Anion-doped nickel-manganese-based layered oxide, its preparation, and application in sodium-ion batteries

Abstract

The present invention belongs to the field of sodium ion batteries, and specifically relates to an anion-doped nickel-manganese-based layered oxide, the chemical formula of which is: Na a Ni b Mn c Me d O 2‑x A x , where Me represents a doped transition metal element and A represents an anion; where a is 0.6≤a≤1.2, b is 0.1<b<0.9, c is 0.1<c<0.9, d is 0≤d≤0.5, and x is 0<x<1.0; A comprises five or more anions capable of forming a high-entropy configuration, and the value of each anion is greater than 0 and less than or equal to 0.1. The present invention also includes the preparation and application of the material. The present invention provides a high-entropy anion material that can effectively improve the stability of the O layer and improve the high-voltage performance of the material.

Description

Technical field:

[0001] The present invention belongs to the field of battery materials, and specifically relates to the technical field of sodium ion battery positive electrode materials. Background technology:

[0002] Due to the excellent electrochemical performance and complete industrial lines of lithium-ion batteries, the demand for lithium-ion batteries has ushered in explosive growth. Coupled with the sharp fluctuations in lithium prices in the past few years, people have raised concerns about the insufficient supply and scarcity of lithium resources. The uncertainty of lithium resources requires the battery industry to develop other practical and commercially viable alternatives. In this regard, sodium-ion batteries (SIBs) are considered to be the most promising alternative to lithium-ion batteries due to their abundant natural reserves. Among the various candidate materials for the positive electrode of sodium-ion batteries, layered transition metal oxides Na x TMO2 (TM refers to transition metal ions) has attracted much attention due to its high specific capacity, simple preparation, and environmental friendliness. However, as the charging process continues, sodium ions gradually escape, leading to structural degradation due to sliding of the transition metal plates, triggering a series of side reactions including volume strain, microcracks, and electrolyte side reactions.

[0003] But in addition to the above problems, the problem of lattice O precipitation in the deep sodium-depleted state also needs to be solved urgently. The special oxygen element configuration in the sodium-ion layered oxide causes electrons to be extracted from the 2p energy level of oxygen. The electrons in the 2p orbital of non-bonding oxygen participate in charge compensation, realizing the additional capacity brought by the anion redox reaction. At the same time, based on X-ray absorption spectroscopy and density functional theory, it is believed that at low sodium content, due to the nickel-oxygen antibonding eg* state, the charge distribution between nickel ions and oxygen ions will be redistributed, promoting the anion redox reaction. When the anion redox reaction occurs, O2 precipitation is prone to occur, which is reflected in the electrochemical performance as fluctuations in charge and discharge efficiency and a significant deterioration in cycle performance; it is reflected in practical applications as the occurrence of battery bloating and bulging, which poses a safety hazard.

[0004] In response to the above-mentioned lattice oxygen evolution problem under deep sodium removal, the current high-entropy oxide materials for sodium ion batteries are more often doped with transition metal elements into layered oxide positive electrode materials to reduce inter-plate sliding during sodium removal, but the improvement of the lattice oxygen evolution problem is limited. For example, the Chinese patent document with publication number CN115064657A discloses a high-entropy layered metal oxide, the doped cations of which include at least 5 of Li+, Cu2+, Ni2+, Ni3+, Co3+, Fe3+, Al3+, Mn3+, Mn4+, Ti4+, Sn4+, and Sb5+. CN116169280A and CN116605918A also reported some similar schemes of high entropy through transition elements.

[0005] In summary, in order to solve the problem of unsatisfactory high-voltage stability of sodium batteries, the main idea of ​​existing technologies is based on cation high entropy, but the selection of cation high entropy doping elements is currently mainly concentrated on some high-cost elements, which increases the preparation cost of the material; there is currently no solution based on anion high entropy. Summary of the invention:

[0006] In response to the problems of sodium ion battery layered oxide anion redox leading to battery gas production, poor crystal stability, and unsatisfactory electrochemical performance, especially high-voltage performance, the first aspect of the present invention is to provide an anion-doped nickel-manganese-based layered oxide material, aiming to provide a new material with improved electrochemical performance based on anion high entropy.

[0007] The second purpose of the present invention is to provide a preparation method of the anion-doped nickel-manganese-based layered oxide material and its application in sodium batteries.

[0008] The third object of the present invention is to provide a sodium ion battery and a positive electrode and positive electrode material thereof comprising the above-mentioned material for improving electrochemical performance by high entropy of anions.

[0009] An anion-doped nickel-manganese-based layered oxide, the chemical formula of which is: Na a Ni b Mn c Me d O 2-x A x , where Me represents the doping transition metal element and A represents the anion;

[0010] Wherein a is 0.6≤a≤1.2, b is 0.1<b<0.9, c is 0.1<c<0.9, d is 0≤d≤0.5, and x is 0<x<1.0;

[0011] The A includes more than 5 kinds of anions and can form a high entropy configuration, and the value of each anion is greater than 0 and less than or equal to 0.1.

[0012] The present invention provides a novel anionic high-entropy nickel-manganese-based layered oxide, which can effectively mitigate phase transitions, exhibits excellent lattice stability, and exhibits superior high-voltage performance. Furthermore, compared to cationic high-entropy materials, the anionic high-entropy material of the present invention not only stabilizes transition metal layer slip, thereby inhibiting phase transitions; in particular, it can significantly inhibit the oxidation of lattice oxygen, reducing the production of O2 due to self-oxidation and the production of gases such as CO2 and CxHy due to side reactions with the electrolyte. In other words, the anionic high-entropy-doped material can significantly inhibit gassing in batteries, reducing the possibility of battery bulging and threats to safety performance.

[0013] The present invention also shows that further optimization of A based on the anion high entropy innovation can further synergistically improve the performance of the material under high pressure.

[0014] In the present invention, the A includes Cl - 、F-、I-、Br - 、SO3 2- 、SO4 2- 、S2O8 2- 、SiO3 2- 、SiO4 4- 、Si2O5 2- PO4 3- PO3 3- 、P2O7 4- , BO3 3- 、B4O7 2- More than five of them.

[0015] Preferably, the A comprises Aa and Ab, and the Aa comprises Cl-, F-, I-, Br - 1 to 3 of the above; the Ab includes SO3 2- 、SO4 2- 、S2O8 2- 、SiO3 2- 、SiO4 4- 、Si2O5 2- PO4 3- PO3 3- 、P2O7 4- , BO3 3- 、B4O7 2- At least one of the following, wherein the anion species of A1 and A2 are 5 to 6;

[0016] More preferably, the Aa contains at least F - ; The Ab contains at least SiO3 2- 、SiO4 4- 、Si2O5 2- At least one of;

[0017] Preferably, said A includes F - 、SiO3 2- 、P2O7 4- .

[0018] Preferably, the value of each anion is greater than 0, less than or equal to 0.05, further preferably 0.01 to 0.04, and further preferably 0.02 to 0.03.

[0019] In the present invention, the Me-doped transition metal element includes, but is not limited to, one or more of Li, Mg, Zn, Sn, Al, V, Co, Fe, Cu, Nb, Mo, Ru, Sb, Bi, and Ti. More preferably, Me is selected from one or more of Mg, Zn, Al, Fe, Cu, and Ti. Even more preferably, Me is selected from one or more of Mg, Zn, Al, and Fe.

[0020] In the present invention, the values ​​of a, b, c, and d for the anion-doped nickel-manganese-based layered oxide species can be adjusted as needed to meet the battery application requirements. In an optional embodiment of the present invention, a is 0.9 to 1; b is 0.3 to 0.4; c is 0.3 to 0.4; and d is 0.3 to 0.4; and x is 0.1 to 0.5, preferably 0.1 to 0.3, and more preferably 0.1 to 0.15. In x, the molar content of each anion is ±50% of the average molar content, preferably ±10% of the average molar amount. Studies have shown that optimal anion high-entropy hybridization effects can be achieved at the optimal ratio.

[0021] In the present invention, the anion-doped nickel-manganese-based layered oxide is a P2 and O3 phase oxide.

[0022] The present invention also provides a method for preparing the anion-doped nickel-manganese-based layered oxide, comprising mixing stoichiometric raw materials of various elements (i.e., mixing Na, Ni, Mn, Me, and A in a molar ratio of a:b:c:d:x), calcining, and cooling to obtain the anion-doped nickel-manganese-based layered oxide.

[0023] Wherein, the calcination temperature is 800~1200℃;

[0024] The cooling process includes two stages, wherein the first stage is furnace cooling with a cutoff temperature above 600°C and less than or equal to 0.9 times the calcination temperature; the second stage is air cooling with a cutoff temperature of 5-100°C.

[0025] Previous research by the present inventors has shown that calcining only raw materials containing multiple anions is prone to problems such as anion segregation and lattice distortion, making it difficult to successfully achieve anion high entropy and obtain the desired high-pressure stable materials. To address this issue, the present inventors innovatively employ a two-stage cooling process: first furnace cooling followed by air cooling, combined with the combined control of parameters such as the calcination temperature and the cutoff temperatures of the two cooling stages. This effectively addresses the problems of segregation and lattice distortion associated with anion doping, successfully achieving the described anion high entropy, and effectively improving the high-pressure performance of the prepared materials.

[0026] In the present invention, in order to avoid the hybridization effect of heteroelement on the final product, the raw material for providing the metal can be a simple substance, various oxides, carbonates, bicarbonates, organic acid salts, nitrates, etc. The raw material for providing the anion A, in addition to the anion A, its cations are, for example, H, ammonium ions, metal Ni, Mn, and Me, etc. For example, the fluoride anion salt selected is one or more of NaF, NH4F, NH4HF2, MnF2, HF, etc., the chloride anion salt is one or more of NaCl, NH4Cl, SiCl4, SO2Cl2, etc., the bromide anion salt is one or more of NaBr, NaBrO3, HBr, NiBr2, MnBr2, etc., the iodide anion salt is one or more of NaI, NaIO3, NH4I, ICl, IBr, PI3, the sulfur anion salt is NaHSO3, The phosphorus anion salt is one or more of Na2SO4, NH4HSO3, B2S3, SiS2, Na2S2O8, etc., the phosphorus anion salt is one or more of NH4H2PO4, P2O5, H3PO4, H2PO3F, HPF6, Na4P2O7, etc., the boron anion salt is one or more of B2O3, H3BO3, B2S3, NaBF4, etc., and the silicon anion salt is one or more of H2SiF6, SiO2, Na2SiF6, SiS2, Na2SiO3, etc. Further preferably, the selected fluoride anion salt is one or more of NaF, NH4F, NH4HF2, etc., the chloride anion salt is one or more of NaCl, NH4Cl, etc., the bromide anion salt is one or more of NaBr, NaBrO3, etc., the iodide anion salt is one or more of NaI, NaIO3, the sulfur anion salt is one or more of NaHSO3, Na2SO4, NH4HSO3, B2S3, etc., the phosphorus anion salt is one or more of NH4H2PO4, P2O5, etc., the boron anion salt is one or more of B2O3, H3BO3, B2S3, NaBF4, etc., and the silicon anion salt is one or more of H2SiF6, Na2SiO3, etc.

[0027] In the present invention, a pre-calcination process is further included before calcination, wherein the holding temperature of the pre-calcination is 300-700°C, and further can be 500-600°C. Studies of the present invention have shown that the use of the preferred two-stage calcination process, combined with the two-stage cooling mechanism described in the present invention, can further facilitate the preparation of the anionic high-entropy material.

[0028] Preferably, the holding time at the pre-calcination temperature is 3-9 hours, and further can be 4-6 hours.

[0029] In the present invention, the calcination temperature is 850-1000°C, preferably 880-920°C;

[0030] Preferably, the calcination time is more than 9 hours, preferably 10 to 20 hours.

[0031] In the present invention, the calcined material is subjected to a two-stage cooling treatment, and the cut-off temperature is jointly controlled, so that the problems of anion segregation and difficulty in achieving anion high entropy can be solved in a coordinated manner.

[0032] The cooling process includes two stages, wherein the first stage of the cooling process has a cutoff temperature of 650-800°C, further 700-780°C, and further 740-760°C;

[0033] The cut-off temperature of the second cooling process is 15-50°C, and can further be room temperature (such as 20-45°C);

[0034] Preferably, the air-cooling atmosphere is air.

[0035] The present invention also provides a positive electrode material for a sodium ion battery, comprising a positive electrode active material, a binder and a conductive agent, wherein the positive electrode active material comprises the anion-doped nickel-manganese-based layered oxide;

[0036] Preferably, in the positive electrode active material, the content of the anion-doped nickel-manganese-based layered oxide is above 50 wt.%. In order to better discover the advantages of the new material of the present invention, the anion-doped nickel-manganese-based layered oxide can be directly used.

[0037] The present invention also provides a positive electrode of a sodium ion battery, comprising a current collector and a positive electrode material composited on the surface of the current collector, wherein the positive electrode material is the positive electrode material of the present invention.

[0038] The present invention also provides a sodium ion battery comprising the positive electrode of the present invention.

[0039] The sodium ion battery of the present invention, except for the new anion-doped nickel-manganese-based layered oxide of the present invention, can have conventional components and part structures.

[0040] Beneficial effects:

[0041] 1. The present invention provides an anion-doped nickel-manganese-based layered oxide material. The present invention prepares an anion high entropy doped layered oxide positive electrode material Na by doping five or more anion-doped nickel-manganese-based layered oxide positive electrode materials. a Ni b Mn c Me d O 2-x A xThe new material described in the present invention has excellent O layer stability, can adapt to high-voltage application requirements, can inhibit high-voltage structural attenuation, lattice O precipitation and TM migration, and improve the material's cycling performance under high pressure.

[0042] 2. Anions are disorderly distributed in the oxygen site lattice, increasing the disorder of the material. The greater the disorder, the greater the entropy and the lower the energy. At the same time, since the high-entropy anion doping site is the O site, the lattice O energy is reduced and the lattice O stability is enhanced. Through the enhanced lattice O stability, the sliding of the metal plate is suppressed by the solid crystal framework in the deep desodium state, and the irreversible phase transition process in the deep desodium state is alleviated.

[0043] 3. The present invention innovatively employs a two-stage cooling process: first furnace cooling followed by air cooling, combined with the combined control of parameters such as the calcination temperature and the cutoff temperature of the two-stage cooling. This effectively addresses the problems of segregation and lattice distortion associated with anion doping, successfully achieving the described anion high-entropy process and effectively improving the high-pressure performance of the prepared material. The present invention introduces multiple anions into the material through a simple, single-stage sintering process, eliminating the need for additional steps and saving costs. Description of the drawings:

[0044] Figure 1 This is the XRD pattern of the material finally obtained in Example 2;

[0045] Figure 2 This is the SEM image of the material finally obtained in Example 2;

[0046] Figure 3 This is the XRD pattern of the material finally obtained in Example 7;

[0047] Figure 4 This is the SEM image of the material finally obtained in Example 7;

[0048] Figure 5 This is a comparison chart of the 2-4.2V cycle performance of the materials finally prepared in Example 1 and Comparative Example 1;

[0049] Figure 6 2-4.2V first charge-discharge curves of the materials finally prepared in Example 1 and Comparative Example 10;

[0050] Figure 7 This is a comparison chart of the 2-4.2V cycle performance of the materials finally prepared in Example 1 and Comparative Example 12; Specific implementation method:

[0051] The specific embodiments of the present invention are described in detail below. It should be understood that the examples are only for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention. The methods described in the present invention are all conventional methods and there is no special method.

[0052] The present invention discloses an anion-doped nickel-manganese-based layered oxide, the chemical formula of which is: Na a Ni b Mn c Me d O 2-x A x , where Me represents the doping transition metal element and A represents the anion;

[0053] A more typical anion-doped nickel-manganese-based layered oxide of the present invention has the chemical formula: Na a Ni b Mn c Me d O 2-x (A 1o A 2p A 3q A 4r A 5s A 6t ), where A1, A2, A3, A4, A5, and A6 represent different doping anions.

[0054] Preferably, 0<o≤0.1, 0<p≤0.1, 0<q≤0.1, 0<r≤0.1, 0<s≤0.1, 0≤t≤0.1.

[0055] More preferably, 0<o≤0.05, 0<p≤0.05, 0<q≤0.05, 0<r≤0.05, 0<s≤0.05, 0≤t≤0.05.

[0056] More preferably, in the above chemical formula, 0.02≤o≤0.04, 0.02≤p≤0.04, 0.02≤q≤0.04, 0.02≤r≤0.04, 0.02≤s≤0.04, and 0≤t≤0.04.

[0057] Preferably, in some embodiments, the anion high entropy doped layered oxide is a P2 phase or an O3 phase.

[0058] The second aspect of the present invention is to provide a method for preparing anion high entropy doped nickel-manganese based doped layered oxide, characterized in that the steps include:

[0059] Step S1, according to the chemical formula of the anion-doped nickel-manganese-based layered oxide, corresponding masses of sodium source, manganese source and nickel source, the transition metal doping element source, and the corresponding anion source are weighed and mixed in a mixer.

[0060] Step S2, then sending it into a roller kiln for calcination.

[0061] Step S3, after cooling, the product is passed through a jaw crusher, a roller crusher, sieved, gas-broken, and packaged to obtain anion-doped nickel-manganese-based layered oxide.

[0062] Preferably, the sodium source in step S1 is selected from one or more of Na2CO3, NaHCO3, NaOH, and NaCH3COO.

[0063] Further preferably, in step S1, the sodium source is selected from one or more of Na2CO3 and NaHCO3.

[0064] Preferably, the nickel source, manganese source and Me source in step S1 are one or more of the hydroxides, carbonates, bicarbonates, oxides, sulfates, nitrates and organic acid salts of the respective metals.

[0065] Further preferably, the nickel source, manganese source and Me source are one or more of the hydroxides, carbonate oxides and oxides of the respective metals.

[0066] More preferably, the nickel source, manganese source and Me source are one or more of the hydroxides and oxides of the respective metals.

[0067] In step S1, the mixing method is wet mixing or dry mixing.

[0068] Preferably, the mixing is done in a dry vertical mixer.

[0069] In some embodiments, the raw material is a nickel-manganese-based precursor mixed with a sodium source and an anion salt and calcined;

[0070] In the preferred step S2 of the present invention, the calcination process is a two-stage heat preservation calcination with a heating rate of 1-10°C / min, a first stage of heat preservation at 300-700°C for 3-9 hours, and a second stage of heat preservation at 800-1200°C for 10-20 hours;

[0071] Preferably, the second-stage calcination temperature is 850-1000° C., preferably 880-920° C., and the holding time is 12-18 hours.

[0072] In the preferred step S3 of the present invention, the cooling process includes two cooling processes, wherein the first cooling process is slow cooling with the furnace, with a cutoff temperature of above 600°C and less than or equal to 0.9 times the calcination temperature; the second cooling process is air cooling, with a cutoff temperature of room temperature.

[0073] Preferably, the first stage cooling cut-off temperature is 650-800°C.

[0074] The sintering atmosphere is one of argon, nitrogen, oxygen and air; preferably, it is one of oxygen and air.

[0075] More preferably, it is dehumidified air.

[0076] In the present invention, the furnace cooling refers to the process of natural cooling after the heating device is stopped.

[0077] In the present invention, the gas cooling (air cooling) refers to the process of cooling by passing room temperature gas.

[0078] In the present invention, the room temperature may be 20-45°C, and further may be 20-30°C.

[0079] In a third aspect, an example of the present invention further provides a positive electrode sheet for a sodium ion battery, the positive electrode sheet comprising:

[0080] The current collector and the active material layer coated on the current collector are characterized in that the active material layer contains the anion high-entropy doped sodium ion battery high-voltage oxide positive electrode material described in the first aspect.

[0081] Example 1

[0082] An anion high entropy doped layered oxide cathode material with the chemical formula NaNi 0.33 Fe 0.34 Mn 0.33 O 1.9 0Cl 0.02 F 0.02 (SiO3) 0.02 (P2O7) 0.02 (B4O7) 0.02 , prepared by the following steps:

[0083] (1) According to the stoichiometric ratio, Na2CO3, NiO, Mn2O3, Fe2O3, NaCl, NaF, Na2SiO3, Na4P2O7, and (NH4)2B4O7 were weighed and mixed in a vertical mixer.

[0084] (2) The material in step (1) is transported into a roller kiln, dehumidified air is introduced, and the temperature is increased at a heating rate of 5°C / min to a first-stage insulation temperature (T1) of 550°C for 5 hours, and then increased to a second-stage insulation temperature (T2) of 900°C for 12 hours.

[0085] (3) The material obtained by burning in step (2) is cooled to 750° C. in the furnace and then air-cooled to room temperature, and then subjected to jaw crusher, roller crusher, sieving, air breaking, and packaging in sequence to obtain anion high-entropy doped layered oxide positive electrode material.

[0086] Example 2

[0087] Compared with Example 1, the only difference is that the raw materials in step (1) are replaced by nickel iron manganese hydroxide, Na2CO3, NaCl, NaF, Na2SiO3, Na4P2O7, and (NH4)2B2O7, and the other preparation conditions are the same as those in Example 1.

[0088] Example 3

[0089] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.88 Cl 0.02 F 0.02 (SiO3) 0.02 (P2O7) 0.02 (B4O7) 0.02 (SO4) 0.02 Weigh Na2CO3, NiO, Mn2O3, Fe2O3, NaCl, NaF, Na2SiO3, Na4P2O7, (NH4)2B4O7, and Na2SO4 and mix them in a vertical mixer. Other preparation conditions are the same as those in Example 1.

[0090] Example 4

[0091] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.90 Cl 0.02 F 0.02 (SO4 2- ) 0.02 (PO4) 0.02 (BO3) 0.02 Na2CO3, NiO, Mn2O3, Fe2O3, NaCl, NaF, Na2SO4, NH4H2PO4, and H3BO3 were weighed in a stoichiometric ratio and mixed in a vertical mixer. Other preparation conditions were the same as those in Example 1.

[0092] Example 5

[0093] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.90 F 0.02 (PO4) 0.02 (SiO3) 0.02 (SO4) 0.02 (B4O7) 0.02Na2CO3, NiO, Mn2O3, Fe2O3, NaF, NH4H2PO4, Na2SiO3, Na2SO4, and (NH4)2B4O7 were weighed in a stoichiometric ratio and mixed in a vertical mixer. Other preparation conditions were the same as those in Example 1.

[0094] Example 6

[0095] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.75 Cl 0.05 F 0.05 (SiO3) 0.05 (P2O7) 0.05 (B4O7) 0.05 Na2CO3, NiO, Mn2O3, Fe2O3, NaCl, NaF, Na2SiO3, Na4P2O7, and (NH4)2B4O7 were weighed in a stoichiometric ratio and mixed in a vertical mixer. Other preparation conditions were the same as those in Example 1.

[0096] Example 7

[0097] Compared with Example 1, the only difference is that the second insulation time in step (2) is replaced with 10 hours, and the other preparation conditions are the same as those in Example 1.

[0098] Example 8

[0099] Compared with Example 1, the only difference is that in step (2), the first stage insulation temperature T1 is 600°C and the time is 4 hours; the second stage insulation temperature T2 is replaced by 850°C and the time is 16 hours. Other preparation conditions are the same as those in Example 1.

[0100] Example 9

[0101] Compared with Example 1, the only difference is that the first cooling cut-off temperature in step (3) is replaced with 700° C., and the other preparation conditions are the same as those in Example 1.

[0102] Example 10

[0103] Compared with Example 1, the only difference is that in step (2), the first insulation process is cancelled, and the other operations and parameters are the same as Example 1.

[0104] Comparative Example 1

[0105] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33O2 weighed Na2CO3, NiO, Mn2O3, and Fe2O3 and mixed them in a vertical mixer. Other preparation conditions were the same as those in Example 1.

[0106] Comparative Example 2

[0107] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.9 F 0.2 Weigh Na2CO3, NiO, Mn2O3, Fe2O3, and NaF and mix them in a vertical mixer. Other preparation conditions are the same as those in Example 1.

[0108] Comparative Example 3

[0109] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.9 (SiO3) 0.1 Weigh Na2CO3, NiO, Mn2O3, Fe2O3, and Na2SiO3 and mix them in a vertical mixer. Other preparation conditions are the same as those in Example 1.

[0110] Comparative Example 4

[0111] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.9 (P2O7) 0.05 Weigh Na2CO3, NiO, Mn2O3, Fe2O3, and Na4P2O7 and mix them in a vertical mixer. Other preparation conditions are the same as those in Example 1.

[0112] Comparative Example 5

[0113] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.9 F 0.04 (P2O7) 0.04 Weigh Na2CO3, NiO, Mn2O3, Fe2O3, NaF, and Na4P2O7 and mix them in a vertical mixer. Other preparation conditions are the same as those in Example 1.

[0114] Comparative Example 6

[0115] Compared with Example 1, the only difference is that in step (1), NaNi0.33 Fe 0.34 Mn 0.33 O 1.9 F 0.02 (P2O7) 0.04 (SiO3) 0.01 Weigh Na2CO3, NiO, Mn2O3, Fe2O3, Na2SiO3, NaF, and Na4P2O7 and mix them in a vertical mixer. Other preparation conditions are the same as those in Example 1.

[0116] Comparative Example 7

[0117] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 O 1.9 Cl 0.02 F 0.04 (SiO3) 0.03 (P2O7) 0.02 Weigh Na2CO3, NiO, Mn2O3, Fe2O3, NaCl, NaF, Na2SiO3, and Na4P2O7 and mix them in a vertical mixer. Other preparation conditions are the same as those in Example 1.

[0118] Comparative Example 8

[0119] Compared with Example 1, the only difference is that in step (1), NaNi 0.33 Fe 0.34 Mn 0.33 OCl 0.2 F 0.2 (SiO3) 0.2 (P2O7) 0.2 (B4O7) 0.2 Na2CO3, NiO, Mn2O3, Fe2O3, NaCl, NaF, Na2SiO3, Na4P2O7, and (NH4)2B4O7 were weighed according to the stoichiometric ratio and mixed in a vertical mixer. Other preparation conditions were the same as those in Example 1.

[0120] Comparative Example 9

[0121] Compared with Example 1, the only difference is that the second-stage insulation temperature T2 in step (2) is replaced with 750°C, and the other preparation conditions are the same as those in Example 1.

[0122] Comparative Example 10

[0123] Compared with Example 1, the only difference is that in step (2), the cooling stage is a single air cooling process, the final cutoff temperature is the room temperature of Example 1, and the other preparation conditions are the same as Example 1.

[0124] Comparative Example 11

[0125] Compared with Example 1, the only difference is that the cooling system in step (3) is a single furnace cooling, the final cut-off temperature is the same as room temperature in Example 1, and the other preparation conditions are the same as Example 1.

[0126] Comparative Example 12

[0127] Compared with Example 1, the only difference is that the cutoff temperature of the first cooling process in step (3) is 500°C, and the other preparation conditions are the same as those in Example 1.

[0128] The active material (0.32 g of active material prepared in Examples 1-9 and Comparative Examples 1-12), acetylene black (AB), and polyvinylidene fluoride (PVDF) were added to an n-methyl-2-pyrrolidone (NMP) solution in a mass ratio of 8:1:1. The slurry was coated on treated aluminum foil and dried in a vacuum drying oven at 80°C for 10 hours to obtain a positive electrode. The above-mentioned electrode and sodium sheet were assembled into a button cell in a glove box. The electrolyte was 1 mol / L NaClO4 dissolved in propylene carbonate (PC), with an additional 2% by volume of fluoroethylene carbonate (FEC). Subsequent electrochemical performance tests will focus on button cells.

[0129] The obtained button cell was subjected to electrochemical testing. The battery capacity at 2-4.0V and 1C was 130mAh / g, and at 2-4.2V and 1C was 170mAh / g. The results are shown in Table 1.

[0130] Table 1 Electrochemical test results

[0131]

[0132]

[0133] According to Table 1, the comparison between Example 1 and Comparative Example 1 shows that the 100-cycle capacity retention rate of Example 2-4.2V is 89.17%, which is much higher than 32.01% of Comparative Example 1. It can be seen that the anion high entropy doping effectively improves the high voltage performance and suppresses the loss of lattice oxygen. By comparing Example 1 with Example 3, Example 4, Example 5, and Example 6, it can be seen that there are preferred types and preferred doping amounts of high entropy doped anions, including F - 、SiO3 2- 、P2O7 4-The appropriate amount of high entropy doping formed by more than five elements including can effectively improve the lattice stability of the material and inhibit crystal oxygen loss; Comparative Example 1 and Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, Comparative Example 7, Comparative Example 8 can be seen that anion high entropy doping is different from simple multi-element doping, and the formation of high entropy configuration is a key factor in achieving high-voltage stability; Comparative Example 1 and Comparative Example 9, Comparative Example 10 can be seen that the 2-4V discharge specific capacity of Example 1 is 136.89mAh / g, the 2-4.2V discharge specific capacity is 170.34mAh / g, and the 100-cycle capacity retention rate is 89.17%, and the 2-4V discharge specific capacity of Comparative Example 9 is 100.2 3mAh / g, the 2-4.2V discharge specific capacity is 122.46mAh / g, and the 100-cycle capacity retention rate is 68.89%. The 2-4V discharge specific capacity of Comparative Example 10 is 112.32mAh / g, the 2-4.2V discharge specific capacity is 146.23mAh / g, and the 100-cycle capacity retention rate is 15.34%, indicating that the calcination system has a great relationship with the crystal crystallinity and lattice integrity, and seriously affects the stability of the crystal structure and the high-voltage performance of the material; by comparing Example 1 with Comparative Example 11 and Comparative Example 12, it can be seen that the two-stage cooling system plays an important role in the high-voltage stability of the material, and air cooling after furnace cooling to an appropriate temperature can greatly improve the high-voltage stability of the material.

[0134] Finally, it should be clearly stated that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit it. Although the embodiments have described the technical solution in detail, ordinary technicians in this field should understand that they can still make appropriate modifications to the embodiments involved in the technical solution, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solution of the embodiments of the present invention.

Claims

1. An anion-doped nickel-manganese-based layered oxide, characterized in that: Its chemical formula is: Na a Ni b Mn c Me d O 2-x A x , where Me represents the doping transition metal element and A represents the anion; Wherein a is 0.6≤a≤1.2, b is 0.1<b<0.9, c is 0.1<c<0.9, d is 0≤d≤0.5, and x is 0<x<1.0; The A includes more than 5 kinds of anions and can form a high entropy configuration, and the value of each anion is greater than 0 and less than or equal to 0.

1.

2. The anion-doped nickel-manganese-based layered oxide according to claim 1, wherein: Said A includes Cl - 、F - , I - Br - 、SO3 2- 、SO4 2- 、S2O8 2- 、SiO3 2- 、SiO4 4- 、Si2O5 2- PO4 3- PO3 3- 、P2O7 4- , BO3 3- 、B4O7 2- More than five of them.

3. The anion-doped nickel-manganese-based layered oxide according to claim 2, wherein: The A includes Aa and Ab, and the Aa includes Cl - 、F - , I - Br - 1 to 3 of the above; the Ab includes SO3 2- 、SO4 2- 、S2O8 2- 、SiO3 2- 、SiO4 4- 、Si2O5 2- PO4 3- PO3 3- 、P2O7 4- , BO3 3- 、B4O7 2- At least one of the following, wherein the anion types of A1 and A2 are 5 to 6.

4. The anion-doped nickel-manganese-based layered oxide according to claim 3, wherein: The Aa contains at least F - ; The Ab contains at least SiO3 2- 、SiO4 4- 、Si2O5 2- At least one of .

5. The anion-doped nickel-manganese-based layered oxide according to claim 1, wherein The A includes F - 、SiO3 2- 、P2O7 4- At least one of .

6. The anion-doped nickel-manganese-based layered oxide according to claim 1, wherein: The value of each anion is greater than 0 and less than or equal to 0.

05.

7. The anion-doped nickel-manganese-based layered oxide according to claim 6, wherein: The value of each anion is 0.01~0.

04.

8. The anion-doped nickel-manganese-based layered oxide according to claim 7, wherein: The value of each anion is 0.02~0.

03.

9. The anion-doped nickel-manganese-based layered oxide according to claim 1, wherein: Me-doped transition metal elements include one or more elements of Li, Mg, Zn, Sn, Al, V, Co, Fe, Cu, Nb, Mo, Ru, Sb, Bi, and Ti.

10. The anion-doped nickel-manganese-based layered oxide according to claim 1, wherein The a is 0.9-1; the b is 0.3-0.4; the c is 0.3-0.4; the d is 0.3-0.4; and the x is 0.1-0.

5.

11. The anion-doped nickel-manganese-based layered oxide according to claim 1, wherein The anion-doped nickel-manganese-based layered oxides are P2 and O3 phase oxides.

12. A method for preparing an anion-doped nickel-manganese-based layered oxide according to any one of claims 1 to 11, characterized in that: Mixing raw materials of various elements in stoichiometric amounts, calcining, and cooling to obtain the anion-doped nickel-manganese-based layered oxide; Among them, the calcination temperature is 800~1200℃; The cooling process includes two stages, wherein the first stage is furnace cooling with a cutoff temperature above 600°C and less than or equal to 0.9 times the calcination temperature; the second stage is air cooling with a cutoff temperature of 5-100°C.

13. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 12, wherein: The process includes a pre-calcination process before calcination, wherein the pre-calcination holding temperature is 300-700°C.

14. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 13, wherein: The holding time at the pre-calcination temperature is 3-9h.

15. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 12, wherein: The calcination temperature is 850~1000℃.

16. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 15, wherein: The calcination temperature is 880~920℃.

17. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 12, wherein: The calcination time is more than 9 hours.

18. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 17, wherein: The calcination time is 10 to 20 hours.

19. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 12, wherein: The cooling process includes two stages of cooling, wherein the first stage of cooling is performed at a cut-off temperature of 650-800°C; the second stage of cooling is performed by air cooling, with a cut-off temperature of 15-50°C.

20. The method for preparing anion-doped nickel-manganese-based layered oxide according to claim 19, wherein: The air-cooling atmosphere is air.

21. A positive electrode material for a sodium ion battery, comprising a positive electrode active material, a binder and a conductive agent, characterized in that: The positive electrode active material comprises the anion-doped nickel-manganese-based layered oxide according to any one of claims 1 to 11.

22. The positive electrode material for a sodium ion battery according to claim 21, wherein In the positive electrode active material, the content of the anion-doped nickel-manganese-based layered oxide is above 50 wt.%.

23. A positive electrode for a sodium ion battery, comprising a current collector and a positive electrode material composited on the surface thereof, characterized in that: The positive electrode material is the positive electrode material according to claim 21 or 22.

24. A sodium ion battery, characterized in that: Comprising the positive electrode according to claim 23.

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