A p2 / o3 dual-phase composite structure battery cathode material and a preparation method and application thereof

Abstract

The application provides a battery positive electrode material with a P2 / O3 dual-phase composite structure, which comprises the following components in percentage by mass: 92-96% of an active substance, 2-4% of a conductive agent and 2-4% of a binder; the active substance is a layered material with a P2 / O3 dual-phase composite structure. The application also provides a preparation method of the battery positive electrode material with the P2 / O3 dual-phase composite structure and application thereof. By coating the outer surface of the O3 phase material with a proper amount of P2 phase material, the application can effectively solve the problem that the single-phase P2 type and O3 type materials cannot have high capacity and high rate at the same time. The battery positive electrode material with the P2 / O3 dual-phase composite structure is applied to a sodium ion battery, and has better rate capability, higher energy density and longer cycle life. The preparation method is simple, easy to operate, low in cost, short in preparation time and easy to realize large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and particularly relates to a battery cathode material with a P2 / O3 dual-phase composite structure, its preparation method and application. Background Technology

[0002] Sodium-ion batteries (SIBs) are considered a promising alternative to lithium-ion batteries (LIBs) in large-scale energy storage due to the abundance and uniform distribution of sodium resources. Among them, layered transition metal oxides (TLOs) have become a research focus due to their significant advantages such as high specific capacity, flexible composition, and convenient synthesis, including O3-type and P2-type LTOs. O3-type materials have abundant sodium content and high theoretical capacity; however, due to the high sodium migration energy barrier and complex phase transitions during charge and discharge, they typically exhibit poor rate capability and rapid capacity decay. P2-type materials possess rapid sodium-ion diffusion channels through triangular prism sites, exhibiting better rate performance; however, their low sodium content leads to low initial capacity, limiting their application in full cells. Furthermore, both P2-type and O3-type materials face irreversible phase evolution during deep deoxygenation, resulting in poor high-voltage cycling stability.

[0003] Currently, neither of the two aforementioned structural materials can meet the market demand for SIB cathode materials that combine high capacity and high speed performance due to their respective drawbacks. Although strategies such as element doping / substitution, coating, and microstructure design can be used to improve single-phase layered materials, it is still difficult to completely overcome the inherent shortcomings of single-phase structures. Summary of the Invention

[0004] This invention provides a battery cathode material with a P2 / O3 dual-phase composite structure, its preparation method, and its application. It aims to solve the problems faced by existing P2-type and O3-type materials during deep deoxygenation, such as irreversible phase evolution, poor high-voltage cycling stability, and inability to meet the market demand for SIB cathode materials with both high capacity and high speed performance.

[0005] To achieve the above objectives, in one aspect, embodiments of the present invention provide a battery cathode material with a P2 / O3 dual-phase composite structure, comprising the following components by mass percentage: 92%–96% active material, 2%–4% conductive agent, and 2%–4% binder; wherein the active material is a layered material having a P2 / O3 dual-phase composite structure.

[0006] As a preferred embodiment, the layered material having the P2 / O3 dual-phase composite structure is prepared by the following method:

[0007] S01. O3-NNMO, Mn(CH3COO)2 and CH3COONa are added to a solvent and mixed evenly to obtain a mixture; the solid content of the mixture is 40% to 60%;

[0008] S02. Add oxalic acid solution to the mixture from step S01, stir well, and obtain M. x (C2O4) precipitate mixture; wherein, M = Na and Mn;

[0009] S03, M from step S02 x The (C2O4) precipitate mixture was dried to obtain particulate matter; the particulate matter was then calcined in an oxygen atmosphere to obtain a layered material with a P2 / O3 dual-phase composite structure (i.e., a material with P2-NMO coated with O3-NNMO).

[0010] In a preferred embodiment, in step S01,

[0011] The molar ratio of O3-NNMO, Mn(CH3COO)2 and CH3COONa is 1:(0.02~0.4):(0.04~0.42), preferably 1:0.05:0.07;

[0012] The solvent is ethanol.

[0013] In a preferred embodiment, in step S02,

[0014] With the M x The mass percentage of the (C2O4) precipitate mixture is 10% to 40% based on 100% of the total mass.

[0015] The oxalic acid solution is a 0.2M oxalic acid ethanol solution.

[0016] The stirring time is ≥1 hour.

[0017] In a preferred embodiment, in step S03...

[0018] The drying process involves drying at 120°C for 10 hours.

[0019] The calcination temperature is 700℃~900℃, and the calcination time is 14h~16h.

[0020] In a preferred embodiment, the conductive agent is at least one of nano carbon black or micron graphite.

[0021] In a preferred embodiment, the adhesive is polyvinylidene fluoride.

[0022] On the other hand, embodiments of the present invention also provide a method for preparing the battery cathode material with the P2 / O3 dual-phase composite structure, comprising the following steps: adding 92% to 96% of active material, 2% to 4% of conductive agent and 2% to 4% of binder to NMP solvent, mixing evenly to obtain the battery cathode material with the P2 / O3 dual-phase composite structure; the percentages are mass percentages.

[0023] Based on the mass of the battery cathode material with the P2 / O3 dual-phase composite structure being 100%, the solid content of the battery cathode material with the P2 / O3 dual-phase composite structure is 52% to 56%.

[0024] Furthermore, embodiments of the present invention also provide the application of the battery cathode material with the P2 / O3 dual-phase composite structure, wherein the battery cathode material with the P2 / O3 dual-phase composite structure is applied in sodium-ion batteries.

[0025] Compared to existing technologies, the present application offers the following technical advantages: By coating an appropriate amount of P2 phase material onto the surface of the O3 phase material, the present invention effectively addresses the limitation that single-phase P2 and O3 materials cannot simultaneously achieve high capacity and high rate capability. Furthermore, the P2-NMO outer layer stabilizes the sodium ion diffusion path and structural transformation, thereby achieving high reversibility during Na delamination / intercalation. The vacancy-rich P2-NMO interface possesses a low diffusion barrier, promoting charge transfer between the O3-NNMO core layer (i.e., the inner layer) and its surface, effectively improving the electrochemical kinetics of the cycling process. Compared to existing sodium-ion batteries, the battery cathode material with the P2 / O3 dual-phase composite structure of this application, when used in sodium-ion batteries, exhibits better rate capability, higher energy density, and longer cycle life. The preparation method of this application is simple, convenient, low-cost, and quick, facilitating large-scale industrial production. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a layered material with a P2 / O3 dual-phase composite structure according to an embodiment of this application. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, top, bottom, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0030] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0031] It should be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0032] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0033] This application uses an O3 phase structure as the core to provide sufficient Na storage, while the P2 phase structure acts as a protective outer layer to limit structural changes, thus constructing a P2-Na... 2 / 3 O3-NaNi is uniformly coated with MnO2 (P2-NMO, outer layer). 0.5 Mn 0.5The O2 (O3-NNMO, inner layer) heterostructure material possesses a robust interface and rapid sodium ion diffusion channels, which effectively improves the surface stability and reversibility of the cathode and enhances the electrochemical kinetics during cycling, overcoming the inherent drawbacks of single-phase structures. Sodium-ion batteries fabricated using this material exhibit high energy density, excellent rate capability, and stable cycling performance.

[0034] Specifically, in one aspect, embodiments of the present invention provide a battery cathode material with a P2 / O3 dual-phase composite structure, comprising the following components by mass percentage: 92% to 96% (which may be 92%, 93%, 95%, 96%, etc., depending on actual use requirements) of active material, 2% to 4% (which may be 2%, 3%, 3.5%, 4%, etc., depending on actual use requirements) of conductive agent, and 2% to 4% (which may be 2%, 3%, 3.5%, 4%, etc., depending on actual use requirements) of binder; wherein the active material is a layered material having a P2 / O3 dual-phase composite structure.

[0035] As a preferred embodiment, the layered material having the P2 / O3 dual-phase composite structure is prepared by the following method:

[0036] S01. Add O3-NNMO, Mn(CH3COO)2 and CH3COONa to the solvent and mix evenly to obtain a mixture; the solid content of the mixture is 40% to 60% (it can be 40%, 53%, 55%, 60%, etc., depending on the actual needs of use).

[0037] S02. Add oxalic acid solution to the mixture from step S01, stir well, and obtain M. x (C2O4) precipitate mixture; wherein, M = Na and Mn;

[0038] S03, M from step S02 x The (C2O4) precipitate mixture was dried to obtain particulate matter; the particulate matter was then calcined in an oxygen atmosphere to obtain a layered material with a P2 / O3 dual-phase composite structure (i.e., a material with P2-NMO coated with O3-NNMO).

[0039] In a preferred embodiment, in step S01,

[0040] The molar ratio of O3-NNMO, Mn(CH3COO)2 and CH3COONa is 1:(0.02-0.4):(0.04-0.42); depending on actual needs, the molar ratio of O3-NNMO, Mn(CH3COO)2 and CH3COONa can be 1:0.02:0.04, or 1:0.4:0.42, or 1:0.2:0.3, or 1:0.15:0.4, etc., preferably 1:0.05:0.07;

[0041] By controlling the proportions of O3-NNMO, Mn(CH3COO)2, and CH3COONa, the content of the outer (protective) P2-NMO layer can be effectively controlled. Excessive P2-NMO content in the protective layer leads to a decrease in Ni content and the formation of a dense coating, thereby affecting reversible capacity and rate capability.

[0042] The solvent is ethanol.

[0043] In a preferred embodiment, in step S02,

[0044] With the M x The mass percentage of the (C2O4) precipitate mixture is 10% to 40% (depending on the actual needs, it can be 10%, 20%, 30%, 40%, etc.).

[0045] The oxalic acid solution is a 0.2M oxalic acid ethanol solution.

[0046] The stirring time is ≥1 hour.

[0047] In a preferred embodiment, in step S03...

[0048] The drying process involves drying at 120°C for 10 hours.

[0049] The calcination temperature is 700℃~900℃ (it can be 700℃, 750℃, 800℃, 900℃, etc., depending on the actual needs of use), and the calcination time is 14h~16h (it can be 14h, 14.5h, 15h, 16h, etc., depending on the actual needs of use).

[0050] In a preferred embodiment, the conductive agent is at least one of nano carbon black or micron graphite.

[0051] In a preferred embodiment, the adhesive is polyvinylidene fluoride.

[0052] On the other hand, embodiments of the present invention also provide a method for preparing the battery cathode material with the P2 / O3 dual-phase composite structure, comprising the following steps: adding 92% to 96% of active material, 2% to 4% of conductive agent and 2% to 4% of binder to NMP solvent, mixing evenly to obtain the battery cathode material with the P2 / O3 dual-phase composite structure; the percentages are mass percentages.

[0053] Based on the mass of the battery cathode material of the P2 / O3 dual-phase composite structure being 100%, the solid content of the battery cathode material of the P2 / O3 dual-phase composite structure is 52% to 56% (depending on the actual needs, it can be 52%, 53%, 55%, 56%, etc.).

[0054] The P2 / O3 dual-phase composite battery cathode material is coated onto an aluminum foil current collector and dried to obtain a cathode sheet. This cathode sheet can be used as a cathode sheet for sodium-ion batteries.

[0055] Example 1

[0056] A battery cathode material with a P2 / O3 dual-phase composite structure comprises the following components by mass percentage: 93% active material, 3.5% conductive agent and 3.5% binder; wherein the active material is a layered material having a P2 / O3 dual-phase composite structure.

[0057] The layered material with the P2 / O3 dual-phase composite structure was prepared by the following method:

[0058] S01. O3-NNMO, Mn(CH3COO)2 and CH3COONa are added to a solvent and mixed evenly to obtain a mixture; the solid content of the mixture is 50%;

[0059] S02. Add oxalic acid solution to the mixture from step S01, stir well, and obtain M. x (C2O4) precipitate mixture; wherein, M = Na and Mn;

[0060] S03, M from step S02 x The (C2O4) precipitate mixture was dried to obtain particulate matter; the particulate matter was then calcined in an oxygen atmosphere to obtain a layered material with a P2 / O3 dual-phase composite structure (i.e., 5% P2@O3).

[0061] In step S01,

[0062] The molar ratio of O3-NNMO, Mn(CH3COO)2 and CH3COONa is 1:0.05:0.07;

[0063] The solvent is ethanol.

[0064] In step S02,

[0065] With the M x The mass percentage of the (C2O4) precipitate mixture is 100%, and the mass percentage of the oxalic acid solution is 20%.

[0066] The oxalic acid solution is a 0.2M oxalic acid ethanol solution.

[0067] The stirring time is 1 hour.

[0068] In step S03,

[0069] The drying process involves drying at 120°C for 10 hours.

[0070] The calcination temperature is 800℃, and the calcination time is 15h.

[0071] The conductive agent is nano-carbon black.

[0072] The adhesive is polyvinylidene fluoride.

[0073] The preparation method of the battery cathode material with the P2 / O3 dual-phase composite structure includes the following steps: adding 93% active material, 3.5% conductive agent and 3.5% binder to NMP solvent, mixing them evenly to obtain the battery cathode material with the P2 / O3 dual-phase composite structure; the percentages are mass percentages.

[0074] Based on the mass of the battery cathode material with the P2 / O3 dual-phase composite structure being 100%, the solid content of the battery cathode material with the P2 / O3 dual-phase composite structure is 52%.

[0075] The P2 / O3 dual-phase composite battery cathode material is coated onto an aluminum foil current collector using a coating machine, and then dried in an oven to obtain a cathode sheet. This cathode sheet can be used as a cathode sheet for sodium-ion batteries.

[0076] Example 2

[0077] The scheme of Example 2 is the same as that of Example 1, except that the molar ratio of O3-NNMO, Mn(CH3COO)2 and CH3COONa is 1:0.02:0.04.

[0078] Example 3

[0079] The scheme of Example 3 is the same as that of Example 1, except that the molar ratio of O3-NNMO, Mn(CH3COO)2 and CH3COONa is 1:0.1:0.12.

[0080] Example 4

[0081] The scheme of Example 4 is the same as that of Example 1, except that the calcination temperature is 900℃ and the calcination time is 14h.

[0082] Comparative Example 1

[0083] A method for preparing P2-NMO:

[0084] S01. Add Mn(CH3COO)2 and CH3COONa to ethanol solvent in a molar ratio of 1:1, stir until homogeneous, and obtain a mixture; the solid content of the mixture is 50%;

[0085] S02. Add oxalic acid solution to the mixture from step S01, stir well, and obtain M. x (C2O4) precipitate mixture; wherein, M = Na and Mn;

[0086] S03, M from step S02 x The (C2O4) precipitate mixture was dried to obtain particulate matter; the particulate matter was then calcined in an oxygen atmosphere to obtain P2-NMO.

[0087] In step S02,

[0088] With the M x The mass percentage of the (C2O4) precipitate mixture is 100%, and the mass percentage of the oxalic acid solution is 20%.

[0089] The oxalic acid solution is a 0.2M oxalic acid ethanol solution.

[0090] The stirring time is 1 hour.

[0091] In step S03,

[0092] The drying process involves drying at 120°C for 10 hours.

[0093] The calcination temperature is 800℃, and the calcination time is 15h.

[0094] The preparation method of P2-NMO cathode material includes the following steps: adding 93% active material P2-NMO, 3.5% nano carbon black and 3.5% polyvinylidene fluoride to NMP solvent, mixing evenly to obtain P2-NMO cathode material; the percentages are mass percentages.

[0095] Based on the mass of the P2-NMO cathode material being 100%, the solid content of the P2-NMO cathode material is 52%.

[0096] The P2-NMO cathode material is coated onto an aluminum foil current collector using a coating machine, and then dried in an oven to obtain a cathode sheet. This cathode sheet can be used as a cathode sheet for sodium-ion batteries.

[0097] Comparative Example 2

[0098] The preparation method of O3-NNMO cathode material includes the following steps: adding 93% active material O3-NNMO, 3.5% nano carbon black and 3.5% polyvinylidene fluoride to NMP solvent, mixing evenly to obtain O3-NNMO cathode material; the percentages are mass percentages.

[0099] Based on the mass of the O3-NNMO cathode material being 100%, the solid content of the O3-NNMO cathode material is 52%.

[0100] The O3-NNMO cathode material is coated onto an aluminum foil current collector using a coating machine, and then dried in an oven to obtain a cathode sheet. This cathode sheet can be used as a cathode sheet for sodium-ion batteries.

[0101] Effect Example

[0102] The positive electrode sheets from Examples 1-4 and Comparative Examples 1-2 were used as positive electrode sheets for sodium-ion batteries, and the performance of each sodium-ion battery was examined. The results are shown in Table 1 below. As can be seen from Table 1, the positive electrode sheets from Examples 1-4 of this application, when applied to sodium-ion batteries, exhibit better rate capability, higher energy density, and longer cycle life.

[0103] Table 1 shows the performance test results of sodium batteries using the positive electrode sheets of Examples 1-4 and Comparative Examples 1-2 as positive electrode sheets.

[0104]

[0105] In the description of this specification, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0106] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a battery cathode material with a P2 / O3 dual-phase composite structure, characterized in that, The process includes the following steps: adding 92%–96% by mass of active material, 2%–4% by mass of conductive agent, and 2%–4% by mass of binder to NMP solvent, mixing thoroughly to obtain a battery cathode material with a P2 / O3 dual-phase composite structure; based on the mass of the battery cathode material with the P2 / O3 dual-phase composite structure being 100%, the solid content of the battery cathode material with the P2 / O3 dual-phase composite structure is 52%–56%; The active material is a layered material with a P2 / O3 dual-phase composite structure; the layered material with the P2 / O3 dual-phase composite structure is prepared by the following method: S01, O3-NaNi 0.5 Mn 0.5 O2, Mn(CH3COO)2, and CH3COONa are added to a solvent and mixed thoroughly to obtain a mixture; the solid content of the mixture is 40%–60%. S02. Add oxalic acid solution to the mixture from step S01, stir well, and obtain M. x (C2O4) precipitate mixture; where M = Na and Mn, and x is 1 to 2; S03, M from step S02 x The (C2O4) precipitate mixture was dried to obtain particulate matter; the particulate matter was calcined in an oxygen atmosphere to obtain a layered material with a P2 / O3 dual-phase composite structure. In step S01, the O3-NaNi 0.5 Mn 0.5 O2, the molar ratio of Mn(CH3COO)2 and CH3COONa is 1:(0.02~0.4):(0.04~0.42); In step S03, the calcination temperature is 700℃~900℃, and the calcination time is 14h~16h.

2. The method for preparing the battery cathode material with a P2 / O3 dual-phase composite structure according to claim 1, characterized in that, In step S01, The solvent is ethanol.

3. The method for preparing the battery cathode material with a P2 / O3 dual-phase composite structure according to claim 1, characterized in that, In step S02, the M x The mass percentage of the (C2O4) precipitate mixture is 10% to 40% based on 100% of the mass of the oxalic acid solution.

4. The method for preparing the battery cathode material with a P2 / O3 dual-phase composite structure according to claim 3, characterized in that, In step S02, the oxalic acid solution is a 0.2 M oxalic acid ethanol solution; The stirring time is ≥1 hour.

5. The method for preparing the battery cathode material with a P2 / O3 dual-phase composite structure according to claim 1, characterized in that, In step S03, the drying process involves drying at 120°C for 10 hours.

6. The method for preparing the battery cathode material with a P2 / O3 dual-phase composite structure according to claim 1, characterized in that, The conductive agent is at least one of nano carbon black or micron graphite.

7. The method for preparing the battery cathode material with a P2 / O3 dual-phase composite structure according to claim 1, characterized in that, The adhesive is polyvinylidene fluoride.

8. The application of the battery cathode material with a P2 / O3 dual-phase composite structure obtained by the preparation method according to any one of claims 1 to 7, characterized in that, The P2 / O3 dual-phase composite structure battery cathode material is used in sodium-ion batteries.

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