Battery negative electrode material, and preparation method therefor and use thereof

Abstract

A battery negative electrode material, and a preparation method therefor and a use thereof. The battery negative electrode material comprises 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, on the one hand, the battery negative electrode material can enhance the dispersion effect of the conductive carbon material, phosphorus and crystalline bismuth, effectively preventing the occurrence of agglomeration; and on the other hand, because the bismuth phosphate is an inactive ingredient, the presence of bismuth phosphate in the active material can effectively mitigate a large volume change during charging and discharging, facilitating the stability of an SEI film, thereby endowing electrode materials with better cycle stability.

Description

Battery negative electrode material and preparation method and application thereof TECHNICAL FIELD

[0001] The present application belongs to the field of batteries, and particularly relates to a battery negative electrode material and a preparation method and application thereof. BACKGROUND

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

[0003] Recently, bismuth has attracted attention due to its relatively high theoretical specific capacity, reasonable voltage plateau and cost-effectiveness. In particular, bismuth has a layered crystal structure and semimetallic conductivity, with a large interlayer spacing along the c-axis which makes it an ideal candidate for rechargeable battery anode materials. However, due to the large ionic radius of K + , the Bi anode undergoes significant volume change during cycling, leading to material pulverization and continuous side reactions between the electrode and electrolyte. In addition, the wrinkled layer structure and semimetallic conductivity of the bismuth anode also limit electron transport and K + diffusion. Therefore, it is urgent to solve the problem of large volume expansion of the Bi anode, improve electron conductivity and improve K + diffusion to improve its electrochemical performance.

[0004] SUMMARY

[0005] In order to overcome the problems existing in the prior art, one of the purposes of the present application is to provide a battery negative electrode material.

[0006] The second purpose of the present application is to provide a preparation method of the above-mentioned battery negative electrode material.

[0007] The third purpose of the present application is to provide a battery negative electrode.

[0008] The fourth purpose of the present application is to provide a potassium ion battery.

[0009] The fifth purpose of the present application is to provide the application of the above-mentioned battery negative electrode material and / or battery negative electrode in the field of batteries.

[0010] In order to achieve the above-mentioned purposes, the technical scheme adopted by the present application is:

[0011] The first aspect of the present application provides a battery negative material, comprising an active material; the active material is a composite material containing bismuth phosphate, phosphorus, bismuth and conductive carbon material.

[0012] Preferably, the bismuth phosphate is amorphous.

[0013] Preferably, the bismuth is crystalline.

[0014] Preferably, the mass percentage of the bismuth phosphate is 20-40%, for example, can be selected from 20%, 25%, 30%, 35%, 40%, based on the total mass percentage of the composite material being 100%.

[0015] Preferably, the phosphorus is red phosphorus.

[0016] Preferably, the mass percentage of the conductive carbon material is 10-30%, for example: can be 10%, 15%, 20%, 25%, 30%, based on the total mass percentage of the bismuth phosphate, the phosphorus and the bismuth being 100%.

[0017] The second aspect of the present application provides a preparation method of the battery negative material provided by the first aspect of the present application, comprising the following steps:

[0018] After mixing the raw materials of the active material, grinding is performed to obtain; the raw materials of the active material include bismuth oxide, phosphorus and conductive carbon material.

[0019] Preferably, the grinding step adopts ball milling.

[0020] Preferably, the rotation speed of the ball milling is 100-1000 rpm; further preferably, the rotation speed of the ball milling is 500-1000 rpm; more preferably, the rotation speed of the ball milling is 500-900 rpm.

[0021] Preferably, the ball milling time is 1-10 h; further preferably, the ball milling time is 4-10 h; more preferably, the ball milling time is 6-10 h.

[0022] Preferably, the mass ratio of the grinding ball and the raw materials of the active material is (30-40):1.

[0023] Preferably, the ball milling step is performed under the protection of inert gas.

[0024] Preferably, the inert gas is selected from at least one of nitrogen, xenon, argon.

[0025] Preferably, the molar ratio of the bismuth oxide and phosphorus is 1:(0.1-20); further preferably, the molar ratio of the bismuth oxide and phosphorus is 1:(0.1-10); more further preferably, the molar ratio of the bismuth oxide and phosphorus is 1:(1-10); more preferably, the molar ratio of the bismuth oxide and phosphorus is 1:(1-3).

[0026] In the present application, the amorphous bismuth phosphate (BiPO4, which is a non-active ingredient) is formed in situ during the ball milling process. The bismuth phosphate can also play a role in the ball milling process, reducing the aggregation and regeneration of active ingredients (conductive carbon material, phosphorus and crystalline bismuth), increasing the dispersibility of active ingredients, and helping to reduce the particle size of active ingredients and improve the utilization rate of active ingredients. In addition, by doping active ingredients with non-active ingredients, the present application can solve the problem of volume expansion of active ingredients, improve the huge volume change during the charging and discharging process of the battery negative electrode material, and help to stabilize the SEI film, thereby imparting better cycle stability to the electrode material.

[0027] 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).

[0028] Preferably, the conductive carbon material includes at least one of graphite, graphene, carbon nanotubes, carbon nanofibers, carbon nanodots, carbon nanotapers, coke, activated carbon, conductive carbon black, acetylene black. When the conductive carbon material is two or more, the two or more conductive carbon materials can be mixed in any ratio. Further preferably, the conductive carbon material is selected from at least one of graphite, conductive carbon black, acetylene black.

[0029] Chemical bonds are formed between bismuth, phosphorus and conductive carbon material during the ball milling process, improving the electrochemical performance of the active material, but the resulting composite material may have agglomeration, and the dispersibility is significantly lower than the active material doped with bismuth phosphate in the present application. In addition, amorphous bismuth phosphate can withstand greater volume changes than crystalline bismuth, and due to its isotropic nature, it can also promote ion diffusion and solve the problem of electrode volume expansion.

[0030] The third aspect of the present application provides a battery negative electrode comprising the battery negative electrode material of the first aspect of the present application.

[0031] The fourth aspect of the present application provides a potassium ion battery comprising the battery negative electrode material of the first aspect of the present application; or, the battery negative electrode of the third aspect of the present application.

[0032] The fifth aspect of the present application provides the use of the battery negative electrode material of the first aspect of the present application and / or the battery negative electrode of the third aspect of the present application in the field of batteries.

[0033] The battery negative electrode material in the present application can improve the dispersion effect of the conductive carbon material, phosphorus and crystal bismuth by introducing bismuth phosphate into the active material, on the one hand, and avoid the occurrence of agglomeration; on the other hand, the bismuth phosphate is a non-active component, and the bismuth phosphate existing in the active material can effectively improve the huge volume change in the charging and discharging process, benefit the stability of the SEI film, thereby endowing the electrode material with better cycle stability, improving the ion diffusion rate of the battery, and improving the cycle performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0034] Fig. 1 is a preparation process flow chart of the battery negative electrode material in Example 1.

[0035] Fig. 2 is an XRD test chart of the battery negative electrode material in Example 1 and Comparative Examples 1-2.

[0036] Fig. 3 is an SEM chart of the battery negative electrode material in Example 1.

[0037] Fig. 4 is an HRTEM chart of the battery negative electrode material in Example 1.

[0038] Fig. 5 is an EDS mapping chart of the battery negative electrode material in Example 1.

[0039] Fig. 6 is an X-ray CT spectrum chart of the battery negative electrode material in Example 1 and Comparative Examples 1-2.

[0040] Fig. 7 is a thermogravimetric curve test chart of the battery negative electrode material in Example 1.

[0041] Fig. 8 is a cycle performance test chart of the half battery formed by Bi@P@BiPO4@C, Bi@P@C and Bi@C in the embodiment of the present application.

[0042] Fig. 9 is a TEM chart of the battery negative electrode material in Example 1 and Comparative Example 1 after 500 times of charge and discharge cycles.

[0043] Fig. 10 is an X-ray CT spectrum chart of the battery negative electrode material in Example 1 and Comparative Example 1 before and after cycles.

[0044] Fig. 11 is a structural schematic diagram of the full battery assembled by Bi@P@BiPO4@C in Example 1.

[0045] Fig. 12 is a cycle performance test chart of the full battery formed by Bi@P@BiPO4@C in Example 1.

[0046] Fig. 13 is a charge and discharge performance test chart of the battery negative electrode material in Example 1 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0047] The present application is further described in detail by the following specific embodiments combined with the accompanying drawings and examples, but the implementation and protection of the present application are not limited thereto. It should be noted that if the following processes are not specifically described in detail, they can be implemented or understood by referring to the prior art. If the reagents or instruments used are not specified by the manufacturer, they are conventional products that can be purchased on the market.

[0048] Example 1

[0049] Referring to the preparation flow chart in FIG. 1, the present example provides a preparation method of a battery negative electrode material, and the specific steps are as follows:

[0050] In a stainless steel milling bowl, the following raw materials were added: P (0.11 g) and Bi2O3 (Aladdin, AR, 0.551 g), and ball milling was performed at a speed of 800 rpm for 6 hours in an Ar atmosphere to obtain a mixture. Then, 0.5 g of the mixture was taken out and added to a stainless steel milling bowl, and 0.1 g of conductive carbon black (Super P, 20 wt% based on 100% of the total mass of the mixture) was added. The mass ratio of the steel ball to the powder (i.e., the mixture and Super P) was 40:1, and ball milling was performed at a speed of 800 rpm for 6 hours in an Ar atmosphere to obtain amorphous bismuth phosphate (BiPO4) doped crystalline Bi@P nanocomposite (denoted as: Bi@P@BiPO4@C), which is the battery negative electrode material in the present example. The mass percentage of bismuth phosphate was 30 wt% based on 100% of the mass of the battery negative electrode material.

[0051] Comparative Example 1

[0052] The present example provides a preparation method of a battery negative electrode material, and the specific steps are as follows:

[0053] In a stainless steel milling bowl, the following raw materials were added: P (0.11 g) and Bi (Aladdin, AR, 0.742 g), and ball milling was performed at a speed of 800 rpm for 6 hours in an Ar atmosphere to obtain a mixture. Then, 0.5 g of the mixture was taken out and added to a stainless steel milling bowl, and 0.1 g of conductive carbon black (Super P, 20 wt% based on 100% of the total mass of the mixture) was added. The mass ratio of the steel ball to the powder (i.e., the mixture and Super P) was 40:1, and ball milling was performed at a speed of 800 rpm for 6 hours in an Ar atmosphere to obtain Bi@P nanocomposite (denoted as: Bi@P@C), which is the battery negative electrode material in the present example.

[0054] Comparative Example 2

[0055] The present example provides a preparation method of a battery negative electrode material, and the specific steps are as follows:

[0056] The following raw materials were added to a stainless steel mill bowl: conductive carbon black (Super P, amount 0.1 g, based on 100% of the mass of Bi, the mass percentage of conductive carbon black is 20 wt%), Bi (Aladdin, AR, amount 0.5 g) 80 wt%, the mass ratio of steel ball to powder (i.e. Super P and Bi) was 40:1, and the ball milling was carried out at a speed of 800 rpm for 6 hours in an Ar atmosphere to obtain a Bi nanocomposite (denoted as: Bi@C), which is the negative electrode material in this example.

[0057] Performance test

[0058] (1) XRD test

[0059] 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, and the specific test results are shown in Figure 2. As shown in Figure 2, all the diffraction peaks in the XRD curves of Bi@P@BiPO4@C, Bi@P@C and Bi@C correspond to the rhombohedron phase with space group R-3m (JCPDS No. 44-1246), and the calculated lattice parameters are and It is indicated that the BiPO4 introduced in Bi@P@BiPO4@C is in amorphous state.

[0060] (2) SEM and TEM test

[0061] The surface morphology of Bi@P@BiPO4@C in Example 1 was tested by scanning electron microscope, and the specific test results are shown in Figure 3. As shown in Figure 3, a is the SEM graph with a scale of 2 μm, and b is the SEM graph with a scale of 200 nm. As shown in Figure 3, in the Bi@P@BiPO4@C sample, the presence of bismuth phosphate prevents the dense agglomeration of Bi@P particles, thereby improving the dispersibility and uniformity of the active material in the electrode preparation process.

[0062] The HRTEM graph of Bi@P@BiPO4@C in Example 1 was tested by high-resolution transmission electron microscope (HRTEM), and the specific test results are shown in Figure 4. As shown in Figure 4, there are amorphous red P and Bi crystals in the amorphous carbon matrix. In addition, in the Bi@P@BiPO4@C composite material, the metal Bi exists in the form of nanoparticles in the amorphous carbon matrix.

[0063] (3) EDS analysis

[0064] An energy dispersive X-ray spectroscopy (EDS) mapping of the Bi@P@BiPO4@C in Example 1 was tested, and the specific test results are shown in FIG. 5. As shown in FIG. 5, P, Bi, C and O in the Bi@P@BiPO4@C composite are uniformly distributed, and the presence of a small amount of O may be due to the partial oxidation of P and Bi caused by the exposure of the Bi@P@BiPO4@C composite to air.

[0065] (4) Microstructure test

[0066] X-ray CT spectra of the Bi@P@C in Comparative Example 1 and the Bi@P@BiPO4@C in Example 1 were tested, respectively, and the specific test results are shown in FIG. 6a and FIG. 6b, respectively. As shown in FIG. 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 result of the scanning electron microscope.

[0067] (5) Thermogravimetric analysis

[0068] The thermogravimetric curve of the Bi@P@BiPO4@C in Example 1 in air was tested, and the specific test results are shown in FIG. 7. As shown in FIG. 7, 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 very consistent with the theoretical values. Therefore, the proposed molar ratio of Bi2O3 to red phosphorus RP for synthesizing the Bi@P@BiPO4@C composite material can be described as follows: 4Bi2O3+3P=3BiPO4+5Bi

[0069] (6) Battery cycle performance test

[0070] The Bi@P@BiPO4@C, Bi@P@C and Bi@C prepared in Example 1 and Comparative Examples 1-2 were respectively used as active materials, polyvinylidene fluoride (PVDF) and N-methyl pyrrolidone (NMP) were used as binders, and 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 prepared into a working electrode, copper foil was used as a current collector, potassium metal was used as a counter electrode, and a 2.5mol / L potassium bisfluorosulfonylimide (KFSI) solution in triethyl phosphate (TEP) was used as an electrolyte. A half-cell was assembled, and the cycle stability of the half-cell was tested. The test conditions were as follows: constant current charge and discharge, current density was 0.5A·g -1 , and the voltage interval was 0.01-3.0V. The test results are shown in FIG. 8. As shown in FIG. 8, the initial specific capacity of the Bi@P@BiPO4@C in Example 1 was about 340mA·h·g-1 After 1700 cycles, the specific capacity thereof is about 330.0 mA·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 very poor cycle stability.

[0071] TEM images of Bi@P@BiPO4@C in Example 1 and Bi@P@C in Comparative Example 1 after 500 cycles of charging and discharging according to the above test conditions were tested, respectively, and the specific test results are shown in Figure 9a and Figure 9b, respectively. As can be seen from Figure 9, after 500 cycles, the Bi@P@BiPO4@C anode in Example 1 forms a uniform solid electrolyte interface (SEI) with a thickness of about 15 nm, while the Bi@P@C anode in Comparative Example 1 forms a non-uniform SEI with a thickness of about 20-30 nm. The formation of a uniform SEI on the Bi@P@BiPO4@C anode is crucial to ensure stable and efficient electrochemical reactions throughout the cycle process, which can reduce the adverse effects of side reactions, promote efficient ion transport, and slow down capacity decay.

[0072] X-ray CT spectra of Bi@P@BiPO4@C in Example 1 and Bi@P@C in Comparative Example 1 before and after 500 cycles of charging and discharging according to the above test conditions were tested, respectively, and the specific test results are shown in Figure 10, wherein Figure 10a and Figure 10b are X-ray CT spectra of Bi@P@C and Bi@P@BiPO4@C before charging and discharging, respectively; Figure 10c and Figure 10d are X-ray CT spectra of Bi@P@C and Bi@P@BiPO4@C after 500 cycles of charging and discharging, respectively. As can be seen from Figure 10, Bi@P@BiPO4@C does not break after 500 cycles of charging and discharging and has the function of self-adaptive shrinkage, while Bi@P@C breaks after 500 cycles of testing and does not have the function of self-adaptive shrinkage.

[0073] Bi@P@BiPO4@C in Example 1 and commercial 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were assembled into a full cell (as shown in Figure 11), and then charged and discharged at a current density of 0.1 mA·g -1 -1 -1 ​​discharge capacity. The Bi@P@BiPO4@C full cell in Example 1 was connected to an electric fan with a power output of 1.0 W, as shown in Fig. 12b. As shown in Fig. 12b, the Bi@P@BiPO4@C full cell in Example 1 successfully powered the electric fan with a power output of 1.0 W, confirming the practicability of using Bi@P@BiPO4@C in TEP electrolyte.

[0074] The charge-discharge performance of Bi@P@BiPO4@C in Example 1 was tested. The specific test method was: constant current charge-discharge, the current density was 0.1 A·g -1 , and the voltage interval was 0.01-3.0 V. The specific test results are shown in Fig. 13a. The charge-discharge performance of Bi@P@BiPO4@C, Bi@P@C and Bi@C was tested. The specific test method was: constant current charge-discharge, the voltage interval was 0.01-3.0 V, and the rate test was carried out at different current densities in the voltage interval. The specific test results are shown in Fig. 13b. The test data in Fig. 13b was processed and redrawn to obtain the test graph in Fig. 13c. As shown in Fig. 13a, the reversible capacity of Bi@P@BiPO4@C electrode was as high as 474.3 mA·h·g -1 , and the initial coulombic efficiency (ICE) was 61.0%. The initial coulombic efficiency of Bi@P@C in Comparative Example 1 was 55.39% under the same test conditions, and the initial coulombic efficiency of Bi@C in Comparative Example 2 was 59.64% under the same test conditions. The battery performance of Comparative Examples 1 and 2 was significantly lower than that of Example 1. As shown in Fig. 13b, the charge-discharge rate capability of Bi@P@BiPO4@C was better than that of Bi@C and Bi@P@C in KFSI electrolyte. As shown in Fig. 13c, the reversible capacity of Bi@P@BiPO4@C was 454.6 mA·h·g -1 , 417.7 mA·h·g -1 , 324.9 mA·h·g -1 , and 188.4 mA·h·g -1 at current densities of 0.1 A·g -1 , 0.2 A·g -1 , 0.5 A·g -1 , and 1.0 A·g -1 , respectively, and had good charge-discharge cycle performance.

[0075] To sum up, the battery negative electrode material in the application 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 a non-active component, which can effectively improve the huge volume change in the charging and discharging process, and is beneficial to the stability of the SEI film, thereby giving the electrode material better cycle stability, improving the ion diffusion rate of the battery, and improving the cycle performance of the battery.

[0076] The above has described the embodiments of the application in detail, but the application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the application. In addition, the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A battery anode material, characterized by: The active material comprises bismuth phosphate, phosphorus, bismuth and conductive carbon material.

2. The battery anode material of claim 1, wherein: The bismuth phosphate is amorphous; and / or, the bismuth is crystalline.

3. The battery anode material of claim 1, wherein: The mass percentage of the bismuth phosphate is 20-40% based on 100% of the total mass percentage of the composite material.

4. The battery anode material of any one of claims 1-3, wherein: The mass percentage of the conductive carbon material is 10-30% based on 100% of the total mass percentage of the bismuth phosphate, the phosphorus and the bismuth.

5. The method of producing a battery anode material according to any one of claims 1 to 4, characterized by: The method comprises the following steps: The raw materials of the active material are mixed and ground to prepare; The raw materials of the active material comprise bismuth oxide, phosphorus and conductive carbon material.

6. The method of claim 5, wherein: The grinding step uses ball milling, and the ball milling step has at least one of the following characteristics: (a) the rotation speed of the ball mill is 100-1000 rpm; (b) the ball milling time is 1-10 h; (c) the mass ratio of the grinding balls to the raw materials of the active material is (30-40) : 1; (d) the ball milling step is carried out under inert gas protection.

7. The method of claim 5, wherein the method further comprises: The molar ratio of the bismuth oxide to the phosphorus is 1: (0.1-20); And / or, the ratio of the total mass of the bismuth oxide and the phosphorus to the mass of the conductive carbon material is 100: (10-30).

8. A battery anode, characterized by: The battery negative electrode material according to any one of claims 1-4.

9. A potassium-ion battery, characterized by: The battery negative electrode material according to any one of claims 1-4; or, the battery negative electrode according to claim 8.

10. The battery negative electrode material according to any one of claims 1-4 and / or the battery negative electrode according to claim 8 in the field of batteries.

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