An interface-modified lithium manganate positive electrode material and a preparation method thereof

Abstract

This invention discloses an interface-modified lithium manganese oxide cathode material and its preparation method, belonging to the field of cathode material technology. The interface-modified lithium manganese oxide cathode material comprises: a LiMn₂O₄ core, a W and M-doped lithium manganese oxide first coating layer covering at least a portion of the core surface, and M₂WO₄ coating layer covering at least a portion of the first coating layer surface. 6‑z N z The second coating layer. The two coating layers of this invention form a significant synergistic effect: the S / Se doping in the second coating layer works in conjunction with the M and W doping in the first coating layer to enhance the overall structural stability of the coating layer, effectively suppressing cracking and shedding during long-term cycling, and ensuring long-term protection of the lithium manganese oxide matrix interface; at the same time, the lattice defects introduced by the S / Se doping complement the lattice matching advantages of the first coating layer, optimize the lithium-ion migration kinetics, and simultaneously improve the electronic conductivity and interface stability of the material.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, specifically relating to an interface-modified lithium manganese oxide cathode material and its preparation method. Background Technology

[0002] Lithium-ion batteries are widely used in various energy storage scenarios, and their performance largely depends on the cathode material. Spinel-type lithium manganese oxide (LiMn2O4) has become an important research direction for power battery cathode materials due to its abundant resources, low cost, environmental friendliness, excellent safety, and outstanding rate performance, and possesses good commercialization potential. Spinel-type LiMn2O4 has a three-dimensional tunnel structure, providing a convenient channel for reversible lithium-ion insertion and extraction, with a theoretical specific capacity of 148 mAh / g.

[0003] In practical applications, the electrochemical performance of LiMn2O4 is constrained by two major issues: First, frequent interfacial side reactions occur. During charging and discharging, the contact between the positive electrode and the electrolyte triggers reactions such as hydrofluoric acid generation, manganese dissolution, and abnormal CEI film growth, which damage the crystal structure, leading to battery capacity decay and deterioration in cycle performance. Second, poor conductivity results in low electronic conductivity and ion mobility, leading to high electron transport resistance, which affects battery rate performance and charge / discharge efficiency, failing to meet high-power requirements. Existing modification methods, such as surface coating, ion doping, and carbon-based composites, can only improve interfacial stability or conductivity individually, making it difficult to achieve synergistic improvement and fundamentally solve the performance bottleneck. Therefore, developing technical solutions that can simultaneously reduce interfacial side reactions and improve conductivity, achieving synergistic optimization of both, is of great significance for promoting the large-scale industrial application of LiMn2O4. Summary of the Invention

[0004] To address the above problems, the purpose of this invention is to provide an interface-modified lithium manganese oxide cathode material and its preparation method.

[0005] In a first aspect, the present invention provides an interface-modified lithium manganese oxide cathode material, comprising: a LiMn2O4 core, a W and M doped LiMn2O4 first coating layer covering at least a portion of the surface of the core, and M2WO3 coating layer covering at least a portion of the surface of the first coating layer. 6-z N z The second coating layer, wherein: M is selected from one or more of Sb, Bi, Cr and Fe, N is selected from one or two of S and Se, and 0.01% <z≤1%。

[0006] Preferably, N is selected from two of S and Se.

[0007] Secondly, the present invention provides an interface-modified lithium manganese oxide cathode material, comprising the following steps:

[0008] S1. After mixing the tungsten source and the M source, place them in a sintering furnace for the first stage of electric field sintering. After sintering, introduce the N source gas into the sintering furnace for the second stage of electric field sintering to obtain the coating material.

[0009] S2. After mixing the coating material with LiMn2O4, the mixture is sintered under an inert atmosphere to obtain an interface-modified lithium manganese oxide cathode material.

[0010] Preferably, in step S1, the tungsten source is one or more of tungsten trioxide, ammonium tungstate, and ammonium paratungstate.

[0011] Preferably, in step S1, the source of M is one or more of the oxides, acetates, and nitrates of M.

[0012] Preferably, in step S1, the ratio of the number of moles of W in the tungsten source to the number of moles of M in the M source is 1:(2~2.1).

[0013] Preferably, in step S1, the N source gas is one or both of H2S and H2Se; the ratio of the number of moles of N in the N source gas to the number of moles of W in the tungsten source is (0.01~2):100.

[0014] Preferably, in step S1, the electric field strength of the first electric field sintering or the second electric field sintering is independently 200~400V / cm.

[0015] Preferably, in step S1, the temperature of the first electric field sintering or the second electric field sintering is independently 600~900℃.

[0016] Preferably, in step S1, the sintering time of the first electric field is 1~8h; and the sintering time of the second electric field is 0.1~0.3h.

[0017] Preferably, in step S2, the mass of the coating material is 1 to 10% of the mass of LiMn2O4.

[0018] Preferably, in step S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere; the electric field strength of the electric field sintering is 200~300V / cm, the electric field sintering temperature is 450~550℃, and the electric field sintering time is 0.1~0.5h.

[0019] Preferably, in step S2, the method for preparing LiMn2O4 includes the following steps: after fully mixing manganese dioxide and lithium carbonate, pressure sintering is performed to obtain LiMn2O4.

[0020] More preferably, the molar ratio of manganese dioxide to lithium carbonate is 1:(0.25~0.253).

[0021] More preferably, the pressure of the pressure sintering is 0.01~0.1 MPa; the pressure sintering temperature is 700~850℃; and the pressure sintering time is 5~12h.

[0022] Thirdly, the present invention provides a battery comprising the aforementioned interface-modified lithium manganese oxide cathode material.

[0023] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects:

[0024] In this invention, the first coating layer, W-doped and M-doped lithium manganese oxide, share the same spinel structure as the LiMn2O4 core, exhibiting high lattice matching. This significantly reduces the resistance to lithium-ion migration across the interface, thereby improving rate performance. The high-valence W doping introduces trace electron-hole pairs, enhancing the material's electronic conductivity, while the M element (one or more of Sb, Bi, Cr, and Fe) precisely substitutes for Mn. 3+ / Mn 4+ The site effectively suppresses Jahn-Teller distortion, stabilizes the spinel framework, and reduces Mn ion dissolution, thereby improving cycle stability and high-temperature adaptability. The second coating layer M2WO in this invention... 6-z N z With a dense lattice structure, it effectively blocks the penetration of electrolyte and the diffusion of dissolved Mn ions into the electrolyte, avoiding the aggravation of polarization caused by their deposition on the negative electrode; N element (one or both of S and Se) has a similar atomic radius to O, which can stably replace lattice oxygen, thus optimizing the chemical stability of the coating layer and suppressing the growth of interfacial impedance. It also increases the active sites for lithium ion migration by forming lattice defects through S / Se doping, and works synergistically with W and M elements in the first coating layer to build an efficient electronic conduction network, achieving a dual improvement in interface protection and conductivity. Attached Figure Description

[0025] Figure 1 SEM image of the interface-modified lithium manganese oxide cathode material prepared in Example 1.

[0026] Figure 2 Fe2WO3, the coating material prepared in Example 4 5.995 S 0.0025 Se 0.0025 EDS plot.

[0027] Figure 3 The cycling performance diagrams are for batteries assembled with the cathode materials prepared in Examples 1-7 and Comparative Examples 1-3. Detailed Implementation

[0028] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0029] As previously stated, in a first aspect, the present invention provides an interface-modified lithium manganese oxide cathode material, comprising: a LiMn2O4 core, a W and M-doped LiMn2O4 first coating layer covering at least a portion of the surface of the core, and M2WO3 coating layer covering at least a portion of the surface of the first coating layer. 6-z N z The second coating layer, wherein: M is selected from one or more of Sb, Bi, Cr and Fe, N is selected from one or two of S and Se, and 0.01% <z≤1%。

[0030] In the W and M-doped lithium manganese oxide first coating layer of this invention, W is a high-valence metal element that forms a small number of electron holes in the crystal lattice, which can reduce the electron transition energy barrier and enhance the electronic conductivity of the material; M (one or more of Sb, Bi, Cr, and Fe) precisely substitutes for Mn. 3+ / Mn 4+ The site effectively suppresses Jahn-Teller distortion, stabilizes the spinel framework, and reduces Mn ion dissolution, thereby improving cycle stability and high-temperature adaptability. Furthermore, the W and M-doped lithium manganese oxide in the first coating layer has a similar spinel crystal structure to the LiMn2O4 core, with high lattice matching, which effectively reduces the migration resistance of lithium ions at the core-shell interface, enabling rapid cross-interface transport of lithium ions.

[0031] In this invention, M2WO 6-z N z The second coating layer has a dense structure that can block electrolyte penetration and prevent dissolved manganese ions from diffusing into the electrolyte, thus avoiding increased negative electrode polarization caused by manganese ion deposition on the negative electrode surface and reducing battery capacity decay. By doping with nitrogen (S and / or Se), some oxygen atoms in the second coating layer lattice can be stably replaced. This optimizes the chemical stability of the coating layer, enhances its compatibility with the electrolyte, and reduces the increase in interfacial impedance. Furthermore, the introduction of S / Se further improves the electronic conductivity of the second coating layer, synergistically constructing more efficient electronic conduction channels with W and M doping, thus balancing interface protection and conductivity enhancement.

[0032] In this invention, a significant synergistic effect is formed between the two coating layers. Specifically, the doping effect of S / Se elements in the second coating layer, together with the doping effect of M and W elements in the first coating layer, complements and reinforces each other, effectively improving the overall structural stability of the coating layer. This significantly suppresses the cracking and peeling of the coating layer during long-term cycling, ensuring long-term protection of the lithium manganese oxide matrix interface. At the same time, the lattice defects introduced by S / Se element doping precisely echo and complement the lattice matching advantages of the first coating layer itself, further optimizing the lithium ion migration kinetics rate. This achieves a simultaneous improvement in the material's electronic conductivity and interface stability, successfully breaking through the performance bottlenecks of traditional lithium manganese oxide materials in terms of cycle stability and ion transport efficiency, and significantly improving the comprehensive electrochemical performance of lithium manganese oxide materials.

[0033] In some embodiments, N is selected from two of S and Se.

[0034] In some embodiments, 0.2% <z≤0.8%。

[0035] Secondly, the present invention provides an interface-modified lithium manganese oxide cathode material, comprising the following steps:

[0036] S1. After mixing the tungsten source and the M source, place them in a sintering furnace for the first stage of electric field sintering. After sintering, introduce the N source gas into the sintering furnace for the second stage of electric field sintering to obtain the coating material.

[0037] S2. After mixing the coating material with LiMn2O4, the mixture is sintered under an inert atmosphere to obtain an interface-modified lithium manganese oxide cathode material.

[0038] In the method of this invention, dense M2WO6 is prepared by electric field sintering, and then doped with a gas containing an N source under the action of an electric field to obtain the coating material M2WO6. 6-z N z Its preparation method is simple, and the prepared coating material has both a dense structure and high conductivity.

[0039] In the method of the present invention, after the coating material is mixed with lithium manganese oxide, it is sintered under an inert atmosphere and an electric field. This allows for the doping of W and M elements into the surface lithium manganese oxide, thereby forming an intermediate layer of W and M-doped lithium manganese oxide. This not only improves the electrochemical performance of lithium manganese oxide, but also helps to reduce the interfacial resistance between the coating material and lithium manganese oxide.

[0040] In some embodiments, in step S1, the tungsten source is one or more of tungsten trioxide, ammonium tungstate, and ammonium paratungstate.

[0041] In some embodiments, in step S1, the source of M is one or more of the oxides, acetates, and nitrates of M.

[0042] In some embodiments, in step S1, the ratio of the number of moles of W in the tungsten source to the number of moles of M in the M source is 1:(2~2.1).

[0043] In some embodiments, in step S1, the N source gas is one or both of H2S and H2Se; the ratio of the number of moles of N in the N source gas to the number of moles of W in the tungsten source is (0.01~2):100, including but not limited to: 0.01:100, 0.05:100, 0.1:100, 0.2:100, 0.5:100, 0.8:100, 1:100, 1.2:100, 1.5:100, 1.8:100, 2:100, etc., preferably (0.4~1.4):100.

[0044] In some embodiments, in step S1, the electric field strength of the first electric field sintering or the first electric field sintering is independently 200~400V / cm, including but not limited to: 200V / cm, 250V / cm, 300V / cm, 350V / cm, 400V / cm, etc.

[0045] In some embodiments, in step S1, the temperature of the first electric field sintering or the second electric field sintering is independently 600~900℃, including but not limited to: 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, etc.; in some embodiments, in step S1, the time of the first electric field sintering is 1~8h, including but not limited to: 1h, 2h, 3h, 3h, 4h, 5h, 6h, 7h, 8h, etc.; the time of the second electric field sintering is 0.1~0.3h, including but not limited to: 0.1h, 0.2h, 0.3h, etc.

[0046] In some embodiments, in step S2, the mass of the coating material is 1 to 10% of the mass of LiMn2O4, including but not limited to: 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., preferably 2 to 5%.

[0047] In some embodiments, in step S2, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere; the electric field strength of the electric field sintering is 200~300V / cm, including but not limited to: 200V / cm, 220V / cm, 250V / cm, 280V / cm, 300V / cm, etc.; the electric field sintering temperature is 450~550℃, including but not limited to: 450℃, 480℃, 500℃, 520℃, 550℃, etc.; the electric field sintering time is 0.1~0.5h, including but not limited to: 0.1h, 0.2h, 0.3h, 0.4h, 0.5h.

[0048] Preferably, in step S2, the method for preparing lithium manganese oxide includes the following steps: after fully mixing manganese dioxide and lithium carbonate, pressure sintering is performed to obtain LiMn2O4.

[0049] More preferably, the molar ratio of manganese dioxide to lithium carbonate is 1:(0.25~0.253).

[0050] More preferably, the pressure of the pressure sintering is 0.01~0.1MPa; the pressure sintering temperature is 700~850℃, including but not limited to: 700℃, 720℃, 750℃, 780℃, 800℃, 820℃, 850℃, etc.; and the pressure sintering time is 5~12h, including but not limited to: 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc.

[0051] Thirdly, the present invention provides a battery comprising the aforementioned interface-modified lithium manganese oxide cathode material.

[0052] Preparation Example 1: Preparation of Lithium Manganese Oxide

[0053] Manganese dioxide and lithium carbonate were thoroughly mixed at a molar ratio of 1:0.252 and then placed in a sintering furnace for pressure sintering. The pressure sintering pressure was 0.05 MPa, the pressure sintering temperature was 780 °C, and the sintering time was 10 h to obtain lithium manganate LiMn2O4.

[0054] Example 1

[0055] In this embodiment, the interface-modified lithium manganese oxide cathode material includes: a LiMn2O4 core, a W and Fe-doped LiMn2O4 first coating layer covering at least a portion of the core surface, and Fe2WO3 coating layer covering at least a portion of the first coating layer surface. 5.995 S 0.005 The second coating layer is prepared using the following method:

[0056] S1. WO3 and Fe2O3 were mixed uniformly at a molar ratio of 1:1 and then placed in a sintering furnace for electric field sintering for 4 hours. The process parameters for electric field sintering were: electric field strength of 300 V / cm and sintering temperature of 750℃. Then, under the condition that the electric field sintering process remained unchanged, H2S gas was introduced and electric field sintering was continued for 12 minutes. The molar ratio of S to WO3 in the introduced H2S gas was 0.008:1. The resulting coating material was subjected to ICP testing, and the ratio of S to W in the coating material was found to be approximately 0.005:1. The chemical formula of the coating material was Fe2WO3. 5.995 S 0.005 .

[0057] S2: Coating material Fe2WO 5.995 S 0.005 The lithium manganese oxide (LiMn2O4) prepared in Preparation Example 1 was mixed with the lithium manganese oxide (LiMn2O4) at a mass ratio of 2:100. After being mixed evenly, the mixture was placed in a sintering furnace and subjected to electric field sintering for 18 min under a nitrogen atmosphere. The process parameters for electric field sintering were: electric field strength of 250 V / cm and sintering temperature of 500 °C. The interface-modified lithium manganese oxide cathode material was obtained.

[0058] The TEM image of the cross-section of the interface-modified lithium manganese oxide cathode material prepared in this embodiment is shown below. Figure 1 As shown, it can be seen that it consists of three distinct layers, including a LiMn2O4 core, a W and Fe-doped lithium manganese oxide first coating layer, and a Fe2WO3 layer. 5.995 S 0.005 Second coating layer.

[0059] Comparative Example 1

[0060] The lithium manganese oxide prepared in Example 1 was used as the positive electrode material.

[0061] Comparative Example 2

[0062] The interface-modified lithium manganese oxide cathode material in this comparative example includes: a LiMn2O4 core, a W and Fe-doped LiMn2O4 first coating layer covering at least a portion of the core surface, and a Fe2WO6 second coating layer covering at least a portion of the first coating layer surface; the specific preparation method is as follows:

[0063] S1. After mixing WO3 and Fe2O3 evenly at a molar ratio of 1:1, the mixture is placed in a sintering furnace and sintered in an electric field under a nitrogen atmosphere for 4 hours. The process parameters for electric field sintering are: electric field strength of 300V / cm and sintering temperature of 600℃; the coating material Fe2WO6 is obtained.

[0064] S2. Except for the coating material Fe2WO6, the rest is the same as step S2 in Example 1.

[0065] Comparative Example 3

[0066] The interface-modified lithium manganese oxide cathode material in this comparative example includes: a LiMn2O4 core, with Fe2WO3 coating at least a portion of the surface of the core. 5.995 S 0.005 The second coating layer is prepared using the following method:

[0067] S1, the same as step S1 in Example 1.

[0068] S2, Apply Fe2WO3 coating material 5.995 S 0.005 After being mixed evenly with the lithium manganese oxide prepared in Preparation Example 1 at a mass ratio of 2:100, the mixture was placed in a sintering furnace and sintered at 500°C for 18 minutes under a nitrogen atmosphere to obtain an interface-modified lithium manganese oxide cathode material.

[0069] Example 2

[0070] In this embodiment, the interface-modified lithium manganese oxide cathode material includes: a LiMn2O4 core, a W and Fe-doped LiMn2O4 first coating layer covering at least a portion of the core surface, and Fe2WO3 coating layer covering at least a portion of the first coating layer surface. 5.995 S 0.005 The second coating layer is prepared using the following method:

[0071] S1. WO3 and Fe2O3 are mixed evenly at a molar ratio of 1:1 and placed in a sintering furnace for 4 hours at 750℃. Then, under unchanged sintering conditions, H2S gas is introduced and sintering continues for 12 minutes. The molar ratio of S to WO3 in the introduced H2S gas is 0.008:1. The resulting coating material is subjected to ICP testing, and the ratio of S to W in the coating material is approximately 0.005:1. The chemical formula of the coating material is Fe2WO3. 5.995 S 0.005 .

[0072] S2, the same as step S2 in Example 1.

[0073] Example 3

[0074] In this embodiment, the interface-modified lithium manganese oxide cathode material includes: a LiMn2O4 core, a W and Fe-doped LiMn2O4 first coating layer covering at least a portion of the core surface, and Fe2WO3 coating layer covering at least a portion of the first coating layer surface. 5.995 Se 0.005 The second coating layer is prepared using the following method:

[0075] S1. WO3 and Fe2O3 were mixed uniformly at a molar ratio of 1:1 and then subjected to electric field sintering in a sintering furnace for 4 hours. The process parameters for electric field sintering were: electric field strength of 300 V / cm and sintering temperature of 750℃. Then, under the condition that the electric field sintering process parameters remained unchanged, H2Se gas was introduced and electric field sintering was continued for 12 minutes. The molar ratio of Se to WO3 in the introduced H2Se gas was 0.008:1. The resulting coating material was subjected to ICP testing, and the ratio of the molar ratio of Se to W in the coating material was found to be approximately 0.005:1. The chemical formula of the coating material was Fe2WO3. 5.995 Se 0.005 .

[0076] S2: Coating material Fe2WO 5.995 Se 0.005 After being mixed evenly with the lithium manganese oxide (LiMn2O4) prepared in Preparation Example 1 at a mass ratio of 2:100, the mixture was placed in a sintering furnace and subjected to electric field sintering for 18 min under a nitrogen atmosphere. The process parameters for electric field sintering were: electric field strength of 250 V / cm and sintering temperature of 500 °C, thus obtaining an interface-modified lithium manganese oxide cathode material.

[0077] Example 4

[0078] In this embodiment, the interface-modified lithium manganese oxide cathode material includes: a LiMn2O4 core, a W and Fe-doped LiMn2O4 first coating layer covering at least a portion of the core surface, and Fe2WO3 coating layer covering at least a portion of the first coating layer surface. 5.995 S 0.0025 Se 0.0025 The second coating layer is prepared using the following method:

[0079] S1. WO3 and Fe2O3 were mixed uniformly at a molar ratio of 1:1 and then sintered in a sintering furnace under an electric field for 4 hours. The electric field sintering parameters were: electric field strength of 300 V / cm and sintering temperature of 750℃. Then, with the electric field sintering parameters unchanged, a mixed gas of H2S and H2Se with a volume ratio of 1:1 was introduced, and electric field sintering continued for 12 minutes. The ratio of the total moles of S and Se in the introduced mixed gas to the moles of WO3 was 0.008:1. The resulting coating material was subjected to ICP testing, and the ratio of the moles of S and Se to the moles of W in the coating material was approximately 0.0025:0.0025:1. The chemical formula of the coating material was Fe2WO3. 5.995 S 0.0025 Se 0.0025 .

[0080] S2: Coating material Fe2WO 5.995 S 0.0025 Se0.0025 After being mixed evenly with the lithium manganese oxide (LiMn2O4) prepared in Preparation Example 1 at a mass ratio of 2:100, the mixture was placed in a sintering furnace and subjected to electric field sintering for 18 min under a nitrogen atmosphere. The process parameters for electric field sintering were: electric field strength of 250 V / cm and sintering temperature of 500 °C, thus obtaining an interface-modified lithium manganese oxide cathode material.

[0081] The coating material Fe2WO prepared in this embodiment 5.995 S 0.0025 Se 0.0025 The EDS characterization diagram is visible Figure 2 As can be seen from the figure, Fe2WO 5.995 S 0.0025 Se 0.0025 The presence of S and Se elements on the surface indicates that S and Se are simultaneously doped in the second coating layer.

[0082] Example 5

[0083] In this embodiment, the interface-modified lithium manganese oxide cathode material includes: a LiMn2O4 core, a W and Cr-doped LiMn2O4 first coating layer covering at least a portion of the surface of the core, and a Cr2WO3 coating layer covering at least a portion of the surface of the first coating layer. 5.998 S 0.001 Se 0.001 The second coating layer is prepared using the following method:

[0084] S1. WO3 and chromium acetate were mixed uniformly at a molar ratio of 1:2 and then sintered in a sintering furnace under an electric field for 1 hour. The process parameters for electric field sintering were: electric field strength of 400 V / cm and sintering temperature of 900℃. Then, with the electric field sintering process parameters unchanged, a mixed gas consisting of H2S and H2Se in a volume ratio of 1:1 was introduced and electric field sintering continued for 8 minutes. The molar ratio of the total amount of S and Se in the mixed gas to WO3 was 0.003:1. The resulting coating material was subjected to ICP testing, and the ratio of the molar number of S, the molar number of Se to the molar number of W in the coating material was approximately 0.001:0.001:1. The chemical formula of the coating material was Cr2WO3. 5.998 S 0.001 Se 0.001 .

[0085] S2: Apply Cr2WO3 coating material 5.998 S 0.001 Se 0.001After being mixed evenly with the lithium manganese oxide (LiMn2O4) prepared in Preparation Example 1 at a mass ratio of 4:100, the mixture was placed in a sintering furnace and subjected to electric field sintering for 8 minutes under a nitrogen atmosphere. The process parameters for electric field sintering were: electric field strength of 300 V / cm and sintering temperature of 550 °C, thus obtaining an interface-modified lithium manganese oxide cathode material.

[0086] Example 6

[0087] In this embodiment, the interface-modified lithium manganese oxide cathode material includes: a LiMn2O4 core, a W and Sb-doped LiMn2O4 first coating layer covering at least a portion of the surface of the core, and an Sb2WO3 coating layer covering at least a portion of the surface of the first coating layer. 5.992 S 0.004 Se 0.004 The second coating layer is prepared using the following method:

[0088] S1, ammonium tungstate (W) 12 O 40 N6H 26 After being thoroughly mixed with Sb₂O₃ at a molar ratio of 1:24, the mixture was placed in a sintering furnace for electric field sintering for 8 hours. The process parameters for electric field sintering were: electric field strength of 200 V / cm and sintering temperature of 600℃. Then, with the electric field sintering process parameters unchanged, a mixed gas consisting of H₂S and H₂Se in a volume ratio of 1:1 was introduced and electric field sintering was continued for 18 minutes. The ratio of the total moles of S and Se in the mixed gas to the moles of W in ammonium tungstate was 0.015:1. The resulting coating material was subjected to ICP testing, and the ratio of the moles of S and Se to the moles of W in the coating material was found to be approximately 0.004:0.004:1. The chemical formula of the coating material is Sb₂WO₃. 5.992 S 0.004 Se 0.004 .

[0089] S2: Apply the coating material Sb2WO 5.992 S 0.004 Se 0.004 After being mixed evenly with the lithium manganese oxide (LiMn2O4) prepared in Preparation Example 1 at a mass ratio of 3:100, the mixture was placed in a sintering furnace and subjected to electric field sintering for 30 min under a nitrogen atmosphere. The process parameters for electric field sintering were: electric field strength of 200 V / cm and sintering temperature of 450 °C, resulting in an interface-modified lithium manganese oxide cathode material.

[0090] Example 7

[0091] In this embodiment, the interface-modified lithium manganese oxide cathode material includes: a LiMn2O4 core, a W and Bi-doped lithium manganese oxide first coating layer covering at least a portion of the core surface, and a Bi2WO3 coating layer covering at least a portion of the first coating layer surface.5.994 S 0.003 Se 0.003 The second coating layer is prepared using the following method:

[0092] S1, ammonium tungstate (W) 12 O 40 N6H 26 After being uniformly mixed with Bi₂O₃ at a molar ratio of 1:24, the mixture was placed in a sintering furnace for electric field sintering for 6 hours. The process parameters for electric field sintering were: electric field strength of 280 V / cm and sintering temperature of 800℃. Then, with the electric field sintering process parameters unchanged, a mixed gas consisting of H₂S and H₂Se in a volume ratio of 1:1 was introduced and electric field sintering was continued for 10 minutes. The ratio of the total moles of S and Se in the mixed gas to the moles of W in ammonium tungstate was 0.009:1. The resulting coating material was subjected to ICP testing, and the ratio of the moles of S and Se to the moles of W in the coating material was found to be approximately 0.003:0.003:1. The chemical formula of the coating material is Bi₂WO₃. 5.994 S 0.003 Se 0.003 .

[0093] S2: Apply Bi2WO coating material 5.994 S 0.003 Se 0.003 After being mixed evenly with the lithium manganese oxide (LiMn2O4) prepared in Preparation Example 1 at a mass ratio of 5:100, the mixture was placed in a sintering furnace and subjected to electric field sintering for 15 min under a nitrogen atmosphere. The process parameters for electric field sintering were: electric field strength of 240 V / cm and sintering temperature of 510 °C, thus obtaining an interface-modified lithium manganese oxide cathode material.

[0094] The lithium manganese oxide cathode materials prepared in Examples 1-7 and Comparative Examples 1-3 were assembled into batteries. The cathode material, conductive graphite, and PVDF were weighed and ground in a mass ratio of 8:1:1. Then, an appropriate amount of N-methylpyrrolidone (NMP) was added, and grinding and stirring continued to form a uniform slurry. The slurry was then uniformly coated onto aluminum foil using a mold to a thickness of 200 μm, and placed in a drying oven at 90°C for 10 hours. The coated foil was then cut into 12 mm diameter discs. The discs were used as the cathode, and lithium foil as the anode. The electrolyte consisted of a solvent and LiPF6, with a LiPF6 concentration of 1 mol / L. The electrolyte solvent was a mixture of EC, DEC, and DMC in a volume ratio of 1:1:1. The batteries were assembled in a glove box according to the coin cell assembly sequence. The assembled batteries were subjected to performance testing. The assembled batteries, which had been left to stand overnight, were placed in a LAND2001CT battery test chamber for charge-discharge testing. The tests were conducted at 45°C, 1C rate, and a cycle voltage of 2-4V, with 100 cycles. The test results are shown below. Figure 3 See Table 1.

[0095] Table 1

[0096]

[0097] From Table 1 and Figure 3 The data shows that in Comparative Example 1, the lithium manganese oxide was not coated, resulting in poor initial specific capacity and cycle stability of the battery assembled from the corresponding cathode material. In Example 1, the interface-modified cathode material showed a significant improvement in both initial specific capacity and cycle stability compared to Comparative Example 1. In Comparative Example 2, the second coating layer was not doped with S, resulting in some improvement in initial specific capacity and cycle stability compared to Comparative Example 1, but significantly lower than Example 1. In Comparative Example 3, no intermediate coating layer was formed, resulting in some improvement in initial specific capacity and cycle stability compared to Comparative Example 1, but significantly lower than Example 1. In Example 2, the coating material was not sintered using an electric field, leading to a decrease in initial specific capacity and cycle stability compared to Example 1, possibly due to insufficient structural stability of the coating material without electric field sintering. In Example 3, Se was used to dope the coating material, resulting in some fluctuation in initial specific capacity and cycle stability compared to Example 1. In Example 4, S and Se were used to co-dop the coating material. The initial specific capacity and cycle stability of the battery assembled with the corresponding cathode material were further improved compared with Examples 1 and 3, possibly due to the synergistic effect between S and Se. In Examples 5-7, the process parameters were adjusted, and the initial specific capacity and cycle stability of the battery assembled with the corresponding cathode material fluctuated to some extent, but overall, they all exhibited excellent electrochemical performance.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an interfacially modified lithium manganate cathode material, characterized in that, Includes the following steps: S1. After mixing the tungsten source and the M source, place them in a sintering furnace for the first stage of electric field sintering. After sintering, introduce the N source gas into the sintering furnace for the second stage of electric field sintering to obtain the coating material. S2. After mixing the coating material with LiMn2O4, the mixture is sintered under an inert atmosphere to obtain an interface-modified lithium manganese oxide cathode material. The interface-modified lithium manganese oxide cathode material comprises: a LiMn2O4 core, a W and M-doped LiMn2O4 first coating layer covering at least a portion of the surface of the core, and M2WO3 coating layer covering at least a portion of the surface of the first coating layer. 6-z N z The second coating layer, wherein: M is selected from one or more of Sb, Bi, Cr and Fe, N is selected from one or two of S and Se, and 0.01% <z≤1%; In step S1, the electric field strength of the first electric field sintering or the second electric field sintering is independently 200~400V / cm; the temperature of the first electric field sintering or the second electric field sintering is independently 600~900℃; the sintering time of the first electric field is 1~8h; and the sintering time of the second electric field is 0.1~0.3h. In step S2, the electric field strength of the electric field sintering is 200~300V / cm, the electric field sintering temperature is 450~550℃, and the electric field sintering time is 0.1~0.5h.

2. The method for preparing the interface-modified lithium manganese oxide cathode material according to claim 1, characterized in that, The N is selected from two of S and Se.

3. The method for preparing the interface-modified lithium manganese oxide cathode material according to claim 1, characterized in that, In step S1, the tungsten source is one or more of tungsten trioxide, ammonium tungstate, and ammonium paratungstate; And / or: M source is one or more of the oxides, acetates, and nitrates of M; And / or: The ratio of the number of moles of W in the tungsten source to the number of moles of M in the M source is 1:(2~2.1); And / or: The N source gas is one or both of H2S and H2Se; And / or: the ratio of the number of moles of N in the N source gas to the number of moles of W in the tungsten source (0.01~2):

100.

4. The method for preparing the interface-modified lithium manganese oxide cathode material according to claim 1, characterized in that, In step S2, the mass of the coating material is 1 to 10% of the mass of LiMn2O4.

5. The method for preparing the interface-modified lithium manganese oxide cathode material according to claim 1, characterized in that, In step S2, the inert atmosphere is either nitrogen or argon.

6. The method for preparing the interface-modified lithium manganese oxide cathode material according to claim 1, characterized in that, In step S2, the preparation method of LiMn2O4 includes the following steps: manganese dioxide and lithium carbonate are thoroughly mixed and then pressure sintered to obtain LiMn2O4.

7. The method for preparing the interface-modified lithium manganese oxide cathode material according to claim 6, characterized in that, The molar ratio of manganese dioxide to lithium carbonate is 1:(0.25~0.253); the pressure of the pressure sintering is 0.01~0.1 MPa; the pressure sintering temperature is 700~850℃; and the pressure sintering time is 5~12h.

8. A battery, characterized by The interface-modified lithium manganese oxide cathode material prepared by any of the preparation methods described in claims 1 to 7.

Images