Self-Purifying Primary Solvation Sheath Enables Stable Electrode-Electrolyte Interfaces for Nickel-Rich Cathodes.

Herein, we optimize the primary solvation sheath to investigate the fundamental correlation between battery performance and electrode-electrolyte interfacial properties through electrolyte solvation chemistry. Experimental and theoretical analyses reveal that the primary solvation sheath with a self-purifying feature can "positively" scavenge both the HF and PF5 (hydrolysis of ion-paired LiPF6), stabilize the PF6 anion-derived electrode-electrolyte interfaces, and thus boost the cycling performances. Being attributed with these superiorities, the NCM811//Li Li metal battery (LMB) with the electrolyte containing the optimized solvation sheath delivers 99.9% capacity retention at 2.5 C after 250 cycles. To circumvent the impact of excess Li content of Li metal on the performance of NCM811 cathode, the as-fabricated NCM811//graphite Li ion battery (LIB) also delivers a high-capacity retention of 90.1% from the 5th to the 100th cycle at 1 C. This work sheds light on the strong ability of the primary solvation sheath to regulate cathode interfacial properties.

High-Efficiency Separator Capacity-Compensation Strategy Applied to Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are expected to replace partial reliance on lithium-ion batteries (LIBs) in the field of large-scale energy storage as well as low-speed electric vehicles due to the abundance, wide distribution, and easy availability of sodium metal. Unfortunately, a certain amount of sodium ions are irreversibly trapped in the solid electrolyte interface (SEI) layer during the initial charging process, causing the initial capacity loss (ICL) of the SIBs. A separator capacity-compensation strategy is proposed, where the capacity compensator on the separator oxidizes below the high cut-off voltage of the cathode to provide additional sodium ions. This strategy shows attractive advantages, including adaptability to current production processes, no impairment of cell long-cycle life, controlled pre-sodiation degree, and strategy universality. The separator capacity-compensation strategy is applied in the NaNi1/3 Fe1/3 Mn1/3 O2 (NMFO)||HC full cell and achieve a compensated capacity ratio of 18.2%. In the Na3 V2 (PO4 )3 (NVP)||HC full cell, the initial reversible specific capacity is increased from 61.0 mAh g-1 to 83.1 mAh g-1 . The separator capacity-compensation strategy is proven to be universal and provides a new perspective to enhance the energy density of SIBs.

Surficial Oxidation of Phosphorus for Strengthening Interface Interaction and Enhancing Lithium-Storage Performance.

By virtue of high theoretical capacity and appropriate lithiation potential, phosphorus is considered as a prospective next-generation anode material for lithium-ion batteries. However, there are some problems hampering its practical application, such as low ionic conductivity and serious volume expansion. Herein, we demonstrated an in situ preoxidation strategy to build a oxidation function layer at phosphorus particle. The oxide layer not only acted as a protective layer to prolong the storage time of phosphorus anode in air but also carbonized N-methyl pyrrolidone and poly (vinylidene fluoride), strengthening the interfacial interaction between phosphorus particles and binder. The oxide layer further induced the formation of a stable solid electrolyte interface with high lithium-ion conductivity. The oxidized P-CNT maintained high specific capacity of 1306 mAh g-1 and 89% capacity after 100 cycles, much higher than that of pristine P-CNT (17.1%). The strategy of in situ oxidation is facile and conducive to the practical application of phosphorus-based anodes.