Preparation method of LiNi0. 5Mn1. 5O4 material with excellent electrochemical performance

Abstract

The invention discloses a preparation method of a high-voltage lithium ion battery positive electrode material LiNi < 0.5 > Mn < 1.5 > O < 4 > with excellent electrochemical performance. The preparation method comprises the following steps: firstly, dissolving a lithium salt, a nickel salt and a manganese salt in water, then adding a chelating agent for stirring reaction, then drying and removing water to obtain gel, and finally roasting the gel in an air atmosphere at 800 DEG C for 3 hours to obtain the product LiNi0. 5Mn1. 5O4. The LiNi < 0.5 > Mn < 1.5 > O < 4 > material prepared by the method has a pure-phase disordered structure and does not have an impurity phase. The LiNi0. 5Mn1. 5O4 material prepared by the technology is used as a positive electrode and is assembled with a lithium sheet to form a half battery, the first specific discharge capacity at 0.1 C reaches 128.04 mAh.g <-1 >, the capacity is not attenuated after 100 times of charge and discharge cycles, the capacity retention ratio is 94.4% after 200 times of charge and discharge, and the lithium ion battery has excellent electrochemical performance. According to the technology, the problems of complex preparation process, high energy consumption, high cost and the like of the existing pure-phase disordered structure LiNi0. 5Mn1. 5O4 material are solved, and the preparation cost can be reduced; and meanwhile, the problem of poor charge-discharge cycle performance of the LiNi0. 5Mn1. 5O4 material is also solved, and the material is convenient to popularize and apply.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery positive electrode materials, and specifically is a high voltage lithium ion battery positive electrode material LiNi with excellent electrochemical performance. 0.5 Mn 1.5 Preparation method of O4. Background Art

[0002] In modern society, lithium-ion batteries (LIBs) have been widely used in portable devices, electric vehicles (EVs), and hybrid electric vehicles (HEVs), completely changing our lifestyles. However, existing commercial LIBs have become a major limitation to the rapid development of EVs and HEVs due to their limited energy density. Since the theoretical capacity of the negative electrode carbon materials of current lithium-ion batteries is much higher than that of the positive electrode materials, the use of cheaper and higher energy density positive electrode materials is the key to improving the energy density of lithium-ion batteries.

[0003] LiFePO4, the most commercially used positive electrode material for lithium-ion batteries, has high cycle performance and safety, but its energy density is low. Although cobalt-containing ternary positive electrode materials and LiCoO2 materials have high energy density, the radioactivity of cobalt and its high price limit their commercial application.

[0004] Therefore, people are in urgent need of another non-toxic cathode material with low cost and high energy density. 0.5 Mn 1.5 O4) has a high operating voltage of 4.7V and 650Wh·kg -1 High energy density, exceeding the 518Wh·kg of LiCoO2 -1 、400Wh·kg of LiMn2O4 -1 、LiFePO4 495Wh·kg -1 The energy density of LiNi is high, and it is simple to prepare, inexpensive, safe and non-toxic. Therefore, this LiNi with higher voltage platform and higher energy density 0.5 Mn 1.5 O4 material has become the most promising candidate for the next generation of lithium-ion battery positive electrode materials. 0.5 Mn 1.5 O4 materials also have problems such as complex preparation process and poor charge and discharge cycle performance. Summary of the invention

[0005] The purpose of the present invention is to provide a LiNi2O3 with excellent electrochemical performance in order to solve the above problems. 0.5 Mn 1.5 Preparation method of O4 material.

[0006] The technical solution adopted by the present invention is as follows: a LiNi with excellent electrochemical performance 0.5 Mn 1.5 The preparation method of O4 material is characterized in that: the preparation method comprises the following steps:

[0007] S1: nickel salt and manganese salt are weighed in a certain proportion and dissolved in deionized water, and then polyethylene glycol is weighed and added to the above solutions and stirred to dissolve to obtain S1 solution;

[0008] S2: Weigh lithium salt in a certain proportion and add it to S1 solution, stir and dissolve to obtain S2 solution;

[0009] S3: Weigh a certain amount of starch, heat and stir to dissolve to obtain a starch solution;

[0010] S4: adding S2 solution into starch solution and stirring to form a sol state;

[0011] S5: then placing the obtained sol in a forced air drying oven to dry and remove water to obtain a gel;

[0012] S6: The obtained gel is then placed in a muffle furnace and calcined at 800°C for 3 hours in an air atmosphere to obtain a pure phase LiNi with a disordered structure. 0.5 Mn 1.5 O4 material.

[0013] S7: Through XRD (X-ray diffraction), SEM (scanning electron microscope), IR (infrared), Ramann and other characterizations, it was found that the LiNi prepared by this technology 0.5 Mn 1.5 O4 material is a pure phase disordered structure.

[0014] S8 prepared LiNi 0.5 Mn 1.5 O4 material is used as the positive electrode material, lithium sheet is used as the negative electrode, and the electrolyte is 1M lithium hexafluorophosphate dissolved in ethylene carbonate: ethyl methyl carbonate: diethyl carbonate = 1:1:1, assembled into a button battery. Its electrochemical performance, including charge and discharge platform, rate performance, and cycle performance, is tested to evaluate the advantages and disadvantages of its electrochemical performance. It is found that the first discharge specific capacity at 0.1C reaches 128.04mAh·g -1 After 100 charge and discharge cycles, the capacity did not decay, and after 200 charge and discharge cycles, the capacity retention rate was 94.4%, which has excellent electrochemical performance.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0016] In the present invention, starch chelating agent is used for the first time to prepare LiNi by sol-gel method. 0.5Mn 1.5 O4 positive electrode material, the calcination procedure is simple, directly drying and removing water to obtain the gel in air atmosphere at 800 ° C for 3 hours to obtain. At the same time, the material prepared by the technology of the present invention is a pure phase disordered structure, has a good regular polyhedral morphology, no agglomeration phenomenon, and the size is micro-nano material. These characteristics are the reason why the material prepared by the present invention has excellent electrochemical properties.

[0017] This technology solves the disordered structure of pure phase LiNi 0.5 Mn 1.5 O4 material and has good regular morphology without agglomeration of micro-nano LiNi 0.5 Mn 1.5 The preparation of O4 materials is complex. For example, it requires multi-step calcination and a long calcination time. This saves energy. 0.5 Mn 1.5 O4 materials have poor charge and discharge cycle performance. Currently, most LiNi 0.5 Mn 1.5 The battery capacity retention rate of O4 material after 100 charge and discharge cycles is less than 80%. 0.5 Mn 1.5 The capacity of the O4 material did not decay after 100 charge and discharge cycles, and the capacity retention rate reached 94.4% after 200 charge and discharge cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a product characterization diagram of the present invention;

[0019] in Figure 1-1 The XRD spectrum of the product of the present invention in the range of 5-120°;

[0020] Figure 1-2 This is the SEM image of the product in the present invention;

[0021] Figure 1-3 Figure a is the Raman spectrum of the product, and figure b is the infrared spectrum of the product;

[0022] Figure 2 The electrochemical performance diagram of the product of the present invention, wherein a is the charge and discharge platform, b is the rate performance, and c is the charge and discharge cycle diagram; the rate performance diagram (b) shows that at 0.1C, 0.2C, 0.5C, 1C, and 2C rates, the first discharge specific capacity is 128.04 mAh g -1 、123.91mAh·g -1 、115.74mAh·g -1 、105.01mAh·g -1 、86.90mAh·g -1The cycle performance curve (c) at 1C shows that the capacity has almost no attenuation after 100 cycles, and the capacity retention rate is 94.4% after 200 charge and discharge cycles;

[0023] Figure 3 The present invention is a flow chart of the preparation method. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0025] Example:

[0026] Reference Figure 1-3 , a LiNi with excellent electrochemical performance 0.5 Mn 1.5 The preparation method of O4 material comprises the following steps:

[0027] S1: nickel salt and manganese salt are weighed in a certain proportion and dissolved in deionized water, and then polyethylene glycol is weighed and added to the above solutions and stirred to dissolve to obtain S1 solution;

[0028] S2: Weigh lithium salt in a certain proportion and add it to S1 solution, stirring and dissolving to obtain S2 solution;

[0029] S3: Weigh a certain amount of starch, heat and stir to dissolve to obtain a starch solution;

[0030] S4: adding S2 solution into starch solution and stirring to form a sol state;

[0031] S5: then placing the obtained sol in a forced air drying oven to dry and remove water to obtain a gel;

[0032] S6: The obtained gel is then placed in a muffle furnace and calcined at 800°C for 3 hours in an air atmosphere to obtain LiNi 0.5 Mn 1.5 O4 material;

[0033] S7: Prepare LiNi 0.5 Mn 1.5 O4 material and lithium sheet are assembled into button batteries, and their electrochemical properties are tested, including charge and discharge platform, rate performance, and cycle performance, to evaluate the pros and cons of their electrochemical performance.

[0034] In step S1, weighing is performed according to a molar ratio of Li:Ni:Mn=1.05:0.5:1.5; the weighed nickel salt and manganese salt are successively dissolved in deionized water to form a uniform solution.

[0035] In step S2, weigh according to the molar ratio of Li:Ni:Mn=1:0.5:1.5; add the weighed lithium salt to the S1 solution, and stir it thoroughly with a stirrer to form a uniform solution.

[0036] In step S3, an appropriate amount of starch is weighed, heated, stirred and dissolved to obtain a starch solution;

[0037] The assembled button cell includes: a lithium sheet as a negative electrode, a prepared material as a positive electrode material active substance, and an electrolyte of 1M lithium hexafluorophosphate dissolved in ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) = 1:1:1.

[0038] like Figure 1-1 As shown, Figure 1-1 The XRD spectrum of the product in the range of 5-120° shows sharp diffraction peaks at 2θ=18.7°, 36.3°, 38.0°, 44.2°, 48.4°, 58.5°, 64.3° and 67.7°, which is consistent with the disordered structure of LiNi 0.5 Mn 1.5 The characteristic peak of O4 positive electrode material belongs to Fd-3m space group such as Figure 1-2 As shown, the product is a spinel-type micro-nano material with uniform particle size and no agglomeration.

[0039] like Figure 1-3 As shown, Figure 1-3 Figure a is the Raman spectrum of the product. Figure 1-3 b is the infrared spectrum of the product;

[0040] Raman spectra were observed at 158, 397, 489, 593, and 627 cm -1 There are five distinguishable spectral peaks at 0.5 Mn 1.5 Raman spectrum of O4 material Figure 1 The infrared spectrum of the sample showed that the peaks at 478, 502, 555, 587 and 622 cm -1 There are five obvious characteristic peaks at the LiNi phase, and no ordered structural characteristic peaks, which is different from the disordered spinel phase. 0.5 Mn 1.5 O4 material infrared spectrum Figure 1 To.

[0041] Based on the above, XRD, Raman, and infrared characterization, it is determined that the pure phase disordered spinel LiNi 0.5 Mn 1.5 O4 material, belongs to Fd-3m space group.

[0042] like Figure 2 As shown, Figure 2Figure 1 is the electrochemical performance diagram of the product, a is the charge and discharge platform diagram, b is the rate performance diagram, and c is the charge and discharge cycle diagram.

[0043] Figure 2 This is the electrochemical performance diagram of the product and lithium sheet assembled into a button battery. Figure 2 (a) It can be seen that the initial discharge capacity at 0.1C is 128.04 mAh g -1 There are corresponding discharge platforms at ~4.7V and ~4.0V respectively. The rate performance diagram (b) shows that at 0.1C, 0.2C, 0.5C, 1C, and 2C rates, the first discharge capacity is 128.04mAh·g -1 、123.91mAh·g -1 、115.74mAh·g -1 、105.01mAh·g -1 、86.90mAh·g -1 The cycle performance curve (c) at 1C shows that the capacity has almost no decay after 100 cycles, and the capacity retention rate is 94.4% after 200 charge and discharge cycles.

[0044] From the above, it can be seen that: the present invention solves (1) LiNi 0.5 Mn 1.5 O4 materials have poor charge and discharge cycle performance. Currently, most LiNi 0.5 Mn 1.5 The battery capacity retention rate of O4 material after 100 charge and discharge cycles is less than 80%; (2) It solves the current problem of preparing pure phase disordered structure LiNi 0.5 Mn 1.5 The preparation procedure of O4 materials is complicated, for example, it requires multi-step roasting and a long roasting time, so energy saving is required.

[0045] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A LiNi with excellent electrochemical performance 0.5 Mn 1.5 The preparation method of O4 material is characterized in that: The preparation method comprises the following steps: S1: nickel salt and manganese salt are weighed in a certain proportion and dissolved in deionized water, and then polyethylene glycol is weighed and added to the above solutions and stirred to dissolve to obtain S1 solution; S2: Weigh lithium salt in a certain proportion and add it to S1 solution, stir and dissolve to obtain S2 solution; S3: Weigh a certain amount of starch, heat and stir to dissolve to obtain a starch solution; S4: adding S2 solution into starch solution and stirring to form a sol state; S5: then placing the obtained sol in a forced air drying oven to dry and remove water to obtain a gel; S6: The obtained gel is then placed in a muffle furnace and calcined at 800°C for 3 hours in an air atmosphere to obtain a pure phase LiNi with a disordered structure. 0.5 Mn 1.5 O4 material.

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