Surface‐to‐Bulk Synergistic Modification of Single Crystal Cathode Enables Stable Cycling of Sulfide‐Based All‐Solid‐State Batteries at 4.4 V

Abstract

The interfacial stability between sulfide solid‐state electrolytes (SSEs) and high voltage Ni‐rich oxide cathodes is critical to the electrochemical performances of all‐solid‐state batteries (ASSBs), yet it is challenging to solve the interface issues by surface coating modification. Here, a surface‐to‐bulk synergistic modification is proposed to achieve a highly stable interface through the combination of TiNb2O7‐coated and Ti‐doped LiNi0.6Mn0.2Co0.2O2 single crystals (DC‐TNO@SCNCM). The TiNb2O7 coating layer with thermodynamic/electrochemical stability and electronic insulation avoids the decomposition of SSEs. The strong TiO bond in SCNCM achieved by Ti doping can stabilize lattice oxygen and avoid further electrochemically oxidizing sulfide electrolytes to form oxygenated sulfurous and phosphorous species. The modified DC‐TNO@SCNCM cathode exhibits excellent long‐cycle stability with a capacity retention rate of 92.2% after 140 cycles at a high cut‐off voltage of 4.4 V. This surface‐to‐bulk synergistic modification strategy provides a new perspective for the design of high‐voltage sulfide‐based ASSBs.

Coupling novel Li7TaO6 surface buffering with bulk Ta-doping to achieve long-life sulfide-based all-solid-state lithium batteries

“…S18, ESI†), which suggests that the surface-to-bulk synergy can effectively suppress the interfacial reactions, particularly the formation of oxygenated sulfurous and phosphorous species (SO 3 2− /SO 4 2− and PO 4 3− ), avoiding the generation of high interface resistance. 17 These findings are consistent with the EIS, GITT and SEM results described above.…”

“…16 Therefore, a coupling design of surface buffer coatings with bulk doping is expected to realize high-performance sulfide-based ASSLBs. 17 Simultaneously, there is also an urgent need to achieve the above coupling design with a low-cost and scalable method. 18–20…”

Fundamentals of the Cathode‐Electrolyte Interface in All‐solid‐state Lithium Batteries

“…[148] As a result, the sulfide SE-based LCO ASSB showed a high discharge capacity of 142 mAh g À 1 at 0.2 C and room temperature while that of the uncoated LCO ASSB was only 107 mAh g À 1 . Similar protective oxide coating layers, such as Li 3 N, [145] TiNb 2 O 7 , [149] Li 4 Ti 5 O 12 , [59,150] Al 2 O 3 , [151] Li 2 SiO 3 , [152] Li 3 PO 4 , [153] Li 0.35 La 0.5 Sr 0.05 TiO 3 [154] and NASI-CON-type SEs, [155,156] have also been investigated. However, most oxide coatings are brittle and unable to accommodate cathode volume changes during cycling, [157] and contact degradation still remains unsettled during long-term cycling.…”

Recent Advances in Conduction Mechanisms, Synthesis Methods, and Improvement Strategies for Li1+xAlxTi2−x(PO4)3 Solid Electrolyte for All‐Solid‐State Lithium Batteries

“…However, sulfides are chemically unstable in air and can produce toxic H 2 S gas in the presence of water. [28,29] In contrast to SSEs consisting of polymers and sulfides, oxides-based SSEs, sodium superionic conductor (NASICON) structured materials in general, can exhibit both good thermal/ structural stability and high ionic conductivity, and they are becoming the hot materials for SSB. [30,31] In particular, Li 1+x Al x Ti 2−x (PO 4 ) 3 (LATP), as a typical NASICON-type oxide SSE, exhibits high ionic conductivity (≈10 −4 -10 −3 S cm −1 ) and excellent stability in the presence of air and water.…”