Preparation method of lithium ion battery negative electrode material containing lithium, carbon, copper and oxygen

Abstract

The invention relates to the technical field of energy materials, in particular to a preparation method of a lithium ion battery negative electrode material. The preparation method comprises the following steps: weighing a certain amount of LiOH and C10H14CuO4, fully grinding to form a mixture in which the molar ratio of Li to Cu is 1: (1-1.5), putting the mixture into a muffle furnace, and calcining at 500-700 DEG C in an air atmosphere for 1-3 hours to obtain the final material. Tests show that the prepared material and an elemental lithium sheet form a half battery, the first specific discharge capacity of the material under 0.1 Ag <-1 > reaches up to 350mAh g <-1 >, the specific discharge capacity of the material after 100 cycles under 0.1 Ag <-1 > is still more than 90mAh g <-1 >, and good cycle stability is shown. The preparation method is simple, low in cost, clean, free of pollution and suitable for industrial large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of energy materials, and in particular, to a preparation method of a lithium-containing carbon copper oxide negative electrode material for a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, low self-discharge rate, etc., and have been widely used in many fields such as energy storage, electric vehicles, aerospace, etc. Research shows that the performance of the negative electrode material in a lithium-ion battery is closely related to the life, cost, safety and other characteristics of the lithium-ion battery. Therefore, selecting a suitable negative electrode material is crucial for improving the overall performance of the lithium-ion battery. Currently, the commercially available negative electrode materials for lithium-ion batteries are mainly graphite and lithium titanate (Li4Ti5O 12 ). Research shows that during the charge and discharge process, especially during overcharge, lithium dendrites precipitate on the surface of graphite. In some special cases, the lithium dendrites will pierce the separator, causing short circuit between the positive and negative electrodes. Therefore, there are certain safety hazards in using graphite as the negative electrode material for lithium-ion batteries. Lithium titanate (Li4Ti5O 12 ) has the advantages of long cycle life, good fast charge and discharge performance, high safety and stability, etc., but its disadvantages such as low electrical conductivity and relatively high charge and discharge platforms greatly limit its application in high-energy density batteries. Therefore, developing new negative electrode materials for lithium-ion batteries remains one of the hot issues in the research field of lithium-ion batteries. The existing preparation methods for negative electrode materials of lithium-ion batteries mainly include: Ge Hao et al. (CN112736236A) disclosed a preparation method of a new negative electrode material for lithium-ion batteries, namely, a method for preparing biomass carbon-coated biphasic Li4Ti5O 12 / TiO2; Wang Jing et al. (CN118039886A) disclosed a preparation method of a negative electrode material for lithium-ion batteries containing SiO2, silicon and lithium silicate; Liu Xiaochao et al. (CN118771443A) disclosed a preparation method of a composite material of nitrogen-doped carbon nanotubes and Li4Ti5O 12 nanoparticles. The above preparation methods generally have the disadvantages of complex preparation processes and high production costs. Therefore, researching new preparation methods for negative electrode materials of lithium-ion batteries is still one of the current research hot issues. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of a lithium-containing carbon copper oxide negative electrode material for a lithium-ion battery. This preparation method has the advantages of easily available raw materials, simple preparation process, low cost, and being suitable for industrial-scale production, and has great commercial development value.

[0004] The object of the present invention is achieved as follows. A novel material is prepared by calcining a mixture of LiOH and copper acetylacetonate, and this material is used as the anode material of a lithium-ion battery. Electrochemical tests show that at 0.1 A g -1 the initial discharge specific capacity of this material is as high as 350 - 400 mAh g -1 , which is much higher than the theoretical specific capacity of commercial lithium titanate (175 mAh g -1 ). At 0.1 A g -1 , 0.3 A g -1 , 0.5 A g -1 , 0.7 A g -1 and 1.0 A g -1 , the capacities after 5 cycles are 309 - 320 mAh g -1 , 190 - 220 mAh g -1 , 150 - 180 mAh g -1 , 130 - 150 mAh g -1 and 100 - 120 mAh g -1 respectively, showing good rate performance. Especially at 1.0 A g -1 , the discharge specific capacity after 100 cycles is still as high as 90 - 100 mAh g -1 , the Coulombic efficiency is between 90 - 100%, and the battery capacity retention rate is between 55 - 65%, showing excellent high-rate and long-cycle performance.

[0005] Specifically, the preparation method of the present invention includes the following steps:

[0006] (1) Raw material preparation

[0007] Lithium hydroxide (LiOH); copper acetylacetonate (C 10 H 14 CuO4); 1 mol L -1 LiPF6 organic electrolyte; acetylene black; polyvinylidene fluoride (PVDF); N-methylpyrrolidone (NMP);

[0008] (2) Material preparation

[0009] Weigh LiOH and copper acetylacetonate according to the molar ratio of Li to Cu of 1:(1.0 - 1.5) respectively, place the two in an agate mortar and grind for 10 - 50 min to form a mixture. Then place the obtained mixture in a muffle furnace and calcine at 500°C - 700°C for 1 - 3 h in an air atmosphere to obtain the prepared material, which contains lithium, carbon, copper and oxygen;

[0010] (3) Preparation of electrodes and assembly of batteries

[0011] Weigh the prepared material, PVDF, and acetylene black according to a mass ratio of (8 - 9):(1 - 1.5):(1 - 1.5). After placing the three in an agate mortar, grind them thoroughly for 10 - 50 min. Then, add NMP drop by drop while stirring to make a paste of the mixture of the three. Subsequently, evenly apply the paste on a commercial copper foil current collector with a glass slide. After that, put the coated copper foil into a vacuum drying oven and dry it at 100°C - 130°C for 4 - 8 h. Take it out after naturally cooling to room temperature, and the electrode of the prepared material is obtained.

[0012] Use the prepared electrode as the positive electrode, a lithium sheet as the negative electrode, a Celgard 2400 microporous polypropylene membrane as the separator, and LiPF6 as the electrolyte to assemble a half-cell in a glove box filled with nitrogen for electrochemical performance testing.

[0013] As a preferred condition, in step (2), weigh lithium hydroxide and copper acetylacetonate and grind them, where the molar ratio of Li to Cu is 1:1.1.

[0014] As a preferred condition, in step (2), the calcination temperature of the mixture of lithium hydroxide and copper acetylacetonate in a muffle furnace is 600°C.

[0015] As a preferred condition, in step (2), the calcination time of the mixture of lithium hydroxide and copper acetylacetonate in a muffle furnace is 2 h.

[0016] As a preferred condition, in step (2), grind the mixture of lithium hydroxide and copper acetylacetonate in an agate mortar for 20 min.

[0017] As a preferred condition, in step (3), the mass ratio of the prepared material, PVDF, and acetylene black is 8:1:1.

[0018] As a preferred condition, in step (3), the concentration of the LiPF6 electrolyte is 1 mol / L -1 .

[0019] As a preferred condition, in step (3), the grinding time of the mixture of the prepared material, acetylene black, and PVDF is 20 min.

[0020] As a preferred condition, in step (3), during the electrode preparation process, the drying temperature in the vacuum drying oven is 120°C.

[0021] As a preferred condition, in step (3), during the electrode preparation process, the drying time is 6 hours.

[0022] The infrared spectrum and XRD pattern of the material prepared in this invention are different from those of commercially available copper oxide (CuO). XPS testing shows that the chemical formula of this material is approximately Li2C4CuO4. Literature research indicates that, so far, there has been no report on this chemical formula at home and abroad. Electrochemical testing shows that this material is a new type of anode material for lithium-ion batteries with excellent performance. The preparation method of this invention is simple in process, easy to operate, and low in preparation cost, and is suitable for large-scale industrial applications.

[0023] The beneficial effects of this invention are as follows: A new type of anode material for lithium-ion batteries containing lithium, carbon, copper, and oxygen is prepared by calcining a mixture of LiOH and copper acetylacetonate. This material has a high discharge specific capacity, good rate performance, and excellent high-rate cycle stability, and has potential application prospects. Its preparation process is simple, the cost is low, and it is suitable for large-scale industrial applications. Description of the Drawings

[0024] Figure 1 is the XRD pattern of the prepared material;

[0025] Figure 2 is the FTIR pattern of the prepared material;

[0026] Figure 3 is the XPS pattern of the prepared material, Figure 3 where a is the wide-scan XPS measurement spectrum, Figure 3 where b is the Cu 2p XPS spectrum, Figure 3 where c is the Li 1s XPS spectrum, Figure 3 where d is the O1s XPS spectrum;

[0027] Figure 4 is the first charge-discharge curve of the half-cell assembled with the prepared material and a lithium sheet at 0.1 A g -1 ;

[0028] Figure 5 is the charge-discharge cycle diagram of the half-cell assembled with the prepared material and a lithium sheet at 0.1 A g -1 , 0.3 A g -1 , 0.5 A g -1 , 0.7 A g -1 and 1.0 A g -1 ;

[0029] Figure 6 is the relationship diagram between the discharge capacity and the number of cycles when the battery cycles 100 times at 1.0 A g -1 ;

[0030] Figure 7 is the cyclic voltammogram of the half-cell assembled with the prepared material and a lithium sheet. Detailed Embodiments

[0031] The following examples serve to illustrate the invention.

[0032] Example 1

[0033] LiOH and copper acetylacetonate were weighed according to a molar ratio of Li to Cu of 1:1, placed in an agate mortar and ground for 20 minutes to form a mixture. The obtained mixture was then placed in a muffle furnace and calcined at 600° C. for 2 hours in an air atmosphere to obtain the prepared material.

[0034] The prepared material, PVDF and acetylene black were weighed in a mass ratio of 9:1:1.5, and the three were placed in an agate mortar and fully ground for 20 minutes. After that, NMP was added dropwise, and the mixture was stirred while adding and adjusted into a paste. Subsequently, the paste was evenly applied on a commercial copper foil current collector with a glass sheet, and the coated copper foil was placed in a vacuum drying oven, dried at 120°C for 6 hours, and taken out after naturally cooling to room temperature, and the electrode of the prepared material was obtained.

[0035] The prepared electrode was used as the positive electrode, the lithium sheet as the negative electrode, the Celgard2400 microporous polypropylene membrane as the separator, and 1 mol L -1 LiPF6 was used as the electrolyte and half-cells were assembled in a nitrogen-filled glove box for electrochemical performance testing.

[0036] See Figure 1 , Figure 1 The XRD diagram of the prepared material and commercially available copper oxide (CuO). As shown in the figure, in the spectrum of the prepared material, the diffraction peaks at 32.6°, 35.7°, 38.9°, 49.0°, 53.8°, 58.4°, 61.7°, 66.5°, 68.3°, 72.6°, and 75.3° correspond to the (110), (002), (200), (-202), (020), (202), (-113), (-311), (220), (311), and (-222) crystal planes of CuO (JCPDS, No. 5-661), which indicates that the crystal form of the prepared material is consistent with that of copper oxide. Interestingly, in the XRD spectrum of the prepared material, new diffraction peaks appeared at 21.4°, 30.7° and 32.1°, which shows that the prepared material is different from pure CuO and is a new type of material.

[0037] See Figure 2 , Figure 2 The infrared spectra (FTIR) of the prepared material and commercially available CuO are shown in Figure 2. The infrared spectra of the prepared material of the present invention are different from those of commercially available CuO. -1 and 862cm -1New absorption peaks appear at these positions respectively. Generally, the absorption peak at 1429 cm -1 is attributed to the stretching vibration of the C-O bond, while the absorption peak at 862 cm -1 is attributed to the bending vibration of the O-Cu-O bond. The differences in the infrared spectra indicate that the material prepared by the present invention is different from CuO and is a new material.

[0038] See Figure 3 , Figure 3 for the XPS diagram of the prepared material. From the full XPS scan spectrum, Figure (a), it can be seen that the prepared material contains Li, C, Cu, and O elements, and the atomic content ratio of Li, C, Cu, and O elements is 2:4:1:4, that is, the chemical formula of the prepared material is approximately Li2C4CuO4. Literature research shows that so far, there has been no report on this chemical formula at home and abroad. Figure (b) is the high-resolution XPS spectrum of Cu 2p of the material. Among them, the binding energy peaks at 934.2 eV and 954.1 eV correspond to Cu 2+ 2p 3 / 2 and Cu 2+ 2p 1 / 2 orbits, while the binding energy peaks at 942.3 eV and 962.1 eV are generally considered to be the satellite peaks of Cu 2+ . This indicates that Cu exists in the form of Cu 2+ in the prepared material. Figure (c) is the high-resolution XPS spectrum of Li 1s of the material. The binding energy peak at 55.2 eV corresponds to the 1s orbit of lithium ions, proving the existence of lithium ions (Li + ). Figure (d) is the high-resolution XPS spectrum of O1s of the material. Generally, the binding energy peak at 529.9 eV is related to the lattice oxygen atoms in the prepared material, while the binding energy peak at 531.89 eV is related to the -OH groups on the surface of the prepared material. The XPS spectrum shows that the prepared material mainly contains lithium, carbon, copper, and oxygen and is a new material.

[0039] See Figure 4 , Figure 4 for the first charge-discharge curve of the half-cell assembled with the prepared material and a lithium sheet at 0.1 Ag -1 . It can be seen that a discharge plateau appears at about 1.3 V, and the first discharge specific capacity is as high as 359 mAh g -1 , much higher than the theoretical specific capacity of commercial lithium titanate (175 mAh g -1 ).

[0040] See Figure 5 , Figure 5 for the rate performance diagram of the half-cell assembled with the prepared material and a lithium sheet. In the figure, the half-cell was subjected to 5 charge-discharge tests at each current density. At 0.1 Ag-1 , 0.3 Ag -1 , 0.5 Ag -1 , 0.7 Ag -1 and 1.0 Ag -1 The average discharge specific capacities are 309 mAh g -1 , 192 mAh g -1 , 153 mAh g -1 , 131 mAh g -1 and 106 mAh g -1 . After the above tests are completed, when the current density returns to 0.1 Ag -1 again, the average discharge specific capacity of the battery is still 255 mAh g -1 , showing good rate reversibility.

[0041] See Figure 6 , Figure 6 Figure, which is the relationship diagram between the discharge capacity and the number of cycles when the half-cell assembled with the prepared material and the lithium sheet is cycled 100 times at 1.0 Ag -1 . It can be seen that the initial discharge specific capacity of the battery is 169 mAh g -1 , and the discharge specific capacity after 100 cycles is 96 mAh g -1 . The capacity retention rate is close to 57%, indicating that the prepared material has good high-rate cycle stability. During the whole cycle process, the Coulomb efficiency (CE) value of the battery is about 95%, indicating that the energy loss is small during the whole test period.

[0042] See Figure 7 , Figure 7 Figure, which is the cyclic voltammogram of the half-cell assembled with the prepared material and the lithium sheet. The voltage test range is 0.01 V - 3 V, and the potential sweep rate is 1 mV s -1 . Multiple sets of redox peaks appear in the cyclic voltammogram curve. Generally, the oxidation peak corresponds to the process of lithium ion extraction, while the reduction peak corresponds to the process of lithium ion insertion. This indicates that lithium ions can freely insert and extract in the prepared material. In other words, the prepared material has the function of storing lithium and is a new type of anode material for lithium-ion batteries.

[0043] Example 2

[0044] Weigh LiOH and copper acetylacetonate according to the molar ratio of Li to Cu of 1:1.1 respectively. Place the two in an agate mortar and grind for 20 min to form a mixture. Then place the obtained mixture in a muffle furnace and calcine at 550 °C for 2 h in an air atmosphere to obtain the prepared material.

[0045] Weigh the prepared material, PVDF, and acetylene black according to a mass ratio of 9:1:1. After placing the three in an agate mortar, grind them thoroughly for 25 min. Then, add NMP drop by drop while stirring to adjust the mixture of the three into a paste. Subsequently, evenly apply the paste on a commercial copper foil current collector using a glass slide. Place the coated copper foil in a vacuum drying oven and dry it at 110 °C for 7 h. After naturally cooling to room temperature, take it out to obtain the electrode of the prepared material. Then, assemble it into a half-cell according to the method described in Example 1, and finally conduct an electrochemical performance test. The results show that at 0.1 Ag -1 the initial discharge specific capacity is 355 mAh g -1 ; at a high current density of 1.0 Ag -1 the discharge specific capacity after 100 cycles is 95 mAh g -1 , the Coulombic efficiency is close to 96%, and the battery capacity retention rate is close to 65%.

[0046] Example 3

[0047] Weigh LiOH and copper acetylacetonate according to a molar ratio of Li to Cu of 1:1.2. Place the two in an agate mortar and grind for 18 min to form a mixture. Then, place the obtained mixture in a muffle furnace and calcine it at 650 °C for 2 h in an air atmosphere to obtain the prepared material. Weigh the prepared material, PVDF, and acetylene black according to a mass ratio of 8:1:1. After placing the three in an agate mortar, grind them thoroughly for 22 min. Then, add NMP drop by drop while stirring to adjust the mixture of the three into a paste. Subsequently, evenly apply the paste on a commercial copper foil current collector using a glass slide. Place the coated copper foil in a vacuum drying oven and dry it at 120 °C for 8 h. After naturally cooling to room temperature, take it out to obtain the electrode of the prepared material. Then, assemble it into a half-cell according to the method described in Example 1, and finally conduct an electrochemical performance test. The results show that at 0.1 Ag -1 the initial discharge specific capacity is 365 mAh g -1 ; at a high current density of 1.0 Ag -1 the discharge specific capacity after 100 cycles is 96 mAh g -1 , the Coulombic efficiency is close to 96%, and the battery capacity retention rate is close to 66%.

[0048] Example 4

[0049] LiOH and copper acetylacetonate were weighed according to a molar ratio of Li to Cu of 1:1.3, and the two were placed in an agate mortar and ground for 25 minutes to form a mixture. The obtained mixture was then placed in a muffle furnace and calcined at 700°C for 2 hours in an air atmosphere to obtain the prepared material. The prepared material, PVDF and acetylene black were weighed according to a mass ratio of 8:1:1. The three were placed in an agate mortar and ground thoroughly for 25 minutes. After that, NMP was added dropwise, and the mixture of the three was adjusted into a paste while adding and stirring. Subsequently, the paste was evenly applied on a commercial copper foil current collector with a glass sheet, and the coated copper foil was placed in a vacuum drying oven, dried at 100°C for 7 hours, and taken out after naturally cooling to room temperature to obtain the electrode of the prepared material. Afterwards, a half-cell was assembled according to the method described in Example 1, and finally the electrochemical performance was tested. The results showed that at 0.1Ag -1 The first discharge capacity is 365 mAh g -1 ; at 1.0Ag -1 The discharge capacity after 100 cycles at a high current density is 93 mAh g -1 , the Coulombic efficiency is close to 95%, and the battery capacity retention rate is close to 62%.

[0050] Example 5

[0051] LiOH and copper acetylacetonate were weighed according to a molar ratio of Li to Cu of 1:1.4, and the two were placed in an agate mortar and ground for 20 minutes to form a mixture. The obtained mixture was then placed in a muffle furnace and calcined at 600°C for 1 hour in an air atmosphere to obtain the prepared material. The prepared material, PVDF and acetylene black were weighed according to a mass ratio of 8:1.4:1.4, and the three were placed in an agate mortar and ground thoroughly for 20 minutes. After that, NMP was added dropwise, and the mixture of the three was adjusted into a paste while adding and stirring. Subsequently, the paste was evenly applied on a commercial copper foil current collector with a glass sheet, and the coated copper foil was placed in a vacuum drying oven, dried at 110°C for 8 hours, and taken out after naturally cooling to room temperature to obtain the electrode of the prepared material. Afterwards, a half-cell was assembled according to the method described in Example 1, and finally the electrochemical performance was tested. The results showed that at 0.1Ag -1 The first discharge capacity is 375 mAh g -1 ; at 1.0Ag -1 The discharge capacity after 100 cycles at a high current density is 98 mAh g -1 , the Coulomb efficiency is close to 95%, and the battery capacity retention rate is close to 66%.

[0052] Example 6

[0053] LiOH and copper acetylacetonate were weighed according to a molar ratio of Li to Cu of 1:1.5, and the two were placed in an agate mortar and ground for 20 minutes to form a mixture. The resulting mixture was then placed in a muffle furnace and calcined at 600°C for 2.5 hours in an air atmosphere to obtain the prepared material. The prepared material, PVDF and acetylene black were weighed according to a mass ratio of 8:1.2:1.2. The three were placed in an agate mortar and ground for 25 minutes. After that, NMP was added dropwise, and the mixture was adjusted into a paste while adding and stirring. Subsequently, the paste was evenly applied to a commercial copper foil current collector with a glass sheet, and the coated copper foil was placed in a vacuum drying oven, dried at 110°C for 6 hours, and taken out after naturally cooling to room temperature to obtain the electrode of the prepared material. Afterwards, a half-cell was assembled according to the method described in Example 1, and finally the electrochemical performance was tested. The results showed that at 0.1Ag -1 The first discharge capacity is 365 mAh g -1 ; at 1.0Ag -1 The discharge capacity after 100 cycles at a high current density is 97 mAh g -1 , the Coulomb efficiency is close to 97%, and the battery capacity retention rate is close to 61%.

Claims

1. A preparation method of a lithium-ion battery anode material containing lithium, carbon, copper and oxygen, characterized in that, It includes the following steps: (1) Preparation of materials The materials include lithium hydroxide, copper acetylacetonate, 1 mol L -1 LiPF6 organic electrolyte, acetylene black, polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP); (2) Preparation of the inventive material Weigh lithium hydroxide and copper acetylacetonate respectively according to the molar ratio of Li to Cu being 1:(1.0 - 1.5). Place the two in an agate mortar and grind for 10 - 50 min to form a mixture. Subsequently, place the obtained mixture in a muffle furnace and calcine it at 500°C - 700°C for 1 - 3 h in an air atmosphere to obtain the prepared material; (3) Preparation of the electrode and assembly of the battery Weigh the prepared material, PVDF, and acetylene black according to the mass ratio of (8 - 9):(1 - 1.5):(1 - 1.5). Place the three in an agate mortar and grind thoroughly for 10 - 50 min. Then, gradually add NMP drop by drop while stirring to make the mixture of the three into a paste. Subsequently, use a glass slide to evenly coat the paste on a commercial copper foil current collector. Then, place the coated copper foil current collector in a vacuum drying oven and dry it at 100 - 130°C for 4 - 8 h. Take it out after naturally cooling to room temperature to obtain the electrode containing the prepared material; Use the prepared electrode as the positive electrode, a lithium sheet as the negative electrode, a Celgard 2400 microporous polypropylene membrane as the separator, and LiPF6 as the electrolyte to assemble a half-cell in a glove box filled with nitrogen for electrochemical performance testing.

2. The preparation method according to claim 1, characterized in that: In step (2), when weighing and grinding lithium hydroxide and copper acetylacetonate, the molar ratio of Li to Cu is 1:1.

1.

3. The preparation method according to claim 1, characterized in that: In step (2), the calcination temperature of the mixture of lithium hydroxide and copper acetylacetonate in the muffle furnace is 600°C.

4. The preparation method according to claim 1, characterized in that: In step (2), the calcination time of the mixture of lithium hydroxide and copper acetylacetonate in the muffle furnace is 2 h.

5. The preparation method according to claim 1, characterized in that: In step (2), the mixture of lithium hydroxide and copper acetylacetonate is ground in an agate mortar for 20 min.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of the prepared material, PVDF, and acetylene black is 8:1:

1.

7. The preparation method according to claim 1, characterized in that: In step (3), the concentration of the LiPF6 electrolyte is 1 mol / L -1 .

8. The preparation method according to claim 1, characterized in that: In step (3), the grinding time of the mixture of the prepared material, acetylene black, and PVDF is 20 min.

9. The preparation method according to claim 1, wherein: In step (3), during the electrode preparation process, the drying temperature in the vacuum drying oven is 120°C.

10. The preparation method according to claim 1, characterized in that: In step (3), during the electrode preparation process, the drying time is 6 hours.

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