Positive plate, battery and electronic equipment
By optimizing the stacked structure of the positive electrode and the electrolyte additives, the structural degradation and side reactions caused by lithium replenishment agents in lithium-ion batteries were solved, resulting in improved first-time coulombic efficiency, cycle performance, and storage performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-24
AI Technical Summary
Existing lithium replenishing agents in lithium-ion batteries have problems such as causing structural degradation of active materials during cell cycling, decreased cycle retention, gas generation due to side reactions during storage, impact on packaging safety and stability, and insufficient lithium release efficiency, making it difficult to fully play the role of improving the first coulombic efficiency.
The positive electrode design employs a stacked structure, including a first active layer and a second active layer. The first active layer contains a lithium-rich compound lithium supplement. By adjusting the matching ratio between its particle size and the porosity of the second active layer, the direct contact between the lithium supplement and the electrolyte is reduced, optimizing the internal structure of the battery. Combined with electrolyte additives, a dense CEI film is formed, suppressing side reactions.
It significantly improves the battery's initial coulombic efficiency, cycle performance, and storage performance, reduces electrolyte decomposition and gas production, ensures battery safety and stability, and improves lithium-ion transport efficiency.
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Abstract
Description
Technical Field
[0001] This application relates to the field of battery technology, and in particular to positive electrode plates, batteries and electronic devices. Background Technology
[0002] Lithium-ion batteries are widely used in 3C digital products, power tools, aerospace, energy storage, and electric vehicles due to their advantages such as high specific energy, no memory effect, and long cycle life. The rapid development of electronic information technology and consumer products has placed higher demands on the electrochemical performance of lithium-ion batteries.
[0003] Among them, cathode lithium replenishment agents, as a key technology for improving cell energy density and initial coulombic efficiency, have been widely and deeply studied and applied in the field of electrochemical energy storage. Their core advantage lies in their ability to compensate for irreversible lithium loss caused by the formation of the SEI film and side reactions at the electrode interface during the first cycle of the cell by releasing active lithium, thereby significantly improving the initial coulombic efficiency. However, the practical engineering application of lithium replenishment agents still faces key bottlenecks: First, the introduction of lithium replenishment agents may cause structural degradation of the active material during cell cycling, leading to a decrease in cycle retention; second, side reactions are prone to occur during cell storage, resulting in gas generation, affecting battery packaging safety and storage stability; third, some lithium replenishment agents have problems such as insufficient lithium release efficiency and poor compatibility with electrodes / electrolytes, making it difficult to fully realize their lithium replenishment and efficiency-enhancing effects.
[0004] Therefore, developing lithium replenishment optimization technology that can ensure high initial coulombic efficiency, improve cycle stability, and suppress storage gas generation has become a key issue that urgently needs to be addressed in the current research and development of high energy density battery cells. Summary of the Invention
[0005] To address or partially address the problems existing in related technologies, this application provides a positive electrode, a battery, and an electronic device that enables the battery to exhibit excellent first coulombic efficiency, cycle performance, and storage performance.
[0006] This application provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector; the positive electrode coating comprising a first active layer and a second active layer stacked thereon, the first active layer being disposed on the surface of the positive current collector; the first active layer comprising a positive electrode lithium supplementer, the positive electrode lithium supplementer comprising a lithium-rich compound; the battery satisfies the following relationship: 4≤a 1 / 2 / b≤10; The median particle size Dv50 of the lithium-rich compound is a μm; the porosity of the second active layer is b.
[0007] The positive electrode as described in the first aspect, wherein 2≤a≤4.
[0008] The positive electrode as described in the first aspect, wherein 0.15 ≤ b ≤ 0.4.
[0009] The positive electrode as described in the first aspect, wherein the chemical formula of the lithium-rich compound is Li2XO3, wherein X is at least one of Mn, Ni, and Fe.
[0010] As described in the first aspect, the positive electrode sheet includes a positive electrode active material in both the first active layer and the second active layer, wherein the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium iron phosphate.
[0011] A second aspect of this application provides a battery comprising a positive electrode as described in the first aspect.
[0012] The battery as described in the second aspect further includes an electrolyte, the electrolyte including electrolyte additives, the electrolyte additives including lithium difluorooxalate borate and fluoroethylene carbonate.
[0013] The battery as described in the second aspect, wherein the lithium difluorooxalate borate in the electrolyte has a mass percentage of c%, 0.1 ≤ c ≤ 3; And / or, the mass percentage of the fluoroethylene carbonate in the electrolyte is d%, 0.5≤d≤4.
[0014] The battery as described in the second aspect, wherein the battery satisfies the following relationship: 3≤a×(c+d)≤6.
[0015] A third aspect of this application provides an electronic device comprising a battery as described in the second aspect.
[0016] The technical solution provided in this application can include the following beneficial effects: On the one hand, adding a lithium replenishing agent to the first active layer near the current collector can significantly reduce the direct contact area between the lithium replenishing agent and the electrolyte, effectively suppress the occurrence of side reactions between the two, thereby reducing the decomposition and gas generation of the electrolyte, and ultimately improving the battery's initial coulombic efficiency, cycle performance, and storage performance; On the other hand, by controlling the matching ratio between the particle size of the lithium replenishing agent and the porosity of the second active layer, it is possible to avoid the problems of excessive interface contact and aggravated side reactions caused by the lithium replenishing agent having too small a particle size or the second active layer having too large a porosity, and it is also possible to prevent the lithium-ion transport path from being blocked and the lithium replenishing efficiency from being reduced due to the lithium replenishing agent having too large a particle size or the second active layer having too small a porosity, thereby improving the battery's initial coulombic efficiency, cycle performance, and storage performance.
[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation
[0018] To facilitate understanding of this application, it will be described in detail below. However, before describing this application in detail, it should be understood that this application is not limited to the specific embodiments described. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be restrictive.
[0019] Where a numerical range is provided, it should be understood that every intermediate value between the upper and lower limits of the range and any other specified or intermediate value within the specified range is covered within this application. The upper and lower limits of these smaller ranges may be independently included in the smaller range and are also covered within this application, subject to any explicitly excluded limits within the specified range. Where the specified range includes one or two limits, the range excluding any or both of those included limits is also included within this application.
[0020] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While the methods and materials described herein, or any equivalent methods and materials, may also be used in the implementation or testing of this application, preferred methods and materials are now described.
[0021] As a key technology for improving the energy density and initial coulombic efficiency of battery cells, cathode lithium replenishment agents have been widely and deeply studied and applied in the field of electrochemical energy storage. Their core advantage lies in their ability to compensate for irreversible lithium loss caused by the formation of the SEI film and side reactions at the electrode interface during the first cycle of the cell by releasing active lithium, thereby significantly improving the initial coulombic efficiency. However, the practical engineering application of lithium replenishment agents still faces key bottlenecks: First, the introduction of lithium replenishment agents may cause structural degradation of the active material during cell cycling, leading to a decrease in cycle retention; second, side reactions are prone to occur during cell storage, resulting in gas generation, affecting battery packaging safety and storage stability; third, some lithium replenishment agents have problems such as insufficient lithium release efficiency and poor compatibility with electrodes / electrolytes, making it difficult to fully realize their lithium replenishment and efficiency-enhancing effects.
[0022] To address the aforementioned problems, this application provides a positive electrode sheet, which includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector; the positive electrode coating includes a first active layer and a second active layer stacked thereon, the first active layer being disposed on the surface of the positive current collector; the first active layer includes a positive electrode lithium supplement agent, which includes a lithium-rich compound; the battery satisfies the following relationship: 4≤a 1 / 2 / b≤10; where the median particle size Dv50 of the lithium-rich compound is a μm; and the porosity of the second active layer is b.
[0023] This application does not limit the choice of the positive current collector; for example, the positive current collector can be aluminum foil. The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector. The positive electrode coating of this application includes two layers, namely a first active layer and a second active layer. The first active layer is disposed on the surface of the positive current collector, and the second active layer is disposed on the surface of the first active layer away from the positive current collector.
[0024] The first active layer of this application includes a positive electrode lithium replenishing agent, which includes a lithium-rich compound containing a high lithium content. Adding the lithium-rich compound to the first active layer allows it to release active lithium, compensating for lithium consumed during SEI film formation and other processes, thereby improving the battery's initial coulombic efficiency.
[0025] The battery in this application satisfies the following relationship: 4≤a 1 / 2 / b≤10, for example, a 1 / 2 / b can be 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, etc.; among which, the median particle size Dv50 of the lithium-rich compound is a μm; the porosity of the second active layer is b.
[0026] According to the above-mentioned scheme provided in this application, applying this positive electrode sheet to a battery enables the battery to have excellent initial coulombic efficiency, cycle performance, and storage performance. The applicant analyzed the principle behind this and believes that the reasons are as follows: On the one hand, adding a lithium supplement to the first active layer near the current collector can significantly reduce the direct contact area between the lithium supplement and the electrolyte, effectively suppressing the occurrence of side reactions between the two, thereby reducing the decomposition and gas production of the electrolyte, and ultimately improving the initial coulombic efficiency, cycle performance, and storage performance of the battery; on the other hand, by controlling the matching ratio between the particle size of the lithium supplement and the porosity of the second active layer, it is possible to avoid the problems of excessive interfacial contact and aggravated side reactions caused by the lithium supplement particle size being too small or the porosity of the second active layer being too large, and it is also possible to prevent the lithium-ion transport path from being blocked and the lithium supplement efficiency from being reduced due to the lithium supplement particle size being too large or the porosity of the second active layer being too small, thereby improving the initial coulombic efficiency, cycle performance, and storage performance of the battery.
[0027] In one specific embodiment, 2 ≤ a ≤ 4, for example, a can be 2, 2.5, 3, 3.5, or 4. When the particle size of the lithium-rich compound is within the above range, a suitable particle size can reduce the diffusion resistance of lithium inside the lithium-rich compound, allowing the lithium-rich compound to quickly and completely release active lithium during the first charge, replenishing the lithium irreversibly consumed during the formation of the SEI film, and avoiding the inability of internal lithium to be effectively extracted due to excessively large particle size, thus effectively improving the first coulombic efficiency of the battery. At the same time, this particle size can match the pore structure of the positive electrode coating, reduce the contact resistance with the electrolyte and positive electrode active material, reduce side reactions, and thus improve the cycle stability and storage performance of the battery. In addition, a reasonable particle size of the lithium-rich compound can ensure the uniform dispersion of the lithium-rich compound in the first active layer, and can also avoid stress concentration in the electrode layer due to excessively large particle size, reducing the probability of cracking of the positive electrode coating during cycling, thereby ensuring the cycle life of the battery.
[0028] In one specific embodiment, 0.15 ≤ b ≤ 0.4, for example, b can be 0.15, 0.2, 0.25, 0.3, 0.35, or 0.4. When the porosity of the second active layer is within the above range, a reasonable pore structure can ensure rapid lithium ion transport, reduce side reactions between the electrolyte and lithium-rich compounds in the first active layer, and improve the storage safety and lifespan of the battery. Furthermore, a suitable porosity can serve as a sufficient channel for electrolyte wetting and lithium ion migration, effectively reducing ion transport impedance during charging and discharging, and improving the cycle performance of the battery. At the same time, this porosity range can cleverly balance the electrode structure strength and volume buffer space, preventing the electrolyte from being unable to penetrate due to excessively low porosity and the electrode from cracking due to volume changes, while also preventing the electrode structure from becoming loose and lacking mechanical strength due to excessively high porosity, thereby improving the cycle stability of the battery.
[0029] In one specific embodiment, the lithium-rich compound has the chemical formula Li₂XO₃, wherein X is at least one of Mn, Ni, and Fe. When the above-mentioned lithium-rich compound is selected as the positive electrode lithium replenisher, the positive electrode lithium replenisher can efficiently release lithium during charging and discharging, replenish the irreversible lithium loss of the battery, improve the initial coulombic efficiency of the battery, and reduce the side reactions between the positive electrode lithium replenisher and the electrolyte, thus ensuring the cycle performance and storage performance of the battery.
[0030] In one specific embodiment, both the first active layer and the second active layer include a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium iron phosphate. The positive electrode active materials in the first and second active layers can be the same or different, and can be selected according to actual needs. When the above-mentioned positive electrode active material is added to the first and second active layers, the positive electrode active material can fully utilize its inherent properties, improve electron conduction efficiency and structural stability by optimizing the kinetics of lithium-ion insertion / extraction, thereby improving the electrochemical performance of the battery.
[0031] A second aspect of this application provides a battery including the aforementioned positive electrode. This battery exhibits excellent initial coulombic efficiency, cycle performance, and storage performance.
[0032] In one specific embodiment, the battery further includes an electrolyte, which comprises electrolyte additives, including lithium difluorooxalate borate and fluoroethylene carbonate. The addition of these two additives to the electrolyte allows them to synergistically interact with the lithium replenishing agent in the first active layer, participating in the formation of the CEI film on the surface of the positive electrode lithium replenishing agent. This significantly improves the density, toughness, and stability of the CEI film, effectively blocking contact between the electrolyte and the positive electrode lithium replenishing agent, further reducing the incidence of side reactions between the positive electrode lithium replenishing agent and the electrolyte, and alleviating cell gas generation, thereby improving the battery's cycle performance and storage performance. Simultaneously, it ensures the lithium replenishing performance of the positive electrode lithium replenishing agent, improving the battery's initial coulombic efficiency.
[0033] In one specific embodiment, the mass percentage of lithium difluorooxalate borate in the electrolyte is c%, where 0.1 ≤ c ≤ 3. For example, c can be 0.1, 0.5, 1, 1.5, 2, 2.5, or 3, etc. When the mass percentage of lithium difluorooxalate borate in the electrolyte is within the above range, the stability and density of the CEI film are higher, which reduces the probability of direct contact between the positive electrode lithium supplement and the electrolyte, further reducing gas generation and heat accumulation problems, and reducing side reactions caused by excessive lithium difluorooxalate borate. This results in better initial coulombic efficiency, cycle performance, and storage performance of the battery.
[0034] In one specific embodiment, the mass percentage of fluoroethylene carbonate in the electrolyte is d%, 0.5 ≤ d ≤ 4, for example, d can be 0.5, 1, 1.5, 2, 2.5, 3, 3.5, or 4, etc. When the mass percentage of fluoroethylene carbonate in the electrolyte is within the above range, it can further improve the density and stability of the CEI film, reduce the occurrence of side reactions between the lithium supplement and the electrolyte, and also avoid other side reactions caused by excessive fluoroethylene carbonate, thereby improving the electrochemical performance of the battery.
[0035] In one specific embodiment, the battery satisfies the following relationship: 3 ≤ a × (c + d) ≤ 6, for example, a × (c + d) can be 3, 3.5, 4, 4.5, 5, 5.5, or 6, etc. When the ratio between the particle size of the positive electrode lithium replenisher and the amount of electrolyte additive is within the above range, the CEI film formed by the electrolyte additive on the surface of the positive electrode lithium replenisher has better density, toughness, and stability. It can not only tightly cover the surface of the lithium replenisher to form an effective protective barrier, but also adapt to the volume changes during charging and discharging without being easily damaged. This more thoroughly blocks the direct contact between the electrolyte and the positive electrode lithium replenisher, greatly reduces the occurrence of side reactions between the two, reduces the ineffective consumption of active lithium and electrolyte, and alleviates the gas generation phenomenon of the cell during cycling and storage, thereby making the battery exhibit higher initial coulombic efficiency, cycle performance, and storage performance.
[0036] In one specific embodiment, the first active layer and the second active layer further include a conductive agent and a binder. The conductive agent includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene, and vapor-grown carbon fiber (VGCF). The binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, polyvinylidene fluoride, and polytetrafluoroethylene.
[0037] In one specific embodiment, the electrolyte of this application further includes an organic solvent and an electrolyte lithium salt. This application does not limit the selection of organic solvent and electrolyte lithium salt, and can select them according to actual needs, as long as the electrolyte lithium salt and electrolyte additives can be fully dissolved and have high stability.
[0038] In one specific embodiment, the battery of this application further includes a negative electrode sheet, which includes a negative electrode current collector and a negative electrode coating disposed on at least one side surface of the negative electrode current collector. This application does not limit the selection of the negative electrode current collector; it can be selected according to actual needs, such as copper foil. The negative electrode coating of this application includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material of this application is a graphite-silicon-carbon system, that is, a mixture of graphite and silicon-carbon materials. The conductive agent and binder in the negative electrode active material layer of this application can both be selected from conventional materials in the art.
[0039] In one specific embodiment, the lithium-ion battery further includes a separator. The embodiments of this application do not have any particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effect of this application. It may include porous sheet-like or non-woven fabric-like materials with excellent liquid retention. The materials of the resin or glass fiber separator include, but are not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc., and can be set according to needs.
[0040] In one embodiment, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte.
[0041] In one specific embodiment, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch-type soft pack. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.
[0042] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape.
[0043] A third aspect of this application provides an electronic device including the aforementioned battery. This electronic device has advantages corresponding to the aforementioned battery, which will not be elaborated further.
[0044] The application fields of the electronic devices in this application embodiment are not particularly limited, and they can be used in consumer electronics products, new energy vehicles, and energy storage, among other fields. For example, the aforementioned electronic devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., without any particular limitation.
[0045] The present application will be further described in detail below through specific embodiments.
[0046] Example 1 1. Preparation of positive electrode sheet The positive electrode active material lithium cobalt oxide and the positive electrode lithium supplementing agent lithium iron oxide (Li2FeO3) were mixed with the conductive agent carbon black and the binder polyvinylidene fluoride at a mass ratio of 97.2:1.0:1.0:0.8. N-methylpyrrolidone (NMP) was added and the mixture was stirred under vacuum until the system was homogeneous to obtain the first active layer slurry.
[0047] The positive electrode active material lithium cobalt oxide, conductive agent carbon black, and binder polyvinylidene fluoride were mixed at a mass ratio of 98.2:1:0.8. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until the system was homogeneous to obtain the second active layer slurry.
[0048] A first active layer slurry is coated onto the positive electrode current collector aluminum foil to obtain a first active layer. Subsequently, a second active layer slurry is coated onto the surface of the first active layer to obtain a second active layer. The above operation is repeated on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode sheet. The coating surface density of the first active layer and the second active layer is 1:1.
[0049] Among them, the median particle size Dv50 (a) of lithium ferrite is 2 μm; according to theoretical calculations, the porosity (b) of the second active layer is 0.15.
[0050] The method for calculating the porosity of the second active layer is as follows: Measure the actual thickness d and ρ of the second active layer. 表观密度 =W 面密度 / d, Theoretical density = (Mass percentage of each substance in the active material layer) * Sum of actual theoretical densities, Porosity = 1 - ρ 表观密度 Theoretical density.
[0051] 2. Preparation of electrolyte In an environment with a water content of less than 10 ppm, diethyl carbonate (DEC) and ethylene carbonate (EC) are mixed at a mass ratio of 2:1. Based on the total mass of the electrolyte, lithium hexafluorophosphate (LiPF6) is added to the solvent, dissolved, and mixed evenly. Then, electrolyte additives are added to obtain the electrolyte. The mass percentage of LiPF6 in the electrolyte is 12.5%, and the electrolyte additives include lithium difluorooxalate borate and fluoroethylene carbonate (FEC). The mass percentage of lithium difluorooxalate borate in the electrolyte (c) is 1.5%, and the mass percentage of FEC in the electrolyte (d) is 1.5%.
[0052] 3. Preparation of negative electrode sheet Graphite, silicon carbide, dispersant (CMC), binder (SBR), and conductive agent (SP) are mixed in a ratio of 81:15:1:2:1, and then water is added to adjust the solid content to 48%. The mixture is stirred in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on one surface of a 6μm thick copper foil for negative electrode current collectors and dried. The above operation is repeated on the other surface of the copper foil for negative electrode current collectors to obtain a negative electrode sheet.
[0053] 4. Manufacturing of lithium-ion batteries The positive and negative electrode sheets are stacked in sequence, and the stacked electrode sheets are wound with a separator to obtain an electrode assembly. The electrode assembly is placed in a pre-formed aluminum-plastic film and dehydrated at 80°C. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation, and shaping processes.
[0054] The main differences between Examples 2-60 and Comparative Examples 1-25 and Example 1 are the parameters of the first active layer, the second active layer, and the electrolyte, as shown in Table 1.
[0055] Table 1
[0056] Example 61 The battery preparation method in this embodiment is roughly the same as that in Example 1, except that the positive electrode lithium replenishing agent is Li2MnO3.
[0057] Example 62 The battery preparation method in this embodiment is largely the same as that in Example 1, except that the positive electrode lithium replenishing agent is Li2NiO3.
[0058] Test case The following performance tests were performed on the batteries prepared in the examples and comparative examples: 1. Initial Coulomb efficiency After the lithium-ion battery formation and capacity grading are completed, record the formation charging capacity C0, the first charge capacity of the capacity grading cycle C1, and the first discharge capacity of the capacity grading cycle C2. The coulombic efficiency of the first cycle = C2 / (C0+C1)×100%.
[0059] The average cycle life of each group of 5 batteries is recorded in Table 2.
[0060] 2. Cyclic performance test In a constant temperature chamber at (25±2)℃, the lithium-ion battery was charged at a constant current and constant voltage of 0.5C to 4.53V, then charged at a constant voltage to 0.05C, and after resting for 5 minutes, discharged at 0.2C to 2.8V. The capacity obtained in this step was taken as the initial capacity. Cyclic tests were performed using 1.2C charging / 0.5C discharging, and the capacity retention rate of the battery after 400 cycles was calculated.
[0061] Cycle capacity retention (%) = Discharge capacity at 400th cycle (mAh) / Discharge capacity at first cycle (mAh) × 100% The average cycle life of each group of 5 batteries is recorded in Table 2.
[0062] 3. Storage performance test The battery cell was charged to 4.53V at room temperature with a constant current and constant voltage of 0.5C and a cutoff current of 0.05C. The battery cell was then placed in a constant temperature chamber at (60±2)℃ and left to stand until gas was produced. The gas production status of the battery cell was observed every 1 day.
[0063] Table 2
[0064] As shown in Table 2, based on the comparison between Examples 1-60 and Comparative Examples 1-25, it can be seen that when 4 ≤ a1 / 2 When / b≤10, the battery has higher initial coulombic efficiency, cycle performance and storage performance.
[0065] Based on the comparison of Examples 1-6, 24-27, 43-45 and Comparative Examples 16-25, it can be seen that when 2≤a≤4, the battery can exhibit higher initial coulombic efficiency, cycle performance and storage performance.
[0066] Based on the comparisons of Examples 2-4, Comparative Examples 16 and 17, Examples 1, 5 and 6, Comparative Examples 18-20, Examples 24-27, Comparative Examples 21 and 22, Examples 43-45, and Comparative Examples 23-25, it can be seen that when 0.15 ≤ b ≤ 0.4, the battery's initial coulombic efficiency, cycle performance, and storage performance are superior.
[0067] Based on the comparison of Examples 1, 7-23, Examples 28-42, and Examples 46-60, it can be seen that when 0.1≤c≤3 and 0.5≤d≤4, the battery has better initial coulombic efficiency, cycle performance, and storage performance.
[0068] According to the comparison of Examples 1 to 60, the electrochemical performance of the battery is better when 3≤a×(c+d)≤6.
[0069] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one surface of the positive current collector; the positive electrode coating includes a first active layer and a second active layer stacked thereon, the first active layer being disposed on the surface of the positive current collector; the first active layer includes a positive lithium supplement agent, the positive lithium supplement agent including a lithium-rich compound; the battery satisfies the following relationship: 4≤a 1 / 2 / b≤10; The median particle size Dv50 of the lithium-rich compound is a μm; the porosity of the second active layer is b.
2. The positive electrode sheet according to claim 1, characterized in that, 2≤a≤4。 3. The positive electrode sheet according to claim 1, characterized in that, 0.15≤b≤0.4。 4. The positive electrode sheet according to claim 1, characterized in that, The chemical formula of the lithium-rich compound is Li2XO3, wherein X is at least one of Mn, Ni, and Fe.
5. The positive electrode sheet according to claim 1, characterized in that, Both the first active layer and the second active layer include a positive electrode active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, and lithium iron phosphate.
6. A battery, characterized in that, Includes the positive electrode sheet as described in any one of claims 1 to 5.
7. The battery according to claim 6, characterized in that, The battery also includes an electrolyte, which includes electrolyte additives, including lithium difluorooxalate borate and fluoroethylene carbonate.
8. The battery according to claim 7, characterized in that, The lithium difluorooxalate borate in the electrolyte has a mass percentage content of c%, 0.1≤c≤3; And / or, the mass percentage of the fluoroethylene carbonate in the electrolyte is d%, 0.5≤d≤4.
9. The battery according to claim 8, characterized in that, The battery satisfies the following relationship: 3≤a×(c+d)≤6.
10. An electronic device, characterized in that, Includes the battery as described in any one of claims 6 to 9.