Phase-controllable high-entropy sodium ion battery positive electrode material and preparation method thereof

Abstract

The invention discloses a phase-controllable high-entropy sodium ion battery positive electrode material and a preparation method thereof. The chemical formula of the material is Na0. 8TMO2, TM must contain four elements of nickel, copper, manganese and titanium, and also contains one or more elements of cobalt, iron, magnesium, zirconium, zinc, aluminum and molybdenum. The preparation method comprises the following steps: ball-milling and mixing a sodium source, a nickel source, a manganese source, a copper source, a titanium source and a transition metal source according to a certain stoichiometric ratio, and calcining at high temperature. The process cost is low, the steps are simple and easy to operate, the double-phase or P2 pure-phase high-entropy sodium ion battery positive electrode material is prepared through weighted average cation potential constant calculation and calcination temperature regulation and control, the prepared material can broaden a sodium ion diffusion channel, the rate capability can be improved, the cycling stability of the material is improved, and the application prospect is wide. And meanwhile, the structural stability of the material is improved through the high-entropy effect, and the two-phase material has the advantages of discharge capacity and high rate performance at the same time.

Description

Technical Field

[0001] This invention belongs to the field of materials synthesis and energy technology, specifically relating to a phase-controllable high-entropy sodium-ion battery cathode material and its preparation method. Background Technology

[0002] Energy storage technology, as a key link in promoting the development of new energy sources, can compensate for the intermittency and instability of clean energy. Electrochemical energy storage technology, as an important component of energy storage technology, mainly achieves the storage and release of electrical energy through batteries. The main battery types include lithium-ion batteries, lead-acid batteries, sodium-sulfur batteries, and flow batteries. Among them, lithium-ion batteries, with their high operating voltage, high energy density, excellent cycle stability, compact size, and environmental friendliness, have long been the core power source for electronic products, electric vehicles, and large-scale energy storage. However, with the explosive growth in energy storage demand, the scarcity of lithium resources, the need to control costs, and the need to improve safety, sodium-ion batteries, as a "second track" for promoting new energy development, have not only alleviated the pressure on lithium-ion batteries but also, to a certain extent, ensured the sustainable development of the new energy industry.

[0003] However, current sodium-ion battery cathode materials face challenges such as irreversible phase transitions during charge and discharge and insufficient stability in water and air. These issues significantly hinder the large-scale industrial production of layered cathode materials. In light of these problems, those skilled in the art need to develop a new sodium-ion secondary battery cathode material that possesses high initial discharge specific capacity, good rate performance, good cycle performance, and good stability in water and air. Summary of the Invention

[0004] The purpose of this invention is to calculate the elemental composition and proportion of the material by guiding the cationic potential, thereby controlling the phase structure of the layered material and obtaining a biphase high-entropy material with strong cycle stability and few irreversible phase changes.

[0005] To achieve the above objectives, this invention proposes a phase-controllable high-entropy sodium-ion battery cathode material with the chemical formula Na. 0.8 TMO2, where TM is a transition metal element, must contain nickel, copper, manganese, and titanium, and also contains one or more elements selected from cobalt, iron, magnesium, zirconium, zinc, aluminum, and molybdenum. The weighted average cation potential of the transition metals in the high-entropy sodium-ion battery cathode material is between 55 and 57. The high-entropy sodium-ion battery cathode material has a P2 / O3 dual-phase or pure P2 phase crystal phase, and the cathode material has a layered structure, in which the TM elements belong to the transition metal layers and are arranged randomly, while Na belongs to the alkali metal layers.

[0006] A method for preparing a phase-controllable high-entropy sodium-ion battery cathode material as described above includes the following steps: (1) According to the stoichiometric ratio, sodium source, nickel source, manganese source, copper source, titanium source and transition metal source powder are placed in a ball mill jar, a certain amount of dispersant is added, and the raw materials are mixed evenly by ball milling. The ball milling time is 1 to 10 hours and the rotation speed is 300 to 600 rpm. (2) After the ball-milled raw material mixture is pressed into tablets, it is placed in a muffle furnace and calcined at 800-1000℃. Then it is naturally cooled to room temperature to obtain high-entropy sodium-ion battery cathode material. Among them, by adjusting the calcination temperature to 800-920℃, P2 / O3 dual-phase high-entropy sodium-ion battery cathode material is obtained; by adjusting the calcination temperature to 920-1000℃, P2 phase high-entropy sodium-ion battery cathode material is obtained.

[0007] Preferably, the sodium source in step (1) is selected from one or more of the following compounds: sodium carbonate, sodium nitrate, sodium acetate, sodium hydroxide, and sodium oleate; The nickel source in step (1) is selected from one or more of the following compounds: nickel oxide, nickel nitrate, nickel carbonate, nickel acetate, nickel hydroxide, and nickel acetate; The manganese source is selected from one or more of the following compounds: manganese oxide, manganese nitrate, manganese carbonate, manganese acetate, manganese hydroxide, and manganese acetate. The copper source is selected from one or more of the following compounds: copper oxide, copper nitrate, copper carbonate, copper acetate, copper hydroxide, and copper acetate. The titanium source is selected from one or more of the following compounds: titanium oxide, titanium carbonate, titanium acetate, titanium hydroxide, and titanium acetate.

[0008] Preferably, the transition metal source in step (1) is selected from one or more of the following: transition metal oxides, transition metal carbonates, transition metal acetates, transition metal nitrates, and transition metal acetates; the particle size D of the transition metal source powder used is... 50 Satisfying 2 μm < D 50 <1000 μm; the impurity content of the transition metal source used is <0.5%.

[0009] Preferably, the dispersant in step (1) is one or a combination of ethanol, water, and acetone.

[0010] Preferably, in step (2), the heating rate of calcination is 1~10℃ / min, the calcination time is 5~20h, and then the temperature is reduced at a rate of 5~10℃ / min to obtain the high-entropy sodium-ion battery cathode material.

[0011] Preferably, the particle size D of the high-entropy sodium-ion battery cathode material is... 50 Satisfying 0.5μm < D 50 <15μm, in which the elements are uniformly distributed and the transition metals are randomly distributed.

[0012] Preferably, when preparing the dual-phase cathode material for high-entropy sodium-ion batteries, the total molar proportion of the essential elements nickel, copper, manganese, and titanium shall not be less than 80% of the total molar amount of the transition metal layer, and the molar proportion of manganese shall not be less than 40% of the total molar amount of the transition metal layer elements.

[0013] Preferably, in the prepared high-entropy sodium-ion battery biphase cathode material, nickel has a valence state of +2, copper has a valence state of +2, manganese has a valence state of +4, and titanium has a valence state of +4.

[0014] The technical solution adopted in this invention has the following advantages compared with the prior art: 1. This invention prepares biphase materials by controlling the constant cation potential, and controls the phase content by adjusting the calcination temperature. Materials with different structures can be obtained by simply adjusting the calcination temperature, and each has different advantages.

[0015] 2. This invention can stably obtain biphase materials by controlling the cation potential. Based on this, by adding elements, metal elements with different functions can be incorporated, while improving their entropy effect, thereby improving the cycling stability and structural stability of the material.

[0016] 3. The layered metal oxide cathode material prepared by this invention retains over 80% of its capacity after being exposed to air for 14 days. This layered metal oxide cathode material exhibits a capacity retention of over 80% at 120 mA g. -1 Under the specified current, the capacity retention rate reaches over 80% after 100 cycles. Furthermore, the coulombic efficiency of this cathode material is greater than 95% in the first cycle. Attached Figure Description

[0017] Figure 1 Na in Example 1 0.8 Ni 0.23 Mn 0.5 Cu 0.12 Ti 0.07 Co 0.08 X-ray diffraction pattern of O2.

[0018] Figure 2 Na in Example 2 0.8 Ni 0.22 Mn 0.544 Cu 0.1157 Ti 0.01 Co 0.055 Fe 0.055 O2 material at 120mA g -1 Cyclic curves at current density.

[0019] Figure 3 Na in Example 3 0.8 Ni 0.25 Mn 0.5526 Cu 0.05Ti 0.0144 Co 0.05 Fe 0.033 Zn 0.05 The first charge-discharge curve of O2 material.

[0020] Figure 4 Na in Example 3 0.8 Ni 0.25 Mn 0.5526 Cu 0.05 Ti 0.0144 Co 0.05 Fe 0.033 Zn 0.05 Scanning electron microscope image of O2. Detailed Implementation

[0021] The present invention will be further illustrated by the following examples, but is not limited thereto.

[0022] Table 1. Information on valence state, ionic radius, and ionic potential of corresponding element ions. Example 1 A phase-controllable high-entropy sodium-ion battery cathode material with the chemical formula Na 0.8 Ni 0.23 Mn 0.5 Cu 0.12 Ti 0.07 Co 0.08 The specific steps for preparing this material are as follows: (O2) (1) According to the stoichiometric ratio, 0.084 mol sodium carbonate (5% excess), 0.023 mol nickel oxide, 0.05 mol manganese dioxide, 0.012 mol copper oxide, 0.007 mol titanium oxide, and 0.00267 mol cobalt tetroxide were placed in a ball mill jar, and 5 ml ethanol was added as a dispersant. The raw materials were mixed evenly by ball milling for 5 h at a speed of 450 rpm. (2) The ball-milled raw material mixture was compressed into tablets and placed in a muffle furnace. It was kept at 850℃ for 15 h, with a heating rate of 5℃ / min and a cooling rate of 5℃ / min, and cooled to room temperature to obtain the product. The Na prepared in this example... 0.8 Ni 0.23 Mn 0.5 Cu 0.12 Ti 0.07 Co 0.08 O2 material is a two-phase material, and its X-ray diffraction pattern is as follows: Figure 1 As shown, the peaks represent the characteristic peaks of a two-phase structure, in which nickel, manganese, copper, titanium, and cobalt are uniformly distributed in the transition metal layer of the material. The prepared material consists of uniformly sized blocky particles with a particle size of approximately 2.5 μm. Na0.8 Ni 0.23 Mn 0.5 Cu 0.12 Ti 0.07 Co 0.08 The first-cycle discharge specific capacity of the O2 material is 110.20 mAh g. -1 The first-cycle coulomb efficiency was 96.3% at 120 mA g. -1 The capacity retention rate is 92.51% after 100 cycles at a current of 1200 mA g. -1 Even under high current, it still has 74 mAh g -1 The discharge capacity demonstrates its excellent cycle performance and rate capability. After 14 days of storage, the capacity was 93.67 mAh g⁻¹. -1 The capacity retention rate is 85%. Meanwhile, its weighted average cation potential = 0.23*28.985 + 0.5*75.4717 + 0.12*27.397 + 0.07*66.1157 + 0.08*41.8 = 55.66.

[0023] Example 2 A phase-controllable high-entropy sodium-ion battery cathode material with the chemical formula Na 0.8 Ni 0.22 Mn 0.544 Cu 0.1157 Ti 0.01 Co 0.055 Fe 0.055 The specific steps for preparing this material are as follows: (O2) (1) According to the stoichiometric ratio, 0.084 mol sodium carbonate (5% excess), 0.022 mol nickel oxide, 0.0544 mol manganese dioxide, 0.01157 mol copper oxide, 0.001 mol titanium oxide, 0.00183 mol cobalt tetroxide, and 0.00275 mol iron oxide were placed in a ball mill jar, and 4.5 ml ethanol was added as a dispersant. The raw materials were mixed evenly by ball milling for 5 h at a speed of 500 rpm. (2) The ball-milled raw material mixture was compressed into tablets and placed in a tube furnace. It was kept at 860℃ for 20 h, with a heating rate of 7℃ / min and a cooling rate of 7℃ / min, and cooled to room temperature to obtain the product. The Na prepared in this example... 0.8 Ni 0.22 Mn 0.544 Cu 0.1157 Ti 0.01 Co 0.055 Fe 0.055O2 material is a two-phase material in which six elements—nickel, manganese, copper, titanium, cobalt, and iron—are uniformly distributed in the transition metal layer. The prepared material consists of uniform blocky particles with a particle size of approximately 5 μm. Na 0.8 Ni 0.22 Mn 0.544 Cu 0.1157 Ti 0.01 Co 0.055 Fe 0.055 The first-cycle discharge specific capacity of the O2 material is 104.71 mAh g. -1 The first-cycle coulomb efficiency was 95.5% at 120 mA g. -1 The capacity retention rate after 100 cycles at a current of 1200 mA g is 84.89%. -1 Even under high current, it still has 85.86 mAh g. -1 The discharge capacity is further improved compared to the rate performance of the material in Example 1. After 14 days of storage, the capacity is 94.239 mAh g⁻¹. -1 The capacity retention rate is 90%. Meanwhile, its weighted average cation potential = 0.22*28.985 + 0.544*75.4717 + 0.1157*27.397 + 0.01*66.1157 + 0.055*41.8 + 0.055*46.511 = 56.122.

[0024] Example 3 A phase-controllable high-entropy sodium-ion battery cathode material with the chemical formula Na 0.8 Ni 0.25 Mn 0.5526 Cu 0.05 Ti 0.0144 Co 0.05 Fe 0.033 Zn 0.05 The specific steps for preparing this material are as follows: (O2) (1) According to the stoichiometric ratio, 0.084 mol sodium carbonate (5% excess), 0.025 mol nickel oxide, 0.05526 mol manganese dioxide, 0.005 mol copper oxide, 0.00144 mol titanium oxide, 0.00167 mol cobalt tetroxide, 0.00165 mol iron oxide, and 0.005 mol zinc oxide were placed in a ball mill jar, and 5 ml water was added as a dispersant. The raw materials were mixed evenly by ball milling for 3 hours at a speed of 550 rpm. (2) The ball-milled raw material mixture was compressed into tablets and placed in a tube furnace. It was held at 850℃ for 12 h, with a heating rate of 7℃ / min and a cooling rate of 10℃ / min, until cooled to room temperature to obtain the product. The Na prepared in this example... 0.8 Ni0.25 Mn 0.5526 Cu 0.05 Ti 0.0144 Co 0.05 Fe 0.033 Zn 0.05 O2 material is a two-phase material, in which seven elements—nickel, manganese, copper, titanium, cobalt, iron, and zinc—are uniformly distributed in the transition metal layer of the material. Figure 4 As shown, the prepared material consists of uniformly sized blocky particles with a particle size of approximately 2 μm. Na 0.8 Ni 0.25 Mn 0.5526 Cu 0.05 Ti 0.0144 Co 0.05 Fe 0.033 Zn 0.05 The first-cycle discharge specific capacity of the O2 material is 139.66 mAhg. -1 The first-cycle coulomb efficiency was 99.42% at 120 mA g. -1 The capacity retention rate was 86.2% after 100 cycles at the specified current. After 14 days of storage, the initial capacity was 128.48 mAh g. -1 The capacity retention rate is 92%. It is at 1200 mA g -1 Even under high current, it still has 104.91 mAh g. -1 The discharge capacity is further improved compared to the rate performance of the materials in Examples 1 and 2. Its weighted average cation potential = 0.25*28.985 + 0.5526*75.4717 + 0.05*27.397 + 0.0144*66.1157 + 0.05*41.8 + 0.033*46.511 + 0.05*27.02 = 56.249.

[0025] Example 4 A phase-controllable high-entropy sodium-ion battery cathode material with the chemical formula Na 0.8 Ni 0.23 Mn 0.5 Cu 0.1 Ti 0.07 Co 0.1 The specific steps for preparing this material are as follows: (O2) (1) According to the stoichiometric ratio, 0.084 mol sodium carbonate (5% excess), 0.023 mol nickel oxide, 0.05 mol manganese dioxide, 0.01 mol copper oxide, 0.007 mol titanium oxide, and 0.00333 mol cobalt tetroxide were placed in a ball mill jar, and 5 ml ethanol was added as a dispersant. The raw materials were mixed evenly by ball milling for 3 h at a speed of 550 rpm. (2) The ball-milled raw material mixture was compressed into tablets and placed in a muffle furnace. It was kept at 960℃ for 20 h, with a heating rate of 3℃ / min and a cooling rate of 5℃ / min, and cooled to room temperature to obtain the product. The Na prepared in this example... 0.8 Ni 0.23 Mn 0.5 Cu 0.1 Ti 0.07 Co 0.1 O2 material is a P2 single-phase material in which five elements—nickel, manganese, copper, titanium, and cobalt—are uniformly distributed in the transition metal layer. The prepared material consists of uniform blocky particles with a particle size of approximately 6 μm. Na 0.8 Ni 0.23 Mn 0.5 Cu 0.1 Ti 0.07 Co 0.1 The first-cycle discharge specific capacity of the O2 material is 105.4 mAh g. -1 The first-cycle coulomb efficiency was 97.2% at 120 mA g. -1 The capacity retention rate is 93.3% after 100 cycles at a current of 1200 mA g. -1 Even under high current, it still has 78.4 mAh g. -1 The discharge capacity demonstrates its excellent cycle performance and rate capability. After 14 days of storage, the capacity was 92.33 mAh g⁻¹. -1 The capacity retention rate is 87.6%. Meanwhile, its weighted average cation potential = 0.23*28.985 + 0.5*75.4717 + 0.1*27.397 + 0.07*66.1157 + 0.1*41.8 = 55.95.

[0026] Comparative Example 1 Na is used in the solid-state preparation of non-high-entropy sodium-ion batteries. 0.8 Ni 0.3 Mn 0.55 Cu 0.1 Ti 0.05 The specific steps for using O2 cathode material are as follows: (1) According to the stoichiometric ratio, 0.084 mol sodium carbonate (5% excess), 0.03 mol nickel oxide, 0.055 mol manganese dioxide, 0.01 mol copper oxide, and 0.005 mol titanium oxide were placed in a ball mill jar, and 5 ml ethanol was added as a dispersant. The raw materials were mixed evenly by ball milling for 5 h at a speed of 450 rpm. (2) The ball-milled raw material mixture was compressed into tablets and placed in a muffle furnace. It was held at 850℃ for 15 h at a heating rate of 5℃ / min, and then cooled to room temperature at 5℃ / min to obtain the product. The Na prepared in this example...0.8 Ni 0.3 Mn 0.55 Cu 0.1 Ti 0.05 O2 material is a two-phase material in which nickel, manganese, copper, and titanium are uniformly distributed in the transition metal layer of the material, and the prepared material consists of uniform block particles with a particle size of about 3 μm. Na 0.8 Ni 0.3 Mn 0.55 Cu 0.1 Ti 0.05 The initial discharge capacity of O2 was 110.7 mAh g. 1 The first-cycle coulombic efficiency was 85.2%, lower than the 96.3% of the first-cycle coulombic efficiency in Example 1, and the discharge specific capacity after 100 cycles was 84.183 mAh g. 1 The capacity retention rate was only 76.53%, lower than the 92.51% in Example 1. After 14 days of storage, the discharge specific capacity was 91.9 mAh g. 1 The capacity retention rate was 82.3%, lower than 85% in Example 1.

Claims

1. A phase-controllable high-entropy sodium-ion battery cathode material, characterized in that, The chemical formula of the positive electrode material is Na. 0.8 TMO2, where TM is a transition metal element, must contain nickel, copper, manganese, and titanium, and also contains one or more elements selected from cobalt, iron, magnesium, zirconium, zinc, aluminum, and molybdenum. The weighted average cation potential of the transition metals in the high-entropy sodium-ion battery cathode material is between 55 and 57. The high-entropy sodium-ion battery cathode material has a P2 / O3 dual-phase or pure P2 phase crystal phase, and the cathode material has a layered structure, in which the TM elements belong to the transition metal layers and are arranged randomly, while Na belongs to the alkali metal layers.

2. A method for preparing the phase-controllable high-entropy sodium-ion battery cathode material as described in claim 1, characterized in that, Includes the following steps: (1) According to the stoichiometric ratio, sodium source, nickel source, manganese source, copper source, titanium source and transition metal source powder are placed in a ball mill jar, a certain amount of dispersant is added, and the raw materials are mixed evenly by ball milling. The ball milling time is 1 to 10 hours and the rotation speed is 300 to 600 rpm. (2) After the ball-milled raw material mixture is pressed into tablets, it is placed in a muffle furnace and calcined at 800-1000℃. Then it is naturally cooled to room temperature to obtain high-entropy sodium-ion battery cathode material. Among them, by adjusting the calcination temperature to 800-920℃, P2 / O3 dual-phase high-entropy sodium-ion battery cathode material is obtained; by adjusting the calcination temperature to 920-1000℃, P2 phase high-entropy sodium-ion battery cathode material is obtained.

3. The method as described in claim 2, characterized in that, The sodium source in step (1) is selected from one or more of the following compounds: sodium carbonate, sodium nitrate, sodium acetate, sodium hydroxide, and sodium oleate; The nickel source in step (1) is selected from one or more of the following compounds: nickel oxide, nickel nitrate, nickel carbonate, nickel acetate, nickel hydroxide, and nickel acetate; The manganese source is selected from one or more of the following compounds: manganese oxide, manganese nitrate, manganese carbonate, manganese acetate, manganese hydroxide, and manganese acetate. The copper source is selected from one or more of the following compounds: copper oxide, copper nitrate, copper carbonate, copper acetate, copper hydroxide, and copper acetate. The titanium source is selected from one or more of the following compounds: titanium oxide, titanium carbonate, titanium acetate, titanium hydroxide, and titanium acetate.

4. The method as described in claim 2, characterized in that, The transition metal source in step (1) is selected from one or more of the following: transition metal oxides, transition metal carbonates, transition metal acetates, transition metal nitrates, and transition metal acetates; the particle size D of the transition metal source powder used is... 50 Satisfying 2 μm < D 50 <1000 μm; the impurity content of the transition metal source used is <0.5%.

5. The method according to claim 2, characterized in that, The dispersant in step (1) is one or a combination of ethanol, water, and acetone.

6. The method as described in claim 2, characterized in that, In step (2), the heating rate of calcination is 1~10℃ / min, the calcination time is 5~20h, and then the temperature is reduced at a rate of 5~10℃ / min to obtain the high-entropy sodium-ion battery cathode material.

7. The method as described in claim 2, characterized in that, The high-entropy sodium-ion battery cathode material has a particle size D. 50 Satisfying 0.5μm < D 50 <15μm, in which the elements are uniformly distributed and the transition metals are randomly distributed.

8. The method as described in claim 2, characterized in that, When preparing biphase cathode materials for high-entropy sodium-ion batteries, the total molar proportion of the essential elements nickel, copper, manganese, and titanium must be no less than 80% of the total molar proportion of the transition metal layer, and the molar proportion of manganese must be no less than 40% of the total molar proportion of the transition metal layer elements.

9. The method as described in claim 2, characterized in that, In the prepared high-entropy sodium-ion battery biphase cathode material, nickel has a valence state of +2, copper has a valence state of +2, manganese has a valence state of +4, and titanium has a valence state of +4.

Images