Electrochemical Analysis the influence of Propargyl Methanesulfonate as Electrolyte Additive for Spinel LTO Interface Layer

Effects of Butadiene Sulfone as an Electrolyte Additive on the Formation of Solid Electrolyte Interphase in Lithium-Ion Batteries Based on Li4Ti5O12 Anode Materials

In this study, butadiene sulfone (BS) was selected as an efficient electrolyte additive to stabilize the solid electrolyte interface (SEI) film on the lithium titanium oxide (LTO) electrodes in Li-ion batteries (LIBs). It was found that the use of BS as an additive could accelerate the growth of stable SEI film on the LTO surface, leading to the improved electrochemical stability of LTO electrodes. It can be supported by the BS additive to effectively reduce the thickness of SEI film, and it significantly enhances the electron migration in the SEI film. Consequently, the LIB-based LTO anode in the electrolyte containing 0.5 wt.% BS showed a superior electrochemical performance to that in the absence of BS. This work provides a new prospect for an efficient electrolyte additive for next-generation LIBs-based LTO anodes, especially when discharged to low voltage.

Enhanced Thermal Stability of Mesoporous Carbon Microbeads-Based Lithium-Ion Batteries by Propargyl Methacrylate as Electrolyte Additive

In this current work, propargyl methacrylate (PMA) was successfully adopted to be an efficient electrolyte additive to stabilize the formation of a solid electrolyte interface (SEI) layer on mesoporous carbon microbeads (MCMB) in Li-ion batteries, especially at elevated temperatures. According to a series of material and electrochemical characterizations, the optimized concentration of PMA additive in the electrolyte was found to be 0.5 wt.%. The MCMB electrode cycled with the optimized 0.5 wt.% PMA-containing electrolyte exhibited impressive capacity retention of 90.3% after 50 cycles at 0.1C at elevated temperature, which was remarkably higher than that using the PMA-free electrolyte (83.5%). The improved electrochemical stability at elevated temperature could be ascribed to the rapid formation of stable and thin SEI layer on MCMB surface, which were investigated and suggested to be formed via PMA copolymerization reactions.

Optimal Quantity of Nano-Silicon for Electrospun Silicon/Carbon Fibers as High Capacity Anodes

In this study, silicon/carbon composite nanofibers (Si@CNFs) were prepared as electrode materials for lithium-ion batteries via a simple electrospinning method and then subjected to heat treatment. The morphology and structure of these materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the structure provides good electrical conductivity and affords sufficient space to accommodate volume expansion during charging/discharging. Furtherly, electrochemical performance tests show that the optimized Si@CNFs have an initial reversible capacity of 1,820 mAh g⁻¹ at a current density of 400 mA g⁻¹ and capacity retention of 80.7% after 100 cycles at a current density of 800 mA g⁻¹. Interestingly, the optimized Si@CNFs have a superior capacity of 1,000 mAh g⁻¹ (400 mA g⁻¹) than others, which is attributed to the carbon substrate nanofiber being able to accommodate the volume expansion of Si. The SEI resistance generated by the Si@CNFs samples is smaller than that of the Si nanoparticles, which confirms that SEI film generated from the Si@CNFs is much thinner than that from the Si nanoparticles. In addition, the connected carbon substrate nanofiber can form a fiber network to enhance the electronic conductivity.

Heterostructured SnO2-SnS2@C Embedded in Nitrogen-Doped Graphene as a Robust Anode Material for Lithium-Ion Batteries

Tin-based anode materials with high capacity attract wide attention of researchers and become a strong competitor for the next generation of lithium-ion battery anode materials. However, the poor electrical conductivity and severe volume expansion retard the commercialization of tin-based anode materials. Here, SnO₂-SnS₂@C nanoparticles with heterostructure embedded in a carbon matrix of nitrogen-doped graphene (SnO₂-SnS₂@C/NG) is ingeniously designed in this work. The composite was synthesized by a two-step method. Firstly, the SnO₂@C/rGO with a nano-layer structure was synthesized by hydrothermal method as the precursor, and then the SnO₂-SnS₂@C/NG composite was obtained by further vulcanizing the above precursor. It should be noted that a carbon matrix with nitrogen-doped graphene can inhibit the volume expansion of SnO₂-SnS₂ nanoparticles and promote the transport of lithium ions during continuous cycling. Benefiting from the synergistic effect between nanoparticles and carbon matrix with nitrogen-doped graphene, the heterostructured SnO₂-SnS₂@C/NG further fundamentally confer improved structural stability and reaction kinetics for lithium storage. As expected, the SnO₂-SnS₂@C/NG composite exhibited high reversible capacity (1201.2 mA h g⁻¹ at the current rate of 0.1 A g⁻¹), superior rate capability and exceptional long-life stability (944.3 mAh g⁻¹ after 950 cycles at the current rate of 1.0 A g⁻¹). The results demonstrate that the SnO₂-SnS₂@C/NG composite is a highly competitive anode material for LIBs.

2,3,4,5,6-Pentafluorophenyl Methanesulfonate as a Versatile Electrolyte Additive Matches LiNi0.5Co0.2Mn0.3O2/Graphite Batteries Working in a Wide-Temperature Range

An electrolyte using 2,3,4,5,6-pentafluorophenyl methanesulfonate (PFPMS) as a versatile additive is investigated through calculating the molecular orbital energies of additives and solvents and designing the electrolyte composition, and the comparative performances of LiNi_0.5Co_0.2Mn_0.3O₂/graphite cells operating in a wide-temperature range are improved. It is revealed that PFPMS can form interfacial films on both the cathode and anode surfaces, resulting in a decrease of the cell impedance and the side reactions between the active materials and electrolyte. Compared to the cells without additive of 74.9% and those with vinylene carbonate (VC) of 76.7%, the cycling retention of the cell with 1.0 wt % PFPMS reaches 91.7% after 400 cycles at room temperature. In particular, for the high-temperature storage at 60 °C for 7 d, the cell containing 1.0 wt % PFPMS exhibits optimal capacity retention of 86.3% and capacity recovery of 90.6%; for the low-temperature discharge capacity retention at -20 °C, the cell with 1.0 wt % PFPMS maintains at 66.3% at 0.5 C, while for the cells without additive and containing 1.0 wt % VC, their retention values are 55.0 and 62.1%, respectively. The excellent cycling, wide-temperature practicability, and rate capability of the cells with PFPMS demonstrate that the electrolyte with PFPMS additive is promising for applications in LiNi_0.5Co_0.2Mn_0.3O₂/graphite batteries.

Effect of Nb and F Co-doping on Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material for High-Performance Lithium-Ion Batteries

The Li_1.2Mn_0.54-xNb_xCo_0.13Ni_0.13O_2-6xF_6x (x = 0, 0.01, 0.03, 0.05) is prepared by traditional solid-phase method, and the Nb and F ions are successfully doped into Mn and O sites of layered materials Li_1.2Mn_0.54Co_0.13Ni_0.13O₂, respectively. The incorporating Nb ion in Mn site can effectively restrain the migration of transition metal ions during long-term cycling, and keep the stability of the crystal structure. The Li_1.2Mn_0.54-xNb_xCo_0.13Ni_0.13O_2-6xF_6x shows suppressed voltage fade and higher capacity retention of 98.1% after 200 cycles at rate of 1 C. The replacement of O^2- by the strongly electronegative F^- is beneficial for suppressed the structure change of Li₂MnO₃ from the eliminating of oxygen in initial charge process. Therefore, the initial coulombic efficiency of doped Li_1.2Mn_0.54-xNb_xCo_0.13Ni_0.13O_2-6xF_6x gets improved, which is higher than that of pure Li_1.2Mn_0.54Co_0.13Ni_0.13O₂. In addition, the Nb and F co-doping can effectively enhance the transfer of lithium-ion and electrons, and thus improving rate performance.