Lithium phosphate composite modified tin oxide thin film negative electrode material and preparation method thereof

Abstract

The application discloses a lithium phosphate composite modified tin oxide thin film negative material and a preparation method thereof. The method adopts high-purity Li3PO4 with tin metal pieces pasted on the surface as target material, and adopts a magnetron sputtering method to sputter and deposit the lithium phosphate composite modified tin oxide thin film on the surface of a substrate. By adding Li3PO4, the volume expansion of SnO2 in the cycle process is relieved, a good ion conductive network is formed in the electrode material, and the cycle performance of the material is improved. In addition, the introduction of Li3PO4 also improves the coulomb efficiency of the material, and promotes the application of the SnO2 negative electrode in the thin film battery.

Description

Technical Field

[0001] This invention belongs to the field of thin-film battery technology and relates to a lithium phosphate composite modified tin oxide thin-film anode material and its preparation method. Background Technology

[0002] Limited by the ion transport rate in thin films, the finite film thickness results in low single-cell capacity in thin-film lithium batteries. Therefore, finding alternative electrode materials with high specific capacity is crucial for developing next-generation high-energy and high-power-density thin-film lithium-ion batteries to meet the urgent needs of emerging energy technologies.

[0003] Regarding anode materials, tin dioxide (SnO2) is favored due to its high specific capacity (1494 mAh g / g). -1 10220mAh cm -3 ) and moderate lithiation potential (1.0V vs Li / Li) + It has attracted widespread attention because of this. It is well known that tin dioxide stores lithium ions through two steps, namely the first conversion reaction (SnO2 + Li2O2)... + →Sn+LiO2) produces 731mAh g -1 The capacity, the second alloying reaction (Sn + 4,4Li) + →Li 4.4 Sn) produced 763 mAh g -1 However, the capacity loss of tin dioxide is mainly hindered by electrode degradation caused by large volume changes during cycling.

[0004] Researchers are dedicated to solving the above problems and achieving high capacity and improved cycling stability of Sn-based thin film anodes. Currently, there are two main approaches. One approach is to design Sn-based electrodes with different nanostructures (e.g., porous, layered, etc.). Hyuk Sang Kwon et al. prepared a multilayer Sn electrode using electrodeposition, achieving a first-cycle coulombic efficiency of 95%. However, this method only reduces structural instability in the initial cycle; in subsequent cycles, Sn nanoparticles still tend to aggregate and form larger particles, thus increasing volume change (Journal of Power Sources, 2010, 195(15):5067-5070). Another approach is to prepare Sn-based composite thin film electrodes with a buffering effect on volume change. Using a metallic material (M) as the matrix for Sn nanoparticles helps mitigate the volume effect and maintain structural stability. Here, M acts as a relatively soft "buffer matrix" to release the volume change caused by the active phases Sn and LixSn. Mukaibo et al. prepared Sn-Ni alloy films using electrodeposition. By optimizing the Sn / Ni ratio, they found that the reversible capacity of the Sn alloy film containing 62 attom% could reach up to ~650 mAh g⁻¹ after 70 cycles. -1 However, its long-term cycling stability is not ideal after hundreds of cycles within the required voltage range (Electrochemical and Solid-State Letters 2003, 6, A218). Summary of the Invention

[0005] This invention aims to provide a lithium phosphate composite modified tin oxide thin film anode material and its preparation method. The method involves combining Li3PO4 and SnO2 in a thin film electrode using magnetron sputtering, thereby suppressing volume expansion and improving cycle stability.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] The preparation method of lithium phosphate composite modified tin oxide thin film anode material specifically includes the following steps:

[0008] Step 1: A tin metal sheet is attached to the surface of a high-purity Li3PO4 target to obtain the target material used for magnetron sputtering;

[0009] Step 2: Using the target material obtained in Step 1, a lithium phosphate composite modified tin oxide film is sputtered and deposited on the substrate surface by magnetron sputtering in a high-purity Ar and high-purity O2 atmosphere.

[0010] Preferably, in step 1, the area ratio of the high-purity Li3PO4 target to the Sn metal sheet is 6:1 to 14:1, more preferably 10:1.

[0011] Preferably, in step 2, the power supply used for magnetron sputtering is an RF power supply.

[0012] Preferably, in step 2, the magnetron sputtering deposition temperature is 25°C.

[0013] Preferably, in step 2, the atmosphere is Ar:O2 = 20 sccm:5 sccm.

[0014] Preferably, in step 2, the working gas pressure for magnetron sputtering is 1 to 2 Pa.

[0015] Preferably, in step 2, the magnetron sputtering power is 120W.

[0016] Preferably, in step 2, the substrate is stainless steel.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] This invention successfully prepared SnO2 / Li3PO4 composite thin-film anode materials via magnetron sputtering. The composite with inactive Li3PO4, at the cost of some capacity, effectively suppressed the volume expansion of the material during cycling, resulting in a better cycle life for the composite electrode. Furthermore, Li3PO4, as a fast ion conductor, forms a good ion conduction network in the composite electrode, leading to enhanced Li3PO4 performance. + Diffusion coefficient. Furthermore, the introduction of Li3PO4 effectively improves the coulombic efficiency of the battery, expanding the application of Sn-based materials in thin-film batteries. Attached Figure Description

[0019] Figure 1 This is a SEM image of the SnO2 / Li3PO4 thin film prepared in Example 2.

[0020] Figure 2 The diagram shows the charge-discharge cycle diagrams of SnO2 / Li3PO4 with different composite ratios prepared in Examples 1, 2, and 3.

[0021] Figure 3 This is a charge-discharge cycle diagram of pure SnO2 prepared in Comparative Example 1.

[0022] Figure 4 The SnO2 / Li3PO4 prepared in Example 2 and Comparative Example 1 and the Li3PO4 prepared from pure SnO2 are compared with those prepared in Example 2 and Comparative Example 1. + Diffusion coefficient comparison chart.

[0023] Figure 5 This is a comparison chart of the coulombic efficiencies of pure SnO2 and SnO2 / Li3PO4 prepared in Comparative Example 1 and Example 2. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the content of the present invention is not limited thereto.

[0025] Example 1

[0026] Sn metal sheets were adhered to the surface of a high-purity Li3PO4 target with an area ratio of 6:1 to obtain the target material for magnetron sputtering. Radio-frequency reactive magnetron sputtering was employed, using the above-mentioned material (purity >99%) as the target material. The sputtering gas consisted of high-purity Ar and high-purity O2 in a ratio of 20 sccm:5 sccm, with a working pressure of 1–2 Pa and a sputtering power of 120 W. A SnO2 / Li3PO4 composite negative electrode film was sputtered and deposited on a stainless steel substrate. The resulting negative electrode sheet for lithium-ion batteries was then cut into 12 mm diameter circular electrode sheets for assembling button batteries.

[0027] In an argon-protected environment within a glove box, using 1M LiPF6 / (EC / DEC) as the electrolyte and a 16mm Celgard polypropylene membrane as the separator, the prepared thin-film electrodes, separator, and metallic Li electrodes were assembled into a button cell within the glove box. Charge-discharge cycle tests were then conducted on a LAND battery testing system with an operating voltage of 0.01-3V (vs. Li / Li). + ).

[0028] Example 2

[0029] Sn metal sheets were adhered to the surface of a high-purity Li3PO4 target with an area ratio of 10:1 to obtain the target material for magnetron sputtering. Radio-frequency reactive magnetron sputtering was employed, using the above-mentioned material (purity >99%) as the target material. The sputtering gas consisted of high-purity Ar and high-purity O2 in a ratio of 20 sccm:5 sccm, with a working pressure of 1–2 Pa and a sputtering power of 120 W. A SnO2 / Li3PO4 composite negative electrode film was sputtered and deposited on a stainless steel substrate. The resulting negative electrode sheet for lithium-ion batteries was then cut into circular electrode sheets with a diameter of 12 mm for use in assembling button batteries.

[0030] In an argon-protected environment within a glove box, using 1M LiPF6 / (EC / DEC) as the electrolyte and a 16mm Celgard polypropylene membrane as the separator, the prepared thin-film electrodes, separator, and metallic Li electrodes were assembled into a button cell within the glove box. Charge-discharge cycle tests were then conducted on a LAND battery testing system with an operating voltage of 0.01-3V (vs. Li / Li). + ).

[0031] Example 3

[0032] Sn metal sheets were adhered to the surface of a high-purity Li3PO4 target with an area ratio of 14:1 to obtain the target material for magnetron sputtering. Radio-frequency reactive magnetron sputtering was employed, using the above-mentioned material (purity >99%) as the target material. The sputtering gas consisted of high-purity Ar and high-purity O2 in a ratio of 20 sccm:5 sccm, with a working pressure of 1–2 Pa and a sputtering power of 120 W. A SnO2 / Li3PO4 composite negative electrode film was sputtered and deposited on a stainless steel substrate. The resulting negative electrode sheet for lithium-ion batteries was then cut into 12 mm diameter circular electrode sheets for assembling button batteries.

[0033] In an argon-protected environment within a glove box, using 1M LiPF6 / (EC / DEC) as the electrolyte and a 16mm Celgard polypropylene membrane as the separator, the prepared thin-film electrodes, separator, and metallic Li electrodes were assembled into a button cell within the glove box. Charge-discharge cycle tests were then conducted on a LAND battery testing system with an operating voltage of 0.01-3V (vs. Li / Li). + ).

[0034] Comparative Example 1

[0035] This comparative example is basically the same as Example 1, except that the target material used for magnetron sputtering is SnO2 target material.

[0036] like Figure 1 As shown, the SnO2 / Li3PO4 thin film anode material prepared in Example 2 is a dense film, consistent with the SnO2 thin film reported in the literature.

[0037] Figure 2 The SnO2 / Li3PO4 composite films prepared in Examples 1, 2, and 3 are demonstrated as anode materials for lithium-ion batteries, exhibiting excellent long-term cycling performance in the 0.01-3V voltage range. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) -1 At the specified current density, the first-week discharge capacity of Examples 1, 2, and 3 was 743 mAh g, respectively. -1 585mAh g -1 and 523mAh g -1 As the amount of Li3PO4 recombination increases, the discharge capacity in the first week shows a decreasing trend. After about 50 cycles, the capacities of Examples 1, 2, and 3 tend to stabilize at 405 mAh g⁻¹. -1 712mAh g -1 and 195mAh g -1 And maintain this for 160 laps.

[0038] Figure 3 The study demonstrates the long-term cycling performance of the pure SnO2 thin film prepared in Comparative Example 1 as a negative electrode material for lithium-ion batteries in the voltage range of 0.01-3V, exhibiting poor cycling performance. (The text abruptly ends here, likely due to an incomplete sentence or missing information.)-1 After cycling at a current density of 160 times, the comparative specific capacity decreased from 1148 mAh g in the first cycle. -1 Reduced to 192mAh g -1 And it is still showing a downward trend.

[0039] Figure 4 The discharge process of pure SnO2 and SnO2 / Li3PO4 lithium-ion battery anodes prepared in Comparative Example 1 and Example 2 within the voltage range of 0.01-3V is demonstrated. + Diffusion coefficient comparison chart. This result was obtained from GITT testing. The comparison shows that the SnO2 / Li3PO4 composite film of Example 2 has a higher Li3PO4 diffusion coefficient than the pure SnO2 sample of Comparative Example 1. + The diffusion coefficient indicates that the introduction of Li3PO4 also enhances the diffusion kinetics of the thin film electrode.

[0040] Figure 5 The diagram shows a comparison of the coulombic efficiencies of pure SnO2 and SnO2 / Li3PO4 lithium-ion battery anodes prepared in Comparative Example 1 and Example 2 during the discharge process within the voltage range of 0.01-3V. Compared with the pure SnO2 sample in Comparative Example 1, the coulombic efficiency of the SnO2 / Li3PO4 composite film in Example 2 showed an increasing trend in the initial 20 cycles. After stabilization, the coulombic efficiency of the sample in Example 2 was around 99%, while that of the sample in Comparative Example 1 was only around 97%.

Claims

1. A method for preparing lithium phosphate composite modified tin oxide thin film anode material, characterized in that, Specifically, the following steps are included: Step 1: A tin metal sheet is attached to the surface of a high-purity Li3PO4 target to obtain the target material used for magnetron sputtering. The area ratio of the high-purity Li3PO4 target to the Sn metal sheet is 10:

1. Step 2: Using the target material obtained in Step 1, a lithium phosphate composite modified tin oxide film is sputtered and deposited on the substrate surface by magnetron sputtering in a high-purity Ar and high-purity O2 atmosphere.

2. The preparation method according to claim 1, characterized in that, In step 2, the power supply used for magnetron sputtering is an RF power supply.

3. The preparation method according to claim 1, characterized in that, In step 2, the magnetron sputtering deposition temperature is 25°C.

4. The preparation method according to claim 1, characterized in that, In step 2, the atmosphere is Ar:O2 = 20 sccm: 5 sccm.

5. The preparation method according to claim 1, characterized in that, In step 2, the working gas pressure for magnetron sputtering is 1~2 Pa.

6. The preparation method according to claim 1, characterized in that, In step 2, the magnetron sputtering power is 120W, and the substrate is stainless steel.

7. The lithium phosphate composite modified tin oxide thin film anode material prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the lithium phosphate composite modified tin oxide thin film anode material according to claim 7 in thin film lithium-ion batteries.

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