Improved Cycling Stability of Ni-Rich Cathode Material by In Situ Introduced TM-B-O Amorphous Surface Structure.

Current research has found the amorphous/crystal interface has some unexpected electrochemical behaviors. This work designed a surface modification strategy using NaBH4 to induce in situ conversion of the surface structure of Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) into TM-B-O amorphous interface layer. Oxidizing the surface from transition metals (TM) with high valence and reductive BH4- in a weak polar medium of ethanol results in an easy redox reacton. A TM-B-O amorphous structure is formed on NCM811 surface. The action of reactive wetting ensures a complete and uniform structure evolution of the surface crystals. The complete coverage protects the outer crystal and the heterogeneous interface impedance between the modified layer and bulk is reduced. More importantly, this amorphous interface layer through in situ conversion enhances the heterogeneous link at interface and its own structural stability. The modified NCM811 (TB2@NCM) treated with 1 wt % NaBH4 shows excellent electrochemical performance, especially cyclic stability. At a high cutoff voltage of 4.5 V, the capacity retention was 72.5% at 1 C after 500 cycles. The electrode achieves 173.7 mAh·g-1 at 10 C. This work creates a modifying strategy with potential application prospect due to simple technology with low-cost raw material under mild operating conditions.

Selective recovery of metals in spent batteries by electrochemical precipitation to cathode material for sodium-ion batteries.

The recycling of key components in waste lithium-ion batteries (LIBs) is an important route to make up for the shortage of battery materials. Metal separation and purification is an important step. It is of great significance to propose an efficient and green separation technology. In this paper, an electrochemical precipitation method was applied to metal separation from spent LiNi0.5Mn1.5O4 cathode material. The Li and metal elements were effective separated and the precipitates were then used as precursor to synthesize high-performance R-O3-NaNFM cathode material for sodium-ion batteries. The R-O3-NaNFM exhibits excellent electrochemical cycling stability. The capacity retains 71.3 mAh g-1 after a long-term cycling of 200 times at 1 C. This method offers a referable strategy of the recycling for the waste cathode material in spent LIBs.

Green Synergy Conversion of Waste Graphite in Spent Lithium-Ion Batteries to GO and High-Performance EG Anode Material.

The increasing demand for graphite and the higher lithium content than environment abundance make the recycling of anode in spent lithium-ion batteries (LIBs) also become an inevitable trend. This work proposes a simple pathway to convert the retired graphite to high-performance expanded graphite (EG) under mild conditions. After the oxidation and intercalation by FeCl3 for the retired graphite, H2 O2 molecules are more likely to penetrate into the extended layers. And the gas phase diffusion caused by the produced O2 from the redox reaction between FeCl3 and H2 O2 further promotes lattice expansion of interlayers (0.535 nm), which is beneficial to the stripping of graphene oxide (GO) with fewer layers. The EG exhibits excellent electrochemical performances in both LIBs and sodium-ion batteries (SIBs). It delivers 331.5 mAh g-1 at 3C (1C = 372 mA g-1 ) in LIBs, while it achieves 176.8 mAh g-1 at 3C (1C = 120 mA g-1 ) in SIBs. Then the capacity retains 753.6 (LIBs) and 201.6 (SIBs) mAh g-1 after a long-term cycling of 500 times at 1C, respectively. The full cells with the EG electrodes after prelithium/presodiation also show excellent cycle stability. Thus, this work offers another referable strategy for the recycling of waste graphite in spent LIBs.

Nickel Acetate-Assisted Graphitization of Porous Activated Carbon at Low Temperature for Supercapacitors With High Performances.

Catalytic graphitization opens a route to prepare graphitic carbon under fairly mild conditions. Biomass has been identified as a potentially attractive precursor for graphitic carbon materials. In this work, corn starch was used as carbon source to prepare hollow graphitic carbon microspheres by pyrolysis after mixing impregnation with nitrate salts, and the surface of these carbon microspheres is covered with controllable pores structure. Under optimal synthesis conditions, the prepared carbon microspheres show a uniform pore size distribution and high degree of graphitization. When tested as electrode materials for supercapacitor with organic electrolyte, the electrode exhibited a superior specific capacitance of 144.8 F g-1 at a current density of 0.1 A g-1, as well as large power density and a capacitance retention rate of 93.5% after 1,000 cycles in galvanostatic charge/discharge test at 1.0 A g-1. The synthesis extends use of the renewable nature resources and sheds light on developing new routes to design graphitic carbon microspheres.

Synergy ascension of SnS/MoS2 binary metal sulfides on initial coulombic efficiency and stable capacity for lithium storage.

Numerous efforts have been devoted to capability improvement and cycling stability in the past decades, and these performances have been significantly enhanced. Low initial coulombic efficiency is still a problem in the metal sulfide-based anode materials. This study developed a strategy to achieve high initial coulombic efficiency and superior capacity retention by interpenetrating binary metal sulfides of SnS and MoS2 in a conductive carbon matrix. The synergy ascension of electrochemical performances for the metal sulfides is attributed to their mutual impeding effects on coarsening of metal grains and the capsule-shaped coating structure embedded in the carbon sheet architecture. The SnS/MoS2/C composite was prepared by a simple NaCl template-assisted ball milling method, and showed excellent electrochemical performances in terms of a high initial coulombic efficiency up to 90.2% and highly stable reversibility with a specific capacity of 515.4 mA h g-1 after 300 cycles at 1.0 A g-1. All of these characteristics suggest that the proposed materials are superior among the previously reported metal sulfide-based anode materials for lithium-ion batteries.

Three-Dimension Hierarchical Al2O3 Nanosheets Wrapped LiMn2O4 with Enhanced Cycling Stability as Cathode Material for Lithium Ion Batteries.

A three dimensional (3D) Al2O3 coating layer was synthesized by a facile approach including stripping and in situ self-assembly of γ-AlOOH. The uniform flower-like Al2O3 nanosheets with high specific area largely sequesters acidic species produced by side reaction between electrode and electrolyte. The inner coating layer wrapping spinel LiMn2O4 effectively inhibits the dissolution of Mn by suppressing directive contact with electrolyte to enhance cycling stability. The rate performance is improved because of the better electrolyte storage of the assembled hierarchical architecture of the 3D coating layer affording unimpeded Li(+) diffusion from electrode to electrolyte. The electrochemical results reveal the as-prepared coated LiMn2O4 sample with the amount of Al2O3 at 1 wt % exhibits superior cycle stability under room temperature even at elevated temperature. The initial specific discharge capacity is 128.5 mAh g(-1) at 0.1 C and retains 89.8% of the initial capacity after 800 cycles at 1 C rate. When cycling at 55 °C, the composite shows 93.6% capacity retention after 500 cycles. This facile surface modification and effective structure of coating layer can be adopted to enhance the cycling performance and thermal stability of other electrode materials for which Al2O3 plays its role.