Hydrogen-bond-rich domain pre-lithium binder for silicon-based negative electrode of lithium ion battery, preparation method and application

Abstract

The invention belongs to the technical field of chemical power sources, and discloses a hydrogen-bond-domain-rich pre-lithium binder for a silicon-based negative electrode of a lithium ion battery, a preparation method and application. The preparation method comprises the following steps: (1) preparing polyacrylic acid (PAA) powder into a polymer aqueous solution (a1); (2) adding lithium hydroxide (LiOH) into a1 to obtain a lithium polyacrylate aqueous solution (a2); (3) freeze-drying the a2 to obtain powder (PAALi); (4) respectively preparing PAA and PAALi into polymer solutions (b1 and b2) with the same concentration according to the step (1); and (5) compounding b1 and b2 according to a certain proportion to obtain the lithium polyacrylate pre-lithium binder containing the hydrogen bond enrichment domain. According to the binder, on one hand, an extra lithium source and lithium ion transmission sites can be provided for the surfaces of electrode particles, on the other hand, the cohesion strength of the binder can be fully maintained through an internal hydrogen bond enrichment domain, and the adhesion performance of the electrode is improved.

Description

Technical Field

[0001] This invention belongs to the field of chemical power source technology, specifically a hydrogen-rich bond domain pre-lithium binder for silicon-based anodes of lithium-ion batteries, its preparation method, and its application. Background Technology

[0002] With the depletion of non-renewable energy sources becoming increasingly urgent, the development of new energy sources has become a top priority in global research. Electrochemical energy storage, as a crucial part of new energy applications, converts electrical energy into chemical energy for storage, offering advantages such as stable and continuous power output, quiet operation, and miniaturization. Lithium-ion batteries (LIBs), due to their high energy density, high reliability, and low self-discharge, have become the most widely used electrochemical energy storage devices. Currently, graphite anodes, widely used in commercial lithium-ion batteries, have been nearly pushed to their performance limits. To overcome performance bottlenecks, silicon, with its ultra-high theoretical specific capacity, low chemical potential, high safety, environmental friendliness, and high elemental abundance, holds immense potential to propel lithium-ion batteries to even higher capacity eras. In the research of silicon anode materials, high-performance binders are crucial for fully leveraging the theoretical specific capacity advantage of silicon and maintaining battery cycle stability.

[0003] The two major challenges currently facing silicon-based anodes are the enormous volume expansion (~400%) during lithiation and severe interfacial side reactions. The development of high-performance binders can not only improve electrode mechanical stability by optimizing electrode mechanical strength but also suppress side reactions by optimizing the interfacial environment. Polyacrylic acid and lithium polyacrylate, as important commercially available silicon-based binders, effectively improve the electrochemical performance of silicon-based anodes due to their rich hydrogen bond networks and interfacial lithium supplementation advantages, respectively. Theoretically, controlling the lithiation degree of polyacrylic acid can achieve a synergistic effect between these two advantages. However, in lithium-based polyacrylic acid obtained by traditional control methods (such as pH control and lithium oxide feeding control), the carboxyl and lithium carboxyl groups are randomly distributed. At medium to high lithiation degrees, the overall hydrogen bond network stability is significantly reduced compared to polyacrylic acid, and the interaction with active particles, conductive agents, and copper foil is weak, severely limiting the performance of silicon-based anode materials. This invention combines polyacrylic acid with fully lithium-ionized polyacrylate, thereby constructing intermolecular hydrogen-rich domains in the binder system while maintaining the same degree of lithium replenishment. This effectively optimizes the regional hydrogen bond network, improves the adhesion strength of the electrode, and thus improves the electrochemical performance of the silicon-based anode. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a hydrogen-rich pre-lithiation binder for silicon-based anodes in lithium-ion batteries, its preparation method, and its application. This method can achieve lithium replenishment at the silicon-based anode interface while maintaining the hydrogen bond network between electrode materials, thereby improving electrode stability.

[0005] The present invention adopts the following technical solution:

[0006] A hydrogen-rich bond domain pre-lithium binder for silicon-based anodes in lithium-ion batteries, its preparation method, and its application, characterized by comprising the following steps:

[0007] S1: At room temperature, mix polyacrylic acid (PAA) powder with deionized water (H2O) in a 250ml beaker for 4-24 hours to prepare a polymer aqueous solution (a-PAA) with a concentration of 3-10wt%.

[0008] S2: Based on the mass of polyacrylic acid material in the solution, add lithium hydroxide powder (LiOH) in the same molar ratio as the solute repeating unit, and stir for 8-24 hours to obtain a fully lithiated lithium polyacrylate aqueous solution (a-PAALi).

[0009] S3: Transfer a-PAALi to an evaporating dish with a diameter of 20 cm, freeze it thoroughly in a refrigerator, and then put it into a freeze dryer for freeze drying. After 3 to 7 days, take out the completely freeze-dried solid sample and grind it thoroughly with a mortar and pestle to obtain a powder sample (PAALi).

[0010] S4: Prepare polymer solutions (b-PAA and b-PAALi) of the same concentration in 250ml beakers at room temperature. The solutions are a mixture of H2O and dimethyl sulfoxide (DMSO).

[0011] S5: Mix b-PAA and b-PAALi at a certain feeding ratio and stir for 5 to 30 minutes to obtain PPL, a pre-lithium polyacrylate binder containing hydrogen bond enrichment domains.

[0012] The present invention also has the following technical features:

[0013] The molecular weight (Mw) of the polyacrylic acid mentioned in step S1 is 100,000 to 4,000,000.

[0014] The LiOH powder used in step S2 is one or more of anhydrous lithium hydroxide and lithium hydroxide monohydrate.

[0015] The freeze-drying process described in step S3 is characterized by a temperature range of -60℃ to -40℃ and a pressure range of 10 to 100 Pa.

[0016] The concentration range described in step S4 is 2–8 wt%.

[0017] The mass ratio m of H2O to DMSO mentioned in step S4 H2O / m DMSO The range is between 50% and 900%.

[0018] In step S5, the mass ratio m of b-PAA to b-PAALi is recorded. b-PAA / m b-PAALi The range is between 10% and 900%.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By compounding polyacrylic acid with fully lithium polyacrylate, intermolecular hydrogen-rich domains are constructed in the binder system while maintaining the same degree of lithium replenishment. This effectively optimizes the regional hydrogen bond network, improves the adhesion strength of the electrode, and thus improves the electrochemical performance of the silicon-based anode. The nano-pure silicon anode prepared by this binder has a higher first-cycle coulombic efficiency than PAA at a current density of 0.3C and more stable cycling performance than PAALi. Attached Figure Description

[0021] Figure 1 These are Fourier transform infrared spectra of Examples 1-3 prepared according to the present invention, the control group PAA, and the fully lithiumized PAALi.

[0022] Figure 2 The first-efficiency and initial voltage curves of the nano-silicon anodes prepared in Examples 1-3 of this invention and the control group PAA and PAALi are shown at a current density of 0.05C.

[0023] Figure 3 This is a cycle capacity diagram of the nano-silicon anodes prepared in Examples 1-3 of the present invention and the control group PAA and PAALi at a current density of 0.3C. Detailed Implementation

[0024] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Figure 1 These are the Fourier transform infrared spectra of Examples 1-3 prepared in this invention, the control group PAA, and the fully lithiated PAALi. Analysis of the results reveals that at medium to high lithiation levels, the 3325 cm⁻¹... -1The strong intermolecular hydrogen bond domain peaks at 1710–1750 cm⁻¹ can be directly observed; and with increasing lithiation, the carboxylic acid dimer exhibits peaks at 1710–1750 cm⁻¹. -1 The C=O double bond vibration peak gradually changes to the carboxylate (-COO) group. - 1615~1650cm -1 The double bond vibration peaks in the sample indicate that the method for controlling the degree of lithiation is reliable.

[0026] Figure 2 The curves show the initial efficiency and initial voltage of half-cells (with lithium metal on the opposite side) using nano-silicon anodes prepared in Examples 1-3 of this invention, the control group PAA, and fully lithiated PAALi, at a current density of 0.05C. The results indicate that the charge / discharge efficiency increases synchronously with the degree of lithiation, reaching 82.2%, 87.5%, and 87.6% for Examples 1-3, respectively.

[0027] Figure 3 The figures show the cycling curves of half-cells (with lithium metal on the opposite side) prepared using nano-silicon anodes (Examples 1-3 of this invention, control group PAA, and fully lithium-modified PAALi) at a current density of 0.3C. The results indicate that Example 3 exhibits the best capacity retention and cycling stability, maintaining a discharge specific capacity of 1716.03 mAh / g after 150 cycles, demonstrating a significant improvement in electrochemical performance compared to the two control groups.

[0028] Example 1:

[0029] The preparation method in this example is as follows:

[0030] S1: At room temperature, polyacrylic acid (PAA) powder and deionized water (H2O) are thoroughly stirred in a 250ml beaker for 18h to prepare a polymer aqueous solution (a-PAA) with a concentration of 6wt%.

[0031] S2: Based on the mass of polyacrylic acid material in the solution, add lithium hydroxide powder (LiOH) in the same molar ratio as the solute repeating unit, and stir for 18 hours to obtain a fully lithiated lithium polyacrylate aqueous solution (a-PAALi).

[0032] S3: Transfer a-PAALi to an evaporating dish with a diameter of 20 cm, freeze it thoroughly in a refrigerator, and then put it into a freeze dryer for freeze drying. After 5 days, take out the completely freeze-dried solid sample and grind it thoroughly with a mortar and pestle to obtain a powder sample (PAALi).

[0033] S4: Prepare 4wt% polymer solutions (b-PAA and b-PAALi) of PAA and PAALi separately in 250ml beakers at room temperature. The solutions are mixtures of H2O and dimethyl sulfoxide (DMSO). H2O / m DMSO The value is 900%;

[0034] S5: Combine b-PAA and b-PAALi according to m b-PAA / m b-PAALi The value is 300% compounded, and after stirring for 5 minutes, Example 1 can be obtained.

[0035] Comparative Example 1:

[0036] Polyacrylic acid (PAA) powder and deionized water (H2O) were thoroughly stirred in a 250 ml beaker for 18 h at room temperature to prepare a polymer aqueous solution with a concentration of 4 wt%, which is Comparative Example 1.

[0037] Comparative Example 2:

[0038] S1: At room temperature, polyacrylic acid (PAA) powder and deionized water (H2O) are stirred thoroughly in a 250ml beaker for 18h to prepare a polymer aqueous solution (a-PAA) with a concentration of 6wt%.

[0039] S2: Based on the mass of polyacrylic acid material in the solution, add lithium hydroxide powder (LiOH) in the same molar ratio as the solute repeating unit, and stir for 18 hours to obtain a fully lithiated lithium polyacrylate aqueous solution (a-PAALi).

[0040] S3: Transfer a-PAALi to an evaporating dish with a diameter of 20 cm, freeze it thoroughly in a refrigerator, and then put it into a freeze dryer for freeze drying. After 5 days, take out the completely freeze-dried solid sample and grind it thoroughly with a mortar and pestle to obtain a powder sample (PAALi).

[0041] S4: PAALi powder and deionized water (H2O) were thoroughly stirred in a 250ml beaker at room temperature for 18 hours to prepare a polymer aqueous solution with a concentration of 4wt%, which is Comparative Example 2.

[0042] Example 2:

[0043] The preparation method in this example is exactly the same as that in Example 1, except for the following point:

[0044] In step S5, m b-PAA / m b-PAALi The value is 100%.

[0045] Example 3:

[0046] The preparation method in this example is exactly the same as that in Example 1, except for the following point:

[0047] In step S5, m b-PAA / m b-PAALi The value is 33.3%.

[0048] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A hydrogen-rich bond domain pre-lithium binder for silicon-based anodes in lithium-ion batteries, its preparation method, and its application, characterized in that, Includes the following steps: S1: At room temperature, mix polyacrylic acid (PAA) powder with deionized water (H2O) in a 250ml beaker for 4-24 hours to prepare a polymer aqueous solution (a-PAA) with a concentration of 3-10wt%. S2: Based on the mass of polyacrylic acid material in the solution, add lithium hydroxide powder (LiOH) in the same molar ratio as the solute repeating unit, and stir for 8-24 hours to obtain a fully lithiated lithium polyacrylate aqueous solution (a-PAALi). S3: Transfer a-PAALi to an evaporating dish with a diameter of 20 cm, freeze it thoroughly in a refrigerator, and then put it into a freeze dryer for freeze drying. After 3 to 7 days, take out the completely freeze-dried solid sample and grind it thoroughly with a mortar and pestle to obtain a powder sample (PAALi). S4: Prepare polymer solutions (b-PAA and b-PAALi) of the same concentration in 250ml beakers at room temperature. The solutions are a mixture of H2O and dimethyl sulfoxide (DMSO). S5: Mix b-PAA and b-PAALi at a certain feeding ratio and stir for 5 to 30 minutes to obtain PPL, a pre-lithium polyacrylate binder containing hydrogen bond enrichment domains.

2. The hydrogen-rich bond domain pre-lithium binder for silicon-based anodes of lithium-ion batteries according to claim 1, its preparation method, and its application, characterized in that: The molecular weight (M) of polyacrylic acid mentioned in step S1 w The range is 100,000 to 4,000,000.

3. The hydrogen-rich bond domain pre-lithium binder for silicon-based anodes of lithium-ion batteries according to claim 1, its preparation method, and its application, characterized in that: The LiOH powder used in step S2 is one or more of anhydrous lithium hydroxide and lithium hydroxide monohydrate.

4. The hydrogen-rich bond domain pre-lithium binder for silicon-based anodes of lithium-ion batteries according to claim 1, its preparation method, and its application, characterized in that: The freeze-drying process described in step S3 is characterized by a temperature range of -60℃ to -40℃ and a pressure range of 10 to 100 Pa.

5. The hydrogen-rich bond domain pre-lithium binder for silicon-based anodes of lithium-ion batteries according to claim 1, its preparation method, and its application, characterized in that: The concentration range described in step S4 is 2–8 wt%.

6. The hydrogen-rich bond domain pre-lithium binder for silicon-based anodes of lithium-ion batteries according to claim 1, its preparation method, and its application, characterized in that: The mass ratio m of H2O to DMSO mentioned in step S4 H2O / m DMSO The range is between 50% and 900%.

7. The hydrogen-rich bond domain pre-lithium binder for silicon-based anodes of lithium-ion batteries according to claim 1, its preparation method, and its application, characterized in that: In step S5, the mass ratio m of b-PAA to b-PAALi is recorded. b-PAA / m b-PAAL i is in the range of 10% to 900%.

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