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

Abstract

Disclosed in the present application are a secondary battery, an irreversible additive for a positive electrode and a preparation method therefor, a positive electrode sheet, and an electric device. The secondary battery comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode active material and an irreversible additive for a positive electrode; the irreversible additive for a positive electrode comprises an active metal ion supplement and a catalyst; and the catalyst comprises AM2O4, where A comprises a metal element having a charge of +2, M comprises a metal element having a charge of +3, and A and M are different. The irreversible additive for a positive electrode of the present application can improve the first-cycle specific charge capacity of a battery containing same and prolong the cycle life thereof.

Description

Secondary batteries, irreversible additives for positive electrodes and their preparation methods, and electrical equipment.

[0001] Priority information

[0002] This application claims priority and benefit to patent application 202411223579.8, filed with the China National Intellectual Property Administration on September 2, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] 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 electrical equipment. Background Technology

[0004] 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.

[0005] 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. The formation of the SEI film consumes a large number of active metal ions (such as lithium and sodium ions), resulting in a low initial charge capacity. During the charge and 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. However, current irreversible additives are in their early stages of development and still have many shortcomings in production and application. Summary of the Invention

[0006] 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 of the secondary battery.

[0007] To achieve the above objectives, the first aspect of this application proposes a secondary battery, the secondary battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material and a positive electrode irreversible additive, the positive electrode irreversible additive comprising an active metal ion supplement and a catalyst, the catalyst comprising AM2O4; wherein A comprises a metal element with a valence of +2, M comprises a metal element with a valence of +3, and A and M are different.

[0008] This application includes at least the following beneficial effects: the secondary battery of this application contains an irreversible positive electrode additive, which contains a bimetallic catalyst AM2O4 of two metal elements with oxidation states of +2 and +3, which can improve the first charge capacity of the secondary battery containing it.

[0009] In some embodiments, the mass ratio of the catalyst to the active metal ion supplement is 1:(5-50). This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0010] In some embodiments, the catalyst is spherical or near-spherical. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0011] In some embodiments, the catalyst has at least a portion of its surface with channels extending into the interior of the catalyst, and at least a portion of the active metal ion supplement is located within the channels. This can thereby improve the initial charge capacity and cycle life of the secondary battery containing it.

[0012] In some embodiments, the active metal ion supplement is formed on at least a portion of the surface of the catalyst. This can thereby improve the initial charge capacity and cycle life of the secondary battery containing it.

[0013] In some embodiments, the irreversible positive electrode additive is spherical or near-spherical. This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0014] In some embodiments, the catalyst has a volume average particle size Dv50 of 0.2 μm to 4 μm. This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0015] In some embodiments, the catalyst has a volume average particle size Dv50 of 0.3 μm-1 μm, thereby improving the initial charge capacity and cycle life of the secondary battery containing it.

[0016] In some embodiments, the catalyst has a BET specific surface area of ​​50 m². 2 / g-200m 2 / g, thereby improving the first charge capacity and cycle life of secondary batteries containing it.

[0017] In some embodiments, the catalyst has an electronic conductivity of 1.0 × 10⁻⁶. -4 S·cm -1 -3.0S·cm -1 This can improve the initial charge capacity and cycle life of secondary batteries containing it.

[0018] In some embodiments, the electronic conductivity of the catalyst is 2.0×10 -3 S·cm -1 −0.5S·cm -1 . Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0019] In some embodiments, at least one of the following conditions is satisfied: A includes at least one of Mg, Co, Zn, Fe, Ni, Mn or Cd; B includes at least one of Fe, Co or Mn. Thereby, the first-cycle charge capacity per gram of the secondary battery containing the same can be improved.

[0020] In some embodiments, the catalyst includes at least one of CoFe2O4, ZnFe2O4, MnFe2O4, ZnMn2O4, CoMn2O4 or MnCo2O4. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0021] In some embodiments, the active metal ion supplement includes a lithium supplement or a sodium supplement. Thereby, the first-cycle charge capacity per gram and the cycle life of the secondary battery containing the same can be improved.

[0022] In some embodiments, the active metal ion supplement includes Q x C a O b H c N d , wherein 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.

[0023] In some embodiments, the active metal ion supplement includes at least one of 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, the active metal ion supplement includes at least one of Li2CO3, Li2C2O4, Li2C4O4, CH3COOLi, CH3CH2COOLi, Li3C6O7H5, CH2(COOLi)2, Li2C6O6, Li2C 10 O8H14 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.

[0024] 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.

[0025] 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.

[0026] In a second aspect, this application proposes a positive electrode irreversible additive, comprising an active metal ion supplement and a catalyst, wherein the catalyst comprises AM2O4; wherein A comprises a metal element with a +2 valence, and M comprises a metal element with a +3 valence, and A and M are different. Therefore, the positive electrode irreversible additive of this application, which contains a bimetallic catalyst AM2O4 comprising two metal elements with +2 and +3 valences respectively, can improve the first-cycle capacity and cycle life of secondary batteries containing it.

[0027] In some embodiments, the mass ratio of the catalyst to the active metal ion supplement is 1:(5-50). This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0028] In some embodiments, at least one of the following conditions is met: the catalyst is spherical or near-spherical; the surface of the catalyst has channels extending into the interior of the catalyst, and at least a portion of the active metal ion supplement is located within the channels; the active metal ion supplement is formed on at least a portion of the surface of the catalyst. This can improve the initial charge capacity and cycle life of the secondary battery containing it.

[0029] In some embodiments, the volume average particle size Dv50 of the catalyst is 0.2 μm - 4 μm. Thereby, the first-cycle charging specific capacity and cycle life of the secondary battery containing the same can be improved.

[0030] In some embodiments, the BET specific surface area of the catalyst is 50 m 2 / g - 200 m 2 / g. Thereby, the first-cycle charging specific capacity and cycle life of the secondary battery containing the same can be improved.

[0031] In some embodiments, the electronic conductivity of the catalyst is 1.0×10 -4 S·cm -1 -3.0 S·cm -1 . Thereby, the first-cycle charging specific capacity and cycle life of the secondary battery containing the same can be improved.

[0032] In some embodiments, at least one of the following conditions is satisfied: A includes at least one of Mg, Co, Zn, Fe, Ni, Mn or Cd; B includes at least one of Fe, Co or Mn. Thereby, the first-cycle charging specific capacity and cycle life of the secondary battery containing the same can be improved.

[0033] In some embodiments, the catalyst includes at least one of CoFe2O4, ZnFe2O4, MnFe2O4, ZnMn2O4, CoMn2O4 or MnCo2O4. Thereby, the first-cycle charging specific capacity and cycle life of the secondary battery containing the same can be improved.

[0034] In some embodiments, the active metal ion supplement includes a lithium supplement or a sodium supplement. Thereby, the first-cycle charging specific capacity and cycle life of the secondary battery containing the same can be improved.

[0035] 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 charging specific capacity and cycle life of the secondary battery containing the same can be improved.

[0036] In some embodiments, the active metal ion supplement includes Na2CO3, Na2C2O4, Na2C4O4, CH3COONa, CH3CH2COONa, Na3C6O7H5, CH2(COONa)2, Na2C6O6, Na2C 10 O8H 14N2, 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, 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.

[0037] In a third aspect of this application, a method for preparing an irreversible additive for a positive electrode is proposed, comprising:

[0038] An irreversible positive electrode additive comprising an active metal ion supplement and a catalyst, wherein the catalyst comprises AM2O4;

[0039] In this designation, A includes metallic elements with a oxidation state of +2, and M includes metallic elements with a oxidation state of +3, and A and M are different. This results in secondary batteries containing the irreversible cathode additive obtained through this method exhibiting excellent initial charge capacity.

[0040] In some embodiments, the method includes dissolving an active metal ion supplement in water, adding a catalyst, and spray drying to obtain an irreversible positive electrode additive. This can improve the initial charge capacity and cycle life of secondary batteries containing the additive.

[0041] In some embodiments, the catalyst is prepared by dissolving soluble A salt and soluble M salt in a solvent, adding additives, performing a solvothermal reaction, and drying to obtain the catalyst. This can improve the initial charge capacity and cycle life of secondary batteries containing the catalyst.

[0042] In some embodiments, at least one of the following conditions is met: the solvent includes at least one of ethyl acetate, ethylene glycol, or triethanolamine; the additive includes at least one of urea or CH3COOK; the temperature of the solvothermal reaction is 150°C-250°C; and the time of the solvothermal reaction is 10h-50h.

[0043] In a fourth aspect of this application, an electrical device is proposed, including the secondary battery described in the first aspect of this application.

[0044] 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

[0045] 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:

[0046] Figure 1 is a schematic diagram of a battery according to one embodiment of this application.

[0047] Figure 2 is an exploded view of the battery according to one embodiment of this application shown in Figure 1.

[0048] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0049] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0050] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0051] Figure 6 is a schematic diagram of an electrical device in which a battery is used as a power source according to an embodiment of this application.

[0052] Figure 7 is a scanning electron microscope image of the catalyst prepared in Example 1 of this application.

[0053] Figure 8 is a scanning electron microscope image of the irreversible positive electrode additive prepared in Example 1 of this application.

[0054] Figure 9 is a transmission electron microscope image of the irreversible positive electrode additive prepared in Example 1 of this application.

[0055] Figure 10 is a distribution diagram of Na element in the irreversible positive electrode additive prepared in Example 1 of this application.

[0056] Explanation of reference numerals in the attached drawings: 1. Battery cell; 11. Housing; 12. Electrode assembly; 13. Cover plate; 2. Battery module; 3. Battery pack; 31. Upper casing; 32. Lower casing. Detailed Implementation

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0061] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] The secondary battery in this application embodiment includes an irreversible positive electrode additive, which uses a catalyst AM2O4. A comprises a metal element with a +2 valence, and M comprises a metal element with a +3 valence, and A and M are different. Compared to single-atom transition metal oxide catalysts, the dual transition metal atoms in AM2O4 increase the interaction sites with O atoms in the irreversible positive electrode additive, thereby improving the decomposition efficiency of the irreversible positive electrode additive. Compared to single transition metal oxides, a higher catalytic effect is achieved with a smaller dosage, thus increasing the initial specific capacity of the battery.

[0067] 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.

[0068] The first aspect of this application proposes a secondary battery, the secondary battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material and a positive electrode irreversible additive, the positive electrode irreversible additive comprising an active metal ion supplement and a catalyst, the catalyst comprising AM2O4; wherein A comprises a metal element with a valence of +2, M comprises a metal element with a valence of +3, and A and M are different.

[0069] The secondary battery of this application uses the catalyst AM2O4 in the irreversible positive electrode additive. A comprises a metal element with a +2 valence, and M comprises a metal element with a +3 valence, and A and M are different. Compared to single-atom transition metal oxide catalysts, the dual transition metal atoms in AM2O4 increase the interaction sites with O atoms in the irreversible positive electrode additive, thereby improving the decomposition efficiency of the irreversible positive electrode additive and thus increasing the initial specific capacity of the battery. Furthermore, the catalyst possesses a spinel structure, with +3 valence M ions filling the octahedral centers and +2 valence A ions filling the tetrahedral centers. This significantly enhances the structural stability of the bimetallic oxide compared to single-metal transition metal oxide catalysts, thereby substantially reducing side reactions in the electrolyte or cathode active material. This can, to some extent, reduce the consumption of residual active metal ions (such as sodium and lithium ions) in the battery cell system, thus improving the battery's cycle life. On the other hand, bimetallic oxides exhibit better electronic conductivity; their application in batteries can improve the overall electronic conductivity on the cathode side, significantly enhancing the battery's rate performance. In summary, this can improve the battery's initial charge capacity, cycle life, and rate performance.

[0070] It is understood that in the embodiments of this application, the main role of the catalyst is to catalyze the decomposition of the active metal ion supplement. However, after the active metal ion supplement decomposes, the catalyst will remain in the cell system. Therefore, it is desirable for the remaining catalyst structure to be as stable as possible. When the catalyst structure itself is not stable enough, even if it can effectively promote the decomposition of the active metal ion supplement and provide more active metal ions during the first week of charging, in the later battery cycles, the catalyst itself will catalyze the oxidative decomposition reaction of the electrolyte or positive electrode active material due to its unstable structure, thereby accelerating the consumption of active metal ions in the battery. Conversely, when the catalyst structure is relatively stable, this side reaction catalyzing the electrolyte or positive electrode active material will be significantly reduced, thereby reducing the consumption of active metal ions to a certain extent and improving the battery's cycle performance.

[0071] In a secondary battery, conduction is achieved through the transfer of active metal ions between the positive and negative electrodes: when the battery is charging, active metal ions in the positive electrode active material are released, 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. Irreversible additives for the positive electrode refer to substances containing active metal ions added to the positive electrode. The function of irreversible additives is to irreversibly replenish the active metal ions lost during the charging and discharging process.

[0072] Specifically, active metal ion supplements refer to substances that can provide active metal ions, including lithium supplements or sodium supplements. The active metal ion in lithium-ion batteries and lithium metal batteries is lithium ions, and lithium supplements can replenish active lithium ions. The active metal ion in sodium-ion batteries and sodium metal batteries is sodium ions, and sodium supplements can replenish active sodium ions.

[0073] It is understandable that the oxidation states of metal elements A and B in the catalyst AM2O4 can be determined using the following methods:

[0074] The valence of different metallic elements was determined using XPS (X-ray Photoelectron Spectroscopy).

[0075] The composition of the catalyst AM2O4 can be determined by XRD.

[0076] In some embodiments of this application, the mass ratio of the catalyst to the active metal ion supplement is 1:(5-50). For example, the mass ratio of the catalyst to the active metal ion supplement can be 1:(5-49), 1:(10-40), 1:(15-35), 1:(20-30), etc. Specifically, controlling the mass ratio of the catalyst to the active metal ion supplement within the above range can not only improve the specific capacity of the battery during the first charge cycle, but also achieve higher activity compared to single transition metal oxides, thus achieving a higher catalytic effect with a smaller amount added.

[0077] It is understood that "the ratio of the mass of the catalyst 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:

[0078] Weigh a certain mass of the positive electrode irreversible additive, dissolve it in excess nitric acid, and make up the volume. Use ICP (inductively coupled plasma optical emission spectrometry) to test the content of metal (lithium or sodium) in the metal and active metal ion supplement, and convert it into the corresponding mass of catalyst (m1) and active metal ion supplement (m2), and then obtain the mass ratio of the catalyst to the active metal ion supplement.

[0079] In some embodiments of this application, the active metal ion supplement is formed on at least a portion of the surface of the catalyst. Thus, the active metal ion supplement can isolate at least a portion of the catalyst from contact with the electrolyte, thereby reducing the probability of catalytic electrolyte decomposition and improving the battery's cycle performance.

[0080] It is understood that the structure of the active metal ion supplement formed on at least a portion of the surface of the catalyst in the embodiments of this application can be determined by the following methods:

[0081] 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.

[0082] In some embodiments of this application, the catalyst is spherical or near-spherical. Thus, compared to the irregular morphology of existing catalysts, the morphology of the irreversible positive electrode additive obtained in the embodiments of this application is also spherical or near-spherical. The resulting irreversible positive electrode additive is also spherical or near-spherical, which results in a high packing density of the irreversible positive electrode additive. The spherical or near-spherical irreversible positive electrode additive particles will significantly reduce the distance between particles, increase the compaction density of the positive electrode sheet, and facilitate the construction of a highly efficient electrode conductive network, thereby improving the rate performance of the battery containing it.

[0083] It is understandable that spherical or near-spherical means that the catalyst has a spherical or nearly spherical morphology.

[0084] In some embodiments of this application, the positive electrode irreversible additive is spherical or near-spherical. Spherical or near-spherical positive electrode irreversible additive particles will significantly reduce the distance between particles, increase the compaction density of the positive electrode sheet, and facilitate the construction of an efficient electrode conductive network, thereby improving the rate performance of the battery containing it.

[0085] In some embodiments of this application, the catalyst has at least a portion of its surface with channels extending into the interior of the catalyst, and at least a portion of the active metal ion supplement is located within these channels. Thus, the catalyst has a loose, porous structure with a larger specific surface area, and the partial entry of the active metal ion supplement into the interior of the catalyst results in a larger contact area between the active metal ion supplement and the catalyst, which can improve the decomposition efficiency of the irreversible additives in the positive electrode, thereby increasing the initial specific capacity of the battery. Furthermore, bimetallic oxides have better electronic conductivity; their application in the battery can improve the overall electronic conductivity on the positive electrode side, and the rate performance of the battery is also significantly improved.

[0086] In some embodiments of this application, the volume average particle size Dv50 of the catalyst is 0.2 μm-4 μm. For example, the volume average particle size Dv50 of the catalyst can be 0.2 μm-4 μm, 0.5 μm-3.5 μm, 1 μm-3 μm, 1.5 μm-2.5 μm, etc. Specifically, controlling the volume average particle size Dv50 of the catalyst within the above range allows for sufficient contact between the catalyst and the active metal ion supplement, improving the decomposition efficiency of the irreversible additive in the positive electrode, thereby increasing the initial specific capacity of the battery. It also reduces the contact area between the catalyst and the electrolyte, improving the stability of the electrolyte and thus enhancing the cycle performance of the battery. In other embodiments of this application, the volume average particle size Dv50 of the catalyst is 0.3 μm-1 μm.

[0087] 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 catalyst can be determined using methods known in the art, for example, by the following methods:

[0088] The volume average particle size Dv50 of the catalyst was tested using a laser particle size analyzer (e.g., Malvern Master Sizer 3000) in accordance with standard GB / T 19077-2016.

[0089] In some embodiments of this application, the BET specific surface area of ​​the catalyst is 50 m². 2 / g-200m 2 / g. For example, the BET specific surface area of ​​the catalyst can be 50m². 2 / g-199m 2 / g, 60m 2 / g-190m 2 / g, 80m 2 / g-170m 2 / g, 100m 2 / g-150m 2 / g, 120m 2 / g-130m2 Specifically, the BET specific surface area of ​​the catalyst is controlled within the above range. The catalyst has a large specific surface area and a porous structure, which allows the active metal ion supplement to easily enter the porous structure of the catalyst. The contact area between the active metal ion supplement and the catalyst is large, resulting in more uniform compounding and better catalytic effect, thereby further improving the first-cycle specific capacity of the battery.

[0090] It is understood that "BET specific surface area" is a well-known definition in the art and can be measured using methods well-known in the art, such as the following methods:

[0091] The irreversible additives at the positive electrode were thoroughly washed with water to remove the active metal ion supplements, resulting in a catalyst sample. Using a Mach-McGen Gemini VII 2390 fully automated BET surface area and porosity analyzer, approximately 7g of the sample was placed in a 9cc long tube with a bulb and degassed at 200°C for 2 hours. Subsequently, the sample was placed in the main unit for testing to obtain the BET (specific surface area) data of the catalyst.

[0092] In some embodiments of this application, the electronic conductivity of the catalyst is 1.0 × 10⁻⁶. -4 S·cm -1 -3.0S·cm -1 For example, the electronic conductivity of the catalyst can be 1.0 × 10⁻⁶. -4 S·cm -1 -2.9S·cm -1 1.0×10 -3 S·cm -1 -2.5S·cm -1 1.0×10 -2 S·cm -1 -2.0S·cm -1 0.1 S·cm -1 -1.5S·cm -1 0.5 S·cm -1 -1.0S·cm -1 The electronic conductivity of the catalyst is controlled within the above range. High electronic conductivity of the catalyst can improve the rate performance of batteries containing it. In other embodiments of this application, the electronic conductivity of the catalyst is 2.0 × 10⁻⁶. -3 S·cm -1 -0.5S·cm -1 .

[0093] It is understood that the "electronic conductivity of a catalyst" is a well-known definition in the art and can be determined using methods known in the art, such as the following methods:

[0094] The electronic conductivity of the catalyst was tested using the four-probe method. The test method was as follows: the catalyst to be tested was prepared into a thin film, and the conductivity was calculated by measuring the resistance value of the sample surface using a four-probe tester.

[0095] In some embodiments of this application, A includes at least one of Mg, Co, Zn, Fe, Ni, Mn, or Cd. Specifically, the oxidation state of the aforementioned metal element in the catalyst is +2, and the catalyst AM2O4 has a spinel structure, wherein +3 valence M ions fill the octahedral centers, and 2+ valence A ions fill the tetrahedral centers. This significantly improves the structural stability of the aforementioned bimetallic oxide compared to single-metal transition metal oxide catalysts, and can reduce the residual relative active metal ions (such as sodium ions, lithium ions, etc.) in the battery cell system to a certain extent. The consumption of ) increases the cycle life of the battery; compared with single-atom transition metal oxide catalysts, the dual transition metal atoms in AM2O4 increase the interaction sites with O atoms in the irreversible additives of the positive electrode, which can improve the decomposition efficiency of the irreversible additives of the positive electrode. Compared with single transition metal oxides, it achieves a higher catalytic effect with a smaller amount, thereby improving the first-cycle specific capacity of the battery; compared with single metal oxides, dual metal oxides have better electronic conductivity. When applied to batteries, they can improve the overall electronic conductivity of the positive electrode side, and the rate performance of the battery is also significantly improved.

[0096] In some embodiments of this application, B includes at least one of Fe, Co, or Mn. Specifically, the oxidation state of the aforementioned metal element in the catalyst is +3, and the catalyst AM2O4 has a spinel structure, wherein the +3 valence M ions fill the octahedral centers, and the 2+ valence A ions fill the tetrahedral centers. This significantly improves the structural stability of the aforementioned bimetallic oxide compared to single-metal transition metal oxide catalysts, which can reduce the consumption of residual active metal ions (such as sodium ions, lithium ions, etc.) in the battery cell system to a certain extent, thereby improving the cycle life of the battery. Compared to single-atom transition metal oxide catalysts, it can improve the decomposition efficiency of irreversible additives in the positive electrode. Compared to single transition metal oxides, it achieves a higher catalytic effect with a smaller amount of additive, thereby improving the first-cycle specific capacity of the battery. Compared to single metal oxides, bimetallic oxides have better electronic conductivity. When applied to batteries, they can improve the overall electronic conductivity on the positive electrode side, and the rate performance of the battery is also significantly improved.

[0097] In some embodiments of the present application, the catalyst includes at least one of CoFe2O4, ZnFe2O4, MnFe2O4, ZnMn2O4, CoMn2O4 or MnCo2O4. Thus, the above-mentioned double metal oxide has a spinel structure, and its structural stability is significantly improved compared with that of single-metal transition metal oxide catalysts, which can reduce the consumption of active metal ions (such as sodium ions, lithium ions, etc.) in the residual relative to the battery cell system to a certain extent, thereby improving the cycle life of the battery; compared with single-atom transition metal oxide catalysts, it can improve the decomposition efficiency of irreversible additives in the positive electrode. Compared with single transition metal oxides, higher catalytic effects can be achieved with less dosage, thereby increasing the first-cycle specific capacity of the battery; compared with single metal oxides, the double metal oxide has better electronic conductivity. When applied to the battery, it can improve the electronic conductivity of the positive electrode side as a whole, and the rate performance of the battery is also significantly improved.

[0098] In some embodiments of the present application, the active metal ion supplement includes a lithium supplement or a sodium supplement. The lithium supplement is used for lithium secondary batteries, and the sodium supplement is used for sodium secondary batteries. By using the above-mentioned active metal ion supplement in combination with the catalyst AM2O4, the first-cycle charge specific capacity, cycle life and rate performance of the battery can be improved.

[0099] In some embodiments of the present 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 be fully decomposed during battery charge and discharge, improving the first-cycle charge specific capacity and cycle life of the battery.

[0100] 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.

[0101] It can be understood that the values of x, a, b, c and d should satisfy charge balance. And it can be understood that Q x C a O b H c N d is the general formula of the chemical formula, including organic and inorganic substances. Whether it is an organic or inorganic substance, as long as its chemical formula conforms to the general formula of the present application, it falls within the scope of the present application.

[0102] 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 a sodium supplement. When added to the irreversible additive of the positive electrode, the sodium supplement has a low decomposition potential. When combined with the catalyst AM2O4, it can improve the decomposition efficiency of the sodium supplement. A higher catalytic effect can be achieved with a smaller amount of catalyst, thereby improving the first-cycle specific capacity of the battery. It can also improve the overall electronic conductivity of the positive electrode side, and the rate performance and cycle performance of the battery are also significantly improved.

[0103] 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 12 At 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, it has a low decomposition potential. When combined with the catalyst AM2O4, it can improve the decomposition efficiency of the lithium supplement agent. It can achieve a higher catalytic effect with a smaller amount of catalyst, thereby improving the specific capacity of the battery in the first cycle. It can also improve the electronic conductivity of the positive electrode side as a whole, and the rate performance and cycle performance of the battery are also significantly improved.

[0104] In a second aspect of this application, this application proposes a positive electrode irreversible additive, which includes an active metal ion supplement and a catalyst, wherein the catalyst includes AM2O4; wherein A includes a metal element with a +2 valence, M includes a metal element with a +3 valence, and A and M are different.

[0105] The secondary battery in this application embodiment includes an irreversible positive electrode additive, which uses a catalyst AM2O4. A comprises a metal element with a +2 valence, and M comprises a metal element with a +3 valence, and A and M are different. Compared to single-atom transition metal oxide catalysts, the dual transition metal atoms in AM2O4 increase the interaction sites with O atoms in the irreversible positive electrode additive, thereby improving the decomposition efficiency of the irreversible positive electrode additive. Compared to single transition metal oxides, a higher catalytic effect is achieved with a smaller dosage, thus increasing the initial specific capacity of the battery.

[0106] 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.

[0107] In a third aspect of this application, a method for preparing an irreversible additive for a positive electrode is proposed, comprising:

[0108] S1. Prepare an irreversible positive electrode additive comprising an active metal ion supplement and a catalyst, wherein the catalyst comprises AM2O4;

[0109] Wherein, A includes metallic elements with a oxidation state of +2, and M includes metallic elements with a oxidation state of +3, and A and M are different.

[0110] This results in batteries containing the irreversible positive electrode additive obtained by this method having excellent first-charge capacity.

[0111] In some embodiments of this application, step S1 includes:

[0112] S11. Dissolve the active metal ion supplement in water, add the catalyst, and spray dry to obtain the positive electrode irreversible additive.

[0113] Specifically, an active metal ion supplement is dissolved in water to prepare a homogeneous solution, and then an insoluble bimetallic oxide, AM2O4, is added to it. During the spray drying process, the porous properties of the bimetallic oxide and the interaction between the transition metal and the active metal ion supplement are utilized to promote the growth of the metal ion supplement on the surface and / or in the pores of the bimetallic oxide, thus creating an irreversible additive for the positive electrode.

[0114] In some embodiments of this application, the catalyst is prepared by the following method:

[0115] S101. Dissolve soluble A salt and soluble M salt in a solvent, add additives, perform a solvothermal reaction, and dry to obtain a catalyst.

[0116] Specifically, the bimetallic catalyst AM2O4 is prepared using the aforementioned solvothermal method, which is conducive to the formation of spherical or spheroidal catalysts. The catalyst is loose and porous (e.g., sea urchin-like) with a large specific surface area. During the spray drying process for preparing the irreversible additive for the positive electrode, it promotes the growth of metal ion supplements on the surface and / or in the pores of the bimetallic oxide to become irreversible additives for the positive electrode. This further increases the contact area between the active metal ion supplements and the catalyst, thereby improving the decomposition efficiency of the irreversible additive for the positive electrode and thus increasing the first-cycle specific capacity of the battery.

[0117] In some embodiments of this application, the solvent includes at least one of ethyl acetate, ethylene glycol, or triethanolamine. The solvent can dissolve soluble A salt and soluble M salt, and facilitates the formation of bimetallic oxides during solvothermal reactions.

[0118] In some embodiments of this application, the additive includes at least one of urea or CH3COOK. After the additive is used, it is beneficial to generate spherical or near-spherical bimetallic oxides and increase the specific surface area of ​​the generated bimetallic oxides.

[0119] The temperature of the solvothermal reaction is 150℃-250℃, for example, it can be 150℃-249℃, 170℃-240℃, 190℃-230℃, 200℃-220℃, etc. Controlling the temperature of the solvothermal reaction within the above range is beneficial to generating spherical or near-spherical bimetallic oxides and increasing the specific surface area of ​​the generated bimetallic oxides.

[0120] The solvothermal reaction time is 10h-50h. For example, it can be 10h-49h, 20h-40h, 30h-35h, etc. Controlling the solvothermal reaction time within the above range facilitates the full reaction of soluble A salt and soluble M salt to generate spherical or near-spherical bimetallic oxides, thereby increasing the specific surface area of ​​the generated bimetallic oxides.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.).

[0125] 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.

[0126] 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 0.1O2 (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.

[0127] 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.

[0128] 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.

[0129] 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 effect 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 the active metal ion supplement, replenishing active lithium ions, thereby improving the battery's initial charge capacity.

[0130] 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 the active metal ion supplement, replenishing active lithium ions, thereby improving the battery's initial charge capacity.

[0131] In some embodiments of this application, 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.

[0132] 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.

[0133] In some embodiments of this application, 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.

[0134] In some embodiments of this application, the polyanionic compound may be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. 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.

[0135] In some embodiments of this application, the polyanionic compound may also be a sodium ion, transition metal ion, or tetrahedral (YO4) compound. 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.

[0136] In some embodiments of this application, 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.

[0137] 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).

[0138] In some embodiments of this application, Prussian blue compounds may be compounds containing 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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 specific capacity, cycle life, and rate performance.

[0143] 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 and replenish active sodium ions, thereby improving the battery's first charge capacity, cycle life, and rate performance.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.).

[0150] 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.

[0151] 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).

[0152] 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.

[0153] 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)).

[0154] 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.

[0155] 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.

[0156] In some embodiments of this application, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] In some embodiments of this application, the positive electrode, the negative electrode, and the separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0165] 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.

[0166] 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.

[0167] It is understood that the secondary battery mentioned above in this application is a single battery cell.

[0168] 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 1 shows a square battery cell 1 as an example.

[0169] In some embodiments of this application, referring to FIG2, 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 cover 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 the battery cell 1 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0170] 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.

[0171] Figure 3 shows a battery module 2 as an example. Referring to Figure 3, 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 manner. Furthermore, these multiple battery cells 1 can be fixed in place using fasteners.

[0172] Optionally, the battery module 2 may also include a housing with a receiving space in which multiple battery cells 1 are received.

[0173] 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.

[0174] Figures 4 and 5 show an example battery pack 3. Referring to Figures 4 and 5, the 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.

[0175] In addition, this application also provides an electrical device, which includes the secondary battery provided in the first aspect of this application. 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.

[0176] As the electrical equipment, battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0177] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. 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.

[0178] 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.

[0179] 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.

[0180] Example 1

[0181] Preparation of irreversible additives for the positive electrode:

[0182] Preparation of CoFe₂O₄ catalyst: 1.0 mmol Co(CH₃COO)₂·4H₂O, 2.0 mmol FeCl₃·6H₂O, and 1.2 mmol CH₃COOK·3H₂O were added to a mixed solution of 4.0 mL ethyl acetate and 50 mL ethylene glycol, and sonicated until completely dissolved and dispersed. The dispersion was then added to a high-pressure reactor and heated at 200 °C for 20 hours, followed by natural cooling to room temperature. The precipitate was collected by centrifugation, washed with distilled water and anhydrous ethanol, and dried under vacuum at 80 °C for 8 hours to obtain CoFe₂O₄ nanoparticles. The obtained particles had a Dv₅₀ diameter of approximately 400 nm and a specific surface area of ​​123 m². 2 / g, electronic conductivity is 2.5×10 -2 S·cm -1 .

[0183] Sodium oxalate (Na₂C₂O₄), an active metal ion supplement, was dissolved in deionized water to prepare a 30% wt aqueous solution. Then, CoFe₂O₄ catalyst was added to the aqueous solution at a mass ratio of catalyst to active metal ion supplement of 1:20, and the mixture was stirred to form a homogeneous suspension. Spray drying yielded an irreversible positive electrode additive, in which sodium oxalate was embedded in the pores of CoFe₂O₄ and coated on its surface.

[0184] 1. Preparation of positive electrode sheet

[0185] NaFe, the positive electrode active material 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, the above-prepared irreversible positive electrode additive, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in a weight ratio of 90:5:2.5:2.5. Then, N-methylpyrrolidone solvent is added, and a positive electrode slurry is obtained under the action of a vacuum stirrer. The slurry is then mixed evenly, and then coated, cold-pressed, and slit on a current collector to obtain the positive electrode sheet.

[0186] 2. Preparation of negative electrode sheet

[0187] Hard carbon (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were dispersed 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 .

[0188] 3. Preparation of electrolyte

[0189] 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.

[0190] 4. Separating membrane

[0191] Polypropylene film is used as the separator.

[0192] 5. Preparation of secondary batteries

[0193] 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.

[0194] Example 2

[0195] This is essentially the same as Example 1, except that the active metal ion supplement sodium oxalate (Na2C2O4) is replaced with sodium squartzate (Na2C4O4).

[0196] Example 3

[0197] Preparation of irreversible additives for the positive electrode:

[0198] Preparation of ZnFe₂O₄ nanoparticles: 2.0 mmol FeCl₃·6H₂O and 1.0 mmol ZnCl₂ were added to 20.0 mL of ethylene glycol and sonicated until completely dissolved and dispersed. Then, 10.0 mmol urea was added, and stirring was continued for 30 min. The mixture was then transferred to a high-pressure reactor and heated at 200 °C for 48 hours, followed by natural cooling to room temperature. The precipitate was collected by centrifugation, washed with distilled water and anhydrous ethanol, and dried under vacuum at 60 °C for 8 hours to obtain ZnFe₂O₄ nanoparticles. The particle size distribution (Dv₅₀) is approximately 500 nm; the electronic conductivity is 6.9 × 10⁻⁶. -3 S·cm -1 .

[0199] Sodium oxalate (Na₂C₂O₄), an active metal ion supplement, was dissolved in deionized water to prepare a 30% wt aqueous solution. Then, ZnFe₂O₄ catalyst was added to the aqueous solution at a mass ratio of catalyst to active metal ion supplement of 1:20, and the mixture was stirred to form a homogeneous suspension. Spray drying yielded an irreversible positive electrode additive, in which sodium oxalate was embedded in the pores of ZnFe₂O₄ and coated on its surface.

[0200] The remaining preparation steps are the same as in Example 1.

[0201] Example 4

[0202] Preparation of the catalyst MnFe2O4: 1.0 mmol MnCl2·4H2O and 2.0 mmol FeCl3·6H2O were added to 20.0 mL of ethylene glycol and sonicated until completely dissolved and dispersed. Then, 30.0 mmol urea was added, and stirring was continued for 30 min. The mixture was then added to a high-pressure reactor and heated at 200 °C for 20 h, followed by natural cooling to room temperature. The precipitate was collected by centrifugation, washed with distilled water and anhydrous ethanol, and dried under vacuum at 60 °C for 8 h to obtain ZnFe2O4 nanoparticles. The particle size distribution (Dv50) was approximately 400 nm; the electronic conductivity was 4.1 × 10⁻⁶. -3 S·cm -1 .

[0203] Sodium oxalate (Na₂C₂O₄), an active metal ion supplement, was dissolved in deionized water to prepare a 30% wt aqueous solution. Then, MnFe₂O₄ catalyst was added to the aqueous solution at a mass ratio of catalyst to active metal ion supplement of 1:20, and the mixture was stirred to form a homogeneous suspension. Spray drying yielded an irreversible positive electrode additive, in which sodium oxalate was embedded in the pores of MnFe₂O₄ and coated on its surface.

[0204] The remaining preparation steps are the same as in Example 1.

[0205] Example 5

[0206] Preparation of CoMn₂O₄ catalyst: 2.0 mmol MnCl₂·4H₂O and 1.0 mmol CoCl₂·6H₂O were added to 20.0 mL of ethylene glycol and sonicated until completely dissolved and dispersed. Then, 30.0 mmol urea was added, and stirring was continued for 30 min. The mixture was then added to a high-pressure reactor and heated at 200 °C for 20 h, followed by natural cooling to room temperature. The precipitate was collected by centrifugation, washed with distilled water and anhydrous ethanol, and dried under vacuum at 60 °C for 8 h to obtain ZnFe₂O₄ nanoparticles. The particle size distribution (Dv₅₀) was approximately 300 nm; the electronic conductivity was 1.2 × 10⁻⁶. -3 S·cm -1 .

[0207] Sodium oxalate (Na₂C₂O₄), an active metal ion supplement, was dissolved in deionized water to prepare a 30% wt aqueous solution. Then, CoMn₂O₄ catalyst was added to the aqueous solution at a mass ratio of catalyst to active metal ion supplement of 1:20, and the mixture was stirred to form a homogeneous suspension. Spray drying yielded an irreversible positive electrode additive, in which sodium oxalate was embedded in the pores of CoMn₂O₄ and coated on its surface.

[0208] The remaining preparation steps are the same as in Example 1.

[0209] The preparation methods of sodium-ion batteries in Examples 2-12 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.

[0210] In Comparative Example 1, no irreversible additives were prepared or added to the positive electrode, while in Comparative Example 2, Co3O4 was used as a catalyst.

[0211] Table 1

[0212] Example 13

[0213] The preparation method of the irreversible additive for the positive electrode is the same as in Example 1, except that sodium oxalate is replaced with lithium oxalate.

[0214] 1. Preparation of positive electrode sheet

[0215] 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. Then, N-methylpyrrolidone solvent is added, and a negative electrode slurry is obtained under the action of a vacuum stirrer. The slurry is then mixed evenly, coated on a current collector, cold-pressed, and slit to obtain the positive electrode sheet.

[0216] 2. Preparation of negative electrode sheet

[0217] Hard carbon (negative electrode active material), carbon black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were dispersed 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 .

[0218] 3. Preparation of electrolyte

[0219] 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.

[0220] 4. Separating membrane

[0221] Polypropylene film is used as the separator.

[0222] 5. Preparation of secondary batteries

[0223] 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.

[0224] The preparation methods of the lithium-ion batteries in Examples 14-21 and Comparative Examples 3-4 are the same as those in Example 13, except that the process of preparing the irreversible positive electrode additive is different. Specifically, the preparation method of the irreversible positive electrode additive in Example 15 is the same as that in Example 3, except that sodium oxalate is replaced with lithium oxalate; the preparation method of the irreversible positive electrode additive in Example 16 is the same as that in Example 4, except that sodium oxalate is replaced with lithium oxalate; the preparation method of the irreversible positive electrode additive in Example 17 is the same as that in Example 5, except that sodium oxalate is replaced with lithium oxalate. The details are shown in Table 2.

[0225] In Comparative Example 3, no irreversible additives were prepared or added to the positive electrode, while in Comparative Example 4, Co3O4 was used as a catalyst.

[0226] Table 2

[0227] A scanning electron microscope image of the catalyst prepared in Example 1 was obtained, as shown in Figure 7. It can be seen that the catalyst prepared in Example 1 of this application is spherical with a Dv50 particle size of about 400 nm. The surface of the catalyst has channels that extend into the interior of the catalyst, giving it a loose and porous structure and a large specific surface area.

[0228] The scanning electron microscope image of the irreversible positive electrode additive prepared in Example 1 is shown in Figure 8. It can be seen that the morphology of the irreversible positive electrode additive prepared in Example 1 is spherical.

[0229] The irreversible positive electrode additive prepared in Example 1 was subjected to transmission electron microscopy (TEM) to obtain Figure 9. The cross-section of the particles was tested by ion polishing to determine the distribution of Na element in the composite sodium supplement, which was obtained in Figure 10. It can be seen that Na element is more distributed on the catalyst surface than in the middle part of the spherical particles, indicating that the sodium supplement not only enters the pores of the catalyst, but also coats the catalyst surface more extensively.

[0230] The specific capacity, cycle performance and rate performance of the batteries in Examples 1-12 and Comparative Examples 1-2 were characterized, and the characterization results are shown in Table 3.

[0231] 1. Battery first-cycle formation test:

[0232] Charge the capacitor at 0.1C constant current to 4.0V at 45℃, then charge it at a constant voltage of 4.0V to a current of 0.05C, let it rest for 5 minutes, and then discharge it at 1 / 3C to 1.5V at 25℃. The resulting capacity is recorded as the initial capacity D0.

[0233] 2. Battery capacity retention test

[0234] 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 4.0V with a constant current of 1 / 3C, then charged to a current of 0.05C with a constant voltage of 4.0V, 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 300 points P1, P2...P100 as the vertical axis and the corresponding number of cycles as the horizontal axis, a curve of battery capacity retention rate versus number of cycles corresponding to the lithium manganese oxide positive electrode active material of Example 1 is obtained.

[0235] During this test, the first cycle corresponds to n=1, the second cycle to n=2, ..., the 100th cycle to n=300. The battery capacity retention rate data corresponding to Example 1 in Table 1 is the data measured after 300 cycles under the above test conditions, i.e., the value of P300. The test process for the comparative example and other examples is the same as above.

[0236] 3. Battery rate performance test:

[0237] Taking Example 1 as an example, the battery rate test process is as follows: At 25°C, the battery corresponding to Example 1 is charged to 4.0V with a constant current of 1C, then charged to 0.05C with a constant voltage of 4.0V, left to stand for 5 minutes, and then discharged to 1.5V with 1C. The resulting discharge capacity is recorded as the discharge capacity at the 1C rate. The discharge capacity at the 1C rate can be calculated, and the results are shown in Table 3.

[0238] Table 3

[0239] As shown in Table 3, the batteries of Examples 1-12 exhibited higher initial charge capacity at a test voltage limit of 4.0V. This indicates that the addition of bimetallic catalysis improved the oxidative decomposition kinetics of the sodium supplement and reduced its decomposition potential. Furthermore, the initial charge capacity, capacity retention after 300 cycles, and 1C discharge capacity of the batteries of Examples 1-12 were significantly higher than those of Comparative Examples 1-2. This demonstrates that by adding the irreversible positive electrode additive of this application, not only can the initial charge capacity of the battery containing it be improved, but also the cycle life and rate performance of the battery can be enhanced.

[0240] The specific capacity, cycle performance and rate performance of the batteries in Examples 13-21 and Comparative Examples 3-4 were characterized, and the characterization results are shown in Table 4.

[0241] 1. Battery capacity test during the first charge cycle:

[0242] Charge the capacitor at 0.1C constant current at 45℃ to 3.9V, then charge it at a constant voltage of 3.65V to a current of 0.05C, let it rest for 5 minutes, and then discharge it at 1 / 3C to 2.5V at 25℃. The resulting capacity is recorded as the initial capacity D0.

[0243] 2. Battery capacity retention test

[0244] 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 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left to rest for 5 minutes, and then discharged to 2.5V at 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 using the 500 points P1, P2...P500 as the vertical axis and the corresponding number of cycles as the horizontal axis.

[0245] 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.

[0246] 3. Battery rate performance test:

[0247] Taking Example 13 as an example, the battery rate test process is as follows: At 25°C, the battery corresponding to Example 1 is charged to 3.65V with a constant current of 1C, then charged to 0.05C with a constant voltage of 3.65V, left to stand for 5 minutes, and then discharged to 2.5V with 1C. The resulting discharge capacity is recorded as the discharge capacity at the 1C rate. The discharge capacity at the 1C rate can be calculated, and the results are shown in Table 4.

[0248] Table 4

[0249] As shown in Table 4, the batteries of Examples 13-21 exhibited higher first-cycle charge specific capacity at a test voltage limit of 3.9V. This indicates that the addition of bimetallic catalysis improved the oxidative decomposition kinetics of the lithium replenishment agent and reduced its decomposition potential. Furthermore, the first-cycle charge specific capacity, capacity retention after 500 cycles, and 1C discharge specific capacity of the batteries of Examples 13-21 were significantly higher than those of Comparative Examples 3-4. This demonstrates that by adding the irreversible positive electrode additive of this application, not only can the first-cycle charge specific capacity of the battery containing it be improved, but also the cycle life and rate performance of the battery can be enhanced.

[0250] 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, cycle life, and rate performance of the battery containing it.

[0251] 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, wherein, The secondary battery includes a positive electrode sheet, the positive electrode sheet includes a positive active material and a positive irreversible additive, the positive irreversible additive includes an active metal ion supplement and a catalyst, the catalyst includes AM2O4; Wherein, A includes metallic elements with a oxidation state of +2, and M includes metallic elements with a oxidation state of +3, and A and M are different.

2. The secondary battery according to claim 1, wherein, The mass ratio of the catalyst to the active metal ion supplement is 1:(5-50).

3. The secondary battery according to claim 1 or 2, wherein, The catalyst is spherical or near-spherical.

4. The secondary battery according to any one of claims 1-3, wherein, The catalyst has at least a portion of its surface with channels extending into the interior of the catalyst, and at least a portion of the active metal ion supplement is located within the channels.

5. The secondary battery according to any one of claims 1-4, wherein, The active metal ion supplement is formed on at least a portion of the surface of the catalyst.

6. The secondary battery according to any one of claims 1-5, wherein, The irreversible additive for the positive electrode is spherical or near-spherical.

7. The secondary battery according to any one of claims 1-6, wherein, The catalyst has a volume average particle size Dv50 of 0.2 μm-4 μm.

8. The secondary battery according to any one of claims 1-7, wherein, The catalyst has a volume average particle size Dv50 of 0.3 μm-1 μm.

9. The secondary battery according to any one of claims 1-8, wherein, The catalyst has a BET specific surface area of ​​50 m². 2 / g-200m 2 / g.

10. The secondary battery according to any one of claims 1-9, wherein, The catalyst has an electronic conductivity of 1.0 × 10⁻⁶. -4 S·cm -1 -3.0S·cm -1 .

11. The secondary battery according to any one of claims 1-10, wherein, The catalyst has an electronic conductivity of 2.0 × 10⁻⁶. -3 S·cm -1 -0.5S·cm -1 .

12. The secondary battery according to any one of claims 1-11, wherein, At least one of the following conditions must be met: A includes at least one of Mg, Co, Zn, Fe, Ni, Mn, or Cd; B includes at least one of Fe, Co, or Mn.

13. The secondary battery according to claim 12, wherein, The catalyst includes at least one of CoFe2O4, ZnFe2O4, MnFe2O4, ZnMn2O4, CoMn2O4, or MnCo2O4.

14. The secondary battery according to any one of claims 1-13, wherein, The active metal ion supplement includes lithium supplements or sodium supplements.

15. The secondary battery according to any one of claims 1-14, wherein, 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。 16. The secondary battery according to any one of claims 1-15, wherein, 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.

17. The secondary battery according to any one of claims 1-16, wherein, 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.

18. The secondary battery according to any one of claims 1-17, wherein, 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.

19. A positive electrode irreversible additive, wherein, The positive electrode irreversible additive includes an active metal ion supplement and a catalyst, wherein the catalyst includes AM2O4; Wherein, A includes metallic elements with a oxidation state of +2, and M includes metallic elements with a oxidation state of +3, and A and M are different.

20. The irreversible positive electrode additive according to claim 19, wherein, The mass ratio of the catalyst to the active metal ion supplement is 1:(5-50).

21. The irreversible positive electrode additive according to claim 19 or 20, wherein, At least one of the following conditions must be met: The catalyst is spherical or near-spherical; The surface of the catalyst has channels extending into the interior of the catalyst, and at least a portion of the active metal ion supplement is located within the channels; The active metal ion supplement is formed on at least a portion of the surface of the catalyst.

22. The irreversible positive electrode additive according to any one of claims 19-21, wherein, The catalyst has a volume average particle size Dv50 of 0.2 μm-4 μm.

23. The irreversible positive electrode additive according to any one of claims 19-22, wherein, The catalyst has a BET specific surface area of ​​50 m². 2 / g-200m 2 / g.

24. The irreversible positive electrode additive according to any one of claims 19-23, wherein, The catalyst has an electronic conductivity of 1.0 × 10⁻⁶. -4 S·cm -1 -3.0S·cm -1 .

25. The irreversible positive electrode additive according to any one of claims 19-24, wherein, At least one of the following conditions must be met: A includes at least one of Mg, Co, Zn, Fe, Ni, Mn, or Cd; B includes at least one of Fe, Co, or Mn.

26. The irreversible positive electrode additive according to claim 25, wherein, The catalyst includes at least one of CoFe2O4, ZnFe2O4, MnFe2O4, ZnMn2O4, CoMn2O4, or MnCo2O4.

27. The irreversible positive electrode additive according to any one of claims 19-26, wherein, The active metal ion supplement includes lithium supplements or sodium supplements.

28. The irreversible positive electrode additive according to any one of claims 19-27, wherein, 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。 29. The irreversible positive electrode additive according to any one of claims 19-28, wherein, 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.

30. A method for preparing an irreversible additive for a positive electrode, wherein, include: An irreversible positive electrode additive comprising an active metal ion supplement and a catalyst, wherein the catalyst comprises AM2O4; Wherein, A includes metallic elements with a oxidation state of +2, and M includes metallic elements with a oxidation state of +3, and A and M are different.

31. The method according to claim 30, wherein, include: The active metal ion supplement is dissolved in water, a catalyst is added, and the mixture is spray-dried to obtain an irreversible additive for the positive electrode.

32. The method according to claim 30 or 31, wherein, The catalyst is prepared by the following method: Soluble salts A and M are dissolved in a solvent, additives are added, a solvothermal reaction is carried out, and the mixture is dried to obtain a catalyst.

33. The method according to claim 32, wherein, At least one of the following conditions must be met: The solvent includes at least one of ethyl acetate, ethylene glycol, or triethanolamine; The additive includes at least one of urea or CH3COOK; The temperature of the solvothermal reaction is 150℃-250℃; The solvothermal reaction time is 10h-50h.

34. An electrical appliance, wherein, The secondary battery includes any one of claims 1-18.

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