Silicon-carbon negative electrode material, preparation method and application thereof
By introducing phosphorus surface active sites into the silicon-carbon anode material, a Li3P-LiF inorganic dual-phase SEI is formed, which solves the problem of SEI structure instability in silicon-based anode materials during charge and discharge, achieving high stability and fast lithium-ion transport, and improving the cycle life and rate performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGCHUN INSTITUTE OF APPLIED CHEMISTRY CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2026-02-10
- Publication Date
- 2026-05-12
AI Technical Summary
Existing silicon-based anode materials suffer from unstable solid electrolyte interphase (SEI) structure due to severe volume expansion during charge and discharge, resulting in continuous increase in interfacial impedance, exacerbation of electrolyte side reactions, and limited cycle life. It is difficult to achieve both low polarization and high stability under high rate and long cycle conditions.
By introducing phosphorus-containing surface active sites on the surface of silicon-carbon anode material, selective decomposition reactions of the electrolyte are induced at the interface, promoting the directional formation of the Li3P phase and forming a Li3P-LiF inorganic dual-phase SEI. LiF serves as the chemically stable and electronically insulating component of the SEI, while Li3P, as a lithium-ion conductive inorganic phase, provides a low-impedance Li+ transport channel, jointly undertaking the functions of interfacial mechanical support and stress regulation.
It significantly reduces the rate of increase in interface impedance, improves cycle stability and rate performance, extends battery life, and maintains stable battery operation under conditions of limited lithium source and actual positive and negative electrode coupling.
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Figure CN121672533B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a silicon-carbon anode material, its preparation method, and its application, belonging to the field of lithium-ion battery electrode and interface control technology. Background Technology
[0002] With the rapid development of lithium-ion batteries in electric vehicles and large-scale energy storage, the requirements for battery energy density and cycle life are constantly increasing. Silicon-based anode materials, due to their extremely high theoretical specific capacity, are considered ideal candidates to replace traditional graphite anodes and realize the next generation of high-energy-density lithium-ion batteries. However, in practical applications, silicon-based anodes undergo significant volume expansion and contraction during charge and discharge, leading to repeated interface structure rupture, which severely restricts their cycle stability and practical applications.
[0003] During the operation of silicon-based anodes, a solid electrolyte interphase (SEI) film inevitably forms on the electrode surface. This SEI film plays a crucial role in inhibiting the continuous decomposition of the electrolyte, maintaining interfacial stability, and ensuring the reversible transport of lithium ions. However, due to the drastic volume changes of silicon-based materials, traditional SEI films often struggle to maintain structural integrity, easily rupturing and regenerating during cycling. This leads to a continuous increase in interfacial impedance, ongoing consumption of active lithium, and gradual failure of the electrode structure.
[0004] To improve the interfacial stability of silicon-based anodes, various SEI (Sediment Interphase) modulation strategies have been proposed in existing technologies, with the construction of SEI films rich in inorganic components, especially LiF, being a representative example. LiF, due to its high chemical stability and excellent electronic insulation properties, is widely considered helpful in suppressing side reactions and improving interfacial durability. Therefore, constructing LiF-rich SEIs through electrolyte additives, surface fluorination, or electrolyte composition modulation has become the mainstream approach in current research and applications.
[0005] However, practice has shown that single LiF-rich SEI films still have significant limitations. On the one hand, LiF has low intrinsic lithium-ion conductivity, which can easily become a limiting factor for interfacial ion transport under high-rate or long-cycle conditions, leading to increased polarization and decreased rate performance. On the other hand, LiF-rich SEIs typically exhibit high brittleness, and are still prone to microcracks and structural failure under repeated volume changes in silicon-based anodes, making it difficult to fundamentally solve the problems of repeated interfacial fracture and continuous growth. Therefore, relying solely on a single inorganic phase for SEI design cannot simultaneously meet the multiple requirements of chemical stability, mechanical adaptability, and rapid lithium-ion transport.
[0006] Furthermore, some studies have attempted to improve the strain buffering capacity of the SEI by introducing inorganic or organic components with a certain degree of flexibility. However, these approaches often focus on improving mechanical adaptability while paying insufficient attention to the interfacial lithium-ion transport kinetics, making it difficult to achieve a stable, low-impedance interfacial reaction environment under high load and long-life conditions. Currently, there is a lack of a silicon-based anode SEI design strategy that can achieve synergistic optimization between structural stability, mechanical load-bearing capacity, and lithium-ion transport performance.
[0007] Therefore, there is an urgent need to propose a new SEI construction strategy that can simultaneously ensure mechanical stability and rapid lithium-ion transport at the interface scale. While ensuring the chemical stability and electronic insulation of the SEI film, it is necessary to introduce inorganic components that are conducive to rapid lithium-ion transport and achieve multifunctional synergy through controlled interface construction, thereby effectively alleviating the interface failure problem faced by silicon-based anodes under long-term cycling and high-rate conditions. Summary of the Invention
[0008] To address the problems of unstable solid electrolyte interphase (SEI) structure, continuously increasing interfacial impedance, aggravated electrolyte side reactions, and limited cycle life caused by the drastic volume expansion during charging and discharging of existing silicon-carbon anodes, which makes it difficult to simultaneously achieve low polarization and high stability under high rate and long cycle conditions, this invention provides a silicon-carbon anode material, its preparation method, and its applications.
[0009] The technical solution of this invention:
[0010] One objective of this invention is to provide a method for preparing silicon-carbon anode materials, the method comprising the following steps:
[0011] (1) Using biomass porous carbon material as substrate and silane mixed gas as gaseous precursor, after CVD deposition, the mixture is placed in the supernatant obtained by centrifuging toluene and asphalt mixture, heated to evaporate the solution and then calcined to obtain silicon carbon material;
[0012] (2) After the obtained silicon-carbon material is mixed evenly with the phosphorus source, it is placed in a tube furnace for heat treatment under low vacuum conditions to obtain silicon-carbon anode material.
[0013] Further specifying, the CVD deposition process in (1) is as follows: placing the biomass porous carbon material in a CVD furnace, heating it to 520°C at a rate of 5°C / min, introducing a silane mixed gas for deposition, and the deposition time is 60 min.
[0014] Further specified, the mass fraction of toluene in the toluene and asphalt mixture in (1) is 15%.
[0015] Further specifying, (1) the silane mixture is a mixture of SiH4 and Ar in a volume ratio of 5:95.
[0016] Further specifying, the calcination process in (1) is as follows: heating to 300℃ at a rate of 2℃ / min and holding for 180min, heating to 900℃ at a rate of 5℃ / min and holding for 120min.
[0017] Further specifying, in (2), the mass ratio of silicon-carbon material to phosphorus source is 9:1.
[0018] Further specified, (2) the heat treatment process is as follows: heat up to 450℃ at a rate of 5℃ / min, cool down to 280℃ at a rate of 5℃ / min, and hold for 1200min.
[0019] Further specifying, in (2), the phosphorus source is red phosphorus or a phosphorus-containing compound.
[0020] The second objective of this invention is to provide a silicon-carbon anode material obtained by the above preparation method.
[0021] The third objective of this invention is to provide an application of the aforementioned silicon-carbon anode material. Specifically, the silicon-carbon anode material is assembled with a layered transition metal oxide cathode and an FEC electrolyte to form a lithium-ion battery. During the electrochemical charge and discharge process, an inorganic dual-phase SEI, Li3P-LiF, is formed on the surface of the silicon-carbon anode material.
[0022] Beneficial effects:
[0023] This invention introduces phosphorus-containing surface active sites onto the silicon-carbon anode surface, inducing selective decomposition reactions of the electrolyte at the interface during subsequent electrochemical cycling. These sites participate in the evolution of the inorganic components of the SEI (Sediment Ion Exchange), promoting the directional formation of the Li3P phase. Simultaneously, the fluorine-containing components in the electrolyte form LiF at the interface, thus forming an in-situ inorganic biphase composite SEI containing Li3P and LiF. LiF serves as the chemically stabilizing and electronically insulating component of the SEI, suppressing the continuous decomposition of the electrolyte and the occurrence of side reactions. Li3P, as a lithium-ion conductive inorganic phase, provides low-impedance Li-ion exchange. + The transport channel is formed and a composite structure with LiF at the nanoscale is established to jointly undertake the functions of interfacial mechanical support and stress regulation. The constructed biphase SEI can effectively disperse the interfacial stress caused by the volume change of silicon-based anode during cycling, slow down the accumulation of SEI defects and repeated cracking-repair behavior, thereby significantly reducing the interfacial impedance growth rate and improving cycling stability. It shows significant advantages in initial coulombic efficiency, rate performance and long-term cycling stability. Moreover, this performance improvement can be further extended to the whole cell system. It still maintains stable operation under the conditions of limited lithium source and actual positive and negative electrode coupling, and has good engineering application potential.
[0024] Furthermore, this invention avoids the uncontrollable process of traditional SEI relying on random decomposition of the electrolyte, and induces selective decomposition reaction of the electrolyte at the interface, thereby realizing the directional evolution and precise control of inorganic SEI components at the interface. Attached Figure Description
[0025] Figure 1 The diagram shows the construction of the silicon-carbon anode materials prepared in Example 1 and Comparative Examples 2-3 based on the formation of SEI at surface active sites.
[0026] Figure 2 The distribution of surface active sites in the silicon-carbon anode materials prepared in Example 1 and Comparative Examples 2-3 is characterized.
[0027] Figure 3 The results of successfully constructing SEI based on surface active sites for the silicon-carbon anode materials prepared in Example 1 and Comparative Examples 2-3 are shown in the figure.
[0028] Figure 4 Comparison of the structural stability of the SEI constructed from the silicon-carbon anode materials prepared in Example 1 and Comparative Examples 1-3;
[0029] Figure 5 Comparison of performance tests of lithium metal half-cells assembled with silicon-carbon anode materials prepared in Example 1 and Comparative Examples 1-3;
[0030] Figure 6 The silicon-carbon anode material prepared in Example 1 and LiNi 0.6 Co 0.2 Mn 0.2 Electrochemical performance of the full cell assembled with O2 cathode in the voltage range of 3.0~4.3V and current density of 160mA / g. Detailed Implementation
[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.
[0032] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art may make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.
[0033] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.
[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.
[0035] Example 1:
[0036] The method for preparing silicon-carbon anode material in this embodiment includes the following steps:
[0037] (1) Preparation of silicon-carbon materials:
[0038] Wash the poplar wood shavings 1-2 times with clean water, place them in an oven and dry at 105℃ for later use.
[0039] 10g of poplar sawdust and 20g of KOH were placed in a 250mL plastic beaker, and 200mL of deionized water was added. The mixture was stirred at a constant temperature of 85℃ for 3 hours, and then dried at 105℃ for 6 hours. The mixture was then placed in a tube furnace, and argon gas was introduced as a protective gas. The temperature was increased to 800℃ at a rate of 5℃ / min and held for 2 hours to obtain biomass porous carbon material.
[0040] The biomass porous carbon material was placed in a CVD furnace, and the temperature was raised to 520°C at a rate of 5°C / min. After the temperature was reached, a silane mixture gas (SiH4 to Ar volume ratio of 5:95) was introduced, and the deposition time was controlled to be 60 min.
[0041] Toluene and asphalt were mixed to prepare a toluene / asphalt solution with a toluene mass fraction of 15%. The mixture was stirred for 20 min and centrifuged at 4000 rpm to obtain a supernatant. The deposited product was placed in the supernatant, and the solution was heated to evaporate. The solution was then placed in a tube furnace and heated to 300°C at a rate of 2°C / min and held for 180 min. The temperature was then increased to 900°C at a rate of 5°C / min and held for 120 min to obtain silicon-carbon material.
[0042] (2) Synthesis of Si / C@P materials:
[0043] The silicon-carbon material prepared in step (1) above was mixed with red phosphorus at a mass ratio of 9:1 and placed in a tube furnace under low vacuum conditions. The mixture was heated to 450°C at a rate of 5°C / min and cooled to 280°C at a rate of 5°C / min. The mixture was held at this temperature for 1200 min to obtain Si / C@P material.
[0044] Example 2:
[0045] The difference between this embodiment and Comparative Example 1 is that elemental sulfur is used instead of red phosphorus in step (2), while the remaining process steps and process parameters are the same as in Example 1.
[0046] Comparative Example 1:
[0047] The difference between this comparative example and Example 1 is that step (2) was not performed, and the silicon-carbon material obtained in step (1) was used as the silicon-carbon anode material. The obtained silicon-carbon anode material was named Si / C.
[0048] Comparative Example 2:
[0049] The difference between this comparative example and Example 1 is that: step (2) involves mixing the silicon-carbon material prepared in step (1) with CoF at a mass ratio of 3:1, placing it in a tube furnace, heating it to 400°C at a rate of 5°C / min under low vacuum conditions, and holding it at that temperature for 360 min. The resulting silicon-carbon anode material is named Si / C@F.
[0050] Comparative Example 3:
[0051] The difference between this comparative example and Example 1 is that: step (2) involves mixing the silicon-carbon material prepared in step (1) with sulfur at a mass ratio of 9:1, placing it in a tube furnace, heating it to 450°C at a rate of 5°C / min under low vacuum conditions, and holding it at that temperature for 180 min. The resulting silicon-carbon anode material is named Si / C@S.
[0052] Example of results:
[0053] (1) The surface active sites of the silicon-carbon anode materials prepared in Example 1 and Comparative Examples 2-3 were characterized, and the results are as follows: Figure 2 As shown in the figure, XPS quantitative results indicate that the elemental contents at the sites of the three types of samples are on the same order of magnitude: 4.39 at% for F in Si / C@F, 4.07 at% for S in Si / C@S, and 4.48 at% for P in Si / C@P. This result demonstrates that all three modification routes can achieve controllable element introduction and eliminate the interference factor of "different interface behaviors due to differences in doping amount" at the content level. This provides the necessary premise for subsequent comparison of the functional roles of different element sites. Elemental surface distribution analysis further confirms that the three types of sites have good spatial uniformity at the particle scale.
[0054] (2) The silicon-carbon anode materials prepared in Examples 1 and Comparative Examples 1-3 were used as anodes in lithium-ion batteries. The first charge-discharge cycle was performed in a lithium-containing organic electrolyte system (FEC electrolyte). A solid electrolyte interphase (SEI) film was constructed on the surface of the silicon-carbon anode material. The structure and composition of the obtained SEI were characterized, and the results are as follows: Figure 3As shown in the figure, the Si / C prepared in Comparative Example 1 and the Si / C@F prepared in Comparative Example 2 induced single-phase interface SEIs (named ConSEI and LiF-rich SEI, respectively) during the electrochemical process. Con SEI and LiF-rich SEI are dominated by organic components, with discontinuous LiF distribution, uneven interface film thickness, and significant increase in interface impedance during cycling. The Si / C@P prepared in Example 1 induced the construction of a Li3P-LiF biphase interface (named Li3P-LiF SEI) during electrochemical processes. This is because, under electrochemical action, the fluorine-containing components in the electrolyte undergo interfacial reactions. Guided by the active sites of phosphorus, phosphorus preferentially participates in the evolution of inorganic components during the interfacial reaction, promoting the directional formation of the Li3P phase. This, in turn, induces selective decomposition reactions of the electrolyte at the interface. Simultaneously, the fluorine-containing components in the electrolyte form LiF at the interface, thus forming an inorganic biphase composite SEI containing Li3P and LiF in situ. The resulting biphase SEI is covered on the negative electrode surface, with Li3P and LiF coexisting at the nanoscale. The Si / C@S prepared in Comparative Example 3 induced the construction of a Li2S-LiF biphase interface (named Li2S-LiF SEI) during electrochemical processes. Based on the above analysis, it can be seen that the different surface active sites (F, S, P) of different silicon-carbon negative electrode materials guide the SEI construction process as follows... Figure 1 As shown.
[0055] (3) The stability of the SEI constructed from the silicon-carbon anode materials prepared in Example 1 and Comparative Examples 2-3 is characterized as follows: Figure 4 As shown in the figure, the multiphase inorganic SEI not only improves the mechanical strength of the interface, but more importantly, it improves the continuity and uniformity of the interface structure, thereby simultaneously suppressing the two degradation paths of structural fracture and amplification of local side reactions. Li3P-LiF SEI achieves a more uniform surface and a higher modulus.
[0056] (4) The silicon-carbon anode materials prepared in Examples 1-2 and Comparative Examples 1-3 were used as anodes to assemble lithium-ion half-cells for testing. The specific electrolyte was FEC electrolyte. The test results are as follows: Figure 5As shown in the figure, although the LiF-rich SEI constructed from the silicon-carbon anode material prepared in Comparative Example 2 exhibits certain chemical stability, its interfacial ion transport resistance is relatively high, making it prone to interfacial breakage and regeneration during cycling, resulting in limited long-term cycling stability. This indicates that enriching a single LiF phase alone is insufficient to achieve long-term stable control of the silicon-carbon anode interface. The Li2S-LiF SEI constructed from the silicon-carbon anode material prepared in Comparative Example 3 improves the mechanical adaptability of the interface to some extent, but compared to the Li3P-LiF SEI constructed from the silicon-carbon anode material prepared in Example 1, its ion transport capacity is limited, and the interfacial impedance increase during cycling is still quite significant. This demonstrates that the selection of the second inorganic phase in the dual-phase SEI has a decisive influence on the interfacial performance, and simply introducing strain-buffered components is insufficient to achieve a highly stable interface.
[0057] (5) The silicon-carbon anode material prepared in Example 1 was used as the anode of a lithium-ion battery, and assembled into a lithium-ion full cell for testing. The specific electrolyte was FEC electrolyte, and the positive electrode was NCM622. Its cycle performance was tested, and the results are as follows: Figure 6 As shown in the figure, under the condition of limited lithium source and actual positive and negative electrode capacity matching, the full cell can maintain stable capacity output during multiple cycles, indicating that the constructed Li3P-LiF dual-phase SEI can effectively maintain interface stability and ion transport continuity in the actual battery system.
[0058] The above description is only a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.
Claims
1. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material has phosphorus-containing surface active sites introduced onto its surface, and the silicon-carbon anode material is prepared by the following steps: (1) Using biomass porous carbon material as substrate and silane mixed gas as gaseous precursor, after CVD deposition, the mixture is placed in the supernatant obtained by centrifuging toluene and asphalt mixture, heated to evaporate the solution and then calcined to obtain silicon carbon material; (2) After the obtained silicon-carbon material is mixed evenly with the phosphorus source, it is placed in a tube furnace for heat treatment under low vacuum conditions to obtain silicon-carbon anode material; The heat treatment process is as follows: the temperature is increased to 450°C at a rate of 5°C / min, then decreased to 280°C at a rate of 5°C / min, and held for 1200 min.
2. The silicon-carbon anode material according to claim 1, characterized in that, (1) The CVD deposition process is as follows: the biomass porous carbon material is placed in the CVD furnace and heated to 520°C at a rate of 5°C / min. A silane mixed gas is introduced for deposition, and the deposition time is 60 min.
3. The silicon-carbon anode material according to claim 1, characterized in that, (1) The mass fraction of toluene in the mixture of toluene and asphalt is 15%.
4. The silicon-carbon anode material according to claim 1, characterized in that, (1) The silane mixture is made by mixing SiH4 and Ar in a volume ratio of 5:
95.
5. The silicon-carbon anode material according to claim 1, characterized in that, (1) The calcination process is as follows: the temperature is increased to 300℃ at a rate of 2℃ / min and held for 180min, and then increased to 900℃ at a rate of 5℃ / min and held for 120min.
6. The silicon-carbon anode material according to claim 1, characterized in that, (2) The mass ratio of silicon-carbon material to phosphorus source is 9:
1.
7. The silicon-carbon anode material according to claim 1, characterized in that, (2) The phosphorus source is red phosphorus or a phosphorus-containing compound.
8. The application of the silicon-carbon anode material according to any one of claims 1 to 7, characterized in that, The silicon-carbon anode material is assembled with a layered transition metal oxide cathode and an FEC electrolyte to form a lithium-ion battery. During the electrochemical charge and discharge process, a Li3P-LiF inorganic dual-phase SEI is formed on the surface of the silicon-carbon anode material.