High-safety long-circulation layered oxide positive electrode material and preparation method thereof
By coating bismuth-containing compounds onto layered oxide cathode materials, the structural instability of sodium-ion batteries during charging and discharging is solved, improving thermal safety and cycle life, and achieving higher thermal stability and interface stability.
Patent Information
- Application Number
- CN202511635425.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-10
- Publication Date
- 2026-03-03
AI Technical Summary
Layered sodium-ion transition metal oxides exhibit unstable structural phase transitions during charge and discharge, resulting in an unstable electrode/electrolyte interface and poor thermal stability. This leads to a low thermal decomposition temperature, affecting the safety and cycle life of sodium-ion batteries.
By using bismuth-containing compounds to coat and modify layered oxide cathode materials, the strong affinity of Bi3+ inhibits the migration of reactive oxygen species, forms a stable interface, reduces oxygen release, and improves thermal safety and structural stability.
It effectively suppressed oxygen release, enhanced the thermal safety and structural stability of the material, and improved the cycle performance of sodium-ion batteries.
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Figure CN121601616A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a high-safety, long-cycle layered oxide cathode material and its preparation method. Background Technology
[0002] Sodium-ion batteries, due to the abundance of sodium on Earth, low cost, and unique battery safety characteristics, are important candidates for future large-scale energy storage systems such as wind and solar power. Therefore, high demands are placed on the battery's cycle life, power characteristics, and the manufacturing performance of its materials. Although layered sodium-ion transition metal oxides have high volumetric energy density, their poor reversibility of phase transitions during charge and discharge, instability at the electrode / electrolyte interface, and poor thermal stability severely hinder their commercial application.
[0003] Especially at high cutoff voltages, transition metals (TM) are oxidized to high valence states, which reduces the stability of the TM-O bond. Simultaneously, lattice oxygen, acting as redox centers, participates in charge compensation, leading to its oxidation. The oxidized lattice oxygen becomes less stable and more susceptible to temperature-induced degradation, further lowering the material's thermal decomposition temperature. To achieve the industrial application of layered oxides, it is necessary to further improve their thermal stability, reduce energy release during thermal decomposition, and ensure the safety of sodium-ion batteries.
[0004] To address the aforementioned problems, this invention employs bismuth-containing compounds to coat and modify layered oxide cathode materials; because Bi... 3+ It has a strong affinity for oxygen, and its structure can tolerate a certain number of oxygen vacancies. The bismuth-containing compound coating can suppress active oxygen species migrating from the core of the layered oxide, while forming a more stable interface, inhibiting the release of oxygen into the electrolyte, and improving thermal safety and structural stability. Summary of the Invention
[0005] Existing technologies using inert oxide coatings only isolate the cathode material from the electrolyte, failing to fundamentally address the issue of decreased thermal stability caused by reactive oxygen species release during the reaction. This invention provides a high-safety, long-cycle layered oxide cathode material and its preparation method. By adding a bismuth-containing compound during the secondary calcination process, the bismuth-containing compound coating layer suppresses reactive oxygen species migrating from the layered oxide core, while simultaneously forming a more stable interface, inhibiting oxygen release into the electrolyte and improving thermal safety and structural stability.
[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a method for preparing a high-safety, long-cycle layered oxide cathode material, comprising the following steps: S1. Nickel, iron, manganese, and sodium sources are ball-milled and mixed, then sintered at high temperature. After pulverization and sieving, Na is obtained. w Ni x Fe y Mn z O2 material, where 0.9 < w < 1.1, 0.4 < x < 0.1, 0.4 < y < 0.1, 0.4 < z < 0.1; S2. Put Na w Ni x Fe y Mn z O2 material and bismuth-containing compound are ball-milled and mixed, sintered at high temperature, and then crushed and sieved to obtain layered oxide cathode material.
[0007] Furthermore, the nickel source mentioned in step S1 is at least one of nickel oxide and nickel hydroxide.
[0008] Further, the iron source mentioned in step S1 is at least one of iron oxide, ferric oxide, and ferrous sulfate.
[0009] Furthermore, the manganese source mentioned in step S1 is at least one of manganese tetroxide and manganese dioxide.
[0010] Furthermore, the sodium source mentioned in step S1 is at least one of sodium carbonate and sodium bicarbonate.
[0011] Furthermore, in step S1, the high-temperature sintering temperature is 800–1000℃, and the holding time is 10–15 hours.
[0012] Further, the amount of bismuth-containing compound added in step S2 is 0.1% to 0.5% of the mass of material a.
[0013] Further, the bismuth-containing compound mentioned in step S2 is one or more of bismuth ferrite, bismuth titanate, sodium bismuth titanate, and bismuth oxide.
[0014] Furthermore, in step S2, the high-temperature sintering temperature is 500–800°C, and the holding time is 10–15 hours.
[0015] The second aspect of the present invention provides a high-safety, long-cycle layered oxide cathode material, which is obtained by the preparation method described in the first aspect above.
[0016] The beneficial effects of this invention are: This invention employs bismuth-containing compounds to coat and modify layered oxide cathode materials. Because Bi... 3+It has a strong affinity for oxygen, and its structure can tolerate a certain number of oxygen vacancies. The bismuth-containing compound coating can suppress active oxygen species migrating from the core of the layered oxide, while forming a more stable interface, inhibiting the release of oxygen into the electrolyte, and improving thermal safety and structural stability.
[0017] Specifically, the bismuth-containing compound layer can passivate corrosive substances (such as HF) present in the electrolyte and reduce CEI side reactions; the bismuth-containing coating layer can reduce lattice stress under high sodium desodium state and inhibit structural distortion and oxygen vacancy formation / migration; the bismuth-containing compound coating can inhibit oxygen evolution and surface reconstruction under high voltage and maintain the integrity of the layered structure. Attached Figure Description
[0018] The invention will now be further described with reference to the accompanying drawings.
[0019] Figure 1 These are in-situ differential electrochemical mass spectra of the cathode materials a, b1, b2, b3, and a1 obtained in Examples 1-3 and Comparative Example 1 of this invention; Figure 2 The Na prepared in Example 1 of this invention 1.01 Ni 0.33 Fe 0.33 Mn 0.33 Electron micrograph of O2@BFO; Figure 3 This is a comparison chart of the cycle performance of cathode material a and cathode material b1 prepared in Example 1 of the present invention; Figure 4 These are the XRD patterns of cathode material a and cathode material b1 prepared in Example 1 of this invention. Detailed Implementation
[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] Example
[0022] Example 1
[0023] S1. Weigh 1120g of nickel oxide, 960g of iron oxide, 900g of manganese tetroxide, and 1920g of battery-grade sodium carbonate, add them to a ball mill jar, mix them by high-speed ball milling, pour the mixture into a crucible, sinter it in an atmosphere furnace at 900℃ for 15 hours, and after natural cooling, remove and pulverize to obtain O3 phase cathode material: Na 1.01 Ni 0.33 Fe 0.33 Mn0.33 O2, denoted as material a; S2. Weigh 500g of material a and 1g of bismuth ferrite, ball mill and mix them, then sinter at a high temperature of 600℃ for 10 hours. After natural cooling, pulverize and sieve to obtain layered oxide cathode material: Na. 1.01 Ni 0.33 Fe 0.33 Mn 0.33 O2@BFO, denoted as material b1.
[0024] Example 2
[0025] The only difference compared to Example 1 is: S2. Weigh 500g of material a and 1g of bismuth titanate, ball mill and mix them, then sinter at a high temperature of 600℃ for 10 hours. After natural cooling, pulverize and sieve to obtain layered oxide cathode material: Na. 1.01 Ni 0.33 Fe 0.33 Mn 0.33 O2@BTO, denoted as material b2.
[0026] Example 3
[0027] The only difference compared to Example 1 is: S2. Weigh 500g of material a and 1g of sodium bismuth titanate, ball mill and mix them, then sinter at a high temperature of 600℃ for 10 hours. After natural cooling, pulverize and sieve to obtain the layered oxide cathode material: Na. 1.01 Ni 0.33 Fe 0.33 Mn 0.33 O2@NBTO, denoted as material b3.
[0028] Comparative Example
[0029] Comparative Example 1
[0030] The only difference compared to Example 1 is: S2. Weigh 500g of material a and 1g of alumina, ball mill them together, and then sinter them at a high temperature of 600℃ for 10 hours. After natural cooling, pulverize and sieve to obtain the layered oxide cathode material: Na. 1.01 Ni 0.33 Fe 0.33 Mn 0.33 O2@A, denoted as material a1.
[0031] Performance testing
[0032] The positive electrode materials a, b1, b2, b3, and a1 obtained in Examples 1-3 and Comparative Example 1 were respectively mixed with SP, PVDF, and CNT in a ratio of 96:0.9:2:1.1 to form electrode sheets, which were then used to fabricate pouch cells with hard carbon negative electrodes. In these cells, oxygen-free nitrile butadiene was used instead of carbonate solvent in the electrolyte. The amount of oxygen generated during each cycle was quantitatively detected using DEMS in-situ differential electrochemical mass spectrometry. The test results are shown below. Figure 1 As shown.
[0033] Depend on Figure 1 It can be seen that surface coating of material a can effectively reduce the generation of gas during circulation. Compared with inert alumina, the bismuth compound coating layer has a more obvious effect on gas suppression.
[0034] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a high-safety, long-cycle layered oxide cathode material, characterized in that, Includes the following steps: S1. Nickel, iron, manganese, and sodium sources are ball-milled and mixed, then sintered at high temperature. After pulverization and sieving, Na is obtained. w Ni x Fe y Mn z O2 material, where 0.9 < w < 1.1, 0.4 < x < 0.1, 0.4 < y < 0.1, 0.4 < z < 0.1; S2. Put Na w Ni x Fe y Mn z O2 material and bismuth-containing compound are ball-milled and mixed, sintered at high temperature, and then crushed and sieved to obtain layered oxide cathode material.
2. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, The nickel source mentioned in step S1 is at least one of nickel oxide and nickel hydroxide.
3. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, The iron source mentioned in step S1 is at least one of iron oxide, ferric oxide, and ferrous sulfate.
4. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, The manganese source mentioned in step S1 is at least one of manganese tetroxide and manganese dioxide.
5. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, The sodium source mentioned in step S1 is at least one of sodium carbonate and sodium bicarbonate.
6. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, In step S1, the high-temperature sintering temperature is 800–1000℃, and the holding time is 10–15 h.
7. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, The amount of bismuth-containing compound added in step S2 is 0.1% to 0.5% of the mass of material a.
8. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, The bismuth-containing compound mentioned in step S2 is one or more of bismuth ferrite, bismuth titanate, sodium bismuth titanate, and bismuth oxide.
9. The method for preparing a high-safety, long-cycle layered oxide cathode material according to claim 1, characterized in that, In step S2, the high-temperature sintering temperature is 500–800℃, and the holding time is 10–15 hours.
10. A high-safety, long-cycle layered oxide cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.