Li 5-x Na x FeO4@C composite positive electrode lithium supplementing material and preparation and application thereof

Abstract

The application relates to the field of positive electrode materials, and particularly discloses a Li 5‑x Na x FeO4@C composite positive electrode lithium supplementing material which has a core-shell structure, wherein the core is Li 5‑x Na x FeO4, the shell is amorphous carbon, and x is 0.01-0.15. The application further discloses a preparation method of the material and application of the material in lithium supplementing additives. The material has excellent lithium supplementing activity and air stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of energy storage devices, and particularly relates to a positive electrode lithium supplement material technical field. BACKGROUND

[0002] Li in Li-ion battery + All come from the positive electrode material, and the negative electrode generally adopts a graphite material. When the battery is charged for the first time, the negative electrode surface of the lithium ion battery will consume Li + to form a layer of SEI film, causing the initial capacity loss (ICL) problem, and the ICL of the lithium ion battery with a graphite negative electrode is about 7% to 10%. A high-capacity silicon negative electrode material is gradually applied to the lithium ion battery, but the ICL of the silicon negative electrode is as high as 50% to 70%. Therefore, it is of extremely important significance to develop a simple and efficient lithium supplement technology.

[0003] Li5FeO4 is a lithium-rich transition metal oxide with a reverse fluorite structure, has a very high specific capacity, which can reach 867 mAh / g, and has a very low first charge-discharge efficiency, can maximize the delithiation and supplement the ICL on the negative electrode, so Li5FeO4 has great application potential in the field of solving the ICL problem of the lithium ion battery. However, the sintering process conditions for preparing the conventional Li5FeO4 reported at present are harsh, the air stability is very poor, the large-current delithiation performance is poor, the synthesized Li5FeO4 has a large particle size and low electronic conductivity, which affects the electrochemical performance of Li5FeO4 and its application.

[0004] In view of the poor air stability and difficult performance of Li5FeO4, the existing technology reports some carbon-coated and Fe-hybridized methods, for example, the Chinese patent document with the publication number CN115000362A discloses a Li5Fe x M y O4@C composite material, which comprises a core and a carbon shell encapsulated on the surface thereof; the core is Li5Fe x M y O4, wherein x is 0.8 to 0.9, 3x+Ay=3; M is a transition metal element; and A is the valence state of M.

[0005] As described above, the existing technology can obtain good technical effects, but mainly lies in the doping modification of the Fe site, and the technical idea has a great homogenization problem, and the technical effect is difficult to have a greater improvement space. SUMMARY

[0006] In view of the single improvement means of the existing Li5FeO4 and the difficulty in having a greater breakthrough in effect, the application provides a Li 5-x Na xThe FeO4@C composite cathode lithium replenishment material aims to provide a novel material that improves stability and high-current delithiation activity by constructing Li vacancies through Na-induced lattice distortion at Li sites.

[0007] The second objective of this invention is to provide the aforementioned Li 5-x Na x Preparation method of FeO4@C composite cathode lithium replenishment material and its application in cathode lithium replenishment.

[0008] A third objective of this invention is to provide a product comprising the Li 5-x Na x Lithium-ion batteries with FeO4@C composite cathode lithium supplementation materials, as well as their cathodes and cathode materials.

[0009] A Li 5-x Na x FeO4@C composite cathode lithium supplementation material has a core-shell structure, wherein the core is Li 5-x Na x FeO4, with an amorphous carbon shell, wherein x is 0.01 to 0.15, preferably 0.01 to 0.1, and more preferably 0.03 to 0.05.

[0010] This invention provides a novel chemical formula material based on the lattice hybridization of large-sized Na with small-sized Li, forming a controllable lattice distortion and constructing suitable Li vacancies, thereby improving its air stability and high-current delithiation activity.

[0011] In this invention, the mass ratio of the core to the shell can be adjusted as needed, for example, it can be 97-99:1-3. The carbon shell is a thin layer of carbon with a thickness of less than 5 nm, and more specifically, it can be 1-5 nm.

[0012] The present invention also attempts to provide the aforementioned Li 5-x Na x The preparation method of FeO4@C composite cathode lithium supplementation material has been explored, but early research revealed that using large-atomic-size Na to dope the small-size Li crystal lattice easily leads to lattice collapse, resulting in material preparation failure. Furthermore, the numerous lithium site configurations make it difficult to control the construction method of lithium sites, thus hindering the realization of the ideal technical approach. To address these material preparation challenges, this invention, through in-depth research, provides the following improved solutions:

[0013] A Li 5-x Na x The preparation method of FeO4@C composite cathode lithium supplementation material involves wet ball milling of raw materials containing sodium carboxylate, lithium source, and iron source to obtain a slurry, followed by spray drying-heat treatment of the slurry, or spray pyrolysis treatment of the slurry; to obtain the Li 5-xNa x FeO4@C composite positive electrode lithium supplement material;

[0014] The chemical formula of the sodium carboxylate is R-COONa, wherein R is C1-C6 alkyl, C3-C6 cycloalkyl, C3-C6 oxacycloalkyl or C3-C6 azacycloalkyl, wherein the alkyl, cycloalkyl, oxacycloalkyl or azacycloalkyl can be substituted with at least one substituent selected from hydroxyl, halogen, nitro, trifluoromethyl, phenyl, benzyl and alkoxy. 10 The chemical formula of the sodium carboxylate is R-COONa, wherein R is C1-C6 alkyl, C3-C6 cycloalkyl, C3-C6 oxacycloalkyl or C3-C6 azacycloalkyl, wherein the alkyl, cycloalkyl, oxacycloalkyl or azacycloalkyl can be substituted with at least one substituent selected from hydroxyl, halogen, nitro, trifluoromethyl, phenyl, benzyl and alkoxy.

[0015] In view of the problem that the material is difficult to prepare, the sodium carboxylate, the lithium source and the iron source are subjected to wet ball milling and spray treatment, so that the Na-Li lattice hybridization can be unexpectedly realized, the crystal structure collapse can be avoided, the lithium vacancy construction mode can be controlled, in-situ carbon encapsulation can be realized, and the material can be successfully prepared.

[0016] In the application, the Na and -COO- in the sodium carboxylate are in a chemical coordination state, which plays multiple roles of Na donor, modifier and covalent in-situ thin carbon donor in the application, and the sodium carboxylate is subjected to ball milling and spray treatment, so that the Na-Li atomic adaptation effect can be synergistically improved, the Na-Li lattice hybridization can be facilitated, the crystal structure collapse can be avoided, and the carbon layer with the in-situ thin layer feature can be formed.

[0017] The application further finds that the composition of the sodium carboxylate can be controlled to further improve the Na lattice hybridization effect.

[0018] In the application, the sodium carboxylate is at least one of sodium gluconate, sodium acetate and sodium lactate; preferably, the sodium carboxylate is a mixture of sodium acetate and sodium gluconate.

[0019] The application further finds that the lithium source is not particularly required, and for example, can be at least one of Li2O, Li2CO3, LiF, Li3PO4 and Li2C2O4; further preferably, the lithium source is at least one of Li2O and Li2C2O4.

[0020] The application further finds that the Fe source is not particularly required, and for example, can be at least one of Fe2O3, Fe3O4, iron powder and FeC2O4; further preferably, the Fe source is at least one of Fe2O3 and Fe3O4.

[0021] The molar ratio of Li, Na and Fe in the raw material is 4.8-5.8:0.01-0.1:1, preferably 5-5.5:0.03-0.05:1.

[0022] In the present application, the solvent in the slurry is water or a mixture of water and organic solvent.

[0023] Preferably, the concentration of the iron source in the slurry is 100-300 g / L.

[0024] Preferably, an activator is further added to the slurry, and the activator is a quaternary ammonium salt having C 10 -C 20 a long chain alkyl group, preferably C 12 -C 18 alkyl trimethyl ammonium salt.

[0025] Preferably, the amount of the activator is 0.02-0.1 times, preferably 0.04-0.06:1, of the weight of the iron source.

[0026] Preferably, the activator is added before ball milling.

[0027] In the present application, the ball-to-material ratio in the ball milling process is not particularly limited and can be adjusted as needed, for example, it can be 2-4:1.

[0028] In the present application, the rotation speed of the ball milling is not particularly limited and can be, for example, 200-500 r / min, preferably 300-400 r / min.

[0029] In the present application, the ball milling time can be adjusted as needed, for example, it can be 1-20 h, and considering the preparation efficiency, it can be 2-5 h.

[0030] In the present application, the slurry can be directly subjected to spray drying followed by heat treatment. Alternatively, the slurry can be directly subjected to spray pyrolysis. The spray drying, heat treatment and spray pyrolysis processes are preferably carried out in a protective gas, for example, nitrogen or inert gas.

[0031] In the present application, the temperature for spray drying is 120-300 °C, and further can be 140-190 °C.

[0032] In the present application, the temperature for heat treatment is 600-950 °C, preferably 800-900 °C.

[0033] In the present application, the heat treatment time is 10-48 h, preferably 15-25 h.

[0034] In the present application, the temperature for spray pyrolysis is 600-950 °C, preferably 800-900 °C.

[0035] In the present application, the feeding speed of the spray drying and spray pyrolysis process is 10-40 ml / min, preferably 20-30 ml / min.

[0036] The present application also provides a Li 5-x Na x The application of the FeO4@C composite cathode lithium supplement material as a lithium supplement additive in the preparation of a lithium supplement cathode and a lithium supplement cathode material.

[0037] The present application also provides a lithium supplement cathode material comprising a cathode active material and a lithium supplement additive, wherein the lithium supplement additive is the Li 5-x Na x FeO4@C composite cathode lithium supplement material.

[0038] Preferably, the cathode active material is at least one of LiMO2 and LiNPO4; M is preferably at least one of Ni, Co and Mn; and N is preferably at least one of Fe and Mn.

[0039] Preferably, in the lithium supplement cathode material, the content of the lithium supplement additive is 1-15 wt.%, and can further be 4-6 wt.%.

[0040] In the present application, the lithium supplement cathode material further comprises a binder and a conductive agent. The binder and the conductive agent can be conventional components, and their amounts can be adjusted according to conventional industry theories. For example, in the lithium supplement cathode material, the content of the conductive agent and the binder is below 15 wt.%, and is preferably 1-15 wt.%.

[0041] The present application also provides a lithium supplement cathode comprising a current collector and a lithium supplement cathode material compounded on the surface of the current collector, wherein the lithium supplement cathode material is the lithium supplement cathode material of the present application.

[0042] The present application also provides a lithium secondary battery comprising a battery cell and an electrolyte infiltrating the battery cell, wherein the battery cell comprises a cathode, a separator and an anode compounded in sequence, and the cathode is the lithium supplement cathode of the present application.

[0043] In the present application, the lithium secondary battery is, for example, a lithium ion battery and a lithium metal battery.

[0044] In the present application, the lithium secondary battery, in addition to adding the lithium supplementing material, other components and structural parts can be conventional.

[0045] Compared with the prior art, the present application has the advantages of:

[0046] 1. The present application provides a novel chemical formula material, which is based on large size Na to small size Li lattice hybridization, forms lattice controllable distortion, and constructs suitable Li vacancies, thereby facilitating its air stability and large current delithiation activity.

[0047] 2. The present application innovatively carries out wet ball milling and spray treatment on sodium carboxylate, lithium source and iron source, which can unexpectedly realize Na-Li site lattice hybridization, avoid crystal structure collapse, and realize in-situ carbon encapsulation, thereby successfully preparing the material. The material prepared by the preparation method of the present application can improve its air stability and large current delithiation activity based on lithium lattice distortion and lithium vacancy.

[0048] 3. The present application has wide raw material sources, simple preparation process, is easy to realize and easy to industrialize. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 SEM image of Li 5-x Na x FeO4@C prepared in Example 1. DETAILED DESCRIPTION

[0050] In order to facilitate the understanding of the present application, the following will combine the preferred embodiments to describe the present application more fully and in detail, but the protection scope of the present application is not limited to the following specific embodiments.

[0051] Unless otherwise defined, all professional terms used in the following are the same as those commonly understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application.

[0052] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods. The ball-to-material ratio of the ball milling process can be 2-4:1.

[0053] Example 1

[0054] Preparation of lithium supplementing material

[0055] (1) Li2O, Fe2O3, sodium acetate were dispersed in water (the concentration of Fe2O3 was 140-160 g / L) to obtain a raw material solution, wherein the molar ratio of Li / Fe / Na elements was 5.5:1:0.03; the slurry was obtained by ball milling at a speed of 400 r / min for 3 h;

[0056] (2) The slurry obtained in step (1) was subjected to spray treatment at 160°C to obtain a uniformly mixed precursor, and the feeding speed was 30 ml / min;

[0057] (3) The precursor obtained in step (2) was sintered at 800°C for 24 h in an Ar atmosphere. After cooling, a uniformly mixed Li 4.97 Na 0.03 FeO4@C (lithium supplement) was obtained. The SEM is shown in Figure 1 . The particle size was 6 μm; the specific surface area was 600 m 2 ·g -1 ; and the thickness of the C layer was 3 nm.

[0058] Example 2

[0059] Compared with Example 1, the only difference was that the source of Na was changed, the total amount of Na element was changed, and other conditions were the same as in Example 1. The experimental groups were as follows:

[0060] A: The source of Na was sodium gluconate, and other conditions were the same as in Example 1.

[0061] B: The source of Na was sodium gluconate and sodium acetate, and the molar ratio of Na elements was 1:1.

[0062] C: The molar ratio of Li / Fe / Na elements was controlled to be 5.5:1:0.01.

[0063] D: The molar ratio of Li / Fe / Na elements was controlled to be 5.5:1:0.1.

[0064] Example 3

[0065] Compared with Example 1, the only difference was that the source of Fe was Fe3O4, the source of Li was Li2C2O4, and the ratio of the components was changed to a molar ratio of Li:Fe of 5.5, the sintering temperature in step 3 was 900°C, and the time was 16 h,

[0066] and other conditions were the same as in Example 1.

[0067] Example 4

[0068] Compared with Example 1, the only difference was that an activating agent (cetyltrimethylammonium bromide) was added to the raw material solution in step 1, and the weight ratio of the activating agent to Fe2O3 was 0.05:1. Other conditions were the same as in Example 1.

[0069] Comparative Example 1

[0070] The difference between Example 1 and Comparative Example 1 is that sodium acetate is not contained in step (1).

[0071] Comparative Example 2

[0072] The difference between Example 1 and Comparative Example 2 is that the ball milling in step (1) is replaced by magnetic stirring.

[0073] Comparative Example 3

[0074] The difference between Example 1 and Comparative Example 3 is that the spray treatment is not performed, but the slurry is placed in an oven for treatment, and the treatment time is 12 h.

[0075] Comparative Example 4

[0076] The difference between Example 1 and Comparative Example 4 is that sodium nitrate is used to replace sodium acetate.

[0077] Comparative Example 5

[0078] The difference between Comparative Example 4 and Comparative Example 5 is that in step 1, acetic acid is additionally added, and the molar ratio of acetic acid to sodium nitrate is 1:1, and the other operations and parameters are the same as in Example 1.

[0079] Comparative Example 6

[0080] The difference between Example 1 and Comparative Example 6 is that the molar ratio of Li / Fe / Na elements is controlled to be 5.5:1:0.2.

[0081] Performance data:

[0082] I. Air stability experiment

[0083] The cycle stability data of the lithium supplementing additives prepared in each case after being stored in an air atmosphere at a temperature of 30°C and a humidity of 30% for different times is shown in Table 1: Note: 0h refers to the material freshly prepared and directly stored in an Ar atmosphere; 2d refers to the material freshly prepared and continuously stored in an air atmosphere at a temperature of 30°C and a humidity of 30% for 2 days (2d).

[0084] II. Electrochemical performance test

[0085] 1. Positive electrode material

[0086] After mixing NCM811 (75wt%), lithium supplementing agent (5wt%), Super P (10wt%) and PVDF (10wt%) uniformly, a positive electrode sheet is obtained by slurry mixing, coating, drying, and rolling.

[0087] 2. Negative electrode material:

[0088] After mixing graphite (90wt%), Super P (5wt%) and PVDF (5wt%) uniformly, the negative electrode sheet is obtained by mixing, coating, drying and rolling.

[0089] 3. The positive and negative electrode sheets are separated by PP diaphragm, LB002 electrolyte is added dropwise, 2025 lithium ion battery is assembled, and the lithium supplement of the negative electrode material is realized in the first charge-discharge cycle at 25 DEG C, 0.1C and 2C.

[0090] The test results of air stability and large current are shown in Table 1, respectively.

[0091] Table 1

[0092]

[0093]

[0094] Note: (a) 0h refers to no exposure in air, for example, the material is stored in Ar atmosphere.

[0095] As can be seen from the examples and comparative examples, the technical scheme of the present application can effectively improve the stability and improve the cycle stability in air.

Claims

1. A Li 5-x Na x FeO4@C composite positive electrode lithium supplement material, characterized in that, having a core-shell structure, wherein the core is Li 5- x Na x FeO4, the shell is amorphous carbon, and x is 0.01-0.

15. The Li 5-x Na x The preparation method of the FeO4@C composite positive electrode lithium supplement material is as follows: raw materials containing sodium carboxylate, a lithium source and an iron source are subjected to wet ball milling to obtain a slurry, and the slurry is subjected to spray drying-heat treatment; and the Li 5-x Na x FeO4@C composite positive electrode lithium supplement material is obtained. The chemical formula of the sodium carboxylate is R-COONa, wherein R is C1-C 10 alkyl, C3-C6 cycloalkyl, C3-C6 oxacycloalkyl, C3-C6 azacycloalkyl, wherein at least one substituent of hydroxyl, halogen, nitro, trifluoromethyl, phenyl, benzyl, alkoxy is allowed to exist on the alkyl, cycloalkyl, oxacycloalkyl, azacycloalkyl.

2. The Li 5-x Na x FeO4@C composite positive electrode lithium supplement material, characterized by, The mass ratio of the core and the shell is 97-99:1-3.

3. A Li of claim 1 or 2 5-x Na x A preparation method of the FeO4@C composite positive electrode lithium supplement material, characterized in that, The raw material containing sodium carboxylate, a lithium source and an iron source is subjected to wet ball milling to obtain a slurry, and the slurry is subjected to spray drying-heat treatment; thus, the Li 5-x Na x FeO4@C composite positive electrode lithium supplementing material is obtained. The chemical formula of the sodium carboxylate is R-COONa, wherein R is C1-C 10 alkyl, C3-C6 cycloalkyl, C3-C6 oxacycloalkyl, C3-C6 azacycloalkyl, wherein at least one substituent of hydroxyl, halogen, nitro, trifluoromethyl, phenyl, benzyl, alkoxy is allowed to exist on the alkyl, cycloalkyl, oxacycloalkyl, azacycloalkyl.

4. The production method according to claim 3, wherein The sodium carboxylate is at least one of sodium gluconate, sodium acetate, and sodium lactate.

5. The production method according to claim 4, wherein The sodium carboxylate is a mixture of sodium acetate and sodium gluconate.

6. The production method according to claim 3, wherein The lithium source is at least one of Li2O, Li2CO3, LiF, Li3PO4, and Li2C2O4.

7. The production method according to claim 6, wherein The excess coefficient of lithium is 1-1.05 times.

8. The production method according to claim 3, wherein The Fe source is at least one of Fe2O3, Fe3O4, iron powder, and FeC2O4.

9. The production method according to claim 3, wherein In the raw material, the molar ratio of Li, Na, and Fe is 4.8-5.8:0.01-0.1:

1.

10. The production method according to claim 9, wherein In the raw material, the molar ratio of Li, Na, and Fe is 5-5.5:0.03-0.05:

1.

11. The production method according to claim 3, wherein The solvent in the slurry is water or a mixture of water and an organic solvent.

12. The production method according to claim 3, wherein The concentration of the Fe source in the slurry is 100-300 g / L.

13. The production method according to claim 3, wherein The slurry further comprises an activator, wherein the activator is a C 10 ~C 20 quaternary ammonium salt of a long chain alkyl.

14. The production method according to claim 13, wherein The quaternary ammonium salt in the slurry is C 12 ~C 18 alkyltrimethylammonium salts.

15. The production method according to claim 13, wherein The activator is 0.02-0.1 times the weight of the Fe source.

16. The production method according to claim 3, wherein The ball-to-material ratio in the ball milling process is 2-4:

1.

17. The production method according to claim 3, wherein The rotation speed of the ball milling is 200-500 r / min.

18. The production method according to claim 3, wherein The ball milling time is 1-20 h.

19. The production method according to claim 3, wherein The temperature of the spray drying is 120-300℃.

20. The production method according to claim 3, wherein The temperature of the spray drying is 140-190℃.

21. The production method according to claim 3, wherein The temperature of the heat treatment is 600-950℃.

22. The production method according to claim 21, wherein The temperature of the heat treatment is 800-900℃.

23. The production method according to claim 21, wherein The heat treatment time is 10-48 h.

24. The production method according to claim 23, wherein The heat treatment time is 15-25 h.

25. The production method according to claim 3, wherein The temperature of the spray pyrolysis is 600-950℃.

26. The production method according to claim 25, wherein The temperature of the spray pyrolysis is 800-900℃.

27. The production method according to claim 3, wherein The feeding speed in the spray drying and spray pyrolysis process is 10-40 ml / min.

28. The production method according to claim 27, wherein The feeding speed in the spray drying and spray pyrolysis process is 20-30 ml / min.

29. The Li 5-x Na x FeO4@C composite cathode lithium supplement material or the preparation method of any one of claims 3-28. 5-x Na x The application of the FeO4@C composite cathode lithium supplement material is characterized in that, The lithium supplement additive is used as a lithium supplement additive for preparing a lithium supplement positive electrode and a lithium supplement positive electrode material.

30. A lithium supplementing cathode material, characterized in that, A positive electrode active material and a lithium supplementing additive, the lithium supplementing additive being Li 5-x Na x FeO4@C composite positive electrode lithium supplementing material or the Li 5-x Na x FeO4@C composite positive electrode lithium supplementing material.

31. The lithium supplementing cathode material of claim 30, wherein, The positive electrode active material is at least one of LiMO2 and LiNPO4. M is at least one of Ni, Co, and Mn. N is at least one of Fe and Mn.

32. The lithium supplementing cathode material of claim 30, wherein, In the lithium supplement positive electrode material, the content of the lithium supplement additive is 1-15 wt.%.

33. The lithium supplementing cathode material of claim 30, wherein, The lithium supplement positive electrode material further comprises a binder and a conductive agent.

34. A lithium supplementing cathode comprising a current collector and a lithium supplementing cathode material complexed on a surface thereof, characterized in that, The lithium supplement positive electrode material is the lithium supplement positive electrode material of any one of claims 30-33.

35. A lithium secondary battery comprising an electrode assembly and an electrolyte solution impregnating the electrode assembly, the electrode assembly comprising a positive electrode, a separator and a negative electrode which are sequentially laminated, characterized in that, The positive electrode is the lithium supplement positive electrode of claim 34.

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