Secondary battery, positive electrode irreversible additive, preparation method of positive electrode irreversible additive and electric device

Abstract

The invention discloses a secondary battery, a positive irreversible additive, a preparation method of the positive irreversible additive and a power utilization device, the secondary battery comprises a positive pole piece, an isolating membrane and a negative pole piece, the positive pole piece comprises a positive active material and the positive irreversible additive, and the positive irreversible additive comprises an inner core, a negative active material and a positive irreversible additive, the inner core comprises a substance containing transition metal; the coating layer is formed on at least part of the surface of the inner core, the coating layer comprises an active metal ion supplement, and the active metal ion supplement comprises a lithium supplement agent or a sodium supplement agent. The positive electrode irreversible additive can improve the first-circle charging gram volume and the cycle life of the battery containing the positive electrode irreversible additive.

Description

Technical Field

[0001] This application belongs to the field of secondary batteries, specifically relating to a secondary battery, an irreversible additive for the positive electrode and its preparation method, and an electrical device. Background Technology

[0002] Secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] Improving the energy density and cycle life of rechargeable batteries has become a research hotspot in the field. The loss of active metal ions in rechargeable batteries is a direct cause of battery degradation. For example, during the first charge and discharge cycle, a solid electrolyte interphase (SEI) film forms on the negative electrode surface. This SEI film formation consumes a large number of active metal ions (such as lithium and sodium ions), resulting in a low initial charge capacity. During the charge-discharge cycle, the cracking and fragmentation of the positive electrode active material particles, the thickening and repair of the SEI film, all consume active metal ions, leading to a significant decrease in the battery's cycle performance. Adding irreversible additives to the positive electrode can improve the initial charge capacity and cycle life of rechargeable batteries. However, current irreversible additives for the positive electrode are in their early stages of development, and there are still many shortcomings in production and application. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a secondary battery, which aims to improve the initial charge capacity and cycle life of the secondary battery.

[0005] To achieve the above objectives, the first aspect of this application proposes a secondary battery, the secondary battery comprising a positive electrode, a separator, and a negative electrode, the positive electrode comprising a positive active material and a positive irreversible additive, the positive irreversible additive comprising: a core comprising a substance containing a transition metal; and a coating layer formed on at least a portion of the surface of the core, the coating layer comprising an active metal ion supplement, the active metal ion supplement comprising a lithium supplement or a sodium supplement.

[0006] This application includes at least the following beneficial effects: The secondary battery of this application contains an irreversible positive electrode additive, and the coating layer containing an active metal ion supplement is coated on the surface of a material containing a transition metal, which can improve the first charge capacity and cycle life of the secondary battery containing it.

[0007] In some embodiments, the volume average particle size Dv50 of the transition metal-containing substance is 0.2 μm - 1 μm. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0008] In some embodiments, the mass ratio of the core to the active metal ion supplement is (0.02 - 5):100. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0009] In some embodiments, the core includes at least one of a transition metal oxide or a noble metal element. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0010] In some embodiments, the core includes at least one of Fe2O3, Fe3O4, Co3O4, Mn3O4, MoO3, TiO2, NiO, α-MnO2, RuO2, Pt, Pd, Au, Ru, ZnCo2O4, NiCo2O4, FeCo2O4 or ZnCo2O4. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0011] In some embodiments, the core includes at least one of ZnCo2O4, NiCo2O4, FeCo2O4 or ZnCo2O4. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0012] In some embodiments, the active metal ion supplement includes Q x C a O b H c N d , where Q includes Li or Na, 0 < x ≤ 4, 2 ≤ a ≤ 10, 2 ≤ b ≤ 9, 0 ≤ c ≤ 15, 0 ≤ d ≤ 3. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0013] In some embodiments, the active metal ion supplement includes Na2CO3, Na2C2O4, Na2C4O4, CH3COONa, CH3CH2COONa, Na3C6O7H5, CH2(COONa)2, Na2C6O6, Na2C 10 O8H 14 N2, Na3C 10 O9H 15 N2 or Na4C 10 O8H 12 N2 or at least one of them; or,

[0014] The active metal ion supplement includes Li2CO3, Li2C2O4, Li2C4O4, CH3COOLi, CH3CH2COOLi, Li3C6O7H5, CH2(COOLi)2, Li2C6O6, and Li2C 10 O8H 14 N2, Li3C 10 O9H 15 N2 or Li4C 10 O8H 12 At least one of N2. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0015] In some embodiments, the coating layer further includes a conductive agent. This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0016] In some embodiments, the mass ratio of the conductive agent to the active metal ion supplement is (2-12):100. This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0017] In some embodiments, the conductive agent includes at least one of carbon nanotubes, graphene, or reduced graphene oxide. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0018] In some embodiments, the positive electrode active material comprises at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue sodium compounds and their respective modified compounds; or, the positive electrode active material comprises a lithium phosphate with an olivine structure. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0019] In some embodiments, the positive electrode active material includes Na. y At least one of MO2, Na3V2(PO4)3, or a Prussian blue compound, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, or Cu, and 0 < y ≤ 1; or, the positive electrode active material includes lithium iron phosphate. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0020] In some embodiments, after the first cycle of the secondary battery, the porosity of the positive electrode sheet is 6%-25%. This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0021] In the second aspect of the present application, a positive electrode irreversible additive is proposed. The positive electrode irreversible additive includes: a core, the core includes a substance containing a transition metal; a coating layer, the coating layer is formed on at least a part of the surface of the core, and the coating layer includes an active metal ion supplement, and the active metal ion supplement includes a lithium supplement or a sodium supplement. Thus, for the positive electrode irreversible additive of the present application, the coating layer containing the active metal ion supplement is coated on the surface of the substance containing the transition metal, which can improve the first-cycle charging specific capacity and cycle life of the secondary battery containing it.

[0022] In some embodiments, the volume average particle size Dv50 of the substance containing the transition metal is 0.2 μm - 1 μm. Thus, the first-cycle charging specific capacity and cycle life of the secondary battery containing it can be improved.

[0023] In some embodiments, the mass ratio of the core to the active metal ion supplement is (0.02 - 5):100. Thus, the first-cycle charging specific capacity and cycle life of the secondary battery containing it can be improved.

[0024] In some embodiments, the core includes at least one of a transition metal oxide or a noble metal element. Thus, the first-cycle charging specific capacity and cycle life of the secondary battery containing it can be improved.

[0025] In some embodiments, the core includes at least one of Fe2O3, Fe3O4, Co3O4, Mn3O4, MoO3, TiO2, NiO, α-MnO2, RuO2, Pt, Pd, Au, Ru, ZnCo2O4, NiCo2O4, FeCo2O4 or ZnCo2O4. Thus, the first-cycle charging specific capacity and cycle life of the secondary battery containing it can be improved.

[0026] In some embodiments, the core includes at least one of ZnCo2O4, NiCo2O4, FeCo2O4 or ZnCo2O4. Thus, the first-cycle charging specific capacity and cycle life of the secondary battery containing it can be improved.

[0027] In some embodiments, the active metal ion supplement includes Q x C a O b H c N d , where Q includes Li or Na, 0 < x ≤ 4, 2 ≤ a ≤ 10, 2 ≤ b ≤ 9, 0 ≤ c ≤ 15, 0 ≤ d ≤ 3. Thus, the first-cycle charging specific capacity and cycle life of the secondary battery containing it can be improved.

[0028] In some embodiments, the active metal ion supplement includes Na2CO3, Na2C2O4, Na2C4O4, CH3COONa, CH3CH2COONa, Na3C6O7H5, CH2(COONa)2, Na2C6O6, and Na2C 10 O8H 14 N2, Na3C 10 O9H 15 N2 or Na4C 10 O8H 12 At least one of N2; or,

[0029] The active metal ion supplement includes Li2CO3, Li2C2O4, Li2C4O4, CH3COOLi, CH3CH2COOLi, Li3C6O7H5, CH2(COOLi)2, Li2C6O6, and Li2C 10 O8H 14 N2, Li3C 10 O9H 15 N2 or Li4C 10 O8H 12 At least one of N2. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0030] In some embodiments, the coating layer further includes a conductive agent. This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0031] In some embodiments, the mass ratio of the conductive agent to the active metal ion supplement is (2-12):100. This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0032] In some embodiments, the conductive agent includes at least one of carbon nanotubes, graphene, or reduced graphene oxide. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0033] In a third aspect of this application, a method for preparing an irreversible additive for a positive electrode is proposed, comprising:

[0034] A coating layer is formed on at least a portion of the surface of the core to obtain an irreversible positive electrode additive;

[0035] The core comprises a substance containing a transition metal, and the coating layer comprises an active metal ion supplement, which includes a lithium supplement or a sodium supplement.

[0036] As a result, secondary batteries containing the irreversible additives in the cathode obtained by this method have excellent first-charge capacity and cycle life.

[0037] In some embodiments, the method includes: dissolving an active metal ion supplement in a solvent, adding a substance containing a transition metal, and spray drying to obtain an irreversible positive electrode additive. This can improve the initial charge capacity and cycle life of a secondary battery containing the additive.

[0038] In some embodiments, the solvent includes at least one selected from water, ethanol, methanol, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, 1,3-dioxolane, or 2-methyltetrahydrofuran. This can improve the initial charge capacity and cycle life of secondary batteries containing the solvent.

[0039] In some embodiments, the method includes: dissolving an active metal ion supplement in a solvent, adding a substance containing a transition metal and a conductive agent, and spray drying to obtain an irreversible positive electrode additive. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0040] In a fourth aspect of this application, an electrical device is proposed, comprising the secondary battery described in the first aspect of this application.

[0041] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0042] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0043] Figure 1 This is a schematic diagram of the structure of the positive electrode irreversible additive according to one embodiment of this application.

[0044] Figure 2 This is a schematic diagram of a battery according to one embodiment of this application.

[0045] Figure 3 yes Figure 2 An exploded view of a battery according to one embodiment of this application is shown.

[0046] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0047] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0048] Figure 6 yes Figure 5An exploded view of a battery pack according to one embodiment of this application is shown.

[0049] Figure 7 This is a schematic diagram of an electrical device in which a battery is used as a power source according to one embodiment of this application.

[0050] Figure 8 This is a scanning electron microscope image of the irreversible positive electrode additive prepared in Example 1 of this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] 100 Substance containing transition metals; 200 Coating layer; 1 Battery cell; 11 Casing; 12 Electrode assembly; 13 Cover plate; 2 Battery module; 3 Battery pack; 31 Upper casing; 32 Lower casing. Detailed Implementation

[0053] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0054] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0055] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0057] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0058] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0059] Currently, judging from market trends, the application of rechargeable batteries is becoming increasingly widespread. Rechargeable batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace, among other fields.

[0060] Irreversible additives in the positive electrode can replenish the active metal ions lost during battery cycling. Taking sodium replenishers as an example, on the one hand, they can compensate for the loss of active sodium ions caused by the formation of the SEI during the first charge and discharge cycle, ensuring that the battery has sufficient reversible active sodium ions in subsequent cycles, thus improving the battery's initial charge capacity. On the other hand, sodium replenishers can also compensate for sodium consumption during cycling, improving the battery's cycle performance. Based on their position in the battery, sodium replenishers can be divided into positive electrode sodium replenishers and negative electrode sodium replenishers.

[0061] Taking sodium replenishers as an example, compared with the actual operating voltage window of existing sodium-ion / sodium metal batteries (sodium ion < 4.2V, sodium metal < 3.8V), the sodium removal potential of existing sodium replenishers needs to be further reduced. On the one hand, this can reduce the increase in the actual decomposition potential of the sodium replenisher caused by other polarization problems in the battery during actual application (such as formation at room temperature or high rate), ensuring complete decomposition of the sodium replenisher. On the other hand, reducing the sodium removal potential of the sodium replenisher can further improve its applicability to different sodium secondary batteries. Therefore, further reducing the sodium removal potential of sodium replenishers is extremely important, as it is crucial for improving the performance of sodium secondary batteries in the future.

[0062] Generally, researchers reduce the desodium potential of sodium supplements in the following ways: First, by carbon coating or by incorporating a large amount of conductive carbon during material synthesis to improve the conductivity of the material. However, this method requires the addition of a large amount of conductive carbon and uniform mixing / composite with the material. This undoubtedly reduces the specific capacity of the active metal ion supplement and increases the manufacturing cost of the battery in actual battery applications, making it difficult to truly achieve the goal of improving the specific capacity of the battery in the first charge cycle. Second, by directly mixing transition metal compounds with sodium supplements to prepare mixed sodium supplements. This method makes it difficult to truly control the uniformity of the mixing between sodium supplements and transition metal compounds, especially when the sodium supplement particles are large particles at the micron level. If the two are not mixed uniformly, the catalytic effect of the transition metal cannot be truly exerted, thus failing to completely catalyze the decomposition of the sodium supplement. In addition, the transition metal in the sodium supplement will come into contact with the electrolyte, catalyzing the decomposition of the electrolyte, which in turn causes gas production and a decrease in battery cycle life.

[0063] The secondary battery of this application embodiment includes an irreversible positive electrode additive. In this additive, a transition metal-containing material is disposed in the core and coated with a layer containing an active metal ion supplement. The transition metal-containing material has high catalytic activity, providing empty 3d orbitals that interact strongly with electron-rich O or N atoms in the active metal ion supplement. This promotes the adsorption of the active metal ion supplement on the surface of the noble metal-containing material, resulting in a complete reaction. This enhances the electrochemical activity of the active metal ion supplement, alters its decomposition pathway, and catalyzes its decomposition, thereby reducing its decomposition potential and promoting complete decomposition. This, in turn, improves the battery's initial charge capacity and cycle life. Furthermore, the coating layer reduces the contact between the transition metal-containing material and the electrolyte, decreasing its catalytic effect on electrolyte decomposition and further improving cycle life. In summary, the battery proposed in this application, containing an irreversible positive electrode additive, can improve the battery's initial charge capacity and cycle life.

[0064] The secondary battery disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0065] The first aspect of this application discloses a secondary battery, which includes an irreversible additive at the positive electrode. (See [link to relevant documentation]). Figure 1 The positive electrode irreversible additive includes: a core and a coating layer 200, wherein the core includes a substance 100 containing a transition metal; the coating layer 200 is formed on at least a portion of the surface of the core, and the coating layer 200 includes an active metal ion supplement, wherein the active metal ion supplement includes a lithium supplement or a sodium supplement.

[0066] In the secondary battery of this application embodiment, the transition metal-containing substance 100 in the positive electrode irreversible additive is disposed in the core and coated by a coating layer 200 containing an active metal ion supplement. The transition metal-containing substance 100 has high catalytic activity and provides empty 3d orbitals that interact strongly with electron-rich O or N atoms in the active metal ion supplement. This promotes the adsorption of the active metal ion supplement on the surface of the noble metal-containing substance and completes the reaction, thereby improving the electrochemical activity of the active metal ion supplement, changing the decomposition path of the active metal ion supplement, catalyzing the decomposition of the active metal ion supplement, reducing the decomposition potential of the active metal ion supplement, and promoting the complete decomposition of the active metal ion supplement, thereby improving the first charge capacity and cycle life of the battery. On the other hand, the aforementioned transition metal-containing substance 100 is embedded in the inner layer containing the active metal ion supplement. During the first cycle of battery formation, the direct contact between the transition metal-containing substance 100 and the electrolyte is reduced to a certain extent, minimizing the occurrence of side reactions and improving the cycle life of the battery. In summary, the battery containing irreversible additives in the positive electrode proposed in this application has excellent first-charge capacity and cycle life.

[0067] It is understood that the kernel and the overlay layer in the embodiments of this application can be determined using the following methods:

[0068] The irreversible additive in the positive electrode was polished using an IB-19500CP ion cross-section polisher to obtain a polished sample with a cut surface. The morphology of the sample was then observed using a ZEISS Sigma 300 scanning electron microscope according to standard JY / T010-1996.

[0069] In a secondary battery, conductivity is achieved through the transfer of active metal ions between the positive and negative electrodes: when the battery is charging, active metal ions are released from the positive electrode active material, move through the electrolyte to the negative electrode, and embed themselves; when the battery discharges, the active metal ions embedded in the negative electrode are released and move back to the positive electrode. Active metal ions can include sodium ions and lithium ions. The role of irreversible additives in the positive electrode is to replenish the active metal ions lost during the charging and discharging process.

[0070] Specifically, active metal ion supplements refer to substances that can provide active metal ions, typically lithium or sodium supplements. The active metal ion in lithium-ion and lithium metal batteries is lithium ions, and lithium supplements replenish active lithium ions. Similarly, the active metal ion in sodium-ion and sodium metal batteries is sodium ions, and sodium supplements replenish active sodium ions. Substances containing transition metals (100) refer to substances containing transition metal elements.

[0071] In some embodiments of this application, the volume average particle size Dv50 of the transition metal-containing substance 100 is 0.2 μm-1 μm. For example, the volume average particle size Dv50 of the transition metal-containing substance 100 can be 0.2 μm-0.9 μm, 0.3 μm-0.8 μm, 0.4 μm-0.7 μm, 0.5 μm-0.6 μm, etc. Specifically, by controlling the volume average particle size Dv50 of the transition metal-containing substance 100 within the above range, the transition metal-containing substance 100 has a large specific surface area, resulting in a large contact area with the active metal ion supplement in the coating layer 200. This promotes the adsorption of the active metal ion supplement on the surface of the transition metal compound and facilitates a full reaction, thereby improving the electrochemical activity of the active metal ion supplement, altering its decomposition pathway, catalyzing its decomposition, and reducing its decomposition potential. This promotes the full decomposition of the active metal ion supplement, thereby improving the battery's first-charge specific capacity and cycle life.

[0072] It is understood that the volume average particle size Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%. The volume average particle size Dv50 of the transition metal-containing substance 100 can be determined using methods known in the art, for example, by the following methods:

[0073] Referring to standard GB / T 19077-2016, the volume average particle size Dv50 of substance 100 containing transition metals was tested using a laser particle size analyzer (e.g., Malvern Master Sizer3000).

[0074] In some embodiments of this application, the mass ratio of the kernel to the active metal ion supplement is (0.02-5):100. For example, the mass ratio of the kernel to the active metal ion supplement is (0.02-4.9):100, (0.1-45):100, (0.5-4):100, (1-3.5):100, (1.5-3):100, (2-2.5):100, etc., controlling the mass ratio of the kernel to the active metal ion supplement to be above a certain level. Within the aforementioned range, it is sufficient to play a catalytic role, which can reduce the insignificant decrease in the decomposition potential of the irreversible additive in the positive electrode caused by insufficient transition metal 100, thus ensuring the complete decomposition of the active metal ion supplement; it can also reduce the excessive mass occupied by the irreversible additive in the positive electrode caused by excessive transition metal 100, ensuring the gram capacity of the battery in the first charge cycle, and can reduce the increased probability of contact with the electrolyte caused by excessive transition metal 100, thereby reducing the probability of side reactions with the electrolyte and improving the cycle life of the battery.

[0075] It is understood that the "ratio of the mass of the kernel to the mass of the active metal ion supplement" is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0076] Weigh a certain mass of the positive electrode irreversible additive, dissolve the positive electrode irreversible additive in excess nitric acid, make up the volume, and use ICP (inductively coupled plasma optical emission spectrometry) to test the content of transition metals or noble metals and metals (lithium or sodium) in the active metal ion supplement, and convert them into the corresponding mass of the core (m1) and the mass of the active metal ion supplement (m2). Then the ratio of the mass of the core to the mass of the active metal ion supplement = m1 / m2 × 100%.

[0077] In some embodiments of this application, the core comprises at least one of a transition metal oxide or a noble metal element. These substances exhibit high catalytic activity and provide empty 3d orbitals that interact strongly with electron-rich O or N atoms in the active metal ion supplement. This promotes the adsorption of the active metal ion supplement on the surface of the transition metal compound, facilitating a full reaction and enhancing its electrochemical activity. It also alters the decomposition pathway of the active metal ion supplement, catalyzing its decomposition and reducing its decomposition potential. This, in turn, promotes the complete decomposition of the active metal ion supplement, thereby improving the battery's initial charge capacity and cycle life.

[0078] It is understandable that precious metals include eight metallic elements: gold, silver, and the platinum group metals (ruthenium, rhodium, palladium, osmium, iridium, and platinum).

[0079] In some embodiments of this application, the core includes at least one of Fe2O3, Fe3O4, Co3O4, Mn3O4, MoO3, TiO2, NiO, α-MnO2, RuO2, Pt, Pd, Au, Ru, ZnCo2O4, NiCo2O4, FeCo2O4, or ZnCo2O4. Specifically, the above substances, as catalysts, contain transition metal elements or noble metal elements, exhibiting high catalytic activity. They provide empty 3d orbitals that interact strongly with electron-rich O or N atoms in the active metal ion supplement, promoting the adsorption of the active metal ion supplement on the surface of the transition metal compound for a complete reaction. This can improve the electrochemical activity of the active metal ion supplement, alter its decomposition pathway, catalyze its decomposition, reduce its decomposition potential, and promote its complete decomposition, thereby improving the battery's initial charge capacity and cycle life.

[0080] It is understandable that noble metals such as Pt, Pd, Au, and Ru, due to their high electrical conductivity as elemental metals, can also improve the electrochemical activity of the active metal ion supplement. However, because of their stable chemical properties and low probability of causing oxidation and decomposition of the electrolyte, in principle, their dosage can be reduced relative to the catalyst containing transition metal elements to achieve a similar effect, and thus can also be used as the core of the positive electrode irreversible additive in this application.

[0081] In some other embodiments of this application, the inner core includes at least one of ZnCo2O4, NiCo2O4, FeCo2O4, or ZnCo2O4. Thus, the first-cycle charge capacity per gram and the cycle life of the battery containing it can be improved. The reason why the above substances are effective in improving the first-cycle charge capacity per gram and the cycle life of the battery as the inner core may be that the Co-containing transition metal compound has a relatively strong binding force with oxygen in the x1 C a1 O b1 H c1 N d1 or Li x2 C a2 O b2 H c2 N d2 system, so this type of catalyst is easy to combine with oxygen atoms, thereby making more effective use of the electrochemical activity of the catalyst.

[0082] In some embodiments of this application, the active metal ion supplement includes Q x C a O b H c N d , where Q includes Li or Na, 0 < x ≤ 4, 2 ≤ a ≤ 10, 2 ≤ b ≤ 9, 0 ≤ c ≤ 15, 0 ≤ d ≤ 3. The de-lithiation or de-sodiation potential of the above substances is low, and they are more likely to decompose fully during battery charge and discharge, improving the first-cycle charge capacity per gram and the cycle life of the battery.

[0083] For example, x can be 0 - 3, 1 - 3, 1 - 2, 2 - 3, etc., a can be 2 - 9, 3 - 8, 4 - 7, 5 - 6, etc., b can be 2 - 8, 3 - 7, 4 - 6, etc., c can be 0 - 14, 1 - 13, 2 - 12, 3 - 11, 4 - 10, 5 - 9, 6 - 8, etc., d can be 0 - 2, 1 - 2, 2 - 3, etc.

[0084] It is understandable that the values of x, a, b, c, and d should satisfy charge balance. And it is understandable that Q x C a O b H c N dIt is a general formula for chemical formulas, including organic and inorganic substances. Whether organic or inorganic, as long as its chemical formula conforms to the general formula of this application, it falls within the scope of this application.

[0085] In some embodiments of this application, when the battery is a sodium secondary battery, the active metal ion supplement includes sodium carbonate (Na2CO3), sodium oxalate (Na2C2O4), sodium squartzate (Na2C4O4), sodium acetate (CH3COONa), sodium propionate (CH3CH2COONa), sodium citrate (Na3C6O7H5), and disodium EDTA (Na2C4O4). 10 O8H 14 N2), EDTA-trisodium (Na3C) 10 O9H 15 N2), EDTA-tetrasodium (Na4C) 10 O8H 12 At least one of sodium malonate (CH2(COONa)2) and sodium rosehipate (Na2C6O6) is used as an active metal ion supplement. When added to the positive electrode irreversible additive, the active metal ion supplement has a low decomposition potential and is adsorbed on the surface of the transition metal compound to fully react. This can improve the electrochemical activity of the active metal ion supplement, change the decomposition path of the active metal ion supplement, catalyze the decomposition of the active metal ion supplement, reduce the decomposition potential of the active metal ion supplement, and promote the full decomposition of the active metal ion supplement, thereby improving the first charge capacity and cycle life of the battery.

[0086] In some embodiments of this application, when the battery is a lithium secondary battery, the active metal ion supplement includes lithium carbonate (Li2CO3), lithium oxalate (Li2C2O4), lithium squaric acid (Li2C4O4), lithium acetate (CH3COOLi), lithium propionate (CH3CH2COOLi), lithium citrate (Li3C6O7H5), and EDTA-dilithium (Li2C4O4). 10 O8H 14 N2), EDTA-trilithium (Li3C) 10 O9H 15 N2), EDTA-tetralithium (Li4C) 10 O8H 12At least one of N2), lithium malonate (CH2(COOLi)2), and lithium rose red oxide (Li2C6O6) is used as a lithium supplement agent. When added to the irreversible additive of the positive electrode, the active metal ion supplement has a low decomposition potential and is in the core-shell structure of the irreversible additive of the positive electrode. The active metal ion supplement is adsorbed on the surface of the transition metal compound and reacts fully, which can improve the electrochemical activity of the active metal ion supplement, change the decomposition path of the active metal ion supplement, catalyze the decomposition of the active metal ion supplement, reduce the decomposition potential of the active metal ion supplement, promote the full decomposition of the active metal ion supplement, and thus improve the specific capacity of the battery in the first charge and the cycle life.

[0087] In some embodiments of this application, the coating layer 200 further includes a conductive agent. Specifically, since the amount of the transition metal-containing substance 100 added in the core is relatively small, there may be situations in the coating layer 200 where the active metal ion supplement cannot come into contact with the transition metal-containing substance 100, resulting in low electronic conductivity. Therefore, the added conductive agent has high electronic conductivity and can synergistically enhance the electrochemical activity of the irreversible positive electrode additive by working with the transition metal-containing substance 100 in the core. This alters the decomposition pathway of the active metal ion supplement and catalyzes the decomposition of the irreversible positive electrode additive, thereby reducing the decomposition potential of the active metal ion supplement and improving the first-charge specific capacity and cycle life of the battery containing it.

[0088] It is understood that this application does not limit the position of the conductive agent in the coating layer 200. The conductive agent can be dispersed in the active metal ion supplement or it can be a separate layer. When it is a separate layer, the conductive agent layer can be between the core and the active metal ion supplement layer, or it can be outside the active metal ion supplement layer. All of the above situations are within the protection scope of this application.

[0089] In some embodiments of this application, the mass ratio of the conductive agent to the active metal ion supplement is (2-12):100. For example, the mass ratio of the conductive agent to the active metal ion supplement is (2-11):100, (3-10):100, (4-9):100, (5-8):100, (6-7):100. Specifically, controlling the mass ratio of the conductive agent to the active metal ion supplement within the above range can improve the conductivity of the coating layer 200, further enhancing the first charge capacity and cycle life of the battery containing it.

[0090] It is understood that the "ratio of the mass of the conductive agent to the mass of the active metal ion supplement" is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0091] Referring to standard GB / T 6730.61-2005, the sample is weighed and heated and burned in the oxygen flow of a high-frequency induction furnace. The generated carbon dioxide (or carbon monoxide) and sulfur dioxide are carried by oxygen to the measuring chamber of the infrared analyzer. Carbon dioxide (or carbon monoxide) and sulfur dioxide absorb infrared energy of a specific wavelength. The absorption energy is proportional to its concentration. The carbon and sulfur content can be measured according to the change in energy received by the detector, which corresponds to the mass m1 of the conductive agent.

[0092] Weigh the remaining solid, dissolve it in excess nitric acid, and make up to a final volume. Use ICP (inductively coupled plasma optical emission spectrometry) to test the content of metals (lithium or sodium) in the active metal ion supplement, and convert it into the corresponding mass (m2) of the active metal ion supplement. Then, the ratio of the mass of the core to the mass of the active metal ion supplement = m1 / m2 × 100%.

[0093] It is understandable that noble metal elements such as Pt, Pd, Au, and Ru, due to their high conductivity, can also enhance the electrochemical activity of active metal ion supplements. However, because of their stable chemical properties, they do not cause oxidative decomposition of the electrolyte. Therefore, in principle, their dosage can be reduced compared to substances containing transition metals to achieve similar effects. Thus, they can also serve as the core of the irreversible positive electrode additive in this application, and the dosage of conductive agent can be reduced accordingly to further improve the decomposition efficiency of active metal ion supplements.

[0094] In some embodiments of this application, the conductive agent includes at least one of carbon nanotubes, graphene, or reduced graphene oxide. These conductive agents possess high electronic conductivity and, synergistically with the core, enhance the electrochemical activity of the active metal ion supplement, alter its decomposition pathway, and catalyze its decomposition. This reduces the decomposition potential of the active metal ion supplement, thereby increasing the initial charge capacity and cycle life of the battery containing it.

[0095] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active metal ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0096] In some embodiments of this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector, wherein the positive active material layer includes the aforementioned irreversible positive electrode additive.

[0097] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0098] In some embodiments of this application, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0099] In some embodiments of this application, when the battery is a lithium secondary battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries.

[0100] As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. The modified compounds of the above materials may be for doping modification and / or surface coating modification of the materials.

[0101] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Li content changes when the positive electrode active material is applied to the battery system.

[0102] In the examples of positive electrode active materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0103] In some embodiments of this application, when the secondary battery is a lithium secondary battery, the positive electrode active material includes a lithium phosphate with an olivine structure. Lithium phosphates with an olivine structure have good stability, and the insertion and extraction of lithium ions have little impact on the crystal lattice, thus exhibiting good reversibility. Combined with the irreversible positive electrode additives of this application, it can better promote the full decomposition of active metal ion supplements, replenishing active lithium ions, thereby improving the battery's first-charge specific capacity and cycle life.

[0104] In some embodiments of this application, when the secondary battery is a lithium secondary battery, the positive electrode active material includes lithium iron phosphate. Lithium iron phosphate has good stability, and the insertion and extraction of lithium ions have little impact on the crystal lattice, thus exhibiting good reversibility. Combined with the irreversible positive electrode additives of the embodiments of this application, it can better promote the full decomposition of active metal ion supplements, replenish active lithium ions, thereby improving the battery's first charge capacity and cycle life.

[0105] In some embodiments, when the battery is a sodium secondary battery, the positive electrode active material may be a positive electrode active material known in the art for sodium-ion batteries.

[0106] As an example, the positive electrode active material may include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue sodium compounds, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. The modified compounds of the above materials may be for doping modification and / or surface coating modification of the materials.

[0107] In some embodiments, the transition metal in the sodium transition metal oxide can be at least one selected from Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu. The chemical formula of the sodium transition metal oxide can satisfy Na y MO2, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu, and 0 < y ≤ 1.

[0108] In some embodiments, the polyanionic compound may be a sodium ion, a transition metal ion, or a tetrahedral (YO4) compound. n- A class of compounds with anionic units. The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si; n represents (YO4). n- The price state.

[0109] In some embodiments, the polyanionic compound may also have sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds containing anionic units and halide anions. Transition metals may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si, where n represents (YO4). n- The valence state of halogens can include at least one of F, Cl, and Br.

[0110] In some embodiments, the polyanionic compound may also be a tetrahedral compound containing sodium ions (YO4). n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. M may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, Y may include at least one of P, S and Si, and n represents (YO4). n- The valence state, Z represents transition metal, m represents (ZO) y ) m+ The valence state of halogens can include at least one of F, Cl, and Br.

[0111] As an example, polyanionic compounds can satisfy the chemical formulas NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes at least one of V, Fe, Mn and Ni), and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0112] In some embodiments, Prussian blue compounds may contain sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds. Transition metals may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce.

[0113] As an example, Prussian blue compounds can satisfy the chemical formula Na a Me b Me' c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, and 0 < c < 1.

[0114] During the charging and discharging process of a battery, sodium (Na) undergoes insertion / extraction and consumption, resulting in varying molar Na content at different discharge states. In the examples of positive electrode active materials in this application, the molar Na content refers to the initial state of the material, i.e., the state before material addition. After charge-discharge cycles, the molar Na content changes when the positive electrode active material is applied to the battery system.

[0115] In the examples of positive electrode active materials for sodium-ion batteries in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0116] In some embodiments of this application, when the secondary battery is a sodium secondary battery, the positive electrode active material includes at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue sodium compounds, as well as their respective modified compounds. The above-mentioned positive electrode active material, in conjunction with the irreversible positive electrode additives of the embodiments of this application, can better promote the complete decomposition of active metal ion supplements, replenish active sodium ions, thereby improving the battery's first charge capacity and cycle life.

[0117] In some embodiments of this application, when the secondary battery is a sodium secondary battery, the positive electrode active material includes Na. yAt least one of MO2, Na3V2(PO4)3, or a Prussian blue compound, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, or Cu, and 0 < y ≤ 1. For example, y can be 0.1-0.9, 0.2-0.8, 0.3-0.7, 0.4-0.6, etc. The above-mentioned positive electrode active material, combined with the positive electrode irreversible additive of the embodiments of this application, can better promote the full decomposition of active metal ion supplements, replenish active sodium ions, thereby improving the specific capacity and cycle life of the battery in the first charge.

[0118] In some embodiments of this application, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorinated acrylate resin.

[0119] In some embodiments of this application, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0120] In some embodiments of this application, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0121] In some embodiments of this application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder, positive irreversible additive and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0122] In some embodiments of this application, the battery further includes a positive electrode sheet, and the porosity of the positive electrode sheet after the first cycle of the battery is 6%-25%. For example, the porosity of the positive electrode sheet after the first cycle of the battery can be 6%-24%, 8%-22%, 10%-20%, 12%-15%, etc. Specifically, since the irreversible additives in the positive electrode decompose during the first charge and discharge process, replenishing active metal ions, and leaving voids on the positive electrode sheet after decomposition, the porosity of the positive electrode sheet increases after the first cycle of the battery, which is beneficial to the shuttle transport of active metal ions during subsequent charge and discharge cycles and improves the cycle life of the battery.

[0123] It is understood that after the first cycle of the battery, the porosity of the positive electrode sheet is a well-known definition in the art and can be measured using methods known in the art, such as the following methods:

[0124] The porosity was determined according to the national standard GB / T24586-2009, "Determination of Apparent Density, True Density and Porosity of Iron Ore". The specific testing method was as follows: The battery was disassembled to obtain the positive electrode sheet, which was then immersed in ethyl methyl carbonate (EMC) for cleaning. Based on the gas displacement method, the positive electrode sheet was placed in a true density analyzer, the testing system was sealed, and helium gas was introduced according to the procedure. The pressure of the gas in the sample chamber and the expansion chamber was measured. The porosity is the percentage of the pore volume to the total volume of the electrode sheet, calculated using the formula: Porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume.

[0125] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector.

[0126] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0127] In some embodiments of this application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0128] In some embodiments of this application, the negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and titanates. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. When the battery is a lithium-ion battery, the titanate includes lithium titanate; when the battery is a sodium-ion battery, the titanate includes sodium titanate. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0129] In some embodiments of this application, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0130] In some embodiments of this application, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0131] In some embodiments of this application, the negative electrode active material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0132] In some embodiments of this application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0133] This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0134] In some embodiments of this application, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0135] In some embodiments of this application, when the battery is a lithium-ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, or lithium tetrafluorooxalate phosphate.

[0136] In some embodiments of this application, when the battery is a sodium-ion battery, the electrolyte salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalate borate, sodium tetrafluoroborate, sodium dioxalate borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethanesulfonyl)imide.

[0137] In some embodiments of this application, the solvent may include at least one selected from ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone, or diethyl sulfone.

[0138] In some embodiments of this application, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0139] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0140] In some embodiments of this application, the material of the separator may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0141] The secondary batteries of this application include single-cell battery forms, battery module forms, and battery pack forms. The following description, with appropriate reference to the accompanying drawings, will illustrate the single-cell battery, battery module, and battery pack of this application.

[0142] In some embodiments of this application, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0143] In some embodiments of this application, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0144] In some embodiments of this application, the outer packaging of the battery cell 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, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0145] In a second aspect of this application, an irreversible additive for the positive electrode is proposed; please refer to [link to relevant documentation]. Figure 1 The positive electrode irreversible additive includes: a core and a coating layer 200, wherein the core includes a substance 100 containing a transition metal; the coating layer 200 is formed on at least a portion of the surface of the core, and the coating layer 200 includes an active metal ion supplement, wherein the active metal ion supplement includes a lithium supplement or a sodium supplement.

[0146] In the irreversible positive electrode additive of this application embodiment, the transition metal-containing substance 100 is disposed in the core and coated by the coating layer 200 containing the active metal ion supplement. The transition metal-containing substance 100 has high catalytic activity and provides empty 3d orbitals that have strong interactions with the electron-rich O or N atoms in the active metal ion supplement. This promotes the adsorption of the active metal ion supplement on the surface of the noble metal-containing substance and completes the reaction, thereby improving the electrochemical activity of the active metal ion supplement, changing the decomposition path of the active metal ion supplement, catalyzing the decomposition of the active metal ion supplement, reducing the decomposition potential of the active metal ion supplement, and promoting the complete decomposition of the active metal ion supplement, thereby improving the first charge capacity and cycle life of the battery. On the other hand, the aforementioned transition metal-containing substance 100 is embedded in the inner layer containing the active metal ion supplement. During the first cycle of battery formation, the direct contact between the transition metal-containing substance 100 and the electrolyte is also reduced to a certain extent, minimizing the occurrence of side reactions and improving the cycle life of the battery. In summary, the irreversible positive electrode additive proposed in this application results in batteries containing it exhibiting excellent first-charge capacity and cycle life.

[0147] It is understood that the additional features of the positive electrode irreversible additive in the embodiments of this application have been described in detail above and will not be repeated here.

[0148] In a third aspect of this application, a method for preparing an irreversible additive for a positive electrode is proposed, comprising:

[0149] S1. A coating layer is formed on at least a portion of the surface of the core to obtain an irreversible positive electrode additive;

[0150] The core comprises a substance containing a transition metal, and the coating layer comprises an active metal ion supplement, which includes a lithium supplement or a sodium supplement.

[0151] As a result, batteries containing the irreversible cathode additives obtained by this method have excellent first-charge capacity and cycle life.

[0152] In some embodiments of this application, step S1 includes:

[0153] S11. Dissolve the active metal ion supplement in a solvent, add a substance containing transition metals, and spray dry to obtain an irreversible positive electrode additive.

[0154] Specifically, by utilizing the Coulomb interaction between the empty 3d orbitals of transition metals or noble metals and the electron-rich structure of oxygen or nitrogen atoms in the active metal ion supplement, the solution containing the active metal ion supplement undergoes heterogeneous nucleation growth of crystals with the transition metal-containing material as the nucleus during spray drying, thus obtaining the core-shell structured irreversible positive electrode additive of this application. This method not only reduces the inhomogeneity caused by the transition metal-containing material directly contacting the electrolyte and catalyzing the decomposition of the electrolyte due to the inhomogeneity of conventional preparation methods, but also helps to maximize the catalytic efficiency of the transition metal-containing material, and maximizes the decomposition of the active metal ion supplement while ensuring that the amount of transition metal-containing material and conductive agent is minimized.

[0155] In some embodiments of this application, the solvent includes at least one of water, ethanol, methanol, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, 1,3-dioxolane, or 2-methyltetrahydrofuran. Thus, the above solvent can dissolve the active metal ion supplement, but cannot dissolve substances containing transition metals. This facilitates the heterogeneous nucleation growth of crystals using substances containing transition metals as nuclei during the spray drying process of the solution containing the active metal ion supplement, thereby obtaining the core-shell structured irreversible positive electrode additive of this application.

[0156] In some embodiments of this application, when the positive electrode irreversible additive includes a conductive agent, step S11 includes:

[0157] S111. Dissolve the active metal ion supplement in a solvent, add a substance containing a transition metal and a conductive agent, and spray dry to obtain an irreversible positive electrode additive. In this way, the Coulomb interaction between the empty 3d orbitals of the transition metal or noble metal and the electron-rich structure of the oxygen or nitrogen atoms in the active metal ion supplement, due to the weak interaction between the conductive agent and the sodium supplement, facilitates the formation of an irreversible positive electrode additive with the substance containing the transition metal as the core and the active metal ion supplement and conductive agent as the shell. This improves the contact between the active metal ion supplement and the substance containing the transition metal and the conductive agent to a certain extent, thereby further improving the electrochemical activity of the active metal ion supplement.

[0158] It is understood that the secondary battery mentioned above in this application is a single battery cell.

[0159] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 Here is a square-structured battery cell 1 as an example.

[0160] In some embodiments of this application, reference is made to Figure 3 The outer packaging may include a housing 11 and a cover plate 13. The housing 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 11 has an opening communicating with the receiving cavity, and the cover plate 13 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The number of electrode assemblies 12 contained in a single battery cell 1 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0161] In some embodiments of this application, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0162] Figure 4 This is battery module 2 as an example. (See reference...) Figure 4 In battery module 2, multiple battery cells 1 can be arranged sequentially along the length of battery module 2. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 1 can be fixed in place using fasteners.

[0163] Optionally, the battery module 2 may also include a housing with a receiving space in which multiple battery cells 1 are received.

[0164] In some embodiments of this application, the battery modules described above can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0165] Figure 5 and Figure 6 This is battery pack 3 as an example. (See reference...) Figure 5 and Figure 6The battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box includes an upper box 31 and a lower box 32, with the upper box 31 covering the lower box 32 to form a closed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0166] In addition, this application also provides an electrical device, which includes a secondary battery provided in the first aspect of this application or a secondary battery prepared by the method described in the second aspect. The battery cell, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0167] As the electrical device, a single battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0168] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0169] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0170] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0171] Example 1

[0172] Preparation of irreversible additives for the positive electrode:

[0173] The active metal ion supplement CH3COONa (sodium acetate) was completely dissolved in deionized water, heated to 80℃ and stirred for 1 hour to promote dissolution, achieving a concentration of 5 g / mL. Then, Fe3O4, a transition metal-containing substance, was mixed and stirred at a ratio of 0.8% of the transition metal-containing substance to the active metal ion supplement (core mass to active metal ion supplement mass ratio of 0.8:100). Spray drying was then performed to prepare a positive electrode irreversible additive with a transition metal-containing substance as the core and the active metal ion supplement as the shell.

[0174] 1. Preparation of positive electrode sheet

[0175] NaFe, the positive electrode active material 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, the above-prepared irreversible positive electrode additive, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in a weight ratio of 90:5:2.5:2.5. The above slurry is then mixed evenly, coated on the current collector, cold-pressed, and slit to obtain the positive electrode sheet.

[0176] 2. Preparation of negative electrode sheet

[0177] Hard carbon (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were dissolved in deionized water at a weight ratio of 95.2:1.8:1.8:1.2. The resulting negative electrode slurry was prepared under vacuum stirring. This slurry was then uniformly coated onto copper foil. After drying the copper foil at room temperature, it was transferred to a 120°C oven for 4 hours. The resulting sheet was then cold-pressed and slit to obtain the negative electrode sheet, with a coating weight of 0.17 g / 1540.25 mm². 2 .

[0178] 3. Preparation of electrolyte

[0179] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly at a volume ratio of 3 / 7. 12.5% ​​NaPF6 sodium salt was added and dissolved in the organic solvent and stirred evenly to obtain the electrolyte of Example 1.

[0180] 4. Separating membrane

[0181] Polypropylene film is used as the separator.

[0182] 5. Preparation of secondary batteries

[0183] The above-mentioned positive electrode, separator, and negative electrode are stacked in sequence, then placed into a casing, welded, injected with electrolyte, pre-charged, formed, and coated to obtain a sodium-ion battery.

[0184] The preparation methods of sodium-ion batteries in Examples 2-14 and Comparative Examples 1-2 are the same as those in Example 1, except that the process of preparing the irreversible additive for the positive electrode is different, as shown in Table 1.

[0185] In Comparative Example 1, no irreversible positive electrode additive was prepared or added. In Comparative Example 2, NaC2O2H3 and Fe3O4 were mixed and ball-milled to obtain an irreversible positive electrode additive.

[0186] Table 1

[0187]

[0188]

[0189] Example 15

[0190] Preparation of irreversible additives for the positive electrode:

[0191] The active metal ion supplement CH3COOLi (lithium acetate) was completely dissolved in deionized water, heated to 80℃ and stirred for 1 hour to promote dissolution, achieving a concentration of 5 g / mL. Then, Fe3O4, a transition metal-containing substance, was mixed and stirred at a ratio of 0.8% of the transition metal-containing substance to the active metal ion supplement (core mass to active metal ion supplement mass ratio of 0.8:100). Spray drying was then performed to prepare an irreversible positive electrode additive with a transition metal-containing substance as the core and the active metal ion supplement as the shell.

[0192] 1. Preparation of positive electrode sheet

[0193] The positive electrode active material LiFePO4, the above-prepared irreversible positive electrode additive, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are mixed evenly in a weight ratio of 90:5:2.5:2.5. The slurry is then mixed evenly and then coated, cold-pressed, and slit on the current collector to obtain the positive electrode sheet.

[0194] 2. Preparation of negative electrode sheet

[0195] Hard carbon (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were dissolved in deionized water at a weight ratio of 95.2:1.8:1.8:1.2. The resulting negative electrode slurry was prepared under vacuum stirring. This slurry was then uniformly coated onto copper foil. After drying the copper foil at room temperature, it was transferred to a 120°C oven for 4 hours. The resulting sheet was then cold-pressed and slit to obtain the negative electrode sheet, with a coating weight of 0.17 g / 1540.25 mm². 2 .

[0196] 3. Preparation of electrolyte

[0197] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed evenly at a volume ratio of 3 / 7. 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent and stirred evenly to obtain the electrolyte of Example 1.

[0198] 4. Separating membrane

[0199] Polypropylene film is used as the separator.

[0200] 5. Preparation of secondary batteries

[0201] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting bare cell is then wound, tabs are welded onto it, and the cell is placed in an aluminum casing. It is then baked at 80°C to remove moisture, followed by the injection of electrolyte and sealing to obtain a non-charged battery. This non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation, shaping, and capacity testing to obtain a lithium-ion battery.

[0202] The preparation methods of the lithium-ion batteries in Examples 16-24 and Comparative Examples 3-4 are the same as those in Example 15, except that the process of preparing the irreversible additive for the positive electrode is different, as shown in Table 2.

[0203] In Comparative Example 3, no irreversible positive electrode additive was prepared or added. In Comparative Example 4, LiC2O2H3 and Fe3O4 were mixed and ball-milled to obtain an irreversible positive electrode additive.

[0204] Table 2

[0205]

[0206] The irreversible cathode additive prepared in Example 1 was polished using an IB-19500CP ion cross-section polisher to obtain a polished sample with a cut surface. Then, the sample morphology was observed using a ZEISS Sigma 300 scanning electron microscope according to standard JY / T010-1996. Figure 8 As can be seen, the positive electrode irreversible additive in Example 1 has a core-shell structure, with the core being a substance 100 containing a transition metal and the shell being a coating layer 200 formed by CH3COOLi.

[0207] The first-cycle charge capacity and cycle performance of the batteries in Examples 1-14 and Comparative Examples 1-2 were characterized, and the characterization results are shown in Table 3.

[0208] 1. Battery capacity test during the first charge cycle:

[0209] Charge at 0.1C constant current to 4.1V at 45℃, then charge at a constant voltage of 4.1V to a current of 0.05C, let stand for 5 minutes, and then discharge at 1 / 3C to 1.5V at 25℃. The resulting capacity is recorded as the first charge capacity D0.

[0210] 2. Battery capacity retention test:

[0211] Taking Example 1 as an example, the battery capacity retention rate test process is as follows: At 25°C, the battery corresponding to Example 1 is charged to 4.1V with a constant current of 1 / 3C, then charged to a current of 0.05C with a constant voltage of 4.1V, left to rest for 5 minutes, and then discharged to 1.5V with a constant current of 1 / 3C. The resulting capacity is recorded as the initial capacity D0. The above steps are repeated for the same battery, and the discharge capacity Dn of the battery after the nth cycle is recorded. Then, the battery capacity retention rate Pn after each cycle is Pn = Dn / D0 × 100%. With the 100 points P1, P2...P100 as the vertical axis and the corresponding cycle number as the horizontal axis, a curve of battery capacity retention rate versus cycle number corresponding to the lithium manganese oxide positive electrode active material of Example 1 is obtained.

[0212] During this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 100th cycle to n=100. The battery capacity retention rate data corresponding to Example 1 in Table 1 is the data measured after 100 cycles under the above test conditions, i.e., the value of P100. The test process for other examples and comparative examples is the same as above.

[0213] 3. Porosity test of the positive electrode sheet after the first cycle:

[0214] The porosity was determined according to the national standard GB / T24586-2009, "Determination of Apparent Density, True Density and Porosity of Iron Ore". The specific test method was as follows: the electrode was cleaned by immersing it in ethyl methyl carbonate (EMC); based on the gas displacement method, the positive electrode was placed in a true density analyzer, the test system was sealed, and helium gas was introduced according to the procedure. The pressure of the gas in the sample chamber and the expansion chamber was measured. The porosity is the percentage of the pore volume to the total volume of the electrode, calculated using the formula: Porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume. The results are shown in Table 3.

[0215] Table 3

[0216]

[0217]

[0218] As shown in Table 3, in Examples 1-14 of this application, the addition of the irreversible positive electrode additive of this application resulted in a relatively high porosity of the positive electrode sheet after the first cycle of the battery. This is attributed to the decomposition of the active metal ion supplement in the irreversible positive electrode additive. Comparative Example 1 did not add the irreversible positive electrode additive, while Comparative Example 2 directly obtained the irreversible positive electrode additive by ball milling a mixture of CH3COONa and Fe3O4. After the first cycle of both Comparative Examples 1 and 2, the porosity of the positive electrode sheets was relatively low, indicating that the active metal ion supplement in the irreversible positive electrode additive added in Comparative Example 2 was not completely decomposed.

[0219] The first charge capacity and capacity retention of the batteries in Examples 1-14 are significantly higher than those in Comparative Examples 1-2. It can be seen that by adding the irreversible positive electrode additive of the present application, the first charge capacity and cycle life of the battery containing it can be improved.

[0220] The specific capacity and cycle performance of the batteries in Examples 15-24 and Comparative Examples 3-4 were characterized, and the characterization results are shown in Table 4.

[0221] 1. Battery capacity test during the first charge cycle:

[0222] Charge the capacitor at 0.1C constant current at 45℃ to 4.2V, then charge it at a constant voltage of 4.2V to a current of 0.05C, let it rest for 5 minutes, and then discharge it at 1 / 3C to 2.0V at 25℃. The resulting capacity is recorded as the initial capacity D0.

[0223] 2. Battery capacity retention test

[0224] Taking Example 15 as an example, the battery capacity retention rate test process is as follows: At 25°C, the battery corresponding to Example 15 is charged to 3.8V with a constant current of 1 / 3C, then charged to a current of 0.05C with a constant voltage of 3.8V, left to rest for 5 minutes, and then discharged to 1.9V with a constant current of 1 / 3C. The resulting capacity is recorded as the initial capacity D0. The above steps are repeated for the same battery, and the discharge capacity Dn of the battery after the nth cycle is recorded. Then, the battery capacity retention rate after each cycle is Pn = Dn / D0 × 100%. The curve of the battery capacity retention rate versus the number of cycles is obtained by plotting the 500 points P1, P2...P500 as the vertical axis and the corresponding number of cycles as the horizontal axis.

[0225] During this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 500th cycle to n=500. The battery capacity retention rate data corresponding to Example 1 in Table 1 are the data measured after 500 cycles under the above test conditions, i.e., the value of P500. The test results are shown in Table 4.

[0226] 3. Porosity test of the positive electrode sheet after the first cycle:

[0227] The porosity was determined according to the national standard GB / T24586-2009, "Determination of Apparent Density, True Density and Porosity of Iron Ore". The specific test method was as follows: the electrode was cleaned by immersing it in ethyl methyl carbonate (EMC); based on the gas displacement method, the positive electrode was placed in a true density analyzer, the test system was sealed, and helium gas was introduced according to the procedure. The pressure of the gas in the sample chamber and the expansion chamber was measured. The porosity is the percentage of the pore volume to the total volume of the electrode, calculated using the formula: Porosity = (V - V0) / V × 100%, where V0 is the true volume and V is the apparent volume. The results are shown in Table 4.

[0228] Table 4

[0229]

[0230] As shown in Table 4, in Examples 15-24 of this application, the addition of the irreversible positive electrode additive of this application resulted in a relatively large porosity of the positive electrode sheet after the first cycle of the battery. This is attributed to the decomposition of the active metal ion supplement in the irreversible positive electrode additive. Comparative Example 3 did not add the irreversible positive electrode additive, while Comparative Example 4 directly obtained the irreversible positive electrode additive by ball milling a mixture of CH3COOLi and Fe3O4. After the first cycle of both Comparative Examples 3 and 4, the porosity of the positive electrode sheet was relatively small, indicating that the active metal ion supplement in the irreversible positive electrode additive added in Comparative Example 4 was not completely decomposed.

[0231] The first charge capacity and capacity retention of the batteries in Examples 15-24 are significantly higher than those in Comparative Examples 3-4. This shows that by adding the irreversible positive electrode additive of the present application, the first charge capacity and cycle life of the battery containing it can be improved.

[0232] In summary, the addition of an irreversible positive electrode additive to the positive electrode sheet in this embodiment of the application can improve the first charge capacity and cycle life of the battery containing it.

[0233] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, characterized in that, The secondary battery includes a positive electrode, a separator, and a negative electrode. The positive electrode includes a positive active material and an irreversible positive additive. The irreversible positive additive includes: The core, comprising a substance containing a transition metal; A coating layer formed on at least a portion of the surface of the core, the coating layer comprising an active metal ion supplement, the active metal ion supplement comprising a lithium supplement or a sodium supplement.

2. The secondary battery according to claim 1, characterized in that, The volume average particle size Dv50 of the transition metal-containing material is 0.2 μm-1 μm.

3. The secondary battery according to claim 1 or 2, characterized in that, The mass ratio of the kernel to the active metal ion supplement is (0.02-5):

100.

4. The secondary battery according to any one of claims 1-3, characterized in that, The core comprises at least one of a transition metal oxide or a noble metal element.

5. The secondary battery according to any one of claims 1-4, characterized in that, The core includes at least one of Fe2O3, Fe3O4, Co3O4, Mn3O4, MoO3, TiO2, NiO, α-MnO2, RuO2, Pt, Pd, Au, Ru, ZnCo2O4, NiCo2O4, FeCo2O4, or ZnCo2O4.

6. The secondary battery according to any one of claims 1-5, characterized in that, The core includes at least one of ZnCo2O4, NiCo2O4, FeCo2O4, or ZnCo2O4.

7. The secondary battery according to any one of claims 1-6, characterized in that, The active metal ion supplement includes Q x C a O b H c N d Where Q includes Li or Na, 0 <x≤4,2≤a≤10,2≤b≤9,0≤c≤15,0≤d≤3。 8. The secondary battery according to any one of claims 1-7, characterized in that, The active metal ion supplement includes Na2CO3, Na2C2O4, Na2C4O4, CH3COONa, CH3CH2COONa, Na3C6O7H5, CH2(COONa)2, Na2C6O6, and Na2C 10 O8H 14 N2, Na3C 10 O9H 15 N2 or Na4C 10 O8H 12 At least one of N2; or, The active metal ion supplement includes Li2CO3, Li2C2O4, Li2C4O4, CH3COOLi, CH3CH2COOLi, Li3C6O7H5, CH2(COOLi)2, Li2C6O6, and Li2C 10 O8H 14 N2, Li3C 10 O9H 15 N2 or Li4C 10 O8H 12 At least one of N2.

9. The secondary battery according to any one of claims 1-8, characterized in that, The coating layer also includes a conductive agent.

10. The secondary battery according to claim 9, characterized in that, The mass ratio of the conductive agent to the active metal ion supplement is (2-12):

100.

11. The secondary battery according to claim 9 or 10, characterized in that, The conductive agent includes at least one of carbon nanotubes, graphene, or reduced graphene oxide.

12. The secondary battery according to any one of claims 1-11, characterized in that, The positive electrode active material includes at least one of sodium transition metal oxides, polyanionic compounds, and Prussian blue sodium compounds and their respective modified compounds; or, The positive electrode active material includes lithium phosphate with an olivine structure.

13. The secondary battery according to any one of claims 1-12, characterized in that, The positive electrode active material includes Na. y At least one of MO2, Na3V2(PO4)3, or a Prussian blue compound, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, or Cu, and 0 < y ≤ 1; or, The positive electrode active material includes lithium iron phosphate.

14. The secondary battery according to any one of claims 1-13, characterized in that, After the first cycle of the secondary battery, the porosity of the positive electrode sheet is 6%-25%.

15. A positive electrode irreversible additive, characterized in that, The irreversible additive for the positive electrode includes: The core, comprising a substance containing a transition metal; A coating layer formed on at least a portion of the surface of the core, the coating layer comprising an active metal ion supplement, the active metal ion supplement comprising a lithium supplement or a sodium supplement.

16. The positive electrode irreversible additive according to claim 15, characterized in that, The volume average particle size Dv50 of the transition metal-containing material is 0.2 μm-1 μm.

17. The positive electrode irreversible additive according to claim 15 or 16, characterized in that, The mass ratio of the kernel to the active metal ion supplement is (0.02-5):

100.

18. The irreversible positive electrode additive according to any one of claims 15-17, characterized in that, The core comprises at least one of a transition metal oxide or a noble metal element.

19. The irreversible positive electrode additive according to any one of claims 15-18, characterized in that, The core includes at least one of Fe2O3, Fe3O4, Co3O4, Mn3O4, MoO3, TiO2, NiO, α-MnO2, RuO2, Pt, Pd, Au, Ru, ZnCo2O4, NiCo2O4, FeCo2O4, or ZnCo2O4.

20. The irreversible positive electrode additive according to any one of claims 15-19, characterized in that, The core includes at least one of ZnCo2O4, NiCo2O4, FeCo2O4, or ZnCo2O4.

21. The irreversible positive electrode additive according to any one of claims 15-20, characterized in that, The active metal ion supplement includes Q x C a O b H c N d Where Q includes Li or Na, 0 <x≤4,2≤a≤10,2≤b≤9,0≤c≤15,0≤d≤3。 22. The irreversible positive electrode additive according to any one of claims 15-21, characterized in that, The active metal ion supplement includes Na2CO3, Na2C2O4, Na2C4O4, CH3COONa, CH3CH2COONa, Na3C6O7H5, CH2(COONa)2, Na2C6O6, and Na2C 10 O8H 14 N2, Na3C 10 O9H 15 N2 or Na4C 10 O8H 12 At least one of N2; or, The active metal ion supplement includes Li2CO3, Li2C2O4, Li2C4O4, CH3COOLi, CH3CH2COOLi, Li3C6O7H5, CH2(COOLi)2, Li2C6O6, and Li2C 10 O8H 14 N2, Li3C 10 O9H 15 N2 or Li4C 10 O8H 12 At least one of N2.

23. The irreversible positive electrode additive according to any one of claims 15-22, characterized in that, The coating layer also includes a conductive agent.

24. The irreversible positive electrode additive according to claim 23, characterized in that, The mass ratio of the conductive agent to the active metal ion supplement is (2-12):

100.

25. The positive electrode irreversible additive according to claim 23 or 24, characterized in that, The conductive agent includes at least one of carbon nanotubes, graphene, or reduced graphene oxide.

26. A method for preparing an irreversible additive for a positive electrode, characterized in that, include: A coating layer is formed on at least a portion of the surface of the core to obtain an irreversible positive electrode additive; The core comprises a substance containing a transition metal, and the coating layer comprises an active metal ion supplement, which includes a lithium supplement or a sodium supplement.

27. The method according to claim 26, characterized in that, include: The active metal ion supplement is dissolved in a solvent, a substance containing transition metals is added, and the mixture is spray-dried to obtain an irreversible positive electrode additive.

28. The method according to claim 27, characterized in that, The solvent includes at least one of water, ethanol, methanol, tetrahydrofuran, dimethyl carbonate, ethyl methyl carbonate, 1,3-dioxolane, or 2-methyltetrahydrofuran.

29. The method according to any one of claims 26-28, characterized in that, include: The active metal ion supplement is dissolved in a solvent, and a substance containing transition metals and a conductive agent are added. The mixture is then spray-dried to obtain an irreversible positive electrode additive.

30. An electrical appliance, characterized in that, The secondary battery includes any one of claims 1-14.

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