A doped oxide sodium-ion battery high-voltage positive electrode material and a preparation method thereof

Abstract

The application discloses a doped oxide sodium ion battery high-voltage positive electrode material and a preparation method thereof, and belongs to the technical field of sodium ion battery high-voltage positive electrode materials. The Li / Ti element co-doped layered oxide positive electrode material is prepared by mixing, drying, ball milling, tabletting and roasting of a commercial nickel-iron-manganese layered hydroxide precursor and a metal oxide. The sodium ion battery high-voltage positive electrode material and the preparation method thereof can inhibit the adverse phase change of the sodium ion layered oxide in the electrochemical reaction and the loss of lattice oxygen in the charging and discharging process, and improve the high-voltage cycle stability.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of high-voltage positive electrode materials of sodium ion batteries, and in particular to a doped oxide high-voltage positive electrode material of a sodium ion battery and a preparation method thereof. BACKGROUND

[0002] Sodium ion batteries (SIBs) have emerged as a replacement for lithium ion batteries (LIBs) in the large-scale energy storage field. Compared with lithium, sodium has abundant reserves, a wide distribution range, low cost, and a higher electrode potential. In terms of performance, sodium ion batteries have better cost, low temperature, fast charging, and thermal stability, but their main weakness is the low energy density. The positive electrode is a key component of LIBs and SIBs, and has an important influence on the cost, energy output, and cycle life of the battery. In SIBs based on ion intercalation electrochemistry, transition metal layered oxides, tunnel-type oxides, prussian blue analogues (PBAs), and polyanion compounds are widely concerned by scholars.

[0003] Among them, transition metal layered oxides are the preferred materials for compact positive electrode design because of their high theoretical capacity and voltage, fast electron conduction ability, optimized high-rate performance, and higher tap density compared with PBAs and polyanion compounds, thus standing at the forefront of SIBs positive electrode research. In addition, due to the similarity in chemical structure between sodium ion layered oxides and lithium ion layered oxides, such as LiNi x Co y Mn 1-x-y O2, the commonality in production process and technology between the two provides the possibility of resource sharing, greatly promoting the research, development, and application of related materials. However, although sodium ion layered oxide positive electrodes have been extensively studied in the past decade, because of their chemical instability in air and electrolyte, poor structural reversibility at high voltage, and chemical-mechanical loss during repeated charge and discharge, the last step from the laboratory to the market is still challenging.

[0004] Transition metal oxides can be divided into P2 and O3 types according to the structure, and the differences in crystal structure between P2 (space group P63 / mmc) and O3 (space group ) positive electrodes result in their unique performance characteristics. Specifically, the sodium-poor P2 positive electrode provides high discharge capacity but low initial charge capacity in a wide voltage range, which indicates abnormal initial coulombic efficiency (ICE); the sodium-rich O3 positive electrode exhibits high charge / discharge capacity and normal ICE of less than 100%, but has slow Na +Diffusion kinetics and poor air stability. Compared with P2-type oxides, O3-type oxides have a narrower voltage range and lower energy density, which is not competitive in the field of high-performance battery materials.

[0005] Among the ternary transition metal layered oxides studied, O3-NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2(NFM333) is a very promising sodium-ion battery cathode candidate material. By using cost-effective transition metal elements Fe and Mn, its commercial value is significantly improved. In addition, NFM333 exhibits an appreciable capacity of more than 130mA h g -1 (at 0.1C) and a relatively simple phase transition (O3-P3-P3-O3) in the voltage range of 2.0-4.0V.

[0006] The redox of lattice oxygen triggered at high voltage is an effective strategy to improve the energy density of cathode materials, which allows more Na + deintercalation and intercalation, which can contribute additional capacity compared to traditional transition metal redox reactions. Doping Li elements to construct superlattice structures in the transition metal layer of layered oxides is a common method to activate the redox of lattice oxygen, and the incorporation of Li can also reduce the J-T effect of Fe and Mn elements, and the occupation effect can also inhibit the irreversible migration of Fe elements. However, when the voltage is higher than 4.0V, the loss of lattice oxygen will cause irreversible phase transition of O3-type oxides, which seriously damages the cycle performance of NFM333. The loss of lattice oxygen is caused by the generation of transition metal vacancy clusters and charged molecules O. Therefore, it is necessary to introduce other elements (such as Ti) to pin vacancies and hinder the generation of clusters; at the same time, high bond energy transition metal-oxygen (TM-O) bonds can be formed to reduce the generation of O2. Therefore, based on the commercially available large-scale prepared nickel-iron-manganese hydroxide precursor, the method of Li / Ti co-doping is expected to realize the application of commercial NFM333 at high voltage, improve its energy density, and strengthen its competitiveness. SUMMARY

[0007] The purpose of the present application is to provide a doped oxide sodium-ion battery high-voltage cathode material and a preparation method thereof, which adopts a solid-phase reaction method and realizes element doping by mixing a commercially available nickel-iron-manganese layered hydroxide precursor with a metal oxide, inhibits the adverse phase transition of sodium-ion layered oxides in electrochemical reactions and the loss of lattice oxygen in the charging and discharging process, and improves the high-voltage cycle stability.

[0008] To achieve the above purpose, the present application provides a preparation method of a doped oxide sodium-ion battery high-voltage cathode material, comprising the following steps:

[0009] S1, uniformly mix Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2, and then grind to obtain a premixed powder;

[0010] S2, dry the premixed powder in an oven to obtain a dry powder;

[0011] S3, ball mill the dry powder, and then press into a tablet to obtain a round tablet;

[0012] S4, sinter the round tablet at high temperature in a high-temperature tube furnace to obtain a doped oxide sodium-ion battery high-voltage positive electrode material, denoted as Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 O2.

[0013] Preferably, in S1, the amounts of Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2 are: according to the stoichiometric ratio in Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 O2, the amounts of Ni, Fe, Mn and Ti are the calculated values, and the actual amounts of Na and Li are 5% more than the calculated values.

[0014] Preferably, in S2, the drying temperature is 50-80℃, and the drying time is 12-14h.

[0015] Preferably, in S3, the rotation speed of the ball mill is 300-400r / min, and the ball milling time is 2-3h.

[0016] Preferably, in S3, the pressure for tabletting is 14-18MPa.

[0017] Preferably, in S4, the specific operation during high-temperature sintering is: argon is used as the protective gas, first heated to 400-500℃ at a heating rate of 2-5℃ / min, and then kept at this temperature for 4h; then continue to heat to 900-910℃ at a heating rate of 6-10℃ / min, and then keep at this temperature for 24h.

[0018] The application provides a doped oxide sodium-ion battery high-voltage positive electrode material prepared by the above preparation method.

[0019] Therefore, the sodium-ion battery high-voltage positive electrode material doped with an oxide and a preparation method thereof has the following beneficial effects:

[0020] (1) The high-performance sodium-ion battery positive electrode material of the present application realizes metal doping by mixing metal oxides and commercial nickel-iron-manganese layered hydroxide precursors, stabilizes the oxygen lattice, suppresses high-pressure phase transition, and thus optimizes the high-pressure cycle stability of the sodium-ion battery.

[0021] (2) The sodium-ion battery has good cycle stability, and the capacity retention rate is up to 78.9% after 200 cycles at a current density of 1C, and the capacity retention rate is up to 67.4% after 1000 cycles at a current density of 5C.

[0022] The technical solutions of the present application will be further described in detail below with the aid of drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the XRD pattern of NLT812 prepared by the sodium-ion battery high-voltage positive electrode material doped with an oxide and a preparation method thereof according to Embodiment One of the present application and the XRD pattern of NFM333 prepared by Comparative Example One;

[0024] Figure 2 is the scanning electron microscope and element distribution pattern of NLT812 prepared by the sodium-ion battery high-voltage positive electrode material doped with an oxide and a preparation method thereof according to Embodiment One of the present application;

[0025] Figure 3 is the scanning electron microscope and element distribution pattern of NFM833 prepared by Comparative Example One of the sodium-ion battery high-voltage positive electrode material doped with an oxide and a preparation method thereof according to the present application;

[0026] Figure 4 is the first cycle charge-discharge curve of the button cell assembled by NLT812 prepared by the sodium-ion battery high-voltage positive electrode material doped with an oxide and a preparation method thereof according to Embodiment One of the present application at 0.1C;

[0027] Figure 5 is the first cycle charge-discharge curve of the button cell assembled by NFM333 prepared by Comparative Example One of the sodium-ion battery high-voltage positive electrode material doped with an oxide and a preparation method thereof according to the present application at 1C;

[0028] Figure 6 is the cycle number-specific capacity-coulombic efficiency curve of the button cell assembled by NLT812 prepared by the sodium-ion battery high-voltage positive electrode material doped with an oxide and a preparation method thereof according to Embodiment One of the present application and NFM333 prepared by Comparative Example One at 1C;

[0029] Figure 7The cycle number-specific capacity-coulombic efficiency curve of the button cell assembled by the NLT812 prepared according to the sodium ion battery high-voltage positive electrode material doped with an oxide according to the embodiment one of the present application and the NFM333 prepared according to the comparative example one at 5C. DETAILED DESCRIPTION

[0030] The technical solutions of the present application are further described below through the drawings and examples.

[0031] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those skilled in the art to which the present application belongs.

[0032] Embodiment one

[0033] The preparation method of the sodium ion battery high-voltage positive electrode material doped with an oxide comprises the following steps:

[0034] S1, according to Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 The amount of Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2 in O2 is calculated, the amount of Ni, Fe, Mn and Ti is the calculated value, and the actual amount of Na and Li is 5% more than the calculated value. The weighed Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2 are mixed uniformly and then ground to obtain a premixed powder;

[0035] S2, the premixed powder is dried in an oven, the drying temperature is 50℃, and the drying time is 12h to obtain a dry powder;

[0036] S3, the dry powder is put into a ball mill for ball milling, the rotation speed of the ball mill is 400r / min, and the ball milling time is 2h to obtain a gray-brown powder, which is then put into a tablet press for tabletting, and the pressure of the tabletting is 16MPa to obtain a round tablet;

[0037] S4, the round tablet is placed in a high-temperature tube furnace for high-temperature sintering, argon is used as a protective gas, the temperature is first increased to 450℃ at a rate of 5℃ / min, and then kept for 4h; then the temperature is continuously increased to 900℃ at a rate of 10℃ / min, and then kept for 24h to obtain the sodium ion battery high-voltage positive electrode material doped with an oxide, which is recorded as Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2O2, denoted as NLT812.

[0038] Example Two

[0039] The preparation method of the doped oxide sodium-ion battery high-voltage positive electrode material comprises the following steps:

[0040] S1, according to Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 The stoichiometric ratio in O2 is used to calculate the amount of Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2, the amount of Ni, Fe, Mn and Ti is the calculated value, and the actual amount of Na and Li is 5% more than the calculated value. After the weighed Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2 are mixed uniformly and ground, a premixed powder is obtained;

[0041] S2, the premixed powder is dried in an oven, the drying temperature is 60℃, and the drying time is 12h, a dry powder is obtained;

[0042] S3, the dry powder is put into a ball mill for ball milling, the rotating speed of the ball mill is 300r / min, the ball milling time is 3h, a gray-brown powder is obtained, and then the powder is put into a tablet press for tabletting, the pressure of the tabletting is 16MPa, a round tablet is obtained;

[0043] S4, the round tablet is placed in a high-temperature tube furnace for high-temperature sintering, argon is used as the protective gas, first, the temperature is raised to 400℃ at a rate of 5℃ / min, and the temperature is kept for 4h; then, the temperature is continuously raised to 900℃ at a rate of 10℃ / min, and the temperature is kept for 24h, a doped oxide sodium-ion battery high-voltage positive electrode material is obtained, denoted as Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 O2, denoted as NLT812.

[0044] Example Three

[0045] The preparation method of the doped oxide sodium-ion battery high-voltage positive electrode material comprises the following steps:

[0046] S1, according to Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2. The actual amount of Na and Li is 5% more than the calculated value. The weighed Na2CO3, (NiFeMn) 1 / 3 (OH)2, Li(OH)2·H2O and TiO2are mixed uniformly and then ground to obtain a premixed powder;

[0047] S2, the premixed powder is dried in an oven, the drying temperature is 80℃, and the drying time is 12h to obtain a dry powder;

[0048] S3, the dry powder is put into a ball mill for ball milling, the rotation speed of the ball mill is 350r / min, and the ball milling time is 2.5h to obtain a gray-brown powder, which is then put into a tablet press for tabletting, and the pressure of the tabletting is 16MPa to obtain a round tablet;

[0049] S4, the round tablet is placed in a high-temperature tube furnace for high-temperature sintering, argon is used as the protective gas, the temperature is first raised to 500℃ at a rate of 5℃ / min, and then the temperature is continuously raised to 910℃ at a rate of 10℃ / min, and the temperature is kept for 24h to obtain a doped oxide sodium-ion battery high-voltage positive electrode material, which is denoted as Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 O2, denoted as NLT812.

[0050] Comparative Example One

[0051] The preparation method of commercial NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, comprising the following steps:

[0052] The preparation method of a doped oxide sodium-ion battery high-voltage positive electrode material, comprising the following steps:

[0053] S1, according to NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, the amount of Na2CO3and (NiFeMn) 1 / 3 (OH)2is calculated. The weighed Na2CO3and (NiFeMn) 1 / 3 (OH)2are mixed uniformly and then ground to obtain a premixed powder;

[0054] S2, the premixed powder is dried in an oven, the drying temperature is 50℃, and the drying time is 12h to obtain a dry powder;

[0055] S3, the dry powder was put into a ball mill for ball milling, the rotation speed of the ball mill was 400 r / min, the ball milling time was 2 h, a grayish brown powder was obtained, and the powder was put into a tablet press for tabletting, the pressure of the tabletting was 16 MPa, and a round tablet was obtained;

[0056] S4, the round tablet was put into a high-temperature tube furnace for high-temperature sintering, argon was used as a protective gas, first, the temperature was raised to 450 °C at a rate of 5 °C / min, and the temperature was kept for 4 h; then, the temperature was continuously raised to 900 °C at a rate of 10 °C / min, and the temperature was kept for 24 h, and NaNi 1 / 3Fe 1 / 3 Mn 1 / 3 O2, denoted as NFM333.

[0057] Test Test One

[0058] According to Figure 1 , the XRD results of NLT812 prepared in Comparative Example One and NFM333 prepared in Comparative Example One were compared, the peak positions of the two were basically the same, but the peak positions of NLT812 were shifted to the left as a whole compared with NFM333, because the introduction of Ti element reduced the Na element, which led to the increase of the interlayer spacing. At the same time, the characteristic peak at 2θ = 18.6° proved that the Li / Ti co-doping successfully introduced the superlattice structure in the material.

[0059] Figure 2 The scanning electron microscope and element distribution diagram of NLT812 prepared in Example One are shown in Figure 3 , and the scanning electron microscope and element distribution diagram of NFM333 prepared in Comparative Example One are shown in Figure 2 and Figure 3 It can be seen from the comparison that the Ti element is successfully introduced into NLT812.

[0060] Test Test Two

[0061] In order to test the effect of Li / Ti co-doping on improving the high-pressure electrochemical performance of the layered positive oxide material, NLT812 prepared in Example One and NFM333 prepared in Comparative Example One were respectively assembled into half-batteries in a glove box for testing, and the specific steps were as follows:

[0062] NLT812 or NFM333 was used as a positive electrode, a metal sodium sheet was used as a negative electrode, and an electrolyte was 1M NaClO4 in PC = 100 Vol% with 5% FEC. A type 2032 button cell was used to assemble a battery in an argon-protected glove box.

[0063] Under the condition of a current of 0.1C, the first circle charge-discharge curves of the button cells assembled by NLT812 and NFM333 were respectively as shown in Figure 4 , Figure 5As shown in the figure, during the charging process of NLT812 to 4.4V, there is no obvious charge / discharge step as seen in NFM333, indicating that its structure does not follow the Na... + Significant structural changes occurred during the extraction process. Simultaneously, the NLT812 exhibited a high first-cycle discharge specific capacity of 161.39 mA hg. -1 It is much higher than the 151.18 mA hg of NFM333. -1 This means that the stable superlattice constructed by doping with Li successfully activated the reversible redox reaction mechanism of the oxygen lattice.

[0064] The cycle life-specific capacity-coulombic efficiency curves of the coin cell assembled from NLT812 and NFM333 under 1C current conditions are shown in [reference needed]. Figure 6 .Depend on Figure 6 It can be seen that the discharge specific capacity of NLT812 at a current density of 1C is as high as 119.84 mA hg. -1 It is much higher than the 96 mA hg of NFM333. -1 Furthermore, after 200 cycles, it still retains 77.69% of its capacity.

[0065] The cycle life-specific capacity-coulombic efficiency curves of the coin cells assembled from NLT812 and NFM333 under 5C current conditions are shown in [reference needed]. Figure 7 .Depend on Figure 7 It can be seen that the discharge specific capacity of NLT812 at a 5C current density is as high as 95.62 mA hg. -1 Furthermore, after 1000 cycles, it still retains 69.20% of its capacity, while the NFM333 has a discharge specific capacity of 92.86 mA hg. -1 After approximately 200 cycles, the structure showed significant collapse, and after 1000 cycles, almost no capacity remained. This indicates that the stable superlattice structure constructed with Li / Ti co-doping exhibits significantly improved capacity and stability under high pressure compared to NFM333.

[0066] Therefore, the present invention adopts the above-mentioned sodium-ion battery high-voltage cathode material and preparation method of doped oxide, and achieves element doping by mixing commercial nickel-iron-manganese layered hydroxide precursor with metal oxide, thereby suppressing the unfavorable phase transition of sodium-ion layered oxide in electrochemical reaction and the loss of lattice oxygen during charge and discharge process, and improving high-voltage cycle stability.

[0067] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a high-voltage cathode material for sodium-ion batteries doped with oxides, characterized in that, Includes the following steps: S1, Na2CO3, (NiFeMn) 1 / 3 After uniformly mixing (OH)2, Li(OH)2·H2O and TiO2, they are ground to obtain a premixed powder; S2. Dry the premixed powder in an oven to obtain a dry powder; S3. The dried powder is ball-milled and then compressed into tablets to obtain round tablets; S4. The wafer is placed in a high-temperature tube furnace for high-temperature sintering to obtain a sodium-ion battery high-voltage cathode material doped with oxides, denoted as Na. 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 O2; In S3, the ball mill speed is 300-400 r / min, the ball milling time is 2-3 h, and the tableting pressure is 14-18 MPa; In S4, the specific operation during high-temperature sintering is as follows: using argon as the protective gas, the temperature is first raised to 400-500℃ at a heating rate of 2-5℃ / min and held for 4 hours; then the temperature is further raised to 900-910℃ at a heating rate of 6-10℃ / min and held for 24 hours.

2. The preparation method according to claim 1, characterized in that, In S1, Na2CO3 and (NiFeMn) 1 / 3 The amounts of (OH)2, Li(OH)2·H2O, and TiO2 are: based on Na 0.8 Ni 025 Fe 0.25 Mn 0.25 Li 0.1 Ti 0.2 The stoichiometric ratios of O2 are calculated, and the amounts of Ni, Fe, Mn and Ti are calculated. The actual amounts of Na and Li are 5% more than the calculated values.

3. The preparation method according to claim 1, characterized in that, In S2, the drying temperature is 50-80℃ and the drying time is 12-14h.

4. A high-voltage cathode material for sodium-ion batteries doped with oxides, characterized in that, The high-voltage cathode material for sodium-ion batteries, doped with oxides, was prepared using the method described in any one of claims 1-3.

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