A battery negative electrode material and its preparation method and application

Abstract

The present invention discloses a battery negative electrode material, its preparation method, and application. The battery negative electrode material includes an active material; the active material is a composite material containing bismuth phosphate, phosphorus, bismuth, and a conductive carbon material. By introducing bismuth phosphate into the active material, the battery negative electrode material of the present invention can, on the one hand, improve the dispersion of the conductive carbon material, phosphorus, and crystalline bismuth, thereby preventing agglomeration. Furthermore, since bismuth phosphate is an inactive component, the presence of bismuth phosphate in the active material can effectively mitigate the significant volume changes during charge and discharge, facilitating the stabilization of the SEI film, thereby imparting improved cycling stability to the electrode material.

Description

Technical Field

[0001] The present invention belongs to the field of batteries, and in particular relates to a battery negative electrode material and a preparation method and application thereof. Background Art

[0002] Compared with lithium-ion batteries and sodium-ion batteries (NIBs), potassium-ion batteries (PIBs) have become a promising alternative due to their abundant potassium resources. + Compared with / Na (-2.71 V), PIBs showed a lower K + / K redox potential (-2.93V), and a small Stokes radius in common electrolytes Therefore, PIBs have the advantage of low production cost and are the main candidate materials for large-scale energy storage systems.

[0003] Recently, bismuth has attracted much attention due to its relatively high theoretical specific capacity, reasonable voltage platform and cost-effectiveness. In particular, bismuth has a layered crystal structure and semi-metallic conductivity with a large interlayer spacing along the c-axis. This makes it an ideal candidate for anode materials in rechargeable batteries. + The ionic radius of Bi anode is large, and the volume change of Bi anode is significant during the cycle, which leads to material pulverization and continuous side reactions between electrode and electrolyte. In addition, the wrinkled layer structure and semi-metallic conductivity of Bi anode also limit the electron transport and K + Therefore, it is imperative to solve the problem of large volume expansion of Bi anode, improve electronic conductivity and improve K + diffusion to improve its electrochemical performance. Summary of the Invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, one of the objectives of the present invention is to provide a battery negative electrode material.

[0005] A second object of the present invention is to provide a method for preparing the above-mentioned battery negative electrode material.

[0006] A third object of the present invention is to provide a battery negative electrode.

[0007] A fourth object of the present invention is to provide a potassium ion battery.

[0008] A fifth object of the present invention is to provide applications of the above-mentioned battery negative electrode material and / or battery negative electrode in the battery field.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] A first aspect of the present invention provides a battery negative electrode material, comprising an active material; the active material is a composite material containing bismuth phosphate, phosphorus, bismuth and a conductive carbon material.

[0011] Preferably, the bismuth phosphate is amorphous.

[0012] Preferably, the bismuth is crystalline.

[0013] Preferably, based on the total mass percentage of the composite material being 100%, the mass percentage of the bismuth phosphate is 20-40%, for example, can be selected from 20%, 25%, 30%, 35%, and 40%.

[0014] Preferably, the phosphorus is red phosphorus.

[0015] Preferably, based on the total mass percentage of the bismuth phosphate, the phosphorus and the bismuth being 100%, the mass percentage of the conductive carbon material is 10-30%, for example, 10%, 15%, 20%, 25% or 30%.

[0016] The second aspect of the present invention provides a method for preparing the battery negative electrode material provided in the first aspect of the present invention, comprising the following steps:

[0017] The raw materials of the active material are mixed and then ground to obtain the active material; the raw materials of the active material include bismuth oxide, phosphorus and conductive carbon material.

[0018] Preferably, the grinding step is performed by ball milling.

[0019] Preferably, the ball milling speed is 100 to 1000 rpm; further preferably, the ball milling speed is 500 to 1000 rpm; further preferably, the ball milling speed is 500 to 900 rpm.

[0020] Preferably, the ball milling time is 1 to 10 hours; further preferably, the ball milling time is 4 to 10 hours; more preferably, the ball milling time is 6 to 10 hours.

[0021] Preferably, the mass ratio of the grinding balls to the raw materials of the active material is (30-40):1.

[0022] Preferably, the ball milling step is performed under the protection of an inert gas.

[0023] Preferably, the inert gas is selected from at least one of nitrogen, xenon and argon.

[0024] Preferably, the molar ratio of bismuth oxide to phosphorus is 1:(0.1-20); further preferably, the molar ratio of bismuth oxide to phosphorus is 1:(0.1-10); further preferably, the molar ratio of bismuth oxide to phosphorus is 1:(1-10); more preferably, the molar ratio of bismuth oxide to phosphorus is 1:(1-3).

[0025] In the present invention, the amorphous bismuth phosphate (BiPO4, an inactive ingredient) is formed in situ during the ball milling process. Bismuth phosphate can also play a grinding aid role during the ball milling process, reducing the aggregation and regeneration of active ingredients (conductive carbon material, phosphorus and crystalline bismuth), increasing the dispersibility of the active ingredients, and facilitating the reduction of the particle size of the active ingredients and improving the utilization rate of the active ingredients. In addition, by doping the active ingredients with inactive ingredients, the present invention can solve the volume expansion problem of the active ingredients, improve the huge volume change during the charge and discharge process of the battery negative electrode material, and facilitate the stability of the SEI film, thereby giving the electrode material better cycle stability.

[0026] Preferably, the ratio of the total mass of the bismuth oxide (Bi2O3) and P to the mass of the conductive carbon material is 100:(10-30).

[0027] Preferably, the conductive carbon material comprises at least one of graphite, graphene, carbon nanotubes, carbon nanofibers, carbon nanodots, carbon nanocones, coke, activated carbon, conductive carbon black, and acetylene black. When two or more conductive carbon materials are present, the two or more conductive carbon materials may be mixed in any proportion. Further preferably, the conductive carbon material is selected from at least one of graphite, conductive carbon black, and acetylene black.

[0028] During ball milling, chemical bonds are formed between bismuth, phosphorus, and the conductive carbon material, improving the electrochemical performance of the active material. However, the resulting composite material may agglomerate, significantly reducing its dispersibility compared to the bismuth phosphate-doped active material of the present invention. Furthermore, amorphous bismuth phosphate can withstand greater volume changes than crystalline bismuth. Its isotropic nature also promotes ion diffusion, addressing the problem of electrode volume expansion.

[0029] The third aspect of the present invention provides a battery negative electrode, comprising the battery negative electrode material described in the first aspect of the present invention.

[0030] The fourth aspect of the present invention provides a potassium ion battery, comprising the battery negative electrode material described in the first aspect of the present invention; or the battery negative electrode described in the third aspect of the present invention.

[0031] The fifth aspect of the present invention provides the use of the battery negative electrode material described in the first aspect of the present invention and / or the battery negative electrode described in the third aspect of the present invention in the battery field.

[0032] The beneficial effects of the present invention are as follows: the battery negative electrode material of the present invention can improve the dispersion effect of the conductive carbon material, phosphorus, and crystalline bismuth by introducing bismuth phosphate into the active material, thereby avoiding the occurrence of agglomeration; on the other hand, bismuth phosphate is an inactive component, and the bismuth phosphate present in the active material can effectively improve the huge volume change during the charge and discharge process, which is beneficial to the stability of the SEI film, thereby giving the electrode material better cycle stability, increasing the ion diffusion rate of the battery, and improving the battery cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the preparation process of the battery negative electrode material in Example 1.

[0034] Figure 2 These are XRD test patterns of the battery negative electrode materials in Example 1 and Comparative Examples 1-2.

[0035] Figure 3 This is the SEM image of the battery negative electrode material in Example 1.

[0036] Figure 4 This is the HRTEM image of the battery negative electrode material in Example 1.

[0037] Figure 5 This is the EDS mapping diagram of the battery negative electrode material in Example 1.

[0038] Figure 6 1 and 2 are X-ray CT spectra of the battery negative electrode materials in Example 1 and Comparative Examples 1 and 2.

[0039] Figure 7 This is a thermogravimetric curve test diagram of the battery negative electrode material in Example 1.

[0040] Figure 8 This is a cycle performance test diagram of a half-cell formed by Bi@P@BiPO4@C, Bi@P@C, and Bi@C in an embodiment of the present invention.

[0041] Figure 9 TEM images of the battery negative electrode materials in Example 1 and Comparative Example 1 after 500 charge and discharge cycles.

[0042] Figure 10 The X-ray CT spectra of the battery negative electrode materials in Example 1 and Comparative Example 1 before and after cycling.

[0043] Figure 11 Schematic diagram of the structure of the full battery assembled from Bi@P@BiPO4@C in Example 1.

[0044] Figure 12This is a cycle performance test diagram of the full battery formed by Bi@P@BiPO4@C in Example 1.

[0045] Figure 13 This is a test chart of the charge and discharge performance of the battery negative electrode materials in Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0046] The specific implementation of the present invention will be further described in detail below in conjunction with the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0047] Example 1

[0048] Reference Figure 1 The preparation flow chart in this example provides a method for preparing a battery negative electrode material, and the specific steps are as follows:

[0049] The following raw materials were added to a stainless steel grinding bowl: P (0.11 g) and Bi2O3 (Aladdin, AR, 0.551 g). The mixture was ball-milled at 800 rpm in an Ar atmosphere for 6 hours to obtain a mixture. Then, 0.5 g of the mixture was removed and added to a stainless steel grinding bowl. 0.1 g of conductive carbon black (Super P) was added, with the weight ratio of steel ball to powder (i.e., mixture and Super P) being 40:1. The mixture was ball-milled at 800 rpm in an Ar atmosphere for 6 hours to obtain a crystalline Bi@P nanocomposite material doped with amorphous bismuth phosphate (BiPO4) (denoted as Bi@P@BiPO4@C), which served as the battery negative electrode material in this example. The weight percentage of bismuth phosphate was 30 wt%, based on the weight percentage of the battery negative electrode material as 100%.

[0050] Comparative Example 1

[0051] This example provides a method for preparing a negative electrode material for a battery, the specific steps of which are:

[0052] The following raw materials were added to a stainless steel grinding bowl: P (in an amount of 0.11 g) and Bi (Aladdin, AR, in an amount of 0.742 g), and ball milled at 800 rpm in an Ar atmosphere for 6 hours to obtain a mixture. Then, 0.5 g of the mixture was taken out and added to a stainless steel grinding bowl, and 0.1 g of conductive carbon black (Super P, based on the total mass percentage of the mixture as 100%, the mass percentage of the conductive carbon black is 20 wt%) was added to make the mass ratio of steel ball to powder (i.e., the mixture and Super P) 40:1. The mixture was ball milled at 800 rpm in an Ar atmosphere for 6 hours to obtain a Bi@P nanocomposite material (denoted as: Bi@P@C), which is the battery negative electrode material in this example.

[0053] Comparative Example 2

[0054] This example provides a method for preparing a negative electrode material for a battery, the specific steps of which are:

[0055] The following raw materials were added to a stainless steel grinding bowl: conductive carbon black (Super P, amount is 0.1g, based on the mass percentage of Bi as 100%, the mass percentage of conductive carbon black is 20wt%), Bi (Aladdin, AR, amount is 0.5g) 80wt%, so that the mass ratio of steel ball to powder (i.e., Super P and Bi) is 40:1. Ball milling was carried out at a speed of 800 rpm in an Ar atmosphere for 6 hours to obtain a Bi nanocomposite material (denoted as: Bi@C), which is the battery negative electrode material in this example.

[0056] Performance Testing

[0057] (1) XRD test

[0058] The XRD data of Bi@P@BiPO4@C, Bi@P@C and Bi@C prepared in Example 1 and Comparative Examples 1-2 were tested by X-ray diffractometer. The specific test results are as follows: Figure 2 As shown. Figure 2 It can be seen that all the diffraction peaks in the XRD curves of Bi@P@BiPO4@C, Bi@P@C and Bi@C correspond to the rhombohedral phase with space group R-3m (JCPDS No.44-1246), and the calculated lattice parameters are and This indicates that the BiPO4 introduced into Bi@P@BiPO4@C is amorphous.

[0059] (2) SEM and TEM testing

[0060] The surface morphology of Bi@P@BiPO4@C in Example 1 was tested using a scanning electron microscope. The specific test results are shown in the figure. Figure 3 As shown, Figure 3 a and Figure 3 b are SEM images with scale bars of 2 μm and 200 nm respectively. Figure 3 It can be seen that in the Bi@P@BiPO4@C sample, the presence of bismuth phosphate prevents the Bi@P particles from densely agglomerating, thereby improving the dispersion and uniformity of the active material during the electrode preparation process.

[0061] The HRTEM images of Bi@P@BiPO4@C in Example 1 were tested using a high-resolution transmission electron microscope (HRTEM). The specific test results are shown in FIG. Figure 4 As shown. Figure 4 It can be seen that amorphous red P and Bi crystals exist in the amorphous carbon matrix. In addition, in the Bi@P@BiPO4@C composite material, metallic Bi exists in the form of nanoparticles in the amorphous carbon matrix.

[0062] (3) EDS analysis

[0063] The energy dispersive X-ray spectroscopy (EDS) mapping diagram of Bi@P@BiPO4@C in test example 1 is as follows: Figure 5 As shown by Figure 5 It can be seen that P, Bi, C and O are evenly distributed in the Bi@P@BiPO4@C composite material, and the presence of a small amount of O may be due to the partial oxidation of P and Bi when the Bi@P@BiPO4@C composite material is exposed to air.

[0064] (4) Microstructure testing

[0065] The X-ray CT spectra of Bi@P@C in Comparative Example 1 and Bi@P@BiPO4@C in Example 1 were tested respectively. The specific test results are as follows: Figure 6 a and Figure 6 As shown in b, Figure 6 The microstructure of Bi@P@C and Bi@P@BiPO4@C at the electrode level can be analyzed. Compared with Bi@P@C, the distribution of Bi@P@BiPO4@C particles is more uniform, which is consistent with the results of scanning electron microscopy.

[0066] (5) Thermogravimetric analysis

[0067] Thermogravimetric curve of Bi@P@BiPO4@C in air in test example 1 is as follows: Figure 7 As shown by Figure 7It can be seen that the experimental mass fractions of Bi, P, BiPO4 and C in Bi@P@BiPO4@C are 36.33wt%, 12.6%, 31.7wt% and 19.37%, respectively, which are in good agreement with the theoretical values. Therefore, the proposed molar ratio of Bi2O3 to red phosphorus RP for synthesizing Bi@P@BiPO4@C composites can be described as follows:

[0068] 4Bi2O3+3P=3BiPO4+5Bi

[0069] (6) Battery cycle performance test

[0070] Bi@P@BiPO4@C, Bi@P@C, and Bi@C prepared in Example 1 and Comparative Examples 1 to 2 were respectively used as active materials, polyvinylidene fluoride (PVDF) and N-methylpyrrolidone (NMP) were used as binders, wherein acetylene black was used as a conductive agent; the mass ratio of the active material, the binder, and the conductive agent was 7:2:1; the active material, the binder, and the conductive agent were made into a working electrode, copper foil was used as a current collector, potassium metal was used as a counter electrode, and the electrolyte was a 2.5 mol / L triethyl phosphate (TEP) solution of potassium bis(fluorosulfonyl)imide (KFSI) salt. A half-cell was assembled, and the half-cell was subjected to a cycle stability test. The test conditions were: constant current charge and discharge, and the current density was 0.5 A g -1 The voltage range is 0.01~3.0V. Cyclic test is carried out within this voltage range. The test results are as follows Figure 8 As shown by Figure 8 It can be seen that the initial specific capacity of Bi@P@BiPO4@C in Example 1 is about 340 mA·h·g -1 After 1700 cycles, its specific capacity is about 330.0mA·h·g -1 , has a higher capacity retention rate, that is, better cycle stability, while Bi@P@C in Comparative Example 1 and Bi@C in Comparative Example 2 both have extremely poor cycle stability.

[0071] The TEM images of Bi@P@BiPO4@C in Example 1 and Bi@P@C in Comparative Example 1 after 500 charge and discharge cycles according to the above test conditions are shown in the following table. Figure 9 a and Figure 9 As shown in b. Figure 9It can be seen that after 500 cycles, the Bi@P@BiPO4@C anode in Example 1 formed a uniform solid electrolyte interface (SEI) with a thickness of about 15nm, while the Bi@P@C anode in Comparative Example 1 formed a non-uniform SEI with a thickness of about 20-30nm. The formation of a uniform SEI on the Bi@P@BiPO4@C anode is crucial to ensuring stable and efficient electrochemical reactions throughout the entire cycle, which can mitigate the adverse effects of side reactions, promote efficient ion transport, and slow down capacity decay.

[0072] The X-ray CT spectra of Bi@P@BiPO4@C in Example 1 and Bi@P@C in Comparative Example 1 were tested before and after 500 charge and discharge cycles according to the above test conditions. The specific test results are as follows: Figure 10 As shown, Figure 10 a and Figure 10 b X-ray CT spectra of Bi@P@C and Bi@P@BiPO4@C before charge and discharge cycles; Figure 10 c and Figure 10 d are the X-ray CT spectra of Bi@P@C and Bi@P@BiPO4@C after 500 charge and discharge cycles. Figure 10 It can be seen that Bi@P@BiPO4@C did not break after 500 charge and discharge cycles, and had the function of adaptive shrinkage. Bi@P@C broke after 500 cycle tests and did not have the function of adaptive shrinkage.

[0073] The Bi@P@BiPO4@C in Example 1 and commercial 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were assembled into a full battery (such as Figure 11 As shown), then at 0.1 mA·g -1 The battery performance test results after 100 charge and discharge cycles are as follows: Figure 12 As shown in a. Figure 12 It can be seen from a that the Bi@P@BiPO4@C full battery in Example 1 exhibits good cycle stability at 0.1 mA g -1 After 100 cycles at a current density of 97.83 mA·h·g -1 The Bi@P@BiPO4@C full battery in Example 1 is electrically connected to an electric fan with a power output of 1.0W. The specific physical figure is as follows Figure 12 As shown in b. Figure 12 b It can be seen that the Bi@P@BiPO4@C full battery in Example 1 successfully powered an electric fan with a power output of 1.0 W, confirming the practicality of using Bi@P@BiPO4@C in TEP electrolyte.

[0074] The charge and discharge performance of Bi@P@BiPO4@C in Example 1 was tested by constant current charge and discharge with a current density of 0.1 A·g -1 The voltage range is 0.01~3.0V. Cyclic test is carried out within this voltage range. The specific test results are as follows Figure 13 The charge and discharge performance of Bi@P@BiPO4@C, Bi@P@C and Bi@C was tested by the following method: constant current charge and discharge, voltage range of 0.01~3.0V, and rate tests of different current densities were performed within this voltage range. The specific test results are shown in Figure 1. Figure 13 As shown in b, processing Figure 13 Redraw the test data in b and get Figure 13 c's test image. Figure 13 It can be seen that the reversible capacity of the Bi@P@BiPO4@C electrode is as high as 474.3 mA·h·g -1 , the initial coulombic efficiency (ICE) is 61.0%, while the initial coulombic efficiency of Bi@P@C in Comparative Example 1 under the same test conditions is 55.39%, and the initial coulombic efficiency of Bi@C in Comparative Example 2 under the same test conditions is 59.64%. The battery performance of Comparative Examples 1 and 2 is significantly lower than that of Example 1. Figure 13 b It can be seen that in KFSI electrolyte, the charge and discharge rate capability of Bi@P@BiPO4@C is better than that of Bi@C and Bi@P@C. Figure 13 c shows that at 0.1A·g -1 , 0.2A·g -1 , 0.5A·g -1 and 1.0A·g -1 At a current density of 1.57 Å, the reversible capacities of Bi@P@BiPO4@C are 454.6 mA·h·g -1 、417.7mA·h·g -1 、324.9mA·h·g -1 and 188.4 mA·h·g -1 , with good charge and discharge cycle performance.

[0075] In summary, the battery negative electrode material in the present invention can improve the dispersion effect of the conductive carbon material, phosphorus, and crystalline bismuth by introducing bismuth phosphate, and avoid the occurrence of agglomeration; on the other hand, bismuth phosphate is an inactive ingredient, which can effectively improve the huge volume change during the charge and discharge process, which is beneficial to the stability of the SEI film, thereby giving the electrode material better cycle stability, increasing the battery's ion diffusion rate, and improving the battery's cycle performance.

[0076] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for preparing a battery negative electrode material, characterized in that: The following steps are involved: The raw materials of the active material are mixed and then ground to obtain; The raw materials of the active material include bismuth oxide, phosphorus and conductive carbon material; The battery negative electrode material includes an active material; the active material is a composite material containing bismuth phosphate, phosphorus, bismuth and a conductive carbon material.

2. The method for preparing a negative electrode material for a battery according to claim 1, wherein: The grinding step adopts ball milling, and the ball milling step has at least one of the following characteristics: (a) the ball milling speed is 100 to 1000 rpm; (b) the ball milling time is 1 to 10 hours; (c) The mass ratio of the grinding balls to the active material raw materials is (30-40):1; (d) The ball milling step is carried out under the protection of inert gas.

3. The method for preparing a negative electrode material for a battery according to claim 1, wherein: The molar ratio of the bismuth oxide to phosphorus is 1:(0.1-20).

4. The method for preparing a negative electrode material for a battery according to claim 1, wherein: The ratio of the total mass of the bismuth oxide and phosphorus to the mass of the conductive carbon material is 100:(10-30).

5. The method for preparing a negative electrode material for a battery according to claim 1, wherein: The bismuth phosphate is amorphous.

6. The method for preparing a negative electrode material for a battery according to claim 1, wherein: The bismuth is in the form of crystals.

7. The method for preparing a negative electrode material for a battery according to claim 1, wherein: Taking the total mass percentage of the composite material as 100%, the mass percentage of the bismuth phosphate is 20-40%.

8. The method for preparing a negative electrode material for a battery according to claim 1, wherein: Based on the total mass percentage of the bismuth phosphate, the phosphorus and the bismuth being 100%, the mass percentage of the conductive carbon material is 10-30%.

9. Application of the method for preparing the battery negative electrode material according to any one of claims 1 to 8 in the field of batteries.

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