Xiaofei Bian

Electrochemical performance and thermal stability of Li1.18Co0.15Ni0.15Mn0.52O2 surface coated with the ionic conductor Li3VO4

Li1.18Co0.15Ni0.15Mn0.52O2 cathode material was prepared by the sol–gel method. The material was coated with the ionic conductor Li3VO4via direct reaction with NH4VO3 at 350 °C. The Li3VO4 coated material had a higher ordered hexagonal layered structure, and less Li+/Ni2+ cation mixing. The surface of the coated material was composed of Li3VO4 polycrystals, which were impregnated into the bulk of the active material. The surface coating protected the material from contact with CO2 in the air, thus inhibiting the formation of an Li2CO3 layer. Electrochemical studies showed that the Li3VO4 surface coating improved the activation of Mn4+ ions, resulting in a high discharge capacity. It also prohibited the growth of a solid electrolyte interface film, and facilitated the charge transfer reactions at the electrode/electrolyte interface, thus improving the rate capability and cycle stability of the material. DSC analysis of the fully charged electrode showed that the temperature of the exothermic peak increased from 205.2 °C to 232.8 °C, and that the amount of heat that was released was reduced from 807.5 J g−1 to 551.0 J g−1, highlighting the improved thermal stability of the material after coating with Li3VO4 .

Hybrid graphene@MoS2@TiO2 microspheres for use as a high performance negative electrode material for lithium ion batteries

A graphene@MoS2@TiO2 hybrid material was successfully prepared by a multi-step solution chemistry method. Few-layered MoS2 nanosheets were impregnated into the nanovoids of mesoporous TiO2 microspheres and the composite was further encapsulated by a graphene layer. When used as a negative electrode material for lithium ion batteries, the nanovoids of TiO2 reduced aggregation of MoS2 and suppressed the large volume change of the active material. Moreover, the dissolution and shuttle of polysulfides were effectively suppressed by the hybrid bonding between MoS2 and TiO2. The nano-sized MoS2 and TiO2 particles encapsulated by a high electronic conductive graphene layer improved the charge transfer reaction of the electrode. Due to these merits, the graphene@MoS2@TiO2 showed a large discharge capacity of 980 mA h g−1 at 0.1 A g−1 current density with a capacity retention of 89% after 200 cycles. Moreover, the material delivered 602 mA h g−1 at 2 A g−1 current density, much larger than 91 mA h g−1 for the pristine MoS2. This demonstrated that the hybrid graphene@MoS2@TiO2 microspheres have great potential as a high-performance negative electrode material for lithium ion batteries.

Multi-Functional Surface Engineering for Li-Excess Layered Cathode Material Targeting Excellent Electrochemical and Thermal Safety Properties.

The Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2 cathode material is modified by a Li4M5O12-like heterostructure and a BiOF surface layer. The interfacial heterostructure triggers the layered-to-Li4M5O12 transformation of the material which is different from the layered-to-LiMn2O4 transformation of the pristine Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. This Li4M5O12-like transformation helps the material to keep high working voltage, long cycle life and excellent rate capability. Mass spectrometry, in situ X-ray diffraction and transmission electron microscope show that the Li4M5O12-like phase prohibits oxygen release from the material bulk at elevated temperatures. In addition, the BiOF coating layer protects the material from harmful side reactions with the electrolyte. These advantages significantly improve the electrochemical performance of Li(Li(0.18)Ni(0.15)Co(0.15)Mn(0.52))O2. The material shows a discharge capacity of 292 mAh g(-1) at 0.2 C with capacity retention of 92% after 100 cycles. Moreover, a high discharge capacity of 78 mAh g(-1) could be obtained at 25 C. The exothermic temperature of the fully charged electrode is elevated from 203 to 261 °C with 50% reduction of the total thermal release, highlighting excellent thermal safety of the material.

A long cycle-life and high safety Na+/Mg2+ hybrid-ion battery built by using a TiS2 derived titanium sulfide cathode

The practical uses of magnesium-ion batteries are hindered by their poor rate capability and fast capacity decay. Moreover, traditional sodium ion batteries suffer from serious safety problems resulting from the sodium dendrites formed on the anode. In order to circumvent these problems, we designed a highly reversible Na+/Mg2+ hybrid-ion battery composed of a metallic Mg anode, a TiS2 derived titanium sulfide cathode and a 1.0 M NaBH4 + 0.1 M Mg(BH4)2/diglyme hybrid electrolyte. The battery showed remarkable electrochemical performances with a large discharge capacity (200 mA h g−1 at the 1C rate), high rate capability (75 mA h g−1 at the 20C rate) and long cycle life (90% capacity retention after 3000 cycles). Moreover, it exhibited excellent safety properties due to dendrite-free Mg deposition of the anode and the high thermal stability of the cathode. These merits demonstrate the great potential of the reported Na+/Mg2+ hybrid-ion battery for large-scale energy storage.

Lithium-Rich Layered Oxide Li1.18Ni0.15Co0.15Mn0.52O2 as the Cathode Material for Hybrid Sodium-Ion Batteries

Li-rich layered oxide Li1.18 Ni0.15 Co0.15 Mn0.52 O2 (LNCM) is, for the first time, examined as the positive electrode for hybrid sodium-ion battery and its Na(+) storage properties are comprehensively studied in terms of galvanostatic charge-discharge curves, cyclic voltammetry and rate capability. LNCM in the proposed sodium-ion battery demonstrates good rate capability whose discharge capacity reaches about 90 mA h g(-1) at 10 C rate and excellent cycle stability with specific capacity of about 105 mA h g(-1) for 200 cycles at 5 C rate. Moreover, ex situ ICP-OES suggests interesting mixed-ions migration processes: In the initial two cycles, only Li(+) can intercalate into the LNCM cathode, whereas both Li(+) and Na(+) work together as the electrochemical cycles increase. Also the structural evolution of LNCM is examined in terms of ex situ XRD pattern at the end of various charge-discharge scans. The strong insight obtained from this study could be beneficial to the design of new layered cathode materials for future rechargeable sodium-ion batteries.

Li+/Mg2+ Hybrid-Ion Batteries with Long Cycle Life and High Rate Capability Employing MoS2 Nano Flowers as the Cathode Material.

The demand for large-scale and safe energy storage is increasing rapidly due to the strong push for smartphones and electric vehicles. As a result, Li+ /Mg2+ hybrid-ion batteries (LMIBs) combining a dendrite-free deposition of Mg anode and Li+ intercalation cathode have attracted considerable attention. Here, a LMIB with hydrothermal-prepared MoS2 nano flowers as cathode material was prepared. The battery showed remarkable electrochemical properties with a large discharge capacity (243 mAh g-1 at the 0.1 C rate), excellent rate capability (108 mAh g-1 at the 5 C rate), and long cycle life (87.2 % capacity retention after 2300 cycles). Electrochemical analysis showed that the reactions occurring in the battery cell involved Mg stripping/plating at the anode side and Li+ intercalation at the cathode side with a small contribution from Mg2+ adsorption. The excellent electrochemical performance and extremely safe cell system show promise for its use in practical applications.

VS4 Nanoparticles Anchored on Graphene Sheets as a High-Rate and Stable Electrode Material for Sodium Ion Batteries

The size and conductivity of the electrode materials play a significant role in the kinetics of sodium-ion batteries. Various characterizations reveal that size-controllable VS4 nanoparticles can be successfully anchored on the surface of graphene sheets (GSs) by a simple cationic-surfactant-assisted hydrothermal method. When used as an electrode material for sodium-ion batteries, these VS4 @GS nanocomposites show large specific capacity (349.1 mAh g-1 after 100 cycles), excellent long-term stability (84 % capacity retention after 1200 cycles), and high rate capability (188.1 mAh g-1 at 4000 mA g-1 ). A large proportion of the capacity was contributed by capacitive processes. This remarkable electrochemical performance was attributed to synergistic interactions between nanosized VS4 particles and a highly conductive graphene network, which provided short diffusion pathways for Na+ ions and large contact areas between the electrolyte and electrode, resulting in considerably improved electrochemical kinetic properties.

Dual Roles of Li3N as an Electrode Additive for Li-Excess Layered Cathode Materials: A Li-Ion Sacrificial Salt and Electrode-Stabilizing Agent

Li2 CO3 -passivated Li3 N with high stability is prepared by aging Li3 N powder in dry air, and is then used as an electrode additive for a Li(Li0.18 Ni0.15 Co0.15 Mn0.52 )O2 (LLMO) cathode material. The material shows a large irreversible capacity of 800 mA h g-1 during the first charge, with the formation of a Li2 N intermediate product. Acting as a Li+ sacrificial salt for a LLMO(+)/graphite(-) Li-ion battery, 2 wt % Li3 N results in a 10 % increase in discharge capacity. The Li2 N intermediate product reacts with the electrolyte, forming a uniform and regular surface film on the cathode. Moreover, chemical bonding between LLMO and N improves the electrode stability, resulting in excellent electrochemical performance.