A lithium-rich manganese-based layered oxide material, a preparation method thereof and a lithium ion battery

Abstract

The present application provides a kind of lithium-rich manganese-based layered oxide material and its preparation method and lithium ion battery, the material morphology is spherical particle, from the center of spherical particle to surface layer, the proportion of manganese element in transition metal element gradually reduces.By adjusting the trend of element concentration change, for example, linear change, steep change presents exponential function, so that the capacity of material can be played, so that lithium-rich manganese-based positive material can provide high capacity while having structural stability, obtain better thermal stability and cycle performance.At the same time, by introducing reaction bottom liquid in the preparation process, the supersaturation in the early stage is significantly increased, the nucleation rate is increased, the situation that the precursor core is not dense is reduced, so that the material does not occur after sintering core-shell separation, thereby affecting the material performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a lithium-rich manganese-based crystalline oxide material, its preparation method, and a lithium-ion battery. Background Technology

[0002] With the rapid development of new energy vehicles and large-scale energy storage systems, the market demand for high-energy-density, long-life, and low-cost lithium-ion batteries has increased dramatically. The energy density of lithium-ion batteries mainly depends on the energy density of the electrode materials, and the specific capacity and operating voltage of the cathode material are key factors determining its energy density. Given the current lack of mature and commercially viable high-voltage electrolyte systems, improving the reversible specific capacity of the cathode material remains the primary path to increasing battery energy density.

[0003] Existing commercially available or near-commercially available lithium-ion battery cathode materials mainly include layered lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2), spinel-structured lithium manganese oxide (LiMn2O4), olivine-structured lithium iron phosphate (LiFePO4), and nickel-cobalt-manganese ternary layered materials (LiNiO2, LiCoO2, LiNi ... x Co y Mn z Lithium oxide materials such as O2 are used. The specific capacity of these materials is usually below 200 mAh / g. As their structural stability and reversible lithium insertion / extraction range gradually approach their limits, the insufficient capacity of cathode materials has become a bottleneck for further improving the energy density of lithium-ion batteries, and there is an urgent need to develop new cathode material systems with high capacity.

[0004] Lithium-rich manganese-based substrate cathode material x Li2MnO3·(1 xLiTMO2 (TM, composed of transition metal elements such as Ni, Co, and Mn) possesses a unique anion / cation synergistic redox mechanism, achieving a discharge specific capacity of approximately 300 mAh / g at room temperature. This capacity can be further increased at higher temperatures. Simultaneously, its average discharge plateau voltage is approximately 3.5-3.7 V, and its theoretical energy density is significantly higher than existing commercial cathode materials. Furthermore, the system has a high manganese content, offering advantages such as low cost, abundant resources, and environmental friendliness, making it a promising candidate cathode material for next-generation high-energy-density lithium-ion batteries for electric vehicles and large-scale energy storage. This material typically consists of a composite structure formed by Li2MnO3 and LiTMO2 phases in a specific ratio. The Li2MnO3 component not only helps stabilize the material structure but also provides additional capacity under high-voltage conditions. However, lithium-rich manganese-based substrate cathode materials still face a series of key challenges in practical applications: during high-voltage activation, surface lattice oxygen is prone to irreversible precipitation, leading to a significant reduction in initial coulombic efficiency; simultaneously, the dissolution of transition metal ions on the material surface in the electrolyte induces structural reconstruction, easily causing voltage decay and a decrease in capacity retention; furthermore, the intensification of interfacial side reactions under high voltage promotes abnormal thickening of the cathode electrolyte interphase (CEI) film and a rapid increase in interfacial impedance, thereby significantly shortening the battery cycle life. To alleviate these problems, existing research typically employs strategies such as surface coating, elemental doping, and morphology control, but these still generally suffer from limitations such as insufficient stability of the modified layer, restricted ion / electron transport, difficulty in suppressing structural evolution, or insufficient process consistency and scalability. It remains difficult to achieve a stable and controllable material interface and structure while simultaneously achieving high capacity and long lifespan.

[0005] Chinese patent application CN 107785551 A discloses a lithium-rich manganese-based crystalline oxide material with a gradient of phase structure ratios. The invention offers the following technical advantages: A lithium-rich manganese-based crystalline oxide material with a gradient of two structural unit ratios was prepared via a co-precipitation-solid-phase synthesis method. This material consists of spherical particles, with the monoclinic Li₂MnO₃ structural units gradually decreasing and the rhombic LiTMO₂ structural units gradually increasing from the particle center to the surface. By controlling the ratio of monoclinic Li₂MnO₃ to rhombic LiTMO₂ structural units from the particle interior to the surface, the cycle stability, discharge specific capacity, and safety performance of the lithium-rich manganese-based crystalline oxide material in lithium-ion batteries can be regulated.

[0006] The aforementioned existing technologies do not take full advantage of the capacity of the core components of lithium-rich manganese-based basal oxide materials. Summary of the Invention

[0007] To address the challenge of achieving both capacity and structural stability in lithium-rich manganese-based cathode materials, this invention provides a lithium-rich manganese-based morphological oxide material, its preparation method, and a lithium-ion battery.

[0008] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for preparing a lithium-rich manganese-based layered oxide material, comprising: S1, Dissolve nickel salt, cobalt salt and manganese salt in water to obtain solution 1; Dissolve nickel salt, cobalt salt and manganese salt in water to obtain solution 2; wherein, the total concentration of transition metal ions in solution 1 and solution 2 is the same, and the molar percentage of manganese in the total amount of nickel, cobalt and manganese in solution 2 is less than the molar percentage of manganese in the total amount of nickel, cobalt and manganese in solution 1. S2, add solution 2 to solution 1 which is under stirring. At the same time, add the mixed salt solution of solution 1 and solution 2, Na2CO3 solution and ammonia water to the reaction vessel containing the bottom liquid for co-precipitation reaction to obtain lithium-rich manganese-based layered oxide material precursor. The flow rate ratio of solution 2 to the flow rate of the mixed salt solution is (0.5-2):1. The bottom liquid is a transition metal salt solution obtained by dissolving nickel salt, cobalt salt and manganese salt in water. The total concentration of nickel, cobalt and manganese in the transition metal salt solution is 0.1-0.2 M, and the molar ratio of nickel, cobalt and manganese is the same as that of solution 1. S3, the lithium-rich manganese-based morphological oxide material precursor is mixed with Li2CO3 and calcined to obtain the lithium-rich manganese-based morphological oxide material.

[0009] Preferably, in S1, the molar ratio of nickel, cobalt and manganese in solution 1 is 1:1:(4-5); and the molar ratio of nickel, cobalt and manganese in solution 2 is 1:1:(1-2).

[0010] Preferably, in S1, the nickel salt, cobalt salt, and manganese salt are nickel sulfate, cobalt sulfate, and manganese sulfate, respectively.

[0011] Preferably, in S2, the reaction temperature is 55-65 ℃ and the reaction time is 20-50 h.

[0012] Preferably, in S2, the stirring speed is 800-1200 rpm.

[0013] Preferably, in S3, the ratio of the number of moles of lithium in the Li2CO3 to the total number of moles of Ni, Mn and Co in the precursor is (1.25-1.35):1.

[0014] Preferably, in S3, the calcination process is as follows: pre-calcination at 450-550 ℃ for 3-8 h in an air atmosphere, followed by heating to 800-850 ℃ and holding for 10-16 h.

[0015] Secondly, the present invention provides a lithium-rich manganese-based basal oxide material obtained by the preparation method described above. The material has a morphology of spherical particles, and the proportion of manganese in the transition metal elements gradually decreases from the center of the spherical particles to the surface.

[0016] Preferably, the molar ratio of the transition metal at the center of the spherical particle is Ni:Co:Mn=1:1:4, and the molar ratio of the transition metal on the surface of the spherical particle is Ni:Co:Mn=1:1:2.

[0017] Thirdly, the present invention provides a lithium-ion battery, comprising a positive electrode and a negative electrode, wherein the active component of the positive electrode is the lithium-rich manganese-based layered oxide material described in the present invention.

[0018] Compared with the prior art, the present invention has the following beneficial effects: In the method for preparing lithium-rich manganese-based basal oxide materials of this invention, the molar proportion of manganese in solution 2 relative to the total amount of nickel, cobalt, and manganese is less than that in solution 1. Simultaneously with adding solution 2 to solution 1, a mixed salt solution of solutions 1 and 2 is added to a reaction vessel containing a bottom liquid for co-precipitation. Initially, solution 1 constitutes a larger proportion of the mixed salt solution, resulting in a higher molar proportion of manganese in the total amount of nickel, cobalt, and manganese. As time progresses, the amount of solution 1 gradually decreases, and consequently, the molar proportion of manganese in the mixed salt solution also gradually decreases. This allows for control of the spatial distribution of bulk elements in the lithium-rich manganese-based basal oxide material. The spatial gradient distribution design of bulk elements enables functional partitioning of the cathode material. The high-Mn content component at the core provides higher oxygen activity, achieving a higher discharge specific capacity during charge and discharge. The low-Mn content component on the surface acts as a robust barrier, reducing surface side reactions and achieving high structural stability. Meanwhile, by adjusting the flow rate ratio of solution 2 to the mixed salt solution, this invention can control the variation trend of transition metal elements, ensuring that the Mn element content in the transition metal elements follows a specific functional variation law from the center to the surface of the particle. This adjusts the trend of element concentration change, such as a linear, gradual change or a steep exponential function change, to maximize the material's capacity. This design concept enables lithium-rich manganese-based cathode materials to provide high capacity while maintaining structural stability, achieving better thermal stability and cycle performance. Furthermore, by using the transition metal salt solution as the reaction substrate, this invention significantly increases the initial supersaturation, increases the nucleation rate, and reduces the occurrence of non-dense precursor cores, preventing core-shell separation after sintering and thus avoiding impact on material performance.

[0019] Furthermore, in this invention, the ratio of the number of moles of lithium in Li2CO3 to the total number of moles of Ni, Mn, and Co in the precursor is (1.25-1.35):1. This invention reduces the amount of lithium carbonate mixed in, thereby reducing the material preparation cost. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of the component gradient design for lithium-rich manganese-based basal oxide materials.

[0022] Figure 2 The X-ray diffraction pattern of the lithium-rich manganese-based matrix oxide material obtained in Example 1 is shown.

[0023] Figure 3 This is a scanning electron microscope image of the lithium-rich manganese-based basal oxide material obtained in Example 1.

[0024] Figure 4 This is a cross-sectional energy dispersive X-ray spectral line scan of the lithium-rich manganese-based matrix oxide material obtained in Example 1.

[0025] Figure 5 The first charge-discharge curves of the lithium-rich manganese-based basal oxide materials obtained in Example 1 and Comparative Example 1 are shown.

[0026] Figure 6 This is a schematic diagram of the cycling performance of the lithium-rich manganese-based matrix oxide materials obtained in Example 1 and Comparative Example 1.

[0027] Figure 7 This is a schematic diagram of the high-temperature cycling performance at 45°C of the lithium-rich manganese-based matrix oxide materials obtained in Example 1 and Comparative Example 1.

[0028] Figure 8 Differential scanning calorimetry (DSC) results of the lithium-rich manganese-based matrix oxide materials obtained in Example 1 and Comparative Example 1 are shown. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0031] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not intended to limit the order of the method steps or define the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0032] The method for preparing the lithium-rich manganese-based crystalline oxide material of the present invention includes: S1, Dissolve nickel salt, cobalt salt and manganese salt in water to obtain solution 1; Dissolve nickel salt, cobalt salt and manganese salt in water to obtain solution 2; wherein, the molar percentage of manganese in the total amount of nickel, cobalt and manganese in solution 2 is less than the molar percentage of manganese in the total amount of nickel, cobalt and manganese in solution 1; S2, add solution 2 to solution 1 which is under stirring. At the same time, add the mixed salt solution of solution 1 and solution 2, Na2CO3 solution and ammonia water to the reaction vessel containing the bottom liquid for co-precipitation reaction to obtain lithium-rich manganese-based layered oxide material precursor. The flow rate ratio of solution 2 to the flow rate of the mixed salt solution is (0.5-2):1. The bottom liquid is a transition metal salt solution obtained by dissolving nickel salt, cobalt salt and manganese salt in water. The total concentration of nickel, cobalt and manganese in the transition metal salt solution is 0.1-0.2 M, and the molar ratio of nickel, cobalt and manganese is the same as that of solution 1. S3, the lithium-rich manganese-based morphological oxide material precursor is mixed with Li2CO3 and calcined to obtain the lithium-rich manganese-based morphological oxide material.

[0033] In the preparation method of this invention, the molar proportion of manganese in the total amount of nickel, cobalt, and manganese in solution 2 is less than that in solution 1. Simultaneously with adding solution 2 to solution 1, a mixed salt solution of solutions 1 and 2 is added to a reaction vessel containing a bottom liquid for co-precipitation. Initially, solution 1 constitutes a larger proportion of the mixed salt solution, resulting in a larger molar proportion of manganese in the total amount of nickel, cobalt, and manganese. As time progresses, the amount of solution 1 gradually decreases, and consequently, the molar proportion of manganese in the mixed salt solution also gradually decreases. This allows control over the spatial distribution of bulk elements in the lithium-rich manganese-based basal oxide material, resulting in a gradual decrease in the proportion of manganese among transition metal elements from the particle center to the surface. This reduces the content of the surface Li2MnO3 phase, increases the interfacial stability of the material, and simultaneously achieves higher discharge specific capacity and better structural stability.

[0034] This invention controls the variation trend of transition metal element concentration by adjusting the flow rate ratio of solution 2 to the mixed salt solution. For example, from the center of the particle to the surface, the Mn element content varies with different functions from 67% to 50%. Simultaneously, this invention thoroughly studies the influence of the manganese element concentration variation trend on material performance. The results show that when the flow rate ratio of solution 2 added to solution 1 to the flow rate of the mixed salt solution added to the reactor is 1:2, the Mn element concentration changes linearly with time, resulting in optimal material performance.

[0035] This invention uses a transition metal salt solution as the reaction substrate to increase the supersaturation of the early reaction, making the nucleation process more stable, the spherical cores more complete and uniformly stacked, and preventing core-shell separation after sintering.

[0036] In some embodiments of the present invention, the preparation of Ni as the core component can be controlled by adjusting the feeding process (the ratio of transition metal elements in solution 1 and solution 2, the flow rate, and the volume) during the co-precipitation reaction. 0.17 Co 0.17 Mn 0.65 CO3, surface component is Ni 0.25 Co 0.25 Mn 0.5 CO3, with Ni as its overall component 0.2 Co 0.2 Mn 0.6 The carbonate precursor of CO3 has a gradient distribution of transition metal elements in the radial direction.

[0037] In some preferred embodiments of the present invention, in S1, the molar ratio of nickel, cobalt and manganese in solution 1 is 1:1:(4-5); and the molar ratio of nickel, cobalt and manganese in solution 2 is 1:1:(1-2).

[0038] In some preferred embodiments of the present invention, in S1, the nickel salt, cobalt salt and manganese salt are nickel sulfate, cobalt sulfate and manganese sulfate, respectively.

[0039] In some preferred embodiments of the present invention, in S2, the reaction temperature is 55-65 °C and the reaction time is 20-50 h.

[0040] In some preferred embodiments of the present invention, in S2, the stirring speed is 800-1200 rpm.

[0041] In some preferred embodiments of the present invention, in S3, the ratio of the number of moles of lithium in the Li2CO3 to the total number of moles of Ni, Mn and Co in the precursor is (1.25-1.35):1.

[0042] In some preferred embodiments of the present invention, in S3, the calcination process is as follows: pre-calcination at 450-550 ℃ for 3-8 hours in an air atmosphere, followed by heating to 800-850 ℃ and holding for 10-16 hours.

[0043] The lithium-rich manganese-based basal oxide material obtained by the method of this invention has a spherical particle morphology. From the center to the surface of the spherical particles, the proportion of manganese in the transition metal elements gradually decreases, resulting in a continuous decrease in the proportion of the Li2MnO3 phase. Figure 1 As shown.

[0044] In some embodiments of the present invention, the molar ratio of the transition metal at the center of the spherical particle is Ni:Co:Mn=1:1:4, and the molar ratio of the transition metal on the surface of the spherical particle is Ni:Co:Mn=1:1:2.

[0045] The lithium-ion battery of the present invention includes a positive electrode and a negative electrode, wherein the active component of the positive electrode is the lithium-rich manganese-based crystalline oxide material of the present invention.

[0046] The active component of the negative electrode can be graphite, artificial graphite, silicon carbide, lithium metal, or lithium-carbon negative electrode material.

[0047] Example 1 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0048] (2) 5000 mL of solution 2 was added at a constant rate to 4800 mL of solution 1 under stirring conditions. At the same time, a mixed salt solution of solution 1 and solution 2, a 2 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia solution were added at a constant rate to the reactor. The bottom liquid in the reactor was a 0.1 M transition metal salt solution (Ni:Co:Mn=1:1:4) prepared from NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O. The flow rate of solution 2 added to solution 1 was 1:2 compared with the flow rate of the mixed salt solution added to the reactor. The stirring speed was controlled at 1000 rpm, the reaction temperature was 60 ℃, the pH value was 8.1, and the reaction time was 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0049] (3) The precursor is mixed with Li2CO3 (the ratio of the molar number of lithium to the total molar number of Ni, Mn and Co is 1.3:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based basal oxide material with a radial gradient of transition metal element concentration; the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0050] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) at a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0051] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes linearly with time. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the concentration of Mn in solution 1, in mol / L. t represents the reaction time, in hours.

[0052] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 324.6 mAh / g for the first charge cycle and a specific capacity of 292.5 mAh / g for the first discharge cycle, with a coulombic efficiency of 90.1% for the first cycle. After 100 cycles under a current density of 1 C and a voltage range of 2.0-4.6V, the capacity retention rate was 91.6%.

[0053] Example 2 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0054] (2) 5000 mL of solution 2 was added at a constant rate to 6930 mL of solution 1 under stirring conditions. At the same time, the mixed salt solution of solution 1 and solution 2, as well as 2 mol / L Na2CO3 solution and 0.2 mol / L ammonia water were added at a constant rate to the reactor. The bottom liquid in the reactor was a 0.1 M transition metal salt solution (Ni:Co:Mn=1:1:4) prepared from NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O. The flow rate of solution 2 added to solution 1 was 1:1 to that of the mixed salt solution added to the reactor. The stirring speed was controlled at 1000 rpm, the reaction temperature was 60 ℃, the pH value was 8.1, and the reaction time was 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0055] (3) The precursor is mixed with Li2CO3 (the ratio of the molar number of lithium to the total molar number of Ni, Mn and Co is 1.3:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based basal oxide material with a radial gradient of transition metal element concentration; the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0056] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) at a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0057] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes exponentially with time. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the concentration of Mn in solution 1, in mol / L. t represents the reaction time, in hours.

[0058] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 312.4 mAh / g for the first charge cycle and a specific capacity of 284.9 mAh / g for the first discharge cycle, with a coulombic efficiency of 91.2%. After 100 cycles under a current density of 1 C and a voltage range of 2.0-4.6V, the capacity retention rate was 89.9%.

[0059] Example 3 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L, respectively. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0060] (2) 5000 mL of solution 2 was added at a constant rate to 5800 mL of solution 1 under stirring conditions. At the same time, a mixed salt solution of solution 1 and solution 2, a 2 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia solution were added at a constant rate to the reactor. The bottom liquid in the reactor was a 0.1 M transition metal salt solution (Ni:Co:Mn=1:1:4) prepared from NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O. The flow rate ratio of solution 2 added to solution 1 to the flow rate of the mixed salt solution added to the reactor was 2:1. The stirring speed was controlled at 1000 rpm, the reaction temperature at 60 ℃, the pH value at 8.1, and the reaction time at 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0061] (3) The precursor is mixed with Li2CO3 (the ratio of the molar number of lithium to the total molar number of Ni, Mn and Co is 1.3:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based basal oxide material with a radial gradient of transition metal element concentration; the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0062] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) in a ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0063] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes with time according to a power function relationship. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the initial Mn concentration in solution 1, in mol / L. t represents the reaction time, in hours.

[0064] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 318.1 mAh / g for the first charge cycle and a specific capacity of 284.4 mAh / g for the first discharge cycle, with a coulombic efficiency of 89.4%. After 100 cycles under a current density of 1 C and a voltage range of 2.0-4.6V, the capacity retention rate was 83.8%.

[0065] Example 4 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0066] (2) 5000 mL of solution 2 was added at a constant rate to 3000 mL of solution 1 under stirring conditions. At the same time, the mixed salt solution of solution 1 and solution 2, as well as 2 mol / L Na2CO3 solution and 0.2 mol / L ammonia water were added at a constant rate to the reactor. The bottom liquid in the reactor was a 0.1 M transition metal salt solution (Ni:Co:Mn=1:1:4) prepared from NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O. The ratio of the flow rate of solution 2 added to solution 1 to the flow rate of the mixed salt solution added to the reactor was 1:2. The stirring speed was controlled at 1000 rpm, the reaction temperature was 60 ℃, the pH value was 8.1, and the reaction time was 25 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0067] (3) The precursor is mixed with Li2CO3 (the ratio of the number of moles of lithium to the total number of moles of Ni, Mn and Co is 1.3:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based basal oxide material with a radial gradient of transition metal element concentration: the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0068] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) at a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0069] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes linearly with time. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the initial Mn concentration in solution 1, in mol / L. t represents the reaction time, in hours.

[0070] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 309.1 mAh / g for the first charge cycle and a specific capacity of 273.3 mAh / g for the first discharge cycle, with a coulombic efficiency of 88.4%. After 100 cycles under a current density of 1 C and a voltage range of 2.0-4.6V, the capacity retention rate was 81.6%.

[0071] Example 5 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0072] (2) 5000 mL of solution 2 was added at a constant rate to 4800 mL of solution 1 under stirring conditions. At the same time, a mixed salt solution of solution 1 and solution 2, a 2 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia solution were added at a constant rate to the reactor. The bottom liquid in the reactor was a 0.2 M transition metal salt solution (Ni:Co:Mn=1:1:4) prepared from NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O. The ratio of the flow rate of solution 2 added to solution 1 to the flow rate of the mixed salt solution added to the reactor was 1:2. The stirring speed was controlled at 1000 rpm, the reaction temperature at 60 ℃, the pH value at 8.1, and the reaction time at 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0073] (3) The precursor is mixed with Li2CO3 (the ratio of the molar number of lithium to the total molar number of Ni, Mn and Co is 1.3:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based basal oxide material with a radial gradient of transition metal element concentration; the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0074] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) at a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0075] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes linearly with time. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the initial Mn concentration in solution 1, in mol / L. t represents the reaction time, in hours.

[0076] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 310.5 mAh / g for the first charge cycle and a specific capacity of 282.2 mAh / g for the first discharge cycle, with a coulombic efficiency of 90.8%. After 100 cycles under a current density of 1 C and a voltage range of 2.0-4.6V, the capacity retention rate was 88.6%.

[0077] Example 6 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0078] (2) 5000 mL of solution 2 was added at a constant rate to 4800 mL of solution 1 under stirring conditions. At the same time, a mixed salt solution of solution 1 and solution 2, a 2 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia solution were added at a constant rate to the reactor. The bottom liquid in the reactor was a 0.1 M transition metal salt solution (Ni:Co:Mn=1:1:4) prepared from NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O. The flow rate of solution 2 added to solution 1 was 1:2 compared with the flow rate of the mixed salt solution added to the reactor. The stirring speed was controlled at 1000 rpm, the reaction temperature was 60 ℃, the pH value was 8.1, and the reaction time was 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0079] (3) The precursor is mixed with Li2CO3 (the ratio of the molar number of lithium to the total molar number of Ni, Mn and Co is 1.25:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based morphological oxide material with a radial gradient of transition metal element concentration; the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0080] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) at a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0081] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes linearly with time. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the initial Mn concentration in solution 1, in mol / L. t represents the reaction time, in hours.

[0082] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 302.4 mAh / g for the first charge cycle and a specific capacity of 277.4 mAh / g for the first discharge cycle, with a coulombic efficiency of 91.7%. After 100 cycles under a current density of 1 C and a voltage range of 2.0-4.6V, the capacity retention rate was 87.6%.

[0083] Example 7 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0084] (2) 5000 mL of solution 2 was added at a constant rate to 4800 mL of solution 1 under stirring conditions. At the same time, a mixed salt solution of solution 1 and solution 2, a 2 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia solution were added at a constant rate to the reactor. The bottom liquid in the reactor was a 0.1 M transition metal salt solution (Ni:Co:Mn=1:1:4) prepared from NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O. The flow rate of solution 2 added to solution 1 was 1:2 compared with the flow rate of the mixed salt solution added to the reactor. The stirring speed was controlled at 1000 rpm, the reaction temperature was 60 ℃, the pH value was 8.1, and the reaction time was 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0085] (3) The precursor is mixed with Li2CO3 (the ratio of the molar number of lithium to the total molar number of Ni, Mn and Co is 1.35:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based morphological oxide material with a radial gradient of transition metal element concentration; the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0086] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) at a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0087] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes linearly with time. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the initial Mn concentration in solution 1, in mol / L. t represents the reaction time, in hours.

[0088] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a first-cycle charging capacity of 318.0 mAh / g and a first-cycle discharging capacity of 280.3 mAh / g, with a first-cycle coulombic efficiency of 88.3%. After 100 cycles under a current density of 1C and a voltage range of 2.0-4.6V, the capacity retention rate was 87.0%.

[0089] Comparative Example 1 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare a solution with a total concentration of transition metal elements of 2 mol / L. The molar ratio of nickel, cobalt and manganese in the solution was 0.2:0.2:0.6.

[0090] (2) 5000 mL of solution was added to the reactor at a constant rate. The bottom liquid in the reactor was a 0.1 M transition metal salt solution (Ni:Co:Mn=1:1:3) prepared from NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O. 2 mol / L Na2CO3 solution and 0.2 mol / L ammonia water were added to the reactor. The stirring speed was controlled at 1000 rpm, the reaction temperature at 60℃, the pH value at 8.1, and the reaction time at 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor.

[0091] (3) The precursor is mixed with Li2CO3 (the ratio of the number of moles of lithium to the total number of moles of Ni, Mn and Co is 1.3:1), and kept at 500 °C for 5 h in air atmosphere, and then heated to 820 °C for 12 h to obtain a lithium-rich manganese-based matrix oxide material with uniform distribution of transition metal element concentration.

[0092] (4) The obtained lithium-rich manganese-based morphological oxide material was used as the positive electrode material and mixed with carbon black and PVDF (dissolved in NMP solution) at a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0093] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 305.1 mAh / g for the first charge cycle and a specific capacity of 269.0 mAh / g for the first discharge cycle, with a coulombic efficiency of 88.1%. After 100 cycles under a current density of 1 C and a voltage range of 2.0-4.6V, the capacity retention rate was 81.6%.

[0094] Comparative Example 2 (1) NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O were added to water to prepare solutions 1 and 2 with a total transition metal element concentration of 2 mol / L. The molar ratio of nickel, cobalt and manganese in solution 1 was 0.17:0.17:0.67, and the molar ratio of nickel, cobalt and manganese in solution 2 was 0.33:0.33:0.33.

[0095] (2) 5000 mL of solution 2 was added at a constant rate to 4800 mL of solution 1 under stirring conditions. At the same time, a mixed salt solution of solution 1 and solution 2, a 2 mol / L Na2CO3 solution, and a 0.2 mol / L ammonia solution were added at a constant rate to the reactor. The bottom liquid in the reactor was deionized water. The ratio of the flow rate of solution 2 added to solution 1 to the flow rate of the mixed salt solution added to the reactor was 1:2. The stirring speed was controlled at 1000 rpm, the reaction temperature at 60 ℃, the pH value at 8.1, and the reaction time at 40 h. The obtained product was filtered, washed, and dried to obtain a lithium-rich manganese-based matrix oxide material precursor with a gradient of manganese content.

[0096] (3) The precursor is mixed with Li2CO3 (the ratio of the molar number of lithium to the total molar number of Ni, Mn and Co is 1.3:1), kept at 500 ℃ for 5 h in air atmosphere, and then heated to 820 ℃ for 12 h to obtain a lithium-rich manganese-based basal oxide material with a radial gradient of transition metal element concentration; the molar ratio of transition metal elements in the center of the material particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metal elements on the surface of the particles is Ni:Co:Mn=1:1:2.

[0097] (4) The obtained positive electrode material was mixed with carbon black and PVDF (dissolved in NMP solution) in a mass ratio of 80:10:10 to obtain a black viscous slurry. The slurry was coated on aluminum foil and dried at 120 °C for 4 h to obtain a lithium-ion battery positive electrode sheet. The lithium sheet was used as the counter electrode, and a 1 mol / L LiPF6 solution (solvents including EC and DMC in a volume ratio of 3:7) was used as the electrolyte. The separator was Celgar2502 separator. The cells were assembled into 2032 coin cells and charged and discharged.

[0098] (5) Under this feed rate ratio, taking Mn as an example, the element concentration changes linearly with time. V0 is the initial volume of solution 1, Q1 is the flow rate of the mixed salt solution into the reactor, and Q2 is the flow rate of solution 2 into solution 1, all in L / h. C1 is the Mn concentration in the mixed salt solution, C2 is the Mn concentration in solution 2, and C... 10 t represents the initial Mn concentration in solution 1, in mol / L. t represents the reaction time, in hours.

[0099] Testing revealed that, under a current density of 0.1 C and a voltage range of 2.0-4.8V for the first charge-discharge cycle, the half-cell assembled from the above materials achieved a specific capacity of 303.1 mAh / g for the first charge cycle and a specific capacity of 265.0 mAh / g for the first discharge cycle, with a coulombic efficiency of 87.4%. After 100 cycles under a current density of 1C and a voltage range of 2.0-4.6V, the capacity retention rate was 80.1%.

[0100] Table 1 below shows the test data for each embodiment and comparative example.

[0101] Table 1. Performance Comparison of Examples and Comparative Examples

[0102] By comparing Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Example 1, it can be found that the radial gradient distribution of transition metal element concentration in the material can affect the initial discharge capacity and cycle stability of the material. Combining the examples and the comparative example, it is clear that the radial gradient distribution of transition metal element concentration in the material can improve the initial discharge capacity and cycle stability. Specifically, comparing Examples 1-3, the ratio of the flow rate of solution 2 added to solution 1 to the flow rate of the mixed salt solution added to the reactor affects the trend of element concentration change, which in turn affects the electrochemical performance of the obtained material. It can be seen that the best electrochemical performance is achieved when the manganese element concentration exhibits a linear gradient change. Examples 1 and 4 show that the reaction time has a certain impact on the material performance; a reaction time of 40 hours is the most suitable synthesis time to obtain the best performance. Comparing Examples 1, 5, and Comparative Example 2, it can be seen that compared to using water as the base solution, using a transition metal salt solution as the base solution results in higher discharge capacity and coulombic efficiency. Furthermore, when the transition metal ion concentration in the base solution is 0.1 M, the precursor nucleation is more stable, resulting in the best performance. By comparing Examples 1, 6, and 7, it can be seen that the amount of lithium has a certain impact on the electrochemical performance of the material. The electrochemical performance of the material is optimal when the amount of lithium is 1.3. Among them, the process parameters in Example 1 achieved the best electrochemical performance.

[0103] Figure 2 The X-ray diffraction pattern of the lithium-rich manganese-based substrate oxide material obtained in Example 1 is shown below. Figure 2 It can be seen that the material is composed of two phases, LiTMO2 and Li2MnO3.

[0104] Figure 3 This is a scanning electron microscope image of the lithium-rich manganese-based basal oxide material obtained in Example 1. Figure 3 It can be seen that the material is composed of secondary spherical particles assembled from primary particles.

[0105] Figure 4 This is a cross-sectional energy-dispersive X-ray spectral line scan of the lithium-rich manganese-based substrate oxide material obtained in Example 1. Figure 4 It can be seen that the Mn element gradually decreases from the core to the surface of the material.

[0106] Figure 5 The first charge-discharge curves of the lithium-rich manganese-based matrix oxide materials in Example 1 and Comparative Example 1 show that the discharge capacity of the material in Example 1 is significantly better than that in Comparative Example 1.

[0107] Figure 6 The diagram shows the cycling performance of lithium-rich manganese-based matrix oxide materials in Example 1 and Comparative Example 1. It can be seen that the cycling performance of the material in Example 1 is significantly better than that in Comparative Example 1.

[0108] Figure 7 The diagram shows the high-temperature cycling performance of lithium-rich manganese-based base oxide materials in Example 1 and Comparative Example 1 at 45°C. It can be seen that the thermal stability of the material in Example 1 is significantly better than that in Comparative Example 1.

[0109] Figure 8 The differential scanning calorimetry (DSC) results for the lithium-rich manganese-based matrix oxide materials of Example 1 and Comparative Example 1 show that the thermal stability of the material in Example 1 is significantly better than that in Comparative Example 1.

[0110] The above results show that, using the method of the present invention, under optimal feed conditions and with a 0.1 M transition metal salt solution as the reaction substrate, lithium-rich manganese-based morphological oxide materials with a radial gradient distribution of transition metal elements (manganese concentration gradually decreases from the center to the outer layer) can be prepared. Compared to lithium-rich manganese-based morphological oxide materials with uniform transition metal element concentration or gradually increasing manganese concentration from the center to the outer layer, the lithium-rich manganese-based morphological oxide material of the present invention exhibits superior capacity and cycle stability.

[0111] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing a lithium-rich manganese-based basal oxide material, characterized in that, include: Nickel salts, cobalt salts, and manganese salts are dissolved in water to obtain solution 1; nickel salts, cobalt salts, and manganese salts are dissolved in water to obtain solution 2; wherein, the total concentration of transition metal ions in solution 1 and solution 2 is the same, and the molar percentage of manganese in the total amount of nickel, cobalt, and manganese in solution 2 is less than the molar percentage of manganese in the total amount of nickel, cobalt, and manganese in solution 1. Solution 2 is added to solution 1 which is under stirring. At the same time, the mixed salt solution of solution 1 and solution 2, along with Na2CO3 solution and ammonia water, are added to a reaction vessel containing a bottom liquid for co-precipitation reaction to obtain a lithium-rich manganese-based layered oxide material precursor. The flow rate ratio of solution 2 to the flow rate of the mixed salt solution is (0.5-2):

1. The bottom liquid is a transition metal salt solution obtained by dissolving nickel salt, cobalt salt and manganese salt in water. The total concentration of nickel, cobalt and manganese in the transition metal salt solution is 0.1-0.2 M, and the molar ratio of nickel, cobalt and manganese is the same as that of solution 1. The lithium-rich manganese-based morphological oxide material precursor was mixed with Li2CO3 and calcined to obtain the lithium-rich manganese-based morphological oxide material.

2. The method for preparing the lithium-rich manganese-based basal oxide material according to claim 1, characterized in that, In solution 1, the molar ratio of nickel, cobalt, and manganese is 1:1:(4-5); in solution 2, the molar ratio of nickel, cobalt, and manganese is 1:1:(1-2).

3. The method for preparing the lithium-rich manganese-based basal oxide material according to claim 1, characterized in that, The nickel, cobalt, and manganese salts are nickel sulfate, cobalt sulfate, and manganese sulfate, respectively.

4. The method for preparing the lithium-rich manganese-based basal oxide material according to claim 1, characterized in that, The reaction temperature for the coprecipitation reaction is 55-65 ℃, and the reaction time is 20-50 h.

5. The method for preparing the lithium-rich manganese-based basal oxide material according to claim 1, characterized in that, The stirring speed is 800-1200 rpm.

6. The method for preparing the lithium-rich manganese-based basal oxide material according to claim 1, characterized in that, The ratio of the number of moles of lithium in the Li2CO3 to the total number of moles of Ni, Mn and Co in the precursor is (1.25-1.35):

1.

7. The method for preparing the lithium-rich manganese-based basal oxide material according to claim 1, characterized in that, The calcination process is as follows: pre-calcination at 450-550 ℃ for 3-8 h in air atmosphere, followed by heating to 800-850 ℃ and holding for 10-16 h.

8. A lithium-rich manganese-based layered oxide material obtained by the preparation method according to any one of claims 1-7, characterized in that, The material has the morphology of spherical particles, and the proportion of manganese in the transition metal elements gradually decreases from the center of the spherical particles to the surface.

9. The lithium-rich manganese-based basal oxide material according to claim 8, characterized in that, The molar ratio of transition metals at the center of the spherical particles is Ni:Co:Mn=1:1:4, and the molar ratio of transition metals on the surface of the spherical particles is Ni:Co:Mn=1:1:

2.

10. A lithium-ion battery, characterized in that, It includes a positive electrode and a negative electrode, wherein the active component of the positive electrode is the lithium-rich manganese-based crystalline oxide material as described in claim 8.

Images