Study of induced liquid-phase sintering effect in lithium-ion battery cathode upcycling
Mingi Hwang, Jae Hong Choi, Song-Yi Lee, J. H. Hwang, Sung-Woo Park, Sumyeong Choi, Minhu Kim, Heesoo Lim, Hyuntae Lim, Miran Oh, Sumin Song, Geumju Shin, Minjoon Park, Young‐Ki Kim, Dong‐Hwa Seo, Pilgun Oh
Abstract
As concerns over the sustainability of lithium-ion batteries (LIBs) intensify, direct upcycling has emerged as a promising alternative to conventional recycling methods. However, its practical adoption is hindered by the need for high-pressure processing and the limited particle size of regenerated materials. Here, we present a new upcycling method, direct exposure heating (DEH), which selectively accelerates beneficial reaction kinetics while suppressing detrimental side reactions. DEH prevents liquid-phase depletion by eliminating the non-equilibrium heating ramp stage and minimizes irreversible phase transitions by bypassing prolonged intermediate temperatures. Under mild pressure (∼5 MPa), this process transforms secondary particles from spent LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) into large, structurally stable single-crystal LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622) particles. Grounded in thermodynamic and kinetic control, DEH resolves the long-standing trade-off between particle size and structural integrity, offering a scalable strategy not only for accelerating LIB upcycling commercialization but also for broadening advanced material synthesis.