An outer pressure-free long cycle all-solid-state battery and silicon negative electrode and a preparation method thereof

Abstract

A long cycle all-solid-state battery without external pressure and a silicon negative electrode and a preparation method thereof, which utilizes Li 21 Si5 alloy low Young's modulus characteristics, under high stacking pressure to induce Li 21 Si5 alloy stress sintering phenomenon, get dense, integrated alloy negative electrode. At the same time, the use of Li 21 Si5 alloy high electron / ion conductive characteristics, the construction of the negative electrode upper layer of the electronic / ion double conductor layer (Li 21 Si5) and the lower layer of the mixed three-dimensional conductive layer (Si-Li 21 Si5). The structure provides a uniform electric field for the negative electrode of the all-solid-state battery, disperses the cycle expansion stress of Si evenly at the bottom of the negative electrode, stabilizes the interface between the solid electrolyte and the negative electrode, reduces the side reaction, and thus realizes the super-high initial efficiency and stable long cycle performance of the all-solid-state battery without external pressure.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy battery silicon negative electrode, and particularly relates to a long-cycle full-solid-state battery without external pressure, a silicon negative electrode and a preparation method thereof. BACKGROUND

[0002] With the development and application of high ionic conductivity solid-state electrolytes such as sulfides and chlorides, full-solid-state lithium ion batteries have shown amazing performance. Among them, the energy density of lithium metal / silicon-based full-solid-state lithium ion batteries is expected to exceed 500 Wh kg -1 .

[0003] However, to make these full-solid-state batteries achieve ultra-high performance, they often need to work under relatively high external pressure. Many research reports point out that appropriate stacking pressure (such as 80 MPa) can improve the critical current density of the lithium metal negative electrode, thereby inhibiting the formation of lithium dendrites. For the silicon negative electrode, a higher stacking pressure (such as 370 MPa) is needed to inhibit the volume expansion of the silicon negative electrode, thereby stabilizing the interface between the negative electrode and the solid-state electrolyte. The above-mentioned stacking pressure encapsulates the full-solid-state battery mold, which can provide an external pressure stress of 20-80 MPa for the full-solid-state battery, thereby realizing the high performance of the full-solid-state battery under high external pressure.

[0004] In fact, it is very difficult to achieve high external pressure under the actual working conditions of full-solid-state batteries in large quantities. Secondly, in order to maintain such a high pressure environment, some mechanical equipment will inevitably be introduced, which reduces the energy density of the full-solid-state battery. These problems will greatly hinder the industrialization process of solid-state batteries. Therefore, how to realize the high performance and long cycle of full-solid-state batteries under the condition of no external pressure has become a key technical problem that needs to be solved.

[0005] During the cycle process of the full-solid-state battery without external pressure, the deposition behavior of lithium ions on the surface of the lithium metal negative electrode is highly dependent on the electric field distribution. Weak interface is easily affected by electric field polarization, thereby producing lithium dendrites, which leads to the inability to realize high capacity and high critical density under cycle. Different is that the silicon negative electrode stores lithium ions in the bulk phase of silicon through the alloying process, which makes the critical current density of the silicon negative electrode much higher than that of the lithium metal negative electrode. However, during the first cycle process, the volume expansion of the silicon negative electrode is as high as 300%, which will cause the negative electrode structure to be fragmented, seriously damage the interface between the negative electrode and the solid-state electrolyte, and lead to the growth of lithium dendrites.

[0006] In 2021, Meng et al. published in Science, "Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes", which demonstrated the prospect of carbon-free silicon-based solid-state batteries, revealed the beneficial passivation effect of sulfide solid electrolytes on silicon anodes, and proposed the key role of lithium-silicon alloy in the charge-discharge process of silicon-based solid-state batteries. However, due to the low intrinsic conductivity of silicon and the accompanying large cyclic expansion stress, silicon-based solid-state batteries must be operated under an external pressure of ~50 MPa.

[0007] In 2024, Pan et al. published in Nature Communications, "A solid-state lithium-ion battery with micron-sized silicon anode operating free from external pressure", which proposed an elastic organic electrolyte to adapt to the expansion stress of the silicon anode, thereby realizing the external pressure-free cycling of solid-state batteries. However, the introduction of organic solid-state electrolytes inevitably reduces the ionic conductivity of the electrolyte and the ignition point of the solid-state battery. In summary, it is particularly important to develop a silicon-based all-solid-state battery with external pressure-free long cycling. SUMMARY

[0008] The present application aims to solve the above-mentioned problem that all-solid-state batteries in the prior art must be cycled under high external pressure, and to provide a Li 21 Si5 / Si-Li 21 Si5 anode and a method for preparing a solid-state battery without external pressure cycling.

[0009] The present application utilizes the low Young's modulus of Li 21 Si5 alloy to induce stress sintering of Li 21 Si5 alloy under high stacking pressure, resulting in a dense and integrated alloy anode. At the same time, the high electronic / ionic conductivity of Li 21 Si5 alloy is utilized to construct an upper layer of the anode as an electronic / ionic dual conductor layer (Li 21 Si5) and a lower layer as a mixed three-dimensional conductive layer (Si-Li 21 Si5). This structure provides a uniform electric field for the anode of the solid-state battery, homogenizes and disperses the cyclic expansion stress of Si at the bottom of the anode, stabilizes the interface between the solid-state electrolyte and the anode, reduces side reactions, and thus realizes the ultra-high initial efficiency and stable long cycling performance of the solid-state battery under no external pressure.

[0010] To achieve the above object, the present application adopts the following technical solutions:

[0011] A silicon negative electrode preparation method for an external pressure-free long cycle all-solid-state battery, comprising the following steps:

[0012] 1) mixing Si powder and Li 21 Si5 powder under argon atmosphere to obtain Si-Li 21 Si5 powder;

[0013] 2) using cold pressing technology to press the Si-Li 21 Si5 powder into a Si-Li 21 Si5 sheet in a mold;

[0014] 3) adding Li 21 Si5 powder on the surface of the Si-Li 21 Si5 sheet and pressing into a sheet to obtain a Li 21 Si5 / Si-Li 21 Si5 negative electrode.

[0015] In steps 2) and 3), the applied pressure is 300-900 MPa.

[0016] In steps 2) and 3), the applied pressure is 600 MPa.

[0017] A preparation method of an external pressure-free long cycle all-solid-state battery, comprising the following steps:

[0018] 1) adding a sulfide solid-state electrolyte on the surface of a Li 21 Si5 / Si-Li 21 Si5 negative electrode, and then adding a chloride solid-state electrolyte, and then simple pre-pressing;

[0019] 2) mixing and grinding a positive electrode material and the chloride solid-state electrolyte, placing the mixed substance on the surface pre-pressed in step 1), then placing an aluminum foil, and finally cold pressing into a shape;

[0020] 3) removing the pressure of step 2) to ensure that there is no residual pressure stress on the surface of the positive electrode caused by the mold, to obtain an all-solid-state battery.

[0021] In step 2), the applied pressure is 200-400 MPa, preferably 350 MPa.

[0022] The positive electrode material comprises a lithium cobaltate positive electrode material, a ternary positive electrode material, and a lithium iron phosphate positive electrode material.

[0023] The prepared external pressure-free long cycle all-solid-state battery has a surface capacity of 0.6 mAh cm -2 -7.8 mAh cm -2 .

[0024] The present application has the following beneficial effects compared with the prior art:

[0025] 1. The negative electrode provided by the present application is simple to prepare, and does not require additional conductive agents and binders. Li 21 Si5 alloy powder and silicon powder are directly mixed and cold-pressed to obtain Si-Li 21 Si5, and then Li 21 Si5 alloy powder is added to the surface of Si-Li 21 Si5, and cold-pressing is continued to obtain Li 21 Si5 / Si-Li 21 Si5 negative electrode sheet. Li 21 Si5 alloy powder has a low Young's modulus, which is conducive to the cold-pressing of the mixed negative electrode. Under the induction of pressure, Li 21 Si5 alloy is sintered around the Si particles to form a dense integrated negative electrode.

[0026] 2. The silicon negative electrode provided by the present application has super-high electronic / ion conductivity, which provides a uniform electric field for the negative electrode. Due to the lithium enrichment of Li 21 Si5 alloy, Li 21 Si5 alloy has electronic / ion conductivity far exceeding that of silicon particles. At the same time, the stress-induced sintering mechanism of Li 21 Si5 alloy makes Li 21 Si5 alloy become an electronic / ion dual-conductor layer, which can homogenize the electric field on the surface of the negative electrode and facilitate the rapid transmission of lithium ions.

[0027] 3. The negative electrode provided by the present application has excellent structural / interface stability and an extremely low expansion rate of 14.5%. When lithium ions react with the negative electrode, they are quickly transmitted to the bottom of the negative electrode to alloy with Si particles, thereby realizing the interface stability between the surface layer of the negative electrode and the solid-state electrolyte. Moreover, the uniform electric field can homogenize the expansion stress of the dispersed silicon particles, avoiding the destruction of the stress to the negative electrode phase structure.

[0028] 4. The silicon-based full solid-state battery provided by the present application realizes a first coulomb efficiency (ICE) of 97.69%, excellent high-rate cycle performance and long cycle performance under the test conditions of no external pressure. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Surface electron scanning images of Li 21 Si5 alloy of Example 1 under cold pressing at different stacking pressures.

[0030] Figure 2 Surface electron scanning images of Li 21 Si5 / Si-Li21 The cross-section of the Si5 negative electrode (a~b), and the Li on the negative electrode surface. 21 Si5 layer (c), and Si-Li on the back of the negative electrode 21 Electron scanning image of the Si5 mixed layer (d).

[0031] Figure 3 Si-Li as described in Example 2 21 Si5 electrode and Li 21 Si5 / Si-Li 21 Charge-discharge cycle curves of a symmetrical cell with a Si5 electrode.

[0032] Figure 4 The Si anode (a) of Example 3, Si-Li 21 Si5 negative electrode (b), and Li 21 Si5 / Si-Li 21 Charge-discharge cycle curves of an all-solid-state battery composed of Si5 anode (c) without external pressure.

[0033] Figure 5 The all-solid-state battery of Example 3, after one cycle without external pressure, Li 21 Si5 / Si-Li 21 Si5 electrodes (a-b) and Si-Li 21 Cross-sectional electron scanning images of Si5 electrodes (c-d).

[0034] Figure 6 The images show the EIS spectra of the all-solid-state battery of Example 3 after one cycle without external pressure (a-b) and after long-term cycling (c).

[0035] Figure 7 This is a comparison chart of data from the all-solid-state battery in Example 3 under different external pressures, current densities, and cycle numbers with data from previously reported literature.

[0036] Figure 8 The figures show the initial charge-discharge cycle curves under different high load conditions in Example 4; the black, yellow, and red curves represent areal capacities of 1.7, 5.4, and 7.8 mAh cm⁻¹, respectively. -2 The first charge-discharge curve of the battery.

[0037] Figure 9 Li in Example 5 21 Si5 / Si-Li 21 Rate curves of a solid-state battery composed of Si5 anode under different current densities; where red, black and blue represent the charging rate curve, discharging rate curve and charging / discharging coulombic efficiency curve, respectively. Detailed Implementation

[0038] To make the technical problems, technical solutions, and beneficial effects of this invention clearer and more understandable, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, the scope of protection of this invention is not limited to the following embodiments.

[0039] Example 1

[0040] In a glove box where the water and oxygen content were both ≤0.1ppm, seven 10mg portions of Li were weighed out. 21 Si5 powder. Place the cut copper foil into a tableting mold, and then... 21 Si5 powder was placed on the surface of copper foil in a pressing mold. After being subjected to stacking pressures of 100MPa, 200MPa, 300MPa, 400MPa, 500MPa, 600MPa and 700MPa, seven electrode sheets were obtained by cold pressing and sintering under different pressures.

[0041] like Figure 1 As shown, under the action of stacking pressure, Li 21 Si5 particles come into contact with each other, inducing stress sintering and ultimately resulting in an integrated electrode. Specifically, at a stacking pressure of 600 MPa, Li... 21 Si5 particles are completely sintered into a dense, integrated Li. 21 Si5 layer.

[0042] In a glove box where the water and oxygen content are both ≤0.1ppm, 0.5g of Li was weighed out. 21 Si5 alloy powder and 0.5g of silicon powder were mixed and ground in an agate mortar for 5 minutes to obtain Li. 21 Si-Li alloy powder comprising 50 wt% of the total mass of Si5 alloy powder 21 Si5 powder. Place the cut copper foil in a tableting mold and weigh out 10 mg of Si-Li. 21 Si5 powder is placed on the surface of copper foil in a tableting mold and subjected to a pressure of 600 MPa to obtain Si-Li. 21 Si5 electrode. 10 mg of Li was further added to the electrode surface. 21 Si5 powder was subjected to a pressure of 600 MPa to obtain Li. 21 Si5 / Si-Li 21 Si5 negative electrode.

[0043] like Figure 2 As shown, Li 21 Si5 / Si-Li 21 The Si5 anode consists of the upper Li layer 21 Si5 layer and the underlying Si-Li 21 Composed of a Si5 mixed layer. The upper surface has Li... 21Si5 layer is flat and dense, with a thickness of 57.5 pm, which can provide uniform electric field for the anode; the lower surface of Si-Li 21 The thickness of Si5 mixed layer is 47.5 pm, and the Li 21 Si5 alloy can provide efficient three-dimensional conductive network for silicon, which can evenly disperse the cyclic expansion stress of Si particles. In addition, the lithiation reaction under this structure is at the bottom of the anode, far away from the electrolyte, which can well protect the interface stability between the anode and the electrolyte, and thus realize the long cycle of full solid-state battery without external pressure.

[0044] Example 2

[0045] In a glove box with water and oxygen content ≤0.1 ppm, 0.5 g of Li 21 Si5 alloy powder and 0.5 g of silicon powder were mixed and ground in an agate mortar for 5 min to obtain Li 21 Si5 alloy powder accounts for 50wt% of the total mass of Si-Li 21 Si5 powder. The cut copper foil was placed in the tabletting die, and 10 mg of Si-Li 21 Si5 powder was placed on the surface of the copper foil in the tabletting die, and after 600 MPa pressure, Si-Li 21 Si5 electrode. 10 mg of Li 21 Si5 powder was added on the surface of the electrode, and after 600 MPa pressure, Li 21 Si5 / Si-Li 21 Si5 electrode. Two 10 mg of Li 21 Si5 powder was placed on the surface of the copper foil in the tabletting die, and after 600 MPa pressure, two Li 21 Si5 electrode.

[0046] Then the above Si-Li 21 Si5 electrode and Li 21 Si5 / Si-Li 21 Si5 electrode surface was added with 30 mg of Li6PS5Cl, and after simple pre-pressing, 50 mg of Li3InCl6 was added, and after 350 MPa pressure, a double-layer solid-state electrolyte layer was obtained.

[0047] Finally, Li 21 Si5 electrode was placed on the surface of the two double-layer solid-state electrolyte layers, and after simple pre-pressing, Si-Li 21 Si5 electrode and Li 21 Si5 / Si-Li 21The Si5 electrode is a symmetrical cell with a counter electrode. Note that the nut on the solid-state battery mold should not be tightened here to ensure that the symmetrical cell operates under no external pressure.

[0048] The solid-state battery was connected to the Blue Lightning testing system, and charge-discharge tests were performed on the battery at different current densities. Specifically, after allowing the battery to stand at 45°C for 30 minutes, the cycle current density was increased from 1 mA / cm². -2 Gradually increase to 10 mAcm -2 Meanwhile, the circulating surface capacity increased from 1 mAh cm⁻¹ -2 Gradually increase to 10mAh cm -2 .

[0049] like Figure 3 As shown in Figure a, Si-Li 21 Si5 electrode and Li 21 A symmetrical cell composed of Si5 electrodes exhibited a 4 mA / cm² reading. -2 The critical current density of Li 21 Si5 / Si-Li 21 Si5 electrode and Li 21 A symmetrical cell composed of Si5 electrodes exhibited a 10 mA cm⁻¹. -2 The ultra-high critical current density.

[0050] Furthermore, Figure 3 In section b, the above symmetrical cell is subjected to a 2mAcm -2 and 2mAh cm -2 Long-term charge-discharge cycle tests were conducted on the areal capacity. Among them, Si-Li... 21 Si5 electrode and Li 21 A symmetrical cell composed of Si5 electrodes developed an extremely high polarization voltage after 8 cycles, leading to cell failure. This indicates that the interface and bulk phase of this structure are unstable and severely damaged. In contrast, a Li-based cell... 21 Si5 / Si-Li 21 Si5 electrode and Li 21 The symmetrical cell composed of Si5 electrodes exhibited stable cycling for more than 200 hours (100 cycles), indicating that the bulk phase and interface of the structure remained stable.

[0051] Example 3

[0052] In a glove box where the water and oxygen content are both ≤0.1ppm, 10mg of silicon powder was weighed and placed on the surface of copper foil in a pressing mold. After being subjected to a pressure of 600MPa, a Si electrode was obtained. 0.5g of Li was weighed... 21 Si5 alloy powder and 0.5g of silicon powder were mixed and ground in an agate mortar for 5 minutes to obtain Li. 21Si5 alloy powder 50wt% of total mass Si-Li 21 Si5 powder. The cut copper foil was placed in the tablet press mold, and 10 mg of Si-Li 21 Si5 powder, placed on the surface of the copper foil in the tablet press mold, after 600 MPa pressure, Si-Li 21 Si5 electrode. 10 mg of Li was continuously added to the surface of the electrode 21 Si5 powder, after 600 MPa pressure, Li 21 Si5 / Si-Li 21 Si5 electrode.

[0053] Then on the above Si electrode, Si-Li 21 Si5 electrode and Li 21 Si5 / Si-Li 21 Si5 electrode surface added 30 mg of Li6PS5Cl, after simple pre-pressing, then added 50 mg of Li3InCl6, after 350 MPa pressure, obtained a double-layer solid-state electrolyte layer.

[0054] Finally, 1 g of LCO and Li3InCl6 were weighed as positive electrode powder in a mass ratio of 6:4, mixed and ground in an agate mortar for 5 min, 33 mg of positive electrode powder (LCO surface mass density was 19.8 mg cm -2 ) was placed on the surface of the double-layer solid-state electrolyte layer, and a cut aluminum foil was placed on the surface, and the solid-state battery mold nut was loosened under a pressure of 350 MPa for 3 min, and then the solid-state battery mold nut was loosened, to obtain a solid-state battery without external pressure. Note that the solid-state battery mold nut cannot be tightened at this point to ensure that the symmetrical battery operates under no external pressure.

[0055] The solid-state battery was connected to the blue light test system, and the above three batteries were subjected to charge and discharge test. The specific operation was as follows: at 45°C, the battery was placed for 30 min, then charged to 4.2V at low rate, then discharged to 2V, and then long cycle was carried out.

[0056] As shown in a of Figure 4 , the ICE of Si-based all-solid-state battery is only 66.92%, the specific discharge capacity is low (80 mAh g -1 ), and the battery fails after 20 cycles. It is shown that pure silicon negative electrode lacks effective electron / ion conduction network, and is accompanied by huge cycle expansion stress in the cycle process, and the negative electrode structure and interface have been fragmented.

[0057] As shown in b of Figure 4 , the Si-Li 21 Si5-based all-solid-state battery exhibits an ICE of 92.74%, which indicates that Li 21The addition of Si5 alloy can provide an efficient electron / ion conduction network for the silicon negative electrode. However, after 30 cycles, the battery has a soft short circuit behavior, and after 680 cycles, the battery suddenly fails. It shows that during the cycle process, there is growth of lithium dendrites at the negative electrode interface.

[0058] By contrast, Figure 4 As shown in c, Li 21 Si5 / Si-Li 21 The Si5-based all-solid-state battery exhibits an ICE of 97.69% and stable long cycle for more than 1000 cycles, which shows that Li 21 The Si5 layer further homogenizes the electric field on the negative electrode surface, stabilizes the interface between the negative electrode and the solid-state electrolyte, and realizes the stable long cycle of the silicon-based all-solid-state battery without external pressure.

[0059] Figure 5 In the present application, Li 21 Si5 / Si-Li 21 Si5-based all-solid-state battery and Si-Li 21 The Si5-based all-solid-state battery is disassembled, and the cycled Li 21 Si5 / Si-Li 21 Si5 negative electrode Figure 5 In a-b) and Si-Li 21 Si5 negative electrode Figure 5 In c-d), the cross-section scanning electron test is carried out. Li 21 Si5 / Si-Li 21 The Si5 negative electrode is electrochemically sintered into a stable integrated electrode after cycling, and the interface between the negative electrode and the electrolyte maintains good contact. After cycling, Li 21 Si5 / Si-Li 21 The thickness of the Si5 negative electrode is 120.3 μm, and compared with 105 μm Figure 2 In a), the expansion rate of the electrode is 14.5%. By contrast, Si-Li 21 The Si5 negative electrode is fragmented after cycling, and lithium dendrite growth behavior occurs. It shows that the silicon negative electrode of the present application embeds lithium ions into the silicon particle body phase under the action of an electric field, and the silicon particles are fused with Li 21 Si5 particle grain boundaries, and electrochemically sintered to form an integrated electrode.

[0060] Figure 6 In a-b) of the present application, the above three batteries are cycled for one cycle, and then electrochemical impedance testing and equivalent circuit simulation are carried out. As Si-Li 21 Si5 mixed layer and Li 21The sequential addition of Si5 layer, Rs, Rsei and Rct are significantly reduced. After long cycling, the above three batteries are again subjected to electrochemical impedance test Figure 6 In the middle c), it is found that the impedance of Si-based all-solid-state battery has shown exponential growth, indicating that the negative electrode has been fragmented and cannot provide continuous electronic / ionic conduction. Si-Li 21 The sudden decrease of Rs of Si5-based all-solid-state battery indicates the occurrence of soft short circuit behavior. In contrast, Li 21 Si5 / Si-Li 21 The impedance of Si5-based all-solid-state battery is still small, indicating that Li 21 Si5 / Si-Li 21 The stability of Si5-based all-solid-state battery under no external pressure cycling.

[0061] Further, Figure 7 The present application is compared with the reported literature of solid-state battery, using external pressure, current density and cycle number when the surface capacity retention rate is 80% as the comparison parameter (see Table 1 for detailed data). Comparison shows that the Li 21 Si5 / Si-Li 21 Si5-based all-solid-state battery occupies a clear advantage in the above three comparison indicators, which is the best result reported so far.

[0062] Table 1: Comparison of surface capacity and ICE data of the present application and reported literature.

[0063]

[0064] The reported solid-state battery literature is as follows:

[0065] 1. Han, S. Y. et al. Stress evolution during cycling of alloy-anode solid-state batteries. Joule 5, 2450-2465 (2021).

[0066] 2. Gao, X. et al. Solid-state lithium battery cathodes operating at low pressures. Joule 6, 636-646 (2022).

[0067] 3. Huang, Y., Shao, B., Wang, Y. & Han, F. Solid-state silicon anode with extremely high initial coulombic efficiency. Energy Environ. Sci. 16, 1569-1580 (2023).

[0068] 4. Cangaz, S. et al. Enabling high-energy solid-state batteries with stable anode interphase by the use of columnar silicon anodes. Adv. Energy Mater. 10, 2001320 (2020).

[0069] 5. Yamamoto, M., Terauchi, Y., Sakuda, A., Kato, A. & Takahashi, M. Effects of volume variations under different compressive pressures on the performance and microstructure of all-solid-state batteries. J. Power Sources 473, 228595 (2020).

[0070] 6. Kim, D. H. et al. Sheet-type Li6PS5Cl-infiltrated Si anodes fabricated by solution process for all-solid-state lithium-ion batteries. J. Power Sources 426, 143-150 (2019).

[0071] 7. Oh, J. et al. Anode-less all-solid-state batteries operating at room temperature and low pressure. Adv. Energy Mater. 13, 2301508 (2023).

[0072] 8. Doux, J. et al. Stack pressure considerations for room-temperature all-solid-state lithium metal batteries. Adv. Energy Mater. 10, 1903253 (2020).

[0073] 9. Chen, C. et al. Sustainable interfaces between Si anodes and garnet electrolytes for room-temperature solid-state batteries. ACS Appl. Mater. Interfaces 10, 2185-2190 (2018).

[0074] 10. Tan, D. H. S. et al. Carbon-free high-loading silicon anodes enabled by sulfide solid electrolytes. Science 373, 1494-1499 (2021).

[0075] 11. Xu, X. et al. Nano silicon anode without electrolyte adding for sulfide-based all-solid-state lithium-ion batteries. Small 19, 2302934 (2023).

[0076] 12. Zhang, Z. et al. An all-electrochem-active silicon anode enabled by spontaneous Li-Si alloying for ultra-high performance solid-state batteries. Energy Environ. Sci. 17, 1061-1072 (2024).

[0077] 13. Jun, S. et al. Interlayer engineering and prelithiation: empowering Si anodes for low-pressure-operating all-solid-state batteries. Small 2309437 (2024).

[0078] Example 4

[0079] In a glovebox with water and oxygen content ≤0.1 ppm, 0.5 g of Li 21 Si5 alloy powder and 0.5 g of silicon powder were mixed and ground in an agate mortar for 5 min to obtain Si-Li 21 Si5 alloy powder accounted for 50 wt% of the total mass of Si-Li 21 Si5 powder. The cut copper foil was placed in the tablet press mold, and three 10 mg Si-Li 21 Si5 powder was placed on the surface of the copper foil in the tablet press mold, and after 600 MPa pressure, Si-Li 21 Si5 electrode was obtained. On the surface of the three electrodes, 10 mg of Li 21 Si5 powder was added, and after 600 MPa pressure, Li 21 Si5 / Si-Li 21 Si5 electrode.

[0080] Then 30 mg of Li6PS5Cl was added to the surface of the Li 21 Si5 / Si-Li 21 Si5 electrode, and after simple pre-pressing, 50 mg of Li3InCl6 was added, and after 350 MPa pressure, a double-layer solid-state electrolyte layer was obtained.

[0081] Finally, 1 g of LCO and Li3InCl6 was weighed as the positive electrode powder with a mass ratio of 6:4, mixed and ground in an agate mortar for 5 min, and 20, 60 and 90 mg of positive electrode powder (LCO surface mass density was 12, 36 and 54 mg cm -2 ) was placed on the surface of the double-layer solid-state electrolyte layer, and a cut aluminum foil was placed on the surface, and the pressure was maintained at 350 MPa for 3 min, then the screw cap of the solid-state battery mold was loosened, and a solid-state battery without external pressure was obtained. Note that the screw cap of the solid-state battery mold cannot be tightened at this point to ensure that the symmetrical battery operates under no external pressure.

[0082] Connect the solid-state battery to the Blue Lightning testing system to perform charge-discharge tests on the three types of batteries mentioned above. Specifically, after allowing the battery to stand at 45°C for 30 minutes, charge it to 4.2V at a low rate, and then discharge it to 2V. Figure 8 As shown, Li 21 Si5 / Si-Li 21 The Si5-based all-solid-state battery exhibited 1.7, 5.4, and 7.8 mAh cm⁻¹ under the aforementioned cathode loads. -2 The surface capacity.

[0083] Example 5

[0084] In a glove box where the water and oxygen content are both ≤0.1ppm, 0.5g of Li was weighed out. 21 Si5 alloy powder and 0.5g of silicon powder were mixed and ground in an agate mortar for 5 minutes to obtain Li. 21 Si-Li alloy powder comprising 50 wt% of the total mass of Si5 alloy powder 21 Si5 powder. Place the cut copper foil in a tableting mold and weigh out 10 mg of Si-Li. 21 Si5 powder is placed on the surface of copper foil in a tableting mold and subjected to a pressure of 600 MPa to obtain Si-Li. 21 Si5 electrode. 10 mg of Li was further added to the electrode surface. 21 Si5 powder was subjected to a pressure of 600 MPa to obtain Li. 21 Si5 / Si-Li 21 Si5 electrode.

[0085] Then in Li 21 Si5 / Si-Li 21 30 mg of Li6PS5Cl was added to the surface of the Si5 electrode. After simple pre-compression, 50 mg of Li3InCl6 was added. After being subjected to a pressure of 350 MPa, a double-layer solid electrolyte layer was obtained.

[0086] Finally, 1g of LCO and Li3InCl6 were weighed out at a mass ratio of 6:4 as positive electrode powder, mixed, and ground in an agate mortar for 5 minutes. 38mg of the positive electrode powder (LCO surface mass density is 22.8mg / cm³) was then weighed out. -2 Place the aluminum foil on the surface of the double-layer solid electrolyte layer, and then place a pre-cut aluminum foil on the surface. Hold the pressure at 350 MPa for 3 minutes, and then loosen the nut of the solid battery mold to obtain a solid battery without external pressure. Note that the nut of the solid battery mold should not be tightened at this point to ensure that the symmetrical battery operates under no external pressure conditions.

[0087] The solid-state battery was connected with the blue electric test system for charge-discharge test. Specifically, the battery was placed at 45℃ for 30 min, then charged to 4.2V at different rates, and then discharged to 2V. As shown in FIG. 8, the Li Figure 9 Si5 / Si-Li 21 Si5 / Si-Li 21 The Si5-based solid-state battery exhibited discharge specific capacities of 141.8, 99, 79, 62.2, 52.7, 43.3, 33.8, 24.3 and 14.5 mAh g -2 at current densities of 0.3, 0.6, 1.3, 2.5, 3.8, 5.0, 6.3, 7.6 and 9 mA cm -1 respectively, indicating that the Li 21 Si5 / Si-Li 21 The Si5-based solid-state battery has excellent rate performance under pressure-free test environment.

Claims

1. A method for preparing a silicon anode for a long-cycle, pressure-free all-solid-state battery, characterized in that, Includes the following steps: 1) Mix Si powder and Li 21 Si5 powder was mixed uniformly under an argon atmosphere to obtain Si-Li. 21 Si5 powder; 2) Using cold pressing technology in a mold to bond Si-Li 21 Si5 powder is pressed into Si-Li 21 Si5 wafers; 3) In Si-Li 21 Li is added to the surface of Si5 wafers 21 Si5 powder was pressed into sheets to obtain Li 21 Si5 / Si-Li 21 Si5 negative electrode.

2. The method for preparing a silicon anode for a long-cycle, all-solid-state battery without external pressure as described in claim 1, characterized in that: In steps 2) and 3), the applied pressure is 300-900 MPa.

3. The method for preparing a silicon anode for a long-cycle, all-solid-state battery without external pressure as described in claim 1, characterized in that: In steps 2) and 3), the applied pressure is 600 MPa.

4. A silicon anode for a long-cycle, pressure-free, all-solid-state battery, characterized in that: Prepared by any one of the preparation methods of claims 1 to 3.

5. A method for preparing a long-cycle all-solid-state battery without external pressure, characterized in that, Includes the following steps: 1) A sulfide solid electrolyte and a chloride solid electrolyte are sequentially added to the surface of the silicon anode as described in claim 4, and pre-pressurized; 2) Mix and grind the positive electrode material and chloride solid electrolyte, place the mixed material on the pre-pressed surface in step 1), then place aluminum foil on it, and finally cold press it into shape; 3) Remove the pressure from step 2) to obtain an all-solid-state battery.

6. The method for preparing a long-cycle all-solid-state battery without external pressure as described in claim 5, characterized in that: In step 2), the applied pressure is 200-400 MPa.

7. The method for preparing a long-cycle all-solid-state battery without external pressure as described in claim 6, characterized in that: In step 2), the applied pressure is 350 MPa.

8. The method for preparing a long-cycle all-solid-state battery without external pressure as described in claim 5, characterized in that: The cathode materials include lithium cobalt oxide cathode materials, ternary cathode materials, and lithium iron phosphate cathode materials.

9. A long-cycle, all-solid-state battery without external pressure, characterized in that: Prepared by any one of the preparation methods of claims 5 to 8.

10. The all-solid-state battery with no external pressure and long cycle life as described in claim 9, characterized in that: The surface capacity is 0.6mAh / cm³. -2 ~7.8mAh cm -2 .

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