First-cycle Efficiency Research Articles

Towards Rational Design of Battery Formation Protocols: From Electrochemical Modeling to Factory Deployment

In battery manufacturing, the formation process is both paramount and problematic. It is paramount since all batteries undergo formation charging and aging steps to build a resilient solid electrolyte interphase (SEI) and to screen for defects. It is problematic because the formation process is expensive to operate, remains a major source of factory energy demand, requires larger factory footprints, and takes an order of magnitude longer than nearly every other manufacturing step. Despite the centrality of the formation process in battery manufacturing, steps taken to optimizing formation protocols remain ad-hoc in the absence of design principles and physical models.We highlight recent progress in developing a principled understanding of the SEI formation process applied towards industrial battery formation process (i.e. in the context of a full cell). We review a reduced-order electrochemical model of the formation process that captures first cycle charge dynamics and subsequent cycling and aging degradation behavior [1]. The model predicts measurable quantities such as first cycle efficiency (FCE) and irreversible thickness growth under multiple formation protocols. We discuss opportunities to integrate the electrochemical formation model with differential voltage analysis (DVA) to visualize the connection between first cycle charge dynamics from the perspective of shifting electrode stoichiometries [2] and comment on applications towards physics-informed battery lifetime prediction [3]. We finally share recent data elucidating the effect of formation temperature, pressure, and protocol on cycle life.

Ab Initio Tomography Analysis of Lithium Incorporation and Diffusion in Multidomain Silicon Suboxide Anode Materials

Silicon is considered a promising anode material to supplant conventional graphite materials in lithium-ion batteries due to its higher theoretical energy-storage capacity compared to graphite. However, the widespread application of Si anodes has been hindered because the capacity of Si anodes decreases rapidly as the charge/discharge cycle proceeds. The controlled incorporation of oxygen into Si is often considered as a feasible approach for employing Si as an anode material in the form of silicon suboxide. Silicon suboxide exhibits a lower energy capacity compared to pure Si, but offers enhanced stability against volume expansion. Consequently, silicon suboxide materials have been commercialized by blending them with graphite. However, the blending ratio of silicon suboxide with graphite is limited to low levels due to its poor first-cycle efficiency, so-called initial Coulombic efficiency. In-depth understanding of the lithium interaction characteristics within multidomain silicon suboxide is indispensable for optimizing the electrochemical performance of silicon suboxide anode materials for lithium-ion batteries. In this study, we investigate the domain-dependent thermodynamic and kinetic properties of lithium atoms within systematically designed multidomain silicon suboxide models composed of Si, SiO2, and Si/SiO2 interface by performing a series of computational simulations combined with a unique tomography-like sampling scheme. We find that the Si/SiO2 interfacial region exhibits preferential thermodynamics and kinetics for lithiation and can serve as a critical lithium transport channel during charge-discharge cycles, while the SiO2 domain is likely to be excluded from lithiation due to its high resistance to lithium diffusion. Consequently, a significant fraction of lithium is expected to be trapped at the Si/SiO2 interface during the discharge process, which ultimately contributes to a low initial Coulombic efficiency. This theoretical understanding suggests that the formation of continuously connected lithium-transportable Si/SiO2 interfacial channels surrounding the Si domains, along with a well-structured shallow SiO2 framework through the use of appropriate synthesis methods, is essential for maximizing the electrochemical performance of silicon suboxide anode materials. Our theoretical approach offers new insights into the atomistic characteristics of silicon suboxide during lithiation/delithiation processes, ultimately enabling the identification of the origin of low ICE and strategies for addressing it.References(1) Chae, S.; Lim, H.-K.; Lee, S. Energy Landscapes for Lithium Incorporation and Diffusion in Multidomain Silicon Suboxide Anode Materials. ACS Applied Materials & Interfaces 2023, 15 (49), 57059-57069. DOI: 10.1021/acsami.3c12846. Figure 1

Modeling Battery Formation: Boosted SEI Growth, Multi-Species Reactions, and Irreversible Expansion

This work proposes a semi-empirical model for the SEI growth process during the early stages of lithium-ion battery formation cycling and aging. By combining a full-cell model which tracks half-cell equilibrium potentials, a zero-dimensional model of SEI growth kinetics, and a semi-empirical description of cell thickness expansion, the resulting model replicated experimental trends measured on a 2.5 Ah pouch cell, including the calculated first-cycle efficiency, measured cell thickness changes, and electrolyte reduction peaks during the first charge dQ/dV signal. This work also introduces an SEI growth boosting formalism that enables a unified description of SEI growth during both cycling and aging. This feature can enable future applications for modeling path-dependent aging over a cell’s life. The model further provides a homogenized representation of multiple SEI reactions enabling the study of both solvent and additive consumption during formation. This work bridges the gap between electrochemical descriptions of SEI growth and applications toward improving industrial battery manufacturing process control where battery formation is an essential but time-consuming final step. We envision that the formation model can be used to predict the impact of formation protocols and electrolyte systems on SEI passivation and resulting battery lifetime.

A facile procedure to improve the performance of food-waste-derived carbons in sodium-ion batteries

The anode of Na-ion batteries under development is dominated by carbon materials, especially hard carbons with poorly organized structures. The production of carbon materials by pyrolysis of food waste is less expensive and more environmentally friendly than from pure organic compounds. In this work, the sulfuric acid pre-treatment of ground coffee grains before carbonization is evaluated as a simple but efficient tool to improve the electrochemical performance of the resulting carbon for the anode of sustainable Na-ion batteries. The carbon product shows a significant reduction in inorganic impurities and a decrease in crystallinity, which results in a reversible capacity close to 33 % higher, enhanced first-cycle efficiency, and better kinetic response than the non-pre-treated materials. Thus, reversible capacities at C/10 increase from ca. 150 mAhg−1 to 200 mAhg−1 after acid treatment, and the capacity of the non-acid-treated samples falls to negligible values at 2C kinetics, in contrast with significant retention of the acid-treated one.

Surprising Dependence of the Exfoliation of Graphite During Formation on Electrolyte Composition

Graphite is the most used lithium intercalation host for the negative electrode of the lithium-ion battery. Extensive research has been carried out to achieve high Coulombic Efficiency (CE) and long cycle life for the graphite anode. Here, LFP/graphite (graphite from Vendor 1) cells that undergo formation at 40 °C with either 1.2 M LiPF6 dissolved in ethylene carbonate:dimethyl carbonate (EC:DMC), or ethylene carbonate:ethylmethyl carbonate (EC:EMC) have excellent first cycle efficiency (FCE). However, when the formation is done at 20 °C, EC:EMC and ethylene carbonate:diethyl carbonate (EC:DEC) cells show much reduced FCE while EC:DMC cells retain high FCE. We prove by a variety of experiments that the reduced FCE is caused by solvent co-intercalation. We explore the impact of temperature, different graphites, electrolyte additives, and varied salt content on this effect. We show that basic additives, such as vinylene carbonate, are sufficient to eliminate the co-intercalation. With a well-designed electrolyte system containing additives, graphites that show co-intercalation in the absence of additives perform equivalently or better than graphites that do not show co-intercalation in the absence of additives.

Printed Lithium for Next Generation Battery Technologies

Next generation lithium ion batteries will need to utilize anode materials that offer higher energy density and faster charging rates compared to graphite anode. However, widespread commercialization of anodes containing more than a few percent of high energy density materials such as silicon and tin has been hindered by issues such as high first cycle inefficiency and poor cycle life. Loss of active lithium from cathode materials due to SEI formation permanently lowers the cell energy density. Pre-lithiation employs an external, sacrificial source of lithium to offset active lithium losses during the first cycle, allowing more efficient use of lithium from the cathode and therefore raising the cell energy density1,2,3.Livent has developed a proprietary approach to pre-lithiation called Printable Lithium Technology (PLT) that incorporates SLMP into a stable printable formulation. Printable Lithium Formulation (PLF) is comprised of SLMP dispersed in a compatible solvent along with other rheology and performance modifiers to create a formulation that is chemically stable and not prone to separation for extended periods of time. The technology is scalable using industry standard equipment to apply the formulation to the surface of a prefabricated anode. Printable Lithium Technology (PLT) is anode and cathode chemistry agnostic4,5,6. PLT can be used in anodes with a range of silicon content, because lithium loading could be accurately controlled based on the applications’ requirements. Lithium loading control is achieved through the print head designed for pattern printing. We will also discuss safety benefits of using our approach.Figure 1a shows the dQ/dV curve of for baseline SiO/Li half-cell compared to a half-cell with PLF treated SiO. Figure 1a shows the absence of solvent reduction peak in the 0.4V – 0.2V range for the cell incorporating PLT, indicating PLF eliminate the irreversible capacity loss. The voltage vs. capacity curve on the right shows that the first cycle efficiency (FCE) has been improved from 69% in the baseline cell to 87% in the cell with PLT incorporated. Initial voltage is lowered from 1.6V to 0.2V in the cell with treated anode.It can be seen in Figure 2 that PLT can be used in a variety of cell chemistries to improve the cell FCE. Figure 1

Enabling > 4C Fast Charging of Li-Ion Batteries with Graphite/Hard Carbon Hybrid Anodes to Overcome Energy/Power Density Tradeoffs

Li-ion batteries with high energy density and fast-charge capability are required to realize the widespread use of electric vehicles. However, current graphite-anode-based Li-ion batteries are unable to achieve fast charging without adversely impacting battery performance. This is because when graphite anodes are subjected to fast charging conditions, large cell polarizations reduce the accessible capacity and induce Li plating on the anode surface. The formation of metallic Li on the graphite anode surface results in irreversible loss of Li inventory, leading to significant capacity fade. In contrast to graphite, hard carbon is known to exhibit enhanced power performance. However, the high redox potential, low first-cycle efficiency, and low material density have prevented the adoption of hard carbon in high-energy-density battery systems. Thus, there is a unmet need to develop Li-ion technology to achieve both high energy density and power performance.In this work, we demonstrate hybrid anodes fabricated by mixing graphite and hard carbon to achieve fast-charging Li-ion batteries with high energy density, using industrially relevant multi-layer pouch cells (> 1Ah) and electrode loadings (3 mAh/cm2). Standard roll-to-roll slurry casting was performed to fabricate the hybrid anodes, demonstrating the compatibility with existing Li-ion manufacturing. By tuning the blend ratio of graphite and hard carbon, it is shown that the battery performance can be tailored to simultaneously achieve high energy density and power performance. As a result of the hybrid anode design, we demonstrate pouch cells with > 96% and > 93% capacity retention over 100 cycles of 4C and 6C fast-charge cycling respectively. Synchrotron tomography was employed to investigate the microstructure effects (porosity, tortuosity, and pore size) on the electrochemical performance. Electrochemical dynamic simulations were also performed to provide mechanistic insight into the origins of the improved fast-charging performance of the graphite/hard carbon hybrid anodes.

Ni/Li Disordering in Layered Transition Metal Oxide: Electrochemical Impact, Origin, and Control.

Lithium ion batteries (LIBs) not only power most of today's hybrid electric vehicles (HEV) and electric vehicles (EV) but also are considered as a promising system for grid-level storage. Large-scale applications for LIBs require substantial improvement in energy density, cost, and lifetime. Layered lithium transition metal (TM) oxides, in particular, Li(NixMnyCoz)O2 (NMC, x + y + z = 1) are the most promising candidates as cathode materials with the potential to increase energy densities and lifetime, reduce costs, and improve safety. In order to further boost Li storage capacity, a great deal of attention has been directed toward developing Ni-rich layered TM oxides. However, structural disorder as a result of Ni/Li exchange in octahedral sites becomes a critical issue when Ni content increases to high values, as it leads to a detrimental effect on Li diffusivity, cycling stability, first-cycle efficiency, and overall electrode performance. Increasing effort has been dedicated to improving the electrochemical performance of layered TM oxides via reduction of cationic mixing. Therefore, it is important to summarize this research field and provide in-depth insight into the impact of Ni/Li disordering on electrochemical characteristics in layered TM oxides and its origin to accelerate the future development of layered TM oxides with high performance. In this Account, we start by introducing the Ni/Li disordering in LiNiO2, the experimental characterization of Ni/Li disordering, and analyzing the impact of Ni/Li disordering on electrochemical characteristics of layered TM oxides. The antisite Ni in the Li layer can limit the rate performance by impeding the Li ion transport. It will also degrade the cycling stability by inducing anisotropic stress in the bulk structure. Nevertheless, the antisite Ni ions do not always bring drawbacks to the electrochemical performance; some studies including our works found that it can improve the thermal stability and the cycling structure stability of Ni-rich NMC materials. We next discuss the driving forces and the kinetic advantages accounting for the Ni/Li exchange and conclude that the steric effect of cation size and the magnetic interactions between TM cations are the two main driving forces to promote the Ni/Li exchange during synthesis and the electrochemical cycling, and the low energy barrier of Ni2+ migration from the 3a site in the TM layer to the 3b site in the Li layer further provides a kinetic advantage. Based on this understanding, we then review the progress made to control the Ni/Li disordering through three main ways: (i) suppressing the driving force from the steric effect by ion exchange; (ii) tuning the magnetic interaction by cationic substitution; (iii) kinetically controlling Ni migration. Finally, our brief outlook on the future development of layered TM oxides with controlled Ni/Li disordering is provided. It is believed that this Account will provide significant understanding and inspirations toward developing high-performance layered TM oxide cathodes.

Exploring Lithium-Cobalt-Nickel Oxide Spinel Electrodes for ≥3.5 V Li-Ion Cells.

Recent reports have indicated that a manganese oxide spinel component, when embedded in a relatively small concentration in layered xLi2MnO3·(1-x)LiMO2 (M = Ni, Mn, or Co) electrode systems, can act as a stabilizer that increases their capacity, rate capability, cycle life, and first-cycle efficiency. These findings prompted us to explore the possibility of exploiting lithiated cobalt oxide spinel stabilizers by taking advantage of (1) the low mobility of cobalt ions relative to that of manganese and nickel ions in close-packed oxides and (2) their higher potential (∼3.6 V vs Li0) relative to manganese oxide spinels (∼2.9 V vs Li0) for the spinel-to-lithiated spinel electrochemical reaction. In particular, we revisited the structural and electrochemical properties of lithiated spinels in the LiCo1-xNixO2 (0 ≤ x ≤ 0.2) system, first reported almost 25 years ago, by means of high-resolution (synchrotron) X-ray diffraction, transmission electron microscopy, nuclear magnetic resonance spectroscopy, electrochemical cell tests, and theoretical calculations. The results provide a deeper understanding of the complexity of intergrown layered/lithiated spinel LiCo1-xNixO2 structures when prepared in air between 400 and 800 °C and the impact of structural variations on their electrochemical behavior. These structures, when used in low concentrations, offer the possibility of improving the cycling stability, energy, and power of high energy (≥3.5 V) lithium-ion cells.

Precise Perforation and Scalable Production of Si Particles from Low-Grade Sources for High-Performance Lithium Ion Battery Anodes.

Alloy anodes, particularly silicon, have been intensively pursued as one of the most promising anode materials for the next generation lithium-ion battery primarily because of high specific capacity (>4000 mAh/g) and elemental abundance. In the past decade, various nanostructures with porosity or void space designs have been demonstrated to be effective to accommodate large volume expansion (∼300%) and to provide stable solid electrolyte interphase (SEI) during electrochemical cycling. However, how to produce these building blocks with precise morphology control at large scale and low cost remains a challenge. In addition, most of nanostructured silicon suffers from poor Coulombic efficiency due to a large surface area and Li ion trapping at the surface coating. Here we demonstrate a unique nanoperforation process, combining modified ball milling, annealing, and acid treating, to produce porous Si with precise and continuous porosity control (from 17% to 70%), directly from low cost metallurgical silicon source (99% purity, ∼ $1/kg). The produced porous Si coated with graphene by simple ball milling can deliver a reversible specific capacity of 1250 mAh/g over 1000 cycles at the rate of 1C, with Coulombic efficiency of first cycle over 89.5%. The porous networks also provide efficient ion and electron pathways and therefore enable excellent rate performance of 880 mAh/g at the rate of 5C. Being able to produce particles with precise porosity control through scalable processes from low-grade materials, it is expected that this nanoperforation may play a role in the next generation lithium ion battery anodes, as well as many other potential applications such as optoelectronics and thermoelectrics.

High dispersion of 1-nm SnO2 particles between graphene nanosheets constructed using supercritical CO2 fluid for sodium-ion battery anodes

Supercritical CO2 (SCCO2) fluid, which has gas-like diffusivity, extremely low viscosity, and near-zero surface tension, is used to synthesize SnO2 nanoparticles (a 1-nm diameter is achievable), which are uniformly dispersed and tightly anchored on graphene nanosheets (GNSs) and carbon nanotubes (CNTs). The discharge capacity, rate capability, and cyclic stability of the synthesized SnO2/GNS and SnO2/CNT nanocomposites are compared. This study also tunes the SCCO2 temperature (and thus its fluid density) and finds that this factor crucially affects the SnO2 size and distribution, determining the resulting electrochemical properties. The sodiation/desodiation mechanism of the SnO2/GNS electrode is examined using synchrotron ex situ X-ray absorption and X-ray diffraction techniques, together with transmission electron microscopy. We confirm that while the oxide conversion reaction is reversible, the sluggish Sn–Na alloying/dealloying reaction is responsible for the lower measured capacity as compared to the theoretical value. The first-cycle efficiency loss is mainly attributed to the trapping of Na in the electrode surface solid electrolyte interphase layer.

Structural, Compositional and Electrochemical Control of Integrated Layered-Layered-Spinel Cathodes

A concerted effort is being made at Argonne National Laboratory to stabilize high capacity ‘layered-layered’ xLi2MnO3•(1-x)LiMO2 electrodes, in which M is typically Mn, Ni and Co, when cycled to high potentials. The strategy being adopted is to marginally reduce the lithium content in ‘layered-layered’ structures in order to induce the formation of a spinel component, thereby introducing stabilizing transition metal ion pillars in the lithium layers of structurally-integrated ‘layered-layered-spinel’ (1-y)[xLi2MnO3•(1-x)LiMO2]•yLi0.5MO2 electrodes. This approach, which follows earlier related work on the composite ‘layered-spinel’ system, xLi2MnO3•(1-x)LiMn2-zLizO4 (0≤z≤0.33) [1], has yielded positive results with improvements in first-cycle efficiency, discharge capacity, and cycling stability being reported, particularly when targeting 5-15% of spinel in the electrode structure [2, 3]. In this presentation, the results of structural studies of ‘layered-layered-spinel’ materials using a combination of X-ray and neutron diffraction, transmission electron microscopy techniques, coupled to complementary electrochemical data, will be reported. One of the major goals of the study is to determine at what value of y do the transition metal ions start to drop into the lithium layers for any given system and composition, and to what extent can a lithium deficiency in the ‘layered-layered’ structure be compensated by changes in the oxidation state of the M cations while keeping the layered configuration intact. References C. S. Johnson, N. Li, J. T. Vaughey, S. A. Hackney, M. M. Thackeray, Electrochem. Commun., 7, 528 (2005).D. Kim, G. Sandi, J. R. Croy, K. G. Gallagher, S.-H. Kang, E. Lee, M. D. Slater, C. S. Johnson, M. M. Thackeray, J. Electrochem. Soc., 160, A31 (2013).B. R. Long, J. R. Croy, J. S. Park, J. Wen, D. J. Miller, M. M. Thackeray, J. Electrochem. Soc, 161, A2160 (2014). Acknowledgment Support for this work from the Office of Vehicle Technologies of the U.S. Department of Energy, in particular, Tien Duong, David Howell and Peter Faguy, is gratefully acknowledged. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

Design and Processing of Advanced Lithium-Ion Electrode Materials

Significant interest in lithium- and manganese-rich (LMR) cathodes exists within the lithium-ion battery community. LMR electrodes, which incorporate a Li2MnO3 motif into the structure [1], exhibit high capacities and have relatively low raw materials costs [2]. Despite these attributes, significant challenges to commercialization remain, including industrial considerations related to materials processing. Synthesis of commercialized materials and electrodes such as those based on LiCoO2 (LCO) and LiNi­0.8Co0.15Al0.05O2 (NCA) has been highly optimized. However, less work has been done on the optimization and processing of promising new LMR compositions. Specifically, structurally-integrated “layered-layered-spinel” cathodes have been shown to provide improved rate capability, first-cycle efficiency, and possibly structural stability with cycling than their “layered-layered” counterparts [3]. However, these new chemistries have to date received little attention in the way of optimizing electrochemical performance through improved particle synthesis. This poster will detail important considerations for LMR particle synthesis through reactive crystallization, and highlight ongoing work at Argonne National Laboratory on the design and synthesis of advanced lithium-metal-oxide electrode materials. References M. M. Thackeray, C. S. Johnson, J. T. Vaughey, N. Li and S. A. Hackney, J. Mater. Chem. 15, 2257 (2005).K. G. Gallagher, S. Goebel, T. Greszler, M. Mathias, W. Oelerich, D. Eroglu, V. Srinivasan, Energy & Environ. Sci. 7, 1555 (2014).B.R. Long, J. R. Croy, J.S. Park, J. Wen, D.J. Miller and M.M. Thackeray, J. Electrochem. Soc. 161, A2167 (2014). Acknowledgments Funding for this work from the Office of Vehicle Technologies of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, is gratefully acknowledged. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

The lamella SnSbCux/MCMB/carbon composite as high stability and durable anodes for lithium ion battery

Lamella SnSbCux/MCMB/carbon composite were prepared by a multi-step synthesis method for high stability and long life lithium ion battery electrodes. The lamella composite were synthesized via co-precipitation method combining with high-speed ball milling and subsequent pyrolysis. The resultant composite are consisted of nano SnSbCux particles, lamella mesophase carbon microbeads (MCMB, after ball milling) and amorphous carbon coating pyrolyzed from phenolic resin. The lamella MCMB was treated as the inner terrace, which offered efficient electron conducting pathway for connection of nano SnSbCux particle and pyrolysis carbon. With the increasing of the content of inactive element Cu, the SnSbCux/MCMB/carbon composite are propitious to improve the cycling performance. When cycled at a constant current of 100mAg−1 between 0.01 and 2.0V, the coulombic efficiency of first cycle exceeds 88.45% and the reversible capacity of 100th cycle attains to 485mAhg−1 (91.4% capacity retention) in SnSbCu0.5/MCMB/carbon alloy anodes.

Improve First-Cycle Efficiency and Rate Performance of Layered-Layered Li1.2Mn0.6Ni0.2O2 Using Oxygen Stabilizing Dopant.

The poor first-cycle Coulombic efficiency and rate performance of the Li-rich layered-layered oxides are associated with oxygen gas generation in the first activation charging and sluggish charge transportation along the layers. In this work, we report that barium doping improves the first-cycle efficiency of Li-rich layered-layered Li1.2Mn0.6Ni0.2O2 via suppression of the oxidation of O(2-) ions in the first charging. This effect can be attributed to the stabilizing effect of the barium cations on the oxygen radical intermediates generated during the oxidation of O(2-). Meanwhile, because the stabilized oxygen radicals likely facilitate the charge transportation in the layered-layered structure, the barium-doped Li1.2Mn0.6Ni0.2O2 exhibits significant improvement in rate performance. Stabilizing the oxygen radicals could be a promising strategy to improve the electrochemical performance of Li-rich layered-layered oxides.

Nanostructured hybrid layered-spinel cathode material synthesized by hydrothermal method for lithium-ion batteries.

Nanostructured spinel LiMn1.5Ni0.5O4, layered Li1.5Mn0.75Ni0.25O2.5 and layered-spinel hybrid particles have been successfully synthesized by hydrothermal methods. It is found that the nanostructured hybrid cathode contains both spinel and layered components, which could be expressed as Li1.13Mn0.75Ni0.25O2.32. Diffraction-contrast bright-field (BF) and dark-field (DF) images illustrate that the hybrid cathode has well dispersed spinel component. Electrochemical measurements reveal that the first-cycle efficiency of the layered-spinel hybrid cathode is greatly improved (up to 90%) compared with that of the layered material (71%) by integrating spinel component. Our investigation demonstrates that the spinel containing hybrid material delivers a high capacity of 240 mAh g(-1) with good cycling stability between 2.0 and 4.8 V at a current rate of 0.1 C.

Oxidized FeCoNi alloys as novel anode in Li-ion batteries

Oxidised FeCoNi alloys are prepared by an electrodeposition-annealing method. The performances of this type of nanostructured electrode are studied by the combination of structural techniques (transmission electron microscopy and X-ray diffraction) and electrochemical tests in lithium cells. The oxidised FeCoNi alloy achieves an excellent Coulombic efficiency in first cycle (85–90%) as well as a minimal discharge polarization on subsequent cycles because the voltage plateau ascribable to metal reduction is kept invariable at around 0.8 V. These results disclose new pathways to fabricate low-cost and high-performance conversion electrodes as anode material for Li-ion secondary batteries.

Si–graphite composites as anode materials for lithium secondary batteries

Two types of Si–graphite (Si–C) composites are synthesized and evaluated for anode materials of lithium secondary batteries. The mechano-chemical milling and the rotational impact blending methods are applied to synthesize two types of Si–C composites. Graphite powders having Si on the surface (type A) is synthesized by mechano-chemical milling using the pitch as a binder. Si embedded inside the graphite particle (type B) is synthesized by rotational impact blending. The loading level of Si is about 20 wt% for both type Si–C composites. The location of Si is verified by observing cross sectional images of particle and conducting EDS mapping. The initial discharge capacity of type B has larger value than that of type A, while the type A shows better cycle performance than type B. The efficiency of first cycle is about 87% for both types A and B.

Electrochemical Activities in Li2MnO3

is shown to be electrochemically active, with a maximum charge capacity of and a discharge capacity of at . A total of of Li can be extracted from , and the first cycle efficiency is regardless of state of charge. Larger charge-discharge capacity is obtained from materials with smaller particle size and larger amount of stacking faults. Composition and structural analyses indicate that Li are removed from both the Li and transitional metal layers of the material during charging. Results from X-ray-absorption fine-structure measurements suggest that the valence of Mn remains at during charging but is reduced during discharging. Charging is accompanied by gas generation: at , oxygen is the main gas detected, and the total amount accounts for of generation from . At an elevated temperature, amount of increases due to electrolyte decomposition. shows poor cycle performance, which is attributed to phase transformation and low charge-discharge efficiency during cycling. Low first-cycle efficiency, gas generation, and poor cycle performance limit the usage of in practical batteries.

Nano-sized SnSbCu x alloy anodes prepared by co-precipitation for Li-ion batteries

Nano-sized SnSbCu x alloy anode materials are prepared by reductive co-precipitation method combining with the aging treatment in water bath at 80 °C. The microstructure, morphology and electrochemical properties of synthesized SnSbCu x alloy powders are evaluated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and galvanostatical cycling tests. The results indicate that the average particle size is reduced and the Cu 6Sn 5, Cu 2Sb phases appear successively along with the increase of Cu content in the SnSbCu x alloy. The reduction of average particle size, the existence of inactive element Cu and the complex multi-step reaction mechanism in SnSbCu x alloy anodes are propitious to improve the structure stability and thus improve the cycling performance. When cycled at a constant current density of 0.1 mA cm −2 between 0.02 and 1.50 V, the coulomb efficiency of first cycle exceeds 74% and the reversible capacity of 20th cycle attains to 490 mAh g −1 in SnSbCu 0.5 alloy anode.