The growing accumulation of spent lithium-ion batteries (LIBs) presents significant environmental challenges, while the complex composition of battery waste complicates efficient resource recovery. Herein, a phosphoric acid-assisted upcycling strategy is developed to recover multimetallic constituents from spent LIBs and reconstruct them into multicomponent phosphate (R-MCP) catalysts for lithium-sulfur batteries, reducing the need for extensive component separation. The resulting R-MCP, containing Ni, Mn, Fe, Cu, and Al, exhibits favorable polysulfide adsorption and sulfur-conversion behavior compared with recycled Ni-Mn-Fe phosphate (R-NMP). Experimental characterizations and density functional theory calculations provide insights into the electronic interactions and favorable sulfur redox kinetics of R-MCP. Consequently, the R-MCP modified separator delivers an initial capacity of 1075 mAh g^-1 at 0.5 C and stable cycling over 2000 cycles at 1 C, with a capacity decay rate of 0.029% per cycle. Stable cycling is also achieved at a sulfur loading of 10.14 mg cm^-2. This work demonstrates a practical route for converting multimetallic battery waste into functional catalytic materials.