Electrochemical Performance For Lithium-ion Batteries Research Articles

Enhancement of electrochemical performance of lithium-ion battery by single-ion conducting polymer addition in ceramic-coated separator

Single-ion conducting polymers have been widely reported in the literature as solid polymer electrolytes, but their low ionic conductivity has limited industrial applications at ambient temperature. Here, we employed a perfluoroalkyl sulfonamide-based single-ion conducting polymer-lithiated poly(perfluoroalkylsulfonyl)imide (LiPFSI) to promote the migration of free Li-ions and diminish cell polarization in lithium-ion batteries. After blending with Al2O3 powder, the LiPFSI/Al2O3 composite was coated on a commercial polyethylene separator. Adding the high surface energy of Al2O3 particles and the exceptional ionic conductivity of LiPFSI resulted in a LiPFSI/Al2O3 composite-coated separator with excellent wettability and low impedance. A LiFePO4/Li half-cell with this separator showed a highly improved charge–discharge cyclability up to 130 mAh/g that maintained 98% retention of the original reversible capacity after 220 charge–discharge cycles at a high current rate of 2 C (1 C = 170 mAh/g). Even at a high rate of 5 C, the cell capacity could be maintained above 100 mAh/g. Herein, we present a simple and effective method to optimize the separator with the LiPFSI/Al2O3 composite and thus improve the high rate charge–discharge performance of Li-ion batteries.

Microwave-Assisted Preparation and Characterization of a Polyoxometalate-Based Inorganic 2D Framework Anode for Enhancing Lithium-Ion Battery Performance.

A pure inorganic 2D network molybdophosphate, [Mn3 Mo12 O24 (OH)6 (HPO3 )8 (H2 O)6 ]4- (1 a), synthesized through microwave irradiation with the existence of Mn2+ and organic cations and isolated as [(CH3 )2 NH2 ]3 Na[Mn3 Mo12 O24 (OH)6 (HPO3 )8 (H2 O)6 ]⋅12 H2 O (1), is found to possess highly enhanced performance in lithium-ion batteries' anode materials. The molecule shows multielectron redox properties suitable for producing anode materials with a specific capacity of 602 mA h g-1 at 100 mA g-1 after 50 cycles in lithium-ion batteries, although its specific capacity is the highest among all the reported pure inorganic 2D polyoxometalates to date, the cyclic stability is not that satisfactory. A hybrid nanocomposite of this 2D network and polypyrrole cations effectively reduces the capacity fading in initial cycles, and increases the stability and improves the electrochemical performance of lithium-ion batteries as well.

3D yolk–shell Si@void@CNF nanostructured electrodes with improved electrochemical performance for lithium-ion batteries

Si-based anode materials are studied to overcome the limitations of high-capacity lithium-ion batteries (LIBs). However, Si-based anodes have critical drawbacks such as volumetric electrode expansion during cycling in LIBs, that result in deterioration in cycling performance. Herein, we prepare 3D yolk–shell Si and carbon nanofiber (CNF) nanostructured electrodes with different void portions (Si@void@CNF-x) using oxidation, etching, and electrospinning process. The portions of the void in the Si@void@CNF electrodes can be controlled by electrospinning with Si powder oxidized at 700°C under an air atmosphere for a reaction time (x) of 3, 6, and 9h followed by chemically etching in HF solution. The electrodes are structurally characterized using X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The charge/discharge and rate performance of the electrodes is evaluated in the coin-type cells. Si@void@CNF-6 shows a highest reversible discharge capacity of 304.9mAhg−1 at a current density of 200mAg−1 after 500 cycles and an improved high rate performance (166@2000mAg−1 after 500 cycles), compared to Si@void@CNF-3 and Si@void@CNF-9. The particular void portion in the Si@void@CNF-6 can be responsible for the superior LIB performance, representing the efficiently volumetric expansion-relieved electrode structure during cycling.

Identifying compatibility of lithium salts with LiFePO4 cathode using a symmetric cell

The electrochemical performance of lithium-ion batteries is dominated by the interphase electrochemistry between the electrolyte and electrode materials. A multitude of efforts have been dedicated to the solid electrolyte interphase (SEI) formed on the anode. However, the interphase on the cathode, namely the cathode electrolyte interphase (CEI), is left aside, partially due to the fact that it is hard to single out the CEI considering the complicated anode-cathode inter-talk. Herein, a partially delithiated lithium iron phosphate (Li0.25FePO4) electrode is used as the anode. Owing to a high voltage plateau (≈3.45 V vs. Li/Li+), negligible reduction reactions of electrolyte occur on the L0.25FePO4 anode. Therefore, the CEI can be investigated exclusively. Using a LiFePO4|Li0.25FePO4 symmetric cell configuration, we scrutinize the compatibility of the electrolytes containing a wide spectrum of lithium salts, Li[(FSO2)(Cm F2m+1SO2)N] (m = 0, 1, 2, 4), with the LiFePO4, in both cycling and calendar tests. It is found that the Li[(FSO2)(n-C4F9SO2)N] (LiFNFSI)-based electrolyte exhibits the highest compatibility with LiFePO4.

Polyaniline-encapsulated silicon on three-dimensional carbon nanotubes foam with enhanced electrochemical performance for lithium-ion batteries

Seeking free volume around nanostructures for silicon-based anodes has been a crucial strategy to improve cycling and rate performance in the next generation Li-ion batteries. Herein, through a simple pyrolysis and in-situ polymerization approach, the low cost commercially available melamine foam as a soft template converts carbon nanotubes into highly dispersed and three-dimensionally interconnected framework with encapsulated silicon/polyaniline hierarchical nanoarchitecture. This unique core-sheath structure based on carbon nanotubes foam integrates a large number of mesoporous, thus providing well-accessible space for electrolyte wetting, whereas the carbon nanotubes matrix serves as conductive thoroughfares for electron transport. Meanwhile, the outer polyaniline coated on silicon nanoparticles provides effective space for volume expansion of silicon, further inhibiting the active material escape from the current collector. As expected, the PANI-Si@CNTs foam exhibits a high initial specific capacity of 1954 mAh g−1 and retains 727 mAh g−1 after 100 cycles at 100 mA g−1, which can be attributed to highly electrical conductivity of carbon nanotubes and protective layer of polyaniline sheath, together with three-dimensionally interconnected porous skeleton. This facile structure can pave a way for large scale synthesis of high durable silicon-based anodes or other electrode materials with huge volume expansion.

α-Fe2O3 nanoplates with superior electrochemical performance for lithium-ion batteries

On account of the high theoretical capacity, high corrosion resistance, environmental benignity, abundant availability and low cost, the research on α-Fe2O3 has been gradually fastened on as promising anodes materials toward lithium-ion batteries (LIBs). A high-performance anode for LIBs based on α-Fe2O3 nanoplates have been selectively prepared. The α-Fe2O3 nanoplates can be synthesized with iron ion-based ionic liquid as iron source and template. The α-Fe2O3 nanoplates as the anode of LIBs can display high capacity of around 1950 mAh g−1 at 0.5 A g−1 which have exceeded the theoretical capacity of α-Fe2O3. On account of unique nanoplate structures and gum arabic as binder, the α-Fe2O3 nanoplates also exhibit high rate capability and excellent cycling performance.

Hierarchically Structured LiFePO4/C with Enhanced Electrochemical Performance for Lithium-Ion Batteries

Hierarchically Structured LiFePO4/C with Enhanced Electrochemical Performance for Lithium-Ion Batteries

Boron and nitrogen co-doped CNT/Li4Ti5O12 composite for the improved high-rate electrochemical performance of lithium-ion batteries

A novel Li4Ti5O12 (LTO) composite with multiwalled carbon nanotubes (CNTs) co-doped with nitrogen (N) and boron (B) (B,N-CNT), denoted N-B-C-LTO, was successfully obtained from a mixture of N,B-CNT and LTO after calcination. For comparison, LTO, C-LTO (LTO/CNT), N-doped N,C-LTO (LTO/N,CNT) and B-doped B,C-LTO (LTO/B,CNT) were also synthesized. Among the samples, N-B-C-LTO demonstrated the best performance in electrochemical measurements. The reversible capacity of N-B-C-LTO could reach 120 mAh/g, even at a rate of 20 C. After 150 cycles at 20 C, 97.5% of the capacity was retained with negligible capacity fading. The excellent electrochemical performance was possibly due to the separate forms of N and B in the co-doped CNTs, which not only maintained the benefits of the N and B additives, i.e., good electron-donating and electron-accepting capabilities, but also led to a synergistic effect from the unique electronic structure.

Novel in-situ redox synthesis of Fe3O4/rGO composites with superior electrochemical performance for lithium-ion batteries

Coupling transition metal oxides with nanocarbonaceous materials is an effective approach to construct high-efficiency anode materials for lithium-ion batteries (LIBs). In the present study, we demonstrate a novel in-situ redox strategy for facile and cost-effective synthesis of Fe3O4/reduced graphene oxide (Fe3O4/rGO) composites as LIBs anodes. Fe3O4/rGO composites are facilely obtained through redox reaction between highly-oxidized graphene oxide and ferrous salt under basic atmosphere, followed by stabilization treatment ranging from 5 min to 5 h. Well crystallized Fe3O4 nanoparticles with diameters of 10–30 nm are tightly and homogeneously anchored on the flexible graphene substrate. Owing to the distinctive composite nanostructure, including strong integration, homogeneous distribution and surface modification effect, the as-prepared Fe3O4/rGO composites exhibit superior electrochemical lithium-storage performance, especially at high current densities. The Fe3O4/rGO-2h composite delivers a remarkable reversible capacity of 1024 mA h g−1 at the current density of 1000 mA g−1, and retains 584 mA h g−1 at 5000 mA g−1 even after 450 cycles. It is believed that the study will provide a feasible strategy to facilely produce transition metal oxide/carbon composite electrodes with superior electrochemical performance for LIBs.

Cobalt-doped Zn2GeO4 nanorods assembled into hollow spheres as high-performance anode materials for lithium-ion batteries

The synthesis of novel Co doped Zn2GeO4 hollow micro-spheres and the enhanced electrochemical performance for lithium-ion batteries.

Self-assembled 3D flower-like Fe3O4/C architecture with superior lithium ion storage performance

3D flower-like Fe3O4/C with a stable structure, improved electrical conductivity, and excellent kinetic performance exhibits superior electrochemical performance for lithium-ion batteries.

Electrospun Poly(ether ether ketone) Nanofibrous Separator with Superior Performance for Lithium-Ion Batteries

The thermal stability of a separator is extremely important for the safety of lithium-ion batteries (LIBs). Poly(ether ether ketone) (PEEK) is a potential material for use as a separator due to its good heat resistance and chemical stability. However, PEEK has inferior solubility, and is not easy to be prepared a porous separator. Herein, we report a novel soluble PEEK derivative containing polar and bulk groups and a series of porous separators prepared via an electrospinning technique. The synthesis of the PEEK was confirmed by Fourier transform infrared spectroscopy (FTIR), and the morphology of the membrane was examined by scanning electron microscopy (SEM). Several important properties, such as the thermal stability, liquid electrolyte uptake, contact angle, and lithium-ion conductivity, were measured. These electrospun PEEK separators including PEEK-5, PEEK-8 and PEEK-10 exhibited better thermal stability and wettability than a commercial polypropylene (PP) separator. Notably, the PEEK-8 separator exhibited the largest liquid electrolyte uptake of 524% and the highest ionic conductivity of 3.81 mS cm−1. More notably, the electrospun PEEK separators did not exhibit shrinkage at 150°C, and a coin cell assembled with the electrospun PEEK-8 separator possessed a discharge capacity of 118.9 mAh g−1 (LiFePO4/Li+) after 200 cycles at an elevated temperature of 60°C. Thus, the obtained electrospun PEEK separators can effectively enhance the safety and electrochemical performance of LIBs.

Hierarchical MoO3/SnS2 core–shell nanowires with enhanced electrochemical performance for lithium-ion batteries

Two-dimensional (2D) tin disulfide (SnS2) is a promising anode material for lithium-ion batteries (LIBs) because of its high theoretical capacity. The main challenges associated with the SnS2 electrodes are the poor cycling stability and low rate capability due to structural degradation in the discharge/charge process. Here, a facile two-step synthesis method is developed to fabricate hierarchical MoO3/SnS2 core-shell nanowires, where ultrathin SnS2 nanosheets are vertically anchored on MoO3 nanobelts to induce a heterointerface. Benefiting from the unique structural and compositional characteristics, the hierarchical MoO3/SnS2 core-shell nanowires exhibit excellent electrochemical performance and deliver a high reversible capacity of 504 mA h g-1 after 100 stable cycles at a current density of 100 mA g-1, which is far superior to the MoO3 and SnS2 electrodes. An analysis of lithiation dynamics based on ab initio molecular dynamics simulations demonstrates that the formation of a hierarchical MoO3/SnS2 core-shell heterostructure can effectively suppress the rapid dissociation of shell-layer SnS2 nanosheets via the interfacial coupling effect and the central MoO3 backbone can trap and support the polysulfide in the discharge/charge process. The results are responsible for the high storage capacity and rate capability of MoO3/SnS2 electrode materials. This work provides a novel design strategy for constructing high-performance electrodes for LIBs.

Interconnected Si-coated NiO nanosheet arrays with enhanced electrochemical performance for lithium-ion batteries

NiO/Si composite film is prepared by chemical bath deposition and magnetron sputtering techniques. The sample is characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The film is constructed by interconnected Si-coated NiO nanosheet arrays. As an anode material for lithium-ion batteries, the film is analyzed by galvanostatic discharge-charge and cyclic voltammetry (CV). NiO/Si nanosheet arrays deliver higher capacity than that of NiO nanosheet arrays, and shows better cycling stability that of Si film. The enhanced electrochemical performance is ascribed to the interconnected Si-coated NiO nanosheet array structure.

Synthesis of Li(Ni0.6Co0.2Mn0.2)O2 with sodium DL-lactate as an eco-friendly chelating agent and its electrochemical performances for lithium-ion batteries

(Ni0.6Co0.2Mn0.2)(OH)2 precursor has been successfully prepared using hydroxide co-precipitation method. The thermodynamic model of hydroxide co-precipitation with sodium DL-lactate as an eco-friendly chelating agent is proposed. The microstructures of (Ni0.6Co0.2Mn0.2)(OH)2 precursors and Li(Ni0.6Co0.2Mn0.2)O2 cathode materials are investigated using X-ray diffractometer and scanning electronic microscopy, while the electrochemical performances of Li(Ni0.6Co0.2Mn0.2)O2 cathode materials are measured using a charge–discharge test. The influences of pH value on the structure and morphological and electrochemical performances of Li(Ni0.6Co0.2Mn0.2)O2 cathode materials have been discussed in detail. The results show that the sample at pH = 11.5 exhibits the best lamellar structure and lowest cation mixing, while the sample at pH = 11.0 delivers the most uniform and full particles and possesses the highest initial charge–discharge performance of 183.4 mAh/g and the best coulombic efficiency of 77.9% at the voltage range of 3.0–4.3 V. Even after 100 cycles, its discharge capacity still remains 165.2 mAh/g with the best retention rate of 90.1%. Furthermore, the sample at pH = 11.0 delivers the highest discharge capacity at each current density. Even if discharged at 5C (1000 mA/g), the capacity of 115.6 mAh/g has been achieved. The sample at pH = 11.0 exhibits the highest Li-ion diffusion coefficients (2.072 × 10−12 cm2/s).

Facile triethanolamine-assisted combustion synthesized layered LiNi1/3Co1/3Mn1/3O2 cathode materials with enhanced electrochemical performance for lithium-ion batteries

The present study introduces a facile triethanolamine-assisted combustion method, wherein stoichiometric hydrate transition metal acetate with and without the addition of triethanolamine (TEA) were dissolved and mixed uniformly in deionized water and heated to burn. The ashes were then grinded and calcinated to synthesize layered LiNi1/3Co1/3Mn1/3O2 cathode materials. The structure, morphology, and electrochemical performance of two kinds of LiNi1/3Co1/3Mn1/3O2 materials were investigated and compared systematically. The results indicate that the sample with TEA possesses smaller particles and exhibits less aggregation and a better hexagonal layered structure. On the contrary, the sample with TEA exhibits lower polarization, a better cycling ability, a significantly improved rate performance, and better electronic conductivity. The enhanced electronic conductivity and electrochemical performance may be ascribed to a higher combustion enthalpy and better dispersion in the solvent following the introduction of TEA. This simple synthetic strategy presents a promising synthetic model for the enhancement of electrochemical performance cathode materials for lithium-ion batteries.

Revisiting on the effect and role of TiO2 layer thickness on SnO2 for enhanced electrochemical performance for lithium-ion batteries

Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO2)) on metal oxide anodes (such as tin (IV) oxide (SnO2)) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO2 overlayer on SnO2 can have significant influence in the overall parameters of electrochemistry. It is revealed that TiO2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g−1 even at high current density (5000 mA g−1). Surprisingly, it was further discovered that TiO2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO2. The improvements in both ionic and electrical conductivity of TiO2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO2@SnO2, which demonstrates that TiO2 overlayer results in homogeneous and thinner interphase layer compared with SnO2 NTs.

A scalable approach to fabricate metal sulfides/graphene/carbon nanotubes composites with superior electrochemical performances for lithium and sodium ion batteries

Metal sulfide composites have been regarded as a new class of the most promising anode materials for the both lithium ion batteries (LIBs) and sodium ion batteries (SIBs). However, their practical applications have been restricted by their relative poor cyclabilities and low rate performances. Herein, the numerous metal sulfides/graphene/carbon nanotubes (MxSy/GC) composites with a sandwiched architecture assembled by uniform MxSy nanoparticles anchored in the GC matrix are fabricated for high-performance LIBs/SIBs via a scalable calcination approach. As a result of the superiorities of small particle size, preferable structural flexibility and the sandwiched architecture, the as-prepared MxSy/GC composites exhibit a significant improvement in LIBs performance. Among them, the FeS/GC composite demonstrates excellent electrochemical performances in LIBs with favorable cycling stability, high specific capacity (∼870 mAh g−1 at 0.25 A g−1) and remarkable rate performance. When applied as an anode material for SIBs, the FeS/GC composite still exhibits a superior reversible capacity of 300 mAh g−1 at a current density of 0.1 A g−1 after 100 cycles.

Surface Modification of Li(Ni0.6Co0.2Mn0.2)O₂ Cathode Materials by Nano-Al₂O₃ to Improve Electrochemical Performance in Lithium-Ion Batteries.

Al2O3-coated Li(Ni0.6Co0.2Mn0.2)O2 cathode materials were prepared by simple surface modification in water media through a sol-gel process with a dispersant. The crystallinity and surface morphology of the samples were characterized through X-ray diffraction analysis and scanning electron microscopy observation. The Li(Ni0.6Co0.2Mn0.2)O2 cathode material was of a polycrystalline hexagonal structure and agglomerated with particles of approximately 0.3 to 0.8 μm in diameter. The nanosized Al2O3 particles of low concentration (0.06–0.12 wt %) were uniformly coated on the surface of Li(Ni0.6Co0.2Mn0.2)O2. Measurement of electrochemical properties showed that Li(Ni0.6Co0.2Mn0.2)O2 coated with Al2O3 of 0.08 wt % had a high initial discharge capacity of 206.9 mAh/g at a rate of 0.05 C over 3.0–4.5 V and high capacity retention of 94.5% at 0.5 C after 30 cycles (cf. uncoated sample: 206.1 mAh/g and 90.8%, respectively). The rate capability of this material was also improved, i.e., it showed a high discharge capacity of 166.3 mAh/g after 5 cycles at a rate of 2 C, whereas the uncoated sample showed 155.8 mAh/g under the same experimental conditions.

Simple synthesis of Si/Sn@C-G anodes with enhanced electrochemical properties for Li-ion batteries

A silicon/tin@amorphous carbon-graphite (Si/Sn@C-G) composite material was successfully prepared by a simple high energy ball milling and annealing process, exhibiting excellent electrochemical performance in lithium-ion batteries. Structural characterization showed that the phase separated Si/Sn mixture was coated by amorphous carbon and were highly dispersed into the graphitic sheets. As a result, the Si/Sn@C-G composite exhibited a high initial coulombic efficiency of 81.5% and a stable reversible capacity of 612.6 mAh g−1 even after 100 cycles. Cyclic voltammetry and electrochemical impedance spectroscopy results indicated that the Sn acted as an active matrix and could obviously decrease the polarization resistance (Rp). And the ductile Sn could not only cushion the volumetric deformation of Si, but could also improve the Si dispersion. This work demonstrated a facile approach to synthesize highly stable Si/Sn@C-G composite in lithium-ions batteries.