Transition metal doped black phosphorus-graphite composite material based on secondary ball milling method and application thereof

Abstract

The invention discloses a preparation method of a transition metal doped black phosphorus-graphite composite material based on a secondary ball milling method, which comprises the following steps: carrying out ball milling on black phosphorus and a transition metal precursor in an inert atmosphere to enable atomic-scale metal to preferentially react with the black phosphorus and form a stable M-P bond to obtain the transition metal doped black phosphorus; then, the obtained doped product and graphite are subjected to secondary ball milling, so that the doped product is uniformly embedded into a carbon material framework, a continuous conductive network is constructed, the obtained composite material can effectively inhibit irreversible collapse and serious volume expansion of a black phosphorus structure in the circulation process, interface bonding between the black phosphorus and the graphite is enhanced, and the performance of the composite material is improved. The charge transfer impedance is obviously reduced, the lithium ion diffusion rate is improved, and the electron transmission efficiency of the material is obviously improved; meanwhile, the atomic-scale dispersion structure can achieve a higher metal atom utilization rate, and when the composite negative electrode material is applied to a lithium ion battery, the composite negative electrode material has high specific capacity and excellent cycling stability and rate capability and has a wide fast charge energy storage application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemical material preparation and application, and particularly relates to a preparation method of a transition metal doped black phosphorus-graphite composite material based on a secondary ball milling method and application thereof in lithium ion batteries. BACKGROUND

[0002] With the rapid development of new energy vehicles, consumer electronics and energy storage systems, secondary batteries are required to have higher energy density, longer cycle life and faster charge and discharge performance. Black phosphorus, as a new type of layered phosphorus material, has a theoretical specific capacity of 2596 mAh g -1 , which is about 7 times that of graphite; at the same time, its electronic conductivity can reach 300 S m -1 , and the lithium ion diffusion energy barrier is as low as about 0.05 eV, which has the potential of high energy density and fast charge and discharge, and is considered to be an ideal candidate for negative electrode materials.

[0003] However, black phosphorus will undergo a multi-stage phase transformation initiated by P-P bond rupture during lithium ion charge and discharge, gradually transform into LiP chain structure through Li3P7 intermediate phase, and finally generate Li3P. Except for the transformation between Li3P7 and LiP, the remaining stages are prone to evolve into disordered phases during delithiation, leading to structural irreversible collapse and gradual capacity decay. At the same time, black phosphorus is accompanied by more than 300% volume expansion during alloying, which easily causes particle pulverization and destruction of the conductive framework, limiting its cycle life and rate performance. To improve the above problems, the prior art mostly composites black phosphorus with carbon materials (such as graphite, carbon nanotubes, etc.) to improve the conductivity and buffer the volume change. For example: the patent application with publication number CN113437281A composites black phosphorus, nano-graphite powder and nitrogen-doped carbon nanotube by ball milling, effectively improves the stability of the black phosphorus composite negative electrode material by constructing P-C and P-O-C bonds. The patent with publication number CN116826005A composites black phosphorus, β-Al2O3 and acetylene black by ball milling, effectively improves the rate performance and cycle stability of the black phosphorus composite negative electrode material by constructing P-C and P-Al chemical bonds. The patent with publication number CN116825968A dissolves butadiene rubber, sodium carboxymethyl cellulose and cationic polyacrylamide in water according to a certain mass ratio to prepare a self-healing adhesive, so that the black phosphorus composite negative electrode material has better rate performance and cycle stability. The patent with publication number CN119029160A composites black phosphorus, Na3Zr2Si2PO 12And carbon nanotube ball milling composite, by strong coupling way and the generation P-O-C bond, improve the rate performance and cycle stability of black phosphorus negative electrode material. Although the above strategy has played a certain effect, but so far disclosed technology has failed to solve the black phosphorus or black phosphorus composite negative electrode sheet in the long cycle process interface easy to loose and peeling, composite network structure is unstable, difficult to long-term maintain continuous electron / ion channel problem. On the other hand, metal doping is considered to be an important way to enhance the stability of black phosphorus structure, however, traditional large particle materials or nanocluster materials and ball milling composite can not solve the problem of low first coulomb efficiency, more can not solve the problem of low first coulomb efficiency while considering the problem of improving the cycle stability. More importantly, in the common one-step ball milling process, if graphite and metal precursors are introduced at the same time, there will be competition between graphite and metal in the bonding, resulting in insufficient M-P bond between black phosphorus and metal, insufficient doping, thereby limiting the stability and performance of the composite structure. SUMMARY

[0004] In order to solve the problem that black phosphorus is easy to collapse in the cycle process, volume expansion and weak combination with carbon material leads to unstable composite structure in the prior art, and aiming at the defect that there is a competition between black phosphorus and graphite in the one-step ball milling method, resulting in insufficient transition metal doping, the present application provides a preparation method of transition metal doped black phosphorus-graphite composite negative electrode material based on secondary ball milling method.

[0005] The preparation method of the transition metal doped black phosphorus-graphite composite negative electrode material of the present application is as follows: (1) Under inert atmosphere, mix black phosphorus and transition metal precursor, add grinding balls, mix ball mill at 700-1700 rpm for 10-20 h, to obtain transition metal doped black phosphorus (M-BP); The transition metal precursor is selected from phthalocyanine iron, phthalocyanine cobalt, phthalocyanine nickel, tetraphenylporphyrin iron, tetraphenylporphyrin cobalt, tetraphenylporphyrin nickel, and hematin; the mass ratio of black phosphorus to transition metal precursor is 9:1-7:3; (2) Under inert atmosphere, mix the transition metal doped black phosphorus with graphite powder, add grinding balls, secondary ball mill at 700-1700 rpm for 10-20 h, to obtain transition metal doped black phosphorus-graphite composite material.

[0006] The graphite powder is a conventional commercially available product with a particle size of less than 1 μm, and the mass ratio of transition metal doped black phosphorus to graphite powder is 9:1-5:5; The ball milling method in the above method is high-energy planetary ball milling, the ball milling tank is a stainless steel ball milling tank or an agate ball milling tank, and the grinding balls are selected from zirconia balls, agate balls or stainless steel balls; the diameter of the grinding balls is 1-15 mm, and the mass ratio of the grinding balls to the mixed materials in step (1) or step (2) is 50-100:1; The transition metal doped black phosphorus / graphite composite material prepared by the above method is used as a negative electrode of a lithium ion battery, and in the electrochemical performance test, the stable performance can still be maintained under high rate conditions, and excellent capacity retention and rate performance are exhibited under long cycle and fast charging conditions.

[0007] Advantages or technical effects of the present application: 1. The present application can effectively limit the irreversible rupture and disordered transformation of P-P bonds in the alloying / deloyling process by preferentially forming stable M-P bonds in the first step of ball milling, so as to anchor metal atoms to the black phosphorus skeleton, thereby inhibiting structural collapse, significantly slowing down capacity decay and improving cycle stability; 2. In the second step of ball milling, the pre-doped M-BP is uniformly compounded into the graphite skeleton, the graphite provides a flexible conductive network, can disperse stress during charging and discharging, cooperates with the M-P bond to relieve up to 300% volume expansion, avoids particle pulverization and electrode structure damage; compared with the composite of traditional nanoclusters or large particle materials, the metal atoms in the atomic level transition metal material are uniformly distributed on the surface of black phosphorus in an isolated form, forming high-density active sites, and avoiding the agglomeration problem of active sites in nanoclusters or large particle materials; 3. The introduction of transition metal enhances the interface bonding between black phosphorus and graphite, avoiding the problem of interface loosening and falling off in the traditional BP / G composite material; at the same time, the continuous graphite conductive skeleton significantly reduces the charge transfer impedance, improves the electronic conductivity and lithium ion diffusion rate, so that the stable performance can still be maintained under high rate conditions; 4. Different from direct co-milling, the secondary ball milling strategy of the present application avoids the competition between graphite and transition metal in bonding, ensures that the metal is fully doped into black phosphorus and forms more stable M-P bonds, so that the stability of the composite structure is greatly improved. Therefore, the negative electrode material exhibits excellent capacity retention and rate performance under long cycle and fast charging conditions, and has good practical application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 The atomic phase aberration electron microscopy (AC-TEM) spectrum of the composite material FePc-BP / G-2 of Example 1 of the present application; Figure 2 The electrochemical impedance spectroscopy (EIS) graph of the composite material FePc-BP / G-2 of Example 1 of the present application and the composite material of Comparative Example 1; Figure 3The long cycle performance comparison chart under the current density of 15 A·g of the composite material FePc-BP / G-2 of the embodiment 1 of the present application and the composite material of the comparative example 1. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material FePc-BP / G-2 of the embodiment 1 of the present application and the composite material of the comparative example 1. Figure 4 The long cycle performance comparison chart under the current density of 15 A·g of the composite material FePc-BP / G-2 of the embodiment 1 of the present application and the composite material Fe-BP / G-1 of the comparative example 2. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material FePc-BP / G-2 of the embodiment 1 of the present application and the composite material Fe-BP / G-1 of the comparative example 2. Figure 5 The long cycle performance comparison chart under the current density of 15 A·g of the composite material FePc-BP / G-2 of the embodiment 1 of the present application and the composite material Fe-RP / G-2 of the comparative example 3. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material FePc-BP / G-2 of the embodiment 1 of the present application and the composite material Fe-RP / G-2 of the comparative example 3. Figure 6 The long cycle performance comparison chart under the current density of 15 A·g of the composite material CoPc-BP / G-2 of the embodiment 2 of the present application and the comparative example 1. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material CoPc-BP / G-2 of the embodiment 2 of the present application and the comparative example 1. Figure 7 The long cycle performance comparison chart under the current density of 15 A·g of the composite material NiPc-BP / G-2 of the embodiment 2 of the present application and the comparative example 1. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material NiPc-BP / G-2 of the embodiment 2 of the present application and the comparative example 1. Figure 8 The long cycle performance comparison chart under the current density of 15 A·g of the composite material TPPFeCl-BP / G-2 of the embodiment 2 of the present application and the comparative example 1. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material TPPFeCl-BP / G-2 of the embodiment 2 of the present application and the comparative example 1. Figure 9 The long cycle performance comparison chart under the current density of 15 A·g of the composite material Heme-BP / G-2 of the embodiment 2 of the present application and the comparative example 1. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material Heme-BP / G-2 of the embodiment 2 of the present application and the comparative example 1.

[0009] Figure 10 The long cycle performance comparison chart under the current density of 15 A·g of the composite material of the embodiment 3 of the present application and the comparative example 1. -1 The long cycle performance comparison chart under the current density of 15 A·g of the composite material of the embodiment 3 of the present application and the comparative example 1. DETAILED DESCRIPTION

[0010] The present application will be further described below in conjunction with specific examples, but it should be understood that these examples are only used to illustrate the technical solutions of the present application and do not constitute a limitation on the protection scope of the present application. Any equivalent replacement or modification based on the present application should be considered to fall within the protection scope of the present application without departing from the concept of the present application. Unless otherwise specified, the experimental methods used in the examples are conventional methods known to those skilled in the art; and unless otherwise specified, the reagents and raw materials used are conventional commercial goods.

[0011] In the following examples, the particle size of the graphite powder is less than 1 μm. Example 1: Preparation method of transition metal doped black phosphorus-graphite composite negative electrode material based on secondary ball milling method as follows: 1. In an argon-filled glove box (O2 and H2O content is not higher than 0.10 ppm), 0.9 g of black phosphorus and 0.1 g of iron phthalocyanine powder were weighed and mixed in a 50 mL stainless steel ball mill pot, 80 g of zirconium oxide grinding balls were added, the grinding balls were composed of different particle sizes, including 6 balls with a diameter of 15 mm and 20 balls with a diameter of 5 mm; high-energy planetary ball milling was used, the ball milling speed was set to 1700 rpm, and continuous ball milling was carried out for 12 h in bidirectional operation mode. After that, the ball mill pot was opened in the argon environment of the glove box and the product was collected, obtaining iron phthalocyanine doped black phosphorus (FePc-BP) powder; 2. 0.7 g of iron phthalocyanine doped black phosphorus (FePc-BP) powder and 0.3 g of commercially available micron-sized graphite powder were placed in a 50 mL stainless steel ball mill pot, 80 g of zirconium oxide grinding balls were added, the grinding balls were composed of different particle sizes, including 6 balls with a diameter of 15 mm and 20 balls with a diameter of 5 mm; high-energy ball milling was used, the ball milling speed was set to 1700 rpm, and continuous ball milling was carried out for 12 h in bidirectional operation mode. After that, the ball mill pot was opened in the argon environment of the glove box and the product was collected, obtaining iron phthalocyanine doped black phosphorus-graphite composite material (FePc-BP / G-2) powder; the atomically resolved transmission electron microscopy (AC-TEM) image of the composite material FePc-BP / G-2 is shown in Figure 1 As can be seen from the figure, the single atoms of the composite material FePc-BP / G-2 appear as discrete bright spots, and the single atoms are uniformly distributed, showing atomic-level dispersion characteristics; Meanwhile, comparative example 1, comparative example 2 and comparative example 3 were set up. Comparative example 1: In an argon-filled glove box (O2 and H2O content is not higher than 0.10 ppm), 0.7 g of black phosphorus and 0.3 g of graphite powder (mass ratio 7:3) were weighed and placed in a 50 mL stainless steel ball mill pot, and about 80 g of zirconium oxide grinding balls were added. The grinding balls were composed of different particle sizes, including 6 balls with a diameter of 15 mm and 20 balls with a diameter of 5 mm, high-energy planetary ball milling was used, the ball milling speed was set to 1700 rpm, and continuous ball milling was carried out for 12 h in bidirectional operation mode. After that, the ball mill pot was opened in the argon environment of the glove box and the product was collected, obtaining black phosphorus-graphite composite material (BP / G) powder.

[0012] Comparative Example 2 is a composite material prepared by one-step grinding method. In an argon-filled glove box (O2 and H2O content is not higher than 0.10 ppm), 0.63 g of black phosphorus, 0.07 g of iron powder and 0.3 g of graphite powder were weighed and placed in a 50 mL stainless steel ball mill jar, 80 g of zirconium oxide grinding balls were added, the grinding balls were composed of different particle size balls, including 6 balls with a diameter of 15 mm and 20 balls with a diameter of 5 mm, a high-energy planetary ball mill was used, the rotation speed was set to 1700 rpm, and the continuous ball milling was carried out for 12 h under bidirectional operation mode. After that, the ball mill jar was opened in the argon environment of the glove box and the product was collected to obtain an iron-doped black phosphorus-graphite composite material (Fe-BP / G-1) powder based on one-step method; Comparative Example 3 composite material Fe-RP / G-2 was prepared by the same method as Example 1, except that red phosphorus was used to replace black phosphorus and iron powder was used to replace iron phthalocyanine powder; 3. The above composite materials were tested by using Chenhua 760 workstations for AC impedance test, the test range was 0.01-10000 kHz, and the results were shown in Figure 2 The charge transfer impedance of the composite material FePc-BP / G-2 of the present example was 24.26 ohm, which was much smaller than 748.0 ohm of the composite material BP / G of Comparative Example 1, indicating that the composite material of the present application had a lower interface charge transfer impedance.

[0013] 4. Electrochemical performance test The composite materials prepared in Example 1 and Comparative Examples 1-3 were used as negative electrodes of lithium ion batteries, the composite materials, conductive carbon black (conductive agent) and sodium alginate (binder) were mixed in a mass ratio of 7:1.5:1.5, and then coated on a copper foil with a coating thickness of 150 μm. After vacuum drying for one night, the electrode sheet was cut and prepared; CR2023 button cell batteries were assembled in an argon-filled glove box environment (O2 and H2O content was not higher than 0.10 ppm). The prepared and dried electrode sheet was transferred into the glove box, matched with a metal lithium sheet (counter electrode and reference electrode), separated by a polypropylene separator, and dropped with several drops of 1M LiPF6 solution in EC:DEC (volume ratio 1:1) containing 5wt% FEC additive electrolyte solution; finally, the battery was sealed and placed for 8 hours. The rested battery was placed in a new battery test system for testing, wherein the charge and discharge voltage window was set to 0.01-3V; the charge and discharge was carried out in a constant current mode, the current density was 15A·g -1 , the detection results were shown in Figure 3 、 4 , 5; From the long cycle curve of Figure 3 , it can be seen that the current density was 15A·g -1After 400 cycles at a current density, the discharge specific capacity of the FePc–BP / G-2 composite material in this embodiment increased from 1150.95 mAh g⁻¹. -1 Decreased to 929.82mAhg -1 The corresponding capacity retention rate was 80.85%; the discharge specific capacity of the composite material in Comparative Example 1 was 1012.24 mAh g. -1 Decreased to 412.89 mAhg -1 The corresponding capacity retention rate is 40.79%. Due to the doping of transition metal iron, the interfacial combination between black phosphorus and graphite is enhanced, forming a stable composite network structure. This avoids the problems of interface loosening and shedding in traditional BP / G composite materials. At the same time, it significantly reduces charge transfer impedance, improves electronic conductivity and lithium-ion diffusion rate, thereby improving the rate performance and cycle stability of lithium-ion batteries.

[0014] Depend on Figure 4 It can be seen that the discharge specific capacity of the Fe-BP / G-1 composite material in Comparative Example 2 is 1021.2 mAh g. -1 Decayed to 320.49 mAhg -1 The corresponding capacity retention rate was 31.38%. In the preparation of the composite material in Example 1, the transition metal precursor was first ball-milled with black phosphorus, allowing the metal to be fully doped and form a greater number of MP bonds with black phosphorus, thereby significantly enhancing the structural stability and interfacial bonding performance of the material. In contrast, Comparative Example 2 used a one-step method to simultaneously ball-mill black phosphorus, graphite, and transition metal. Due to the competition between graphite and black phosphorus at bonding sites, the number of MP bonds formed was limited, the doping was insufficient, and the stability of the composite structure was significantly insufficient. Therefore, its long-cycle performance was significantly lower than that of the material in Example 1.

[0015] Depend on Figure 5 It can be seen that the discharge specific capacity of the Fe–RP / G-2 composite material in Comparative Example 3 is 989.72 mAh g⁻¹. -1 Decreased to 565.43 mAhg -1 The corresponding capacity retention rate was 57.13%. Red phosphorus was used instead of black phosphorus. Although secondary ball milling and doping were also performed, red phosphorus itself has low electronic and ionic conductivity and an amorphous structure. It does not have the layered and plate-like characteristics of black phosphorus and it is difficult to construct a stable composite network. This results in poor interfacial bonding and discontinuous transport channels. Therefore, its cycle performance is significantly worse than that of the composite material in Example 1.

[0016] Example 2: The preparation of the composite material in this example is the same as in Example 1, except that cobalt phthalocyanine powder, nickel phthalocyanine powder, tetraphenylporphyrin iron, and heme are used to replace iron phthalocyanine powder, respectively, to prepare composite materials CoPc–BP / G-2, NiPc–BP / G-2, TPPFeCl–BP / G-2, and Heme-BP / G-2. The battery assembly and electrochemical performance testing methods are the same as in Example 1, and the results are shown in 6-9; Depend on Figure 6 It can be seen that at 15A·g -1 After 400 cycles at a current density, the discharge specific capacity of the composite material CoPc–BP / G-2 increased from 1230.95 mAh g. -1 Decreased to 750.63 mAhg -1 The corresponding capacity retention rate is 60.98%, and its rate performance and cycle stability are better than those of Comparative Example 1. Depend on Figure 7 It can be seen that at 15A·g -1 After 400 cycles at a current density, the discharge specific capacity of the NiPc–BP / G-2 composite material increased from 995.21 mAh g⁻¹. -1 Decreased to 654.15mAhg -1 The corresponding capacity retention rate is 65.73%, and its rate performance and cycle stability are better than those of Comparative Example 1. Depend on Figure 8 It can be seen that at 15A·g -1 After 400 cycles at a current density, the discharge specific capacity of the composite material TPPFeCl–BP / G-2 increased from 1066.37 mAh g⁻¹. -1 Decreased to 569.4 mAhg -1 The corresponding capacity retention rate was 53.40%, and its rate performance and cycle stability were better than those of Comparative Example 1. Depend on Figure 9 It can be seen that at 15A·g -1 After 400 cycles at a current density, the discharge specific capacity of the Heme-BP / G-2 composite material increased from 1031.12 mAh g. -1 Decreased to 676.45mAhg -1 The corresponding capacity retention rate is 65.60%, and its rate performance and cycle stability are better than those of Comparative Example 1.

[0017] Example 3: The preparation method of transition metal-doped black phosphorus / graphite composite anode material based on secondary ball milling is as follows: 1. In an argon-filled glove box (O2 and H2O content is not higher than 0.10 ppm), 0.7 g of black phosphorus and 0.3 g of iron phthalocyanine powder were weighed and mixed in a 50 mL stainless steel ball mill jar, 60 g of zirconium oxide grinding balls were added, the grinding balls were composed of balls of different particle sizes, including 15 mm in diameter and 5 mm in diameter; high-energy planetary ball milling was used, the ball milling speed was set to 900 rpm, and the ball milling was continuously carried out for 15 h in a bidirectional operation mode, then the ball mill jar was opened in an argon environment in the glove box, and the product was collected, to obtain iron phthalocyanine doped black phosphorus (FePc-BP) powder; 2. 0.8 g of iron phthalocyanine doped black phosphorus (FePc-BP) powder and 0.2 g of commercially available micron-sized graphite powder were placed in a 50 mL stainless steel ball mill jar, 60 g of zirconium oxide grinding balls were added, the grinding balls were composed of balls of different particle sizes, including 15 mm in diameter and 5 mm in diameter; high-energy ball milling was used, the ball milling speed was set to 900 rpm, and the ball milling was continuously carried out for 15 h in a bidirectional operation mode, then the ball mill jar was opened in an argon environment in the glove box, and the product was collected, to obtain iron phthalocyanine doped black phosphorus / graphite composite material powder; The battery was assembled and the electrochemical performance test was carried out according to the method of Example 1, and the results are shown in Figure 10 The discharge specific capacity of the composite material FePc-BP / G-2 of the present example decreased from 1123.53 mAhg -1 to 768.71 mAhg -1 , and the corresponding capacity retention rate was 68.42%, the rate performance and cycle stability were better than those of Comparative Example 1.

[0018] It should be noted that the embodiments disclosed in the present application are only used to illustrate the technical solutions of the present application, and not to limit the protection scope thereof. Those skilled in the art can make various modifications, substitutions or improvements to the above embodiments without departing from the core idea of the present application, and these equivalent technical solutions should be covered within the protection scope of the present application.

Claims

1. A method for preparing transition metal-doped black phosphorus-graphite composite based on a secondary ball milling method, characterized in that, The method comprises the following steps: (1) mixing black phosphorus and transition metal precursor under inert atmosphere, adding grinding balls, mixing ball milling at a speed of 700-1700 rpm for 10-20 h to obtain transition metal doped black phosphorus; (2) mixing the transition metal doped black phosphorus and graphite powder under inert atmosphere, adding grinding balls, secondary ball milling at a speed of 700-1700 rpm for 10-20 h to obtain transition metal doped black phosphorus-graphite composite material.

2. The production method according to claim 1, characterized by, The transition metal precursor in step (1) is selected from phthalocyanine iron, phthalocyanine cobalt, phthalocyanine nickel, tetraphenylporphyrin iron, tetraphenylporphyrin cobalt, tetraphenylporphyrin nickel, and hematin.

3. The method of claim 1, wherein: The mass ratio of black phosphorus to transition metal precursor is 9:1-7:

3.

4. The method of claim 1, wherein: The mass ratio of transition metal doped black phosphorus to graphite powder is 9:1-5:

5.

5. The method of claim 1, wherein: The diameter of the grinding ball is 1-15 mm, and the mass ratio of grinding ball to mixed material in step (1) or step (2) is 50-100:

1.

6. Application of the transition metal doped black phosphorus-graphite composite material prepared by the preparation method in any one of claims 1-5 to negative electrode of lithium ion battery.

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