A dual-site doped cobalt-free high-nickel oxide cathode material, its preparation method and application

Abstract

The present invention belongs to the technical field of lithium-ion batteries, and discloses a cobalt-free high-nickel oxide cathode material with double-site doping, its preparation method and application. The chemical formula of the cathode material is Li 1‑ x Mg x (Ni 0.8 Mn 0.2 ) 1‑y Sn y O2, where 0 < x ≤ 0.02 and 0 < y ≤ 0.015. It is prepared by ball-milling and mixing a transition metal precursor, a lithium compound, a magnesium compound and a tin compound, drying, heat-treating at 450 - 550 °C, and then sintering at 700 - 900 °C. When the voltage window is 2.8 - 4.4 V and the current density is 200 mA g ‑1 , the voltage decay rate of the cathode material can be as low as 0.2375 mV / cycle, and the highest capacity can reach 189.56 mAh g ‑1 . The capacity retention rate after 200 cycles is as high as over 80%, and it can be applied in the field of lithium-ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and more specifically, relates to a cobalt-free high-nickel oxide cathode material with dual-site doping, its preparation method, and its application. Background Technology

[0002] With the rapid development of portable electronic devices, electric vehicles, and energy storage systems, the market has placed higher demands on lithium-ion batteries, particularly in terms of high energy density, long cycle life, high safety, low manufacturing cost, and environmental friendliness. As a key component determining battery energy density and output performance, improving the performance of cathode materials is of great significance. Existing commercial cathode materials, such as lithium iron phosphate (LFP), lithium cobalt oxide (LCO), and nickel-cobalt-manganese ternary (NCM) materials, while achieving large-scale application, still generally suffer from limited specific capacity, high raw material costs, or insufficient resource sustainability. Cobalt, in particular, has limited reserves and fluctuating prices; its mining and smelting processes may also pose environmental and supply chain risks. Therefore, developing low-cobalt or even cobalt-free cathode materials has become an important research direction in the field of high-energy-density lithium-ion batteries. Cobalt-free high-nickel cathode materials, due to their higher nickel content, can provide higher reversible specific capacity and better energy density. Furthermore, by reducing or eliminating the use of cobalt, they are expected to significantly reduce material costs and improve resource dependence, thus demonstrating promising application prospects. However, cobalt-free high-nickel cathode materials still face many technical bottlenecks in practical applications, such as the Ni content in high-nickel systems. 2+ With Li + Similar ionic radii easily lead to cation mixing, which in turn hinders lithium-ion diffusion kinetics and reduces structural stability. Under high voltage and repeated charge-discharge conditions, side reactions easily occur on the material surface, lattice oxygen activity is enhanced and phase transitions are induced, microcracks propagate, and transition metals dissolve, resulting in accelerated capacity decay, deterioration of rate performance, and decreased thermal stability. Furthermore, existing methods for preparing cobalt-free high-nickel cathode materials mostly employ co-precipitation combined with high-temperature sintering, but these methods still face challenges in industrialization, such as difficulty in controlling compositional uniformity, narrow sintering windows, poor particle morphology consistency, and insufficient batch stability, thus affecting the electrochemical performance and large-scale application of the materials. Therefore, how to further improve the structural stability, interfacial stability, and process controllability of cobalt-free high-nickel cathode materials while reducing or eliminating cobalt content remains a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] To address the shortcomings and drawbacks of the existing technology, the present invention aims to provide a cobalt-free high-nickel oxide cathode material with dual-site doping. This cathode material, through the incorporation of tin ions, introduces new electronic states into the crystal, providing additional electrons to nearest-neighbor oxygen atoms and forming strong Sn-O bonds. This effectively prevents excessive oxidation of oxygen anions and increases the redox stability of oxygen ions, resulting in a more stable material structure and ensuring that the battery can perform long-term, high-capacity cycling.

[0004] Another objective of this invention is to provide a method for preparing the aforementioned dual-site doped cobalt-free high-nickel oxide cathode material. This method involves high-temperature calcination using a high-temperature solid-state method. Magnesium and tin ions are introduced into the lithium layer and transition metal layer of the cobalt-free high-nickel layered oxide cathode material, respectively, to achieve structural micro-tuning. The introduced magnesium ions enter the lithium layer and exert a pillar effect, suppressing the periodic contraction of the c-axis during charge and discharge. This method overcomes the shortcomings of rapid capacity decay and poor cycle stability of cobalt-free high-nickel layered oxide cathode materials. Furthermore, the processing steps are simple, the conditions are easy to control, and the repeatability is good. Simultaneously, the material does not contain the precious metal cobalt, offering advantages such as low cost and environmental friendliness, and possesses significant commercial potential.

[0005] Another object of the present invention is to provide the application of the above-mentioned dual-site doped cobalt-free high-nickel oxide cathode material.

[0006] The objective of this invention is achieved through the following technical solution: A cobalt-free high-nickel oxide cathode material with dual-site doping, its chemical formula being Li 1-x Mg x (Ni 0.8 Mn 0.2 ) 1- y Sn y O2, 0 <x≤0.02,0<y≤0.015。

[0007] Preferably, the cobalt-free high-nickel oxide cathode material is prepared by ball milling a transition metal precursor, a lithium compound, a magnesium compound, and a tin compound, vacuum drying the resulting slurry at 80-150°C to obtain a mixed powder, compacting the mixed powder, heat-treating it at 450-550°C, sintering it at 700-900°C, and then grinding and sieving the sintered material.

[0008] Preferably, the lithium compound is one or more of lithium carbonate, lithium hydroxide, lithium nitrate, or lithium acetate; the magnesium compound is one or more of magnesium oxide, magnesium hydroxide, or magnesium carbonate; the tin compound is tin oxide; and the transition metal precursor is a transition metal hydroxide precursor.

[0009] More preferably, the transition metal carbonate precursor is TM(OH)2, where TM = Mn or / and Ni.

[0010] Preferably, the molar ratio of transition metal ions in the transition metal precursor to lithium ions in the lithium salt is 1:(1.2~1.6), the molar ratio of transition metal ions in the transition metal precursor to lithium ions in the lithium compound is 1:(1.2~1.6), and the molar ratio of magnesium ions in the magnesium compound, tin ions in the tin compound, and transition metal ions in the transition metal precursor is (0.1~2.5):(0.1~2.5):100.

[0011] The preparation method of the dual-site doped cobalt-free high-nickel oxide cathode material includes the following specific steps: S1. Transition metal precursors, lithium compounds, magnesium compounds and tin compounds are ball-milled and mixed using zirconia balls as the grinding medium and anhydrous ethanol as the dispersant. After ball milling, the slurry is vacuum-dried at 80~150℃ to obtain a mixed powder. S2. Compact the mixed powder, heat treat it at 450~550℃, then sinter it at 700~900℃, grind the sintered material and sieve it to obtain a cobalt-free high-nickel oxide cathode material with dual-site doping.

[0012] Preferably, the ball milling time in step S1 is 3-6 hours; the heating rate of the vacuum drying is 1-4°C / min, and the time is 6-12 hours.

[0013] Preferably, the heat treatment time in step S2 is 6~12 h, the sintering heating rate is 3~5℃ / min, and the sintering time is 8~20 h.

[0014] The application of the aforementioned dual-site doped cobalt-free high-nickel oxide cathode material in the field of lithium-ion batteries.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses a method of dual-site doping modification with magnesium and tin compounds to prepare cobalt-free high-nickel oxide cathode materials with dual-site doping. This method overcomes the shortcomings of cobalt-free high-nickel oxide cathode materials, such as rapid capacity decay and poor cycle stability. Furthermore, the processing steps are simple, the conditions are easy to control, and the repeatability is good. At the same time, the material does not contain the precious metal cobalt, and has the advantages of low cost and environmental friendliness, thus possessing great commercial potential.

[0016] 2. The main phase of the cobalt-free high-nickel oxide cathode material with dual-site doping in this invention uses magnesium and tin compounds to micro-tune the structure of the cobalt-free high-nickel oxide cathode material. Mg ions are successfully introduced into the lithium layer, effectively suppressing the collapse of the layered structure during deep delithiation. Sn ions are also successfully introduced into the crystal structure, providing additional electrons to the nearest-neighbor oxygen atoms and forming a strong Sn-O bond. This effectively prevents excessive oxidation of oxygen anions and increases the redox stability of oxygen ions. This makes the material structure more stable, ensuring that the battery can perform high-capacity cycling for a long time.

[0017] 3. The cobalt-free high-nickel oxide cathode material with dual-site doping of this invention overcomes the shortcomings of previous materials, such as short cycle life and rapid capacity decay. When the voltage window is 2.8~4.4 V and the current density is 200 mA g... -1 At that time, the discharge specific capacity of this type of cathode material reached a maximum of 189.56 mAh g. -1 Even after 200 cycles, the capacity remains as high as 153.96 mAh g. -1 With a capacity retention rate of over 80%, the introduction of Mg and Sn ions greatly improves the cycle stability of cobalt-free high-nickel oxide cathode materials, making them applicable in the field of lithium-ion batteries. Attached Figure Description

[0018] Figure 1 Li, as in Example 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 X-ray diffraction pattern of O2 powder.

[0019] Figure 2 Li, as in Example 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 SEM image of O2 powder.

[0020] Figure 3 Li, as in Example 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 XPS image of Mg element in O2 powder.

[0021] Figure 4 Li, as in Example 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2) 0.99 Sn 0.01 XPS image of Sn element in O2 powder.

[0022] Figure 5 For example, Li 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 When O2 powder is used as the positive electrode, 20 mA g at room temperature -1 The initial charge-discharge curve at that time.

[0023] Figure 6 For example, Li 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder as positive electrode at room temperature 200 mAg -1 Capacity stability curve.

[0024] Figure 7 For example 2, Li 0.995 Mg 0.005 (Ni 0.8 Mn 0.2 ) 0.995 Sn 0.005 O2 powder was used as the positive electrode at room temperature with an A value of 200 mA / g. -1 Capacity stability curve.

[0025] Figure 8 For example 3, Li 0.985 Mg 0.02 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder as positive electrode at room temperature 200 mAg -1 Capacity stability curve.

[0026] Figure 9 For example 4, Li 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.985 Sn 0.015 O2 powder was used as the positive electrode at room temperature with an A value of 200 mA / g. -1 Capacity stability curve.

[0027] Figure 10 For example 5, Li 0.98 Mg 0.02 (Ni0.8 Mn 0.2 ) 0.985 Sn 0.015 O2 powder was used as the positive electrode at room temperature with an A value of 200 mA / g. -1 Capacity stability curve.

[0028] Figure 11 To compare the application example 1, Li 0.985 Mg 0.015 Ni 0.8 Mn 0.2 O2 powder was used as the positive electrode at room temperature (20 mA g). -1 The initial charge-discharge curve at that time.

[0029] Figure 12 To compare the application example 1, Li 0.985 Mg 0.015 Ni 0.8 Mn 0.2 O2 powder was used as the positive electrode at room temperature at 200 mA g. -1 Capacity stability curve.

[0030] Figure 13 For comparison, in application example 2, Li(Ni) 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder was used as the positive electrode at room temperature (20 mA g). -1 The initial charge-discharge curve at that time.

[0031] Figure 14 For comparison, in application example 2, Li(Ni) 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder was used as the positive electrode at room temperature at 200 mA g. -1 Capacity stability curve. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments, but these should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0033] Example 1

[0034] 1. Weigh 0.9103 g of the transition metal hydroxide precursor (Ni 0.8 Mn 0.20.4428 g of lithium compound (LiOH), 0.0062 g of magnesium oxide (MgO) and 0.0151 g of tin oxide (SnO2) were thoroughly mixed and loaded into a ball mill jar. Zirconia balls were used as the grinding medium and anhydrous ethanol was used as the dispersant. The mixture was ground in a high-speed ball mill for 6 h to obtain a slurry with uniform particle size. The slurry was then dried in a box-type forced-air drying oven at 120°C for 8 h and ground to obtain a mixed powder. 2. The mixed powder was loaded into a corundum boat and placed in a tube furnace at 750°C for 12 h. After cooling in the furnace, it was ground again to obtain Li. 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 (x=0.015, y=0.01) powder is a cobalt-free high-nickel oxide cathode material with dual-site doping.

[0035] Figure 1 Li in this embodiment 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 X-ray diffraction pattern of O2 powder. From Figure 1 It can be seen that Li 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 The O2 powder exhibits a typical hexagonal monolayer α-NaFeO2 structure. Figure 2 Li in this embodiment 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 SEM images of O2 powder. From Figure 2 It can be seen that Li 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 The O2 powder is assembled into 4.4μm microspheres. Figure 3 For the use of Li in Example 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 XPS plot of Mg element in O2 powder. (From...) Figure 3It can be seen that Mg is Mg 2+ The state exists. Figure 4 Li, as in Example 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 XPS plot of Sn element in O2 powder. Figure 4 It can be seen that Sn is Sn 4+ The state exists. From Figure 3 and 4 It can be seen that Mg and Sn elements have been incorporated into the crystal structure of the material.

[0036] Application Example 1 The Li prepared in Example 1 with a mass ratio of 8:1:1 was tested using coin cells. 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are uniformly stirred and coated onto aluminum foil, which is then cut into circular electrodes with a diameter of 14 mm. A lithium metal sheet serves as the counter electrode. 1 mol·L -1 The electrolyte was LiPF6 / EC + EMC (EC to EMC volume ratio 3:7), the separator was polypropylene, the battery testing system was Xinwei, the charge / discharge voltage window was 2.8~4.4 V, and the charge / discharge current density was selected as 20 mAg. -1 and 200mAg -1 .

[0037] Figure 5 For example Li in application 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder was used as the positive electrode at room temperature (20 mAg). -1 The initial charge-discharge curve at that time. Figure 5 It can be seen that at 20 mA g -1 The initial discharge specific capacity at the charge / discharge current density is 206.26 mAh g. -1 This indicates that the material exhibits good electrochemical performance when used as the positive electrode in lithium-ion batteries. Figure 6 For example Li in application 1 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01O2 powder was used as the positive electrode at room temperature at 200 mA g. -1 Capacity stability curve. (From) Figure 6 It can be seen that the discharge specific capacity can reach 189.56 mAh g. -1 The capacity retention rate after 200 cycles was 81.55%, indicating that the introduction of magnesium and tin ions can greatly improve the cycle stability of cobalt-free oxide cathode materials.

[0038] Example 2

[0039] The difference from Example 1 is that in step 1, 0.9103 g of Ni 0.8 Mn 0.2 LiOH, 0.4428 g of LiOH, 0.0062 g of MgO and 0.0151 g of SnO2 were thoroughly mixed to prepare Li. 0.995 Mg 0.005 (Ni 0.8 Mn 0.2 ) 0.995 Sn 0.005 O2 (x=0.005, y=0.005) is a cobalt-free high-nickel oxide cathode material with dual-site doping.

[0040] Application Example 2 The coin cells were assembled using the same method as in Application Example 1, except that the positive electrode active material was Li prepared in Example 2. 0.995 Mg 0.005 (Ni 0.8 Mn 0.2 ) 0.995 Sn 0.005 O2 powder. Figure 7 For example 2, Li 0.995 Mg 0.005 (Ni 0.8 Mn 0.2 ) 0.995 Sn 0.005 O2 powder was used as the positive electrode at room temperature at 200 mA g. -1 Capacity stability curve. (From) Figure 7 It can be seen that this material at 200 mA g -1 The first-cycle discharge specific capacity under charge-discharge conditions is 180.66 mAh g. -1 After 200 cycles, the discharge specific capacity is 143.00 mAh g. -1 The capacity retention rate was 79.16%, indicating that the dual-site doped cobalt-free high-nickel oxide cathode material obtained by the lower co-doping ratio can maintain a high capacity output and has a certain cycle stability, but its overall performance is still lower than that of the sample shown in Example 1.

[0041] Example 3

[0042] The difference from Example 1 is that in step 1, 0.9103 g of Ni 0.8 Mn 0.2 LiOH, 0.0083 g of MgO, and 0.0151 g of SnO2 were thoroughly mixed to prepare Li 0.98 Mg 0.02 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 (x=0.02, y=0.01) is a cobalt-free high-nickel oxide cathode material with dual-site doping.

[0043] Application Example 3 The coin cells were assembled using the same method as in Application Example 1, except that the positive electrode active material was Li prepared in Example 3. 0.98 Mg 0.02 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder. Figure 8 For example 3, Li 0.985 Mg 0.02 (Ni 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder was used as the positive electrode at room temperature with an A value of 200 mA / g. -1 Capacity stability curve. (From) Figure 8 It can be seen that this material at 200 mA g -1 The first-cycle discharge specific capacity under charge-discharge conditions is 173.90 mAh g. -1 After 200 cycles, the discharge specific capacity is 149.18 mAh g. -1 The capacity retention rate was 85.78%, indicating that the dual-site doped cobalt-free high-nickel oxide cathode material obtained under this ratio exhibits a relatively balanced characteristic between capacity output and cycle stability, but its overall performance is still lower than that of the sample shown in Example 1.

[0044] Example 4

[0045] The difference from Example 1 is that in step 1, 0.9057 g of Ni 0.8 Mn 0.2 LiOH, 0.4428 g of LiOH, 0.0062 g of MgO and 0.0227 g of SnO2 were thoroughly mixed to prepare Li. 0.985 Mg 0.015 (Ni 0.8 Mn0.2 ) 0.985 Sn 0.015 O2 (x=0.015, y=0.015) is a cobalt-free high-nickel oxide cathode material with dual-site doping.

[0046] Application Example 4 The coin cell was assembled using the same method as in Application Example 1, except that the positive electrode active material was Li prepared in Example 4. 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.985 Sn 0.015 O2 powder. Figure 9 For example 4, Li 0.985 Mg 0.015 (Ni 0.8 Mn 0.2 ) 0.985 Sn 0.015 O2 powder was used as the positive electrode at room temperature with an A value of 200 mA / g. -1 Capacity stability curve. (From) Figure 9 It can be known that this material is at 200 mA g -1 The first-cycle discharge specific capacity under charge-discharge conditions is 159.49 mAh g. -1 After 200 cycles, the discharge specific capacity is 140.72 mAh g. -1 The capacity retention rate was 88.23%, indicating that as the Sn doping amount is further increased, the dual-site doped cobalt-free high-nickel oxide cathode material obtained by this ratio is more conducive to improving cycle stability, but the capacity output is lower than that of the sample shown in Example 1.

[0047] Example 5

[0048] The difference from Example 1 is that in step 1, 0.9057 g of Ni 0.8 Mn 0.2 LiOH, 0.4406 g of LiOH, 0.0083 g of MgO, and 0.0227 g of SnO2 were thoroughly mixed to prepare Li. 0.98 Mg 0.02 (Ni 0.8 Mn 0.2 ) 0.985 Sn 0.015 O2 (x=0.02, y=0.015) is a cobalt-free high-nickel oxide cathode material with dual-site doping.

[0049] Application Example 5 The coin cells were assembled using the same method as in Application Example 1, except that the positive electrode active material was Li prepared in Example 5. 0.98Mg 0.02 (Ni 0.8 Mn 0.2 ) 0.985 Sn 0.015 O2 powder. Figure 10 For example 5, Li 0.98 Mg 0.02 (Ni 0.8 Mn 0.2 ) 0.985 Sn 0.015 O2 powder was used as the positive electrode at room temperature with an A value of 200 mA / g. -1 Capacity stability curve. (From) Figure 10 It can be known that this material is at 200 mA g -1 The first-cycle discharge specific capacity under charge-discharge conditions is 155.64 mAh g. -1 After 200 cycles, the discharge specific capacity is 137.96 mAh g. -1 The capacity retention rate was 88.64%, indicating that the ratio is more inclined to improve the cycle stability of the material, but the capacity sacrifice is relatively more obvious, and its overall performance is still lower than that of the sample shown in Example 1.

[0050] Comparative Example 1 The difference from Example 1 is that SnO2 was not added in step 1, resulting in the preparation of Li. 0.985 Mg 0.015 Ni 0.8 Mn 0.2 O2 powder is a magnesium-doped, cobalt-free, high-nickel oxide cathode material.

[0051] Comparative Application Example 1 The electrode used in this comparative application example is the Li prepared in Comparative Example 1. 0.985 Mg 0.015 Ni 0.8 Mn 0.2 O2 powder. Figure 11 To compare the application example 1, Li 0.985 Mg 0.015 Ni 0.8 Mn 0.2 O2 powder was used as the positive electrode at room temperature (20 mA g). -1 The initial charge-discharge curve at that time. From Figure 11 It can be seen that at 20 mA g -1 The initial discharge specific capacity at the charge / discharge current density is 208.47 mAh g. -1 This indicates that the Mg-doped sample has a high initial discharge specific capacity, suggesting a strong initial lithium storage capacity. Figure 12 To compare the application example 1, Li 0.985 Mg 0.015 Ni 0.8 Mn0.2 O2 powder was used as the positive electrode at room temperature at 200 mA g. -1 Capacity stability curve. From Figure 12 It can be seen that the highest discharge specific capacity is 184.82 mAh g. -1 The capacity retention rate after 200 cycles was 76.81%, indicating that the doping amount can still improve the specific capacity of the material, but at the expense of cycle performance.

[0052] Comparative Example 2 The difference from Example 1 is that magnesium oxide (MgO) was not added in step 1 to obtain Li(Ni) 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder is a tin-doped, cobalt-free, high-nickel oxide cathode material.

[0053] Comparative Application Example 2 The electrode used in this comparative application example is the Li(Ni) electrode prepared in Comparative Example 2. 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder. Figure 13 For comparison, in application example 2, Li(Ni) 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder was used as the positive electrode at room temperature (20 mA g). -1 The initial charge-discharge curve at that time. From Figure 13 It can be seen that at 20 mA g -1 The initial discharge specific capacity at the specified charge / discharge current density is 195.48 mAh g. -1 This indicates that the Sn-doped sample still exhibits good initial discharge capability. Figure 14 For comparison, in application example 2, Li(Ni) 0.8 Mn 0.2 ) 0.99 Sn 0.01 O2 powder was used as the positive electrode at room temperature at 200 mA g. -1 Capacity stability curve. From Figure 14 It can be seen that the highest discharge specific capacity is 158.48 mAh g. -1 The capacity retention rate after 200 cycles was 84.18%, indicating that the doping amount can still improve the cycling stability of the material, but reduce the capacity.

[0054] Therefore, it can be seen that the cobalt-free high-nickel oxide cathode material with dual-site doping of the present invention is effective in a voltage window of 2.8~4.4 V and a current density of 200 mA g. -1At that time, the discharge specific capacity reached a maximum of 189.56 mAh g. -1 Even after 200 cycles, the capacity remains as high as 153.96 mAh g. -1 The retention rate reached over 80%, indicating that the introduction of Mg and Sn ions improved the cycle stability of the cobalt-free lithium-rich manganese-based oxide cathode material, overcoming the shortcomings of previous materials such as short cycle life and rapid capacity decay, and making it applicable to the field of lithium-ion batteries.

[0055] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A cobalt-free high-nickel oxide cathode material with dual-site doping, characterized in that, The cobalt-free high-nickel oxide positive electrode material has a chemical formula of Li 1-x Mg x (Ni 0.8 Mn 0.2 ) 1-y Sn y O2, 0 < x ≤ 0.02, 0 < y ≤ 0.

015.

2. The dual-site doped cobalt-free high-nickel oxide cathode material according to claim 1, characterized in that, The cobalt-free high-nickel oxide cathode material is prepared by ball milling and mixing a transition metal precursor, a lithium compound, a magnesium compound, and a tin compound, then vacuum drying the resulting slurry at 80-150°C to obtain a mixed powder; compacting the mixed powder, heat-treating it at 450-550°C, then sintering it at 700-900°C, and finally grinding and sieving the sintered material.

3. The cobalt-free high-nickel oxide cathode material with dual-site doping according to claim 2, characterized in that, The lithium compound is one or more of lithium carbonate, lithium hydroxide, lithium nitrate, or lithium acetate; the magnesium compound is one or more of magnesium oxide, magnesium hydroxide, or magnesium carbonate; the tin compound is tin oxide; and the transition metal precursor is a transition metal hydroxide precursor.

4. The cobalt-free high-nickel oxide cathode material with dual-site doping according to claim 3, characterized in that, The transition metal carbonate precursor is TM(OH)2, where TM = Mn or / and Ni.

5. The cobalt-free high-nickel oxide cathode material with dual-site doping according to claim 2, characterized in that, The molar ratio of transition metal ions in the transition metal precursor to lithium ions in the lithium compound is 1:(1.2~1.6), and the molar ratio of magnesium ions in the magnesium compound, tin ions in the tin compound, and transition metal ions in the transition metal precursor is (0.1~2.5):(0.1~2.5):

100.

6. The method for preparing the cobalt-free high-nickel oxide cathode material with dual-site doping according to any one of claims 1-5, characterized in that, The specific steps include the following: S1. Transition metal precursors, lithium compounds, magnesium compounds and tin compounds are ball-milled and mixed using zirconia balls as the grinding medium and anhydrous ethanol as the dispersant. After ball milling, the slurry is vacuum-dried at 80~150℃ to obtain a mixed powder. S2. Compact the mixed powder, heat treat it at 450~550℃, then sinter it at 700~900℃, grind the sintered material and sieve it to obtain a cobalt-free high-nickel oxide cathode material with dual-site doping.

7. The method for preparing the cobalt-free high-nickel oxide cathode material with dual-site doping according to claim 6, characterized in that, The ball milling time in step S1 is 3~6h; the heating rate of the vacuum drying is 1~4℃ / min, and the time is 6~12h.

8. The method for preparing the cobalt-free high-nickel oxide cathode material with dual-site doping according to claim 6, characterized in that, The heat treatment time in step S2 is 6~12 h, the sintering heating rate is 3~5℃ / min, and the sintering time is 8~20 h.

9. The application of the dual-site doped cobalt-free high-nickel oxide cathode material according to any one of claims 1-5 in the field of lithium-ion batteries.

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