On the preparation of multifunctional conversion coatings of FePO 4 /LiFePO 4

S. Valverde-Pérez (1) , R. Figueroa (1) , X.R. Nóvoa (1) , D.S. Ramírez-Rico (2) , Vincent Vivier (2)

1 Universidade de Vigo
2 LRS - Laboratoire de Réactivité de Surface

This research aims to take advantage of the properRes of phosphate coaRngs to overcome the problems inherent in using LiFePO4 as a powder. LiFePO4 coaRngs have been prepared on iron sheets using cyclic voltammetry in an aqueous soluRon of H3PO4 and LiOH. The voltammograms evolved from the iniRal acRve-passive behaviour, typical for iron in H3PO4 soluRon, to a reversible redox behaviour upon cycling. The resulRng coaRng was characterised morphologically (via SEM and opRcal microscopies), chemically (via XPS) and electrochemically (via EIS and SECM). The results showed a two-layered coaRng (a porous outer layer and a compact inner layer) with the behaviour of a porous electrode that reversibly exchanges Li + ions with the environment and reduces the emission of ionic species (Fe 2+ , Fe 3+ ) as its thickness increases.

Introduc<on

Phosphate coaRngs have a long tradiRon as treatments to increase the corrosion resistance of metallic substrates, improve the adhesion of organic coaRngs, or increase the wear resistance.

Metallic substrates such as plain carbon steel, galvanized steel, stainless steel, and Mg or Al alloys, are protected by conversion coaRngs usually grown by relaRvely simple, fast, and low-cost

Furthermore, baeeries based on LiFePO4 (LFP) are nowadays the automoRve industry's reference technology. LFP is a non-toxic, low-cost, safe and highly reversible material for posiRve electrodes [7,8]. The LiFePO4 olivine structure as a suitable material for posiRve electrodes was recognised in 1997 [9], which makes LFP baeeries a mature technology opRmised by numerous researchers [10]. The theoreRcal capacity is 170 Ah/kg, the cyclic charge/discharge stability and the minimal capacity loss on cycling make LiFePO4 interesRng for commercial use [11-14]. In addiRon, the low electronic conducRvity of the pure LiFePO4 cathode is a drawback that has been overcome by focusing on parRcle size reducRon or carbon doping [11,15,16].

Domaines: Chimie

S. Valverde-Pérez, R. Figueroa, X.R. Nóvoa, D.S. Ramírez-Rico, Vincent Vivier. On the preparation of multifunctional conversion coatings of FePO 4 /LiFePO 4. Surface and Coatings Technology, 2024, 479, pp.130548. ⟨10.1016/j.surfcoat.2024.130548⟩. ⟨hal-04775533⟩