Lithium-free transition metal monoxides for positive electrodes in lithium-ion batteries

Abstract

Lithium-ion batteries based on intercalation compounds have dominated the advanced portable energy storage market. The positive electrode materials in these batteries belong to a material group of lithium-conducting crystals that contain redoxactive transition metal and lithium. Materials without lithium-conducting paths or lithium-free compounds could be rarely used as positive electrodes due to the incapability of reversible lithium intercalation or the necessity of using metallic lithium as negative electrodes. These constraints have significantly limited the choice of materials and retarded the development of new positive electrodes in lithium-ion batteries. Here, we demonstrate that lithium-free transition metal monoxides that do not contain lithium-conducting paths in their crystal structure can be converted into high-capacity positive electrodes in the electrochemical cell by initially decorating the monoxide surface with nanosized lithium fluoride. This unusual electrochemical behaviour is attributed to a surface conversion reaction mechanism in contrast with the classic lithium intercalation reaction. Our findings will o er a potential new path in the design of positive electrode materials in lithium-ion batteries.

Applications of Voltammetry in Lithium Ion Battery Research

“…Many studies referred to CV with various scan rates have been reported, as shown in Fig. 5c, and most of the electrode materials tended to follow quasi-reversible processes in which the peak potential increased as the scan rate increased [20,21,[26][27][28][29][30][31][32]. Sweep rate CV technique is used to obtain a clue as to how the mechanism of each electrode proceeds through the electrochemical reaction.…”

“…A sweep rate CV technique is useful to investigate pseudo-capacitive electrochemical behaviors of cathode materials (e.g. Lithium-free LiF-MO) [30]. Unlike Li + intercalating cathode materials, approximately 94% of the total capacity is derived from a surface-controlled reaction.…”

“…The sweep rate CV technique can be used for calculating the diffusion coefficients of both cathode and anode materials. In practice, it has been extensively used for various cathode materials such as layered [39], spinel [40], olivine [19,41], and even LiF-MO [30] nanocomposite. In addition, the overall average Li + diffusivity of various anode materials also can be estimated.…”

Electrochemically driven conversion reaction in fluoride electrodes for energy storage devices

“…Similar to electrochemical splitting of Li 2 O x and Li 2 S, LiF can also be split under the participation of transition metal, low-valence transition metal oxide or fluoride, enabling the construction of ′ion batteries′. [68][69][70] Inspired by the decomposition products of FeF 3 , a pristine composite electrode consisting of nanostructured Fe and LiF was prepared. 68,71 However, the Fe/LiF electrode failed to achieve the expected capacity owing to lattice mismatch and poor phase distribution.…”

Electrochemical Conversion of Nitrogen Trifluoride as a Gas-to-Solid Cathode in Li Batteries

“…Overall, the reduction process is remarkably wellbehaved, yielding clean LiF layers with high Faradaic efficiency; thus, this work also opens new opportunities for applications where conformal LiF coatings may prove beneficial in electrode materials synthesis, such as advanced Li-ion battery cathodes. 36,37 ASSOCIATED CONTENT Supporting Information. Experimental section, thermodynamics and kinetics calculations, and additional figures and tables.…”