A kind of silicon-carbon composite microsphere negative electrode material and preparation method thereof

Abstract

The invention discloses a silicon-carbon composite microsphere anode material and its preparation method. the preparation method comprises the following steps: firstly, nano-silicon particles and a first macromolecular solution are mixed, and first composite microspheres are formed after spray drying; then, the first composite microspheres and a second macromolecular solution are mixed to carry out surface coating on the first composite microspheres, and second composite microspheres with a core-shell structure are formed after solvent evaporation; and finally, the second composite microspheres undergo oxidation and carbonization treatments to form the silicon-carbon composite microsphere anode material. By the preparation method which has a simple technology, is low-cost and is easy to operate, the silicon-carbon composite microsphere anode material is prepared. In addition, no etching operation for pore-forming is required by the preparation method. Raw materials used in the preparation method can be selected from a number of sources. According to the silicon-carbon composite microsphere anode material obtained, advantages of nano-silicon and a carbon substrate are combined effectively. Thus, electrochemical performance of the silicon-carbon composite microsphere anode material used as a negative electrode of a lithium ion battery is enhanced.

Description

technical field [0001] The invention relates to a silicon-carbon composite microsphere negative electrode material for a lithium ion battery and a preparation method thereof. Background technique [0002] The negative electrode material of lithium-ion batteries is generally carbon material. The theoretical lithium storage capacity of the existing widely used graphite negative electrode is 372mAh / g, which is difficult to meet the increasing requirements of high-capacity lithium-ion batteries for electrode materials. Therefore, research and The development of high-capacity anode materials has become a key factor in improving the performance of lithium-ion batteries. The theoretical lithium storage capacity of silicon material is 4200mAh / g, which is an ideal material to increase the capacity of the negative electrode. However, the structure of silicon materials is unstable, and the volume expansion can reach 400% during the lithium intercalation process, and the volume shrinks...

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Problems solved by technology

However, the porous carbon matrix of the silicon-carbon composite material is an open structure, and the electrolyte can penetrate into the composite material through the pores, and the preparation cost is high, which is not conducive to large-scale production.

Li et al. (Journal of Power Sources 248 (2014) 721.) spray-dried the mixture of graphite, nano-silicon particles and citric acid to obtain graphite as the inner core and a composite of Si and porous carbon as the shell. Granular composite materials, when used as the negative electrode of lithium-ion batteries, exhibit good electrochemical performance, reaching a reversible capacity of 600mAh / g, and can be cycled stably for 100 cycles, but the capacity is low, and the silicon particles are exposed outside the composite material , leading to structural instability of the material

The carbon matrix of the porous silicon-carbon composites prepared in these studies is an open system, which cannot fully isolate the electrolyte, making it easy for the electrolyte to penetrate into the interior of the composite through the pores, resulting in an unstable structure of the negative electrode material. sex

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