Lithium-rich manganese-based positive electrode material and preparation method thereof, electrode plate and lithium ion battery

Abstract

The invention provides a lithium-rich manganese-based positive electrode material and a preparation method thereof, an electrode plate and a lithium ion battery. According to the invention, Li / Mn in a transition metal layer is introduced into the bulk phase of the positive electrode material to disorderly induce MnO6 octahedron directional distortion, so that Mn 3d and O 2p orbital hybridization is enhanced, and bulk phase lattice oxygen is stabilized from the electronic structure level; and intercalation protons are introduced into a surface phase lithium layer of the material to change an oxygen coordination environment, so that a stable H-O bond is formed, and irreversible release of unsaturated oxygen on the surface is inhibited. By designing a Li / Mn disordered structure in a bulk phase transition metal layer and surface lithium layer intercalation proton modification coordinated regulation, the anion oxidation reduction reversibility of the positive electrode material is remarkably improved, irreversible release of oxygen in an electrochemical cycle process is inhibited, and the first coulombic efficiency is improved. The prepared layered lithium-rich manganese-based positive electrode is excellent in electrochemical performance, the preparation method does not need to introduce noble metal or complex coating materials, the process is simple, the cost is controllable, and the method is suitable for manufacturing a high-energy-density lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a lithium-rich manganese-based cathode material, its preparation method, electrode sheet, and lithium-ion battery. Background Technology

[0002] With the continuous increase in demand for high-energy-density lithium-ion batteries from fields such as electric vehicles and large-scale energy storage systems, traditional layered transition metal oxide cathode materials (such as LiCoO2, LiNi) are becoming increasingly important. x Co y Mn z O2's energy density is limited by the charge compensation mechanism of transition metal cation redox reactions, making it difficult to exceed 550 Wh / kg. -1 The current bottleneck can no longer meet the application requirements of next-generation energy storage technologies. Layered lithium-rich manganese-based cathode materials, such as xLi₂MnO₃•(1-x)LiMO₂ (0 < x < 1, where M is selected from a combination of transition metal elements composed of Ni, Co, and Mn), stand out as a highly promising high-energy-density cathode material due to their unique "cation redox + anion redox" dual-charge compensation mechanism. The structural feature of this material is that excess lithium partially occupies some sites in the transition metal layer, forming an ordered LiMn₆ six-membered ring structure within the layer. Simultaneously, it activates the redox reaction of lattice oxygen (O₂O₃•(1-x)LiMO₂). 2- O n- This allows the system to achieve a reversible specific capacity of 270-320 mAh g. -1 Its energy density is nearly double that of traditional material systems, providing a new path to solve the core needs of high-energy-density batteries.

[0003] However, lithium-rich manganese-based cathode materials face the key problem of poor lattice oxidation stability: bulk Mn 3d Electron orbit and O 2p The weak electron orbital hybridization and weak covalent bonding of Mn-O lead to easy dissociation of lattice oxygen during redox processes. Furthermore, the unsaturated coordination of surface-phase lattice oxygen at the interface results in low thermodynamic stability, further exacerbating irreversible oxygen release during cycling and causing problems such as low first-cycle coulombic efficiency, poor cycling stability, and severe voltage decay. Existing solutions, such as surface coating, can form a physical barrier at the interface, but suffer from drawbacks such as lattice incompatibility between the two phases, high interfacial stress, and slow kinetic transport. Single bulk or surface modification strategies cannot simultaneously address the stability issues of both bulk and surface oxygen, failing to achieve high reversibility of anionic redox reactions. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems of poor lattice oxygen stability and low anion redox reversibility in lithium-rich manganese-based cathode materials, which lead to low first-cycle coulombic efficiency, irreversible oxygen release, and electrochemical performance degradation. The invention provides a lithium-rich manganese-based cathode material with highly reversible anion redox behavior, its preparation method, electrode sheet, and lithium-ion battery.

[0005] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution.

[0006] The first aspect of this invention provides a lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction, the chemical formula of which is xLi₂MnO₃. (1-x)LiMO2; where 0 < x < 1, and M is selected from one or more of Ni, Co, and Mn; the bulk phase of the cathode material has a disordered Li / Mn structure in the transition metal layer, and the lithium layer on the surface phase has intercalated protons.

[0007] Preferably, in the disordered Li / Mn transition metal layer, the occupancy rate of Mn at Li sites is 15-35%; wherein the Li sites are... C2 / m Space group, site 2b.

[0008] Preferably, the amount of intercalated protons is 1-10% of the molar amount of Li in the cathode material.

[0009] Preferably, the positive electrode material has the chemical formula Li. 1.2 Ni 0.2 Mn 0.6 O2, with x=0.5, and LiMO2 is LiNi. 0.5 Mn 0.5 O2; the chemical formula of the cathode material can also be selected from LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 has a typical lithium-rich layered structure, which balances capacity and structural stability.

[0010] A second aspect of the present invention provides a method for preparing the above-mentioned lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction, comprising the following steps: (1) Ni precursor y Mn 1-y CO3 was dispersed in ammonia water and stirred, then separated, washed, and dried to obtain a modified precursor with partial Ni leaching; wherein 0.1≤y≤0.4; (2) The modified precursor was mixed with Li2CO3 and then calcined to obtain an intermediate material with a Li / Mn disordered structure in bulk phase; (3) The intermediate material is dispersed in an acid solution and stirred, then separated, washed and dried to obtain the final product.

[0011] Preferably, the stirring time in step (1) is 10-40 min; the drying temperature is 70-100℃; and the drying time is 10-24 h. This parameter range can precisely control the leaching amount of Ni and avoid excessive leaching that could lead to structural collapse.

[0012] Preferably, the calcination in step (2) is as follows: the temperature is increased to 450-550℃ at a heating rate of 2-4℃ / min and held for 4-6h; then the temperature is increased to 850-950℃ at a heating rate of 2-4℃ / min and held for 10-14h, and then naturally cooled to room temperature; the slow heating and segmented holding can ensure that the precursor and lithium source react fully to form a stable layered structure and a bulk Li / Mn disordered structure.

[0013] Preferably, the acid solution in step (3) is selected from an acetic acid solution; more preferably, the acid solution is selected from an acetic acid solution with a concentration of 0.05-0.2 mol / L; a mild acetic acid solution can achieve surface selective lithium layer proton insertion and avoid damage to the bulk structure.

[0014] Preferably, the stirring time in step (3) is 10-30 min, the drying temperature is 80-100℃, and the drying time is 10-14 h.

[0015] A third aspect of the present invention provides an electrode sheet comprising the above-described lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction and / or the lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction prepared according to the above-described preparation method.

[0016] Preferably, the electrode sheet is prepared by the following method: a lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction, conductive carbon black (Super-P) and polyvinylidene fluoride (PVDF) are mixed, N-methylpyrrolidone (NMP) is added for dispersion, coated on aluminum foil, dried at 80°C and cut to obtain the electrode sheet.

[0017] Preferably, the mass ratio of the lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction, conductive carbon black, and polyvinylidene fluoride is 8:1:1.

[0018] A fourth aspect of the present invention provides a lithium-ion battery comprising the electrode sheet described above.

[0019] Preferably, the lithium-ion battery is a button cell; more preferably, the lithium-ion battery is a CR2032 type button cell.

[0020] Preferably, the lithium-ion battery is prepared by the following method: using a lithium sheet as the negative electrode and a Celgard 2400 polypropylene membrane as the separator; dissolving 1 mol / L LiPF6 in a 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the electrolyte; the assembly sequence from top to bottom is: positive electrode shell, positive electrode sheet, separator, negative electrode, steel sheet, spring sheet, and negative electrode shell.

[0021] Compared with existing technologies, the present invention has the following advantages: Traditional modification techniques only target single-dimensional modifications of the bulk phase (e.g., doping) or surface (e.g., inorganic coating), failing to simultaneously address the dual problems of weak Mn-O covalent bonding in the bulk phase and unsaturated oxygen coordination on the surface, resulting in poor thermodynamic stability in lithium-rich manganese-based materials. To address this, this invention provides a lithium-rich manganese-based cathode material with high reversible anionic redox capability, its chemical formula being xLi₂MnO₃. (1-x)LiMO2; where 0 < x < 1, and M is selected from one or more of Ni, Co, and Mn; in specific embodiments, x corresponding to this chemical formula can be selected from 0.5, or can be replaced with 0.4 or 0.6, etc., and LiMO2 is LiNi. 0.5 Mn 0.5 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc. The bulk phase of the cathode material has a Li / Mn disordered structure within the transition metal layer, and intercalated protons in the surface lithium layer. The Li / Mn disordered structure within the bulk transition metal layer can induce octahedral distortion of MnO6, enhancing the Mn... 3d With O 2p Orbital hybridization enhances the covalent nature of Mn-O bonds, stabilizing bulk lattice oxygen at the electronic structure level, improving its stability, and suppressing oxygen framework distortion and lattice oxygen dissociation under high voltage. Protons intercalated in the surface lithium layer alter the coordination environment of the surface lattice oxygen, forming a stable HO coordination structure. By designing a synergistic regulation of the disordered Li / Mn structure within the bulk transition metal layer and the intercalated protons in the surface lithium layer, the anion redox reversibility of the cathode material is significantly improved, suppressing irreversible release of surface oxygen during electrochemical cycling and increasing the initial coulombic efficiency. Furthermore, the modification layer does not disrupt the main layered structure, ensuring the stability of the Li... + Transport kinetics. Through the above-mentioned regulation, the redox reversibility of the cathode material is significantly improved, effectively suppressing material structural failure. The prepared layered lithium-rich manganese-based cathode exhibits excellent electrochemical performance. The preparation method does not require the introduction of precious metals or complex coating materials, is simple in process, and has controllable cost, making it suitable for the manufacture of high-energy-density lithium-ion batteries. Attached Figure Description

[0022] Figure 1The image shows a scanning electron microscope (SEM) image of the secondary spherical particles of the lithium-rich manganese-based cathode material in Example 1. Figure 2 The image shows a scanning electron microscope (SEM) image of the secondary spherical particles of the lithium-rich manganese-based cathode material in Comparative Example 1. Figure 3 The images show the X-ray diffraction (XRD) patterns of the lithium-rich manganese-based cathode materials of Examples 1, 2, 3 and Comparative Example 1. Figure 4 The charge-discharge curves of the coin cells of Examples 1, 2, and 3, which use lithium-rich manganese-based cathode materials as cathode active materials, and the coin cell of Comparative Example 1, which uses lithium-rich manganese-based cathode materials as cathode active materials, are shown at a current density of 25 mA / g (test temperature is 25°C).

[0023] Figure 5 The graph shows a comparison of the cycling curves (at 25°C) of the coin cells using lithium-rich manganese-based cathode materials as the positive electrode active material in Examples 1, 2, and 3, and the coin cell using lithium-rich manganese-based cathode material as the positive electrode active material in Comparative Example 1, at a current density of 250 mA / g.

[0024] Figure 6 The voltage decay curve of the coin cell with lithium-rich manganese-based cathode material as the cathode active material in Comparative Example 1 is shown in the cycle discharge curve at a current density of 250 mA / g (temperature is 25℃).

[0025] Figure 7 The voltage decay curve of the coin cell using the lithium-rich manganese-based cathode material prepared in Example 1 as the cathode active material is shown at a current density of 250 mA / g (temperature 25°C).

[0026] Figure 8 The in-situ differential electrochemical mass spectrum of the coin cell with lithium-rich manganese-based cathode material as the cathode active material in Comparative Example 1 is shown at a current density of 25 mA / g (temperature 25 °C).

[0027] Figure 9 The in-situ differential electrochemical mass spectrum (temperature 25°C) of a coin cell using the lithium-rich manganese-based cathode material prepared in Example 1 as the cathode active material is shown. Detailed Implementation

[0028] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention are commercially available or can be prepared by existing methods. Similar elements in different embodiments are referred to by associated similar element designations. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the invention are not shown or described in the specification to avoid overwhelming the core of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0030] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0031] In this article, "room temperature" refers to 25±2℃.

[0032] Example 1 A lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction is prepared by the following steps: (1) Ni precursor 0.25 Mn 0.75 CO3 was dispersed in excess ammonia water, stirred for 20 min, washed with deionized water, and the supernatant was removed three times by centrifugation. After centrifugation, the washed sample was placed in a 90℃ forced-air oven and dried for 18 h to obtain a modified precursor with partial Ni leaching. This step utilizes the fact that the coordination ability of nickel-ammonia complex is stronger than that of manganese-ammonia complex to achieve selective leaching of Ni.

[0033] (2) The modified precursor and Li2CO3 were manually ground and mixed at a molar ratio of 3:4, and then placed in an alumina crucible. The temperature was raised to 500°C at a heating rate of 3°C / min and held for 5 hours. Then the temperature was raised to 900°C at a heating rate of 3°C / min and held for 12 hours. The mixture was then naturally cooled to room temperature to obtain an intermediate material with a disordered Li / Mn structure in the transition metal layer in the bulk phase. During the calcination process, the adjustment of the Ni content can induce the disordered distribution of Li and Mn in the transition metal layer to form a disordered Li / Mn structure in the bulk phase.

[0034] (3) Disperse the intermediate material in an excess acetic acid solution of 0.1 mol / L, stir for 20 min, wash with deionized water, and remove the upper filtrate three times with a centrifuge. After centrifugation, dry the washed sample in a 90℃ forced-air oven for 18 hours to obtain the final product. The proton intercalation in the surface lithium layer can be achieved through mild acid solution post-treatment without destroying the layered structure of the cathode material.

[0035] The chemical formula of the obtained lithium-rich manganese-based cathode material is Li 1.2 Ni 0.2 Mn 0.6 O2, the scanning electron microscope (SEM) image of the secondary spherical particles of this material is as follows Figure 1 As shown, the particle size is approximately 10 micrometers, with no obvious residual alkali particles. The XRD pattern of this material is as follows. Figure 3 As shown, comparison with the standard card reveals that its space group is C2 / m, with no impurity phase present. However, the characteristic peaks associated with the transition metal layer superstructure weaken and disappear, indicating that its bulk phase has a Li / Mn disordered structure within the transition metal layer, with Mn at the Li sites ( C2 / m The space group (2b site) occupancy rate is 24%; the lithium layer on the surface has intercalated protons, and the amount of proton substitution is 7% of the molar amount of Li in the cathode material. This material has a typical lithium-rich layered structure.

[0036] Example 2 A lithium-rich manganese-based cathode material with superior lattice oxygen redox reversibility is prepared by the following steps: (1) Ni precursor 0.25 Mn 0.75 CO3 was dispersed in excess ammonia water, stirred for 20 min, washed with deionized water, and the supernatant was removed three times by centrifugation. After centrifugation, the washed sample was placed in a 90℃ forced-air oven and dried for 18 h to obtain the modified precursor with partial Ni leaching.

[0037] (2) The modified precursor and Li2CO3 were manually ground and mixed at a molar ratio of 3:4, and then placed in an alumina crucible. The temperature was raised to 500°C at a heating rate of 3°C / min and held for 5 hours. Then the temperature was raised to 900°C at a heating rate of 3°C / min and held for 12 hours. The mixture was then naturally cooled to room temperature to obtain an intermediate material with a disordered Li / Mn structure in the transition metal layer in the bulk phase.

[0038] The chemical formula of the obtained lithium-rich manganese-based cathode material is Li 1.2 Ni 0.2 Mn 0.6 O2, the XRD pattern of this material is as follows Figure 3 As shown, comparison with the standard card reveals that its space group is C2 / m, with no impurity phase present. However, the characteristic peaks associated with the transition metal layer superstructure weaken and disappear, indicating that its bulk phase has a Li / Mn disordered structure within the transition metal layer, with Mn at the Li sites ( C2 / m The occupancy of the space group (2b site) is 24%, and the material has a typical lithium-rich layered structure.

[0039] Example 3 A lithium-rich manganese-based cathode material with high first-cycle coulombic efficiency is prepared by the following steps: (1) Ni precursor 0.25 Mn 0.75 CO3 and Li2CO3 were manually ground and mixed in a molar ratio of 3:4, and then placed in an alumina crucible. The temperature was increased to 500℃ at a heating rate of 3℃ / min and held for 5 hours. The temperature was then increased to 900℃ at a heating rate of 3℃ / min and held for 12 hours. The mixture was then allowed to cool naturally to room temperature to obtain a lithium-rich manganese-based intermediate material.

[0040] (3) Disperse the intermediate material in an excess acetic acid solution of 0.1 mol / L, stir for 20 min, wash with deionized water, and remove the supernatant filtrate three times by centrifugation. After centrifugation, dry the washed sample in a 90℃ forced-air oven for 18 hours to obtain the final product.

[0041] The chemical formula of the obtained lithium-rich manganese-based cathode material is Li 1.2 Ni 0.2 Mn 0.6 O2, the XRD pattern of this material is as follows Figure 3 As shown, by comparing with the standard card, its space group is C2 / m, there is no impurity phase, and its bulk phase has an ordered superstructure of LiMn6 six-membered rings; the lithium layer in the surface phase has intercalated protons, and the amount of proton substitution is 7% of the molar amount of Li in the cathode material. This material has a typical lithium-rich layered structure.

[0042] Comparative Example 1 A cathode material, the preparation method of which includes the following steps: Ni precursor 0.25 Mn 0.75 CO3 and Li2CO3 were manually ground and mixed in a molar ratio of 3:4, and then placed in an alumina crucible. The temperature was increased to 500℃ at a rate of 3℃ / min and held for 5 hours. Then the temperature was increased to 900℃ at a rate of 3℃ / min and held for 12 hours. The mixture was then allowed to cool naturally to room temperature to obtain the final product.

[0043] The chemical formula of the obtained cathode material is Li 1.2 Ni 0.2 Mn 0.6 O2, the scanning electron microscope (SEM) image of the secondary spherical particles of this material is as follows Figure 2 As shown, the particle size is approximately 10 micrometers, with no obvious residual alkali particles. The XRD pattern of this material is as follows. Figure 3 As shown, by comparing with the standard card, its space group is C2 / m, there is no impurity phase, its bulk phase has an ordered superstructure arrangement of LiMn6 six-membered rings, and the material has a typical lithium-rich layered structure.

[0044] Verification Example 1 Preparations before electrochemical performance testing 1. Preparation of positive electrode sheet The positive electrode materials, conductive carbon black (Super-P), and binder polyvinylidene fluoride (PVDF) prepared in Examples 1-3 and the comparative example were thoroughly mixed in a mortar at a mass ratio of 8:1:1, and then transferred to a beaker. An appropriate amount of N-methylpyrrolidone (NMP) was added for dispersion, with a PVDF to NMP mass ratio of 1:25. The beaker was placed on a magnetic stirrer and stirred thoroughly for 3 hours. The mixture was then evenly coated onto aluminum foil, which was then transferred to an 80°C forced-air oven for drying. After drying for two hours, the foil was cut into 10mm diameter discs. The cut electrode discs were then transferred to a 110°C vacuum oven for drying for 20 hours before use.

[0045] 2. Preparation of the battery negative electrode The negative electrode of the battery is a commercially available lithium sheet with a diameter of 14mm (AVIC Lithium).

[0046] 3. Button cell battery assembly CR2032 coin cells were assembled in an argon-filled glove box. A 1 mol / L LiPF6 solution was dissolved in a 1:1 volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the electrolyte, and a Celgard 2400 polypropylene membrane was used as the separator. The assembly sequence from top to bottom was: positive electrode shell, positive electrode plate, separator, negative electrode, steel plate, spring plate, and negative electrode shell. After assembly, the cells were allowed to stand for 6 hours before use.

[0047] 4. Battery performance test The electrochemical testing of the battery was conducted using the Xinwei electrochemical testing system. By placing the coin cell on the Xinwei electrochemical testing channel and adjusting the measured voltage range to 2.0V-4.8V, the cycle stability performance of the battery was compared and tested.

[0048] Test results are as follows Figure 4-9 As shown. Among them Figure 4 The results show the comparison of the first-cycle coulombic efficiency of Examples 1, 2, 3, and Comparative Example 1. From... Figure 4 The comparison shows that the coin cell with the cathode material of Comparative Example 1 as the cathode active material has a discharge capacity of 220 mAh / g and a coulombic efficiency of 73.88%. The lithium-rich manganese-based cathode material prepared in Example 2 shows a significant improvement in the first-cycle charge-discharge capacity, indicating that the enhanced Mn-O bond covalentity through the disordered bulk Li / Mn structure significantly improves the lattice oxygen redox activity. The improved first-cycle coulombic efficiency of the lithium-rich manganese-based cathode material prepared in Example 3 indicates that the irreversible release of surface lattice oxygen is suppressed through the coordination of surface-intercalated protons with lattice oxygen. The coin cell with the lithium-rich manganese-based cathode material prepared in Example 1 as the cathode active material exhibits the best electrochemical performance, with a discharge capacity of 281.3 mAh / g and a coulombic efficiency of 91.72%. Clearly, the cathode material provided by this invention shows significant improvements in both the first-cycle discharge capacity and the first-cycle coulombic efficiency.

[0049] Figure 5 This section presents a comparison of the capacity retention rates during long-term charge-discharge cycles for Examples 1, 2, and 3, and Comparative Example 1. From... Figure 5 As can be seen, the capacity retention of the cathode material in Comparative Example 1 decreased rapidly with increasing cycle count, dropping from 177.6 mAh / g at the start of the first cycle to 91.1 mAh / g at the 500th cycle, representing a capacity retention of 48.39%. The lithium-rich manganese-based material in Example 2 showed a relatively improved cycle capacity retention, indicating an increase in the reversibility of lattice oxygen redox caused by the disordered structure of the bulk Li / Mn. The lithium-rich manganese-based material in Example 3 exhibited relatively stable cycle capacity retention in the first 100 cycles, indicating the inhibitory effect of surface-phase intercalated protons on the irreversible release of surface-phase lattice oxygen; however, after long cycles, rapid capacity decay still occurred due to the unstable behavior of bulk-phase lattice oxygen. The lithium-rich manganese-based cathode material in Example 1 showed the least impact from increasing cycle count, dropping from 225.1 mAh / g at the start of the first cycle to 215.9 mAh / g at the 500th cycle, representing a capacity retention of 95.91%. The results show that lithium-rich manganese-based cathode materials with synergistic regulation of the lattice oxygen local environment can improve the electrochemical performance of the cathode material, especially significantly improving the capacity retention rate under long cycling cycles.

[0050] Figure 6-7 This is a comparison of the long-term cyclic discharge voltage decay results between Example 1 and Comparative Example 1. From... Figure 6 It can be seen that, during long-term cycling, the cathode material of Comparative Example 1 experiences irreversible structural degradation, resulting in a continuous decrease in the average discharge voltage, with a decay rate of 2.014 mV / cycle, leading to a continuous reduction in the material's energy density; from Figure 7 It can be seen that the lithium-rich manganese-based cathode material of Example 1 effectively suppressed the decay of the average discharge voltage during long-term cycling, with a decay rate of 0.935 mV / cycle. The results indicate that synergistic structural regulation suppressed the irreversible degradation of the material structure during cycling.

[0051] Figure 8-9 This is a comparison of oxygen release results between Example 1 and Comparative Example 1. (From Appendix...) Figure 8 As can be seen, the lithium-rich manganese-based cathode material in Comparative Example 1 produces a large amount of oxygen when charged to a high voltage state; from Figure 9 It can be seen that the oxygen production of the lithium-rich manganese-based cathode material in Example 1 is significantly reduced when charged to a high voltage state. The results show that the synergistic regulation of the lattice oxygen local environment enhances the covalent nature of Mn-O bonds and the thermodynamic stability of surface lattice oxygen, stabilizes the oxygen framework of the lithium-rich manganese-based cathode material, thereby inhibiting the continuous dissociation of lattice oxygen during cycling and preventing the release of irreversible oxygen.

[0052] The above detailed embodiments provide a specific description of the technical solutions involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction, characterized in that, Its chemical formula is xLi2MnO3 (1-x)LiMO2; where 0 < x < 1, and M is selected from one or more of Ni, Co, and Mn; the bulk phase of the cathode material has a disordered Li / Mn structure in the transition metal layer, and the lithium layer on the surface phase has intercalated protons.

2. The cathode material according to claim 1, characterized in that, In the disordered Li / Mn transition metal layer, the occupancy of Mn at Li sites is 15-35%; Where the Li site is C2 / m Space group, site 2b.

3. The cathode material according to claim 1, characterized in that, The amount of intercalated protons is 1-10% of the molar amount of Li in the cathode material.

4. The method for preparing lithium-rich manganese-based cathode material with highly reversible lattice oxygen oxidation-reduction as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Ni precursor x Mn 1-x CO3 was dispersed in ammonia water and stirred, then separated, washed, and dried to obtain a modified precursor with partially leached Ni; wherein 0.1≤x≤0.4; (2) The modified precursor was mixed with Li2CO3 and then calcined to obtain an intermediate material with a Li / Mn disordered structure in bulk phase; (3) The intermediate material is dispersed in an acid solution and stirred, then separated, washed and dried to obtain the final product.

5. The preparation method according to claim 4, characterized in that, The stirring time in step (1) is 10-40 min; the drying temperature is 70-100℃ and the drying time is 10-24 h.

6. The preparation method according to claim 4, characterized in that, In step (2), the calcination process is as follows: the temperature is increased to 450-550℃ at a heating rate of 2-4℃ / min, and held for 4-6 hours; then the temperature is increased to 850-950℃ at a heating rate of 2-4℃ / min, and held for 10-14 hours, and then naturally cooled to room temperature.

7. The preparation method according to claim 4, characterized in that, The acid solution mentioned in step (3) is selected from acetic acid solution.

8. The preparation method according to claim 4, characterized in that, The stirring time in step (3) is 10-30 min, the drying temperature is 80-100℃, and the drying time is 10-14 h.

9. An electrode sheet, characterized in that, This includes lithium-rich manganese-based cathode materials with highly reversible lattice oxygen oxidation-reduction as described in any one of claims 1-3 and / or lithium-rich manganese-based cathode materials with highly reversible lattice oxygen oxidation-reduction prepared by the preparation method described in any one of claims 4-8.

10. A lithium-ion battery, characterized in that, Includes the electrode sheet according to claim 9.

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