Silicon-based solid-state battery and preparation method thereof

Abstract

The present invention belongs to the field of solid-state batteries, and specifically relates to a method for preparing silicon-based solid-state batteries. Nanosilicon is modified in a modifying solution containing a compound of formula 1#imgabs0# to produce modified nanosilicon; the modified nanosilicon is used as a negative electrode active material and composited onto a current collector to form a silicon negative electrode; a precursor solution of an azo compound of formula 2#imgabs1# and an organic lithium salt is soaked in a porous membrane material to produce a liquid-absorbing porous membrane material; the positive electrode, the liquid-absorbing porous membrane material, and the silicon negative electrode are composited to form a battery cell, which is then packaged and subjected to a first cycle of charge and discharge to produce the silicon-based solid-state battery, wherein the first cycle of charge and discharge is performed with the assistance of ultrasound. The present invention also includes a solid-state battery produced by the method. The method of the present invention can improve the low-temperature cycle stability and high-rate performance of silicon-based solid-state batteries.

Description

Technical Field

[0001] The present invention belongs to the field of solid electrode negative electrode preparation, and specifically relates to the field of silicon negative electrode for silicon-based solid-state batteries. Background Art

[0002] Silicon negative electrodes have excellent capacity and other properties, but they also have problems such as large volume expansion and poor conductivity. This disadvantage of silicon negative electrodes will be further amplified in solid-state battery systems, which will further increase the difficulty of adapting silicon negative electrodes to solid-state batteries.

[0003] To address this issue, existing technologies also have some improvement measures, mainly focusing on lithium insertion, coating, and structural optimization of silicon negative electrodes. For example:

[0004] Chinese patent publication number CN119008858A discloses a porous silicon-carbon anode for solid-state batteries, comprising a negative electrode active material layer comprising porous silicon carbon, conductive carbon black, and a binder, wherein the binder comprises at least one of polyvinylidene fluoride, polyacrylic acid, polyacrylonitrile, and carboxymethyl cellulose. Chinese patent publication number CN118943319A discloses a lithium molybdate-coated silicon anode material, its preparation method, and application, wherein the lithium molybdate-coated silicon anode material has a core-shell structure, wherein the core comprises silicon powder and the shell comprises lithium molybdate. Patent publication number CN221994503U discloses a solid-state battery silicon anode sheet, comprising a negative electrode current collector, a conductive carbon layer, a lithium metal layer, and a silicon negative electrode active layer stacked in sequence, wherein the silicon negative electrode active layer has a concave-convex pattern on the side away from the negative electrode current collector. The Chinese patent document with publication number CN118888690A discloses a composite lithium metal negative electrode sheet, a preparation method and an application. The composite lithium metal negative electrode sheet includes a substrate in a sheet shape with a front side and a back side; a lithium metal layer covering the front side and the back side of the substrate; and a nano-silicon layer attached to the lithium metal layer.

[0005] In summary, there are some improvements in the existing technology to improve the adaptation of silicon negative electrodes to solid-state battery systems, but the means of improvement are still relatively scarce, and it is difficult to fundamentally solve the problems caused by the low conductivity and high expansion of silicon, especially it is difficult to effectively improve the capacity utilization rate, low-temperature stability and fast charging performance of solid-state batteries. Summary of the Invention

[0006] In response to the problems existing in solid-state silicon-based solid-state batteries, the first purpose of the present invention is to provide a method for preparing silicon-based solid-state batteries, aiming to prepare solid-state silicon-based batteries that have excellent capacity utilization, low-temperature stability and fast charging performance.

[0007] The second purpose of the present invention is to provide a silicon-based solid-state battery produced by the preparation method.

[0008] Silicon-based solid-state batteries have difficulty effectively realizing their theoretical capacity due to their significant volume expansion and low electrical conductivity, and are also difficult to adapt to application requirements under low-temperature and high-rate conditions. To address this issue, the present invention has conducted research and provided the following improvement solutions:

[0009] A method for preparing a silicon-based solid-state battery comprises modifying nano-silicon in a modifying solution containing a compound of formula 1 to obtain modified nano-silicon;

[0010]

[0011] The R1 is a C1-C6 alkyl group, or

[0012] The R2 to R4 are independently C1 to C6; the R5 and R6 are independently H or C1 to C6;

[0013] Using modified nano-silicon as negative electrode active material and compounding it on the current collector to form a silicon negative electrode;

[0014] Soaking the porous membrane material in a precursor solution of Formula 2, an azo compound, and an organic lithium salt to obtain a liquid-absorbing porous membrane material;

[0015]

[0016] The R7 is H, C1-C6 alkyl or substituted alkyl; the substituted alkyl is an alkyl containing at least one of hydroxyl, amino, and ester groups;

[0017] The positive electrode, the liquid-absorbing porous membrane material and the silicon negative electrode are composited to form a battery core, which is then packaged and charged and discharged for the first cycle to obtain the silicon-based solid-state battery, wherein the charging process of the first cycle is carried out under the assistance of ultrasound.

[0018] The present invention innovatively pre-modifies the nano-silicon material with the component of formula 1, and then assembles it with a porous membrane material that absorbs a precursor solution of formula 2 and an azo compound to form a battery, and performs the first cycle charging under the assistance of ultrasound. This can facilitate the mechanical effect of the volume expansion of the silicon negative electrode in combination with ultrasound, which can improve the hierarchical interface between the materials, reduce the interfacial impedance, and release the expansion space, thereby significantly optimizing the capacity utilization of the material and improving the low-temperature cycle stability and high-rate performance of the silicon-based solid-state battery.

[0019] In the present invention, the nano-silicon modification process, the precursor solution composition, and the in-situ curing of the dual effects of ultrasound and the mechanical action of silicon negative electrode expansion are the key to optimizing interface effects, reducing interface impedance, unblocking expansion space, and improving the material's capacity release rate, low-temperature stability, and fast charging performance.

[0020] In the present invention, nano-silicon is modified in advance by the formula 1, and then combined with subsequent processes, which can help improve the interface impedance of the solid-state battery and construct a suitable electrical conductivity, thereby helping to improve the capacity utilization rate, low-temperature cycle stability and fast charging performance of the prepared silicon-based solid-state battery.

[0021] In the present invention, the formula 1 includes formula 1A and / or formula 1B;

[0022]

[0023] Preferably, Formula 1 is a composite of Formula 1A and Formula 1B. Further preferably, the weight ratio of Formula 1A to Formula 1B is 5 to 20:100. Studies in the present invention have shown that the preferred Formulas 1A and 1B help further optimize the surface structure of nano-silicon, facilitate further integration with subsequent modification processes, and help further improve the capacity utilization, low-temperature cycle stability, and fast-charging performance of the prepared silicon-based solid-state battery.

[0024] In the present invention, the weight ratio of nano-silicon to the compound of formula 1 is 2 to 5:100.

[0025] Preferably, the D50 of the nano-silicon is 20-300 nm.

[0026] In the present invention, the modified nano-silicon can be used as a negative electrode active material based on conventional means to prepare the desired silicon negative electrode. For example, the negative electrode material of the silicon negative electrode also contains a conductive agent and a binder. The content of nano-silicon in the negative electrode material is 70-90 wt.%. The surface loading of the silicon negative electrode is 0.5-2 mg / cm 2 .

[0027] In the present invention, Formula 2 and azo compounds are innovatively used to pre-modify the porous membrane material, and then combined with the subsequent ultrasonic first-cycle charging treatment. In this way, based on the dual effects of ultrasound and the mechanical expansion of the silicon material itself, the interface structure and ion-electron conduction network can be optimized in situ, thereby optimizing the capacity utilization, low-temperature cycle stability and fast charging performance of the prepared silicon-based solid-state battery.

[0028] In the present invention, the azo compound includes at least one of azobisisobutyronitrile and azobisisoheptanenitrile.

[0029] The organic lithium salt may be any conductive lithium salt in the industry, for example, at least one of lithium bis(oxalatoborate), lithium trifluoromethanesulfonyl imide, and lithium bis(fluorosulfonyl imide).

[0030] Preferably, the weight ratio of the compound of formula 2 to the azo compound is 20-100:1 (furthermore, it may be 40-60:1), wherein the concentration of the organic lithium salt in the precursor solution is 0.5-5M (furthermore, it may be 0.7-1.5M).

[0031] Preferably, the precursor solution further comprises a component of formula 3;

[0032] Research in the present invention shows that adding the formula 3 to the precursor solution can further cooperate with the silicon first expansion and ultrasonic dual combined process to further optimize the capacity utilization, low-temperature cycle stability and fast charging performance of silicon-based solid-state batteries.

[0033] Preferably, the weight of Formula 3 is 5-20% of that of Formula 2.

[0034] In the present invention, the porous membrane material is a glass fiber membrane.

[0035] Preferably, the weight ratio of the porous membrane material to the precursor solution is 1:0.3-0.8.

[0036] In the present invention, the positive electrode may be a positive electrode known in the industry, for example, a commercial positive electrode, or may be prepared based on conventional principles and means.

[0037] For example, the positive electrode comprises a current collector and a positive electrode material composited on its surface, wherein the positive electrode material comprises a lithium-containing positive electrode active material, preferably comprising at least one of lithium iron phosphate, a binary material, and a ternary material. The binary material is a lithium-containing or sodium-containing salt comprising two elements of Ni, Co, Mn, and Al. The ternary material is a lithium-containing or sodium-containing salt comprising three elements of Ni, Co, Mn, and Al. Furthermore, trace elements are permitted in the positive electrode active material.

[0038] Preferably, the capacity ratio of the positive electrode to the silicon negative electrode is 1.05 to 1.4:1.

[0039] In the present invention, after the battery cells are assembled to obtain a battery, they are charged under ultrasound. In this way, based on the combination of ultrasound and the mechanical action of the first cycle of silicon-based materials, an excellent interface can be constructed to optimize the capacity utilization rate, low-temperature cycle stability and fast charging performance of the prepared silicon-based solid-state battery.

[0040] In the present invention, the power, temperature and current in the first cycle charging stage are further optimized, which helps to further improve the capacity utilization, low-temperature cycle stability and fast charging performance of the prepared silicon-based solid-state battery.

[0041] Preferably, the power of ultrasound is 500-1000W.

[0042] Preferably, the temperature during the first cycle of charge and discharge is 50-60°C.

[0043] Preferably, the current in the first cycle charge and discharge stage is 1-5 mA / cm2.

[0044] The cut-off voltage for charge and discharge is 2.75~4V.

[0045] In the present invention, the preferred solution is that the first cycle charging includes two ultrasonic-assisted treatment processes, wherein the power of the first ultrasonic-assisted process is 500-700W, and the power of the second ultrasonic-assisted process is 800-1000W. In the present invention, based on the two-stage gradient ultrasonic-assisted charging, it is possible to further combine ultrasound and silicon in-situ expansion to help further synergistically optimize the interface and further optimize the low-temperature fast charging performance of the resulting silicon-based solid-state battery.

[0046] In the present invention, the first stage of ultrasonic-assisted charging is performed to a charge level of 40-60%.

[0047] In the present invention, the first-cycle discharge process in the first-cycle charge and discharge stage may be performed under ultrasound or not.

[0048] The present invention also includes a silicon-based solid-state battery prepared by the preparation method.

[0049] The preparation method of the present invention can give the prepared silicon-based solid-state battery special physical and chemical characteristics, and the silicon-based solid-state battery prepared by the preparation method can improve capacity utilization, low-temperature cycle stability and fast charging performance.

[0050] Beneficial effects:

[0051] The present invention can significantly optimize the interface structure of silicon-based solid-state batteries through the modification of nano-silicon and the combined modification of the precursor solution of the porous mold, and further cooperate with the mechanical action of ultrasound and silicon-based in-situ expansion, which helps to improve the capacity utilization, low-temperature cycle stability and fast charging performance of silicon-based solid-state batteries.

[0052] The present invention also shows that adding a certain amount of Formula 3 to the precursor solution and / or combining the first-cycle charging treatment with the gradient ultrasonic power can help further optimize the interface and improve the low-temperature and fast-charging performance of the prepared silicon-based battery. DETAILED DESCRIPTION

[0053] The present invention will be described in detail below with reference to the embodiments, but the present invention is not limited thereto.

[0054] In the present invention, the nano-silicon may be a nano-silicon material that can be used in solid-state batteries. For example, as an optional solution, the D50 of the nano-silicon may be 150±10 nm.

[0055] Example 1

[0056] Step 1: Silicon Modification

[0057] Pretreat the nanosilicon. Disperse the nanosilicon in anhydrous ethanol and, while stirring, add a pretreatment agent (Formula 1A:Formula 1B) in a 20:100 ratio, with the ratio of pretreatment agent to nanosilicon being 3:100. Stir for 5 minutes, then centrifuge at 8,000-12,000 rpm to separate the silicon. Then, vacuum dry the mixture to obtain the pretreated silicon.

[0058] Step 2:

[0059] The nanosilicon negative electrode was prepared using conventional methods, with an areal loading of 1.5±0.1 mg / cm². The positive electrode was prepared using commercially available positive electrode materials. The positive-to-negative electrode capacity ratio was 1.2:1.

[0060] Negative electrode: The negative electrode active material (modified nanosilicon from step 1), conductive agent SP, binder LA-133, and CMC are weighed in a ratio of 90:5:3:2 for use. After dry grinding the weighed negative electrode active material, SP, and CMC in an agate mortar for a certain period of time, LA-133 and an appropriate amount of deionized water are added and wet-grinded for a certain period of time to obtain a homogeneous slurry. Cut the current collector (copper foil) into long sheets of appropriate size, wipe both surfaces clean with alcohol, and lay the smooth surface down on an automatic coating machine. After spraying an appropriate amount of alcohol, gently wipe the current collector with filter paper until it is flat. After the alcohol evaporates, transfer the slurry to the current collector in a narrow and long manner, and then use a scraper to evenly coat it into a sheet so that the slurry is evenly attached to the surface of the current collector; carefully transfer the coated electrode sheet to an oven (80°C) and dry it for 12 hours for later use.

[0061] Positive electrode: The positive electrode active material (NCM111), conductive carbon black SP, and binder (PVDF) are weighed in a mass ratio of 8:1:1 and fully ground in an agate mortar (dry grinding first, then adding solvent for wet grinding) to make a homogeneous slurry material; the current collector (aluminum foil) is cut into long sheets of appropriate size, both surfaces are wiped clean with alcohol, and laid flat on a flat glass with the smooth side facing down. After spraying an appropriate amount of alcohol, the current collector is gently wiped flat with filter paper. After the alcohol evaporates, the slurry is transferred narrowly and long to the top of the current collector, and then evenly coated into a sheet with a scraper so that the slurry is evenly attached to the surface of the current collector; the coated electrode is carefully transferred to an oven (120°C) and dried for 12 hours for use.

[0062] Liquid-carrying glass fiber membrane: Mix n-butyl acrylate, azobisisobutyronitrile, and lithium trifluoromethanesulfonyl imide to obtain a precursor solution. The weight ratio of n-butyl acrylate to azobisisobutyronitrile is 40:1, and the concentration of lithium trifluoromethanesulfonyl imide is 1M. Then, completely immerse the glass fiber membrane in the mixed solution for 1 hour to obtain a liquid-carrying glass fiber membrane. The weight ratio of the glass fiber membrane to the precursor solution is 1:0.4.

[0063] Step 4:

[0064] The negative electrode sheet, the liquid-carrying glass fiber membrane, the positive electrode sheet and the commercial nickel foam gasket in step 3 are stacked in sequence to form a button battery.

[0065] Step 5: Formation

[0066] Place the above-mentioned battery in a constant temperature box at 50-60℃, and pass a current of 2mA / cm2 for one charge and discharge (the charge and discharge cut-off voltage is 2.75~4V). The first cycle of charging is carried out with the assistance of ultrasound, and the power of the ultrasound is 600W. The first cycle of discharging is not carried out with the assistance of ultrasound, and the required new silicon electrode solid-state battery can be obtained.

[0067] Step 6:

[0068] The solid-state battery in step 5 was tested at 25°C and -15°C, with a test current rate of 0.25C and a voltage range of 2.75 to 4V. A rate charge and discharge test was also performed at 25°C with a test current rate of 2.5C.

[0069] Example 2

[0070] Compared with Example 1, the only difference is that the treatment agent in step 1 is changed. The experimental groups are:

[0071] Group A: The treatment agent is Formula 1A, and the amount of the treatment agent and other conditions are the same as in Example 1;

[0072] Group B: The treatment agent is Formula 1B, and the amount of the treatment agent and other conditions are the same as those in Example 1.

[0073] Example 3

[0074] Compared with Example 1, the only difference is that in step 5, the ultrasonic conditions are changed. The experimental groups are:

[0075] Group A: The ultrasonic power was set to 900 W, and other operating conditions were the same as in Example 1;

[0076] Group B: charged to half of the capacity at a power of 600 W, and then charged to the cut-off voltage at a power of 900 W. Other operations and parameters are the same as those in Example 1.

[0077] Example 4

[0078] Compared with Example 1, the only difference is that in step 3, the compound of formula 3 is further added to the precursor solution, and the added amount is 10% by weight of n-butyl acrylate. Other operations and parameters are the same as in Example 1.

[0079] Example 5

[0080] Compared with Example 1, the only difference is that in step 1, the ratio of the pretreatment agent to the nano-silicon is 5:100 in the mixed solution of Formula 1A:Formula 1B = 30:100. The treatment time is 10 minutes. In step 2, the precursor solution is a solution of propyl acrylate, azobisisobutyronitrile, and lithium trifluoromethanesulfonyl imide, wherein the weight ratio of propyl acrylate to azobisisobutyronitrile is 50:1, and the concentration of lithium trifluoromethanesulfonyl imide is 0.8M. The glass fiber membrane is then completely immersed in the mixed solution for 1.5 hours. The weight ratio of the glass fiber membrane to the precursor solution is 1:0.6. All other operations and parameters are the same as in Example 1.

[0081] Comparative Example 1

[0082] Compared with Example 1, the only difference is that step 1 is not performed, and nano-silicon is directly used as a raw material for subsequent processing. Other operations and parameters are the same as those in Example 1.

[0083] Comparative Example 2

[0084] Compared with Example 1, the only difference is that in step 5, ultrasonic treatment is not performed.

[0085] The test results of step 6 of each case are shown in Table 1:

[0086] Table 1

[0087]

[0088] Note: (a): The number of cycles mentioned refers to the number of cycles until the capacity decays to 80% of the initial capacity;

[0089] (b): The number of cycles mentioned refers to the number of cycles in which the capacity decays to 80% of the initial capacity;

[0090] It can be seen from the examples and comparative examples that by combining the modification of nano-silicon and the modification of the precursor solution of the porous membrane, and further combining the mechanical action of ultrasound and silicon-based in-situ expansion, the interface structure of the silicon-based solid-state battery can be significantly optimized, which helps to improve the silicon-based solid-state battery and can improve the capacity utilization rate, low-temperature cycle stability and fast charging performance. It can be seen from Examples 1 and 2 that the combined formula 1A and formula 1B can be combined with the subsequent ultrasound-silicon-based self-mechanical combined action to optimize the interface, improve the capacity utilization rate of the silicon-based solid-state battery, and improve the low temperature and fast charging performance. In addition, it can be seen from Examples 1 and 3B that the gradient ultrasound-assisted silicon-based in-situ expansion double action can help to further strengthen the interface characteristics of the prepared material, help to further strengthen the capacity utilization rate of the prepared material, and improve its low temperature and fast charging performance. In addition, it can be seen from Examples 1 and 4 that adding a certain formula 3 to the precursor solution can cooperate with the combined action of the silicon in-situ machinery and ultrasound to further optimize the interface structure and further optimize the performance of the obtained silicon-based solid-state battery.

Claims

1. A method for preparing a silicon-based solid-state battery, characterized in that: Modifying nano-silicon in a modification solution containing a compound of formula 1 to obtain modified nano-silicon; Formula 1 The R1 is a C1~C6 alkyl group, or ; The R2 to R4 are independently C1 to C6; the R5 and R6 are independently H or C1 to C6; Using modified nano-silicon as negative electrode active material and compounding it on the current collector to form a silicon negative electrode; Soaking the porous membrane material in a precursor solution of Formula 2, an azo compound, and an organic lithium salt to obtain a liquid-absorbing porous membrane material; Formula 2 The R7 is H, C1-C6 alkyl or substituted alkyl; the substituted alkyl is an alkyl containing at least one of hydroxyl, amino, and ester groups; The positive electrode, the liquid-absorbing porous membrane material and the silicon negative electrode are composited to form a battery core, which is then packaged and charged and discharged for the first cycle to obtain the silicon-based solid-state battery, wherein the charging process of the first cycle is carried out under the assistance of ultrasound.

2. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The formula 1 includes formula 1A and / or formula 1B; Formula 1A Formula 1B.

3. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The weight ratio of nano-silicon to the compound of formula 1 is 2-5:

100.

4. The method for preparing a silicon-based solid-state battery according to claim 3, wherein: The D50 of nano-silicon is 20~300nm.

5. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The negative electrode material of the silicon negative electrode also contains a conductive agent and a binder.

6. The method for preparing a silicon-based solid-state battery according to claim 5, wherein: In the negative electrode material, the content of nano-silicon is 70-90wt.%.

7. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The surface loading of silicon negative electrode is 0.5~2mg / cm 2 .

8. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The organic lithium salt includes at least one of lithium bis(oxalatoborate), lithium trifluoromethanesulfonyl imide, and lithium bis(fluorosulfonyl imide).

9. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The azo compound includes at least one of azobisisobutyronitrile and azobisisoheptanenitrile.

10. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The porous membrane material is a glass fiber membrane.

11. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The weight ratio of the compound of formula 2 to the azo compound is 20-100:1, wherein the concentration of the organic lithium salt in the precursor solution is 0.5-5M.

12. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The precursor solution further includes a component of formula 3; Formula 3.

13. The method for preparing a silicon-based solid-state battery according to claim 12, wherein: The formula 3 is 5-20% of the weight of the formula 2.

14. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The weight ratio of the porous membrane material to the precursor solution is 1:0.3-0.

8.

15. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The positive electrode comprises a current collector and a positive electrode material composited on the surface of the current collector, wherein the positive electrode material comprises a lithium-containing positive electrode active material.

16. The method for preparing a silicon-based solid-state battery according to claim 15, wherein: The positive electrode active material includes at least one of lithium iron phosphate, binary material, and ternary material.

17. The method for preparing a silicon-based solid-state battery according to claim 15, wherein: The capacity ratio of the positive electrode and the silicon negative electrode is 1.05~1.4:

1.

18. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The power of ultrasound is 500~1000W.

19. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The temperature during the first cycle of charge and discharge is 50~60℃.

20. The method for preparing a silicon-based solid-state battery according to claim 1, wherein: The current of the first cycle charge and discharge stage is 1~5mA / cm 2 ;The cut-off voltage is 2.5~4V.

21. The method for preparing a silicon-based solid-state battery according to any one of claims 1 to 20, wherein: The first round of charging includes two ultrasonic-assisted processing processes, in which the power of the first ultrasonic assistance is 500~700W, and the power of the second ultrasonic assistance is 800~1000W.

22. A silicon-based solid-state battery produced by the method according to any one of claims 1 to 21.

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