Anode For Li-ion Batteries Research Articles

Design a multiphase interfaced Ge(GeOx)/T-Nb2O5−x/C anode with synergistic high capacity and durability for Li-ion batteries

Germanium-based anodes for lithium-ion batteries have attracted strong focus due to an exceptional storage capacity as high as four times of commercial carbon. Inferior capacity retention, however, caused by large volume changes during cycling impedes their widespread application. Herein, we report a multi-phase Ge(GeOx)/T-Nb2O5−x/C composite synthesized using a simple and scalable high-energy ball milling approach. During ball milling, Nb2O5 substrate would react with Ge to produce amorphous GeOx on the interface of them to realize a unique construction. The Ge(GeOx)/T-Nb2O5−x/C demonstrated far longer durable and reversible capacity for Li storage (960 mAh g−1 at 0.1C and 745 mAh g−1 after 150 cycles at 0.5C, with a capacity retention of up to 86.6%) and much higher initial coulombic efficiency (87.3%) than milled Ge and Ge-T-Nb2O5-C mixture samples. The underlying mechanism is unveiled using thorough experimental characterization and density functional theory calculations. Both clearly and consistently decoupled key factors: the synergistic effects of (i) formation of multiphase structure and (ii) suppression of Ge volume expansion by forming a rigid Li2O from the GeOx on the interface of Ge and T-Nb2O5 over the cycling process. To evaluate the feasibility for practical applications the Ge(GeOx)/T-Nb2O5−x/C without prelithiation is coupled with LiFePO4 or LiCoO2 cathodes for the full-cell test. The initial coulombic efficiency is measured as high as 82.3%. Our study provides a clue to the design of highly reversible capacitive and durable anodes for Li-ion batteries.

Consequences of utilizing a redox-active polymeric binder in Li-ion batteries

Development of new polymeric binders can help enable the use of silicon-rich anodes in Li-ion batteries, by providing stronger adhesion to the active material particles. The compositional features that improve interfacial interactions and mechanical properties can often impart electronic conductivity and redox activity to these polymers, which are generally seen as beneficial to cell performance. Alternatively, it is also possible that the addition of charge-transferring centers to the electrode can accelerate cell degradation. Here, we use an aromatic polyimide (∼320 mA h/g of reversible capacity) to explore how a redox-active conductive polymer can affect cell performance. We demonstrate that the lithiated polymer is less stable than the traditional binders upon storage, leading to increased rates of calendar aging. Furthermore, we determine that the adhesion properties of the polymer deteriorate upon repeated cycling, to an extent that is proportional to the degree of delithiation of the binder. More critically, we establish that progressive degradation of the redox behavior of the polymer leads to the release of “extra” Li+ into the cell, which can give the false perception of good performance even under conditions of poor stability. Our work suggests that redox-active conductive binders can sometimes be detrimental to cell performance, and that works evaluating new polymers must include careful experimental validation under realistic conditions.

Disordered GaSiP solid solution anodes with liquid metal phase for high-performance Li-ion batteries

Silicon (Si) has become the most promising next-generation anode to replace commercial graphite for Li-ion batteries (LIBs) profiting from its large reversible capacity of 4,200 mA h g−1. However, its sluggish reaction kinetics and large volume effect need to be resolved. Herein, we prepare a ternary GaSiP solid solution with a disordered lattice by a facile mechanochemistry method. As anodes of LIBs, the GaSiP provides a reversible capacity of 1,527 mA h g−1 at 100 mA g−1 with an initial Coulombic efficiency (ICE) of 90.8% based on the reversible Li-storage mechanism integrated intercalation and subsequent conversion processes as confirmed by crystallography characterization and electrochemical measurements. Importantly, the GaSiP carbon composite presents a long cycling stability of maintaining 1,362 mA h g−1 after 50 cycles at 0.1 A g−1, and 75% capacity retention rate after 1,200 cycles at 2 A g−1, and a high-rate performance of remaining 440 mA h g−1 at 20 A g−1. Broadly, this work opens the door to develop ternary phosphides with disordered lattice and liquid metallic phase using for electrochemical energy conversion and storage.

Understanding the Electrolyte Chemistry Induced Enhanced Stability of Si Anodes in Li-Ion Batteries based on Physico-Chemical Changes, Impedance, and Stress Evolution during SEI Formation

The volume expansion/contraction of Si-based anodes during electrochemical lithiation/delithiation cycles causes a loss in mechanical integrity and accrued instability of the solid electrolyte interphase (SEI) layer, culminating into capacity fade. Electrolyte additives like fluoroethylene carbonate (FEC) improve SEI stability, but the associated causes still under debate. This work reveals some of the roles of FEC via post-mortem observations/analyses, operando stress measurements and a comprehensive study of the impedance associated with the formation/evolution of SEI during lithiation/delithiation. Usage of 10 vol.% FEC as electrolyte additive leads to significant improvements in cyclic stability, Coulombic efficiency and facilitates smoother/compact/crack-free surface/SEI, in contrast to the cracked/pitted/uneven surface upon non-usage of FEC. Operando stress measurements during SEI formation reveal compressive stress development, followed by loss in mechanical integrity, upon non-usage of electrolyte additive, in contrast to insignificant stress development associated with SEI formation upon usage of FEC. The EIS model proposed here facilitates good fit with the impedance data at all states-of-charges, with the SEI resistance and capacitance exhibiting expected variations with cycling and the SEI resistance progressively decreasing with cycle number in the presence of FEC. By contrast, in the absence of FEC, severe fluctuations observed with the SEI resistance and capacitance indicate instability.

Fe2O3/carbon derived from peanut shell hybrid as an advanced anode for high performance lithium ion batteries

Carbon materials derived from biomass behave sustainability, easy availability, low cost and environmentally benign. And Fe2O3 are considered as promising anodes for high-performance Li-ion batteries (LIBs) because of their rich electrochemical properties, higher theoretical capacity (1007 mAh g−1), non-toxicity, high corrosion resistance and safety. However, the high irreversible capacity loss and poor cycling stability of Fe2O3 hinders its commercial applications in LIBs. In this work, we have developed a Fe2O3@C derived from peanut shell composite by two-step hydrothermal method and low-temperature calcination with the assistance of Fe(NO3)3. As an anode for LIBs, the Fe2O3@C composite an excellent electrochemical performance in term of the specific capacity of 1000.8 mAh g−1 at 200 mA g−1 after 100 cycles, and high rate capability of 573.5 mAh g−1 even at 1 A g−1 after 200 cycles. This enhancement could be attributed to the porous carbon matrix combined with Fe2O3 nanoparticles which could increase contact area between electrolyte and active materials, improve conductivity, and accommodate the volume variations via additional void space during cycling. This work may be provide a new approach to improve anode materials using carbon derived-from biomass with larger reversible capacity and long cycle life in LIBs.

Synthesis of a Yolk-Shell Nanostructured Silicon-Based Anode for High-Performance Li-Ion Batteries

Silicon is a desirable anode material for Li-ion batteries owing to its remarkable theoretical specific capacity of over 4000 mAh/g. Nevertheless, the poor cycling performance of pure Si electrodes caused by dramatic volume expansion has limited its practical application. To alleviate the adverse effects of Si expansion, we have synthesized anode materials of nano-Si particles trapped in a buffering space and outer carbon-based shells (Si@Void@C). The volume ratio of Si nanoparticle to void space could be adjusted accurately to approximately 1:3, which maintained the structural integrity of the as-designed nanoarchitecture during lithiation/delithiation and achieved a notable specific capacity of ~750 mAh/g for as-prepared half-cells. The yolk-shell nanostructure alleviates volumetric expansion on both material and electrode levels, which enhances the rate performance and cycling stability of the silicon-based anode.

Improved Technology for Rounding Graphite: Machine Structure and Industrial Test

The graphite, which is treated to be potato-shaped, is widely applied in Li-ion batteries as the anodic material. Sequential batch shaping is the main method at present. However, the small height of the shaping cavity of the existing structure leads to the problem of low processing capacity and high cost. In this work, a new structure of the shaping machine was developed with the aim of shaping graphite by large output and costless. The equipment system for graphite rounding in a pilot scale at a treatment amount of 25 kg raw material each run was established. The results showed that the ratio of the diameters of the final product by an undersized percentage corresponding to 10% was 11.15 μm, 50% was 18.94 μm, and 90% was 29.54 μm, and tap density was 0.945 g/cm3, the yield reached 48%, under the optimized conditions of 1833 rpm rotating speed of shaping disk, 2646 rpm rotating speed of classifier, and 40 min shaping period. All the above characteristics of the rounded graphite are in line with the requirements for applying in the anode of Li-ion batteries. In short, the present study aims to provide a new structure of the shaping machine, contributing to the efficient and cost-effective rounding of graphite and revealing the structure of the shaping machine, contributing to promoting the wide improvement of the shaping machine.

Engineering Polymer-Assisted Self-Assembly Process for High-Capacity and Cycle-Stable Si-on-Graphite Anode of Li-Ion Batteries

A facile and ready for scale-up process based on polymer-assisted solution self-assembly is developed for manufacturing high-capacity and cycle-stable silicon-on-graphite (Si@G) lithium-ion battery anode materials. The process involves first coating a polyelectrolyte poly(diallyldimethylammonium chloride, anchored by a cross-linked polyvinyl alcohol-glutaraldehyde matrix, onto micron-sized graphite particles using spray-drying. Process optimization succeeds in imparting the graphite particles with a permanent high positive zeta potential (>40 mV), which enables attracting Si nanoparticles (NPs) (zeta potential= -28.5 mV) uniformly and firmly onto the graphite surfaces in water. Collected by filtration, the resulting Si@G composite particles are finally subjected to a high-temperature (1000 oC) treatment in Ar to turn the polymer coating into a carbon layer, which engulfs the Si NPs. A Si@G composite powder containing nearly 7 wt.% Si and produced in a batch size of approximately 20 gram is demonstrated to have a high specific capacity of 605 mAh g-1, a remarkable cycle stability showing only 11% capacity loss after 300 cycles and notably high coulombic efficiencies comparable to those of a graphite electrode upon cycling. The designed polymer coating realizes charge-carrying graphite particle without damaging its surface structure and eventually leads to a surface carbon layer that prevents Si NP detachment, improves powder conductivity, and mitigates solid-electrolyte-interphase formation.

Low Temperature Niobium Tungsten Oxides as Anodes for Fast Charging Li-Ion Batteries

The development of fast-charging Li-ion batteries is one of the important steps in building electric vehicles that need high power and fast charging. The reduction in the particle size to the nanometre length scale drastically improves the charging rate by increasing the surface area but lowers the volumetric energy density and can potentially result in more rapid degradation of the electrolyte via electrode-catalysed reactions. Recent reports show that niobium tungsten oxides (NbWOs) with µm sized particles serve as good anode materials for Li-ion batteries having high volumetric capacity with good cyclability at high rates while avoiding solid electrolyte interphase formation (SEI). The high rate performance of NbWOs is attributed to the topochemical charge storage mechanism that exhibits (i) minimal, highly reversible structural changes during the charge-discharge cycles, (ii) high Li-ion diffusion coefficients due to the presence of fast conducting tunnels, and (iii) high electronic conductivity upon lithiation.1,2 The NbWOs are known to crystallize into two families of different crystal structures depending on the composition and synthesis conditions. The NbWOs phases can either have tungsten bronze-type structures or block-type structures (commonly referred to as Wadsley-Roth phases). Different NbWO phases are reported in the literature3 which could serve as potential anode materials with better performance.In this work, a series of new NbWO phases have been synthesized at reduced annealing temperatures and the structure of these phases has been established using X-ray and neutron diffraction data. The electrochemical properties of NbWO/Li half cells were examined through a series of galvanostatic (dis)charge tests at varying current rates ranging from 0.2 C to 20 C. The NbWO phases delivers a high reversible capacity of 200 and 130 mAh/g at 0.2C and 10 C respectively vs. Li metal. Here we use operando powder X-ray diffraction to investigate the structural changes occurring at the anode during the charge-discharge process in the newly synthesised NbWO phases. Reference s : 1 K. J. Griffith, K. M. Wiaderek, G. Cibin, L. E. Marbella and C. P. Grey, Nature, 2018, 559, 556–563.2 C. P. Koçer, K. J. Griffith, C. P. Grey and A. J. Morris, Chem. Mater., 2020, 32, 3980–3989.3 N. C. Stephenson, Acta Crystallogr. Sect. B Struct. Crystallogr. Cryst. Chem., 1968, 24, 637–653. Figure 1

Gas Additives for Silicon Anode Lithium-Ion Batteries

While many organic liquid and electrolyte salt formulations have been explored to improve the stability of lithium-ion batteries, less research has been done to determine the role of evolved gasses in the performance of commercial Li-ion battery chemistries, let alone novel combinations of gas additives that may affect the solid-electrolyte interphase (SEI) formation and evolution.[1,2] Many gases are generated during Li-ion battery cycling, any of which could have possible beneficial or harmful effects on performance. Currently, only the effect of carbon dioxide (CO2) gas addition to Li-ion batteries with Si anodes has been studied.[3-4] In addition to CO2, ethylene gas (C2H4) is a promising additive for Si anode systems because it is a precursor in polyethylene polymerization reactions, nCH2=CH2 --> [-CH2-CH2-]n. In addition, polyethylene oxide (PEO) has been observed in the Si-anode SEI and contributes to its passivation while maintaining flexibility.[5] Therefore, creating polyethylene and increasing PEO concentration in situ via ethylene gas doping may yield an improved SEI and more-stable battery.This work investigates the potential of gas-phase additives, including CO2 and C2H4, to improve the performance of Si anodes for Li-ion batteries. The pressure decay of the gasses at different starting pressures dissolving in GenF3 electrolyte (1.2 M LiPF6 in 3:7 wt:wt ethylene carbonate to ethyl methyl carbonate + 3 wt% fluoroethylene carbonate) was monitored to determine the saturation concentration of dissolved gas. The experimental pressure decay curve was fit to a model and extrapolated to predict the final pressure at equilibrium.[6] The relationship between partial pressure and concentration of dissolved gas in GenF3 at equilibrium was plotted and a curve was drawn to determine the Henry’s law constant. Varying volumes of gas were injected into battery pouch cells containing Si nanoparticle anodes and LiFePO4 (LFP) cathodes to pressurize them to different pressures. Electrochemical cycling and subsequent multi-phase analyses, including vibrational spectroscopy and X-ray characterization of the SEI surface layer and GC-MS/FID were conducted to determine the impact of gas doping on the capacity, SEI, and gas phase reaction products.

The Role of Entropy on the Electrochemistry of Entropy-Stabilized Oxides and Their Lithium Storage Mechanism

Metals and semimetals oxides have been investigated as an alternative Li-ion battery anode due to their higher energy storage density relative to the state-of-the-art graphite electrodes. Entropy-stabilized oxides have recently gained significant interest due to their high energy and power density, but their mechanism of lithium storage is still poorly understood, in part owing to the difficulty in characterizing the chemical structure at the nanoscale. It has been hypothesized that entropy plays a significant role on the electrochemistry of this class of material. This work aims at investigating the role of entropy in this class of materials, and their Li storage mechanism using solid-state NMR spectroscopy.

Vacancy diffusion and its consequences for void growth at the interface of a stripping metal electrode and solid electrolyte

It is commonly observed that voids can nucleate and grow in the lithium anode of a solid state Li-ion battery at a location adjacent to the solid electrolyte during the stripping (discharge) phase of the battery; a similar phenomenon is observed in sodium-based batteries. It is hypothesised in the current literature that the formation of these voids is due to the coalescence of vacancies that have been generated at the electrode/electrolyte interface when metal atoms are oxidized and transported into the electrolyte: the slow diffusion of the vacancies away from the electrolyte interface into the adjacent electrode results in their coalescence and the consequent growth of voids. These hypotheses are challenged in the current study by using the Onsager formalism to generate a variational principle for vacancy diffusion. Our analysis reveals that no driving force exists for the diffusion of vacancies into a homogeneous metal electrode that thins by stripping. This finding is contrary to models in the literature which have mistakenly assumed that the vanishing flux at the current collector prevents rigid body motion (drift) of the electrode which in turn prevents thinning of the electrode during stripping. Based on our analysis, we conclude that vacancy diffusion within a homogeneous electrode is not responsible for the nucleation and growth of voids at the interface between a stripping metal electrode and a solid electrolyte.

Aging-driven composition and distribution changes of electrolyte and graphite anode in 18650-type Li-ion batteries

Aging-driven composition and distribution changes of electrolyte and graphite anode in 18650-type Li-ion batteries

Preparation of micron-sized silicon monoxide (SiOx)@carbon nanotube (CNT)/polymethyl methacrylate (PMMA) composite capsules as Li-ion battery anodes via a novel pickering emulsion template method

Li-ion batteries (LIBs) with micron-sized silicon monoxide (SiOx) anodes are promising, ascribed to their favorable cost affordability and remarkable theoretical capacity, while the huge volume expansion and inferior Li+/e− conductivity of SiOx have severely restricted their further development. Herein, a micron-sized SiOx@carbon nanotube (CNT)/polymethyl methacrylate (PMMA) composite capsule is designed for advanced LIB anode via a novel Pickering emulsion template method. The volume variation of SiOx during (de)lithiation reactions is alleviated by the reserved space inside capsules, and the capsule shells of PMMA/CNT engage a significant Li+/e− conductivity as well. Besides, the activity of SiOx greatly remains due to the capsule protection and avoidance of high-temperature treatment. The experimental results indicate that the SiOx@CNT/PMMA composite anodes can present improved lithium storage abilities in aspects of capacity retention, rate performance, and coulombic efficiency. This proposed method hopes to provide a novel micron-scale structure design for Si-based anodes in LIBs.

Hybrid Sub-1 nm Nanosheets of Co-assembled MnZnCuOx and Polyoxometalate Clusters as Anodes for Li-ion Batteries.

Transition metal oxide (TMO) anode materials in lithium-ion batteries (LIBs) usually suffer from serious volume expansion leading to the pulverization of structures, further giving rise to lower specific capacity and worse cycling stability. Herein, by introducing polyoxometalate (POM) clusters into TMOs and precisely controlling the amount of POMs, the MnZnCuOx -phosphomolybdic acid hybrid sub-1 nm nanosheets (MZC-PMA HSNSs) anode is successfully fabricated, where the special electron rich structure of POMs is conducive to accelerating the migration of lithium ions on the anode to obtain higher specific capacity, and the non-covalent interactions between POMs and TMOs make the HSNSs possess excellent structural and chemical stability, thus exhibiting outstanding electrochemical performance in LIBs, achieving a high reversible capacity (1157 mAh g-1 at 100 mA g-1 ) and an admirable long-term cycling stability at low and high current densities.

A Multifunctional Interlocked Binder with Synergistic In Situ Covalent and Hydrogen Bonding for High-Performance Si Anode in Li-ion Batteries.

Silicon has garnered significant attention as a promising anode material for high-energy density Li-ion batteries. However, Si can be easily pulverized during cycling, which results in the loss of electrical contact and ultimately shortens battery lifetime. Therefore, the Si anode binder is developed to dissipate the enormous mechanical stress of the Si anode with enhanced mechanical properties. However, the interfacial stability between the Si anode binder and Cu current collector should also be improved. Here, a multifunctional thiourea polymer network (TUPN) is proposed as the Si anode binder. The TUPN binder provides the structural integrity of the Si anode with excellent tensile strength and resilience due to the epoxy-amine and silanol-epoxy covalent cross-linking, while exhibiting high extensibility from the random coil chains with the hydrogen bonds of thiourea, oligoether, and isocyanurate moieties. Furthermore, the robust TUPN binder enhances the interfacial stability between the Si anode and current collector by forming a physical interaction. Finally, the facilitated Li-ion transport and improved electrolyte wettability are realized due to the polar oligoether, thiourea, and isocyanurate moieties, respectively. The concept of this work is to highlight providing directions for the design of polymer binders for next-generation batteries.

A Ternary Metal Oxide-Reduced Graphene Oxide Composite as High Capacity and Durable Anode for Li-Ion Batteries

A ternary metal oxide, bismuth stannate and its carbon composite are prepared by a solution synthesis approach. The as-prepared materials are checked for phase purity by X-ray diffraction and characterized by various characterization techniques. The composite electrode performs better compared to pristine material when investigated as anodes for Li-ion batteries (LIBs). The use of an electrolyte additive leads to improved performance. High capacity of 960 mAh g−1 is obtained at 100 mA g−1 for LIBs. At a high-rate of 1000 mA g−1, 1250 stable cycles are observed with very good capacity retention, and the capacity is ∼475 mAh g−1 at the end of the cycling. As investigated by different techniques, both conversion and alloying reactions are responsible for such high performance. The carbon network improves the conductivity and stabilize the intermediates formed during cycling. Further, the full cell studies with the composite anode and LiFePO4 cathode show good performance.

Doped micro-silicon and vanadium carbide MXene composite as anode for high stability and high capacity Li-ion batteries

The demand for high-energy lithium-ion batteries (LIBs) has been rising exponentially. Silicon (Si) is gaining increased attention and popularity as an anode material due to its high theoretical capacity (4200 mAhg−1, Li4.4Si) and ample abundance, but the huge volume expansion of Si restricts its use in practical applications. Herein, we propose a composite consisting of nitrogen (N) and phosphorus (P) doped micron Si/graphite with vanadium carbide (V2C) MXene, which effectively helps to buffer the mechanical stresses initiated by the volume expansion of Si. The lithium storage specific capacity of the composite is 2003 mAhg−1 (based on the weight of Si) after a long-term cycling of 500 cycles (1C rate) along with a good high rate performance. The improved performance of the composite electrode can be attributed to V2C as well as N/P doping, which significantly enhance the electron/ion conduction pathways. Also, low-cost micron Si can provide high tap density in practical applications where volumetric performance is desired. Thus, this work provides an approach to develop high-performance micron Si-based materials for LIBs.

Preparation of nanoporous SiO2/C derived from rice husk as anode material in SiO2/C||LiFePO4 full-cell through alkaline activation treatment

Silicon-based materials such as pure silicon (Si), silicon monoxide (SiO), silica (SiO2), are considered promising anode for future high power energy Li-ion batteries. Among them, SiO2 has garnered attention owing to its outstanding features such as high theoretical capacity (1961 mAh g−1), abundant reserve, and low-cost processing. However, the large expansion and shrinkage of the Si and SiO2 volume during lithiation/delithiation reaction are still the main barriers for practical application. In this study, SiO2 derived from rice husks and activated by KOH displayed a nanoporous structure with a porous matrix carbon that can absorb the volume expansion during lithiation process and facilitate the diffusion of Li+ ion along the pores to minimise the dendrite growth at the local area. Through activation treatment, the surface area of SiO2 increases up to 278.875 m2 g−1 with a pore volume of 0.191 cm3 g−1 and the average pore diameter is about 0.771 nm. The cycling results showed that rice husk ash mixed with KOH at a ratio of 1:0.5 offered the best capacity retention of SiO2/C anode material in half-cell. In full-cell configuration of SiO2/C||LiFePO4, the the negative electrode/positive electrode capacity ratio (N/P) ratio of 1.2 exhibited the most stable performance with the highest capacity retention.

A self-supporting Cu2S/CP lithium-ion battery anode

Lithium-ion (Li-ion) batteries have been widely used in portable electronic devices and new energy vehicles in recent years. Although commercial graphite anode has good safety and low cost, its low theoretical capacity cannot better meet the demand for higher-capacity of power batteries. As an excellent electrode material, copper sulfide (Cu2S) has the advantages of high capacity and stability. Herein, Cu2S deposited on carbon paper (Cu2S@CP) was prepared by simple copper electrodeposition on carbon paper and sulphidation, which can be used to the anode of Li-ion batteries directly. Based on the three-dimensional structure of carbon paper and the high capacity of copper sulfide, the composite anode shows good lithium storage performance, which provides a new possibility for commercial power lithium-ion battery anode materials.