Wood-metal lithium composite negative electrode material and preparation method and application thereof

Abstract

The application belongs to the technical field of secondary batteries, and discloses a wood-metal lithium composite negative electrode material and a preparation method and application thereof, which comprises the following steps: cutting the wood part of natural wood into blocks to obtain wood block samples with a preset size; immersing the wood block samples with the preset size in an organic solvent for extraction treatment, naturally air-drying, and then slicing along the transverse section direction of the wood to obtain wood part slices; drying and water-removing the wood part slices to obtain wood slices after water removal; stacking the wood slices after water removal and metal lithium strips up and down, and performing roll pressing treatment so that the metal lithium is pressed into the pores of the wood, thereby obtaining the wood-metal lithium composite negative electrode material; the application realizes rapid and simple preparation of the composite negative electrode, avoids methods such as molten lithium pouring or electrodeposition which are time-consuming, complicated and have safety hazards; and the composite negative electrode can reduce charge and discharge polarization, prolong the cycle life of the battery, and improve the capacity retention rate in different battery systems.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, and specifically relates to a wood-lithium metal composite anode material, its preparation method, and its application. Background Technology

[0002] Lithium metal, with its ultra-high theoretical specific capacity and ultra-low standard electrode potential, has become a highly promising anode material for next-generation high-energy-density rechargeable batteries. Using lithium metal as the anode, various cathode materials can be matched to assemble diverse lithium metal battery systems; for example, lithium iron phosphate, lithium nickel cobalt manganese oxide, sulfur cathodes, and oxygen cathodes are commonly used in lithium-ion batteries. However, during cycling, lithium metal batteries experience uneven deposition and extraction of lithium metal, leading to dendrite formation on the surface of the lithium metal anode. This causes rapid electrode volume expansion, resulting in poor cycle stability, increased charge-discharge polarization, reduced coulombic efficiency, and rapid lifespan degradation. Furthermore, the further growth of lithium dendrites can puncture the separator, causing short circuits due to contact between the positive and negative electrodes, and even triggering severe thermal runaway and safety accidents. Therefore, inducing uniform deposition and extraction of lithium metal, and avoiding the formation of lithium dendrites and massive volume expansion, are key issues currently being addressed in the practical application of lithium metal battery systems.

[0003] To address the aforementioned issues, researchers have introduced electrode framework materials with micro / nano three-dimensional porous structures to construct lithium metal composite anodes. Compared to traditional framework-less lithium metal anodes, the high specific surface area of ​​the electrode framework materials can effectively create three-dimensional lithium metal electrodes, thereby reducing local current density. Secondly, the abundant pores and interconnected porous three-dimensional structure provide more deposition space for lithium metal, effectively limiting the huge volume expansion of the lithium metal anode. In addition, some framework materials can also regulate the electric field distribution on the surface of the lithium metal electrode and guide lithium ion flow, thereby inducing more uniform lithium metal deposition and extraction behavior.

[0004] In existing research papers, materials such as reduced graphene oxide, three-dimensional copper foil, copper nanowires, and polyacrylonitrile have been reported for use in preparing lithium metal anode frameworks. However, most of the existing framework materials have limited raw material sources, are cumbersome to prepare and have high costs, or have complex methods for constructing three-dimensional structures. In addition, the framework is initially in a lithium-free state and cannot be directly matched with cathode materials without lithium sources under high-capacity conditions.

[0005] To combine the framework and lithium metal, the main methods used are molten lithium infusion or pre-electrodeposition. Molten lithium infusion involves melting lithium metal at high temperatures and then infusing it into a three-dimensional framework material while the lithium metal is in a liquid state. This process is complex and dangerous. Electrodeposition involves depositing a certain capacity of lithium metal onto the framework first. This method is also relatively cumbersome and prone to uneven deposition, and the deposition capacity is also easily limited. Therefore, it is still necessary to explore widely available and low-cost framework raw materials and simple and easy-to-implement composite anode preparation processes. Summary of the Invention

[0006] In view of the technical problems existing in the prior art, the present invention provides a wood-lithium metal composite anode material, its preparation method and application, so as to solve the technical problems of complex preparation process of existing lithium metal composite anodes and high risk of composite operation of framework and lithium metal.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for preparing a wood-lithium metal composite anode material, comprising:

[0009] The xylem of natural wood is cut into blocks to obtain wood block samples of a predetermined size;

[0010] The wood block sample of the preset size was immersed in an organic solvent for extraction treatment, and after natural air drying, it was sliced ​​along the cross section of the wood to obtain xylem slices.

[0011] The xylem slices are dried and dehydrated to obtain dehydrated wood chips;

[0012] After dehydration, wood chips and lithium metal strips are stacked one on top of the other and subjected to roller pressing to press the lithium metal into the pores of the wood, thus obtaining the wood-lithium metal composite negative electrode material.

[0013] Furthermore, the natural wood is one of eucalyptus, fir, pine, poplar, paulownia, balsa wood, and birch.

[0014] Furthermore, the organic solvent is a mixture of toluene and ethanol, a mixture of benzene and ethanol, or a mixture of toluene, benzene, and ethanol.

[0015] Furthermore, in the mixed system of toluene and ethanol, the volume ratio of toluene to ethanol is 2:1; in the mixed system of benzene and ethanol, the volume ratio of benzene to ethanol is 2:1; and in the mixed system of toluene, benzene and ethanol, the volume ratio of toluene, benzene and ethanol is 1:1:1.

[0016] Furthermore, the process of slicing the wood along its cross-section after natural air drying to obtain xylem slices is as follows: the naturally air-dried wood block is sliced ​​along its cross-section while being moistened with deionized water to obtain xylem slices.

[0017] Furthermore, the wood chips are dried and dehydrated to obtain dehydrated wood chips. During this process, the dried wood chips are transferred to a water jacket box for further dehydration. The water and oxygen concentrations in the glove box are both below 0.1 ppm.

[0018] Furthermore, the thickness of the xylem slice is 20-100 μm, and the thickness of the lithium metal strip is 20-100 μm.

[0019] Furthermore, during the process of stacking the dehydrated wood chips and lithium metal strips on top of each other and rolling them, the rolling gap of the rolling mill is 1-3mm and the rolling speed is 10-30mm / s.

[0020] The present invention also provides a wood-lithium metal composite anode material, which is prepared using the aforementioned method for preparing the wood-lithium metal composite anode material.

[0021] The present invention also provides an application of a wood-lithium metal composite anode material, which is used in lithium metal batteries and serves as the anode of the lithium metal battery.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The wood-lithium metal composite anode material and its preparation method provided by this invention use natural wood with a three-dimensional structure as a lithium metal skeleton, which can effectively transform the originally two-dimensional planar lithium metal anode into a three-dimensional structure, reducing the local current density. The insulating wood skeleton can adjust the electric field strength near the surface of the lithium metal electrode to become more uniform, thereby guiding the lithium ion flow and making the lithium metal deposition / deposition behavior more uniform, effectively inhibiting the growth of lithium dendrites. At the same time, the wood block sample is extracted using an organic solvent. After organic solvent treatment, more micro-nano pores inside the wood are exposed. The porous structure can confine the lithium metal, providing sufficient space for lithium deposition and effectively mitigating the volume expansion of the electrode during cycling. Secondly, there is no need to carbonize the wood, avoiding the strong... The loss of wood's pore structure due to heat loss is addressed by using a method that preserves the inherent mechanical strength of the wood and utilizes its flexibility and ductility to fill the wood pores with lithium metal through rolling. This method achieves rapid and simple composite anode preparation, avoiding time-consuming, cumbersome, and potentially dangerous methods such as molten lithium filling or electrodeposition. Furthermore, by adjusting the length, width, and thickness of the wood slices, composite lithium metal anodes of different sizes and capacities can be produced to meet the needs of various applications. In this invention, natural wood is used as the raw material, and a framework material suitable for lithium metal anodes is obtained through simple pretreatment steps. Compared with other metal, carbon, and synthetic polymer framework materials, wood has significant advantages such as abundant reserves, low cost, and biodegradability.

[0024] The wood-lithium metal composite anode material prepared by this invention can be matched with different types of cathodes such as lithium iron phosphate, lithium nickel cobalt manganese oxide, and sulfur / carbon composites to assemble various lithium metal batteries. Compared with bare lithium anodes without wood skeletons, this composite anode can play a beneficial role in reducing charge and discharge polarization, extending battery cycle life, and improving capacity retention in different battery systems. Attached Figure Description

[0025] Figure 1 This is a photograph of the eucalyptus-lithium metal composite anode material prepared in Example 1;

[0026] Figure 2 The image shows a scanning electron microscope (SEM) image of the microstructure of the eucalyptus-lithium metal composite anode material prepared in Example 1.

[0027] Figure 3 The image shows a scanning electron microscope (SEM) image of the microstructure of the cedarwood-lithium metal composite anode material prepared in Example 2.

[0028] Figure 4 The battery long-cycle performance curves of the coin lithium metal battery in Example 1 and the coin lithium metal battery in the comparative example at a 0.5C rate are shown.

[0029] Figure 5 The figures show the long-cycle performance curves of the coin lithium metal battery in Example 2 and the coin lithium metal battery in the comparative example at a rate of 0.4C. Detailed Implementation

[0030] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0031] This invention provides a method for preparing a wood-lithium metal composite anode material, comprising the following steps:

[0032] Step 1: Pre-treatment of wood raw materials:

[0033] The xylem of natural wood is cut into blocks to obtain wood block samples of a predetermined size. The wood block samples of the predetermined size are completely immersed in an organic solvent for extraction treatment until the reflux liquid is colorless, thus obtaining the extracted sample. The natural wood is one of eucalyptus, fir, pine, poplar, paulownia, balsa wood, and birch. The organic solvent is a mixture of toluene and ethanol, a mixture of benzene and ethanol, or a mixture of toluene, benzene, and ethanol. Preferably, in the mixture of toluene and ethanol, the volume ratio of toluene to ethanol is 2:1; in the mixture of benzene and ethanol, the volume ratio of benzene to ethanol is 2:1; and in the mixture of toluene, benzene, and ethanol, the volume ratio of toluene, benzene, and ethanol is 1:1:1.

[0034] Step 2, Treatment of the wooden framework:

[0035] After extraction, the sample was air-dried to remove organic solvents. Then, while wetted with deionized water, it was sliced ​​along the cross-section of the wood using an ultrathin slicer to obtain xylem slices. The thickness of the xylem slices was 20-100 μm. The xylem slices were placed in an oven for drying, and then transferred to a glove box with water and oxygen concentrations below 0.1 ppm for dehydration treatment to obtain dehydrated wood chips, which are the wood skeleton.

[0036] Step 3: Preparation of wood-lithium metal composite anode material:

[0037] The dehydrated wood chips and lithium metal strips are stacked one on top of the other to form an assembly; wherein the thickness of the lithium metal strip is 20-100μm; then, the assembly is fed into an electric rolling mill for rolling treatment, so that the lithium metal is pressed into the pores of the wood to obtain the wood-lithium metal composite negative electrode material; wherein the rolling gap of the rolling mill is 1-3mm and the rolling speed is 10-30mm / s.

[0038] The present invention also provides an application of a wood-lithium metal composite anode material, specifically: the wood-lithium metal composite anode material is used in a lithium metal battery and serves as the anode of the lithium metal battery; wherein the lithium metal battery is a coin cell battery, comprising a negative electrode, a separator, an electrolyte, and a positive electrode.

[0039] Specifically, the negative electrode sheet is made by cutting wood-lithium metal composite negative electrode material; wherein, the wood-lithium metal composite negative electrode material is sliced ​​using a battery slicer to obtain a wood-lithium metal composite negative electrode of a preset size, thus obtaining the negative electrode sheet.

[0040] The diaphragm is one of polypropylene diaphragm, polyethylene diaphragm, Al2O3-coated polypropylene diaphragm, Al2O3-coated polyethylene diaphragm, and glass fiber diaphragm; preferably, the diaphragm is a polypropylene diaphragm.

[0041] The electrolyte is selected from one of the following: EC / DEC (v / v = 1:1) + 1.0 M LiPF6, DME + HFE + LiFSI (molar ratio 1.3:2:1), DOL / DME (v / v = 1:1) + 1.0 M LiTFSI + 2.0 wt.% LiNO3, or DOL / DME (v / v = 1:3) + 1.0 M LiTFSI + 5.0 wt.% LiNO3.

[0042] The positive electrode sheet is prepared by uniformly mixing positive electrode material, conductive carbon, and binder in a solvent, coating it onto an aluminum foil current collector, and then drying it. The positive electrode material is selected from lithium iron phosphate, lithium nickel cobalt manganese oxide, and sulfur / carbon composites. The conductive carbon includes carbon nanotubes, Super-P, acetylene black, and Ketjen black. The binder includes polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), and polyacrylates (LA132 or LA133). The solvent includes N-methylpyrrolidone (NMP), water, and ethanol. The mass ratio of the positive electrode material, conductive carbon, and binder is (7-8.5):(0.5-2):(0.5-1.5).

[0043] Preparation principle:

[0044] The preparation method of the wood-lithium metal composite anode material of the present invention involves completely immersing the wood block sample in an organic solvent for extraction treatment. This process exposes the micro- and nano-pores in the wood, which serve as a space for lithium deposition, effectively mitigating the volume expansion of the electrode during cycling. Compared to the prior art of carbonizing the wood, this method avoids the loss of the wood's pore structure due to strength loss after carbonization. The dehydrated wood chips are then stacked with lithium metal strips and rolled to utilize the flexibility and ductility of lithium metal to fill the pores of the wood chips, preserving the inherent strength of the wood. It possesses certain mechanical strengths and does not require molten lithium charging or electrodeposition operations, resulting in a high level of safety and efficiency in the preparation process. In this invention, natural wood is used as raw material, and a framework material applicable to lithium metal anodes can be obtained through simple pretreatment steps. Using natural wood with a three-dimensional structure as a lithium metal framework can effectively transform the originally two-dimensional planar lithium metal anode into a three-dimensional structure, reducing the local current density. The insulating wood framework can adjust the electric field strength near the surface of the lithium metal electrode to become more uniform, thereby guiding the lithium ion flow and making the lithium metal deposition / deposition behavior more uniform, effectively inhibiting the growth of lithium dendrites.

[0045] The wood-lithium metal composite anode material prepared in this invention can be matched with different types of cathodes such as lithium iron phosphate, lithium nickel cobalt manganese oxide, and sulfur / carbon composites to assemble a variety of lithium metal batteries. In different battery systems, it can play a beneficial role in reducing charge and discharge polarization, extending battery cycle life, and improving capacity retention.

[0046] Example 1

[0047] This embodiment 1 provides a method for preparing a wood-lithium metal composite anode material, including the following steps:

[0048] Step 1: Select eucalyptus wood as the raw material, and cut the xylem of the eucalyptus wood into eucalyptus wood samples with dimensions of length × height × width = 2.5 × 2 × 2 cm; completely immerse the eucalyptus wood samples in a mixture of toluene and ethanol for extraction treatment until the reflux liquid is colorless, and obtain the extracted sample; wherein, in the mixture of toluene and ethanol, the volume ratio of toluene to ethanol is 2:1.

[0049] Step 2: After extraction, the sample is air-dried to remove toluene and ethanol. Then, while wetted with deionized water, it is sliced ​​into 50μm xylem slices along the cross-section of the wood using an ultrathin slicer. After that, the xylem slices are dried in an oven at 105°C, and then transferred to a glove box with water and oxygen concentrations below 0.1ppm for dehydration treatment to obtain dehydrated wood chips.

[0050] Step 3: Stack the dehydrated wood chips and a 50μm thick lithium metal strip on top of each other to form an assembly; then, feed the assembly into an electric rolling mill and roll it at a rolling gap of 1.5mm and a rolling speed of 15mm / s to press the lithium metal into the pores of the wood, thus obtaining the wood-lithium metal composite anode material, i.e., the eucalyptus-lithium metal composite anode material.

[0051] As attached Figure 1-2 As shown, attached Figure 1 The paper provides photographs of the eucalyptus-lithium metal composite anode material prepared in Example 1, with accompanying images. Figure 2 The attached image shows a scanning electron microscope (SEM) image of the microstructure of the eucalyptus-lithium metal composite anode material prepared in Example 1; from the attached image... Figure 1-2 As can be seen from the results, after eucalyptus wood chips and lithium metal strips are combined by roll pressing, the surface of the eucalyptus-lithium metal composite anode material is smooth and has a clear eucalyptus wood texture. Observation of its microstructure shows that lithium metal has been successfully filled into the pores of eucalyptus wood, and no obvious structural deformation or crushing phenomenon is observed in the eucalyptus wood skeleton, indicating that the composite anode has been successfully prepared.

[0052] This embodiment 1 also provides a coin cell lithium metal battery, as detailed below:

[0053] Lithium iron phosphate, acetylene black, and polyvinylidene fluoride were weighed in a mass ratio of 8:1:1, thoroughly mixed in N-methylpyrrolidone, coated onto aluminum foil current collector, and dried in an oven at 60°C. A positive electrode sheet with a diameter of 13 mm was then obtained using a battery slicing machine. The eucalyptus-lithium metal composite negative electrode material was then cut into negative electrode discs with a diameter of 15 mm using the same slicing machine to obtain the eucalyptus-lithium metal composite negative electrode. Using the aforementioned positive electrode sheet as the positive electrode and the eucalyptus-lithium metal composite negative electrode as the negative electrode, a polypropylene separator was matched, and EC / DEC (v / v = 1:1) + 1.0 M LiPF6 was used as the electrolyte for battery assembly, thus obtaining a coin cell lithium metal battery.

[0054] Example 2

[0055] This embodiment 2 provides a method for preparing a wood-lithium metal composite anode material, including the following steps:

[0056] Step 1: Select cedar wood as the raw material, cut the xylem of the cedar wood into cedar wood samples with dimensions of length × height × width = 2 × 2 × 2 cm; completely immerse the cedar wood samples in a mixture of benzene and ethanol for extraction treatment until the reflux liquid is colorless, and obtain the extracted sample; wherein, in the mixture of benzene and ethanol, the volume ratio of benzene to ethanol is 2:1.

[0057] Step 2: After extraction, the sample is air-dried to remove benzene and ethanol. Then, while wetted with deionized water, it is sliced ​​into 75μm xylem slices along the cross-section of the wood using an ultrathin slicer. After that, the xylem slices are dried in an oven at 105°C, and then transferred to a glove box with water and oxygen concentrations below 0.1ppm for dehydration treatment to obtain dehydrated wood chips.

[0058] Step 3: Stack the dehydrated wood chips and a 50μm thick lithium metal strip on top of each other to form an assembly; then, feed the assembly into an electric rolling mill and roll it at a rolling gap of 2mm and a rolling speed of 30mm / s to press the lithium metal into the pores of the wood, thus obtaining the wood-lithium metal composite anode material, i.e., the fir-lithium metal composite anode material.

[0059] As attached Figure 3 As shown, attached Figure 3 The attached image shows a scanning electron microscope (SEM) image of the microstructure of the cedarwood-lithium metal composite anode material prepared in Example 2; from the attached image... Figure 3 The results show that lithium metal was successfully filled into the pores of the fir wood, and no obvious structural deformation or crushing was observed in the fir wood skeleton, indicating the successful preparation of the composite anode.

[0060] This embodiment 2 also provides a button-type lithium metal battery, as detailed below:

[0061] Lithium nickel cobalt manganese oxide, Super-P, and polyvinylidene fluoride were weighed in a mass ratio of 8:1:1 and thoroughly mixed in N-methylpyrrolidone. The mixture was then coated onto aluminum foil used as a current collector and dried in an oven at 60°C. A positive electrode sheet with a diameter of 13 mm was obtained using a battery slicing machine. The cedar wood-lithium metal composite negative electrode material was then cut into negative electrode discs with a diameter of 15 mm using the same battery slicing machine to obtain the cedar wood-lithium metal composite negative electrode. Using the aforementioned positive electrode sheet as the positive electrode and the cedar wood-lithium metal composite negative electrode as the negative electrode, a polypropylene separator was matched, and DME+HFE+LiFSI (molar ratio of 1.3:2:1) was used as the electrolyte to assemble the battery, thus obtaining a coin cell lithium metal battery.

[0062] Example 3

[0063] This embodiment 3 provides a method for preparing a wood-lithium metal composite anode material, including the following steps:

[0064] Step 1: Select paulownia wood as raw material, cut the wood of paulownia into blocks and process them into paulownia samples with dimensions of length × height × width = 2 × 2 × 2 cm; completely immerse the paulownia sample in a mixture of toluene, benzene and ethanol for extraction treatment until the reflux liquid is colorless, and obtain the extracted sample; wherein, in the mixture of toluene, benzene and ethanol, the volume ratio of toluene, benzene and ethanol is 1:1:1.

[0065] Step 2: After extraction, the sample is air-dried to remove toluene, benzene, and ethanol. Then, while wetted with deionized water, it is sliced ​​into 75μm xylem slices along the cross-section of the wood using an ultrathin slicer. After that, the xylem slices are dried in an oven at 105°C, and then transferred to a glove box with water and oxygen concentrations below 0.1ppm for dehydration treatment to obtain dehydrated wood chips.

[0066] Step 3: Stack the dehydrated wood chips and a 75μm thick lithium metal strip on top of each other to form an assembly; then, feed the assembly into an electric rolling mill and roll it at a rolling gap of 2.5mm and a rolling speed of 15mm / s to press the lithium metal into the pores of the wood, thus obtaining the wood-lithium metal composite anode material, i.e., the paulownia-lithium metal composite anode material.

[0067] This embodiment 3 also provides a coin cell lithium metal battery, as detailed below:

[0068] The sulfur / carbon composite, Ketjen Black, and LA132 were weighed in a mass ratio of 7:2:1, thoroughly mixed in ethanol, coated onto a current collector aluminum foil, and dried in an oven at 60°C. A positive electrode sheet with a diameter of 13 mm was then obtained using a battery slicing machine. The paulownia-lithium metal composite negative electrode material was then cut into negative electrode discs with a diameter of 15 mm using the same slicing machine to obtain the paulownia-lithium metal composite negative electrode. Using the aforementioned positive electrode sheet as the positive electrode and the paulownia-lithium metal composite negative electrode as the negative electrode, a polypropylene separator was matched, and the electrolyte was DOL / DME (v / v = 1:1) + 1.0 M LiTFSI + 2.0 wt.% LiNO3. The battery was then assembled to obtain a coin cell lithium metal battery.

[0069] Example 4

[0070] This embodiment 4 provides a method for preparing a wood-lithium metal composite anode material, including the following steps:

[0071] Step 1: Select balsa wood as the raw material, cut the xylem of balsa wood into balsa wood samples with dimensions of length × height × width = 2 × 2 × 2 cm; completely immerse the balsa wood sample in a mixture of toluene and ethanol for extraction treatment until the reflux liquid is colorless, and obtain the extracted sample; wherein, in the mixture of toluene and ethanol, the volume ratio of toluene to ethanol is 2:1.

[0072] Step 2: After extraction, the sample is air-dried to remove toluene and ethanol. Then, while wetted with deionized water, it is sliced ​​into 100μm xylem slices along the cross-section of the wood using an ultrathin slicer. After that, the xylem slices are dried in an oven at 105°C, and then transferred to a glove box with water and oxygen concentrations below 0.1ppm for dehydration treatment to obtain dehydrated wood chips.

[0073] Step 3: Stack the dehydrated wood chips and a 100μm thick lithium metal strip on top of each other to form an assembly; then, feed the assembly into an electric rolling mill and roll it at a rolling gap of 2.5mm and a rolling speed of 10mm / s to press the lithium metal into the pores of the wood, thus obtaining the wood-lithium metal composite anode material, i.e., balsa wood-lithium metal composite anode material.

[0074] This embodiment 4 also provides a coin cell lithium metal battery, as detailed below:

[0075] The sulfur / carbon composite, Ketjen Black, and LA133 were weighed in a mass ratio of 8:1.5:0.5, thoroughly mixed in ethanol, coated onto aluminum foil current collector, and dried in an oven at 60°C. A positive electrode sheet with a diameter of 13 mm was then obtained using a battery slicing machine. The balsa wood-lithium metal composite negative electrode material was then cut into negative electrode discs with a diameter of 15 mm using the same slicing machine to obtain the balsa wood-lithium metal composite negative electrode. Using the aforementioned positive electrode sheet as the positive electrode and the balsa wood-lithium metal composite negative electrode as the negative electrode, a polypropylene separator was matched, and the electrolyte was DOL / DME (v / v = 1:3) + 1.0 M LiTFSI + 5.0 wt.% LiNO3. The battery was then assembled to obtain a coin cell lithium metal battery.

[0076] Example 5

[0077] This embodiment 5 provides a method for preparing a wood-lithium metal composite anode material, including the following steps:

[0078] Step 1: Select pine wood as the raw material, cut the xylem of the pine wood into pine wood samples with dimensions of length × height × width = 2 × 2 × 2 cm; completely immerse the pine wood sample in a mixture of benzene and ethanol for extraction treatment until the reflux liquid is colorless, and obtain the extracted sample; wherein, in the mixture of benzene and ethanol, the volume ratio of benzene to ethanol is 2:1.

[0079] Step 2: After extraction, the sample is air-dried to remove benzene and ethanol. Then, while wetted with deionized water, it is sliced ​​into 20μm xylem slices along the cross-section of the wood using an ultrathin slicer. After that, the xylem slices are dried in an oven at 105°C, and then transferred to a glove box where the water and oxygen concentrations are both below 0.1ppm for dehydration treatment to obtain dehydrated wood chips.

[0080] Step 3: Stack the dehydrated wood chips and a 20μm thick lithium metal strip on top of each other to form an assembly; then, feed the assembly into an electric rolling mill and roll it at a rolling gap of 1.0mm and a rolling speed of 10mm / s to press the lithium metal into the pores of the wood, thus obtaining the wood-lithium metal composite anode material, i.e., the pine wood-lithium metal composite anode material.

[0081] This embodiment 5 also provides a coin cell lithium metal battery, as detailed below:

[0082] Lithium iron phosphate, carbon nanotubes, and polyvinylidene fluoride were weighed in a mass ratio of 7.5:1.5:1, thoroughly mixed in N-methylpyrrolidone, coated onto aluminum foil current collector, and dried in an oven at 60°C. A positive electrode sheet with a diameter of 13 mm was then obtained using a battery slicing machine. The pine-lithium metal composite negative electrode material was then cut into negative electrode discs with a diameter of 15 mm using the same slicing machine to obtain the pine-lithium metal composite negative electrode. Using the aforementioned positive electrode sheet as the positive electrode and the pine-lithium metal composite negative electrode as the negative electrode, a polyethylene separator coated with Al2O3 was used, and EC / DEC (v / v = 1:1) + 1.0 M LiPF6 was used as the electrolyte to assemble the battery, thus obtaining a coin cell lithium metal battery.

[0083] Examples 6-7

[0084] The preparation process and principle of the wood-lithium metal composite anode material provided in Examples 6-7 are basically the same as those of the wood-lithium metal composite anode material provided in Example 1 above. The difference is that poplar wood is used as the wood raw material in Example 6 and birch wood is used as the wood raw material in Example 7. The rest of the operation process is basically the same and will not be described in detail here.

[0085] Comparative Example 1:

[0086] Comparative Example 1 provides a coin cell lithium metal battery that is essentially the same as the coin cell lithium metal battery described in Example 1 or 2, except that the eucalyptus-lithium metal composite negative electrode in Example 1 is replaced with a bare lithium negative electrode, or the cedar-lithium metal composite negative electrode in Example 2 is replaced with a bare lithium electrode.

[0087] As attached Figure 4 As shown, attached Figure 4 The appendix provides the long-cycle performance curves of the coin lithium metal battery in Example 1 and the coin lithium metal battery in the comparative example at a 0.5C rate; from the appendix... Figure 4 As can be seen, the comparative example showed capacity decay first around 70 cycles, accompanied by a significant decrease in coulombic efficiency. In contrast, the introduction of the eucalyptus wood skeleton slowed down the capacity decay process, with a capacity retention rate of 77.5% at 100 cycles, significantly higher than the 68.0% capacity retention rate of the comparative example. This indicates that the introduction of the wood-composite negative electrode has a positive effect on improving the battery's cycle performance.

[0088] As attached Figure 5 As shown, attached Figure 5 The appendix provides the long-cycle performance curves of the coin lithium metal battery in Example 2 and the coin lithium metal battery in the comparative example at a 0.4C rate; from the appendix... Figure 5 As can be seen from the data, Example 2 maintained a higher capacity and a more stable coulombic efficiency compared to the comparative example, indicating that the introduction of the wood-composite negative electrode has a positive effect on improving the battery cycle performance.

[0089] The wood-lithium metal composite anode material and its preparation method described in this invention use wood as raw material. Through pretreatment steps including organic solvent extraction, air drying, drying, and dehydration, a framework material suitable for lithium metal anodes is obtained. Using natural wood with a three-dimensional structure as the lithium metal framework effectively transforms the originally two-dimensional planar lithium metal anode into a three-dimensional structure, reducing local current density. The insulating wood framework can adjust the electric field strength near the surface of the lithium metal electrode to become more uniform, thereby guiding lithium ion flow and making the lithium metal deposition / deposition behavior more uniform, effectively inhibiting the growth of lithium dendrites. The process involves rolling... This method fills lithium metal into the pores of wood, enabling rapid and simple preparation of composite anodes. It avoids time-consuming, cumbersome, and potentially dangerous methods such as molten lithium filling or electrodeposition. Simultaneously, it preserves the inherent mechanical strength of the wood. By adjusting the length, width, and thickness of the wood slices, composite lithium metal anodes of different sizes and capacities can be produced to meet the needs of various applications. Compared to bare lithium anodes without a wood skeleton, this composite anode can reduce charge-discharge polarization, extend battery cycle life, and improve capacity retention in different battery systems.

[0090] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A method for preparing a wood-lithium metal composite anode material, characterized in that, include: The xylem of natural wood is cut into blocks to obtain wood block samples of a predetermined size; The wood block sample of the preset size was immersed in an organic solvent for extraction treatment, and after natural air drying, it was sliced ​​along the cross section of the wood to obtain xylem slices. The xylem slices are dried and dehydrated to obtain dehydrated wood chips; After dehydration, wood chips and lithium metal strips are stacked one on top of the other and subjected to roller pressing to press the lithium metal into the pores of the wood, thus obtaining the wood-lithium metal composite negative electrode material. The natural wood used is one of the following: eucalyptus, fir, pine, poplar, paulownia, balsa wood, and birch. The organic solvent is a mixture of toluene and ethanol, a mixture of benzene and ethanol, or a mixture of toluene, benzene, and ethanol. After dehydration, the wood chips and lithium metal strips are stacked one on top of the other and rolled together. During the rolling process, the rolling gap of the rolling mill is 1-3mm and the rolling speed is 10-30mm / s. In the mixture of toluene and ethanol, the volume ratio of toluene to ethanol is 2:1; in the mixture of benzene and ethanol, the volume ratio of benzene to ethanol is 2:1; in the mixture of toluene, benzene and ethanol, the volume ratio of toluene, benzene and ethanol is 1:1:

1. During the drying and dehydration process of the wood chips to obtain dehydrated wood chips, the dried wood chips are transferred to a glove box for further dehydration; wherein the water and oxygen concentrations in the glove box are both below 0.1 ppm. The thickness of the xylem slice is 20-100 μm, and the thickness of the lithium metal strip is 20-100 μm.

2. A wood-lithium metal composite anode material, characterized in that, It was prepared using the method for preparing wood-lithium metal composite anode material as described in claim 1.

3. An application of a wood-lithium metal composite anode material, characterized in that, The wood-lithium metal composite anode material as described in claim 2 is used in lithium metal batteries and serves as the anode of lithium metal batteries.

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