Interphase Stabilization of LiNi_0.5 Mn_1.5 O₄ Cathode for 5 V-Class All-Solid-State Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• High-voltage cobalt-free spinel lithium nickel manganese oxide (LNMO) offers high energy density and cost-effectiveness for batteries.
• Challenges exist in integrating LNMO cathodes with solid electrolytes in all-solid-state batteries (ASSBs).
• Chemical incompatibility and oxidative instability limit the performance of LNMO with sulfide solid electrolytes.

Purpose of the Study:

• To investigate the interfacial limitations of LNMO cathodes with solid electrolytes in ASSBs.
• To explore strategies for enhancing the electrochemical stability and cycle performance of LNMO in ASSBs.
• To provide guidance for the development of stable high-voltage cathode interfaces in ASSBs.

Main Methods:

• Analysis of the interphase formed between LNMO and various solid electrolytes (Li6PS5Cl, Li3InCl6).
• Implementation of iron (Fe) doping and a lithium phosphate (Li3PO4) protective coating on the LNMO cathode.
• Electrochemical testing of modified LNMO cathodes in ASSBs at high voltages (approx. 4.7 V).

Main Results:

• Intrinsic chemical incompatibility and poor oxidative stability were identified as limitations for LNMO with Li6PS5Cl.
• Even stable halide electrolytes like Li3InCl6 formed resistive interphases with LNMO.
• Fe-doping and Li3PO4 coating on LNMO with Li3InCl6 resulted in stable cycling and a stabilized interphase at high voltage.

Conclusions:

• Interfacial engineering through doping and protective coatings is crucial for enabling stable high-voltage operation of LNMO cathodes in ASSBs.
• Achieving a stable interphase extends the electrochemical stability window, leading to enhanced cycle performance.
• This work offers valuable insights for utilizing high-voltage cathodes and highlights the importance of interfacial stability in ASSB development.