Ultra-thin amorphous nano-structured coated lithium-ion battery cathode material and method of making same

Abstract

The application relates to a super-thin amorphous nano-structure coated lithium ion battery positive electrode material and a preparation method thereof, and relates to the technical field of positive electrode materials for lithium ion batteries. The super-thin amorphous nano-structure coating layer is Li x MnO y The coated lithium ion battery positive electrode material comprises a lithium-rich manganese-based layered oxide (Li 1.2 Mn 0.57 Ni 0.17 Co 0.06 O2, Li2MnO3), a ternary positive electrode material (LiNi 0.6 Mn 0.2 Co 0.2 O2), lithium manganese iron phosphate (LiMn 0.6 Fe 0.4 PO4), lithium manganate (LiMn2O4) and lithium cobaltate (LiCoO2); wherein the preparation raw material is a common lithium ion battery positive electrode material powder, a lithium source and a manganese source; and the preparation method is that the lithium ion battery positive electrode material powder is added into a lithium source and a manganese source solution to perform a hydrothermal reaction. The button cell prepared from the super-thin amorphous nano-structure coated positive electrode material provided by the application has a great improvement in cycle stability compared with common positive electrode materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of positive electrode materials for lithium ion batteries, in particular to an ultra-thin amorphous nano-structured coated positive electrode material for lithium ion batteries. BACKGROUND

[0002] Since the invention of lithium ion batteries, they have attracted extensive attention from researchers. Currently, they have been applied to all aspects of life, from electric vehicles and artificial intelligence to mobile phones and laptops. With the rapid development of the energy storage field, people's demand for lithium ion batteries is no longer limited to high energy density, but also seeks longer cycle stability. Therefore, how to achieve long cycle stability is the focus of research.

[0003] Among common positive electrode materials for lithium ion batteries, lithium-rich manganese-based layered oxides, ternary positive electrodes, lithium manganese iron phosphate, lithium manganate and lithium cobaltate have attracted widespread attention. Lithium-rich manganese-based layered oxides xLi2MnO3.(1-x)LiTMO2(TM=Mn,Ni,Co) have a high operating voltage of 3.6V, release a high discharge specific capacity (up to 280mAh / g) when charged to 4.6V, and an energy density of up to 1000Wh / kg. They are considered to be the most promising high-energy lithium ion battery positive electrode materials, but their disadvantage is poor cycle stability, which prevents them from being applied to areas requiring long cycle use. The ternary positive electrode material NMC also has the disadvantage of high energy density but poor cycle stability. Lithium manganese iron phosphate (LiMnPO4) and lithium manganate (LiMn2O4) have good cycle stability, but Mn dissolution prevents further improvement of their cycle stability. Similarly, lithium cobaltate (LiCoO2) also has poor cycle stability when charged to high voltage. In order to solve the problems of these positive electrode materials, many solutions have been proposed, such as element doping, structure design and surface coating. Although these methods have some effect on the cycle stability of the positive electrode materials, the effect is not obvious. Therefore, in order to improve the cycle stability of the positive electrode materials, we used a hydrothermal reaction method to construct an ultra-thin amorphous nanoscale LiMnO2 coating layer on the positive electrode materials. This coating layer construction successfully improves the cycle stability of the positive electrode materials during the charging and discharging cycle. x Fe 1-x PO4) and lithium manganate (LiMn2O4) have good cycle stability, but Mn dissolution prevents further improvement of their cycle stability. Similarly, lithium cobaltate (LiCoO2) also has poor cycle stability when charged to high voltage. In order to solve the problems of these positive electrode materials, many solutions have been proposed, such as element doping, structure design and surface coating. Although these methods have some effect on the cycle stability of the positive electrode materials, the effect is not obvious. Therefore, in order to improve the cycle stability of the positive electrode materials, we used a hydrothermal reaction method to construct an ultra-thin amorphous nanoscale LiMnO2 coating layer on the positive electrode materials. This coating layer construction successfully improves the cycle stability of the positive electrode materials during the charging and discharging cycle. x MnO y SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provides a method for coating lithium ion battery positive electrode materials with an ultra-thin amorphous nano-structure.

[0005] ​The technical scheme of the present application is: a preparation method of a super-thin amorphous nano-structure coated lithium ion battery cathode material, which is based on forming an amorphous Li x MnO y coating layer, wherein Li x MnO y The thickness of the amorphous coating layer is 2-10 nm, Li x MnO y xy is not limited, Li x MnO y The whole represents an amorphous Li-Mn-O material. The cycle performance of the material is improved.

[0006] To achieve the above-mentioned purpose, the preparation method of the super-thin amorphous nano-structure coated lithium ion battery cathode material of the present application has the following specific steps:

[0007] (1) After the cathode material powder is weighed according to a certain stoichiometric ratio, a certain amount of deionized water is added and ultrasonic treatment is performed for a period of time, so that the powder is uniformly dispersed;

[0008] (2) After the cathode powder is uniformly dispersed, a certain amount of CH3COOH is added for pretreatment for a period of time;

[0009] (3) After the reaction is completed, the manganese source is added while stirring the liquid, and then ultrasonic treatment is performed for a period of time, so that the mixture is uniformly mixed;

[0010] (4) After the cathode powder and the manganese source are uniformly mixed, the lithium source is added while stirring, and then ultrasonic treatment is performed for a period of time, so that the mixture is uniformly mixed;

[0011] (5) After the added substances are uniformly mixed, they are transferred to a stainless steel autoclave lined with polytetrafluoroethylene, and then heated in a water bath at a certain temperature for a period of time;

[0012] (6) After the reaction is completed, the powder is collected, washed and dried, and finally the amorphous Li x MnO y coated cathode material is obtained.

[0013] The cathode material powder in step (1) can be lithium-rich manganese-based layered oxide, ternary cathode material, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium manganate and lithium cobaltate, etc.

[0014] The concentration of CH3COOH in step (2) is 0.1-1 mol / L.

[0015] The manganese source in step (3) can be at least one of MnSO4, Mn(NO3)2, Mn(CH3COO)2 and MnCl2.

[0016] The positive electrode material mentioned in step (3) has a mass ratio of Mn = 1:99.

[0017] The lithium source mentioned in step (4) can be LiOH. . At least one of H2O, Li2CO3, LiNO3, CH3COOLi, and LiF.

[0018] The positive electrode material in step (4) is Li = 2:98 (mass ratio).

[0019] The reaction temperature in step (5) is 150-220℃ and the reaction time is 10-50h.

[0020] Advantages of the present invention

[0021] 1. This invention can form an ultra-thin amorphous coating layer on the surface of the cathode material through simple hydrothermal treatment, which has the advantages of simple method and low cost.

[0022] 2. By constructing an ultrathin amorphous Li layer on the surface of the cathode material x MnO y Nano-coatings can effectively improve the cycle stability of cathode materials. Attached Figure Description

[0023] Figure 1 It is the ultrathin amorphous Li in Example 1 x MnO y TEM image of Li2MnO3 coated cathode material.

[0024] Figure 2 It is the uncoated original Li2MnO3 cathode material and the ultrathin amorphous Li in Example 1. x MnO y Comparison of cycle performance of Li2MnO3 coated cathode materials.

[0025] Figure 3 It is the uncoated original Li in Example 2 1.2 Mn 0.57 Ni 0.17 Co 0.06 O2 cathode material and ultrathin amorphous Li x MnO y Li coating 1.2 Mn 0.57 Ni 0.17 Co 0.06 Comparison chart of cycle performance of O2 cathode materials.

[0026] Figure 4 It is the uncoated raw LiNi in Example 3 0.6 Mn 0.2 Co0.2 O2 cathode material and ultra-thin amorphous Li x MnO y coated LiNi 0.6 Mn 0.2 Co 0.2 Cycle performance comparison chart of O2 cathode material.

[0027] Figure 5 is the original LiMn 0.6 Fe 0.4 PO4 cathode material and ultra-thin amorphous Li x MnO y coated LiMn 0.6 Fe 0.4 Cycle performance comparison chart of PO4 cathode material. DETAILED DESCRIPTION

[0028] The present application is described below by specific examples, the purpose of providing examples is to facilitate a better understanding of the present application, rather than limiting the present patent.

[0029] Example 1

[0030] (1) The lithium-rich manganese-based layered oxide powder (Li2MnO3) was weighed according to a certain stoichiometric ratio and placed in a 100ml small beaker, then a certain amount of deionized water was added to the small beaker and ultrasonic for a period of time, so that it was uniformly dispersed;

[0031] (2) After the cathode powder was uniformly dispersed, 0.1mol / L CH3COOH was added and pretreated for 1h;

[0032] (3) After the reaction was completed, Mn(CH3COO)2 was added while stirring with a glass rod, then ultrasonic for a period of time, so that it was mixed uniformly, wherein Li2MnO3:Mn=1:99(mass ratio);

[0033] (4) After the cathode powder and Mn(CH3COO)2 were mixed uniformly, LiOH . H2O was added while stirring with a glass cup, then ultrasonic for a period of time, so that it was mixed uniformly, wherein Li2MnO3:Li=2:98(mass ratio);

[0034] (5) After the added substances were mixed uniformly, it was transferred to a 90ml stainless steel autoclave lined with polytetrafluoroethylene, then heated in a water bath at 200℃ for 20h;

[0035] (6) After the reaction was completed, the powder was collected, washed and dried, and finally the amorphous Li x MnO y coated cathode material was obtained.

[0036] Figure 1 is a super-thin amorphous nanostructured Li x MnO y TEM image of Li2MnO3 coated. As shown, a 3-5 nm amorphous layer can be clearly observed uniformly coating the surface of Li2MnO3 material.

[0037] Figure 2 is an uncoated original Li2MnO3 cathode material and a super-thin amorphous Li x MnO y Cycle performance comparison chart of Li2MnO3 cathode material coated. As shown, the capacity retention of the coated material after 50 cycles of charge and discharge at a current density of 20 mA / g can be observed to be 72%, while the uncoated is only 8%.

[0038] Example 2

[0039] (1) Li-rich manganese-based layered oxide powder (Li 1.2 Mn 0.57 Ni 0.17 Co 0.06 O2) was weighed according to a certain stoichiometric ratio and placed in a 100 ml beaker, then a certain amount of deionized water was added to the beaker and ultrasonicated for a period of time to make it uniformly dispersed;

[0040] (2) After the cathode powder was uniformly dispersed, 0.1 mol / L CH3COOH was added and pretreated for 1 h;

[0041] (3) After the reaction was completed, a glass rod was used to stir while Mn(CH3COO)2 was added, then ultrasonicated for a period of time to make it mixed uniformly, wherein Li 1.2 Mn 0.57 Ni 0.17 Co 0.06 O2:Mn=1:99 (mass ratio);

[0042] (4) After the cathode powder and Mn(CH3COO)2 were mixed uniformly, a glass cup was used to stir while LiOH . H2O was added, then ultrasonicated for a period of time to make it mixed uniformly, wherein Li 1.2 Mn 0.57 Ni 0.17 Co 0.06 O2:Li=2:98 (mass ratio);

[0043] (5) After the added substances were mixed uniformly, they were transferred to a 90 ml stainless steel autoclave lined with polytetrafluoroethylene, then heated in a water bath at 200°C for 20 h;

[0044] (6) After the reaction is completed, the powder is collected, washed, and dried, and finally the amorphous Li x MnO y coated positive electrode material.

[0045] Figure 3 is an uncoated original Li 1.2 Mn 0.57 Ni 0.17 Co 0.06 O2 positive electrode material and an ultra-thin amorphous Li x MnO y coated Li 1.2 Mn 0.57 Ni 0.17 Co 0.06 O2 positive electrode material. As shown in the figure, it can be observed that the capacity retention rate of the coated material after 100 cycles of charge and discharge at a current density of 200 mA / g is 96.9%, while the capacity retention rate of the uncoated material is only 89.8%.

[0046] Example 3

[0047] (1) A ternary positive electrode powder (LiNi 0.6 Mn 0.2 Co 0.2 O2) is weighed according to a certain stoichiometric ratio and then placed in a 100 ml beaker. Then a certain amount of deionized water is added to the beaker and ultrasonic treatment is performed for a period of time to make it uniformly dispersed;

[0048] (2) After the positive electrode powder is uniformly dispersed, 0.1 mol / L CH3COOH is added and pretreated for 1 h;

[0049] (3) After the reaction is completed, Mn(CH3COO)2 is added while stirring with a glass rod, and then ultrasonic treatment is performed for a period of time to make it uniformly mixed, wherein LiNi 0.6 Mn 0.2 Co 0.2 O2:Mn=1:99 (mass ratio);

[0050] (4) After the positive electrode powder and Mn(CH3COO)2 are uniformly mixed, LiOH . H2O is added while stirring with a glass cup, and then ultrasonic treatment is performed for a period of time to make it uniformly mixed, wherein LiNi 0.6 Mn 0.2 Co 0.2 O2:Mn:Li=2:98 (mass ratio);

[0051] (5) After the added substances are uniformly mixed, they are transferred to a 90 ml stainless steel autoclave lined with polytetrafluoroethylene, and then heated in a water bath at 200°C for 20 h;

[0052] (6) After the reaction is completed, the powder is collected, washed, and dried, and finally an amorphous Li x MnO y coated positive electrode material is obtained.

[0053] Figure 4 is an uncoated original LiNi 0.6 Mn 0.2 Co 0.2 O2 positive electrode material and an ultra-thin amorphous Li x MnO y coated LiNi 0.6 Mn 0.2 Co 0.2 O2 positive electrode material. As shown in the figure, it can be observed that the capacity retention rate of the coated material after 100 cycles of charge and discharge at a current density of 200 mA / g is 94.3%, while the capacity retention rate of the uncoated material is only 84.9%.

[0054] Example 4

[0055] (1) Lithium iron manganese phosphate powder (LiMn 0.6 Fe 0.4 PO4) is weighed according to a certain stoichiometric ratio and then placed in a 100 ml beaker. Then a certain amount of deionized water is added to the beaker and ultrasonic treatment is performed for a period of time to uniformly disperse the powder;

[0056] (2) After the positive electrode powder is uniformly dispersed, 0.1 mol / L CH3COOH is added and pretreated for 1 h;

[0057] (3) After the reaction is completed, Mn(CH3COO)2 is added while stirring with a glass rod, and then ultrasonic treatment is performed for a period of time to uniformly mix the powder, wherein LiMn 0.6 Fe 0.4 PO4:Mn = 1:99 (mass ratio);

[0058] (4) After the positive electrode powder and Mn(CH3COO)2 are uniformly mixed, LiOH . H2O is added while stirring with a glass rod, and then ultrasonic treatment is performed for a period of time to uniformly mix the powder, wherein LiMn 0.6 Fe 0.4 PO4:Li = 2:98 (mass ratio);

[0059] (5) After the added substances are uniformly mixed, they are transferred to a 90 ml stainless steel autoclave lined with polytetrafluoroethylene, and then heated in a water bath at 200°C for 20 h;

[0060] (6) After the reaction is completed, the powder is collected, washed, and dried, and finally the coated positive electrode material of amorphous Li x MnO y PO4is uncoated.

[0061] Figure 5 PO4is uncoated. 0.6 Fe 0.4 PO4is uncoated. x MnO y PO4is uncoated. 0.6 Fe 0.4 PO4is uncoated.

[0062] Example 5

[0063] (1) Lithium manganate powder (LiMn2O4) is weighed according to a certain stoichiometric ratio and placed in a 100-ml small beaker. Then a certain amount of deionized water is added to the small beaker and ultrasonicated for a period of time to uniformly disperse it.

[0064] (2) After the positive electrode powder is uniformly dispersed, 0.1 mol / L CH3COOH is added for pretreatment for 1 h.

[0065] (3) After the reaction is completed, a glass rod is used to stir while adding Mn(CH3COO)2, and then ultrasonicated for a period of time to uniformly mix it, wherein LiMn2O4:Mn = 1:99 (mass ratio).

[0066] (4) After the positive electrode powder and Mn(CH3COO)2are uniformly mixed, a glass beaker is used to stir while adding LiOH . H2O, and then ultrasonicated for a period of time to uniformly mix it, wherein LiMn2O4:Li = 2:98 (mass ratio).

[0067] (5) After the added substances are uniformly mixed, they are transferred to a 90-ml stainless steel autoclave lined with polytetrafluoroethylene, and then heated in a water bath at 200°C for 20 h.

[0068] (6) After the reaction is completed, the powder is collected, washed, and dried, and finally the coated positive electrode material of amorphous Li x MnO y PO4is uncoated.

[0069] Example 6

[0070] (1) LiCoO2 powder is weighed according to a certain stoichiometric ratio and then put into a 100-ml beaker, and then a certain amount of deionized water is added to the beaker and ultrasonic treatment is performed for a period of time to make the powder uniformly dispersed;

[0071] (2) After the positive electrode powder is uniformly dispersed, 0.1 mol / L CH3COOH is added and pre-treated for 1 h;

[0072] (3) After the positive electrode powder is uniformly dispersed, Mn(CH3COO)2 is added while stirring with a glass rod, and then ultrasonic treatment is performed for a period of time to make the mixture uniformly mixed, wherein LiCoO2:Mn = 1:99 (mass ratio);

[0073] (4) After the positive electrode powder and Mn(CH3COO)2 are uniformly mixed, LiOH . H2O is added while stirring with a glass rod, and then ultrasonic treatment is performed for a period of time to make the mixture uniformly mixed, wherein LiCoO2:Li = 2:98 (mass ratio);

[0074] (5) After the added substances are uniformly mixed, they are transferred to a 90-ml stainless steel autoclave lined with polytetrafluoroethylene, and then heated in a water bath at 200°C for 20 h;

[0075] (6) After the reaction is completed, the powder is collected, washed, and dried, and finally an amorphous Li x MnO y coated positive electrode material is obtained.

[0076] The purpose of the embodiments described herein is to make it more convenient for those skilled in the art to understand and apply the present application. Those skilled in the art can easily modify or replace the conditions in the embodiments, and then apply the general principles described herein to other embodiments without having to undergo creative labor. Therefore, improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application are within the scope of protection of the present application.

Claims

1. A method for preparing an ultrathin amorphous nanostructured coated lithium-ion battery cathode material, characterized in that, based on the formation of an amorphous Li x MnO y coating layer, wherein Li x MnO y The thickness of the amorphous coating layer is 2-10 nm, Li x MnO y xy is not limited, Li x MnO y Overall represents the amorphous Li-Mn-O material; The method comprises the following steps: (1) a certain amount of positive electrode material powder is weighed according to a certain stoichiometric ratio, then added into a certain amount of deionized water, and then ultrasonic treated for a period of time to make the positive electrode material powder uniformly dispersed; (2) after the positive electrode material powder is uniformly dispersed, a certain amount of CH3COOH is added to pre-treat for a period of time; (3) after the reaction is completed, a manganese source is added while stirring the liquid, and then ultrasonic treated for a period of time to make the manganese source uniformly mixed; (4) after the positive electrode material powder and the manganese source are uniformly mixed, a lithium source is added while stirring, and then ultrasonic treated for a period of time to make the lithium source uniformly mixed; (5) after the added substances are uniformly mixed, the substances are transferred into a stainless steel autoclave with a polytetrafluoroethylene inner liner, and then heated in a water bath at a certain temperature for a period of time; (6) After the reaction is completed, the powder is collected, washed, and dried, and finally the amorphous Li x MnO y coated positive electrode material; The reaction temperature in step (5) is 150-220 ℃, and the reaction time is 10-50 h.

2. The method of claim 1, wherein, The positive electrode material powder in step (1) is a lithium-rich manganese-based layered oxide, a ternary positive electrode material, lithium iron phosphate, lithium manganese phosphate, lithium manganese iron phosphate, lithium manganate, and lithium cobaltate.

3. The method of claim 1, wherein, The concentration of CH3COOH in step (2) is 0.1-1 mol / L.

4. The method of claim 1, wherein, The manganese source in step (3) is at least one of MnSO4, Mn(NO3)2, Mn(CH3COO)2, and MnCl2.

5. The method of claim 1, wherein, The mass ratio of the positive electrode material to Mn in step (3) is 1:

99.

6. The method of claim 1, wherein, The source of lithium described in step (4) is LiOH . at least one of H2O, Li2CO3, LiNO3, CH3COOLi, and LiF.

7. The method of claim 1, wherein, The mass ratio of the positive electrode material to Li in step (4) is 2:98.

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