Electrochemical device and electronic device including the same

Abstract

The present application provides an electrochemical device and an electronic device including the electrochemical device. In the electrochemical device, instead of disposing a negative electrode active material on the negative electrode plate, ceramic coatings are provided on two surfaces of the negative electrode current collector in its own thickness direction. During the charging process of the electrochemical device, the ceramic coatings can promote the uniform deposition of Li + on the negative electrode current collector to form a lithium metal layer, and the lithium metal layer is formed between the negative electrode current collector and the ceramic coatings. The lithium metal layer is uniform and dense. At the same time, the ceramic coatings can also absorb lithium dendrites. In this way, the thickness space originally occupied by disposing the negative electrode active material is saved, and the saved thickness space can be used to meet the energy density of the electrochemical device by adding a low-cost positive electrode active material to the positive electrode plate. Moreover, the cost of the ceramic coatings is lower than that of the negative electrode active material layer. Thus, the production cost of the electrochemical device is effectively reduced.

Description

Technical Field

[0001] This application relates to the field of electrochemistry technology, and particularly relates to an electrochemical device and an electronic device including the electrochemical device. Background Art

[0002] As a new type of movable energy storage device, secondary batteries (such as lithium-ion batteries) have the advantages of large energy storage density, high open-circuit voltage, low self-discharge rate, long cycle life, good safety performance, etc. The demand in the fields of portable small electronic devices such as mobile phones, laptop computers, and cameras, as well as in the fields of large-scale electric transportation work and renewable energy storage, is increasing. However, for electronic products that only require a small number of charge and discharge cycles, such as disposable electronic cigarettes, the requirement for the cycle life of secondary batteries is relatively low. Therefore, how to obtain market competitiveness by reducing the production cost of such secondary batteries has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0003] This application provides an electrochemical device and an electronic device including the electrochemical device to reduce the production cost of the electrochemical device.

[0004] It should be noted that in the summary of the invention of this application, a lithium-ion battery is used as an example of the electrochemical device to explain this application. However, the electrochemical device of this application is not limited to lithium-ion batteries.

[0005] In a first aspect of this application, an electrochemical device is provided, including a positive electrode plate and a negative electrode plate; the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a lithium-containing positive electrode active material; the negative electrode plate includes a negative electrode current collector and ceramic coatings provided on two surfaces of the negative electrode current collector in the thickness direction of the negative electrode current collector itself. The negative electrode plate further includes a lithium metal layer formed by deposition of lithium ions in the lithium-containing positive electrode active material on the surface of the negative electrode current collector during the charging process of the electrochemical device, and the lithium metal layer is located between the negative electrode current collector and the ceramic coatings; the negative electrode plate does not include a negative electrode active material.

[0006] The applicant has found through a large amount of research that the negative electrode plate does not provide a negative electrode active material, but ceramic coatings are provided on two surfaces of the negative electrode current collector in its own thickness direction. During the charging process of the electrochemical device, the ceramic coatings can promote Li ions (Li +)Uniform deposition on the negative electrode current collector forms a lithium metal layer, which is formed between the negative electrode current collector and the ceramic coating. The lithium metal layer is uniform and dense, and at the same time, the ceramic coating can also absorb lithium dendrites. In this way, the thickness space originally occupied by the negative electrode active material is saved, and the saved thickness space can be used to meet the energy density of the electrochemical device by adding low-cost positive electrode active material to the positive electrode plate. Moreover, the cost of the ceramic coating is lower than that of the negative electrode active material layer. Therefore, the electrochemical device has a lower material cost while meeting the energy density and cycling performance, effectively reducing the production cost of the electrochemical device.

[0007] In some embodiments of the present application, the electrochemical device further includes an electrolyte, and the electrolyte includes fluoroethylene carbonate and lithium difluoro(oxalato)borate; based on the mass of the electrolyte, the mass percentage content W1 of fluoroethylene carbonate is 0.1% to 10%, and the mass percentage content W2 of lithium difluoro(oxalato)borate is 0.05% to 5%. The electrolyte in the electrochemical device includes fluoroethylene carbonate and lithium difluoro(oxalato)borate, and adjusting the mass percentage contents of fluoroethylene carbonate and lithium difluoro(oxalato)borate within the above ranges is beneficial to forming a better solid electrolyte interface (SEI) film on the surface of the negative electrode plate, which is beneficial to Li + Uniform deposition on the negative electrode current collector forms a dense and uniform lithium metal layer, thereby realizing the reversibility and stability of lithium metal layer electroplating and meeting the cycling performance of the electrochemical device. Therefore, the electrochemical device has a lower material cost while meeting the energy density and cycling performance, effectively reducing the production cost of the electrochemical device.

[0008] In some embodiments of the present application, the lithium-containing positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium titanate, or lithium fluoroacid. Selecting the above types of lithium-containing positive electrode active materials is more conducive to the electrochemical device having a lower material cost while meeting the energy density and cycling performance, effectively reducing the production cost of the electrochemical device.

[0009] In some embodiments of the present application, the positive electrode active material layer further includes a positive electrode lithium supplement agent, and the positive electrode lithium supplement agent includes at least one of Li2O or Li x MO y where 2 ≤ x ≤ 6, 2 ≤ y ≤ 4, and M includes at least one of Al, Ni, Co, Mg, Mn, Cu, Fe, or Ti; based on the mass of the positive electrode active material layer, the mass percentage content W3 of the positive electrode lithium supplement agent is 3% to 10%. Selecting the above types of positive electrode lithium supplement agents and adjusting the mass percentage content W3 of the positive electrode lithium supplement agent in the positive electrode active material layer within the above range enables Li2O to release more Li at a lower potential +To provide an additional lithium source, so that during the long-term cycling process of the electrochemical device, the irreversible loss of lithium in the initial lithium-free anode active material electrochemical device can be offset, the reversibility and stability of lithium metal layer electroplating can be achieved, thereby improving the cycling performance of the electrochemical device. Thus, the electrochemical device can further improve its cycling performance while reducing production costs.

[0010] In some embodiments of the present application, the positive electrode active material layer further includes a positive electrode additive, the positive electrode additive includes a composite material formed by an inorganic lithium salt and a first conductive agent, and the mass ratio of the inorganic lithium salt to the first conductive agent is 1:3 to 1:7; based on the positive electrode active material layer, the mass percentage content W4 of the positive electrode additive is 4% to 8%. The selection of the above positive electrode additive and the regulation of the mass percentage content W4 of the positive electrode additive in the positive electrode active material layer within the above range can release more Li during the charge and discharge cycling process of the electrochemical device. + To provide an additional lithium source, improve the first discharge capacity of the electrochemical device, reduce the charge transfer impedance of the electrochemical device, and improve the energy density, cycling performance and rate performance of the electrochemical device. In this way, during the long-term cycling process of the electrochemical device, the irreversible loss of lithium in the initial lithium-free anode electrochemical device can be offset, the reversibility and stability of lithium metal layer electroplating can be achieved, thereby improving the cycling performance of the electrochemical device. Thus, the energy density, cycling performance and rate performance of the electrochemical device are further improved while reducing production costs.

[0011] In some embodiments of the present application, the inorganic lithium salt includes Li s Q a N b O t , 2≤s≤8, 0≤a≤1, 0≤b≤1, a + b≥1, 2≤t≤6, Q is selected from any one of Fe, Co, Mn, Ni, Zr, V, Nb or Mo; N is selected from any one of Al, Mg, Ti, Cr, Y, Sr, Si, W, Ga or Zn; the first conductive agent includes at least one of graphene, acetylene black, single-walled carbon nanotubes or multi-walled carbon nanotubes. The selection of the above inorganic lithium salt and the first conductive agent is more conducive to further improving the cycling performance of the electrochemical device while reducing production costs.

[0012] In some embodiments of the present application, the positive electrode tab further includes the ceramic coating, and the ceramic coating is disposed on the surface of the positive electrode active material layer. Disposing the ceramic coating on the surface of the positive electrode active material layer is more conducive to blocking the lithium dendrites precipitated from the negative electrode tab from inserting into the positive electrode tab, thereby improving the safety performance and thermal stability of the electrochemical device.

[0013] In some embodiments of the present application, the ceramic coating includes inorganic powder and a first binder; based on the mass of the ceramic coating, the mass percentage content W5 of the inorganic powder is 85% to 95%, and the mass percentage content W6 of the first binder is 5% to 15%. Selecting the above materials to form the ceramic coating and controlling the mass percentage content of the inorganic powder and the first binder in the ceramic coating within the above range is more conducive to the exertion of the function of the ceramic coating. In this way, under the condition of meeting the energy density and cycle performance, the electrochemical device has a lower material cost, effectively reducing the production cost of the electrochemical device.

[0014] In some embodiments of the present application, the inorganic powder includes at least one of alumina, magnesia, zirconia or boehmite, and the first binder includes at least one of polyacrylic acid, polyvinylidene fluoride, polyimide or polyvinyl alcohol. The selection of the above materials is more conducive to the formation of the ceramic coating and the exertion of its function. In this way, under the condition of meeting the energy density and cycle performance, the electrochemical device has a lower material cost, effectively reducing the production cost of the electrochemical device. In some embodiments of the present application, the coating weight of the ceramic coating is 5 mg / 5000 mm 2 to 20 mg / 5000 mm 2 . Controlling the coating weight of the ceramic coating within the above range is more conducive to improving the rate performance and cycle performance of the electrochemical device. Thus, under the condition of reducing the production cost, the rate performance and cycle performance of the electrochemical device are further improved.

[0015] In some embodiments of the present application, the thickness of the ceramic coating is 1 μm to 3 μm. Controlling the thickness of the ceramic coating within the above range enables the effective exertion of the function of the ceramic coating in the present application. Thus, under the condition of meeting the energy density and cycle performance, the electrochemical device has a lower material production cost, effectively reducing the production cost of the electrochemical device.

[0016] In some embodiments of the present application, the negative electrode sheet further includes a conductive layer, the conductive layer is disposed between the negative electrode current collector and the ceramic coating, and the lithium metal layer is disposed between the negative electrode current collector and the conductive layer. The setting of the conductive layer can receive Li + released from the positive electrode sheet, inhibit the formation of lithium deposition and dead lithium, thereby improving the safety performance and cycle performance of the electrochemical device.

[0017] In some embodiments of the present application, the conductive layer includes a second conductive agent and a second binder; based on the mass of the conductive layer, the mass percentage content W7 of the second conductive agent is 60% to 70%, and the mass percentage content W8 of the second binder is 30% to 40%.

[0018] In some embodiments of the present application, the second conductive agent includes at least one of amorphous carbon, single-walled carbon nanotubes, or multi-walled carbon nanotubes; and the second binder includes at least one of styrene-butadiene rubber, carboxymethyl cellulose, or polyvinyl alcohol.

[0019] The above materials are used to form the conductive layer, and the mass percentage of the second conductive agent and the second binder is controlled within the above range, which is more conducive to the role of the conductive layer. In this way, the conductive layer can absorb the Lithium ions released from the positive electrode sheet. + , inhibiting the formation of lithium plating and dead lithium, thereby improving the safety and cycle performance of electrochemical devices.

[0020] A second aspect of the present application provides an electronic device comprising the electrochemical device described in any of the aforementioned embodiments.

[0021] Beneficial effects of this application:

[0022] In the embodiment of the present application, a ceramic coating is provided on both surfaces of the negative electrode current collector in the thickness direction instead of providing a negative electrode active material on the negative electrode plate. The ceramic coating can promote the charging of the Li + A lithium metal layer is formed by uniform deposition on the negative electrode current collector, so that the lithium metal layer is formed between the negative electrode current collector and the ceramic coating. The lithium metal layer is uniform and dense, and the ceramic coating can also absorb lithium dendrites. In this way, the thickness space originally occupied by the negative electrode active material is eliminated, and the saved thickness space can be used to meet the energy density of the electrochemical device by adding low-cost positive electrode active materials to the positive electrode sheet. In addition, the cost of the ceramic coating is lower than that of the negative electrode active material layer. As a result, the electrochemical device has a lower material cost while meeting the energy density and cycle performance, which effectively reduces the production cost of the electrochemical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and a person skilled in the art can also obtain other drawings based on these drawings.

[0024] Figure 1 Schematic diagram of the cross-sectional structure of an electrochemical device according to some embodiments of the present application;

[0025] Figure 2 Schematic diagram of the cross-sectional structure of the positive electrode sheet in some embodiments of the present application;

[0026] Figure 3 Schematic diagram of the cross-sectional structure of the negative electrode sheet in some embodiments of the present application.

[0027] Description of reference numerals:

[0028] 10 positive electrode sheet; 11 positive electrode current collector; 12 positive electrode active material layer; 20 negative electrode sheet; 21 negative electrode current collector; 22 lithium metal layer; 23 conductive layer; 40 ceramic coating; 30 separator; 100 electrochemical device. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of this application more clearly understood, the present application is further described below with reference to the accompanying drawings and examples. It is apparent that the described examples are only a portion of the embodiments of this application, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the examples in this application are intended to fall within the scope of protection of this application.

[0030] It should be noted that, in the specific embodiments of the present application, a lithium-ion battery is used as an example of an electrochemical device to explain the present application, but the electrochemical device of the present application is not limited to a lithium-ion battery.

[0031] In a first aspect, the present application provides an electrochemical device, comprising a positive electrode plate and a negative electrode plate; the positive electrode plate comprises a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector, the positive electrode active material layer comprises a lithium-containing positive electrode active material; the negative electrode plate comprises a negative electrode collector and a ceramic coating arranged on both surfaces of the negative electrode collector, the negative electrode plate also comprises a lithium metal layer formed by the lithium ions in the lithium-containing positive electrode active material being deposited on the surface of the negative electrode collector during charging, the lithium metal layer being located between the negative electrode collector and the ceramic coating; the negative electrode plate does not contain a negative electrode active material.

[0032] The applicant has found through extensive research that the negative electrode sheet does not have a negative electrode active material, but a ceramic coating is provided on both surfaces of the negative electrode current collector in the thickness direction. The ceramic coating can promote the charging process of the electrochemical device. + A lithium metal layer is formed by uniform deposition on the negative electrode current collector, so that the lithium metal layer is formed between the negative electrode current collector and the ceramic coating. The lithium metal layer is uniform and dense, and the ceramic coating can also absorb lithium dendrites. In this way, the thickness space originally occupied by the negative electrode active material is eliminated (in the prior art, the thickness of the negative electrode active material layer containing the negative electrode active material is usually greater than 100 μm), and the saved thickness space can be used to increase the energy density of the electrochemical device by adding low-cost positive electrode active materials to the positive electrode sheet. In addition, the cost of the ceramic coating is lower than that of the negative electrode active material layer. As a result, the electrochemical device has a lower material cost while meeting the energy density and cycle performance, which effectively reduces the production cost of the electrochemical device.

[0033] In the present application, the positive electrode current collector includes two opposite first surfaces and second surfaces in the thickness direction. For the above-mentioned "positive electrode active material layer provided on at least one surface of the positive electrode current collector", those skilled in the art should understand that the positive electrode active material layer can be provided on the first surface, can also be provided on the second surface, or can be provided on both the first surface and the second surface at the same time. Those skilled in the art can make a choice according to actual needs. It should be noted that the above-mentioned "surface" can be the entire area of the first surface and / or the second surface, or can be a partial area of the first surface and / or the second surface. There is no special limitation in the present application as long as the purpose of the present application can be achieved. It should be understood that the statement "the negative electrode tab does not contain negative electrode active material" in the present application means that the negative electrode tab does not contain a negative electrode active material layer.

[0034] Exemplarily, Figure 1 The cross-sectional structure schematic diagram of the electrochemical device according to some embodiments of the present application is shown, as Figure 1 shown, the electrochemical device 100 includes a positive electrode tab 10, a negative electrode tab 20, and a separator 30 provided between the positive electrode tab 10 and the negative electrode tab 20. The separator 30 is provided to separate the positive electrode tab 10 and the negative electrode tab 20, prevent internal short circuit of the electrochemical device 100, allow electrolyte ions to pass freely, and complete the function of the electrochemical charge and discharge process. The positive electrode tab 10 includes a positive electrode current collector 11 and positive electrode active material layers 12 provided on two surfaces in the thickness direction of the positive electrode current collector 11 itself. The positive electrode active material layer 12 includes a lithium-containing positive electrode active material. Li in the lithium-containing positive electrode active material + deposits on the surface of the negative electrode current collector 21 to form a lithium metal layer 22 during the charging process of the electrochemical device 100. The negative electrode tab 20 includes a negative electrode current collector 21 and ceramic coatings 40 provided on two surfaces in the thickness direction of the negative electrode current collector 21 itself, and also includes two layers of lithium metal layers 22 located between the negative electrode current collector 21 and the ceramic coatings 40.

[0035] It should be noted that in the present application, the inorganic powder selected in the ceramic coating exists in a particulate state, and there are gaps between the particles in the ceramic coating. Therefore, there will be particle gaps between the ceramic coating and the negative electrode current collector, and the lithium metal layer is formed in a discontinuous state in the particle gaps. The above-mentioned "lithium metal layer is located between the negative electrode current collector and the ceramic coating" can also be understood as: the discontinuous lithium metal layer is located in the particle gaps in the ceramic coating near the negative electrode current collector. Among them, the lithium metal layer is elemental lithium, and the thickness of the lithium metal layer is greater than 0 μm and less than or equal to 100 μm.

[0036] In some embodiments of the present application, the electrochemical device further includes an electrolyte, and the electrolyte includes fluoroethylene carbonate (FEC) and lithium difluoro(oxalato)borate (LiDFOB); based on the mass of the electrolyte, the mass percentage content W1 of fluoroethylene carbonate is 0.1% to 10%, preferably 0.1% to 6%, and the mass percentage content W2 of lithium difluoro(oxalato)borate is 0.05% to 5%, preferably 3% to 4%. For example, the mass percentage content W1 of fluoroethylene carbonate can be 0.1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value between any two of the above numerical ranges. The mass percentage content W2 of lithium difluoro(oxalato)borate can be 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5% or any value between any two of the above numerical ranges. The electrolyte in the electrochemical device includes fluoroethylene carbonate and lithium difluoro(oxalato)borate, and regulating the mass percentage contents of fluoroethylene carbonate and lithium difluoro(oxalato)borate within the above ranges is beneficial to forming a better SEI film on the surface of the negative electrode sheet, which is beneficial to the uniform deposition of Li + on the negative current collector, forming a dense and uniform lithium metal layer, thereby realizing the reversibility and stability of lithium metal layer electroplating and meeting the cycling performance of the electrochemical device. Thus, the electrochemical device has lower material costs while meeting the energy density and cycling performance, effectively reducing the production cost of the electrochemical device.

[0037] In some embodiments of the present application, the lithium-containing positive electrode active material includes at least one of lithium cobaltate (LiCoO2), lithium manganate, lithium nickel cobalt manganate, lithium titanate or lithium fluoroate. Selecting the above types of lithium-containing positive electrode active materials is more conducive to the electrochemical device having lower material costs while meeting the energy density and cycling performance, effectively reducing the production cost of the electrochemical device.

[0038] In some embodiments of the present application, the positive electrode active material layer further includes a positive electrode lithium supplementing agent, and the positive electrode lithium supplementing agent includes at least one of Li2O or Li x MO y ; preferably, the positive electrode lithium supplementing agent includes Li2O and Li x MO y ; 2 ≤ x ≤ 6, 2 ≤ y ≤ 4, and M includes at least one of Al, Ni, Co, Mg, Mn, Cu, Fe or Ti. Based on the mass of the positive electrode active material layer, the mass percentage content W3 of the positive electrode lithium supplementing agent is 3% to 10%. For example, the mass percentage content W3 of the positive electrode lithium supplementing agent can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value between any two of the above numerical ranges. Selecting the above types of positive electrode lithium supplementing agents and regulating the mass percentage content W3 of the positive electrode lithium supplementing agent in the positive electrode active material layer within the above ranges enables Li2O to release more Li at a lower potential+ to provide an additional lithium source, enabling the electrochemical device to offset the irreversible loss of lithium in the initial lithium-free anode active material electrochemical device during long-term cycling, realizing the reversibility and stability of lithium metal layer electroplating, thereby improving the cycling performance of the electrochemical device. Thus, the electrochemical device can further improve its cycling performance while reducing production costs. When the cathode lithium supplement agent includes both Li2O and Li x MO y , Li x MO y can further catalyze Li2O to release more Li at a lower potential + to provide an additional lithium source, so that the electrochemical device can further improve its cycling performance while reducing production costs.

[0039] Furthermore, when the cathode lithium supplement agent includes Li2O and Li x MO y , the mass ratio of Li2O and Li x MO y is not particularly limited as long as the object of the present application can be achieved. Preferably, the mass ratio of Li2O and Li x MO y is from 30:70 to 35:65.

[0040] In some embodiments of the present application, the cathode active material layer further includes a cathode additive, and the cathode additive includes a composite material formed by an inorganic lithium salt and a first conductive agent. The mass ratio of the inorganic lithium salt to the first conductive agent is from 1:3 to 1:7; based on the cathode active material layer, the mass percentage content W4 of the cathode additive is from 4% to 8%. For example, the mass ratio of the inorganic lithium salt to the first conductive agent is 1:3, 1:4, 1:5, 1:6, 1:7 or any ratio between any two of the above ratio ranges. The mass percentage content W4 of the cathode additive can be 4%, 5%, 6%, 7%, 8% or any value between any two of the above value ranges. The selection of the above cathode additive and the regulation of the mass percentage content W4 of the cathode additive in the cathode active material layer within the above range can release more Li + to provide an additional lithium source, improve the first discharge capacity of the electrochemical device, reduce the charge transfer impedance of the electrochemical device, and improve the energy density, cycling performance and rate performance of the electrochemical device. In this way, during the long-term cycling of the electrochemical device, the irreversible loss of lithium in the initial lithium-free anode electrochemical device can be offset, and the reversibility and stability of lithium metal layer electroplating can be realized, thereby improving the cycling performance of the electrochemical device. Thus, the energy density, cycling performance and rate performance of the electrochemical device are further improved while reducing production costs.

[0041] In some embodiments of the present application, the inorganic lithium salt includes Li s Q a N b O t , where 2 ≤ s ≤ 8, 0 ≤ a ≤ 1, 0 ≤ b ≤ 1, a + b ≥ 1, 2 ≤ t ≤ 6, Q is selected from any one of Fe, Co, Mn, Ni, Zr, V, Nb or Mo; N is selected from any one of Al, Mg, Ti, Cr, Y, Sr, Si, W, Ga or Zn; the first conductive agent includes at least one of graphene, acetylene black, single-walled carbon nanotubes or multi-walled carbon nanotubes. The selection of the above inorganic lithium salt and the first conductive agent is more conducive to further improving the cycle performance of the electrochemical device while reducing the production cost.

[0042] The present application does not particularly limit the preparation method of the cathode additive, as long as the object of the present application can be achieved. For example, the preparation method of the cathode additive includes the following steps:

[0043] (1) Dissolve the lithium-containing compound, the compound containing the Q element, and the compound containing the N element in a solvent according to the molar ratio of Li, Q, and N of s:a:b, stir to obtain a homogeneous mixed solution, and then evaporate the solvent and dry to obtain a precursor of the inorganic lithium salt; where 2 ≤ s ≤ 8, 0 ≤ a ≤ 1, 0 ≤ b ≤ 1, a + b ≥ 1, 2 ≤ t ≤ 6, Q is selected from any one of Fe, Co, Mn, Ni, Zr, V, Nb or Mo; N is selected from any one of Al, Mg, Ti, Cr, Y, Sr, Si, W, Ga or Zn;

[0044] (2) Calcinate the precursor of the inorganic lithium salt obtained in step (1) under a protective gas atmosphere, and then cool and ball-mill to obtain inorganic lithium salt particles, namely Li s Q a N b O t ;

[0045] (3) Ultrasonically disperse the inorganic lithium salt particles in a solution containing the first conductive agent, evaporate the solvent and dry to obtain a composite material formed by the inorganic lithium salt and the conductive agent, namely the cathode additive; where the mass ratio of the inorganic lithium salt to the first conductive agent is 1:3 to 1:7.

[0046] In some embodiments of the present application, the cathode electrode sheet further includes a ceramic coating, and the ceramic coating is disposed on the surface of the cathode active material layer. It should be noted that the surface of the cathode active material layer refers to one of the two surfaces of the cathode active material layer itself that is not in contact with the cathode current collector. Disposing the ceramic coating on the surface of the cathode active material layer is more conducive to blocking the lithium dendrites precipitated from the anode electrode sheet from inserting into the cathode electrode sheet, thereby improving the safety performance and thermal stability of the electrochemical device.

[0047] Exemplarily, Figure 2 The structural schematic diagram of the positive electrode plate in some embodiments of the present application is shown, as Figure 2 shown, the positive electrode plate 10 includes a positive electrode current collector 11, a positive electrode active material layer 12, and a ceramic coating 40. Among them, two positive electrode active material layers 12 are respectively disposed on two surfaces of the positive electrode current collector 11 in its own thickness direction, and two ceramic coatings 40 are independently disposed on one surface of the positive electrode active material layer 12 in its own thickness direction that does not contact the positive electrode current collector 11, so that the positive electrode active material layer 12 is located between the positive electrode current collector 11 and the ceramic coating 40. Among them, the two positive electrode active material layers 12 may be the same or different, and the two ceramic coatings 40 may be the same or different. In some other embodiments of the present application, as Figure 2 shown in the positive electrode plate 10, the ceramic coating 40 may also be disposed only on any one surface of the two positive electrode active material layers 12. The present application does not limit this, as long as the purpose of the present application can be achieved.

[0048] In some embodiments of the present application, the ceramic coating includes inorganic powder and a first binder; based on the mass of the ceramic coating, the mass percentage content W5 of the inorganic powder is 85% to 95%, and the mass percentage content W6 of the first binder is 5% to 15%. For example, the mass percentage content W5 of the inorganic powder may be 85%, 87%, 89%, 91%, 93%, 95%, or any value between any two of the above numerical ranges. For example, the mass percentage content W6 of the first binder may be 5%, 7%, 9%, 11%, 13%, 15%, or any value between any two of the above numerical ranges. Selecting the above materials to form the ceramic coating and controlling the mass percentage content of the inorganic powder and the first binder in the ceramic coating within the above range is more conducive to the exertion of the function of the ceramic coating. In this way, the electrochemical device has a lower material cost while meeting the energy density and cycle performance, effectively reducing the production cost of the electrochemical device.

[0049] In some embodiments of the present application, the inorganic powder includes at least one of alumina, magnesia, zirconia, or boehmite, and the first binder includes at least one of polyacrylic acid, polyvinylidene fluoride, polyimide, or polyvinyl alcohol. The selection of the above materials is more conducive to the formation of the ceramic coating and the exertion of its function. In this way, the electrochemical device has a lower material cost while meeting the energy density and cycle performance, effectively reducing the production cost of the electrochemical device.

[0050] In some embodiments of the present application, the coating weight of the ceramic coating is 5 mg / 5000 mm 2 to 20 mg / 5000 mm 2 . For example, the coating weight of the ceramic coating is 5 mg / 5000 mm2 、10mg / 5000mm 2 、15mg / 5000mm 2 , 20mg / 5000mm 2 or any value between any two of the above ranges. Controlling the coating weight of the ceramic coating within the above range allows the ceramic coating to evenly cover the negative electrode current collector, further improving the uniformity and stability of the lithium metal layer electroplating, thereby further improving the rate performance and cycle performance of the electrochemical device. This further improves the rate performance and cycle performance of the electrochemical device while reducing production costs.

[0051] In some embodiments of the present application, the thickness of the ceramic coating is 1 μm to 3 μm. For example, the thickness of the ceramic coating can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or any value between any two of the above numerical ranges. If the thickness of the ceramic coating is too small (for example, less than 1 μm), the mechanical strength of the ceramic coating is insufficient and the purpose of the present application cannot be achieved; if the thickness of the ceramic coating is too large (for example, greater than 3 μm), the volume of the electrochemical device will increase, which will affect the energy density of the electrochemical device. The thickness of the ceramic coating is regulated within the above range so that the role of the ceramic coating in the present application can be effectively played. As a result, the electrochemical device has a lower material production cost while meeting the energy density and cycle performance, so that the production cost of the electrochemical device is effectively reduced.

[0052] In some embodiments of the present application, the negative electrode plate further includes a conductive layer, which is disposed between the negative electrode current collector and the ceramic coating, and the lithium metal layer is disposed between the negative electrode current collector and the conductive layer. The conductive layer is configured to receive the Li metal released from the positive electrode plate. + , inhibiting the formation of lithium plating and dead lithium, thereby improving the safety and cycle performance of electrochemical devices.

[0053] For example, Figure 3 Schematic diagram of the structure of the negative electrode sheet in some embodiments of the present application is shown. Figure 3 As shown, the negative electrode current collector 21 includes a first surface 21a and a second surface 21b that are opposite to each other in the thickness direction thereof, and a lithium metal layer 22, a conductive layer 23 and a ceramic coating 40 are independently provided on the first surface 21a and the second surface 21b. Among them, the conductive layer 23 is provided between the negative electrode current collector 21 and the ceramic coating 40, and the lithium metal layer 22 is provided between the negative electrode current collector 21 and the conductive layer 23. It can be seen that in the direction away from the first surface 21a, the lithium metal layer 22, the conductive layer 23 and the ceramic coating 40 are provided in sequence on the first surface 21a; in the direction away from the second surface 21b, the lithium metal layer 22, the conductive layer 23 and the ceramic coating 40 are provided in sequence on the second surface 21b. It can be understood that, as Figure 3In the negative electrode sheet 20 shown, the two conductive layers 23 can be the same or different, and the two ceramic coating layers 40 can be the same or different.

[0054] In some embodiments of the present application, the conductive layer includes a second conductive agent and a second binder; based on the mass of the conductive layer, the mass percentage W7 of the second conductive agent is 60% to 70%, and the mass percentage W8 of the second binder is 30% to 40%. For example, the mass percentage W7 of the second conductive agent can be 60%, 62%, 64%, 66%, 68%, 70% or any value between any two of the above numerical ranges. For example, the mass percentage W8 of the second binder can be 30%, 32%, 34%, 36%, 38%, 40% or any value between any two of the above numerical ranges. Selecting the above materials to form the conductive layer and regulating the mass percentages of the second conductive agent and the second binder within the above range is more conducive to the role of the conductive layer. In this way, the conductive layer can receive the Li ions released from the positive electrode sheet. + , inhibiting the formation of lithium plating and dead lithium, thereby improving the safety and cycle performance of electrochemical devices.

[0055] In some embodiments of the present application, the second conductive agent includes at least one of amorphous carbon, single-walled carbon nanotubes, or multi-walled carbon nanotubes; the second binder includes at least one of styrene-butadiene rubber, carboxymethyl cellulose, or polyvinyl alcohol. The selection of the above materials is more conducive to the formation of the conductive layer and the performance of its function. In this way, the conductive layer can receive the Lithium ions released from the positive electrode sheet. + , inhibiting the formation of lithium plating and dead lithium, thereby improving the safety and cycle performance of electrochemical devices.

[0056] In some embodiments of the present application, the thickness of the conductive layer is 0.5 μm to 3 μm. For example, the thickness of the conductive layer can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm or any value between any two of the above numerical ranges. If the thickness of the conductive layer is too small (for example, less than 0.5 μm), the mechanical strength of the conductive layer is insufficient, and the purpose of the present application cannot be achieved; if the thickness of the conductive layer is too large (for example, greater than 3 μm), the volume of the electrochemical device will increase, which will affect the energy density of the electrochemical device. The thickness of the conductive layer is regulated within the above range so that the role of the conductive layer in the present application can be effectively played. As a result, the electrochemical device has better safety performance and cycle performance with lower material costs.

[0057] The present application has no particular limitation on the positive current collector, as long as the object of the present application can be achieved. For example, the positive current collector may include aluminum foil, aluminum alloy foil, composite current collector, etc. In the present application, there is no particular limitation on the thickness of the positive current collector and the positive active material layer, as long as the object of the present application can be achieved. For example, the thickness of the positive current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. The thickness of the single-sided positive active material layer is 30 μm to 120 μm.

[0058] The present application has no particular limitation on the negative current collector, as long as the object of the present application can be achieved. For example, the negative current collector may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, composite current collector, etc. In the present application, there is no particular limitation on the thickness of the negative current collector, as long as the object of the present application can be achieved. For example, the thickness of the negative current collector is 6 μm to 10 μm.

[0059] The electrolyte of the present application further includes a lithium salt and a non-aqueous solvent.

[0060] The present application has no particular limitation on the lithium salt. For example, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium tetraphenylborate (LiB(C6H5)4), lithium methyl sulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiN(SO2CF3)2), LiC(SO2CF3)3, lithium hexafluorosilicate (LiSiF6), lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate (LiF2OB). For example, LiPF6 can be selected as the lithium salt because it has high ionic conductivity and improves the cycling performance.

[0061] The present application has no particular limitation on the non-aqueous solvent. For example, the non-aqueous solvent can be at least one of a carbonate compound, a carboxylate compound, an ether compound, or other organic solvents. The above carbonate compound can be at least one of a chain carbonate compound, a cyclic carbonate compound, or a fluorinated carbonate compound. Examples of the above chain carbonate compounds are at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or ethyl methyl carbonate (EMC). Examples of the cyclic carbonate compounds are at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene ethylene carbonate (VEC). Examples of the fluorinated carbonate compounds are at least one of 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate. Examples of the above carboxylate compounds are at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, or caprolactone. Examples of the above ether compounds are at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. Examples of the above other organic solvents are at least one of propyl propionate, dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate ester. Based on the mass of the electrolyte solution, the total content of the above non-aqueous solvent is 5% to 90%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any range therebetween.

[0062] The electrochemical device of the present application further includes a separator, and the present application has no particular limitation on the separator as long as it can achieve the purpose of the present application.

[0063] The electrochemical device of the present application has no particular limitation, and it can include any device that undergoes an electrochemical reaction. In some embodiments, the electrochemical device can include, but is not limited to: a lithium metal secondary battery, a lithium ion battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery, etc.

[0064] The preparation process of the electrochemical device is well-known to those skilled in the art, and there is no particular limitation in this application. For example, it may include but is not limited to the following steps: stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and winding them as needed to obtain a wound structure electrode assembly, placing the electrode assembly into a packaging case, injecting the electrolyte into the packaging case and sealing it to obtain the electrochemical device; or, stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence, and then fixing the four corners of the entire laminated structure with tape to obtain a laminated structure electrode assembly, placing the electrode assembly into a packaging case, injecting the electrolyte into the packaging case and sealing it to obtain the electrochemical device. In addition, an overcurrent protection element, a guide plate, etc. may be placed in the packaging case as needed to prevent the pressure inside the electrochemical device from rising and overcharging and discharging.

[0065] The second aspect of this application provides an electronic device, which includes the electrochemical device described in any of the foregoing embodiments. Therefore, the production cost of this electronic device is also reduced.

[0066] There is no particular limitation on the electronic device of this application, and it may include but is not limited to the following types: laptop computer, pen-input computer, mobile computer, e-book player, portable phone, portable fax machine, portable copier, portable printer, head-mounted stereo headphones, video recorder, liquid crystal TV, portable cleaner, portable CD player, minidisc, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, car, motorcycle, moped, bicycle, lighting fixture, toy, game console, clock, power tool, flashlight, camera, and large household battery, etc.

[0067] Examples

[0068] Hereinafter, examples and comparative examples are given to illustrate the embodiments of this application more specifically. Various tests and evaluations are carried out according to the following methods.

[0069] Testing method and device:

[0070] Material cost calculation logic:

[0071] The material cost of a single lithium-ion battery is the sum of the material costs of each component. Each component material is the four major main materials and auxiliary materials. Among them, the four major main materials are the positive electrode active material, the negative electrode active material, the separator, and the electrolyte, and the auxiliary materials are the negative electrode current collector, the positive electrode current collector, the conductive agent, the binder, the solvent, the adhesive tape, the tab roll material, the packaging case, etc. The material cost of each component = unit price × unit consumption.

[0072] Material cost ratio (%) = material cost of lithium-ion battery in each example / material cost of lithium-ion battery in Comparative Example 1 × 100%.

[0073] Initial discharge capacity test:

[0074] The test temperature is 25°C. First, fully charge the lithium-ion battery, and then discharge it at a constant current of 0.2C to 3.0V. The discharged capacity is obtained.

[0075] Capacity retention rate test:

[0076] Perform a cyclic capacity retention rate test on the lithium-ion battery: The test temperature is 25°C. Charge it at a constant current of 0.2C to the rated voltage, then charge it at a constant voltage to 0.025C. After standing for 5 minutes, discharge it at 0.2C to 3.0V. The capacity obtained in this step is the initial capacity. Conduct a cyclic test of 0.2C charge / 0.2C discharge, and calculate the ratio of the capacity after each cycle to the initial capacity to obtain the capacity decay curve. The capacity retention rate can be directly obtained from the capacity decay curve.

[0077] Example 1-1

[0078] <Preparation of the positive electrode sheet>

[0079] Mix the lithium-containing positive electrode active material LiCoO2, the conductive agent conductive carbon, and the positive electrode binder polyvinylidene fluoride (PVDF) in a mass ratio of 95.8:2.0:2.2. Then add N-methylpyrrolidone (NMP) as a solvent to prepare a positive electrode slurry with a solid content of 75 wt%. Stir it evenly. Coat the positive electrode slurry evenly on one surface of an aluminum foil with a thickness of 9μm and dry it at 90°C to obtain a positive electrode sheet with a positive electrode active material layer thickness of 100μm. Then repeat the above steps on the other surface of the positive electrode sheet to obtain a positive electrode sheet with a positive electrode active material layer coated on both sides. Cold press and cut the positive electrode sheet into sheets with a specification of 74mm×867mm for use.

[0080] <Preparation of the negative electrode sheet>

[0081] Prepare a ceramic coating slurry by mixing the inorganic powder alumina and the first binder polyacrylic acid in a mass ratio of 90:10. Coat the ceramic coating slurry evenly on one surface of a copper foil with a thickness of 6μm and dry it at 110°C to obtain a negative electrode sheet with a single-sided ceramic coating with a ceramic coating thickness of 3μm. Then repeat the above coating steps on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a ceramic coating coated on both sides. Cold press and cut the negative electrode sheet into sheets with a specification of 76mm×851mm for use. Among them, the coating weight of the ceramic coating is 18.5mg / 5000mm 2 .

[0082] <Preparation of the electrolyte>

[0083] In a dry argon atmosphere, organic solvents EC, EMC, and DEC were mixed in a mass ratio of 30:50:20. Then, LiPF6 was added to the organic solvents, dissolved, and mixed evenly to obtain a basic solution. Subsequently, FEC and LiDFOB were added to the basic solution. Among them, the molar concentration of LiPF6 in the electrolyte was 1.15 mol / L; based on the mass of the electrolyte, the mass percentage content W1 of FEC was 1%, and the mass percentage content W2 of LiDFOB was 0.6%.

[0084] <Preparation of Lithium-Ion Battery>

[0085] Using a polyethylene porous polymer film with a thickness of 9 μm as the separator, the above-prepared positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, with the separator placed in the middle of the positive and negative electrodes to play an insulating role, and then wound to obtain an electrode assembly. The electrode assembly was placed in a packaging shell, injected with the prepared electrolyte, and sealed. After processes such as formation, degassing, and edge trimming, a lithium-ion battery was obtained. The formation process was as follows: the formation charging current was 0.1C, the formation temperature was 85°C, and the formation standing time was 180 seconds.

[0086] Examples 1-2 to Examples 1-9

[0087] Except for adjusting the relevant preparation parameters according to Table 1, the mass percentage contents of the basic solution and the lithium salt in the electrolyte changed accordingly, with the electrolyte mass being 100%, the rest was the same as Example 1-1.

[0088] Examples 1-10 to Examples 1-21

[0089] Except for adjusting the relevant preparation parameters according to Table 1, the rest was the same as Example 1-9.

[0090] Example 2-1

[0091] Except for adding a positive electrode lithium supplement agent Li2O with a mass percentage content W3 of 3% in the <Preparation of Positive Electrode Sheet>, and the mass percentage content of the positive electrode active material was reduced to 92.8%, the rest was the same as Example 1-9.

[0092] Examples 2-2 to Examples 2-7

[0093] Except for adjusting the relevant preparation parameters according to Table 2, the rest was the same as Example 2-1.

[0094] Example 3-1

[0095] Except for adding a positive electrode additive (the mass ratio of inorganic lithium salt Li5FeO4 and the first conductive agent graphene was 1:5) with a mass percentage content W4 of 6% in the <Preparation of Positive Electrode Sheet>, and the mass percentage content of the positive electrode active material was reduced to 89.8%, the rest was the same as Example 1-9.

[0096] Examples 3-2 to 3-8

[0097] Except for adjusting the relevant preparation parameters according to Table 3, the rest is the same as that of Example 3-1.

[0098] Example 3-9

[0099] Except that in the <Preparation of the positive electrode sheet>, ceramic coatings are provided on both surfaces of the positive electrode active material layer, and the ceramic coatings are the same as those in the <Preparation of the negative electrode sheet> in Example 1-1, the rest is the same as that of Example 3-3.

[0100] Example 4-1

[0101] <Preparation of the negative electrode sheet>

[0102] The ceramic coating slurry is prepared by mixing the inorganic powder alumina and the first binder polyacrylic acid in a mass ratio of 90:10.

[0103] The conductive layer slurry is prepared by mixing the second conductive agent amorphous carbon and the second binder styrene-butadiene rubber in a mass ratio of 65:35.

[0104] The conductive layer slurry and the ceramic coating slurry are successively and uniformly coated on one surface of a copper foil with a thickness of 6 μm, and dried at 110 °C to obtain a negative electrode sheet with a single-sided ceramic coating having a conductive layer thickness of 1.5 μm and a ceramic coating thickness of 2 μm. Then, the above coating steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with both sides coated with a conductive layer and a ceramic coating. The negative electrode sheet is cold-pressed and cut into sheets with a specification of 76 mm × 851 mm for use. Among them, the coating weight of the conductive layer is 0.5 mg / 5000 mm 2 and the coating weight of the ceramic coating is 13.6 mg / 5000 mm 2 .

[0105] The rest is the same as that of Example 1-9.

[0106] Example 4-2

[0107] Except that the <Preparation of the positive electrode sheet> is the same as that of Example 3-9, the rest is the same as that of Example 4-2.

[0108] Examples 4-3 to 4-4

[0109] Except for adjusting the relevant preparation parameters according to Table 4, the rest is the same as that of Example 4-2.

[0110] Comparative Example 1

[0111] <Preparation of the negative electrode sheet>

[0112] The graphite as the negative electrode active material, the conductive carbon black as the conductive agent, and the styrene-butadiene rubber (SBR) as the binder are mixed at a mass ratio of 85:5:10. Then, deionized water is added as a solvent to prepare a negative electrode slurry with a solid content of 70 wt%. The slurry is stirred evenly and uniformly coated on one surface of a copper foil with a thickness of 6 μm. After drying at 110°C, a negative electrode sheet with a single-sided coated negative electrode active material layer having a thickness of 130 μm is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coated negative electrode active material layer. The negative electrode sheet is cold-pressed and cut into sheets with a specification of 76 mm × 851 mm for use.

[0113] In the <Preparation of electrolyte>, FEC and LiDFOB are not added.

[0114] The rest is the same as in Example 1-1.

[0115] The preparation parameters and performance parameters of each example and comparative example are shown in Tables 1 to 4.

[0116] Table 1

[0117]

[0118]

[0119] Note: The “\” in Table 1 indicates no corresponding parameter.

[0120] It can be seen from Example 1-1 to Example 1-9, Example 1-21, and Comparative Example 1 that when the negative electrode sheet of the lithium-ion battery does not contain the negative electrode active material, a ceramic coating within the scope of this application is provided on the surface of the negative electrode current collector, and the electrolyte contains FEC and LiDFOB within the mass percentage range of this application, the lithium-ion battery has a good first discharge capacity and can meet the requirements of products with a small number of charge and discharge cycles, while reducing the material cost.

[0121] The types of inorganic powder and the first binder in the ceramic coating usually also affect the material cost, first discharge capacity, and capacity retention rate of the lithium-ion battery. It can be seen from Example 1-9 to Example 1-14 that for lithium-ion batteries with the types of inorganic powder and the first binder within the scope of this application, they have a good first discharge capacity and can meet the requirements of products with a small number of charge and discharge cycles, while reducing the material cost.

[0122] The mass percentage content of the inorganic powder and the first binder in the ceramic coating usually also affects the material cost, the first discharge capacity, and the capacity retention rate of the lithium-ion battery. It can be seen from Examples 1-9, Examples 1-15, and Examples 1-16 that for a lithium-ion battery with the mass percentage content of the inorganic powder and the first binder within the scope of this application, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge-discharge cycles, the material cost is reduced.

[0123] The coating weight of the ceramic coating usually also affects the material cost, the first discharge capacity, and the capacity retention rate of the lithium-ion battery. It can be seen from Examples 1-9, Examples 1-17, and Examples 1-18 that for a lithium-ion battery with the coating weight of the ceramic coating within the scope of this application, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge-discharge cycles, the material cost is reduced.

[0124] The thickness of the ceramic coating usually also affects the material cost, the first discharge capacity, and the capacity retention rate of the lithium-ion battery. It can be seen from Examples 1-9, Examples 1-19, and Examples 1-20 that for a lithium-ion battery with the thickness of the ceramic coating within the scope of this application, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge-discharge cycles, the material cost is reduced.

[0125] Table 2

[0126]

[0127] Note: The "\ " in Table 2 indicates no corresponding parameter.

[0128] The type of the cathode lithium supplement agent and the mass percentage content of the cathode lithium supplement agent in the cathode active material layer usually also affect the material cost, the first discharge capacity, and the capacity retention rate of the lithium-ion battery. It can be seen from Examples 1-9, Examples 2-1 to Examples 2-7 that for a lithium-ion battery with the type and the mass percentage content of the cathode lithium supplement agent within the scope of this application, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge-discharge cycles, the material cost is reduced.

[0129] Table 3

[0130]

[0131]

[0132] Note: The "\ " in Table 3 indicates no corresponding parameter.

[0133] The types of the positive electrode additives, their mass percentage content in the positive electrode active material layer, and the mass ratio of the inorganic lithium salt and the first conductive agent usually also affect the material cost, the first discharge capacity, and the capacity retention rate of the lithium ion battery. It can be seen from Examples 1-9, Examples 3-1 to Examples 3-8 that for the lithium ion battery with the types of the positive electrode additives, their mass percentage content in the positive electrode active material layer, and the mass ratio of the inorganic lithium salt and the first conductive agent within the scope of this application, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge and discharge cycles, the material cost is reduced.

[0134] The setting of the ceramic coating in the positive electrode sheet usually also affects the material cost, the first discharge capacity, and the capacity retention rate of the lithium ion battery. It can be seen from Examples 3-2 and Examples 3-9 that for the lithium ion battery with a ceramic coating provided in the positive electrode sheet, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge and discharge cycles, the material cost is reduced.

[0135] Table 4

[0136]

[0137] Note: The "\ " in Table 4 indicates no corresponding parameter.

[0138] The setting of the conductive layer in the negative electrode sheet usually also affects the material cost, the first discharge capacity, and the capacity retention rate of the lithium ion battery. It can be seen from Examples 3-2 and Examples 4-1, Examples 3-9 and Examples 4-2 that for the lithium ion battery with a conductive layer provided in the negative electrode sheet, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge and discharge cycles, the material cost is reduced.

[0139] The mass percentage content of the second conductive layer and the second binder in the conductive layer usually also affects the material cost, the first discharge capacity, and the capacity retention rate of the lithium ion battery. It can be seen from Examples 4-2 to Examples 4-4 that for the lithium ion battery with the mass percentage content of the second conductive layer and the second binder in the conductive layer within the scope of this application, while having a good first discharge capacity and being able to meet the requirements of products with a small number of charge and discharge cycles, the material cost is reduced.

[0140] The above are only the preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the scope of protection of this application.

Claims

1. An electrochemical device, comprising a positive electrode sheet and a negative electrode sheet; The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and the positive electrode active material layer includes a lithium-containing positive electrode active material; The negative electrode sheet includes a negative electrode current collector and a ceramic coating provided on two surfaces of the negative electrode current collector. The negative electrode sheet further includes a lithium metal layer formed by deposition of lithium ions in the lithium-containing positive electrode active material on the surface of the negative electrode current collector during charging, and the lithium metal layer is located between the negative electrode current collector and the ceramic coating; the negative electrode sheet does not contain a negative electrode active material; The negative electrode sheet further includes a conductive layer provided between the negative electrode current collector and the ceramic coating, and the lithium metal layer is provided between the negative electrode current collector and the conductive layer; Among them, The ceramic coating includes inorganic powder and a first binder, and the inorganic powder includes at least one of alumina, magnesia, zirconia or boehmite; And wherein, based on the mass of the ceramic coating, the mass percentage content W5 of the inorganic powder is 85% to 95%, and the mass percentage content W6 of the first binder is 5% to 15%.

2. The electrochemical device according to claim 1, further comprising an electrolyte, and the electrolyte includes fluoroethylene carbonate and lithium difluoro(oxalato)borate; Based on the mass of the electrolyte, the mass percentage content W1 of the fluoroethylene carbonate is 0.1% to 10%, and the mass percentage content W2 of the lithium difluoro(oxalato)borate is 0.05% to 5%.

3. The electrochemical device according to claim 1, wherein, The lithium-containing positive electrode active material includes at least one of lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium titanate or lithium fluoroacid.

4. The electrochemical device according to claim 1, wherein, The positive electrode active material layer further includes a positive electrode lithium supplementing agent; The positive electrode lithium supplement includes at least one of Li2O or Li x MO y where 2 ≤ x ≤ 6, 2 ≤ y ≤ 5, and M includes at least one of Al, Ni, Co, Mg, Mn, Cu, Fe, or Ti; Based on the mass of the positive electrode active material layer, the mass percentage content W3 of the positive electrode lithium supplementing agent is 3% to 10%.

5. The electrochemical device according to claim 1, wherein, The positive electrode active material layer further includes a positive electrode additive, and the positive electrode additive includes a composite material formed by an inorganic lithium salt and a first conductive agent, and the mass ratio of the inorganic lithium salt to the first conductive agent is 1:3 to 1:7; Based on the positive electrode active material layer, the mass percentage content W4 of the positive electrode additive is 4% to 8%.

6. The electrochemical device according to claim 5, wherein, The inorganic lithium salt includes Li s Q a N b O t , 2 ≤ s ≤ 8, 0 ≤ a ≤ 1, 0 ≤ b ≤ 1, a + b ≥ 1, 2 ≤ t ≤ 6, Q is selected from any one of Fe, Co, Mn, Ni, Zr, V, Nb or Mo, and N is selected from any one of Al, Mg, Ti, Cr, Y, Sr, Si, W, Ga or Zn; The first conductive agent includes at least one of graphene, acetylene black, single-walled carbon nanotubes or multi-walled carbon nanotubes.

7. The electrochemical device according to claim 1, wherein, The positive electrode sheet further includes the ceramic coating, and the ceramic coating is provided on the surface of the positive electrode active material layer.

8. The electrochemical device according to claim 1, wherein, The first binder includes at least one of polyacrylic acid, polyvinylidene fluoride, polyimide or polyvinyl alcohol.

9. The electrochemical device according to claim 1, wherein The coating weight of the ceramic coating is 5 mg / 5000 mm 2 to 20 mg / 5000 mm 2 .

10. The electrochemical device according to claim 1, wherein, The thickness of the ceramic coating is 1 μm to 3 μm.

11. The electrochemical device according to claim 1, wherein, The conductive layer includes a second conductive agent and a second binder; Based on the mass of the conductive layer, the mass percentage content W7 of the second conductive agent is 60% to 70%, and the mass percentage content W8 of the second binder is 30% to 40%.

12. The electrochemical device according to claim 11, wherein, The second conductive agent includes at least one of amorphous carbon, single-walled carbon nanotubes or multi-walled carbon nanotubes; The second binder includes at least one of styrene-butadiene rubber, carboxymethyl cellulose or polyvinyl alcohol.

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

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