Full-cell Lithium-ion Batteries Research Articles

Evaluating Polyacrylic Acid as a Universal Aqueous Binder for Ni-Rich Cathodes NMC811 and Si Anodes in Full Cell Lithium-ion Batteries.

Silicon (Si) and silicon/graphite (Si/Gr) composite anodes are promising candidates due to their high theoretical capacity, low operating potential and natural abundance for high energy density Li-ion batteries. Green electrode production, eliminating organic volatile solvents require advancement of aqueous electrodes. Engineering the binder plays a critical role for improving waterborne electrodes. Lithium substituted polyacrylic acid LiPAA has been demonstrated as a promising binder for Si/Gr anodes and for Ni-rich cathodes in different cell configurations. LiPAA is utilized to minimize the volume expansion during cycling for Si/Gr anodes. LiPAA is formed in situ during cathode slurry preparation to regulate the pH and dimmish the Li loss. Using advanced characterization techniques, we investigated the slurries, electrodes, and active material reaction with LiPAA and its effect to the cycling performance. Our results indicate that the performance of high Si containing anode is limited by the amount of Si in the electrode. The failure mechanism with respect to high Si content was studied thoroughly. Aqueous processed cathodes with LiPAA binder in combination with Si anodes outperformed NMP based cathodes. Hence, LiPAA was successfully utilized as an active binder for both a high Si containing anode and for a Ni rich cathode.

3D Progression of Dead Li on Graphite Electrodes during Extended Fast Charging

Long charging times of commercial lithium-ion batteries (LIBs) constitute one of the critical remaining bottlenecks in the widespread deployment of electric vehicles (EVs). Therefore, there is a global push towards extreme fast charging (XFC)1in 10–15 minutes for 80% of the pack capacity. However, existing LIBs cannot achieve these XFC goals without significant capacity fade during cycling over battery lifetime.2 One of the key XFC degradation mechanisms is “Li plating,” which occurs when Li metal forms on the graphite electrode due the liquid electrolyte and solid-phase (graphite) mass transport limitations and sluggish charge-transfer kinetics of the Li intercalation reaction.3 This is mostly attributed to the formation of dead Li,4 which is the irreversibly plated Li that has become electronically disconnected from the graphite electrode. Since dead Li constitutes most of the XFC-related capacity loss, it is extremely important to unravel the link between its morphological evolution/progression, and battery capacity fade during extended XFC cycling.In this work, we report non-destructive, in-situ three-dimensional (3D) characterization of dead Li on graphite electrodes in full-cell LIBs during extended XFC using high-resolution (pixel size: ~ 7.8 µm; effective spatial resolution: ~25-30 µm) neutron micro-computed tomography (µCT). Specifically, we imaged batteries in the discharged state at the following cycle numbers at 6C charging rate: 10, 25, 50, and 150 cycles. Neutron µCT is promising for in-situ 3D Li detection on graphite electrodes because it provides strong contrast between Li and C (~ 71.87: 5.55 barns5). To leverage high-resolution neutron µCT for this work, we designed a custom neutron-friendly LIB coin-cell that provided exceptional neutron transmission at the graphite-separator-electrolyte interface as well as standard XFC performance at 6C between 3.0 and 4.1 V. We performed these imaging experiments at the MARS (CG-1D) beamline6 at the High Flux Isotope Reactor, Oak Ridge National Laboratory.Our results reveal 3D evolution of dead Li morphology from isolated plated deposits on only one edge of the graphite electrode after 25 cycles at 6C charging, to increasingly mossy-like covering the entire circumference of the graphite electrode after 150 cycles. Based on our imaging data, we did not observe any dead Li after only 10 XFC cycles. However, we noticed that dead Li started to nucleate around a partial edge of the graphite electrode after 25 XFC cycles, and then grew to the other edges after 50 XFC cycles, eventually forming a complete ring after 150 XFC cycles. At 150 XFC cycles, we also observed the dead Li ring outgrowths away from the edges of the graphite electrode onto the separator. In the extended XFC-cycled samples, 50 and 150 XFC cycles, we found significant dried out salt deposits on the separator, spacers, spring, and casing, which may be due to other parasitic reactions occurring at increased XFC cycling. Lastly, we determined quantitative relationships between the amount of dead Li in 3D, XFC cycling number, and XFC-related capacity loss of the battery.In conclusion, this work contributed to the advanced understanding of the 3D progression of dead Li and its relationship with XFC-related capacity loss on graphite electrodes during extended XFC cycling. We believe insights from this work will help develop improved 3D graphite electrode architectures that will minimize Li plating during repeated XFC cycling in fast-charged LIBs.

Toward Commercial Cylindrical Anode Free Li-Metal Batteries: Electrochemical Study and Improvement

Lithium-ion batteries (LIBs) are one of the favorite energy storage devices that are applied to mobile and stationary energy storage applications. The widespread use of Li-ion batteries requires an increase in the energy density of each battery cell. Anode-free Li-ion Batteries (AFLIBs) are new types of LIBs models that offer high energy density. However, there are still many challenges in fabricating AFLIBs toward commercial use, mainly improving the battery cycle and the efficiency of intercalation/deintercalation of Li-ion between two electrodes. In this research, the fabrication of AFLIBs is studied, optimized, and integrated with cathode materials to be commercial cylindrical full-cell LIBs. The comparison of an active cathode material between LiFePO4 (LFP) and NMC622 showed that NMC622 performed better than LFP. The optimum condition of cathode materials coating thickness is 200 microns achieving 2.75 mAh cm-2 of area capacity. Furthermore, the gold platting strategy is proposed to modify the Cu foil surface to improve the electrical performance and stability of AFLBs. As a result, the control gold plating with 5 nm thickness increases the full-cell capacity of AFLBs to 142.89 mAh g-1 with a capacity retention percentage of 95.41% after five cycles.

Multi-layering of carbon conductivity enhancers for boosting rapid recharging performance of high mass loading lithium ion battery electrodes

The ability of lithium ion batteries (LIBs) to provide rapid charging characteristics while retaining a substantial energy storage capacity is of paramount significance for their applicability in portable smart electronic devices. In this research, an effective approach to enhance re-charging rates of LIB cells was developed through incorporating carbon nanotube (CNT) conductivity boosters strategically into Li4Ti5O12 (LTO) electrodes. A layer-by-layer spray coating was exploited to manufacture multi-layer architectures that comprise sequential, discrete electrode layers of CNT-rich LTO and CNT-free LTO, aiming at promoting charge transfer kinetics of high mass loading electrodes. Initially, the optimal proportion of a CNT-rich layer and its best location within multi-layer electrode structures were investigated in half-cell configurations. The best performing multi-layer was then paired with a spray-coated LiFePO4 (LFP) positive electrode in full-cell LIBs, offering attractive power performance of ∼ 1500 W/kg that outperformed conventional LTO || LFP combinations.

Development of Electrolyte Additives to Enable High-Voltage LiNi0.5Mn1.5O4 Lithium Ion Batteries

Electrochemical energy storage (EES) is still key to realize wide spread use of renewable energies. For large-scale EES production, the development of high energy density, non-toxic, cost-effective materials is necessary. In this study, a cobalt free active material, Lithium Nickel Manganese Oxide, LiNi0.5Mn1.5O4 (LNMO), was employed in the production of cathodes for high voltage lithium ion battery (LIB) applications. LNMO is an attractive cathode active material due to its high operating potential (~4.7 vs. Li/Li+ [1]), non-toxicity and low cost. The practical application of LNMO cathodes in LIBs has been relatively limited, especially for large scale application, due challenges associated with the material (i.e. electrolyte decomposition at high voltage, self-discharge and dissolution of the transition metals [2]).Electrolyte additives are an effective way to address these challenges, without major cost increase or changes to the production approach. In this study the role of different electrolyte additives in high-voltage full-cell LIBs with both graphite and silicon-graphite anodes is investigated. Additives known for their solid electrolyte interphase (SEI) forming ability (i.e. vinylene carbonate (VC) and fluoroethylene carbonate (FEC)), as well as additives that play additional roles such as cathode electrolyte interface formation or HF scavenging (i.e. tris(trimethylsilyl) phosphite (TMSP) and succinate anhydride (SA)), are used [3]. Galvanostatic cycling measurements were performed in 3-electrode cells in order to investigate the rate capability and long term cycling stability of LMNO/Gr and LMNO/Gr-Si full-cells with different electrolyte additives. The electrochemical characterization was verified with post mortem analysis to confirm the SEI composition, chemical and mechanical stability of the electrodes and lack of lithium plating. Post mortem investigations were done with Raman spectroscopy, scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) and optical microscopy. Improved rate performance and better long term cycling stability of both full-cell chemistries was achieved for electrolytes containing the TMSP additive.

Enhancing lithium-ion storage performance of hollow CoS2/MoS2 nanospheres via N-doped carbon-coating

Transition metal sulfides (TMSs) have been considered as up-and-coming anode materials for lithium-ion batteries (LIBs) owing to their large theoretical capacity and good reversibility. However, obvious volume variation and sluggish kinetics greatly limit their practical application. To address this issue, we successfully design and fabricate hollow CoS2/MoS2 nanospheres and effectively enhance their lithium storage performance via N-doped carbon-coating (CoS2/MoS2@N-C). The unique hollow structure provides shortened ion-diffusion path, while the N-doped carbon shells buffer the severe volume changes during cycling and improve the electronic conductivity of the electrode. When used as an anode material for LIBs, the CoS2/MoS2@N-C displays high specific capacity (1056.9 mA h g−1 at 100 mA g−1), excellent cycling stability (653.9 mA h g−1 after 250 cycles at 1000 mA g−1), and rate capability (685 mA h g−1 at 2000 mA g−1). The CoS2/MoS2@N-C||LiFePO4 full-cell LIB is also assembled and exhibits remarkable performance. The remarkable electrochemical performance of CoS2/MoS2@N-C electrode could be assigned to the synergistic enhancement effect of the N-doped carbon coating and hollow structure, which efficiently shorten the ion diffusion path, boost the charge transfer rate, and alleviated the volume changes of the electrode upon cycling.

Spray fabrication of additive-free electrodes for advanced Lithium-Ion storage technologies

Polymer binders and carbon conductivity enhancers are inevitably required to make improvements in structural durability and electrochemical performance of lithium-ion battery (LIB) electrodes, although these additive constituents incur weight and volume penalties on the overall battery capacity. Here, additive-free electrode architectures were successfully fabricated over 20 × 20 cm2 electrode areas using a layer-by-layer spray coating approach, with the ultimate goal to boost gravimetric/volumetric electrode capacity and to reduce the total cost of LIB cells. Initially, the binder fraction of spray-coated Li4Ti5O12 (LTO) electrodes was reduced progressively, from 40 to 0 wt%. The electrochemical behavior of electrodes was then re-optimized as a proportion of conductivity enhancers within the binder-free electrode decreased to zero. Further, the otherwise identical spray coating process was applied to manufacture LiFePO4 (LFP) positive electrodes, leading to all-additive-free full-cell LIB configurations with attractive energy density of ∼310 Wh/kg and power performance of ∼1500 W/kg.

Prelithiation Effects in Enhancing Silicon-Based Anodes for Full-Cell Lithium-Ion Batteries Using Stabilized Lithium Metal Particles

Prelithiation Effects in Enhancing Silicon-Based Anodes for Full-Cell Lithium-Ion Batteries Using Stabilized Lithium Metal Particles

Exploring the Effects of Dopamine and DMMP Additives on Improving the Cycle Boosting and Nonflammability of Electrolytes in Full-Cell Lithium-Ion Batteries (18650)

Concerns over recyclability, performance, and safety have grown as the use of commercial Li-ion batteries to meet our energy needs has increased. Electrolytes may aid in increased flammability, capacity loss, and safety. Dimethyl methyl phosphonate (DMMP), a flame retardant, and dopamine hydrochloride (DOP) are utilized to increase the cycle life and graphite anode compatibility. The optimal additive formulation (5% wt DMMP and 0.1% wt DOP) reduces inflammability and increases cycle life and reversible capacity (99.14%). Molecular dynamics simulations provide a comprehensive atomistic account of the dynamics of Li+ ion solvation in the electrolytes and in the presence of additives. Dopamine and DMMP increase the Li-ion solvation-free energy in the electrolyte formulation. While increasing the Li-ion conductivity, additive addition reduces the electrolyte viscosity and enables the formation of a smaller, stronger Li-DMMP-DOP complex than the larger Li-carbonate complex found in Li-neat electrolyte systems. When DMMP and DOP are added to the electrolyte, the carbonates are displaced from the Li-carbonate complex by these additives. The Li-ion solvating nature or compatibility was improved upon the addition of DMMP/DOP further aided by a faster diffusive behavior of the Li complex, which in part would be instrumental in enhancing the performance and safety of the battery electrolyte additive formulations. The modified electrolyte (DMMP 5% wt, DOP 0.1% wt) has a conductivity of 18.60 mS cm–1 and a low viscosity at 25 °C. This formulation was evaluated using graphite/NMC-532 cylindrical cells with commercial electrodes. The performance of the graphite/NMC-532 cells containing the modified electrolyte was comparable to those of regular electrolytes based on carbonates: ethylene carbonate/dimethyl carbonate/ethylmethylcarbonate (EC/DMC/EMC) (1:1:1) additions. These findings indicate that DOP and DMMP have a lower oxidation potential (4.3 V) than most commercial electrolytes (4.5 V), preventing cathode deterioration. These insights should pave the path for rational design of practical and cost-effective Li-ion battery electrolyte additive combinations aimed toward lower flammability and improved performance.

Synergetic Effect of Hybrid Conductive Additives for High-Capacity and Excellent Cyclability in Si Anodes.

Silicon is a promising anode material that can increase the theoretical capacity of lithium-ion batteries (LIBs). However, the volume expansion of silicon remains a challenge. In this study, we employed a novel combination of conductive additives to effectively suppress the volume expansion of Si during charging/discharging cycles. Rather than carbon black (CB), which is commonly used in SiO anodes, we introduced single-walled carbon nanotubes (SWCNTs) as a conductive additive. Owing to their high aspect ratio, CNTs enable effective connection of SiO particles, leading to stable electrochemical operation to prevent volume expansion. In addition, we explored a combination of CB and SWCNTs, with results showing a synergetic effect compared to a single-component of SWCNTs, as small-sized CB particles can enhance the interface contact between the conductive additive and SiO particles, whereas SWCNTs have limited contact points. With this hybrid conductive additive, we achieved a stable operation of full-cell LIBs for more than 200 cycles, with a retention rate of 91.1%, whereas conventional CB showed a 74.0% specific capacity retention rate.

High-energy–density carbon-coated bismuth nanodots on hierarchically porous molybdenum carbide for superior lithium storage

The use of carbon-based supports, such as graphene and porous carbon, is a well-established approach to overcome the rapid capacity fading issues associated with alloy-based anode materials in lithium-ion batteries (LIBs). However, adopting carbonaceous materials that typically exhibit a low density eventually diminishes the primary purpose of alloys as high-energy–density anode materials. In this study, we introduce three-dimensional hierarchically porous molybdenum carbide (PMC) with high energy density, robust mechanical strength, and high electronic conductivity, which make it a promising alternative support for suppressing the huge volume expansion of alloying-based materials. Carbon-coated, ultrasmall Bi nanodots with an average size of 6.4 nm are uniformly embedded on the PMC surface (denoted as C-Bi/PMC) by facilitating heterogeneous nucleation. When tested as an anode in an LIB, the C-Bi/PMC electrode exhibits a high reversible capacity of 422 mAh g−1 at 50 mA g−1, high-rate capacity of 268 mAh g−1 at 1000 mA g−1, and long-term stability of 400 mAh g−1 at 250 mA g−1 over 500 cycles followed by 0.002 mAh g−1 decay per cycle at 5000 mA g−1 over subsequent 1000 cycles. When paired with LiNi0.5Co0.2Mn0.3O2 cathode as full-cell LIBs, the C-Bi/PMC anode deliver high gravimetric and volumetric energy densities of 352 Wh kg−1 and 563 Wh L–1, respectively. In-situ X-ray diffraction patterns captured during cycling reveal that the Li+-ion insertion mechanism in the voltage plateau region at 0.7–1.0 V consists of the intercalation between Bi layers followed by the formation of triclinic LiBi phase and the subsequent transition of triclinic LiBi to cubic Li3Bi phase.

Ceramic-Coated Separator to Enhance Cycling Performance of Lithium-ion Batteries at High Current Density

Given the global demand for green energy, the battery industry is positioned to be an important future technology. Lithium-ion batteries (LIBs), which are the most widely used battery in the market, are the focus of various research and development efforts, from materials to systems, that seek to improve their performance. The separator is one of the core materials in LIBs and is a significant factor in the lifespan of high-performance batteries. To improve the performance of present LIBs, electrochemical testing and related surface analyses of the separator is essential. In this paper, we prepared a ceramic (Boehmite, γ-AlOOH) coated polypropylene separator and a porous polyimide separator to compare their electrochemical properties with a commercialized polypropylene (PP) separator. The prepared separators were assembled into nickelmanganese-cobalt (NMC) cathode half-cell and full-cell lithium-ion batteries. Their cycling performances were evaluated using differential capacity and electrochemical impedance spectroscopy with ethylene carbonate:dimethylcarbonate (EC:DMC) electrolyte. The ceramic coated polypropylene separator exhibited the best cycle performance at a high 5 C rate, with high ionic conductivity and less resistive solid electrolyte interphase. Also, it was confirmed that a separator solid electrolyte interface (SSEI) layer formed on the separator with cycle repetition, and it was also confirmed that this phenomenon determined the cycle life of the battery depending on the electrolyte.

Melamine-assisted synthesis of vanadium nitride quantum dots: Application for full-cell lithium-ion batteries

We report a facile method of preparing vanadium nitride quantum dots on nitrogen-doped carbon matrix further applied as an active material for lithium-ion batteries. The solution-phase assisted thermal nitridation yields homogeneously dispersed vanadium nitride quantum dots with an average size of 2–3 nm. The prepared quantum dots display a high specific capacity of 602 mAh g–1, which corresponds to 89.3% of initial capacity after 250 cycles. Furthermore, the ex-situ X-ray diffraction (XRD) analysis verifies the reversible electrochemical conversion reaction of lithium nitride (Li3N). We further fabricated a full-cell, consisting of vanadium nitride quantum dots and lithium iron phosphate (LiFePO4), which displays outstanding electrochemical performance featuring a specific capacity of 147 mAh g–1 at 0.1 C and 131.3 mAh g–1 at 0.5 C with 83.8% retention after 500 cycles. The present investigation suggests that reducing the particle size to nanoscale and designing composite electrodes effectively relieves the lithiation caused mechanical pressure and confirms its potential as an active material for large-scale energy storage applications.

Nitrogen‐doped reduced graphene oxide incorporated porous rod‐like cobalt molybdate as an anode for high‐capacity long‐life lithium‐ion batteries

Modification of volume expansion and poor conductivity of ternary metal molybdates as an anode for lithium-ion batteries (LIBs) results in the improvement of their reversibility and rate capability. Herein, porous rod-like cobalt molybdate incorporated with nitrogen (N) doped reduced graphene oxide (rGO) was fabricated using a silicone oil-bath method and further heated at 500°C (designated as CMO500@N-G) and 600°C (CMO600@N-G). The well-designed CMO500@N-G and CMO600@N-G electrodes were explored as an anode for LIBs. Notably, the CMO500@N-G electrode exhibited a discharge capacity of 612 mA h g−1 over 250 cycles at 100 mA g−1, while the CMO600@N-G was restricted to 199.5 mA h g−1. Besides, the CMO500@N-G electrode was sustained for 2000 cycles with a remarkable discharge capacity of 665 mA h g−1 even at a high current density of 1000 mA g−1. Finally, using a newly developed CMO500@N-G anode, a full cell LIB was also fabricated and showed good reversibility and excellent rate performance. This outstanding performance of the electrode can be ascribed to the unique rod-like morphology of cobalt molybdate with a highly conductive N doped rGO, which suggests a new strategy to fabricate high-capacity anode materials for LIBs.

Layered Heterostructure Ionogel Electrolytes for High-Performance Solid-State Lithium-Ion Batteries.

Ionogel electrolytes based on ionic liquids and gelling matrices offer several advantages for solid-state lithium-ion batteries, including nonflammability, wide processing compatibility, and favorable electrochemical and thermal properties. However, the absence of ionic liquids that are concurrently stable at low and high potentials constrains the electrochemical windows of ionogel electrolytes and thus their high-energy-density applications. Here, ionogel electrolytes with a layered heterostructure are introduced, combining high-potential (anodic stability: >5V vs Li/Li+ ) and low-potential (cathodic stability: <0V vs Li/Li+ ) imidazolium ionic liquids in a hexagonal boron nitride nanoplatelet matrix. These layered heterostructure ionogel electrolytes lead to extended electrochemical windows, while preserving high ionic conductivity (>1mScm-1 at room temperature). Using the layered heterostructure ionogel electrolytes, full-cell solid-state lithium-ion batteries with a nickel manganese cobalt oxide cathode and a graphite anode are demonstrated, exhibiting voltages that are unachievable with either the high-potential or low-potential ionic liquid alone. Compared to ionogel electrolytes based on mixed ionic liquids, the layered heterostructure ionogel electrolytes enable higher stability operation of full-cell lithium-ion batteries, resulting in significantly enhanced cycling performance.

One-dimensional hierarchical anode/cathode materials engineering for high-performance lithium ion batteries

The large-scale integration of 1D hierarchical anode/cathode electrodes has huge application prospects in lithium ion battery (LIB) engineering. 1D geometric topology shapes have been adapted in coin-type half-/full-scale and pouch-type cell LIBs, which demonstrate electron stream movements and Li+ ion diffusions in 1D-hierarchical anode/cathode electrode materials. Controlling the geometrical and morphological configurations of 1D-hierarchical anode/cathode electrodes shows great potential in designing the charge/discharge capacity of LIBs with long-term stable cycles, rapid electron and Li+ ion diffusion kinetics, and maximum rate capacity and capacity storage. Coin-type full-cell LIBs show a distinct reversibility and rate capability performance and a superb Coulombic efficiency of ~99.7% after going through lithiation/delithiation (discharge/charge) cycling processes. LIB pouch-type cell assemblies are fabricated by densely packing 1D hierarchical anode/cathode electrode geometrics in collar-stacked layers. A pouch-type cell battery has a full recovery rate capability to withstand formidable long-term cycles (>>2000 cycles), a substantial areal discharge capacity (≈2.85 mAh/cm2), and remarkable gravimetric and volumetric cell energy densities of ≈187.39 Wh/kg and 243.37 Wh/L, respectively. We expect that the tradeoff requirements and demands in electric vehicles can be improved by these variable LIB designs based on 1D electrode patterns.

Layer-by-Layer Self-Assembled Nanostructured Electrodes for Lithium-Ion Batteries.

Gaining control over the nanoscale assembly of different electrode components in energy storage systems can open the door for design and fabrication of new electrode and device architectures that are not currently feasible. This work presents aqueous layer-by-layer (LbL) self-assembly as a route towards design and fabrication of advanced lithium-ion batteries (LIBs) with unprecedented control over the structure of the electrode at the nanoscale, and with possibilities for various new designs of batteries beyond the conventional planar systems. LbL self-assembly is a greener fabrication route utilizing aqueous dispersions that allow various Li+ intercalating materials assembled in complex 3D porous substrates. The spatial precision of positioning of the electrode components, including ion intercalating phase and electron-conducting phase, is down to nanometer resolution. This capable approach makes a lithium titanate anode delivering a specific capacity of 167 mAh g-1 at 0.1C and having comparable performances to conventional slurry-cast electrodes at current densities up to 100C. It also enables high flexibility in the design and fabrication of the electrodes where various advanced multilayered nanostructures can be tailored for optimal electrode performance by choosing cationic polyelectrolytes with different molecular sizes. A full-cell LIB with excellent mechanical resilience is built on porous insulating foams.

Compatibility of Porous Silicon with Lithium Polysulfides for Full Cell Lithium Ion Battery Applications with Sulfur Cathodes

Crystalline silicon is an ideal anode candidate for lithium ion batteries as it offers a high Li+ ion storage capacity, direct current pathway and is a stable and earth abundant element. In order to match the high theoretical energy density of silicon in lithium ion batteries a suitable cathode material is required. Sulfur based cathodes have a high theoretical storage capacity for application in lithium ion batteries, based on the conversion reaction of the cyclic S8 molecule with lithium to form smaller lithium polysulfides up to Li2S, and are also cheap and earth abundant. One of the major drawbacks of lithium sulfur cathode materials is the tendency of lithium polysulfides to be dissolved by the electrolyte, which causes the polysulfides to migrate away from the cathode, leading to an overall capacity loss. For application of porous silicon in a full cell lithium ion battery with sulfur it is important to understand the impact the presence of lithium polysulfides can have on the functionality of porous silicon as an anode. In this study porous silicon anodes with thicknesses of 6 µm and 12 µm were cycled in a half cell in the presence of varying concentrations of Li2S6 (0 M, 0.017 M and 0.083 M). For the electrolyte with 0.017 M Li2S6 the cycling behavior was comparable, or better, than the electrolyte with no polysulfides. The SEI layer formed on the surface of the porous silicon anodes was investigated ex situ with X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy after one, five and ten cycles. It was seen that in the first cycle lithium polysulfides are contained in the SEI and undergo an oxidation reaction to form sulfates over the following cycles. This leads to a more inorganic SEI layer in the presence of polysulfides, especially in the case of the 12 µm porous silicon, and long term cycling stability. The 12 µm porous silicon anode cycled in the presence of 0.083 M Li2S6 showed stable cycling behavior over one hundred cycles, with limited capacity loss and coulombic efficiencies of 96.2 % after one hundred cycles.

Sophisticated rGO synthesis and pre-lithiation unlocking full-cell lithium-ion battery high-rate performances

For the application to portable devices and storage of renewable energies, high-performance lithium-ion batteries are in great demand. To this end, the development of high-performance electrode materials has been actively investigated. However, even if new materials exhibit high performance in a simple evaluation, namely half-cell tests, it is often impossible to obtain satisfactory performance with an actual battery (full cell). In this study, the structure of graphene analogs is modified in various ways to change crystallinity, disorder, oxygen content, electrical conductivity, and specific surface area. These graphene analogs are evaluated as negative electrodes for lithium-ion batteries, and we found reduced graphene oxide prepared by combination of chemical reduction and thermal treatment was the optimum. In addition, a full cell is fabricated by combining it with LiCoO2 modified with BaTiO3, which is applicable to high-speed charge–discharge cathode material developed in our previous research. In general, pre-lithiation is performed for the anode when assembling full cells. In this study, we optimized a "direct pre-lithiation" method in which the electrode and lithium foil were in direct contact before assembling a full cell, and created a lithium-ion battery with an output of 293 Wh kg−1 at 8,658 W kg−1.

Investigations on electrochemical performance of the full cell fabricated LiCoO2 wrapped with MgO and ZnO for advanced lithium ion battery applications

Developing electrodes with the high efficiency for full cell lithium ion batteries (LIBs) are still challenging. In the present report, we discussed about the performance of LiCoO2 which is analysed by full cell prepared by solid state route. To enhance the electrochemical performance, MgO and ZnO are assigned on the surface of LiCoO2 for better performance. Both ZnO and MgO are synthesized via hydrothermal route. The full cell fabricated with MgO-coated LiCoO2 delivers the high capacity of about 145 mAh/g. The performance of full cell confirms the effect of MgO and ZnO on the surface of LiCoO2 which enhances the efficiency of LIBs.