A positive electrode material and its preparation method and application

Abstract

The present invention provides a positive electrode material and its preparation method and application. The positive electrode material is an O3 phase layered oxide as shown in formula 1; Na x Ni a Fe b Mn c M d O e Formula 1, where M is a doping element; 0.9 < x ≤ 1.25, 0.11 ≤ a ≤ 0.33, 0.22 ≤ b ≤ 0.33, 0.33 ≤ c ≤ 0.66, 0 ≤ d ≤ 0.33, 1.8 ≤ e ≤ 2.2, and a + b + c + d = 1; and the stacking factor of the positive electrode material is 0.67-0.72. The positive electrode material has a higher stacking factor, resulting in a more complete unit cell structure and morphology. A battery including the positive electrode material has excellent cycle performance and capacity.

Description

Technical Field

[0001] The present invention relates to a positive electrode material and a preparation method and application thereof, belonging to the technical field of secondary batteries. Background Art

[0002] As a new type of power battery, sodium-ion batteries have attracted considerable attention due to their low cost and high energy density. Meanwhile, the scarcity and rising price of lithium resources have driven the development of sodium-ion batteries in power batteries. Currently, sodium-rich layered oxides are widely used as cathode materials in sodium-ion batteries.

[0003] Sodium-rich layered oxides mainly include sodium, manganese, iron, nickel and doping elements (fourth-class transition metals). In the prior art, sodium-rich layered oxides are mainly prepared by a one-step calcination treatment of a raw material system including a sodium source, a manganese source, an iron source and a doping element source. Studies have found that in the sodium-rich layered oxide obtained by the one-step calcination treatment, Na is easily present on the surface of the sodium-rich layered oxide, resulting in a high residual alkali content on the surface of the sodium-rich layered oxide, which is not conducive to the cycle performance of the battery; and because Na is present on the surface of the sodium-rich layered oxide rather than in the bulk phase, the stacking factor of the sodium-rich layered oxide is small, resulting in a poor capacity of the battery including the sodium-rich layered oxide. Summary of the Invention

[0004] The present invention provides a positive electrode material having a higher stacking factor, and thus having a more complete unit cell structure and morphology. A battery including the positive electrode material has excellent cycle performance and capacity.

[0005] The present invention provides a method for preparing a positive electrode material. The method can prepare the positive electrode material mentioned above, and the preparation process is simple, and is suitable for wide promotion and application.

[0006] The present invention provides a battery, which comprises the above-mentioned positive electrode material and thus has excellent cycle performance and discharge gram capacity.

[0007] The present invention provides a positive electrode material, wherein the positive electrode material is an O3 phase layered oxide as shown in Formula 1;

[0008] Na x Ni a Fe b Mn c M d O e Formula 1

[0009] In formula 1, M is a doping element;

[0010] 0.9<x≤1.25, 0.11≤a≤0.33, 0.22≤b≤0.33, 0.33≤c≤0.66, 0≤d≤0.33, 1.8≤e≤2.2, a+b+c+d=1;

[0011] The stacking factor of the positive electrode material is 0.67-0.72.

[0012] The positive electrode material as described above, wherein the surface carbonate content of the positive electrode material is 100-20000 ppm.

[0013] The positive electrode material as described above, wherein 0.11≤d≤0.33.

[0014] The positive electrode material as described above, wherein the compaction density of the positive electrode material is 3.2 to 3.8 g / cm at 5 MPa. 3 .

[0015] The positive electrode material as described above, wherein the stacking factor of the positive electrode material is 0.68-0.69.

[0016] The present invention provides a method for preparing the positive electrode material as described above, which comprises the following steps:

[0017] A first raw material system including a raw material source is subjected to a first calcination treatment to obtain a first intermediate positive electrode material; the raw material source includes a sodium source, a nickel source, an iron source, a manganese source and an M source, and I Na ≤I Na理论 , I Ni ≤I Ni理论 , I Fe ≤I Fe理论 , I Mn ≤I Mn理论 , I M ≤I M理论 ;

[0018] Obtain the actual stacking factor PF of the first intermediate positive electrode material 实际 , and the actual molar percentage of Na in the first intermediate positive electrode material I Na实际 , the actual molar percentage of Ni I Ni实际 , the actual molar percentage of Fe I Fe实际 , the actual molar percentage of Mn I Mn实际 , the actual molar percentage of M I M实际 ;

[0019] Determine the PF of the first intermediate cathode material 实际 and the theoretical stacking factor PF of the cathode material 理论 Whether the first expected relationship is satisfied, the I of the first intermediate positive electrode material is determined Na实际 , INi实际 , I Fe实际 , I Mn实际 , I M实际 and I Na理论 , I Ni理论 , I Fe理论 , I Mn理论 , I M理论 Whether the second expected relationship is met;

[0020] If the first expected relationship and the second expected relationship are satisfied, the first intermediate positive electrode material is the positive electrode material;

[0021] Among them, I Na is the molar percentage of Na in the first raw material system; I Ni is the molar percentage of Ni in the first raw material system; I Fe is the molar percentage of Fe in the first raw material system; I Mn is the molar percentage of Mn in the first raw material system; I M is the molar percentage of M in the first raw material system; I Na理论 is the theoretical molar percentage of Na in the positive electrode material; I Ni理论 is the theoretical molar percentage of Ni in the positive electrode material; I Fe理论 is the theoretical molar percentage of Fe in the positive electrode material; I Mn理论 is the theoretical molar percentage of Mn in the positive electrode material; I M理论 is the theoretical molar percentage of M in the positive electrode material;

[0022] The first expected relationship is: |PF 实际 -PF 理论 |<0.001;

[0023] The second expected relationship is: |I Na实际 -I Na理论 ∣<0.02、∣I Ni实际 -I Ni理论 ∣<0.02、∣I Fe实际 -I Fe理论 ∣<0.02、∣I Mn实际 -I Mn理论 |<0.02 and |I M实际 -I M理论 ∣<0.02.

[0024] The preparation method as described above, wherein, if the third expected relationship is satisfied: |PF 实际 -PF 理论 |≥0.001; and / or, satisfying the fourth expected relationship: |I Na实际 -I Na理论∣≥0.02, ∣I Ni实际 -I Ni理论 ∣≥0.02, ∣I Fe实际 -I Fe理论 ∣≥0.02, ∣I Mn实际 -I Mn理论 ∣≥0.02 or ∣I M实际 -I M理论 ∣≥0.02, including:

[0025] 1) adding at least one of the sodium source, nickel source, iron source, manganese source, and M source to the first intermediate cathode material and performing a second calcination process to obtain a second intermediate cathode material;

[0026] Among them, if |PF 实际 -PF 理论 |≥0.001, then adding a sodium source to the first intermediate positive electrode material; and / or,

[0027] If | I Na实际 -I N理论 |≥0.02, then adding a sodium source to the first intermediate positive electrode material; and / or,

[0028] If | I Ni实际 -I Ni理论 |≥0.02, then adding a nickel source to the first intermediate positive electrode material; and / or,

[0029] If | I Fe实际 -I Fe理论 |≥0.02, then add an iron source to the first intermediate positive electrode material; and / or,

[0030] If | I Mn实际 -I Mn理论 |≥0.02, then add a manganese source to the first intermediate positive electrode material; and / or, if |I M实际 -I M理论 |≥0.02, then add M source to the first intermediate positive electrode material;

[0031] 2) Obtaining the PF of the second intermediate cathode material 实际 , and I of the second intermediate positive electrode material Na实际 , I Ni实际 , I Fe实际 , I Mn实际 , I M实际 ,

[0032] 3) Determine the PF of the second intermediate cathode material 实际 With PF 理论 Whether the first expected relationship is met, the I of the second intermediate positive electrode material is determined Na实际 , I Ni实际, I Fe实际 , I Mn实际 , I M实际 and I Na理论 , I Ni理论 , I Fe理论 , I Mn理论 , I M理论 Whether the second expected relationship is met;

[0033] 4) Repeating steps 1)-3) 0-N times until the first expected relationship and the second expected relationship are satisfied, thereby obtaining the positive electrode material, N≥1.

[0034] The preparation method as described above, wherein, comprises the following steps:

[0035] A first raw material system including a raw material source is subjected to a first calcination treatment to obtain a first intermediate positive electrode material; the raw material source includes a sodium source, a nickel source, an iron source, a manganese source and an M source, and I Na 0.78-0.9, I Ni =I Ni理论 , I Fe =I Fe理论 , I Mn =I Mn理论 , I M =I M理论 ;

[0036] A sodium source is added to the first intermediate positive electrode material to obtain a second raw material system, and the second raw material system is subjected to a second calcination treatment to obtain the positive electrode material.

[0037] In the preparation method as described above, in the second raw material system, the ratio of the molar percentage of Na in the sodium source to the molar percentage of Na in the first intermediate positive electrode material is (0.05-0.2):1.

[0038] The preparation method as described above, wherein, during the calcination treatment, the temperature is 800-1000°C, the heating rate is 1-5°C / min, and the time is 10-15h;

[0039] The calcination treatment is a first calcination treatment and / or a second calcination treatment.

[0040] The present invention provides a battery, comprising the positive electrode material as described above.

[0041] The positive electrode material of the present invention has a higher stacking factor and a more complete unit cell structure and morphology. The battery comprising the positive electrode material has excellent cycle performance and capacity.

[0042] The preparation method of the positive electrode material of the present invention can prepare the composite positive electrode material mentioned above, and the preparation method is simple to operate and suitable for wide promotion and application.

[0043] The battery of the present invention, because it includes the above-mentioned positive electrode material, has excellent cycle performance and discharge capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0045] Figure 1 is a graph showing the stacking factor and discharge gram capacity of the positive electrode material of the present invention;

[0046] Figure 2 1 is the XRD pattern of the first intermediate positive electrode material and the second intermediate positive electrode material in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0048] A first aspect of the present invention provides a positive electrode material, wherein the positive electrode material is an O3 phase layered oxide represented by Formula 1;

[0049] Na x Ni a Fe b Mn c M d O e Formula 1

[0050] In formula 1, M is a doping element;

[0051] 0.9<x≤1.25, 0.11≤a≤0.33, 0.22≤b≤0.33, 0.33≤c≤0.66, 0≤d≤0.33, 1.8≤e≤2.2, a+b+c+d=1;

[0052] The stacking factor of the positive electrode material is 0.67-0.72.

[0053] In the present invention, the O3-phase layered oxide refers to an oxide having an O3-phase layered crystal structure in the XRD pattern of the positive electrode material. The positive electrode material of the present invention includes at least sodium, nickel, iron, and manganese, and may further include a doping element. The doping element may be a doping element commonly used in the art. For example, the doping element M may be at least one of Cu, Zn, Zr, Ti, Ta, Nb, Ti, Sb, Al, Mg, K, Li, B, P, S, F, and Se.

[0054] In the present invention, the packing factor refers to the volume percentage occupied by the ions themselves in the unit cell, that is, the ratio of the volume of the ions contained in the unit cell to the unit cell volume. The packing factor of the present invention can be calculated using Formula 2.

[0055] PF=∑N*V 离子体积 / V 晶胞体积 Formula 2

[0056] In formula 1, PF is the stacking factor;

[0057] V 离子体积 is the volume of the ions in the unit cell;

[0058] V 晶胞体积 is the unit cell volume;

[0059] N is the number of ions.

[0060] Among them, V 离子体积 According to V = (4 / 3)πr 3 Where r is the ionic radius, which can be obtained by consulting technical data. For example, Na + The ionic radius is Ni 2+ The ionic radius is Mn 4+ The ionic radius is Fe 3+ The ionic radius is O 2- The ionic radius is Cu 2+ The ionic radius is Zn 2+ The ionic radius is

[0061] V 晶胞体积 It can be obtained by refining the XRD spectrum of the positive electrode material using the Rietveld method.

[0062] It is well known in the art that defect-free O3-phase layered oxides have three Na +, 6 O 2- , 3 other metal ions (including Ni 2+ 、Fe 3+ 、Mn 4+ and M ions), considering that there are defects in the crystal phase of the positive electrode material, Na + The number of elements is 3*the actual molar percentage of Na element, Ni 2+ The number of elements is 3*the actual molar percentage of Ni element, Fe 3+ The number of elements is 3*the actual molar percentage of Fe, Mn 4+ The number of M ions is 3*the actual molar percentage of Mn element, the number of M ions is 3*the actual molar percentage of M element, 2- The number of is 6.

[0063] The present invention does not impose any particular limitation on the morphology of the positive electrode material, and the morphology may be irregular or spherical single crystal particles, or secondary particles formed by the aggregation of primary particles.

[0064] Figure 1 The graph of the stacking factor and discharge gram capacity of the positive electrode material in the present invention is shown in FIG. Figure 1 It can be seen that the stacking factor of the positive electrode material is positively correlated with the discharge gram capacity of the positive electrode material, so it can be understood that the higher the stacking factor of the positive electrode material, the higher its discharge gram capacity; however, in actual applications, it is almost difficult to make the stacking factor of the positive electrode material infinitely high, and the higher the stacking factor, the more complicated its preparation process is, the poorer its feasibility is, which is not conducive to the promotion and application of positive electrode materials.

[0065] The positive electrode material of the present invention has a stacking factor of 0.67-0.72. When used in a battery, this positive electrode material can improve the battery's discharge capacity. Furthermore, due to the high stacking factor of this positive electrode material, it indicates that more of the sodium in the positive electrode material is present within the bulk phase of the positive electrode material rather than on its surface. Therefore, the surface residual alkali content of the positive electrode material is low. When used in a battery, this positive electrode material is less likely to generate gas during the battery cycle, which helps improve the battery's cycle performance. Furthermore, this positive electrode material has excellent implementability.

[0066] In the present invention, the surface carbonate content of the positive electrode material can be used to represent the surface residual alkali content of the positive electrode material. In some embodiments of the present invention, when the surface carbonate content of the positive electrode material is 100-20000 ppm, the positive electrode material is less likely to produce gas during the battery cycle, which helps to further improve the battery's cycle performance. The present invention can use potentiometric titration to test the surface carbonate content of the positive electrode material.

[0067] It is understood that the content of the doping element will also have a significant impact on the performance of the positive electrode material. When the positive electrode material contains a doping element, the content of the doping element can be further selected to further improve the overall performance of the positive electrode material. In some embodiments of the present invention, when 0.11≤d≤0.33, the positive electrode material has a more excellent discharge capacity and surface residual alkali content.

[0068] Since the positive electrode material of the present invention has a high packing factor, the internal vacancies and atomic stacking gaps of the positive electrode material are relatively small, and thus the positive electrode material has a high compaction density. In some embodiments of the present invention, the compaction density of the positive electrode material is 3.2 to 3.8 g / cm at 5 MPa. 3 When the positive electrode material has a higher discharge capacity.

[0069] Furthermore, when the stacking factor of the positive electrode material is 0.68-0.69, the preparation process can be simplified and the feasibility of the positive electrode material can be improved while ensuring the comprehensive performance of the positive electrode material.

[0070] A second aspect of the present invention provides a method for preparing the above-mentioned positive electrode material, which comprises the following steps:

[0071] A first raw material system including a raw material source is subjected to a first calcination treatment to obtain a first intermediate positive electrode material; the raw material source includes a sodium source, a nickel source, an iron source, a manganese source and an M source, and I Na ≤I Na理论 , I Ni ≤I Ni理论 , I Fe ≤I Fe理论 , I Mn ≤I Mn理论 , I M ≤I M理论 ;

[0072] Obtain the actual stacking factor PF of the first intermediate positive electrode material 实际 , and the actual molar percentage of Na in the first intermediate positive electrode material I Na实际 , the actual molar percentage of Ni I Ni实际 , the actual molar percentage of Fe I Fe实际 , the actual molar percentage of Mn I Mn实际 , the actual molar percentage of M I M实 际 ;

[0073] Determine the PF of the first intermediate cathode material 实际 and the theoretical stacking factor PF of the cathode material 理论 Whether the first expected relationship is satisfied, the I of the first intermediate positive electrode material is determined Na实际1 , INi实际1 , I Fe实际1 , I Mn实际1 , I M实际1 and I Na理论 , I Ni理论 , I Fe理论 , I Mn理论 , I M理论 Whether the second expected relationship is met;

[0074] If the first expected relationship and the second expected relationship are satisfied, the first intermediate positive electrode material is the positive electrode material;

[0075] Among them, I Na is the molar percentage of Na in the first raw material system; I Ni is the molar percentage of Ni in the first raw material system; I Fe is the molar percentage of Fe in the first raw material system; I Mn is the molar percentage of Mn in the first raw material system; I M is the molar percentage of M in the first raw material system; I Na理论 is the theoretical molar percentage of Na in the positive electrode material; I Ni理论 is the theoretical molar percentage of Ni in the positive electrode material; I Fe理论 is the theoretical molar percentage of Fe in the positive electrode material; I Mn理论 is the theoretical molar percentage of Mn in the positive electrode material; I M理论 is the theoretical molar percentage of M in the positive electrode material;

[0076] The first expected relationship is: |PF 实际 -PF 理论 |<0.001;

[0077] The second expected relationship is: |I Na实际 -I Na理论 ∣<0.02、∣I Ni实际 -I Ni理论 ∣<0.02、∣I Fe实际 -I Fe理论 ∣<0.02、∣I Mn实际 -I Mn理论 |<0.02 and |I M实际 -I M理论 ∣<0.02.

[0078] Specifically, according to the molar percentage ratio of each element in the expected positive electrode material, the theoretical stacking factor of the positive electrode material is simulated and obtained;

[0079] According to the molar percentage of each element in the expected positive electrode material, a first raw material system including a sodium source, an iron source, a manganese source, and an M source is prepared. In order to save raw materials and avoid waste, the molar percentages of Na, Fe, Mn, and M in the first raw material system are all less than or equal to the molar percentages of Na, Fe, Mn, and M in the expected positive electrode material;

[0080] Performing a first calcination treatment on the first raw material system to obtain an actual stacking factor of the first intermediate positive electrode material and an actual molar percentage content of each element in the first intermediate positive electrode material;

[0081] Comparing the actual stacking factor of the first intermediate positive electrode material with the theoretical stacking factor, and comparing the actual molar percentage of each element in the first intermediate positive electrode material with the molar percentage of each element in the expected positive electrode material;

[0082] If the actual stacking factor of the first intermediate positive electrode material and the theoretical stacking factor satisfy the first expected relationship, it is proved that the actual stacking factor of the first intermediate positive electrode material is consistent with the expected stacking factor; and the actual molar percentage of each element in the first intermediate positive electrode material and the molar percentage of each element in the expected positive electrode material satisfy the second expected relationship, it is proved that the molar percentage of each element in the first intermediate positive electrode material is consistent with the molar percentage of each element in the expected positive electrode material, indicating that the first intermediate positive electrode material is the expected positive electrode material.

[0083] In the present invention, the first intermediate positive electrode material can be subjected to an XRD test to obtain an XRD spectrum of the first intermediate positive electrode material, and the XRD spectrum of the first intermediate positive electrode material can be refined by the Rietveld method to obtain the unit cell volume of the first intermediate positive electrode material, and then the actual stacking factor of the first intermediate positive electrode can be obtained according to Formula 2.

[0084] In the present invention, the first intermediate cathode material may be subjected to an ICP test to obtain the actual molar percentage content of each element in the first intermediate cathode material.

[0085] The present invention does not particularly limit the sodium source, as long as it can provide sodium element. Exemplarily, the sodium source can be one or more of sodium carbonate, sodium bicarbonate and sodium hydroxide; the present invention does not particularly limit the nickel source, as long as it can provide nickel element. Exemplarily, the nickel source can be one or more of nickel oxide, nickel nitrate and nickel acetate; the present invention does not particularly limit the iron source, as long as it can provide iron element. Exemplarily, the iron source can be one or more of manganese tetraoxide, ferric nitrate and ferric oxide; the present invention does not particularly limit the manganese source, as long as it can provide manganese element. Exemplarily, the manganese source can be one or more of manganese carbonate, manganese acetate, manganese trioxide and manganese tetraoxide.

[0086] In the present invention, the M source can be selected from one or more of a Cu source, a Zn source, a Zr source, a Ta source, a Nb source, a Ti source, a Sb source, an Al source, a Mg source, a Li source, a K source, a P source, a S source, a F source, a B source, and a Se source. When the M source is a Cu source, the Cu source can be one or more of copper oxide, copper sulfate, and copper nitrate; when the M source is a Zn source, the Zn source can be one or more of zinc oxide, zinc sulfate, and zinc nitrate; when the M source is a Zr source, the Zr source can be ZrO2; when the M source is a Ta source, the Ta source can be Ta2O5; when the M source is a Nb source, the Nb source can be Nb2O5; when the M source is a Ti source, the Ti source can be TiO2; when the M source is a Sb source, the Sb source can be one or more of Sb2O3 and Sb2O5; when the M source is an Al source, the Al source can be one or more of Al2O3 and Al(OH)3; when the M source is a Mg source, the Mg source can be MgO and Mg(OH)2 one or more; when the M source is a Li source, the Li source may be one or more of LiOH, Li2O and Li2CO3; when the M source is a K source, the K source may be one or more of KOH and K2S; when the M source is a P source, the P source may be one or more of NH4H2PO4, Li3PO4, H3PO4 and FePO4; when the M source is a S source, the S source may be one or more of Na2S and K2S; when the M source is a F source, the F source may be one or more of NaF, LiF, KF and NH4F; when the M source is a B source, the B source may be one or more of H3BO3 and B2O3; when the M source is a Se source, the Se source may be one or more of Se and SeO2.

[0087] The preparation method of the present invention can prepare a positive electrode material having the same crystal phase structure as the expected positive electrode material while saving raw materials. The preparation method has low preparation cost and is suitable for wide promotion and application.

[0088] In some embodiments of the present invention, if the third expected relationship is satisfied: |PF 实际 -PF 理论 |≥0.001; and / or, satisfying the fourth expected relationship: |I Na实际 -I Na理论 ∣≥0.02, ∣I Ni实际 -I Ni理论 ∣≥0.02, ∣I Fe实际 -I Fe理论 ∣≥0.02, ∣I Mn实际 -I Mn理论 ∣≥0.02 or ∣I M实际 -I M理论 ∣≥0.02, including:

[0089] 1) adding at least one of a sodium source, a nickel source, an iron source, a manganese source, and an M source to the first intermediate cathode material, and performing a second calcination treatment to obtain a second intermediate cathode material;

[0090] Among them, if |PF 实际 -PF 理论 |≥0.001, then add a sodium source to the first intermediate positive electrode material; and / or,

[0091] If | I Na实际 -I N理论 |≥0.02, then add a sodium source to the first intermediate positive electrode material; and / or,

[0092] If | I Ni实际 -I Ni理论 |≥0.02, then add a nickel source to the first intermediate positive electrode material; and / or,

[0093] If | I Fe实际 -I Fe理论 |≥0.02, then add an iron source to the first intermediate positive electrode material; and / or,

[0094] If | I Mn实际 -I Mn理论 | ≥ 0.02, then add a manganese source to the first intermediate positive electrode material; and / or, if | I M实际 -I M理论 |≥0.02, then add M source to the first intermediate positive electrode material;

[0095] 2) Obtaining the PF of the second intermediate cathode material 实际 , and I of the second intermediate cathode material Na实际 , I Ni实际 , I Fe实际 , I Mn实际 , I M实际 ;

[0096] 3) Determine the PF of the second intermediate cathode material 实际 With PF 理论 Whether the first expected relationship is met, the I of the second intermediate positive electrode material is determined Na实际 , I Ni实际 , I Fe实际 , I Mn实际 , I M实际 and I Na理论 , I Ni理论 , I Fe理论 , I Mn理论 , I M理论 Whether the second expected relationship is met;

[0097] 4) Cycle steps 1)-3) 0-N times until the first expected relationship and the second expected relationship are satisfied, thereby obtaining a positive electrode material.

[0098] Specifically, 1) if the third expected relationship and / or the fourth expected relationship are satisfied (the first expected relationship and the second expected relationship are not satisfied), it is proved that the obtained first intermediate positive electrode material is significantly different from the expected positive electrode material. At least one of a sodium source, a nickel source, an iron source, a manganese source, and an M source can be added to the first intermediate positive electrode material and a second calcination treatment can be performed to obtain a second intermediate positive electrode material;

[0099] Furthermore, if |PF 实际 -PF 理论 |≥0.001, indicating that the Na element in the bulk phase of the first intermediate positive electrode material is insufficient, and it is necessary to add a sodium source to the first intermediate positive electrode material to increase the Na in the bulk phase of the first intermediate positive electrode material, thereby improving the actual stacking factor; and / or,

[0100] If | I Na实际 -I Na理论 |≥0.02, indicating that the Na content in the first intermediate positive electrode material is lower than that in the positive electrode material, a sodium source is added to the first intermediate positive electrode material to increase the Na content in the first intermediate positive electrode material; and / or,

[0101] If | I Ni实际 -I Ni理论 |≥0.02, indicating that the Ni content in the first intermediate positive electrode material is lower than that in the positive electrode material, a nickel source is added to the first intermediate positive electrode material to increase the Ni content in the first intermediate positive electrode material; and / or,

[0102] If | I Fe实际 -I Fe理论 |≥0.02, indicating that the Fe content in the first intermediate positive electrode material is lower than that in the positive electrode material, an iron source is added to the first intermediate positive electrode material to increase the Fe content in the first intermediate positive electrode material; and / or,

[0103] If | I Mn实际 -I Mn理论 |≥0.02, indicating that the Mn content in the first intermediate positive electrode material is lower than that in the positive electrode material, a manganese source is added to the first intermediate positive electrode material to increase the Mn content in the first intermediate positive electrode material; and / or,

[0104] If | I M实际 -I M理论 |≥0.02, indicating that the M content in the first intermediate positive electrode material is lower than that in the positive electrode material, and an M source is added to the first intermediate positive electrode material to increase the M content in the first intermediate positive electrode material;

[0105] 2) obtaining an actual stacking factor of the second intermediate cathode material and an actual molar percentage of each element in the second intermediate cathode material;

[0106] 3) determining whether the actual stacking factor and the theoretical stacking factor of the second intermediate positive electrode material satisfy a first expected relationship, and determining whether the actual molar percentage of each element in the second intermediate positive electrode material and the expected molar percentage of the positive electrode material satisfy a second expected relationship. If the first expected relationship and the second expected relationship are satisfied, respectively, it is proved that the second intermediate positive electrode material and the expected positive electrode material have a similar crystal phase structure and a similar composition, and therefore the second intermediate positive electrode material is a positive electrode material;

[0107] 4) If it does not meet the first expected relationship and the second expected relationship (meets the third expected relationship and / or the fourth expected relationship), repeat steps 1) to 3) until the actual stacking factor of the obtained intermediate positive electrode material and the theoretical stacking factor meet the first expected relationship, and the actual molar percentage content of each element in the obtained intermediate positive electrode material and the expected molar percentage content of the positive electrode material meet the second expected relationship, thereby obtaining the positive electrode material.

[0108] It can be understood that in the preparation method of the present invention, when the content of the M source in the raw material source is 0, a positive electrode material without doping elements can be obtained.

[0109] In some embodiments of the present invention, the method for preparing the cathode material of the present invention may include the following steps:

[0110] A first raw material system including a raw material source is subjected to a first calcination treatment to obtain a first intermediate positive electrode material; the raw material source includes a sodium source, a nickel source, an iron source, a manganese source and an M source, and I Na 0.78-0.9, I Ni =I Ni理论 , I Fe =I Fe理论 , I Mn =I Mn理论 , I M =I M理论 ;

[0111] A sodium source is added to the first intermediate positive electrode material to obtain a second raw material system, and the second raw material system is subjected to a second calcination treatment to obtain a positive electrode material.

[0112] Specifically, a first raw material system including a sodium source, a nickel source, an iron source, a manganese source, and an M source is prepared such that the molar percentage of the sodium element in the first raw material system is 0.78-0.9, the molar percentages of the nickel element, the iron element, and the manganese element are all the same as the molar percentages of the nickel element, the iron element, and the manganese element in the expected positive electrode material, and the molar percentage of the M element is less than or equal to the molar percentage of the M element in the expected positive electrode material.

[0113] performing a first calcination process on the first raw material system to obtain a first intermediate positive electrode material;

[0114] Obtain the actual molar percentage of each element in the first intermediate positive electrode material and the actual stacking factor of the first intermediate positive electrode material; generally, during the first calcination treatment, it is difficult for the Na element to completely enter the unit cell of the first intermediate positive electrode material, but it is more present on the surface of the unit cell. Therefore, the actual stacking factor of the first intermediate positive electrode material obtained is quite different from the theoretical stacking factor, that is, the actual stacking factor of the first intermediate positive electrode material satisfies |PF 实际 -PF 理论 | ≥ 0.001, and usually in the first calcination treatment, the loss of sodium element is large, so the molar percentage of sodium element in the first intermediate positive electrode material is much smaller than the theoretical molar percentage of the expected positive electrode material, that is, the actual molar percentage of sodium element in the first intermediate positive electrode material satisfies | I Na实际 -I Na理论 ∣≥0.02;

[0115] Therefore, it is necessary to add a sodium source to the first intermediate positive electrode material to obtain a second raw material system, and perform a second calcination treatment on the second raw material system to allow more sodium elements to enter the unit cell of the second intermediate positive electrode material, thereby increasing the actual stacking factor of the second intermediate positive electrode material, thereby obtaining a second intermediate positive electrode material close to the theoretical stacking factor. Moreover, through the second intermediate calcination treatment, the molar percentage of the sodium element in the second intermediate positive electrode material can be increased, and a second intermediate positive electrode material close to the molar percentage of the sodium element in the expected positive electrode material can be obtained. Since the actual stacking factor of the second intermediate positive electrode material conforms to the first expected relationship, and the actual molar percentage of each element conforms to the second expected relationship, the second intermediate positive electrode material is the expected positive electrode material.

[0116] By specifically designing the molar percentage of the Na element in the first raw material system, the present invention can obtain a positive electrode material through two calcination processes. This not only allows more sodium to be present within the unit cells of the positive electrode material, thereby improving the packing factor of the positive electrode material and reducing the residual alkali content on the surface of the positive electrode material, but also avoids excessive loss of the sodium element and improves the element utilization rate of the sodium element. Furthermore, the operation steps are simplified, saving production costs.

[0117] Furthermore, in order to more accurately obtain the desired positive electrode material through the two-step calcination process, in the second raw material system, the ratio of the molar percentage of Na in the sodium source to the molar percentage of Na in the first intermediate positive electrode material is (0.05-0.2):1.

[0118] By specifically designing the molar percentage of the sodium element in the second raw material system, the present invention can more accurately obtain the desired positive electrode material through a two-step calcination process. In addition, while improving the element utilization rate of the sodium element, more sodium element can be further introduced into the unit cells of the positive electrode material, thereby improving the stacking factor of the positive electrode material and reducing the surface residual alkali content of the positive electrode material.

[0119] In the present invention, the parameters of the calcination process (the first calcination process and the second calcination process) can be further selected to obtain the desired positive electrode material more quickly while saving operating steps. In some embodiments of the present invention, during the calcination process, the temperature is 800-1000°C, the heating rate is 1-5°C / min, and the time is 10-15 hours;

[0120] The calcination treatment is a first calcination treatment and / or a second calcination treatment.

[0121] A third aspect of the present invention provides a battery comprising the above-mentioned positive electrode material.

[0122] In the present invention, the above-mentioned positive electrode material can be used to prepare a positive electrode sheet, and then a battery can be prepared using the positive electrode sheet containing the above-mentioned positive electrode material.

[0123] In some embodiments, the preparation process of the positive electrode sheet includes: mixing the positive electrode material, the conductive agent, the solvent and the binder to obtain a positive electrode slurry, setting the positive electrode slurry on at least one functional surface of the positive electrode collector, and obtaining a positive electrode sheet including a positive electrode active layer after drying.

[0124] The battery of the present invention, because it includes the above-mentioned positive electrode material, has excellent discharge capacity and cycle performance. In some embodiments, when the stacking factor of the positive electrode material is 0.67-0.72, the positive electrode material has excellent capacity, and the full battery including the positive electrode material has a discharge capacity of 17mAg in the voltage window of 2-4.2V. -1 The discharge capacity can be 100-140 mAh g -1 .

[0125] Hereinafter, the technical solution of the present invention will be further explained in conjunction with specific embodiments.

[0126] Example 1

[0127] The battery of this embodiment is prepared by a method comprising the following steps:

[0128] 1. Preparation of positive electrode materials

[0129] 1) Expected preparation of Na 0.89 Ni 0.33 Fe0.23 Mn 0.44 O2, theoretical stacking factor PF 理论 is 0.68352;

[0130] Sodium carbonate, nickel oxide, ferrosoferric oxide, and manganese tetraoxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn=0.83:0.33:0.23:0.44, and then calcined at 930°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0131] The first intermediate cathode material was digested and ICP tested, and the actual molar percentage of each element in the first intermediate cathode material was obtained to be Na:Ni:Fe:Mn=0.8013:0.32902:0.2302:0.44078. The first intermediate cathode material was subjected to XRD testing, and the XRD pattern of the first intermediate cathode material was as follows: Figure 2 As shown;

[0132] 2) mixing the first intermediate cathode material with sodium carbonate to obtain a second raw material system, and then calcining the second raw material system at 930° C. for 12 hours at a heating rate of 2° C. / min to obtain a second intermediate cathode material; in the second raw material system, the ratio of the molar percentage of Na in the first intermediate cathode material to the molar percentage of Na in the sodium carbonate is 0.8013:0.0987;

[0133] The second intermediate positive electrode material was digested and ICP tested, and the actual molar percentage of each element in the second intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn=0.8902:0.3285:0.2321:0.4394. The actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material satisfied the second expected relationship. The second intermediate positive electrode material was subjected to XRD testing to obtain an XRD pattern of the second intermediate positive electrode material, see Figure 2 ; The XRD pattern of the second intermediate positive electrode material is refined by the Rietveld method to obtain the V 晶胞体积 for The PF of the second intermediate cathode material is calculated according to Formula 2 实际 The PF of the second intermediate cathode material is 0.68410. 实际 With PF 理论 The first expected relationship is satisfied, and the second intermediate positive electrode material is the expected positive electrode material;

[0134] The compaction density of the positive electrode material was obtained by holding 2 g of the positive electrode material at 5 MPa for 60 s using a CARVER 4350 press. The test results are shown in Table 1.

[0135] 30 g of the positive electrode material was dispersed and stirred in 100 ml of water to obtain a solution. 10 ml of the solution was taken and water was added to 60 ml. The carbonate content of the positive electrode material was tested by 888 automatic potentiometric titration. The test results are shown in Table 1.

[0136] 2. Preparation of batteries

[0137] The positive electrode material, conductive agent Super-P and binder PVDF were mixed in a mass ratio of 91:4.5:4.5, and an appropriate amount of NMP solution was added to form a positive electrode slurry. The positive electrode slurry was coated on the two functional surfaces of the aluminum foil, dried, and baked in a vacuum oven at 120°C for 12 hours to obtain a positive electrode sheet;

[0138] Hard carbon, conductive agent Super-P, and binder PVDF are mixed in a mass ratio of 93:2:5 to obtain a negative electrode slurry, which is then applied to two functional surfaces of a copper foil and dried to obtain a negative electrode sheet.

[0139] The positive electrode sheet, the separator and the negative electrode sheet are stacked to obtain an electrode assembly, the electrode assembly is placed in an outer package, and an electrolyte is injected into the outer package to obtain a battery;

[0140] The electrolyte includes NaClO4, EC and EMC, the volume ratio of EC to EMC is 3:7, and the concentration of NaClO4 is 1 mol / L.

[0141] The first cycle charge and discharge test was performed in the constant current charge and discharge mode at 0.1C within the voltage window of 1.5-4.3V to obtain the battery's discharge capacity in grams. The test results are shown in Table 1.

[0142] The battery was cyclically charged and discharged at a rate of 1C to obtain the capacity retention rate of the battery after 500 cycles. The results are shown in Table 1.

[0143] Example 2

[0144] The preparation method of the battery of this embodiment is basically the same as that of Example 1, except that:

[0145] 1. Preparation of positive electrode materials

[0146] 1) Expected preparation of Na 0.95 Ni 0.22 Fe 0.27 Mn 0.4 Cu 0.11 O2, theoretical stacking factor PF 理论 is 0.68352;

[0147] Sodium carbonate, nickel oxide, ferrosoferric oxide, manganese oxide, and copper oxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn:Cu=0.83:0.22:0.27:0.4:0.11, and then calcined at 950°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0148] The first intermediate cathode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the first intermediate cathode material was obtained as Na:Ni:Fe:Mn:Cu=0.8287:0.22921:0.27502:0.42452:0.07125;

[0149] 2) mixing the first intermediate cathode material with sodium carbonate and copper oxide to obtain a second raw material system, and then calcining the second raw material system at 950° C. for 15 hours at a heating rate of 2° C. / min to obtain a second intermediate cathode material; in the second raw material system, the ratio of the molar percentage of Na in the first intermediate cathode material, the molar percentage of Na in the sodium carbonate, and the molar percentage of Cu in the copper oxide is 0.8013:0.0987:0.03875;

[0150] The second intermediate positive electrode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the second intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn:Cu=0.9498:0.22012:0.27021:0.40012:0.10955, and the actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material met the second expected relationship; the second intermediate positive electrode material was subjected to XRD testing to obtain the XRD spectrum of the second intermediate positive electrode material; the XRD spectrum of the second intermediate positive electrode material was refined by the Rietveld method to obtain the V 晶胞体积 for The PF of the second intermediate cathode material is calculated according to Formula 2 实际 The PF of the second intermediate cathode material is 0.68951. 实际 With PF 理论 The first expected relationship is satisfied, and the second intermediate positive electrode material is the expected positive electrode material.

[0151] Example 3

[0152] The preparation method of the battery of this embodiment is basically the same as that of Example 1, except that:

[0153] 1. Preparation of positive electrode materials

[0154] 1) Expected preparation of Na 0.91 Ni 0.22 Fe 0.22 Mn0.4 Cu 0.16 O2, theoretical stacking factor PF 理论 is 0.6858;

[0155] Sodium carbonate, nickel oxide, ferrosoferric oxide, manganese oxide, and copper oxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn:Cu=0.85:0.22:0.23:0.44:0.11, and then calcined at 950°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0156] The first intermediate cathode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the first intermediate cathode material was obtained as Na:Ni:Fe:Mn:Cu=0.8198:0.23011:0.23015:0.42452:0.11522;

[0157] 2) mixing the first intermediate cathode material with sodium carbonate and copper oxide to obtain a second raw material system, and then calcining the second raw material system at 950° C. for 15 hours at a heating rate of 2° C. / min to obtain a second intermediate cathode material; in the second raw material system, the ratio of the molar percentage of Na in the first intermediate cathode material, the molar percentage of Na in the sodium carbonate, and the molar percentage of Cu in the copper oxide is 0.8198:0.1002:0.04478;

[0158] The second intermediate positive electrode material is digested and ICP tested, and the actual molar percentage of each element in the second intermediate positive electrode material is obtained as Na:Ni:Fe:Mn:Cu=0.9112:0.21981:0.22101:0.40058:0.15810, and the actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material meet the second expected relationship; the second intermediate positive electrode material is subjected to XRD testing to obtain the XRD spectrum of the second intermediate positive electrode material; the XRD spectrum of the second intermediate positive electrode material is refined by the Rietveld method to obtain the V 晶胞体积 for The PF of the second intermediate cathode material is calculated according to Formula 2 实际 The PF of the second intermediate cathode material is 0.68591. 实际 With PF 理论 The first expected relationship is satisfied, and the second intermediate positive electrode material is the expected positive electrode material.

[0159] Example 4

[0160] The preparation method of the battery of this embodiment is basically the same as that of Example 1, except that:

[0161] 1. Preparation of positive electrode materials

[0162] 1) Expected preparation of Na 0.95 Ni 0.22 Fe 0.27 Mn 0.4 Zn 0.11 O2, theoretical stacking factor PF 理论 is 0.68972;

[0163] Sodium carbonate, nickel oxide, ferrosoferric oxide, manganese-manganese oxide, and zinc oxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn:Zn=0.85:0.22:0.27:0.4:0.11, and then calcined at 950°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0164] The first intermediate cathode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the first intermediate cathode material was obtained as Na:Ni:Fe:Mn:Zn=0.8381:0.22521:0.27128:0.42097:0.08254;

[0165] 2) mixing the first intermediate positive electrode material with sodium carbonate and zinc oxide to obtain a second raw material system, and then calcining the second raw material system at 950° C. for 15 hours at a heating rate of 2° C. / min to obtain a second intermediate positive electrode material; in the second raw material system, the ratio of the molar percentage of Na in the first intermediate positive electrode material, the molar percentage of Na in the sodium carbonate, and the molar percentage of Zn in the zinc oxide is 0.8381:0.1219:0.02746;

[0166] The second intermediate positive electrode material was digested and tested by ICP, and the actual molar percentage of each element in the second intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn:Zn=0.9501:0.22008:0.27015:0.40081:0.10896, and the actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material met the second expected relationship; the second intermediate positive electrode material was subjected to XRD testing to obtain the XRD spectrum of the second intermediate positive electrode material; the XRD spectrum of the second intermediate positive electrode material was refined by Rietveld method to obtain the V 晶胞体积 for The PF of the second intermediate cathode material is calculated according to Formula 2 实际 The PF of the second intermediate cathode material is 0.68971. 实际 With PF 理论 The first expected relationship is satisfied, and the second intermediate positive electrode material is the expected positive electrode material.

[0167] Example 5

[0168] The preparation method of the battery of this embodiment is basically the same as that of Example 1, except that:

[0169] 1. Preparation of positive electrode materials

[0170] 1) Expected preparation of Na 0.91 Ni 0.22 Fe 0.22 Mn 0.4 Zn 0.16 O2, theoretical stacking factor PF 理论 is 0.68525;

[0171] Sodium carbonate, nickel oxide, ferrosoferric oxide, manganese-manganese oxide, and zinc oxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn:Zn=0.85:0.22:0.23:0.44:0.11, and then calcined at 950°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0172] The first intermediate cathode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the first intermediate cathode material was obtained as Na:Ni:Fe:Mn:Zn=0.8201:0.23008:0.23115:0.4287:0.11007;

[0173] 2) mixing the first intermediate positive electrode material with sodium carbonate and zinc oxide to obtain a second raw material system, and then calcining the second raw material system at 950° C. for 15 hours at a heating rate of 2° C. / min to obtain a second intermediate positive electrode material; in the second raw material system, the ratio of the molar percentage of Na in the first intermediate positive electrode material, the molar percentage of Na in the sodium carbonate, and the molar percentage of Zn in the zinc oxide is 0.8201:0.0999:0.04993;

[0174] The second intermediate positive electrode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the second intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn:Zn=0.9105:0.22002:0.22065:0.40087:0.15846, and the actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material met the second expected relationship; the second intermediate positive electrode material was subjected to XRD testing to obtain the XRD spectrum of the second intermediate positive electrode material; the XRD spectrum of the second intermediate positive electrode material was refined by the Rietveld method to obtain the V 晶胞体积 for The PF of the second intermediate cathode material is calculated according to Formula 2 实际The PF of the second intermediate cathode material is 0.68610. 实际 With PF 理论 The first expected relationship is satisfied, and the second intermediate positive electrode material is the expected positive electrode material.

[0175] Example 6

[0176] The preparation method of the battery of this embodiment is basically the same as that of Example 1, except that:

[0177] 1. Preparation of positive electrode materials

[0178] 1) Expected preparation of Na 0.95 Ni 0.2 Fe 0.2 Mn 0.4 Zn 0.11 Cu 0.09 O2, theoretical stacking factor PF 理论 is 0.68754;

[0179] Sodium carbonate, nickel oxide, ferrosoferric oxide, manganese oxide, zinc oxide, and copper oxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn:Zn:Cu=0.85:0.2:0.2:0.4:0.11:0.09, and then calcined at 950°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0180] The first intermediate cathode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the first intermediate cathode material was obtained as Na:Ni:Fe:Mn:Zn:Cu=0.8121:0.22156:0.22451:0.42987:0.0721:0.05196;

[0181] 2) mixing the first intermediate positive electrode material with sodium carbonate, copper oxide, and zinc oxide to obtain a second raw material system, and then calcining the second raw material system at 950° C. for 15 hours at a heating rate of 2° C. / min to obtain a second intermediate positive electrode material; in the second raw material system, the molar percentage of Na in the first intermediate positive electrode material, the molar percentage of Na in the sodium carbonate, the molar percentage of Zn in the zinc oxide, and the molar percentage of Cu in the copper oxide are 0.8121:0.1479:0.0379:0.03804;

[0182] The second intermediate positive electrode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the second intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn:Zn:Cu=0.94213:0.20031:0.2081:0.40486:0.10412:0.08261, and the actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material met the second expected relationship; the second intermediate positive electrode material was subjected to XRD testing to obtain the XRD spectrum of the second intermediate positive electrode material; the XRD spectrum of the second intermediate positive electrode material was refined by the Rietveld method to obtain the V 晶胞体积 for The PF of the second intermediate cathode material is calculated according to Formula 2 实际 The PF of the second intermediate cathode material is 0.68670. 实际 With PF 理论 The first expected relationship is satisfied, and the second intermediate positive electrode material is the expected positive electrode material.

[0183] Example 7

[0184] The preparation method of the battery of this embodiment is basically the same as that of Example 1, except that:

[0185] 1. Preparation of positive electrode materials

[0186] 1) Expected preparation of Na 0.91 Ni 0.18 Fe 0.18 Mn 0.4 Zn 0.12 Cu 0.12 O2, theoretical stacking factor PF 理论 is 0.68243;

[0187] Sodium carbonate, nickel oxide, ferrosoferric oxide, manganese oxide, zinc oxide, and copper oxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn:Zn:Cu=0.85:0.18:0.18:0.4:0.12:0.12, and then calcined at 950°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0188] The first intermediate cathode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the first intermediate cathode material was obtained as Na:Ni:Fe:Mn:Zn:Cu=0.8098:0.20451:0.20518:0.42111:0.08546:0.08374;

[0189] 2) mixing the first intermediate positive electrode material with sodium carbonate, copper oxide, and zinc oxide to obtain a second raw material system, and then calcining the second raw material system at 950° C. for 15 hours at a heating rate of 2° C. / min to obtain a second intermediate positive electrode material; in the second raw material system, the molar percentage of Na in the first intermediate positive electrode material, the molar percentage of Na in the sodium carbonate, the molar percentage of Zn in the zinc oxide, and the molar percentage of Cu in the copper oxide are 0.8098:0.1102:0.03454:0.03626;

[0190] The second intermediate positive electrode material was digested and subjected to ICP testing, and the actual molar percentage of each element in the second intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn:Zn:Cu=0.9085:0.18211:0.18712:0.40957:0.11412:0.10708, and the actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material met the second expected relationship; the second intermediate positive electrode material was subjected to XRD testing to obtain the XRD spectrum of the second intermediate positive electrode material; the XRD spectrum of the second intermediate positive electrode material was refined by the Rietveld method to obtain the V 晶胞体积 for The PF of the second intermediate cathode material is calculated according to Formula 2 实际 The PF of the second intermediate cathode material is 0.68236. 实际 With PF 理论 The first expected relationship is satisfied, and the second intermediate positive electrode material is the expected positive electrode material.

[0191] Comparative Example 1

[0192] The preparation method of the battery of this comparative example is basically the same as that of Example 1, except that:

[0193] 1. Preparation of positive electrode materials

[0194] 1) Expected preparation of Na 0.89 Ni 0.33 Fe 0.23 Mn 0.44 O2;

[0195] Sodium carbonate, nickel oxide, ferrosoferric oxide, and manganese tetraoxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn=0.96:0.33:0.23:0.44, and then calcined at 930°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0196] The first intermediate cathode material was digested and subjected to ICP testing, and the actual molar ratio of the metal elements in the first intermediate cathode material was obtained as Na:Ni:Fe:Mn=0.8245:0.32813:0.2331:0.44061;

[0197] 2) mixing the first intermediate cathode material with sodium carbonate to obtain a second raw material system, and then calcining the second raw material system at 930° C. for 12 hours at a heating rate of 2° C. / min to obtain a second intermediate cathode material; in the second raw material system, the molar percentage of Na in the first intermediate cathode material and the molar percentage of Na in the sodium carbonate are 0.8213:0.0655;

[0198] The second intermediate positive electrode material was digested and ICP tested, and the actual molar percentage of each element in the second intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn=0.8923:0.3279:0.2302:0.4419. The actual molar percentage of each element in the second intermediate positive electrode material and the theoretical molar percentage of each element in the positive electrode material met the second expected relationship, and the second intermediate positive electrode material was a positive electrode material.

[0199] Comparative Example 2

[0200] The preparation method of the battery of this comparative example is basically the same as that of Example 1, except that:

[0201] 1. Preparation of positive electrode materials

[0202] 1) Expected preparation of Na 0.89 Ni 0.33 Fe 0.23 Mn 0.44 O2, theoretical stacking factor PF 理论 is 0.68352;

[0203] Sodium carbonate, nickel oxide, ferrosoferric oxide, and manganese tetraoxide were uniformly mixed in a molar ratio of Na:Ni:Fe:Mn=0.89:0.33:0.23:0.44, and then calcined at 680°C for 12 hours at a heating rate of 2°C / min to obtain a first intermediate positive electrode material;

[0204] The first intermediate positive electrode material was digested and subjected to ICP testing, and the actual molar percentage content of each element in the first intermediate positive electrode material was obtained to be Na:Ni:Fe:Mn=0.8891:0.33012:0.22912:0.44076. The actual molar percentage content of each element in the first intermediate positive electrode material and the theoretical molar percentage content of the positive electrode material had a second expected relationship, and the first intermediate positive electrode material was a positive electrode material.

[0205] Table 1

[0206]

[0207]

[0208] It can be seen from Table 1 that the battery in the embodiment of the present invention has both excellent cycle performance and discharge capacity.

[0209] Furthermore, it can be seen from the Examples and Comparative Example 1 that although the positive electrode material of the expected elemental composition can be obtained by two calcination treatments in Comparative Example 1, the molar percentage of the sodium element is excessive during the first calcination treatment in Comparative Example 1, and therefore the element utilization rate of the sodium element is low, which is not conducive to cost saving; and it can be seen that the positive electrode material in the Examples of the present application has a lower residual alkali content on the surface of the positive electrode material than that in Comparative Example 1, and the battery of the Examples has a higher discharge capacity and an excellent capacity retention rate than the battery of Comparative Example 1, indicating that the positive electrode material prepared by considering the stacking factor has better overall performance;

[0210] It can be seen from the Examples and Comparative Example 2 that the positive electrode material in the Examples has a lower residual alkali content on the surface than the positive electrode material in Comparative Example 2, and the battery in the Examples has a higher discharge capacity per gram and an excellent capacity retention rate than the battery in Comparative Example 2. This indicates that although the positive electrode material of Comparative Example 2 can obtain the expected elemental composition through a single calcination treatment, the positive electrode material obtained by the single calcination treatment has more sodium present on the surface of the positive electrode material (high residual alkali content on the surface) rather than within the unit cells of the positive electrode material, which is detrimental to the capacity retention rate and discharge capacity per gram of the battery.

[0211] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, 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 solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode material, characterized in that The positive electrode material is an O3 phase layered oxide as shown in Formula 1; Na x Ni a Fe b Mn c M d O e formula 1 In formula 1, M is a doping element; 0.9<x≤1.25, 0.11≤a≤0.33, 0.22≤b≤0.33, 0.33≤c≤0.66, 0≤d≤0.33, 1.8≤e≤2.2, a+b+c+d=1; The stacking factor of the positive electrode material is 0.67-0.72; The stacking factor is calculated by formula 2; PF=∑N*V 离子体积 / V 晶胞体积 2 In formula 2, PF is the stacking factor; V 离子体积 is the volume of the ions in the unit cell, V 离子体积 According to V=(4 / 3)πr 3 We get, r is the ionic radius; V 晶胞体积 is the unit cell volume, V 晶胞体积 It is obtained by refining the XRD spectrum of the positive electrode material by the Rietveld method; N is the number of ions.

2. The positive electrode material according to claim 1, characterized in that The surface carbonate content of the positive electrode material is 100-20000 ppm.

3. The positive electrode material according to claim 1 or 2, characterized in that 0.11≤d≤0.33。 4. The positive electrode material according to claim 1 or 2, characterized in that At 5 MPa, the compaction density of the positive electrode material is 3.2 to 3.8 g / cm 3 .

5. The positive electrode material according to claim 3, characterized in that At 5 MPa, the compaction density of the positive electrode material is 3.2 to 3.8 g / cm 3 .

6. The positive electrode material according to any one of claims 1, 2 and 5, characterized in that: The stacking factor of the positive electrode material is 0.68-0.

69.

7. The positive electrode material according to claim 3, characterized in that The stacking factor of the positive electrode material is 0.68-0.

69.

8. The positive electrode material according to claim 4, characterized in that The stacking factor of the positive electrode material is 0.68-0.

69.

9. A method for preparing the positive electrode material according to any one of claims 1 to 8, characterized in that: The following steps are involved: A first raw material system including a raw material source is subjected to a first calcination treatment to obtain a first intermediate positive electrode material; the raw material source includes a sodium source, a nickel source, an iron source, a manganese source and an M source, and I Na ≤I Na理论 , I Ni ≤I Ni理论 , I Fe ≤I Fe理论 , I Mn ≤I Mn理论 , I M ≤I M理论 ; Obtain the actual stacking factor PF of the first intermediate positive electrode material 实际 , and the actual molar percentage of Na in the first intermediate positive electrode material I Na实际 , the actual molar percentage of Ni I Ni实际 , the actual molar percentage of Fe I Fe实际 , the actual molar percentage of Mn I Mn实际 , the actual molar percentage of M I M实际 ; Determine the PF of the first intermediate cathode material 实际 and the theoretical stacking factor PF of the cathode material 理论 Whether the first expected relationship is satisfied, the I of the first intermediate positive electrode material is determined Na实际 , I Ni实际 , I Fe实际 , I Mn实际 , I M实际 and I Na理论 , I Ni理论 , I Fe理论 , I Mn理论 , I M理论 Whether the second expected relationship is met; If the first expected relationship and the second expected relationship are satisfied, the first intermediate positive electrode material is the positive electrode material; Among them, I Na is the molar percentage of Na in the first raw material system; I Ni is the molar percentage of Ni in the first raw material system; I Fe is the molar percentage of Fe in the first raw material system; I Mn is the molar percentage of Mn in the first raw material system; I M is the molar percentage of M in the first raw material system; I Na理论 is the theoretical molar percentage of Na in the positive electrode material; I Ni理论 is the theoretical molar percentage of Ni in the positive electrode material; I Fe理论 is the theoretical molar percentage of Fe in the positive electrode material; I Mn理论 is the theoretical molar percentage of Mn in the positive electrode material; I M理论 is the theoretical molar percentage of M in the positive electrode material; The first expected relationship is: |PF 实际 -PF 理论 |<0.001; The second expected relationship is: |I Na实际 -I Na理论 ∣<0.02、∣I Ni实际 -I Ni理论 ∣<0.02、∣I Fe实际 -I Fe理论 ∣<0.02、∣I Mn实际 -I Mn理论 |<0.02 and |I M实际 -I M理论 ∣<0.

02.

10. The preparation method according to claim 9, characterized in that If the third expected relationship is met: |PF 实际 -PF 理论 |≥0.001; and / or, satisfying the fourth expected relationship: |I Na实际 -I Na理论 ∣≥0.02, ∣I Ni实际 -I Ni理论 ∣≥0.02, ∣I Fe实际 -I Fe理论 ∣≥0.02, ∣I Mn实际 -I Mn理论 ∣≥0.02 or ∣I M实际 -I M理论 ∣≥0.02, including: 1) adding at least one of the sodium source, nickel source, iron source, manganese source, and M source to the first intermediate cathode material and performing a second calcination process to obtain a second intermediate cathode material; Among them, if |PF 实际 -PF 理论 |≥0.001, then adding a sodium source to the first intermediate positive electrode material; and / or, If | I Na实际 -I N理论 |≥0.02, then adding a sodium source to the first intermediate positive electrode material; and / or, If | I Ni实际 -I Ni理论 |≥0.02, then adding a nickel source to the first intermediate positive electrode material; and / or, If | I Fe实际 -I Fe理论 |≥0.02, then add an iron source to the first intermediate positive electrode material; and / or, If | I Mn实际 -I Mn理论 |≥0.02, then add a manganese source to the first intermediate positive electrode material; and / or, If | I M实际 -I M理论 |≥0.02, then add M source to the first intermediate positive electrode material; 2) Obtaining the PF of the second intermediate cathode material 实际 , and I of the second intermediate positive electrode material Na实际 , I Ni实际 , I Fe实际 , I Mn实际 , I M实际 ; 3) Determine the PF of the second intermediate cathode material 实际 With PF 理论 Whether the first expected relationship is met, the I of the second intermediate positive electrode material is determined Na实际 , I Ni实际 , I Fe实际 , I Mn实际 , I M实际 and I Na理论 , I Ni理论 , I Fe理论 , I Mn理论 , I M理论 Whether the second expected relationship is met; 4) Repeating steps 1)-3) 0-N times until the first expected relationship and the second expected relationship are satisfied, thereby obtaining the positive electrode material, N≥1.

11. The preparation method according to claim 9 or 10, characterized in that: The following steps are involved: A first raw material system including a raw material source is subjected to a first calcination treatment to obtain a first intermediate positive electrode material; the raw material source includes a sodium source, a nickel source, an iron source, a manganese source and an M source, and I Na 0.78-0.9, I Ni =I Ni理论 , I Fe =I Fe理论 , I Mn =I Mn理论 , I M =I M理论 ; A sodium source is added to the first intermediate positive electrode material to obtain a second raw material system, and the second raw material system is subjected to a second calcination treatment to obtain the positive electrode material.

12. The preparation method according to claim 11, characterized in that In the second raw material system, the ratio of the molar percentage of Na in the sodium source to the molar percentage of Na in the first intermediate positive electrode material is (0.05-0.2):

1.

13. The preparation method according to any one of claims 9, 10 and 12, characterized in that: During the calcination treatment, the temperature is 800-1000°C, the heating rate is 1-5°C / min, and the time is 10-15h; The calcination treatment is a first calcination treatment and / or a second calcination treatment.

14. The preparation method according to claim 11, characterized in that During the calcination treatment, the temperature is 800-1000°C, the heating rate is 1-5°C / min, and the time is 10-15h; The calcination treatment is a first calcination treatment and / or a second calcination treatment.

15. A battery, characterized in that: The positive electrode material comprises the positive electrode material according to any one of claims 1 to 8.

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