Partially Reduced Titanium Niobium Oxide: A High-Performance Lithium-Storage Material in a Broad Temperature Range.

The existing electrode materials for lithium-ion batteries (LIBs) generally suffer from poor rate capability at low temperatures, severely limiting their applications in winter and cold climate area. Here, partially reduced TiNb 24 O 62 (PR-TNO) are reported that demonstrates excellent electrochemical performance in a broad temperature range, notably at low temperatures. Its crystal structure is similar to that of Ti 2 Nb 10 O 29 upon partial reduction in H 2 . The titanium and niobium ions in PR-TNO enable multielectron transfer, safe operation, and high Coulombic efficiencies. Benefiting from the increased electronic conductivity of the partially reduced phase and its robust crystal structure with a large interlayer spacing, PR-TNO shows fast electron and Li + transport, small volume change associated with Li + storage, and notable capacitive behavior, resulting in good electrochemical performance even at very low temperatures. At -20 °C, a large reversible capacity of 313 mAh g -1 is obtained at 0.1C, reaching 83.3% of that at 25 °C. At 5C, high rate capability (58.3% of that at 0.5C) is achieved, only slightly lower than that at 25 °C (60.7%). Furthermore, PR-TNO demonstrates excellent cyclic stability with 99.2% of the initial capacity after 1680 cycles, confirming its excellent suitability for low-temperature LIBs.