The cold spray method has great potential to prepare lithium ion battery electrode coatings. This paper compares the characteristics of the coating method and the cold spray method to prepare silicon-based anodes. It is proposed that the bonding characteristics of the cold spray method are beneficial to improve the cycle performance and capacity performance of silicon-based anodes. With 10 μm Si powder as active material and sodium carboxymethyl cellulose (CMC) as binder, the active material, conductive agent, and binder were mixed according to the mass ratio of Si∶Super P∶CMC=6∶2∶2. An appropriate amount of deionized water was added as a solvent. It was stirred evenly, and then applied on 50 μm thick single-sided copper foil. All the sprayed samples were prepared by self-developed spraying equipment. 10 μm Si powder and conductive carbon black (Super P) were mixed in a mass ratio of 3∶1 and then put into a ball mill for 2 h to obtain composite powder. The copper foil was cut into 10 cm×10 cm and fixed on the cold spray sample stage. At spraying temperature: 300 ℃, spraying pressure: 1 MPa, spraying distance: 5 cm, spraying pass: 1 time, powder feeding rate: 3.3 g/min, and with powder carrier gas as the air, the deposition of single particle was achieved by reducing the powder feeding rate and increasing the substrate moving speed. The microscopic morphologies of the samples were characterized by a field emission scanning electron microscope (FESEM, Nova400). Elemental analyses were performed on an energy dispersive spectrometer (EDS) attached to the field emission scanning electron microscope. The bonding strength between the electrode coating and the substrate copper foil was tested with an electronic universal testing machine of model E1000. The electrode samples were cut into the same size, a 3M tape was adhered to its surface with the same sticking area, the electrode sample was fixed on the upper part of the testing machine, and the unaffixed end of the tape was fixed on the lower part, at a stripping angle relative to the sticking position of the tape: 180°, stripping speed: 15 mm/min. Its test was continued under load until the 3M tape was separated from the electrode sample, and a force-displacement curve was obtained. The constant current charge-discharge test was carried out in an incubator with LAND test system (LAND-CT3001AU) in the voltage range of 0.05-2 V. The electrode specific capacity was calculated based on the total weight of Si. The cyclic voltammetry curve (current-voltage) was tested by electrochemical workstation (CHI604E) in 0-2 V and at 0.1 mV/s. Under the same stripping conditions, the Si-sprayed samples had high bonding strength and the stripping phenomenon appeared later. The average load of the Si-sprayed samples was 2.04 N, which was larger than that of the Si-coated samples (1.51 N). The adhesion between the Si-coated electrode material and the current collector was poor, and there were a large number of pore structures between the copper foil and the coating and inside the coating material. The Si-sprayed electrode active material was uniformly deposited in the cluster bulges gaps on the surface of the copper foil. The thin coating did not cover the cluster bulges. The silicon particles could not be deposited continuously to form a thicker coating, and were only deposited on the surface of the copper foil in an embedded manner. The capacity of the Si-sprayed electrode was only 51 mAh/g after 200 cycles, while the capacity of the Si-sprayed electrode was as high as 240 mAh/g after 200 cycles. The Rct of the Si-sprayed electrode was smaller than that of the Si-coated electrode. The lithium ion diffusion coefficient of the Si-coated electrode was always one order of magnitude higher than that of the Si-sprayed electrode from the 1st to the 200th lithium-intercalation. The silicon-based anode prepared by cold spraying has higher bonding strength. The Si-sprayed electrode active material is uniformly deposited in the cluster bulges gaps on the surface of the copper foil, which is beneficial to alleviate the volume effect, improve the structural stability, and show better cycle performance and capacity performance. Compared with Si-coated electrodes, Si-sprayed electrodes have smaller charge transfer resistance and larger lithium ion diffusion resistance. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.
