A composite modified lithium-rich manganese-based positive electrode material, a preparation method thereof and a battery

Abstract

The application belongs to the field of lithium ion battery related materials, and discloses a composite modified lithium-rich manganese-based positive electrode material, a preparation method thereof and a battery. 1‑ x Fe x Cl4 and Li 1+m Mn 1‑m‑n N n O2, sintering under a protective atmosphere, and the like are obtained; wherein N is one or two of Fe, Co and Zn, 0.1<=x<=0.9; 0.1<=m<=0.3, 0<=n<=0.3. Li2Mn 1‑ x Fe x Cl4 material and the lithium-rich manganese-based positive electrode material are mechanically mixed, and then subjected to sintering composite treatment, so that the chlorine element in the coating layer enters the core material, chlorine defects appear in the coating layer, and the combination of the two can effectively improve the conductivity and ion transmission performance of the positive electrode material and improve the electrochemical rate performance of the positive electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of lithium ion battery related materials, and relates to a positive electrode material, in particular to a composite modified lithium-rich manganese-based positive electrode material and a preparation method and a battery thereof. BACKGROUND

[0002] At present, the lithium-rich manganese-based positive electrode material is widely concerned due to its high specific capacity (> 250 mAh / g), high working voltage, low cost, environmental friendliness and the like. The lithium-rich manganese-based positive electrode material has poor conductivity, which is easy to cause polarization of the battery.

[0003] In the prior art, the lithium-rich manganese-based material is usually modified by doping or coating. The doping generally introduces Mg 2+ , Al 3+ and the like into the lithium-rich manganese-based positive electrode material to improve the conductivity by changing the lattice structure or generating oxygen vacancies, but the solubility of the doped ions exists, and excessive doping ions will cause lattice distortion or even form a second phase, thereby hindering the electron transmission. In addition, the doped ions are unevenly distributed in the lattice, and only the local area can be improved in conductivity, and the overall electron path cannot be connected. The coating generally coats a carbon layer or a metal oxide layer on the surface of the lithium-rich manganese-based material to build a conductive path or a protective barrier on the surface of the positive electrode material, but a crystal boundary barrier is easily formed between the coating layer and the substrate. Although the carbon coating can improve the electronic conductivity, the amorphous carbon has low lattice matching degree with the lithium-rich manganese-based material, and charge accumulation is generated at the interface, thereby increasing the ion transmission resistance; and although the metal oxide coating can stabilize the structure, the metal oxide itself has poor conductivity, and excessive coating will cause the overall resistance to rise.

[0004] The coating and doping processes have their own limitations, and the improvement effect on the conductivity of the lithium-rich manganese-based material is limited. SUMMARY

[0005] In view of the defects and deficiencies in the prior art, in a first aspect, the application provides a preparation method of a composite modified lithium-rich manganese-based positive electrode material; in a second aspect, the application provides a composite modified lithium-rich manganese-based positive electrode material; and in a third aspect, the application provides a battery.

[0006] In a first aspect, the application provides a preparation method of a composite modified lithium-rich manganese-based positive electrode material, which comprises ball-milling Li2Mn 1-x Fe x Cl4 and Li 1+m Mn 1-m-n N n O2, sintering under a protective atmosphere, and obtaining the same; wherein N is one or two of Fe, Co and Zn, 0.1≤x≤0.9, 0.1≤m≤0.3, and 0≤n≤0.3.

[0007] Preferably, Li2Mn1-x Fe x Cl4 and Li 1+m Mn 1-m-n N n The mass ratio of O2 is 0.01~0.06∶1.

[0008] Preferably, the sintering temperature is 800~900℃ and the sintering time is 0.5~2h.

[0009] Preferably, the ball milling speed is 300~500 rpm and the ball milling time is 2~6 hours.

[0010] Preferably, Li2Mn 1-x Fe x The preparation process of Cl4 includes: ball milling to mix lithium chloride, manganese chloride, and ferrous chloride, followed by sintering under a protective atmosphere.

[0011] Preferably, the molar ratio of lithium chloride, manganese chloride, and ferrous chloride is 2:0.1~0.9:0.1~0.9.

[0012] Preferably, the sintering temperature is 500~700℃ and the sintering time is 3~6h.

[0013] Preferably, the ball milling speed is 300~500 rpm and the ball milling time is 2~6 hours.

[0014] Preferably, the gas providing the protective atmosphere is nitrogen or argon.

[0015] Secondly, the present invention provides a composite modified lithium-rich manganese-based cathode material, which is prepared by the above-described preparation method.

[0016] Thirdly, the present invention provides a battery comprising a composite modified lithium-rich manganese-based cathode material prepared by the above-described preparation method.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] Li2Mn 1-x Fe x After mechanically mixing Cl4 material with lithium-rich manganese-based cathode material and then sintering composite treatment, chlorine elements in the coating layer enter the core material, and chlorine defects appear in the coating layer. The combination of the two can effectively improve the conductivity and ion transport performance of the cathode material, and improve the electrochemical rate performance of the cathode material.

[0019] The preparation process provided by this invention is simple and easy to operate, which is conducive to industrialization and large-scale production. Attached Figure Description

[0020] Figure 1 This is a cross-sectional mapping diagram of the composite modified lithium-rich manganese-based cathode material prepared in Example 1;

[0021] Figure 2 Examples 1-3, Comparative Example 1, and untreated Li 1.2 Mn 0.6 Fe 0.2 Cycle performance test diagram of a battery assembled from O2 materials;

[0022] Figure 3 Examples 1-3, Comparative Example 1, and untreated Li 1.2 Mn 0.6 Fe 0.2 Rate performance test chart of batteries assembled with O2 materials;

[0023] Figure 4 Examples 1-3, Comparative Example 1, and untreated Li 1.2 Mn 0.6 Fe 0.2 Impedance diagram of a battery assembled from O2 material. Detailed Implementation

[0024] The present invention provides the following specific technical solutions.

[0025] In a first aspect, the present invention provides a method for preparing a composite modified lithium-rich manganese-based cathode material, comprising ball milling and mixing Li₂Mn. 1-x Fe x Cl4 and Li 1+m Mn 1-m-n N n O2, sintering, to obtain; where 0.1≤x≤0.9, 0.1≤m≤0.3, 0≤n≤0.3.

[0026] The inventors discovered through research that Li2Mn 1-x Fe xAfter mechanically mixing Cl4 material with lithium-rich manganese-based cathode material, a composite sintering process is performed, allowing chlorine from the coating layer to enter the core material, resulting in a cathode material with a unique structure. The core is a lithium-rich manganese-based matrix material doped with Cl, while the coating layer is a metal chloride material with Cl defects. The core layer provides high capacity, and the coating layer solves interfacial impedance and stability problems, overcoming the issues of traditional single doping or coating methods. This improves the conductivity and ion transport performance of the cathode material, enhancing its electrochemical rate performance. Through elemental matching, both the core and shell contain Mn and Fe. The addition of Mn to the shell is to form the same manganese-based structure as the lithium-rich manganese-based material in the core, resulting in a more compact core-shell structure and smoother ion transport. The addition of Fe to the shell creates Fe-Cl bonds in the structure. At high temperatures, Fe-Cl bonds are extremely unstable and easily volatilize and decompose, forming active sites lacking both transition metal Fe and anion Cl. The dual active sites with co-deficient anions and cations provide a large number of surplus channels for ion and electron transport in lithium-rich manganese-based cathode materials, effectively improving the electrochemical rate performance of the materials.

[0027] The preparation process provided by this invention is simple and easy to operate, which is conducive to industrialization and large-scale production.

[0028] Preferably, Li2Mn 1-x Fe x Cl4 and Li 1+m Mn 1-m-n N n The mass ratio of O2 is 0.01~0.06∶1.

[0029] Through research, the inventors discovered that within the aforementioned preferred dosage range, a moderate coating thickness facilitates the uniform doping of Cl ions into the internal structure of the lithium-rich manganese-based cathode material. This readily forms complete dual active sites with co-deficient anions and cations, providing ample surplus channels for ion and electron transport in the lithium-rich manganese-based cathode material. Furthermore, ensuring the uniformity of the coating allows for the formation of complete dual active sites with co-deficient anions and cations, thereby enhancing ion transport performance.

[0030] Preferably, the sintering temperature is 800~900℃ and the sintering time is 0.5~2h.

[0031] Preferably, the ball milling speed is 300~500 rpm and the ball milling time is 2~6 hours.

[0032] Preferably, Li2Mn 1-x Fe x The preparation process of Cl4 includes: ball milling to mix lithium chloride, manganese chloride, and ferrous chloride, followed by sintering under a protective atmosphere.

[0033] The inventors discovered through research that all three chlorides are ionic compounds. During ball milling, the particles are refined and fully contacted, forming a uniformly mixed precursor. At high temperatures, the chlorides melt or sublimate, undergoing ionic recombination, and Li... + Mn 2+ Fe 2+ With Cl - Stable complex chloride phases can be formed through lattice matching.

[0034] Preferably, the molar ratio of lithium chloride, manganese chloride, and ferrous chloride is 2:0.1~0.9:0.1~0.9.

[0035] The inventors discovered through research that Li2Mn produced under the above-mentioned preferred ratio... 1-x Fe x Cl4 has a more stable structure and is less prone to structural collapse during subsequent calcination.

[0036] Preferably, the sintering temperature is 500~700℃ and the sintering time is 3~6h.

[0037] Through research, the inventors discovered that at the above-mentioned preferred sintering temperature, the Fe-Cl bond is extremely unstable and easily volatilizes and decomposes, forming active sites lacking transition metal Fe and active sites lacking anion Cl. Furthermore, it can reduce the possibility of excessive volatilization of Fe-Cl bonds and partial volatilization of Li elements, ensuring the structural stability of the surface coating layer, thereby ensuring the overall structural stability of the cathode material.

[0038] Preferably, the ball milling speed is 300~500 rpm and the ball milling time is 2~6 hours.

[0039] Preferably, the gas providing the protective atmosphere is nitrogen or argon.

[0040] Secondly, the present invention provides a composite modified lithium-rich manganese-based cathode material, which is prepared by the above-described preparation method.

[0041] Thirdly, the present invention provides a battery comprising a composite modified lithium-rich manganese-based cathode material prepared by the above-described preparation method.

[0042] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0043] 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.

[0044] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0045] Example 1:

[0046] A method for preparing a composite modified lithium-rich manganese-based cathode material includes the following steps:

[0047] Step 1, Preparation of Li2Mn 0.5 Fe 0.5 Cl4: Lithium chloride, manganese chloride, and ferrous chloride were ball-milled to obtain mixture A, with a molar ratio of lithium chloride, manganese chloride, and ferrous chloride of 2:0.5:0.5. The ball milling speed was 400 rpm, and the ball milling time was 4 h. Mixture A was then sintered at 600℃ for 4.5 h to obtain Li2Mn. 0.5 Fe 0.5 Cl4.

[0048] Step 2, take 0.3g of Li2Mn obtained in Step 1. 0.5 Fe 0.5 Cl4 and 10gLi 1.2 Mn 0.6 Fe 0.2 O2 was used to ball mill and mix the mixture to obtain mixture B. The ball milling speed was 400 rpm and the ball milling time was 4 h. Mixture B was then sintered at 850℃ for 1 h. The resulting solid particles are the composite modified lithium-rich manganese-based cathode material.

[0049] Example 2:

[0050] A method for preparing a composite modified lithium-rich manganese-based cathode material includes the following steps:

[0051] Step 1, Preparation of Li2Mn 0.1 Fe 0.9 Cl4: Lithium chloride, manganese chloride, and ferrous chloride were ball-milled to obtain mixture A, with a molar ratio of lithium chloride, manganese chloride, and ferrous chloride of 2:0.1:0.9. The ball milling speed was 300 rpm, and the ball milling time was 6 h. Mixture A was then sintered at 500℃ for 6 h to obtain Li2Mn. 0.1 Fe 0.9 Cl4.

[0052] Step 2, take 0.1g of Li2Mn obtained in Step 1. 0.1 Fe 0.9 Cl4 and 10gLi 1.1 Mn 0.4 Co 0.3O2 was used to ball mill and mix the mixture to obtain mixture B. The ball milling speed was 300 rpm and the ball milling time was 6 h. Mixture B was then sintered at 800℃ for 2 h. The resulting solid particles are the composite modified lithium-rich manganese-based cathode material.

[0053] Example 3:

[0054] A method for preparing a composite modified lithium-rich manganese-based cathode material includes the following steps:

[0055] Step 1, Preparation of Li2Mn 0.9 Fe 0.1 Cl4: Lithium chloride, manganese chloride, and ferrous chloride were ball-milled to obtain mixture A, with a molar ratio of lithium chloride, manganese chloride, and ferrous chloride of 2:0.9:0.1. The ball milling speed was 500 rpm, and the ball milling time was 2 h. Mixture A was then sintered at 700℃ for 3 h to obtain Li2Mn. 0.9 Fe 0.1 Cl4.

[0056] Step 2, take 0.3g of Li2Mn obtained in Step 1. 0.9 Fe 0.1 Cl4 and 10gLi 1.1 Mn 0.1 O2 was used to ball mill and mix the mixture to obtain mixture B. The ball milling speed was 500 rpm and the ball milling time was 2 h. Mixture B was then sintered at 900℃ for 0.5 h. The resulting solid particles are the composite modified lithium-rich manganese-based cathode material.

[0057] Comparative Example 1:

[0058] A method for preparing a composite modified lithium-rich manganese-based cathode material includes the following steps:

[0059] Step 1, Preparation of Li2Mn 0.5 Fe 0.5 Cl4: Lithium chloride, manganese chloride, and ferrous chloride were ball-milled to obtain mixture A, with a molar ratio of lithium chloride, manganese chloride, and ferrous chloride of 2:0.5:0.5. The ball milling speed was 400 rpm, and the ball milling time was 4 h. Mixture A was then sintered at 600℃ for 4.5 h to obtain Li2Mn. 0.5 Fe 0.5 Cl4.

[0060] Step 2, take 0.3g of Li2Mn obtained in Step 1. 0.5 Fe 0.5 Cl4 and 10gLi 1.2 Mn 0.6 Fe 0.2O2 was used to ball mill and mix the materials to obtain mixture B. The ball milling speed was 400 rpm and the ball milling time was 4 h. The resulting solid particles are the composite modified lithium-rich manganese-based cathode material.

[0061] Figure 1 The image shows a cross-sectional mapping of the composite modified lithium-rich manganese-based cathode material prepared in Example 1. It can be seen from the image that both the core and shell of the cathode material contain Cl elements, which proves that the Cl elements in the coating layer have entered the interior of the main material structure, and it can be inferred that Cl defects have been formed in the coating layer.

[0062] Examples 1-3, Comparative Example 1, and untreated Li were compared. 1.2 Mn 0.6 Fe 0.2 The positive electrode material prepared by O2 was weighed and ground according to the mass ratio of positive electrode material:conductive graphite:PVDF of 8:1:1. Then, an appropriate amount of N-methylpyrrolidone (NMP) was added and the mixture was ground and stirred to form a uniform slurry. The slurry was then evenly 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 positive electrode, and lithium foil as the negative electrode. The electrolyte consisted of a solvent and LiPF6, with a LiPF6 concentration of 1 mol / L. The solvent for the electrolyte 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 then subjected to performance testing. After being left to stand overnight, the assembled batteries were placed in a LAND2001CT battery test chamber for charge-discharge testing at 25°C, 1C, and a cycle voltage of 2.8~4.8V for 100 cycles.

[0063] Figure 2 Examples 1-3, Comparative Example 1, and untreated Li 1.2 Mn 0.6 Fe 0.2 Cycle performance test chart of a battery assembled from O2 materials. From Figure 2 The electrochemical performance of Examples 1-3 shows that the electrochemical stability is the best, which proves that the lithium-rich manganese-based cathode material with chlorine doping and a coating layer of double-deficient active sites provided by the present invention has excellent electrochemical cycling stability, and further illustrates that the structural stability of the material is also good after long cycling.

[0064] Comparative Example 1 and Untreated Li 1.2 Mn 0.6 Fe 0.2 O2 exhibits the second-highest electrochemical stability, likely due to the fact that only ball milling coating was performed without calcination. This means the coating layer, lacking chlorine defects, offers limited performance improvement to the lithium-rich manganese-based cathode material, failing to achieve the desired effect. Untreated Li... 1.2Mn 0.6 Fe 0.2 The O2 material exhibits the worst electrochemical performance, which may be because the unmodified lithium-rich manganese-based material is susceptible to corrosion by the electrolyte, thus affecting the structural stability and electrochemical reversibility of the lithium-rich manganese-based material.

[0065] Examples 1-3, Comparative Example 1, and untreated Li 1.2 Mn 0.6 Fe 0.2 Batteries assembled from O2 were subjected to rate testing under the following conditions: 2.8~4.8V; test rate: 0.1~5C; test temperature: 25℃.

[0066] Figure 3 Examples 1-3, Comparative Example 1, and untreated Li 1.2 Mn 0.6 Fe 0.2 Rate performance test chart of batteries assembled with O2 materials; from Figure 3 The rate performance of Examples 1-3 shows that the rate performance is better, which proves that the lithium-rich manganese-based cathode material with chlorine doping and a coating layer of dual-deficient active sites provided by the present invention has excellent ion transport performance and exhibits excellent rate capacity.

[0067] Comparative Example 1 and Untreated Li 1.2 Mn 0.6 Fe 0.2 O2 exhibits the second-highest electrochemical stability, likely because the coating is only ball-milled without calcination. This means the coating layer, lacking chlorine defects, offers limited improvement to the ion transport performance of lithium-rich manganese-based cathode materials, failing to achieve the desired effect. Untreated Li... 1.2 Mn 0.6 Fe 0.2 The O2 material exhibits the worst rate performance, which may be due to the limited conductivity and ion transport capacity of the unmodified lithium-rich manganese-based material, resulting in poor rate performance.

[0068] The resistance and ion transport performance of the battery were calculated based on impedance simulation and ion transport performance. The calculated data are shown in Table 1.

[0069] Table 1 Examples 1-3, Comparative Example 1, and Untreated Li 1.2 Mn 0.6 Fe 0.2 O2 performance

[0070]

[0071] Figure 4 Examples 1-3, Comparative Example 1, and untreated Li 1.2 Mn 0.6 Fe0.2 Impedance plot of a battery assembled from O2 material. Combined with... Figure 4 As can be clearly seen from Table 1, Examples 1-3 have lower impedance and higher ion transport performance. Figure 2 The test results for the rate performance showed a consistent trend.

[0072] In summary, it can be fully demonstrated that the lithium-rich manganese-based cathode material with a coating layer containing dual missing anion and cation active sites, combined with chlorine doping, provided by this invention, has excellent ion transport performance and exhibits excellent rate capacity and cycle stability.

[0073] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite modified lithium-rich manganese-based cathode material, characterized in that, Including ball-milled Li2Mn 1- x Fe x Cl4 and Li 1+m Mn 1-m-n N n O2 is sintered under a protective atmosphere to obtain the product; wherein N is one or two of Fe, Co, and Zn, 0.1≤x≤.9; 0.1≤m≤0.3, 0<n≤0.3; Li2Mn 1-x Fe x Cl4 and Li 1+m Mn 1-m-n N n The mass ratio of O2 is 0.01~0.06∶1.

2. The preparation method of the composite modified lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The sintering temperature is 800~900℃, and the sintering time is 0.5~2h.

3. The preparation method of the composite modified lithium-rich manganese-based cathode material as described in claim 1, characterized in that, Li2Mn 1- x Fe x The preparation process of Cl4 includes: ball milling to mix lithium chloride, manganese chloride, and ferrous chloride, followed by sintering under a protective atmosphere.

4. The preparation method of the composite modified lithium-rich manganese-based cathode material as described in claim 3, characterized in that, The molar ratio of lithium chloride, manganese chloride, and ferrous chloride is 2:0.1~0.9:0.1~0.

9.

5. The method for preparing the composite modified lithium-rich manganese-based cathode material as described in claim 3 or 4, characterized in that, The sintering temperature is 500~700℃, and the sintering time is 3~6h.

6. A composite modified lithium-rich manganese-based cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 5.

7. A battery, characterized in that, The composite modified lithium-rich manganese-based cathode material prepared by the preparation method according to any one of claims 1 to 5.

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