discharged state. Positive electrode material was scraped off from one surface of the positive current collector. A positive electrode sheet sample with a width of 20 mm and a length of 160 mm was then cut. The sample was adhered to a steel plate with a width of 20 mm and a length of 300 mm using double-sided tape with the positive current collector facing the steel plate. A paper strip of the same width and length as the positive electrode sheet, 200 mm long, was connected and fixed to a section of the sample strip. The sample was then tested using a high-speed rail AI-3000 tensile testing machine. The test sample was fixed on the test table, the paper strip was folded upwards 180° and secured with clamps, and then the tensile testing machine began pulling the paper strip at a speed of 50 mm / min. The tensile displacement was 50 mm. The adhesion force F between the first positive electrode material layer and the positive current collector was calculated when the curve flattened and the displacement was greater than 10 mm. The unit is N / m.

[0099] Resistivity (ρ) test method:

[0100] A positive electrode sample is obtained by disassembling a lithium-ion battery in a fully charged state. The total thickness of the positive electrode is measured, and then the resistance R of the positive electrode is measured using a film resistivity meter (PPM), where the probe area of ​​the PPM is S. The positive electrode material layer is then scraped off, and the thickness of the positive electrode current collector is measured. The thickness h of the positive electrode material layer is calculated. In this application, the resistance of the positive electrode current collector is negligible, and the resistance R of the positive electrode measured by the PPM can represent the resistance of the positive electrode material layer. Therefore, the resistivity of the positive electrode material layer is ρ = R × S / h, in Ω·m.

[0101] Cyclic performance test:

[0102] At 25°C, the lithium-ion battery was charged at a constant current rate of 3C to 4.53V, then charged at a constant voltage rate until the current was less than or equal to 0.05C, and then discharged at a constant current rate of 0.5C to 3V. This constitutes one charge-discharge cycle. The discharge capacity of the lithium-ion battery in the first cycle was recorded. The lithium-ion battery was charged and discharged in the same manner, and the discharge capacity of each cycle was recorded, until the discharge capacity of the lithium-ion battery decreased to 80% of the discharge capacity of the first cycle. The number of charge-discharge cycles was recorded.

[0103] Security performance test:

[0104] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 0.5C to a voltage of 4.53V, followed by constant voltage charging at 4.53V to a current of 0.025C, resulting in a fully charged lithium-ion battery. The fully charged battery was transferred to a nail-piercing tester. Maintaining the test environment temperature at 25°C ± 2°C, a 4mm diameter steel nail was driven through the center of the battery at a constant speed of 30mm / s for 300s. The battery was considered to have passed if it did not catch fire or explode. Ten lithium-ion batteries were tested in each embodiment or comparative example. The nail-piercing test pass rate (N / 10) was used as an indicator to evaluate the safety performance of the lithium-ion battery, where N is the number of lithium-ion batteries that passed the nail-piercing test.

[0105] Volumetric energy density test:

[0106] The lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 0.5C to a voltage of 4.53V, followed by constant voltage charging at 4.53V to a current of 0.05C, and finally discharged at 0.5C to a voltage of 3.0V. The discharge energy (in Wh) was recorded. The volumetric energy density VED = discharge energy / (length × width × thickness of lithium-ion battery), in Wh / L. Here, length, width, and thickness refer to the length, width, and thickness of the packaged lithium-ion battery.

[0107] Example 1

[0108] <Preparation of the positive electrode>

[0109] The first active material Li5FeO4 and the binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 97:3, and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, a first cathode material slurry with a solid content of 45wt% was prepared.

[0110] The second active material, lithium cobalt oxide (LiCoO2), conductive carbon black, carbon nanotubes, and binder polyvinylidene fluoride were mixed in a mass ratio of 97.4:0.5:0.5:1.4. NMP was added as a solvent, and the mixture was stirred evenly to prepare a second cathode material slurry with a solid content of 75wt%.

[0111] The prepared first positive electrode material slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil for the positive electrode current collector. After drying, a positive electrode sheet with a single-sided first positive electrode material layer was obtained. Then, a second positive electrode material slurry was uniformly coated onto the surface of the first positive electrode material layer, and dried to obtain a positive electrode sheet with both a single-sided first and second positive electrode material layer. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. The sheet was then vacuum-dried at 120°C for 6 hours, followed by cold pressing, cutting, and welding of tabs to obtain a positive electrode sheet with dimensions of 74 mm × 867 mm for later use. The thickness of the single-sided first positive electrode material layer was 2.6 μm, and the coating weight of the first positive electrode material layer was 5 mg / 1540 mm. 2 The thickness of the single-sided second cathode material layer is 43.6 μm, and the coating weight of the second cathode material layer is 230 mg / 1540 mm. 2 .

[0112] <Preparation of Negative Electrode Sheets>

[0113] The negative electrode active material silicon carbide and artificial graphite, binder polyacrylic acid, thickener sodium carboxymethyl cellulose, and conductive agent conductive carbon black were mixed in a mass ratio of 20:77.5:1.5:0.5:0.5. Deionized water was added as a solvent to prepare a slurry with a solid content of 45 wt%. The slurry was stirred evenly in a vacuum mixer to obtain the negative electrode slurry. The negative electrode slurry was uniformly coated on one surface of a 6 μm thick copper foil for the negative electrode current collector and dried at 120 °C to obtain a negative electrode sheet with a single-sided coating of negative electrode material layer. The coating weight of the negative electrode material layer was 105 mg / 1540 mm². 2 Then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 120℃ for 6 hours, it is then cold-pressed, cut, and has its tabs welded to obtain a negative electrode sheet with dimensions of 78mm × 875mm for later use. The thickness of the single-sided negative electrode material layer is 35.5μm.

[0114] <Preparation of the separating membrane>

[0115] A 16μm thick polyethylene film (supplied by Celgard) was used as the separator.

[0116] <Preparation of Electrolyte>

[0117] In an environment with a water content of less than 10 ppm, ethylene carbonate and propylene carbonate were mixed at a mass ratio of 50:50 to obtain a non-aqueous solvent. Then, lithium salt LiPF6 was added to the non-aqueous solvent and mixed thoroughly to obtain the electrolyte. The concentration of lithium salt was 1.15 mol / L.

[0118] <Preparation of Lithium-ion Batteries>

[0119] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets to provide isolation. The electrode assembly is then wound to obtain the electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag and dried in an 85°C vacuum oven for 12 hours to remove moisture. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation, degassing, and edge trimming. The formation process involves charging the lithium-ion battery at a constant current rate of 0.1C for 10 minutes at 45°C, followed by constant current charging at a constant current rate of 0.5C to 4.53V, and then constant voltage charging to a current of 0.05C.

[0120] Examples 2 to 9

[0121] Except for adjusting the relevant parameters as shown in Table 1, everything else is the same as in Example 1. Specifically, the coating weight of the first positive electrode material layer can be adjusted to make A as shown in Table 1, and the coating weight of the negative electrode material layer can be adjusted to make B as shown in Table 1.

[0122] Examples 10 to 14

[0123] Except for the further introduction of inorganic materials into the first positive electrode material layer and the adjustment of relevant parameters as shown in Table 1, the rest is the same as in Example 1. Specifically, the mass percentage of the delithiation products of the first active material is adjusted by controlling its mass percentage content. When the mass percentage content of the first active material and / or the inorganic material changes, the mass percentage content of the binder changes accordingly, and the sum of the mass percentage contents of the three is 100%.

[0124] Examples 15 to 17

[0125] Except for adjusting the mass percentage of silicon carbon to achieve the mass percentage of silicon and the value of B as shown in Table 1, everything else is the same as in Example 12. Specifically, when the mass percentage of silicon carbon changes, the mass percentage of artificial graphite changes accordingly, while the mass percentages of binder, thickener, and conductive agent remain constant.

[0126] Examples 18 to 27

[0127] Except for adjusting the relevant parameters as shown in Table 1, the rest is the same as in Example 10. Specifically, the mass percentage of the delithiation product of the first active material is adjusted by controlling its mass percentage content. When the mass percentage content of the first active material and / or the inorganic material changes, the mass percentage content of the binder changes accordingly, and the sum of the mass percentage contents of the three is 100%.

[0128] Comparative Example 1

[0129] Except for the positive electrode sheet prepared by the following <Preparation of Positive Electrode Sheet>, the rest is the same as in Example 1.

[0130] <Preparation of the positive electrode>

[0131] The second cathode material slurry was prepared using the process described in Example 1.

[0132] The prepared second positive electrode material slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil used as a positive electrode current collector. After drying, a positive electrode sheet with a single-sided second positive electrode material layer was obtained. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided second positive electrode material layer. The sheet was then vacuum-dried at 120°C for 6 hours, followed by cold pressing, cutting, and welding of tabs to obtain a positive electrode sheet with dimensions of 74 mm × 867 mm for later use. The thickness of the single-sided second positive electrode material layer was 46.2 μm, and the coating weight of the second positive electrode material layer was 235 mg / 1540 mm. 2 .

[0133] Comparative Example 2

[0134] Except for the positive electrode sheet prepared by the following <Preparation of Positive Electrode Sheet>, the rest is the same as in Example 1.

[0135] The second cathode material slurry was prepared using the process described in Example 1.

[0136] Inorganic material Al2O3 and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 95:5, and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, a first cathode material slurry with a solid content of 45wt% was prepared.

[0137] The prepared first positive electrode material slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil for the positive electrode current collector. After drying, a positive electrode sheet with a single-sided first positive electrode material layer was obtained. Then, a second positive electrode material slurry was uniformly coated onto the surface of the first positive electrode material layer, and dried to obtain a positive electrode sheet with both a single-sided first and second positive electrode material layer. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. The sheet was then vacuum-dried at 120°C for 6 hours, followed by cold pressing, cutting, and welding of tabs to obtain a positive electrode sheet with dimensions of 74 mm × 867 mm for later use. The thickness of the single-sided first positive electrode material layer was 2.6 μm, and the coating weight of the first positive electrode material layer was 5 mg / 1540 mm. 2 The thickness of the single-sided second cathode material layer is 43.6 μm, and the coating weight of the second cathode material layer is 230 mg / 1540 mm. 2 .

[0138] Comparative Example 3

[0139] Except for the steps used to prepare the first cathode material layer slurry, the rest is the same as Comparative Example 2.

[0140] Inorganic material Al2O3, conductive agent conductive carbon black (SP), and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 93:2:5, and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, a first cathode material slurry with a solid content of 45wt% was prepared.

[0141] Comparative Examples 4 to 7

[0142] Except for adjusting the relevant parameters as shown in Table 1, the rest is the same as in Example 10.

[0143] The relevant parameters and performance of each embodiment and comparative example are shown in Table 1.

[0144] As can be seen from Examples 1 to 27 and Comparative Examples 1 to 7, by using positive and negative electrode sheets within the scope of this application and adjusting the mass percentage of silicon and the A / B ratio within the scope of this application, the positive electrode material layer can have a suitable resistivity, and the first positive electrode material layer and the current collector have a high bonding force. The lithium-ion battery simultaneously exhibits higher volumetric energy density, pin penetration rate, and more cycle times, indicating that the lithium-ion battery simultaneously possesses higher energy density, better safety performance, and better cycle performance. In Comparative Example 1, no first positive electrode material layer was provided. The composition of the first positive electrode material layers in Comparative Examples 2 and 3 is not within the scope of this application. In Comparative Examples 4 to 7, at least one of the A / B ratio or the mass percentage of silicon is not within the scope of this application. The lithium-ion batteries in Comparative Examples 1, 3 to 7 cannot simultaneously achieve high volumetric energy density, pin penetration rate, and a large number of cycle times, indicating poor overall performance. Because the resistivity of the first positive electrode material layer in Comparative Example 2 is too high, the lithium-ion battery cannot operate, and no relevant performance data was measured.

[0145] The type of the first active material and its delithiation products typically affect the energy density, safety performance, and cycle performance of a lithium-ion battery. As can be seen from Examples 1 to 9, by selecting the first active material within the scope of this application, whose delithiation products are shown in Table 1, the lithium-ion battery can simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that the lithium-ion battery simultaneously exhibits higher energy density, better safety performance, and better cycle performance.

[0146] The values ​​of A / B and A / C typically affect the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 10 to 14, adjusting the values ​​of A / B and A / C within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle counts, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.

[0147] The mass percentage of silicon typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries.

[0148] As can be seen from Examples 10, 15 to 17, by adjusting the mass percentage of silicon within the scope of this application, lithium-ion batteries can simultaneously have higher volumetric energy density, pin penetration rate, and more cycle times, indicating that lithium-ion batteries simultaneously have higher energy density, better safety performance, and better cycle performance.

[0149] The mass percentage of delithiation products in the first active material typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 1, 12, and 18, adjusting the mass percentage of delithiation products in the first active material within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.

[0150] The mass percentage of inorganic materials typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 19 to 23, by adjusting the mass percentage of inorganic materials within the scope of this application, lithium-ion batteries can simultaneously exhibit higher volumetric energy density, pin penetration rate, and more cycle times, indicating that lithium-ion batteries simultaneously possess higher energy density, better safety performance, and better cycle performance.

[0151] The type of inorganic material typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 19 to 23, selecting inorganic materials within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.

[0152] The type of second active material typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 12, 26, and 27, selecting the second active material within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.

[0153] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0154] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0155] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. An electrochemical device comprising a positive electrode and a negative electrode, the positive electrode comprising a positive current collector and a positive electrode material layer, the positive electrode material layer comprising a first positive electrode material layer and a second positive electrode material layer, the first positive electrode material layer being disposed between the positive current collector and the second positive electrode material layer; The first positive electrode material layer includes a first active material, and the delithiation products of the first active material include Li. 5-x FeO 4-y Li 5-x CoO 4-y Li 2-z MnO2, Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O2 or Li 1-t At least one of FePO4, wherein 4≤x≤5, 2≤y≤3, 1.6≤z≤2, 1≤r≤1.2, 0.8≤t≤1; The second positive electrode material layer includes a second active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide. The negative electrode sheet includes a negative electrode material layer, the negative electrode material layer includes silicon, and the mass percentage of silicon is 1% to 50% based on the mass of the negative electrode material layer. The mass of the delithiation product of the first active material in the positive electrode sheet is A mg / 1540 mm. 2 The mass of silicon in the negative electrode is B mg / 1540 mm². 2 29% ≤ A / B ≤ 230%.

2. The electrochemical device according to claim 1, wherein, 39% ≤ A / B ≤ 200%.

3. The electrochemical device according to claim 1, wherein, The delithiation products of the first active material include LiFeO2, CoO2, MnO2, and Ni. 0.13 Fe 0.13 Mn 0.54 At least one of O2, FePO4, FeO2, Fe2O3, or FeO.

4. The electrochemical device according to claim 1, wherein, Based on the mass of the first cathode material layer, the mass percentage of the delithiation product of the first active material is 30% to 96%.

5. The electrochemical device according to any one of claims 1 to 4, wherein, The mass of the second active material in the positive electrode sheet is C mg / 1540 mm. 2 0.45% ≤ A / C ≤ 6%.

6. The electrochemical device according to claim 5, wherein, 0.9% ≤ A / C ≤ 4.5%.

7. The electrochemical device according to any one of claims 1 to 4, wherein, Based on the mass of the negative electrode material layer, the mass percentage of silicon element is between 1% and 20%.

8. The electrochemical device according to claim 5, wherein it satisfies at least one of the following characteristics: (1)1mg / 1540mm 2 ≤A≤14mg / 1540mm 2 ; (2)3mg / 1540mm 2 ≤B≤12mg / 1540mm 2 ; (3)200mg / 1540mm 2 ≤C≤300mg / 1540mm 2 。 9. The electrochemical device according to any one of claims 1 to 4, wherein, The first positive electrode material layer also includes inorganic materials, which include at least one of alumina, lithium lanthanum zirconium oxide, lithium lanthanum titanate, lithium titanium aluminum phosphate, antimony-doped tin oxide, or titanium oxide. Based on the mass of the first cathode material layer, the inorganic material has a mass percentage content of 5% to 60%.

10. The electrochemical device according to any one of claims 1 to 4, wherein, The specific capacity of the first cathode material layer is 130 mAh / g to 780 mAh / g.

11. The electrochemical device according to claim 10, wherein, The specific capacity of the first positive electrode material layer is greater than or equal to the specific capacity of the second positive electrode material layer.

12. The electrochemical device according to any one of claims 1 to 4, wherein, The first active material includes at least one of the following compounds: Li5QO4 or Li5QO6, where Q includes at least one of Ni, Co, Fe, Sn or Mn, and the valence state of element Q is lower than its highest oxidation state. Li q Fe 0.5(1+q) PO4,1≤q≤5; Li 2-a-b-c-d Ni a R b Mn c M d O 2-f , 0≤a<0.35, 0<b<0.5, 0.3<c≤0.6, 0≤d<0.05, 0.7<a+b+c+d<0.9, 0≤f<0.2, R includes at least one of Fe or Co, and M includes at least one of Mg, Al, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, La or W; Li 1+e Mn 1-p X p O 2-s Y s -0.1 < e < 0.2, 0 ≤ p < 0.2, 0 ≤ s < 0.2, X includes at least one of Fe, Co, Ni, Ti, Zn, Mg, Al, V, Cr or Zr, and Y includes at least one of S, N, F, Cl or Br.

13. The electrochemical device according to claim 10, wherein, The first active material includes Li5FeO4, Li5CoO4, Li2MnO2, and Li 1.2 Ni 0.13 Fe 0.13 Mn 0.54 At least one of O2 or LiFePO4.

14. The electrochemical device according to any one of claims 1 to 4, wherein, The negative electrode material layer includes a negative electrode active material, which includes at least one of silicon, silicon-carbon, or silicon-oxygen.

15. The electrochemical device according to claim 14, wherein, The negative electrode active material also includes at least one of graphite, hard carbon, soft carbon, or mesophase micro carbon spheres.

16. The electrochemical device according to any one of claims 1 to 4, wherein, The resistivity of the positive electrode material layer is ρΩ·m, 44≤ρ≤155.

17. An electronic device comprising the electrochemical device according to any one of claims 1 to 16.

Images