Sodium-ion battery cathode materials, preparation methods, sodium-ion batteries, and related electrical equipment

Abstract

This invention discloses a sodium-ion battery cathode material, a preparation method, a sodium-ion battery, and related electrical equipment. The sodium-ion battery cathode material includes a core and a shell. The core is a sodium-ion layered oxide, and the shell comprises a perovskite-structured LaNi. x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element. This invention simultaneously incorporates Ni and Cr at the B position in the general formula ABO3, resulting in LaNi. x Cr y M z O3 has good electrical conductivity and corrosion resistance, which improves the structural stability of the cathode material while ensuring good electrical conductivity and electrochemical activity of the sodium-ion battery cathode material.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more specifically, to sodium-ion battery cathode materials, preparation methods, sodium-ion batteries, and related electrical equipment. Background Technology

[0002] When sodium-ion layered oxide cathode materials undergo sodium removal, their oxidizing properties increase, making them highly susceptible to chemical and electrochemical reactions with the electrolyte. This leads to oxygen loss and transition metal dissolution. Especially under high voltage, the electrolyte may be oxidized, producing H₂. + This increases the acidity of the electrolyte, damages the surface film of the electrode material, alters the interfacial composition and structure, and severely affects the electrochemical and cycle performance of the material. Therefore, a sodium-ion battery cathode material with superior overall performance is particularly necessary. Summary of the Invention

[0003] The purpose of this invention is to provide a sodium-ion battery cathode material, a preparation method, a sodium-ion battery, and electrical equipment to improve the overall performance of the cathode material.

[0004] This invention is implemented as follows:

[0005] In a first aspect, the present invention provides a sodium-ion battery cathode material, comprising a core and a shell, wherein the core is a sodium-ion layered oxide, and the shell comprises a perovskite-structured LaNi0. x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element.

[0006] In an optional embodiment, M is selected from at least one of Sc, Ti, V, Mn, Fe, Co, Cu, and Zn.

[0007] In an optional embodiment, M is selected from at least one transition metal ion having a positive trivalent valence.

[0008] In an optional implementation, the positive electrode material satisfies at least one of the following conditions:

[0009] (1) The mass ratio of the outer shell to the core is 1.0 wt% to 3 wt%;

[0010] (2) The thickness of the outer shell is 50nm to 200nm;

[0011] (3) The mass fraction of residual hydroxide ions in the cathode material is less than 0.1 wt%.

[0012] In an optional embodiment, the general chemical formula of the sodium ion layered oxide is Na.a Ni i Fe j Mn k N 1-i-j- k O2, where 0.8≤a≤1.1, 0.2≤i≤0.3, 0.1≤j≤0.2, 0.4≤k≤0.5, and N is selected from at least one of the elements Cu, Zn, Sn, Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, and B.

[0013] Secondly, the present invention provides a method for preparing a sodium-ion battery cathode material, comprising subjecting a first mixture including a core material and a shell material to a first calcination to obtain the cathode material; wherein the shell material comprises a perovskite-structured LaNi x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element.

[0014] In an optional implementation, the positive electrode material satisfies at least one of the following conditions:

[0015] a. The temperature of the first calcination is 400℃-800℃, and the time is 5h-20h;

[0016] b. The heating rate of the first calcination is 1℃ / min-5℃ / min;

[0017] c. The core material comprises sodium ion layered oxide;

[0018] Optionally, the general chemical formula of the sodium ion layered oxide is Na. a Ni i Fe j Mn k N 1-i-j-k O2, where 0.8≤a≤1.1, 0.2≤i≤0.3, 0.1≤j≤0.2, 0.4≤k≤0.5, and N is selected from at least one of the elements Cu, Zn, Sn, Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, and B;

[0019] d. The M is selected from at least one of Sc, V, Cr, Mn, Fe, Co, and Ni;

[0020] e. M is selected from at least one transition metal ion with a positive trivalent valence.

[0021] In an optional embodiment, the method for preparing the outer shell material includes: mixing metal oxides comprising La, Ni, Cr, and M and then subjecting them to a second calcination to obtain the perovskite structure LaNi. x Cr y M z O3, wherein M is selected from at least one transition metal element;

[0022] Optionally, the second calcination temperature is 650℃-1100℃, and the time is 5h-20h.

[0023] Thirdly, the present invention provides a sodium-ion battery, comprising the sodium-ion battery cathode material described in any one of the foregoing embodiments, or the sodium-ion battery cathode material prepared by the sodium-ion battery cathode material preparation method described in any one of the foregoing embodiments.

[0024] Fourthly, the present invention provides an electrical device including the sodium-ion battery described in the foregoing embodiments.

[0025] The present invention has the following beneficial effects:

[0026] The sodium-ion battery cathode material provided by this invention comprises a LaNi alloy with a perovskite (ABO3) structure as its outer shell. x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element. Simultaneous doping of Ni and Cr elements at the B position in the general formula ABO3 can provide the outer shell with good conductivity and corrosion resistance, thereby improving the structural stability of the cathode material while ensuring good conductivity and electrochemical activity.

[0027] When Ni and Cr are incorporated into the B position along with other transition metal elements, the shell material becomes highly entropy-dependent, making it more prone to forming a single-phase solid solution. This is beneficial for further improving the structural stability of the shell material, thereby enhancing the structural stability of the cathode material. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1Here is a SEM image of the core material from Example 1;

[0030] Figure 2 Here is a SEM image of the sodium-ion battery cathode material from Example 1;

[0031] Figure 3 This is a cross-sectional SEM image of the sodium-ion battery cathode material from Example 1;

[0032] Figure 4 The image shows the XRD pattern of the core material in Example 1.

[0033] Figure 5 The images show the XRD patterns of the sodium-ion battery cathode materials in Examples 1-4. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0035] This invention provides a sodium-ion battery cathode material, comprising a core and a shell, wherein the core is a sodium-ion layered oxide, and the shell comprises a perovskite-structured LaNi. x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element.

[0036] In the positive electrode material of the embodiments of this application, the La in the outer shell 3+ with Na + With similar ionic radii, ion exchange reactions can be carried out on the surface of the material, which can significantly increase the overpotential of the surface oxygen evolution reaction and suppress the production of lattice oxygen, stabilize the valence state changes of transition metals during charging and discharging, and improve the stability of the material.

[0037] In the cathode material of this application, the outer shell comprises LaNi with a perovskite structure (ABO3). x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element. Simultaneous doping of Ni and Cr elements at the B position in the general formula ABO3 can provide the outer shell with good conductivity and corrosion resistance, thereby improving the structural stability of the cathode material while ensuring good conductivity and electrochemical activity.

[0038] When Ni and Cr are incorporated into the B position along with other transition metal elements, the shell material becomes highly entropy-dependent, making it more prone to forming a single-phase solid solution. This is beneficial for further improving the structural stability of the shell material, thereby enhancing the structural stability of the cathode material.

[0039] In an optional embodiment, M is selected from at least one of Sc, Ti, V, Mn, Fe, Co, Cu, and Zn.

[0040] The stability of perovskite structure materials is related to the tolerance factor t. When M is selected from at least one of Sc, Ti, V, Mn, Fe, Co, Cu, and Zn, the tolerance factor is 0.75≤t≤1.0, and the outer shell is a stable perovskite structure.

[0041] In an optional embodiment, M is selected from at least one transition metal ion with a positive trivalent valence, for example, M can be at least one of Mn, Fe or Co.

[0042] Trivalent metal ions such as Mn, Fe, or Co with Ni 3+ Cr 3+ With similar ionic radii, it is less likely to produce lattice distortion after solid solution with Ni and Cr, which is more conducive to improving the stability of the material. At the same time, it can undergo some redox reactions during charge and discharge and provide some capacity.

[0043] In an optional embodiment, the mass ratio of the outer shell to the core in the positive electrode material is 1.0 wt% to 3 wt%, specifically, it can be any value between 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2.0 wt%, 2.2 wt%, 2.4 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, or 1.0 wt% to 3.0 wt%.

[0044] By appropriately selecting the mass fraction of the outer shell, a uniform and continuous outer shell can be formed without reducing the capacity of the positive electrode material.

[0045] In an optional implementation, the shell thickness is 50nm to 200nm, specifically 50nm, 80nm, 110nm, 140nm, 170nm, 200nm or any value between 50nm and 200nm.

[0046] The outer shell has a certain thickness, which effectively improves the sodium ion diffusion rate while better isolating the core and electrolyte. This helps the cathode material resist electrolyte erosion, thereby improving the discharge specific capacity and capacity retention of the cathode material. A certain shell thickness also effectively reduces residual alkali on the surface of the cathode material, suppressing gelation during battery slurry preparation and gas generation during charge-discharge cycles, thus improving battery safety and cycle stability. However, as the shell thickness increases, its effects on stability improvement and residual alkali reduction tend to stabilize; therefore, the shell should not be too thick.

[0047] In an optional embodiment, the residual hydroxide ion mass fraction in the positive electrode material is less than 0.1 wt%, specifically it can be any value of 0.1 wt%, 0.09 wt%, 0.08 wt%, 0.07 wt%, 0.06 wt%, 0.05 wt%, 0.04 wt%, 0.03 wt%, 0.02 wt%, 0.01 wt%, or less than 0.1 wt%.

[0048] In an optional embodiment, the general chemical formula of the sodium ion layered oxide is Na. a Ni i Fe j Mn k N 1-i-j- k O2, where 0.8≤a≤1.1, 0.2≤i≤0.3, 0.1≤j≤0.2, 0.4≤k≤0.5, and N is selected from at least one of the elements Cu, Zn, Sn, Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, and B.

[0049] The sodium ion layered oxide in this application embodiment can be a commercially available product or prepared by a high-temperature solid-state sintering method. Specific steps include: uniformly mixing a sodium source (sodium carbonate or sodium hydroxide, etc.) with a transition metal source (precursor hydroxide, oxide, carbonate, etc.) at a molar ratio of 0.7-1.2:1.0, calcining at 650℃-1100℃ for 5-20 hours under an oxygen-containing atmosphere at a heating rate of 1-5℃ / min, and then cooling to room temperature before crushing and sieving through a 400-mesh sieve to obtain the chemical formula Na. a Ni i Fe j Mn k N 1-i-j-k Sodium ion layered oxide of O2.

[0050] This invention also provides a method for preparing a sodium-ion battery cathode material, comprising subjecting a first mixture including a core material and a shell material to a first calcination to obtain the cathode material; wherein the shell material comprises a perovskite-structured LaNi x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element.

[0051] The sodium-ion battery cathode material described above is prepared by high-temperature solid-state sintering, which is a simple and easy-to-operate process.

[0052] In an optional implementation, the positive electrode material satisfies at least one of the following conditions:

[0053] a. The temperature of the first calcination is 400℃-800℃, specifically it can be any value between 400℃, 500℃, 600℃, 700℃ or 400℃-800℃; the time is 5h-20h, specifically it can be any value between 5h, 10h, 15h, 20h or 5h-20h.

[0054] b. The heating rate of the first calcination is 1℃ / min-5℃ / min, specifically it can be any value between 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min or 1℃ / min-5℃ / min; the atmosphere is an oxygen-containing atmosphere, such as air;

[0055] Appropriate calcination temperature and time are conducive to the relatively uniform and firm coating of the outer shell material onto the core surface, so that the outer shell can adhere firmly to the core surface during the cycle, which is beneficial to improving the stability of the cathode material.

[0056] c. The core material comprises sodium ion layered oxide;

[0057] Optionally, the general chemical formula of the sodium ion layered oxide is Na. a Ni i Fe j Mn k N 1-i-j-k O2, where 0.8≤a≤1.1, 0.2≤i≤0.3, 0.1≤j≤0.2, 0.4≤k≤0.5, and N is selected from at least one of the elements Cu, Zn, Sn, Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, and B;

[0058] d. The M is selected from at least one of Sc, V, Cr, Mn, Fe, Co, and Ni;

[0059] e. M is selected from at least one transition metal ion with a positive trivalent valence; for example, M can be at least one of Mn, Fe or Co.

[0060] In an optional embodiment, the method for preparing the outer shell material includes: mixing metal oxides comprising La, Ni, Cr, and M and then subjecting them to a second calcination to obtain the perovskite structure LaNi. x Cr y M z O3, wherein M is selected from at least one transition metal element;

[0061] Optionally, the second calcination temperature is 650℃-1100℃, specifically any value between 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃ or 650℃-1100℃; the time is 5h-20h, specifically any value between 5h, 10h, 15h, 20h or 5h-20h.

[0062] Suitable calcination temperature and time are beneficial to the perovskite structure of LaNi x Cr y M z The formation of O3.

[0063] The present invention also provides a sodium-ion battery, comprising the sodium-ion battery cathode material described in any one of the foregoing embodiments, or the sodium-ion battery cathode material prepared by the sodium-ion battery cathode material preparation method described in any one of the foregoing embodiments.

[0064] The present invention also provides an electrical device, including the sodium-ion battery described in the foregoing embodiments.

[0065] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0066] Example 1

[0067] This embodiment prepares a sodium-ion battery cathode material, wherein the specific preparation method of the core is as follows: Na₂CO₃, NiO, Fe₂O₃, MnO₂, and MgO are weighed according to the stoichiometric molar ratio, and then added to a mixer at a speed of 2000 r / min for 3 min. The uniformly mixed material is placed in a muffle furnace and heated at 950℃ for 12 hours in air atmosphere, then cooled in the furnace. After being crushed by a universal pulverizer and sieved through a 400-mesh sieve, the material with the molecular formula Na₂CO₃ is obtained. 0.9 Ni0.29 Fe 0.2 Mn 0.45 Mg 0.06 Layered oxides of O2, SEM image as follows Figure 1 As shown, the XRD pattern is as follows Figure 4 As shown.

[0068] The specific preparation method of the outer shell is as follows: According to the stoichiometric molar ratio of the chemical formula, weigh the corresponding weights of La₂O₃, NiO, and Cr₂O₃, and then add them to a mixer at a speed of 2000 r / min for 3 min. Place the uniformly mixed material into a muffle furnace and heat it at 970℃ for 15 hours in air atmosphere. Then cool it with the furnace, crush it using a universal pulverizer, and sieve it through a 400-mesh sieve to obtain the material with the molecular formula LaNi. 0.5 Cr 0.5 O3 perovskite-type materials.

[0069] The specific preparation method of sodium-ion battery cathode material is as follows: Na... 0.9 Ni 0.29 Fe 0.2 Mn 0.45 Mg 0.06 O2 and LaNi 0.5 Cr 0.5 O3 was mixed at a mass ratio of 50:1 and heated in an air atmosphere at 650°C for 12 hours. The mixture was then cooled in the furnace, crushed using a universal pulverizer, and sieved through a 400-mesh sieve to obtain the sodium-ion battery cathode material. SEM images and cross-sectional SEM images are shown below. Figure 2 and 3 As shown, the XRD pattern is as follows Figure 5 As shown.

[0070] from Figure 1 and Figure 2 It can be seen that the core material has a relatively rounded single-crystal morphology. After coating, the material surface has a relatively flat and uniform outer shell. Figure 3 The average thickness of the outer shell on the core surface is 100 nm. Figure 4 and Figure 5 It can be seen that the core material is the O3 phase, and after coating, a perovskite structure peak appears near 2θ = 32.5°. Combining SEM and XRD, it can be concluded that the outer shell of the cathode material is a perovskite-structured LaNi. 0.5 Cr 0.5 O3.

[0071] Example 2

[0072] This embodiment prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 1, the main difference being that in the outer shell preparation process, corresponding weights of La2O3, NiO, Cr2O3, and Co2O3 are weighed and kept at a constant temperature of 1000℃ to prepare LaNi. 1 / 3 Cr 1 / 3 Co 1 / 3 O3.

[0073] Example 3

[0074] This embodiment prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 2, the main difference being that in the outer shell preparation process, corresponding weights of La2O3, NiO, Cr2O3, and Mn2O3 are weighed and kept at a constant temperature of 1030℃ to prepare LaNi. 1 / 3 Cr 1 / 3 Mn 1 / 3 O3.

[0075] Example 4

[0076] This embodiment prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 2, the main difference being that in the outer shell preparation process, corresponding weights of La2O3, NiO, Cr2O3, and Fe2O3 are weighed and kept at a constant temperature of 980℃ to prepare LaNi. 1 / 3 Cr 1 / 3 Fe 1 / 3 O3.

[0077] Example 5

[0078] This embodiment prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 2, the main difference being that in the outer shell preparation process, corresponding weights of La2O3, NiO, Cr2O3, and Co2O3 are weighed and kept at a constant temperature of 1000℃ to prepare LaNi. 0.2 Cr 0.3 Co 0.5 O3.

[0079] Example 6

[0080] This embodiment prepares a sodium-ion battery cathode material, and its preparation method is basically the same as that in Example 2. The main difference is that in the preparation process of the sodium-ion battery cathode material, the core and the outer shell are mixed and kept at a constant temperature of 550°C.

[0081] Example 7

[0082] This embodiment prepares a sodium-ion battery cathode material, and its preparation method is basically the same as that in Example 2. The main difference is that in the preparation process of the sodium-ion battery cathode material, the core and the outer shell are mixed and kept at a constant temperature of 750°C.

[0083] Example 8

[0084] This embodiment prepares a sodium-ion battery cathode material, and its preparation method is basically the same as that in Example 2. The main difference lies in the preparation process of the sodium-ion battery cathode material, where Na... 0.9 Ni 0.29 Fe 0.2 Mn 0.45 Mg 0.06 O2 and LaNi 1 / 3 Cr 1 / 3 Co 1 / 3 The mass ratio of O3 is 50:0.75.

[0085] Example 9

[0086] This embodiment prepares a sodium-ion battery cathode material, and its preparation method is basically the same as that in Example 2. The main difference lies in the preparation process of the sodium-ion battery cathode material, where Na... 0.9 Ni 0.29 Fe 0.2 Mn 0.45 Mg 0.06 O2 and LaNi 1 / 3 Cr 1 / 3 Co 1 / 3 The mass ratio of O3 is 50:1.25.

[0087] Example 10

[0088] This embodiment prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 2, the main difference being that in the outer shell preparation process, corresponding weights of La2O3, NiO, Cr2O3, and Sc2O3 are weighed and kept at a constant temperature of 1050℃ to prepare LaNi. 1 / 3 Cr 1 / 3 Sc 1 / 3 O3.

[0089] Example 11

[0090] This embodiment prepares a sodium-ion battery cathode material. The main difference between this method and that of Example 2 lies in the core preparation process. Appropriate weights of Na₂CO₃, NiO, Fe₂O₃, MnO₂, CuO, MgO, and ZrO₂ are weighed to prepare Na₂CO₃. 0.95 Ni 0.25 Fe 0.15 Mn 0.41 Cu0.08 Mg 0.07 Zr 0.04 O2.

[0091] Example 12

[0092] This embodiment prepares a sodium-ion battery cathode material. The main difference between this method and that of Example 2 lies in the core preparation process. Appropriate weights of Na₂CO₃, NiO, Fe₂O₃, and MnO₂ are weighed to prepare Na₂CO₃. 0.87 Ni 0.35 Fe 0.17 Mn 0.48 O2.

[0093] Comparative Example 1

[0094] The sodium-ion battery cathode material prepared in this comparative example is: Na 0.9 Ni 0.29 Fe 0.2 Mn 0.45 Mg 0.06 O2, without an outer shell, is prepared using the same method as the core in Example 1.

[0095] Comparative Example 2

[0096] This comparative example prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 1. The main difference is that in the preparation process of the outer shell, the corresponding weights of La2O3 and NiO are weighed and kept at a constant temperature of 920℃ to prepare LaNiO3.

[0097] Comparative Example 3

[0098] This comparative example prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 1. The main difference is that in the preparation process of the outer shell, the corresponding weights of La2O3 and Cr2O3 are weighed and kept at a constant temperature of 930℃ to prepare LaCrO3.

[0099] Comparative Example 4

[0100] This comparative example prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 1, the main difference being that in the outer shell preparation process, corresponding weights of La2O3, NiO, and Co2O3 are weighed and kept at a constant temperature of 950℃ to prepare LaNi. 0.5 Co 0.5 O3.

[0101] Comparative Example 5

[0102] This comparative example prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 1, the main difference being that in the outer shell preparation process, corresponding weights of La₂O₃, Cr₂O₃, and Co₂O₃ are weighed and kept at a constant temperature of 980℃ to prepare LaCr₂O₃. 0.5 Co 0.5 O3.

[0103] Comparative Example 6

[0104] This comparative example prepares a sodium-ion battery cathode material. The preparation method is basically the same as that in Example 1, except that in the outer shell preparation process, corresponding weights of La₂O₃, NiO, MnO₂, and Co₂O₃ are weighed and kept at a constant temperature of 1000℃ to prepare LaNi₂O₃. 1 / 3 Co 1 / 3 Mn 1 / 3 O3.

[0105] Comparative Example 7

[0106] The sodium-ion battery cathode material prepared in this comparative example is: Na 0.95 Ni 0.25 Fe 0.15 Mn 0.41 Cu 0.08 Mg 0.07 Zr 0.04 O2, without an outer shell, is prepared using the same method as the core in Example 11.

[0107] Comparative Example 8

[0108] The sodium-ion battery cathode material prepared in this comparative example is: Na 0.87 Ni 0.35 Fe 0.17 Mn 0.48 O2, without an outer shell, is prepared using the same method as the core in Example 12.

[0109] The residual hydroxide content and pH of the cathode materials prepared in the above embodiments and comparative examples were tested using the following methods:

[0110] (1) pH test: Take 5g of sample and 50g of deionized water and put them in a 250mL beaker. Stir magnetically for 10min and then perform pH test using a pH meter.

[0111] (2) Residual hydroxide test: Take 10g of sample and 100g of anhydrous ethanol into a 250mL beaker, stir magnetically for 20min, filter, and take 50g of clear filtrate into a 100mL beaker for potentiometric titration with hydrochloric acid standard solution.

[0112] The test results are shown in Table 1.

[0113] Sodium-ion battery preparation

[0114] The positive electrode materials prepared in the above examples and comparative examples were stirred evenly with conductive agents and binders in NMP solvent, and then coated onto aluminum foil. Afterwards, they were baked, rolled, and sliced ​​to form positive electrode sheets. Finally, the positive electrode sheets were assembled with separators, sodium sheets, and spacers to form sodium-ion coin cells. The fabricated sodium-ion coin cells were tested using a battery testing cabinet. The test conditions were: sodium sheet negative electrode, voltage range of 2.0-4.2V, and test temperature of 25±1℃. The battery performance test results are shown in Table 1.

[0115] Table 1

[0116]

[0117] As shown in Table 1, compared to Comparative Example 1, Examples 1-10 coated LaNi x Cr y M z After O3 treatment, the battery's specific capacity, rate performance, and cycle stability were all improved. Compared to Example 1, the LaNi coating in Examples 2-10... 1 / 3 Cr 1 / 3 Co 1 / 3 O3, LaNi 1 / 3 Cr 1 / 3 Mn 1 / 3 O3, LaNi 1 / 3 Cr 1 / 3 Fe 1 / 3 O3, LaNi 1 / 3 Cr 1 / 3 Sc 1 / 3 After O3 was applied, the specific capacity, rate performance, and cycle stability were further improved. In Examples 6-9, after changing the coating temperature or coating amount, the specific capacity, rate performance, and cycle stability remained at a good level, but the overall performance was slightly lower than in Examples 2-5. When M is selected with Ni... 3+ Cr 3+ Co with similar ionic radii 3+ Fe 3+ Mn 3+ When M is Sc 3+ This results in better overall performance.

[0118] Furthermore, as shown in Table 1, the residual alkali of the coated material is significantly reduced, which helps to suppress the gelation phenomenon during battery slurry preparation and the gas generation phenomenon during charge-discharge cycles, thereby improving the safety and cycle stability of the battery.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sodium-ion battery cathode material, characterized in that, It includes a core and a shell, wherein the core is a sodium-ion layered oxide and the shell comprises a perovskite-structured LaNi x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one of Sc, Ti, V, Mn, Fe, Co, Cu, and Zn.

2. The sodium-ion battery cathode material according to claim 1, characterized in that, M is selected from at least one transition metal ion with a positive trivalent valence.

3. The sodium-ion battery cathode material according to any one of claims 1-2, characterized in that, The cathode material satisfies at least one of the following conditions: (1) The mass ratio of the outer shell to the core is 1.0wt%~3wt%; (2) The thickness of the outer shell is 50nm~200nm; (3) The mass fraction of residual hydroxide ions in the cathode material is less than 0.1 wt%.

4. The sodium-ion battery cathode material according to claim 1, characterized in that, The general chemical formula of the sodium ion layered oxide is Na. a Ni i Fe j Mn k N 1-i-j-k O2, where 0.8≤a≤1.1, 0.2≤i≤0.3, 0.1≤j≤0.2, 0.4≤k≤0.5, and N is selected from at least one of the elements Cu, Zn, Sn, Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, and B.

5. A method for preparing a sodium-ion battery cathode material, characterized in that, The cathode material is obtained by first calcining a first mixture including a core material and a shell material; wherein the shell material comprises a perovskite-structured LaNi x Cr y M z O3, wherein 0.2≤x≤0.5, 0.2≤y≤0.5, 0≤z≤0.5, x+y+z=1, and M is selected from at least one transition metal element.

6. The method for preparing the sodium-ion battery cathode material according to claim 5, characterized in that, The cathode material satisfies at least one of the following conditions: a. The temperature of the first calcination is 400℃-800℃, and the time is 5h-20h; b. The heating rate of the first calcination is 1℃ / min-5℃ / min; c. The core material comprises sodium ion layered oxide.

7. The method for preparing the sodium-ion battery cathode material according to claim 6, characterized in that, The general chemical formula of the sodium ion layered oxide is Na. a Ni i Fe j Mn k N 1-i-j-k O2, where 0.8≤a≤1.1, 0.2≤i≤0.3, 0.1≤j≤0.2, 0.4≤k≤0.5, and N is selected from at least one of the elements Cu, Zn, Sn, Ti, Co, Al, Zr, Y, Ca, Li, Rb, Cs, W, Ce, Mo, Ba, Mg, Ta, Nb, V, Sc, Sr, and B; d. The M is selected from at least one of Sc, V, Cr, Mn, Fe, Co, and Ni; e. M is selected from at least one transition metal ion with a positive trivalent valence.

8. The method for preparing the sodium-ion battery cathode material according to claim 5, characterized in that, The preparation method of the outer shell material includes: mixing metal oxides comprising La, Ni, Cr and M and then subjecting them to a second calcination to obtain the perovskite structure LaNi. x Cr y M z O3, wherein M is selected from at least one transition metal element.

9. The method for preparing the sodium-ion battery cathode material according to claim 8, characterized in that, The second calcination temperature is 650℃-1100℃, and the time is 5h-20h.

10. A sodium-ion battery, characterized in that, Includes the sodium-ion battery cathode material according to any one of claims 1-4, or includes the sodium-ion battery cathode material prepared by the preparation method of the sodium-ion battery cathode material according to any one of claims 5-9.

11. An electrical-related device, characterized in that, Including the sodium-ion battery of claim 10.

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