Carbon-coated composite nickel cobalt lithium manganate lithium battery

Abstract

The invention relates to the technical field of lithium batteries, and discloses a carbon-coated composite nickel cobalt lithium manganate lithium battery, which is prepared by the following steps: selecting 3 parts of steady-state nickel powder, 5 parts of steady-state manganese powder, 1 part of steady-state drilling powder, 1 part of carbon material and solvent; particularly, a mixture formed by mixing steady-state nickel-cobalt-manganese powder, vertical array-shaped carbon nanotubes and mesoporous carbon according to the mass ratio of 10: 1 is selected as a lithium material in a positive electrode to prepare positive electrode mixed slurry, so that the carbon-coated battery negative electrode material has more excellent performance, and meanwhile, the optimal selection of the negative electrode material is matched; according to the lithium ion battery, the shuttle effect and dendritic crystal growth in the continuous charging and discharging process can be effectively weakened, the lithium ion battery shows better cycle performance, rate performance and safety performance compared with conventional metal lithium, then the carbon-coated nickel-cobalt-manganese composite material is used as a positive active material, and a mixture formed by combining ketjen black and nano carbon according to the mass ratio of 1: 3 is used as a conductive agent, so that the lithium ion battery is prepared. A mixed system formed by mixing polyvinylpyrrolidone and polyethyleneimine according to the volume ratio of 2: 1 is used as a binder.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a carbon-coated composite nickel-cobalt-manganese-oxide lithium battery. Background Art

[0002] Lithium battery is a kind of battery that uses lithium metal or lithium alloy as positive / negative electrode material and non-aqueous electrolyte solution. Battery carbon coating is a material modification method, which is mainly used for battery electrode materials, especially lithium-ion batteries. In this process, the material is wrapped with a layer of carbon, which is called "coating". The main purpose of this technology is to improve the performance of the battery, such as increasing conductivity, reducing internal resistance, and improving energy efficiency. Carbon-coated composite nickel cobalt manganese oxide is a positive electrode material for lithium-ion batteries. Carbon-coated composite nickel cobalt manganese oxide lithium battery is a commonly used lithium-ion battery positive electrode material. This material improves its conductivity and structural stability by coating a layer of carbon on the surface of NCM particles. Carbon coating can not only enhance the electrochemical properties of the material, but also improve its stability during charging and discharging, thereby extending the service life of the battery. At present, there are many positive electrode materials for lithium-ion batteries, but from the perspectives of safety and cost, lithium iron phosphate positive electrode material is preferred. Lithium iron phosphate (LiFePO4) has a relatively high theoretical reversible specific capacity (about 170mAh / g). It also has the advantages of abundant resources, relatively low pollution in preparation, good safety performance, and good cycle stability. It is currently an ideal positive electrode material for power and energy storage lithium-ion batteries and is widely used in various mobile power supply fields, especially the large power supply field required for electric vehicles.

[0003] However, lithium iron phosphate materials have low lithium ion diffusion coefficient and conductivity, so the capacity and life of lithium iron phosphate as a rate-type battery electrode material are limited, especially in low-temperature environments, where the charge and discharge performance of lithium iron phosphate is greatly reduced. These structural limitations lead to low ion and electronic conductivity of lithium iron phosphate, which is only suitable for charging and discharging at low current density. The specific capacity is reduced during high-rate charge and discharge, which limits the application of this material.

[0004] In view of the above problems, the main solution at present is the preparation of positive electrode composite materials, selecting 3 parts of stable nickel powder, 5 parts of stable manganese powder, 1 part of stable diamond powder, 1 part of carbon material and solvent, and especially selecting a mixture of stable nickel cobalt manganese powder and vertical array carbon nanotubes and mesoporous carbon in a mass ratio of 10:1 as the lithium material in the positive electrode to prepare the positive electrode mixed slurry, so that the carbon-wrapped battery negative electrode material has more excellent performance, and at the same time, the battery prepared by the preparation method of the present invention with the optimally selected negative electrode material shows a smaller impedance, can effectively reduce the shuttle effect and dendrite growth during continuous charge and discharge, and shows better cycle performance, rate performance and safety performance than conventional metallic lithium. Summary of the invention

[0005] 1. Technical issues to be solved

[0006] In view of the difference from the existing technology, the present invention provides a carbon-coated composite nickel cobalt manganese oxide lithium battery, which has more excellent performance. At the same time, the battery made with the optimally selected negative electrode material exhibits smaller impedance, can effectively reduce the shuttle effect and dendrite growth during continuous charging and discharging, and exhibits better cycle performance, rate performance and safety performance than conventional metallic lithium, thus solving the battery performance problem.

[0007] (II) Technical solution

[0008] To achieve the above object, the present invention provides the following technical solution: a carbon-coated composite nickel cobalt manganese oxide lithium battery, wherein the preparation of the positive electrode material and the negative electrode material comprises the following steps:

[0009] S1. Raw material selection

[0010] 3 parts of stable nickel powder, 5 parts of stable manganese powder, 1 part of stable cobalt powder, 1 part of carbon material and solvent are selected, and a mixture of stable nickel cobalt manganese powder and vertical array carbon nanotubes and mesoporous carbon in a mass ratio of 10:1 is particularly selected as the lithium material in the positive electrode to prepare a positive electrode mixed slurry;

[0011] S2. Selection of positive electrode material

[0012] A carbon-coated composite nickel-cobalt-manganese composite material is used as a positive electrode active material, a mixture of Ketjen black and nanocarbon in a mass ratio of 1:3 is used as a conductive agent, and a mixed system of polyvinyl pyrrolidone and polyethyleneimine in a volume ratio of 2:1 is used as a binder;

[0013] S3. Preparation process

[0014] The preparation process includes steps such as mixing, high-temperature solid-phase reaction and carbonization;

[0015] 1. According to the mass calculation, the solvent is weighed according to the proportion of 30% solid content, and the solid includes the carbon-coated composite nickel-cobalt-manganese composite material and the conductive agent;

[0016] 2. uniformly mixing the carbon-coated nickel-cobalt-manganese composite material and the conductive agent according to the mass ratio;

[0017] 3. After the carbon-coated nickel-cobalt-manganese composite material is mixed with the conductive agent, it is poured into the solvent in which the binder has been dissolved, and further stirred evenly to prepare a positive electrode slurry.

[0018] (III) Beneficial effects

[0019] Compared with the prior art, the present invention provides a carbon-coated composite nickel cobalt manganese oxide lithium battery, which has the following beneficial effects:

[0020] 1. The carbon-coated composite nickel cobalt manganese oxide lithium battery, in the process of raw material selection, selects 3 parts of stable nickel powder, 5 parts of stable manganese powder, 1 part of stable diamond powder, 1 part of carbon material and solvent, and especially selects a mixture of stable nickel cobalt manganese powder and vertical array carbon nanotubes and mesoporous carbon in a mass ratio of 10:1 as the lithium material in the positive electrode to prepare the positive electrode mixed slurry, so that the carbon-coated battery negative electrode material has more excellent performance, and at the same time, the battery prepared by the preparation method of the present invention with the optimally selected negative electrode material shows a smaller impedance, can effectively reduce the shuttle effect and dendrite growth during continuous charge and discharge, and shows better cycle performance, rate performance and safety performance than conventional metal lithium. (IV) Description of the drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative labor:

[0022] Figure 1 This is a table diagram of the over-discharge test of the present invention;

[0023] Figure 2 This is a physical picture of the over-discharge test of the present invention;

[0024] Figure 3 This is a table diagram of the overcharge test of the present invention;

[0025] Figure 4 This is a physical picture of the overcharge test of the present invention;

[0026] Figure 5 It is a table diagram of the extrusion test of the present invention;

[0027] Figure 6 This is a physical picture of the extrusion test of the present invention;

[0028] Figure 7 This is a table diagram of a short circuit test of the present invention;

[0029] Figure 8 This is a physical picture of the short circuit test of the present invention;

[0030] Fig. 9 This is a table diagram of high temperature testing of the present invention;

[0031] Fig.10 This is a high temperature test curve diagram of the present invention;

[0032] Fig.11 This is a table diagram of low temperature test of the present invention;

[0033] Fig.12 This is a low temperature test curve diagram of the present invention;

[0034] Fig.13 This is a table diagram of the rate discharge performance test of the present invention. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Embodiment 1

[0037] A carbon-coated composite nickel cobalt manganese oxide lithium battery, wherein the preparation of the positive electrode material and the negative electrode material comprises the following steps:

[0038] S1. Raw material selection

[0039] 3 parts of stable nickel powder, 5 parts of stable manganese powder, 1 part of stable cobalt powder, 1 part of carbon material and solvent are selected, and a mixture of stable nickel cobalt manganese powder and vertical array carbon nanotubes and mesoporous carbon in a mass ratio of 10:1 is particularly selected as the lithium material in the positive electrode to prepare a positive electrode mixed slurry;

[0040] S2. Selection of positive electrode material

[0041] A carbon-coated composite nickel-cobalt-manganese composite material is used as a positive electrode active material, a mixture of Ketjen black and nanocarbon in a mass ratio of 1:3 is used as a conductive agent, and a mixed system of polyvinyl pyrrolidone and polyethyleneimine in a volume ratio of 2:1 is used as a binder;

[0042] S3. Preparation process

[0043] The preparation process includes steps such as mixing, high-temperature solid-phase reaction and carbonization;

[0044] 1. According to the mass calculation, the solvent is weighed according to the proportion of 30% solid content, and the solid includes the carbon-coated composite nickel-cobalt-manganese composite material and the conductive agent;

[0045] 2. uniformly mixing the carbon-coated nickel-cobalt-manganese composite material and the conductive agent according to the mass ratio;

[0046] 3. After the carbon-coated nickel-cobalt-manganese composite material is mixed with the conductive agent, it is poured into the solvent in which the binder has been dissolved, and further stirred evenly to prepare a positive electrode slurry.

[0047] The carbon-coated composite nickel-cobalt-manganese-oxide lithium battery first selects 3 parts of stable nickel powder, 5 parts of stable manganese powder, 1 part of stable cobalt powder, 1 part of carbon material and solvent, and uses a mixture of stable nickel-cobalt-manganese powder and vertical array carbon nanotubes and mesoporous carbon in a mass ratio of 10:1 as the lithium material in the positive electrode to prepare a positive electrode mixed slurry, then uses a carbon-coated composite nickel-cobalt-manganese composite material as a positive electrode active material, a mixture of Ketjen black and nanocarbon in a mass ratio of 1:3 as a conductive agent, and a mixed system of polyvinylpyrrolidone and polyethyleneimine in a volume ratio of 2:1 as a binder, and finally weighs a solvent according to mass calculation and a solid content of 30%, wherein the solid includes the carbon-coated composite nickel-cobalt-manganese composite material and the conductive agent, and finally mixes the carbon-coated composite nickel-cobalt-manganese composite material and the conductive agent evenly according to the mass ratio, and then pours the mixture into a solvent in which the binder has been dissolved to prepare a positive electrode slurry.

[0048] Carbon-coated composite nickel cobalt manganese oxide materials can significantly improve their electrochemical performance by coating a layer of carbon material on the surface of traditional nickel cobalt manganese oxide materials. This coating can improve the electronic conductivity of the material, thereby improving the rate performance and cycle stability. In addition, carbon coating can also reduce the corrosion of hydrofluoric acid in the electrolyte on the surface of the active material, thereby improving the cycle stability. Carbon-coated composite nickel cobalt manganese oxide materials have obvious cost advantages compared to traditional materials such as lithium cobalt oxide. This is because the cost of nickel and manganese is lower than that of cobalt, which helps to reduce the production cost of the entire battery. Carbon-coated composite nickel cobalt manganese oxide materials also show positive characteristics in terms of environmental protection. Since carbon materials are widely available and recyclable, this material has better environmental sustainability in life cycle assessment.

[0049] The carbon-coated composite nickel-cobalt-manganese-oxide lithium battery, test method:

[0050] At 23±2℃, the battery is charged to 4.20V at 1C constant current and constant voltage, with a cut-off current ≤0.02C, and left for 2h. The battery is discharged to 3.0V at 1C, and then discharged for another 7h with an external 30Q load. According to this test method, it can be concluded that Figure 1 and Figure 2 Over discharge test results;

[0051] At 23±2℃, charge the battery to 4.20V at 1C constant current and constant voltage, with a cut-off current ≤0.02C, leave it for 2h, discharge it to 3.0V at 1C, and then charge it to 4.60V at 3℃ constant current and constant voltage, so that the battery can be charged continuously for 8h. According to this test method, it can be concluded that Figure 3 and Figure 4 Overcharge test results;

[0052] At 23±2℃, charge the battery to 4.20V at 1C constant current and constant voltage, with a cut-off current ≤0.02C, and place it for 2h. Place the battery in two planes and squeeze it perpendicular to the direction of the plates. Apply a squeezing force of 13.0±0.2kN between the two plates. Once the pressure reaches the maximum value, stop the squeezing test. During the test, the battery cannot have an external short circuit. According to this test method, it can be concluded that Figure 5 and Figure 6 Extrusion test results;

[0053] After fully charging the battery or battery pack, place it in an environment of 20℃±5℃. After the battery surface temperature reaches 20℃±5℃, place it for 30 minutes. Then connect the positive and negative terminals of the battery with wires, and ensure that the total external resistance is 80mΩ±20mΩ. Monitor the battery temperature changes during the test. The test terminates when one of the following two situations occurs: (A) The battery temperature drops to 20% below the peak value; (B) The short-circuit time reaches 24 hours. Either of the two situations can be stopped. Based on this test method, it can be concluded that Figure 7 and Figure 8 Short circuit test results.

[0054] Three batteries were set up and the capacity retention rate was measured at 1C rate at 25℃, 1C rate at 60℃, and 3A rate at 60℃. According to this experimental method, we can get Fig. 9 and Fig.10 High temperature test results;

[0055] Set up four batteries and discharge them at 1C rate at 25℃, 0.2C rate at -20℃, 1C rate at -20℃, and 3A rate at -20℃ to measure the capacity retention rate. According to this experimental method, we can get Fig.11 and Fig.12 Low temperature test results.

[0056] Set up four batteries, charge them to the upper limit voltage at 1C constant current and constant voltage in a 20℃±5℃ environment, with a cut-off current of 0.01C, leave them for 10 minutes, and then test the discharge current at different rates, requiring constant current discharge to 3.0V. According to this experimental method, we can get Fig.13 Rate discharge performance test results.

[0057] The carbon-coated composite nickel-cobalt-manganese-oxide lithium battery has the following advantages:

[0058] according to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8The test results show that these tests are safety tests. There is no fire or explosion in the test results using different methods, indicating high safety performance.

[0059] according to Fig. 9 , Fig.10 , Fig.11 and Fig.12 The test results show that: high and low temperature test, according to SJ / T11796HC18350-950mAh test, -20℃ low temperature test capacity retention rate ≥70%; 60℃ high temperature test capacity retention rate ≥98%, the battery has no deformation, no explosion, can be used in a wide range of ambient temperature, high capacity retention rate, easy to store;

[0060] according to Fig.13 The test results show that the rate discharge performance test shows that the rate meets the 3C continuous discharge requirements, the voltage attenuation rate is low, and the rate performance is good.

[0061] 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 terms "include", "comprise" or any other variants thereof are 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 statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

Claims

1. A carbon-coated composite nickel-cobalt-manganese-oxide lithium battery, characterized in that: The preparation of the positive electrode material and the negative electrode material comprises the following steps: S1. Raw material selection 3 parts of stable nickel powder, 5 parts of stable manganese powder, 1 part of stable cobalt powder, 1 part of carbon material and solvent are selected, and a mixture of stable nickel cobalt manganese powder and vertical array carbon nanotubes and mesoporous carbon in a mass ratio of 10:1 is particularly selected as the lithium material in the positive electrode to prepare a positive electrode mixed slurry; S2. Selection of positive electrode material A carbon-coated composite nickel-cobalt-manganese composite material is used as a positive electrode active material, a mixture of Ketjen black and nanocarbon in a mass ratio of 1:3 is used as a conductive agent, and a mixed system of polyvinyl pyrrolidone and polyethyleneimine in a volume ratio of 2:1 is used as a binder; S3. Preparation process The preparation process includes steps such as mixing, high-temperature solid-phase reaction and carbonization; 1. According to the mass calculation, the solvent is weighed according to the proportion of 30% solid content, and the solid includes the carbon-coated composite nickel-cobalt-manganese composite material and the conductive agent; 2. uniformly mixing the carbon-coated nickel-cobalt-manganese composite material and the conductive agent according to the mass ratio; 3. After the carbon-coated nickel-cobalt-manganese composite material is mixed with the conductive agent, it is poured into the solvent in which the binder has been dissolved, and further stirred evenly to prepare a positive electrode slurry.

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