A lithium-ion secondary battery anode material, its preparation method and application

Abstract

This invention discloses a lithium-ion secondary battery anode material, its preparation method, and its application, belonging to the field of lithium-ion secondary battery technology. The chemical formula of the lithium-ion battery anode material of this invention is Cu. x GeSe y Where x and y represent the atomic ratio of Cu and Se elements in the stoichiometric ratio of the negative electrode material, respectively, with a range of 0.1≤x≤5, 0.1≤y≤5, and 0.02≤x / y≤5. The lithium-ion negative electrode material of this invention possesses excellent comprehensive properties such as high specific capacity, cycle stability, rate performance, and low volume expansion rate. Therefore, applying the negative electrode material of this invention to lithium-ion secondary batteries can enable lithium-ion secondary batteries to exhibit superior performance.

Description

Technical Field

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

[0002] A lithium-ion battery is a type of rechargeable battery that primarily functions by the movement of lithium ions between the positive and negative electrodes. During charging and discharging, lithium ions repeatedly insert and extract between the two electrodes: during charging, lithium ions extract from the positive electrode, pass through the electrolyte, and insert into the negative electrode, leaving the negative electrode in a lithium-rich state; the reverse occurs during discharging.

[0003] With the rapid growth in demand for portable energy in the electrical, electronics, automotive, and aerospace industries, the market is placing higher demands on the performance of lithium-ion batteries, including high specific capacity, excellent cycle stability, and high safety. As a core component of lithium-ion batteries, the performance of electrode materials directly determines the overall performance of the battery.

[0004] Currently, commercially available lithium-ion battery anode materials mainly use graphite, with a theoretical specific capacity of approximately 372 mAh / g, which is insufficient to meet the ever-increasing demand for high energy density. Although silicon-based anode materials have a higher theoretical specific capacity (3579 mAh / g), their volume expansion rate exceeds 300% during charge and discharge, which can lead to electrode structure damage, resulting in a sharp decline in cycle performance and even safety accidents, severely limiting their practical applications.

[0005] Therefore, it is necessary to provide a lithium-ion secondary battery anode material and apply it to lithium-ion batteries to give them better overall performance and expand the application scenarios of anode materials. Summary of the Invention

[0006] To overcome the problems in the prior art, this invention utilizes the large ionic radius (1.98 Å) of Se in the anode material to increase bond length and weaken the crystal field effect, thereby enabling the anode material to form an ordered zincblende or layered structure. The ordered zincblende structure possesses natural three-dimensional lithium-ion diffusion channels, which can significantly reduce the kinetic resistance of lithium-ion migration, improve the ion transport efficiency of the material, and contribute to improved rate performance and fast charging capability. The layered structure has good interlayer buffering effect, effectively absorbing volume changes during charge and discharge, improving structural stability and cycle life. Furthermore, the Li₂Se byproduct generated during the lithium insertion / deintercalation process of the material of this invention has high chemical stability, which can, to a certain extent, suppress side reactions between the material surface and the electrolyte, thereby improving interfacial stability and enhancing the long-term cycle performance and practical application safety of the material.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] This invention proposes a lithium-ion secondary battery anode material, wherein the chemical formula of the lithium-ion battery anode material is Cu. x GeSe y , where x and y represent the ratio of the number of Cu and Se atoms in the stoichiometric ratio of the negative electrode material, respectively, and their ranges are: 0.1≤x≤5, 0.1≤y≤5, and 0.02≤x / y≤5.

[0009] Preferably, the negative electrode material is in powder form with a particle size of 0.1 nm-500 μm.

[0010] In another aspect, the present invention provides a method for preparing the above-mentioned negative electrode material, the method comprising the following steps:

[0011] (1) Weigh Cu powder, Ge powder and Se powder according to stoichiometric ratio and mix them to obtain a mixture;

[0012] (2) Under vacuum conditions, the mixture obtained in step (1) is heated and kept at a constant temperature, and then cooled to room temperature in the furnace to obtain ingots;

[0013] (3) Grind the ingot in step (2) into powder, and use the powder as raw material for discharge plasma sintering to obtain lithium-ion secondary battery negative electrode material.

[0014] Preferably, in step (2), the heating temperature is 1173K, the holding time is 72h, and the vacuum degree is 10. -4 Pa.

[0015] Preferably, in step (3), the discharge plasma sintering temperature is 648K, the sintering pressure is 45MPa, and the sintering time is 10min.

[0016] This invention also proposes the application of the above-mentioned negative electrode material in a negative electrode sheet, wherein the negative electrode sheet is composed of a current collector and an active material layer, the active material layer covering the surface of the current collector, and the active material layer comprising a mixture of the lithium-ion secondary battery negative electrode material and a binder. The current collector is selected from conventional current collectors in the art, such as copper foil current collectors, and the binder is selected from conventional binders in the art, such as polyvinylidene fluoride (PVDF).

[0017] Preferably, in the active material layer, the mass ratio of binder to lithium-ion secondary battery negative electrode material is negative electrode material: binder = 6~10:1~5.

[0018] Preferably, the active material layer further includes a conductive agent, wherein the mass ratio of the lithium-ion secondary battery negative electrode material, binder, and conductive agent in the active material layer is negative electrode material: binder: conductive agent = 6~10:1~5:1~3. The conductive agent is a conventional conductive agent in the art, such as conductive carbon black.

[0019] Preferably, the active material layer in the negative electrode sheet has a thickness of 10-500 μm.

[0020] This invention also proposes the application of the above-mentioned negative electrode sheet in the manufacture of lithium-ion secondary batteries.

[0021] Finally, this invention proposes the application of the above-mentioned negative electrode material in the manufacture of lithium-ion secondary batteries.

[0022] The beneficial effects of this invention are:

[0023] 1. By using a negative electrode material with an ordered zincblende or layered structure, this invention significantly enhances the diffusion rate of lithium ions within the material, which helps to improve rate performance and fast charging capability.

[0024] 2. This invention utilizes Cu x GeSe y As a negative electrode material for lithium-ion secondary batteries, it utilizes the stable Li2Se protective layer formed in situ at the electrode interface during charging and discharging. The high stability of this layer reduces the probability of side reactions with the electrolyte, thereby effectively suppressing the occurrence of side reactions and improving the interface stability of the negative electrode material. This allows for the achievement of good cycle performance and rate performance without the need for additional modifications such as coating or doping of the negative electrode material. This simplifies the application process of the negative electrode material and reduces the material application cost.

[0025] 3. The specific capacity of the negative electrode material of the present invention can reach more than 500 mAh / g. After 1000 hours of normal cycling, the capacity retention rate can reach more than 90%. After 1000 hours of high-rate (20C) cycling, the capacity retention rate can reach more than 80%. The volume expansion rate can be as low as 12%. The negative electrode material of the present invention has excellent comprehensive performance. When used as a negative electrode material for lithium-ion secondary batteries, it can make the negative electrode material of lithium-ion secondary batteries have excellent performance. Attached Figure Description

[0026] Figure 1 Figure 1 shows the performance test results of the negative electrode material in Example 1 of the present invention, where Figure a shows the rate performance of the negative electrode material and Figure b shows the cycle stability of the negative electrode material. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0028] In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents used in the experiments were commercially available analytical grade.

[0029] Example 1

[0030] In this embodiment, the negative electrode material is prepared by the following method:

[0031] First, high-purity Cu powder (99.999%), Ge powder (99.99%), and Se powder (99.999%) were weighed and mixed according to stoichiometric ratios and then placed into a quartz tube; the quartz tube was then evacuated to a vacuum level of 10. -4 The ingot was then sealed; it was then slowly heated to 1173 K and held for 72 hours to ensure a complete reaction; subsequently, it was cooled to room temperature in the furnace. The resulting ingot was ground into fine powder and further sintered under vacuum conditions by spark plasma sintering (SPS) at 648 K and 45 MPa for 10 minutes to obtain a dense bulk material. The bulk material was then crushed and ground to obtain powdered anode material.

[0032] For ease of experimentation, this embodiment uses the negative electrode material to fabricate the negative electrode sheet, which is then used to fabricate a lithium-ion secondary battery. The specific fabrication process is as follows:

[0033] (1) Preparation of negative electrode sheet: In this embodiment, Cu2GeSe3 powder with a particle size of 1μm was selected as the negative electrode material, and PVDF was selected as the binder. First, 80g of negative electrode material and 10g of binder powder were added to N-methylpyrrolidone (NMP) solvent and mixed evenly to obtain a solution. The amount of solvent was determined according to the actual dissolution situation, and it was determined that the negative electrode material and binder could be completely dissolved, or it could be in excess. The solution was coated on the surface of a copper foil current collector with a thickness of 12μm, and the coating amount was 10mg / cm. 2 Then, the copper foil current collector is vacuum dried to remove the solvent, resulting in a negative electrode with an active material layer thickness of 200 μm.

[0034] (2) Preparation of the positive electrode sheet: In this embodiment, conductive carbon black was selected as the conductive agent, PVDF as the binder, NMP as the solvent, and conventional positive electrode active material in the art was selected. In this embodiment, LiFePO4 was selected. First, 5g each of the conductive agent and the binder (accounting for 5% of the total mass of the positive electrode material) were weighed and added to 30 mL of NMP solvent, and stirred evenly to form a solution. Then, 90g of LiFePO4 powder (accounting for 90% of the total mass) was added, and stirring was continued to form a uniform slurry. The total mass of the obtained slurry was 100g, and the solid content was about 60%. The slurry was uniformly coated on an aluminum foil current collector with a thickness of 10μm and a coating amount of 20mg / cm². Then, it was dried in a vacuum drying oven at 80℃ to obtain the positive electrode sheet.

[0035] (3) Fabrication of lithium-ion batteries: A conventional separator in the art is selected as the lithium-ion battery separator. In this embodiment, a polyolefin microporous membrane is selected, and a conventional electrolyte in the art is selected. In this embodiment, a 1M LiPF6 / (EC+DEC, 1:1) commercial electrolyte is selected, which is composed of 1 mol / L lithium hexafluorophosphate (LiPF6) dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1. The prepared positive electrode, negative electrode, and separator are assembled in a conventional winding manner, and encapsulated with tabs and an aluminum-plastic film to obtain a soft-pack lithium-ion battery.

[0036] Based on the soft-pack lithium-ion battery fabricated in this embodiment, the performance of the negative electrode material in the lithium-ion battery was tested, and the results are as follows: Figure 1 As shown.

[0037] pass Figure 1 As can be seen, the anode material of this invention exhibits good rate performance at different rates, maintaining a reversible capacity of approximately 270 mAh / g even at a high current density of 3 A / g; when restored to a low rate of 0.1 A / g, the capacity is almost completely recovered, indicating excellent material structural stability and reaction reversibility. Figure 1 As shown in b, after 50 cycles at a current density of 0.5 A / g, the material still maintains approximately 90% of its capacity retention, demonstrating good cycling stability. Furthermore, the coulombic efficiency remained close to 100% throughout the rate test and cycling process, indicating that the material exhibits few side reactions during electrochemical reactions and possesses high reversibility and interfacial stability.

[0038] Example 2

[0039] This embodiment uses the same method as Example 1 to prepare the lithium-ion battery and the negative electrode material. The difference is that in this embodiment, the negative electrode material is CuGeSe (x=1, y=1, x / y=1), the amount of negative electrode material is 90g, the mass of binder is 10g (mass ratio 9:1), the particle size of the negative electrode material is 0.1nm, and the thickness of the active material layer is 10μm.

[0040] The anode material in this embodiment belongs to a typical layered structure material with x / y≈1 within the scope of this invention. It has certain van der Waals gaps between the layers, which can buffer volume changes during lithium-ion insertion / extraction and maintain structural integrity. The anode material in this embodiment exhibits a volume expansion rate of less than 12% during cycling, maintains a good electrode structure, and has a capacity comparable to Example 1. While its rate performance is slightly lower than Example 1, it still meets the requirements for high-rate operation. Overall, it demonstrates excellent interface stability and coulombic efficiency, making it suitable for applications requiring long lifespans.

[0041] Example 3

[0042] This embodiment uses the same method as Example 1 to fabricate the lithium-ion battery and negative electrode material, the difference being that: this embodiment uses Cu. 0.1 GeSe5 was used as the negative electrode material (x=0.1, y=5, x / y=0.02). The mass ratio of negative electrode material: binder: conductive agent was 6:1:1. The particle size of the negative electrode material was 500μm, and the thickness of the active material layer was 500μm.

[0043] In this embodiment of the anode material, due to the extremely low Cu content, the Cu-Se electronic conduction network is not obvious, and the electronic conductivity is lower than that of Example 1. However, the proportion of Ge is relatively increased, and its alloying reaction dominates the lithium storage process, enabling it to provide a relatively high capacity. The rate performance of the anode material in this embodiment is slightly lower than that of Example 1, but the initial capacity is maintained above 500 mAh / g, the cycle stability is basically controllable, and the interface reaction is mild, indicating that even under extremely low x conditions, the anode material of this invention still has good overall performance.

[0044] Example 4

[0045] This embodiment uses the same method as in Example 1 to prepare the lithium-ion battery and the negative electrode material. The difference is that the negative electrode material in this embodiment is Cu5GeSe (x=5, y=1, x / y=5), and the mass ratio of negative electrode material: binder: conductive agent is 10:5:3.

[0046] The anode material in this embodiment contains a large amount of copper-rich phase, which helps to build a continuous electronic conductivity network, thereby significantly improving electronic conductivity and rate performance. It maintains a high reversible capacity even under high-rate discharge (>10C) conditions, but due to the excessively high proportion of Cu phase, the lithium-ion diffusion channels are reduced, resulting in a slightly lower capacity (approximately 480 mAh / g). Furthermore, the material exhibits a slightly rigid structure and a slight increase in volume expansion (approximately 15%) during lithium intercalation, but its cycle stability remains good, and the interface SEI film is dense and uniform, making it suitable for high-power applications.

[0047] Example 5

[0048] This embodiment uses the same method as in Embodiment 1 to prepare the lithium-ion battery and the negative electrode material. The difference is that the negative electrode material in this embodiment is still Cu2GeSe4, and the mass ratio of the negative electrode material to the binder is set to 8:3.

[0049] Because the anode material in this embodiment has high electronic conductivity and its three-dimensional structure forms effective electron channels, its overall rate performance remains excellent even without the addition of a conductive agent. The capacity is stable at conventional rates (0.1C~1C), and while the capacity retention at 20C is slightly lower than the system containing a conductive agent, it is still above 70%. This indicates that under certain conditions, the use of a conductive agent can be omitted, which helps simplify the preparation process and reduce costs, making it suitable for practical scenarios where formulation simplification is required.

[0050] Comparative Example

[0051] This comparative example uses CuGe2P3 as the negative electrode material to prepare a lithium-ion secondary battery. Other additives and preparation methods are the same as in Example 1.

[0052] CuGe2P3, as a phosphorus-based material, has certain advantages in electronic structure, including high electronic conductivity, strong lithium-ion diffusion capability, and good rate performance, making it suitable for battery systems with certain power output requirements.

[0053] However, from a comprehensive application perspective, CuGe2P3 still has certain limitations in terms of cycle stability and interfacial stability. On the one hand, the interfacial products formed during lithium intercalation are prone to side reactions in the electrolyte, making it difficult to maintain the stability of the interfacial film and potentially leading to capacity decay. On the other hand, its structure lacks an effective interlayer buffering mechanism, which may result in electrode structure damage after prolonged use. In addition, this material usually requires surface modification through coating or doping to improve its interfacial compatibility and process stability, making the preparation process relatively complex.

[0054] In comparison, the Cu used in Example 1 x GeSe yThe material exhibits higher energy output per unit volume, demonstrating a superior volumetric energy density. This is primarily due to the material's high reversible capacity and relatively low crystal density. Under the same electrode volume or electrode thickness conditions, Cu... x GeSe y The material can accommodate more active components while releasing more charge, thereby increasing the energy storage level per unit volume. Furthermore, the anode material of this invention does not require additional surface coating or doping treatment, resulting in a simpler electrode structure that is beneficial for improving compaction density and electrode loading, further optimizing volume utilization. Structurally, the anode material of this invention forms an ordered crystal structure by controlling the Cu / Se ratio, providing a continuous channel for lithium-ion migration while also possessing a certain buffering capacity, helping to alleviate volume expansion and improve cycle stability. The stable Li2Se interface products generated during the reaction can form a dense and uniform interface film on the material surface, effectively suppressing side reactions and enhancing interface stability and coulombic efficiency.

[0055] For ease of comparison, the parameters of the negative electrode materials in the embodiments of the present invention and the comparative examples are summarized in Table 1.

[0056] Table 1

[0057]

[0058] In summary, the present invention Cu x GeSe y Without relying on complex modifications, the anode material simultaneously achieves high capacity, good cycle performance, process adaptability, and high volumetric energy density, making it suitable for applications with high requirements for battery lightweighting, miniaturization, and integration, and possessing good potential for widespread application.

Claims

1. A lithium-ion secondary battery anode material, characterized in that: The chemical formula for the lithium-ion secondary battery anode material is Cu. x GeSe y , where x and y represent the ratio of the number of Cu and Se atoms in the stoichiometric ratio of the negative electrode material, respectively, and their ranges are: 0.1≤x≤5, 1≤y≤5, and 0.02≤x / y≤5; The preparation method of the lithium-ion secondary battery anode material includes the following steps: (1) Weigh Cu powder, Ge powder and Se powder according to stoichiometric ratio and mix them to obtain a mixture; (2) Under vacuum conditions, the mixture obtained in step (1) is heated and kept at a constant temperature, and then cooled to room temperature in the furnace to obtain ingots; (3) Grind the ingot in step (2) into powder, and use the powder as raw material for discharge plasma sintering to obtain lithium-ion secondary battery negative electrode material; In step (2), the heating temperature is 1173K, the holding time is 72h, and the vacuum degree is 10. -4 Pa; In step (3), the discharge plasma sintering temperature is 648K, the sintering pressure is 45MPa, and the sintering time is 10min.

2. The lithium-ion secondary battery anode material according to claim 1, characterized in that: The negative electrode material is in powder form with a particle size of 0.1 nm to 500 μm.

3. A negative electrode sheet, characterized in that: The negative electrode sheet includes the lithium-ion secondary battery negative electrode material as described in claim 1 or 2. The negative electrode sheet is composed of a current collector and an active material layer. The active material layer covers the surface of the current collector and includes a mixture of the lithium-ion secondary battery negative electrode material and a binder.

4. The negative electrode sheet according to claim 3, characterized in that: In the active material layer, the mass ratio of binder to lithium-ion secondary battery negative electrode material is negative electrode material: binder = 6~10:1~5.

5. The negative electrode sheet according to claim 3, characterized in that: The active material layer also includes a conductive agent. In the active material layer, the mass ratio of lithium-ion secondary battery negative electrode material, binder and conductive agent is negative electrode material: binder: conductive agent = 6~10:1~5:1~3.

6. The negative electrode sheet according to claim 3, characterized in that: In the negative electrode sheet, the thickness of the active material layer is 10-500 μm.

7. The application of the negative electrode sheet according to claim 3 in the manufacture of lithium-ion secondary batteries.

8. The application of the lithium-ion secondary battery negative electrode material as described in claim 1 or 2 in the manufacture of lithium-ion secondary batteries.

Images