NaaLixMnyNzO2 (at) conductive ceramic modified lithium-manganese-based sodium electroactive material as well as preparation and application thereof in sodium ion battery

Abstract

The invention belongs to the field of sodium ion batteries, and particularly relates to a NaaLixMnyNzO2-coated conductive ceramic modified lithium manganese-based sodium electroactive material, which comprises a base material and a coating material coating the base material, and is characterized in that the chemical formula of the base material is NaaLixMnyNzO2, and the chemical formula of the coating material is conductive ceramic; wherein a is greater than or equal to 0.6 and less than or equal to 1.05, 0lt; x is greater than or equal to 0.5 and less than or equal to 0.4, y is greater than or equal to 0.5 and less than or equal to 0.9, z is greater than or equal to 0 and less than or equal to 0.2, x + y + kz = 1, and the element N represents one or more of B, Mg, Zn, Sn, Al, V, Co, Fe, Cu, Nb, Mo, Ru, Sb, Bi and Ti; k is the valence of N; the conductive ceramic comprises an AbBc conductive ceramic material, an element A comprises one or more of Si, Ta, W, Ti, Al and B, and an element B comprises one or two of C and N; b is the valence value of the element B; and c is the valence of the element A. The invention provides preparation and application of the material. The material disclosed by the invention can improve the high-temperature and fast-charging performance of the lithium-manganese-based sodium electroactive material.

Description

Technical Field

[0001] The present invention belongs to the field of positive electrode materials, and specifically relates to the technical field of positive electrode materials for sodium ion batteries. Background Art

[0002] As an alternative energy storage technology to lithium-ion batteries, sodium-ion batteries have attracted widespread attention in recent years. Layered oxide cathode materials are an important type of cathode material in sodium-ion batteries, with high theoretical capacity and good cycle performance. The advantages of layered oxide materials include: high theoretical energy density, relatively abundant raw material resources, and low cost. However, layered oxide cathode materials for sodium-ion batteries still face some challenges in practical applications, mainly including low actual specific capacity, poor cycle stability, and uncontrollable stress and strain.

[0003] There are many types of layered oxides for sodium-ion batteries, for example, mainly nickel-based, iron-based, lithium-manganese-based, etc. Different materials have different physicochemical properties and face different problems. For example, lithium-manganese-based positive electrode materials can provide additional capacity due to the anion redox reaction under high voltage, making it one of the most influential positive electrode matrix materials. However, excessive redox reactions of lattice oxygen during charging and discharging will lead to the generation and escape of oxygen, thereby reducing the cycle stability of sodium-ion batteries. In addition, the volume strain of lithium-manganese-based layered oxides under high voltage, insufficient electronic (ionic) conductivity, interfacial side reactions, and high-temperature storage problems caused by the dissolution of transition metal Mn at high temperatures are all problems that need to be solved in the current industrialization of LiMn-based layered oxides. Therefore, researchers continue to optimize materials through modification, doping, coating and other methods to improve their battery performance, especially to improve the redox reversibility of oxygen, inhibit oxygen precipitation, and reduce material stress and strain.

[0004] For example, a Chinese patent document with publication number CN118867209A discloses a modified sodium ion battery positive electrode material, comprising an O3 phase sodium transition metal oxide matrix and a coating layer 1 located on at least a portion of the surface of the matrix, wherein the coating layer 1 has a tunnel phase and a spinel phase, and the chemical formula of the coating layer 1 is [Na x Li 0.44-x ][MnyLi 1-y ]O 2 , wherein 0.39≤x≤0.4, 0.03≤y≤0.06, and also includes a coating layer 2, and the substrate, coating layer 1 and coating layer 2 are arranged in sequence from the inside to the outside; the coating layer 2 is Na 3 RuO 4For example, the Chinese patent document with publication number CN117254007A discloses a battery layered positive electrode material and its preparation method and application, whose molecular formula is: (Li / Na)aMO2@Na-β”-Al2O3; the inner layer material of the battery layered positive electrode material is (Li / Na)aMO2, and the coating layer material is Na-β”-Al2O3.

[0005] In summary, although there are a few improvement methods for lithium-manganese-based sodium cathode active materials in the existing technology, it is still difficult to effectively solve the problems of high voltage, high temperature, and unsatisfactory high-rate performance caused by the characteristics of lithium-manganese-oxygen release. Summary of the invention

[0006] To solve the above problems, the first object of the present invention is to provide a Na a Li x Mn y N z O 2 @Conductive ceramic modified lithium manganese-based sodium electroactive materials are designed to synergistically solve problems such as high capacity, high safety, high rate, and insufficient high temperature stability under high voltage.

[0007] The second object of the present invention is to provide the Na a Li x Mn y N z O 2 @Preparation method of conductive ceramic modified lithium manganese based sodium electroactive materials and their application in sodium ion batteries.

[0008] The third object of the present invention is to provide a method comprising a Li x Mn y N z O 2 @Sodium-ion batteries and their positive electrodes and positive electrode materials using conductive ceramic modified lithium manganese-based sodium electroactive materials.

[0009] Different from conventional layered oxide positive electrode active materials, lithium manganese-based active materials have anion redox reactions at high voltages, thereby providing additional capacity characteristics. However, they have a special problem of capacity decay caused by oxygen release at high voltages during the cycle process. Aiming at the problems faced by lithium manganese sodium electroactive materials, the present invention has provided the following improvement schemes after in-depth research:

[0010] Na a Li x Mn y N z O 2@The conductive ceramic modified lithium manganese-based sodium electroactive material includes a matrix material and a coating material coating the substrate material. The chemical formula of the matrix material is Na a Li x Mn y N z O 2 , where 0.6 ≤ a ≤ 1.05, 0 < x ≤ 0.4, 0.5 ≤ y ≤ 0.9, 0 ≤ z ≤ 0.2, and x + y + kz = 1. The element N represents one or more of B, Mg, Zn, Sn, Al, V, Co, Fe, Cu, Nb, Mo, Ru, Sb, Bi, Ti; the k is the valence of N;

[0011] The conductive ceramic includes A b B c conductive ceramic material, where the element A includes one or more of Si, Ta, W, Ti, Al, B, and the element B includes one or two of C and N; b is the valence value of the element B; the c is the valence of the element A.

[0012] Aiming at the special problems faced by the lithium manganese-based sodium electroactive material, the research of the present invention shows that innovatively using the conductive ceramic to coat it can adapt to the physical and chemical characteristics of the matrix material, can solve problems such as oxygen release of the lithium manganese matrix material, and can significantly improve its stability and electrochemical performance under high voltage, high temperature, and fast charging.

[0013] In the present invention, the a is 0.6 - 0.8 (further can be 0.6 - 0.65); the x is 0.1 - 0.3 (further can be 0.15 - 0.25); the y is 0.7 - 0.9 (further can be 0.75 - 0.85); the N includes at least one of Zn, Mg, Sn; further preferably includes two or more of them. Research shows that using the preferred N can further cooperate internally and externally with the coating process of the present invention, contribute to further improving the oxygen release problem under high voltage, and can further cooperate to improve the performance of the material under high voltage, high temperature, and fast charging.

[0014] Preferably, the A b B c conductive ceramic material includes at least one of SiC, TaC, WC, Si3N4, TiN, AlN.

[0015] Preferably, the conductive ceramic is also allowed to include at least one auxiliary ceramic material of AlPO 4 , ZrSiO 4 , Al 2 SiO 4 , MgSiO 3 .

[0016] Preferably, the coating material comprises a first coating material and a second coating material; the first coating material is A b B c Conductive ceramic material; the second coating material includes A b B c At least one of a conductive ceramic material and an auxiliary ceramic material; wherein the first coating material and the second coating material are selected from different materials. Studies have shown that under the coating of the preferred composite conductive ceramic, the characteristics of the lithium manganese matrix can be further adapted, and the high voltage, high temperature and fast charging performance of the material can be further improved.

[0017] Further preferably, the first coating material is selected from SiC, TaC, WC, Si 3 N 4 At least one of the following; the second coating material is selected from SiC, TaC, WC, Si 3 N 4 、AlPO 4 、ZrSiO 4 、Al 2 SiO 5 MgSiO 3 At least one of .

[0018] More preferably, the first coating material is SiC and the second coating material is Si 3 N 4 The present invention has shown that under this preferred combination, strong synergy can be unexpectedly achieved, and better performance can be obtained compared to other synergistic combinations, which can further improve the fast charging performance of lithium manganese materials at high voltage and high temperature.

[0019] Preferably, the first coating material accounts for 40-60% of the molar amount of the coating material.

[0020] Preferably, the first coating material is coated on the surface of the base material, and the second coating material is coated on the surface of the first coating material. The present invention shows that on the basis of the innovation of the combined coating material, further optimizing the hierarchical structure of the coating material can further enhance the synergy of the materials, which helps to further improve the fast charging performance of lithium manganese materials under high voltage and high temperature.

[0021] In the present invention, the molar ratio of the substrate to the coating material is 1:0.5-5%, and can further be 1-2%.

[0022] The present invention also provides a kind of Na a Li x Mn y N z O 2@Preparation method of conductive ceramic modified lithium manganese based sodium electroactive material, Na a Li x Mn y N z O 2 and A b B c After mixing, positive pressure sintering is performed to obtain the Na a Li x Mn y N z O 2 @Conductive ceramic modified lithium manganese based sodium electroactive materials.

[0023] In view of the problems faced by lithium manganese-based active materials, the present invention innovatively adopts A b B c The coating modification is further combined with the positive pressure sintering process, so that synergy can be achieved, the combined synergy of the matrix and the coating material can be achieved, the problem of oxygen release under high voltage of the material can be suppressed, and the high voltage, high temperature and fast charging performance of the prepared material can be improved.

[0024] In the present invention, the Na a Li x Mn y N z O 2 It can be prepared based on known means and methods. For example, in the present invention, the Na a Li x Mn y N z O 2 Obtained by calcining a mixture of raw materials containing stoichiometric amounts;

[0025] Preferably, the mixed raw material comprises a Na source, a Li source, a Mn source and a N source;

[0026] Preferably, the Na source, Li source, Mn source and N source are at least one of oxides, hydroxides, carbonates, bicarbonates, nitrates and organic acid salts of the respective elements;

[0027] Preferably, in the mixed raw material, Na is 1 to 1.08 times the theoretical molar amount;

[0028] Preferably, the calcination temperature is 750-1000° C., and further can be 900-950° C. Further, the calcination process also includes a pre-calcination process, wherein the temperature of the pre-calcination stage is 450-650° C. The pre-calcination time can be 3-8 hours.

[0029] Preferably, the calcination time is 8 to 15 hours.

[0030] The synthesis scheme 1 of the present invention innovatively mixes the conductive ceramic and the matrix and then performs the positive pressure sintering, which can improve the coating interface and surface properties, improve the combined synergy of the matrix and the coating material, and improve the stability of the prepared material under high voltage and high temperature.

[0031] In the present invention, the D90 of the conductive ceramic is controlled below 50 um.

[0032] In the present invention, the temperature in the positive pressure sintering stage is 450 to 650°C, and may be 500 to 600°C.

[0033] Preferably, the pressure in the positive pressure sintering stage is +20 to +100 Pa.

[0034] Preferably, the positive pressure sintering time is 5 to 15 hours.

[0035] According to a preferred embodiment of the present invention, when preparing the gradient coated material, the two-stage coating can be used. For example, the base material and the first coating material are mixed in advance for the first coating, and then mixed with the second coating material for the second coating to obtain a preferred composite material.

[0036] The present invention also includes a Na a Li x Mn y N z O 2 @The application of conductive ceramic modified lithium manganese-based sodium electroactive materials as positive electrode active materials to prepare sodium ion batteries.

[0037] In the present invention, the material of the present invention can be used as a positive electrode active material based on known means to prepare a sodium ion battery and its required component materials.

[0038] The present invention also provides a positive electrode material for a sodium ion battery, including a positive electrode active material, wherein the positive electrode active material contains the Na a Li x Mn y N z O 2 @Conductive ceramic modified lithium manganese based sodium electroactive materials.

[0039] Preferably, in the positive electrode active material, the Na a Li x Mn y N z O 2 @The content of the conductive ceramic modified lithium manganese-based sodium electroactive material is above 50wt.%. In the present invention, the Na in the positive electrode active material can be increased. a Li x Mny N z O 2 @The content of lithium manganese-based sodium electroactive materials modified by conductive ceramics is used to further give full play to the performance of the materials.

[0040] In the present invention, the positive electrode material further comprises a conductive agent and a binder, and both the conductive agent and the binder can be components known in the industry.

[0041] In the present invention, in the positive electrode material, the weight ratio of the positive electrode active material, the conductive agent and the binder is 70-95:5-15:5-15.

[0042] 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 described in the present invention.

[0043] The present invention also provides a sodium ion battery, which comprises the positive electrode described in the present invention.

[0044] Beneficial Effects

[0045] The present invention innovatively adopts the b B c The lithium manganese matrix is ​​coated with conductive ceramics, which can achieve adaptive synergy between the matrix and the coating material, and can significantly improve its stability and electrochemical performance under high voltage, high temperature and fast charging.

[0046] The present invention innovatively adopts A b B c The conductive ceramic is coated and modified, and further combined with the positive pressure sintering process, so that synergy can be achieved, and the combined synergy of the matrix and the coating material can be achieved, and the high voltage, high temperature and fast charging performance of the prepared material can be improved.

[0047] The study also shows that the combined use of the materials, coupled with the optimized control of the coating layer relationship of the combined components, can help further improve the high voltage, high temperature, and high rate stability of the lithium manganese material. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The ceramic material SiC coated Na obtained in Example 1 0.6 Li 0.2 Mn 0.8 O 2 XRD patterns of positive electrode materials.

[0049] Figure 2 The ceramic material SiC coated Na obtained in Example 1 0.6 Li 0.2 Mn 0.8O 2 SEM image of the positive electrode material.

[0050] Figure 3 The ceramic material SiC coated Na obtained in Example 1 0.6 Li 0.2 Mn 0.8 O 2 Positive electrode material and comparative synthesized Na 0.6 Li 0.2 Mn 0.8 O 2 First charge and discharge curve of positive electrode material.

[0051] Figure 4 The ceramic material SiC coated Na obtained in Example 1 0.6 Li 0.2 Mn 0.8 O 2 Positive electrode material and Na synthesized in Comparative Example 1 0.6 Li 0.2 Mn 0.8 O 2 Cycling curve of the positive electrode material under 1C conditions.

[0052] Figure 5 The ceramic material SiC coated Na obtained in Example 1 0.6 Li 0.2 Mn 0.8 O 2 Positive electrode material and Na synthesized in Comparative Example 1 0.6 Li 0.2 Mn 0.8 O 2 Cycle curve of positive electrode material under 5C conditions.

[0053] Figure 6 The ceramic material SiC coated Na obtained in Example 1 0.6 Li 0.2 Mn 0.8 O 2 Positive electrode material and Na synthesized in Comparative Example 1 0.6 Li 0.2 Mn 0.8 O 2 Cycle curve of positive electrode material at 45°C.

[0054] Figure 7 The ceramic material SiC coated Na obtained in Example 1 0.6 Li 0.2 Mn 0.8 O 2 Positive electrode material and Na synthesized in Comparative Example 1 0.6 Li 0.2Mn 0.8 O 2 Cycle curve of positive electrode material under 2-4.2V conditions. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the embodiments described are only a part of the embodiments of the present invention, rather than the features in all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0056] Na a Li x Mn y N z O 2 The preparation method of the conductive ceramic modified lithium manganese-based sodium electroactive material comprises the following steps:

[0057] (1) According to the stoichiometric ratio of each element in the lithium manganese-based positive electrode material, sodium source, lithium source, manganese source and other N source material compounds are weighed and mixed evenly, and the lithium manganese-based positive electrode material (Na a Li x Mn y N z O 2 );

[0058] (2) The conductive ceramic material (A b B c ) is fully crushed, mixed evenly with the positive electrode material obtained in step (1) in proportion, and subjected to positive pressure sintering treatment in a certain atmosphere according to a specific sintering system to obtain a lithium manganese-based positive electrode material coated with a conductive ceramic material.

[0059] In step (1), the selected alkali metal source is one or more of sulfates, carbonates, bicarbonates, nitrates, chlorides, acetates, and hydroxides of the metal element; the N source is at least one of sulfates, carbonates, bicarbonates, nitrates, chlorides, acetates, hydroxides, organic acid salts, and oxides of the N element;

[0060] In step (1), the sintering system is gradient sintering, and the sintering atmosphere is air or oxygen-enriched atmosphere;

[0061] Preferably, the first stage sintering temperature is 400-600°C, and the holding time is 5-8h;

[0062] Preferably, the second stage sintering temperature is 750-1000°C, and can further be 900-950°C, and the holding time is 8-15h;

[0063] The crushing method in step (2) adopts jaw crusher, cone crusher, impact crusher, hammer crusher, roller crusher, air flow crusher, etc.; the mixing method adopts one or more of stirring mixing, dispersion mixing, diffusion mixing, and shear mixing; and the sintering stage adopts positive pressure sintering.

[0064] Preferably, the particle size of the conductive ceramic after crushing is controlled to D90≤50um;

[0065] Preferably, the conductive ceramic layer material is Na a Li x Mn y N z O 2 1 to 5 wt% of a mixture of a conductive ceramic material;

[0066] Preferably, in step 2, the sintering temperature is 450-650° C., and can be further kept at 500-600° C. for 5-15 hours. The sintering atmosphere is air or oxygen-rich atmosphere, and the sintering pressure is +20-+100 Pa.

[0067] A more typical preparation process of the modified material of the present invention is, for example:

[0068] Step 1: Preparation of Li-Mn-based cathode material Na a Li x Mn y N z O 2

[0069] Take Na 2 CO 3 , Li 2 CO 3 , Mn 2 O 3 Mix with other transition metal oxides and sinter to obtain Na a Li x Mn y N z O 2 According to an embodiment of the present invention, Na 2 CO 3 , Li 2 CO 3 , Mn 2 O 3Mix the material with other transition metal oxides according to the molar ratio of sodium, lithium, manganese and transition metal of a:x:y:z, where 0.6≤a≤1.05, 0<x≤0.4, 0.5≤y≤0.9, 0≤z≤0.2, and x + y + kz = 1 (k is the valence of N). There are no special limitations on the mixing parameters, and the criterion is to be evenly mixed without white spots. According to the embodiments of the present invention, the mixing speed is 1500 rpm to 2500 rpm, and the mixing time is 5 to 15 minutes;

[0070] Further, in the preparation of the lithium manganese-based cathode material, gradient sintering is adopted. The specific process of the gradient sintering is to keep the temperature at 400 - 600 °C for 5 - 8 hours first, and then raise the temperature to 750 - 1000 °C, which can further be 900 - 950 °C for 8 - 15 hours.

[0071] Step 2: Crush the conductive ceramic material:

[0072] Feed the conductive ceramic material evenly into the crushing chamber through the feed hopper, and control the feeding speed at 80 - 150 kg / min. After extrusion and shear crushing, obtain the ceramic material in the form of fine particles. The crushed ceramic particles fall onto the vibrating screen mesh to obtain the ceramic particles meeting the particle size requirements, where the particle size is controlled such that D90≤50um. The ceramic particles not meeting the particle size requirements return to the crushing chamber from the return port at the higher section of the vibrating screen mesh for re-crushing.

[0073] Step 3: High-voltage and high-rate lithium manganese-based cathode material

[0074] Mix the lithium manganese-based cathode material and the crushed conductive ceramic material evenly, and then sinter the mixture in a box furnace under an oxygen-containing atmosphere at a pressure of +20 to +100 Pa at 450 - 650 °C, which can further be 500 - 600 °C for 5 - 15 hours. Among them, the conductive ceramic material is Na a Li x Mn y N z O 2 and 1 - 5 wt% of the mixture of the conductive ceramic material. There are no special limitations on the mixing parameters, and the criterion is to be evenly mixed without white spots. According to the embodiments of the present invention, the mixing speed is 1500 rpm to 2500 rpm, and the mixing time is 5 to 15 minutes.

[0075] The following are more typical implementation cases, for example:

[0076] Example 1

[0077] In this example, a ceramic SiC material-coated sodium battery cathode material and its preparation method are provided, including the following steps:

[0078] (1) Sodium carbonate, lithium carbonate, and manganese dioxide are mixed in a molar ratio of Na, Li, and Mn of 0.6:0.2:0.8 to obtain a mixed raw material, and an organic solvent (specifically ethanol) is added at the same time. The mixture is placed in a ball mill lined with polytetrafluoroethylene (using zirconium oxide balls at a ball-to-material mass ratio of 1:4), and wet ball milling is performed at a speed of 400 r / min for 8 hours. The mixed solution is placed in a blast oven for drying to obtain a uniformly mixed precursor material. The precursor material is placed in an air box furnace and sintered at a constant temperature of 600°C (marked as T1) for 5 hours (marked as t1), and then sintered at a constant temperature of 950°C (marked as T2) for 10 hours (marked as t2). After sintering, Na 0.6 Li 0.2 Mn 0.8 O 2 Positive electrode material (matrix material).

[0079] (2) The coating material (in this case, SiC ceramic material, which is 1% of the molar amount of the base material in step 2) is crushed by jaw crusher to a particle size of D90≤50um, and mixed with the positive electrode material in (1), and placed in an air box furnace, and sintered for 8 hours at 500°C and a furnace pressure of +50Pa. After sintering, Na2O3 coated with the coating material is obtained. 0.6 Li 0.2 Mn 0.8 O 2 Positive electrode material.

[0080] Example 2

[0081] Compared with Example 1, the only difference is that the coating material in step 2 is changed. The experimental groups are:

[0082] Group A: coating material is TaC;

[0083] Group B: The covering material is WC;

[0084] Group C: Coating material is Si 3 N 4 ;

[0085] Group D: The coating material is SiC and Si with a molar ratio of 1:1 3 N 4

[0086] Group E: The coating material is 50% TaC and 50% WC in molar ratio;

[0087] Group F: The coating material is 60% AlPO 4 +40%SiC;

[0088] Group G: The coating material is 60% ZrSiO4 +40%SiC;

[0089] Group H: The coating material is 60% Al in molar ratio 2 SiO 5 +40%SiC;

[0090] Unless otherwise stated, the amount of coating material used and other operations and parameters are the same as those in Example 1.

[0091] Example 3

[0092] Compared with Example 1, the only difference is that the base material of step 1 can be changed, specifically, the ratio of the elements of the raw materials of step 1 is changed. Other operations and parameters are the same as those of Example 1. The experimental groups are:

[0093] Group A: In step 1, a magnesium-doped matrix material is prepared, that is, magnesium oxide is also added to the mixed raw material, wherein the molar ratio of Na, Mg, Li, and Mn is 0.6:0.05:0.1:0.8, and the chemical formula of the matrix material finally obtained is Na 0.6 Mg 0.05 Li 0.1 Mn 0.8 O 2 ;

[0094] Group B: In step 1, a Zn-doped matrix material is prepared, that is, zinc oxide is also added to the mixed raw material, wherein the molar ratio of Na, Zn, Li, and Mn is 0.6:0.05:0.1:0.8, and the Na of the matrix material finally obtained is 0.6 Zn 0.05 Li 0.1 Mn 0.8 O 2 ;

[0095] Group C: In step 1, a Sn-doped matrix material is prepared, that is, Sn oxide is also added to the mixed raw material, wherein the molar ratio of Na, Sn, Li, and Mn elements is 0.6:0.05:0.1:0.8, and the Na of the matrix material finally obtained is 0.6 Sn 0.05 Li 0.1 Mn 0.8 O 2 ;

[0096] Group D: In step 1, a Mg- and Zn-doped matrix is ​​prepared, that is, magnesium oxide and zinc oxide are also added to the mixed raw materials, wherein the molar ratio of Na, Mg, Zn, Li, and Mn is 0.6:0.05:0.1:0.8, and the matrix material finally obtained is a matrix material group in which Mg and Zn are co-doped, and the chemical formula is Na 0.6 Mg0.025 Zn 0.025 Li 0.1 Mn 0.8 O 2 .

[0097] Example 4

[0098] Compared with Example 1, the only difference is that in step 1, the temperature T1 is 500°C, the time t1 is 6 hours; the temperature T2 is 900°C, the time t2 is 15 hours, and in step 2, the amount of coating material added is 0.7% of the molar amount of the base material. Other operations and parameters are the same as in Example 1.

[0099] Example 5

[0100] Compared with Example 1, the only difference is that in step 2, the treatment temperature is 600°C, the pressure in the treatment stage is changed to +100 Pa, the sintering time is 5 hours, the amount of coating material added is 1.8% of the molar amount of the base material, and other operations and parameters are the same as in Example 1.

[0101] Example 6

[0102] Compared with Example 1, the only difference is that in step 2, two stages of composite coating are performed, and the experimental groups are:

[0103] Group A: Substrate@SiC@Si 3 N 4 :Preliminary use of SiC for Na 0.6 Li 0.2 Mn 0.8 O 2 The positive electrode material is first coated, and then Si 3 N 4 The first-stage coating material is used as a coating material for the second-stage coating, wherein SiC or Si 3 N 4 The dosage is Na 0.6 Li 0.2 Mn 0.8 O 2 0.5% of the molar amount of the positive electrode material; and the parameters such as temperature, pressure and time of the two coating stages are the same as step 3 of the embodiment.

[0104] Group B: Substrate@Si 3 N 4 @SiC: Pre-adoption of Si 3 N 4 To Na 0.6 Li 0.2 Mn 0.8 O 2The positive electrode material is coated in the first stage, and then SiC is used as the coating material to coat the first stage coating material in the second stage, wherein the SiC or Si 3 N 4 The dosage is Na 0.6 Li 0.2 Mn 0.8 O 2 0.5% of the molar amount of the positive electrode material; and the parameters such as temperature, pressure and time of the two coating stages are the same as step 3 of the embodiment.

[0105] Comparative Example 1

[0106] Compared with Example 1, the only difference is that the coating treatment in step 2 is not performed, and the base material prepared in step 2 is directly used as the active material.

[0107] Comparative Example 2

[0108] Compared with Example 1, the only difference is that in step 2, other coating materials are used for coating, and other operations and parameters are the same as those in Example 1, with the following differences:

[0109] Group A: Coating material is Al 2 O 3 ;

[0110] Group B: coating material is TiO;

[0111] Group C: coating material is ZrO;

[0112] Group D: Coating material is AlPO 4

[0113] Group E: Coating material is ZrSiO 4

[0114] Group F: Coating material is Al 2 SiO 5 .

[0115] Comparative Example 3

[0116] Compared with Example 1, the only difference is that in step 2, the sintering stage is normal pressure sintering, and the other operations and parameters are the same as those in Example 1.

[0117] The active material (0.32 g of active material prepared in each case), acetylene black (AB) and polyvinylidene fluoride (PVDF) were added to the n-methyl-2-pyrrolidone (NMP) solution in a mass ratio of 8:1:1, and the above slurry was coated on the treated aluminum foil and dried at 80°C in a vacuum drying oven for 10 hours to obtain the positive electrode. The above-mentioned electrode and sodium sheet were assembled into a button cell in a glove box. The electrolyte is 1 mol / L NaClO4 dissolved in propylene carbonate (PC), and 2% of fluoroethylene carbonate (FEC) is additionally added by volume. Subsequent electrochemical performance tests will focus on button cells.

[0118] The obtained button cells were subjected to electrochemical tests. Table 1 lists the electrochemical performance of each case material at 2-4V, 0.1C, 1C, 5C and room temperature (25°C) conditions, and Table 2 lists the electrochemical performance of each case at 45°C and 2-4.2V conditions.

[0119] Table 1

[0120]

[0121]

[0122] Table 2

[0123]

[0124]

[0125] In summary, it can be seen from Example 1 and Comparative Examples 1 to 3 that the innovative use of the conductive ceramic to coat it can adapt to the physical and chemical characteristics of the matrix material, can solve problems such as oxygen release of the lithium manganese matrix material, and can significantly improve its stability and electrochemical performance under high voltage, high temperature and fast charging.

[0126] In addition, it can be seen from Examples 1 and 2 that the combined coating materials, especially SiC, Si 3 N 4 The combined coating materials can achieve better high voltage, high temperature and fast charging performance of lithium manganese-based materials.

[0127] It can be seen from Examples 1 and 3 that innovative and moderate hybridization of the matrix can obtain better high voltage, high temperature and fast charging performance of lithium manganese-based materials.

[0128] It can be seen from Example 2D, Example 6A and Example 6B that the method of first SiC and then Si 3 N 4The two-stage coating process can further enhance the synergy of the materials and further improve the high voltage, high temperature and fast charging performance of lithium manganese-based materials.

Claims

1. A Na a Li x Mn y N z O2@ conductive ceramic modified lithium manganese-based sodium electroactive material, including a base material and a coating material coating the base material, characterized in that: The chemical formula of the matrix material is Na a Li x Mn y N z O2, the chemical formula of the coating material is conductive ceramic; Among them, 0.6 ≤ a ≤ 1.05, 0 < x ≤ 0.4, 0.5 ≤ y ≤ 0.9, 0 ≤ z ≤ 0.2, and x + y + kz = 1. The element N represents one or more of B, Mg, Zn, Sn, Al, V, Co, Fe, Cu, Nb, Mo, Ru, Sb, Bi, Ti; the k is the valence of N. Conductive ceramics include A b B c Conductive ceramic material, wherein element A includes one or more of Si, Ta, W, Ti, Al, and B, and element B includes one or two of C and N; b is the valence value of element B; and c is the valence value of element A.

2. Na as claimed in claim 1 a Li x Mn y N z O2@ conductive ceramic modified lithium manganese-based sodium electroactive material, characterized in that: The a is 0.6 - 0.8; the x is 0.1 - 0.3; the y is 0.7 - 0.9; the N includes at least one of Zn, Mg, Sn. Preferably, the A b B c The conductive ceramic material includes at least one of SiC, TaC, WC, Si3N4, TiN, and AlN; Preferably, the conductive ceramic is also allowed to include at least one auxiliary ceramic material of AlPO4, ZrSiO4, Al2SiO5, MgSiO3. Preferably, the coating material comprises a first coating material and a second coating material; the first coating material is A b B c Conductive ceramic materials; The second coating material includes A b B c At least one of a conductive ceramic material and an auxiliary ceramic material; wherein the first coating material and the second coating material are selected from different materials; More preferably, the first coating material is selected from at least one of SiC, TaC, WC, Si3N4; the second coating material is selected from at least one of SiC, TaC, WC, Si3N4, AlPO4, ZrSiO4, Al2SiO5, MgSiO3. Even more preferably, the first coating material is SiC and the second coating material is Si3N4. Preferably, the first coating material accounts for 40 - 60% of the molar amount of the coating material. Preferably, the first coating material coats the surface of the matrix material, and the second coating material coats the surface of the first coating material.

3. Na as claimed in claim 1 or 2 a Li x Mn y N z O2@ conductive ceramic modified lithium manganese-based sodium electroactive material, characterized in that: The molar ratio of the matrix to the coating material is 1:0.5 - 5%, and further can be 1 - 2%.

4. A Na according to any one of claims 1 to 3 a Li x Mn y N z The preparation method of O2@ conductive ceramic modified lithium manganese-based sodium electroactive material is characterized in that: Will Na a Li x Mn y N z O2 and A b B c After mixing, positive pressure sintering is performed to obtain the Na a Li x Mn y N z O2@ conductive ceramic modified lithium manganese based sodium electroactive materials.

5. Na as claimed in claim 4 a Li x Mn y N z The preparation method of O2@ conductive ceramic modified lithium manganese-based sodium electroactive material is characterized in that: The Na a Li x Mn y N z O2 is obtained by calcining a mixed raw material containing stoichiometric amounts; Preferably, the mixed raw materials include a Na source, a Li source, a Mn source, and an N source. Preferably, the Na source, Li source, Mn source, and N source are at least one of oxides, hydroxides, carbonates, bicarbonates, nitrates, and organic acid salts of each element. Preferably, in the mixed raw materials, Na is 1 - 1.08 times the theoretical molar amount. Preferably, the roasting temperature is 750 - 1000 °C, and further can be 900 - 950 °C. Preferably, the roasting time is 8 - 15 h.

6. Na as claimed in claim 4 a Li x Mn y N z The preparation method of O2@ conductive ceramic modified lithium manganese-based sodium electroactive material is characterized in that: The temperature in the positive pressure sintering stage is 450 - 650 °C, and further can be 500 - 600 °C. Preferably, the pressure in the positive pressure sintering stage is +20 - +100 Pa. Preferably, the positive pressure sintering time is 5 - 15 h.

7. A Na according to claim 1 to 3 a Li x Mn y N z O2@ conductive ceramic modified lithium manganese-based sodium electroactive material or Na prepared by the preparation method according to any one of claims 4 to 6 a Li x Mn y N z Application of O2@ conductive ceramic modified lithium manganese-based sodium electroactive material, characterized in that: Using it as a positive electrode active material, a sodium ion battery is prepared.

8. A positive electrode material for a sodium ion battery, comprising a positive electrode active material, characterized in that: The positive electrode active material contains the Na a Li x Mn y N z O2@ conductive ceramic modified lithium manganese-based sodium electroactive material or Na prepared by the preparation method according to any one of claims 4 to 6 a Li x Mn y N z O2@conductive ceramic modified lithium manganese-based sodium electroactive materials; Preferably, in the positive electrode active material, the Na a Li x Mn y N z The content of O2@conductive ceramic modified lithium manganese-based sodium electroactive material is above 50wt.%; Preferably, in the positive electrode material, a conductive agent and a binder are further included. Preferably, in the positive electrode material, the weight ratio of the positive electrode active material, the conductive agent, and the binder is 70 - 95:5 - 15:5 - 15.

9. A positive electrode of 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 as claimed in claim 9.

10. A sodium ion battery, characterized in that: Including the positive electrode as claimed in claim 9.

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