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CN-121672533-B - Silicon-carbon negative electrode material and preparation method and application thereof

CN121672533BCN 121672533 BCN121672533 BCN 121672533BCN-121672533-B

Abstract

The invention discloses a silicon-carbon negative electrode material, a preparation method and application thereof, and belongs to the technical field of lithium ion battery electrodes and interface regulation and control thereof. The invention solves the problems of unstable structure of solid electrolyte interface film (SEI), continuous increase of interface impedance, aggravation of electrolyte side reaction, limited cycle life and the like caused by severe volume expansion in the charge and discharge process of the existing silicon-carbon anode. According to the invention, the surface active site containing the phosphorus element is introduced to the silicon-carbon anode, so that the electrolyte is induced to undergo a selective decomposition reaction at the interface in the subsequent electrochemical circulation process, and thus, the inorganic dual-phase composite SEI containing Li 3 P and LiF is formed in situ. The constructed dual-phase SEI can effectively disperse interface stress caused by volume change of a silicon-based negative electrode in a cyclic process, and slow down SEI defect accumulation and repeated cracking-repairing behaviors, so that the interface impedance growth rate is obviously reduced, the cyclic stability is improved, and the dual-phase SEI has good engineering application potential.

Inventors

  • CHENG YONG
  • WANG CHUNLI
  • LIANG YAO
  • YIN DONGMING
  • YUAN JIANGUANG
  • WANG ZHAOMIN
  • WANG LIMIN

Assignees

  • 中国科学院长春应用化学研究所

Dates

Publication Date
20260512
Application Date
20260210

Claims (8)

  1. 1. The silicon-carbon negative electrode material is characterized in that a surface active site containing phosphorus is introduced into the surface of the silicon-carbon negative electrode material, and the silicon-carbon negative electrode material is prepared through the following steps: (1) Taking a biomass porous carbon material as a substrate, taking silane mixed gas as a gaseous precursor, depositing by CVD, placing in a supernatant obtained by centrifuging a toluene and asphalt mixed solution, heating an evaporation solution, and calcining to obtain a silicon carbon material; (2) Uniformly mixing the obtained silicon-carbon material with a phosphorus source, and then placing the mixture in a tube furnace for heat treatment under a low vacuum condition to obtain a silicon-carbon anode material; The heat treatment process is that the temperature is raised to 450 ℃ at the speed of 5 ℃ per minute, the temperature is lowered to 280 ℃ at the speed of 5 ℃ per minute, and the temperature is kept for 1200 minutes.
  2. 2. The silicon-carbon anode material according to claim 1, wherein the CVD deposition process in (1) is that the biomass porous carbon material is placed in a CVD furnace, heated to 520 ℃ at a rate of 5 ℃ per minute, and silane mixture gas is introduced for deposition for 60 minutes.
  3. 3. The silicon-carbon negative electrode material according to claim 1, wherein the mass fraction of toluene in the toluene and pitch mixture in (1) is 15%.
  4. 4. The silicon-carbon anode material according to claim 1, wherein the silane mixture in (1) is mixed by SiH 4 and Ar in a volume ratio of 5:95.
  5. 5. The silicon-carbon negative electrode material according to claim 1, wherein the calcination process in (1) is to raise the temperature to 300 ℃ at a rate of 2 ℃ per minute, keep the temperature for 180 minutes, raise the temperature to 900 ℃ at a rate of 5 ℃ per minute, and keep the temperature for 120 minutes.
  6. 6. The silicon-carbon negative electrode material according to claim 1, wherein the mass ratio of the silicon-carbon material to the phosphorus source in (2) is 9:1.
  7. 7. The silicon-carbon negative electrode material according to claim 1, wherein the phosphorus source in (2) is red phosphorus or a phosphorus-containing compound.
  8. 8. The use of the silicon-carbon negative electrode material according to any one of claims 1-7, wherein the silicon-carbon negative electrode material, a layered transition metal oxide positive electrode and an FEC electrolyte are assembled into a lithium ion battery, and Li 3 P-LiF inorganic dual-phase SEI is formed on the surface of the silicon-carbon negative electrode material in the electrochemical charging and discharging process.

Description

Silicon-carbon negative electrode material and preparation method and application thereof Technical Field The invention relates to a silicon-carbon negative electrode material, a preparation method and application thereof, and belongs to the technical field of lithium ion battery electrodes and interface regulation and control thereof. Background With the rapid development of lithium ion batteries in the fields of electric vehicles and large-scale energy storage, the requirements on battery energy density and cycle life are continuously improved. The silicon-based anode material is considered as an ideal candidate for replacing the traditional graphite anode and realizing the next generation of high-energy-density lithium ion battery due to extremely high theoretical specific capacity. However, in practical application, the silicon-based negative electrode can undergo significant volume expansion and shrinkage in the charge and discharge process, so that the interface structure is repeatedly broken, and the cycle stability and practical application of the silicon-based negative electrode are severely restricted. During operation of a silicon-based anode, a solid electrolyte interface film (Solid Electrolyte Interphase, SEI) is inevitably formed on the electrode surface. The interface film has key effects of inhibiting continuous decomposition of electrolyte, maintaining interface stability and guaranteeing reversible transmission of lithium ions. However, due to the severe volume change of the silicon-based material, the conventional SEI film tends to be difficult to maintain structural integrity, and is easily broken and regenerated during cycling, resulting in continuous increase of interfacial resistance, continuous consumption of active lithium, and gradual failure of electrode structure. In order to improve the interfacial stability of silicon-based negative electrodes, various SEI regulation strategies have been proposed in the prior art, wherein SEI films rich in inorganic components, especially rich in LiF, are represented. LiF is widely considered to contribute to suppression of side reactions and improvement of interface durability due to its high chemical stability and good electronic insulating properties. Therefore, construction of LiF-rich SEI by means of electrolyte additives, surface fluorination or electrolyte composition regulation, etc., has become the dominant idea in current research and application. However, practice has shown that there are significant limitations to a single LiF-rich SEI film. On one hand, liF has lower intrinsic lithium ion conductivity, is easy to become a limiting factor of interface ion transmission under high multiplying power or long cycle conditions, and leads to polarization aggravation and multiplying power performance reduction, and on the other hand, liF-SEI is generally high in brittleness, microcracks and structural failure are still easy to occur under the repeated volume change effect of a silicon-based negative electrode, and the problems of repeated interface cracking and continuous growth are difficult to fundamentally solve. Therefore, SEI designs relying on only a single inorganic phase have difficulty meeting multiple requirements of chemical stability, mechanical adaptability, and rapid lithium ion transport at the same time. In addition, some researches try to improve the strain buffering capacity of SEI by introducing inorganic or organic components with certain flexibility, but related schemes tend to focus on improvement of mechanical adaptability, but insufficient attention is paid to interfacial lithium ion transmission dynamics, and stable and low-impedance interfacial reaction environment is still difficult to realize under the working conditions of high load and long service life. The prior art is not provided with a silicon-based negative electrode SEI design strategy capable of realizing cooperative optimization among structural stability, mechanical bearing capacity and lithium ion transmission performance. Therefore, a new SEI construction strategy capable of combining mechanical stability and rapid lithium ion transmission capability at the interface scale is needed to be provided, inorganic components beneficial to rapid lithium ion transmission are introduced while chemical stability and electronic insulation of an SEI film are ensured, and multifunctional coordination is realized through a controlled interface construction mode, so that the interface failure problem of a silicon-based negative electrode under the conditions of long-term circulation and high multiplying power is effectively relieved. Disclosure of Invention The invention provides a silicon-carbon negative electrode material and a preparation method and application thereof, and aims to solve the problems that the existing silicon-carbon negative electrode is unstable in structure, continuous in interface impedance increase, aggravated in electrolyte side reaction,