Electrochemical Performance For Lithium-ion Batteries Research Articles

Novel Sponge-like Structure of a High-Capacity Nitrogen–Fluorine Codoped Reduced Graphene (N, F-rGO) Film Electrode and Electrochemical Performance in Lithium-Ion Batteries

The nitrogen–fluorine-codoped reduced GO film (N, F-rGO film) is prepared by a simple one-step pyrolysis process. The as-prepared N, F-rGO film displays a loose porous structure between layers, and the N- and F-doping contents of the resulting N, F-rGO film were 4 and 1.3%, respectively. As a negative electrode for lithium-ion batteries (LIBs), the as-prepared N, F-rGO film exhibits high reversible capacity and good cycle stability. It delivers an initial discharge capacity of 2133 mA h g–1 and a high reversible specific discharge capacity of 878 mA h g–1 at the current density of 200 mA g–1. Even at the current density of 2 A g–1, the reversible specific capacity could be 344 mA h g–1 after 500 cycles. The N, F-double doping and the high-surface area mesoporous structure of rGO provide efficient ionic diffusion path, offering sufficient active sites for lithium-ion storage, resulting in excellent electrochemical performance.

Regulation of Cathode-Electrolyte Interphase via Electrolyte Additives in Lithium Ion Batteries.

As the power supply of the prosperous new energy products, advanced lithium ion batteries (LIBs) are widely applied to portable energy equipment and large-scale energy storage systems. To broaden the applicable range, considerable endeavours have been devoted towards improving the energy and power density of LIBs. However, the side reaction caused by the close contact between the electrode (particularly the cathode) and the electrolyte leads to capacity decay and structural degradation, which is a tricky problem to be solved. In order to overcome this obstacle, the researchers focused their attention on electrolyte additives. By adding additives to the electrolyte, the construction of a stable cathode-electrolyte interphase (CEI) between the cathode and the electrolyte has been proven to competently elevate the overall electrochemical performance of LIBs. However, how to choose electrolyte additives that match different cathode systems ideally to achieve stable CEI layer construction and high-performance LIBs is still in the stage of repeated experiments and exploration. This article specifically introduces the working mechanism of diverse electrolyte additives for forming a stable CEI layer and summarizes the latest research progress in the application of electrolyte additives for LIBs with diverse cathode materials. Finally, we tentatively set forth recommendations on the screening and customization of ideal additives required for the construction of robust CEI layer in LIBs. We believe this minireview will have a certain reference value for the design and construction of stable CEI layer to realize desirable performance of LIBs.

Rhombic dodecahedron-like CoMoO4/C composite: A facile construction and excellent electrochemical performances for lithium-ion batteries

The design of an unique micro/nanoscale structure and the composite construction with conductive materials are the two effective means to improve the electrochemical energy storage for transition metal oxides anode. However, the rational design and controllable synthesis of complex ternary transition metal oxide (such as CoMoO4) composite with polyhedron morphology is still a challenge. Herein, we report a facile and effective strategy to synthesize rhombic dodecahedron-like (denoted as RD-like) CoMoO4/C composite, which involves the initial pre-reaction between the newly made ZIF-67 with H2MoO4 in ethanol and the subsequent calcination for the resultant precursor powders in air. It is found that the calcination temperature plays a key role in determining the microstructures and the content of the generated activated carbon. Below 400 °C, the CoMoO4/C composite cannot be derived, whereas the perfect and regular RD morphology for CoMoO4/C composite also cannot be acquired over 500 °C. Moreover, a plausible mechanism for the construction of RD-like CoMoO4/C composite has also been proposed and explained. Benefiting from its unique structural merits and the significant synergistic effect of the in-situ composite activated carbon, the obtained RD-like CoMoO4/C composite at 500 °C displays outstanding electrochemical performances with high reversible capacity (532.5 mAh g−1/500th cycle at 1C), excellent cycling stability and better rate capability when it tested as anode materials for lithium-ion batteries. It is conceivable that this three-in-one strategy can be extended to design and construct other cobalt-based oxyacid/C composites with unique polyhedron morphology, and markedly boost their electrocehmical performaces.

New Thiourea-Based Ionic Liquid as an Electrolyte Additive to Improve Cell Safety and Enhance Electrochemical Performance in Lithium-Ion Batteries.

Our society is critically dependent on lithium-ion batteries (LIBs) as a power source for portable electronic gadgets. One of the major problems with these batteries is the degradation of the materials inside them. In addition to the reduced cell life, building-up of these degraded products inside the cells is very detrimental to the safe operation. Herein, we report the synthesis and characterization of a novel thiourea-based room temperature ionic liquid (IL), 3-heptyl-1-(3-(3-heptyl-3-phenylthioureido)propyl)-1H-imidazole-3-ium hexafluorophosphate. Its electrochemical and thermal properties including transport phenomena have been studied. It is proposed to be used as a nominal additive to commercially used electrolytes, ethylene carbonate and di-methyl carbonate mixtures. The comparative performance characteristics of the LIBs in the presence and the absence of this IL additive have been demonstrated with a traditional lithium nickel cobalt manganese oxide cathode (NMC111), a graphite anode, and an ethylene carbonate and di-methyl carbonate (1:1, v/v) electrolyte. It is further demonstrated that use of this electrolyte additive in batteries helps to address some of the major concerns of the conventional electrolytes such as safety issues and cycling performance as well as coulombic efficiency with enhanced discharge capacities.

Spinel-structured high entropy oxide (FeCoNiCrMn)3O4 as anode towards superior lithium storage performance

High entropy oxide (HEO) is a new-type inorganic material composed of multiple principle metal elements with a single-phase structure and is proved to display many potential unexpected properties such as high structural stability and superionic conductivity. Herein, a novel spinel-structured high entropy oxide (FeCoNiCrMn)3O4 is prepared by high-temperature solid state reaction and evaluated as anode for lithium-ion batteries (LIBs). In-situ high-temperature X-ray diffraction (HT-XRD) is used to reveal structure evolution of mixed oxides with the calcination temperature increase and a single-phase spinel-structured (FeCoNiCrMn)3O4 is obtained at 900 °C. The effect of temperature on structure and electrochemical performance of HEO were investigated, and the HEO-900 anode with commercial mass loading exerts higher capacity (discharge/charge, 1034/680 mAh g−1) and better rate capability (182 mAh g−1 at 2 Ag-1) than HEO-950 and HEO-1000 for its moderate particle size, and all the three samples show excellent cycling stability. Ex-situ XRD and transmission electron microscope are applied to unravel the lithium-storage mechanism of (FeCoNiCrMn)3O4, an amorphization reaction process occurs during the initial discharging and the amorphous structure is maintained in subsequent cycles. The synergetic effect of multiple metal cations with different radius, valence states and reaction potentials and entropy stabilization effect make the HEO display a superior electrochemical performance in LIBs. This work provides a new concept to design multi-element transition metal oxide anode materials by high entropy strategy.

Preparing graphene-based anodes with enhanced electrochemical performance for lithium-ion batteries

The present study investigates the structural and chemical factors contributing to the performance of graphene oxide anode materials produced by Hummers (GOH) and Tour (GOT) for lithium-ion batteries (LIBs). The GO synthesized by these methods were studied using FTIR and Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Thorough electrochemical analysis including cycling stability, rate capability, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were also conducted. We show that the improved performance of GOT (almost twice) compared with that of GOH is due to the key role of the protective agent (H3PO4) in reducing/inhibiting the hole formation during the synthesis of the GOT surface which in turn results in superior cycling performance over the GOH. The results and proposed mechanism presented in this work elucidates the role of structural factors and defects in preparing graphene-based anodes with enhanced electrochemical efficiency.

In situ formed Li5AlO4-coated LiNi0·8Co0·1Mn0·1O2 cathode material assisted by hydrocarbonate with improved electrochemical performance for lithium-ion batteries

LiNi0·8Co0·1Mn0·1O2 has become a promising candidate as a cathode material of lithium ion batteries (LIBs) because of their high specific capacity, while the poor cycling and rate performances limit its commercial application. Herein, a thin layer of Li5AlO4 was in situ formed on the surface of LiNi0·8Co0·1Mn0·1O2 through a slow deposition process assisted by NaHCO3 and solid phase co-lithiation sintering. By employing the optimal amount (3 wt %) of Li5AlO4 coating on LiNi0·8Co0·1Mn0·1O2 cathode material (denoted as 3-NCM), the capacity retention rate of 3-NCM after 100 cycles increased from 75.06% to 89.15% at 2.8–4.3 V, and it also shows the most significantly enhanced rate performance. The outstanding electrochemical performance can be attributed to that the Li5AlO4 coating can impede the contact between the active materials and electrolyte, stabilize the material structure and inhibit the dissolution of transition metals during repeated charge–discharge cycles. And the superior conductivity of Li5AlO4 can improve the lithium ion diffusion rate. All these results connote that Li5AlO4-coated LiNi0·8Co0·1Mn0·1O2 cathode material might be employed in advanced lithium-ion batteries.

Polyimide binder for a high-energy-density composite anode electrode with graphite and silicon

Different types of binders, including polyimide(PI), polyvinylidene difluoride (PVdF), and Styrenebutadiene rubber/carboxymethylcellulose (SBR/CMC) are used to produce high-energy-density anode electrodes with various combinations of graphite and silicon active materials, and these anodes are investigated to improve electrochemical performance in lithium-ion batteries. The PI binder efficiently provides good electrochemical performance by holding Si as well as graphite, whereas SBR/CMC and PVdF present reasonable performance with a pure graphite electrode. FT-IR results confirm that PI forms an effective chemical interaction on the Si powder, maintaining the electrochemical performance of the graphite in the composite electrode. Because of these effective characteristics, the electrochemical performance of a cell with 30 wt% Si and 70 wt% graphite and a PI binder is greatly enhanced, showing 84% cycle retention and 75% rate capability under a 10C rate (49% and 68%, respectively, for the same combination with the SBR/CMC binder). In particular, systematic electrochemical analyses with AC impedance and galvanostatic intermittent titration techniques are performed to understand the different binder behavior in the different electrodes. Semi-in-situ FE-SEM results on the same position of the electrode support the concept that the PI binder is effective in holding the active materials during repeated charge and discharge cycles that cause large volume changes.

Low heat yielding electrospun phosphenanthrene oxide loaded polyacrylonitrile composite separators for safer high energy density lithium-ion batteries.

Battery-induced fire scenarios are on the rise globally. The severity of battery fires is directly linked to the combustion behavior of battery components such as the separator and electrolyte which constitute the main combustible materials in the battery. To achieve safer batteries, components with a low combustibility must be employed in the new lithium-ion batteries. In this work, aiming to alleviate the battery separator's combustibility and preserve the electrochemical performance of lithium-ion batteries, we designed a novel low heat releasing composite separator by incorporating 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) into the polyacrylonitrile (PAN) matrix via electrospinning technique. Notably, the membranes containing DOPO remarkably exhibited a decreased peak heat release rate (pHRR) which was evidenced by a 33% and 49% decrease for PAN-15DOPO and PAN-20DOPO samples respectively, evaluated using a microscale-combustion calorimeter (MCC). Furthermore, compared to pristine PAN based cells having an initial discharge capacity of 117 mAhg−1 at a C-rate of 0.6C, the PAN-15DOPO based cells showed a superior initial discharge capacity of 131 mAhg−1 and a capacity retention of 83% at a C-rate of 0.6C after 100 cycles. This strategy of electrospinning PAN with DOPO, provides a feasible design for fabricating batteries with simultaneously improved electrochemical properties and safety.

Atomic-scale tuned interface of nickel-rich cathode for enhanced electrochemical performance in lithium-ion batteries

The Ni-rich layered LiNi0.6Mn0.2Co0.2O2 (NMC622) is one promising cathode for lithium-ion batteries (LIBs), but suffers from poor cycling stability under high cutoff potentials. The performance degradation was reflected as capacity fading and voltage drop, having their roots in instable interface of NMC622. Aimed at improving interfacial stability, in this study, we deposited nanoscale ZrO2 coatings conformally over NMC622 cathodes using atomic layer deposition (ALD). We found that, under a high cutoff voltage (4.5 V), the ALD ZrO2 coatings evidently improved the performance of NMC622 cathode, showing better cyclability and higher sustainable capacity. In addition, the ALD coatings dramatically boosted the rate capability of NMC622. All these compelling performance results are ascribed to the atomic-scale tunable ZrO2 coatings via ALD, which create stable interface and thereby inhibit unfavorable evolutions. In the study, we utilize a suite of characterization tools and various analyses to clarify the effects of ALD ZrO2 coatings. This study will be helpful for improving the performance of nickel-rich cathodes via interfacial engineering using ALD.

Carbon-encapsulated Bi2Te3 derived from metal-organic framework as anode for highly durable lithium and sodium storage

Carbon-encapsulated Bi2Te3 (Bi2Te3@C) was successfully synthesized through a MOF-derived two-step facile process. First, Bi(BTC) (DMF)·DMF·(CH3OH)2 (Bi-BTC) was prepared by a solvothermal process and then converted into Bi2Te3@C composite by a simple tellurization reaction. As anode for lithium ion batteries (LIBs), the Bi2Te3@C electrode shows outstanding cycling stability with a specific discharge capacity of 738.5 mAh g−1 at 100 mA g−1 after 500 cycles. Meanwhile, the Bi2Te3@C composite also demonstrates a specific discharge capacity of 236.4 mAh g−1 at 100 mA g−1 after 100 cycles in sodium ion batteries (SIBs). The significant electrochemical performance in LIBs and SIBs is attributed to the nano size of Bi2Te3, which can not only reduce the migration path of electron and ions, but also tolerate the volume variations in the cycle life. Besides, the carbon derived from Bi-BTC can enhance the electrical conductivity of Bi2Te3 nanoparticles and prevent their agglomeration. Electrochemical kinetic analysis of Bi2Te3@C indicates the capacitive contribution accounts for a substantial part for the capacity, which can enhance the rate performance of Bi2Te3@C electrode. This work demonstrates that Bi2Te3@C has a promising application in practical lithium and sodium storage.

Mo-doped δ-MnO2 anode material synthesis and electrochemical performance for lithium-ion batteries

The present study synthesized Mo-doped δ-MnO2 powders with different doping ratios by implementing hydrothermal method. Various analyses, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), the Brunauer–Emmett–Teller (BET) method, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectrometer (XRF), and electrochemical measurements, were applied to characterize the dependence of the δ-MnO2 structure, morphology and electrochemical performance on Mo-doping. The experimental results indicated Mo6+ ions entered into the δ-MnO2 crystal lattice and occupied the Mn sites. Appropriate amount of Mo6+ ions doping decreases the charge transfer resistance and increases the Li+ ion diffusion coefficient, thus producing optimal electrochemical performance. The Mo 5% sample with Mo6+/Mn2+ molar ratio of 5:100 in the original solution presented a specific charge capacity of 476.8 mAh g−1 after 100 cycles at 1000 mA g−1 as well as capacity retention ratio of 112.7%.

Ultrafast synthesis of single-phase Mn1−xCoxCO3/GO with enhanced electrochemical performance for lithium-ion batteries

Transition metal carbonates (TMCs) were studied as anode material for lithium-ion battery (LIB) by virtue of the high capacity; however, low ionic conductivity, poor electronic conductivity, and unstable cycle performances hindered their applications. Therefore, in this work, single-phase Mn1−xCoxCO3 and graphene oxide composites were synthesized by an ultrafast low temperature reaction route assisted with microwave. A high specific capacity of 1204 mA h g−1 was achieved by the composites. It also delivers 659.9 mA h g−1 after 100 cycles at 200 mA g−1 and 476 mA h g−1 after 500 cycles even at 1000 mA g−1. Such preferable electrochemical performance is caused by the synergistic effect of single-phase Mn–Co crystal structure and the functionality of graphene oxide. Therefore, it is promising to obtain mixed transition metal carbonate and graphene oxide composites through ultrafast microwave solvothermal process.

Superior performance for lithium-ion battery with organic cathode and ionic liquid electrolyte

The lithium-ion batteries with calix[6]quinone (C6Q) cathode and Li[TFSI]/[PY13][TFSI] ionic liquid electrolyte showed superior electrochemical performance in both rate and long cycle. Organic small structure quinones go with ionic liquids electrolytes would exhibit ultrastable electrochemical properties. In this study, calix[6]quinone (C6Q) cathode was matched with ionic liquid electrolyte Li[TFSI]/[PY13][TFSI] (bis(trifluoromethane)sulfonimide lithium salt/ N -methyl- N -propylpyrrolidinium bis(trifluoromethanesulfonyl)amide) to assemble lithium-ion batteries (LIBs). The electrochemical performance of LIBs was systematically studied. The capacity retention rates of C6Q through 1000 cycles at current densities of 0.2 C and 0.5 C were 70% and 72%, respectively. At 5 C, the capacity was maintained at 190 mAh g −1 after 1000 cycles, and 155 mAh g −1 even after 10,000 cycles, comparable to inorganic materials. This work would give a big push to the practical process of organic electrode materials in energy storage.

Artificial Solid Electrolyte Interphase Acting as “Armor” to Protect the Anode Materials for High-performance Lithium-ion Battery

The electrochemical performances of lithium-ion batteries(LIBs) are closely related to the interphase between the electrode materials and electrolytes. However, the development of lithium-ion batteries is hampered by the formation of uncontrollable solid electrolyte interphase(SEI) and subsequent potential safety issues associated with dendritic formation and cell short-circuits during cycling. Fabricating artificial SEI layer can be one promising approach to solve the above issues. This review summarizes the principles and methods of fabricating artificial SEI for three types of main anodes: deposition-type(e.g., Li), intercalation-type(e.g., graphite) and alloy-type(e.g., Si, Al). The review elucidates recent progress and discusses possible methods for constructing stable artificial SEIs composed of salts, polymers, oxides, and nanomaterials that simultaneously passivate anode against side reactions with electrolytes and regulate Li+ ions transport at interfaces. Moreover, the reaction mechanism of artificial SEIs was briefly analyzed, and the research prospect was also discussed.

Solvothermal-assisted assembly of MoS2 nanocages on graphene sheets to enhance the electrochemical performance of lithium-ion battery

An ordered hollow MoS2 nanocages/RGO nanocomposite is constructed by a simple solvothermal-assisted assembly method combined with freeze-drying and annealing. In this novel nanostructure, hollow MoS2 nanocages are homogeneously distributed on graphene sheets with a tight bond of C-O-Mo. The nanosized and hollow MoS2 nanocages can effectively accommodate the huge volume change during charge/discharge process and increase the number of electrochemical reaction active sites, accelerating the kinetics of lithiation/delithiation. The tight C-O-Mo bond between graphene and MoS2 further reinforces the structural stability, thus improve the electrical conductivity and substantially enhance the lithium storage performance of MoS2 anode material. As a result, this novel nanocomposite shows a long-cycle stability of 717.4 mAhg−1 after 800 cycles at a high current density of 3 Ag−1, exhibiting great potential as an anode nanocomposite for advanced lithiumion batteries.

Effect of Acid Leaching on Silicon Nanoparticles and Their Electrochemical Performance in Lithium-Ion Batteries.

In this work, crystalline Si nanoparticles are synthesized on a large scale via a low temperature molten salt method. The crystal morphologies and electrochemical properties of the samples after HCl and HF leaching are studied in detail. The electrochemical properties of the as-produced silicon samples, which are used as anode materials in lithium-ion batteries (LIBs), are evaluated. The final product, which contains more Si and less SiO², improves cyclic stability because it buffers the volumetric effect of Si during lithiation/delithiation. The HF acid leach removes the impurity of SiO². However, the prepared sample exhibits lower electrochemical properties. The sample with a low SiO² content can deliver a capacity of 1503 mAh g-1 after 50 cycles at a higher current density of 1 A g-1, and the Coulombic efficiency is approximately 100%. However, the sample after HF acid leaching only delivers a discharge capacity of 389 mAh g-1 at 1 A g-1 after 50 cycles.

Acrylic random copolymer and network binders for silicon anodes in lithium-ion batteries

The choice of a binder can greatly influence the electrochemical performance of lithium-ion batteries (LIBs), especially for silicon (Si) anodes. To systematically modulate the mechanical properties of binders and to investigate their impact on the electrochemical properties, we synthesize a series of random copolymers consisting of acrylic acid (AA) and n-butyl acrylate (n-BA) via reversible addition-fragmentation chain-transfer (RAFT) polymerization. The electrochemical properties of Si nanoparticle (SiNP) anodes prepared using copolymer binders exhibit a strong dependence on the relative composition of AA and n-BA. The incorporation of a moderate amount of n-BA (10–30 mol%) in the copolymer binder provides better cycling stability compared to a SiNP anode prepared using poly(acrylic acid) (PAA) binder. The binder containing 30 mol% of n-BA is further crosslinked by in-situ crosslinking using a variable amount of polyethylene glycol diglycidyl ether (PEGDE). The electrochemical properties (3050 mAh g−1 in the 1st cycle and 40% capacity retention in the 100th cycle at 0.5 A g−1) of a SiNP anode prepared using the crosslinked binder with 14 wt% of PEGDE show further improvement compared to those of a SiNP anode prepared using PAA binder (2310 mAh g−1 and 32% capacity retention in the 100th cycle at 0.5 A g−1).

Integrated and Three-Dimensional Network Structure of a SiNWs/CNTs@MOFs Composite to Enhance the Silicon Anode’s Electrochemical Performance in Lithium-Ion Batteries

Constructing the architectural stable silicon composite is significantly critical to enhance the Si electrode cycle life of lithium-ion batteries in which the inevitable volume expansion exerts huge mechanical stress within the Si anode, then bringing about the destruction of the silicon structure and unsatisfactory cyclic performance. In this work, we report an integrated and three-dimensional (3D) network structure of the SiNWs/CNTs@MOFs composite, prepared by a facile in situ growth method. The metal–organic framework (MOF)-derived porous coating and the 3D conducting network structure of the SiNWs/CNTs@C precursor, hand in hand, construct a structurally stable composite, with the SiNW cores fully covered by the MOF coating. Attributing to MOF-derived porous coating, high conductivity of CNTs, and the stable three-dimensional network structure, not only the transport of ions and electrons facilitates but also the stability of the structure during the electrochemical process maintains. The resulting integrated SiNWs/CNTs@MOFs composite enhances the electrode durability and presents a reversible capacity of 1223 mAh g–1 at a current density of 100 mA g–1 for 100 cycles and a rate capacity of 765 mAh g–1 at a high current density of 5 A g–1.

Oxygen-deficient NiMoO4-xSx nanosheets perpendicularly grown on N-doped carbon nanosheets for high performance lithium-ion batteries

The ordered nanostructural arrays on conductive matrix and oxygen vacancies for improving the electrochemical performance of lithium-ion batteries (LIBs) are attracted considerable attention. In this work, the ordered ultrathin NiMoO4-xSx nanosheets with oxygen vacancies on N-doped carbon nanosheets (NC@NiMoO4-xSx) are designed and synthesized through a facile hydrothermal procedure. The resulting nanostructures with strong Mo–N chemical bonding combined with the oxygen vacancies can enhance the electroactive surface sites, maintain the structural integrity, and facilitate the electron and lithium ion transfer across the interface. The electrochemical studies demonstrate that the as-developed NC@NiMoO4-xSx displays the reversible capacity of 980 mAh g−1 after 100 cycles at 100 mA g−1 and a reversible capacity of 644 mAh g−1 after 500 cycles even at high rate of 5000 mA g−1. The proposed cooperation of oxygen vacancies and the ordered nanostructural arrays on carbon nanosheets may pave the way for designing the high performance electrodes for LIBs.